JP2008285767A - Highly heat-resistant fiber material for reinforcing rubber and method for producing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a highly heat-resistant polyamide fiber material for a tire cord capable of retaining the shape of fibers composing reinforcing cords of a belt or a carcass of a tire at a high temperature, particularly a temperature of not lower than the melting point of the polyamide, and to provide a method for producing the fiber material. <P>SOLUTION: The highly heat-resistant fiber material for reinforcing rubber which is a fiber material for reinforcing the rubber including the polyamide as a principal component has a cross-linked structure in at least a part of the polyamide molecular chain without causing hot-melt flow at a temperature of the melting point of the polyamide which is the principal component+20°C. The method for producing the highly heat-resistant fiber material for reinforcing the rubber includes irradiating the fiber material selected from an undrawn yarn prepared by melt-spinning a resin including the polyamide as the principal component, a drawn yarn obtained by hot-drawing the undrawn yarn, a twisted yarn cord prepared by twisting one or more drawn yarns together and a tire fabric prepared by weaving the twisted yarn cord, with ionizing radiation. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a rubber reinforcing fiber material, and more particularly, a fiber material constituting a reinforcing cord for a tire belt or a carcass, and is in a form without melting and flowing even at a high temperature, particularly above the melting point of a polymer. The present invention relates to a polyamide-based rubber reinforcing fiber material excellent in high heat resistance and capable of retaining the heat resistance.

  In general, polyester, polyamide and rayon are well known as organic fibers as typical examples of fibers 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 a carcass material is arranged from bead to bead approximately perpendicular to the tire rotation direction (radial direction) and a cord is arranged in the tire rotation direction. However, this belt layer is preferably made of steel having a high elastic modulus and little elongation, and the carcass material is made of inexpensive polyester that has good elastic modulus, fatigue resistance, and excellent creep resistance. . On the other hand, a polyamide tire is mainly used for a bias tire having a cord reinforcing layer that crosses diagonally (bias) from a bead to a bead because of excellent strength and fatigue resistance. In addition, rayon tire cords have a very low shrinkage due to the intrinsic properties of rayon fibers, are excellent in thermal dimensional stability and form stability, and are mainly used in radial tires for high-speed running such as passenger cars.

  Further, in recent years, tires have been developed that can run flat (that is, can run at a predetermined speed for a certain distance even if the tire pressure is punctured and the tire internal pressure becomes 0 kPa). 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, a tire cord made of polyester fiber or polyamide 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. Therefore, it was not suitable as a cord material for a run-flat tire. However, since these fibers are very abundant in supply, stable, inexpensive and lightweight, runflat tires are made of these polyester fibers and polyamide fibers in order to spread more widely. It is desirable to use a code.

Various methods for improving the heat resistance of polyamide tire cords in tire rubber have been proposed so far. For example, a new crystal is formed in a heat treatment process such as a vulcanization process by forming a fiber by adding 0.005 to 2.0% by weight of a amide compound or a tertiary amine-containing phosphorus compound that is highly compatible with polyamide in a polyamide resin. The generation is suppressed, and the fiber structure fracture time in the fatigue test can be delayed (for example, see Patent Document 1). The relationship between the acid concentration per 1 kg of polyamide and the base concentration is (base concentration) − (acid concentration) ≧ 5 mmol. In addition, there is a development example (for example, see Patent Document 2) in which a fiber structure with high thermal structure stability can be obtained by satisfying the above and satisfying a change value of tan δmax by the boiling water treatment of 0.015 or less. However, these are all improvements in heat resistance in a temperature region lower than the melting point, and are not capable of maintaining the shape above the melting point of the polyamide and maintaining the predetermined strength and elastic modulus.
JP-A-6-173116 JP-A-7-166420

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a highly heat-resistant rubber-reinforcing fiber material capable of maintaining its form even at a high temperature, particularly above the melting point of polyamide, and a method for producing the same. It is something to be offered.

  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 a part between the polyamide molecular chains, thereby completing the present invention. It came.

