JP5486146B2 - Aromatic vinyl compound resin composition and method for producing the same - Google Patents

Description

  The present invention relates to an aromatic vinyl compound-based resin composition having a small amount of volatile components, dimer / trimer components, and less odor, and a method for producing the same.

  Aromatic vinyl compound-based resins have excellent injection moldability and good appearance, and are widely used in various miscellaneous goods and electrical products. In addition, it is inexpensive and easy to foam, so it is also used for packing materials and food packaging materials. In particular, food packaging materials include trays for fresh food products and cup noodle containers that are secondarily processed from foamed sheets of styrene resin. It is provided. In such food applications, since the resin container and the food are in direct contact with each other, reduction of volatile components and dimer / trimer components contained in the resin component is required from the viewpoint of odor transfer and heat resistance reduction.

  On the other hand, in the industrial production of aromatic vinyl compound resins, there is a trend to improve the production efficiency by changing the process from batch suspension polymerization to continuous bulk polymerization. Dispersants, which are essential in batch suspension polymerization, are not necessary in continuous bulk polymerization, so the quality of the resin can be improved by process conversion. On the other hand, the thermal history in the devolatilization process has increased, resulting in thermal degradation. There is a tendency for volatile matter and dimer / trimer components derived from to increase.

  When polymerizing aromatic vinyl compounds in a continuous bulk polymerization process and removing unreacted monomers and solvents by devolatilization, the temperature of the devolatilization process is significantly higher than the polymerization process in order to perform sufficient devolatilization. It is necessary to make it high, and generation of volatile components and dimer / trimer components derived from thermal decomposition at that time cannot be avoided. Since the thermal decomposition in the devolatilization process is thought to be caused by the generation of alkyl radicals by polymer chain scission in the absence of oxygen, a compound that directly captures alkyl radicals has been developed and is effective for suppressing molecular weight reduction and gelation. It is marketed as an inhibitor (Non-patent document 1, Non-patent document 2). Moreover, the technique which suppresses the production | generation of volatile matters, such as a monomer, and a dimer / trimer by using these degradation inhibitors is also disclosed (patent documents 2 and 3). However, these deterioration inhibitors are relatively high in volatility, and if an antioxidant is added before the devolatilization step of the continuous bulk polymerization process, a considerable proportion will be removed in the devolatilization step, which is more than necessary. There was a problem that the addition amount had to be increased, resulting in an increase in cost.

JP 2000-95888 A Synthetic resin industry, 37 (12), 74 (1990) Polymers & Polymer Compositions, vol. 8, no. 1,37-50 (2000) Japanese Patent Laid-Open No. 5-170825 JP 2002-121215 A

  It is an object of the present invention to provide an aromatic vinyl compound-based resin composition having a reduced odor and a reduced volatile content and dimer / trimer components derived from thermal decomposition in an aromatic vinyl compound-based resin composition. It is.

  As a result of intensive studies in view of the present situation, the present inventors contain a specific amount of a compound having a specific structure, and make the total volatile content, the dimer amount of the aromatic vinyl compound, and the trimer amount not more than the specific amount. As a result, it was found that an aromatic vinyl compound-based resin composition having less odor and excellent heat resistance was obtained, and the present invention was achieved.

（式中、ｎは１２〜１８の整数を示す。）

That is, the aromatic vinyl compound resin composition according to the present invention is a styrene monomer homopolymer or a copolymer of at least one of acrylonitrile, methacrylic acid ester and acrylic acid ester and a styrene monomer. A compound having 200 to 2000 ppm of a compound having at least one thioether bond in the molecule with respect to the aromatic vinyl compound resin made of a polymer and having the thioether bond is represented by the following general formula (I). A dimer of the styrenic monomer that is a compound having a structure or a compound having a structure represented by the following general formula (II), has a total volatile content of 500 ppm or less measured by gas chromatography, and is measured by gas chromatography the total amounts and trimer content of not more than 1500 ppm, immediately before as degassing step, heavy To the aromatic vinyl compound type resin obtained by the process are those obtained by adding a compound having a thioether bond.
The method for producing an aromatic vinyl compound-based resin composition according to the present invention is a method of polymerizing a styrenic monomer alone by bulk polymerization, or at least one of acrylonitrile, methacrylic acid ester and acrylic acid ester. a polymerization step of copolymerizing a styrene monomer and a devolatilization step of removing the unreacted monomers and solvent, has, the immediately before as degassing step, an aromatic vinyl obtained by the polymerization step A compound having a structure represented by the following general formula (I) or a compound having a structure represented by the following general formula (II) is added to the compound-based resin in an amount of 200 to 2000 ppm, and the total volatile content measured by gas chromatography is 500 ppm or less. And the total of the dimer amount and trimer amount of the styrenic monomer measured by gas chromatography is 1500 ppm or less Obtaining a sulfonyl compound resin composition.

