JPH0335040A - Highly oriented acrylic fiber-reinforced rubber composition - Google Patents

Abstract

PURPOSE:To obtain a highly oriented acrylic fiber-reinforced rubber composition excellent in strength, heat and oil resistance by blending a diene-based rubber with carbon black and acrylic fiber having a specific value or above of X-ray orientation degree in a specific proportion. CONSTITUTION:A rubber composition obtained by blending (A) 50-80wt.% diene- based rubber (preferably acrylonitrile-butadiene copolymer rubber) with (B) 1-30wt.% carbon black (e.g. furnace black for rubber), (C) 5-40wt.% acrylic fiber of >=95wt.% X-ray orientation degree, preferably containing >=90wt.% acrylonitrile units and having preferably >=10g/d, more preferably >=15g/d tensile strength, 0.1-10mm length of short fiber, 0.1-10d size of the short fiber and 10-1000 aspect ratio and, as necessary, various additives, mixing the components in a kneader while heating and vulcanizing the resultant mixture and molding the vulcanized mixture.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an acrylic fiber-reinforced rubber composition that has excellent strength, heat resistance, and oil resistance.

(Prior Art) As a general method of increasing the strength of rubber, a method of embedding various reinforcing materials into rubber is known. However, these methods involve weaving or knitting the reinforcing material in the form of long fibers and then lining the material with rubber, which requires a very complicated process. If rubber products could be reinforced by dispersing short fibers in rubber, the manufacturing process for the composition would involve mixing rubber, additives, and reinforcing short fibers, and then extrusion molding or injection molding. Therefore, it is expected that the method will be significantly simplified compared to the method using a woven or knitted fabric made of long fibers described above.

For such purposes, for example, Japanese Patent Application Laid-Open No. 57-1065
No. 2 and JP-A-58-105539 disclose techniques for reinforcing diene rubber with microorganic short fibers. However, in order to produce a reinforcing effect in these methods, the glass transition temperature of the amorphous part must be below 50°C or above 120°C, and the melting point of the crystalline part must be 160°C.
If the above is υ, it is necessary to add ultra-fine special bottle-shaped fibers with an average short fiber length of a and an average short fiber diameter of IIL02 to 8 μm to S~50 μm.

And Microorganic II! Specific examples of polymers constituting fibers include polypropylene, poly-4-
Methyl-1-pentene, polyvinylidene fluoride, polyvinylidene chloride, poly p-tert-butylstyrene,
Poly-p-chlorostyrene, polydichlorostyrene, poly-α-methylstyrene, poly-p-phenylstyrene, tt: I) -.

-vinylbenzyl alcohol, poly-p-vinylbenzyl alcohol, polyvinylnaphthalene, polyoxymethylene, poly-bisphenol A carbonate, 1.4 poly-2,3 dimethylbutadiene, etc. are only exemplified.

(Problems to be Solved by the Invention) In view of the current situation as described above, the present inventors have investigated the diene rubber described in the above-mentioned JP-A-57-10652 and JP-A-58-
As a result of intensive studies on what organic short fibers other than the microorganic short fibers disclosed in Japanese Patent No. 103539 can be blended to create a reinforcing rubber composition with excellent tensile strength, diene thread rubber, carbon black, and acrylic fibers were combined. The present invention has been achieved by discovering that the desired objective can be achieved by combining and blending each in a specific range of proportions.

(Means for Solving the Problems) The gist of the present invention is that diene rubber 50-80
Masaru Shigege, carbon black 1~-50 weight range, ``In a composition consisting of acrylic fibers 5~4 ON weight ratio, high quality carbon black characterized by using acrylic fibers with an X-ray orientation degree of 95 coefficients or higher. Oriented acrylic fiber reinforced rubber composition.The acrylic fiber 1a of the present invention is not particularly limited as long as the degree of Xm orientation is 95 coefficients or more.Generally, vulcanization of rubber is carried out in the presence of an alkali such as an amine and at high temperature. However, at that time #Ji
If the degree of orientation of the acrylonitrile polymer molecules in m is low, vulcanization accelerators such as amines will diffuse into the fibers, causing decomposition of the acrylonitrile polymer. However, in acrylic fibers with an X-ray orientation of 95 scratches or more, the acrylonitrile polymer molecules are regularly arranged in the fiber axis direction, so vulcanization accelerators such as amines do not diffuse into the fibers, so acrylic fibers hardly deteriorate. do not have.

Further, the polymer composition constituting the acrylic fiber used preferably has acrylonitrile units of 90 or more by weight. In order to effectively reinforce the rubber, it is preferable to use strong back-filled acrylic fiber, preferably 101F/11 or more, more preferably 15F/11 or more, and more preferably 15F/11 or more.
/ e (It is preferable to use the above. Furthermore, regarding the form of the acrylic fiber, the short fiber length is (11 to 1
0+w, the fineness of the short fibers is preferably (Ll (L~10d1), the aspect ratio is preferably in the range of 10~1aao, and the length of b0 short fibers is less than (Ll-), the rubber composition cannot be effectively reinforced. If it exceeds 10 cm, the dispersibility of the acrylic fibers in the rubber composition decreases, which is not preferable.

Furthermore, if the fineness of the short fibers is less than 1 (Ll), the dispersibility of the acrylic fibers will decrease, and if it exceeds 101, the effective surface area of the acrylic fibers will be relatively reduced, making it impossible to obtain a sufficient reinforcing effect.

