U.S. patent number RE38,087 [Application Number 09/506,201] was granted by the patent office on 2003-04-22 for fuel hose and method of its production.
This patent grant is currently assigned to Tokai Rubber Industries, Ltd.. Invention is credited to Eiichi Daikai, Hiroaki Ito, Kazuhiro Kato, Koyo Murakami, Katsuhiko Yokoe.
United States Patent |
RE38,087 |
Yokoe , et al. |
April 22, 2003 |
Fuel hose and method of its production
Abstract
The fuel hose of this invention is a fuel hose comprising a
tubular fluororesin inner ply and, as laminated onto the peripheral
surface thereof, a thermoplastic resin or rubber outer ply, the
tubular fluororesin inner ply having been molded from a fluororesin
with an F/C ratio, i.e. ratio of the number of fluorine atoms (F)
to the number of carbon atoms (C), of not greater than 1.6 and the
peripheral surface layer of the fluororesin inner ply having been
modified into the following treated layer (A). (A) a layer with a
distribution of oxygen atoms and having an F/C ratio, i.e. ratio of
the number of fluorine atoms (F) to the number of carbon atoms (C),
of not greater than 1.12 and an O/C ratio, i.e. ratio of the number
of oxygen atoms (O) to the number of carbon atoms (C), of not less
than 0.08. In this fuel hose of the invention, the treated layer
(A) of the tubular fluororesin inner ply has a remarkably increased
adhesive affinity for thermoplastic resin and rubber, with the
result that the bond strength between the tubular fluororesin inner
ply and the thermoplastic resin or rubber outer layer is as high as
not less than 1.2 N/mm.
Inventors: |
Yokoe; Katsuhiko (Nagoya,
JP), Kato; Kazuhiro (Nagoya, JP), Murakami;
Koyo (Nagoya, JP), Daikai; Eiichi (Inuyama,
JP), Ito; Hiroaki (Kasugai, JP) |
Assignee: |
Tokai Rubber Industries, Ltd.
(Komaki, JP)
|
Family
ID: |
27331114 |
Appl.
No.: |
09/506,201 |
Filed: |
February 16, 2000 |
PCT
Filed: |
September 09, 1994 |
PCT No.: |
PCT/JP94/01501 |
PCT
Pub. No.: |
WO95/07176 |
PCT
Pub. Date: |
March 16, 1995 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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Reissue of: |
424469 |
May 9, 1995 |
05718957 |
Feb 17, 1998 |
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Foreign Application Priority Data
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Sep 10, 1993 [JP] |
|
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5-225980 |
Nov 12, 1993 [JP] |
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5-307414 |
Dec 3, 1993 [JP] |
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6-339245 |
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Current U.S.
Class: |
428/36.91;
138/118.1; 156/244.13; 156/244.17; 156/244.23; 156/244.24; 427/536;
427/539; 428/34.5; 428/34.7; 428/36.2; 428/475.8 |
Current CPC
Class: |
B29C
48/0016 (20190201); B32B 27/16 (20130101); B29C
48/21 (20190201); B32B 27/304 (20130101); B29C
59/142 (20130101); B32B 1/08 (20130101); F16L
11/045 (20130101); B32B 27/08 (20130101); B32B
27/28 (20130101); B29C 48/151 (20190201); B32B
27/34 (20130101); F16L 11/127 (20130101); B32B
25/08 (20130101); B32B 38/0008 (20130101); B29C
48/09 (20190201); F16L 11/125 (20130101); B32B
25/14 (20130101); B32B 27/322 (20130101); B29D
23/001 (20130101); B32B 2327/12 (20130101); B29K
2027/12 (20130101); Y10T 428/1314 (20150115); B32B
2307/202 (20130101); B32B 2309/105 (20130101); Y10T
428/1321 (20150115); B29L 2009/00 (20130101); B32B
2319/00 (20130101); B29K 2021/00 (20130101); B29K
2077/00 (20130101); F16L 2011/047 (20130101); Y10T
428/31743 (20150401); Y10T 428/1393 (20150115); B32B
2597/00 (20130101); Y10T 428/1366 (20150115); B29L
2023/005 (20130101) |
Current International
Class: |
B32B
27/28 (20060101); B29C 47/02 (20060101); B32B
1/00 (20060101); B29C 59/00 (20060101); F16L
11/04 (20060101); B29C 47/06 (20060101); B32B
1/08 (20060101); B29C 59/14 (20060101); B32B
27/08 (20060101); B32B 27/34 (20060101); B29D
023/00 () |
Field of
Search: |
;428/36.9,36.91,34.5,34.7,36.2,475.8 ;427/536,539 ;138/118.1,125.7
;156/244.13,244.23,244.24,272.6,244.17 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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4310159 |
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Oct 1993 |
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DE |
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0 385 731 |
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Sep 1990 |
|
EP |
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0 479 592 |
|
Apr 1992 |
|
EP |
|
0 551 094 |
|
Jul 1993 |
|
EP |
|
582301 |
|
Feb 1994 |
|
EP |
|
1 094 785 |
|
Dec 1967 |
|
GB |
|
1 432 824 |
|
Apr 1976 |
|
GB |
|
5 245989 |
|
Sep 1993 |
|
JP |
|
Primary Examiner: Dye; Rena
Attorney, Agent or Firm: Armstrong, Westerman & Hattori,
LLP
Claims
What is claimed is:
1. A fuel hose comprising a tubular fluororesin inner ply having an
F/C ratio .ltoreq.1.6, the outer surface of which is modified to
have an oxygen-containing layer having an F/C ratio of
.ltoreq.1.12, and an O/C ratio of .gtoreq.0.08; and a tubular
rubber or thermoplastic resin outer ply; wherein the inner surface
of the outer ply is laminated directly onto the outer surface of
the inner ply and wherein the initial bond strength of the laminate
between the inner and outer plies is not less than 1.2 N/mm.
2. A fuel hose according to claim 1, wherein the outer surface of
the inner ply was modified by a vacuum plasma treatment.
3. A fuel hose according to claim 1 or 2, wherein the thermoplastic
resin is a polyamide resin.
4. A fuel hose according to claim 1 or 2, wherein the thickness of
the inner ply is 0.05-1.00 mm.
5. A fuel hose according to claim 1 or 2, wherein the tubular
fluororesin inner ply is electrically conductive.
6. A fuel hose according to claim 5, wherein the tubular
fluororesin inner ply is a multi-layer ply at least one layer of
which is electrically conductive.
7. A fuel hose comprising a tubular fluororesin inner ply having an
F/C ratio of >1.6.ltoreq.2.0, the outer surface .Iadd.of
.Iaddend.which is modified to have an oxygen-containing layer
.[.having an F/C ratio of 0.8-1.8 and an O/C ratio of >0.2 minus
0.09 times the F/C ratio;.]. .Iadd.which is within the combination
of the following two relationships (a) and (b); (a) when F/C is
less than 0.8, then O/C must be not less than 0.08; and (b) when
F/C is in the range F/C=0.8 to 1.8, then O/C must satisfy the
relationship:
and a tubular rubber or thermoplastic resin outer ply; wherein the
inner surface of the outer ply is laminated directly onto the outer
surface of the inner ply and wherein the initial bond strength of
the laminate between the inner and outer plies is not less then 1.2
N/mm.
8. A fuel hose according to claim 7, wherein the outer surface
layer of the inner tubular ply was modified by a vacuum plasma
treatment.
9. A fuel hose according to claim 7 or 8, wherein the thermoplastic
resin is a polyamide resin.
10. A fuel hose according to claim 7 or 8, wherein the thickness of
the inner ply is 0.05-1.00 mm.
11. A fuel hose according to claim 7 or 8, wherein the tubular
fluororesin inner ply is electrically conductive.
12. A fuel hose according to claim 11, wherein the tubular
fluororesin inner ply is a multi-layer ply at least one layer of
which is electrically conductive.
13. A fuel hose according to claims 1, 2, 7 or 8, which further
comprises a rubber or elastomer sheath overlying the outer surface
of the outer ply.
14. A fuel hose according to any of claims 1, 2, 7 or 8, which
further comprises a reinforcing cord ply between the rubber or
elastomer sheath and the outer surface of the outer ply.
15. A method of producing a fuel hose comprising a rubber or
thermoplastic resin outer ply laminated directly onto a tubular
fluororesin inner ply, which comprises: extrusion-molding a tubular
fluororesin, modifying the outer surface of the tubular fluororesin
by a vacuum plasma treatment, and extrusion-molding a rubber or
thermoplastic resin directly onto the modified surface of the
tubular inner ply.Iadd., wherein the fluororesin has an F/C ratio
of .ltoreq.1.6, and the modified outer surface of the tubular
fluororesin has an F/C ratio of .ltoreq.1.12 and an O/C ratio of
.gtoreq.0.08.Iaddend...[.
16. A method of producing a fuel hose according to claim 15,
wherein the fluororesin has an F/C ratio of .ltoreq.1.6, and the
modified outer surface of the tubular fluororesin has an F/C ratio
of .ltoreq.1.12 and an O/C ratio of .gtoreq.0.08..].
