Aluminum acrylate composition and method for producing the same

Abstract

To provide an aqueous solution form of an aluminum acrylate composition and a method for producing the same, the composition being capable of being coated onto paper to improve strength and water resistance and exhibiting excellent solution stability.SOLUTION: The present invention provides an aluminum acrylate composition that contains 1 to 35 mass% of aluminum acrylate, is in an aqueous solution form within a pH range of 3 to 10, and contains aluminum in an amount of 2 to 15 mass% calculated as Al2O3, acrylic acid in an amount of 2 to 30 mass%, a hydroxy acid in an amount of 4 to 25 mass%, and an alkaline component in an amount of 0 to 15 mass%, and also provides a method for producing the aluminum acrylate composition.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention provides an aluminum acrylate composition mainly containing aluminum acrylate. The aluminum acrylate composition of the present invention is in the form of an aqueous solution that is stable over a wide pH range of 3 to 10, and can be coated on paper and cured to improve its strength and water resistance. [Background technology]

[0002] Aluminum acrylate is used in healthcare and civil engineering / construction applications, such as the production of water-absorbent resins and hydrogels, and for the production of water-stopping and waterproof seals. It is also used as a processing agent for defibrating, adsorbing, flocculating, and crosslinking paper, pulp, and fibers, and for improving physical properties such as strength. It is also used in a wide range of applications, including surface treatments for improving adhesion and water resistance of metals, glass, pigments, rubber, and nonwoven fabrics, and for forming fine dispersions. However, aluminum acrylate is inherently a powder that is poorly soluble in water and organic solvents. Its application range is extremely limited, requiring strong acid or alkaline conditions for dissolution, posing challenges in many fields. In particular, in recent years, there has been a growing demand for high-performance paper as an alternative to resin materials due to environmental considerations. In these cases, materials that can be easily processed by coating to impart properties such as improved strength and water resistance are needed.

[0003] Japanese Patent Laid-Open Publication No. 48-091012 (Patent Document 1) discloses a method for obtaining aluminum acrylate in an aqueous solution by neutralizing aluminum sulfate or the like to obtain gel-like aluminum hydroxide and adding acrylic acid. However, in practice, the resulting aqueous solution of aluminum acrylate is extremely unstable, and crystals of a basic salt that is poorly soluble in water are likely to form. Furthermore, if sulfate radicals remain, they form a complex salt with acrylic acid, which easily stabilizes the aqueous solution, but the pH of the aqueous solution is extremely low, at 1 to 2, making it difficult to handle.

[0004] Japanese Patent Laid-Open Publication No. 03-131649 (Patent Document 2) describes a polymer containing an alkaline earth metal salt of acrylate and a trivalent metal salt, with the trivalent metal salt preferably being water-soluble, and also describes aluminum acrylate alongside aluminum sulfate, etc. However, as mentioned above, when an inorganic acid is contained, it is highly corrosive, and aluminum acrylate alone is insoluble in water. Furthermore, Example 2 of Patent Document 2 describes a 30% aqueous aluminum acrylate solution, but the ingredients and method are not specified, and the preparation cannot be carried out due to lack of reproducibility. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Unexamined Patent Publication No. 48-091012 [Patent Document 2] Japanese Patent Application Publication No. 03-131649 Summary of the Invention [Problem to be solved by the invention]

[0006] An object of the present invention is to provide an aluminum acrylate composition in the form of an aqueous solution which can be applied to paper to improve its strength and water resistance and has excellent solution stability, and a method for producing the same. [Means for solving the problem]

[0007] That is, the present invention provides the following aspects: [1] An aluminum acrylate composition containing 1 to 35% by mass of aluminum acrylate and in the form of an aqueous solution in the pH range of 3 to 10, Aluminum: 2 to 15 mass% in terms of Al2O3, 2 to 30 mass% of acrylic acid, 4 to 25% by weight of a hydroxy acid, and Alkaline component: 0 to 15% by mass An aluminum acrylate composition comprising: [2] The aluminum acrylate composition according to [1], wherein the hydroxy acid is at least one selected from lactic acid, gluconic acid, and glycolic acid. [3] The aluminum acrylate composition according to [1] or [2], wherein the hydroxy acid is supplied in the form of aluminum hydroxy acid, and the ratio of the number of moles of hydroxy acid in the aluminum hydroxy acid (I) to the number of moles of Al2O3 (II) calculated from the number of moles of aluminum in the aluminum hydroxy acid is I / II = 1.0 to 2.5. [4] The aluminum acrylate composition according to [1] or [2], wherein the alkali component is at least one selected from the group consisting of monovalent alkali metals, ammonia, and water-soluble amines. [5] When the number of moles of aluminum in terms of Al2O3 in the aluminum acrylate composition is [A], the number of moles of hydroxy acid is [B], the number of moles of acrylic acid is [C], and the number of moles of alkali component is [D], the following relational formula (1) or (2) is satisfied: (1) [B] / [A]=1.0~2.5, [C] / [A]=1.0~2.5, [D] / [A]=0, or (2)[B] / [A]=1.0~2.5, [C] / [A]=3.5~4.5, [D] / [A]=4.5~7.5 The aluminum acrylate composition according to [1] or [2], wherein the ratio is within the range of either of the following: [6] The method for producing the aluminum acrylate composition according to [1] or [2], characterized in that an aluminum hydroxide gel is obtained by neutralizing an inorganic aluminum salt and an alkaline agent at a temperature of 0 to 40°C and a pH of 6 to 8, and the aluminum hydroxide gel is then washed with water, and a hydroxy acid is added to form an aluminum hydroxy acid, followed by adding acrylic acid, and if necessary, an alkali component is added to adjust the pH to 3 to 10. [7] The method for producing an aluminum acrylate composition according to [6], wherein the alkaline agent is at least one selected from sodium aluminate, sodium carbonate, ammonia, and a water-soluble amine. [8] The method for producing an aluminum acrylate composition according to [6], wherein the hydroxy acid is at least one selected from lactic acid, gluconic acid, and glycolic acid. [9] The method for producing an aluminum acrylate composition according to [6], wherein the alkali component is at least one selected from the group consisting of monovalent alkali metals, ammonia, and water-soluble amines. [Effects of the Invention]

