U.S. patent application number 10/394571 was filed with the patent office on 2004-04-22 for method of producing a shaped article having excellent barrier properties.
This patent application is currently assigned to KURARAY CO. LTD. Invention is credited to Chan, Hong-Ta James, Hayashi, Nahoto, Lambert, William Scott, Watanabe, Tomoyuki.
Application Number | 20040076780 10/394571 |
Document ID | / |
Family ID | 27085647 |
Filed Date | 2004-04-22 |
United States Patent
Application |
20040076780 |
Kind Code |
A1 |
Chan, Hong-Ta James ; et
al. |
April 22, 2004 |
Method of producing a shaped article having excellent barrier
properties
Abstract
A powder of a barrier material (B) is, after having been melted,
applied to a substrate of a polyolefin (A) according to flame spray
coating process to give a shaped article, in which the barrier
material (B) firmly adheres to the polyolefin (A) even when the
surface of the substrate is not subjected to primer treatment. The
shaped article is favorable to components to fuel containers, fuel
tanks for automobiles, fuel pipes, etc.
Inventors: |
Chan, Hong-Ta James;
(Pasadena, TX) ; Watanabe, Tomoyuki;
(Kurashiki-city, JP) ; Lambert, William Scott;
(Pasadena, TX) ; Hayashi, Nahoto; (Pasadena,
TX) |
Correspondence
Address: |
OBLON, SPIVAK, MCCLELLAND, MAIER & NEUSTADT, P.C.
1940 DUKE STREET
ALEXANDRIA
VA
22314
US
|
Assignee: |
KURARAY CO. LTD
Okayama
JP
|
Family ID: |
27085647 |
Appl. No.: |
10/394571 |
Filed: |
March 24, 2003 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10394571 |
Mar 24, 2003 |
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09813890 |
Mar 22, 2001 |
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09813890 |
Mar 22, 2001 |
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09608011 |
Jun 30, 2000 |
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Current U.S.
Class: |
428/35.7 |
Current CPC
Class: |
Y10T 428/26 20150115;
Y10T 428/31938 20150401; Y10T 428/1352 20150115; B05D 7/54
20130101; Y10T 428/1379 20150115; Y10T 428/1383 20150115; B05D 1/10
20130101; Y10T 428/31504 20150401 |
Class at
Publication: |
428/035.7 |
International
Class: |
B65D 001/00 |
Claims
What is claimed is:
1. A method of producing a shaped article, which comprises applying
a powder of a barrier material (B), after melting it, to a
substrate of a polyolefin (A) according to a flame spray coating
process.
2. The method of producing a shaped article as claimed in claim 1,
which is characterized in that the thickness of the coating film of
the barrier material (B) falls between 1 and 500 .mu.m.
3. The method of producing a shaped article as claimed in claim 1,
which comprises applying a powder of a carboxylic acid-modified or
boronic acid-modified polyolefin, after melting it, to a substrate
of a polyolefin (A) according to a flame spray coating process,
followed by applying a powdery coating substance of a barrier
material (B), after melting it, to the resulting carboxylic
acid-modified or boronic acid-modified polyolefin layer according
to a flame spray coating process.
4. The method of producing a shaped article as claimed in claim 3,
which is characterized in that the thickness of the coating film of
the barrier material (B) falls between 1 and 500 .mu.m, and the
thickness of the coating film of the carboxylic acid-modified or
boronic acid-modified polyolefin falls between 1 and 500 .mu.m.
5. The method of producing a shaped article as claimed in claim 3,
wherein the carboxylic acid modified polyolefin is at least one
selected from a group consisting of ethylene-methacrylic acid
copolymers (EMAA), ethylene-acrylic acid copolymers (EAA),
ethylene-methyl methacrylate copolymers (EMMA), maleic
anhydride-modified polyethylenes, maleic anhydride-modified
polypropylenes and their metal salts.
6. The method of producing a shaped article as claimed in claim 3,
wherein the carboxylic acid modified polyolefin is
ethylene-methacrylic acid copolymers (EMAA) and their metal
salts.
7. The method of producing a shaped article as claimed in claim 1,
which comprises applying a powder of a barrier material (B), after
melting it, to a substrate of a polyolefin (A) according to a flame
spray coating process, followed by applying a powder of a
thermoplastic resin (C) having an elastic modulus at 20.degree. C.
of at most 500 kg/cm.sup.2, after melting it, to the resulting
layer of the barrier material (B) according to a flame spray
coating process.
8. The method of producing a shaped article as claimed in claim 7,
which is characterized in that the thickness of the coating film of
the barrier material (B) falls between 1 and 500 .mu.m, and the
thickness of the coating film of the thermoplastic resin (C) falls
between 1 and 500 .mu.m.
9. The method of producing a shaped article as claimed in claim 5,
wherein the thermoplastic resin (C) is copolymers of aromatic vinyl
compounds and conjugated diene compounds, and ethylene-propylene
copolymer elastomers (EPR).
10. A method of producing a shaped article, which comprises
applying a powder of a thermoplastic resin (C) having an elastic
modulus at 20.degree. C. of at most 500 kg/cm.sup.2, after melting
it, to a substrate of a polyolefin (A) according to a flame spray
coating process, followed by applying a powder of a barrier
material (B), after melting it, to the resulting layer of the
thermoplastic resin (C) according to a flame spray coating
process.
11. The method of producing a shaped article as claimed in claim
10, which is characterized in that the thickness of the coating
film of the barrier material (B) falls between 1 and 500 .mu.m, and
the thickness of the coating film of the thermoplastic resin (C)
falls between 1 and 500 .mu.m.
12. The method of producing a shaped article as claimed in claim
10, wherein the thermoplastic resin (C) is copolymers of aromatic
vinyl compounds and conjugated diene compounds, and
ethylene-propylene copolymer elastomers (EPR).
13. The method of producing a shaped article as claimed in claim 1,
wherein the polyolefin (A) is a high-density polyethylene.
14. The method of producing a shaped article as claimed in claim 1,
wherein the barrier material (B) is a thermoplastic resin through
which the gasoline permeation amount is at most 100 g.multidot.20
.mu.m/m.sup.2.multidot.day (measured at 40.degree. C. and 65% RH)
or the oxygen transmission rate is at most 100 cc.multidot.20
.mu.m/m.sup.2.multidot.day.multidot.atm (measured at 20.degree. C.
and 65% RH).
15. The method of producing a shaped article as claimed in claim 1,
wherein the barrier material (B) is at least one selected from a
group consisting of ethylene-vinyl alcohol copolymers, polyamides,
aliphatic polyketones and polyesters.
16. The method of producing a shaped article as claimed in claim 1,
wherein the barrier material (B) is ethylene-vinyl alcohol
copolymers having an ethylene content of from 5 to 60 mol % and a
degree of saponification of at least 85%.
17. The method of producing a shaped article as claimed in claim 1,
wherein the barrier material (B) is a resin composition comprising
from 50 to 95% by weight of an ethylene-vinyl alcohol copolymer and
from 5 to 50% by weight of a boronic acid-modified polyolefin.
18. The method of producing a shaped article as claimed in claim 1,
wherein the barrier material (B) is a resin composition comprising
from 50 to 95% by weight of an ethylene-vinyl alcohol copolymer and
from 5 to 50% by weight of multi-layered polymer particles.
19. A shaped article produced by applying a powder of a barrier
material (B), after melting it, to at least a part of the surface
of a substrate of a polyolefin (A) according to a flame spray
coating process.
20. The shaped article as claimed in claim 19, which is
characterized in that the thickness of the coating film of the
barrier material (B) falls between 1 and 500 .mu.m.
21. The shaped article as claimed in claim 19, which is a product
of injection molding.
22. The shaped article as claimed in claim 19, which is a head of a
tubular container.
23. The shaped article as claimed in claim 19, which is a component
for fuel containers.
24. The shaped article as claimed in claim 19, which is a
multi-layered container that comprises an interlayer of a barrier
resin (D) and inner and outer layers of a polyolefin (A).
25. The multi-layered container as claimed in claim 22, which is a
fuel container.
26. The multi-layered container as claimed in claim 22, which is a
fuel tank for automobiles.
27. A multi-layered fuel container that comprises an interlayer of
a barrier resin (D) and inner and outer layers of a polyolefin (A),
of which the portion having poor barrier properties is coated with
a melted powder of a barrier material (B) according to a flame
spray coating process.
28. The multi-layered fuel container as claimed in claim 27,
wherein the portion having poor barrier properties is at least one
selected from a group consisting of the cutting face of the
pinch-off part of the co-extrusion blow-molded container, the
cutting face of the heat seal part of the co-extrusion thermoformed
container, the cutting face of the opening formed through the body
of the container, thin area of the container, and the component for
the container.
29. The multi-layered fuel container as claimed in claim 25, which
is a co-extrusion blow-molded fuel container.
30. The co-extrusion blow-molded fuel container as claimed in claim
29, of which the cutting face of the pinch-off part is coated with
a melted powder of a barrier material (B) according to a flame
spray coating process.
31. The co-extrusion blow-molded fuel container as claimed in claim
29, of which the cutting face of the pinch-off part is coated with
a melted powder of a carboxylic acid-modified or boronic
acid-modified polyolefin according to a flame spray coating
process, and followed by applying a powder of a barrier material
(B) to the resulting layer of a carboxylic acid-modified or boronic
acid-modified polyolefin according to a flame spray coating
process.
32. The multi-layered fuel container as claimed in claim 25, which
is a co-extrusion thermoformed fuel container.
33. The co-extrusion thermoformed fuel container as claimed in
claim 32, of which the cutting face of the heat seal part is coated
with a melted powder of a barrier material (B) according to a flame
spray coating process.
34. The co-extrusion blow-molded fuel container as claimed in claim
32, of which the cutting face of the heat seal part is coated with
a melted powder of a carboxylic acid-modified or boronic
acid-modified polyolefin according to a flame spray coating
process, and followed by applying a powder of a barrier material
(B) to the resulting layer of a carboxylic acid-modified or boronic
acid-modified polyolefin according to a flame spray coating
process.
35. The multi-layered fuel container as claimed in claim 25, which
is constructed to have an opening through its body and in which the
cutting face of the layer existing outside the interlayer is coated
with a melted powder of a barrier material (B) according to a flame
spray coating process.
36. The multi-layered fuel container as claimed in claim 25, which
is constructed to have an opening through its body with a component
attached to the opening.
37. The multi-layered fuel container as claimed in claim 26,
wherein the component is coated with a melted powder of a barrier
material (B) according to a flame spray coating process.
38. The multi-layered fuel container as claimed in claim 25, which
is constructed to have an opening through its body with a component
attached to the opening by heat sealing.
39. The co-extrusion blow-molded fuel container as claimed in claim
30, which is constructed to have an opening through its body with a
component attached to the opening and in which the component is
coated with a melted powder of a barrier material (B) according to
a flame spray coating process.
40. The co-extrusion thermoformed fuel container as claimed in
claim 33, which is constructed to have an opening through its body
with a component attached to the opening and in which the component
is coated with a melted powder of a barrier material (B) according
to a flame spray coating process.
41. The multi-layered fuel container as claimed in claim 25, which
is constructed to have an opening through its body with a component
attached to the opening and in which the component is coated with a
melted powder of a barrier material (B) according to a flame spray
coating process.
42. The multi-layered fuel container as claimed in claim 41, which
is the container is a co-extrusion blow-molded fuel container or a
co-extrusion thermoformed fuel container.
43. The shaped article as claimed in claim 19, which is a
multi-layered pipe that comprises an interlayer of a barrier resin
(D) and inner and outer layers of a polyolefin (A).
44. The multi-layered pipe as claimed in claim 43, which is a fuel
pipe or a floor heating pipe.
45. The shaped article as claimed in claim 19, which is a connector
of floor heating pipes that comprises a polyolefin (A).
46. The shaped article as claimed in claim 19, wherein the
polyolefin (A) is a high-density polyethylene.
47. The shaped article as claimed in claim 19, wherein the barrier
material (B) is a thermoplastic resin through which the gasoline
permeation amount is at most 100 g.multidot.20
.mu.m/m.sup.2.multidot.day (measured at 40.degree. C. and 65% RH)
and/or the oxygen transmission rate is at most 100 cc.multidot.20
.mu.m/m.sup.2.multidot.day.multidot.at- m (measured at 20.degree.
C. and 65% RH).
48. The shaped article as claimed in claim 19, wherein the barrier
material (B) is at least one selected from a group consisting of
ethylene-vinyl alcohol copolymers, polyamides, aliphatic
polyketones and polyesters.
49. The shaped article as claimed in claim 19, wherein the barrier
material (B) is ethylene-vinyl alcohol copolymers having an
ethylene content of from 5 to 60 mol % and a degree of
saponification of at least 85%.
50. The shaped article as claimed in claim 19, wherein the barrier
material (B) is a resin composition comprising from 50 to 95% by
weight of an ethylene-vinyl alcohol copolymer and from 5 to 50% by
weight of a boronic acid-modified polyolefin.
51. The shaped article as claimed in claim 19, The method of
producing a shaped article as claimed in claim 1, wherein the
barrier material (B) is a resin composition comprising from 50 to
95% by weight of an ethylene-vinyl alcohol copolymer and from 5 to
50% by weight of multi-layered polymer particles.
52. The multi-layered fuel container as claimed in claim 25,
wherein the barrier resin (D) is at least one selected from a group
consisting of ethylene-vinyl alcohol copolymers, polyamides and
aliphatic polyketones.
53. The multi-layered fuel container as claimed in claim 25,
wherein the barrier resin (D) is ethylene-vinyl alcohol copolymers
having an ethylene content of from 5 to 60 mol % and a degree of
saponification of at least 85%.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a method of producing a
shaped article, which comprises applying a powder of a barrier
material (B), after melting it, to a shaped article of a polyolefin
(A) according to a flame spray coating process. The invention also
relates to a shaped article produced by applying a powder of a
barrier material (B), after melting it, to at least a part of the
surface of a substrate of a polyolefin (A) according to a flame
spray coating process.
[0003] 2. Description of the Background
[0004] Polyolefin is a resin having good water resistance,
mechanical strength and moldability, and is molded in melt into
various shapes of-films, bottles and others of many applications.
On the other hand, for making shaped articles of such polyolefin
have barrier properties and oil resistance, preferred are
embodiments of multi-layered shaped articles which comprises a
polyolefin layer and a barrier material layer. However, barrier
materials of typically ethylene-vinyl alcohol copolymer
(hereinafter referred to as EVOH) and others are not all the time
satisfactorily adhesive to polyolefin, and the multi-layered shaped
articles often undergo interlayer peeling between the polyolefin
layer and the barrier layer.
[0005] To solve the problem, various types of adhesive resins have
been developed, including maleic anhydride-modified polyolefins
(polyethylene, polypropylene, ethylene-vinyl acetate copolymers),
ethylene-ethyl acrylate-maleic anhydride copolymers, etc. With
these adhesive resins, multi-layered shaped articles of polyolefin
and a barrier material are formed through co-extrusion or the like,
in which the polyolefin substrate is laminated with the barrier
material via the adhesive resin therebetween, and they have many
applications.
[0006] However, there is a problem in using adhesive resins as
above, since it is required an additional step in the production
process and therefore increase the production costs. For
complicated shapes, preferred is injection molding. However, it is
not easy to mold multi-layered shapes by injection. It is often
difficult to obtain injection-molded multi-layer articles of
polyolefin laminated with a barrier material via an adhesive resin
therebetween, and the shape of such injection-molded multi-layer
articles is often limited.
[0007] For making such complicated shapes have barrier properties,
known is one method of coating the shapes with a solution of a
barrier material. One example of the method is disclosed in U.S.
Pat. No. 4,487,789, in which the technique disclosed comprises
forming a layer of a solution of EVOH dissolved in a mixed solvent
of alcohol-water, on a substrate, followed by drying it to form a
film thereon. In general, however, the method often requires
complicated primer treatment and even adhesive treatment for
ensuring sufficient interlayer adhesion strength between the
substrate and EVOH, therefore resulting in the increase in the
production costs.
[0008] Japanese Patent Laid-Open No. 115472/1991 discloses a
powdery coating resin of EVOH, and plastics are referred to therein
as one example of the substrates to be coated with the powdery
coating resin. However, the laid-open specification says nothing
about a technique of applying the powdery coating resin of EVOH to
polyolefins.
[0009] Co-extrusion blow-molded plastic containers are favorably
used these days for storing therein various types of fuel such as
gasoline. One example is a fuel tank for automobiles. For the
plastic material for such containers, polyethylene (especially
very-high-density polyethylene) is expected as being inexpensive
and having good moldability and workability and good mechanical
strength. However, polyethylene fuel tanks are known to have a
drawback in that vapor or liquid of gasoline stored therein readily
evaporates away in air through the polyethylene wall of the
containers.
[0010] To overcome the drawback, disclosed is a method of applying
a stream of halogen gas (fluorine, chlorine, bromine), sulfur
trioxide (SO.sub.3) or the like into polyethylene containers to
thereby halogenate or sulfonate the inner surface of the
containers. Also disclosed is a method of forming a multi-layered
structure of polyamide resin and polyethylene resin (Japanese
Patent Laid-Open No. 134947/1994, U.S. Pat. No. 5,441,781). Apart
from these, known is a method of forming a multi-layered structure
of EVOH resin and polyethylene resin (U.S. Pat. No. 5,849,376, EP
759,359). For improving its gasoline barrier properties, known is a
multi-layered fuel tank in which the barrier layer is shifted to
the inner layer (Japanese Patent Laid-Open No. 29904/1997, EP
742,096).