17. A method of producing a fuel hose .[.according to claim 15,.].
.Iadd.comprising a rubber or thermoplastic resin outer ply
laminated directly onto a tubular fluororesin inner ply, which
comprises: extrusion-molding a tubular fluororesin, modifying the
outer surface of the tubular fluororesin by a vacuum plasma
treatment, and extrusion-molding a rubber or thermoplastic resin
directly onto the modified surface of the tubular inner ply,
.Iaddend.wherein the fluororesin has an F/C ratio of
>1.6.ltoreq.2.0, and the outer modified surface of the tubular
fluororesin contains oxygen and .[.has an F/C ratio of 0.8-1.8 and
an O/C ratio of >0.2 minus 0.09 times the F/C ratio.]. .Iadd.is
within the combination of the following two relationships (a) and
(b); (a) when F/C is less than 0.8, then O/C must be not less than
0.08; and (b) when F/C is in the range F/C=0.8-1.8, then O/C must
satisfy the relationship:
18. The method of producing a fuel hose according to claim 15,
wherein the thermoplastic resin outer ply is formed by melting a
thermoplastic resin, extruding the molten thermoplastic resin onto
the outer surface of the tubular inner ply, and cooling the
extruded thermoplastic resin to solidify and adhere the
thermoplastic resin to the outer surface of the tubular inner
ply.
19. A method of producing a fuel hose according to claim 15,
wherein the thermoplastic resin is a polyamide resin.
20. A method of producing a fuel hose according to claim 15,
wherein the thickness of the inner ply is 0.05-1.00 mm..Iadd.
21. The method of producing a fuel hose according to claim 17,
wherein the thermoplastic resin outer ply is formed by melting a
thermoplastic resin onto the outer surface of the tubular inner
ply, and cooling the extruded thermoplastic resin to solidify and
adhere the thermoplastic resin to the outer surface of the tubular
inner ply..Iaddend..Iadd.
22. A method of producing a fuel hose according to claim 17,
wherein the thermoplastic resin is a polyamide
resin..Iaddend..Iadd.
23. A method of producing a fuel hose according to claim 17,
wherein the thickness of the inner ply is 0.05-1.00 mm..Iaddend.
Description
TECHNICAL FIELD
This invention relates to a fuel hose for use in the fuel system of
a motor vehicle or other equipment, particularly a fuel hose
consisting of a tubular fluororesin inner ply and a thermoplastic
resin or rubber outer ply with a high inter-ply bond strength, a
method of producing it, and a vacuum plasma apparatus for use in
said method.
PRIOR ART
Generally the fuel hoses used in the fuel systems of cars and other
equipment have multi-ply structures consisting of various rubber
and resin plies or layers. Among such multi-ply fuel hoses, the
two-ply fuel hose consisting of a tubular fluororesin inner ply and
a thermoplastic resin or rubber outer ply laminated on the
peripheral surface of said tubular inner ply is in prevalent use.
The rationale is that, being not only resistant to the common
corrosive agents such as chemicals and gasoline but also resistant
to the sour gasoline which forms on oxidation of gasoline (sour
gasoline resistance), fluororesin is generally regarded as the
optimal molding material for the inner ply of the hose which is
directly exposed to the fuel. The thermoplastic resin or other
outer ply mentioned above is provided as a reinforcing member of
the hose for imparting wear resistance and other dynamic
characteristics to the fuel hose.
In the manufacture of a fuel hose of the above-mentioned structure,
an inner ply made of a special fluororesin, rather than a ply of
ordinary fluororesin, which has a modified surface for lamination
with said thermoplastic resin or other outer ply is employed. The
reason for this is that because the bonding affinity of ordinary
fluororesin for other structural materials is very low, said two
plies cannot be firmly bonded using an adhesive alone. The fuel
hose, in particular, is required to have an initial bond strength
(bond strength prior to use) value of not less than 1.2 N/mm which
is higher than the bond strength required of the ordinary resin
hose. This is because, as far as the fuel hose for use typically in
the fuel system of a motor vehicle is concerned, unless it has an
initial bond strength value not below the above-mentioned level
under the service conditions where a fuel such as gasoline flows
down it, there is the risk of partial delamination of the tubular
fluororesin inner ply from the outer ply. In the event such a
partial exfoliation of the tubular fluororesin inner ply takes
place, the tubular fluororesin inner ply may collapse in the
vicinity of delamination so that its tubular (hollow) structure is
no longer preserved but is occluded to prevent a smooth flow of
gasoline or other fuel.
As examples of said surface-modified fluorine-containing resins,
the following three (two) fluororesins are known. (1) A fluororesin
material whose surface has been etched with a sodium metal complex
(e.g. one described in Ind. Eng. Chem., 50, 329, 1958) (2) a
fluororesin material whose surface has been roughened by sputtering
(e.g. one described in JP Publication S-58-25742).
However, the above surface-modified fluororesin materials have
various disadvantages. Thus, the fuel hose fabricated using the
first-mentioned fluororesin (1) having a sodium metal
complex-modified surface suffers aging in adhesion. This loss of
adhesion is particularly remarkable when the hose is exposed to
ultraviolet radiation. Moreover, since the above surface
modification with a sodium metal complex requires the step of
immersing fluororesin in a solution of the sodium metal complex and
subsequently washing it, this technology has the drawback of being
a time-consuming, complicated process. Moreover, the sodium metal
complex solution is hazardous to health.
The latter fluororesin having a sputtered surface (2) does not
provide for sufficient adhesion when the flowability of the
adhesive is low and has the additional disadvantage that the
recesses and projections formed by sputtering are easily evened out
by friction. Therefore, in the manufacture of a fuel hose using the
sputtered fluororesin material, its handling calls for sufficient
care and this consideration detracts from the efficiency of
production of the fuel hose.
Furthermore, these prior art fluororesins have the common problem
that they provide for only poor adhesion when a thermoplastic resin
or the like is directly bonded thereto without the aid of an
adhesive. For the manufacture of a fuel hose using a fluororesin
and a thermoplastic resin such as polyamide resin, not only the
above-mentioned method of bonding the two resins with an adhesive
but, at least theoretically, the method of heating the
thermoplastic resin to achieve the necessary fusion can be
employed. According to the latter thermal fusion technique, the
step for application and drying of the adhesive can be dispensed
with to reduce the production sequence and, in addition, since an
organic solvent for dissolving the adhesive is not required, a
safer working environment can be insured. Actually, however, the
conventional surface-modified fluororesin materials provide for
only poor adhesion by the thermal fusion technique, with the result
that the above-mentioned inherent advantages of the technique
cannot be exploited.
Meanwhile, paying attention to the atomic composition of the
surface layer of a fluororesin, a fluororesin material having an
adhesion-expressing atomic composition in the surface layer has
been proposed (JP Publication H-2-54848). To be specific, the
surface of a specified fluororesin is modified to bring the F/C
ratio, i.e. ratio of the number of fluorine atoms (F) to the number
of carbon atoms (C) and the O/C ratio, i.e. ratio of the number of
oxygen atoms (O) to the number of carbon atoms (C), into specified
ranges, respectively. With this surface-modified fluororesin, the
above-mentioned drawbacks of the conventional fluororesins can be
overcome. However, only a few kinds of fluororesins are available
to which the surface modification by this technique can be
successfully applied and, moreover, the technique has the
disadvantage that the expression of adhesion cannot be uniformly
obtained over a spectrum of fluororesins each having its own useful
performance characteristics. Furthermore, the range of said F/C
ratio and of said O/C ratio is very limited so that an elaborate,
delicate control technology is essential for converging the surface
of any fluororesin into said narrow ranges of atomic ratios, with
the result that the production is inevitably complicated.
Thus, because of the lack of sufficient adhesion of the prior art
surface-modified fluororesins, fuel hoses manufactured using them
are not possessed of the initial bond strength or green bond
strength necessary for service. Moreover, the fuel hoses
manufactured by the conventional production technologies are not
free from problems in the aspects of work safety, production
efficiency and cost. However, since the fuel hose having a
fluororesin inner ply has a high performance quality and a long
life as mentioned above, there is an ardent demand for a solution
to the above-mentioned problems.
OBJECT OF THE INVENTION
This invention has for its object to provide a fuel hose having a
sufficiently high initial bond strength of not less than 1.2 N/mm
between the fluororesin inner ply and the thermoplastic resin or
other ply, which is easy to manufacture and free from problems in
work safety and cost, a method for production of the hose, and a
vacuum plasma apparatus for use in the method.
DISCLOSURE OF THE INVENTION
Having been developed to accomplish the above object, this
invention is directed, in a first aspect, to a fuel hose having a
laminated structure comprising a tubular or hollow fluororesin
inner ply and, as laminated onto the peripheral surface thereof, a
thermoplastic resin or rubber outer ply, said tubular fluororesin
inner ply having been molded from a fluororesin having an F/C
ratio, i.e. a ratio of the number of fluorine atoms (F) to the
number of carbon atoms (C), of .ltoreq.1.6 and said outer ply
overlying said tubular fluororesin inner ply having been treated to
present the following layer (A). (A) a layer having a distribution
of oxygen atoms, an F/C ratio, i.e. ratio of the number of fluorine
atoms (F) to the number of carbon atoms (C), of .ltoreq.1.12 and an
O/C ratio, i.e. ratio of the number of said oxygen atoms (O) to the
number of carbon atoms (C), of .gtoreq.0.08.
