JPS5915417A - Production of dispersant - Google Patents

Abstract

PURPOSE:To produce a dry polymer solid suitable as an agent for dispersing bentonite in water, by adding an azo catalyst and a reducing agent to a specified aqueous solution of an acrylic monomer, and polymerizing it while evaporating the water by the heat of polymerization. CONSTITUTION:(Meth)acrylic acid is mixed with (meth)acrylamide at a molar ratio of 100:0-50:50, and an ammonia water, etc., are added to this mixture to form an aqueous monomer solution in which at least 60% of the (meth)acrylate acid has been converted into a salt and which contains 40-60wt%, based on (meth)acrylic acid, water.Then, to this aqueous monomer solution are added an azo catalyst (e.g., azobisisobutyronitrile) and an amount of a reducing agent (e.g., sodium hydrogensulfite) sufficient to reduce the total dissolved oxygen in the monomer, and the monomer solution is subjected to polymerization while the water is being evaporated by the heat of polymerization.

Description

[Detailed description of the invention] The present invention relates to a method for producing a stabilizer.

Specifically, the present invention relates to a method for producing a polymer that can be used as a dispersant for Pe/tonite used in a stabilizing liquid.

Stabilizing liquid is used to fill the excavated space during soil layer excavation in poling, continuous wall construction methods, etc., and prevent the collapse of the soil layer wall by increasing the internal pressure, and also to retain the soil and sand mixed in the liquid. It is a general term for liquids that

OMO has traditionally been used as a dispersant for bentonite.
Since it is a natural product, it rapidly loses its effectiveness due to putrefaction as a result of being decomposed by microorganisms.

Even if OMO was added to the putrid muddy water, it would decompose immediately and the effect could not be restored, so there was no choice but to throw away the putrid muddy water. To prevent this, it is desirable to prepare the stabilizer with a synthetic material that is not subject to microbial decomposition, such as a water-soluble acrylic polymer. As mentioned above, the dispersant used in the stabilizing liquid needs to have a thickening effect in order to retain the earth and sand in the liquid.

However, commercially available water-soluble acrylic polymers cannot be used as dispersants because they have the property of agglomerating earth and sand mixed into the liquid.

Also, acrylic polymers with very low molecular weights do not exhibit a flocculating effect, but they do not have a thickening effect, so they cannot be used for stable a\. .

The properties of such conventional water-soluble polymers depend on the polymerization conditions, and are common to polymers produced using redox-based or azo-based catalysts.

The present inventor conducted a polymerization using a reducing agent and an azo catalyst together as a result of various studies on such conditions.

We have discovered that it is possible to produce a dispersant with a thickening effect that can be used in stabilized liquids, and have arrived at the present invention.

Although the reason why the polymer in the present invention is specifically effective is unknown, it is thought to be due to the molecular structure of the polymer.

The water-soluble acrylic polymer used in the present invention is (
The composition has a molar ratio of meth)acrylic acid and (meth)acrylamide of 100:0 to 50:50, and 60% or more of the acrylic acid is amine.

Preferably, it is in the form of an acrylate that has been neutralized with ammonium or an alkali metal.

As a catalyst for polymerization initiation, azobisui:Nobutyro=l-!
J/L=, 7zobisisocyanovaleric acid, azo-based catalysts such as azohisamidinopropane are suitable, and persulfates, hydrogen peroxide, and organic peroxides are unsuitable. Sulfites and hydrogen sulfites are most preferred as reducing agents. dithionite,
Thiosulfates have poor performance, and heavy metal ions such as ferrous sulfate are ineffective.

These reducing agents are added in an amount more than enough to consume the entire amount of dissolved oxygen in the monomer, and are usually added at a concentration of 50 to 50% per monomer solution.
The desired viscosity is selected within the range of 0,000 ppm.

The concentration of the monomer solution during polymerization is important, and by adjusting the water content to 40 to 60% by weight relative to the acrylic monomer, the water can be vaporized by the heat of one polymerization, and after polymerization, it can be pulverized into a fine powder without going through a drying process. You can get it.

The solubility can also be improved by mixing an alkali metal salt such as soda carbonate with the obtained powder.

The polymerization vessel must be open at the top to allow the water vapor to diffuse away, and polymerization on an endless belt gives good results.

The present invention will be specifically explained below using Examples.

Example 1 30% ammonia water 351 to 72 g of acrylic acid
Mix while cooling to 0°C to prepare the monomer solution and add AI
After mixing a solution of BNQ, 7f dissolved in acetone 7me,
Immediately after adding and mixing 21 parts of sodium bisulfite dissolved in 87 parts of aqueous ammonia, polymerization was carried out in a Teflon-coated shallow dish to obtain a dry polymer solid having a drying loss of 9%.

After pulverization, the polymer concentration was dissolved in IN saline solution at a concentration of 1%.The viscosity at 25°C measured with a rotation meter was 8.5 cp.
Met.

This powder is designated as Sample 1.

Comparative Example 1 30% ammonia water 43g to 72y acrylic acid
Prepare the monomer solution by mixing while cooling to
BNo. 71i' and dodecyl mercaptan 0.0
Immediately after mixing, a solution of 77 dissolved in 7 ml of acetone was transferred to a Teflon shallow dish and polymerized, resulting in a drying loss of 9%.

One solution in INN saline solution yielded a dry polymer solid with a viscosity of 8.7 cp.

This powder is designated as Sample 2.

Example 2 Acrylamide 287. 11 grams of acrylic acid, 501 grams of potassium acrylate. A solution prepared by dissolving 07'% of ruazobisamidinopropane hydrochloride and 7 tq of sodium hydrogen sulfite in 41 i' of water was added to a mixed solution of 267 ml of water. After mixing, the solution was immediately transferred to a Teflon-coated shallow dish and allowed to polymerize, resulting in a drying loss of 9.5 ml. %, INN 1 solution viscosity in saline solution 8
．． 5 cp of polymer dry solid was obtained.

This powder is designated as sample 3.

Comparative Example 2 Polymerization was carried out under the same conditions as Example 2 except that sodium bisulfite was not added, and the loss on drying was 9.5%, IN
A solution of 1 in N saline solution yielded a dry polymer solid with a viscosity of 9.7 Cp.

Fill the sample with this powder.

Effect test 42 g of bentonite is added to 700 m6 of tap water while stirring in a mixer, 3 minutes later, 10 g of a 2% aqueous dispersant solution is added, and stirring is continued for an additional 5 minutes.

- After standing still overnight, the mixture was stirred with a stirrer for 5 minutes, and the funnel viscosity and P water amount were measured.

Funnel viscosity can be measured using a funnel viscometer (500rn
e/500 rrtl) in seconds, and the P water amount is m/number in 3' kg/crrt/30 minutes using an API standard filtration tester.

Claims (1)

[Claims] The molar ratio of acrylic acid and acrylamide is 10020 to 5
An azo catalyst is added to a seven-mer aqueous solution in which the ratio is 0:50, 60% or more of the acrylic acid is in the form of acrylate, and the water content is 40 to 60% by weight based on the total acrylic monomer. 50 to 50
A method for producing a dispersant for adjusting a stable liquid, characterized by adding 000 ppm of a reducing agent.