Modified polyvinyl alcohol, method for producing the same, and coating material and use thereof

Abstract

The application relates to the technical field of polyvinyl alcohol, and discloses modified polyvinyl alcohol, a preparation method thereof, and paint and application thereof. The modified polyvinyl alcohol has a structure shown in formula (I); wherein n is 1000-3000, X is a halogen atom, R1, R2 and R3 are the same or different and each is a C1-C 18 alkyl group; Y is a C1-C2 alkylene group or a C1-C2 alkylene alcohol; the modified polyvinyl alcohol has high ink absorption performance and can meet the performance requirements of color inkjet printing paper.

Description

Technical Field

[0001] This invention relates to the field of polyvinyl alcohol technology, specifically to a modified polyvinyl alcohol, its preparation method, and coatings and their applications. Background Technology

[0002] Polyvinyl alcohol (PVA) is a water-soluble organic polymer prepared by free radical polymerization of vinyl acetate followed by hydrolysis under alkaline conditions. It possesses excellent film-forming properties, adhesion, gas barrier properties, antistatic properties, and resistance to oil and chemical solvents. PVA is commonly used as an adhesive and surface sizing agent in color inkjet printing paper. However, conventional partially hydrolyzed PVA adhesives suffer from drawbacks such as poor ink absorption and poor colorfastness, making it difficult to meet the increasingly demanding performance requirements of inkjet paper.

[0003] Therefore, researching and developing a modified polyvinyl alcohol is of great significance. Summary of the Invention

[0004] The purpose of this invention is to overcome the defects of poor ink absorption and poor color fastness caused by the presence of polyvinyl alcohol adhesives in the prior art, and to provide a modified polyvinyl alcohol, its preparation method, coating and its application. The modified polyvinyl alcohol has high ink absorption performance and can meet the performance requirements of color inkjet printing paper.

[0005] To achieve the above objectives, a first aspect of the present invention provides a modified polyvinyl alcohol, wherein the modified polyvinyl alcohol has the structure shown in formula (I);

[0006]

[0007] Where n is between 1000 and 3000;

[0008] X is a halogen atom;

[0009] R1, R2, and R3 may be the same or different, each with a C1-C2 value. 18 Alkyl groups;

[0010] Y is a C1-C3 alkylene group or a C1-C3 alkylene alcohol.

[0011] A second aspect of the present invention provides a method for preparing modified polyvinyl alcohol, wherein the preparation method includes:

[0012] (1) Under alkaline conditions, the polyvinyl alcohol represented by formula (II) and the modifier represented by formula (III) are reacted with the solvent;

[0013]

[0014] Where n is between 1000 and 3000;

[0015] X is a halogen atom;

[0016] R1, R2, and R3 may be the same or different, each with a C1-C2 value. 18 Alkyl groups;

[0017] Y is a C1-C3 alkylene group or a C1-C3 alkylene alcohol;

[0018] (2) The product after step (1) is cooled, washed, filtered and dried to obtain modified polyvinyl alcohol.

[0019] A third aspect of the present invention provides a modified polyvinyl alcohol prepared by the preparation method described above.

[0020] A fourth aspect of the present invention provides a coating comprising the aforementioned modified polyvinyl alcohol.

[0021] The fifth aspect of the present invention provides an application of the aforementioned coating in inkjet printing paper.

[0022] Through the above technical solution, the modified polyvinyl alcohol provided by the present invention has high ink absorption performance, which can meet the performance requirements of color inkjet printing paper. Detailed Implementation

[0023] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0024] As mentioned above, the first aspect of the present invention provides a modified polyvinyl alcohol, wherein the modified polyvinyl alcohol has the structure shown in formula (1);

[0025]

[0026] Where n is between 1000 and 3000;

[0027] X is a halogen atom;

[0028] R1, R2, and R3 may be the same or different, each with a C1-C2 value. 18 Alkyl groups;

[0029] Y is a C1-C3 alkylene group or a C1-C3 alkylene alcohol.

[0030] According to the present invention, in a preferred embodiment, n is 1700-2400.

[0031] According to the present invention, in a preferred embodiment, X is a chlorine atom and / or a bromine atom.

[0032] According to the present invention, in a preferred embodiment, R1, R2 and R3 may be the same or different, and each is a C1-C3 alkyl group.

