JPH0542447B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a method for producing vinyl chloride resin, and more specifically, a method for producing vinyl chloride resin by graft copolymerizing vinyl chloride onto an acrylic polymer latex with stable particle size using a suspension polymerization method. It relates to a method of manufacturing. [Prior Art] Vinyl chloride resin has excellent physical and mechanical properties and has many uses such as hard, semi-hard, and soft. When vinyl chloride homopolymer is used for hard materials, it has the disadvantage of poor impact resistance and weather resistance. As a method to improve these drawbacks, polymer blends of vinyl chloride homopolymers and various elastomers can be mentioned. According to this method, impact resistance can be improved, but on the other hand, it has the disadvantage that weather resistance and flexural modulus are reduced. Furthermore, vinyl chloride graft copolymers obtained by graft copolymerizing vinyl chloride onto acrylic polymers are known to have excellent impact resistance, weather resistance, and flexural modulus. One way to obtain this vinyl chloride graft copolymer is to graft copolymerize vinyl chloride onto acrylic rubber, but this method involves a step of cutting the rubber into small pieces, and then swelling the cut rubber with vinyl chloride. It requires a step of dissolving, which poses a problem in workability, and is therefore disadvantageous for industrial implementation. As a method for solving the above problem, there is a method in which vinyl chloride is graft copolymerized onto an acrylic polymer latex. If this method is adopted, workability is improved, but since the polymerization form is suspension polymerization in the presence of an emulsifier contained in the acrylic polymer latex, a large amount of dispersant is required, and
Variations in particle size tend to occur, making it impossible to obtain a product with stable particle size. [Problems to be Solved by the Invention] The present invention provides an emulsion-suspension polymerization method, that is, a method in which an acrylic polymer latex obtained by emulsion polymerization is graft-copolymerized with vinyl chloride by a suspension polymerization method. The purpose is to obtain a product with stable particle size. [Means for Solving the Problems] As a result of extensive research in order to achieve the above object, the present inventors coagulated an acrylic polymer latex in a graft copolymerization reaction tank, and then coagulated vinyl chloride. It has been discovered that a product with stable particle size can be obtained by adding the above particles and carrying out graft copolymerization using a suspension polymerization method, leading to the present invention. That is, in the present invention, when producing a graft copolymer by graft copolymerizing vinyl chloride onto an acrylic polymer, after coagulating the acrylic polymer latex with an organic acid salt in a graft copolymerization reaction tank, This is a method for producing a vinyl chloride resin with stable particle size, which is characterized by graft copolymerizing vinyl chloride using a suspension polymerization method. The acrylic polymer latex used in the present invention is a copolymer latex mainly composed of alkyl acrylate and/or alkyl methacrylate, and containing other copolymerizable monomers as necessary. Examples of alkyl acrylate and alkyl methacrylate include methyl acrylate,
Ethyl acrylate, n-propyl acrylate, iso-butyl acrylate, n-butyl acrylate, n-hexyl acrylate, 2-ethylhexyl acrylate, n-octyl acrylate, n-decyl acrylate, n-dodecyl acrylate, lauryl acrylate and their methacrylates. can give. In addition, copolymerizable monomers include monofunctional monomers such as olefins such as ethylene, propylene, and hexene, aromatic vinyls such as styrene, α-methylstyrene, and vinyltoluene, and acrylonitrile and methacrylonitrile. Unsaturated nitriles, vinyl esters such as vinyl acetate and vinyl propionate, vinyl ethers such as butyl vinyl ether and lauryl vinyl ether, polyfunctional monomers such as ethylene glycol diacrylate, diethylene glycol diacrylate, triethylene glycol diacrylate,
Mono or polyalkylene glycols such as ethylene glycol dimethacrylate, diethylene glycol dimethacrylate, triethylene glycol dimethacrylate, 1,3-propylene glycol dimethacrylate, 1,3-butylene glycol dimethacrylate, 1,4-butylene glycol dimethacrylate, etc. Examples include acrylates or methacrylates, di- or triallyl compounds such as diallyl phthalate, diallyl maleate, diallyl fumarate, diallyl succinate, triallyl isocyanurate, and divinyl compounds such as divinylbenzene and butadiene. The alkyl acrylate, alkyl methacrylate, and copolymerizable monomers may be used alone or in combination of two or more to obtain a latex. The amount of acrylic polymer latex added is also determined depending on the intended use of the final product. The acrylic polymer latex used in the present invention is obtained by emulsion polymerization, and the average particle size of the latex is preferably about 0.01 to 10 μm. To produce acrylic polymer latex using the general emulsion polymerization method, for example, pure water, an anionic emulsifier, and a water-soluble polymerization initiator are charged into a jacketed polymerization reactor, and the air inside the can is excluded. Then, monomers copolymerizable with alkyl acrylate and/or alkyl methacrylate are charged, and after emulsification, the inside of the can is heated with a jacket to start the reaction. The reaction is exothermic, and the internal temperature is controlled by the jacket as necessary. After the reaction is complete, unreacted monomers are removed from the can,
