JPH11349608A - Preparation of vinyl chloride based polymer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a resin which has much components of low polymerization degree and gelling time of which is short by using a vinyl chloride-based resin polymerized by a usual method as a seed resin, adding pure water, a dispersant, an initiator, a vinyl chloride-based monomer and the like and re-polymerizing the same by suspension polymerization. SOLUTION: Vinyl chloride-based resins used as a seed resin include homopolymers of vinyl chloride and copolymers of vinyl chloride with other monomers. The average degree of polymerization of the vinyl chloride-based resin is preferably 1,000-3,000. Re-polymerization is preferably conducted such that the ratio of the seed resin to the total polymer does not exceed 50 wt.%. Water is used such that the weight ratio of the total amount of water at the initial time of polymerization to a vinyl chloride-based monomer is 0.8-1.5 and water may further be added continuously, intermittently or at a time to the extent that the amount of water does not exceed a decrease with the progress of polymerization, of the slurry solution due to the difference in specific gravities between the vinyl chloride monomer and the polymer.

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, and more particularly, to a method for producing a vinyl chloride polymer characterized by a two-stage polymerization method.

[0002]

2. Description of the Related Art Conventionally, extruded products of a vinyl chloride resin alone or a vinyl chloride resin composition have been widely used in the fields of pipes, flat plates, sheets and the like. In such a field, in order to improve productivity, a resin having a short gelation time is desired, but the gelation time is generally shorter when the average degree of polymerization is smaller, while the strength of the molded product is lower. On the contrary, the larger the average degree of polymerization is, the stronger the average degree of polymerization is.

[0003]

Recently, attempts have been made to increase the low polymerization degree component in the resin in order to shorten the gelation time without changing the average polymerization degree. For example,
It is an attempt to change the polymerization temperature during the polymerization. However, this method requires stable polymerization,
The temperature could not be changed rapidly, and a vinyl chloride resin having a sufficient amount of a low polymerization degree component could not be produced.

[0004]

Means for Solving the Problems The present inventors have conducted intensive studies to solve the problem of increasing the low polymerization degree component in the resin, which is newly required as described above, and as a result, By producing a vinyl chloride resin by the developed two-stage polymerization method, it was found that the above problem could be solved,
The present invention has been completed. That is, the present invention includes a method for producing a vinyl chloride polymer using a two-stage polymerization method in which repolymerization is performed by suspension polymerization using a vinyl chloride resin polymerized by an ordinary method as a seed resin.

[0005]

First, a vinyl chloride resin serving as a seed resin is prepared. This includes vinyl chloride homopolymers and copolymers of vinyl chloride with other monomers copolymerizable therewith. The average degree of polymerization of the produced vinyl chloride resin is not particularly limited, but is preferably from 1,000 to 3,000.
It is. The average degree of polymerization of the vinyl chloride resin is JIS.
It conforms to K6721.

Next, repolymerization is performed by suspension polymerization using this as a seed resin. First, an aqueous solution of a dispersant, or an aqueous dispersion, an oil-soluble initiator, and pure water, as well as a seed resin or a reslurried material obtained by previously impregnating the seed resin with water are charged into a polymerization reactor. Next, after degassing the polymerization reactor, a vinyl chloride monomer is charged and polymerization is performed. At this time, it is desirable to perform the repolymerization so that the ratio of the seed resin to the entire polymer does not exceed 50 wt%.

In the present invention, the amount of water used for the polymerization is not particularly limited, and may be determined so as to achieve both productivity and quality as long as polymerization stability is not impaired. For example, the total amount of water at the start of the polymerization may be 0.8 to 1.5 in terms of the weight ratio of water to the vinyl chloride-based monomer, and as the polymerization proceeds, the vinyl chloride-based monomer and the polymer Although the slurry solution decreases due to the difference in specific gravity, water may be added continuously, intermittently, or collectively as long as the amount does not exceed the reduced amount.

