JP2016176168A - Cord for rubber reinforcement - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a cord for rubber reinforcement high in initial strength, high in strength retention rate after a heat treatment and excellent in fatigue resistance.SOLUTION: There is provided a cord for rubber reinforcement consisting of an organic fiber by conducting upper twisting with taking out at least two or more lower twisting cords, where at least one of the lower twisting cords is one by twisting a pretreated yarn by impregnating an epoxy compound in an aramid fiber skeleton having no hysteresis of drying to moisture percentage after spinning twist of less than 15 mass% and drying to the moisture percentage of 7 mass% or less, initial elasticity of the pretreated yarn is 300 cN/dtex to 750 cN/dtex and twist coefficients during lower twisting and upper twisting are in range of 2 to 10. There is provided a cord for rubber reinforcement to which an adhesive mainly containing resorcin formalin rubber latex (RFL) is added. It is preferable to contain one in which nylon yarn is twisted in at least one of the lower twisted cords.SELECTED DRAWING: None

Description

  The present invention relates to a rubber reinforcing cord made of organic fibers, and more particularly to a rubber reinforcing cord having high initial strength, high strength retention after heat treatment, and excellent fatigue resistance.

  Reinforcing fiber cords are embedded in rubber products such as transmission belts, conveyor belts, tires, rubber hoses and the like. As a reinforcing fiber cord, an aramid fiber cord having a high strength and a low elongation property is widely known. Aramid fiber cords have high strength, high elastic modulus, high heat resistance, flame resistance, chemical resistance, etc., and are used as industrial materials for reinforcing materials such as automobile and bicycle tires, conveyor belts, ropes, fish nets, etc. Widely used. As aramid fiber cords, a plurality of raw yarns are arranged into a twisted yarn, which is then subjected to a dipping treatment with a resorcin / formalin / rubber latex (hereinafter referred to as RFL) solution to give an adhesive. Has been. In the belt using the aramid fiber cord as the reinforcing cord, the fraying property of the cord and the bending fatigue resistance of the belt are improved.

  However, when making aramid fiber cords, it is common to add a twist to the original yarn and then draw two of the yarns together to make a twisted cord with an upper twist in the opposite direction to the twist. It is. In Patent Document 1, an aramid yarn is subjected to epoxy treatment, and then an aramid fiber material immersed in an RFL solution is twisted, three of which are aligned and twisted, and then immersed in a solution of rubber paste. The code is disclosed.

  Patent Document 2 discloses a cord in which two aramid fibers treated with epoxy are aligned and twisted, three of these lower twisted yarns are aligned, subjected to upper twisting in the opposite direction, and then immersed in an RFL solution. Has been.

Japanese Patent Laid-Open No. 9-210139 JP 2005-171431 A

However, these cords have a problem that strength retention after heat treatment is lowered and fatigue resistance is inferior.
An object of the present invention is to provide a cord for rubber reinforcement made of organic fiber that has high initial strength, high strength retention after fatigue, and excellent fatigue resistance.

As a result of intensive studies by the present inventors in order to achieve the above-mentioned problems, the epoxy compound was infiltrated into the aramid fiber skeleton having no history of drying after spinning to a moisture content of less than 15% by mass. The pretreated yarn dried to less than mass% is superior in strength retention after heat treatment to the conventional aramid fiber not subjected to epoxy pretreatment, and at least two or more twisted cords are aligned. The present inventors have found that a cord with an upper twist is excellent in fatigue resistance, and have reached the present invention.
Furthermore, it has been found that the strength retention after fatigue is drastically improved by including at least one of the under-twist cords with a twisted nylon yarn.

  That is, the present invention is as follows.

1) A rubber-reinforcing cord made of an organic fiber in which at least two or more lower twisted cords are aligned and subjected to upper twisting, and at least one of the lower twisted cords has a moisture content after spinning of 15 For reinforcing rubber, characterized in that an epoxy compound is infiltrated into an aramid fiber skeleton having no history dried to less than mass%, and the pretreated yarn is twisted and dried to a moisture content of 7 mass% or less. code.
2) The cord for rubber reinforcement as described in 1) above, wherein the twist coefficient at the time of the lower twist is in the range of 2 to 10, and the twist coefficient at the time of the upper twist is in the range of 2 to 10.
3) The rubber reinforcing cord according to 1) or 2) above, wherein the pretreatment yarn impregnated with the epoxy compound has an initial elastic modulus of 300 cN / dtex to 750 cN / dtex.
4) A rubber reinforcing cord obtained by adding an adhesive mainly composed of resorcin, formalin, rubber latex (RFL) to the rubber reinforcing cord according to any one of 1) to 3) above.
5) The rubber reinforcing cord according to any one of 1) to 4) above, wherein at least one of the lower twisted cords includes a twisted nylon yarn.

