JPH06220109A - Dispersion assistant for suspension polymerization of vinyl compound - Google Patents

Abstract

PURPOSE:To obtain a dispersion assistant composed of an aqueous dispersion liquid containing a specific (meth)acrylate polymer and giving porous particles having large diameter, sharp particle size distribution, high packing density and excellent handleability when used in the suspension polymerization of a vinyl compound. CONSTITUTION:The dispersion assistant is an aqueous dispersion liquid containing a (meth)acrylate polymer having an average polymerization degree of >=8,000 and an average particle diameter of <=0.8mum as a dispersoid. Styrenic polymer having similar shape may be used in place of the (meth)acrylate polymer.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dispersion aid for suspension polymerization of vinyl compounds, and more specifically, when the suspension polymerization of vinyl compounds such as vinyl chloride is carried out, the obtained vinyl polymer particles are made porous. The present invention relates to a dispersion aid having excellent ability.

[0002]

2. Description of the Related Art Conventionally, when a vinyl-based polymer such as a vinyl chloride-based resin is industrially produced, the vinyl chloride-based monomer and the like are dispersed in an aqueous medium in the presence of a dispersion stabilizer. A suspension polymerization method in which a vinyl compound is dispersed and polymerization is performed using an oil-soluble catalyst is widely practiced. In general, factors that control the quality of vinyl polymers include polymerization rate, water-monomer ratio, polymerization temperature, type and amount of catalyst, type of polymerization tank, stirring speed or type of dispersion stabilizer. In particular, it is known that the influence of the type of dispersion stabilizer is extremely large.

The performance required of a dispersion stabilizer for suspension polymerization of vinyl compounds is (i) that it has the function of making the particle size distribution of the resulting vinyl polymer particles as sharp as possible, and (ii) plasticity. In order to increase the absorption rate of the agent to facilitate processability, to facilitate the removal of vinyl chloride monomers and the like present in the polymer particles, and to prevent the formation of fish eyes and the like in the molded product. Therefore, it has the function of making each polymer particle as uniform and porous as possible, and (iii) having the function of forming polymer particles having a high filling specific gravity.

Conventionally, as a dispersion stabilizer for suspension polymerization of vinyl compounds, cellulose derivatives such as methyl cellulose and carboxymethyl cellulose, partially saponified polyvinyl alcohol (hereinafter sometimes abbreviated as PVA), etc., are used alone or in combination. It is used. However, the conventional dispersion stabilizer has a low ability to make the vinyl polymer particles porous, has a slow plasticizer absorption rate,
Further, there is a drawback that it is difficult to remove the residual vinyl monomer. In JP-A-56-167745, a polyvinyl alcohol having a saponification degree of 65 mol% or more and an average degree of polymerization of 100 to 3000 is used as a dispersant, and a saponification degree of 20 to 6 is used.
There is described an aqueous dispersion containing 5 mol% and a polyvinyl ester having an average degree of polymerization of 1000 or less as a dispersoid, and it is described that the aqueous dispersion can be used as a dispersion aid for suspension polymerization of vinyl chloride. However, even if this aqueous dispersion was used, the above-mentioned problems were not sufficiently solved, and various problems remained in practical use. In addition, JP-A-1-19860
No. 6 discloses that an aqueous dispersion obtained by previously emulsifying and dispersing poly (meth) acrylic acid ester, polystyrene and the like using PVA as a main dispersant is used for suspension polymerization of a vinyl compound. With this method, it is difficult to reduce the average particle size of the poly (meth) acrylic acid ester having a high degree of polymerization and the polystyrene having a high degree of polymerization, and the porosity of the obtained vinyl polymer particles is improved. However, only those with a low bulk density were obtained. Furthermore, the research group of the inventors of the present invention discloses that in JP-A-4-85303, a polyvinyl ester polymer having a saponification degree of less than 50 mol% and an average polymerization degree of 4000 or more is used as a dispersion aid for suspension polymerization of vinyl compounds. When used as, it was shown that the above (i) to (iii) are satisfied. However, since this dispersion aid is insoluble in water, it is a major obstacle in terms of workability, and although there is some improvement in the packing specific gravity, there is room for further improvement.

[0005]

[Means for Solving the Problems] Under such circumstances,
The present inventors have conducted extensive studies to overcome the above problems and develop a superior dispersion aid for suspension polymerization. As a result, (1) Suspension of vinyl compound consisting of an aqueous dispersion containing a (meth) acrylic acid ester polymer having an average degree of polymerization of 8000 or more and an average particle diameter of 0.8 μm or less as a dispersoid. A dispersion aid for polymerization, and (2) an average degree of polymerization of 8000 or more and an average particle size of 0.8 μ
A dispersion aid for suspension polymerization of vinyl compounds, which comprises an aqueous dispersion containing a styrene-based polymer of m or less as a dispersoid,
The present invention has been completed.

