Specification
MM
1 -
Description
Title of Invention: BELT
Technical Field
[0001]
The present invention relates to a belt (excluding
toothed belts) utilized for power transmission,
conveyance and the like, particularly to a belt in which
the whole or a part of a belt body is formed from a
specific thermoplastic resin composition.
Background Art
[0002]
Conveyance belts and transmission belts require
bending fatigue resistance, abrasion resistance, heat
resistance, durability and the like, for example, as flat
belts, V-belts and the like. Belts are usually imparted
with a tension and used in an elongated state. Belts are
used in combination with resin-made or metal-made pulleys
rotating at a high speed, and are contacted with pulleys,
and caused to be wound therearound and to be rubbed
together, and are exposed to collision with and rubbing
on conveyed materials, and the like.
[0003]
Japanese Patent Laid-Open Nos, 2009-197896 and 2011-
121689 disclose conveyance flat belts whose belt body is
M^
formed from a thermoplastic elastomer such as a
thermoplastic polyurethane elastomer.
[0004]
However, if conventional flat belts and V-belts
having a belt body thereof formed from a thermoplastic
elastomer such as a thermoplastic polyurethane elastomer
are used as high-load power transmission belts, the belt
body abrades and cracks in an early stage, and provides
the belts with insufficient durability in some cases.
Citation List
Patent Literature
[0005]
Patent Literature 1: Japanese Patent Laid-Open No. 2009-
197896
Patent Literature 2: Japanese Patent Laid-Open No. 2011-
121689
Summary of Invention
Technical Problem
[0006]
Therefore, it is an object of the present invention
to provide a belt (excluding toothed belts) which does
not cause abrasion, damage, cracks, breakage, and the
like on the belt body in an early stage, and is thus
remarkably excellent in durability even if being used at
a high load for power transmission and the like.
- 3 -
Solution to Problem
[0007]
As a result of exhaustive studies to achieve the
above-mentioned object, the present inventors have found
that if a belt body of a belt, such as a flat belt or a
V-belt, is formed by using a thermoplastic resin
composition comprising a thermoplastic resin and a
modified ethylene copolymer, and obtained by dispersing
the modified ethylene copolymer into the thermoplastic
resin, the belt remarkably improved in abrasion
resistance and bending fatigue resistance and remarkably
excellent in durability can be obtained; and this finding
has led to the completion of the present invention.
[0008]
That is, the present invention provides a belt
(excluding toothed belts), wherein the whole or a part of
a belt body is formed from a thermoplastic resin
composition (C) comprising a thermoplastic resin (A) and
a modified ethylene copolymer (B), and obtained by
dispersing the modified ethylene copolymer (B) into the
thermoplastic resin (A).
[0009]
The modified ethylene copolymer (B) is preferably a
copolymer, modified with an unsaturated carboxylic acid
or a derivative thereof, of ethylene with at least one
monomer component selected from the group consisting of
^B
_ 4 -
(i) olefin components except for ethylene, (ii) diene
components and (iii) ester components having an
ethylenically unsaturated group.
[0010]
The thermoplastic resin (A) is preferably at least
one selected from polyamide resins, polyester resins,
polycarbonate-based resins and polyacetal resins.
[0011]
The thermoplastic resin (A) is preferably a
thermoplastic elastomer (TPE) (Al) as well. The
thermoplastic elastomer (Al) is preferably at least one
selected from the group consisting of polyurethane-based
thermoplastic elastomers (All), polyester-based
thermoplastic elastomers (A12) and polyamide-based
thermoplastic elastomers (A13).
[0012]
The modified ethylene copolymer (B) is preferably an
ethylene-propylene-diene copolymerized rubber modified
with an unsaturated carboxylic acid or a derivative
thereof.
[0013]
The weight proportion [(B)/(A)] of the modified
ethylene copolymer (B) to the thermoplastic resin (A) is,
for example, in the range of 0.1/99.9 to 60/40.
[0014]
^A
- 5 -
The thermoplastic resin composition (C) preferably
has a hardness (JIS K6253, durometer type A) of not less
than 60.
[0015]
In the present description, the hardness is a value
measured according to JIS K6253 (durometer type A ).
However, in Examples, there were cases where measurement
was carried out using durometer type D (which will be
described to the effect}.
Advantageous Effects of Invention
[0016]
The belt according to the present invention, since a
belt body is formed from a specific thermoplastic resin
composition, is excellent not only in abrasion resistance
but also in bending fatigue resistance, and hardly causes
abrasion, damage, cracks, breakage and the like on the
belt body in an early stage and is remarkably excellent
in durability, even if the belt is used at a high load
for a long time.
Brief Description of Drawings
[0017]
[Figure 1] Figure 1 is a SEM photograph of a pellet
cross-section of a thermoplastic elastomer alloy (an
alloy of an EPDM and an etheric TPU) obtained in
Comparative Example 4.
^H
- 6 -
[Figure 2] Figure 2 is a SEM photograph of a pellet
cross-section of a thermoplastic elastomer alloy (an
alloy of a maleic anhydride-modified EPDM and an etheric
TPU) obtained in Example 4.
[Figure 3] Figure 3 is a SEM photograph of a pellet
cross-section of a thermoplastic elastomer alloy (an
alloy of an EPDM and an esteric TPU) obtained in
Comparative Example 6.
[Figure 4] Figure 4 is a SEM photograph of a pellet
cross-section of a thermoplastic elastomer alloy (an
alloy of a maleic anhydride-modified EPDM and an esteric
TPU) obtained in Example 7.
[Figure 5] Figure 5 is a graph indicating a relationship
between the blend ratio of a modified ethylene copolymer
in a thermoplastic resin composition and the bending
fatigue resistance.
[Figure 6] Figure 6 is a TEM photograph of a sheet crosssection
of a resin composition obtained in Example 14.
[Figure 7] Figure 7 is a TEM photograph of a sheet crosssection
of a resin composition obtained in Example 19.
[Figure 8] Figure 8 is a TEM.photograph of a sheet crosssection
of a resin composition obtained in Comparative
Example 11.
[Figure 9] Figure 9 is an AFM photograph of a pellet
cross-section of a thermoplastic elastomer alloy (an
alloy of a maleic anhydride-modified EPDM and an etheric
TPU) obtained in Example 4.
- 7 -
[Figure 10] Figure 10 is an AFM photograph of a pellet
cross-section of a thermoplastic elastomer alloy (an
alloy of a maleic anhydride-modified EPDM and an esteric
TPU) obtained in Example 7,
[Figure 11] Figure 11 is a schematic perspective diagram
illustratively showing one example of a method for
producing the belt according to the present invention.
Description of Embodiments
[0018]
The whole or a part of a belt body of the belt
according to the present invention is formed from a
thermoplastic resin composition (C) comprising a
thermoplastic resin (A) and a modified ethylene copolymer
(B), and the thermoplastic resin composition (C) is
obtained by dispersing the modified ethylene copolymer
(B) into the thermoplastic resin (A) . Here, the belt
according to the present invention does not include
toothed belts.
[0019]
In the present invention, the belt is not especially
limited as long as being a belt excluding toothed belts,
and examples thereof include known belts such as flat
belts, V-belts and V-ribbed belts. A belt is usually
constituted of a belt body and core wires (tension
members) embedded in the interior of the belt body. A
belt may spare core wires. A belt may have, as required.
%
- 8 -
other members and components, coating layers and the like,
A belt may be of a single layer or may be of a two or
more-layer laminate.
[0020]
[Thermoplastic resin (A) ]
In the present invention, as a thermoplastic resin
(A), a known thermoplastic resin can be used. The
thermoplastic resin (A) can be used singly or in
combinations of two or more. The thermoplastic resin (A)
does not include a substance (compound) corresponding to
a modified ethylene copolymer (B),
[0021]
Examples of the thermoplastic resin (A) include
polyurethane-based resins, polyester-based resins,
polyamide-based resins, polyimide-based resins,
polystyrenic resins, polycarbonate-based resins,
polyolefinic resins, acrylic resins, methacrylic resins,
fluororesins, silicone-based resins, polyacetal resins
(polyoxymethylene), polyarylate resins, polyphenylene
ethers, polyphenylene sulfides, polysulfones,
polyethersulfones, polyetheretherketones, vinyl chloride
resins and polyvinylic resins, but are not limited
thereto as long as they are capable of dispersing a
modified ethylene copolymer (B) (dispersing and
containing a modified ethylene copolymer (B)). The
thermoplastic resin (A) may be used singly or plurally,
or may use a multicomponent singly or plurally such as
»
- 9
copolymers, additions, blends and alloys. The
thermoplastic resin (A) has a weight-average molecular
weight of, for example, 5,000 to 1,000,000, and
preferably 10,000 to 500,000.
[0022]
More specific examples of the thermoplastic resin
(A) include, for example, polyamide-based resins such as
polyamide 11, polyamide 12, polyamide 6, polyamide 66,
polyamide 610, polyamide 612, polyamide 666, polyamide 46,
polyamide lOT, polyamide 6T and aramid resins (whole
aromatic polyamide); polyester-based resins such as
polyethylene terephthalate, polybutylene terephthalate
and polyethylene naphthalate; polyimide; polystyrene;
polycarbonate; polyolefinic resins such as polyethylenes
and polypropylenes; fluororesins such as polyvinylidene
fluorides, polytetrafluoroethylenes, polyvinyl fluorides,
polychlorotrifluoroethylenes, perfluoroalkoxyfluororesins,
ethylene tetrafluoride-propylene hexafluoride copolymers,
ethylene-ethylene tetrafluoride copolymers and ethylenechlorotrifluoroethylene
copolymers; polyacetal resins;
polyethersulfones; polyetheretherketones; and polyvinylic
resins such as polyvinyl alcohols and ethylene vinyl
alcohols. Additives such as reinforcing fillers such as
glass fibers may be incorporated in these thermoplastic
resins (A). Also amorphous materials (thermoplastic
resins) having no distinct melting point, in the case of
being molded by a thermoplastic resin molding machine,
*
- 10
can be incorporated. The thermoplastic resin (A) may be
resins obtained from fossil raw materials and natural
resins as well.
[0023]
Among the above, the thermoplastic resin (A) is
preferably at least one selected from the group
consisting of polyamide-based resins, polyester-based
resins, polycarbonate-based resins and polyacetal resins.
