KR870000216B1 - Separation of water-soluble polymer - Google Patents

Abstract

Fractionation of water-sol. polymers(I) contg. neutralized acid gps. by sepn. of their solns. in a mixt. of water and polar solvent(II) into an aq. phase contg. a high mol. wt. fraction and an organic phase contg. a low mol. wt. fraction. The acid groups of (I) are n% neutralized with cations from Na or K (when n=1055), NH4 (n=10-70), or Li(n=30-90); and (II) is a C1-5 alcohol. Pref. (II) is isopropanol, esp. in 0.5-1:1 mixts. with the water; polymer concn. in the mixt. is min. 10 wt.% and each phase contains 20-80 wt.% polymer. One or both polymer fractions has polydispersity 1.05-1.45.

Description

Separation Method of Water-Soluble Polymer

The present invention relates to a process for the separate preparation of water soluble polymers formed of one or more unsaturated monomers and containing acid groups selected from carboxylic acids and sulfuric acid and sulfonic acid groups or water soluble salts thereof.

Low molecular weight, water soluble polymers, and especially polymers containing acidic groups that can be partially or fully neutralized, are well known as valuable as pigment dispersants (including microdispersants). This polymer generally has a molecular weight (MW) of 1,000 to 10,000. However, this polymer is always a mixture of molecules whose molecular weight differs depending on the number of units in each molecule. Indeed, commercial polymers are mixtures of molecules of various chain lengths.

For example, a polymer with a molecular weight of 5,000 appears to contain a significant amount of molecules with a molecular weight of 1,000 or less and 6,000 or more. The extent to which chain lengths of home appliances molecules form a special product can be seen by their complexity.

Complex dispersion (PD) of a product is the average molecular weight divided by the average molecular weight. Thus, with a PD value of 1, the polymer consists entirely of molecules of single chain length. In fact, PD is always much larger, usually two or more.

British specification 1414164 describes certain vinyl acetate copolymers used in dispersion chalk, which, according to Example 2, describe the polymer as having an average molecular weight of 1,200 to 2,300. When fractionated and precipitated, it is described as having an average molecular weight number of 150 to 4,000. In addition, in Example 3, a slightly different method can be used to obtain parts showing a narrower molecular weight distribution, such as 960 to 3,000, but the molecular weight range of each part is not described.

Although this specification does not describe the use or properties of these parts, the polymer of Example 3 (which is a mixture of parts having an average molecular weight of 960 to 3,000) has better properties than the composition of Example 2, It is intended to contribute to the "effective use of molecular weight distribution". Since the polymers of Examples 2 and 3 can be broken down into polymer moieties of varying molecular weight ranges, it is clear that in both cases 2 and 3 have a high degree of complex dispersion of the polymer.

In addition, since the complex dispersion value may vary depending on the classification method, it is virtually impossible to predict what the complex dispersion value of the polymer parts is, but it is estimated to exceed 1.7.

There is no explanation in this specification of what the polymer parts are for. The most commercial products as dispersants are polyacrylic acid and 2-acrylic acid-2-acrylamidomethyl propane sulfonic acid (AMPS) copolymers. A widely used polyacrylic acid (as sodium salt) is Dispex N40 (Dexex trade name) made by the inventor.

This product, which we sell, generally has a complex dispersion of at least 1.8 and most of the commercially available products have a complex dispersion of at least 2. We think it is uneconomical and unnecessary to get a lower value of the complex variance, but sometimes we make a series of polymers with low complex variances of less than 1.8, but this is a polymer with a larger complex variance during storage. It is always mixed with the fields.

The process for preparing a water-soluble acidic polymer such as polyacrylic acid is usually made by solution polymerization when the solvent is a mixture of water and an organic liquid such as isopropanol. The product of the polymerization reaction is carried out by a unit which does not react with some oligomers simultaneously. Solution of the contained polymer. Conventional methods for the removal of unnecessary low molecular weight elements, such as oligomers and monomers, include the addition of excess sodium hydroxide to the solution to neutralize all acidic groups, so that the mixture is mixed with the upper isopropanol moiety containing the unnecessary low molecular weight elements. There is a method to separate into the lower aqueous portion containing the required polymer. This fractionation merely consists of separating useful polymers from unnecessary by-products, which are mixtures of molecules of various molecular weights and the PD values recited above are the values of purified polymers.

