TECHNICAL FILED
The present invention relates to a transmission belt such as a V-belt, a V-ribbed
belt or a flat belt, and in detail, relates to a transmission belt having excellent durability
performance.
BACKGROUND ART
, J
A friction transmission belt such as a V-belt, a V-ribbed belt or a flat belt, and a
synchronous power transmission belt such as a toothed belt are conventionally known as a
transmission belt transmitting power. Those transmission belts have a core wire
embedded in a rubber body along a lengthwise direction of the belt and this core wire plays
a role of transmitting power from a drive pulley to a driven pulley. Such transmission
belts are generally provided with an adhesive rubber layer in order to enhance
adhesiveness between the core wire and a rubber.
Patent Document 1 discloses a rubber V-belt containing an extensible rubber layer
and a compressed rubber layer each having short fibers having high elastic modulus
arranged in a width direction of the belt, provided on the upper and lower sides of an
adhesive rubber layer having a cord embedded therein, in which the adhesive rubber layer
is constituted of a rubber composition containing 100 parts by weight of a chloroprene
rubber, from 1 to 20 parts by weight of at least one metal oxide vulcanizing agent selected
from zinc oxide, magnesium oxide and lead oxide, from 5 to 30 parts by weight of silica,
from 15 to 50 parts by weight of a reinforcing filler, and from 2 to 10 parts by weight of
bismaleimide. It is described that in this rubber V-belt, cros slinking density can be
increased by compounding bismaleimide to thereby form an adhesive rubber having high
elastic modulus, therefore stress concentration between the adhesive rubber and a fibercontaining
rubber (a compressed rubber or an extensible rubber) is decreased, and
additionally, since the adhesive rubber layer has excellent fatigue resistance, belt life can
be prolonged.
However, in a layout in which a belt greatly bends and a load is high (for example,
a state that a belt moves inward in a radius direction of a pulley and the belt greatly bends,
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like in a variable speed belt, or a state that a belt is attached by bending to a plurality of
pulleys, like in a V-ribbed belt), a mere increase in elastic modulus (rubber hardness) of an
adhesive rubber layer is not sufficient to prevent interfacial peeling between the adhesive
rubber layer and a compressed rubber layer (or an extensible rubber layer) and peeling
between a core wire and the adhesive rubber layer. Furthermore, in the case where rubber
hardness of the adhesive rubber layer is excessively increased, there is a possibility that
bending fatigue resistance is deteriorated.
On the other hand, in the case where rubber hardness of an adhesive rubber layer
is merely decreased (for example, crosslinking density is decreased by decreasing the
amount of a reinforcing filler added or using a smaller amount of a vulcanization type
compounding ingredient) for the purpose of the improvement in bending fatigue resistance
and adhesiveness, great difference is generated in rubber hardness between a compressed
rubber layer (or an extensible rubber layer) and the adhesive rubber layer, and peeling
occurs early at the interface between the adhesive rubber layer and the compressed rubber
layer (or the extensible rubber layer). For this reason, it was difficult in the conventional
technique to prevent interfacial peeling and improve durability without deterioration of
bending fatigue resistance.
PRIOR ART DOCUMENTS
PATENT DOCUMENT
Patent Document 1: JP-A-61-290255
SUMMARY OF THE INVENTION
PROBLEMS THAT THE INVENTION IS TO SOLVE
Accordingly, an object of the present invention is to provide a transmission belt
that prevents interfacial peeling of an adhesive rubber layer from an inner surface layer and
a back surface layer and has excellent durability without deteriorating bending fatigue
resistance.
MEANS FOR SOLVING THE PROBLEMS
As a result of earnest investigations to achieve the above problems, the present
inventors have found that by forming an adhesive rubber layer of a transmission belt by a
vulcanized rubber composition containing a rubber component, a fatty acid amide and a
silica, interfacial peeling of an adhesive rubber layer from an inner surface rubber layer
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and a back surface rubber layer is prevented and durability can be improved without
deteriorating bending fatigue resistance, and have completed the present invention.
That is, the transmission belt according to the present invention is a transmission
belt containing a core wire extending in a lengthwise direction of the belt, an adhesive
rubber layer (adhesive layer) in contact with at least a part of the core wire, a back surface
rubber layer (back surface layer) formed on one surface of the adhesive rubber layer, and
an inner surface rubber layer (inner surface layer) formed on the other surface of the
adhesive rubber layer and engaging or in contact with a pulley, in which the adhesive
rubber layer is formed by a vulcanized rubber composition containing a rubber component,
a fatty acid amide and a silica. The proportion of the fatty acid amide may be from about
0.3 to 10 parts by mass per 100 parts by mass of the rubber component (raw material
rubber). The proportion of the fatty acid amide may be from about 1 to 30 parts by mass
per 100 parts by mass of the silica. The fatty acid amide may contain a fatty acid amide
having a saturated or unsaturated higher fatty acid residue having from 10 to 26 carbon
atoms or a higher amine residue having from 10 to 26 carbon atoms. The silica may have
a nitrogen adsorption specific surface area in accordance with BET method of from about
50 to 400 m /g. The rubber component may contain chloroprene rubber. The
transmission belt according to the present invention may be a friction transmission belt.
ADVANTAGEOUS EFFECTS OF THE INVENTION
In the present invention, because an adhesive rubber layer of a transmission belt is
formed by a vulcanized rubber composition containing a rubber component, a fatty acid
amide and a silica, interfacial peeling of the adhesive rubber layer from an inner surface
rubber layer and a back surface rubber layer (particularly, interfacial peeling between the
adhesive rubber layer and the inner surface rubber layer) can be suppressed even though
rubber hardness of the adhesive rubber layer is not increased. As a result, durability of
the belt can be improved without the deterioration of bending fatigue resistance.
BRIEF DESCRIPTION OF THE DRAWINGS
[FIG. 1] FIG. 1 is a schematic cross-sectional view illustrating one example of the
transmission belt of the present invention.
[FIG. 2] FIG. 2 is a schematic view for describing a durability traveling test in the
Examples.
MODE FOR CARRYING OUT THE INVENTION
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[Vulcanized rubber composition of adhesive rubber layer]
The adhesive rubber layer (an adhesive layer) is provided in contact with at least a
part of a core wire for the purpose of adhering the core wire and a rubber material forming
a belt. The adhesive rubber layer of the present invention is formed by a vulcanized
rubber composition containing a rubber component, a fatty acid amide and a silica.
In the present invention, because the fatty acid amide acts as a dispersant,
dispersibility of the silica in the vulcanized rubber composition can be improved and
variation in properties of the adhesive rubber layer can be made small. Furthermore, the
silica has many silanol groups (-SiOH) as reactive functional groups on the surface
thereof, and can be chemically bonded to the rubber component by the silanol groups. In
the present invention, by combining the silica with the fatty acid amide, the silanol groups
in the silica and amide groups (-CONH- etc.) in the fatty acid amide are interacted with
each other to thereby highly enhance dispersibility of the silica in the rubber composition,
and additionally, adhesiveness between the silica and the rubber component can be
improved. As a result, mechanical characteristics (such as tensile stress and tear force) of
the adhesive rubber layer can be further improved.
(Fatty acid amide)
The fatty acid amide acts as a dispersant as described hereinbefore, and
additionally acts as an internal lubricant in the rubber composition. When it acts as an
internal lubricant, modulus of the adhesive rubber layer tends to be decreased (softened).
However, the decrease in modulus can be suppressed by using silica in combination.
That is, by using the fatty acid amide and the silica in combination, mechanical
characteristics can be improved without excessively increasing hardness of the adhesive
rubber layer. Furthermore, such combination does not require to increase rubber hardness
of the adhesive rubber layer by compounding a large amount of an enhancer (reinforcing
filler) such as carbon black and co-crosslinking agent such as maleimide, and can improve
bending fatigue ability of a belt and fuel saving properties (particularly, fuel saving
properties in the case where a belt travels with wound around small pulleys).
