JPH05230115A - Suspension polymerization of vinyl chloride mononomer - Google Patents

Abstract

PURPOSE:To obtain a vinyl chloride polymer having high quality in short polymerization starting time and polymerization time while suppressing the deposition of scale on the inner surface of a polymerizer by using hot water and a specific suspending agent. CONSTITUTION:A vinyl chloride monomer is suspension-polymerized in an aqueous medium in the presence of an oil-soluble initiator to complete the suspension polymerization within 6hr. The above process is carried out by using hot water of >=40 deg.C and a suspending agent consisting of (a) a partially saponified polyvinyl acetate having a saponification degree of 75-85mol% and an average polymerization degree of 1,000-3,000, (b) a partially saponified polyvinyl acetate having a saponification degree of 65-75mol% and an average polymerization degree of 500-900 and (c) a partially saponified polyvinyl acetate having a saponification degree of 25-54mol% and an average polymerization degree of 200-900. The sum of (a) and (b) is 0.03-0.15 pts.wt. based on 100 pts.wt. of the monomer, the weight ratio of (a)/(b) is 1/3 to 3/1 and the amount of (c) is 0.01-0.1 pts.wt. based on 100 pts.wt. of the monomer.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improved suspension polymerization method for vinyl chloride monomers, and more particularly to a suspension polymerization method for producing a high quality vinyl chloride resin.

[0002]

2. Description of the Related Art Conventionally, when a vinyl chloride resin is produced, a partially saponified polyvinyl acetate having a specific saponification degree and polymerization degree (also called partially saponified polyvinyl alcohol).
Various suspension polymerization methods have been proposed. For example, in JP-B-63-39606, (a) a polyvinyl alcohol having a saponification degree of 60 to 90 mol% and a polymerization degree of 300 to 3000 ( b) A method of using polyvinyl alcohol having a degree of saponification of 20 to 55 mol% and a degree of polymerization of 100 to 1000 at a ratio of (a) / (b) of 1/9 to 8/2, and JP-A-62- No. 263206 shows (a) partially saponified polyvinyl acetate having a saponification degree of 85 to 90 mol% and a viscosity of 4% aqueous solution at 20 ° C. of 25 to 65 cps, and (b) a saponification degree of 65 to 75 mol%. And the viscosity is 5
6 cps of partially saponified polyvinyl acetate and (c) partially saponified polyvinyl acetate having a degree of saponification of 35 to 50 mol% and a degree of polymerization of 200 to 800 are (a) / (b) 9/1 to 1/1 ,
A method of using ((a) + (b)) / (c) in a weight ratio of 8/1 to 2/1 is disclosed. However, in any of these methods, if the so-called high-speed polymerization that completes the polymerization within 6 hours is carried out, the resulting vinyl chloride-based resin has the drawback of causing deterioration in quality such as fish eyes, plasticizer absorption, and particle size. there were.

In recent years, with the improvement of the jacket structure of the polymerization vessel and the progress of the operation technology of the reflux condenser, the ability of the polymerization vessel to remove the heat of the polymerization reaction has been greatly improved, so that it has been adopted on an industrial scale. Even in a large-scale polymerization vessel having an internal volume of 40 m ³ or more, high-speed polymerization capable of completing the polymerization within 6 hours became possible in terms of heat removal capacity. However, in the conventional technology, when such high-speed polymerization is carried out in a large-sized polymerization vessel, problems such as a sharp increase in fish eyes and difficulty in controlling particle size occur, and it is difficult to produce a high-quality resin. Was said.

In the case of batch-type suspension polymerization of vinyl chloride-based monomers, a polymerization vessel was charged with water at room temperature, a suspending agent, a polymerization initiator, monomers and other additives, and a jacket was heated with warm water. The contents are heated to a predetermined polymerization temperature by a means such as circulating the above to carry out the polymerization. But,
Especially in a large-sized polymerization vessel, the amount of charge is large and the heat transfer area of the jacket is relatively small compared to the capacity of the polymerization vessel, so it takes a long time to raise the temperature, which hinders the operating rate of the polymerization vessel. It was one of the factors to do.

