Method for producing alkaline-neutralization of low molecular weight carboxyl group-containing polymer

Abstract

To provide a method capable of efficiently obtaining an alkaline neutralization of a carboxyl-group-containing polymer with a molecular weight of 40,000 or less, and capable of adjusting a range of a molecular weight.SOLUTION: A method for producing an alkaline neutralization of a low molecular weight carboxyl group-containing polymer disclosed herein involves using as a starting material at least one alkaline neutralization of a carboxyl group-containing polymer selected from the group consisting of (I) a copolymer of an alpha-olefin or vinyl compound with maleic anhydride, (II) a copolymer of a vinyl compound and (meth)acrylic acid, and (III) (meth)acrylic acid polymer. By treating this starting material with a cleaving agent, the starting material is cleaved, thereby producing an alkaline neutralization of a carboxyl group-containing polymer with a molecular weight of 40,000 or less. Preferably, 5 to 100 pts.wt. of the cleaving agent is added per 100 pts.wt. of the starting material, and the starting material is cleaved by heating in the range of 70 to 98°C.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 Art

[0002] Water-soluble polymers that are carboxyl group-containing polymers are produced by polymerizing general-purpose monomers and functional monomers in an organic solvent other than water using a polymerization initiator, a chain transfer agent, and a catalyst (see, for example, Patent Document 1, “Example 1(i)”). Their grades range from low molecular weight to high molecular weight and are diverse. However, when producing low molecular weight products, it is difficult to produce them under the same solvent conditions as in the case of high molecular weight products. Due to the presence of isomers and insufficient removal of residual solvents, polymerization may proceed slightly. Furthermore, since most of them have a closed anhydride ring with the terminal of maleic acid, to solubilize the powdered product, it is neutralized with an alkali in the presence of water to form a solution for use, or further dehydrated to obtain a powder of the alkali salt, and it is widely used.

[0003] On the other hand, these water-soluble polymers are used with the molecular length selected according to the application, and the molecular weight varies depending on the application. High molecular weight powders are used as resinified products or adhesives, and recently are used as flocculants and as a base for water-absorbing resins. Low molecular weight products are used in a wide range of applications such as pesticides, fertilizers, ceramic binders and dispersants, as well as inks, pigments, paints, and cement. However, the particles used have various shapes and sizes, and it is becoming increasingly important to understand the length and molecular form of the adsorbed low molecular weight products.

[0004] As described above, to produce low molecular weight water-soluble polymers of carboxyl group-containing polymers, there is no other way but to use the same method as in the case of producing high molecular weight products. Therefore, it is not easy to produce low molecular weight products, and it is not easy to control the molecular weight range according to a predetermined purpose.

Prior Art Documents

Patent Documents

[0005] Patent Document 1 Japanese Patent Application Laid-Open No. 55-016928 Summary of the Invention Problems to be Solved by the Invention

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

[0007] In order to achieve the above object, according to a first aspect of the present invention, there is provided a method for producing an alkali-neutralized product of a low molecular weight carboxyl group-containing polymer, comprising: (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. At least one carboxyl group-containing polymer alkali-neutralized product selected from the group consisting of 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 40,000 or less.

[0008] 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 efficiently obtained, and the molecular weight range can be adjusted by the amount of the cleavage agent.

[0009] According to a second aspect of the present invention, there is provided a method for producing an alkali-neutralized product of a low molecular weight carboxyl group-containing polymer according to the first aspect, wherein 5 to 100 parts by weight of the cleavage agent is added to 100 parts by weight of the starting material, and heating is performed 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, wherein a peroxide is used as the cleavage agent.

[0012] 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 even 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, wherein the cleavage agent is allowed to act on the starting material, and an antifoaming agent is allowed to act.

[0014] According to this configuration, foaming due to the use of a peroxide as the cleavage 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 even more efficiently.

Advantages of the Invention

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

Brief Description of the Drawings

[0016]

Figure 1

Figure 2

Modes for Carrying Out the Invention

[0017] The method for producing an alkali neutralized product of a low molecular weight carboxyl group-containing polymer according to an embodiment of the present invention 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 vinyl compound and maleic anhydride, (II) a copolymer of a vinyl compound and (meth)acrylic acid, and (III) a (meth)acrylic acid polymer. By allowing a cleavage agent to act on this starting material, the starting material is cleaved, thereby producing an alkali neutralized product of a carboxyl group-containing polymer having a molecular weight of 40,000 or less. Thereby, as demonstrated by the examples described below, an alkali neutralized product of a carboxyl group-containing polymer having a molecular weight of 40,000 or less can be efficiently obtained, and moreover, the molecular weight range can be adjusted according to the amount of the cleavage agent.