Furthermore, in the present invention, because the adhesive rubber layer contains
the fatty acid amide, the fatty acid amide blooms (precipitates) or bleeds out on the surface
(a part of friction transmission surface) of the adhesive rubber layer, and the fatty acid
amide precipitated acts as an external lubricant. As a result, friction coefficient of the
surface of the adhesive rubber layer can be reduced. Particularly, in a friction
transmission belt such as a V-belt (a raw edge belt or a raw edge cogged V-belt), friction
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between the adhesive rubber layer and the pulley can be smoothed by reducing friction
coefficient of the adhesive rubber layer surface in contact with the pulley, and this prevents
that excessive shear force acts to a rubber layer in contact with a pulley during belt
traveling, and can improve durability of the belt. That is, if friction coefficient is high,
shear force received from a pulley is increased, and peeling of the adhesive rubber layer
from the inner surface rubber layer and the back surface rubber layer (particularly, the
inner surface rubber layer) and generation of a crack on the inner surface rubber layer
surface easily occur, leading to short life of a belt; but such occurrence can be suppressed.
The fatty acid amide has a long chain fatty acid group (e.g., a fatty acid group
having from about 10 to 40 carbon atoms) and an amide group in its molecule, and is a
thermally and chemically stable solid surfactant. Examples of the fatty acid amide
include higher fatty acid mono amides (e.g., saturated or unsaturated C12-24 fatty acid
amides or monoamides such as lauric amide, myristic amide, palmitic amide, stearic
amide, hydroxystearic amide, oleic amide, ricinoleic amide, arachic amide, behenic amide,
and erucamide); saturated or unsaturated higher fatty acid bisamides, for example,
alkylenebis saturated or unsaturated higher fatty acid amides (e.g., C1.10 alkylenebis
saturated or unsaturated C12-24 fatty acid amides such as methylenebis-lauric amide,
methylenebis-stearic amide, methylenebis-hydroxystearic amide, methylenebis-oleic
amide, ethylenebis-caprylic amide, ethylenebis-capric amide, ethylenebis-lauric amide,
ethylenebis-stearic amide, ethylenebis-isostearic amide, ethylenebis-behenic amide,
ethylenebis-erucamide, ethylenebis-oleic amide, tetramethylenebis-stearic amide,
hexamethylenebis-stearic amide, hexamethylenebis-hydroxystearic amide,
hexamethylenebis-oleic amide, and hexamethylenebis-behenic amide), and bisamides of
dicarboxylic acid and higher amine (e.g., bisamides formed by a reaction of C6.12 alkane
dicarboxylic acid and higher C12-24 amine, such as N,N'-distearyladipic amide, N,N'-
distearylsebacic amide, N,N'-dioleyladipic amide, andN,N'-dioleylsebacic amide).
I
Examples of the fatty acid amide further include aromatic bisamides (e.g.,
bisamides of an aromatic diamine and a saturated or unsaturated higher fatty acid, such as
xylylenebis-stearic amide, and bisamides of an aromatic dicarboxylic acid and a higher
amine, such as N,N'-distearylphthalic acid amide), substituted amides (e.g., higher fatty
acid amides in which a saturated or unsaturated C12-24 fatty acid residue is amide-bonded to
a nitrogen atom of an amide group, such as N-lauryl lauric amide, N-palmityl palmitic
amide, N-stearyl stearic amide, N-stearyl oleic amide, N-oleyl stearic amide, N-stearyl
erucamide, and N-stearylhydroxy stearic amide), ester amides (e.g., ester amides in which
a hydroxyl group of alkanolamine is ester-bonded to a higher fatty acid and an amino
group of the alkanolamine is amide-bonded to a C12-24 fatty acid, such as ethanolamine
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dipalmitate, ethanolamine distearate, ethanolamine dibehenate, propanolamine dipalmitate,
and propanolamine distearate), alkanolamides (e.g., methylolamides such as methylol Cn-
24 fatty acid monoamides such as methylolstearic amide and methylolbehenic amide; and
N-hydroxy C2-4 alkyl C12-24 fatty acid monoamide such as stearic monoethanol amide and
erucic acid monoethanol amide), and substituted ureas (e.g., substituted ureas in which
higher fatty acid is amide-bonded to a nitrogen atom of urea, such as N-butyl-N'-stearyl
urea, N-phenyl-N'-stearyl urea, N-stearyl-N'-stearyl urea, xylylenebis-stearyl urea,
toluylenebis-stearyl urea, hexamethylenebis-stearyl urea, and diphenylmethanebis-stearyl
urea). In those fatty acid amides, the carbon number of higher fatty acid or higher amine
(in the case of bismaleimide or the like, each higher fatty acid or each higher amine) may
be from about 10 to 34 (for example, from 10 to 30, preferably from 10 to 28, more
preferably from 10 to 26, and particularly preferably from 12 to 24). Those fatty acid
amides can be used alone or in combination of two kinds or more thereof.
The melting point of the fatty acid amide can be selected from a range of from
about 50 to 200°C, and is generally from 65 to 150°C, preferably from 75 to 130°C (e.g.,
from 80 to 120°C), and more preferably from 90 to 110°C (e.g., from 95 to 105°C).
In the fatty acid amides, the carbon number of a carbon chain constituting a higher
fatty acid residue or a higher amine residue is preferably from, for example, about 10 to 26
(particularly, from 12 to 24). The reason for this is not clear, but it can be assumed that if
a higher fatty acid residue or a higher amine residue has too long structure, that is, has a
large carbon number, the density of amide groups in a molecule is relatively decreased to
reduce the rate of the interaction between amide groups in the fatty acid amide and silanol
groups in silica, and as a result, dispersibility of silica in a rubber composition and
adhesiveness between silica and the rubber composition cannot be sufficiently enhanced.
The proportion of the fatty acid amide is, for example, from 0.3 to 10 parts by
mass, preferably from 0.4 to 8 parts by mass, and more preferably from 0.5 to 6 parts by
mass (particularly, from 1 to 5 parts by mass), per 100 parts by mass of the rubber
component (raw material rubber). From the standpoint of excellent balance of various
characteristics, it may be, for example, from about 0.7 to 7 parts by mass (particularly,
from 1 to 6.5 parts by mass). The proportion of the fatty acid amide is, for example, from
1 to 35 parts by mass, preferably from 1 to 30 parts by mass, more preferably from 1.5 to
25 parts by mass, and still more preferably from 2 to 20 parts by mass (particularly, from 3
to 15 parts by mass), per 100 parts by mass of the silica. From the standpoint of excellent
balance of various characteristics, it may be, for example, from about 2.5 to 30 parts by
mass (particularly, from 3 to 25 parts by mass).
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In the present invention, mechanical characteristics of the adhesive rubber layer
can be improved by appropriately adjusting the proportion of the fatty acid amide.
Further, because the friction coefficient of the surface (a part of friction transmission
surface) can be appropriately reduced, interfacial peeling of the adhesive rubber layer from
an inner surface rubber layer or a back surface rubber layer due to lateral pressure from a
pulley during belt traveling can be prevented. Furthermore, because hardness of the
adhesive rubber layer is not excessively increased, bending stress can be reduced, and
bending fatigue resistance of the belt can be improved.
In the case where the proportion of the fatty acid amide is too small, interaction
between the silica and the fatty acid amide is not sufficient, and there is a possibility that
mechanical characteristics of the adhesive rubber layer are insufficient or blooming of the
fatty acid amide on the adhesive rubber layer surface (a part of traction transmission
surface) is decreased, resulting in decrease in the effect of reducing friction coefficient.
Regarding the mechanical characteristics, particularly in a V-ribbed belt, if tear force of the
adhesive rubber layer is low, the phenomenon that a core wire projects from an edge of a
belt (an edge of the adhesive rubber layer) during belt traveling, that is, a so-called pop-out
occurs, and the life of the belt becomes short.
