U.S. patent application number 15/039954 was filed with the patent office on 2017-01-19 for fiber cord for reinforcement and method for producing the same.
This patent application is currently assigned to TEIJIN LIMITED. The applicant listed for this patent is TEIJIN LIMITED. Invention is credited to Shuhei OKAMURA, Shintaro SHIMADA.
Application Number | 20170016176 15/039954 |
Document ID | / |
Family ID | 53402269 |
Filed Date | 2017-01-19 |
United States Patent
Application |
20170016176 |
Kind Code |
A1 |
SHIMADA; Shintaro ; et
al. |
January 19, 2017 |
FIBER CORD FOR REINFORCEMENT AND METHOD FOR PRODUCING THE SAME
Abstract
A fiber cord for reinforcement has an adhesive treatment agent
attached to a surface thereof and includes, in an inner layer part
thereof, two kinds of compounds each having a molecular weight of
less than 1,000. The main compound is an aromatic compound or
contains an .alpha.-dicarboxylic acid component, and the other
compound is an aliphatic compound or an alicyclic compound. It is
preferable that the adhesive treatment agent is a
resorcin-formalin- latex-based adhesive, that the fiber cord
includes a twisted synthetic fiber, that the aromatic compound is a
heterocyclic compound, that the main compound is located only in
the inner layer part of the fiber cord, that a compound having a
hexamethylene diisocyanate trimer structure is present, and that no
latex is present in the inner layer part of the fiber cord. This
fiber cord is produced through a two-stage treatment with a
pre-treatment liquid and adhesive treatment liquid.
Inventors: |
SHIMADA; Shintaro; (Osaka,
JP) ; OKAMURA; Shuhei; (Osaka, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
TEIJIN LIMITED |
Osaka |
|
JP |
|
|
Assignee: |
TEIJIN LIMITED
Osaka-shi, Osaka
JP
|
Family ID: |
53402269 |
Appl. No.: |
15/039954 |
Filed: |
December 18, 2013 |
PCT Filed: |
December 18, 2013 |
PCT NO: |
PCT/JP2013/083833 |
371 Date: |
May 27, 2016 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C08J 5/06 20130101; D02G
3/04 20130101; D06M 15/55 20130101; D02G 3/36 20130101; D06M
2200/35 20130101; D06M 13/395 20130101; D06M 15/41 20130101; D06M
15/227 20130101; D06M 15/693 20130101; D01F 6/62 20130101; D06M
2101/32 20130101 |
International
Class: |
D06M 13/395 20060101
D06M013/395; D06M 15/693 20060101 D06M015/693; D01F 6/62 20060101
D01F006/62; D06M 15/41 20060101 D06M015/41 |
Claims
1. A fiber cord for reinforcement, comprising an adhesive treatment
agent attached to a surface thereof, characterized in that the
fiber cord includes, in an inner layer part thereof, a compound
A.sub.1 having a molecular weight of less than 1,000 and a smaller
amount of a compound B.sub.1 than the compound A.sub.1, the
compound A.sub.1 being an aromatic compound or a compound
containing an .alpha.-dicarboxylic acid component, the compound
B.sub.1 being an aliphatic compound or an alicyclic compound.
2. The fiber cord for reinforcement according to claim 1, wherein
the adhesive treatment agent is a resorcin-formalin-latex
(RFL)-based adhesive.
3. The fiber cord for reinforcement according to claim 1, wherein
the fiber cord includes a twisted multifilament fiber.
4. The fiber cord for reinforcement according to claim 1, wherein
the fiber cord includes a synthetic fiber.
5. The fiber cord for reinforcement according to claim 1, wherein
the aromatic compound is a heterocyclic compound.
6. The fiber cord for reinforcement according to claim 1, wherein
the compound A.sub.1 is located only in the inner layer part of the
fiber cord.
7. The fiber cord for reinforcement according to claim 1, wherein a
compound having a hexamethylene diisocyanate (HDI) trimer structure
is present in the inner layer part of the fiber cord.
8. The fiber cord for reinforcement according to claim 1, wherein
no latex is present in the inner layer part of the fiber cord.
9. A method for producing a fiber cord for reinforcement, including
treating a fiber cord in two stages with a pre-treatment liquid and
an adhesive treatment liquid, the method being characterized in
that the pre-treatment liquid contains two kinds of blocked
isocyanate compounds that are a compound A.sub.2 and a smaller
amount of a compound B.sub.2, the compound A.sub.2 having an
isocyanate group blocked with an aromatic compound or a compound
containing an .alpha.-dicarboxylic acid component, the compound
B.sub.2 having an isocyanate group blocked with an aliphatic
compound or an alicyclic compound, and a fiber cord having the
pre-treatment liquid attached thereto is once subjected to a heat
treatment, and then the adhesive treatment liquid is attached
thereto, followed by a drying treatment.
10. The method for producing a fiber cord for reinforcement
according to claim 9, wherein the aromatic compound is a
heterocyclic compound.
11. The method for producing a fiber cord for reinforcement
according to claim 9, wherein the unblocking temperature of the
compound A.sub.2 is lower than the unblocking temperature of the
compound B.sub.2.
12. The method for producing a fiber cord for reinforcement
according to claim 9, wherein the compound A.sub.2 has a
hexamethylene diisocyanate (HDI) trimer structure.
13. The method for producing a fiber cord for reinforcement
according to claim 9, wherein the compound B.sub.2 has an
isocyanate group blocked with an aliphatic compound or an alicyclic
compound.
14. The fiber cord for reinforcement according to claim 2, wherein
the fiber cord includes a twisted multifilament fiber.
15. The method for producing a fiber cord for reinforcement
according to claim 10, wherein the unblocking temperature of the
compound A.sub.2 is lower than the unblocking temperature of the
compound B.sub.2.
Description
TECHNICAL FIELD
[0001] The present invention relates to a fiber cord for
reinforcement. It more specifically relates to a fiber cord for
reinforcement having significantly improved fraying resistance, and
also to a method for producing the same.
BACKGROUND ART
[0002] In recent years, to deal with the global environmental
destruction, petroleum resource depletion, and like problems, a
great amount of attention has been paid to energy saving and energy
substitution for automobiles, electric appliances, etc. In
particular, with automotive weight reduction for improving the fuel
efficiency, the need for the weight and size reduction of
components is rapidly increasing. As such components,
fiber-reinforced composite materials have been widely used.
[0003] However, such composite materials containing fibers for
reinforcement have the problem that when the material is once
shaped and then cut, the fibers are frayed at the cut face. This
phenomenon is especially prominent in fiber-reinforced rubber
composite materials such as belts. Because the rubber forming the
matrix of the composite is prone to deformation, high-strength
fibers for reinforcement, which hardly follow the deformation, are
exposed at the end face of the composite material, and this is
likely to cause the problematic fraying.
[0004] As one technique for reducing such fraying, a method that
treats a fiber with a solvent-based adhesive is known (e.g., PTL 1
and PTL 2). However, such organic-solvent-based adhesive treatments
have problems in that a heavy load is placed on the safety or
working environment, and also the costs for adhesive treatment
facilities, recovery/waste liquid disposal, and peripheral
facilities thereof are extremely high.
[0005] Thus, in order to deal with the above problems, a method for
producing an adhesive-treated fiber using a water-based adhesive
has been tried. For example, PTL 3 proposes a fiber cord for
reinforcement, in which a first layer of the fiber cord is treated
with a water-based adhesive including a water-based urethane resin,
an epoxy compound, a blocked polyisocyanate, and a rubber latex,
and a second layer is treated with a resorcin-formalin-latex
(RFL)-based adhesive.
[0006] However, with these water-based techniques, under the
present circumstances, the high-level adhesion, fraying resistance,
and fatigue resistance required for automotive transmission belts,
etc., have not been achieved to the levels of solvent-based
techniques.
[0007] PTL 1: JP-A-9-158989
[0008] PTL 2: JP-A-11-81152
[0009] PTL 3: JP-A-2003-221787
SUMMARY OF THE INVENTION
Technical Problem
[0010] The invention has been accomplished in view of the above
background problems and art. An object of the invention is to
provide a fiber cord for reinforcement having significantly
improved fraying resistance and being excellent in adhesion to the
matrix and fatigue resistance (durability), and also a method for
producing the same.
Solution to Problem
[0011] The fiber cord for reinforcement of the invention is a fiber
cord for reinforcement having an adhesive treatment agent attached
to the surface thereof, characterized in that the fiber cord
includes, in an inner layer part thereof, a compound A.sub.1 having
a molecular weight of less than 1,000 and a smaller amount of a
compound B.sub.1 than the compound A.sub.1, the compound A.sub.1
being an aromatic compound or a compound containing an
.alpha.-dicarboxylic acid component, the compound B.sub.1 being an
aliphatic compound or an alicyclic compound.
