Poly(p-phenylene terephthalamide) fiber composite, code using the same

Abstract

To provide a polyparaphenylene terephthalamide fiber composite that does not require a drying step after application of the curable epoxy compound and has an excellent adhesion to rubber and resin, and to provide a cord using the same.SOLUTION: Provided are: a polyparaphenylene terephthalamide fiber composite characterized in that a cured film of a curable epoxy compound and an uncured curable epoxy compound in an amount exceeding the cured amount are adhered to the surface of the polyparaphenylene terephthalamide fiber; an adhesive-treated polyparaphenylene terephthalamide fiber composite in which an adhesive is adhered to the composite; and a cord in which they are used.SELECTED DRAWING: None

Description

[Technical Field]

[0001] This invention relates to a poly(p-phenylene terephthalamide) fiber composite and a cord using the same. [Background technology]

[0002] Poly(p-phenylene terephthalamide) fibers (sometimes referred to as "PPTA") are synthetic fibers that possess high functionality such as high strength, high modulus of elasticity, high heat resistance, non-conductivity, and rust resistance, as well as the flexibility and lightness characteristic of organic fibers. For this reason, they are used as reinforcing fibers for various tires, belts, conveyors, etc. However, because PPTA fibers have poor adhesion to rubber and resins, it is known that PPTA fibers are treated with epoxy compounds to create epoxy pre-treated yarn in order to improve adhesion.

[0003] For example, Patent Document 1 discloses a method for improving the adhesion of aramid fibers by using an organic amine as a curing agent for an epoxy compound and forming an epoxy coating with a free epoxy compound content of 10 mmol / 1 kg of fiber or less. Specifically, the document discloses a method in which an epoxy compound and a curing agent are simultaneously applied to undried yarn, followed by drying and curing at 240°C (Example 1, etc.), and a method in which an epoxy compound and a curing agent are simultaneously applied to dried yarn, followed by drying and curing at 240°C (Example 2, etc.).

[0004] Patent Document 2 discloses that by applying an oil containing a curable epoxy compound to PPTA fibers with a moisture content of 15 to 200% by mass, and impregnating the fiber skeleton with the curable epoxy compound, a PPTA fiber composite is created that retains the inherent high heat resistance and high Young's modulus of PPTA fibers while having high adhesive strength and is useful for reinforcing rubber materials and resin materials. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 59-094640 [Patent Document 2] Japanese Patent Publication No. 2012-207326 [Disclosure of the Invention] [Problems that the invention aims to solve]

[0006] However, the epoxy pretreatment described in References 1 and 2 requires a "drying process" in addition to the spinning process, where the yarn is dried after applying the curable epoxy compound, which presents challenges in terms of manufacturing and cost. Furthermore, Reference 1 presents environmental challenges not only due to its high manufacturing costs, but also because it requires organic amines, which are a concern as environmentally harmful substances, to cure the curable epoxy compound.

[0007] The object of the present invention is to provide a poly(p-phenylene terephthalamide) fiber composite that does not require a curing agent (organic amine) for curing the curable epoxy compound and a drying step for drying the poly(p-phenylene terephthalamide) fibers treated with the curable epoxy compound, and that has excellent adhesion to rubber and resin, as well as a cord using the same. [Means for solving the problem]

[0008] To achieve the above objectives, the present inventors conducted diligent research and found that by applying a curable epoxy compound, or a curable epoxy compound and a water-soluble oil, to poly-p-phenylene terephthalamide fibers with a predetermined moisture content, a cured film of the curable epoxy compound is formed on the fiber surface; the poly-p-phenylene terephthalamide fibers with the cured film formed do not require a drying process; there is an optimal range for the degree of curing of the curable epoxy compound; and the adhesive-treated poly-p-phenylene terephthalamide fiber composite obtained by attaching an adhesive to the resulting poly-p-phenylene terephthalamide fiber composite exhibits significantly improved adhesion, thus leading to the present invention.

