JPH04323208A - Production of vinyl chloride polymer - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention relates to a method for producing a vinyl chloride polymer, and in particular, a suspension polymerization method for obtaining a high quality vinyl chloride polymer with high productivity and under stable operation. The present invention relates to a method for producing a vinyl chloride polymer.

0002

[Prior Art] Suspension polymerization of vinyl chloride is usually carried out in a batch process, in which an aqueous medium, a suspending agent, and a polymerization initiator are placed in a polymerization vessel equipped with a stirrer, a jacket for heating and cooling, and a reflux condenser. After charging the agent, the gas phase inside the polymerization vessel is degassed using a vacuum pump. After degassing, vinyl chloride monomer is charged, temperature is started to increase, and when a predetermined polymerization temperature is reached, polymerization is started. During this temperature rise, bubbles are generated from the charge mixture for suspension polymerization and float to cover the surface of the liquid layer of the charge mixture. Since these bubbles do not disappear easily even with stirring, they are subjected to polymerization in their foam form. For this reason, a) scale adheres to the interface between the gas phase and the liquid phase, where bubbles adhere, resulting in a decrease in productivity; and b) foam-like polymer is generated, resulting in a decrease in yield. c) Fish eyes are generated, leading to a deterioration in product quality, and this problem tends to increase as the size of the reflux condenser increases. To solve this problem, a method has been proposed in which the reflux condenser is heated at the beginning of polymerization to suppress the generation of bubbles due to the gas lift of vinyl chloride during temperature rise, but the operation is complicated and the bubble suppression effect is not sufficient. It wasn't perfect. It has also been considered to suppress foaming by increasing the proportion of dispersants with low viscosity in the polymerization formulation, but this has the paradox that although foaming can be suppressed, the bulk specific gravity of the product polymer cannot be increased. was there.

0003

SUMMARY OF THE INVENTION Therefore, it is an object of the present invention to significantly suppress scale build-up on the nozzle leading to the gas phase of a polymerization vessel, inside the reflux condenser, and on the surface of the upper mirror of the polymerization vessel body, and to prevent bubbles from forming. A method for producing high-quality vinyl chloride-based polymers with minimal fish eyes and high bulk specific gravity with high productivity without the need for equipment changes or complicated operations. is to provide.

0004

[Means for Solving the Problems] The present invention has been achieved as a result of intensive research by the present inventors in order to achieve the above-mentioned problems. Used as a dispersion stabilizer during suspension polymerization of vinyl chloride monomer or a mixture of vinyl monomers mainly composed of vinyl chloride in an aqueous medium in a polymerization vessel equipped with a cooling jacket and a reflux condenser. (A) The degree of saponification is 65 to 75 mol%, and the average degree of polymerization is
Partially saponified polyvinyl alcohol having a viscosity of 750 to 850 and a 4% by weight aqueous solution at 20°C of 5 to 10 cps, and (B) a degree of methoxy substitution of 26 to 30% by weight and a degree of hydroxypropoxy substitution of 4 to 15% by weight. , and the viscosity of its 2% aqueous solution at 20°C is 5 to 100c
hydroxypropyl methylcellulose which is ps,
(C) has an average degree of polymerization of 1,500 to 2,700 and is saponified. It is characterized by adding partially saponified polyvinyl alcohol having a content of 75 to 85 mol%.

[0005] The present invention will be explained in more detail below. In the method of the present invention, the partially saponified polyvinyl alcohol as component A, which is a dispersion stabilizer used before the start of polymerization, has a degree of saponification of 65 to 75 mol% and an average degree of polymerization of 750 to 850, 4% by weight. % aqueous solution has a viscosity of 5 to 10 cps at 20°C. This means that if the degree of saponification is less than 65 mol% or the average degree of polymerization is less than 750,
The suspension system becomes unstable, producing coarse particles and blocks. In addition, the degree of saponification is 75 mol%, the average degree of polymerization is 850, and the viscosity is
If any one of 10 cps is exceeded, bubbles will be generated more frequently during polymerization temperature rise, scale will grow in the gas phase,
Inconveniences such as foamy polymer being mixed into the slurry occur.

Hydroxypropyl methylcellulose as component B, which is a similar dispersion stabilizer, has a degree of methoxy substitution of 26 to 30% by weight and a degree of hydroxypropoxy substitution of 4.
~15% by weight, and a 2% by weight aqueous solution thereof has a viscosity of 5 to 100 cps at 20°C. If the degree of methoxy substitution and the degree of hydroxypropoxy substitution are out of the above range, the suspension system will become unstable, the particle size distribution will widen, blocks will occur, and the viscosity will decrease to 100c.
If it exceeds ps, it is not preferable because the generation of bubbles cannot be suppressed. The ratio of both components A and B used is 25:1 to 8 by weight.
:3 is preferable. The total amount of both components used is usually 0.04 to 0.2% by weight based on the monomers charged.

