JPH0367522B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention prevents whitening of molded products, decrease in transparency, etc. caused by emulsifiers contained in vinyl chloride resin for paste processing or moisture absorbed by the emulsifiers, and prevents polymerization. The present invention relates to a method for producing granular vinyl chloride resin for paste processing with high stability and productivity. (Prior art) Vinyl chloride resin for paste is usually produced by emulsion polymerization,
Primary particles with an average particle size of 0.2 to 2 microns, which are close to true spheres, are produced through a seeded emulsion polymerization or fine suspension polymerization process, a spray drying process, and a crushing process combined with these in some cases. It is aggregated into particles with a diameter of several tens of microns, and is usually processed in powder form. When processing, first,
A resin composition called a paste sol is obtained by mixing and dispersing vinyl chloride resin powder in a plasticizer together with a heat stabilizer, filler, pigment, and other compounding agents. This paste-like composition is then molded into a final molded product by a molding method such as cast molding, slush molding, rotary molding, spread coating molding such as knife coating or roll coating, or screen coating molding. Processed. Depending on the processing method of these paste sol and the type and amount of components other than the resin in the paste sol, the emulsifier and small amount of water contained in the resin may remain as air bubbles in the paste sol and cause pins to form in the molded product. Holes may occur, and the molded product may easily absorb moisture, causing it to turn white or become less transparent. Also, the remaining emulsifier may precipitate. In order to improve these drawbacks, it is conceivable to reduce the amount of emulsifier used, but this results in the generation of lumps and a decrease in mechanical stability, which significantly impairs productivity. Therefore, in order to obtain a vinyl chloride resin with good water resistance and less precipitation, a compatible and highly dispersible emulsifier is desired. Furthermore, in the industrial production of vinyl chloride resin, it is important from the viewpoint of productivity to obtain a latex with a high solid content concentration, few lumps, and high mechanical stability. (Problems to be Solved by the Invention) The present inventor has created a molded article from a paste sol that has good thermal stability, water resistance, and transparency, and has a granular paste that has a stable polymerization reaction and good productivity. As a result of intensive research to develop a method for producing vinyl chloride resin, the present invention was discovered. (Means for Solving the Problems) That is, the present invention provides vinyl chloride or a mixture of vinyl chloride and a vinyl compound copolymerizable with vinyl chloride under a water-soluble polymerization catalyst or a water-soluble reducing agent and an organic hydroperoxide. Under a redox polymerization catalyst, a mixture of a maleic acid copolymer salt and at least one selected from sulfonate salts, ether-type sulfuric ester salts, and higher fatty acid salts having 8 to 22 carbon atoms is used as an emulsifier to produce an aqueous medium. A vinyl chloride resin aggregate is prepared by adding and mixing an organic liquid that is sparingly soluble in water and does not dissolve or swell the vinyl chloride resin into the resulting vinyl chloride resin emulsion. The present invention relates to a method for producing a vinyl chloride resin for paste, characterized in that the aggregate is then dehydrated and dried to recover granular vinyl chloride resin. Vinyl compounds copolymerizable with vinyl chloride in the present invention include vinyl esters such as vinyl acetate, vinyl propionate, vinyl myristate, vinyl oleate, and vinyl benzoate; acrylic acid, methacrylic acid, maleic acid, and fumaric acid. , unsaturated carboxylic acids such as cinnamic acid or their anhydrides; esters of acrylic acid such as methyl, ethyl, butyl, octyl, and benzyl; esters of methacrylic acid such as methyl, ethyl, butyl, octyl, and benzyl;
Unsaturated carboxylic acid esters such as maleate, fumarate, and cinnamate; vinyl ethers such as methyl, ethyl, butyl, octyl, and myristyl vinyl ether; monomers such as ethylene, propylene, butene, and pentene. Olefins: One or more ordinary vinyl compounds that can radically copolymerize with vinyl chloride, such as vinylidene chloride, styrene and its derivatives, acrylonitrile, methacrylonitrile, etc., and usually 50% by weight in a mixture with vinyl chloride. It can be used in a range up to %. The water-soluble polymerization catalyst in the present invention includes persulfates such as ammonium persulfate, sodium persulfate, and potassium persulfate, hydrogen peroxide, etc., and the amount of this catalyst used is 0.005 to 1% by weight based on the monomer. It is. Water-soluble reducing agents include ethylenediaminetetraacetic acid,
Its sodium or potassium salt, ethylenediaminetetraacetic acid, or complex compounds of its sodium or potassium salt with heavy metals such as iron, copper, chromium, etc., sulfuric acid, its sodium or potassium salt, l-ascorbic acid, its sodium,
Common radical redox compounds that are soluble in water, such as potassium or calcium salts, ferrous pyrophosphate, ferrous sulfate, ferrous ammonium sulfate, sodium sulfite, sodium bisulfite, sodium formaldehyde sulfoxylate, and reducing sugars. At least one type of reducing agent used as a polymerization catalyst component. The amount of the reducing agent used is usually 0.00001 to 5% by weight based on the monomer, and if it is out of this range, a smooth polymerization reaction cannot be carried out. The reducing agent is added at the initial stage of polymerization. Examples of the organic hydroperoxide in the present invention include tertiary amyl hydroperoxide, tert-butyl hydroperoxide, isopropyl hydroperoxide, cumene hydroperoxide, paracymene hydroperoxide, and tert-butyl isopropylbenzene hydroperoxide. oxide,
Examples include diisopropylbenzene hydroperoxide, paramenthane hydroperoxide, and decalin hydroperoxide.