[0011] However, the fuel containers produced according to the
above-mentioned methods are not as yet all the time satisfactory
for preventing gasoline permeation through them. The recent
tendency in the art is toward gasoline saving and global
environment protection, for which is therefore desired a method of
further reducing gasoline permeation through fuel tanks.
[0012] As in the above, it is desired to develop a method of
producing shaped articles having excellent barrier properties,
which is applicable even to complicated shapes of a polyolefin
substrate without requiring any complicated primer treatment. Of
such shaped articles having excellent barrier properties, more
desired are those having a multi-layered structure of polyolefin
and a barrier material and effective for preventing gasoline
permeation therethrough.
SUMMARY OF THE INVENTION
[0013] The present invention is to provide a method of producing
shaped articles having excellent barrier properties, which is
applicable even to complicated shapes of a polyolefin substrate
without requiring any complicated primer treatment. Specifically,
the invention is a method of producing a shaped article, which
comprises applying a powder of a barrier material (B), after
melting it, to a substrate of a polyolefin (A) according to a flame
spray coating process. The invention also relates to a shaped
article produced by applying a powder of a barrier material (B),
after melting it, to at least a part of the surface of a substrate
of a polyolefin (A) according to a flame spray coating process.
[0014] Another preferred embodiment of the method of producing a
shaped article of the invention comprises applying a powder of a
carboxylic acid-modified or boronic acid-modified polyolefin, after
melting it, to a substrate of a polyolefin (A), followed by
applying a powder of a barrier material (B), after melting it, to
the resulting carboxylic acid-modified or boronic acid-modified
polyolefin layer.
[0015] Still another preferred embodiment of the method of
producing a shaped article of the invention comprises applying a
powder of a barrier material (B), after melting it, to a substrate
of a polyolefin (A), followed by applying a powder of a
thermoplastic resin (C) having an elastic modulus at 20.degree. C.
of at most 500 kg/cm.sup.2, after melting it, to the resulting
layer of the barrier material (B).
[0016] Also preferred is an embodiment that comprises applying a
powder of a thermoplastic resin (C) having an elastic modulus at
20.degree. C. of at most 500 kg/cm.sup.2, after melting it, to a
substrate of a polyolefin (A), followed by applying a powder of a
barrier material (B), after melting it, to the resulting layer of
the thermoplastic resin (C).
[0017] In a preferred embodiment of the invention, the polyolefin
(A) is a high-density polyethylene.
[0018] In another preferred embodiment of the invention, the
barrier material (B) is at least one selected from a group
consisting of ethylene-vinyl alcohol copolymers, polyamides,
aliphatic polyketones and polyesters.
[0019] In still another preferred embodiment of the invention, the
barrier material (B) is a thermoplastic resin through which the
gasoline permeation amount is at most 100 g.multidot.20
.mu.m/m.sup.2.multidot.day (measured at 40.degree. C. and 65% RH)
and/or the oxygen transmission rate is at most 100 cc.multidot.20
.mu.m/m.sup.2.multidot.day.multidot.at- m (measured at 20.degree.
C. and 65% RH).
[0020] In still another preferred embodiment of the invention, the
barrier material (B) is a resin composition comprising from 50 to
95% by weight of an ethylene-vinyl alcohol copolymer and from 5 to
50% by weight of a boronic acid-modified polyolefin. In still
another preferred embodiment of the invention, the barrier material
(B) is a resin composition comprising from 50 to 95% by weight of
an ethylene-vinyl alcohol copolymer and from 5 to 50% by weight of
multi-layered polymer particles.
[0021] The invention also relates to a shaped article produced by
applying a powder of a barrier material (B), after melting it, to
at least a part of the surface of a substrate of a polyolefin (A)
according to a flame spray coating process. In a preferred
embodiment of the invention, the shaped article produced through
injection molding. In other words, the preferred embodiment of the
shaped article is a product of injection molding.
[0022] Another preferred embodiment of the shaped article is a head
of a tubular container. Still another preferred embodiment of the
shaped article is a component for fuel containers.
[0023] Another preferred embodiment of the shaped article is a
multi-layered container that comprises an interlayer of a barrier
resin (D) and inner and outer layers of a polyolefin (A). More
preferably, the above-mentioned multi-layered container is a
co-extrusion blow-molded container or a co-extrusion thermoformed
container. Even more preferably, the co-extrusion blow-molded
container or the co-extrusion thermoformed container is a fuel
container. Still more preferably, the co-extrusion blow-molded fuel
container or the co-extrusion thermoformed container has a laminate
structure of such that the interlayer of a barrier resin (D) is
laminated with inner and outer layers of high-density polyethylene
via an adhesive resin layer of a carboxylic acid-modified
polyolefin.
[0024] In still another preferred embodiment of the shaped article,
the barrier resin (D) is at least one selected from a group
consisting of ethylene-vinyl alcohol copolymers, polyamides and
aliphatic polyketones. In still another preferred embodiment of the
shaped article, the barrier resin (D) is a thermoplastic resin
through which the gasoline permeation amount is at most 100
g.multidot.20 .mu.m/m.sup.2.multidot.day (measured at 40.degree. C.
and 65% RH) and/or the oxygen transmission rate is at most 100
cc.multidot.20 .mu.m/m.sup.2.multidot.day.multidot.atm (measured at
20.degree. C. and 65% RH).
[0025] Still another preferred embodiment of the shaped article of
the invention is a multi-layered container comprising an interlayer
of a barrier resin (D) and inner and outer layers of a polyolefin
(A), of which the cutting face of the pinch-off part is coated with
a melted powder of a barrier material (B). More preferably, the
multi-layered container is a co-extrusion blow-molded fuel
container or a co-extrusion thermoformed fuel container.
[0026] Still another preferred embodiment of the shaped article of
the invention is a multi-layered container comprising an interlayer
of a barrier resin (D) and inner and outer layers of a polyolefin
(A), which is constructed to have an opening through its body and
in which the cutting face of the layer existing outside the
interlayer is coated with a melted powder of a barrier material
(B). More preferably, the multi-layered container is a co-extrusion
blow-molded fuel container or a co-extrusion thermoformed fuel
container.
[0027] Still another preferred embodiment of the shaped article of
the invention is a multi-layered fuel container comprising an
interlayer of a barrier resin (D) and inner and outer layers of a
polyolefin (A), which is constructed to have an opening through its
body with a component attached to the opening and in which the
component is coated with a melted powder of a barrier material
(B).
BRIEF DESCRIPTION OF DRAWINGS
[0028] FIG. 1 is a view showing fuel transmission through the
pinch-off part of a co-extrusion blow-molded fuel container (in
which 11 indicates a polyolefin (A); and 12 indicates a barrier
resin (D)).
[0029] FIG. 2 is a view showing fuel transmission through the
opening of the body of a co-extrusion blow-molded fuel container
equipped with a component to the opening (in which 21 indicates a
polyolefin (A); 22 indicates a barrier resin (D); 23 indicates a
connector to the fuel container; and 24 indicates a fuel pipe).
[0030] FIG. 3 is a view showing an injection-molded, cylindrical
single-layered article (connector-like article).
[0031] FIG. 4 is a view showing one embodiment of using a
connector-like article (in which 41 indicates a connector-like
article; 42 indicates the body of a container; and 43 indicates a
pipe).
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0032] Preferably, the polyolefin (A) for use in the invention is
any of olefin homopolymers or copolymers such as linear low-density
polyethylene, low-density polyethylene, medium-density
polyethylene, high-density polyethylene, ethylene-vinyl acetate
copolymers, ethylene-propylene copolymers, polypropylene,
propylene-.alpha.-olefin copolymers (with .alpha.-olefin having
from 4 to 20 carbon atoms), polybutene, polypentene, etc.;
carboxylic acid-modified polyolefins, boronic acid-modified
polyolefins, etc. In case where the shaped article of the invention
is a component for fuel containers or a multi-layered fuel
container (preferably, a co-extrusion blow-molded fuel container or
a co-extrusion thermoformed fuel container), high-density
polyethylene is especially preferred for the polyolefin (A) in view
of its stiffness, impact resistance, moldability, draw-down
resistance and gasoline resistance.
[0033] Preferably, the lowermost limit of the melt flow rate (MFR,
measured at 190.degree. C. under a load of 2160 g) of the
polyolefin (A) for use in the invention is at least 0.01 g/10 min,
more preferably at least 0.05 g/10 min, even more preferably at
least 0.1 g/10 min. The uppermost limit of MFR thereof is
preferably at most 50 g/10 min, more preferably at most 30 g/10
min, most preferably at most 10 g/10 min.
[0034] The substrate of a polyolefin (A) in the invention may be a
single layer or may also be a multilayer which comprises a
plurality of different resins. For improving the adhesiveness
between the barrier material (B) and the substrate of a polyolefin
(A), it is desirable that the substrate of a polyolefin (A) is
multi-layered structure comprising a substantially non-modified
polyolefin and a carboxylic acid-modified or boronic acid-modified
polyolefin. A barrier material (B) is, after having been melted,
applied to the layer of a carboxylic acid-modified or boronic
acid-modified polyolefin of the multi-layered structure, thereby
ensuring good adhesiveness between the two layers. An especially
preferred embodiment of the multi-layered structure comprises a
layer of high-density polyethylene and a layer of a carboxylic
acid-modified or boronic acid-modified polyolefin.
[0035] The carboxylic acid-modified polyolefin for use in the
invention is a copolymer comprising an olefin, especially an
.alpha.-olefin and at least one comonomer selected from a group
consisting of unsaturated carboxylic acids, unsaturated
carboxylates and unsaturated carboxylic acid anhydrides, and it
includes polyolefins having a carboxyl group in the molecule and
those in which all or a part of the carboxyl group forms a metal
salt. The base polyolefin of the carboxylic acid-modified
polyolefin may be any type of polyolefins, and its preferred
examples are polyethylene (e.g., high-density polyethylene (HDPE),
low-density polyethylene (LDPE), linear low-density polyethylene
(LLDPE), very-low-density polyethylene (VLDPE), etc.),
polypropylene, propylene copolymers, ethylene-vinyl acetate
copolymers, etc.
[0036] The unsaturated carboxylic acids include acrylic acid,
methacrylic acid, maleic acid, monomethyl maleate, monoethyl
maleate, itaconic acid, etc.; and especially preferred is acrylic
acid or methacrylic acid. The unsaturated carboxylic acid content
of the modified polyolefin preferably falls between 0.5 and 20 mol
%, more preferably between 2 and 15 mol %, even more preferably
between 3 and 12 mol %.
[0037] Preferred examples of the unsaturated carboxylates are
methyl acrylate, ethyl acrylate, isopropyl acrylate, isobutyl
acrylate, n-butyl acrylate, 2-ethylhexyl acrylate, methyl
methacrylate, isobutyl methacrylate, diethyl maleate, etc.
Especially preferred is methyl methacrylate. The unsaturated
carboxylate content of the modified polyolefin preferably falls
between 0.5 and 30 mol %, more preferably between 1 and 25 mol %,
even more preferably between 2 and 20 mol %.
[0038] Examples of the unsaturated carboxylic acid anhydrides are
itaconic anhydride, maleic anhydride, etc. Especially preferred is
maleic anhydride. The unsaturated carboxylic acid anhydride content
of the modified polyolefin preferably falls between 0.0001 and 5
mol %, more preferably between 0.0005 and 3 mol %, even more
preferably between 0.001 and 1 mol %. Examples of other monomers
that may be in the copolymers are vinyl esters such as vinyl
propionate, and carbon monoxide, etc.
[0039] The metal ion of the metal salt of the carboxylic
acid-modified polyolefin includes, for example, alkali metals such
as lithium, sodium, potassium, etc.; alkaline earth metals such as
magnesium, calcium, etc.; transition metals such as zinc, etc. The
degree of neutralization of the metal salt of the carboxylic
acid-modified polyolefin may be up to 100%, but is preferably at
most 90%, more preferably at most 70%. The lowermost limit of the
degree of neutralization will be generally at least 5%, but
preferably at least 10%, more preferably at least 30%.
[0040] Of the above-mentioned carboxylic acid-modified polyolefins,
preferred are ethylene-methacrylic acid copolymers (EMAA),
ethylene-acrylic acid copolymers (EAA), ethylene-methyl
methacrylate copolymers (EMMA), maleic anhydride-modified
polyethylenes, maleic anhydride-modified polypropylenes and their
metal salts, in view of their adhesiveness to the barrier material
(B). Especially preferred are ethylene-methacrylic acid copolymers
(EMAA) and their metal salts.
[0041] Preferably, the lowermost limit of the melt flow rate (MFR,
at 190.degree. C. under a load of 2160 g) of the carboxylic
acid-modified polyolefin for use in the invention is 0.01 g/10 min,
more preferably at least 0.05 g/10 min, even more preferably at
least 0.1 g/10 min. The uppermost limit of MFR thereof is
preferably at most 50 g/10 min, more preferably at most 30 g/10
min, most preferably at most 10 g/10 min. These carboxylic
acid-modified polyolefins may be used either singly or as combined
to be a mixture of two or more of them.
[0042] The boronic acid-modified polyolefin for use in the
invention is a polyolefin having at least one functional group
selected from boronic acid groups, borinic acid groups, and
boron-containing groups capable of being converted into boronic
acid groups or borinic acid groups in the presence of water.
[0043] In the polyolefin having at least one functional group
selected from boronic acid groups, borinic acid groups, and
boron-containing groups capable of being converted into boronic
acid groups or borinic acid groups in the presence of water, which
is for use in the invention, at least one functional group selected
from boronic acid groups, borinic acid groups, or boron-containing
groups capable of being converted into boronic acid groups or
borinic acid groups in the presence of water is bonded to the main
chain, the side chain or the terminal via boron-carbon bonding
therebetween. Of such polyolefins, preferred are those having the
functional group bonded to the side chain or to the terminal. The
terminal is meant to include one terminal and both terminals of the
polymer. In view of their adhesiveness to the barrier material (B),
especially preferred are polyolefins with the functional group
bonded to the side chain.
[0044] The carbon of the boron-carbon bonding is derived from the
base polymer of polyolefin to be mentioned below, or from the boron
compound to be reacted with the base polymer. One preferred
embodiment of the boron-carbon bonding is bonding of boron to the
alkylene group in the main chain, the terminal or the side chain of
the polymer. Boronic acid group-having polyolefins are preferred
for use in the invention, and these will be described below. The
boronic acid group referred to herein is represented by the
following formula (I): 1
[0045] The boron-containing group capable of being converted into a
boronic acid group in the presence of water (this will be
hereinafter referred to as a boron-containing group) may be any and
every boron-containing group capable of being hydrolyzed in the
presence of water to give a boronic acid group of formula (I).
Representative examples of the group are boron ester groups of the
following general formula (II), boronic acid anhydride groups of
the following general formula (III), and boronic acid salt groups
of the following general formula (IV): 2
[0046] wherein X and Y each represent a hydrogen atom, an aliphatic
hydrocarbon group (e.g., a linear or branched alkyl or alkenyl
group having from 1 to 20 carbon atoms), an alicyclic hydrocarbon
group (e.g., a cycloalkyl group, a cycloalkenyl group), or an
aromatic hydrocarbon group (e.g., a phenyl group, a biphenyl
group); X and Y may be the same or different, and X and Y may be
bonded to each other, but X and Y must not be hydrogen atoms at the
same time; R.sup.1, R.sup.2 and R.sup.3 each represent a hydrogen
atom, an aliphatic hydrocarbon group, an alicyclic hydrocarbon
group, or an aromatic hydrocarbon group, like X and Y, and R.sup.1,
R.sup.2 and R.sup.3 may be the same or different; M represents an
alkali metal or an alkaline earth metal; and the groups X, Y
R.sup.1, R.sup.2 and R.sup.3 may have any other groups such as a
carboxyl group, a halogen atom, etc.
[0047] Specific examples of the groups of formulae (II) to (IV) are
boronic acid ester groups such as a dimethyl boronate group, a
diethyl boronate group, a dipropyl boronate group, a diisopropyl
boronate group, a dibutyl boronate group, a dihexyl boronate group,
a dicyclohexyl boronate group, an ethylene glycol boronate group, a
propylene glycol boronate group (1,2-propanediol boronate group,
1,3-propanediol boronate group), a trimethylene glycol boronate
group, a neopentyl glycol boronate group, a catechol boronate
group, a glycerin boronate group, a trimethylolethane boronate
group, etc.; boronic acid anhydride groups; boronic acid alkali
metal salt groups, boronic acid alkaline earth metal salt groups,
etc. The boron-containing group capable of being converted into a
boronic acid group or a borinic acid group in the presence of water
is meant to indicate a group capable of being converted into a
boronic acid group or a borinic acid group when the polyolefin
containing it is hydrolyzed in water or in a mixed liquid
comprising water and an organic solvent (toluene, xylene, acetone,
etc.) at a reaction temperature falling between 25.degree. C. and
150.degree. C. and for a reaction time falling between 10 minutes
and 2 hours.
