A high-stability papermaking dry-strength agent based on acrylamide and a preparation method thereof

Abstract

The application discloses a high-stability papermaking dry-strength agent based on acrylamide and a preparation method thereof, which comprises the following components in parts by weight: 25-40 wt% of acrylamide 40-60 parts, 45-55 wt% of cationic monomer 8-26 parts, 50-65 wt% of anionic monomer 10-24 parts, 12-24 parts of organic silicon waterproof agent, 15-28 parts of chain transfer agent, 14-22 parts of hexamethylenetetramine, 15-27 parts of photosensitive initiator, 10-20 parts of azo initiator, 8-16 parts of free radical trapping agent and 12-18 parts of isocyanate. Through polymerization, the amphoteric polyacrylamide is generated, the amphoteric polyacrylamide can be adsorbed on the surface of the negatively charged fiber in the paper pulp, so that the binding force between the fibers is increased, and the paper strength is improved.

Description

Technical Field

[0001] This invention relates to the field of papermaking technology, specifically to a highly stable papermaking dry strength agent based on acrylamide and its preparation method. Background Technology

[0002] Paper is composed of randomly arranged, interwoven fiber layers. Within the fiber layers, cellulose molecular chains are linked together by hydrogen bonds. Therefore, by adding various dry strength agents to the pulp, they can be combined with the pulp fibers through chemical or physical interactions, thereby strengthening the adsorption between fiber layers and various particles and increasing the dry paper strength. Dry strength agents are an important class of chemicals used in the papermaking industry to increase paper strength. Dry strength agents are usually used to compensate for the decrease in paper strength caused by the addition of fillers or low-grade fibers (such as recycled fibers).

[0003] Most dry strength agents on the market are compounds containing acrylamide or its derivatives. The acrylamide in the dry strength agent reacts with the fibers in the pulp to increase the strength of the paper. However, the polymerization process of acrylamide and its derivatives may be relatively unstable. The resulting polymer molecular chains may be incomplete or have an uneven structure, making them susceptible to environmental conditions (such as temperature and pH) and pulp composition. They are prone to degradation or performance changes, affecting the chemical stability and durability of the paper, and thus the performance of the final product.

[0004] Therefore, we propose a highly stable papermaking dry strength agent based on acrylamide and its preparation method. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a highly stable papermaking dry strength agent based on acrylamide and its preparation method, which can effectively solve the problems in the background technology.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] A highly stable dry strength papermaking agent based on acrylamide, comprising the following components by weight: 40-60 parts of 25-40 wt% acrylamide, 8-26 parts of 45-55 wt% cationic monomer, 10-24 parts of 50-65 wt% anionic monomer, 12-24 parts of silicone waterproofing agent, 15-28 parts of chain transfer agent, 14-22 parts of hexamethylenetetramine, 15-27 parts of photosensitizer, 10-20 parts of azo initiator, 8-16 parts of free radical scavenger, and 12-18 parts of isocyanate.

[0008] Preferably, the cationic monomer is at least one of acryloyloxyethyltrimethylammonium chloride, methacryloyloxyethyltrimethylammonium chloride, dimethyldiallylammonium chloride, acryloyloxyethylbenzyldimethylammonium chloride, and methacryloyloxyethylbenzyldimethylammonium chloride.

[0009] Preferably, the anionic monomer is at least one of ethylene sulfonate, acrylate, maleate, and maleate.

[0010] Preferably, the chain transfer agent is one or more of sodium bisulfite, sodium metabisulfite, sodium thiosulfate, n-dodecyl mercaptan, tert-dodecyl mercaptan, mercaptoacetic acid, mercaptoethanol, and isopropanol.

[0011] Preferably, the photosensitizer is one of benzophenone, a water-soluble derivative of benzophenone, a benzoin derivative, or a fluorescein.

[0012] Preferably, the free radical scavenger is one of hydroquinone, benzoquinone, ferric chloride, copper acetate, sodium bisulfite, and ascorbic acid.

