JPS6028282B2 - Dispersion stabilizer for suspension polymerization of vinyl compounds - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to 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 vinyl chloride monomers are dispersed in an aqueous medium in the presence of a suspension dispersion stabilizer and polymerized using an oil-soluble catalyst. There is.

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 the dispersion stabilizer is said to have the greatest influence. ing. 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, the porosity of each polymer particle can be kept 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 amount of residual monomer in vinyl chloride polymer particles to less than a few traces, and for this purpose, steam is usually blown into a packed tower filled with polymer particles to remove the remaining monomer. A method of expelling the monomer is adopted, but if the porosity is constant, the purification efficiency such as the speed of demonomerization will be almost constant for all particles, so the process can be well controlled with the minimum necessary steam treatment. In addition to being extremely easy to process, particles with a constant porosity have a uniform plasticizer absorption rate and each particle melts homogeneously during molding, resulting in a molded product of good quality without the occurrence of fish eyes etc. There is a big advantage. Conventionally, cellulose derivatives such as methylcellulose and carboxymethylcellulose, or so-called water-dropping polymers such as polyvinyl alcohol have been used as dispersion stabilizers.
Furthermore, as an improvement thereof, polyvinyl alcohol into which a carbonyl group has been introduced has also been proposed. However, although these dispersion stabilizers can satisfy the requirements of ■ and ■ to some extent, they are not necessarily sufficient and it is completely impossible to satisfy the requirements of ■. The reality is that a dispersion stabilizer that satisfies both requirements has not yet been found.

However, as a result of intensive research in order to solve this problem, the present inventors found that a polyvinyl ester obtained by polymerizing vinyl ester in the coexistence of a higher alkyl mercaptan whose alkyl group has 4 or more carbon atoms was produced by saponifying the polyvinyl ester. When using polyvinyl alcohol having a higher alkyl group introduced at the terminal and having an average saponification degree of 60 to 90 mol% and a polymerization degree of 2000 or less as a dispersion stabilizer, the resulting vinyl chloride polymer particles have a large porosity; In addition, it satisfies all of the above requirements, such as the value being almost constant among each particle and the particle size distribution being sharp, and furthermore, the average saponification with the above-mentioned higher alkyl group-containing polyvinyl alcohol. Degree of polymerization: 60 to 90 mol%, degree of polymerization: 100 to 3000
The inventors have now completed the present invention by discovering that when used in combination with polyvinyl alcohol, such effects can be further improved, and in particular, the requirement (2) can be significantly improved.

The main feature of the dispersion stabilizer of the present invention is that it is polyvinyl alcohol with a higher alkyl group introduced at the end as described above, but not only that, but also the method of manufacturing it is based on the presence of a higher alkyl mercaptan. It has to be a specific method of polymerizing vinyl esters. If the only means is to introduce an alkyl group at the end, for example, a method of saponifying a polyvinyl ester obtained by polymerizing a vinyl ester in the coexistence of a higher aliphatic aldihyde, etc. is also adopted, but such a manufacturing method Even if an alkyl group is introduced at the terminal end, it is difficult to obtain the remarkable effects of the present invention. It is also essential that the wind dispersion stabilizer has an average saponification degree of 60 to 90 mol%, preferably 60 to 85 mol%, and a polymerization degree of 2000 or less, preferably 50 to 1500.

When the degree of saponification is 90 mol% or more, the porosity of particles decreases,
If it is less than 60 mol %, water-repellency becomes a problem. On the other hand, if the degree of polymerization is 2000 or more, the particle size distribution becomes broad, which poses a practical problem. For the production of the dispersion stabilizer in the present invention, it is an essential condition that a higher alkyl mercaptan having an alkyl group having 4 or more carbon atoms be present in the polymerization of the vinyl ester.

