Modified reinforcing agent as well as preparation method and application thereof

Abstract

The invention discloses a modified reinforcing agent and a preparation method and application thereof.The preparation method comprises the steps that after a guar gum aqueous solution is heated to 30-60 DEG C, chloropropene is added under the alkaline condition, a reaction is conducted for 30-180 min at the temperature of 40-85 DEG C, and a modified guar gum aqueous solution is prepared; adjusting the pH value of the modified guar gum aqueous solution to 3-5; nitrogen is introduced, the temperature is increased to 60-85 DEG C, a first initiator and a monomer mixture aqueous solution with the concentration being 30%-60% are dropwise added, the temperature is controlled to range from 70 DEG C to 95 DEG C, and the first initiator is dropwise added later than the monomer mixture aqueous solution; and dropwise adding a first initiator, keeping the temperature for a period of time, dropwise adding a second initiator, keeping the temperature to react at 80-90 DEG C, and adding a terminating agent to terminate the reaction when the viscosity of the reaction liquid reaches 3000-15000mPa. S, thereby obtaining the modified reinforcing agent. While the paper strength is guaranteed, the retention and drainage assisting effects can be effectively improved.

Description

Technical Field

[0001] The invention relates to the technical field of paper reinforcing agents, and in particular to a modified reinforcing agent and a preparation method and application thereof. Background Art

[0002] In recent years, as waste paper is recycled more and more times, the strength of fiber raw materials has become increasingly poor. At the same time, in order to save energy, reduce emissions and cut costs, more and more manufacturers have added sludge, sawdust, etc. during papermaking, resulting in further reduction in paper strength. For this reason, reinforcing agents need to be added during papermaking to compensate for the strength of the paper.

[0003] In the prior art, cationic starch, polyacrylamide dry strength agent, and cationic guar gum are commonly used as strengthening agents, but the retention rate of cationic starch is low, which can easily cause abnormally high BOD and COD of white water, increasing the cost of white water treatment; cationic guar gum has a low degree of substitution, and has a good retention effect on thin paper, but the strengthening effect is limited; and although the polyacrylamide dry strength agent can effectively enhance the strength of paper, it will affect the water filtration performance. Therefore, it is necessary to study a modified strengthening agent that can improve the comprehensive performance of paper. Summary of the invention

[0004] In order to overcome the above-mentioned shortcomings, the purpose of the present invention is to provide a modifying enhancer and a preparation method and application thereof, which can effectively improve the retention and filtration effects while ensuring the strength of paper.

[0005] In order to achieve the above object, one of the technical solutions adopted by the present invention is: a method for preparing a modified reinforcing agent, comprising the following steps: (1) dissolving a guar gum raw material in water to prepare a guar gum aqueous solution with a concentration of 0.2% to 1.5%, heating the solution to 30 to 60°C, adding an appropriate amount of allyl chloride under alkaline conditions, and reacting the solution at 40 to 85°C for 30 to 180 minutes to obtain a modified guar gum aqueous solution; wherein the mass ratio of allyl chloride to guar gum is 0.05 to 0.3:1; (2) adjusting the pH value of the modified guar gum aqueous solution to between 3 and 5; heating the solution to 60 to 85° C. under nitrogen, and dropping a first initiator and a 30% to 60% monomer mixture aqueous solution respectively, wherein the temperature is controlled between 70 to 95° C. during the dropping process, and the first initiator is dropped later than the monomer mixture aqueous solution; after keeping the temperature for a period of time, dropping a second initiator, and keeping the temperature between 80 and 90° C. for reaction, and when the viscosity of the reaction liquid reaches 3000 to 15000 mPa·s, adding a terminator to terminate the reaction, thereby obtaining a modified enhancer; wherein the mass ratio of the solute in the modified guar gum aqueous solution to the solute in the monomer mixture aqueous solution is 1 to 15:85 to 99; The monomer mixture aqueous solution comprises a first monomer, a second monomer, a third monomer, a cross-linking agent, a molecular weight regulator and water; The first monomer is selected from at least one of acrylamide, methacrylamide, and N,N-dimethylacrylamide; The second monomer is selected from at least one of dimethyldiallylammonium chloride, dimethylaminoethyl acrylate, acryloyloxyethyldimethylbenzylammonium chloride, acryloyloxyethyltrimethylammonium chloride, dimethylaminoethyl methacrylate, methacryloyloxyethyldimethylbenzylammonium chloride, methacryloyloxyethyltrimethylammonium chloride, diethylaminoethyl acrylate, acryloyloxyethyldiethylbenzylammonium chloride, acryloyloxyethylmethyldiethylammonium chloride, diethylaminoethyl methacrylate, methacryloyloxyethyldiethylbenzylammonium chloride, methacryloyloxyethylmethyldiethylammonium chloride, dimethylaminopropylacrylamide, acryloyltrimethylammonium chloride, dimethylaminopropylmethacrylamide, and methacryloyltrimethylammonium chloride; The third monomer is selected from at least one of acrylic acid, methacrylic acid, itaconic acid, maleic acid, maleic anhydride, fumaric acid, fumaric anhydride, 2-acrylamido-2-methylpropane sulfonic acid, sodium vinyl sulfonate, sodium vinylbenzene sulfonate, and styrene sulfonic acid.