[0012] Further, it is preferable that the adhesive treatment agent
is a resorcin-formalin-latex (RFL)-based adhesive, the fiber cord
includes a twisted multifilament fiber or a synthetic fiber, and
the aromatic compound is a heterocyclic compound. In addition, it
is preferable that the compound A.sub.1 is located only in the
inner layer part of the fiber cord, a compound having a
hexamethylene diisocyanate (HDI) trimer structure is present in the
inner layer part of the fiber cord, and no latex is present in the
inner layer part of the fiber cord.
[0013] In addition, the method for producing a fiber cord for
reinforcement of the invention is a method for producing a fiber
cord for reinforcement, including treating a fiber cord in two
stages with a pre-treatment liquid and an adhesive treatment
liquid. The method is characterized in that the pre-treatment
liquid contains two kinds of blocked isocyanate compounds that are
a compound A.sub.2 and a smaller amount of a compound B.sub.2, the
compound A.sub.2 having an isocyanate group blocked with an
aromatic compound or a compound containing an .alpha.-dicarboxylic
acid component, the compound B.sub.2 having an isocyanate group
blocked with an aliphatic compound or an alicyclic compound, and a
fiber cord having the pre-treatment liquid attached thereto is once
subjected to a heat treatment, and then the adhesive treatment
liquid is attached thereto, followed by a drying treatment.
[0014] Further, it is preferable that the aromatic compound is a
heterocyclic compound, and the unblocking temperature of the
compound A.sub.2 is lower than the unblocking temperature of the
compound B.sub.2. In addition, it is preferable that the compound
A.sub.2 has a hexamethylene diisocyanate (HDI) trimer structure,
and the compound B.sub.2 has an isocyanate group blocked with an
aliphatic compound or an alicyclic compound.
Advantageous Effects of the Invention
[0015] According to the invention, a fiber cord for reinforcement
having significantly improved fraying resistance and being
excellent in adhesion to the matrix and fatigue resistance
(durability) and a method for producing the same are provided.
DESCRIPTION OF EMBODIMENTS
[0016] The fiber cord for reinforcement of the invention has an
adhesive treatment agent attached to the surface thereof. The
adhesive treatment agent herein is not particularly limited and
selected from those suitable for a structure (matrix) to be
reinforced with fibers. However, more specifically, for example, in
the case where the matrix is a rubber or the like, it is preferable
that the adhesive treatment agent is a resorcin-formalin-latex
(RFL)-based adhesive.
[0017] Then, the fiber forming the fiber cord for reinforcement
used in the invention is in a fibrous form to reinforce the matrix
of the structure, and it is preferable that this fiber is a
synthetic fiber. More specifically, for example, it is preferable
that the fiber is a synthetic fiber made of at least one kind of
synthetic resin selected from polyesters, polyarylates, aliphatic
polyamides, vinylon, wholly aromatic polyamides,
polyparabenzobisoxazole, and carbon fibers. Among them, organic
fibers are preferable, and polyester fibers and wholly aromatic
polyamide fibers are particularly preferable. Examples of preferred
polyester fibers include a polyethylene terephthalate fiber, a
polybutylene terephthalate fiber, and a
polyethylene-2,6-naphthalate fiber. Examples of preferred wholly
aromatic polyamide fibers include wholly aromatic para-type
polyamide fibers and meta-type polyamide fibers. However, in terms
of reinforcement, high-strength para-type aromatic polyamide fibers
are preferable. In addition, in terms of the balance between
strength and adhesion, further, it is preferable that the fiber
forming the fiber cord is at least one kind of polyester fiber
selected from polyethylene terephthalate,
polyethylene-2,6-naphthalate, and the like.
[0018] As the applications of the fiber cord for reinforcement of
the invention, it is preferable that the fiber cord is used as a
rubber fiber composite, particularly a cord of a rubber belt. In
particular, in the case where the fiber cord is used as a belt
cord, the use of the above fiber makes the fiber cord more optimal
in terms of tensile strength performance, dimensional stability,
durability, and general versatility.
[0019] Here, it is preferable that the fiber cord for reinforcement
of the invention is a single yarn or an assembly of several yarns.
Then, it is also preferable that a single yarn forming the fiber
cord for reinforcement itself is an assembly of several fiber
filaments in the form of a bundle. It is preferable that the
fineness of the single yarn (assembly of fiber filaments) is 500 to
4,000 dtex, still more preferably 1,000 to 3,000 dtex. Such a yarn
is particularly effective in terms of handle ability in the steps
of twisting, adhesive treatment, and shaping. It is preferable that
the total fineness of the fiber cord for reinforcement of the
invention, which is an assembly of such yarns, is 500 to 15,000
dtex. Incidentally, no particular limitations are imposed on the
number of filaments of the fiber, its cross-sectional shape, the
physical properties of the fiber, the microstructure, the polymer
properties (molecular weight, terminal functional group
concentration, etc.), additives in the polymer, etc. In addition,
it is also preferable that the fiber yarn has been previously
pre-treated with an epoxy resin, a urethane resin, or the like in
the stage of yarn-making or after yarn making.
[0020] The fiber cord for reinforcement used in the invention is an
assembly of one or more such yarns, and it is still more preferable
that it is a twisted cord. Further, it is preferable that the fiber
cord is obtained by aligning and twisting one or more such yarns
(first twisting) and then aligning and twisting two or more such
twisted yarns (second twisting). Twisting particularly improves the
bending fatigue resistance and the like. Here, it is preferable
that the number of twists represented by the following equation (1)
is within a range such that the twist coefficient K satisfies 300
to 1,200, more preferably K=500 to 1,000. When such a number of
twists is satisfied, the bending fatigue resistance is satisfied
while maintaining the penetration of the adhesive into the fiber
cord to exert fraying resistance.
[Equation 1]
K=T.times. D (1)
(wherein K: twist coefficient, T: the number of twists per m
[twists/m], D: total fineness [dtex])
[0021] When the twist coefficient K is less than 300, the bending
fatigue resistance and adhesion tend to decrease. Meanwhile, in the
case where K is more than 1,200, there is a tendency that the
strength decreases, and also the treatment agent (first adhesive
treatment agent) is unlikely to sufficiently penetrate into the
fiber cord, resulting in a decrease in fraying resistance.
[0022] Incidentally, in the case where the fiber cord for
reinforcement of the invention is obtained by aligning and twisting
one or more fiber yarns (first twisting) and then aligning and
twisting two or more such twisted yarns (second twisting) as
described above, it is preferable that the first twisting and
second twisting both satisfy the twist coefficient K=300 to 1,200,
and the twist coefficients of the first twisting and the second
twisting may be the same or different.
[0023] The fiber cord for reinforcement of the invention is a fiber
cord for reinforcement having an adhesive treatment agent attached
to the surface of such a fiber cord. Then, the fiber cord includes,
in the inner layer part thereof, a compound A.sub.1 having a
molecular weight of less than 1,000 and a smaller amount of a
compound B.sub.1 than the compound A.sub.1. Here, the compound
A.sub.1 is an aromatic compound or a compound containing an
.alpha.-dicarboxylic acid component, and the compound B.sub.1 is an
aliphatic compound or an alicyclic compound. Here, it is preferable
that the compound B.sub.1 is a compound other than the compound
A.sub.1, which is structurally different from the compound A.sub.1.
More specifically, it is preferable that the compound B.sub.1 is a
compound that does not contain an aromatic compound or an
.alpha.-dicarboxylic acid component.
[0024] Here, the compound A.sub.1 present in the inner layer part
of the fiber cord of the invention is a compound having a molecular
weight of less than 1,000, and is an aromatic compound or a
compound containing an .alpha.-dicarboxylic acid component. Such
compounds are structurally prone to resonance because of the
presence of a double bond. In addition, here, aromatic compounds
are not limited to ordinary aromatic compounds composed only of
carbon atoms. Heterocyclic compounds having a cyclic structure
formed by nitrogen or like atoms in addition to carbon and having
aromatic properties, that is, heterocyclic aromatic compounds, are
also preferable. Specific examples of compounds particularly
preferable as the compound A.sub.1 include phenols such as phenol,
thiophenol, cresol, and resorcinol, aromatic secondary amines such
as diphenylamine and xylidine, heterocyclic compounds such as
dimethylpyrazole, and .alpha.-dicarboxylic acids such as diethyl
malonic acid. Among them, dimethylpyrazole, which is a heterocyclic
aromatic compound, is particularly preferable.
[0025] In addition, the compound B.sub.1 present inside the fiber
cord in an amount smaller than that of the compound A.sub.1 (weight
ratio) is an aliphatic compound or alicyclic compound having no
aromatic properties. Such compounds B.sub.1 are ordinary compounds
that do not have a resonance structure like the compound A.sub.1.
In addition, with respect to the molecular weight of the compound
B.sub.1, similarly to the compound A.sub.1, a compound having a
molecular weight of less than 1,000 is preferable. More
specifically, examples of compounds particularly preferable as the
compound B.sub.1 include phthalic imides, lactams such as
caprolactam and valerolactam, oximes such as methylethylketoxime,
and aliphatic compounds such as acidic sodium sulfite. Among them,
.epsilon.-caprolactam, which is a lactam, is particularly
preferable. Further, in the case where dimethylpyrazole is used as
the compound A.sub.1, when a lactam is combined therewith as the
compound B.sub.1, the impregnation of the agent into the fiber is
excellent, and the performance of the fiber cord is particularly
improved.
