JPH10329507A - Dip cord for rubber reinforcement - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide yarn cord for rubber reinforcement with remarkably improved adhesion property and anti-fatigue property which is the defect of a polybenzazole fiber capable of realizing the high strength and elastic modulus which is an excellent characteristic of polybernzazole fiber as a reinforcement material. SOLUTION: This dip cord for rubber reinforcement is formed by twisting together plural yarns with the strength of 18 g/d or more consisting of a polybenzazole fiber and has a strength of 16 g/d or more in which a dip treatment is applied and a strong force utilization rate is 50% or more. In the dip treatment for improving the adhesion property to a rubber, using a treatment liquid of the combination or independence of the water dispersion of an epoxy resin, water dispersion of blocked isocyanate, water dispersion of resorcine formaldehyde resin-rubber latex mixed liquid, one stage or two or more multistage treatment is generally employed, and the other treatment is acceptable.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a spinning polybenzazole fiber having unprecedented strength and strength retention with improved adhesion and fatigue resistance used as a rubber reinforcing material for tires, hoses and belts. It relates to a yarn cord.

[0002]

2. Description of the Related Art Conventionally, fibers used as rubber reinforcing materials for tires, hoses, belts and the like have mainly been nylon fibers, polyester fibers, glass fibers and steel fibers. Aromatic polyamide fibers represented by Kevlar have been used as various rubber reinforcing materials.

[0003] Polybenzazole fibers, which have much higher strength and elastic modulus than the aromatic polyamide fibers, and are also excellent in heat resistance and dimensional stability, are attracting attention as rubber reinforcing materials. In the field of rubber materials, the use of conventional organic fibers as reinforcement fibers in applications requiring higher strength and higher heat resistance, which has been insufficient in performance, has been studied.

[0004] However, the polybenzazole fiber has the above-mentioned excellent properties, but has a drawback that its adhesion to rubber matrix and fatigue resistance are inferior to those of other organic fibers. Therefore, as a method for improving the adhesion to a rubber matrix, Japanese Patent Application Laid-Open No.
6029, JP-A-7-102473, JP-A-6-344708, JP-A-6-280169, JP-A-6-280167 and JP-A-6-280167.
Although it is disclosed in Japanese Patent No. 287866, at present, sufficient adhesiveness has not been obtained. Further, as one means for improving fatigue resistance, as described in JP-A-9-49139, polybenzazole fibers exhibit extremely good fatigue resistance on the low twist side with single twist. However, considering the balance between fatigue resistance and adhesive strength, its performance is not sufficient.

[0005]

SUMMARY OF THE INVENTION Adhesion and fatigue resistance, which are the drawbacks of polybenzazole fibers, are remarkably improved, and high strength and elastic modulus, which are excellent properties of polybenzazole fibers, are realized as a reinforcing material. It is an object of the present invention to provide a spun yarn cord for rubber reinforcement.

[0006]

That is, the present invention comprises a plurality of twisted spun yarns of polybenzazole fiber having a strength of 18 g / d or more, and 16 g of a dip-treated spun yarn.
A rubber reinforcing dip cord having a strength of at least / d. Further, the above-mentioned dip cord for rubber reinforcement has a strong utilization rate of 50% or more.

Hereinafter, the present invention will be described in detail. The polybenzazole fiber in the present invention refers to a fiber made of a polybenzazole polymer, and a polybenzazole (PB)
Z) means polybenzoxazole (PBO) homopolymer, polybenzothiazole (PBT) homopolymer, and random, sequential or block copolymers of PBO and PBT. Here, polybenzoxazole, polybenzothiazole and their random, sequential or block copolymers are described, for example, in "Liquid Crystalline Polym
er Compositions, Process and Products "U.S. Patent No. 4,703,103 (October 27, 1987)," Liqu
id Crystalline Polymer Compositions, Process and P
roducts "U.S. Pat. No. 4,533,692 (August 1985)
6), “Liquid Crystalline Poly (2,6-Benzothiaz
ole) Compositions, Process and Products, US Patent No. 4,533,724 (August 6, 1985), "Liquid
Crystalline Polymer Compositions, Process and Pro
ducts, US Patent No. 4,533,693 (August 6, 1985); Evers, "Thermooxidatively Stable Articul.
ated p-Benzobisoxazole and-Benzobisthiazole Polyme
rs "U.S. Pat. No. 4,539,567 (November 1, 1982)
6) Tsai et al., “Method for making Heterocyclic B
lock Copolymer "U.S. Pat. No. 4,578,432 (198
March 25, 2006). The structural unit contained in the PBZ polymer is preferably selected from a lyotropic liquid crystal polymer. The monomer units consist of the monomer units described in structural formulas (a) to (h), and more preferably essentially consist of structural formulas (a) to (c)
Consisting of monomer units selected from:

[0008]

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[0009]

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[0010] Suitable solvents for forming the dope of the PBZ polymer include cresol and non-oxidizing acids capable of dissolving the polymer. Examples of suitable acid solvents include polyphosphoric acid, methanesulfonic acid and concentrated sulfuric acid or mixtures thereof. Further suitable solvents are polyphosphoric acid and methanesulfonic acid. The most suitable solvent is polyphosphoric acid.

