JPS5945684B2 - Production method of water-soluble acrylamide polymer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to method 3 for producing a water-soluble acrylamide polymer.

As a general method for producing water-soluble acrylamide-based polymers, a method is well known in which a free radical polymerization initiator is added to an aqueous solution of a monomer, such as acrylamide, to carry out aqueous solution polymerization.

When producing a polymer that is water-soluble and has a high molecular weight (molecular weight (10 million or more)), it is necessary to (a) ensure that cross-linking does not occur in the polymer and make part or most of it insoluble in water; In order to improve the effective utilization rate of monomers and reduce problems such as toxicity during handling, we aim to increase the conversion rate to polymers and reduce the residual rate of unreacted monomers as much as possible. It is easy to control, especially the temperature, which is one of the factors that seriously affects the increase in molecular weight and the formation of crosslinks. d) Polymer aqueous solution (
The proportion of water in the aqueous polymer solution (or aqueous polymer gel) is as small as possible - this is important for reducing packaging and transportation costs when handling the aqueous polymer solution (or aqueous polymer gel), and also In the case of subsequent powdering, sufficient consideration must be given to matters such as the size and capacity of drying equipment, etc., which are important factors in reducing construction costs and operating costs.

For extremely high molecular weight polymers, the viscosity of the aqueous polymer solution produced during the polymerization process is extremely high, and mixing and diffusion is not easy, so stirring and cooling are less effective. increases significantly. Conventionally, in such cases, a so-called redox polymerization initiator, which uses a combination of a peroxide and a reduced product, has been used more often than a peroxide alone.

However, even with the use of redox initiators, it is not easy to obtain satisfactory results. The reason for this is that in order to obtain a polymer with a high molecular weight, it is necessary to lower the initiator concentration, but as the initiator concentration decreases, the residual rate of unreacted monomers decreases inversely. This is because it increases. Furthermore, as the monomer concentration in the polymerization reaction system increases, the temperature rise due to heat generation becomes significant. It is extremely difficult to suppress the rapid temperature rise by cooling or other means, and the result is a polymer with poor water solubility or a polymer with a molecular weight significantly below the target molecular weight.

The cause of the loss of water solubility is not clear, but when exposed to high temperatures, the monomers, polymers, and initiators present in the polymerization reaction system or each other react in a complex manner. This is thought to be due to the formation of cross-bonds. The present inventors have arrived at the present invention as a result of intensive research to solve the above-mentioned problems. In the production method of the present invention, the thermal stability during drying of the polymer is lower than that produced by other methods. It is possible to obtain an acrylamide-based polymer that has excellent water solubility compared to other polymers and has an extremely high molecular weight.

That is, when acrylamide or a monomer mixture containing acrylamide as a main component is polymerized or copolymerized in an aqueous medium, air or oxygen is present in a saturated state in a 10 to 40% by weight aqueous solution of the monomer. Thereafter, using a polymerization initiator composed of a water-soluble bromate, a water-soluble ferric salt, a chelating agent, and a water-soluble sulfite, the temperature was increased to 10 to 50°C.
An acrylamide-based polymer which is characterized by being polymerized or copolymerized at a temperature of It provides a manufacturing method.

The effects of the present invention can be achieved using conventionally known methods, such as the
There are four methods for polymerizing acrylamide using a water-soluble bromate and a water-soluble sulfite, as described in the specification of Japanese Patent No. 6-444, and a method using a ferrous salt and/or EDTA as other polymerization initiator components. is clearly different.

That is, whereas the above-mentioned known methods exclude the presence of air or oxygen in the polymerization system as a negative factor for polymerization, the present invention actively utilizes air or oxygen. The effects of the present invention are achieved using an initiator composed of a water-soluble bromate, a water-soluble ferric salt, a chelating agent, and a water-soluble sulfite, and dissolved oxygen as essential elements; However, the purpose of the present invention cannot be achieved.

The difference between the production method of the present invention and known methods is that there is less sudden heat generation and temperature rise due to monomer polymerization, and the heat generation is gradual and continuous, so temperature control is easy.

Therefore, since the maximum temperature reached is low, it is thought that the formation of cross-bonds in the produced polymer chains is suppressed.

Although it is difficult to theoretically clarify such excellent effects, some of them can be considered as follows. That is, the oxygen and chelating agent (E
Chelating agents such as DTA (which are known to act as stabilizers for oxidizing and/or reducing agents) act independently or cooperatively to effect the redox reaction between bromate and sulfite. It is thought that this will be suppressed.

