JP2021042503A - Hybrid cord for rubber reinforcement - Google Patents

Abstract

To provide a cord for rubber reinforcement that retains high adhesiveness between a rubber and a fiber even after being exposed to high temperature.SOLUTION: A hybrid cord for rubber reinforcement is composed of a composite fiber cord comprising an aliphatic polyamide fiber and a para-aramid fiber and a surface treatment agent comprising an epoxy-based adhesive and a resorcin/formalin/latex (RFL)-based adhesive adhered to the surface of the composite fiber cord in which an adhesion amount of the total of the epoxy-based adhesive and the resorcin/formalin/latex-based adhesive is 6 to 15 wt% based on the total weight of the fiber.SELECTED DRAWING: None

Description

The present invention relates to a rubber reinforcing cord used for reinforcing rubber tires, belts, hoses and the like.

In order to improve the strength and durability of rubber products such as rubber tires, belts and hoses, it is widely practiced to embed a cord, which is a reinforcing fiber, in rubber.

Aliphatic polyamide fibers, polyester fibers, paraaramid fibers, rayon fibers and the like have been used as tire cord materials. With the increase in the traveling speed of vehicles equipped with tires, there is a demand for tire cords capable of maintaining the stability and durability of the tires even during high-speed traveling.

Tire cords are classified according to the parts and roles used in the tire, and are divided into a carcass part that supports the tire as a whole, a belt part that supports the load during high-speed driving, and a cap ply part that prevents deformation of the belt part. To.

In recent years, as the traveling speed of a car increases, the belt portion of the tire is deformed, causing problems such as a decrease in riding comfort. Therefore, the importance of the cap ply portion for preventing the deformation of the belt portion has occurred. Is increasing. So far, aliphatic polyamide fibers and paraaramid fibers have been used as materials for cap ply tire cords.

Of these, aliphatic polyamide fibers have excellent adhesive performance and fatigue resistance, and are therefore widely applied to tires. However, the aliphatic polyamide fiber has a low modulus and a large modulus change due to a temperature change, which causes a flat spot phenomenon in which the tire is deformed when the vehicle equipped with the tire is parked for a long time. ..

On the other hand, the para-aramid fiber has a very high modulus property, and the amount of change in the modulus at room temperature and high temperature is small, so that the flat spot phenomenon hardly occurs. However, the paraaramid fiber has a disadvantage that it is relatively difficult to form a tire because of its high modulus, and its fatigue resistance is lower than that of an aliphatic polyamide fiber because it has a low elongation at break.

Among these, composite cords in which aliphatic polyamide fibers and paraaramid fibers are composited have been developed. In order to embed the composite cord in the rubber of the tire and bond it to the rubber, usually, the aliphatic polyamide fiber and the paraaramid fiber are each under-twisted, then combined and over-twisted, and then the surface is in the state of the fiber cord. Is subjected to an adhesive treatment, or the surface is subjected to an adhesive treatment after being made into a rubber woven fabric. However, even if the usual adhesive treatment for rubber reinforcing fibers is performed, the heat-resistant adhesiveness is inferior, and in particular, the adhesiveness in the rubber when left in a high temperature atmosphere is inferior.

International Publication No. 2013/187364

The present invention has been made against the background of the above circumstances, and an object of the present invention is to provide a rubber reinforcing cord that maintains a high adhesive force with a rubber even after being exposed to a high temperature.

The present invention is a rubber composed of a composite fiber cord composed of an aliphatic polyamide fiber and a paraaramid fiber, and a surface treatment agent composed of an epoxy adhesive and a resorcin formarin latex (RFL) adhesive adhering to the surface thereof. It is a reinforcing hybrid cord, and is characterized in that the total adhesion amount of the epoxy adhesive and the resorcin / formarin / latex adhesive of the surface treatment agent is 6 to 15% by weight with respect to the total weight of the fibers. , A hybrid cord for rubber reinforcement.

The present invention also contains a composite fiber cord composed of an aliphatic polyamide fiber and a paraaramid fiber, first bathed with a pretreatment liquid containing an epoxy compound, and then containing a resorcin formarin latex (RFL) -based adhesive. This is a method for manufacturing a hybrid cord for rubber reinforcement, which comprises treating with a second bath with an adhesive treatment liquid.

