JPH0479363B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention provides a blending resin for polyvinyl chloride paste resin, which has good fluidity when used together with polyvinyl chloride paste resin and is made into a plastisol with a plasticizer, and which has excellent quality of molded products obtained by heat molding this sol. This relates to a manufacturing method. Polyvinyl chloride paste resin is stirred and kneaded with plasticizers, secondary plasticizers, diluents, stabilizers, and other fillers to form a sol, which is used in various finished products by coating, dipping, casting, spraying, etc. be done. Therefore, from the point of view of processability, fluidity suitable for each molding method,
A sol with viscosity is required. In particular, in sol molding under high shear such as coating methods, a blending resin for paste resin is often used to reduce the viscosity of the sol. Blending resin is also used to make the surface of a molded product matte. Such a blending resin for paste resin is preferably a single particle having an average particle size of 20 to 80 microns, low porosity, and a dense and smooth surface. During this manufacture, special materials must be present in the polymerization system in order to obtain dense, spherical beads of polymer or copolymer with the desired particle size and distribution. The first important material is an average degree of polymerization of 1000 as a suspending or dispersing agent.
~2500, saponification degree 60~85mo1%. It is a vinyl alcohol whose cloud point is below the polymerization temperature. The suspending agents described above are only applicable to the present method in combination with nonionic surfactants as described below. The suspending or dispersing agent is used in an amount ranging from 0.1 to 2.0%, preferably about 0.5 to 1.5% by weight, based on the total monomer charge.
Dispersants can be added to the reaction system at any time before the start of the reaction. However, it is usually added to the reaction system as an aqueous solution prior to the addition of the monomers. One of the most important aspects of this invention is the use of certain suitable surfactants in the polymerization of monomers. The surfactant used together with the above-mentioned polyvinyl alcohol is nonionic and hydrophilic, and has an HLB of 15 or more. Preferably, the surfactant has an HLB of 17 or more.
The higher the HLB of the surfactant, the better, ie, the more easily the surfactant dissolves in water, the more desirable properties will be obtained. The effectiveness of nonionic surfactants is related to the polarity of the molecule, ie the relationship between polar hydrophilic groups and nonpolar hydrophobic groups. The polarity of this nonionic surfactant is determined by an empirical numerical value called HLB, as described above. The amount of surfactant used in this invention ranges from about 0.05 to 1.0% by weight based on the total monomer charge. If the amount is less than 0.05%, the effect will not be sufficient, and if it is more than 1.0%, the sol viscosity lowering effect may be adversely affected. The combined HLB
One or more surfactants can be used in combination, as long as the surfactants do not become less than 15. The surfactants used here have the effect of working together with polyvinyl alcohol as described above to form smaller, spherical particles with a narrow particle size distribution. As mentioned above, nonionic surfactants with suitable HLB include fatty acid esters of polyoxyethylene, aromatic esters of polyoxyethylene, aliphatic and aromatic ethers of polyoxyethylene, and polyoxyethylene sorbitan fatty acids. It is included in the category of esters, polyoxyethylene sorbitol fatty acid esters, block copolymers of polyoxyethylene and polyoxypropylene, etc. Suitable surfactants include polyoxyethylene lauryl ether, oleyl ether, octylphenyl ether, nonylphenyl ether, polyoxyethylene monostearate, palmitate, oleate, and the like. Surfactants can be added to the reaction system at any time prior to polymerization. However, it is usually added before the addition of the monomers, and its form can be either solid or an aqueous solution. The catalyst or initiator used in the present invention is soluble in the monomer. For example, azobisisobutyronitrile, 2,2'-azobis(2,4-dimethylvaleronitrile), tert-butyl peroxypivalate, benzoyl peroxide, dioctylcyclohexylsulfonyl peroxide,
Oil-soluble catalysts or free radical initiators with low aqueous solution such as tert-butylperoxyneodecanate, acetylcyclohexylsulfonyl peroxide. The catalyst or initiator selected in this invention is used in an amount ranging from about 0.01 to 0.5% by weight, based on the total monomer charge. Catalysts or initiators can be added to the reaction system at any time as long as the reaction system is maintained below the decomposition temperature of the particular catalyst. However, in the present invention, the catalyst or initiator is added as the last addition component before raising the reaction system to a predetermined temperature. The reaction temperature in the present invention is usually about 30 to 70°C.
within the range of Particularly satisfactory results are obtained when the reaction temperature is in the range of 50-60°C. The reaction time is usually 6 to 12 hours, and the reaction system is stirred throughout the reaction time. Agitation is usually constant during the reaction cycle, but may be varied if necessary. It is clear that the combination of polyvinyl alcohol with a cloud point below the polymerization temperature and a hydrophilic surfactant used in the present invention produces particles of vinyl chloride resin that are spherical and free of porosity. The polyvinyl alcohol used in the present invention precipitates within the polymerization system at the polymerization temperature,
Since it exists as fine particles, it seems to act independently of the hydrophilic surfactant. The hydrophilic surfactant determines the size of the monomer droplets and the size of the vinyl chloride resin produced along with stirring, and contributes to reducing the porosity of the particles. If the HLB of the surfactant is less than 15, a portion of the surfactant will dissolve in the monomer layer and proceed to the polymer/monomer interface inside the polymer during the polymer formation process, hindering the fusion of primary particles and causing porosity. give. Furthermore, polyvinyl alcohol, at the polymerization temperature,
This is to prevent coalescence and aggregation of the vinyl chloride resin particles dispersed by the same action as an inorganic dispersant due to mutual stirring and shearing.
When the degree of saponification of polyvinyl alcohol exceeds 85 mo1%, the cloud point exceeds the polymerization temperature and exists as an aqueous solution during the reaction. Therefore, they exist in the same region as the hydrophilic surfactant, canceling out their individual effects and destabilizing the polymerization system. The present invention will be explained below using examples.
The contents of the examples are not intended to limit the scope of the invention. Example 1 Polymerization was carried out using 30 kg of pure water, average degree of polymerization 2000, and degree of saponification 75 mo1 in an autoclave equipped with 50 stirring blades.
%, an aqueous solution of 100 g of polyvinyl alcohol with a cloud point of 40°C dissolved in 3 kg of pure water, 10 g of polyoxyethylene lauryl ether, α,α′-azobis-2,
After adding 10 g of 4-dimethylvaleronitrile,
The autoclave was sealed and oxygen from the polymerization system was evacuated. After charging 20 kg of vinyl chloride monomer, stirring was started, the temperature was raised to 63°C, and the polymerization reaction was started. Polymerization was stopped when the autoclave internal pressure decreased to 7.5 Kg/cm ³ . The polymer slurry was removed from the reactor, washed with water and dried in the usual manner. Examples 2 to 5 Polymers were obtained in the same manner as in Example 1, except that the surfactants shown in Table 1 were used in place of polyoxyethylene lauryl ether. Comparative Example 1 A polymer was produced by polymerization in the same manner as in Example, but no emulsifier was added. Comparative Example 2 A polymer was obtained in the same manner as in Example 1, except that polyoxyethylene nonylphenyl ether was used instead of polyoxyethylene lauryl ether. The physical property values shown in Table 1 were evaluated by the following method. 1 Average particle size Measured by Coulter counter in water. For operations and equipment, see “Particle Size Measurement” by T. Allen, Chapter 13, 2nd edition (1975). Published by Ohapman and Hall, London;
It is stated in 2 Intraparticle porosity Polymer particles are dispersed in n-butyl alcohol, and immediately after that, the sample is exposed to transmitted light and observed using an optical microscope. Particles with internal pores reflect transmitted light diffusely and are observed as black particles. The number of pores was determined based on the ratio of the number of black particles to the total number of particles. 3 Sol viscosity Blending resin 30g, paste resin 70
After adding 50 g of dioctyl phthalate as a plasticizer to g, the mixture was stirred and dispersed using a mixer, and defoamed to prepare plastisol. The paste resin used was one with a sol viscosity of 9660 cps, consisting of 100 parts by weight of the paste resin and 50 parts by weight of dioctyl phthalate. The measurement was carried out using a Bruckfield viscometer at 20 rotations per minute using a No. 5 spindle and at a measurement temperature of 23°C.