(In the formula, n represents an integer of 12 to 18.)

  The aromatic vinyl resin composition of the present invention has less volatile components and dimer / trimer components, and is particularly suitable for food packaging applications from the viewpoint of odor and heat resistance. In addition, the atmospheric emission during resin molding is reduced, contributing greatly to the environment.

Hereinafter, the present invention will be described in detail.
Examples of the compound having at least one thioether bond in the molecule constituting the present invention include distearyl thiodipropionate, dimyristyl thiodipropionate, tetrakis [methylene-3- (dodecylthio) propionate] methane, thiodiethylene Bis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate], bis [2-methyl-4- (3-alkylthiopropionyloxy) -5-tert-butylphenyl] sulfides, 4 , 6-bis (n-alkylthiomethyl) -o-cresols, 4,4′-thiobisphenols and the like.

（式中、ｎは６〜１８の整数を示す。） Among the compounds having the thioether bond, 4,6-bis (n-alkylthiomethyl) -o-cresols in which the sulfur atom of the following general formula (I) is bonded to phenols, and the following general formula (II) 4,4′-thiobisphenols are more preferred in the present invention.

(In the formula, n represents an integer of 6 to 18.)

（式中、Ｒ１〜Ｒ４は水素、または炭素数１〜４のアルキル基を示す。） The carbon number n of the side chain adjacent to the sulfur atom is 6 to 18, and considering the volatilization at the time of devolatilization, it is preferable that the carbon number is large. However, considering the solubility in a solvent or use in heat melting, n Is particularly preferably 12-16. When the number of carbon atoms in the carbon side chain is small, the odor after devolatilization tends to be strong, and when n is less than 6, the odor during resin processing is particularly strong, which is not preferable.

(In the formula, R1 to R4 represent hydrogen or an alkyl group having 1 to 4 carbon atoms.)

  The total of the dimer amount and trimer amount of the aromatic vinyl compound contained in the aromatic vinyl compound-based resin composition of the present invention is 1500 ppm or less. Exemplifying the case where the aromatic vinyl compound is styrene, the dimer refers to 2,4-diphenyl-1-butene having a linear structure, 1,2-diphenylcyclobutane having a cyclic structure, and 1,3-diphenylcyclobutane. Trimers are 2,4,6-triphenyl-1-hexene having a linear structure, 2,4,6-triphenylcyclohexane having a cyclic structure, 1,2,3,4-tetrahydro-1- (1′- Phenylethyl) -4-phenylnaphthalene.

  The addition amount of the compound having a thioether structure used in the present invention is 200 to 2000 ppm, more preferably 600 to 1300 ppm. When the addition amount is small, the oligomer reduction effect is decreased, and when it is large, the odor is not only strong, but the oligomer reduction effect corresponding to the addition amount is not seen.

  The total volatile content of the aromatic vinyl compound-based resin composition obtained in the present invention is 500 ppm or less. Monomers have a low boiling point and can be reduced in principle by tightening devolatilization conditions, but in reality it is difficult to cause thermal decomposition under the influence of thermal history and shearing under devolatilization conditions, resulting in new monomer components. Therefore, the addition of the compound used in the present invention is extremely effective. The volatile substances in the present invention refer to five substances (styrene, toluene, ethylbenzene, n-propyl) specified in the standards for equipment and containers and packaging related to the Food Sanitation Law (Ministry of Health and Welfare Notification No. 370 in 1959). Benzene and isopropylbenzene).

