JPH0791406B2 - Method for producing expandable styrene-modified polyolefin resin particles - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for producing expandable styrene-modified polyolefin resin particles.

(B) Problems to be Solved by Conventional Techniques and Inventions Styrene-modified polyolefin-based resin particles (hereinafter referred to as modified resin particles) obtained by polymerizing styrene-based monomers with polyolefin-based resin particles are impregnated with a foaming agent. Then, the method for producing the expandable styrene-modified polyolefin-based resin particles is as follows. The modified resin particles are put into a sealed pressure-resistant container such as a V-type, C-type, or DC-type rotary mixer and allowed to flow, There are a method of introducing the foaming agent, a method of suspending the modified resin particles in an aqueous medium in a closed pressure-resistant container equipped with a stirrer, and introducing the foaming agent.

The expandable styrene-modified polyolefin resin particles impregnated with the foaming agent by such a method are pre-foamed in a heating medium such as steam, then filled in the mold cavity of the molding machine, and steam is injected again. Then, the pre-expanded particles are fused and integrated with each other, and a foam-molded article that passes through the mold cavity can be obtained.

In producing the expandable resin particles, it is rare that the modified resin particles are prepared and the foaming agent is immediately impregnated with the modified resin particles. Normally, keep it in a paper bag or transformer bag,
If necessary, the modified resin particles that have been stored are used to impregnate the foaming agent. However, when pre-expanding using the expandable resin particles obtained in this way, the bubbles on the surface and inside often become very fine pre-expanded particles, and even if they are formed, only a poor foamed molded product is obtained. There is a problem that there is no.

Specifically, the bubbles of the pre-expanded particles are very fine, that is, the number of bubbles per unit area is too large,
a) The heat resistance of the pre-expanded particles is lowered and the pre-expanded particles are shrunk by heat during molding, so that the appearance of the foamed molded product is significantly deteriorated. b) The resulting foamed product has poor fusion-bonding properties, resulting in poor mechanical strength.

Therefore, the inventors of the present invention investigated the storage state of the modified resin particles and the number of bubbles in the pre-expanded particles, and found that the pre-expanded foam obtained as a trace amount of water contained in the modified resin particles escaped during storage. Knowing that the number of air bubbles in the particles increases, the modified resin particles were first dispersed in an aqueous medium, and then 110-1
We have proposed expandable resin particles impregnated with a foaming agent at a high temperature of 40 ° C. (see JP-A-1-279935).

Further, the inventors of the present invention can easily obtain pre-expanded particles having an appropriate number of bubbles even with modified resin particles in which water has been dissipated from the inside, and the appearance is excellent and the fusion property is excellent. Various studies were continued in order to obtain a good foamed molded product. as a result,
The present inventors have found that the above problem can be solved by impregnating the modified resin particles with a certain organic compound and impregnating the foaming agent, and thus reached the present invention.

(C) Means for Solving the Problem That is, according to the present invention, styrene-modified polyolefin resin particles having a reduced water content, 100 parts by weight of the particles in a closed container system, a carbon number of 16 to 24. Ester compound of saturated fatty acid and saturated alcohol having 24 to 32 carbon atoms 0.01
Provided is a method for producing expandable styrene-modified polyolefin resin particles, which comprises impregnating a volatile foaming agent in the presence of 0.5 to 0.5 parts by weight and 0.1 to 4 parts by weight of water.

The styrene-modified polyolefin-based resin particles used in the present invention are polyolefin-based resin particles modified by polymerizing a styrene-based monomer, particularly in an aqueous medium in which 100 parts by weight of the polyolefin-based resin particles are dispersed and held. It is preferable that 30 to 300 parts by weight of a styrene-based monomer be added and polymerized. As the polyolefin resin particles, it is preferable to use polyethylene or ethylene-vinyl acetate copolymer resin particles having a vinyl acetate content of 10% or less. The polymer resin particles used in the present invention can be prepared, for example, by the same method as described in JP-B-52-10150. In the resin particles, "decrease in water content" means that the water content is substantially lower than at the time of production due to storage after production, external air conditions and the like. For example, the initial moisture content is 0.7-0.5%
However, it may be reduced to 0.5% or less, particularly to 0.4% or less (the water content means the value measured by the Karl Fischer method).

