JPS6140698B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing thermoplastic resin particles. More specifically, this invention uses 20 to 50 parts by weight of a styrene-maleic anhydride copolymer resin containing 20 to 30% by weight of a maleic anhydride component and having an average degree of polymerization of 10 to 250, and a formula RX (wherein X is dicarbonyl). 1 to 18 parts by weight of a compound represented by a functional group that reacts with an oxo group (R is an aliphatic residue having one double bond) and a polymerization catalyst are dissolved in 79 to 32 parts by weight of a vinyl aromatic monomer, The present invention relates to a method for producing thermoplastic resin particles, which comprises suspending this solution in an aqueous medium, reacting it, and adding a blowing agent during or after the reaction to obtain foamable thermoplastic resin particles. Although polystyrene resins are widely used as resins for molding materials and foaming materials, they have a low heat distortion temperature and cannot be used in applications that require heat resistance. On the other hand, styrene-maleic anhydride copolymer resin has a high heat distortion temperature, but controlling the reaction is extremely difficult and complicated in order to uniformly distribute the maleic acid component in the molecular chain and make it a polymer. This required a unique method, and the resin produced had to be expensive. By the way, styrene-maleic anhydride copolymer resins with low polymerization degrees, such as an average degree of polymerization of 10 to 250, can be obtained relatively easily with various styrene/maleic anhydride acid ratios, and can be obtained in various ways. It is commonly used for a wide range of purposes. In view of the above-mentioned current situation, the inventors of the present invention have developed a thermoplastic resin with excellent heat resistance (heat distortion temperature) by utilizing the easily available styrene-maleic anhydride copolymer resin with a low degree of polymerization. The research was based on the idea of whether or not it could be obtained. As a result, a styrene-maleic anhydride copolymer resin with a low degree of polymerization containing 20 to 30% by weight of maleic anhydride component, and a compound having a functional group capable of reacting with a carboxylic acid anhydride and a double bond in the same molecule. (herein referred to as the bonding monomer) and a vinyl aromatic monomer are mixed, treated in the presence of a polymerization catalyst, and the above X of the bonding monomer is reacted with a carboxylic acid anhydride (ring-opening reaction), while the bonding monomer is discovered that a thermoplastic resin with a high heat distortion temperature could be obtained by polymerizing the double bond of R and a vinyl aromatic monomer,
This invention was arrived at after further study. In this invention, a styrene-maleic anhydride copolymer resin containing 20 to 30% by weight of a maleic anhydride component and having an average degree of polymerization of 10 to 250 is used. If the maleic anhydride component content in the styrene-maleic anhydride copolymer resin exceeds 30% by weight, it will be difficult to dissolve in the vinyl aromatic monomer, and if it is less than 20% by weight, the maleic anhydride component content in the thermoplastic resin produced. is undesirable because the desired heat resistance is not obtained. A styrene-maleic anhydride copolymer resin with an average degree of polymerization of 10 to 250 is used if maleic anhydride and styrene monomer undergo a 1:1 alternating copolymerization reaction, and if the resin has a low degree of polymerization. This is because by changing the initial mixing ratio of maleic anhydride and styrene, a copolymer resin having the above maleic anhydride component content can be obtained extremely easily and in large quantities. The vinyl aromatic monomers used in this invention include styrene, α-methylstyrene, ethylstyrene, chlorostyrene, bromostyrene, vinyltoluene, vinylxylene, isopropylxylene, etc. alone or in combination of two or more thereof. 50% vinyl aromatic monomer
It may be a mixture of a vinyl aromatic monomer and a copolymerizable monomer, such as acrylonilyl, methyl methacrylate, or methyl acrylate, containing at least % by weight. The weight ratio of the styrene-maleic anhydride copolymer resin to the vinyl aromatic monomer is 20 to 50 parts by weight of the styrene-maleic anhydride copolymer resin to 79 to 32 parts by weight of the vinyl aromatic monomer. If the amount of copolymer resin used is less than this range, the final thermoplastic resin obtained will have a low heat distortion temperature, which is undesirable, and if the amount of copolymer resin used is more than this range, the copolymer resin will not dissolve. This is not preferable because it requires a long time and becomes highly viscous, making it difficult to control the reaction. As the bonding monomer, a compound represented by the formula RX (wherein X is a functional group that reacts with a dicarbonyloxo 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,
Examples include Nn-butyloxymethylacrylamide. These compounds are generally known as polymer modifiers, and compounds similar to these are used. The amount of the binding monomer used in this invention is 1 to 18 parts by weight per 20 to 50 parts by weight of the styrene-maleic anhydride copolymer resin (this is about 5 parts by weight based on the maleic anhydride component of the styrene-maleic anhydride copolymer resin). (equivalent to ~100 mol%). If the amount of the bonding monomer used is less than this range, the resulting resin will have poor thermal properties, and if it exceeds this range, no improvement in the thermal properties will be observed. Examples of the polymerization catalyst used in this invention include organic oxides such as benzoyl peroxide, tert-butyl perbenzoate, lauroyl peroxide, tert-butyl peroxy-2-ethylhexanate, and tet-butyl peroxide; Examples include azo compounds such as isobutyronitrile and azobisdimethylvaleronitrile. In this invention, first, the above-mentioned styrene-maleic anhydride copolymer resin, binding monomer, and polymerization catalyst are dissolved in a vinyl aromatic monomer, and this is suspended in an aqueous medium and reacted. A dispersing agent is usually used for suspension in an aqueous medium. Examples of dispersants include partially saponified polyvinyl alcohol,
Compounds such as polyacrylate, polyvinylpyrrolidone, carboxymethylcellulose, methylcellulose, calcium stearate, and ethylene bisstearamide are used. The treatment reaction in this invention is carried out by heating and stirring at a temperature of 65 to 95°C, preferably around 80 to 90°C for 2 to 12 hours, and further heating and stirring a very small amount of unreacted components at a temperature of 120 to 140°C. The reaction is completed by doing this. 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. In this invention, the thermoplastic resin particles further include a blowing agent. 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, n-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 is completed, for example, the thermoplastic resin particles are suspended in a suspension containing the suspending agent 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 the compounds, inorganic compounds consisting of fine powder hardly soluble in water, such as calcium pyrophosphate, calcium phosphate, calcium carbonate, magnesium carbonate, magnesium phosphate, magnesium pyrophosphate, and magnesium oxide, can be used. 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 used 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. The expandable thermoplastic resin particles obtained by the present invention have better heat resistance than polystyrene, and can be easily obtained in large quantities with a desired particle size. Next, the present invention will be explained with reference to Examples. Example 1 2000 g of water and 50 g of a 2% aqueous solution of partially saponified polyvinyl alcohol were charged into a polymerization vessel with an internal volume of 5.
Furthermore, 800 g of a styrene-maleic anhydride copolymer resin with a maleic anhydride content of 25% by weight and an average degree of polymerization of 19, 4.0 g of benzoyl peroxide, 1.2 g of tert-butyl perbenzoate, and 300 g of glycidyl methacrylate were added to 900 g of styrene monomer. A mixed solution dissolved in the above was added, and the temperature was raised to 90°C while stirring with a stirring blade at 100 revolutions/minute. After maintaining the temperature at 90°C for 7 hours, the stirring was increased to 250 rpm, and the temperature was raised to 130°C and maintained for 2 hours to complete the reaction. During the reaction period at 90° C., 25 g of a 2% aqueous solution of partially saponified polyvinyl alcohol was added every hour. The resin obtained here was passed through a JIS standard sieve.
They were pearl-like particles with a 70% distribution between ~30 meshes. Further, after 4 hours of immersion in hot toluene at 130°C, the amount of insoluble matter was 75% by weight, and the softening temperature was 105°C. Example 2 1200 g of the resin obtained in Example 1, 2800 g of water, 4.8 g of metathetical magnesium pyrophosphate, 10 g of a 2% aqueous solution of sodium dodecylbenzenesulfonate, and 36 g of toluene were charged into an autoclave having an internal volume of 5. After 120 g of butane was injected under pressure in a sealed state while stirring, the temperature was raised to 85°C and maintained for 14 hours. Thereafter, it was 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 24 hours. When the expandable beads obtained here were foamed with steam at 100°C, foamed particles having a bulk density of 0.030 kg/ were obtained. After leaving the expanded particles in a room for 24 hours, the mold was slightly overfilled and molded with steam at 0.8 kg/cm ² (gauge pressure). When the resulting foamed molded product was left in a 90°C air circulation constant temperature bath for one week, it shrank by 3.8% in one direction relative to its original size. Comparative example Glycyldyl methacrylate 300 of Example 1
The softening point of the resin obtained by polymerizing under the same conditions except that 300 g of styrene monomer was used instead of 95 g was 95.
It was warm at ℃. Also, beads containing a foaming agent were obtained under the same conditions as in Example 2. These beads were foamed with steam at 95°C to obtain foamed particles having a bulk density of 0.028 kg/. However, although a mold was overfilled with the foamed particles, a sufficient molded product could not be obtained. Example 3 A resin obtained by reacting under the same conditions as in Example 1 except that the ratio of glycidyl methacrylate and styrene monomer was changed as follows showed the following softening temperature.