Furthermore, if the aspect ratio is less than 10, the tensile strength of the acrylic fiber-reinforced rubber composition will not be sufficiently high, while if it exceeds 1000, the dispersibility of the acrylic fibers in the rubber composition will decrease, which is not desirable.

If the content of acrylic fibers in the acrylic fiber reinforced rubber composition is less than 5% by weight, there is almost no reinforcing effect;
If it exceeds 1it4, the processability in the step of kneading the obtained acrylic fiber reinforced rubber composition is unfavorable.

The acrylic fiber used in the present invention can be obtained by dissolving an acrylonitrile polymer in a suitable solvent and then cutting filaments obtained by wet, wet-dry or dry spinning methods, or by reinforcing acrylic fibers. In order to increase the tensile strength of the rubber composition, it is desirable to use acrylic fibers with high tensile strength. Such acrylic fibers are made from, for example, a high molecular weight acrylonitrile polymer with a weight average molecular weight of 200,000 or more. It is produced under specific conditions. Polymerization methods for polymers suitable for such purposes are disclosed in JP-A-59-191704, JP-A-61-12704, JP-A-61-14206, and the like. The spinning technology was published in Japanese Patent Application Publication No. 6゜-13980.
No. 9, JP-A-60-139810, JP-A-61-11
No. 9708, JP-A-61-119710, JP-A-61
-167013, Japanese Patent Application Laid-open No. 62-57910, and other publications.

! The diene rubber used in the present invention includes natural rubber, synthetic polyisopropylene rubber, butyl rubber, halogenated butyl rubber, polybutadiene rubber, styrene-butadiene copolymer rubber, acrylonitrile-butadiene copolymer rubber, and ethylene-propylene rubber. Examples include diene copolymer rubber, but acrylonitrile-butadiene copolymer rubber is particularly desirable from the viewpoint of interfacial affinity with acrylic fibers.

The carbon black used in the present invention is not particularly limited, but for example, carbon black for rubber in a rubber furnace (Japan pIP).

FBIP, GBF), etc. The carbon black content in the acrylic fiber-reinforced rubber composition must be 21 to 50% carbon bluff by weight.

If the carbon black content is less than 1% by weight, the resulting molded product from the acrylic fiber-reinforced rubber composition will not only have low tensile strength but also extremely poor weather resistance.On the other hand, if it exceeds 50% by weight, the processability will be poor and unfavorable. !I don't like it.

The acrylic fiber-reinforced rubber composition of the present invention may further contain compounding agents such as a vulcanizing agent, a promoter, a filler such as silica, and a softening agent within the range of usual compounding amounts.

The acrylic fiber-reinforced rubber composition of the present invention is prepared by adding the aforementioned acrylic fibers, diene rubber, and carbon black, as well as various additives as necessary, subjecting them to heat treatment, and mixing them in a kneader without vulcanization. Obtained by extrusion molding or injection molding.

(Example) The present invention will be described in detail below with reference to Examples.

The degree of xlI orientation was measured as follows.

Using the X-ray diffraction method, a diffraction profile in the azimuthal direction was obtained for the reflection near the scattering angle 2θ = 17° in the equatorial direction of the acrylic fiber, and a baseline was drawn on the graph to calculate the peak half-value width TIV4C degrees) using the following formula. I asked for it.

80 Examples 1-3. Comparative Examples 1 to 3 Rubber, short fibers, carbon black, and additives were mixed at the compounding ratio shown in Table 1, kneaded in a Banbury mixer at 160°C for 20 minutes, and then extruded at 160°C to form a 3cm diameter
It was cut into strands of 8 lengths. Add this further to J
Technique 8 In order to sample a dumbbell test piece according to the test method described in K6501, it was extruded into a sheet at 160°C. The short H & miscellaneous property and shape used in the test and the tensile test of the obtained rubber sheet were determined by J Engineering 13 16501.
I followed it.

table The results are shown in Table 2.

The acrylic fibers in the table were prepared using polyacrylonitrile obtained by the method described in JP-A No. 61-14206, and according to the spinning method described in JP-A-61-167013. However, acrylic fibers with four levels of X-ray orientation were tested by changing the polymer molecular weight and stretching ratio.

Table 2 Example 4. Comparative Example 4 The dumbbell test piece used in Example 1 and Comparative Example 3 was
Placed in the dryer at °C. Tensile strength retention rate at this time is 50%
As a result of comparing the time at I understand.

Example 5. Comparative Example 5 The dumbbell test pieces used in Example 1 and Comparative Example 3 were
It was subjected to an oil resistance test at 40° C. for 22 hours according to K2SO3. As a result, the tensile strength retention rate of Example 1 was 76
4. The swelling oil was 105%, while the tensile strength retention of Comparative Example 3 was 59% and the swelling oil was 1234, indicating that the acrylic fiber-reinforced rubber composition of the present invention also has excellent oil resistance. .

(Effects of the Invention) As described above, the acrylic fiber-reinforced rubber composition according to the present invention can be easily produced through a simple process, and the manufacturing process is significantly simpler than that of conventional long fiber-reinforced rubber compositions. The acrylic fiber-reinforced rubber composition has high tensile strength, heat resistance, and oil resistance, making it suitable as a raw material for various rubber products such as hoses, packing, vibration-proofing materials, and sealing materials. Therefore, the industrial benefits are truly large.

Claims (1)

[Claims] Diene rubber 50~80% by weight, carbon black 1~
A highly oriented acrylic fiber-reinforced rubber composition characterized in that the composition comprises 50% by weight of acrylic fibers and 5 to 40% by weight of acrylic fibers, using acrylic fibers having an X-ray orientation degree of 95% or more.