DESCRIPTION
ADHESIVERESINCOMPOSITIONANDMULTILAYERSTRUCTUREUSINGTHESAME
5 TECHNICAL FIELD
[OOOl]
The present invention relates to an adhesive resin
composition comprising a modified ethylene polymer composition
which has less elution amount at high temperature and in which
10 the molecular weight of polymers eluted at high temperature is
high. In more detail, the present invention relates to an
adhesive resin composition which retains sufficient interlayer
adhesive strength even when in contact with gasoline or light gas
oil, andhas excellent interlayer adhesionunderhightemperature,
15 excellent impact resistance, and excellent long-term durability
and durability in high-temperature fuels. The present invention
also relatesto amultilayer structure suitable for an automotive
fuel tank which has excellent long-term durability in
high-temperature gasoline or light gas oil and excellent
20 low-temperature drop impact strength.
BACKGROUND ART
[0002]
As a multilayer structure suitable as an automotive fuel
tank, there has been proposed a multilayer structure formed from
a polyethylene resin layer/an adhesive layer/an ethylene-vinyl
acetate copolymer saponification product layer (hereinafter also
abbreviated as the "EVOH") or formed from a polyethylene resin/a
5 mixture layer of an adhesive and an ethylene-vinyl acetate
copolymer saponification product (for example, Patent Document
1) -
[0003]
As the adhesive layer of this multilayer structure, a
10 composition containing an ethylene polymer partly or wholly
graft-modified with an acid anhydride is used. However, if a
modified ethylene polymer with low density is used, the resultant
adhesive layer, when immersed in a fuel oil, may be swollen, and
may have reduced adhesive strength at high temperature. On the
15 other hand, if a modified ethylene polymer with high density is
used, the resultant multilayer structure may have reduced
low-temperature drop impact strength.
The demand for higher performance of automotive fuel tanks
20 has been increasing. For example, as a result of diesel
automobiles adopting a common rail system, in addition to the
performance required so far, the automotive fuel tanks are
required to have long-term durability when in contact with
high-temperature fuels. Specifically, for example, the
multi-layer structure is required to be free from problems such
as delaminationbetween respective layers and delamination at the
pinch-off part, even when in contact with high-temperature fuel.
CITATION LIST
PATENT DOCUMENT
Patent Document 1: JP-A-10-156978
SUMMARY OF THE INVENTION
TECHNICAL PROBLEM
It is an object of the present invention to provide an
adhesive resin composition, suitable for a multilayer structure,
15 which retains sufficient adhesive strength even when in contact
with gasoline or light gas oil, and has excellent long-term
durabilityanddurabilityinhigh-temperature fuels andexcellent
adhesive strength at high temperature.
[0007]
20 It is another object of the present invention to provide
a multilayer structure, suitable for an automotive fuel tank,
which retains sufficient adhesive strength even when in contact
with gasoline or light gas oil, and has excellent long-term
durability and excellent adhesive strength at high temperature.
TECHNICAL SOLUTION
[0008]
The present inventors have their earnest studies and have
5 found that an adhesive resin composition having specific
properties, andamultilayer structure obtained fromthe adhesive
resincompositionachieveexcellenteffectstosolvetheproblems,
thereby completing the present invention.
[0009]
10 That is, an embodiment of the present invention is:
[I] An adhesive resin composition comprising 2 to 40 wt%
of a modified ethylene polymer (Al) which is graft-modified with
an unsaturated carboxylic acid or a derivative thereof and which
has a density of 930 to 980 kg/m3, and 60 to 98 wt% of an unmodified
15 ethylene polymer (A2) having a density of 910 to 929 kg/m3 where
(Al) + (A2) =I00 wt%, wherein the adhesive resin composition has a
melt flow rate (MFR) [ASTM D 1238 (temperature: 19O0C, 2160 g
load)] of 0.1 to 3 9/10 min and a density of 920 to 930 kg/m3,
and has an elution amount of 60 wt% or less at 85'C or lower as
20 determined by cross-fractionation chromatography. Preferable
embodiments are described below.
[2] The adhesive resin composition, which further
comprises Oto 30wt% ofanunmodifiedethylenepolymer (A3) having
a density of 930 to 980 kg/m3 where (Al)+(A2)+(A3)=100 wt%.
[3] The adhesive resin composition, wherein the graft
amount ofthe unsaturated carboxylic acid or a derivative thereof
is 0.1 to 5 wt%.
[4] The adhesive resin composition, which has an Izod
5 impact strength as measured in accordance with ASTM D 256 under
-40'C atmosphere of 10 k~/m*or more.
[5] A multilayer structure comprising an adhesive layer
I (A) formed from the above adhesive resin composition, a
polyethylene resin layer (B), and a polymer layer (C) selected
10 from the group consisting of an ethylene-vinyl acetate copolymer
saponification product and a polyamide.
[6] Themultilayer structure, wherein the ethylene-vinyl
acetate copolymer saponification product is a polymer having a
saponification degree of 90 to 100% which is obtained by
15 saponifying an ethylene-vinyl acetate copolymer having an
ethylene content percentage of 15 to 70 mol%.
[7] The multilayer structure, wherein the polyamide is
at least any of nylon 6, nylon 66, nylon 610, nylon 12, nylon 11,
MXD nylon, an amorphous nylon and a copolymerized nylon.
