Anionic dry strength agent for papermaking and its preparation method

Abstract

The invention discloses an emulsion type anionic dry strength agent for papermaking and a preparation method thereof, belonging to the technical field of paper additive processing, and is used to solve the technical problem that the physical property improvement effect of the starch-based anionic emulsion type dry strength agent in the prior art on papermaking paper needs to be further improved; the invention comprises the following components by weight: 5-6 parts of carboxyl modified starch, 4-5 parts of hydroxymethyl chitosan and 40-45 parts of polyolefin emulsion, and the anionic dry strength agent emulsion is prepared by preparing carboxyl modified starch and hydroxymethyl chitosan to cooperate with each other to enhance the polyolefin emulsion containing sulfonate, so as to prepare the anionic dry strength agent emulsion, which not only effectively improves the tensile properties of papermaking samples, but also improves the tear resistance of the samples.

Description

Technical Field

[0001] The invention relates to the technical field of papermaking additive processing, and in particular to an emulsion type anionic dry strength agent for papermaking and a preparation method thereof. Background Art

[0002] The papermaking industry is an important part of modern industry. As an indispensable material in daily life, paper has increasingly higher performance requirements, especially in terms of dry strength, burst resistance, flexibility, etc. Dry strength agents are commonly used chemicals in the papermaking process to improve the dry strength and other physical properties of paper. Traditional paper dry strength agents mainly include natural polymers, such as starch and its modifications (such as cationic starch, anionic starch, cross-linked starch), and synthetic polymers, such as polyacrylamide, polyvinyl alcohol, etc. These dry strength agents effectively improve the dry strength of paper by interacting with fibers such as forming hydrogen bonds.

[0003] Prior art, a Chinese invention patent with publication number CN102121207A, discloses a papermaking dry strength agent, which is composed of 0.5-2.5% by weight of modified starch, 10-40% of polyanionic cellulose, 40-84% of acrylamide, 1-20% of acrylic acid or its esters, 1-10% of carboxylic acid ester, 1-10% of acrylonitrile, pH regulator, 1-5% anti-crosslinking agent, 0.1-1% reaction inhibitor, 0.5-2% multi-composite catalyst, and 0.5-2% ripening agent, which can improve the physical strength of paper, improve the dry strength, bursting strength, folding strength, and tearing strength of paper.

[0004] Anionic emulsion dry strength agents can better adsorb on the fiber surface due to their interaction with the negative charge on the fiber surface, thereby improving the dry strength and other properties of paper. However, the existing technology, including the modified starch used in the above-mentioned patent, has poor hydrophilicity, resulting in poor dispersibility and stability of starch-containing dry strength agents in water, making the dry strength agent unevenly distributed in the paper, affecting the strengthening effect, resulting in the need to further improve the physical properties of papermaking paper by traditional starch-based anionic emulsion dry strength agents. Summary of the invention

[0005] The object of the present invention is to provide an emulsion type anionic dry strength agent for papermaking and a preparation method thereof, so as to solve the technical problem that the effect of starch-based anionic emulsion type dry strength agent in the prior art on improving the physical properties of papermaking paper needs to be further improved.

[0006] The object of the present invention can be achieved by the following technical scheme: an emulsion type anionic dry strength agent for papermaking, characterized in that the following steps are performed: sulfonic acid modified butadiene, glycidyl methacrylate, sodium acrylate and emulsion are mixed and stirred, the temperature of the reaction system is raised to 70-80°C, an initiator solution is added dropwise to the reaction system, and after the addition is completed, the reaction is carried out by heat preservation for 3-5 hours, and post-treatment is performed to obtain a polyolefin emulsion;

[0007] The sulfonic acid modified butadiene is prepared by mixing (E)-but-2-ene-1,4-diamine, 1,3-propane sultone and tetrahydrofuran, raising the temperature of the reaction system to 55-65° C., keeping the temperature for 4-6 hours, adding sodium hydroxide solution to the reaction system, adjusting the pH of the system to 7, and treating to obtain;

