JP2912954B2 - Suspension polymerization of vinyl chloride - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a suspension polymerization method for vinyl chloride or a monomer mixture containing vinyl chloride as a main component and copolymerizable therewith (hereinafter referred to as vinyl chloride). Also, the present invention relates to a suspension polymerization method for improving productivity in a polymerization step by shortening a heating time, and also for improving fisheye, particle size distribution and preventing scale adhesion.

[0002]

2. Description of the Related Art Generally, suspension polymerization of vinyl chloride is carried out in a batch system. After deionized water, a suspending agent, a polymerization initiator and additives are charged into an autoclave, the inside of the system is degassed, and vinyl chloride or the like is degassed. , And warm water circulation or steam is passed through the autoclave jacket with stirring, and the temperature is raised to the polymerization temperature to start the polymerization reaction. Thereafter, from the point when the polymerization reaction heat comes out, cooling is performed to keep the polymerization temperature constant by passing cooling water through the autoclave jacket, the reaction is continued until a predetermined polymerization rate is reached, and then a monomer gas such as vinyl chloride is discharged. A series of polymerization operations for recovering and discharging the polymer from the autoclave are performed.

[0003]

However, in the above-mentioned conventional method, the time required for the temperature rise time is one of the causes of a decrease in productivity. In order to solve such a problem, various methods have been considered.

A method in which water, a suspending agent, vinyl chloride, etc. and a polymerization initiator which are heated to a polymerization temperature or higher as disclosed in JP-A-57-5704 are charged together in an autoclave, and a polymerization reaction is immediately started. However, in this method, vinyl chloride, water, and a suspending agent come into contact at a temperature around the polymerization temperature, so that the particle size becomes unstable, and the number of products particularly coarse is increased. In addition, there is a disadvantage in quality that the number of fish eyes is remarkably increased, which is not a good idea.

Alternatively, a method in which a suspending agent, a polymerization initiator, other additives and vinyl chloride are charged into an autoclave as disclosed in JP-A-60-47007, and then water heated at or above the polymerization temperature is charged. However, in this method, scale is generated on the inner wall of the polymerization can, and it is difficult to homogenize the polymerization in the initial stage of charging hot water, coarse particles are generated, and the product has poor fisheye.

In addition, Japanese Patent Application Laid-Open No.
In a method in which water at 0 ° C or lower, a suspending agent and a polymerization initiator are charged into an autoclave, then vinyl chloride is charged, and the mixture is stirred and mixed, then heated water is charged to start polymerization, and considerable scale is generated on the inner wall of the polymerization can. And has practical problems.

[0007]

Means for Solving the Problems The inventors of the present invention have intensively studied to solve this drawback and to shorten the cycle time of the polymerization step. As a result, the timing of starting the stirring and the method of charging the polymerization initiator have been devised. By doing so, the above-mentioned drawbacks have been solved, and the present invention has been achieved.

That is, in the present invention, in the suspension polymerization of vinyl chloride, first, 20 to 50% by weight of room temperature deionized water and a suspending agent, based on the total amount of water in the polymerization system, are charged into an autoclave, and stirring is started. The polymerization system is heated to a reaction temperature by charging vinyl chloride and deionized water heated to a polymerization temperature of 50 to 80% by weight of the total water content of the polymerization system, and then emulsified in an aqueous medium. An object of the present invention is to provide a suspension polymerization method of vinyl chloride, wherein polymerization is carried out by charging a dispersed polymerization initiator.

The present invention will be described in more detail.

[0010] The total amount of deionized water used in the present invention is:
90 to 200 parts by weight is preferable for 100 parts by weight of vinyl chloride.

The suspending agent used in the present invention may be any of those conventionally known, including styrene / maleic acid copolymer, partially saponified polyvinyl alcohol, methylcellulose, hydroxypropylmethylcellulose, ethylcellulose, gelatin, calcium carbonate , Calcium phosphate and the like are used alone or in combination of two or more.

The suspending agent is used in an amount of 0.001 to 5 parts by weight based on 100 parts by weight of vinyl chloride. A stable dispersion state can be obtained by sufficiently mixing the suspending agent and water at room temperature.

More specifically, it is preferable to carry out the above-mentioned mixing at a temperature not higher than the cloud point or thermal gelation temperature of the suspending agent used,
Above this temperature, the formation of coarse particles increases.

As described above, 20 to 50 deionized water at room temperature is used.
After charging the suspending agent to the weight%, the inside of the autoclave is usually subjected to a deaeration treatment to remove air existing in the autoclave. After the stirring is started, preferably, after the stirring is in a steady state, vinyl chloride and 50 to 80% by weight of the total amount of water to be present in the polymerization system are charged with deionized water heated to a polymerization temperature or higher. The temperature inside the polymerization system is raised to a predetermined reaction temperature, and then a polymerization initiator emulsified and dispersed in an aqueous medium is charged to immediately polymerize.