The easily volatile foaming agent used in the method of the present invention may be any of gaseous and liquid forms generally known in the art, but propane, butane, pentane, trichloromonofluoromethane, dichlorodifluoromethane, Monochlorodifluoromethane is mentioned as a preferable one, and one or more selected from these can be used. The amount of the foaming agent added is preferably 6 to 15 parts by weight with respect to 100 parts by weight of the resin particles.

In the method of the present invention, an ester compound of a saturated fatty acid having 16 to 24 carbon atoms and a saturated alcohol having 24 to 32 carbon atoms (hereinafter referred to as a long chain ester) is used in an amount of 0.01 to 0.5 parts by weight with respect to 100 parts by weight of the resin particles. Parts, preferably 0.05 to 0.3 parts by weight.

The use of the above long-chain ester constitutes a feature of the method of the present invention.

The long-chain ester is generally used as an antistatic agent, and the effect of the modified resin particles on the fusion property of the foam after the foaming agent treatment is not known.

Specific examples of the long chain ester used in the present invention include the following.

Examples of the fatty acid having 16 to 24 carbon atoms include palmitic acid, stearic acid, behenic acid, and lignoceric acid, and examples of the saturated alcohol having 24 to 32 carbon atoms include ceryl alcohol and myricyl alcohol. Of these esters, the ester of lignoceric acid and myricyl alcohol is particularly preferable.

The ester of lignoceric acid and myricyl alcohol is known as the main component of hydrogenated rice bran oil obtained by hydrogenating rice bran oil.

In the method of the present invention, since the volatile foaming agent is impregnated, it can be carried out in a closed container according to a conventional method.

As one of them, a so-called wet method performed in an aqueous medium is used. The other is the use of the so-called dry method, which is carried out under substantially anhydrous conditions. However, it has been found that the dry method cannot achieve the predetermined purpose. In the case of this invention, at least 100 parts by weight of the resin particles, a small amount of water,
It is necessary to add at least 0.1 part by weight. On the other hand, addition of 4 parts by weight or more of water is not preferable from the viewpoint of workability. Although the working mechanism affecting the effect of the addition of such a trace amount of water is not clear, in fact, it affects the modification of the expandable resin particles by the synergistic action with the above-mentioned agents.

The reaction temperature of the present invention can be 100 ° C. or lower, for example, 50 to 80 ° C. in both wet and dry processes. The reaction time is about 3 to 6 hours.

The water content of the expandable resin particles obtained by the method of the present invention is almost the same as that of the resin particles of the raw material or a slight increase, but when pre-expanded, the treatment of the method of the present invention is performed. A remarkable difference is brought about in appearance, fusion property and the like with the non-expandable resin particles.

(D) Examples Hereinafter, the present invention will be described in detail with reference to Examples and Comparative Examples, but the present invention is not limited thereto.

(Preparation of styrene-modified polyethylene-based resin particles) 100 parts by weight of pure water, 0.45 parts by weight of magnesium pyrophosphate, and 0.02 parts by weight of sodium dodecylbenzenesulfonate are added to an autoclave having an internal volume of 100 to make an aqueous medium, and then a polyethylene resin is added thereto. 40 parts by weight of particles (Evatate D1042, trade name, manufactured by Sumitomo Chemical Co., Ltd.) were suspended and stirred at a rotation speed of 250 rpm.

Separately, 0.3 part by weight of benzoyl peroxide and 0.01 part by weight of t-butylperoxybenzoate were used as a polymerization catalyst, and 0.25 part by weight of dicumyl peroxide was used as a crosslinking agent.
It was dissolved in 60 parts by weight of a styrene monomer to prepare a monomer solution, and the solution was added to the aqueous medium to carry out polymerization while maintaining the temperature of 85 ° C. for 4 hours while absorbing the polyethylene resin particles.

Then, the temperature was raised to 143 ° C. and maintained for 3 hours, then cooled and styrene modified polyethylene resin particles (hereinafter referred to as modified resin particles) were taken out.