A simple method for shortening the heating time is as follows:
In the above method, preheated water is used instead of room temperature water. However, this method has many problems in that scale is attached to the wall of the polymerization vessel, the produced polymer particles become coarse particles, and the number of fish eyes is extremely large. Various methods have been proposed to solve such problems when using pre-warmed water, but they are as follows: It is only a technique related to the mixing method and the charging procedure for the four kinds of monomers and initiators, and no method by suspension formulation has been found.

Japanese Patent Publication Nos. 62-39601 and 60-26
No. 488 shows a method in which a polymerization initiator is dissolved in a monomer in advance and the mixture is charged. However, this method requires facilities such as a tank and a mixer for preparing the mixture, not only complicates the operation for charging, but also lowers the temperature of the mixture in order to prevent the polymerization from starting during the preparation. However, there was a restriction that the polymerization initiator should be kept at 1, the ratio of the polymerization initiator charged to the monomer should be reduced, or only the polymerization initiator having a high decomposition temperature should be used.
Further, during the charging, it is considered that the mixture is rapidly suspended at the same time when the mixture comes into contact with warm water before being uniformly suspended and stabilized as an oil droplet in the aqueous medium in the polymerization vessel and becomes stable. Had a large amount of coarse particles and had the disadvantage of increasing fish eyes.

Japanese Unexamined Patent Publication (Kokai) No. 58-21408 describes a method in which a monomer and a polymerization initiator are charged into a polymerization vessel and uniformly mixed, and then heated water is charged. But this too
The monomer mixture comes into direct contact with the inner wall surface of the polymerization vessel during charging, and the polymerization is initiated there.Therefore, the scale is remarkably large, and particle size and fish eye are disadvantageous in that only low quality polymer can be obtained. there were.

On the other hand, Japanese Examined Patent Publication No. 60-26488 describes a method of heating water in which a suspending agent is dissolved (a suspension aqueous solution). In this method, probably because the surface activity of the suspending agent is lowered by heating, a large amount of scale adheres to the inner wall surface of the polymerization vessel to increase fish eyes, and the resulting polymer particles are coarse. There is a defect that the particles are granulated and, in a remarkable case, they are solidified in a lump form and it is difficult to discharge them from the polymerization vessel.

On the other hand, JP-B-58-50603 discloses a method of preventing the formation of coarse particles and the increase of fish eyes of polymer particles by adding a suspending agent and a part of water present in the polymerization system. A method has been proposed in which cold water is charged, then monomers are charged, and finally heated water is charged. However, according to this method, there is an effect that it is possible to prevent the generation of coarse particles and the increase of fish eyes,
Since the water and the monomer are sequentially charged, the charging time cannot be shortened, and cold water or hot water is also used as the charging water, which makes the charging operation complicated.

[0010]

Although any of these known methods has the advantage that the heating time can be shortened, scales adhere to the wall surface of the polymerization vessel, which is a drawback when using preheated water. However, the polymer particles obtained have a large amount of coarse particles and increase in fish eyes, which leads to a deterioration in quality.

The object of the present invention is to increase the temperature by shortening the temperature rising time and carrying out high-speed polymerization without causing the scale to adhere to the inner wall surface of the polymerization vessel, even if preheated water is used. It is an object of the present invention to provide a suspension polymerization method of a vinyl chloride-based monomer capable of producing a high-quality vinyl chloride-based resin with high productivity.

[0012]

According to the present invention, when a monomer mainly composed of vinyl chloride is suspension-polymerized in an aqueous medium using an oil-soluble initiator and polymerized within 6 hours, the temperature is set to 40 ° C. in advance. Using the water heated above, (a) a saponification degree of 75 to 85 mol% and an average degree of polymerization of 1000 as a suspending agent.
˜3000 partially saponified polyvinyl acetate, (b) saponification degree 65-75 mol%, average polymerization degree 500-900 partially saponified polyvinyl acetate, (c) saponification degree 20-54 mol%, average polymerization Three kinds of partially saponified polyvinyl acetate having a degree of 200 to 900 are (a) + per 100 parts by weight of the monomer.
The amount of (b) is 0.03 to 0.15 parts by weight, (a) /
Vinyl chloride characterized in that the weight ratio of (b) is 1/3 to 3/1 and the amount of (c) per 100 parts by weight of the monomer is 0.01 to 0.1 parts by weight. The present invention provides a suspension polymerization method for a system monomer.

