JPH0469644B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a method for producing a chlorinated vinyl chloride resin. More specifically, in producing chlorinated vinyl chloride resin, the pre-process of producing vinyl chloride resin is carried out using a specific polymerization method, and then chlorinated according to a conventional method to produce chlorinated vinyl chloride resin. Relating to a method of manufacturing. [Problems to be solved by conventional technology/invention] Chlorinated vinyl chloride resin (hereinafter referred to as CPVC) has the property of improving the softening temperature of vinyl chloride resin (hereinafter referred to as PVC). ,
Manufactured by post-chlorinating PVC. PVC as a raw material resin for CPVC is usually mixed with suspension stabilizers such as partially saponified polyvinyl alcohol, methyl cellulose, hydroxypropyl methyl cellulose, and lauroyl peroxide, di-2-ethylhexyl peroxy neodecanoate, t-butyl peroxy neodecanoate, etc. decanoate,
Polymerization is generally carried out by suspension polymerization using an oil-soluble polymerization initiator such as α,α'-azobis-2,4-dimethylvaleronitrile. However, since PVC obtained by the suspension polymerization method usually has its particle surface covered with a dispersant film, it has poor gelling properties and plasticizer absorption properties compared to those obtained by the emulsion polymerization method.
It is known that it is inferior to PVC. Using PVC obtained by the above suspension polymerization method
When manufacturing CPVC, only CPVC with inferior gelling properties and initial coloring properties can be obtained. On the other hand, PVC obtained by emulsion polymerization has extremely small basic particles, has good gelling properties and plasticizer absorption, and is superior to PVC obtained by suspension polymerization in terms of processability. The polymer obtained by salting out is fine and has a low bulk density, contains a large amount of impurities, and has poor thermal stability. Using PVC obtained by the emulsion polymerization method described above,
When producing CPVC, problems such as poor thermal stability due to the contamination of PVC impurities and low bulk specific gravity persist with CPVC, and the cost increase due to the salting-out operation when obtaining PVC directly adds to the cost of CPVC. is also affected. Therefore, PVC has both the advantages of suspension polymerization and emulsion polymerization, that is, it has a low impurity content, and the basic particles form aggregates like those of emulsion polymers, and the particulate form that is produced by suspension polymerization is low. CPVC, which has the appearance of PVC as a raw material resin, has no dispersant film on the surface of the particles, and can be obtained without salting out operations, can be produced using suspension polymerization or emulsion polymerization. PVC was used as the raw material resin.
It is thought that it has excellent characteristics different from CPVC and can be manufactured at low cost. Japanese Patent Publication No. 54-30833 describes a method for polymerizing raw material resin for CPVC having such characteristics in the absence of an emulsifier in an aqueous medium in the presence of a polymerization initiator soluble in the medium. ) (hereinafter referred to as soap-free emulsion polymerization method) is disclosed. However, this method has drawbacks such as the aggregate system becomes unstable when basic particles aggregate to form spherical particles, it is difficult to preheat, and the amount of attached scale is extremely large. The present invention solves the above-mentioned problems of the soap-free emulsion polymerization method.
This was done to solve the problems of CPVC using PVC. [Means for Solving the Problems] The present inventors have conducted intensive research on the soap-free emulsion polymerization method using a pressure-resistant glass polymerization machine that allows the state inside the polymerization system to be seen through, and have found that the basic particles are agglomerated. discovered that by adding a poorly water-soluble inorganic phosphate before the polymerization system becomes unstable, it is possible to generate spherical particles while maintaining the fluidity of the polymerization system, and the amount of attached scale can be reduced. The present invention has been made based on the above-mentioned findings, and consists of using a vinyl chloride monomer or a mixture with other monomers copolymerizable with it in an aqueous medium, and using a water-soluble persulfate as a polymerization initiator. This invention relates to a method for producing a chlorinated vinyl chloride resin, which comprises starting polymerization in the absence of an emulsifier and adding a poorly water-soluble inorganic phosphate during polymerization to post-chlorinate the obtained vinyl chloride resin. [Example] Other monomers that can be copolymerized with the vinyl chloride monomer used in the present invention include, for example, olefins such as ethylene and propylene, vinyl esters such as vinyl acetate and vinyl stearate, and methyl acrylate. , acrylic esters such as methyl methacrylate, acid esters and anhydrides such as maleic acid or fumaric acid, nitrile compounds such as acrylonitrile, and vinylidene compounds such as vinylidene chloride. In the present invention, when vinyl chloride monomer or a mixture with other monomers copolymerizable with vinyl chloride monomer is polymerized in an aqueous medium, a water-soluble persulfate is used as a polymerization initiator in the absence of an emulsifier. is started. In the aqueous medium, a polymerization initiator such as a water-soluble persulfate such as potassium persulfate or ammonium persulfate is added to water, and if necessary, trichlorethylene, propionaldehyde, n
- An aqueous liquid containing a molecular weight regulator such as pentane or 2-mercaptoethanol, and a reducing agent such as sodium sulfite or sodium bisulfite. The water-soluble persulfate, molecular weight regulator, reducing agent, etc. used in the polymerization reaction may be added all at once to the water at the beginning, or may be added in portions during the polymerization reaction. The amount of water-soluble persulfate added to water is usually 0.01 to 1.0% (wt%) based on the monomer, considering the impact on productivity and quality. , hereinafter the same), preferably
0.05-0.2%, usually 0-0 in the case of molecular weight regulator
10%, preferably 0-5%, and in the case of reducing agents usually 0-0.5%, preferably 0.01-0.1%. The ratio of vinyl chloride monomer or other monomers that can be copolymerized with it to water in the mixture is determined by the final water/monomer ratio from the viewpoint of productivity, heat removal in the polymerization machine, etc.