20 [8] The multilayer structure, which comprises a rigrind
layer (D) between the layer (B) and the layer (A).
[9] An automotive fuel tank comprising the above
multilayer structure.
ADVANTAGEOUS EFFECTS OF THE INVENTION
[OOlO]
Theadhesiveresincompositionofthepresentinventionwhen
used as an adhesive layer of a multilayer structure provides a
5 multilayer structurewhichhas high initial adhesive strengthand
retains high adhesive strength after in contact with gasoline or
light gas oil, and has excellent adhesive strength at high
temperature and excellent long-termdurability and durabilityin
high-temperature fuels.
10 [OOll]
Furthermore, byusingthe adhesive resin composition ofthe
present invention, there is provided a multilayer structure
suitabl& for an automotive fuel tank which retains sufficient
adhesive strength even when in contact with high-temperature
15 gasoline or light gas oil, and has excellent long-term durability
and excellent low-temperature drop impact strength.
DESCRIPTION OF EMBODIMENTS
20
The modified ethylene polymer (Al) , which is one component
of the adhesive resin composition of the present invention, is
a polymer which is graft-modified with an unsaturated carboxylic
acid or a derivative thereof and has a density of 930 to 980 kg/m3,
p r e f e r a b l y 940 t o 970 kg/m3. The use of t h e modified ethylene
polymer ( A l ) having a density within such range e a s i l y provides
a composition e x c e l l e n t i n h e a t - r e s i s t a n t adhesion. I f a
modified ethylene polymer having a d e n s i t y of l e s s than 930 kg/m3
5 is used and blended with an unmodified ethylene polymer, the
r e s u l t a n t adhesive r e s i n composition may have an e l u t i o n amount
of more than 60 w t % a t 85°C or lower as determined by
c r o s s - f r a c t i o n a t i o n chromatography.
[0013]
10 Themodifiedethylenepolymer ( A l ) according t o t h e present
invention usually has a melt flow r a t e (MFR) [ASTM D 1238 (190 "C,
2160 g l o a d ) ] of 0.01 t o 3.0 g/10 min, more preferably 0.05 t o
1.5 g/10 min. I f a polymer having MFR of less than 0.01 g/10 min
is used, extrusion molding of the r e s u l t a n t adhesive r e s i n
15 compositionmaybe d i f f i c u l t , a n d t h e p r e s s u r e increasemayexceed
the pressure l i m i t of a molding machine. On the other hand, i f
a polymer having MFR of more than 3 g/10 min is used, the adhesive
r e s i n composition tends t o provide an product having a poor
uniformityinitsthickness, andhavinga reducedmolecularweight,
I 20 which may reduce the drop impact s t r e n g t h of a multilayer
I
I s t r u c t u r e .
[0014]
The g r a f t amount of the unsaturated carboxylic acid o r a
d e r i v a t i v e thereof is usually 0.01 t o 10 w t % , preferably 0.02 t o
5 wt%. If the graft amount is too small, the adhesivity may be
insufficient. If the graft amount is too large, crosslinking
readily occurs and it is difficult to keep the quality of the
resultant modified ethylene polymer.
[0015]
Examples ofthe unsaturatedcarboxylic acidor a derivative
thereof according to the present invention include unsaturated
carboxylic acids such as acrylic acid, maleic acid, fumaric acid,
tetrahydrophthalic acid, itaconic acid, citraconic acid,
crotonic acid, isocrotonic acid, and Nadic acid
(endocis-bicyclo[2.2.l]hepto-5-ene-dicarboxylc acid); and
derivatives thereof such as acid halides, amides, imides,
anhydrides and esters. Specific examples of the derivatives
includemaleylchloride, maleimide, maleic anhydride, citraconic
anhydride, monomethyl maleate, dimethyl maleate and glycidyl
maleate. Of these, unsaturated dicarboxylic acids or acid
anhydrides thereof are preferred. Particularly, maleic acid,
Nadic acid, or acid anhydrides thereof are preferably used.
[0016]
Themodifiedethylenepolymer (Al) according tothe present
inventionmaybeproducedbyvarious knownmethods. For example,
in one method, an ethylene polymer is dissolved in an organic
solvent to prepare a solution, and to the solution an unsaturated
carboxylic acid or a derivative thereof, andoptionallya radical
initiator such as an organoperoxide are added. Then, the mixture
is allowed to undergo reaction usually at a temperature of 60 to
350°C, preferably 80 to 19OoC, for 0.5 to 15 hours, preferably
1 to 10 hours. In another method, with an extruder or the like,
5 in the absence of solvents, an ethylene polymer, an unsaturated
carboxylic acid or a derivative thereof and optionally a radical
initiator such as an organoperoxide are added, and the mixture
is allowed to undergo reaction usually at a temperature of higher
than the melting point of the ethylene polymer, preferably 120
10 to 35O0C, for 0.5 to 10 minutes.