On the other hand, in the case where the proportion of the fatty acid amide is too
large, there is a possibility that excess fatty acid amide that does not interact with the silica
acts as an internal lubricant and modulus of the vulcanized rubber composition forming the
adhesive rubber layer is greatly decreased, or that excess fatty acid amide blooms on the
surface (the surface in contact with a core wire) of the adhesive rubber layer to form a
coating film and adhesive force between the adhesive rubber layer and the core wire is
decreased.
(Silica)
Silica is an ultrafine and bulky white powder formed by silicic acid and/or silicate,
and has a plurality of silanol groups on the surface thereof. Therefore, the silica can be
chemically bonded to the rubber component.
The silica includes dry silica, wet silica and surface-treated silica. Further, the
silica also can be classified into, for example, dry process white carbon, wet process white
carbon, colloidal silica, and precipitated silica, depending on the classification by
processes. Those silicas can be used alone or in combination of two kinds or more
thereof. Of those, wet process white carbon containing hydrated silicic acid as a main
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component is preferred from the standpoints of many surface silanol groups and strong
chemical bonding force to a rubber.
The silica has an average particle diameter of, for example, from 1 to 1,000 nm,
preferably from 3 to 300 nm, and more preferably from 5 to 100 nm (for example, from 10
to 50 nm). In the case where the particle size of the silica is too large, mechanical
characteristics of the adhesive rubber layer is deteriorated; whereas if it is too small, it is
difficult to uniformly disperse.
The silica may be non-porous silica and may be porous silica. Nitrogen
adsorption specific surface area by BET method is, for example, from 50 to 400 m2/g,
preferably from 70 to 350 m2/g, and more preferably from 100 to 300 m2/g (particularly,
from 150 to 250 m2/g). In the case where the specific surface area is too large, it is
difficult to uniformly disperse; whereas if the specific surface area is too small, mechanical
characteristics of the adhesive rubber layer are deteriorated.
The proportion of the silica is, for example, from 1 to 100 parts by mass,
preferably from 3 to 80 parts by mass, and more preferably from 5 to 40 parts by mass (for
example, from 10 to 35 parts by mass), per 100 parts by mass of the rubber component
(raw material rubber). In the case where the proportion of the silica is too large, elasticity
and adhesive force of the adhesive rubber layer are deteriorated; whereas if it is too small,
rubber hardness of the adhesive rubber layer is deteriorated and strength and tear force are
also deteriorated.
(Rubber component)
Examples of the rubber component include vulcanizable or crosslinkable rubbers,
for example, diene rubbers (e.g., natural rubber, isoprene rubber, butadiene rubber,
chloroprene rubber, styrene-butadiene rubber (SBR), acrylonitrile-butadiene rubber (nitrile
rubber), or hydrogenated nitrile rubber), ethylene-a-olefin elastomers, chlorosulfonated
polyethylene rubbers, alkylated chlorosulfonated polyethylene rubbers, epichlorohydrin
rubbers, acrylic rubbers, silicone rubbers, urethane rubbers, and fluorine rubbers. Those
rubber components can be used alone or in combination of two kinds or more thereof.
Of those, ethylene-a-olefin elastomers (e.g., ethylene-a-olefin rubbers such as
ethylene-propylene rubber (EPR) and ethylene-propylene-diene monomer (e.g., EPDM))
and chloroprene rubbers are preferred, and chloroprene rubbers are particularly preferably
contained. In the rubber component, the proportion of the chloroprene rubber may be
about 50% by mass or more (particularly, from 80 to 100% by mass). The chloroprene
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rubber may be sulfur-modified type and may be sulfur-unmodified type. The chloroprene
rubber has high adhesiveness (cohesiveness), and a rubber composition containing the
chloroprene rubber as a main component generally tends to have high friction coefficient.
However, in the present invention, the fatty acid amide acts as an external lubricant.
Therefore, even though the chloroprene rubber is used, the increase in friction coefficient
can be suppressed. That is, in the case of using the chloroprene rubber, the action of the
fatty acid amide as an external lubricant is remarkably exhibited.
(Other additives)
As necessary, the vulcanized rubber composition for forming the adhesive rubber
layer may contain a vulcanizing agent or a crosslinking agent (or a crosslinking agent
type), a co-crosslinking agent, a vulcanization assistant, a vulcanization accelerator, a
vulcanization retarder, a metal oxide (e.g., zinc oxide, magnesium oxide, calcium oxide,
barium oxide, iron oxide, copper oxide, titanium oxide, or aluminum oxide), an enhancer
(e.g., carbon black), a filler (e.g., clay, calcium carbonate, talc, or mica), a softener (e.g.,
oils such as paraffin oil and naphthenic oil), a processing agent or a processing aid (e.g.,
stearic acid, stearic acid metal salt, wax or paraffin), an adhesiveness improving agent
[e.g., a resorcin-formaldehyde co-condensate, an amino resin (a condensate of a nitrogencontaining
cyclic compound and formaldehyde, for example, a melamine resin such as
hexamethylol melamine and hexaalkoxymethyl melamine (e.g., hexarnethoxymethyl
melamine or hexabutoxymefhyl melamine), a urea resin such as methylol urea, a
benzoguanamine resin such as methylolbenzoguanamine resin, etc.), and those cocondensates
(such as a resolcin-melamine-formaldehyde co-condendate), etc.], an age
resister (e.g., an antioxidant, a thermal age resister, an antiflex-cracking agent, or an
antiozonant), a colorant, a tackifier, a plasticizer, a coupling agent (e.g., a silane coupling
agent), a stabilizer (e.g., an ultraviolet absorber or a thermal stabilizer), a flame retardant,
an antistatic agent, and the like. The metal oxide may act as a crosslinking agent.
Further, in the adhesiveness improving agent, the resorcin-formaldehyde co-condensate
and the amino resin may be an initial condensate (a prepolymer) of a nitrogen-containing
cyclic compound such as resorcin and/or melamine, and formaldehyde.
As the vulcanizing agent or crosslinking agent, conventional components can be
used depending on the kind of the rubber component, and examples thereof include the
above-described metal oxides (e.g., magnesium oxide or zinc oxide), organic peroxides
(e.g., diacyl peroxide, peroxyester or dialkyl peroxide), and sulfur vulcanizing agents.
Examples of the sulfur vulcanizing agent include powdered sulfurs, precipitated sulfurs,
colloidal sulfurs, insoluble sulfurs, high-dispersible sulfurs, and sulfur chlorides (e.g.,
sulfur monochloride or sulfur dichloride). Those crosslinking agents or vulcanizing
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agents may be used alone or in combination of two kinds or more thereof. In the case
where the rubber component is chloroprene rubber, the metal oxide (e.g., magnesium oxide
or zinc oxide) may be used as the vulcanizing agent or the crosslinking agent. The metal
oxide may be used by combining with other vulcanizing agents (e.g., sulfur vulcanizing
agent), and the metal oxide and/or the sulfur vulcanizing agent may be used alone or by
combining with a vulcanization accelerator.
The proportion of the vulcanizing agent can be selected from a range of from
about 1 to 20 parts by mass per 100 parts by mass of the rubber component, depending on
the kind of the vulcanizing agent and the rubber component. For example, the amount of
the organic peroxide used as a vulcanizing agent can be selected from a range of from 1 to
8 parts by mass, preferably from 1.5 to 5 parts by mass, and more preferably from 2 to 4.5
parts by mass, per 100 parts by mass of the rubber component. The proportion of the
metal oxide can be selected from a range of from 1 to 20 parts by mass, preferably from 3
to 17 parts by mass, and more preferably from 5 to 15 parts by mass (for example, from 7
to 13 parts by mass), per 100 parts by mass of the rubber component.