According to the present invention, it is possible to provide a rubber reinforcing cord that maintains a high adhesive force with a rubber even after being exposed to a high temperature.

[Composite fiber cord]
The composite fiber cord consists of an aliphatic polyamide fiber and a para-aramid fiber.
As the aliphatic polyamide fiber, a fiber polycondensed by an amide bond typified by nylon 66 and nylon 6 is preferably used. It is preferable that the molecule does not contain aromatics and is composed only of aliphatics. For example, nylon 11, nylon 12, nylon 46, nylon 66, nylon 6, preferably nylon 66, nylon 6 are used.

As the para-aramid fiber, for example, polyparaphenylene terephthalamide fiber, copolyparaphenylene, 3,4'-oxydiphenylene, terephthalamide fiber can be used, and polyparaphenylene terephthalamide fiber is preferable.

The composition ratio of the aliphatic polyamide fiber and the para-aramid fiber in the composite fiber cord is preferably 80:20 to 20 to 80 in terms of the weight ratio of the aliphatic polyamide fiber: the para-aramid fiber. If the amount of the aliphatic polyamide fiber is less than 20% by weight, the modulus becomes high and the elongation of the cord becomes low, which is not preferable in that it becomes difficult to mold the tire. It is not preferable because the tire is easily deformed inside.

The composite fiber cord is preferably one in which an aliphatic polyamide fiber and a para-aramid fiber are each down-twisted, then combined and top-twisted.

As a form of twisting of the composite fiber cord, a method of twisting the aliphatic polyamide fiber and the para-aramid fiber in the lower direction and then twisting them together and twisting them in the upper direction. For example, a method of top-twisting the combined yarn cord as it is as a combined yarn cord, or a method of combining the above-mentioned lower twisted yarn cord or the lower twisted cord of an aliphatic polyamide fiber or a paraaramid fiber alone and then twisting the upper yarn is used. Can be done.
Of these, it is preferable to use a method in which the aliphatic polyamide fiber and the para-aramid fiber are each down-twisted, then combined and top-twisted.

[Surface treatment agent]
In the rubber reinforcing hybrid cord of the present invention, a surface treatment agent composed of an epoxy adhesive and a resorcin formarin latex (RFL) adhesive is attached to the surface of the composite fiber cord.

The total solid content weight of the adhered epoxy adhesive and resorcin formalin latex adhesive is 6 to 15% by weight, preferably 8 to 14% by weight, based on the total weight of the fibers constituting the composite fiber cord. %, More preferably 10 to 14% by weight. If it is less than 6% by weight, sufficient adhesive strength cannot be obtained, while if it exceeds 15% by weight, the cord becomes hard and fatigue resistance deteriorates. In order to make the amount of solid content adhered to 6 to 15% by weight, in the treatment step of adhering the treatment liquid containing the adhesive, for example, after adjusting the concentration of the adhesive in the treatment liquid to 20 to 25% by weight, A method of immersing the composite fiber cord in the treatment liquid and adjusting the adhesion amount by squeezing with a squeeze roller and a suction device can be used. Further, the amount of adhesion can be adjusted by relaxing the tension applied to the composite fiber cord while immersing the composite fiber cord in the treatment liquid.

[Epoxy adhesive]
The epoxy compound constituting the epoxy adhesive is preferably a compound containing at least two or more epoxy groups in one molecule in an amount of 2 g or more per 1 kg of the compound. Specifically, reaction products of polyhydric alcohols such as ethylene glycol, glycerol, sorbitol, pentaerythritol, and polyethylene glycol with halogen-containing epoxides such as epichlorohydrin, resorcin, pis (4-hydroxyphenyl) dimethylmethane, and phenol. -A reaction product of polyhydric phenols such as formaldehyde resin, resorcin / formaldehyde resin and the halogen-containing epoxides, polyepoxide compound obtained by oxidizing an unsaturated compound with peracetic acid or hydrogen peroxide, that is, 3,4 -Epoxide cyclohexene epoxides, 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexene carboxylate, bis (3,4-epoxy-6-methyl-cyclohexylmethyl) adibate can be mentioned. Of these, the reaction product of the polyhydrin and epichlorohydrin, that is, the polyglycidyl ether compound of the polyhydrin is preferable because it exhibits excellent performance.

