JPS5852328A - Production of polypropylene resin foam - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a polypropylene resin foam molded article.

BACKGROUND ART Conventionally, as a method for obtaining a polyolefin resin 2 such as a polyethylene resin foam molded article, a method using pre-expanded particles obtained from crosslinked polyethylene resin particles has been known. In this method, a constant internal pressure is applied to the pre-expanded particles regardless of the expansion ratio of the pre-expanded particles, and then the particles are molded to obtain a foamed molded article.

On the other hand, regarding polypropylene resin, it has great mechanical strength and heat resistance as its own properties.

Due to its excellent properties such as chemical resistance, oil resistance, low temperature properties, and low-temperature properties, it has been desired to develop a foam molded product. Although products in the shape of fibers are manufactured, it was not possible to obtain products in the shape of multiple fibers. However, the applicant conducted further research and obtained a molded article using pre-expanded particles. We have successfully developed a so-called bead molding method, and have previously proposed a method for manufacturing pre-expanded particles and a method for manufacturing molded objects using it. Therefore, as a result of further investigation to obtain a method for manufacturing improved molded bodies, we found that polypropylene resin pre-expanded particles can be molded by applying a constant internal pressure to the particles regardless of the expansion ratio, as in the case of polyethylene resin. However, it has been found that it is generally difficult to obtain a molded body with a good welding state and no shrinkage.

An object of the present invention is to provide a method for producing a polypropylene resin foam molded product having excellent properties and good properties, and in order to achieve the above object, the present inventors have developed an internal pressure of pre-expanded particles. As a result of intensive research focusing on the relationship between foaming ratio and foaming ratio, we succeeded in establishing a method for producing a suitable foamed molded product with excellent properties, and completed the present invention.

In other words, in the present invention, the internal pressure of pre-expanded particles and the apparent expansion ratio are expressed by the formula: 0.01 m4F! 0.5 xi (in the formula.

P is the internal pressure of pre-expanded particles (Y/j (G)) -vn F
i The appearance of pre-expanded particles indicates the expansion ratio. The gist of the present invention is a method for manufacturing a polypropylene resin foam molded article, which is characterized by molding using pre-expanded polypropylene resin particles having the relationship expressed by the following.

The base resin of the pre-expanded polypropylene resin particles used in the present invention includes a propylene homopolymer and an ethylene-propylene random copolymer.

Examples include ethylene-propylene block copolymer configuration,
These may be either crosslinked or non-crosslinked, but non-crosslinked ones are particularly useful.

The pre-expanded polypropylene 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 the bipolymer particles, 1! F consists of a step of dispersing polymer particles in a dispersion medium and heating it to a predetermined temperature in a closed container, and a step of opening one end of the container and simultaneously releasing the particles and the dispersion medium into an atmosphere at a lower pressure than inside the container. It can be produced by a pre-foaming method.

Volatile blowing agents used in this method include 2, aliphatic hydrocarbons such as propane, butane, pentane, hexane, heptane, etc., cyclobutane, cyclopenta7, etc.
etc., and trichlorofluoromethane, dichlorosifu 0 romethane, dichlorosifu 0 romethane, etc.
Lomethane.

Halogenated hydrocarbons such as methyl chloride, ethyl chloride, methylene chloride, etc. are used. The amount of this blowing agent added is not determined by ll#, but is usually 5 to 30 parts by weight per 100 parts by weight of the polymer particles. Used frequently. There is no particular limitation on the timing of incorporating the volatile blowing agent into the polymer particles.

Therefore, the polymer particles should contain a foaming agent in advance.

The polymer particles containing the blowing agent may be placed in a closed container and dispersed in a dispersion medium within the closed container.

Alternatively, the polymer particles and the blowing agent may be placed in a closed container and dispersed in a dispersion medium in the closed container so that the polymer particles contain the blowing agent. In addition, in step 1.1 of heating the particles to a predetermined temperature in a sealed II container, or after heating, a blowing agent is placed in the airtight container and the blowing agent is applied to the particles while dispersing the particles and the blowing agent. It may be included. The temperature at which the blowing agent is incorporated into the particles marked with * is also arbitrary.

It is not limited to nutrition.

In this method, 1 polymer particles and a volatile blowing agent are separately dispersed, and the volatile blowing agent is incorporated into the polymer particles, and then dispersed in 2 dispersion media. Aluminum oxide and titanium oxide, basic acid! Gnesium, basic zinc sulfate, calcium sulfate, etc. can be used.

The amount of this dispersant added is usually 1 polymer particle 100 weight 11
The amount is 0.01 to 10 parts by weight. The dispersion medium may be any solvent that does not dissolve the polymer particles.For example, one of water, ethylene glycol, glycerin, methanol, and ethanol, or a mixture of two or more thereof, is exemplified, but it is usually used. Water is preferred.

