JPH0127084B2 - - Google Patents

Description

[Detailed description of the invention]

This invention relates to an improved process for producing water-soluble polymers in the dispersed phase of water-in-oil emulsions. More particularly, the present invention relates to such a process, which can significantly reduce the amount of coagulum associated with conventional such manufacturing. Water-soluble polymers derived from water-soluble monomers are typically prepared in aqueous solution. however,
Many of the polymers produced in this way are produced as steel gels that must be further processed to form useful products. Typically, water-
After drying, the polymer gel is shredded into a powdered solid, which is then dissolved in water for use. The polymer can only be prepared as a dilute aqueous solution, usually less than 1 weight percent, without modification of the gel structure. Preparation of dilute solutions must be done carefully and requires a long time. For many applications, dilute solutions must be prepared remote from the site of use and require the transportation of large amounts of water for the very small amounts of useful polymer. To overcome the problems associated with these gel polymers and their aqueous solutions, recent developments have led to the production of the polymers in the dispersed phase of water-in-oil emulsions. In this process, the amount of monomer to form the polymer is dissolved in water, and the resulting aqueous monomer solution is emulsified in a suitable oil to form a water-in-oil emulsion. Then polymerization is carried out to form the desired polymer in the dispersed aqueous phase,
The water-in-oil emulsion thus obtained is the desired product. For use in applications where water-soluble polymers are useful, the emulsion is usually inverted to an oil-in-water emulsion at the point of use;
and discharges the polymer into a continuous aqueous phase in which it readily dissolves. A reversing agent is used which can be present in the initial emulsion or added afterwards. Since emulsions are usually inverted in large volumes of water at useful doses, the concentration of inverting polymer is insufficient to produce a gel upon dissolution. For many applications involving water-soluble polymers, these water-in-oil emulsions have become the preferred product format, resulting in their large production. However, there are several problems in its manufacture that reduce production capacity, increase manufacturing costs, and otherwise complicate manufacturing. A difficult problem that arises in the production of water-in-oil emulsions of water-soluble polymers is the excessive amount of coagulum that results. This coagulum must be removed after the production of each batch in order to prevent the formation of further coagulum in subsequent batches. The formation and removal of such coagulum reduces the effective amount of polymer produced, reduces effective reactor uptime due to the arduous cleaning operations required, and increases manufacturing costs. A continuous process for the production of such water-in-oil emulsions has not yet been developed, but its success would still require minimizing coagulum problems. Thus, there is a need for an improved process for making water-in-oil emulsions of water-soluble polymers that can reduce the amount of coagulum produced. The provision of such a method would satisfy a long-standing need and would represent a significant advance in the art. In accordance with the present invention, an aqueous solution of at least one water-soluble monomer is prepared, the aqueous solution having from about 2 weight percent dissolved therein up to the limit of solubility in water. the monomer solution thus obtained is emulsified in a water-insoluble hydrocarbon oil to form a water-in-oil emulsion; and the monomer is polymerized in the dispersed phase to obtain the desired A method of making a nonionic or anionic water-soluble polymer is provided comprising forming a polymer. The process of the present invention provides the desired water-in-oil water-soluble polymer emulsion with significantly reduced amounts of coagulum compared to conventional processes. Surprisingly, the method of the present invention is effective in such preparations when the water-soluble polymer is non-ionic or anionic in nature, but not when the water-soluble polymer is cationic in nature. Not valid. In carrying out the process of the present invention, the only difference from conventional processes for providing water-in-oil emulsions containing water-soluble polymers in the dispersed phase is that the aqueous monomer solution contains a sufficient amount of salts and use only monomers that yield nonionic or anionic polymers. Thus, no new techniques are required for emulsion preparation or polymerization reactions, etc. Cationic monomers should not be used since they will result in cationic polymers. Regarding the use of salts, which is a novel aspect of the process of the present invention, any oil-insoluble ionizable water-soluble salt can be used. Typical useful salts include sodium sulfate, sodium chloride, ammonium chloride, ammonium sulfate, and the like, which are suitably water-soluble and oil-insoluble and do not interfere with the polymerization reaction. Certain water-soluble organic salts can also be used, such as, for example, sodium acetate. It is preferred to use sodium sulfate because of its ionic strength, low cost and ready availability. The amount of salt added to the water in which the monomers are dissolved depends on many factors, such as the particular salt used, the amount of the particular monomer used, the initiator system used to carry out the polymerization, etc. and can vary widely. Generally, the amount of salt used will vary from about 2 percent by weight of the aqueous phase to nearly complete solubility levels of the salt in the aqueous phase, and should be about 2 to 5 percent by weight of the aqueous phase. is preferred. As mentioned above, the process of the present invention is effective for conventional water-soluble monomers used to produce water-soluble nonionic and anionic polymers in the aqueous phase of water-in-oil emulsions. can be applied. Suitable monomers include acrylamide