[0008] The aluminum acrylate composition of the present invention is in the form of an aqueous solution that is stable at a pH of 3 to 10. The aluminum acrylate composition of the present invention is easy to handle because it is stable over a wide pH range, and moreover, it is possible to improve the strength and water resistance of paper by a simple method of coating the composition on paper and polymerizing it. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, the present invention will be described in detail based on preferred embodiments, but the present invention is not limited to the following embodiments and various modifications are possible within the scope of the claims. Furthermore, in the present invention, the expression "numeric value 1 to numerical value 2" in a numerical range indicates that numerical value 1 is the lower limit and numerical value 2 is the upper limit. This means a range including both numerical values ​​1 and 2, and is synonymous with "numerical value 1 or more and numerical value 2 or less." Furthermore, in the present invention, the term "aluminum acrylate composition" means a mixture in the form of an aqueous solution containing at least aluminum acrylate, and includes unreacted components added during production and aluminum reacted with acids other than acrylic acid in the form of monovalent to trivalent salts.

[0010] (Aluminum acrylate composition) In the aluminum acrylate composition of the present invention, aluminum acrylate is a compound having the chemical formula [(CH2=CHCOO)3·Al], and is contained in an amount of 1 to 35% by mass, preferably 2 to 33% by mass, and more preferably 2 to 30% by mass. If the amount is less than 1%, the effective amount of Al is insufficient, while if the amount is more than 35%, the solubility is insufficient, causing precipitation and resulting in instability. The amount of aluminum acrylate is calculated assuming that the aluminum acrylate has the chemical structure of the above chemical formula. In reality, this includes aluminum acrylates with one or two acrylic acid groups attached to the aluminum atom, but for calculation purposes, the above chemical formula, i.e., three acrylic acid groups attached to the aluminum atom, is considered.

[0011] The aluminum acrylate composition of the present invention maintains the form of an aqueous solution in the pH range of 3 to 10. This means that the aluminum acrylate composition is stable over a wide pH range. The pH range is preferably 3 to 9.5, more preferably 3 to 9. If the pH is less than 3, the composition is highly acidic, resulting in problems with corrosiveness and durability, while if the pH exceeds 10, the composition is unstable and its storage stability deteriorates.

[0012] The aluminum acrylate composition of the present invention contains aluminum in an amount of 2 to 15% by mass, preferably 2 to 14% by mass, and more preferably 2 to 13% by mass, calculated as Al2O3. The aluminum (Al) concentration is expressed in terms of Al2O3. Aluminum exists as a compound with various anions, and in this field, aluminum (Al) is expressed in terms of Al2O3. The aluminum content is 2 to 15% by mass, calculated as Al2O3. If the aluminum content is less than 2%, the effective amount of aluminum is insufficient, and if it exceeds 35%, the solubility is insufficient, causing precipitation and resulting in instability.

[0013] The aluminum acrylate composition of the present invention contains 2 to 30% by mass of acrylic acid. If the acrylic acid content is less than 2% by mass, the composition will not cure sufficiently and will have insufficient performance, while if the acrylic acid content exceeds 30% by mass, the composition will be prone to precipitation and will be unstable. The amount of acrylic acid is preferably 2 to 28% by mass, more preferably 2 to 26% by mass. "Acrylic acid" forms various compounds, but regardless of the compound form, the amount of "acrylic acid" in the compound, i.e., the amount of CH2CHCOOH, is calculated.

[0014] The aluminum acrylate composition of the present invention contains 4 to 25% by mass of hydroxy acid. If the hydroxy acid content is less than 4% by mass, the stabilizing effect of aluminum is insufficient, resulting in instability. If the hydroxy acid content exceeds 25% by mass, the amount of stabilizer is too high, adversely affecting physical properties. The amount of hydroxy acid is preferably 5 to 24% by mass, more preferably 6 to 23% by mass. Specifically, the hydroxy acid is one or more selected from lactic acid, gluconic acid, and glycolic acid. "Hydroxy acid" forms various compounds, and regardless of the compound form, the amount of "hydroxy acid" in that compound is calculated. For example, in the case of lactic acid, the amount is calculated as the amount of CH3CH(OH)COOH.

