JPH0431448A - Production of expandable styrene-modified polyolefin resin particle - Google Patents

Abstract

PURPOSE:To obtain the title particles which can give a foam having excellent appearance and good fusibility by impregnating styrene-modified polyolefin resin particles of a decreased water content with an easily volatile blowing agent in the presence of a small amount of a specified organic compound in a sealed vessel. CONSTITUTION:Styrene-modified polyolefin resin particles of a decrased water content (e.g. particles prepared by adding 30-300 pts.wt. styrene monomer to an aqueous medium in which 100 pts.wt. polyolefin resin particles are dispersed, polymerizing the monomer, and decreasing the water content by storing them after the production) are impregnated with an easily volatile blowing agent (e.g. butane) in the presence of 0.01-0.5 pt.wt., per 100 pts.wt. said particles, polyoxyethylenehydroxyalkylamine of the formula (wherein R is linear or branched 10-18C alkyl, and n is 1-20) in a sealed vessel. In this way, the title particles which can give a foam whose number of cells per unit area can be controlled so as not to be excessively large and which has good appearance, excellent fusibility and excellent mechanical properties can be obtained.

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) Problems to be solved by conventional technology and the invention Styrene-modified polyolefin resin particles (hereinafter referred to as modified resin particles) obtained by polymerizing polyolefin resin particles with a styrene monomer are impregnated with a blowing agent. The method for producing expandable styrene-modified polyolefin resin particles includes: ■ Putting the modified resin particles in a closed pressure-resistant container that is a rotary mixer such as a V-type, C-type, or DC-type and allowing it to flow. ,
Methods for introducing a blowing agent include (1) 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 particle, each pre-expanded particle is fused and cured, and a foamed molded article can be obtained in accordance with 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 further investigated the storage conditions of the modified resin particles and the number of bubbles in the pre-expanded particles. Knowing that the number of cells in foamed particles increases, we first proposed foamable resin particles in which modified resin particles were dispersed in an aqueous medium and impregnated with a blowing agent in a closed system at a high temperature of 110-140°C. (Refer to Japanese Patent Application Laid-Open No. 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 using the formula f:\OHH However, R is a linear or branched alkyl group having 10 to 18 carbon atoms, and n is an integer of 1 to 20.
, 511 parts by weight is provided. A method for producing expandable styrene-modified polyolefin resin particles is provided, which comprises impregnating an easily volatile blowing agent in the presence of 511 parts by weight of styrene-modified polyolefin resin particles.

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 for polymerization. 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 by a method similar to that described in PI, for example, Japanese Patent Publication No. 52-10150.

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 any gaseous or liquid blowing agent known in the art, including propane, butane, pentane, trichloromonofluoromethane, dichlorodifluoromethane, Monochlorodifluoromethane is mentioned as preferred, and IN 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 this invention, polyoxyethylene hydroxyalkylamine represented by formula (1) is added to the resin particles 10.
For 0 parts by weight, 0. O is used in an amount of 1 to 0.5 parts by weight, preferably 0.05 to 0.3 parts by weight.

The use of the polyoxyethylene hydroxyalkylamines described above constitutes a feature of the process of the invention. The above-mentioned polyoxyethylene hydroxyalkylamine is generally used as an antistatic agent, and its effect on the fusion properties of the foam after treating the modified resin particles with a blowing agent as in the present invention is completely unknown. do not have.

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 does not achieve the desired objectives. 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 the present invention is almost the same as that of the raw material resin particles or slightly increased. There is a significant 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.

(Creation of styrene-modified polyethylene resin particles) Add 100 parts by weight of pure water, 0.45 parts by weight of magnesium pyrophosphate, and 0.02 parts by weight of sodium dodecylbenzenesulfonate to an autoclave with an internal volume of 100 (2) to prepare an aqueous medium.
Next, 40 parts by weight of polyethylene resin particles (manufactured by Sumima Kagaku Co., Ltd., trade name Evatate D1042) were suspended in this, and the mixture was stirred at a rotational speed of 25 rpm.

Separately, 0.3% benzoyl peroxide is used as a polymerization catalyst.
Part by weight and t-butyl peroxybenzoate 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.

Then, after raising the temperature to 143℃ and maintaining it for 3 hours,
After cooling, 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 I The above modified resin particles 1 were placed in a pressure-resistant V-type blender with an internal volume of 5Q.
00 parts by weight, 0.5 parts by weight of water, 0.2 parts by weight of polyoxyethylene hydroxyalkylamine (manufactured by Tanaka Chemical Research Institute, trade name: Antistar 80FS), 1 part by weight of toluene.
．． 5 parts by weight were added, and 210 parts by weight of pigs were press-fitted 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. 1 am” of the pre-expanded particles obtained here.
The number of bubbles per unit was measured.

The pre-expanded particles were left to stand for 7 days, then 400x300x1
00 (-m) into the mold cavity in the molding machine, 0.7 kg/a
Steam at a pressure of m'' was injected for 60 seconds to heat it. After cooling for 10 minutes, the foam molded product was taken out.

After evaluating the appearance of the obtained foamed molded product, it was divided into two parts, and the proportion of particles that were broken not from the grain boundaries but from the particles themselves on the fracture surface was measured.

Table 1 The results are shown in Table 1.

Example 2 In Example 1, instead of adding 0.2 parts by weight of polyoxyethylene hydroxyalkylamine (Antistar 80FS), 0.05 parts by weight was added, and the foamability was obtained in the same manner as in Example 1 except for the addition of 0.05 parts by weight. Styrene-modified polyolefin resin particles were manufactured.

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 changed to 0.1 part by weight instead of 0.5 part by weight. did.

The results are shown in Table 1.

Comparative Examples 1 to 3 In Example 1, instead of adding 0.5 parts by weight of water, O or 0.02 parts by weight was added, or instead of adding 0.2 parts by weight of polyoxyethylene hydroxyalkylamine. Expandable styrene-modified polyolefin resin particles were produced in the same manner as in Example I except for adding the above.

The results are shown in Table 2.

Table 2 Example 4 100 of the above modified resin particles were placed in a 512 sealed pressure-resistant container with a stirrer.
parts by weight, and 100 parts by weight of water, 0.02 parts by weight of sodium dodecylbenzenesulfonate, and 0.2 parts by weight of polyoxyethylene hydroxyalkylamine (Antistar 80FS).
5 parts by weight and 1.5 parts by weight of toluene were added and sealed. Next, while stirring, 210 parts by weight of pork was press-fitted. After press-fitting, the temperature was raised to 70° C. and impregnated for 4 hours, and 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 2 to 5 cells per am' were obtained. Examples of these pre-expanded particles! When molded in the same manner as above, 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 the 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,
Formula I: ▲There are mathematical formulas, chemical formulas, tables, etc.▼ (I) (where R is a linear or branched alkyl group having 10 to 18 carbon atoms, and n is an integer of 1 to 20) Polyoxy Ethylene hydroxyalkylamine 0.01-0.
A method for producing expandable styrene-modified polyolefin resin particles, which comprises impregnating an easily volatile blowing agent in the presence of 5 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.