JPH0361687B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing high molecular weight water-soluble polyN-vinylcarboxylic acid amide. More specifically, the present invention relates to a method of polymerizing an aqueous solution of N-vinylcarboxylic acid amide using a water-soluble azo compound as a radical polymerization initiator to obtain a high molecular weight polymer with excellent water solubility. N-vinylcarboxylic acid amide is a water-soluble monomer having a vinyl group and an amide group in the molecule, and a water-soluble polymer can be obtained by polymerization. If a high molecular weight polymer can be obtained, it can be expected to have many uses as a water-soluble polymer such as polyacrylamide.
Since it produces amino groups upon hydrolysis, it is promising as a raw material for polycations used as coagulants and flocculants. However, the polymerization behavior of N-vinylcarboxylic acid amide is significantly different from that of acrylamide, and even if it is polymerized in an aqueous solution like acrylamide using an initiator such as ammonium persulfate or potassium persulfate, a smooth polymerization reaction does not occur and polymerization does not occur. Difficult to obtain coalescence. Although the polymerization progresses to some extent by using hydrogen peroxide, it is necessary to successively add an initiator to complete the polymerization. N-
Since vinylcarboxylic acid amide is stable in organic solvents, the polymerization reaction proceeds smoothly, but it has been difficult to obtain high molecular weight polymers due to chain transfer reactions of the solvent during the polymerization reaction. The present inventors conducted intensive studies on a method of polymerizing N-vinylcarboxylic acid amide to obtain a water-soluble polymer.
When polymerization is carried out using a water-soluble azo compound with a half-life of 1000 minutes or less at the polymerization temperature as a radical polymerization initiator in an aqueous solution under the conditions of 10, the polymerization reaction proceeds extremely smoothly, unlike in the case of polymerization using inorganic peroxides. The present invention was achieved by discovering that a high molecular weight water-soluble polymer can be obtained in good yield. That is, the gist of the present invention is to provide a method for obtaining a water-soluble polymer by polymerizing a compound represented by the general formula () CH ₂ =CHNHCOR () (where R represents a hydrogen atom or a methyl group). An aqueous solution of the compound of formula () or a mixture of 50% by weight or more of the compound of general formula () and 50% by weight or less of other water-soluble vinyl monomers is prepared under conditions of pH 6 to 10, and the half-life of the polymerization initiator at the polymerization temperature is A method for polymerizing N-vinylcarboxylic acid amide is characterized in that the polymerization time is 1000 minutes or less using a water-soluble azo compound as a radical polymerization initiator. The present invention will be explained in more detail below. The compound of general formula () used in the method of the present invention is N-vinylacetamide or N-vinylformamide, preferably N-vinylacetamide.
The polymerization method of the present invention is homopolymerization using a compound of general formula () as a monomer or polymerization using a compound of general formula () as a monomer.
It is applied to copolymerization using a mixture of the compound of general formula () containing 50% by weight or more and other water-soluble vinyl monomers as monomers. As the water-soluble vinyl monomer used when copolymerizing with the compound of general formula (), any radically polymerizable water-soluble vinyl monomer can be used, but acrylic monomers are preferred. Preferred water-soluble vinyl monomers include nonionic acrylic monomers such as acrylonitrile, acrylamide, methacrylamide, N-methylacrylamide, N,N-dimethylacrylamide, hydroxyethyl acrylate, hydroxyethyl methacrylate; acrylic acid, methacrylic acid, 2-acryloyl Alkali metal salts and ammonium salts of anionic monomers such as oxyethanesulfonic acid, 2-methacryloyloxyethanesulfonic acid, 2-acryloyloxypropanesulfonic acid, 2-acrylamidoethanesulfonic acid, and 2-acrylamido-2methylpropanesulfonic acid; β-methacryloyloxyethyltrimethylammonium chloride,
2-methacryloyloxyethyltrimethylammonium methyl sulfate, 2-acryloyloxyethyltrimethylammonium chloride, 2-methacryloyloxyethyldimethylbenzylammonium chloride, 2-hydroxy-3-methacryloyloxypropyltrimethylammonium chloride, 2-acrylamidoethyltrimethylammonium chloride , 3-acrylamidopropyltrimethylammonium chloride, 3-acrylamido-3-methylbutyltrimethylammonium chloride, 3-methacrylamidopropyltrimethylammonium chloride, and other quaternary ammonium salts; dimethylaminoethyl acrylate, diethylaminoethyl acrylate, dimethylaminoethyl methacrylate, Examples include salts of mineral acids and organic acids of tertiary amines such as diethylaminoethyl methacrylate, dimethylaminoethyl acrylamide, dimethylaminopropylacrylamide, 3-acrylamido-3-methylbutyldimethylamine, and dimethylaminopropyl methacrylamide. More preferred are acrylates, acrylamide, acrylic acid derivatives and acrylamide derivatives.
Compound of general formula () or 50 mol% or more of compound of general formula () and 50% of other water-soluble vinyl monomers