Obtain an acrylic polymer latex. The method of charging into the polymerization reactor is not limited. Further, if necessary, a latex particle size adjusting agent, a catalyst decomposition accelerator, etc. may be added to control the reaction. Acrylic polymer latex is made by the above method.
It is possible to manufacture up to a concentration of 50wt%, but due to manufacturing
For handling purposes, a concentration of 10 to 30 wt% is advantageous. Coagulants used in the present invention include salts of organic acids such as lactic acid, tartaric acid, malic acid, citric acid, and alginic acid, and their salts include sodium, potassium, lead, copper, silver, magnesium, calcium, barium, zinc, Examples include salts with aluminum, ammonium, etc. It is desirable to use the coagulant in an optimum amount that can stably carry out suspension polymerization without impeding the effect of the dispersant used. If the pH of the suspension decreases, it may be neutralized with a basic substance such as sodium hydroxide, calcium hydroxide, or aqueous ammonia to prevent the effect of the dispersant from decreasing. do not have. When carrying out an aqueous suspension polymerization method, the amount of water used is 1 to 5 times, preferably 1 to 3 times, the total amount of the base polymer copolymer and vinyl chloride monomer. To obtain a graft copolymer resin by the suspension polymerization method of the present invention, for example, pure water, a coagulant, a radical polymerization initiator, and, if necessary, a degree of polymerization regulator are placed in a jacketed polymerization reactor, and the mixture is stirred. An acrylic polymer latex is placed at the bottom and allowed to solidify, then the air inside the can is removed, a dispersant such as hydroxypropyl methyl cellulose is added, and then vinyl chloride is charged, along with other vinyl compounds as required. Thereafter, the inside of the can is heated with a jacket to start graft copolymerization. Graft copolymerization is an exothermic reaction, and the internal temperature is controlled by the jacket as necessary. After the reaction is completed, unreacted vinyl chloride is removed from the can to obtain a slurry of graft copolymer resin. The slurry is dehydrated and dried according to a conventional method to obtain a graft copolymer resin. In carrying out the present invention, it is advantageous to carry out the graft copolymerization by a radical polymerization method, and the radical polymerization initiators used for this purpose include lauroyl peroxide, tert-butyl peroxypivalate, diisopropyl peroxydi carbonate, organic peroxides such as dioctyl peroxydicarbonate, 2,2'-azobisisobutyronitrile, 2,2'-azobis-2,
Examples include oil-soluble polymerization initiators such as azo compounds such as 4-dimethylvaleronitrile, and water-soluble polymerization initiators such as potassium persulfate and ammonium persulfate. The amount of these polymerization initiators used is 100% vinyl chloride.
The amount is preferably 0.005 to 1.0 parts by weight. Dispersants include methylcellulose, ethylcellulose, hydroxypropylmethylcellulose, hydroxyethylcellulose, polyvinyl alcohol and partially saponified products thereof, gelatin, polyvinylpyrrolidone, starch, maleic anhydride.
Examples include styrene copolymers, which may be used alone or in combination. The amount added is 0.01 to 1.0 parts by weight per 100 parts by weight of vinyl chloride. Furthermore, in the present invention, a chain transfer agent used in conventional methods for polymerizing vinyl monomers may be added in an amount of 0.001 to 10 parts by weight per 100 parts by weight of vinyl chloride. The graft copolymer resin obtained by the method of the present invention has a stable average particle size of 90 to 120 μm and is very easy to handle during processing. The graft copolymer resin obtained in the present invention can be obtained by blending usual stabilizers, lubricants, processing aids, antioxidants, fillers, ultraviolet absorbers, pigments, etc. used in the molding process of vinyl chloride resin. It can be subjected to normal molding processes, and is suitable for use as building materials due to its excellent impact resistance and weather resistance. [Example] Hereinafter, the present invention will be specifically explained with reference to Examples. Reference Example 1 (Manufacture of acrylic latex) 2000 kg of deionized water, 7.0 kg of anionic emulsifier, 0.7 kg of ammonium persulfate, and 700 kg of n-butyl acrylate were placed in a polymerization machine with an internal volume of 5 m ³ equipped with a stirring blade.
After adding 35 kg of 1,3-butylene glycol dimethacrylate and replacing the internal air with nitrogen, the