[0018] Preferably, 5 to 100 parts by weight of a cleavage agent is added to 100 parts by weight of the starting material, and the starting material is cleaved by heating in the range of 70 to 98°C. Thereby, an alkali neutralized product of a carboxyl group-containing polymer having a molecular weight of 40,000 or less can be obtained more efficiently. When the desired molecular weight is not reached, even if the amount of the cleavage agent exceeds 100 parts by weight, cleavage can be performed, but attention should be paid to the fact that the remaining cleavage agent may cause deterioration and coloring of the solution.

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

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

[0021] The α-olefin means an unsaturated hydrocarbon having a straight-chain or branched carbon number of 2 to 12, preferably 2 to 8. 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, 2-methyl-4-dimethyl-2-pentene. Here, isobutylene also means return BB containing isobutylene.

[0022] The vinyl compound refers to an unsaturated compound that can copolymerize with maleic anhydride. For example, 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, particularly isobutylene, is more preferable in view of the object of the present invention.

[0023] In the maleic anhydride copolymer, the composition ratio of the α-olefin or vinyl compound and maleic anhydride may be any degree 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 each copolymer of ethylene, isobutylene, styrene, or methyl vinyl ether and maleic anhydride, which is preferably used in the present invention, it is about 1 to 3 moles, and often about 1 mole, of ethylene, isobutyl, styrene, or methyl vinyl ether per 1 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 at 30 °C in a dimethylformaldehyde solution is 0.05 to 10 (deciliters / g), preferably 0.1 to 8 (deciliters / g), and more preferably 0.2 to 5 (deciliters / g). A decrease in the molecular weight with an intrinsic viscosity less than 0.1 has little meaning and the effect of cleavage decreases.

[0026] The (meth)acrylic acid polymer will 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 also includes those obtained by hydrolyzing poly(meth)acrylic esters, poly(meth)acrylonitrile, poly(meth)acrylamide, etc. Also, a small amount of a vinyl compound copolymerizable with polyacrylic acid may be copolymerized. The molecular weight of these (meth)acrylic acid polymers is such that the intrinsic viscosity [η] measured at 30 °C in an aqueous solution containing an electrolyte is 0.1 to 10 (deciliters / g), preferably 0.5 to 8 (deciliters / g).

[0027] Alkali metal hydroxides refer to sodium hydroxide, potassium hydroxide, lithium hydroxide, calcium hydroxide, magnesium hydroxide, etc. They react with the carboxylic acid or acid anhydride of the carboxyl group-containing polymer to render the carboxyl group-containing polymer water-soluble or to impart hydrophilic groups even if it is not completely soluble in water. The use of this water-soluble alkali metal is essential, but they may be used in combination, or ammonia may be used as another alkali. Alkali metals and ammonia may be used in combination.

[0028] Next, the cleavage method will be described. The water-soluble polymer to be used is a closed-ring substance with a determined molecular weight and mostly exists in the form of granules. When using this, it is neutralized with an alkali in water to form an aqueous solution. The solution obtained by this dissolution, with determined solution viscosity, solid content, pH, etc., is used for various applications. In the latter half of the solution production, by performing cleavage, the molecular weight of the polymer can be adjusted to the desired size.

[0029] Depending on the type and usage of the cleavage agent, in addition to the alkali salt in the solution, sulfate groups or carbonate groups remain. Assuming the presence of the alkali salt during the dissolution of the polymer is inevitable, peroxides can be used as the cleavage agent so that various other groups do not exist. The cleavage agent can be not only one type but also a combination of two or three types for cleavage. Also, the remaining sulfonates or alkali metals may have a favorable effect. For example, the scale prevention effect in water purification can be improved, and the scale removal effect can be adjusted by pH shift. Note that "scale" means calcium, magnesium, silica, etc. in water.

[0030] However, peroxides may generate a large amount of foam during use, and as a method that can also address the bumping phenomenon that may occur even with persulfates, the inventor of the present application proposes the use of an antifoaming agent. By adding the antifoaming agent, the foam on the liquid surface decreases, while on the other hand, the foam in the solution contains hydrogen peroxide and has been found to assist in cleavage. Therefore, it has been found that cleavage proceeds safely in a short time and hydrogen peroxide finally gasifies and does not remain. Furthermore, the antifoaming agent also stops decomposing. As a result, only a low-molecular compound of the alkali salt could be obtained.