On the other hand, ferric salts have the effect of promoting the above-mentioned redox reaction, and furthermore, the complex formed from the ferric salt and a part of the chelating agent also participates in some way, resulting in an overall favorable and desired effect. It is estimated that it will give. Monomers that can be used in the present invention include acrylamide alone and vinyl monomers that are water-soluble or copolymerizable with acrylamide or are soluble in an aqueous acrylamide solution or an aqueous monomer solution, and specifically, acrylamide N -Alkyl (C
1-4) Sulfonic acid and its alkali metal salt or ammonium salt, N,N-dimethylacrylamide, acrylonitrile, acrylic acid and its alkali metal salt or ammonium salt, methyl acrylate, ethyl acrylate, methyl methacrylate, vinyl acetate, Vinyl methyl ether, vinyl sulfonic acid and its alkali metal salts, dimethylaminoethyl acrylate (dimethylaminoethyl acrylate), diethylaminoethyl acrylate (diethylaminoethyl acrylate), dimethylaminoethyl methacrylate, diethylaminoethyl methacrylate (diethylaminoethyl methacrylate) /-, dipropylaminoethyl methacrylate (dipropylaminoethyl methacrylate) and a quaternary ammonium derivative of the amino group-containing ester, such as trimethylammonioethyl bromide acrylate with dimethylaminoethyl acrylate and methyl bromide. Some of the monomers listed above are not substantially water-soluble, but the concentration is selected to be below the level that allows them to be dissolved in an aqueous solution of acrylamide and other water-soluble monomers. By copolymerizing acrylamide with other monomers, the proportion of monomers other than acrylamide should be 30 moles or less to obtain a high molecular weight polymer. In addition, when using a hydrophobic monomer as a copolymerization component, care must be taken that the proportion should be such that the water solubility of the resulting polymer is not impaired.The molecular weight of the resulting polymer and Although it is difficult to determine uniformly because it varies depending on the composition, in the case of ethyl acrylate, it is usually 10% mole or less based on the total monomers.The polymerization initiator used in the present invention is sodium bromate. , a salt of an alkali metal such as potassium, but practically sodium bromate is preferable, and the amount is 0.01 to 0.5 based on the monomer.
Weight % is appropriate.

As the water-soluble sulfite, sodium sulfite is suitable.

Alkali metal salts other than sodium, bisulfite, and metabisulfite can also be used in the same way as sodium sulfite, but there is no difference in effectiveness between them, especially if the standard reduction equivalent concentration is the same. Hard to admit. Therefore, sodium sulfite is suitable because it is easily available and has few stability problems. It is desirable to use the sodium sulfite in an amount of 0.005 to 0.05% by weight per monomer and in an amount equal to or less than the amount of bromate.

Water-soluble ferric salts include ferric chloride, ferric nitrate, ferric sulfate, etc., and have a Fe+++ content of 0.00 per monomer.
05 to 0.005% by weight is selected as required.

Chelating agents include nitrilotriacetic acid, ethylenediaminetetraacetic acid, hydroxyethylethylenediaminetriacetic acid,
Although alkali metal salts (including partial salts) such as diethylenetriaminepentaacetic acid can be used, the alkali metal salts of ethylenediamine, tetraacetic acid and hydroxyethylethylenediaminetriacetic acid are conveniently used.

Although any alkali metal salt (including partial salts) may be used, the alkali metal salts of ethylenediaminetetraacetic acid and hydroxyethylethylenediaminetriacetic acid are conveniently used.

The preferred range of use of the chelating agent is 0.0 based on the monomer.
05~0.05 weight? It is.

The above-mentioned amounts of the components and dissolved oxygen preferably act mutually to effectively initiate and progress polymerization.

In order to effectively carry out the present invention, it is desirable that the monomer concentration, pH, and temperature be within appropriate ranges.

However, this condition is not determined by the only factor; the amount of initiator and the ratio of the initiator components are the dominant factors, but the monomer concentration, pH, and temperature are also important factors that cannot be ignored. It has an influence on the polymerization reaction. In order to minimize these complex mutual influences, the monomer concentration should be 10-40% by weight, preferably 20-30% by weight, PH4-8, preferably PH5-7 and temperature 10-40°C, preferably 20°C. By setting the temperature to ~30°C, adjustment can be made simply by increasing or decreasing the initiator amount ratio. The present invention will be explained below with reference to Examples.

(Parts and % are based on weight) Example 1 4000 parts of acrylamide and 150 parts of deionized water were placed in a reaction vessel equipped with a stirrer, a thermometer and a jacket type cooling device.
00 parts and stirred while blowing air into the liquid for 10 minutes to dissolve acrylamide.

Then, 1% aqueous sodium hydroxide solution was added to adjust the pH to 7. O
After adjusting to
Add 0 parts one by one and stir. Seal the reaction vessel to isolate it from the outside air. Immediately run (circulate) water at a temperature of 20C through the cooling jacket. While keeping the outside temperature constant, slowly heat at around 10 rpm. Continue stirring. The polymerization reaction started approximately 20 minutes after the addition of the polymerization initiator, and reached a maximum temperature of 61° C. 2 hours later. Five hours after the start of the polymerization reaction, the internal temperature and external temperature became almost equal, and the polymerization reaction was completed. The resulting polymer was a hard, rubbery gel containing many bubbles, but was completely water-soluble.