[Resorcin-formalin latex (RFL) -based adhesive]
As the resorcin-formalin latex (RFL) -based adhesive, one having a molar ratio of resorcin to formaldehyde of preferably 1: 0.8 to 1: 5, and more preferably 1: 1 to 1: 4 is used. If the amount of formaldehyde is less than this range, the crosslink density of the condensate of resorcin formalin decreases and the molecular weight decreases, and the cohesive force of the resorcin formalin latex (RFL) adhesive decreases and the adhesiveness decreases. There is a risk and it is not preferable. On the other hand, if the amount of formaldehyde is more than this range, the resorcin-formalin condensate becomes hard due to the increase in the crosslink density, and the compatibility between RFL and the rubber is inhibited during co-vulcanization with the adherend rubber, resulting in a decrease in adhesiveness. At the same time, the treated fibers become extremely hard, and the strength and fatigue property are reduced, which is not preferable.

The mixing ratio of resorcin / formalin and latex is preferably 1: 3 to 1:20, more preferably 1: 5 to 1:15, with respect to resorcin / formalin: latex as the weight ratio of the solid content. If the mixing ratio of latex is lower than this range, the surface-treated composite fiber cord becomes hard and fatigue resistance tends to decrease, and co-vulcanization with rubber as an adherend becomes insufficient and adhesiveness decreases. There is a risk and it is not preferable. On the other hand, if the ratio of latex is higher than this range, sufficient strength cannot be obtained as an adhesive film, so that not only a satisfactory adhesive strength and rubber adhesion rate may not be obtained, but also the adhesiveness of the processing cord Is extremely high, which causes stains in the dip processing process and stains in the product manufacturing process, which is not preferable.

As the latex, for example, natural rubber latex, styrene / butadiene rubber latex, vinylpyridine / styrene / butadiene copolymer latex, acrylonitrile / butadiene latex, and chloroprene latex can be used. These may be used alone or in combination. Of these, it is preferable to use vinylpyridine / styrene / butadiene copolymer latex alone.

[Crosslinking agent]
It is preferable to add a cross-linking agent to the above surface treatment agent. As the cross-linking agent, for example, amine, ethylene urea, or isocyanate compound can be used, and the isocyanate compound is particularly preferable from the viewpoint of the temporal stability of the surface treatment agent and the interaction with the pretreatment agent.

The isocyanate compound is preferably a blocked polyisocyanate compound in which the isocyanate group is blocked. This blocked polyisocyanate compound is an addition compound of the polyisocyanate compound and a blocking agent, and the blocking component is liberated by heating to produce an active polyisocyanate compound.

Examples of the polyisocyanate compound include polyisocyanates such as tolylene diisocyanate, metaphenylene diisocyanate, diphenylmethane diisocyanate, hexamethylene diisocyanate, polymethylene polyphenyl isocyanate, and triphenylmethane triisocyanate, or two or more of these polyisocyanates and active hydrogen atoms. Examples thereof include a polyol adduct polyisocyanate containing a terminal isocyanate group obtained by reacting a compound such as trimethylolpropane or pentaerythritol with a molar ratio of isocyanate group (-NCO) to hydroxyl group (-OH) exceeding 1. Be done. In particular, aromatic polyisocyanates such as tolylene diisocyanate, diphenylmethane diisocyanate, and polymethylene polyphenyl isocyanate are preferable because they exhibit excellent performance.

Examples of the blocking agent for the blocked polyisocyanate compound include phenols such as phenol, thiophenol, cresol, and resorcinol, diphenylamine, aromatic secondary amines such as xylidine, lactam such as imide phthalate, caprolactam, and valerolactam, acetoxime, and methylethylketone. Examples thereof include oximes such as oxime and cyclohexane oxime and acidic sodium sulfite.

