JPH0566254B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for manufacturing a porous rubber elastic body.

(Prior Art) For example, the following method is known as a method for manufacturing a porous rubber elastic body.

(b) Mix soluble substances such as salt and starch with rubber,
A method of dissolving and extracting this soluble substance after vulcanization molding (JP-A-49-53256, JP-A-49-53257)
(see publication).

(b) A method of mixing and sintering rubber powder, PVC (polyvinyl chloride) powder, and plasticizer (Unexamined Japanese Patent Publication No. 1983-
(See Publication No. 64537).

(Problems to be Solved by the Invention) The method of conventional technology (a) requires a large number of steps to obtain a porous body, such as mixing rubber and a soluble substance, vulcanization, extraction, and drying. Furthermore, since the wastewater generated by extraction contains soluble substances, it becomes difficult to treat the wastewater.

In the method of conventional technology (b), the porous body obtained is
Since the rubber powders are bonded together via the PVC powder, depending on the number of contact points between the rubber powder and the PVC powder, or around each rubber powder.
Depending on whether the PVC powder is properly dispersed or not,
This depends on the strength of this porous body. Therefore, in order to obtain a porous body with high strength and homogeneity, it is necessary to uniformly disperse rubber powder and PVC powder, but in reality, these powders may differ in particle size and other properties. It is difficult to obtain a uniformly dispersed state.

(Means and effects for solving the problems) The present invention, as a means to solve the above-mentioned conventional problems, contains at least one of foamed vulcanized rubber powder or non-foamed vulcanized rubber powder and heat-fusible particles. A porous rubber elastic body was obtained by mixing the powder with latex and drying it to form a powder with a two-layer structure having a heat-melting film, and by sintering this powder. A manufacturing method is provided.

The above non-foamed vulcanized rubber powder is prepared by adding a vulcanizing agent, a vulcanization accelerator, and a base rubber such as natural rubber, isoprene rubber, styrene-butadiene rubber, nitrile rubber, chloroprene rubber, butyl rubber, ethylene propylene rubber, or urethane rubber. Various compounds such as sulfur aids, fillers, reinforcing agents, softeners, and organic or inorganic pigments are mixed as appropriate depending on the use of the porous rubber elastic body to be manufactured, and the mixed and vulcanized mixture is finely pulverized. Alternatively, it can be obtained by powdering rubber emulsion polymerized at high temperature by spray drying. Further, the foamed vulcanized rubber powder can be obtained by pulverizing porous rubber obtained by mechanically foaming and gelling using a foaming stabilizer, after vulcanization.

In addition, the above-mentioned latexes include latexes prepared by dispersing thermoplastic resins such as PVC, vinyl acetate, vinylpyridine resin, carboxy-modified acrylic resin, glycidyl-modified acrylic resin, amine-modified acrylic resin, saponified vinyl acetate in water, and carboxy-modified acrylonitrile.・Butadiene latex etc. can be used. The heat-melting particles of the thermoplastic or thermosetting resin or rubber in this latex preferably have a particle diameter of 5 μm or less in order to form a uniform film.

Furthermore, in the above manufacturing method, when a plasticizer is used, the plasticizer is added after the drying step and sintering is performed. Examples of the plasticizer include phthalate esters, phosphate esters, epoxidized vegetable oils, polyester plasticizers, adipic acid polyesters, and liquid
NBR, chlorinated paraffins, etc. can be used.

According to the above manufacturing method, the heat-fusible particles in the latex form a heat-fusible film on the surface of the vulcanized rubber powder by drying, and the vulcanized rubber powders are welded together to form a heat-fusible film on the surface of the vulcanized rubber powder. This will result in a combination. In this case, the entire surface of the vulcanized rubber powder becomes easily wetted by mixing with the latex, so a heat-melting film is applied over the entire surface of each vulcanized rubber powder to a thickness of, for example, 1 to 10 μm. can be reliably formed. Since each vulcanized rubber powder has a heat-fusible film, a porous body having uniform sintering strength can be obtained without problems such as poor dispersion.

In addition, vulcanized rubber powder maintains high elasticity even when heated and has little thermal shrinkage, so it has good dimensional stability when forming (sintering) porous bodies, and therefore can be used for low-density porous bodies. By simply changing the amount of powder, it can be molded to have high strength without causing sink marks.

(Effect of the invention) Therefore, according to the present invention, since a heat-melting film is formed on each individual vulcanized rubber powder, the above-mentioned heat-melting film can be formed with a relatively small number of steps and without causing problems such as poor dispersion. A porous rubber elastic body having uniform strength can be obtained by welding the meltable films together, and also has good dimensional stability during molding, improving quality and productivity.

(Example) Examples of the present invention will be described below.

