JPH08259609A - Dispersion stabilizer for suspension polymerization of vinylic compound - Google Patents

Abstract

PURPOSE: To obtain a dispersion stabilizer for suspension polymerization of vinylic compound composed of a specific modified PVA, capable of readily controlling polymerization temperature, excellent in defoaming effect, capable of providing a polymer having a sharp size distribution, having a large packing specific gravity and large absorption rate of a plasticizer and good processability. CONSTITUTION: This dispersion stabilizer for suspension polymerization of vinylic compound comprises (A) a modified water-soluble or water-dispersible PVA- based polymer having 1-24mol.% ethylene unit content and >=80% saponification degree and having sulfonic acid group, amino group, ammonium group, carboxyl group or cation group or further preferably comprises mixing the component A with (B) a PVA-based polymer having 60-95% saponification degree and >=600 polymerization degree in a weight ratio of the component A/B of (1/9) to (8/2).

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a dispersion stabilizer for suspension polymerization of vinyl compounds. More specifically, it relates to a dispersion stabilizer for suspension polymerization of vinyl compounds such as vinyl chloride, which has an excellent antifoaming effect.

[0002]

2. Description of the Related Art When a vinyl polymer such as a vinyl chloride resin is industrially produced, a vinyl compound such as vinyl chloride is dispersed in an aqueous medium in the presence of a dispersion stabilizer to obtain an oil-soluble catalyst. Suspension polymerization in which polymerization is carried out using is widely used. 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. Among them, 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 that it has the function of making the particle size distribution of the resulting vinyl polymer particles as sharp as possible, and increases the absorption rate of the plasticizer. Each polymer particle is made porous to facilitate processability, facilitate removal of monomers such as vinyl chloride remaining in the polymer particle, and prevent formation of fish eyes in the molded product. And 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 and the like have been used alone or in combination. However,
The conventional dispersion stabilizers have a problem that they do not satisfy the above required performances.

Suspension polymerization of vinyl compounds such as vinyl chloride is usually carried out in a batch system, and an aqueous medium, a dispersion stabilizer, a polymerization initiator, a vinyl compound and the like are charged in a polymerization vessel and further required. After adding the additive, it is common to raise the temperature to carry out the polymerization reaction. Recently, in order to improve productivity, it is required to shorten the time required for one batch of polymerization, and in the suspension polymerization of vinyl compounds, a reflux condenser or the like may be installed to improve the heat removal efficiency of the polymerization heat. A method of shortening the temperature rising time by a method of charging a preheated aqueous medium (hot charging method) is used. However, when a conventional dispersion stabilizer for suspension polymerization of vinyl-based compounds is used, the foaming during the polymerization is severe, so the effective volume in the polymerization vessel decreases and the productivity decreases, and the reflux condenser is used. There was a fatal defect that the temperature could not be controlled by using the attached polymerization vessel, and the porosity of the vinyl polymer particles was lowered by using the hot charge method. On the other hand, when an antifoaming agent or the like is added to prevent foaming, there is a problem that the thermal stability of the vinyl polymer particles produced is lowered.

Japanese Patent Application Laid-Open No. 01-95104 [Publication (a)] discloses a suspension polymerization of vinyl chloride having an saponification degree of 40 mol% or less and an ethylene / vinyl ester copolymer having an ionic group in a side chain. Dispersion aids are described.
However, when the dispersion aid described in the known document (a) is used alone, the stability of suspension polymerization of vinyl compounds cannot be ensured. Further, when the dispersion aid is used in combination with a conventional partially saponified polyvinyl alcohol, there is a problem that the foamability in the polymerization vessel with the reflux condenser is severe. Japanese Patent Laid-Open No. 03-140
No. 303 [Publication (b)] shows that the degree of saponification is 40 mol%.
A dispersion stabilizer for suspension polymerization of vinyl chloride is described which is composed of an ethylene / vinyl ester copolymer having an ionic group in a side chain at a ratio of greater than 80 mol%. However, when the dispersion stabilizer described in the known document (b) is used, the above-mentioned required performances 1 to 4 are satisfied, but there is a problem that the foamability in the polymerization vessel with the reflux condenser is severe.