According to the present invention, the initial strength is high, the strength retention after heat treatment is high, and the strength retention after fatigue is 70% or more, in some cases 80% or more, further 90% or more. It is possible to provide a rubber reinforcing cord excellent in the above. In addition, by aligning the pre-twisted cord of the pretreated yarn in which the epoxy compound is infiltrated into the aramid fiber and the twisted cord of the nylon yarn and applying the upper twist, the strength retention after fatigue is 98% or more, and further 99% This can be significantly increased.
As a result, it is possible to obtain a rubber reinforcing cord with constant initial strength and strength after fatigue and without quality variations. By using this cord, high-quality car tires and bicycle tires with stable strength can be transported. A belt or the like can be provided.

The rubber reinforcing cord comprising the organic fiber of the present invention is a rubber reinforcing cord in which at least two or more lower twisted cords are aligned and subjected to upper twisting, and at least one of the lower twisted cords is spun. A pretreated yarn obtained by impregnating an epoxy compound into an aramid fiber skeleton having no history dried to a moisture content of less than 15% by mass and drying to a moisture content of 7% by mass or less is twisted. In the present invention, the moisture content (R) is a value determined by the following formula.
R = {(m ₁ −m ₂ ) / m ₂ } × 100
R: Moisture content [%]
m ₁ : Mass at the time of sampling [g]
m ₂ : Absolute dry mass of the sample [g]

  In the present invention, an aramid fiber is a fiber having at least one divalent aromatic group that may be generally substituted in a repeating unit of a polymer forming the fiber, and having at least one amide bond. There is no particular limitation as long as it is a known aromatic polyamide fiber or aramid fiber. In the above, “an optionally substituted divalent aromatic group” means a divalent aromatic group which may have one or more substituents which are the same or different.

  The aramid fibers include para-aramid fibers and meta-aramid fibers. The present invention is particularly effective and preferable for high-strength para-aramid fibers. Examples of the para-aramid fiber include polyparaphenylene terephthalamide fiber (DuPont USA, manufactured by Toray DuPont, trade name “Kevlar” (registered trademark)), copolyparaphenylene-3,4′-oxydiphenylene. Examples include terephthalamide fiber (trade name “Technola” (registered trademark), manufactured by Teijin Techno Brodacts Corporation). Examples of meta-aramid fibers include polymetaphenylene terephthalamide fibers (manufactured by DuPont, USA, trade name “NOMEX” (registered trademark)). Among these aramid fibers, polyparaphenylene terephthalamide fibers are desirable.

In the present invention, an aramid fiber having no history of moisture content being less than 15% by mass after spinning means that the moisture content in the fiber has become less than 15% by mass after fiber spinning. Means that.
The reason why the moisture content in the aramid fiber is 15% by mass or more is that when the moisture content is less than 15% by mass, the structure of the aramid fiber becomes dense and the epoxy compound is allowed to uniformly penetrate into the fiber skeleton. This is because it becomes difficult and a crosslinking effect with rubber cannot be obtained. The moisture content in the aramid fiber is preferably 25% by mass or more in order to allow the epoxy compound to uniformly penetrate into the fiber skeleton.
Moreover, it is preferable that the moisture content in an aramid fiber is 100 mass% or less. A high moisture content is not particularly problematic for imparting an epoxy compound. However, if the amount of moisture is too large, the epoxy compound will become moisture when it comes into contact with a guide or the like after the infiltration of the epoxy compound and before the winding process. There is a possibility of dropping out together.
The moisture content in the aramid fiber that allows the epoxy compound to permeate is more preferably 25 to 70% by mass, and particularly preferably 25 to 50% by mass.

