阅读说明：本技术 一种纸张增强剂的制备方法 (Preparation method of paper reinforcing agent ) 是由 陈文新 杨文杰 董雪峰 于 2021-10-29 设计创作，主要内容包括：本发明涉及一种纸张增强剂的制备方法,其包括以下步骤,先将第一份反应单体和第一份助剂投入共聚容器中,然后将第二份反应单体和第二份助剂投入共聚容器中,再采用氮气对共聚容器解除真空并充压,向共聚容器内滴加偶氮引发剂,当共聚容器内反应物粘度达到8000mPa·s时,向共聚容器内加入终止剂1-10份,停止共聚反应,得到纸张增强剂。本发明在丙烯酰胺单体和阳离子单体的基础上,加入适当的链转移剂、交联剂、过氧化物引发剂和偶氮引发剂来控制共聚过程的交联程度,并通过分批添加共聚反应单体和助剂进行分步共聚,最终获得抗干扰能力强、交联程度高、流动性好、共聚物中分子结构中阳离子分布均匀、应用性能优越的纸张增强剂。(The invention relates to a preparation method of a paper reinforcing agent, which comprises the following steps of firstly putting a first part of reaction monomer and a first part of auxiliary agent into a copolymerization container, then putting a second part of reaction monomer and a second part of auxiliary agent into the copolymerization container, then adopting nitrogen to remove vacuum and pressurize the copolymerization container, dropwise adding an azo initiator into the copolymerization container, adding 1-10 parts of a terminator into the copolymerization container when the viscosity of reactants in the copolymerization container reaches 8000mPa & s, and stopping copolymerization reaction to obtain the paper reinforcing agent. According to the invention, on the basis of acrylamide monomers and cationic monomers, proper chain transfer agents, crosslinking agents, peroxide initiators and azo initiators are added to control the crosslinking degree in the copolymerization process, and copolymerization reaction monomers and auxiliaries are added in batches to carry out fractional copolymerization, so that the paper reinforcing agent with strong anti-interference capability, high crosslinking degree, good fluidity, uniform distribution of cations in molecular structures in the copolymer and excellent application performance is finally obtained.)

1. A preparation method of a paper reinforcing agent is characterized by comprising the following steps: comprises the following steps of (a) carrying out,

s1 taking a proper amount of deionized water, 65-75 parts of acrylamide monomer, 30-60 parts of cationic monomer, 1-10 parts of chain transfer agent, 0.5-1.0 part of cross-linking agent and 1-3 parts of peroxide initiator, putting the raw materials into a storage container in sequence under the stirring condition of 15-25r/min, then adjusting the pH value to 2.7-3.0 by using aerobic acid, and stirring for 10-15min to obtain a reaction monomer with the raw material content of 15%;

s2, preheating a copolymerization container to 60 ℃, putting a first part of reaction monomer and a first part of auxiliary agent into the copolymerization container under the stirring condition of 15-25r/min, heating to 65-70 ℃ under static normal pressure, gradually increasing the vacuum degree of the copolymerization container to 80 +/-2 Pa in the process, and carrying out copolymerization reaction for 2-3h when the temperature in the copolymerization container reaches 75 +/-2 ℃;

s3, adding a second part of reaction monomer and a second part of auxiliary agent into a copolymerization container, continuously stirring for 5-10min, then removing vacuum of the copolymerization container by adopting nitrogen, pressurizing to 0.15 +/-0.02 MPa, and statically heating to 80-85 ℃ under normal pressure; in the process, 1-10 parts of azo initiator is dripped into the copolymerization container for 0.5-1.0h, and then the heat preservation reaction is continued at the temperature of 85 +/-2 ℃ to obtain polyacrylamide resin;

s4 when the viscosity of the reactant in the copolymerization container reaches 8000 mPa.s, adding 1-10 parts of a terminator into the copolymerization container, and stopping the copolymerization reaction to obtain the paper reinforcing agent.

2. The method for preparing a paper strength agent according to claim 1, characterized in that: in the step S2, 100 parts of the reactive monomer and 40 parts of the auxiliary agent are divided into two parts in advance, and the weight ratio of the first part of the reactive monomer to the second part of the reactive monomer is (1-3): 1, the weight ratio of the first part of auxiliary agent to the second part of auxiliary agent is (1-4): 1.