A unique method for separating unnecessary by-products is described in European Patent Publication No. 4673. The patent describes that aqueous solutions of polyacrylic acid can be neutralized and the neutralized polymers can be treated with polar solvents, methanol, ethanol, propanol, isopropanol, acetone and tetrahydrofuran by conventional methods. In the examples, 80 g of sodium polyacrylate, which is completely neutralized, is fractionated in a solution containing 400 g of methanol or 40 g of isopropanol and 500 g of water, in which case a lighter organic acid is removed. This process thus appears to be a conventional fractionation method for removing oligomers, so that the product will be a common molecular weight mixture. If the initial polymer mixture is of normal molecular weight, the molecular weight and complex dispersion of the extruded polymer paper will also have a normal value, such as a PD value of 1.8 or more.

The above patentees have issued British Patent No. 2109363, which generally gave a similar announcement of treating an aqueous polymer with a polar solvent, except for the lack of a detailed description of the method, in which the organic moiety is molecular weight. It is described as a useful product with a distribution of 400 to 1,200 and the aqueous portion is described as having a molecular weight range of 1,200 to 12,000.

Whenever a water soluble acidic polymer is prepared, partially neutralized salts or free acids may be used in some cases, but are generally used in the form of fully neutralized salts.

The polymer may be provided to the user, for example, as a solution originally made or, optionally, as a solution after distilling some organic solvent out of the solution, or the polymer may be separated from the solution, for example by precipitating by adding an insoluble substance such as excess acetone. have.

Since the minimal variety of polymerization reaction conditions used to make the polymer can greatly affect the activity of the product for any particular purpose, the manufacturer has to optimize these reaction conditions to produce a product that exhibits the optimal activity as intended. It is well known that we must experiment with great care.

U. S. Patent Nos. 3759860 and 3839405 describe the use of alkylsulfides, sulfones or sulfoxides, for example as emulsifiers, in which oligomers are linked at the end having an alkyl group of C ₆ or higher. Large alkyl groups appear to be essential for functioning as emulsifiers because of the tendency for polymers to enter solution and micelle in water, thereby contributing to hydrophobicity.

This property is in contrast to the properties required for the dispersant. There is no mention that the polymer should be used in disperse pigments, which can have the following PD values and often have low PD values between 1.4 and 1.5.

Contrary to this publication, no commercial use of low complex dispersion-soluble water-soluble polymers for any purpose has been proposed since, in particular, no mention has been made of pigment dispersions in particular. Since it is much easier for polymers to have higher PDs than lower PDs, nobody has ever tried to make them commercially because no one has realized that there are unique values within these polymerisations.

European Patent Specification 68887 describes insoluble low molecular weight polymers having low values of complex dispersion, but these polymers cannot be used as insoluble immersion dispersants.

If the polymer has a much narrower molecular weight range than previously used, i.e., if the PD value decreases to substantially below the normal value of 1.8, and above l.5, then a small or relatively low molecular weight water soluble polymer dispersant will disperse the pigment. It has already been found that it significantly increases its properties.

Thus, for some particular purpose, it was found that optimal results were obtained if the polymer consisted of molecules with a very limited range of chain lengths. The presence of molecules of different chain lengths is bad for two reasons,

First and foremost, these different molecules preclude the beneficial effects of molecules that have good effects, probably because of preferential absorption or some other opposing harmful mechanism.

Second, the polymer is diluted so that these different molecules contain less than the theoretical maximum of molecules with good effect.

The present invention provides unique polymers with low complexity and unique composition using such polymers. Most of the components disperse the unique material in the aqueous medium and are the third composition containing the polymer as the remaining limited detergent enhancer. The present invention also provides a unique method of separating the polymer into large and small portions.