The ratio is preferably 1/1 to 5/1, and more preferably 1/1 to 3/1. In addition, when using a mixture of vinyl chloride monomer and other monomers that can be copolymerized with vinyl chloride monomer, the composition must contain 70% or more of vinyl chloride monomer in the entire mixture for quality reasons. It is preferable from this point of view, and more preferably 85% or more. Various theories have been proposed regarding the mechanism by which polymerization proceeds in the absence of an emulsifier, but sulfate radicals (.
It is thought that the monomer (M) reacts with SO ₄ ^- ), and the oligomer (MM...MSO ₄ ^- ) having a sulfate group at its end functions as an emulsifier. Therefore, if the oligomer having a polymerization initiator decomposition product at its end does not function as an emulsifier, polymerization will not proceed at all or the polymerization rate will be very low. It is essential to use a water-soluble persulfate as the polymerization initiator. In the present invention, a poorly water-soluble inorganic phosphate is added during polymerization. Examples of the sparingly water-soluble inorganic phosphates include calcium salts, strontium salts, barium salts, magnesium salts, aluminum salts, and lead salts of phosphoric acid. Among these, calcium phosphate has poor polymerization stability, quality, cost, etc. It is preferable from the point of view. Although there is no particular limitation on the amount of the slightly water-soluble inorganic phosphate used, it is preferable to use 0.01 to 1 part per 100 parts (parts by weight, the same applies hereinafter) of vinyl chloride monomer or a mixture thereof to improve polymerization stability and quality. The amount is preferably 0.05 to 0.5 parts, and more preferably 0.05 to 0.5 parts. It is preferable to add the poorly water-soluble inorganic phosphate before the latex becomes unstable at the initial stage of polymerization, and although it varies depending on the polymerization conditions, the polymerization conversion rate is generally 5 to 50%, more preferably 10 to 30%. % range. The addition of the inorganic phosphate salt is not limited to one time, and may be added two or more times if necessary, but the first addition is preferably carried out within the above-mentioned polymerization conversion range. Even if the inorganic phosphate is added after the latex-like material agglomerates and becomes unstable in the early stage of polymerization, the effect of the present invention will be small; conversely, if the inorganic phosphate is added at the time of preparation, the basic particles will agglomerate. Intraparticle voids of spherical particles that affect the state
(porosity) tends to become smaller. A surfactant, a suspension stabilizer, a PH adjuster, etc. may be added simultaneously with or after the addition of the poorly water-soluble phosphate. The temperature range of the polymerization reaction in the present invention is usually 40~
The temperature is 75°C, but is not particularly limited. By the method used in the present invention as explained above,
When PVC is produced, there is no dispersant film on the particle surface, and spherical particles consisting of aggregates of basic particles can be polymerized with a small amount of scale attached in the polymerization vessel and with easy heat removal. Furthermore, unlike the emulsion polymerization method, there is no need for a salting-out operation, so the process is short, there is less contamination of impurities, and PVC with good thermal stability can be obtained. According to the method used in the present invention, the particle size is usually 1
Spherical particles of PVC with a diameter of about 8 mm are obtained, which are once separated from the aqueous medium and then subjected to a post-chlorination reaction to produce CPVC. It is not necessary to crush the spherical particles before the post-chlorination reaction, but it increases the uniformity of the chlorination reaction, increases the chlorination reaction rate, and improves the initial coloring property, thermal stability, and other qualities of CPVC. From the viewpoint of improving the quality of the material, pulverization is preferable. When pulverizing spherical particles, it may be pulverized by a method commonly used for pulverizing solids using a pulverizer such as a hammer mill, impeller breaker, ball mill, or tube mill. As the post-chlorination reaction, methods such as an aqueous suspension method, an organic solvent suspension method, a solution method, and a gas phase method are known, and any method can be adopted. Among these methods, the aqueous suspension method is used because the poorly water-soluble inorganic phosphate added during polymerization is eluted into the aqueous medium under strongly acidic conditions during the post-chlorination reaction, and hardly remains in the polymer. It is preferable in terms of quality (especially transparency). Next, the method of the present invention will be explained based on Examples and Comparative Examples, but the present invention is not limited thereto. In addition, the following physical property evaluation was performed according to the following method. (Particle size distribution) Based on the sieve shaking method. (Bulk specific gravity) According to JIS K 6721. (Porosity) Using a mercury intrusion porosimeter (model 5-7118) manufactured by AMINCO in the United States, the absolute pressure was 11 to 1011 psi.