Examples of the co-crosslinking agent (a crosslinking aid or a co-agent) include
conventional crosslinking aids, for example, polyfunctional (iso)cyanurates [e.g., triallyl
isocyanurate (TAIC) or triallyl cyanurate (TAC)], polydiene (e.g., 1,2-polybutadiene),
metal salts of unsaturated carboxylic acid [e.g., zinc (meth)acrylate or magnesium
(meth)acrylate], oximes (e.g., quinone dioxime), guanidines (e.g.,, diphenyl guanidine),
polyfunctional (meth)acrylates [e.g., ethylene glycol di(meth)acrylate, butanediol
di(meth)acrylate or trimethylolpropane tri(meth)acrylate], bismaleimides (e.g., aliphatic
bismaleimides such as N,N'-l,2-ethylene bismaleimide and l,6'-bismaleimide-(2,2,4-
trimethyl)-cyclohexane; and arene bismaleimides or aromatic bismaleimides, such as
N,N'-m-phenylene bismaleimide, 4-methyl-l,3-phenylene bismaleimide, 4,4'-
diphenylmethane bismaleimide, 2,2-bis[4-(4-maleimide phenoxy)phenyl]propane, 4,4'-
diphenylether bismaleimide, 4,4'-diphenylsulfone bismaleimide, and l,3-bis(3-maleimide
phenoxy)-benzene. Those crosslinking aids can be used alone or in combination of two
kinds or more thereof. Of those crosslinking aids, bismaleimides (arene bismaleimides or
aromatic bismaleimides, such as N,N'-m-phenyIene dimaleimide) are preferred. The
addition of bismaleimides can increase the degree of crosslinking to prevent adhesive wear.
The proportion of the co-crosslinking agent (crosslinking aid) can be selected
from, for example, a range of from about 0.01 to 10 parts by mass per 100 parts, by mass of
the rubber component, in terms of the solid content. However, since rubber hardness of
the adhesive rubber layer is not required to be excessively increased by virtue of the
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combination of the fatty acid amide and the silica, the proportion of the co-crosslinking
agent (particularly, bismaleimides) may be comparatively a small amount, and may be, for
example, from 0.1 to 5 parts by mass, preferably from 0.3 to 4.8 parts by mass, and more
preferably from 0.5 to 4.5 parts by mass (particularly, from 1 to 4 parts by mass).
Examples of the vulcanization accelerator include thiuram accelerators [e.g.,
tetramethyl thiuram monosulfide (TMTM), tetramethyl thiuram disulfide (TMTD),
tetraethyl thiuram disulfide (TETD), tetrabutyl thiuram disulfide (TBTD),
dipentamethylene thiuram tetrasulfide (DPTT), or N,N'-dimethyI-N,N'- diphenyl thiuram
disulfide], thiazole accelerators [e.g., 2-mercaptobenzothiazole, a zinc salt of 2-
mercaptobenzothiazole, 2-mercaptothiazoline, dibenzothiazyl disulfide, or 2-(4'-
morpholinodithio)benzothiazole], sulfanamide accelerators [e.g., N-cyclohexyl-2-
benzothiazyl sulfenamide (CBS) or N,N'-dicyclohexyl-2-benzothiazyl sulfenamide],
bismaleimide accelerators (e.g., N,N'-ra-phenylene bismaleimide or N,N'-l,2-ethylene
bismaleimide), guanidines (e.g., diphenyl guanidine or di-o-tolyl guanidine), urea or
thiourea accelerators (e.g., ethylene thiourea), dithiocarbamates, and xanthates. Those
vulcanization accelerators can be used alone or in combination of two kinds or more
thereof. Of those vulcanization accelerators, TMTD, DPTT, CBS and the like are widely
used.
The proportion of the vulcanization accelerator may be, for example, from 0.1 to
15 parts by mass, preferably from 0.3 to 10 parts by mass, and more preferably from 0.5 to
5 parts by mass per 100 parts by mass of the rubber component, in terms of a solid content.
The proportion of the enhancer and the filler can be selected from a range of from
about 1 to 100 parts by mass per 100 parts by mass of the rubber component. However,
in the present invention, since rubber hardness of the adhesive rubber layer is not required
to be excessively increased by virtue of the combination of the fatty acid amide and the
silica, the proportion of the enhancer and the filler (particularly, the enhancer such as
carbon black) may be comparatively a small amount, and may be, for example, from 1 to
50 parts by mass, preferably from 3 to 30 parts by mass, and more preferably from 5 to 25
parts by mass (particularly, from 10 to 20 parts by mass).
The proportion of the softener (oils such as naphthenic oil) may be, for example,
from 1 to 30 parts by mass, and preferably from 3 to 20 parts by mass (for example, from 5
to 10 parts by mass), per 100 parts by mass of the rubber component. Furthermore, the
proportion of the processing agent or the processing aid (e.g., stearic acid) may be, for
example, 10 parts by mass or less (for example, from 0 to 10 parts by mass), preferably
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from 0.1 to 5 parts by mass, and more preferably from 0.3 to 3 parts by mass (particularly,
from 0.5 to 2 parts by mass), per 100 parts by mass of the rubber component.
The proportion of the adhesiveness improving agent (e.g., resorcin-formaldehyde
co-condensate or hexamethoxymethyl melamine) may be from 0.1 to 20 parts by mass,
preferably from 0.3 to 10 parts by mass, and more preferably from 0.5 to 5 parts by mass
(from 1 to 3 parts by mass), per 100 parts by mass of the rubber component.
The proportion of the age resister may be, for example, from 0.5 to 15 parts by
mass, preferably from 1 to 10 parts by mass, and more preferably from 2.5 to 7.5 parts by
mass (for example, from 3 to 7 parts by mass), per 100 parts by mass of the rubber
component.
(Characteristics of adhesive rubber layer)
The mechanical characteristics of the adhesive rubber layer can be appropriately
selected depending on required performance and rubber hardness can be, for example, in a
range of from 80 to 90° in the method in accordance with JIS K6253 (2012). Since
mechanical characteristics are improved by the combination of the fatty acid amide and the
silica, hardness of the adhesive rubber layer is not required to be excessively increased, and
the rubber hardness may be from about 80 to 83° (particularly, from 80 to 82°). An
adhesive rubber layer having relatively high rubber hardness may be formed and the rubber
hardness may be adjusted to, for example, from about 84 to 90° by compounding large
amounts of a reinforcing filler or a vulcanization compounding ingredient.
The thickness of the adhesive rubber layer can be appropriately selected
depending on the kind of a belt, and may be, for example, from 0.4 to 3.0 mm, preferably
from 0.6 to 2.2 mm, and more preferably from 0.8 to 1.4 mm.
[Transmission belt]
The transmission belt of the present invention contains the adhesive rubber layer.
In detail, the transmission belt contains a core wire extending in a lengthwise direction of
the belt, an adhesive rubber layer in contact with at least a part of the core wire, a back
surface rubber layer formed on one surface of the adhesive rubber layer, and an inner
surface rubber layer formed on the other surface of the adhesive layer and at a side (inner
side) engaging or being in contact with a pulley. Examples of the transmission belt
include friction transmission belts such as a V-belt, a V-ribbed belt and a flat belt, and
synchronous power transmission belts such as a toothed belt. Of those, the friction
transmission belt such as a V-belt or a V-ribbed belt is preferred, and a V-belt in which the
13
surface (a part of friction transmission surface) of the adhesive rubber layer is in contact
with a pulley (particularly, a variable speed belt used in a transmission in which
transmission gear ratio is continuously variable during belt traveling) is particularly
preferred. Examples of the V-belt include a raw edge belt and a raw edge cogged V-belt
which has cogs provided on the inner surface rubber layer side or both the inner surface
rubber layer side and the back surface rubber layer side of the raw edge belt.
