JPH1046468A - Production of polybenzazole fiber having improved adhesion property with rubber - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a polybenzazole fiber having a high strength, a high elasticity and a high heat resistance, excellent in adhesion property and useful for a tire, etc., by treating the polybenzazole fiber under a specific condition and then heat-treating the fiber. SOLUTION: This method for producing a polybenzazole fiber having an improved adhesion property with a rubber is constituted by immersing the polybenzazole fiber applied with a plasma discharge treatment at the surface thereof into a first treating liquid consisting of an epoxy compound having >=2 epoxy groups such as a sorbitol polyglycidyl ether and a rubber latex of an acrylonitrile butadiene copolymer having >=10 deg.C glass transition temperature as main constituting materials for sticking the components to the fiber by a reaction, then immersing the fiber into a second treating liquid containing a resorcin formaldehyde condensation material and a rubber latex for sticking the second components to the fiber, and then heat-treating the resultant fiber at 240-260 deg.C to obtain the treated polybenzazole fiber.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a method for producing a polybenzazole fiber having improved adhesion to a rubber compound.

[0002]

2. Description of the Related Art Conventionally, fibers used as reinforcing materials for rubber materials such as tires and power transmission belts have mainly been nylon fibers, polyester fibers, glass fibers and steel fibers, but have high strength and high elastic modulus. With the emergence of aromatic polyamide fibers represented by Kevlar, it has been widely used as a reinforcing material for various rubber materials and the like.

However, for example, attempts have been made to use this aromatic polyamide fiber as a substitute for steel cord in order to reduce the weight of tires, but the aromatic polyamide fiber has poor strength and abrasion resistance. It has not been realized enough.

[0004] As a material beyond the aromatic polyamide fiber, polybenzazole fiber has been receiving attention. Polybenzazole fiber has better strength, elastic modulus and heat resistance than aromatic polyamide fiber, and is a substitute for steel cord that could not be realized by aromatic polyamide fiber, and rubber material such as tires and belts In the field, use as a reinforcing fiber in application fields requiring higher strength and high heat resistance is being studied.

[0005] Since the polybenzazole fiber has a tensile strength and a tensile modulus approximately twice that of the aromatic polyamide fiber, when used as a carcass material for a tire for a passenger car, for example, a remarkable weight reduction which could not be achieved conventionally has been achieved. It becomes possible.

[0006] In the use of such fibers in rubber materials, the adhesion between the matrix rubber and the reinforcing fibers is one of the very important points. In rubber materials, poor adhesion leads to a decrease in fatigue resistance.However, when such polybenzazole fibers are used as reinforcing fibers for rubber materials such as tire cords and power transmission belts, it is necessary to use a conventionally treated polybenzazole fiber. Benzazole fiber is
There was a drawback that the adhesion to rubber was slightly inferior to that of aromatic polyamide fibers.

As a method for bonding polybenzazole fiber and rubber, Japanese Patent Application Laid-Open Nos. 7-102473 and
Although it is disclosed in JP-A-280169 and JP-A-6-280167, sufficient adhesiveness is not obtained.

[0008]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned conventional disadvantages of polybenzazole fibers, that is, the problem of poor adhesion to rubber as a matrix, and provides high strength, high elastic modulus, and high heat resistance. It is an object of the present invention to provide a method for bonding polybenzazole fiber and rubber having excellent properties and excellent adhesiveness.

[0009]

That is, the present invention provides a first treatment comprising a polybenzazole fiber comprising an epoxy compound having two or more epoxy groups and a rubber latex having a glass transition point of -10 ° C or more. A polybenzazole fiber with improved adhesion to rubber, characterized by reacting and fixing to a liquid, then adhering to a second treatment liquid containing resorcinol formaldehyde condensate and rubber latex, and then heat treating. A method for producing a polybenzasol fiber in which rubber latex, which is a main component of the first treatment liquid, is improved in adhesion to rubber, which is an acrylonitrile-butadiene copolymer, and a plasma discharge treatment is further performed on the surface of the fiber. This is a method for producing polybenzazole fiber having improved adhesion to rubber, which is subjected to the treatment described above after the application.

In the present invention, the polybenzazole fiber (PBZ) refers to a homopolymer of polybenzoxazole (PBO), a homopolymer of polybenzothiazole (PBT) and a random, sequential or block copolymer of PBO and PBT. Say.

As the epoxy compound used in the present invention, a known epoxy compound can be used as long as it has two or more epoxy groups in its molecule. For example, sorbitol polyglycidyl ether, polyglycerol polyglycidyl ether, diglycerol polyglycidyl ether, glycerol polyglycidyl ether and the like are preferred.Epoxy equivalent is preferably 180 or less, average molecular weight is 200 or more and 600 or less, the epoxy compound. is there.