That is, the present invention has the following configuration.
1. It is a fiber material for reinforcing rubber with polyamide as a main component, and has a crosslinked structure in at least a part of the polyamide molecular chain, and does not cause hot melt flow at a temperature of the melting point of the main component polyamide + 20 ° C. High heat resistant rubber reinforcing fiber material characterized by
2. The high heat-resistant rubber reinforcing fiber material according to the first aspect, wherein the main component polyamide is at least one selected from polyamide 6, polyamide 66, polyamide 46, polyamide 6T, and polyamide 9T.
3. The fiber material for reinforcing a high heat-resistant rubber according to the above 1 or 2, wherein the main component polyamide is blended with 0.2 to 10% by weight of a compound polymerizable by ionizing radiation.
4). In the first aspect, the main component polyamide is blended in an amount of 0.1 to 3% by weight of a compound having at least one epoxy group and aliphatic unsaturated group as a compound polymerizable by ionizing radiation. Or the fiber material for high heat-resistant rubber reinforcement as described in 2nd.
5. The high heat-resistant rubber reinforcing fiber material according to any one of the first to fourth aspects, wherein the strength is 4.5 cN / dtex or more.
6). A tire cord using at least part of the high heat-resistant rubber reinforcing fiber material according to any one of the first to fifth aspects.
7). A tire cord for a run-flat tire using at least a part of the fiber material for reinforcing a high heat resistance rubber according to any one of the first to fifth aspects.
8). A radial tire using at least a part of the high heat-resistant rubber reinforcing fiber material according to any one of the first to fifth aspects.
9. It is selected from unstretched yarn obtained by melt spinning a resin mainly composed of polyamide, stretched yarn obtained by heat-stretching the unstretched yarn, twisted cord obtained by twisting one or more of the stretched yarns, and silk weave woven from the twisted cord. A method for producing a fiber material for reinforcing a high heat-resistant rubber, which comprises irradiating a fiber material with ionizing radiation.
10. The method for producing a fiber material for reinforcing a high heat-resistant rubber as described in the above item 9, wherein a resin in which 0.2 to 10% by weight of a compound polymerizable by ionizing radiation is blended with polyamide as a main component is melt-spun. .
11. Melt spinning a resin containing 0.1 to 3% by weight of a compound having at least one epoxy group and an aliphatic unsaturated group as a compound that can be polymerized by ionizing radiation to the main component polyamide The manufacturing method of the fiber material for high heat-resistant rubber reinforcement as described in said 9th.
12 The method for producing a fiber material for reinforcing a high heat-resistant rubber according to any one of the ninth to eleventh aspects, wherein the ionizing radiation is an electron beam or a gamma ray.

  According to the present invention, it is possible to provide a highly heat-resistant polyamide fiber material for rubber reinforcement capable of maintaining its form at a high temperature, particularly at a temperature equal to or higher than the melting point of polyamide, and an efficient production method thereof.

  Hereinafter, the present invention will be described in detail. As described above, the present invention can 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 exceeds the melting point of polyamide. It is another object of the present invention to provide a polyamide fiber material for rubber reinforcement that has a highly improved heat resistance and can maintain a predetermined strength and elastic modulus at a high temperature, particularly above the melting point of polyamide. Even if it is above the melting point of the polyamide, it is not easy to confirm that the form is maintained in the entire temperature range up to infinite temperature. Therefore, in the present invention, the melting point of the polyamide as the main component in which the crosslinked structure is not formed. It is specified that no hot melt flow occurs at a temperature 20 ° C. higher than that.

  Examples of the polyamide in the present invention include aliphatic dicarboxylic acids such as adipic acid, suberic acid, sebacic acid and dodecanoic acid, aromatic dicarboxylic acids such as terephthalic acid and isophthalic acid, 1,4-aminobutane, hexamethylenediamine and nanondiamine. Various polycondensates with aliphatic diamines such as metaxylylenediamine, etc., polycondensates of aminocarboxylic acids such as 11-aminoundecanoic acid, lactams such as ε-caprolactam, undecane lactam, lauryl lactam, etc. Ring-opening polymers and the like. Each of these components may be polymerized singly or a plurality of components may be copolymerized, but suitable for the high heat-resistant rubber reinforcing fiber material of the present invention are polyamide 6 and polyamide having a relatively high melting point. 66, polyamide 46, polyamide 6T, and polyamide 9T. Polyamide 6 is a ring-opening polymer of ε-caprolactam, polyamide 66 is a polycondensate of adipic acid and hexamethylenediamine, polyamide 46 is a polycondensate of adipic acid and diaminobutane, and polyamide 6T is terephthalic acid and hexamethylenediamine. Polyamide 9T is a polycondensate of terephthalic acid and nanondiamine. These may be used alone or in combination of two or more.

