JPH06228357A - Foaming resin composition, foaming agent-containing resin composition and foam - Google Patents

Abstract

(57) [Summary] [Structure] 60% by weight or more of the soft component particles have a single occlusion structure with an average particle size of 0.6 μ or less, and the methyl ethyl ketone / toluene insoluble content is 15 to 35.
A resin composition for foaming comprising a rubber-modified polystyrene-based resin composition having a content of 5% by weight of methanol, a content of 5% by weight or less of methanol, and a content of 20% by weight or less of hexane. [Effect] It is possible to obtain a foam that is excellent in flexibility and shock absorption, has a high expansion ratio, is free from deformation and shrinkage during foam molding, and can be recycled.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a foaming resin composition, a foaming agent-containing resin composition and a foam. More specifically, the present invention contains a rubber-modified polystyrene resin composition as a main component, is excellent in flexibility and impact absorption, can obtain a high expansion ratio, and is free from deformation and shrinkage during foam molding,
The present invention also relates to a reusable foam, a foaming resin composition for obtaining the foam, and a foaming agent-containing resin composition.

[0002]

2. Description of the Related Art For example, a foam obtained by foaming a resin composition is widely used as a so-called cushioning material that absorbs external shocks applied to glass products and various precision instrument products to protect the products. ing. Further, one of the essential characteristics that the cushioning material should have is that it has excellent shock absorption.

Polystyrene-based resins have the advantages that they are excellent in rigidity and dimensional stability and are inexpensive, but on the other hand, they have the drawback that they are inferior in impact resistance, which hinders their expansion of applications. Further, when a polystyrene resin is used for foam molding, it results in lack of softness and impact absorption, which is a problem. On the other hand, a foam made of a polyethylene-based resin has excellent flexibility but is poor in rigidity, and since it has a narrow melt viscosity region suitable for foaming, it needs to be cross-linked and therefore used foam resin is regenerated. There is a problem that it is difficult to use so-called recycling. Further, the foam made of polypropylene resin is excellent in flexibility and impact absorption and is superior in rigidity to polyethylene foam. However, in order to make the polypropylene-based resin into a foam, more large-scale equipment is required than in the case of using other resins, which increases the manufacturing cost and is inconvenient from the viewpoint of industrial implementation.

In order to make up for the drawbacks of the polyethylene resin, it has been attempted to use it as a so-called polymer alloy, which is a composite of a polyethylene resin and a polystyrene resin. However, the polyethylene-based resin, which is a polyolefin-based resin, and the polystyrene-based resin, which is not a polyolefin-based resin, have poor compatibility, and the resulting foam has poor flexibility and impact resistance. As a method of improving such a defect, there is a method of impregnating a polyethylene resin with a styrene monomer and then performing graft polymerization to form a composite (for example, JP-A-48-1).
No. 01457 and Japanese Patent Laid-Open No. 49-97884).
However, this method has the problems that the graft polymerization step is complicated, the manufacturing cost is further increased, further crosslinking is required, and recycling cannot be used.

By the way, a styrene resin composition obtained by polymerizing a styrene monomer in the coexistence of a rubber-like polymer and having soft component particles in a styrene resin as a matrix is a so-called rubber-modified resin. It is known as a styrene resin composition (HIPS). Then, for example, Japanese Patent Publication No. 51-46536 discloses a technique using HIPS as a foam. However, the foam using the rubber-modified styrene resin composition obtained by such a conventional method has a problem that it is inferior in flexibility and impact absorption.

[0006]

In such a situation,
The problem to be solved by the present invention is to obtain a foam which is excellent in flexibility and impact absorption, has a high expansion ratio, is free from deformation and shrinkage during foam molding, and is recyclable, and the foam. The present invention provides a resin composition for foaming and a resin composition containing a foaming agent.

[0007]

The present inventors have arrived at the present invention as a result of intensive studies to solve the above problems.

That is, the first invention of the present invention relates to a foaming resin composition comprising the following (A). (A): 60% by weight or more of the soft component particles have a single occlusion structure having an average particle size of 0.6 μ or less,
Rubber-modified polystyrene resin composition having a methyl ethyl ketone / toluene insoluble content of 15 to 35% by weight, a methanol soluble content of 5% by weight or less, and a hexane soluble content of 20% by weight or less.

A second invention of the present invention relates to a foaming agent-containing resin composition comprising 99 to 90% by weight of (A) and 10 to 1% by weight of a volatile foaming agent.

