JPS6140700B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing thermoplastic resin particles. More specifically, this invention provides a styrene-maleic anhydride copolymer resin having a maleic anhydride content of 15 to 30% by weight and an average degree of polymerization of 500 or more, a styrene-maleic anhydride copolymer resin having the formula RX (wherein X is a functional group that reacts with a dicarbonyloxo group, R is an aliphatic residue having one double bond) and a polymerization catalyst are dissolved in a vinyl aromatic monomer, this solution is suspended in an aqueous medium, and reacted, and during the reaction or reaction. By adding a blowing agent afterwards, the maleic anhydride component is
The present invention relates to a method for producing thermoplastic resin particles, which comprises forming expandable thermoplastic resin particles with a weight of 10%. Polystyrene resins are widely used as resins for molding materials and foaming materials, but their heat distortion temperature is low, making them unsuitable for use in applications requiring heat resistance. On the other hand, styrene-maleic anhydride copolymer resin has a high heat deformation temperature, but it is currently difficult to obtain pearl-like and small particles due to the manufacturing method. Generally, when particles with a large particle size are used as a molding material, there will be large fluctuations in penetration when feeding into the hopper of a molding machine, and it will take time to melt in the cylinder of the molding machine. Furthermore, when particles with such a large particle size are used as expandable particles (beads), it is possible to not only mold large objects, but also to manufacture small molded objects, thin walled objects, and objects that require thin details. Have difficulty. From this point of view, various attempts have been made to make the particles of styrene-maleic anhydride copolymer resins smaller, but none have been successful. For example, when the copolymer resin is pelletized using an extruder, only large-sized pellets can be obtained even if the copolymer resin is hot-cut or cooled with water before cutting. In an attempt to improve this to some extent, strand cutting, which involves stretching and cutting the molten resin extruded from the extruder's discharge port, causes polymer orientation and thermal deterioration in the stretching direction, making it difficult to use these pellets. When foam molding is performed using beads containing a foaming agent, there are problems such as it is difficult to obtain a low-density foam molded product and the molding width is narrow (the range of molding conditions to obtain a good molded product is narrow). Ta. Furthermore, the styrene-maleic anhydride copolymer resin is
It is difficult to form a polymer in which the maleic anhydride component is polymerized so as to be uniformly distributed within the molecule, requiring complicated control and resulting in an expensive product. The inventors of this invention arrived at this invention as a result of intensive research in order to solve the above-mentioned problems. The inventors first developed a styrene-maleic anhydride copolymer resin with a relatively high maleic anhydride content, formula
A compound represented by RX (herein referred to as a bonding monomer) and a polymerization catalyst are dissolved in a vinyl aromatic monomer, this solution is suspended in water, and polymerized in a suspended state in the presence of a polymerization catalyst to form thermoplastic resin particles. It has been found that by doing so, the particles obtained can be made small and uniform. When these resin particles are used as a molding material, the variation in penetration during feeding into the hopper of the molding machine is small, and the melting time in the cylinder of the molding machine is short.
In addition, when foam molding is performed using beads containing a foaming agent, a low-density foam molded product can be easily obtained, and a wide range of molding conditions can be applied, and small molded products, thin wall thickness, and thin details are required. It was discovered that it could be produced. Furthermore, by using a bonding monomer, the content of styrene-maleic anhydride copolymer resin can be reduced while still maintaining heat resistance (high heat distortion temperature or softening temperature, low heat shrinkage at high temperatures).
can be maintained. As the styrene-maleic anhydride copolymer resin in this invention, one containing 15 to 30% by weight of maleic anhydride is used. This copolymer is
It is obtained by copolymerizing styrene and maleic anhydride using methods known in the art. If the content of maleic anhydride component, which is one of the copolymerized components in the styrene-maleic anhydride copolymer resin, is less than 15% by weight, no improvement in thermal properties can be expected, and if it exceeds 30% by weight, vinyl aromatic This is not preferable because the styrene-maleic anhydride copolymer becomes difficult to dissolve in the monomer. As the styrene-maleic anhydride copolymer resin, one having a so-called high degree of polymerization is used. A polymer having an average degree of polymerization of at least about 500 or more is used. If a material with an average degree of polymerization of less than 500 is used, the resulting resin particles will have low mechanical strength when molded into a molded product, and if the degree of polymerization is too high, the resulting resin will become brittle and have a strength of approximately 4000.