[0048] The functional group content of the polymer is not
specifically defined, but preferably falls between 0.0001 and 1
meq/g (milli-equivalent/g), more preferably between 0.001 and 0.1
meq/g.
[0049] The base polymer of the polyolefin which has the
boron-containing group is a polymer of olefinic monomers of
typically .alpha.-olefins such as ethylene, propylene, 1-butene,
isobutene, 3-methylpentene, 1-hexene, 1-octene, etc.
[0050] The base polymer is a polymer of one, two, three or more of
such monomers. For the base polymer, especially preferred are
ethylenic polymers {very-low-density polyethylene, low-density
polyethylene, medium-density polyethylene, high-density
polyethylene, linear low-density polyethylene, ethylene-vinyl
acetate copolymers, ethylene-acrylate copolymers, metal salts of
ethylene-acrylic acid copolymers (Na, K, Zn ionomers),
ethylene-propylene copolymers}.
[0051] A typical method for producing the olefinic polymers for use
in the invention, which have a boronic acid group or a
boron-containing group-having, is described. Olefinic polymers
having a boronic acid group or a boron-containing group capable of
being converted into a boronic acid group in the presence of water
can be obtained by reacting a carbon-carbon double bond-having
olefinic polymer with a borane complex and a trialkyl borate in a
nitrogen atmosphere to give a dialkyl boronate group-having
olefinic polymer followed by further reacting the resulting polymer
with water or an alcohol. In case where an olefinic polymer having
a double bond at the terminal is processed according to the method,
the resulting olefinic polymer shall have a boronic acid group or a
boron-containing group capable of being converted into a boronic
acid group in the presence of water, at the terminal. On the other
hand, in case where an olefinic polymer having a double bond in the
side chain or in the main chain is processed according to the
method, the resulting olefinic polymer shall have a boronic acid
group or a boron-containing group capable of being converted into a
boronic acid group in the presence of water, in the side chain.
[0052] Typical methods for producing the starting, double
bond-having olefinic polymer are (1) a method of utilizing the
double bond being present in a small amount at the terminal of an
ordinary olefinic polymer; (2) a method of pyrolyzing an ordinary
olefinic polymer in the absence of oxygen to give an olefinic
polymer having a double bond at the terminal; and (3) a method of
copolymerizing an olefinic monomer and a dienic polymer to give a
copolymer of the olefinic monomer and the dienic monomer. For (1),
usable is any known method of producing ordinary olefinic polymers,
in which, however, preferably used is a metallocene polymerization
catalyst, and hydrogen serving as a chain transfer agent is not
used (for example, DE 4,030,399). In (2), an olefinic polymer is
pyrolyzed in the absence of oxygen, for example, in a nitrogen
atmosphere or in high vacuum at a temperature falling between
300.degree. C. and 500.degree. C. in an ordinary manner (for
example, U.S. Pat. Nos. 2,835,659, 3,087,922). For (3), usable is a
method for producing olefin-diene copolymers in the presence of a
known Ziegler catalyst (for example, Japanese Patent Laid-Open No.
44281/1975, DE 3,021,273).
[0053] Starting from the double bond-having olefinic polymers
produced in the above-mentioned methods (1) and (2), obtained are
polyolefins having at least one functional group selected from
boronic acid groups, borinic acid groups, and boron-containing
groups capable of being converted into boronic acid groups or
borinic acid groups in the presence of water, at the terminal.
Starting from the double bond-having olefinic polymers produced in
the method (3), obtained are polyolefins having the functional
group in the side chain.
[0054] Preferred examples of the borane complex are
boranete-trahydrofuran complex, borane-dimethylsulfide complex,
borane-pyridine complex, borane-trimethylamine complex,
borane-triethylamine, etc. Of these, more preferred are
borane-triethylamine complex and borane-triethylamine complex. The
amount of the borane complex to be applied to the olefinic polymer
preferably falls between 1/3 equivalents and 10 equivalents to the
double bond of the polymer. Preferred examples of the trialkyl
borates are lower alkyl esters of boric acid such as trimethyl
borate, triethyl borate, tripropyl borate, tributyl borate. The
amount of the trialkyl borate to be applied to the olefinic polymer
preferably falls between 1 and 100 equivalents to the double bond
of the polymer. The solvent is not necessarily used for the
reaction, but it is, when ever used, preferably a saturated
hydrocarbon solvent such as hexane, heptane, octane, decane,
dodecane, cyclohexane, ethylcyclohexane, decalin, etc.
[0055] For the reaction for introducing a dialkyl boronate group
into olefinic polymers, the temperature preferably falls between
25.degree. C. and 300.degree. C., more preferably between 100 and
250.degree. C.; and the time preferably falls between 1 minute and
10 hours, more preferably between 5 minutes and 5 hours.
[0056] For the reaction of the dialkyl boronate group-having
olefinic polymer with water or an alcohol, generally used is an
organic solvent such as toluene, xylene, acetone, ethyl acetate,
etc. In such a reaction solvent, the olefinic polymer is reacted
with a large excessive amount, from 1 to 100 equivalents or more to
the boronate group in the polymer, of water or an alcohol such as
methanol, ethanol, butanol or the like, or a polyalcohol such as
ethylene glycol, 1,2-propanediol, 1,3-propanediol, neopentyl
glycol, glycerin, trimethylolethane, pentaerythritol,
dipentaerythritol or the like, at a temperature falling between
25.degree. C. and 150.degree. C. for from 1 minute to 1 day or so.
Of the above-mentioned functional groups, the boron-containing
group capable of being converted into a boronic acid group is meant
to indicate a group capable of being converted into a boronic acid
group when the polymer having it is hydrolyzed in water or in a
mixed solvent of water and an organic solvent (toluene, xylene,
acetone, etc.) for a reaction period of time falling between 10
minutes and 2 hours at a reaction temperature falling between
25.degree. C. and 150.degree. C.
[0057] Preferably, a powder of a both barrier material (B) and
thermoplastic resin (C) having an elastic modulus at 20.degree. C.
of at most 500 kg/cm.sup.2 is, after having been melted, applied to
the substrate of a polyolefin (A) according to a flame spray
coating process, at sequential order. The order of powder coating
applied on the substrate of a polyolefin (A) is not limitative. The
layer constitution of the resulting multi-layered structure
includes arbitrary combinations such as A/B/C, A/B/C/B, A/C/B,
A/C/B/C, and so on. The layer constitution is not limited to these.
To improve the impact strength of the coating film of the barrier
material (B), the thermoplastic resin (C) can be located in any
position.
[0058] The impact strength of the coating film of the barrier
material (B) can be improved by applying a powder of the
thermoplastic resin (C), after melting it, to the substrate of a
polyolefin (A) according to a flame spray coating process, followed
by applying a powder of the barrier material (B), after melting it,
to the resulting layer of the thermoplastic resin (C) according to
a flame spray coating process.
[0059] The impact strength of the coating film of the barrier
material (B) can also be improved by applying a powder of the
barrier material (B), after melting it, to the substrate of a
polyolefin (A) according to a flame spray coating process, followed
by applying a powder of the thermoplastic resin (C), after melting
it, to the resulting layer of the barrier material (B) according to
a flame spray coating process. In view of protection of the surface
of the barrier material (B) from moisture or abrasion, preferably,
a powder of a thermoplastic resin. (C) is applied to the resulting
of the barrier material (B) according to a flame spray coating
process.
[0060] Preferred examples of the thermoplastic resin (C) having an
elastic modulus at 20.degree. C. (measured according to ASTM D882)
of at most 500 kg/cm.sup.2, which is employed in the invention, are
rubbers such as EPDM (ethylene-propylene-diene rubber), NR (natural
rubber), isoprene rubber, butadiene rubber, IIR (butyl rubber),
etc.; as well as very-low-density polyethylene (VLDPE),
ethylene-vinyl acetate copolymers (EVA), copolymers of aromatic
vinyl compounds and conjugated diene compounds, ethylene-propylene
copolymer elastomers (EPR), etc. However, these are not limitative.
Of these, preferred are copolymers of aromatic vinyl compounds and
conjugated diene compounds, and ethylene-propylene copolymer
elastomers (EPR). The ethylene-propylene copolymers are not
specifically defined, including, for example, ethylene-propylene
random copolymers and block copolymers. For the monomer blend ratio
to give copolymers having good flexibility, it is desirable that
the amount of one monomer is at least 20 parts by weight.
[0061] In the copolymers of aromatic vinyl compounds and conjugated
diene compounds for use in the invention, the aromatic vinyl
compounds are not specifically defined. The compounds include, for
example, styrenes such as styrene, .alpha.-methylstyrene,
2-methylstyrene, 4-methylstyrene, 4-propylstyrene,
4-t-butylstyrene, 4-cyclohexylstyrene, 4-dodecylstyrene,
2-ethyl-4-benzylstyrene, 4-(phenylbutyl)styrene,
2,4,6-trimethylstyrene, monofluorostyrene, difluorostyrene,
monochlorostyrene, dichlorostyrene, methoxystyrene,
t-butoxystyrene, etc.; vinyl group-containing aromatic compounds
such as 1-vinylnaphthalene, 2-vinyinaphthalene, etc.; vinylene
group-containing aromatic compounds such as indene, acenaphthylene,
etc. The copolymers may comprise one or more different types of
aromatic vinyl monomer units, for which, however, preferred are
units derived from styrenes.
[0062] In the copolymers of aromatic vinyl compounds and conjugated
diene compounds for use in the invention, the conjugated diene
compounds are not also specifically defined. The compounds include,
for example, butadiene, isoprene, 2,3-dimethylbutadiene,
pentadiene, hexadiene, etc. The conjugated diene compounds may be
partially or completely hydrogenated. Examples of copolymers of
partially hydrogenated aromatic vinyl compounds and conjugated
diene compounds are styrene-ethylene.multidot.butylene-styrene
triblock copolymers (SEBS),
styrene-ethylene.multidot.propylene-styrene triblock copolymers
(SEPS), hydrogenated derivatives of styrene-conjugated diene
copolymers, etc.
[0063] The barrier material (B) for use in the invention is
preferably a thermoplastic resin through which the gasoline
permeation amount is at most 100 g.multidot.20
.mu.m/m.sup.2.multidot.day (measured at 40.degree. C. and 65% RH)
and/or the oxygen transmission rate is at most 100 cc.multidot.20
.mu.m/m.sup.2.multidot.day.multidot.atm (measured at 20.degree. C.
and 65% RH). More preferably, the uppermost limit of the gasoline
permeation amount through the resin is at most 10 g.multidot.20
.mu.m/m.sup.2.multidot.day, even more preferably at most 1
g.multidot.20 .mu.m/m.sup.2.multidot.day, still more preferably at
most 0.5 g.multidot.20 .mu.m/m.sup.2.multidot.day, most preferably
at most 0.1 g.multidot.20 .mu.m/m.sup.2.multidot.day. Gasoline to
be used for determining the gasoline permeation amount through the
resin is a model gasoline of mixed toluene/isooctane (=1/1 by
volume), which is referred to as Ref. fuel C. More preferably, the
uppermost limit of the oxygen transmission rate through the resin
is at most 50 cc.multidot.20
.mu.m/m.sup.2.multidot.day.multidot.atm, even more preferably at
most 10 cc.multidot.20 .mu.m/m.sup.2.multidot.day.multidot.atm ,
most preferably at most 5 cc.multidot.20
.mu.m/m.sup.2.multidot.day.multidot.atm.
[0064] In the present invention, the step of applying the powder of
a barrier material (B), after melting it, to the substrate of a
polyolefin (A) is effected according to a flame spray coating
process. Accordingly, the barrier material (B) is preferably a
thermoplastic resin. For further improving the gasoline barrier
properties of the shaped article of the invention, it is desirable
that the thermoplastic resin for the barrier material (B) has a
solubility parameter (obtained according to the Fedors' formula) of
larger than 11.
[0065] Also preferably, the barrier material (B) for use herein is
at least one selected from a group consisting of ethylene-vinyl
alcohol copolymers (EVOH), polyamides, aliphatic polyketones and
polyesters. In view of its oxygen barrier properties, the barrier
material (B) is more preferably a polyamide or EVOH, most
preferably EVOH. In view of their gasoline barrier properties,
however, preferred are polyamides, polyesters and EVOH, and most
preferred is EVOH.
[0066] Preferably, EVOH for the barrier material (B) in the
invention is a resin to be obtained by saponifying an
ethylene-vinyl ester copolymer, and its ethylene content may fall
between 5 and 60 mol %. The lowermost limit of the ethylene content
of the resin is preferably at least 15 mol %, more preferably at
least 25 mol %, even more preferably at least 30 mol %, still more
preferably at least 35 mol %, most preferably at least 40 mol %.
The uppermost limit of the ethylene content of the resin is
preferably at most 55 mol %, more preferably at most 50 mol %. The
melt moldability of EVOH having an ethylene content of smaller than
5 mol % is poor, and uniformly coating the EVOH melt over the
substrate of a polyolefin (A) is difficult. On the other hand, the
gasoline barrier properties and oxygen barrier properties of EVOH
having an ethylene content of larger than 60 mol % are poor.
[0067] The degree of saponification of the vinyl ester moiety of
EVOH for use in the present invention is at least 85%. Preferably,
it is at least 90%, more preferably at least 95%, even more
preferably at least 98%, most preferably at least 99%. The gasoline
barrier properties and the oxygen barrier properties and even the
thermal stability of EVOH having a degree of saponification of
smaller than 85% are poor.
[0068] One typical example of the vinyl ester to be used for
producing EVOH is vinyl acetate. However, any other vinyl esters of
fatty acids (vinyl propionate, vinyl pivalate, etc.) are also
usable for producing it. EVOH may contain from 0.0002 to 0.2 mol %
of a comonomer, vinylsilane compound. The vinylsilane compound
includes, for example, vinyltrimethoxysilane, vinyltriethoxysilane,
vinyltri(.beta.-methoxy-etho- xy)silane,
.beta.-methacryloxypropylmethoxysilane. Of these, preferred are
vinyltrimethoxysilane and vinyltriethoxysilane. Not interfering
with the object of the invention, EVOH may be copolymerized with
any other comonomers, for example, propylene, butylene, or
unsaturated carboxylic acids and their esters such as (meth)acrylic
acid, methyl (meth)acrylate, ethyl (meth)acrylate, etc.,
vinylpyrrolidones such as N-vinylpyrrolidone, etc.
[0069] Also not interfering with the object of the invention, a
boron compound may be added to EVOH. The boron compound includes
boric acids, borates, salts of boric acids, boron hydrides, etc.
Concretely, boric acids include orthoboric acid, metaboric acid,
tetraboric acid, etc.; borates includes trimethyl borate, triethyl
borate, etc.; and salts of boric acids include alkali metal salts
and alkaline earth metal salts of the above-mentioned boric acids,
as well as borax, etc. Of these compounds, preferred is orthoboric
acid. In case where such a boron compound is added to EVOH, the
boron compound content of EVOH preferably falls between 20 and 2000
ppm, more preferably between 50 and 1000 ppm, in terms of the boron
element.
[0070] As being effective for improving the interlayer adhesiveness
between EVOH and the substrate of a polyolefin (A), an alkali metal
salt is preferably added to EVOH in an amount of from 5 to 5000 ppm
in terms of the alkali metal element.
[0071] More preferably, the alkali metal salt content of EVOH falls
between 20 and 1000 ppm, even more preferably between 30 and 500
ppm, in terms of the alkali metal element. The alkali metal
includes lithium, sodium, potassium, etc. The alkali metal salt
includes mono-metal salts of aliphatic carboxylic acids, aromatic
carboxylic acids and phosphoric acids, as well as mono-metal
complexes, etc. For example, it includes sodium acetate, potassium
acetate, sodium phosphate, lithium phosphate, sodium stearate,
potassium stearate, sodium ethylenediaminetetraacetate, etc. Of
these, preferred are sodium acetate and potassium acetate.
[0072] Also preferably, EVOH for use in the invention contains a
phosphate compound in an amount of from 20 to 500 ppm, more
preferably from 30 to 300 ppm, most preferably from 50 to 200 ppm,
in terms of the phosphate radical. In case where the phosphate
compound content of EVOH is smaller than 20 ppm or larger than 500
ppm, the thermal stability of EVOH may be low. If so, there is
possibility that a melt of powdery EVOH applied to the substrate of
a polyolefin (A) will often gel and the thickness of the coating
layer of EVOH could not be uniform.
[0073] The type of the phosphate compound to be added to EVOH is
not specifically defined. It includes various acids such as
phosphoric acid, phosphorous acid, etc., and their salts. Any
phosphate of any type of primary phosphates, secondary phosphates
and tertiary phosphates may be in EVOH, and its cation is not
specifically defined. Preferred are alkali metal salts and alkaline
earth metal salts. Above all, especially preferred for the
phosphate compound are sodium dihydrogenphosphate, potassium
dihydrogenphosphate, disodium hydrogenphosphate and dipotassium
hydrogenphosphate.