[0008] Diethylenetriamine pentaacetic acid, sodium hypophosphite and sodium hydroxide solution are mixed and stirred until the system is dissolved, and the pretreated starch is added to the reaction system, the temperature of the reaction heat exchange medium is increased to 120-130°C, and the reaction is kept warm for 6-8 hours, and post-processed to obtain carboxyl modified starch;

[0009] Then, 5-6 parts of the carboxyl modified starch prepared in the above step and 40-45 parts of the polyolefin emulsion are mixed by weight, and then 4-5 parts of hydroxymethyl chitosan is added and mixed thoroughly to obtain the emulsion type anionic dry strength agent.

[0010] Furthermore, the amount ratio of the sulfonic acid modified butadiene, glycidyl methacrylate, sodium acrylate, emulsion and initiator solution is 3g:2g:5g:45mL:5g, the emulsion is composed of polyvinyl alcohol, AEO-3 and deionized water in a ratio of 2g:3g:80mL, the initiator solution is composed of azobisisobutyronitrile and deionized water in a weight ratio of 1:8, and the post-treatment includes: after the reaction is completed, the temperature of the reaction system is reduced to room temperature, and the mixture is sieved through a 100-mesh screen to obtain a polyolefin emulsion.

[0011] Furthermore, the amount ratio of the (E)-but-2-ene-1,4-diamine 86.14, 1,3-propane sultone 122.14 and tetrahydrofuran is 1g:2.8g:10mL, and the post-treatment includes: after the reaction is completed, transferring the reaction solution to a rotary evaporator with a water bath temperature of 60°C, and removing low boiling points under reduced pressure to obtain sulfonic acid-modified butadiene.

[0012] Furthermore, the dosage ratio of the diethylenetriamine pentaacetic acid, sodium hypophosphite, sodium hydroxide solution and pretreated starch is 5g:1g:10mL:5g, the concentration of the sodium hydroxide solution is 0.03-0.05mol / L, and the post-treatment comprises: after the reaction is completed, the temperature of the reaction system is lowered to room temperature, purified water is added to the reaction system, and stirred for 20-30min, the filter cake is washed twice with 0.1mol / L hydrochloric acid, and then washed with deionized water until the filtrate is neutral, the filter cake is transferred to a drying oven at a temperature of 70-80°C, and vacuum dried to constant weight to obtain carboxyl modified starch.

[0013] Further, starch and deionized water are mixed, the temperature of the reaction system is increased to 90-96° C., and the mixture is stirred for 60-80 min. The temperature of the reaction system is reduced to 60-70° C., anhydrous ethanol is added to the reaction system, and the mixture is stirred for 30-50 min. The mixture is post-treated to obtain pretreated starch.

[0014] The present invention also provides a method for preparing an emulsion type anionic dry strength agent for papermaking, which comprises the following steps: adding carboxyl modified starch and hydroxymethyl chitosan to a polyolefin emulsion, raising the temperature of the reaction system to 70-80°C, stirring and dispersing for 40-60 minutes, and naturally cooling to room temperature to obtain a dry strength agent emulsion.

[0015] The reaction formula for the synthesis of polyolefin emulsion in the present invention is:

[0016]

[0017] Where:

[0018] The synthesis reaction mechanism is:

[0019] During the reaction, sulfonic acid-modified butadiene, glycidyl methacrylate and sodium acrylate are mixed in an emulsion, and a free radical polymerization reaction is initiated under the action of a free radical initiator to prepare a polyolefin emulsion modified with sulfonate, acetate and epoxy groups.

[0020] In the present invention, the synthetic reaction formula of sulfonic acid modified butadiene is:

[0021]

[0022] The synthesis reaction mechanism is:

[0023] During the reaction, when (E)-but-2-ene-1,4-diamine and 1,3-propane sultone are mixed in tetrahydrofuran solvent and heated, the amino group of the amine attacks the carbonyl carbon of the sultone, resulting in the opening of the sultone ring, wherein the carbonyl carbon atom of the sultone is connected to the amino group of the amine to form a carbon-nitrogen bond, so that the sulfonic acid group is connected to the skeleton of butadiene, and the pH is adjusted by sodium hydroxide to convert the sulfonic acid group into sodium sulfonate, thereby preparing a butadiene molecule modified with sodium sulfonate.