This invention is further directed, in a second aspect, to a fuel
hose comprising a tubular or hollow fluororesin inner ply and, as
laminated onto the peripheral surface thereof, a thermoplastic
resin or rubber outer ply, said tubular fluororesin inner ply
having been molded from a fluororesin with an F/C ratio, i.e. a
ratio of the number of fluorine atoms (F) to the number of carbon
atoms (C), of 2.0>(F/C)>1.6 and said outer ply overlying said
tubular fluororesin inner ply having been treated to present the
following treated layer (B). (B) a layer having a distribution of
oxygen atoms, with its F/C ratio, i.e. ratio of the number of
fluorine atoms (F) to the number of carbon atoms (C), and O/C
ratio, i.e. ratio of the number of oxygen atoms (O) to the number
of carbon atoms (C), being within the range combining the following
two ranges (a) and (b). (a) The ratio of the number of fluorine
atoms (F) to the number of carbon atoms (C) is less than F/C=0.8
and the ratio of the number of oxygen atoms (O) to the number of
carbon atoms (C) is not less than O/C=0.08. (b) The ratio of the
number of fluorine atoms (F) to the number of carbon atoms (C) is
within the range of F/C=0.8-1.8 and the O/C ratio of the number of
oxygen atoms (O) to the number of carbon atoms (C) is within the
range defined by the following relation.
[In the above relation (1), F/C=0.8-1.8]
This invention is further directed, in a third aspect, to a method
for producing a fuel hose having a laminated structure consisting
of a tubular fluororesin inner ply and, as disposed on the
peripheral surface thereof, a thermoplastic resin or rubber outer
ply, which comprises a step of extrusion-molding a tubular
fluororesin inner ply, a step of subjecting the peripheral surface
of said tubular fluororesin inner ply to plasma treatment under
reduced pressure to form a treated layer, and a step of
extrusion-molding a thermoplastic resin or rubber ply on the
peripheral surface of said tubular fluororesin inner ply.
This invention is further directed, in a fourth aspect, to a vacuum
plasma apparatus comprising a hermetic chamber, an electrode means
for generating a plasma in said hermetic chamber, and a
decompression means for establishing a reduced pressure in said
hermetic chamber, said hermetic chamber being equipped with an
inlet and an outlet each adapted to accept a hose and each of said
inlet and outlet being formed of an elastomeric rubber seal element
having a through-hole smaller in inner diameter than the outer
diameter of the hose.
Thus, the inventors of this invention did a series of studies for
improving the adhesion of fluororesin to other structural
materials. Exploring into the mechanism of expression of
adhesiveness of fluororesin as part of their research, the
inventors discovered that the relative proportions of oxygen atoms
and fluorine atoms in the surface layer of fluororesin have
significant implications for the expression of adhesion of the
resin. They accordingly scrutinized the relative proportions of
oxygen and fluorine atoms and discovered that when the ratio (O/C)
of the number of oxygen atoms (O) to the number of carbon atoms (C)
and the ratio (F/C) of the number of fluorine atoms (F) to the
number of carbon atoms (C) are controlled within the
above-mentioned ranges, a fluororesin and a thermoplastic resin or
the like can be firmly bonded with an initial bond strength of not
less than 1.2 N/mm. They further discovered that the availability
ratios of fluorine and oxygen atoms (F/C ratio, O/C ratio) can be
set within the above-specified ranges by means of vacuum plasma
treatment without resort to any extraordinary apparatus or
equipment. It was also discovered that when the vacuum plasma
apparatus equipped with said elastomeric rubber seals is used for
vacuum plasma treatment, a stable plasma can be easily generated.
This and said other findings taken together, the inventors
succeeded in the development of this invention. This invention
makes it possible to provide a high performance fuel hose easily
and at low cost.
It should be understood that, as mentioned in this specification,
the number of carbon atoms (C), the number of fluorine atoms (F),
and the number of oxygen atoms (O), are the values determined by
photoelectron spectrometric analysis (ESCA).
This invention is now described in detail.
The fuel hose of this invention comprises a tubular fluororesin
inner ply consisting in a specified fluorine-containing resin and,
as disposed on the peripheral surface of said tubular inner ply, a
thermoplastic or rubber outer ply.
In this invention, said tubular fluororesin inner ply constituting
the inner wall member of the hose is whichever of the following two
alternative plies, viz. tubular fluororesin inner ply (X) and
tubular fluororesin inner ply (Y).
The tubular fluororesin inner ply (X) comprises a fluororesin with
an F/C ratio, i.e. ratio of the number of fluorine atoms (F) to the
number of carbon atoms (C), of not greater than 1.6 and a
peripheral outer ply disposed on the following treated layer (A).
(A) a layer having a distribution of oxygen atoms, with its F/C
ratio, i.e. ratio of the number of fluorine atoms (F) to the number
of carbon atoms (C), being not greater than 1.12 and O/C ratio,
i.e. a ratio of the number of said oxygen atoms (O) to the number
of carbon atoms (C), being not less than 0.08.
The fluororesin with an F/C ratio of not greater than 1.6 includes
ethylene-tetrafluoroethylene copolymer (ETFE), polyvinylidene
fluoride (PVDF), polychlorotrifluoroethylene (CTFE),
ethylene-chlorotrifluoroethylene copolymer (ECTFE), vinylidene
fluoridetetrafluoroethylene copolymer, vinylidene
fluoridetetrafluoroethylene-hexafluoropropylene terpolymer, and
vinylidene fluoride-hexafluoropropylene copolymer, among other
polymers. These polymers can be used singly or in combination.
Preferred in view of high impermeability to gasoline are CTFE and
ETFE, and ETFE is most useful.
For improved physical properties, among other purposes, a variety
of fillers can be incorporated in the above fluororesin. Among such
fillers can be mentioned titanium dioxide, barium sulfate, calcium
carbonate, silica, carbon black, magnesium silicate, aluminum
silicate, zinc oxide, alumina, calcium sulfate, aluminum sulfate,
calcium hydroxide, aluminum hydroxide, talc, molybdenum dioxide,
whiskers, short staple fibers, graphite, finely divided metal
particles, and so on. The formulating amount of such fillers is not
greater than 30 parts by weight (hereinafter referred to briefly as
parts) relative to 100 parts of the fluororesin.
The fluororesin constituting said tubular fluororesin inner ply is
preferably made electrically conductive for dissipating the static
charge which is generated as the fuel (gasoline or the like) flows
down the hose. This impartment of electrical conductivity to
fluororesin can be accomplished by, for example, incorporating an
electrically conductive additive in the fluororesin matrix. The
electrically conductive additive may for example be carbon black,
finely divided stainless steel filaments or the like. The
proportion of such electrically conductive additives is preferably
0.5-30 parts based on 100 parts of fluororesin. When the
electrically conductive additive is added within the above range,
the volume resistivity of the tubular fluororesin inner ply of the
product fuel hose is not greater than 10.sup.10 .OMEGA..cm, with
the result that the generated static electricity can be discharged
from the hose. As a consequence, hazards such as ignition of the
fuel by the accumulated static charge can be precluded.
As can alternative to the use of said tubular fluororesin inner ply
(single ply) molded from such a fluororesin containing said filler
and electrically conductive additive, it is also possible to use a
multiple-layer tubular inner ply which can be provided by
laminating a fluororesin containing said filler and additive with a
plain fluororesin. The innermost layer of such a multiple-layer
tubular fluororesin inner ply, which comes into direct contact with
the fuel in service, is usually molded from the fluororesin
containing said electrically conductive additive but this invention
is not limited to the particular structure. Thus, the generated
static charge can be discharged from the hose even when the
innermost layer is a fluororesin layer not containing the
electrically conductive additive, with the fluororesin containing
the additive being disposed immediately on the peripheral surface
of said innermost layer, only if the thickness of said innermost
layer is sufficiently thin.
Now, using such a fluororesin with an F/C ratio of not greater than
1.6, a tubular inner ply is molded typically by extrusion molding.
Then, the peripheral surface layer of this tubular fluororesin
inner ply is subjected to a vacuum plasma treatment, which is
described hereinafter, so as to form said treated layer (A). This
treated layer (A) has an F/C ratio of not greater than 1.12,
preferably F/C 0.1-1, and an O/C ratio of not less than 0.08,
preferably O/C 0.1-0.5. This is because if the F/C ratio exceeds
1.12 and/or the O/C ratio is less than 0.08, the expression of
adhesion will not be sufficient. Moreover, when the F/C ratio and
O/C ratio are respectively controlled within the above-mentioned
preferred ranges, expression of very high adhesion can be
expected.
The tubular fluororesin inner ply (Y) mentioned above is made of a
fluororesin with an F/C ratio, i.e. ratio of the number of fluorine
atoms (F) to the number of carbon atoms (C), within the range of
over 1.6 but not exceeding 2.0 and having a peripheral surface
layer processed into the following treated layer (B).
