JP2566594B2 - Dispersion stabilizer for suspension polymerization of vinyl compounds - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION A. Field of Industrial Application The present invention relates to a monomer mixture containing a vinyl compound, particularly vinyl chloride or another monomer copolymerizable therewith (hereinafter referred to as vinyl chloride-based monomer collectively). Dispersion stabilizer for use in suspension polymerization of a) in an aqueous medium.

B. Conventional technology When industrially producing a vinyl chloride resin, a suspension polymerization method in which a vinyl chloride monomer is dispersed in an aqueous medium in the presence of a dispersion stabilizer and polymerization is carried out using an oil-soluble catalyst is known. Widely implemented. In general, factors that govern the quality of the resin include a polymerization rate, a water-monomer ratio, a polymerization temperature, a type and amount of a catalyst, a type of a polymerization tank, a stirring speed or a type of a dispersion stabilizer, and the like. It is known that the effect of the type of dispersion stabilizer is very large.

As the performance required for a dispersion stabilizer for suspension polymerization of vinyl chloride-based monomers, (i) it shows a high dispersive power when used in a small amount, and functions to make the particle size distribution of the obtained vinyl chloride-based polymer particles as sharp as possible. And (ii) to increase the absorption rate of the plasticizer to facilitate processability, and to facilitate removal of the vinyl chloride monomer remaining in the polymer particles, and in addition, the filler in the molded product. In order to prevent the formation of polymer particles, 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.

C. Problems to be Solved by the Invention Conventionally, as a dispersion stabilizer for suspension polymerization of vinyl compounds, methylcellulose, cellulose derivatives such as carboxymethyl cellulose, partially saponified polyvinyl alcohol, etc. are used alone or in combination. . However, these have the drawback that the ability to make the vinyl chloride polymer particles porous is low, the plasticizer absorption rate is low, and it is difficult to remove the residual vinyl chloride monomer.

Further, for the purpose of improving these drawbacks, water-insoluble and oil-soluble polyvinyl alcohol having a saponification degree of 60 mol% or less, preferably 25 to 55 mol% (hereinafter, polyvinyl alcohol is abbreviated as PVA) is conventionally known. A method of using together with a dispersant has been proposed. However, the degree of saponification is 60
Although PVA of less than mol% is oil-soluble, it is insoluble in vinyl chloride-based monomers. Probably because of this, although a porous vinyl chloride-based resin can be obtained, there is a fatal drawback that the filling specific gravity tends to decrease. It was

Further, a method of using a copolymer of ethylene and vinyl acetate or a saponified product thereof together with a conventionally known dispersion stabilizer has been proposed. However, in this case as well, there is a drawback in that it is difficult to obtain a vinyl chloride resin that is porous and has a high filling specific gravity.

D. Means for Solving the Problems The present inventors have overcome such drawbacks, and
As a result of intensive research to develop a dispersion stabilizer that simultaneously satisfies the required performance of (iii), surprisingly, cellulose derivatives such as methylcellulose, hydroxypropylmethylcellulose, and carboxymethylcellulose used as conventionally known dispersants for polymerization, gelatin,
Alternatively, a water-soluble polymer such as PVA is used as the main dispersant (A), and the saponification degree of the vinyl ester unit of the ethylene / vinyl ester copolymer or the copolymer containing an ionic group on the chain side is 40 mol%. When a dispersion stabilizer in which the following partially saponified product is also used as a polymerization aid (B) is used, it has reproducibly almost the same particle size distribution, the particle size distribution is sharp, and each particle is porous. The inventors have found that all of the above-mentioned performances (i) to (iii) are satisfied, such as excellent uniformity and high filling specific gravity, and have completed the present invention.

The ethylene / vinyl ester copolymer containing an ionic group in the side chain, which is a polymerization aid used in the present invention,
It can be obtained by copolymerizing a monomer containing an ionic group shown below 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.

First, among the ionic groups, examples of the monomer containing a cationic group include monomers represented by the following general formulas (I) to (V).

