JP2006265744A - Fiber material for reinforcing rubber and method for producing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fiber material for rubber reinforcement, composed of an aromatic polyester having high heat resistance, excellent in dimensional stability and strength physical property at high temperature and capable of retaining the shape also at temperatures not lower than the melting point of an aromatic polyester. <P>SOLUTION: The present invention provides the fiber material for rubber reinforcement and a method for producing the fiber material. In the fiber material for reinforcement of rubber mainly composed of an aromatic polyester, a crosslinked structure is formed in at least part of a polyester resin in which an aliphatic unsaturated group is introduced through an urethane bond/or an amide bond to the molecular terminals of the aromatic polyester. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  TECHNICAL FIELD The present invention relates to a rubber reinforcing fiber material, and more specifically, a fiber material constituting a tire belt or a carcass reinforcing cord, and maintains its form at a high temperature, particularly above the melting point of an aromatic polyester. The present invention relates to a rubber reinforcing fiber material comprising an aromatic polyester fiber excellent in high heat resistance.

  In general, polyester, nylon, and rayon are well known as organic fibers as typical examples of fibers that are generally used as rubber reinforcing materials for tires, and steel and glass fibers are typical as inorganic fibers. . These materials are used in place due to their inherent properties.

  For example, today's mainstream radial tire is a tire having a belt layer in which carcass cords are arranged from bead to bead approximately perpendicular to the tire rotation direction (radial direction), and further, cords are arranged in the tire rotation direction. However, this belt layer is preferably made of steel with high elastic modulus and low elongation, and as the carcass material, inexpensive polyester with excellent elastic modulus, fatigue resistance and excellent creep resistance is used. Yes. On the other hand, nylon-based fibers that are excellent in strength and fatigue resistance are mainly used in bias tires having cord reinforcement layers that cross diagonally (bias) from bead to bead. In addition, rayon fibers have a very low shrinkage due to the inherent properties of rayon, have excellent thermal dimensional stability and form stability, and are mainly used in radial tires for high-speed running such as passenger cars.

  Furthermore, in recent years, tires that can run flat (that is, can run at a predetermined speed for a certain distance even when the tire pressure is punctured and the tire internal pressure becomes 0 kPa) have been developed. This run-flat tire has a side reinforcement type that is reinforced by placing a relatively hard rubber layer with a crescent cross section on the inner surface of the carcass from the bead portion of the tire sidewall to the shoulder area, and the rim portion in the tire air chamber. Further, a core type in which a ring core made of metal or synthetic resin is attached is known.

  Among these, if the tire punctures and the air escapes during running, the side reinforcing type supports the load by the rigidity inherent to the sidewall reinforced with the reinforcing rubber layer, and can run at a predetermined speed at a predetermined distance. In particular, in the case of a tire type having a large deflection under a high load, the tire internal temperature may be extremely high, such as 200 ° C. or higher, and more locally. For this reason, rayon fibers, aramid fibers, steel, etc., which are excellent in heat-resistant melting property, have been proposed and used as preferred cord materials for the carcass ply cords of run-flat tires.

  On the other hand, the fiber cord for reinforcing rubber made of polyester fiber or nylon fiber begins to break the adhesion interface with the tire rubber at a high temperature of 150 to 200 ° C., and the strength and elastic modulus rapidly decrease, and further to a temperature higher than the melting point. In this case, the shape of the fiber cannot be maintained and melt fracture occurs, which makes it unsuitable as a cord material for a run-flat tire. However, since these fibers are very rich in supply, cheap in price, and light in weight, run cords made from these polyester fibers and nylon fibers are used to make run-flat tires more widespread. It is hoped that.

  So far, various methods for improving the heat resistance of the polyester tire cord in the tire rubber have been proposed. For example, a method for suppressing hydrolysis in rubber by reducing the amount of terminal carboxylic groups of polyester fibers (see, for example, Patent Document 1 and Patent Document 2), a polymer comprising acrylic acid and / or methacrylic acid (For example, see Patent Document 3), a method for containing a fluorine-based polymer (for example, see Patent Document 4), a method for containing a cyclic olefin polymer (for example, see Patent Document 5), and the like. . However, these are all improvements in strength properties relating to heat resistance at 150 to 160 ° C., and were not able to maintain the shape above the melting point of the polyester and maintain the predetermined strength and elastic modulus.