[0009] In other words, the present invention is as follows:

[0010] (1) Curing of a curable epoxy compound on the surface of a poly(p-phenylene terephthalamide) fiber quilt A poly(p-phenylene terephthalamide) fiber composite characterized by the adhesion of a film (cured) and an uncured curable epoxy compound (free) in a molar ratio (cured / free) in the range of 0.3 to 1.0. (2) Hardening quilt The poly(p)phenylene terephthalamide fiber composite described in (1) above, wherein the film and the uncured curable epoxy compound are obtained by applying a curable epoxy compound, or a curable epoxy compound and a water-soluble oil (but without applying a curing agent). (3) The poly(p-phenylene terephthalamide) fiber composite according to (1) or (2) above, wherein the water solubility of the curable epoxy compound is 85% or more. (4) An adhesive-treated poly-p-phenylene terephthalamide fiber composite obtained by attaching an adhesive to any of the poly-p-phenylene terephthalamide fiber composites described in (1) to (3) above. (5) A code made using a poly(p)phenylene terephthalamide fiber composite described in any of (1) to (3) above or an adhesive-treated poly(p)phenylene terephthalamide fiber composite described in (4) above. (6) Flocculated short fibers obtained by cutting the poly(p-phenylene terephthalamide) fiber composite described in any of (1) to (3) above or the adhesive-treated poly(p-phenylene terephthalamide) fiber composite described in (4) above. [Effects of the Invention]

[0011] In the poly(p-phenylene terephthalamide) fiber composite of the present invention, a coating is formed on the surface of the poly(p-phenylene terephthalamide) fiber when the curable epoxy compound partially hardens, making it possible to fix the curable epoxy compound to the fiber surface. In addition, by leaving some uncured epoxy compound, the uncured epoxy compound functions as a chemical bonding point with adhesives such as RFL, resulting in superior adhesion compared to conventionally obtained epoxy pre-treated yarns. [Modes for carrying out the invention]

[0012] In the present invention, poly(p-phenylene terephthalamide) (PPTA) is a polymer obtained by polycondensation of terephthalic acid and paraphenylenediamine, and copolymers with small amounts of dicarboxylic acid and diamine can also be used. The molecular weight of the polymer or copolymer is usually preferably 20,000 to 25,000.

[0013] Conventional PPTA fibers are obtained by dissolving PPTA in concentrated sulfuric acid, extruding the viscous solution through a spinneret to spin it into filaments, neutralizing and washing it with an alkaline aqueous solution, and finally drying and heat-treating it at 120-500°C.

[0014] In contrast, the PPTA fiber composite of the present invention can be obtained by spinning PPTA fibers into filaments, neutralizing and washing them with an alkaline aqueous solution, drying them at a low temperature to adjust the moisture content to 3-15% by mass, and then applying a curable epoxy compound, or a curable epoxy compound and a water-soluble oil agent to the PPTA fibers. In this specification, the moisture content of the fibers is the ratio of moisture to the fiber mass when the moisture content of poly(p-phenylene terephthalamide) fibers is converted to 0%, and is measured by the method described below. The PPTA fiber composite of the present invention obtained by this method is characterized in that the curable epoxy compound is partially cured, and a cured film of the curable epoxy compound and uncured curable epoxy compound are attached to the surface of the PPTA fibers.

[0015] Here, the water adhering to the surface of the PPTA fibers in the state of being dried at a low temperature after neutralization and washing contains alkali ions derived from the alkali used in the neutralization treatment. Therefore, the higher the moisture content of the PPTA fibers, the greater the amount of alkali ions around the PPTA fibers. As a result, the higher the moisture content of the PPTA fibers, the easier it is to form a cured film of the curable epoxy compound due to the catalytic action of the alkali ions, and the uncured curable epoxy compound tends to decrease. On the other hand, the lower the moisture content of the PPTA fibers, the smaller the amount of alkali ions around the PPTA fibers, so it becomes difficult to form a cured film of the epoxy compound on the surface of the PPTA fibers. When an excessive amount of uncured epoxy compound is present, there may be an inconvenience such that it is necessary to cure the uncured epoxy compound by a drying treatment in order to improve the adhesiveness of the PPTA fiber composite.

[0016] In the present invention, if the moisture content of the PPTA fibers at the time of applying the curable epoxy compound and the water-soluble sizing agent is 15% by mass or less, the curable epoxy compound can be cured using the alkali ions obtained from the water adhering to the surface of the PPTA fibers as a catalyst. Since it becomes possible to twist, cut, or perform an adhesive treatment on the PPTA fiber composite without providing a drying step for drying the PPTA fiber composite, as a result, one drying step can be omitted.