The rubber latex, which is a main component of the first treatment liquid, needs to have a glass transition point of -10 ° C. or higher. If the temperature is lower than −10 ° C., the adhesive layer becomes hard, and the adhesive strength is reduced. Preferably it is 0 ° C. or higher.
Specifically, acrylonitrile-butadiene copolymer (NB
R) A rubber latex styrene-butadiene copolymer (SBR) rubber latex. In any case, those containing a carboxyl-modified product or a third component can be used.

As a result of intensive studies, we have found that the combination of an epoxy resin having a flexible structure and a hard rubber latex improves the adhesion between polybenzazole fiber and rubber. Although the reason is not clear, in order to cover the elastic modulus difference between the very high elasticity polybenzazole fiber and the matrix rubber, and to realize an adhesive layer that can easily follow deformation, a latex with a high elastic modulus and An adhesive layer having an epoxy compound that easily follows the deformation seems to be effective. For this reason, if a crosslinking agent such as a blocked isocyanate is added to the first treatment liquid, the adhesive layer becomes too hard, cannot follow the deformation, causes a decrease in adhesion, and may further reduce fatigue resistance. Therefore, the object of the present invention is not achieved.

The first treatment liquid of the present invention can be prepared by mixing by a general method, and if necessary, it is solubilized in water using a suitable surfactant. The application method includes immersing the polybenzazole fiber in the treatment liquid, roll application, spray spraying and the like. The weight ratio E / L of the solid content of the epoxy compound (E) and the rubber latex (L) in the first treatment liquid is 1
/ 1 to 1/5. If the amount of the latex compounded in the first treatment liquid of the present invention is too small, the cord becomes hard and causes a decrease in fatigue resistance, and if it is too large, there is a possibility of causing a decrease in adhesion.

The amount of the first treatment liquid adhered is 1 to 8% by weight, preferably 3 to 5% by weight on a solid basis after drying with respect to the polybenzazole fiber. If the amount is small, sufficient adhesive strength cannot be obtained, and if the amount is too large, the treated cord becomes extremely hard and the strength of the cord is reduced. Further, the fibers fall off to the hot plate and the hot roller, and the thermal decomposition product increases the friction between the fiber and the metal. For this reason, productivity and quality are reduced.

[0016] The polybenzazole fiber is subjected to
After the treatment with the first treatment liquid, drying is performed at a temperature of 100 to 150 ° C., and a heat treatment is performed at a temperature of, for example, 160 to 260 ° C., preferably 240 to 260 ° C.

The polybenzazole fiber cord treated with the first treatment liquid is then treated with an RFL liquid commonly used as an adhesive between the fiber and rubber. The RFL solution used in the present invention is an initial condensate obtained by reacting resorcinol (R) and formalin (F) under an acid or alkali catalyst.
(RF), styrene / butadiene copolymer latex, carboxyl group-containing styrene / butadiene copolymer latex, vinylpyridine / styrene / butadiene copolymer latex, acrylonitrile / butadiene copolymer latex, polychloroprene latex, polybutadiene latex , Latex such as natural rubber latex (L)
It is a mixed aqueous dispersion with one or two or more of R / F
(Molar ratio) is preferably in the range of 1 / 0.5 to 1/4, and RF / L (solid content ratio) is preferably in the range of 5/95 to 50/60. Furthermore, the adhesion is further improved by appropriately adding a blocked isocyanate, carbon black, or the like to the second treatment liquid.

The RFL solution can be applied in the same manner as the first processing solution. The amount of the RFL liquid attached to the polybenzazole fiber cord is 4 to 15% by weight, preferably 6 to 10% by weight. If the amount is too small,
Adhesiveness deteriorates, and if too large, stickiness becomes severe, workability deteriorates, and adhesiveness decreases. The treated polybenzazole fiber is dried, for example, at 100 to 150 ° C.
Heat treatment is performed at a temperature of 0 to 270 ° C, preferably 230 to 270 ° C. The polybenzazole fiber cord treated with the first treatment liquid and the second treatment liquid according to the present invention is buried in a vulcanizable uncured rubber, integrated and flowed to form a rubber / cord composite. be able to.

Further, a better adhesion can be obtained by activating the fiber surface by a plasma treatment, preferably a corona discharge treatment, in a known manner. The method of corona discharge treatment of polybenzazole fibers is described in, for example, JP-A-7-26415 and JP-A-7-102473.

According to the present invention, the polybenzazole fiber cord is treated with a mixture comprising a combination of an epoxy compound having two or more epoxy groups and an NBR rubber latex, and then treated with RFL. By adding a specific rubber latex to the first treatment liquid, the adhesion between the rubber and the polybenzazole fiber cord is improved, and the durability of the polybenzazole fiber reinforced rubber product is further increased. Further, the adhesion to rubber is further improved by treating the polybenzazole fiber, which has been surface-treated in advance by a plasma discharge treatment, in accordance with the present invention.