[0017]
An unmodified ethylene polymer serving as a raw material
of the modified ethylene polymer (Al) according to the present
invention is an ethylene homopolymer or a copolymer of ethylene
15 and an a-olefin. The a-olefin to be copolymerized with ethylene
is an a-olefin having 3 or more carbon atoms, preferably 3 to 10
carbon atoms, with specific examples including propylene,
1-butene, 1-pentene, 1-hexene, 1-octene, 1-decene,
4-methyl-1-pentene and combination of two or more of these. The
20 copolymerizationamountofthea-olefin, which is not particularly
limited as long as the resultant density falls within the range
described below, is usually not more than 10 mol%.
[0018]
The unmodified ethylene polymer according to the present
invention is not particularly limited as long as the resultant
modifiedethylenepolymer (Al) has adensitywithintheaboverange,
but the unmodified ethylene polymer according to the present
invention usually has a density of 930 to 980 kg/m3 and MFR of
5 0.1 to 50 g/10 min.
[0019]
This ethylene polymer maybe producedby knownmethods such
as high-pressure method or low-pressure method using e. g., a
Ziegler-type Ti-based catalyst or Co-based catalyst, or a
10 metallocene-based catalyst.
[0020]

The unmodified ethylene polymer (A2), which is another
component of the adhesive resin composition of the present
15 invention, has a density of 910 to 940 kg/m3, preferably 915 to
935 kg/m3. If an unmodified ethylene polymer having a density
i of less than 910 kg/m3 is used and is blended with I the modified
ethylene polymer, the resultant adhesive resin composition may
have an elution amount of more than 60 wt% at 85°C or lower as
20 determined by cross-fractionation chromatography.
[0021]
The unmodified ethylene polymer (A2) usually has MFR [ASTM
D 1238 (l9OoC, 2160 g load)] of 0.01 to 10 g/10 min, preferably
0.10 to 5 g/10 min. If a polymer having MFR of less than 0.01
g/lOminisused, e x t r u s i o n m o l d i n g o f t h e r e s u l t a n t a d h e s i v e r e s i n
compositionmaybe d i f f i c u l t , andthepressurebecomesincreased,
which may exceed the pressure l i m i t of a molding machine. On the
o t h e r hand, i f a polymer having MFR of more than 10 9/10 min is
5 used, t h e r e s u l t a n t adhesive r e s i n composition tends t o provide
an product having a poor uniformity i n i t s thickness, and having
a reduced molecular weight, which may reduce the drop impact
s t r e n g t h i n the case of a m u l t i l a y e r s t r u c t u r e .
[0022]
10
The adhesive r e s i n composition of t h e present invention
comprises t h e modified ethylene polymer ( A l ) i n an amount of 2
t o 40 w t % , p r e f e r a b l y 10 t o 35 w t % , and t h e unmodified ethylene
polymer (A2) i n an amount of 60 t o 98 w t % , p r e f e r a b l y 65 t o 90
15 w t % where (Al)+(A2)=100 w t % , wherein the adhesive r e s i n
composition has a m e l t flow r a t e (MFR) [ASTM D 1238 (19OoC, 2160
1 g load) ] of 0.1 t o 3 9/10 min, p r e f e r a b l y 0.5 t o 2.0 9/10 min and I
a density of 920 t o 930 kg/m3, p r e f e r a b l y 925 t o 929 kg/m3, and
h a s a n e l u t i o n amount of 60 w t % or l e s s , p r e f e r a b l y 55 w t % or l e s s ,
20 a t 85'C o r lower as determined by c r o s s - f r a c t i o n a t i o n
chromatography ( h e r e i n a f t e r a l s o abbreviated as "CFC"), and
p r e f e r a b l y an e l u t i o n amount of 10 w t % or more, more p r e f e r a b l y
40 w t % o r more, a t 85'C or lower as determined by
c r o s s - f r a c t i o n a t i o n chromatography (CFC), andwherein the weight
average molecular weight (Mw) of eluted components at a
temperatureofhigherthan85"Cispreferab1ynot1essthan100,000,
more preferably not less than 120,000.
100231
5 In the adhesive resin composition ofthe present invention,
preferably, the content of the graft-modified unsaturated
carboxylic acid or a derivative thereof is 0.001 to 10 wt%, more
preferably 0.002 to 1 wt%. If the content of the graft-modified
unsaturated carboxylic acid or a derivative thereof is too small,
10 the adhesive power may be insufficient. If the content of the
graft-modified unsaturated carboxylic acid or a derivative
thereof is too large, crosslinking reaction readily occurs, and
it is difficult to stabilize the quality of the adhesive resin
composition.
15 [0024]
Theadhesive resincomposition, byhavingMFRfallingwithin
the above range, has good moldability. In an adhesive resin
composition having MFR of more than 3.0 g/10 min, Mw of eluted
components at a temperature of higher than 85'C as determined by
20 CFC may be less than 100,000.
[0025]
If an adhesive resin composition having a density of less
than 920 kg/m3 is used for, e-g., a gasoline tank, the gasoline
tank may be swollen by gasoline and may have reduced mechanical
strength, and tends to have reduced interlayer adhesive power at
a high temperature of 80°C or higher. On the other hand, if an
adhesive resin compositionhavingadensityofmorethan930 kg/m3
is used, for example together with an ethylene-vinyl acetate
5 copolymer saponification product to form a multilayer structure,
the multilayer structure easily has unstable interlayer adhesive
power, and tends to have reduced low-temperature drop impact
strength. An adhesive resin composition with a density of less
than 920 kg/m3 may have an elution amount of more than 60 wt% at
10 85'C or lower as determined by cross-fractionation
chromatography.