[0006] The beneficial effects of the preparation method of a modified reinforcing agent of the present invention are: In step (1), guar gum and allyl chloride can undergo etherification reaction under alkaline conditions to obtain modified guar gum containing carbon-carbon double bonds. Then, step (2) allows the carbon-carbon double bonds (unsaturated monomers) on the modified guar gum to fully undergo free radical polymerization reaction with the unsaturated monomers (first monomer, second monomer, third monomer) in the aqueous solution of the monomer mixture under the action of the first initiator and the second initiator, so as to solve the problem of low graft substitution degree of cationic guar gum in the prior art. In addition, since the first monomer, the second monomer, and the third monomer can provide a large number of amide groups, amino groups, Quaternary ammonium group, carboxyl group, sulfonic acid group, hydroxyl group and other active or cross-linking groups, guar gum can provide hydroxyl group, galacturonic acid and other active or cross-linking groups in free radical polymerization reaction, while amide group and hydroxyl group can hydrogen bond with hydroxyl group in paper fiber, amino group and quaternary ammonium group can ionically bond with carboxyl group on paper fiber, carboxyl group, sulfonic acid group and galacturonic acid can form coordination bond with carboxyl group on paper fiber through aluminum ion, under the action of the above-mentioned multiple binding forces, paper fiber can form a dense three-dimensional network structure, and the junction of the network point is hydrogen bond, ionic bond or coordination bond, thereby effectively enhancing the strength of paper. Therefore, the modified reinforcing agent prepared by the preparation method of the present invention can synergistically exert the enhancement, retention and drainage effects of guar gum and polyacrylamide, and improve the dry strength such as ring crush strength, interlayer bonding strength and bursting resistance of paper.

[0007] Furthermore, the mass ratio of the first monomer, the second monomer, and the third monomer is 65-90:5-30:3-15.

[0008] Further, the total amount of the first initiator and the second initiator is 0.1% to 2% of the mass of the modified enhancer, wherein the amount of the first initiator accounts for 50% to 80% of the total amount of the first initiator and the second initiator, and the amount of the second initiator accounts for 20% to 50% of the total amount of the first initiator and the second initiator. Adding the first initiator and the second initiator separately twice can make the polymerization reaction more thorough and eliminate the residual unsaturated monomers in the reaction solution as much as possible.

[0009] Furthermore, the guar gum raw material is selected from at least one of natural guar gum, hydroxyethyl guar gum, hydroxypropyl guar gum, carboxymethyl guar gum, carboxymethyl hydroxypropyl guar gum, carboxymethyl hydroxyethyl guar gum, cationic guar gum, cationic hydroxypropyl guar gum, cationic hydroxyethyl guar gum and amphoteric guar gum.

[0010] Further, the crosslinking agent is selected from at least one of N,N-methylenebisacrylamide, N-hydroxymethylacrylamide, polyethylene glycol diallyl ether, ethylene glycol dimethacrylate, diethylene glycol dimethacrylate, trimethylolpropane triacrylate, pentaerythritol triallyl ether, pentaerythritol triacrylate, dipentaerythritol hexaallyl ether, dipentaerythritol hexaacrylate, and 1,3,5-triacrylamide-hexahydrotriazine.

[0011] Furthermore, the molecular weight regulator is selected from at least one of sodium hypophosphite, sodium pyrosulfite, sodium sulfite, sodium bisulfite, sodium formate, isopropyl alcohol, sodium propylene sulfonate and sodium methyl propylene sulfonate.