Two or more of these can also be used as combined components. The amount of organic hydroperoxide used is usually 0.001 to 5% by weight based on the monomer. Examples of the sulfonate of the first component of the emulsifier in the present invention include sodium, potassium, and ammonium salts of alkyl or alkyl ether sulfonic acids such as alkylbenzene sulfonates, dialkyl sulfosuccinates, and alkyl diphenyl ether disulfonic acids. . In addition,
The alkyl group has 6 or more carbon atoms. Examples of the ether type sulfate ester salts include sodium, potassium, and ammonium salts of alkoxyalkyl sulfates such as polyoxyethylene alkyl sulfate and polyoxypropylene alkyl sulfate. The alkyl group has 8 or more carbon atoms. Further, higher fatty acid salts having 8 to 22 carbon atoms include octylic acid, lauric acid, myristic acid, palmitic acid, stearic acid, oleic acid, isostearic acid, behenic acid, etc.; Ammonium salts are preferred. It is also possible to use two or more types of the first component of these emulsifiers in combination. The amount used is usually in the range of 0.01 to 1.0% by weight based on the monomer. If it is less than 0.01% by weight, a large amount of lumps will occur, and if it exceeds 1.0% by weight, the water resistance of the polymer will decrease. The maleic acid copolymer salt (hereinafter sometimes referred to as the second component), which is the other component of the emulsifier in the present invention, includes maleic acid or maleic anhydride, styrene, ethylene, propylene,
Examples include mono- or diammonium, sodium, and potassium salts of copolymers such as vinyl acetate, methyl vinyl ether, and butadiene. The copolymerization ratio of maleic acid or maleic anhydride in the copolymer is preferably 10 to 90 mol%.
It is 30-60 mol%. The amount of maleic acid copolymer salt to be used is preferably 0.04 to 1.5% by weight based on the monomer from the viewpoint of stability of the polymerization reaction.
If it is less than 0.04% by weight, a large amount of lumps will be generated, and if it is more than 1.5% by weight, the polymerization reaction rate will be significantly delayed and the water resistance of the polymer will often decrease. Further, the total amount of the first component and the second component of the emulsifier is usually 0.05 to 2.0% by weight based on the monomer. If this proportion is less than 0.05% by weight, a large amount of lumps will be generated, and if it exceeds 2.0% by weight, the water resistance of the polymer will be poor. Further, the ratio of the first component and the second component of the emulsifier is preferably 1/30 or more, more preferably 1/5 to 5 by weight. If this ratio is less than 1/30, there are problems such as the generation of lumps, a decrease in the mechanical stability of the latex, or a decrease in the polymerization reaction rate. In addition, when a non-salt maleic acid copolymer is used as the second component of the emulsifier, a large amount of agglomerates are generated, or sometimes only agglomerates are obtained, and a latex may not be obtained. In the polymerization in the present invention, the pH of the aqueous medium is preferably 6 or higher during the polymerization period in order to suppress the generation of lumps. Preparation of PH is usually made with ammonia,
This can be done using sodium hydroxide, sodium hydrogen carbonate, ammonium carbonate, etc. In the production of the resin in the present invention, vinyl chloride or a mixture of vinyl chloride and a vinyl compound copolymerizable with vinyl chloride, an emulsifier, water, a polymerization catalyst, a PH regulator, and if necessary a chain transfer agent, seeds, etc. are reacted in advance in their entirety. It is carried out by emulsion polymerization method or seeded emulsion polymerization method in which the polymerization reaction is carried out under normal conditions by placing the polymer in a container or by adding it continuously. When the maleic acid copolymer salt is continuously added during the polymerization, the resulting vinyl chloride resin paste sol has a low viscosity and is suitable. In addition, the polymerization temperature is 35°C from the viewpoint of polymerization stability.
