JPH06184218A - Production of vinyl chloride-based polymer - Google Patents

Abstract

PURPOSE:To obtain the subject polymer, hardly causing a reduction in bulk specific gravity due to the electrification and excellent in powder fluidity, etc., by dehydrating a slurry, containing a vinyl chloride-based polymer and prepared by the suspension (co)polymerization and then adding boric acid as an aqueous solution thereto. CONSTITUTION:Vinyl chloride monomer or a mixture of vinylic monomers consisting essentially of the vinyl chloride is initially and usually subjected to the suspension (co)polymerization in the presence of a suspending agent and a polymerization initiator in an aqueous medium to provide a vinyl chloride- based polymer. A slurry containing the resultant vinyl chloride-based polymer is then dehydrated and boric acid in an amount of 0.001-0.5 pt.wt. based on the vinyl chloride-based polymer as an aqueous solution is subsequently added to the prepared polymer cake or vinyl chloride-based polymer powder obtained by drying the cake. Furthermore, e.g. vinyl acetate and methyl acrylate can be used as the vinylic monomers copolymerizable with the vinyl chloride.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a vinyl chloride polymer by a suspension polymerization method, and more particularly to a method for producing a vinyl chloride polymer having excellent powder fluidity.

[0002]

2. Description of the Related Art Vinyl chloride polymers are usually produced by a suspension polymerization method, purified by separation from a slurry, dried, etc., transported by air transportation and then stored or packed.

However, the vinyl chloride polymer thus obtained is charged with static electricity due to friction with itself and other substances during transport and bagging, and its fluidity is lowered,
Since the bulk specific gravity is reduced as compared with the vinyl chloride polymer immediately after production, there is a problem that it becomes extremely difficult to handle and seriously hinders work.

As a method for reducing the adverse effects of such polymer charging, conventionally, a method of adding a nonionic surfactant or a cationic surfactant, which is an antistatic agent, to a vinyl chloride polymer or steam. The method of controlling the humidity by blowing the vinyl chloride polymer has been used.

[0005]

However, the above-mentioned method of adding a surfactant cannot sufficiently prevent the decrease of the bulk specific gravity of the polymer, and further the heat stability and the initial colorability of the product are not improved. It has the drawback of having an adverse effect. Further, the method of blowing steam has drawbacks such as an increase in required labor force and complication of equipment.

Therefore, an object of the present invention is to provide a method for producing a vinyl chloride polymer having good quality which is unlikely to decrease in bulk specific gravity due to electrification.

[0007]

Means for Solving the Problems The present inventors have completed the present invention as a result of intensive studies to achieve the above object. That is, the present invention is to produce a vinyl chloride-based polymer by suspension-polymerizing a vinyl chloride-based monomer or a mixture of vinyl-based monomers containing vinyl chloride as a main component in an aqueous medium. The method for producing a vinyl chloride-based polymer is characterized in that 0.001 to 0.5 part by weight of boric acid is added as an aqueous solution to the vinyl chloride-based polymer after the slurry containing is dehydrated.

In the method of the present invention, a vinyl chloride polymer is first synthesized by the suspension polymerization method. Examples of vinyl chloride-based polymers include homopolymers of vinyl chloride and copolymers with other polymerizable vinyl-based monomers copolymerizable with vinyl chloride. Examples of vinyl monomers copolymerizable with vinyl chloride include alkyl vinyl esters such as vinyl acetate, alkyl vinyl ethers such as cetyl vinyl ether, α-monoolefin monomers such as ethylene and propylene, and acrylic acid. Examples thereof include acrylic acid alkyl esters such as methyl, and methacrylic acid alkyl esters such as methyl methacrylate.

Suspension polymerization of vinyl chloride type polymers is well known, and a vinyl chloride monomer or a vinyl chloride monomer and another polymerizable vinyl unifying vinyl monomer are used as a suspending agent and polymerized. Polymerization is carried out in an aqueous medium in the presence of an initiator, and a suspension containing a vinyl chloride polymer can be obtained by this suspension polymerization method.

Next, according to the method of the present invention, after dehydrating the slurry containing the vinyl chloride polymer, the obtained polymer cake or the polymer cake is dried into powder of the vinyl chloride polymer. The acid is added as an aqueous solution. The amount of boric acid added is preferably 0.001 to 0.5 parts by weight with respect to 100 parts by weight of the vinyl chloride polymer.
If the added amount is less than 0.001 part by weight, it is not possible to prevent an extreme decrease in bulk specific gravity due to electrification. On the other hand, even if the amount added exceeds 0.5 parts by weight, the effect of the addition does not increase any more, which is not economical.