Polymerization was carried out at °C. Fifteen hours after the start of polymerization, the internal temperature began to rise rapidly, so heat was removed through a jacket and a backflow condenser, and the reaction was continued for another 10 hours, then the polymerization reaction was stopped. The concentration of the obtained latex was 25%, and the particle size was 0.07 μm. Example 1 2700 kg of deionized water, 0.45 kg of calcium citrate, 0.9 kg of partially saponified polyvinyl alcohol, 0.9 kg of methyl cellulose, and 2,2'-azobisisobutyro were placed in a polymerization machine with an internal volume of 7 m ³ equipped with a stirring blade. After adding 0.45 kg of nitrile and removing the air inside with a vacuum pump, 840 kg of acrylic polymer latex (solid content 210 kg) with a composition shown in Table 1 at a concentration of 25% was charged with stirring. The combined latex was allowed to solidify. After that, 1290 kg of vinyl chloride was charged,
Polymerization was carried out at 60°C. Eleven hours after the start of polymerization, the internal pressure of the polymerization machine decreased to 6.5 Kg/cm ² , so the polymerization reaction was stopped. After removing the unreacted vinyl chloride monomer, the slurry was dehydrated and dried by a conventional method to obtain 1215 kg of white powder particles. The average particle size of this white powder was 113 μm, and the particle size distribution was also narrow and stable. Example 2 2700 kg of deionized water, 0.45 kg of aluminum tartrate, 1.0 kg of partially saponified polyvinyl alcohol, 1.0 kg of methyl cellulose, and 2,2'-azobisisobutyronitrile were placed in a polymerization machine with an internal volume of 7 m ³ equipped with a stirring blade. After adding 0.075 kg of 2,2'-azobis-2,4 dimethylvaleronitrile and 0.24 kg of 2,2'-azobis-2,4 dimethylvaleronitrile and removing the air inside with a vacuum pump, the concentration of the composition shown in Table 1 was obtained.
600 kg of 15% acrylic polymer latex (solid content: 90 kg) was charged under stirring and allowed to solidify. Thereafter, 1410 kg of vinyl chloride was charged and polymerization was carried out at 57°C. 10 hours after the start of polymerization, the internal pressure of the polymerization machine was 6.5.
The polymerization reaction was stopped when the amount decreased to Kg/cm ² . After removing unreacted vinyl chloride, the slurry was dehydrated and dried using a conventional method, and 1210 particles of white powder were obtained.
Kg was obtained. The average particle size of this white powder was 107 μm, and the particle size distribution was also narrow and stable. Comparative Example 1 Polymerization was carried out in the same manner as in Example-1, except that 2.25 kg of partially saponified polyvinyl alcohol and 2.25 kg of methyl cellulose were added, and no coagulant was added. Obtained. This white powder had a large average particle size of 255 μm and a wide particle size distribution. Comparative Example 2 Polymerization was carried out in the same manner as in Comparative Example 1 except that 2.325 kg of partially saponified polyvinyl alcohol and 2.325 kg of methyl cellulose were used in Comparative Example 1 to obtain 1200 kg of white powder particles. The average particle size of this white powder was 76 μm, and the particle size distribution was wide. Comparative Example 3 In Example-2, 1.95 kg of partially saponified polyvinyl alcohol and 1.95 kg of methyl cellulose
Polymerization was carried out in the same manner as in Example 2, except that the weight was increased to 1,210 kg and that no coagulant was charged, to obtain 1210 kg of white powder particles. The average particle size of this white powder was 189 μm, and the particle size distribution was wide. Comparative Example 4 In Comparative Example-3, 2.025 kg of partially saponified polyvinyl alcohol and 2.025 kg of methyl cellulose were used.
Polymerization was carried out in the same manner as in Comparative Example 3, except that the weight was changed to 1,205 kg, to obtain white powder particles of 1205 kg. The average particle size of this white powder was 80 μm, and the particle size distribution was wide. The results of the above Examples and Comparative Examples are summarized in Table 1. In addition, the particle size distribution is JIS standard sieve 60, 80,
Stack 100, 150, 200, 270 meshes and saucers in that order and place 50g of sample on the sieve located at the top.
After applying vibration for 15 minutes using a shaker, the proportion of resin present on each sieve and on the saucer was determined and expressed in weight %. In addition, the average particle size is determined by plotting the cumulative total of the remaining percentage of each mesh on the horizontal axis of the regularity probability table and the aperture (μm) of each mesh on the vertical axis.
Expressed as 50% eye opening (μm).

【table】

〔Effect of the invention〕

In the method of the present invention, since the acrylic polymer latex is coagulated once, the particle size distribution of the resulting vinyl chloride graft copolymer particles is sharp, and the average particle size is also sufficiently large. It is. On the other hand, when solidification is not performed, a large amount of dispersant is required, and as seen in the comparative example, even a slight difference in the dispersant causes extreme changes in the particle size distribution and average particle diameter.

Claims (1)

[Claims] 1. When producing a graft copolymer by graft copolymerizing vinyl chloride onto an acrylic polymer, the acrylic polymer latex is coagulated with an organic acid salt in a reaction tank for graft copolymerization, and then the vinyl chloride is coagulated with an organic acid salt. A method for producing vinyl chloride resin, which comprises graft copolymerization using a suspension polymerization method.