[0015] The aluminum acrylate composition of the present invention contains 0 to 15% by mass of an alkali component. If the alkali component exceeds 15% by mass, the pH becomes too high and the solution tends to become unstable. The amount of the alkali component is preferably 0 to 14% by mass, more preferably 0 to 13% by mass. Specifically, the alkali component is one or more selected from monovalent alkali metals, ammonia, and water-soluble amines. The "alkali component" exists in the aluminum acrylate composition as various salt compounds, but regardless of the salt compound form, the amount of the "alkali component" in that compound is calculated. For example, if the alkali metal is sodium (Na), the amount of Na is calculated. If it is ammonia, the amount of NH3 is calculated.

[0016] The aluminum acrylate composition of the present invention satisfies the following (1) or (2), where the number of moles of aluminum calculated as Al2O3 in the aluminum acrylate composition is [A], the number of moles of hydroxy acid is [B], the number of moles of acrylic acid is [C], and the number of moles of alkali is [D]: (1) [B] / [A]=1.0~2.5, [C] / [A]=1.0~2.5, [D] / [A]=0, or (2)[B] / [A]=1.0~2.5, [C] / [A]=3.5~4.5, [D] / [A]=4.5~7.5 The ratio is preferably either of the following. The number of moles described in this relational formula means the total amount of components added to the production of the aluminum acrylate composition. Therefore, the number of moles of aluminum is the total number of moles of aluminum involved in the production of the aluminum acrylate composition, the number of moles of hydroxy acid is the total number of moles of hydroxy acid added during the production of the aluminum acrylate composition, and the number of moles of alkali component is the total number of moles of alkali component added during the production of the aluminum acrylate composition.

[0017] The appropriate range of the amounts of components present in the aluminum acrylate composition in the case of (1) above is [B] / [A] = 1.0 to 2.5. If it is less than 1.0, precipitation and sedimentation are likely to occur, and if it exceeds 2.5, the amount of acrylic acid added is relatively small, making polymerization difficult. [C] / [A] = 1.0 to 2.5. If it is less than 1.0, the amount of acrylic acid is small, making polymerization weak, and if it exceeds 2.5, precipitation and sedimentation are likely to occur, which is not preferable. [D] / [A] = 0, and no alkali component is contained. Therefore, the case of (1) above is one in which no alkali component is added.

[0018] On the other hand, when pH adjustment is performed using an alkaline component, the above case (2) applies. In this case, [B] / [A] is in the range of 1.0 to 2.5. If it is less than 1.0, precipitation is likely to occur, and if it exceeds 2.5, the amount of acrylic acid added is relatively small, making polymerization difficult. [C] / [A] is in the range of 3.5 to 4.5. If it is less than 3.5, it is unstable and precipitation is likely to occur, and if it exceeds 4.5, it becomes too acidic, which is undesirable. [D] / [A] is in the range of 4.5 to 7.5. If it is less than 4.5, precipitation is likely to occur, and if it exceeds 7.5, the pH becomes too high and becomes unstable.

[0019] (Method of producing aluminum acrylate composition) The aluminum acrylate composition of the present invention is produced by adding a predetermined amount of acrylic acid to an aqueous solution of aluminum hydroxylate, and then adjusting the pH to 3-10 by adding an alkali component as needed.

[0020] First, an aqueous solution of aluminum hydroxylate is synthesized by neutralizing inorganic aluminum and an alkaline agent in the presence of water as a solvent at a temperature of 0 to 40°C or less and controlling the pH to a range of 6 to 8 to obtain an aqueous dispersion of aluminum hydroxide gel.

[0021] The inorganic aluminum salt may be aluminum sulfate, aluminum chloride, aluminum nitrate, aluminum phosphate, or various basic salts, and one or more of these may be used. The alkaline agent may be one or more of sodium aluminate, sodium carbonate, ammonia, or water-soluble amines. The amount of inorganic aluminum salt and alkaline agent used depends on the H content in the inorganic aluminum salt. + The number of OH contained in the alkaline agent ー The neutralization is carried out within the range of neutralization equivalents where the number of is equal, but priority is given to controlling the pH range described below.

[0022] The reaction is carried out at a temperature of 0 to 40°C or lower, with the pH controlled within the range of 6 to 8. The reaction temperature is preferably 0 to 40°C, and more preferably 5 to 30°C. If the reaction temperature exceeds 40°C, the aluminum hydroxide gel is likely to deteriorate, while if the reaction temperature is below 0°C, the solvent water may freeze or the solution viscosity may increase, which is undesirable. The pH is 6 to 8, preferably 6 to 7; if the pH is less than 6, the aluminum hydroxide gel may aggregate and solidify, while if the pH is higher than 8, the aluminum hydroxide gel may deteriorate.

[0023] The aluminum hydroxide gel obtained by the above reaction is washed with water and desalted, and then a hydroxy acid is added and heated to dissolve, forming aluminum hydroxylate. Washing the aluminum hydroxide gel removes impurities such as salts. Examples of solid-liquid separation devices capable of water washing include, but are not limited to, centrifuges and single-plate filters. The washed aluminum hydroxide gel is obtained as a wet cake or aqueous dispersion, and a hydroxy acid is added and heated to dissolve. The heating temperature is preferably 60 to 110°C, with 70 to 110°C being preferred. Temperatures below 60°C take too long to dissolve the gel, while temperatures above 110°C cause the solution to boil and splash, which is undesirable. The heating time is 0.5 to 15 hours, with 1 to 8 hours being preferred. Heating less than 0.5 hours results in insufficient gel dissolution, while heating more than 15 hours results in deterioration of the gel, making it difficult to dissolve, and is uneconomical due to the long heating time required. The resulting aqueous solution of aluminum hydroxylate is optionally filtered to obtain a clear solution. Examples of filtration devices include, but are not limited to, cartridge filters and pressure filters.

