JPH0439338A - Production of expandable styrene-modified polyolefin resin particle - Google Patents

Abstract

PURPOSE:To obtain the subject resin particle giving a foamed article having controllable number of cells and excellent appearance, fusibility, etc., by impregnating a highly volatile foaming agent in a styrene-modified polyolefin resin particle having lowered water-content in the presence of a specific ester compound. CONSTITUTION:The objective particle is produced by impregnating a highly volatile foaming agent (e.g. propane and butane) in a closed vessel into 100pts. wt. of a styrene-modified polyolefin resin particle having lowered water-content in the presence of 0.01-0.5pts.wt. of an ester compound derived from a 16-24C saturated fatty acid (e.g. palmitic acid) and a 24-32C saturated alcohol (e.g. ceryl alcohol) and 0.1-4pts.wt. of water.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Industrial Application Field This invention relates to a method for producing expandable styrene-modified polyolefin resin particles.

(B) Conventional technology and invention or problem to be solved Styrene-modified polyolefin resin particles (hereinafter referred to as modified resin particles; l) obtained by polymerizing polyolefin resin particles with styrene and a spinning wheel are foamed. The method for manufacturing expandable styrene-modified polyolefin resin particles impregnated with the agent is as follows: ■ The modified resin particles are placed in a sealed pressure-resistant container using a rotary mixer such as a V-type, C-type, or DC-type. Put it in and let it flow,
Methods for introducing a blowing agent: (1) There is a method in which modified resin particles are suspended in an aqueous medium in a sealed pressure-resistant container equipped with a stirrer, and a blowing agent is introduced.

The expandable styrene-modified polyolefin resin particles impregnated with a blowing agent in this way are pre-foamed in a heating medium such as steam, and then filled into the mold cavity of a molding machine, and steam, etc. is injected again. By heating and treating each pre-expanded grain, it is possible to obtain a foamed molded product that has integrated structure and conforms to the mold cavity.

When producing the above-mentioned expandable resin particles, it is rare that the modified resin particles are impregnated with a blowing agent immediately after they are produced. Normally, the modified resin particles are stored in paper bags, transformer bags, etc., and the stored modified resin particles are used to impregnate the foaming agent as needed. However, when the expandable resin particles obtained in this way are used for pre-foaming, the air bubbles on the surface and inside often become very fine, resulting in pre-foamed particles, and even if these particles are molded, only inferior foam molded products can be obtained. The problem is that there is no.

Specifically, because the bubbles in the pre-expanded particles are very fine, that is, the number of bubbles per unit area is too large,
) The heat resistance of the pre-expanded particles decreases and they shrink due to the heat during molding, resulting in a markedly poor appearance of the foamed molded product. b) The result is a foamed molded product with poor fusion properties and poor mechanical strength.

Therefore, the present inventors investigated the storage conditions of the modified resin particles and the number of bubbles in the pre-expanded particles, and found that as the amount of water contained inside the modified resin particles evaporated during storage, Knowing the fact that the number of bubbles in the pre-expanded particles increases, we first dispersed the modified resin particles in an aqueous medium and heated them in a closed system for 11 hours.
We have proposed foamable resin particles impregnated with a foaming agent at a high temperature of 0 to 140°C (see JP-A-1-279935).

Furthermore, the present inventors have discovered that pre-expanded particles with an appropriate number of cells can be easily obtained even from modified resin particles in which water has evaporated from the inside, and that they have excellent appearance and fusion properties. Various studies were continued in order to obtain a good foam molded product. the result,
The inventors have discovered that the above problem can be solved by impregnating the modified resin particles with a blowing agent in the coexistence of a certain organic compound, and have thus arrived at the present invention.

(c) Means for solving the problem, that is, according to the present invention, styrene-modified polyolefin resin particles with a reduced water content are added to 100 parts by weight of the particles in a closed container system, and the particles have a carbon number of 16 to 24. Production of expandable styrene-modified polyolefin resin particles characterized by impregnating an easily volatile blowing agent in the presence of 0.01 to 05 parts by weight of an ester compound of a saturated fatty acid and a saturated alcohol having 24 to 32 carbon atoms. law is provided.