[0013] This invention also provides a method for preparing a highly stable papermaking dry strength agent based on acrylamide, comprising the following steps:

[0014] S1: Place acrylamide, cationic monomer and anionic monomer into a wide-mouth bottle and add an appropriate amount of deionized water. Mix for 10-15 minutes to prepare a transparent microemulsion system with a monomer concentration of 50-65 wt%, wherein the acrylamide content accounts for 65-80 wt% of the total monomer mass.

[0015] S2: Pour the prepared microemulsion into a four-necked bottle, add chain transfer agent, organosilicon waterproofing agent, photoinitiator and azo initiator, hexamethyltetramine, and isocyanate, and mix well to form a polymerization liquid;

[0016] S3: Stir the polymer solution obtained in S2, and introduce nitrogen gas under stirring conditions to remove oxygen from the polymer solution. After purging with nitrogen for half an hour, irradiate the polymer emulsion with ultraviolet light and react at 70-95℃ for 1.5-2 hours. Adjust the pH to 4-6 using a pH adjuster, and finally add a free radical scavenger. Mix the obtained products to obtain a paper dry strength agent with a viscosity of 3500-5000 mPa·s.

[0017] Preferably, in S3, when the pH of the system before adjustment is higher than 6, the pH adjuster is an acid (such as hydrochloric acid, sulfuric acid, acetic acid, phosphoric acid, etc.), and when the pH of the system before adjustment is lower than 4, the pH adjuster is an alkali, such as NaOH or ammonia water with a weight concentration of 10-15%.

[0018] Preferably, the ultraviolet light source in S3 is a high-pressure mercury lamp with a wavelength of 100-1000 nm, and its power is adjusted according to the size of the reaction vessel.

[0019] Compared with the prior art, the present invention provides an ultra-high performance waterproof mortar and its preparation method, which has the following beneficial effects:

[0020] Hexamethylenetetramine (HMDA), a multifunctional compound containing four amino groups, exhibits high reactivity. During the preparation of dry strength agents, the amino groups of HMDA can react with the functional groups in pulp fibers to form chemical bonds. This bonding enhances the connection between pulp fibers, improving the strength and durability of the paper. The introduction of HMDA can also improve the wet strength of the paper, allowing it to maintain good strength properties even under wet conditions.

[0021] 2. The NCO group of isocyanate can react with the amino group of hexamethylenetetramine and other functional groups on paper fibers to form a cross-linked structure. This cross-linked structure not only enhances the connection between fibers, but also improves the overall strength and stability of the paper. Through the cross-linking effect of isocyanate, the dry strength and wet strength of the paper are significantly improved.

[0022] 3. Acrylamide monomer, as the nonionic component, participates in the polymerization reaction together with cationic and anionic monomers. Chain transfer agents can adjust the chain length of the polymerization reaction, affecting the molecular weight distribution and branching degree of the polymer, thereby optimizing the polymer performance. Photoinitiators and azo initiators can generate free radicals under light and heat conditions, initiating the polymerization reaction. These monomers are linked together by covalent bonds to form amphoteric polyacrylamide. The chemical chains of the generated amphoteric polyacrylamide are relatively stable, maintaining their structural and performance stability during use and not easily degrading or changing. Amphoteric polyacrylamide dry strength agent can compensate for the decrease in paper strength caused by the addition of fillers or low-grade fibers (such as recycled fibers). It can form hydrogen bonds with fibers in the pulp, thereby improving the dry and wet strength and bursting strength of the paper. Furthermore, the anionic groups on the amphoteric polyacrylamide molecular chain can repel anionic impurities in the pulp and protect the cationic groups from being neutralized, allowing the amphoteric polyacrylamide to be adsorbed on the surface of negatively charged fibers in the pulp, thereby increasing the bonding force between fibers and improving paper strength. Detailed Implementation

[0023] To make the technical means, creative features, and achieved objectives and effects of this invention readily understandable, the invention will be further described below in conjunction with its embodiments. Obviously, the described embodiments are merely a part of the embodiments of this invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0024] The present invention will be further described below with reference to the embodiments.