[0024] Examples of hydroxy acids used to form the aqueous aluminum hydroxy acid solution include monobasic acids such as lactic acid, gluconic acid, and glycolic acid, with lactic acid being preferred. These hydroxy acids may be used singly or in combination. The ratio (I) of the moles of hydroxy acid to the moles (II) of aluminum in the aluminum hydroxy acid, calculated as Al2O3, is I / II = 1.0 to 2.5, preferably 1.0 to 2.3, and more preferably 1.0 to 2.0. If the I / II ratio is less than 1.0, the solution will tend to solidify and become unstable. If the I / II ratio exceeds 2.5, the solubility of the aluminum compound will decrease and the solution will tend to precipitate, making it unstable.

[0025] The aluminum hydroxylate used in the present invention is preferably in the form of an aqueous solution, and the concentration of the aluminum hydroxylate aqueous solution in terms of Al2O3 is preferably 1 to 25% by mass. A concentration of less than 1% by mass is uneconomical due to the low concentration, while a concentration of more than 25% by mass results in high viscosity and poor handleability. If necessary, the aluminum concentration in terms of Al2O3 can be adjusted by diluting with water.

[0026] Next, acrylic acid is added to the synthesized aqueous aluminum hydroxylate solution to form an aluminum acrylate composition. The pH of the aluminum acrylate composition may be adjusted by adding an alkali component, if necessary. The reaction between acrylic acid and aluminum hydroxylate is carried out at a temperature in the range of 0 to 40°C. Temperatures above 40°C are undesirable because the aluminum salt tends to hydrolyze and become cloudy. Temperatures below 0°C are uneconomical because crystalline materials tend to precipitate. The reaction temperature is preferably 0 to 35°C. Pressure control is not required throughout the reaction, and the reaction can be carried out at normal pressure. At this time, filtration may be carried out as necessary to remove sediment or foreign matter.

[0027] The alkaline component used to adjust the pH includes monovalent alkali metals, ammonia, and water-soluble amines, and is preferably an alkali metal or ammonia. These may be used alone or in combination of two or more. The pH of the resulting aluminum acrylate composition is preferably 3 to 10, and more preferably 3 to 9. The wide pH range of 3 to 10 ensures a wide pH range.

[0028] The aluminum acrylate composition of the present invention can also be made into a dry powder. The powder can be used as a solution by adding a predetermined amount of water when necessary to dissolve it. The drying temperature to obtain a dried product is 20 to 200°C. If the temperature is lower than 20°C, it will take a long time to dry, which is uneconomical, and if the temperature is higher than 200°C, it will turn yellow or become cloudy when dissolved, which is not preferable.

[0029] (Characteristics or Properties of Aluminum Acrylate Composition) The aluminum acrylate composition of the present invention exhibits excellent storage stability, exhibiting no precipitation or settling for more than three months at room temperature to 40°C. While the reasons for the enhanced water solubility and improved storage stability of the aluminum acrylate composition of the present invention are unclear, they are thought to be due to the metal chelating action of the hydroxy acid. In the acidic range of pH less than 7, stability is significantly improved by not completely forming a salt with the hydroxy acid and acrylic acid relative to the Al2O3-equivalent molar amount of aluminum, but by leaving a certain amount of hydroxyl groups. In the neutral to alkaline range of pH 7 or higher, even when the aluminum is completely neutralized with the hydroxy acid and acrylic acid relative to the Al2O3-equivalent molar amount of aluminum, the strong chelating action prevents precipitation and improves stability.

[0030] (Coating liquid of aluminum acrylate composition) By coating paper with the aluminum acrylate composition of the present invention and curing it with UV light, the paper can be strengthened and made water-resistant to high humidity. Coating solutions often contain a base monomer and a polymerization initiator. Hydrophilic resins are often used as base monomers for functional paper coatings because of their adhesion to the paper substrate, coatability, and environmental safety. However, this approach can lead to problems such as reduced strength and poor water resistance due to humidity. By adding the aluminum acrylate composition of the present invention to a coating solution and curing it with UV light, the strength and water resistance of paper materials can be improved.

[0031] The base monomer of the coating liquid is, for example, an acrylic monomer, specifically a (meth)acrylate, more specifically a hydrophilic monofunctional or bifunctional (meth)acrylate. Examples of such (meth)acrylate monomers include polyethylene glycol di(meth)acrylate, polyethylene glycol mono(meth)acrylate, 2-hydroxyethyl (meth)acrylate, 2-(meth)acryloyloxyethyl succinate, 2-(meth)acryloyloxyethyl acid phosphate, 2-(meth)acryloylmorpholine, methylenebisacrylamide, and dimethylacrylamides.

[0032] Coating fluids are often cured by photopolymerization. In the case of photopolymerizable coating fluids, a photopolymerization initiator is blended into the coating fluid. Common photopolymerization initiators such as acylphosphine oxides, α-hydroxyacetophenones, and α-aminoacetophenones can be used.