The water-soluble or water-dispersible polymer suspension stabilizer used in the present invention includes partially saponified polyvinyl acetate, methylcellulose, hydroxypropylmethylcellulose, carboxymethylcellulose, polyvinylpyrrolidone, polyacrylic acid, and vinyl acetate. Maleic acid copolymer, styrene-maleic acid copolymer, gelatin, starch and the like can be mentioned. More preferably, at least one of the above dispersants is used in combination with polyethylene oxide. When the dispersing agent is used alone, unless the amount of the dispersing agent is considerably increased, the protective power of the monomer oil droplets at the time of initial dispersion is weak, and a sufficient protective power is secured by combining at least one of these with polyethylene oxide. Is done.

[0009] The amount of the dispersant used is a vinyl chloride monomer 1
The amount is 0.005 to 0.1 part by weight, preferably 0.01 to 0.08 part by weight, per 100 parts by weight. This amount is 0.00
If the amount is less than 5 parts by weight, the initial dispersing power of the monomer is insufficient, and the amount of coarse particles of the produced resin increases. On the other hand, if it exceeds 0.1 part, the dispersing power becomes too strong, resulting in so-called overdispersion, and the particle size distribution of the resin to be formed becomes wide and the number of fine particles increases.

Next, when polyethylene oxide is used in combination, the amount thereof is 0.001 to 0.02 parts by weight, preferably 0.002 to 0.02 parts by weight per 100 parts by weight of the vinyl chloride monomer.
0.01 parts by weight. If the amount is less than 0.001 part by weight, the protective power of the initially dispersed monomer is insufficient, so that the amount of coarse particles of the formed resin increases, or in extreme cases, the polymerization is not normally performed and the whole is hardened. May form clumps. 0.0
If the amount exceeds 2 parts by weight, the protective power is too strong, and the particle size distribution of the produced resin is widened and the number of fine particles increases.

Among these, particularly preferred dispersants include a combination of partially saponified polyvinyl acetate having a saponification degree of 60 to 95% and a polymerization degree of 400 to 4000, and polyethylene oxide having an average molecular weight of 600,000 or more. In the present invention, the stirring operation is important for dispersing the vinyl chloride monomer oil droplets in the polymerization vessel into warm water by stirring shear force and homogenizing as quickly as possible. Although the stirring speed varies depending on the shape of the stirring blade, the effect of the present invention can be easily exhibited when the stirring speed is 5 m / sec or more. 5m
If the peripheral speed of the stirring blade is less than / sec, the homogenization of the dispersion system becomes incomplete, causing an increase in the particle size distribution and an increase in coarse particles and fine particles. The stirring paddle suitable for maintaining the stirring blade peripheral speed of 5 m / sec or more includes an inclined paddle.

As the polymerization initiator in the present invention, conventionally known polymerization initiators may be used, but one or more of these initiators having a 10-hour half-life temperature of 30 to 65 ° C. are preferably used. preferable. The amount of the initiator used varies depending on the type and polymerization temperature, but is preferably 0.005 to 0.5 part per 100 parts by weight of the vinyl chloride monomer. By using this amount of initiator, the polymerization time can be reduced to 6 hours or less. As such a polymerization initiator, acetylcyclohexylsulfonyl peroxide,
2,4,4 trimethylpentyl-2-peroxyneodecanoate, di-2-ethylhexylperoxydicarbonate, di (2-ethoxyethyl) peroxydicarbonate, t-butylperoxypivalate, t-butyl Organized oxide-based initiators such as peroxyneodecanoate and 3,5,5-trimethylhexanoyl peroxide, azobisisobutyronitrile, azovir-2,4
And azo-based initiators such as dimethylpareronitrile, which can be used alone or in combination of two or more.

These oil-soluble initiators are used after being dissolved in a solvent. Examples of the solvent include aromatic hydrocarbons such as toluene, xylene and benzene, aliphatic hydrocarbons such as hexane and isoparaffin, acetone, methyl ethyl ketone and the like. Ketones, esters such as ethyl acetate, butyl acetate, and dioctyl phthalate.
More than one kind can be used in combination.

The monomer used in the present invention is a monomer containing vinyl chloride as a main component, and specifically, a vinyl chloride monomer alone or containing vinyl chloride in an amount of 70% by weight or more, And a copolymerizable monomer. Examples of monomers copolymerizable with vinyl chloride include vinyl esters such as vinyl acetate and vinyl propionate, α-olefins such as ethylene, propylene and isobutyl vinyl ether, and 1-chloropropylene and 2-chlorobutylene. Chlorinated olefins, (meth) acrylic esters such as methyl (meth) acrylate, maleic anhydride, acrylonitrile, styrene, vinylidene chloride, etc., are used alone or in combination of two or more. It is also possible.