If an adhesive resin composition having an elution amount
of more than 60 wt% at 85'C or lower as determined by CFC is used
15 for a multilayer structure, the multilayer structure has larger
swelling with respect to fuel oils such as gasoline, easily loses
mechanical strength, andeasilyhas poor adhesive strengthat high
temperature.
LO0271
20 If an adhesive resin composition wherein Mw of eluted
components at a temperature of higher than 85'C as determined by
CFC is less than 100,000 is used to form a multilayer structure,
the adhesive resin composition tends to have poor adhesive
strengthathightemperaturewithe.g.,theethylene~vinylacetate
I copolymer saponification product.
[0028]
The elution amount at 85°C or lower as determined by CFC
can be arbitrarily adjusted by a skilled person. For example,
5 an adhesive resin composition obtained by using a modified
ethylene polymer with a high density but with a wide composition
distribution may have an elution amount of more than 60 wt% at
85'C or lower as determined by CFC.
[0029]
10 The adhesive resin composition of the present invention
preferably has an Izod impact strength as measured in accordance
with ASTM D 256 under -40°C atmosphere of 10 k~/m*or more,
preferably 12 k ~ / mor~ m ore. If an adhesive resin composition
having a low Izod impact strength under -40°C atmosphere is used
I 15 to form a multilayer structure, the multilayer structure tends
I I to have reduced low-temperature drop impact strength.
I
I
I [0030]
I
i The adhesive resin composition ofthe present inventionmay
beproducedbyvarious knownmethods. For example, in onemethod,
20 the modified ethylene polymer (Al) is dry-blended with the
unmodified ethylene polymer (A2) each in the above range with a
Henschel mixer, a tumbler blender, a V-blender or the like. In
another method, after dry blending, the mixture is melt kneaded
with a monoaxial extruder, a multiaxial extruder, a Banbury mixer
or the like. In still another method, the components are stirred
and mixed in the presence of a solvent.
[0031]
The adhesive resin composition ofthe present inventionmay
5 comprise, together with the modified ethylene polymer (Al) and
the unmodified ethylene polymer (AZ), an unmodified ethylene
polymer (A3) having a density of 930 to 980 kg/m3. When the
unmodified ethylene polymer (A3) is contained, the amount of the
unmodified ethylene polymer (A3) is preferably not more than 30
10 wt% with respect to 100 wt% of the total amount of the modified
ethylene polymer (Al) , the unmodified ethylene polymer (A2) and
unmodified ethylene polymer (A3). When the unmodified ethylene
polymer (A3) is added, the preparation methods described above
may be adopted.
15 [0032]
The adhesive resin composition ofthe present inventionmay
optionally contain common additives such as antioxidants,
weathering stabilizers, antistatic agents, anti-fogging agents,
antiblocking agents, lubricants, nucleating agent and pigments,
20 other polymers and rubbers, as long as the object of the present
invention is not impaired.
[0033]

Themultilayer structure ofthe present invention comprises
an adhesive layer (A) formed from the above adhesive resin
composition; a polyethylene resin layer (B) formed on at least
one side of the adhesive layer (A) ; and a barrier resin layer (C)
formed on the other side of the adhesive layer (A).
5 [0034]
In the multilayer structure of the present invention,
between the polyethylene resin layer (B) and the adhesive layer
(A), a rigrind layer (D) may be present. The rigrind layer (D)
according to the present invention is prepared by grinding burrs
10 (unnecessary portions) generated when molding the multilayer
structures, collected multilayer structures (scraps), defective
products and the like occurring in molding procedure, and then
optionally by melt kneading the resultant grind product with an
extruder or the like (rigrind). The rigrind layer (D) does not
15 necessarilyneedto be composed ofthe above collectedmultilayer
structures alone, and thus the rigrind layer (D) may be blended
with, for example the polyethylene resin used for the layer (B) ,
to thereby improve mechanical properties.
[0035]
20 The components (A), (B) , (C) and (D) , which constitute the
multilayer structure of the present invention, may contain known
additives such as fillers, stabilizers, lubricants, antistatic
agents, flame retardants, foaming agents, in a range that does
not impair the object of the present invention.
[0036]

The polyethylene r e s i n t h a t c o n s t i t u t e s the polyethylene
r e s i n l a y e r (B) of the m u l t i l a y e r s t r u c t u r e of the present
invention is an ethylene homopolymer, o r a random copolymer of
ethylene and an a - o l e f i n . The copolymerization amount of the
a - o l e f i n , which is not p a r t i c u l a r l y l i m i t e d as long as the
polyethylene r e s i n h a s a d e n s i t y w i t h i n t h e rangedescribedbelow,
is p r e f e r a b l y n o t m o r e t h a n 1 0 mol%, morepreferablynotmorethan
5 mol%. The a - o l e f i n is p r e f e r a b l y an a - o l e f i n having 3 t o 10
carbonatoms, with specificexamplesthereofincludingpropylene,
1-butene, 1-hexene, 4-methyl-1-pentene, 1-octene and 1-decene.