A mixture with mol% or less is used in the polymerization in the form of an aqueous solution with a total monomer concentration of 10 to 60% by weight. A particularly preferred total monomer concentration is in the range of 20 to 60% by weight in order to obtain a polymer with high molecular weight and good solubility. More preferably, it is 35 to 50% by weight. Although an aqueous monomer solution is generally unstable, by adjusting the pH to 6 to 10 and using a water-soluble azo compound as a polymerization initiator, side reactions during the polymerization reaction can be sufficiently prevented. PH7
In the range of 9 to 9, no side reactions occur during polymerization.
Moreover, this effect is more effective as the concentration of the monomer aqueous solution is higher. PH of monomer aqueous solution is less than 6 and 10
If it exceeds this amount, the monomer tends to decompose or become colored, and the molecular weight and yield of the product tend to decrease significantly.
As the radical polymerization initiator in the method of the present invention, a water-soluble azo compound having a half-life at the polymerization temperature of 1000 minutes or less, preferably 500 minutes or less is used. When a water-soluble peroxide is used as an initiator, a polymer cannot be obtained or the yield of the polymer is significantly reduced regardless of the activity of the initiator or the pH of the aqueous monomer solution, but if the pH is 6 to
When polymerization is carried out using a water-soluble azo compound with a half-life of 1000 minutes or less at the polymerization temperature under conditions 10, a high-molecular-weight, highly soluble polymer can be obtained in good yield. Examples of preferred water-soluble azo compounds include 2,
2'-azobis-2-amidinopropane hydrochloride,
Sulfate and acetate; 4,4'-azobis-4-cyanovaleric acid and its sodium salt, potassium salt, ammonium salt; Azobis-N,N'-dimethyleneisobutyramidine and its hydrochloride, sulfate, nitrate; Examples include acetate. The particularly preferable relationship between the polymerization temperature of these water-soluble azo compounds is 60 to 80°C in the case of a salt of 2,2'-azobis-2-aminopropane;
In the case of cyanovalerate, the temperature is 75-95°C, and in the case of azobis-N,N'-dimethyleneisobutyramidine, it is 50-70°C. By polymerizing under such conditions, particularly high molecular weight polymers can be obtained with a yield of 95% or more. The amount of water-soluble azo compound used is the compound of general formula () or general formula ()
It is used in a weight range of 100 to 20,000 ppm based on the weight of the monomer consisting of a mixture of the compound and the water-soluble vinyl monomer, and can be adjusted as appropriate depending on the polymerization temperature and the half-life of the initiator. Generally, the polymerization temperature is usually carried out in the range of 40℃ to 90℃, but the polymerization reaction
It is best to select conditions that allow the process to be completed in 0.5 to 10 hours, so the preferred conditions are to use a water-soluble azo compound at a temperature of 50°C to 80°C in a weight range of 500 to 5000 ppm based on the weight of the monomer. . Polymerization of an aqueous solution of the compound of general formula () or a mixture of the compound of general formula () and another water-soluble vinyl monomer is not restricted by the order of addition or polymerization method, but when polymerizing in the form of an aqueous solution, the aqueous solution is heated with nitrogen gas. After sufficient substitution to remove oxygen, it is preferable to add a water-soluble azo compound and maintain it at a predetermined temperature under a nitrogen gas atmosphere. The concentration of the aqueous solution is 50-60
Since the product has a very high molecular weight when expressed as % by weight, it is obtained as a water-containing solid substance, and a water-soluble solid polymer can be obtained by cutting this, extracting it with alcohol or acetone, or drying it with heat. However, by the method of the present invention, 0.1
To produce a highly water-soluble, high-molecular-weight polymer with a reduced viscosity of 4 dl/g (equivalent to polyacrylamide with a molecular weight of 1 x 10 ⁶ ) or higher when measured as a solution of (g/dl) at 25°C with an extremely high yield. It is also possible to obtain a polymer having a reduced viscosity of 15 dl/g or more (corresponding to polyacrylamide with a molecular weight of 6 x 10 ⁶ ). The method of the present invention will be explained in more detail below with reference to Examples. Examples 1 to 8 and Comparative Examples 1 to 4 2 g N-vinylacetamide was placed in a 20 ml test tube equipped with a three-way cap. Next, demineralized water, 5% by weight of the polymerization initiator shown in Table 1, and a small amount of hydrochloric acid or caustic soda for pH adjustment were added to form an aqueous solution containing 40% by weight of N-vinylacetamide and a pH of 8.2. Prepared. Under ice-cooling, one side of the three-way pot was degassed using a vacuum pump, the other one was switched, and the test tube was filled with nitrogen gas. After repeating this procedure five times, the three-way pot was closed and polymerization was carried out at the temperature and time shown in Table 1. I went there. Table 1 shows the polymerization rate and reduced viscosity of the product. The polymerization rate was measured from the rate of decrease in UV absorption of 225 mμ N-vinylacetamide.