  A continuous polymerization process is mentioned as a manufacturing method of the aromatic vinyl compound-type resin composition of this invention. That is, in producing an aromatic vinyl compound-based resin by polymerizing an aromatic vinyl compound in a polymerization process by bulk polymerization and removing unreacted monomers and solvents in a devolatilization process, depolymerization is performed after the polymerization process or polymerization process. The aromatic vinyl compound-based resin composition of the present invention can be produced by adding 200 to 2000 ppm of the compound having a thioether bond immediately before the volatilization process to the resin obtained by the final reactor.

  As the structural unit of the aromatic vinyl compound-based resin composition of the present invention, styrene, α-methyl styrene, o-methyl styrene, p-methyl styrene or the like can be arbitrarily used or a mixture thereof, but styrene is particularly preferable. . In addition, monomers that can be copolymerized with these aromatic vinyl compound monomers, for example, monomers such as acrylonitrile, methacrylic acid ester, and acrylic acid ester are copolymerized to such an extent that the effects of the present invention are not impaired. Also good.

  In addition, the aromatic vinyl compound-based resin composition in the present invention may be a rubber-modified resin, that is, a conjugated diene rubber-like polymer may be previously dissolved in the aromatic vinyl compound in the polymerization step and graft polymerization may be performed. . Examples of the conjugated diene rubber-like polymer in this case include polybutadiene, styrene-butadiene random copolymer, styrene-butadiene block copolymer, and the like.

  The polymerization step in the present invention is generally radical polymerization, but anionic polymerization may be used as necessary. In the case of radical polymerization, thermal polymerization may be used, but a radical polymerization initiator may be used in consideration of dimers and trimers derived from thermal polymerization. As radical polymerization initiators, benzoyl peroxide, azobisisobutyronitrile, t-butylperoxybenzoate, 1,1-di (t-butylperoxy) cyclohexane, 1,1-bis (t-butylperoxy) -3,3,5-trimethylcyclohexane, t-butylperoxyisopropyl carbonate, dicumyl peroxide, t-butylcumyl peroxide, t-butylperoxyacetate, t-butylperoxy-2-ethylhexanoate, 2,2-bis (4,4-di-t-butylperoxycyclohexyl) propane, ethyl-3,3-di (t-butylperoxy) butyrate, t-butylperoxyisobutyrate, polyether tetrakis ( Examples thereof include organic peroxides such as t-butyl peroxycarbonate. In the case of anionic polymerization, alkyllithium such as n-butyllithium and s-butyllithium can be used, and tetrahydrofuran, tetramethylethylenediamine, and alkylmagnesium can be used in combination as a polymerization regulator.

  In the polymerization step of the present invention, aromatic hydrocarbons such as benzene, toluene and ethylbenzene, and aliphatic hydrocarbons such as hexane and cyclohexane can be used as a solvent. In the case of radical polymerization, a chain transfer agent such as aliphatic mercaptan, α-methylstyrene dimer or terpinolene may be used as necessary.

  The compounds used in the resin composition of the present invention have already been described. For example, octadecyl-3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate, ethylenebis (oxyethylene) bis [3- ( Other phenolic antioxidants such as 5-t-butyl-4-hydroxy-m-tolyl) propionate, pentaerythritol tetrakis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate] , 2,2-methylenebis (4,6-di-t-butylphenyl) octyl phosphite, bis (2,6-di-t-butyl-4-methylphenyl) pentaerythritol diphosphite, etc. You may use together with an agent. As addition amount of these antioxidant used together, it is 200-3000 ppm, More preferably, it is 300-2000 ppm. Further, it is particularly preferable to add 0.5 to 2 times the amount of the antioxidant used in combination with the compound of the present invention.

  EXAMPLES Hereinafter, although an Example demonstrates this invention in detail, this invention is not limited to this. First, the analysis method in the present invention will be described below.