[0031] Even with percarbonates, foam generation and bumping may occur, and the addition of a similar antifoaming agent covers safety. Percarbonates also have the effect of increasing the solid content as well as some scattering as carbon dioxide gas. As shown in the examples described later, it was confirmed that when cleavage is repeated, finally both the antifoaming agent and the cleavage agent disappear due to heat and moisture scattering. Although the end point of cleavage is difficult to read, the presence of the cleavage agent can be examined. The Pack Test (manufactured by Kyoritsu Chemical-Check Laboratory Co., Ltd.) H2O2 is convenient as a simple water quality measuring instrument. H2O2 can be read as mg / liter (ppm) with a reaction time of 1 minute. If it is 0.05 or less, there is no problem.

[0032] Next, the cleavage agent will be described. The cleavage agent is used when making water-soluble polymers by polymerization. It is also widely used as a polymerization initiator, chain transfer agent, solvent, etc. In the case of an aqueous system, organic substances are not required, and mainly inorganic persulfates such as potassium persulfate (KPS), sodium persulfate (SPS), ammonium persulfate (APS), percarbonates such as potassium percarbonate, sodium percarbonate, ammonium percarbonate, and peroxides such as hydrogen peroxide, sodium peroxide, peracetic acid, lithium peroxide, ammonium peroxide, etc. can be mentioned. Among those with good solubility in water, KPS, SPS, and APS, which are persulfates, are used. However, since sulfonates ionize in water and also have an effect of preventing the generation of scale in water, they are rather preferably used as water treatment agents.

[0033] The cleavage of polymer by inorganic cleavage agent is carried out in water at a temperature of 80 °C or higher, so bumping often occurs. In particular, it is dangerous if the dissolution of the polymer is not complete. Therefore, the addition of an antifoaming agent is desirable. When an antifoaming agent is added, the liquid surface becomes stable and the cleavage proceeds in the liquid. Even if some undissolved polymer exists in the liquid, foaming can be suppressed, and since the amount used is small, it does not interfere physically.

[0034] The cleavage agent should be added and stirred slowly over time for better cleavage effect, longer life of other additives, and the ability to eliminate discoloration and turbidity.

[0035] Next, the antifoaming agent will be described. It is known that the roles of antifoaming agents are distinguished into defoaming, foam suppression, and foam removal (dissolving foam). Although there is no clear positioning for each antifoaming agent, in most cases, it seems to function as a foam suppressant. The classifications of antifoaming agents include mineral-based, oil and fat-based, fatty acid ester-based, alcohol-based, amide-based, phosphate ester-based, metal soap-based, silicone-based, emulsion type, etc. A very small amount of antifoaming agent is sufficient. Regarding the antifoaming agent, it is effective at 1% (by weight) or less based on 100 (by weight) of the water-soluble polymer. However, considering the use of the resulting low-molecular solution, in cases such as applications where foaming is suppressed with as little as possible, cleavage may be carried out without using it. However, it is desirable to make devices such as enlarging the reaction vessel, lowering the temperature, and stopping stirring so that the solution foamed from the container does not spill.

[0036] The timing of using the antifoaming agent is as follows. 1. Prepare a vertically long circular kettle equipped with a stirrer and provided with a coil pipe. Put water into it, first add an alkaline substance, and stir to make the temperature 40 - 50 °C. 2. Slowly add the water-soluble polymer to the heated water and start dissolving it. Send warm water (80 °C) to the coil pipe to add heat. First, neutralize the anhydrous ring polymer powder with alkali. After confirming that the whole has dissolved, add the antifoaming agent. 3. After the bubbles disappear from the liquid surface due to the addition of the defoaming agent, the cleavage agent is added little by little and spread throughout. Then, stirring is gradually continued until the temperature reaches 96°C or lower.

[0037] When the defoaming agent is added to the solution, the bubbles disappear from the liquid surface and nothing seems to happen. However, in water, it is considered that there are lumps of undissolved polymer. The addition amount is 1% (by weight) or less based on 100 of the polymer. In the examples which are demonstration tests, as the defoaming agent, those having the functions of defoaming and foam suppression were selected.

