JPH0257561B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an improvement in a method for suspension polymerizing vinyl chloride alone or a mixture of vinyl chloride and other vinyl monomers copolymerizable with it in an aqueous medium.
By using a specific compound in combination, the vinyl chloride monomer (hereinafter referred to as
The present invention relates to a method for obtaining vinyl chloride resin for the purpose of reducing the amount of VCM (abbreviated as VCM), improving the absorption of stabilizers and plasticizers, and reducing the amount of residual VCM in molded products. Recently, there have been reports that VCM can cause liver damage as an effect on the human body.
Reducing the concentration of VCM and the concentration of VCM remaining in molded products is required, and is considered an urgent hygiene issue. Conventionally, vinyl chloride monomers or vinyl chloride monomers and monomer mixtures copolymerizable therewith are often polymerized mainly by suspension polymerization.
When carrying out suspension polymerization in an aqueous medium in the presence of an organic peroxide-based or azo-based oil-soluble radical initiator,
Water-soluble polymeric substances such as partially saponified polyvinyl alcohol, methyl cellulose, hydroxymethyl cellulose, methyl vinyl ether maleic anhydride copolymer, starch, and gelatin are used as suspending agents, and the polymerization is carried out at 50-70℃, and after the polymerization is completed,
The polymer slurry is heated under reduced pressure with stirring, dehydrated, and dried to obtain a polyvinyl chloride resin product. However, there is no residual VCM in the polyvinyl chloride resin in the slurry after the unreacted VCM removal process.
1000 ppm or more of VCM is present, and the product polyvinyl chloride resin after dehydration and drying contains 100 ppm or more of residual VCM. This not only worsens the working environment during the polymerization process and molding process, but also causes VCM to remain in the molded product, which is unfavorable from a sanitary standpoint. Vinyl chloride resin or vinyl chloride-based copolymers produced by suspension polymerization are widely used as base resins for various moldings in the hard and soft fields. Excellent properties, less buildup, and residual
It is required that VCM be small. These tendencies become more pronounced as the resin becomes easier to process and has a lower degree of polymerization. The degree of polymerization is determined by the polymerization temperature,
As the polymerization temperature increases, the degree of polymerization decreases, and as the polymerization temperature increases, the proportion of non-porous transparent spheres increases. The amount of residual VCM depends on the drying conditions of the molded resin and the blending conditions of the composition, but is greatly influenced by the particle structure of the polymer. That is, the resin with a microporous particle structure and a lower proportion of transparent spheres is easier to remove residual VCM, so making the particles porous is an important issue. As methods for solving this problem, for example, there are methods described in Japanese Patent Publications No. 53-13515 and Japanese Patent Publication No. 49-31746, which employ the use of sulfur-containing compounds, and various other methods have also been proposed. It has been recognized that it is effective to some extent. However, these known methods not only have insufficient VCM removal effects, but also have drawbacks such as granulation properties during polymerization, making it difficult to obtain satisfactory porosity. The present invention solves the above-mentioned drawbacks, and provides a polyvinyl chloride resin that is porous, has a small amount of residual VCM, has little fissure, and has excellent thermal stability.
