JPS62132942A - Expanded polypropylene based resin particle - Google Patents

Abstract

PURPOSE:Polypropylene based resin particles, consisting of a propylene-alpha-olefin random copolymer and specific ethylenic copolymer, having improved foaming property, moldability and containing expanded particles having uniform and coarse cells. CONSTITUTION:Expanded polypropylene based resin particles obtained by blending (A) 80-99pts.wt. propylene-alpha-olefin random copolymer with 0.5-30wt%, preferably 1-20wt% content of an alpha-olefin, e.g. ethylene or butene-1, etc., and 0.1-50g/10min melt index with (B) 0.1-20pts.wt., preferably 0.5-10pts.wt. ethylenic copolymer having (B1) 65-98.5% ethylene constituent units, (B2) 1-30wt% ester constituent units selected from alkyl (meth)acrylates having 1-8C alkyl group and (B3) 0.5-10wt% unsaturated dicarboxylic acid anhydride constituent units and further blending the resultant polypropylene based resin particles with an evaporation type foaming agent, e.g. propane, etc.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Field of Application> The present invention relates to foamed polypropylene resin particles that have excellent foamability and moldability, and have uniform and coarse cells.

<Prior art> Generally, polypropylene has excellent properties such as excellent heat resistance and chemical resistance, high mechanical strength, greater flexibility than polystyrene, and greater rigidity than polyethylene. Therefore, many attempts have been made to obtain foam molded products using polypropylene having such excellent properties, and sheet-like foam products by extrusion molding and foam products by bead molding have been obtained.

It is known that an ethylene-propylene random copolymer or a mixture of a copolymer containing the copolymer as a main component and a low-density polyethylene and/or an ethylene-vinyl acetate copolymer can bead-foamed without crosslinking. (Unexamined Japanese Patent Publication No. 5
7-90027, JP-A-58-65784).

According to these methods, expanded particles can be obtained relatively easily from polypropylene resin particles, but they have the following problems, and there is still room for improvement. That is, <1) It is difficult to obtain a product with a high expansion ratio.

(2) Due to poor viscoelastic fluidity and narrow temperature range for foaming, it is technically difficult to foam: /L
(8) The cells in the resulting expanded particles tend to be fine. Therefore, even if a molded object is obtained using such foamed particles, it is difficult to obtain a strong foam with good dimensional accuracy.
There was a problem with J.

<Problems to be Solved by the Invention> Under the present circumstances, one problem to be solved by the present invention is that the purpose of the present invention is to easily obtain foamed particles with a high expansion ratio from polypropylene resin particles, and to reduce the air bubbles of the foamed particles. The purpose of the present invention is to provide foamed polypropylene resin particles that are uniform and rough.

<Means for Solving the Problems> The present invention provides: (A) a propylene-α-olefin random copolymer having an α-olefin content of 0.5 to 80% by weight, 80 to 99% by weight;
(b) 66 to 98.5% by weight of ethylene structural units, 1 to 80% by weight of ester structural units selected from alkyl acrylates or alkyl methacrylates having an alkyl group having 1 to 8 carbon atoms, and unsaturated Dicarboxylic anhydride'P
A substance characterized by foaming polypropylene resin particles comprising 0.5 to 20 parts by weight of an ethylene copolymer containing 0.5 to 103 JZ4 component units using an evaporative foaming agent. These are non-crosslinked polypropylene resin foam particles that solve the above-mentioned conventional problems.

The present invention will be explained in detail below.

Propylene-α-olefin random co-shinto polymer used in the present invention, α-olefin content is 0.5 to 80 weight s
% preferably 1 to 20% by weight, melt index (
Ml) is 0.1-60F/10 min, preferably 1-2
It is a binary or 8-component random copolymer with 0 p/10 min.

Examples of the α-olefin include ethylene, butene-11hexene-1,8-methyl-butene-1°4-methyl-pentene-11octene-1, and decene-1. For example, a propylene-α-olefin random copolymer may be used.

Propylene-ethylene copolymer, propylene-butene-
1 copolymer, propylene-4-methyl 81funtene-11#ltf combination, and propylene-ethylene-butene-1 copolymer are preferably used.

Next, the ethylene copolymer used in the present invention is as follows:
66 to 98.6% by weight of ethylene NII constituent units, 1 to 80 M of ester constituent units selected from alkyl acrylates and alkyl methacrylates having an alkyl group having 1 to 8 carbon atoms, and unsaturated dicarboxylic anhydride constituent units. It has a weight of 0.5 to 10%.

Examples of monomers having ester structural units contained in the ethylene copolymer include methyl acrylate, ethyl acrylate, butyl acrylate, methyl methacrylate, ethyl methacrylate, 2-ethylhexyl methacrylate, and butyl methacrylate (hereinafter referred to as unsaturated ester compounds). and mushrooms).

