JPH0576966B2 - - Google Patents

Description

[Detailed description of the invention]

"Industrial Field of Application" The present invention is directed to the production of vinyl chloride resins having desirable properties such as those obtainable by emulsion polymerization in a preferred form such as those obtainable by suspension polymerization. The present invention relates to a method for producing a vinyl chloride resin having a sharp particle size distribution with a small particle size that is easy to control. "Prior Art" Vinyl chloride polymers produced by emulsion polymerization have fine polymer particles and excellent processability. On the other hand, when producing vinyl chloride polymers by suspension polymerization, the particles produced are coarse;
After the polymerization reaction is completed, dehydration, washing, drying, etc. are easy, and the resulting polymer has excellent thermal stability, electrical properties, transparency, weather resistance, etc., and is easy to handle during processing. Attempts to produce vinyl chloride resins having desirable properties such as those obtained by emulsion polymerization in a desirable form such as those obtained by suspension polymerization have been made, for example, as described in Japanese Patent Publication No. 45-30834. It is publicly known. In this method, 5 to 90% of the total amount of the polymer to be finally obtained is produced by emulsion polymerization, and then water, a suspending agent, and an oil-soluble polymerization initiator are added to the reaction system to carry out the remaining polymerization. It is produced by suspension polymerization method. Although this known method has characteristics similar to vinyl chloride resins produced by emulsion polymerization, and can be subjected to post-treatment similar to suspension polymerization, the particle size distribution of the resulting polymer is not constant. Moreover, it has the disadvantage that the particle size distribution is quite wide, and it is not necessarily satisfactory in the current field of vinyl chloride resin processing where technological progress is rapid. Specifically, in this method, the coarse particles that are by-produced in the latex after being obtained by emulsion polymerization remain as they are, and the latex agglomerated particles are not controlled at the latex stage. The particle size distribution of vinyl chloride resin produced by suspension polymerization is wide and has a large variation, which causes lumps and hard eyes in molded products, which often makes them unsuitable for practical use. Ta. Furthermore, during suspension polymerization, polymer scale was significantly attached to the can wall. "Problems to be Solved by the Invention" The present inventors have developed a vinyl chloride-based resin that takes advantage of the characteristics of the above-mentioned prior art and has desirable properties like a vinyl chloride-based polymer obtained by emulsion polymerization. We have conducted intensive research on a method for producing vinyl chloride resin that can be produced in a preferred form such as a polymer obtained by suspension polymerization, has less adhesion to can walls, is easy to control particle size, and has a sharp particle size distribution. , arrived at the present invention. "Means for Solving the Problems" Therefore, the gist of the present invention is to carry out suspension polymerization of vinyl chloride or a mixture copolymerizable with vinyl chloride in an aqueous medium using an oil-soluble polymerization initiator. In the method for producing a vinyl chloride resin, a vinyl chloride polymer latex produced separately by an emulsion polymerization method or a fine suspension polymerization method and from which coarse particles of 60 mesh or more are removed is pre-existing in the reaction system. , a method for producing a vinyl chloride resin characterized by adding an electrolyte before or during the reaction. The present invention will be explained in detail below. Monomers to which the method of the present invention can be applied include vinyl chloride alone, and combinations of vinyl chloride and one or more vinyl monomers copolymerizable therewith. The vinyl monomers mentioned here include, for example, oil-soluble monomers such as vinyl acetate, styrene, acrylonitrile, acrylic esters, methacrylic esters, and ethylene; water-soluble monomers such as acrylic acid, methacrylic acid, maleic acid, and crotonic acid. sexual monomer;
Examples include inorganic salts of vinyl monomers such as sodium acrylate, sodium fumarate, and calcium acrylate. Furthermore, as the monomer, a vinyl monomer having a polyfunctional group copolymerizable with vinyl chloride, such as divinylbenzene, diallyl phthalate, diallyl maleate, etc., can be used. These vinyl monomers having polyfunctional groups yield polymers having a crosslinked structure. In order to effectively achieve the present invention, it is first necessary to carry out emulsion polymerization or microsuspension polymerization. React vinyl chloride alone, or vinyl chloride with a desired monomer selected from the above monomer group, water, an emulsifier and a water-soluble polymerization initiator, or an oil-soluble polymerization initiator, and in some cases a PH regulator. The mixture is placed in a container, and after substitution with an inert gas, polymerization is carried out. As the emulsifier that can be used in emulsion polymerization, water-soluble emulsifiers are suitable, and anionic emulsifiers are particularly desirable. The amount of emulsifier is monomer
The content is preferably 2.0 parts by weight or less per 100 parts by weight. As the water-soluble polymerization initiator, hydrogen peroxide, potassium persulfate, ammonium persulfate, etc. are used. As the oil-soluble polymerization initiator, an initiator that generates free radicals such as benzoyl peroxide, lauroyl peroxide, and tertiary butyl peroxide is used. Additionally, oxidation-reduction (redox) initiators can also be used. After 80% or more of the above composition is polymerized by emulsion polymerization or fine suspension polymerization, coarse particles of 60 mesh or more are removed from the resulting latex. Next, vinyl chloride alone, or vinyl chloride and a desired monomer selected from the above monomer group, and water,
