JP2648246B2 - Suspension polymerization of vinyl chloride monomer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a suspension polymerization method for vinyl chloride monomers. More specifically, the present invention relates to a suspension polymerization method for producing a high-quality vinyl chloride resin with high productivity by using a large-sized polymerization reactor equipped with a reflux condenser and using a specific suspension agent formulation.

[0002]

2. Description of the Related Art Vinyl chloride resin is industrially used in a polymerization vessel equipped with a jacket and a stirrer for heating and cooling.
Produced by batch suspension polymerization. In order to improve the productivity of the resin in such batch polymerization, the heat removal capacity of the polymerization vessel is increased, the polymerization rate is increased to the limit of the heat removal capacity, and the polymerization is completed in a short time. It is important to increase the production volume per batch by increasing the size.

In order to shorten the polymerization time, a highly active initiator is selected according to the polymerization temperature (JP-A-53-73280).
), And by increasing the amount of addition, and by making the polymerization rate uniform by combining initiators having different activities (Japanese Patent Application Laid-Open No. 56-149407), the polymerization rate reaches the limit of the heat removal capability of the polymerization vessel. Can be increased.

[0004] Increasing the size of the polymerization vessel reduces the jacket area per internal volume and reduces the heat removal capability. For this reason, the material of the polymerization vessel should be a material having good thermal conductivity (Japanese Patent Publication No. 58-58).
No. 8405), increasing the speed of the water flow in the jacket, or improving the flow path by passing water through the baffle and improving the flow path (Japanese Utility Model Application Laid-Open No. 58-160241). .

Further, in order to perform high-speed polymerization for 5 hours or less using a large-sized polymerization vessel having an internal volume of 40 m ³ or more, it has been proposed to increase a cooling load by adding a reflux condenser (Japanese Patent Publication No. Hei. -18082). However, when a reflux condenser is used, as described in JP-A-61-207410, fish eye (particularly a polyester plastic or the like having a relatively small plasticizing ability and a high viscosity plasticizer-based plasticizer) is used. ), And a remarkable foaming phenomenon occurs after the middle stage of polymerization.

In order to solve these operational and quality problems, various physical and chemical means have been proposed, including those relating to suspending agents, those relating to raw material preparation procedures, and those relating to mechanical foaming. , And those related to heat removal timing restrictions in the condenser.

Among the suspending agents, Japanese Patent Application Laid-Open No. 54-148092 discloses that the surface tension of water during polymerization is always 70 dyne / cm (25 ° C.) by adding a dispersant having a protective colloid property. A method for keeping below is disclosed. JP-A-60-158206 discloses that a suspension stabilizer is used in combination with polyvinyl alcohol having a low degree of saponification and an oil-soluble surfactant or an oil-soluble cellulose ether,
Further, a method using a reflux condenser having a structure in which a portion in contact with vinyl chloride can be entirely cooled by a jacket is disclosed.

Japanese Patent Application Laid-Open No. 61-115908 discloses a method using a partially saponified polyvinyl alcohol having an average degree of saponification of 85 mol% or more as a suspension stabilizer. Japanese Patent Application Laid-Open No. 61-207410 discloses that the HLB value is 6 to
14 nonionic surfactants were converted to vinyl chloride monomer 10
A method of adding 0.001 to 0.1 part by weight to 0 part by weight is disclosed. Further, JP-A-1-256504
And JP-A-1-268702 discloses a method using a combined system of partially saponified polyvinyl alcohol having a degree of saponification of 70 to 76 mol% and polyethylene oxide or polyvinylpyrrolidone having a molecular weight of 100,000 or more as a dispersant. Have been.

[0009]

By the way, in recent years, with the improvement of the jacket structure of the polymerization reactor and the advancement of the technology for using the reflux condenser, the ability of the polymerization reactor to remove the heat of polymerization reaction has been greatly improved. Large-scale polymerization reactors with an internal volume of 40 m ³ or more that are used on
So-called high-speed polymerization, which completes the polymerization within an hour, has become possible.

