JPH062840B2 - Polypropylene resin foam particles - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Field of Industrial Application> The present invention relates to a polypropylene-based resin foamed particle having excellent foamability and moldability, and having uniform and rough foamed particles.

<Prior Art> Generally, polypropylene has excellent properties such as excellent heat resistance and chemical resistance, high mechanical strength, high flexibility as compared with polystyrene, and high rigidity as compared with polyethylene. However, various attempts have been made to obtain a foamed molded product by using polypropylene having such excellent properties, and a sheet-shaped foamed product by an extrusion molding method and a foamed product by a bead molding method have been obtained.

It is known that an ethylene-propylene random copolymer or a mixture of the copolymer containing the copolymer as a main component and a low-density polyethylene and / or an ethylene-vinyl acetate copolymer foams non-crosslinked beads. (JP-A-57
-90027, JP-A-58-65734).

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 high expansion ratio, (2) there is technical difficulty in foaming because the viscoelastic fluidity is poor and the temperature range suitable for foaming is narrow. ) The bubbles of the obtained expanded particles tend to be fine. Therefore, even if a molded product is obtained using such expanded particles, there is a problem that it is difficult to obtain a foamed product having good dimensional accuracy and firmness.

<Problems to be Solved by the Invention> Under such circumstances, the problems to be solved by the present invention, that is, the object of the present invention is to easily obtain expanded particles with a high expansion ratio from polypropylene resin particles, and To provide uniform and rough expanded polypropylene resin particles.

<Means for Solving Problems> The present invention comprises (A) 80 to 99.9 parts by weight of a propylene-α-olefin random copolymer having an α-olefin content of 0.5 to 30% by weight, and (B) an ethylene structural unit. 65 to 98.5% by weight, carbon number 1 to
1 ester constitutional unit selected from alkyl acrylate or alkyl methacrylate having 8 alkyl groups
To 30% by weight and 0.5 to 10% by weight of an unsaturated dicarboxylic acid anhydride constituent unit, an ethylene copolymer 0.1 to 2
A substantially non-crosslinked polypropylene-based resin foamed particle, characterized in that the polypropylene-based resin particle consisting of 0 parts by weight is foamed by using an evaporative foaming agent, which solves the above-mentioned conventional problems. It is a thing.

The present invention will be described in detail below.

The propylene-α-olefin random copolymer used in the present invention has an α-oeufine content of 0.5 to 30% by weight,
The melt index (M
I) is 0.1 to 50 g / 10 minutes, preferably 1 to 20 g /
It is an original or ternary random copolymer that is 10 minutes. α
-Olefin includes ethylene, butene-1, hexene-1, 3-methyl-butene-1, 4-methyl-pentene-1, octene-1, decene-1 and the like. As the propylene-α-olefin random copolymer,
For example, propylene-ethylene copolymer, propylene-
Butene-1 copolymer, propylene-4-methyl-pentene-1 copolymer and propylene-ethylene-butene-1 copolymer are preferably used.

Next, as the ethylene copolymer used in the present invention, an ethylene constitutional unit is 65 to 98.5% by weight, and an ester constitutional unit selected from an alkyl acrylate and an alkyl methacrylate having an alkyl group having 1 to 8 carbon atoms is 1 to 30%.
% By weight, 0.5 to 1 unsaturated dicarboxylic acid anhydride structural unit
It has 0% by weight.

Examples of the monomer having an ester constitutional unit 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 compound). ) Is mentioned.

The amount of the ester constitutional unit contained in the ethylene copolymer is in the range of 1 to 30% by weight, preferably 2 to 25% by weight. Outside of this range, the compatibility with the propylene-α olefin copolymer becomes poor, which is not preferable.

Examples of the monomer having an unsaturated dicarboxylic acid anhydride constitutional unit include maleic anhydride, citraconic anhydride, itaconic anhydride, tetrahydrophthalic anhydride, and the like. Among them, maleic anhydride is most preferably used.

The amount of these unsaturated dicarboxylic acid anhydride structural units contained in the ethylene copolymer is in the range of 0.5 to 10% by weight, preferably 1 to 5% by weight. If it is less than the lower limit, the polar groups are poor and the effect of improvement is lacking. If it is more than the upper limit, the polarity is too strong and the propylene-α-olefin copolymer is not well compatible with it.

The method for producing the ethylene copolymer is not particularly limited, and known methods such as a solution polymerization method, an emulsion polymerization method and a high pressure bulk polymerization method are applied. Among them, a high-pressure polymerization method in which ethylene is copolymerized in the presence of a radical generator, at 500 to 3,000 atm, and at 100 to 300 ° C in the presence or absence of a suitable solvent or chain transfer agent is the most general. Is. In such a high-pressure polymerization method, a method in which a solution of the above-mentioned unsaturated dicarboxylic acid anhydride dissolved in the above-mentioned unsaturated ester compound is pressurized by a high-pressure pump and directly introduced into a tank-shaped or tubular reactor is introduced. . The melt index of the ethylene copolymer thus obtained (JISK67
60)) is in the range of 0.5 to 300, preferably 1 to 2
Those in the range of 00 are suitable.

The composition ratio of the ethylene copolymer in the polypropylene resin particles of the present invention is 0.1 to 20 parts by weight, preferably 0.5 to
10 parts by weight. If it is less than 0.1 parts by weight, the improvement effect is poor, and if it is more than 20 parts by weight, the foamability is adversely affected, which is not preferable.

The propylene-α-olefin random copolymer and the ethylene copolymer are kneaded using an ordinary kneading method, for example, a roll, Banbury mixer, single screw extruder, twin screw extruder or the like to obtain polypropylene resin particles. At this time, various additives such as a heat stabilizer, an antioxidant, an ultraviolet absorber, a weather resistance agent, a lubricant, an antistatic agent, and a colorant may be added, if necessary.