In the present invention, the best mode for imparting an epoxy compound to an aramid fiber having a history of moisture content of less than 15% by weight after spinning is to dissolve polyparaphenylene terephthalamide (PPTA) in concentrated sulfuric acid. A viscous solution of 18 to 20% by mass is discharged from a spinneret, spun into air for a short time, and then spun into water. At this time, it is preferable to set the shear rate during discharge of the die to 25,000 to 50,000 sec ⁻¹ . Then, after neutralizing the fiber coagulated in the spinning bath with an aqueous sodium hydroxide solution, the moisture content is preferably adjusted by drying at 100 to 160 ° C., preferably for 5 to 20 seconds. In this state, an epoxy compound is added to the aramid fiber and the fiber is allowed to penetrate. The application temperature is not particularly limited, and may be performed in a temperature range of about 5 to 90 ° C. At the time of drying, it is preferable that the PPTA fiber keeps the crystal size of the PPTA fiber less than 50 angstroms and keeps the moisture content of 15 to 100% by mass, and the epoxy compound is allowed to permeate there.

  Subsequently, by drying the aramid fiber to which the epoxy compound has been added to make the moisture content 7% by mass or less, it is possible to obtain a pretreated yarn infiltrated with the epoxy compound.

  The epoxy compound should be infiltrated in an amount of 0.1 to 2.0% by mass, preferably 0.2 to 1.0% by mass, with respect to the fiber mass in which the moisture content of the aramid fiber is converted to 0%. A curing agent can also be added to the epoxy compound. In this case, the curing agent should be infiltrated by 0.02 to 1.0% by mass, preferably 0.04 to 0.5% by mass.

  The epoxy compound is preferably one or more or a mixture of two or more selected from glycidyl ethers of polyhydric alcohols such as glycerol, sorbitol, and polyglycerol. Examples thereof include glycerol diglycidyl ether, glycerol triglycidyl ether, sorbitol polyglycidyl ether, polyglycerol polyglycidyl ether, and the like.

  As the curing agent, an amine is preferable, and a tertiary amine is particularly preferable. Examples thereof include dimethyloctylamine, dimethyldecylamine, dimethyllaurylamine, and long-chain alkylpolyoxyethylene type tertiary amine obtained by adding ethylene oxide to an aliphatic primary amine.

  A compatibilizer, an antistatic agent, a surfactant, a smoothness improver, and the like may be added to the epoxy compound as an oil component. By adding these oil agent components, the strength retention after fatigue can be further increased. An oil agent component will not be restrict | limited especially if it is a well-known compound, Each may be used independently, and may be used in combination of 2 or more types as appropriate. Examples of the surfactant include nonionic surfactants, anionic surfactants, cationic surfactants, and amphoteric surfactants. Examples of the smoothness improver include fluorine, silicone, and mineral oil.

Examples of the compatibilizing agent include glycol ether compounds represented by the general formula (I).
R ¹ —O— (AO) n—R ² (I)
In the general formula (I), R ¹ is an alkyl group or alkenyl group having 1 to 10 carbon atoms, preferably 4 to 8 carbon atoms, and R ² is a hydrogen atom or alkyl having 1 to 5 carbon atoms. A group or an alkenyl group having 1 to 5 carbon atoms; Preferably, R ² is a hydrogen atom. A represents an alkylene group having 2 to 4 carbon atoms, preferably an alkylene group having 2 to 3 carbon atoms, and n represents an average number of added moles of the oxyalkylene group (AO), preferably 1 to 10. It is an integer, more preferably 2-8. In-(AO)-, the same oxyalkylene group may be added alone, or two or more kinds of oxyalkylene groups may be added.
Specific examples of the compound represented by the general formula (I) include diethylene glycol monobutyl ether, diethylene glycol mono 2-ethylhexyl ether, dipropylene glycol monobutyl ether, polypropylene glycol (n = 3) glyceryl ether and the like.

  The method for imparting an epoxy compound, a curing agent, an oil component, etc. to an aramid fiber is not particularly limited, and any conventionally known method may be employed, for example, an immersion oil supply method, a spray oil method, a roller oil method, a metering It is applied to the aramid fiber by a method such as a guide oiling method using a pump.

