JPH05247105A - Method for suspension polymerization of vinylic monomer - Google Patents

Abstract

(57) [Summary] [Purpose] A high-quality vinyl-based polymer that can significantly shorten the polymerization time for one batch, has a small number of fish eyes, and has good plasticizer absorbability and demonomerization over a wide range of grades. To develop a suspension polymerization method that can obtain coalescence. [Structure] (a) Heating water medium at 40 ° C. or higher, and (b)
This is a suspension polymerization method of a vinyl monomer (for example, vinyl chloride) in which a dispersion aid composed of a polyvinyl ester polymer having a saponification degree of 60 mol% or less and an average polymerization degree of 1000 or more is introduced into a polymerization reaction system.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improved suspension polymerization method for vinyl monomers. More specifically, the polymerization time for one batch can be greatly shortened, and high productivity and high quality vinyl can be obtained. The present invention relates to a suspension polymerization method capable of obtaining a system polymer.

[0002]

Suspension polymerization of vinyl-based monomers such as vinyl chloride-based monomers is usually carried out in a batch system, and an aqueous medium and a dispersant (suspended) are placed in a polymerization vessel. In general, a turbidity agent), a polymerization initiator, a vinyl chloride-based monomer and the like are charged, and after necessary additives are added, the temperature is raised to carry out the polymerization reaction. But,
In order to improve the productivity, it is required to shorten the time required for one batch of polymerization. For that purpose, it is necessary to shorten the heating time as well as the charging time and the reaction time. is there. Particularly, in a large-sized polymerization vessel or a polymerization vessel with a condenser, the heating capacity of the jacket or the like is relatively small compared to the internal volume, so it was necessary to develop a more effective temperature raising method. For this reason, in suspension polymerization of vinyl chloride-based monomers, a method has been used in which a preheated aqueous medium is charged to eliminate the heating time and improve the productivity.
However, when such a method is used, the obtained vinyl chloride-based resin has a fatal drawback that it has many fish eyes and has poor plasticizer absorbability and demomerization property.

Further, JP-A-56-167745 discloses that the degree of saponification is 65 mol% or more and the average degree of polymerization is 100 to 30.
Polyvinyl alcohol of 00 is used as a dispersant, and saponification degree is 2
Disclosed is an aqueous dispersion containing 0 to 65 mol% and a polyvinyl ester having an average degree of polymerization of 1000 or less as a dispersoid.
In addition, there is a statement that the aqueous dispersion can be used as a dispersion aid for suspension polymerization of vinyl chloride, but no consideration is given from the viewpoint of shortening the polymerization time. others,
In WO91 / 15518, the saponification degree is 60 mol% or less,
It is disclosed that an aqueous dispersion containing a terminal ionic group-modified polyvinyl ester polymer having an average degree of polymerization of 50 to 3000 as a dispersoid is used as a dispersion aid for suspension polymerization of vinyl monomers such as vinyl chloride. ing. According to this technique, vinyl polymer particles having a sharp particle size distribution, a high packing specific gravity and good plasticizer absorbency can be obtained, but no consideration has been made from the viewpoint of shortening the polymerization time and the like. ..

[0004]

[Means for Solving the Problems] Under such circumstances,
The present inventors have conducted extensive studies to overcome the above problems. As a result, when suspension-polymerizing a vinyl-based monomer such as vinyl chloride, a polyvinyl ester-based polymer having a saponification degree of 60 mol% or less and an average polymerization degree of 1000 or more is added to a polymerization reaction system along with a heated aqueous medium. It was found that all the above problems can be solved by introducing a dispersion aid consisting of The present invention has been completed based on these findings.

That is, in the present invention, in suspension-polymerizing a vinyl-based monomer, (a) a heating aqueous medium at 40 ° C. or higher and (b) a saponification degree of 60 mol% or less and an average degree of polymerization of 1000.
It is intended to provide a suspension polymerization method for a vinyl-based monomer, which comprises introducing the above-mentioned dispersion aid comprising a polyvinyl ester-based polymer (PVES-based polymer) into a polymerization reaction system.