It is preferable to use a polymer having a degree of polymerization of up to . These copolymer resins can be used as raw materials for the present invention even if they contain small amounts of additives to improve or impart desired properties. For example, if a small amount of synthetic rubber such as butadiene rubber is added, the impact resistance will be improved. As the bonding monomer, a compound represented by the formula RX (wherein X is a functional group that reacts with a dicarbonyloxy group, and R is an aliphatic residue having one double bond) is used. The functional group in the definition of formula RX means a group that can react with the dioxocarbonyl group of the maleic anhydride moiety in the styrene-maleic anhydride copolymer resin. Examples of such functional groups include hydroxy groups, amide groups, and epoxy groups. The hydroxy group or amide group is preferably bonded to the vinyl group via one or two carbon atoms. In addition, the epoxy group is
It may be bonded to the vinyl group via an oxygen atom or a carbon atom. Specific compounds include allyl glycidyl ether, glycidyl acrylate, glycidyl methacrylate, allyl alcohol, Nn-butoxymethyl acrylamide, and the like. These compounds are generally known as polymer modifiers, and compounds similar to these are used. In this invention, it is preferable to graft at least one site per molecule of the copolymer resin. From this point of view, it is desirable that the amount of the binding monomer used in the present invention be selected depending mainly on the maleic anhydride content in the copolymer resin. The binding monomer is 0.1 to 20 mol%, preferably 0.1 to 20 mol% based on the maleic anhydride component in the copolymer resin.
Use 0.2-10 mol%. The functional group of the binding monomer attacks the carboxylic anhydride site in the molecular chain of the styrene-maleic anhydride copolymer to open the ring. This introduces into the molecular chain of the copolymer a double bond that can be copolymerized with the vinyl aromatic monomer. The vinyl aromatic monomers used in this invention include styrene, α-methylstyrene, ethylstyrene, chlorostyrene, bromostyrene, vinyltoluene, vinylxylene, isopropylxylene, etc. alone or in a mixture of two or more, and 50 of these vinyl aromatic monomers
It may be a mixture of a vinyl aromatic monomer and a copolymerizable monomer, such as acrylonitrile, methyl methacrylate, methyl acrylate, maleic anhydride, etc., containing at least % by weight. The weight ratio of the styrene-maleic anhydride copolymer resin and the vinyl aromatic monomer is selected so that the maleic anhydride content in the resin of the thermoplastic resin particles to be produced is 2 to 10% by weight. If the maleic anhydride content is less than this range, the final thermoplastic resin will have a low heat deformation temperature, which is undesirable.If it exceeds this range, the amount of copolymer resin that must be dissolved in the manufacturing process will increase, resulting in a monomer. becomes difficult to dissolve. Examples of the polymerization catalyst used in this invention include benzoyl peroxide, tert-butyl perbenzoate, lauroyl peroxide, and tert-butyl peroxide.