A suspending agent and an oil-soluble polymerization initiator are placed in a reactor, and the above-mentioned vinyl chloride polymer latex is added to the suspension polymerization reaction system after substitution with an inert gas.After the reaction temperature is reached, the electrolyte is added. is added to carry out suspension polymerization. Alternatively, the latex and electrolyte may be added at the same time. As the suspending agent, those commonly used in suspension polymerization can be used. Examples include various saponified products of polyvinyl acetate, various water-soluble cellulose derivatives, maleic acid copolymers, gelatin, etc., and these can be used alone or in combination of two or more. Moreover, these suspending agents and certain surfactants can also be used in combination. As the oil-soluble polymerization initiator, those mentioned above can be used. Furthermore, water-soluble salts can be used as the electrolyte. These salts are water-soluble salts belonging to group 1 of the periodic table, and the type and quantity of the salts are selected according to the purpose of quality of the resin to be produced. The type and amount of salts are determined through preliminary studies, but they must be at least in an amount that will allow the added latex to coagulate within the polymerization time. Examples of these salts include hydrochloric acid, sulfuric acid, calcium chloride, calcium acetate, aluminum chloride, magnesium chloride, and the like. As described above, the method of the present invention is characterized by a combination of emulsion polymerization or fine suspension polymerization and suspension polymerization, but the polymerization conditions for emulsion polymerization and suspension polymerization can be changed as desired. For example, the polymerization temperature may be different and the degree of polymerization of the polymer obtained by emulsion polymerization may be different. Further, during the polymerization by both polymerization methods, the polymerization can be continued while adding monomers to the reaction system stepwise or continuously. Furthermore, when producing a copolymer, emulsion polymerization and suspension polymerization may be carried out using different combinations of monomer compositions. "Function" The polymer obtained by the method of the present invention is different from a mere mixture of fine particles produced by emulsion polymerization or fine suspension polymerization and coarse particles produced by suspension polymerization. It also has favorable properties brought about by the polymerization method. First, when polymerization is carried out by emulsion polymerization, fine particles of 2 microns or less are obtained according to the reaction mechanism of ordinary emulsion polymerization. Similarly, fine particles of 2 microns or less can be obtained by fine suspension polymerization. After adding these fine particles to the suspension polymerization reaction system, when an electrolyte is added, the fine particles aggregate together, and the polymer produced in the suspension polymerization process wraps them, resulting in a 500 microns (average particle size approx.
150 microns). Therefore, after the completion of the reaction, salting out as in the usual emulsion polymerization method is not required, and dehydration, washing and drying can be easily carried out as in the usual suspension polymerization method. "Effects" The method of the present invention and the vinyl chloride resin obtained by the method of the present invention have the following excellent characteristics. 1. In the conventional technology, the particle size distribution was not constant and varied over a wide range, but according to the present invention, the particle size distribution becomes sharp and can be easily controlled. 2. During suspension polymerization, there was a significant amount of polymer scale attached to the can wall, but this was reduced in the present invention. 3. The thermal stability of the polymer obtained according to the present invention is as excellent as that of a polymer obtained by a conventional suspension polymerization method. Next, embodiments of the present invention will be described in detail with reference to Examples, but the present invention is not limited to the following Examples unless the gist thereof is exceeded. Example 1 Water 1000g Vinyl chloride 500g Sodium lauryl sulfate 0.5g Potassium persulfate 0.3g Sodium bisulfite 0.3g Sodium bicarbonate 0.4g The above composition was added to a stainless steel autoclave with a capacity of 3 equipped with a stirrer, and after purging with nitrogen,
After emulsion polymerization at 58°C for 5 hours with stirring at 200 rpm,
Unreacted vinyl chloride was separated by degassing. The polymerization rate of the initially charged monomer was 90% and the particle size
It is a latex with a diameter of 0.2 microns and a solid content of 30%.
Since this contains coarse grains, it was used at 100 mesh. Next, using the latex, 1400 g of water, 700 g of vinyl chloride monomer, 400 g of latex, 40 g of 2% polyvinyl alcohol solution, and 2.1 g of lauroyl peroxide were added to the stainless steel autoclave equipped with a stirrer in Step 3, and after the temperature inside the container reached 58°C,
10 g of calcium acetate was added and suspension polymerization was carried out for 8 hours. After the polymerization reaction was completed, the dechlorinated vinyl monomer was washed, dehydrated and dried to obtain a polyvinyl chloride resin with an average degree of polymerization of 1050. The total amount of polyvinyl chloride at this time was 700 g. In addition, almost no adhesion was observed in the stainless steel autoclave equipped with a stirrer. The average particle diameter of the obtained polyvinyl chloride was 150μ, and the particle size distribution is shown in Table 1.