The residual rate of unreacted monomers contained in this polymer is 0.5
% or less, and the intrinsic viscosity of the polymer measured using a 1N sodium mononitrate solution as a medium was 18.6.

(The calculated molecular weight is approximately 11.2 million.) 30 g of the polymer gel, which was formed into a sheet with an average thickness of approximately 3 mm, was placed in a hot air circulation dryer at a temperature of 120° C.
After drying for a period of time, the resulting transparent granular particles were substantially completely dissolved in water and had an intrinsic viscosity of 18.0 in a 1N sodium mononitrate solution.

(Molecular weight approximately 10.7 million) Example 2 Wall thickness 0.51tm1
Diameter 12 cr! L1 length 50c: RrL stainless steel (
Acrylamide 12009 in a cylindrical container made of SUS27)
, acrylic acid 3009 and deionized water 20009 were added and dissolved, and while the container was externally cooled with water, 10% sodium hydroxide was added to adjust the concentration to 6.0.

After cooling the internal temperature to 25°C, each was made into a 1% aqueous solution of sodium bromate 759 and ferric chloride 6g (10ppm).
, cedroxyethylethylenediamine triacetic acid disodium salt 9! and sodium sulfite 159 were added sequentially. (The weight of the contents of the container at this time was 5300 f!) Immediately thereafter, the container was covered with a lid and immersed in a constant temperature water bath at 25°C. After about 15 minutes had elapsed since the time of immersion in the constant temperature water bath, the thermometer attached to the container indicated that the exothermic polymerization reaction had started. The maximum temperature reached 67°C, and the reaction was substantially completed in about 3 hours. The obtained polymer was a colorless and transparent gel with extremely high elasticity, showed good water solubility, and had an intrinsic viscosity of 24.6.

The polymer gel was cut into pieces with a maximum diameter of about 5 m71 t, dehydrated by immersion in methanol, dried at 110° C. for 30 minutes, and then ground to obtain a white powder.

This polymer powder easily dissolves in water, and the viscosity of a 1% aqueous solution is 8000 cps (B type viscometer rotor waterfall 312 rpm)
and the intrinsic viscosity was 23.4. Example 3 The polymerization reaction vessel shown in Example 1 was used.

First, put 10,000 parts of deionized water and 2,000 parts of dimethylaminoethyl methacrylate into a reaction vessel, and add 10%
Add hydrochloric acid little by little to reach a pH of about 6. After adjusting the temperature to O, 4,000 parts of acrylamide was added, a small amount of deionized water was added, and air was blown into the mixture in the form of small bubbles to dissolve it with stirring to obtain a homogeneous aqueous solution.

Next, 300 parts, 5 parts, 25 parts, and 3 parts of sodium bromate, ferric sulfate, ethylenediaminetetraacetic acid trisodium salt, and sodium sulfite were added as 4% aqueous solutions, respectively.
0 parts were added sequentially.

The total weight of the aqueous solution at this time was 21,800 parts, and the pH was 5.
5. The temperature was 31°C. Then, the reaction vessel was immediately sealed, and water circulation at 30°C±0.2°C was started through the jacket.

Polymerization began after an induction period of about 20 minutes, reaching a maximum temperature of 58°C. After about 5 hours, there was almost no difference between the internal temperature and the external temperature, and the reaction was substantially completed. Although the obtained polymer was a gel-like material containing many bubbles, it had good water solubility and an intrinsic viscosity of 17.5.

After dehydrating a part of this polymer by immersing it in acetone,
Drying for 30 minutes at 0° C. resulted in a slightly yellowish-white solid that was virtually completely water-soluble, free of water-insoluble materials, and had an intrinsic viscosity of 16.9.

Comparative Example A control product was manufactured in the same manner as in Example 2 except that only the conditions listed in Table 1 were changed, and Table 2 shows the results of comparison with the product obtained by the manufacturing method of the present invention. Ta.

Claims (1)

[Claims] 1 When polymerizing or copolymerizing acrylamide or a monomer mixture containing acrylamide as a main component in an aqueous medium, after making air or oxygen exist in a saturated state in the aqueous medium containing the monomer, the water-soluble bromate,
Polymerization or copolymerization is carried out using a polymerization initiator composed of a water-soluble ferric salt, a chelating agent, and a water-soluble sulfite at a monomer concentration of 10 to 40% by weight at a temperature of 10 to 50°C. Characteristic manufacturing method of water-soluble acrylamide polymer.