The process according to the invention for separating polymers can be used to prepare polymers having PD values of 1.5 or less, in the process of the invention to neutralize 10% to 90% in a mixture of polar solvent, water and base. A water-soluble polymer containing a sufficient amount of acidic groups is formed, and the solution is subjected to phase separation of the solution into an organic phase containing a water-phase low molecular weight portion containing a high molecular weight portion to select the solvent and the base or the amount of the solvent, and finally these Use two parts. Since the precise separation between the low molecular weight moiety and the high molecular weight can be achieved by modifying the conditions of the separation method, in particular the degree of neutralization, the method of the present invention is above all possible to simply separate the acidic water-soluble polymer into the preselected molecular weight moiety. It provides a way to do it. Unlike conventional methods that usually remove the organic moiety, both parts of the polymer are commercially useful in the present invention, where the organic phase moiety is useful when a low molecular weight polymer moiety is needed, and the aqueous phase moiety is useful when a high molecular weight is required. It is available.

In addition, it has been found that, in general, the polymer contained in each part surprisingly has a much higher activity than at least the initial polymer and activity. Often, one part of the polymer is one type of significantly increased activity (eg, a viscous agent), while the other part of the polymer may have another type of significantly increased activity (eg, a dispersant). In addition, the polymer of each part will have a lower complex dispersion (average molecular weight divided by the average molecular weight number) than the initial polymer. For example, the initial value is almost always 1.6 or more and sometimes 2 or more, but the part obtained in the present invention. Are less than 1.5, and some are between 1.05 and 1.45 and most are between 1.1 and 1.4.

Each polymer solution can be used in the form obtained by phase separation, such as by simply mixing the solution to be treated with water or another solution, or the polymer can be recovered from the solution using evaporation, precipitation, or conventional recovery methods. have. In general, each polymer contained in this separated solution is in a partially neutralized state and can be acidified or partially neutralized by conventional methods if necessary.

Methodological conditions that can alter the effect of separating the high and low molecular weight portions are the choice of solvent, the choice of base, the amount of solvent and the amount of base. Until now, it has been stereotyped that acidic groups can be usefully fractionated by partially neutralizing acidic groups, whereas the neutralization of acidic groups is completely neutralized as in the prior art, and the appropriate fractions or fractions can be determined by appropriate selection of solvents, bases and their respective amounts. You can get it.

The choice of particular solvent may depend on the nature of the polymer and the molecular weight of the patented polymer.

For example, as the polar solvent, alcohols having 1 to 5 carbon atoms and aliphatic ketone compounds having 3 to 8 carbon atoms (generally C ₃ or C ₄ ) are selected. Most commonly, isopropanol or acetic acid is used. Alcohols are very suitable for a wide range of polymers, but especially good for low molecular weight polymers having a molecular weight of 100,000 or less, usually 30,000 or less, and in particular 10,000 or less. Ketone compounds, on the other hand, are best for fractionating high molecular weight polymers having a molecular weight of, for example, 50,000 or more, generally 100,000 or more, or 200,000 or more, even 500,000 or more.

According to one method of the present invention, a polar solution of a water-soluble polymer containing a neutralized acid group is mixed with water to form a solution, and the solution contains an aqueous phase containing a high molecular weight portion of the polymer and a low molecular weight portion of the polymer. Separate into organic phase.

In this method, the polar solvent is an alcohol having 1 to 5 carbon atoms, which neutralizes the acidic group with a cation selected from sodium, potassium, lithium, and ammonium, and the acidic group is 10 to 55% by weight when sodium and potassium are selected. When the ammonium is selected, it is neutralized at a ratio of 10 to 70% by weight and when lithium is selected, it is 30 to 90% by weight.

The polymer can be made by conventional polymerization methods, which can be separated from any liquid phase formed, for example, in the solid phase and can be re-dissolved in an aqueous organic solution containing the base used in the present invention.

In general, however, the process of the invention is treated in a solution of the polymer obtained with a polymerization solution of the appropriate monomers. A good solution for the polymerization medium is a kind of aqueous solution containing a suitable initiator or any other polymerization promoter such as, for example, water-soluble peroxides and persulfates, or redox catalysts or catalysts for copolymerization, generally organic solvents such as molecular weight control, for example. It will include. If desired, other known molecular weight modifiers (eg, -COOH, -OH, or one to three carbon atoms in the alcohol group) may be included in the solution.

Once the polymerization is taking place, it can be sufficiently stirred to prevent separation, and then the polymerization solution can be treated in the presence of a solvent, base and water that require fractionation in order to allow the polymerization mixture to separate. In general, however, the polymerization is carried out in the presence of an appropriate amount of solvent, base and water so that no separation occurs and after the polymerization takes place. In some methods, the solution of the polymer is made by polymerizing in a mixture of water and organic solvent, which organic solvent may be provided for use as an organic liquid in the present invention.