(B) a layer with a distribution of oxygen atoms, with its F/C
ratio, i.e. ratio of the number of fluorine atoms (F) to the number
of carbon atoms (C), and O/C ratio, i.e. ratio of the number of
oxygen atoms (O) to the number of carbon atoms (C), being within
the combination of the following ranges (a) and (b). (a) The ratio
of the number of fluorine atoms (F) to the number of carbon atoms
(C) is less than F/C=0.8 and the ratio of the number of oxygen
atoms (O) to the number of carbon atoms (C) is not less than
O/C=0.08. (b) the F/C ratio of the number of fluorine atoms (F) to
the number of carbon atoms (C) is within the range of F/C 0.8-1.8
and the O/C ratio of the number of oxygen atoms (O) to the number
of carbon atoms (C) is within the range defined by the following
relation:
[In the above relation (1), F/C=0.8-1.8]
The fluororesin having an F/C ratio greater than 1.6 but not
exceeding 2.0 includes polytetrafluoroethylene (PTFE),
tetrafluoroethylene-hexafluoropropylene copolymer (FEP),
tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA),
tetrafluoroethylene-hexafluoropropylene-perfluoroalkoxyethylene
terpolymer, vinylidine fluoride-tetrafluoroethylene copolymer,
vinylidene fluoride-hexafluoropropylene copolymer, and vinylidene
fluoride-tetrafluoroethylene-hexafluoropropylene terpolymer, among
others. These polymers can be used singly or in combination. Among
them, because of their excellent impermeability to gasoline, FEP
and vinylidene fluoride-tetrafluoroethylene-hexafluoropropylene
terpolymer are preferred, and vinylidene
fluoride-tetrafluoroethylene-hexafluoropropylene terpolymer is most
useful.
To the above fluororesin, too, the filler and electrically
conductive additive mentioned hereinbefore can be added for
improved physical properties and other purposes. The formulating
amount of such filler and electrically conductive additive and the
mode of use of such a fluororesin containing the filler and
electrically conductive additive may also be the same as those
described hereinbefore.
Using a fluororesin with an F/C ratio greater than 1.6 but not
exceeding 2.0, a tubular inner ply is molded by, for example,
extrusion molding. Then, the peripheral surface layer of this
tubular fluororesin inner ply is subjected to vacuum plasma
treatment, for example under the conditions described hereinafter,
to form the above-mentioned treated layer (B). This treated layer
(B) is such that its F/C ratio and 0/C ratio are within the
combination of the above two ranges (a) and (b). Provided that this
combination range is adhered to, a treated layer with good
expression of adhesion can be obtained. The ranges of F/C ratio and
O/C ratio are now described in further detail. The above-mentioned
range (a) is such that the F/C ratio is less than 0.8, preferably
F/C 0.1-0.5, while the O/C ratio is not less than 0.08, preferably
O/C 0.1-0.5. The above-mentioned range (b) is such that the F/C
ratio is within the rang of F/C 0.8-1.8, preferably F/C 0.8-1.5,
while the O/C ratio is within the range defined by the
above-mentioned relation (1), preferably within the range of O/C
0.1-0.5. In the above relation (1), the range of 0.8-1.8 is
substituted for the F/C ratio. If the above F/C ratio and O/C ratio
are outside the above-mentioned upper and lower limits, the
expression of adhesion of fluororesin will be insufficient. When
the F/C ratio and O/C ratio are controlled within the above
preferred ranges, the adhesion of the resin is remarkably improved.
The combination of said ranges (a) and (b) for the tubular
fluororesin inner ply (Y) means the total range covered by said
ranges (a) and (b).
The thermoplastic resin or rubber ply mentioned above is provided
for imparting structural strength to the hose.
There is no particular limitation on the molding material that can
be used for said thermoplastic resin ply, thus including various
resins such as polyamide resin, polyester resin, urethane resin,
etc. and modified resins such as those obtainable by modification
of the above-mentioned resins. Among them, polyamide resin is
preferred for its excellent dynamic characteristics such as wear
and abrasion resistance. The polyamide resin mentioned above
includes nylon 6, nylon 66, nylon 11 and nylon 12, among others,
and these species of resin can be used singly or in combination.
The preferred are nylon 11 and nylon 12 which are outstanding in
abrasion resistance and moldability.
For improved processability and flexibility, a plasticizer may be
added to said polyamide resin where necessary. The plasticizer that
can be used includes sulfonamides and hydroxybenzoic esters. The
formulating amount of such plasticizers is generally not greater
than 20 parts relative to 100 parts of polyamide resin.
The rubber mentioned as another molding material for the fuel hose
of this invention is not particularly critical in kind, either,
thus including epichlorohydrin rubber (CO),
epichlorohydrin-ethylene oxide equimolar copolymer (ECO, alias
CHC), acrylonitrile butadiene rubber (NBR)-polyvinyl chloride (PVC)
blend rubber (NBR/PVC), chloroprene rubber (CR), chlorosulfonated
polyethylene (CSM), chlorinated polyethylene (CPE), and
ethylene-propylene-diene rubber (EPDM), among other rubbers. Among
them, ECO, NBR/PVC and CSM are preferred for their high heat
resistance and high ozone resistance.
The fuel hose of this invention can be manufactured from the above
materials by molding a tubular fluororesin inner ply, subjecting
the peripheral surface layer of said tubular fluororesin inner ply
to vacuum plasma treatment to form a treated layer and depositing a
thermoplastic resin or rubber layer on top of said treated layer. A
typical process for fabricating this fuel hose is now
described.
Illustrated in FIG. 2 is a vacuum plasma apparatus 30 that can be
used in the method of this invention. Using this apparatus 30, the
fuel hose of this invention can be fabricated typically by the
following procedure.
First, a mandrel 11 is supplied from a mandrel feeder 10 to an
inner ply extruder 20 at a speed of 3-20 m/min. Then, the extruder
20 extrudes said fluororesin onto the mandrel 11 to provide a
tubular fluororesin inner ply 21. This tubular fluororesin inner
ply is generally adjusted to the geometrical range of about 4-50 mm
in inside diameter and about 0.05-1 mm in thickness.
Now, the mandrel 11 carrying said tubular inner ply 21 travels
through a seal element 13 to a reaction chamber 32 of the vacuum
plasma apparatus 30. For establishing a stable plasma, the air in
the reaction chamber 32 is evacuated by a decompression means
(vacuum pump) 34 and, then, supplied with an electrical discharge
gas from a gas supply means 35. The reaction chamber 32 is
maintained at a vacuum or reduced pressure of 0.005-8 Torr. As the
above-mentioned electrical discharge gas, it is preferable to
employ Ar gas alone but a mixed gas of Ar and N.sub.2, or N.sub.2
gas alone can likewise be employed. Electrodes 32a define, between
them, a plasma treatment zone into which the mandrel 1 carrying
said tubular fluororesin inner ply 21 is guided and the peripheral
surface layer of the ply 21 is subjected to plasma treatment. In
this plasma treatment, an impedance-matched high-frequency,
high-output current is applied to the electrodes 32a for a
predetermined time from a high-frequency power source 40 and a
matching box 41 to induce an electrical discharge between said
electrodes and thereby ionize said electrical discharge gas to form
a plasma. The frequency used is in the range of 0.1-1000 MHz,
preferably 1-100 MHz. The output of said high frequency power
source is in the range of 2-300 W, preferably 5-200 W. The
treatment time is dependent on the type and size of the fluororesin
material but is generally 2-180 seconds and preferably 5-60
seconds. By this vacuum plasma treatment, the peripheral surface
layer of the tubular fluororesin inner ply is modified into said
treated layer (A) or (B). The conditions of plasma treatment for
the formation of said treated layer (A) or (B) are selected
according to the type of fluororesin used, among other factors. The
vacuum plasma treatment for the formation of treated layer (A) or
(B) is preferably a glow discharge plasma treatment using an Ar
gas-containing atmosphere. By this glow discharge plasma treatment,
said treated layer (A) or (B) can be easily formed. Since this glow
discharge plasma treatment does not require a high degree of
vacuum, there is the advantage that the vacuum plasma apparatus
need not be an elaborate, high performance equipment but be an
ordinary one. The Ar-containing gas mentioned above includes Ar gas
alone, and a mixture of Ar gas and N.sub.2, H.sub.2 or O.sub.2 gas,
for instance. The proportion of Ar gas in such a mixture gas is
preferably not less than 50 volume % based on the total gas. After
the above plasma treatment, the mandrel 11 further travels through
the seal 13 and is withdrawn from the vacuum plasma apparatus 30.
Immediately thereafter, a sheath ply extruder 50 extrudes a
thermoplastic resin or rubber onto the peripheral surface of said
tubular inner ply 21 to form a sheath or outer ply 51. When this
ply 51 is formed using a thermoplastic resin, the thermal fusion
technique mentioned hereinbefore can be employed. Thus, since the
thermoplastic resin for extrusion molding is generally in hot
molten state, this melt can be directly extruded onto the
peripheral surface of said tubular inner ply 21 and, then, chilled
to solidify, whereby an outer ply 51 of thermoplastic resin is
firmly bonded to the peripheral surface of the tubular fluororesin
inner ply 21. By this thermal fusion technique, the step of
applying an adhesive can be dispensed with so that the efficiency
of production of a fuel hose is enhanced. When a rubber ply is to
be formed, the extrusion step must be followed by a vulcanizing
step. The conditions of this vulcanization can be selected
according to the kind of rubber used but is generally
150.degree.-180.degree. C..times.20-90 minutes. The thickness of
said outer ply 51 is generally in the range of about 0.2-4 mm and
preferably about 0.5-3 mm. The mandrel 11 carrying the tubular
inner ply 21 and outer ply 51 is taken up by a mandrel takeup
device 60. The fuel hose of this invention can be manufactured by
the above-described continuous series of steps.
