JP2001164025A - Foaming acrylonitrile/styrene resin particle and foamed product by using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide foaming acrylonitrile/styrene resin particles excellent in mechanical properties of its foamed product and generating less smell on heating the foamed product to reduce its volume, and its foamed product. SOLUTION: This foaming acrylonitrile/styrene resin particles are obtained by impregnating 3-15 wt.% butane based on acrylonitrile and styrene to resin particles having 300,000-600,000 weight-average molecular weight based on the polystyrene and obtained by performing a suspension polymerization of a mixture of 10-50 wt.% acrylonitrile and 50-90 wt.% styrene in the presence of α- methylstyrene dimmer by a radical polymerization initiator, and a foam product is obtained by using the above resin particles.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to expandable acrylonitrile / styrene resin particles having excellent mechanical strength of the foam and less generation of odor when the foam is heated and melted, and a foam molded article using the same.

[0002]

2. Description of the Related Art Acrylonitrile / styrene resin has higher chemical resistance, oil resistance, mechanical strength, and
It is known that it has excellent heat resistance, etc., and in the field of foam molding materials, it is used for applications requiring chemical resistance and oil resistance, which were not possible with conventional expanded polystyrene. .

[0003] Foamable acrylonitrile / styrene resin particles are prepared by using a mercaptan compound such as t-dodecyl mercaptan as a chain transfer agent in the presence of a dispersant to synthesize resin particles by suspension polymerization, and then impregnating the foaming agent. The resin pellets synthesized by bulk polymerization are re-pelletized to a target size, and the pellets are impregnated with a foaming agent in the presence of a dispersant to produce the pellets.

[0004]

However, acrylonitrile / t-dodecylmercaptan using t-dodecyl mercaptan as a chain transfer agent has been proposed.
When the styrene resin has a weight-average molecular weight of 300,000 or more, the foamability is poor and a low-density product cannot be obtained. This is because the fluidity of the resin is poor. Also,
Resin recyclability has become a major issue due to growing interest in environmental issues.Acrylonitrile / styrene resin foams can also be heat-reduced and foamed into foamed products, and if ingots can be used, they can be used as resin materials for injection molding for other uses. Can be recycled. However, an acrylonitrile-styrene resin foam produced using a mercaptan-based chain transfer agent has a strong odor at the time of heat-dissolution and has very poor workability.

On the other hand, those produced from acrylonitrile / styrene resin produced by bulk polymerization have excellent foaming properties, but most of the molded articles have strength equal to or less than that of EPS, and acrylonitrile / styrene "High mechanical strength", one of the features of resin, is not utilized. This is due to the method of producing the expandable resin particles, and when a resin produced by bulk polymerization is used,
The "cell diameter" of the foam molded article is likely to be non-uniform, and as a result, it is difficult to obtain a molded article having high mechanical strength.

The present invention has been made in view of these problems, and has been made in consideration of the above problems. The foamable acrylonitrile / styrene has excellent mechanical strength of the foam and less odor when the foam is heat-reduced. It is intended to provide a method for producing resin particles and a foam molded article using the same.

[0007]

According to the present invention, a mixture of 10 to 50% by weight of acrylonitrile and 50 to 90% by weight of styrene is subjected to suspension polymerization using a radical polymerization initiator in the presence of α-methylstyrene dimer. Polystyrene equivalent weight average molecular weight of 300,000 to 600,
The present invention relates to expandable acrylonitrile-styrene resin particles obtained by impregnating 3 to 15% by weight of butane with respect to acrylonitrile and styrene into 000 resin particles, and a foamed molded article using the same.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, embodiments of the expandable acrylonitrile-styrene resin particles of the present invention and an expanded molded article thereof will be described. The composition ratio of the expandable acrylonitrile / styrene resin particles produced in the present invention is such that acrylonitrile is 10 to 50% by weight and styrene is 50 to 90% by weight, and preferably, acrylonitrile is 20 to 40% by weight and styrene is 60-80% by weight
It is said. If the amount of acrylonitrile is less than 10% by weight, the characteristics as an acrylonitrile-styrene resin are hardly exhibited, and if it exceeds 50% by weight, the foaming property is reduced and a low-density product cannot be obtained.