[0033] According to the present invention, in a preferred embodiment, Y is a C1-C2 alkylene group and / or a C1-C2 alkylene alcohol; in a more preferred embodiment, Y is a methylene group and / or a methylene alcohol.

[0034] The inventors of this invention have discovered that cationic polyvinyl alcohol (PVA) is a modified product obtained by introducing cationic groups into the molecular structure of PVA, and is an important functional polymer. Cationic PVA, used as a coating adhesive in inkjet printing paper, can replace expensive synthetic resins and casein, significantly reducing the cost of inkjet printing paper. Furthermore, due to its high positive charge, it can firmly bond negatively charged pigments to each other and to paper fibers, improving the printing performance of the paper, reducing dusting and linting, and improving color depth and fixation. As a fixing agent for inkjet printing, it controls the ink absorption, smoothness, gloss, and whiteness of the paper, improving the printing effect.

[0035] Furthermore, the inventors of this invention discovered that introducing quaternary ammonium groups into the polyvinyl alcohol structure, with their high positive charge, can stably bind with negatively charged pigments, greatly improving the affinity between paper and ink, significantly increasing ink absorbency, and noticeably improving the printing effect of the paper. Simultaneously, the quaternary ammonium groups enhance the electrostatic repulsion between molecular chains, causing the molecular chains to tend to extend. Introducing more alkyl groups, utilizing the ease with which their intermolecular chains entangle to form a network structure, also provides a certain degree of reinforcement to the paper.

[0036] Furthermore, the surface water absorption (Cobb) value of the coated paperboard made of modified polyvinyl alcohol can reach 50-60, preferably 52-60, and more preferably 52.6-59.

[0037] A second aspect of the present invention provides a method for preparing modified polyvinyl alcohol, wherein the preparation method includes:

[0038] (1) Under alkaline conditions, the polyvinyl alcohol represented by formula (II) and the modifier represented by formula (III) are reacted with the solvent;

[0039]

[0040] Where n is between 1000 and 3000;

[0041] X is a halogen atom;

[0042] R1, R2, and R3 may be the same or different, and each is a C1-C18 alkyl group;

[0043] Y is a C1-C3 alkylene group or a C1-C3 alkylene alcohol;

[0044] (2) The product after step (1) is cooled, washed, filtered and dried to obtain modified polyvinyl alcohol.

[0045] According to the present invention, in a preferred embodiment, n is 1700-2400.

[0046] According to the present invention, in a preferred embodiment, X is a chlorine atom and / or a bromine atom.

[0047] According to the present invention, in a preferred embodiment, R1, R2 and R3 may be the same or different, and each is a C1-C3 alkyl group.

[0048] According to the present invention, in a preferred embodiment, Y is a C1-C2 alkylene group and / or a C1-C2 alkylene alcohol; preferably, Y is a methylene group and / or a methylene alcohol.

[0049] According to the present invention, the degree of hydrolysis of the polyvinyl alcohol represented by formula (II) is 80-100% (mol%), preferably 85-100%; more preferably, the polyvinyl alcohol represented by formula (II) is selected from one or more of polyvinyl alcohol 1788, polyvinyl alcohol 1795, polyvinyl alcohol 1799, polyvinyl alcohol 2099, and polyvinyl alcohol 2499. In the present invention, it should be noted that polyvinyl alcohol 1788, wherein 1788 represents a degree of polymerization of 1700 and a degree of hydrolysis of 88%.

[0050] According to the present invention, preferably, the modifier represented by formula (III) is a quaternary ammonium salt with a main chain alkyl group containing at least 3 carbon atoms and at least one chlorine or bromine atom; more preferably, the modifier represented by formula (III) is selected from one or more of 3-bromopropyltrimethylammonium bromide, 3-bromopropyltriethylammonium bromide, 3-chloro-2-hydroxypropyltripropylammonium chloride, (3-chloro-2-hydroxypropyl)dodecyldimethylammonium chloride, and (3-chloro-2-hydroxypropyl)dimethyloctadecylammonium chloride. In the present invention, when two or more modifiers are selected, the ratio of any two is not specifically limited, but preferably it can be 1:(1-3).