[0033] If necessary, other additives such as antioxidants, dispersants, thickeners, chain transfer agents, polymerization inhibitors, reinforcing agents, compatibilizers, adhesion agents, colorants, etc. may be added appropriately to the coating liquid.

[0034] (Example) The present invention will be described in more detail with reference to examples. The present invention should not be construed as being limited to these examples. In the examples, % and parts are based on mass unless otherwise specified.

[0035] Example 1 A 3-L separable flask was charged with 678.6 g of water and stirred at 200 rpm. 314.7 g of an aqueous aluminum chloride solution (10.0% Al2O3) and 250.8 g of an aqueous sodium aluminate solution (20.0% Al2O3) were simultaneously added to obtain 1244.1 g of an aluminum hydroxide gel dispersion. The temperature was 20-25°C, and the pH was 6.5-7. The resulting gel dispersion was centrifuged at 2000 rpm for 1 minute in a centrifuge (Kansai Centrifuge Manufacturing Co., Ltd., Model KBS-12). The gel was washed three times with 4 L of water, and then transferred to a 1-L separable flask. 90% lactic acid was added and the mixture was heated at 100°C for 2.5 hours to obtain 1500 g of a basic aluminum lactate solution (8.4% Al2O3, lactic acid / Al2O3 molar ratio: 2.0). 151.5 g of acrylic acid was added to this solution (temperature: 25°C) to obtain an aluminum acrylate composition (aluminum acrylate 10.3%, pH = 3.5). The obtained aluminum acrylate composition was stable without precipitation even after 3 months at 40°C.

[0036] Example 2 To 1500 g of the basic aluminum lactate solution of Example 1, 348.4 g of acrylic acid was added, and then 392.3 g of 25% aqueous ammonia was added at a temperature of 35°C to obtain an aluminum acrylate composition (aluminum acrylate 17.5%, pH = 7.1). The obtained aluminum acrylate composition was stable without precipitation even after 3 months at 40°C.

[0037] Example 3 To 1500 g of the basic aluminum lactate solution of Example 1, 348.4 g of acrylic acid was added, and then 502.2 g of 25% aqueous ammonia was added at a temperature of 35° C. to obtain an aluminum acrylate composition (aluminum acrylate 16.7%, pH=9.2). The obtained aluminum acrylate composition was stable without precipitation even after 3 months at 40° C.

[0038] Example 4 The washed aluminum hydroxide gel from Example 1 was placed in a 1-L separable flask, and 50% gluconic acid was added thereto and heated at 100°C for 2.5 hours to obtain 1750 g of a basic aluminum gluconate solution (Al2O3 = 4.0%, molar ratio of gluconic acid / Al2O3: 2.0). 73.1 g of acrylic acid was added to this solution (temperature 25°C) to obtain an aluminum acrylate composition (aluminum acrylate 4.5%, pH = 3.3). The obtained aluminum acrylate composition remained stable without precipitation even after 3 months at 40°C.

[0039] Example 5 A 3-L separable flask was charged with 604.8 g of water and stirred at 200 rpm. A mixture of 432.9 g of aluminum sulfate (8.0% Al2O3), 160.3 g of sodium aluminate (20.0% Al2O3), and 46.1 g of 99% sodium carbonate was simultaneously added to obtain 1244.1 g of aluminum hydroxide gel dispersion. The temperature was 15-20°C, and the pH was 6.5-7. The resulting gel dispersion was centrifuged at 2000 rpm for 1 minute in a centrifuge (Kansai Centrifuge Manufacturing Co., Ltd., Model KBS-12). The gel was washed three times with 4 L of water, and then transferred to a 1-L separable flask. 90% lactic acid was added and the mixture was heated at 90°C for 3.5 hours to obtain 1500 g of basic aluminum lactate solution (8.1% Al2O3, lactic acid / Al2O3 molar ratio: 2.0). To this solution, 147.9 g of acrylic acid was added (temperature: 25°C) to obtain an aluminum acrylate composition (aluminum acrylate 10.1%, pH = 3.2). The obtained aluminum acrylate composition was stable without precipitation even after 3 months at 40°C.

[0040] (Comparative Example 1) A 3-L separable flask was charged with 678.6 g of water and stirred at 200 rpm. 314.7 g of an aqueous aluminum chloride solution (10.0% Al2O3 equivalent) and 250.8 g of an aqueous sodium aluminate solution (20.0% Al2O3 equivalent) were simultaneously added to obtain 1244.1 g of an aluminum hydroxide gel dispersion. The temperature was 25-30°C, and the pH was 9.5-10.5. The resulting gel dispersion was centrifuged at 2000 rpm for 1 minute in a centrifuge (Kansai Centrifuge Manufacturing Co., Ltd., Model KBS-12). The gel was washed three times with 4 L of water, then transferred to a 1-L separable flask. 90% lactic acid was added and the mixture was heated at 100°C for 2.5 hours. However, a large amount of unreacted residue was generated, and a basic aluminum lactate solution was not obtained.

[0041] (Comparative Example 2) An aluminum acrylate composition (aluminum acrylate 16.6%, pH = 2.9) was obtained by adding 259.5 g of acrylic acid to 1500 g of the basic aluminum lactate solution of Example 1 (temperature: 25°C). The obtained aluminum acrylate composition became cloudy with precipitation after 3 days at 40°C.