【table】

[Table] Comparative Example 3 Instead of polyvinyl alcohol, average degree of polymerization
A polymer was produced in the same manner as in Example 1, except that maleic acid-modified polyvinyl alcohol having a saponification degree of 75 mol% and a maleic acid content of 1.5 mol% was used, and its physical properties were evaluated. As a result, the average particle diameter was 35μ, the intraparticle porosity was almost 100%, and the sol viscosity was 8300 cps. Comparative Example 4 A polymer was produced in the same manner as in Example 1 except that the amount of polyvinyl alcohol added was 0.08% by weight based on the monomer, 16 g, and its physical properties were evaluated. As a result, the particle size was 100μ or more, and the porosity inside the particle was 5%.
Below, the sol viscosity was 3800 cps. Comparative Example 5 A polymer was produced in the same manner as in Example 1 except that the amount of polyoxyethylene lauryl ether added was 0.005% by weight, 1 g, based on the monomer, and its physical properties were evaluated. As a result, the particle size was 100μ or more,
The intraparticle porosity was 5% or less, and the sol viscosity was 3700 cps.

Claims (1)

[Claims] 1. A process for producing polymers and copolymers of vinyl chloride by suspension polymerization in the presence of a vinyl chloride monomer-soluble catalyst and one or more suspension stabilizers, optionally PH-buffers, comprising: As an agent, average degree of polymerization 1000-2500, degree of saponification 60
~85 mol%, polyvinyl alcohol with a cloud point below the polymerization temperature, 0.1 to 2.0% by weight of the monomer, and a hydrophilic nonionic surfactant with an HLB of 15 or more, 0.01 to 1.0% by weight of the monomer. A method for producing a blending resin for polyvinyl chloride paste resin.