Alternatively, the present invention provides a method for producing a copolymer resin mainly composed of vinyl chloride by suspension polymerization. That is, the present invention uses a specific oil-soluble initiator and a suspending agent when carrying out suspension polymerization of vinyl chloride or a mixture of vinyl chloride and a monomer copolymerizable with it, and at the same time uses a specific unsaturated chlorinated hydrocarbon. This is a production method characterized by using a compound and/or a specific sulfur-containing compound and a specific nitrogen-containing compound in combination. This application uses a specific nitrogen-containing compound consisting of an ammonium salt having an NH ₄ group, a chlorine-containing ethylene hydrocarbon having two carbon atoms, and/or a specific sulfur-containing compound having a mercapto group and a hydroxyl group or a carboxyl group as a chain transfer agent. It is distinctive in that it is used as a Among the suspending agents used in the present invention, partially saponified polyvinyl alcohol is used alone or in combination with water-soluble cellulose ester, but partially saponified polyvinyl alcohol has an average degree of polymerization of 500 to 500.
2,500, preferably 600 to 2,400, a degree of saponification of 65 to 85 mol%, and a 4% aqueous solution whose viscosity at 20° C. is 50 cp or less, preferably 40 cp or less, as measured by a Hepler viscometer. In addition, the water-soluble cellulose ester used has an average degree of polymerization of 70 to 300, preferably 100 to 250,
A 2% aqueous solution measured at 20° C. using an Ubbelohde viscometer is preferably 500 cp or less, preferably 20 to 400 cp. The suspending agent is used alone or in combination with a water-soluble ester, and the total amount used is 0.03 to 0.20 parts by weight, preferably 0.04 to 0.12 parts by weight. If a suspending agent that deviates from the above-mentioned specified values is used, the powder properties of the produced vinyl chloride resin will be poor, and it will often completely solidify in the polymerization tank, which is not preferable. In addition, examples of oil-soluble radical initiators include acetylcyclohexane sulfonyl peroxide, isobutyryl peroxide, 2,2-azobis(4-methoxy-2,4-dimethylvaleronitrile), cumylperoxyneodecanate, diisopropylperoxy Dicarbonate, di-Sec-
Octyl peroxydicarbonate, di-3-methoxybutyl peroxydicarbonate, di-2
-Ethylhexylperoxydicarbonate, di-2ethoxyethylperoxydicarbonate, di-methoxyisopropylperoxydicarbonate, t-butylperoxyneodecanate, t-hexylperoxyneodecanate,
2,2'-azobis-(2,4-dimethylvaleronitrile), t-butylperoxypivalate, t
-hexyl peroxypivalate, lauryl peroxide, etc. Among the above initiators, the general formula is (In the formula, R ₁ and R ₂ are alkyl groups.)
A mixture of more than one species can be used. The amount used is 0.01 to 0.2 parts by weight, preferably 0.03 to 0.2 parts by weight, per 100 parts by weight of vinyl chloride monomer.
It is 0.10 parts by weight. Furthermore, an ethylenically unsaturated chlorinated hydrocarbon compound (B) having 2 carbon atoms and/or a sulfur-containing compound (C) having a mercapto group and a hydroxyl group or a carboxyl group and an NH ₄ group as a chain transfer agent to be used in combination. Nitrogen-containing compounds (D) consisting of ammonium salts are used together, and these compounds are listed in Table 2, and the amount used is (A)/(B) based on the oil-soluble radical initiator. /(D)=1/10~20/0.4~1 (A)/(C)/(D)=1/0.1~0.5/0.1~0.5 or (A)/(C)+(B)/(D )=1/5 to 10/0.2 to 0.7. If polymerization is carried out outside this range of ratio conditions, the granulation properties will become unstable, and coarse particles may sometimes occur.
This method is unsuitable because it is not possible to obtain the desired average degree of polymerization, and it is also impossible to obtain a porous vinyl chloride resin or a copolymer resin therewith, which is the object of the present invention.

