JPH0410886B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing water-soluble polymers and water-absorbing crosslinked polymers by reverse-phase suspension polymerization. More specifically, polyacrylic acid, polymethacrylic acid, acrylic acid or methacrylic acid, whose use has been expanded in recent years, such as thickeners, flocculants, sizing agents, water absorbing agents, water retention agents, and coagulants, etc. The present invention relates to a method for producing copolymers with these salts. (Prior art) These acrylic acid or methacrylic acid monomers
A method of obtaining a hydrophilic or water-absorbing polymer by copolymerizing (A), (A) and its salts (B), and further adding a polyfunctional aqueous vinyl monomer to (A) and (B). For this purpose, various methods such as static polymerization, solution polymerization, precipitation polymerization, and reversed-phase suspension polymerization have been proposed and put into practice. However, acrylic acid or methacrylic acid monomer (A)
is polymerized at a high concentration in a vinyl monomer aqueous solution with a composition that is 1.5 times (molar ratio) or more that of its salt (B), and the non-neutralized carboxylic acid becomes the neutralized carboxylic acid.
When trying to efficiently obtain a polymer with a molar ratio of 1.5 times or more, it is known that the above-mentioned polymerization method has various drawbacks as described later. For example, the commonly used stationary polymerization method polymerizes salts (B) of acrylic acid or methacrylic acid monomers,
Suitable for obtaining high molecular weight polymers with excellent thickening and coagulating effects. However, if acrylic acid or methacrylic acid monomer (A) is present in this monomer at a high concentration,
The problem with (A) is that steam is easily generated, which can easily cause health and safety problems in the raw material charging process, polymer extraction process, crushing process, and drying process. In the solution polymerization method, there is a phenomenon in which the viscosity of the solution increases significantly as the polymerization progresses.
It is generally used to produce low molecular weight polymers in relatively high yields. (Problems to be Solved by the Invention) Therefore, if a polymer having a high concentration of carboxylic acid is to be obtained in a high molecular weight and in a high yield, there will be operational difficulties during production, and in practice There is a problem in manufacturing efficiency that it is not possible to increase the concentration of the product. In the precipitation polymerization method, since a non-solvent is used for the polymer formed in the continuous phase, there is a problem that a low molecular weight polymer precipitates immediately after polymerization, essentially making it impossible to obtain a high molecular weight polymer. . When producing a polymer with a high concentration of carboxylic acid using a reversed-phase suspension polymerization method, acrylic acid or methacrylic acid monomer (A) is partially distributed in the organic solvent normally used in the continuous phase. However, in many cases, the distributed monomer polymerizes in the organic solvent, producing the same polymer as in the precipitation polymerization method, and destroying the dispersion polymerization system. Therefore, it has been thought that the reverse phase suspension polymerization method is not an appropriate method when the concentration of acrylic acid or methacrylic acid monomer (A) is high. (Means for Solving the Problems) As a result of extensive research into the drawbacks of each of the above-mentioned polymerization methods, the present inventors have discovered that the molecular weight can be controlled relatively easily, and that non-neutralized carboxylic acids are replaced by neutralized carboxylic acids. We have discovered a method to efficiently produce a polymer that has a molecular weight of more than 1.5 times that of carboxylic acid (mole ratio). That is, the present inventors formed a stable dispersion polymerization system by a reversed-phase suspension polymerization method, using lubricating oil in the continuous phase in an amount equal to or more than the monomer aqueous solution that is the dispersed phase, It was discovered that a uniform pearl-like polymer could be obtained. Usually, the organic solvents used in continuous reverse phase suspension polymerization are
51-36791, JP 51-47156, JP 53-46389
As described in , etc., n-heptane, n-hexane, xylene, high boiling point isoparaffin (trade name: Isopar M; manufactured by Exxon Chemical Co., Ltd.), percrene, etc. can be mentioned. When the suspension polymerization method is carried out, as mentioned above, precipitation polymerization occurs partially and often destroys the dispersion polymerization system. However, if a lubricating oil, specifically turbine oil, diesel oil, spindle oil, liquid paraffin, machine oil, etc. is used in this continuous phase, preferably turbine oil, liquid paraffin, more preferably liquid paraffin, It has been found that the distribution of acrylic acid or methacrylic acid monomer (A) into the continuous phase is suppressed, and a stable dispersion polymerization system can be obtained. The present inventors have conducted further research and have found that even when mixed oils, in which the high viscosity of these lubricating oils is reduced by adding a high-boiling hydrocarbon solvent, are used as a continuous phase, they are as stable as in the case of lubricating oils. It was discovered that a dispersion polymerization system can be formed, and the present invention was completed. That is, the present invention provides acrylic acid or methacrylic acid monomers (A), (A)