[0024]
[Thermoplastic elastomer (Al)]
As the thermoplastic resin (A), a thermoplastic
elastomer (TPE) (Al) may be preferably used. The
thermoplastic elastomer (Al) comprises a hard phase (hard
segment) and a soft phase (soft segment), and though
exhibiting properties as a rubber at normal temperature,
is a polymer exhibiting thermoplasticity at high
temperatures. Use of the thermoplastic elastomer (Al)
can improve the abrasion resistance, mechanical strength
and molding processability of a thermoplastic resin
composition.
[0025]
The thermoplastic elastomer (Al) may be used singly
or as a mixture of two or more. As the thermoplastic
resin (A), a thermoplastic elastomer (Al) and a resin
other than a thermoplastic elastomer may be concurrently
used.
[0026]
.jf
- 11 -
Examples of the thermoplastic elastomer (Al) include
polyurethane-based thermoplastic elastomers (All),
polyester-based thermoplastic elastomers (A12),
polyamide-based thermoplastic elastomers (A13),
polystyrenic thermoplastic elastomers (A14),
fluoropolymer-based thermoplastic elastomers (A15),
polyvinyl chloride-based thermoplastic elastomers (A16),
polyolefinic thermoplastic elastomers (A17) and
polyimide-based elastomers (A18), but are not limited
thereto. The thermoplastic elastomer (Al) may also be a
thermoplastic elastomer in which a resin, an elastomer
and/or an oligomer component are blended (mixed). The
thermoplastic elastomer (Al) may be used singly or in
combinations of two or more. Among the above
thermoplastic elastomers (Al), preferable are
polyurethane-based thermoplastic elastomer (All),
polyester-based thermoplastic elastomers (A12) and
polyamide-based thermoplastic elastomers (A13), and
especially preferable are polyurethane-based
thermoplastic elastomers (All).
[0027]
[Polyurethane-based thermoplastic elastomer (All)]
As the polyurethane-based thermoplastic elastomer
(All), known thermoplastic polyurethanes (TPU) can be
used. The thermoplastic polyurethane can be used singly
or in combinations of two or more. The thermoplastic
polyurethane is usually obtained by reacting a
- 12 -
polyisocyanate, a long-chain polyol and a chain extender,
and as required, other isocyanate-reactive compounds.
[0028]
The polyisocyanate is not especially limited as long
as it is a compound having at least two isocyanate groups
in the molecule. The polyisocyanate includes, for
example, aliphatic polyisocyanates, alicyclic
polyisocyanates, aromatic polyisocyanates and araliphatic
(aromatic-aliphatic) polyisocyanates. The polyisocyanate
can be used singly or in combinations of two or more.
[0029]
Examples of the aliphatic polyisocyanate include
aliphatic diisocyanates such as 1,3-trimethylene
diisocyanate, 1,4-tetramethylene diisocyanate, 1,5-
pentamethylene diisocyanate, 1,5-hexamethylene
diisocyanate, 1,2-propylene diisocyanate, 1,2-butylene
diisocyanate, 2,3-butylene diisocyanate, 1,3-butylene
diisocyanate, 2-methyl-l,5-pentamethylene diisocyanate,
3-methyl-l,5-pentamethylene diisocyanate, 2,4,4-
trimethyl-1,6-hexamethylene diisocyanate and 2,2,4-
trimethyl-1,6-hexamethylene diisocyanate.
[0030]
Examples of the alicyclic polyisocyanate include
alicyclic diisocyanates such as 1,3-cyclopentane
diisocyanate, 1,4-cyclohexane diisocyanate, 1,3-
cyclohexane diisocyanate, 3-isocyanatomethyl-3,5,5-
trimethylcyclohexyl isocyanate {isophorone diisocyanate),
0
13
4,4'-methylenebis(cyclohexyl isocyanate), methyl-2,4-
cyclohexane diisocyanate, methyl-2,6-cyclohexane
diisocyanate, 1,3-bis(isocyanatomethyl)cyclohexane, 1,4-
bis(isocyanatomethyl)cyclohexane and norbornane
diisocyanate.
[0031]
Examples of the aromatic polyisocyanate include
aromatic diisocyanates such as m-phenylene diisocyanate,
p-phenylene diisocyanate, 2,4-tolylene diisocyanate, 2,6-
tolylene diisocyanate, naphthylene 1,4-diisocyanate,
naphthylene 1,5-diisocyanate, 4,4'-diphenyl diisocyanate
(4,4'-biphenyl diisocyanate), 4,4'-diphenylmethane
diisocyanate, 2,4'-diphenylmethane diisocyanate, 2,2'-
diphenylmethane diisocyanate, 4,4'-diphenyl ether
diisocyanate, 2,2'-diphenylpropane-4,4'-diisocyanate,
3,3'-dimethyldiphenylmethane-4,4'-diisocyanate and 4,4'-
diphenylpropane diisocyanate.
[0032]
Examples of the araliphatic polyisocyanate include
araliphatic diisocyanates such as 1,3-xylylene
diisocyanate, 1,4-xylylene diisocyanate, G),©'-
diisocyanato-1,4-diethylbenzene, 1,3-bis{1-isocyanato-lmethylethyl)
benzene, 1,4-bis(1-isocyanato-l-methylethyl)
benzene and 1,3-bis(a,a-dimethylisocyanatomethyl)benzene,
[0033]
As the polyisocyanate, suitably usable are 1,6-
hexamethylene diisocyanate, 4,4'-methylenebis(cyclohexyl
^^m
- 14 -
isocyanate), 1,3-bis(isocyanatomethyl)cyclohexane, 1,4-
bis(isocyanatomethyl)cyclohexane, isophorone diisocyanate,
2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate,
4,4'-diphenylmethane diisocyanate, 1,3-xylylene
diisocyanate, 1,4-xylylene diisocyanate, norbornane
diisocyanate and 1,3-bis(a,adimethylisocyanatoraethyl)
benzene.
[0034]
As the polyisocyanate, also usable are dimers,
trimers, reaction products or polymers of the above
exemplified aliphatic polyisocyanates, alicyclic
polyisocyanates, aromatic polyisocyanates and araliphatic
polyisocyanates {for example, a dimmer or a trimer of
diphenylmethane diisocyanate, reaction products of
trimethylolpropane and tolylene diisocyanate, reaction
products of trimethylolpropane and hexamethylene
diisocyanate, polymethylene polyphenyl isocyanates,
polyether polyisocyanates, polyester polyisocyanates and
the like) and the like.
[0035]
Examples of the long-chain polyol include polyether
polyols, polyester polyols, polycarbonate polyols,
polyolefin polyols and polyacryl polyols. The long-chain
polyol has a number-average molecular weight of usually
not less than 500, preferably 500 to 10,000, still more
preferably 600 to 6,000, and further still more
^K
- 15 -
preferably 800 to 4,000. The long-chain polyol can be
used singly or in combinations of two or more.
[0036]
Examples of the polyether polyol include
polyalkylene ether glycols such as polyethylene ether
glycols, polypropylene ether glycols and
polytetramethylene ether glycols (PTMG), and additionally
copolymers containing a plurality of alkylene oxides
(alkylene oxide-another alkylene oxide) as monomer
components, such as ethylene oxide-propylene oxide
copolymers. Among the polyether polyols, especially
preferable are polytetramethylene ether glycols (PTMG).
[0037]
As the polyester polyol, usable are, for example,
polycondensates of a polyhydric alcohol and a polyvalent
carboxylic acid, ring-opened polymers of cyclic esters
(lactones), and reaction products of three components of
a polyhydric alcohol, a polyvalent carboxylic acid and a
cyclic ester (lactone). In the polycondensates of a
polyhydric alcohol and a polyvalent carboxylic acid, as
the polyhydric alcohol, usable are, for example, ethylene
glycol, diethylene glycol, propylene glycol, dipropylene
glycol, 1,3-propanediol, 1,3-butanediol, 1,4-butanediol,
2-methyl-l,3-propanediol, 1,5-pentanediol, neopentyl
glycol, 1,6-hexanediol, 3-methyl-l,5-pentanediol, 2,4-
diethyl-1,5-pentanediol, 1,9-nonanediol, 1,lO-decanediol,
glycerol, trimethylolpropane, trimethylolethane.
- 16
cyclohexanediols (1,4-cyclohexanediol and the like),
cyclohexanedimethanols (1,4-cyclohexanediitiethanol and the
like), bisphenols (bisphenol A and the like), and sugar
alcohols (xylitol, sorbitol and the like) . On the other
hand, examples of the polyvalent carboxylic acid include
aliphatic dicarboxylic acids such as malonic acid, maleic
acid, succinic acid, glutaric acid, adipic acid, suberic
acid, azelaic acid, sebacic acid and dodecanedioic acid;
alicyclic dicarboxylic acids such as 1,4-
cyclohexanedicarboxylic acid; and aromatic dicarboxylic
acids such as terephthalic acid, isophthalic acid, orthophthalic
acid, 2,6-naphthalenedicarboxylic acid, paraphenylenedicarboxylic
acid and trimellitic acid. In the
ring-opened polymers of cyclic esters, examples of the
cyclic ester include propiolactone, p-methyl-5-
valerolactone and 8-caprolactone. In the reaction
products of three components, the above exemplified
polyhydric alcohols, polyvalent carboxylic acids and
cyclic esters and the like can be used. Among the
polyester polyols, preferable are adipate-based polyester
polyols [for example, C2-6 alkylene adipates such as
poly(ethylene adipate), poly(diethylene adipate),
poly(propylene adipate), poly(tetramethylene adipate),
poly(hexamethylene adipate) and poly(neopentylene
adipate)] which are polycondensates of adipic acid and a
polyhydric alcohol (for example, one or two or more of
alkane diols having 2 to 6 carbon atoms such as ethylene
17 -
glycol, 1,4-butanediol, neopentyl glycol and 1,6-
hexanediol), caprolactone polyols obtained by ringopening
polymerization of s-caprolactone, polyester
polyols obtained by ring-opening polymerization of pmethyl-
6-valerolactone using a polyhydric alcohol such as
ethylene glycol, and the like.