【table】

[Table] The vinyl chloride resin in the present invention includes not only vinyl chloride homopolymers but also those containing vinyl monomers copolymerizable with vinyl chloride within 20 parts by weight. . Examples of such vinyl monomers include α-olefins such as ethylene and propylene, vinyl esters such as vinyl acetate and vinyl stearate, vinyl ethers such as methyl vinyl ether and cetyl vinyl ether, acrylic acid, methacrylic acid, and Unsaturated fatty acids including these esters, vinyl halides other than vinyl chloride such as vinyl bromide and vinyl fluoride, aromatic vinyl such as styrene and α-styrene, maleic acid, fumaric acid and anhydride, acrylonitrile, Examples include vinylidene chloride. In the present invention, a specific unsaturated chlorinated hydrocarbon (B) and/or a specific sulfur-containing compound (C) and a specific nitrogen-containing compound ( It is characterized by the combined use of D). Hereinafter, the present invention will be explained in more detail according to Examples.
Each characteristic value was determined according to the following evaluation method. Apparent specific gravity: JISK-6741 Particle size distribution: JISZ-8801 Fixture eye: 100 parts by weight of resin, DDP50
parts by weight, 3 parts by weight of tribasic lead sulfate, and 1 part by weight of lead stearate, and kneaded with a mixing roll at 150°C for 7 minutes to prepare a roll sheet with a wall thickness of 0.1 mm. The number of transparent spheres with a size of 100 μ or more existing in 50 cm ² of this roll sheet was defined as the fisheye number. Content of vinyl chloride monomer: Vinyl chloride resin or copolymer resin with vinyl chloride resin is dissolved in tetrahydrofuran, a solvent, and the chloride in vinyl chloride resin or copolymer resin with vinyl chloride resin is dissolved by gas chromatography. The content of vinyl monomer was determined. Plasticizer absorption rate: 50 parts by weight of plasticizer (DOP) was added using a planetary mixer, measured at a jacket temperature of 80°C, and expressed as the time (minutes) required until the compound dried up and the stirring torque suddenly decreased. Example 1 (Experiment Nos. 1 to 4) In a stainless steel polymerization vessel with an internal volume of 2.5 m ³ , 500 kg of vinyl chloride monomer, 1000 kg of pure water, 500 g of a specific partially saponified polyvinyl alcohol shown in Table 1, and an initiator were placed. (A) as t-butyl peroxypivalate;
300 to 500 g of specific unsaturated chlorinated hydrocarbons (B), specific sulfur-containing compounds (C), and specific nitrogen-containing compounds (D) shown in Table 2 were charged, while stirring. The polymerization reaction was carried out at a temperature of 60°C, and when the steady pressure inside the polymerization vessel decreased by 2 kg/cm ² , unreacted vinyl chloride monomer was purged to stop the polymerization reaction. After the reaction, the temperature of the polymerization reactor was further increased to 70°C, and vacuum degassing was performed until the temperature reached 250 mmHg, thereby reducing the amount of vinyl chloride remaining adsorbed on the vinyl chloride resin. Subsequently, the slurry was dehydrated by centrifugation and further dried by hot air drying to obtain a vinyl chloride resin, which was used to measure each characteristic value. The results are as shown in Table 3, and all were satisfactory. Comparative Example 1 (Experiment Nos. 5 and 6) A vinyl chloride resin was obtained by carrying out the same polymerization and operation as in Example 1, except that the specific nitrogen-containing compound was not used. The resins thus obtained were as shown in Table 3, but none of them gave satisfactory results. Comparative Example 2 (Experiment Nos. 7 to 8) In Example 1, except that the specific unsaturated chlorinated hydrocarbon and the specific sulfur-containing compound were not used, the polymerization temperature was set to 67°C, and other similar polymerization was carried out. and operations were performed to obtain a vinyl chloride resin. The resins thus obtained were as shown in Table 3, but none of them gave satisfactory results. Comparative Example 3 (Experiment Nos. 9 to 10) In Example 1, the initiator was changed to di-2-ethylhexyl peroxydicarbonate, and other similar polymerization and operations were performed to obtain a vinyl chloride resin. The resins thus obtained were as shown in Table 3, but none of them gave satisfactory results.