[0037]
The polyethylene r e s i n according t o the present invention
p r e f e r a b l y has a m e l t flow r a t e (MFR) [ASTM D 1238 (temperature:
190°C, load: 2160 g l o a d ) ] of 0.01to 3.0g/10minf morepreferably
0.05 t o 1.5 g/10 min; and p r e f e r a b l y has density of 0.940 t o 0.980
g/cm3, more preferably 0.950 t o 0.970 g/cm3. I f a polyethylene
resinhavingMFRexceedingtheaboverangeis u s e d f o r a l a r g e - s i z e
m u l t i l a y e r s t r u c t u r e , the l a r g e - s i z e m u l t i l a y e r s t r u c t u r e may
h a v e i n s u f f i c i e n t impact s t r e n g t h . Thepolyethylene resinhaving
such MFR may be poor i n blow moldability, and a multilayer
s t r u c t u r e formed from a l a r g e - s i z e blow product may be d i f f i c u l t
t o be molded. On the other hand, a polyethylene r e s i n having MFR
of less than the above range tends to be difficult to be
extrusion-molded. Apolyethylene resin having a density of less
than the above range may provide a multilayer structure having
poor fuel permeability.
5 [0038]
The barrier resin that constitutes the gas barrier resin
layer (C) of the multilayer structure of the present invention
may be various known resins having barrier properties, examples
10 of which are resins excellent in barrier properties including an
ethylenesvinyl acetate copolymer saponification product, a
polyamide resin, a polyvinylidene chloride-based resin and
polyacrylonitrile. Among these, ethylenemvinyl acetate
copolymer saponification product and polyamide resin are
15 preferable.
[0039]

The ethylene-vinyl acetate copolymer saponification
product [also called ethylene-vinyl alcohol copolymer (EVOH)]
20 according to the present invention is preferably a polymer which
is obtained by saponifying an ethylene-vinyl acetate copolymer
having an ethylene content percentage of 15 to 70 mol%, and which
has saponificationdegreeof 90to100%. Asaponificationproduct
having an ethylene content percentage of less than 15 mol%, in
w h i c h i t s m e l t i n g p o i n t is close t o its decompositiontemperature,
may be d i f f i c u l t t o f i n e l y disperse i n the ethylene polymer. A
saponificationproducthavingan ethylene c o n t e n t percentage t h a t
is t o o l a r g e may have reduced b a r r i e r p r o p e r t i e s , and may d e v i a t e
5 from the object of the present invention.
[0040]

Examples ofthepolyamideaccordingtothepresentinvention
i n c l u d e n y l o n 6 , nylon66, nylon 610, nylon12, n y l o n l l , MXDnylon,
10 an amorphous nylon and a copolymerized nylon.
[0041]

Examples o f t h e l a y e r s t r u c t u r e o f t h e multilayer s t r u c t u r e
of the present invention include:
15 three-layer s t r u c t u r e s such as:
polyethylene r e s i n l a y e r (B) [ h e r e i n a f t e r abbreviated as
"PE l a y e r (B) "1 /adhesive l a y e r (A) formed from the adhesive r e s i n
composition [ h e r e i n a f t e r abbreviated as 'adhesive l a y e r
(A)"]/ethylene-vinyl a c e t a t e copolymer saponification product
20 l a y e r [ h e r e i n a f t e r abbreviated as "EVOH layerN] ( C - 1 ) ; and PE
l a y e r (B) /adhesive layer (A) /polyamide r e s i n layer [ h e r e i n a f t e r
abbreviated as "NY layer"] (C-2) ;
four-layer s t r u c t u r e s such as:
PE l a y e r (B) / r i g r i n d l a y e r (D) /adhesive l a y e r (A) /EVOH l a y e r
(c-1) ; PE layer (B) /rigrind layer (D) /adhesive layer (A) / layer
(C) composed of a polyamide resin; PE layer (B) /adhesive layer
(A) /EVOH layer (C-1) /adhesive layer (A) ; and PE layer (B) /adhesive
layer (A) /NY layer (C-2) /adhesive layer (A) ;
5 LO0421
five-layer structures such as:
PE layer (B) /rigrind layer (D) /adhesive layer (A) /EVOH
layer (C-1) /adhesive layer (A) ; PE layer (B) /rigrind layer
ri adhesive layer ri a layer (C-2)/adhesivelayer (A); PElayer
10 (B) /adhesive layer (A) /EVOH layer (C-1) /adhesive layer
! (A) /PE (B) ; and PE layer (B) /adhesive layer (A) /NY layer
1 (C-2) /adhesive layer (A) /PE layer (B) ;
I
[0043]
six-layer structures such as:
15 PE layer (B)/rigrind layer (D)/adhesive layer (A)/EVOH
layer (c-1) /adhesive layer (A) /PE layer (B) ; and PE layer
I (B) /rigrind layer (D) /adhesive layer (A) /NY layer (C-2) /adhesive
layer (A)/PE layer (B); and
[0044]
20 seven-layer structures such as:
PE layer (B) /rigrind layer (D) /adhesive layer (A) /EVOH
layer (c-l)/adhesive layer (A)/rigrind layer (D)/PE layer (B);
and PE layer (B) /rigrind layer (D) /adhesive layer (A) /NY layer
(c-2) /adhesive layer (A) /rigrind layer (D) /PE layer (B) .