[0026] In the inner layer part of the fiber cord for reinforcement
of the invention, the compounds A.sub.1 and B.sub.1 each having a
molecular weight of less than 1,000 as described above are
contained, and further it is preferable that the molecular weights
of these compounds are each 60 or more and less than 600.
[0027] In addition, it is necessary that the content of the
compound A.sub.1 in the fiber cord inner layer part is higher than
the content of the compound B.sub.1 (weight ratio), and further it
is preferable that the abundance ratio between the compound A.sub.1
and the compound B.sub.1 (weight ratio), A.sub.1/B.sub.1 ratio, is
within a range of 60/40 to 95/5.
[0028] Here, when the solids weight ratio of compound
A.sub.1/compound B.sub.2 is increased, the film formation inside
the fiber bundle tends to take place more effectively. Thus, a firm
film is formed, and, when the fiber cord of the invention is
eventually used for a composite, improved fraying resistance is
provided. This attributes to the fact that the compound A.sub.1,
which is a compound prone to having a resonance structure, has high
reactivity and is effective in film formation. That is,
specifically, it is preferable that the abundance ratio of
A.sub.1/B.sub.1 is at least 60/40. Meanwhile, in the case where the
solids weight ratio of compound A.sub.1/compound B.sub.2 is too
high, there is a tendency that the film inside the fiber is likely
to be hard and brittle, and the bending fatigue resistance and
durability tend to decrease. It is preferable that the solids
weight ratio of compound A.sub.1/compound B.sub.2 is 95/5 or less.
It is preferable that such compounds A.sub.1 and B.sub.1 are
attached in an amount within a range of 0.0001 to 0.2 wt % relative
to the fiber.
[0029] In addition, in the inner layer part of the fiber cord for
reinforcement of the invention, in addition to these relatively
low-molecular compounds, it is preferable that high-molecular
compounds derived from epoxy compounds and the like are also
present. Further, with respect to the compounds A.sub.1and B.sub.1
present inside the fiber bundle, it is preferable that the total
amount thereof attached is within a range of 0.01 wt % to 2 wt %
relative to the amount (weight) of other components attached to the
fiber, such as high-molecular compounds. When such high-molecular
compounds, that is, resin-like substances, are present in large
amounts in the inner layer of the fiber bundle, high bundling
properties can be obtained. When the abundances of the compounds
A.sub.1 and B.sub.1 are too high, conversely, the adhesion to the
matrix tends to decrease, while when the abundances are too low,
there is a tendency that the fiber cord is difficult to bundle,
resulting in a decrease in fraying resistance.
[0030] Here, as high-molecular compounds present in the fiber
bundle inner layer of the invention, epoxy compounds, latex
rubbers, and the like are preferable. As epoxy compounds, it is
preferable that an epoxy compound having an epoxy group is attached
to the fiber surface, followed by a heat treatment or the like to
increase the molecular weight. Specific examples thereof include
reaction products between a polyalcohol such as ethylene glycol,
glycerol, sorbitol, pentaerythritol, or polyethylene glycol and a
halogen-containing epoxide such as epichlorohydrin; reaction
products between a polyphenol such as resorcin,
bis(4-hydroxyphenyl)dimethylmethane, a phenol-formaldehyde resin,
or a resorcin-formaldehyde resin and a halogen-containing epoxide
as described above; and polyepoxide compounds prepared by oxidizing
an unsaturated compound with peracetic acid, hydrogen peroxide, or
the like, that is, 3,4-epoxycyclohexene epoxide,
3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexene carboxylate, bis
(3,4-epoxy-6-methylcyclohexylmethyl) adipate, and the like. Among
them, a reaction product between a polyalcohol and epichlorohydrin,
that is, a polyglycidyl ether compound of a polyalcohol, develops
excellent performance and thus is particularly preferable. It is
preferable that the ratio between the epoxy compound and the total
amount of the compounds A.sub.1 and B.sub.1 (epoxy
compound)/(compound A.sub.1+compound B.sub.1) is within a range of
1/2 to 6/1.
[0031] Further, in order to facilitate adhesion to the surface
adhesive layer or to the matrix component of the final composite
material, it is preferable that an isocyanate component is
contained in the inner layer of the fiber cord. In particular, in
order to suppress deactivation during the process, it is preferable
that an isocyanate component derived from a blocked polyisocyanate
compound is contained.
[0032] Further, in the invention, it is preferable that the
isocyanate component is derived from a compound having a
hexamethylene diisocyanate (HDI) trimer structure represented by
the following chemical structural formula (I).
##STR00001##
[0033] As shown in the above chemical structural formula (I), this
compound is a compound having, as its basic structure, a trimer
structure in which three terminal NCO groups of the hexamethylene
diisocyanate (HDI) form a cyclic structure. Further, as each trimer
structure, as shown in the following chemical structural formula
(II), for example, a compound condensed to further increase the
functionality is also preferable. Here, R of chemical structural
formula (II) can be selected from polyglycols, such as polyethylene
glycol, without impairing the affinity for water and heat
resistance.
##STR00002##
[0034] In addition, as the isocyanate component, it is preferable
that the number of NCO functional groups present in the molecule is
three or more, whereby the adhesion can be further improved.
[0035] As other isocyanate components, components derived from a
diphenylmethane diisocyanate (MDI) compound are preferable.
Components derived from a compound having a hexamethylene
diisocyanate (HDI) trimer structure described above are flexible,
while components derived from a diphenylmethane diisocyanate (MDI)
compound are rigid. Accordingly, when these two kinds of components
are present together, a film that is firm, dense, and also flexible
is formed in the inner layer part of the fiber cord. Then, the
fiber cord for reinforcement of the invention allows for more
significant improvements in, in addition to fraying resistance,
bending fatigue resistance and adhesion.
[0036] In the fiber cord for reinforcement of the invention, as
described above, the compound A.sub.1 and the compound B.sub.1 are
contained in the inner layer part of the fiber cord, and the
surface of the fiber cord has attached thereto an adhesive
treatment agent. Here, the adhesive treatment agent can be suitably
changed according to the object to be reinforced with the fiber
cord. Among them, particularly in the case where the fiber cord of
the invention is used to reinforce a rubber product such as a belt,
it is preferable to use a resorcin-formalin-latex (RFL)-based
adhesive as the adhesive treatment agent.
[0037] Here, RFL-based adhesives preferable to use will be
described. It is preferable that the molar ratio between resorcin
and formaldehyde in the resorcin-formalin-rubber latex (RFL) is
within a range of 1/0.6 to 1/8, more preferably within a range of
1/0.8 to 1/6. When the amount of formaldehyde added is too small,
the crosslinking density of the resorcin-formalin condensate
decreases, and the molecular weight also decreases. Accordingly,
the cohesive strength of the adhesive layer may decrease, resulting
in a decrease in adhesion and also a decrease in bending fatigue
resistance. In addition, on the other hand, when the amount of
formaldehyde added is too large, the resorcin-formalin condensate
tends to be hard due to an increase in crosslinking density. Then,
at the time of covulcanization with the adherend rubber, the
compatibilization between RFL and the rubber maybe inhibited,
resulting in a decrease in the adhesion of the fiber cord for
reinforcement.
[0038] In addition, with respect to the blending ratio between
resorcin-formalin (RF) and latex (L) in this adhesive, the RF/L
solids weight ratio is 1/3 to 1/16, more preferably 1/4 to 1/10.
When the proportion of the rubber latex is too low, the amount of
components to be covulcanized with a rubber is small, and thus the
adhesion strength is likely to decrease. On the other hand, when
the proportion of the rubber latex is too high, it becomes
difficult to obtain sufficient strength as an adhesive film.
Further, the adhesion strength and durability tend to decrease, and
also the stickiness of the adhesive-treated fiber cord tends to be
too high. Accordingly, gumming-up, handle ability deterioration, or
the like may occur in the adhesive treatment step or shaping step,
resulting in a decrease in process-passing properties.
[0039] Further, as the latex forming the RFL-based adhesive,
various latexes such as vinyl pyridine-styrene-butadiene (VpSBR)
latex, chlorosulfonated polyethylene (CSM) latex, and polybutadiene
(PB) latex are usable. It is particularly preferable that the latex
includes VpSBR latex and/or CSM latex and PB latex. In addition,
with respect to their solids weight ratio, defining the total
weight of "VpSBR latex and/or CSM latex" as L.sub.1 and the weight
of "PB latex" as L.sub.2, it is preferable that the L.sub.1/L.sub.2
ratio is within a range of 25/75 to 75/25.