A third aspect of the present invention relates to a foam having the resin component (A).

A fourth aspect of the present invention relates to a foam obtained by foaming the above foaming agent-containing resin composition.

The details will be described below. The rubber-modified polystyrene-based resin composition (A) used in the present invention has a single occlusion structure in which 60% by weight or more of the soft component particles have an average particle size of 0.6 μ or less, and the methyl ethyl ketone / toluene insoluble content is 15%. The rubber-modified polystyrene resin composition has a content of ˜35% by weight, a content of methanol-soluble matter of 5% by weight or less, and a content of hexane-soluble content of 20% by weight or less.

The rubber-modified polystyrene resin composition is
A resin composition obtained by polymerizing a styrene-based monomer in the coexistence of a rubber-like polymer, and / or two or more styrene-based resin compositions, or a block copolymer of a conjugated diene compound and a vinyl aromatic compound, or A resin composition obtained by melt-kneading a hydrogenated product of a copolymer, wherein soft component particles are present in a styrene resin as a matrix. Examples of the styrene-based monomer include styrene and methyl styrene. Examples of the rubber-like polymer include polybutadiene rubber, polyisoprene rubber, acrylonitrile-butadiene copolymer rubber and the like. A rubber-modified polystyrene-based resin composition containing methyl methacrylate or a vinyl-substituted aromatic compound may be used.

At least 60% by weight of the soft component particles must have a single occlusion structure with an average particle size of 0.6 μ or less. Here, the single occlusion structure is also called a core-shell structure, a capsule structure, or the like, and a core portion that is a single continuous phase made of a styrene-based resin and a rubber-like polymer that occludes the core portion. It refers to a particle-like structure composed of a shell part composed of coalesced particles. In the present invention, by using a certain amount or more of the specific soft component particles, the resulting foam can have excellent flexibility and impact absorption.
If the average particle size is too large, the foam has poor impact absorption.
Further, if the content of the soft component particles is too small, the flexibility and impact absorption of the foam will be poor. Here, the determination of the structure of the soft component particles and the measurement of the average particle diameter are performed by a transmission electron micrograph of an ultrathin section of the resin composition. The average particle diameter is calculated by the following formula by measuring the particle diameter of 500 single occlusion structure particles in the photograph.

Average particle size = Σn _i D _i ² / Σn _i D _i :
Here, n _i is the number of particles having the particle size D _i .

Methyl ethyl ketone / toluene insoluble matter is 1
It is 5 to 35% by weight, preferably 20 to 35% by weight.
If the insoluble content is too small, the flexibility and impact absorption of the foam will be poor. On the other hand, if the insoluble content is too large, the expansion ratio cannot be increased and the compressive strength of the foam will be poor. The methyl ethyl ketone / toluene insoluble matter is measured by the following method. That is, 0.5 g of the resin composition was mixed with 5 parts of a mixed solvent of methyl ethyl ketone / toluene (10 / l volume mixing ratio).
It is dissolved in 0 ml by stirring at room temperature for 2 hours, the insoluble matter is separated by a centrifuge, and the supernatant is discarded. To this insoluble matter, 50 ml of the same mixed solvent as described above is added, further dissolved, and the insoluble matter is separated again by centrifugation. The total insoluble matter obtained by separation is dried and weighed, and the weight ratio of the dry insoluble matter to the composition used first is defined as the methyl ethyl ketone / toluene insoluble matter.

The methanol-soluble content is 5% by weight or less, preferably 3% by weight or less. If the fusible portion is excessive, the deformation and shrinkage during molding of the foam will increase. The methanol-soluble content is measured by the following method. That is, about 1 g of the resin composition is dissolved in 10 ml of methyl ethyl ketone at room temperature, 300 ml of methanol is added to reprecipitate, the solid content is collected by filtration, dried and precisely weighed. The weight ratio of the resin composition component reduced by such an operation to the resin composition used first is defined as the methanol-soluble component.

The hexane-soluble content is 20% by weight or less, preferably 15% by weight or less. When the soluble content is excessive, the retention time of the foaming agent becomes short and a high expansion ratio cannot be obtained. The hexane-soluble content is measured by the following method. That is, 10 g of the resin composition was added to 30-40 dichloromethane.
It is dissolved in ml at room temperature, and 300 ml of n-hexane is gradually added with stirring. Allow to stand for 4 hours or more, collect the supernatant, concentrate to dryness, and weigh accurately. The weight ratio of the resin composition component obtained by such an operation to the resin composition used first is defined as the hexane-soluble component.