[0017] On the other hand, in the present invention, when the moisture content of the PPTA fibers at the time of applying the curable epoxy compound and the water-soluble sizing agent exceeds 15% by mass, the frictional resistance with metal or ceramic rolls in the subsequent processing steps significantly increases, which becomes a factor deteriorating the process passing property due to rubbing fluff or the like. Further, when the moisture content of the PPTA fibers at the time of applying the curable epoxy compound and the water-soluble sizing agent is less than 3% by mass, there is no residual water on the surface of the PPTA fibers, so it becomes difficult to cure the curable epoxy compound.

[0018] The moisture content of the PPTA fibers at the time of applying the curable epoxy compound and the water-soluble sizing agent is preferably in the range of 3 to 15% by mass, more preferably 5 to 13% by mass, and even more preferably 9 to 11% by mass.

[0019] In the PPTA fiber composite of the present invention, a cured film (cured) of the curable epoxy compound and an uncured curable epoxy compound (free) are present. The functions of these two types of curable epoxy compounds are not clear, but are presumed to be as follows: The presence of the uncured curable epoxy compound (free epoxy compound) causes a strong chemical bond to form between the uncured epoxy compound and the adhesive (RFL, etc.). On the other hand, a cured film of the curable epoxy compound exists on the surface of the PPTA fiber composite, and the adhesive can be immobilized on the PPTA fiber composite through affinity or reaction with the uncured epoxy compound. Furthermore, the cured film of the curable epoxy compound on the surface of the PPTA fiber composite itself exhibits affinity for the adhesive, as is conventionally known, and is presumed to improve the adhesion between the PPTA fiber composite and the adhesive in combination with the action of the uncured curable epoxy compound.

[0020] The molar ratio (cured / free) of the cured film (cured) of the curable epoxy compound to the uncured curable epoxy compound (free) is preferably 0.3 to 1.0, more preferably 0.5 to 1.0, and particularly preferably 0.7 to 0.9. The molar ratio (cured / free) of the cured film (cured) to the uncured epoxy compound (free) can be adjusted by changing the moisture content of the PPTA fibers and / or the type of oil used.

[0021] In the PPTA fiber composite of the present invention, one or more curable epoxy compounds selected from aliphatic epoxy compounds and epoxy compounds having aromatic rings can be used as the curable epoxy compound to be imparted to the PPTA fibers having a moisture content of 15% by mass or less. When two or more are used, they may be used in combination or separately.

[0022] As the aliphatic epoxy compound, one or more mixtures selected from glycidyl ether compounds of polyhydric alcohols such as glycerol, sorbitol, and polyglycerol are preferred. Examples include glycerol diglycidyl ether, glycerol triglycidyl ether, polyglycerol polyglycidyl ether, sorbitol polyglycidyl ether, trimethylolpropane polyglycidyl ether, and pentaerythritol polyglycidyl ether. Among these epoxy compounds, polyfunctional epoxy compounds (polyepoxides) having two or three glycidyl groups are more preferred.

[0023] As epoxy compounds having aromatic rings, one or more mixtures selected from bisphenol-type epoxy resins are preferred. Examples include glycidyl ether compounds such as bis(4-hydroxyphenyl)methane [bisphenol F], 2,2-bis(4-hydroxyphenyl)propane [bisphenol A], and 2,2-bis(3-methyl-4-hydroxyphenyl)propane [bisphenol C]. Among these, glycidyl ether compounds of bisphenol A and bisphenol F are more preferred because they are liquid at room temperature.

[0024] The curable epoxy compound used in this invention preferably has a water solubility of 85% or more, more preferably 90% or more, and particularly preferably 95% or more. Water solubility refers to the solubility when 10 parts by mass of the curable epoxy compound are dissolved in 90 parts by mass of water at room temperature. If the water solubility is less than 85%, the compatibility between the curable epoxy compound and the water adhering to the surface of the PPTA fiber after spinning, neutralization, and washing decreases, and the alkaline ions (curing agent) in the adhering water cannot mix with the curable epoxy compound, making it difficult to form a cured film.