Example 1 In this example, the average particle size of the vulcanized rubber powder was 100μ as shown in the micrograph (80x magnification) in Figure 1.
NBR (acrylonitrile butadiene rubber: Kleinak 1411 manufactured by Polycer) was used, and PVC latex with a particle size of 0.1 to 0.3μ (G150X-15 manufactured by Nippon Zeon Co., Ltd.) was used as the latex, and the following steps were performed in order to make it porous. A rubber elastic body was obtained.

Mixing process Add 80 parts by weight of the above vulcanized rubber powder while stirring.
By adding 20 parts by weight (solid content) of PVC latex little by little, this vulcanized rubber powder and
Mix with PVC latex.

Drying process: Heat the mixture obtained in the mixing process in an oven at 60°C.
Leave it for a while to dry (wick away the moisture from the latex).

Plasticizer addition step While stirring the material obtained in the drying step, 20 parts by weight of DOA (dioctyl adipate) as a plasticizer was added little by little at an ambient temperature of 80°C.
Stirring is continued until the DOA is completely absorbed to obtain a powder with a heat-meltable film. The appearance of this powder is as shown in the micrograph (80x magnification) in Figure 2, with minute irregularities on the surface, and the cross section of this powder is as shown in the micrograph (6000x magnification) in Figure 3. It has a two-layer structure in which a heat-melting film (white part around it) is formed on the surface of vulcanized rubber powder (black part in the center), and heat-melting particles (PVC particles) are interposed inside by impregnation. It has become a thing. Also, the fourth
As shown in the figure, a micrograph (6000x) of the Cl-K image of the cross section of the above powder, Cl (chlorine) is sensitive and appears in a donut shape, and the white part in Figure 3 is
It can be seen that it is a heat-melting film made of PVC.

Sintering process: Fill a mold with the above plasticizer-added powder at a volume ratio of 300%, and heat it at 150℃ using a press for pressure and heating.
Hold for a minute to obtain a porous rubber elastic body.

This porous rubber elastic body had elasticity (strength) that would not break even when bent at 180 degrees, and its hardness was 50 on the Asker hardness tester type C manufactured by Kobunshi Keiki Co., Ltd. Furthermore, when this porous rubber elastic body was impregnated with ink and used as an ink roll, clear impressions were obtained even after 200,000 prints or more.

Example 2 This example uses foamed vulcanized rubber powder. This vulcanized rubber powder is obtained by foaming a mixture according to the following formulation at a foaming ratio of 300% using an oak mixer, gelling this with soda silica, and pulverizing the porous rubber after vulcanization. It is.

Compounding ingredients Parts by weight Rubber latex 115 Vulcanizing agent 5.5 Foam stabilizer 1.8 Anti-aging agent (SP-10) 0.5 ZnO 0.5 Total 123.3 The rubber latex consists of Nipole Latex531 and Nipole Latex2507 manufactured by Nippon Zeon Co., Ltd.
The vulcanizing agent consists of FDS-100 manufactured by Nippon Zeon Co., Ltd. and sulfur. The foaming stabilizer is Trimenbase FR-14 manufactured by Shiraishi Calcium Co., Ltd.

When producing a porous rubber elastic body, carboxy-modified rubber is added to the foamed vulcanized rubber powder while stirring.
NBR latex (JSR-0911 manufactured by Japan Synthetic Rubber Co., Ltd.)
After adding and mixing 10 parts by weight (solid content) little by little, the powder obtained by drying was filled into a mold at a volume ratio of 300% and held under pressure at 160°C for 8 minutes. Make sintering.

The obtained porous rubber elastic body did not break even when bent at 180 degrees, and its hardness was measured as Asker hardness tester type C.
It was 43. Further, when this porous rubber elastic body was used as an ink roll, good results similar to those in Example 1 were obtained.

In addition, each of the above examples uses only either non-foamed vulcanized rubber powder or foamed vulcanized rubber powder, but this non-foamed vulcanized rubber powder and foamed vulcanized rubber powder You may use a mixture of both.

In addition, in the above example, the porous rubber elastic body was applied to the ink roll, but it can also be used for printing materials, rolls for office machines, etc.
Of course, it can be used for various products such as rolls for electronic devices and various pine materials.

[Brief explanation of the drawing]

Figure 1 is a micrograph showing the particle structure of the vulcanized rubber powder, Figure 2 is a microscope picture showing the particle structure of the powder with a heat-melting film, and Figure 3 is a microscope picture showing the cross-sectional structure of the powder. , FIG. 4 is a micrograph showing the distribution of chlorine in the powder.

Claims (1)

[Scope of Claims] 1. A method of mixing at least one of foamed vulcanized rubber powder or non-foamed vulcanized rubber powder with latex containing heat-melting particles and then drying the mixture to form a heat-melting film. A method for producing a porous rubber elastic body, which comprises forming a powder having a two-layer structure and sintering the powder. 2. The method for producing a porous rubber elastic body according to claim 1, wherein the heat-melting particles in the latex have a particle size of 5 μm or less.