  The rubber reinforcing cord made of the organic fiber of the present invention is obtained by aligning at least two or more lower twisted cords and applying an upper twist, but at least one of the lower twisted cords is obtained by the above method. A twisted pretreated yarn obtained by impregnating an epoxy compound into the obtained aramid fiber skeleton is used. By including at least one lower twisted cord, the rubber has high strength, high elastic modulus, high heat resistance, flame resistance, chemical resistance, and high initial strength, strength after fatigue, and strength retention after fatigue. A reinforcing cord can be provided.

  In the rubber reinforcing cord made of the organic fiber of the present invention, it is preferable that at least one of the lower twisted cords includes a nylon yarn twisted. Thereby, the strength retention after fatigue is drastically improved. Nylon yarn is preferably nylon 66 fiber (polyhexamethylene adipamide fiber) from the viewpoint of excellent thermal dimensional stability, heat resistance, and the like. Nylon 6 fiber, nylon 46 fiber, etc. may be used. Nylon 66 fiber is composed of hexamethylene adipamide units at least 95 mol%, and may contain a copolymer component as long as it is 5 mol% or less. Examples of the copolymer component include ε-caproamide, tetramethylene adipamide, hexamethylene sebacamide, hexamethylene isophthalamide, tetramethylene terephthalamide, xylylene phthalamide, and the like.

  The number of the lower twisted cords may be at least two, and the number is not limited. 2-8 are preferable, More preferably, it is preferable that it is about 2-5. That is, for example, when the number of lower twisted cords is two, it is essential to include at least one lower twisted cord that has been impregnated with an epoxy compound. There is a method of twisting a yarn twisted cord and a method of twisting a pretwisted cord of the pretreated yarn and a yarn of other fibers.

  Examples of other fibers other than the pretreated yarn and nylon yarn in which the epoxy compound is infiltrated into the aramid fiber skeleton include polyester yarn and the like, and are used as long as the effect of the rubber reinforcing cord of the present invention is not impaired. be able to.

  As the twist coefficient of the rubber reinforcing cord of the present invention, the twist coefficient of the pre-treated yarn and the nylon yarn in which the epoxy compound is infiltrated into the aramid fiber skeleton at the time of lower twist (under twist cord) is in the range of 2 to 10. It is preferable that it is in the range of 4-8. When a twisted yarn consisting of a pre-treated yarn with an epoxy compound infiltrated into the aramid fiber skeleton and a twisted cord containing nylon yarn or nylon yarn are twisted together, the adhesive treatment liquid must penetrate into the cord. In order to carry out uniformly, it is preferable to make the number of twists of both yarns the same. Moreover, it is preferable that the twist coefficient at the time of a top twist (upper twist cord) is the range of 2-10, More preferably, it is the range of 4-8.

Here, the twist coefficient (K) is a value obtained by the following formula.
Twist coefficient (K) = 0.0033 x T x D ^1/2
T: Number of twists (T / 10cm)
D: Total fineness (dtex) of aramid fiber

  When the twist is applied to the fiber, the cord is given an elongation of a structural factor, and the force applied to the cord during bending is relaxed to improve the fatigue resistance. When the twist coefficient is too small, the fatigue resistance of the fiber cord tends to be insufficient. On the contrary, when the twist coefficient is too large, the elastic modulus of the aramid fiber tends to be a low value, and the strength tends to decrease.

  The initial elastic modulus of the pretreated yarn in which an epoxy compound is infiltrated into the aramid fiber skeleton used in the fiber cord of the present invention is preferably 300 cN / dtex to 750 cN / dtex, more preferably 300 cN / dtex to 430 cN. / Dtex is preferred. When the initial elastic modulus exceeds 750 cN / dtex, the elongation of the fiber itself is extremely low, and only the elongation of the structure factor of the twisted cord cannot absorb the force applied to the cord at the time of bending, resulting in poor fatigue resistance. It tends to be sufficient. On the other hand, when the initial elastic modulus is less than 300 cN / dtex, it becomes difficult to control the moisture after spinning in the production of the aramid fiber, and an aramid fiber having a history of drying to a moisture content of less than 15% by mass is produced. I can't do that.