[0011] The polymer concentration in the solvent is preferably at least about 7% by weight, more preferably at least 1% by weight.
0% by weight, most preferably at least 14% by weight. The maximum concentration is limited by practical handling properties such as, for example, polymer solubility and dope viscosity. Because of these limiting factors, the polymer concentration usually does not exceed 20% by weight.

[0012] Suitable polymers, copolymers or dopes are synthesized by known techniques. See, eg, Wolfe et al., US Pat. No. 4,533,693 (August 6, 1985), Sy.
U.S. Pat. No. 4,772,678 to S. bert et al. (September 20, 1988); U.S. Pat.
(July 11, 1989). P
BZ polymers are disclosed in US Pat. No. 5,085,959 to Gregory et al.
According to No. 1 (February 8, 1992), it is possible to increase the molecular weight at a high reaction rate under a relatively high temperature and high shear condition in a dehydrating acid medium.

From the polymerized dope, a polybenzazole fiber having a high strength and a high elastic modulus is produced by known means. For example, US Pat. No. 5,294,390 (1)
The dry-wet spinning method described on May 15, 994) is suitable.

The spun yarn used in the cord of the present invention preferably has a single fiber fineness of 1 denier to 3 denier. When the fineness is less than 1 denier, only the yarn with insufficient strength of the spun yarn is obtained due to the increase in the fluff of the yarn. On the other hand, when the fineness exceeds 3 denier, the strength of the spun yarn is reduced due to a decrease in the number of fibers constituting the spun yarn. Preferably it is 1 to 2.5 denier.

The average fiber length is desirably 30 mm or more and 200 mm or less. If it is less than 30 mm, the spun yarn strength is undesirably reduced, while if it exceeds 200 mm, the texture of the spun yarn is impaired, and the fluff of the spun yarn is utilized to improve the adhesion to the rubber matrix. Cannot be expected.

The number of twists of the spun yarn preferably satisfies the following equation (1). If K · (L) ^1/3 is smaller than 7.0,
Since there is little entanglement between fibers, sufficient strength cannot be obtained. If K · (L) ^1/3 is larger than 13.0,
The strength of the spun yarn decreases with a decrease in the strength utilization rate due to twisting. In addition, the twist coefficient K is preferably 1.0 to 3.0. 7.0 ≦ K · (L) ^1/3 ≦ 13.0 Formula (1) K: Twisting factor = T / (Ne) ^1/2 L: Average fiber length (mm) T : Number of twists (T / in) Ne: English cotton count

As an example of a method for obtaining a spun yarn, there is a method in which a tow is cut off to form a sliver, and then a roving and spinning process is performed to form a spun yarn. At this time, it is effective that the fiber fineness is 1 to 3 denier in order to facilitate towing of the tow, to secure the fiber parallelism of the obtained sliver, and to reduce unevenness in the sliver thickness.

This so-called draw-off method is a preferred example of a method for obtaining a spun yarn used for the cord of the present invention. The reason is effective not only for securing the fiber parallelism and reducing the thickness unevenness, but also for securing the strength of the spun yarn. In the spinning process using a normal card, it is necessary to crimp the fiber in order to secure the card passing property. Since spinning can obtain spun yarn without applying crimp to the fiber, spinning is extremely effective in reducing damage to the fiber and obtaining a high-strength spun yarn made of polybenzazole fiber. Is the way.

The rubber reinforcing cord of the present invention provides a single twist or a multi-twist using a ring twisting machine or the like from the viewpoint of improving the convergence of fibers and improving fatigue resistance by aligning a plurality of the spun yarns. Can be Usually, in a long fiber cord, the cord strength decreases with an increase in the number of twists, and the number of twists is determined by a balance between fatigue resistance and strength. On the other hand, the spun yarn cord of the present invention hardly causes a decrease in strength due to twisting. This is considered to be because the spun yarn is made of short fibers of polybenzazole fiber, and the binding force between the single fibers is improved by the twisted yarn. In the case of long fiber cords, stress concentration occurs due to resin adhesion due to so-called dip treatment, and strength decreases. On the other hand, in the spun yarn cord, strength does not decrease due to improvement in binding force due to resin adhesion.
For this reason, the spun yarn cord hardly undergoes a drop in strength even after passing through the twisting and dipping treatment steps, and a rubber reinforcing cord can be realized with a very high strength utilization rate.

The spun yarn thus obtained is at least 18 g / d, preferably at least 20 g / d, and the strength of the twisted yarn and the dip cord that has been subjected to the dip treatment step is at least 16 g / d, preferably at least 18 g / d. . And the strength utilization rate (= dip cord strength / filament strength) is 50% or more, preferably 55% or more. The strength of the spun yarn is 1
If it is less than 8 g / d, the amount of fiber used cannot be reduced, which is not preferable from the viewpoint of weight reduction. For the same reason, it is desirable that the strong utilization rate is 50% or more.