[0012] Furthermore, the first initiator and the second initiator are both water-soluble initiators, and the water-soluble initiator is selected from at least one of ammonium persulfate, sodium persulfate, potassium persulfate, ammonium cerium nitrate, azobisisobutyramidine hydrochloride, azobisisopropylimidazoline hydrochloride, sodium bisulfite, and sodium pyrosulfite.

[0013] Furthermore, the terminator is selected from at least one of sodium sulfite, sodium pyrosulfite, sodium bisulfite, sodium thiosulfate, p-hydroxyanisole, and sodium ascorbate.

[0014] The second technical solution adopted by the present invention is: a modified reinforcing agent, which is prepared by any of the above-mentioned preparation methods. The modified reinforcing agent of the present invention can synergistically exert the reinforcing and retention and filtration effects of guar gum and polyacrylamide, improve the dry strength such as the ring crush strength, interlayer bonding strength and bursting resistance of paper, and is particularly suitable for paper reinforcement scenarios with a large amount of sludge and sawdust added, and has excellent retention and retention effects. At the same time, it is easily biodegradable and green and environmentally friendly.

[0015] The third technical solution adopted by the present invention is: application of the above-mentioned modifying and reinforcing agent in papermaking. DETAILED DESCRIPTION

[0016] The preferred embodiments of the present invention are described in detail below so that the advantages and features of the present invention can be more easily understood by those skilled in the art, thereby making a clearer and more explicit definition of the protection scope of the present invention. It should be noted that the following embodiments are for a better understanding of the present invention, are not limited to the best embodiments, and do not limit the content and protection scope of the present invention. Any product identical or similar to the present invention obtained by anyone under the inspiration of the present invention or by combining the features of the present invention with other prior arts shall fall within the protection scope of the present invention.

[0017] It should be noted that, in the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "illustrative embodiments", "examples", "specific examples", or "some examples" 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 may be combined in any one or more embodiments or examples in a suitable manner.

[0018] In addition, if the specific experimental steps or conditions are not specified in the examples, the operations or conditions of the conventional experimental steps described in the literature in the art can be carried out. The numerical ranges shown by "~" in the examples indicate the ranges containing the values ​​recorded before and after "~" as the minimum and maximum values, respectively. If the manufacturers of the reagents or instruments are not specified, they are all conventional reagent products that can be obtained commercially.

[0019] A method for preparing a modified enhancer of the present invention comprises the following steps: (1) Preparing a modified guar gum aqueous solution containing a carbon-carbon double bond structure: adding water to a reaction kettle, slowly adding a guar gum raw material under stirring, stirring and dissolving to prepare a 0.2% to 1.5% guar gum aqueous solution, heating to between 30 and 60° C., adding alkali, adjusting the pH value to between 9.5 and 11, adding an appropriate amount of allyl chloride dropwise after 5 to 30 minutes, and reacting at 40 to 85° C. for 30 to 180 minutes. During the reaction, the pH value was controlled at 8.5 to 11.0 by adding alkali to obtain a modified guar gum aqueous solution; wherein the mass ratio of allyl chloride to the guar gum raw material is 0.05 to 0.3:1; (2) Preparation of modified enhancer: Add modified guar gum aqueous solution to a reactor, adjust the pH value to between 3 and 5 with acid under stirring; pass nitrogen and heat to 60-85°C, drop the first initiator and monomer mixture aqueous solution (the concentration of the monomer mixture aqueous solution is 30%-60%), wherein the monomer mixture aqueous solution is dripped in 30-120 minutes, the first initiator is dripped in 45-135 minutes, and the first initiator is dripped 15 minutes later than the monomer mixture aqueous solution, and the temperature is controlled between 70-95°C during the dripping process; after the first initiator is dripped, keep the temperature between 82-92°C for 15 minutes, then drop the second initiator, and keep the temperature between 80-90°C for reaction, when the viscosity of the reaction liquid reaches 3000-15000 mPa·s, add a terminator to terminate the reaction, and the modified enhancer is obtained. The mass ratio of the solute of the modified guar gum aqueous solution to the solute of the monomer mixture aqueous solution is 1-15:85-99.

[0020] The monomer mixture aqueous solution includes a first monomer, a second monomer, a third monomer, a crosslinking agent, a molecular weight regulator and water. In the monomer mixture aqueous solution, the mass ratio of the first monomer, the second monomer and the third monomer is 65-90:5-30:3-15.

