JP4746464B2 - Method for producing rubber reinforcing fiber - Google Patents

Description

  The present invention relates to a method for producing rubber reinforcing fibers, and more particularly to a method for producing rubber reinforcing fibers suitably used for rubber / fiber composites such as tires, hoses and belts.

  Fibers have excellent physical properties such as high strength and high Young's modulus, and rubber structures using reinforcing fibers taking advantage of these properties are widely used in applications such as tires, hoses, and belts. As a rubber / fiber adhesive composition for adhering a rubber structure and a fiber for reinforcing it, a so-called RFL adhesive mainly composed of resorcin, formalin, and rubber latex is widely used. (For example, Patent Document 1 and Patent Document 2).

  However, since the condensation state of RFL adhesive changes with time, the adhesiveness and process passability deteriorate from the initial performance, the pot life of the adhesive is limited, and the product performance is kept constant. It was difficult to do. Thus, Patent Document 3 has been proposed as a rubber reinforcing fiber that does not use an RFL-based adhesive, but there is still a problem that the adhesive strength, particularly when exposed to high temperatures during use, is not sufficient. .

JP-A-54-73994 JP 2002-53830 A JP 2005-89679 A

  An object of the present invention is to provide a rubber reinforcing fiber having excellent adhesive performance, particularly heat resistant adhesive performance.

  The method for producing a reinforcing fiber of the present invention is a production method in which a fiber is treated with a treatment agent containing a thermoplastic elastomer, wherein the thermoplastic elastomer has a castor oil-based polyol structure in a soft segment, The treating agent includes a thermoplastic elastomer, a blocked isocyanate, and a rubber latex.

  Furthermore, the hard segment of the thermoplastic elastomer is isophorone diisocyanate (IPDI) or hydrogenated methylene diphenyl isocyanate (hydrogenated MDI), or the isocyanate having a bifunctional or higher functional block isocyanate is a blocking group having active hydrogen. A blocked structure is preferred.

  Further, in the production method of the present invention, the fiber to be used is pretreated with a pretreatment liquid containing a blocked isocyanate, and the pretreatment liquid further comprises a compound having an epoxy group or a compound having an amino group and a hydroxyl group. A pretreatment liquid containing at least one of them is preferable.

  ADVANTAGE OF THE INVENTION According to this invention, the fiber for rubber reinforcement excellent in adhesive performance, especially heat resistant adhesive performance is provided.

  The production method of the present invention is a production method in which a fiber is treated with a treatment agent containing a thermoplastic elastomer, wherein the thermoplastic elastomer has a castor oil-based polyol structure in its soft segment, and the thermoplastic elastomer is It is essential that the treating agent contained contains a thermoplastic elastomer, a blocked isocyanate and a rubber latex.

  The fiber used in the present invention is preferably a synthetic fiber having excellent physical properties such as high strength and high Young's modulus. More specifically, examples thereof include polyester fiber, polyamide fiber, aromatic polyamide fiber, and the like. I can do it. The production method of the present invention is particularly effective for increasing the adhesive strength of polyester fibers or aromatic polyamide fibers. The polyester fiber is preferably a fiber made of polyester having terephthalic acid or naphthalenedicarboxylic acid as a main acid component and ethylene glycol, 1,3-propanediol or tetramethylene glycol as a main glycol component. As the aromatic polyamide fiber, polyparaaminobenzamide, polyparaphenylene terephthalamide, polyparaaminobenzhydrazide terephthalamide, polyterephthalic acid hydrazide, polymetaphenylene isophthalamide, or a so-called aramid fiber made of a copolymer thereof is used. It is preferable to be used effectively for para-aramid fibers having particularly high strength. There are no restrictions on the denier, filament number, cross-sectional shape, etc. of these synthetic fibers, and the fibers of the present invention include various fiber aggregate forms such as yarns, cords, nonwoven fabrics, and woven and knitted fabrics.

  The production method of the present invention is a production method in which such a fiber is treated with a treatment agent containing a thermoplastic elastomer, a blocked isocyanate and a rubber latex, and the thermoplastic elastomer used here has a castor oil-based polyol structure in its soft segment. It is essential to have this.

