JPH0127086B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing a water-soluble polymer. In particular, it relates to a method for producing an acrylamide polymer. Water-soluble polymers are useful as flocculants, paper strength agents, fiber treatment agents, adhesives, etc. For example, acrylamide polymers are useful as flocculants. Conventionally, in order to produce such water-soluble polymers, water is usually a good solvent for both monomers and polymers, so
Aqueous solution polymerization is being carried out. Moreover, the polymer solution has a viscosity that is too high to be stirred and cooled, resulting in a significant temperature rise during the polymerization process. For this reason, redox polymerization initiators have conventionally been used as polymer initiators capable of generating radicals over a wide temperature range. but,
When a redox-based polymerization initiator is used, the components of the redox-based polymerization initiator react with the polymer during polymerization and drying, forming cross bonds, and the reducing agent causes induced decomposition, resulting in the polymerization initiator's efficacy not lasting. Problems such as unreacted monomer remaining have been pointed out. On the other hand, various studies have been conducted to solve these problems, but all of them involve the combination of redox-based polymerization initiators and other polymerization initiators, and as long as redox-based polymerization initiators are used, essentially It didn't solve the problem. In view of these problems, the present inventors conducted intensive research and established a method for producing a water-soluble polymer that does not have the above-mentioned drawbacks and produces remarkable results, thereby completing the present invention. That is, the present invention uses 2,2'-azobis(N,N'-dimethyleneisobutyramidine) or a salt thereof, 2,2'-azobis(2-amidinopropane) or a salt thereof, or 4 , 4'-azobis-4-cyanovaleric acid or a salt thereof. The salt refers to an acid addition salt of an inorganic acid such as hydrochloric acid, sulfuric acid, or phosphoric acid, or an acid addition salt of an organic acid such as acetic acid, propionic acid, or benzoic acid. In the method of the present invention, 2,2'-azobis(N,N'-dimethyleneisobutyramidine (hereinafter abbreviated as ADIA) or its salt used as a polymerization initiator has a fast decomposition rate, so redox-based polymerization can be initiated. It can be used alone as it can be polymerized at low temperature like other agents, but on the other hand, in the production of water-soluble polymers,
It is generally desirable that the percentage of water in the polymer solution be as low as possible to save on subsequent drying costs, transportation costs, equipment capacity, and the like. However, since the higher the solids content of the polymerization solution, the higher the final temperature, the presence of a polymerization initiator capable of generating radicals at high temperatures is preferred. Like the redox-based polymerization initiator, peroxide as a polymerization initiator reacts with the polymer to form a cross bond, and therefore an azo compound is preferably used in combination. The characteristics of the azo compound, such as low chain transfer and no induced decomposition, combined with the characteristics of ADIA or its salts, provide even more excellent effects. There are various azo compounds used in combination for this purpose, among which 2,
Particularly effective is the use of 2'-azobis(2-amidinopropane) or a salt thereof, or 4,4'-azobis-4-cyanovaleric acid or a salt thereof. In the method of the present invention, the monomers constituting the water-soluble polymer include at least monomers that are soluble in water, or monomers that are soluble in an aqueous solution of such water-soluble monomers. It suffices if it is a quantitative substance. For example, acrylic acid or its salts, methacrylic acid or its salts, acrylic acid amide, methacrylic acid amide, hydroxyalkyl esters such as hydroxyethyl ester of acrylic acid or methacrylic acid,
