U.S. patent application number 11/006715 was filed with the patent office on 2005-06-16 for fiber for reinforcing rubber products.
This patent application is currently assigned to Asahi Fiber Glass Company, Limited. Invention is credited to Ando, Kimihiro.
Application Number | 20050129943 11/006715 |
Document ID | / |
Family ID | 34510552 |
Filed Date | 2005-06-16 |
United States Patent
Application |
20050129943 |
Kind Code |
A1 |
Ando, Kimihiro |
June 16, 2005 |
Fiber for reinforcing rubber products
Abstract
Fiber for reinforcing rubber products, which comprises fiber
coated with a coating film formed by a treating agent, wherein the
treating agent comprises a rubber latex containing at least a
vinylpyridine/styrene/buta- diene terpolymer, a latex of an
acrylonitrile/butadiene/styrene terpolymer, and a water-soluble
condensate of resorcinol and formaldehyde.
Inventors: |
Ando, Kimihiro; (Tokyo,
JP) |
Correspondence
Address: |
OBLON, SPIVAK, MCCLELLAND, MAIER & NEUSTADT, P.C.
1940 DUKE STREET
ALEXANDRIA
VA
22314
US
|
Assignee: |
Asahi Fiber Glass Company,
Limited
Tokyo
JP
101-0045
|
Family ID: |
34510552 |
Appl. No.: |
11/006715 |
Filed: |
December 8, 2004 |
Current U.S.
Class: |
428/375 |
Current CPC
Class: |
C03C 25/34 20130101;
Y10T 428/2933 20150115; C03C 25/26 20130101; C08J 2321/00 20130101;
D06M 15/41 20130101; C03C 25/27 20180101; C08J 5/06 20130101; C08L
2205/035 20130101; C08L 39/08 20130101; D06M 15/233 20130101; D06M
15/227 20130101; D06M 15/3562 20130101 |
Class at
Publication: |
428/375 |
International
Class: |
D02G 003/00 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 12, 2003 |
JP |
2003-414153 |
Claims
What is claimed is:
1. Fiber for reinforcing rubber products, which comprises fiber
coated with a coating film formed by a treating agent, wherein the
treating agent comprises a rubber latex containing at least a
vinylpyridine/styrene/butadiene terpolymer, a latex of an
acrylonitrile/butadiene/styrene terpolymer, and a water-soluble
condensate of resorcinol and formaldehyde.
2. The fiber for reinforcing rubber products according to claim 1,
wherein the latex of an acrylonitrile/butadiene/styrene terpolymer
is a latex of the terpolymer wherein, when the total of the
copolymerized ratios of the respective comonomers is 100 mass %,
acrylonitrile is from 20 to 40 mass %, butadiene is from 25 to 50
mass %, and styrene is from 25 to 50 mass %.
3. The fiber for reinforcing rubber products according to claim 1,
wherein the treating agent comprises, as calculated as solid
contents, 100 parts by mass of the rubber latex containing at least
a vinylpyridine/styrene/b- utadiene terpolymer, from 15 to 70 parts
by mass of the latex of an acrylonitrile/butadiene/styrene
terpolymer, and from 2 to 25 parts by mass of the water-soluble
condensate of resorcinol and formaldehyde.
4. The fiber for reinforcing rubber products according to claim 2,
wherein the treating agent comprises, as calculated as solid
contents, 100 parts by mass of the rubber latex containing at least
a vinylpyridine/styrene/b- utadiene terpolymer, from 15 to 70 parts
by mass of the latex of an acrylonitrile/butadiene/styrene
terpolymer, and from 2 to 25 parts by mass of the water-soluble
condensate of resorcinol and formaldehyde.
Description
[0001] The present invention relates to fiber for reinforcing
rubber products, which is used as a reinforcing material for
various rubber products such as rubber tires or rubber belts
including timing belts.
[0002] It is common that reinforcing fiber to be used to increase
the strength or durability of various rubber products such as
rubber tires or rubber belts including timing belts, is coated with
a coating film formed by a rubber type treating agent in order to
increase the adhesion between the fiber and a rubber base material
in a rubber product and in order to increase the durability of the
rubber product by protecting the fiber itself. As such a rubber
type treating agent, a treating agent comprising a condensate of
resorcinol and formaldehyde, and a rubber latex, as the main
components (hereinafter sometimes referred to as "RFL treating
agent"), is known.
[0003] Particularly, a driving belt such as a timing belt to be
used for an automobile engine is required to have durability under
a severe condition such as a high temperature. Accordingly, the
rubber as its base material and the reinforcing fiber are required
to have heat resistance. Accordingly, as reinforcing fiber to be
used for such a timing belt, fiber is known which is coated with a
coating film formed by a RFL treating agent, having a highly heat
resistant rubber latex, such as a halogen-containing polymer,
incorporated.
[0004] For example, JP-A-1-221433 and JP-A-5-311577 disclose a RFL
treating agent which comprises a resorcinol/formaldehyde resin, a
butadiene/styrene/vinylpyridine terpolymer and a chlorosulfonated
polyethylene.