However, when such a high-speed polymerization is carried out,
Problems such as frequent occurrence of fish eyes and coarsening of the produced polymer occur, and it has been more difficult to produce a high quality resin. Especially when using a reflux condenser,
There are many operational and quality problems such as adhesion of polymer to the reflux condenser due to foaming during polymerization, blockage of the condenser, destabilization of the water dispersion system, increase in fisheye products, and decrease in bulk specific gravity. That has already been mentioned. In addition, in the case of high-speed polymerization in which the polymerization time is within 6 hours, it is necessary to increase the amount of gasification and reflux of the monomer, so that the polymerization suspension tends to foam and the dispersion system tends to be unstable. In addition, the quality problem becomes even greater.

[0011] However, none of the methods of the prior art is sufficient to solve the above-mentioned problems, and the foaming of the polymerization suspension is completely suppressed, and the particle size characteristics, and the quality requirements such as specific gravity and fish eye are completely satisfied. The suspension polymerization method for producing a satisfactory vinyl chloride resin with high productivity has not been established technically. That is, the above-mentioned JP-A-60-15820
In the method of No. 6, the prevention of foaming in a large-sized polymerization vessel is insufficient, and in the production method of JP-A-61-115908, fish eyes when using a polyester plasticizer are extremely large. Also, JP-A-1-256504, 1-268702
The combined use of the two specific suspending agents indicated in the above item is not sufficient to solve operational and quality problems.

Under such circumstances, the present invention relates to a reflux condenser which is used to complete suspension polymerization in a short time, such as within 6 hours, using a large-sized polymerization vessel having an internal volume of 40 m ³ or more. To provide an improved method for producing a vinyl chloride-based polymer which does not cause quality problems in operation such as adhesion of the polymer to the surface, blockage, increase in product fish eyes, and decrease in bulk specific gravity. The purpose was.

[0013]

According to the present invention, an oil-soluble polymerization initiator is prepared by using a monomer mainly composed of vinyl chloride by using a polymerization vessel having a stirrer, a jacket and a reflux condenser having an internal volume of 40 m ³ or more. The suspension polymerization is carried out in an aqueous medium using the following method. When the polymerization is completed within 6 hours, (A) a saponification degree of 75 to 81 mol% and an average polymerization degree of 1000
(B) a degree of saponification of 65 to 75 mol% and an average degree of polymerization of 500 to 4,000.
900 partially saponified polyvinyl acetate; (C) a degree of saponification of 15 to 54 mol%, an average degree of polymerization of 100 to
1200 partially saponified polyvinyl acetates, and the total amount of (A) and (B) per 100 parts by weight of monomer is 0.03-0.15 parts by weight and the amount of (C) Wherein the weight ratio (A) / (B) of (A) / (B) is from 0.01 to 0.1 parts by weight, and the suspension weight of the vinyl chloride-based monomer is from 1 to 4. Offer legality.

Hereinafter, the present invention will be described in detail. In the present invention, a polymerization vessel having an internal volume of 40 m ³ or more is used. Such a large polymerization vessel having an internal volume of 40 m ³ or more is suitable for mass production of a vinyl chloride polymer. The shape of the stirrer used in such a large-scale polymerization vessel and the stirrer used if desired, such as a baffle, are not particularly limited, and are generally employed in a conventional suspension polymerization method of a vinyl chloride monomer. A known stirring device can be used.
That is, examples of the stirring blade include a turbine blade, a fan turbine blade, a Faudler blade, and a blue margin blade, and examples of the baffle include a plate type, a cylindrical type, a D type, a loop type, and a finger type.

The reflux condenser is attached to the gas phase of the polymerization reactor, and has a heat transfer area corresponding to the required heat removal capacity.
The structure is not particularly limited as long as it has thermal conductivity. Generally, a multi-tube reflux condenser is exemplified, and the heat removal capacity of such a reflux condenser is 10 to 6 with respect to the heat generated by polymerization.
It is preferable to set it to about 0%.

In the present invention, the time from the start of the polymerization to the completion of the polymerization, that is, the polymerization time, is determined from the time when the internal temperature reaches a predetermined polymerization temperature by heating and raising the temperature after the completion of charging the monomers and the like. After the pressure changes for a while at the natural temperature at the reaction temperature, the pressure starts to drop as the unreacted monomer decreases, and is defined as the time until the drop becomes 1.5 kg / cm ² .