  As a method for obtaining such a polyamide, it is not necessary to employ special polymerization conditions, and it can be synthesized by a known method.

  In addition, the polyamide may be used with commonly used additives such as inorganic phosphorus compounds such as phosphoric acid and sodium diphosphite, organic phosphorus compounds such as phenylphosphonic acid and triphenyl phosphite, phosphorus-nitrogen complexes, phosphorus -Polymerization catalyst such as nitrogen compounds, copper compounds such as copper acetate, copper bromide, copper iodide, 2-mercaptobenzimidazole copper complex, 2-mercaptobenzimidazole, tetrakis- [methylene-3- (3,5- Di-t-butyl-4-hydroxyphenyl) -propionate] -thermal stabilizers such as methane, light stabilizers such as manganese lactate and manganese diphosphite, matting agents such as titanium dioxide and kaolin, cyclic phenol, ethylene Includes lubricants such as bisstearylamide and calcium stearate, plasticizers, crystallization inhibitors, antioxidants, radical scavengers, antistatic agents, etc. You can have it.

  Polyamide undergoes a certain degree of cross-linking reaction by ionizing radiation without the addition of cross-linking aids, but in order to obtain a high cross-linking density for the purpose of efficient cross-linking with less radiation energy, a compound that can be polymerized by ionizing radiation is used. You may mix | blend with polyamide.

  The compound polymerizable by ionizing radiation used in the present invention is a compound containing two or more functional groups containing an aliphatic carbon-carbon double bond or carbon-carbon triple bond in the molecule. Is not particularly limited, including acrylic, methacrylic, allyl, acryloyl, methacryloyl, acryloxy, methacryloxy, propenyl, isopropenyl, butenyl, crotyl, isobutenyl, Mention may be made of compounds containing a hexenyl group, a vinyl ether group or the like. Specifically, ethylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, triethylene glycol di (meth) acrylate, polyethylene glycol di (meth) acrylate, 1,3-butylene glycol di (meth) acrylate, 1 , 4-butanediol di (meth) acrylate, 1,6-hexanediol di (meth) acrylate, 1,9-nonanediol di (meth) acrylate, neopentyl glycol di (meth) acrylate, ethoxylated bisphenol A di ( (Meth) acrylate, trimethylolpropane tri (meth) acrylate, EO-modified trimethylolpropane tri (meth) acrylate, PO-modified trimethylolpropane tri (meth) acrylate, tetramethylolmethanetetraa Relate, pentaerythritol tri (meth) acrylate, ethoxylated isocyanuric acid tri (meth) acrylate, pentaerythritol tetra (meth) acrylate, dipentaerythritol pentaacrylate, epoxy (meth) acrylates, urethane (meth) acrylates, etc. Polyfunctional allyl monomers such as functional (meth) acrylic compounds, triallyl isocyanurate, triallyl cyanurate, allyl (meth) acrylate, diallyl (meth) acrylate, diallyl (iso) phthalate, diallylbenzene phosphonate, Examples include polyfunctional allyl prepolymers obtained by polymerizing these polyfunctional monomers, polyfunctional acryloyl monomers such as trisacryloyloxyethyl phosphate, and the like. Not intended to be. These compounds may be used alone or in combination of two or more.

  The addition amount of the compound polymerizable by ionizing radiation to the polyamide is preferably 0.2 to 10% by weight. Even if the addition amount is zero, some cross-linking structure is formed in the polyamide by ionizing radiation and is not excluded from the present invention. However, when the addition amount is less than 0.2% by weight, the cross-linking reaction is accelerated. This is not preferable because the effect of the resin is insufficient. When the content is more than 10% by weight, the thermal crosslinking reaction is promoted during melt spinning, which causes gelation of the resin.

  Furthermore, in the present invention, a compound having at least one epoxy group and at least one aliphatic unsaturated group is blended with the polyamide. When the polyamide and the compound are melt-kneaded, The carboxyl group and / or amino group at the end of the polyamide molecule reacts with the epoxy group, so that a crosslinking group can be directly introduced into the end of the polyamide molecule.