Addition of these dispersion stabilizers to the polymerization system is as follows:
This is done directly during the preparation of water or as an aqueous solution. Alternatively, it may be pressurized into the reactor during or after charging the vinyl chloride monomer. Note that the water charging temperature is preferably within the range of 20 to 50°C. If it is less than 20°C, it will take too long to raise the temperature, which is not suitable from a productivity standpoint, and if it exceeds 50°C, it will be difficult to maintain a uniform reaction at the beginning of polymerization, which will cause fish eyes to form. .

The partially saponified polyvinyl alcohol as component C which is added later has an average degree of polymerization of 1,500 to 1,500.
2,700 and a degree of saponification of 75 to 85 mol%, but if either the average degree of polymerization or the degree of saponification is outside this range, the bulk specific gravity of the resulting polymer will not be high. It is important to add this after the start of polymerization until the polymerization conversion rate reaches 5% to 60%. If it is added when the polymerization conversion rate is less than 5% or exceeds 60%, the particle size will become finer. The bulk specific gravity does not increase. The addition may be carried out continuously or intermittently, in small portions, or all at once. The amount added is preferably 0.02 to 0.52% by weight of the monomer weight.

The vinyl chloride monomer to be polymerized in the method of the present invention includes not only vinyl chloride alone, but also a mixture of vinyl monomers mainly consisting of vinyl chloride and copolymerizable with it (
Usually vinyl chloride is 50% by weight or more). Comonomers copolymerized with vinyl chloride include ethylene, propylene, 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene, 1-nonene, 1-
α-olefins such as decene, 1-undecene, 1-dodecene, 1-tridecene, and 1-tetradecene; acrylic acid or its esters such as acrylic acid, methyl acrylate, and ethyl acrylate; methacrylic acids such as methacrylic acid and methyl methacrylate Acids or esters thereof; maleic acid or esters thereof; vinyl esters such as vinyl acetate and vinyl propionate; lauryl vinyl ether,
Examples include vinyl ethers such as isobutyl vinyl ether; maleic anhydride; acrylonitrile; styrene; vinylidene chloride; and other monomers copolymerizable with vinyl chloride, and these may be used alone or in combination of two or more.

The polymerization initiator may be one conventionally used in vinyl chloride polymerization, such as diisopropyl peroxydicarbonate, di-2-ethylhexyl peroxydicarbonate, diethoxyethyl peroxydicarbonate, etc. Percarbonate compounds such as;
-butylperoxyneodecanate, t-butylperoxypivalate, t-hexylperoxypivalate,
α-cumyl peroxyneodecanate, 2, 4, 4
- Perester compounds such as trimethylpentyl-2-peroxy-2-neodecanate; acetylcyclohexylsulfonyl peroxide, 2, 4, 4-trimethylpentyl-2-peroxyphenoxy acetate,
Peroxides such as 3, 5, 5-trimethylhexanoyl peroxide and lauroyl peroxide; azobis-
Azo compounds such as 2,4-dimethylvaleronitrile and azobis(4-methoxy-2,4-dimethylvaleronitrile) can be used alone or in combination of two or more. In addition, water-soluble catalysts such as potassium persulfate, ammonium persulfate, hydrogen peroxide, and cumene hydroperoxide may be used alone or in combination with these oil-soluble catalysts.
It is also possible to use a combination of more than one species. The amount of these polymerization initiators added is the total amount of vinyl chloride monomer or a mixture of vinyl monomers mainly composed of vinyl chloride.
The amount is 0.01 to 0.3 parts by weight relative to 0 parts by weight. This addition method may be a commonly practiced method, and is not particularly limited, such as directly charging it as it is into the polymerization vessel, or adding it in the form of an emulsion using a dispersant.

[0011] Other conditions for this polymerization, the method of charging the aqueous medium to the polymerization vessel, the vinyl chloride monomer, other comonomers in some cases, dispersion aids, polymerization initiators, etc., and the charging ratios are the same as before. You can go to Furthermore, this polymerization system may contain polymerization modifiers, chain transfer agents, pH adjusters, gelling improvers, antistatic agents, crosslinking agents, stabilizers, and fillers that are appropriately used in vinyl chloride polymerization. It is also optional to add agents, antioxidants, buffers, scale inhibitors, and the like.

