JPH0423656B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to expandable thermoplastic copolymer particles that have excellent heat resistance and solvent resistance, as well as good foamability and moldability. As expandable polymer particles, expandable polystyrene resin particles are well known, and by using these particles, a molded foamed article can be easily obtained at low cost. However, since the monomer constituting the polymer is styrene, this foam molded product has poor heat resistance for use in relatively high-temperature pipe insulation materials, roof insulation materials, automobile parts, solar system insulation materials, etc. There are drawbacks that prevent it from being used for the required purpose. Furthermore, when used in combination with other materials, especially in automobile parts, etc., it also has the disadvantage that it is difficult to select an adhesive because of its poor solvent resistance. The present inventors have determined that in order to obtain expandable thermoplastic polymer particles having sufficient heat resistance and solvent resistance for practical use, the monomer composition constituting the polymer should be 10% or more of alpha methylstyrene. and obtain copolymer particles containing 5% or more of acrylonitrile,
It was thought that it was necessary to incorporate an easily volatile foaming agent into the resin particles. However, after pre-foaming such expandable thermoplastic copolymer particles, molding is performed to obtain a foamed molded product, and if the foamed molded product is left under high temperature, the dimensional change of the foamed molded product will not change. Although there are almost no visible irregularities on the surface of the molded product due to the expansion of the foamed particles forming the surface layer of the molded product (hereinafter referred to as tertiary foaming)
It has become clear that this problem is occurring and the aesthetic appearance is severely damaged. As a result of extensive research in view of these drawbacks, the present inventors have found that by applying a specific plasticizer to the surface of expandable thermoplastic copolymer particles using the above method, tertiary foaming can be achieved even under high temperature conditions. The present inventors have discovered that it is possible to obtain expandable thermoplastic copolymer particles that give a foamed molded article with excellent heat resistance and almost no dimensional change, and have completed the present invention. That is, in the present invention, the monomers constituting the polymer include 10 to 80% by weight of alphamethylstyrene, 5 to 50% by weight of acrylonitrile, and further styrene, chlorostyrene, paramethylstyrene, t-butylstyrene, acrylic ester, and methacrylate. Contains 0 to 70% by weight of at least one compound selected from acid esters, 2 to 15% by weight of an easily volatile blowing agent, and the surface is coated with a plasticizer that is liquid at room temperature with a solubility parameter value of 8.0 to 9.5. The material contains expandable thermoplastic copolymer particles. The amount of alphamethylstyrene used in the present invention is in the range of 10 to 80% by weight, and is determined depending on the desired heat resistance and expansion ratio, but if it is less than 10% by weight, the effect of improving heat resistance is not observed. Gone, 80 again
It is very difficult to produce a copolymer containing alpha methyl styrene in an amount exceeding % by weight at a high polymerization conversion rate. In order to obtain heat resistance of 100℃ with a 50x foam molded product,
It is necessary to use 20 to 50% by weight of alpha methylstyrene, and in order to obtain heat resistance of 110°C with a 5 to 15 times foamed product, it is necessary to use 50 to 80% by weight of alpha methylstyrene. Furthermore, the acrylonitrile used in the present invention is
It is necessary to make the foam exhibit oil resistance, and conventionally, alpha methylstyrene is used in large quantities.