(1) Measurement of content of styrene dimer and trimer in resin composition Dissolve 200 mg of resin composition completely in 2 ml of dichloromethane, then add 2 ml of methanol to precipitate the polymer, and after static value, gas chromatograph the supernatant. And measured under the following conditions.
Gas chromatograph: HP-5890 (manufactured by Hewlett-Packard Company)
Capillary column: DB-1, 0.2 mm × 30 m, film thickness 0.1 μm
Injection temperature: 250 ° C
Column temperature: 100-300 ° C., 10 ° C./min
Detector temperature: 300 ° C
Split ratio: 50/1
Internal reference material: n-eicosane

(2) Measurement of total volatile content in resin composition 500 mg of the resin composition was dissolved in 10 ml of DMF containing cyclopentanol as an internal standard substance, and measured under the following conditions using gas chromatography.
Gas chromatograph: HP-5890 (manufactured by Hewlett-Packard Company)
Column: HP-WAX, 0.25 mm × 30 m, film thickness 0.5 μm
Injection temperature: 220 ° C
Column temperature: 60 ° C to 150 ° C, 10 ° C / min
Detector temperature: 220 ° C
Split ratio: 30/1

  The odor evaluation method in the aromatic vinyl resin composition of the present invention was carried out as follows.

(3-1) Creation of Injection Molded Product A rectangular container having an opening width of 100 mm, a depth of 75 mm, a depth of 45 mm, and a thickness of 1 mm was created by injection molding under the following conditions.
Injection molding machine: JSW100EP manufactured by Nippon Steel
Cylinder temperature: 230 ° C
Mold temperature: 40 ℃

(3-2) Odor evaluation Odor was determined according to the following criteria.
A: No odor is felt at all in the molded product immediately after injection molding.
○: Slight odor is felt in the molded product immediately after injection molding, but no odor is felt in the molded product after cooling.
X: Odor is felt immediately after injection molding or in the molded product after cooling.

Example 1
Three complete mixing tank reactors (first to third, 30 L each) are connected in series, and two devolatilization tanks (first and second) equipped with a plurality of tube type preheaters are connected in series. The continuous polymerization apparatus was connected. The first to third reactors were set to 105 ° C., 110 ° C., and 115 ° C., respectively, and the first and second devolatilization tanks were set to preheater temperatures of 180 ° C./600 mmHg and 220 ° C./6 mmHg, respectively. After mixing styrene monomer and ethylbenzene at a mass ratio of 8: 2 as a raw material, and further adding 1,1-di (t-butylperoxy) cyclohexane to 800 ppm with respect to the styrene monomer mass, a flow rate of 9 L per hour Supplied with. A static mixer was installed between the third reactor and the first devolatilization tank, and 4,6-bis (dodecylthiomethyl) -o-cresol (trade name IRGANOX 1726, Ciba Specialty Chemicals) from the upstream side of the mixer. Was continuously added as an ethylbenzene solution or an ethylbenzene slurry (4,6-bis (dodecylthiomethyl) -o-cresol: 5% by mass) to 1000 ppm with respect to the resin obtained by the third reactor. did. The resin composition was directly made into a strand from the outlet end of the second devolatilization tank, cooled with water, introduced into a pelletizer, and pelletized to obtain an aromatic vinyl compound-based resin composition. Table 1 shows the total volatile content, dimer and trimer amounts of the obtained resin composition, the content of 4,6-bis (dodecylthiomethyl) -o-cresol in the resin composition, and odor evaluation results.

Regarding the content of 4,6-bis (dodecylthiomethyl) -o-cresol in the resin composition, 200 mg of the resin composition was completely dissolved in 2 ml of dichloromethane, and then 2 ml of methanol was added to precipitate the polymer. -After the static value, the supernatant was measured by liquid chromatography as follows.
Liquid chromatograph: Alliance 2695 (Nippon Waters)
Column: TSKgel ODS-120T, 6.0 mm × 15 cm (manufactured by Tosoh Corporation)
Column temperature: 40 ° C
Mobile phase: methanol

Example 2
The same procedure as in Example 1 was performed except that 4,6-bis (dodecylthiomethyl) -o-cresol was continuously added to 1500 ppm in Example 1. The evaluation results of the obtained resin composition are shown in Table 1.

Example 3
The same operation as in Example 1 was conducted except that 4,6-bis (dodecylthiomethyl) -o-cresol was continuously added to 800 ppm in Example 1. The evaluation results of the obtained resin composition are shown in Table 1.

