JPS6031845B2 - Method for producing polyvinyl alcohol with improved quality - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a method for producing polyvinyl alcohol having properties suitable for use as a dispersion stabilizer for suspension polymerization of vinyl compounds, particularly vinyl chloride.

When producing vinyl chloride resins industrially, a suspension polymerization method is widely used, in which pinyl chloride monomer is dispersed in an aqueous medium in the presence of a suspension dispersion stabilizer, and polymerization is carried out using an oil-soluble catalyst. .

In general, the factors that control the quality of the resin include the polymerization rate, water-monomer ratio, polymerization temperature, amount of catalyst, and type and amount of dispersion stabilizer, among which it is said that the dispersion stabilizer has the greatest influence. It is being said. The performance required of a dispersion stabilizer for vinyl chloride polymerization is: ■ It must exhibit sufficient dispersion power when used in a small amount, and it must have the ability to sharpen the particle size distribution of the resulting vinyl chloride polymer particles. ■ Polymer In order to increase the rate of absorption of plasticizer in the particles and facilitate molding processability, the particles have the function of making the particles porous with a high porosity, ■removal of the vinyl chloride monomer remaining in the porous particles, or In order to prevent the formation of fish eyes and the like in the molded product, it has the function of keeping the porosity of each polymer particle within a substantially constant range. Particularly recently, there has been a strong demand for satisfying the performance described in (2).

In other words, due to pollution issues, it is considered essential to reduce the residual molymer content in vinyl chloride polymer particles to less than a few degrees, and for this purpose, steam is usually introduced into a packed tower filled with polymer particles. A method of blowing out the remaining monomer is used, but if the porosity is constant, the purification efficiency such as the demonomerization rate will be almost constant for all particles, so the process can be completed easily with the minimum necessary steam treatment. In addition to being extremely easy to manage, particles with a constant porosity absorb the plasticizer at a uniform rate and each particle melts homogeneously during molding, making it possible to produce high-quality molded products without the occurrence of fish eyes. There are great benefits to be gained. However, although polyvinyl alcohol is often used as a dispersion stabilizer, it is impossible to satisfy the requirements of ■ and ■ to some extent, but it is completely impossible to satisfy the requirements of ■ and ■. The reality is that no dispersion stabilizer has yet been found that satisfies both requirements. However, as a result of extensive research in order to solve this problem, the present inventors polymerized vinyl ester in the presence of 2,4-diphenyl-4-methyl-1-pentene and saponified the resulting polypinyl ester. In this case, when the resulting polyvinyl alcohol is used as a dispersion stabilizer as described above, it increases the porosity of the vinyl chloride polymer particles, keeps the porosity constant for each particle, and The present inventors have discovered that this method has the remarkable effect of sharpening the diameter distribution, and have completed the present invention relating to a new method for producing polyvinyl alcohol.

Although it is not clear why the polyvinyl alcohol produced in the present invention has the above-mentioned useful performance,
2,4-diphenyl-4-methyl-1-pentene present during the polymerization of vinyl ester is introduced into the molecule, and the resulting polyvinyl alcohol contains phenyl groups, resulting in hydrophilic hydroxyl groups, hydrophobic phenyl groups, and residual It is thought that the balance with acetic acid groups and the distribution state of residual acetic acid groups and phenyl groups provides optimal HLB conditions and changes the dispersion of the vinyl chloride monomer and polymer in water to a desirable state.

In carrying out the method of the present invention, vinyl ester is first polymerized in the presence of 2,4-diphenyl-4-methyl-1-bentene.

Vinyl esters used in the present invention include vinyl formate, vinyl acetate, vinyl propionate, vinyl stearate, vinyl saturated branched fatty acids, vinyl benzoate, etc., but vinyl acetate is the most important in practical terms, and the Vinyl propionate is important.

Other vinyl esters are often used in combination with vinyl acetate or vinyl propionate. It is also possible to use monomers that can be copolymerized with these vinyl esters, and such comonomers include olefins such as ethylene, propylene, isobutylene, Q-octene, Q-dodecene, and Q-octadecene, acrylic acid, methacrylic acid,
Unsaturated carboxylic acids or their salts such as crotonic acid and maleic acid, or their alkyl esters, nitriles such as acrylonitrile and methacrylonitrile, amides such as acrylamide and methacrylamide, ethylene sulfonic acid, allyl sulfonic acid, methalylsulfonic acid Olefin sulfonic acids or salts such as N-vinylimidazole,
Basic monomers such as 2-, 3- or 4-vinylpyridine, dimethylaminoethyl acrylate, mono(2-hydroxyethyl acrylate) acid phosphate,
Examples include phosphoric acid group-containing monomers such as mono(2-hydroxyethyl methacrylate) acid phosphate, vinyl ether, vinyl ketone, N-vinylpyrrolidone, vinyl halide, and vinylidene halide.

When these comonomers are used, their proportion in the copolymer is preferably less than 50 mol%, particularly less than 20 mol%. In addition, 2,4-diphenyl-4-methyl-1-bentene is not only used alone, but also 2,4-diphenyl-4-methyl-2-pentene and 1,1,3-trimethyl-3-phenyl, which are created during the production of pentene. Those containing indane etc. can also be used.

Hereinafter, the production method of the present invention will be explained in more detail using vinyl acetate as an example, but as described above, the vinyl ester is not limited to vinyl acetate in the present invention.

Any method such as bulk polymerization, solution polymerization, suspension polymerization, emulsion polymerization, etc. can be used to polymerize vinyl acetate.

Usually, bulk polymerization method and solution polymerization method are used. Organic solvents such as alcohols, esters, and aromatic hydrocarbons are used during solution polymerization. Polymerization is performed in the absence of a solvent or by adding 2,4-diphenyl-4-methyl-1-bentene and pinyl acetate monomers and known radical catalysts such as azobisisobutyronitrile, acetyl peroxide, penzoyl peroxide, lauroyl peroxide, etc. to the above organic solvent. This is done by heating it. The amount of 2,4-diphenyl-4-methyl-1-bentene used is preferably about 0.01 to 5% by weight of vinyl acetate.

If a solvent is used, the amount is: solvent: vinyl acetate = 10
The following range (weight ratio) is appropriate. Also, the heating temperature is 10
~80oC is preferred. The phenyl group-containing polyvinyl acetate obtained by polymerization in this manner is saponified according to a conventional method.

That is, for saponification, the polymer is dissolved in alcohol, hydrous alcohol, or alcohol-methyl acetate mixture, and saponified with acid or alkali. Examples of the alcohol include methanol, ethanol, propanol, etc., and methanol is preferably used. The concentration of polymer in the alcohol is usually selected from the range 10 to 8% by weight.
As saponification catalysts, alkali catalysts such as alkali metal hydroxides and alcoholates such as potassium hydroxide, sodium hydroxide, sodium methylate, sodium ethylate, potassium methylate, and potassium ethylate, sulfuric acid, hydrochloric acid, etc. An acid catalyst is used. The appropriate amount of such catalyst to be used is usually 5 to 100 mmol based on vinyl acetate. The temperature of the saponification reaction is not particularly limited, but is between 10 and 5
0oo preferably in the range of 20 to 40°C. or,
In addition to the above-mentioned method, the saponification reaction can also be carried out by the following method.

A saponification catalyst is added to an alcoholic solution or an alcohol-methyl acetate mixed solution of polyvinyl acetate polymerized in the coexistence of 2,4-diphenyl-4-methyl-1-pentene. A so-called dispersion saponification method is carried out in which the material is dispersed in an inert medium that exhibits almost no compatibility with the methyl acetate solution and the polyvinyl alcohol produced, and saponification is performed.

