EP4711518A1

EP4711518A1 - Coated fibers and molded body using same

Info

Publication number: EP4711518A1
Application number: EP24807158.1A
Authority: EP
Inventors: Ryohei Watanabe; Yoshifumi Aso; Minoru Okamoto; Ayaka FUJII
Original assignee: Kuraray Co Ltd
Current assignee: Kuraray Co Ltd
Priority date: 2023-05-12
Filing date: 2024-05-10
Publication date: 2026-03-18
Also published as: CN121195097A; JPWO2024237206A1; WO2024237206A1; TW202503143A; KR20260010383A

Abstract

Provided are coated fibers in which an adhesive composition free of resorcin and formaldehyde is used, and which have excellent adhesiveness to rubber and convergence, and high strength after friction and can be produced while suppressing contamination of a production facility, in which the coated fibers are fibers coated with a coating containing one or more kinds selected from the group consisting of an adhesive composition containing a conjugated diene-based rubber and a reaction product of the adhesive composition, and a molecular weight distribution curve obtained by GPC analysis of the coating satisfies the following conditions (1) and (2), and a molded body using the coated fibers:
<Condition (1)> at least one peak is present in a molecular weight range of 2,600 to 19,000,
<Condition (2)> an area ratio [(A)/(B)] in which (A) represents an area under the curve in a molecular weight range of 2,600 to 19,000 and (B) represents an area under the curve in a molecular weight range of 19,000 to 540,000 is 0.5 to 9.0.

Description

Technical Field

The present invention relates to coated fibers having excellent adhesiveness to rubber, and a molded body using the same.

Background Art

In industrial rubber products, such as a tire, a conveyor belt, and a hose (e.g., a hydraulic brake hose for automobiles), synthetic fibers, such as vinylon and rayon, or natural fibers, such as cotton are generally used for reinforcement. In order to sufficiently exhibit excellent physical properties (e.g., high strength and high elastic modulus) of rubber in the products, firm adhesion between fibers and rubber is required. Conventionally, as a method for the adhesion, a method using an adhesive containing a resorcin-formaldehyde resin and a rubber latex as main components, which is referred to as RFL, has been widely known (PTLs 1 and 2).
However, formaldehyde is suspected of being a carcinogen, and resorcin is suspected of being an endocrine disruptor. Therefore, the development of an alternative material is desired. Specifically, PTL 3 describes reinforcement fibers that include an adhesive component containing a conjugated diene-based rubber and an oil on at least part of the surface of the fibers, and in which the vapor pressure at 20°C of the oil is 10 Pa or less.
Further, PTL 4 describes surface-modified fibers that include fibers and a surface-modifying layer covering at least part of the surface of the fibers, and in which a solid surface zeta potential on the surface of the surface-modifying layer is within a specific range. Furthermore, PTL 5 describes reinforcement fibers that include fibers, a surface-modifying layer covering at least part of the surface of the fibers, and an adhesive layer containing a conjugated diene-based rubber covering at least part of the surface-modifying layer, and in which the surface-modifying layer contains a polyamine compound having one or more functional groups selected from primary to tertiary amino groups and an imino group and having a weight average molecular weight (Mw) of 300 or more.

Citation List

Patent Literature

PTL 1: JPS54-4976A
PTL 2: JPS58-2370A
PTL 3: WO2020/175404
PTL 4: WO2021/106559
PTL 5: WO2022/044460

Summary of Invention

Technical Problem

In the reinforcement fibers described in PTLs 3 to 5, a liquid rubber having a relatively high molecular weight is attached to fibers serving as a raw material to improve adhesiveness of the fibers to the rubber. Such reinforcement fibers achieve sufficient adhesion between the fibers and the rubber, but a further improvement in adhesiveness was desired. When the liquid rubber having a relatively high molecular weight was attached to the surface of the fibers, a holding roller through which the fibers pass in a production process was sometimes contaminated to reduce productivity.
Accordingly, a technique that is an adhesion method achieving an excellent adhesive force like the conventional method using RFL and not deteriorating fibers, and can achieve efficient production with minimal contamination of a production facility has been desired.
An object of the present invention is to provide coated fibers in which an adhesive composition free of resorcin and formaldehyde is used, and that have excellent adhesiveness to rubber and convergence, and high strength after friction and can be produced while suppressing contamination of a production facility, and a molded body using the coated fibers.

Solution to Problem

The present inventors have intensively investigated to solve the problems, and as a result, found that even when a conjugated diene-based rubber having a relatively low molecular weight is used as an adhesive composition, coated fibers having excellent adhesiveness to the rubber and convergence, and high strength after friction without resorcin and formaldehyde are obtained by adjustment to obtain a peak in a specific range of a molecular weight distribution curve obtained by GPC analysis of the coating and to achieve a specific ratio between two areas in a specific range obtained by GPC analysis, and contamination of a production facility can be suppressed. Thus, the present invention has been completed.
Specifically, the present invention relates to the following [1] to [12].

[1] Coated fibers obtained by coating fibers with a coating containing one or more kinds selected from the group consisting of an adhesive composition containing a conjugated diene-based rubber and a reaction product of the adhesive composition, in which a molecular weight distribution curve obtained by GPC analysis of the coating satisfies the following conditions (1) and (2):
- <Condition (1)>
  at least one peak is present in a molecular weight range of 2,600 to 19,000; and
- <Condition (2)>
  an area ratio [(A)/(B)] in which (A) represents an area under the curve in a molecular weight range of 2,600 to 19,000 and (B) represents an area under the curve in a molecular weight range of 19,000 to 540,000 is 0.5 to 9.0.
[2] The coated fibers according to [1], in which the adhesive composition further contains a crosslinking agent.
[3] The coated fibers according to [2], in which the reaction product is a reaction product including the conjugated diene-based rubber bonded to itself via the crosslinking agent and/or a reaction product including the conjugated diene-based rubber bonded to the fibers via the crosslinking agent.
[4] The coated fibers according to [2] or [3], in which the crosslinking agent is one or more kinds selected from the group consisting of an epoxy resin and an isocyanate resin.
[5] The coated fibers according to any one of [1] to [4], in which an attachment amount of the coating is 0.01 to 10.0 parts by mass with respect to 100 parts by mass of the fibers.
[6] The coated fibers according to any one of [1] to [5], in which the molecular weight distribution curve obtained by GPC analysis of the coating has a peak in a molecular weight range of 2,600 to 15,000.
[7] The coated fibers according to any one of [1] to [6], in which the conjugated diene-based rubber is in a liquid state.
[8] The coated fibers according to any one of [1] to [7], in which the conjugated diene-based rubber has a monomer unit derived from one or more kinds selected from the group consisting of butadiene, isoprene, chloroprene, acrylonitrile, and farnesene.
[9] The coated fibers according to any one of [1] to [8], in which the adhesive composition further contains an oil having a vapor pressure at 20°C of 10 Pa or less.
[10] The coated fibers according to any one of [1] to [9], in which the fibers are one or more kinds selected from the group consisting of polyamide-based fibers, polyvinyl alcohol-based fibers, polyester-based fibers, and regenerated cellulose-based fibers.
[11] The coated fibers according to any one of [1] to [10], in which the coated fibers are obtained by attaching an aqueous adhesive containing the conjugated diene-based rubber to the fibers, followed by heating.
[12] A molded body using the coated fibers according to any one of [1] to [11].

Advantageous Effects of Invention

The present invention can provide coated fibers in which an adhesive composition free of resorcin and formaldehyde is used, and that have excellent adhesiveness to rubber and convergence, and high strength after friction and can be produced while suppressing contamination of a production facility, and a molded body using the coated fibers.

Brief Description of Drawings

[Fig. 1] Fig. 1 is a schematic diagram illustrating a metal friction tester of coated fibers.
[Fig. 2] Fig. 2 is a reference drawing of a molecular weight distribution curve having a maximum near a molecular weight of 7,000.
[Fig. 3] Fig. 3 is a reference drawing of a molecular weight distribution curve having a maximum near a molecular weight of 10,000.

Description of Embodiments

[Coated Fibers]

Coated fibers of the present invention are coated fibers obtained by coating fibers with a coating containing one or more kinds selected from the group consisting of an adhesive composition containing a conjugated diene-based rubber and a reaction product of the adhesive composition, and in which a molecular weight distribution curve obtained by GPC analysis of the coating satisfies the following conditions (1) and (2). The molecular weight distribution curve obtained by GPC analysis in the present invention refers to a molecular weight distribution curve obtained by analysis in accordance with a method described in Examples.

In the present invention, the molecular weight distribution curve obtained by GPC analysis of the coating has at least one peak in a molecular weight range of 2,600 to 19,000. The peak as used herein means a maximum in the molecular weight distribution curve. For example, in the molecular weight distribution curve shown in Fig. 2, a maximum is recognized near a molecular weight of approximately 7,000 and represents a peak. In the molecular weight distribution curve shown in Fig. 3, a maximum is recognized near a molecular weight of 10,000 and also represents a peak. In the present invention, the peak means that at least one maximum is present in a specific range.
In a preferred aspect of the present invention, the peak is derived from a component containing a conjugated diene-based rubber. Even when a conjugated diene-based rubber having a low molecular weight is used, adhesiveness to rubber, particularly adhesiveness to a rubber having low polarity, such as EPDM (ethylene-propylene-diene rubber), can be improved due to the presence of at least one peak in the range. The presence of a peak means that a component having a molecular weight of a specific range is present in a larger amount than another component. The component having a molecular weight of the specific range can exhibit adhesiveness with a component having a molecular weight near the specific range. Further, when adjustment is performed so as to obtain at least one peak in the above-mentioned range, the coating does not contain a compound having an excessively high molecular weight, and hence process contamination can be suppressed during production of the coated fibers. At least one peak can be obtained in the above-mentioned range by using a conjugated diene-based rubber having a low molecular weight. Moreover, at least one peak can be obtained, for example, by cross-linking the conjugated diene-based rubber having a low molecular weight to itself with a crosslinking agent to be described later to such an extent that does not result in excessive increase in molecular weight. In the present invention, at least one peak needs only to be obtained in the range, and the number of peak is preferably one. The range of the molecular weight where the one peak is present is preferably 2,600 to 15,000, more preferably 4,500 to 14,000, still more preferably 6,000 to 13,000, still more preferably 7,000 to 12,000, and particularly preferably 8,000 to 11,000.

In the present invention, the area ratio [(A)/(B)] in which (A) represents the area under the molecular weight distribution curve of the coating by GPC analysis in a molecular weight range of 2,600 to 19,000 and (B) represents the area under the curve in a molecular weight range of 19,000 to 540,000 is 0.5 to 9.0. When the area ratio is within the above-mentioned range, balance between a compound having a relatively low molecular weight and a compound having a relatively high molecular weight in the coating is satisfactory, and process contamination can be suppressed while improving adhesiveness to the rubber. Further, the convergence of the coated fibers and the strength after friction can be improved. From these viewpoints, the area ratio [(A)/(B)] is preferably 1.0 to 8.8, more preferably 1.4 to 8.7, and still more preferably 1.8 to 8.5. In a preferred aspect of the present invention, the areas (A) and (B) are derived from the component containing a conjugated diene-based rubber. In a preferred aspect, the area ratio [(A)/(B)] is preferably 1.0 to 5.0, more preferably 1.5 to 3.5, and still more preferably 2.0 to 3.5 from the viewpoint of the balance of the effects of the present invention.
The area ratio can be achieved, for example, by using a conjugated diene-based rubber having a low molecular weight and cross-linking the conjugated diene-based rubber having a low molecular weight to itself with a crosslinking agent to be described later.

The adhesive composition used in the present invention contains a conjugated diene-based rubber. In a preferred aspect of the present invention, the adhesive composition contains a modified conjugated diene-based rubber. In the present invention, fibers are coated with a coating containing one or more kinds selected from the group consisting of an adhesive composition containing a conjugated diene-based rubber having a relatively low molecular weight (preferably a modified conjugated diene-based rubber) and a reaction product of the adhesive composition (i.e., a reaction product obtained by a reaction within the conjugated diene-based rubber (preferably within the modified conjugated diene-based rubber)), and the reaction product is obtained by adjustment to prevent excessive reaction. Accordingly, an excellent effect that does not contaminate a production process is exhibited while achieving excellent adhesiveness. Further, the reaction product includes a compound having a moderate molecular weight, and hence the coated fibers of the present invention also have excellent convergence and high strength after friction.
In the present invention, the "coated fibers" may be an aspect in which at least part of the surface of the fibers needs only to be coated with the coating, and, for example, an aspect in which the coating is present as a film or a layer on at least part of the surface of the fibers, or an aspect in which a raw material for the fibers contains the coating and the coating is present on part of the surface of the fibers themselves.
Hereinafter, a compound used for the adhesive composition and the reaction product of the adhesive composition will be described in detail.

[Conjugated Diene-based Rubber]

