JPS58215327A - Manufacture of polyolefin resin molding foamed in force - Google Patents

Abstract

PURPOSE:To mass produce a foamed molding with limited use of energy employing a small equipment by heat foaming more than one kind of polyolefin resin prefoamed particles different in the internal pressure after it is mixed to fill a force. CONSTITUTION:100pts.wt. of ethylene-propylene random copolymer particles, 10- 20pts.wt. of dichlorodifluoromethane, 1pt.wt. of fine grannular aluminum oxide and 100pts.wt. of water are placed into an autoclave and heated under agitation. After it is heated to 140-150 deg.C, one end of the vessel is opened and the polymer and water are released under the atmosphere simultaneously to obtain prefoamed particles, a part of which is imparted an internal pressure by pressure curing. The prefoamed particles pressure cured and not fill a force at a specified mixing rate and undergoes a heat foaming with the steam of 2.6kg/cm<2>G to obtain a foamed molding.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a polyolefin resin indoor foam molded product.

Conventionally, synthetic resin foam moldings 2 such as polystyrene foam moldings and polyethylene foam moldings have been used in a wide variety of applications such as packaging materials and cushioning materials. These foam molded bodies are produced, for example, by extrusion molding or by the so-called bead molding method using pre-expanded particles. (bead molding method here) When obtaining a polyolefin resin foam molded product, after producing the pre-expanded particles, pressure aging is performed to impart a desired internal pressure to the pre-expanded particles, and then the pre-expanded particles are molded. It was filled into a mold and heated and foamed to obtain a foamed molded product. However, this method has the disadvantage that it is necessary to expand equipment such as pressure tanks for pressure aging as the production volume of foam moldings increases, and the energy used for pressure aging also increases. be.

The purpose of the present invention is to provide a method for producing a polyolefin resin indoor foam molded product that eliminates the drawbacks of the above-mentioned prior art. By mixing and using two or more types of pre-expanded particles with different values, it is possible to produce in large quantities without increasing the size of equipment such as pressurized tanks, and the amount of energy used is small. They discovered that foam molded products have moldability and physical properties that are equal to or better than conventional products, and also succeeded in developing a manufacturing method (7), leading to the completion of the present invention (2).

In other words, the gist of the present invention is a patented method for producing an in-mold foamed olefin resin article, which is characterized in that pre-expanded polyolefin resin particles of 2 seconds or more with different internal pressures are mixed and filled into a mold and then heated and foamed. It is.

In the present invention, the material of the pre-expanded polyolefin resin particles is 2, for example, low density polyethylene (hereinafter referred to as LDP).
It is abbreviated as E. ), linear low-density polyethylene (hereinafter referred to as L
It is abbreviated as LDPE. ).

Polyethylene and polypropylene homopolymers such as high-density polyethylene (hereinafter abbreviated as HDPE).

Polypropylene resins such as ethylene-globylene copolymers, ethylene-α-olefin co-X polymers.

Examples include propylene-α-olefin copolymer, ethylene-butadiene copolymer, and polybutene. Both crosslinked and non-crosslinked polyolefin resins can be used, but non-crosslinked ones are advantageous.

The pre-expanded polyolefin resin particles used in the present invention can be produced, for example, by the following pre-expanding method. That is, a step of incorporating a volatile blowing agent into one polymer particle, a step of dispersing the polymer particles in a dispersion medium in a closed container and heating it to a predetermined temperature, and a step of opening one end of the container and dispersing the particles and the dispersion medium. At the same time, the inside of the container can also be manufactured by a pre-foaming method comprising a step of releasing the foam into a low-pressure atmosphere.

Volatile blowing agents used in this method include 2, for example, aliphatic hydrocarbons such as propane, butane, pentane, hexane, heptane, etc., cycloaliphatic hydrocarbons such as cyclobutane, cyclopentane, etc.; Halogenated hydrocarbons such as trichlorofluoromethane, dichlorofluoromethane, dichlorotetrafluoroethane, methyl chloride, ethyl chloride, methylene chloride, etc. are used. The amount of the blowing agent added is usually 5 to 40 parts by weight per 100 parts by weight of the polymer particles.

In this method, the polymer particles and the volatile blowing agent are dispersed in a dispersion medium either separately or after the volatile blowing agent is contained in the polymer particles. Also, titanium oxide, basic magnesium carbonate, basic zinc carbonate, calcium carbonate, etc. can be used. The amount of this dispersant added is usually 10 polymer particles.
The amount is 0.01 to 10 parts by weight relative to 0 parts by weight. The dispersion medium may be any solvent that does not dissolve the polymer particles2.For example, water, ethylene glycol, glycerin, methanol, ethanol, etc., or a mixture of two or more thereof, may be used as the dispersion medium, but water is usually used. preferable.

In this method, one end of the container is opened and the polymer particles and dispersion medium are simultaneously released into an atmosphere with a lower pressure than the inside of the container. At this time, the temperature inside the container is preferably 90 to 170°C, and the pressure is volatile. The pressure may be higher than or lower than the vapor pressure of the blowing agent, and the atmosphere to be discharged is normally selected to be at normal pressure.

The pre-expanded particles obtained in this way vary depending on the amount of volatile blowing agent, temperature, pressure, etc., but are usually 0.01 to 0.
．． It has a density of 597 crl.