In the polymerization reaction system of the present invention, (a) the heated water medium and (b) the dispersion aid are introduced into the polymerization reaction system. The heating water medium (a) used here has a temperature of 40 ° C. or higher. The upper limit of this temperature is not particularly limited, and hot water of 95 ° C. or higher may be used. If the temperature of the heated water medium is less than 40 ° C, the polymerization reaction system cannot be sufficiently heated in a short time, and the object of the present invention cannot be achieved. The medium constituting the (a) heated water medium is not limited to pure water, but is used for suspension polymerization of vinyl-based monomers such as an aqueous solution containing various additive components or an aqueous medium containing other organic solvent. A variety of aqueous media can be mentioned as long as they do not interfere. The amount of (a) the heating water medium to be introduced when it is introduced into the polymerization reaction system may be appropriately determined depending on various situations as long as it can sufficiently heat the polymerization reaction system.

Next, the dispersion aid (b) has a degree of saponification of 60 mol% or less, preferably 40 mol% or less, more preferably 20 mol% or less, and particularly preferably 0 to 5 mol% PV.
It is composed of an ES polymer. Also, this PVES
The average degree of polymerization of the system polymer is 1000 or more, preferably 4000 or more, and more preferably 7000 or more. Further, as the vinyl ester unit constituting the PVES polymer, there are units derived from various vinyl ester compounds, such as vinyl acetate, vinyl formate,
Vinyl ester units derived from vinyl propionate, vinyl butyrate, vinyl isobutyrate, vinyl pivalate, vinyl caprylate, vinyl versatate and the like can be mentioned. Among these vinyl ester units, vinyl acetate units are industrially used. Is preferred. As the dispersion aid (b), it is particularly effective to use it in the form of an aqueous dispersion containing the above PVES polymer as a dispersoid. The average particle size of the dispersoid is usually 100 μm or less, preferably 30 μm or less, more preferably 10 μm.
Or less, more preferably 2 μm or less, and further preferably 1
It is not more than μm, most preferably not more than 0.5 μm.

Here, P constituting the above-mentioned (b) dispersion aid
The average degree of polymerization of the VES-based polymer is obtained by completely saponifying the PVES-based polymer, acetylating it to polyvinyl acetate, and then calculating the viscosity average from the intrinsic viscosity number in an acetone solution at 30 ° C. according to the following equation. It is represented by the degree of polymerization (P). P = ([η] × 10 ³ /7.94) ^{(1 / 0.62)} Also, the degree of saponification means the degree of saponification of the vinyl ester component, and when other components are copolymerized, the component is Not included. The degree of saponification can be analyzed by a conventionally known chemical analysis method, nuclear magnetic resonance analysis method, or the like. Further, the average particle size of the dispersoid is measured by a sieving method when measured as a solid, and a light transmission type particle size distribution analyzer when measured as an aqueous dispersion,
It is measured using a sedimentation type particle size distribution analyzer or a dynamic light scattering particle size distribution analyzer.

In order to produce the (b) dispersion aid (PVS) polymer of the present invention, any of the known methods such as bulk polymerization, solution polymerization, suspension polymerization, emulsion polymerization and dispersion polymerization can be used. Although it can be adopted, industrially, solution polymerization,
Emulsion polymerization and dispersion polymerization are preferred. Further, as the polymerization process, it is possible to manufacture by any of batch process, semi-batch process and continuous process. When the PVES polymer of the present invention is a partially saponified product, a polyvinyl ester can be saponified to obtain a PVES polymer.
Specifically, a generally known method, that is, alkali saponification,
Although either acid saponification can be adopted, industrially, methanol decomposition using a sodium solvent as a catalyst with sodium hydroxide or sodium methoxide is most advantageous. The saponification temperature is not particularly limited, but it is preferably 20 to 60 ° C. from the viewpoint of preventing coloration of the obtained PVES polymer. The amount of sodium hydroxide or sodium methoxide used as a catalyst is usually 1 mol of vinyl ester unit.
The amount of 0.2 mol or less is preferable from the viewpoints of preventing coloration of the PVES-based polymer obtained and suppressing the amount of sodium acetate to a low level.