The conjugated diene-based rubber used in the present invention has a monomer unit derived from at least one conjugated diene (hereinafter also referred to as "conjugated diene unit") in the molecule, and preferably has a monomer unit derived from a conjugated diene, for example, in an amount of 50 mol% or more with respect to all the monomer units of the conjugated diene-based rubber.
Examples of the conjugated diene monomer include butadiene, 2-methyl-1,3-butadiene (hereinafter sometimes referred to as "isoprene"), 2,3-dimethylbutadiene, 2-phenylbutadiene, 1,3-pentadiene, 2-methyl-1,3-pentadiene, 1,3-hexadiene, 1,3-octadiene, 1,3-cyclohexadiene, 2-methyl-1,3-octadiene, 1,3,7-octatriene, myrcene, chloroprene, acrylonitrile, and farnesene. One kind of the conjugated dienes may be used alone, or two or more kinds thereof may be used in combination. The conjugated diene-based rubber preferably has a monomer unit derived from one or more kinds selected from the group consisting of butadiene, isoprene, chloroprene, acrylonitrile, and farnesene, and more preferably has a monomer unit derived from one or more kinds selected from butadiene and isoprene from the viewpoint of reactivity during vulcanization.
The conjugated diene-based rubber used in the present invention may have a unit derived from an additional monomer other than the conjugated diene monomer as long as adhesion is not inhibited. Examples of the additional monomer include ethylenically unsaturated copolymerizable monomers and aromatic vinyl compounds.
Examples of the ethylenically unsaturated monomers include olefins, such as ethylene, 1-butene, and isobutylene.
Examples of the aromatic vinyl compounds include styrene, α-methylstyrene, 2-methylstyrene, 3-methylstyrene, 4-methylstyrene, 4-propylstyrene, 4-t-butylstyrene, 4-cyclohexylstyrene, 4-dodecylstyrene, 2,4-dimethylstyrene, 2,4-diisopropylstyrene, 2,4,6-trimethylstyrene, 2-ethyl-4-benzylstyrene, 4-(phenylbutyl)styrene, 1-vinylnaphthalene, 2-vinylnaphthalene, vinylanthracene, N,N-diethyl-4-aminoethylstyrene, vinyl pyridine, 4-methoxystyrene, monochlorostyrene, dichlorostyrene, and divinylbenzene. One kind of the components may be used alone, or two or more kinds thereof may be used in combination.
When the conjugated diene-based rubber has a monomer unit derived from the additional monomer other than the conjugated diene monomer, the content thereof is preferably 30 mol% or less, more preferably 10 mol% or less, and still more preferably 5 mol% or less.
The conjugated diene-based rubber used in the present invention may be an unmodified conjugated diene-based rubber, and is preferably a conjugated diene-based rubber having a functional group in part thereof, preferably a conjugated diene-based rubber having a hydrogen-bonding functional group, and more preferably a modified conjugated diene-based rubber having a conjugated diene unit on at least some polymer chain and having a hydrogen-bonding functional group on a side chain or terminal of the polymer chain. The unmodified conjugated diene-based rubber and the modified conjugated diene-based rubber may be used in combination.
In the case of the modified conjugated diene-based rubber, the rubber and the fibers serving as adherends are interacted with each other, leading to effective adhesion between the rubber and the fibers. When the modified conjugated diene-based rubber and an adherend rubber are vulcanized to form a covalent bond, a strong cohesion strength is generated to further improve adhesiveness.
In addition, when hydrophile fibers are used as the fibers, it is considered that the hydrogen-bonding functional group contained in the modified conjugated diene-based rubber forms a hydrogen bond with the hydrophile fibers to improve adhesiveness.
The "hydrogen bond" as used herein means a bonding interaction to be formed between a hydrogen atom (donor) that is bonded to an atom having a large electronegativity (e.g., O, N, and S) and is polarized to be electropositive, and an electronegative atom (acceptor) having a lone electron pair.
In the present invention, the "hydrogen-bonding functional group" refers to a functional group capable of functioning as the doner and the acceptor in the hydrogen bond. Specific examples thereof include a hydroxy group, an ether group, a mercapto group, a carboxy group, a carbonyl group, an aldehyde group, an amino group, an imino group, an imidazole group, an urethane group, an amide group, a urea group, an isocyanate group, a nitrile group, a silanol group, and derivatives thereof. Examples of the derivative of the aldehyde group include acetal derivatives of the aldehyde group. Examples of the derivative of the carboxy group include salts of the carboxy group, ester derivatives of the carboxy group, amide derivatives of the carboxy group, and acid anhydrides of the carboxy group. Examples of the derivative of the silanol group include ester derivatives of the silanol group. Examples of the carboxy group include a group derived from a monocarboxylic acid and a group derived from a dicarboxylic acid. Of these, one or more kinds selected from a hydroxy group, an aldehyde group, an acetal derivative of an aldehyde group, a carboxy group, a salt of a carboxy group, an ester derivative of a carboxy group, an acid anhydride of a carboxy group, a carbonyl group, a silanol group, an ester derivative of a silanol group, an amino group, an imidazole group, and a mercapto group are preferred.
Of these, one or more kinds selected from a hydroxy group, a carboxy group, a carbonyl group, a salt of a carboxy group, an ester derivative of a carboxy group, and an acid anhydride of a carboxy group are preferred, one or more kinds selected from a carboxy group, an ester derivative of a carboxy group, and an acid anhydride of a carboxy group are more preferred, and an ester derivative of maleic anhydride and a functional group derived from maleic anhydride are still more preferred from the viewpoint of improving adhesiveness and from the viewpoint of ease of production of the modified conjugated diene-based rubber.
The number of the hydrogen-bonding functional group in the modified conjugated diene-based rubber is preferably two or more, and more preferably three or more on average per molecule from the viewpoint of obtaining coated fibers having excellent adhesiveness to the rubber. The number of the hydrogen-bonding functional group is preferably 80 or less, more preferably 40 or less, still more preferably 30 or less, still more preferably 20 or less, and even still more preferably 10 or less on average per molecule from the viewpoint of controlling the viscosity of the modified conjugated diene-based rubber within an appropriate range to improve handleability.
The average number of the hydrogen-bonding functional group per molecule of the modified conjugated diene-based rubber is calculated from the equivalent (g/eq) of the hydrogen-bonding functional group of the modified conjugated diene-based rubber and the number-average molecular weight Mn in terms of styrene by the following expression. The equivalent of the hydrogen-bonding functional group of the modified conjugated diene-based rubber means the mass of the conjugated diene and the additional monomer other than conjugated diene contained if necessary that are bonded to one hydrogen-bonding functional group.
Average number of hydrogen-bonding functional group per molecule = [(number-average molecular weight (Mn))/(molecular weight of styrene unit) × (average molecular weight of conjugated diene and additional monomer unit other than conjugated diene contained if necessary)]/(equivalent of hydrogen-bonding functional group)
A method for calculating the equivalent of the hydrogen-bonding functional group may be appropriately selected depending on the kind of the hydrogen-bonding functional group.
Examples of a method for producing the modified conjugated diene-based rubber include: a method for producing the modified conjugated diene-based rubber by adding a modifying compound to a polymerized compound of the conjugated diene monomer (hereinafter also referred to as "production method (1)"); a method for producing the modified conjugated diene-based rubber by oxidizing a conjugated diene polymer (hereinafter also referred to as "production method (2)"); a method for producing the modified conjugated diene-based rubber by copolymerizing the conjugated diene monomer and a radical-polymerizable compound having a hydrogen-bonding functional group (hereinafter also referred to as "production method (3)"); and a method for producing the modified conjugated diene-based rubber by adding a modifying compound that may react with a polymerization-active terminal before adding a polymerization terminator to a polymerized compound of the unmodified conjugated diene monomer having the polymerization-active terminal (hereinafter also referred to as "production method (4)").

· Method for Producing Modified Conjugated Diene-based Rubber (1)

The production method (1) is a method in which a modifying compound is added to a polymerized compound of the conjugated diene monomer, that is, an unmodified conjugated diene-based rubber (hereinafter also referred to as "unmodified conjugated diene-based rubber").
The unmodified conjugated diene-based rubber can be obtained by polymerizing a conjugated diene and if necessary, an additional monomer other than the conjugated diene, for example, through an emulsion polymerization method or a solution polymerization method.
Of the above-mentioned methods, the method for producing the unmodified conjugated diene-based rubber is preferably a solution polymerization method.
A known method or a method equivalent to the known method may be applied to the solution polymerization method. For example, a predetermined amount of a monomer containing a conjugated diene is polymerized in a solvent using a Ziegler catalyst, a Metallocene catalyst, or an anionic-polymerizable active metal or active metal compound in the presence of a polar compound, if necessary.
Examples of the solvent include aliphatic hydrocarbons, such as n-butane, n-pentane, isopentane, n-hexane, n-heptane, and isooctane; alicyclic hydrocarbons, such as cyclopentane, cyclohexane, and methylcyclopentane; and aromatic hydrocarbons, such as benzene, toluene, and xylene.
Examples of the anionic-polymerizable active metal include alkali metals, such as lithium, sodium, and potassium; alkaline earth metals, such as beryllium, magnesium, calcium, strontium, and barium; and lanthanoid-based rare earth metals, such as lanthanum and neodymium. Of the anionic-polymerizable active metals, the alkali metals and the alkaline earth metals are preferred, and the alkali metals are more preferred.
The anionic-polymerizable active metal compound is preferably an organic alkali metal compound. Examples of the organic alkali metal compound include organic monolithium compounds, such as methyllithium, ethyllithium, n-butyllithium, sec-butyllithium, t-butyllithium, hexyllithium, phenyllithium, and stilbene lithium; multifunctional organic lithium compounds, such as dilithiomethane, dilithionaphthalene, 1,4-dilithiobutane, 1,4-dilithio-2-ethylcyclohexane, and 1,3,5-trilithiobenzene; sodium naphthalene, and potassium naphthalene. Of these organic alkali metal compounds, the organic lithium compounds are preferred, and the organic monolithium compounds are more preferred.
The usage amount of the organic alkali metal compound can be appropriately set according to the melt viscosity, the molecular weight, and the like of the target unmodified conjugated diene-based rubber and the target modified conjugated diene-based rubber, and the organic alkali metal compound is usually used in an amount of 0.01 to 3 parts by mass with respect to 100 parts by mass of all the monomers containing the conjugated diene.
The organic alkali metal compound may be used in the form of an organic alkali metal amide to be obtained by a reaction with a secondary amine, such as dibutylamine, dihexylamine, or dibenzylamine.
The polar compound is usually used in anionic polymerization to adjust a microstructure of a conjugated diene moiety without inactivating the reaction. Examples of the polar compound include ether compounds, such as dibutyl ether, tetrahydrofuran, ethylene glycol diethyl ether, and 2,2-di(2-tetrahydrofuryl)propane; tertiary amines, such as tetramethyl ethylene diamine, and trimethylamine; alkali metal alkoxides, and phosphine compounds. The polar compound is usually used in an amount of 0.01 to 1,000 mol with respect to 1 mol of the organic alkali metal compound.
The temperature of the solution polymerization is usually -80 to +150°C, preferably 0 to 100°C, and more preferably 10 to 90°C. The polymerization mode may be a batch mode or a continuous mode.
The polymerization reaction can be terminated by adding a polymerization terminator. Examples of the polymerization terminator include alcohols, such as methanol and isopropanol. The unmodified conjugated diene-based rubber can be isolated by pouring the resulting polymerization reaction liquid to a poor solvent, such as methanol, to deposit the polymerized compound, or by washing the polymerization reaction liquid with water, followed by separation and drying.
A known method or a method equivalent to the known method may be applied to the emulsion polymerization method. For example, a predetermined amount of the monomer containing a conjugated diene is emulsified and dispersed in the presence of an emulsifier and subjected to emulsion polymerization with a radical polymerization initiator.
Examples of the emulsifier include long-chain fatty acid salts having 10 or more carbon atoms, and rosin acid salts. Examples of the long-chain fatty acid salts include a potassium salt or a sodium salt of fatty acids, such as capric acid, lauric acid, myristic acid, palmitic acid, oleic acid, and stearic acid.
Water is usually used as a dispersion solvent, and the dispersion solvent may contain a water-soluble organic solvent, such as methanol or ethanol, as long as stability during polymerization is not inhibited.
Examples of the radical polymerization initiator include persulfate salts, such as ammonium persulfate and potassium persulfate, organic peroxide salts, and hydrogen peroxide.
A chain-transfer agent may be used to adjust the molecular weight of the resulting unmodified conjugated diene-based rubber. Examples of the chain-transfer agent include mercaptans, such as t-dodecylmercaptan and n-dodecylmercaptan; carbon tetrachloride, thioglycolic acid, diterpene, terpinolene, γ-terpinen, and α-methylstyrene dimer.
The temperature of the emulsion polymerization can be appropriately set depending on the kind of the used radical polymerization initiator, and the like, and is usually 0 to 100°C, and preferably 0 to 60°C. The polymerization mode may be continuous polymerization mode or batch polymerization mode.
The polymerization reaction can be terminated by adding a polymerization terminator. Examples of the polymerization terminator include amine compounds, such as isopropyl hydroxylamine, diethyl hydroxylamine, and hydroxylamine, quinone-based compounds, such as hydroquinone and benzoquinone, and sodium nitrite.
After terminating the polymerization reaction, an antiaging agent may be added, if necessary. After terminating the polymerization reaction, the unreacted monomer is removed from the resulting latex, if necessary. Next, the polymerized compound is coagulated by adding a salt, such as sodium chloride, calcium chloride, or potassium chloride, as a coagulant while the pH of a coagulation system is adjusted to a predetermined value by adding an acid, such as nitric acid or sulfuric acid, if necessary. Subsequently, the dispersion solvent is separated to collect the polymerized compound. Next, the polymerized compound is washed with water, dehydrated, and then dried to obtain the unmodified conjugated diene-based rubber. In the coagulation, the latex and an extension oil used as an emulsion dispersion liquid may be mixed in advance if necessary, and a mixture may be collected as an extended unmodified conjugated diene-based rubber.

(Modifying Compound used in Production Method (1))

The modifying compound used in the production method (1) is not particularly limited, and a modifying compound having a hydrogen-bonding functional group is preferred from the viewpoint of improving the adhesiveness of the coated fibers. Examples of the hydrogen-bonding functional group include those described above. Of these, an amino group, an imidazole group, a urea group, a hydroxy group, a mercapto group, a silanol group, an aldehyde group, a carboxy group, and derivatives thereof are preferred from the viewpoint of the strength of a hydrogen bonding force. The derivative of the carboxy group is preferably a salt of the carboxy group, an ester derivative of the carboxy group, an amide derivative of the carboxy group, or an acid anhydride of the carboxy group. One kind of the modifying compounds having a hydrogen-bonding functional group may be used alone, or two or more kinds thereof may be used in combination.
Examples of the modifying compound include unsaturated carboxylic acids, such as maleic acid, fumaric acid, citraconic acid, and itaconic acid; unsaturated carboxylic anhydrides, such as maleic anhydride, citraconic anhydride, 2,3-dimethylmaleic anhydride, and itaconic anhydride; unsaturated carboxylic acid esters, such as maleic acid ester, fumaric acid ester, citraconic acid ester, and itaconic acid ester; unsaturated carboxylic acid amides, such as maleic acid amide, fumaric acid amide, citraconic acid amide, and itaconic acid amide; unsaturated carboxylic acid imides, such as maleic acid imide, fumaric acid imide, citraconic acid imide, and itaconic acid imide; and silane compounds, such as vinyltrimethoxysilane, γ-methacryloxypropyltrimethoxysilane, mercaptomethylmethyldiethoxysilane, mercaptomethyltriethoxysilane, 2-mercaptoethyltrimethoxysilane, 2-mercaptoethyltriethoxysilane, 2-mercaptoethylmethoxydimethylsilane, 2-mercaptoethylethoxydimethylsilane, 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, 3-mercaptopropyldimethoxymethylsilane, 3-mercaptopropyldiethoxymethylsilane, 3-mercaptopropyldimethoxyethylsilane, 3-mercaptopropyldiethoxyethylsilane, 3-mercaptopropylmethoxydimethylsilane, and 3-mercaptopropylethoxydimethylsilane.
The usage amount of the modifying compound is preferably 0.1 to 100 parts by mass, more preferably 0.5 to 50 parts by mass, and still more preferably 1 to 30 parts by mass, with respect to 100 parts by mass of the unmodified conjugated diene-based rubber.
The reaction temperature is preferably 0 to 200°C, and more preferably 50 to 200°C, generally.
The addition amount of the modifying compound in the modified conjugated diene-based rubber is preferably 0.5 to 40 parts by mass, more preferably 1 to 30 parts by mass, and still more preferably 1.5 to 20 parts by mass, with respect to 100 parts by mass of the unmodified conjugated diene-based rubber. The amount of the added modifying compound in the modified conjugated diene-based rubber can be calculated from the acid value of the modifying compound. Further, the amount can be determined using a variety of analyzers for infrared spectroscopy, nuclear magnetic resonance spectroscopy, or the like. It is difficult to uniformly measure the addition amount of the modifying compound by a specific measurement method, and hence it is necessary to select an appropriate analysis method according to the kind of the used modifying compound.
The method for adding the modifying compound to the unmodified conjugated diene-based rubber is not particularly limited, and includes a method in which the unmodified conjugated diene-based rubber in a liquid state, one or more modifying compounds selected from the unsaturated carboxylic acid, the unsaturated carboxylic acid derivative, and the silane compound, and if necessary, a radical generator are added and heated in the presence or absence of an organic solvent. The used radical generator is not particularly limited, and an organic peroxide, an azo compound, hydrogen peroxide, or the like, which is commercially available, may be usually used.
In general, examples of the organic solvent used in the method include hydrocarbon-based solvents and halogenated hydrocarbon-based solvents. Of the organic solvents, the hydrocarbon-based solvents, such as n-butane, n-hexane, n-heptane, cyclohexane, benzene, toluene, and xylene, are preferred.
Alternatively, the modifying compound is grafted onto the unmodified conjugated diene-based rubber to introduce a hydrogen-bonding functional group, a modifying compound capable of reacting with the functional group may be further added to introduce an additional hydrogen-bonding functional group into the polymer. Specifically, there is a method in which maleic anhydride is grafted onto an unmodified conjugated diene-based rubber obtained by living anionic polymerization, and then reacted with a compound having a hydroxy group, such as 2-hydroxyethyl methacrylate or methanol, or a compound, such as water.
Further, when a reaction of adding the modifying compound to the unmodified conjugated diene-based rubber or the modified conjugated diene-based rubber (a conjugated diene-based rubber having an introduced hydrogen-bonding functional group to be obtained by the above-mentioned method) is carried out, an antiaging agent may be added from the viewpoint of suppressing a side reaction. As the antiaging agent, a commercially available product may be used, and examples include butylated hydroxytoluene (BHT) and N-phenyl-N'-(1,3-dimethylbutyl)-p-phenylenediamine (NOCRAC 6C).
The addition amount of the antiaging agent is preferably 0.01 to 10 parts by mass, and more preferably 0.05 to 5 parts by mass, with respect to 100 parts by mass of the unmodified conjugated diene-based rubber. When the addition amount of the antiaging agent is within the above-mentioned range, a side reaction can be suppressed, and the modified conjugated diene-based rubber can be obtained with high yield.