Among the monomers mainly comprising vinyl chloride in the present invention, the monomers copolymerizable with vinyl chloride include:
Examples thereof include alkyl vinyl esters such as vinyl acetate, alkyl vinyl ethers such as cetyl vinyl ether, α-monoolefins such as ethylene and propylene, and alkyl (meth) acrylates such as methyl acrylate and methyl methacrylate. But not limited to these.

The oil-soluble polymerization initiator used in the present invention comprises:
Peroxydicarbonate-based initiators such as di-2-ethylhexylperoxydicarbonate and di- (2-ethoxyethyl) peroxydicarbonate;
A diacyl peroxide-based initiator such as trimethylhesaquinoyl peroxide, α, α-azobis-2,4
An azo compound-based initiator such as dimethyl valeronitrile,
And perester-based initiators such as 2,4,4-trimethylpentyl peroxy neodecanoate, tertiary heptyl peroxy neodecanoate, tertiary hexyl peroxy pivalate, and the like. It is not limited to the initiator.

The type and amount of these initiators are selected so as to provide a polymerization time of at most 6 hours at a predetermined polymerization temperature, and one type or a combination of two or more types is used. Normal,
By charging 0.01 to 2 parts by weight per 100 parts by weight of the monomer, the polymerization can be completed within 6 hours.

The suspending agent used in the present invention is three kinds of partially saponified polyvinyl acetates having the following characteristics. (A) Degree of saponification 75 to 81 mol%, average degree of polymerization 1000
(B) 65 to 75 mol% of saponification degree, average polymerization degree of 500 to
900; (C) a degree of saponification of 15 to 54 mol%, an average degree of polymerization of 100 to
1200; These partially saponified polyvinyl acetates (A), (B) and (C) are commercially available by themselves and are known.

The suspending agents (A) and (B) stably suspend monomer oil droplets and polymer particles during polymerization in an aqueous medium,
It is intended to produce particles having a high bulk specific gravity and a porous internal structure by appropriately adjusting the particle size and the particle size distribution. When the degree of saponification and the average degree of polymerization of the suspending agents (A) and (B) are out of the above ranges, the object of the present application cannot be achieved.

That is, the degree of saponification of the suspension (A) is 75
% Or the average degree of polymerization is less than 1000,
Suspension stability is insufficient and bubbling is likely to occur, and the bulk specific gravity of the obtained particles is reduced.
When the content exceeds 81 % or the average degree of polymerization exceeds 4000, fish eyes sharply increase. When the degree of saponification of the suspending agent (B) is less than 65 mol% or the average degree of polymerization is less than 500, the suspension stability becomes insufficient,
High quality polymers cannot be obtained. When the degree of saponification exceeds 75 mol% or when the average degree of polymerization is 90%
If it exceeds 0, porosity is impaired and fish eyes increase.

The total amount of (A) and (B) charged per 100 parts by weight of the monomer is 0.03-0.15 parts by weight,
And the weight ratio of (A) and (B), that is, (A) / (B)
Is 1 to 4. If the total of (A) and (B) is less than 0.03 parts by weight, the suspension stability of the monomer oil droplets and polymer particles during polymerization is impaired, and the coarse fraction increases. Also 0.1
If the amount exceeds 5 parts by weight, foaming is likely to occur, the particle size becomes small, and the bulk specific gravity becomes small. The total of (A) and (B) is preferably 0.04 to 0.12 parts by weight.

If the charged weight ratio of (A) and (B) is less than 1, bubbling tends to occur during the polymerization, and the bulk specific gravity of the obtained polymer particles becomes small. On the other hand, if the charged weight ratio of (A) and (B) exceeds 4, foaming is also likely to occur,
The porosity of the obtained polymer particles is impaired, and the quality such as fish eye and plasticizer absorption is reduced.

When each of the suspending agents (A) and (B) is used alone without being used together, foaming is severe or dispersion stability is poor, and the resulting polymer has poor particle properties. Inferior physical properties are as described in known literature. The mechanism of the foaming preventing effect when the suspending agents (A) and (B) are used at the specific weight ratio as described above is not clear, but both suspending agents are present in an aqueous solution and the surface of the monomer oil droplets It is presumed that the interaction on the surface of the polymer particles accompanying the progress of polymerization inhibits the stability of bubbles generated by evaporation of the vinyl chloride monomer and suppresses the foaming phenomenon.

