JP4229822B2 - Method for producing aramid fiber cord for belt reinforcement - Google Patents

Description

  The present invention relates to a method for producing an aramid fiber cord for reinforcing a belt that can be suitably used as a reinforcing cord for a power transmission belt or the like, and more particularly to an aramid fiber treated cord that is optimally used for a chloroprene rubber composition.

  Aramid fiber cords generally have excellent properties such as strength, elastic modulus, dimensional stability, heat resistance, etc., so excellent reinforcing fibers for rubber composites such as tires, belts and hoses used under severe conditions Useful as. In particular, because of its high specific strength and specific elastic modulus, demand for aramid fiber cords is expected to increase more and more as a lightweight reinforcing fiber for steel and wire replacement.

  And especially when used for reinforcement of power transmission belts, the adhesion performance with the adherend rubber is very important because it greatly affects the load resistance and durability of the belt, and the adhesion between the aramid fiber cord and the rubber matrix With regard to the above, various RFL adhesives by two-stage treatment of an epoxy compound and resorcin / formalin / rubber latex have been proposed. (Patent Document 1, Patent Document 2, etc.)

  However, the aramid fiber, which is an aromatic polyamide, has an inert surface, has difficulty in wettability with respect to RFL, and is currently excellent in heat resistance, oil resistance, ozone resistance, and other mechanical properties as rubber. However, since many chloroprene rubber compositions having poor adhesion have been used, the present situation is that the adhesive strength is still not satisfactory.

JP-A-9-3769 Japanese Patent Laid-Open No. 11-12929

  The present invention has been made in view of the above-mentioned problems of the prior art, and the object thereof is an aramid fiber for belt reinforcement capable of firmly adhering to a rubber compound constituting an adhesive rubber layer of a transmission belt. To provide code.

  In the method for producing an aramid fiber cord for belt reinforcement of the present invention, an aramid fiber is treated with a first treating agent comprising an aqueous dispersion of a polyepoxide compound and a blocked polyisocyanate compound, and then resorcin-formalin-rubber latex (RFL) is treated. A process for continuously treating with a second treating agent and a third treating agent, comprising chloroprene latex / styrene-butadiene-vinylpyridine ternary in rubber latex in the RFL of each of the second treating agent and the third treating agent After the ratio of the copolymer latex is 20/80 to 80/20 and the second treatment agent is applied, preliminary drying at 170 ° C. or less and main drying at 180 ° C. or more are performed, and after the third treatment agent is applied. Only pre-drying at 170 ° C. or lower is performed. Furthermore, it is preferable that the second treating agent and / or the third treating agent contains a chlorophenol compound.

  According to the production method of the present invention, an aramid fiber cord for belt reinforcement having excellent adhesion to a transmission belt and having a strong reinforcing effect is provided.

Hereinafter, the present invention will be described in detail.
Examples of aramid fibers used in the present invention include meta-aramid fibers and para-aramid fibers. The meta-aramid fiber is a meta-aromatic polyamide fiber, for example, polymetaphenylene isophthalamide fiber. Para-aramid fibers are para-aromatic polyamide fibers, such as polyparaphenylene terephthalamide (for example, Twaron manufactured by Teijin Limited) or copolyparaphenylene 3,4′oxydiphenylene terephthalamide (for example, Technora manufactured by Teijin Limited) ) Among these, highly strong para-aramid fibers are preferable. Moreover, as the aramid fiber for belt reinforcement, the strength is preferably 10 to 100 cN, and more preferably 15 to 30 cN practically.

  The aramid fiber used in the present invention is a filament yarn made of the above-mentioned aramid fiber and a spun yarn, as well as a cord made of this filament yarn and a spun yarn. Any suitable twisted yarn configuration can be taken. In the present invention, it is also preferable to use a so-called epoxy pretreated yarn obtained by adding a polyepoxide compound to an aramid fiber in advance at the yarn production stage.