  The rubber reinforcing cord made of the organic fiber according to the present invention is prepared by infiltrating an epoxy compound into the aramid fiber skeleton to obtain an epoxy pretreated yarn, and then twisting the pretreated yarn to produce a lower twisted cord. By preparing a plurality of primary twisted cords including at least one primary twisted cord and preparing an upper twisted cord, and then applying an adhesive mainly composed of resorcin, formalin, rubber latex (RFL) Can be produced. Alternatively, an upper twisted cord is prepared by arranging a plurality of lower twisted cords including at least one lower twisted cord of epoxy pretreated yarn and at least one lower twisted cord of nylon yarn, and then resorcin / formalin -It can produce by providing the adhesive which has rubber latex (RFL) as a main component.

  As a method for applying the adhesive, a known dipping method in which an RFL treatment liquid is immersed and applied to an aramid fiber cord using a dipping machine, and then dried and heat-treated under tension conditions can be used. The process from the immersion of the treatment liquid to the heat treatment may be completed only once, or may be completed in two steps. In order to exhibit high initial strength and strength after fatigue, the heat history is low 1 Twice treatment is preferred, and twice treatment is preferred in order to exhibit high adhesive strength. The adhesive component in the case of performing the treatment twice may be the same component or may be different.

  Examples of 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. Examples of the resorcin-formaldehyde initial condensate include novolak condensates obtained by condensing resorcin-formaldehyde in the presence of an acid catalyst or an alkali catalyst. In the treatment liquid, one or more compounds selected from an epoxy compound, a blocked polyisocyanate compound, an ethyleneimine compound, a reaction product of polyisocyanate and ethyleneimine, and the like may be mixed.

In the rubber reinforcing cord of the present invention, the epoxy compound penetrates the surface and the inside of the aramid fiber, so that the adhesion of the RFL treatment liquid is good, and the RFL and the fiber cord are firmly bonded to each other and have high adhesive strength. There is an advantage of expression. In addition, since the heat history that the raw yarn receives in the manufacturing process is small, there is an advantage that the strength of the cord is hardly lowered when the high temperature treatment is performed. Moreover, the PPTA fiber composite in which the epoxy compound penetrates into the fiber skeleton has an advantage that the epoxy compound easily reacts due to the catalytic effect of the curing agent.
Furthermore, by combining with nylon yarn, the initial strength is lower than that of dip cords made with aramid pretreated yarn, but the strength after fatigue is higher than that of dip cords made of conventional aramid fiber yarns. A high strength product after fatigue can be obtained, so that a high-quality product can be provided.

  Rubbers that use rubber reinforcement cords include acrylic rubber, acrylonitrile-butadiene rubber, hydrogenated acrylonitrile-butadiene rubber, isoprene rubber, urethane rubber, ethylene-propylene rubber, chloroprene rubber, silicone rubber, styrene-butadiene rubber, polysulfide rubber. , Natural rubber, butadiene rubber, fluorine rubber and the like. In addition to the main component rubber, the above rubber includes inorganic fillers such as carbon black and silica, organic fillers such as coumarone resin and phenolic resin, and softeners such as naphthenic oil for material modification. It may be included.

  Such a fiber reinforced rubber material can be molded by, for example, arranging the necessary number of the above-mentioned rubber reinforcing cords, sandwiching them with rubber, and pressurizing and heating them with a press. The fiber reinforced rubber material exhibits excellent durability against bending deformation and the like. Specific examples of the fiber reinforced rubber material include a belt, a hose, a tire cord, and the like.

EXAMPLES The present invention will be described more specifically with reference to examples below, but the present invention is not limited thereto. In the following examples and the like, “mass%” is abbreviated as “%” unless otherwise specified.
(1) Initial elastic modulus Using a tensile tester (manufactured by INSTRON, trade name: INSTRON, model: 5565 type), using a yarn test chuck, measured under the following conditions based on the procedure of ASTM D7269 / D7269M-10 Carried out.
[Measurement condition]
Measurement environment temperature: 24 ± 3 ℃
Humidity: 55 ± 5%
Test speed: 250 mm / min Distance between chucks: 500 mm

(2) Initial strength Using a tensile tester (trade name: Tensilon, model: RTM1T, manufactured by A & D), measurement was performed under the following conditions based on the procedure of the method of JIS L 1017: 2002.
[Measurement condition]
Measurement environment temperature: 20 ± 3 ℃
Humidity: 65 ± 5%
Test speed: 100 mm / min Distance between chucks: 250 mm