[0024] Molecular weight by mass spectrometry: 374.3851

[0025] Mass-to-charge ratio of mass spectrometry analysis: m / z: 374.0558 (100.0%), 375.0592 (10.8%), 376.0516 (9.0%), 375.0552 (1.6%), 376.0601 (1.2%).

[0026] In the present invention, the synthesis reaction mechanism of carboxyl modified starch is:

[0027] During the reaction, diethylenetriamine pentaacetic acid is dehydrated under sodium hypophosphite and high temperature conditions to generate anhydride, and then the anhydride undergoes esterification reaction with the active hydroxyl groups on the starch particles to form a large number of carboxyl modifications on the starch particles to prepare carboxyl-modified starch.

[0028] In the present invention, the synthesis reaction mechanism of pretreated starch is:

[0029] During the reaction, starch is mixed with deionized water and then exposed to high temperature, causing starch particles to absorb water and swell, destroying the hydrogen bonds between starch molecules, causing the starch granules to disintegrate and form starch paste. The chain segments of the starch molecules become more flexible and easy to react with other molecules or reagents, thereby increasing their reactivity. Ethanol is a poor solvent for starch and can reduce the solubility of starch in water, causing the starch molecules to precipitate from the solution to prepare pretreated starch.

[0030] The present invention has the following beneficial effects:

[0031] 1. The emulsion-type anionic dry strength agent for papermaking of the present invention is compounded by carboxyl modified starch, hydroxymethyl chitosan and polyolefin emulsion to form a multi-component synergistic reinforcement system. The carboxyl modified starch enhances the hydrophilicity and reactivity of starch by introducing carboxyl groups. The carboxyl groups can form hydrogen bonds with hydroxyl groups of cellulose fibers to enhance the binding force between fibers. Carboxymethyl chitosan has good flexibility and film-forming properties and can enhance the flexibility and mechanical strength of the emulsion. Sulfonic acid modified butadiene, glycidyl methacrylate and sodium acrylate in the polyolefin emulsion form a high molecular polymer by copolymerization. The carboxyl modified starch and hydroxymethyl chitosan enhance the binding force between fibers by hydrogen bonds and electrostatic effects. The polyolefin emulsion further strengthens this effect by chemical crosslinking, thereby significantly improving the tensile and tearing properties of paper.

[0032] 2. The emulsion type anionic dry strength agent for papermaking of the present invention uses corn starch as raw material and adopts a pretreatment method of high temperature gelatinization combined with ethanol washing to effectively remove impurities and non-crystalline areas in starch, improve the reactivity of starch, and can more fully react with diethylenetriamine pentaacetic acid and sodium hypophosphite, improve the substitution degree and uniformity of carboxylation reaction, make the distribution of carboxyl groups more uniform, thereby improving its hydrophilicity and reactivity, etc., so that it can be uniformly mixed with polyolefin emulsion and hydroxymethyl chitosan in the emulsion, improve the stability of the emulsion, and carboxyl modified starch The carboxyl groups in carboxymethyl chitosan can form hydrogen bonds with the hydroxyl groups of cellulose fibers to form a denser hydrogen bond network, which can significantly enhance the bonding force between paper fibers, thereby improving the tensile strength, tensile energy absorption index and tear resistance index of the paper. In addition, carboxymethyl chitosan, as a water-soluble polymer, has excellent dispersibility and thickening effects, which can improve the stability of the emulsion and prevent particle aggregation. The thickening and dispersing effects of carboxymethyl chitosan can enhance the dispersing effect of carboxyl-modified starch, make the emulsion more evenly adhere to the fiber surface, and improve the dry strength effect of the paper.

