JPS59223702A - Separation of acidic water-soluble polymer - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Low molecular weight water-soluble polymers, especially those containing acidic groups which may be partially or fully neutralized, are said to be useful as pigment dispersants (including grinding aids). It is being Its polymers generally.

i,ooo~l O,000 molecular weight (weight average molecular weight.

Mw). However, polymers always
It consists of a blended mixture of molecules of different molecular weights due to the number of seven-unit units in each molecule. In reality, each commercially available polymer is a mixture of molecules with a very wide range of chain lengths. For example, Mw = 5.00
Polymers with 0 are less than or equal to 1.000 and 6.00
It generally contains a significant amount of molecules with molecular weights greater than zero. The degree to which a particular product is formed with molecules having a range of chain lengths is measured by its polydispersity.

The polydispersity (PD) of the product is 1 weight average molecule 15t (M
w) divided by the number average molecular weight (Mn'f.P
If D-1, the polymer consists of molecules of exactly one chain length. In practice, PD is always quite high, typically 2 or higher.

GB 141496.4 describes certain vinyl acetate copolymers for dispersing chalk. In Example 2, the polymer is described as having a number average molecular weight of 1.200 to 2.300, and fractional precipitation of the polymer has a number average molecular weight of 150 to 4,000.
states that a fractional distillation having a number average molecular weight of
The slightly different processing conditions of Example 3 resulted in a narrower molecular weight distribution and 960-3. It states that it gives a fractional distillation of ooo. Molecular weight ranges within each fraction are not disclosed. Although this specification does not disclose the use or nature of these fractions, the polymer of Example 3 (which is a fractionated blend mixture with an average molecular weight of 960 to 3.000) was the same as that of Example 2. It is believed that this is due to the ``optimistic molecular weight distribution.'' Since the polymers of Examples 2 and 3 can be separated into polymer fractions with a wide range of molecular weights, it is clear that both the polymers of Examples 2 and 3 have high polydispersity values, perhaps on the order of 2. Since this varies depending on the fractionation method, it is not possible to predict what polydispersity value the polymer will have fractionated. There is no suggestion for what purpose the polymer fraction is to be used.

The most commercially successful products as dispersants are polyacrylic acid and acrylic acid-2-acrylamide 2-methylpropanesulfonic acid (AMPS) copolymers. A widely used polyacrylic acid is the applicant's product Dispex N 4 Q (Dj 5p
ex is a trademark name). Products sold by Applicants generally have polydispersity values of 1.8 or greater, while the majority of commercially available products have polydispersity values of 2 or greater. We consider it to be uneconomical and unnecessary to boil down for low polydispersity values, and a group of polymers with a polydispersity slightly lower than 1.8 is also prepared batchwise (in this case). However, during storage, they are usually blended with a group of polymers having a high polydispersity.

It is common practice to prepare water-soluble acidic polymers such as polyacrylic acid by solution polymerization, where the solvent may be a blended mixture of an organic liquid such as Impropatol and water. The polymerization product is a polymer solution with oligomers and unreacted monomers.

One method used to remove unwanted low molecular weight components, ie oligomers and monomers.

Excess sodium hydroxide is added to the solution to neutralize all acidic groups, and the mixture is divided into an upper impropatul fraction containing unwanted low molecular weight components and a lower aqueous fraction containing the desired polymer. It is to separate into. This fractionation method is a simple process that separates useful polymers from unwanted by-products.
It has been regarded as one method. Useful polymers are blended mixtures of molecules of various molecular weights, including the PDs described above.
Values are for purified polymer.

A special method for removing unwanted by-products is described in European Patent Publication No. 46573. In this publication, an aqueous solution of polyacrylic acid is neutralized and Polymers.

It is stated that it can be treated with the above-mentioned polar solvents, methanol, ethanol, propatool, inpropatol, acetone, and tetrahydrofuran. In an example, 80 grams of fully neutralized sodium polyacrylate is mixed with 400 grams of methanol or 40 grams of sodium polyacrylate.
gram of inproper tool in a 500 gram aqueous solution.