In this method, one end of the container is opened and the polymer particles and the dispersion medium are mixed at the same time. It is discharged into an atmosphere with a lower pressure than the inside of the container, but the pressure inside the container at this time may be either higher than or lower than the vapor pressure of the volatile blowing agent.The atmosphere to be discharged is normally selected to be a normal pressure atmosphere.

The pre-expanded particles obtained in this manner usually have an apparent expansion ratio of 3 to 60 times, although this varies depending on the temperature, pressure, etc. at the time of one expansion.

Inside this pre-expanded particle, for example, 3 to 72
0.3 to 8 kg/f
f1 (G) for 3 to 72 hours, and this pressure aging causes KO33 to 51'#/aII (
G) An internal pressure of preferably 3 kf/j (G) or less is applied.

Here, the inorganic gases are air, nitrogen, and argon.

Helium or the like is used.

Note that, if the pre-expanded particles have pressure ripening*KL and a suitable internal pressure, pressure ripening is not necessary.

In the present invention, the internal pressure of the pre-expanded particles and the apparent expansion ratio are calculated using the formula: 0.01≦P0.5 m (wherein, the internal pressure of the P-expanded pre-expanded particles (Y/m (G)) 2 m is The appearance of the pre-expanded particles indicates the expansion ratio.] Pre-expanded polypropylene resin particles are used which have the following relationship.

If the internal pressure is less than 0.01 m or more than 0.5 m, the fusion state may be poor due to the normal amount of water vapor during molding (1).
(If it exceeds 0, Sia, the fusion inside the molded body is poor), a good molded body cannot be obtained, and if the amount of water vapor is increased to improve the fusion state, the shrinkage of the molded body increases. It is not practical, and since it uses a large amount of water vapor, it requires a large amount of cooling water, which ultimately consumes a large amount of energy, resulting in high costs and reduced productivity. The internal pressure and appearance of pre-expanded particles are the expansion ratio f14IK, and the preferred range is the formula:
The range is 0.015 m≦P≦0.1 m (in the formula, P and blades have the same meanings as above).

The real deal! In jl, the apparent expansion ratio of the pre-expanded particles is the reciprocal of the apparent density of the pre-expanded particles divided by the resin density of the polymer particles. Here, the density of the pre-expanded particles is determined by filling a graduated cylinder with a pre-expanded volume with the pre-expanded particles and keeping the weight constant, for example, 1 weight/volume.

In the present invention, when the internal pressure of the pre-expanded particles is imparted by, for example, pressure aging, and the gas introduced into each particle is, for example, air, the internal pressure of the pre-expanded particles is determined by the following formula: 0.082 gas constant, t is temperature.

1.0332 indicates a coefficient for converting *tm- to yu/-. ) K) can be found.

When molding is performed using the pre-expanded particles as described above, the pre-expanded particles are filled into a mold that can be closed but cannot be sealed, and then filled with water vapor of 1.0 to 1.0 to L5 kII/cj (G) o. A m;11 orttm body can be obtained by heating and expanding the m;

The BOPP propylene resin foam molded product obtained by the present invention can be used as a buffering material, a packaging material, a vehicle component, II construction material 1 food*a
It can be used for insulation materials, flotation materials, etc.

As explained above, the present invention specifies the apparent expansion ratio and internal pressure of 0@, and uses pre-expanded particles to achieve a good fusion state of the particles during molding. It is possible to obtain a foamed molded product with excellent properties and less shrinkage.

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

Examples 11 to 6 and Comparative Examples 1 to 5 Ethylene-propylene random copolymer resin particles (Example 1
1-6) 100 parts by weight, dichloromethane in the amounts shown in Table 1, 0.5 parts by weight of aluminum oxide and 2 parts by weight of water.
50 parts by weight was placed in a closed container, and the temperature was raised to the predetermined temperature shown in Table 1 while stirring.

While maintaining the pressure inside the container at about 30 ky/j (G)K, open one end of the container, release the resin particles and water into the atmosphere at the same time, and dry them to give the apparent foaming ratio shown in Table 1. Various pre-expanded particles were obtained.

The obtained pre-expanded particles were left at room temperature and pressure for 5 hours, and then heated at 25°C for 0.3-6. Pressure aging was carried out for 50 hours in Ok&/j (G) air to give the internal pressure shown in Table 1. After that, fill the mold for forming waterfall and 13 to 6.5 yu/j.
Perform the acid layer at the water vapor pressure of (G). The degree of fusion and shrinkage of the resulting specimen was examined.

Claims (1)

[Claims] The internal pressure and apparent expansion ratio of pre-expanded particles are expressed by the formula: 0.01m
≦P≦0.5 wL (in the formula, the internal pressure of Company P pre-expanded particles (
k#/aj(G)), the appearance of pre-expanded particles from 11 companies indicates the expansion ratio, respectively. ) A method for producing a foamed polypropylene resin laminate, which involves treating pre-expanded polypropylene resin particles with an acid moiety.