JPH0618804B2 - Dispersion stabilizer for suspension polymerization - Google Patents

Description

Detailed Description of the Invention A. TECHNICAL FIELD The present invention relates to a dispersion stabilizer for suspension polymerization of vinyl compounds, especially vinyl chloride.

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 performed using an oil-soluble catalyst is widely practiced. Generally, factors that control the quality of the resin include polymerization rate, water-monomer ratio, polymerization temperature, type and amount of catalyst, type of polymerization tank, stirring speed or type and amount of dispersion stabilizer, among others. It is known that the effect of the type of dispersion stabilizer is very large.

As the performance required for the dispersion stabilizer for suspension polymerization of vinyl chloride-based monomers, (i) shows a high dispersibility even when used in a small amount,
It has a function to make the particle size distribution of the obtained vinyl chloride polymer particles as sharp as possible. (Ii) To increase the absorption rate of the plasticizer to facilitate workability and to retain the vinyl chloride in the polymer particles. In order to facilitate the removal of the monomer and to prevent the formation of fuchsia eye in the molded product, it has the function of making each polymer particle as uniform and porous as possible (iii) A polymer particle with a high filling specific gravity It has a working function.

B. 2. Description of the Related Art 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 singly or in combination.

C. Problems to be Solved by the Invention However, these have the drawbacks that the ability to make the vinyl chloride polymer particles porous is low, the plasticizer absorption rate is slow, and it is difficult to remove residual vinyl chloride monomer.

D. Means for Solving the Problems In view of such a current situation, the inventors of the present invention have investigated a better dispersion stabilizer for suspension polymerization, and as a result, have found that fluorine-containing compounds at the terminal end via a sulfid bond (-S-). By using a specific polyvinyl alcohol (hereinafter, polyvinyl alcohol may be abbreviated as PVA) -based polymer having a group and a saponification degree of 60 mol or more and a polymerization degree of less than 2000 as a dispersion stabilizer, Suspension polymer particles of vinyl chloride-based monomer with sharp particle size distribution, large porosity, and large packing specific gravity are obtained. The suspension-polymerized vinyl chloride-based polymer has a plasticizer absorption rate. Big thing,
In addition, it has excellent performance such as easy removal of vinyl chloride monomer remaining in polymer particles, less scattering of powder during handling, and good biteability into molding machines. Heading The present invention has been completed. Sulfide bond (-S used in the present invention
The PVA-based polymer having a fluorine-containing group at the terminal via-) has various fluorine-containing groups at the terminal through the sulfido bond (-S-), preferably having 2 or more carbon atoms, more preferably 4 or more carbon atoms. A PVA-based polymer having a fluorine-containing group such as a fluorinated alkyl group or a fluorinated alkyl ether group, having a saponification degree of 60 mol% or more, preferably 60 to 99 mol%, more preferably 65 to 99 mol%, and polymerized. A PVA polymer having a degree of less than 2000, preferably less than 1000.

The PVA-based polymer having a fluorine-containing group at the terminal via the sulfide bond (-S-) of the present invention has a sulfide bond (-S).
Any PVA-based polymer having a fluorine-containing group at the terminal via-) can be used without limitation in its production method. For example, a compound having an active group such as a thiol group or a compound having an active group such as thiol is allowed to coexist as a chain transfer agent to polymerize a vinyl ester, and then the vinyl ester unit is saponified to form a terminal via a sulfido bond (-S-). It is produced by a method of obtaining a PVA-based polymer having a fluorine-containing group, a method of introducing a group having a fluorine-containing group at a terminal through a chemical reaction through a sulfid bond (-S-) of the PVA-based polymer, and the like. It However, it is more economical and more efficient to introduce a fluorine-containing group into the terminal via a sulfidic bond (-S-), and to introduce a fluorine-containing group into the terminal via a sulfidic bond (-S-) exhibiting excellent dispersion stability. PVA with fluorine group
As a method of obtaining a system polymer, a method of polymerizing vinyl esters such as vinyl acetate in the presence of a thiol having a fluorine-containing group (hereinafter sometimes referred to as fluorine-containing thiol) and then saponifying is preferable. .