[0021] The first monomer is selected from at least one of acrylamide, methacrylamide, and N,N-dimethylacrylamide; The second monomer is selected from at least one of dimethyldiallylammonium chloride, dimethylaminoethyl acrylate, acryloyloxyethyldimethylbenzylammonium chloride, acryloyloxyethyltrimethylammonium chloride, dimethylaminoethyl methacrylate, methacryloyloxyethyldimethylbenzylammonium chloride, methacryloyloxyethyltrimethylammonium chloride, diethylaminoethyl acrylate, acryloyloxyethyldiethylbenzylammonium chloride, acryloyloxyethylmethyldiethylammonium chloride, diethylaminoethyl methacrylate, methacryloyloxyethyldiethylbenzylammonium chloride, methacryloyloxyethylmethyldiethylammonium chloride, dimethylaminopropylacrylamide, acryloyltrimethylammonium chloride, dimethylaminopropylmethacrylamide, and methacryloylpropyltrimethylammonium chloride; The third monomer is selected from at least one of acrylic acid, methacrylic acid, itaconic acid, maleic acid, maleic anhydride, fumaric acid, fumaric anhydride, 2-acrylamido-2-methylpropane sulfonic acid, sodium vinyl sulfonate, sodium vinylbenzene sulfonate, and styrene sulfonic acid.

[0022] The crosslinking agent is selected from at least one of N,N-methylenebisacrylamide, N-methylolacrylamide, polyethylene glycol diallyl ether, ethylene glycol dimethacrylate, diethylene glycol dimethacrylate, trimethylolpropane triacrylate, pentaerythritol triallyl ether, pentaerythritol triacrylate, dipentaerythritol hexaallyl ether, dipentaerythritol hexaacrylate, and 1,3,5-triacrylamide-hexahydrotriazine. Furthermore, the amount of the crosslinking agent is 0.01% to 0.5% of the mass of the modified enhancer.

[0023] The molecular weight regulator is selected from at least one of sodium hypophosphite, sodium pyrosulfite, sodium sulfite, sodium bisulfite, sodium formate, isopropyl alcohol, sodium propylene sulfonate and sodium methpropylene sulfonate.

[0024] In some embodiments, in step (1), the guar gum raw material is selected from at least one of natural guar gum, hydroxyethyl guar gum, hydroxypropyl guar gum, carboxymethyl guar gum, carboxymethyl hydroxypropyl guar gum, carboxymethyl hydroxyethyl guar gum, cationic guar gum, cationic hydroxypropyl guar gum, cationic hydroxyethyl guar gum, and amphoteric guar gum. The base is selected from at least one of sodium hydroxide, potassium hydroxide, sodium methoxide, and sodium ethoxide.

[0025] In step (2), the acid is selected from at least one of hydrochloric acid, sulfuric acid, phosphoric acid, nitric acid, formic acid, acetic acid, and citric acid. The first initiator and the second initiator are both water-soluble initiators, and the water-soluble initiator is selected from at least one of ammonium persulfate, sodium persulfate, potassium persulfate, ammonium cerium nitrate, azobisisobutylamidine hydrochloride, azobisisopropylimidazoline hydrochloride, sodium bisulfite, and sodium pyrosulfite. The terminator is selected from at least one of sodium sulfite, sodium pyrosulfite, sodium bisulfite, sodium thiosulfate, p-hydroxyanisole, and sodium ascorbate.

[0026] Furthermore, the total amount of the first initiator and the second initiator is 0.1% to 2% of the mass of the modified enhancer, wherein the amount of the first initiator accounts for 50% to 80% of the total amount of the first initiator and the second initiator, and the amount of the second initiator accounts for 20% to 50% of the total amount of the first initiator and the second initiator. Adding the first initiator and the second initiator separately twice can make the polymerization reaction more thorough and eliminate the residual unsaturated monomers in the reaction solution as much as possible.