(A) and (B) whose mole is 1.5 times or more that of the salt (B), or a polyfunctional aqueous vinyl monomer that can be copolymerized with (A) and (B). When obtaining water-soluble or water-absorbing polymers by phase suspension polymerization, lubricating oil is used as a continuous phase in an amount equal to or more than the monomer aqueous solution that is a dispersed phase, or a high-boiling hydrocarbon solvent is added to the lubricating oil. A method for producing a vinyl polymer, characterized by using a mixed oil agent. It is related to. The high boiling point hydrocarbon solvent mentioned here is generally referred to as an odorless solvent, and has an initial boiling point of 180.
℃ or higher and an average molecular weight of 160gr/mol. or higher. Specifically, the product name is EXSOL D60.
(manufactured by Exxon Chemical), EXSOL D80 (manufactured by Exxon Chemical), EXSOL D100 (manufactured by Exxon Chemical), Isopar M (manufactured by Exxon Chemical), No.7 Solvent (manufactured by Exxon Chemical), DOSB (manufactured by Ciel Chemical), Dispersol (manufactured by Ciel Chemical), When a mixture of these high-boiling hydrocarbons and lubricating oil is used continuously, the mixing ratio (weight) is
The ratio of high-boiling hydrocarbons to 1.0 of the lubricating oil is 5.0 or less, more preferably 2.5 or less, but this mixing ratio can be changed as appropriate depending on the composition of the dispersed phase and the ratio of the dispersed phase to the continuous phase (dispersion ratio). It is possible. The polymeric dispersants and emulsifiers used in the present invention have low lipophilicity/hydrophilicity (HLB),
Any emulsifier may be used as long as it stabilizes the water-in-oil system. Examples of emulsifiers include sorbitan monooleate (HLB = 4.3) and sorbitan monostearate (HLB = 4.4). The methacrylic acid esters described in 135501/1987 are suitable. The amount of these polymer dispersants and emulsifiers used is 0.01 to 5 wt%, preferably 0.1 to 5 wt%, based on the dispersed phase.
It is 2wt%. In the dispersed phase used in the present invention, the acrylic acid or methacrylic acid monomer (A) is preferably 1.2 times or more (molar ratio) or more preferably 1.5 times (molar ratio) the amount of the salts (B) thereof. ) or more, and the concentration is preferably 40 to 99 wt%, more preferably 50 to 90 wt% or less,
A polymerization initiator, a chain transfer agent, and a polyfunctional aqueous vinyl monomer are added. Further, when carrying out the present invention, the weight ratio (dispersion ratio) of the dispersed phase and the continuous phase is preferably 1:5 to 1:
1, more preferably 1:4 to 1:2. As the polymerization initiator used in the present invention, water-soluble ones are used, and ammonium persulfate, potassium persulfate, and azo-based ones include 2,2'azobis2-amidinopropane hydrochloride (V-50 : Wako Pure Chemical Industries, Ltd.), 2,2'-azobis2-amidinoacetate, azobis N,N'-dimethyleneisobutyramideine hydrochloride (V-56: Wako Pure Chemical Industries, Ltd.), and more preferably, 2,2'-azobis2-
Amidinopropane hydrochloride. Furthermore, when a low molecular weight polymer is to be obtained in the present invention, a chain transfer agent can be used. Examples of these chain transfer agents include propionamide, isopropyl alcohol, and sodium hypophosphite. When a crosslinked water-absorbing polymer is intended, a polyfunctional aqueous vinyl monomer is added to the dispersed phase in advance, preferably from 0.0005 to 5 wt% of the total monomer.
More preferably, it is used in a range of 0.01 to 1 wt%. Examples of the acrylates or methacrylates used in the present invention include alkali metal salts such as sodium acrylate, lithium acrylate, potassium acrylate, sodium methacrylate, lithium methacrylate, and potassium methacrylate. Examples of the polyfunctional aqueous vinyl monomer used in the present invention include methylene bisacrylamide, polyethylene glycol diacrylate, pentaerythritol diacrylate, trimethylolpropane diacrylate, and methylene bis dimethacrylate. Examples will be described below. (Example) Example 1 Five-necked device equipped with a stirring device, nitrogen introduction tube, temperature measurement tube inside the pot, cooling tube with an Arling ball, and sample introduction port.
A continuous phase (liquid paraffin: 298 parts by weight, sorbitan monooleate: 1 part by weight, polymer dispersant: 1 part by weight) was charged in advance into a 500 ml round-bottom separable flask, the temperature inside the kettle was adjusted to 40°C, and nitrogen purge was carried out. Stir while doing this. A dispersed phase prepared in advance (acrylic acid: 72 parts by weight, water 28 parts by weight, V-50:
14.4×10 ^-3 parts by weight) and polymerize. After the polymerization is completed, the polymer is separated using a nuttie, washed three times with n-hexane, and dried using a vacuum dryer to obtain a polymer. The properties of this product are shown in Table 1. Example 2 The same procedure as in Example 1 was carried out using the same equipment and only changing the composition. These compositions and results are shown in Table 1.

【table】

[Table] The polymerization results were all good, with no deposits in the pot after polymerization, and pearl-like particles with a particle size of 15 to 500 μm were obtained as polymer particles after washing and drying. The polymer dispersant used in this example was a copolymer of methacrylic acid 2-ethylhexyl ester and methacrylic acid dimethylaminoethyl ester. As mentioned above, if a lubricating oil or a mixed solvent of a lubricating oil and a high-boiling hydrocarbon solvent is used as the continuous phase,
A polymer having a composition in which the amount of non-neutralized carboxylic acid is 1.5 times or more (molar ratio) that of the neutralized carboxylic acid can be efficiently produced by a reversed-phase suspension polymerization method.

Claims (1)

[Claims] 1 acrylic acid or methacrylic acid monomer (A),
(A) and (B), where (A) is 1.5 times or more mole or more of its salt (B);
Or these are polyfunctional aqueous vinyl monomers that can be copolymerized with (A) and (B). A method for producing a vinyl polymer, which comprises using a lubricating oil in an amount equal to or more than the same amount (weight) as a monomer aqueous solution as a dispersed phase, or a mixed lubricant prepared by adding a high-boiling hydrocarbon solvent to the lubricating oil.