Even if a lower alkyl mercaptan having an alkyl group having 3 or less carbon atoms is used, there is a drawback that the porosity becomes small and the practicality is poor. The alkyl mercaptans used include n-butyl mercaptan, te-butyl mercaptan, n-amyl mercaptan, tert-amyl mercaptan, n-hexyl mercaptan, cyclohexyl mercaptan, n-octyl mercaptan, and
Examples include t-octyl mercaptan, tert-nonyl mercaptan, n-dodecyl mercaptan, rt-dodecyl mercaptan, n-tetradecyl mercaptan, and n-octadecyl mercaptan. Also, vinylesters include pinyl acetate and fluoride. . Various vinyl esters include vinyl pionate, vinyl formate, and most preferably vinyl acetate. The method for producing the dispersion stabilizer of the present invention will be described in detail below, focusing on the case where vinyl acetate is used, but it goes without saying that the vinyl ester in the present invention is not limited to vinyl acetate. Any method such as bulk polymerization, solution polymerization, suspension polymerization, emulsion polymerization, etc. can be used to polymerize vinyl acetate, but bulk polymerization and solution polymerization are usually carried out. Organic solvents such as alcohols, esters, and aromatic hydrocarbons are used during solution polymerization. Polymerization is carried out without a solvent or in the presence of the above solvent using vinyl acetate monomer, higher alkyl mercaptan, and a radical catalyst (
For example, azobisisoputilonitrile, acetyl peroxide, pensolyl peroxide, lauroyl peroxide, etc.) are mixed and heated. The amount of higher alkyl mercaptan used is preferably about 0.01 to 5% based on the weight of vinyl acetate. When a solvent is used, it is appropriate that the solvent/vinyl acetate (weight ratio) be in a range of 10 or less. Also, the heating temperature is 10~
80oo is preferred. The timing of adding the higher alkyl mercaptan to the system may be arbitrary, and for example, it can be added all at once at the start of polymerization, continuously or in portions during polymerization, etc., as appropriate. It is also possible to use vinyl acetate together with a monomer that can be copolymerized with vinyl acetate, such comonomers include ethylene, propylene,
Olefins such as isobutylene, Q-octene, Q-dodecene, Q-octadecene, unsaturated carboxylic acids such as acrylic acid, methacrylic acid, crotonic acid, maleic acid, or salts thereof, or alkyl esters thereof, acrylonitrile, methacrylonitrile, etc. Amides such as nitrile, acrylamide, methacrylamide, olefin sulfonic acids or salts such as ethylene sulfonic acid, allyl sulfonic acid, methalylsulfonic acid, N-vinylimidazole, 2-, 3- or 4-vinylpyridine, dimethylaminoethyl Basic monomers such as acrylates, mono(2-
Examples include phosphate group-containing monomers such as hydroxyethyl acrylate) acid phosphate and 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%. 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.
Saponification catalysts include alkali catalysts such as alkali metal hydroxides and alcoholates such as potassium hydroxide, sodium hydroxide, sodium methylate, sodium ethylate, potassium methylate, and potassium ethylate, or acids such as sulfuric acid and hydrochloric acid. A catalyst is used. The appropriate amount of such catalyst to be used is usually 5 to 100 mmol based on vinyl acetate. There is no particular restriction on the temperature of the saponification reaction, but it is between 10 and 5
0 qo is preferably selected from a range of 20 to 40 qo. Moreover, the saponification reaction can also be carried out by the following method in addition to the above method.

A saponification catalyst is added to an alcohol solution or an alcohol-methyl acetate mixed solution of polyvinyl acetate polymerized in the coexistence of a higher alkyl mercaptan, and this is added to the polyvinyl acetate alcohol solution or alcohol-methyl acetate solution and the produced polyvinyl acetate. A so-called dispersion saponification method is carried out in which the dispersion is dispersed in an inert medium that shows almost no compatibility with alcohol, and queso-formation is carried out.