The present invention will be described in detail below. Among the monomers mainly composed of vinyl chloride monomers used in the present invention, examples of the monomers other than vinyl chloride include, for example, alkyl vinyl esters represented by vinyl acetate and alkyl vinyl ethers represented by cetyl vinyl ether. Examples include α-monoolefins such as ethylene and propylene, (meth) acrylic acid alkyl esters such as methyl acrylate and methyl methacrylate, vinylidene chloride, styrene and the like, provided that they are copolymerizable. It is not limited to these.

The oil-soluble initiator used in the present invention is not particularly limited, but has a 10-hour half-life temperature of 30 to 60.
It is preferable to use one or two or more of those having a temperature of ° C. Although the charged amount of the initiator varies depending on the type of the initiator used and the polymerization conditions such as the polymerization temperature, it is usually
It is possible to polymerize within 6 hours by charging 0.01 to 2 parts by weight per 100 parts of polymerized monomers.

Examples of such an initiator include di-2-ethylhexyl peroxydicarbonate, di (2-ethoxyethyl) peroxydicarbonate, t-butyl peroxy neodecanoate, α-cumyl peroxy neodeca. Noate, t-butyl peroxypivalate, 2,
Examples include 4,4-trimethylpentyl-2-peroxy neodecanoate, (α, α-bis-neodecanoylperoxy) diisopropylbenzene, and the like.

As the suspending agent used in the present invention, the above-mentioned saponification degree and polymerization degree are different (a), (b) and (c).
3 partially saponified polyvinyl acetate are used in the above-specified amounts and ratios.

The suspending agents (a) and (b) are used to stably suspend monomer oil droplets and polymer particles during polymerization in an aqueous medium, and to control the particle size and bulk specific gravity to an appropriate degree and to obtain porosity. It is used for producing particles having a high quality internal structure, but the total amount of (a) and (b) charged per 100 parts by weight of the monomer is 0.03 to 0.15 parts by weight. It is preferably 0.04 to 0.1 part by weight, and the charging weight ratio (a) / (b) of (a) and (b) is 1/3 to 3/1.

The sum of the charged amounts of (a) and (b) is 0.
If the amount is less than 03 parts by weight, the suspension stability of the monomer oil droplets and the polymer particles during the polymerization will be impaired, the coarse particles will increase and the porosity will decrease, and if it exceeds 0.15 parts by weight. The grain size becomes finer and the bulk specific gravity decreases, which is a disadvantage.

Charged weight ratio of (a) and (b) (a) /
Similarly, if (b) is less than 1/3, the particle size becomes finer and the bulk specific gravity decreases, and if it exceeds 3/1, the porosity is impaired and the quality such as fish eye and plasticizer absorbability deteriorates. Therefore, the object of the present invention cannot be achieved.

When the degree of saponification and the average degree of polymerization of the suspending agents (a) and (b) are out of the above ranges, particularly when the degree of saponification of the suspending agent (a) exceeds 85 mol%, the fish. When the number of eyes increases sharply and the saponification degree of the suspending agent (b) is less than 65 mol%, suspension stability is impaired and coarse particles are produced. I can't.

The suspending agent (c) is porous and has less fish eyes by preventing the formation of a skin layer on the surface of the polymer particles and the agglomeration of basic particles of the order of 1 to several μ inside the particles. This is for obtaining a resin having good plasticizer absorbability. When the saponification degree and the average polymerization degree of the suspension agent (c) are out of the above-mentioned ranges, the monomer 100
If the charging amount of (c) per part by weight is less than 0.01 part by weight, these effects cannot be exhibited. Also,
If the charged amount exceeds 0.1 parts by weight, the particle size becomes finer and the bulk specific gravity decreases, which is a disadvantage.