[0074] In the invention, the powder of barrier material (B) is
applied to the substrate of a polyolefin (A) according to a flame
spray coating process. In view of its gasoline barrier properties
and oxygen barrier properties, the barrier material (B) is most
preferably EVOH. Therefore, it is preferred that the fluidity of
the melt of EVOH is high. Preferably, the melt flow rate (MFR, at
190.degree. C. under a load of 2160 g) of EVOH for the barrier
material (B) in the invention falls between 0.1 and 50 g/10 min,
more preferably between 1 and 40 g/10 min, even more preferably
between 5 and 30 g/10 min.
[0075] For EVOH having a melting point of around 190.degree. C. or
above 190.degree. C., its MFR is measured under a load of 2160 g at
different temperatures not lower than its melting point. The data
are plotted on a semi-logarithmic graph with the horizontal axis
indicating the reciprocal of the absolute temperature and the
vertical axis indicating the logarithm of the melt flow rate
measured, and the value corresponding to 190.degree. C. is
extrapolated from the curve of the thus-plotted data. One type of
EVOH resin or two or more different types thereof may be used
either singly or as combined.
[0076] Not interfering with the object of the invention, any of
thermal stabilizers, UV absorbents, antioxidants, colorants, other
resins (polyamides, polyolefins, etc.) and also plasticizers such
as glycerin, glycerin monostearate or the like may be added to
EVOH. Adding metal salts of higher aliphatic carboxylic acids and
hydrotalcite compounds to EVOH is effective for preventing EVOH
from being thermally degraded.
[0077] Examples of hydrotalcite compounds usable herein are double
salts of
M.sub.xAl.sub.y(OH).sub.2x+3y-2z(A).sub.z.multidot.aH.sub.2O (where
M represents Mg, Ca or Zn; A represents CO.sub.3 or HPO.sub.4; and
x, y, z and a each are a positive integer). Preferred examples of
the compounds are mentioned below.
Mg.sub.6Al.sub.2(OH).sub.16CO.sub.3.4H.sub.2O
Mg.sub.8Al.sub.2(OH).sub.20CO.sub.3.5H.sub.2O
Mg.sub.5Al.sub.2(OH).sub.14CO.sub.3.4H.sub.2O
Mg.sub.10Al.sub.2(OH).sub.22(CO.sub.3).sub.2.4H.sub.2O
Mg.sub.6Al.sub.2(OH).sub.16HPO.sub.4.4H.sub.2O
Ca.sub.6Al.sub.2(OH).sub.16CO.sub.3.4H.sub.2O
Zn.sub.6Al.sub.6(OH).sub.16CO.sub.3.4H.sub.2O
Mg.sub.4.5Al.sub.2(OH).sub.13CO.sub.3.3.5H.sub.2O
[0078] Also usable herein is a hydrotalcite solid solution,
[Mg.sub.0.75Zn.sub.0.25].sub.0.67Al.sub.0.33(OH).sub.2(CO.sub.3).sub.0.16-
7.0.45H.sub.2O described in Japanese Patent Laid-Open No.
308439/1989 (U.S. Pat. No. 4,954,557).
[0079] Metal salts of higher aliphatic carboxylic acids for use
herein are those of higher fatty acids having from 8 to 22 carbon
atoms. For those, higher fatty acids having from 8 to 22 carbon
atoms include lauric acid, stearic acid, myristic acid, etc. Metals
include sodium, potassium, magnesium, calcium, zinc, barium,
aluminium, etc. Of those, preferred are alkaline earth metals such
as magnesium, calcium, barium, etc.
[0080] The content of such a metal salt of a higher aliphatic
carboxylic acid or a hydrotalcite compound to be in EVOH preferably
falls between 0.01 and 3 parts by weight, more preferably between
0.05 and 2.5 parts by weight, relative to 100 parts by weight of
EVOH.
[0081] Polyamides usable herein for the barrier material (B) are
amido bond-having polymers, including, for example, homopolymers
such as polycapramide (nylon-6), polyundecanamide (nylon-11),
polylauryllactam (nylon-12), polyhexamethylene adipamide
(nylon-6,6), polyhexamethylene sebacamide (nylon-6,12);
caprolactam/lauryllactam copolymer (nylon-6/12),
caprolactam/aminoundecanoic acid polymer (nylon-6/11),
caprolactam/.omega.-aminononanoic acid polymer (nylon-6,9),
caprolactam/hexamethylenediammonium adipate copolymer
(nylon-6/6,6), caprolactam/hexamethylenediammonium
adipate/hexamethylenediammonium sebacate copolymer
(nylon-6/6,6/6,12); aromatic nylons such as adipic
acid/metaxylenediamine copolymer (hereinafter referred to as
MXD-6), hexamethylenediamine/m,p-phthalic acid copolymer, etc. One
or more of these polyamides are usable herein either singly or as
combined.
[0082] Of these polyamides, preferred are nylon-6 and nylon-12, as
having good gasoline barrier properties. In view of its oxygen
barrier properties, preferred is adipic acid/metaxylenediamine
copolymer (MXD-6).
[0083] Aliphatic polyketones usable for the barrier material(B) in
the invention are carbon monoxide-ethylene copolymers, which are
obtained by copolymerizing carbon monoxide and ethylene, or by
copolymerizing essentially carbon monoxide and ethylene with other
unsaturated compounds except ethylene. The unsaturated compounds
except ethylene include .alpha.-olefins having at least 3 carbon
atoms, styrenes, dienes, vinyl esters, aliphatic unsaturated
carboxylates, etc. The copolymers may be random copolymers or
alternate copolymers. Alternate copolymers having a higher degree
of crystallinity are preferred, in view of their barrier
properties.
[0084] More preferred are alternate copolymers containing a third
component in addition to carbon monoxide and ethylene, as their
melting point is low and therefore their melt stability is good.
.alpha.-olefins are preferred for the comonomer, including, for
example, propylene, butene-1, isobutene, pentene-1,
4-methylpentene-1, hexene-1, octene-1, dodecene-1, etc. More
preferred are .alpha.-olefins having from 3 to 8 carbon atoms; and
even more preferred is propylene. The amount of the comonomer,
.alpha.-olefin preferably falls between 0.5 and 7% by weight of the
polyketone, as ensuring good crystallinity of the polymer. Another
advantage of the polyketone of which the comonomer content falls
within the defined range is that the coatability of the melt of its
powder is good.
[0085] For the other comonomers, dienes preferably have from 4 to
12 carbon atoms, including butadiene, isoprene, 1,5-hexadiene,
1,7-octadiene, 1,9-decadiene, etc. Vinyl esters include vinyl
acetate, vinyl propionate, vinyl pivalate, etc. Aliphatic
unsaturated carboxylic acids and their salts and esters include
acrylic acid, methacrylic acid, maleic anhydride, maleic acid,
itaconic acid, acrylates, methacrylates, monomaleates, dimaleates,
monofumarates, difumarates, monoitaconates, diitaconates (these
esters may be alkyl esters such as methyl esters, ethyl esters,
etc.), salts of acrylic acid, salts of maleic acid, salts of
itaconic acid (these salts may be mono- or di-valent metal salts).
Not only one but also two or more of these comonomers may be used
in preparing the copolymers, either singly or as combined.
[0086] Polyketones for use herein may be produced in any known
method, for example, according to the methods described in U.S.
Pat. No. 2,495,286, and Japanese Patent Laid-Open Nos. 128690/1978,
197427/1984, 91226/1986, 232434/1987, 53332/1987, 3025/1988,
105031/1988, 154737/1988, 149829/1989, 201333/1989, 67319/1990,
etc., but are not limited thereto.
[0087] Preferably, the melt flow rate (MFR, at 230.degree. C. under
a load of 2160 g) of the polyketone for use in the invention falls
between 0.01 and 50 g/10 min, most preferably between 0.1 and 30
g/10 min. The polyketone has good fluidity, so far as its MFR falls
within the defined range, and the coatability of the melt of a
powder of the polyketone is good.
[0088] Polyesters usable for the barrier material (B) in the
invention are preferably thermoplastic polyester resins. The
thermoplastic polyester resins are polycondensates comprising, as
the essential ingredients, aromatic dicarboxylic acids or their
alkyl esters and diols. For attaining the object of the invention,
especially preferred are polyester resins comprising ethylene
terephthalate as one essential ingredient. Preferably, the total
(in terms of mol %) of the terephthalic acid unit and the ethylene
glycol unit constituting the polyester resin for use in the
invention is at least 70 mol %, more preferably at least 90 mol %
of all structural units constituting it. Polyester are preferred
for the barrier material (B), as having good gasoline barrier
properties. Even to alcohol-containing gasoline with methanol,
ethanol or the like and to oxygen-containing gasoline such as MTBE
(methyl tert-butyl ether)-containing gasoline or the like,
polyesters still enjoy good gasoline barrier properties.
[0089] EVOH is especially preferred for the barrier material (B)
for use in the invention, as having good gasoline barrier
properties and good oxygen barrier properties.
[0090] For the barrier material (B), also preferred is a resin
composition comprising from 50 to 95% by weight of an
ethylene-vinyl alcohol copolymer and from 5 to 50% by weight of a
boronic acid-modified polyolefin. A powder of the resin composition
for the barrier material (B) is, after having been melted, applied
to a substrate of a polyolefin (A) according to a flame spray
coating process. In the resulting shaped article coated with the
barrier material (B), the impact strength of the coating film is
improved. The boronic acid-modified polyolefin content of the resin
composition falls between 5% by weight and 50% by weight. If it is
smaller than 5% by weight, the impact strength of the barrier
material (B) of the resin composition could not be high. On the
other hand, if the boronic acid-modified polyolefin content of the
resin composition is larger than 50% by weight, the barrier
properties of the resin film are poor. In view of the balance of
the barrier properties and the impact strength of the resin film,
it is more desirable that the resin composition comprises from 60
to 95% by weight of an ethylene-vinyl alcohol copolymer and from 5
to 40% by weight of a boronic acid-modified polyolefin, even more
desirably from 70 to 95% by weight of an ethylene-vinyl alcohol
copolymer and from 5 to 30% by weight of a boronic acid-modified
polyolefin. In view of the impact strength of the coating film of
the barrier material (B), it is desirable that the boronic
acid-modified polyolefin to be added to EVOH has at least one
functional group selected from boronic acid groups, borinic acid
groups and boron-containing groups capable of being converted into
boronic acid or borinic acid groups in the presence of water, at
its terminal.
[0091] The resin composition for the barrier material (B) that
comprises EVOH and a boronic acid-modified polyolefin may be a dry
blend of a powder of EVOH and a powder of a boronic acid-modified
polyolefin. However, for ensuring stable morphology of the resin
composition that comprises EVOH and a boronic acid-modified
polyolefin, and for ensuring uniform coats of the barrier material
(B), it is desirable that the two components are kneaded in
melt.
[0092] Also preferably, the resin composition for the barrier
material (B) comprises from 50 to 95% by weight of an
ethylene-vinyl alcohol copolymer and from 5 to 50% by weight of
multi-layered polymer particles. A powder of the resin composition
for the barrier material (B) is, after having been melted, applied
to a substrate of a polyolefin (A) according to a flame spray
coating process. In the resulting shaped article coated with the
barrier material (B), the impact strength of the coating film is
improved. The content of the multi-layered polymer particles in the
resin composition falls between 5% by weight and 50% by weight. If
it is smaller than 5% by weight, the impact strength of the barrier
material (B) of the resin composition could not be improved. On the
other hand, if the content of the multi-layered polymer particles
in the resin composition is larger than 50% by weight, the barrier
properties of the resin film are poor. In view of the balance of
the barrier properties and the impact strength of the resin film,
it is more desirable that the resin composition comprises from 60
to 95% by weight of an ethylene-vinyl alcohol copolymer and from 5
to 40% by weight of multi-layered polymer particles, even more
desirably from 70 to 95% by weight of an ethylene-vinyl alcohol
copolymer and from 5 to 30% by weight of multi-layered polymer
particles.
[0093] The multi-layered polymer particles for use in the invention
have at least a hard layer and a rubber layer. Either of the two
layers may be the outermost layer of each particle, but it is
desirable that the hard layer is the outermost layer and the rubber
layer is inside the particles. The rubber layer referred to herein
is a polymer layer having a glass transition point (hereinafter
referred to as Tg) of not higher than 25.degree. C.; and the hard
layer is a polymer layer having Tg of higher than 25.degree. C. For
their structure, the multi-layered polymer particles may be
composed of two or three layers, or even four or more layers.
Two-layered particles will have a structure of rubber layer (core
layer)/hard layer (outermost layer); three-layered particles will
have a structure of hard layer (core layer)/rubber layer
(interlayer)/hard layer (outermost layer), or rubber layer (core
layer)/rubber layer (interlayer)/hard layer (outermost layer), or
rubber layer (core layer)/hard layer (interlayer)/hard layer
(outermost layer); and one example of the structure of four-layered
particles is rubber layer (core layer)/hard layer
(interlayer)/rubber layer (interlayer)/hard layer (outermost
layer).
[0094] The composition of the rubber layer in the multi-layered
polymer particles for use in the invention is not specifically
defined. For example, polymers preferred for the layer are
conjugated dienic polymers such as polybutadiene, polyisoprene,
butadiene-isoprene copolymers, polychloroprene, styrene-butadiene
copolymers, acrylonitrile-butadiene copolymers, acrylate-butadiene
copolymers, etc.; hydrogenated derivatives of such conjugated
dienic polymers; olefinic rubbers such as ethylene-propylene
copolymers, etc.; acrylic rubber such as polyacrylates, etc.; as
well as polyorganosiloxanes, thermoplastic elastomers, ethylenic
ionomer copolymers, etc. One or more of these polymers may be used
for the rubber layer. Of these, preferred are acrylic rubbers,
conjugated dienic polymers or hydrogenated derivatives of
conjugated dienic polymers.
[0095] Acrylic rubbers for the layer may be formed by polymerizing
acrylates. The acrylates may be alkyl acrylates, including, for
example, methyl acrylate, ethyl acrylate, propyl acrylate, butyl
acrylate, 2-ethylhexyl acrylate, octyl acrylate, etc. Of these,
preferred is butyl acrylate or ethyl acrylate.
[0096] Acrylic rubbers or conjugated dienic polymers for the layer
may be produced through polymerization of a monomer system that
comprises essentially alkyl acrylates and/or conjugated dienic
compounds. If desired, the acrylic rubbers or conjugated dienic
polymers may be copolymerized with any other mono-functional
polymerizable monomers in addition to the above-mentioned monomers.
The mono-functional comonomers include methacrylates such as methyl
methacrylate, ethyl methacrylate, propyl methacrylate, butyl
methacrylate, amyl methacrylate, hexyl methacrylate, 2-ethylhexyl
methacrylate, cyclohexyl methacrylate, octyl methacrylate, decyl
methacrylate, dodecyl methacrylate, octadecyl methacrylate, phenyl
methacrylate, benzyl methacrylate, naphthyl methacrylate, isobornyl
methacrylate, etc.; aromatic vinyl compounds such as styrene,
.alpha.-methylstyrene, etc.; acrylonitrile, etc. Preferably, the
mono-functional comonomer accounts for at most 20% by weight of all
polymerizable monomers to form the rubber layer.
[0097] Preferably, the rubber layer that forms a part of the
multi-layered polymer particles for use in the invention has a
crosslinked molecular chain structure to express rubber elasticity.
Also preferably, the molecular chains constituting the rubber layer
are grafted with those of the adjacent layers via chemical bonding
therebetween. For this, it is often desirable that the monomer
system to give the rubber layer through polymerization contains a
small amount of a poly-functional polymerizable monomer that serves
as a crosslinking agent or a grafting agent.
[0098] The poly-functional polymerizable monomer has at least two
carbon-carbon double bonds in the molecule, including, for example,
esters of unsaturated carboxylic acids, such as acrylic acid,
methacrylic acid, cinnamic acid or the like, with unsaturated
alcohols such as allyl alcohol, methallyl alcohol or the like, or
with glycols such as ethylene glycol, butanediol or the like;
esters of dicarboxylic acid, such as phthalic acid, terephthalic
acid, isophthalic acid, maleic acid or the like, with unsaturated
alcohols such as those mentioned above, etc. Specific examples of
the poly-functional polymerizable monomer are allyl acrylate,
methallyl acrylate, allyl methacrylate, methallyl methacrylate,
allyl cinnamate, methallyl cinnamate, diallyl maleate, diallyl
phthalate, diallyl terephthalate, diallyl isophthalate,
divinylbenzene, ethylene glycol di(meth)acrylate, butanediol
di(meth)acrylate, hexanediol di(meth)acrylate, etc. The terminology
"di(meth)acrylate" is meant to indicate "diacrylate" and
"dimethacrylate". One or more of these monomers may be used either
singly or as combined. Of these, preferred is allyl
methacrylate.
[0099] Preferably, the amount of the poly-functional polymerizable
monomer is at most 10% by weight of all the polymerizable monomers
to form the rubber layer. This is because, if the poly-functional
polymerizable monomer is too much, it will worsen the rubber
properties of the layer, and will therefore lower the flexibility
of the thermoplastic resin composition containing the multi-layered
polymer particles. In case where the monomer system to form the
rubber layer comprises, as the main ingredient, a conjugated dienic
compound, it does not necessarily require a poly-functional
polymerizable monomer since the conjugated dienic compound therein
functions as a crosslinking or grafting point by itself.