In each case the light organic phase is removed. Therefore, this is a routine fractionation method to remove oligomers.

The 5 products considered are blended mixtures of conventional molecular weights. If the starting polymer mixture is conventional, the Mw of the distilled polymer.

M +1 and Ij D values are also conventional, e.g. 1'
D is 1.8 or more.

Certain sulfide-, sulfone-, or sulphoxide-terminated oligomers are suitable for use as emulsions, for example.
No. 3,759,860, which does not suggest that they be used for dispersing pigments. Apart from this statement, no one is suggesting the commercial use of low polydispersity water-soluble polymers for any purpose, especially pigment dispersion. There is no indication that it should be used in products.In reality, high PD values are higher than low PD values.
Since it is much easier to make polymers with
The possibility of producing them on a commercial scale could probably not have been envisioned by anyone in advance, just as no one could have realized in advance that there would be any particular value.

Insoluble low molecular weight poly"7- with low polydispersity values are described in European Patent No. L8887, but because these polymers are insoluble they cannot be used as pigment dispersions.

We believe that if the polymer has a much narrower range of molecular weights than previously used, i.e. if the PD is substantially lower than the conventional value of 1.8 and above 1.5, It has been discovered that molecular weight water-soluble polymeric dispersions have significantly improved pigment dispersion properties. We have now discovered that optimal results for any particular purpose are obtained when the polymer is composed of molecules with a very limited range of chain lengths. The presence of molecules of other chain lengths is disadvantageous for two reasons. First, and most importantly, these other molecules are likely to preferentially absorb other harmful or rebellious mechanisms.
negates the beneficial effects of preferred molecules. Second, these other molecules dilute the polymer to less than the theoretical maximum of the preferred molecule.

The present invention provides a new method for making polymers with improved properties and specific uses for certain polymers. In this case, a solution is formed of a blended mixture of a polar solvent and water of a water-soluble polymer containing neutralized acidic groups, and an aqueous phase containing a high molecular weight fraction of the polymer; and an organic phase containing a low molecular weight fraction of the polymer, in which the polar solvent is
~5 alcohol, the acidic group is neutralized with cations selected from sodium, potassium, lithium and ammonium, the quality of the neutralized acidic group is 10 ~ when the cation is selected from sodium and potassium 5
5%, and when the cation is ammonium, 10~
70% and 36-9 when the cation is lithium
It is 0%.

The exact boundaries between low and high molecular weight fraction amounts depend on processing conditions,
and in particular by varying the degree of neutralization, the present invention provides for the first time a simple method by which acidic water-soluble polymers can be fractionated into preselected molecular weight fractions. Unlike conventional methods in which organic fractions are usually removed, in the present invention both fractions of the polymer are usefully recovered and used, and the fraction in the organic phase is removed where lower molecular weight is desired. Fractionates in the aqueous phase are useful where high molecular weights are desired.

Further, Fubenban et al. found that the polymer in each fraction was generally
It has been discovered by chance that the polymer has at least one activity that is significantly improved compared to that of the starting polymer. Often, the polymers of one fraction have one type of highly improved activity (e.g. as a viscosity agent) and the polymers of the other fraction have highly improved activities of the other type (e.g. as a dispersant). It may also have other activities.

The polymer in each fraction has a lower polydispersity (weight average molecular weight divided by number average molecular weight) than the starting polymer. For example, the initial value is almost always greater than or equal to 1.6, often greater than or equal to 2, whereas the fractional value obtained with the present invention is less than or equal to 1.5, often between 1.05 and 1.45, most preferably 1. It has a value of .1 to 1.4.

Each polymer solution can be used in a form obtained by phase separation, for example by simply mixing the solution with water or other processing fluids, or the polymer can be prepared by evaporation, precipitation or other conventional processes. It can also be recovered from solution using various recovery techniques.

The polymer in each separated solution is generally in a partially neutralized state and can be oxidized or completely neutralized, if desired, in a conventional manner.