[0042] (Comparative Example 3) The washed aluminum hydroxide gel from Example 1 was placed in a 10 L separable flask, and water and 90% lactic acid were added thereto and heated at 100°C for 2.5 hours to obtain 5040 g of aluminum lactate solution (Al2O3 = 2.5%, lactic acid / Al2O3 molar ratio: 5.5). 42.3 g of acrylic acid was added to this solution (temperature 25°C) to obtain an aluminum acrylate composition (aluminum acrylate 0.9%, pH = 2.0). The obtained aluminum acrylate composition became cloudy with precipitation after 1 week at 40°C.

[0043] Comparative Example 4 To 1500 g of the basic aluminum lactate solution of Example 1, 348.4 g of acrylic acid was added, and then 672 g of 25% aqueous ammonia was added at a temperature of 35° C. to obtain an aluminum acrylate composition (aluminum acrylate 15.6%, pH=10.6). The obtained aluminum acrylate composition gelled after 3 days at 40° C.

[0044] Table 1 lists the material components and information obtained in the examples and comparative examples, including the amount of aluminum acrylate, pH, the amount of aluminum converted to Al2O3, the amount of acrylic acid, the amount of hydroxy acid, and the amount of alkali. Table 1 also lists the molar ratios: [A] (moles of aluminum converted to Al2O3), [B] (moles of hydroxy acid), [C] (moles of acrylic acid), and [D] (moles of alkali). The aluminum hydroxylate composition also lists I / II, which is the ratio of the number of moles of hydroxy acid in the aluminum hydroxylate (I) to the number of moles of Al2O3 (II) calculated from the number of moles of aluminum in the aluminum hydroxylate. The pH values ​​were measured at 20°C using a portable pH meter HM-40P manufactured by Toa DKK Corporation. Table 1 also lists the results of the following evaluations of the appearance of the resulting aluminum acrylate compositions after storing them at 40°C for 3 months.

[0045] The appearance after 3 months at 40°C was visually observed and reported in Table 1 according to the following criteria: ○: No turbidity, no change. △: Slightly cloudy. ×: Precipitation and sedimentation occurred.

[0046] The method for calculating the mass percentages of acrylic acid, hydroxy acid (lactic acid), and alkali components in Table 1 will be explained below. The mass percentages of acrylic acid, hydroxy acid (lactic acid), and alkali component for Example 1 are calculated. Since 151.5 g of acrylic acid was added, 151.5 / (151.5 + 1500 g) × 100 = 9.17 mass%, rounded to 9.2 mass%. Regarding the hydroxy acid (lactic acid), since 1500 g of basic aluminum lactate solution (Al2O3 = 8.4%, lactic acid / Al2O3 molar ratio: 2.0) was used, the actual number of moles of lactic acid was 2.47 moles. The amount of lactic acid was 2.47 moles × molecular weight of lactic acid (90) = 222.3 g. The mass percentage is 222.3 ÷ (1500 g + 151.5 g) × 100 = 13.46 mass%, rounded to 13.5 mass%. Since no alkali component was used in Example 1, the mass percentage of the alkali component is 0.

[0047] In Example 1, the number of moles of aluminum [A] is 1.235 moles. The number of moles of hydroxy acid (lactic acid) [B] is 2.47 moles. The number of moles of acrylic acid [C] is 151.5 g ÷ 72 (molecular weight) = 2.10 moles. Therefore, [B] / [A] = 2, and [C] / [A] = 1.7. Since [D] is 0, [D] / [A] = 0.

[0048] In the case of Example 2, the alkaline component is "392.3 g of 25% ammonia water," so 98.075 g is ammonia. 98.1 g of ammonia is contained in 1500 g of aluminum lactate aqueous solution and 348.4 g of acrylic acid, so 98.1 ÷ (1500 + 348.4 + 392.3) × 100 is 4.37 mass%, or 4.4 mass% when rounded up or down. The same calculations were performed for the other Examples and Comparative Examples, and the results are shown in Table 1.

[0049] [Table 1]

[0050] Example 6 A coating solution was prepared by adding 30 parts of the aluminum acrylate composition obtained in Example 1 to 100 parts of polyethylene glycol dimethacrylate (commercially available as "9G" from Shin-Nakamura Chemical Co., Ltd.) and adding 0.5 parts of a 20% methanol solution of 1-[4-(2-hydroxyethoxy)-phenyl]-2-hydroxy-2-methyl-1-propan-1-one (Omnirad 2959; manufactured by IGM Resins) as a photopolymerization initiator.

[0051] Dust-free paper (EX Clean EX72A4, manufactured by Sakurai Co., Ltd.) was cut into the shape of a JIS K7139 small tensile test piece a) Type CW, and the coating liquid was applied to a thickness of 90 μm using a bar coater. The coating was then cured by irradiating it with ultraviolet (UV) light from a metal halide lamp for 10 minutes, and the paper was left to stand in a desiccator for 24 hours to obtain an initial sample piece.