In general, this solvent can be mixed well with an aqueous polymer solution such as alcohol or acetic acid. The most common solvent in the polymerization solution is isopropanol, and sometimes a mixture of water and isopropanol is most suitable in the present invention. When the polymerization takes place in the presence of the selected solvent, fractionation can be obtained by appropriately adjusting the cations in the solution. In general, polymerization occurs with many monomers in the free acid form of the unit, where the adjustment of the base can be effected by the addition of an appropriate amount of alkali or other type of cation. If the polymerization takes place in a fully neutralized form of the monomer (for example in the polymerization of vinyl sodium sulfate), cation adjustment can be effected by adding enough free acid to partially oxidize the neutralized group to form a polymer with as many neutralized groups as necessary. To be able. The free acid added should be strong enough to acidify the acidic group of the neutralized polymer, which is an inorganic acid such as hydrochloric acid or sulfuric acid. The free acid may also be in the free acid form of an acidic polymer or may be a water-insoluble acidic polymer, preferably an anionic (generally sulfuric acid or other strong acid) ion exchange resin.

In another method, the polymerization takes place in the presence of a base in an amount sufficient to neutralize 10 to 90% of the acidic groups and phase separation occurs by addition of the required amount of polar solvent.

If the amount of cation in the polymerization mixture is not suitable for phase separation, an extra base (or acidic) may be added to the polar solvent in order to neutralize as much as necessary.

In the process of the present invention, no matter whether the solution is made by mixing a preformed polymer, the water, an organic solvent, and a base, or by adding a base to the polymerization product by an aqueous organic liquid or by any other method, This requires a phase separation between the organic phase and the aqueous phase in the presence of a preformed solvent and the required amount of cations.

The base is preferably a basic compound of monovalent cations such as sodium, potassium, lithium and ammonium, and in general, it is better to use the base as it is known that other bases have less satisfactory fractionation effects in most solvents. . Lower alkylamines (e.g. ethylamines) are suitable for some polymers when the polyatomic cation is a basic compound (unless the amount and type of cation causes precipitation of the polymer). Suitable polyvalent cations include Ca, Zn, Cu, Mg, Al, and the like.

Basic compounds are, for example, oxides, hydroxides, carbonates, bicarbonates, alkoxides, phosphates, hydrogen phosphates, phosphates with organic acids weaker than the acid of the polymer, for example acidic sulfonic acid or sulfuric acid of the polymer, such as acetate sodium, adipic acid or citrate. Phonic acid, polyphosphoric acid or organic carboxylate salts. Fractionation is controlled by the degree of neutralization of the acidic groups; the results obtained in any particular method depend, in particular, on concentration, polymer type and solvent, but in practice the minimum degree of neutralization is less than that which does not occur. The size can be maintained in a uniform solution. The degree of neutralization is usually at least 10% when the cation of the base is sodium, potassium or lithium, and sometimes at least 15% and preferably at least 25%, whereas the degree of neutralization is usually at least 30 when the cation is lithium %, Preferably at least 40% and generally at least 50%. If the degree of neutralization is too high, the size of the low molecular weight portion is significantly smaller. In addition, when the cation of the base is sodium or potassium, the degree of neutralization is 55% or less, preferably 50% or less, and most preferably 40% or less. When the cation of the base is ammonium, the degree of neutralization is usually 70% or less, preferably 60% or less and most preferably 50% or less. When the cation of the base is lithium, the degree of neutralization is usually 90% or less, preferably 70% or less.

In some particular methods, for example, the size of the high molecular weight moiety may be increased by increasing the amount of base, due to the accompanying decrease in average molecular weight and the accompanying decrease in average molecular weight Conversely, as the amount of base decreases, the size of the low molecular weight may increase. The conditions in this method are chosen so that each part contains 20 to 80% good, most preferably 30 to 70% containing about 10 to 90% of the initial polymer weight.