[0038]
Examples of the polycarbonate polyol include
reaction products of a polyhydric alcohol and phosgene, a
chloroformate ester, a dialkyl carbonate or a diaryl
carbonate (a polyhydric alcohol and a compound selected
from the group consisting of phosgene, a chloroformate
ester, a dialkyl carbonate and a diaryl carbonate); and
ring-opened polymers of cyclic carbonate esters {alkylene
carbonates and the like). In the reaction products of a
polyhydric alcohol and phosgene, as the polyhydric
alcohol, specifically usable are the above exemplified
polyhydric alcohols (for example, ethylene glycol,
propylene glycol, 1,3-butanediol, 1,4-butanediol,
neopentyl glycol, 1,5-pentanediol, 1,6-hexanediol and
1,9-nonanediol). In the ring-opened polymers of cyclic
carbonate esters, examples of the alkylene carbonate
include ethylene carbonate, triraethylene carbonate,
tetramethylene carbonate and hexamethylene carbonate.
Here, the polycarbonate polyol suffices if being a
compound having carbonate bonds in the molecule and
having hydroxyl groups at the terminals, and may have
18 -
ester bonds together with the carbonate bonds. Typical
examples of the polycarbonate polyol include
poly(hexamethylene carbonate) diols, diols obtained by
ring-opening addition polymerization of a lactone to a
poly(hexamethylene carbonate) diol, and cocondensates of
a poly(hexamethylene carbonate) diol and a polyester diol
or a polyether diol.
[0039]
The polyolefin polyol is a polyol having an olefin
as a component of a skeleton (or a main chain) of a
polymer or a copolymer, and having at least two hydroxyl
groups in the molecule (particularly at the terminals).
The above olefin may be an olefin (for example, an aolefin
such as ethylene or propylene) having a carboncarbon
double bond at the terminal, may be an olefin (for
example, isobutene) having a carbon-carbon double bond at
a site other than the terminals, or further may be a
diene (for example, butadiene or isoprene). Typical
examples of the polyolefin polyol include substances
(compounds) obtained by modifying, with hydroxyl groups,
the terminals of butadiene- or isoprene-based polymers
such as butadiene homopolymers, isoprene homopolymers,
butadiene-styrene copolymers, butadiene-isoprene
copolymers, butadiene-acrylonitrile copolymers,
butadiene-2-ethylhexyl acrylate copolymers, butadiene-noctadecyl
acrylate copolymers.
[0040]
- 19 -
The polyacryl polyol is a polyol having a
(meth)acrylate as a component of a skeleton (or a main
chain) of a polymer or a copolymer, and having at least
two hydroxyl groups in the molecule (particularly at the
terminals). As the (meth)acrylate, suitably used are
alkyl (meth) acrylate esters [for example, Ci-20 alkyl
(meth)acrylate esters]. As the polyol, every material
other than materials cited here can be used.
[0041]
As the chain extender, usable are chain extenders
usually used in production of thermoplastic polyurethanes,
and the type thereof is not especially limited, and lowmolecular
weight polyols and polyamines and the like can
be used. The chain extender has a molecular weight of
usually less than 500, and preferably not more than 300.
The chain extender can be used singly or in combinations
of two or more.
[0042]
Typical examples of the chain extender include
polyols (particularly, diols) such as ethylene glycol,
diethylene glycol, propylene glycol, 1,3-propanediol,
1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, 1,2-
pentanediol, 2,3-pentanediol, neopentyl glycol, 1,6-
hexanediol, 3-methyl-l,5-pentanediol, 1,4-cyclohexanediol
and 1,4-cyclohexanedimethanol, and polyamines
(particularly, diamines) such as hexamethylenediamine,
3,3'-dimethyl-4,4'-diaminodicyclohexylmethane and 4,4'-
- 20 -
methylenebis-2-chloroaniline. Among these, diols are
especially preferable.
[0043]
As the thermoplastic polyurethane, preferable are
thermoplastic polyurethanes obtained by reacting a
polyisocyanate, a long-chain polyol and a chain extender
in the range of the ratio (NCO/isocyanate-reactive
groups), of the molar number of isocyanate groups of the
polyisocyanate and the molar number of isocyanatereactive
groups (hydroxyl group, amino group and the
like) of the long-chain polyol and the chain extender, of
0.9 to 1.3, especially 0.95 to 1.1. The proportion of
the long-chain polyol to the chain extender, [the former
/ the latter (molar ratio)] , can suitably be selected in
the range of, for example, 0.1 to 1.0, and preferably 0.2
to 2, according to physical properties and the like of
the thermoplastic polyurethane. In the above reaction,
in order to promote the reaction, as required, a catalyst
such as a tertiary amine, an organometal compound or a
tin compound may be used.
[0044]
The thermoplastic polyurethane usually has a weightaverage
molecular weight Mw of 5,000 to 1,000,000.
The thermoplastic polyurethane has thermoplasticity,
though some exhibit no distinct melting point. The
thermoplastic polyurethane has thermoplasticity, and can
be molded by a common thermoplastic resin molding machine
4
21
such as extrusion, injection molding, heat press or the
like.
[0045]
The hardness of the thermoplastic polyurethane, but
not limited to, from the viewpoint of raising mechanical
properties of the thermoplastic resin composition
(thermoplastic elastomer alloy and the like) according to
the present invention, is preferably not less than 60
(for example, 60 to 96), more preferably not less than 78
(for example, 78 to 96), still more preferably not less
than 8 9 (for example, 89 to 95), and especially
preferably not less than 91 (for example, 91 to 94), in
hardness of JIS K6253 (durometer type A) . From the
viewpoint of letting the thermoplastic resin composition
(thermoplastic elastomer alloy and the like) have
reasonable flexibility and raising the bending fatigue
resistance, the thermoplastic polyurethane has a hardness
in the range of, for example, 60 to 93, and especially
preferably 78 to 91 (particularly 78 to 88).
[0046]
The thermoplastic polyurethane preferably uses a
polyester polyol or a polyether polyol as the long-chain
polyol. Jtaiong these, the thermoplastic polyurethane is
especially preferably adipate-based TPUs using an
adipate-based polyester polyol as the long-chain polyol,
caprolactone-based TPUs using a caprolactone polyol as
the long-chain polyol, and PTMG-based TPUs using a
4
- 22 -
polytetramethylene ether glycol (PTMG) as the long-chain
polyol.
[0047]
As the thermoplastic polyurethane, commercially
available products can be used. Examples of the
commercially available products include an adipate-based
TPU of 80 in hardness {an adipate-based TPD with a
hardness of 80, a hardness of 80), an adipate-based TPU
of 90 in hardness, a caprolactone-based TPU of 90 in
hardness, a PTMG-based TPU of 92 in hardness, and an
adipate'-based TPU of 92 in hardness.
[0048]
[Polyester-based thermoplastic elastomer (A12)]
As the polyester-based thermoplastic elastomer (A12),
known polyester-based thermoplastic elastomers can be
used. The polyester-based thermoplastic elastomer (A12)
can be used singly or in combinations of two or more.
The polyester-based thermoplastic elastomer (A12) can be
produced by a known method such as the esterification
reaction or the transesterification reaction.
[0049]
The polyester-based thermoplastic elastomer (A12) is
preferably, for example, polyester-based thermoplastic
elastomers having as main constituting units a hard
segment composed of an aromatic polyester unit and a soft
segment composed of an aliphatic polyether unit and/or an
aliphatic polyester unit.
4
- 23 -
[0050]
The aromatic polyester unit is mainly a unit formed
of an aromatic dicarboxylic acid or an ester-forming
derivative thereof (a C1-4 alkyl ester, an acid halide or
the like) and a diol or an ester-forming derivative
thereof (an acetylated derivative, an alkaline metal salt
or the like). Specific examples of the aromatic
dicarboxylic acid include terephthalic acid, isophthalic
acid, phthalic acid, naphthalene-2,6-dicarboxylic acid,
naphthalene-2,7-dicarboxylic acid, anthracenedicarboxylic
acid, diphenyl-4,4'-dicarboxylic acid,
diphenoxyethanedicarboxylic acid, 4,4'-diphenyl ether
dicarboxylic acid, 5-sulfoisophthalic acid and sodium 3-
sulfoisophthalate. Specific examples of the diol include
diols having a molecular weight of not more than 400, and
include, for example, aliphatic diols such as 1,4-
butanediol, ethylene glycol, trimethylene glycol,
pentamethylene glycol, hexamethylene glycol and neopentyl
glycol, decamethylene glycol; alicyclic diols such as
1,1-cyclohexanedimethanol, 1,4-dicyclohexanedimethanol
and tricyclodecanedimethanol; and aromatic diols such as
xylylene glycol, bis(p-hydroxy)diphenyl, bis(phydroxy)
diphenylpropane, 2,2'-bis[(4-(2-
hydroxyethoxy)phenyl)]propane, bis[4-(2-
hydroxyethoxy)phenyl] sulfone, 1,1-bis[4-(2-
hydroxyethoxy)phenyl]cyclohexane and 4,4'-dihydroxy-pterphenyl.
These aromatic dicarboxylic acids or ester¥
24
forming derivatives thereof, and diols and ester-forming
derivatives thereof may be concurrently used in two or
more, respectively. Preferable aromatic polyester units
include a polybutylene terephthalate unit derived from
terephthalic acid and/or dimethyl terephthalate and 1,4-
butanediol, and a unit composed of a polybutylene
terephthalate unit derived from terephthalic acid and/or
dimethyl terephthalate and a polybutylene isophthalate
unit derived from isophthalic acid and/or dimethyl
isophthalate and 1,4-butanediol.
[0051]
Examples of an aliphatic polyether constituting the
aliphatic polyether unit include poly(ethylene oxide)
glycols, poly(propylene oxide) glycols,
poly(tetramethylene oxide) glycols, poly(hexamethylene
oxide) glycols, copolymers of ethylene oxide and
propylene oxide, ethylene oxide addition polymers of
poly(propylene oxide) glycols and copolymer glycols of
ethylene oxide and tetrahydrofuran. Among these,
preferable are poly(tetramethylene oxide) glycols,
ethylene oxide addition products of poly(propylene oxide)
glycols and copolymer glycols of ethylene oxide and
tetrahydrofuran. Examples of an aliphatic polyester
constituting the aliphatic polyester unit include poly(scaprolactone)
s, polyenantholactones, polycaprolactones,
polybutylene adipates and polyethylene adipates. Among
^
- 25 -
these, preferable are poly (s-caprolactone)s, polybutylene
adipates, polyethylene adipates, and the like.