[0040] It is optimal to use the above latexes particularly in the
case where the fiber cord for reinforcement of the invention is
used, among rubber reinforcement applications, particularly for a
transmission belt. Usually, in a compressed rubber layer of a
transmission belt, a low-adhesion, high-performance synthetic
rubber, such as ethylene-.alpha.-olefin-diene rubber, chloroprene
rubber, hydrogenated nitrile rubber, chlorosulfonated polyethylene
rubber, or styrene-butadiene rubber, is used. In contrast, the
fiber cord for reinforcement of the invention employs the above
composition and compositional proportions, and thus has high
affinity and covulcanizability. In the invention, it is important
to have high affinities both for the polymer forming the fiber cord
and for other agents, and it has become possible to improve the
fraying resistance, bending fatigue resistance, and adhesion at
higher levels.
[0041] It is preferable that the solids weight ratio of
L.sub.1/L.sub.2 in the fiber cord of the invention is within a
range of 25/75 to 75/25 as described above. Further, it is more
preferable that the solids weight ratio of L.sub.1/L.sub.2 is 30/70
to 70/30. In the case where L.sub.1 is too low, the affinities for
the polymer forming the fiber cord and for the rubber forming the
transmission belt decrease. Accordingly, the adhesion strength
tends to decrease, and the bending fatigue resistance and adhesion
of the final product also tend to decrease. Meanwhile, in the case
where L.sub.1 is too large, the unsaturated bonding of the latex in
the adhesive treatment agent is reduced. Accordingly, there is a
tendency that the covulcanizability with the rubber forming the
transmission belt decreases, resulting in decreases in bending
fatigue resistance and adhesion.
[0042] Examples of resorcin compounds used for the adhesive
treatment agent include pre-oligomerized resorcin-formalin initial
condensates and polynuclear chlorophenol-based resorcin-formalin
initial condensates prepared by oligomerizing chlorophenol,
resorcin, and formalin. They may be used alone or in combination as
necessary.
[0043] In addition, it is also preferable that a crosslinking agent
is used together with this adhesive treatment agent. Examples of
preferred crosslinking agents to be added include amines, ethylene
urea, and blocked polyisocyanate compounds. Considering the
temporal stability of the treatment agent, the interaction with the
pre-treatment agent, and the like, it is preferable to use a
blocked polyisocyanate compound.
[0044] It is preferable that the proportion of a crosslinking
agent, such as a blocked polyisocyanate, added to this adhesive
treatment agent is within a range of 0.5 to 40 wt %, preferably 10
to 30 wt %, relative to the resorcin-formalin-rubber latex (RFL).
An increase in the amount added usually improves the adhesion
strength. Meanwhile, when the amount added is too large,
conversely, there is a tendency that the compatibility of the
adhesive with rubbers decreases, resulting in a decrease in
adhesion strength to rubbers.
[0045] Further, it is preferable that the fiber cord for
reinforcement of the invention does not contain an organic solvent.
When an organic solvent is not contained, the environment is not
adversely affected, and it has also become possible to prevent the
degradation of performance with time. Such a fiber cord for
reinforcement can be obtained using, for example, not an
organic-solvent-based treatment liquid but a water-based treatment
liquid.
[0046] Like this, in the fiber cord for reinforcement of the
invention, the adhesive treatment agent is attached to the surface
of the fiber cord, and the compound A.sub.1 and the compound
B.sub.1 are contained in the inner layer part of the fiber cord.
Then, in the fiber cord for reinforcement of the invention, it is
preferable that the compound A.sub.1 is not present in the surface
of the fiber cord, but is located only in the inner layer part of
the fiber cor. When the compound A.sub.1 is located only in the
fiber cord inner layer part, there is a tendency that the adhesion
inside the fiber cord is improved, whereby the bundling properties
are likely to be further improved. This effect is particularly
prominent in the case where an epoxy compound is present inside the
fiber bundle, which is considered to be attributable to the
affinity between the epoxy compound and the compound A.sub.1. In
addition, it is preferable that a compound having a hexamethylene
diisocyanate (HDI) trimer structure is present in the inner layer
part of the fiber cord, and no latex is present in the inner layer
part of the fiber cord. The presence of a latex in the fiber cord
inner layer part inhibits the affinity between the compound A.sub.1
and epoxy and thus is undesirable. In addition, it is preferable
that the compound B.sub.1 is unevenly located in the fiber cord
inner layer part. This is because the presence of the compound
B.sub.1 weakens the interaction between the latex and the compound
A.sub.1. In the invention, because of such a configuration of the
inner layer part, moderate joining can be maintained between fiber
filaments in the fiber cord inner layer, and further the fraying
resistance can be improved.
[0047] In addition, such a fiber cord for reinforcement of the
invention can be obtained by a method for producing a fiber cord
for reinforcement, which is another embodiment of the invention.
That is, the fiber cord for reinforcement of the invention can be
obtained by a method for producing a fiber cord for reinforcement,
including treating a fiber cord in two stages with a pre-treatment
liquid and an adhesive treatment liquid. The pre-treatment liquid
contains two kinds of blocked isocyanate compounds, that is, a
compound A.sub.2 and a smaller amount of a blocked isocyanate
compound B.sub.2. The compound A.sub.2 has an isocyanate group
blocked with an aromatic compound or a compound containing an
.alpha.-dicarboxylic acid component, and the compound B.sub.2 has
an isocyanate group blocked with an aliphatic compound or an
alicyclic compound. A fiber cord having the pre-treatment liquid
attached thereto is once subjected to a heat treatment, and then
the adhesive treatment liquid is attached thereto, followed by a
drying treatment.
[0048] The fiber forming the fiber cord used for the method of the
invention should be, as described above, a fibrous material for
reinforcing the matrix of a structure. Synthetic fibers are
particularly preferable.
[0049] In addition, with respect to the configuration of the fiber
cord for reinforcement of the invention, as described above, it is
preferable that fiber cord is a single yarn or an assembly of
several yarns. It is also preferable that the fiber has been
previously treated with an epoxy resin, a urethane resin, or the
like in the stage of yarn-making or after yarn making. Further, it
is preferable that the fiber cord is a twisted cord. As described
above, it is preferable that the fiber cord is obtained by aligning
and twisting one or more fiber yarns (first twisting) and then
aligning and twisting two or more such twisted yarns (second
twisting).
[0050] The method for producing a fiber cord for reinforcement of
the invention is a method in which, first, such a fiber cord is
treated with a pre-treatment liquid. Here, the pre-treatment liquid
contains a blocked isocyanate compound A.sub.2 (hereinafter
sometimes referred to as compound A.sub.2) and a blocked isocyanate
compound B.sub.2 (hereinafter sometimes referred to as compound
B.sub.2), and the content of the compound A.sub.2 is lower than the
content of the compound B.sub.2. Further, here, it is preferable
that the isocyanate group unblocking temperature of the compound
A.sub.2 is lower than the isocyanate group unblocking temperature
of the compound B.sub.2.
[0051] Here, a blocked polyisocyanate compound used in the method
of the invention is an addition reaction product between a
polyisocyanate compound and a blocking agent, which is the
isocyanate protecting group. When heated, the blocked
polyisocyanate compound releases the block component to produce an
active polyisocyanate compound. In particular, a polyisocyanate
containing terminal isocyanate groups obtained by a reaction
between isocyanate groups (--NCO) and hydroxyl groups (--OH) in a
molar ratio of more than 1 exerts excellent performance and thus is
preferable. Examples of blocking agents include phenols such as
phenol, thiophenol, cresol, and resorcinol, aromatic secondary
amines such as diphenylamine and xylidine, heterocyclic compounds
such as dimethylpyrazole, .alpha.-dicarboxylic acids such as
diethyl malonic acid, phthalic imides, lactams such as caprolactam
and valerolactam, aliphatic compounds such as acidic sodium
sulfite, phenols such as phenol, thiophenol, cresol, and
resorcinol, aromatic secondary amines such as diphenylamine and
xylidine, phthalic imides, lactams such as caprolactam and
valerolactam, oximes such as acetoxime, methylethylketoxime, and
cyclohexanone oxime, and acidic sodium sulfite.
[0052] Then, the blocked polyisocyanate compounds used in the
method for producing a fiber cord for reinforcement of the
invention include both of the blocked polyisocyanate compound
A.sub.2 blocked with an aromatic compound or a compound containing
an .alpha.-dicarboxylic acid component and the blocked
polyisocyanate compounds B.sub.2 blocked with an aliphatic compound
or an alicyclic compound. It is still more preferable that the
isocyanate group unblocking temperature of the compound A.sub.2 is
lower than the isocyanate group unblocking temperature of the
compound B.sub.2. Further, it is preferable that the unblocking
temperature of the compound A.sub.2 is less than 160.degree. C.,
particularly within a range of 100 to 150.degree. C. Meanwhile, it
is preferable that the unblocking temperature of the compound
B.sub.2 is 160.degree. C. or more, particularly within a range of
160 to 200.degree. C. In addition, it is preferable that the
abundance of the compound A.sub.2 is higher than the abundance of
the compound B.sub.2, and further it is preferable that the solids
weight ratio of compound A.sub.2/compound B.sub.2 is 99/1 to
60/40.