· Method for Producing Modified Conjugated Diene-based Rubber (2)

Examples of the production method (2) include a method in which an unmodified conjugated diene-based rubber serving as a raw material is oxidized to obtain an oxidized conjugated diene-based rubber having a functional group and a bond that contain oxygen generated by an oxidation reaction in the molecule. Specific examples of the functional group and the bond include a hydroxy group, an aldehyde group, a carbonyl group, a carboxy group, and an ether bond.
The unmodified conjugated diene-based rubber can be obtained by the same method as the production method (1).
Examples of a method for oxidizing the conjugated diene-based rubber as a raw material include: a method in which the conjugated diene-based rubber as a raw material is subjected to heat treatment at a temperature equal to or more than the oxidation temperature (hereinafter also referred to as "production method (2-1)"); and a method in which the conjugated diene-based rubber as a raw material is activated by irradiation with light having an absorption wavelength of the conjugated diene-based rubber as a raw material, and reacted with oxygen (hereinafter also referred to as "production method (2-2)"). Of these, the method in which the conjugated diene-based rubber as a raw material is subjected to heat treatment at a temperature equal to or more than the oxidation temperature (production method (2-1)) is preferred.
A stage of performing the oxidation reaction of the conjugated diene-based rubber is not particularly limited. This stage may be performed before mixing the conjugated diene-based rubber with an oil, may be performed after mixing the conjugated diene-based rubber with an oil, or may be performed after a mixture of the conjugated diene-based rubber with an oil is attached to fibers.

· Method for Producing Oxidized Conjugated Diene-based Rubber (2-1)

The production method (2-1) is a method in which the unmodified conjugated diene-based rubber as a raw material is subjected to heat treatment at a temperature equal to or more than the oxidation temperature. The heat treatment is performed under an atmosphere containing oxygen, preferably in air.
The temperature of the heat treatment is not particularly limited as long as it is a temperature at which the conjugated diene-based rubber as a raw material is oxidized. The temperature is preferably 150°C or more, more preferably 170°C or more, and still more preferably 190°C or more from the viewpoint of increasing the oxidation reaction rate and improving productivity. When the oxidation of the conjugated diene-based rubber as a raw material is carried out on the surface of hydrophile fibers as described below, the temperature is preferably 240°C or less, and more preferably 220°C or less from the viewpoint of preventing deterioration of the fibers.
The time of the heat treatment is not particularly limited as long as the conjugated diene-based rubber as a raw material is not deteriorated. The time is preferably 30 minutes or less, and more preferably 20 minutes or less. The time of the heat treatment is preferably 1 second or more, more preferably 10 seconds or more, and still more preferably 30 seconds or more from the viewpoint of sufficiently oxidizing the unmodified conjugated diene-based rubber.
Further, a temperature required for the oxidation reaction can be decreased by adding a thermal radical generator to the conjugated diene-based rubber as a raw material.
Examples of the thermal radical generator include peroxides, azo compounds, and redox initiators. Of these, peroxides are preferred since the thermal radical generator is bonded to the conjugated diene-based rubber to add a structure containing oxygen to the conjugated diene-based rubber.
Examples of the peroxides include t-butyl hydroperoxide, cumene hydroperoxide, t-butyl peroxyacetate, t-butyl peroxybenzoate, t-butyl peroxyoctanoate, t-butyl peroxyneodecanoate, t-butyl peroxyisobutyrate, lauroyl peroxide, t-amyl peroxypivalate, t-butyl peroxypivalate, dicumyl peroxide, benzoyl peroxide, potassium persulfate, and ammonium persulfate.
Examples of the azo compounds include azobisisobutyronitrile (AIBN), 2,2'-azobis(isobutylonitrile), 2,2'-azobis(2-butanenitrile), 4,4'-azobis(4-pentanoate), 1,1'-azobis(cyclohexanecarbonitrile), 2-(t-butylazo)-2-cyanopropane, 2,2'-azobis[2-methyl-N-(1,1)-bis(hydroxymethyl)-2-hydroxyethyl]propionamide, 2,2'-azobis(2-methyl-N-hydroxyethyl)propionamide, 2,2'-azobis(N,N'-dimethyleneisobutylamidine) dichloride, 2,2'-azobis(N,N'-dimethyleneisobutylamide), 2,2'-azobis(2-methyl-N-[1,1-bis(hydroxymethyl)-2-hydroxyethyl]propionamide), and 2,2'-azobis(isobutylamide) dihydrate.
One kind of the thermal radical generators may be used alone, or two or more kinds thereof may be used in combination.
As the thermal radical generator, a redox initiator may be used. Examples of the redox initiator include a combination of persulfate, acid sodium sulfite, and ferrous sulfate, a combination of t-butyl hydroperoxide, acid sodium sulfite, and ferrous sulfate, and a combination of p-menthane hydroperoxide, ferrous sulfate, sodium ethylenediaminetetraacetate, and sodium formaldehyde sulfoxylate.

· Method for Producing Oxidized Conjugated Diene-based Rubber (2-2)

The production method (2-2) is a method in which the unmodified conjugated diene-based rubber as a raw material is activated by irradiation with light having an absorption wavelength of the unmodified conjugated diene-based rubber and reacted with oxygen.
The production method (2-2) is performed under an atmosphere containing oxygen, preferably in air. The wavelength of used light is not particularly limited as long as it is a wavelength to be absorbed by the conjugated diene-based rubber as a raw material, resulting in a radical reaction. Ultraviolet light that is highly absorbed by the conjugated diene-based rubber as a raw material is preferred.
Further, the irradiation dose of light required for the oxidation reaction can be decreased by adding a photo-radical generator to the conjugated diene-based rubber as a raw material.
Examples of the photo-radical generator include acetophenone, acetophenone benzyl ketal, 1-hydroxycyclohexylphenyl ketone, 2,2-dimethoxy-1,2-diphenylethan-1-one, xanthone, fluorenone, benzaldehyde, fluorene, anthraquinone, triphenylamine, carbazole, 3-methylacetophenone, 4,4'-dimethoxybenzophenone, benzoin propyl ether, benzyl dimethyl ketal, 1-(4-isopropylphenyl)-2-hydroxy-2-methylpropan-1-one, 2-hydroxy-2-methyl-1-phenylpropan-1-one, thioxanthone, diethyl thioxanthone, 2-methyl-1-[4-(methylthio)phenyl]-2-morpholino-propan-1-one, 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)-1-butanone-1,4-(2-hydroxyethoxy)phenyl-(2-hydroxyethoxy-2-propyl) ketone, 2,4,6-trimethylbenzoyldiphenyl phosphine oxide, and bis(2,6-dimethoxybenzoyl)-2,4,4-trimethylpentylphosphine oxide. One kind of the photo-radical generators may be used alone, or two or more kinds thereof may be used in combination.

· Method for Producing Modified Conjugated Diene-based Rubber (3)

Examples of the production method (3) include a method in which the conjugated diene monomer and a radical-polymerizable compound having a hydrogen-bonding functional group are subjected to random copolymerization, block copolymerization, or graft copolymerization through a known method.

(Radical-polymerizable Compound having Hydrogen-bonding Functional Group used in Production Method (3))

The radical-polymerizable compound having a hydrogen-bonding functional group used in the production method (3) is not particularly limited as long as it is a compound having both a hydrogen-bonding functional group and a reactive multiple bond in the molecule. Specific examples thereof include aldehydes having a reactive multiple bond, acetal derivatives of the aldehydes; monocarboxylic acids having a reactive multiple bond, salts of the monocarboxylic acids, ester derivatives of the monocarboxylic acids, acid anhydrides of the monocarboxylic acids; dicarboxylic acids having a reactive multiple bond, salts of the dicarboxylic acids, ester derivatives of the dicarboxylic acids, acid anhydrides of the dicarboxylic acids; and amine compounds having a reactive multiple bond.
Of the aldehydes having a multiple bond, examples of an aldehyde having a reactive carbon-carbon double bond include unsaturated aldehydes, such as alkenals having 3 to 30 carbon atoms, and preferably alkenals having 3 to 25 carbon atoms, including acrolein, methacrolein, crotonaldehyde, 3-butenal, 2-methyl-2-butenal, 2-methyl-3-butenal, 2,2,-dimethyl-3-butenal, 3-methyl-2-butenal, 3-methyl-3-butenal, 2-pentenal, 2-methyl-2-pentenal, 3-pentenal, 3-methyl-4-pentenal, 4-pentenal, 4-methyl-4-pentenal, 2-hexenal, 3-hexenal, 4-hexenal, 5-hexenal, 7-octenal, 10-undecenal, 2-ethylcrotonaldehyde, 3-(dimethylamino)acrolein, myristoleic aldehyde, palmitoleic aldehyde, oleic aldehyde, elaidic aldehyde, vaccenic aldehyde, gadoleic aldehyde, erucic aldehyde, nervonic aldehyde, linoleic aldehyde, citronellal, cinnamaldehyde, and vanillin; alkadienals having 5 to 30 carbon atoms, and preferably alkadienals having 5 to 25 carbon atoms, including 2,4-pentadienal, 2,4-hexadienal, 2,6-nonadienal, and citral; alkatrienals having 7 to 30 carbon atoms, and preferably alkatrienals having 7 to 25 carbon atoms, including linolenic aldehyde and eleostearic aldehyde; alkatetraenals having 9 to 30 carbon atoms, and preferably alkatetraenals having 9 to 25 carbon atoms, including stearidonic aldehyde and arachidonic aldehyde; and alkapentaenals having 11 to 30 carbon atoms, and preferably alkapentaenals having 11 to 25 carbon atoms, including eicosapentaenoic aldehyde. The aldehydes having cis-trans isomerism include both the cis isomer and the trans isomer. One kind of the aldehydes may be used alone, or two or more kinds thereof may be used in combination.
Of the acetal derivatives of the aldehydes having a multiple bond, examples of an acetal derivative of the aldehyde having a reactive carbon-carbon double bond include acetal derivatives of the aldehyde, and specifically include 3-(1,3-dioxolan-2-yl)-3-methyl-1-propene that is an acetal derivative of 2-methyl-3-butenal, and 3-(1,3-dioxolan-2-yl)-2-methyl-1-propene that is an acetal derivative of 3-methyl-3-butenal.
Of the aldehydes having a multiple bond and the acetal derivatives of the aldehydes, examples of an aldehyde having a reactive carbon-carbon triple bond and an acetal derivative thereof include aldehydes having a carbon-carbon triple bond, such as propiolaldehyde, 2-butyn-1-al, and 2-pentyn-1-al, and acetal derivatives of the aldehydes.
Of the aldehydes having a multiple bond and the acetal derivatives of the aldehydes, the aldehydes having a reactive carbon-carbon double bond are preferred, and for example, one or more kinds selected from acrolein, methacrolein, crotonaldehyde, 3-butenal, 2-methyl-2-butenal, 2-methyl-3-butenal, 2,2,-dimethyl-3-butenal, 3-methyl-2-butenal, 3-methyl-3-butenal, 2-pentenal, 2-methyl-2-pentenal, 3-pentenal, 3-methyl-4-pentenal, 4-pentenal, 4-methyl-4-pentenal, 2-hexenal, 3-hexenal, 4-hexenal, 5-hexenal, 7-octenal, 2-ethylcrotonaldehyde, 3-(dimethylamino)acrolein, and 2,4-pentadienal are preferred. Of these, one or more kinds selected from acrolein, methacrolein, crotonaldehyde, and 3-butenal are preferred since reactivity during copolymerization is satisfactory.
Examples of the monocarboxylic acids having a multiple bond, the salts of the monocarboxylic acids, the ester derivatives of the monocarboxylic acids, and the acid anhydrides of the monocarboxylic acids include carboxylic acids having a reactive carbon-carbon double bond, salts of the carboxylic acids, ester derivatives of the carboxylic acids, and acid anhydrides of the carboxylic acids, such as (meth)acrylic acid, a sodium salt of (meth)acrylic acid, a potassium salt of (meth)acrylic acid, methyl (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate, propyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 3-hydroxybutyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, vinyl (meth)acrylate, 2-(trifluoromethyl)acrylic acid, methyl 2-trifluoromethylacrylate, ethyl 2-trifluoromethylacrylate, propyl 2-trifluoromethylacrylate, 2-butyl 2-trifluoromethylacrylate, 2-hydroxylethyl 2-trifluoromethylacrylate, vinyl 2-trifluoromethylacrylate, methyl cinnamate, vinyl cinnamate, methyl crotonate, vinyl crotonate, methyl 3-methyl-3-butenoate, vinyl 3-methyl-3-butenoate, methyl 4-pentenoate, vinyl 4-pentenoate, methyl 2-methyl-4-pentenoate, vinyl 2-methyl-4-pentenoate, methyl 5-hexenoate, vinyl 5-hexenoate, methyl 3,3-dimethyl-4-pentenoate, vinyl 3,3-dimethyl-4-pentenoate, methyl 7-octenoate, vinyl 7-octenoate, methyl trans-3-pentenoate, vinyl trans-3-pentenoate, methyl trans-4-decenoate, vinyl trans-4-decenoate, ethyl 3-methyl-3-butenoate, ethyl 4-pentenoate, ethyl 2-methyl-4-pentenoate, ethyl 5-hexenoate, ethyl 3,3-dimethyl-4-pentenoate, ethyl 7-octenoate, ethyl trans-3-pentenoate, ethyl trans-4-decenoate, methyl 10-undecenoate, vinyl 10-undecenoate, (meth)acrylic anhydride, 2-(trifluoromethyl)acrylic anhydride, cinnamic anhydride, crotonic anhydride, 3-methyl-3-butenoic anhydride, 4-pentenoic anhydride, 2-methyl-4-pentenoic anhydride, 5-hexenoic anhydride, 3,3-dimethyl-4-pentenoic anhydride, 7-octenoic anhydride, trans-3-pentenoic anhydride, trans-4-decenoic anhydride, and 10-undecenoic anhydride; and carboxylic acids having a reactive carbon-carbon triple bond and ester derivatives of the carboxylic acids, such as propiolic acid, methyl propiolate, ethyl propiolate, vinyl propiolate, tetrolic acid, methyl tetrolate, ethyl tetrolate, and vinyl tetrolate.
The "(meth)acrylic acid" as used herein means the generic term of "acrylic acid" and "methacrylic acid."
Examples of the dicarboxylic acids having a multiple bond, the salts of the dicarboxylic acids, the ester derivatives of the dicarboxylic acids, and the acid anhydrides of the dicarboxylic acids include dicarboxylic acids having a reactive carbon-carbon double bond, salts of the dicarboxylic acids, ester derivatives of the dicarboxylic acids, and acid anhydrides of the dicarboxylic acids, such as maleic acid, sodium meleate, potassium meleate, methyl maleate, dimethyl maleate, maleic anhydride, itaconic acid, methyl itaconate, dimethyl itaconate, itaconic anhydride, himic acid, methyl himate, dimethyl himate, and himic anhydride.
The monocarboxylic acids having a multiple bond, the salts of the monocarboxylic acids, the ester derivatives of the monocarboxylic acids, the monocarboxylic anhydrides, the dicarboxylic acids having a multiple bond, the salts of the dicarboxylic acids, the ester derivatives of the dicarboxylic acids, and the acid anhydrides of the dicarboxylic acids are preferably compounds having a reactive carbon-carbon double bond. Of these, since reactivity during copolymerization is satisfactory, one or more kinds selected from methyl (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate, vinyl (meth)acrylate, (meth)acrylic anhydride, 2-(trifluoromethyl)acrylic anhydride, cinnamic anhydride, crotonic anhydride, methyl maleate, dimethyl maleate, maleic anhydride, methyl itaconate, dimethyl itaconate, and itaconic anhydride are more preferred.
Of the amine compounds having a multiple bond, examples of an amine compound having a reactive carbon-carbon double bond include allylamine, 3-butenylamine, 4-pentenylamine, 5-hexenylamine, 6-heptenylamine, 7-octenylamine, oleylamine, 2-methylallylamine, 4-aminostyrene, 4-vinylbenzylamine, 2-allylglycine, S-allylcysteine, α-allylalanine, 2-allylaniline, geranylamine, vvigabatrin, 4-vinylaniline, and 4-vinyloxyaniline. Of these, since reactivity during copolymerization is satisfactory, one or more kinds selected from allylamine, 3-butenylamine, and 4-pentenylamine are preferred.