[0100] Radical-polymerizable monomers are used for forming the hard
layer in the multi-layered polymer particles for use herein. For
example, they include alkyl methacrylates such as methyl
methacrylate, ethyl methacrylate, propyl methacrylate, butyl
methacrylate, etc.; alicyclic skeleton-having methacrylates such as
cyclohexyl methacrylate, isobornyl methacrylate, adamantyl
methacrylate, etc.; aromatic ring-having methacrylates such as
phenyl methacrylate, etc.; aromatic vinyl compounds such as
styrene, .alpha.-methylstyrene, etc.; acrylonitrile, etc. One or
more of these radical-polymerizable monomers may be used either
singly or as combined. For the radical-polymerizable monomer system
for use herein, preferred is methyl methacrylate or styrene alone,
or a combination comprising, as the main ingredient, any of them
along with additional radical-polymerizable monomers.
[0101] Preferably, the multi-layered polymer particles for use
herein has at least one functional group that is reactive with or
has affinity for hydroxyl groups, as their dispersibility in EVOH
is good. With the polymer particles of that type, the impact
strength of the coating film of the barrier material (B) is higher.
Accordingly, in polymerization to give the multi-layered polymer
particles for use herein, it is desirable to use, as a part of the
monomer, a radical-polymerizable compound having a functional group
that is reactive with or has affinity for hydroxyl groups or having
a protected functional group of that type.
[0102] Copolymerizable compounds which are reactive with or have
affinity for hydroxyl groups and which are preferably used for
forming the above-mentioned functional group in the multi-layered
polymer particles are unsaturated compounds having a group capable
of reacting with hydroxyl groups in EVOH to form chemical bonds
therewith under the mixing condition mentioned below or those
having a group capable of forming intermolecular bonds such as
hydrogen bonds with hydroxyl groups in EVOH also under that mixing
condition. The functional group that is reactive with or has
affinity for hydroxyl groups includes, for example, a hydroxyl
group, an epoxy group, an isocyanate group (--NCO), an acid group
such as a carboxyl group, etc., an acid anhydride group such as
that derived from maleic anhydride, and a protected group which is
de-protected under the mixing condition mentioned below to give any
of these functional groups.
[0103] Specific examples of the unsaturated compounds are hydroxyl
group-having polymerizable compounds such as 2-hydroxyethyl
(meth)acrylate, 3-hydroxypropyl (meth)acrylate, 2-hydroxyethyl
crotonate, 3-hydroxy-1-propene, 4-hydroxy-1-butene,
cis-4-hydroxy-2-butene, trans-4-hydroxy-2-butene, etc.; epoxy
group-having polymerizable compounds such as glycidyl acrylate,
glycidyl methacrylate, allyl glycidyl ether, 3,4-epoxybutene,
4,5-epoxypentyl (meth)acrylate, 10,11 -epoxyundecyl methacrylate,
p-glycidylstyrene, etc.; carboxylic acids such as acrylic acid,
methacrylic acid, crotonic acid, cinnamic acid, itaconic acid,
maleic acid, citraconic acid, aconitic acid, mesaconic acid,
methylenemalonic acid, etc. The terminology "di(meth)acrylate"
referred to herein is meant to indicate "diacrylate" and
"dimethacrylate"; and the terminology "(meth)acrylic acid" also
referred to herein is meant to indicate "acrylic acid" and
"methacrylic acid".
[0104] Of the above-mentioned functional groups that are reactive
with or have affinity for hydroxyl groups, preferred are acid
groups such as carboxyl groups, etc., acid anhydride groups such as
those derived from maleic anhydride, and epoxy groups. Especially
preferred are acid groups such as carboxyl groups, etc., and epoxy
groups. Acid groups such as carboxyl groups, etc. include, for
example, those from methacrylic acid and acrylic acid; and epoxy
groups include, for example, those from glycidyl methacrylate,
glycidyl acrylate, etc.
[0105] In forming the multi-layered polymer particles for use
herein, the amount of the radical-polymerizable compound to be
used, which has a functional group reactive with or having affinity
for hydroxyl groups or has a protected functional group of the
type, preferably falls between 0.01 and 75% by weight, more
preferably between 0.1 and 40% by weight of all the monomers to
form the particles. The protected functional group may be any and
every one capable of being de-protected to give the free functional
group of the type mentioned above, under the condition to be
mentioned hereinunder, under which the compound is mixed with EVOH,
but this must not interfere with the object of the invention. One
example of the protected functional group-having,
radical-polymerizable compounds is t-butyl methacrylcarbamate.
[0106] In the multi-layered polymer particles having a functional
group that is reactive with or has affinity for hydroxyl groups, it
is desirable that the functional group is in the molecular chains
that constitute the outermost hard layer of the particles. However,
so far as the functional group in the multi-layered polymer
particles that are combined with EVOH to give a resin composition
for use herein can substantially react with the hydroxyl groups in
EVOH or can form intermolecular bonds with them, it may in any
layer (outermost layer, interlayer, inner layer) of the polymer
particles.
[0107] Preferably, the rubber layer accounts for from 50 to 90% by
weight of the multi-layered polymer particles. If the amount of the
polymer moiety to form the rubber layer in the particles is too
small, the flexibility of the resin composition comprising the
particles is poor. On the other hand, if the amount of the polymer
moiety to form the outermost layer in the particles is too small,
the particles are difficult to handle.
[0108] The method of polymerization to give the multi-layered
polymer particles for use in the invention is not specifically
defined. For example, spherical multi-layered polymer particles can
be produced in ordinary emulsion polymerization. For these,
emulsion polymerization can be effected in any ordinary manner
generally employed by those skilled in the art. If desired, a chain
transfer agent such as octylmercaptan, laurylmercaptan or the like
may be added to the polymerization system. The multi-layered
polymer particles formed through such emulsion polymerization are
separated and taken out from the polymer latex in any ordinary
manner (for example, through solidification, drying, etc.)
generally employed by those skilled in the art.
[0109] The mean particle size of the individual multi-layered
polymer particles thus formed is not specifically defined. However,
particles of which the mean particle size is too small will be
difficult to handle; but too large particles will be ineffective
for enhancing the impact strength of the coating film of the
barrier material (B) comprising them. Accordingly, the mean
particle size of the individual multi-layered polymer particles
preferably falls between 0.02 and 2 .mu.m, more preferably between
0.05 and 1.0 .mu.m. The shape of the multi-layered polymer
particles for use herein is not also specifically defined. For
example, the particles may be in any form of pellets, powders,
granules and the like where the particles are partly fused or
aggregated together at their outermost layer part (these will be
hereinafter referred to as aggregated particles). The particles may
be completely independent of each other, or may be in the form of
such aggregated particles.
[0110] In the resin composition for the barrier material (B) that
comprises EVOH and multi-layered polymer particles, the condition
of the particles dispersed in EVOH is not specifically defined. The
multi-layered polymer particles will be uniformly dispersed in EVOH
in such a manner that the particles are completely independent of
each other in EVOH; or a plurality of multi-layered polymer
particles are fused or aggregated together to give aggregated
particles, and the aggregated particles will be uniformly dispersed
in EVOH; or completely independent particles and aggregated
particles will be uniformly dispersed in EVOH. The resin
composition for use herein may be in any form of these dispersions.
Including the completely independent particles and the aggregated
particles, the dispersed, multi-layered polymer particles
preferably have a mean particle size of at most 10 .mu.m, more
preferably at most 5 .mu.m, even more preferably at most 2 .mu.m.
Still more preferably, the particles having a mean particle size of
from 0.03 to 1 .mu.m are uniformly dispersed in EVOH. Multi-layered
polymer particles having a particle size of larger than 10 .mu.m
are difficult to uniformly disperse in the matrix of EVOH. As a
result, the impact strength of the coating film of the barrier
material (B) of the resin composition containing such large
particles is low. The resin composition for the barrier material
(B) that comprises EVOH and multi-layered polymer particles may be
a dry blend to be prepared by blending in dry a powder of EVOH and
the particles. However, for ensuring stable morphology of the resin
composition that comprises EVOH and multi-layered polymer
particles, and for ensuring uniform coats of the barrier material
(B), it is desirable that the two components are kneaded in
melt.
[0111] The invention also relates to a shaped article produced by
applying a powder of a barrier material (B), after melting it, to
at least a part of the surface of the substrate of the article
according to a flame spray coating process. One preferred
embodiment of the shaped article is a multi-layered container that
comprises an interlayer of a barrier resin (D) and inner and outer
layers of a polyolefin (A). More preferably, the multi-layered
container is a fuel container. Even more preferably, the
multi-layered fuel container is a co-extrusion blow-molded
container or a co-extrusion thermoformed container.
[0112] The barrier resin (D) for use herein is preferably a
thermoplastic resin through which the gasoline permeation amount is
at most 100 g.multidot.20 .mu.m/m.sup.2.multidot.day (measured at
40.degree. C. and 65% RH) and/or the oxygen transmission rate is at
most 100 cc.multidot.20 .mu.m/m.sup.2.multidot.day.multidot.atm
(measured at 20.degree. C. and 65% RH).
[0113] Also preferably, the barrier resin (D) is at least one
selected from a group consisting of ethylene-vinyl alcohol
copolymers, polyamides and aliphatic polyketones. The
ethylene-vinyl alcohol copolymers, polyamides and aliphatic
polyketones for the barrier resin (D) may be the same as those for
the barrier material (B).
[0114] In the multi-layered fuel container (preferablly, a
co-extrusion blow-molded container or a co-extrusion thermoformed
container) of the invention, the polyolefin (A) that forms the
inner and outer layers is preferably high-density polyethylene. The
high-density polyethylene may be any ordinary commercial product.
In view of its stiffness, impact resistance, moldability, draw-down
resistance and gasoline resistance, however, the high-density
polyethylene for the layers preferably has a density of from 0.95
to 0.98 g/cm.sup.3, more preferably from 0.96 to 0.98 g/cm.sup.3.
Also preferably, the melt flow rate (MFR) of the high-density
polyethylene to form the inner and outer layers of the
multi-layered fuel container falls between 0.01 and 0.5 g/10 min
(at 190.degree. C. under a load of 2160 g), more preferably between
0.01 and 0.1 g/10 min (at 190.degree. C. under a load of 2160
g).
[0115] In case where the barrier resin (D) to form the interlayer
of the multi-layered fuel container is EVOH, its ethylene content
falls between 5 and 60 mol %. The lowermost limit of the ethylene
content of EVOH is preferably at least 15 mol %, more preferably at
least 25 mol %. The uppermost limit of the ethylene content thereof
is preferably at most 55 mol %, more preferably at most 50 mol %.
EVOH having an ethylene content of lower than 5 mol % is
unfavorable as its melt moldability is poor. On the other hand,
EVOH having an ethylene content of larger than 60 mol % is also
unfavorable, as its gasoline-barrier properties and oxygen barrier
properties are not good. The degree of saponification of the vinyl
ester moiety of EVOH for the barrier resin (D) is at least 85%. It
is preferably at least 90%, more preferably at least 95%, even more
preferably at least 98%, most preferably at least 99%. EVOH having
a degree of saponification of smaller than 85% is unfavorable since
its gasoline barrier properties and oxygen barrier properties are
not good and its thermal stability is poor. In case where the
barrier resin (D) to form the interlayer of the multi-layered fuel
container is EVOH, its melt flow rate (MFR, measured at 190.degree.
C. under a load of 2160 g) preferably falls between 0.01 and 100
g/10 min, more preferably between 0.05 and 50 g/10 min, even more
preferably between 0.1 and 10 g/10 min.
[0116] An especially important embodiment of the invention is a
co-extrusion blow-molded fuel container or a co-extrusion
thermoformed fuel container having an interlayer of a barrier resin
(D) and an inner and outer layers of a polyolefin (A), of which the
portion having poor barrier properties is coated with a melted
powder of a barrier material (B) according to a flame spray coating
process. Concretely, the portion of the container having poor
barrier properties includes, for example, the cutting face of the
pinch-off part of the co-extrusion blow-molded container, the
cutting face of the heat seal part (flange) of the co-extrusion
thermoformed container, the cutting face of the opening formed
through the body of the container, thin area of the container, and
the component for the container.
[0117] In a more preferred embodiment of the co-extrusion
blow-molded fuel container or the co-extrusion thermoformed fuel
container that comprises inner and outer layers of high-density
polyethylene and an interlayer of a barrier resin (D), the
constituent layers are in the form of a laminate formed by
laminating them in that order via an adhesive resin layer of a
carboxylic acid-modified polyolefin therebetween. Still more
preferably, the fuel container is a gasoline tank for
automobiles.
[0118] In a blow-molding process for producing plastic containers,
a parison formed through melt extrusion is, while being held by a
pair of blow molds, pinched off with one pinched-off part being
sealed, and the thus pinched-off parison is blown to be a container
having a predetermined shape. For large-size containers such as
fuel tanks for automobiles, however, the parison held by blow molds
is sealed under pressure, but is not pinched off between the molds.
For most of such containers, the portion having protruded out of
their surface is cut with a cutter or the like so as to have a
predetermined height. Of the blow-molded containers, the sealed and
bonded portion is a pinch-off part, and the face of the portion
having been pinched off between the molds, or the face thereof
having been cut with a cutter or the like is the cutting face of
the pinch-off part. For its cross section, the pinch-off part
protrudes to be thinner in the direction of the thickness of the
container wall, and has a tapered form.
[0119] In case where the parison has a multi-layered structure that
comprises an interlayer of a barrier resin (D) and inner and outer
layers of a polyolefin (A), its blown container could not be
satisfactorily resistant to transmission of fuel such as gasoline
or the like therethrough. This is because the cutting face of the
pinch-off part of the container, or that is, the face of the
portion thereof having been pinched off by molds or the face of the
portion thereof having been cut with a cutter or the like is not
covered with the barrier resin. Concretely referred to is a
co-extrusion blow-molded container of a laminate that comprises
inner and outer layers 11 of a polyolefin (A) and an interlayer 12
of a barrier resin (D), as in FIG. 1. In case where fuel is in the
illustrated container, it passes away through the container at the
cutting face of the pinch-off part, precisely, through the layer of
the polyolefin (A) existing between the facing layers of the
barrier resin (D), as illustrated.
[0120] In a thermoformed process for producing plastic containers,
a multi-layered sheet is co-extruded. Preferably, the multi-layered
sheet comprises inner and outer layers of high-density polyethylene
and an interlayer of a barrier resin (D), the constituent layers
are in the form of a laminate formed by laminating them in that
order via an adhesive resin layer of a carboxylic acid-modified
polyolefin therebetween. And then the sheet is heated. And the
heated sheet is formed to a expected shape, one sheet is for top
aspect of the container and another sheet is bottom aspect of the
container, according to thermoforming process. Thermoforming in the
present invention is a process for heating and softening a sheet
stock and then causing it to conform to a metal mold by vacuum or
compressed air, if necessary, in combination with a plug. This
forming process is classified variously into straight forming,
drape forming, air slip forming, snap back forming, and plug-assist
forming.
[0121] And the thermoformed top and bottom container is adhered by
heat sealing on each edge part. It is favorable that the width of
heat seal part (flange) is usually wide to obtain good enough heat
seal strength and the useless flange is cut out after heat sealing
to avoid deteriorating impact strength at dropping of the fuel
container.
[0122] The thermoformed container could not be satisfactorily
resistant to transmission of fuel such as gasoline or the like
therethrough. This is because the cutting face of the heat seal
part (flange) of the container is not covered with the barrier
resin. This situation is similar to the pinch-off part of a
co-extrusion blow-molded container.
[0123] A fuel tank for automobiles is connected with a fuel port,
an engine, a canister, etc. via pipes therebetween. Therefore, the
body of the tank is formed to have openings therethrough, via which
the tank is connected to the pipes, and various components (fuel
tank connectors, etc.) for connecting the tank to the pipes are
fitted to the tank. In case where the fuel tank for automobiles is
a co-extrusion blow-molded or thermoformed container having an
interlayer of a barrier resin and an inner and outer layers of a
polyolefin, the cutting face of the opening is not covered with the
barrier resin. Therefore, fuel in the tank passes away through the
tank via the cutting face of the layer existing outside the
interlayer of the barrier resin. Concretely, as in FIG. 2, a fuel
tank component such as a fuel tank connector 23 is fitted to the
opening of the body of a co-extrusion blow-molded or thermoformed
container having a laminate structure that comprises inner and
outer layers 21 of a polyolefin (A) and an interlayer 22 of a
barrier resin (D), and a fuel pipe 24 is fitted to the connector
23. Even though both the connector 23 and the fuel pipe 24 are
resistant to fuel transmission through them, fuel still passes away
through the tank via the cutting face of the opening of the body of
the tank, precisely, via the layer existing outside the layer of
the barrier resin (D).
[0124] Recently, it tends to attach importance to expanding inside
the automobile. And the fuel tank of the automobile is often
stuffed into narrow limited space with the other parts (for
example, transmission gear and so on). Therefore, lots of the tank
is required having a shape of complex geometry.
[0125] Blow molding of shapes of complex geometry generates wall
thickness which can vary dramatically depending upon the
variability in blow up ratios. The thin areas of the tank wall
thickness are typically found in the corner or convex areas of blow
molded fuel container which have been stretched by blow mold
process. There is possibility that the fuel permeation from the
fuel container increases at these thin areas.