[0027] Example 1 The modified reinforcing agent was prepared as follows: Add 980 parts of deionized water to a reactor equipped with a stirrer, a thermometer, and a reflux condenser, start stirring, add 10 parts of natural guar gum, stir and dissolve, heat to 40°C, add 7.5 parts of 48% sodium hydroxide solution, adjust the pH value to 10.5, react for 15 minutes, drop 2.5 parts of propylene chloride, and drip it within 5 minutes, add 48% sodium hydroxide solution in time to control the pH value of the system between 9.5 and 10.5, react at 60°C for 75 minutes, and obtain a modified guar gum aqueous solution with a solid content of 1.8%; 100 parts of deionized water and 500 parts of a modified guar gum aqueous solution with a solid content of 1.8% are added to a reactor, and the pH value is adjusted to 3.2 with 20% sulfuric acid under stirring, nitrogen is passed, the temperature is raised to 75°C, 20 parts of a 5% ammonium persulfate aqueous solution and 280 parts of a monomer mixture aqueous solution are added dropwise, the monomer mixture aqueous solution is added dropwise within 90 minutes, and the ammonium persulfate aqueous solution is added dropwise within 105 minutes. During the dropping process, the temperature is controlled between 75 and 93°C, and after the dropping is completed, the temperature is kept between 82 and 92°C for 15 minutes, 10 parts of a 5% ammonium persulfate aqueous solution is added, and the reaction is kept between 80 and 90°C. When the viscosity of the reaction liquid reaches 6800 mPa·s, sodium sulfite is added to terminate the reaction, and a modified enhancer with a solid content of 15.3% is obtained. The monomer mixture aqueous solution includes 220 parts of 50% acrylamide aqueous solution, 6 parts of dimethylaminoethyl methacrylate, 8 parts of methacryloyloxyethyl dimethylbenzyl ammonium chloride, 10 parts of acryloyloxyethyl trimethyl ammonium chloride, 7.5 parts of itaconic acid, 0.05 parts of N,N-methylenebisacrylamide, 4.8 parts of sodium methacrylate sulfonate, and the balance is deionized water.

[0028] Example 2 The modified reinforcing agent was prepared as follows: Add 970 parts of deionized water to a reactor equipped with a stirrer, a thermometer, and a reflux condenser, start stirring, add 12 parts of carboxymethyl hydroxypropyl guar gum, stir and dissolve, heat to 45°C, add 12 parts of 30% potassium hydroxide solution, adjust the pH value to 11, react for 20 minutes, drop 2 parts of propylene chloride, and drip it within 10 minutes, add 30% sodium hydroxide solution in time to control the pH value of the system between 10.0 and 10.8, react at 60°C for 120 minutes, and obtain a modified guar gum aqueous solution with a solid content of 1.9%; 200 parts of deionized water and 400 parts of a modified guar gum aqueous solution with a solid content of 1.9% are added to a reactor, and the pH value is adjusted to 3.5 with 15% hydrochloric acid under stirring, nitrogen is passed, the temperature is raised to 78°C, 30 parts of a 5% sodium persulfate aqueous solution and 297.5 parts of a monomer mixture aqueous solution are added dropwise, the monomer mixture aqueous solution is added dropwise within 75 minutes, and the sodium persulfate aqueous solution is added dropwise within 90 minutes. During the dropping process, the temperature is controlled between 78 and 92°C, and after the dropping is completed, the temperature is kept at 85 to 91°C for 15 minutes, 10 parts of a 5% sodium persulfate aqueous solution is added, and the reaction is kept at 83 to 88°C. When the viscosity of the reaction liquid reaches 5500 mPa·s, sodium pyrosulfite is added to terminate the reaction, and a modified enhancer with a solid content of 15.7% is obtained. The aqueous solution of the monomer mixture includes 230 parts of a 50% acrylamide aqueous solution, 8 parts of dimethylaminoethyl acrylate, 4 parts of dimethyldiallyl ammonium chloride, 12 parts of methacryloyloxyethyltrimethylammonium chloride, 4.5 parts of acrylic acid, 4.5 parts of 2-acrylamido-2-methylpropanesulfonic acid, 0.02 parts of pentaerythritol triallyl ether, 5.5 parts of sodium methacrylic acid, and the balance is deionized water.

[0029] Example 3 The modified reinforcing agent was prepared as follows: Add 970 parts of deionized water to a reactor equipped with a stirrer, a thermometer, and a reflux condenser, start stirring, add 15 parts of carboxymethyl hydroxypropyl guar gum, stir and dissolve, heat to 35°C, add 1 part of sodium ethoxide, adjust the pH value to 10.0, react for 30 minutes, drop 2.8 parts of propylene chloride, and drip it within 15 minutes, add 48% sodium hydroxide solution in time to control the pH value of the system between 9.8 and 10.8, react at 70°C for 60 minutes, and obtain a modified guar gum aqueous solution with a solid content of 2.2%; 200 parts of deionized water and 320 parts of a modified guar gum aqueous solution with a solid content of 2.2% are added to a reactor, and the pH value is adjusted to 3.8 with 50% phosphoric acid under stirring, nitrogen is passed, the temperature is raised to 78°C, 30 parts of a 5% ammonium persulfate aqueous solution and 281.3 parts of a monomer mixture aqueous solution are added dropwise, the monomer mixture aqueous solution is added dropwise within 105 minutes, and the ammonium persulfate aqueous solution is added dropwise within 120 minutes. During the dropping process, the temperature is controlled between 80 and 95°C, and after the dropping is completed, the temperature is kept between 85 and 90°C for 15 minutes, 8 parts of a 5% azobisisobutylamidine hydrochloride aqueous solution is added, and the reaction is kept between 85 and 89°C. When the viscosity of the reaction liquid reaches 5300 mPa·s, sodium pyrosulfite is added to terminate the reaction, and a modified enhancer with a solid content of 14.9% is obtained. The aqueous solution of the monomer mixture includes 220 parts of a 50% acrylamide aqueous solution, 1.5 parts of N,N-dimethylacrylamide, 10 parts of dimethyldiallyl ammonium chloride, 5 parts of methacryloyloxyethyltrimethylammonium chloride, 5 parts of dimethylaminopropyl methacrylamide, 6.5 parts of acrylic acid, 1.0 part of itaconic acid, 0.02 parts of pentaerythritol triallyl ether, 0.01 parts of polyethylene glycol diallyl ether, 5.8 parts of sodium methacrylic acid, and the balance is deionized water.

[0030] Comparative Example 1 The cationic guar gum grafted polyacrylamide reinforcing agent was prepared as follows: 600 parts of deionized water were added into the reactor, stirring was started, and 5 parts of cationic guar gum (Rhodia C-16, France) were slowly added. After complete dissolution, the pH value was adjusted to 3.2 with 20% sulfuric acid, nitrogen was passed, the temperature was raised to 75°C, 20 parts of 5% ammonium persulfate aqueous solution and 280 parts of monomer mixture aqueous solution were added dropwise, the monomer mixture aqueous solution was dripped within 90 minutes, and the 5% ammonium persulfate aqueous solution was dripped within 105 minutes. During the dripping process, the temperature was controlled between 75 and 93°C; after dripping, the temperature was kept between 82 and 92°C for 15 minutes, 10 parts of 5% ammonium persulfate aqueous solution were added, and the reaction was continued at 80 to 90°C. When the viscosity reached 8000mPa.s, sodium sulfite was added to terminate the reaction, and a cationic guar gum grafted polyacrylamide enhancer with a solid content of 15.2% was obtained. The aqueous solution of the monomer mixture includes 220 parts of 50% acrylamide aqueous solution, 5 parts of dimethylaminoethyl methacrylate, 8 parts of methacryloyloxyethyl dimethylbenzyl ammonium chloride, 10 parts of acryloyloxyethyl trimethyl ammonium chloride, 7.5 parts of itaconic acid, 0.05 parts of N,N-methylenebisacrylamide, 4.8 parts of sodium methacrylate sulfonate, and the balance is deionized water.

[0031] Comparative Example 2 The compound reinforcing agent of cationic guar gum and acrylamide dry strength agent was prepared according to the following steps: 170 parts of deionized water were added into the reactor, stirring was started, 5 parts of cationic guar gum were slowly added into the reactor, after stirring and dissolving completely, 725 parts of HM-2900 dry strength agent were added, and stirring was continued to be uniform, thus obtaining a composite reinforcing agent with a solid content of 15%.

[0032] Comparative Example 3 The amphoteric polyacrylamide dry strength agent sold by Hangzhou Harima Company was used as the reinforcing agent, wherein the solid content was 20%, and the product model was HM-2900.

[0033] Application Examples The modified reinforcing agents prepared in Examples 1-3 and the reinforcing agents in Comparative Examples 1-3 were evaluated for application, and the addition amount was 3.0 kg / t paper on an absolute dry basis. The test items included paper strength performance, water filtration, and ash retention.