[0005] Further, it is known that in order to increase the heat
resistance of such a timing belt, a rubber composition containing a
hydrogenated nitrile rubber (hereinafter sometimes referred to as
"H-NBR") as the main component, is used as the base material, and
the above-mentioned reinforcing fiber is required to have good
adhesion to such a rubber composition containing H-NBR as the main
component. As such a RFL treating agent, for example, JP-A-4-103634
discloses a RFL treating agent comprising a water-soluble
condensate of resorcinol and formaldehyde, a latex of a
vinylpyridine/styrene/butadiene terpolymer and a latex of an
acrylonitrile/butadiene copolymer.
[0006] The above-mentioned conventional reinforcing fibers show
fairly strong adhesion to a rubber composition containing
chlorosulfonated polyethylene rubber as the main component, or a
rubber composition containing H-NBR having a relatively low
saturation degree as the main component and using sulfur mainly as
a vulcanizing agent, among rubber compositions to be used as base
materials for rubber products such as timing belts.
[0007] However, their adhesion is inadequate to a rubber
composition containing heat resistant H-NBR having a high
saturation degree as the main component and having a peroxide
incorporated as a vulcanizer.
[0008] Accordingly, when the conventional reinforcing fibers and a
rubber composition containing highly saturated H-NBR as the main
component are combined, there has been a problem such that the heat
resistance or bending fatigue resistance of the finally obtainable
rubber product such as a timing belt, tends to be inadequate.
[0009] Further, in a case where the above-mentioned conventional
reinforcing fibers are bonded to a H-NBR rubber composition, the
adhesion tends to deteriorate in an environment where they are in
contact with water, whereby there has been a problem that the water
resistance of the finally obtainable rubber product such as a
timing belt, tends to be poor.
[0010] Accordingly, the present invention has been made to solve
such problems of the prior art, and its object is to provide fiber
for reinforcing rubber products, which is suitable particularly for
a timing belt for an automobile engine and which is capable of
imparting excellent heat resistance and water resistance to such a
timing belt.
[0011] To solve the above-mentioned problems, the fiber for
reinforcing rubber products of the present invention, is fiber for
reinforcing rubber products, which comprises fiber coated with a
coating film formed by a treating agent, wherein the treating agent
comprises a rubber latex containing at least a
vinylpyridine/styrene/butadiene terpolymer, a latex of an
acrylonitrile/butadiene/styrene terpolymer, and a water-soluble
condensate of resorcinol and formaldehyde.
[0012] According to the fiber for reinforcing rubber products of
the present invention, the treating agent for forming the coating
film to cover the reinforcing fiber, contains the latex of an
acrylonitrile/butadiene/styrene terpolymer, whereby the fiber has
excellent adhesion to a H-NBR rubber composition, particularly to a
rubber composition containing highly saturated H-NBR as the main
component and having a peroxide incorporated as a vulcanizer, and
the adhesion will not deteriorate even in an environment where it
is in contact with water. Thus, the fiber for reinforcing rubber
products of the present invention is provided with both heat
resistance and water resistance and is thus suitable as a
reinforcing material for a timing belt for an automobile
engine.
[0013] Further, in the fiber for reinforcing rubber products of the
present invention, the latex of an acrylonitrile/butadiene/styrene
terpolymer is preferably a latex of the terpolymer wherein, when
the total of the copolymerized ratios of the respective comonomers
is 100 mass %, acrylonitrile is from 20 to 40 mass %, butadiene is
from 25 to 50 mass %, and styrene is from 25 to 50 mass %.
[0014] By the use of the latex of an
acrylonitrile/butadiene/styrene terpolymer having such
copolymerized ratios of the comonomers, an effect will be obtained
such that the coating film formed by such a treating agent, will
have excellent heat resistance while maintaining excellent
flexibility.
[0015] Further, in the fiber for reinforcing rubber products of the
present invention, the treating agent preferably comprises, as
calculated as solid contents, 100 parts by mass of the rubber latex
containing at least a vinylpyridine/styrene/butadiene terpolymer,
from 15 to 70 parts by mass of the latex of an
acrylonitrile/butadiene/styrene terpolymer, and from 2 to 25 parts
by mass of the water-soluble condensate of resorcinol and
formaldehyde.
[0016] By adopting such proportions, the balance will be good
between the adhesion of the reinforcing fiber to a rubber base
material constituting a rubber product and the bending fatigue
resistance of the finally obtainable timing belt or the like.
[0017] The fiber for reinforcing rubber products of the present
invention has both excellent heat resistance and water resistance,
whereby it is possible to substantially improve the durability at a
high temperature or the durability against contact with water, of a
rubber product such as a timing belt wherein such a fiber is used
as a reinforcing material.
[0018] Now, the present invention will be described in detail. In
the following description "parts" means "parts by mass", and "%"
means "% by mass" , unless otherwise specified.