In the production method of the present invention, it is necessary to first treat the aramid fiber with a first treating agent comprising an aqueous dispersion of a polyepoxide compound and a blocked polyisocyanate compound.
The polyepoxide compound used here is preferably a compound containing 0.2 g equivalent or more per molecule of at least two epoxy groups per molecule. Such polyepoxide compounds include reaction products of polyhydric alcohols such as ethylene glycol, glycerol, sorbitol, pentaerythritol, and polyethylene glycol with halogen-containing epoxides such as epichlorohydrin, resorcin bis (4-hydroxyphenyl) dimethylmethane, phenol. A reaction product of a polyhydric phenol such as formaldehyde resin or resorcin / formaldehyde resin and the halogen-containing epoxide, or a polyepoxide compound obtained by oxidizing an unsaturated compound with peracetic acid or hydrogen peroxide. Specific examples of such polyepoxide compounds include 3,4 monoepoxycyclohexane epoxide, 3,4-epoxycyclohexanemethyl, 3,4-epoxycyclohexanecarboxylate, bis (3,4-epoxy-6-methyl-cyclohexane. Hexylmethyl) adipate. In particular, a reaction product of a polyhydric alcohol and epichlorohydrin, that is, a polyglycidyl ether compound of a polyhydric alcohol is preferable because it exhibits excellent performance. These compounds are usually used as an emulsified liquid, but in order to make an emulsified liquid or solution, a known emulsifier such as a compound obtained by dissolving the compound as it is or in a small amount of a solvent as necessary, for example, It is emulsified or dissolved using sodium alkylbenzene sulfonate, dioctyl sulfosuccinate sodium salt, nonylphenol ethylene oxide adduct and the like.

  In addition, it is essential for the first treating agent of the present invention to use a blocked polyisocyanate compound together with a polyepoxy compound. This blocked polyisocyanate compound is an adduct of a polyisocyanate compound and a blocking agent, and releases a block component 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, triphenylmethane triisocyanate, or two or more of these polyisocyanates and active hydrogen atoms. For example, trimethylolpropane, pentaerythritol, polyalkylene glycol, and the like having a terminal isocyanate group-containing compound obtained by reacting an isocyanate group (—NCO) and a hydroxyl group (—OH) in a molar ratio exceeding 1. And monohydric alcohol adduct polyisocyanate. In particular, aromatic polyisocyanates such as triresin isocyanate, diphenylmethane diisocyanate, and polymethylene polyphenyl isocyanate exhibit preferable performance.

  Examples of the blocking agent include phenols such as phenol, thiophenol, cresol and resorcinol, aromatic secondary amines such as diphenylamine and xylidine, lactams such as phthalimides, caprolactam and valerolactam, acetoxime and methyl ethyl ketone. Examples include oximes such as oxime and cyclohexane oxime, and acidic sodium sulfite.

  The first treating agent used in the present invention is composed of the polyepoxide compound and the broccid polyisocyanate compound, and the blending ratio thereof is not particularly limited. Usually, the block polyisocyanate compound is added in an amount of 2 to 1 part by weight of the polyepoxide compound. 5 parts by weight is preferable. The concentration of the epoxy compound in the treating agent is 5% or less, preferably 0.5 to 3.0%, from the viewpoint of handleability.

  Although the method for applying the first treatment agent to the aramid fiber is arbitrary, the immersion heat treatment method is usually employed. After the first treatment agent is applied by dipping in the first treatment agent, it is preferably heat-treated at 130 ° C. to 250 ° C. for 30 seconds to 210 seconds and dried and cured. It is preferable that the 1st processing agent adheres 1-8 weight% with respect to fiber weight, Furthermore, the adhesion amount of 3-5 weight% is preferable.

  In the present invention, it is essential to treat the aramid fiber with the first treatment agent containing such a polyepoxide compound, but in addition to that, a polyepoxide compound is preliminarily applied together with an oil agent or the like in the aramid fiber spinning process before the treatment. It is also preferable. The amount of the polyepoxide compound attached to the fiber during the pretreatment is preferably in the range of 0.1 to 5% by weight. When the adhesion amount of the polyepoxide compound is less than 0.1% by weight, the effect of the pretreatment is hardly obtained. On the other hand, when the adhesion amount of the polyepoxide compound in the pretreatment exceeds 5% by weight, the fiber becomes very hard and not only difficult to impart in the yarn production process, but also the permeability of the treatment agent to be treated in the subsequent process and after. As a result, the adhesion performance tends to decrease eventually.

  In the present invention, it is necessary to successively treat the aramid fiber treated with the first treatment agent with the second treatment agent containing resorcin / formalin / rubber latex (RFL) and the third treatment agent. The resorcin / formalin / rubber latex is generally called RFL, and is obtained by mixing and aging an initial condensate of resorcin, formaldehyde, and rubber latex.

  In the present invention, it is necessary to use a blend of chloroprene latex and styrene-butadiene-vinylpyridine terpolymer latex as the rubber latex used in the RFL of each of the second treatment agent and the third treatment agent. In that case, it is essential that the blending ratio of chloroprene latex / styrene-butadiene-vinylpyridine terpolymer latex is in the range of 20/80 to 80/20 (weight ratio). By using chloroprene latex in the above range, an aramid fiber cord suitable for reinforcement of a power transmission belt excellent in heat resistance, oil resistance, ozone resistance and other mechanical properties can be obtained.