[0025] In the specific implementation process:

[0026] Example 1

[0027] A highly stable papermaking dry strength agent based on acrylamide, comprising the following components by weight: 50 parts of 35wt% acrylamide, 17 parts of 50wt% cationic monomer, 17 parts of 55wt% anionic monomer, 18 parts of organosilicon waterproofing agent, 21.5 parts of chain transfer agent, 18 parts of hexamethylenetetramine, 21 parts of photoinitiator, 15 parts of azo initiator, 12 parts of free radical scavenger, and 15 parts of isocyanate;

[0028] The cationic monomer is at least one of acryloyloxyethyltrimethylammonium chloride, methacryloyloxyethyltrimethylammonium chloride, dimethyldiallylammonium chloride, acryloyloxyethylbenzyldimethylammonium chloride, and methacryloyloxyethylbenzyldimethylammonium chloride;

[0029] The anionic monomer is at least one of ethylene sulfonate, acrylate, maleate, and maleate;

[0030] The chain transfer agent is one or more of sodium bisulfite, sodium metabisulfite, sodium thiosulfate, n-dodecyl mercaptan, tert-dodecyl mercaptan, mercaptoacetic acid, mercaptoethanol, and isopropanol.

[0031] The photosensitizer is one of benzophenone, water-soluble derivatives of benzophenone, benzoin derivatives, or fluorescein.

[0032] The free radical scavenger is one of hydroquinone, benzoquinone, ferric chloride, copper acetate, sodium bisulfite, and ascorbic acid;

[0033] This invention also provides a method for preparing a highly stable papermaking dry strength agent based on acrylamide, comprising the following steps:

[0034] S1: Place acrylamide, cationic monomer and anionic monomer into a wide-mouth bottle and add an appropriate amount of deionized water. Mix for 10-15 minutes to prepare a transparent microemulsion system with a monomer concentration of 55wt%, wherein the acrylamide content accounts for 70wt% of the total monomer mass.

[0035] S2: Pour the prepared microemulsion into a four-necked bottle, add chain transfer agent, organosilicon waterproofing agent, photoinitiator and azo initiator, hexamethyltetramine, and isocyanate, and mix well to form a polymerization liquid;

[0036] S3: Stir the polymer solution obtained in S2, and purge with nitrogen to remove oxygen from the polymer solution. After purging with nitrogen for half an hour, irradiate the polymer emulsion with ultraviolet light and react at 70-95°C for 1.5-2 hours. The ultraviolet light source is a high-pressure mercury lamp with a wavelength of 100-1000 nm, and its power is adjusted according to the size of the reaction vessel. Use a pH adjuster to adjust the pH to 4-6. When the pH of the system is higher than 6 before adjustment, the pH adjuster is an acid (such as hydrochloric acid, sulfuric acid, acetic acid, phosphoric acid, etc.). When the pH of the system is lower than 4 before adjustment, the pH adjuster is an alkali, such as NaOH or ammonia water with a weight concentration of 10-15%. Finally, add a free radical scavenger and mix the products to obtain a paper dry strength agent with a viscosity of 3500-5000 mPa·s.

[0037] Example 2

[0038] The preparation method is the same as in Example 1, except that:

[0039] A highly stable papermaking dry strength agent based on acrylamide, comprising the following components by weight: 40 parts of 35wt% acrylamide, 8 parts of 50wt% cationic monomer, 10 parts of 55wt% anionic monomer, 12 parts of organosilicon waterproofing agent, 15 parts of chain transfer agent, 14 parts of hexamethylenetetramine, 15 parts of photoinitiator, 10 parts of azo initiator, 8 parts of free radical scavenger, and 12 parts of isocyanate.