[Table] Example 2 (Experiment No. 11-12), Comparative Example 4 (Experiment No. 13-
18) In a stainless steel polymerization vessel with an internal volume of 2.5 ^m3 , 500 kg of vinyl chloride monomer, 1000 kg of pure water, and t as an initiator were added.
- The types of partially saponified polyvinyl alcohol and methyl cellulose were changed with 500 g of butyl peroxypivalate, 250 g of specific sulfur-containing compound No. 4 (Table 2), and 150 g of specific nitrogen-containing compound No. 11 (Table 2). The reaction was carried out at a polymerization temperature of 60°C. As shown in Table 6, the results show that the degree of saponification of partially saponified polyvinyl alcohol is 60 to 85 mol%, and the viscosity of a 2% aqueous solution of methyl cellulose at 20°C is
I couldn't get a satisfactory value unless it was 500 cp or less.

【table】

[Table] Comparative Example 5 (Experiment Nos. 19 to 22) In a stainless steel polymerization vessel with an internal volume of 2.5 ^m3 , 500 kg of vinyl chloride monomer, 1000 kg of pure water, and t as an initiator were added.
-Butyl peroxypivalate 300~1000Kg, No.
Partially saponified polyvinyl alcohol 250 of 3 (Table 1)
A specific unsaturated chlorinated hydrocarbon, a specific sulfur-containing compound, and a specific nitrogen-containing compound were added in the proportions shown in Table 5 to 250 g of methylcellulose of No. 7 (Table 1) and polymerized at 60°C. The reaction was carried out. As shown in Table 5, satisfactory values were not obtained.

[Table] Example 3 (Experiment Nos. 23 to 25) In a stainless steel polymerization vessel with an internal volume of 2.5 m ³ , 450 kg of vinyl chloride monomer, 50 kg of monomers such as propylene, ethylene, and vinyl acetate, 1000 kg of pure water, and starting 500g of t-butyl peroxypivalate as agent, Table 2,
250 g of the specific sulfur-containing compound No. 4 and 150 g of the specific nitrogen-containing compound No. 11 in Table 2 were charged, and otherwise the reaction was carried out in the same manner as in Example 1 at a polymerization temperature of 60°C. As shown in Table 6, the polymerization results were satisfactory in all cases. Comparative Example 6 (Experiment Nos. 26 to 28) Polymerization was carried out based on the polymerization conditions of Example 3 except that the specific nitrogen-containing compound shown in Table 2 No. 11 was excluded. As shown in Table 6, the results were not satisfactory in any case.

【table】

Claims (1)

[Claims] 1. When polymerizing a vinyl chloride monomer alone or a mixture of vinyl chloride monomers and monomers copolymerizable with it in an aqueous medium, as an initiator the general formula [Formula] (in the formula R ₁ , _R2 represents an alkyl group), an average polymerization degree of 500 to 2500, a saponification degree of 65 to 85 mol%, and a suspending agent of 4.
Partially saponified polyvinyl alcohol whose viscosity at 20°C in a 2% aqueous solution is 50 cp or less and/or whose average degree of polymerization is 70 to 300, and whose viscosity at 20°C in a 2% aqueous solution is
Using a water-soluble cellulose ester having a molecular weight of 500 cp or less, an ethylenically unsaturated chlorinated hydrocarbon compound (B) having 2 carbon atoms and/or a sulfur-containing compound (C) having a mercapto group and a hydroxyl group or a carboxyl group and NH ₄ A method for producing a vinyl chloride resin, which comprises adding and polymerizing a nitrogen-containing compound (D) consisting of an ammonium salt having a group. 2 The amount of oil-soluble radical initiator (A) used is 0.03 to 0.10 parts by weight per 100 parts by weight of vinyl chloride monomer, unsaturated chlorinated hydrocarbon compound (B), sulfur-containing compound (C) and/or The amount of the nitrogen compound (D) is (A)/(B)/(C)=1/10 to 20/to the oil-soluble radical initiator (A).
0.4~1, (A)/(C)/(D)=1/0.1~0.5/0.1~0.5 or (A)/(B)+(C)/(D)=1/5~10/0.2~ Claim 1 used in a weight ratio range of 0.7
The method for producing vinyl chloride resin described in Section 1.