Although it has been difficult to obtain a high polymerization conversion rate in suspension polymerization, it has been made possible by the combined use of acrylonitrile. If the amount of acrylonitrile used is less than 5% by weight, the polymerization conversion rate of the composition will be low and the oil resistance will not be effective, which is not preferable. Also 50% by weight
Even if it is used in excess of this amount, the polymerization conversion rate will not change and the resin will be colored yellowish brown, which is not preferable. Monomers other than alphamethylstyrene and acrylonitrile include styrene, various substituted styrenes such as chlorostyrene, paramethylstyrene, and t-butylstyrene, acrylic acid esters such as methyl acrylate, ethyl acrylate, and butyl acrylate, methyl methacrylate, and ethyl styrene. One or more types of methacrylic acid esters such as methacrylate and butyl methacrylate can be used as appropriate. Easily volatile blowing agents used in the present invention include:
Aliphatic hydrocarbons such as propane, butane, pentane; cycloaliphatic hydrocarbons such as cyclobutane, cyclopentane, cyclohexane; trichlorofluoromethane, dichlorofluoromethane, dichlorodifluoromethane, methyl chloride, Examples include halogenated hydrocarbons such as chlortetrafluoromethane and ethyl chloride. The amount of these blowing agents to be used varies depending on the desired expansion ratio of the foamed molded product, but by containing 2 to 15% by weight, a foamed molded product that is 2 times to 100 times larger can be obtained. is possible. The present invention is characterized in that, in addition to the above composition, the particle surface is coated with a plasticizer that is liquid at room temperature and has a solubility parameter value of 8.0 to 9.5. Conventional techniques for modifying the surface of expandable thermoplastic resin particles by coating them with a coating agent include coating expandable polystyrene resin particles with various lubricants to improve the surface properties during pre-foaming of the particles. Technologies such as preventing blocking, improving fusion properties during molding, and shortening molding cooling time are known, but the various lubricants used in these technologies can be replaced with the copolymer of the present invention. Even when used in a combined composition, it does not have any significant effect on the molding process and the resulting foam. This is because the copolymer in the present invention has oil resistance due to the monomer used. However, if conventionally expandable styrene resin particles were coated with a plasticizer that is liquid at room temperature, cracks would occur on the particle surface and the foaming agent in the particles would quickly dissipate, causing problems in use. It was hot. However, in the present invention, when the above composition is coated with a plasticizer that is liquid at room temperature and has a solubility parameter value of 8.0 to 9.5, cracks occur on the particle surface and the blowing agent in the particles quickly evaporates. There were no such problems, and a remarkable effect was obtained in suppressing tertiary foaming of the foam molded product obtained using the particles. Plasticizer solubility parameter value less than 8.0 and 9.5
The effect of suppressing tertiary foaming becomes smaller when the temperature exceeds 100. Plasticizers used in the present invention for this purpose include phthalate esters such as dibutyl phthalate, di-2-ethylhexyl phthalate, di-n-octyl phthalate, diisodecyl phthalate, and butylbenzyl phthalate; Various plasticizers include aliphatic dibasic acid esters such as 2-ethylhexyl, dioctyl azelaate, and dibutyl sebacate; aliphatic esters such as butyl stearate and butyl oleate; in particular, di-2-phthalate; -Ethylhexyl, isodecyl phthalate, butylbenzyl phthalate, di-2 adipate
- Ethylhexyne, dibutyl sebacate are preferred. The amount of these plasticizers used varies depending on the type of plasticizer used, but is preferably 0.01 to 1.0% by weight based on the expandable thermoplastic copolymer particles. If it is less than 0.01% by weight, the effect of suppressing tertiary foaming will be small;
If it is used in excess of 1% by weight, the moldability will deteriorate when the particles are pre-foamed and then molded, and the condition range for obtaining a molded product having the shape of the mold and a smooth surface will be extremely narrow. , or disappear altogether, which is not desirable. As a method for obtaining the expandable thermoplastic copolymer particles of the present invention, a copolymer of the above composition is obtained by an emulsion polymerization method, and then pelletized and impregnated with an easily volatile blowing agent in an autoclave. A method of coating expandable thermoplastic polymer particles with a plasticizer. A copolymer of the above composition is obtained by a copolymerization method, and then pelletized and impregnated with an easily volatile blowing agent in an autoclave. A method of coating expandable thermoplastic copolymer particles with a plasticizer, in which copolymer particles of the above composition are obtained by suspension polymerization, and then impregnated with an easily volatile blowing agent. Examples include a method of coating the combined particles with a plasticizer. However, in the emulsion polymerization method, there is an increase in cost due to the complexity of the process and a decrease in quality due to the contamination of emulsifiers and coagulants. It is inferior to the suspension polymerization method in terms of the complexity of the process, which requires subsequent impregnation with a blowing agent. Conventionally, it has been extremely difficult to obtain a copolymer with a high molecular weight that can be put to practical use by using a large amount of alphamethylstyrene as described above and carrying out suspension polymerization or polymerization. In the present invention, what makes it possible to polymerize an alphamethylstyrene-acrylonitrile copolymer with a high molecular weight that can be put to practical use through suspension polymerization and polymerization is the use of a specific initiator. The choice is the use and polymerization temperature conditions.