JP 61-252332 A JP-A-7-166420 JP-A-55-166235 JP-A-6-264307 JP-A-8-74126

  The present invention has been made in view of the above problems, and its object is to reinforce a rubber made of a highly heat-resistant aromatic polyester capable of maintaining its form even at a high temperature, particularly above the melting point of the aromatic polyester. A fiber material is provided.

  In order to solve the above-mentioned problems, the present inventors have conducted intensive research, and as a result, found that the problems can be solved by forming a crosslinked structure in at least part of the polyester molecular chains, and the present invention has been completed. It came.

That is, the present invention is 1. A fiber material for reinforcing rubber comprising an aromatic polyester as a main component, which is crosslinked to at least a part of a polyester in which an aliphatic unsaturated group is introduced via a urethane bond and / or an amide bond at a molecular terminal of the aromatic polyester. A rubber material for reinforcing rubber, characterized in that a structure is formed.
2. A substantially linear aromatic polyester, each having at least one isocyanate group and an aliphatic unsaturated group, and / or at least one oxazoline group and an aliphatic unsaturated group, respectively; A method for producing a rubber-reinforcing fiber material, comprising melt-spinning a resin composition containing a compound having the following, and irradiating the obtained yarn with ionizing radiation.
3. The method for producing a fiber material for rubber reinforcement as described in 2 above, wherein the ionizing radiation is an electron beam or a γ-ray.
4). A tire cord using the rubber reinforcing fiber material described in any one of 1 to 3 above.
5. A pneumatic radial tire using the tire cord described in 4 above as a carcass material.
Is to provide

  ADVANTAGE OF THE INVENTION According to this invention, the fiber material for rubber reinforcement which consists of highly heat-resistant aromatic polyester which can maintain a form at high temperature, especially above melting | fusing point of aromatic polyester can be provided.

  Hereinafter, the present invention will be described in detail. As described above, the present invention can also be used as a carcass ply cord for a run-flat tire that may be punctured to lower the internal pressure and have a tire internal temperature of 200 ° C. or higher, and locally a very high temperature that is higher than the melting point of the aromatic polyester. For rubber reinforcement consisting of aromatic polyester with high heat resistance that can be used at high temperatures, especially above the melting point of aromatic polyester that does not have a cross-linked structure, and can maintain the prescribed strength and elastic modulus A fiber material is provided.

  The aromatic polyester in the present invention is a polycondensation product of an aromatic dicarboxylic acid component and a diol component, and is not particularly limited including known ones. Examples of the aromatic dicarboxylic acid component include terephthalic acid, isophthalic acid, naphthalene dicarboxylic acid, diphenyl dicarboxylic acid, diphenyl ether dicarboxylic acid, 5-sodium sulfoisophthalic acid, and the like. Of these, terephthalic acid and naphthalenedicarboxylic acid are preferred. Examples of the diol component include aliphatic diols such as ethylene glycol, diethylene glycol, triethylene glycol, trimethylene glycol, and tetramethylene glycol; alicyclic diols such as cyclohexanediol and cyclohexanedimethanol; and aromatics such as naphthalenediol, bisphenol A, and resorcin. Group diols can be exemplified. Of these, aliphatic diols such as ethylene glycol and trimethylene glycol are preferred. In addition, the aromatic polyester of the present invention may be an aromatic dicarboxylic acid component and a diol component each composed of a single component or a copolyester composed of two or more types. Further, it may be a blend of two or more kinds of aromatic polyester resins.

  Further, in the aromatic polyester, a small amount of other optional polymers, antioxidants, radical scavengers, antistatic agents, dyeing improvers, dyes, pigments, matting agents, fluorescent whitening agents, inert fine particles, etc. The additive may be contained.

  As a method for obtaining such an aromatic polyester, it is not necessary to employ special polymerization conditions, and a polyester is obtained by polycondensing a reaction product of an aromatic dicarboxylic acid component and / or an ester-forming derivative thereof and a diol component. It can be synthesized by any method employed. The polymerization apparatus may be a batch type or a continuous type. Furthermore, after the polyester obtained in the liquid phase polycondensation step is granulated and pre-crystallized, it can also be subjected to solid phase polymerization in an inert gas atmosphere or under reduced pressure vacuum at a temperature below the melting point.