-55°C, preferably 40-50°C. Further, the weight ratio of monomer/water may be a normal ratio, and is 0.3 to 1.3, preferably 0.6 to 1.0. The organic liquid used to recover particulate vinyl chloride resin from the vinyl chloride resin emulsion thus prepared is one that is sparingly soluble in water and does not dissolve or swell the resin.
Generally, the organic liquid used has a melting point of 20° C. or lower and a boiling point at normal pressure higher than the temperature at which the resin is recovered in the present invention, preferably 200° C. or higher. If an organic liquid having a boiling point lower than the temperature at the time of resin recovery is used, it will volatilize and require additional equipment for recovery, which is not economical. Of course,
As a single product, even if it does not meet the above-mentioned conditions, it may be used as a mixture as long as it satisfies the above-mentioned requirements. There are two reasons why organic liquids are required to be poorly soluble in water. The first reason is to reduce the amount entrained in the aqueous phase to be separated after mixing with the emulsion, thereby preventing loss of organic liquid and reducing the effort of wastewater treatment. This is because, in order to aggregate resin particles dispersed in water via an organic liquid, it is necessary that the organic liquid exists as a liquid phase with an interface between the resin particles and water. Also. If the organic liquid dissolves or swells the resin, this is disadvantageous because the resin particles may be deformed or altered in quality. It should be noted that since most of the organic liquid used in the present invention remains in the product resin, it is necessary to avoid those that have an adverse effect on the processability and quality of the molded product. In view of the above points, it is most rational to use a liquid compounding agent used in ordinary paste processing as the organic liquid. Examples of the organic liquid in the present invention are as follows (1)
~ (9) can be mentioned. (1) Phthalic acid alkyl ester plasticizers such as dioctyl phthalate, dinonyl phthalate, butyl lauryl phthalate, and methyl oleyl phthalate (2) Aromatic carboxylic acid ester plasticizers such as trioctyl trimellitate and diethylene glycol dibenzoate (3) ) Aliphatic dibasic acid ester plasticizers such as dioctyl adipate, dibutyl sebacate, and dioctyl tetrahydrophthalate (4) Phosphate ester plasticizers such as trioctyl phosphate and trichloroethyl phosphate (5) Diethylene glycol dicapry rate, 1,
Fatty acid glycol ester plasticizers such as 4-butylene glycol di-2-ethylhexanoate (6) Polyester plasticizers (7) Butyl oleate, methyl acetyl ricinolate, 2,2,4-trimethyl-1, Fatty acid ester-based secondary plasticizers such as 3-pentanediol diisobutyrate, epoxidized soybean oil, epoxy-based secondary plasticizers such as epoxy octyl stearate, chlorinated fatty acid methyl, chlorinated paraffin-based plasticizers such as chlorinated paraffin, etc. Secondary plasticizers, aliphatic dibasic acid ester secondary plasticizers such as dioctyl succinate (8) Petroleum-based diluents such as mineral spirits and mineral turpentine, long-chain alkylbenzene diluents such as dodecylbenzene (9) High grade Liquid lubricant such as alcohol, liquid paraffin, higher fatty acid alkyl ester, etc. The amount of organic liquid used depends on the resin in the emulsion.