[0019] Firstly, the treating agent (hereinafter referred to as the
first treating agent) comprising the rubber latex containing at
least a vinylpyridine/styrene/butadiene terpolymer (hereinafter
referred to also simply as the rubber latex), the latex of an
acrylonitrile/butadiene/styr- ene terpolymer and the water-soluble
condensate of resorcinol and formaldehyde, will be described.
[0020] As the vinylpyridine/styrene/butadiene terpolymer latex
(hereinafter referred to also as the vinylpyridine latex) to be
incorporated in the first treating agent, one which is commonly
used for the treatment of fiber for reinforcing rubber products may
be used.
[0021] Among them, it is preferred to use a latex of a
vinylpyridine/styrene/butadiene terpolymer wherein, when the total
of the copolymerized ratios of the respective comonomers is 100
mass %, vinylpyridine is from 10 to 20 mass %, styrene is from 10
to 20 mass % and butadiene is from 60 to 80 mass %. As such a
vinylpyridine latex, Nipol-2518FS (tradename, manufactured by ZEON
CORPORATION) or Pyratex (tradename, manufactured by NIPPON A&L
INC.) may, for example, be suitably used.
[0022] Further, as the rubber latex of the present invention
containing at least such a vinylpyridine latex, the above-mentioned
vinylpyridine latex may be used alone, or the vinylpyridine latex
and a rubber latex other than the acrylonitrile/butadiene/styrene
terpolymer latex (hereinafter referred to as "another rubber
latex") may be used in combination.
[0023] As such another rubber latex, a latex of a rubber having
remaining double bonds (i.e. an unsaturated rubber) or a latex of a
halogen-containing polymer is preferably used. As the latex of a
rubber having remaining double bonds, a latex of an acrylate type
polymer, a latex of a styrene/butadiene copolymer, a latex of a
carboxyl-modified styrene/butadiene copolymer, or a latex of a
polybutadiene, may, for example, be mentioned. As the latex of a
halogen-containing polymer, a latex obtained from a
halogen-containing polymer such as chlorinated rubber, chloroprene
rubber or chlorosulfonated polyethylene, may, for example, be
mentioned.
[0024] Further, the latex of an acrylonitrile/butadiene/styrene
terpolymer (hereinafter referred to also as "ABS latex") to be
incorporated to the first treating agent, is preferably a latex of
a terpolymer wherein, when the total of the copolymerized ratios of
the respective comonomers is 100 mass %, acrylonitrile is from 20
to 40 mass %, butadiene is from 25 to 50 mass % and styrene is from
25 to 50 mass %, and the above copolymerized ratios are more
preferably such that acrylonitrile is from 25 to 35 mass %,
butadiene is from 30 to 40 mass %, and styrene is from 30 to 40
mass %. As such an ABS latex, Nipol-1577 (tradename, manufactured
by ZEON CORPORATION) may, for example, be suitably used.
[0025] Further, as the water-soluble condensate of resorcinol and
formaldehyde (hereinafter referred to also as "the RF condensate")
to be incorporated in the first treating agent, it is possible to
use a water-soluble addition condensate rich in oxymethyl groups,
which is obtained by reacting resorcinol and formaldehyde in the
presence of an alkaline catalyst such as an alkali metal hydroxide,
ammonia or an amine. Particularly preferred is a RF condensate
obtained by reacting resorcinol and formaldehyde in a molar ratio
of 1:0.3 to 2.5.
[0026] To the first treating agent, the same additives as commonly
used in conventional RFL treating agents, such as an anti-aging
agent and a stabilizer, may be incorporated in addition to the
rubber latex, the ABS latex and the RF condensate, as the case
requires.
[0027] As the anti-aging agent, a liquid emulsified product of a
mineral oil may, for example, be mentioned, and as the stabilizer,
aqueous ammonia or an aqueous sodium hydroxide solution may, for
example, be mentioned.
[0028] The first treating agent in the present invention can be
obtained by uniformly mixing the components such as the rubber
latex, the ABS latex, the RF condensate and the additives which are
incorporated as the case requires, with water as a dispersant, in
accordance with a usual method.
[0029] In such a first treating agent, it is preferred to
incorporate the ABS latex in a proportion of from 15 to 70 parts,
more preferably from 20 to 50 parts, per 100 parts of the rubber
latex, as calculated as solid contents.
[0030] If the proportion of the ABS latex is less than 15 parts,
the adhesion, to a H-NBR composition of the obtainable reinforcing
fiber tends to be inadequate, and the heat resistance or water
resistance of the finally obtainable timing belt tends to be poor.
Further, the proportion of the rubber latex relatively increases,
whereby tackiness of the obtained reinforcing fiber tends to be too
high, whereby a trouble may be caused in its production.
[0031] On the other hand, if the proportion of the ABS latex
exceeds 70 parts, the coating film to be formed by the first
treating agent, tends to be hard whereby the flexibility of the
rubber reinforcing fiber thereby obtained, tends to be low, and the
bending fatigue resistance of the finally obtainable timing belt,
tends to be inadequate.