Next, the effects of the present invention will be described with reference to examples. The present invention is not limited to the embodiments.

【Example】

(Examples 1 to 5, Comparative Examples 1 to 7) <Production of polybenzobisoxazole fiber> Intrinsic viscosity 2
5 (methanesulfonic acid solution, 25 ° C.) polybenzobisoxazole polymer in polyphosphoric acid at 14 wt%
The spin dope containing at a concentration of 0.3% is spun into the air from a spinneret having a diameter of 0.3 mm and heated to 160 ° C., passed through a coagulation bath, and then subjected to a polyphosphoric acid extraction step and drying. It was wound after passing through a process and a heat treatment process. During this step, stretching is not substantially performed.

The obtained multifilament has a constitution of 976 denier / 664 filament and a tensile strength of 5.9.
GPa (43 grams / denier), tensile modulus 230G
It had high mechanical properties of Pa (1660 grams / denier).

<Corona treatment discharge of multifilament>
The above fibers (excluding those of Example 5) were treated using a corona discharge treatment device manufactured by Kasuga Electric Co., Ltd. using a bar-shaped electrode at a corona discharge irradiation dose of 3000 watts / m2 / min.

Polybenzazole fiber cord (1000D
/ 30 × 30), and treated with the first treatment liquid under the conditions shown in Table 1, and then, as a second treatment liquid, formalin 1
6.7 parts by weight (solid content 37%), 15 parts by weight of resorcinol and an aqueous solution of caustic soda (solid content 12%) were added to 500 parts by weight of water, aged at 25 ° C. for 7 hours, and then 433 parts by weight of VP latex (solids). 40%), 2.3 parts by weight of aqueous ammonia (solids 25%) and 23.7 parts by weight of water and aged at 20 ° C. for 41 hours, and then 50 parts by weight of blocked isocyanate (solids content). 20%) added RFL was used. Drying temperature 120 ° C, drying time 1
The dipping process was performed for 235 ° C. for 1 minute and a heat treatment time of 1 minute to obtain a dip code. After embedding this dip cord in an unvulcanized compounded rubber composition and performing a vulcanization treatment, a pull-out test and a peeling test were performed to evaluate the adhesion to rubber. Table 1 shows the measured results.

<Measurement of Glass Transition Point of Latex> The glass transition point was measured using a differential scanning calorimeter (DSC-50: manufactured by Shimadzu Corporation). 10 mg of latex previously dried at room temperature is sealed in a predetermined aluminum pan, and
The temperature was raised from 0 ° C. to 100 ° C. at a rate of 5 ° C./min, and the glass transition point of each latex was measured.

[0027]

[Table 1]

As is clear from Examples 1 to 5 in Table 1, the polybenzazole fiber obtained by combining the epoxy compound with an NBR latex or SBR latex having a glass transition point of -10 ° C. or more has excellent adhesion. Performance is obtained. On the other hand, NBR latex was not added (Comparative Example 1) or NBR latex having a glass transition point of -10 ° C or lower (Comparative Examples 2 to 4).
It can be seen that when 4) was used, sufficient adhesive strength could not be obtained, and when VP latex was used instead of NBR latex (Comparative Examples 5 and 6), the adhesive performance was insufficient. Further, it can be seen that when an isocyanate is added to the first treatment liquid (Comparative Example 7), the adhesive performance is reduced. This is thought to be due to the fact that the adhesive layer was too hard, so that a sufficient effect could not be obtained.

According to the present invention, a polybenzazole fiber cord is treated as a first treatment liquid with an aqueous dispersion of an epoxy / NBR latex, then treated with RFL, and then vulcanized integrally with uncured rubber. By doing so, the adhesion to rubber can be improved.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code Agency reference number FI Technical display location D06M 10/00 GH

Claims (3)

[Claims] 1. A polybenzazole fiber having two epoxy groups.
Epoxy compound having at least -10 ° C and a glass transition point of -10 ° C
Adhesion to rubber characterized by reacting and fixing the above-mentioned rubber latex to a first processing liquid having a main component, and then adhering to a second processing liquid containing a resorcinol formaldehyde condensate and rubber latex, and then heat-treating. For producing polybenzazole fibers with improved properties. 2. A polybenzasol fiber having improved adhesion to rubber, wherein the rubber latex, which is a main component of the first treatment liquid, is an acrylonitrile-butadiene copolymer. 3. A method for producing a polybenzazole fiber having improved adhesion to rubber, comprising subjecting the fiber surface to a plasma discharge treatment and then performing the treatment according to claim 1.