The vinyl chloride used in the present invention includes:
Mixtures of vinyl chloride or monomers based on vinyl chloride and copolymerizable therewith can be used. Examples of the component copolymerizable with vinyl chloride include ethylene, vinyl acetate, methyl acrylate, acrylonitrile, and vinylidene chloride.

The polymerization initiator emulsified and dispersed in an aqueous medium is obtained by emulsifying and dispersing a substance generally used as a polymerization initiator in the polymerization of vinyl chloride in an aqueous medium using an emulsifier and / or a dispersant. Use the emulsified material.

The concentration of the emulsion is not limited, but is preferably 5 to 70% by weight. This is because by emulsifying and dispersing the polymerization initiator, the polymerization initiator can be uniformly dispersed, and the stability of particles and the reduction of fish eyes can be achieved. If the concentration is less than 5% by weight, the effect of emulsification and dispersion does not change and it is not economical. If it exceeds 70% by weight, the effect of emulsification and dispersion may not be sufficiently exhibited.

The aqueous medium used in the present invention is preferably water (deionized water). .

The emulsifier used in the present invention may be a nonionic surfactant. Examples of the emulsifier include alkyl and alkyl allyl polyoxyethylene ethers such as ether type, and sorbitan ester polyoxyethylene ether as ether ester type. As the ester type, there are sorbitan esters and the like, and one or more of them are used in combination.

Examples of the dispersant used in the present invention include partially saponified polyvinyl alcohol having a saponification degree of 60 to 85%, ethyl cellulose, methyl cellulose and the like. In the present invention, an emulsifier and a dispersant are used in combination. It doesn't matter.

The polymerization initiator used in the present invention includes azo compounds such as azobis-α, α'-dimethylvaleronitrile and 2,2'-azobis-2,4-dimethyl-4-methoxyvaleronitrile, and diisopropylperoxy. Dicarbonate, di-2-ethylhexylperoxydicarbonate, di- (β-ethoxyethyl) peroxydicarbonate, t-butylperoxydicarbonate, acetylcyclohexylsulfonyl peroxide, t-butylperoxypivalate, t-butylperoxydicarbonate Organic peroxides such as butylperoxyneodecanate and lauroyl peroxide are exemplified.

The polymerization initiator is used in an amount of 0.0001 to 5 parts by weight based on 100 parts by weight of vinyl chloride.

As other additives, those used in ordinary suspension polymerization of vinyl chloride, such as a polymerization degree regulator, a processability improver, an antistatic agent, a pH regulator, an antioxidant, a scale inhibitor, etc. One type or two or more types can be used.

The timing of adding the additives may be in any of the polymerization steps, but is usually charged in the same manner as the charging of the suspending agent.

The process of the present invention can be carried out in a temperature range in which ordinary suspension polymerization of vinyl chloride is carried out.

Therefore, the temperature of the heated deionized water to be used is preferably the polymerization temperature to 100 ° C., preferably 60 to 9 ° C.
The temperature is 0 ° C., which can be appropriately determined according to the polymerization temperature, the amount of hot water charged, the heating capacity from the jacket, the polymerization recipe, and the like.

[0027]

EXAMPLES The present invention will be described below with reference to examples, but the present invention is not limited by these examples. Evaluation Evaluation of powder characteristics and the like in Examples was performed as follows. 1. Particle size distribution Measured using a JIS standard sieve. 2. Fisheye A blended resin 100 parts by weight DOP50 {Ca-Zn-based stabilizer 2} ultramarine blue 3} B evaluation The above blend was kneaded with a mixing roll at 150 ° C for 3 minutes to prepare a 0.35 mm sheet. Using this sheet, the number of fish eyes in 50 cm ² was counted. 3. Scale adhesion status ○ good × bad 4. Generation of glassy particles ○ Not generated × Generated.

Example 1 55 parts by weight of deionized water and 0.06 parts by weight of partially saponified polyvinyl alcohol were added to 100 parts by weight of vinyl chloride at room temperature in a 1 m ³ autoclave, and the inside of the autoclave was degassed. After starting stirring, vinyl chloride 1 at 30 ° C
Then, 75 parts by weight of deionized water heated to 80 ° C. was charged, and the temperature in the autoclave was lowered to 5 parts by weight.
After the temperature was raised to 7 ° C., 0.02 parts by weight of di-2-ethylhexyl peroxydicarbonate emulsified and dispersed in deionized water and emulsified to 40% by weight was charged to initiate polymerization. When the pressure in the autoclave dropped 2.0 kg / cm ² due to the saturated vapor pressure of vinyl chloride at 57 ° C., polymerization was stopped, unreacted vinyl chloride was recovered, and stirring was stopped. The obtained slurry was dehydrated and dried to obtain a vinyl chloride polymer. Table 1 shows the particle size distribution of the obtained polymer and the results of the fisheye test.

Example 2 The procedure of Example 1 was repeated except that 100 parts by weight of vinyl chloride at 30 ° C. and 75 parts by weight of deionized water heated to 80 ° C. were simultaneously charged, and the temperature in the autoclave was set to 57 ° C. The same was done. Table 1 shows the test results of the obtained polymer.