In the present invention, the pigment dispersion in an aqueous medium is a water-soluble polymer formed from one or more ethylenically unsaturated heptamers and an acidic group selected from the carboxyl and sulfone groups. or a water-soluble salt thereof, have a polydispersity of 15 or less and a low molecular weight.The Mw is usually at least about i,o o .

and up to about 6.900, preferably about 5.900.
Up to 000. Particularly preferred products are those with a PD of 1.4 or less and a Mw of i,ooo to 4,000.

Generally PD is 1.05-1.45, especially 1.1-1.
It is 1.4. Best results are obtained with a PD of 1.4 or less, preferably 1.35 or less. A value as close to l as possible is desirable, but generally a value of 1.25 or more is acceptable.

Preferably, the polymer is acrylic acid or a copolymer thereof with AMPS (2-acrylamido-2-methylpropanesulfonic acid). Any acidic polymer herein may be present in partial or complete salt form with an alkali metal, often sodium, or with ammonia or amines or other cations that produce water-soluble salts. For example, the polymer may be a copolymer of acrylic acid with a salt of AMPS, or a complete salt of an acrylic acid AMPS copolymer or a partial or complete salt of acrylic acid. In this specification, all molecular weights are determined as the complete sodium salt.

Although these are preferred polymers, other water-soluble polymers, generally ethylenically unsaturated polymers containing acidic groups alone or in conjunction with other ethylenically unsaturated polymerizing agents, are preferred. It is also possible to use polymers obtained by polymerization of the monomers in question. Oligomers formed from the corresponding monomers may be used in place of the 7-mer. The acid group is generally a carboxylic acid or a sulfonic acid group.
are often acrylic monomers, and therefore preferred acidic monomers are one or more methacrylic acid or especially acrylic acid or 2 to acrylic reamide-2
A wide variety of polymerizable acidic monomers can be used, including methylpropanesulfonic acid, such as maleic acid or vinylsulfonic acid. Any comonomer that can be copolymerized with the acidic monomer to form the water-soluble polymer can be used, including the seven-day monomers of acrylamide, acrylonitrile, and acrylic esters. 50% by weight and often at least 80% by weight are acidic monomers.The polymer is generally a linear polymer.

There are certain specific value areas within the broad inventive concept described above.

As mentioned above, certain low molecular weight agitated vinyl acetate copolymers are described in British Patent No. 1,414,964 for dispersing Kanwa 1 and as grinding dispersants for pigments. However, in reality, these do not have any impact commercially, and the commonly used Tanizan
It is generally a low molecular weight polyacrylic acid having a PI of 1.8 or more, L.

According to one aspect of the invention, the pigment dispersion in water has a PD of 1.5 or less and a dispersant of from about 1.000 to about 3.
．． 300, preferably 1,000 to 3.0'
00° most preferably in the range of about 1.800 to about 2.200, with best results generally achieved at values of about 2.000. PD preferably ranges from 1.05 to 1.4, most preferably 1
．． It ranges from 1 to 1.3 or 1.35.

These dispersions can be conventionally made by simply blending the particulate pigment with water in the presence of a dispersant, and the pigment and dispersant caps are conventional. For example, the dispersant is often 0.05 to 0.3% by weight of the dry polymer based on the dry pigment. The M of the pigment is often 10 to 90% by weight of the dispersion, most preferably 5%.
0 or 60-80% by weight. The pigment is selected depending on the intended usage of the dispersion. Dispersions are often used in the paper industry, for example for surface coating of paper, and suitable pigments include china clay, talc, titanium dioxide, precipitated calcium acetate. Particle size is generally 05-100 microns,
Preferably it is 1 to 50 microns.

Special problems arise when producing concentrated pigment dispersions by grinding calcium carbonate in water, especially when very fine particle sizes are required.

This is discussed in our European Patent No. 108842. That document (here, M
How to routinely use W2.800 sodium polyacrylate and improve results with acrylic acid-
It is stated that the best results (lowest viscosity) were obtained using AMPS copolymer with a Mw of FJ 5.700.