  The compounds having at least one epoxy group and aliphatic unsaturated group used in the present invention are not particularly limited, including known ones, but glycidyl acrylate, glycidyl methacrylate, allyl glycidyl ether, 2-allyl Phenyl glycidyl ether, 2,4-diallylphenyl glycidyl ether, 2,6-diallylphenyl glycidyl ether, 2,4,6-triallylphenyl glycidyl ether, 2-crotylphenyl glycidyl ether, 2,4-dicrotylphenyl glycidyl Ether, 2,6-dicrotylphenyl glycidyl ether, 2,4,6-tricrotylphenyl glycidyl ether, 4-vinylphenyl glycidyl ether, 1,4-diglycidyloxy-2,6-diallylbenzene, 4 Vinyl-1-cyclohexylene-1,2-epoxide, 3,4-epoxycyclohexylmethyl acrylate, 3,4-epoxycyclohexylmethyl methacrylate, 3,4-epoxycyclohexylethyl acrylate, 3,4-epoxycyclohexylethyl methacrylate, 3,4-epoxycyclohexylbutyl acrylate, 3,4-epoxycyclohexylbutyl methacrylate, allyl 2,3-oxypropyl carbonate, propenyl 2,3-oxypropyl carbonate, butenyl 2,3-oxypropyl carbonate, di Acrylic monoglycidyl cyanurate, dimethacrylic monoglycidyl cyanurate, diallyl monoglycidyl cyanurate, diacryloyl monoglycidyl cyanurate, dicrotyl monog Cidyl cyanurate, diallyl monoglycidyl isocyanurate, diacrylic monoglycidyl isocyanurate, dimethacrylic monoglycidyl isocyanurate, diacryloyl monoglycidyl isocyanurate, dicrotyl monoglycidyl isocyanurate, monoacrylic diglycidyl cyanurate, monomethacrylic diglycidylsia Nurate, monoallyl diglycidyl cyanurate, monoacryloyl diglycidyl cyanurate, monochlorotyl diglycidyl cyanurate, monoacrylic diglycidyl isocyanurate, monomethacrylic diglycidyl isocyanurate, monoallyl diglycidyl isocyanurate, monoacryloyl diglycidyl isocyanurate , Monochlorodiglycidyl isocyanurate, and glycidi of the above compounds N-allylglycidyloxybenzamide, N, N-, a compound in which the alkyl group is replaced with 2,3-epoxybutyl group, 2,3-epoxy-2-methylpropyl group, 2,3-epoxy-2-methylbutyl group, etc. Diallylglycidyloxybenzamide, N, N-diallylglycidyloxyisophthalamide, N, N-diallylglycidyloxyterephthalamide, diallylglycidylamine, diallylbisphenol A diglycidyl ether, diacrylbisphenol A diglycidyl ether, dimethacrylbisphenol A Diglycidyl ether, 2,2-bis (3-allyl-4-glycidyloxyphenyl) methane, 2,2-bis (3-allyl-4-glycidyloxyphenyl) propane, 1,1-bis (3-allyl- 4-glycidyloxyphenyl) Rhohexane, 2,2-bis (3,5-diallyl-4-glycidyloxyphenyl) methane, 2,2-bis (3,5-diallyl-4-glycidyloxyphenyl) propane, bis (3-allyl-4- Glycidyloxyphenyl) ether, bis (3,5-diallyl-4-glycidyloxyphenyl) ether, bis (3-allyl-4-glycidyloxyphenyl) sulfone, bis (3,5-diallyl-4-glycidyloxyphenyl) Examples include sulfone, 3,3′-diallyl-4,4′-diglycidyloxybenzophenone, N- [4- (2,3-epoxypropoxy) -3,5-dimethylbenzyl] acrylamide and the like. Among the above compounds, diallylphenyl glycidyl ether, diallyl monoglycidyl isocyanurate, diacryl monoglycidyl isocyanurate, dimethacryl monoglycidyl isocyanurate, diacryloyl monoglycidyl isocyanate having two or more aliphatic unsaturated groups in the molecule Nurate, diallyl bisphenol A diglycidyl ether and the like are preferably used. 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.

  The addition amount of the compound having at least one epoxy group and aliphatic unsaturated group to the polyamide is preferably 0.1 to 3% by weight. If the amount added is less than 0.1% by weight, the effect of accelerating the crosslinking reaction is insufficient, which is not preferable. If it is more than 3% by weight, the thermal crosslinking reaction is accelerated during melt spinning, and the resin is gelled. It is not preferable because it causes it.

