JPS58152027A - Preparation of polyolefin resin type foam - Google Patents

Abstract

PURPOSE:To obtain the titled foam having improved fusing between particles, by expanding a mixture of polyolefin type resin particles with a foaming agent under heating, impregnating or coating the resultant expanded particles with an organic compound having a melting point and boiling point in specific ranges filling the impregnated or coated expanded particles in a mold, and molding the particles. CONSTITUTION:In impregnating polyolefin type resin particles, e.g. particles of random copolymeric particles of propylene with ethylene, with a foaming agent, e.g. propane or dichlorofluoromethane, or after impregneating the polyolefin type resin particles with the foaming agent and expanding the particles under heating, an organic compound, e.g. a phthalic or fatty acid ester, having <=100 deg.C melting point and >=150 deg.C boiling point and preferably 6.0-10.0 solubility parameter value in an amount of usually 0.01-10pts.wt. based on 100pts.wt. resin particles is impregnated into or applied to the resin particles. The resultant resin particles are then filled in a mold and molded under heating to give the aimed resin foam.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a molded article having a desired shape by molding expanded polyolefin resin particles in a mold. The present invention relates to a method for producing a polyolefin resin foam with good moldability.

As a method for molding a foam in a mold, a foaming agent is contained in a particulate base resin, foamed by heating etc. to form foamed particles, and then the foamed particles are filled into a mold having a desired shape. A common method is heat molding. This in-mold molding process yields a foam molded product with a complex shape, but since pre-expanded foamed particles are used, if the heating conditions during molding are low, the fusion between the particles will be insufficient. This results in a brittle molded product. Therefore, in order to obtain a molded article with good fusion bonding, it is necessary to heat the resin to a temperature higher than its softening temperature. In particular, when polyolefin resins such as polyethylene and polypropylene are used, since they are crystalline polymers, they must be hardened to a temperature higher than the melting point of the resin.

Such strong heating conditions cause various disadvantages such as deterioration of the appearance of the molded product and increase in molding cost.

The present inventors have completed the present invention as a result of intensive research aimed at eliminating these disadvantages and inexpensively manufacturing a polyolefin-based in-mold foam molded product with good fusion between particles.

That is, the present invention provides a method in which polyolefin resin particles are made to contain a blowing agent and heated to form polyolefin resin foam particles, which are then filled into a mold and heat-molded.
This is a method for producing a polyolefin resin foam, which is characterized by coating or impregnating an organic compound with a melting point of C or higher and a melting point of 100C or lower. The present invention will be explained in detail below.

The method of the present invention is applied to resin particles whose main component is polyolefin resin, and polyolefin resins include polyethylene polymers and polypropylene polymers, but propylene and polypropylene having a high melting point are used as polyolefin resins. This method is particularly effective for polypropylene resins such as tyrene random copolymers.

The organic compound to be applied or impregnated onto the expanded particles has a boiling point of 1
50°C or higher, preferably 200°C or higher, melting point 100
It is necessary that the temperature is below 80°C, preferably below 80°C. When the boiling point is less than 150°C, it is difficult to stably localize near the surface of the foamed particles due to volatilization from the surface of the foamed particles and diffusion into the resin. Therefore, the purpose of plasticizing only the vicinity of the particle surfaces and promoting fusion is is not suitable. When a large amount of such an organic compound is applied, it diffuses into the interior and deteriorates the physical properties of the foam, while when it is applied in a small amount, the plasticization of the resin is insufficient, thus promoting the desired fusion. I can't do it. In addition, if the melting point exceeds 100°C, it takes time to melt and penetrate into the resin, and the function of plasticizing the particle surface during molding decreases, so it cannot be expected to improve the desired fusion. It disappears.

In addition, in order to effectively plasticize the vicinity of the surface of the foamed particles during heat molding in a small amount and promote fusion, it is preferable that the compatibility between the polyolefin and the organic compound is good, and the solubility parameter value (SP value) It is preferable that it is 6.0-10.0. Examples of organic compounds that meet the above conditions include phthalate ester compounds such as diptyl phthalate, di-2-ethylhexyl phthalate, and butylbenzyl phthalate; -2-ethylhexyl adipate, di-2-ethylhexyl azelaate, diptyl sepacate, etc. fatty acid esters such as butyl phenylstearate; glycerin esters such as soybean oil and coconut oil; diethylene glycol dibenzoate.