[Table] In addition, 3 parts by weight of dibutyltin maleate was added to 100 parts by weight of this polyvinyl chloride, and after kneading with a heated roll, the thermal stability was tested in a gear oven at 180°C. The resulting polymer was colored pale yellow in 90 minutes, and although the degree of coloration was slightly inferior to that of the commercially available suspension polymerization method, it was much more colored than the commercially available emulsion method polymer that was similarly colored in 40 minutes. It showed good thermal stability. In addition, using the same formulation as above, the gelation time was measured at 170°C using a Brabender plastograph, and it was 80 seconds. The gelation time of the polymer with an average degree of polymerization of 1050 was 150 seconds. The results show that the processability of the polymer obtained by the present invention is far superior to that of a polymer obtained by suspension polymerization. Comparative Examples 1400g of water, 700g of vinyl chloride monomer, 40g of 2% polyvinyl alcohol solution, and 2.1g of lauroyl peroxide were added to the stainless steel autoclave with a stirrer in Comparative Examples 1 and 3, and after the temperature inside the container reached 58°C, the mixture obtained in Example 1 was added. 400 g of latex passed through a 100 mesh was added, and suspension polymerization was carried out for 8 hours. After the polymerization reaction was completed, there was a lot of adhesion to the stainless steel autoclave equipped with a stirrer, and the waste water became cloudy, and the amount of polyvinyl chloride in the waste water was 20 g. The amount of polyvinyl chloride obtained was 600 g, and the average particle size was 300 microns, which was very coarse. The particle size distribution is shown in Table 2.

[Table] Example 2 1400 g of water, 700 g of vinyl chloride monomer, 40 g of 2% methylcellulose solution, and 2.1 g of lauroyl peroxide were added to the stainless steel autoclave equipped with a stirrer in Example 2, and the latex obtained in Example 1 was prepared.
After adding 400g and the temperature inside the container reaching 58℃,
10 g of calcium acetate was added and suspension polymerization was carried out for 8 hours. After the polymerization reaction was completed, the dechlorinated vinyl monomer was washed, dehydrated and dried to obtain a polyvinyl chloride resin with an average degree of polymerization of 1050. In addition, almost no adhesion to the can wall of the stainless steel autoclave equipped with an agitator was observed. The average particle diameter of the obtained polyvinyl chloride was 150 microns, and the particle size distribution is shown in Table 3.

[Table] Next, 3 parts by weight of dibutyltin maleate was added to 100 parts by weight of this polyvinyl chloride, and after kneading with heated rolls, the thermal stability was tested in a gear oven at 180°C. The obtained polymer is 25
The degree of coloration is slightly inferior to that of the commercially available suspension polymerization method, but the thermal stability is much better than that of the commercially available emulsification method polymer, which is similarly colored within 40 minutes. Indicated. In addition, using the same formulation as above, gelation time was measured at 170°C using a Brabender plastograph, and it was 75 seconds.For comparison, the gelation time was 75 seconds. The gelation time of the polymer with an average degree of polymerization of 1050 was 150 seconds.
The results show that the processability of the polymer obtained by the present invention is far superior to that of a polymer obtained by suspension polymerization. Example 3 1000 g of water, 475 g of vinyl chloride, 25 g of vinyl acetate, 0.5 g of sodium lauryl sulfate, 0.3 g of potassium persulfate, 0.3 g of sodium bisulfite, and 0.4 g of sodium bicarbonate were added to a stainless steel autoclave with a capacity of 3 and equipped with a stirrer, and after purging with nitrogen,
After emulsion polymerization at 58°C for 5 hours under stirring at 200 rpm,
Unreacted vinyl chloride and vinyl acetate were separated by degassing operation. The polymerization rate of the initially charged monomer was 90%, and the particle size was
The latex was 0.2 microns and had a solids content of 30%.
Because this latex contains coarse particles,
I spent 100 meals. Next, 1400 g of water, 700 g of vinyl chloride monomer, 40 g of 2% polyvinyl alcohol solution, and 2.1 g of lauroyl peroxide were added to the stainless steel autoclave equipped with a stirrer in step 3, and the latex obtained above was mixed with 400 g of lauroyl peroxide.
After the temperature inside the container reached 58° C., 10 g of calcium acetate was added and suspension polymerization was carried out for 8 hours. After the polymerization reaction was completed, the dechlorinated vinyl monomer was washed, dehydrated and dried to obtain a polyvinyl chloride resin. The total amount of polyvinyl chloride at this time was 700 g. In addition, almost no adhesion to the can wall of the stainless steel autoclave equipped with an agitator was observed. The average particle diameter of the obtained polyvinyl chloride was 150 microns, and the particle size distribution is shown in Table 4.