[0052]
The soft segment composed of an aliphatic polyether
unit and/or an aliphatic polyester unit has a numberaverage
molecular weight of preferably 300 to 6,000, and
especially preferably 500 to 4,000, in the copolymerized
state.
[0053]
The ratio of the hard segment composed of an
aromatic polyester unit and the soft segment composed of
an aliphatic polyether unit and/or an aliphatic polyester
unit in the polyester-based thermoplastic elastomer is
not especially limited, but is, for example, the former /
the latter (weight ratio) = 1/99 to 99.5/0.5, and
preferably 50/50 to 99/1.
[0054]
[Polyamide-based thermoplastic elastomer (A13)]
As the polyamide-based thermoplastic elastomer (A13),
known polyamide-based thermoplastic elastomers can be
used. The polyamide-based thermoplastic elastomer (A13)
can be used singly or in combinations of two or more.
[0055]
As the polyamide-based thermoplastic elastomer (A13),
preferable are, for example, polyamide-based
thermoplastic elastomers having as main constituting
units a hard segment composed of a polyamide unit and a
26 -
soft segment composed of an aliphatic polyether unit
and/or an aliphatic polyester unit.
[0056]
Examples of a polyamide constituting the polyamide
unit include nylon 6, nylon 66, nylon 11 and nylon 12.
Examples of an aliphatic polyether constituting the
aliphatic polyether unit include the same aliphatic
polyethers as exemplified in the term of the polyesterbased
thermoplastic elastomer. Among these, preferable
are poly(tetramethylene oxide) glycols, ethylene oxide
additions of poly(propylene oxide) glycols, and copolymer
glycols of ethylene oxide and tetrahydrofuran. Examples
of an aliphatic polyester constituting the aliphatic
polyester unit include the same aliphatic polyesters as
exemplified in the term of the polyester-based
thermoplastic elastomer. Among these, preferable are
poly (8-caprolactone)s, polybutylene adipates,
polyethylene adipates, and the like.
[0057]
[Other thermoplastic elastomers]
As the polystyrenic thermoplastic elastomer (A14),
the fluoropolymer-based thermoplastic elastomer (A15),
the polyvinyl chloride-based thermoplastic elastomer
(A16), the polyolefinic thermoplastic elastomer (A17) and
the polyimide-based elastomer (A18), usable are
respective known elastomers.
[0058]
- 27 -
As the thermoplastic resin (A), from the viewpoint
of the adhesion with a modified ethylene copolymer (B),
preferable are resins having, in the molecule (for
example, on the main chain, terminals and side chains of
a polymer), functional groups (or functional groups
having affinity) reactive, in heating and mixing, with
modifying groups (for example, a carboxyl group or its
salt, a carboxylate ester group, an acid anhydride group,
a carboxylic acid halide group, an amido group, an imido
group, a glycidyl group (epoxy group), a halogen atom, an
amino group, an imido group, a phosphino group, a thioxy
group and a silicon-containing group, which will be
described later) of the modified ethylene copolymer (B).
Examples of such a resin include thermoplastic resins
having, on the terminals of a polymer main chain,
functional groups such as a hydroxyl group, a carboxyl
group, an amino group and a thiol group, for example,
polyamide-based resins, polyester-based resins,
polycarbonate-based resins, polyacetal resins,
polyphenylene ethers, polyphenylene sulfides,
polyurethane-based thermoplastic elastomers (All),
polyester-based thermoplastic elastomers (A12) and
polyamide-based thermoplastic elastomers (A13).
[0059]
[Modified ethylene copolymer (B)]
In the present invention, as the modified ethylene
copolymer (B), usable are known modified ethylene
- 28
copolymers. The modified ethylene copolymer (B) can be
used singly or in combinations of two or more. The
modified ethylene copolymer (B) has a weight-average
molecular weight of, for example, 5,000 to 1,000,000, and
preferably 10,000 to 500,000.
[0060]
The modified ethylene copolymer (B) is an ethylene
copolymer modified with an unsaturated carboxylic acid or
a derivative thereof or another functional group.
Examples of the ethylene copolymer include copolymers of
ethylene with at least one monomer component selected
from (i) olefin components except for ethylene, (ii)
diene components and (iii) ester components having an
ethylenically unsaturated group. Examples of the olefin
component except for ethylene include a-olefins having 3
to 12 carbon atoms such as propylene, 1-butene, 1-pentene,
1-hexene, 1-heptene, 1-octene and 1-decene. Examples of
the diene component include non-conjugated dienes such as
ethylidene norbornene, dicyclopentadiene and 1,4-
hexadiene. Examples of the ester component having an
ethylenically unsaturated group include alkyl
{meth)acrylate esters such as methyl (meth)acrylate and
ethyl (meth)acrylate, and vinyl carboxylate esters such
as vinyl acetate and vinyl propionate.
[0061]
Typical examples of the ethylene copolymer include
ethylene-propylene-diene copolymers (ethylene-propylenete
29 -
diene copolymerized rubber, ethylene-propylene-diene
rubbers; EPDM), ethylene-propylene copolymers (ethylenepropylene
rubbers; EPM), ethylene-methyl (meth)acrylate
copolymers, ethylene-ethyl (meth)acrylate copolymers and
ethylene-vinyl acetate copolymers. Among these,
especially preferable are ethylene-propylene-diene
copolymers (ethylene-propylene-diene rubbers; EPDM) and
ethylene-propylene copolymers (ethylene-propylene
rubbers; EPM).
[0062]
Examples of an unsaturated carboxylic acid used for
modification of the ethylene copolymer include acrylic
acid, methacrylic acid, maleic acid, fumaric acid,
tetrahydrophthalic acid, itaconic acid, citraconic acid,
crotonic acid, isocrotonic acid and
norbornenedicarboxylic acid. Examples of a derivative of
an unsaturated carboxylic acid include esters of
unsaturated carboxylic acids [for example, glycidyl
(meth)acrylate and maleate esters], acid anhydrides
(maleic anhydride and the like), salts, acid halides,
amides and imides. An ethylene copolymer modified with
an unsaturated carboxylic acid or a derivative thereof
has, in the molecule, a carboxyl group or a salt thereof,
a carboxylate ester, an acid anhydride group, a carboxyl
acid halide group, an amido group, an imido group or the
like.
[0063]
- s o other
functional groups used for modification of the
ethylene copolymer are not especially limited as long as
they are capable of chemically modifying the ethylene
copolymer. The other functional groups include, for
example, a glycidyl group (epoxy group), a halogen atom,
an amino group, an imido group, a phosphino group, a
thioxy group, a silicon atom-containing group. These
functional groups may be incorporated singly or in two or
more.
[0064]
Modification of an ethylene copolymer can be carried
out, for example, by heating and kneading the ethylene
copolymer and an unsaturated carboxylic acid or a
derivative thereof in the presence of a graft
polymerization initiator [for example, a peroxide
initiator such as 1>3-bis(t-butylperoxyisopropyl)benzene
or dicumyl peroxide]. Modification of an ethylene
copolymer can be carried out also by further using an
unsaturated carboxylic acid (acrylic acid, methacrylic
acid or the like) as another comonomer when ethylene and
a comonomer such as an ester having an ethylenically
unsaturated bond [methyl (meth)acrylate, ethyl
(meth)acrylate, vinyl acetate or the like] are
copolymerized. Further, modification of an ethylene
copolymer with the above another functional group can
also be carried out by a known method. Modification may
use a chemical reaction such as random copolymerization.
- 31 -
alternating copolymerization, block copolymerization or
graft copolymerization, may use a state of a reaction
intermediate, or may use a physical modification such as
addition, coexistence or generation.
[0065]
The modification ratio with an unsaturated
carboxylic acid or a derivative thereof or the another
functional group in the modified ethylene copolymer (B)
is, as a content rate of a structural unit containing
groups originated (derived) from the unsaturated
carboxylic acid or the derivative thereof, or a
structural unit containing the another functional group,
for example, about 0.1 to 20 wt%, preferably about 0.5 to
10 wt%, and still more preferably about 1 to 8 wt%, with
respect to the whole modified ethylene copolymer (a whole
amount of the modified ethylene copolymer). If the
content rate is too low, the improving effect of the
abrasion resistance and the bending fatigue resistance in
blending with a thermoplastic resin (A) is liable to
become small. By contrast, if the content rate is too
high, properties as a copolymer intrinsic to an ethylene
copolymer become liable to decrease, making difficult the
maintenance of the copolymer and also making difficult
the regulation of the properties.
[0066]
The modification of an ethylene copolymer may be
carried out independently for the ethylene copolymer
32 -
before being blended with a thermoplastic resin, or may
be carried out simultaneously in a stage of blending a
before-modification ethylene copolymer with a
thermoplastic resin. An unreacted carboxylic acid or
derivative thereof may be removed, or may be used as it
remains.
[0067]
The modified ethylene copolymer (B) is preferably a
copolymer, modified with an unsaturated carboxylic acid
or a derivative thereof, of ethylene with at least one
monomer component selected from (i) olefin components
except for ethylene (particularly, a-olefins containing
at least propylene), (ii) diene components and (iii)
ester components having an ethylenically unsaturated
group. Among these, especially preferable are polymers
obtained by modifying a copolymer of ethylene, an olefin
except for ethylene (particularly, a-olefin containing at
least propylene) and/or a diene with an unsaturated
carboxylic acid or a derivative thereof (particularly
maleic anhydride).
[0068]
A preferable modified ethylene copolymer (B)
includes modified ethylene-propylene-diene copolymerized
rubbers (modified EPDM) (Bl), modified ethylene-propylene
rubbers (modified EPM) (B2) and carboxylic acid-modified
ethylene acryl rubbers (acid-modified ethylene acryl
elastomers) (B3). Among these, preferable are modified
^
33 -
ethylene-propylene-diene copolymerized rubbers (modified
EPDM) (Bl).
[0069]
[Modified ethylene-propylene-diene copolymerized
rubber (Bl)]
In the present invention, as the modified ethylenepropylene-
diene copolymerized rubber (Bl) (modified EPDM),
usable are known modified ethylene-propylene-diene
copolymerized rubbers. The modified ethylene-propylenediene
copolymerized rubber (Bl) can be used singly or in
combinations of two or more.