FIG. 1 is a schematically cross-sectional view illustrating one example of the
transmission belt (raw edge cogged V-belt) of the present invention. In this example, a
core wire 2 is embedded in an adhesive rubber layer 1, an inner surface rubber layer 3 is
laminated on one surface of the adhesive rubber layer 1, and a back surface rubber layer 4
is laminated on the other surface of the adhesive rubber layer 1. The core wire 2 is
integrally embedded with being sandwiched between a pair of adhesive rubber sheets. A
reinforcing cloth 5 is laminated on the inner surface rubber layer 3, and a cog part 6 is
formed by a cogged forming die. The laminate of the inner surface rubber layer 3 and the
reinforcing cloth 5 is integrally formed by vulcanizing the laminate of the reinforcing cloth
and an inner surface rubber layer sheet (unvulcanized rubber sheet).
(Core wire)
The adhesive rubber layer is required to be in contact with at least a part of the
core wire, is not limited to the embodiment that the core wire is buried in the adhesive
rubber layer, may be the embodiment in which the core wire is embedded between the
adhesive rubber layer and the back surface rubber layer or between the adhesive rubber
layer and the inner surface rubber layer, and may be the embodiment in which a part of an
adhesive rubber layer at which the adhesive rubber layer is in contact with a tooth part is
formed so as to expand toward a back side (back surface layer side) or a tooth part side
(inner surface rubber layer side) relative to the core wire, like the toothed belt disclosed in
JP-A-2009-41768.
Examples of the fiber constituting the core wire include synthetic fibers, for
example, polyolefin fibers (e.g., polyethylene fiber or polypropylene fiber), polyamide
fibers (e.g., polyamide 6 fiber, polyamide 66 fiber, polyamide 46 fibe,r or aramide fiber),
polyalkylene arylate fibers [e.g., poly C2-4 alkylene Ce-i4 arylate fibers such as
polyethylene terephthalate (PET) fiber and polyethylene naphthalate (PEN) fiber], vinylon
fibers, polyvinyl alcohol fibers, and polyparaphenylene benzobisoxasol (PBO) fiber;
natural fibers such as cotton, hemp and wool; and inorganic fibers such as carbon fiber.
Of those, synthetic fibers such as polyester fiber or aramide fiber, and inorganic fibers such
as glass fiber or carbon fiber are widely used from the standpoint of high modulus, and
14
polyester fibers such as polyethylene terephthalate fiber or polyethylene naphthalate fiber,
and aramide fibers are particularly preferred from the standpoint that a belt slip ratio can be
decreased. The polyester fibers may be a multifilament yarn. Denier value of the core
wire constituted of the multifilament yarn may be, for example, from about 2,000 to 10,000
deniers (particularly, from 4,000 to 8,000 deniers). The core wire may be subjected to a
conventional adhesive treatment such as an adhesive treatment by a resorcin-formalin-latex
liquid (RFL liquid) for the purpose of improving adhesiveness to the rubber component.
Twisted cord using a multifilament yarn (e.g., organzine, single twist or Lang lay)
can be generally used as the core wire. The average wire diameter of the core wire (fiber
diameter of twisted cord) may be, for example, from 0.5 to 3 mm, preferably from 0.6 to 2
mm, and more preferably from 0.7 to 1.5 mm. The core wires may be embedded in the
lengthwise direction of the belt with being arranged in parallel with each other to the
lengthwise direction of the belt at predetermined pitches.
(Inner surface rubber layer and back surface rubber layer)
The vulcanized rubber composition for forming the inner surface rubber layer
(inner surface layer or internal layer) and the back surface rubber layer (back surface, layer)
may contain a rubber component e.g., chloroprene rubber), a vulcanizing agent or a
crosslinking agent (e.g., a metal oxide such as magnesium oxide and zinc oxide, or a sulfur
vulcanizing agent such as sulfur), a co-crosslinking agent or a crosslinking aid (e.g., a
maleimide crosslinking agent such as N,N'-m-phenylene dimaleimide), a vulcanization
accelerator (e.g., TMTD, DPTT or CBS), an enhancer (e.g., carbon black or silica), a
softener (e.g., oils such as naphthenic oil), a processing agent or a processing aid (e.g.,
stearic acid, a stearic acid metal salt, a wax, or a paraffin), an age resister, an adhesiveness
improving agent, a filler (e.g., clay, calcium carbonate, talc or mica), a colorant, a tackifier,
a plasticizer, a coupling agent (e.g., a silane coupling agent), a stabilizer (e.g., an ultraviolet
absorber or a thermal stabilizer), a flame retardant, an antistatic agent, and the like, similar
to the vulcanized rubber composition of the adhesive rubber layer. As necessary, the
inner surface rubber layer and the back surface rubber layer may contain fatty acid amide
and/or silica in order to improve durability of a belt, similar to the adhesive rubber layer.
The vulcanized rubber composition for forming the inner surface rubber layer and
the back surface rubber layer may further contain short fibers. Examples of the short
fiber include the same fibers as in the core wire. Preferred is a short fiber containing the
synthetic fiber or the natural fiber among the above-described fibers, particularly, the
synthetic fiber (e.g., polyamide fiber or polyalkylene arylate fiber), above all, at least
aramide fiber from the view point of having rigidity, high strength and modulus. The
15
average length of the short fiber is, for example, from 1 to 20 mm, preferably from 2 to 15
mm, and more preferably from 3 to 10 mm, and the average fiber diameter thereof is, for
example, from 5 to 50 (am, preferably from 7 to 40 um, and more preferably from 10 to 35
urn. The short fiber may be subjected to an adhesive treatment (or a surface treatment),
similar to the core wire.
In the rubber composition, rubbers of the same series (e.g., diene rubber) or the
same kind (e.g., chloroprene rubber) as the rubber component in the rubber composition of
the adhesive rubber layer are often used as the rubber component.
The proportions of the vulcanizing agent or crosslinking agent, the co-crosslinking
agent or crosslinking aid, the vulcanization accelerator, the enhancer, the softener, the
processing agent or processing aid, the age resister, the fatty acid amide, and the silica can
be selected from the same range as in the rubber composition of the adhesive rubber layer,
respectively. The proportion of the short fiber can be selected from a range of from about
5 to 50 parts by mass per 100 parts by mass of the rubber component, and may be
generally from about 10 to 40 parts by mass, preferably from 15 to 35 parts by mass, and
more preferably from 20 to 30 parts by mass.
The thickness of the inner surface rubber layer can be appropriately selected
depending on the kind of the belt, and is, for example, from about 2 to 25 mm, preferably
from 3 to 16 mm, and more preferably from 4 to 12 mm. The thickness of the back
surface rubber layer can be also appropriately selected depending on the kind of the belt,
and is from about 0.8 to 10.0 mm, preferably from 1.2 to 6.5 mm, and more preferably
from 1.6 to 5.2 mm.
(Reinforcing cloth)
The case of using a reinforcing cloth in the transmission belt is not limited to the
embodiment in which the reinforcing cloth is laminated on the surface of the inner surface
rubber layer, and may be, for example, the embodiment in which the reinforcing cloth may
be laminated on the surface of the back surface rubber layer (the surface opposite the
adhesive rubber layer), or the embodiment in which the reinforcing layer is embedded in
the inner surface rubber layer and/or the back surface rubber layer (e.g., the embodiment
described in JP-A-2010-230146). The reinforcing cloth can be formed by, for example, a
cloth material such as a woven fabric, a wide-angle canvas, a knitted fabric, or a nonwoven
fabric (preferably a woven fabric), and as necessary, it may be laminated on the
surface of the inner surface rubber layer and/or the back surface rubber layer after being
subjected to the adhesive treatment described above such as a treatment with RFL liquid
16
(e.g., dipping treatment), friction in which the adhesive rubber layer is rubbed in the cloth
material, or lamination (coating) of the adhesive rubber and the cloth material.