  As RFL used for the second treating agent of the present invention, the molar ratio of resorcin to formaldehyde is in the range of 1 / 0.1 to 1/8, and further in the range of 1 / 0.5 to 1/5. It is preferable. As the rubber latex, a blend of chloroprene latex and styrene-butadiene-vinylpyridine terpolymer latex is used.

  Moreover, as RFL used for the 3rd processing agent of this invention, the molar ratio of a resorcinol and formaldehyde is the range of 1 / 0.6-1 / 2, especially 1 / 0.7-1 / 1.5. A range is preferable. Furthermore, the weight ratio (RF / L) of resorcin-formalin condensate (RF) and chloroprene latex / styrene-butadiene-vinylpyridine terpolymer latex is preferably in the range of 1/10 to 1/50. By blending like this, the third adhesive film is slightly three-dimensionally cross-linked to increase the adhesiveness of the cord itself without deteriorating the adhesion, and to adhere to the unvulcanized rubber during belt molding Can be increased.

  Furthermore, it is preferable to mix | blend a chlorophenol compound with the 2nd processing agent and / or 3rd processing agent containing said RFL. The chlorophenol compound is a compound obtained by co-condensing parachlorophenol and resorcin with formaldehyde. Although the blending ratio of the chlorophenol compound and resorcin / formalin slightly changes depending on the blending of the rubber to be adhered, generally, the blending ratio of the RF and the chlorophenol compound is 20/80 to 80/20 ( Weight ratio).

  The adhesion amount of the second treatment agent is preferably 1 to 8% by weight, more preferably 2 to 6% by weight, based on the fiber weight. The method of applying the second treatment agent is not particularly limited as in the case of the first treatment agent, but usually an immersion method is employed.

  In the production method of the present invention, it is necessary to perform preliminary drying at 170 ° C. or lower and main drying at 180 ° C. or higher on the cord after application of the second treatment agent. More specifically, it is preferable to dry at 130 ° C. to 170 ° C. for 30 seconds to 210 seconds in a state where the cord does not sag, and then to perform heat treatment at 180 ° C. to 250 ° C. for 30 seconds to 210 seconds. If the heat treatment temperature is too low, adhesion to rubber tends to be insufficient, while if the temperature is too high, the adhesive itself hardens, making the fibers stiff and causing strong deterioration, making it difficult to put to practical use. Become.

  The third treatment agent is further adhered to the aramid cord subjected to the second treatment agent. The adhesion amount of the third treatment agent is preferably 1 to 5% by weight with respect to the fiber weight. The method for applying the third treatment agent is not particularly limited as in the case of the first and second treatment agents, but an immersion method is usually employed.

  In the production method of the present invention, the cord after the third treatment agent is applied only needs to be pre-dried at 170 ° C. or lower. More specifically, heat treatment is preferably performed at 130 ° C. to 180 ° C. for 120 seconds to 240 seconds in a state where the cord does not sag. By making the third adhesive film semi-cured in this way, the adhesive film made of the third treatment liquid can increase the adhesion when the power transmission belt is molded and can improve the adhesion.

  Another aspect of the present invention is an aramid fiber cord for belt reinforcement obtained by these production methods. The aramid fiber cord for belt reinforcement of the present invention has a high adhesive strength with rubber used for the belt and a high fiber strength, so that the reinforcing effect is extremely high, and for power transmission used under severe conditions such as a timing belt of an automobile engine. It is used suitably for the belt of this.

Hereinafter, the present invention will be specifically described by way of examples, but is not limited thereto. In addition, evaluation of characteristics in the examples was performed according to the following method.
(1) Strength and elongation It conformed to the method of JIS L1017.

(2) Cord peeling adhesive strength Five fiber cords subjected to adhesion treatment are arranged at intervals of 25.4 mm, embedded in chloroprene unvulcanized rubber, and press vulcanized at a temperature of 150 ° C. and a pressure of 90 kg / cm ² for 30 minutes. Next, the force (N / 25.4 mm) required to peel the fiber cord from the rubber was measured.