[0052] The initial test pieces obtained were subjected to a tensile test at 5 mm / sec (n = 3 per level) using a tensile tester (manufactured by MinebeaMitsumi Inc.) to measure the maximum stress value (N). Next, the test pieces were left to stand at a relative humidity of 70% RH for 7 days, and then a tensile test was performed at 5 mm / sec (n = 3 per level) using the same tensile tester to measure the maximum stress value. The initial maximum stress values ​​and the maximum stress values ​​after the 7-day humidity environmental test are listed in Table 2. The reduction rate (%) of the maximum stress values ​​for both maximum stress values, expressed by the following formula, is also listed in Table 2. Decrease rate of maximum stress value (%) = 1 - (maximum stress value of test piece left at 70% RH for 7 days / maximum stress value of initial test piece) x 100

[0053] The thickness of the coating film on the initial test piece and the test piece after the 7-day humidity environment test was measured with a digital caliper, and the variation (%) in the film thickness was calculated using the following formula. The results are shown in Table 2. Film thickness variation (%) = 1 - (minimum film thickness / maximum film thickness of test piece left at 70% RH for 7 days) x 100

[0054] (Comparative Examples 5 to 8) In Example 6, the following materials were added instead of 30 parts of the aluminum acrylate composition obtained in Example 1 to prepare a coating liquid (Comparative Example 8 used only polyethylene glycol dimethacrylate). The amounts added were 5 parts of basic aluminum acrylate in Comparative Example 5, 30 parts of a 35% aqueous solution of magnesium acrylate in Comparative Example 6, 30 parts of a 25% aqueous solution of calcium acrylate in Comparative Example 7, and 100 parts of polyethylene glycol dimethacrylate in Comparative Example 8. The basic aluminum acrylate used in Comparative Example 5 was prepared by reacting aluminum sulfate with sodium acrylate in an aqueous solvent, washing the resulting hydrate with water and filtering it, and then drying and dry-pulverizing the resulting solid. Comparative Example 5: Basic aluminum acrylate (powder) Comparative Example 6: 35% aqueous solution of magnesium acrylate Comparative Example 7: 25% aqueous solution of calcium acrylate Comparative Example 8: Polyethylene glycol dimethacrylate (manufactured by Shin-Nakamura Chemical Co., Ltd., product number "9G")

[0055] Using the obtained coating liquid, the maximum stress value, the rate of reduction (%), the film thickness and its variation (%) were measured in the same manner as in Example 6. The results are shown in Table 2.

[0056] [Table 2]

[0057] As shown in Table 1, in Examples 1 to 5, by controlling various molar ratios, including the amount of aluminum in terms of Al2O3, the amount of acrylic acid, the amount of hydroxy acid, and the amount of alkali component, it was confirmed that solutions stable over a wide pH range could be obtained even after 3 months at 40°C. On the other hand, in Comparative Example 1, aluminum hydroxide gel was prepared at a high pH range of 9.5 to 10.5, which prevented the synthesis of basic aluminum lactate, the precursor to the aluminum acrylate composition of the present invention. In Comparative Example 2, the ratio [C] / [A] of the number of moles of acrylic acid [C] to the number of moles of aluminum [A] was 2.9, resulting in instability and precipitation. In Comparative Example 3, the lactic acid ratio of the precursor basic aluminum lactate was set to a molar ratio of 5.5 in terms of lactic acid / Al2O3, which was outside the range, resulting in instability and precipitation. In Comparative Example 4, the final pH was set to a high 10.6, which was outside the range of the present invention, resulting in instability and gelation.

[0058] As shown in Table 2, adding the aluminum acrylate composition obtained in Example 1 of the present invention to a monomer and UV-curing it improved strength, and the strength did not decrease even after a humidity test at 70% RH, suggesting that it is effective in providing water resistance. On the other hand, Comparative Example 5 showed a decrease in strength after a similar humidity test, and white powder was observed on the film surface. This indicates that the powdered aluminum acrylate is insoluble and has low activity, and therefore is hardly incorporated into the paper substrate or polymer. Comparative Examples 6 and 7 also showed a decrease in strength and a change in film thickness after a similar humidity test. This is thought to be due to the extremely high hydrophilicity of the magnesium or calcium polymer, which causes swelling upon hydration. When only the base resin of Comparative Example 8 was used, strength also decreased after a similar humidity test. Therefore, the effectiveness of the aluminum acrylate composition of the present invention as a functional agent for improving strength and providing water resistance was confirmed.

[0059] The aluminum acrylate composition of the present invention has excellent stability over a wide pH range of 3 to 10, and can be coated on paper and cured to improve its strength and water resistance. [Industrial Applicability]

[0060] As mentioned above, the product of the present invention can impart functionality to paper, such as improving its water resistance. Furthermore, in addition to metal crosslinking using aluminum ions, crosslinking with acrylic groups is also possible, enabling applications in a wide range of fields. Furthermore, because it can be designed to contain almost no corrosive inorganic acids or residual alkaline elements, it is expected to be used in life science and general industrial applications, such as water-absorbent resins, hydrogels, fibers, nonwoven fabrics, and cellulose, as well as in semiconductor-related coatings and doping materials, sintered body binders, and as a functional additive for electronic materials, such as alumina thin film formation.