[0070]
An ethylene-propylene-diene copolymer (EPDM) is a
copolymer of ethylene, propylene and a non-conjugated
diene. Examples of the diene include 5-ethylidene-2-
norbornene, dicyclopentadiene and 1,4-hexadiene. A
modified ethylene-propylene-diene copolymerized rubber
(modified EPDM) (Bl) used in the present invention is
obtained by modifying an EPDM with, for example, an
unsaturated carboxylic acid or a derivative thereof (an
ester, an acid anhydride, a salt, an acid halide, an
amide, an imide, or the like) or another functional group.
Examples of the unsaturated carboxylic acid or the
derivative thereof include, as in the above, acrylic acid,
methacrylic acid, maleic acid, fumaric acid,
tetrahydrophthalic acid, itaconic acid, citraconic acid,
crotonic acid, isocrotonic acid, norbornenedicarboxylic
34 -
acid, glycidyl (math)acrylate, maleate esters and maleic
anhydride, and the unsaturated carboxylic acid or the
derivative thereof may have a structure of an ester salt,
a metal salt thereof and the like. Among these,
preferable are acrylic acid, methacrylic acid and maleic
anhydride, and especially preferable is maleic anhydride.
The another functional group includes, for example, a
glycidyl group, a halogen atom, an amino group, an imido
group, a phosphino group and a thioxy group.
[0071]
Modification of an EPDM can be carried out, for
example, by heating and kneading the EPDM and an
unsaturated carboxylic acid or a derivative thereof in
the presence of a graft polymerization initiator [for
example, a peroxide initiator such as l,3-bis(tbutylperoxyisopropyl)
benzene or dicumyl peroxide]. The
ratio of ethylene and propylene in an EPDM used as a raw
material is, from the viewpoint of properties thereof as
an elastomer, and the like, for example, the former / the
latter (weight ratio) = 10/90 to 95/5, and preferably
about 50/50 to 85/15. The content rate of a structural
unit originated from a diene component in an EPDM is, for
example, about 0.1 to 25 wt%, preferably about 1 to 20
wt%, and more preferably about 2 to 10 wt%, to the whole
EPDM.
[0072]
- 35 -
The modification ratio with an unsaturated
carboxylic acid or a derivative thereof in the modified
ethylene-propylene-diene copolymerized rubber (Bl) is, as
a content rate of a structural unit originated from the
unsaturated carboxylic acid or the derivative thereof,
for example, about 0.1 to 20 wt%, preferably about 0.5 to
10 wt%, and more preferably about 1 to 8 wt%, with
respect to the whole modified EPDM. If the content rate
is too low, the improving effect of the abrasion
resistance and the bending fatigue resistance in blending
with a thermoplastic resin (A) [for example, the
polyurethane-based thermoplastic elastomer (Al)] is
liable to become small. By contrast, if the content rate
is too high, the function as an elastomer becomes liable
to decrease.
[0073]
The modification of an EPDM may be carried out
independently for the EPDM before being blended with a
TPU, or may be carried out simultaneously in a stage of
blending a before-modification EPDM with a TPU. An
unreacted carboxylic acid or a derivative thereof may be
removed, or may be used as it remains.
[0074]
The modified ethylene-propylene-diene copolymerized
rubber (Bl) has a melt flow rate (ASTM D1238, 280°C/2.16
kg) of, for example, 5 to 80 g/lO-min, and preferably 10
to 40 g/lO-min.
36 -
[0075]
As the modified ethylene-propylene-diene
copolymerized rubber (Bl), commercially available
products may be used. Examples of the commercially
available product include "Fusabond N416" by trade name
(maleic anhydride-modified EPDM, Du Pont K.K.).
[0076]
A modified ethylene-propylene-diene copolymerized
rubber (Bl) to become a dispersoid in a resin composition
may be crosslinked, or uncrosslinked. For example,
dynamic crosslinking means, in which crosslinking is
carried out with thermoplasticity being maintained, may
be used.
[0077]
Although a modified ethylene-propylene-diene
copolymerized riibber (Bl) is often crosslinked and then
utilized as industrial rubber products so far, and has
not been so much used as a modifier for other resins, it
has been found according to the present invention that
making the copolymerized rubber dispersed and contained
in a thermoplastic resin can remarkably improve
properties of the thermoplastic resin.
[0078]
As the modified ethylene-propylene copolymerized
rubber (modified EPM) (B2) as well, known n modified
ethylene-propylene copolymerized rubbers can be used.
The modified ethylene-propylene copolymerized rubber can
- 37 -
be used singly or in combinations of two or more. An
ethylene-propylene copolymer (EPM) is a copolymer of
ethylene and propylene, and the modification of the EPM
can be carried out similarly to the modification of the
EPDM. As the acid-modified ethylene acryl elastomer (B3)
as well, known acid-modified ethylene acryl elastomers
can be used. The acid-modified ethylene acryl elastomer
(B3) can be used singly or in combinations of two or more.
[0079]
[Thermoplastic resin composition (C)]
The thermoplastic resin composition (C) according to
the present invention is a resin composition comprising
the thermoplastic resin (A) and the modified ethylene
copolymer (B), and the thermoplastic resin composition
(C) is obtained by dispersing the modified ethylene
copolymer (B) into the thermoplastic resin (A) ((a resin
composition comprising the thermoplastic resin {A) and
the modified ethylene copolymer (B), and obtained by
dispersing the modified ethylene copolymer (B) into the
thermoplastic resin (A)), as described above.
[0080]
In the present invention, the weight proportion
[(B)/(A)] of the (B) to (A) is, though depending on the
kinds of the components (A) and (B), usually in the range
of 0.1/99.9 to 60/40. The lower limit of the proportion
(ratio) is preferably 1/99, more preferably 3/97, and
especially preferably 7.5/92.5; and the upper limit
- 38 -
thereof is preferably 55/45, more preferably 50/50, still
more preferably 30/70, and especially preferably 25/75
(particularly, 22/78). More specifically, the weight
proportion [(B)/(A)] of the (B) to (A) is preferably
0.1/99.9 to 30/70, more preferably 1/99 to 25/75, and
still more preferably 3/97 to 22/78 (particularly,
7.5/92.5 to 22/78). If the proportion is too low, the
improving effect of the durability of the abrasion
resistance, and the bending fatigue resistance becomes
small. By contrast, if the proportion is too high,
properties (mechanical strength and the like) intrinsic
to the thermoplastic resin become liable to decrease.
[0081]
The present inventors have found that in a resin
composition which is obtained by dispersing a modified
ethylene copolymer into a thermoplastic resin and which
comprises the thermoplastic resin and the modified
ethylene copolymer, the durability such as the bending
fatigue resistance of molded articles of the resin
composition exhibits a more improved value than a value
anticipated for the each material as a single material.
That is, it has been found that an actually acquired
value of the bending fatigue resistance of a blend of a
thermoplastic resin (A) and a modified ethylene copolymer
(B) is higher than a value thereof calculated on the
assumption of the additivity being held in the blend,
thus providing a synergistic effect. For example, in
- 39 -
Figure 5 [which is a graph indicating a relationship
between the blend ratio (wt%) of a modified ethylene
copolymer (MAH-EPDM) and the bending fatigue resistance,
based on data of Examples and Comparative Examples
described later], a line (dotted line in Figure 5)
connecting values of the bending numbers of times by a
straight line in the cases of the blend ratio of MAH-EPDM
being 0 wt% and 100 wt% indicates values of the bending
numbers of times in respective blend ratios on the
assumption of the additivity being held. By contrast,
the result of a resin composition (solid line in Figure
5) is a result of the bending numbers of times, which are
by far more than the dotted line, thus being conceivably
a synergistic effect. The synergistic effect is large in
the case of using a thermoplastic elastomer (Al) as the
thermoplastic resin (A) (for example, a polyurethanebased
thermoplastic elastomer), and is remarkable
particularly in the case of using a modified ethylenepropylene-
diene copolymerized rubber as the modified
ethylene copolymer (B).
[0082]
In the thermoplastic resin composition (C), in
addition to the above (A) and (B), as required, additives
can be blended. Examples of the additives include
antioxidants, ultraviolet absorbers, plasticizers,
stabilizers, mold lubricants, surfactants, antistatic
agents, electroconductive materials, colorants (pigments.
- 40 -
dyes), flame retardants, foaming agents, slip agents,
lubricants, bulking agents, crosslinking agents, solvents,
developing solutions, extenders, waxes, oils, greases,
processing aids, processing agents, reinforcing materials,
fillers, antiblocking agents and antiaging agents.
[0083]
In the thermoplastic resin composition (C), in
addition to the above (A) and (B), as required,
reinforcing materials can be incorporated. Examples of
the reinforcing materials include fibers, powders,
clothes, substrate materials, long fibers, short fibers,
glass clothes, fabrics, carbon nanotubes, fullerenes,
graphites, carbon blacks, silicas, foams, beads,
inorganic fillers, heat dissipation fillers,
electreconductive fillers, ceramics, fine ceramics and
carbon fibers.
[0084]
In the thermoplastic resin composition (C), the
total content of the thermoplastic resin (A) and the
modified ethylene copolymer (B) is, for example, not less
than 60 wt%, preferably not less than 80 wt%, and more
preferably not less than 90 wt%.
[0085]
The modified ethylene copolymer (B) in the
thermoplastic resin composition (C) has preferably an
average dispersed particle aspect ratio (= major diameter
/ minor diameter) of 1 to 3.5, more preferably 1 to 3,
41 -
and much more preferably 1 to 2. An average dispersed
particle aspect ratio near 1 means that in an actual
thermoplastic resin composition, the shape (disperse
shape) of the (B) dispersed is near a true sphere. Here,
the average dispersed particle aspect ratio is calculated
from a major dieimeter / a minor diameter of island phases
(disperse phase) in a planarized visual field when a
disperse state of a material at an arbitrary place of a
thermoplastic resin composition is observed by known
means (SEM, TEM, AFM or the like). The modified ethylene
copolymer (B) in the thermoplastic resin composition (C)
has preferably an average dispersed particle diameter of
not more than 3 \m, and more preferably not more than 1
pm. An average dispersed particle aspect ratio nearer 1,
that is, nearer a true sphere, is better. A smaller
average dispersed particle diameter is better. If the
average dispersed particle aspect ratio is in the above
range, since the degree of anisotropicity is very low and
there is no directivity, a high rigidity is exhibited on
stresses from every direction. Consequently, the
dispersed particle exhibits the effect as a reinforcing
filler in every direction.