When the cross-linking agent is blended, the blending amount is, for example, 0.5 to 30% by weight, preferably 2 to 25% by weight, based on the total weight of the solid content of the surface treatment agent. If it is less than 0.5% by weight, sufficient adhesion cannot be obtained, and if it exceeds 30% by weight, the film-forming property of the surface treatment agent is remarkably lowered, and it does not adhere uniformly on the cord.

〔Production method〕
In the rubber reinforcing hybrid cord of the present invention, a composite fiber cord composed of an aliphatic polyamide fiber and a paraaramid fiber is first bathed with a first bath treatment liquid which is an adhesive treatment liquid containing an epoxy compound, and this is dried. It can be produced by performing a second bath treatment with a second bath treatment liquid which is an adhesive treatment liquid containing a resorcin formalin latex (RFL) -based adhesive, and then drying and heat-treating the second bath treatment liquid. ..

The first bath treatment is performed by immersing the composite fiber cord in the first bath treatment liquid, and then drying and heat treating at a temperature of 220 to 250 ° C. for 0.5 to 5 minutes, preferably 1 to 3 minutes. If the temperature of drying and heat treatment is lower than this, the adhesion to rubber tends to be insufficient, while if the temperature is higher than this, the composite fiber cord melts and fuses, or causes a significant decrease in strength, which can be put into practical use. It disappears. The concentration of the adhesive in the first bath treatment liquid is, for example, 1 to 30% by weight, preferably 5 to 20% by weight in terms of total solid content concentration.

The second bath treatment is performed by applying the second bath treatment liquid in contact with the composite fiber cord by a roller, by spraying from a nozzle, or by immersing the second bath treatment liquid in the composite fiber cord second bath treatment liquid. After that, it is dried at a temperature of 150 to 200 ° C. for 0.5 to 5 minutes, and subsequently heat-treated at a temperature of 220 to 250 ° C. for 0.5 to 5 minutes.

In both the first bath treatment and the second bath treatment, in order to control the amount of solid content of the treatment liquid adhering to the composite fiber cord, squeezing with a pressure welding roller, scraping with a scrubber, etc., blowing off with air blowing, suction, tapping with a beater Such means can be used. On the other hand, in order to increase the amount of adhesion, it may be adhered a plurality of times.

The present invention will be further described by way of examples. Various characteristics were measured by the following methods.
(1) Solid content adhesion rate The composite fiber cord with the surface treatment agent attached is twisted and decomposed into aliphatic polyamide fibers and paraaramid fibers, and each of the aliphatic polyamide fibers and paraaramid fibers is dissolved in a solvent. The weight of each residue was measured. The para-aramid fiber was immersed in sulfuric acid to dissolve and remove the fiber side, and the weight of the residue was measured. The aliphatic polyamide fiber was immersed in formic acid to dissolve and remove the fiber side, and the weight of the residue was measured. The solid content adhesion rate was calculated from the weight of the residue with respect to the weight of the composite fiber cord excluding the surface treatment agent.
(2) Initial adhesive strength
On an unvulcanized rubber sheet (22 cm x 2.5 cm, thickness 0.4 cm) containing carcass containing natural rubber as the main component, three composite fiber cords to be evaluated (length 22 cm) are placed on the surface of the composite fiber cord. Was buried so as to be hidden behind the surface of the rubber sheet, and vulcanized at a temperature of 150 ° C. for 30 minutes ^{under a press pressure of 50 kg / cm 2} to prepare a test piece. This test piece was subjected to a peeling test in an atmosphere of 20 ° C. In the peeling test, a universal material testing machine manufactured by Instron is used to grasp the three ends of the composite fiber cord of the test piece with a flat plate chuck and peel the rubber sheet so that the angle between the cord and the cord is 90 °. , The force required for this peeling was measured. The average value of the peeling force for a peeling distance of 16 cm was taken as the initial adhesive force.
(3) Heat-Resistant Adhesive Strength The test piece for evaluating the initial adhesive strength was subjected to the same peeling test as the measurement of the initial adhesive strength in an atmosphere of 100 ° C. in a constant temperature bath, and the heat-resistant adhesive strength was measured.

[Example 1]
A polyepoxide compound having a sorbitol polyglycidyl ether structure (Denacol EX-614B manufactured by Nagase ChemteX Corporation) was dissolved in an alkaline aqueous solution together with a surfactant to prepare an aqueous solution having a total solid content concentration of 2% by weight. This was used as the first bath treatment liquid for the first bath treatment.

