JPS6239604A - Production of acrylamide based polymer - Google Patents

Abstract

PURPOSE:To increase the polymerization rate and produce an acrylamide based polymer having a high molecular weight and improved water-solubility, by polymerizing acrylamide monomer in the presence of a specific amount of copper ions in an aqueous solution. CONSTITUTION:Acrylamide is polymerized in the presence of a persulfate, formaldehyde sodium sulfoxylate and an azo compound, e.g. 2,2'-azobis-2- amidinopropane or 4,4'-cyanovaleric acid, as a polymerization initiator under basic conditions of normally 10-30pH in an aqueous solution to give the aimed acrylamide based polymer In the preocess, the polymerization is carried out in the presence of 1-100ppb, preferably 2-50ppb, more preferably 3-20ppb based on the above-mentioned monomer, copper ions. USE:Used as a thickening agent, flocculant, wet paper strengthening agent, mucilaginous agent in paper making industry, etc.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing an acrylamide polymer. Specifically, the present invention provides a method for producing an acrylamide-based polymer that increases the polymerization rate, has excellent water solubility, and has a high molecular weight by carrying out aqueous solution polymerization of acrylamide monomers under specific polymerization conditions. be.

Water-soluble polymers mainly composed of acrylamide are used as thickeners,
It is a polymer that is useful in many applications such as flocculants, paper strength enhancers in the paper industry, sticky agents for paper making, filler retention improvers, and water-based improvers, especially as flocculants and sticky agents for paper making. requires a polymer with good solubility and extremely high molecular weight.

BACKGROUND OF THE INVENTION Such high molecular weight acrylamide-based polymers are usually produced by aqueous solution polymerization, but in the polymerization of this type of monomer, as soon as the polymerization starts, the entire polymerization system becomes extremely viscous or gel-like and cannot be stirred. Since this becomes extremely difficult, it is virtually impossible to remove the polymerization heat and the temperature has to be allowed to rise.

Therefore, in order to avoid a decrease in molecular weight and the formation of insoluble polymers due to an increase in polymerization temperature, it is necessary to start polymerization at the lowest temperature possible, and to use different polymerization initiators with different decomposition rates in combination according to the increase in polymerization temperature. Methods such as

Examples of the combination of polymerization initiators include the combination of a redox initiator and an azo compound. This is because while redox initiators can initiate polymerization at low temperatures, they tend to produce insoluble polymers at high temperatures, and azo compounds generate radicals at high temperatures. In general, there is little branching even at high temperatures,
That is, it skillfully utilizes the ability to change polymers with good solubility.As an example of this combination, recently, for example, Japanese Patent Application Laid-Open No. 58-21920, which is also the subject of the present application,
The method described in Publication No. 5 can be mentioned.

However, in order to obtain a water-soluble acrylamide polymer with excellent solubility and high molecular weight by using a system that uses such a specific polymerization initiator, we need to study its polymerization behavior and In the process of various studies on the performance etc. of the obtained polymer, we found that the polymerization rate was slow or that the polymerization rate was not sufficient, especially when polymerization was carried out under basic conditions where a part of the acrylamide component was hydrolyzed during polymerization. It was found that there were problems such as the inability to obtain high molecular weight polymers.

Summary of the invention for solving Wataru 1 point L51: As a result of intensive research to solve the above problem, the present invention surprisingly solves the problem by allowing a trace amount of copper ions to be present during polymerization. This was discovered to be extremely effective for solving the problem.

That is, in the present invention, when producing a water-soluble acrylamide-based polymer by carrying out aqueous solution polymerization under basic conditions using an acrylamide monomer as a polymerization initiator using persulfate, formaldehyde sodium sulfoxylate, and an Ab compound, The polymerization is carried out at a rate of 1 to 10% for the acrylamide monomer.
The gist of this invention is a method for producing a water-soluble acrylamide polymer, which is characterized in that it is carried out in the presence of 0 ppb of copper ions.

According to the present invention, the polymerization rate can be increased several times compared to the case where copper ions are not present. At the same time, polymers with high molecular weights of about 100,000 or more, which have excellent water solubility, can be produced extremely stably. It is possible to manufacture it efficiently.