[0126] Thermoforming of co-extrusion multi-layered sheet comprising
an interlayer of a barrier resin (D) and inner and outer layers of
a polyolefin (A) could also meet same problems. It may be liable to
extreme thinning at corners and streaking and wrinkling at the
thermoforming step. These defects lead to a decrease in impact
resistance of the thermoformed container. There is possibility that
the fuel permeation from the fuel container increases at these thin
areas. In the case that the barrier resin (D) is EVOH, the tendency
is outstanding.
[0127] From the above, it is presumed that the gasoline barrier
properties of the entire fuel container could be improved by
coating the portion of the container having poor barrier
properties. The portion includes the cutting face of the pinch-off
part of the co-extrusion blow-molded container, the cutting face of
the heat seal part (flange) of the co-extrusion thermoformed
container, the cutting face of the opening formed through the body
of the container, thin area of the container, the component for the
container, and so on. For realizing it, however, there still remain
some problems that shall be solved.
[0128] One problem is that coating the portion of the container
having poor barrier properties (the cutting face of the pinch-off
part of the co-extrusion blow-molded container, the cutting face of
the heat seal part (flange) of the co-extrusion thermoformed
container, the cutting face of the opening formed through the body
of the container, thin area of the container, the component for the
container, and so on) with a barrier material is not always easy.
In general, fuel tanks for automobiles are complicated shapes, as
they must be efficiently disposed in a limited space. As being such
a complicated shape, one co-extrusion blow-molded fuel tank often
has a plurality of pinch-off parts. In addition, one fuel tank
generally has a plurality of openings through its body.
[0129] To coat the portion of the fuel container of such a
complicated shape having poor barrier properties with a barrier
material, a solution coating method or an emulsion coating method
is taken into consideration. However, good solvents are not all the
time available for the barrier material for that purpose, and it is
often difficult to prepare a solution or emulsion of the barrier
material. For these reasons, the barrier material employable for
the purpose is limited.
[0130] In general, barrier resins having good gasoline barrier
properties have a large solubility parameter. Concretely, one good
barrier material, EVOH has a solubility parameter (obtained
according to the Fedors' formula) is larger than 11. On the other
hand, the solubility parameter (obtained according to the Fedors'
formula) of high-density polyethylene for the inner and outer
layers of co-extrusion blow-molded or thermoformed containers is
6.7. Therefore, the resin affinity between EVOH and high-density
polyethylene is low, and in case where the two resins are
laminated, they could not enjoy good interlayer adhesion
therebetween. For example, in case where EVOH and high-density
polyethylene are laminated through co-extrusion, they are generally
adhered to each other via an adhesive resin therebetween for
preventing interlayer peeling.
[0131] Accordingly, in case where the cutting face of the pinch-off
part and/or the cutting face of the heat seal part (flange) and/or
the cutting face of the opening of containers is coated with EVOH
in a solution coating or emulsion coating method, it requires
complicated primer treatment or adhesive treatment for ensuring
sufficient interlayer adhesion strength between the cutting face of
polyolefin and the coating layer of EVOH.
[0132] Given that situation, we, the present inventors have
assiduously studied the problems, and, as a result, have found
that, when a powder of a barrier material (B) is, after having been
melted, applied to a substrate of a polyolefin (A) according to a
flame spray coating process, then the coating film of the barrier
material (B) can firmly adhere to the polyolefin substrate (A)
without requiring any specific primer treatment. On the basis of
this finding, we have completed the present invention. In one
preferred embodiment of the invention, the polyolefin (A) is
high-density polyethylene, and the barrier material (B) is EVOH. As
so mentioned hereinabove, good interlayer adhesion between EVOH and
high-density polyethylene cannot be attained in a solution coating
method. Even in a co-extrusion molding method in which different
types of resins are melted and layered into laminate structures,
good interlayer adhesion between EVOH and high-density polyethylene
cannot also be attained. Unexpectedly, however, layers of
high-density polyethylene and EVOH can enjoy good interlayer
adhesion therebetween only when a powder of EVOH is, after having
been melted, applied to the substrate of high-density polyethylene
according to a flame spray coating process.
[0133] The method of applying a powder of a barrier material (B),
after melting it, to a substrate of a polyolefin (A) is a flame
spray coating process. Though not clear, the reason why the barrier
material (B) firmly adheres to the polyolefin substrate (A) when a
powder of the barrier material (B) is, after having been melted,
applied to the polyolefin substrate (A) according to a flame spray
coating process will be because, while a melt of a powdery resin of
the barrier material (B) is sprayed over the surface of the
polyolefin substrate (A) through a nozzle along with a flame being
applied thereover, and is deposited thereon, the surface of the
polyolefin substrate (A) is processed with the flame applied
thereto, whereby the interlayer adhesion between the polyolefin
substrate (A) and the layer of the barrier material (B) formed
thereon could be enhanced.
[0134] Preferably, the surface of the substrate of polyolefin (A)
is heated in advance before applying a powder of barrier material
(B) to the substrate according to a flame spray coating. It is
possible to improve adhesiveness between the barrier material (B)
and the substrate of polyolefin (A) by the preheating. The
temperature of the preheating is not limitative. It is preferably
40 to 160.degree. C., more preferably 80 to 150.degree. C., and
even more preferably 100 to 150.degree. C.
[0135] The method of preheating of the surface of the substrate of
polyolefin (A) is not limitative. Suitable methods include heating
the whole surface of the shaped article of polyolefin (A); heating
a part of the surface of the shaped article which will be coated
with a barrier material (B). In case the shaped article is small
(for example, a component for fuel containers fuel containers, a
connector of floor heating pipes and so on), it may be preferable
to heat the whole surface of the shape article. On the other hand,
however, it is usually preferable to heat the part of the surface
of the shaped article. Especially to maintain the size of shaped
article during preheating, to heat the part of the surface of the
shaped article is suitable.
[0136] For example, in case of applying a barrier material (B) to
pinch-off part or heat seal part of the multi-layered fuel
container, it is reasonable to heat only these part of the
container in view of saving energy. Moreover, preheating the whole
surface of the container requires a lot of time and energy. If the
container is heated for a long time, there is possibility that
deformation occurs.
[0137] Concretely, the method of preheating of the surface of the
shaped article of polyolefin (A) includes storing in a thermostat
chamber at a predetermined temperature; using various heaters and
so on. Especially, the present inventors recommend the method which
is characterized in processing the surface with flame.
[0138] In one preferred embodiment of the method, the surface of
the shaped article of polyolefin (A) is heated with flame to reach
expected temperature, followed by applying a powder of a barrier
material (B) to the resulting surface according to a flame coating
process before the surface gets cold. It is required to heat the
surface by flame itself prior to coat barrier material (B) with
flame to improve adhesive strength between surface and coating
barrier material (B). It is convenient to heat up the shaped
article by flame without powdery barrier material (B), since using
same facility is able to avoid drop temperature down before coating
barrier material (B).
[0139] The distance from gun nozzle of the facility to the surface
of the shaped article preferably falls between 10 and 30 inches,
more preferably between 15 and 20 inches. While applying a powder
of a barrier material (B) to the resulting surface according to a
flame coating process, it is preferable that the speed of moving of
the gun nozzle falls between 1 and 4 inches per second, more
preferably between 2 and 3 inches per second.
[0140] Preferably, the grain size of the powder of the barrier
material (B) to be applied to the substrate according to such a
flame spray coating process falls between 20 and 100 meshes (JIS
K-8801) (that is, the powder passes through a 20-mesh sieve but not
through a 100-mesh sieve). More preferably, the grain size falls
between 30 and 100 meshes. In case where a large amount of a rough
powder not passing through a 20-mesh sieve is used in a flame spray
process, it will clog the nozzle and the surface of the coating
film will be roughened. That is, a coating film having a smooth
surface is difficult to obtain in that case. On the other hand, in
case where a large amount of a fine powder passing through a
100-mesh sieve is used in the process, the powder will be readily
burnt by the flame applied thereto. In addition, preparing such a
fine powder costs a lot.
[0141] Though not specifically defined, the thickness of the
coating film of the barrier material (B) preferably falls between 1
and 500 .mu.m. The lowermost limit of the thickness of the coating
film of the barrier material (B) is more preferably at least 5
.mu.m, even more preferably at least 10 .mu.m. The uppermost limit
of the thickness of the coating film of the barrier material (B) is
more preferably at most 300 .mu.m, even more preferably at most 250
.mu.m. Coating films of the barrier material (B) having a thickness
of smaller than 1 .mu.m will have poor gasoline barrier properties
and poor oxygen barrier properties. On the other hand, coating
films of the barrier material (B) having a thickness of larger than
500 .mu.m will be readily peeled off from substrates.
[0142] From the viewpoint of the adhesion strength of the coating
film of the barrier material (B) in the shaped article of the
invention, one preferred embodiment of producing the shaped article
comprises applying a powder of a carboxylic acid-modified or
boronic acid-modified polyolefin to the substrate of a polyolefin
(A) according to a flame spray coating process, followed by
applying a powder of a barrier material (B) to the resulting
carboxylic acid-modified or boronic acid-modified polyolefin layer
also according to a flame spray coating process.
[0143] The thickness of the carboxylic acid-modified or boronic
acid-modified polyolefin layer is not specifically defined so far
as it is enough for ensuring good adhesion of the layer to both the
polyolefin substrate (A) and the layer of the barrier material (B),
but preferably falls between 1 and 500 .mu.m. The lowermost limit
of the thickness of the carboxylic acid-modified or boronic
acid-modified polyolefin layer is more preferably at least 5 .mu.m,
even more preferably at least 10 .mu.m. The uppermost limit of the
thickness of the carboxylic acid-modified or boronic acid-modified
polyolefin layer is more preferably at most 250 .mu.m. If its
thickness is smaller than 1 .mu.m, the carboxylic acid-modified or
boronic acid-modified polyolefin layer could not satisfactorily
exhibit its function as an adhesive between the polyolefin (A) and
the barrier material (B). On the other hand, if its thickness is
larger than 500 .mu.m, the layer will easily peel off from the
substrate. From the viewpoint of the gasoline barrier properties
and the oxygen barrier properties of the shaped article to be
obtained herein, the step of applying a powder of the barrier
material (B), after melting it, to the carboxylic acid-modified or
boronic acid-modified polyolefin layer is preferably so effected
that the carboxylic acid-modified or boronic acid-modified
polyolefin layer is, without being exposed outside, covered with
the layer of the barrier material (B).
[0144] On the other hand, from the viewpoint of the impact strength
of the coating film of the barrier material (B) in the shaped
article of the invention, the shaped article is produced in another
preferred embodiment that comprises applying a powder of a barrier
material (B), after melting it, to the substrate of a polyolefin
(A), followed by applying a powder of a thermoplastic resin (C)
having an elastic modulus at 20.degree. C. of at most 500
kg/cm.sup.2, after melting it, to the resulting layer of the
barrier material (B). Similarly, for improving the impact strength
of the coating film of the barrier material (B) in the shaped
article of the invention, also preferred is still another
embodiment that comprises applying a powder of a thermoplastic
resin (C) having an elastic modulus at 20.degree. C. of at most 500
kg/cm.sup.2, after melting it, to the substrate of a polyolefin
(A), followed by applying a powder of a barrier material (B), after
melting it, to the resulting layer of the thermoplastic resin (C).
In these embodiments, the powder of a barrier material (B) and the
powder of a thermoplastic resin (C) are applied to the polyolefin
substrate (A) according to a flame spray coating process.
[0145] The thickness of the layer of the thermoplastic resin (C) is
not specifically defined, but preferably falls between 1 and 500
.mu.m. The lowermost limit of the thickness of the layer of the
thermoplastic resin (C) is more preferably at least 5 .mu.m, even
more preferably at least 10 .mu.m. The uppermost limit of the
thickness of the layer of the thermoplastic resin (C) is more
preferably at most 250 .mu.m. If the thickness of the layer of the
thermoplastic resin (C) is smaller than 1 .mu.m, the effect of the
layer for improving the impact resistance of the layer of the
barrier material (B) will be poor; but if larger than 500 .mu.m,
the layer will easily peel off. From the viewpoint of the gasoline
barrier properties and the oxygen barrier properties of the shaped
article to be obtained herein, the step of applying a powder of the
barrier material (B), after melting it, to the layer of the
thermoplastic resin (C) is preferably so effected that the layer
(C) is, without being exposed outside, covered with the layer of
the barrier material (B).
[0146] The invention relates to a shaped article produced by
applying a powder of a barrier material (B), after melting it, to
at least a part of the surface of a substrate of a polyolefin (A)
according to a flame spray coating process. The invention is
especially effective for the shaped article produced through
injection molding. According to the invention, even the shaped
article of such a complicated shape can be coated with a barrier
material (B) to have barrier properties. To this effect, the
meaning of the invention is significant. Preferred examples of the
shaped article produced through injection molding are a head of a
tubular container, and a component for fuel containers.
[0147] The component for fuel containers is a member to be attached
to fuel containers, including, for example, connectors for fuel
containers, caps for fuel containers, release valves for fuel
containers, etc. However, these are not limitative. The component
for fuel containers may have a single-layered structure, or may
have a multi-layered structure that comprises a layer of a
polyolefin (A) and a barrier layer of a barrier resin (D).
[0148] One preferred embodiment of the connector for fuel
containers is such that a flexible pipe for fuel transportation is
fitted to the connector that is fitted to the body of a fuel tank,
but this is not limitative. For fitting the connector to the body
of a fuel tank, for example, employable is any method of screwing,
embedding, heat sealing, etc. Preferred is heat sealing, as its
process is simple and the heat-sealed portion is resistant to fuel
leak.
[0149] The cap for fuel containers is a member for closing fuel
ports. The method of fitting the cap to a fuel container is not
specifically defined, including, for example, screwing, embedding,
etc. Preferred is screwing. At present, many caps for fuel
containers are made of metal. However, thermoplastic resin caps are
being popularized these days, as being lightweight and recyclable.
A fuel port is connected to the body of a fuel tank via a fuel pipe
and a connector therebetween. Heretofore, metal caps for fuel
containers are said to be problematic in that metal oxides from
rusted metal caps contaminate fuel in tanks. To that effect, the
meaning of thermoplastic resin caps is great.
[0150] For making a fuel container component of a polyolefin (A)
have barrier properties, the component is attached to the body of a
fuel container, and then a powder of a barrier material (B) is,
after having been melted, applied thereto; or a powder of a barrier
material (B) is, after having been melted, applied to the
component, and then the thus-coated component is attached to the
body of a fuel container. In the latter case, the component is
preferably heat-sealed to the body of a fuel container. In one
preferred embodiment for the case, the area except the heat-sealed
portion is coated with the barrier material (B).
[0151] The multi-layered shaped article of the invention, which is
obtained by applying a powder of a barrier material (B), after
melting it, to a substrate of a polyolefin (A), is favorable to
fuel pipes and floor heating pipes. Fuel pipes are usable not only
as those for automobiles but also as fuel lines for transporting
fuel from oil fields. A plurality of such fuel pipes are often
connected to each other via connectors therebetween. The connectors
are complicated shapes (preferably, these are produced in a process
of injection molding), and are required to have gasoline barrier
properties and/or oxygen barrier properties. Therefore, the
multi-layered shaped article of the invention is favorable to the
connectors.
[0152] The fuel pipes and the floor heating pipes are preferably
multi-layered pipes of a laminate that comprises an interlayer of a
barrier resin (D) and inner and outer layers of a polyolefin (A).
For connecting such multi-layered pipes to each other via
connectors therebetween, often employed is a process of first
expanding the diameter of the edges of each pipe by means of a
specific expanding tool, in which the step of expanding the
diameter is effected gradually and several times. In the process,
the barrier resin (D) is often cracked in the portion of the
expanded multi-layered pipe. In particular, in case where such
multi-layered pipes are worked in the environment in which the
outside air temperature is extremely low, for example, in the
district where floor heaters are installed, the layer of the
barrier resin (D) is often seriously cracked. The cracks detract
from the gasoline barrier properties and/or the oxygen barrier
properties of the bonded portion of the multi-layered pipes.
[0153] However, by applying a powder of a barrier material (B),
after melting it, to the expanded portion of the multi-layered
pipes, the gasoline barrier properties and/or the oxygen barrier
properties of the bonded portion of the pipes can be significantly
enhanced.
EXAMPLES
[0154] The invention is described in more detail with reference to
the following Examples, which, however, are not intended to
restrict the scope of the invention.
(1-1) Evaluation of the Fuel Permeation Amount of the Barrier
Material (B)
[0155] A specimen of a layered product including a layer of barrier
material (B) was prepared as explained below, the fuel permeation
amount of this layered product was determined, and converted into
the permeation amount of barrier material (B) of a predetermined
thickness.