[0040] Example 3

[0041] The preparation method is the same as in Example 1, except that:

[0042] A highly stable papermaking dry strength agent based on acrylamide, comprising the following components by weight: 60 parts of 35wt% acrylamide, 26 parts of 50wt% cationic monomer, 24 parts of 55wt% anionic monomer, 24 parts of organosilicon waterproofing agent, 28 parts of chain transfer agent, 22 parts of hexamethylenetetramine, 27 parts of photoinitiator, 20 parts of azo initiator, 16 parts of free radical scavenger, and 18 parts of isocyanate.

[0043] Comparative Example 1

[0044] The difference from the components in Example 1 is:

[0045] A highly stable papermaking dry strength agent based on acrylamide, comprising the following components by weight: 50 parts of 35wt% acrylamide, 17 parts of 55wt% anionic monomer, 18 parts of organosilicon waterproofing agent, 21.5 parts of chain transfer agent, 18 parts of hexamethylenetetramine, 21 parts of photoinitiator, 15 parts of azo initiator, 12 parts of free radical scavenger, and 15 parts of isocyanate;

[0046] The difference between this comparative example and Example 1 lies in the preparation method of the acrylamide-based high-stability paper dry strength agent:

[0047] S1: Place acrylamide and anionic monomer into a wide-mouth bottle and add an appropriate amount of deionized water. Mix for 10-15 minutes to prepare a transparent microemulsion system with a monomer concentration of 55wt%, wherein the acrylamide content accounts for 70wt% of the total monomer mass.

[0048] Comparative Example 2

[0049] The difference from the components in Example 1 is:

[0050] A highly stable dry strength papermaking agent based on acrylamide, comprising the following components by weight: 50 parts of 35wt% acrylamide, 17 parts of 50wt% cationic monomer, 18 parts of organosilicon waterproofing agent, 21.5 parts of chain transfer agent, 18 parts of hexamethylenetetramine, 21 parts of photoinitiator, 15 parts of azo initiator, 12 parts of free radical scavenger, and 15 parts of isocyanate.

[0051] The difference between this comparative example and Example 1 lies in the preparation method of the acrylamide-based high-stability paper dry strength agent:

[0052] S1: Place acrylamide and cationic monomer into a wide-mouth bottle and add an appropriate amount of deionized water. Mix for 10-15 minutes to prepare a transparent microemulsion system with a monomer concentration of 55wt%, wherein the acrylamide content accounts for 70wt% of the total monomer mass.

[0053] Comparative Example 3

[0054] The difference from the components in Example 1 is:

[0055] A highly stable dry strength papermaking agent based on acrylamide, comprising the following components by weight: 50 parts of 35wt% acrylamide, 18 parts of organosilicon waterproofing agent, 21.5 parts of chain transfer agent, 18 parts of hexamethylenetetramine, 21 parts of photoinitiator, 15 parts of azo initiator, 12 parts of free radical scavenger, and 15 parts of isocyanate.

[0056] The difference between this comparative example and Example 1 lies in the preparation method of the acrylamide-based high-stability paper dry strength agent:

[0057] S1: Put acrylamide into a wide-mouth bottle and add an appropriate amount of deionized water. Mix for 10-15 minutes to prepare a transparent solution with a concentration of 55wt%.

[0058] Comparative Example 4

[0059] The difference from the components in Example 1 is:

[0060] A highly stable papermaking dry strength agent based on acrylamide, comprising the following components by weight: 50 parts of 35wt% acrylamide, 17 parts of 50wt% cationic monomer, 17 parts of 55wt% anionic monomer, 18 parts of organosilicon waterproofing agent, 21.5 parts of chain transfer agent, 21 parts of photoinitiator, 15 parts of azo initiator, 12 parts of free radical scavenger, and 15 parts of isocyanate.