Partial neutralization of the acidic polymer is achieved by adding cations to the dissolved polymer in selected amounts of hydroxide or other base to provide the selected cation. Mixtures of water or more cations may be used, with the proportions selected to have the same effect as the appropriate amount of each cation. This depends on the degree of neutralization and the type of cation as well as the concentration of the polymer and the amount and choice of alcohol or other solvent for the particular polymer. Isopropanol is preferred as the alcohol, but alcohols other than propanol, in particular C ₂ to C ₅ alcohols, may be used. The weight ratio of water to alcohol or other solvent is preferably 1: 0.2 to 1: 5, most preferably from 1: 0.5 to 1: 2 with the best results, especially when the solvent is ispropanol and the cation is sodium The ratio is about 1: 1. The proportion here should be chosen such that the polymer concentration of each phase is at least 5% by weight, generally at least 10% by weight, preferably at least 15% by weight, given the degree and nature of the neutralization.

The amount of polymer (measured as acid polymer) comprises at least 5% by weight and preferably at least 10% by weight, based on the weight of the polymer, solvent and water (including water with alkali). The concentration is not so high that the system is viscous, which significantly hinders mixing and phase separation, which is generally 30% or less and preferably 15-25% by weight.

Phase separation can also be influenced by the temperature at which the reaction takes place and is preferably between 15 and 80 ° C., preferably between 30 and 70 ° C.

The reaction can be accomplished by combining the necessary elements of the solution, for example by adding an aqueous alkali to the aqueous organic reaction product obtained by the polymerization of monomers or monomers in an aqueous organic solution. The reaction can occur continuously or in batches. Phase separation can occur quickly or slowly depending on the degree of neutralization, strength and type of base, concentration of polymer, amount and temperature of solvent.

In practice, for example, this may happen suddenly, or it may be necessary to leave the system for a period of, for example, 5 minutes to 2 hours, typically 30 minutes to 1 hour. Separation can be carried out generally or continuously by injecting the mixture through a common separation column or separation reactor.

The two phases can be separated and completely neutralized with the same or different alkalis and the organic solvent can come out of the organic phase by kind.

Each polymer portion separated is eventually recovered for commercial use. The very low molecular weight fraction obtained by this method is good as a medicament to prevent scale formation and scale sedimentation, in particular as a descaling agent. For example, the highest alkalinity that can be maintained in solution has been shown to increase with decreasing PD. Therefore, the best results are obtained when the MW is 350 to 1,000 and the PD is 1.5 or less, preferably 1.05 to 1.3.

Hereinafter, the present invention will be described in detail with reference to Examples.

In the following examples, Example 1 describes the preparation of polymers with the required PD and MW values by careful polymerization, and Examples 2 and 3 describe how the polymers can be obtained by partial neutralization and fractionation. It is describing.

Example 1

Three separate mixtures were continuously added over 6 hours to a 700 cm ³ resin pot equipped with a thermometer stirrer and an external heater.

Feed 1: 340 g ice sheet acrylic acid in 266 g water,

Feed 2: 10.5 g / 100 hydrogen peroxide and 57.1 g water

Feed 3: 28 g thiol glycolic acid and 38.6 g water.

The pot contents were kept at reflux during addition and one more hour before cooling. The percentage of unpolymerized acrylic acid was determined by gas liquid chromatography and was found to be 0.3% of the amount added.

The residual polymer was neutralized sufficiently by adding 46.6% of sodium hydroxide and the final product was diluted to obtain 40% by weight of sodium polyacrylate solution.

The viscosity of the product at 25% was 12.1 cS (suspension viscometer, No. 2,25 ° C.), and the results of GPC analysis showed MW = 174Q, Mn = 1321 and complex dispersion = 1.32.

Example 2

A 23% solution of polyacrylic acid (weight ratio) in a mixture of isopropanol and water in a weight ratio was prepared by polymerization of acrylic acid using a superacid ammonium as a starting material according to a conventional method.

A sample of the product was extracted while the other sample was neutralized with the addition of various amounts of sodium hydroxide introduced into 46% aqueous solution. After addition of sodium hydroxide, the samples were each left for a sufficient time to allow the aqueous phases to separate into organic phases (which would contain some water) and these phases were separated from one another in a conventional manner. Each phase was then neutralized sufficiently with sodium hydroxide and the remaining alcohol was distilled off. The yield of polymer in each of the phases was recorded.