At this time, if necessary, it is also possible to use a small amount of a surfactant. Examples of the inert medium include liquid paraffin, spindle oil, kerosene, etc., and the weight ratio of the inert medium to the alcoholic solution of polyvinyl acetate is 0.2:1 to 5:1.
is appropriate. The saponification temperature in the dispersion saponification method is 5
-60oo preferably selected from the range of 20-40°C. Such a dispersion saponification method is a useful method for producing partially saponified polyvinyl alcohol with a relatively low degree of saponification. The degree of polymerization, degree of saponification, phenyl group content, etc. of the polyvinyl alcohol produced by the method of the present invention are not particularly limited, and may be adjusted depending on the intended use.

For example, when used as a dispersion stabilizer for suspension polymerization of vinyl compounds, the degree of polymerization is 2000 or less, preferably 50 to 1.
500, saponification degree is 90 mol% or less, preferably 60 to
The content of phenyl group is 85 mol %, and the absorbance of a 1% aqueous solution at a wavelength of 25 mt.

When used for uses other than the above, the degree of saponification, degree of polymerization, and phenyl group content can be changed arbitrarily, so the range cannot be specifically limited, but the polyvinyl alcohol used in the present invention usually has a degree of polymerization of 50 ~300 mirror stars, saponification degree 2
Approximately 0 to 100 mol%, phenyl group content 0.01 to 5
It can be produced arbitrarily at a concentration of about 0 mol%. When vinyl chloride is subjected to suspension polymerization using the polyvinyl alcohol obtained by the method of the present invention as a dispersion stabilizer, the dispersion stabilizer is usually added to an aqueous medium, the vinyl chloride monomer is dispersed, and the vinyl chloride monomer is dispersed in the presence of an oil-soluble catalyst. It will be done.

The dispersion stabilizer is added to the aqueous medium as a powder or in the form of a solution. When added in the form of a solution, it can be added as an aqueous solution, or as a solution dissolved in an organic solvent such as alcohol, ketone, or ester, or a mixed solvent with water. The dispersion stabilizer is used in an amount of 0.01 to 5% by weight, preferably 0.01 to 3% by weight, based on the vinyl chloride monomer. The catalyst used may be any oil-soluble catalyst, such as penzoyl peroxide, lauroyl peroxide, diisopropyl peroxydicarbonate, Q, Q'
-Azobisisobutyronitrile, Q,Q'-azobis-2,4-dimethylvaleronitrile, acetylcyclohexylsulfonyl peroxide or mixtures thereof are used. The polymerization temperature is selected from a range of about 30 to 70 qo.

It is also possible to use various surfactants, protective colloids, inorganic dispersants, etc. as additives during polymerization. The above description has mainly been about the use of polyvinyl alcohol obtained by the method of the present invention as a dispersion stabilizer. However, the polyvinyl alcohol of the present invention is not only used as a dispersion stabilizer, but also for various molded products such as films, fibers, pipes, sheets, etc.
Leak-proof membranes, temporary membranes, water port fibers for chemical lace, adhesives for wood, paper, aluminum foil, etc., pressure-sensitive adhesives, hot melt adhesives, adhesives for interlining, re-wetting glue, raw materials for non-woven fabrics, binders for non-woven fabrics, Fibrous binder, paper clear coating agent, pigment binder, fiber sizing agent, fiber processing agent such as warp glue, nylon, Tetron, pinyl chloride resin, polyethylene, polypropylene, ethylene-vinyl acetate copolymer or its saponified product, etc. Blends of various resins, hair styling products,
Its uses are extremely wide, including emulsifiers for emulsion polymerization of vinyl chloride, acrylic monomers, and vinyl acetate, and its industrial value is extremely high.

Next, the method of the present invention will be explained in more detail by giving examples.

Example 1 50 parts by weight of vinyl acetate (parts by weight, the same applies hereinafter),
Methanol 3 anchors, 2,4-diphenyl-4-methyl-
1-bentene was mixed in a ratio of 3 parts, and one-vowel polymerization was carried out using azobisisobutyronitrile as a polymerization catalyst and maintained at a temperature of 70 to 75 qo, and the polymerization was stopped at a polymerization rate of 75%.
Methanol vapor was blown into the solution to produce unpolymerized vinyl acetate, thereby obtaining a methanol solution of polyvinyl acetate.

