JP2002146083A - Heat-resistant and flame-retardant acrylonitrile- styrene resin bead and foamed product using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a foamed product excellent in heat resistance, flame retardancy and mechanical properties. SOLUTION: This heat-resistant and flame-retardant acrylonitrile-styrene resin bead is obtained by impregnating hexabromocyclododecane having <=200 μm mean particle diameter as a flame retardant in an amount of 2-5 wt.% and an organic peroxide as an auxiliary flame retardant in an amount of 0.05-0.5 wt.% based on a resin bead with 3-10 wt.% of an easy-volatile foaming agent into the acrylonitrile-styrene resin bead obtained by polymerizing 10-50 wt.% of acrylonitrile and 50-90 wt.% of styrene and the foamed product is obtained by using the acrylonitrile-styrene resin bead.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to heat-resistant and flame-retardant acrylonitrile / styrene resin particles which exhibit little blocking during prefoaming and have excellent mechanical strength, heat resistance and flame retardancy, and foamed molded articles thereof.

[0002]

2. Description of the Related Art Conventionally, styrene resin foams have been used as heat insulating materials such as pipe covers for hot and cold water pipes because of their excellent heat insulating properties. However, styrene resin has poor heat resistance, so it is used in applications requiring heat resistance higher than the softening temperature of styrene resin, such as thermal insulation for heat pipes, metal roof insulation in buildings, bathroom insulation, and automobile roof insulation. I couldn't. Further, the styrene-based resin foam has a drawback that it is easily flammable due to its structure, and cannot be used in application fields requiring flame retardancy such as building materials.

[0003] When a flame retardant is added to a styrene resin, the mechanical strength, especially the compressive strength, is reduced. Therefore, it is necessary to increase the foam density in order to obtain the required mechanical strength. For this reason, there is a problem that the material cost is disadvantageous in addition to being disadvantageous for weight reduction.

Therefore, various attempts have been made to improve heat resistance. For example, a blend with a heat-resistant polymer such as high-density polyethylene or crystalline polypropylene is used as the base resin (Japanese Patent Laid-Open No. 54-6316,
JP-A-54-63195, JP-A-52-1012
No. 68) has been proposed, but in this case, the moldability is reduced due to the difficulty in mixing with the styrene resin and the poor retention of the easily volatile foaming agent, and a good-quality foam cannot be obtained. And so on.

[0005] An example of improving the heat resistance by using a styrene-maleic anhydride copolymer for these resins is introduced (JP-A-47-39186). In this method, a very complicated suspension polymerization step is required due to the reactivity of maleic anhydride, and the resin component easily adheres to a metal, so that there is a difficulty in mold releasability during molding.

JP-A-60-206846, 20684
No. 7,206,848 proposes a copolymer containing α-methylstyrene, acrylonitrile and styrene as main components. However, α-methylstyrene has poor reactivity and requires a long time for polymerization, which lowers productivity. There was a problem. Further, it is difficult to completely polymerize α-methylstyrene for the above-mentioned reason, and it is easy to remain in the resin. If α-methylstyrene remains in the resin, the plasticity to the resin is large, so that the blocking during pre-foaming increases. There was a problem that the foaming workability was reduced.

[0007] Flame retardants generally known as flame retardants for styrenic resin particles include those having relatively low molecular weight and low melting point, such as tetrabromoethane, tribromophenol, tetrabromobisphenol A diallyl ether, and tetrabromobisphenol A. Organic brominated flame retardants are known. As the flame retarding method, various methods such as addition during polymerization or surface coating of resin particles have been studied.

[0008] Addition of a flame retardant during polymerization has disadvantages such as a decrease in polymerization rate and yield, and non-uniformity in impregnation of the flame retardant. Therefore, in order to impart sufficient flame retardancy,
Large amounts of flame retardants were required and were not economical. Further, the use of a large amount of the flame retardant has a problem in that blocking occurs at the time of preliminary foaming and foaming workability is reduced. Further, the method of coating the surface of the resin particles has a problem of contamination of the inside of the foaming machine and the mold due to desorption of the flame retardant.

[0009]

DISCLOSURE OF THE INVENTION The present invention provides a heat-resistant and flame-retardant acrylonitrile-styrene resin particle which has less blocking during pre-foaming and is excellent in mechanical strength, heat resistance and flame retardancy, and a foam molded article thereof. To provide.