[Example 1]
Two 1670 dtex, 1000-filament aramid fibers (trade name: Technora; manufactured by Teijin Ltd.) made of coparaphenylene, 3-4′-oxydiphenylene, and terephthalamide that have been treated with a polyepoxide compound in advance at the yarn-making stage are arranged. A twist of 175 T / m was applied in the Z direction, then three lower twisted yarns were aligned, and an upper twist of 132 T / m was applied in the S direction to obtain a 1670 dtex / 2X3 cord. This cord was a raw cord having a strength of 1690 N, an elongation of 4%, and 8350 dtex. Using the obtained raw cord, a polyepoxide compound (trade name: Denacol EX611; manufactured by Nagase Kasei Co., Ltd., sorbitol glycidyl ether) and a blocked polyisocyanate compound (trade name: S3) ; Manufactured by Meisei Chemical Co., Ltd.) in an active ingredient ratio of 20:80 is immersed in a treatment liquid adjusted to a 5% by weight aqueous dispersion, and a tension that does not sag is applied at 135 ° C. It was dried for 5 minutes and then heat treated at 235 ° C. for 1 minute.

Subsequently, the 2nd processing agent and 3rd processing agent which consist of RFL adhesives were adjusted.
As the second treatment agent, a resorcin / formalin initial condensate reacted with an acidic catalyst in water added with aqueous caustic soda and aqueous ammonia: Sumikanol 700S (Sumitomo Chemical Co., Ltd., 65% aqueous solution) is sufficiently added. Allow to stir. To this, formalin is added and mixed uniformly so that the resorcin / formalin (R / F) ratio is 1/2 (molar ratio). Next, a latex of a blend of chloroprene latex and styrene-butadiene-vinylpyridine terpolymer latex having a weight ratio of 75/25 is converted into a weight ratio of the resorcin-formalin condensate (RF) to the terpolymer latex (RF / L) was mixed to 1/5, and Elastolon BN-69 (Daiichi Kogyo Seiyaku Co., Ltd., diphenylmethane diisocyanate methyl ethyl ketone oxime block 33% aqueous dispersion) was added, and Denabond E (Nagase Chem) was added just before use. Tex Co., Ltd., 20% chlorophenol compound solution) was added so that the Denabond E / RFL ratio was 2/1, and the mixture was sufficiently stirred to adjust the treatment agent.

  Further, as the third treating agent, formalin has an R / F ratio of 1/1, a weight ratio of resorcin-formalin condensate (RF) and chloroprene latex / styrene-butadiene-vinylpyridine terpolymer latex (RF / Adjustment was performed in the same manner as treatment agent 2 except that L) was 1/15.

  Both of these RFL adhesives use a blend of chloroprene latex and styrene-butadiene-vinylpyridine terpolymer latex as latex (L), and the weight ratio is 75/25.

  The treatment cord was dipped in the second treatment agent, dried at 150 ° C. for 2 minutes, and continuously heat-treated at 220 ° C. for 1.5 minutes. Further, the cord was dipped in the third treatment agent and then dried at 150 ° C. for 2 minutes. The peel adhesion strength of the obtained adhesion-treated aramid fiber cord was measured, and Table 1 shows the results.

  When this aramid fiber cord was used for reinforcing a power transmission belt, it had excellent strength and durability.

[Examples 2 and 3, Comparative Examples 1 and 2]
Except for changing the weight ratio of chloroprene latex and styrene-butadiene-vinylpyridine terpolymer latex in latex (L) in the RFL adhesive from 75/25 of Example 1 to the weight ratio shown in Table 1, The same treatment as in Example 1 was performed to obtain an adhesion-treated aramid fiber cord. Table 1 also shows the results.

  The aramid fiber cord for belt reinforcement obtained in the present invention has high adhesive strength and fiber strength with rubber, and is suitably used for a power transmission belt used under severe conditions such as a timing belt of an automobile engine.

Claims (3)

  The aramid fiber is treated with a first treating agent comprising an aqueous dispersion of a polyepoxide compound and a blocked polyisocyanate compound, and then successively with a second treating agent and a third treating agent containing resorcin-formalin-rubber latex (RFL). The ratio of chloroprene latex / styrene-butadiene-vinylpyridine terpolymer latex in the rubber latex in the RFL of each of the second treatment agent and the third treatment agent is 20/80 to 80/20. Yes, after the second treatment agent is applied, preliminary drying at 170 ° C. or less and main drying at 180 ° C. or more are performed, and after the third treatment agent is applied, only preliminary drying at 170 ° C. or less is performed. A method for producing an aramid fiber cord for belt reinforcement.   The method for producing an aramid fiber cord for belt reinforcement according to claim 1, wherein the second treating agent and / or the third treating agent contains a chlorophenol compound.   An aramid fiber cord for belt reinforcement obtained by the production method according to claim 1 or 2.