In the present invention, as described above, it is necessary to use a certain amount or more of the soft component particles having a single occlusion structure, but a soft component that can be used in combination with the soft component particles having a single occlusion structure. The component particles are preferably soft component particles having a salami structure, a block copolymer of an aromatic vinyl compound and a conjugated diene compound, or a hydrogenated product of the block copolymer. This makes it possible to improve flexibility while maintaining good foamability. The salami structure refers to a structure in which small particles of styrene resin are scattered in the rubber-like polymer phase.

The rubber modified polystyrene resin composition (A) of the present invention is used as a foaming agent-containing resin composition comprising 99 to 90% by weight of (A) and 10 to 1% by weight of a volatile foaming agent. Examples of the volatile foaming agent include normal butane, isobutane, normal pentane, isopentane,
Freon etc. can be mentioned. If the volatile foaming agent is too small, a sufficient expansion ratio cannot be obtained, while if the volatile foaming agent is too large, a uniform foam cannot be obtained.

To obtain the foam of the present invention, (A) 99 to 90% by weight of the rubber-modified polystyrene resin composition and 10 to 1% by weight of a volatile foaming agent, and optionally a flame retardant,
An antioxidant, a heat stabilizer, an ultraviolet absorber, a lubricant, an antistatic agent, a pigment, a dye, carbon and the like may be used in combination and foamed by a usual method to form a foam. In addition to the (A) rubber-modified polystyrene-based resin composition of the present invention, a resin other than the present invention, such as regenerated polystyrene, may be used in combination within a range that does not impair the effects of the present invention.

An example of a specific method for carrying out the present invention is as follows. That is, in the presence of a rubber-like polymer, a rubber-modified polystyrene-based resin composition obtained by polymerizing a styrene-based monomer and / or two or more rubber-modified resin compositions or a conjugated diene compound and a vinyl aromatic compound A block copolymer or a hydrogenated product of this copolymer is melt-kneaded with a melt-kneader such as a single-screw extruder or a twin-screw extruder. Resin particles are produced by a cutter such as strand cut, underwater cut, hot cut, or the like. For example, a method in which the resin particles are suspended in an aqueous medium in an autoclave and a volatile foaming agent is impregnated under pressure, or in the extruder, after the molten foaming agent and the resin are sufficiently mixed, the resin is extruded through pores at the tip of the die. Then, the resin particles containing a foaming agent are produced by a method in which they are rapidly introduced into water and rapidly cooled to form particles in a state where they do not foam. These foaming agent-containing resin particles are made into a foamed molded product by a molding foam manufacturing machine.

[0023]

EXAMPLES Next, the present invention will be described with reference to examples. In the measurement and evaluation, the average particle diameter and structure of the soft component particles, the methyl ethyl ketone / toluene insoluble content, the methanol soluble content and the hexane soluble content were carried out by the above-mentioned method, and the other items were as follows. It was carried out as follows.

(1) Expansion ratio This is a value obtained by dividing the density of the base resin composition by 1 g / L and dividing it by the density of the pre-expanded particles or the molded product. (2) Compressive Strength (25%) The foamed molded product was cut into a size of 100 × 100 × 25 mmt, and the 25% compressive strength was determined according to JIS A9511. (3) Bending Strength and Maximum Bending Deflection The foamed molded body was cut into a size of 300 × 75 × 25 mmt, and the bending strength was determined according to JIS A9511. In addition, the bending amount at the maximum load was defined as the bending maximum bending amount.

(4) Flexibility Ten samples were prepared by cutting the foamed molded product into 200 × 30 × 20 mmt. Also, with a length of 200 mm, diameters 100, 90, 80, 70, 60, 50, 40, 30,
A cylinder of 20, 10 mm was prepared. First, 100 mmφ
The sample was wound around the cylinder No., and if no crack was generated in the sample, it was wound around the smaller cylinder of 90 mmφ. A small cylinder was successively wound until a crack was generated, and the diameter of the cylinder when the crack was generated was recorded. The same test was repeated on 10 samples, and the average value was used as the flexibility test result. When the total amount of 100 mmφ cracked, it was indicated as 100 or more, and when the total amount of 10 mmφ did not occur, it was indicated as 10 or less. That is, the smaller the value, the better the flexibility.