[0045]
The multilayer s t r u c t u r e of the present invention may be
produced f o r example by known coextrusion blow moldingmethod as
follows. With a p l u r a l i t y of extruders capable of melting the
5 polyethylene r e s i n used f o r the layer ( B ) , the adhesive r e s i n
composition used f o r the adhesive layer ( A ) , the b a r r i e r r e s i n
used f o r the layer ( C ) , and o p t i o n a l l y the r i g r i n d product used
f o r t h e r i g r i n d layer ( D ) , respective polymers and the l i k e are
molten and laminated, and then a r e coextruded as a molten parison
10 from a t i p from the extruders, and the parison is s e t in a mold.
Thereafter, i n t o the parison, pressurized f l u i d is poured t o mold
a desiredshape. T h e p a r i s o n t h u s m o l d e d i s c o o l e d a n d s o l i d i f i e d ,
and then collected.
[0046]
15 The multilayer s t r u c t u r e of the present invention has
excellent f u e l b a r r i e r p r o p e r t i e s , high impact strength
r e s i s t a n c e , and excellent i n t e r l a y e r adhesive power, d u r a b i l i t y
and h e a t - r e s i s t a n t adhesion, and therefore is s u i t a b l y used
p a r t i c u l a r l y a s automotive f u e l tanks.
20
EXAMPLES
[0047]
The present invention is described i n more d e t a i l with
reference t o Examples, but the present invention is in no way
limited to these Examples, unless going beyond the summary of the
invention.
[0048]
In Examples and Comparative Examples, properties were
5 measured in the methods described below.
(1) MFR (g/10 min)
MFR was measured in accordance with ASTM D 1238 at a
temperature of 190'C under a load of 2160 g.
(2) Density (kg/m3)
10 Density was measured in accordance with ASTM D 1505.
(3) Elution amount at 85'C or lower (g)
I Elution amount at 85'C or lower was measured by
cross-fractionation chromatography (CFC).
(4) Weight average molecular weight (Mw) of eluted components at
15 a temperature of higher than 85'C
By cross-fractionation chromatography, eluted components
I
I at 85'C, at 90°C, at 95°C and at 100'C were collected, and the
weight average molecular weights of the eluted components were
measuredby gelpermeationchromatography (GPC) inaccordancewith
20 an ordinary method.
(5) Izod impact strength (k~/m*)
Izod impact strength was measured in accordance with ASTM
D 256, under -40°C atmosphere.
(6) Initial adhesive strength (N/10 mm)
The initial adhesive strength of the multilayer structure
was measured as follows. A sample of 10 mm in width was cut out
from the side of the four-kind six-layer multilayer structure,
and regarding this sample, the adhesive strength between the
5 adhesive resincomposition [layer (A)] providedonthe innerlayer
side and the ethyleneevinyl acetate copolymer saponification
product layer [layer (C-1) ] was measured both at room temperature
(23 "C) and in a thermostat bath at 80 "C. The peeling measurement
test was performed by T-peeling method at a peeling rate of 50
10 mm/min. Thismeasurementwasperformedfivetimes, andanaverage
value thereof was determined.
(7) Adhesive strength after immersion in fuels (N/10 mm)
The adhesive strength after immersion in fuels was
I determined as follows. In the same manner as in the initial
1
I 15 adhesive strength, a sample of 10 mm in width was cut out from I
the side of the four-kind six-layer multilayer structure. This
sample was immersed in Fuel-C at 65 "C, CE50 at 65'C and light gas
oil at 80°C, for 2000 hours. Thereafter, the adhesive strength
between the adhesive resin composition [layer (A)] provided on
20 the inner layer side and the ethylene-vinyl acetate copolymer
saponification product layer [layer (C-l)] was measured in a
thermostat bath at room temperature (23'C). The peeling
measurement test was performed by T-peeling method at a peeling
rate of 50 mm/min. This measurement was performed five times,
and an average value thereof was determined.
(8) Low-temperature drop impact strength
The low-temperature drop impact strength was determined as
follows. The four-kind six-layer multilayer structure had
5 ethylene glycolenclosedtherein, andcooledto -40°C, anddropped
from a height of 6 m. At this time, whether the multilayer
structure underwent cracking or not was evaluated. This
measurement was performedtwotimes. Whether there was cracking
or not was visually observed. Evaluation results of the
10 low-temperature drop impact strength are indicated in Table 2.
Judgment by observation was conducted as follows.
[0049]
AA: no cracking was observed two times.
[0050]
15 BB: cracking was observed at least one time.
[0051]
The modified ethylene polymers (Al) [hereinafter referred
to as the "modified PE"] and the unmodified ethylene polymer (A2)
[hereinafter referred to as the "PE"] used in the adhesive resin
20 compositions of Examples and Comparative Examples are indicated
in Table 1. In Table, MAH amount refers to the graft amount of
maleic anhydride used as an unsaturated carboxylic acid or a
derivative thereof.