[0038] (Examples) In the demonstration tests described below as examples, the following method was adopted regarding the molecular weight. Those obtained by polymerizing organic substances in an organic solvent are used as the original body. However, it cannot be said that the target substance by polymerization is 100% in the original body. There are isomers, those with long molecules, and those with short molecules, and there are also cases where the solvent remains as it is. In order to implement the present invention, pretreatment is also important. The original body was examined, and for example, by sieving classification, the part with the most of the original body was also selected. It was also recognized that some of the large particles were solidified with the residual solvent, and there were many half-finished isomers in the fine powder where the polymerization had not progressed much. The inventor of the present application has excluded these by sieving classification. However, with prior notice, there are also cases where those not excluded are shown as examples. Also, it may be removed by cleavage.

[0039] Furthermore, regarding the presence or absence of the cleavage effect of the substance neutralized with an alkali to form an alkali salt, the change in viscosity was observed using a B-type viscometer. When the viscosity increased significantly, it was judged that the polymerization had further progressed. When it was almost the same or the viscosity increased by the amount of the alkali salt, it was judged that there was almost no cleavage effect. In this case, since only the viscosity information was insufficient, the solid content was also measured.

[0040] In the case where cleavage is obvious, it can be determined by the significant decrease in viscosity. Most of the examples show the effect of cleavage. For some samples of the examples, the effect was confirmed using GPC (Gel Permeation Chromatography) measurement. The intrinsic viscosity was also referred to, but it showed almost the same tendency as the B-type viscosity. Therefore, it was judged that the B-type viscosity was sufficient.

[0041] (Example 1: In the case of sodium polyacrylate) Attempts were made to cleave using a reagent of a water-soluble polymer with a determined molecular weight. The procedure carried out in Example 1 is as follows. 1. Weigh sodium polyacrylate into a glass bottle, add water and dissolve it, and measure the physical properties after dissolution. 2. Add an antifoaming agent to the dissolved solution. 3. Next, add a cleavage agent and mix well. 4. Place the glass bottle in a water bath at 65°C and observe while stirring. 5. Keep the water bath at 96°C, continue stirring, and take it out after about 3 hours. 6. Measure the physical properties of the sample whose temperature has dropped to room temperature. Table 1 shows the results of the experiment.

[0042]

Table 1

[0043] The results of the experiment show that the viscosity has decreased, indicating cleavage. Summarizing the results of the experiment is as follows. Test 1: The total solid content decreases, but the viscosity decreases significantly more. Test 2: The total solid content increases, but the viscosity decreases significantly more. These results indicate that the molecular weight can be decreased by cleavage.

[0044] (Example 2: In the case of isobutylene-maleic anhydride "Isoban #06") Kuraray Co., Ltd. provides polymers with different molecular weights as grades for isobutylene - maleic anhydride. The same polymerization solvent is used for grades such as Isoban #18, #10, #06, and #04. "Isoban" is a product name of Kuraray Co., Ltd. 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 them, a grade with a different solvent, #600, is being sold. The molecular weight of #600 is 5,500 - 6,500. There are no products with intermediate molecular weights, and those with molecular weights less than #600 are not sold.

[0045] Those with intermediate molecular weights need to be made by polymerization. Especially for low - molecular - weight ones, the development for various dispersant applications is urgent, and the molecular weight of the polymer affects the size of the particles and the adsorption performance. Therefore, fine adjustment of the molecular weight is required. The most convenient method for fine adjustment of the molecular weight is to open the anhydride ring with an alkali and cleave it with a solution dissolved in water.

[0046] Any grade can be used for cleavage, but #06 is the most physically stable as the raw material of the molecular weight to be used. It is often seen that polymers containing 2 - 3 copolymers contain trace amounts of residual solvents. When this solvent is neutralized and dissolved by an alkali, it may form isomers, emit an abnormal odor due to the solvent itself being an organic substance, or deteriorate the hue. The operation of cleavage can reduce or eliminate the solvent if it is safe, and can also decompose the isomers that can be formed. The present invention has not only the effect of reducing the molecular weight but also the effect of leaving the main structure clean.

[0047] In the demonstration test conducted as Example 2, Isoban #06 was used. When NaOH was used as the solvent, four different degrees of neutralization α, namely α = 0.4, 0.5, 0.6, and 0.8, were tested. For the solvent NH3OH, α = 0.8 was the target. An alkaline solution without a cleavage agent was prepared, and a cleavage agent was added to 100 g of the solution, which was then heated in a water bath at a temperature of 96 °C or higher for 4 hours to effect cleavage. Three types of cleavage agents, KPS, APS, and SPS, were tested.