  The polymerization catalyst is not particularly limited as long as it has a desired catalytic activity, but an antimony compound, a titanium compound, a germanium compound, and an aluminum compound are preferably used. When these catalysts are used, they may be used alone or in combination of two or more, and the amount used is preferably 0.002 to 0.1 mol% with respect to the aromatic dicarboxylic acid component constituting the polyester. .

  Moreover, it is preferable that intrinsic viscosity (IV) of the substantially linear aromatic polyester in this invention is 0.6 or more, More preferably, it is 0.8 or more. When IV is 0.6 or less, the decrease in strength and elastic modulus due to thermal deterioration of the yarn becomes large, which is not preferable. Moreover, it is preferable that the carboxyl terminal group amount of aromatic polyester is 50 eq / ton or less, More preferably, it is 30 eq / ton or less. If it exceeds 50 eq / ton, the heat resistance in the rubber is deteriorated and the durability as a fiber material for rubber reinforcement is deteriorated.

  The rubber reinforcing fiber material of the present invention is an unstretched yarn obtained by melt spinning the above aromatic polyester, a stretched yarn obtained by stretching it, a twisted cord obtained by twisting several strands, or a woven fabric obtained by weaving it It is.

  The fiber material for rubber reinforcement comprising the aromatic polyester as a main component of the present invention is at least one polyester resin in which an aliphatic unsaturated group is introduced via a urethane bond and / or an amide bond at the molecular terminal of the aromatic polyester. The aliphatic unsaturated group is a functional group containing a carbon-carbon double bond or a carbon-carbon triple bond, including known ones. It is not limited. For example, an acrylic group, methacryl group, allyl group, acryloyl group, methacryloyl group, acryloxy group, methacryloxy group, propenyl group, isopropenyl group, butenyl group, crotyl group, isobutenyl group, hexenyl group, vinyl ether group, etc. it can.

  In general, it is well known that heat-resistant melting property is improved or solubility in a solvent is lowered by forming a crosslinked structure in a polymer, and these can serve as an index indicating the degree of crosslinking (crosslinking degree). In the present invention, the degree of cross-linking is not particularly limited, but it is not less than the melting point of the aromatic polyester resin before forming the crosslinked structure, preferably not less than 265 ° C., more preferably not less than 280 ° C., more preferably not less than 300 ° C. It is preferable that the rubber reinforcing fiber material, which is a product of the present invention in which a crosslinked structure is formed, does not heat-melt and flow and can maintain the form of the fiber material.

  Moreover, it is preferable that the gel fraction which shows the ratio of the insoluble residue with respect to a predetermined solvent is the range of 1-90 weight%, Furthermore, it is preferable that it is 5-90 weight%. When the gel fraction is lower than 1% by weight, the degree of cross-linking is too low, and the dimensional stability and strength of the rubber reinforcing fiber material at high temperatures are insufficient, which is not preferable. On the other hand, if the gel fraction is higher than 90%, the crosslinking density becomes too high, and the strength and elastic modulus at room temperature are lowered, which is not preferable. The solvent for measuring the gel fraction is not particularly limited as long as it is an organic solvent that completely dissolves the aromatic polyester before forming a crosslinked structure at a predetermined temperature and a predetermined time. For example, phenol, o-chlorophenol , M-chlorophenol, p-chlorophenol, 2,3-dichlorophenol, 2,4-dichlorophenol, 2,5-dichlorophenol, 2,6-dichlorophenol, 3,4-dichlorophenol, 3,5- Dichlorophenol, 2,3,4-trichlorophenol, 2,3,5-trichlorophenol, 2,3,6-trichlorophenol, 2,4,5-trichlorophenol, 2,4,6-trichlorophenol, 3, 4,5-trichlorophenol, 1,1,1,2-tetrachloroethane, 1,1,2,2-tetrachloroe Down, chloroform, can be exemplified dichloromethane, carbon tetrachloride, dichloro acetic acid, hexafluoroisopropanol and the like, which may be used in combination one kind even or two or more kinds. Although the temperature of the solvent at the time of melt | dissolution is not specifically limited, For example, it is 20 to 200 degreeC. The dissolution time is not particularly limited, but may be a time required for the dissolution to reach a saturated state, for example, 10 minutes to 5 hours.

