JPS5876229A - Manufacture of polypropylene resin foamed and molded body - Google Patents

Abstract

PURPOSE:To improve the dimensional stability, pulling strength and tear strength, by filling a mold, which can be closed, but not be tightly closed, with polypropylene resin prefoamed particles, heating the prefoamed particles to be allowed to foam, and heating the molded body to a temperature >= its heat distorsion temperature. CONSTITUTION:The prefoamed particles are produced by incorporating 5- 40pts.wt. volatile foaming agent such as aliphatic hydrocabons, cycloaliphatic hydrocarbons, halogenated hydrocarbons, etc. into 100pts.wt. polypropylene polymer such as ethylene/propylene random copolymer, propylene monopolymer, etc. The prefoamed particles are matured at normal temperature under normal pressure, and then are matured under a prescribed pressure for a prescribed period using an inorganic gas. Then the mold having tiny holes in the surface is filled with the prefoamed particles, and the prefoamed particles are heated and allowed to foam using steam of 2-5kg/cm<2>G to obtain a foamed and molded body.

Description

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

The present applicant has successfully developed a bead molding method using pre-expanded particles in producing polypropylene resin foam moldings, and has already proposed the pre-foaming method tζ (Japanese Patent Publication No. 56-1344 issue).

This pre-foaming method involves dispersing a single coalesced particle containing a volatile blowing agent in a closed container, maintaining the pressure inside the container at the vapor pressure of the blowing agent or higher, and raising the temperature to a temperature higher than the softening temperature of the polymer. After heating, one end below the water surface in the container is opened, and the nine-layer particles and water are simultaneously discharged into the container and into a low-pressure atmosphere, thereby obtaining pre-expanded particles. The pre-expanded particles obtained by this method are revolutionary and have excellent properties of high foaming, and the foamed molded products obtained using these pre-expanded particles have excellent properties. There is still room for improvement in dimensional stability such as shrinkage, especially when used as a soothing material, heat insulating material, heat insulating material, etc. at high temperatures.

The object of the present invention is to provide a method for producing a polypropylene resin foam molded product that is a further improvement over the above-mentioned conventional technology.

As a result of intensive research in order to achieve the above object, 1. The foam molded body was heat treated at a specific temperature or higher.

He discovered that it was possible to obtain a polypropylene resin foam molded product with dimensional stability, and also succeeded in developing a method for producing VC, thereby completing the present invention.9.

In other words, in the present invention, pre-expanded particles of a poly-10-pyrene resin are filled into a mold that can close the particles but cannot be sealed, and are heated and foamed to obtain a foamed molded product, followed by limb foam molding. The gist of the present invention is a method for producing a polyglopylene resin foam molded body, which is characterized by heating the body to a temperature higher than the heat deformation temperature of the cough molded body.

The material for the pre-expanded polypropylene resin particles used in the present invention is a propylene homopolymer.

Examples include ethylene-propylene random copolymer and ethylene-propylene block copolymer.

These may be crosslinked or non-crosslinked, but non-crosslinked ones are beneficial. Among the above mentioned polymers.

An ethylene-propylene random copolymer is preferred, and a copolymer having an ethylene component of 0.5 to 10% by weight is particularly preferred.

The pre-expanded polypropylene resin particles used in the present invention can be produced, for example, by the following pre-expanding method. In other words, there is a step of incorporating a volatile blowing agent into the bipolymer particles, 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. It can be manufactured using a pre-foaming force fJ211C which consists of a step of simultaneously releasing the foam into an atmosphere having a lower pressure than that in the container.

Volatile blowing agents used in this method include aliphatic hydrocarbons such as propane, butane, pentane, hexane, hegetane, etc., and cyclic aliphatic hydrocarbons such as cyclobutane/clopentane. and trichlorofluoromethane, dichlorosiphon, cyclotetophylfluoroethane.

Laterally combed with methyl chloride, ethyl chloride, methylene chloride, etc., etc., are used. The amount of the blowing agent added is usually about 5 to 40 parts by weight per 100 parts by weight of the polymer.

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 incorporated into 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 0.01-10 parts by weight per 100 parts by weight of the polymer particles. Further, the dispersion medium may be any solvent as long as it does not dissolve the polymer particles.

For example, water, ethylene glycol, glycerin.

One or two of methanol, ethanol, etc.
Although a mixture of more than one species is exemplified, water is usually preferred.

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. The temperature at which the foaming agent is vaporized may be higher than or lower than the vapor pressure of the blowing agent.
Pressure 2 Although it varies depending on the amount of foaming agent, etc., it usually has an apparent foaming ψ wheel of 3 to 60 times.

The above pre-expanded particles are aged at room temperature and pressure for a predetermined time and then pressurized at a predetermined pressure for a predetermined time using an inorganic gas such as nitrogen, air, t, or a mixed gas of an inorganic gas and a volatile blowing agent. be matured.