[0033] 3. The emulsion-type anionic dry strength agent for papermaking of the present invention introduces sulfonic acid groups into polyolefin emulsion to enhance the water solubility and anionic properties of the polymer. At the same time, the strong hydrophilicity and charge repulsion of the sulfonic acid groups reduce the aggregation between particles and improve the stability of the emulsion under shear force and temperature changes. The sulfonic acid-modified butadiene has better water solubility and dispersibility. At the same time, its sulfonic acid groups can give the polymer certain hydrophilicity and ionicity, which is conducive to the combination of the polymer and pulp fibers. This combination can enhance the fiber-to-fiber interaction of paper, thereby improving the overall strength of the paper. The epoxy groups contained in the glycidyl methacrylate in the polyolefin emulsion provide chemical crosslinking sites, which can undergo crosslinking reactions with the active functional group sites on the cellulose fibers, enhance the bonding force between the fibers, and further enhance the overall strength of the papermaking sample. The carboxylic acid groups of sodium acrylate in the polyolefin emulsion have good water solubility and can be evenly distributed in the process of paper formation, thereby ensuring the uniformity of paper performance. The sulfonic acid-modified butadiene and sodium acrylate are combined to give full play to the advantages of both, produce a synergistic effect, and further improve the tensile and tearing properties of the paper. DETAILED DESCRIPTION

[0034] The technical solution of the present invention will be clearly and completely described below in conjunction with the embodiments. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention. Example 1

[0035] This embodiment provides a method for preparing an emulsion type anionic dry strength agent for papermaking, comprising the following steps:

[0036] S1. Preparation of pretreated starch

[0037] Weigh: 50 g of corn starch and 400 mL of deionized water are added to a three-necked flask and stirred. The temperature of the three-necked flask is increased to 90° C. and stirred for 60 min. The temperature of the three-necked flask is reduced to 60° C., 1000 mL of anhydrous ethanol is added to the three-necked flask, and stirred for 30 min. The temperature of the three-necked flask is reduced to room temperature and centrifuged. After the filter cake is washed 3 times with anhydrous ethanol, it is transferred to a drying oven at a temperature of 70° C. and vacuum dried to constant weight to obtain pretreated starch.

[0038] S2. Preparation of carboxyl modified starch

[0039] Weigh: 50 g of diethylenetriamine pentaacetic acid, 10 g of sodium hypophosphite and 100 mL of 0.03 mol / L sodium hydroxide solution, add them into a three-necked flask and stir until the system is dissolved, add 50 g of pretreated starch into the three-necked flask, place the three-necked flask in an oil bath at 120°C and stir, keep warm for 6 hours, lower the temperature of the three-necked flask to room temperature, add 300 mL of purified water into the three-necked flask, stir for 20 minutes, wash the filter cake twice with 0.1 mol / L hydrochloric acid, and then wash with deionized water until the filtrate is neutral, transfer the filter cake to a drying oven at 70°C, vacuum dry to constant weight, crush, and pass through a 100-mesh sieve to obtain carboxyl-modified starch.

[0040] S3. Preparation of sulfonic acid modified butadiene

[0041] Weigh: (E)-but-2-ene-1,4-diamine 20g, 1,3-propane sultone 56g and tetrahydrofuran 200mL, add into nitrogen-protected three-necked flask and stir, raise the temperature of the three-necked flask to 55°C, keep warm and react for 4h, add 0.1mol / L sodium hydroxide solution into the three-necked flask, adjust the system pH to 7, transfer the reaction solution into a rotary evaporator with a water bath temperature of 60°C, remove low boiling points under reduced pressure, and obtain sulfonic acid-modified butadiene.