(5) Falling ball impact JIS K7211 except that the foamed molded body was cut into 200 × 40 × 25 mmt and the weight of the ball was 255 g.
The test was carried out according to the above, and the 50% breaking height was taken as the test result. The higher the value, the higher the impact strength. (6) Deformation / shrinkage of molded product The appearance of the foamed product was visually evaluated, and those without deformation / shrinkage were rated as ◯, and those with deformation / shrinkage were rated as x.

Examples 1 to 3 and Comparative Examples 1 to 3 Resin compositions having the formulations shown in Tables 1 and 2 were melted at 220 ° C. in a 40 mmφ extruder to obtain resin particles having a pellet weight of about 1.5 mg. . The resin particles were put into an aqueous medium obtained by adding 900 g of pure water, 18 g of tribasic calcium phosphate as a dispersant and 0.027 g of sodium lauryl sulfate, and heated to 125 ° C. with stirring. Next, 54 g of pentane was added over 60 minutes, the temperature was kept at the same temperature for 10 hours, and then cooled to room temperature. The content was separated from water and taken out, tricalcium phosphate was dissolved and removed with nitric acid, washed with water, dehydrated, and dried with warm air at about 45 ° C., and then coated with an antistatic agent and an antiblocking agent. The resin particles thus obtained were aged in a closed container at 0 ° C. for 24 hours, and then steamed at 97 to 10 by steam using a 30 L batch type pre-foaming machine.
It heated at 0 degreeC and obtained 25 g / L of pre-expanded particles. After aging the pre-expanded particles for 1 day, length 300 mm, width 10
It is filled in a mold having a mold bulk of 0 mm and a wall thickness of 25 mm and having vapor permeation holes, and heated for 20 seconds with steam having a pressure of 0.8 kg / cm ² G to expand and mutually fuse the pre-expanded particles. And then cooled to obtain a molded product foam molding. This molded product was left at 60 ° C. for 10 hours, dried, and then left at 20 ° C. for 2 days to stabilize the temperature of the molded product, and then subjected to measurement and evaluation. The conditions and results are shown in Tables 1-2.

The following can be seen from the results. All the examples satisfying the conditions of the present invention are. Excellent results are shown in all evaluation items. On the other hand, the average particle size is 0.6
Comparative Example 1 which does not contain the soft component particles (specific soft component particles) having a single occlusion structure of μ or less is inferior in flexibility and impact absorbability (maximum bending deflection and falling ball impact). In Comparative Example 2 in which the hexane-soluble content is excessive, the foam moldability is poor, and a foam molded article cannot be obtained. Comparative Example 3 in which the amount of methanol-soluble matter is excessive is inferior in foam moldability.

Table 1 −−−−−−−−−−−−−−−−−−−−−−−−−−−−−− Example 1 2 3 Formulation wt% * 1 HIPS1 97 92 90 HIPS2 0 5 0 SBS 0 0 7 Oil 3 3 3 Specific soft component particle ratio * 2 100 95 78 MEK / TOL Insoluble matter wt% * 3 25 25 23 Methanol soluble matter wt% 3.0 2.8 2.9 Hexane soluble matter wt% 4.9 4.9 10.5 Other than specific soft component particles None Soft component particles of salami block * 4 Copolymer * 5 Volatile blowing agent ratio wt% * 4 6.5 6.2 6.0 Evaluation expansion ratio 40 40 40 Compressive strength kg / cm ² G 1.4 1.5 1.2 Bending strength kg / cm ² G 2.8 3.0 2.6 Maximum bending amount mm 23 25 29 Flexibility mm φ 86 82 54 Falling ball impact cm 29 34 38 Deformation / shrinkage of molded product ○ ○ ○ −−−−−−−−−−−− −−−−−−−−−−−−−−−−−−

Table 2 −−−−−−−−−−−−−−−−−−−−−−−−−−−− Comparative Example 1 2 3 Formulation wt% * 1 HIPS1 0 80 94 HIPS2 98 0 0 SBS 0 18 0 Oil 2 2 6 Specific soft component particle ratio * 2 0 54 100 MEK / TOL Insoluble matter wt% * 3 21 20 24 Methanol soluble matter wt% 2.1 2.6 5.8 Hexane soluble matter wt% 3.3 22.1 7.2 Other than specific soft component particles Soft component particles without salami block Copolymer * 5 Volatile blowing agent ratio wt% * 4 6.5 4.5 6.0 Evaluation expansion ratio 40 15 40 Compressive strength kg / cm ² G 1.5 1.3 Bending strength kg / cm ² G 3.1 Constant 2.9 Bending maximum deflection mm 16 Not 24 Flexibility mmφ> 100 Function 89 Falling ball impact cm 18 25 Deformation / contraction of molded product ○ × × −−−−−−−−−−−−−−−−− −−−−−−−−−−−−