[0051] According to the present invention, the solvent is an organic alcohol and / or water; wherein the organic alcohol may be one or more of methanol, ethanol, propanol, isopropanol, and n-butanol of industrial grade or higher purity, and the water may be one or more of deionized water, distilled water, and purified water of industrial grade or higher purity. Furthermore, in the present invention, if the solvent is a mixture of organic alcohol and water, the weight ratio of the organic alcohol to water is 100:(1-20).

[0052] According to the present invention, the alkaline conditions are carried out under a pH value of 7.2-8; in the present invention, an inorganic base can be used to adjust the pH value, wherein the inorganic base can be industrial grade or higher purity sodium hydroxide and / or potassium hydroxide.

[0053] According to the present invention, the reaction conditions include: a temperature of 50-90°C and a time of 2-10 hours; preferably, a temperature of 60-70°C and a time of 6-8 hours.

[0054] According to the present invention, the weight ratio of polyvinyl alcohol to solvent shown in formula (II) is (4-100):1, preferably (4-50):1.

[0055] According to the present invention, the amount of the modifier shown in formula (III) is 0.1-5% by weight of the amount of polyvinyl alcohol shown in formula (II), preferably 1-3% by weight.

[0056] According to a particularly preferred embodiment of the present invention, a method for preparing modified polyvinyl alcohol includes:

[0057] (1) Disperse polyvinyl alcohol in a solvent in a container, stir until uniform, and add modifier while stirring to mix thoroughly;

[0058] (2) Heat and stir the reactants at 50-90℃ for 2-10 hours. During the reaction, slowly add an alkaline solution to adjust the pH value to maintain at 7.2-8.

[0059] (3) After the reaction is complete, cool to room temperature, wash, filter and dry.

[0060] A third aspect of the present invention provides a modified polyvinyl alcohol prepared by the preparation method described above.

[0061] A fourth aspect of the present invention provides a coating comprising the aforementioned modified polyvinyl alcohol.

[0062] According to the present invention, the coating further contains silica and / or an antifoaming agent.

[0063] According to the present invention, the weight ratio of the modified polyvinyl alcohol to the silicon dioxide is (20-40):100; that is, the amount of the modified polyvinyl alcohol is 20-40 parts by weight relative to 100 parts by weight of the silicon dioxide.

[0064] According to the present invention, the amount of the defoamer is 5-20 parts by weight relative to 100 parts by weight of the silica.

[0065] The fifth aspect of the present invention provides an application of the aforementioned coating in inkjet printing paper.

[0066] The present invention will be described in detail below through embodiments.

[0067] In the following examples and comparative examples:

[0068] The water absorption parameter of the paper surface was measured by the Cobb value method; the polyvinyl alcohol raw material was a commercially available product from Sichuan Weihua Chemical Co., Ltd. with brand names 1788, 1995, 1799, 2099, and 2499.

[0069] Example 1

[0070] The purpose of this embodiment is to provide a highly absorbent cationic modified polyvinyl alcohol, which is obtained by modifying polyvinyl alcohol 1788 with the modifier 3-bromopropyltrimethylammonium bromide under alkaline conditions. The amount of 3-bromopropyltrimethylammonium bromide added is 0.1% of the mass of polyvinyl alcohol, wherein the amount of polyvinyl alcohol added is 600g.

[0071] The preparation method includes the following steps:

[0072] Step 1: Disperse polyvinyl alcohol 1788 powder in 4 times its mass of solvent in a container. The solvent is a mixture of methanol and water in a ratio of 99:1, where the methanol is industrial grade and the water is deionized water.

[0073] Step 2: While stirring, add the prescribed amount of 3-bromopropyltrimethylammonium bromide to the container; heat and stir the reactants at 60°C for 8 hours, slowly add a 1% (w / w) alkaline solution during the reaction, adjust the pH value to maintain at 7.5, and cool to room temperature after the reaction is completed. The alkaline is industrial grade sodium hydroxide.

[0074] Step 3: Wash and filter, dry at room temperature for 12 hours to obtain 492g of highly absorbent cationic modified polyvinyl alcohol.

[0075] The reaction principle is as follows:

[0076]

[0077] Where n is 1700.