[0053] Here, an unblocking temperature refers to a temperature at
which the blocking group is released from a blocked isocyanate by
heat, whereby the isocyanate activity is developed. As preferred
conditions for the method of the invention, first, through the
first-stage heat treatment, the blocked polyisocyanate compound
A.sub.2 blocked with an aromatic compound or a compound containing
an .alpha.-dicarboxylic acid component is unblocked and
crosslinked. Then, through the subsequent second-stage heat
treatment, the blocked polyisocyanate compound B.sub.2 is
unblocked, and the compound-B.sub.2-derived compound is crosslinked
with the cross linked isocyanate derived from the compound A.sub.2.
Further, it is preferable that the first-stage heat treatment is a
low-temperature heat treatment, and the second-stage heat treatment
is a high-temperature heat treatment. In the method of the
invention, crosslinking is performed in two stages like this,
whereby a tough, dense film of the pre-treatment liquid (first bath
adhesive) can be formed inside and on the surface of the fiber
cord. Accordingly, the fiber cord can be provided with enhanced
fraying resistance, bending fatigue resistance, and adhesion. In
particular, the obtained fiber cord is optimal for rubber
reinforcement applications, particularly for use as a cord for a
transmission belt.
[0054] Here, with respect to the difference in unblocking
temperature between the compound A.sub.2 and the compound B.sub.2,
the greater the better. It is preferable that the difference in
unblocking temperature between the compounds A.sub.2 and
B.sub.2[=(unblocking temperature of the compound
B.sub.2)-(unblocking temperature of the compound A.sub.2)] is
30.degree. C. or more. When the temperature difference is
sufficient, the two-stage isocyanate crosslinking reaction can take
place more easily. When the temperature difference is too small,
this results in a competing reaction, in which the crosslinking
reactions of the compound A.sub.2 and the compound B.sub.2 take
place at the same time. As a result, it tends to be difficult to
control the crosslinked structure. In addition, this is likely to
expose the difference in the strength of the pre-treatment liquid
film between the inner and outer layers of the fiber cord due to
the difference in heat distribution. In such a case, the fraying
resistance and bending fatigue resistance tend to decrease. More
specifically, as unblocking temperatures, it is preferable that the
unblocking temperature of the compound A.sub.2 is 110 to
130.degree. C., and the unblocking temperature of the compound
B.sub.2 is 160.degree. C. to 180.degree. C.
[0055] The compound A.sub.2 used in the method of the invention is
the above compound A.sub.2 and has an isocyanate group blocked with
an aromatic compound or a compound containing an
.alpha.-dicarboxylic acid component. Further, as the aromatic
compound, a heterocyclic compound having a cyclic structure
containing nitrogen or like atoms in addition to carbon atoms is
preferable, and it is particularly preferable that the aromatic
compound is a heterocyclic aromatic compound such as
dimethylpyrazole (DMP). As the compound containing an
.alpha.-dicarboxylic acid component, a compound blocked with
diethyl malonate is preferable. Such a compound A.sub.2 is prone to
having a resonance structure, allowing for unblocking at a lower
temperature.
[0056] In addition, the compound B.sub.2 used in the method of the
invention is the above compound B.sub.2 and has an isocyanate group
blocked with an aliphatic compound or an alicyclic compound. More
specifically, those blocked with an oxime such as
methylethylketoxime or a lactam such as .epsilon.-caprolactam are
preferable.
[0057] In addition, the unblocking temperature is significantly
affected by the block-forming compound structure. In the method of
the invention, it is particularly preferable that the block
structure of the compound A.sub.2 is a dimethylpyrazole (DMP) block
structure, and the block structure of the compound B.sub.2 is an
.epsilon.-caprolactam block structure.
[0058] In addition, in the invention, it is preferable that the
blocked polyisocyanate compound A.sub.2 is composed of a compound
having a hexamethylene diisocyanate (HDI) trimer structure
represented by the following chemical structural formula (I).
##STR00003##
[0059] As shown in the above chemical structural formula (I), this
blocked polyisocyanate compound is a compound having, as its basic
structure, a trimer structure in which three terminal NCO groups of
the hexamethylene diisocyanate (HDI) form a cyclic structure. It is
also preferable that each trimer structure is, as shown in the
following chemical structural formula (II), for example, a
condensed compound having further increased functionality. Here, R
of chemical structural formula (II) can be selected from
polyglycols, such as polyethylene glycol, without impairing the
affinity for water and heat resistance.
##STR00004##
[0060] In addition, in the invention, it is preferable that the
blocked isocyanate compound A.sub.2 is such that the number of
functional groups present in the molecule after unblocking is three
or more. In the case where the number of functional groups is two
or less, the crosslinking reactivity with the pre-treatment liquid
and the reactivity to the adhesive treatment liquid tend to be
insufficient. In particular, in the case where the fiber cord for
reinforcement of the invention is used for rubber reinforcement,
such as a belt core material, a resorcin-formalin-latex (RFL)-based
adhesive is usually used as the adhesive treatment liquid; however,
there is a tendency that with the small amount of
resorcinol-derived hydroxyl groups contained in RFL alone, the
reactivity is likely to be insufficient.
[0061] Meanwhile, as the blocked polyisocyanate compound B.sub.2,
an .epsilon.-caprolactam-blocked diphenylmethane diisocyanate (MDI)
compound is particularly preferable. In the invention, an epoxy
compound and a flexible blocked polyisocyanate compound A.sub.2 are
crosslinked through the first-stage heat treatment, and then a
blocked polyisocyanate compound B.sub.2 having a rigid MDI
structure is further crosslinked through the second-stage heat
treatment. As a result, a pre-treatment liquid film, which is
particularly firm, dense, and also flexible, is formed inside and
also on the surface layer of the fiber cord. Then, it has become
possible to achieve significant improvements in fraying resistance,
bending fatigue resistance, and adhesion, which have been difficult
to achieve by the conventional aqueous adhesive treatment.
[0062] In addition, in the method for producing a fiber cord for
reinforcement of the invention, it is preferable that the
pre-treatment liquid contains an epoxy compound in addition to the
above two kinds of blocked isocyanate compounds.
[0063] Here, as the epoxy compound used in the invention, a
compound having at least two epoxy groups in one molecule is
preferable. In particular, a compound containing at least 2 g
equivalents of epoxy groups per kg of compound is preferable. More
specifically, examples thereof include reaction products between a
polyalcohol such as ethylene glycol, glycerol, sorbitol,
pentaerythritol, or polyethylene glycol and a halogen-containing
epoxide such as epichlorohydrin; reaction products between a
polyphenol such as resorcin, bis(4-hydroxyphenyl)dimethylmethane, a
phenol-formaldehyde resin, or a resorcin-formaldehyde resin and a
halogen-containing epoxide as described above; and polyepoxide
compounds prepared by oxidizing an unsaturated compound with
peracetic acid, hydrogen peroxide, or the like, that is,
3,4-epoxycyclohexene epoxide,
3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexene carboxylate,
bis(3,4-epoxy-6-methylcyclohexylmethyl)adipate, and the like. Among
them, a reaction product between a polyalcohol and epichlorohydrin,
that is, a polyglycidyl ether compound of a polyalcohol, develops
excellent performance and thus is particularly preferable.
[0064] In addition, it is also preferable that latexes and like
components are used with and contained in the pre-treatment liquid
used in the invention.
[0065] In addition, in the method of the invention, it is
preferable that the fiber cord is a fiber cord including a twisted
fiber. When the fiber cord is twisted, the pre-treatment liquid
penetrates into the fiber cord more effectively. In addition, it is
preferable that the pre-treatment liquid also contains an epoxy
compound in addition to the two kinds of blocked polyisocyanate
compounds. When an epoxy compound is used together with the two
kinds of blocked polyisocyanate compounds, the effect of the
unblocking temperature difference between the two kinds of blocked
isocyanate compounds is exerted more clearly.
[0066] The blocked polyisocyanate compounds used in the invention
have high affinity for the fiber-forming polymer and have excellent
penetration and cohesive strength. Further, in order to promote the
adhesion to the fiber surface and the polyisocyanate crosslinking
reaction and obtain a firm adhesive film, it is preferable to use
an epoxy compound together. Further, in the case where an epoxy
compound is used together with the pre-treatment liquid of the
invention like this, it is preferable that the epoxy compound is
used such that the solids weight ratio of epoxy compound/blocked
polyisocyanate compounds is 5/95 to 30/70, more preferably 10/90 to
25/75, particularly 15/85 to 25/75.