[0048] Tables 2 to 17 show the results of the demonstration test. Among these tables, Table 2 shows various properties in the case without a cleavage agent for comparison. In the table, "α" represents the degree of neutralization, where α = 1.0 corresponds to 100% neutralization and α = 0 corresponds to 0%. The solid content is the value (%) measured by a far-infrared moisture meter. In the table, the upward arrow "↑" and the downward arrow "↓" indicate that the viscosity tends to increase (↑) or decrease (↓) after measurement. The decrease in molecular weight can be read from the B-type viscosity and the solid content. However, the cleavage effect varies depending not only on the type and amount of the cleavage agent, but also on the way of polymer neutralization, 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 cleavage effect.

[0049]

Table 2

[0050] As shown above, the main raw material in Table 2 uses the powder of Isoban #06 (molecular weight 80,000 - 90,000) as the raw material. Table 2 shows the basic physical properties and characteristics. Isoban #06 is the easiest product number to produce in the production of Isoban, and the polymerization is carried out stably, and it is said that there is little variation in performance. Therefore, it was judged to be suitable as a starting material for low molecular weight reduction.

[0051] As factors affecting cracking, the type of alkali used for neutralization and the degree of neutralization are particularly important. The practical degree of neutralization α ranges from about 0.3 to about 1.0, and generally, a range of about 0.5 to about 0.8 is used. This range was selected as the basic formulation for the case of cracking. It can be said that its viscosity and solid content concentration are the starting values.

[0052] When the degree of neutralization α is low, in the example of NaOH, it shows a viscosity of ten thousand units. To examine the progress of cracking by viscosity, the solid content concentration must be at a level that is easy to measure, and it is not preferable for the low-molecular isobutene formed by cracking to have an excessively low value. For this reason, the preferred concentration was kept in the range of about 20% to about 30%, and it was considered desirable to bring the viscosity due to cracking close to 0. As shown in Table 2, the viscosity at the degree of neutralization α = 0.4 to 0.5 is shown, and the solid content concentration was up to 50% at most. When the solid content concentration exceeds this, due to polymerization starting with the remaining solvent during cracking, etc., the viscosity increases even more. According to experiments, in the dissolution of NaOH, when the degree of neutralization α is low, unlike the viscosity decrease due to cracking, the viscosity instead becomes high and difficult to handle.

[0053] Ultimately, considering the progress of cracking, to obtain an optimal product in terms of viscosity level, the initial solid content concentration was considered to be around 50%, and the desirable solid content concentration after cracking was considered to be about 20% taking into account usability. The B-type viscosity can be adjusted so that the solid content concentration is about 20% and becomes almost 0. The experimental examples were arranged to conduct variable tests by organizing the factors as much as possible so that they can be organized in terms of viscosity level. In the following table, when foaming occurs and fluidity is lost, cracking does not occur, and if the viscosity is 3000 or less, it can be said that cracking is progressing.

[0054]

Table 3

[0055] Table 3 shows the results when KPS is used as the cracking agent. When the neutralization degree α = 0.6, the solid content is 47.4% and the viscosity is 3022 mPa·S. However, even when KPS is added, it becomes as high as 4484 mPa·S. When the neutralization degree α is set to 0.8 and the solid content concentration is reduced to 39.4%, the viscosity decreases to 714 mPa·S due to the addition of the cracking agent. Therefore, just by adding the cracking agent, the viscosity can be further reduced. Note that "g / 100" is used as an abbreviation for "1 part by weight per 100 parts by weight of the polymer". The same applies to other tables and text.

[0056]

Table 4

[0057] Table 4 shows that when KPS is increased from the beginning to 4.5 g / 100, the viscosity is as low as 1295 mPa·S and the solid content is 37.9%, showing a tendency to be even lower and in a liquid state.

[0058]

Table 5

[0059] In Table 5, KPS is 6 g / 100 and an antifoaming agent is added. However, when the neutralization degree α = 0.4 or 0.5, cracking cannot occur, indicating that cracking with KPS is difficult. When the neutralization degree α = 0.6 - 0.8, the viscosity reaches as low as 747 mPa·S. From the perspective of the solid content, it can be understood that further cracking progresses by increasing the cracking agent.