[0034] The pulp used for sheet making is waste paper pulp, wood fiber, and papermaking sludge, with a mass percentage of 87:10:3 and a beating degree of 31°SR. The pulp concentration is diluted to 1.0% with tap water, and the filler is added in an amount of 15%. The sheet is made into 0.03m thick sheets using a KRK2542-A semi-automatic sheet former (KRK, Japan). 2 Round paper sheet, paper weight is 100g / m 2 After being dried in a rotary dryer and balanced under standard temperature and humidity conditions for 24 hours, the paper was tested for its ring crush index, internal bonding strength and bursting strength, water filtration (Canadian freeness meter) and ash content. The test results are shown in Table 1.

[0035] Table 1 Test results of paper properties of Examples 1-3 and Comparative Examples 1-3

[0036] According to Table 1, we can see that: 1. Under the same dosage, the ring crush index, internal bonding strength and bursting index of the modified reinforcing agent prepared by using Examples 1-3 of the present invention are better than those of Comparative Examples 1-3, which shows that the modified reinforcing agent of the present invention has a better reinforcing effect on the strength of paper; the water filtration amount of the modified reinforcing agent prepared by using Examples 1-3 of the present invention is significantly greater than that of Comparative Examples 1-3, and the grayscale is also significantly higher than that of Comparative Examples 1-3, which shows that the modified reinforcing agent of the present invention has better retention and filtration effects.

[0037] 2. According to the test results of Example 1 and Comparative Example 1, it can be known that in Comparative Example 1, cationic guar gum is directly grafted and copolymerized onto polyacrylamide. Although the copolymerization reaction can synergistically exert the enhancement, retention and drainage effects of guar gum and polyacrylamide, the cationic guar gum lacks unsaturated groups such as carbon-carbon double bonds, resulting in a low grafting rate of the cationic guar gum and a low degree of polymerization between the cationic guar gum and the polyacrylamide, thereby affecting the final enhancement effect.

[0038] 3. According to the test results of Example 1 and Comparative Example 2, the cationic guar gum and the polyacrylamide dry strength agent are directly compounded for use in Comparative Example 2. Since the guar gum and the polyacrylamide do not undergo a polymerization reaction, the reinforcing agent of Comparative Example 2 can only play the reinforcing role of the cationic guar gum and the polyacrylamide dry strength agent separately, and cannot achieve a synergistic reinforcing effect.

[0039] 4. According to the test results of Example 1 and Comparative Example 3, it can be seen that Comparative Example 3 directly uses polyacrylamide dry strength agent, and its enhancement, retention and drainage effects are far lower than those of Example 1.

[0040] It can be seen that the modified reinforcing agent prepared by the preparation method of the present invention first modifies guar gum through step (1) to obtain modified guar gum with an unsaturated monomer carbon-carbon double bond structure, thereby solving the problem of low graft substitution rate of guar gum; and then through step (2), the modified guar gum with a carbon-carbon double bond structure can be grafted and copolymerized with the unsaturated monomer in the monomer mixture, so as to synergistically exert the reinforcing, drainage and retention effects of guar gum and polyacrylamide.