Resolcin / formalin initial condensate (aqueous dispersion having a molar ratio of resorcin / formalin of 1 / 0.6 and a solid content concentration of 65% by weight) is dispersed in water under alkaline conditions to have a solid content concentration of 9% by weight. A formalin aqueous dispersion was used.

99 parts by weight of vinylpyridine, styrene, butadiene turbolimer latex (aqueous dispersion having a solid content of 41% by weight, PYRATEX manufactured by Nippon A & L Inc.) and 87 parts by weight of water were used as the above-mentioned resorcin with a solid content of 9% by weight. It was added to 57 parts by weight of the formalin aqueous dispersion and aged for 48 hours to obtain an aqueous dispersion having a solid content concentration of 20% by weight. This was used as a second bath treatment liquid for the second bath treatment.

1400 dtex / 384 filament multifilament yarn made of nylon 6 and 6 and 1680 dtex / 1000 filament multifilament yarn made of para-aramid fiber (Twaron (registered trademark) manufactured by Teijin Aramid Co., Ltd.) are used, and 32T is used for each multifilament yarn. A composite fiber cord was obtained by lower twisting at / 10 cm and upper twisting at 32 T / cm while aligning one nylon 6 or 6 fiber and two para-aramid fibers.

The obtained composite fiber cord is immersed in the above-mentioned first bath treatment liquid using a commutatorizer processing machine (manufactured by CA Ritzler Co., Ltd., tire cord processing machine), and then dried at a temperature of 150 ° C. for 2 minutes. Then, heat treatment is performed at a temperature of 235 ° C. for 1 minute, then immersed in the second bath treatment liquid, dried at a temperature of 170 ° C. for 2 minutes, and subsequently heat-treated at a temperature of 235 ° C. for 1 minute. I got a hybrid cord for rubber reinforcement.

In the obtained hybrid cord for reinforcing rubber, the solid content adhesion rate of the surface treatment agent derived from the first bath treatment liquid and the second bath treatment liquid was 12% by weight based on the weight of the composite fiber cord. The initial adhesive strength and heat-resistant adhesive strength of the obtained hybrid cord for rubber reinforcement were evaluated. The results are shown in Table 1.

[Comparative Example 1]
The same procedure as in Example 1 was carried out except that the solid content concentration of the second bath treatment liquid was changed to 10% by weight in Example 1 to obtain a hybrid cord having a solid content adhesion rate of 5% by weight of the surface treatment agent. .. The evaluation results are shown in Table 1.

[Comparative Example 2]
The same procedure as in Example 1 was carried out except that the solid content concentration of the second bath treatment liquid was changed to 30% by weight in Example 1 to obtain a hybrid cord having a solid content adhesion rate of 16% by weight of the surface treatment agent. .. The evaluation results are shown in Table 1.

The rubber reinforcing hybrid cord of the present invention can be used as a rubber reinforcing cord for tires, hoses, belts and the like.

Claims (3)

A rubber reinforcing hybrid cord composed of a composite fiber cord composed of an aliphatic polyamide fiber and a paraaramid fiber, and a surface treatment agent composed of an epoxy adhesive and a resorcin / formarin / latex adhesive adhering to the surface thereof. , A hybrid cord for rubber reinforcement, characterized in that the total amount of adhesion of the epoxy adhesive and the resorcin, formalin, and latex adhesive as surface treatment agents is 6 to 15% by weight based on the total weight of the fibers. The hybrid cord for rubber reinforcement according to claim 1, wherein the composite fiber cord is obtained by lower-twisting an aliphatic polyamide fiber and a para-aramid fiber, and then applying a combined yarn and an upper twist. In the method for producing a hybrid cord for rubber reinforcement, a composite fiber cord composed of an aliphatic polyamide fiber and a paraaramid fiber is first bathed with a pretreatment liquid containing an epoxy compound, and then a resorcin / formarin / latex adhesive is applied. A method for producing a hybrid cord for rubber reinforcement, which comprises performing a second bath treatment with a contained adhesive treatment liquid.