alone or acrylamide and acrylic acid with acrylic acid comprising up to about 50 weight percent of the acrylamide-acrylic acid charge. The invention will be explained in more detail in the following examples, in which parts and percentages are by weight unless otherwise specified. The following general procedures and test methods are used in each example. General Procedures Nonionic Polymers Oil Phase Low Odor Paraffinic Solvent, LOPS (Exxon Corporation) 584g Sorbitan Monooleate (Aracel 80 Atlas) 49g Total 633g Water Phase Hydrous Acrylamide (50%) 1268g Water (deionized) 336g Ethylenediamine Tetra Acetic acid, disodium salt (EDTA) (5.6% aqueous solution) 22.6g total 1626.6g Catalyst system separate components Oxidizing agent t-butyl hydroperoxide (70×-Pennwald) (2% aqueous solution) 3.2g Reducing agent 16 ~ per hour Sodium metabisulfite (0.04-0.4% aqueous solution) to give 20% conversion Procedure: Place water in a beaker containing acrylamide and EDTA and adjust the pH to 5.0 if necessary.
If a salt is used, it is dissolved in the aqueous phase, preferably in water before addition of the other ingredients. The oxidizing agent component of the catalyst system may be added during the preparation of the aqueous phase, or may be added after forming the emulsion. Preparation of water-in-oil emulsion Add the water phase to the oil phase using a homogenizer, such as a Silverson homogenizer. Homogenize on low speed for a few minutes, then on medium speed for an additional minute or two. The viscosity of the emulsion produced should be approximately 500-1500 centipoise. Polymerization Place the emulsion in a 2.5 glass knurled reactor or a stainless steel reactor with a knurled plate. If t-butyl hydroperoxide is not added to the aqueous phase used in the preparation of the emulsion, it is added to the emulsion and replacement of the atmosphere with nitrogen is continued in the conventional manner. Then, while maintaining a nitrogen atmosphere, the sodium metabisulfite solution was added continuously at a rate of about 20% per hour.
% conversion. Approximately 50~
After 90 minutes the temperature rises to approximately 40°C and is maintained at this temperature for the remainder of the reaction. In the reactor for about 6.5 hours, 98
% monomer conversion occurs. Low Concentration Anionic Polymer (3% Acrylic Acid) The oil phase is prepared by dissolving sorbitan monooleate (15 g) in a low odor paraffinic solvent (179 g). Acrylamide (50% water content) 375g, deionized water 105g, acrylic acid 5.9g, EDTA (5.6% solution)
6.9g, 4.8g ammonia and t-butyl hydroperoxide (70x) to adjust PH to 5.5
A separate aqueous phase is prepared by mixing 1.0 g of a 1.93% aqueous solution. Add the aqueous phase to the oil phase and homogenize as above. The polymerization is carried out as described above, except that it is carried out in a stainless steel reactor of No. 1. Highly concentrated anionic polymer (30% acrylic acid) 15.3g Sorbitan Monooleate 177g
The oil phase is prepared by dissolving in a low odor paraffin solvent. 264 g acrylamide (50% water content), 138 g deionized water, 13 g EDTA solution (5.6% water solution), 56 g acrylic acid, 28 g ammonia to adjust the pH to 5.0 and t-butyl hydroperoxide (70 g
×) By mixing 1.0 g of 1.88% aqueous solution,
Prepare a separate aqueous phase. Emulsification is carried out in the same manner as above. The polymerization is carried out in the same manner as described above, except that one stainless steel reactor is used. Determination of Coagulum Bulk Coagurate Stir 100 ml of the oil/Aracel 9/1 solution in a 250 ml polyethylene beaker. While stirring,
Add 25 g of the emulsion to be analyzed. Stir for 20-30 seconds to make a homogeneous solution. Pass the solution through a weighed 150 mesh sieve. Wash out the beaker contents using a wash bottle containing the oil/Aracel solution and drain into a sieve. sieve
Let it air dry for 15 minutes, then wipe it with a paper towel and weigh it. Obtain the solidified material using the following formula. Coagulum % = sieve weight increase x 100 / emulsion weight x polymer weight fraction (0.28) Since coagulum consists of polymer, water, oil, etc., the total coagulum percentage can reach 357. . Accumulated coagulum Drain the reactor contents as completely as possible. Determine the cumulative coagulum from the initial weight of the reactor and stirrer and the corresponding weight after use of the reactor by the following formula: Cumulative coagulum % = weight gain x 100/emulsion weight x polymer weight percentage (0
.28) As mentioned above, coagulum can reach 357%. Example 1 A nonionic polymer was prepared according to the general procedure described above. The test was conducted with two glass reactors side by side. In a comparative test, no salt was used in one reactor. In the tests according to the invention, 5% Na ₂ SO ₄ was used in the second reactor relative to the aqueous phase added before emulsification. A series of consecutive production runs were conducted in each reactor without cleaning the reactor between each production. Using salt in the aqueous phase, 6
2.0 in the 6th production.
% bulk coagulum and 7% cumulative coagulum were obtained. When no salt is used, 50% bulk coagulum (<5% cumulative) occurs after two productions, and due to the fact that such a large amount of coagulum has already formed, after two productions the continuation The test was canceled. Example 2 The procedure of Example 1 was repeated except that a stainless steel reactor was used. With salt, the bulk coagulum is 2% after three productions and the cumulative coagulum is 19
It was %. When no salt was used, the cumulative coagulum was 100% after two productions, and due to the formation of such a large amount of coagulum, continued testing was stopped after the second production. Example 3 A highly concentrated anionic polymer was prepared according to the general procedure described above. Tests were conducted using three 1 stainless steel reactors side by side. One reactor contained no salt and one reactor contained 2 salts added to the aqueous phase before emulsification.
% salt and the other reactor also contained 4% salt. The procedure was the same as in Example 1. The results are shown in Table 1.