[0025] Among curable epoxy compounds, aliphatic epoxy compounds are preferred due to their low viscosity and ease of application during the spinning process. Glycerol-based epoxy compounds such as glycerol diglycidyl ether and glycerol triglycidyl ether are particularly preferred from the viewpoint of high water solubility and ease of forming a cured film.

[0026] In this invention, the curable epoxy compound and the water-soluble oil may be applied separately in two steps, or they may be applied as a mixture. When applied in two steps, the order does not matter. The preferred application method is to apply the curable epoxy compound and the water-soluble oil as a mixture. This is because applying them separately to the PPTA fibers would result in a two-step process, which would be less economical.

[0027] As a water-soluble oiling agent, polyglycol esters are preferred due to their high compatibility with epoxy compounds and high smoothness, which is necessary for fiber oiling agents. Polyglycol esters also have the effect of reducing abrasion with the traveler when twisting PPTA fiber composites. Fatty acid polyglycol esters are a preferred example of polyglycol esters.

[0028] Examples of fatty acid polyglycol esters include ester compounds of fatty acids and polyalkylene glycols represented by general formula (I) and / or general formula (II). General formula (I) represents monoester type compounds, and general formula (II) represents diester type compounds. [ka] (In the formula, R 1 R is an alkyl or alkenyl group having 5 to 30 carbon atoms. 2 m is an alkylene group with 2 to 3 carbon atoms, and m is an oxyalkylene group (R 2 This is an integer representing the average number of moles added (R). 2 In -O), the same oxyalkylene group may be attached, or two or more different oxyalkylene groups may be attached.

[0029] [ka] (In the formula, R 1 and R 3 Both are alkyl or alkenyl groups having 5 to 30 carbon atoms, and may be the same or different.2 is an alkylene group having 2 to 3 carbon atoms, and n is an integer representing the average number of moles of oxyalkylene group (R 2 -O) added. In (R 2 -O), the same oxyalkylene group may be added, or two or more kinds of oxyalkylene groups may be added.)

[0030] In the above general formula (I) or (II), when the number of carbon atoms of R 1 and R 3 is less than 5, the convergence property of the PPTA fiber is low, so the process passing property becomes poor. When it exceeds 30, the hydrophobicity of the ester compound becomes high, so it cannot be mixed with the curable epoxy compound or the affinity may become low. Considering the adhesion of the ester compound to the rubber and the solubility with the curable epoxy compound, the number of carbon atoms of R 1 and R 3 is preferably 7 to 28, more preferably 9 to 26, still more preferably 11 to 24, and particularly preferably 1 to 3. 22 is.

[0031] Specific examples of the fatty acid constituting the ester compound represented by the general formula (I) or (II) include saturated or unsaturated fatty acids. For example, caproic acid, caprylic acid, capric acid, lauric acid, myristic acid, palmitic acid, margaric acid, stearic acid, arachidic acid, behenic acid and other saturated fatty acids, palmitoleic acid, oleic acid, vaccenic acid, elaidic acid, alkene acid and other unsaturated fatty acids, 12-hydroxystearic acid, etc. can be mentioned. Among these fatty acids, saturated or unsaturated fatty acids having 13 to 22 carbon atoms are preferable in that the viscosity of the ester compound does not become extremely high and the handleability is excellent.

[0032] In the above general formula (I) or (II), m and n (average number of moles of oxyalkylene groups added) are preferably 5 to 100. If it is less than 5, it may be difficult to mix with the epoxy compound, and the adhesion to the rubber when RFL is applied may be low. If it is greater than 100, the viscosity of the oil may increase, which may worsen the oil application. m and n are preferably 5 to 50, and more preferably 9 to 30.

[0033] Examples of polyalkylene glycols include polyethylene glycol, a polymer of ethylene oxide; polypropylene glycol, a polymer of propylene oxide; and copolymers of ethylene oxide and propylene oxide. Among these, polyethylene glycol is preferred because it yields ester compounds with excellent solubility for epoxy compounds.