The method for producing expanded particles is a method of taking polypropylene resin particles in a closed container and directly impregnating them with a foaming agent,
A method in which resin particles are dispersed in water in a closed container using a small amount of a dispersant and a foaming agent is pressed in is selected.

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

As the dispersant, water-soluble polymers such as polyvinyl alcohol, methyl cellulose and N-polyvinylpyrrolidone, inorganic substances that are poorly soluble in water such as calcium phosphate, magnesium pyrophosphate, zinc carbonate and magnesium carbonate, or a small amount of these inorganic substances. A combination of anionic surfactants such as sodium dodecylbenzene sulfonate and sodium α-olefin sulfonate is used.

Further, in order to uniformly and finely arrange the bubbles of the foamed body, inorganic fine particles can be added to the polypropylene resin particles. As the inorganic substance having such a bubble adjusting effect, inorganic calcium salts such as calcium sulfate, calcium carbonate and calcium silicate, silica, magnesium silicate, activated alumina and the like are used. Furthermore, a small amount of a higher fatty acid metal salt such as calcium stearate may be used in combination therewith. These foam control agents are used in the amount of 0.001 to 2w with respect to the resin when granulating polypropylene resin particles.
It is desirable to add t% kneading.

Next, the polypropylene resin particles are heated to a temperature at which they are softened or higher, but the heating temperature is appropriately selected within a range in which bubbles are suitably foamed without being destroyed, and usually 120 to
It is 170 ° C. The heating simultaneously impregnates the blowing agent into the particles.

Further, while maintaining the pressure in the container at a pressure equal to or higher than the vapor pressure of the foaming agent, one end of the container is opened, and the particles and water are simultaneously released into an atmosphere having a pressure lower than that in the container so that the polypropylene type Obtain resin foam particles.

The atmosphere for releasing the particles to be impregnated and the water at the same time in the foaming agent may be at a pressure lower than that in the container, and an atmosphere at normal pressure is usually selected.

To produce a foamed molded article using the polypropylene resin foamed particles of the present invention, for example, after aging the foamed particles at a predetermined temperature under normal pressure, the foamed particles are subjected to an inorganic treatment under a predetermined temperature at a predetermined pressure. Pressure aging is performed with a gas or a mixed gas of an inorganic gas and a foaming agent to give an increased pressure to the inside of the particles, and then the expanded particles are filled in a molding die and heated and foamed. Thus, it is possible to obtain a molded body as the mold.

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

(Method for producing ethylene copolymer sample) 1.2 solution containing ethylene containing a small amount of propane as a chain transfer agent and maleic anhydride in various unsaturated ester compounds shown in Table 1 in a reactor equipped with a stirrer Was continuously fed under pressure and controlled at a polymerization temperature of 180 ° C. to perform copolymerization at a rate of 1.5 to 3.2 kg / hr under a pressure of 1,600 kg / cm ₃ to obtain various samples shown in Table 1 below. It was

Example 1 Propylene-ethylene random copolymer (ethylene content
4.6%, MI = 8) 97 parts by weight, ethylene copolymer (a)
(Details of each sample are shown in Table 1) Calcium stearate is added to 100 parts by weight of the compound made up of 3 parts by weight.
0.1 parts by weight, zetas butyl-p-cresol (BHT) 0.1 parts by weight, tetrakis- [methylene-3-
(3 ', 5'-di-t-butyl-4'-hydroxyphenyl) propionate] methane (Irg1010) 0.1 part by weight,
0.05 parts by weight of calcium silicate was mixed and added, and granulated to obtain polypropylene resin particles. This resin particle 100
Parts, water 300 parts, suspension agent magnesium pyrophosphate 1 part,
And put 30 parts of n-butane in a pressure vessel and put the system at 135 ° C.
The mixture was kept for 2 hours and stirred for 2 hours. While keeping the system at 135 ℃,
When one end of the container was opened and the pressure was released, foamed particles were obtained.
The expansion ratio of the expanded beads was 27 times. The bubbles of the expanded particles were uniform and rough.

Comparative Example 1 The results were shown in Table 2 in the same manner as in Example 1 except that the ethylene copolymer (a) was not used.

Examples 2 and 8 The same procedure as in Example 1 was carried out except that the kind and blending amount of the ethylene copolymer were changed. The results are shown in Table 2.

Example 4 The same procedure as in Example 2 was carried out except that the foaming temperature was lowered to 132 ° C. and the blending amount of the ethylene copolymer was changed. Second result
Shown in the table.

<Effects of the Invention> According to the present invention, polypropylene resin particles composed of a propylene-α-olefin random copolymer and a specific ethylene copolymer have excellent foamability, and the bubbles of the foamed particles obtained are uniform and rough, Provided are polypropylene resin expanded particles which are significantly improved as compared with a conventional propylene-α-olefin random copolymer.

Claims (1)

[Claims] 1. A content of (A) α-olefin is 0.5 to 30% by weight.
Propylene-α-olefin random copolymer 80-
99.9 parts by weight, (B) ethylene structural unit 65 to 98.5% by weight, carbon number 1 to
1 ester constitutional unit selected from alkyl acrylate or alkyl methacrylate having 8 alkyl groups
To 30% by weight and 0.5 to 10% by weight of an unsaturated dicarboxylic acid anhydride constituent unit, an ethylene copolymer 0.1 to 2
A substantially non-crosslinked polypropylene resin foamed particle, characterized in that 0 parts by weight of polypropylene resin particles are foamed using an evaporative foaming agent.