  The thermoplastic elastomer used in the present invention is composed of a soft segment and a hard segment, and preferably has elastomer characteristics at room temperature and melts at a high temperature of 170 ° C. or higher. The soft segment contains a castor oil-based polyol and is mainly composed of it, and it is preferable that the total amount of the soft segment is composed of a castor oil-based polyol, but other components include polyethylene oxide and polypropylene oxide. It is also possible to use a diol component such as polybutadiene in combination.

  Examples of the hard segment include diisocyanates such as isophorone diisocyanate (IPDI), hydrogenated methylene diphenyl isocyanate (hydrogenated MDI), tolylene diisocyanate (TDI), metaphenylene diisocyanate, and hexamethylene diisocyanate. Of these, the hard segment of the thermoplastic elastomer is preferably isophorone diisocyanate (IPDI) or hydrogenated methylene diphenyl isocyanate (hydrogenated MDI).

Thermoplastic elastomer used in the present invention as a film physical properties of the sole 100% modulus of preferably 10~150kg / cm ^2, more be a 30~100kg / cm ^2, as is preferably the 300% modulus 60~200kg / cm ^2, preferably further it is 90~230kg / cm ^2. The breaking elongation is preferably 200% or more, and more preferably 300 to 1000%. The physical properties are measured by forming a film with a thickness of 0.9 mm and molding it into a No. 3 dumbbell according to the JIS K6251 standard.

  When the modulus is too small, the modulus of the fiber / rubber interface also decreases, and in particular, the pull-out adhesion tends to be reduced. On the other hand, when the modulus is too large, the compatibility of the adhesion treating agent with rubber tends to decrease, and the adhesive strength tends to decrease in general. Even when the elongation at break is too small, the stress distribution at the fiber / rubber interface tends to be insufficient, and the peel adhesive strength tends to decrease.

  Further, the melt elongation rate due to its own weight when the thermoplastic elastomer film used in the present invention is heated at 180 ° C. for 3 hours is preferably 150% or less, and more preferably 100 to 140%. This was measured using a 0.9 mm thick film shaped into a JIS No. 3 dumbbell of a thermoplastic elastomer film, as in the physical property measurement. When the melt elongation rate due to its own weight is large, the high-temperature adhesive force tends to decrease and the degree of thermal fatigue of the rubber / fiber composite tends to increase.

The solid content in all active ingredients in the thermoplastic elastomer treatment liquid is preferably 30 to 80% by weight. By using such a thermoplastic elastomer, in the present invention, the adhesive force, particularly the heat-resistant adhesive force, can be increased, and further, the product can have a long life and high reliability.
The treating agent used in the production method of the present invention contains blocked isocyanate and rubber latex in addition to the thermoplastic elastomer.

  The blocked isocyanate compound used in the present invention is an addition reaction product of a polyisocyanate compound and a blocking agent, and releases a block component upon heating to produce an active polyisocyanate compound. In this case, the terminal isocyanate group is preferably 2 or more, more preferably 3 or more polyfunctional isocyanates. Examples of the polyisocyanate compound include tolylene diisocyanate, metaphenylene diisocyanate, diphenylmethane diisocyanate, hexamethylene diisocyanate, tris (hexamethylene diisocyanate), polymethylene polyphenyl isocyanate, triphenylmethane triisocyanate and the like, or these polyisocyanates. Terminal isocyanate obtained by reacting a compound having two or more active hydrogen atoms, such as trimethylolpropane, pentaerythritol, etc., at a molar ratio of isocyanate group (—NCO) to hydroxyl group (—OH) exceeding 1. Group-containing polyalkylene glycol adduct polyisocyanate, polyisocyanate such as polymethylene polyphenyl isocyanate It preferred because it exhibits excellent performance. Examples of the blocking agent include phenols such as phenol, thiophenol, cresol and resorcinol, aromatic secondary amines such as diphenylamine and xylidine, phthalimides, lactams such as caprolactam and valerolactam, acetoxime, methyl ethyl keto Examples include oximes such as oxime and cyclohexanone oxime, and acidic sodium sulfite.