Although various fluorine-containing thiols can be used, those represented by the general formulas Rf-SH and Rf-X-SH can be used. Rf is a group containing a fluorine atom, which preferably has 2 or more carbon atoms, more preferably 4 or more carbon atoms, and represents a fluorine-containing group such as an alkyl fluoride or an alkyl ether fluoride, and X represents a group containing a fluorine atom. The group connecting SH represents an alkyl chain, an alkyl ether chain, an amide bond-containing alkyl chain, an alkyl thioether chain, and the like. As an alkyl chain n = 1-5, as the alkyl ether chain m = 1-5, n = 1-5, as an amide bond n = 1-5 is preferable.

Specifically showing what is represented by Rf-X-SH, F (CF ₂ ) ₈ CH ₂ CH ₂ SH, F (CF ₂ ) ₉ CH ₂ CH ₂ SH, F (CF ₂ ) ₁₀ CH ₂ CH ₂ SH, F (CF ₂ ) ₈ (CH ₂ ) ₄ SH, F (CF ₂ ) ₁₀ SCH ₂ CH ₂ SH, F (CF ₂ ) ₈ CH ₂ CH ₂ S (CH ₂ ) ₃ SH, F (CF ₂ ) ₈ -SCH ₂ CH ₂ OCH ₂ CH ₂ SH, F (CF ₂ ) ₈ SCH ₂ CH ₂ SCH ₂ CH ₂ SH, F (CF ₂ ) ₃ CONHCH ₂ CH ₂ SH, F (CF ₂ ) ₇ CONHCH ₂ CH ₂ SH, Etc. Also, as shown by Rf-SH, C ₂ F
₅ SH, C ₄ F ₉ SH, Etc.

Further, fluorine-substituted aromatic or alicyclic hydrocarbons can be used as Rf, but aliphatic fluorine-substituted compounds such as alkyl fluorinated and fluorinated alkyl ether are more preferable because of their superior performance.

The criterion for selection from these fluorine-containing thiol groups is to improve the dispersion stability of the PVA-based polymer having a fluorine-containing group at the end of the present invention.
Rf is _{H (CF 2) n - F} (CF 2) n than - is preferably, n
Must be greater than or equal to 2. The upper limit of n is about 20, though it is not particularly limited. Preferably, n is 4-18, more preferably 6-18. Further, Rf is more preferably linear, rather than branched.

When polymerizing vinyl esters such as vinyl acetate in the presence of fluorine-containing thiol, the amount and method of addition of fluorine-containing thiol to the polymerization system are appropriately selected. The fluorine-containing thiol acts as a chain transfer agent, the amount of the fluorine-containing thiol added to the polymerization system, the addition method is the degree of polymerization of the resulting polymer,
Since it affects the distribution of the degree of polymerization, it can be appropriately determined from the viewpoint of the required dispersion stability performance of the PVA-based polymer, but it is possible to efficiently introduce a fluorine-containing group at the terminal through a sulfid bond (-S-), which is excellent. In order to obtain a PVA-based polymer having excellent performance, it is preferable to add a thiol according to the reaction rate of the vinyl ester in the polymerization system so that the amount of thiol in the reaction system does not change much with respect to the vinyl ester. By doing so, the introduction efficiency of the fluorine-containing group at the terminal via the sulfido bond (-S-) is improved, the distribution of the degree of polymerization is narrowed, and a dispersion stabilizer having excellent performance is obtained, which is preferable.
It is desirable that the ratio _W / _{N of the} weight average degree of polymerization ( _W ) and the number average degree of polymerization ( _N ) showing the degree of distribution does not exceed 4.0.