[0006]

DISCLOSURE OF THE INVENTION An object of the present invention is to use a conventional general suspension polymerization method for vinyl compounds, that is, a method for charging an aqueous medium at room temperature into a polymerization vessel (cold charge method) and the inside of the polymerization vessel. The defoaming effect in the polymerization vessel is remarkable not only in the method of controlling the polymerization temperature by using the jacket or coil, but also in the method of using a polymerization vessel with a condenser, the hot charging method and the hot charging method using a polymerization vessel with a condenser. An object of the present invention is to provide a dispersion stabilizer which is excellent and simultaneously satisfies the above required properties.

[0007]

As a result of intensive studies to solve the above-mentioned problems, the present inventors have found that modified polyvinyls having an ethylene unit content of 1 to 24 mol% and a saponification degree of more than 80 mol%. Dispersion stabilizer for suspension polymerization of vinyl compound consisting of alcohol (A) (hereinafter abbreviated as the first invention); the modified polyvinyl alcohol (A) further contains sulfonic acid group, amino group, ammonium group, carboxyl group or A dispersion stabilizer for suspension polymerization of a water-soluble or water-dispersible vinyl compound having a cationic group (hereinafter abbreviated as the second invention); and the modified polyvinyl alcohol (A) and a saponification degree of 60 to 95 mol%. And a polyvinyl alcohol-based polymer (B) having a degree of polymerization of 600 or more
The weight ratio of (A) component / (B) component is 1/9 to 8/2.
The inventors have found a dispersion stabilizer for suspension polymerization of vinyl compounds (hereinafter abbreviated as the third invention), which is obtained by mixing the above components in a ratio of (3) to complete the present invention. That is, when the dispersion stabilizer of the present invention is used, a method of charging an aqueous medium at room temperature, which is a conventional general suspension polymerization method for vinyl compounds, into a polymerization vessel (cold charge method) and a polymerization vessel The defoaming effect in the polymerization vessel is remarkable not only in the method of controlling the polymerization temperature by using the jacket or coil, but also in the method of using a polymerization vessel with a condenser, the hot charging method and the hot charging method using a polymerization vessel with a condenser. They have found that they are excellent and simultaneously satisfy the required properties (1) to (3), and have completed the present invention.

First, the first invention will be described. The modified polyvinyl alcohol (A) of the present invention has a saponification degree of more than 80 mol%, preferably 88 to 99 mol%, and more preferably 92 to 98 mol%. The content of ethylene units is 1 to 24 mol%, preferably 1.5 to 1
It is 5 mol%, more preferably 2 to 9 mol%. Although the degree of polymerization is not particularly limited, it is preferably 3500 or less.

The modified polyvinyl alcohol (A) in the present invention is obtained by saponifying a copolymer of vinyl ester and ethylene. Examples of vinyl esters include vinyl formate, vinyl acetate, vinyl propionate, vinyl pivalate, and the like, with vinyl acetate being most preferred.

Further, modified polyvinyl alcohol (A)
May be a copolymer of ethylenically unsaturated monomers copolymerizable within a range that does not impair the effects of the present invention. Examples of such ethylenically unsaturated monomers include acrylonitrile, methacrylonitrile, ethyl vinyl ether, butyl vinyl ether, N-vinylpyrrolidone, vinyl chloride, vinyl bromide, vinyl fluoride, vinylidene chloride, vinylidene fluoride, And tetrafluoroethylene. In the presence of a thiol compound such as thiol acetic acid, a vinyl ester-based monomer such as vinyl acetate is copolymerized with ethylene to saponify it.
A terminal modified product obtained by a conventionally known method can also be used.

Next, the second invention of the present invention will be described.
Modified polyvinyl alcohol (A) used in the second invention
Is water-soluble or water-dispersible and is obtained by introducing a sulfonic acid group, an amino group, an ammonium group, a carboxyl group or a cation group into the modified polyvinyl alcohol (A) of the first invention. The modified amount of the ionic group is 0.
01 mol% to 10 mol% is preferable. The method for modifying the ionic group is not particularly limited, but it can be obtained by copolymerizing a monomer containing an ionic group with ethylene and a vinyl ester monomer. Further, the partially saponified product of the copolymer can be obtained by partially saponifying the copolymer by a known method.

The polymerizable monomer having a sulfonic acid group used in the present method is not particularly limited, but for example, ethylene sulfonic acid, (meth) allyl sulfonic acid,
Examples thereof include sulfonic acid-containing monomers such as sulfoalkyl maleates, sulfoalkyl (meth) acrylamides, sulfoalkyl (meth) acrylates, and acrylamido-2-methylpropanesulfonic acid, and salts thereof.