According to a second aspect of the invention, the dispersion of calcium hydroxide in water has a PD of less than or equal to 1.5 and from about 2.500 to about 4.5.
It is made by grinding calcium carbonate in water in the presence of a dispersant which is a polyacrylic acid having a Mw in the range 0.00 and most preferably in the range 3.300 to 3.900.

According to a third aspect of the invention, the dispersion of calcium oxate in water has a PD of less than or equal to 1.5 and from about 1.500 to about 3.5.
00, most preferably about 2.250 to about 2.7
It is made by milling calcium formate in water in the presence of a dispersant which is a copolymer of acrylic acid and AMIIS with a Mw of 50.

The preferred molecular weight for homopolymers is about 3.600 and the preferred molecular weight for copolymers is about 2.500. The weight ratio of acrylic acid and AMPS is preferably 99:1 to 5.
It is 0:50.

When calcium carbonate is ground according to any of these aspects of the invention, the PI) is preferably between 1.05 and 1,
4, most preferably 1.1 to 1.3.

The pulverization is preferably carried out by Santgerinding, and the particle size of the calcium carbonate (marble) produced is preferably 2 microns or less. Preferably, the weight of the pigment in the resulting dispersion is greater than 70%, most preferably 75%.
% or more. To further explain suitable grinding techniques, reference to particle size and concentration can be found in European Patent Publication No. 1.
It is described in the specification of No. 08842.

U.S. Pat. No. 3,840,487 and British Patent No. 1,505,555 (in which various aqueous dispersion coatings comprising pigments and low molecular weight polymerizable dispersants are described. For this purpose, certain polyallylic acid-ester copolymers are used, although in many other cases polyacrylic acid homopolymers, especially Disspec N40, are generally considered quite satisfactory. The inventors have found that even better results can be obtained by using the novel polymers described in this specification.
According to an aspect of the invention, an aqueous dispersion coating composition comprises a pigment, a coating binder, and a pigment dispersant, the dispersant having a PD of 1.5 or less and a PD of about 1.500 to about 6.000. It is a polyacrylic acid having an Mw of . PD is 1.05-1.
4 is preferred, most preferably c is 1.1 to 1.3, and the molecular weight is preferably in the range of 1.500 to 4.500. The aqueous medium of the paint is either water (or a mixture of a polar solvent, generally a glycol, and water).

The pigment is generally titanium dioxide, china clay, or calcium acetate, and has a general size of Q, 1 to 50 microns,
Preferably it has a particle size of 02 to 25 microns.

The amount of pigment in the paint may be conventional, typically 5-50% by weight of the paint. Binders and other ingredients in the coatings may be conventional, such as those described in, for example, US Pat. No. 1, US Pat.

The low polydispersity value required by the present invention can be obtained by various techniques. For example, the polymer can be prepared using conventional polymerization techniques, such as solution polymerization, to obtain a product with a high polydispersity value (typically 2 or more);
Careful fractional precipitation can then be carried out to obtain fractions each having a polydispersity of 1.5 or less. The conditions for carrying out the fractional precipitation must be such as to obtain a low polydispersity and are
It must be added isothermally and without solvent as detailed in Chapter B1, published by Manfred Kantau.

Another way to obtain the desired polymer is to carry out the synthesis under conditions conducive to its formation. For example, the polymer can be made by solution polymerization in the presence of isopronoRnol as a chain regulator. The method relies on very homogeneous and monitored conditions, e.g. controlled feeding of monomer and initiator, and about 7? It must be carried out at A level. If the resulting product has a polydispersity greater than the desired value, it must be removed or treated to reduce its polydispersity.

Another way to obtain the desired polymer is to prepare an insoluble acrylate polymer with the desired PD and Mw values, for example as described in Example 40 of EP 68887, and then to and 85
The acrylate is hydrolyzed to the free acid by reacting at C for 6 hours or as long as necessary to achieve hydrolysis. The reaction is generally carried out in the presence of methanol as the diluent.