Example 4
The same operation as in Example 1 was conducted except that 4,6-bis (dodecylthiomethyl) -o-cresol was continuously added to 600 ppm in Example 1. The evaluation results of the obtained resin composition are shown in Table 1.

Reference Example 5
In Example 1, instead of 4,6-bis (dodecylthiomethyl) -o-cresol, 4,6-bis (octylthiomethyl) -o-cresol (trade name: IRGANOX1520L, manufactured by Ciba Specialty Chemicals) was used as the third product. The same procedure as in Example 1 was carried out except that the resin obtained by the reactor was continuously added at 1000 ppm. The evaluation results of the obtained resin composition are shown in Table 1. The content of 4,6-bis (octylthiomethyl) -o-cresol in the resin composition is the same as the content of 4,6-bis (dodecylthiomethyl) -o-cresol. It was measured.

Reference Example 6
The same operation as in Reference Example 5 was performed except that 4,6-bis (octylthiomethyl) -o-cresol was continuously added to 600 ppm in Reference Example 5. The evaluation results of the obtained resin composition are shown in Table 1.

Example 7
In place of 4,6-bis (dodecylthiomethyl) -o-cresol, 4,4′-thiobis (6-tert-butyl-3-methylphenol) (trade name Yoshinox SR, manufactured by API Corporation) It implemented like Example 1 except having added continuously so that it might become 1000 ppm with respect to resin obtained with the reactor.

For the content of 4,4′-thiobis (6-tert-butyl-3-methylphenol in the resin composition, 200 mg of the resin composition was completely dissolved in 2 ml of dichloromethane, and then 2 ml of methanol was added. After polymer precipitation and static value, the supernatant was measured under the following conditions using gas chromatography.
Gas chromatograph: HP-5890 (manufactured by Hewlett-Packard Company)
Capillary column: DB-1, 0.2 mm × 30 m, film thickness 0.1 μm
Injection temperature: 250 ° C
Column temperature: 100-300 ° C., 10 ° C./min
Detector temperature: 300 ° C
Split ratio: 50/1
Internal reference material: n-eicosane

Example 8
The same operation as in Example 7 was carried out except that 4,4′-thiobis (6-tert-butyl-3-methylphenol) was continuously added to 2000 ppm in Example 7. The evaluation results of the obtained resin composition are shown in Table 1.

Example 9
In addition to 4,4′-thiobis (6-tert-butyl-3-methylphenol), 2,2-methylenebis (4,6-di-tert-butylphenyl) octyl phosphite (trade name ADK STAB HP-10, Asahi This was carried out in the same manner as in Example 7, except that Denka Kogyo Kogyo Co., Ltd.) was continuously added to the resin obtained by the third reactor so as to be 1000 ppm each. The evaluation results of the obtained resin composition are shown in Table 1. The content of 2,2-methylenebis (4,6-di-t-butylphenyl) octyl phosphite in the resin composition is 4,4′-thiobis (6-t-butyl-3-methylphenol). It measured by the method similar to content.

Example 10
In addition to 4,4′-thiobis (6-tert-butyl-3-methylphenol), dimyristyl thiodipropionate (trade name DMTP “Yoshitomi”, manufactured by API Corporation) was obtained by the third reactor. It implemented like Example 7 except having added continuously so that it might become 1000 ppm, respectively with respect to resin. The evaluation results of the obtained resin composition are shown in Table 1. The content of dimyristylthiodipropionate in the resin composition was measured by the same method as that for 4,6-bis (dodecylthiomethyl) -o-cresol.

Comparative Example 1
The same procedure as in Example 1 was performed except that 4,6-bis (dodecylthiomethyl) -o-cresol was not added. The evaluation results of the obtained resin composition are shown in Table 1.

Comparative Example 2
The same operation as in Example 1 was conducted except that 4,6-bis (dodecylthiomethyl) -o-cresol was continuously added so as to be 180 ppm in Example 1. The evaluation results of the obtained resin composition are shown in Table 1.

