JPH0357122B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a dispersion stabilizer for suspension polymerization of vinyl compounds. For example, when industrially producing a polymer of a vinyl compound such as a vinyl chloride resin, the monomer of the vinyl compound is dispersed in an aqueous medium in the presence of a dispersion stabilizer, and the polymerization is carried out using an oil-soluble catalyst. Polymerization methods are widely practiced, and dispersion stabilizers are said to have a great influence on the performance of vinyl compound polymers. Conventional suspension stabilizers include methylcellulose,
Cellulose derivatives such as carboxymethylcellulose or so-called water-soluble polymers such as polyvinyl alcohol are often used, but these are not always fully satisfactory. That is, although the water-soluble polymer described above does not produce coarse polymer particles, it lacks the ability to make coarse polymer particles uniform in terms of particle size distribution, and the scale of the vinyl compound polymer may adhere to the polymerization vessel. There are factors that need to be improved, such as the fact that they are easy to remove and that their removal requires a great deal of time and effort, and it is clear that if these problems can be solved, it will be possible to polymerize vinyl compounds industrially even more advantageously. However, as a result of extensive research in order to achieve the above object, the present inventors have found that partially saponified polyvinyl alcohol with an average degree of saponification of 60 to 95 mol% and an average degree of polymerization of 100 to 3000 per dry weight of the polyvinyl alcohol. When partially saponified polyvinyl alcohol treated with glyoxal obtained by mixing 0.005 to 3% glyoxal or acetalization reaction is used as a dispersion stabilizer, it is preferable to use a vinyl compound with a sharp particle size distribution. The present invention was completed after discovering that suspension polymerization can be carried out with industrial advantages, such as polymerization and hardly any scale of the polymer adhering to the polymerization can during polymerization. Ivy. The partially saponified polyvinyl alcohol treated with glyoxal in the present invention refers to the average degree of saponification
Glyoxal is mixed directly with powder of partially saponified polyvinyl alcohol having an average degree of polymerization of 60 to 95 mol% and an average degree of polymerization of 100 to 3,000, or by dispersing or dissolving it in an appropriate solvent. Any of these can be used. Depending on the temperature conditions during mixing, drying conditions, or any conditions such as the active presence of an acid catalyst, the mixture can substantially form acetal between the aldehyde group in glyoxal and the hydroxyl group in polyvinyl alcohol. Various cases can be considered, such as cases in which the chemical reaction does not occur, cases in which the acetalization reaction occurs, etc., but in the present invention, the effect remains the same in either case, and in short, the glyoxal component and the polyvinyl alcohol component coexist. It is only necessary that they react, and the above-mentioned remarkable effects can be obtained regardless of whether they react or not. When treating partially saponified polyvinyl alcohol with glyoxal, glyoxal may be directly added and mixed, but in order to carry out a uniform treatment, glyoxal should be dissolved or dispersed in an appropriate solvent and mixed. is advantageous. Examples of the solvent include water, alcohols such as methanol, ethanol, propanol, and isopropanol, ketones such as acetone and ethyl methyl ketone, ethers such as diethyl ether and dioxane, and esters such as methyl acetate and ethyl acetate.
These may be used alone or in combination, for example as a methanol-methyl acetate mixture. It is desirable to use glyoxal in a proportion of 0.005 to 3% by weight, preferably 0.01 to 2% by weight, based on the partially saponified polyvinyl alcohol (dry basis). Further, other aldehydes may be used in combination if necessary. The partially saponified polyvinyl alcohol used has an average saponification degree of 60 to 95 mol% and an average polymerization degree of 100 to 3,000, preferably an average saponification degree of 65 to 90 mol% and an average polymerization degree of about 300 to 2,500. Ru. If the degree of saponification is less than 60 mol%, the protective colloidal properties will decrease, and if it is more than 95 mol%, the surface activity will decrease and the particle size distribution of the particles will become broad. Furthermore, if the average degree of polymerization is less than 100, a product with a large polymer particle size is likely to be obtained, while if it is more than 3000, the particle size distribution becomes broad, which poses a practical problem. The polyvinyl alcohol mentioned above may be either a wet cake of polyvinyl alcohol before drying or a dried powder product, as long as it is produced by saponifying polyvinyl acetate in a methanol solution in the presence of an alkaline catalyst. . The polyvinyl alcohol mentioned above is not limited to saponified polyvinyl acetate, but also contains ethylenically unsaturated monomers copolymerizable with vinyl acetate, such as ethylene, propylene, isobutylene, α-octene, α-dodecene, α- Olefins such as octadecene, unsaturated carboxylic acids such as acrylic acid, methacrylic acid, crotonic acid, maleic acid, maleic anhydride, itaconic acid, and their salts, as well as their mono- or dialkyl esters, acrylonitrile, methacrylonitrile, etc. Nitriles, amides such as acrylamide and methacrylamide, ethylene sulfonic acid, allyl sulfonic acid,