Preferred methods are those described above. This can be done with any of the above sitapolymers.

The average molecular weight of the polymer to be fractionated can vary within a wide range, provided it is not so high that the polymer becomes insoluble. -The membranous striations are 5 to 1 million,
The average molecular weight is less than or equal to 1.000, and the average molecular weight is less than or equal to 30,000, especially 1.000.
.

The most valuable benefits are obtained between, for example, about 1500 to 4500.

The polymer can be made at °C by any conventional polymerization process and then isolated from any liquid phase in which it is formed, eg, as a solid.

Furthermore, it can be redissolved in the aqueous organic narkali solution used in the present invention. However, the process of the invention is generally carried out with polymer solutions obtained by solution polymerization of suitable heptamers. Preferred solution polymerization media are aqueous solutions containing suitable initiators or other polymerization promoters, such as water-soluble peroxides and persulfates, or redox or photopolymerization catalysts, such as molecular weight regulators. It generally contains organic solvents. Other known molecular weight modifiers may be included in the solution if desired.

When the polymer solution is prepared by polymerization in a mixture of water and an organic solvent, this organic solvent serves as the organic liquid for use in the present invention. A very common solvent in solution polymerization is Impropatol, and blended mixtures of water and Impropatol are suitable for the process of the present invention.

The solution is prepared by blending a preformed polymer, water, an organic solvent, and an alkali, or by adding an alkali to the reaction product of polymerization in an aqueous organic liquid, or by the Pond method. Regardless, the process of the invention requires that phase separation occur between the aqueous and organic phases in the presence of a specified solvent and a specified class of cations. If other solvents, other cations or other amounts of the specified cations are used, generally
Not only does the variable fraction of the present invention not be obtained, but useful results are not obtained or only the width oligomers and monomers are removed from the product. For example, if the organic solvent is acetone or tetrahydrofuran, or if the cation is an amine such as ethylamine, the degree of fractionation cannot be selected.

The degree of neutralization of acidic groups controls fractionation. Although the results obtained with any particular method will depend, among other things, on the concentration, type of polymer, and solvent, there is a minimum degree of neutralization below which virtually no fractionation occurs and the system remains as a homogeneous solution. do. When the cation is sodium, potassium or lithium, the degree of neutralization is usually at least 10%, often at least 15%, preferably at least 25%.
If the cation is lithium, the degree of neutralization is usually at least about 30%, preferably at least 40%, and generally less than 50%. If the degree of neutralization is too high, low molecular weight fractions when the cation is sodium or potassium, the degree of neutralization is usually less than 55%, preferably less than 50%,
Most preferably it is 40% or less. When the cation is ammonium, the degree of neutralization is usually less than 70%, preferably less than 60%, most preferably less than 50%. When the cation is lithium, the degree of neutralization is usually less than 90%, preferably less than 70%.

In any particular method, for example, the size of the high molecular weight fraction can be increased by increasing the amount of alkali (with a consequent decrease in the average molecular weight and nizing of the low molecular weight fraction and a consequent decrease in the average molecular weight). conversely, the size of the low molecular weight fraction can be increased by decreasing the amount of alkali.

Processing conditions are preferably selected such that each fraction contains 20-80% by weight, most preferably 30-70% by weight of the starting polymer.

Partial neutralization of acidic polymers is usually achieved by adding a selected amount of a compound, usually a hydroxide, to the dissolved polymer that imparts selected cations.
It will be done. Mixtures of two or more of the four cations may also be utilized, the proportions being selected to achieve a similar effect to the amounts specified for the individual cations. .

For any particular polymer, the extent of fractionation will depend not only on the degree of neutralization and cation type, but also on the polymer concentration and the choice and amount of alcohol. , propatool and other alcohols, especially those having 2 to 5 carbon atoms, can also be used.