[0060]

Table 6

[0061] Table 6 shows an example in which 30% H2O2 was added in KPS because cracking is difficult to progress as in Table 5. It is clear from Table 6 that the addition makes cracking easier to progress, and both the viscosity and the solid content have decreased. In the case of NaOH with a neutralization degree α = 0.5 - 0.8 and in the case of aqueous ammonia with a neutralization degree α = 0.8, since the solutions have low viscosities, it is understood that cracking is proceeding smoothly.

[0062]

Table 7

[0063] Tables 6 and 7 show that with H2O2 water having a cracking effect compared to KPS, both the viscosity and the solid content can be easily reduced. That is, it is understood that further addition of a cracking agent promotes low molecular weightization.

[0064]

Table 8

[0065] Table 8 shows an example in which ammonium salt APS was used as a cracking agent. When neutralized with ammonia, the solid content concentration decreases rapidly, but in the case of NaOH with different neutralization degrees α, the viscosity is easily reduced.

[0066]

Table 9

[0067] As shown in Table 9, it can be seen that when the amount of the cracking agent is increased at once, the effect becomes weaker. When the cracking agent is APS, it is very similar to the case of KPS, but the levels are different.

[0068]

Table 10

[0069] Regarding Table 10 as well, when the cracking agent is APS, it shows a tendency very similar to that of KPS, but the levels are different.

[0070]

Table 11

[0071] Regarding Table 11, in the case of NaOH with the neutralization degree α changed, the cleavage agent is quite similar to the case of KPS, but the effect of KPS is greater. When additional H2O2 water is used, the cleavage effect is even higher.

[0072]

Table 12

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

[0074]

Table 13

[0075]

Table 14

[0076]

Table 15

[0077] Tables 13, 14, and 15 show examples using sodium persulfate (SPS) as the neutralizing cleavage agent. Even for the same persulfate, the effects decrease in the order of potassium salt, sodium salt according to the ionization tendency, and the effect of the ammonium salt is also smaller compared to the potassium salt.

[0078]

Table 16

[0079]

Table 17

[0080] Tables 16 and 17 show the results when the cleavage agent H2O2 is additionally added. Even when using the cleavage agent SPS, sufficient effects are exerted, and a low viscosity is obtained despite the high solid content. It can be said that it is a preferable method as a cleavage method. More specifically, it is as follows.

[0081] In the case of NaOH dissolution with a small degree of neutralization α, the viscosity conversely increases, and it seems that polymerization proceeds rather than cleavage. Therefore, as shown in Tables 6 and 7, tests using H2O2 water as a cleavage agent in combination were also conducted. Tables 6 and 7 show the respective results when the same test is conducted twice. The same applies to Tables 11, 12, 16, and 17.

[0082] As a result of the demonstration experiment, it is understood that by adding a cleavage agent, the viscosity of the sample decreases and the low molecular weight of isobutylene-maleic anhydride progresses. When the degree of neutralization α is low, depending on the cleavage agent, the molecular weight seems to conversely increase. Otherwise, it is understood that by increasing the input amount of the cleavage agent, the viscosity further decreases and the low molecular weight progresses further.

[0083] It was also confirmed that the foaming, spilling, and bumping that occur during cleavage can be avoided by adding an antifoaming agent. By using an antifoaming agent in combination, a polymer without turbidity and coloring can be obtained.

[0084] (Example 3: In the case of isobutylene-maleic anhydride "Isoban #04") In Example 3, an attempt was made to obtain a low molecular weight equivalent to Isoban #600 by cleavage. Among various grades of "Isoban", the grade that is easiest to produce in the factory is #06, and it is also easy to cleave. However, in Example 3, #04 was selected instead of #06. The reasons are that in terms of the low molecular weight, #04 has the closest molecular weight to #600 with a different polymerization solvent, which is around 40,000, and the particles of the produced product are small, and it is difficult to process fine powder due to reasons such as granulation, etc.

[0085] Generally, high molecular weight powders are averaged, but when classified, their properties are unexpectedly different. Isomers may exist after polymerization, or there may be variations in viscosity when the polymerization solvent cannot be completely removed and is used. There is a definite range for the particle size, and if they dissolve or crack outside this range, the viscosity may increase in some cases. The inventor of the present application always observes the behavior of polymers according to their size from the classification and physical properties (viscosity after alkali neutralization, pH, solid content) of the incoming polymers.