[0078] This example demonstrates the modification of polyvinyl alcohol (PVA) under alkaline conditions using 3-bromopropyltrimethylammonium bromide as a modifier. The increased quaternary ammonium groups on the side chains of the modified PVA, along with its high positive charge, allow it to bind firmly with negatively charged pigments, significantly improving the affinity between paper and ink, greatly enhancing ink absorbency, and substantially improving the printing effect of the paper.

[0079] Example 2

[0080] The purpose of this embodiment is to provide a highly absorbent cationic modified polyvinyl alcohol (PVA), which is obtained by modifying PVA 1795 with the modifier 3-bromopropyltriethylammonium bromide under alkaline conditions. The amount of 3-bromopropyltriethylammonium bromide added is 0.5% of the mass of PVA, wherein the amount of PVA added is 300g.

[0081] The preparation method includes the following steps:

[0082] Step 1: Disperse polyvinyl alcohol 1795 powder in 9 times its weight of solvent in a container. The solvent is a mixture of ethanol and water in a ratio of 95:5, where the ethanol is industrial grade and the water is deionized water.

[0083] Step 2: While stirring, add the prescribed amount of 3-bromopropyltriethylammonium bromide to the container; heat and stir the reactants at 65°C for 6 hours, slowly add a 2% (w / w) alkaline solution during the reaction, adjust the pH value to maintain at 7.5, and cool to room temperature after the reaction is completed. The alkaline is industrial grade potassium hydroxide.

[0084] Step 3: Wash and filter, dry at 30℃ for 10 hours to obtain 238g of highly absorbent cationic modified polyvinyl alcohol.

[0085] The reaction principle is as follows:

[0086]

[0087] Where n is 1700.

[0088] This example demonstrates the modification of polyvinyl alcohol (PVA) under alkaline conditions using 3-bromopropyltriethylammonium bromide as a modifier. The increased quaternary ammonium groups on the side chains of the modified PVA, along with its high positive charge, allow it to bind firmly with negatively charged pigments, significantly improving the affinity between paper and ink, greatly enhancing ink absorbency, and substantially improving the printing effect of the paper.

[0089] Example 3

[0090] The purpose of this embodiment is to provide a highly absorbent cationic modified polyvinyl alcohol (PVA), which is obtained by modifying PVA 1799 with the modifier 3-chloro-2-hydroxypropyltripropylammonium chloride under alkaline conditions. The amount of 3-chloro-2-hydroxypropyltripropylammonium chloride added is 1% of the mass of PVA, wherein the amount of PVA added is 200g.

[0091] The preparation method includes the following steps:

[0092] Step 1: Disperse polyvinyl alcohol 1799 powder in 14 times its weight of solvent in a container. The solvent is a mixture of methanol and water in a ratio of 90:10, where methanol is a chemical alcohol and water is distilled water.

[0093] Step 2: While stirring, add the prescribed amount of 3-chloro-2-hydroxypropyltripropylammonium chloride to the container; heat and stir the reactants at 70°C for 5 hours, slowly add a 3% (w / w) alkaline solution during the reaction, adjust the pH value to maintain at 7.5, and cool to room temperature after the reaction is completed. The alkaline is chemically pure sodium hydroxide.

[0094] Step 3: Wash and filter, vacuum dry at 50℃ for 8 hours to obtain 145g of highly ink-absorbing cationic modified polyvinyl alcohol.

[0095] The reaction principle is as follows:

[0096]

[0097] Where n is 1700.

[0098] This example demonstrates the modification of polyvinyl alcohol (PVA) under alkaline conditions using 3-chloro-2-hydroxypropyltripropylammonium chloride as a modifier. The introduction of quaternary ammonium groups into the PVA structure, with their high positive charge, allows for stable bonding with negatively charged pigments. This improves the affinity between paper and ink, significantly enhancing ink absorbency and improving printing quality. Simultaneously, the quaternary ammonium groups strengthen the electrostatic repulsion between molecular chains, causing them to extend. Furthermore, the introduction of more alkyl groups facilitates the formation of a network structure through chain entanglement, providing a degree of reinforcement to the paper.

[0099] Example 4

[0100] The purpose of this embodiment is to provide a highly absorbent cationic modified polyvinyl alcohol (PVA), which is obtained by modifying PVA 2099 with a modifier (3-chloro-2-hydroxypropyl)dodecyl dimethyl ammonium chloride under alkaline conditions. The amount of 3-(3-chloro-2-hydroxypropyl)dodecyl dimethyl ammonium chloride added is 1.5% of the mass of PVA, wherein the amount of PVA added is 150g.