Although the mechanism of action of copper ions in the present invention is not clear, the effect is unique to basic conditions, and judging from the fact that the polymerization rate increases, some This is presumed to be due to the fact that the influence of polymerization inhibition caused by impurities was removed by the activation of the initiator system by copper ions. Conventionally, copper salt (copper ion)
Considering that the compound has a strong inhibiting effect on polymerization and is generally known as an inhibitor, the effect of promoting polymerization under the specific polymerization conditions of the present invention is completely unexpected.

Detailed Description of the Invention: [1,1 Copper Ion In the present invention, copper ions are present in an acrylamide monomer aqueous solution in an amount of 1 to 100 ppb, preferably 2 to 5 opppb, and polymerization is carried out.

Examples of copper ion sources include copper oxides, hydroxides,
Examples include copper compounds such as inorganic acid salts, organic acid salts, and complex salts, and metals. Among these, inorganic or organic acid salts with high solubility in water such as copper sulfate, copper nitrate, and copper acetate are used. It is preferable from this point of view.

These copper compounds, etc. may be used alone or in combination of two or more, and the timing of addition is not only at the start of polymerization but also during the production, purification, storage, etc. of the acrylamide monomer, as long as it is present at the time of polymerization. It may be either.

In addition, the expression "copper ion" in the present invention refers to the case where it is assumed that all the copper elements present in the polymerization system exist as copper ions, and copper is present in a compound or free state, or It does not matter whether it exists in a colloid, a copper ion, a complex ion, or the like.

This is because it is not necessarily clear what state a trace amount of copper is in in a complex aqueous solution containing 1ffi acrylamide, a basic substance, etc. as in the present invention.

In any case, the objects and effects of the present invention can be achieved if "copper ions" are present in the above-mentioned layer.

(2) Polymerization initiator The polymerization initiator used in the present invention consists of a persulfate, sodium formaldehyde sulfoxylate, and an azo compound, and the first two form a redox system.

Typical persulfates are alkali metal salts, especially potassium and sodium salts, and ammonium salts. The dihydrate of formaldehyde sodium sulfoxylate is known as longalisoto, and although the dihydrate is preferably used in the present invention, anhydrous or other forms can also be used.

Examples of azo compounds include 2,2'-azobis-2-amidinopropane, 4,4'-azobis-4-
Various compounds are used such as cyanovaleric acid, 2,2'-azobisisobutyronitrile, among which 2,
Preference is given to using 2'-azobis-2-amidinopropane, especially its hydrochloride.

In the present invention, a non-essential amount of polymerization initiator components other than those described above may be present as long as the effects of the present invention are not impaired.

(3) Basic conditions In the present invention, copper ions have a remarkable effect under basic conditions, especially strong basic conditions where a part of the acrylamide monomer is hydrolyzed. Therefore, the present invention is suitable for producing partially hydrolyzed acrylamide polymers by hydrolyzing acrylamide monomers during polymerization. As the hydrolyzing agent, a system in which a strong alkaline substance such as caustic soda or caustic potash is combined with a weak acid such as boric acid, carbonic acid, or acetic acid is usually used. The pH of the system at the initial stage of polymerization is in the range of about 10 to 13, depending on the type and amount of the hydrolyzing agent added in accordance with the desired degree of hydrolysis.

(4) Aqueous solution polymerization The aqueous solution polymerization of the present invention is carried out under basic conditions where a part of the acrylamide component is particularly hydrolyzed and hydrolyzed as described above, but it is essentially different from the conventional acrylamide aqueous solution polymerization. is no different.

Polymerization is usually carried out at a concentration of acrylamide monomer in the aqueous solution of about 15 to 50% by weight, a polymerization initiation temperature of about 0 to 30°C, and substantially adiabatic conditions from the outside of the polymerization system. The polymer is obtained as a gel-like aggregate, which after being crushed into small pieces,
If necessary, dry and crush to form a granular polymer.

In the present invention, a part of the acrylamide monomer may be replaced with other monomers copolymerizable with acrylamide, such as meccrylamide, acrylonitrile, methyl acrylate, etc., as long as the effects of the present invention are not impaired. .