[0042] S4. Preparation of polyolefin emulsion

[0043] Mix polyvinyl alcohol, AEO-3 and deionized water in a ratio of 2g:3g:80mL to obtain an emulsion for later use;

[0044] Azobisisobutyronitrile and deionized water were mixed uniformly in a weight ratio of 1:8 to obtain an initiator solution for later use;

[0045] Weigh: 30 g of sulfonic acid modified butadiene, 20 g of glycidyl methacrylate, 50 g of sodium acrylate, and 450 mL of emulsion, add into a three-necked flask and stir, raise the temperature of the three-necked flask to 70°C, add 50 g of initiator solution dropwise into the three-necked flask, after the addition is complete, keep warm and react for 3 hours, lower the temperature of the three-necked flask to room temperature, pass through a 100-mesh sieve to obtain a polyolefin emulsion.

[0046] S5. Preparation of dry strength agent emulsion

[0047] Weigh by weight: 5 parts of carboxyl modified starch, 4 parts of hydroxymethyl chitosan and 40 parts of polyolefin emulsion, add into a three-necked flask and stir, raise the temperature of the three-necked flask to 70° C., stir and disperse for 40 minutes, and cool naturally to room temperature to obtain a dry strength agent emulsion. Example 2

[0048] This embodiment provides a method for preparing an emulsion type anionic dry strength agent for papermaking, comprising the following steps:

[0049] S1. Preparation of pretreated starch

[0050] Weigh: 50 g of corn starch and 400 mL of deionized water are added to a three-necked flask and stirred. The temperature of the three-necked flask is increased to 93° C. and stirred for 70 min. The temperature of the three-necked flask is reduced to 65° C., 1000 mL of anhydrous ethanol is added to the three-necked flask, and stirred for 40 min. The temperature of the three-necked flask is reduced to room temperature and centrifuged. After the filter cake is washed 3 times with anhydrous ethanol, it is transferred to a drying oven at a temperature of 75° C. and vacuum dried to constant weight to obtain pretreated starch.

[0051] S2. Preparation of carboxyl modified starch

[0052] Weigh: 50 g of diethylenetriamine pentaacetic acid, 10 g of sodium hypophosphite and 100 mL of 0.04 mol / L sodium hydroxide solution, add them into a three-necked flask and stir until the system is dissolved, add 50 g of pretreated starch into the three-necked flask, place the three-necked flask in an oil bath at 125°C and stir, keep warm for 7 hours, lower the temperature of the three-necked flask to room temperature, add 300 mL of purified water into the three-necked flask, stir for 25 minutes, wash the filter cake twice with 0.1 mol / L hydrochloric acid, and then wash with deionized water until the filtrate is neutral, transfer the filter cake to a drying oven at 75°C, vacuum dry to constant weight, crush, and pass through a 100-mesh sieve to obtain carboxyl-modified starch.

[0053] S3. Preparation of sulfonic acid modified butadiene

[0054] Weigh: (E)-but-2-ene-1,4-diamine 20g, 1,3-propane sultone 56g and tetrahydrofuran 200mL, add into nitrogen-protected three-necked flask and stir, raise the temperature of the three-necked flask to 60°C, keep warm and react for 5h, add 0.2mol / L sodium hydroxide solution into the three-necked flask, adjust the system pH to 7, transfer the reaction solution into a rotary evaporator with a water bath temperature of 60°C, remove low boiling points under reduced pressure, and obtain sulfonic acid-modified butadiene.

[0055] S4. Preparation of polyolefin emulsion

[0056] Mix polyvinyl alcohol, AEO-3 and deionized water in a ratio of 2g:3g:80mL to obtain an emulsion for later use;

[0057] Azobisisobutyronitrile and deionized water were mixed uniformly in a weight ratio of 1:8 to obtain an initiator solution for later use;

[0058] Weigh: 30 g of sulfonic acid modified butadiene, 20 g of glycidyl methacrylate, 50 g of sodium acrylate, and 450 mL of emulsion, add into a three-necked flask and stir, raise the temperature of the three-necked flask to 75°C, add 50 g of initiator solution dropwise into the three-necked flask, after the addition is complete, keep warm and react for 4 hours, lower the temperature of the three-necked flask to room temperature, pass through a 100-mesh sieve to obtain a polyolefin emulsion.