The polymerization method of the present invention is a generally known method such as bulk polymerization,
Although any of solution polymerization, kendaku polymerization and emulsion polymerization can be employed, industrially solution polymerization using methanol, toluene or the like is most preferable. Further, the polymerization process can be carried out by any of the batch method, the semi-batch method and the continuous method. As the initiator used in the polymerization of the present invention, a known radical polymerization initiator is usually used.
For example, 2,2'-azobisisobutyronitrile, 2,2-
Examples thereof include azobis (4-methoxy-2,4-dimethylvaleronitrile) benzoyl peroxide, diisopropyl peroxydicarbonate, potassium persulfate and the like.
The polymerization temperature can be appropriately set depending on the initiator used, but is preferably 10 to 90 ° C.

To obtain a polyvinyl alcohol-based polymer by saponifying a polyvinyl ester-based polymer having a fluorine-containing group at the terminal via a sulfid bond (-S-), a generally known method, that is, either alkali saponification or acid saponification is used. Although it can be adopted, industrially, the methanol decomposition using NaOH or CH ₃ ONa as a catalyst in a methanol solvent is most advantageous. The saponification temperature is not particularly limited, but it is preferably 20 to 60 ° C. from the viewpoint of preventing coloring of the obtained polyvinyl alcohol polymer. In addition, the amount of NaOH or CH ₃ ONa used as a catalyst is usually in the range of 0.001 to 0.2 mol with respect to 1 mol of the vinyl ester unit, which can prevent coloring of the obtained polyvinyl alcohol-based polymer and keep the amount of sodium acetate low. It is preferable from the point. When there is a copolymer unit such as an acid that consumes an alkali, it is necessary to perform saponification in addition to the amount in the above range.

The PVA-based polymer having a fluorine-containing group at the terminal via the sulfido bond (-S-) of the present invention is a PVA-based polymer having a fluorine-containing group at the terminal within a range not impairing the effects of the present invention. Other PVA-based polymers can be used in combination. As a PVA-based polymer other than the PVA-based polymer having a fluorine-containing group at the terminal, a polyvinyl alcohol-based polymer having a saponification degree of 60 to 99 mol% and a polymerization degree of 100 to 3500 can be used in the production method and the like. Can be used without restrictions. (This PVA-based polymer is sometimes referred to as (b) combined PVA-based polymer.) The combined PVA-based polymer can be produced by a method of polymerizing and saponifying a vinyl ester such as vinyl acetate by a usual method.
The PVA-based polymer may contain a small proportion of the third component in addition to the vinyl alcohol unit and vinyl acetate unit normally contained in PVA. The third component may contain an ionic group such as anion or cation, or may contain a nonionic group.

(B) The proportion of the combined PVA-based polymer used is (a) P having a fluorine-containing group at the terminal via a sulfido bond (-S-).
The VA-based polymer can be arbitrarily used as long as the effect of the VA polymer is not impaired, but it is more preferably equal weight or less. A preferred use ratio is (a) / (b) = 50/50 to 95/5 (weight ratio). For example, it is preferable to use PVA having a relatively high degree of polymerization of 500 or more, preferably 1000 or more, in equal weight or less in order to improve the polymerization stability and obtain polyvinyl chloride having excellent porosity. In this case, those having a relatively high saponification degree can be used. However (a)
A PVA having a low degree of polymerization as a PVA having a fluorine-containing terminal at the terminal via a sulfid bond (-S-), for example, 500 or less, preferably 300 or less, more preferably 150 or less.
And (b) when the combined PVA-based polymer is mixed with this, the degree of polymerization of the combined PVA-based polymer is 2000 or less,
It may be 1000 or less, and it may be preferable to use the same weight ratio or more. For example, the usage rate is (a) / (b) = 50 /
50 to 20/80 (weight ratio).

The degree of polymerization of the PVA-based polymer of the present invention is determined by acetylating the PVA-based polymer to obtain polyvinyl acetate (PVAc), and then measuring the intrinsic viscosity in an acetone solution, which is based on the Nakajima equation (Akio Nakajima:
Polymer Chemistry 6 , 451 (1949)). Also, the weight average degree of polymerization ( _W ) and the number average degree of polymerization ( _N )
The value of the ratio _W / _N can be determined by measuring the polyvinyl acetate polymer obtained by reacetylation by gel permeation chromatography (GPC). The degree of saponification means the degree of saponification of the vinyl ester component and does not include that component when other components are copolymerized. The degree of saponification can be analyzed by a conventionally known chemical analysis method, nuclear magnetic resonance analysis method, or the like.