The method for manufacturing the fuel hose of this invention has
been described above, taking the procedure employing a mandrel as
an example, but the fuel hose can also be manufactured without
enlisting the help of a mandrel. Thus, the use of a mandrel for the
production of a hose is intended to retain the shape of a hose
throughout the process, and particularly since the tubular
fluororesin inner ply 21 of the fuel hose of this invention is as
thin as 0.05-1.00 mm, the tubular ply tends to collapse in the
absence of a mandrel, thus failing to retain its hollow structure.
If the tubular fluororesin inner ply 21 collapses in this manner, a
thermoplastic resin or other ply may hardly be formed on the
peripheral surface of the inner ply. However, since the production
technology for a fuel hose in accordance with this invention is a
vacuum plasma process, no such troubles are encountered even in the
absence of a mandrel. Thus, whereas the internal plenum of the
tubular fluororesin inner ply 21 is atmospheric air, the reaction
chamber of the vacuum plasma apparatus 30 is maintained under a
reduced pressure of 0.005-8 Torr as mentioned above, with the
result that as said tubular inner ply 21 is guided into the vacuum
plasma apparatus 30, the very pressure differential helps retain
the shape of the hose in the absence of a mandrel. Therefore, in
the above description of the apparatus and method for fabricating a
fuel hose (FIG. 2), the mandrel feeder 11 can be dispensed with and
the tubular fluororesin inner ply 21 emerging from the inner ply
extruder 20 can be immediately guided into the vacuum plasma
apparatus 30. Then, the same procedure as described above can be
followed. In this manner, the fuel hose can be manufactured without
employing a mandrel. When the use of a mandrel is dispensed with in
this manner, the operation for slipping out the mandrel is no
longer required and, therefore, the efficiency of production of the
fuel hose is further enhanced.
In the above description of the procedure for fabricating a fuel
hose, the three production stages of tubular inner ply molding,
vacuum plasma treatment, and formation of a thermoplastic resin or
other ply on the peripheral surface of the inner ply are
continuously carried out but this mode of operation is not an
exclusive choice. A typical alternative procedure comprises taking
up the tubular fluororesin inner ply 21 immediately as it emerges
from the inner ply extruder 20 on a takeup device (not shown),
paying out the tubular inner ply 21 from the takeup device to the
vacuum plasma apparatus, and molding a thermoplastic resin or other
layer on the plasma-treated peripheral surface of said inner ply.
The rationale is that whereas the first-mentioned continuous
process is preferred for the manufacture of a long hose, the latter
process which is a partial bath process may prove more efficient
for the manufacture of a short fuel hose. Moreover, in this partial
batch process, the material for the tubular inner ply and/or that
for the thermoplastic resin or rubber outer ply can be easily
changed for each production lot.
The method for producing a fuel hose has been described above by
taking the fabrication of a double-ply fuel hose as an example but
this invention is not limited to such a structure. Thus, while the
basic structure of the fuel hose of this invention is a double-ply
hose consisting of a tubular fluororesin inner ply 21 and a
peripheral thermoplastic resin or rubber ply 51, a three-ply,
four-ply or other multiple-ply fuel hose can also be manufactured
in accordance with this invention by superimposing a reinforcing
cord ply, a sheath ply, and/or other ply on top of said outer ply
51.
A typical three-ply fuel hose comprises, as illustrated in FIG. 8,
said tubular fluororesin inner ply 21, said outer ply 51 disposed
on the treated layer 21a of said inner ply, and a rubber or
elastomer sheath ply 61 disposed on the peripheral surface of said
outer ply 51. The rubber sheath ply 61 may be molded from any of
CSM, CR, NBR/PVC, ECO, EPR, etc. mentioned hereinbefore. The
elastomer sheath ply 61 may be molded from a thermoplastic
elastomer such as urethane, olefinic, nitrile and amide elastomers.
The thickness of such rubber or elastomer sheath layer 61 is
generally about 0.5-5.0 mm and preferably about 0.5-3.0 mm. The
fuel hose equipped with the sheath ply 61 has flame resistance and
chipping resistance in addition to the gasoline impermeability,
corrosion resistance and other characteristics of the two-ply hose
described above.
A typical four-ply fuel hose is illustrated in FIG. 9, which shows
a fuel hose consisting of a tubular fluororesin inner ply 21, an
outer ply 51 formed on the treated layer 21a of said inner ply 21,
a reinforcing cord ply 71 disposed on the peripheral surface of
said outer ply 51, and said rubber or elastomer sheath ply 61
disposed on the peripheral surface of said ply 71. The reinforcing
cord ply 71 is a knitted or interplaced ply of natural fiber such
as linen, cotton, etc., of a synthetic yarn such as polyester yarn,
vinylon yarn, etc. or of metal filaments or wires. With the
provision of said reinforcing cord ply 71, the pressure resistance
of the fuel hose is increased. The thickness and material of said
sheath layer 61 of this 4-ply fuel hose can be the same as those of
the sheath layer 61 of said 3-ply fuel hose.
When the reinforcing cord ply 71 and sheath ply 61 described above
are provided, a knitting or interlacing device and an extruder are
disposed downstreams of said outer ply extruder 50 shown in FIG. 2,
so that a multiple-ply fuel hose having said reinforcing cord ply
and sheath ply can be manufactured through knitting/interlacing and
extrusion steps.
In the manufacture of the fuel hose according to this invention,
after said vacuum plasma treatment of the peripheral surface layer
of the tubular fluororesin inner ply to form said treated layer, an
adhesive may be applied, as in the prior art process for producing
a fuel hose, to said treated layer and, then, a thermoplastic resin
or rubber ply may be superimposed. In this case, an adhesive
applicator (not shown) is disposed between the vacuum plasma
apparatus 30 and the outer ply extruder 50 shown in FIG. 2 so that
application of the adhesive can be integrated into a continuous
production flow. With the aid of such an adhesive layer, the bond
strength of the fuel hose can be further increased. The effect of
this increased bond strength is particularly remarkable when said
rubber ply is employed.
It is preferable that, as illustrated in FIG. 3, the tubular
fluororesin inner ply 21 be caused to traverse a cooling zone 15
before it is guided through the vacuum plasma apparatus 30. This is
because the tubular fluororesin inner ply just extruded is still
hot and soft so that it has poor shape retentivity. Incidentally,
in FIG. 2 and FIG. 3, the like parts are indicated by the like
numerals.
The vacuum plasma apparatus for use in this invention is now
described.
While the production of a fuel hose was described above referring
to a vacuum plasma apparatus equipped with internal electrodes
(FIG. 2), the vacuum plasma equipment that can be used is not
limited to that particular apparatus. Thus, aside from the
equipment having internal electrodes, a vacuum plasma equipment
equipped with an induction coil electrode means 32b on the
periphery of the equipment body 30 as illustrated in FIG. 4 can be
employed. In FIG. 4, too, the like numerals are used to designate
the like parts of FIG. 2.
As mentioned hereinbefore, the plasma treatment according to this
invention is carried out at a subatmospheric or negative pressure.
If the sealing effect of the seal 13 of the vacuum plasma apparatus
30 is poor, it is difficult to control the degree of vacuum within
the apparatus at a constant level so that a stable plasma cannot be
generated. This has serious implications particularly in the
continuous production of a long hose. As mentioned hereinbefore,
when the conventional vacuum plasma equipment is employed, it is
necessary to use a batch method or provide a series of vacuum zones
utilizing a differential evacuation system at the hose inlet and
outlet of the equipment. Using the former method, viz. a batch
method, results in a considerable decrease in production
efficiency. In the case of the latter system, special devices
(vacuum zones) must be provided in the vacuum plasma equipment so
that an additional capital expenditure is required. Therefore, in
this invention, the seals 13 of the vacuum plasma apparatus are
formed of a rubber-like elastomer to keep the vacuum plasma
apparatus air-tight, whereby the above-mentioned problems of
decreased production efficiency and increased cost are obviated.
The rubber-like elastomer mentioned above is preferably one with a
hardness of 45-80 (JIS A). The type of rubber-like elastomer is not
particularly critical but good results are obtained when silicone
rubber or NBR is employed. Thus, the seals 13 formed of such a
suitable type of rubber-like elastomer having an appropriate
hardness are highly capable of yielding in intimate contact with
the hose (tubular fluororesin inner ply 21) introduced into the
vacuum plasma apparatus 30 and withdrawn from the apparatus at a
given speed so that even when the introduction and withdrawal speed
of said hose is increased to a fairly high level (about 5-20
m/min.), the air-tightness of the vacuum plasma chamber can be
sufficiently maintained. By increasing the introduction and
withdrawal speed of the hose in this manner, the production
efficiency of the fuel hose can be enhanced. The rubber-like
elastomer seal may be configured typically as illustrated in FIG.
6, namely seal 13a, or as illustrated in FIG. 7, namely seal 13b.