[0034] The weight-average molecular weight (Mw) of polyethylene glycol is preferably 400 to 1,300, more preferably 400 to 920, even more preferably 480 to 840, and particularly preferably 570 to 750. When the weight-average molecular weight (Mw) of polyethylene glycol is 400 or higher, the hydrophilicity of the polyglycol ester increases, making it easier to mix with the curable epoxy compound. On the other hand, when the weight-average molecular weight (Mw) of polyethylene glycol exceeds 1,300, the viscosity of the polyglycol ester increases, reducing the oil application efficiency in the process and worsening the process passability. The weight-average molecular weight of polyethylene glycol can be measured by gel permeation chromatography (GPC).

[0035] Preferred specific examples of ester compounds represented by general formula (I) or (II) include polyethylene glycol (m=10-20) lauric acid monoester and / or diester, polyethylene glycol (m=10-20) oleic acid monoester and / or diester, polyethylene glycol (m=10-20) stearic acid monoester and / or diester, and the like.

[0036] When using a mixture of a curable epoxy compound and a water-soluble oil, it is preferable that (a) the curable epoxy compound and (b) the polyglycol ester are included in a ratio of (a) / (b) = 50 / 50 to 90 / 10 (mass ratio), and more preferably 50 / 50 to 70 / 30. The higher the ratio of polyglycol ester to curable epoxy compound, the more the adhesion of the curable epoxy compound to the rubber is inhibited, while conversely, the lower the ratio, the more the PPTA fibers tend to pass through the process due to the effects of friction. Furthermore, if there is an excess of polyglycol ester in the oil, the more the adhesion of the PPTA fibers to the rubber tends to be inhibited, so the range of (a) / (b) = 55 / 45 to 65 / 35 is particularly preferable.

[0037] The water-soluble oil used in this invention may contain known surfactants such as smoothing agents, nonionic surfactants, anionic surfactants, cationic surfactants, and amphoteric surfactants, as well as antistatic agents, to the extent that they do not hinder the effects of the present invention. Furthermore, a curing agent is not necessary as the reaction will proceed even without it. However, this does not preclude the inclusion of a known curing agent if necessary.

[0038] The amount (total) of the above-mentioned curable epoxy compound and water-soluble oil adhering to the PPTA fibers is preferably 0.3 to 5% by mass, more preferably 0.4 to 3% by mass, and particularly preferably 0.5 to 2% by mass, relative to the mass of the fiber composite (on a dry basis). If it is less than 0.3% by mass, the coating effect will be insufficient, and if it exceeds 5% by mass, entanglement with the roll due to adhesion is likely to occur.

[0039] The method for applying the curable epoxy compound and water-soluble oil to the PPTA fibers is not particularly limited, and any conventionally known method may be used, such as immersion lubrication, spray lubrication, roller lubrication, and guided lubrication using a metering pump.

[0040] Next, the PPTA fiber composite coated with a curable epoxy compound and a water-soluble oil is wound onto a bobbin in the winding process. After winding, the PPTA fiber composite is kept at room temperature without heat treatment or tensioning, and it is desirable to maintain a moisture content of 3 to 15% by mass.

[0041] The PPTA fiber composite of the present invention is useful for various applications, but is particularly useful for reinforcing rubber and resin materials. Therefore, the wound PPTA fiber composite can then be unwound from the bobbin and subjected to adhesive treatment or twisting treatment.

[0042] PPTA fiber composites become suitable as reinforcing fibers for rubber or resins (thermoplastic resins, thermosetting resins) after being treated with an adhesive. The adhesive treatment may be performed once or two or more times. The adhesive treatment can be applied to PPTA fiber composite bundles, single-twist (under-twist) cords made by aligning one or more PPTA fiber composite bundles and applying an appropriate twist, or multi-twist cords made by bundling two or three or more of the under-twist cords and adding an over-twist.

[0043] The cord obtained in this way exhibits no traveler abrasion during twisting, high breaking strength, and excellent adhesion to rubber, making it widely usable as a reinforcing cord for rubber products such as belts, tires, and hoses. Furthermore, the cord of the present invention may be a composite cord with nylon fibers such as nylon 6 and nylon 66, polyester fibers such as polyethylene terephthalate, vinylon fibers, polyketone fibers, etc. The cord of the present invention exhibits particularly excellent effects when used as a cord for tires or for bamboo blinds.