The PVA-based polymer of the present invention needs to be water-soluble PVA which can be dissolved or dispersed in water. Those that are not water-soluble are not preferred because of poor dispersion stability performance.

When the PVA-based polymer of the present invention is used as a dispersion stabilizer, vinyl chloride is used alone or as a main component, and when suspension-polymerizing a mixture with a monomer copolymerizable therewith, it is usually dispersed in an aqueous medium. It is carried out in the presence of an oil-soluble catalyst by adding an agent and dispersing a vinyl chloride monomer or a mixture thereof with a monomer copolymerizable therewith. The dispersion stabilizer can be added to the aqueous medium as a powder or as an aqueous solution. It is free to use other dispersion stabilizers, such as conventionally used cellulose derivatives, within the range in which the effects of the present invention are not impaired.

The dispersion stabilizer is 0.005 with respect to a vinyl chloride monomer or a mixture of a vinyl chloride monomer as a main component and a monomer copolymerizable therewith.
~ 1% by weight, preferably 0.01-0.5% by weight.

The catalyst used in 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 70 ° C.

A conventionally known dispersion stabilizer may be appropriately used as an auxiliary agent during the polymerization.

As the monomer copolymerizable with vinyl chloride, vinylidene halide, vinyl ether, vinyl acetate, acrylic acid, methacrylic acid and their esters, maleic acid and its anhydride, itaconic acid, styrene and the like are used.

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 may be used for the suspension polymerization of vinyl compounds such as styrene and methacrylate.

E. Action and Effect of the Invention The present invention is a dispersion stabilizer for suspension polymerization, preferably a fluorinated alkyl group or fluorinated alkyl ether group having 2 or more carbon atoms, more preferably 4 or more carbon atoms at the terminal via a sulfid bond (-S-). Have fluorine-containing groups such as
Ability to make vinyl chloride polymer particles porous by using a specific PVA polymer having a degree of polymerization of less than 2000 at a mol% or more, as compared with a normal PVA polymer having no fluorine-containing group at the end. Shows excellent performance such as very high absorption rate of plasticizer and easy removal of residual vinyl chloride monomer, and has a large particle size and a sharp distribution to reduce scattering of powder during handling. This shows that a suspension polymer having excellent performance such as good biteability into a molding machine can be obtained and that it is excellent as a dispersion stabilizer for suspension polymerization.

On the other hand, P having an unfluorinated hydrocarbon group at the end
Although VA-based polymers are known as excellent dispersion stabilizers for suspension polymerization, PVA-based polymers having a fluorine-containing group at the terminal via a sulfido bond (-S-) of the present invention are more stable in dispersion. It has excellent properties and has the advantage that the amount used can be reduced.

PV in which a fluorine-containing group is introduced into the side chain by copolymerization
Although the A-based polymer also exhibits excellent surface-active ability, when it is used as a dispersion stabilizer for suspension polymerization, a specific polymer having a fluorine-containing group at the terminal via the sulfido bond (-S-) of the present invention is used. It is not as effective as the PVA-based polymer and is unsatisfactory in its effect.

The conventionally known PVA for use as a dispersion stabilizer for suspension polymerization cannot exhibit excellent dispersion stability unless it is a PVA having a relatively low degree of saponification, for example, so-called partially saponified PVA having a content of 88 mol% or less. Bond (-S-)
PVA having a fluorine-containing group at the terminal via the is also characterized by having a relatively high degree of saponification, for example, 90 mol% or more, showing excellent performance.