In both diagrams, the tubular fluororesin inner ply is indicated by
the reference numeral 21. Referring to FIG. 6, when the rubber-like
elastomer (seal 13a) is configured in a generally frustoconical
profile like that of a cup, the area of contact with the hose
(tubular fluororesin inner ply) is reduced to lower the contact
frictional force so that the hose can be smoothly introduced and
withdrawn and, at the same time, the equipment can be kept
sufficiently air-tight. In FIG. 6, the arrowmark indicates the
direction of advance of the hose. As an alternative, the
rubber-like elastomer (seal 13b) may be disk-shaped as illustrated
in FIG. 7. When the seal is such a rubber-like elastomer disk, the
air-tightness of the vacuum plasma apparatus 30 is further
increased. As an alternative, each of said seals may take the form
of a seal chamber as illustrated in FIG. 14. The seal chamber
comprises a disk-shaped rubber-like elastomer seal element 13b
disposed at either end of a cylindrical housing 81. To the barrel
of said housing 81 is connected a pipe 17a through which the seal
chamber communicates with a vacuum pump (not shown). In the
diagram, the tubular fluororesin inner ply is indicated at 21. By
means of said vacuum pump, this seal chamber is decompressed to
approximately the same degree of vacuum as the auxiliary vacuum
chamber to be described hereinafter. When the seal is in the form
of a seal chamber, the air-tightness of the vacuum plasma apparatus
is further improved. Similarly satisfactory results can also be
obtained when the seal member 13a shown in FIG. 6 is formed at
either end of said cylindrical housing 81.
As still another mode of seal, auxiliary vacuum chambers 31 each
having two serial seals may be provided as shown in FIG. 5. Each
auxiliary vacuum chamber 31 is an air-tight compartment isolated
from the reaction chamber 32 by a divider 16, and this auxiliary
vacuum chamber 31 communicates with a vacuum pump 36 via a line 17.
In the diagram, the reference numeral 18 indicates a valve
installed partway in said line 17. The seal means 13 of this
auxiliary vacuum chamber through which the hose (tubular
fluororesin inner ply 21) goes in and out can be similar to said
rubber-like elastomer seal elements. The geometry of such a
rubber-like elastomer seal element is not particularly restricted
but may for example take any of the two configurations 13a and 13b
described above or the form of said seal chamber, among others, but
the disk-shaped rubber-like elastomer seal 13b (FIG. 7) is
preferred. In FIG. 5, the like numerals are used to designate the
like parts of FIG. 2.
The introduction and withdrawal of the tubular fluororesin inner
ply 21 with respect to the vacuum plasma apparatus 30 via said
auxiliary vacuum chambers 31 are carried out as follows. For
introduction, in the first place, the tubular fluororesin inner ply
21 is passed from one side of a first auxiliary vacuum chamber 31
through its seal 13 into the auxiliary vacuum chamber 31 and, then,
passed through the seal 13 at the other end of the chamber 31 into
the vacuum plasma apparatus 30. Withdrawal of the tubular
fluororesin inner ply 21 is performed in the reverse order. When
the tubular fluororesin inner ply 21 traverses the auxiliary vacuum
chamber 31, the internal pressure within the auxiliary vacuum
chamber has been set under moderate reduced pressure (about 0.1-10
Torr), by the vacuum pump 36 via line 17, as compared with the
reaction chamber 32. With this provision of the auxiliary vacuum
chambers 31, the entry of external air from the hose inlet and
outlet into the vacuum plasma apparatus 30 can be completely
prevented. As a result, the degree of vacuum within the reaction
chamber 32 can be exactly controlled so as to insure generation of
a stable plasma.
By the vacuum plasma treatment under the above specified
conditions, the peripheral surface layer of the tubular fluororesin
inner ply can be modified into a treated layer (A) or (B) having
both the F/C ratio and O/C ratio within the specified ranges. The
F/C and O/C ratios are the values determined by ESCA as mentioned
hereinbefore. The ESCA is a technique for analyzing the peripheral
surface of the plasma-treated tubular fluororesin inner ply using a
photoelectron spectrometer (e.g. ES-200, Kokusai Denki). The
typical parameter settings of this spectrometric instrument are as
follows.
Exciting X-rays: AL, K.alpha..sub.1,2 line (1486.6 eV)
X-ray output: 10 kV, 20 mA
Temperature: 20.degree. C.
Degree of vacuum: 3.times.10.sup.-8 Torr
When, in this manner, a fluororesin having an F/C ratio within the
specified range is employed and its surface layer is modified into
a treated layer with F/C and O/C ratios within the specified
ranges, typically by vacuum plasma treatment, the necessary
adhesion to other materials is expressed. Although the mechanism of
this expression of adhesion cannot be categorically explained, the
inventors of this invention advance the following assumption on the
basis of findings obtained in their research into the fuel hose.
Thus, when the surface layer of a fluororesin is activated by, for
example, vacuum plasma treatment, fluorine and hydrogen atoms are
driven off from the molecular skeleton of the fluororesin, leaving
carbon radicals. Therefore, in at least some part of the surface
layer, a crosslinking reaction takes place between carbon radicals
to form a tough surface layer. In the other part of the surface
layer, the carbon radicals are bound to oxygen in the air to form
functional groups such as carboxyl, aldehyde and ketone groups. The
treated layer having such functional groups has a remarkably
enhanced affinity for thermoplastic resins such as polyamide resin
containing amido linkages within the molecular skeleton or for
rubber. It is supposed that the expression of adhesion occurs as a
consequence in the surface layer of the fluororesin.
As described above, the fuel hose of this invention comprises a
tubular fluororesin inner ply and a thermoplastic resin or rubber
ply as disposed on the periphery of said inner ply, said tubular
fluororesin inner ply having been molded from a fluororesin having
an F/C ratio within the specified range and the peripheral surface
layer of said tubular fluororesin inner ply having been modified
into a treated layer controlled within the specified ranges of F/C
ratio and O/C ratio. Since the fluororesin having a treated layer
of such a specified atomic composition is employed, the fuel hose
of this invention features a very firm bond, with an initial bond
strength value of not less than 1.2 N/mm, between the fluororesin
ply and the thermoplastic resin or rubber ply. Therefore, the fuel
hose of this invention is free from troubles such as obstruction
due to exfoliation of the tubular fluororesin inner ply from said
thermoplastic resin ply during the transport of the fuel such as
gasoline. Moreover, when a polyamide resin having especially good
abrasion resistance and other dynamic characteristics is
selectively used for the molding of said outer ply to be laminated
onto the peripheral surface of said tubular fluororesin inner ply,
the service life of the fuel hose can be prolonged. Moreover, when
the thickness of the tubular fluororesin inner ply is reduced to as
small as about 0.05-1.00 mm, savings can be realized in fluororesin
which is expensive so that the cost of the fuel hose can be
lowered. It is also possible to further improve the bond strength
of the fuel hose by interposing an adhesive layer between the
tubular fluororesin inner ply and the outer ply disposed on the
peripheral surface of said inner ply.
The method of this invention for producing a fuel hose comprises
forming a tubular fluororesin inner ply by an extrusion or other
molding technique, subjecting the peripheral surface layer of said
inner ply to vacuum plasma treatment to create a treated layer, and
forming a thermoplastic resin or rubber ply on the surface of said
treated layer. These respective steps can be respectively carried
out in a continuous manner and can also be performed as a whole in
a continuous sequence. Therefore, the method of this invention for
producing a fuel hose is a method providing for a high production
efficiency. Furthermore, in the formation of said thermoplastic
resin or other outer ply, the resin or the like can be heated and
directly fused to the peripheral surface (treated layer) of the
tubular fluororesin inner ply to form said thermoplastic resin or
other outer ply.
The vacuum plasma apparatus for use in the method of this invention
for the production of a fuel hose incorporates a special sealing
contrivance. Thus, in order to retain the necessary negative
pressure within the apparatus, the seals of the vacuum plasma
apparatus are made of a rubber-like elastomer. Therefore, this
vacuum plasma apparatus permits continuous treatment, and unlike
the conventional plasma equipment, does not require a special
device (a vacuum zone or the like). And yet, even in the production
of a hose of great length, the apparatus permits application of a
stable plasma treatment to its tubular fluororesin inner ply. When
said rubber elastomer seal is made of a rubber-like elastomer with
a hardness of 45-80 (JIS A), a greater air-tightness of the
apparatus can be insured and, at the same time, the seal may yield
well in intimate contact with the tubular fluororesin inner ply so
that the inner ply can be introduced and withdrawn at a high speed.
Furthermore, when the seal is formed as a seal chamber as
illustrated in FIG. 14, the degree of vacuum in the vacuum plasma
apparatus can be maintained still more certainly so that a very
satisfactory plasma can be generated over a long time.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is an elementary diagram showing the fuel hose of this
invention;
FIG. 2 is a schematic diagram illustrating the method for producing
a fuel hose in accordance with this invention;
FIG. 3 is a schematic diagram illustrating an embodiment in which a
cooling zone is used in the method for producing a fuel hose in
accordance with this invention.
FIG. 4 is a schematic diagram illustrating an embodiment in which a
vacuum plasma apparatus equipped with an induction coil electrode
means is used in the above method for producing a fuel hose in
accordance with this invention;
FIG. 5 is a schematic diagram illustrating an embodiment in which a
vacuum plasma apparatus having auxiliary vacuum chambers is used in
the method for producing a fuel hose in accordance with this
invention;
FIG. 6 is an elementary view illustrating a sealing element for the
vacuum plasma apparatus of this invention;
FIG. 7 is an elementary diagram illustrating an alternative seal
element for the vacuum plasma apparatus of this invention;
FIG. 8 is an elementary view showing an embodiment of the fuel hose
of this invention which is provided with a sheath ply;
FIG. 9 is an elementary view showing an embodiment of the fuel hose
of this invention which is provided with a reinforcing cord ply and
a sheath ply;
FIG. 10 is an elementary view of a testpiece used for determination
of the bond strength of the fuel hose;
FIG. 11 is a diagrammatic representation of the relationship
between F/C ratio and O/C ratio in the treated layer of the tubular
fluororesin inner ply of a fuel hose according to this
invention;
FIG. 12 is a diagrammatic representation of the relationship
between F/C ratio and O/C ratio in the treated layer of the tubular
fluororesin inner ply of a fuel hose according to this
invention;
FIG. 13 is a diagrammatic representation of the relationship
between F/C ratio and O/C ratio in the treated layer of the tubular
fluororesin inner ply of a fuel hose according to this
invention;
FIG. 14 is an elementary view illustrating an alternative seal
means of the vacuum plasma equipment of this invention.