Further, (b) PV which is the dispersion aid of the present invention
The ES polymer is preferably a dispersoid having an average particle size of 100 μm or less in the aqueous dispersion as described above, but any method may be used for its production. For example, a method in which an aqueous dispersion obtained by suspension polymerization, emulsion polymerization, or dispersion polymerization is used as it is or a method in which these are saponified in a slurry state as an aqueous dispersion is possible.
In addition, once a PVES polymer or partially saponified PVE
After isolation as an S-based polymer, a method of mechanically pulverizing with a jet mill or the like, an ionic or nonionic surfactant, or a generally known polyvinyl alcohol (PVA) or the like is used to reduce the performance of the present invention. A method of obtaining an aqueous dispersion liquid having an average particle diameter of 100 μm or less is possible by adding it to the extent that it is not allowed. Further, a method in which the above PVES polymer is isolated once and dissolved with a generally known dispersion stabilizer is also possible. The PVES polymer of the present invention does not prevent inclusion of ionic groups, hydrophilic groups and lipophilic groups in the molecule in an amount of 10 mol% or less. There is no particular limitation on the concentration of the aqueous dispersion.

In the method of the present invention, the use of a dispersion stabilizer is effective in smoothly proceeding the polymerization reaction. Here, the dispersion stabilizer may be one normally used when polymerizing vinyl monomers such as vinyl chloride in an aqueous medium, and examples thereof include methyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, hydroxypropyl methyl cellulose and the like. Water-soluble cellulose ether, partially saponified polyvinyl alcohol (saponification degree 6
0-95 mol%, average degree of polymerization of 500 or more), acrylic acid polymer, water-soluble polymer such as gelatin, sorbitan monolaurate, sorbitan trioleate, glycerin tristearate, oil-soluble emulsifier such as ethylene oxide propylene oxide block copolymer, Examples include water-soluble emulsifiers such as polyoxyethylene sorbitan monolaurate, polyoxyethylene glycerin oleate, and sodium laurate, and these are added alone or in combination of two or more. The amount added is preferably 0.03 to 0.15 part by weight per 100 parts by weight of the vinyl-based monomer.

As described above, the suspension polymerization method of the present invention uses a heating aqueous medium of 40 ° C. or higher at the time of introduction into the polymerization reaction system, that is, at the time of charging, and the vinyl-based monomer and the polymerization initiator are used. The order and ratio of the dispersion stabilizer, the heating water medium and the other additives are not limited.

As various additives used as necessary in the present invention, acetaldehyde, butyraldehyde, trichloroethylene, perchlorethylene, mercaptans and other polymerization degree regulators, phenol compounds, sulfur compounds, N-oxide compounds, etc. Polymerization inhibitors, etc. Further, it is optional to add a pH adjuster, a scale inhibitor, a cross-linking agent, etc., and a plurality of the above additives may be used in combination. It is also effective to attach a condenser such as a condenser to the polymerization device. On the other hand, the polymerization initiator may also be one that has been conventionally used for the polymerization of vinyl-based monomers such as vinyl chloride, which includes diisopropyl peroxydicarbonate, di-2-ethylhexyl peroxydicarbonate and diethoxyethyl. Percarbonate compounds such as peroxydicarbonate, perester compounds such as t-butylperoxyneodecanate, α-cumylperoxyneodecanate, acetylcyclohexylsulfonyl peroxide, 2,4,4-trimethylpentyl-2- Examples thereof include peroxides such as peroxyphenoxyacetate and azo compounds such as azobis-2,4-dimethylvaleronitrile and azobis (4-methoxy-2,4-dimethylvaleronitrile). Further, these may be used in combination with potassium persulfate, ammonium persulfate, hydrogen peroxide and the like. This addition amount is 0.02 to 0.1 per 100 parts by weight of the vinyl-based monomer.
A range of 3 parts by weight is preferred.

The vinyl-based monomer to be polymerized by the method of the present invention includes vinyl chloride alone and a monomer mixture mainly composed of vinyl chloride (vinyl chloride 50% by polymerization or more). Comonomers to be copolymerized with vinyl acetate, vinyl propionate and other vinyl esters, methyl acrylate, ethyl acrylate and other acrylate or methacrylic acid esters, ethylene, propylene and other olefins, maleic anhydride, acrylonitrile, Examples thereof include itaconic acid, styrene, vinylidene chloride, vinyl ether, and other vinyl chloride copolymerizable monomers. Furthermore, the method of the present invention can also be applied to homopolymerization or copolymerization of the above vinyl compound containing no vinyl chloride.