The amount is usually 0.5 to 30 parts by weight, preferably 1 to 15 parts by weight per 100 parts by weight. If the amount is less than 0.5 parts by weight, the resin will not be able to aggregate sufficiently through the organic liquid, and if it exceeds 30 parts by weight, sol-like aggregates will likely be formed, and even if granular aggregates are formed, the resin will not be able to aggregate sufficiently through the organic liquid. Since the content is large, it becomes difficult to remove residual liquid in the subsequent drying process, which may lead to a decrease in productivity. Note that the organic liquid may be added to the emulsion all at once, or may be added in portions or continuously. As a device for mixing the emulsion and the organic liquid, a batch type stirring tank type mixer, a container rotating type mixer, etc. are suitable. The organic liquid and the emulsion are mixed at a temperature of 70°C or lower and at a temperature at which the organic liquid used does not dissolve or swell the resin, but the higher the temperature, the faster the rate of swelling of the resin by the organic liquid increases, so it is preferably 50°C. Should be done below. Above 70°C, there is a risk that not only will the organic liquid be absorbed into the resin faster, but the resin will soften and coalesce, making the final product no longer suitable for processing. Next, when dehydrating the aggregated resin particles via the organic liquid, a known method is employed depending on the shape of the captured resin. However, the temperature must be below 70°C to prevent softening and coalescence of the resin. The resin particles separated in the dehydration process are then sent to a drying process to remove adhering moisture. Normal drying equipment can be used in this drying process, but
It is necessary to set conditions such that the strength of resin aggregation and coalescence does not impair dispersibility during processing. In other words, the temperature of the resin to be dried during the drying process is 70℃ or less,
Preferably, the temperature is 50°C or lower. Note that if the resin is recovered from the vinyl chloride resin emulsion obtained by the above polymerization method by a normal drying method such as spray drying, coagulation using a coagulant, dehydration drying, or direct over-dehydration drying, the polymerization In some cases, it is difficult to sufficiently remove the emulsifier used, and coagulants and the like are mixed in, making it impossible to obtain resin molded articles with excellent thermal stability, transparency, water resistance, etc. as in the present invention. (Effects of the Invention) According to the present invention, the polymerization reaction is stable and the recovery efficiency when recovering particulate resin is also extremely high.
Furthermore, since the obtained resin is granular, it has less powder scattering during paste sol production and has excellent fluidity. Furthermore, it has good dispersibility when made into a paste sol, improving the thermal stability, transparency, and
It also has excellent water resistance. (Example) The present invention will be described below with reference to Examples. Example 1 In a 13-capacity pressure-resistant reactor (hereinafter referred to as the reactor) equipped with a stainless steel stirrer and jacket, 44 grams of deionized water, a vinyl chloride resin with an average particle size of 0.50 microns, a minimum particle size of 0.35 microns, and a maximum particle size of 0.55 microns were added. 30
After charging 0.5 kg of emulsion containing % by weight, 1 g of sodium hydroxide, and 4 g of ammonium persulfate, deoxidizing by repeating nitrogen substitution and degassing under reduced pressure, 3 kg of vinyl chloride was charged, and the contents adjusted to pH 10 were stirred. The jacket was heated and the temperature was continuously adjusted to 50°C. On the other hand, a mixed aqueous solution of 15 g of sodium polyoxyethylene lauryl sulfate (-1), 15 g of diammonium salt (-1) of an equimolar copolymer of methyl vinyl ether and maleic anhydride, and 600 g of water was separately prepared. One hour after the start of the reaction, add 40% of the above emulsifier mixed aqueous solution.
With a plunger metering pump at a rate of cc/hour,
was introduced into the reaction system. The polymerization reaction was thus carried out for 16 hours, and after the polymerization conversion rate reached approximately 90%, unreacted monomers were removed. The vinyl chloride resin emulsion thus obtained was passed through a screen fitted with a wire mesh with openings of 74 microns, and water was added to the passed emulsion to adjust the solid content to 35% by weight. Next, 11,000 g of this emulsion was placed in a tank-type mixing device with a diameter of 20 cm and an internal volume of 12, and at the same time stirring was started at 1,100 rpm, di-2-ethylhexyl phthalate was injected from the bottom of the mixing device at a rate of 5 g per minute for 60 minutes. . After the injection was completed, the stirring operation was continued for another 60 minutes at 1100 rpm, and an aqueous dispersion of granular resin was obtained. When this dispersion was vacuum-filtered using a cloth with an aeration rate ^of 80 c.c./sec.cm2, the granular resin was separated.
5700 g of wet granules were obtained. When this was dried at 30℃ for 15 hours in a hot air circulation dryer,
4120 g of granular vinyl chloride resin (A) was obtained. Example 2 15 g of sodium dodecylbenzenesulfonate (-2) was used in place of the emulsifier sodium polyoxyethylene lauryl sulfate (-1) used in Example 1.
4125 g of granular vinyl chloride resin (B) was obtained in the same manner as in Example 1 except that . Example 3 4110 g of granular vinyl chloride resin was prepared in the same manner as in Example 1 except that 10 g of ammonium stearate (-3) was used instead of the emulsifier polyoxyethylene sodium lauryl sulfate (-1) used in Example 1. I got (C). Example 4 Instead of the emulsifier diammonium salt (-1) of methyl vinyl ether/maleic anhydride equimolar copolymer used in Example 1, a monopotassium salt (-1) of styrene/maleic anhydride equimolar copolymer was used.