[0067] In the case where an epoxy compound is used together, in the
stage where water is distilled from the attached fiber and a heat
treatment is performed, the epoxy compound and the blocked
polyisocyanate compounds are thermally diffused into the fiber cord
over a sufficient period of time, and then the two kinds of
blocking agents are released, causing a crosslinking reaction. As a
result, high interface reinforceability is obtained. At the time of
this thermal diffusion, it is preferable that the epoxy compound
and the blocked polyisocyanate compounds are low-molecular-weight
components having high reaction activity. Accordingly, it is
preferable that the pre-treatment liquid does not contain a
hydroxyl group or alkali component which crosslinks the epoxy
compound or blocked polyisocyanate compounds or deactivates them
with water.
[0068] Here, with respect to the solids weight ratio of epoxy
compound/blocked polyisocyanate compounds, in the case where the
compositional proportion of epoxy is too low, the curing reaction
rate of the isocyanate compounds tends to decrease. Thus, a firm
crosslinked film is less likely to be obtained, and the fraying
resistance is less likely to be improved. Meanwhile, in the case
where the compositional proportion of the epoxy compound is
excessive, the crosslinked film tends to be hard and brittle.
Accordingly, the bending fatigue resistance and durability are less
likely to be improved.
[0069] In the invention, in the case where the above epoxy compound
and blocked isocyanate compounds are used together, it is
preferable that the pre-treatment liquid (first adhesive treatment
agent) is a water dispersion. Specifically, it is preferable to use
a water dispersion containing them at a solids concentration of 2
to 20 wt %, more preferably 5 to 15 wt %, at the time of
application to the fiber.
[0070] In the method of the invention, for the application of such
a water dispersion (pre-treatment liquid) to the fiber, it is
possible to employ techniques such as contact with a roller,
application by spraying from a nozzle, or immersion in a solution.
In addition, it is preferable that the amount of solids of the
pre-treatment liquid attached to the fiber is within a range of 0.5
to 5.0 wt %. When the amount attached is too small, the filaments
forming the fiber cord cannot be sufficiently bundled, resulting in
a decrease in fraying resistance. In particular, in the case where
the fiber cord for reinforcement of the invention is used as a belt
core material, it tends to be difficult to obtain a sufficient and
uniform pre-treatment liquid film for protecting the fiber
interface from rubber vulcanization at the time of shaping a belt
or aminolysis at the time of using the belt. Meanwhile, in the case
where the amount attached is too large, there is a tendency that
gumming-up or the like occurs in the subsequent adhesive treatment
step or shaping step, resulting in a decrease in process passing
properties. Therefore, it is preferable that the amount of solids
of the pre-treatment liquid attached to the fiber is 0.5 to 5.0 wt
%, still more preferably 1.0 to 3.0 wt %. The amount of solids
attached can be controlled by techniques such as squeezing with a
pressure-welding roller, scraping off with a scraper or the like,
blowing off by air blowing, suction, or a beater. In order to
increase the amount attached, attachment may be performed several
times.
[0071] In the method of the invention, the pre-treatment liquid is
applied to the fiber cord, followed by a heat treatment. Here, as
preferred heat treatment conditions, two-stage heating is
preferable. Specifically, for example, it is preferable that drying
is performed at a temperature of 80 to 150.degree. C. for 60 to 120
seconds, and then a heat treatment is performed at a temperature of
180 to 240.degree. C. for 60 to 180 seconds.
[0072] That is, first, through the first-stage heat treatment,
moisture on the cord surface and inside the cord is distilled off,
and the pre-treatment liquid containing blocked polyisocyanate
compounds are thermally diffused into the fiber cord at the same
time. In the case where the treatment condition is such that the
temperature is low or the time is short, moisture tends to remain
not-distilled off. Accordingly, there is a tendency that the
isocyanate compounds and the like are deactivated in the subsequent
high-temperature heat treatment, making it impossible to obtain a
firm crosslinked film. On the other hand, in the case where the
first-stage heat treatment is a high-temperature treatment, the
crosslinking reaction of the isocyanate compounds and the like
takes place as a competing reaction with hydrolysis, and thus the
film tends to be brittle. Further, there is a tendency that the
remaining moisture in the fiber cord undergoes bumping, whereby the
penetration of the pre-treatment liquid (first adhesive treatment
agent) into the fiber cord is inhibited. In addition, in the case
where the heat treatment time is long, there is a tendency that the
isocyanate compounds are air-oxidized, and the film performance
decreases. As the conditions for the first-stage heat treatment, it
is more preferable that the treatment is performed at a temperature
of 90 to 120.degree. C. for 60 to 120 seconds.
[0073] It is preferable that following this first-stage heat
treatment (drying heat treatment), a second-stage heat treatment is
performed at a temperature of 180 to 240.degree. C. for 60 to 180
seconds. As a result, the crosslinking reaction takes place in the
state where moisture has been sufficiently distilled from the fiber
cord and the blocked polyisocyanate compounds and the like have
uniformly permeated into the fiber cord. In the case of a
low-temperature treatment or a short-time treatment, there is a
tendency that the crosslinking reaction does not sufficiently
progress, and the film is likely to be brittle. On the other hand,
in the case of a high-temperature treatment or a long-time
treatment, there is a tendency that the isocyanate compounds and
the like are pyrolyzed or air-oxidized, making it difficult to
exert the performance. As the conditions for the second-stage heat
treatment, it is more preferable that the treatment is performed at
a temperature of 200 to 235.degree. C. for 60 to 120 seconds.
[0074] In the method for producing a fiber cord for reinforcement
of the invention, as described above, a pre-treatment liquid (first
adhesive treatment agent) is attached to the fiber cord, then the
fiber cord having attached thereto the pre-treatment liquid is once
heat-treated, and subsequently an adhesive treatment liquid is
attached thereto, followed by a drying treatment.
[0075] Here, the adhesive treatment liquid is to be suitably
changed according to the matrix for which the fiber cord for
reinforcement of the invention is used. For example, in the case
where the fiber cord is used for a rubber structure such as a belt,
it is preferable to use a resorcin-formalin-latex (RFL)-based
adhesive as the adhesive treatment liquid (second adhesive
treatment agent).
[0076] This RFL-based adhesive has the above composition. Those
having a resorcin/formaldehyde molar ratio within a range of 1/0.6
to 1/8 are preferably used, and various latexes are usable.
[0077] In addition, it is also preferable that a crosslinking agent
is used together with this resorcin-formalin-latex (RFL) -based
adhesive treatment agent to serve as a treatment agent, and
examples thereof include amines, ethylene urea, and blocked
polyisocyanate compounds. Among them, considering the temporal
stability of the treatment agent, the interaction with the
pre-treatment agent, and the like, it is preferable to use a
blocked polyisocyanate compound. It is preferable that the
proportion of the crosslinking agent added is within a range of 0.5
to 40 wt % relative to the RFL component. This is because although
an increase in the amount added usually improves the adhesion
strength, when the amount added is too large, conversely, there is
a tendency that the compatibility of the adhesive with rubbers
decreases, resulting in a decrease in adhesion strength to
rubbers.
[0078] In the invention, it is preferable that an adhesive liquid
(second adhesive treatment agent) is used as a treatment liquid
composed of a water dispersion, and that the total solids
concentration of the water dispersion is within a range of 5 to 30
wt %. In the case where the total solids concentration of the
treatment liquid is lower than the above range, the surface tension
of the adhesive increases, and the adhesion to the fiber surface
becomes less uniform. At the same time, with a decrease in the
amount of solids attached, the adhesion tends to decrease. On the
other hand, in the case where the total solids concentration is
higher than the above range, the viscosity of the treatment agent
increases. Thus, there is a tendency that the amount of solids
attached becomes too large, resulting in a decrease in process
passing properties, such as gumming-up in the adhesive treatment
step or shaping step.
[0079] In order to attach the adhesive treatment liquid (second
adhesive treatment agent) to the fiber like this, it is possible to
employ techniques such as contact with a roller, application by
spraying from a nozzle, or immersion in a solution. In addition, it
is preferable that the amount of solids attached to the fiber cord
is within a range of 1.0 to 10.0 wt %, still more preferably within
a range of 1.5 to 8.0 wt %. The amount of solids attached to the
fiber cord can be controlled, similarly to the above, by techniques
such as squeezing with a pressure-welding roller, scraping off with
a scraper or the like, blowing off by air blowing, suction, or a
beater. In order to increase the amount attached, attachment may be
performed several times.
[0080] In the method of the invention, the adhesive treatment
liquid is attached to the fiber cord and dried. As the heat
treatment conditions for drying, it is preferable that the drying
heat treatment is performed in two or more stages at a temperature
of 100.degree. C. to 250.degree. C. for 60 to 240 seconds. It is
more preferable that drying is performed in a temperature range of
120 to 180.degree. C. for 60 to 180 seconds, and then a heat
treatment is performed at a temperature of 200 to 245.degree. C.
for 60 to 180 seconds. When this drying/heat treatment temperatures
are too low, the adhesion to rubbers tends to be insufficient,
while when the drying/heat treatment temperatures are too high,
there is tendency that the air oxidation of the adhesive components
at high temperatures is promoted, resulting in a decrease in
adhesion activity.