· Method for Producing Modified Conjugated Diene-based Rubber (4)

The production method (4) is a method in which before adding a polymerization terminator to a polymerized compound of an unmodified conjugated diene monomer having a polymerization-active terminal (unmodified conjugated diene-based rubber), a modifying compound that may react with the polymerization-active terminal is added. The unmodified conjugated diene-based rubber having a polymerization-active terminal can be obtained, for example, by polymerizing the conjugated diene monomer and if necessary, an additional monomer other than the conjugated diene monomer through an emulsion polymerization method or a solution polymerization method, similarly to the production method (1).
Examples of the modifying compound used in the production method (4) include modifiers, such as dimethyldiethoxysilane, tetramethoxysilane, tetraethoxysilane, 3-aminopropyltriethoxysilane, tetraglycidyl-1,3-bis(aminomethyl)cyclohexane, 2,4-tolylene diisocyanate, carbon dioxide, ethylene oxide, succinic anhydride, 4,4'-bis(diethylamino)benzophenone, N-vinylpyrrolidone, N-methylpyrrolidone, 4-dimethylamino benzylidene aniline, and dimethylimidazolidinone; and other modifies described in JP 2011-132298 A .
For example, when an organic alkali metal compound is used in polymerization, the usage amount of the modifying compound in the production method (4) is preferably 0.01 to 100 molar equivalents with respect to the organic alkali metal compound. The reaction temperature is usually -80 to +150°C, preferably 0 to 100°C, and more preferably 10 to 90°C.
Alternatively, before adding a polymerization terminator, the modifying compound is added to introduce a hydrogen-bonding functional group into the unmodified conjugated diene-based rubber, a modifying compound that may react with the functional group may be further added to introduce an additional hydrogen-bonding functional group into the polymer.
The modified conjugated diene-based rubber may contain a unit derived from an additional monomer other than the conjugated diene monomer and the radical-polymerizable compound having a hydrogen-bonding functional group as long as adhesion is not inhibited. Examples of the additional monomer include ethylenically-unsaturated monomers and aromatic vinyl compounds that are copolymerizable. Specifical compounds and contents are the same as described above.
The method for producing the modified conjugated diene-based rubber is not particularly limited, and the modified conjugated diene-based rubber is produced preferably by the production method (1), (2), or (3), more preferably by the production method (1) or (3), and still more preferably by the production method (1) from the viewpoint of productivity.

(Physical Properties of Conjugated Diene-based Rubber)

The weight-average molecular weight (Mw) of the conjugated diene-based rubber is not particularly limited, and the conjugated diene-based rubber preferably includes a conjugated diene-based rubber having a low molecular weight of at least the following range. Specifically, the weight-average molecular weight of the conjugated diene-based rubber having a low molecular weight is preferably 1,000 or more, more preferably 2,000 or more, still more preferably 3,000 or more, still more preferably 4,000 or more, and still more preferably 5,000 or more, and may be 7,000 or more from the viewpoint of improving adhesiveness, and is preferably 26,000 or less, more preferably 20,000 or less, still more preferably 15,000 or less, still more preferably 12,000 or less, and still more preferably 10,000 or less from the viewpoint of handleability. More specifically, the weight-average molecular weight is preferably 1,000 to 26,000, more preferably 2,000 to 20,000, still more preferably 3,000 to 15,000, still more preferably 4,000 to 12,000, still more preferably 5,000 to 10,000, and still more preferably 7,000 to 10,000.
In a preferred aspect of the coating in the coated fibers of the present invention, two or more kinds of different conjugated diene-based rubbers are contained. As used herein, the expression "different kinds of conjugated diene-based rubbers" means that the conjugated diene-based rubbers are different in at least one of various physical properties and features, such as the kind of a monomer unit contained, the presence or absence of a functional group (the presence or absence of modification), the kind or number of the functional group, a weight-average molecular weight, and a number-average molecular weight.
The number-average molecular weight (Mn) of the conjugated diene-based rubber is not particularly limited, is preferably 1,000 or more, more preferably 2,000 or more, still more preferably 2,500 or more, still more preferably 3,000 or more, and still more preferably 3,500 or more from the viewpoint of improving adhesiveness, and is preferably 20,000 or less, more preferably 18,000 or less, and still more preferably 15,000 or less from the viewpoint of handleability. More specifically, the number-average molecular weight is preferably 1,000 to 20,000, more preferably 2,000 to 18,000, still more preferably 2,500 to 15,000, still more preferably 3,000 to 15,000, and still more preferably 3,500 to 15,000.
The Mw and Mn of the conjugated diene-based rubber are the weight-average molecular weight and the number-average molecular weight, respectively, determined in terms of polystyrene by measurement by gel permeation chromatography (GPC). Specifically, they can be determined by methods described in Examples.
The weight-average molecular weight and the number-average molecular weight of the conjugated diene-based rubber can be set to desired values by adjusting the kind and the amount of a solvent in the production method.
The molecular weight distribution (Mw/Mn) of the conjugated diene-based rubber is preferably 1.0 to 5.0, more preferably 1.0 to 3.0, still more preferably 1.0 to 2.0, still more preferably 1.0 to 1.5, and particularly preferably 1.0 to 1.3. When the Mw/Mn is within the above-mentioned range, the conjugated diene-based rubber exhibits low viscosity variation and is easy to handle. The molecular weight distribution (Mw/Mn) means the ratio of the weight average molecular weight (Mw) to the number average molecular weight (Mn) in terms of standard polystyrene determined by measurement by GPC.
In addition, the conjugated diene-based rubber is preferably in a liquid state from the viewpoint of adhesiveness of the conjugated diene-based rubber to the fibers.
The "liquid state" as used herein represents that the melt viscosity of the conjugated diene-based rubber measured at 38°C is 4,000 Pa·s or less. The melt viscosity is preferably 0.1 Pa·s or more, more preferably 0.5 Pa·s or more, and still more preferably 1.0 Pa·s or more from the viewpoint of improving adhesiveness, and is preferably 2,000 Pa·s or less, more preferably 1,500 Pa·s or less, and still more preferably 1,000 Pa·s or less from the viewpoint of handleability. More specifically, the melt viscosity measured at 38°C is preferably 0.1 to 4,000 Pa·s, more preferably 0.1 to 2,000 Pa·s, still more preferably 0.5 to 1,500 Pa·s, and still more preferably 1.0 to 1,000 Pa·s. When the melt viscosity is within the above-mentioned range, handleability can be made satisfactory while improving the adhesiveness of the conjugated diene-based rubber.
The melt viscosity of the conjugated diene-based rubber means the viscosity measured at 38°C with a Brookfield viscometer (B type viscometer), and can be specifically measured by a method described in Examples.
The glass transition temperature (Tg) of the conjugated diene-based rubber may vary depending on the vinyl content of the conjugated diene unit, the kind of the conjugated diene, the content of the unit derived from the additional monomer other than the conjugated diene, and the like, and is preferably -100 to +10°C, more preferably -100 to 0°C, and still more preferably -100 to -5°C. When the Tg is within the above-mentioned range, an increase in viscosity can be suppressed, and the conjugated diene-based rubber becomes easy to handle. The Tg can be determined by a method described in Examples.
The vinyl content of the conjugated diene-based rubber is preferably 80 mol% or less, more preferably 50 mol% or less, and still more preferably 30 mol% or less. The lower limit value of the vinyl content may be 0 mol%, and the vinyl content may be 0 mol%. When the vinyl content is within the above-mentioned range, adhesiveness is improved.
The "vinyl content" as used herein means the total molar percentage of conjugated diene units bonded via a 1,2-bond or a 3,4-bond (conjugated diene units bonded via a bond other than a 1,4-bond) in 100 mol% in total of the conjugated diene unit contained in the conjugated diene-based rubber. The vinyl content can be calculated from the integrated value ratio of the signal derived from the conjugated diene units bonded via a 1,2-bond or a 3,4-bond to the signal derived from the conjugated diene units bonded via a 1,4-bond by ¹H-NMR.
The content of the conjugated diene-based rubber in an aqueous adhesive to be described later is preferably 0.1 mass% or more, more preferably 0.5 mass% or more, still more preferably 1 mass% or more, and is preferably 25 mass% or less, more preferably 15 mass% or less, still more preferably 10 mass% or less, and still more preferably 5 mass% or less, from the viewpoint of improving the adhesiveness to the rubber. More specifically, the content of the conjugated diene-based rubber in the aqueous adhesive to be described later is preferably 0.1 to 25 mass%, more preferably 0.5 to 15 mass%, still more preferably 1 to 10 mass%, and still more preferably 1 to 5 mass%. When the content of the conjugated diene-based rubber in the aqueous adhesive is within the above-mentioned range, the viscosity of the aqueous adhesive can be prevented from becoming extremely high while achieving a sufficient adhesion force.

[Crosslinking agent]

In the present invention, the adhesive composition preferably contains a crosslinking agent. Even in the case of using the conjugated diene-based rubber having a low molecular weight, by the use of the crosslinking agent, it is possible to allow the conjugated diene-based rubbers having a low molecular weight to bond via a covalent bond, and to allow the conjugated diene-based rubber and the fibers to bond via a covalent bond. Even when the temperature is high during vulcanization due to the use of a crosslinking agent, the conjugated diene-based rubber is unlikely to be absorbed into rubber as an adhesion object (adherend), and hence a sufficient adhesion force can be exhibited. In particular, in the present invention, the use of the crosslinking agent provides excellent adhesiveness to an adherend including a high-polar rubber. In the present invention, the use of the crosslinking agent can improve the convergence of the coated fibers, and can improve the strength after friction.
The crosslinking agent used in the present invention is not particularly limited. The crosslinking agent is not particularly limited as long as it is a compound capable of forming a covalent bond with both the conjugated diene-based rubber and the fibers. Examples of the crosslinking agent include an epoxy resin, an isocyanate resin, an oxazoline group-containing resin, a carbodiimide group-containing resin, an amino resin, and a polyester resin. Of these, one or more kinds selected from the group consisting of an epoxy resin and an isocyanate resin are preferred, and the use of an epoxy resin and an isocyanate resin in combination is more preferred.
The content of the crosslinking agent in the aqueous adhesive to be described later is preferably 0.01 mass% or more, more preferably 0.5 mass% or more, and still more preferably 0.8 mass% or more, and is preferably 15 mass% or less, more preferably 10 mass% or less, and still more preferably 5 mass% or less, from the viewpoint of suppressing the absorption of the conjugated diene-based rubber into rubber as an adherend and improving an adhesion force. More specifically, the content of the crosslinking agent in the aqueous adhesive to be described later is preferably 0.01 to 15 mass%, more preferably 0.5 to 10 mass%, and still more preferably 0.8 to 5 mass%. When the content of the crosslinking agent in the aqueous adhesive is equal to or more than the lower limit value, the crosslinking agent can be reacted with the conjugated diene-based rubber to suppress the absorption of the conjugated diene-based rubber into an elastomer. In addition, the convergence of the coated fibers can be improved, and the strength after friction can also be improved. In contrast, when the content of the crosslinking agent in the aqueous adhesive is equal to or less than the upper limit value, an excessive increase in adhesion force of the adhesive composition can be suppressed.
The content of the crosslinking agent in the aqueous adhesive to be described later is preferably 10 parts by mass or more, more preferably 30 parts by mass or more, and still more preferably 45 parts by mass or more, and is preferably 100 parts by mass or less, more preferably 90 parts by mass or less, and still more preferably 80 parts by mass or less, with respect to 100 parts by mass of the conjugated diene-based rubber from the viewpoint of improving the adhesiveness to the rubber. More specifically, the content of the crosslinking agent in the aqueous adhesive to be described later is preferably 10 to 100 parts by mass, more preferably 30 to 90 parts by mass, and still more preferably 45 to 80 parts by mass, with respect of 100 parts by mass of the conjugated diene-based rubber.

[Oil]

In the present invention, it is preferable that the adhesive composition further contains an oil having a vapor pressure at 20°C of 10 Pa or less. When the adhesive composition contains the oil, the uneven application of the adhesive composition is less likely to be caused. This is because the oil is not volatilized for a long period of time even after the adhesive composition is applied to the surface of the fibers. Accordingly, the adhesiveness of the adhesive composition can be improved, and the contamination of a production facility can be suppressed during production. When the conjugated diene-based rubber and the oil having a vapor pressure at 20°C of 10 Pa or less are used in combination, the convergence of the coated fibers is also improved. From these viewpoints, the vapor pressure of the oil at 20°C is preferably 5 Pa or less, more preferably 1 Pa or less, still more preferably 0.1 Pa or less, and still more preferably 0.01 Pa or less. In the present invention, the oil having a vapor pressure at 20°C of 10 Pa or less, or so-called a non-volatile oil is preferably used.
In the present invention, the vapor pressure at 20°C of an oil refers to a value calculated from an optimum curve obtained by applying an Antoine equation to a measured value obtained by measurement through a gas saturation method.
The oil having a vapor pressure at 20°C of 10 Pa or less that can be used in the present invention is not particularly limited as long as it is compatible with the conjugated diene-based rubber. Examples of the oil include natural oils and synthetic oils. Examples of the natural oils include mineral oils and vegetable oils.
Examples of the mineral oils include paraffinic mineral oils, aromatic mineral oils, and naphthene-based mineral oils that are obtained by a general purification method, such as solvent purification or hydrogenation purification, waxes produced by the Fischer-Tropsch process or the like (gas-to-liquid wax), and mineral oils produced by isomerization of waxes.
Examples of commercially available products of the paraffinic mineral oils include "Diana Process Oil" series manufactured by Idemitsu Kosan Co., Ltd., and "Super Oil" series manufactured by JX Energy Corporation.
Examples of the vegetable oils include a linseed oil, a camellia oil, a macadamia seed oil, a corn oil, a mink oil, an olive oil, an avocado oil, a sasanqua oil, a castor oil, a safflower oil, a jojoba oil, a sunflower oil, an almond oil, a rapeseed oil, a sesame oil, a soybean oil, a peanut oil, a cottonseed oil, a coconut oil, a palm kernel oil, and a rice bran oil.
Examples of the synthetic oils include hydrocarbon-based synthetic oils, ester-based synthetic oils, and ether-based synthetic oils. Examples of the hydrocarbon-based synthetic oils include α-olefin oligomers such as polybutene, polyisobutylene, a 1-octene oligomer, a 1-decene oligomer, and an ethylene-propylene copolymer, or a hydrogenated product thereof, alkyl benzene, and alkyl naphthalene. Examples of the ester-based synthetic oils include triglyceride fatty acid esters, diglyceride fatty acid esters, monoglyceride fatty acid esters, monoalcohol fatty acid esters, and polyhydric alcohol fatty acid esters. Examples of the ether-based synthetic oils include polyoxyalkylene glycol and polyphenyl ether. Examples of commercially available products of the synthetic oils include "LINEALENE" series manufactured by Idemitsu Kosan Co., Ltd., and "FGC32," "FGC46," and "FGC68" manufactured by Anderol B.V.
Of these, triglyceride fatty acid esters, phthalic acid esters, and adipic acid esters are preferred, and triglyceride 2-ethylhexanoate and adipic acid esters are more preferred from the viewpoint of suppressing the uneven application of the adhesive composition and improving adhesiveness.
The oil may be one kind selected from the natural oils and the synthetic oils, or a mixture of two or more kinds of the natural oils, two or more kinds of the synthetic oils, or one or more kinds of the natural oils and one or more kinds of the synthetic oils.
In the present invention, the mineral oils are preferred, and one or more kinds selected from the paraffinic mineral oils and the naphthene-based mineral oils are more preferred from the viewpoint of setting the viscosity of the adhesive composition within an appropriate range to improve workability.
The flashpoint of the oil used in the present invention is preferably 70°C or more from the viewpoint of safety. From this viewpoint, the flashpoint of the oil is more preferably 100°C or more, still more preferably 130°C or more, and still more preferably 140°C or more. The upper limit value of the flashpoint of the oil is not particularly limited, and is preferably 320°C or less.
The content of the oil in the aqueous adhesive to be described later is preferably 0.1 mass% or more, more preferably 0.5 mass% or more, still more preferably 1 mass% or more, and still more preferably 2 mass% or more, and is preferably 25 mass% or less, more preferably 15 mass% or less, and still more preferably 10 mass% or less. More specifically, the content of the oil in the aqueous adhesive to be described later is preferably 0.1 t 25 mass%, more preferably 0.5 to 15 mass%, still more preferably 1 to 10 mass%, and still more preferably 2 to 10 mass%.
The content of the oil in the aqueous adhesive to be described later is preferably 50 parts by mass or more, more preferably 60 parts by mass or more, and still more preferably 70 parts by mass or more, and is preferably 300 parts by mass or less, more preferably 280 parts by mass or less, and still more preferably 250 parts by mass or less, with respect to 100 parts by mass of the conjugated diene-based rubber from the viewpoint of improving the adhesiveness to the rubber and from the viewpoint of improving the convergence of the coated fibers. More specifically, the content of the oil in the aqueous adhesive to be described later is preferably 50 to 300 parts by mass, more preferably 60 to 280 parts by mass, and still more preferably 70 to 250 parts by mass, with respect of 100 parts by mass of the conjugated diene-based rubber.