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
to 60 p.m., preferably 20 to 40 p.m. Such a dispersion saponification method is a useful method for producing partially saponified polyvinyl alcohol with a relatively low degree of saponification. In the present invention, the effect can be obtained by using together the polyvinyl alcohol with an alkyl group introduced into the wind end obtained as described above and the polyvinyl alcohol having an 'B-average saponification degree of 60 to 90 mol% and a polymerization degree of 100 to 3000. It is recommended to use them together as it will further improve the performance.

Among such combinations, the combination with polyvinyl alcohol having a saponification degree of 60 to 85 mol% as W and a polymerization degree of 50 to 1000 as B' and a polyvinyl alcohol having a saponification degree of 60 to 85 mol% as B' and a polymerization degree of 300 to 2500 is preferable. It is particularly desirable in terms of active ability and protective colloid power. If the degree of saponification of the dispersion stabilizer 'B- is less than 60 mol%, the protective colloid property will decrease and the particle size distribution of the particles will become broad, and if it is more than 90 mol%, the surface activity will decrease and the porosity of the particles will decrease. There are drawbacks. On the other hand, when the degree of polymerization is 100 or less, a product with a large polymer particle size is likely to be obtained, and when it is 3000 or more, the particle size distribution becomes broad. When using Kaze and Tsukuda together, the mixing weight ratio is Kaze Hachi B' =
9/1~0.1/9. Number office preferably 7 no 3 ~ 0.5/9
．． It is appropriate to choose from 5. As mentioned above, the combined use of [B'] and [B'] can be done not only by simply mixing the two components, polyvinylfluorol, but also by any other method. For example, a method in which a vinyl ester is polymerized without the presence of a higher alkyl mercaptan at the beginning of the polymerization, and a higher alkyl mercaptan is added midway through and the resulting polyvinyl ester is saponified. A method of saponifying the polyvinyl ester obtained by continuing the polymerization in the presence of alkyl mercaptan from the middle without the presence of an alkyl mercaptan, and further polymerizing in the presence of an alkyl mercaptan by any method such as a batch method or a multistage polymerization method. A method is adopted in which the obtained polyvinyl ester and the polyvinyl ester obtained by polymerization in the absence of an alkyl mercaptan are mixed and saponified, but in any case, when used in combination, the dispersion stabilizer of the present invention is In the end, as long as the negative component and the musical component coexist, a remarkable effect can be obtained. The following may be considered as the reason why such an effect is obtained. The performance as a dispersion stabilizer is mainly influenced by the average degree of polymerization and average saponification degree of polyvinyl alcohol, but since conventionally used polyvinyl alcohol has a sharp distribution of degree of polymerization or degree of saponification, In contrast, in the case of the combination dispersion stabilizer of the present invention, a higher alkyl group is introduced at the terminal, and the distribution of the degree of polymerization and saponification of polyvinyl alcohol is widened. degree, saponification degree,
This is thought to be due to the fact that various desirable performances as dispersion stabilizers that they have are multifaceted depending on the terminal alkyl group.

In addition, the dispersion stabilizer of the present invention can be used by mixing two or more kinds of products with different degrees of saponification and degrees of polymerization, as long as they both satisfy the provisions of the present application. .
When vinyl chloride is subjected to suspension polymerization using 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 pinyl chloride monomer. Further, 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/gu oxide or mixtures thereof are used. The polymerization temperature is selected from a range of about 30 to 70 qo. It is also possible to appropriately use various surfactants, protective colloids, inorganic dispersants, etc. as auxiliaries during polymerization. In addition to homopolymerization of vinyl chloride,
Copolymerization of this with monomers that can be polymerized is also carried out.

Copolymerizable monomers include vinylidene halide,
Examples include vinyl ether, vinyl acetate, vinyl benzoate, acrylic acid, methacrylic acid and its ester, maleic acid and its anhydride, styrene, and the like. Although the above description has mainly focused on the polymerization of pinyl chloride, the dispersion stabilizer of the present invention is not necessarily limited to the polymerization of vinyl chloride, but can also be used for the suspension polymerization of vinyl compounds such as styrene methacrylate.

