JPH0565307A - Dispersant - Google Patents

Abstract

PURPOSE:To obtain a dispersant excellent in the ability to disperse, etc., and desirable as, e.g. a dispersant for the emulsion polymerization of a vinyl compound. CONSTITUTION:A modified polyvinyl alcohol containing 0.1-20mol% functional groups of the formula (wherein R1 is H or 1-5C alkyl) in the molecule is produced and is used as a dispersant. An example of a process for producing the modified polyvinyl alcohol comprises copolymerizing a vinyl ester (e.g. vinyl acetate) with a vinyl compound having a functional group of the formula (e.g. N-vinyl-formamide) and hydrolyzing the formed modified polyvinyl ester. When the obtained dispersant is used for the emulsion polymerization of a vinyl compound, the formed emulsion has a viscosity small in temperature dependency and an excellent stability even when left to stand.

Description

Detailed Description of the Invention

[0001]

This invention relates to dispersants. More specifically, it relates to a dispersant for emulsion polymerization of vinyl compounds, a dispersant for suspension polymerization of vinyl compounds, and a dispersant for pigments.

[0002]

2. Description of the Related Art Polyvinyl alcohol (hereinafter abbreviated as PVA) is widely used as a dispersant for emulsion polymerization of vinyl compounds, particularly vinyl esters represented by vinyl acetate. Widely used in various adhesives, paints, paper or textile processing. However, although the vinyl acetate emulsion has excellent adhesiveness and workability, it has drawbacks such as poor water resistance of the film and large temperature dependence of emulsion viscosity. These properties were used for emulsion polymerization. It is known that it depends largely on the dispersant. That is, PVA as a dispersant for emulsion polymerization generally includes fully saponified PVA having a saponification degree of about 98 mol% and partially saponified PVA having a saponification degree of about 88 mol%. When the former is used, it is relatively water resistant. Although it has good properties, it has a drawback that the viscosity of the emulsion increases remarkably at low temperature and gelation easily occurs. On the other hand, when the latter PVA is used, there is a drawback that the water resistance of the film is inferior although the viscosity increase and gelation tendency of the emulsion at low temperature are improved. In order to improve such drawbacks, both PVA's are used in combination, PVA having an intermediate saponification degree between them is used.
Both the water resistance of the film and the small temperature dependence of the emulsion viscosity have not been sufficiently satisfied. In addition, in order to improve the water resistance of the film, urea resin and various cross-linking agents are added to the emulsion using partially saponified PVA, but the water resistance is improved to some extent, but the viscosity at the time of use increases. Workability deteriorates, and these methods have not obtained sufficiently satisfactory results. Next, 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 widely practiced. ing. Generally, the factors controlling the quality of the resin include the polymerization rate and water-
Examples include the monomer ratio, polymerization temperature, type and amount of catalyst, type of polymerization tank, stirring speed, and type and amount of dispersion stabilizer. Among them, it is known that the type of dispersion stabilizer has a very large effect. There is. Regarding the performance required for a dispersion stabilizer for suspension polymerization of vinyl chloride-based monomers, (i) shows a high dispersive power even when used in a small amount, and functions to make the particle size distribution of the resulting vinyl chloride-based polymer particles as sharp as possible. (Ii) In order to increase the absorption rate of the plasticizer to facilitate the processability and to facilitate removal of the vinyl chloride monomer remaining in the polymer particles, and also to remove fish eyes, etc. in the molded product. In order to prevent the formation, it has a function of making each polymer particle as uniform and porous as possible (iii) having a function of making polymer particles having a high filling specific gravity. Conventionally, as a dispersant for suspension polymerization of vinyl compounds, cellulose derivatives such as methyl cellulose and carboxymethyl cellulose, partially saponified PVA and the like have been used alone or in combination. However, the conventional dispersants have a drawback that they have a low ability to make the vinyl chloride polymer particles porous, have a slow plasticizer absorption rate, and are difficult to remove residual vinyl chloride monomer. Next, as a pigment dispersant, conventionally, P
VA-based polymers or polyacrylic acid-based polymers have been used, but they have a problem that the concentration of the dispersion liquid cannot be increased.