The weight ratio of water:alcohol is preferably l:o, from 2 to 135, most preferably from 10.5 to l:2, with the best effectiveness generally being achieved, especially when the alcohol is improvised. and when the cation is sodium and monolayering is about 1:1 (this is achieved), the weight ratio is such that each phase is at least 5% by weight of the phase, taking into account the degree and nature of neutralization. Generally the number should be selected to have a concentration of at least 10% by weight, preferably at least 15% by weight.

The amount of polymer (measured as acidic polymer) is usually at least 5% by weight based on the weight of polymer, alcohol and water (including water introduced with the alkali).
, preferably at least 10% by weight. The concentration should not be so high that the system is so viscous that mixing and 4" separation are significantly hindered, so generally 3"
It is 0% or less. Preferably the concentration is 15-25% by weight.

Phase separation is also affected by the temperature G at which the treatment is performed.

The treatment temperature may be 15-80"C, but preferably 30-70"C.

The treatment is carried out by combining the basic components of the solution in any conventional manner, e.g. by adding an aqueous alkali to the aqueous organic reaction product obtained by the polymerization of 7mer in an aqueous organic solution. This can be done by The treatment can be carried out continuously or batchwise. Depending on the degree of neutralization, type and strength of base, polymer concentration, amount of solvent and temperature, phase separation occurs rapidly or slowly. For example, the phase separation may occur substantially instantaneously or over a period of time.
It may be necessary to leave the system undisturbed for e.g. 5 minutes to 2 hours, typically 30 minutes to 1 hour. Phase separation involves feeding the mixture into a conventional separation column or separation reactor. This can be done batchwise or continuously.

The two phases can be completely neutralized with the same or different alkalis while remaining separated, and the organic solvent can be removed from the organic phase by distillation ζ.

Each polymer fraction is recovered for subsequent commercial use.

The very low molecular weight fractions obtained by this technique are of particular value as scale formation and settlement inhibitors, especially as desalination aids. For example, what is the highest level of alkalinity that can be maintained in a solution?

It was confirmed that G increases as PD decreases.The best result is that Mw is 350-1.000 and PD is 1.5.
The following is most preferably achieved when the ratio is 1.05 to 13.

In the following examples, Example 1 shows that by careful polymerization the polymer can be made directly to the desired PD and Mwl, and Examples 2 and 3
This shows that the polymer can be obtained by partial neutralization and fractionation.

Example 1 700 equipped with thermometer, stirring means and external heating means
Add the three separate mixtures sequentially over a 6 hour period to the resin pot of cA.

Supply l: Water 226! Ice acrylic acid 340F supply 2:
Hydrogen peroxide 10.5g100vol. and water57.
l J' Feed 3: 28 f thioglycolic acid and 386 g water The contents of the pot are maintained at reflux temperature during the addition and then cooled after several hours. The proportion of unpolymerized acrylic/L/acid was determined by gas-liquid chromatography and was added @0.3%. The remaining polymer is completely neutralized by the addition of 46.6% sodium hydroxide and the final product is diluted to give a 40% w/w sodium polyacrylate solution.

The viscosity of the product was 12.1 cs at 25% (hanging level viscometer, NO3, 25°C). GPC analysis number: MW=1740, Mn=1321. Polydispersity −
1,32 was shown.

Example 2 A 23% by weight solution of polyacrylic acid in a blended mixture of equal parts by weight of Improper Tool and water was prepared by polymerization of acrylic acid in a conventional manner using ammonium persulfate as the initiator. Product samples were extracted and other samples were neutralized by addition of varying amounts of sodium hydroxide introduced as a 46% by weight aqueous solution. Each sample is allowed to stand for a sufficient time after the addition of the sodium hydroxide to separate the aqueous phase from the organic phase (possibly containing some water), and these phases are then separated from each other in a conventional manner. Furthermore, each phase is thoroughly neutralized with sodium hydroxide, and residual alcohol is removed by distillation.

Polymer yield in each phase was recorded.

Example 3 A 20% solution of polyacrylic acid having Mw of 3131 and 1)D (polydispersity) of 1.677 was neutralized with various basic compounds.
The medium was dissolved and the two layers were separated.