[0101] The preparation method includes the following steps:

[0102] Step 1: Disperse polyvinyl alcohol 2099 powder in a container in 19 times its weight of solvent, which is a mixture of ethanol and water in a ratio of 85:15, where the ethanol is a chemical alcohol and the water is dedistilled water;

[0103] Step 2: While stirring, add the prescribed amount of (3-chloro-2-hydroxypropyl)dodecyl dimethylammonium chloride to the container; heat and stir the reactants at 75°C for 4 hours, slowly add a 5% (w / w) alkaline solution during the reaction, adjust the pH value to maintain at 7.5, and cool to room temperature after the reaction is completed. The alkaline is chemically pure potassium hydroxide.

[0104] Step 3: Wash and filter, vacuum dry at 60℃ for 7 hours to obtain 104g of highly ink-absorbing cationic modified polyvinyl alcohol.

[0105] The reaction principle is as follows:

[0106]

[0107] Where n is 2000.

[0108] This example demonstrates the modification of polyvinyl alcohol (PVA) under alkaline conditions using (3-chloro-2-hydroxypropyl)dodecyldimethylammonium chloride as a modifier. The introduction of quaternary ammonium groups into the PVA structure, with their high positive charge, allows for stable bonding with negatively charged pigments. This improves the affinity between paper and ink, significantly enhancing ink absorbency and improving printing quality. Simultaneously, the quaternary ammonium groups strengthen the electrostatic repulsion between molecular chains, causing them to extend. Furthermore, the introduction of more alkyl groups facilitates the formation of a network structure through chain entanglement, providing a degree of reinforcement to the paper.

[0109] Example 5

[0110] The purpose of this embodiment is to provide a highly absorbent cationic modified polyvinyl alcohol (PVA), which is obtained by modifying PVA 2499 with a modifier (3-chloro-2-hydroxypropyl)octadecyl dimethyl ammonium chloride under alkaline conditions. The amount of (3-chloro-2-hydroxypropyl)octadecyl dimethyl ammonium chloride added is 3% of the mass of PVA, wherein the amount of PVA added is 100g.

[0111] The preparation method includes the following steps:

[0112] Step 1: Disperse polyvinyl alcohol 2499 powder in 29 times its weight of solvent in a container. The solvent is a mixture of ethanol and water in a ratio of 80:20, where the ethanol is analytical grade and the water is purified water.

[0113] Step 2: While stirring, add the prescribed amount of (3-chloro-2-hydroxypropyl)dodecyl octamethylammonium chloride to the container; heat the reactants at 80°C and stir for 3 hours. During the reaction, slowly add an 8% (w / w) alkaline solution to adjust the pH value to 7.5. After the reaction is completed, cool to room temperature. The alkaline is analytical grade sodium hydroxide.

[0114] Step 3: Wash and filter, vacuum dry at 65℃ for 5 hours to obtain 76g of highly ink-absorbing cationic modified polyvinyl alcohol.

[0115] The reaction principle is as follows:

[0116]

[0117] Where n is 2400.

[0118] This example demonstrates the modification of polyvinyl alcohol (PVA) under alkaline conditions using (3-chloro-2-hydroxypropyl)octadecyldimethylammonium chloride as a modifier. The introduction of quaternary ammonium groups into the PVA structure, with their high positive charge, allows for stable bonding with negatively charged pigments. This improves the affinity between paper and ink, significantly enhancing ink absorbency and improving printing quality. Simultaneously, the quaternary ammonium groups strengthen the electrostatic repulsion between molecular chains, causing them to extend. Furthermore, the introduction of more alkyl groups facilitates the formation of a network structure through chain entanglement, providing a degree of reinforcement to the paper.

[0119] Example 6

[0120] The purpose of this embodiment is to provide a highly absorbent cationic modified polyvinyl alcohol (PVA), obtained by modifying PVA 1788 under alkaline conditions using a modifier. The modifier is a composition of 3-bromopropyltrimethylammonium bromide and 3-chloro-2-hydroxypropyltripropylammonium chloride in a 1:1 mass ratio, added at 5% of the mass of PVA, specifically 125g of PVA.