The suspending agents (a), (b) and (c) are preferably used as a liquid prepared by adjusting and mixing them in a ratio and a charge amount specified in advance and dissolving or dispersing them in water.

In the present invention, the polymerization time means that the pressure in the polymerization vessel is the natural pressure at the polymerization temperature from when the internal temperature reaches a predetermined polymerization temperature by heating and raising the temperature after the charging of the monomers and the like. It is defined as the time after which the pressure starts to drop as the unreacted monomer decreases after a certain period of time and the width of the drop reaches 1.5 kg / cm ² . The polymerization time can be adjusted empirically by changing the type and amount of the above-mentioned polymerization initiator.

The method of terminating the polymerization in the present invention includes a method of adding a polymerization inhibitor when the pressure in the polymerization vessel drops to a predetermined pressure, and a method of recovering unreacted monomers from the polymerization vessel. Can be mentioned.

In carrying out high-speed polymerization within 6 hours in the present invention, the internal jacket type polymerization device described in Japanese Patent Publication No. 3-4249, that is, the passage of a cooling / heating medium on the inner surface of the main body of the polymerization device, is used to transfer the heat. It can be advantageously carried out by using a polymerization vessel having improved thermal performance. In particular, it is reasonable to equip a large-scale polymerization vessel with an internal volume of 40 m ³ or more with an internal jacket. Of course, it is also possible to adopt a method of attaching a reflux condenser to the polymerization vessel and removing the heat of polymerization reaction.

The stirring at the time of carrying out the polymerization is not special, and a known stirring device which has been generally adopted in the suspension polymerization method of vinyl chloride-based monomers can be used. Turbine blades, fan turbine blades, Fowler blades, blue margin blades, and the like, and examples of baffles include plate type, cylindrical type, D type, loop type, and finger type.

Water used to form the aqueous medium is preliminarily set to 40 ° C. or higher in order to shorten the temperature rising time up to the initiation of polymerization, and its upper limit is determined from the heat capacity of the entire polymerization reaction system. It suffices that the entire system has a polymerization initiation temperature.

The polymerization temperature is a well-known temperature depending on the kind of the oil-soluble polymerization initiator, and is usually about 30 to 80 ° C.

The monomer / water weight ratio is usually in the range of 0.5 to 1, but it is also possible to supplement the decrease in the liquid level due to volumetric shrinkage accompanying the polymerization by additionally injecting water during the polymerization. This is preferable because it can suppress the formation of fish eyes.

In the present invention, as a procedure for charging water, a vinyl chloride monomer, a suspending agent and an initiator, any method used in ordinary suspension polymerization of a vinyl chloride monomer can be adopted. While simultaneously charging 70% by weight or more of the total charged amount of each of the monomer and preheated water into the polymerization vessel, and at least the total charged amount of the suspending agent during charging of the monomer. 20% by weight was charged, and 100% from the time when the charged amount of the monomer reached 30% of the total charged amount.
A method in which the total amount of the polymerization initiator is charged until the weight ratio of the monomer in the polymerization vessel to water is 1.5 or less before reaching 100% is preferable for shortening the charging time.

If desired, chain transfer agents such as mercaptoalkanols and thioglycolic acid alkyl esters, nonionic surfactants such as glycerin esters and sorbitan esters of higher fatty acids, pH adjusting agents, antioxidants, etc. Additives may be used.

[0032]

As described above, according to the present invention, by using specific amounts of the above-mentioned three kinds of partially saponified polyvinyl acetate, regardless of the charging procedure, the charging water previously heated to 40 ° C. or higher is used. It is possible to shorten the temperature rise time by using, and obtain a high-quality vinyl chloride resin with excellent particle size characteristics and less fish eyes in a short time within 6 hours without attaching scale to the inner wall surface of the polymerization vessel. That is, it is possible to solve the problems that were difficult to achieve with the conventional technology,
Very useful from an industrial point of view.