[0044] Furthermore, by cutting the adhesive-treated PPTA fiber composite, to which the adhesive has been applied, to a predetermined length (for example, 0.1 to 10 mm, preferably 0.1 to 5 mm) as needed, short fibers (flocculated) suitable for reinforcing rubber or resin can be obtained.

[0045] Examples of the adhesives mentioned above include resorcinol-formaldehyde-rubber latex (RFL) treatment agents and urethane resins. The RFL treatment agent is, for example, an aqueous treatment solution containing approximately 5 to 25% by mass of a mixture of approximately 2 to 20 parts by mass of resorcinol-formaldehyde initial condensate per 100 parts by mass of rubber latex. For PPTA fiber composites to which an adhesive mainly composed of RFL is attached, a heat treatment method can be employed under the same conditions as conventional methods (100 to 260°C).

[0046] Examples of the above-mentioned rubber latex include vinylpyridine-styrene-butadiene copolymer rubber latex, styrene-butadiene rubber latex, acrylonitrile-butadiene rubber latex, chloroprene rubber latex, chlorosulfonated polyethylene rubber latex, acrylate rubber latex, and natural rubber latex. Examples of the resorcinol-formaldehyde initial condensate include novolac-type condensates obtained by condensing resorcinol-formaldehyde under an acid catalyst or alkali catalyst. The RFL treatment solution may contain a mixture of one or more compounds selected from blocked polyisocyanate compounds, ethyleneimine compounds, and reaction products of polyisocyanate and ethyleneimine.

[0047] Examples of the above-mentioned rubbers include acrylic rubber (ACM), acrylonitrile-butadiene rubber (NBR), hydrogenated acrylonitrile-butadiene rubber (HNBR), isoprene rubber (IR), urethane rubber (AU, EU), ethylene-propylene rubber (EPM), ethylene-propylene-diene copolymer rubber (EPDM), chloroprene rubber (CR), styrene-butadiene rubber (SBR), butadiene rubber (BR), natural rubber (NR), silicone rubber, fluororubber, polysulfide rubber, etc. In addition to the main component rubber, the rubber may also contain various compounding agents commonly used in the rubber industry, such as inorganic fillers like carbon black, silica, and aluminum hydroxide, organic fillers like coumarone resin and phenolic resin, vulcanization accelerators, antioxidants, and softeners.

[0048] Furthermore, the PPTA fiber composite of the present invention, which has not been treated with adhesive, and the short fibers obtained by cutting it, are useful for paper, textiles, knitted fabrics, nonwoven fabrics, sheets, etc. for gears. [Examples]

[0049] The present invention will be described in detail below using examples and comparative examples, but the present invention is not limited to the following examples. The measurements in the examples were taken according to the following methods.

[0050] (1) Moisture content of poly(p-phenylene terephthalamide) fibers The mass (before drying) of approximately 5g of sample is measured. Then, after heat treatment at 300°C for 20 minutes, it is left to stand at 25°C and 65% RH for 5 minutes, and the mass (after drying) is measured again. Moisture content (mass%) = [(mass before drying - mass after drying) / (mass after drying)] x 100

[0051] (2) Amount of epoxy compound on the fiber surface (mmol / kg) a) The total amount of oil mixture (a mixture of curable epoxy compound and oil) attached to the PPTA fiber composite (hereinafter referred to as the sample) is determined by the weight change using the heating gravimetric method before and after attachment, and the total amount of oil mixture attached per 1 kg of sample (Eg) is calculated. The number of millimoles of epoxy groups present per 1 kg of sample is then calculated as the theoretical amount of epoxy compound using the following formula. Note that the epoxy equivalent represents the molecular weight per epoxy group of the curable epoxy compound. [Theoretical epoxy compound content (mmol / kg)] = 1000 × E × (Curable epoxy compound content in oil mixture (%) / 100) / epoxy equivalent b) Separately, place approximately 10 g (actual weight Ag) of the sample in a beaker, extract the free epoxy compounds adhering to the sample surface with acetone, remove the acetone, and measure the weight of the extract. Add 20 ml of hydrochloric acid / 1,4-dioxane mixed solution (15 / 1000 (volume ratio)) and 30 ml of ethanol to the extract, and perform a neutralization titration with a 0.5 mol / L NaOH solution (titration volume: C ml). Perform a blank titration (titration volume: D ml) on the hydrochloric acid / 1,4-dioxane mixed solution without the extract, and calculate the amount of free epoxy compounds, specifically the number of millimoles of free epoxy groups present per 1 kg of sample, using the following formula. [Amount of free epoxy compound (mmol / kg)] = 0.5 × 1000 × (DC) / A c) The amount of cured epoxy compound is calculated by determining the number of millimoles of cured epoxy groups present per 1 kg of sample using the following formula. [Amount of cured epoxy compound (mmol / kg)] = Theoretical amount of epoxy compound (mmol / kg) - Amount of free epoxy compound (mmol / kg)