[Here, n is 0 to 3, m is 1 to 10, R ¹ , R ² , R ⁶ , R ⁷ , and R ⁸
Is a hydrogen atom or a methyl group, R ³ and R ⁴ are lower alkyl groups (which may include a substituent), X is a negative group that forms a salt with ammonium nitrogen, A is an amine or ammonium nitrogen atom, and (I) The groups connecting the nitrogen atom of the amide group in the formula or the oxygen atom in the formula (III) are respectively shown. In addition, specific examples of the monomer represented by the formula (I) among the polymerizable monomers having a cationic group used in this method include, for example, N- (1,1-dimethyl-3-dimethyl). Aminopropyl) (meth) acrylamide, N-
(1,1-Dimethyl-3-dimethylaminobutyl) (meth) acrylamide, N- (1-methyl-1,3-diphenyl-3-diethylaminopropyl) (meth) acrylamide, N- (3-dimethylaminopropyl) (Meta)
Acrylamide, N- (2-dimethylaminoethyl)
(Meth) acrylamide, N- (4-dimethylaminobutyl) (meth) acrylamide, and alkyl halides thereof, especially methyl chloride or ethyl chloride,
Alternatively, a monomer quaternized with a quaternizing agent such as dimethyl sulfate or methyl p-toluenesulfonate may be used.

Specific examples of the monomer represented by the formula (II) include:
Examples thereof include N-vinylimidazole, 2-methyl-N-vinylimidazole and monomers obtained by quaternizing them with the above-mentioned quaternizing agent.

Further, specific examples of the monomer represented by the formula (III) include, for example, vinyl-3-dimethylaminopropyl ether, vinyl-2-dimethylaminoethyl ether, vinyl-4-dimethylaminobutyl ether, and isopropenyl-3-. Dimethylaminopropyl ether, isopropenyl-2-dimethylaminoethyl ether, allyl-
Examples thereof include 3-dimethylaminopropyl ether, allyl-2-dimethylaminoethyl ether, allyl-4-dimethylaminobutyl ether, and monomers obtained by quaternizing them with the above-mentioned quaternizing agent.

Specific examples of the monomer represented by the formula (IV) include allyldimethylamine, methallyldimethylamine, 3-
Examples include butenedimethylamine and monomers obtained by quaternizing them with the above-mentioned quaternizing agent.

Further, specific examples of the monomer represented by the formula (V) include
For example, dimethyl diallyl ammonium chloride, diethyl diallyl ammonium chloride, etc. are mentioned.

Next, among the ionic groups, examples of monomers containing anionic groups include carboxyl group-containing monomers such as crotonic acid, maleic acid, fumaric acid, itaconic acid, (meth) acrylic acid and salts thereof, and ethylene sulfonic acid. ,
(Meth) allyl sulfonic acid, sulfoalkyl maleate (alkyl group has 2 to 4 carbon atoms), sulfoalkyl (meth) acrylamide (alkyl group has 2 to 4 carbon atoms) sulfoalkyl (meth) acrylate (alkyl group Examples thereof include sulfonic acid group-containing monomers having 2 to 4 carbon atoms and salts thereof.

The content of ionic groups in the ethylene / vinyl ester copolymer and its partially saponified product is preferably 0.01 to 10 mol%, more preferably 0.1 to 5 mol%.
If the content of ionic groups is less than 0.01 mol%, the filling specific gravity of vinyl chloride resin will be small,
When it exceeds, the packing specific gravity of the vinyl chloride resin becomes small, and the porosity also decreases, which is not preferable.

The vinyl ester used in this method includes
Examples thereof include vinyl acetate, vinyl propionate, and vinyl formate, with vinyl acetate being preferred from the economical point of view.

The ethylene / vinyl ester copolymer having a side chain containing an ionic group or a partially saponified ethylene / vinyl ester copolymer used in the present invention has a molar ratio of (ethylene) / (vinyl ester) = 0.1. ~ 99.9 ~ 95/5
Is more preferable, and more preferably 10/90 to 50/50.

The ethylene / vinyl ester copolymer or a partially saponified product thereof used in the present invention has a total of 50 ethylene units, vinyl ester units and vinyl alcohol units.
It is preferable that the content of the ionic group is 10 mol% or less and the content of ionic group is 10 mol% or less. In some cases, 40 mol% of propylene, styrene, alkyl vinyl ether, alkyl acrylate (alkyl group has 1 to 10 carbon atoms), (meth) acrylic acid alkyl ester (alkyl group has 1 to 10 carbon atoms), etc. Those containing less than can also be used.