In the present invention, the pre-expanded particles to which internal pressure has been applied by the above-mentioned pressure aging are used in a mold 1 for molding which can close the particles but cannot be sealed.Usually, a heating medium such as water vapor is passed through the mold surface. Fill it into a mold with small holes, for example 2 to 5k.
A foamed molded product is obtained by heating and foaming with i9/cJ (G) water vapor.

In the present invention, the foamed molded product is heated to a temperature equal to or higher than the heat deformation temperature of the molded product to shrink it. When the heating temperature is lower than the heat distortion temperature, the foamed molded product does not shrink and it is difficult to obtain dimensional stability of the foamed molded product.

The degree of shrinkage of the molded product due to the above-mentioned heating is not particularly limited, but in consideration of the effect of one-dimensional stability, uniformity of shrinkage, etc., it is preferable to shrink the molded product by 3 to 35 degrees from its original volume. Heating again! I11. Although the temperature was higher than the heat distortion temperature, when the temperature was relatively cool, the thickness of the foam molded product varied.92
Because the surface tends to be uneven and not shrink uniformly,
Although it varies depending on the material of the molded body, the temperature is preferably 100 to 140°C.

9 The heat distortion temperature of each polymer used in the present invention is 90~
Preferably, the temperature is in the range of 130°C.

An example is shown below.

Base material Heat distortion temperature ('C) ethylene-
Propylene random copolymer 103 (ethylene component: 4% by weight) Ethylene-propylene block copolymer 1
15 (Ethylene component = 20% by weight) Propylene homopolymer 117 In the present invention, 2 Methods of heating the foam molding include 9 For example, a method of storing the foam molding in a heating furnace and heating 2. In the method of heating while applying a constant load, or the method of heating while applying a constant load,
A method is used in which a pattern or the like is applied to the outer box while shrinking the foam molded product by applying a load using a material with a suitable pattern or the like. The 1j42 foam molded product is cooled after the heat treatment, and this cooling method may be slow cooling, rapid cooling, or a combination thereof.

Examples of the foamed molded products obtained according to the present invention are as follows.

It can be used for packaging materials, cushioning materials, heat retaining materials, insulation materials, building materials, wheel members, flotation materials, etc., and is particularly effective when used at high temperatures.

As explained above, according to the present invention, it is possible to shrink a foam molded product by heating it at a temperature higher than the heat deformation temperature of the molded product to improve dimensional stability, and to prevent shrinkage, etc., especially when used at high temperatures. It is possible to obtain a foamed molded article which has excellent thermal dimensional stability without causing any damage, and has improved physical properties such as tensile strength, tensile elongation, tear strength, and compression set.

The present invention will be explained in more detail below with reference to Examples and Comparative Examples.

Examples 1 to 5 and Comparative Examples 1 to 4 Average weight 5 m & degree of thermal deformation as particles 96°C (melting point 15
0℃) ・Ethylene-propylene random copolymer iookg with 3.5% ethylene component, dichlorodifluoromethane 23, and aluminum oxide with a particle size of 9.20μ = 2A 0.5
kg + 300kl of water? was stored in a sealed container, the temperature was raised to 139°C #C under stirring and held for 05 hours, and one end of the container was opened while maintaining the pressure inside the container at approximately 30 #/aJ(G)K. The polymer particles and water were simultaneously discharged into the atmosphere to obtain pre-expanded particles with an expansion ratio of 35 times. The obtained pre-foamed powder was aged under pressure at 30°C for 50 hours in air at 2.5 kg/cIi (G).

1000111X 600WX 6011II filling mold for molding, 2. A foam molded product was obtained by heating and foaming using water vapor of skp/aj (c). The obtained foam molded product was heat-treated at the heating temperature shown in Table 1 for 20 hours. Various physical properties were measured for the finished product after heat treatment.

The results are also shown in Table #I1.

*1 Volumetric shrinkage rate was measured using a hot air dryer (manufactured by Yawa Riko).
This is the rate of change in expansion ratio after heating at a target temperature and cooling.

*2 - The variation in thickness was determined using the following formula, and the ranks were determined as shown below.

Q-Less than 5 △-5 ~ Less than 15 yo I judged it.

Q - 5 or less Δ - 6 or more and 30 or less × - 31 or more *4 - Flexibility was measured by NDS method and judged as Shitamachi.

〇 - No change 8 - Some cracks and fissures occurred between particles × - Fracture * 5 - The thermal deformation state was heated at a temperature of 110°C for 22 hours according to JIS K6767 K, and the thermal deformation rate was calculated using the following formula. By]
Find 4 as below! tl was determined.

0 to less than 5 inches △ -5 inches to less than 10 inches x -10 inches or more *6.7.8.9 - Tensile strength [O and tensile elongation are JIS
According to K6767A - Tear strength and compression set were determined as #j according to JIS K6767.

*10-h joint price was determined based on the following criteria.

◎－Everything is O △－／Those with / Something with x −X

Claims (1)

[Claims] Pre-expanded polyglupyrene resin particles are filled into a mold that can close the particles but cannot be sealed, and are heated and foamed to obtain a foamed molded product. A method for producing a polypropylene resin foam molded article, the method comprising heating the polypropylene resin foam to a temperature above.