JPS58114932A - Method of cleaning mold for molding rubber article and cleaning rubber composition used therefor - Google Patents

Abstract

PURPOSE:To remove completely contaminators adhered to the inner surfaces of molds without requiring any particular apparatus and operation, by mixing small amounts of specific cleaning constituents together with vulcanizing agent, etc. into a rubber main material, charging this rubber composition into the molds, and vulcanizing the rubber composition. CONSTITUTION:A cleaning rubber composition made up of monoethanolamine, small amounts of a fatty acid soap and an ammonium generator as a cleaning constituent is mixed with a rubber main material consisting of natural rubber, a synthetic rubber or its blend together with usual rubber aditives such as a vulcanizer, a vulcanization accelerator, vulcanization additives, etc., the rubber composition is charged into the molds, and is heated under pressure to be vulcanized, and the vulcanized rubber item is removed from the molds. Without requiring any specific apparatus and operation for cleaning the molds but only by carrying out an operation similar to the usual vulcanizing operation for rubber items, contaminators adhered to the inner surfaces of the molds can be completely removed.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for cleaning dirt on the surface of a mold for molding rubber products, and a cleaning rubber composition suitably used for that purpose.

As is well known, in the production of rubber molded products, molds (
A rubber compound is placed in the mold, or an unvulcanized rubber molded product preformed using the rubber compound into a shape similar to the shape of the finished product is placed in a mold, and the product is pressurized and vulcanized using a press machine. The final product is completed by vulcanizing the rubber compound.

The mold has a hollow space formed therein which has the dimensions, shape, and pattern of the desired finished product and a shape that matches the anvil, and its inner surface is finished with a mirror finish. This mold is generally made of steel or aluminum.

or an alloy thereof, and in some cases the inner surface is metallized. In addition, the mold is generally divided into two parts, such as an upper mold and a lower mold, each of which is removably fixed on the heating plate of the press device, and is equipped with hydraulic or hydraulic pressure. When the mold is opened and closed up and down, the mold is also opened and closed accordingly.

With the mold open as above, the preformed unvulcanized rubber compound is charged into the internal cavity, the upper and lower molds are closed using a press, and the mold is heated under pressure. Complete the sulfur.

The above is called the compression vulcanization method, but in addition to this,
One of the methods used for molding rubber molded products is the so-called injection vulcanization method, in which an unvulcanized rubber compound is injected into a mold at high temperature and pressure, and vulcanization is completed in a short time.

Regardless of which vulcanization method is used, each time the mold is repeatedly used for vulcanization, tar-like decomposition products generated from the rubber compound are baked onto the inner surface of the mold. This deposit forms undesirable spots and depressions on the surface of the product that is subsequently vulcanized and molded using the mold, significantly impairing its commercial value.

For this reason, up until now, the above molds have been prepared by immersing them in an alkaline aqueous solution as necessary, or by using the so-called sandblasting method, in which fine sand particles or gaff balls are sprayed with compressed air on the inner surface of the mold. It has been treated to be more clean.

Regardless of which method is adopted, the mold cannot be used while these cleaning operations are being carried out, and the necessary special equipment must be kept at hand, which requires a considerable amount of labor and effort. time is spent.

The present invention solves the above-mentioned problems and cleans the inner surface of the mold by simply performing the same operation as the vulcanization operation of ordinary rubber molded products without requiring any special equipment or operation for cleaning the mold. It is an object of the present invention to provide a mold cleaning means that completely removes adhered contaminants, and in particular to provide a cleaning rubber composition suitable for the purpose.

In order to achieve the above objectives, the present invention uses a rubber-based material. On the other hand, a cleaning rubber composition containing a small amount of cleaning active ingredient 1 and ordinary rubber compounding agents such as a vulcanizing agent is charged into the mold, and the inner surface of the gold layer is vulcanized by vulcanizing the mineralized product. The main point is to remove dirt from the surface.

The rubber main material of the cleaning rubber composition used to embody the method of the present invention may be natural rubber, polyisoprene rubber, styrene-butadiene copolymer rubber, polybutadiene rubber, nitrile rubber, or other known synthetic rubber. Can be used with any rubber. Blends of these rubbers can also be used. However, in the present invention, the composition containing the above rubber is
Since it is not used to manufacture rubber products and is simply used for cleaning molds, from an economical point of view, cheaply available ductile rubber materials such as styrene-butadiene copolymer rubber are sufficient. It is.

According to the present invention, a small amount of 1 is added to the above rubber base material, for example, monoethanolamine in a weight ratio of about 30±6 parts and stearin in a weight ratio of about 10±2 parts per 100 parts of the rubber base material. A cleaning active consisting of a fatty acid soap such as acid glycerol and an ammonia generating agent such as urea is mixed. These cleaning active ingredients are monoethanol-tvy
A paste is made by adding one fatty acid and an ammonia generator to the paste, and mixed with the main rubber material using a mixed wire roll or kneader.