[0052]
[Table 11
Table 1
[Example 11
5 30 wt% of the modified PE-1 and 70 wt% of PE-1 that are
described in Table 1 were melt-kneaded with a monoaxial extruder
at 230°C, to prepare an adhesive resin composition (adhesive
resin-1). Then, the following components were used:
the adhesive resin-1 as a polymer for the layer (A);
10 a high-density polyethylene having a density of 950 kg/m3
and MFR under a load of 2160 g at 190°C of 6 9/10 min, as a polymer
for the layer (B);
an ethylene-vinyl acetate copolymer saponification product
(manufactured by KURARAY CO., LTD., trade name: EVAL FlOlB) , as
15 a polymer for the layer (C) ; and
a rigrind material prepared by grinding the multilayer
structure composed of the layer (A), the layer (B) and the layer
(C), as the layer (D) .
(Al)
(A2)
Unit
Modified PE-1
Modified PE-2
Modified PE-3
Modified PE-4
Modified PE-5
PE-1 (LLDPE)
PE-2 (HDPE)
MFR
9/10 min
0.3
5
0.3
0.5
0.3
1.5
0.8
Density
~ ~ / m ~
950
965
920
940
950
920
950
MAH
amount
wt%
1.0
2.4
1.0
0.5
0.5
-
-
Elution
amount at
85'C or
lower as
determined
by CFC
wt%
0.30
26.67
50.56
5.00
3.00
59.61
0.30
These components were extruded in this order: layer
(B) /layer (Dl /layer (A) /layer (C) /layer (A) /layer (B) , from a
co-extrusion blowing die (die temperature was set at 230°C) as
a parison. The parison was held by a mold, and then into the
5 parison, compressed air was blown. The resultant parison was
cooledandcollected. Thismethodprovideda four-kind six-layer
multilayer structure having a thickness percentage proportion of
13/40/2/3/2/40, a total thickness of 6 mrn and a volume of 40 L.
[0053]
10 Properties of the resultant multilayer structure were
measured by the methods described above. Results are set forth
in Table 2.
[0054]
[Example 21
15 The procedure was performed in the same manner as Example
1, except that the adhesive resin-1 used in Example 1 was replaced
withtheadhesiveresincompositiondescribedinTable 2 (adhesive
resin-2), to obtain a four-kind six-layer multilayer structure.
[0055]
20 Properties of the resultant multilayer structure were
measured by the methods described above. Results are set forth
in Table 2.
LO0561
[Example 31
The procedure was performed in the same manner as Example
I 1, except that the adhesive resin-1 used in Example 1 was replaced
withtheadhesive resincompositiondescribedinTable 2 (adhesive
resin-3), to obtain a four-kind six-layer multilayer structure.
5 [0057]
Properties of the resultant multilayer structure were
measured by the methods described above. Results are set forth
in Table 2.
[0058]
10 [Comparative Example 11
The procedure was performed in the same manner as Example
1, except that the adhesive resin-1 used in Example 1 was replaced
withtheadhesiveresincompositiondescribedinTable2 (adhesive
resin-4), to obtain a four-kind six-layer multilayer structure.
15 [0059]
Properties of the resultant multilayer structure were
measured by the methods described above. Results are set forth
in Table 2.
[0060]
20 [Comparative Example 21
The procedure was performed in the same manner as Example
1, except that the adhesive resin-1 used in Example 1 was replaced
withthe adhesive resincompositiondescribedinTable 2 (adhesive
resin-5), to obtain a four-kind six-layer multilayer structure.
Properties of the resultant multilayer structure were
measured by the methods described above. Results are set forth
in Table 2.
5 [0062]
[Comparative Example 31
The procedure was performed in the same manner as Example
1 except that the adhesive resin-1 used in Example 1 was replaced
withtheadhesiveresincompositiondescribedinTable2 (adhesive
10 resin-6), to obtain a four-kind six-layer multilayer structure.
[0063]
Properties of the resultant multilayer structure were
measured by the methods described above. Results are set forth
in Table 2.
15 [0064]
[Comparative Example 41
The procedure was performed in the same manner as Example
1 except that the adhesive resin-1 used in Example 1 was replaced
with the adhesive resin composition describe din Table 2 (adhesive
20 resin-7), to obtain a four-kind six-layer multilayer structure.
[0065]
Properties of the resultant multilayer structure were
measured by the methods described above. Results are set forth
in Table 2.
[0066]
[Table 21
Table 2
h
(A1
(A2
Properties
Initial
adhesive
strength
Adhesive
strength
after
immersion
in fuels
Dropping
test
Modified PE-1
Modified PE-2
Modified PE-3
Modified PE-4
Modified PE-5
PE-1 (LLDPE)
PE-2 (HDPE)
Density
MFR
MAH content
Elution amount at
85°C or lower
Mw of eluted
components at 85'C
Mw of eluted
components at 90°C
Mw of eluted
components at 95°C
Mw of eluted
components at 100°C
Izod at -40'C
23°C atmosphere
80°C atmosphere
Fuel-C/65"C
Light gas oil/80°C
-4O'C
Unit
wt%
kg /m3
g/10 min
wt%
wt%
-
-
-
-
k ~/m'
N/10 mm
N/10 mm
Ex. 1
Adhesive
resin-1
3 0
7 0
92 8
0.9
0.3
5 3
126500
142000
150200
164200
12
232
215
152
167
AA
Ex.2
Adhesive
resin-2
15
70
15
92 8
1.1
0.15
5 1
121000
145600
158200
162300
12
218
203
131
14 3
AA
Ex.3
Adhesive
resin-3
15
8 5
922
0.9
0.15
59
124300
132500
142300
142200
14
196
178
11 9
131
AA
Comp .