[0059] S5. Preparation of dry strength agent emulsion

[0060] Weigh by weight: 5.5 parts of carboxyl modified starch, 4.5 parts of hydroxymethyl chitosan and 43 parts of polyolefin emulsion, add into a three-necked flask and stir, raise the temperature of the three-necked flask to 75° C., stir and disperse for 50 minutes, and cool naturally to room temperature to obtain a dry strength agent emulsion. Example 3

[0061] This embodiment provides a method for preparing an emulsion type anionic dry strength agent for papermaking, comprising the following steps:

[0062] S1. Preparation of pretreated starch

[0063] Weigh: 50 g of corn starch and 400 mL of deionized water are added to a three-necked flask and stirred. The temperature of the three-necked flask is increased to 96° C. and stirred for 80 min. The temperature of the three-necked flask is reduced to 70° C., 1000 mL of anhydrous ethanol is added to the three-necked flask, and stirred for 50 min. The temperature of the three-necked flask is reduced to room temperature and centrifuged. After the filter cake is washed 3 times with anhydrous ethanol, it is transferred to a drying oven at a temperature of 80° C. and vacuum dried to constant weight to obtain pretreated starch.

[0064] S2. Preparation of carboxyl modified starch

[0065] Weigh: 50 g of diethylenetriamine pentaacetic acid, 10 g of sodium hypophosphite and 100 mL of 0.05 mol / L sodium hydroxide solution, add them into a three-necked flask and stir until the system is dissolved, add 50 g of pretreated starch into the three-necked flask, place the three-necked flask in an oil bath at a temperature of 130°C and stir, keep warm for 8 hours, lower the temperature of the three-necked flask to room temperature, add 300 mL of purified water into the three-necked flask, stir for 30 minutes, wash the filter cake twice with 0.1 mol / L hydrochloric acid, and then wash with deionized water until the filtrate is neutral, transfer the filter cake to a drying oven at a temperature of 80°C, vacuum dry to constant weight, crush, and pass through a 100-mesh sieve to obtain carboxyl-modified starch.

[0066] S3. Preparation of sulfonic acid modified butadiene

[0067] Weigh: (E)-but-2-ene-1,4-diamine 20g, 1,3-propane sultone 56g and tetrahydrofuran 200mL, add into nitrogen-protected three-necked flask and stir, raise the temperature of the three-necked flask to 65°C, keep warm and react for 6h, add 0.3mol / L sodium hydroxide solution into the three-necked flask, adjust the system pH to 7, transfer the reaction solution into a rotary evaporator with a water bath temperature of 60°C, remove low boiling points under reduced pressure, and obtain sulfonic acid-modified butadiene.

[0068] S4. Preparation of polyolefin emulsion

[0069] Mix polyvinyl alcohol, AEO-3 and deionized water in a ratio of 2g:3g:80mL to obtain an emulsion for later use;

[0070] Azobisisobutyronitrile and deionized water were mixed uniformly in a weight ratio of 1:8 to obtain an initiator solution for later use;

[0071] Weigh: 30 g of sulfonic acid modified butadiene, 20 g of glycidyl methacrylate, 50 g of sodium acrylate, and 450 mL of emulsion, add into a three-necked flask and stir, raise the temperature of the three-necked flask to 80°C, add 50 g of initiator solution dropwise into the three-necked flask, after the addition is complete, keep warm for 5 hours, lower the temperature of the three-necked flask to room temperature, pass through a 100-mesh sieve to obtain a polyolefin emulsion.

[0072] S5. Preparation of dry strength agent emulsion

[0073] Weigh by weight: 6 parts of carboxyl modified starch, 5 parts of hydroxymethyl chitosan and 45 parts of polyolefin emulsion, add into a three-necked flask and stir, raise the temperature of the three-necked flask to 80° C., stir and disperse for 60 minutes, and cool naturally to room temperature to obtain a dry strength agent emulsion.

[0074] Comparative Example 1

[0075] The difference between this comparative example and Example 3 is that step S1 is eliminated, and the pretreated starch in step S2 is replaced by corn starch in step S1.

[0076] Comparative Example 2

[0077] The difference between this comparative example and Example 3 is that step S1 and step S2 are eliminated, and the carboxyl-modified starch in step S5 is replaced by corn starch in step S1.

[0078] Comparative Example 3

[0079] The difference between this comparative example and Example 3 is that step S3 is eliminated, and the sulfonic acid-modified butadiene in step S4 is replaced by an equimolar amount of sodium fumarate.

[0080] Comparative Example 4

[0081] The difference between this comparative example and Example 3 is that hydroxymethyl chitosan is not added in step S5.

[0082] Performance Test:

[0083] The dry strength agent emulsion prepared in Examples 1-3 and Comparative Examples 1-4 was added to the papermaking pulp at an addition amount of 18 kg / t to prepare paper with a basis weight of 85-87 g / m 2 Papermaking samples;

[0084] The tensile strength and tensile energy absorption index of paper samples were determined according to the standard GB / T12914-2018 "Determination of tensile strength of paper and paperboard - Constant tension method (20 mm / min)";

[0085] The tear index of the papermaking sample was measured with reference to the standard GB / T455-2002 "Determination of tear resistance of paper and paperboard"; the specific test results are shown in Table 1 below.

[0086] Table 1-Performance test data of samples

[0087]

[0088] Data Analysis:

[0089] Comparative analysis of the data in Table 1 above shows that the emulsion type anionic dry strength agent for papermaking prepared by the present invention is added to the papermaking pulp at an addition amount of 18 kg / t, and the tensile strength of the prepared papermaking sample reaches 68.6 kN / m, which is 18.8 kN / m higher than that of the papermaking sample without adding the dry strength agent, and the longitudinal tensile energy absorption index reaches 3.18 J / g, which is 1.33 J / g higher than that of the papermaking sample without adding the dry strength agent, and the transverse tensile energy absorption index reaches 2.81 J / g, which is 1.79 J / g higher than that of the papermaking sample without adding the dry strength agent, and the tear index reaches 22.1 mN·m 2 / g, which is 11.8mN·m higher than that of paper samples without dry strength agent. 2 / g, and all performance test data are better than those of the comparative example. The data show that the present invention prepares anionic dry strength agent emulsion by preparing carboxyl modified starch and hydroxymethyl chitosan to strengthen the polyolefin emulsion containing sulfonate, which not only effectively improves the tensile properties of papermaking samples, but also improves the tear resistance of the samples.

[0090] The above contents are merely examples and explanations of the structure of the present invention. The technicians in this technical field may make various modifications or additions to the specific embodiments described or replace them in a similar manner. As long as they do not deviate from the structure of the invention or exceed the scope defined by the claims, they should all fall within the protection scope of the present invention.

[0091] In the description of this specification, the description with reference to the terms "one embodiment", "example", "specific example", etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0092] The preferred embodiments of the present invention disclosed above are only used to help explain the present invention. The preferred embodiments do not describe all the details in detail, nor do they limit the invention to only specific implementation methods. Obviously, many modifications and changes can be made according to the content of this specification. This specification selects and specifically describes these embodiments in order to better explain the principles and practical applications of the present invention, so that those skilled in the art can understand and use the present invention well. The present invention is limited only by the claims and their full scope and equivalents.