As the amino group and ammonium group, for example, N- (1,1-dimethyl-3-dimethylaminopropyl) (meth) acrylamide, N- (1,
1-dimethyl-3-dimethylaminobutyl) (meth) acrylamide, N-vinylimidazole, 2-methyl-N-vinylimidazole, vinyl-3-dimethylaminopropyl ether, vinyl-2-dimethylaminoethyl ether, allyl-3-dimethylaminopropyl ether, allyl Examples thereof include dimethylamine, methallyldimethylamine, and quaternized monomers thereof.

The carboxyl group is, for example,
Examples thereof include crotonic acid, maleic acid, fumaric acid, itaconic acid, (meth) acrylic acid, and the like.

Further, a vinyl ester type monomer such as vinyl acetate is copolymerized with ethylene in the presence of a thiol compound such as thiolacetic acid or mercaptopropionic acid, and then saponified to obtain a conventionally known method. The end-modified product obtained can also be used.

Next, the third invention of the present invention will be explained.
The modified polyvinyl alcohol (A) used in the third invention is the same as the modified polyvinyl alcohol (A) used in the first invention or the second invention. The degree of saponification of the polyvinyl alcohol-based polymer (B) in the third invention is 60 to 95 mol% and is 65 to 8
8 mol% is preferable, and 68 to 82 mol% is more preferable. The degree of polymerization of the polyvinyl alcohol polymer (B) is 600 or more, more preferably 650 to 3500, even more preferably 680 to 2500.

Weight ratio of component (A) and component (B) (A) /
(B) is 1/9 to 8/2, more preferably 3/7 to 7/3, and even more preferably 6/4 to 6/4.

In the present invention, the polyvinyl alcohol polymer (B) is used as the dispersion stabilizer of the first invention or the second invention.
A form in which is used together is also called a dispersion stabilizer. The method for producing the polyvinyl alcohol polymer (B) of the present invention is not particularly limited, and conventionally known ones are preferably used.

Next, a method for producing a vinyl polymer by suspension polymerization of a vinyl compound using the dispersion stabilizers of the first to third inventions will be described. The temperature of the aqueous medium used in the method for producing a vinyl polymer is not particularly limited and may be 20
Not only cold water at about 0 ° C but also warm water at 90 ° C or higher is preferably used. Examples of the medium constituting the heated aqueous medium include pure water, an aqueous solution containing various additive components, and an aqueous medium containing other organic solvent. Further, the supply amount when charging the heating aqueous medium to the polymerization reaction system,
The amount may be such that the polymerization reaction system can be sufficiently heated. Further, a polymerization vessel with a reflux condenser is also preferably used in order to enhance the heat removal efficiency. In the method for producing a vinyl polymer, the amount of the dispersion stabilizer used is not particularly limited, but is usually 5 parts by weight or less, preferably 0.01 to 1 part by weight, and 0 to 100 parts by weight of the vinyl compound. .02-0.2
Even more preferred are parts by weight. Although the dispersion stabilizer of the present invention may be used alone, methyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, hydroxypropyl methyl cellulose usually used in suspension polymerization of vinyl compounds such as vinyl chloride in an aqueous medium. Water-soluble cellulose ether such as, water-soluble polymer such as gelatin, sorbitan monolaurate, sorbitan trioleate, glycerin tristearate, oil-soluble emulsifier such as ethylene oxide propylene oxide block copolymer, polyoxyethylene sorbitan monolaurate, polyoxyethylene Glycerin oleate,
You may use together water-soluble emulsifiers, such as sodium laurate. The amount of addition is not particularly limited, but it is 0. 0 per 100 parts by weight of vinyl compound such as vinyl chloride.
01 to 1.0 parts by weight is preferable. It is also possible to add 1 to 100 parts by weight of a so-called polyvinyl ester dispersion aid having a saponification degree of less than 60 mol% to 100 parts by weight of the dispersion stabilizer of the present invention. In this case, the dispersion aid may be unmodified or may have an ionic group such as a carboxyl group in its side chain or terminal at 10 mol% or less.