The solder of the ester structural unit contained in the ethylene copolymer is preferably 1 to 80 Wites1, preferably 2 to 253K.
It is in the range of jX%. Outside this range, propylene-α-
The compatibility of the olefin coconjugate is affected, which is not preferable.

Examples of the leather body having an unsaturated dicarboxylic anhydride constituent unit include maleic anhydride, citraconic anhydride, itaconic anhydride, and tetrahydrophthalic anhydride, among which maleic anhydride is most preferably used.

The content of these unsaturated dicarboxylic anhydride structural units in the ethylene copolymer is 0.5 to 10% by weight,
Preferably, it is in the range of 1 to 5 weight. If it is less than the lower limit, there will be insufficient polar groups and the improvement effect will be lacking, and if it is more than the upper limit, the polarity will be too strong and it will not be compatible with the propylene-α-olefin copolymer.

The method for producing the ethylene copolymer is not particularly limited, and known methods such as melt polymerization, emulsion polymerization, and high-pressure bulk polymerization can be used. Among these, the most common is a high-pressure polymerization method in which copolymerization is carried out with ethylene in the presence of a radical generator at 500 to 8,000 atm and 100 to 800°C in the presence or absence of an appropriate solvent or chain transfer agent. It is. In such a high-pressure polymerization method, a suitable method is to pressurize a solution of the above-mentioned unsaturated dicarboxylic anhydride dissolved in the above-mentioned unsaturated ester compound using a high-pressure pump and directly transport it into a cypress-shaped or tubular reactor. . Melt index of the ethylene copolymer thus obtained (JISK67
60) ranges from 0.5 to 800, preferably from 1 to 800.
A range of 200 is suitable.

The composition ratio of the ethylene copolymer in the polypropylene resin particles of the present invention is 0.1 to 2 (Nl parts by weight, preferably 0.5 to 10 parts by weight. Below 0.1 parts by weight, the improvement effect is poor; If the amount is more than 1 part by weight, it is not preferable because it adversely affects foamability.

The propylene-α-olefin random copolymer and ethylene copolymer are kneaded using a conventional kneading method, such as a roll, a Banbury mixer, a single-screw extruder, or a twin-screw extruder, to obtain polypropylene resin particles. . At this time, various additives such as a heat stabilizer, an antioxidant, an ultraviolet absorber, a weathering agent, a lubricant, a band 11L inhibitor, and a coloring agent may be added as necessary.

The foamed particles can be produced by placing polypropylene resin particles in a sump tank and directly adding a blowing agent to impregnate the particles.
A method is selected in which resin particles are dispersed in water using a small amount of dispersant in a closed container, and a blowing agent is press-fitted.

The evaporative blowing agent used in the present invention has a boiling point of
0-120°C hydrocarbons or halogenated hydrocarbons, such as propane, butane, pentane, hexane, heptane, cyclopenkune, cyclohexane, monochloromethane, dichloromethane, monochloroethane, trichloromonofluoromethane, dichlorodifluoromethane, dichloromono Fluoromethane, trichlortrifluoromethane,
Examples include dichlorotetrafluoroethane, and these may be used alone or in combination of two or more. These foaming agents vary depending on the type of foaming agent and foaming conditions, but the amount of these foaming agents is 5 to 40 parts by weight per 100 parts by weight of the polypropylene resin particles.
]i foot is added.

In addition, Hs+ may contain inorganic substances that are sparingly soluble in water, such as polyvinyl alcohol, methylcellulose, N-polyvinylpyrrolidone, etc., calcium phosphate, magnesium pyrophosphate, ib carbonate, magnesium carbonate, or these inorganic substances. A small amount of an anionic surfactant such as sodium dodecylbenzenesulfonate or sodium α-olefinsulfonate is used.

In addition, inorganic fine particles can be added to the polypropylene resin particles in order to make the cells of the foam uniform and fine. Inorganic substances having such a bubble regulating effect include inorganic calcium salts such as calcium sulfate, calcium carbonate, and calcium silicate, silica, magnesium silicate, and activated alumina. Furthermore, higher fatty acid metal salts such as calcium stearate can be used in combination with these for mold receiving. These air bubble regulators are added at a concentration of 0.1 to 2 w relative to the resin during granulation of polypropylene resin particles.
It is desirable to knead and add t.

Next, the polypropylene resin particles are heated to a temperature higher than the temperature at which they soften, but this heating temperature is appropriately selected within a range that does not destroy the bubbles and allows for good foaming.
The temperature is 0 to 170°C. This heating simultaneously impregnates the blowing agent into the particles.