[0041] The above implementation modes are only for illustrating the technical concept and features of the present invention, and their purpose is to enable people familiar with this technology to understand the content of the present invention and implement it, and they cannot be used to limit the protection scope of the present invention. Any equivalent changes or modifications made according to the spirit of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for preparing a modifying enhancer, characterized in that: The steps include: (1) dissolving a guar gum raw material in water to prepare a guar gum aqueous solution with a concentration of 0.2% to 1.5%, heating the temperature to 30 to 60°C, adding an appropriate amount of allyl chloride under alkaline conditions, and reacting the mixture at 40 to 85°C for 30 to 180 minutes to obtain a modified guar gum aqueous solution; wherein the mass ratio of allyl chloride to the guar gum raw material is 0.05 to 0.3:1; (2) adjusting the pH value of the modified guar gum aqueous solution to between 3 and 5; heating the solution to 60 to 85° C. under nitrogen, and dropping a first initiator and a 30% to 60% monomer mixture aqueous solution respectively, wherein the temperature is controlled between 70 to 95° C. during the dropping process, and the first initiator is dropped later than the monomer mixture aqueous solution; after keeping the temperature for a period of time, dropping a second initiator, and keeping the temperature between 80 and 90° C. for reaction, and when the viscosity of the reaction liquid reaches 3000 to 15000 mPa·s, adding a terminator to terminate the reaction, thereby obtaining a modified enhancer; wherein the mass ratio of the solute in the modified guar gum aqueous solution to the solute in the monomer mixture aqueous solution is 1 to 15:85 to 99; The monomer mixture aqueous solution comprises a first monomer, a second monomer, a third monomer, a cross-linking agent, a molecular weight regulator and water; The first monomer is selected from at least one of acrylamide, methacrylamide, and N,N-dimethylacrylamide; The second monomer is selected from at least one of dimethyldiallylammonium chloride, dimethylaminoethyl acrylate, acryloyloxyethyldimethylbenzylammonium chloride, acryloyloxyethyltrimethylammonium chloride, dimethylaminoethyl methacrylate, methacryloyloxyethyldimethylbenzylammonium chloride, methacryloyloxyethyltrimethylammonium chloride, diethylaminoethyl acrylate, acryloyloxyethyldiethylbenzylammonium chloride, acryloyloxyethylmethyldiethylammonium chloride, diethylaminoethyl methacrylate, methacryloyloxyethyldiethylbenzylammonium chloride, methacryloyloxyethylmethyldiethylammonium chloride, dimethylaminopropylacrylamide, acryloyltrimethylammonium chloride, dimethylaminopropylmethacrylamide, and methacryloyltrimethylammonium chloride; The third monomer is selected from at least one of acrylic acid, methacrylic acid, itaconic acid, maleic acid, maleic anhydride, fumaric acid, fumaric anhydride, 2-acrylamido-2-methylpropane sulfonic acid, sodium vinyl sulfonate, sodium vinylbenzene sulfonate, and styrene sulfonic acid.

2. The method for preparing the modifying and reinforcing agent according to claim 1, characterized in that: The mass ratio of the first monomer, the second monomer and the third monomer is 65-90:5-30:3-15.

3. The method for preparing the modifying and reinforcing agent according to claim 1, characterized in that: The total amount of the first initiator and the second initiator is 0.1% to 2% of the mass of the modified enhancer, wherein the amount of the first initiator accounts for 50% to 80% of the total amount of the first initiator and the second initiator, and the amount of the second initiator accounts for 20% to 50% of the total amount of the first initiator and the second initiator.

4. The method for preparing the modifying and reinforcing agent according to claim 1, characterized in that: The guar gum raw material is selected from at least one of natural guar gum, hydroxyethyl guar gum, hydroxypropyl guar gum, carboxymethyl guar gum, carboxymethyl hydroxypropyl guar gum, carboxymethyl hydroxyethyl guar gum, cationic guar gum, cationic hydroxypropyl guar gum, cationic hydroxyethyl guar gum and amphoteric guar gum.

5. The method for preparing the modifying and enhancing agent according to claim 1, characterized in that: The crosslinking agent is selected from at least one of N,N-methylenebisacrylamide, N-hydroxymethylacrylamide, polyethylene glycol diallyl ether, ethylene glycol dimethacrylate, diethylene glycol dimethacrylate, trimethylolpropane triacrylate, pentaerythritol triallyl ether, pentaerythritol triacrylate, dipentaerythritol hexaallyl ether, dipentaerythritol hexaacrylate, and 1,3,5-triacrylamide-hexahydrotriazine.

6. The method for preparing the modifying and enhancing agent according to claim 1, characterized in that: The molecular weight regulator is selected from at least one of sodium hypophosphite, sodium pyrosulfite, sodium sulfite, sodium bisulfite, sodium formate, isopropyl alcohol, sodium propylene sulfonate and sodium methyl propylene sulfonate.

7. The method for preparing the modifying and enhancing agent according to claim 1, characterized in that: The first initiator and the second initiator are both water-soluble initiators, and the water-soluble initiator is selected from at least one of ammonium persulfate, sodium persulfate, potassium persulfate, ammonium cerium nitrate, azobisisobutyramidine hydrochloride, azobisisopropylimidazoline hydrochloride, sodium bisulfite, and sodium pyrosulfite.

8. The method for preparing the modifying and enhancing agent according to claim 1, characterized in that: The terminator is selected from at least one of sodium sulfite, sodium pyrosulfite, sodium bisulfite, sodium thiosulfate, p-hydroxyanisole, and sodium ascorbate.

9. A modifying and reinforcing agent, characterized in that: The method is prepared by any one of claims 1 to 8.

10. Use of the modifying and reinforcing agent according to claim 9 in papermaking.

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