JPS58108212A - Preparation of water-soluble high-molecular weight substance - Google Patents

Abstract

PURPOSE:To obtain easily a water-soluble high-molecular weight substance in a high concentration of monomer, by adding a specific amount of a lower alcohol to a mixture of vinyl monomers containing acrylic acid, etc. in an aqueous solvent with the progress of a reaction so that the polymerization reaction is carried out with controlling the viscosity of the reaction system. CONSTITUTION:0.2-5wt% (preferably 0.5-2.5wt%) based on total amount of polymerization reaction system of lower alcohol (one <=6C alcohol such as methanol, etc. or its mixture) is added to acrylic acid and/or its salt alone, or a vinyl monomer mixture (a concentration of the monomer in the total polymerization reaction system is <=50wt%) containing a major amount of acrylic acid and/or its salt in an aqueous solvent, and polymerization is started. The lower alcohol is added to the reaction system with the progress of the reaction so that the polymerization reaction is carried out while controlling the viscosity of the reaction system, to give the desired water-soluble high-molecular weight substance (polyacrylic acid). USE:A food additive, a flocculant for precipitation, treatment for waste water, etc.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a polymer (hereinafter referred to as acrylic acid polymer) whose main component is acrylic acid and its salt (hereinafter referred to as acrylic acid etc.), Especially high degree of polymerization (
The present invention provides an economical method for producing an acrylic acid polymer having an intrinsic viscosity (1 or more) measured in an aqueous 2NIIi soda solution at 80°C.

Acrylic acid polymers are widely used as food additives, precipitating flocculants, wastewater treatment agents, etc., and are expected to be used for other applications.

For example, it is used in many fields such as in the alumina manufacturing process, as a sedimentation accelerator for purifying salt water, and in wastewater treatment in the food industry.

By the way, it is well known that the flocculating ability of such polymer flocculants tends to be approximately proportional to its molecular weight, and acrylic acid-based polymers can also be used to further increase the flocculating ability and to make it more widely available. (In order to be effectively utilized in one field, there is a strong demand for products with even higher molecular weights.

Conventional methods for synthesizing such high molecular weight acrylic acid polymers are roughly divided into aqueous solution polymerization and precipitation polymerization.The former is most suitable for synthesizing high polymers, but the reaction solution The latter has the disadvantage that it becomes very viscous and is extremely difficult to handle; the latter is advantageous in that it allows the product to be taken out as an easy-to-use powder, but because an organic solvent is used as the reaction solvent, There is a problem of chain transfer associated with the use of this organic solvent, and there is a drawback that it is difficult to obtain a high polymer. A method disclosed in Japanese Patent Application Laid-open No. 51-59988 is known as a method for solving the drawbacks of the precipitation polymerization method. This is done by starting a polymerization reaction of acrylic acid, etc., or a vinyl monomer mixture consisting of a predominant amount of acrylic acid, etc., in an aqueous solvent, and then mixing it with water as the reaction progresses. This is a method for producing a water-soluble polymer having a high degree of polymerization, which comprises adding the compound to a reaction system and carrying out a polymerization reaction while controlling the viscosity of the reaction system.

According to this method, since polymerization is initiated using an aqueous solvent, it is possible to suppress the influence of chain transfer associated with the use of an organic solvent, and a polymer with a high degree of polymerization can be obtained. Moreover, by adding a solvent to adjust the viscosity of the reaction slurry, the heat of polymerization can be removed as a snow, and the reaction solution can be easily handled as a powder, which can be easily taken out.

However, even with this method, the viscosity of the reaction system tends to increase due to the high stickiness of the polymer particles precipitated in the reaction slurry, especially in the initial stage of the reaction. The weight must be less than or equal to 1.

For this reason, the present inventors have intensively studied the solvent and reaction conditions used in this method, and have found conditions that enable stable reaction even at higher monomer concentrations, and have developed the present invention. It has been completed.

In other words, the present invention relates to an improvement in the method for producing water-soluble polymers described in JP-A No. 51-59988, in which acrylic acid or/and a salt thereof alone or a predominant amount of acrylic acid or/and a salt thereof is used. In a method for producing a water-soluble high molecular weight polymer by polymerizing a vinyl monomer mixture containing a salt,
The monomer concentration in the total polymerization reaction system is 50% by weight or less, and the polymerization is initiated in an aqueous solvent containing a lower alcohol in an amount of 0.2 to 6% by weight based on the total amount of the polymerization reaction system, and as the polymerization reaction progresses. This method of producing a water-soluble high molecular weight polymer is characterized in that the polymerization reaction is carried out while controlling the viscosity of the reaction system by adding a lower alcohol to the reaction system.