[0086]
The average dispersed particle aspect ratio and the
average dispersed particle diameter can be measured by a
scanning electron microscope (SEM), a transmission
m
- 42 -
electron microscope (TEM), further an atomic force
microscope (AFM), and the like.
[0087]
The hardness of the thermoplastic resin composition
(C) is not especially limited, but the hardness in JIS
K6253 (durometer type A) is preferably not less than 60
(for example, 60 to 95), more preferably not less than 7 8
(for example, 78 to 95), still more preferably not less
than 8 9 (for example, 89 to 95), and especially
preferably not less than 91 (for example, 91 to 95).
From the viewpoint of having a reasonable flexibility and
enhancing the bending fatigue resistance, the hardness of
the thermoplastic resin composition (C) is, for example,
in the range of 60 to 93, and especially preferably in
the range of 77 to 91 (particularly 77 to 88). The
hardness of the thermoplastic resin composition (C) can
be regulated by the hardness of a thermoplastic resin (A),
the weight proportion of the modified ethylene copolymer
(B) to the thermoplastic resin (A), the kinds and amounts
of additives, and the like.
[0088]
The breaking strength (JIS K7311) of the
thermoplastic resin composition (C) depends largely on a
resin to become a continuous phase (sea phase). The
breaking strength (JIS K7311) of the thermoplastic resin
composition (C) is, for example, 25 to 100 MPa,
preferably 30 to 80 MPa, and more preferably 35 to 75
43 -
MPa; and the breaking elongation (JIS K7311) is, for
example, 300 to 1,000%, preferably 350 to 800%, and more
preferably 400 to 700%.
[0089]
The thermoplastic resin composition (C) can be
produced by mixing the thermoplastic resin (A), the
modified ethylene copolymer (B), and the additives used
according to needs by the same method as the case of
preparing usual polymer alloys or polymer blends. For
example, the thermoplastic resin composition can be
produced by pre-mixing the thermoplastic resin (A), the
modified ethylene copolymer (B), and the additives used
according to needs in predetermined proportions, and
thereafter, kneading the mixture under heating, under
pressure, in the presence of a solvent or the like by
using a single-screw extruder, a twin-screw extruder, a
mixing roll, a Banbury mixer, a batch-type kneader, a
reactor, a reactive molding machine, an injection molding
machine or the like. In the case of carrying out heating
and kneading using an extruder, the composition is
extruded in a strand form, and may be cut into a suitable
length to thereby make a granule such as a pellet.
Besides the above method, the thermoplastic resin
composition {C} can be produced also by charging and
mixing the modified ethylene copolymer (B) and/or the
additives during the production of the thermoplastic
resin (A) . In the case of using a thermoplastic
44 -
elastomer (Al) such as a thermoplastic polyurethane
(polyurethane-based thermoplastic elastomer) as the
thermoplastic resin (A), a thermoplastic elastomer alloy
can be obtained.
[0090]
The average dispersed particle aspect ratio and the
average dispersed particle diameter of the modified
ethylene copolymer (B) in the thermoplastic resin
composition (C) can be regulated by the kinds and the
degrees of crosslinking of the thermoplastic resin (A)
and the modified ethylene copolymer (B), the viscosity
ratio and the volume ratio of the thermoplastic resin (A)
and the modified ethylene copolymer (B), the magnitude of
a shearing force impressed in kneading a mixture
containing the thermoplastic resin (A) and the modified
ethylene copolymer (B), and the like. In more detail,
the disperse state of the composition can be controlled
by regulating respective amounts (vol%) and shearing
viscosities of the thermoplastic resin (A) and the
modified ethylene copolymer (B) and regulating a molding
method and the like, for example, at a temperature and a
shearing rate at which both the thermoplastic resin (A)
and the modified ethylene copolymer (B) become flowable.
In a completely incompatible blend system, the case where
one component has a higher vol% than the other or the
case where one component has a lower shearing viscosity
than the other basically takes a sea-island structure;
45
and the higher-vol% and/or lower-shearing viscosity
component forms a sea side (continuous phase). The case
where respective vol% and shearing viscosities approach
closely provides a structure in which both components
form micro-continuous phases. On the other hand, the
case where the shearing viscosity of a sea component
becomes higher than that of an island component due to a
reaction of the components during kneading includes a
case where the sea-island structure reverses during the
kneading; and a dual-continuous phase develops, though
being a very complicate structure, during the phase
transformation. The reaction used here may be a
crosslinking (curing) of one component, or may involve a
viscosity decrease due to a molecular weight decreasing
phenomenon by transesterification, hydrolysis and the
like of the other component. In the case of a dualcontinuous
phase, although the average dispersed particle
aspect ratio becomes large, since a shearing force can be
most highly transmitted to both components, a microdispersion
can be provided if kneading is carried out
through this process. Further in a sea-island structure,
with respect to the shape of the island side, a shape
near a spherical one is resultantly obtained in the case
where an island-side resin is strongly and quickly
kneaded in a sea-side resin having a relatively low
shearing viscosity as compared with the island side
rather than in the case where both the components have
- 46
shearing viscosities close to each other. For example,
by using the above-mentioned resin kneading machine for a
suitable time (for example, 30 sec to 15 min) and at a
suitable shearing force according to the materials and
the like, the average dispersed particle aspect ratio and
the average dispersed particle diameter of the modified
ethylene copolymer (B) can be made in the above-mentioned
range. The composition is returned to normal temperature
at a rate as near quenching as possible so that these
disperse states are not destroyed. Thereby, a
thermoplastic resin composition having a desired fixed
disperse state can be obtained. As described above, the
simultaneous satisfaction of both the spherical
dispersion and the micro-dispersion is difficult.
However, by designing the viscosities, the amounts and
the kinds of components of the thermoplastic resin
composition, the kneading method and the molding
condition, the present invention can achieve the
simultaneous satisfaction of both, and can obtain a
thermoplastic resin composition more excellent in the
durability.
[0091]
The thermoplastic resin composition (C) can be
subjected to melt molding, thermal processing, press
molding and the like, and can provide various types of
molded articles by an optional method such as extrusion.
_ 47 -
injection molding, blow molding, calendar molding,
casting, coating, sheeting and lamination.
[0092]
A production method of molded articles of the
thermoplastic resin composition (C) is not especially
limited; molding may be carried out after the
thermoplastic resin composition is fabricated in advance,
or the thermoplastic resin composition (C) can also be
produced simultaneously when molding is carried out (for
example, a side feed system and a dry blend system). The
side feed system is a method in which for example, two
components are charged from different feeders to an
extruder in order to regulate mutual melt states to be
blended in a polymer blend. The dry blend system
involves mixing resin materials to be blended in a pellet
form in advance and charging the mixture in the state in
a molding machine {a resin molding machine such as an
extruder or an injection molding machine). The
thermoplastic resin composition (C) suffices if holding
thermoplasticity in the fabrication time of the
composition, and after the fabrication, may or may not
have the thermoplasticity. There are cases where a final
product is a resin composition having no thermoplasticity,
for example, by addition of a crosslinking agent.
[0093]
[Production of Belt]
^
m - 49 -
[0094]
The thermoplastic resin composition (C)
(thermoplastic elastomer alloy or the like), since being
capable of being melt molded or thermally processed, can
be produced by utilizing an optional molding method such
as extrusion, injection molding, blow molding,
calendering or casting.
[0095]
Figure 11 is a schematic perspective diagram
illustratively showing one example of a method for
producing the belt according to the present invention.
In this example, the thermoplastic resin composition (C)
(thermoplastic elastomer alloy or the like) is
continuously melt extruded in a sheet form with an
extruder 4 from a die (T-die) at the end thereof; while
the melt resin 20 (thermoplastic resin) is poured, at the
vicinity of the die, into a cavity formed between the
surface of a mold roll 5 for molding a belt (flat belt or
the like) 1 as an object and a steel band 9; and core
wires 3 (aramid cords, glass cords, steel cords or the
like) are drawn in to thereby mold the belt. A press
roll 6, a roll 7 and a roll 8 are disposed in the
vicinity of the molding mold roll 5; the steel band 9 is
stretched between each roll 6 to 8, and is made to turn
together in cooperation with the molding mold roll 5,
The core wires 3 are embedded in the melt resin by a
pressure of the molding mold roll 5 and the steel band 9
50 -
to thereby mold a long-sized belt (flat belt or the like)
1.
[0096]
An endless belt can be manufactured as follows from
the long-sized belt thus obtained. That is, the longsized
belt obtained above is cut into a necessary length
by a certain-width finger (W)-shaped blade; both ends of
the cut belt are abutted, and set in a mold having a
convexo-concave shape conforming to a belt tooth profile
on the surface; and the abutted portion is fused by hot
press to form a joint to thereby make an endless belt.
Here, although the core wires (steel cords or the like)
are divided at the cut portions, the resin portions fuse
and are united to thereby hold a strength necessary as a
belt. An endless belt may be a seamless belt having no
joint. The seamless belt having no joint makes a further
highly durable belt.
[0097]
The belt according to the present invention is
excellent not only in abrasion resistance but also in
bending fatigue resistance, and hardly causes abrasion,
damage, cracks, breakage and the like even if being
continuously or intermittently used at a high load for a
longtime, and is thus remarkably excellent in durability
and has an elongated life.
Examples
k
- 51 -
[0098]
Hereinafter, the present invention will be described
more specifically by way of Examples and Comparative
Examples. The present invention is not any more limited
thereto. The average dispersed particle aspect ratio and
the average dispersed particle diameter of dispersed
particles in a thermoplastic resin composition
(thermoplastic elastomer alloy or the like) were measured
by a scanning electron microscope (SEM), a transmission
electron microscope (TEM) and an atomic force microscope
(AFM).
[0099]
Materials used in Examples and the like are shown
below.
[0100]
(1) TPU-1: an adipate-based TPU (thermoplastic
polyurethane) of 90 in hardness
(2) TPU-2: a caprolactone-based TPU (thermoplastic
polyurethane) of 90 in hardness
(3) TPU-3: a PTMG-based TPU (thermoplastic polyurethane)
of 92 in hardness
(4) TPU-4: an adipate-based TPU (thermoplastic
polyurethane) of 92 in hardness
(5) TPU-5: an adipate-based TPU (thermoplastic
polyurethane) of 80 in hardness
m
52 -
(6) TPEE: trade name "Hytrel 4777" (a thermoplastic
polyester elastomer, made by Du Pont-Toray Co., Ltd.)