2) Same as Example 1 except that 15g was used.
4120g of granular vinyl chloride resin (D) was obtained. Example 5 Water 4 used in Example 1 was changed to 3.6, and l-ascorbic acid was used instead of ammonium persulfate.
A separately prepared cumene hydroperoxide emulsion containing 900 mg and 30 mg of ferrous ion sodium ethylenediaminetetraacetic acid complex salt was introduced into the reactor at a rate of 25 c.c./hour through a plunger-type metering pump. The separately prepared cumene hydroperoxide emulsion consists of 400 mg of cumene hydroperoxide, 0.5 g of sodium polyoxyethylene lauryl sulfate (-1), and a diammonium salt of an equimolar copolymer of methyl vinyl ether and maleic anhydride. (-1) 0.5g and 400g of water were mixed using a high speed stirrer. Except for the above, 4115 g of granular vinyl chloride resin (E) was obtained in the same manner as in Example 1. Comparative Example 1 A vinyl chloride resin emulsion obtained by the same polymerization method as in Example 1 was dried with a spray dryer at an inlet temperature of 170°C and an outlet temperature of 50°C, and pulverized with a tabletop pulverizer to obtain a finely powdered vinyl chloride resin ( F) was obtained. Comparative Example 2 A vinyl chloride resin emulsion obtained by the same polymerization method as in Example 1 was used, except that only 15 g of sodium polyoxyethylene lauryl sulfate (-1) was used instead of the mixed emulsifier in Example 1. When the mixture was stirred and mixed with di-2-ethylhexyl phthalate under the same conditions as in Example 1, the entire contents became cream-like and no granular resin was obtained. Comparative Example 3 3790 g of granular vinyl chloride resin (G) was prepared in the same manner as in Example 1, except that 30 g of sodium polyoxyethylene lauryl sulfate (-1) was used in Comparative Example 2.
I got it. (Evaluation of vinyl chloride resin properties) Recovery efficiency, powder properties (angle of repose, bulk specific gravity) and sol (50 g of resin, di-2-ethylhexyl phthalate
(Prepared by mixing 30g of Ba/Zn stabilizer with 1g of Ba/Zn stabilizer) Characteristics (North Finesse,
Thermal stability, transparency, water resistance) were evaluated as follows. The results are shown in the table. Recovery efficiency = Weight of vinyl chloride resin sieved on cloth / Weight of vinyl chloride resin in charged vinyl chloride resin emulsion x 100 (%) Angle of repose A numerical value that indicates the ease of fluidity of powder. The smaller the value, the better the fluidity. Bulk specific gravity This is the apparent density of the powder, and the larger the value, the better the handling properties. North Fineness This indicates the particle size of the resin particles in the sol, and the larger the number, the finer it is (8 is the finest and 0 is the coarsest). Thermal stability The sol was poured into an aluminum mold and the 190
Changes in color tone after 30 minutes in a hot air atmosphere at ℃ are displayed in 5 levels from A (small change) to E (large change). Transparency A sheet of 0.5 mm thick sol was heated at 190°C for 10 minutes, and the light transmittance (%) was measured using an integrating sphere spectrophotometer. Water resistance Light transmittance (%) of the same sheet used for transparency measurement immersed in water at 23℃ for 24 hours
was measured.

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Claims (1)

[Claims] 1. Vinyl chloride or a mixture of vinyl chloride and a vinyl compound copolymerizable with vinyl chloride is mixed with a sulfonate or an ether as an emulsifier under a water-soluble polymerization catalyst or under a redox polymerization catalyst consisting of a water-soluble reducing agent and an organic hydroperoxide. Polymerize in an aqueous medium using a mixture of a maleic acid copolymer salt and at least one selected from sulfuric acid ester salts and higher fatty acid salts having 8 to 22 carbon atoms, and to the obtained vinyl chloride resin emulsion, An aggregate of vinyl chloride resin is prepared by adding and mixing an organic liquid that is sparingly soluble in water and does not dissolve or swell the vinyl chloride resin, and then dehydrating this aggregate,
A method for producing a granular vinyl chloride resin for paste, which comprises recovering granular vinyl chloride resin by drying.