  The solid content in all active ingredients of the blocked isocyanate compound is preferably 5 to 30% by weight. When the content is too small, the chemical affinity for the fiber surface is insufficient, and the adhesive strength tends to be insufficient. On the other hand, if the amount is too large, the adhesive layer becomes hard and the cord strength does not develop, and there is a tendency that problems such as impregnation dipping and removal of the adhesive layer during the processing process occur.

  Examples of the rubber latex used in the present invention include natural rubber latex, styrene / butadiene copolymer latex, vinylpyridine / styrene / butadiene terpolymer latex (hereinafter referred to as VP latex), nitrile rubber latex, and chlorobrene rubber latex. , Ethylene / propylene / diene monomer latex and the like, and these can be used alone or in combination. Of these, vinyl pyridine / styrene / butadiene terpolymer latex is preferably used alone or in combination with another. When used in combination, excellent performance is obtained when the vinylpyridine / styrene / butadiene terpolymer latex is used in an amount of 1/3 or more of the total latex weight. The solid content in the rubber latex treatment liquid is preferably about 30 to 80% by weight.

  The total solid concentration of the treatment agent containing the thermoplastic elastomer, blocked isocyanate and rubber latex used in the present invention is 1 to 30% by weight, more preferably 1.5 to 20% by weight, most preferably 2 to 15% by weight. % Is preferred. If the total solid content concentration is too low, the adhesive surface tension increases, the uniform adhesion to the polyester fiber surface decreases, and the adhesion decreases due to a decrease in the solid content adhesion amount. On the other hand, if the concentration of the treatment liquid is too high, not only is the production cost disadvantageous, but the amount of solids attached becomes too large and the fatigue property of the fiber / rubber composite that can be hardened tends to decrease.

  When the composition of the treatment agent is used as an aqueous dispersion, an appropriate amount of the surfactant as the dispersant is 15% by weight or less, preferably 10% by weight or less, based on the total solid content of the treatment agent. Preferably there is. This is because the adhesiveness tends to decrease as the amount of the surfactant increases.

  The amount of the solid component attached to the fiber by the production method of the present invention is preferably in the range of 0.1 to 10% by weight, more preferably 0.3 to 7% by weight, most preferably 0.5. It is preferably ˜5% by weight. In order to control the amount of the solid component attached to the fiber, means such as squeezing with a pressure roller, scraping with a scraper, blowing off with air blowing, suction, hitting with a beater, etc. can be employed. In order to increase the amount of adhesion, or in order to further increase the uniformity, it may be adhered multiple times.

  Although this invention makes it essential to process with the processing agent containing the above thermoplastic elastomers, it is preferable that the fiber is previously processed with the pretreatment liquid containing block isocyanate. As block isocyanate, the thing similar to what was used by description of said processing agent can be used.

  Further, the pretreatment liquid containing the blocked isocyanate is preferably a pretreatment liquid containing at least one of a compound having an epoxy group or a compound having an amino group and a hydroxyl group. These compounds have a function of reacting with blocked isocyanate by heat treatment to form a higher-order cross-linked structure and further strengthening the aggregated structure of the adhesive.

  As the compound having an epoxy group, a conventionally known adhesive epoxy compound can be used. The compound having an amino group and a hydroxyl group is preferably a compound having an aliphatic amino group having 1 to 10 functional groups, more preferably 2 to 3 functional amino groups. If the number of amino groups is too large, the stability in water of the emulsion / dispersion such as latex may be inhibited, which may cause gelation or precipitation. This amino group mainly functions as a catalyst with the blocked polyisocyanate. The number of hydroxyl groups is preferably 3-12 functional, more preferably 4-5 functional aliphatic hydroxyl. In order to cause uniform crosslinking, the number of hydroxyl groups is preferably an appropriate number. In order to improve water solubility, it is particularly preferable to use a hydroxyl group at the polymerization terminal of polyethylene oxide or polypropylene oxide in addition to the number. Further, in the case of a phenolic OH compound, the crosslinking performance tends to be lowered, and therefore other hydroxyl groups are preferred. These compounds have a function of reacting with blocked isocyanate by heat treatment to form a higher-order cross-linked structure and further strengthening the aggregated structure of the adhesive. In particular, in the production method of the present invention, when a compound having an amino group and a hydroxyl group is used together with a blocked isocyanate as a fiber pretreatment agent, the effect of improving the adhesive strength is remarkable.