  When adding the compound to the polyamide, a catalyst for promoting the reaction may be added at the same time. The catalyst is not particularly limited and used, for example, an alkali metal compound represented by sodium acetate, potassium acetate, lithium acetate, sodium stearate, potassium stearate, lithium stearate and the like, barium acetate, magnesium acetate, Alkaline earth metal compounds such as strontium acetate, barium stearate, magnesium stearate, strontium stearate, triethylamine, tributylamine, trihexylamine, triethanolamine, triethylenediamine, dimethylbenzylamine, pyridine, picoline, etc. Tertiary amines, imidazole compounds such as 2-methylimidazole, 2-ethylimidazole, 2-isopropylimidazole, tetramethylammonium chloride, Quaternary ammonium salts such as laethylammonium chloride, trimethylbenzylammonium chloride, triethylbenzylammonium chloride, phosphine compounds such as trimethylphosphine, triethylphosphine, tributylphosphine, trioctylphosphine, triphenylphosphine, tetramethylphosphonium bromide, tetrabutyl Phosphonium salts such as phosphonium bromide, tetraphenylphosphonium bromide, triphenylbenzylphosphonium bromide, phosphate esters such as trimethyl phosphate, triethyl phosphate, tributyl phosphate, triphenyl phosphate, oxalic acid, p-toluenesulfonic acid, dinonylnaphthalenedisulfonic acid , Dodecylbenzenesulfonic acid Organic acids, boron trifluoride, aluminum tetrachloride, titanium tetrachloride, etc. Lewis acids such as tin tetrachloride may be exemplified. These can be used alone or in combination of two or more. Of these, alkali metal compounds, alkaline earth metal compounds, phosphine compounds, and phosphate ester compounds are preferably used. The addition amount of the catalyst is not particularly limited, but is preferably 0.001 to 1% by weight, more preferably 0.01 to 0.5% by weight, based on the polyamide.

  The high heat resistant rubber reinforcing fiber material of the present invention is an unstretched yarn obtained by melt spinning the above polyamide, 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.

  In the production method of the raw yarn, conventional spinning conditions can be adopted, but the spinning speed is 200 to 4000 m / min, preferably 500 to 3000 m / min. A spinning speed lower than 200 m / min is not preferable because of low productivity.

  When blending a polyamide with a compound polymerizable by ionizing radiation and / or a compound having at least one epoxy group and an aliphatic unsaturated group, for example, melt-kneading the polyamide resin and these compounds Can be pelletized and used as a masterbatch, and when a polyamide resin is melt-spun, these compounds can be directly added and spun, but the method is not limited to these. Absent.

  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 high heat-resistant rubber reinforcing fiber thus obtained is twisted 10 to 100 times per 10 cm according to a conventional method, then a plurality of yarns are combined, and 10 to 100 times per 10 cm in the opposite direction. The twisted cord (upper twist) is used to form a twisted cord. Next, the twisted cord is woven according to a conventional method to form a stale fabric, and further treated with an adhesive according to a conventional method to obtain a dip fabric.

  The strength of the high heat-resistant rubber reinforcing fiber material in the present invention is 4.5 cN / dtex or more. Preferably it is 5 cN / dtex, More preferably, it is 6.0 cN / dtex or more. If the strength is less than 4.5 cN / dtex, not only the physical properties of the final product but also the process passability in the production process is lowered, which is not preferable. The higher the strength, the better. The upper limit is not particularly limited, but it is usually 10 cN / dtex or less, and in the case of run-flat tire applications, it is intended to replace what has conventionally been used in many rayons. For example, it may be 8 cN / dtex or less.

  The high heat resistant rubber reinforcing fiber material of the present invention has a crosslinked structure in at least a part between the polyamide molecular chains of the main component, and this crosslinking is formed by irradiating with ionizing radiation. The ionizing radiation is preferably an electron beam or γ-ray that has a large transmission power of irradiation energy.

  This ionizing radiation can be irradiated in any process from the spinning process of the fiber material for reinforcing the heat-resistant rubber to the production of the dip fabric. However, in terms of ionizing radiation irradiation efficiency and quality stability, twisted yarn It is preferable to irradiate in the state of a cord or a suede fabric. The irradiation dose of ionizing radiation is not particularly limited as long as the desired physical properties are satisfied, but is preferably 20 to 1000 kGy. When the irradiation dose is lower than 20 kGy, the degree of crosslinking tends to be insufficient, and when it is higher than 1000 kGy, the polyamide molecular chain is decomposed and the strength properties are deteriorated. 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. The atmosphere gas for irradiating with ionizing radiation is not particularly limited, but the oxygen concentration is preferably low in order to suppress oxidative decomposition. A preferable oxygen concentration is 5000 ppm or less, and more preferably 1000 ppm or less.