(3) Strength after fatigue, strength retention after fatigue Measured according to JIS L 1017: 2002 using a belt-type bending fatigue tester (manufactured by Ueshima Seisakusho). A cord treated by the method of the present invention is driven into a rubber sheet having a thickness of 4 mm at 16 lines / inch, sandwiched between 0.4 mm rubber sheets and arranged in parallel in two layers, and a pressing pressure of 50 kg / cm ² at 150 ° C. for 30 minutes. Vulcanized in The vulcanized rubber sheet was cut into a belt shape having a 1 inch width × 410 mm length, attached to a roller having a diameter of 1 inch φ, a load of 50 kg was applied, and the reciprocating motion was repeated at a speed of 180 rpm for 24 hours. After the fatigue loaded belt sample was swollen in toluene, the cord was taken out from the layer on the roller ground side of the two rubber sheets, and the strength was measured by the method of JIS L 1017: 2002 to determine the strength after fatigue. It was. Moreover, the strength ratio after fatigue of the initial strength contrast was defined as the strength retention after fatigue (%).

[Example 1]
1 kg of polyparaphenylene terephthalamide (PPTA) (molecular weight of about 20,000) obtained by a known method is dissolved in 4 kg of concentrated sulfuric acid, and a shear rate of 30 mm is obtained from a die having 1,000 holes with a diameter of 0.1 mm. After discharging to 000 sec ⁻¹ and spinning in 4 ° C. water, the solution was neutralized with a 10% aqueous sodium hydroxide solution at 10 ° C. for 15 seconds. Thereafter, dehydration treatment was performed, and low temperature drying was performed at 110 ° C. under a tension of 0.8 g / dtex, and the moisture content was adjusted to 45%. Next, an oil containing 50% or more of an epoxy compound was adhered to 1.0% with respect to the fiber mass when converted to a moisture content of 0%. Thereafter, drying treatment was performed to lower the moisture content to 5%, and PPTA fibers having an initial elastic modulus of 520 cN / dtex were obtained.
The obtained PPTA fiber 1,670 dtex (epoxy pretreated yarn, initial elastic modulus 520 cN / dtex) was twisted in the Z direction at 40 t / 10 cm to prepare a lower twisted cord, and two lower twisted cords were used. A twisted yarn cord was formed by twisting in the direction at 40 t / 10 cm.
The obtained upper twisted yarn cord is immersed in a first adhesive treatment liquid mainly composed of vinylpyridine / styrene / conjugated diene rubber latex and an epoxy compound, and heat treatment is performed at 140 ° C. for 2 minutes to remove moisture. Thereafter, heat treatment was performed at 230 ° C. for 1 minute. Furthermore, it is immersed in a second adhesive treatment liquid mainly composed of resorcin, formalin, rubber latex (RFL), heat treated at 140 ° C. for 2 minutes to remove moisture, and then heat treated at 230 ° C. for 1 minute. Completed an aramid fiber cord. The results are shown in Table 1.

[Example 2]
An upper twisted yarn cord similar to that in Example 1 was prepared. The obtained upper twisted twisted cord is immersed in an adhesive treatment liquid mainly composed of resorcin / formalin / rubber latex (RFL), heat treated at 140 ° C. for 2 minutes to remove moisture, and then at 230 ° C. for 1 Aramid fiber cords were completed by heat treatment for minutes. The results are shown in Table 1.

[Example 3]
1 kg of polyparaphenylene terephthalamide (PPTA) (molecular weight of about 20,000) obtained by a known method is dissolved in 4 kg of concentrated sulfuric acid, and a shear rate of 30 mm is obtained from a die having 1,000 holes with a diameter of 0.1 mm. After discharging to 000 sec ⁻¹ and spinning in 4 ° C. water, the solution was neutralized with a 10% aqueous sodium hydroxide solution at 10 ° C. for 15 seconds. Thereafter, dehydration treatment was performed, and low temperature drying was performed at 110 ° C. under a tension of 0.4 g / dtex to adjust the moisture content to 45%. Next, an oil containing 50% or more of an epoxy compound was adhered to 1.0% with respect to the fiber mass when converted to a moisture content of 0%. Thereafter, drying treatment was performed to lower the moisture content to 5%, and PPTA fibers having an initial elastic modulus of 380 cN / dtex were obtained.
Using the obtained PPTA fiber 1,670 dtex (epoxy pretreated yarn, initial elastic modulus 380 cN / dtex), an upper twisted yarn cord was prepared in the same manner as in Example 1.
An aramid fiber cord was completed by the same method as in Example 1 using the obtained upper twisted yarn cord. The results are shown in Table 1.