Further, it is also preferable to add a rubber latex or a compound polymerized using a vinyl halide group to the pretreatment agent used in advance for the fibers.
As a compound using a vinyl halide group, a film forming temperature is 200 ° C. or lower, more preferably 180 ° C. or lower. When the film forming temperature exceeds 200 ° C., it is difficult to form a uniform film under the bonding treatment conditions. Such a compound used in the present invention is a compound of vinyl chloride alone or variously copolymerized, such as vinyl chloride and vinyl acetate, vinyl chloride and vinylidene chloride, vinyl chloride and acrylonitrile, vinyl chloride. And a copolymer of vinyl acetate and vinyl acetate, a terpolymer of vinyl chloride, vinyl acetate and maleic anhydride, or a mixture thereof.

  The total solid concentration of the pretreatment agent is 1 to 30% by weight, preferably 1.5 to 20% by weight. Moreover, it is preferable to use the solid content adhesion amount of the pretreatment agent with respect to the fiber in the range of 0.1 to 10% by weight, and it is more preferable to adhere in the range of 0.5 to 3% by weight. Moreover, you may make it adhere several times in order to raise the adhesion amount or to ensure uniformity. In the production method of the present invention, by using in combination with such a pretreatment agent, it becomes possible to further improve the adhesive force with rubber by a synergistic effect.

  Such reinforcing fibers obtained by the production method of the present invention have sufficient adhesive strength, particularly when exposed to high temperatures during use, and have excellent fiber strength, high Young's modulus, etc. Since physical properties can be utilized, it is suitably used for rubber structures using reinforcing fibers such as tires, hoses and belts.

  Hereinafter, the present invention will be described in more detail with reference to examples. In addition, the characteristic in an Example was performed with the following measuring method.

(1) Cord peeling adhesive strength This indicates the adhesive strength between the treated cord and rubber. Seven cords are buried near the surface layer of an unvulcanized rubber sheet containing carcass containing natural rubber as a main component, and a press pressure (initial value) of 50 kg / cm ² for 30 minutes at a temperature of 150 ° C. or 180 ° C. For 40 minutes at a temperature of 50 kg / cm ^{2 at} a pressing pressure (heat resistance value), and then leaving the cords at both ends and leaving the three cords at a speed of 200 mm / min in the direction of 90 degrees with respect to the rubber sheet surface. The force required for peeling is indicated by N / 3.

(2) Melt elongation rate (TL)
A 0.9 mm-thick film of thermoplastic elastomer is prepared and shaped into a JIS No. 3 dumbbell shape as a sample. The 100% modulus, 300% modulus and tensile strength are each expressed in kg / cm ² . The melt elongation rate (TL%) is expressed in% by the unit of the elongation rate due to its own weight when one end of the sample is fixed and suspended vertically and heated at 180 ° C. for 3 hours.

[Example 1]
A polyepoxide compound, a block polyisocyanate (manufactured by Meisei Chemical Industry Co., Ltd., DM6011), a VP latex, and a vinyl chloride latex (Vinyl Blanc 609 manufactured by Nissin Chemical Industry Co., Ltd.) are each 6% by weight, 20% by weight, 44% by weight, 30% The pretreatment liquid (1) having a total solid content concentration of 5.5% by weight was obtained by mixing so that the ratio was 5% by weight.

  On the other hand, thermoplastic elastomer (1) (soft segment is castor oil type polyol, hard segment is IPDI), block polyisocyanate (manufactured by Meisei Chemical Industry Co., Ltd., DM6011), and VP latex are 50% by weight and 15% by weight, respectively. The main treatment liquid (1) having a total solid concentration of 20.0% by weight was obtained.