[Surfactant]

In the present invention, an emulsion containing the conjugated diene-based rubber may be prepared by using a surfactant from the viewpoint of conserving the adhesive composition containing the conjugated diene-based rubber for an extended period of time. The surfactant used in the present invention is not particularly limited, and examples thereof include a cationic surfactant, an anionic surfactant, a nonionic surfactant, and an amphoteric surfactant. Of these, the nonionic surfactant is preferred from the viewpoint of compatibility of the adhesive composition with the rubber.
Examples of the nonionic surfactant include polyoxyalkylene-based nonionic surfactants, such as a higher alcohol alkylene oxide adduct, an alkyl phenol alkylene oxide adduct, a styrenated phenol alkylene oxide adduct, a fatty acid alkylene oxide adduct, a polyhydric alcohol aliphatic ester alkylene oxide adduct, a higher alkyl amine alkylene oxide adduct, and a fatty acid amide alkylene oxide adduct, and polyhydric alcohol-based nonionic surfactants, such as alkyl glycoxide and a sucrose fatty acid ester. The nonionic surfactants may be used alone, or if necessary, two or more kinds thereof may be used in combination.
Examples of commercially available products of the nonionic surfactant include "ADEKA TOL TN100," "ADEKA TOL PC-6," "ADEKA TOL PC-8," "ADEKA TOL PC-10," and "ADEKA TOL SO-80" manufactured by ADEKA Corporation.
Examples of the cationic surfactant include alkylammonium acetate salts, alkyl dimethyl benzyl ammonium salts, alkyl trimethyl ammonium salts, dialkyl dimethyl ammonium salts, alkyl pyridinium salts, oxyalkylene alkylamines, and polyoxyalkylene alkylamines. The cationic surfactants may be used alone, or if necessary, two or more kinds thereof may be used in combination.
Examples of the anionic surfactant include carboxylate salts, such as a fatty acid soap, sulfate salts, such as a higher alcohol sulfate salt, a higher alkyl polyalkylene glycol ether sulfate salt, a sulfate salt of a styrenated phenol alkylene oxide adduct, a sulfate salt of an alkyl phenol alkylene oxide adduct, a sulfated oil, a sulfated fatty acid ester, a sulfated fatty acid, and a sulfated olefin, formalin condensates of alkylbenzenesulfonate salts, alkylnaphthalenesulfonate salts, naphthalenesulfonate salts, and naphthalenesulfonic acid, sulfonate salts, such as α-olefinsulfonate salts, paraffinsulfonate salts, and sulfosuccinic acid diester salts, and higher alcohol phosphoric acid ester salts. The anionic surfactants may be used alone, or if necessary, two or more kinds thereof may be used in combination.
If necessary, the nonionic surfactant and the anionic surfactant may be combined.
Examples of the amphoteric surfactant include alkyl carboxybetaines.
The hydrophilic-lipophilic balance (HLB) value of the nonionic surfactant is preferably 6 to 17. When the HLB value is within the above-mentioned range, coated fibers having satisfactory compatibility with the conjugated diene-based rubber and the oil, and satisfactory adhesiveness to the rubber can be obtained. The adhesive composition is preferably attached to the fibers as the emulsion from the viewpoint of the safety of the usage environment and operativity. The lower limit of the HLB value is more preferably 8 or more, and still more preferably 10 or more from the viewpoint of storage stability in water. The upper limit of the HLB value is more preferably 16 or less, and still more preferably 14 or less from the viewpoint of the compatibility with the conjugated diene-based rubber and the oil and the adhesiveness to the rubber.
The HLB value is an indicator indicating the balance between hydrophilicity and lipophilicity, is represented by a value of 0 to 20, and can be calculated, for example, by the following expression (I) based on the Griffin method. $HLB value = 20 \times sum of formula weight of hydrophilic moiety / molecular weight$
In the identification of the nonionic surfactant, a molecular weight and a constituent unit are detected and measured through mass spectrometry, a structure is detected and measured through ¹H- and ¹³C-NMR, and a structure can be identified from these results. Accordingly, the HLB value can be determined using the expression (I) from the identified information. Examples of a method for separating the nonionic surfactant from the adhesive composition include a method in which fractionation and separation are performed through reverse phase liquid chromatography.
The content of the surfactant in the emulsion is preferably 1 part by mass or more, more preferably 5 parts by mass or more, and still more preferably 10 parts by mass or more, and is preferably 30 parts by mass or less, more preferably 25 parts by mass or less, and still more preferably 20 parts by mass or less, with respect to 100 parts by mass of the conjugated diene-based rubber from the viewpoint of improving the stability of the emulsion.
A method for producing the emulsion is not particularly limited. It is preferable that the emulsion be prepared by a mechanical method or a chemical method and used at a predetermined concentration set by dilution or the like.
Examples of the mechanical method include methods using a homogenizer, a homomixer, a disperser mixer, a colloid mill, a pipeline mixer, a high-pressure homogenizer, and an ultrasonic emulsifier. The methods may be used alone or in combination.
Examples of the chemical method include various methods, such as an inverse emulsification method, a D-phase emulsification method, an HLB temperature emulsification method, a gel emulsification method, and a liquid crystal emulsification method. An inverse emulsification method is preferred from the viewpoint of obtaining an emulsion having a fine particle diameter in a simple manner. In order to obtain an emulsion having a fine particle diameter, in some cases, an operation may be preferably performed while heating at an appropriate temperature (e.g., 30 to 80°C) to decrease the viscosity of the conjugated diene-based rubber.
In the present invention, in order to enhance the stability of the emulsion, an alkaline substance, such as sodium hydroxide, potassium hydroxide, or amines, may be added, if necessary, to control the pH for use.
When the alkaline substance is used, the amount of the alkaline substance in the emulsion is preferably 0.01 parts by mass or more, more preferably 0.1 parts by mass or more, and still more preferably 1 part by mass or more, and is preferably 20 parts by mass or less, more preferably 15 parts by mass or less, and still more preferably 10 parts by mass or less, with respect to 100 parts by mass of the conjugated diene-based rubber from the viewpoint of improving the stability of the emulsion.

[Viscosity at 50°C of Adhesive Composition]

The adhesive composition has preferably a viscosity of 500 Pa·s or less as measured at 50°C. When the viscosity is within the above-mentioned range, the adhesive composition can be efficiently attached to the fibers, and the adhesive composition is unlikely to be attached to a production facility. Accordingly, the contamination of the production facility can be suppressed. From this viewpoint, the adhesive composition preferably has a viscosity of 250 Pa·s or less, more preferably 100 Pa·s or less, and still more preferably 80 Pa·s or less as measured at 50°C. As the viscosity is lower, the handleability and the degree of process contamination are higher. The adhesive composition preferably has a viscosity of 0.01 Pa·s or more, more preferably 0.03 Pa·s or more, and still more preferably 0.05 Pa·s or more from the viewpoint of the convergence of the fibers. More specifically, the adhesive composition preferably has a viscosity of 0.01 to 250 Pa·s, more preferably 0.03 to 100 Pa·s, and still more preferably 0.05 to 80 Pa·s as measured at 50°C. The viscosity at 50°C of the adhesive composition means a viscosity measured at 50°C with a Brookfield viscometer (B-type viscometer). A rotor and a rotation number in the measurement are appropriately set so as to be closer to the full scale thereof.
Further, the adhesive composition in the present invention may contain an additional component other than the conjugated diene-based rubber, the oil, the crosslinking agent, the surfactant, and the alkaline substance as long as the adhesiveness to the rubber is not inhibited.
Examples of the additional component include water, another polymer, an acid, an antioxidant, a curing agent, a dispersant, a pigment, a dye, an adhesion aid, and carbon black.
When the adhesive composition contains the additional component, the content of the additional component is preferably 10,000 parts by mass or less, more preferably 1,000 parts by mass or less, still more preferably 100 parts by mass or less, still more preferably 50 parts by mass or less, still more preferably 25 parts by mass or less, and still more preferably 10 parts by mass or less, with respect to 100 parts by mass of the conjugated diene-based rubber.

[Methods for Producing Adhesive Composition and Aqueous Adhesive]

The coating in the present invention is formed as follows. For example, the product in which an aqueous adhesive containing the emulsion containing the conjugated diene-based rubber, the crosslinking agent, water, and if necessary, the additional component is attached to the fibers, is subjected to drying and heat treatment to form a coating containing the adhesive composition and/or a reaction product of the adhesive composition on the surface of the fibers.
A method for producing the aqueous adhesive is not particularly limited. The aqueous adhesive can be produced by mixing the components. Specifically, the aqueous adhesive can be obtained by mixing the emulsion containing the conjugated diene-based rubber, the crosslinking agent, water, and if necessary, the additional component through a known method or the like.
The aqueous adhesive may be a one-component adhesive or a two-component adhesive, and a one-component adhesive is preferred. In the case of a one-component adhesive, an environmental load due to shortening of a treatment process can be reduced as well as space-saving can be achieved in a production facility.
Even when the adhesive composition used in the present invention does not contain formaldehyde harmful to a human body and a resin formed of formaldehyde as a raw material, coated fibers having excellent adhesiveness to the rubber can be obtained. When the adhesive composition contains a resin formed of formaldehyde as a raw material in the present invention, examples of the resin include a resorcin-formaldehyde resin, a phenol-formaldehyde resin, a melamine-formaldehyde resin, and derivatives thereof. When the adhesive composition contains the formaldehyde component (formaldehyde and the resin formed of formaldehyde as a raw material), the content of the formaldehyde component is preferably 10 parts by mass or less, more preferably 5 parts by mass or less, still more preferably 3 parts by mass or less, and particularly preferably 1 part by mass or less, with respect to 100 parts by mass of the conjugated diene-based rubber. It is particularly preferable that the formaldehyde component be not substantially contained. The content of the formaldehyde component can be measured through HPLC or the like after the adhesive composition is extracted with a solvent, such as toluene, from the coated fibers.

Fibers used for the coated fibers of the present invention are not particularly limited. Hydrophile fibers are preferred from the viewpoint of affinity to the adhesive composition. In the present invention, the "fibers" include not only short fibers and long fibers, but also forms of non-woven fabric, woven fabric, knitted fabric, felt, and sponge.
Examples of hydrophilic synthetic fibers include synthetic fibers formed of a thermoplastic resin having a hydrophilic functional group such as a hydroxy group, a carboxy group, a sulfonic acid group, or an amino group, and/or a hydrophilic bond such as an amide bond.
Specific examples of the thermoplastic resin include aliphatic polyamides such as a polyvinyl alcohol-based resin, a polyamide-based resin (polyamide 6, polyamide 66, polyamide 11, polyamide 12, polyamide 610, polyamide 612, and polyamide 9C (a polyamide formed of nonanediamine and cyclohexanedicarboxylic acid); semi-aromatic polyamides synthesized from an aromatic dicarboxylic acid and an aliphatic diamine, such as polyamide 9T (a polyamide formed of nonanediamine and terephthalic acid); a wholly aromatic polyamide synthesized from an aromatic dicarboxylic acid and an aromatic diamine, such as poly-p-phenylene terephthalamide), and a polyacrylamide-based resin.
Of these, the polyvinyl alcohol-based resin and the polyamide-based resin are preferred. One kind of the hydrophilic synthetic fibers may be used alone, or two or more kinds thereof may be used in combination. The hydrophilic synthetic fibers may be further subjected to hydrophilization treatment to be described later to further enhance hydrophilicity.
Examples of hydrophilic natural fibers include natural cellulose fibers including wood pulp such as kraft pulp, and non-wood pulp such as cotton pulp and straw pulp.
Examples of hydrophilic regenerated fibers include regenerated cellulose-based fibers, such as rayon, lyocell, cupra, and polynosic.
One kind of each of the natural fibers and the regenerated fibers may be used alone, or two or more kinds thereof may be used in combination. The hydrophilic natural fibers and the regenerated fibers may be further subjected to hydrophilization treatment to be described later to further enhance hydrophilicity.
At least the surface of the hydrophilic fibers needs only to be hydrophilic. For example, the hydrophilic fibers may be fibers obtained by subjecting the surface of hydrophobic fibers to hydrophilization treatment, or core-sheath type composite fibers having a core of a hydrophobic resin and a sheath of a hydrophilic resin. Examples of the hydrophilic resin constituting the sheath include a description concerning the hydrophilic synthetic fibers. Examples of the hydrophobic fibers formed of the hydrophobic resin include polyolefin-based fibers, such as polyethylene and polypropylene, polyester-based fibers, such as polyethylene terephthalate, and wholly aromatic polyester-based fibers. Of these, the polyester-based fibers are preferred.
The hydrophilization treatment is not particularly limited as long as it is treatment that chemically or physically imparts a hydrophilic functional group to the surface of the fibers. The hydrophilization treatment can be performed, for example, by a method of modifying the hydrophobic fibers formed of the hydrophobic resin with a compound containing a hydrophilic functional group, such as an isocyanate group, an epoxy group, a hydroxy group, an amino group, an ether group, an aldehyde group, a carbonyl group, a carboxy group, or a urethane group, or a derivative thereof, a method of modifying the surface through e-beam irradiation, or the like.
The hydrophile fibers used in the present invention are preferably synthetic fibers or regenerated fibers from the viewpoint of use as the coated fibers. Of these, one or more kinds selected from the group consisting of polyamide-based fibers, polyvinyl alcohol-based fibers, polyester-based fibers, and regenerated cellulose-based fibers are preferred.
In the present invention, particularly when the conjugated diene-based rubber contained in the adhesive composition is the modified conjugated diene-based rubber, the use of the hydrophile fibers causes a strong affinity effect to the hydrophile fibers, and the adhesive composition is strongly coupled to the hydrophile fibers. Accordingly, a more excellent adhesive force to the rubber can be achieved.
Polyvinyl alcohol-based fibers are commercially available from Kuraray Co., Ltd. under the product name "vinylon" and polyvinyl alcohol-based fivers having a single fiber fineness of approximately 0.1 to 30 dtex may be suitably used from the viewpoint of suitably using the coated fibers of the present invention for a hose for automobiles, particularly a hydraulic brake hose for automobiles.
In the present invention, one kind of the fibers may be used alone, or two or more kinds thereof may be used in combination.
The fibers used for the coated fibers of the present invention may be monofilaments or multifilaments, and preferably multifilaments.
In the case of the monofilaments, the single fiber fineness is preferably 30 to 20,000 dtex, more preferably 100 to 10,000 dtex, and still more preferably 300 to 5,000 dtex. In the case of the multifilaments, the single fiber fineness is preferably 0.1 30.0 dtex, more preferably 0.5 to 15.0 dtex, and still more preferably 1.0 to 10.0 dtex, and the total fineness is preferably 50 to 10,000 dtex, more preferably 100 to 6,000 dtex, and still more preferably 250 to 4,500 dtex.