(7) TPAE: trade name "UBESTA XPA 9040X1" (a thermoplastic
polyamide elastomer, made by Ube Industries, Ltd.)
(8) POM: trade name "Duracon M90-44" (a polyacetal resin,
made by Polyplastics Co., Ltd.)
(9) PEN: trade name "Teonex TN8065S" {a polyethylene
naphthalate resin, made by Teijin Chemicals Ltd.)
[0101]
(1) MAH-EPDM: trade name "Fusabond N416" (a maleic
anhydride-modified ethylene-propylene-diene copolymerized
rubber, made by Du Pont K.K.)
(2) X-EA: trade name "Baymac" (an acid-modified ethylene
acryl elastomer, made by Du Pont K.K.)
(3) MAH-EPM: trade name "Tafmer MP0610" (a maleic
anhydride-modified ethylene-propylene copolymerized
rubber, made by Mitsui Chemicals Inc.)
[0102]
EPDM: trade name "EP21" (an ethylene-propylene-diene
copolymerized rubber, made by JSR Corp.)
[0103]
Example 1
100 parts by weight of TPU-1 and 10 parts by weight
of MAH-EPDM were kneaded using a twin-screw extruder
(made by Technovel Corp., trade name "KZW20TW-30"). The
^
53 -
extruder was set at a barrel temperature of 200°C (here,
a feeder portion temperature of 160°C) and a screw
rotation frequency of 300 rpm; and the resins were melt
kneaded, and passed through a pelletizer to thereby
fabricate a pellet. The obtained pellet was injection
molded using an injection molding machine (made by Nissei
Plastic Industrial Co., Ltd., trade name "NEX110-18E") to
thereby fabricate test pieces [100 nvm x 100 mm x 2 mm
thick (for abrasion test), 120 mm x 10 mm x 4 mm thick
(for Demattia flex test)].
[0104]
Comparative Example 1
A pellet and test pieces were fabricated by the same
operation as in Example 1, except for using 100 parts by
weight of TPU-1 alone as a raw material resin.
[0105]
Example 2
A pellet and test pieces were fabricated by the same
operation as in Example 1, except for using 100 parts by
weight of TPU-2 and 10 parts by weight of MAH-EPDM as raw
material resins.
[0106]
Comparative Example 2
A pellet and test pieces were fabricated by the same
operation as in Example 1, except for using 100 parts by
weight of TPU-2 alone as a raw material resin.
[0107]
4
- 54 -
Example 3
A pellet and test pieces were fabricated by the same
operation as in Example 1, except for using 100 parts by
weight of TPU-3 and 5 parts by weight of MAH-EPDM as raw
material resins. An MAH-EPDM particle in an obtained
thermoplastic elastomer alloy had an average dispersed
particle aspect ratio of 1.23 and an average dispersed
particle diameter of 0.35 [om.
[0108]
Example 4
A pellet and test pieces were fabricated by the same
operation as in Example 1, except for using 100 parts by
weight of TPU-3 and 10 parts by weight of MAH-EPDM as raw
material resins. An MAH-EPDM particle in an obtained
thermoplastic elastomer alloy had an average dispersed
particle aspect ratio of 1.11 and an average dispersed
particle diameter of 0.42 \m..
[0109]
Example 5
A pellet and test pieces were fabricated by the same
operation as in Example 1, except for using 100 parts by
weight of TPU-3 and 20 parts by weight of MAH-EPDM as raw
material resins. An MAH-EPDM particle in an obtained
thermoplastic elastomer alloy had an average dispersed
particle aspect ratio of 1.08 and an average dispersed
particle diameter of 0.52 [a.m.
[0110]
4
- 55
Comparative Example 3
A pellet and test pieces were fabricated by the same
operation as in Example 1, except for using 100 parts by
weight of TPU-3 alone as a raw material resin.
[Gill]
Comparative Example 4
A pellet and test pieces were fabricated by the same
operation as in Example 1, except for using 100 parts by
weight of TPU-3 and 10 parts by weight of EPDM as raw
material resins. An EPDM particle in an obtained
thermoplastic elastomer alloy had an average dispersed
particle aspect ratio of 1.1 and an average dispersed
particle diameter of 5.8 |jin.
[0112]
Example 6
A pellet and test pieces were fabricated by the same
operation as in Example 1, except for using 100 parts by
weight of TPU-4 and 5 parts by weight of MAH-EPDM as raw
material resins. An MAH-EPDM particle in an obtained
thermoplastic elastomer alloy had an average dispersed
particle aspect ratio of 1 and an average dispersed
particle diameter of 0.62 \xm.
[0113]
Example 7
A pellet and test pieces were fabricated by the same
operation as in Example 1, except for using 100 parts by
weight of TPU-4 and 10 parts by weight of MAH-EPDM as raw
4
- 56 -
material resins. An MAH-EPDM particle in an obtained
thermoplastic elastomer alloy had an average dispersed
particle aspect ratio of 1.08 and an average dispersed
particle diameter of 0.52 ^m.
[0114]
Example 8
A pellet and test pieces were fabricated by the same
operation as in Example 1, except for using 100 parts by
weight of TPO-4 and 20 parts by weight of MAH-EPDM as raw
material resins. An MAH-EPDM particle in an obtained
thermoplastic elastomer alloy had an average dispersed
particle aspect ratio of 1.85 and an average dispersed
particle diameter of 0.77 |am.
[0115]
Example 9
A pellet and test pieces were fabricated by the same
operation as in Example 1, except for using 100 parts by
weight of TPU-5 and 10 parts by weight of MAH-EPDM as raw
material resins.
[0116]
Comparative Example 5
A pellet and test pieces were fabricated by the same
operation as in Example 1, except for using 100 parts by
weight of TPU-4 alone as a raw material resin.
[0117]
Comparative Example 6
- 57 -
A pellet and test pieces were fabricated by the same
operation as in Example 1, except for using 100 parts by
weight of TPU-4 and 10 parts by weight of EPDM as raw
material resins. An EPDM particle in an obtained
thermoplastic elastomer alloy had an average dispersed
particle aspect ratio of 1.1 and an average dispersed
particle diameter of 3.2 jj.m.
[0118]
Evaluation test A
An abrasion loss (mg) after the rotation number of
1,000 times using a Taber abrasion tester using an
abrasion wheel H-22 at a load of 9.8 N was measured for
the test piece of 100 mm x 100 mm x 2 mm thick, according
to JIS K7311. The results are shown in Table 1.
[0119]
A Demattia flex test was carried out according to
JIS K62 60. A notch of 0.5 mm in depth was cut across the
nearly entire length in the width direction of a middle
portion of the long side {a position of 60 mm from the
end in the longitudinal direction) on the strip test
piece of 120 mm x 10 mm x 4 mm thick, and the notched
test piece was provided for the test. The test was
carried out under the condition of a maximum distance
between chucks of 80 mm, a motion distance between the
chucks of 70 mm and a bending speed of 97 times/min, and
- 58 -
a bending number of times (bending fatigue number of
times) until the depth of a crack from the notch of the
test piece reached 3.5 mm was measured. The results are
shown in Table 1.
[0120]
A hardness was measured according to JIS K6253
{durometer type A) . The pellet was injection molded by
an injection molding machine (made by Nissei Plastic
Industrial Co., Ltd., trade name "NEX110-18E") to thereby
fabricate test pieces of 100 mm x 100 mm x 2 mm thick;
three sheets thereof were stacked to thereby prepare a
test piece of 6 mm in thickness; and a measurement of a
hardness was carried out using the stacked test piece.
The results are shown in Table 1.
[0121]
A tensile test was carried out according to JIS
K7311, and a breaking strength (MPa) and a breaking
elongation (%) were determined. The results are shown in
Table 1. Test pieces for the tensile test were
fabricated by stamping out the test pieces for the
abrasion test.
[0122]
- 59 -
Cross-sections of the pellets obtained by a twinscrew
extruder were cut out by a freezing microtome, and
observed using a scanning electron microscope {made by
Hitachi High-Technologies Corp., trade name "S-4300") at
a magnification of 2,000 times. A SEM photograph of a
cross-section of the pellet obtained in Comparative
Example 4 is shown in Figure 1; a SEM photograph of a
cross-section of the pellet obtained in Example 4, in
Figure 2; a SEM photograph of a cross-section of the
pellet obtained in Comparative Example 6, in Figure 3;
and a SEM photograph of a cross-section of the pellet
obtained in Example 7, in Figure 4. Cross-sections of
the pellets were further observed using an atomic force
microscope (AFM). An AFM photograph of a cross-section
of the pellet obtained in Example 4 is shown in Figure 9;
and an AFM photograph of a cross-section of the pellet
obtained in Example 7 is shown in Figure 10.
[0123]
Observation of molded article cross-sections of the
thermoplastic resin compositions (thermoplastic elastomer
alloys) obtained in the above Examples by a scanning
electron microscope (SEM) reveals that a modified
ethylene copolymer (modified ethylene-propylene-diene
copolymerized rubber) is highly microdispersed in a
matrix comprising a thermoplastic polyurethane (see
Figures 2 and 4). For example, according to the SEM
photographs of a magnification of 2,000 times, in a
- 60 -
thermoplastic elastomer alloy comprising a modified EPDM
and an etheric TPU, although unevenness is slightly
observed, no particle shape cannot be confirmed; and in a
thermoplastic elastomer alloy comprising a modified EPDM
and an esteric TPU, even almost no unevenness is observed.
By contrast, in the case of using a non-modified EPDM in
place of a modified EPDM, particles of the EPDM are
clearly confirmed, and particularly in a thermoplastic
elastomer alloy comprising the EPDM and an esteric TPU,
it is clearly observed that spherical particles of the
EPDM are dispersed in a matrix of the esteric TPU. The
average particle diameter of the particles observed at
this time is a value exceeding 3 \xm. That the
dispersibility is remarkably improved in the
thermoplastic elastomer alloy comprising the modified
EPDM and the TPU (particularly the esteric TPU) is
presumably because the polarity of modified sites in the
modified EPDM has affinity for polar sites of the TPU.