That is, in the present invention, by adding a lower alcohol to the system at the beginning of the reaction, rapid thickening at the initial stage of the reaction can be suppressed, and by using the lower alcohol as an organic solvent, a high monomer concentration can be achieved. The object of the present invention is to provide a method for producing acrylic acid-based polymers that is more economically advantageous than conventional methods.

The present invention will be explained below.

The monomer used in the method of the present invention is acrylic acid or/and its salt alone, or a vinyl monomer mixture containing a predominant amount of acrylic acid or/and its salt, and the monomer in the total polymerization reaction system is The body concentration must be less than 50 F by weight. If the monomer concentration is higher than this, the viscosity of the reaction system becomes too high, making it difficult to stably manage the reaction.

According to the method of the present invention, the lower limit of the monomer concentration is not particularly limited, but industrially advantageously, the lower limit is about 80% by weight.

The lower alcohol added before the start of the polymerization reaction needs to be in an amount of 0.2 to 5% by weight, preferably 0.5 to 2.5% by weight, based on the total amount of the polymerization reaction system.

If the amount added is less than this range, the viscosity increases at the initial stage of the reaction and 1F31 reaction becomes difficult. On the other hand, if the amount added is too large, the reaction will not start or the reaction activity will be low, making it impossible to obtain satisfactory yields and physical properties.

After the reaction starts, when the viscosity of the reaction system reaches a certain state,
Specifically, just before the Weisenberg phenomenon begins to appear, a small amount of lower alcohol is added to the reaction system to reduce the viscosity of the reaction system to a degree of slenderness that does not impair the so-called Tronsdorff effect.This process is repeated up to reaction route r.

As the lower alcohol used in the present invention, one kind or a mixture of two or more kinds of alcohols having a carbon number of about B or less can be used, but monomethanol and octabutanol, which have a small chain transfer effect, are preferable, and methanol is particularly preferable. .

When a solvent other than a lower alcohol is used, stable reaction cannot be managed at a high monomer concentration, for example, at a high monomer concentration of 30 gw.

In the present invention, the use of a dispersant is beneficial for slurry stability and prevention of slurry adhesion to vessel walls. As the dispersant for this purpose, water-soluble polymers such as polyvinyl alcohol and water-soluble cellulose derivatives may be used alone or in mixtures, and small amounts of other surfactants may also be used in combination.

As described above, the present invention enables polymerization at a high monomer concentration, which was impossible with conventional techniques, and has extremely great industrial significance.

The present invention will be specifically explained below using Examples.

Example 1 A mixture of sodium acrylate and acrylamide obtained by mixing the predetermined amounts of methanol shown in Table 1, a total of 6Of of water, 190F of acrylic acid, and 10F of powdered acrylamide, and then neutralizing the mixture with about 225 tons of 454 concentrated aqueous sodium hydroxide solution. Add 5 weight polyvinyl alcohol (PVA Kose) to the aqueous solution.
After adding GH17) aqueous solution 209 and removing the air in the apparatus with nitrogen gas, 1 weight part potassium persulfate aqueous solution and 2 parts by weight tetramethylethylenediamine were added to start the reaction. The reaction temperature was 10°C under a nitrogen stream while stirring.
After polymerizing for about 1.5 hours at a temperature of 1.5 hours, a state was reached just before the Weisenberg phenomenon began to appear, so 15f of methanol was gradually added to lower the system viscosity and the polymerization was continued. Thereafter, 15 f of methanol was added every 0.5 to 2.0 hours to adjust the system viscosity, and polymerization was carried out for about 6 hours. After the completion of the reaction, about 800 f of methanol was added to the reaction system to polymerize. was completely precipitated and heated in an oven to obtain a powdery polymer. This polymer was further washed several times with methanol and then dried under reduced pressure to obtain a product.

The product was white and regular granular, and the polymerization yield and intrinsic viscosity of the product were as shown in Table 1.