[Method for Producing Coated Fibers]

A method for producing the coated fibers of the present invention is not particularly limited. The coated fibers of the present invention are preferably obtained by attaching an aqueous adhesive containing the conjugated diene-based rubber to the fibers, followed by heating. More specifically, the coated fibers are more preferably obtained by a method including: a step of attaching an aqueous adhesive obtained by mixing an emulsion in which the conjugated diene-based rubber, the oil, and the surfactant are mixed, the crosslinking agent, water, and if necessary, the additional component to the fibers; and a step of drying and heating the aqueous adhesive after attaching the aqueous adhesive to the fibers.
It is preferable that the coated fibers be produced by the method in which the aqueous adhesive is attached to the fibers and then heated since the adhesive composition obtained by drying the aqueous adhesive on the surface of the fibers is further subjected a reaction under heat, to produce a reaction product, and the fibers are coated with a coating containing them. The reaction product is a reaction product including the conjugated diene-based rubber bonded to itself via the crosslinking agent and/or a reaction product including the conjugated diene-based rubber bonded to the fibers via the crosslinking agent, and more specifically, the reaction product is preferably a reaction product including the conjugated diene-based rubber bonded to itself via the crosslinking agent and/or a reaction product including the conjugated diene-based rubber bonded to the crosslinking agent. The reaction products are bonded to the fibers to more firmly fix the adhesive composition to the surface of the fibers, improving the adhesiveness to the rubber. That is, when the reaction product contains a reaction product including the conjugated diene-based rubber bonded to itself via the crosslinking agent, the molecular weight of the crosslinking agent contained in the reaction product is moderate, and process contamination is improved while maintaining adhesiveness. Further, when the reaction product contains a reaction product including the conjugated diene-based rubber bonded to the fibers via the crosslinking agent ( more specifically, when the reaction product contains a reaction product including the conjugated diene-based rubber bonded to the crosslinking agent, and the adhesive composition is more firmly fixed to the surface of the fibers), the adhesiveness to the rubber is particularly improved.
A specific method for producing the coated fibers of the present invention is preferably a method (I) for forming the coating containing one or more kinds selected from the group consisting of the adhesive composition and the reaction product of the adhesive composition on the surface of the fibers from the viewpoint of improving the adhesiveness to the rubber.

[Method (I)]

From the viewpoint of improving the adhesiveness to the rubber, the method (I) is preferably a method including the following step I-1. Not only the aqueous adhesive but also another solvent-based (organic solvent-based) adhesive may be used.
Step I-1: a step of attaching the aqueous adhesive to the surface of the fibers.
In the step I-1, a method for attaching the aqueous adhesive to the fibers is not particularly limited, and examples include a method of attaching the aqueous adhesive as it is, and a method of attaching the aqueous adhesive after adding a solvent to the aqueous adhesive, if necessary.
The method for attaching the aqueous adhesive is preferably performed by one or more kinds selected from immersion, a roll coater, an oiling roller, an oiling guide, nozzle (spraying) application, and brush application.
In the present invention, the aqueous adhesive is attached to the fibers, and then aged at a room temperature of approximately 20°C for approximately 3 days to 10 days to obtain the coated fibers of the present invention. In some cases, the following step I-2 may be performed.
Step I-2: a step of subjecting the fibers having the attached aqueous adhesive obtained in the step I-1 to heat treatment.
The heat treatment in the step I-2 is preferably performed at a treatment temperature of 100 to 200°C for a treatment time of 0.1 seconds to 2 minutes. The conjugated diene-based rubber contained in the adhesive composition has a reactive multiple bond, and hence the heat treatment is performed in the presence of oxygen preferably at 200°C or less, more preferably at 175°C or less. When the temperature of the heat treatment is within the above-mentioned range, the conjugated diene-based rubber does not excessively react, and the coated fibers satisfying the conditions (1) and (2) can be obtained. As a result, the coated fibers having excellent adhesiveness to the rubber can be obtained.
From the same viewpoint, the heat treatment time is preferably 90 seconds or less, more preferably 60 seconds or less, and still more preferably 45 seconds or less, and may be 0.1 seconds or more, 0.2 seconds or more, or 0.5 seconds or more.
The attachment amount of the coating in the coated fibers of the present invention is preferably 0.01 to 10.0 parts by mass, more preferably 0.1 to 5.0 parts by mass, and still more preferably 1.0 to 3.0 parts by mass, with respect to 100 parts by mass of the fibers used as a raw material from the viewpoint of improving the adhesiveness of the coated fibers to the rubber.
The coated fibers of the present invention include the fibers and the coatings containing the adhesive composition and/or the reaction product thereof. The coating in the coated fibers of the present invention may contain an additional component in addition to the adhesive composition and/or the reaction product thereof. Examples of the additional component include a crosslinking agent, an acid, a base, an inorganic salt, an organic salt, a pigment, a dye, an antioxidant, a polymerization initiator, and a plasticizer.
The total content of the fibers and the adhesive composition and/or the reaction product thereof in the coated fibers is preferably 80 mass% or more, more preferably 90 mass% or more, and still more preferably 95 mass% or more from the viewpoint of improvement in adhesiveness to the rubber and reinforcing strength.
The content of the coating in the coated fibers of the present invention is preferably 0.1 to 20.0 parts by mass, more preferably 0.3 to 15.0 parts by mass, and still more preferably 0.5 to 10.0 parts by mass, with respect to 100 parts by mass of the fibers. The content of the coating in the coated fibers can be determined by a method described in Examples. Further, the total content of the adhesive composition and/or the reaction product thereof in the coating is preferably 1 to 100 mass%, more preferably 10 to 80 mass%, and still more preferably 20 to 60 mass% from the viewpoint of further exerting the effects of the present invention. From the same viewpoint, the content of the conjugated diene-based rubber in the coating is preferably 1 to 90 mass%, more preferably 5 to 75 mass%, and still more preferably 10 to 50 mass%. The content of the conjugated diene-based rubber in the coating can be determined by a method described in Examples.

In the coated fibers, the single fiber fineness of the fibers as a raw material is preferably 0.1 to 30 dtex, and the coated fibers are preferably multifilaments. The single fiber fineness of the fibers as a raw material may be less than 0.1 dtex, but the fibers having a single fiber fineness of less than 0.1 dtex are difficult to industrially produce. Accordingly, the single fiber fineness of the fibers is preferably 0.1 dtex or more. When the single fiber fineness of the fibers as a raw material is 30 dtex or less, the fiber surface area when the coated fibers are formed is large, and the adhesiveness to the rubber is improved. From the above-mentioned viewpoint, the coated fibers of the present invention are preferably multifilaments, and preferably has a single fiber fineness of 0.3 dtex or more, more preferably 0.5 dtex or more, still more preferably 1 dtex or more, and preferably 20 dtex or less, more preferably 15 dtex or less, and still more preferably 10 dtex or less. More specifically, in the coated fibers of the present invention, the single fiber fineness of the fibers as a raw material is preferably 0.3 to 20 dtex, more preferably 0.5 to 15 dtex, and still more preferably 1 to 10 dtex.
The rubber adhesion force of the coated fibers of the present invention is preferably 15.0 N/25.4 mm or more, more preferably 20.0 N/25.4 mm or more, still more preferably 25.0 N/25.4 mm or more, and still more preferably 30.0 N/25.4 mm, and is usually 200 N/25.4 mm or less. More specifically, the rubber adhesion force of the coated fibers of the present invention is preferably 15.0 to 200 N/25.4 mm, more preferably 20.0 to 200 N/25.4 mm, still more preferably 25.0 to 200 N/25.4 mm, and still more preferably 30.0 to 200 N/25.4 mm. When the rubber adhesion force of the coated fibers is equal to or more than the lower limit value, a woven fabric, a knit fabric, and a molded body having excellent reinforcing strength can be obtained. The rubber adhesion force of the coated fibers can be measured by a method described in Examples.
The coated fibers of the present invention may be used in any form, and are preferably used in the form of a fiber cord, a woven fabric, a knitted fabric, or the like at least part of which includes the coated fibers, and more preferably used as a woven fabric or a knitted fabric at least part of which includes the coated fibers. For example, the coated fibers may be used as a knitted fabric to be adhered to the rubber as described below. Further, the coated fibers may also be used so as to be embedded in a resin, cement, or the like.

[Molded Body]

The molded body of the present invention is not particularly limited as long as it is formed using the coated fibers. In particular, the coated fibers have excellent adhesiveness to the rubber, and hence a molded body formed using the coated fibers and a rubber component (hereinafter also referred to as "rubber molded body") is particularly preferred. The coated fibers used in the rubber molded body are preferably used as a woven fabric or a knitted fabric at least part of which includes the coated fibers, and more preferably used as a laminated body in which a reinforcing layer including a woven fabric or a knitted fabric at least part of which includes the coated fibers, and a rubber layer are laminated, from the viewpoint of holding the form of rubber.
The rubber molded body may be used, for example, as a tire such as a tire for automobiles, a belt such as a conveyor belt or a timing belt, a hose, and a rubber product member such as vibration absorbing rubber, and of these, the rubber molded body is more preferably used as a tire, a belt, or a hose.
In the tire for automobiles, for example, the rubber molded body may be used for various members formed of composite materials including the coated fibers and a rubber component, such as a belt, a carcass ply, a breaker, and a bead tape.
The hose may be used for transporting various fluids in various applications, and is suitable, for example, for a fluid transport hose for automobiles. In particular, the hose is preferably used for a liquid fuel hose for automobiles, a hydraulic brake hose for automobiles, and a refrigerant hose, and more preferably used for a hydraulic brake hose for automobiles.
The rubber molded body is preferably molded by using the coated fibers and a rubber composition obtained by blending a rubber component and a compounding agent usually used in the rubber industry.
The rubber component is not particularly limited, and examples thereof include NR (natural rubber), IR (polyisoprene rubber), BR (polybutadiene rubber), SBR (styrene-butadiene rubber), NBR (nitrile rubber), EPM (ethylene-propylene copolymer rubber), EPDM rubber (ethylene-propylene-non-conjugated diene copolymer rubber), IIR (butyl rubber), halogenated butyl rubber, and CR (chloroprene rubber) . Of these, NR, IR, BR, SBR, EPDM, and CR are preferably used, and EPDM is more preferably used. One kind of the rubber components may be used alone, or two or more kinds thereof may be used in combination. In tire applications, a rubber component generally used in the tire industry may be used. In particular, the use of natural rubber alone, or the use of natural rubber and SBR in combination is preferred. When natural rubber and SBR are combined, the mass ratio of natural rubber to SBR (natural rubber/SBR) is preferably within the range of 50/50 to 90/10 from the viewpoint of suppressing a reduction in physical properties due to vulcanization reversion of rubber.
Examples of the natural rubber include natural rubber and modified natural rubbers such as high-purity natural rubber, epoxidated natural rubber, hydroxylated natural rubber, hydrogenated natural rubber, and grafted natural rubber, which are generally used in the tire industry, for example, TSR (technically specified rubber) such as SMR (TSR from Malaysia), SIR (TSR from Indonesia), and STR (TSR from Thailand), and RSS (ribbed smoked sheet).
As the SBR, a general SBR used in tire applications may be used. Specifically, the styrene content is preferably 0.1 to 70 mass%, more preferably 5 to 50 mass%, and still more preferably 15 to 35 mass%. Further, the vinyl content is preferably 0.1 to 60 mass%, and more preferably 0.1 to 55 mass%.
The weight-average molecular weight (Mw) of the SBR is preferably 100,000 to 2,500,000, more preferably 150,000 to 2,000,000, and still more preferably 200,000 to 1,500,000. When the weight-average molecular weight is within the above-mentioned range, both the workability and the mechanical strength can be achieved. The weight-average molecular weight of the SBR is a weight-average molecular weight in terms of polystyrene determined by measurement through gel permeation chromatography (GPC).
As the SBR, a modified SBR in which a functional group is introduced into the SBR may be used as long as the effects of the present invention are not impaired. Examples of the functional group include an amino group, an alkoxysilyl group, a hydroxy group, an epoxy group, and a carboxy group.
The rubber composition may further contain a filler in addition to the rubber component. Examples of the filler include inorganic fillers, such as carbon black, silica, clay, mica, calcium carbonate, magnesium hydroxide, aluminum hydroxide, barium sulfate, titanium oxide, glass fibers, fibrous fillers, and glass balloon; and organic fillers, such as resin particles, wood powder, fibrous fillers, and cork powder. The fillers are contained in the rubber composition, and hence physical properties, such as mechanical strength, heat resistance, or weather resistance can be improved, the hardness can be adjusted, and the rubber amount can be increased.
Of the fillers, carbon black and silica are preferred from the viewpoint of improving physical properties, for example, improving mechanical strength.
Examples of the carbon black include furnace black, channel black, thermal black, acetylene black, and ketjen black. Of the carbon black, furnace black is preferred from the viewpoint of increasing the cross-linking rate and improving the mechanical strength.
The average particle diameter of the carbon black is preferably 5 to 100 nm, more preferably 5 to 80 nm, and still more preferably 5 to 70 nm. The average particle diameter of the carbon black can be determined by measuring the diameter of each particle with a transmission electron microscope and calculating the average value thereof.
Examples of the silica include wet silica (hydrous silicic acid), dry silica (silicic anhydride), calcium silicate, and aluminum silicate. Of the silica, wet silica is preferred.
The average particle diameter of the silica is preferably 0.5 to 200 nm, more preferably 5 to 150 nm, and still more preferably 10 to 100 nm.
The average particle diameter of the silica can be determined by measuring the diameter of each particle with a transmission electron microscope and calculating the average value thereof.
In the rubber composition, the content of the filler is preferably 20 to 150 parts by mass, more preferably 25 to 130 parts by mass, and still more preferably 25 to 110 parts by mass, with respect to 100 parts by mass of the rubber component.
When a filler other than silica and carbon black is used as the filler, the content of the filler is preferably 20 to 120 parts by mass, more preferably 20 to 90 parts by mass, and still more preferably 20 to 80 parts by mass, with respect to 100 parts by mass of the rubber component. One kind of the fillers may be used alone, or two or more kinds thereof may be used in combination.
The rubber composition may further contain a crosslinking agent for cross-linking the rubber component. Examples of the crosslinking agent include sulfur, sulfur compounds, oxygen, organic peroxides, phenol resins, amino resins, quinone and quinone dioxime derivatives, halogen compounds, aldehyde compounds, alcohol compounds, epoxy compounds, metal halides, and organic metal halides, and silane compounds. One kind of the crosslinking agents may be used alone, or two or more kinds thereof may be used in combination. The content of the crosslinking agent is usually 0.1 to 10 parts by mass, preferably 0.5 to 10 parts by mass, and more preferably 0.8 to 5 parts by mass, with respect to 100 parts by mass of the rubber component from the viewpoint of mechanical properties of a cross-linked product.
For example, when the rubber composition contains sulfur, a sulfur compound, or the like, as the crosslinking agent for cross-linking (vulcanizing) the rubber component, the rubber composition may further contain a vulcanization accelerator. Examples of the vulcanization accelerator include guanidine-based compounds, sulfenamide-based compounds, thiazole-based compounds, thiuram-based compounds, thiourea-based compounds, dithiocarbamic acid-based compounds, aldehyde-amine-based compounds, aldehyde-ammonia-based compounds, imidazoline-based compounds, and xanthate-based compounds. One kind of the vulcanization accelerators may be used alone, or two or more kinds thereof may be used in combination. The content of the vulcanization accelerator is usually 0.1 to 15 parts by mass, and preferably 0.1 to 10 parts by mass, with respect to 100 parts by mass of the rubber component.
For example, when the rubber composition contains sulfur, a sulfur compound, or the like, as the crosslinking agent for cross-linking (vulcanizing) the rubber component, the rubber composition may further contain a vulcanization aid. Examples of the vulcanization aid include fatty acids such as stearic acid, metal oxides such as zinc oxide, and fatty acid metal salts such as zinc stearate. One kind of the vulcanization aids may be used alone, or two or more kinds thereof may be used in combination. The content of the vulcanization aid is usually 0.1 to 15 parts by mass, and preferably 1 to 10 parts by mass, with respect to 100 parts by mass of the rubber component.
When the rubber composition contains silica as the filler, the rubber composition preferably further contains a silane coupling agent. Examples of the silane coupling agent include sulfide-based compounds, mercapto-based compounds, vinyl-based compounds, amino-based compounds, glycidoxy-based compounds, nitro-based compounds, and chlorine-based compounds.
One kind of the silane coupling agents may be used alone, or two or more kinds thereof may be used in combination. The content of the silane coupling agent is preferably 0.1 to 30 parts by mass, more preferably 0.5 to 20 parts by mass, and still more preferably 1 to 15 parts by mass, with respect to 100 parts by mass of silica. When the content of the silane coupling agent is within the above-mentioned range, the dispersibility, the coupling effect, and the reinforcing performance can be improved.
In order to improve the processability, the fluidity, and the like, the rubber composition may contain a process oil such as a silicone oil, an aroma oil, TDAE (treated distilled aromatic extracts), MES (mild extracted solvates), RAE (residual aromatic extracts), a paraffin oil, or a naphthene oil, or a resin component such as an aliphatic hydrocarbon resin, an alicyclic hydrocarbon resin, a C9-based resin, a rosin-based resin, a coumarone-indene-based resin, or a phenol-based resin as a softening agent, if necessary, as long as the effects of the present invention are not impaired. When the rubber composition contains the process oil as the softening agent, the content thereof is preferably less than 50 parts by mass with respect to 100 parts by mass of the rubber component.
In order to improve the weather resistance, the heat resistance, the oxidation resistance, and the like, the rubber composition may contain an additive, such as an antiaging agent, a wax, an antioxidant, a lubricant, a light stabilizer, a scorching inhibitor, a processing aid, a colorant such as a pigment or a dye, a flame retardant, an antistat, a flatting agent, an antiblocking agent, an ultraviolet absorber, a release agent, a foaming agent, an antimicrobial agent, an antifungal agent, or a perfume, if necessary, as long as the effects of the present invention are not impaired. Examples of the antioxidant include hindered phenolic compounds, phosphorus-containing compounds, lactone-based compounds, and hydroxyl-based compounds. Examples of the antiaging agent include amine-ketone-based compounds, imidazole-based compounds, amine-based compounds, phenol-based compounds, sulfur-based compounds, and phosphorus-based compounds. One kind of the additives may be used alone, or two or more kinds thereof may be used in combination.
In a method for producing the rubber molded body, for example, the coated fibers are embedded in the rubber composition before vulcanization, and the rubber composition is then vulcanized to obtain a molded body in which the fibers and the rubber component are bonded via the adhesive component and/or the reaction product thereof.
Examples of the hydraulic brake hose for automobiles include a hydraulic brake hose having an inner rubber layer, an outer rubber layer, and one or two reinforcing layers formed from the coated fibers between the inner rubber layer and the outer rubber layer.
Examples of rubber components constituting the inner rubber layer and the outer rubber layer include those described above. In particular, examples of the rubber component constituting the inner rubber layer include EPDM and SBR, and examples of the rubber component constituting the outer rubber layer include EPDM and CR. The reinforcing layer can be formed by knitting and braiding the coated fibers.
In a method for producing the hydraulic brake hose, a reinforcing layer (a first reinforcing layer) formed by knitting and braiding the coated fibers is formed on the outer surface of the inner rubber layer. When two reinforcing layers are formed, an intermediate rubber layer may be further formed on the outer surface of the first reinforcing layer, and a reinforcing layer (a second reinforcing layer) formed by knitting and braiding the coated fibers may be formed on the outer surface of the intermediate rubber layer. Next, an outer rubber layer can be formed on the outer surface of the reinforcing layer (the first reinforcing layer or the second reinforcing layer), and vulcanized to produce the hydraulic brake hose.
The vulcanization temperature may be appropriately selected depending on the kinds of constituent materials for each layer of the hydraulic brake hose, and the like, and is preferably 200°C or less from the viewpoint of suppressing the deterioration of the rubber and the coated fibers to improve the adhesiveness of the coated fibers to the rubber.