Aromatic carboxylic acid esters such as dipropylene glycol dibenzoate; liquid paraffin, chlorinated paraffin, and the like. These organic compounds may be used alone or in combination of two or more.

The preferable amount of these organic compounds to be used differs depending on the plasticizing effect of each organic compound on the polyolefin foam particles, and if the plasticizing effect is large, a small amount can be used, and if the plasticizing effect is small, a large amount must be used. However, when each organic compound is used in an amount exceeding the optimum amount, the fusion is actually deteriorated. Therefore, usually 0.01 to 10 parts by weight are used, preferably 0.1 to 5 parts by weight, per 100 parts of expanded beads. Even if more than 10 parts by weight is used, the effect is small.

Methods for coating or impregnating foamed particles with these organic compounds include (1) adding the organic compound during the process of impregnating the foaming agent into the particles, and (2) adding the organic compound to the particles after impregnating the particles with the foaming agent. There are methods such as (3) impregnating particles with a foaming agent, foaming them, and then coating the foamed particles.

In (1), the blowing agents used include hydrocarbons such as propane, butane, pentane, and hexane, and halogenated hydrocarbons such as dichlorodifluoromethane, trichloromonofluoromethane, and dichlorotetrafluoroethane. , mainly organic compounds with low boiling points. Methods for impregnating particles with these blowing agents include immersing the particles in a container containing a liquid blowing agent, and mixing the particles and blowing agent vapor in a container. There are two methods: a method in which particles and a blowing agent are suspended and impregnated in an aqueous medium in a container equipped with a stirrer, etc. At this time, a mixing device such as a stirrer is installed in the container,
When the organic compound to be used is added and mixed, the organic compound adheres to the particle surface as it is impregnated with the blowing agent, but because of its large molecular weight, it is impregnated near the particle surface and remains in the expanded particle even after the subsequent foaming process. It exists near the surface. Regarding method (2), after impregnating the foaming agent as described above, the organic compound can be added to the container and mixed so that it is present near the particle surface, or after the particles are taken out from the container. The organic compound can also be applied to the surface of the particles by placing the particles and the organic compound in a container equipped with a stirrer, a rotary container, or the like and mixing them. In method (3), the foamed particles are coated, and can be easily applied by mixing the foamed particles and the organic compound in a container equipped with a stirrer.

In this way, if foamed polyolefin resin particles coated with or impregnated with an organic compound having plasticizing ability are filled into a mold and heated and molded, the amount of heat medium used is reduced.
Moreover, a molded article with a high fusion rate and particles firmly fused together can be obtained.

Hereinafter, the zero-start J will be explained using examples.

Example 1 100 parts by weight of random copolymer particles of propylene and ethylene (ethylene content 4.1%, MI90) and 30 parts by weight of dichlorodifluoromethane were placed in a closed container and heated to a temperature of 6.
After holding at 0°C for 4 hours to make the resin particles contain dichlorodifluoromethane, heating was performed for 30 seconds in steam at a pressure of 1.7/cA, 11.
The foamed particles of a random copolymer resin of propylene and ethylene which were expanded 9 times were prepared (fl). Furthermore, the foamed particles were heated in a closed container at a temperature of 80°C under an air pressure of 25 kq/cfl.
After holding the foam for 4 hours, it was heated for 30 seconds with steam at a pressure of 2.8 kg/c- to foam it to a size 35 times larger. The foamed particles thus obtained were placed in a closed container again at 20klj.
After holding at a temperature of 60°C for 4 hours under an air pressure of /d,
This foamed particle and adipic acid di-2
3.5% by weight of ethylhexyl was placed in a container equipped with a stirrer, and di-2-ethylhexyl adipate was applied to the surface of the foamed particles by stirring and mixing. The particles were filled into a mold at a pressure of 2.8' kq/cA and a temperature of 143
Heating was performed for 30 seconds with water vapor at °C to obtain a molded article with an expansion ratio of 45 times.

A cut with a depth of about 5 mm was made on the surface of this compact using a cutter, and the cut section was broken by hand. The ratio (hereinafter referred to as fusion rate) to the sum of the number of cracked particles was examined and found to be 90%.

Examples 2 to 6 After applying the organic compounds shown in Table 1 to the 35 times expanded foam of the random copolymer resin of propylene and ethylene obtained in Example 1, molding was performed in the same manner as in Example 1. ,
The fusion rate of the obtained foamed molded product was observed.