[0121] The preparation method includes the following steps:

[0122] Step 1: Disperse polyvinyl alcohol 1788 powder in 24 times its weight of solvent in a container. The solvent is a mixture of propanol and water in a ratio of 95:5, where the propanol is analytical grade and the water is purified water.

[0123] Step 2: Add the modifier of the formula amount into the container while stirring; heat and stir the reactants at 85°C for 3 hours. During the reaction, slowly add a 10% (w / w) alkaline solution to adjust the pH value to maintain at 7.5. After the reaction is completed, cool to room temperature. The alkaline is analytical grade potassium hydroxide.

[0124] Step 3: Wash and filter, vacuum dry at 75℃ for 4 hours to obtain 95g of highly ink-absorbing cationic modified polyvinyl alcohol.

[0125] The reaction principle of the obtained highly absorbent cationic modified polyvinyl alcohol is as shown in Examples 1 and 3. The obtained highly absorbent cationic modified polyvinyl alcohol is a mixture of the modified polyvinyl alcohols prepared in Examples 1 and 3, and the ratio of the two is 1:0.9.

[0126] This example demonstrates the modification of polyvinyl alcohol (PVA) under alkaline conditions using a combination of 3-bromopropyltrimethylammonium bromide and 3-chloro-2-hydroxypropyltripropylammonium chloride as a modifier. The introduction of quaternary ammonium groups into the PVA structure, with their high positive charge, allows for stable bonding with negatively charged pigments. This improves the affinity between paper and ink, significantly enhancing ink absorbency and improving printing quality. Simultaneously, the quaternary ammonium groups strengthen the electrostatic repulsion between molecular chains, causing them to extend. Furthermore, the introduction of more alkyl groups facilitates the formation of a network structure through chain entanglement, providing a degree of reinforcement to the paper.

[0127] Example 7

[0128] The purpose of this embodiment is to provide a highly absorbent cationic modified polyvinyl alcohol (PVA), obtained by modifying PVA 1799 under alkaline conditions using a modifier. The modifier is a composition of 3-bromopropyltrimethylammonium bromide and (3-chloro-2-hydroxypropyl)dodecyldimethylammonium chloride, with a mass ratio of 1:2, and is added at 4% of the mass of PVA, specifically 150g of PVA.

[0129] The preparation method includes the following steps:

[0130] Step 1: Disperse polyvinyl alcohol 1799 powder in 19 times its weight of solvent in a container. The solvent is a mixture of methanol and water in a ratio of 85:15, where the methanol is analytical grade and the water is purified water.

[0131] Step 2: Add the amount of the modifier to the container while stirring; heat and stir the reactants at 90°C for 2 hours. During the reaction, slowly add a 6% (w / w) alkaline solution to adjust the pH value to 7-8. After the reaction is completed, cool to room temperature. The alkaline is a combination of chemically pure sodium hydroxide and potassium hydroxide.

[0132] Step 3: Wash and filter, vacuum dry at 80℃ for 4 hours to obtain 96g of highly ink-absorbing cationic modified polyvinyl alcohol.

[0133] The reaction principle of the obtained highly absorbent cationic modified polyvinyl alcohol is as shown in Examples 1 and 4. The obtained highly absorbent cationic modified polyvinyl alcohol is a mixture of the modified polyvinyl alcohols prepared in Examples 1 and 4, and the ratio of the two is 1:0.75.

[0134] This example demonstrates the modification of polyvinyl alcohol (PVA) under alkaline conditions using a combination of 3-bromopropyltrimethylammonium bromide and (3-chloro-2-hydroxypropyl)dodecyldimethylammonium chloride as a modifier. The introduction of quaternary ammonium groups into the PVA structure, with their high positive charge, allows for stable bonding with negatively charged pigments. This improves the affinity between paper and ink, significantly enhancing ink absorbency and improving printing quality. Simultaneously, the quaternary ammonium groups strengthen the electrostatic repulsion between molecular chains, causing them to extend. Furthermore, the introduction of more alkyl groups facilitates the formation of a network structure through chain entanglement, providing a degree of reinforcement to the paper.