Examples

Hereinafter, the present invention will be described more specifically with reference to Examples and the like, but the present invention is not restricted by the examples.

[Production of Modified Liquid Conjugated Diene-based Rubber]

Production Example 1: Production of Modified Conjugated Diene-based Rubber (A-1)

A sufficiently dried 5 L autoclave was purged with nitrogen, charged with 1,260 g of hexane and 132 g of n-butyllithium (17 mass% hexane solution), and heated to 50°C, 1,260 g of butadiene was sequentially added while controlling the polymerization temperature to 50°C under stirring, and polymerization was performed for 1 hour. After that, methanol was added to terminate the polymerization reaction, and a polymer solution was obtained. Water was added to the resulting polymer solution and stirred to wash the polymer solution with water. The stirring was completed, separation of a polymer solution phase and an aqueous phase was confirmed, and water was then separated. The polymer solution after completing the washing was dried in vacuum at 70°C for 24 hours to obtain an unmodified liquid polybutadiene (A'-1).
Subsequently, 500 g of the resulting unmodified liquid polybutadiene (A'-1) was loaded into a 1 L autoclave purged with nitrogen, 25 g of maleic anhydride and 0.5 g of N-phenyl-N'-(1,3-dimethylbutyl)-p-phenylenediamine (product name "NOCRAC 6C" manufactured by Ouchi Shinko Chemical Industrial Co., Ltd.) were added, and a reaction was allowed to proceed at 170°C for 24 hours to obtain maleic anhydride-modified liquid polybutadiene. To 525 g of the resulting maleic anhydride-modified liquid polybutadiene, 8.2 g of methanol was added, and a reaction was allowed to proceed at 80°C for 6 hours to obtain monomethyl maleate-modified liquid polybutadiene (conjugated diene-based rubber (A-1)).

Production Example 2: Production of Modified Conjugated Diene-based Rubber (A-2)

A sufficiently dried 5 L autoclave was purged with nitrogen, charged with 1,260 g of hexane and 90.0 g of n-butyllithium (17 mass% hexane solution), and heated to 50°C, 1,260 g of butadiene was sequentially added while controlling the polymerization temperature to 50°C under stirring, and polymerization was performed for 1 hour. After that, methanol was added to terminate the polymerization reaction, and a polymer solution was obtained. Water was added to the resulting polymer solution and stirred to wash the polymer solution with water. The stirring was completed, separation of a polymer solution phase and an aqueous phase was confirmed, and water was then separated. The polymer solution after completing the washing was dried in vacuum at 70°C for 24 hours to obtain an unmodified liquid polybutadiene (A'-2).
Subsequently, 500 g of the resulting unmodified liquid polybutadiene (A'-2) was loaded into a 1 L autoclave purged with nitrogen, 25 g of maleic anhydride and 0.5 g of N-phenyl-N'-(1,3-dimethylbutyl)-p-phenylenediamine (product name "NOCRAC 6C" manufactured by Ouchi Shinko Chemical Industrial Co., Ltd.) were added, and a reaction was allowed to proceed at 170°C for 24 hours to obtain maleic anhydride-modified liquid polybutadiene. To 525 g of the resulting maleic anhydride-modified liquid polybutadiene, 8.2 g of methanol was added, and a reaction was allowed to proceed at 80°C for 6 hours to obtain monomethyl maleate-modified liquid polybutadiene (conjugated diene-based rubber (A-2)).

Production Example 3: Production of Modified Conjugated Diene-based Rubber (A-3)

A sufficiently dried 5 L autoclave was purged with nitrogen, charged with 1,260 g of hexane and 28.0 g of n-butyllithium (17 mass% hexane solution), and heated to 50°C, 1,260 g of butadiene was sequentially added while controlling the polymerization temperature to 50°C under stirring, and polymerization was performed for 1 hour. After that, methanol was added to terminate the polymerization reaction, and a polymer solution was obtained. Water was added to the resulting polymer solution and stirred to wash the polymer solution with water. The stirring was completed, separation of a polymer solution phase and an aqueous phase was confirmed, and water was then separated. The polymer solution after completing the washing was dried in vacuum at 70°C for 24 hours to obtain an unmodified liquid polybutadiene (A'-3).
Subsequently, 500 g of the resulting unmodified liquid polybutadiene (A'-3) was loaded into a 1 L autoclave purged with nitrogen, 25 g of maleic anhydride and 0.5 g of N-phenyl-N'-(1,3-dimethylbutyl)-p-phenylenediamine (product name "NOCRAC 6C" manufactured by Ouchi Shinko Chemical Industrial Co., Ltd.) were added, and a reaction was allowed to proceed at 170°C for 24 hours to obtain maleic anhydride-modified liquid polybutadiene. To 525 g of the resulting maleic anhydride-modified liquid polybutadiene, 8.2 g of methanol was added, and a reaction was allowed to proceed at 80°C for 6 hours to obtain monomethyl maleate-modified liquid polybutadiene (conjugated diene-based rubber (A-3)).

[Production of Unmodified Liquid Conjugated Diene-based Rubber]

Production Example 4: Production of Unmodified Conjugated Diene-based Rubber (L-1)

A sufficiently dried 5 L autoclave was purged with nitrogen, charged with 1,260 g of hexane and 90.0 g of n-butyllithium (17 mass% hexane solution), and heated to 50°C, 1,260 g of butadiene was sequentially added while controlling the polymerization temperature to 50°C under stirring, and polymerization was performed for 1 hour. After that, methanol was added to terminate the polymerization reaction, and a polymer solution was obtained. Water was added to the resulting polymer solution and stirred to wash the polymer solution with water. The stirring was completed, separation of a polymer solution phase and an aqueous phase was confirmed, and water was then separated. The polymer solution after completing the washing was dried in vacuum at 70°C for 24 hours to obtain an unmodified liquid polybutadiene (L-1).
Methods for measuring and calculating physical properties of the liquid conjugated diene-based rubbers and the like are as described below. The results are shown in Table 1.

The Mw, Mn, and Mw/Mn of a conjugated diene-based rubber was determined as values in terms of standard polystyrene by gel permeation chromatography (GPC). Measurement devices and conditions are as described below.

· Device: GPC device "GPC8020" manufactured by Tosoh Corporation
· Separation column: "TSKgel G4000HXL" manufactured by Tosoh Corporation
· Detector: "RI-8020" manufactured by Tosoh Corporation
· Eluent: tetrahydrofuran
· Eluent flow rate: 1.0 mL/min
· Sample concentration: 5 mg/10 mL
· Column temperature: 40°C

The melt viscosity at 38°C of the conjugated diene-based rubber was measured with a Brookfield viscometer (manufactured by Brookfield Engineering Labs. Inc.).

Ten mg of the liquid conjugated diene-based rubber was sampled in an aluminum pan, a thermogram was obtained under a temperature increasing rate condition of 10°C/min through differential scanning calorimetry (DSC), and the value of a peak top of DDSC was designated as the glass transition temperature.

The average number of the hydrogen-bonding functional group per molecule of the modified conjugated diene-based rubber was calculated from the equivalent (g/eq) of the hydrogen-bonding functional group of the modified conjugated diene-based rubber and the number-average molecular weight Mn thereof in terms of styrene by the following expression. Average number of hydrogen-bonding functional group per molecule = [(number- average molecular weight (Mn))/(molecular weight of styrene unit) × (average molecular weight of conjugated diene and additional monomer unit other than conjugated diene contained if necessary)]/(equivalent of hydrogen-bonding functional group)
A method for calculating the equivalent of the hydrogen-bonding functional group was appropriately selected depending on the kind of the hydrogen-bonding functional group.
The average number of the hydrogen-bonding functional group per molecule of the monomethyl maleate-modified conjugated diene-based rubber was calculated by determining the acid value of the monomethyl maleate-modified conjugated diene-based rubber and calculating the equivalent (g/eq) of the hydrogen bonding functional group from the acid value.
A sample after a modification reaction was washed four times with methanol (5 mL with respect to 1 g of the sample) to remove impurities, such as an antioxidant, and the sample was then dried under reduced pressure at 80°C for 12 hours. 180 mL of toluene and 20 mL of ethanol were added to 3 g of the sample after the pre-treatment to dissolve the sample, the solution was then subjected to neutralization titration with a 0.1 N ethanol solution of potassium hydroxide, and the acid value thereof was determined by the following expression. $Acid Value (mgKOH / g) = (A - B) \times F \times 5.611 / S$

A: Dropwise addition amount (mL) of 0.1 N ethanol solution of potassium hydroxide needed for neutralization
B: Dropwise addition amount (mL) of 0.1 N ethanol solution of potassium hydroxide for blank containing no sample
F: Titer of 0.1 N ethanol solution of potassium hydroxide
S: Mass (g) of weighed sample

The mass of the hydrogen-bonding functional group contained in 1 g of the monomethyl maleate-modified conjugated diene-based rubber was calculated, and the mass except for the functional group (the mass of the polymer main chain) contained in 1 g of the monomethyl maleate-modified conjugated diene-based rubber was calculated, from the acid value by the following expressions. The equivalent (g/eq) of the hydrogen-bonding functional group was then calculated by the following expression. [Mass of hydrogen-bonding functional group per gram] = [acid value]/[56.11] × [molecular weight of hydrogen-bonding functional group]/1000 [Mass of polymer main chain per gram] = 1 - [mass of hydrogen-bonding functional group per gram] [Equivalent of hydrogen-bonding functional group] = [mass of polymer main chain per gram]/([mass of hydrogen-bonding functional group per gram]/[molecular weight of hydrogen-bonding functional group])

[Table 1]

Table 1

Modified conjugated diene-based rubber	Mw (×10³)	Mn (×10³)	Molecular weight distribution (Mw/Mn)	Melt viscosity (Pa·s) at 38°C	Glass transition temperature (°C)	Kind of hydrogen-bonding functional group	Average number of hydrogen-bonding functional group per molecule
L-1	8.7	8.1	1.07	1.5	-95	-	-
A-1	5.9	5.6	1.05	2.0	-85	Monomethyl maleate group	3
A-2	8.7	8.1	1.07	3.8	-95	Monomethyl maleate group	4
A-3	31	29	1.07	198	-88	Monomethyl maleate group	7

Preparative Example 1: Preparation of Emulsion (E-1) of Modified Conjugated Diene-based Rubber (A-1)

Fifty g of the modified conjugated diene-based rubber (A-1) and 100 g of triglyceride 2-ethylhexanoate (hereinafter also referred to as "EHTG," product name "EXCEPARL TGO" manufactured by Kao Corporation, vapor pressure at 20°C: 1.7×10^-7 Pa) were stirred until the mixture was homogeneous.
Further, 9 g of a nonionic surfactant (HLB value = 12.4, product name "ADEKA TOL PC-8" manufactured by ADEKA Corporation) was added and stirred for 5 minutes.
Subsequently, 341 g of 0.06 mol/L aqueous ammonia solution was added in small portions with stirring to obtain an emulsion (E-1) of the mixture of the modified conjugated diene-based rubber (A-1) and the oil.

Preparative Example 2: Preparation of Emulsion (E-2) of Modified Conjugated Diene-based Rubber (A-2)

An emulsion (E-2) of a mixture of the modified conjugated diene-based rubber (A-2) and the oil was obtained in the same manner as in Preparative Example 1 except that the kind of a conjugated diene-based rubber to be used was changed to A-2.