[Example 4]
An upper twisted yarn cord similar to that in Example 3 was prepared. An aramid fiber cord was completed by the same method as in Example 2 using the obtained upper twisted yarn cord. The results are shown in Table 1.

[Comparative Example 1]
1 kg of polyparaphenylene terephthalamide (PPTA) (molecular weight of about 20,000) obtained by a known method is dissolved in 4 kg of concentrated sulfuric acid, and a shear rate of 30 mm is obtained from a die having 1,000 holes with a diameter of 0.1 mm. After discharging to 000 sec ⁻¹ and spinning in water, the solution was neutralized with an aqueous sodium hydroxide solution. Thereafter, dehydration and heat treatment were performed under a tension of 0.8 g / dtex to obtain a PPTA fiber having a moisture content of 15% or less and an initial elastic modulus of 527 cN / dtex.
An aramid fiber cord was completed by the same method as in Example 1 using the obtained PPTA fiber 1,670 dtex (epoxy untreated yarn, initial elastic modulus 527 cN / dtex). The results are shown in Table 1.

[Comparative Example 2]
1 kg of polyparaphenylene terephthalamide (PPTA) (molecular weight of about 20,000) obtained by a known method is dissolved in 4 kg of concentrated sulfuric acid, and a shear rate of 30 mm is obtained from a die having 1,000 holes with a diameter of 0.1 mm. After discharging to 000 sec ⁻¹ and spinning in water, the solution was neutralized with an aqueous sodium hydroxide solution. Thereafter, dehydration and heat treatment were performed under a tension of 0.4 g / dtex to obtain a PPTA fiber having a moisture content of 15% or less and an initial elastic modulus of 375 cN / dtex.
An aramid fiber cord was completed in the same manner as in Example 1 using the obtained PPTA fiber 1,670 dtex (epoxy untreated yarn, initial elastic modulus 375 cN / dtex). The results are shown in Table 1.

  From Table 1, the dip cords (Examples 1 and 2) in which two pre-twisted epoxy pre-treated aramid fiber cords were over-twisted and twisted were aligned, and two un-treated aramid fiber under-twist cords were arranged in a single twist. It can be seen that the initial strength, the strength after fatigue and the strength retention after fatigue are superior to the applied dip cord (Comparative Example 1). Moreover, the same tendency is also observed in the epoxy pretreated aramid fibers (Examples 3 to 4 and Comparative Example 2) having different raw yarn initial elastic moduli. It can be seen that the initial strength of the dip cord, the strength after fatigue, and the strength retention after fatigue are increased by performing the adhesive treatment once.

[Example 5]
One lower twisted cord obtained by twisting PPTA fiber 1,670 dtex (epoxy pretreated yarn, initial elastic modulus 520 cN / dtex) obtained in Example 1 at 40 t / 10 cm in the Z direction, and nylon 66 fiber 1,400 dtex One twisted cord was twisted in the Z direction at 40 t / 10 cm, and twisted at 40 t / 10 cm in the S direction to produce an upper twisted twisted cord.
The obtained upper twisted yarn cord is immersed in a first adhesive treatment liquid mainly composed of vinylpyridine / styrene / conjugated diene rubber latex and an epoxy compound, and heat treatment is performed at 140 ° C. for 2 minutes to remove moisture. Thereafter, heat treatment was performed at 230 ° C. for 1 minute. Furthermore, it is immersed in a second adhesive treatment liquid mainly composed of resorcin, formalin, rubber latex (RFL), heat treated at 140 ° C. for 2 minutes to remove moisture, and then heat treated at 230 ° C. for 1 minute. Completed the dip code. The results are shown in Table 2.