Example 3

A 20% solution of polyacrylic acid having a molecular weight of 3131 and a complex degree of dispersion of 1,677 was dissolved in isopropanol / water at a weight ratio of 50/50 and neutralized with various basic compounds to separate the two layers. The amount and molecular weight of the polymer in each layer was measured, and the results are shown in Table 1 below.

TABLE 1

Example 4

The product obtained in Example 2 was adjusted to 40% active solids and compared with a marble polishing aid as described in Example 11 of British Patent No. 1,414,964 and the results are shown in Table 2.

TABLE 2

In the experiments described, a grinding index of about 0.5 of the surrogate dispersion. It is generally satisfactory because it exhibits commercially acceptable properties to prevent gelation. As can be seen from the table above, the polymers are all aqueous phases after sufficiently neutralizing but become organic phases when a significant amount of the polymer is at a low degree of neutralization. It is also very noteworthy that the grinding index is greatly improved even when the amount of polymer which is an organic phase instead of an aqueous phase is very low. For example at 50% neutralization the amount of polymer in the organic phase is low but the grinding index is about 5 times, which is considered commercially suitable. At a higher degree of neutralization, only a very low amount of polymer is in the organic phase.

Example 5

According to a conventional polymerization method, a polymer was prepared as a 23% solution of acrylic acid in an equivalent amount of isopropanol and water and neutralized to 25% with an aqueous sodium hydroxide solution after polymerization. This allows the reaction mixture to separate into two phases. The phases were separated to distill off isopropanol and the polymer present in these phases was recovered. Samples were taken and sufficiently neutralized with sodium hydroxide solution and adjusted to 40% activity as sodium polyacrylate.

The unfractionated control polymer was also prepared from distilled off isopropanol from a polymer that was not originally neutralized in isopropanol water and neutralized sufficiently with sodium hydroxide to adjust the activity as sodium polyacrylate to 40%.

The product was evaluated as a dispersant for titanium oxide having a particle size of 2 or less at 75% W / W slurry solid content by recording slurry viscosity at 0.6, 0.8 and 1% of dry polymer based on dry pigment. As shown in Table 3.

TABLE 3

Example 6

Samples of sodium polyacrylates with a narrow molecular weight of decreasing molecular weight were evaluated as dispersants for China clay when 64 wt% slurry solids were used at various concentrations at pH6.8-7.0 as in Example 4. As shown in Table 4 below.

TABLE 4

The above results indicate that the most effective sodium polyacrylate as a dispersant for China clay has a molecular weight in the range of 1000-3000, with a preferred molecular weight of approximately 2000.

Example 7

Samples of sodium polyacrylate having similar molecular weight but varying complexity were evaluated as surrogate grinding aids, and the results were expressed as grinding index using the test method described in Example 11 of British Patent No. 1,414,964. As shown in

TABLE 5

The above results show that the effect of sodium poly acrylate on marble grinding depends on the complexity. The lower the complexity, the more effective the product.

Example 8

The correlation between molecular weight and complexity of sodium AMPS / sodium acrylate (20/80 W / W) can be seen to have a decisive effect when the product is evaluated as a marble polishing aid according to Example 11 of British Patent 1,414,964. . The interrelationships between these variables are as shown in the following six.

TABLE 6

The above results indicate that low molecular weight polymers with narrow complex dispersion are the most effective anti-array abrasive aids. The optimum molecular weight ranges from 1500-35009 and the preferred molecular weight is 2500.

Example 9

Samples of sodium polyacrylate having similar molecular weights but varying complex dispersions were taken and evaluated as in Example 4 as a dispersant for precipitated calcium carbonate at 70% by weight slurry fixed contents, and the results are shown in Table 7 below.

TABLE 7

Example 10

Different polymers were prepared using different monomers according to the general method described in Example 2.

When the monomer consisted only of methacrylic acid, the product was partitioned onto low molecular weight isopropanol, useful as a dispersant for China clay and high molecular weight aqueous layers by neutralizing 25% with sodium hydroxide.

When the monomer was composed of equal parts (weight ratios) of itaconic acid and methacrylic acid, the monomer was neutralized with sodium hydroxide and fractionated into a high molecular weight aqueous phase and a low molecular weight isopropanol phase.