Preparative Example 3: Preparation of Emulsion (E-3) of Modified Conjugated Diene-based Rubber (A-3)

An emulsion (E-3) of a mixture of the modified conjugated diene-based rubber (A-3) and the oil was obtained in the same manner as in Preparative Example 1 except that the kind of a conjugated diene-based rubber to be used was changed to A-3.

Preparative Example 4: Preparation of Emulsion (E-4) of Modified Conjugated Diene-based Rubber (A-2)

An emulsion (E-4) of a mixture of the modified conjugated diene-based rubber (A-2) and the oil was obtained in the same manner as in Preparative Example 2 except that a surfactant to be used was changed to two kinds of nonionic surfactants (product name "ADEKA TOL TN-40" and "ADEKA TOL LB-53B" manufactured by ADEKA Corporation).

Preparative Example 5: Preparation of Emulsion (E-5) of Mixture of Two Modified Conjugated Diene-based Rubbers (A-2 and A-3)

An emulsion (E-5) of a mixture of two kinds of the modified conjugated diene-based rubbers (A-2 and A-3) and the oil was obtained in the same manner as in Preparative Example 1 except that the kind of a conjugated diene-based rubber to be used was changed to two kinds: A-2 and A-3, the amount of A-2 was set to 12.5 g, and the amount of A-3 was set to 37.5 g.

Preparative Example 6: Preparation of Emulsion (E-6) of Mixture of Two Modified Conjugated Diene-based Rubbers (A-2 and A-3)

An emulsion (E-6) of a mixture of two kinds of the modified conjugated diene-based rubbers (A-2 and A-3) and the oil was obtained in the same manner as in Preparative Example 5 except that the usage amounts of the conjugated diene-based rubbers A-2 and A-3 to be used were changed to 37.5 g and 12.5 g, respectively.

Preparative Example 7: Preparation of Emulsion (E-7) of Unmodified Conjugated Diene-based Rubber (L-1)

An emulsion (E-7) of a mixture of the unmodified conjugated diene-based rubber (L-1) and the oil was obtained in the same manner as in Preparative Example 1 except that the unmodified conjugated diene-based rubber L-1 was used instead of the modified conjugated diene-based rubber.

The emulsion (E-1) prepared by the above-mentioned method, an isocyanate compound (product name "SUS268-A" manufactured by Meisei Chemical Works, Ltd.), an epoxy resin (product name "DENACOL EX-512" manufactured by Nagase ChemteX Corporation), and water were mixed so as to satisfy a composition listed in Table 2, to prepare an aqueous adhesive (AD-1).
Next, polyvinyl alcohol (PVA) fibers (product name "KURALON 1239", total fineness: 1,330 dtex, single fiber fineness: 6.65 dtex, Kuraray Co., Ltd.) were immersed in the resulting aqueous adhesive, and then squeezed with a roller.
After that, the resulting fibers were subjected to drying treatment at 115°C for 30 seconds, further subjected to heat treatment at 150°C for 30 seconds, and wound to produce PVA fibers coated with a coating containing one or more kinds selected from the group consisting of an adhesive composition and/or a reaction product of the adhesive composition.

PVA fibers coated with a coating were produced in the same manner as in Example 1 except that each of the composition of the aqueous adhesive was changed as described in Table 2.

[Table 2]

Table 2

Aqueous adhesive	Blending (part by mass)
	Emulsion of mixture of modified conjugated diene-based rubber and oil		Crosslinking agent component		Water
	Kind	Usage amount	Isocyanate compound	Epoxy compound	Water
AD-1	E-1	13.3	0.72	0.28	85.7
AD-2	E-2	13.3	0.72	0.28	85.7
AD-3	E-3	13.3	0.72	0.28	85.7
AD-4	E-2	13.3	-	-	86.7
AD-5	E-3	13.3	-	-	86.7
AD-6	E-4	13.3	0.72	0.28	85.7
AD-7	E-4	31.9	1.73	0.67	65.7
AD-8	E-5	13.3	0.72	0.28	85.7
AD-9	E-6	13.3	0.72	0.28	85.7
AD-10	E-7	13.3	0.72	0.28	85.7

Coated fibers to which the adhesive composition was applied were sampled so as to have a yarn length of 100 m, and the mass of the fibers was measured. The fineness (unit: dtex) of the coated fibers to which the adhesive composition was applied was calculated by (the mass (unit: g) of the yarn per 100 m)) × 100.

Fibers before applying the adhesive composition were sampled so as to have a yarn length of 100 m, and the mass after treatment at 105°C for 4 hours (the mass before the treatment) was measured.
Next, the fibers after applying the adhesive composition and performing drying and heat treatment through the methods described in each example were sampled so as to have the same length, and then treated at 105°C for 4 hours, similarly, and the mass of the fibers after the treatment (the mass before the treatment) was measured.
The attachment amount of the adhesive composition (coating) with respect to 100 parts by mass of the fibers before applying the adhesive composition was calculated by [(mass after treatment)-(mass before treatment)]×100/(mass before treatment).
In Table 2, the content (part by mass) of each component in the aqueous adhesive was calculated from the mass ratio of the components (the conjugated diene-based rubber, EHTG, the isocyanate compound, and the epoxy resin) in the aqueous adhesive.

Ten g of the PVA fibers having the coating containing one or more kinds selected from the group consisting of the adhesive composition and the reaction product of the adhesive composition produced in each of Examples 1 to 7 and Comparative Examples 1 to 3 were immersed in tetrahydrofuran (THF), and the coating on the surface of the fibers was extracted. The extract liquid was concentrated with an evaporator, dried in vacuum at 40°C for 16 hours, and then dissolved again in THF to prepare a solution having a concentration of 0.1 w/v%. This solution was subjected to GPC analysis under the following conditions. A molecular weight distribution curve determined by an RI detector is determined using a polymethyl methacrylate (PMMA) as a calibration curve standard by an analyzing software provided with an analyzer. The resulting detection data were subjected to extraction analysis in a detection time range of 8.1 to 10.6 minutes.

Measurement device: OMNISEC RESOLVE, OMNISEC REVEAL (Malvern)
Sample concentration: 0.1 w/v%
Mobile phase solvent: THF
Injection volume: 100 µL
Flow rate: 1.0 mL/min
Measurement temperature: 40°C
Filter filtration: 0.45 µm filter
Column: KF806L (shodex)
Detector: RI detector provided with device
Standard for device calibration: PMMA
Analyzing software: OMNISEC software

In the molecular weight distribution curve obtained by GPC analysis, whether a peak is present in a molecular weight range of 2,600 to 19,000 was judged, and when the peak is present, the molecular weight was calculated.

In the molecular weight distribution curve obtained by GPC analysis, (A) represents the area under the curve in a molecular weight range of 2,600 to 19,000 and (B) represents the area under the curve in a molecular weight range of 19,000 to 540,000. The peak areas (A) and (B) were calculated when the molecular weight range was analyzed by the analyzing software provided with the analyzer (OMNISEC software), and the area ratio [(A)/(B)] was calculated.

For the coated fibers obtained in each of Examples 1 to 7 and Comparative Examples 1 to 3, a sheet for evaluation was prepared by the following method. Next, the force (N/25.4 mm) required for T-peeling of the coated fibers from the rubber (when the coated fibers were peeled at an angle of 180°) was measured and then evaluated as the rubber adhesion force. The results are shown in Table 3.
The evaluation results of the rubber adhesion force show that as the value is larger, the adhesiveness of the coated fibers to the rubber is higher. The sheet for evaluation was prepared as follows.

· Production of Sheet for Evaluation

The coated fibers produced in each of Examples 1 to 7 and Comparative Examples 1 to 3 were twisted at 80 T/m, and 38 of the coated fibers were parallelly arranged on a masking tape in a blind pattern so that the fibers were not superposed, and fixed. The fixed coated fibers were superposed with an unvulcanized rubber composition (hereinafter also referred to as "EPDM unvulcanized rubber," width: 25.4 mm, length: 240 mm) containing as a main component EPDM rubber prepared separately using EPDM rubber ("ESPRENE 501A" manufactured by Sumitomo Chemical Co., Ltd.) at the following blending composition (the length of the portion where the fibers and the EPDM unvulcanized rubber were superposed was 190 mm). Next, the laminate was press-vulcanized under conditions of 150°C and a pressure of 20 kg/cm² for 30 minutes to produce a sheet for evaluation.

(Blending Composition of EPDM Unvulcanized Rubber)

EPDM rubber: 100 parts by mass
Filler (carbon black): 60 parts by mass
Softening agent (paraffin-based process oil): 20 parts by mass
Crosslinking agent (sulfur powder): 1.5 parts by mass
Vulcanization aid (two kinds of zinc oxides and stearic acid): 6 parts by mass
Vulcanization accelerator (thiazole-based, thiuram-based): 1.5 parts by mass

After the PVA fibers (5 kg) having a coating obtained by applying the aqueous adhesive to the fibers in each of Examples 1 to 7 and Comparative Examples 1 to 3 as described in each of examples were wound, the degree (gumming up) of contamination of a holding roller through which the coated fibers were passed after drying and heat treatment was determined in accordance with the following evaluation criteria. The results are shown in Table 3.

· Evaluation criteria

E (excellent): There is no roller contamination by gumming up, or it is extremely limited. The spinning operability is satisfactory.
G (good): There is little roller contamination by gumming up. The spinning operability is not impaired.
B (bad): Roller contamination by gumming up is remarkable. During spinning, single yarns are taken and wound during spinning. The spinning operability is impaired.

The coated fibers (multifilaments having a total fineness of 1,330 dtex and a single fiber fineness of 6.65 dtex) produced in each of Examples 1 to 7 and Comparative Examples 1 to 3 were cut to a length of 120 cm, and the upper end portion of the coated fibers was tied to a hook mounted on a wall surface, and fixed. A 1 kg weight was tied to the lower end portion of the fixed coated fibers so that the weight did not touch the ground, and held in a suspended state. The fibers were cut at a position 100 cm from the knot on the upper side of the fibers tied to the hook mounted on the wall surface, and the length of the coated fibers with disturbed convergence was measured from the resulting lower end after cutting. The results are shown in Table 3.
This evaluation shows that a shorter length of the coated fibers with disturbed convergence provides more excellent convergence.

The coated fibers obtained in each of Examples 1 to 7 and Comparative Examples 1 to 3 were twisted at 80 T/m and subjected to a test. The coated fibers were set to a metal abrasion tester shown in Fig. 1, a moving stage was moved back and forth 1,000 times to produce a sample damaged by friction with metal. The breaking strength of the produced sample was measured, and the residual strength after metal friction was calculated by [breaking strength after metal friction]/[breaking strength before metal friction]×100. The results are shown in Table 3.
This evaluation shows that a higher residual strength provides less damage caused by abrasion.

[Table 3]

Table 3

	Kind of aqueous adhesive	Attachment amount (*1)	GPC measurement of extract		Kind of fibers
	Kind of aqueous adhesive	Attachment amount (*1)	Peak in molecular weight range of 2,600 to 19,000	Area ratio (A/B)	Kind of fibers
Example 1	AD-1	1.7	7,042	8.2	PVA fibers
Example 2	AD-2	1.3	10,304	2.5	PVA fibers
Comparative Example 1	AD-3	1.4	No peak detection	8.0	PVA fibers
Comparative Example 2	AD-4	1.7	10,817	9.3	PVA fibers
Comparative Example 3	AD-5	1.8	39,201	0.2	PVA fibers
Example 3	AD-6	1.2	9,969	7.4	PVA fibers
Example 4	AD-7	4.5	10,042	1.2	PVA fibers
Example 5	AD-8	1.7	11,465	0.6	PVA fibers
Example 6	AD-9	1.8	11,056	1.8	PVA fibers
Example 7	AD-10	1.9	8,993	3.0	PVA fibers

*1 The attachment amount (part by mass) of coating with respect to 100 parts by mass of fibers

Table 3 (continued)

	Performance evaluation
	Rubber adhesion force (N/25.4 mm)	Process contamination	Convergence (cm)	Residual strength (%) of fibers after F/M friction test
Example 1	33.2	E	92	79.2
Example 2	34.0	E	74	82.6
Comparative Example 1	36.1	B	84	68.2
Comparative Example 2	6.9	G	151	83.4
Comparative Example 3	28.3	B	104	82.8
Example 3	30.6	E	53	80.3
Example 4	29.6	E	77	83.2
Example 5	32.9	G	76	82.8
Example 6	31.3	G	87	81.2
Example 7	32.2	E	60	78.7

As apparent from the results of Examples and Comparative Examples, the present invention can provide coated fibers having excellent adhesiveness to rubber. In addition, the present invention can provide coated fibers that have excellent convergence and high strength after friction and can be produced while suppressing contamination of a production facility, and a molded body using the same.
In all Examples, values effective for practical use of adhesiveness and residual strength of fibers were shown. Further, satisfied values of convergence that affects processability were shown. In particular, in Examples 2, 3, and 7, excellent convergence was shown. In Examples 1 to 4 and 7 using only a conjugated diene-based rubber having a low molecular weight as a raw material, the process contamination is lower than that in Examples 5 and 6 using two kinds of conjugated diene-based rubbers having different molecular weights, and the results are satisfactory, and an influence of a conjugated diene-based rubber having a high molecular weight that is presumed to have a complicated cross-linking structure is considered. In Example 4, the attachment amount of the coating is large, but the process contamination is low and the results are satisfactory. The adhesiveness is substantially the same as other Examples.

Reference Signs List

1: fiber fixing base
2: moving stage
3: mirror-finished chrome plating processing guide
4: free roller
5: load (165 g)
6: movement range (90 mm) of moving stage
7: coated fibers sample

Claims

Coated fibers obtained by coating fibers with a coating containing one or more kinds selected from the group consisting of an adhesive composition containing a conjugated diene-based rubber and a reaction product of the adhesive composition, wherein a molecular weight distribution curve obtained by GPC analysis of the coating satisfies the following conditions (1) and (2):
<Condition (1)>
at least one peak is present in a molecular weight range of 2,600 to 19,000; and

<Condition (2)>
an area ratio [(A)/(B)] in which (A) represents an area under the curve in a molecular weight range of 2,600 to 19,000 and (B) represents an area under the curve in a molecular weight range of 19,000 to 540,000 is 0.5 to 9.0.
The coated fibers according to claim 1, wherein the adhesive composition further contains a crosslinking agent.
The coated fibers according to claim 2, wherein the reaction product is a reaction product including the conjugated diene-based rubber bonded to itself via the crosslinking agent and/or a reaction product including the conjugated diene-based rubber bonded to the fibers via the crosslinking agent.
The coated fibers according to claim 2 or 3, wherein the crosslinking agent is one or more kinds selected from the group consisting of an epoxy resin and an isocyanate resin.
The coated fibers according to any one of claims 1 to 4, wherein an attachment amount of the coating is 0.01 to 10.0 parts by mass with respect to 100 parts by mass of the fibers.
The coated fibers according to any one of claims 1 to 5, wherein the molecular weight distribution curve of the coating obtained by GPC analysis has a peak in a molecular weight range of 2,600 to 15,000.
The coated fibers according to any one of claims 1 to 6, wherein the conjugated diene-based rubber is in a liquid state.
The coated fibers according to any one of claims 1 to 7, wherein the conjugated diene-based rubber has a monomer unit derived from one or more kinds selected from the group consisting of butadiene, isoprene, chloroprene, acrylonitrile, and farnesene.
The coated fibers according to any one of claims 1 to 8, wherein the adhesive composition further contains an oil having a vapor pressure at 20°C of 10 Pa or less.
The coated fibers according to any one of claims 1 to 9, wherein the fibers are one or more kinds selected from the group consisting of polyamide-based fibers, polyvinyl alcohol-based fibers, polyester-based fibers, and regenerated cellulose-based fibers.
The coated fibers according to any one of claims 1 to 10, wherein the coated fibers are obtained by attaching an aqueous adhesive containing the conjugated diene-based rubber to the fibers, followed by heating.
A molded body using the coated fibers according to any one of claims 1 to 11.