Table-1 The symbols indicating reaction stability in Table-1 have the following meanings, and this is the same in Table-2 and subsequent Tables.

〇Polymerization using a stable reaction system until the end of the second reaction.

Δ: Although there was a sudden increase in viscosity 1.6 hours after the start of the reaction, the viscosity decreased with the first addition of methanol and the reaction was completed with a stable slurry after that.

X: There was a sudden increase in viscosity 1 hour after the start of the reaction, and the slurry condensed.

In Table-1, - represents unmeasured, which corresponds to Table-2
The same applies hereafter.

1) The initial amount of methanol is the amount of methanol added before the start of the reaction based on the total amount of the polymerization reaction system, expressed in terms of weight. 2) [η] represents the intrinsic viscosity measured in a 2N caustic soda solution at ao°C. .

This is the same after the IIE2 table.

Example 2 After mixing a predetermined amount of organic solvent shown in Table 2, a total of 50 f of water, and 2 GO of acrylic acid, the mixture was neutralized with an aqueous solution of caustic soda having a concentration of 45% by weight. Polyvinyl alcohol (PV Mugosenol G)! After adding 80 f of -171 aqueous solution and removing the air in the apparatus with nitrogen gas, 159 t of 1-weight aqueous potassium persulfate solution and 15 t of 24-tetramethylethylenediamine were added to start the reaction. After polymerization was carried out for about 1 hour at a reaction temperature of 25°C in a stirred room under a stream of gas, the Weizenperg phenomenon was about to begin to appear, so 15f of the same organic solvent that had been added before the start of the reaction was added. It was added gradually to lower the system viscosity and continue the polymerization. After that 0.5～
Polymerization was carried out for about 5 hours while adjusting the viscosity of the reaction system by adding 15 f of the organic solvent every 2.0 hours. After the completion of one reaction, about 800 to 600 f of the organic solvent was added to completely complete the polymerization. A powdery polymer was obtained by precipitation. This electrolyte was further washed several times with the organic solvent and then dried under reduced pressure to obtain a product. The product was white and granular, and the polymerization yield and intrinsic viscosity of the product were as shown in Table 2. Table 2 Comparative Example Same as in Example 1 where the initial methanol addition amount was 2.5 wt. About 1 time after the start of the reaction, at time S, a state was reached just before the Weisenberg phenomenon began to appear. Therefore, acetone 15f was gradually added, but the system viscosity did not decrease, and acetone 409 was further added, but the Weisenberg phenomenon appeared and the reaction system condensed.

Example 8 After mixing a predetermined amount of organic solvent shown in Table 8, a total of 50 tons of water, and 200 f of acrylic acid, the mixture was neutralized with an aqueous solution of caustic soda having a concentration of about 2,402 kg. After adding aqueous solution 809 of polyvinyl alcohol (PVA Gosenol GH-17) and removing the air in the apparatus with mononitrogen gas, a 2-weight aqueous solution 109 of 22'-azobis-2-amidinopropane was added to start the reaction. I became a woman. About 1 at a reaction temperature of 50C in a nitrogen stream F under stirring
At the time of polymerization, the Weisenberg phenomenon was just about to appear, so the same organic solvent as that added to the reaction initiation surface was gradually added to reduce the system viscosity to F.
The polymerization was continued.

After that, add 1 portion of the organic solvent every 0.5 to 1.0 hours.
Polymerization was carried out for about 4 hours while adjusting the system viscosity by adding Or. After completion of the reaction, a product was obtained by the same method as in Example 2. The polymerization yield and intrinsic viscosity of the product are shown in Table 8. .

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Claims (1)

[Claims] (1) In a method for producing a water-soluble high molecular weight polymer by polymerizing acrylic acid or/and its salt alone or a vinyl monomer mixture containing a predominant amount of acrylic acid or/and its salt, the total polymerization reaction Polymerization is initiated in an aqueous solvent containing 0.2 to 5 weight of lower alcohol based on the total amount of the polymerization reaction system, with the monomer concentration in the system being 50 weight, and as the polymerization reaction progresses, the lower alcohol is added. 1. A method for producing a water-soluble polymer, characterized in that the polymerization reaction is carried out while controlling the viscosity of the reaction system by adding to the reaction system. +2) The method according to claim IK (1), wherein the lower alcohol is mechnol.