Further, polymerization degree regulators, chain transfer agents, pH regulators, gelling improvers, antistatic agents, emulsifiers, stabilizers, which are conventionally used for the polymerization or copolymerization of vinyl chloride monomers,
A known technique can be arbitrarily used for the scale inhibitor and the method for preparing these agents without any problem. The polymerization temperature conditions are not particularly limited, but preferably the average polymerization degree is 400
5 which is the condition for preparing a PVC resin of up to 1000
Perform at 7.5-70 ° C.

[0016]

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples, but these do not limit the present invention at all. (Example) As seed resin, S1003 (manufactured by Kaneka Chemical Co., Ltd .: average degree of polymerization: 1300) was used.

In a stainless steel polymerization vessel having an internal volume of 2000 L, in which a stirrer and the like are laid, 1186 L of water at a temperature of 20 ° C. (hereinafter referred to as charged water), a saponification degree of 79%, and a polymerization degree of
8.0 L of a 3% aqueous solution of partially saponified polyvinyl acetate (hereinafter referred to as PVA1), 12.1 L of a 0.5% aqueous solution of polyethylene oxide having an average molecular weight of 4.5 million (hereinafter referred to as PEO1), and 70% t-butyl par 100 kg of seed resin was charged together with 37 g of an oxyneodecaate isoparaffin solution and 59 g of a 75% 3,5,5-trimethylhexanoyl peroxide toluene solution (PVA1 and PE were added to 100 parts of vinyl chloride monomer).
The charged amounts of O1 were 0.08 parts and 0.003 parts, and the charged amounts of t-butylperoxyheodecaate and 3,5,5-trimethylhexanoyl peroxide were 0.014 parts.
Part, 0.024 part), and the stirring blade peripheral speed was 8.6 m /
After the operation was performed while adjusting the number of revolutions so as to reach sec, the inside of the polymerization vessel was evacuated with a vacuum pump. After deaeration, 201 L of vinyl chloride monomer (184 kg: 18 ° C.) was charged.

Next, after the temperature inside the polymerization vessel was raised to 67 ° C., polymerization was carried out while maintaining this temperature, and the polymerization was stopped when the outside temperature of the polymerization vessel was raised to a difference of 1 ° C. from the inside temperature. Then, the unreacted monomer was recovered to terminate the polymerization. The obtained slurry was dehydrated and dried to obtain a vinyl chloride polymer. At this time, the conversion of the vinyl chloride monomer into the polyvinyl chloride polymer was 82%. From this, when the ratio W of the seed resin to the entire polyvinyl chloride polymer is calculated, W = 40 w
t%.

(Comparative Example 1) Internal volume 2 in which a stirrer and the like were laid
8 liters of water at 20 ° C in a stainless steel polymerization vessel
42L, 8.0% of a 3% aqueous solution of partially saponified polyvinyl acetate (hereinafter referred to as PVA1) having a saponification degree of 79% and a polymerization degree of 2000, and a 0.5% aqueous solution 12 of polyethylene oxide having an average molecular weight of 4.5 million (hereinafter referred to as PEO1) 12 .1
L, 37 g of a 70% strength t-butyl peroxy neodecaate solution in isoparaffin, 75% strength 3, 5, 5
-59 g of a toluene solution of trimethylhexanoyl peroxide was charged, and the charged amounts of PVA1 and PEO1 were 0.08 parts,
03 parts, also t-butyl peroxyheodecaate,
(The charged amount of 3,5,5-trimethylhexanoyl peroxide is 0.014 parts and 0.024 parts.) The stirrer is operated by adjusting the rotation speed so that the stirring blade peripheral speed becomes 8.6 m / sec. After that, the inside of the polymerization vessel was degassed by a vacuum pump. After deaeration, 550 L of a vinyl chloride monomer was charged.

Next, after the temperature in the polymerization vessel was raised to 52 ° C., polymerization was carried out while maintaining this temperature, and after 4 hours, the internal temperature was raised to 65 ° C., and polymerization was continued. Then, the polymerization was stopped when the outside temperature of the polymerization vessel rose to a difference of 1 ° C. from the inside temperature, and the unreacted monomer was recovered to terminate the polymerization. After completion of the polymerization, the obtained slurry was dehydrated and dried to obtain a vinyl chloride polymer.