The suspending agent (C) is insoluble or hardly soluble in water, and is porous, less fish-eye, and plasticized by preventing aggregation of basic particles on the order of 1 to several μm inside polymer particles. It produces polymer particles with good agent absorption. When the degree of saponification and the average degree of polymerization of the suspending agent (C) are out of the above ranges, the suspension stability is reduced, the effect of preventing foaming is small, and the effect of suppressing fish eyes cannot be exhibited.

If the amount of (C) per 100 parts by weight of the monomer is less than 0.01 part by weight, the effect of suppressing fish eyes cannot be exhibited. On the other hand, if the amount exceeds 0.1 parts by weight, the effect of preventing foaming during polymerization is reduced, and the particle size of the obtained particles is reduced, and the bulk specific gravity is reduced. The preferable charging amount of such (C) is 0.02 to 0.07.
Parts by weight.

When this suspending agent (C) is present in an amount in a specific range, it is effective in preventing foaming during polymerization, particularly when a reflux condenser is used. Although this mechanism is not clear, the stability of bubbles generated by evaporation of vinyl chloride monomer from the inside of the particles is related to the effect of preventing aggregation of the basic particles inside the polymer particles and developing porosity. It is presumed that it suppresses the foaming phenomenon.

As described in JP-A-57-147502, a so-called internal jacket is provided on the inner surface of the polymerization vessel as a jacket for heating and cooling in the present invention to improve heat transfer performance. The present invention can be carried out more advantageously by using a polymerization vessel. That is, higher-speed polymerization becomes possible, and the polymerization can be completed within 5 hours, for example. When an internal jacket type polymerization vessel is used, the load factor of the reflux condenser can be reduced.

The polymerization temperature is set according to the type of the oil-soluble polymerization initiator, but is usually 30 to 80 ° C. The amount of water in the aqueous medium is usually in the range of 0.5 to 1 in terms of the weight ratio of monomer / water, but it is also possible to inject during polymerization to compensate for the decrease in liquid level due to volume shrinkage accompanying polymerization. Is more preferable from the viewpoint 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. . Further, if desired, other additives include mercapto alkanol, a chain transfer agent such as alkyl thioglycolate, a non-ionic surfactant such as glycerin ester or sorbitan ester of higher fatty acid, a pH adjuster and a polymerization inhibitor. Etc. may be used.

[0032]

As described above, according to the present invention, by using a specific amount of the above-mentioned three kinds of partially saponified polyvinyl acetates, the porosity is large, the bulk specific gravity is as large as 0.5 g / cc or more, A high-quality vinyl chloride resin having excellent particle size characteristics and low fish eyes can be produced in a short time within 6 hours under high productivity without any operational problems. Therefore, it is possible to solve the problem that was difficult to achieve with the conventional techniques of using a large-sized polymerization reactor and a reflux condenser, and is extremely 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, percentages are by weight unless otherwise specified. In addition, the physical property value of the vinyl chloride polymer shown in each Example was measured by the following methods.

(1) Average particle size: It was shown as a 50% passage diameter by sieve analysis using a JIS standard wire mesh. (2) Coarse-grain content: The value is shown by the ratio remaining in the 42-mesh wire net by the sieve analysis of (1). (3) Bulk specific gravity: Measured according to the method specified in JIS K6721977.

(4) Porosity: a vinyl chloride-based polymer which was injected between normal pressure and 120 kg / cm ² G using a mercury intrusion porosimeter (Model 1250-2) manufactured by Carlo Elba. It is indicated by the volume of mercury per gram of particles. (5) Fish eye: 50 g of a vinyl chloride polymer and a polyester plasticizer (SP-105 manufactured by Sanken Kako Co., Ltd.) 25
g, 1.5 g of calcium stearate and 0.2 g of carbon black were added and mixed, then kneaded with an 8-inch roll at 150 ° C. for 7 minutes, pulled out to a sheet having a thickness of 0.2 mm, and placed in a surface of 100 cm ^{3 of the} sheet. Indicated by the number of transparent particles observed.