In carrying out the method of the present invention, the charging ratio of each component, the polymerization temperature, etc. are determined according to the conditions conventionally used in the suspension polymerization of vinyl monomers such as vinyl chloride. It is sufficient, and it should not be particularly limited.

[0016]

The present invention will be described in more detail with reference to the following examples, but the method of the present invention is not limited to these examples. In the following examples, "part" means "part by weight". Examples 1 to 12 and Comparative Example 1 Suspension polymerization of vinyl chloride was carried out by the following method using the dispersion stabilizer and the dispersion aid shown in Table 1. That is, in a glass-lined autoclave, a predetermined amount of a 2 wt% aqueous solution of a dispersion stabilizer (PVA) shown in Table 1, a predetermined amount of a 2 wt% aqueous solution of a dispersion aid (polyvinyl acetate), and 50 parts of diisopropyl peroxydicarbonate were used. Charge 0.009 parts by weight of toluene solution, and set 50 mm inside the autoclave.
After degassing to Hg to remove oxygen, 30 parts of vinyl chloride monomer and 45 parts of deionized water heated to 63 ° C. were charged, and polymerization was carried out with stirring. Inner temperature after preparation is 5
It was 7 ° C. At the start of polymerization, the pressure inside the autoclave is
It was 8.5 kg / cm ² G, but 7 hours after the start of polymerization, 4.
Since the amount was 5 kg / cm ² G, the polymerization was stopped at this point, the unreacted vinyl chloride monomer was 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 performance of this vinyl chloride resin is shown in Table 1.

[0017]

[Table 1]

[0018]

[Table 2]

(1) Average particle diameter It was measured by dry sieve analysis using a wire mesh based on Tyler mesh. (2) Fisheye measurement method 100 parts by weight of vinyl chloride resin obtained by polymerization, 1 part by weight of tribasic lead sulfate, 1.5 parts by weight of lead stearate, 0.2 parts by weight of titanium dioxide, 0.1 parts of carbon black. 25 g of a composition obtained by mixing 50 parts by weight of dioctyl phthalate
Was kneaded with a roll at 145 ° C. for 5 minutes and separated as a 0.2 mm thick sheet, and the number of transparent particles in 100 cm ² of this sheet was shown. (3) Absorption of plasticizer In a planetary mixer connected to a plastograph,
Add 400 g of vinyl chloride resin powder obtained by polymerization, preheat (4 minutes) while stirring at 60 rpm, and heat at 80 ° C.
After that, 200 g of dioctyl phthalate was added thereto, and the time was defined as the plasticizer absorbability (minutes) until the time when the torque decreased due to the addition. (4) Residual vinyl chloride monomer The vinyl chloride monomer content in the vinyl chloride resin was quantified by headspace gas chromatography. (5) The average particle size of the dispersion aid is measured by Otsuka Electronics Co., Ltd.
Made: ELS-800 (when less than 1 μm) or Horiba Co., Ltd .: CAPA-700 (when 1 to 30 μm) or Seishin Enterprise Co., Ltd .: SKC-2000S (30
(when larger than μm) was used.

[0020]

As described above, according to the present invention, the polymerization time for one batch can be greatly shortened, and moreover, various types of grades have little fish eyes, good plasticizer absorbability and good demonomer property. A high quality vinyl polymer can be obtained.

Claims (2)

[Claims] 1. When suspension-polymerizing a vinyl-based monomer, (a) a heated aqueous medium at 40 ° C. or higher and (b) a polyvinyl ester-based polymer having a saponification degree of 60 mol% or less and an average polymerization degree of 1000 or more. A method for suspension polymerization of a vinyl-based monomer, which comprises introducing a dispersion aid into the polymerization reaction system. 2. The suspension polymerization method according to claim 1, wherein the dispersion aid is an aqueous dispersion.