[0135] Example 8

[0136] The purpose of this embodiment is to provide a highly absorbent cationic modified polyvinyl alcohol (PVA), obtained by modifying PVA 2099 under alkaline conditions using a modifier. The modifier is a composition of 3-bromopropyltrimethylammonium bromide and (3-chloro-2-hydroxypropyl)octadecyldimethylammonium chloride in a mass ratio of 1:3, and is added at 2% of the mass of PVA, wherein the amount of PVA added is 300g.

[0137] The preparation method includes the following steps:

[0138] Step 1: Disperse polyvinyl alcohol 2099 powder in 9 times its mass of solvent in a container. The solvent is a mixture of propanol and water in a ratio of 80:20, where the propanol is analytical grade and the water is purified water.

[0139] Step 2: Add the amount of the modifier to the container while stirring; heat and stir the reactants at 90°C for 2 hours. During the reaction, slowly add a 4% (w / w) alkaline solution to adjust the pH value to 7-8. After the reaction is completed, cool to room temperature. The alkaline is a combination of analytical grade sodium hydroxide and potassium hydroxide.

[0140] Step 3: Wash and filter, vacuum dry at 85℃ for 3 hours to obtain 232g of highly ink-absorbing cationic modified polyvinyl alcohol.

[0141] The reaction principle of the obtained highly absorbent cationic modified polyvinyl alcohol is as shown in Examples 1 and 5. The obtained highly absorbent cationic modified polyvinyl alcohol is a mixture of the modified polyvinyl alcohols prepared in Examples 1 and 5, and the ratio of the two is 1:0.5.

[0142] This example demonstrates the modification of polyvinyl alcohol (PVA) under alkaline conditions using a combination of 3-bromopropyltrimethylammonium bromide and (3-chloro-2-hydroxypropyl)octadecyldimethylammonium chloride as a modifier. The introduction of quaternary ammonium groups into the PVA structure, with their high positive charge, allows for stable bonding with negatively charged pigments. This improves the affinity between paper and ink, significantly enhancing ink absorbency and improving printing quality. Simultaneously, the quaternary ammonium groups strengthen the electrostatic repulsion between molecular chains, causing them to extend. Furthermore, the introduction of more alkyl groups facilitates the formation of a network structure through chain entanglement, providing a degree of reinforcement to the paper.

[0143] Comparative Example 1

[0144] This comparative example is unmodified polyvinyl alcohol 1788.

[0145] Comparative Example 2

[0146] This comparative example is unmodified polyvinyl alcohol 1799.

[0147] Comparative Example 3

[0148] This comparative example is unmodified polyvinyl alcohol 2099.

[0149] Comparative Example 4

[0150] This comparative example is unmodified polyvinyl alcohol 2499.

[0151] Comparative Example 5

[0152] This comparative example is unmodified polyvinyl alcohol 1795.

[0153] Comparative Example 6

[0154] Modified polyvinyl alcohol was prepared using the same method as in Example 1, except that "3-bromopropyltrimethylammonium bromide" was replaced with "methacryloyloxyethyltrimethylammonium chloride".

[0155] The result was a modified polyvinyl alcohol.

[0156] Comparative Example 7

[0157] Modified polyvinyl alcohol was prepared using the same method as in Example 1, except that "3-bromopropyltrimethylammonium bromide" was replaced with "acryloyloxyethyltrimethylammonium chloride".

[0158] The result was a modified polyvinyl alcohol.

[0159] Test case

[0160] The modified polyvinyl alcohol prepared in Examples 1-8 and Comparative Examples 1-7 was mixed with well-dispersed silica at a ratio of 20:100, and 5 drops of defoamer were added. The mixture was stirred for 3 minutes to prepare a coating. The coating was then applied using a coating machine at a coating weight of 5 g / m². 2 The paper is dried and calendered to produce coated paperboard. Since most inkjet inks are water-based, the water absorption value is used to represent the ink's absorption capacity, indirectly reflecting the ink absorbency of the inkjet paper. The definition of paper and paperboard surface water absorption (Cobb) value is: the amount of water absorbed by the surface of paper and paperboard per unit area under certain pressure and temperature within a specified time, expressed in g / m². 2 The test results are shown in Table 1.