The porosity was determined by measuring the volume of mercury injected per 100 g of resin between the diameter of 0.17 and 15.9 μm. (Geling time) 100 parts of CPVC, 7 parts of Kane Ace B-22 (manufactured by Kanebuchi Chemical Industry Co., Ltd.), tin-based stabilizer (manufactured by Nitto Kasei Co., Ltd.)
TVS-8831) 2 parts, stearic acid (NOF Corporation)
54g of the compound prepared by stirring (10,000rpm) 2 parts of the product in a homogenizer for 5 minutes (10,000rpm) was placed in a Brabender Plastograph tester under the conditions of a rotor rotation speed of 30rpm and a chamber temperature of 180℃. The time required to reach the maximum torque was measured. (Initial coloration) 100 parts of CPVC, 10 parts of Kane Ace B-22, 2 parts of tin-based stabilizer (TVS-8831 manufactured by Nitto Kasei Co., Ltd.),
After mixing 0.7 parts of lubricant VPH-4 (manufactured by Hoechst) and 1 part of stearic acid (manufactured by NOF Corporation), 185
A roll sheet with a thickness of 1 mm was prepared by kneading for 3 minutes at 190°C, and a press plate with a thickness of 5 mm (pressing conditions: 190°C for 10 minutes) was made from the roll sheet, and its initial colorability was evaluated. (Thermal stability) A roll sheet similar to that used for initial colorability evaluation was prepared, and the sheet was placed in a gear oven at 195°C, and the sheet was taken out every 15 minutes, and the time until blackening was measured. . Example 1 200 parts of water, 0.085 parts of potassium persulfate, and 0.034 parts of sodium sulfite were charged into a polymerization machine with an internal volume of 1.7 m ³ .
After the internal air was removed using a vacuum pump, 100 parts (440 kg) of vinyl chloride monomer was charged, and the temperature was raised to 64°C under predetermined stirring conditions to polymerize. Calcium phosphate 0.1 when polymerization conversion reaches 15%
When the internal pressure decreased to 2.5 kg/cm ² from the steady pressure, unreacted monomers were collected (polymerization time: 6 hours and 5 minutes). The polymerization conversion rate was 85%, the minimum temperature of the jacket during polymerization was 46°C, and the amount of scale adhering inside the can was as small as 0.1% (based on the amount of monomer charged) in the wet state. The obtained PVC has an average particle size of 5160 μm.
They are spherical particles with a very sharp particle size, and as a result of observation using a scanning electron microscope, the spherical particles are agglomerated pairs of elementary particles (particle diameter of about 0.1 to 2 μm), and PVC produced by the normal suspension polymerization method. No dispersant film was observed. These spherical particles are milled to reduce the average particle size.
It was ground into particles of 250 μm. Next, 900g of the PVC powder obtained by crushing and 5100g of water were mixed into an inner volume of 8
The mixture was charged into a reactor equipped with a stirrer and sufficiently stirred to form a suspension, and nitrogen gas was blown into the reactor to replace the air in the reactor with nitrogen. After that, chlorine gas was introduced into this suspension to saturate the reaction system with chlorine, and then the temperature of the reactor was raised to 50°C, and while supplying excess chlorine gas, PVC was heated under irradiation with a high-pressure mercury lamp. Chlorinated. After 3.6 hours, the chlorine content of the product reached 64%, at which time the high-pressure mercury lamp irradiation and the introduction of chlorine were stopped, and nitrogen gas was passed to replace the chlorine in the reactor with nitrogen, and the CPVC in the slurry was replaced with nitrogen. hydroxyalumine hydrochloride to 1.0
% was added and left to stand while stirring to completely remove chlorine. Next, filter it, wash the CPVC thoroughly with ion-exchanged water, neutralize it by adding an aqueous sodium hydroxide solution, wash it with water, filter it, and dry it.