The following examples and comparative examples are further
illustrative of this invention.
EXAMPLES 1-5
By means of the vacuum plasma apparatus illustrated in FIG. 2, a
fuel hose was fabricated using ETFE as the molding material for a
tubular fluororesin inner ply and nylon 12 as the molding material
for an outer ply to be formed on the peripheral surface of said
inner ply.
First, the mandrel 11 was supplied from the mandrel feeder 10 to
the inner ply extruder 20 at a speed of 10 m/min. From this inner
ply extruder 20 was extruded the ETEF onto the peripheral surface
of the mandrel 11 to form a tubular ETFE inner ply with a geometry
of 6.0 mm in inner diameter and 0.25 mm in thickness. This tubular
ETFE inner ply 21 was guided into the discharge chamber 32 of the
vacuum plasma apparatus 30. After the discharge chamber 32 was
decompressed by the vacuum pump 34 to 10.sup.-3 Torr, an electrical
discharge gas was supplied from a gas source 35 to establish a
predetermined negative pressure within the chamber. The electric
discharge gas and degree of vacuum used in each example are shown
below in Table 1.
TABLE 1 Electrical Degree of vacuum Example discharge gas (Torr) 1
Ar 0.1 2 Ar 0.05 3 N.sub.2 0.1 4 N.sub.2 0.05 5 Ar + N.sub.2 0.05 6
Ar 0.05
Then, the tubular ETFE inner ply 21 was guided into position
between the elctrodes 32a within said discharge chamber 32 and
using a high frequency power source 40 and a matching box 41, an
impedance-matched high frequency current with a frequency of 13.56
MHz and an output of 10 W was applied to the electrodes 32a to
generate a plasma by glow discharge, whereby the peripheral surface
layer of said tubular ETFE inner ply 21 was plasma-treated to form
a treated layer 21a (FIG. 1). After this plasma treatment, the
tubular ETFE inner ply 21 was withdrawn from the vacuum plasma
apparatus 30 and fed to an outer ply extruder 50. By this outer ply
extruder 50, a 0.75 mm thick ply 51 made of nylon 12 was laminated
in direct superimposition on said treated layer of the tubular ETFE
inner ply 21. The laminates obtained in the above manner were
respectively taken up on a mandrel takeup 60 to provide fuel hoses
of Examples 1-5. The molding of said ply 51 was performed by
extruding nylon 12 from an extruder 50 at a temperature of
240.degree. C.
EXAMPLE 6
Using a vacuum plasma apparatus illustrated in FIG. 2 for plasma
treatment, ETFE for the tubular fluororesin inner ply and ECO for
the outer ply to be formed on the peripheral surface of said inner
ply, a fuel hose was fabricated. In this production process, Ar gas
was used as the electrical discharge gas, the degree of vacuum was
set at 0.05 Torr, and the thickness of the ECO ply was controlled
at 2 mm. After extrusion of the outer ply from the extruder 50, the
laminate was taken up on the mandrel takeup 60 and the ECO ply 51
was then vulcanized at 160.degree. C. for 45 minutes. Otherwise the
procedure of Examples 1-5 was repeated to provide a fuel hose of
Example 6.
Comparative Example 1
A fuel hose was fabricated in the same manner as Example 1 except
that the tubular ETFE inner ply 21 was not subjected to vacuum
plasma treatment.
Comparative Example 2
A fuel hose was fabricated in the same manner as Example 3 except
that the degree of vacuum for plasma treatment was set to 10
Torr.
EXAMPLES 7 and 8
Except that CTFE was used as the molding material for the tubular
fluororesin inner ply and the electrical discharge gases and
degrees of vacuum shown below in Table 2 were employed, fuel hoses
were fabricated in otherwise the same manner as Examples 1-5.
TABLE 2 Electrical Degree of vacuum Example discharge gas (Torr) 7
N.sub.2 0.1 8 N.sub.2 0.05
Comparative Example 3
A fuel hose was fabricated in the same manner as Examples 7 and 8
except that the tubular CTFE inner ply 21 was not subjected to
vacuum plasma treatment.
Comparative Example 4
A fuel hose was fabricated in the same manner as Example 7 except
that the degree of vacuum for plasma treatment was set to 10
Torr.
EXAMPLES 9-14
Except that FEP was used as the molding material for the tubular
fluororesin inner ply and the electrical discharge gases and
degrees of vacuum shown below in Table 3 were employed, fuel hoses
were fabricated in otherwise the same manner as Examples 1-5.
TABLE 3 Electrical Degree of vacuum Example discharge gas (Torr) 9
Ar 0.1 10 Ar 0.05 11 N.sub.2 0.3 12 N.sub.2 0.1 13 N.sub.2 0.05 14
Ar + N.sub.2 0.05 15 Ar 0.05
Example 15
A fuel hose was fabricated using FEP for the tubular fluororesin
inner ply, ECO as the molding material for the outer ply to be
laminated on the peripheral surface of said inner ply, and the
apparatus of FIG. 2 for vacuum plasma treatment. In this production
process, Ar gas was used as the electrical discharge gas and the
degree of vacuum was set to 0.05 Torr for vacuum plasma treatment.
The thickness of the ECO ply was set to 2 mm. After extrusion of
the outer ply from extruder 50, the hose was taken up on the
mandrel takeup 60 and the ECO ply was vulcanized at 160.degree. C.
for 45 minutes. Otherwise the procedure of Examples 9-14 was
repeated to provide a fuel hose.
Comparative Example 5
A fuel hose was fabricated in the same manner as Examples 9-14
except that the tubular FEP inner ply 21 was not subjected to
vacuum plasma treatment.
Comparative Example 6
A fuel hose was fabricated in the same manner as Example 11 except
that the degree of vacuum for plasma treatment was set to 10
Torr.
Comparative Example 7
A fuel hose was fabricated in the same manner as Example 15 except
that the degree of vacuum for plasma treatment was set to 10
Torr.
EXAMPLE 16
A fuel hose was fabricated in the same manner as Example 1 except
that the degree of vacuum for plasma treatment was set to 5
Torr.
EXAMPLE 17
A fuel hose was fabricated in the same manner as Example 6 except
that the degree of vacuum for plasma treatment was set to 5
Torr.
EXAMPLE 18
A fuel hose was fabricated in the same manner as Example 9 except
that the degree of vacuum for plasma treatment was set to 5
Torr.
EXAMPLE 19
A fuel hose was fabricated in the same manner as Example 15 except
that the degree of vacuum for plasma treatment was set to 5
Torr.
For each of the above fuel hoses of Examples 1-19 and of
Comparative Examples 1-7, the atomic composition of the treated
layer of the tubular fluororesin inner ply, the bond strength
between the inner ply and the outer ply formed on the peripheral
surface thereof, gasoline resistance and thermal aging resistance
were determined. The results are shown in Tables 4-9. These
characteristics were determined by the following methods.
[Atomic composition of the treated layer of the tubular fluororesin
inner ply]
This parameter was determined by ESCA. Thus, using a photoelectron
spectrometer (ES-200, Kokusai Denki), ESCA was made under the
following conditions.
Exciting X-rays: Al, K.alpha..sub.1,2 lines (1486.6 eV)
X-ray output: 10 kV, 20 mA,
Temperature: 20.degree. C.
Degree of vacuum: 3.times.10.sup.-8 Torr
[Bond strength]
The bond strength was determined in accordance with JIS K 6301.
Thus, as illustrated in FIG. 10, each fuel hose was sliced into a
10 mm (L) ring which was then cut in the longitudinal direction to
prepare a sample. The inner ply 21 and outer ply 51 of this sample
were partially peeled off from the section and the peeled ends were
secured stationary with the jig of a tensile tester and a tensile
test was performed at a peeling speed of 25 mm/min. The load found
from this tensile test was regarded as the bond strength between
the two plies.
[Gasoline immersion test]
The testpiece for the above determination of bond strength was
immersed in gasoline at 40.degree. C. for 168 hours and the bond
strength between the tubular fluororesin inner ply and the outer
ply laminated onto the periphery of said inner ply was determined
in the same manner as described above.
[Thermal aging test]
The testpiece for the above determination of bond strength was
heat-treated at 125.degree. C. for 168 hours and, then, the bond
strength between the tubular fluororesin inner ply and the outer
ply laminated onto the periphery of said inner ply was determined
in the same manner.