[0086] In Example 3, aiming to reduce the molecular weight at the #04 level to the #600 level, cleavage was attempted. The starting material, isobutene #04, was sieved to separate the 120M pass product, and after confirming that the viscosity was also appropriate, a solution of caustic soda dissolution (neutralization degree α = 0.50, pH 7, solid content 45%) was prepared at a maximum of 96°C. To this solution, 30% hydrogen peroxide water as a cleavage agent and "Noputer 777" (trade name of San Nopco Ltd.) as an antifoaming agent (foam-breaking / foam-suppressing agent) were added only for the first time, and the cleavage was repeated at 96°C for 2 to 3 hours.

[0087] As a result, it was possible to lower the viscosity up to the isobutene #600 level, and it was confirmed by GPC measurement described later that the molecular weight reduction was achieved. As predicted, there was no bumping, and the operation could be carried out easily. The number of repetitions was 6 to 7 times, there was no turbidity, and a transparent sodium isobutylene-maleic anhydride salt could be prepared.

[0088] For 100 parts of the polymer, the hydrogen peroxide water was 15 g, the final solid content concentration was 28%, and the viscosity was 98 mPa·S. The turbidity caused by the antifoaming agent also disappeared, the original yellow hue became colorless and transparent, and there was no odor.

[0089] Table 18 shows the results of the demonstration test conducted as Example 3. Isoban #04 was mixed with an alkali and water to prepare a 30% DS solution, which was then divided into 100 g portions. A cleavage agent was added to each 30% solution portion, and the mixture was stirred and heated at 50 °C. Heating was carried out at 96 °C for 4 hours with the aim of achieving a solid content of 25 - 35% for easy handling as a product and a viscosity of 100 mPa·S. The B-type viscosity of Isoban #04 at 30 °C before cleavage was 4180 mPa·S. The solvent was NH4OH, and the neutralization degree 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 container with some margin. At the initial stage of adding the cleavage agent, there was a lot of foaming, but there was no bumping or overflow of the foaming material from the top.

[0090]

Table 18

[0091] Table 18 shows the results of an investigation into the progress of cleavage by first neutralizing and dissolving Isoban #04 (using a product with a relatively low molecular weight of about 55,000) with an alkali to make a solution, adding a cleavage agent to the solution, and then heating (at a temperature of 96 °C) and stirring (at 800 rpm). It is understood that cleavage is almost complete approximately 2 hours after the start of cleavage. It is also understood that increasing the amount of the cleavage agent is effective for reducing the molecular weight. More specifically, it is as follows.

[0092] The initial B-type viscosity without the cleavage agent was 4180 mPa·S as described above, but the use of the cleavage agent significantly reduced the B-type viscosity. It is understood that the viscosity decreases as the amount of the cleavage agent increases, and the degree of low molecular weightization can be optimized according to the added amount of the cleavage agent.

[0093] The experiment was carried out with the solid content reduced to about 30% and a relatively large container. In this example, the use of an antifoaming agent was avoided as much as possible, and the experiment was conducted using a container with some margin. Foaming was observed due to the addition of the cleavage agent, but there was no overflow from the container.

[0094] (Example 4: In the case of isobutylene - maleic anhydride “Isoban #600”) In Example 4, attempts were made to reduce the molecular weight by cleavage using Isoban #600 as isobutylene - maleic anhydride. As cleavage agents, two types were used: aqueous hydrogen peroxide (35% aqueous solution of H2O2) and potassium persulfate (KPS). The Isoban #600 used as the starting material had a molecular weight of about 6000, and a commercially available product containing about 5% of a polymerization solvent was used.

[0095] Tables 19 to 26 show the results of the demonstration tests. Among these tables, Table 19 shows various properties in the case where there is no cleavage agent for comparison. Sample symbols such as “Na - 4 - K1” are used to identify the type of alkali, the degree of neutralization, and the cleavage agent. For example, “Na - 4 - K2” indicates that the type of alkali is Na, the degree of neutralization α is 4, the cleavage agent is KPS, and the amount is the second smallest among the same type of cleavage agents. “NH3 - ···” indicates that the type of alkali is NH3.

[0096]

Table 19

[0097] Table 19 shows an example of Isoban #600 (molecular weight 5500 - 6500). The table shows the basic formulation again and further shows 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 solid content of about 40% and a viscosity of 500 mPa·S or less could be made.

[0098]

Table 20

[0099]

Table 21

[0100]

Table 22

[0101] Tables 20 to 22 show examples in the low-molecular region. Table 20 is an example using KPS as the cleavage agent, Table 21 is an example using more KPS as the cleavage agent, and Table 22 shows an example using KPS and 35% H2O2 water as the cleavage agent.