The solution (resin content 60%) was added with 10 parts of methanol and 2 parts of methanol, and the saponification reaction was carried out while maintaining the temperature at 35q0 to obtain a saponification degree of 71 mol%, a polymerization degree of 700, and a phenyl group content.
Partially saponified polyvinyl alcohol with an absorbance of 1.0 at 25 mn of a 1% aqueous solution was obtained. Next, in a stainless steel autoclave with a capacity of 100 and equipped with a drainer, 10 parts of vinyl chloride monomer, 15 parts of water, 0.1 part of the above polyvinyl alcohol, and 0.0 parts of lauroyl peroxide as a polymerization catalyst were placed. Prepare at a ratio of 2 parts and rotate at a speed of 4.
Suspension polymerization was carried out by adjusting the temperature to 60 CO while keeping the temperature at 0 pm. Table 1 shows the performance of the obtained vinyl chloride resin particles. As a control example, the same method as in Example 1 was carried out except that the use of 2,4-diphenyl-4-methyl-1-pentene was omitted.

The results are also listed in Table 1. Table 1 Note (1) Measurement of porosity is based on mercury porosity measurements.

'2) Uniformity of porosity can be determined by adsorbing mineral oil onto vinyl chloride polymer particles, placing it on a slide glass, shining a light source from below, and measuring the number of transparent particles that allow light to pass through out of 100 particles using a microscope. I counted. (Small particles with a porosity of /J become transparent particles and transmit light) Those with 0 to 1 transparent particles are A, 2
~3 items were designated as B, and 4 to 6 items were designated as C. '3) For the particle size distribution, the content of coarse particles measured using a JIS standard sieve of 42 mesh is indicated with *. 42 mesh on content percentage is 1* or less: A, 1 to 5*: B, 5
*The above is indicated by C.

Example 2 50 parts of vinyl acetate, 10 parts of methanol,
2,4-diphenyl-4-methyl-1-pentene 1.5
The polymerization was carried out for 10 hours at a temperature of 70 to 750C using azobis isoptylonitrile as a polymerization catalyst, and the polymerization was stopped at a polymerization rate of 75%, and methanol vapor was blown in to produce unpolymerized vinyl acetate. A methanol solution of extracted polyvinyl acetate was obtained.

To 10 parts of the solution (resin content 45%), 12 parts of methanol was added and the saponification reaction was carried out while maintaining the temperature at 360°C to obtain a degree of saponification of 73 mol%, a degree of polymerization of 1200, and a phenyl group content of 1.
% aqueous solution with an absorbance of 0.4 at a wavelength of 25 hm. Suspension polymerization of vinyl chloride was carried out in the same manner as in Example 1 using the above polypynyl alcohol.

Almost the same results as in the same example were obtained. Example 3 50 parts of vinyl acetate, 10 parts of methanol, and 0.5 parts of 2,4-diphenyl-4-methyl-1-bentene were mixed, and the temperature was maintained at 70 to 75oC using azobisisobutyronitrile as a polymerization catalyst. Polymerization was carried out for 6 hours, and the polymerization rate was 75.
%, the polymerization was stopped, and methanol vapor was blown in to push out unpolymerized vinyl acetate to obtain a methanol solution of polypinyl acetate.

Add 10 parts of the solution (resin content: 45%) to 3 parts of Mariko methanol, and carry out the saponification reaction while maintaining the temperature at 35 qo.
% aqueous solution with an absorbance of 0.25 at a wavelength of 25 cm. Suspension polymerization of vinyl chloride was carried out in the same manner as in Example 1 using the above polyvinyl alcohol.

Claims (1)

[Claims] 1. Polyvinyl alcohol with improved quality characterized by polymerizing vinyl ester in the presence of 2,4-diphenyl-4-methyl-1-pentene and saponifying the resulting polyvinyl ester. manufacturing method. 2. The manufacturing method according to claim 1, wherein the vinyl ester is vinyl acetate.