JPH07115358B2 - Molding method for flame-retardant rubber composition and mold release agent for molding the same - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for molding a flame-retardant rubber composition containing a chlorinated paraffin, and more particularly to a mold release agent used for the molding.

[Prior art]

Conventionally, among flame retardants blended in flame retardant rubber compositions, chlorinated paraffins are widely used alone or together with other flame retardants due to their excellent flame-retarding effect and low cost.

However, this chlorinated paraffin-containing flame-retardant rubber composition generates hydrogen chloride (HCl) due to the heat history during vulcanization, especially vulcanization at high temperature or for a long time, and the hydrogen chloride corrodes the mold. However, there is a problem in that the surface of the obtained rubber molded product is damaged and the appearance is poor. Moreover, this problem could not be solved even when silicone, which is often used as a release agent, is used.

[Object of the Invention] An object of the present invention is to provide a mold molding method and a mold release agent thereof which can solve the above problems in mold molding of a flame-retardant rubber composition containing chlorinated paraffin. Is.

[Structure of Invention]

The present invention provides a method of molding a chlorinated paraffin-containing flame-retardant rubber composition into a mold, by using a basic agent as a release agent on the surface of an unvulcanized molded article made of the flame-retardant rubber composition or the inner surface of the mold. In this method, a mold release agent containing at least one metal oxide and / or a basic metal hydroxide as an essential component is applied, and a mold is formed.

As the basic metal oxide which is an essential component of the release agent of the present invention, zinc oxide (ZnO) and magnesium oxide (MgO) can be exemplified as typical examples, and the basic metal hydroxide is water. An example is calcium oxide [Ca (OH) ₂ ]. Among these, zinc oxide (ZnO) is most preferable in consideration of the fact that the surface of the rubber composition is not cured and the physical properties of the rubber are not changed.

These basic metal oxides and basic metal hydroxides can be used alone or in combination, but they are used by mixing with powdered starch as a bulking / diluting agent or a colorant or carbon black as a masking agent. You can also

When mixed and used with such powdered starch or carbon black, the basic metal oxide and the basic metal hydroxide are preferably blended in the range of about 10 to 100% by weight based on the total weight of the mixture. However, outside this range, it is not possible to sufficiently obtain the above-described effects of the present invention.

Further, the amount of chlorinated paraffin blended in the flame-retardant rubber composition used in the present invention is at least 3 based on the flame-retardant rubber composition from the viewpoint of imparting flame retardancy to the rubber composition.
The weight ratio is preferably in the range of 5 to 20% by weight. In addition to chlorinated paraffin, similar curing can be expected for other organic halogen compounds that undergo thermal decomposition at the vulcanization temperature.

The rubber component constituting the flame-retardant rubber composition includes natural rubber (NR), butyl rubber (IIR), styrene-
Butadiene rubber (SBR), acrylonitrile-butadiene rubber (NBR), chloroprene rubber (CR), butadiene rubber (BR), etc., preferably NR, SBR, BR.

For these rubbers, in combination with other known flame retardants other than the chlorinated paraffin as a flame retardant, or if necessary, other reinforcing agents, fillers, plasticizers, antioxidants, carbon black, A pigment or the like can be appropriately mixed.

The release agent having at least one kind of basic metal oxide and / or basic metal hydroxide used in the present invention as an essential component is usually preferably powdered,
The release agent may be used in the form of an emulsion in which it is dispersed in water using a liquid surfactant.

Such a flame-retardant rubber composition can be molded by a mold, after applying the release agent of the present invention to the surface of the unvulcanized molded product of the flame-retardant rubber composition, and then filling the mold. Then, a method of vulcanizing by heating under a desired pressure or applying the above mold release agent in the form of an emulsion to the inner surface of the mold, and then filling the above flame-retardant rubber composition into this mold and vulcanizing There is a way.

Hereinafter, the effects of the present invention will be described more specifically with reference to Examples.

Examples 1 to 3 and Comparative Examples 1 to 2 Two kinds having the composition shown in Table 1 (all values are parts by weight) prepared by mixing with an internal mixer and then adding an vulcanizing agent with an open roll. Mold molding was performed using the flame-retardant rubber composition of.

That is, 150 x 150 x 5 m consisting of the above two rubber compositions
After evenly applying the release agent shown in Table 2 to the extent that the surface of the sheet of / m is hidden, vulcanization is performed at 148 ° C for 240 minutes using a buffed and polished iron plate and mold. It was

The contact surface of the obtained rubber molded product with the rubber molded product of the iron plate was visually observed to examine the contamination state.

Also, the surface hardness of the vulcanized rubber molded product was measured using a Wallace microhardness tester (IRHD), and the flame retardancy of the vulcanized rubber molded product was also determined by JIS-K-6324 "Conveyor Belt Difficulty". "Flammability performance standard". The results are shown in Table 2.

From Table 2, in each of the cases where the release agent of Comparative Examples 1 to 3 was not used or the silicone release agent was used,
The pollution is severe. It can be seen that simply blending the MgO of the present invention into the rubber composition does not prevent contamination, but conversely, the flame retardancy is significantly reduced. On the other hand, Example 1
It can be seen that Nos. 3 to 3 exhibit excellent pollution prevention with almost no reduction in flame retardancy. Among them, those using ZnO as a release agent are excellent in terms of surface hardness.

Examples 4, 5 and Comparative Examples 4, 5 Using the rubber composition A shown in Table 1, an unvulcanized molded article made of this rubber composition was used as a mold release agent, and zinc oxide (ZnO) alone was used. (ZnO) 20% by weight and starch (Nikka Co., Ltd.)
Manufactured in the same manner as in Examples 1 to 3 (Comparative Examples 1 to 3) by coating a mixture with 80% by weight of Nikkarico "AS-100" and starch alone, and in each case. The relationship between the vulcanization time and the contamination of the iron plate was investigated, and the same test was performed without the release agent.

In the figure, a is zinc oxide (ZnO) alone, and b is zinc oxide (ZnO).
nO) and starch, c is starch alone, and d is no release agent. Further, in the figure, the contamination degrees 0 to 5 are values determined according to Table 3 showing the criteria for determining the degree of contamination of the iron plate (mold).

From the figure, the effect of starch alone is not recognized, but when zinc oxide (ZnO), which is one of the mold release agents of the present invention, is mixed with this starch, an effect close to that of zinc oxide alone is obtained, and uneven coating is also obtained. Due to the small amount of unreacted zinc oxide particles remaining, the appearance of the rubber product was excellent.

[Effects of the Invention] As described above, the molding method and the mold releasing agent of the present invention are used for the mold corrosion of the chlorinated paraffin-containing flame-retardant rubber composition, and the mold corrosion and the resulting poor appearance of the rubber molded product. This problem is solved without impairing the flame retardancy of the flame-retardant rubber composition, and its industrial significance is extremely great.

[Brief description of drawings]

The figure is a graph showing the relationship between the type of release agent and the degree of contamination of the die (iron plate) in the die molding of the flame-retardant rubber composition.

Claims (2)

[Claims] 1. When a flame-retardant rubber composition containing chlorinated paraffin is molded by a mold, a basic metal oxide is formed on the surface of an unvulcanized molded product made of the flame-retardant rubber composition or the inner surface of the mold. And / or at least one basic metal hydroxide
A mold molding method for a flame-retardant rubber composition, which comprises applying a release agent containing a seed as an essential component. 2. A mold release agent for a mold molding of a chlorinated paraffin-containing flame-retardant rubber composition, which contains at least one basic metal oxide and / or basic metal hydroxide as an essential component.