Ex.1
Adhesive
resin-4
5
9 5
923
1.0
0.12
67
121000
129700
150800
71140
12
92 pppp
9 6
9 2
9 6
AA
Comp .
Ex.2
Adhesive
resin-5
15
8 5
922
1.0
0.15
7 2
120600
121200
131100
90160
12
105
5 2
86
86
AA
Comp .
Ex.3
Adhesive
resin-6
10 0
940
0.5
0.5
5
90500
94100
102400
154100
7
11 8
Comp .
Ex. 4
Adhesive
resin-7
100
950
0.3
0.5
3
89520
91200
92230
158600
5
112
109
92
10 1
BB
147
11 5
102
B B
[Evaluation results]
I As shown in Table 2, the multilayer structures obtained in I 1
I Example 1 and Example 2 exhibit superior results in all the items
I
of the evaluation. As compared with the multilayer structures
5 obtained in Example 1 and Example 2 having less elution amount
at 85'C or lower as determined by CFC, the multilayer structure
obtained in Example 3, which has an elution amount of 59 wt% at
85'C or lower as determined by CFC, has a slightly lower adhesive
strength, but the adhesive strength is sufficiently high to use.
10 [0067]
On the other hand, the multilayer structures obtained in
Comparative Example 1 and Comparative Example 2, though composed
of the composition containing the modified ethylene polymer with
highdensityandtheunmodifiedethylenepolymerwithlowdensity,
15 have an uncontrolled elution amount at 85'C or lower, i.e., an
elution amount of more than 60 wt% at 85'C or lower as determined
by CFC, resulting in having lower initial adhesive strength and
lower adhesive strength after immersion in fuels. Themultilayer
structures obtained in Comparative Example 3 and Comparative
20 Example 4 have a density of more than 930 kg/m3 and an Izod impact
strength under -40°C atmosphere of not more than 10 k ~ / m ~ ,
resultinginhavingreducedlow-temperaturedropimpactstrength.
INDUSTRIAL APPLICABILITY
[0068]
The adhesive resin composition can meet the demand for
5 higher performance which is required for automotive fuel tanks
as a result of diesel automobiles adopting a common rail system,
by e.g., maintaining long-term durability when in contact with
high-temperature fuels, and preventing the delamination of
respective layers and the delamination at the pinch-off part in
10 the multilayer structure for long hours when in contact with
high-temperature fuels, and therefore can greatly contribute to
e.g., providing lightweight automobiles.

CLAIMS
1. An adhesive resin composition comprising 2 to 40 wt%
of a modified ethylene polymer (Al) which is graft-modified with
an unsaturated carboxylic acid or a derivative thereof and which
5 has a density of 930 to 980 kg/m3, and 60 to 98 wt% of an unmodified
ethylene polymer (A2) having a density of 910 to 929 kg/m3 where
(Al) t (A2) =I00 wt%, wherein the adhesive resin composition has a
melt flow rate (MFR) [ASTM D 1238 (temperature: 19O0C, 2160 g
load) ] of 0.1 to 3 g/10 min and a density of 920 to 930 kg/m3,
10 and has an elution of 60 wt% or less at 85'C or lower as determined
by cross-fractionation chromatography.
2. The adhesive resin composition according to Claim 1,
which further comprises 0 to 30 wt% of an unmodified ethylene
15 polymer (A3) having a density of 930 to 980 kg/m3 where
(Al)+(A2)t(A3)=100 wt%.
3. The adhesive resin composition according to Claim 1,
wherein the graft amount of the unsaturated carboxylic acid or
20 a derivative thereof is 0.1 to 5 wt%.
4. The adhesive resin composition according to Claim 1,
which has an Izod impact strength as measured in accordance with
ASTM D 256 under -40°C atmosphere of 10 k ~ / omr~ m ore.
(A) formed from the adhesive resin composition according to any
one of Claims 1to 4, apolyethylene resin layer (B), andapolymer
5 layer (C) selected fnom the group consisting of an ethylene-vinyl
acetate copolymer saponification product and a polyamide.
6. The multilayer structure according to Claim 5,
wherein the, ethylenemvinyl acetate copolymer saponification
10 product is a polymer having a saponification degree of 90 to 100% I , which is obtained by saponifying an ethylene-vinyl acetate
copolymer having an ethylene content percentage of 15 to 70 mol%.
1 T 7. The multilayer structure according to Claim 5,
I
I I 15 wherein the polyamide is at least any of nylon 6, nylon 1 66, nylon
610, nylon 12, nylon 11, MXD nylon, an amorphous nylon and a
copolymerized nylon.
8. The multilayer structure according to Claim 5, which
20 comprises a rigrind layer (D) between the layer (B) and the layer
(A) -
9. An automotive fuel tank comprising the multilayer
structure according to any-one of CJ-as 5 t.o R - - -- -
- - - - ----- -- ------ -
Dated this 13' day of September, 2013
[NEHA SRTVASTAVA] a
OF REMFRY & SAGAR
ATTORNEY FOR THE APPLICANTIS]