In the description, in the case where the reinforcing cloth is laminated on the
surface of the inner surface rubber layer or the back surface rubber layer, the inner surface
rubber layer or the back surface rubber layer is defined as the state including the
reinforcing cloth (i.e., the laminate of the inner surface rubber layer or the back surface
rubber layer and the reinforcing cloth).
[Production method of transmission belt]
The production method of the transmission belt of the present invention is not
particularly limited, and the conventional method can be utilized for a lamination step of
each layer (production method of a belt sleeve).
For example, in the case of a cogged V-belt, a laminate of the reinforcing cloth
(lower cloth) and the inner surface rubber layer sheet (unvulcanized rubber) is arranged in
a flat mold with cogs in which tooth portions and groove portions are alternatively
provided, in the state of the reinforcing cloth down, and press-pressurized at a temperature
of from about 60 to 100°C (particularly, from 70 to 80°C) to prepare a cogged pad having
cog portions embossed (a pad which is not completely vulcanized and in a semi-vulcanized
state), and thereafter both ends of the cogged pad may be vertically cut from the top of a
mountain portion of the cog. A molded article may be prepared by covering a cylindrical
mold with an inner matrix having tooth portions and groove portions alternately provided,
and then, winding the cogged pad so as to engage with the tooth portions and groove
portions of the inner matrix and jointing itself at the top of the cog mountain portion,
laminating a first adhesive rubber layer sheet (a lower adhesive rubber: unvulcanized
rubber) on the cogged pad wound, spinning the core wire spirally thereon, and sequentially
winding a second adhesive rubber layer sheet (an upper adhesive rubber: the same as the
above adhesive rubber layer sheet), a back surface rubber layer sheet (unvulcanized
rubber) and, a reinforcing cloth (an upper cloth) further thereon. The mold is thereafter
covered with a jacket and arranged in a vulcanization can, and vulcanization is conducted
at a temperature of from about 120 to 200°C (particularly, from 150 to 180°C) to prepare a
belt sleeve. The belt sleeve may be then cut into a V-shape by using a cutter or the like.
EXAMPLES
The present invention is described below in more detail based on examples, but it
should be understood that the invention is not limited by those examples. In the
17
following examples, measurement method and evaluation method in each property, and
raw materials used in the examples are described below. Unless otherwise indicated, all
parts and % are mass basis.
[Properties of vulcanized rubber composition]
(1) Hardness, tensile test and tear test
Unvulcanized adhesive rubber layer sheets and inner surface rubber layer sheets
(back surface rubber layer sheets) shown in Tables 1 and 2 were press-vulcanized
(pressure: 2.0 MPa) at a temperature of 160°C for a period of 20 minutes to prepare
vulcanized rubber sheets (length: 100 mm, width: 100 mm, thickness: 2 mm).
(Hardness)
In accordance with JIS K6253 (2012), a laminate obtained by stacking three
vulcanized rubber sheets was used as a sample, and its hardness was measured by using a
durometer A type hardness tester.
(Tensile test)
The tensile test was conducted in accordance with JIS K6251 (2010). The
vulcanized rubber sheet was punched into a dumbbell shape as a sample. The sample was
pulled with a tensile tester, and stress (stress at 100% elongation) at the time when the
sample was stretched 100%, and strength (strength at break) and elongation (elongation at
break) at the time of broken were measured. Regarding the adhesive rubber layer sheet, a
tensile test was conducted such that a tensile direction is a rolling direction of the rubber
sheet, and stress at 100% elongation, strength at break and elongation at break were
measured. Regarding the inner surface rubber layer sheet (back surface rubber layer
sheet), a tensile test was conducted by using a sample in which short fibers are oriented in
parallel to a tensile direction and a sample in which short fibers are oriented vertical.
Regarding the parallel direction, strength at break was measured, and regarding the vertical
direction, stress at 100% elongation, strength at break and elongation at break were
measured.
(Tear test)
The tear test was conducted in accordance with JIS K6252 (2007). The
vulcanized rubber sheet was punched into an angle shape, the angle shape was pulled with
a tensile tester, and tear force was measured. Regarding the adhesive rubber layer sheet, a
tear direction was a direction parallel to a rolling direction of the rubber sheet. Regarding
the inner surface rubber layer sheet (back surface rubber layer sheet), orientation of the
18
short fibers was a direction vertical to the tensile direction, that is, a direction parallel to
the tear direction.
(2) Peel force
A plurality of core wires were arranged in parallel on one surface of the
unvulcanized adhesive rubber layer sheets (four kinds of Example 3, Example 5,
Comparative Example 1 and Comparative Example 2) having a thickness of 4 mm as
shown in Table 1 such that a width is 25 mm, and a canvas was laminated on the other
surface. The resulting laminate (core wire, adhesive rubber layer sheet and canvas) was
press-vulcanized (temperature: 160°C, time: 20 minutes and pressure: 2.0 MPa) to prepare
a strip sample for a peel test (width: 25 mm, length: 150 mm; and thickness: 4 mm). In
accordance with JIS K6256 (2006), a peel test was conducted in a tensile rate of 50
mm/min, and peel force (vulcanization adhesive force) between the core wire and the
adhesive rubber layer sheet was measured in a room temperature atmosphere.
[Properties of belt]
As shown in FIG. 2, durability traveling test was conducted by using a two-axial
traveling testing machine consisting of a drive (Dr.) pulley 12 having a diameter of 50 mm
and a driven (Dn.) pulley 13 having a diameter of 125 mm. Next, a raw edge cogged Vbelt
11 was hung on each of the pulleys 12 and 13, a load of 10 N-m (durability traveling
test 1: intermediate load durability) or 15 N-m (durability traveling test 2: high load
durability) was applied to the driven pulley 13 in which the number of revolution of the
drive pulley 12 is 5,000 rpm, and the belt was traveled for at most 60 hours at an
atmosphere temperature of 80°C. When the belt 11 could be traveled for 60 hours, it was
judged that there is no problem in durability. Regarding the belt that was not traveled for
60 hours and generated peeling (separation) at the interface between the adhesive rubber
layer and the inner surface rubber layer, the time when peeling (peeling in a depth of about
1 mm from the belt edge) occurred was confirmed.
[Raw materials]
Fatty acid amide: Stearic acid amide (structural formula: C18H37NO), "AMIDE
AP-1" manufactured by Nippon Kasei Chemical Co., Ltd., melting point: 101°C
Fatty acid bisamide: Ethylenebisoleic acid amide (structural formula:
C38H72N202), "SLIPACKS O" manufactured by Nippon Kasei Chemical Co., Ltd.
Fatty acid ester amide: Ethanolamine distearate, "SLIAID S" manufactured by
Nippon Kasei Chemical Co., Ltd.
Naphthenic oild: "RS700" manufactured by DIC Corporation
19
Silica A: "ULTRASIL VN-3" manufactured by Evonik Degussa Japan, specific
surface area: 155 to 195m2/g
Silica B: "NIPSIL ER" manufactured by Tosoh Silica Corporation, specific
surface area: 70 to 120 m /g
Silica C: "NIPSIL KQ" manufactured by Tosoh Silica Corporation, specific
surface area: 215 to 265 m2/g
Carbon black: "SEAST 3" manufactured by Tokai Carbon Co., Ltd.
Resorcin-formalin copolymer (resorcinol resin): Resorcin-formalin copolymer
having less than 20% of resorcinol and less than 0.1% of formalin
Age resister: "NONFLEX OD3" manufactured by Seiko Chemical Co., Ltd.