[0081] In the method for producing a fiber cord for reinforcement
of the invention, unlike the conventional solvent treatments, the
organic-solvent-based adhesive treatment formulation using an
isocyanate compound having free isocyanate groups is not employed.
Accordingly, this production method is safe for the working
environment and has a reduced environmental impact. Then, a
pre-treatment liquid that easily penetrates into the fiber cord is
applied preferably as a water-based adhesive treatment agent, that
is, a water dispersion, and two kinds of blocked polyisocyanate
compounds are successively unblocked, thereby causing a curing
reaction while suppressing deactivation, whereby a firm, flexible
crosslinked film is formed. The invention enhances the interface
adhesion strength between the fiber surface layer and the fiber
inner layer impregnated with the pre-treatment liquid (first
adhesive treatment agent layer), as well as between the fiber inner
layer (first adhesive treatment agent layer) and the adhesive layer
(second adhesive treatment agent layer). As a result, it has become
possible to achieve improvements in both fraying resistance and
bending fatigue resistance, while ensuring high adhesion.
EXAMPLES
[0082] Hereinafter, the invention will be described with reference
to examples. However, these examples are provided by way of
illustration and do not limit the invention. Incidentally,
evaluations in the examples of the invention were made according to
the following measurement methods.
(1) Measurement of Compound Proportions in Fiber Cord Inner Layer
Part (Pyrolysis GC-MS)
[0083] From an obtained fiber cord for reinforcement, the adhesive
layer (outermost layer part) was peeled off to give a fiber cord
having fibers exposed to the surface. Further, the outside quarter
of the fiber cord was trimmed off. From the inner layer part whose
diameter is 75% of the original fiber cord diameter, a measurement
sample weighing 5 mg was collected.
[0084] Using this sample, the compound proportions (weight ratio)
were determined from the peak areas of the compound A.sub.1 and the
compound B.sub.1 by a cut & weight method using a pyrolyzer
(manufactured by Japan Analytical Industry Co., Ltd., Curie Point
Pyrolyzer "CCP JHP-5") and a gas chromatograph mass spectrometer
(manufactured by Shimadzu Corporation Co., Ltd., "GC-MS
QP2010").
(Measurement Conditions)
CCP (Pyrolyzer)
[0085] Oven temperature; 250.degree. C., Needle temperature;
250.degree. C., Sample heating; 590.degree. C..times.15 sec
GC (Gas Chromatograph)
[0086] Vaporizing chamber temperature; 250.degree. C., Column; DB-5
ms, Split ratio; 1/100,
[0087] Column open program; 60.degree. C..times.2 min, heated at a
temperature rise rate of 10.degree. C./min to 180.degree. C. or
320.degree. C.
MS (Mass Spectrometer)
[0088] Ion source temperature; 200.degree. C., Interface
temperature; 250.degree. C., Mass range; 29 to 600
(2) Unblocking Temperature of Blocked Polyisocyanate
[0089] Using a thermobalance (TG/DTA, manufactured by Rigaku
International Corporation, "TAS-200"), 10 mg of a blocked
polyisocyanate, from which water had been distilled, was heated in
a nitrogen atmosphere from room temperature at a temperature rise
rate of 10.degree. C./min. The temperature at which the weight of
the sample was reduced by 10 wt % was defined as the unblocking
temperature.
(3) Tensile Strength, Breaking Elongation, 150-N Load Elongation
(Intermediate Elongation), and 150.degree. C. Dry Heat Shrinkage of
Cord
[0090] Each was determined by measurement in accordance with JIS
L1017.
(4) Cord Hardness
[0091] Measurement was performed using a Gurley hardness tester
(manufactured by Tester Sangyo Co., Ltd.) in accordance with JIS
L1096-6.20.
(5) Peel Adhesion of Cord
[0092] This shows the peel adhesion between an adhesive-treated
fiber cord and a rubber. Seven cords were embedded in the surface
layer of a sulfur-based EPDM rubber unvulcanized sheet, followed by
vulcanization at a temperature of 150.degree. C. for 30 minutes
under a pressing pressure of 90 kg/cm.sup.2. Next, every other one
of the cords from both ends, four cords in total, were removed, and
the remaining three cords were simultaneously peeled from the
rubber sheet at a rate of 200 mm/min. The forces required for
peeling (N/3 cords) were averaged to determine the peel adhesion
per cord (N/cord).
(6) Bending Fatigue Resistance and Fraying Resistance of Cord
[0093] Eight adhesive-treated fiber cords were embedded at regular
intervals in two unvulcanized rubber sheets of sulfur-based EPDM
rubber (50 mm in width, 500 mm in length, and 2 mm in thickness),
followed by vulcanization at a temperature of 150.degree. C. for 30
minutes under a pressing pressure of 50 kg/cm.sup.2, thereby giving
a belt-like rubber shaped article. Next, while applying a load of
30 kg, the belt-like rubber shaped article was installed on a
roller 20 mm in diameter, and subjected to back-and-forth movements
at 100 rpm in an atmosphere at 100.degree. C. for a roller bending
(contact) distance of 100 mm. After repeating bending 10,000 times,
the cords were taken out, and the remaining strength was measured
to determine the strength retention after bending fatigue. In
addition, after the bending fatigue, the belt-like rubber shaped
body was cut in the direction perpendicular to the embedded fiber
cords, and the bundling conditions of the fiber cords exposed to
the cross-section were observed visually and also under an optical
microscope to evaluate fraying resistance. The fraying resistance
was rated in the following three grades.
[Fraying Resistance (after Bending Fatigue Test)]
[0094] 5: The filaments of the fiber cords are bundled, and no
abnormalities are seen in the appearance; excellent. 3: Some
filaments of the fiber cords have slight bundling failures;
however, good.
[0095] 1: The filaments of the fiber cords have bundling failures
and are not bundled.
Example 1
[0096] To 22.8 g of a polyepoxide compound having a sorbitol
polyglycidyl ether structure ("Denacol EX-614B" manufactured by
Nagase ChemteX Corporation; concentration: 100%) was added 8.8 g of
an aqueous dialkyl sulfosuccinate sodium salt solution ("Neocol
SW-C" manufactured by DKS Co., Ltd.; concentration: 70%) as a
surfactant, followed by stirring, and the mixture was added to
723.7 g of water with stirring and dissolved. Then, 226.5 g of a
dimethylpyrazole block-HDI trimmer condensate having three or more
functional groups ("Trixene 327" manufactured by Baxenden (UK);
unblocking temperature: 115.degree. C., concentration: 38%) as a
blocked polyisocyanate compound A.sub.2 (shows as "a" in Table 1)
and 18.2 g of a bifunctional c-caprolactam-blocked diphenylmethane
diisocyanate ("GRILBOND IL-6" manufactured by EMS; unblocking
temperature: 170.degree. C., concentration: 50%) as a blocked
polyisocyanate compound B.sub.2 (shown as "b" in Table 1) were
added thereto with stirring, thereby preparing a pre-treatment
liquid (water dispersion of a first adhesive treatment agent,
solids concentration: 12%), wherein the solids weight ratio of
epoxy compound/blocked polyisocyanate compounds (the total of the
blocked polyisocyanate compound A.sub.2 and the blocked
polyisocyanate compound B.sub.2) was 20/80, and the solids weight
ratio of blocked polyisocyanate compound A.sub.2/blocked
polyisocyanate compound B.sub.2 was 90/10.
[0097] 19.8 g of a resorcin-formalin initial condensate having a
resorcin/formalin (R/F) molar ratio of 1/0.6 ("Sumikanol 700S"
manufactured by Sumitomo Chemical Co., Ltd.; concentration: 65%)
was dissolved in an aqueous alkali solution prepared by adding 5.0
g of 10% caustic soda and 19.9 g of 20% ammonia water to 154.5 g of
water, and then 138.3 g of a vinylpyridine-styrene-butadiene latex
("Pyratex" manufactured by Nippon A&L Inc.; concentration:
41%), 206.2 g of a polybutadiene latex ("Nippol LX111NF"
manufactured by Zeon Corporation; concentration: 55%), and 363.6 g
of water were added thereto. 16.8 g of 37% formalin water and 75.9
g of a methylethylketoxime-blocked diphenylmethane diisocyanate
("DM6400" manufactured by Meisei Chemical Works, Ltd.;
concentration: 40%) were added to this mixture, followed by aging
at 20.degree. C. for 48 hours, thereby preparing an adhesive
treatment liquid having a solids concentration of 22% (RFL-based
second adhesive treatment agent for second treatment bath).