[0061] The following aspects of the invention are added: [1] An aluminum acrylate composition containing 1 to 35% by mass of aluminum acrylate and in the form of an aqueous solution in the pH range of 3 to 10, Aluminum: 2 to 15 mass% in terms of Al2O3, 2 to 30 mass% of acrylic acid, 4 to 25% by weight of a hydroxy acid, and Alkaline component: 0 to 15% by mass An aluminum acrylate composition comprising: [2] The aluminum acrylate composition according to [1], wherein the hydroxy acid is at least one selected from lactic acid, gluconic acid, and glycolic acid. [3] The aluminum acrylate composition according to [1] or [2], wherein the hydroxy acid is supplied in the form of aluminum hydroxy acid, and the ratio of the number of moles of hydroxy acid in the aluminum hydroxy acid (I) to the number of moles of Al2O3 (II) calculated from the number of moles of aluminum in the aluminum hydroxy acid is I / II = 1.0 to 2.5. [4] The aluminum acrylate composition according to any one of [1] to [3], wherein the alkali component is at least one selected from the group consisting of monovalent alkali metals, ammonia, and water-soluble amines. [5] When the number of moles of aluminum in terms of Al2O3 in the aluminum acrylate composition is [A], the number of moles of hydroxy acid is [B], the number of moles of acrylic acid is [C], and the number of moles of alkali component is [D], the following relational formula (1) or (2) is satisfied: (1) [B] / [A]=1.0~2.5, [C] / [A]=1.0~2.5, [D] / [A]=0, or (2)[B] / [A]=1.0~2.5, [C] / [A]=3.5~4.5, [D] / [A]=4.5~7.5 The aluminum acrylate composition according to any one of [1] to [4], wherein the ratio is within any one of the ranges above. [6] The method for producing the aluminum acrylate composition according to any one of [1] to [5] above, characterized in that an aluminum hydroxide gel is obtained by neutralizing an inorganic aluminum salt and an alkaline agent at a temperature of 0 to 40°C and a pH of 6 to 8, and the aluminum hydroxide gel thus obtained is washed with water, and then a hydroxy acid is added to form an aluminum hydroxy acid, followed by adding acrylic acid, and if necessary, an alkali component is further added to adjust the pH to 3 to 10. [7] The method for producing an aluminum acrylate composition according to [6], wherein the alkaline agent is at least one selected from sodium aluminate, sodium carbonate, ammonia, and a water-soluble amine. [8] The method for producing an aluminum acrylate composition according to [6] or [7], wherein the hydroxy acid is at least one selected from lactic acid, gluconic acid, and glycolic acid. [9] The method for producing an aluminum acrylate composition according to any one of [6] to [8], wherein the alkali component is at least one selected from the group consisting of monovalent alkali metals, ammonia, and water-soluble amines.

Claims

1. An aluminum acrylate composition comprising 1 to 35% by mass of aluminum acrylate and in the form of an aqueous solution having a pH in the range of 3 to 10, Aluminum is Al ２ O ３ Converted to 2 to 15 mass %, 2 to 30% by mass of acrylic acid, 4 to 25% by weight of a hydroxy acid, and Alkaline component: 0 to 15% by mass An aluminum acrylate composition comprising:

2. 2. The aluminum acrylate composition according to claim 1, wherein the hydroxy acid is at least one selected from the group consisting of lactic acid, gluconic acid, and glycolic acid.

3. The hydroxy acid is supplied in the form of aluminum hydroxy acid, and Al is calculated from the number of moles of hydroxy acid (I) in the aluminum hydroxy acid and the number of moles of aluminum in the aluminum hydroxy acid. ２ O ３ 3. The aluminum acrylate composition according to claim 1, wherein the ratio of moles (II) of (I) to (II) is in the range of 1.0 to 2.

5.

4. 3. The aluminum acrylate composition according to claim 1, wherein the alkali component is at least one selected from the group consisting of monovalent alkali metals, ammonia, and water-soluble amines.

5. Al in the aluminum acrylate composition ２ O ３ When the number of moles of aluminum converted is [A], the number of moles of hydroxy acid is [B], the number of moles of acrylic acid is [C], and the number of moles of alkali component is [D], the following relational formula (1) or (2) is satisfied: (1) [B] / [A] = 1.0 to 2.5, [C] / [A] = 1.0 to 2.5, [D] / [A] = 0, or (2) [B] / [A] = 1.0-2.5, [C] / [A] = 3.5-4.5, [D] / [A] = 4.5-7.5 3. The aluminum acrylate composition according to claim 1, wherein the ratio is within the range of any one of the following:

6. 3. The method for producing the aluminum acrylate composition according to claim 1 or 2, wherein the aluminum acrylate composition is obtained by neutralizing an inorganic aluminum salt and an alkali agent at a temperature of 0 to 40°C and a pH of 6 to 8 to obtain an aluminum hydroxide gel, washing the obtained aluminum hydroxide gel with water, adding a hydroxy acid to form an aluminum hydroxy acid, then adding acrylic acid, and optionally further adding an alkali component to adjust the pH to 3 to 10.

7. 7. The method for producing an aluminum acrylate composition according to claim 6, wherein the alkaline agent is at least one selected from the group consisting of sodium aluminate, sodium carbonate, ammonia, and water-soluble amines.

8. 7. The method for producing an aluminum acrylate composition according to claim 6, wherein the hydroxy acid is at least one selected from the group consisting of lactic acid, gluconic acid, and glycolic acid.

9. 7. The method for producing an aluminum acrylate composition according to claim 6, wherein the alkali component is at least one selected from the group consisting of monovalent alkali metals, ammonia, and water-soluble amines.

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