[0052] (4) T-Adhesion strength (adhesion strength between cord and rubber) evaluation In accordance with JIS L1017:2002 Adhesion Strength - Method A, the treated cord was embedded in unvulcanized rubber, and the initial adhesion strength was determined by press vulcanization at 150°C for 30 minutes under pressure. After cooling, the cord was pulled out of the rubber block at a speed of 300 mm / min, and the load required for the pull-out was expressed in N / cm.

[0053] (Example 1) One kilogram of poly(p-phenylene terephthalamide) (molecular weight approximately 20,000), obtained by conventional methods, was dissolved in four kilograms of concentrated sulfuric acid, and the mixture was subjected to a shearing rate of 30,000 seconds through a die with 1,000 holes, each with a diameter of 0.1 mm. -1 The material was extruded in such a manner, spun in water at 4°C, neutralized with a 10% by mass sodium hydroxide aqueous solution at 10°C for 15 seconds, and then heated and dried to obtain poly(p-phenylene terephthalamide) fibers (total fineness 1,670 dtex) with a moisture content of 10% by mass.

[0054] The resulting bundles of poly(p-phenylene terephthalamide) fibers were then coated with a mixture of an epoxy compound with 99% water solubility and a polyglycol ester, which did not contain a curing agent (organic amine), in an amount of 0.7% relative to the fiber mass when converted to a 0% moisture content. The bundles were then rolled up and packaged. The epoxy compound and polyglycol ester were used in a 60 / 40 ratio (by mass).

[0055] A bundle of poly(p-phenylene terephthalamide) fiber composite unwound from the package was twisted in the Z direction at 32t / 10cm to obtain a lower twist cord. Then, two lower twist cords were joined together and twisted in the S direction at 32t / 10cm to obtain a higher twist cord.

[0056] Next, the obtained cord was immersed in an adhesive treatment solution mainly composed of RFL using a computer processing machine (manufactured by Ritzler), dried at 100°C for 150 seconds, and then heat-treated at 220°C for 123 seconds to obtain RFL-treated poly(p-phenylene terephthalamide) fiber cord.

[0057] (Comparative Example 1) A bundle of poly(p-phenylene terephthalamide) fibers, obtained by the same method as in Example 1, was coated with a mixture of an epoxy compound containing an organic amine, with a water solubility of 99%, and a polyglycol ester at a concentration of 0.7% relative to the fiber mass when converted to a 0% moisture content. The bundle was then rolled up and packaged. The epoxy compound and polyglycol ester were used in a 60 / 40 ratio (mass ratio), as in Example 1. A bundle of poly(p-phenylene terephthalamide) fiber composite unwound from the package was twisted in the same manner as in Example 1 to obtain a lower twist cord. Then, two lower twist cords were joined together and twisted in the same manner as in Example 1 to obtain a higher twist cord. Next, the obtained cord was immersed in an RFL adhesive treatment solution under the same conditions as in Example 1, followed by drying and heat treatment to obtain an RFL-treated poly(p-phenylene terephthalamide) fiber cord.

