JPS5876233A - Manufacture of ethylene/propylene copolymer prefoamed particle - Google Patents

Abstract

PURPOSE:To obtain prefoamed particles having a larger cell diameter, by dispersing ethylene/propylene copolymer paticles containing a specific volatile foaming agent into a dispersion medium, heating the dispersion, and opening one end of a container containing the dispersion so that the dispersion is released into a low pressure atmosphere. CONSTITUTION:The volatile foaming agent contains dichlorodifluoromethane and trichlorofluoromethane in a molar ratio of 1.40-0.25. 10-40pts.wt. of said volatile foaming agent are incorporated into 100pts.wt. of the ethylene/propylene copolymer particles, and the mixture is dispersed into a dispersion medium such as water, ethylene glycol, etc. After the dispersion is heated to 90-170 deg.C, the polymer particles and the dispersion medium are simultaneously released into an atmosphere whose pressure is lower than in the container, so that prefoamed particles are obtained. The resulting prefoamed particles generally have an apparent foamed ratio of 3-60 and a cell number of 100/mm.<2> or below.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing ethylene-propylene copolymer pre-expanded particles.

The present applicant has already proposed a method for pre-foaming polymer particles (Japanese Patent Publication No. 56-1344).

In this method, polymer particles containing a volatile blowing agent are dispersed in water in a closed container, and while the pressure inside the container is maintained at the vapor pressure of the blowing agent or higher, the softening temperature of the polymer is increased. After heating to the above extent, preliminary foaming is performed by opening one end of the container below the water surface and simultaneously releasing the polymer particles and water into an atmosphere having a lower pressure than the inside of the container. Although the pre-expanded particles obtained by this method are revolutionary in terms of high foaming, there are still problems with shrinkage during molding due to the small cell diameter (large number of cells), flexibility of the resulting foam molded product, etc. This leaves room for improvement.

An object of the present invention is to provide a method for producing pre-expanded ethylene-propylene copolymer particles that is a further improvement over the pre-expanded particles of the prior art, and the present inventors have discovered that the pre-expanded particles have excellent properties. As a result of intensive research to obtain pre-expanded particles, we found that the average cell diameter (hereinafter referred to as cell diameter) is large (average cell number (
The present inventors have discovered that pre-expanded ethylene-propylene copolymer particles having excellent properties (hereinafter referred to as the number of cells) can be obtained, and have completed the present invention.

That is, in the present invention, the molar ratio of dichlorosiflomethane to trichlorosiflomethane is 1.40 to 0.25.
A step of incorporating a volatile blowing agent containing dichlorosiflomethane and F-lichlorosiflomethane into the ethylene-propylene copolymer particles, a step of dispersing the polymer particles in a dispersion medium and heating them, a step of dispersing the polymer particles in a dispersion medium, and heating the polymer particles. The gist of the present invention is a method for producing pre-expanded ethylene-propylene copolymer particles, which comprises a step of simultaneously releasing a dispersion medium into a low-pressure atmosphere from inside a container.

Examples of the ethylene-propylene copolymer used in the present invention include ethylene-propylene random copolymer, ethylene-propylene plotter copolymer, etc., and they may be either crosslinked or non-crosslinked, but non-crosslinked There are four benefits. This copolymer is polypropylene/
Dumb copolymers are preferred, and those with an ethylene acid content of 10 mM or less, preferably 5% by weight or less are particularly preferred. still,
Propylene homopolymer cannot be used because pre-expanded particles with large cell diameters cannot be obtained.

The volatile blowing agent used in the present invention contains dichlorosiftetramethane and tri-11furylomethane, and the molar ratio of dichlorosiftetramethane to tritaloloistetramethane is 1.40 to 0.25. If the molar ratio exceeds 1.40, the cell diameter will not be large, the shrinkage during molding will be large, and the softness of the foam molded product will be low, making it impossible to achieve the object of the present invention. If the molar ratio is less than 0.25, the plasticization of the pre-expanded particles by tri-11-furylomethane will be too large and the particles will fuse during pre-expanding, making it impossible to obtain a good foamed molded product. The amount of the foaming agent added varies depending on the desired degree of foaming, but is usually 10 to 40 parts by weight per 100 parts by weight of the copolymer particles. In the present invention, the volatile blowing agent basically consists of dichlorosiflomethane and trichloro70lomethane, but other blowing agents may be added as long as they do not impair the effects of the present invention.

In the present invention, the timing of incorporating the blowing agent into the polymer particles is not particularly limited. Therefore, the foaming agent may be contained in the polymer particles in advance, and the polymer particles containing the foaming agent may be placed in a closed container and dispersed in a dispersion medium in the closed container, or the polymer particles and the foamed The foaming agent may be contained in the polymer particles while the foaming agent is placed in a closed container and dispersed in the dispersion medium in the closed container (even in the latter case, the polymer particles containing the foaming agent are dispersed in the dispersion medium). (Needless to say, it is distributed). Alternatively, in the process of heating the particles to IJAIQ above the temperature at which they soften in a closed container, or after heating, a blowing agent is placed in the closed container and the blowing agent is applied to the particles while dispersing the particles and the blowing agent. may be included.

The temperature at which the foaming agent is added to the particles is also arbitrary and not particularly limited.

In the present invention, the polymer particles and the blowing agent are mixed separately or the blowing agent is contained in the polymer particles and then dispersed in a dispersion medium.
At this time, if necessary, dispersants such as fine particles of aluminum oxide and titanium oxide, basic magnesium carbonate, basic zinc carbonate, and calcium sulfate may be used. The amount of the dispersant added is usually 0.01 to 10 parts by weight per 100 parts by weight of the polymer particles. The dispersion medium used in the present invention may be any solvent that does not dissolve the polymer particles, and examples include one of water, ethylene glycol, glycerin, methanol, ethanol, etc., or a mixture of two or more thereof. Water is usually preferred.