  Furthermore, in the present invention, as a method for introducing an aliphatic unsaturated group into a molecular terminal of an aromatic polyester via a urethane bond and / or an amide bond, at least one or more of each of the substantially linear aromatic polyesters is introduced. By blending a compound having an isocyanate group and an aliphatic unsaturated group and / or a compound having at least one oxazoline group and an aliphatic unsaturated group, respectively, and melt-kneading the resin composition It is preferable to obtain. The isocyanate group reacts with the hydroxyl group end and / or the carboxyl group end of the aromatic polyester to form a urethane bond and / or an amide bond. The oxazoline ring undergoes a ring-opening addition reaction at the carboxyl group end of the aromatic polyester to form an amide bond.

  The substantially linear aromatic polyester blended with these compounds is made into fiber by melt spinning, and the blending of the compound into the aromatic polyester resin may be added together with the resin supply in melt spinning. Alternatively, the compound and aromatic polyester may be melt-kneaded and pelletized by a known method in advance, and this may be melt-spun. The kneaded resin can be used as a master batch by blending with other aromatic polyester resins. The temperature at the time of melt-kneading is not particularly limited as long as it is higher than the melting point of the linear aromatic polyester, but a temperature excessively higher than the melting point is not preferable because the polymer is thermally deteriorated. Also, the time for melt kneading is not particularly limited, but is 1 minute to 40 minutes, preferably 2 minutes to 20 minutes.

  The compound having at least one isocyanate group and an aliphatic unsaturated group is not particularly limited, including known ones, but vinyl isocyanate, allyl isocyanate, propenyl isocyanate, isopropenyl isocyanate , Butenyl isocyanate, hexenyl isocyanate, crotyl isocyanate, acryloyl isocyanate, methacryloyl isocyanate, 2-acryloyloxyethyl isocyanate, 2-acryloyloxybutyl isocyanate, 2-acryloyloxypropyl isocyanate, 2-acryloyl Oxyhexyl isocyanate, 2-methacryloyloxyethyl isocyanate, 2-methacryloyloxybutyl isocyanate, 2-methacryloyloxypropyl isocyanate 2-methacryloyloxyhexyl isocyanate, allyl-α, α′-dimethylbenzyl isocyanate, propenyl-α, α′-dimethylbenzyl isocyanate, isopropenyl-α, α′-dimethylbenzyl isocyanate, butenyl- α, α'-dimethylbenzyl isocyanate, hexenyl-α, α'-dimethylbenzyl isocyanate, allyl benzyl isocyanate, propenyl benzyl isocyanate, isopropenyl benzyl isocyanate, butenyl benzyl isocyanate, hexenyl benzyl isocyanate, etc. Is preferably used. The isocyanate group of these compounds may be blocked with a blocking agent such as secondary alcohol, tertiary alcohol, active methylene compound, oximes, lactams, imidazoles, etc. It is necessary that the block dissociates at a temperature lower than the kneading temperature. The above compounds may be used alone or in combination of two or more. Furthermore, it may be a polymer of the above compound, or may be one type of homopolymer or two or more types of copolymers. Furthermore, in the copolymerization, any monomer may be used as long as it is a monomer copolymerizable with the above compound.

  Further, the blending amount of the above compound with respect to the substantially linear aromatic polyester is not particularly limited as long as it satisfies the desired physical properties. Preferably it is 0.05-30 weight part with respect to 100 weight part of aromatic polyester, More preferably, it is 0.1-10 weight part. When the blending amount is less than 0.05 parts by weight, the degree of cross-linking is insufficient, which is not preferable. If it is more than 30 parts by weight, the resin will gel due to thermal crosslinking of unsaturated groups, which is not preferable.

