JPS63275650A - Expandable copolymer particle - Google Patents

Abstract

PURPOSE:To make it possible to form expandable copolymer particles good in gas retentivity, moldability, flexibility, tear strength and solvent resistance, by copolymerizing acrylonitrile with a monomer of a solubility parameter smaller than that of acrylonitrile, other monomers and a crosslinking monomer. CONSTITUTION:The copolymer particles are formed by copolymerizing 100pts.wt. monomer mixture comprising 15-50wt.% acrylonitrile, 10-40wt.% monomer (A) of a solubility parameter <=9.0(Cal/cc)<1/2> and 10-75wt.% other monomers (B) with 0.001-2.0pts.wt. crosslinking monomer. As said monomer (A), 2- ethylhexyl acrylate and/or butyl acrylate are desirable. As said monomer (B) styrene and/or methyl methacrylate are desirable. As said crosslinking monomer, a monomer of formula I (wherein n=2-23 and R is H or -CH3) or 1,3-butylene glycol dimethacrylate is desirable.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention provides resin particles with good gas retention properties, easy foaming, and The present invention relates to copolymer particles for foaming, which enable industrially advantageous production of synthetic resin foams with good flexibility and solvent resistance.

[Conventional technology and problems]

BACKGROUND ART Synthetic resins, especially foams of polyolefin particles, have been widely used due to their flexibility and solvent resistance. However, since the blowing agent impregnated with polyolefin particles tends to escape, it is necessary to quickly perform primary foaming to obtain expanded particles after producing expandable particles. Therefore, there is a disadvantage in storing and transporting bulky particles. Therefore, in order to improve gas retention, which is a drawback of polyolefin particles, many studies have been conducted on methods of impregnating and polymerizing polyolefin particles with styrene monomers, other vinyl monomers, and vinylidene monomers. However, in order to improve gas retention to the same level as polystyrene, it is necessary to impregnate and polymerize a large amount of monomer, which causes the polyolefin to lose its flexibility. On the other hand, a copolymer made by copolymerizing a styrene monomer with acrylate or methacrylate and having a secondary transition temperature of 100°C or less can be foam-molded at 100°C or less, but the copolymer retains gas. It is industrially disadvantageous because its properties deteriorate, and it also has problems in that it lacks solvent resistance and flexibility.

[Means and effects for solving the problems] The present invention provides acrylonitrile (hereinafter referred to as AN), a monomer diagram with a solubility parameter of 9.0 (cal/cc) + or less, and other monomers. It was discovered that by copolymerizing (B), foamable copolymer particles with good gas retention properties, moldability, flexibility, strength, and solvent resistance could be obtained. be.

The present invention improves gas retention by using AN, and then improves foamability and flexibility by copolymerizing a monomer (4) with a lower solubility parameter than AN, and further improves crosslinking properties. By adding a monomer, it is possible to produce expandable particles with strong tear strength, and by adding monomer (B), the particles become uniform and bead-like, which is advantageous during transportation and molding. be.

The monomer diagram used in the present invention includes soluble polymer, t
4ゎ@9.0 (Cat/cc)"UT+7)*II
There is F. Copolymerizing a monomer with such a solubility parameter smaller than AN generates intramolecular repulsion, increases the coefficient of thermal expansion during heating, and increases the expansion ratio, which is preferable as particles for foaming. As a specific example of a monomer diagram, 2
- ethylhexyl acrylate (hereinafter referred to as EHA),
Examples include butyl acrylate (hereinafter referred to as BA), stearyl acrylate, etc., but ERA, which has a small solubility parameter and is widely used industrially, and A, which are inexpensive, are particularly desirable. As monomer ω), monomer (4)
There are no restrictions as long as the monomer is copolymerizable with AN and AN, but styrene (hereinafter referred to as St) and α-methylstyrene,
Examples include styrene derivatives such as chlorostyrene; methacrylates such as methyl methacrylate (hereinafter referred to as MΔIA) and ethyl methacrylate; and acrylates such as ethyl acrylate and methyl acrylate.
St and/or MMA are particularly preferred from the viewpoint of gas retention and foaming properties.

In addition, in the present invention, butylene glycol dimethacrylate, polyethylene glycol dimethacrylate,
It is preferable to add a crosslinkable monomer such as polyethylene glycol diacrylate or trimethylolpropane trimethacrylate to increase tear strength. From the viewpoint of flexibility and foamability, butylene glycol dimethacrylate, polyethylene glycol dimethacrylate (2 to 23 repeating units of ethylene glycol), or polyethylene glycol diacrylate (2 to 23 repeating units of ethylene glycol) are used.
-23) are desirable because they have a long distance between crosslinks.

The amount of AN used is 15 to 50% by weight for gas retention.
It is preferable from the viewpoint of moldability, and particularly preferably 20 to 40% by weight from the viewpoint of gas retention and flexibility. The amount of the monomer used is preferably 10 to 40% by weight from the viewpoint of gas retention and flexibility, and particularly preferably 15 to 80% by weight from the viewpoint of gas retention and moldability. The amount of monomer CB) used is 10 to 75% by weight.
is preferable from the viewpoint of particle shape and moldability, and 30 to 60% by weight is desirable from the viewpoint of gas retention and flexibility. The amount of crosslinking monomer is 0.01 to 2 from the viewpoint of flexibility and tear strength.
．． It is preferably 0 parts by weight, and particularly preferably 0.01 to 1.0 parts by weight from the viewpoint of moldability and tear strength.