In the present invention, after dispersing the polymer particles in a closed container, the polymer particles are heated to a temperature higher than the temperature at which the particles soften, but the heating temperature is within a range that does not destroy bubbles and allows suitable foaming. The temperature is selected as appropriate and is usually 90 to 170°C, although it varies depending on the type of polymer particles.

In the present invention, after heating the polymer particles, one end of the container is opened and the polymer particles and the dispersion medium are simultaneously released into a lower pressure atmosphere than the inside of the container, although there is no particular restriction on the temperature inside the container at this time. The pressure is usually higher than the heat deformation temperature of the polymer particles, and the pressure may be higher than or lower than the vapor pressure of the blowing agent, and is not particularly limited. The atmosphere in which the polymer particles and water are released is usually an atmosphere at normal pressure.

The pre-expanded particles of the present invention obtained as described above usually have an apparent expansion ratio of 3 to 60 times and a number of cells (large cell diameter) of 100/- or less.

The above-mentioned pre-expanded particles are then aged at room temperature and pressure for a predetermined period of time, and then pressure aged at a predetermined temperature and pressure using an inorganic gas or a mixed gas of an inorganic gas and a volatile blowing agent as needed. Internal pressure is applied within the particles. Examples of the inorganic gas include air, nitrogen, argon, helium, etc., but air is usually used.

The pre-expanded particles, which have been given internal pressure, are then filled into a mold,
By heating and expanding using water vapor of 2 to 5 to 9/cd (G), a foam molded product according to the shape can be obtained.

The resulting foam molded product can be used, for example, as packaging materials, cushioning materials, construction materials, vehicle components, heat insulating materials, flotation materials, food containers, and the like.

As explained above, since the pre-expanded particles obtained by the present invention have a large cell diameter (small number of cells), the foamed particles obtained using the pre-expanded particles do not shrink and have high flexibility (
It has good characteristics (having a strong backbone). Furthermore, pre-expanded particles are usually subjected to pressure ripening prior to molding, but the pre-expanded particles of the present invention have the advantage that inorganic gas can be easily introduced into the particles and the pressure ripening process can be shortened.

Hereinafter, the present invention will be explained in more detail with reference to Examples and Comparative Examples.

Examples 1 to 4 and Comparative Examples 1 to 3 Polymer particles, water, a volatile blowing agent, and particulate aluminum oxide were placed in a sealed container in the proportions and amounts shown in Table 1, and heated to 135 to 160°C while stirring. After raising the temperature to 1,
While maintaining the temperature and pressure shown in Table 1, one end of the container is opened and the polymer particles and water are released downward at the same time to perform preliminary foaming, and a preliminary foam having the expansion ratio and number of bubbles shown in Table 1 is prepared. Expanded particles were obtained. The obtained pre-expanded particles had excellent properties such as no fusion and large cell diameter (small number of cells). The fusion state during foaming is also shown in Table 1.

The obtained pre-expanded particles were aged at normal temperature and pressure for 50 hours, and then pressure aged at 20°C with air at 4 kf/-←) for 100 hours. After this, the pre-expanded particles are filled into a mold and each is filled with 2.5 ml (Random copolymer).
, 5.3 #/m1G) (block copolymer), 6
m/cd←) (homopolymer) by heating and expanding with water vapor pressure to obtain a foamed molded product having the expansion ratio shown in Table 1. The appearance of the obtained foamed molded product was observed, and the shrinkage rate and flexibility were measured. The results are shown in Table 2.

2 salary tables *1: A molded body with a thickness of 40 companies was used.

Procedural amendment (voluntary) December 7, 1980 Director General of the Japan Patent Office Shima 1) Haruki Tono1, Indication of the case 1982 Patent Application No. 1759892, Title of the invention Pre-expanded particles of ethylene-propylene copolymer Manufacturing method 3, relationship with the case of the person making the amendment Patent applicant 2-1-1 Uchisaiwai-cho, Chiyoda-ku, Tokyo Japan Styrene Paper Co., Ltd. Representative Kazuyoshi Nagano 4, Agent 101 Kanda Sakuma, Chiyoda-ku, Tokyo Town 2-7 5 Date of amendment order Voluntary amendment 6, Number of inventions increased by amendment None 1, Next to “Also shown” on page 9, line 2 of the specification, “The measurement of the number of bubbles is performed by cutting This was done by observing the surface with an electron microscope.'' Insert.

Written amendment to the above procedure (voluntary) February 20, 1980 Haruki Shimada, Commissioner of the Japan Patent Office 1. Indication of the case 1982 Patent Application No. 175989 2. Name of the invention Method for producing ethylene-propylene copolymer pre-expanded particles 1. Relationship with the case of the person making the amendment Patent applicant 2-1-1 Uchisaiwai-cho, Chiyoda-ku, Tokyo Japan Styrene Paper Co., Ltd. Representative Kazu Nagano 4th Director Managing Director 101 & Date of amendment order Voluntary amendment specification No. Correct "electron microscope" in the second line of page 9 to "microscope".

Claims (1)

[Claims] Dichlorosifu 0 lomethane trichloro 70! Dichlorosifu 0 with a molar ratio to methane of 1,40 to 0,25
a step of incorporating a volatile blowing agent containing lomethane and trichlormethane into ethylene-propylene copolymer particles; a step of dispersing the polymer particles in a dispersion medium and heating; and a step of opening one end of the container; 1. A method for producing pre-expanded ethylene-propylene copolymer particles, comprising the step of simultaneously releasing polymer particles and a dispersion medium from inside a container into a low-pressure atmosphere.