Then, after 20 days of storing the obtained modified resin particles in a paper bag, the internal moisture content was measured by the Karl Fischer method, and it was found to be 0.06%.

Example 1 The modified resin particles 10 were added to a pressure resistant V-type blender having an internal volume of 5
0 part by weight, 0.5 part by weight of water, 0.2 part by weight of an ester compound of lignoceric acid and myricyl alcohol (Kawawax L, manufactured by Kawaken Fine Chemical Co., Ltd.), toluene
1.5 parts by weight of the butane was added, and 10 parts by weight of butane were press-fitted at room temperature while rotating. Then, after the temperature was raised to 70 ° C. and maintained for 4 hours, it was cooled and the expandable styrene-modified polyolefin resin particles were taken out.

Next, the expandable resin particles were pre-expanded with steam to a bulk ratio of 30 times. The number of bubbles per 1 mm ^{2 of the} pre-expanded particles obtained here was measured.

After leaving the pre-expanded particles for 7 days, 400 × 300 × 100 (m
m) was placed in the mold cavity in the molding machine, and steam having a pressure of 0.7 kg / cm ² was injected for 60 seconds to heat the steam. And after cooling for 10 minutes,
The foamed molded product was taken out.

The appearance of the obtained foamed molded product was judged, and then the product was divided into two, and the ratio of those in which the particles themselves were broken, not from the grain boundaries, was measured in the fractured surface, and the result was taken as fusion (%).

The results are shown in Table 1.

Example 2 In Example 1, the expandable styrene-modified polyolefin resin particles were produced in the same manner as in Example 1 except that the amount of Kawawax L added was 0.05 parts by weight instead of 0.2 parts by weight. .

The results are shown in Table 1.

Example 3 Expandable styrene-modified polyolefin resin particles were produced in the same manner as in Example 1 except that the amount of water used in Example 1 was 0.1 part by weight instead of 0.5 part by weight.

The results are shown in Table 1.

Comparative Examples 1 to 3 In Example 1, the amount of water used was 0 or 0.02 parts by weight instead of 0.5 parts by weight, or 0.2 parts by weight of Kawawax L was not added and the other examples 1
The expandable styrene-modified polyolefin resin particles were produced in the same manner as in.

The results are shown in Table 2.

Example 4 100 parts by weight of the above-mentioned modified resin particles, 100 parts by weight of water, 0.02 part by weight of sodium dodecylbenzenesulfonate, an ester compound of lignoceric acid and myricyl alcohol (Kawawax L) 0.25 part by weight in a sealed pressure vessel equipped with a stirrer. And 1.5 parts by weight of toluene were added and the mixture was sealed. Then, 10 parts by weight of butane were pressed in while stirring. After press-fitting, the temperature was raised to 70 ° C. and impregnation was carried out for 4 hours, followed by cooling to take out expandable styrene-modified polyolefin resin particles. When the expandable resin particles were pre-expanded with steam to a bulk ratio of 30 times, pre-expanded particles having a cell number of 5 to 10 per mm ² were obtained. When these pre-expanded particles were molded in the same manner as in Example 1, the foamed molded product obtained had a good appearance with no shrinkage, and the fusion was 90%.

(E) Effect of the Invention According to the present invention, it is possible to control the number of bubbles per unit area so as not to be too large, and it is possible to produce a foamed molded product having a good appearance, excellent fusion properties, and excellent mechanical strength. It is possible to produce expandable styrene-modified polyolefin resin particles.

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Claims (2)

[Claims] 1. A styrene-modified polyolefin-based resin particle having a reduced water content is prepared by mixing a saturated fatty acid having 16 to 24 carbon atoms and a saturated alcohol having 24 to 32 carbon atoms with respect to 100 parts by weight of the particle in a closed container system. A method for producing expandable styrene-modified polyolefin resin particles, which comprises impregnating a volatile foaming agent in the presence of 0.01 to 0.5 part by weight of an ester compound and 0.1 to 4 parts by weight of water. 2. The method according to claim 1, wherein the impregnation of the volatile blowing agent is carried out in an aqueous medium.