Methods for obtaining the copolymer particles for foaming of the present invention include pelletizing the resultant material through bulk polymerization or emulsion polymerization, but the most industrial method is to use an organic solvent for foaming after or at the final stage. Suspension polymerization methods that allow impregnation are preferred. In the case of suspension polymerization, an inorganic dispersant such as calcium phosphate or magnesium phosphate or an organic dispersant such as polyvinyl alcohol or polyvinylpyrrolidone is used as a suspending agent. The inorganic dispersant is used in an amount of 0.1 to 5.0% by weight based on the total monomer, and the organic dispersant is used in an amount of 0.001 to 2% by weight.
It may vary depending on monomer composition and amount.

Further, when an inorganic dispersant is used, it is necessary to add 0.0001 to 001% by weight of a surfactant such as sodium alkylbenzenesulfonate or sodium alkylsulfonate.

Water is generally used as a heating medium in suspension polymerization, and is used in an amount of 80 to 500 parts by weight based on the monomer, but this may vary depending on the particle size of the copolymer particles to be produced.

Polymerization initiators used in copolymerization include benzoyl peroxide, lauroyl peroxide, 3,5.5-trimethylhexanoyl peroxide, cumyl peroxyneodecanoate, di-2-ethylhexyl peroxydicarbonate, and tertiary petite. Examples include peroxide polymerization initiators such as peroxydicarbonate, and azo initiators such as azoisobutyronitrile and azobisdimethylvaleronitrile, either alone or in combination of two or more. In addition, stabilizers, lubricants, and nucleating agents may be added as low additives.

To foam the copolymer particles obtained according to the present invention, volatile foaming agents such as propane, butane, dichlorodifluoroethane, etc. are used.

〔Example〕

The present invention will be explained below with reference to Examples, but these are not intended to limit the present invention in any way.

Examples 1-12, Comparative Examples 1-7 In both Examples and Comparative Examples, copolymerization was carried out by the following method.

Ion exchange water SL in an autoclave with a stirrer of 101
Monomer or monomer mixture aooooy.

Polyethylene glycol dimethacrylate 0-75y1
Calcium phosphate 15y1 Sodium alpha sulfonate 1. Of, add 10.0g of benzoyl peroxide.9
Polymerization was carried out at 5°C for 6 hours. Thereafter, 10 parts by weight of butane was injected into 100 parts by weight of the obtained copolymer particles.
It was impregnated for 3 hours at 0°C and then cooled. One day after the copolymer particles impregnated with butane were filtered and dried, the butane gas retention rate was measured and calculated from the change in the weight of the particles. In addition, the bulk factor was increased to 5 with water vapor at a gauge pressure of 0.3 kq/d.
After 0x primary foaming and air drying for 1 day, 1.0 kq/al
Foam molding was performed in an aluminum mold using water vapor. The molded product is 300WMX200[X] 10mm thick.

The flexibility of the molded product was evaluated by bending the molded product. ◎ is equivalent to polyolefin, ○ is slightly worse than polyolefin, △ is worse than polyolefin, but better than polystyrene.
Items similar to polystyrene were rated x. Regarding tear strength, tear strength was rated ◎ if it was comparable to polyolefin, ○ if it was worse, △ if it was worse than polyolefin but better than polystyrene, and × if it was comparable to polystyrene.

Regarding solvent resistance, the molded product was immersed in acetone and evaluated as ◎ if it did not dissolve at all, ○ if it slightly swelled, △ if it partially dissolved, and × if it completely dissolved. The results are shown in Table-1.

From Table 1 below, it can be seen that when AN is less than 15% by weight based on the total monomers, the gas retention rate is poor and the solvent resistance is also poor.

When AN exceeds 50% by weight, the molded article loses its flexibility. If EHA is less than 10% by weight, the flexibility of the molded product will be poor;
If it exceeds 40% by weight, gas retention will deteriorate. It can be seen that if the crosslinking agent is less than 0.001 parts by weight, the tear strength is weak, and if it is more than 2.0 parts by weight, flexibility is lost.

As described above, the foamable copolymer particles of the present invention can be easily molded into a foamed molded product having good flexibility, solvent resistance, and tear strength.

〔Effect of the invention〕

The foaming copolymer particles according to the present invention have the following features: 1) They have a gas retention property comparable to that of polystyrene, and can be stored and transported while impregnated with a foaming agent, making them easy to handle.

2) The molded product has flexibility, tear strength, and solvent resistance comparable to that of polyolefin, yet can be easily foam-molded.

3) Physical properties such as flexibility and strength of the foamed molded product can be changed arbitrarily by changing the composition of the monomer and crosslinking agent within the claimed range.

It has the following advantages.

Claims (4)

[Claims] (1) 15-50% by weight of acrylonitrile, 10-40% by weight of monomer (A) with a solubility parameter of 9.0 (cal/cc.)^1^/^2, and other monomers Monomer mixture 10 consisting of 10 to 75% by weight of monomer (B)
Foaming copolymer particles obtained by copolymerizing 0 parts by weight with 0.001 to 2.0 parts by weight of a crosslinkable monomer. (2) The foamable copolymer particles according to claim 1, wherein the monomer (A) is 2-ethylhexyl acrylate and/or butyl acrylate. (3) The foamable copolymer particles according to claim 1, wherein the monomer (B) is styrene and/or methyl methacrylate. (4) The crosslinkable monomer is a monomer represented by the structural formula ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ (n = 2 to 23, R is H or -CH_3), or dimethacrylic acid 1 The foamable copolymer particles according to claim 1, which are 3-butylene glycol.