[0032] Further, in a case where the vinylpyridine latex and another
rubber latex are incorporated in the first treating agent, a part
of the blend amount of the vinylpyridine latex is replaced by
another latex so that the total of the vinylpyridine latex and
another latex will be 100 parts. The proportions of the two are
preferably such that, as solid contents, the vinylpyridine latex is
from 70 to 95 parts, while another rubber latex is from 30 to 5
parts.
[0033] Further, in the first treating agent, the RF condensate is
preferably incorporated in a proportion of from 2 to 25 parts, more
preferably from 5 to 15 parts, per 100 parts of the rubber latex,
as calculated as solid contents. If the proportion of the RF
condensate is less than 2 parts, the adhesion of the reinforcing
fiber to the rubber base material constituting a rubber product
such as a timing belt, tends to be inadequate, and if the
proportion of the RF condensate exceeds 25 parts, the finally
obtainable timing belt may sometimes be poor in the bending fatigue
resistance. When the RF condensate is incorporated in a proportion
of from 5 to 15 parts, the balance between the adhesion and the
heat resistance of the reinforcing fiber and the bending fatigue
resistance of the timing belt will be good.
[0034] Still further, the concentration of the first treating
agent, i.e., the total content of components in the first treating
agent including the rubber latex, the ABS latex, the RF condensate
and additives which may be incorporated, as the case requires, is
preferably from 10 to 50%, more preferably from 20 to 40%, as solid
contents. If such a concentration is less than 10%, it may
sometimes become difficult to impregnate the fiber with a
sufficient amount of the first treating agent, and if it exceeds
50%, the stability of the first treating agent tends to be poor,
and gelation may be likely to take place.
[0035] The fiber to be used in the present invention is not
particularly limited, and it may be either inorganic fiber or
organic fiber which is commonly used in a conventional
rubber-reinforcing fiber. As the inorganic fiber, glass fiber or
carbon fiber may be used, and as the organic fiber, aramid fiber,
PBO (polyparaphenylenebenzoxazole) fiber, PET (polyethylene
terephthalate) fiber or PEN (polyethylene naphthalate) fiber may,
for example, be used. To such fibers, it is preferred to
preliminarily apply a binding agent or a sizing agent, prior to
being coated with the first treating agent, in order to improve the
adhesive between the fiber itself and the coating film formed by
the first treating agent.
[0036] Among the above fibers, it is preferred to use glass fiber
in view of the wide applicability, the cost and easy application to
the process for producing timing belts. As such glass fiber, one
obtained by bundling from 200 to 600 glass monofilaments having a
diameter of from 7 to 9 .mu.m, may, for example, be employed.
Further, the composition of the glass fiber is not particularly
limited, and E glass or S glass may, for example, be mentioned.
Further, in the case of glass fiber, it is preferably subjected to
pretreatment with a binding agent containing e.g. a known silane
coupling agent or coating film-forming agent.
[0037] The fiber for reinforcing rubber products of the present
invention is one having the above-described fiber coated with a
coating film (hereinafter referred to also as "the first coating
film") formed by the above first treating agent. However, in order
to further increase the adhesion with a rubber composition which
will be the base material for a rubber product such as a tire or a
rubber belt including a timing belt, it is preferred that the first
coating film is further covered by a coating film (hereinafter
referred to also as "the second coating film") formed by the
following second treating agent.
[0038] As a first example of such a second treating agent
(hereinafter referred to as the first example), a treating agent
containing a rubber, a vulcanizer and an inorganic filler, may be
mentioned. For example, it is possible to employ the treating agent
disclosed in e.g. JP-A-63-126975 or JP-A-11-241275.
[0039] As the rubber to be incorporated in the above first example,
a halogen-containing polymer or a hydrated nitrile rubber may be
mentioned. As such a halogen-containing polymer, chlorinated
rubber, chloroprene rubber, chlorinated polyethylene, chlorinated
ethylene/propylene copolymer, chlorinated polyvinyl chloride or
chlorosulfonated polyethylene may, for example, be used. Among
them, it is particularly preferred to use chlorosulfonated
polyethylene.
[0040] Further, as the vulcanizer, a polynitroso aromatic compound
or a benzoquinone may, for example, be used. As the polynitroso
aromatic compound, p-dinitrosobenzene or poly p-dinitrosobenzene
may, for example, be mentioned. The benzoquinone may, for example,
be tetrachlorobenzoquinone, p-, p'-dibenzoylbenzoquinone dioxime or
p-benzoquinone dioxime. Among them, it is preferred to use poly
p-dinitrosobenzene, tetrachlorobenzoquinone, p-,
p'-dibenzoylbenzoquinone dioxime or p-benzoquinone dioxime.
[0041] As the inorganic filler, one commonly used as a filler for a
rubber composition, such as silica or carbon black, may be
used.
[0042] Further, in the above first example, an isocyanate or an
additive may be incorporated, as the case requires, in addition to
the above-described components.