Furthermore, one end of the container is opened while maintaining the pressure inside the container at a pressure higher than the vapor pressure of the blowing agent.

Expanded polypropylene resin particles are obtained by simultaneously releasing the particles and water into an atmosphere having a lower pressure than the inside of the container.

The atmosphere in which the particles containing the blowing agent and water are released at the same time need only be at a lower pressure than the inside of the container, and usually an atmosphere at normal pressure is passed through.

In order to produce a foamed molded product using the polypropylene resin foam particles of the present invention, for example, after the foam particles are aged at a predetermined temperature and under normal pressure, the foam particles are heated at a predetermined temperature and under a predetermined pressure. Pressurization is performed using gas or a mixed gas of an inorganic gas and a foaming agent to apply a controlled pressure inside the particles, and then the foamed particles are filled into a mold and heated and foamed. In this way, a molded body according to the mold can be obtained.

<Examples> The present invention will be explained in more detail with reference to Examples and Comparative Examples below, but the present invention is not limited by these.

(Production method of ethylene copolymer sample) 1. Dissolve ethylene containing a small amount of propane as a chain transfer agent and maleic anhydride in each unsaturated ester compound listed in Table 1 in a reactor equipped with a stirrer as described in 21. The solution was continuously supplied under pressure to control the polymerization temperature at 180°C.

Example 1 Propylene-ethylene random copolymer (X-tyrene containing 114.6'14% MI = 8) 9731ffi
parts, ethylene copolymer (a) (details of each sample are in Part 1)
Calcium stearate 0.1"It weight part, di-tertiary-butyl-p-cresol (BHT) 0.1 weight part, tetrakis-[ Methylene-8-(8',5'-di-t-butyl-4'-hydroxyphenyl)propionate comethane (Irg 1010) 0.1 part by weight,
0.05 part by weight of calcium silicate was mixed and added and granulated to obtain polypropylene resin particles.

100 parts of the resin particles, 800 parts of water, suspending agent magnesium pyrophosphate t8ts, and 80 parts of n-butane were placed in a pressure-resistant container, and the system was kept at 185° C. and stirred for 2 hours. While maintaining the system at 185° C., one end of the eight vessels was opened to release the pressure, and foamed particles were obtained. The expansion ratio of these foamed particles is 27
It was double that. In addition, the bubbles of the expanded particles were uniform and rough.

Comparative Example 1 The same procedure as in Example 1 was carried out except that the ethylene copolymer (a) was not used. The results are shown in Table 2.

Example 2.8 The same procedure as Example 1 was carried out except that the type and amount of the ethylene copolymer were changed. The results are shown in Table 2.

Example 4 The same procedure as Example 2 was carried out except that the foaming temperature was lowered to 182° C. and the amount of ethylene copolymer was changed. Second result
Shown in the table.

Table 2 <Effects of the Invention> According to the present invention, polypropylene resin particles made of a propylene-α-olefin random copolymer and a specific ethylene copolymer have excellent foamability, and the cells of the obtained expanded particles are uniform. The present invention provides foamed polypropylene resin particles that are coarse and greatly improved over conventional propylene-α-olefin random copolymers.

Procedural amendment (voluntary) February 20, 1985 1. Indication of the case 1985 Patent Application No. 274112 2. Name of the invention Polypropylene resin foam particles 3. Person making the amendment Relationship to the case Patent applicant residence Address: 5-15 Kitahama, Higashi-ku, Osaka Name (20
9) Sumitomo Chemical Co., Ltd. Representative: Hideo Mori 4, Agent address: 5-15 Kitahama, Higashi-ku, Osaka TE1061
220-3404 '5, "Detailed Description of the Invention" column 6 of the specification to be amended, Contents of the amendment (1) Page 4 of the specification, line 8 +2) "0.5~
20 parts by weight" is corrected to "0.1 to 20 parts by weight."

(21, page 10, line 8, “0.1 to 2 wt%” is r
o-oot ~2wt%”.

that's all

Claims (1)

Scope of Claims: (A) Propylene-α-olefin random copolymer having an α-olefin content of 0.5 to 30% by weight, 80 to 99%.
9 parts by weight, (B) 65 to 98.5% by weight of ethylene structural units, 1 to 30% by weight of ester structural units selected from alkyl acrylates or alkyl methacrylates having an alkyl group having 1 to 8 carbon atoms, and Polypropylene resin particles made of 0.1 to 20 parts by weight of an ethylene copolymer containing 0.5 to 10% by weight of saturated dicarboxylic anhydride structural units are foamed using an evaporative foaming agent. Substantially non-crosslinked polypropylene resin foam particles characterized by: