JPH0753234A - Solid lubricating release agent - Google Patents

Abstract

PURPOSE:To be kept without spoiling the appearance quality even when the coated film is peeled off, by incorporating natural rubber, carbon black and sulfur in a specified ratio. CONSTITUTION:The compound is obtained by compounding 35-60wt.% natural rubber, 15-50wt.% carbon black having <=1mum particle size, 15-50wt.% sulfur and, if necessary, a vulcanization accelerator such as tetramethylthiuram disulfide, a vulcanization accelerator auxiliary such as zinc oxide, and a filler such as phenol resin, or the like. Next the compound is kneaded and then is pressed at 140-170 deg.C for 5-60min to cure and mold and produce the solid lubricating release agent consisting of the vulcanized rubber. If necessary, the release agent is applied to a glass press-molding die to mold glass, etc.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solid lubricant release agent used in press molding of glass, and more particularly to a solid lubricant release agent used in press molding of CRT panel glass. is there.

[0002]

2. Description of the Related Art When press-molding a panel glass for a cathode ray tube, as shown in FIG. 1, a glass gob G is fed into a bottom mold 1 and a shell ring 2 which are female (FIG. 1-a), and a male mold is used. After pressing the glass gob G with a certain plunger 3 and holding and cooling for a certain period of time (FIG. 1-b),
The plunger 3 is pulled up to obtain the panel glass P (FIG. 1-c).

In the above process, when the plunger 3 is raised, the side surface portion 3a of the plunger 3 having a small slope is rubbed against the glass, and the inner side surface of the panel glass or the side surface portion 3a of the plunger is easily scratched. It is known. Therefore, a lubricant release agent is usually applied to the entire circumference of the plunger side surface portion 3a to prevent the scratches from being caused by the friction between the plunger and the glass.

Conventionally, a liquid lubricant release agent in which fine graphite particles are dispersed in mineral oil has been used as a lubricant release agent used for this purpose. However, since the coating film formed by this lubricant release agent is thin, it is consumed in a short time (about 15 minutes). Therefore, there is a disadvantage that the lubricant release agent has to be applied frequently.

Therefore, it has been studied to use a solid lubricant release agent capable of forming a thick coating film and maintaining the release effect for a long time.

[0006]

As a solid lubricant release agent, one made of a vulcanized rubber containing natural rubber, graphite and sulfur has been conventionally known. However, although this solid lubricant release agent can maintain the release effect over a longer period of time than liquid ones, if the coating film peels off during use, graphite particles will adhere to the inner surface of the panel glass and It has a problem of degrading quality.

The present invention solves the above-mentioned drawbacks of the conventional solid lubricant release agents, and provides a solid lubricant release agent which hardly deteriorates the appearance quality even if the coating film peels off. With the goal.

[0008]

As a result of various experiments, the present inventors have found that the above object can be achieved by using carbon black in place of graphite, and propose the present invention. .

That is, the solid lubricant release agent of the present invention comprises, by weight percentage, 35 to 60% of natural rubber and 15 to 60% of carbon black.
It is characterized by being made of a vulcanized rubber containing 50% and 15 to 50% of sulfur.

[0010]

The carbon black contained in the solid lubricant release agent of the present invention is ashed at 500 to 600 ° C. and becomes CO ₂ and dissipates. Therefore, even if the coating film peels off from the mold and adheres to a glass molded product such as panel glass, it is ashed by the heat of the glass, so that foreign substances due to the coating film are hard to remain.
Note that it is preferable to use carbon black having a particle size of 1 μm or less. That is, the smaller the particle size of carbon black, the easier it is to ash, and even if it remains on the surface of the glass molded product without being ashed, if the particle size is small, it will hardly affect the appearance quality. is there.

In the solid lubricant release agent of the present invention, the ratio of each component is limited as described above for the following reasons.
If the natural rubber content is less than 35%, it becomes difficult to form a vulcanized rubber, and if it exceeds 60%, the components having a lubricating release effect such as carbon black are relatively small, which is not preferable. If the amount of carbon black is less than 15%, there is no lubricating release effect, and if it is more than 50%, it becomes difficult to apply it to the plunger. This is because if the amount of sulfur is less than 15%, the adhesive force of the coating film becomes weak and the film easily peels from the mold, and if it exceeds 50%, the melting state becomes unstable and it is difficult to form a uniform coating film.

In addition to the above, the solid lubricant release agent of the present invention includes vulcanization accelerators such as tetramethylthylium disulfite, dibenzothiotyl disulfite, zinc white, stearic acid and trimethylolpropane trimeta. A vulcanization accelerating aid such as acrylate or a filler such as high styrene resin or phenol resin may be contained. The proportion of free sulfur contained in the vulcanized rubber as the release agent is preferably 10 to 30% by weight. This is because when the free sulfur is present in the above range, it becomes possible to form a coating film having higher adhesion.

In the solid lubricant release agent of the present invention, the respective raw materials are blended in the above proportions, sufficiently kneaded, and then pressurized at 140 to 170 ° C. for 5 to 60 minutes for vulcanization. It can be manufactured by molding.

When a coating film is formed on the surface of a mold such as a plunger using the solid lubricant release agent of the present invention, 400
It may be rubbed directly on the surface of the mold heated to ˜450 ° C. This lubricant release agent melts due to its heat when it comes into contact with the mold, covers the surface of the mold, and forms a coating film by volatilizing a substance such as high styrene resin which is easily volatilized.

[0015]

EXAMPLES The solid lubricant release agent of the present invention will be described below based on examples.

First, by weight%, natural rubber 43.5%, carbon black 19%, sulfur 30%, high styrene resin 5
%, Zinc white 2%, and tetramethylthylium disulfide 0.5%, and kneaded for 40 minutes. The carbon black used had a particle size of 0.02 μm. Then, it was vulcanized by pressing at 170 ° C. for 7 minutes.

For comparison, a conventionally used solid lubricant release agent was prepared. This is the above formulation with carbon black replaced by the same amount of graphite.

Next, panel glass for cathode ray tubes was press-molded using these mold release agents, and the appearance defect occurrence rate of glass due to peeling of the coating film was examined.

As shown in FIGS. 1a to 1c, first, the glass gob G at about 1000 ° C. is supplied into the bottom mold 1 and the shell ring 2, and the glass gob G is formed by the plunger 3 having the coating film formed on the side surface portion 3a. After pressing and holding and cooling for a certain period of time, the plunger was pulled up to mold the panel glass P for CRT. In this way, each mold release agent was used for a test for one week, and the appearance defect occurrence rate of the panel glass due to the adhesion of the peeled coating film was examined. In addition, the coating film is formed every one hour by the plunger 3 (surface temperature 430
(° C) by directly rubbing the release agent on the side surface portion 3a.

As a result of the test use, when the conventional solid lubricant release agent is used, the defect occurrence rate due to the adhesion of the coating film is 0.5.
%Met. On the other hand, in the case of using the product of the present invention, the defective occurrence rate due to the adhesion of the coating film was 0.05%, which was found to be greatly improved.

For the evaluation of the appearance defect, after the molded panel glass was gradually cooled, the inner surface was visually observed, and foreign matter such as carbon black or graphite was recognized as a defect.

[0022]

EFFECTS OF THE INVENTION The solid lubricant release agent of the present invention is ashed at a temperature of 500 to 600 ° C. and diffuses into the atmosphere even if the coating film is peeled off from the mold. There is almost no loss of appearance quality. Therefore, the molding yield can be improved, and it is suitable as a lubricant release agent for glass molding dies, particularly for molds for CRT panel glass.

[Brief description of drawings]

FIG. 1 is an explanatory view showing a press molding process of a panel glass for a cathode ray tube.

[Explanation of symbols]

 1 Bottom mold 2 Shell ring 3 Plunger G Glass gob P CRT panel glass

Claims (2)

[Claims] 1. A solid lubricant release agent comprising a vulcanized rubber containing 35 to 60% by weight of natural rubber, 15 to 50% of carbon black, and 15 to 50% of sulfur in weight percentage. 2. The solid lubricant release agent according to claim 1, which is applied to a glass press molding die.