For the suspension polymerization of the monomer mixture of acrylonitrile and styrene in the present invention, a conventionally known method can be applied, and a monomer in which an organic peroxide is dissolved in an aqueous medium containing a dispersant is dispersed. The polymerization is carried out by generating radicals. The acrylonitrile-styrene resin particles of the present invention can also be obtained by this method. As the dispersant used for the suspension polymerization and the impregnation of the foaming agent in the present invention, conventionally known dispersants such as a combination of a hardly soluble inorganic salt and a surfactant and an organic dispersant such as polyvinyl alcohol can be applied.

The radical polymerization initiator used for the suspension polymerization in the present invention has a 10-hour half-decomposition temperature of 50 to 50 hours.
A conventionally known one at 120 ° C. can be applied. For example,
Lauroyl peroxide, benzoyl peroxide, t-butylperoxybenzoate, t-butylperoxyisopropyl carbonate, di-t-butylperoxyhexahydroterephthalate, di-t-butylperoxytrimethylcyclohexane, bis (di-t-
Butylperoxycyclohexyl) propane.

In the present invention, α-
Methylstyrene dimer is used. The amount of the α-methylstyrene dimer added is preferably in the range of 0.01 to 2.0% by weight, more preferably 0.05 to 1.0% by weight, based on the total amount of acrylonitrile and styrene monomer. When the addition amount is less than 0.01% by weight, the effect of adding the chain transfer agent is hardly exhibited, and when it exceeds 2.0% by weight, the reaction rate becomes slow, which is not practical.

The weight average molecular weight of the acrylonitrile / styrene resin particles in the present invention is from 300,000 to 60.
It is 0000. If the weight average molecular weight is less than 300,000, the mechanical strength of the molded article will be low, and if it exceeds 600,000, the foamability will be poor, and it will be difficult to obtain a low density product. Resin particles having a weight average molecular weight in this range are represented by α
-It can be obtained by adjusting the addition amount of the methylstyrene dimer and the radical polymerization initiator, the polymerization temperature and the like. The average particle size of the resin particles obtained in the present invention is usually from 0.2 to
The range is 1.5 mm.

As the blowing agent in the present invention, butane, which is generally used in the production of expanded polystyrene, is used. The amount used is 3 to 15% by weight based on acrylonitrile and styrene, preferably 3 to 10%. % By weight. If the amount of the foaming agent is less than 3% by weight, it is difficult to impart foaming properties. If the amount exceeds 15% by weight, the effect as a foaming agent is not improved, and it is uneconomical.

The expandable acrylonitrile / styrene resin particles according to the present invention are impregnated with a blowing agent, subjected to dehydration, drying and classification, and then coated with a surface additive. As the surface additive in the present invention, those used for expanded polystyrene can be applied as they are. For example, there are zinc stearate, triglyceride stearate, hardened castor oil, amide compounds, silicones, antistatic agents and the like. The coating of the foamable acrylonitrile / styrene resin particles with these surface additives can be performed by a Henschel mixer, a Loedige mixer or the like.

The foaming of the expandable acrylonitrile-styrene resin particles of the present invention is performed by steam, hot air, hot water, or the like, and a general foaming method of expandable styrene resin can be applied. The expansion ratio of the expandable acrylonitrile-styrene resin particles of the present invention can be arbitrarily selected from a low ratio to a high ratio. Applications of the foam molded article obtained from the expandable acrylonitrile / styrene resin particles of the present invention include packing materials for engine parts, packing materials for heavy-weight engines and the like.

[0016]

Next, the present invention will be described in more detail with reference to Examples, but the present invention is not limited thereto. Example 1 In a 16 liter autoclave equipped with a stirrer, 6000 g of deionized water, 7.5 g of tricalcium phosphate, and 0.1 g of sodium dodecylbenzenesulfonate were added.
18 g was charged and charged while stirring at 200 revolutions / minute. Subsequently, 4320 g of styrene and acrylonitrile 16
80 g, lauroyl peroxide 42.0 g, di-t
-Butyl peroxytrimethylcyclohexane 3.0
g, 12.0 g of α-methylstyrene dimer,
After completion of the charging, the temperature was raised to 68 ° C. After completion of the heating, 3 hours and 4 hours later, 20 g of tricalcium phosphate was added. Subsequently, after keeping the temperature at 68 ° C. for 5 hours, the temperature was raised to 105 ° C. over 60 minutes and kept for 3 hours to complete the polymerization.