[0043] As the isocyanate, methylenediphenyl isocyanate (MDI),
toluene diisocyanate (TDI), triphenylmethane triisocyanate or
naphthalene diisocyanate (NDI) may, for example, be used. An
isocyanate monomer is highly volatile and is not preferred from the
viewpoint of the safety and the handling efficiency, and it is
preferred to use a polyisocyanate such as a dimer, which has a
relatively small molecular weight and which is rich in reactivity.
Such a polyisocyanate is preferably one having a polymerization
degree of from 2 to 10. Further, as the additive, a softening
agent, an anti-aging agent or a vulcanization accelerator may, for
example, be mentioned.
[0044] The above first example can be obtained by dissolving the
respective components by mixing the rubber, the vulcanizer, the
inorganic filler, and the isocyanate and the additive which may be
incorporated, as the case requires, with an organic solvent, by a
usual method. As such an organic solvent, one commonly used in a
conventional rubber cement may be employed. For example, xylene,
toluene or methyl ethyl ketone may be mentioned.
[0045] In a case where an isocyanate is incorporated to the above
first example, the proportion of the isocyanate to the rubber is
preferably 100:10 to 100, by mass ratio. If the proportion of the
isocyanate is larger than the above range, the heat resistance or
the bending fatigue resistance, of the reinforcing fiber thereby
obtainable tends to deteriorate, and if the proportion of the
isocyanate is smaller than the above range, the adhesion of the
obtained reinforcing fiber to the rubber composition may sometimes
deteriorate.
[0046] Further, in the above first example, the proportion of the
sum of the rubber and the isocyanate is preferably from 3 to 15%,
more preferably from 5 to 10%, based on the entirety including the
organic solvent. If the proportion of both is less than 3%, it
sometimes tends to be difficult to coat the fiber with a sufficient
amount of the second treating agent, and if it exceeds 15%, the
viscosity of the second treating agent tends to be too high, and
non-uniformity may sometimes result when it is coated on glass
fiber.
[0047] Further, in the above first example, the proportion of the
vulcanizer is preferably from 0.3 to 2%, more preferably from 0.6
to 1%, based on the entirety including the organic solvent.
Likewise, the proportion of the inorganic filler is preferably from
0.5 to 5%, more preferably from 1 to 3%. If the proportion of the
vulcanizer is less than 0.3%, the function as the vulcanizer tends
to be inadequate, and peeling may sometimes be likely to take place
between the first coating film and the second coating film of the
reinforcing fiber thereby obtained, and if it exceeds 2%, peeling
may sometimes be likely to take place between the reinforcing fiber
and the base material rubber of the finally obtainable rubber
product.
[0048] The above-described first example is to increase the
adhesion between the reinforcing fiber and the rubber composition
as the base material for a rubber product. However, in the timing
belt to be used for an automobile engine, a rubber composition
comprising as the main component H-NBR having high heat resistance,
is often used as the base material. In the above-described first
example, the adhesion may sometimes be inadequate to a rubber
composition comprising a highly saturated H-NBR as the main
component wherein a peroxide is incorporated as a vulcanizer, which
is employed as the base material to increase the heat resistance of
a timing belt.
[0049] Accordingly, in a case where a rubber composition comprising
highly saturated H-NBR as the main component, is used as the base
material for a timing belt or the like, the second treating agent
is preferably made of a composition of the following second example
(hereinafter referred to also as the second example), in order to
make the adhesion with the rubber composition to be satisfactory.
Such a second example is preferred also from the viewpoint that the
affinity is good between the second coating film thereby formed and
the fist coating film formed by the first treating agent.
[0050] As such a second example, a treating agent comprising an
uncured phenol resin and a rubber, may be mentioned. The treating
agent of such a second example may be obtained by mixing the
uncured phenol resin and the rubber with a solvent in accordance
with a usual method.
[0051] Such an uncured phenol resin to be used in the second
example is one which is uncured among resins obtainable from a
phenol and an aldehyde, i.e. one having a reactivity for curing. As
such an uncured phenol resin, novolak and/or resol may preferably
be mentioned. It is preferred to use novolak from the viewpoint
such that the adhesion between H-NBR and the obtainable reinforcing
fiber, can be increased, and it is preferred to use resol from such
a viewpoint that the adhesion state at the interface between the
first coating film and the second coating film can be made
satisfactory. Further, in order to obtain both of such merits, it
is preferred to use them in a ratio of novolak/resol being
preferably from 10/4 to 10/1, as the solid contents.
[0052] As the rubber in the above second example, it is preferred
to use rubber having a good affinity with the rubber composition,
taking into consideration the compatibility with the rubber
composition which will be the base material of a rubber product to
be reinforced, such as a timing belt. As a preferred example,
chloroprene rubber, chlorosufonated polyethylene,
acrylonitrile/butadiene copolymer rubber (so-called "NBR"), or
H-NBR may, for example, be mentioned. Among them, it is preferred
to use an acrylonitrile/butadiene copolymer rubber in that the
adhesion with H-NBR can be made satisfactory, and the flexibility
of the second coating film formed by the second treating agent can
be made satisfactory.