For rubber main materials, in addition to the above-mentioned cleaning agents, vulcanizing agents represented by sulfur, dibenzothiazyl disulfide and Schiff-12↓a benzothiazyl sulfenamide natural rubber, Vulcanization components such as vulcanization accelerators and vulcanization aids such as zinc oxide and stearic acid, which are commonly used in knife curing of synthetic rubbers, are blended. Further, if necessary, rubber compounding agents such as reinforcing fillers, agents, and plasticizers that are usually compounded in the production of rubber molded products can also be mixed.・When cleaning a mold using the above cleaning rubber composition, form the composition into a sheet with an appropriate thickness and charge it in an amount sufficient to fill the cavity of the mold. Alternatively, the cleaning rubber composition, which has been preliminarily formed into a shape and dimensions that approximately match the shape and dimensions of the finished product to be manufactured from the mold to be cleaned, is charged into the mold. The rubber composition is then vulcanized under conditions sufficient to complete vulcanization.

However, in the case of Venus, which has a large internal cavity such as a pneumatic tire or other large rubber molded article, a large amount of cleaning rubber composition is consumed for each cleaning operation, so it is not eligible. Rubber products that have already been vulcanized and molded using a mold to be cleaned, and whose lifespan has been exhausted through use.

Alternatively, a defective product that has occurred due to some reason in the manufacturing process is reused as the substrate 2, and a sheet rubber of about 2 to 6 HSt made from the cleaning rubber composition of the present invention is applied to the surface 1 of the substrate 2 with an adhesive or an appropriate material. From the viewpoint of resource saving, it is preferable to attach the material using a suitable solvent and then place it in the mold.

The preferred vulcanization conditions for the cleaning rubber composition are about 140 to 1
60°C for about 20 minutes. ``When the predetermined vulcanization operation is completed, the press device is opened and the vulcanized product is taken out from the mold. As a result, due to the chemical reaction between the cleaning active ingredient and the contaminant adhering to the inner surface of the mold, the latter is transferred to the surface of the former, and the inner surface of the mold is cleaned. Once used, the cleaning rubber composition is peeled off from the substrate or removed together with the substrate.
This will be disposed of. - As explained above, according to the method of the present invention, except for using a special cleaning rubber composition, the same operations as those for vulcanization of ordinary rubber molded products are performed, so it is possible to perform the vulcanization process in the same manner as in the conventional method. There is no need for cleaning equipment, and the trouble of removing the mold from the vulcanizer for cleaning work is omitted, and the mold cannot be used for several hours during the cleaning work. is resolved.

Examples of the present invention will be described below.

Example 1 First, a cleaning rubber composition was prepared by adding the following formulation (a rubber base of Al) and the cleaning active ingredient of formulation (B).

Blend [A] Natural rubber 70 parts Styrene-butadiene comb 30 parts Sulfur
5 parts vulcanization accelerator (di-penzothiazid/L/1 part disulfide) Stearic acid 1 part zinc oxide
5 parts hydrogen oxide (white carbon) 40 parts magnesium carbonate
20 parts light calcium carbonate 60
Part diethylene glyco-1L/i, part combination ■) Mono-ethanolamine 30 parts Glycerol stearate 10 parts
10 parts of the above unvulcanized rubber was formed into a sheet with a thickness of about 21 cm using a calendar roll,
This sheet is the surface of a scrap passenger car tire (substrate).

After puffing the tread part and the core part of the mold to be cleaned, which were particularly heavily soiled, a solvent was applied and the mold was pasted.

Next, the substrate prepared as above is loaded into the mold to be cleaned,
The press equipment was closed and vulcanization was carried out at 150° C. for 20 minutes.

After vulcanization was completed, the press equipment was opened again and the substrate was taken out, and the contaminants were completely removed from the inner surface of the upper mold.
Since this had been removed, it was subsequently used for vulcanization of ordinary passenger car tires.

Example 2 A sheet of unvulcanized rubber was prepared by mixing the detergent component of formulation fB) with the rubber matrix of formulation (5) below.

The sheet was placed in the cavity of a shoe sole mold, and then a predetermined vulcanization operation was performed. As a result, the inner surface of the upper mold was completely cleaned.

Compound μ) Styrene fist butadiene rubber 100 parts sulfur
Yellow 2 parts dibenzothiazyl 2 parts disulfide stearic acid 1 part zinc oxide 5 parts white carbon 50 parts titanium oxide
10 parts light calcium carbonate
50 parts anti-aging agent
1 part diethylene glycol 1 part monoethanolamine 25 parts glycerol stearate 12 parts urea
Part 10 As explained above, the present invention provides a means for cleaning molds for molding rubber products that can exhibit excellent mold cleaning effects without requiring special labor, time, and equipment. It is extremely significant industrially.

Claims (3)

[Claims] (1) For rubber main materials made of natural rubber, synthetic rubber, or blends thereof, together with ordinary rubber compounding agents such as vulcanizing agents, vulcanization accelerators, and vulcanization aids. A method for cleaning a mold for molding a rubber product, which comprises removing a rubber molded product containing monoethanolamine as a cleaning component, a small amount of a fatty acid, and an ammonia generator from the mold. (2) Claim No. 1, in which a layer of a cleaning rubber composition is formed on the surface of waste rubber products that have already been vulcanized with the gold to be cleaned 11, and then this aggregate is placed indoors. Cleaning method described in section. (3) A rubber main material made of natural rubber, synthetic rubber, or a blend thereof is mixed with monoethanolamine, a small amount of fatty soap, and an ammonia generator as a vulcanizing agent and vulcanization-promoting cleaning component. A rubber composition for cleaning molds for molding rubber products.