[0098] Two polyethylene terephthalate untreated fibers of 1,100
dtex/192 fil ("P904B" manufactured by Teijin Fibers) were
first-twisted in the S-direction (number of twists: 220/m), and
then three of the first-twisted cords were second-twisted in the
Z-direction (number of twists: 120/m), thereby giving a polyester
fiber cord. Using Computreater (dip cord treater manufactured by
C.A. Litzler), this fiber cord was fed at a rate of 22 m/min and
immersed in the pre-treatment liquid (first adhesive treatment
agent), then dried at a fixed length at 120.degree. C. for 60
seconds, and heat-treated at a fixed length at 235.degree. C. for
60 seconds. Subsequently, the cord was immersed in the adhesive
treatment liquid (second treatment bath), then dried at a fixed
length at 160.degree. C. for 120 seconds, and heat-treated under
3.5% stretching conditions at 230.degree. C. for 150 seconds,
thereby giving a polyester (polyethylene terephthalate)
adhesive-treated fiber cord. This adhesive-treated fiber cord had
attached thereto the pre-treatment liquid (first-bath adhesive
treatment agent) and adhesive treatment liquid (second-bath
adhesive treatment agent) in amounts of 2.6 wt % and 4.8 wt %,
respectively, relative to the weight of the polyester fiber cord on
a solids basis.
[0099] The compound proportions in the inner layer part of the
obtained fiber cord were measured (pyrolysis GC-MS). As a result,
the ratio of the compound A.sub.1 derived from dimethylpyrazole
(DMP) and the compound B.sub.1 derived from .epsilon.-caprolactam
were as follows: A.sub.1/B.sub.1=80/20. The performance evaluation
results of the obtained fiber cord are collectively shown in Table
1.
Examples 2, 3, and 4, Comparative Example 1
[0100] Polyester fiber cords were subjected to an adhesive
treatment in the same manner as in Example 1, except that the
solids weight ratio of blocked polyisocyanate compound
A.sub.2/blocked polyisocyanate compound B.sub.2 in the
pre-treatment liquid (first adhesive treatment agent) of 90/10 in
Example was changed as shown in Table 1 in preparation. The
performance evaluation results of the obtained polyester
adhesive-treated fiber cords are collectively shown in Table 1.
Comparative Example 2
[0101] A polyester fiber cord was subjected to an adhesive
treatment in the same manner as in Example 1, except that in the
pre-treatment liquid (first adhesive treatment agent), only the
blocked polyisocyanate compound A.sub.2 was used, and the blocked
polyisocyanate compound B.sub.2 was not used. The performance
evaluation results of the obtained polyester adhesive-treated fiber
cord are collectively shown in Table 1.
TABLE-US-00001 TABLE 1 Comparative Comparative Example 1 Example 2
Example 3 Example 4 Example 1 Example2 Pre-Treatment Liquid
Compound A.sub.2 a a a a -- a Compound B.sub.2 b b b b b --
A.sub.2/B.sub.2 Ratio 90/10 99/1 70/30 50/50 0/100 100/0 Physical
Properties of Compound A.sub.1/Compound B.sub.1 Ratio 80/20 94/6
65/35 55/45 0/100 100/0 Fiber Cord for Strength (N) 380 382 389 381
392 386 Reinforcement Breaking Elongation (%) 19.2 19.1 20.0 20.8
22.6 23.1 150-N Load Elongation (%) 8.5 8.5 8.6 8.7 9.5 8.6
150.degree. C. Dry Heat Shrinkage (%) 2.1 2.1 2.1 2.1 1.9 1.9 Cord
Hardness (mg) 44,800 28,100 36,200 28,500 21,600 30,600 Peel
Adhesion (N/cord) 29.4 26.9 27.8 23.5 22.7 24.2 Strength Retention
after Bending 94 96 92 84 79 71 Fatigue (%) Fraying Resistance 5 5
5 3 1 1 a; Dimethylpyrazole block-HDI trimmer condensate b;
.epsilon.-Caprolactam-blocked diphenylmethane diisocyanate
Examples 5, 6, and 7
[0102] Polyester fiber cords were subjected to an adhesive
treatment in the same manner as in Example 1, except that the
solids weight ratio of epoxy compound/blocked polyisocyanate
compounds (total amount) in the pre-treatment liquid (first
adhesive treatment agent) of 20/80 in Example 1 was changed as
shown in Table 2 in preparation. The performance evaluation results
of the obtained polyester adhesive-treated fiber cords are
collectively shown in Table 2.
Example 8
[0103] A polyester fiber cord was subjected to an adhesive
treatment in the same manner as in Example 1, except that in the
pre-treatment liquid (first adhesive treatment agent), the blocked
polyisocyanate compound A.sub.2 was changed from the
dimethylpyrazole block-HDI trimmer condensate used in Example 1 to
a diethyl malonate-HDI trimmer condensate having three or more
functional groups (unblocking temperature: 120.degree. C.,
concentration: 25%) (shown as in Table 2). The performance
evaluation results of the obtained polyester adhesive-treated fiber
cord are collectively shown in Table 2.
Example 9
[0104] A polyester fiber cord was subjected to an adhesive
treatment in the same manner as in Example 1, except that in the
adhesive treatment liquid (RFL-based second adhesive treatment
agent for second treatment bath), 138.3 g of VpSBR (concentration:
41%) in the vinylpyridine-styrene-butadiene latex (VpSBR) and
polybutadiene latex (PB) in Example 1 was replaced with 127.5 g of
a chlorosulfonated polyethylene (CSM) latex (Sepolex CSM,
manufactured by Sumitomo Seika Chemicals Co., Ltd.; concentration:
40%) (L1). The performance evaluation results of the obtained
polyester adhesive-treated fiber cord are collectively shown in
Table 2.
TABLE-US-00002 TABLE 2 Example 1 Example 5 Example 6 Example 7
Example 8 Example 9 Pre-Treatment Liquid Compound A.sub.2 a a a a
a' a Compound B.sub.2 b b b b b b A.sub.2/B.sub.2 Ratio 90/10 90/10
90/10 90/10 90/10 90/10 Epoxy/(A.sub.2 + B.sub.2) Ratio 20/80 10/90
5/95 30/70 20/80 20/80 Adhesive Treatment Latex Component Vp/BP
Vp/BP Vp/BP Vp/BP Vp/BP CSM/BP Liquid Physical Properties of
Compound A.sub.1/Compound B.sub.1 Ratio 80/20 80/20 80/20 80/20
80/20 80/20 Fiber Cord for Strength (N) 380 386 375 381 381 382
Reinforcement Breaking Elongation (%) 19.2 19.7 18.7 19.0 18.4 19.1
150-N Load Elongation (%) 8.5 8.5 8.4 8.3 8.2 8.5 150.degree. C.
Dry Heat Shrinkage (%) 2.1 2.1 2.1 2.2 2.2 2.0 Cord Hardness (mg)
44,800 41,500 38,100 40,800 40,800 44,100 Peel Adhesion (N/cord)
29.4 28.3 26.0 26.4 27.9 29.2 Strength Retention after Bending 94
93 96 80 92 95 Fatigue (%) Fraying Resistance 5 5 5 5 5 5 a;
Dimethylpyrazole block-HDI trimmer condensate a'; Diethyl
malonate-HDI trimmer condensate b; .epsilon.-Caprolactam-blocked
diphenylmethane diisocyanate Vp; VpSBR latex CSM; CSM latex BP; BP
latex
[0105] In Examples 1 to 9 of the invention, as compared with
comparative examples, the cords had high hardness and excellent
bending fatigue resistance, and the fraying resistance after
bending fatigue was also excellent. In addition, in the examples,
the cord strength and breaking elongation tended to be lower as
compared with the comparative examples having poor bundling
properties; this is considered to be the influence of an increase
in bundling properties caused by the formation of a firm film due
to the penetration of the pre-treatment liquid (first adhesive
treatment agent) into the fiber cord. However, the strength
retention after bending fatigue of each fiber cord is high, and
also the modulus (intermediate elongation) and dry heat shrinkage,
which are important as a belt cord, are maintained at values
indicating sufficient performance.
[0106] However, in the case where the proportion of, among the
blocked isocyanate compounds in the pre-treatment liquid, the rigid
high-temperature-dissociation blocked isocyanate compound B.sub.2
is high as in Example 4, or in the case where the proportion of the
epoxy compound in the pre-treatment liquid is high as in Example 7,
there is a tendency that the adhesion film is slightly weak,
resulting in slight decreases in cord hardness, fraying resistance,
and adhesion.
[0107] In addition, in Comparative Example 1, only a bifunctional
high-temperature-dissociation diisocyanate compound B.sub.2 was
used as a blocked isocyanate compound. As a result, the cord
hardness, fraying resistance, adhesion, and bending fatigue
resistance were all lower as compared with the examples.
INDUSTRIAL APPLICABILITY
[0108] According to the invention, a fiber cord for reinforcement
having significantly improved fraying resistance and being
excellent in adhesion to rubbers, bending fatigue resistance, and
durability is obtained. In particular, the fiber cord for
reinforcement of the invention is suitable for rubber
reinforcement, particularly as a transmission belt cord. The fiber
cord is particularly optimal for automobiles, where weight
reduction is required. In addition, in the method of the invention,
water-based adhesive treatments can also be employed. Thus, as an
environment-conscious method for producing an adhesive-treated
fiber cord, the method can be significantly effective in reducing
the environmental impact and cost.
* * * * *