[0053] Further, in the second example, it is preferred to
incorporate an uncured epoxy resin in addition to the
above-mentioned uncured phenol resin and rubber, in that the
adhesion between H-NBR and the obtained reinforcing fiber can be
made satisfactory, and the good adhesion can be maintained even
during heating.
[0054] Such an uncured epoxy resin is one which is not yet cured
among epoxy resins, i.e. one having reactivity for curing. As such
an epoxy resin, preferably, a bisphenol A type epoxy resin, a
bisphenol F type epoxy resin, a phenol novolak type epoxy resin, or
a cresol novolak type epoxy resin may, for example, be mentioned.
Among them, a bisphenol A type epoxy resin is preferred, since the
adhesion with H-NBR is particularly high.
[0055] The proportions of the uncured phenol resin and the rubber
in the above second example, are such that the rubber is preferably
from 10 to 60 parts, particularly preferably from 30 to 40 parts,
per 100 parts of the uncured phenol resin. If the proportion of the
rubber is less than 10 parts, the flexibility of the second coating
film formed by the second treating agent may sometimes become poor.
On the other hand, if it exceeds 60 parts, an adverse effect may
sometimes be brought about to the adhesion between the fiber and
the rubber composition as the base material for a rubber
product.
[0056] Further, in a case where uncured epoxy resin is
incorporated, the uncured epoxy resin is preferably from 2 to 20
parts, particularly preferably from 5 to 10 parts, per 100 parts of
the uncured phenol resin. If the proportion of the epoxy resin is
less than 2 parts, no adequate effect for improving the adhesion
between the fiber and the rubber composition as the base material
for a rubber product tends to be obtained. On the other hand, if it
exceeds 20 parts, the flexibility of the second coating film formed
by the second treating agent may sometimes become poor. Here, the
above-mentioned proportions of the respective components are
proportions as solid contents.
[0057] In the above second example, in addition to the
above-described components, an inorganic filler or an additive may
be incorporated, as the case requires. As such an inorganic filler,
one which is common as a filler for a rubber composition, such as
silica or carbon black, may be employed. As the additive, a
softening agent, an anti-aging agent or a vulcanization accelerator
which is common as an additive for a rubber composition, may be
used.
[0058] Further, as a solvent to dissolve or disperse the
above-mentioned respective components in the treating agent of the
above second example, one or a combination of two or more may be
used among those which are commonly used for conventional rubber
cement, but it is preferred to use a solvent of a ketone type or an
ester type. As a preferred example, methyl ethyl ketone (MEK),
methyl isobutyl ketone (MIBK) or ethyl acetate, may, for example,
be mentioned.
[0059] Further, the concentration of the above second example, i.e.
the total content of components including the uncured phenol resin,
the rubber, and the uncured epoxy resin, the inorganic filler or
the additive, which may be incorporated as the case requires, is
preferably from 3 to 20%, particularly preferably from 5 to 15%, as
solid contents. If such a concentration is less than 3%, it may
sometimes become difficult to coat the fiber with a sufficient
amount of the second treating agent. On the other hand, if it
exceeds 20%, the stability of the second treating agent may
sometimes deteriorate.
[0060] The fiber for reinforcing rubber products of the present
invention may be such that after coated with the second coating
film like the above first example and the second example, the
second coating film may further be coated with a third coating film
formed by a third treating agent, as disclosed in JP-A-3-269177 or
JP-A-7-190149.
[0061] Now, the process for producing the fiber for reinforcing
rubber products of the present invention will be described.
[0062] Firstly, fiber to be coated is continuously immersed in a
bath filled with the first treating agent to have the first
treating agent deposited and impregnated on the fiber. Then, the
fiber is continuously heated in e.g. a hot air oven of from 200 to
350.degree. C. to dry and solidify the first treating agent to form
a first coating film thereby to obtain coated fiber having the
first coating film.
[0063] Here, the deposited amount of the first coating film to the
coated fiber is preferably from 12 to 25%, more preferably from 16
to 22%, as solid content, based on the mass of the coated fiber. If
the deposited amount is less than 12%, individual monofilaments of
the coated fiber tend to be hardly adequately covered by the first
coating film, and the monofilaments are likely to contact one
another and tend to be abraded by friction, so that the resistant
to fatigue from flexing of the finally obtainable timing belts,
etc., tends to be poor, such being undesirable. On the other hand,
if the deposited amount exceeds 25%, the flexibility of the coating
film tends to be poor, and the bending fatigue resistance of the
finally obtainable rubber belts, etc., likely tends to be low, such
being undesirable.
[0064] Then, the above coated fibers are, individually or in
combination of a plurality of them, subjected to primary twisting
by a twisting machine such as a ring twisting machine to obtain a
primary twisted yarn. The number of twists in this primary twisting
step is preferably from 0.5 to 4 twists/25 mm. Otherwise, the
coated fiber once taken up in a non-twisted state, may be subjected
to primary twisting to obtain a primary twisted yarn, or a take-up
apparatus in the above step of obtaining a coated fiber is modified
to be a twisting machine, so that a step of obtaining a coated
fiber and a primary twisting step may be carried out simultaneously
to obtain a primary twisted yarn.