The twisted cord is subjected to a so-called dip in order to improve adhesion to rubber. Examples of the treatment liquid include (A) an aqueous dispersion of an epoxy resin, (B) an aqueous dispersion of a blocked isocyanate, (C) an aqueous dispersion of a rubber latex, and (D) a mixed solution of a resorcinol-formaldehyde resin and a rubber latex. In general, the treatment is performed in a single step or in a multi-step treatment of two or more steps in combination or alone. However, other prescriptions may of course be used. In particular, in this formulation, the uniformity of migration in the cord is particularly important for enhancing the fatigue resistance and the utilization of the strength and elastic modulus.

Since the rubber reinforcing cord thus obtained hardly suffers from a drop in strength due to the twisting and dipping steps, it is possible to improve the fatigue resistance with a high strength utilization rate by setting the number of twists high. In addition, the effect of the fluff possessed by the spun yarn provides a higher adhesive strength to the rubber matrix than that of the long fiber cord, and since the cord is made of a spun yarn that is an aggregate of short fibers, it has excellent fatigue resistance. From the above, by using a spun yarn made of polybenzazole fiber having high strength and high elastic modulus, a rubber reinforcing cord with unprecedented high strength and high utilization rate, and excellent in adhesiveness and fatigue resistance is obtained. It became feasible.

[0023]

EXAMPLES Next, the effects of the present invention will be described using examples. Of course, the present invention is not limited to the embodiments. (Samples 1 to 5) 14 wt% of cis-polybenzobisoxazole (PBO) having an intrinsic viscosity of 30 dl / g was added to polylinic acid.
The melted spinning dope was extruded from a 334 nozzle having an orifice diameter of 0.22 mm at a temperature of 160 ° C. and a single hole discharge rate of 0.122 cc. The fibrous dope extruded from the nozzle passes through an air gap of 22 cm, is pulled therein, passes through a coagulation bath adjusted to about 22 ° C., and is continuously fed at a traveling speed of about 200 m / min.
It was washed with a pair of rollers or more, then dried without being wound up once, applied with an oil agent, and wound up. The fibers were aligned and twisted to obtain a raw cord. 30 fibers
After the yarn was plied to a 2,000-denier tow, crimping was applied with a push-in crimper and cut with a rotary cutter to obtain a polybenzobisoxazole staple. PB obtained
A 20th twin yarn spun yarn was manufactured from O staple (...
Sample 2). Further, the fiber was twisted into a 30000 denier tow and simultaneously cut. The drawing sliver made of the fiber was subjected to a roving / spinning process to produce a 27th spun yarn (... samples 3, 4, and 5).

(Samples 6 and 7) Using aramid fiber "Twaron" (product name of AKZO Corporation), the fiber was twined on a 30,000-denier tow, crimped with a push-in crimper, and cut with a rotary cutter. I got staples. From the obtained Twaron staple, a spun yarn of 20th count double yarn was manufactured. Table 1 shows each physical property. As shown in Samples 2 to 5, spun yarns composed of polybenzazole fibers, particularly the spun yarns of Samples 3 to 5, can provide unprecedented high-strength spun yarns due to their high tenacity. Using these, a rubber reinforcing dip cord was prepared.

[0025]

[Table 1]

(Examples 1 to 6, Comparative Examples 1 to 6) Using the filaments and spun yarns shown in Table 1, a plurality of each of them were aligned and twisted to obtain a raw cord. The raw cord was subjected to two-step dip processing to prepare a dip code. The first dipping treatment liquid is (1) an aqueous dispersion of an epoxy resin or (2) a mixed liquid of an epoxy resin and a latex aqueous dispersion. The treatment temperature is 240 ° C., and the second dipping treatment liquid is an RFL liquid. And the processing temperature was 235 ° C. Table 2 shows the characteristics of the obtained cord. Comparative Examples 1 and 5
Is Sample 1, Comparative Examples 2 and 3 are Sample 2, Comparative Example 4 is Sample 7,
Comparative Example 6 used Sample 6. Examples 1 to 6 correspond to sample 4
Was used.

[0027]

[Table 2]

As can be seen from Table 2, the rubber reinforcing cord of the present invention using a spun yarn having a tenacity of 20 g / d or more has a strong utilization rate per original yarn tenacity even after passing through a twisting and dipping treatment step. And is as high as 50% or more, and has strength comparable to long fiber cord of polybenzbisoxazole (PBO) fiber. Furthermore, it has significantly improved adhesive strength and fatigue resistance as compared with the long fiber cord of the PBO fiber.

[0029]

As described above, a rubber reinforcing cord using a spun yarn made of polybenzazole fiber simultaneously satisfies mechanical properties, adhesiveness, and fatigue resistance at a level that could not be achieved until now. can do.

Claims (2)

[Claims] (1) a polybenzazole fiber having a strength of 1
A rubber-reinforcing dip cord obtained by twisting a plurality of spun yarns of 8 g / d or more and having a strength of 16 g / d or more subjected to a dip treatment. 2. The rubber reinforcing dip cord according to claim 1, wherein a strong utilization rate is 50% or more.