JPH0431449A - 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 fatty acid ester in a sealed vessel. CONSTITUTION:Styrene-modified polyolefin resin particles of a decreased 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 0.01-5 pts.wt., per 100 pts.wt. said particles, at least one fatty acid ester selected from among glycerol fatty acid ester, sorbitan fatty acid ester and pentaerythritol fatty acid ester 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 brought out as a fused material, 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 investigated the storage conditions 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 inside the modified resin particles evaporates during storage. Knowing the fact that the number of bubbles in the particles increases, we first dispersed the modified resin particles in an aqueous medium and dispersed them in a closed system at 110
We proposed foamable resin particles impregnated with a foaming agent at a high temperature of ~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 present inventors have discovered that the above-mentioned problems can be solved by allowing a certain type of organic compound to coexist with the modified tree R'fJ and impregnating it with a blowing agent, thereby achieving 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 mixed with glycerin fatty acid ester, sorbitan fatty acid At least one fatty acid ester selected from the group of esters and pentaerythritol fatty acid esters. A method for producing expandable styrene-modified polyolefin resin particles is provided, which comprises impregnating an easily volatile blowing agent in the presence of 1 to 0.5 parts by weight of O.

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, the polyolefin resin particles may be polyethylene or vinyl acetate-containing particles.
It is preferable to use ethylene-vinyl acetate copolymer resin particles of 110% or less. The polymer resin particles used in this 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 moisture content" means that the moisture content is substantially lower than at the time of manufacture due to storage after manufacture, outside air conditions, etc. For example, the initial water content may be 0.7 to 0.5%, but it may be reduced to 0.5% or less, especially 0.4% or less (here, the water 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, dichloronofluoromethane, etc. Preferred examples include methane and monochlorodifluoromethane, 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 the present invention, the fatty acid ester is added to 100 parts by weight of the resin particles in an amount of 0. O1~0.5 weight! part, preferably 0.605 to 0.3 part by weight. The use of fatty acid esters constitutes a feature of the process of the invention. Fatty acid ester is said to have the effect of reducing air bubbles when added when impregnating styrene resin particles with a blowing agent, but it has the opposite effect when impregnating the resin particles with a blowing agent according to the present invention. This can be said to be a completely unexpected finding.

Among the fatty acid esters used in this invention, glycerin mono (di or tri)
Examples include caprylic acid ester, glycerin mono (di or tri) stearate, glycerin mono (di or tri) oleate, and glycerin mono (di or tri) behenate.

In addition, sorbitan fatty acid esters include sorbitan mono(di, tri, or tetra) laurate, sorbitan mono(di, tri, or tetra) palmitate, sorbitan mono(di, tri, or tetra) stearate, sorbitan mono(di, tri, or tetra) ) oleate etc.
Furthermore, as pentaerythritol fatty acid ester,
Pentaerythritol mono(di, tri, or tetra) laurate, pentaerythritol mono(di, tri, or tetra) stearate, pentaerythritol mono(di, tri, or tetra) oleate, and the like can be mentioned.

The above fatty acid esters can be used alone or in a mixture of two or more.

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 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 1ooQ to form an aqueous medium. 40 parts by weight of polyethylene resin particles (manufactured by Sumima Kagaku Co., Ltd., trade name Evatate D 1042) were suspended in this, and the mixture was stirred at a rotational speed of 250 rpm.

Separately, benzoyl peroxide 0,3 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. Polymerization was carried out.

After that, the temperature was raised to 143°C and maintained 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 As shown in Table 1, 100 parts by weight of the modified resin particles and 0.5 or 0.5 parts by weight of water were added to a pressure-resistant V-type blender with an internal volume of 5e.
1 part by weight, glycerin monostearate 0.2
Or add 0.05 parts by weight and 1.5 parts by weight of toluene,
While rotating, 10 parts by weight of butane was injected at room temperature. 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 1 mm of the pre-expanded particles thus obtained was measured.

The pre-expanded particles were left for 7 days, then 400X300X1
0.00 (3 m) mold cavity in a molding machine, 0.7 kg/c
It was heated by injecting steam at a pressure of +s' 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 the proportion of the particles that were broken not from the grain boundaries but from the particles themselves on the fractured surface was measured and determined as fusion (%).

The results are shown in Table 1.

(Left below) Table 1 Comparative example! In Example 1, instead of adding 0.5 or 0.1 parts by weight of water, O or 0.02 parts by weight was added, or 0.2 or 0.05 parts by weight of glycerin monostearate was added. Expandable styrene-modified polyolefin resin particles were produced and evaluated in the same manner as in Example 1, except that the particles were not added. Table 1 shows the results.
Shown below.

Example 2 Expandable styrene-modified polyolefin resin particles were produced in the same manner as in Example 1 except that sorbitan distearate was added instead of glycerin monostearate in Example 1, We conducted the evaluation. The results are shown in Table 2.

Table 2 Refine resin particles were manufactured and evaluated.

The results are shown in Table 3.

Table 3 Example 3 Expandable styrene-modified polio Example 4 Stirring in the same manner as in Example 1 except that pentaerythritol distearate was added instead of glycerin monostearate in Example 1. 100 parts by weight of the above modified resin particles, 100 parts by weight of water, 0.02 parts by weight of sodium dodecylbenzenesulfonate, 0.25 parts by weight of glycerin monostearate, and 1.5 parts by weight of toluene in a 5Q airtight pressure-resistant container with a machine. was added and sealed. 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 the expandable resin particles were pre-foamed with water vapor to a bulk multiple of 30 times, Pre-expanded particles with a cell count of 5 to 10 cells per mt of lII were obtained.

When the pre-expanded particles were molded in the same manner as in Example 1, the resulting foamed molded product had no shrinkage and had a good appearance, and the fusion was 90%.

Example 5 Expandable styrene-modified polyolefin resin particles were produced in the same manner as in Example 4 except that sorbitan tetrastearate was added instead of glycerin monostearate. When these expandable resin particles were pre-foamed with water vapor to a bulk multiple of 30 times, pre-foamed particles having 10 to 20 cells per lag were obtained. These pre-foamed particles were used in Examples!
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 85%.

Example 6 Expandable styrene-modified polyolefin resin particles were produced in the same manner as in Example 4 except that pentaerythritol distearate was added instead of glycerin monostearate.

When these expandable resin particles were pre-foamed with water vapor to a bulk multiple of 30 times, pre-foamed particles having 10 to 20 cells per lu++' were obtained. When these pre-expanded particles were molded in the same manner as in Example 1, the obtained foamed molded product had no shrinkage and had a good appearance, and the fusion bond was 85.
%Met.

(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,
At least one fatty acid ester selected from the group of glycerin fatty acid ester, sorbitan fatty acid ester, and pentaerythritol fatty acid ester 0.01 to 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.