Esters of amino alcohols such as dimethylaminoethanol, diethylaminoethanol, and diethylaminopropanol of acrylic acid or methacrylic acid, and salts thereof, or quaternary ammonium salts, methyl acrylic acid or methacrylic acid,
Examples include alkyl esters such as ethyl and n-butyl. In addition, vinyl alkyl ethers such as vinyl methyl ether and vinyl ethyl ether, vinyl sulfonic acids such as vinyl sulfonic acid, allyl sulfonic acid, or their salts, vinyl pyrrolidone, vinyl pyridine, N-methylol acrylamide, diacetone acrylamide, acrylonitrile, and vinyl acetate. etc. Next, explaining the process according to the method of the present invention, the polymerization process can be carried out under normal conditions. For example, in aqueous solution polymerization, oxygen in the polymerization system is generally replaced with an inert gas such as nitrogen gas or carbon dioxide gas. The monomer is usually prepared in a 5 to 30% aqueous solution, and the amount of ADIA or its salt and azo compound added as a polymerization initiator is usually adjusted to the monomer.
It is used at about 0.0001 to 1.0%. The polymerization initiation temperature is from room temperature to 50°C. The method of the present invention can be carried out not only in aqueous solution polymerization but also in ordinary polymerization steps for water-soluble polymers in emulsion polymerization and reverse phase (aqueous phase/oil phase) suspension polymerization. Among the water-soluble polymers obtained by the present invention, for example, polyacrylamide-based polymers obtained by aqueous solution polymerization, when compared with polymers obtained by conventional methods, ADIA or its salt has a lower decomposition rate. Since it is a fast polymerization initiator, polymerization is possible without using a redox polymerization initiator.
At the same time, since an azo compound is also used as a radical generation source at high temperatures, there are disadvantages of redox-based polymerization initiators (i.e., cross-linking is generated. It solves the problem of unreacted monomers remaining in the polymer, and has a high molecular weight, little branching, and good water solubility, and has a remarkable effect as a flocculant. In addition, when water-soluble polymers such as polyacrylamide-based polymers are stored as dilute solutions for long periods of time, they undergo changes, although the cause and structure are still unknown, and when used for various purposes,
There was a problem that the effect was reduced. Regarding this point as well, the combination of ADIA or its salt according to the present invention and an azo compound as a polymerization initiator results in less change than conventional polymerization initiators such as redox-based polymerization initiators. The percentage is extremely low. The present invention will be explained in more detail with reference to Examples below. Note that parts in the examples are parts by weight. Example 1 5 parts of acrylamide and 75 parts of distilled water are added and dissolved in a reaction vessel equipped with a stirrer. Further, a predetermined amount of a polymerization initiator is added, and the mixture is polymerized under stirring in a nitrogen stream at a predetermined temperature for a predetermined time, and the resulting viscous liquid is dried on a double drum drier to obtain a white scaly dried product. Example 1 is used as Comparative Examples 1 and 2 for comparison with a case where 2,2'-azobis(N,N'-dimethyleneisobutyramide) hydrochloride and an azo compound are used together as a polymerization initiator. Table 1 shows the results obtained when a conventionally used redox polymerization initiator was used as a polymerization initiator under these conditions. However, the intrinsic viscosity was measured using an Ubbelohde viscometer.