Various other additives can be added as required. Examples of the various additives include polymerization degree regulators such as acetaldehyde, butyraldehyde, trichloroethylene, perchloroethylene or mercaptans, and polymerization inhibitors such as phenol compounds, sulfur compounds and N-oxide compounds. Further, it is optional to add a pH adjuster, a scale inhibitor, a cross-linking agent and the like, and a plurality of the above-mentioned additives may be used in combination.
On the other hand, the polymerization initiator may also be one conventionally used for the polymerization of vinyl compounds such as vinyl chloride, and examples thereof include diisopropyl peroxydicarbonate and di-2-
Percarbonate compounds such as ethylhexyl peroxydicarbonate and diethoxyethyl peroxydicarbonate, t-butyl peroxyneodecanate, α-
Perester compounds such as cumyl peroxyneodecanate and t-butyl peroxyneodecanate, acetylcyclohexylsulfonyl peroxide, 2,4,4-
Peroxides such as trimethylpentyl-2-peroxyphenoxyacetate, 2,2'-azobisisobutyronitrile, azobis-2,4-dimethylvaleronitrile,
Examples thereof include azo compounds such as azobis (4-methoxy-2,4-dimethylvaleronitrile), and these can also be used in combination with potassium persulfate, ammonium persulfate, hydrogen peroxide and the like.

The vinyl compound which can be suspension-polymerized by using the dispersion stabilizer of the present invention is specifically vinyl chloride alone or a monomer mixture containing vinyl chloride as a main component (vinyl chloride 50% by weight). % Or more) and as a comonomer to be copolymerized with this vinyl chloride, vinyl acetate, vinyl ester such as vinyl propionate, and (meth) acrylic acid such as methyl (meth) acrylate and ethyl (meth) acrylate can be used. Examples thereof include esters, olefins such as ethylene and propylene, maleic anhydride, acrylonitrile, itaconic acid, styrene, vinylidene chloride, vinyl ether, and other monomers copolymerizable with vinyl chloride. Furthermore, the dispersion stabilizer of the present invention can be used even in homopolymerization or copolymerization of the above vinyl compound containing no vinyl chloride. In carrying out suspension polymerization using the dispersion stabilizer of the present invention, the charging ratio of each component, the polymerization temperature, etc. may be determined according to the conditions conventionally used in suspension polymerization of vinyl compounds such as vinyl chloride. Good.
Further, the order and ratio of the vinyl compound, the polymerization initiator, the dispersion stabilizer, the heated aqueous medium and the other additives are not limited at all. Further, a method in which hot water is used and at the same time the vinyl compound is heated before charging the vinyl compound into the polymerization vessel is also suitably used.

[0022]

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, "%" and "part" are "% by weight" unless otherwise specified.
And "parts by weight".

Reference Example (Production of ethylene-modified PVA) 50 kg of vinyl acetate and 9.2% of methanol in a 100 L pressure reaction tank equipped with a stirrer, a nitrogen inlet, an ethylene inlet and an initiator inlet.
After charging kg, the temperature was raised to 60 ° C., and then the system was replaced with nitrogen by nitrogen bubbling for 30 minutes. Next, the reactor pressure is 6
Ethylene was introduced and charged so as to be kg / cm ² . A 2,4′-azobis (4-methoxy-2,4-dimethylvaleronitrile) solution as an initiator was dissolved in methanol to prepare a 1.4 g / L concentration solution, which was bubbled with nitrogen gas to substitute nitrogen. After adjusting the temperature inside the reaction tank to 60 ° C., 56 mL of the above initiator solution was injected to start polymerization. During the polymerization, ethylene was introduced to increase the reactor pressure to 6 k.
The polymerization temperature was maintained at 60 ° C. at g / cm ² , and the above initiator solution was continuously added at 180 mL / hr. After 6 hours, when the degree of polymerization reached 40%, the polymerization was stopped by cooling.
The reaction vessel was opened to remove ethylene, and nitrogen gas was bubbled to completely remove ethylene. Then, the unreacted vinyl acetate monomer was removed under reduced pressure to obtain a methanol solution. The molar ratio of the solution adjusted to 20% (the number of moles of NaOH /
Saponification was carried out by adding a methanol solution of NaOH (molar number of polyvinyl acetate) 0.045 (10% concentration). Obtained modified P
The degree of saponification of VA was 94.2 mol%.

Polymerization, a methanol solution of PVAc obtained by removing unreacted vinyl acetate monomer was precipitated in n-hexane, and reprecipitation purification was carried out by dissolving with acetone.
It was dried under reduced pressure at 0 ° C. to obtain purified PVAc. The ethylene modification amount obtained by measuring the alkali consumption of the PVAc is 5.
It was 5 mol%. The above-mentioned methanol solution of PVAc is saponified at an alkali molar ratio of 0.2, then subjected to methanol soxhlet for 3 days, and then dried to obtain purified modified PVA.
I got The average degree of polymerization of the modified PVA is determined according to JIS K
It was 1400 as measured according to 6726.

Examples 1 to 6 and Comparative Examples 1 to 3 (Polymerization of vinyl chloride) In a glass-lined autoclave equipped with a reflux condenser, 1 part of deionized water prepared by dissolving the dispersion stabilizer shown in Table 1 and diisopropyl peroxide. Oxydicarbonate 70% toluene solution 0.0
After charging 4 parts and degassing the inside of the autoclave to 50 mmHg to remove oxygen, 39 parts of warm water at 85 ° C. and 30 parts of vinyl chloride monomer were simultaneously charged under stirring. The liquid level at the end of the charging was 60% above the bottom of the polymerization vessel, and the internal temperature was 57 ° C. After that, the internal temperature was kept at 57 ° C. to continue the polymerization. At the start of the polymerization, the pressure in the autoclave was 7.3 kg / cm ² G, but the polymerization was stopped 6 hours after the start of the polymerization and reached 4.2 kg / cm ² G, and the unreacted vinyl chloride monomer was removed. After purging, the contents were taken out and dehydrated and dried. The polymerization yield of the vinyl chloride polymer was 85%, and the average degree of polymerization was 1050. Polymerization evaluation results and vinyl chloride resin performance evaluation results were evaluated by the following methods, and the results are shown in Table 2.

(1) Absorption of plasticizer In a planetary mixer connected to a plastograph,
Put 400 g of the obtained vinyl chloride polymer powder into 60 r
After preheating (4 minutes) while stirring at pm to 88 ° C., 200 g of dioctyl phthalate was added to this, and the time from the time of addition to the time point when the torque decreased was defined as the plasticizer absorbability (minute). (2) CPA (Cold Plasticizer A)
bsorption: cold plasticizer absorption amount) ASTM-D3
The absorption amount of dioctyl phthalate at 23 ° C. was measured by the method described in 367-75. (3) Evaluation of foaming property At the end of the polymerization, the foaming state in the polymerization vessel was visually observed,
It is indicated by the following symbols. ⊚: No foaming ◯: Bubbles were observed up to a height of 62 to 65% from the bottom of the polymerization vessel. B: Bubbles were observed up to a height of 66 to 70% from the bottom of the polymerization vessel. A: Bubbles were recognized up to a height of 90 to 100% from the bottom of the polymerization vessel. X: Bubbles were recognized up to a height of 100% from the bottom of the polymerization vessel, and the reflux condenser was also clogged with bubbles.

[0027]

[Table 1]

[0028]

[Table 2]

[0029]

The vinyl polymer obtained by suspension polymerization of a vinyl compound, particularly vinyl chloride, using the dispersion stabilizer of the present invention has a sharp particle size distribution and a large packing specific gravity. , The plasticizer has a high absorption rate and good processability, it is easy to remove monomers such as vinyl chloride remaining in the polymer particles, and each polymer particle is porous, so Has less fish eyes. further,
Since the foaming during the polymerization is small, it is easy to control the polymerization temperature and the adhesion of scale due to the foaming is small.

Claims (3)

[Claims] 1. A dispersion stabilizer for suspension polymerization of a vinyl compound, which comprises a modified polyvinyl alcohol having an ethylene unit content of 1 to 24 mol% and a saponification degree of more than 80 mol%. 2. The dispersion stabilizer for suspension polymerization of vinyl compounds according to claim 1, wherein the modified polyvinyl alcohol is water-soluble or water-dispersible having a sulfonic acid group, an amino group, an ammonium group, a carboxyl group or a cationic group. . 3. The modified polyvinyl alcohol (A) according to claim 1 or 2, and the polyvinyl alcohol polymer (B) having a saponification degree of 60 to 95 mol% and a polymerization degree of 600 or more in a weight ratio of (A). Component / (B) component is 1
A dispersion stabilizer for suspension polymerization of a vinyl compound, which is mixed at a ratio of / 9 to 8/2.