[0156] The high-density polyethylene (HDPE) BA-46-055 (having a
density of 0.970 g/cm.sup.3, and a MFR of 0.03g/10 min at
190.degree. C. and 2160 g) by Paxon was used; for the adhesive
resin, ADMER GT-6A (having a MFR of 0.94g/10 min at 190.degree. C.
and 2160 g) by Mitsui Chemicals, Inc. was used. A barrier material
(B) to be tested, the high-density polyethylene and the adhesive
resin were given into separate extruders, and a coextrusion sheet
with a total thickness of 120 .mu.m having the structure
high-density polyethylene/adhesive resin/barrier material
(B)/adhesive resin/high-density polyethylene (film thickness 50
.mu.m/5 .mu.m/10 .mu.m/5 .mu.m/50 .mu.m) was obtained by extrusion
molding. In the above coextrusion sheet molding, the high-density
polyethylene was extruded from an extruder (barrel temperature: 170
to 210.degree. C.) having a uniaxial screw of 65 mm diameter and
L/D=24, the adhesive resin was extruded from an extruder (barrel
temperature: 160 to 210.degree. C.) having a uniaxial screw of 40
mm diameter and L/D=22, and the barrier material (B) was extruded
from an extruder (barrel temperature: 170 to 210.degree. C.) having
a uniaxial screw of 40 mm diameter and L/D=22 into a
feed-block-type die (600 mm width and temperature adjusted to
210.degree. C.) to obtain a coextrusion sheet (a1).
[0157] One side of the coextrusion sheet (a1) was covered with
aluminum adhesive tape (product by FP Corp., trade name
"Alumi-seal"; fuel permeation amount of 0 g.multidot.20
.mu.m/m.sup.2.multidot.day), thereby obtaining the aluminum-covered
sheet (b1).
[0158] Both the coextrusion sheet (a1) and the aluminum-covered
sheet (b1) were cut into pieces of 210 mm.times.300 mm size. Then
these pieces were folded in the middle so their size became 210
mm.times.150 mm, and using the Heat Sealer T-230 by Fuji Impulse
Co., pouches were prepared by heat-sealing of any two sides with
dial 6 so that the seal width becomes 10 mm. Thus, pouches (a2)
made of the coextrusion sheet only and aluminum-covered pouches
(b2) were obtained. The aluminum-covered pouches (b2) were made so
that the aluminum layer was on the outside.
[0159] Then, 200 ml of Ref. fuel C (toluene/isooctane=1/1 by
volume) was filled as model gasoline into the pouches through the
opening portions, and then the pouches were heat-sealed with a
sealing width of 10 mm by the afore-mentioned method.
[0160] The pouches, filled with gasoline, were shelved in an
explosion-proof thermo-hygrostat chamber (at 40.degree. C. and 65%
RH), and the weight of the pouches was measured every seven days
over a period of three months. This experiment was carried out on
five each of the coextrusion sheet pouches (a2) and the
aluminum-covered pouches (b2). The weight of the pouches before and
during the shelf-test was measured, and the gasoline permeation
amount (fuel permeation amount) was calculated from the slope of a
curve prepared according to the weight change of the pouches over
the shelf time.
[0161] The fuel permeation amount of the pouches (a2) made only of
the coextrusion sheet corresponds to the sum of the permeation
amount through the pouch surface and through the heat-sealing
portions, whereas the fuel permeation amount of the
aluminum-covered pouches (b2) corresponds to the permeation amount
through the heat-sealing portions.
[0162] {fuel permeation amount through (a2)}-{fuel permeation
amount through (b2)}was taken as the fuel permeation amount per 10
.mu.m of the barrier material (B). Converting this into the
permeation amount per 20 .mu.m of a barrier material (B) layer, the
resulting value was taken as the fuel permeation amount
(g.multidot.20 .mu.m/m.sup.2.multidot.day) of the barrier material
(B).
(1-2) Evaluation of the Fuel Permeation Amount of Polyolefin
(A)
[0163] Toyo Seiki's Laboplastomil equipped with a single screw
having a diameter of 20 mm and L/D of 22 was used. Through its
coathanger die having a width of 300 mm, a polyolefin (A) was
extruded out at a temperature higher by 20.degree. C. than its
melting point to prepare a 100 .mu.m sheet. The sheet was cut into
a size of 210 mm.times.300 mm.
[0164] Then these pieces were folded in the middle so their size
became 210 mm.times.150 mm, and using the Heat Sealer T-230 by Fuji
Impulse Co., pouches were prepared by heat-sealing of any two sides
with dial 6 so that the seal width becomes 10 mm.
[0165] Then, 200 ml of Ref. fuel C (toluene/isooctane=1/1 by
volume) was filled as model gasoline into the resulting pouches
through the opening portions, and then the pouches were heat-sealed
with a sealing width of 10 mm by the aforementioned method.
[0166] The pouches, filled with gasoline, were shelved in an
explosion-proof thermo-hygrostat chamber (at 40.degree. C. and 65%
RH), and the weight of the pouches was measured every six hours
over a period of three days. This experiment was carried out on
five pouches. The weight of the pouches before and during the
shelf-test was measured, and the gasoline permeation amount (fuel
permeation amount) was calculated from the slope of a curve
prepared according to the weight change of the pouches over the
shelf time. By thickness conversion, the permeation amount
(g.multidot.20 .mu.m/m.sup.2.multidot.day) was calculated.
(1-3) Evaluation of the Fuel Permeation Amount of the Barrier Resin
(C)
[0167] The fuel permeation amount was measured using the same
method as for the barrier material (B).
(2) Measurement of Oxygen Barrier Properties of Barrier Material
(B)
[0168] Toyo Seiki's Laboplastomil equipped with a single screw
having a diameter of 20 mm and L/D of 22 was used. Through its
coathanger die having a width of 300 mm, a barrier material (B) was
extruded out at a temperature higher by 20.degree. C. than its
melting point to prepare a 25 .mu.m film. Using an oxygen
transmission rate measuring device, Modern Control's Ox-Tran-100,
the oxygen transmission rate through the film was measured at
20.degree. C. and 65% RH. The data obtained are given in Table
1.
1TABLE 1 List of Barrier Materials Fuel Oxygen permeation
Transmission amount*1 Rate*2 b-1 EVOH having an ethylene content of
-- 3.2 48 mol%, a degree of saponification of 99.6%, and MFR of
13.1 g/10 min (at 190.degree. C. under a load of 2160 g) b-2 EVOH
having an ethylene content of 0.003 0.4 32 mol%, a degree of
saponification of 99.5%, and MFR of 4.6 g/10 min (at 190.degree. C.
under a load of 2160 g) b-3 Ube Kosan's Nylon 3014U 30 200 b-4
(b-1)/boronic acid-modified -- 3.6 polyethylene produced in
Synthesis Example 1 = 90/10% by weight b-5 (b-1)/multi-layered
polymer particles -- 3.5 produced in Synthesis Example 2 = 90/10%
by weight *1 g .multidot. 20 .mu.m/m.sup.2 .multidot. day *2 cc
.multidot. .mu.m/m.sup.2 .multidot. day .multidot. atm
Example 1
[0169] Polyethylene having MFR of 0.3 g/10 min (at 190.degree. C.
under a load of 2160 g) and a density of 0.952
g/cm.sup.3(hereinafter referred to as HDPE) was injection-molded
into pieces having a size of 10 cm.times.10 cm and a thickness of 1
mm. On the other hand, a barrier material (B) of pellets (b-1)
{EVOH having an ethylene content of 48 mol %, a degree of
saponification of 99.6%, and MFR of 13.1 g/10 min (at 190.degree.
C. under a load of 2160 g)} was powdered in a low-temperature mill
(in which was used liquid nitrogen). The resulting powder was
sieved, and its fraction having passed through a 40-mesh sieve but
not through a 100-mesh sieve was collected. According to a flame
spray coating process, the resulting barrier material powder (b-1)
was sprayed on one surface of the injection-molded piece by using
Innotex's spray gun, and then left cooled in air. The thickness of
the coating layer was 50 .mu.m.
(3) Measurement of Oxygen Transmission Rate Through Sheet
[0170] The injection-molded piece of HDPE that had been coated with
a powder of the barrier material (B) was set in an oxygen
transmission rate measuring device, Modern Control's Ox-Tran-100,
in such a manner that its surface coated with the barrier material
(B) could be exposed to oxygen therein. Being thus set in the
device, the oxygen transmission rate through the test piece was
measured at 20.degree. C. and 65% RH. It is given in Table 2.
(4) Impact Strength
[0171] The injection-molded piece of HDPE that had been coated with
a powder of the barrier material (B) was subjected to a dart impact
test according to JIS K-7124. The total of the dart and the weight
used in the test was 320 g. The height for the test was 150 cm. The
sample piece was so set in the tester that the dart could be shot
nearly at the center of its surface coated with the barrier
material (B). After the dart impact test, the condition of the
coating film of the barrier material (B) of the tested sample piece
was macroscopically checked as to how and to what degree the
coating film was damaged by the dart. According to the criteria
mentioned below, the tested sample piece was evaluated for its
impact resistance and adhesiveness. The test results are given in
Table 2.
Impact Resistance
[0172] A: Not cracked.
[0173] B: Slightly cracked.
[0174] C: Cracked a little in and around the dart-shot portion.
[0175] C: Cracked over the surface.
Adhesiveness
[0176] A: The barrier material (B) did not peel.
[0177] B: Partly peeled in and around the dart-shot portion.
[0178] C: Peeled over the surface.
Example 2
[0179] Another barrier material (B) of (b-2) {EVOH having an
ethylene content of 32 mol %, a degree of saponification of 99.5%,
and MFR of 4.6 g/10 min (at 190.degree. C. under a load of 2160 g)}
was tested and evaluated in the same manner as in Example 1. The
test results are given in Table 2.
Example 3
[0180] Another barrier material (B) of (b-3) {Ube Kosan's nylon-12,
Nylon 3014U} was tested and evaluated in the same manner as in
Example 1. The test results are given in Table 2.
Example 4
[0181] Polyethylene having MFR of 0.3 g/10 min (at 190.degree. C.
under a load of 2160 g) and a density of 0.952 g/cm.sup.3 was
injection-molded into pieces having a size of 10 cm.times.10 cm and
a thickness of 1 mm. One surface of each piece was sprayed with a
powder of ethylene-methacrylic acid copolymer (hereinafter referred
to as EMAA) {Mitsui DuPont Polychemical's Nucrel 0903HC, having a
methacrylic acid (MM) content of 9% by weight and having MFR of 5.7
g/10 min (at 210.degree. C. under a load of 2160 g)--this was
powdered in the same manner as in Example 1} according to a flame
spray coating process. The thickness of the coating layer was 50
.mu.m. Next, the barrier material (b-1) having been powdered in the
same manner as in Example 1 was sprayed on the coating film of EMMA
also according to a flame spray coating process. Its thickness was
50 .mu.m. The injection-molded pieces of HDPE that had been thus
coated with a powder of EMAA and a powder of the barrier material
(B) were tested and evaluated in the same manner as in Example 1.
The test results are given in Table 2.
Example 5
[0182] An ethylene-propylene copolymer (hereinafter referred to as
EPR; Mitsui Chemical's Tafmer P0280 having an elastic modulus of
smaller than 500 kg/cm.sup.2--this was powdered in the same manner
as in Example 1) was sprayed on the coating film of the barrier
material (b-1) of the injection-molded pieces of HDPE produced in
Example 1 (these were coated with a 50 .mu.m layer of the barrier
material (b-1)), according to a flame spray coating process. The
thickness of the coating film of EPR was 50 .mu.m. The
injection-molded pieces of HDPE that had been thus coated with a
powder of the barrier material (B) and a powder of EPR were tested
and evaluated in the same manner as in Example 1. The test results
are given in Table 2.
Synthesis Example 1
[0183] 1000 g of very-low-density polyethylene {MFR, 7 g/10 min (at
210.degree. C. under a load of 2160 g); density, 0.89 g/cm.sup.3;
terminal double bond content, 0.048 meq/g} and 2500 g of decalin
were put into a separable flask equipped with a condenser, a
stirrer and a dropping funnel, then degassed at room temperature
under reduced pressure, and thereafter purged with nitrogen. To
this were added 78 g of trimethyl borate and 5.8 g of
borane-triethylamine complex, and reacted at 200.degree. C. for 4
hours. Next, an evaporator was fitted to the flask, and 100 ml of
methanol was gradually dripped thereinto. After methanol was thus
added thereto, the system was evaporated under reduced pressure to
remove low-boiling-point impurities such as methanol, trimethyl
borate and triethylamine from it. Next, 31 g of ethylene glycol was
added to the system, and stirred for 10 minutes. Acetone was added
thereto for reprecipitation, and the deposit was taken out and
dried. The product thus obtained is boronic acid-modified
very-low-density polyethylene having an ethylene glycol boronate
content of 0.027 meq/g and having MFR of 5 g/10 min (at 210.degree.
C. under a load of 2160 g).
Example 6
[0184] 10 parts by weight of the boronic acid-modified
very-low-density polyethylene that had been prepared in Synthesis
Example 1, and 90 parts by weight of a barrier material (b-1) were
put into a double-screw vent extruder, and extruded out for
pelletization in the presence of nitrogen at 220.degree. C. The
pellets are of a barrier material (b-4). These were powdered in the
same manner as in Example 1.
[0185] The barrier material (B) of a powder of the barrier material
(b-4) that had been prepared herein was tested and evaluated in the
same manner as in Example 1. The test results are given in Table
2.
Synthesis Example 2
[0186] 600 parts by weight of distilled water, and 0.136 parts by
weight of sodium laurylsarcosinate and 1.7 parts by weight of
sodium stearate both serving as an emulsifier were put into a
polymerization reactor equipped with a stirrer, a condenser and a
dropping funnel, in a nitrogen atmosphere, and dissolved under heat
at 70.degree. C. into a uniform solution. Next, at the same
temperature, 100 parts by weight of butyl acrylate, 60 parts by
weight of ethyl acrylate, and 2.0 parts by weight of a
poly-functional polymerizable monomer, allyl methacrylate were
added thereto, and stirred for 30 minutes. Then, 0.15 parts by
weight of potassium peroxo-disulfate was added thereto to start
polymerization. After 4 hours, it was confirmed through gas
chromatography that all monomers were consumed.
[0187] Next, 0.3 part by weight of potassium peroxo-disulfate was
added to the resulting copolymer latex, and thereafter a mixture of
60 parts by weight of methyl methacrylate, 20 parts by weight of
methacrylic acid, and 0.1 part by weight of n-octylmercaptan
serving as a chain transfer agent was dropwise added thereto
through the dropping funnel over a period of 2 hours. After the
addition, this was further reacted at 70.degree. C. for 30 minutes.
After it was confirmed that all monomers were confirmed, the
polymerization was finished. The latex thus obtained had a mean
particle size of 0.20 .mu.m. This was cooled at -20.degree. C. for
24 hours for coagulation, and the thus-coagulated solid was taken
out and washed three times with hot water at 80.degree. C. Next,
this was dried under reduced pressure at 50.degree. C. for 2 days.
The product is a latex of two-layered polymer particles having an
inner layer of acrylic rubber of essentially butyl acrylate
(Tg=-44.degree. C.) and an outermost hard layer of methyl
methacrylate and methacrylic acid (Tg=128.degree. C.). The particle
size of the multi-layered polymer particles in the thus-prepared
latex was measured according to a dynamic light scattering process
using a laser particle size analyzer system, PAR-III (from Otuka
Electronics). As a result, the mean particle size of the
multi-layered polymer particles was 0.20 .mu.m.
Example 7
[0188] 10 parts by weight of the above-mentioned multi-layered
polymer particles, and 90 parts by weight of a barrier material
(b-1) were put into a double-screw vent extruder, and extruded out
for pelletization in the presence of nitrogen at 220.degree. C. The
pellets are of a barrier material (b-5). These were powdered in the
same manner as in Example 1. The barrier material (B) of a powder
of the barrier material (b-5) that had been prepared herein was
tested and evaluated in the same manner as in Example 1. The test
results are given in Table 2.
Comparative Example 1
[0189] Polyethylene having MFR of 0.3 g/10 min (at 190.degree. C.
under a load of 2160 g) and a density of 0.952 g/cm.sup.3 was
injection-molded into pieces having a size of 10 cm.times.10 cm and
a thickness of 1 mm. The oxygen transmission rate through the piece
was 50 cc/m.sup.2.multidot.day.multidot.atm.
Comparative Example 2
[0190] A barrier material (b-1) was dissolved in a mixed solvent of
water/isopropyl alcohol=35 parts by weight/65 parts by weight,
under heat at 80.degree. C. to prepare an EVOH solution, in which
the amount of the barrier material EVOH was 10 parts by weight.
[0191] One surface of an injection-molded piece (10 cm.times.10 cm
in size, 1 mm in thickness) of polyethylene (having MFR of 0.3 g/10
min at 190.degree. C. under a load of 2160 g, and a density of
0.952 g/cm.sup.3) that had been prepared in the same manner as in
Example 1 was coated with the EVOH solution according to a solution
coating process. The coating film of EVOH had a mean thickness of
20 .mu.m. The thus EVOH-coated, injection-molded piece was
immediately dried in a hot air drier at 80.degree. C. for 5
minutes, but the coating film of the barrier material (b-2) peeled
off while the piece was dried.