[0010]

SUMMARY OF THE INVENTION The present invention relates to acrylonitrile-styrene resin particles obtained by polymerizing 10 to 50% by weight of acrylonitrile and 50 to 90% by weight of styrene. Diameter 20
0-micron or less hexabromocyclododecane 2
5% by weight and an organic peroxide as a flame retardant auxiliary 0.05 to
The present invention relates to heat-resistant and flame-retardant acrylonitrile / styrene resin particles obtained by impregnating 0.5% by weight with an easily volatile blowing agent of 3 to 10% by weight, and a foamed molded article using the same.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION The acrylonitrile / styrene resin particles used in the present invention have a material ratio of 10 to 50% by weight of acrylonitrile and 50 to 9% of styrene.
0% by weight, preferably 20 to acrylonitrile.
40% by weight and 60 to 80% by weight of styrene. If the acrylonitrile content is less than 10% by weight, the heat resistance and the mechanical strength decrease, and if the acrylonitrile content exceeds 50% by weight, the foaming property decreases.

The weight average molecular weight in terms of polystyrene of the acrylonitrile / styrene resin particles in the present invention is preferably in the range of 250,000 to 500,000 from the viewpoint of heat resistance, mechanical strength and foamability.

The flame retardant used in the present invention is hexabromocyclododecane, and its average particle size is 200 microns or less, preferably 100 microns or less. If the average particle size exceeds 200 microns, the impregnation of the resin particles becomes insufficient, and the flame retardancy decreases.

The compounding amount of the flame retardant is 2 to the above resin particles.
2% by weight to 5% by weight, and 2.5% by weight to 3% by weight.
It is preferably at most 5% by weight. If it is less than 2% by weight, sufficient flame retardancy cannot be obtained, and if it exceeds 5% by weight, blocking during prefoaming increases.

The flame retardant auxiliary used in the present invention is preferably an organic peroxide having a 10-hour half-life temperature of 150 to 250 ° C.
Examples of the flame retardant aid include dicumyl peroxide, t
-Butyl hydroperoxide and cumene hydroperoxide. The compounding amount of the flame retardant auxiliary is 0.05 to 0.5% by weight based on the resin particles, and 0.05 to 0.5% by weight.
0.3% by weight is preferred. If the amount of the flame retardant auxiliary is less than 0.05% by weight, sufficient flame retardancy cannot be obtained, and if it exceeds 0.5% by weight, the heat resistance decreases.

As the volatile volatile foaming agent used in the present invention, a volatile organic compound which is liquid or gas at normal pressure and normal temperature and does not dissolve the resin particle composition is used. Examples thereof include aliphatic hydrocarbons such as propane, butane, normal butane, isopentane and normal pentane, and cycloaliphatic hydrocarbons such as cyclohexane and cyclopentane. The amount of the foaming agent is 3 to 10% by weight, preferably 6 to 9% by weight, based on the resin particles. If the amount is less than 3% by weight, the foamability is insufficient, and
If the amount exceeds 0% by weight, it becomes difficult to produce expandable particles.

In the present invention, a softener can be used. As the softening agent, those having a boiling point of 150 ° C. or less are preferable. For example, aromatic hydrocarbons such as ethylbenzene, toluene, styrene, benzene, xylene, and 1,2-
Halogenated hydrocarbons such as dichloropropane and trichloroethylene, dioctyl adipate, vegetable oil dibutyl sebacate and the like can be mentioned.

The amount of the softener is preferably 0.05 to 3% by weight, more preferably 0.5 to 1.5% by weight based on the resin particles.
Is more preferred. If the amount is less than 0.05% by weight, the foaming properties are insufficient, and if it exceeds 3% by weight, the blocking during prefoaming increases and the heat resistance decreases. The step of impregnating the resin particles with the blowing agent employs a general step of impregnating the expandable styrene resin particles with the blowing agent. The impregnation step is performed during suspension polymerization or after completion of the polymerization. Here, during polymerization,
The polymerization rate is preferably 70% or more. In the impregnation of the foaming agent at a polymerization rate of less than 70%, the polymers may be united. Further, the impregnation temperature of the foaming agent is preferably from 70 ° C. to 120 ° C. from the viewpoint of foaming properties and the like.

The obtained heat-resistant and flame-retardant acrylonitrile-styrene resin particles are dehydrated, dried, classified, and then coated with a surface additive. Examples of the surface additive used in the present invention include zinc stearate, triglyceride stearate, monoglyceride stearate, hardened castor oil, amide compound, and antistatic agent. The heat-resistant and flame-retardant acrylonitrile / styrene resin particles can be coated with these surface additives by a Henschel mixer, a Loedige mixer or the like.

The heat-resistant and flame-retardant acrylonitrile-styrene resin particles of the present invention are foamed by steam, hot air, hot water, or the like, and the generally used foaming method of foamable styrene resin can be applied as it is. The expansion ratio of the resin particles according to the present invention is arbitrarily selected from a low magnification to a high magnification.