  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) Relative viscosity (RV)
The sample solution was prepared by dissolving the sample in 96.3 ± 0.1 wt% reagent-grade concentrated sulfuric acid so that the polymer concentration was 10 mg / ml, and the water dropped at a temperature of 20 ° C. ± 0.05 ° C. The relative viscosity of the solution is measured using an Ostwald viscometer of several to 7 seconds. In the measurement, using the same viscometer, the relative viscosity RV is calculated from the ratio of the drop time T0 (second) of 20 ml of sulfuric acid and the drop time T1 (second) of 20 ml of the sample solution, which is the same as when the sample solution was adjusted. Calculate using.
Relative viscosity (RV) = T1 / T0

(2) Strength Using “Tensilon” manufactured by Orientic Co., Ltd., with a sample length of 20 mm (length between chucks), an elongation rate of 100% / min, and a stress-strain curve at an ambient temperature of 20 ° C. and a relative humidity of 65% The value obtained by dividing the stress at the breaking point by the fineness was obtained as the strength (cN / dtex). In addition, each value used the average value of five measurements.

(3) Melting point of polymer After heating and melting the sample at 300 ° C. for 2 minutes, 10 mg of the 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.).

(4) Observation of hot melt flow After placing the sample on a hot plate that can be set to a constant temperature for 1 minute, it is judged by an optical microscope whether the hot melt flow is present. Observation was performed at a temperature of the melting point of the polymer + 20 ° C., and the temperature at which heat flow occurred was defined as the heat flow start temperature (° C.).

Example 1
A polyamide 66 dry chip having a relative viscosity of 3.6 was melted with a uniaxial extruder and spun by discharging from a spinneret at 303 ° C. having 336 orifices having a hole diameter of 0.5 mm. At that time, the film was taken up at a speed of 2000 m / min, and was drawn 1.7 times at a drawing temperature of room temperature and a set roller temperature of 140 ° C. to obtain a drawn yarn of 1440 dtex and 336 filaments. The drawn yarns were combined and subjected to 1440 dtex / 2, 43 T / 10 cm, and twisted to form a twisted cord. The strength of this cord was 7.9 cN / dtex. The twisted cord was irradiated with an electron beam of 500 kGy at an acceleration voltage of 600 keV in a nitrogen atmosphere (oxygen concentration of 1000 ppm or less) at room temperature under a constant tension. The results are shown in Table 1. The heat flow starting temperature was 295 ° C., and the form as a twisted cord was maintained without melting even at the melting point of the polyamide 66 or higher. The strength of the cord after electron beam irradiation was 6.9 cN / dtex.

(Example 2)
0.5% by weight of diallyl monoglycidyl isocyanurate and 0.05% by weight of antioxidant Irganox 1010 (manufactured by Ciba Specialty Chemicals) were added to polyamide 66, and the draw ratio was 1.6 times. Except for this, a twisted cord was obtained in the same manner as in Example 1, and irradiated with an electron beam with an acceleration voltage of 600 keV under a constant tension at room temperature in a nitrogen atmosphere (oxygen concentration of 1000 ppm or less). The results are shown in Table 1.

(Example 3)
Diallyl monoglycidyl isocyanurate was added to polyamide 66 by 1.5 wt% and antioxidant Irganox 1010 (manufactured by Ciba Specialty Chemicals) was added by 0.15 wt%, and the draw ratio was 1.5 times. Except for this, a twisted cord was obtained in the same manner as in Example 1, and irradiated with an electron beam with an acceleration voltage of 600 keV under a constant tension at room temperature in a nitrogen atmosphere (oxygen concentration of 1000 ppm or less). The results are shown in Table 1. By adding a compound capable of being polymerized by ionizing radiation, higher heat resistance can be expressed with a smaller irradiation dose than in Example 1.

Example 4
Twisted yarn in the same manner as in Example 1, except that 1.0% by weight of triallyl isocyanurate and 0.1% by weight of antioxidant Irganox 1010 (manufactured by Ciba Specialty Chemicals) were added to polyamide 66. A cord was obtained and irradiated with an electron beam of 300 kGy at an acceleration voltage of 600 keV in a nitrogen atmosphere (oxygen concentration of 1000 ppm or less) at room temperature under a constant tension. The results are shown in Table 1.