[0011]

EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited thereto.

Example 1 100 parts by weight of vinyl chloride monomer, 150 parts by weight of deionized water, 0.1 part by weight of partially saponified polyvinyl alcohol and 0.04 part by weight of 2-ethylhexyl peroxydicarbonate were placed in a stainless steel polymerization vessel. , Temperature of 57 ℃
When the pressure in the polymerization vessel reaches 6.0 kg / cm ² G, unreacted vinyl chloride monomer is recovered and dehydrated to obtain a vinyl chloride polymer cake containing 20% by weight of water. Obtained. To the polymer cake thus obtained, 0.01 part by weight of boric acid was added to the polymer, and then fluidized and dried at 70 ° C. for 2 hours to obtain a vinyl chloride polymer. 50% boric acid
It was added to the polymer cake as an aqueous solution.

Example 2 100 parts by weight of vinyl chloride monomer, 150 parts by weight of deionized water, 0.1 part by weight of partially saponified polyvinyl alcohol and 0.04 part by weight of 2-ethylhexyl peroxydicarbonate were placed in a stainless steel polymerization vessel. , Temperature of 57 ℃
The unreacted vinyl chloride monomer was recovered when the pressure in the polymerization vessel reached 6.0 kg / cm ² G, dehydrated, and then fluidized and dried at 70 ° C. for 2 hours to obtain a vinyl chloride polymer. Got To the obtained vinyl chloride polymer, 0.03 parts by weight of boric acid was added to the polymer in a fluidized state. Boric acid was added to the polymer as an aqueous solution.

Example 3 A vinyl chloride polymer was obtained in the same manner as in Example 2 except that the addition amount of boric acid and the concentration of the aqueous solution were changed to those shown in Table 1.

Comparative Example 1 A vinyl chloride polymer was obtained in the same manner as in Example 2 except that boric acid was not added.

Comparative Example 2 A vinyl chloride polymer was obtained in the same manner as in Example 2 except that a 50% aqueous solution of polyoxyethylene sorbitan monolaurate was used instead of boric acid.

Comparative Example 3 A vinyl chloride polymer was obtained in the same manner as in Example 2 except that the amount of boric acid added and the concentration of the aqueous solution were changed to those shown in Table 1.

The vinyl chloride polymers obtained in Examples 1 to 3 and Comparative Examples 1 to 3 were subjected to the bulk specific gravity measurement test and thermal stability test shown below. The results are shown in Table 1.

1. Bulk specific gravity measurement test After leaving the vinyl chloride polymer in a constant temperature and humidity room at a temperature of 23 ° C. and a relative humidity of 50% for 48 hours, the bulk specific gravity is measured according to JIS K.
It was measured by the method of -6721.

Further, the vinyl chloride polymer left under the same conditions as above for 48 hours was stirred at 60 rpm for 2 minutes with a Brabender planetary mixer, and the bulk specific gravity was compared by the same method as above.

2. Thermal stability To 100 parts by weight of vinyl chloride polymer, 1.0 part by weight of tribasic lead sulfate, 1.5 parts of lead stearate, 1.5 parts of calcium stearate, and 0.5 parts of calcium stearate were mixed and kneaded for 5 minutes with a roll at 190 ° C. Then, a sheet having a thickness of 1 mm was prepared, and the sheet was placed in an oven at 190 ° C. and the time until blackening was measured.

[0022]

[Table 1]

[0023]

As described above, according to the present invention, a vinyl chloride polymer which is less likely to decrease in bulk specific gravity due to electrification, has excellent powder fluidity, and has good quality such as thermal stability. Can be obtained.

Claims (1)

[Claims] 1. A vinyl chloride polymer, which is prepared by suspension polymerization of a vinyl chloride monomer or a mixture of vinyl monomers containing vinyl chloride as a main component in an aqueous medium to produce a vinyl chloride polymer. After dehydrating the slurry containing the above, boric acid as an aqueous solution is added to the vinyl chloride polymer in an amount of 0.0
A method for producing a vinyl chloride-based polymer, which comprises adding 01 to 0.5 part by weight.