[0021]

Next, the present invention will be described by way of examples. The evaluation in the examples was performed as follows. Bromine content in beads: After burning the beads, the bromine content was measured by ion chromatography. Blocking generation amount during prefoaming: In prefoaming,
The occurrence of blocking was investigated. Dimensional change rate: Resin particles are foamed and molded 40 times (ml / g), cured at 40-45 ° C. for 1 day at room temperature, 1 day at room temperature, and then cured for 10 days.
The test piece was cut into 0 × 100 × 25 (mm). After leaving this test piece in a 100 ° C. atmosphere for 168 hours,
The dimensional change rate was measured. Self-extinguishing property: based on JIS A9511 combustion test. Compressive strength: Based on JIS A9511 compressive strength measurement.

Example 1 <Preparation of Flame Retardant Dispersion> Hexabromocyclododecane having an average particle size of 70 μm (SR-10 manufactured by Daiichi Pharmaceutical Co., Ltd.)
3) 175 g and sodium dodecylbenzenesulfonate
6 g was dispersed in 500 g of water for 30 minutes with a homomixer (MODEL 4D manufactured by Tokushu Kogyo Co., Ltd.).

<Blowing agent impregnation step> In a 16-liter autoclave equipped with a stirrer, 300 g of tricalcium phosphate, 6.0 g of sodium dodecylbenzenesulfonate and 6000 water were added.
Acrylonitrile / styrene resin particles having a g and a particle size of 0.7 to 1.0 mm (obtained from 28% by weight of GR-GP acrylonitrile and 72% by weight of styrene manufactured by Hitachi Chemical Co., Ltd., and having a polystyrene equivalent weight average molecular weight of 330,000) 600
0 g was added, and the above-mentioned flame retardant dispersion was added with stirring. Then, 50 g of toluene as a softener and cumene hydroperoxide as a flame retardant aid (Park Mill H80 manufactured by NOF Corporation, 10-hour half-life temperature 165 ° C.) 15
g of an aqueous solution containing 6.0 g of sodium dodecylbenzenesulfonate in a homomixer (MO manufactured by Tokushu Kogyo Co., Ltd.).
The dispersion obtained by DEL 4D) for 20 minutes was added into the autoclave over 60 minutes. After the addition is completed, 105
C., and 450 g of a blowing agent having a composition ratio of 40% by weight of isobutane and 60% by weight of n-butane was divided into two portions,
It was added over 60 minutes per time. Then, after keeping the temperature for 10 hours, it was cooled to 40 ° C. and taken out of the autoclave. Next, after dehydration and drying, the particles were classified after passing through 12 mesh and remaining 26 mesh.

<Post-treatment step> Obtained resin particles 5000
2 g, 5 g of antiblocking agent and castor hardened oil
0 g was added and the surface was coated to obtain heat-resistant and flame-retardant acrylonitrile-styrene resin particles. <Evaluation of molded article> The obtained heat-resistant and flame-retardant acrylonitrile
Styrene resin particles were pre-foamed to a bulk density of 0.025 g / ml using steam as a heat medium, and aged for 24 hours.
Foaming was performed to obtain a molded product. At this time, the amount of blocking generated during prefoaming, the dimensional change at 100 ° C., the self-extinguishing time, the compressive strength, and the bromine content in the beads were measured. The test results are shown in Table 1.

Comparative Example 1 The procedure of Example 1 was repeated, except that the average particle size of the flame retardant used was 500 microns. Table 1 shows the test results.
It was shown to. Comparative example 2 It carried out similarly to Example 1 except having used 175 g of tetrabromoethane as the flame retardant used. The test results are shown in Table 1. Comparative example 3 It carried out similarly to Example 1 except having used 175 g of tetrabromobisphenol A diallyl ethers as a flame retardant. The test results are shown in Table 1.

[0026]

[Table 1]

[0027]

The heat-resistant and flame-retardant acrylonitrile of the present invention
The styrene resin particles provide a foam molded article having excellent heat resistance, flame retardancy, and mechanical properties.

Claims (3)

[Claims] 1. An acrylonitrile / styrene resin particle obtained by polymerizing 10 to 50% by weight of acrylonitrile and 50 to 90% by weight of styrene is used as a flame retardant for the resin particle. Heat-resistant flame-retardant acrylonitrile obtained by impregnating 2 to 5% by weight of bromocyclododecane and 0.05 to 0.5% by weight of an organic peroxide as a flame-retardant aid together with 3 to 10% by weight of a readily volatile blowing agent. -Styrene resin particles. 2. The acrylonitrile / styrene resin particles according to claim 1 having a weight average molecular weight in terms of polystyrene of 25.
Heat-resistant flame-retardant acrylonitrile
Styrene resin particles. 3. A heat-resistant and flame-retardant acrylonitrile / styrene resin foam molded article obtained by prefoaming and molding the heat-resistant and flame-retardant acrylonitrile / styrene resin particles according to claim 1.