  As the fiber, a 1670 dtex / 384 filament multifilament yarn made of polyethylene terephthalate having an intrinsic viscosity of 0.95 is used, and the multifilament yarn is twisted at 40 T / 10 cm, and the two are combined to 40 T / cm. And a 3340 dtex / 768 filament cord was used.

  The cord was immersed in the pretreatment liquid (1) using a contributor processing machine (tire code processing machine manufactured by CA Ritzler Co., Ltd.), then dried at a temperature of 130 ° C. for 2 minutes, and subsequently at a temperature of 240 ° C. A heat treatment was performed at a temperature for 1 minute, followed by immersion in the treatment liquid (1), followed by drying at a temperature of 170 ° C. for 2 minutes, and subsequently a heat treatment at a temperature of 240 ° C. for 1 minute. The obtained reinforcing fiber cord had 1.0% by weight of the pretreatment agent and 1.7% by weight of the treatment agent as solid content of the treatment agent. The above-mentioned method by embedding the obtained reinforcing fiber cord in a carcass blended unvulcanized rubber containing natural rubber as a main component, and vulcanizing at a temperature of 150 ° C. for 30 minutes and at a temperature of 180 ° C. for 60 minutes. It was evaluated by. The results are shown in Table 1.

[Example 2]
As the treatment agent, instead of thermoplastic elastomer (1) (soft segment is castor oil-based polyol, hard segment is IPDI), thermoplastic elastomer (2) (soft segment is castor oil-based polyol: PTMG = 7: 3, hard segment) Was used in the same manner as in Example 1 except that this treating agent (2) using IPDI was used to obtain a reinforcing fiber cord. The results are also shown in Table 1.

[Comparative Example 1]
As this treating agent, instead of thermoplastic elastomer (1) (soft segment is castor oil polyol, hard segment is IPDI), thermoplastic elastomer (3) not satisfying the requirements of the present invention (soft segment is polycarbonate diol, hard segment) However, this treatment agent (3) using IPDI) was used in the same manner as in Example 1 to obtain a reinforcing fiber cord. The results are also shown in Table 1.

[Examples 3 and 4 and Comparative Example 2]
Instead of the pretreatment liquid (1) using an epoxy compound, ethylenediamine ethylene oxide 4 mol adduct, polyfunctional block polyisocyanate (manufactured by Meisei Chemical Industry Co., Ltd., NBP873), VP latex, and vinyl chloride latex (manufactured by Nissin Chemical Industry Co., Ltd.) Viniblanc 609) was mixed at a solid content of 1.5 parts by weight, 100 parts by weight, 50 parts by weight, and 50 parts by weight to prepare a pretreatment liquid (2) having a total solids concentration of 10% by weight. The others were carried out as in Examples and Comparative Examples. Examples corresponding to Examples 1 and 2 and Comparative Example 1 were designated as Examples 3 and 4 and Comparative Example 2, respectively. The results are also shown in Table 1.

Claims (6)

  A process for treating a fiber with a treatment agent containing a thermoplastic elastomer, wherein the thermoplastic elastomer has a castor oil-based polyol structure in a soft segment, and the treatment agent is a thermoplastic elastomer, a blocked isocyanate, and a rubber A method for producing a reinforcing fiber, comprising latex.   The method for producing a reinforcing fiber according to claim 1, wherein the hard segment of the thermoplastic elastomer is isophorone diisocyanate (IPDI) or hydrogenated methylene diphenyl isocyanate (hydrogenated MDI).   The method for producing a reinforcing fiber according to claim 1 or 2, wherein the blocked isocyanate has a structure in which a bifunctional or higher functional isocyanate is blocked with a blocking group having active hydrogen.   The method for producing a reinforcing fiber according to any one of claims 1 to 3, wherein the rubber latex is vinylpyridine / styrene / butadiene latex.   The method for producing a reinforcing fiber according to any one of claims 1 to 4, wherein the fiber is pretreated with a pretreatment liquid containing a blocked isocyanate.   The method for producing a reinforcing fiber according to claim 5, wherein the pretreatment liquid is a pretreatment liquid containing at least one of a compound having an epoxy group or a compound having an amino group and a hydroxyl group.