(Comparative Example 2) Internal volume 2 in which a stirrer and the like were laid
A 2,000 L stainless steel polymerization vessel was charged in the same manner as in Comparative Example 1, and after the temperature in the polymerization vessel was raised to 57 ° C., polymerization was performed while maintaining this temperature. Then, the polymerization was stopped when the outside temperature of the polymerization vessel rose to a difference of 1 ° C. from the inside temperature, and the unreacted monomer was recovered to terminate the polymerization. After completion of the polymerization, the obtained slurry was dehydrated and dried to obtain a vinyl chloride polymer.

(Comparative Example 3) Internal volume 2 in which a stirrer and the like were laid
A 2,000-L stainless steel polymerization vessel was charged in the same manner as in Comparative Example 1. After the temperature in the polymerization vessel was raised to 58 ° C., polymerization was performed while maintaining this temperature. Then, the polymerization was stopped when the outside temperature of the polymerization vessel rose to a difference of 1 ° C. from the inside temperature, and the unreacted monomer was recovered to terminate the polymerization. After completion of the polymerization, the obtained slurry was dehydrated and dried to obtain a vinyl chloride polymer.

The average degree of polymerization, gelation time, and acetone-soluble content of the four resins obtained as described above were measured.
The gelation time mentioned above was measured under the conditions of Table 1 using Labo Plastmill 20C-200 manufactured by Toyo Seiki Co., Ltd.

[0024]

[Table 1]

The measurement of the acetone-soluble matter referred to above means that acetone readily dissolves a component having a low degree of polymerization among PVC-based resins. Is a method of measuring the ratio of a PVC-based resin dissolved in acetone. For a resin having the same average degree of polymerization, a resin having a higher acetone-soluble content than the other has a higher content of a lower polymerization degree component. Specifically, about 1 g of a sample is weighed in a 50 ml Erlenmeyer flask, and 50 ml of acetone is added. A condenser is attached to the Erlenmeyer flask and heated in a warm bath at 50 ° C. for 2 hours. After 2 hours, the acetone-soluble matter is separated and concentrated.
Dry and weigh.

[0026]

[Table 2]

From Table 2, the acetone-soluble matter is first compared between Example and Comparative Example 1. As a result of this test, Example 1
It can be seen that, compared to Comparative Example 1, there are more low polymerization degree components and the polymerization degree distribution is broad. Next, the plasticization time is compared between the example and the comparative example 1. Since the gelation time is greatly affected by the average polymerization degree, vinyl chloride polymers differing only in the average polymerization degree were prepared by adjusting the polymerization conditions and changing only the polymerization temperature (Comparative Examples 2 and 3). Then, the degree of reduction in the gelation time due to the change in the polymerization method was calculated by comparing the example having the same degree of polymerization with Comparative Example 2 and Comparative Example 1 and Comparative Example 3, and comparing which was able to be reduced more.

As a result, in the example, the gel time was 67%.
In contrast, in Comparative Example 1, the gel time was reduced to 83%. From this result, it can be seen that the example can produce a resin having a shorter gelation time than the comparative example 1.

[0029]

As described above, according to the method for producing a vinyl chloride polymer of the present invention, a resin having a low degree of polymerization and a short gelation time can be produced.

Claims (3)

[Claims] Claims: 1. Using a vinyl chloride resin polymerized by an ordinary method as a seed resin, adding pure water, a dispersant, an initiator, a vinyl chloride monomer and the like, and performing repolymerization by suspension polymerization. A method for producing a vinyl chloride polymer produced using a step polymerization method. 2. The method for producing a vinyl chloride polymer according to claim 1, wherein the repolymerization is performed so that the ratio of the seed resin to the whole polymer exceeds 50 wt%. 3. The vinyl chloride polymer according to claim 1 or 2, wherein the average polymerization degree of the seed resin is 1000 to 3000, and the polymerization conditions at the time of repolymerization are the polymerization degree of the vinyl chloride resin having an average polymerization degree of 400 to 1000. A vinyl chloride polymer characterized by the same conditions.