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

[Production Example of PVA-based Polymer Having Fluorine-Containing Group at Terminal via Sulfide Bond (-S-)]

After taking 960 parts of vinyl acetate (hereinafter abbreviated as VAc), 240 parts of methanol and 1.7 parts of F (CF ₂ ) ₇ CH ₂ CH ₂ SH (hereinafter abbreviated as FS) in a reaction vessel and thoroughly replacing the inside with nitrogen, The external temperature was raised to 65 ° C, and when the internal temperature reached 60 ° C, 10 parts of methanol containing 0.18 part of 2,2'-azobisisobutyronitrile was added. Immediately, 60 parts of a mixed solution of methanol / VAc (VAc / (VAc + methanol) concentration 80%) containing 26.3 parts of FS was uniformly added over 5 hours. The polymerization rate after 5 hours was 47%. After 5 hours, the container was cooled, and an operation of expelling VAc remaining under reduced pressure together with methanol out of the system was performed while adding methanol to obtain a methanol solution of PVAc (concentration: 70%). Take a portion of this methanol solution, add a methanol solution of NaOH so that the PVAc concentration is 50% and [NaOH] / [VAc] = 0.009 (molar ratio), saponify at 40 ° C, and saponify degree 91 mol% Polyvinyl alcohol (hereinafter abbreviated as PVA). The degree of polymerization of PVA is purified, and then PVA obtained by re-acetylation is used. Molecular Chemistry 6 , 451 (19
The degree of polymerization is 10 when measured by the method calculated in 49)).
It was 1.

The PVA was washed under reflux with methyl acetate containing a small amount of water, purified by Soxhlet extraction with methanol for 48 hours, and then dissolved in heavy water, followed by nuclear magnetic resonance analysis (hereinafter referred to as N
(Abbreviated as MR). From this, it is confirmed that the presence of the CF ₃ group is present, the F content is confirmed by the elemental analysis, and the PVA has a fluorine-containing F (CF ₂ ) ₇ CH ₂ CH ₂ —S- group at one end of the molecule. It was confirmed that there is. Next, the above-mentioned purified PV
Measurement of gel permeation chromatography (hereinafter abbreviated as GPC) of PVAc obtained by acetylating A. [Device: HLC-802R manufactured by Toyo Soda Kogyo Co., Ltd., column: GM
H6 × 2, solvent: tetrahydrofuran, temperature: 23 ± 1
C.], the result was _W / _N = 2.02.

Examples 1 to 13 and Comparative Examples 1 and 2 Sulfide bonds (-S obtained according to the method described above).
The suspension polymerization of vinyl chloride was carried out by the following method using PVA having a fluorine-containing group at the terminal via-) alone or in combination with PVA.

40 parts deionized water in a glass lined autoclave,
0.75 parts of a 2 wt% aqueous solution of a dispersion stabilizer and a 50 wt% toluene solution of diisopropyl peroxydicarbonate
After charging 0.009 parts and degassing the inside of the autoclave to 50 mmHg to remove oxygen, vinyl chloride monomer was added to 3
0 part was charged and the temperature was raised to 57 ° C. with stirring to carry out polymerization.

At the start of polymerization, the pressure in the autoclave was 8.5 kg / cm ² G, but 10 hours after the start of polymerization, it reached 6.5 kg / cm ² G, so at this point the polymerization was stopped and unreacted vinyl chloride monomer was removed. After purging, the contents were taken out and dehydrated and dried.

Table 1 shows the physical properties and the amount of the dispersion stabilizer used, and Table 2 shows the performance of the obtained vinyl chloride resin. The polymerization yield of the vinyl chloride resin was 85%, and the average degree of polymerization was 1000.

The PVA having a fluorine-containing group at the terminal via the sulfido bond (-S-) of the present invention alone or the dispersion stabilizer for suspension polymerization in which ordinary PVA is used in combination gives a vinyl chloride resin having excellent performance. You can see that it is excellent.

Claims (1)

[Claims] 1. A polyvinyl alcohol polymer having a fluorine-containing group at a terminal through a sulfido bond (—S—) and having a saponification degree of 60 mol% or more and a polymerization degree of less than 2000. A dispersion stabilizer for suspension polymerization of a vinyl compound.