* 1 Blended HIPS1: HIPS containing soft component particles having a single occlusion structure, average particle diameter 0.2 μ, soft component particle ratio 26 wt% HIPS2: HI containing soft component particles having salami structure
PS, average particle size 2.0μ, soft component particle ratio 22wt
% SBS: Kraton D1116 manufactured by Shell Chemical Co., block copolymer of styrene and a conjugated diene compound, styrene content 21%

* 2 Ratio of specific soft component particles Weight ratio (wt%) of soft component particles having a single occlusion structure with an average particle size of 0.6 μ or less * 3 MEK / TOL insoluble matter Methyl ethyl ketone / toluene insoluble matter * 4 Volatility Blowing agent ratio Pentane was used as the volatile blowing agent * 5 Block copolymer Block copolymer of styrene and conjugated diene compound

[0033]

As described above, according to the present invention, a foam which is excellent in flexibility and impact absorption, has a high expansion ratio, is free from deformation and shrinkage during molding of the foam, and is recyclable, and It was possible to provide a foaming resin composition and a foaming agent-containing resin composition for obtaining a foam.

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[Procedure amendment]

[Submission date] March 8, 1994

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0013

[Correction method] Change

[Correction content]

The rubber-modified polystyrene resin composition is
A resin composition obtained by polymerizing a styrene-based monomer in the coexistence of a rubber-like polymer and / or two or more styrene-based resin compositions or a block copolymer of a conjugated diene compound and a vinyl aromatic compound, or A resin composition obtained by melt-kneading a hydrogenated product of a copolymer, wherein soft component particles are present in a styrene resin as a matrix. Examples of the styrene-based monomer include styrene and methyl styrene. Examples of the rubber-like polymer include polybutadiene rubber, polyisoprene rubber, styrene -butadiene copolymer rubber and the like. A rubber-modified polystyrene-based resin composition containing methyl methacrylate or a vinyl-substituted aromatic compound may be used.

[Procedure Amendment 2]

[Document name to be amended] Statement

[Name of item to be corrected] 0024

[Correction method] Change

[Correction content]

(1) Expansion ratio It is a value obtained by dividing the density of the base resin composition by 1 kg / L by the density of the pre-expanded particles or the molded product. (2) Compressive Strength (25%) The foamed molded product was cut into a size of 100 × 100 × 25 mmt, and the 25% compressive strength was determined according to JIS A9511. (3) Bending Strength and Maximum Bending Deflection The foamed molded body was cut into a size of 300 × 75 × 25 mmt, and the bending strength was determined according to JIS A9511. In addition, the bending amount at the maximum load was defined as the bending maximum bending amount.

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Claims (7)

[Claims] 1. A foaming resin composition comprising the following (A): (A): 60% by weight or more of the soft component particles have a single occlusion structure having an average particle size of 0.6 μ or less,
Rubber-modified polystyrene resin composition having a methyl ethyl ketone / toluene insoluble content of 15 to 35% by weight, a methanol soluble content of 5% by weight or less, and a hexane soluble content of 20% by weight or less. 2. The soft component particle having a structure other than a single occlusion structure is a block copolymer of an aromatic vinyl compound and a conjugated diene compound or a hydrogenated product of the block copolymer. Foaming resin composition. 3. The foaming resin composition according to claim 1, wherein the soft component particles having a structure other than the single occlusion structure have a salami structure. 4. The soft component particles having a structure other than a single occlusion structure are a block copolymer of a salami structure and an aromatic vinyl compound and a conjugated diene compound, or a hydrogenated product of the block copolymer. The resin composition for foaming according to 1. 5. (A) 99 to 90% by weight of claim 1.
And a foaming agent-containing resin composition comprising 10 to 1% by weight of a volatile foaming agent. 6. A foamed product in which the resin component is (A) according to claim 1. 7. A foam obtained by foaming the resin composition containing a foaming agent according to claim 5.