Table: The procedure of Example 3 was followed except that a low concentration anionic polymer was prepared according to the general procedure above. The results are shown in Table 2.

[Table]
Example 4 The procedure of Example 3 was repeated except that the content of anionic monomer was increased to give a monomer content of 50%. 187.1g oil (low odor paraffin solvent)
The oil phase was prepared by dissolving 18.9 g of sorbitan monooleate in it. 225 g (50% hydrated) acrylamide, 225 g ammonium acrylate (61% aqueous solution, PH 7.5 due to excess ammonia), 36 g deionized water, 8 g EDTA
The aqueous phase was prepared by mixing the solution (5.6% aqueous solution) and 1.0 g of t-butyl hydroperoxide (70x) (2% aqueous solution). Emulsification was carried out according to the general procedure. Polymerizations were carried out in one stainless steel reactor, with no salt used in one reactor and 4% Na ₂ SO ₄ in the other reactor. After three tests without intermediate cleaning of the reactor, the total coagulum (cumulative plus bulk) was 109% without salt and 56% with salt. Example 5 The method of Example 2 was followed in the details of each material, except that 12% ammonium acrylate was used as the salt. Results after two tests without intermediate reactor cleaning were >50% total coagulum without salt and 14% total coagulum with salt. Example 6 The procedure of Example 2 was also followed, except that 13% NH ₄ Cl was used as the salt. The results after two tests without intermediate reactor cleaning are:
31%, and 11% for salt use. Example 7 Two consecutive manufacturing tests were carried out following the same procedure as in Example 2, but using 5% (NH ₄ ) ₂ SO ₄ as the salt, but without intermediate cleaning of the reactor. Ta. One series of tests was conducted in one stainless steel reactor without salt, and another series of tests was conducted in another stainless steel reactor with the salt as described above. The result after 2 tests was 49% without salt.
of total coagulum, and when salt was used, the total coagulum was 21%. Comparative Example The general procedure described for the preparation of low concentration anionic polymers was followed except that a quaternary ammonium monomer salt was used in place of the anionic monomer. Following the procedure of Example 4, as the added salt
Using 1% or 5% cationic monomer with Na ₂ SO ₄ showed no improvement in the amount of coagulum produced over that of no salt at the 2% or 4% usage levels. I couldn't get it.

Claims (1)

Claims: 1. An aqueous solution of at least one water-soluble monomer is prepared, the aqueous solution containing from about 2 weight percent of the water-soluble, oil-insoluble monomer dissolved therein up to the solubility limit in water. the monomer solution thus formed is emulsified in a water-insoluble hydrocarbon oil to form a water-in-oil emulsion; and the monomer is polymerized in the dispersed phase to obtain the desired 1. A method for producing a nonionic or anionic water-soluble polymer or copolymer, the method comprising producing a polymer. 2. The method according to claim 1, wherein the monomer solution contains acrylamide. 3. The method according to claim 1, wherein the monomer solution contains acrylamide and acrylic acid. 4. The method of claim 1, wherein the salt is Na ₂ SO ₄ . 5. The method of claim 3, wherein the monomer solution contains 97 weight percent acrylamide and 3 weight percent acrylic acid. 6. The method of claim 3, wherein the monomer solution contains 70 weight percent acrylamide and 30 weight percent acrylic acid. 7. The method according to claim 1, wherein the production is repeated in the same reactor without cleaning the reactor in between. 8. The method of claim 5, wherein the salt is Na ₂ SO ₄ . 9. The method of claim 6, wherein the salt is Na ₂ SO ₄ . 10 Claim 7, wherein the salt is Na ₂ SO ₄
The method described in section.