The (meth) acrylic acid ester-based polymer or styrene-based polymer used as the dispersion aid in the present invention has an average degree of polymerization of 8,000 or more, preferably 14
000 or more, more preferably 20000 or more, and particularly preferably 23000 or more. The average particle size of the dispersoid is 0.8 μm or less, preferably 0.7 μm or less, more preferably 0.5 μm or less, and particularly preferably 0.1 μm or less. Here, the average degree of polymerization of the polymer of the dispersion aid is a value measured by using GPC with reference to standard polystyrene. The average particle diameter of the dispersoid is a value measured in the state of the aqueous dispersion using a light transmission type particle size distribution measuring device, a sedimentation type particle size distribution measuring device, a dynamic light scattering particle size distribution measuring device and the like.

The (meth) acrylic acid ester polymer or styrene polymer in the present invention has an average degree of polymerization of 8
Any method may be used as long as it is 000 or more and the average particle diameter is 0.8 μm or less. For example, a method in which an aqueous dispersion obtained by suspension polymerization, emulsion polymerization, or dispersion polymerization is used as it is; or, once isolated as a polymer, mechanically crushed by jet mill crushing; ionic or nonionic It is possible to add a surfactant or the like to such an extent that the effect of the present invention is not reduced to obtain an aqueous dispersion having an average particle size of 0.8 μm or less.

The (meth) acrylic acid ester polymer of the present invention may be a partially hydrolyzed (meth) acrylic acid polymer or (meth) acrylic acid salt polymer. However, the degree of hydrolysis of the (meth) acrylic acid ester unit is preferably not more than 70 mol%. There is no particular limitation on the concentration of the aqueous dispersion.

The constitutional unit of the (meth) acrylic acid ester polymer used in the present invention is, for example, (meth)
Methyl acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, tert- (meth) acrylate
Butylcyclohexyl, amyl (meth) acrylate,
Octyl (meth) acrylate, (meth) acrylic acid 2-
Ethylhexyl, decyl (meth) acrylate, (meth)
Lauryl acrylate, stearyl (meth) acrylate,
Structural units derived from cyclohexyl (meth) acrylate, benzyl (meth) acrylate and the like can be mentioned.

Examples of the structural unit of the styrene-based polymer include structural units derived from styrene, α-methylstyrene, o-chlorostyrene, p-chlorostyrene, vinyltoluene and the like.

In the suspension polymerization of a vinyl compound using the dispersion aid of the present invention, for example, in the case of suspension polymerization of vinyl chloride alone or mainly containing vinyl chloride and a mixture with a monomer copolymerizable therewith, Usually, it is carried out in the presence of an oil-soluble catalyst by adding a dispersion stabilizer to an aqueous medium and dispersing a mixture of vinyl chloride or a monomer copolymerizable therewith. The dispersion stabilizer can be added to the aqueous medium as an aqueous solution or as an aqueous dispersion. In this case, the dispersion aid of the present invention and the dispersion stabilizer may be added separately or after mixing in advance.
The dispersion stabilizer used in combination with the dispersion aid of the present invention is not particularly limited as long as it is a conventionally known dispersant for suspension polymerization of vinyl compounds (or a dispersion stabilizer). Among them, the saponification degree is 60 mol. % And 90 mol% or less and an average degree of polymerization of 500 or more is preferably a PVA polymer. A PVA polymer having a degree of polymerization of 4000 or more is also preferably used. Further, it is also possible to use a conventionally known cellulose derivative. Further, a PVA polymer having a saponification degree of 60 mol% or less, an ion modified product thereof, or a nonion modified product thereof may be used in combination.

The dispersion aid of the present invention has a small fish eye, plasticizer absorbability and desorption property even when a heating aqueous medium of 40 ° C. or higher is charged into the polymerization reaction system for the purpose of shortening the temperature rising time. It is possible to obtain a high-quality vinyl polymer having good monomer properties. The amount of the dispersion aid of the present invention used during suspension polymerization is not particularly limited, but is preferably 0.005 to 5% by weight, more preferably 0.01 to 1% by weight, relative to the vinyl compound which is a polymerization raw material. %, Particularly preferably 0.0
It is 1 to 0.2% by weight. The catalyst used in the suspension polymerization may be any oil-soluble catalyst, for example, benzoyl peroxide, lauroyl peroxide,
Diisopropyl peroxydicarbonate, 2,2'-
Azobisisobutyronitrile, 2,2'-azobis-
2,4-Dimethylvaleronitrile or a mixture thereof is used. The polymerization temperature is generally 30-7.
It is selected from the range of about 0 ° C.