The polymer path and molecular weight in each layer were determined.

The results are shown in Table 1.

Table 1 (Continued) Example 4 The product obtained in Example 2 was adjusted to 40% active solids and made into marble as described in Example 11 of GB 1.414,964. Compare with grinding aid. The results are shown in Table 21.

*The product was prepared in a conventional manner by complete neutralization and then the organic layer was removed by distillation. So there are no fractions.

In test O1, described above, a grinding ratio of about 0.5 is satisfactory when the membrane exhibits commercially acceptable properties for preventing gelation of the marble dispersion.

As is clear from Table 2, after complete neutralization, almost all of the polymer is in the aqueous phase, but at low degrees of neutralization, substantially most of the polymer is in the organic phase. It is quite remarkable that the grinding efficiency is greatly improved even when the amount of polymer in the organic phase is instead quite low. For example, at 50% neutralization, the amount of polymer in the organic tn is low, but
The grinding rate is about 5 times higher than what is considered commercially reasonable. Only when the degree of neutralization is high does a very low amount of polymer pass into the organic phase.

Example 5 A polymer was prepared using conventional polymerization techniques, and after polymerization,
A 23% solution of aqueous acid in equal volumes of impropatur and water was neutralized to 25% with aqueous sodium hydroxide. The reaction mixture was separated into two phases. These were separated and the polymer present in the phase was recovered after removal of the impropatol by distillation.

The sample is completely neutralized with sodium hydroxide solution and adjusted to 40% activity as sodium polyacrylate.

Control polymers that are not fractionated can also be
It can be prepared from initially unneutralized polymer in water by removing the impropatol by distillation, completely neutralizing it with sodium hydroxide, and adjusting it to 40% activity as sodium polyacrylate.

The product was determined by recording the slurry viscosity (CP) at 0.6, 0.8 and 1% dry polymer based on dry pigment at 75% W/W slurry solids content, 97% 2 μm. It was evaluated as a dispersant for titanium dioxide having the following particle size. The results are shown in Table 3.

Table 3 Example 6 Samples of narrow polydispersity sodium polyacrylate with reduced molecular weight were prepared as in Example 4 at pH 6.8 to
It was evaluated as a china clay dispersant at 64% w/w slurry solids content with various testimonials at 7.0.

The results are shown in Table 4.

Table 4 shows that the most effective sodium polyacrylates for china clay powders have molecular weights of 1000 to 3000. Preferably, it has a molecular weight of about 2000.

Example 7 Samples of sodium polyacrylate of similar molecular weight but varying polydispersity were evaluated as marble grinding aids. Grindability was determined using a test method similar to that described in Example 11 of GB 1.414.964. The results are shown in Table 5.

From Table 5 it can be seen that the effectiveness of sodium polyacrylate in marble crushing is dependent on polydispersity.

The lower the polydispersity, the greater the effectiveness of the product.

Example 8 Sodium AMPS/-1-)lium acrylate (2
0/80 w/w) The interrelationship between molecular weight and polydispersity of the copolymer makes the product as described in British Patent No. 1.414
．． Accordingly, when evaluated as a marble crushing aid, Example 111 of the No. 964 specification can be shown to have definitive effectiveness. The interrelationships between these parameters are shown in Table 6.

From Table 6, it can be seen that low molecular weight polymers with narrow polydispersity are the most effective marble grinding aids. The optimum molecular weight is between 1500 and 3500, and a polymer with a molecular weight of 2500 can be selected.

Example 9 Samples of sodium polyacrylate of similar molecular weight or altered polydispersity were prepared as in Example 4 and prepared as a dispersant for precipitated calcium carbonate at 70% W/W slurry solids content. It was evaluated as The results are shown in Table 7.