Example 3 In Example 1, the reaction temperature (the temperature in the autoclave) was set to 64 ° C., the amount of deionized water added was 35 parts by weight of deionized water at room temperature, and deionized water heated to 80 ° C. was added. The procedure was exactly the same except that the weight was changed to 95 parts by weight. Table 1 shows the test results of the obtained polymer.

COMPARATIVE EXAMPLE 1 A 1 m ³ autoclave was charged with 130 parts by weight of deionized water at 30 ° C. containing 0.06 parts by weight of partially saponified polyvinyl alcohol and degassed. Stirring was started, 100 parts by weight of vinyl chloride at 30 ° C. was charged, and the jacket was heated with hot water at 80 ° C., and the temperature in the autoclave was reduced to 57 ° C.
0.02 parts by weight of di-2-ethylhexyl peroxydicarbonate emulsified and dispersed in deionized water to form a 40% by weight emulsion was charged to initiate polymerization. Thereafter, the mixture was treated under the same conditions as in Example 1 to obtain a vinyl chloride polymer. Table 1 shows the test results of the obtained polymer.

Comparative Example 2 55 parts by weight of deionized water and 0.06 parts by weight of partially saponified polyvinyl alcohol were charged into a 1 m ³ autoclave.
The inside of the autoclave was evacuated.

100 parts by weight of vinyl chloride at 30 ° C. and 0.02 parts by weight of non-emulsified di-2-ethylhexyl peroxydicarbonate were charged, and stirring was started. Then, 75 parts by weight of deionized water heated to 80 ° C. was charged, and the temperature in the autoclave was reduced to 57 ° C. to start polymerization. Thereafter, the mixture was treated under the same conditions as in Example 1 to obtain a vinyl chloride polymer. Table 1 shows the test results of the obtained polymer.

Comparative Example 3 The same operation as in Comparative Example 1 was carried out except that the temperature in the autoclave was changed to 64 ° C. Table 1 shows the test results of the obtained polymer.

Comparative Example 4 According to the method described in JP-A-57-5704, 1 m ³
130 parts by weight of deionized water heated to 80 ° C. in a reactor, 0.006 parts by weight of partially saponified polyvinyl alcohol, and 0.002 parts by weight of di-2-ethylhexylperoxydica-ponate. 100 parts by weight of vinyl chloride at 30 ° C. were charged simultaneously with stirring, and the temperature in the autoclave was set to 57 ° C. to initiate polymerization. Thereafter, the mixture was treated under the same conditions as in Example 1 to obtain a vinyl chloride polymer. Table 1 shows the test results of the obtained polymer.

Comparative Example 5 According to the method described in JP-A-60-47007, 30 parts by weight of deionized water, 10 parts by weight of vinyl chloride at 30 ° C., and 0 parts of partially saponified polyvinyl alcohol were placed in a 1 m ³ autoclave. .
06 parts by weight, di-2-ethylhexyl par-oxydica
0.002 parts by weight of carbonate is uniformly mixed at a temperature of 30 ° C. or less, and then, while stirring, deionized water heated to 80 ° C. is charged to 100 parts by weight, and the temperature in the autoclave is increased. At 57 ° C. to initiate polymerization. Thereafter, the first embodiment
The mixture was treated under the same conditions as in Example 1 to obtain a vinyl chloride polymer. Table 1 shows the test results of the obtained polymer.

[0037] according to the method described in Comparative Example 6 Sho 54-47785, 1m ³ O - Tokure - 30 parts by weight of water of 30 ° C. or less during blanking, partially saponified polyvinyl alcohol - Le 0.06 parts by weight, di After charging 0.02 parts by weight of 2-ethylhexylperoxydica-bonate and stirring and mixing, 100 parts by weight of deionized water heated to 80 ° C. was charged to reduce the temperature in the autoclave to 57%.
C. to initiate polymerization. Thereafter, the mixture was treated under the same conditions as in Example 1 to obtain a vinyl chloride polymer. Table 1 shows the test results of the obtained polymer.

[0038]

[Table 1]

[0039]

As is apparent from the above description, according to the method of the present invention, it is possible to remarkably reduce the temperature rise time in the polymerization of vinyl chloride, and to produce fisheye without impairing other physical properties. It is possible to improve the performance.

Claims (1)

(57) [Claims] In a suspension polymerization method of vinyl chloride, 20 to 50% by weight of the total amount of water in a polymerization system is contained in an autoclave.
Of deionized water at room temperature and a suspending agent, stirring is started, and then vinyl chloride and deionized water heated to a polymerization temperature of 50 to 80% by weight or more of the total water amount of the polymerization system are charged. A suspension polymerization method of vinyl chloride, which comprises raising the temperature of a polymerization system to a reaction temperature, and subsequently charging a polymerization initiator emulsified and dispersed in an aqueous medium to carry out polymerization.