  By melting and kneading a compound having at least one isocyanate group and an aliphatic unsaturated group with a substantially linear aromatic polyester, respectively, the carboxyl group terminal of the isocyanate group and the aromatic polyester, and Although it reacts with the hydroxyl group terminal, a catalyst for promoting this reaction may be added at the same time. The catalyst is not particularly limited, and examples thereof include Lewis bases such as amines and phosphine, aluminum, tin, and iron-based organic metals. Examples of amines include triethylamine, N, N-dimethylcyclohexylamine, N, N, N ′, N′-tetramethylethylenediamine, N, N, N ′, N′-tetramethylpropane 1,3-diamine, N , N, N ', N'-tetramethylhexane-1,6-diamine, N, N, N', N ", N" -pentamethyldiethylenetriamine, N, N, N ', N ", N" -penta Methyldipropylene-triamine, tetramethylguanidine, triethylenediamine, N, N'-dimethylpiperazine, N-methyl, N '-(2dimethylamino) -ethylpiperazine, N-methylmorpholine, N. (N', N ' -Dimethylaminoethyl) -morpholine, 1,2-dimethylimidazole, dimethylaminoethanol, dimethylaminoethoxyethanol, N, N, N'-trimethylaminoethyl-ethanolamine, N-methyl-N '-(2hydroxy Chill) - piperazine, N- (2- hydroxyethyl) morpholine, bis (2-dimethylaminoethyl) ether, ethylene glycol bis (3-dimethylamino) - aminopropyl ether can be exemplified. Examples of the organometallic catalyst include stannous octoate, dibutyltin diacetate, dibutyltin dilaurate, dibutyltin marker thiopide, dibutyltin thiocarboxylate, dibutyltin dimaleate, dioctyltin marker peptide, dioctyltin thiocarboxylate, phenylmercury. Examples include propionate and lead octenoate. These can be used alone or in combination of two or more. Although the addition amount of a catalyst is not specifically limited, 0.001-1 weight part is preferable with respect to 100 weight part of aromatic polyester, Furthermore, it is 0.01-0.5 weight part.

  The compounds each having at least one oxazoline group and an aliphatic unsaturated group are not particularly limited, including known ones, but propenyl oxazoline, isopropenyl oxazoline, butenyl oxazoline, isobutenyl oxazoline, etc. Can be illustrated. These compounds may be used alone or in combination of two or more.

  Further, the blending amount of the above compound with respect to the substantially linear aromatic polyester is not particularly limited as long as it satisfies the desired physical properties. Preferably it is 0.05-30 weight part with respect to 100 weight part of aromatic polyester, More preferably, it is 0.1-10 weight part. When the blending amount is less than 0.05 parts by weight, the degree of cross-linking is insufficient, which is not preferable. If it is more than 30 parts by weight, the resin will gel due to thermal crosslinking of unsaturated groups, which is not preferable.

  By melting and kneading the compound having at least one oxazoline group and an aliphatic unsaturated group with a substantially linear aromatic polyester, the oxazoline ring is opened at the carboxyl group terminal of the aromatic polyester. Although an addition reaction is performed, a catalyst for promoting this reaction may be added at the same time. This catalyst is not particularly limited and may be a known catalyst such as an amine salt of an acidic compound. Although the addition amount of a catalyst is not specifically limited, 0.001-1 weight part is preferable with respect to 100 weight part of aromatic polyester, Furthermore, it is 0.01-0.5 weight part.

  In the present invention, the isocyanate group and / or the oxazoline ring react with the carboxyl group terminal of the aromatic polyester, but this reaction only introduces an ionizing radiation-sensitive aliphatic unsaturated group into the molecular terminal of the aromatic polyester. In other words, the carboxyl group terminal amount of the aromatic polyester is reduced. Since rubber reinforcing fiber materials made of aromatic polyester are considered to cause degradation reaction of polyester by autocatalysis of carboxyl group terminal in tires, blocking of carboxyl group terminal by the above reaction also suppresses this deterioration reaction. It becomes possible.

  In the method for producing the raw yarn of the fiber material for rubber reinforcement of the present invention, conventional spinning conditions can be adopted, and spinning is performed at a spinning speed of 1000 to 6000 m / min, preferably 1500 to 4000 m / min. A spinning speed of 1000 m / min or less is not preferable because a spinning stress cannot be sufficiently applied to promote orientation crystallization during spinning.

  The taken-up yarn is wound up once or is heat-drawn by a spin draw method of drawing continuously after spinning. The thermal stretching is performed by high-strength one-stage stretching or two-stage or more multi-stage stretching. The heating method includes a method using a heating roller, superheated steam, a heat plate, a heat box, or the like, and is not particularly limited. The stretching ratio can also be stretched at an arbitrary value depending on the desired physical properties.