[0124]
Further observation of molded article cross-sections
of the thermoplastic resin compositions (thermoplastic
elastomer alloys) obtained in the above Examples by using
an atomic force microscope (AFM) reveals that particles
of the modified EPDM in the matrix (thermoplastic
polyurethane), which are not observed by SEM, are
observed and are highly microdispersed (see Figures 9 and
10) . According to these AFM photographs, it is found
J^
- 61
that the particles are dispersed in an average dispersed
particle diameter of not more than 1 pm in either of the
thermoplastic elastomer alloy comprising the modified
EPDM and the etheric TPU and the thermoplastic elastomer
alloy comprising the modified EPDM and the esteric TPU.
Collectively considering these results and the abovementioned
results by the SEM photographs, the effect of
the affinity of modified sites for the matrix on the
dispersion is clear.
[0125]
From the evaluation results shown in Table 1, it is
clear that the molded articles formed from the
thermoplastic resin composition (thermoplastic elastomer
alloy) used in the present invention are remarkably
better not only in the Taber abrasion loss but also in
the bending fatigue resistance than the molded articles
formed from a thermoplastic resin (thermoplastic
polyurethane) alone, and the molded articles formed from
a thermoplastic elastomer alloy composed of a
thermoplastic resin (thermoplastic polyurethane) and a
non-modified ethylene-propylene-diene copolymerized
rubber. The case where a modified ethylene-propylenediene
copolymerized rubber is added can improve the
abrasion resistance and the bending fatigue resistance
without spoiling the material property of a thermoplastic
polyurethane. Although even the case where a nonmodified
ethylene-propylene-diene copolymerized rubber is
- 62 -
added exhibits an improving affect in some degree of the
bending fatigue resistance in some cases, the cases of
largely improving the abrasion resistance and the bending
fatigue resistance are cases of a thermoplastic
polyurethane alloyed with a modified ethylene-propylenediene
copolymerized rubber. From the results of the
disperse state checking test, it is clear that the
disperse states are better in order of an esteric TPUEPDM
< an etheric TPU-EPDM < an etheric TPU-maleic
anhydride-modified EPDM < an esteric TPU-maleic
anhydride-modified EPDM. It is further clear from the
AFM photograph that any of the thermoplastic elastomer
alloys composed of a modified EPDM and an etheric TPU and
the thermoplastic elastomer alloys composed of a modified
EPDM and an esteric TPU are dispersed in an average
dispersed particle diameter of not more than 1 |jjm.
[0126]
The reason why the Taber abrasion and the bending
number of times are remarkably improved is conceivably
that a retardation effect of crack extension of the
microdispersion of the modified ethylene copolymer
component having an energy absorbing effect changes
states from the severe abrasion progress called adhesion
wearing of TPU to the mild abrasion progress. This is
because the thermoplastic elastomer alloy is obtained as
a combination in which a modified ethylene copolymer
component (elastomer component) is near a spherical shape
- 63 -
like a micro phase separation structure;^ and
microdispersed in a TPU. In a simply blended state in no
consideration of compatibility and shearing viscosity,
the shape of the island (dispersoid) is usually irregular
and in a mechanically crushed-like shape in many cases,
and then, the adhesive force between the island layer
(disperse phase) and the sea layer (continuous phase) is
weak; exfoliation is liable to be caused at the interface
when a stress is impressed on molded articles; and the
resistance to crack generation also from the island shape
becomes poor. These cause inferior durability in some
cases. However, the thermoplastic resin'composition, by
increasing the adhesive surface of the island layer
(disperse phase) and the sea layer (continuous phase) and
raising the adhesive force, can provide a disperse form
in which the island layer (disperse phase) is microdispersed
and in a nearly true spherical shape, and can
be remarkably improved in the durability under the motion
condition impressed with repeated loads, stresses and
deformations. Nobody has developed such properties and
confirmed the effects, and the properties and effects
have been found by exhaustive devices by the present
inventors.
[0127]
&»^m^imei^emm^smmmmmm«m&0m»sm»ii^mm^mim i^*^»i«^mmmswmsmmmmmmmm¥>«mmmmmm»mmmmmimm^
- 73 -
[0142]
A TEM photograph of a sheet cross-section of the
resin composition obtained in Example 14 is shown in
Figure 6 [a photograph of a magnification of 10,000 times
(in a size of 112 ram x 161 mm)] . A TEM photograph of a
sheet cross-section of the resin composition obtained in
Example 19 is shown in Figure 7 [a photograph of a
magnification of 10,000 times (in a size of 112 mm x 161
mm) ] . A TEM photograph of a sheet cross-section of the
resin composition obtained in Comparative Example 11 is
shown in Figure 8 [a photograph of a magnification of
10,000 times (in a size of 112 mm x 161 mm)]. It is
found that the resin compositions obtained in Examples 14
and 19 have a very fine disperse state as compared with
Comparative Example 11.
[0143]
Example 21
A flat belt was manufactured using the pellet
obtained in Example 1 [thermoplastic resin composition
(thermoplastic elastomer alloy)] (see Figure 11). That
is, the thermoplastic resin composition (thermoplastic
elastomer alloy) is continuously melt extruded in a sheet
form from a front end die (T-die) by an extruder 4; while
the melt resin (thermoplastic resin composition) 20 is
poured, at the vicinity of the die, into a cavity formed
between the surface of a mold roll 5 for molding a flat
belt 1 as an object and a steel band 9; and core wires 3
- 74 -
(aramid cords, glass cords, steel cords or the like) are
drawn in to thereby mold the belt. A press roll 6, a
roll 7 and a roll 8 are disposed in the vicinity of the
molding mold roll 5; the steel band 9 is stretched
between each roll 6 to 8, and is made to turn together in
cooperation with the molding mold roll 5. The core wires
3 are embedded in the melt resin by a pressure of the
molding mold roll 5 and the steel band 9 to thereby mold
a long-sized flat belt 1.
The obtained long-sized flat belt was cut into a
necessary length by a certain-width finger (W)-shaped
blade; both ends of the cut belt were abutted, and set in
a mold having a convexo-concave shape conforming to a
belt tooth profile on the surface; and the abutted
portion was fused by hot press to form a joint to thereby
obtain an endless belt (belt width: 25 mm, belt length:
1,200 mm, belt thickness: 2.5 mm). In the obtained flat
belt, the count of the steel cords per 1-inch width is 15.
[0144]
Comparative Example 12
An endless flat belt was manufactured by the same
operation as in Example 21, except for using the pellet
(thermoplastic elastomer) obtained in Comparative Example
1.
[0145]
Evaluation test B
- 75 -
The endless flat belts obtained in Example 21 and
Comparative Example 12 were subjected to a belt life test
using an overload running tester. The conditions of the
running test are as follows. The test was finished at
the time point when the belt lost the rotary transmission
capability.
Layout: simple two-shafts
Belt size: 30 W x 1,000 L
Pulley: (t)90
Rotation frequency: 1,500 rpm
Initial tension: 400 N/30W
As a result, the flat belt of Comparative Example 12
generated damage such as cracks at a bending number of
times of 9.0 x 10^; by contrast, damage such as cracks
was not observed on the flat belt of Comparative Example
21 even when the bending number of times reached 1.2 x
10^
From the above results, it is conceivable that the
life of the flat belt has a correlation with the abrasion
loss in the Taber abrasion test of a thermoplastic resin
composition (thermoplastic elastomer (alloy)) and the
bending number of times in the Demattia flex test thereof
(Table 1).
Industrial Applicability
[0146]
- 76 -
The belt according to the present invention is
excellent not only in abrasion resistance but also in
bending fatigue resistance, and hardly causes abrasion,
damage, cracks, breakage and the like on the belt body in
an early stage and is remarkably excellent in durability,
even if the belt is used at a high load for a long time.
Therefore, the belt can suitably be utilized as belts for
power transmission, conveyance and the like.
Reference Signs List
[0147]
1 BELT
2 BELT BODY
3 CORE WIRE
4 EXTRUDER
5 MOLDING MOLD ROLL
6 PRESS ROLL
7 ROLL
8 ROLL
9 STEEL BAND
20 MELT RESIN (THERMOPLASTIC ELASTOMER ALLOY
OR THE LIKE)
#
- 11 -
Claims
[Claim 1]
A belt (excluding toothed belts), wherein the whole
or a part of a belt body is formed from a thermoplastic
resin composition (C) comprising a thermoplastic resin
(A) and a modified ethylene copolymer (B), and obtained
by dispersing the modified ethylene copolymer (B) into
the thermoplastic resin (A).
[Claim 2]
The belt according to claim 1, wherein the modified
ethylene copolymer (B) is a copolymer modified with an
unsaturated carboxylic acid or a derivative thereof, the
copolymer being a copolymer of ethylene with at least one
monomer component selected from the group consisting of
(i) olefin components except for ethylene, (ii) diene
components and (iii) ester components having an
ethylenically unsaturated group.
[Claim 3]
The thermoplastic resin composition according to
claim 1 or 2, wherein the thermoplastic resin (A) is at
least one selected from the group consisting of
polyamide-based resins, polyester-based resins,
polycarbonate-based resins and polyacetal resins.
[Claim 4]
The belt according to claim 1 or 2, wherein the
thermoplastic resin (A) is a thermoplastic elastomer (Al)
4^
- 78 -
[Claim 5]
The belt according to claim 4, wherein the
thermoplastic elastomer (Al) is at least one selected
from the group, consisting of polyurethane-based
-thermoplastic elastomers (All), polyester-based
thermoplastic elastomers (A12) and polyamide-based
thermoplastic elastomers (A13).
[Claim 6]
The belt according to any one of claims 1 to 5,
wherein the modified ethylene copolymer (B) is an
ethylene-propylene-diene copolymerized rubber modified
with an unsaturated carboxylic acid or a derivative
thereof.
[Claim 7]
The belt according to any one of claims 1 to 6,
wherein a weight proportion [ (B)/ (A)] of the modified
ethylene copolymer (B) to the thermoplastic resin (A) is
in the range of 0.1/99.9 to 60/40.
[Claim 8]
The belt according to any one of claims 1 to 7,
wherein the thermoplastic resin composition (C) has a
hardness (JIS K6253, durometer type A) of not less than
60.