Example 1 416 g of acrylamide aqueous solution (concentration 50% by weight) was placed in a 11-year bottle, to which 10.0 g of boric acid and 6.8 g of caustic soda were added as an aqueous solution, and further 10 ppb of copper ion was added per acrylamide monomer. A corresponding amount of copper nitrate (trihydrate) was added as an aqueous solution, and the total weight was brought to 800 g using ion-exchanged water.

The pH of the aqueous solution at this time was 12.0. After sufficiently removing oxygen in this polymerization system using nitrogen gas, the temperature was maintained at 15°C, and potassium persulfate 25 ppm, formaldehyde sodium sulfoxylate dihydrate 7 o
pρm, 2.2'-azobis-2-amidinopropane hydrochloride 100 ppn+, 2 ml and 5.6, respectively.
It was added as an aqueous solution of m2.0.8 m it. Approximately 5
Polymerization started after a few minutes, and the peak temperature was 90 minutes after the start of polymerization.
The temperature reached 0°C. The obtained rubbery gel was heated at 90°C for 16 hours.
s, leave it to stand, then crush it into small pieces with a meat grinder and dry it in a hot air dryer for 60 minutes.
It was dried at ℃ and crushed into powder.

The viscosity of a 1% by weight aqueous solution of this powdered polymer was measured using a B-type viscometer (6 rpm, 25°C) and found to be 12.500c.
It was ps. When 10 ml of 2N-1hSO was added to 500 g of this solution and the viscosity was measured under acidic conditions (PH=2.3), it was 1.100 cps. Furthermore, when a part of this aqueous solution was taken and the hydrolysis rate was measured, it was 14.2
It was mol%.

Moreover, there was no water-insoluble matter at all.

Example 2 In Example 1, nitric acid gA (
The procedure was carried out in the same manner as in Example 1 except that 5-hydrate (pentahydrate salt) was used.

The induction period of polymerization was about 3 minutes, and the peak temperature reached 90°C 90 minutes after the start of polymerization. The powdered polymer obtained in the same manner as in Example 1 had a viscosity of 1.060 cps and a hydrolysis rate of 14.4 mol% under acidic conditions. Moreover, there was no water-insoluble matter at all.

Example 3 The same procedure as in Example 1 was carried out except that cuprous chloride was used instead of copper nitrate (trihydrate).

The induction period of polymerization was about 3 minutes, and the peak temperature reached 91° C. 85 minutes after the start of polymerization. The powder polymer obtained by +M production similar to Example 1 had a viscosity of 1.080 cps under acidic conditions and a hydrolysis rate of 13.9 mol%. Further, there was no water-insoluble matter at all.

Example 4 The same method as in Example 1 except that 250 ppm of 4.4"-azobis-4-cyanovaleric acid was added in the form of sodium salt instead of 2,2"-azobisamidinopropane hydrochloride. I performed the operation.

The induction period of polymerization was approximately 3 minutes, and a peak temperature of 89° C. was reached 270 minutes after the start of polymerization. The powdered polymer obtained in the same manner as in Example 1 had a viscosity of 960 cρS under acidic conditions and a hydrolysis rate of 13.5 mol%. Further, there was no water-insoluble matter at all.

Comparative Example 1 The same procedure as in Example 1 was carried out except that the copper nitrate (trihydrate) aqueous solution was not added. The induction period of polymerization was about 5 minutes, which was almost the same as in Examples 1 to 3, but it took 8 hours to reach the peak temperature. The viscosity of the obtained polymer under acidic conditions was 405 cp compared to Examples 1 to 4.
The hydrolysis rate was 13.0 mol%.

In addition, when the amount of copper mixed in the acrylamide monomer used in Examples 1 to 4 and Comparative Example 1 was analyzed, it was found that the amount of copper contained in the acrylamide monomer was approximately 1 ppb or less in all cases.

Claims (1)

[Claims] When producing an acrylamide polymer by aqueous solution polymerization under basic conditions using persulfate, sodium formaldehyde sulfoxylate, and an azo compound as a polymerization initiator, the polymerization is carried out to form an acrylamide monomer. 1. A method for producing an acrylamide polymer, which is carried out in the presence of 1 to 100 ppb of copper ions.