  The aromatic polyester fiber thus obtained is twisted 10 to 100 times per 10 cm (bottom twist) in accordance with a conventional method, then a plurality of yarns are combined and twisted 10 to 100 times per 10 cm in the opposite direction. (Top twist) is applied to form a twisted cord. Next, the twisted cord is made into a woven fabric according to a conventional method, and further treated with an adhesive according to a conventional method to obtain a dip fabric.

  The cross-linked structure of the rubber reinforcing fiber material of the present invention is a structure resulting from an aliphatic unsaturated group introduced at the end of an aromatic polyester molecule. The method of generating radicals necessary for forming this crosslinked structure is not particularly limited, including known ones, but a method by irradiation with ionizing radiation such as ultraviolet rays, electron beams, and γ rays is preferable, and in particular, transmission of irradiation energy is possible. Electron beams and γ rays having a large force are preferred. Irradiation of this ionizing radiation can be performed in any process from the spinning process of the raw material of the rubber reinforcing fiber material to the production of the dip fabric, but in terms of the irradiation efficiency and quality stability of the ionizing radiation, Irradiation is preferably performed in the form of a twisted cord or a woven fabric. The irradiation dose of ionizing radiation is not particularly limited as long as the desired physical properties are satisfied, but is 20 to 5000 kGy, preferably 100 to 3000 kGy. If the irradiation dose of ionizing radiation is too low, the degree of crosslinking tends to be insufficient, and if it is too high, the aromatic polyester is decomposed and the strength properties are lowered, which is not preferable. The irradiation process of ionizing radiation is generally a process performed at room temperature, but can be performed in an arbitrary temperature environment of 0 to 200 ° C.

EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to these examples. In addition, the evaluation method of various characteristics followed the following.
(1) Intrinsic viscosity [IV]
A value obtained by dissolving the polymer in a mixed solvent of parachlorophenol / 1,1,2,2-tetrachloroethane = 3/1 at a concentration of 0.4 g / dl (dl / g).
(2) COOH end group amount [AV]
After freeze-grinding and drying sufficiently, 0.1 g of a polymer sample was heated and dissolved with 10 ml of benzyl alcohol, and phenolphthalein was used as an indicator, and a 0.1N NaOH methanol / benzyl alcohol = 1/9 solution was used. The value measured by titration (eq / ton).
(3) OH terminal group amount CDCl ₃ / HFIP-d ₂ (= 1: 1) was added to the sample and dissolved, and further, CDCl ₃ and pyridine were added and stirred well, followed by analysis by H-NMR. It is mol% when terephthalic acid is 100.
(4) Melting point of polymer After heating and melting a sample at 300 ° C. for 2 minutes, 10 mg of a sample obtained by quenching with liquid nitrogen was used, and a differential scanning calorimeter Mac Science DSC 3100S was used in a nitrogen stream. The peak temperature of the endothermic peak accompanying melting when the exothermic / endothermic curve (DSC curve) was measured at a temperature elevation rate of ° C./min was defined as the melting point Tm (° C.).
(5) Gel fraction A mixed solvent of 25 ml of parachlorophenol / 1,1,2,2-tetrachloroethane = 3/1 was added to 0.1 g (weighed) of the sample and immersed in 90 ° C. for 100 minutes, and then 30 ° C. The residue obtained by suction filtration with a glass filter was dried under reduced pressure, and the weight percent of the insoluble matter was defined as the gel fraction (%).
(6) Thermal flow start temperature After placing the sample on a hot plate that can be set to a constant temperature for 1 minute, determine whether it is hot melt flow visually or with a microscope, and determine the temperature at which the thermal flow is occurring. (° C).