[0033]

EXAMPLES The present invention will be described in more detail with reference to the following examples. In the examples and comparative examples,% is based on weight unless otherwise specified. The physical property values of the vinyl chloride-based polymers shown in each example were measured by the following methods.

(1) Average particle size It was shown as a 50% passage size by a sieve analysis using a JIS-standard wire mesh.

(2) Coarse Grain Content (1) was analyzed by a sieve, and the content of the coarse particle content was shown in the 42 mesh wire mesh.

(3) Porosity Mercury injection porosimeter (125
0-2 type) and the volume of mercury injected per 1 g of vinyl chloride polymer particles during the pressurization from atmospheric pressure to 120 kg / cm ² G.

(4) Fisheye To 50 g of vinyl chloride polymer, 25 g of polyester plasticizer (SP-105 manufactured by Sanken Kako Co., Ltd.), 1.5 g of calcium stearate, and 0.2 g of carbon black were added and mixed, The mixture was kneaded with an 8-inch roll at 150 ° C. for 7 minutes, drawn out into a sheet having a thickness of 0.2 mm, and the number of transparent particles observed in 100 cm ² of the surface of the sheet was shown.

(Example 1) Into a 100 L autoclave degassed to 30 mmHg, deionized water 45 k at 57 ° C.
g, 15 g of partially saponified polyvinyl acetate having a saponification degree of 80 mol% and an average degree of polymerization of 2500, 15 g of partially saponified polyvinyl acetate having a saponification degree of 73 mol% and an average degree of polymerization of 800, and an average degree of saponification degree of 33 mol% 9 g of partially saponified polyvinyl acetate having a degree of polymerization of 300 was charged, the jacket temperature was set to 51 ° C., and 30 kg of vinyl chloride monomer was charged under stirring conditions.
The internal temperature at the end of charging was 50 ° C.

Subsequently, 13 g of 2,4,4-trimethylpentyl-2-peroxyneodecanoate, (α-α
6 g of -bis-neodecanoylperoxy) diisopropylbenzene was charged and the polymerization was started at a polymerization temperature of 51 ° C. After 4.8 hours, the pressure inside the autoclave dropped by 1.5 kg / cm ² from the pressure at the start of polymerization.
Polymerization was stopped by adding 3 g of di-t-butyl-4-methylphenol, unreacted vinyl chloride monomer was purged, the contents were taken out, dehydrated and dried. Table 1 shows the scale adhesion state on the inner wall surface of the polymerization vessel and the physical property values of the obtained polymer particles.

(Examples 2 to 5 and Comparative Examples 1 to 3) Under the same conditions as in Example 1 except that the kind, combination and amount of partially saponified polyvinyl acetate were changed as shown in Table 1. Polymerization was performed to obtain polymer particles. Table 1 shows the polymerization time, the scale adhesion state on the inner wall surface of the polymerization vessel, and the physical property values of the obtained polymer particles.

Comparative Example 4 Polymerization was carried out under the same conditions as in Comparative Example 1 except that 9 g of dioctyl peroxydicarbonate was used as the initiator. The polymerization time was 8.2 hours. Table 1 shows the scale adhesion state on the inner wall surface of the polymerization vessel and the physical property values of the obtained polymer particles.

(Comparative Examples 5 and 6) Comparative Examples 2 and 6 except that deionized water at 20 ° C was used instead of deionized water at 57 ° C.
Preparation was carried out under the same conditions as in No. 3. 70 ℃ on the jacket
It took 35 to 37 minutes to circulate the warm water in Example 2 and raise the internal temperature in the polymerization vessel to 51 ° C. Table 1 shows the polymerization time, the scale adhesion state on the inner wall surface of the polymerization vessel, and the physical property values of the obtained polymer particles.