Butyl peroxy-2-ethylhexanate,
Organic peroxides such as tert-butyl peroxide,
Examples include azo compounds such as azobisisobutyronitrile and azobisdimethylvaleronitrile. In this invention, the styrene-maleic anhydride copolymer resin, binding monomer, and polymerization catalyst are usually dissolved in a vinyl aromatic monomer, suspended in an aqueous medium, and reacted. However, the polymerization catalyst may be added after suspending the resin and both monomers. In this case, it is also preferable to dissolve the polymerization catalyst in the styrene monomer and add it to the aqueous medium. Dispersants are used to suspend in aqueous media. Examples of dispersants include organic compounds such as partially saponified polyvinyl alcohol, polyacrylates, polyvinylpyrrolidone, carboxymethyl cellulose, methyl cellulose, calcium stearate, and ethylene bisstearamide, as well as calcium pyrophosphate, calcium phosphate, calcium carbonate,
Examples include inorganic compounds consisting of fine powder hardly soluble in water, such as magnesium carbonate, magnesium phosphate, magnesium pyrophosphate, and magnesium oxide. In the method of this invention, when an inorganic compound is used as a suspending agent, it is preferable to use a surfactant such as sodium dodecylbenzenesulfonate. These dispersants are generally added in an amount of 0.01 to 5% by weight based on water. The reaction in this invention is carried out by heating at a temperature of 65 to 95°C, preferably about 80 to 90°C, for 2 to 12 hours, and further removes a very small amount of unreacted components.
The reaction is completed by heating and stirring at 120-140°C. Under these conditions, attack of the functional group It is thought that polymerization with double bonds in monomers and intermolecular crosslinking due to these reactions occur. The blowing agents used in this invention include easily volatile blowing agents, such as aliphatic hydrocarbons such as propane, n-butane, i-butane, n-pentane, i-pentane, and n-hexane, cyclopentane, Examples include cycloaliphatic hydrocarbons such as cyclohexane, halogenated hydrocarbons such as methyl chloride, ethyl chloride, dichlorodifluoromethane, chlorodifluoromethane, and trichlorofluoromethane. These blowing agents are generally used in an amount of 3 to 40% by weight based on the thermoplastic resin particles. Further, a small amount of an organic solvent such as toluene or xylene may be used in combination. The blowing agent may be added at any time during or after the reaction. Preferably, the product particles are impregnated after the reaction. To impregnate the thermoplastic resin particles with the blowing agent after the reaction, for example, the thermoplastic resin particles are suspended in a suspension in which the suspending agent is suspended in an autoclave, and the blowing agent is forced into the suspension by heating. This is done by The suspending agent used in the aqueous suspension is added to prevent the thermoplastic resin particles from bonding or coalescing with each other during impregnation with the blowing agent, and is a dispersing agent containing the above-mentioned organic In addition to compounds, calcium pyrophosphate, calcium phosphate, calcium carbonate, magnesium carbonate, magnesium phosphate,
Examples include inorganic compounds consisting of fine powders that are poorly soluble in water, such as magnesium pyrophosphate and magnesium oxide. In the method of this invention, when an inorganic compound is used as a suspending agent, it is preferable to use a surfactant such as sodium dodecylbenzenesulfonate. These dispersants are generally added in an amount of 0.01 to 5% by weight based on water. The expandable thermoplastic resin particles obtained as described above are separated from water, washed and dried as appropriate, and then used. According to this invention, a large amount of particles having a uniform and small particle size can be obtained. In addition, when this resin particle is used as a molding material, there is little variation in penetration when feeding into the hopper of a molding machine, and melting in the cylinder of the molding machine takes a short time.In particular, when foam molding is performed, low density foam molding The product can be easily obtained, a range of molding conditions can be accommodated, and small molded products, thin walled products, and products requiring thin details can be produced. Furthermore, the use of a binding monomer allows the content of styrene-maleic anhydride copolymer resin to be reduced while still maintaining heat resistance. Next, the present invention will be explained with reference to Examples. Example 1 2000 g of water, 4.8 g of metathetical magnesium pyrophosphate and 10 g of a 2% by weight aqueous solution of sodium dodecylbenzenesulfonate were charged into a reaction vessel with an internal volume of 5, and styrene-anhydride containing 18% by weight of maleic anhydride was added. 600 g of maleic acid copolymer (average degree of polymerization 1000), 3.5 g of benzoyl peroxide, tert-
A mixed solution of 1 g of butyl perbenzoate and 2.5 g of glycidyl methacrylate dissolved in 1,400 g of styrene monomer was added, and the temperature was raised to 90° C. while stirring at 150 rpm. After reacting at 90°C for 7 hours, the stirring speed was increased to 250 rpm, and the temperature was raised to 130°C and maintained for 2 hours to obtain polymer particles containing 5.4% by weight of maleic anhydride. The polymer obtained here is pearl-like, and its particle size is 70% between 10 and 20 meshes when measured using a JIS standard sieve.