Saponified copolymers of olefin sulfonic acids such as metaallylsulfonic acid and their salts, alkyl vinyl ethers, vinyl ketones, N-vinylpyrrolidone, vinyl chloride, vinylidene chloride, etc. can also be used. Furthermore, urethanized products, formalized products, acetalized products, butyralized products of polyvinyl alcohol, or carboxylic acids,
Esterification products with sulfonic acid and the like can also be used. Polyvinyl alcohol containing a carbonyl group or the like in the molecule or at the end of the molecule can also be used.
Of course, the polyvinyl alcohol derivatives are not limited to those mentioned above. In the treatment of partially saponified polyvinyl alcohol with glyoxal, as described above, glyoxal is added directly or after being dissolved or dispersed in an appropriate solvent to the partially saponified polyvinyl alcohol. At this time, it is of course possible to coexist an acidic catalyst if necessary. After addition and mixing, it can be used directly as a dispersion stabilizer. Drying or heat treatment may be performed as appropriate. The dispersion stabilizer treated in this way fully satisfies the above-mentioned performance, but in addition to this, when the stabilizer is used by dissolving it in water, it has excellent dispersion and solubility in water. Another major feature of the dispersion stabilizer of the present invention is that it exhibits properties. When suspension polymerizing a vinyl compound using the glyoxal-treated partially saponified polyvinyl alcohol of the present invention as a dispersion stabilizer, the dispersion stabilizer is usually added to an aqueous medium to disperse the monomers of the vinyl compound and the oil-soluble catalyst is present. It takes place below. The dispersion stabilizer is added to the aqueous medium as a powder or in the form of a solution. When added in the form of a solution, it can be added as a solution in an aqueous solvent, or in an organic solvent such as alcohol, ketone, ester, or a mixed solvent with water. The dispersion stabilizer is 0.01 for the vinyl compound monomer.
-5% by weight, preferably 0.01-3% by weight. The catalyst used may be any oil-soluble catalyst, such as benzoyl peroxide, lauroyl peroxide, diisopropyl peroxydicarbonate, α,α′-azobisisobutyronitrile, α,α′- Azobis-2,4-
Dimethylvaleronitrile, acetylcyclohexylsulfonyl peroxide or mixtures thereof are used. It is also possible to appropriately use various surfactants, protective colloids, inorganic dispersants, etc. as auxiliaries during polymerization. The vinyl compound that can be suspension-polymerized using the dispersion stabilizer of the present invention may be of any type, and representative examples include vinyl chloride, styrene, methacrylate, and vinyl acetate. These may be used alone or in combination. Furthermore, these vinyl compounds can also be copolymerized with other monomers that can be copolymerized with them. Examples of copolymerizable monomers include vinylidene halides, vinyl ethers, vinyl benzoate, acrylic acid, methacrylic acid and its esters, maleic acid and its anhydrides, ethylene, propylene, isobutylene, and the like. However, it is not necessarily limited to these. Next, the present invention will be explained in more detail by giving examples. Example 1 Production of partially saponified polyvinyl alcohol treated with glyoxal 0.5 g of a 40% aqueous solution of glyoxal was added to 100 g of partially saponified polyvinyl alcohol powder having an average degree of saponification of 80.4% by mole and an average degree of polymerization of 2250 and air-dried. Suspension polymerization of vinyl chloride 100 parts of vinyl chloride monomer, 150 parts of water in a 100 capacity stainless steel autoclave equipped with a stirrer
1 part, 0.1 part of the above-mentioned dispersion stabilizer, and 0.2 part of lauroyl peroxide as a polymerization catalyst, and suspension polymerization was carried out by adjusting the temperature to 60° C. while stirring at a rotational speed of 400 rpm. Table 1 shows the performance of the obtained vinyl chloride resin particles. Example 2 In Example 1, the amount of glyoxal used was 0.2
glyoxal-treated partially saponified polyvinyl alcohol was produced. Using this, suspension polymerization was carried out in the same manner as in Example 1. In addition, as a control example, the average degree of saponification was 80.4 mol%, and the average degree of polymerization was 2250.
Suspension polymerization was carried out in the same manner as in Example 1 using partially saponified polyvinyl alcohol. These results are also shown in Table 1.

[Table] Example 3 100 parts of styrene monomer in a polymerization can with a capacity of 5.
0.35 part of the dispersion stabilizer described in Example 1 and 3 parts of lauroyl peroxide were added, and the rotation speed was
Suspension polymerization was carried out at a temperature of 70° C. while stirring at 160 rpm. As a control example, suspension polymerization was carried out in the same manner as in Example 3 using partially saponified polyvinyl alcohol having an average degree of saponification of 80.4 mol % and an average degree of polymerization of 2250. Table 2 shows the performance of the obtained styrene resin particles.

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Claims (1)

[Claims] 1 Average degree of saponification 60-95 mol%, average degree of polymerization 100
~3000% partially saponified polyvinyl alcohol with 0.005 to 3% per dry weight of the polyvinyl alcohol
A dispersion stabilizer for suspension polymerization of vinyl compounds, the main ingredient of which is partially saponified polyvinyl alcohol treated with glyoxal, which is obtained by mixing % of glyoxal or by acetalization reaction.