The vinyl compound to be polymerized in the present invention includes not only vinyl chloride but also a monomer mixture mainly containing vinyl chloride (50% by weight or more of vinyl chloride), which is copolymerized with this vinyl chloride. Examples of comonomers include vinyl acetate, vinyl propionate, and other vinyl esters; methyl acrylate, ethyl acrylate, and other acrylic or methacrylic acid esters; ethylene, propylene, and other olefins; maleic anhydride, acrylonitrile, itaconic acid, styrene. , Vinylidene chloride, vinyl ether, and other monomers copolymerizable with vinyl chloride are exemplified. Furthermore, the method of the present invention can also be applied to homopolymerization or copolymerization of the above vinyl compound containing no vinyl chloride. Although the polymerization of vinyl chloride has been mainly described above, the dispersion stabilizer of the present invention is not necessarily limited to the suspension polymerization of vinyl chloride, and is also used for the suspension polymerization of vinyl compounds such as styrene and methacrylate. To be

[0014]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples. In the following examples, "part" means "part by weight"
Indicates.

Examples 1 to 12 and Comparative Examples 1 to 11 Suspension polymerization of vinyl chloride using the components (A) (dispersion aid) and (B) (dispersion stabilizer; PVA) shown in Table 1. Was carried out by the following method. That is, a glass-lined autoclave was charged with 50 parts of deionized water, a predetermined amount of a 2 wt% aqueous solution of a dispersion aid and a dispersion stabilizer shown in Table 1 and 0.009 part of a 50 wt% toluene solution of diisopropyl peroxydicarbonate. After degassing the interior of the autoclave to 50 mmHg to remove oxygen, 40 parts of vinyl chloride monomer was charged, and the temperature was raised to 57 ° C. with stirring to carry out polymerization. At the start of the polymerization, the pressure in the autoclave was 8.5 kg / cm ² G, but it reached 4.5 kg / cm ² G 7 hours after the start of the polymerization, so the polymerization was stopped at this point and the unreacted vinyl chloride was removed. The monomers were purged, the contents were taken out and dehydrated and dried. The vinyl chloride resin obtained had a polymerization yield of 88% and an average degree of polymerization of 1050. The first is the physical properties and amount of the dispersion aid and dispersion stabilizer.
Table 2 shows the performance of the obtained vinyl chloride resin.

[0016]

[Table 1]

[0017]

[Table 2]

[0018]

[Table 3]

[0019]

[Table 4]

Examples 13 to 17 and Comparative Example 12 In addition to the component (A) (dispersion aid) and the component (B) (dispersion stabilizer) shown in Table 3, the component (C) shown in Table 3 is further added. Example 1 except that (used as an aqueous dispersion) was also used.
The suspension polymerization of vinyl chloride was carried out in the same manner as described above. The performance of the obtained vinyl chloride resin is shown in Table 4.

[0021]

[Table 5]

[0022]

[Table 6]

The results in Tables 2 and 4 above were evaluated by the following methods. (1) Average particle size It was measured by dry sieve analysis using a wire mesh based on Tyler mesh. (2) Packing specific gravity It was measured according to JIS K6721-1959. (3) Absorption of plasticizer Using a planetary mixer connected to a plastograph, 100 parts of vinyl chloride resin was placed in a container kept at 75 ° C.
50 parts of dioctyl phthalate was added, the kneading torque was recorded for each time while stirring, and the kneading time at the point where the kneading torque decreased was displayed. (4) Residual vinyl chloride monomer A fixed amount of vinyl chloride resin was quantified using a headspace gas chromatograph to determine the vinyl chloride monomer content in the vinyl chloride resin. (5) The average particle diameter of the dispersion aid is measured by Otsuka Electronics Co., Ltd .: ELS-800 (when less than 1 μm) or Horiba Co., Ltd .: CAPA-700 (when 1 μm or more).
Was used.

[0024]

As is clear from the above description, the dispersion aid of the present invention has a very high ability to make the obtained vinyl polymer particles porous and has a high plastic absorption rate.
Moreover, it exhibits excellent performance such as easy removal of residual vinyl chloride monomer. In addition, the obtained vinyl polymer particles have extremely high packing specific gravity, large particle size, a sharp distribution, little scattering of powder during handling, and good biteability into a molding machine, etc. , Excellent in many ways.

Claims (2)

[Claims] 1. A suspension polymerization of a vinyl compound comprising an aqueous dispersion containing a (meth) acrylic acid ester polymer having an average degree of polymerization of 8000 or more and an average particle size of 0.8 μm or less as a dispersoid. Dispersion aid. 2. A dispersion aid for suspension polymerization of a vinyl compound, which comprises an aqueous dispersion containing a styrene polymer having an average degree of polymerization of 8000 or more and an average particle size of 0.8 μm or less as a dispersoid.