(Experimental example 1)
The twisted cord obtained in Example 2 was irradiated with an electron beam of 2000 kGy at an acceleration voltage of 600 keV in a nitrogen atmosphere (oxygen concentration of 1000 ppm or less) at room temperature under a constant tension. The heat flow starting temperature was 305 ° C., and the shape as a twisted cord was maintained without melting even above the melting point of polyamide 66, but the strength was reduced to 4.1 cN / dtex, and it was used as a tire cord application. Slightly lacking in strength.

(Experimental example 2)
The twisted cord obtained in Example 1 was irradiated with 10 kGy of an electron beam with an acceleration voltage of 600 keV in a nitrogen atmosphere (oxygen concentration of 1000 ppm or less) at room temperature under a constant tension, but the heat flow start temperature was 260 ° C. It was found that sufficient heat resistance was not obtained. It is considered that a sufficient degree of crosslinking was not obtained due to insufficient electron beam irradiation.

(Comparative Example 1)
Attempted melt spinning by adding 12 wt% of todiallyl monoglycidyl isocyanurate and 1.2 wt% of antioxidant Irganox 1010 (Ciba Specialty Chemicals) to polyamide 66. Occurred frequently and stable winding was not possible.

  The high heat resistant rubber reinforcing fiber material of the present invention is a polyamide fiber material for tire cords having a cross-linked structure at least at a part between polyamide molecular chains. Compared to high melting point or higher, the shape can be maintained without heat melting, so that the rubber reinforcing fiber is suitable for tire cords for run-flat tires that are punctured to lower internal pressure and are locally exposed to high temperatures. Material.

Claims (12)

  It is a fiber material for reinforcing rubber with polyamide as a main component, and has a crosslinked structure in at least a part of the polyamide molecular chain, and does not cause hot melt flow at a temperature of the melting point of the main component polyamide + 20 ° C. High heat-resistant rubber reinforcing fiber material characterized by   2. The high heat resistant rubber reinforcing fiber material according to claim 1, wherein the main component polyamide is at least one selected from polyamide 6, polyamide 66, polyamide 46, polyamide 6T, and polyamide 9T.   The high heat resistant rubber reinforcing fiber material according to claim 1 or 2, wherein 0.2 to 10% by weight of a compound polymerizable by ionizing radiation is blended with the main component polyamide.   2. A compound having 0.1 to 3% by weight of a compound having at least one epoxy group and one aliphatic unsaturated group as a compound polymerizable by ionizing radiation to a main component polyamide. Or the fiber material for high heat-resistant rubber reinforcement of 2.   The high heat-resistant rubber reinforcing fiber material according to any one of claims 1 to 4, wherein the strength is 4.5 cN / dtex or more.   A tire cord using at least a part of the fiber material for reinforcing a high heat resistance rubber according to any one of claims 1 to 5.   A tire cord for run-flat tires using at least part of the fiber material for reinforcing a high heat-resistant rubber according to any one of claims 1 to 5.   A radial tire using at least a part of the high heat-resistant rubber reinforcing fiber material according to claim 1.   It is selected from unstretched yarn obtained by melt spinning a resin mainly composed of polyamide, stretched yarn obtained by heat-stretching the unstretched yarn, twisted cord obtained by twisting one or more of the drawn yarns, and woven fabric woven from the twisted cord. A method for producing a fiber material for reinforcing a high heat-resistant rubber, which comprises irradiating a fiber material with ionizing radiation.   The method for producing a fiber material for reinforcing a high heat-resistant rubber according to claim 9, wherein a resin in which 0.2 to 10% by weight of a compound polymerizable by ionizing radiation is blended with polyamide as a main component is melt-spun. .   It is characterized by melt spinning a resin in which 0.1 to 3% by weight of a compound having at least one epoxy group and aliphatic unsaturated group as a compound polymerizable by ionizing radiation is blended with a main component polyamide. The method for producing a fiber material for reinforcing a high heat-resistant rubber according to claim 9.   The method for producing a fiber material for reinforcing a high heat-resistant rubber according to any one of claims 9 to 11, wherein the ionizing radiation is an electron beam or a gamma ray.