[0058] (Example 2) A bundle of poly(p-phenylene terephthalamide) fibers, obtained by the same method as in Example 1, was coated with a mixture of an epoxy compound and a polyglycol ester, free of organic amines and with a water solubility of 88%, at a concentration of 0.7% relative to the fiber mass when converted to a 0% moisture content. The bundle was then rolled up and packaged. The epoxy compound and polyglycol ester were used in a 60 / 40 ratio (mass ratio), as in Example 1. A bundle of poly(p-phenylene terephthalamide) fiber composite unwound from the package was twisted in the same manner as in Example 1 to obtain a lower twist cord. Then, two lower twist cords were joined together and twisted in the same manner as in Example 1 to obtain a higher twist cord. Next, the obtained cord was immersed in an RFL adhesive treatment solution under the same conditions as in Example 1, followed by drying and heat treatment to obtain an RFL-treated poly(p-phenylene terephthalamide) fiber cord.

[0059] (Comparative Example 2) Poly(p-phenylene terephthalamide) fibers with a moisture content of 50% by mass (total fineness 1,670 dtex) were obtained according to the method of Example 1. A mixture of an epoxy compound with 99% water solubility and no organic amines, and a polyglycol ester, was applied to the obtained bundle of poly(p-phenylene terephthalamide) fibers in an amount of 0.7% relative to the fiber mass when converted to a moisture content of 0%. The bundle was then dried to a moisture content of 30% by mass, rolled up, and packaged. The epoxy compound and polyglycol ester were used in a 60 / 40 ratio (by mass) as in Example 1.

[0060] A bundle of poly(p-phenylene terephthalamide) fiber composite unwound from the package was twisted in the Z direction at 32t / 10cm to obtain a lower twist cord. Then, two lower twist cords were joined together and twisted in the S direction at 32t / 10cm to obtain a higher twist cord.

[0061] Next, the obtained cord was immersed in an RFL adhesive treatment solution under the same conditions as in Example 1, followed by drying and heat treatment to obtain an RFL-treated poly(p-phenylene terephthalamide) fiber cord.

[0062] Table 1 summarizes the amount of free epoxy compound, the amount of cured epoxy compound, and the ratio of the two in the poly(p-phenylene terephthalamide) fiber composites obtained in the examples and comparative examples, as well as the evaluation results of the RFL-treated poly(p-phenylene terephthalamide) fiber cords.

[0063] In the examples and comparative examples, polyethylene glycol (weight-average molecular weight: 660) oleate ester was used as the polyglycol ester.

[0064] [Table 1]

[0065] The results in Table 1 show that the poly(p-phenylene terephthalamide) fiber composite of the present invention has a higher T-adhesion strength of the adhesive-treated fiber cord compared to the poly(p-phenylene terephthalamide) fiber composite in which the ratio of cured epoxy compound to free epoxy compound is 2.92 (Comparative Example 1) and 17.23 (Comparative Example 2). [Industrial applicability]

[0066] The poly(p)phenylene terephthalamide fiber composite of the present invention can be suitably used as a reinforcement for rubber products such as tires, belts, and hoses.

Claims

1. A poly(p-phenylene terephthalamide) fiber composite characterized in that a cured film (cured) and uncured curable epoxy compound (free) of a curable epoxy compound are attached to the surface of the poly(p-phenylene terephthalamide) fiber in a molar ratio (cured / free) of 0.3 to 1.

0.

2. The poly(p-phenylene terephthalamide) fiber composite according to claim 1, wherein the cured film and the uncured curable epoxy compound are obtained by applying a curable epoxy compound, or a curable epoxy compound and a water-soluble oil (provided that no curing agent is applied).

3. The poly(p-phenylene terephthalamide) fiber composite according to claim 1 or 2, wherein the water solubility of the curable epoxy compound is 85% or more.

4. An adhesive-treated poly-p-phenylene terephthalamide fiber composite comprising a poly-p-phenylene terephthalamide fiber composite according to any one of claims 1 to 3, to which an adhesive is attached.

5. A code comprising a poly(p-phenylene terephthalamide) fiber composite according to any one of claims 1 to 3 or an adhesive-treated poly(p-phenylene terephthalamide) fiber composite according to claim 4.

6. Flocculated short fibers obtained by cutting the poly-p-phenylene terephthalamide fiber composite according to any one of claims 1 to 3 or the adhesive-treated poly-p-phenylene terephthalamide fiber composite according to claim 4.

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