The styrene-modified polyolefin resin particles used in the present invention are polyolefin resin particles modified by polymerizing a styrene monomer, and in particular, are dispersed in an aqueous medium in which 100 parts by weight of the polyolefin resin particles are dispersed. , 30 to 300 parts by weight of a styrene monomer is preferably added and polymerized. Further, 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 a method similar to that described in Japanese Patent Publication No. 10150/1983. With respect to such resin particles, "decreased water content" means that the water content is substantially lower than at the time of production due to storage after production, outside air conditions, etc. For example, the initial moisture content of 0.7 to 0.5% may decrease to 0.5% or less, especially 0.4% or less (here, moisture content refers to the value determined by the Karl Fischer method). ).

The easily volatile blowing agent used in the method of the present invention can be either a gaseous or liquid blowing agent commonly known in the art, but propane, butane, pentane, trichloromonofluoromethane, nochlorofluorofluoromethane, Preferred examples include methane and monochlorodifluoromethane, 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 per 100 parts by weight of the resin particles.

In the method of the present invention, an ester compound (hereinafter referred to as long chain ester) of a saturated fatty acid having 16 to 24 carbon atoms and a saturated alcohol having 24 to 32 carbon atoms is added to the resin particles 10.
001 to 0.5 parts by weight, preferably 0 parts by weight
05 to 0.3 parts by weight is used.

The use of the long-chain esters described above constitutes a feature of the process of the invention.

The above-mentioned long-chain ester is generally used as an antistatic agent, and its effect on the fusing properties of the foam after treating the modified resin particles with a blowing agent as in the present invention is not known at all.

Specific examples of long chain esters used in this invention include the following.

Examples of fatty acids having 16 to 24 carbon atoms include valmitic acid, stearic acid, behenic acid, and lignoceric acid; examples of saturated alcohols having 24 to 32 carbon atoms include:
Examples include ceryl alcohol and myricyl alcohol, and among esters consisting of these, esters of lignoceric acid and myricyl alcohol are particularly preferred.

This 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, impregnation with an easily volatile blowing agent can be carried out in a closed container according to a conventional method.

One of these uses a so-called wet method, which is carried out in an aqueous medium. Another method is the use of a so-called dry method, which is carried out under substantially anhydrous conditions. However, it has been found that the dry method cannot achieve the desired purpose. In the case of this invention, a trace amount of water, based on at least 100 parts by weight of the resin particles,
It is necessary to add at least 0.1 part by weight. On the other hand 4
Addition of more than part by weight of water is not preferable from the viewpoint of workability.

Although the mechanism by which the addition of such a small amount of water exerts its effects is not clear, the fact is that it affects the modification of expandable resin particles through a synergistic action with the above-mentioned agents.

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

The moisture content of the expandable resin particles obtained by the method of this invention is almost the same as that of the raw material resin particles, or slightly increased. There is a noticeable difference in appearance, fusion properties, etc. between the foamable resin particles and the non-foamable resin particles.

(d) Examples The present invention will be explained in detail below using Examples and Comparative Examples, but the present invention is not limited thereto.

(Preparation of styrene-modified polyethylene 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 were added to an autoclave with an internal volume of 100Q to form an aqueous medium. 40 parts by weight of polyethylene resin particles (manufactured by Sumitomo Chemical Co., Ltd., trade name Evatate D 1042) were suspended in this and stirred at a rotation speed of 250 rpm.

Separately, 0.3% benzoyl peroxide is used as a polymerization catalyst.
Part by weight and t-butyl peroquine benzoate 0.0
1 part by weight, 0.2 dicumyl peroxide as a crosslinking agent
5 parts by weight were dissolved in 60 parts by weight of styrene monomer to obtain a monomer solution, and the solution was added to the aqueous medium and maintained at a temperature of 85° C. for 4 hours while absorbing the polyethylene resin particles to polymerize. I did this.