[0065] Then, from 5 to 20 primary twisted yarns are put together
and subjected to second twisting by means of a twisting machine
such as a ring twisting machine or a flier twisting machine to
obtain a second twisted yarn, thereby to obtain the fiber for
reinforcing rubber products of the present invention. The number of
twists in this second twisting step is preferably from 0.5 to 4
twists/25 mm, and like in the conventional fiber for reinforcing
rubber products, the twisting direction in the second twisting step
is adjusted to be opposite to the twisting direction in the primary
twisting step.
[0066] Further, in a case of covering by the second coating film
formed by the second treating agent, in addition to the above step,
treatment by the following step is applied to the second twisted
yarn. Namely, the above-mentioned second twisted yarn is
continuously immersed in a bath filled with the above-described
second treating agent, or the second treating agent is sprayed or
coated on the surface of the above-mentioned second twisted yarn to
have the second treating agent applied to the second twisted yarn.
Then, the second twisted yarn is continuously heated in e.g. a hot
air oven of from 120 to 200.degree. C. to dry and solidify the
second treating agent to form a second coating film thereby to
obtain the fiber for reinforcing rubber products of the present
invention.
[0067] At that time, the deposited amount of the second coating
film to the reinforcing fiber is preferably from 1 to 15%,
particularly preferably from 3 to 10%, as solid content, based on
the mass of the reinforcing fiber. If the deposited amount is less
than 1%, the effect for increasing the adhesion between the
reinforcing fiber and the rubber composition as the base material
for rubber products is likely to be inadequate. Even if the
deposited amount exceeds 15%, the effect for increasing the
adhesion will not increase so much, and the adhesion may rather be
hindered.
[0068] Now, the present invention will be described in further
detail with reference to Examples. However, it should be understood
that the present invention is by no means restricted to such
specific Examples.
EXAMPLE 1
[0069] 100 Parts of a vinylpyridine latex ("Pyratex", tradename,
manufactured by NIPPON A&L INC.), 30 parts of an ABS latex
("Nipol 1577", tradename, manufactured by ZEON CORPORATION), 6.8
parts of a RF condensate (solid content: 7%) and deionized water,
were mixed to obtain a first treating agent having a concentration
of 31%. Here, the above ratio of each component is a mass ratio as
solid content.
[0070] 200 Glass monofilaments made of non alkali glass (E glass)
and having a diameter of 9 .mu.m, were bundled while applying a
binding agent containing an amino silane coupling agent as the main
component, followed by drying to obtain a glass fiber. Three such
glass fibers drawn together were continuously immersed in a bath
filled with the above-mentioned first treating agent to have the
first treating agent deposited and impregnated on the glass
fibers.
[0071] Then, the glass fibers were continuously heated for one
minute in a hot air oven at a temperature of 250.degree. C. to dry
and solidify the first treating agent, to obtain coated glass
fibers having a first coating film. Here, the deposited amount of
the first coating film was 18% as solid content based on the mass
of the coated glass fibers.
[0072] Further, the above coated glass fibers were individually
subjected to primary twisting by means of a ring twisting machine
so that the number of twists became 2 twists/25 mm to obtain
primary twisted yarns. Then, 11 such primary twisted yarns drawn
together, were subjected to second twisting by means of a separate
ring twisting machine in a twisting direction opposite to the
primary twisting so that the number of twists became 2 twists/25
mm, to obtain a second twisted yarn.
[0073] Then, 60 parts of a novolak and 40 parts of resol as an
uncured phenol resin, 35 parts of an acrylonitrile/butadiene
copolymer rubber as a rubber, 7 parts of a bisphenol A type epoxy
resin as an uncured epoxy resin, and a solvent wherein methyl
isobutyl ketone, methyl ethyl ketone and ethyl acetate were mixed
by mass ratio of 8:4:1, were mixed to obtain a second treating
agent having a concentration of 10%. Here, the above ratio of each
component is a mass ratio as solid content.
[0074] The second twisted yarns obtained as described above, were
continuously immersed in a bath filled with the above-mentioned
second treating agent to have the second treating agent coated and
deposited on the second twisted yarns. Then, the second twisted
yarns were continuously heated for one minute in a hot air oven at
a temperature of 130.degree. C. to dry and solidify the second
treating agent to form a second coating film thereby to obtain the
fiber for reinforcing rubber products of the present invention.
Here, the deposited amount of the second coating film was 6% as
solid content based on the mass of the reinforcing fiber.
COMPARATIVE EXAMPLE 1
[0075] 79.4 Parts of a vinylpyridine latex ("Pyratex", tradename,
manufactured by NIPPON A&L INC.), 20.6 parts of a latex of a
styrene/butadiene copolymer ("NIPOL2570X5", tradename, manufactured
by ZEON CORPORATION), 11.1 parts of a latex of a chlorosulfonated
polyethylene ("CSM450", tradename, manufactured by SUMITOMO SEIKA
CHEMICAL CO., LTD.), 5.9 parts of a RF condensate (solid content:
7%) and deionized water, were mixed to obtain a first treating
agent having a concentration of 30%. Here, the above ratio of each
component is a mass ratio as solid content.