Claims

1. An emulsion type anionic dry strength agent for papermaking, characterized by: The sulfonic acid modified butadiene, glycidyl methacrylate, sodium acrylate and emulsion are mixed and stirred, the temperature of the reaction system is raised to 70-80°C, the initiator solution is added dropwise to the reaction system, and after the addition is completed, the reaction is kept warm for 3-5 hours, and post-processed to obtain a polyolefin emulsion; The sulfonic acid modified butadiene is prepared by mixing (E)-but-2-ene-1,4-diamine, 1,3-propane sultone and tetrahydrofuran, raising the temperature of the reaction system to 55-65° C., keeping the temperature for 4-6 hours, adding sodium hydroxide solution to the reaction system, adjusting the pH of the system to 7, and post-treating to obtain the obtained product; Diethylenetriamine pentaacetic acid, sodium hypophosphite and sodium hydroxide solution are mixed and stirred until the system is dissolved, and the pretreated starch is added to the reaction system, the temperature of the reaction heat exchange medium is increased to 120-130°C, and the reaction is kept warm for 6-8 hours, and post-processed to obtain carboxyl modified starch; Then, 5-6 parts of the carboxyl modified starch prepared in the above step and 40-45 parts of the polyolefin emulsion are mixed by weight, and then 4-5 parts of hydroxymethyl chitosan is added and mixed thoroughly to obtain the emulsion type anionic dry strength agent.

2. The emulsion type anionic dry strength agent for papermaking according to claim 1, characterized in that: The dosage ratio of the sulfonic acid modified butadiene, glycidyl methacrylate, sodium acrylate, emulsion and initiator solution is 3g:2g:5g:45mL:5g, the emulsion is composed of polyvinyl alcohol, AEO-3 and deionized water in a ratio of 2g:3g:80mL, the initiator solution is composed of azobisisobutyronitrile and deionized water in a weight ratio of 1:8, and the post-treatment includes: after the reaction is completed, the temperature of the reaction system is reduced to room temperature, and the mixture is sieved through a 100-mesh screen to obtain a polyolefin emulsion.

3. The emulsion type anionic dry strength agent for papermaking according to claim 1, characterized in that: The amount ratio of the (E)-but-2-ene-1,4-diamine, 1,3-propane sultone and tetrahydrofuran is 1g:2.8g:10mL. The post-treatment comprises: after the reaction is completed, transferring the reaction solution to a rotary evaporator with a water bath temperature of 60°C, and removing low boiling points under reduced pressure to obtain sulfonic acid-modified butadiene.

4. The emulsion type anionic dry strength agent for papermaking according to claim 1, characterized in that: The dosage ratio of diethylenetriamine pentaacetic acid, sodium hypophosphite, sodium hydroxide solution and pretreated starch is 5g:1g:10mL:5g, the concentration of the sodium hydroxide solution is 0.03-0.05mol / L, and the post-treatment comprises: after the reaction is completed, the temperature of the reaction system is lowered to room temperature, purified water is added to the reaction system, and stirred for 20-30min, the filter cake is washed twice with 0.1mol / L hydrochloric acid, and then washed with deionized water until the filtrate is neutral, the filter cake is transferred to a drying oven with a temperature of 70-80°C, and vacuum dried to constant weight to obtain carboxyl modified starch.

5. The emulsion type anionic dry strength agent for papermaking according to claim 4, characterized in that: The preparation method of pretreated starch is as follows: starch and deionized water are mixed, the temperature of the reaction system is increased to 90-96°C, the reaction system is stirred for 60-80 minutes, the temperature of the reaction system is decreased to 60-70°C, anhydrous ethanol is added to the reaction system, the reaction system is stirred for 30-50 minutes, and post-processed to obtain pretreated starch.

6. The emulsion type anionic dry strength agent for papermaking according to claim 5, characterized in that: The starch, deionized water and anhydrous ethanol are used in a ratio of 1 g: 8 mL: 20 mL, the starch is corn starch, and the post-treatment comprises: after the reaction is completed, centrifuging, washing the filter cake with anhydrous ethanol for 3 times, transferring it to a drying oven at a temperature of 70-80° C., and vacuum drying to constant weight to obtain pretreated starch.

7. The method for preparing an emulsion type anionic dry strength agent for papermaking according to any one of claims 1 to 6, characterized in that: The preparation method of the emulsion type anionic dry strength agent for papermaking is as follows: carboxyl modified starch and hydroxymethyl chitosan are added to polyolefin emulsion, the temperature of the reaction system is increased to 70-80°C, the mixture is stirred and dispersed for 40-60 minutes, and the temperature is naturally reduced to room temperature to obtain a dry strength agent emulsion.

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