[Table] Example 4 2000 g of water and 50 g of a 2% by weight aqueous solution of partially saponified polyvinyl alcohol were charged into a reaction vessel with an internal volume of 5, and the content of maleic anhydride was 25% by weight in advance, and the average degree of polymerization was 20. 450 g of styrene-maleic anhydride copolymer, 3.2 g of benzoyl peroxide
g, 1.6 g of t-butyl perbenzoate, 350 g of glycidyl methacrylate, and 1300 g of styrene monomer.
A mixed solution dissolved in 50 g was added, and the temperature was raised to 90° C. while stirring with a stirring blade at 100 revolutions/minute. After maintaining the temperature at 90°C for 7 hours, the stirring was increased to 250 rpm, the temperature was increased to 130°C, and the temperature was further maintained at 130°C for 2 hours to complete the reaction. During the reaction period at 90° C., 25 g of a 2% by weight aqueous solution of partially saponified polyvinyl alcohol was added every hour for polymerization. The thus obtained polymer was pearl-like particles having a distribution of 78% between 16 and 30 meshes when measured using a JIS standard sieve. Furthermore, after 4 hours of immersion in hot toluene at 130°C, the amount of insoluble matter was 93% by weight. The softening temperature of these particles was 106°C.

Claims (1)

[Claims] 1 20 to 50 parts by weight of a styrene-maleic anhydride copolymer resin with an average degree of polymerization of 10 to 250 containing 20 to 30% by weight of a maleic anhydride component, formula RX (wherein X is a functional group that reacts with a dicarbonyl oxo group) , R is an aliphatic residue having one double bond) and a polymerization catalyst are dissolved in 79 to 32 parts by weight of a vinyl aromatic monomer, and this solution is poured into an aqueous medium. A method for producing thermoplastic resin particles, which comprises suspending and reacting, and adding a blowing agent during or after the reaction to obtain foamable thermoplastic resin particles.