[Table] In addition, 3 parts by weight of dibutyltin maleate was added to 100 parts by weight of this polyvinyl chloride, and after kneading with a heating roll, the thermal stability was tested in a gear oven at 180°C. The resulting polymer was colored pale yellow in 80 minutes, and the degree of coloration was slightly inferior to that of the commercially available suspension polymerization method polymer, but it was much better than the commercially available emulsion method polymer that was similarly colored in 40 minutes. It showed excellent thermal stability. In addition, using the same formulation as above, gelation time was measured at 170°C using a Brabender plastograph, and it was 75 seconds, compared to the average polymerization time obtained by a commercially available suspension polymerization method. The gel time for the 1050 degree polymer was 150 seconds. As a result,
This shows that the processability of the polymers obtained according to the present invention is far superior to that of polymers obtained by suspension polymerization. Example 4 1000g of water, 9g of lauroyl peroxide, 6g of sodium lauryl sulfate, and 3g of lauryl alcohol were added to a stainless steel autoclave with a capacity of 3 and equipped with a stirrer, and after purging with nitrogen, vinyl chloride was added.
600g was added and maintained at 35°C while stirring at 200rpm. After stirring uniformly, the mixture was dispersed into a desired droplet size using an emulsifier and transferred to a stainless steel autoclave equipped with a stirrer 3, which had been purged with nitrogen in advance. After the transfer of the dispersion is completed, the temperature of the reaction vessel is set to 58°C.
The temperature was raised to 0.degree. C., and fine suspension polymerization was carried out. The latex had a particle size of 0.4 microns and a solids content of 32%. Since this latex contained coarse particles, 100 mesh was used. Next, add 1400 g of water, 700 g of vinyl chloride monomer, 40 g of 2% polyvinyl alcohol solution, and 2.1 g of lauroyl peroxide to the stainless steel autoclave equipped with a stirrer in step 3, add 400 g of the aforementioned latex, and after the temperature inside the container reaches 58°C, add calcium acetate. 10 g was added and suspension polymerization was carried out for 8 hours. After the polymerization reaction is complete,
The dechlorinated vinyl monomer was washed, dehydrated and dried to obtain a polyvinyl chloride resin with an average degree of polymerization of 1050. The average particle diameter of the obtained polyvinyl chloride was 150 microns, and the particle size distribution is shown in Table 5.

[Table] Next, 3 parts by weight of dibutyltin maleate was added to 100 parts by weight of this polyvinyl chloride, and after kneading with a heating roll, the thermal stability was tested in a gear oven at 180°C. The resulting polymer was colored pale yellow in 90 minutes, and the degree of coloration was almost the same as that of the commercially available suspension polymerization method, and it was far more colored than the commercially available emulsion method polymer that was similarly colored in 40 minutes. It showed good thermal stability. In addition, the gelation time of the same formulation as above was measured at 170°C using a Brabender plastograph, and it was 85 seconds. The gelation time of the polymer was 150 seconds. The results show that the processability of the polymer obtained by the present invention is far superior to that of the polymer obtained by suspension polymerization.

Claims (1)

[Claims] 1. In a method for producing a vinyl chloride resin by suspension polymerizing vinyl chloride or a mixture copolymerizable with vinyl chloride in an aqueous medium using an oil-soluble polymerization initiator, the reaction system is preliminarily added to an emulsion polymerization method or A method for producing a vinyl chloride resin, characterized by the presence of a vinyl chloride polymer latex produced by a fine suspension polymerization method and excluding coarse particles of 60 mesh or more, and the addition of an electrolyte before or during the reaction. .