It was distributed. Moreover, the softening temperature was 114°C. Example 2 1200 g of the polymer obtained in Example 1 (having a particle size between 10 and 20 meshes) was mixed with 2800 g of water, 4.8 g of metathesized magnesium pyrophosphate, 10 g of a 2% aqueous solution of sodium dodecylbenzenesulfonate, and toluene. It was placed in an autoclave with an internal volume of 5 containing 48 g. Butane 120 under closed conditions with stirring
g was press-fitted. The temperature was then raised to 100°C, maintained for 20 hours, and then cooled to 30°C to obtain beads containing a foaming agent. After washing, dehydrating, and drying the beads, they were placed in a sealed container and stored at 15° C. for 3 days. When the expandable beads obtained here were foamed with steam at 100°C, foamed particles having a bulk density of 0.021 Kg/ were obtained. After the foamed particles were left indoors for 24 hours, they were filled into a mold and molded with steam at 1.5 kg/cm ² (gauge pressure). The obtained molded product has a density of 0.022 Kg/, and when this molded product was left in a 90°C air circulation constant temperature bath for one week, it had a density of 1.2 in one direction relative to the original size.
% shrinkage. Example 3 The softening temperature and content of hot toluene insolubles of polymer particles obtained by carrying out the reaction in the same manner as in Example 1 except that the amount of glycidyl methacrylate dissolved in the styrene monomer was changed are as shown in Table 1. Ta.

[Table] Example 4 2000 g of water, 4.8 g of metathetical magnesium pyrophosphate, and 10 g of a 2% aqueous solution of sodium dodecylbenzenesulfonate were placed in a reaction vessel with an internal volume of 5, and the content of maleic anhydride was 21% by weight in advance.
500g of styrene-maleic anhydride copolymer
(Average degree of polymerization 800, benzoyl peroxide 3.75g, tert
- 1.2 g of butyl perbenzoate and 4.0 g of glycidyl methacrylate as styrene monomer.
A mixed solution of 1,500 g was added. The temperature was raised to 90°C while stirring at 150 rpm. After reacting at a temperature of 90°C for 7 hours, the stirring was increased to 250 rpm, the temperature was raised to 130°C, and the temperature was maintained at 130°C for 2 hours. Thereafter, it was cooled and the polymer was taken out. The polymer thus obtained is pearl-like, and its particle size is JIS
The distribution was 82% between 10 and 20 meshes using a standard sieve. The softening temperature of the obtained polymer particles was 116
It was warm at ℃. When immersed in hot toluene at 130°C for 4 hours, 72% was found to be insoluble matter. Comparative Example 1 Polymerization was carried out in the same manner as in Example 1 except that glycidyl methacrylate was not used, and the softening temperature of the obtained polymer particles was measured and was 110°C.
It was hot.

Claims (1)

[Scope of Claims] 1. A styrene-maleic anhydride copolymer resin with a maleic anhydride content of 15 to 30% by weight and an average degree of polymerization of 500 or more, formula RX (wherein X is a functional group that reacts with a dicarbonyloxo group, R is an aliphatic residue having one double bond) is dissolved in a vinyl aromatic monomer, this solution is suspended in an aqueous medium, and reacted in the presence of a polymerization catalyst, during which A method for producing thermoplastic resin particles, which comprises adding a blowing agent during or after the reaction to obtain expandable thermoplastic resin particles containing 2 to 10% by weight of a maleic anhydride component. 2 The compound represented by formula RX is present in an amount of 0.1 to 20 mol%, preferably 0.2 to 10 mol%, based on the maleic anhydride component in the styrene-maleic anhydride copolymer resin.
The manufacturing method according to claim 1, which is used.