Vulcanization accelerator TMTM: Tetramethylthiuram-monosulfide
Aramide short fiber: "CORNEX Short Fiber" manufactured by Teijin Techno
Products Limited, short fibers having an average fiber length of 3 mm and an average fiber
diameter of 14 jam, having been subjected to an adhesive treatment with an RFL liquid
(resorcin: 2,6 parts, 37% formalin: 1.4 parts, vinylpyridine-styrene-butadiene copolymer
latex (manufactured by Zeon Corporation): 17.2 parts, water 78.8 parts), and having an
adhesion ratio of solid contents of 6% by mass
Core wire: Fiber obtained by subjecting a plied cord having total denier of 6,000
obtained by twisting PET fibers of 1,000 deniers in twisting structure of 2x3 with a second
twist coefficient of 3.0 and a first twist coefficient of 3.0, to an adhesive treatment
Examples 1 to 5 and Comparative Examples 1 and 2
(Formation of rubber layer)
Rubber compositions shown in Tables 1 and 2 (adhesive rubber layer) and Table 3
(inner surface rubber layer and back surface rubber layer) were kneaded by using a
conventional method such as Banbury mixer, respectively, and the kneaded rubbers were
passed through calender rolls to prepare rolled rubber sheets (adhesive rubber layer sheet,
inner surface rubber layer sheet, and back surface rubber layer sheet).
In Table 3, the inner surface rubber layer material and the back surface rubber
layer material have the same rubber composition, Rubber 1 is for the use in intermediate
load, and Rubber 2 is for the use in high load. Regarding the compounding, Rubber 2 has
the formulation that amounts of aramide short fiber, carbon black and N,N'-m-phenylene
dimaleimide added are make large as compared with Rubber 1, thereby making the rubber
composition hard to increase modulus (lateral pressure resistance).
In Table 1, Examples 4 to 8 have the formulation that the amount of the fatty acid
amide was changed (2,4, 6, 8 and 10 parts), and have the same composition except for the
20
fatty acid amide. Example 1 is the same as Example 4, except that fatty added amide and
stearic acid are added in an amount of 0.3 parts and 1 part, respectively. Examples 2 and
3 are the same as Example 1, except that fatty acid amide is added in an amount of 0.5
parts or 1 part. Comparative Example 1 has the same composition as Example 4, except
that stearic acid is added in an amount of 2 parts in place of fatty acid amide.
Comparative Example 2 has the same composition as Comparative Example 1, except that
N,N'-m-phenylene dimaleimide is added in an amount of 8 parts. Comparative Examples
1 and 2 are materials corresponding to adhesive rubber layers used in the rubber V-belt
disclosed in Patent Document 1 (JP-A-61-290255), as shown in Table 1 below.
In Table 2, Examples 9 and 10 have the same composition as Example 3, except
that silica having different specific surface area is added. Comparative Examples 3 and 4
have the same composition as Comparative Example 1, except that silica having different
specific surface area is added.
Evaluation results of properties of the vulcanized rubber composition obtained in
the examples and the comparative examples are also shown in Tables 1 to 3.
21
[Table 11
Material (parts)
Chloroprene rubber
Fatty acid amide
Stearic acid
N,N' -m-phenylene
dimaleimide
Naphthenic oil
Magnesium oxide
Silica A
Carbon black
Resorcin-formalin
copolymer
Age resister
Zinc oxide
Vulcanization accelerator
TMTD
Hexamethoxymethylol
melamine
Hardness (°)
stress at 100% elongation
(MPa)
Strength at break (MPa)
Elongation at break (%)
Tear force (N/mm)
Peel force (N/25 mm)
Example
1
100
0.3
1
4
5
4
30
20
2
4
5
1
2
80
4.2
18.9
406
60
395
2
100
0.5
1
4
5
4
30
20
2
4
5
1
2
80
4.2
19.4
430
60
411
3
100
1
1
4
5
4
30
20
2
4
5
1
2
81
4.7
19.6
430
62
420
4
100
2
0
4
5
4
30
20
2
4
5
1
2
81
5.0
18.8
400
65
420
5
100
4
0
4
5
4
30
20
2
4
5
1
2
81
5.2
19.4
420
66
437
6
100
6
0
4
5
4
30
20
2
4
5
1
2
81
5.4
19.6
425
65
445
7
100
8
0
4
5
4
30
20
2
4
5
1
2
80
5.1
19.1
489
62
429
8
100
10
0
4
5
4
30
20
2
4
5
1
2
79
4.7
18.4
529
60
430
Comparative
Example
1
100
0
2
4
5
4
30
20
2
4
5
1
2
80
4.0
19.2
450
58
360
2
100
0
2
8
5
4
30
20
2
4
5
1
2
86
5.6
17.8
395
48
352
22
[Table 2Material (parts)
Chloroprene rubber
Fatty acid amide
Stearic acid
N,N'-m-phenylene dimaleimide
Naphthenic oil
Magnesium oxide
Silica A
Silica B
Silica C
Carbon black
Resorcin-formalin copolymer
Age resister
Zinc oxide
Vulcanization accelerator TMTD
Hexamethoxymethylol melamine
Hardness (°)
stress at 100% elongation (MPa)
Strength at break (MPa)
Elongation at break (%)
Tear force (N/mm)
Peel force (N/25 mm)
Example
3
100
1
1
4
5
4
30
0
0
20
2
4
5
1
2
81
4.7
19.6
430
62
420
9
100
1
1
4
5
4
0
30
0
20
2
4
5
1
2
80
4.4
18.0
440
56
421
10
100
1
1
4
5
4
0
0
30
20
2
4
5
1
2
82
5.1
19.9
396
71
402
Compara
Examp
1
100
0
2
4
5
4
30
0
0
20
2
4
5
1
2
80
4.0
19.2
450
58
360
3
100
0
2
4
5
4
0
30
0
20
2
4
5
1
2
78
3.6
17.5
465
52
353
tive
e
4
100
0
2
4
5
4
0
0
30
20
2
4
5
1
2
81
4.5
19.3
391
65
339
23
[Table 3]
Material (parts)
Chloroprene rubber
Aramide short fiber
Naphthenic oil
Magnesium oxide
Carbon black
Age resister
Zinc oxide
N,N'-m-phenylene dimaleimide
Stearic acid
Vulcanization accelerator TMTD
Sulfur
Hardness (°)
stress at 100% elongation (vertical) (MPa)
Strength at break (parallel) (MPa)
Strength at break (vertical) (MPa)
Elongation at break (vertical) (%)
Tear force (parallel) (N/mm)
Rubber 1
100
20
5
4
30
4
5
4
2
1
0.5
88
9
24
11.2
236
70
Rubber 2
100
30
5
4
40
4
5
4
2
1
0.5
94
-
45
11.8
75
85
As is apparent from the results of Table 1, in Examples 4 to 6 in which the
proportion of the fatty acid amide was changed, difference in hardness is not appeared, but
stress at 100% elongation, strength at break and elongation at break were increased with
increasing the amount of the fatty acid amide. This tendency was confirmed in Examples
1 to 3 in which stearic acid was added. On the other hand, in Examples 7 and 8 in which
the proportion of the fatty acid amide is 8 parts or more, elongation at break is improved,
but stress at 100% elongation, strength at break, tear force and peel force were slightly
decreased. This tendency can be assumed to be that excess fatty acid amide that does not
interact with silica is increased and this fatty acid acts as an internal lubricant (softener).
Even though the proportion of the fatty acid amide is 0.3 parts, Example 1 showed high
peel force as compared with Comparative Example 1 in which fatty acid amide is not
added. Even though the proportion of the fatty acid amide is small, adhesiveness was
improved.
In the comparison between Example 4 and Comparative Example 1, Example 4 in
which the fatty acid amide was added showed high stress at 100% elongation, but low
strength at break and lower elongation at break. The reason for this is considered that the
24
fatty acid amide interacts with silica to improve dispersibility of silica and adhesiveness
between the silica and the rubber component, and to enhance modulus (stress at 100%
elongation), thereby making it difficult to stretch.
Comparative Example 2 in which N,N'-m-phenylene dimalemide was added in an
amount of 8 parts by mass showed high hardiness and stress at 100% elongation, but
showed low elongation at break, and along therewith, showed the smallest strength at
break and tear force.