I got CPVC. As shown in Table 1, the obtained CPVC had excellent gelling properties, initial coloring properties, and thermal stability. Example 2 The amount of calcium phosphate used in Example 1 was
Polymerization was carried out in the same manner as in Example 1 except that the amount was changed to 0.4 part.
A post-chlorination reaction was performed to obtain CPVC. As shown in Table 1, the obtained PVC was spherical particles with an average particle size of 3670 μm and a sharp particle size distribution, and the minimum temperature of the jacket during polymerization was as high as 45°C.
The amount of attached scale was also small. was born again
CPVC had good gelling properties, initial coloring properties, and thermal stability. Comparative Example 1 0.065 part of potassium persulfate used in Example 1,
Polymerization and post-chlorination reaction were carried out in the same manner as in Example 1 except that sodium sulfite was used at 0.026 parts and calcium phosphate was not added to obtain CPVC. As shown in Table 1, the resulting CPVC had excellent gelling properties, initial coloring properties, and thermal stability, but the minimum jacket temperature during PVC polymerization was as low as 23°C, and heat removal was difficult during scale-up. However, the amount of scale adhering inside the can was extremely high at 4.5% (based on the amount of monomer charged). Therefore, it can be seen that there is a problem in scale-up when producing CPVC from vinyl chloride monomer using this method. Comparative Example 2 (Suspension polymerization method) In a polymerization machine with an internal volume of 1.7 m ³ , 200 parts of water in which 0.06 part of hydroxypropyl methylcellulose was dissolved, 0.018 part of polymerization initiator (t-butylperoxyneodecanoate), 3.5 parts , 0.024 part of 5-trimethylhexanoyl peroxide was added, and after removing the air inside with a vacuum pump, vinyl chloride monomer was added.
Charge 100 parts (440Kg) and stir under specified stirring conditions.
Suspension polymerization was started by raising the temperature to .degree. C., and unreacted monomers were collected when the internal pressure decreased by 0.5 Kg/ ^cm.sup.2 from the steady pressure (polymerization time: 6 hours). Polymerization conversion rate is 75%,
The minimum temperature of the jacket during polymerization was 47°C, and the amount of scale adhering inside the can was 0.07% (based on the amount of monomer charged) in the wet state. The obtained PVC had an average particle size of 110 μm, and a unique dispersant film was observed on the particle surface. this
A post-chlorination reaction was carried out in the same manner as in Example 1 without pulverizing the PVC powder to obtain CPVC. As shown in Table 1, the obtained CPVC had poor gelling properties and initial coloring properties.

【table】

[Table] [Effects of the invention] When PVC is produced by the method used in the present invention,
PVC granules, which do not have a dispersant film on the particle surface and consist of aggregates of basic particles, can be obtained in a state where the amount of scale adhering to the inside of the polymerization vessel is small and heat can be easily removed. Since there is no need for salting out, PVC with low impurity content can be obtained. In the method of the present invention, such PVC is post-chlorinated to produce CPVC, so it has good gelling properties and
CPVC, which has excellent initial colorability and good thermal stability, can be manufactured on a large scale without salting out.
The industrial value is enormous.

Claims (1)

[Claims] 1. Polymerization of a vinyl chloride monomer or a mixture with other monomers copolymerizable with it in an aqueous medium in the absence of an emulsifier using a water-soluble persulfate as a polymerization initiator. 1. A method for producing a chlorinated vinyl chloride resin, which comprises starting the polymerization and adding a poorly water-soluble inorganic phosphate during polymerization to post-chlorinate the obtained vinyl chloride resin. 2. The manufacturing method according to claim 1, wherein the water-soluble persulfate is potassium persulfate or ammonium persulfate. 3. The manufacturing method according to claim 1, wherein the poorly water-soluble inorganic phosphate is a calcium salt, strontium salt, barium salt, magnesium salt, aluminum salt, lead salt or zinc salt of phosphoric acid. 4. The manufacturing method according to claim 1, wherein the slightly water-soluble inorganic phosphate is added at a time of 5 to 50% by weight in terms of polymerization conversion.