Comparative Example 3
In Example 1, instead of 4,6-bis (dodecylthiomethyl) -o-cresol, 2- [1- (2-hydroxy-3,5-di-t-pentylphenyl) ethyl] -4,6-di The same procedure as in Example 1 was conducted except that -t-pentylphenyl acrylate (trade name: Sumilizer GS, manufactured by Sumitomo Chemical Co., Ltd.) was continuously added so as to be 1000 ppm with respect to the resin obtained by the third reactor. . The evaluation results of the obtained resin composition are shown in Table 1. The content of 2- [1- (2-hydroxy-3,5-di-t-pentylphenyl) ethyl] -4,6-di-t-pentylphenyl acrylate in the resin composition is 4, It measured by the method similar to content of 4'-thiobis (6-t-butyl-3-methylphenol).

Comparative Example 4
In Example 1, instead of 4,6-bis (dodecylthiomethyl) -o-cresol, 5,7-di-tert-butyl-3- (3,4-dimethylphenyl) -3H-benzofuran-2-one ( Product name HP-136 (manufactured by Ciba Specialty Chemicals) was added in the same manner as in Example 1 except that it was continuously added to 1000 ppm with respect to the resin obtained by the third reactor. The evaluation results of the obtained resin composition are shown in Table 1. The content of 5,7-di-tert-butyl-3- (3,4-dimethylphenyl) -3H-benzofuran-2-one in the resin composition is 4,4′-thiobis (6- (t-butyl-3-methylphenol) content was measured by the same method.

  From Table 1, those having a small amount of the compound having at least one thioether bond in the molecule constituting the present invention have a large amount of total volatile components and dimers / trimers, and the resulting resin composition has an odor. strong. Further, it is understood that those using an antioxidant other than the compound having at least one thioether bond in the molecule constituting the present invention have a low ratio and a strong odor contained in the obtained resin composition. .

  The aromatic vinyl compound-based resin composition of the present invention is suitable for food packaging applications because it has a small amount of volatile components and dimer / trimer components and a low odor. Furthermore, the aromatic vinyl compound-based resin composition of the present invention can be widely used for various miscellaneous goods, daily necessities, electrical appliances, and the like, and has a great industrial applicability.

Claims (4)

At least 1 with respect to an aromatic vinyl compound resin comprising a homopolymer of a styrene monomer or a copolymer of at least one of acrylonitrile, methacrylic acid ester and acrylic acid ester and a styrene monomer. Containing 200 to 2000 ppm of a compound having one or more thioether bonds in the molecule;
The compound having a thioether bond is a compound having a structure represented by the following general formula (I) or a compound having a structure represented by the following general formula (II):
And the total volatile matter measured by gas chromatography is 500 ppm or less, and the total of the dimer amount and trimer amount of the styrene monomer measured by gas chromatography is 1500 ppm or less,
Immediately before as degassing step, with respect to the aromatic vinyl compound type resin obtained by the polymerization process, the aromatic vinyl compound type which is characterized in that which was obtained by adding a compound having a thioether bond Resin composition.

(In the formula, n represents an integer of 12 to 18.)

  2. The fragrance according to claim 1, wherein the styrenic monomer is at least one compound selected from the group consisting of styrene, α-methylstyrene, o-methylstyrene, and p-methylstyrene. Group vinyl compound-based resin composition. A polymerization step of polymerizing a styrenic monomer alone in bulk polymerization or copolymerizing at least one of acrylonitrile, methacrylic acid ester and acrylic acid ester with a styrenic monomer;
A devolatilization step for removing unreacted monomers and solvents,
Wherein immediately before as degassing step, wherein the aromatic vinyl compound type resin obtained by the polymerization step, 200 a compound of the structure shown in the compound or the following formula structure represented by the following general formula (I) (II) Aromatic vinyl added with ˜2000 ppm, total volatile content measured by gas chromatography is 500 ppm or less, and total of dimer amount and trimer amount of the styrene monomer measured by gas chromatography is 1500 ppm or less A method for producing an aromatic vinyl compound-based resin composition to obtain a compound-based resin composition.

(In the formula, n represents an integer of 12 to 18.)

  4. The fragrance according to claim 3, wherein the styrenic monomer is at least one compound selected from the group consisting of styrene, α-methylstyrene, o-methylstyrene, and p-methylstyrene. For producing an aromatic vinyl compound-based resin composition.