[0061] The difference between this comparative example and Example 1 lies in the preparation method of the acrylamide-based high-stability paper dry strength agent:

[0062] S2: Pour the prepared microemulsion into a four-necked bottle, add chain transfer agent, organosilicon waterproofing agent, photoinitiator, azo initiator, and isocyanate, and mix well to form a polymerization liquid.

[0063] Comparative Example 5

[0064] The difference from the components in Example 1 is:

[0065] A highly stable papermaking dry strength agent based on acrylamide, comprising the following components by weight: 50 parts of 35wt% acrylamide, 17 parts of 50wt% cationic monomer, 17 parts of 55wt% anionic monomer, 18 parts of organosilicon waterproofing agent, 21.5 parts of chain transfer agent, 18 parts of hexamethylenetetramine, 21 parts of photoinitiator, 15 parts of azo initiator, and 12 parts of free radical scavenger;

[0066] The difference between this comparative example and Example 1 lies in the preparation method of the acrylamide-based high-stability paper dry strength agent:

[0067] S2: Pour the prepared microemulsion into a four-necked bottle, add chain transfer agent, organosilicon waterproofing agent, photoinitiator, azo initiator, and hexamethyltetramine, and mix well to form a polymerization liquid.

[0068] Comparative Example 6

[0069] The difference from the components in Example 1 is:

[0070] A highly stable papermaking dry strength agent based on acrylamide, comprising the following components by weight: 50 parts of 35wt% acrylamide, 17 parts of 50wt% cationic monomer, 17 parts of 55wt% anionic monomer, 18 parts of organosilicon waterproofing agent, 21.5 parts of chain transfer agent, 21 parts of photoinitiator, 15 parts of azo initiator, and 12 parts of free radical scavenger.

[0071] The difference between this comparative example and Example 1 lies in the preparation method of the acrylamide-based high-stability paper dry strength agent:

[0072] S2: Pour the prepared microemulsion into a four-necked bottle, add chain transfer agent, organosilicon waterproofing agent, photoinitiator and azo initiator, mix well to form a polymerization liquid.

[0073] Experimental group:

[0074] Usage process: Dilute the dry strength agent with water to 1wt% and set aside. Prepare the pulp with a freeness of 30°SR. The order of addition is: pulp + aluminum sulfate + dry strength agent. Add aluminum sulfate to the concentrated pulp first, at a rate of 42 kg (liquid) / ton of paper (liquid aluminum sulfate, dried at 150℃ for 30 minutes to obtain a solid content of 38%). Stir for 10 minutes. The designed basis weight is about 125 g / m2. Under the same addition amount of dry strength agent, the application results of Examples 1-3 and Comparative Examples 1-6 of this invention are compared. Weigh an appropriate amount of pulp with added aluminum sulfate, then add the dry strength agent and stir for 2 minutes. After forming and pressing with a square sheeter, let it air dry naturally. Then test the tensile strength (GB / T 12914-1991), ring crush strength (GB / T 2678.8-1995), bursting strength, folding endurance, internal bond strength and other indicators of the paper. The paper without added dry strength agent is used as a blank group.

[0075]

[0076]

[0077] As can be seen from the data in the examples in the table, the paper exhibits the best tensile strength, ring crush strength, and bursting strength when the following components are present by weight: 40 parts of acrylamide (35 wt%), 8 parts of cationic monomer (50 wt%), 10 parts of anionic monomer (55 wt%), 12 parts of silicone waterproofing agent, 15 parts of chain transfer agent, 14 parts of hexamethylenetetramine, 15 parts of photoinitiator, 10 parts of azo initiator, 8 parts of free radical scavenger, and 12 parts of isocyanate.

[0078] Compared with Comparative Example 1, the dry strength agent prepared in Example 1 contained cationic monomers. Compared with Comparative Example 2, the dry strength agent prepared in Example 1 contained cationic monomers. Analyzing the data in the table, the paper prepared with the dry strength agent in Example 1 had the best tensile strength, ring crush strength, bursting strength, and other indicators. It can be seen that the long-chain polymers produced by the polymerization reaction of cationic monomers, anionic monomers, and acrylamide can promote the strength and stability of paper.