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

Next, the obtained modified resin particles were stored in a paper bag, and after 20 days, the internal moisture content was measured by the Karl Fischer method, and it was found to have decreased to 0.06%.

Example 1 The above modified resin particles 1 were placed in a pressure-resistant V-type blender with an internal volume of 5 g.
00 parts by weight, 0.5 parts by weight of water, 0.2 parts by weight of an ester compound of lignoceric acid and millinol alcohol (manufactured by Yoken Fine Chemical Co., Ltd., trade name: Kawawax L), and 1.5 parts by weight of toluene. , 10 parts by weight of butane was injected under pressure at room temperature while rotating.

Then, the temperature was raised to 70° C. and maintained for 4 hours, then cooled and the expandable styrene-modified polyolefin resin particles were taken out.

Next, the foamable resin particles were pre-foamed with water vapor to a bulk ratio of 30 times. The number of cells per Inm'' of the pre-expanded particles thus obtained was measured.

The pre-expanded particles were left for 7 days, then 400X300X1
00 (mm) into the mold cavity in the molding machine, 0.7 kg/C
It was heated by injecting steam at a pressure of m' for 60 seconds. After cooling for 10 minutes, the foamed molded product was taken out.

The obtained foamed molded product was divided into two after its appearance was judged, and on the fractured surface, the proportion of particles that were broken not from the grain boundaries but from the particles themselves was measured and determined as fusion bond (%).

The results are shown in Table 1.

Example 2 In Example 1, the amount of Kawawax L added was changed to 0.05 parts by weight instead of 0.2 parts by weight, and the foamable styrene-modified polyolefin resin was prepared in the same manner as in Example 1 except for the following. Particles were produced.

The results are shown in Table 1.

Example 3 In Example 1, the amount of water used was changed to 0.1 parts by weight instead of 0.5 parts by weight, and expandable styrene-modified polyolefin resin particles were produced in the same manner as in Example 1, except for this. was manufactured.

The results are shown in Table 1.

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 instead of adding 0.2 parts by weight of Kawa Wax L Expandable styrene-modified polyolefin resin particles were produced in the same manner as in Example 1 except for the addition of the above.

The results are shown in Table 2.

(Leaving space below) Table 2 Example 4 100 parts by weight of the above modified resin particles, 100 parts by weight of water, 0.02 parts by weight of sodium dodecylbenzenesulfonate, and an ester compound of lignoceric acid and millinol alcohol in a 5Q sealed pressure-resistant container with a stirrer. (Kawawax L) 0.25
Add 15 parts by weight of toluene and seal. Then, 10 parts by weight of butane was injected under pressure while stirring. After press-fitting, the temperature was raised to 70°C and impregnated for 4 hours, then cooled and the expandable styrene-modified polyolefin resin particles were taken out. When these expandable resin particles were pre-foamed with water vapor to a bulk multiple of 30 times, pre-foamed particles having 5 to 10 cells per 1 mm were obtained. When molded, the obtained foamed molded product had no shrinkage and had a good appearance, and the fusion was 90%.

(E) Effects of the Invention According to this invention, the number of cells per unit area can be controlled so as not to be too large, and a foamed molded product with good appearance, excellent fusion properties, and excellent mechanical strength can be produced. It is possible to produce expandable styrene-modified polyolefin resin particles.

Claims (1)

[Claims] 1. Styrene-modified polyolefin resin particles with reduced water content are prepared in a closed container system for 100 parts by weight of the particles,
Saturated fatty acids with 16 to 24 carbon atoms and 24 to 32 carbon atoms
Ester compound with saturated alcohol of 0.01-0.5
1. A method for producing expandable styrene-modified polyolefin resin particles, which comprises impregnating an easily volatile blowing agent in the presence of parts by weight. 2. The method according to claim 1, wherein the impregnation with the easily volatile blowing agent is carried out by adding 0.1 to 4 parts by weight of water to the resin particles. 3. The method according to claim 1, wherein the impregnation with the easily volatile blowing agent is carried out in an aqueous medium.