0012

[Examples] Specific embodiments of the present invention will be explained below with reference to Examples and Comparative Examples, but the present invention is not limited thereto. Example 1 A stirrer, a jacket for heating and cooling, and a heat transfer area of 4
．． Capacity 2,000 with 5m2 reflux condenser
980 kg of deionized water at 35°C was placed in a L stainless steel polymerization vessel, the degree of saponification was 72.9 mol%, the average degree of polymerization was 780, and the viscosity of a 4% by weight aqueous solution at 20°C was 7.3 cps. 630g of partially saponified polyvinyl alcohol as component A, methoxy substitution degree is 29
．． 2% by weight, the degree of hydroxypropoxy substitution is 8.9% by weight, and the viscosity of a 2% by weight aqueous solution at 20°C is 4%.
70 g of hydroxypropyl methyl cellulose as component B, having a concentration of 9.5 cps, was charged. 50mm inside the vessel
After degassing to Hg, vinyl chloride monomer 700kg
While stirring, 280 g of di-2-ethylhexyl peroxycarbonate was further pressurized using a high-pressure pump, and at the same time, the temperature was raised to initiate polymerization. The polymerization reaction was continued under stirring while maintaining the polymerization temperature at 58°C, and when the polymerization conversion rate reached 30%, the partially saponified polyvinyl alcohol as the C component with an average degree of polymerization of 2250 and a saponification degree of 80 mol%. 700g was prepared. At this time, the reflux condenser is cooled by keeping the cooling water in the jacket at 30°C from before the start of polymerization until the polymerization rate reaches 10%.
However, when the polymerization rate was 10%, the cooling water rose to 40° C. due to reflux of the monomer due to the temperature increase in the polymerization vessel. ) Thereafter, the cooling water in the jacket was circulated until the polymerization was completed, and the temperature at the entrance to the jacket was maintained constant at 52°C. When the internal pressure of the polymerization vessel decreased to 6.0 kg/cm2G, polymerization was stopped, unreacted monomers were collected, and the resulting polymer slurry was extracted from the polymerization vessel, and after washing with water, scale adhesion inside the vessel was removed. I observed the situation. The polymer slurry is also dehydrated and dried.
the amount of foamy polymer for the vinyl chloride polymer obtained;
Bulk specific gravity, particle size distribution, and number of fish eyes were measured by the following methods.

(Measurement of foamy polymer) JIS Z-880
Using a 48-mesh sieve according to 1., the amount remaining on the sieve was measured and taken as the amount of foamy polymer. (Fish eye measurement) Vinyl chloride polymer 10
0 parts by weight dioctyl phthalate
50 Tribasic lead sulfate
0.5 Lead stearate
1.5 Titanium oxide
0.1 Carbon black 0.0
5. Knead 25 g of the mixture prepared from the above recipe at 140°C for 5 minutes using a 6-inch kneading roll, and
A sheet with a thickness of 0 mm and a thickness of 0.2 mm was prepared. The number of transparent particles per 100 cm 2 of the obtained sheet was counted, and this was taken as the number of fish eyes.

Example 2 and Comparative Example 1 Polymerization and measurements were carried out in the same manner as in Example 1, except that the amount and proportion of the dispersant used were changed as shown in Table 1.

Comparative Example 2 In Example 1, the amount of component A added was 0, the amount of component B added was 45.5 g, and the amount of component C added was 409.5 g, and components B and C were charged before the start of polymerization. Other than that, polymerization was carried out and measurements were made in the same manner. The results of each of the above examples are shown in Table 1.

[0016]

[Table 1]

Comparative Example 3 In place of the partially saponified polyvinyl alcohol as component A in Example 1, the saponification degree was 75 mol%, the average degree of polymerization was 2000, and the viscosity at 20°C of a 4% aqueous solution was 2.
Polymerization and measurements were carried out in the same manner except that 7 cps of partially saponified polyvinyl alcohol was used.

Comparative Example 4 In place of hydroxypropylmethylcellulose as component B in Example 1, the degree of methoxy substitution was 20% by weight,
Hydroxypropoxy substitution degree is 8% by weight, 2% by weight
Polymerization and measurements were carried out in the same manner, except that hydroxypropyl methyl cellulose whose aqueous solution had a viscosity of 400 cps at 20° C. was used.

Comparative Example 5 In place of partially saponified polyvinyl alcohol as component A in Example 1, the degree of saponification was 80 mol%, the average degree of polymerization was 600, and the viscosity at 20°C of a 4% by weight aqueous solution was 5.
Polymerization and measurements were carried out in the same manner except that CPS partially saponified polyvinyl alcohol was used. The results of each of the above examples are shown in Table 2.

[0020]

[Table 2]

[0021]

Effects of the Invention According to the present invention, scale adhesion on the nozzle leading to the gas phase of the polymerization vessel, inside the reflux condenser, and on the surface of the upper mirror of the polymerization vessel body can be significantly suppressed, and foam-like polymer can be reduced. It is possible to suppress generation as much as possible and to produce a high quality vinyl chloride polymer with few fish eyes with high productivity, so the industrial effect is extremely large.

Claims (1)

[Claims] Claim 1: Suspending vinyl chloride monomer or a mixture of vinyl monomers mainly consisting of vinyl chloride in an aqueous medium in a polymerization vessel equipped with a stirrer, a jacket for heating and cooling, and a reflux condenser. During turbidity polymerization, as a dispersion stabilizer (
A) The degree of saponification is 65 to 75 mol%, and the average degree of polymerization is 7.
Partially saponified polyvinyl alcohol having a viscosity of 50 to 850 and a 4% by weight aqueous solution at 20°C of 5 to 10 cps, and (B) a degree of methoxy substitution of 26 to 30% by weight and a degree of hydroxypropoxy substitution of 4 to 15% by weight. , and the viscosity of its 2% aqueous solution at 20°C is 5 to 100 cp
s, hydroxypropyl methyl cellulose is used before the start of polymerization, and after the start of polymerization until the polymerization conversion rate reaches 5% to 60%, (C) an average degree of polymerization of 1, 500 to 2,700 and a saponification degree of 75 to 85 mol%.