Table 7

Claims (1)

[Claims] 1. A blended solution of a water-soluble polymer containing neutralized acidic groups in a polar solvent and water is mixed into an aqueous phase containing an intermediate molecular weight fraction and an organic phase containing a low molecular weight fraction. In this method, the polar solvent is an alcohol having 1 to 5 carbon atoms, the acidic group is neutralized with a cation selected from sodium, potassium, lithium or ammonium, and the neutralized acidic group is characterized in that the mass ratio is 10-55% when the cation is selected from sodium and potassium, 10-70% when the cation is ammonium and 30-90% when the cation is lithium. 2. The method according to claim 1, wherein the alcohol is inpropertool and the water:alcohol ratio is 1:0.5 to 1:2. 3. ( Based on polymer, water and alcohol (depending on the weight of the acidic polymer) the polymer concentration is at least 1
0% and each phase comprises 20 to 80% by weight of polymer. 4. The method according to any of the preceding claims, wherein a water-soluble acidic polymer is prepared in a mixed solution and a sufficient amount of alkali is added to partially neutralize the polymer. 5. The cation is selected from sodium and potassium, and the proportion of the neutralized acidic group is 15-40%, or the cation is ammonium, and the proportion of the neutralized acidic group is 15-40%. 50% of the method according to any of the preceding claims. 6. The blended mixture is 1 part of water and 0.5 parts of Improper Tools.
~2 parts of the polymany, 10 parts of the blended mixture
Present at a concentration of ~30% by weight, the polymer is a polymer formed from acidic, heptamers selected from acrylic acid and 2-acrylamido-2-methylpropanesulfonic acid; ~50 overlay%
2. A method according to claim 1, wherein is present as a sodium salt and the remainder of the acid group is a free acid group. 7. Forming the polymer in the free acid form as a solution in the blend mixture by polymerization of the polymerizable supernatant containing the acidic supernatant in the blend mixture and then adding 10 to 50 of the acidic group by adding sodium hydroxide. 7. The method of claim 6, comprising a preliminary step of converting % to sodium salt. 8. Contains a pigment dispersant, the dispersant being a water-soluble polymer formed from one or more ethylenically unsaturated heptamers, an acidic group selected from the carboxyl and sulfone groups, or Containing its water-soluble salts, 1.
PD of 5 or less and about i,oo. ~5.000 M (measured as sodium salt)
Pigment dispersion in an aqueous medium with w. 9. The dispersing agent is polyacrylic acid or a water-soluble salt thereof, and has a PD of 1.5 or less and a Mw ranging from about 1.000 to about 3.300 as measured in the fully sodium salt. Pigment dispersion in water as described in item 8. IQ and Mw are in the range of i, so o to 2.200 (the dispersion according to claim 9). 11, polyacrylic acid or a water-soluble salt thereof, and 5.1
．． 9. The aqueous dispersion of claim 8 made with aqueous milled calcium peroxide comprising a dispersant having a PD of 5 or less and a Mw ranging from about 2.500 to about 4,500. 154, M w ranges from about 3,300 to about 3.900. 13. A copolymer of acrylic acid and AMPS or a salt thereof, with a PD'i6 of 1.5 or less and a Mw ranging from about 1.500 to about 3.500 as measured for the fully sodium salt.
9. An aqueous dispersion according to claim 8, prepared by an in-water milled calcium carbonate containing a dispersant having a dispersing agent having the following properties. 14. The dispersion of claim 13, wherein the Mw ranges from about 2.250 to about 2.750. It consists of a pigment, a paint binder, and a pigment dispersant, the dispersant being polyacrylic acid or a salt thereof, and 1.5
Approximately 1.500 as measured with the following FD and complete sodium salt
Claim 8 having a Mw in the range of ~5.000
Aqueous dispersion paint as described in section. 16. The dispersion coating Fl of claim 15, wherein Mw is in the range of about 1,500 to about 4,500. 17, formed from one or more ethylenically unsaturated heptamers and containing an acid group selected from the carboxyl and sulfonic acid groups or a water-soluble salt thereof; 1.5
i, o measured with the following PD and complete IJ salts
Water-soluble polymer with Mw of o'o ~ 5.000.