[0076] The fiber for reinforcing rubber products in Comparative
Example 1 was obtained by using the same glass fiber and second
treating agent as used in Example 1 by the process under the same
conditions as in Example 1 except that the above first treating
agent was employed.
COMPARATIVE EXAMPLE 2
[0077] 100 Parts of a vinylpyridine latex ("Pyratex", tradename,
manufactured by NIPPON A&L INC.), 44 parts of a latex of an
acrylonitrile/butadiene copolymer ("Nipol 1562", tradename,
manufactured by ZEON CORPORATION), 7.5 parts of a RF condensate
(solid content: 7%) and deionized water, were mixed to obtain a
first treating agent having a concentration of 31%. Here, the above
ratio of each component is a mass ratio as solid content.
[0078] The fiber for reinforcing rubber products in Comparative
Example 2 was obtained by using the same glass fiber and the same
second treating agent as used in Example 1 by the process under the
same conditions as in Example 1, except that the above first
treating agent was employed.
TEST EXAMPLES
[0079] With respect to the respective fibers for reinforcing rubber
products obtained in the above Example 1 and Comparative Examples 1
and 2, the evaluation of the adhesion in the normal condition and
the adhesion after boiling, were carried out by the following
methods, with respect to rubber products using a rubber composition
having the following composition, as the base material. The results
are shown in Table 1.
[0080] Blend Ratio of Rubber Composition
[0081] Hydrogenated nitrile rubber (Zetpol 2000, tradename,
manufactured by ZEON CORPORATION): 100 parts, zinc oxide: 10 parts,
zinc methacrylate: 15 parts, a zinc salt of
2-mercaptobenzimidazole: 1 part, substituted diphenylamine: 1 part,
carbon black (HAF): 3 parts, silica hydrate: 30 parts, dicumyl
peroxide: 10 parts, 1,3-bis(t-butylperoxyisoproypyl)benzen- e: 5
parts, sulfur: 0.3 part, TMTD (tetramethylthiuram disulfide): 1
part, MBT (2-mercaptobenzothiazole): 0.5 part.
[0082] Method for Evaluating the Adhesion in the Normal
Condition
[0083] On a rubber sheet having a thickness of 3 mm, a width of 25
mm and a length of 100 mm, obtained by processing the
above-mentioned rubber composition, reinforcing fibers were
arranged along the lengthwise direction without space. Then, the
same rubber sheet as mentioned above, was placed, so that the
reinforcing fibers were sandwiched between the upper and lower
rubber sheets. This assembly was heated and pressed by means of a
heat pressing apparatus at a temperature of 170.degree. C. under a
pressure of 18.3 kPa for 20 minutes, to obtain a test specimen.
[0084] With respect to this test specimen, peeling between the
reinforcing fiber and the rubber sheet was carried out at a tensile
speed of 50 mm/min by means of an autograph, whereby the adhesive
strength between the reinforcing fiber and the rubber sheet was
measured, and it was used as an index to evaluate the adhesive in
the normal condition.
[0085] Method for Evaluating the Adhesion After Boiling
[0086] A test specimen prepared in the same manner as in the Method
for Evaluating the Adhesion in the Normal Condition, was put into
boiling water and boiled for 5 hours. Then, it was wiped with a
cloth to remove the moisture, and the adhesive strength was
measured in the same manner as in the Method for Evaluating the
Adhesion in the Normal Condition. A value obtained by dividing the
adhesive strength after boiling by the adhesive strength in normal
condition, was converted to a percentage, which was taken as the
retention and was used as an index to evaluate the water
resistance.
1 TABLE 1 Comp. Comp. Ex. 1 Ex. 1 Ex. 2 Adhesive strength in 255
211 251 normal condition (N/25 mm) Adhesive strength after 250 195
226 boiling (N/25 mm) Retention (%) 98 92 90
[0087] As is evident from Table 1, as compared with Comparative
Examples 1 and 2, the rubber product in Example 1 using the
reinforcing fiber of the present invention has high adhesive
strength in the normal condition, and also has high adhesive
strength retention after boiling. Accordingly, in the fiber for
reinforcing rubber products of the present invention, the adhesion
with the rubber composition containing highly saturated H-NBR as
the main component is excellent, and the obtained rubber product is
also excellent in water resistance.
[0088] The fiber for reinforcing rubber products of the present
invention has both excellent heat resistance and water resistance.
Accordingly, it is useful for a rubber product such as a timing
belt wherein such a reinforcing fiber is used as a reinforcing
material.
[0089] The entire disclosure of Japanese Patent Application No.
2003-414153 filed on Dec. 12, 2003 including specification, claims
and summary is incorporated herein by reference in its
entirety.
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