2 TABLE 2 Oxygen Transmission Adhesion Rate*3 Impact Strength
Strength Example 1 1.2 B B Example 2 0.2 C B Example 3 31 B B
Example 4 1.2 A A Example 5 1.2 A B Example 6 1.5 A B Example 7 1.4
A B Comp. Example 1 50 -- -- *3 cc/m.sup.2 .multidot. day
.multidot. atm
[0192] As in the above, the shaped articles of Examples 1 to 7 of
the invention, which had been produced by applying a powder of a
barrier material (B), after melting it, to a substrate of a
polyolefin (A) all had good oxygen barrier properties. Though the
substrate of a polyolefin (A) of these shaped articles was not
subjected to any special primer treatment, the coating film of the
barrier material (B) formed on the substrate had good interlayer
adhesiveness to the substrate.
[0193] In the multi-layered shaped article of Example 6, for which
the barrier material (B) used was a resin composition comprising
90% by weight of EVOH and 10% by weight of a boronic acid-modified
polyolefin, and in the multi-layered shaped article of Example 7,
for which the barrier material (B) used was a resin composition
comprising 90% by weight of EVOH and 10% by weight of multi-layered
polymer particles, the impact strength of the coating film of the
barrier material (B) was higher than that in the shaped article of
Example 1.
[0194] In the multi-layered shaped article of Example 5, which had
been produced by applying a powder of a barrier material (b-1) to
an injection-molded piece of high-density polyethylene according to
a flame spray coating process, followed by applying a powder of EPR
to the resulting layer of the barrier material (b-1) also according
to a flame spray coating process, the impact strength of the
coating film of the barrier material (B) was improved.
[0195] In the multi-layered shaped article of Example 4, which had
been produced by applying a powder of EMAA to an injection-molded
piece of high-density polyethylene according to a flame spray
coating process, followed by applying a powder of a barrier
material (b-1) to the resulting EMAA layer also according to a
flame spray coating process, the impact strength and also the
adhesiveness of the coating film of the barrier material (b-1) were
both improved.
[0196] As opposed to these, however, in the shaped article of
Comparative Example 2, which had been produced by applying a
solution of a barrier material (b-1) to an injection-molded piece
of high-density polyethylene according to a solution coating
process, the barrier material (b-1) did not adhere at all to the
high-density polyethylene. Accordingly, the injection-molded piece
processed in Comparative Example 2 did not have barrier
properties.
Example 8
[0197] Paxon's BA46-055 (this is high-density polyethylene, HDPE,
having a density of 0.970 g/cm.sup.3, and MFR at 190.degree. C.
under a load of 2160 g of 0.03 g/10 min, and the gasoline
permeation amount through it is 4000 g.multidot.20
.mu.m/m.sup.2.multidot.day); Mitsui Chemical's ADMER GT-6A serving
as an adhesive resin (Tie) (this has MFR at 190.degree. C. under a
load of 2160 g of 0.94 g/10 min); and a barrier resin (D),
ethylene-vinyl alcohol copolymer having an ethylene content of 32
mol %, a degree of saponification of 99.5 mol %, and MFR at
190.degree. C. under a load of 2160 g of 1.3 g/10 min (the gasoline
permeation amount through it is 0.003 g.multidot.20
.mu.m/m.sup.2.multidot.day) were blow-molded by the use of a Suzuki
Seikojo's blow-molding machine, TB-ST-6P. Precisely, these resins
were first extruded out at 210.degree. C. into a three-resin,
five-layered parison of (inner side) HDPE/Tie/Barrier/Tie/HD- PE
(outer side), and the parison was blown in a mold at 15.degree. C.,
and then cooled for 20 seconds to be a 35-liter tank of (outer
side) HDPE/adhesive resin/EVOH (D)/adhesive resin/HDPE (inner
side)=2500/100/150/100/2500 (.mu.m) having an overall wall
thickness of 5250 .mu.m. The pinch-off part of the tank had a
length of 920 mm, a width of 5 mm and a height of 5 mm. A part of
the pinch-off part was heated by Innotex's spray gun without powder
of a barrier material (b-1) until temperature of the part reaches
to around 130.degree. C. The temperature is measured by Cole-parmer
instrument's thermometer J type. After the preheating, a powder of
a barrier material (b-1) that had been powdered in the same manner
as in Example 1 was sprayed on the pinch-off part of the fuel tank
by the spray gun according to a flame spray coating process. The
distance from gun nozzle of the facility to the surface of the
shaped article was about 17 inches. While applying a powder of a
barrier material (B) to the resulting surface according to a flame
coating process, the speed of moving of the gun nozzle was about a
few inches per second. The process was repeated, and the whole
pinch-off part was sprayed coated. And then, the tank left cooled
in air. The thickness of the coating film layer of the barrier
material (b-1) was 50 .mu.m, and the barrier material layer spread
over the range of 25 mm around the pinch-off part. The surface of
the resulting shaped article was smooth. The fuel transmission rate
through the pinch-off part of the fuel tank, and the impact
strength of the fuel tank were measured. The data obtained are
given in Table 3.
(5) Fuel Permeation Amount of the Pinch-Off Part of Tank
[0198] Except its pinch-off part, the shaped article, 35-liter tank
was coated with a film of polyethylene 60 .mu.m/aluminium foil 12
.mu.m/polyethylene 60 .mu.m, through heat lamination with ironing
at 170.degree. C. The coating film is for preventing gasoline
permeation through the area except the pinch-off part of the tank.
30 liters of model gasoline, Ref. fuel C (toluene/isooctane=50/50%
by volume) was put into the tank through its mouth (this served as
a blowing mouth while the tank was produced by blow molding), and
the mouth was then sealed with an aluminium tape (FP Kako's
commercial product of Alumiseal this is resistant to gasoline
permeation therethrough, having a gasoline permeation amount of 0
g.multidot.20 .mu.m/m.sup.2.multidot.day). The tank with gasoline
therein was left at 40.degree. C. and 65% RH for 3 months. Three
35-liter tanks of the same type were tested in that manner, and the
weight change of each tank before and after the test was obtained.
The average of the data obtained indicates the fuel permeation
amount through the pinch-off part of the tank.
(6) Drop and Impact Test
[0199] 30 liters of water was put into the tank of which the
pinch-off part had been coated with a barrier material (B), and the
mouth of the tank was sealed with an aluminium tape (FP Kako's
commercial product of Alumiseal--this is resistant to gasoline
permeation therethrough, having a gasoline permeation amount of 0
g.multidot.20 .mu.m/m.sup.2.multidot.da- y). The tank was dropped
down from a height of 10 m with its pinch-off part being prevented
from colliding against the ground. After having been thus dropped
down, the pinch-off part of the tank was checked for its
condition.
Impact Resistance
[0200] A: No change found in the coating film of the barrier
material (B) on the pinch-off part.
[0201] B: The coating film of the barrier material (B) on the
pinch-off part cracked only slightly.
[0202] C: The coating film of the barrier material (B) on the
pinch-off part partly cracked and peeled.
[0203] D: The coating film of the barrier material (B) on the
pinch-off part cracked and peeled over it.
Example 9
[0204] A fuel tank was produced in the same manner as in Example 8,
of which, however, the pinch-off part was coated with a barrier
material (B), (b-2). This was tested and evaluated in the same
manner as in Example 8. The test results are given in Table 3.
Example 10
[0205] The same fuel tank as in Example 8 was processed as follows:
A powder of EMM {Mitsui DuPont Polychemical's Nucrel 0903HC, having
a methacrylic acid (MAA) content of 9% by weight and having MFR of
5.7 g/10 min (at 210.degree. C. under a load of 2160 g)} was
sprayed on the pinch-off part of the tank, according to a flame
spray coating process as in Example 4. The thickness of the coating
layer was 50 .mu.m. The coating layer spread over the range of 20
mm around the pinch-off part. Next, the same barrier material (b-1)
as in Example 8 was sprayed on the thus-coated pinch-off part in
the same manner as in Example 8. The thickness of the barrier layer
coated was 50 .mu.m. The barrier layer spread over the range of 25
mm around the pinch-off part. The thus-processed tank was tested
and evaluated in the same manner as in Example 8. The test results
are given in Table 3.
Example 11
[0206] A fuel tank was produced in the same manner as in Example 8,
of which, however, the pinch-off part was coated with a barrier
material (B), (b-3). This was tested and evaluated in the same
manner as in Example 8. The test results are given in Table 3.
Comparative Example 3
[0207] A fuel tank was produced in the same manner as in Example 8,
of which, however, the pinch-off part was not coated with a barrier
material (B). The fuel transmission rate through the pinch-off part
of the fuel tank was measured. The data obtained are given in Table
3.
3 TABLE 3 Gasoline permeation amount Drop and Impact Test Example 8
<0.01 g/3 months B Example 9 <0.01 g/3 months B Example 10
<0.01 g/3 months A Example 11 <0.01 g/3 months A Comparative
Example 3 0.06 g/3 months --
Example 12
[0208] Polyethylene having MFR of 0.3 g/10 min (at 190.degree. C.
under a load of 2160 g) and a density of 0.952 was fed into an
injection-molding machine, and formed into a cylindrical
single-layered article (FIG. 3) having an inner diameter of 63 mm,
an outer diameter of 70 mm and a height of 40 mm. The shaped
article is like a connector for fuel tanks (this is hereinafter
referred to as a connector-like article. As in FIG. 4, the
connector-like article 41 is fitted to the body 42 of a tank, and a
pipe 43 is fitted into the head of the connector-like article
41.
[0209] On the other hand, an opening having a diameter of 50 mm was
formed through the body of the multi-layered fuel tank produced in
Example 8 (the pinch-off part of the tank was coated with a powdery
barrier material (b-1)). Both the area around the hole of the tank
and the connector-like article produced herein were fused with a
hot iron plate at 250.degree. C. for 40 seconds, and these were
heat-sealed under pressure. Thus was produced a multi-layered tank
with one connector-like article fitted thereto.
[0210] The entire outer surface except the top surface of the head
(that is, the flat top surface of the ring having an outer diameter
of 70 mm and an inner diameter of 63 mm) of the connector-like
article having been fitted into the fuel tank was coated with a
powder of a barrier material (b-1) which had been powdered in the
same manner as in Example 1, according to a flame spray coating
process. The thickness of the barrier layer was 50 .mu.m.
[0211] The gasoline permeation amount through the area of the
connector-like article fitted into the fuel tank was measured. The
data obtained are given in Table 4.
(7) Measurement of Gasoline Permeation Amount Through
Connector-Like Article
[0212] 30 liters of model gasoline (toluene/isooctane=50/50% by
volume) was put into the fuel tank produced herein with a
connector-like article being fitted thereto, through its mouth
(this served as a blowing mouth while the tank was produced by blow
molding), and the mouth was then sealed with an aluminium tape (FP
Kako's commercial product of Alumiseal--this is resistant to
gasoline permeation therethrough, having a gasoline permeation
amount of 0 g.multidot.20 .mu.m/m.sup.2.multidot.da- y). Next, an
aluminium disc having a diameter of 80 mm and a thickness of 0.5 mm
was firmly fitted to the top surface of the connector-like article
not coated with the powdery barrier material (b-1) by the use of an
epoxy adhesive. The thus-fabricated fuel tank with gasoline therein
was kept in an explosion-proof thermo-hygrostat (40.degree. C., 65%
RH) for 3 months. Three 35-liter tanks of the same type were tested
in the same manner, and the data of the weight change (W) of the
tanks before and after the storage test were averaged.
[0213] Three control tanks were prepared. Each control tank was so
fabricated that one hole formed through its body was heat-sealed
with a multi-layered sheet (HDPE/adhesive resin/EVOH/adhesive
resin/HDPE=2100/100/600/100/200 .mu.m--for this, used were the same
resins as those used in preparing the multi-layered tank), and not
with the connector-like article. In this, the 200 .mu.m HDPE layer
of the heat-sealed sheet faced the body of the tank. These control
tanks with gasoline therein were kept in the same explosion-proof
thermo-hygrostat chamber(40.degree. C., 65% RH) for 3 months in the
same manner as herein. The data of the weight change (w) of the
control tanks before and after the storage test were averaged.
[0214] The gasoline permeation amount through the connector is
obtained according to the following equation
[0215] Gasoline permeation amount through connector=W-w
Example 13
[0216] A multi-layered tank with one connector-like article fitted
thereto was produced in the same manner as in Example 12. In this,
however, the outer surface except the top surface of the head of
the connector-like article fitted into the tank was coated with a
barrier material (B) in the manner as follows: First, it was
sprayed with a powder of EMAA {Mitsui DuPont Polychemical's Nucrel
0903HC, having a methacrylic acid (MAA) content of 9% by weight and
having MFR of 5.7 g/10 min (at 210.degree. C. under a load of 2160
g)--this was powdered in the same manner as in Example 1} according
to a flame spray coating process. The thickness of the coating
layer was 50 .mu.m. Next, the entire outer surface except the top
surface of the head (that is, the flat top surface of the ring
having an outer diameter of 70 mm and an inner diameter of 63 mm)
of the thus EMMA-coated, connector-like article fitted into the
tank was further coated with a powder of a barrier material (b-1)
that had been powdered in the same manner as in Example 1,
according to a flame spray coating process, in such a manner that
the underlying EMMA layer was not exposed outside. The gasoline
permeation amount through the area of the connector-like article
fitted into the fuel tank, in which the connector-like article was
coated with the barrier material (b-1) and with EMMA, was measured
in the same manner as in Example 12. The data obtained are given in
Table 4.
Comparative Example 4
[0217] The gasoline permeation amount through the area of the
connector-like article fitted into the fuel tank was measured in
the same manner as in Example 12. In this, however, the
connector-like article was not coated with the barrier material
(B). The data obtained are given in Table 4.
4 TABLE 4 Gasoline permeation amount Example 12 <0.01 g/3 months
Example 13 <0.01 g/3 months Comparative Example 4 6.3 g/3
months
Example 14
[0218] Using an injection-molding machine for tubular containers as
in Japanese Patent Laid-Open No. 25411/1981 (Japanese Patent
Publication No. 7850/1989), low-density polyethylene (LDPE, Mitsui
Petrochemical's Ultzex 3520L) was injection-molded into a head of a
tubular container. In this process where the low-density
polyethylene was fed into the injection-molding machine, a
cylindrical tube to be a body of the container, which had been
prepared previously, was fed into the mold of the machine.
[0219] The injection-molding machine used herein is a 35 mm.phi.
in-line screw-type injection-molding machine. In this, the head of
the tubular container was molded at a cylinder temperature of
240.degree. C. and at a nozzle temperature of 235.degree. C. The
tubular container produced herein had an outer diameter of 35
mm.phi., and the squeeze mouth of its head had an outer diameter of
12 mm.phi. and an inner diameter of 7 mm.phi.. The thickness of the
head was 2 mm. The cylindrical tube had a structure of low-density
polyethylene (LDPE, Mitsui Petrochemical's Ultzex 3520L; thickness
150 .mu.m)/adhesive resin (Mitsui Petrochemical's Admer NF500;
thickness 20 .mu.m)/EVOH (having an ethylene content of 32 mol %, a
degree of saponification of 99.5%, and MFR of 1.6 g/10 min (at
190.degree. C. under a load of 2160 g); thickness 20
.mu.m)/adhesive resin (Mitsui Petrochemical's Admer NF500,
thickness 20 .mu.m)/LDPE (Mitsui Petrochemical's Ultzex 3520L;
thickness 150 .mu.m), and this was produced by co-extrusion through
a ring die.
[0220] The head of the two-piece tubular container produced in the
manner as above was sprayed with a powder of a barrier material
(b-1) that had been powdered in the same manner as in Example 1,
according to a flame spray coating process. The thickness of the
barrier layer was 50 .mu.m. The tubular container of which the head
was coated with the barrier material (b-1) was tested for the
storability of its contents.
(8) Storability of Contents
[0221] Miso (seasoned soybean paste) was filled into the tubular
container of which the head was coated with the barrier material
(b-1), through the opening at its bottom, and the opening was
heat-sealed. Next, a piece of aluminium foil (thickness 25 .mu.m)
was fitted to only the squeeze mouth of its head, and the head was
capped. The tubular container filled with miso was kept in a
thermo-hygrostat at 40.degree. C. and 50% RH. After thus kept
therein for 24 hours, the tubular container was taken out. The Miso
kept in contact with the inner surface of the head of the container
was macroscopically checked as to whether or not it was discolored.
According to the criteria A to D mentioned below, the content
storability of the container was evaluated, and it was on the rank
A.
[0222] A: Not discolored.
[0223] B: Discolored in pale brown.
[0224] C: Discolored in brown.
[0225] D: Discolored in reddish brown.
Comparative Example 5
[0226] A tubular container was produced and tested in the same
manner as in Example 14. In this, however, the head of the tubular
container was not coated with the barrier material (b-1). The
content storability of the tubular container produced herein was on
the rank D.
Effect of the Invention
[0227] According to the method of producing shaped articles of the
invention, it is possible to coat a polyolefin substrate of a
complicated shape with a barrier material, not requiring any
complicated primer treatment. For example, the invention provides
multi-layered shaped articles comprising a polyolefin and a barrier
material, and gasoline permeation through the articles is
effectively retarded. In particular, according to the invention,
even complicated shapes can be easily processed to make them have
barrier properties. Accordingly, the shaped articles of the
invention are favorable to components for fuel containers, fuel
tanks for automobiles, fuel pipes, etc.
* * * * *