Comparative Examples 1 to 5 When no organic compound is applied in Example 1, and Example 1
Table IK also shows the results obtained by applying an organic compound having a lower boiling point than the compounds of -6 and molding in the same manner as in Example 1. In addition, in Comparative Example 1, the organic compound to be applied was
This is an example when one amount is used.

Comparative Example 6 No organic compound was applied to the expanded particles obtained in Example 1,
Fill the mold, pressure 2.8 kq/cd, temperature 150'
Heating was performed for 60 seconds (102 times as much as in the example) using water vapor of C to obtain a molded article with an expansion ratio of 45 times. The fusion rate of this molded body was 50%.

Table 1 (Note 1) Trade name: Niadekasizer E450 (manufactured by Adeka Argus Chemical Co., Ltd.) Examples 7 to 1O Similarly to Example 1, random copolymer particles of propylene and ethylene in which 1 m of dichlorodifluoromethane was added were , after applying each compound shown in Table 2 by mixing in a stirrer (=J container) at a pressure of 1.7 kg/
After foaming by heating with water vapor in step d,
After holding at a temperature of 80° C. for 4 hours under air pressure of kg/al, heating was performed for 30 seconds with steam at a pressure of 2.3 kg/d to obtain expanded particles having the magnification shown in Table 2. After holding each of these particles in a closed container at a temperature of 60 °C under an air pressure of 20 kqlc for 4 hours, they were filled into a mold and heated for 30 seconds with steam at a pressure of 2.8 kg/cm. I did it and molded it. The obtained foamed molded articles each had a fusion rate shown in Table 2.

Comparative Example 6.7 The results when applying a compound with a low boiling point are shown in Comparative Example 6.7.
It is also shown in Table 2.

Table 2 Examples 11 to 14, Comparative Example 8 Low density polyethylene (MI = 1.5, gel fraction 50%) containing dichlorodifluoromethane IO weight % was heated with steam to obtain expanded polyethylene particles. . The expanded particles were placed in a container at a pressure of 9 kg/cA.

After being kept in an air atmosphere at a temperature of 60°C for 2 hours, the internal pressure of the foamed particles was 1.8 kti/cd when taken out.
Met. The particles were coated with di-2-ethylhexyl adipate in the amounts shown in Table 8 by mixing in a container equipped with a stirrer, filled into a mold, and heated under a pressure of 1.5 k.
g/Cd, temperature 188°C, or pressure 2. Okt;//
Ca, heated with steam at a temperature of 140°C for 30 seconds, 27
A molded product twice as large was obtained. The fusion rates of these molded bodies were as shown in Table 3.

Patent applicant Kanebuchi Chemical Industry Co., Ltd.

Claims (9)

[Claims] (1) In a method in which polyolefin resin particles contain a blowing agent and are heated to form polyolefin resin foam particles, the polyolefin resin particles are filled into a mold and heated and molded, the polyolefin resin foam particles have a boiling point of 150°C or higher, A method for producing a polyolefin resin foam, which comprises coating or impregnating an organic compound with a melting point of 100°C or less. (2) The manufacturing method according to claim 1, wherein the polyolefin resin particles are resin particles containing a polypropylene resin as a main component. (3) The manufacturing method according to claim 2, wherein the polypropylene resin particles are resin particles whose main component is a random copolymer resin of propylene and ethylene. (4) The manufacturing method according to claim 1, wherein the organic compound is liquid at room temperature. (5) Solubility parameter value of organic compound is 6.0 to 10
．． 0. The manufacturing method according to claim 1, wherein (6) The manufacturing method according to claim 5, wherein the organic compound is a phthalate ester. (7) The manufacturing method according to claim 5, wherein the organic compound is a fatty acid ester. (8) The manufacturing method according to claim 5, wherein the organic compound is an aliphatic dibasic acid ester. (9) The manufacturing method according to claim 5, wherein the organic compound is an aromatic carboxylic acid ester. 01. The manufacturing method according to claim 5, wherein the organic compound is a fatty acid ester of glycerin. The manufacturing method according to claim 5, wherein the αV organic compound is an aliphatic hydrocarbon or a chlorinated paraffin. 04. The manufacturing method according to claim 5, wherein the organic compound is an aromatic hydrocarbon. Q3: The manufacturing method according to claim 1, wherein the organic compound is applied or impregnated with the polyolefin resin after foaming.