[0102] From the results shown in these tables, it is understood that cleavage also occurs in the case of low-molecular isobutane #600, and low-molecules with a solid content of about 40% and a viscosity of about 200 mPa·S can be obtained. When the molecular weight distribution was measured by DSC (Differential Scanning Calorimetry), Mn 5200 was obtained as the peak of the molecular weight. "Mn" means the number-average molecular weight. If Mn is such that the viscosity becomes 10 mPa·S or less, those up to about Mn 4000 can be obtained. It can be further pulverized as a product at a solid concentration of about 25%, and the handling as a solution is also sufficient.

[0103] In the experiment showing the results 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] As a result of the demonstration experiment as Example 4, when KPS was used as the cleavage agent, the phenomenon of re-polymerization was still observed. However, when hydrogen peroxide water was used, such a phenomenon was not observed. Further, when hydrogen peroxide water was used, regardless of the degree of neutralization α, the higher the addition amount of the cleavage agent, the lower the viscosity, and it is also understood that the degree of low molecular weightization can be optimized by the amount of the cleavage agent. Furthermore, when hydrogen peroxide water was used, bumping due to the defoaming agent was not observed either. In the experiment using KPS, there was also a case where a defoaming agent was added midway through the cleavage.

[0109] (Example 5: Molecular weight measurement by GPC) In Example 5, the products obtained in Examples 2 to 4 were subjected to molecular weight measurement to obtain findings on the molecular weight distribution. The measurement results are shown in FIGS. 1 and 2. The processing details of each sample in FIG. 1 are shown in Table 27. Similarly, the processing details of each sample in FIG. 2 are shown in Table 28. In FIGS. 1 and 2, the horizontal axis "molecular weight" is the "slice 10g molecular weight".

[0110]

Table 27

[0111]

Table 28

[0112] As is clear from FIGS. 1 and 2, the molecular weight decreases by performing cleavage. From this, it is understood that the decrease in viscosity after cleavage confirmed in Examples 2 to 4 is due to the decrease in molecular weight. Moreover, the molecular weight distribution after cleavage is the same as or rather narrower than that before cleavage. This means that the molecular weights of the low molecules obtained by cleavage are relatively uniform, and it can be said that this indicates the usefulness of the low molecular weight polymers obtained by cleavage.

[0113] (Remarks on the examples) For the purpose of demonstrating the invention of the present application, the following remarks are made regarding the experiments shown as examples. A number of experiments were conducted as examples because it was necessary to clarify unknown problems such as whether cleavage occurs in an aqueous solution, whether there are conditions under which cleavage is likely to occur, what is the best cleavage agent, how to simplify the measurement method, and by what means the progress of cleavage can be grasped. As a result of the experiments, the following findings were obtained.

[0114] 1. The molecular weight could be reduced in an aqueous solution. Just add the cleavage agent to the neutralized solution. 2. Regarding whether the predetermined reaction is hindered by bumping or foaming, it became clear that adding an antifoaming agent would be sufficient. 3. The main cleavage agents are persulfates and H2O2, and they can also be used in combination. In particular, with H2O2, a clean product can be obtained. 4. The progress of cleavage can be generally grasped by the B-type viscosity and the solid content. It is not necessary to rely on intrinsic viscosity measurement or GPC. 5. Even if the raw material for cleavage has a high molecular weight, it can be reduced to a low molecular weight depending on the type and amount of the cleavage agent. 6. The heating temperature and stirring time for cleavage can be 90°C to 100°C and 2 hours. 7. In cleavage, if the degree of neutralization is optimized, a sharp molecular weight distribution can be obtained, and the appearance is clean and there is no odor.

Claims

1. (I) an alkali neutralization product of at least one carboxyl group-containing polymer selected from the group consisting of a copolymer of an α-olefin or vinyl compound and maleic anhydride, (II) a copolymer of a vinyl compound and (meth)acrylic acid, (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 neutralization product of a carboxyl group-containing polymer having a molecular weight of 40,000 or less. A method for producing an alkali neutralization product of a low molecular weight carboxyl group-containing polymer.

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

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

4. The method for producing an alkali neutralization product of a low molecular weight carboxyl group-containing polymer according to claim 3, wherein the cleavage agent is allowed to act on the starting material and an antifoaming agent is allowed to act thereon.

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