Example 1 A Faudler type stirring blade having a blade length of 1.7 m, outer diameter of 0.22 m
After degassing a 45 m ³ stainless steel polymerization vessel equipped with four pipe baffles and a multi-tube reflux condenser having a heat transfer area of 100 m ^{2 and} a vinyl chloride monomer 10
0 parts (16.5 tons), 130 parts of water, 0.04 part of partially saponified polyvinyl acetate having a degree of saponification of 80 mol% and an average degree of polymerization of 2500, and a degree of saponification of 73 mol% and an average degree of polymerization of 8
0.02 parts of partially saponified polyvinyl acetate, 0.04 part of partially saponified polyvinyl acetate having a degree of saponification of 33 mol% and an average degree of polymerization of 300, 2,4,4-trimethylpentylperoxy neodeca 0.05 parts of Noate was charged.

The rotation speed of the stirring was set to 100 rpm, and the internal temperature was set to 57 rpm.
After the temperature is raised to ℃, the cooling water is started to flow to the reflux condenser and the amount of cooling water is gradually increased so that the amount of heat removed by the condenser after the first hour becomes 300,000 to 400,000 Kcal / hr. And adjust the internal temperature to 57 with the amount of cooling water to the jacket.
The polymerization was continued while maintaining the temperature at ° C. 8.5kg internal pressure
At the time when the weight of the unreacted monomer was reduced from 7 / cm ² G to 7 kg / cm ² G, the unreacted monomer was recovered, and the content was taken out and dehydrated and dried. After the completion of the polymerization, there was no trace of foaming in the reflux condenser and the conduit, and no adhesion of the polymer was observed.

Examples 2 to 5, Comparative Examples 1 to 6 Polymerization was carried out under the same conditions as in Example 1 except that the kind and the amount of the partially saponified polyvinyl acetate were changed to the conditions shown in Table 1. The combined particles were obtained. Polymerization conditions and the presence or absence of adhesion of the polymer to the reflux condenser and the physical properties of the obtained polymer particles,
Also shown in Table 1.

[0039]

[Table 1]

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Masahisa Okawa 5-1 Sokai-cho, Niihama-shi, Ehime Sumitomo Chemical Industries Co., Ltd. (72) Inventor Isao Ouchi 16 Nishimachi Ochiai, Iwaki-shi, Fukushima Kureha Chemical (72) Inventor Hideki Wakamori 16 Nishikicho Ochiai, Iwaki City, Fukushima Prefecture Kureha Chemical Industry Co., Ltd. (72) Inventor Tamio Yamato 1-2-2 Harumicho, Tokuyama City, Yamaguchi Prefecture Sun Arrow Chemical Co., Ltd. (72) Inventor Yasumichi Ishii 2767-1 Shinhama, Kojima Shioike, Kurashiki-shi, Okayama Nippon Zeon Co., Ltd. (56) References JP-A-62-263206 (JP, A) Takuhiko Motoyama, “Shinkobunko 18 Vinyl acetate Resin emulsion "(Showa 55-7-25) Co., Ltd. 22-23

Claims (2)

(57) [Claims] 1. A polymerization vessel having a stirrer, a jacket and a reflux condenser having an internal volume of 40 m ³ or more, and a monomer mainly composed of vinyl chloride is suspended in an aqueous medium using an oil-soluble polymerization initiator. When the suspension polymerization is carried out and the polymerization is completed within 6 hours, (A) a saponification degree of 75 to 81 mol% and an average polymerization degree of 1000
(B) a degree of saponification of 65 to 75 mol% and an average degree of polymerization of 500 to 4,000.
900 partially saponified polyvinyl acetate; (C) a degree of saponification of 15 to 54 mol%, an average degree of polymerization of 100 to
1200 partially saponified polyvinyl acetates, and the total amount of (A) and (B) per 100 parts by weight of monomer is 0.03-0.15 parts by weight and the amount of (C) Wherein the weight ratio (A) / (B) of (A) / (B) is from 0.01 to 0.1 parts by weight, and the suspension weight of the vinyl chloride-based monomer is from 1 to 4. legal. 2. The suspension polymerization method of a vinyl chloride monomer according to claim 1, wherein the jacket is an inner jacket.