[0079] Compared with Comparative Example 6, the dry strength agent prepared in Example 1 contained isocyanate and hexamethyltetramine. The tensile strength, ring crush strength, bursting strength and internal bond strength of the paper in Example 1 were all higher than those of the paper in Comparative Example 6. It can be seen that hexamethyltetramine and isocyanate can improve the strength properties of paper.

[0080] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the claimed invention.

Claims

1. A highly stable papermaking dry strength agent based on acrylamide, characterized in that, By weight, it comprises the following components: 40-60 parts of 25-40 wt% acrylamide, 8-26 parts of 45-55 wt% cationic monomer, 10-24 parts of 50-65 wt% anionic monomer, 12-24 parts of silicone waterproofing agent, 15-28 parts of chain transfer agent, 14-22 parts of hexamethylenetetramine, 15-27 parts of photosensitizer, 10-20 parts of azo initiator, 8-16 parts of free radical scavenger, and 12-18 parts of isocyanate. The cationic monomer is at least one of acryloyloxyethyltrimethylammonium chloride, methacryloyloxyethyltrimethylammonium chloride, dimethyldiallylammonium chloride, acryloyloxyethylbenzyldimethylammonium chloride, and methacryloyloxyethylbenzyldimethylammonium chloride. The anionic monomer is at least one of ethylene sulfonate, acrylate, maleate, and maleate; The chain transfer agent is one or more of sodium bisulfite, sodium metabisulfite, sodium thiosulfate, n-dodecyl mercaptan, tert-dodecyl mercaptan, mercaptoacetic acid, mercaptoethanol, and isopropanol. The photosensitizer is one of benzophenone, a water-soluble derivative of benzophenone, a benzoin derivative, or a fluorescein. The free radical scavenger is one of hydroquinone, benzoquinone, ferric chloride, copper acetate, sodium bisulfite, and ascorbic acid.

2. A method for preparing a highly stable papermaking dry strength agent based on acrylamide, used to prepare the highly stable papermaking dry strength agent based on acrylamide as described in claim 1, characterized in that, The preparation method of this acrylamide-based high-stability papermaking dry strength agent includes the following steps: S1: Place acrylamide, cationic monomer and anionic monomer into a wide-mouth bottle and add an appropriate amount of deionized water. Mix for 10-15 minutes to prepare a transparent microemulsion system with a monomer concentration of 50-65 wt%, wherein the acrylamide content accounts for 65-80 wt% of the total monomer mass. S2: Pour the prepared microemulsion into a four-necked bottle, add chain transfer agent, organosilicon waterproofing agent, photoinitiator and azo initiator, hexamethyltetramine, and isocyanate, and mix well to form a polymerization liquid; S3: Stir the polymer solution obtained in S2, and introduce nitrogen gas under stirring conditions to remove oxygen from the polymer solution. After purging with nitrogen for half an hour, irradiate the polymer emulsion with ultraviolet light and react at 70-95℃ for 1.5-2 hours. Adjust the pH to 4-6 using a pH adjuster, and finally add a free radical scavenger. Mix the obtained products to obtain a paper dry strength agent with a viscosity of 3500-5000 mPa·s.

3. The method for preparing a highly stable papermaking dry strength agent based on acrylamide according to claim 2, characterized in that, In S3, when the system pH is higher than 6 before adjustment, the pH adjuster is an acid; when the system pH is lower than 4 before adjustment, the pH adjuster is a base.

4. The method for preparing a highly stable papermaking dry strength agent based on acrylamide according to claim 2, characterized in that, The ultraviolet light source mentioned in S3 is a high-pressure mercury lamp with a wavelength of 100–1000 nm.

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