[Example 6]
An upper twisted twisted cord similar to that in Example 5 was dipped in an adhesive treatment liquid mainly composed of resorcin / formalin / rubber latex (RFL), heat treated at 140 ° C. for 2 minutes to remove moisture, and then A dip cord was completed by heat treatment at 230 ° C. for 1 minute. The results are shown in Table 2.

[Example 7]
One lower twisted cord obtained by twisting PPTA fiber 1,670 dtex (epoxy pretreated yarn, initial elastic modulus 380 cN / dtex) obtained in Example 3 at 40 t / 10 cm in the Z direction, and nylon 66 fiber 1,400 dtex One twisted cord was twisted in the Z direction at 40 t / 10 cm, and twisted at 40 t / 10 cm in the S direction to produce an upper twisted twisted cord. A dip cord was completed by the same method as in Example 5 using the obtained upper twisted yarn cord. The results are shown in Table 2.

[Example 8]
An upper twisted twisted cord similar to that in Example 7 was immersed in an adhesive treatment liquid mainly composed of resorcin / formalin / rubber latex (RFL), heat treated at 140 ° C. for 2 minutes to remove moisture, and then A dip cord was completed by heat treatment at 230 ° C. for 1 minute. The results are shown in Table 2.

[Comparative Example 3]
One lower twisted cord obtained by twisting the PPTA fiber obtained in Comparative Example 1 in the Z direction at 40 t / 10 cm, and one lower twisted cord obtained by twisting nylon 66 fibers 1,400 dtex in the Z direction at 40 t / 10 cm. It was used and twisted at 40 t / 10 cm in the S direction to produce an upper twisted yarn cord. A dip cord was completed in the same manner as in Example 5 using the upper twisted yarn cord. The results are shown in Table 2.

[Comparative Example 4]
One lower twisted cord obtained by twisting the PPTA fiber obtained in Comparative Example 2 in the Z direction at 40 t / 10 cm, and one lower twisted cord obtained by twisting nylon 66 fibers 1,400 dtex in the Z direction at 40 t / 10 cm. It was used and twisted at 40 t / 10 cm in the S direction to produce an upper twisted yarn cord. A dip cord was completed in the same manner as in Example 5 using the upper twisted yarn cord. The results are shown in Table 2.

  From Table 2, the dip cords (Examples 5 to 6) of the upper twisted cord in which the nylon 66 fiber lower twisted cord is twisted to the epoxy pretreated aramid fiber lower twisted cord, the nylon 66 It can be seen that the initial strength, the strength after fatigue, and the strength retention after fatigue are superior to the dip cord (Comparative Example 3) of the upper twist cord in which the fiber under-twist cord is twisted. Moreover, the same tendency is seen also in the aramid fibers (Examples 7 to 8 and Comparative Example 4) having different raw yarn initial elastic moduli, and the epoxy pretreated aramid fiber having a low raw yarn initial elastic modulus is more dip-cord It can be seen that the initial strength and the strength after fatigue are high.

  The rubber reinforcing cord of the present invention has significantly improved initial strength, post-fatigue strength, and post-fatigue strength retention compared to conventional cords, so that the power transmission belt, the conveyor belt, which are used under particularly severe conditions, It is useful for reinforcing rubber products such as tires.

Claims (5)

  A rubber-reinforcing cord composed of organic fibers obtained by aligning at least two lower twisted cords and applying an upper twist, wherein at least one of the lower twisted cords has a moisture content after spinning of 15% by mass. A cord for reinforcing a rubber, which is obtained by twisting a pretreated yarn obtained by impregnating an epoxy compound into an aramid fiber skeleton that does not have a history of less drying and drying to a moisture content of 7% by mass or less.   The cord for rubber reinforcement according to claim 1, wherein the twist coefficient at the time of the lower twist is in the range of 2 to 10, and the twist coefficient at the time of the upper twist is in the range of 2 to 10.   The rubber reinforcing cord according to claim 1 or 2, wherein an initial elastic modulus of the pretreated yarn infiltrated with the epoxy compound is 300 cN / dtex to 750 cN / dtex.   A rubber reinforcing cord obtained by adding an adhesive mainly composed of resorcin, formalin, rubber latex (RFL) to the rubber reinforcing cord according to any one of claims 1 to 3.   The rubber reinforcing cord according to any one of claims 1 to 4, wherein at least one of the lower twisted cords includes a twisted nylon yarn.