[0003]

The object of the present invention is to provide a dispersant for emulsion polymerization of vinyl compounds, a dispersant for suspension polymerization of vinyl compounds and a dispersant for pigments, which are free from the above problems. The aim is to provide suitable dispersants for all applications.

[0004]

Means for Solving the Problems The inventors of the present invention have conducted extensive studies to overcome the drawbacks of conventional vinyl acetate emulsions, and as a result, by using a specific modified PVA as a dispersant, The inventors have found that a vinyl compound emulsion having excellent water resistance of the film and having a small temperature dependency of the emulsion viscosity can be obtained, and completed the present invention. Hereinafter, the invention will be described in detail. The dispersant of the present invention is characterized by comprising a modified PVA containing 0.1 to 20 mol% of the functional group represented by the following Chemical formula 2 in the molecule.

[Chemical 2] (Here, R ₁ represents H or an alkyl group having 1 to 3 carbon atoms, and R ₂ represents H or an alkyl group having 1 to 5 carbon atoms)

The method for producing the modified PVA of the present invention is not particularly limited, but the following two methods can be mentioned, among which the method (1) is easy. (1) After a vinyl ester and a vinyl compound having a functional group represented by the above chemical formula 2 are copolymerized to obtain a modified polyvinyl ester, this is saponified by a conventional method. (2) The functional group represented by Chemical Formula 2 above is introduced into PVA by a polymer reaction. As the vinyl ester in the method (1), any vinyl ester capable of radical polymerization can be used, and examples thereof include vinyl formate, vinyl acetate, vinyl propionate, vinyl pivalate, vinyl versatate (Veova10, a trademark of Shell Co.), and laurin. Examples thereof include vinyl acid salt and vinyl stearate. Examples of the vinyl compound having a functional group represented by Chemical Formula 2 in the method (1) include N-vinylformamide, N-vinylmethylformamide, N-vinylacetamide, N-vinylmethylacetamide and the like. The modified PVA of the present invention contains the functional group represented by Chemical formula 2 in an amount of 0.1 to 20 mol%, preferably 0.2 to 15 mol%.
The content of the functional group is 0.1 mol%
When it is less than 1, the temperature dependence of the obtained emulsion viscosity becomes large, and when it exceeds 20 mol%, the water resistance of the film of the vinyl compound emulsion decreases. Further, the modified PVA of the present invention may include other functional groups as long as the gist of the present invention is not impaired. For example, a carboxyl group, a lactone ring, an amide group, an amino group and the like. Modified P of the present invention
Although the saponification degree of VA depends on the content of the functional group represented by Chemical formula 2, it is preferably in the range of 50 mol% to 99 mol%. The degree of polymerization is appropriately selected from the range of 100 to 8000. The vinyl compound to be used as the dispersant for emulsion polymerization of the present invention is not limited to homopolymerization of vinyl ester such as vinyl acetate, but is also useful in an emulsion copolymerization system with other comonomer copolymerizable with vinyl ester. Examples of such comonomers include ethylene, propylene, vinyl chloride, acrylic acid esters, and methacrylic acid esters.

The dispersant for emulsion polymerization of the present invention is 0.1 to 20% by weight, preferably 0.3% by weight based on the vinyl compound.
~ 15 wt% used. If it is less than 0.1% by weight, the polymerization stability is poor, and if it exceeds 20% by weight, the water resistance of the obtained emulsion film is lowered. The dispersant for emulsion polymerization of the present invention is preferably used alone, but other protective colloids and emulsifiers can be used as long as the effects of the present invention are not impaired. For example, conventional PVA, starch, polyacrylamide, hydroxyethyl cellulose, nonionic emulsifier, anionic emulsifier and the like.

Next, a suspension polymerization dispersant for vinyl compounds will be described. As the dispersant for suspension polymerization of a vinyl compound of the present invention, the modified PVA described in the section of the dispersant for emulsion polymerization of a vinyl compound is used. By using the above-mentioned modified PVA as a dispersion stabilizer, suspension polymer particles of a vinyl chloride-based monomer having a sharp particle size distribution and being porous and having a large filling specific gravity can be obtained. A high plasticizer absorption rate, easy removal of vinyl chloride monomer remaining in the polymer particles, less scattering of powder during handling, and good biteability into molding machines. It has been found to have excellent performance such as. Further, the dispersant of the present invention is not limited to suspension polymerization of vinyl chloride, but is also used for suspension polymerization of vinyl compounds such as styrene and methacrylate.

Next, the pigment dispersant will be described. As the dispersant for pigments of the present invention, the modified PVA described in the section of the dispersant for emulsion polymerization of vinyl compounds is used. As the pigment in the present invention, both organic pigments and inorganic pigments are suitable. It was found that a dispersion having a low viscosity and a high concentration can be obtained by using the modified PVA of the present invention as a dispersant.

[0009]

EXAMPLES The present invention will be described in more detail below with reference to examples. In the following examples, "part" and "%"
"Parts by weight" and "% by weight" unless otherwise specified.
Means respectively.

Example 1 <Production of PVA> 100 parts of vinyl acetate, 5 parts of N-vinylacetamide and 3 parts of methanol were placed in a reaction vessel equipped with a stirrer.
The system was replaced with nitrogen by bubbling nitrogen gas. A solution in which 2,2′-azobisisobutyronitrile was dissolved as an initiator was prepared, and nitrogen substitution was performed by bubbling with nitrogen gas. The temperature of the reaction vessel was raised, and when the internal temperature reached 60 ° C., the initiator solution was injected to initiate polymerization. After 3 hours from the start of the reaction, the polymerization rate was 48.
When it reached%, it was cooled. Then, the unreacted vinyl acetate monomer was removed under reduced pressure to obtain a methanol solution of the modified polyvinyl ester, and NaOH was added thereto.
Was added to the mixture to saponify it. The modified PVA thus obtained had a polymerization degree of 1200, a saponification degree of 92.0 mol%,
And the acetamide group content was 4.2 mol%. <Production of emulsion> Stirrer, reflux condenser, thermometer,
Using a reactor equipped with a dropping funnel, 20 g of the above PVA is dissolved in 240 g of water. Next, 20 g of vinyl acetate was added, the internal temperature was raised to 70 ° C., and then 0.3 g of hydrogen peroxide and 0.5 g of tartaric acid were added to initiate polymerization. Subsequently, 180 g of vinyl acetate and 0.3 g of hydrogen peroxide were continuously added over 3 hours. After the addition was completed, the internal temperature was maintained at 80 ° C. for 1 hour for aging. After cooling, 20 g of dibutyl phthalate was added to give a non-volatile content of 47.9% and a viscosity at 30 ° C. of 18,000.
A 0 cp emulsion was obtained. The obtained emulsion was subjected to the following tests. 1) Evaluation of temperature dependency of emulsion viscosity The emulsion viscosity was measured at 30 ° C and 0 ° C, and the temperature dependency was evaluated by the viscosity ratio. 2) Stability at low temperature The sample was left at -5 ° C for 24 hours and observed for changes in emulsion. 3) Water resistance A paper / paper adhesion test is performed under the following conditions. After curing and drying for 24 hours, it was immersed in water at 30 ° C. for 24 hours and then peeled off, and the adhesion state was examined. Paper: B liner (5 pieces of 25 mm x 50 mm each) Application amount: 40 g (wet) / m ² Pressing: Single pressing with a hand roller Curing curing: 23 ° C 65% RH 24Hr The results are shown in Table 1.

Examples 2 and 3 <Production of PVA> Two kinds of modified PVA were produced by the same procedure as in Example 1 except that the monomer composition was changed. <Production of emulsion> Using each of the above PVA,
An emulsion was obtained in the same manner as in Example 1. The results are shown in Table 1. Comparative Examples 1 and 2 <Production of PVA> PVA was obtained by the same operation as in Example 1 except that the monomer composition was changed. <Production of Emulsion> Using PVA, Example 1
An emulsion was obtained by the same method. The results are shown in Table 1.
Shown in. From the above results, using the dispersant of the present invention,
It is clear that an emulsion having good water resistance and a small temperature dependence of the viscosity of the emulsion can be obtained.

[Table 1]

Examples 4 to 6 and Comparative Example 3 Suspension polymerization of vinyl chloride was carried out by the following method, using the (modified) PVA obtained according to the above method alone or in combination with other PVA. 40 parts deionized water in a glass-lined autoclave, 2% aqueous solution of dispersion stabilizer 0.75
Parts and 5 of diisopropyl peroxydicarbonate
0.009 parts of 0% toluene solution was charged, and the interior of the autoclave was degassed to 50 mmHg to remove oxygen, then 30 parts of vinyl chloride monomer were charged, and the mixture was stirred at 57%.
Polymerization was performed by raising the temperature to ° C. At the start of the polymerization, the pressure in the autoclave was 8.5 kg / cm ² G, but it reached 4.5 kg / cm ² G 7 hours after the start of the polymerization, so the polymerization was stopped at this point and the unreacted vinyl chloride was removed. The monomers were purged, the contents were taken out and dehydrated and dried. Table 2 shows the physical properties and the amount of the dispersion stabilizer used, and Table 3 shows the performance of the obtained vinyl chloride resin. The polymerization yield of vinyl chloride resin is 85%,
The average degree of polymerization was 1050. It is understood that a vinyl chloride resin having excellent performance can be obtained by using the modified PVA of the present invention alone or in combination with the conventionally known PVA.

[Table 2]

[Table 3] (1) Particle size distribution: Measured by dry sieve analysis using a Tyler mesh standard wire mesh. (2) Filling specific gravity: measured according to JIS K6721-1959. (3) Uniformity of particle porosity: 100 parts of vinyl chloride resin,
50 parts dioctyl phthalate, 1 dibutyltin maleate
Part, cetyl alcohol 1 part, titanium white 0.25 part, carbon black 0.1 part was kneaded with a roll at 150 ° C. for a predetermined time (3 minutes, 5 minutes, 7 minutes), and a sheet having a thickness of 0.2 mm Was prepared, and light was transmitted therethrough, and the number of fish eyes contained in the sheet per 100 cm ² was counted. The more the fish eyes disappear in a short time, the better the uniformity of the particle porosity. (4) Absorbency of plasticizer: Using a planetary mixer connected to a plastograph, 100 parts of vinyl chloride resin and 50 parts of dioctyl phthalate were put into a container kept at 80 ° C., and kneading was carried out every hour while stirring. The torque is recorded and displayed as the kneading time at the point where the kneading torque has decreased. (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 7 to 8 and Comparative Examples 4 to 5 Using (modified) PVA or sodium polyacrylate obtained according to the above method, calcium carbonate (P-3 manufactured by Shiraishi Kogyo Co., Ltd.) having a concentration of 60% was used. I got a paste. The results are shown in Table 4.
Shown in. It can be seen that the modified PVA of the present invention can provide a dispersion liquid having a low viscosity and good standing stability.

[Table 4]

[0014]

INDUSTRIAL APPLICABILITY The dispersant of the present invention is suitable as a dispersant for all purposes. Among them, as a dispersant for emulsion polymerization of vinyl compounds, a dispersant for suspension polymerization of vinyl compounds and a dispersant for pigments. Particularly preferably used. When it is used as a dispersant for emulsion polymerization of vinyl compounds, the obtained emulsion has a low temperature property of viscosity and good storage stability. When used as a dispersant for suspension polymerization of vinyl compounds, the obtained vinyl compound-based polymer particles have a sharp particle size distribution, high specific gravity, high plasticizer absorbability, and little residual vinyl monomer. The processing characteristics are good. When it is used as a dispersant for pigments, it is possible to increase the concentration of the dispersion liquid, and the leaving stability of the dispersion liquid is also good.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display location C09C 3/10 PBX 6904-4J

Claims (4)

[Claims] 1. A dispersant comprising a modified polyvinyl alcohol containing 0.1 to 20 mol% of the functional group represented by the following chemical formula 1 in the molecule. [Chemical 1] (Here, R ₁ represents H or an alkyl group having 1 to 3 carbon atoms, and R ₂ represents H or an alkyl group having 1 to 5 carbon atoms) 2. A dispersant for emulsion polymerization of a vinyl compound comprising the modified polyvinyl alcohol according to claim 1. 3. A dispersant for suspension polymerization of a vinyl compound comprising the modified polyvinyl alcohol according to claim 1. 4. A dispersant for a pigment of a vinyl compound, which comprises the modified polyvinyl alcohol according to claim 1.