【table】

[Table] Examples 9 to 11 and Comparative Examples 5 to 7 Aqueous solution of N-vinylacetamide of Example 1
Polymerization was carried out in the same manner as in Example 1, except that the PH was changed to the PH values shown in Table 2. The polymerization rate and reduced viscosity of the product are shown in Table 2.

[Table] *1 Examples 12 to 15 involving monomer decomposition Polymerization was carried out in the same manner as in Example 1, except that the concentration of the aqueous solution of N-vinylacetamide in Example 1 was adjusted to the concentration shown in Table 3. I went. Table 3 shows the polymerization rate and reduced viscosity of the product.

[Table] Examples 16 to 17 Polymerization was carried out in the same manner as in Example 1, except that the monomers shown in Table 4 were used in place of N-vinylacetamide in Example 1. Table 4 shows the polymerization rate and reduced viscosity of the product.

【table】

Claims (1)

[Claims] 1. A method for obtaining a water-soluble polymer by polymerizing a compound represented by the general formula () CH ₂ =CHNHCOR () (where R represents a hydrogen atom or a methyl group), An aqueous solution of the compound of general formula () or a mixture of 50% by weight or more of the compound of general formula () and 50% by weight or less of other water-soluble vinyl monomers is added to the polymerization initiator at a polymerization temperature of PH6 to 10. 1. A method for polymerizing N-vinylcarboxylic acid amide, which comprises polymerizing using a water-soluble azo compound having a half-life of 1000 minutes or less as a radical polymerization initiator. 2. In the method for polymerizing N-vinylcarboxylic acid amide according to claim 1, the general formula ()
Aqueous solution of compound or compound of general formula ()
The total monomer concentration in an aqueous solution of a mixture of 50% by weight or more and 50% by weight or less of other water-soluble vinyl monomers is
A method for polymerizing N-vinylcarboxylic acid amide, characterized in that the amount is 20 to 60% by weight.