The obtained pre-expanded particles are aged at room temperature and pressure if necessary.
Next, if necessary, the pre-expanded particles are placed in a pressurized tank or the like, and subjected to pressure ripening using an inorganic gas or a mixed gas of an inorganic gas and a volatile blowing agent to impart internal pressure within the particles. Examples of inorganic gases include air.

Nitrogen, argon, helium, etc. are used.

In the present invention, two or more types of pre-expanded particles with different internal pressures are used; one is usually one that has been given internal pressure by pressure aging, and the other that is prepared immediately after production without pressure aging, or at room temperature and normal pressure. Use matured ones. The internal pressure of the pre-expanded particles subjected to pressure aging is not particularly limited, but is between 0.5 and 1.
A range of 0 klil/1 (G) is preferred. Internal pressure is 0.5
kl? /cj (G), there is a tendency that the effect of reducing the volume of the pressurized curing tank cannot be achieved, and if the internal pressure exceeds xokg/1 (G)t-, the maintenance state of the particle internal pressure becomes unstable and the molding conditions The tolerance range tends to be extremely narrow.

In the present invention, the internal pressure of the pre-expanded particles is determined by the following formula:
It's what I asked for.

(In the formula, Wp is the weight of the pre-expanded particles after pressure ripening, Wo
is the weight of pre-expanded particles sufficiently aged under normal pressure, 0.082
is a gas constant, t is the temperature at the time of measurement, and 1.0332 is a coefficient for converting the atmospheric pressure into 9/-. ) When mixing and filling the above pre-expanded particles into a mold, the mixing ratio (volume) of particles A with high internal pressure and particles B with low internal pressure.
A:B is not particularly limited, but is preferably in the range of 1:10 to 3:1. In addition, it is preferable that the pre-expanded particles be mixed and filled in a dispersed state so that particles with the same internal pressure do not aggregate, and it is preferable to use particles made of the same material. Similarly, three or more types of pre-expanded particles having different internal pressures may be mixed,
Two types of pressure-ripened products may be mixed.

In the present invention, as the molding mold, for example, a normal molding mold having a large number of small holes on the mold surface through which a heating medium passes can be used.
The pre-foamed particles are heated and foamed using water vapor of 0 kg/at (G) to obtain a molded foamed product.

The polyolefin resin in-mold foam molded product obtained by the present invention can be used for, for example, packaging materials, cushioning materials, heat insulating materials, heat insulating materials, N construction materials, vehicle parts, flotation material 2 food containers, and the like.

As explained above, 1. According to the present invention, 2.
Since an in-mold foamed product is obtained using pre-expanded particles of polyolefin resin of more than 100%, there is no need to pressurize and ripen all the pre-expanded particles, so production can be increased without expanding equipment such as pressurized tanks. It has the advantage of being able to do this, and requires less effort, energy, etc.
Furthermore, the foamed molded product obtained by the present invention has moldability, appearance, and physical properties that are equivalent to or better than those of conventional products.

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

Examples 1 to 4 100 parts by weight of ethylene-propylene random copolymer particles containing 2.5% ethylene component, dichlorosif a, four mep
Put 710 to 20 parts by weight, 1 part by weight of finely divided aluminum oxide, and 300 parts by weight of water into an autoclave, stir and heat to raise the temperature to 140 to 150'C, then open one end of the container to separate the polymer particles and water. It is released into the atmosphere at the same time and the density becomes 0.
．． Pre-expanded particles of 03-0, osg/cd were obtained.

The obtained pre-expanded particles were aged for 48 hours at normal temperature and pressure, and then a portion thereof was placed in a pressurized tank and aged under pressure with air to give the internal pressure shown in Table 1.

Next, the pre-expanded particles that were subjected to pressure aging and those that were not subjected to pressure aging were mixed at the mixing ratio shown in Table 1, and were made into 3001 mm long x 30 mm wide particles.
Mixed and filled into a mold of cm x 30 cm thick,
A foamed molded product was obtained by heating and foaming with 2.6'q/cd (G) steam. The moldability and appearance of the resulting foamed product were good), and the amount of pressurized tanks required was only 1/2 to 1/3 compared to the conventional method.

Examples 5 and 6 MI=instead of ethylene-propylene random copolymer
2.1, mp = 122°C, d = 0.930
Pre-expanded particles were obtained in the same manner as in Example 1 except that LLDPE of l/ad was used. A part of the obtained pre-expanded particles was placed in a pressurized tank and aged under pressure with air to give the internal pressure shown in Table 1.

Pre-expanded particles subjected to pressure ripening and pre-expanded particles not subjected to pressure ripening were mixed and filled into the same molding mold as in Example 1 at the mixing ratio shown in Table 1.

1.5 kg/c! A good foam molded product was obtained by heating and foaming with the steam of IL(G). The moldability and appearance of the obtained foamed product were good, and the amount of pressurized tank required was only 1/2 to 1/3 compared to the conventional method.

Claims (1)

[Claims] A method for producing an in-mold foamed polyolefin resin article, which comprises mixing and filling two or more pre-expanded polyolefin resin particles having different internal pressures into a mold and then heating and foaming them.