When the monomer consists of sodium vinylsulfonate, the first polymer is in sodium form, which can be fractionated using isopropanol after neutralization with some acidic ion exchange resin.

Example 11

The calcium resistance of the polymer was measured by the Hampshire test using a calcium ion selective electrode to compare the effect of complex dispersion on the polymer when used as a detergent enhancer in conventional formulations. The highest possible number was required for this test. The figure (water, Ca ²⁺ required per mole of polymer) when the polymer was polyacrylic acid with a molecular weight of about 3000 complex dispersion of about 1.6 was 0.625, while the value was 0.780 when the polymer had a similar molecular weight but polyacrylic acid with a complex dispersion of 1.18.

Example 12

A polishing mud was prepared with bentonite 25ppb, barite 220ppb, gypsum 4ppb, calcium hydroxide 2ppb, and various amounts of polymer were added, and then the viscosity of the mud was measured. The minimum viscosity was obtained in an amount of about 1.2 ppb when the polymer had a molecular weight of about 3000 and a polydispersity of about 1.6. When the polyacrylic acid was fractionated into fractions with complex dispersities ranging from 1.1 to 1.4, the two fractions showed lower viscosity at lower amounts and higher molecular weight fractions showed lower viscosity over a wider range of doses, while lower Fractions of molecular weight showed the lowest viscosity.

Claims (11)

A water-soluble polymer containing an acid group is formed in a mixture of polar solvent water and a base, the composition of which is sufficient to neutralize 10% to 90% water of the acid group to form a solution in which a water-soluble polymer is formed. Phase separation of the solution is carried out by selecting an amount of a solvent, a base and at least one of a base and a solvent so as to separate the aqueous phase containing the fraction and the organic phase containing the low molecular weight fraction, and then use the two phase separated fractions. Process for the separation of water-soluble polymers. The method of claim 1 wherein the polar solvent is a C _1-5 alcohol. The method according to claim 1, wherein the cation is selected from natrum, potassium, lithium and ammonium, wherein the molar ratio of the neutralized group is 10 to 55% when the base is a cation selected from sodium and potassium, and the base contains ammonium 10 to 70% for compounds, 30 to 90% for bases containing lithium. The method of claim 3 wherein the solvent is isopropanol. The method of claim 1 wherein the polymer has a concentration (weight ratio of acid polymer, water and solvent based on polymer) of at least 10%, and each phase contains 20 to 80% of the polymer by weight. The method of claim 1, wherein the mixture is a mixture of 1 part water and 0.5 to 2 parts isopropanol, wherein the polymer is present at a concentration of 10 to 30% by weight of the mixture, and the polymer is acrylic acid and 2-acrylamido-2. -A polymer consisting of an acidic monomer selected from methylpropane sulfonic acid, wherein from 10 to 50% of the weight in the acid groups is in the form of a salt with sodium and the remainder as free acid groups. The method of claim 1, wherein the initial polymer has a complexity of greater than 1.6 and the two phase separated fractions have a complexity of less than 1.5. The method of claim 1 wherein the polar solvent is a C _3-8 aliphatic ketone and the polymer has a molecular weight of 50,000 or greater. The method of claim 1, wherein the preliminary step of preparing a solution containing a water-soluble polymer is to polymerize the water-soluble, acidic, monomer in the mixture to add a base sufficient to partially neutralize the polymer after the solution of the mixture is tongued. Configured. The preliminary step of preparing a solution containing a water-soluble polymer according to claim 1, wherein the preliminary step of preparing a solution containing a water-soluble polymer is a water-soluble polymer in which an aqueous solution of a polymerizable monomer containing an acid monomer in an amount sufficient to neutralize 10 to 90% of an acid group is present. Forming an aqueous solution of the method comprising the step of adding a polar solvent. The acid polymer according to claim 1, wherein the acid polymer is acrylic acid, 2-acrylamido-2-methylpropane sulfonic acid, 2-acrylamido-2-phenylpropane sulfonic acid, methacrylic acid, itaconic acid, vinylsulfonic acid, vinyl sulfate And a polymer obtained by polymerizing a monomer selected from allylsulfonic acid, maleic acid, fumaric acid and croronic acid.