[Table] Reference example 1 Using a 50ml sedimentation test tube with a stopper and an inner diameter of 2cm, Table 2
Add 47.5 ml of each test solution shown in , and shake well to make a suspension. To this, 2.5 ml of the polymers obtained in Example 1 and Comparative Examples 1 and 2 shown in Table 1 were added as aqueous solutions with the concentrations shown in Table 3 to each test solution. Each mixture was mixed by inversion 10 times and then left to stand to measure the aggregation effect. The results obtained are shown in Table 3.
However, the transmittance was measured at 600 nm of the supernatant after 15 minutes, with water as 100%.

【table】

[Table] The acrylamide polymer produced according to the present invention has extremely excellent coagulation effects such as sedimentation rate and transmittance. Example 2 Acrylamide 3 was added to the same reaction pot as in Example 1.
1 part acrylic acid and 70.4 parts distilled water were added and dissolved, and 2,2'-azobis(N,
N'-dimethyleneisobutyramidine) hydrochloride
After adding 0.002 parts and 0.001 parts of 4,4'-azobis-4-cyanovaleric acid sodium salt and reacting at 40°C with stirring in a nitrogen stream for 5 hours, the polymerization rate was 97.5 after neutralization with 5.6 parts of 10% caustic soda solution. % colorless clear viscous liquid was obtained. Measuring the viscosity of a 1% aqueous solution after drying
It showed 6900cps (25℃). However, the viscosity of the 1% aqueous solution was measured at 25°C using a Bruckfield rotational viscometer. Comparative Example 3 Among the conditions of Example 2, 2,
The reaction was carried out under the same conditions as in Example 2 except that 0.003 part of 2'-azobis(N,N'-dimethyleneisobutyramidine) hydrochloride was used, but a colorless clear viscous liquid with a polymerization rate of 87.9% was obtained. Viscosity of 1% aqueous solution after drying
It was 5600 cps (25°C), which was lower than in Example 2. However, the viscosity of the 1% aqueous solution was measured at 25°C using a Bruckfield rotational viscometer. Comparative Example 4 Among the conditions of Example 2, 4,
Sodium 4'-azobis-4-cyanovalerate
The reaction was carried out under the same conditions as in Example 2 except that 0.003 part was used, but the polymerization did not proceed at all. Example 3 Acrylamide 1 was placed in the same reaction pot as in Example 1.
1 part, 3 parts of quaternary ammonium salt of dimethylethyl methacrylate, and 76 parts of distilled water were added and dissolved, and further 0.002 part of 2,2'-azobis(N,N'-dimethyleneisobutyramidine) hydrochloride and 2 parts of 2,2'-azobis(N,N'-dimethyleneisobutyramidine) hydrochloride were added as a polymerization initiator. , 0.001 part of 2'-azobis(2-amidinopropane) hydrochloride was added, and the solution was adjusted to pH 3 with sulfuric acid, and then reacted with stirring at 40 to 60°C in a nitrogen stream for 5 hours to form a colorless product with a polymerization rate of 98.8%. A clear viscous liquid was obtained. The viscosity of a 1% aqueous solution after drying is 132 cps (25℃)
showed that. However, the viscosity of the 1% aqueous solution was measured at 25°C using a Bruckfield rotational viscometer. Example 4 Into the same reaction vessel as in Example 1, 15 parts of acrylamide and 65 parts of distilled water were added and dissolved, and nitrogen gas was introduced to sufficiently remove dissolved oxygen. As a polymerization initiator 2,
0.0015 parts of 2'-azobis(N,N'-dimethyleneisobutyramidine) hydrochloride and 0.0015 parts of 2,2'-azobis(2-amidinopropane) hydrochloride were added to initiate polymerization at 30°C. After the polymerization was started, the polymerization was allowed to stand for 6 hours to obtain a colorless and clear gel-like polymer with a polymerization rate of 99.9%. The final temperature inside the reaction vessel was 79°C. After drying, the 1% aqueous solution becomes a homogeneous solution with a viscosity of
It was 1300cps. (However, the viscosity was measured using a Bruckfield rotational viscometer.) Comparative Example 5 Under the conditions of Example 4, 0.002 part of ammonium persulfate and 0.001 part of sodium sulfite were used as the polymerization initiator.
The conditions were the same as in Example 4, except that the same conditions as in Example 4 were used, and the static polymerization rate was 96.5%, and the final temperature inside the reaction vessel was 72°C.
After drying, some gel insoluble in 1% aqueous acid remained, and the viscosity was 420 cps, lower than in Example 4. However, the viscosity of the 1% aqueous solution was measured at 25°C using a Bruckfield rotational viscometer. Comparative Example 6 Among the conditions of Example 4, 2,
The reaction was carried out under the same conditions as in Example 4 except that 0.003 part of 2'-azobis(N,N'-dimethyleneisobutyramidine) hydrochloride was used, but the polymerization rate was 96.9% and the final temperature inside the reaction vessel was 77%. It was warm at ℃. 1% after drying
The viscosity of the aqueous solution was 920 cps, which was lower than in Example 4. However, the viscosity of the 1% aqueous solution was measured at 25°C using a Bruckfield rotational viscometer. Comparative Example 7 Among the conditions of Example 4, 2,
2'-azobis(2-amidinopropane) hydrochloride
The reaction was carried out under the same conditions as in Example 4 except that 0.003 part was used, but the polymerization rate was 93.5% and the final temperature inside the reaction vessel was 64°C. After drying, the viscosity of the 1% aqueous solution was 1180 cps, which was lower than in Example 4. However, 1
% aqueous solution was measured at 25°C using a Bruckfield rotational viscometer.

Claims (1)

[Claims] 1 As a polymerization initiator, 2,2'-azobis(N,
N'-dimethyleneisobutyramidine) or its salt and 2,2'-azobis(2-amidinopropane) or its salt, or 4,4'-azobis-4-cyanovaleric acid or its salt are used together. A method for producing a water-soluble polymer, characterized by: