Method for producing alkali-neutralized product of low-molecular-weight carboxyl group-containing polymer

Abstract

To provide a method by which an alkali-neutralized product of a carboxyl group-containing polymer having a molecular weight of ≤ 40000 can efficiently be obtained and the range of the molecular weight can be adjusted.SOLUTION: In the method for producing an alkali-neutralized product of a low-molecular-weight carboxyl group-containing polymer according to the present disclosure, an alkali-neutralized product of at least one carboxyl group-containing polymer selected from the group consisting of (I) a copolymer of an α - olefin or a vinyl compound and maleic anhydride, (II) a copolymer of a vinyl compound and (meth) acrylic acid, and (III) a (meth) acrylic acid polymer is used as a starting material, and a cleavage agent is allowed to act on the starting material to cleave the starting material, thereby producing an alkali-neutralized product of a carboxyl group-containing polymer having a molecular weight of 40000 or less. Thereafter, the produced alkali-neutralized product of the carboxyl group-containing polymer is powdered.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a method for producing an alkali-neutralized product of a low-molecular-weight carboxyl group-containing polymer. [Background technology]

[0002] Water-soluble polymers, which are carboxyl group-containing polymers, are produced by polymerizing general-purpose monomers and functional monomers in organic solvents other than water using a polymerization initiator, chain transfer agent, and catalyst (see, for example, Patent Document 1, "Example 1(i)"). They come in a wide variety of grades, from low molecular weight to high molecular weight. However, producing low molecular weight polymers in the same solvent as high molecular weight polymers is difficult, and the presence of isomers or insufficient removal of residual solvent can lead to slight further polymerization. Furthermore, since most of these polymers are anhydrous rings formed by closing the maleic acid terminals, powdered polymers can be made water-soluble by neutralizing them with alkali in the presence of water to form a solution, or by removing the water to obtain an alkali salt powder, which allows for a wide range of uses.

[0003] On the other hand, the molecular length of these water-soluble polymers is selected depending on the application, and the molecular weight varies depending on the application. Polymer powders are used as resins or adhesives, and more recently as sizing agents and as the base for water-absorbent resins. Small molecules have a wide range of uses, including pesticides, fertilizers, ceramic binders and dispersants, as well as inks, pigments, paints, and cement. However, the particles used come in a variety of shapes and sizes, and understanding the length and molecular shape of the small molecules to be adsorbed is becoming increasingly important.

[0004] As described above, in order to produce low molecular weight water-soluble polymers of carboxyl group-containing polymers, there is no other way than to use the same methods as for producing high molecular weight polymers. Therefore, it is not easy to produce low molecular weight polymers, and it is not easy to control the molecular weight range in accordance with a specified purpose. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 55-016928 Summary of the Invention [Problem to be solved by the invention]

[0006] The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide a method for producing an alkali-neutralized product of a low-molecular-weight carboxyl group-containing polymer, which can efficiently produce an alkali-neutralized product of a carboxyl group-containing polymer having a molecular weight of 40,000 or less, and which can also adjust the range of the molecular weight. [Means for solving the problem]

[0007] In order to achieve the above object, a first aspect of the present invention is a method for producing an alkali-neutralized product of a low-molecular-weight carboxyl group-containing polymer, which uses as a starting material an alkali-neutralized product of at least one carboxyl group-containing polymer selected from the group consisting of (I) a copolymer of an α-olefin or a vinyl compound and maleic anhydride, (II) a copolymer of a vinyl compound and (meth)acrylic acid, and (III) a (meth)acrylic acid polymer, and cleaves the starting material by allowing a cleavage agent to act on the starting material, thereby producing an alkali-neutralized product of a carboxyl group-containing polymer having a molecular weight of 40,000 or less.

[0008] According to this method, an alkali-neutralized product of a carboxyl group-containing polymer having a molecular weight of 40,000 or less can be efficiently obtained, and the range of the molecular weight can be adjusted by the amount of the cleavage agent.

[0009] A second aspect of the present invention is a method for producing an alkali-neutralized product of a low-molecular-weight carboxyl group-containing polymer according to the first aspect, in which 5 to 100 parts by weight of the cleaving agent is added to 100 parts by weight of the starting material, and the mixture is heated in the range of 70 to 98°C to cleave the starting material.

[0010] According to this configuration, an alkali-neutralized product of a carboxyl group-containing polymer having a molecular weight of 40,000 or less can be obtained more efficiently.

[0011] A third aspect of the present invention is a method for producing an alkali-neutralized product of a low-molecular-weight carboxyl group-containing polymer according to the second aspect, in which a peroxide is used as the cleaving agent.

[0012] According to this method, an alkali-neutralized product of a carboxyl group-containing polymer having a molecular weight of 40,000 or less can be obtained more efficiently.

[0013] A fourth aspect of the present invention is a method for producing an alkali-neutralized product of a low-molecular-weight carboxyl group-containing polymer according to the third aspect, in which the starting material is reacted with the cleavage agent and an antifoaming agent. According to this configuration, foaming caused by using a peroxide as a cleaving agent is suppressed, and an alkali-neutralized product of a carboxyl group-containing polymer having a molecular weight of 40,000 or less can be obtained more efficiently.

[0014] A fifth aspect of the present invention is a method for producing an alkali-neutralized product of a low-molecular-weight carboxyl group-containing polymer according to any one of the first to fourth aspects, in which the starting material is cleaved to produce an alkali-neutralized product of the carboxyl group-containing polymer having a molecular weight of 40,000 or less, and then the produced alkali-neutralized product of the carboxyl group-containing polymer is powdered. According to this method, a powdered alkali-neutralized product of a carboxyl group-containing polymer can be obtained, which has advantages such as reduced transportation costs. A sixth aspect of the present invention is a method for producing an alkali-neutralized product of a low-molecular-weight carboxyl group-containing polymer according to the fifth aspect, in which the powdering is carried out using a spray-drying method. According to this configuration, powder having a relatively high uniformity of particle size and a shape that is relatively close to a sphere can be obtained relatively efficiently. A seventh aspect of the present invention is a method for producing an alkali-neutralized product of a low-molecular-weight carboxyl group-containing polymer according to the fifth aspect, in which the powdering is carried out using a vat drying method. According to this configuration, a lump powder can be obtained relatively efficiently by lightly crushing using a relatively simple device. [Effects of the Invention]

[0015] As described above, according to the present invention, a method for producing an alkali-neutralized product of a low-molecular-weight carboxyl group-containing polymer can be realized, which can efficiently produce an alkali-neutralized product of a carboxyl group-containing polymer having a molecular weight of 40,000 or less, and further can adjust the range of the molecular weight. [Brief explanation of the drawings]

[0016] [Figure 1] 1 is a graph showing the results of GPC measurement of samples obtained in Examples 2 and 3. [Figure 2] 1 is a graph showing the results of GPC measurement of the sample obtained in Example 4. [Figure 3] FIG. 1 is a process diagram showing an outline of the spray-drying process used in the demonstration test for powderization. [Figure 4] FIG. 1 is a perspective view showing an outline of an apparatus for carrying out a vat drying method used in a demonstration test of powderization. DETAILED DESCRIPTION OF THE INVENTION

[0017] In one embodiment of the present invention, a method for producing an alkali-neutralized low-molecular-weight carboxyl-containing polymer involves starting with an alkali-neutralized product of at least one carboxyl-containing polymer selected from the group consisting of (I) a copolymer of an α-olefin or a vinyl compound with maleic anhydride, (II) a copolymer of a vinyl compound with (meth)acrylic acid, and (III) a (meth)acrylic acid polymer, and cleaving the starting material with a cleavage agent to produce an alkali-neutralized carboxyl-containing polymer having a molecular weight of 40,000 or less. As demonstrated in the examples below, this method efficiently produces an alkali-neutralized carboxyl-containing polymer having a molecular weight of 40,000 or less, and the molecular weight range can be adjusted by adjusting the amount of cleavage agent.

[0018] Preferably, 5 to 100 parts by weight of the cleaving agent is added to 100 parts by weight of the starting material, and the mixture is heated in the range of 70 to 98°C to cleave the starting material. This makes it possible to more efficiently obtain an alkali-neutralized product of a carboxyl group-containing polymer having a molecular weight of 40,000 or less. Note that even if the amount of the cleaving agent exceeds 100 parts by weight, cleavage can still be achieved if the desired molecular weight is not achieved. However, care must be taken because residual cleaving agent can cause deterioration and discoloration of the solution.

[0019] The alkali-neutralized product of a carboxyl group-containing polymer refers to alkali-neutralized products such as the following (i), (ii), and (iii): (i) a maleic anhydride copolymer of an α-olefin or a vinyl compound with maleic anhydride (including maleic anhydride such as maleic acid and maleic esters); (ii) an alkali metal salt or ammonium salt obtained by reacting an alkali metal hydroxide or ammonia with a polymer containing a carboxyl group or a functional group that becomes a carboxylic acid in the presence of an alkali hydroxide, such as an acrylic acid copolymer such as polyacrylic acid or polymethacrylic acid; and (iii) an alkali metal poly(meth)acrylate or ammonia, obtained by polymerizing, for example, (meth)acrylic acid, alkali metal acrylate, or ammonia. When neutralizing with alkali, it is also possible to combine alkali metals with ammonia, etc. The ratio can also be freely selected.

[0020] The maleic anhydride copolymer, which is used in the present embodiment to prepare the alkali-neutralized product of the carboxyl group-containing polymer and is composed of an α-olefin or a vinyl compound and maleic anhydride, will be described below.

[0021] The α-olefin refers to a linear or branched unsaturated hydrocarbon having 2 to 12 carbon atoms, preferably 2 to 8 carbon atoms, and examples thereof include ethylene, propylene, butene-1, butene-2, isobutylene, n-pentene, isoprene, 2-methyl-1-butene, n-hexene, 2-methyl-1-pentene-3-methyl-1-pentene, 4-methyl-1-pentene, 2-ethyl-1-butene, diisobutylene, 1,3-butadiene, 1,3-pentadiene, 1,3-hexadiene, 1,3-octadiene, 2-methyl-4-dimethyl-1-pentene, 2-methyl-4-dimethyl-1-pentene, and 2-methyl-4-dimethyl-2-pentene. Here, isobutylene also refers to a return BB containing isobutylene.

[0022] The vinyl compound refers to an unsaturated compound copolymerizable with maleic anhydride, such as styrene, vinyl chloride, vinyl propionate, acrylonitrile, methyl vinyl ether, acrylic esters, or vinyl alcohol obtained by saponifying vinyl acetate. These monomers may be used alone or in combination of two or more. Among these monomers, α-olefins such as ethylene and isobutylene, ethylene, styrene, or methyl vinyl ether are preferably used, but the use of α-olefins, especially isobutylene, is more preferred in light of the objectives of the present invention.

[0023] The composition ratio of the α-olefin or vinyl compound to maleic anhydride in such a maleic anhydride copolymer may be any ratio as long as the reaction product (alkali metal neutralized product or ammonia neutralized product) obtained by reacting the resulting copolymer with an alkali metal hydroxide or ammonia is soluble in water.

[0024] In the case of copolymers of ethylene, isobutylene, styrene, or methyl vinyl ether with maleic anhydride, which are preferably used in the present invention, the amount of ethylene, isobutyl, styrene, or methyl vinyl ether is about 1 to 3 moles, and in many cases about 1 mole, per mole of maleic anhydride.

[0025] Such maleic anhydride copolymers can be used alone or in combination of two or more. The molecular weight of these copolymers is such that the intrinsic viscosity [η] measured in a dimethylformaldehyde solution at 30°C is 0.05 to 10 (dl / g), preferably 0.1 to 8 (dl / g), and more preferably 0.2 to 5 (dl / g). Although the intrinsic viscosity is less than 0.1, lowering the molecular weight is not very meaningful and reduces the effect of cleavage.

[0026] The (meth)acrylic acid polymer will now be described. Polyacrylic acid is a polymer obtained by polymerizing acrylic acid or methacrylic acid in a solution such as water or an organic solvent, and includes those obtained by hydrolyzing poly(meth)acrylic acid esters, poly(meth)acrylonitrile, poly(meth)acrylamide, etc. Furthermore, a small amount of a copolymerizable vinyl compound may be copolymerized in the polyacrylic acid. The molecular weight of these (meth)acrylic acid-based polymers is such that the intrinsic viscosity [η] measured at 30°C in an aqueous solution containing an electrolyte is 0.1 to 10 (dL / g), preferably 0.5 to 8 (dL / g).

[0027] The alkali metal hydroxide refers to sodium hydroxide, potassium hydroxide, lithium hydroxide, calcium hydroxide, magnesium hydroxide, etc., and reacts with the carboxylic acid or acid anhydride of the carboxyl group-containing polymer to make the carboxyl group-containing polymer water-soluble, or even if it is not completely soluble in water, to impart hydrophilic groups. The use of this water-soluble alkali metal is essential, but they may be used in combination, or ammonia may be used as a separate alkali. An alkali metal and ammonia may also be used in combination.

[0028] Next, the cleavage method will be explained. The water-soluble polymer used is a ring-closed substance with a fixed molecular weight, and in most cases exists as granules. When used, it is neutralized with an alkali in water to form an aqueous solution. The solution obtained by this dissolution has a fixed solution viscosity, solid content, pH, etc., and can be used for various purposes. By performing cleavage in the latter half of this solution preparation, the molecular weight of the polymer can be adjusted to the desired size.

[0029] Depending on the type and use of the cleaving agent, sulfate or carbonate groups may remain in the solution in addition to alkali salts. While the presence of alkali salts is unavoidable when dissolving the polymer, peroxides can be used as cleaving agents to eliminate the presence of other groups. Cleavage can be performed using not only one type of cleaving agent, but also a combination of two or three types. Residual sulfonates and alkali metals can also have a positive effect. For example, they can improve the scale prevention effect in water purification, and scale removal effects can be adjusted by shifting the pH. Note that "scale" refers to calcium, magnesium, silica, etc. in water.

[0030] However, peroxides can generate a large amount of foam during use, and the inventors of this application propose the use of an antifoaming agent as a way to address the bumping phenomenon that can also occur with persulfates. It was found that the addition of an antifoaming agent reduces the amount of foam on the liquid surface, while the bubbles within the solution contain hydrogen peroxide, which aids in cleavage. Therefore, it was found that cleavage proceeds safely and quickly, and the hydrogen peroxide ultimately gasifies and no longer remains. Furthermore, the antifoaming agent also does not decompose. As a result, a low-molecular-weight compound consisting only of an alkali salt was obtained.

[0031] Even percarbonate can cause bubbles and bumping, so adding a similar antifoaming agent ensures safety. Percarbonate also disperses as carbon dioxide gas and has the effect of increasing the solids content. As shown in the examples below, repeated cleavage eventually resulted in the disappearance of both the antifoaming agent and the cleavage agent due to heat and moisture evaporation. While the end point of cleavage is difficult to determine, the presence of the cleavage agent can be checked. A convenient water quality monitor is the Pack Test H2O2 (manufactured by Kyoritsu Chemical Research Institute, Inc.). After a 1-minute reaction time, H2O2 can be read as mg / liter (ppm). A value of 0.05 or less is not a problem.

[0032] Next, we will explain cleaving agents. Cleavage agents are used in the polymerization of water-soluble polymers. They are widely used as polymerization initiators, chain transfer agents, and solvents. However, in aqueous systems, organic substances are not necessary. The main persulfates are inorganic, such as potassium persulfate (KPS), sodium persulfate (SPS), and ammonium persulfate (APS); percarbonates include potassium percarbonate, sodium percarbonate, and ammonium percarbonate; and peroxides include hydrogen peroxide, sodium peroxide, peracetic acid, lithium peroxide, and ammonium peroxide. The persulfates KPS, SPS, and APS are used because they are highly soluble in water. However, because sulfonates ionize in water, they are also effective in preventing scale formation in water, making them preferred water treatment agents.

[0033] Cleavage of high molecular weight polymers using inorganic cleavage agents is carried out in water at temperatures above 80°C, so bumping often occurs. This is particularly dangerous if the polymer is not completely dissolved. For this reason, it is recommended to add an antifoaming agent. Adding an antifoaming agent stabilizes the liquid surface, allowing cleavage to proceed in the liquid. Even if a small amount of undissolved polymer is present in the liquid, foaming is suppressed, and since the amount used is small, it does not interfere with physical properties.

[0034] The cleaving agent is added slowly over time and stirred to achieve a better cleavage effect, extend the life of other additives, and eliminate discoloration and turbidity.

[0035] Next, we will explain about antifoaming agents. It is known that the roles of antifoaming agents are divided into three categories: foam breaking, foam suppression, and defoaming (foam dissolving). There is no clear positioning for each antifoaming agent, but in most cases, they are thought to function as foam suppressors. Antifoaming agents are classified into mineral-based, oil-based, fatty acid ester-based, alcohol-based, amide-based, phosphate ester-based, metal soap-based, silicone-based, emulsion-type, etc. Only a small amount of antifoaming agent is required. Antifoaming agents are effective at 1% (by weight) or less of the water-soluble polymer 100 (by weight), but depending on the intended use of the finished low-molecular-weight solution, they may be used as little as possible to suppress foaming, and cleaved without use. However, it is advisable to take measures such as enlarging the reaction vessel, lowering the temperature, and stopping stirring to prevent the foamed solution from boiling over from the vessel.

[0036] The timing of using the antifoaming agent is as follows: 1. Prepare a vertically long circular kettle equipped with a coiled tube and a stirrer. Pour water into the kettle, then add the alkaline substance, and stir until the temperature reaches 40-50°C. 2. Slowly add the water-soluble polymer to the heated water and allow it to begin to dissolve. Heat is added by passing warm water (80°C) through the hose. First, neutralize the anhydrous polymer powder with alkali. After confirming that the entire polymer has dissolved, add the antifoaming agent. 3. After the bubbles have disappeared from the surface of the liquid due to the addition of the antifoaming agent, add the cleaving agent little by little and distribute it evenly. Then, continue stirring gradually until the temperature drops below 96°C.

[0037] When an antifoaming agent is added to a solution, bubbles disappear from the liquid surface and it appears as if nothing is happening, but it is believed that undissolved polymer clumps exist in the water. The amount added is 1% (by weight) or less relative to 100% polymer. In the examples used as demonstration tests, an antifoaming agent with foam-breaking and foam-suppressing properties was selected.

[0038] (Example) In the demonstration tests described below as examples, the following method was used to determine the molecular weight. Although the bulk material is prepared by polymerizing organic materials in an organic solvent, it cannot be said that the bulk material is 100% polymerized. Isomers, long and short molecules exist, and the solvent may remain. Pretreatment is also important for implementing this invention, and we carefully examined the bulk material and selected the portion with the highest concentration of bulk material, for example, by sieving. Some large particles have solidified with residual solvent, and fine powders often contain incomplete isomers that have not yet polymerized. The inventors of this application have eliminated these by sieving. However, examples may be presented with a clear indication that the isomers have not been eliminated. They may also be removed by cleavage.

[0039] Furthermore, to determine whether or not the alkali salt neutralized with alkali had a cleavage effect, a Brookfield viscometer was used to observe the change in viscosity. When the viscosity increased significantly, it meant that polymerization had progressed further, while when the viscosity remained roughly the same or increased by the amount of alkali salt, it was determined that there had been almost no cleavage effect. In this case, viscosity information alone was insufficient, so the solids content was also measured.

[0040] Clear cleavage can be determined by a significant decrease in viscosity. Most of the examples demonstrate the effect of cleavage. For some of the samples, the effect was confirmed using GPC (Gel Permeation Chromatography) measurement. The intrinsic viscosity was also used as a reference, but showed almost the same tendency as the B-type viscosity. For this reason, it was determined that the B-type viscosity was sufficient.

[0041] (Example 1: Sodium polyacrylate) Cleavage was attempted using a water-soluble polymer reagent with a defined molecular weight. The procedure carried out in Example 1 was as follows. 1. Weigh out sodium polyacrylate and place it in a glass bottle, add water to dissolve it, and measure the physical properties after dissolution. 2. Add antifoaming agent to the solution. 3. Next, add the cleaving agent and mix well. Place the glass bottle in a 4.65°C water bath and observe while stirring. 5. Keep the hot bath at 96°C, continue stirring, and remove after about 3 hours. 6. Measure the physical properties of the sample once it has cooled to room temperature. Table 1 shows the results of the experiment.

[0042] [Table 1]

[0043] The experimental results show that the viscosity has decreased and that cleavage has occurred. The experimental results can be summarized as follows: Test 1: The total solids content is reduced, but the viscosity is reduced even more significantly. Test 2: The total solids content increases, but the viscosity decreases significantly more than that. These results indicate that the molecular weight can be reduced by cleavage.

[0044] (Example 2: Isobutylene-maleic anhydride "ISOBAM #06") Kuraray Co., Ltd. offers isobutylene-maleic anhydride polymers with different molecular weights as grades. Grades Isoban #18, #10, #06, and #04 use the same polymerization solvent. "Isoban" is a Kuraray Co., Ltd. brand name. The molecular weights are 300,000-350,000 for #18, 160,000-170,000 for #10, 80,000-90,000 for #06, and 55,000-65,000 for #04. These have been on the market for a long time. After these, a grade with a different solvent, #600, was released. The molecular weight of #600 is 5,500-6,500. There are no intermediate molecular weight grades, and none below #600 are sold.

[0045] Those with intermediate molecular weights must be produced by polymerization. There is particularly a rush to develop low-molecular-weight polymers for use as dispersants, and the molecular weight of the polymer depends on the size of the particles to be treated and their adsorption performance. Therefore, precise adjustment of the molecular weight is required. The easiest way to precisely adjust the molecular weight is to open the anhydride ring with an alkali and then cleave it in a solution of water.

[0046] Any grade can be used for cleavage, but #06 is the most physically stable raw material for the molecular weight used. Polymers containing copolymers of 2·3 often contain traces of residual solvent. When this solvent is neutralized and dissolved with alkali, it can produce isomers, and because the solvent itself is organic, it can emit an unpleasant odor and cause a poor color. The cleavage process can safely reduce or eliminate the solvent, and can also decompose the resulting isomers. This invention not only reduces the molecular weight, but also leaves the main structure intact.

[0047] In the demonstration test conducted as Example 2, ISOBAM #06 was used. When NaOH was used as the dissolving agent, four neutralization degrees α were tested: α = 0.4, 0.5, 0.6, and 0.8. For the dissolving agent NH3OH, α = 0.8 was used. An alkaline solution containing no cleaving agent was prepared, and the cleaving agent was added to 100 g of the solution. The solution was heated in a water bath at a temperature of 96°C or higher for 4 hours to perform cleavage. Three types of cleaving agents were tested: KPS, APS, and SPS.

[0048] Tables 2 through 17 show the results of the demonstration tests. Table 2 shows various properties without a cleavage agent for comparison. In the tables, "α" represents the degree of neutralization, with α = 1.0 corresponding to 100% neutralization and α = 0 corresponding to 0% neutralization. The solids content is the value (%) measured using a far-infrared moisture meter. In the tables, an up arrow (↑) or a down arrow (↓) indicates a tendency for the viscosity to increase (↑) or decrease (↓) after measurement. The decrease in molecular weight can be read from the B-type viscosity and solids content, but the effect of cleavage varies depending not only on the type and amount of cleavage agent, but also on the method of neutralization of the polymer, the type of neutralizing agent, the original composition of the polymer, the presence of isomers, and the presence of impurities. Therefore, many experiments were conducted to investigate the effect of cleavage.

[0049] [Table 2]

[0050] As mentioned above, the main raw material in Table 2 is powder of Isoban #06 (molecular weight 80,000-90,000). Table 2 also shows the basic physical properties and characteristics. Isoban #06 is the easiest product number to produce in the production of Isoban, and is said to undergo stable polymerization with little variation in performance. Therefore, it was determined to be suitable as a starting material for low-molecular-weight conversion.

[0051] Among the factors affecting cleavage, the type of alkali used for neutralization and the degree of neutralization are particularly important. The practical neutralization degree α is in the range of about 0.3 to about 1.0, and is generally in the range of about 0.5 to about 0.8. This range was selected as the basic recipe for cleavage. The viscosity and solids concentration can be said to be the starting values.

[0052] When the degree of neutralization α is low, in the case of NaOH, the viscosity is in the tens of thousands. To measure the progress of cleavage by viscosity, the solids concentration must be easily measurable; excessively low values ​​are undesirable for the low-molecular-weight isopropyl alcohol produced by cleavage. For this reason, we aimed to limit the preferred concentration to approximately 20% to approximately 30%, with the aim of keeping the viscosity due to cleavage close to zero. As shown in Table 2, the viscosity is shown for a degree of neutralization α of 0.4 to 0.5, with a maximum solids concentration of 50%. Above this level, the viscosity increases due to cleavage, as polymerization of the remaining solvent begins. Experiments have shown that when the degree of neutralization α is low in NaOH solution, the viscosity increases, making it difficult to handle, rather than decreasing due to cleavage.

[0053] Ultimately, to obtain the optimum viscosity level while observing the progress of cleavage, it was determined that the initial solids concentration should be around 50%, and that the desirable solids concentration after cleavage, taking ease of use into account, should be around 20%. Type B viscosity can be adjusted so that it is nearly 0 at a solids concentration of around 20%. In the experimental example, a variable test was conducted, sorting out as many factors as possible so that it could be sorted by viscosity level. In the table below, if bubbles form or fluidity is lost, cleavage has not occurred, and if the viscosity is 3000 or less, it can be said that cleavage is progressing.

[0054] [Table 3]

[0055] Table 3 shows the results when KPS is used as the cleaving agent. When the degree of neutralization α is 0.6, the solids content is 47.4% and the viscosity is 3022 mPa·S, but even with the addition of KPS, it remains high at 4484 mPa·S. When the degree of neutralization α is set to 0.8 and the solids concentration is reduced to 39.4%, the viscosity decreases with the addition of the cleaving agent, to 714 mPa·S. Therefore, the viscosity can be further reduced simply by adding the cleaving agent. Note that "g / 100" is used as an abbreviation for "1 part by weight per 100 parts by weight of polymer." This applies similarly to other tables and text.

[0056] [Table 4]

[0057] Table 4 shows that when the KPS was increased to 4.5 g / 100 from the beginning, the viscosity was 1295 mPa·S and the solid content was 37.9%, which was low and tended to become even lower in the liquid state.

[0058] [Table 5]

[0059] In Table 5, 6 g / 100 of KPS and an antifoaming agent were added, but cleavage was not possible at a neutralization degree of α = 0.4 or 0.5, indicating that cleavage with KPS is difficult. At a neutralization degree of α = 0.6 to 0.8, the viscosity reached a low level of 747 mPa·S. Looking at the solids content, it can be seen that increasing the cleavage agent further promoted cleavage.

[0060] [Table 6]

[0061] Table 6 shows an example in which 30% H2O2 was added because cleavage was difficult with KPS, as shown in Table 5. It is clear from Table 6 that the addition of H2O2 makes cleavage easier, and both the viscosity and solids content are reduced. In both the case of NaOH with a neutralization degree α = 0.5 to 0.8 and the case of ammonia water with a neutralization degree α = 0.8, the solution has a low viscosity, which indicates that cleavage is proceeding smoothly.

[0062] [Table 7]

[0063] Tables 6 and 7 show that the viscosity and solid content can be easily reduced by adding H2O2 water, which has a greater cleavage effect than KPS. In other words, it can be seen that the addition of more cleavage agent leads to further reduction in molecular weight.

[0064] [Table 8]

[0065] Table 8 shows an example where ammonium salt APS was used as the cleavage agent. When neutralized with ammonia, the solids concentration decreased quickly, but when NaOH was used with different neutralization degrees α, the viscosity also decreased easily.

[0066] [Table 9]

[0067] As shown in Table 9, increasing the amount of cleavage agent at once reduces the effect. When the cleavage agent is APS, the results are similar to those of KPS, but at different levels.

[0068] [Table 10]

[0069] Regarding Table 10, when the cleavage agent is APS, a tendency similar to that in the case of KPS is shown, but the level is different.

[0070] [Table 11]

[0071] Regarding Table 11, when NaOH was used with different degrees of neutralization α, the results were similar to those when the cleavage agent was KPS, but KPS was more effective, and the use of additional H2O2 water produced an even greater cleavage effect.

[0072] [Table 12]

[0073] Table 12 shows that H2O2 is also effective when the cleavage agent is APS.

[0074] [Table 13]

[0075] [Table 14]

[0076] [Table 15]

[0077] Tables 13, 14, and 15 show examples where neutralizing sodium persulfate (SPS) is used as the cleavage agent. Even with the same persulfate salt, the effect decreases with increasing ionization tendency from potassium salt to sodium salt, and the effect of ammonium salt is also smaller than that of potassium salt.

[0078] [Table 16]

[0079] [Table 17]

[0080] Tables 16 and 17 show the results when the cleavage agent H2O2 was added. The use of the cleavage agent SPS was also effective, and a low viscosity was obtained despite the high solids content. This can be said to be a preferred cleavage method. More details are as follows.

[0081] In the case of NaOH dissolution, which has a low degree of neutralization α, the viscosity actually increases, suggesting that polymerization is occurring rather than cleavage. For this reason, as shown in Tables 6 and 7, tests were also conducted using H2O2 water as a cleavage agent. Tables 6 and 7 show the results of two identical tests. The same applies to Tables 11, 12, 16, and 17.

[0082] The results of the demonstration experiment show that adding a cleaving agent reduces the viscosity of the sample, indicating that the isobutylene-maleic anhydride is being broken down into smaller molecules. When the degree of neutralization α is low, depending on the cleaving agent, the molecular weight appears to increase. When this is not the case, it is understood that increasing the amount of cleaving agent added reduces the viscosity further, indicating that the breaking down of the isobutylene-maleic anhydride into smaller molecules is progressing.

[0083] It was also confirmed that the foaming, spillage, and bumping that occur during cleavage can be prevented by adding an antifoaming agent. By using an antifoaming agent in combination, a polymer that is free of turbidity and coloration can be obtained.

[0084] (Example 3: Isobutylene-maleic anhydride "ISOBAM #04") In Example 3, an attempt was made to obtain a low molecular weight equivalent to ISOBAM #600 by cleavage. Of the various grades of ISOBAM, #06 is the easiest grade to produce in a factory and is also the easiest to cleave. However, in Example 3, #04 was selected instead of #06. The reasons for this are that, in terms of low molecular weight, #04 is closest to #600, which uses a different polymerization solvent, at around 40,000, and the resulting particles are small, making it difficult to process the fine powder due to factors such as granularity.

[0085] High molecular weight powders are usually uniform in size, but when classified, their properties can unexpectedly change. Viscosity can vary when isomers are present after polymerization or when the polymerization solvent is not completely removed during use. There is a specific range of particle size, and outside of that, dissolution or cleavage can cause an increase in viscosity. The inventors of this application constantly monitor the behavior of polymers by size based on the classification and physical properties (viscosity after alkali neutralization, pH, solids content) of incoming polymers.

[0086] In Example 3, cleavage was attempted with the goal of lowering the molecular weight from the #04 level to the #600 level. The starting material, ISOBAM #04, was sieved to separate the 120M pass product, and after confirming that the viscosity was appropriate, a solution of caustic soda (neutralization degree α = 0.50, pH 7, solids content 45%) was prepared at a maximum temperature of 96°C. To this solution, 30% aqueous hydrogen peroxide as a cleavage agent and Noptum 777 (trade name of San Nopco Ltd.) as an antifoaming agent (foam breaker / foam suppressor) were added only the first time, and cleavage was repeated at 96°C for 2 to 3 hours.

[0087] As a result, the viscosity was reduced to the level of ISOBAM #600, and the GPC measurement described below confirmed that a low molecular weight was achieved. As expected, there was no bumping, and the operation was easy. The process was repeated 6 to 7 times, and a transparent isobutylene-maleic anhydride sodium salt was produced without any cloudiness.

[0088] The ratio of hydrogen peroxide to polymer was 100:15, with a final solids concentration of 28% and viscosity of 98 mPa·S. The turbidity caused by the antifoaming agent had disappeared, the initial yellow hue had become colorless and transparent, and there was no odor.

[0089] Table 18 shows the results of the demonstration test conducted as Example 3. ISOBAM #04, alkali, and water were mixed to prepare a 30% DS solution, which was then divided into 100g portions. The cleavage agent was added to each 30% solution and heated with stirring at 50°C. The solution was heated at 96°C for 4 hours, aiming for a viscosity of 100 mPa·S at a solids content of 25-35%, which is easy to handle commercially. The B-type viscosity of ISOBAM #04 at 30°C before cleavage was 4180 mPa·S. The dissolving agent was NH4OH, and the degree of neutralization α was α = 0.8. The use of the cleavage agent significantly reduced the viscosity. In this example, the use of an antifoaming agent was avoided as much as possible, and the experiment was conducted using a vessel with ample space. There was a lot of foaming when the cleavage agent was first added, but there was no bumping or overflow of foam from the top.

[0090] [Table 18]

[0091] Table 18 shows the results of examining the progress of cleavage after neutralizing ISOBAMM #04 (a low molecular weight of approximately 55,000) with alkali to create a dissolved solution, adding a cleavage agent to the solution, and heating (temperatures below 96°C) and stirring (800 rpm). It can be seen that cleavage is nearly complete about two hours after the start of cleavage. It can also be seen that increasing the amount of cleavage agent added is effective in lowering the molecular weight. More detailed information is provided below.

[0092] As mentioned above, the initial B-type viscosity without any cleavage agent was 4180 mPa·S, but the use of the cleavage agent significantly reduced the B-type viscosity. The viscosity decreased as the amount of cleavage agent increased, and it can be seen that the degree of molecular weight reduction can be optimized by adjusting the amount of cleavage agent added.

[0093] The experiment was carried out by lowering the solid content to about 30% and using a larger container. In this example, the use of antifoaming agents was avoided as much as possible, and the experiment was carried out using a spacious container. Although a lot of foaming was observed when the cleaving agent was added, the container did not overflow.

[0094] (Example 4: Isobutylene-maleic anhydride "ISOBAM #600") In Example 4, ISOBAM #600 was used as the isobutylene-maleic anhydride compound, and attempts were made to reduce the molecular weight of the compound by cleavage. Two cleavage agents were used: hydrogen peroxide (35% aqueous solution of HO) and potassium persulfate (KPS). The ISOBAM #600 used as the base material was a commercially available product with a molecular weight of approximately 6000 and containing approximately 5% polymerization solvent.

[0095] Tables 19 to 26 show the results of the demonstration tests. Of these tables, Table 19 shows various properties without a cleaving agent for comparison. Sample symbols such as "Na-4-K1" are used to identify the type of alkali, the degree of neutralization, and the cleaving agent. For example, "Na-4-K2" indicates that the type of alkali is Na, the degree of neutralization α is 4, the cleaving agent is KPS, and that the amount of KPS is the second smallest among the same type of cleaving agent. "NH3-..." indicates that the type of alkali is NH3.

[0096] [Table 19]

[0097] Table 19 shows an example of ISOBAM #600 (molecular weight 5500-6500). The table shows the basic formulation again, as well as the basic physical properties. The basic physical properties include the viscosity after the neutralization reaction. As can be seen from the appearance of the solution, the viscosity has decreased due to the neutralization reaction, and a solution with a solids content of approximately 40% and a viscosity of less than 500 mPa·S was created.

[0098] [Table 20]

[0099] [Table 21]

[0100] [Table 22]

[0101] Tables 20 to 22 show examples in the low molecular weight range. Table 20 shows an example in which KPS was used as the cleavage agent, Table 21 shows an example in which a larger amount of KPS was used as the cleavage agent, and Table 22 shows an example in which KPS and 35% H2O2 water were used as the cleavage agent.

[0102] From the results shown in these tables, it can be seen that cleavage also occurs in the case of low molecular weight ISOBAM #600, and that a low molecular weight with a viscosity of about 200 mPa·S can be obtained at a solids content of about 40%. When the molecular weight distribution was measured using DSC (Differential Scanning Calorimetry), a peak molecular weight of Mn 5200 was obtained. "Mn" stands for number average molecular weight. If the viscosity is taken as Mn at 10 mPa·S or less, a product with an Mn of up to about 4000 can be obtained. At a solid concentration of about 25%, it can be further powdered for commercial use, and can also be handled satisfactorily as a solution.

[0103] In the experiment whose results are shown in Table 22, H2O2 water was added to suppress the cleavage of KPS, but it did not easily reach the level of H2O2 alone.

[0104] [Table 23]

[0105] [Table 24]

[0106] [Table 25]

[0107] [Table 26]

[0108] The results of the demonstration experiment in Example 4 showed that when KPS was used as the cleavage agent, the phenomenon of additional polymerization was observed, but when H2O2 water was used, such a phenomenon was not observed. Furthermore, when H2O2 water was used, the viscosity decreased as the amount of cleavage agent added increased, regardless of the magnitude of the neutralization degree α, and it can be seen that the degree of low-molecular-weight polymerization can be optimized by the amount of cleavage agent. Furthermore, when H2O2 water was used, bumping due to the antifoaming agent was not observed. In the experiment using KPS, there were cases where antifoaming agent was added midway through the cleavage.

[0109] (Example 5: Molecular weight measurement by GPC) In Example 5, molecular weight measurements were performed on the products obtained in Examples 2 to 4, and knowledge was gained about the molecular weight distribution. Figures 1 and 2 show the measurement results. Table 27 shows the processing details for each sample in Figure 1. Similarly, Table 28 shows the processing details for each sample in Figure 2. In Figures 1 and 2, the horizontal axis "molecular weight" represents "molecular weight per 10 g slice."

[0110] [Table 27]

[0111] [Table 28]

[0112] As is clear from Figures 1 and 2, the molecular weight is reduced by cleavage. This indicates that the decrease in viscosity after cleavage observed in Examples 2 to 4 is due to the decrease in molecular weight. Furthermore, the molecular weight distribution after cleavage is the same as or even narrower than that before cleavage. This means that the molecular weights of the low-molecular-weight polymers obtained by cleavage are relatively uniform, demonstrating the usefulness of low-molecular-weight polymers obtained by cleavage.

[0113] (Additional remarks about the examples) The following remarks are made regarding the experiments conducted for the purpose of demonstrating the present invention and shown as examples. The reason why many experiments were conducted as examples was that it was necessary to clarify unknown issues such as whether cleavage occurs in aqueous solution, whether there are conditions under which it is more likely to occur, what is the best cleavage agent, what means can be used to grasp the progress of cleavage while simplifying the measurement method, etc. As a result of the experiments, the following findings were obtained regarding these issues.

[0114] 1. The molecular weight can be reduced in aqueous solution by adding a cleavage agent to the neutralization solution. 2. Concerning whether the intended reaction is hindered by bumping or bubbles, it was found that adding an antifoaming agent would be sufficient. 3. The cleaving agents are mainly persulfates and H2O2, and they can be used in combination. In particular, H2O2 produces a clean product. 4. The progress of cleavage can be roughly determined by Brookfield viscosity and solids content. There is no need to rely on intrinsic viscosity measurements or GPC. 5. Even if the molecular weight of the raw material for cleavage is high, it can be reduced to a lower molecular weight by adjusting the type and amount of cleavage agent. 6. The heating temperature and stirring time for cleavage are 90 to 100°C and 2 hours. 7. In the cleavage, by optimizing the degree of neutralization, a sharp molecular weight distribution can be obtained, and the product has a clean appearance and no odor.

[0115] (Demonstration test of powder processing) Powdering a polymer has various advantages, such as reducing the cost of transporting the polymer, making it more soluble in water, etc. Below, we will explain a demonstration test conducted on a method for producing a powdered alkali-neutralized carboxyl group-containing polymer by further powdering an alkali-neutralized carboxyl group-containing polymer obtained through cleavage.

[0116] As typical methods for powdering a polymer, the spray drying method and the vat drying method are widely known. First, these drying methods will be briefly explained. Since both are well-known techniques, detailed explanations will be omitted.

[0117] Figure 3 is a process diagram showing an outline of the spray-drying process used in the demonstration test for powderization. A polymer solution, which is liquid raw material 3, is placed in a raw material container 1. The liquid raw material 3 is pumped out by a pump 5 and transported to a nozzle atomizer 9 installed at the top of a drying chamber 7. At the same time, air sucked through a filter 11 is sent to the drying chamber 7 by a blower 13. The air sent to the drying chamber 7 is heated by a hot air heater 15. In the drying chamber 7, the liquid raw material 3 is sprayed from the nozzle atomizer 9 into hot air (e.g., 170°C to 250°C), causing the water to instantly evaporate and resulting in a dried polymer powder.

[0118] The obtained powder is sorted by size using a sieve 17 and packed into product bags 19. Of the powder obtained in the drying chamber 7, relatively small particles are sent to a dust collector 21 and stored in a fine powder collection container 23. Even smaller particles are sorted by the dust collector 21 and stored in a fine powder collection container 27 through a dust collector 25. Compressed air is sent to the dust collector 25 by a blower 29.

[0119] The particles obtained by the spray drying method are round. In contrast, in the vat drying method described below, the particles are lumpy because the material is pulverized from a plate-like body. The concentration of high molecular weight polymer that can be powdered is up to about 20% to 50% solids, and water flies inside the drying chamber 7. A rotating spray nozzle, such as a nozzle atomizer 9, is used. When the molecular weight is high, such as 20,000 to 30,000, stringiness appears and cotton-like particles are formed.

[0120] In the spray drying method, by spraying a carrier in addition to the powder alone, it is possible to make the particles larger and harder. The size of the dried particles can be selected by adjusting the amount and temperature of the hot air used in the spray drying. The size, type, and rotation speed of the spray nozzle, such as the nozzle atomizer 9, can also be changed. The concentration and viscosity of the liquid being pumped can also be changed. It is best to select the conditions for applying water pressure and heat that make it easy to produce powder.

[0121] Figure 4 is a perspective view showing an outline of the apparatus for carrying out the vat drying method used in the demonstration test for powderization. The vat 31 used was made of, for example, aluminum-coated steel plate, and was 450 mm wide, 370 mm deep, and 30 mm high. The dryer (oven) 33 used can accommodate up to 17 trays 31, two in front and two behind, and two rows across. The dryer 33 sends hot air into the interior using a fan (not shown) and heater (not shown) installed on the side wall, and expels air mixed with moisture from the top.

[0122] In the demonstration test, the polymer solution was cast into a tray 31 and inserted into a shelf 35 inside the dryer 33. After closing the door, the dryer 33 was used to heat the container. Water begins to evaporate rapidly above 95°C and almost completely evaporates above 100°C. The solution in the tray 31 was pulverized by heating it, for example, at 95°C to 120°C for several hours to several days. When the tray 31 was then removed from the dryer 33, a plate-like solid material appeared inside the tray 31. By hitting the tray 31 with an open hand, the plate-like solid material crumbled and became a powder. To obtain a finer powder, the material was further pulverized in a coffee mill. A grain grinder or coffee mill is preferably used for pulverization. Large, powerful industrial pulverizers make it difficult to achieve a uniform particle size distribution and particle size. A method similar to grinding in a mortar is preferred.

[0123] (Example 6: Isobutylene-maleic anhydride "ISOBAM #06" and KPS) In Example 6, cleavage was carried out using potassium persulfate (KPS). First, water was placed in a container, and NaOH was added as a neutralizing alkali. The temperature was raised to 65°C to 96°C to neutralize and dissolve the polymer. Then, the solution was sampled. The temperature is first brought to 55-70°C, and the cleavage agent (KPS: potassium peroxide) is added little by little. After the addition is complete, the temperature is gradually raised to carry out the cleavage. The reaction is carried out at a maximum temperature of 96°C for about 4 hours, and then the mixture is left to stand, samples are taken, and the physical properties are measured after the temperature has cooled.

[0124] The various conditions in this example are as shown in Tables 29 to 32.

[0125] [Table 29]

[0126] [Table 30]

[0127] [Table 31]

[0128] [Table 32]

[0129] Next, powdering was carried out by the following methods (1) and (2). (1) The resulting solution was spray-dried to obtain spherical powders with diameters of 20 μm to 40 μm. The moisture content of the powder was 5%, and the solid content of the powder redissolved in water could be up to 70%. The viscosity of the powder prepared from the pale yellow, transparent liquid at 35% of the same solid content was 80 mPa·S. (2) The solution was cast into a tray and heated in an oven at 110°C for 12 hours, after which it was ground in a coffee mill. The resulting powder had a moisture content of 10% and a viscosity of 70 mPa·S.

[0130] Both methods (1) and (2) were able to produce low molecular weight powders. Because SO3H groups exist in water, they can be used as scale inhibitors and water treatment agents. According to the catalogue of Kuraray Co., Ltd., the molecular weight of the raw material, Isoban #06, is 80,000 to 90,000. The molecular weight is significantly reduced by cleavage.

[0131] Even if the molecular weight is slightly high, molecular scission occurs easily and the molecular weight distribution becomes sharp. The alkali metals that neutralize carboxylic acids are potassium, sodium, lithium, calcium, and magnesium. As alkali salt cleaving agents, sulfates of these metals can all be expected to have roughly the same effect.

[0132] (Example 7: Isobutylene-maleic anhydride "ISOBAM #04S" and APS) In Example 7, cleavage was carried out using APS (ammonium persulfate). First, water was placed in a container, and ammonia water (25% ammonia) was added as a neutralizing alkali, and the polymer was dissolved at 80°C or below. At this point, a sample of the solution was taken. The solution temperature was gradually increased, and when it reached 92°C, the temperature was temporarily lowered, and a cleavage agent (ammonium persulfate) was added at 65°C to 70°C. The reaction was carried out at a maximum temperature of 96°C for approximately 2 hours, and the solution was allowed to stand, sampled, and the physical properties were measured after the temperature had dropped.

[0133] The various conditions in this example are as shown in Tables 33 to 36.

[0134] [Table 33]

[0135] [Table 34]

[0136] [Table 35]

[0137] [Table 36]

[0138] Next, powdering was carried out by the following methods (1) and (2). (1) The resulting solution was spray-dried to obtain spherical powder with diameters of 20 μm to 40 μm. The moisture content of the powder was 6%, and the solid content of the powder redissolved in water could be up to 70%. The viscosity of the powder prepared from the pale yellow, transparent liquid at 35% of the same solid content was 80 mPa·S. (2) The solution was placed in a tray, and about 2 to 4 kg of the solution containing the cleavage agent was cast onto each tray. The solution was then dried in an oven at 95°C for 2 hours and at 110°C for 2 hours to obtain a powder.

[0139] The raw material, ISOBAM #04S, is made from fine particles obtained by sieving ISOBAM #04 through a 120 mesh sieve, and was named "#04S." Its molecular weight is estimated to be about 5,000.

[0140] (Example 8: Isobutylene-maleic anhydride "ISOBAM #04" and H2O2 water) In Example 8, cleavage was performed using H2O2 water. An alkali metal was used as the alkali. Regular isobutylene-maleic anhydride products (with molecular weights of 40,000 or more, such as #04 (55,000-65,000), #06 (80,000-90,000), and #10 (160,000-170,000)) were used as raw materials, and molecular cleavage was performed using a cleavage agent. Since regular products are produced in large quantities and many are available as export products, they can be used as raw materials without running out, and different product numbers can be used together. For quicker use, it is convenient to use #04, which has a low molecular weight, as this reduces the reaction time. H2O2 water is the best cleavage agent to use.

[0141] The various conditions used in this example are shown in Tables 37 to 39. In the case of an 800-liter dissolving vessel, the raw material (Isoban #04) was 100 kg, and the amount of molten liquid was 340 kg.

[0142] [Table 37]

[0143] [Table 38]

[0144] [Table 39]

[0145] The process from cleavage to powdering was carried out according to the following procedure. (1) Before cleavage, the carboxylic acid of maleic anhydride is opened with alkali to form an alkali salt in isobutylene. To do this, first put water into a dissolution tank and add alkali. Heat is generated, so stir to make it easier to dissolve. (2) Add the polymer powder to the alkaline water and dissolve it. In the initial stage, there will be a lot of polymer and air bubbles, so use a tank with ample space to prevent overflow from the top, and add an antifoaming agent if it looks like it will overflow. Continue stirring while maintaining the temperature between 70°C and 95°C to create a solution with a large amount of transparency. It is desirable to maintain the liquid temperature up to a maximum of 96°C. (3) If the bubbles have decreased slightly, it can be said that the polymer is dissolving. (4) While checking the state of the liquid, add the cleaving agent with a ladle. (5) Once the measured amount has been added, once the cleavage reaction (large bubbles burst, then turn into smaller bubbles, and this process is repeated vigorously) has subsided, raise the temperature to 90-96°C to stabilize and complete the cleavage. Depending on the amount, about 4 hours is recommended. (6) This completes the process of depolymerization. To confirm that the resulting solution is as desired, the physical properties are measured and analyzed. If depolymerization has been achieved, powderization is possible.

[0146] (7) Next, powdering was carried out using two methods: spray drying and vat drying. (7-1) The spray-drying method produced fine spherical particles with diameters of 20 μm to 50 μm without clogging the atomizer. (7-2) In the vat drying method, after heating at 110°C for 12 hours, a powder that crumbles when touched with the hand is produced, which is then crushed in a coffee mill to produce the product.

[0147] (Example 9: Isobutylene-maleic anhydride "ISOBAM #04" and aqueous ammonia) In Example 9, cleavage was performed using H2O2 water. Ammonia water was used as the alkali. The raw material was a regular isobutylene-maleic anhydride product (#04 with a molecular weight of 40,000 or more (55,000-65,000)) and molecular cleavage was performed using a cleavage agent.

[0148] The various conditions used in this example are shown in Tables 40 and 41. In the case of an 800-liter dissolving vessel, the raw material (Isoban #04) was 100 kg, and the total weight was 300 kg to ensure ample space.

[0149] [Table 40]

[0150] [Table 41]

[0151] The process from cleavage to powdering was carried out according to the following procedure. (1) As in Example 8, the polymer is first neutralized by reacting it with an alkali, but instead of adding a solid like an alkali metal salt (e.g., caustic soda), it is neutralized with aqueous ammonia. Because it is a reaction between liquids, they mix easily, heat is generated quickly, and the reaction is fast. The mixture is mixed and dissolved while continuing to stir, and an alkali-neutralized solution of the polymer is obtained. Since the foam is stable, the significance of an antifoaming agent is not as great as in the case of metal salts, but it is still desirable to add one to stabilize foam breaking. Cleavage occurs below the liquid surface, resulting in efficient cleavage. (2) Cleavage is carried out at 70-95°C until a clear liquid is produced. Add the cleavage agent (H2O2 water) in 20kg, 20kg, and 17kg amounts while closely monitoring the time and the state of the bubbles. (3) Before adding the entire amount of H2O2 water, check the solid content and viscosity at 30°C from time to time to ensure that the final viscosity is 100 mPa·S or less at 35% to 40%. (4) To allow the product to cool sufficiently, stop external heating and leave it for one day before placing it in a suitable container.

[0152] (5) Next, powdering is carried out. Two methods were used: spray drying and vat drying. If the molecules have been broken down into smaller molecules, powdering is possible. (5-1) The spray-drying method produced fine spherical particles with diameters of 20 μm to 50 μm without clogging the atomizer. (5-2) In the vat drying method, after heating at 110°C for 12 hours, a powder that crumbles when touched with the hand is produced, which is then crushed in a coffee mill to produce the product.

[0153] (Example 10: Isobutylene-maleic anhydride "ISOBAM #600") In Example 10, isobutylene-maleic anhydride "ISOBAM #600" (using ethylbenzene as the polymerization solvent) was used. Rather than lowering the molecular weight, we investigated whether it was possible to remove the isomers of the remaining ethylbenzene bond. Note that "ISOBAM #600" contains a large amount of residual solvent and precipitates are also observed. For this reason, it was placed in a tank and left to stand for six months, which was a time-consuming process, and we waited for the isomers to separate before removing them.

[0154] A polymer of "Isoban #600" (molecular weight 5500-6500; according to Kuraray's Isoban catalogue) containing ethylbenzene was dissolved in HaOH and water to create a slightly cloudy yellow to brownish-red solution (the color deepens as the amount increases) with a neutralization degree of α = 0.4, pH 6, and a solids concentration of 35%. Treatment with H2O2 water was attempted in an amount sufficient to remove impurities, so as not to significantly change the molecular weight of the original isobutylene-maleic anhydride.

[0155] Cleavage occurs up to approximately 24.5g of H2O2. Beyond that, cleavage decreases. This is thought to be due to the decomposition of impurities. Products that are not washed with H2O2 water can be baked at high temperatures (i.e., grease (resin) is produced). Increasing the amount of cleavage agent increases heat resistance and reduces grease.

[0156] The conditions and test results in this example are shown in Table 42 and Tables 43 to 44, respectively.

[0157] [Table 42]

[0158] [Table 43]

[0159] [Table 44]

[0160] The viscosity was measured using a Brookfield:LV, DV-EV15COMETER manufactured by Eiko Seiki Co., Ltd. (*) The moisture content was measured by changing the maximum temperature after 10 minutes on the far-infrared moisture meter. The sample was placed in an aluminum dish and heated from above. This measurement allowed us to check the moisture content at high and low temperatures, and also to observe the deterioration of the sample.

[0161] The jorda disappears by GPC. This is a low molecular weight polymer made with a cleavage agent, and the molecular weight distribution shown in curve 5 in Figures 1 and 2 is not obtained. α=0.4, and H2O2 is kept below 20% to prevent cleavage.

[0162] The cleavage wash was found to be useful for obtaining pure polymers, and the cleavage agent disappeared along with the impurities, eliminating excess additives and keeping the solids content constant.

[0163] Example 11 Currently, a substance that is considered to be a low molecular weight substance, a copolymer of acrylic acid and 2-acrylamido-2-methylpropanesulfonic acid (ATBS), is sold as a scale inhibitor by Toa Gosei Co., Ltd. It was thought that these liquids could be powdered as they are easily water-soluble. A commercially available liquid was obtained and powdered by vat drying.

[0164] According to the catalog, ATBS monomer is commercially available with acrylic acid (also available as a sodium salt) and is used as a flocculant or scale inhibitor in wastewater treatment. It is used because SO3H sulfonic acid is present in water. Its melting point is 185°C, and it can be powdered by spray drying.

[0165] The chemical formula for 2-acrylamido-2-methylpropanesulfonic acid is shown below. [ka]

[0166] The conditions and test results for this example are shown in Table 45. Regarding re-dissolution in water, it was found that re-dissolution was easier when about 1% remained as water.

[0167] [Table 45]

[0168] Judging from the viscosity and molecular weight, it is understood that both are in the range of low molecular weight products. The test results showed that the copolymer of acrylic acid and 2-acrylamido-2-methylpropanesulfonic acid (ATBS) used in the test can also be powdered. 1016A is particularly suitable for powdering. The ATBS copolymer corresponds to the acrylic acid copolymer, which is an example of a starting material used in the method of producing an alkali-neutralized low molecular weight carboxyl group-containing polymer of the present invention. It is also possible to reduce the molecular weight of ATBS by cleavage using the production method of the present invention. [Explanation of symbols]

[0169] 1 concentrate container container, liquid raw material 3, drying chamber 7, 9 nozzle atomizer, 31 vat, 33 dryer.

Claims

1. (I) a copolymer of an α-olefin or a vinyl compound and maleic anhydride; (II) a copolymer of a vinyl compound and (meth)acrylic acid; (III) using an alkali-neutralized product of at least one carboxyl group-containing polymer selected from the group consisting of (meth)acrylic acid polymers as a starting material, and cleaving the starting material by allowing a cleavage agent to act on the starting material, thereby producing an alkali-neutralized product of a carboxyl group-containing polymer having a molecular weight of 40,000 or less, The method for producing an alkali-neutralized product of a low-molecular-weight carboxyl group-containing polymer includes powdering the alkali-neutralized product of the carboxyl group-containing polymer produced.

2. The method for producing an alkali-neutralized product of a low-molecular-weight carboxyl group-containing polymer according to claim 1, wherein 5 to 100 parts by weight of the cleaving agent is added to 100 parts by weight of the starting material, and the mixture is heated in the range of 70 to 98°C to cleave the starting material.

3. 3. The method for producing an alkali-neutralized product of a low-molecular-weight carboxyl group-containing polymer according to claim 2, wherein a peroxide is used as the cleaving agent.

4. 4. The method for producing an alkali-neutralized product of a low-molecular-weight carboxyl group-containing polymer according to claim 3, wherein the starting material is reacted with the cleaving agent and an antifoaming agent at the same time.

5. 5. The method for producing an alkali-neutralized product of a low-molecular-weight carboxyl group-containing polymer according to claim 1, wherein the powdering is carried out by a spray-drying method.

6. 5. The method for producing an alkali-neutralized product of a low-molecular-weight carboxyl group-containing polymer according to claim 1, wherein the powdering is carried out by a vat drying method.

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