Furthermore, as is apparent from the results of Table 2, in Example 10 in which
the specific surface area is large, stress at 100% elongation, strength at break and tear force
were largest values, and in Example 9 in which the specific surface area is small, those
properties were smallest values. On the other hand, regarding elongation at break and
peel force, Example 9 in which the specific surface area is small showed the highest value,
and Example 10 in which the specific surface area is large showed the lowest value.
From those results, the silica of Example 3, having the specific surface area that is nearly
the intermediate value between Example 9 and Example 10 had properties having most
excellent balance.
In the comparison between Example 9 and Comparative Example 3, and between
Example 10 and Comparative Example 4, Examples 9 and 10 in which the fatty acid amide
was added showed high hardness, stress at 100% elongation, strength at break, tear force
and peel force. This tendency is the same tendency as recognized in Example 3 with
respect to Comparative Example 1. Therefore, it is seen that the interaction is present
between silica and fatty acid amide even through the specific surface area of silica is
changed.
(Production of belt)
A laminate of a reinforcing cloth and an inner surface rubber layer sheet
(unvulcanized rubber) was arranged in a flat mold with cogs in which tooth portions and
groove portions are alternatively provided, in the state of the reinforcing cloth down, and
press-pressurized at 75°C to prepare a cogged pad having cog portions embossed (a pad
which is not completely vulcanized and in a semi-vulcanized state). Next, both ends of
the cogged pad were vertically cut from the top of a mountain portion of the cog.
A molded article was prepared by covering a cylindrical mold with an inner
matrix having tooth portions and groove portions alternately provided, and then, winding
the cogged pad so as to engage with the tooth portions and groove portions of the inner
25
matrix and jointing itself at the top of the cog mountain portion, laminating an adhesive
rubber layer sheet (a lower adhesive rubber: unvulcanized rubber) on the cogged pad
wound, spinning a core wire spirally thereon, and sequentially winding another adhesive
rubber layer sheet (an upper adhesive rubber: the same as the above adhesive rubber layer
sheet), and a back surface rubber layer sheet (unvulcanized rubber) further thereon. The
mold was thereafter covered with a jacket and arranged in a vulcanization can, and
vulcanization was conducted at a temperature of 160°C for a period of 20 minutes to
prepare a belt sleeve. The sleeve was then cut into a V-shape in a given width in a
lengthwise direction of the belt by using a cutter to shape into a belt having the structure
shown in FIG. 1, that is, a raw edge cogged V-belt which is a variable speed belt having
cogs at a belt inner circumference side (size: upper width 22.0 mm, thickness 11.0 mm,
outer circumference length 800 mm).
The low edge cogged V-belts prepared are 11 kinds in which the combination of
the adhesive rubber layer and the inner surface rubber layer (the back surface rubber layer
has the same formulation as the inner surface rubber layer) was changed. Evaluation
results of the belts obtained in the examples and the comparative examples are shown in
Table 4.
26
As is apparent from the results of Table 4, regarding the durability traveling test 1
under intermediate load, the belts using the adhesive rubber layers of Examples 2 to 6 can
travel for 60 hours, and durability was excellent. On the other hand, in the belts using the
adhesive rubber layers of Comparative Examples 1 and 2, peeling occurred in an early
stage at the interface between the adhesive rubber layer and the inner surface rubber layer.
Regarding the durability traveling test 2 under high load, the belt using the
adhesive rubber layer of Example 4 can travel for 60 hours, and thus durability was
excellent in high load condition. On the other hand, in the belts using the adhesive rubber
layers of Comparative Examples 1 and 2, interfacial peeling was observed at 10 hours and
40 hours, respectively. From the comparison between Comparative Example 1 and
Comparative Example 2 under high load condition, the effect of suppressing interfacial
peeling is recognized by increasing hardness of the adhesive rubber layer, but it is seen that
the effect is not sufficient in severer layout and under high load condition by merely
increasing hardness of the adhesive rubber layer.
Examples 11 and 12
Properties of the vulcanized rubber were evaluated by changing the kind of fatty
acid amide. That is, the formulation of the rubber composition was the same as Example
4 except for changing the kind of fatty acid amide, that is, fatty acid bisamide was added in
Example 11, and fatty acid ester amide was added in Example 12 both in an amount of 2
parts by mass. The results of properties of vulcanized rubbers are shown in Table 5
together with the results of Example 4 and Comparative Example 1.
28
[Table 5]
Material (parts)
Chloroprene rubber
Fatty acid amide
Fatty acid bisamide
Fatty acid ester amide
Stearic acid
Hardness (°)
stress at 100% elongation
(MPa)
Strength at break (MPa)
Elongation at break (%)
Tear force (N/mm)
Example
4
100
2
0
0
0
81
5.0
18.8
400
65
11
100
0
2
0
0
81
4.7
18.7
424
74
12
100
0
0
2
0
81
4.5
18.9
449
71
Comparative
Example
1
100
0
0
0
2
80
4.0
19.2
450
58
As is apparent from the results of Table 5, Examples 4,11 and 12 using fatty acid
amide show high values in hardness, stress at 100% elongation, strength at break and tear
force as compared with those of Comparative Example 1 using stearic acid, and elongation
at break in Examples 4 and 11 was slightly decreased.
Although the present invention has been described in detail and by reference to
the specific embodiments, it is apparent to one skilled in the art that various modifications
or changes can be made without departing the spirit and scope of the present invention.
This application is based on Japanese Patent Application No. 2012-100332 filed
on April 25,2012 and Japanese Patent Application No. 2012-231627 filed on October 19,
2012, the disclosures of which are incorporated herein by reference.
INDUSTRIAL APPLICABILITY
The transmission belt of the present invention can be utilized as various belts in
which transmission loss is required, can be further utilized in a synchronous power
transmission belt such as a toothed belt, and is preferably utilized as a friction transmission
belt. Examples of the friction transmission belt include a low edge belt having a Vshaped
cross-section, a raw edge cogged V-belt having cogs provided at an inner
circumference side or both an inner circumference side and an outer circumference side of
a raw edge belt, and a V-ribbed belt. In particular, it is preferably applied to a belt (a
29
variable speed belt) used in a transmission in which transmission gear ratio is continuously
variable during belt traveling.
DESCRIPTION OF REFERENCE NUMERALS AND SIGNS
1
2
3
4
5
6
12
13
11
Adhesive rubber layer
Core wire
Inner surface rubber layer
Back surface rubber layer
Reinforcing cloth
Cog portion
Drive pulley
Driven pulley
Raw edge cogged V-belt
30
We Claim:
1. A transmission belt comprising a core wire extending in a lengthwise direction of
the belt, an adhesive rubber layer in contact with at least a part of the core wire, a back
surface rubber layer formed on one surface of the adhesive rubber layer, and an inner
surface rubber layer formed on the other surface of the adhesive rubber layer and engaging
or in contact with a pulley,
wherein the adhesive rubber layer is formed by a vulcanized rubber composition
comprising a rubber component, a fatty acid amide and a silica.
2. The transmission belt according to claim 1, wherein the proportion of the fatty
acid amide is from 0.3 to 10 parts by mass per 100 parts by mass of the rubber component.
3. The transmission belt according to claim 1 or 2, wherein the proportion of the
fatty acid amide is from 1 to 30 parts by mass per 100 parts by mass of the silica.
4. The transmission belt according to any one of claims 1 to 3, wherein the fatty acid
amide comprises a fatty acid amide having a saturated or unsaturated higher fatty acid
residue having from 10 to 26 carbon atoms or a higher amine residue having from 10 to 26
carbon atoms.
5. The transmission belt according to any one of claims 1 to 4, wherein the silica has
a nitrogen adsorption specific surface area according to BET method of from 50 to 400
m2/g.
6. The transmission belt according to any one of claims 1 to 5, wherein the rubber
component comprises chloroprene rubber.
7. The transmission belt according to any one of claims 1 to 6, which is a friction
transmission belt.