Initiators to be used from this point of view include:
A difunctional organic peroxide that generates t-butoxy radicals is used, and those having a 10-hour half-life temperature of 60 to 120°C are particularly suitable. Initiators that meet these conditions and can be used in practice include di-t-butylperoxyhexahydroterephthalate, 1,1-di-t-butylperoxy-3,3,5-trimethylcyclohexane, and di-t-butylperoxyhexahydroterephthalate. -butyl peroxyazelate, 2,
5-dimethyl-2,5-di(t-butylperoxy)hexane, 1,1-di-t-butylperoxycyclohexane, 1,3-bis(t-butylperoxyisopropyl)benzene, 2,2-di(t-butylperoxyisopropyl)benzene Examples include (t-butylperoxy)butane, 4,4-di-t-butylperoxyvaleric acid n-butyl ester, di-t-butylperoxytrimethyl adipate, and the like. The amount of these initiators used is 0.1 to 2.0% by weight based on the total amount of monomers. 0.1
If the amount is less than % by weight, an industrially practical polymerization conversion rate may not be obtained at all, or it may take a long time, resulting in extremely poor productivity. If it is used in an amount exceeding 2.0% by weight, the molecular weight will drop significantly and satisfactory foam molding will not be possible, or even if foam molding can be carried out, only a foam molded product with significantly inferior strength will be obtained. In addition, the polymerization temperature when using these initiators is
The temperature is preferably 80 to 130°C. If the temperature is less than 80°C, the polymerization conversion rate will be extremely low, and if it exceeds 130°C, the molecular weight will decrease, making it difficult to obtain a satisfactory foam molded product. The thus obtained expandable thermoplastic copolymer particles of the present invention are heated by a heating medium such as water vapor or hot air.
After pre-foaming to a desired magnification, it is filled into a mold that can be closed but cannot be sealed, and heated again with a heating medium such as steam to form a heat-resistant foam having a desired shape. obtain. The present invention will be explained below with reference to Examples. Example 1 110 parts by weight of pure water in an autoclave equipped with a stirrer,
After adding 0.08 parts by weight of tricalcium phosphate and 0.003 parts by weight of sodium dodecylbenzenesulfonate, 30 parts by weight of alphamethylstyrene was added under stirring.
Monomers consisting of 20 parts by weight of acrylonitrile, 50 parts by weight of styrene, 1.0 parts by weight of toluene, and
Butyl peroxyhexahydroterephthalate
Mix 0.5 parts by weight and add into the autoclave.
After the temperature was raised to 95°C, 0.3 parts by weight of tribasic calcium phosphate was added 3 hours later, and polymerization was continued for an additional 5 hours. The polymerization conversion rate of the obtained composition was 99.4%. Next, 10 parts by weight of butane was added, and impregnation with a blowing agent was carried out at 100° C. for 8 hours. The obtained expandable thermoplastic copolymer particles were used as resin (A), and the following experiments were conducted using this resin (A). Example 2 0.1 part by weight of di-2-ethylhexyl phthalate (SP value: 8.9) and 0.1 part by weight of calcium stearate powder as an antiblocking agent were added to the resin (A) obtained in Example 1 in a blender equipped with a stirrer. coated. Next, the resin is heated with steam to preliminarily lighten to an apparent magnification of 50 times, then filled into a mold that can be closed but cannot be sealed, and heated with steam to form a plate-shaped foam of 45 cm x 30 cm x 2 cm. A molded body was obtained. The above foamed molded product was left in a hot air soaking dryer at 100° C. for one week, and then the state of tertiary foaming on the surface of the molded product was examined, and the results are shown in Table 1. Examples 3 to 5 Examples were carried out in the same manner as in Example 2, except that di-2-ethylhexyl phthalate was changed to dibutyl phthalate, butylbenzyl phthalate, or di-2-ethylhexyl adipate. The results are shown in Table-1. Comparative Examples 1 to 4 In Example 2, a blank without di-2-ethylhexyl phthalate (Comparative Example 1), a paraffinic oil (Comparative Example 2), butyl epoxy stearate ( Comparative Example 3) and diethylene glycol dibenzoate (Comparative Example 4) were used, but the results were shown in Table 1.