[0161] Table 1

[0162] project <![CDATA[Cobb value (g / m 2 )]]> Example 1 52.6 Example 2 53.1 Example 3 59.0 Example 4 56.3 Example 5 55.5 Example 6 55.1 Example 7 58.3 Example 8 57.8 Comparative Example 1 37.5 Comparative Example 2 39.2 Comparative Example 3 38.9 Comparative Example 4 38.4 Comparative Example 5 38.8 Comparative Example 6 44.3 Comparative Example 7 43.9

[0163] As can be seen from the results in Table 1, the surface water absorption (Cobb) value of coated paperboard made of modified polyvinyl alcohol can reach 52.6-59, which is significantly improved compared with unmodified polyvinyl alcohol, indicating that the cationic modified polyvinyl alcohol has excellent ink absorption performance.

[0164] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A modified polyvinyl alcohol, characterized in that, The modified polyvinyl alcohol has the structure shown in formula (Ⅰ); Where n is between 1000 and 3000; X is a halogen atom; R1, R2, and R3 may be the same or different, each with a C1-C2 value. 18 Alkyl groups; Y is a C1-C3 alkylene group or a C1-C3 alkylene alcohol.

2. The modified polyvinyl alcohol according to claim 1, wherein, n is 1700-2400; X is a chlorine atom and / or a bromine atom; R1, R2, and R3 may be the same or different, and each is a C1-C3 alkyl group; Y is a C1-C2 alkylene group and / or a C1-C2 alkylene alcohol; preferably, Y is a methylene group and / or a methylene alcohol.

3. A method for preparing modified polyvinyl alcohol, characterized in that, The preparation method includes: (1) Under alkaline conditions, the polyvinyl alcohol represented by formula (II) and the modifier represented by formula (III) are reacted with the solvent; Where n is between 1000 and 3000; X is a halogen atom; R1, R2, and R3 may be the same or different, each with a C1-C2 value. 18 Alkyl groups; Y is a C1-C3 alkylene group or a C1-C3 alkylene alcohol; (2) The product after step (1) is cooled, washed, filtered and dried to obtain modified polyvinyl alcohol.

4. The preparation method according to claim 3, wherein, n is 1700-2400; X is a chlorine atom and / or a bromine atom; R1, R2, and R3 may be the same or different, and each is a C1-C3 alkyl group; Y is a C1-C2 alkylene and / or a C1-C2 alkylene alcohol; Preferably, Y is methylene and / or methylene alcohol.

5. The preparation method according to claim 3 or 4, wherein, The degree of alcoholysis of the polyvinyl alcohol shown in formula (2) is 80-100%; Preferably, the polyvinyl alcohol represented by formula (2) is selected from one or more of polyvinyl alcohol 1788, polyvinyl alcohol 1795, polyvinyl alcohol 1799, polyvinyl alcohol 2099, and polyvinyl alcohol 2499; And / or, the modifier shown in formula (3) is selected from one or more of 3-bromopropyltrimethylammonium bromide, 3-bromopropyltriethylammonium bromide, 3-chloro-2-hydroxypropyltripropylammonium chloride, (3-chloro-2-hydroxypropyl)dodecyldimethylammonium chloride, and (3-chloro-2-hydroxypropyl)dimethyloctadecylammonium chloride; And / or, the solvent is an organic alcohol and / or water.

6. The preparation method according to claim 3, wherein, The alkaline conditions are carried out under pH conditions of 7.2-8; And / or, the reaction conditions include: a temperature of 50-90°C and a time of 2-10 hours; And / or, the weight ratio of polyvinyl alcohol to solvent shown in formula (II) is (4-100):1, preferably (4-50):1; And / or, the amount of the modifier shown in formula (III) is 0.1-5 by weight of the amount of polyvinyl alcohol shown in formula (II).

7. A modified polyvinyl alcohol prepared by the preparation method according to any one of claims 3-6.

8. A coating, characterized in that, The coating contains the modified polyvinyl alcohol as described in any one of claims 1, 2 and 7.

9. The coating according to claim 8, wherein, The coating also contains silica and / or defoamer; Preferably, the amount of modified polyvinyl alcohol used is 20-40 parts by weight relative to 100 parts by weight of the silica. Preferably, the amount of the defoamer is 5-20 parts by weight relative to 100 parts by weight of the silica.

10. The application of the coating of claim 8 or 9 in inkjet printing paper.

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