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

Example 1 Production of polyvinyl alcohol containing terminal alkyl groups 50 parts by weight of vinyl acetate and 4 parts of n-dodecyl mercaptan were mixed at a temperature of 70 to 753 C using azobisisobutyronitrile as a polymerization catalyst. Keep it at 1
Polymerization was carried out for 1 hour, and when the polymerization rate reached 75%, the polymerization was stopped, and methanol vapor was blown into the solution to produce unpolymerized vinyl acetate, thereby obtaining a methanol solution of polyvinyl acetate.

A saponification reaction was carried out on the solution while maintaining the temperature at 3520° C. to obtain a polyvinyl alcohol containing an alkyl group at the end with a degree of saponification of 72 mol % and a total degree of polymerization of 0. Suspension polymerization of vinyl chloride In a 100-capacity stainless steel autoclave equipped with an accompaniment vessel, 10 parts of vinyl chloride monomer, 150 parts of water, 0.1 part of the above dispersion stabilizer, and 0 lauroyl peroxide as a polymerization catalyst were placed. .Prepare at a ratio of 2 parts and rotate at 40 rpm. p. Suspension polymerization was carried out by adjusting the temperature to 60 qo while keeping the temperature at m.

Table 1 shows the performance of the obtained vinyl chloride resin particles.

Example 2 The terminal alkyl group-containing polyvinyl alcohol of Example 1 0.
Suspension polymerization was carried out in the same manner as in Example 1 except that 0.05 parts of polyvinyl alcohol having a degree of polymerization of 800 and a degree of saponification of 72 mol % were used in combination.

Table 1 shows the performance of the vinyl chloride resin obtained. Illustration
3be9 An experiment was conducted according to Example 1 except that the dispersion stabilizer shown in Table 1 was used.

The results are shown in Table 1. 1st Table Oil'1 - Porosity is measured using a mercury porosity meter.

■ The uniformity of porosity was determined by adsorbing mineral oil onto vinyl chloride polymer particles, placing the particles on a slide glass, shining a light source from below, and using a microscope to calculate the number of opaque particles out of 100 particles that do not transmit light. . (Particles with large porosity become transparent particles and allow light to pass through.) Those with 0 to 1 opaque particles are A.
2 to 3 samples were labeled as B, and 4 to 6 samples were labeled as C.

[3' Particle size distribution is the content of coarse particles measured using a JIS standard sieve of 42 mesh, expressed as %. 42 mesh on content percentage is 1% or less A, 1 to 5% B, 5
% or more is expressed as C.

[4' Fisheye measures the number of spots per 2 melon seeds based on the Roichs test, and those with 0 to 4 are classified as A, and those with 5 to 1
Those with 11 or more particles were labeled as B, and those with 11 or more were labeled as C.

'51 Plasticizer absorption is determined by 6 parts of vinyl chloride polymer and DO
The time until the drying point of the mixture in Part P4 was measured using a Brabender.

It was displayed in

Claims (1)

[Scope of Claims] 1 (A) An average saponification degree of 60 to 90 produced by saponifying a polyvinyl ester obtained by polymerizing a vinyl ester in the coexistence of a higher alkyl mercaptan whose alkyl group has 4 or more carbon atoms. A vinyl compound consisting of polyvinyl alcohol into which a higher alkyl group has been introduced at the end with a mole% degree of polymerization of 2000 or less, or a mixture of this and (B) polyvinyl alcohol with an average saponification degree of 60 to 90 mole% and a polymerization degree of 100 to 3000. Dispersion stabilizer for suspension polymerization. 2. The dispersion stabilizer according to claim 1, wherein the vinyl ester is vinyl acetate. 3. The dispersion stabilizer according to claim 1, wherein the vinyl compound is vinyl chloride.