[0043]

[Table 1]

(Example 6) After degassing an inner jacket type stainless steel polymerization vessel having an internal volume of 45 m ³ , 21.5 tons of preheated water at 65 ° C was stirred at a rate of 1.1 tons / minute. At the same time as continuously charging below, 100 parts (16.5 t) of vinyl chloride monomer, partially saponified polyvinyl acetate having an average degree of polymerization of 2500 with a saponification degree of 80 mol%, and an average of a saponification degree of 73 mol%. A 1% aqueous dispersion of a mixture of partially saponified polyvinyl acetate having a degree of polymerization of 800 and partially saponified polyvinyl acetate having a degree of saponification of 33 mol% and an average degree of polymerization of 300 (4/3/3) (total 0). 1 part) was continuously charged over the above time. Further, when 80 parts of the monomer was charged, 0.05 part of 2,4,4-trimethylpentyl-2-peroxyneodecanoate was collectively charged in 2 minutes. The internal temperature at the end of charging all the components was 56 ° C. The polymerization reaction was carried out while maintaining the internal temperature of the polymerization vessel at 57 ° C.

4.2 hours after the initiation of polymerization, the pressure in the polymerization vessel
Is 8.6 kg / cm²7.1 kg / cm from G ²I fell to G
The reaction is stopped, unreacted monomers are recovered, and the contents are dehydrated.
Dried. Physical property values of the polymer particles thus obtained
Has an average particle size of 133 μm, a coarse particle content of 0, and a porosity of 0.2.
7 ml / g, the bulk specific gravity measured according to JIS K-6721 is 0.5
3 and 5 fish eyes. On the inner wall of the polymerizer
Almost no adhesion of scale was observed.

Comparative Example 7 Preparation was carried out under the same conditions as in Example 6, except that water at 25 ° C. was used instead of the heated water at 65 ° C. At the end of preparation of all ingredients, 2
It was 3 ° C. Circulate warm water of 65 ℃ in the jacket,
It took 60 minutes to raise the inner temperature of the polymerization vessel to 57 ° C. The polymerization time was 4.3 hours. Almost no adhesion of scale was found on the inner wall surface of the polymerization vessel. The physical properties of the obtained polymer particles are as follows: average particle diameter 138 μm, coarse particle content 0, bulk specific gravity 0.52, porosity 0.26 ml / g,
The number of fish eyes was 8.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Masahisa Okawa 5-1 Sokai-cho, Niihama-shi, Ehime Sumitomo Chemical Co., Ltd. (72) Isao Ouchi 16 Ochiai, Nishiki-machi, Iwaki-shi, Fukushima (72) Inventor Hideki Wakamori 16 Ochiai Nishiki-cho, Iwaki City, Fukushima Prefecture Kureha Chemical Industry Co., Ltd. (72) In fact, Mitsuo Yamato 1-2 Harumi-cho, Tokuyama City, Yamaguchi Prefecture Sun Arrow Chemical Co. ) Inventor Yasumichi Ishii One day, 2767, Niihama, Shiojima, Kojima, Kurashiki, Okayama

Claims (2)

[Claims] 1. A method of suspension-polymerizing a vinyl chloride-based monomer using an oil-soluble initiator in an aqueous medium for polymerization within 6 hours is carried out by heating water previously heated to 40 ° C. or higher. Used as a suspending agent (a) saponification degree 75 to 85 mol%, average degree of polymerization 1000
To 3000, partially saponified polyvinyl acetate, (b) Saponification degree 65 to 75 mol%, average degree of polymerization 500 to
900, partially saponified polyvinyl acetate, (c) Saponification degree 20-54 mol%, average degree of polymerization 200-
900 kinds of partially saponified polyvinyl acetate, (a) + (b) per 100 parts by weight of the monomer.
Is 0.03 to 0.15 parts by weight, the weight ratio of (a) / (b) is 1/3 to 3/1, and the amount of (c) per 100 parts by weight of the monomer is 0.01 to A suspension polymerization method of a vinyl chloride-based monomer, which is used in an amount of 0.1 part by weight. 2. A vinyl chloride-based single polymerizer according to claim 1, wherein a large-capacity inner jacket type polymerization reactor having an internal volume of 40 m ³ or more equipped with a stirrer and provided with a passage for a cooling / heating medium on the inner surface of the polymerization reactor main body is used. Suspension polymerization of monomers.