As the polymerization aid (B) used in the present invention, an ethylene / vinyl ester copolymer having an ionic group in the side chain or a saponification degree of a vinyl ester unit of the copolymer of 40 mol% or less is used. Partially saponified is good. When a partially saponified product is used, the saponification degree is more preferably 10
A mol% or less is preferable. If the degree of saponification exceeds 40 mol%, the vinyl chloride-based monomer becomes completely insoluble, and the filling specific gravity of the vinyl chloride-based resin decreases, which is not preferable.

The degree of polymerization of the polymerization aid (B) is preferably 50 or more.

Examples of the main dispersant (A) used in the present invention include cellulose derivatives such as methyl cellulose, hydroxypropyl cellulose, hydroxypropyl methyl cellulose, carboxymethyl cellulose, gelatin, or PVA.
Examples of the water-soluble polymer include, but PVA is preferable. When PVA is used as the main dispersant (A),
PVA having a saponification degree of 65 to 95 mol% and a polymerization degree of 200 to 3000 is preferable. Examples of the PVA used as the main dispersant (A) include anionic groups such as carboxyl group and sulfonic acid group, cationic groups such as amino group and ammonium group, cyclic or acyclic amide group, long-chain alkyl group and the like. Those containing a small amount of 10 mol% or less can also be used.

The dispersion stabilizer of the present invention is used in combination with a main dispersant (A) and an ethylene / vinyl ester copolymer having an ionic group in its side chain or a partially saponified product thereof as a polymerization aid (B). However, the weight ratio of (A) to (B) is (A) / (B) = 90/10 to 30/70, and more preferably (A) / (B) = 80/20 to 40 / It is preferably selected from the range of 60. If it deviates from this range, the above-mentioned performances (i) to (iii) and polymerization stability may not be satisfied at the same time in some cases.

Using the dispersion stabilizer obtained by the above method, vinyl chloride alone or mainly, vinyl chloride monomer or copolymerized with vinyl chloride monomer when suspension-polymerizing a mixture with a monomer copolymerizable with vinyl chloride. It is carried out in the presence of an oil-soluble catalyst in the presence of a dispersion stabilizer by dispersing a mixture with a possible monomer in water.

The dispersion stabilizer is usually added by adding the main dispersant (A) as an aqueous solution to the polymerization system and the polymerization aid (B) as a powder or by dissolving it in a vinyl chloride-based monomer. A method is used in which the aqueous dispersion is charged at the same time as the main dispersant (A) is charged.

The dispersion stabilizer is 0.01% based on a vinyl chloride monomer or a mixture of a vinyl chloride monomer and a monomer copolymerizable therewith.
To 0.2% by weight, preferably 0.03 to 0.07% 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'-azoisobutyronitrile, 2,2 '-Azobis-2,4-dimethylvaleronitrile or mixtures thereof are used.

 The polymerization temperature is selected from the range of about 30 to 100 ° C.

One or more nonionic surfactants and / or anionic surfactants may be used together during the polymerization.

Although the polymerization of vinyl chloride has been mainly described above, the dispersion stabilizer of the present invention is not necessarily limited to the polymerization of vinyl chloride, and vinylidene chloride, alkyl vinyl ether, vinyl acetate, acrylic acid and its ester, meta Acrylic acid and its esters, maleic acid and its anhydrides, itaconic acid, styrene, vinyl chloride, acrylonitrile, isoprene, isobutene, and one or more components selected from the group of ethylene such as α-olefin and ethylene It is also used for suspension polymerization of vinyl compounds.

E. Action and Effect of the Invention The dispersion stabilizer of the present invention comprises a main dispersant (A) and an ethylene / vinyl ester copolymer having an ionic group in a side chain as a polymerization aid (B), or a copolymer thereof. The combined vinyl ester unit is used in combination with a partially saponified product having a saponification degree of 40 mol% or less, and in particular, the combination ratio of (A) and (B) is (A) / (B) = 90 / In the case of 10 to 30/70, more preferably (A) / (B) = 80/20 to 40/60, when this is used to suspension-polymerize a vinyl chloride-based monomer,
It is characterized in that vinyl chloride resin particles having substantially the same particle size distribution with good reproducibility, the particle size distribution being sharp, the particles being porous and having excellent uniformity, and having a large packing specific gravity can be obtained.