Example 1
In a reactor, 100 mole parts of terephthalic acid, 200 mole parts of ethylene glycol, 0.025 mole part of antimony trioxide and 0.3 mole part of triethylamine as a stabilizer are subjected to a dehydration reaction at 250 ° C. and an internal pressure of 2.5 kg / cm 2 for 150 minutes. went. Thereafter, the temperature was gradually raised and reduced, and a polycondensation reaction was performed at 275 ° C. and 0.1 mmHg to a predetermined torque. After completion of the reaction, the polymer was converted into chips according to a conventional method, and further solid phase polymerization was performed at 230 ° C. under a vacuum of 0.01 mmHg to obtain a polyethylene terephthalate chip having an intrinsic viscosity of 1.05. The chips were dried according to a conventional method and then supplied to a melt extruder. At the same time, 2-isocyanatoethyl methacrylate was added from an extruder inlet at a constant flow rate to 3.0% by weight with respect to the polymer. The kneaded polymer was discharged from a spinneret at 310 ° C. having 336 holes with a hole diameter of 0.5 mm, cooled and solidified with cooling air at 70 ° C. and 1.0 m / sec, and after spinning, a spinning speed of 2000 m The film was drawn at a rate of 1 / min, and subsequently drawn up 1.7 times to obtain a drawn yarn of 1400 dtex and 336 filaments. The drawn yarns were combined and subjected to a primary twist and an upper twist of 1440 dtex / 2, 43 T / 10 cm to obtain a twisted cord. This twisted cord was irradiated with 2000 kGy of an electron beam with an acceleration voltage of 300 keV under a constant tension in an air atmosphere. The results are shown in Table 1. The gel fraction after irradiation was 43%, the heat flow starting temperature was 310 ° C, and it was found that the shape as a twisted cord was maintained without melting even at 300 ° C. .

(Example 2)
A twisted cord was obtained in the same manner as in Example 1 except that the amount of isopropenyl oxazoline added was 3.0% by weight based on polyethylene terephthalate, and an electron beam with an acceleration voltage of 300 keV was applied in an air atmosphere under a constant tension. Irradiated with 2000 kGy. The results are shown in Table 1.

(Example 3)
A twisted cord was obtained in the same manner as in Example 1 except that 2-isocyanatoethyl methacrylate and isopropenyl oxazoline were each blended in an amount of 1.5% by weight with respect to polyethylene terephthalate, and an acceleration voltage was obtained in an air atmosphere under a constant tension. A 300 keV electron beam was irradiated at 2000 kGy. The results are shown in Table 1.

(Comparative Example 1)
A twisted cord was obtained in the same manner as in Example 1 except that 2-isocyanatoethyl methacrylate was not added, and an electron beam with an acceleration voltage of 300 keV was irradiated in an air atmosphere under constant tension at 2000 kGy. Although the results are shown in Table 1, the gel fraction was 0%, the heat flow initiation temperature was 260 ° C., and it was found that a crosslinked structure was not formed even when 2,000 kGy electron beam was irradiated to ordinary polyethylene terephthalate fibers. .

(Comparative Example 2)
A twisted cord was obtained in the same manner as in Example 1, but the electron beam irradiation dose was 100 kGy. The results are shown in Table 1, and it was found that the gel fraction was 0.8%, the heat flow starting temperature was 260 ° C., the electron beam irradiation amount was low, and a sufficient degree of crosslinking was not obtained.

  The fiber material for rubber reinforcement comprising the aromatic polyester fiber of the present invention is a fiber material for rubber reinforcement characterized by having a crosslinked structure in at least a part between the polyester molecular chains. Compared to the fiber material for rubber reinforcement, it can maintain its shape without being melted even at a temperature higher than the melting point of the aromatic polyester. It is suitable for a rubber material for reinforcing rubber.

Claims (5)

  A fiber material for reinforcing rubber comprising an aromatic polyester as a main component, which is crosslinked to at least a part of a polyester in which an aliphatic unsaturated group is introduced via a urethane bond and / or an amide bond at a molecular terminal of the aromatic polyester. A rubber material for reinforcing rubber, characterized in that a structure is formed.   The substantially linear aromatic polyester has a compound having at least one isocyanate group and an aliphatic unsaturated group, respectively, and / or at least one oxazoline group and an aliphatic unsaturated group, respectively. A method for producing a rubber-reinforcing fiber material, comprising melt-spinning a resin composition containing a compound having a compound, and irradiating the obtained yarn with ionizing radiation.   The method for producing a rubber-reinforcing fiber material according to claim 2, wherein the ionizing radiation is an electron beam or a gamma ray.   A tire cord using the rubber reinforcing fiber material according to claim 1.   A pneumatic radial tire using the tire cord according to claim 4 as a carcass material.