TABLE 4 Example 1 2 3 4 5 6 F/C 0.65 0.30 0.60 0.32 0.55 0.30 O/C
0.16 0.25 0.14 0.19 0.12 0.25 Bond strength 5.7 6.5 4.5 5.6 4.3 5.2
(N/mm) Gasoline immersion test 4.5 4.8 4.0 4.4 3.8 2.7 (N/mm)
Thermal aging test 5.3 6.5 4.3 5.4 4.2 5.0 (N/mm)
TABLE 5 Comparative Example 1 2 F/C 0.98 0.80 O/C 0.01 0.06 Bond
strength 0.2 0.8 (N/mm) Gasoline immersion test 0 0.3 (N/mm)
Thermal aging test 0 0.5 (N/mm)
TABLE 6 Example Comparative Example 7 8 3 4 F/C 1.02 0.60 1.51 1.10
O/C 0.13 0.18 0 0.06 Bond strength 5.1 5.6 0.1 0.7 (N/mm) Gasoline
immersion test 4.1 4.2 0 0.2 (N/mm) Thermal aging test 4.8 5.4 0
0.4 (N/mm)
TABLE 7 Example 9 10 11 12 13 14 15 F/C 1.48 0.76 1.70 1.08 0.58
1.40 0.76 O/C 0.17 0.26 0.07 0.12 0.23 0.13 0.26 Bond strength 5.5
6.0 4.4 4.9 5.1 4.0 5.1 (N/mm) Gasoline immersion 4.0 4.4 3.8 3.8
4.0 3.3 2.7 test (N/mm) Thermal aging test 5.3 5.9 4.2 4.5 4.8 3.4
4.7 (N/mm)
TABLE 8 Example 16 17 18 19 F/C 0.73 0.73 0.70 0.70 O/C 0.08 0.08
0.08 0.08 Bond strength 1.8 1.6 1.6 1.2 (N/mm) Gasoline immersion
0.8 0.8 0.4 0.6 test (N/mm) Thermal aging test 1.4 1.3 1.1 1.0
(N/mm)
TABLE 9 Comparative Example 5 6 7 F/C 2.00 1.51 1.30 O/C 0 0.06
0.80 Bond strength 0.1 0.9 1.0 (N/mm) Gasoline immersion test 0 0.3
0.6 (N/mm) Thermal aging test 0 0.7 0.7 (N/mm)
It is apparent from Tables 4-9 that all the fuel hoses of Examples
1-19 with F/C and O/C ratios within the specified ranges had
sufficient initial bond strength values (.gtoreq.1.2 N/mm) required
of fuel hoses. Moreover, these hoses retained sufficient bond
strength values even after gasoline immersion and after thermal
aging. It is, therefore, clear that the fuel hose of this invention
has a structural strength sufficient for the intended service and
is a high performance hose without the risk of obstruction. In
contrast, the fuel hoses of Comparative Examples 1-7 which were
outside of the specified ranges of F/C and O/C ratios were
remarkably low in bond strength (<1.2 N/mm). Moreover, they
showed further decreases in bond strength in the gasoline immersion
test and in the thermal aging test and particularly in the fuel
hoses of Comparative Examples 1, 3 and 5, a delamination occurred
between the tubular inner ply and the outer ply.
Based on the results for the above Examples 1-19 and Comparative
Examples 1-7, the relation of F/C and O/C ratios of the treated
layer of the tubular fluororesin ply with the bond strength between
the two plies was plotted as shown in FIGS. 11, 12 and 13.
The diagram of FIG. 11 represents the data of Examples 1-6,
Examples 16 and 17, and Comparative Examples 1 and 2 in which ETFE
(F/C=0.98) was used as the fluororesin. In the diagram, O means a
bond strength of not less than 1.2 N/mm and x means a bond strength
of less than 1.2 N/mm. The upper area (A) demarcated by a dot-dash
line represents the range of treated layer (A) of this invention
(corresponding to the invention of Claim 1). It is clear from the
diagram that the bond strength is .gtoreq.1.2 N/mm in the range of
treated layer (A).
The diagram of FIG. 12 shows the results for Examples 7 and 8 and
Comparative Examples 3 and 4 in which CTFE (F/C=1.51) was used as
the fluororesin. In this diagram, o means a bond strength of not
less than 1.2 N/mm and x means a bond strength of less than 1.2
N/mm. The upper area (A) demarcated by a dot-dash line represents
the range of treated layer (A) of this invention (corresponding to
the invention of Claim 1). It is clear from the diagram that the
bond strength is .gtoreq.1.2 N/mm in the range of treated layer
(A).
The diagram of FIG. 13 shows the results for Examples 9-15,
Examples 18 and 19, and Comparative Examples 5-7 in which FEP
(F/C=2.0) was used as the fluororesin. In the diagram, O means a
bond strength of not less than 1.2 N/mm and x means a bond strength
of less than 1.2 N/mm. The upper area (B) demarcated by a dot-dash
line in the diagram represents the range of treated layer (B) of
this invention (corresponding to the invention of Claim 6). In the
diagram, the left-hand area demarcated by a dot-dash line within
the above range (B) represents the range (a) of treated layer (B)
of this invention, while the right-hand area demarcated by a
dot-dash line represents the range (b) of treated layer (B) of this
invention. The inclined segment of this dot-dash line is the
borderline defined by the relation (1) mentioned hereinbefore. It
is clear from the diagram that the bond strength is .gtoreq.1.2
N/mm within the range of treated layer (B).
EXAMPLE 20
A fuel hose was fabricated in the same manner as Example 1 except
that the mandrel was not used. As a result, despite the thickness
of the tubular ETFE inner ply being as small as 0.25 mm, the ply
did not collapse but retained its tubular shape. Moreover, this
tubular ETFE inner ply could be successfully subjected to vacuum
plasma treatment and formation of an outer layer on its periphery.
Moreover, because the step of slipping out a mandrel was dispensed
with, the fuel hose could be produced with good efficiency.
EXAMPLE 21
After the vacuum plasma,treatment of a tubular ETFE inner ply, a
silane adhesive was applied and an outer ply was extruded over the
periphery of the adhesive layer. Otherwise the procedure of Example
1 was repeated to provide a fuel hose. The bond strength of this
fuel hose was as high as 6.8 N/mm.
The following examples and comparative examples are intended to
describe the vacuum plasma apparatus of this invention in further
detail.
EXAMPLES 22-35
The outer diameter of the tubular fluororesin inner ply was set to
6.5 mm, while the rubber-like elastomer seal element geometry,
rubber hardness, rubber material and mandrel supply speed were as
shown in Tables 10 and 11. Otherwise the procedure of Example 1 was
repeated to fabricate fuel hoses. The plasma condition during
production of each fuel hose was evaluated and the bond strength of
each hose was determined by the method described hereinbefore. The
results are shown in the same table, In the evaluation of plasma
condition, the case in which a stable plasma was established by
glow discharge was rated as o and the case in which an abnormality
of plasma developed was rated as x. Moreover, in the above
determination of bond strength, the case in which the bond strength
was not less than 1.2 N/mm was rated as O and the case in which the
bond strength was less than 1.2 N/mm was rated as x.
TABLE 10 Example 22 23 24 25 26 27 28 Seal geometry* A A A B A A A
Rubber hardness 45 50 60 60 70 80 60 (JIS A) Type of Rubber Sili-
Sili- Sili- Sili- Sili- Sili- Sili- cone cone cone cone cone cone
cone rub- rub- rub- rub- rub- rub- rub- ber ber ber ber ber ber ber
Speed of mandrel 15 15 15 15 15 15 5 feed (m/min.) Plasma condition
.smallcircle. .smallcircle. .smallcircle. .smallcircle.
.smallcircle. .smallcircle. .smallcircle. Bond strength
.smallcircle. .smallcircle. .smallcircle. .smallcircle.
.smallcircle. .smallcircle. .smallcircle. *: Seal geometry A is as
illustrated in FIG. 6; seal geometry B is as illustrated in FIG.
7.
TABLE 11 Example 29 30 31 32 33 34 35 Seal geometry* A B A A B A A
Rubber hardness 60 60 60 60 60 50 70 (JIS A) Type of Rubber Sili-
Sili- Sili- NBR NBR NBR NBR cone cone cone rub- rub- rub- ber ber
ber ber ber ber ber Speed of mandrel 10 10 25 15 15 15 15 feed
(m/min.) Plasma condition .smallcircle. .smallcircle. .smallcircle.
.smallcircle. .smallcircle. .smallcircle. .smallcircle. Bond
strength .smallcircle. .smallcircle. .smallcircle. .smallcircle.
.smallcircle. .smallcircle. .smallcircle. *: Seal geometry A is as
illustrated in FIG. 6; seal geometry B is as illustrated in FIG.
7.
It is apparent from the data in the above Tables 10 and 11 that a
stable plasma could be generated in all the Examples and that the
bond strengths of the resulting fuel hoses were invariably
.gtoreq.1.2 N/mm. It is, therefore, clear that the vacuum plasma
apparatus of this invention is highly air-tight and capable of
performing a satisfactory plasma treatment even when the tubular
fluororesin inner ply is fed to and withdrawn from it at a high
speed.
EXAMPLE 36
A fuel hose was fabricated using the vacuum plasma apparatus having
seal chambers (auxiliary vacuum chambers) illustrated in FIG. 5.
The rubber elements used for sealing the auxiliary vacuum chambers
31 were silicone rubber elements with a hardness of 60 (JIS A).
Otherwise the procedure of Examples 22-35 was repeated to fabricate
a fuel hose. The plasma condition during the production was
evaluated and the bond strength of the resulting fuel hose
determined in the same manner as above. The plasma condition during
production was very stable and the fuel hose had a bond strength of
.gtoreq.1.2 N/mm.
* * * * *