[Table] ○: 〃 Almost none
Δ: Considerably present Examples 6 and 7 Table 2 shows the results of carrying out the same procedure as in Example 2 except that the amount of di-2-ethylhexyl phthalate was changed to 0.05 parts by weight and 0.5 parts by weight.

[Table] Example 8 110 parts by weight of pure water in an autoclave equipped with a stirrer,
After adding 0.08 parts by weight of tricalcium phosphate and 0.003 parts by weight of sodium dodecylbenzenesulfonate, 70 parts by weight of alphamethylstyrene was added under stirring.
A monomer consisting of 30 parts by weight of acrylonitrile,
1,1-di-t-butylperoxy-3,3,5
- Mixing 1.0 part of trimethylcyclohexane,
After adding it to the autoclave and raising the temperature to 100℃,
After 3 hours, 0.3 parts by weight of tribasic calcium phosphate was added, and polymerization was continued for an additional 5 hours. The polymerization conversion rate of the obtained composition was 99.3%. Then 4 parts of butane was added and impregnated with a blowing agent for 15 hours at 100°C. The obtained expandable thermoplastic copolymer particles were used as resin (B), and the following experiments were conducted using this resin (B). Example 9 Di-2-ethylhexyl phthalate was added to the resin (B) obtained in Example 8 in a blender equipped with a stirrer.
0.1 part by weight and 0.1 part by weight of calcium stearate powder as an antiblocking agent. Next, the resin is heated with steam to pre-foam to an apparent magnification of 5 times, and then filled into a mold that can be closed but cannot be sealed, and heated with steam to form a mold of 45 cm x 30 cm.
A plate-shaped foamed molded product with a size of 0.7 cm was obtained. After this plate-shaped foam molded product was left in a hot air soaking dryer at 110° C. for 24 hours, the state of tertiary foaming on the surface of the molded product was examined, and the results are shown in Table 3. Examples 10 to 12 The same procedure as in Example 9 was carried out except that dibutyl phthalate was changed to butyl benzyl phthalate and dioctyl adipate instead of di-2-ethylhexyl phthalate. The results are shown in Table-3. Comparative Example 5 The same procedure as Example 9 was carried out except that di-2-ethylhexyl phthalate was not used.
The results are shown in Table-3. Comparative Examples 6 to 8 The same procedure as Example 9 was carried out except that paraffin oil, butyl epoxy stearate, and diethylene glycol dibenzoate were used in place of di-2-ethylhexyl phthalate. The results are shown in Table-3.

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Claims (1)

[Scope of Claims] 1 The monomers constituting the polymer are 10 to 80% by weight of alphamethylstyrene and 5 to 50% by weight of acrylonitrile.
% by weight, and 0 to 70% by weight of at least one compound selected from styrene, chlorostyrene, paramethylstyrene, t-butylstyrene, acrylic ester, and methacrylic ester, and 2 to 15% by weight of an easily volatile blowing agent. % by weight, the surface of which is coated with a plasticizer that is liquid at room temperature and has a solubility parameter value of 8.0 to 9.5. 2. The expandable thermoplastic copolymer particles according to claim 1, wherein the plasticizer is a phthalate ester. 3. The expandable thermoplastic copolymer particles according to claim 1, wherein the plasticizer is an aliphatic dibasic acid ester. 4 The plasticizer is di-2-ethylhexyl phthalate,
The expandable thermoplastic copolymer particles according to claim 1, which are diisodecyl phthalate or butylbenzyl phthalate. 5. The expandable thermoplastic copolymer particles according to claim 1, wherein the plasticizer is dioctyl adipate or dibutyl sebacate.