The reason why such a remarkable effect is obtained is unknown, but is presumed as follows. That is, the main dispersant (A) of the dispersion stabilizer of the present invention is
Adsorbs to vinyl chloride droplets and exerts protective colloid properties,
While it has the effect of improving the polymerization stability and making the particle size distribution uniform, the ethylene / vinyl ester copolymer as the polymerization aid (B) or its partially saponified product is added to vinyl chloride monomer droplets. It is considered that this is to dissolve or disperse and act from the inside of the vinyl chloride monomer droplets to enhance the porosity and uniformity of the particles.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the dispersion stabilizer of the present invention is not limited to these Examples. In the examples, “parts” indicates “parts by weight”.

Examples 1-4, Comparative Examples 1-6 Deionized water 15 in 100 l glass lined autoclave
0 parts, various dispersion stabilizers and di-2 shown in [Table-1,2]
-Ethylhexyl peroxydicarbonate 0.2 parts was charged, the autoclave was degassed to 50 mmHg to remove oxygen, 100 parts of vinyl chloride monomer was charged, and the temperature was raised to 57 ° C under stirring at 400 rpm. Polymerization was carried out.

At the start of polymerization, the pressure in the autoclave was filed at 8.0 kg / cm ² G, because it was summer and 4.0 kg / cm ² G after the polymerization initiation 7 hours, the polymerization at this point was stopped and the unreacted vinyl chloride monomer After purging, the contents were taken out and dehydrated and dried.

The polymerization yield of vinyl chloride resin is 85% and the average degree of polymerization is 11
It was 00.

 The performance of the obtained vinyl chloride resin is shown in Table 3.

(1) Particle size distribution: Measured by dry sieve analysis using a wire mesh of Tyler-Mesh standard.

(2) Packing specific gravity: Measured according to JIS K6721-1959.

(3) Uniformity of particle porosity: 100 parts of vinyl chloride resin, 50 parts of dioctyl phthalate, 1 part of dibutyltin maleate,
A mixture of 1 part of cetyl alcohol, 0.25 part of titanium white and 0.1 part of carbon black is kneaded with a roll at 150 ° C. for a predetermined time,
Create a sheet with a thickness of 0.2 mm and transmit light to this to 100 cm
The number of fish eyes contained in the sheet per ² was counted. It is shown that the more uniform the fish eyes are in a short time, the better the uniformity of the particle porosity.

(4) Plasticizer absorption: Using a planetary mixer connected to a plastograph, add 100 parts of vinyl chloride resin and 50 parts of dioctyl phthalate into a container kept at 80 ° C,
The kneading torque for each time is recorded while stirring, and the kneading time at the point where the kneading torque is reduced is indicated.

(5) Residual vinyl chloride monomer: A fixed amount of vinyl chloride resin was dissolved in tetrahydrofuran and the content of vinyl chloride monomer in the vinyl chloride resin was determined by gas chromatography.

Examples 5 to 8 Table 4 (mainly (A) /
The same procedure as in Examples 1 to 4 was carried out except that the weight ratio of (B) was changed). The performance of the obtained vinyl chloride resin is shown in Table-5.

Examples 9 to 12 The same procedure as in Examples 1 to 4 was performed except that the type and the amount of the dispersant used were changed as shown in Table 6 (mainly, the ethylene / vinyl ester copolymerization ratio was changed). Ivy. The performance of the obtained vinyl chloride resin is shown in Table-7.

Examples 13 to 15 and Comparative Example 7 Except that the kind and the amount of the dispersant used were changed as shown in Table 8 (mainly, the degree of saponification of partially saponified ethylene / vinyl ester copolymer was changed). Examples 1 to 4
I went the same way. The performance of the obtained vinyl chloride resin is shown in Table-
9 shows.

Comparative Examples 8 to 10 Comparative Examples 8 to 10 were performed in the same manner as in Examples 1 to 4 except that the kind and amount of the dispersant used were changed as shown in Table-10. The performance of the obtained vinyl chloride resin is shown in Table-11.

Claims (1)

(57) [Claims] 1. A main dispersant (A) comprising a water-soluble polymer,
In combination with an ethylene / vinyl ester copolymer having an ionic group in the side chain or a polymerization aid (B) consisting of a partially saponified product having a degree of saponification of vinyl ester units of the copolymer of 40 mol% or less. A dispersion stabilizer for suspension polymerization of a vinyl compound comprising