Subsequently, 1200 g of butane was sequentially injected into the autoclave and kept warm for 8 hours, then cooled to room temperature, and the steps of polymerization and impregnation with a blowing agent were completed. After washing, dehydrating and drying the removed slurry, it passes through 12 mesh,
Classification was performed with 22 mesh remaining to obtain 6200 g of expandable acrylonitrile / styrene resin particles. Subsequently, 1.2 g of dimethyl silicone, 9.3 g of zinc stearate, and 4.0 g of castor hydrogenated oil were added and mixed to coat the surface to obtain expandable acrylonitrile / styrene resin particles. The obtained resin particles are pre-foamed to 40 ml / g, aged for about 18 hours, and molded using a molding machine VS-500 manufactured by Daisen Industries under the conditions of a molded product thickness of 50 mm and a molding pressure of 0.9 kg / cm ^2. Then, a molded product was obtained.

Comparative Example 1 The procedure of Example 1 was repeated except that 12.0 g of α-methylstyrene dimer was changed to 6.0 g of t-dodecylmercaptan and the polymerization temperature was changed to 62 ° C. . [Comparative Example 2] In Example 1, 19.7 g of α-methylstyrene dimer was replaced with 19.7 g of n-octyl mercaptan.
The procedure was performed in the same manner as in Example 1 except that the polymerization temperature was changed to 62 ° C.

Comparative Example 3 In place of expandable acrylonitrile / styrene resin particles, expandable polystyrene resin particles (trade name: Hibeads SSB-TX, manufactured by Hitachi Chemical Co., Ltd.)
-5), pre-foamed to 40 ml / g, aged for about 18 hours, and then used a molding machine VS-500 manufactured by Daisen Industries.
The molded product was molded at a thickness of 50 mm and a molding pressure of 0.7 kg / cm ² to obtain a molded product. Table 1 shows the evaluation results of the expandable resin particle molded products in Example 1 and Comparative Examples 1 to 3. The characteristic evaluation methods shown in Table 1 are as follows. Molecular weight was determined by gel permeation chromatography (eluent:
Tetrahydrofuran, detector: RI detector)
The molecular weight in terms of standard polystyrene was determined.

The bending strength of a molded article having a density of 0.025 g / l was measured in accordance with JIS-A-9511. The odor at the time of heat reduction is determined by the desolvator (product name: Styrol Post SP) used for recycling polystyrene molded products.
BH-20 (manufactured by Suruga Seiki Co., Ltd.) was used to evaluate the odor when a molded article was actually heated and melted to produce an ingot by human smell.

[Odor criterion] +: Weak odor ← ── → ++: Strong odor

[Table 1]

[0022]

The foamable acrylonitrile according to the present invention
By using the styrene resin particles, a foam molded article having excellent mechanical strength and good recyclability can be obtained.

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4F074 AA32A AA33A AB01 BA37 BA38 CA24 CA30 CA34 CC03Y CC27X CC28X CC29X CC32X CC34Y DA02 DA08 DA33

Claims (2)

[Claims] 1. A polystyrene-equivalent weight average molecular weight obtained by subjecting a mixture of 10 to 50% by weight of acrylonitrile and 50 to 90% by weight of styrene to suspension polymerization with a radical polymerization initiator in the presence of α-methylstyrene dimer. Expandable acrylonitrile-styrene resin particles obtained by impregnating 300,000 to 600,000 resin particles with 3 to 15% by weight of butane based on acrylonitrile and styrene. 2. A foamed acrylonitrile / styrene resin product obtained by prefoaming the expandable acrylonitrile / styrene resin particles according to claim 1 with a heating medium and molding the prefoamed particles with a heating medium.