3. the method for preparing a paper strength agent according to claim 1, characterized in that: the acrylamide monomer is acrylamide, methacrylamide or derivatives thereof; the cationic monomer is ethylene amine, allyl amine, methacryloyloxyethyl trimethyl ammonium chloride, methacryloyloxypropyl trimethyl ammonium chloride, dimethyl diallyl ammonium chloride, dimethylaminoethyl methacrylate or dimethylamino propyl methacrylamide.

4. The method for preparing a paper strength agent according to claim 1, characterized in that: the chain transfer agent is sodium pantetheine sulfonate, sodium allylsulfonate, ethanolamine, sodium formate or sodium phosphate; the cross-linking agent is N, N-dimethylacrylamide, N-diallyl acrylamide and vinyl toluene.

5. The method for preparing a paper strength agent according to claim 1, characterized in that: the peroxide initiator is persulfate/sodium bisulfite; the azo initiator is azobisisobutyronitrile, azobis (2-methylpropionamidine), 2-azo-bis (2-amidinopropane) hydrochloride, 1- ((cyano-1-methylethyl) azo) formamide, dimethyl 2, 2' -azobisisobutyrate or azobis (N-aminoethyl) butylamidine; the terminator is sodium sulfite or sodium bisulfite.

6. The method for preparing a paper strength agent according to claim 1, characterized in that: the organic acid is sulfuric acid, formic acid or maleic acid.

7. The method for preparing a paper strength agent according to claim 1, characterized in that: the auxiliary agent is prepared by taking 15-25 parts of aluminide, 4-6 parts of viscosity regulator, 1.5-2.0 parts of bulking agent, 1-2 parts of cosolvent and 0.1-1.0 part of antioxidant, sequentially putting the raw materials into a storage container under the stirring condition of 15-25r/min, adding the raw materials to 40 parts by deionized water, and continuously stirring for 10-15min to obtain the auxiliary agent.

8. The method for preparing a paper strengthening agent according to claim 7, wherein: the aluminide is aluminum sulfate, aluminum chloride, aluminum acetate or aluminum myristate.

9. The method for preparing a paper strengthening agent according to claim 7, wherein: the viscosity modifier comprises a cellulose ether; the bulking agent comprises gaseous aluminum oxide; the cosolvent is N, N-dimethylacetamide and acetone in a volume ratio of 1: 1.

10. The method for preparing a paper strengthening agent according to claim 7, wherein: the antioxidant is tetra [ beta- (3, 5-di-tert-butyl-4-hydroxyphenyl) propionic acid ] pentaerythritol ester, tri [2, 4-di-tert-butylphenyl ] phosphite, 2-thiobis (4-methyl-6-tert-butylphenol) or [ beta- (3, 5-di-tert-butyl-4-hydroxyphenyl) propionic acid ] octadecanol.

Technical Field

The invention relates to the technical field of paper reinforcing agents, in particular to a preparation method of a paper reinforcing agent.

Background

Under the influence of regulation and control of various policies such as national environmental protection, imported waste paper management and the like, production raw materials used by domestic paper-making enterprises gradually turn to domestic waste paper, the quality of secondary fiber raw materials used by the paper-making enterprises is greatly reduced due to the defects of the domestic waste paper in the recovery process, certain indexes of physical strength performance of paper are provided by the strength of the fiber, especially the damage pressure resistance is greatly reduced, the quality of base paper is reduced, and the subsequent base paper processing and application are greatly influenced. In order to solve the problems, the research starts from the actual problems faced by the paper-making enterprises at present, and through continuous research and exploration, the invention provides the polyacrylamide reinforcing agent which has excellent paper breakage resistance reinforcing effect under the condition of using papermaking waste of the whole second country.

Chinese patent with the publication number of CN111848863B discloses an amphoteric polyacrylamide paper reinforcing agent and a preparation method thereof, wherein in a reaction system of AM, DMAA, SMAS, EDTA and AA, a cationic monomer acryloyl morpholine ACMO with a six-membered ring and without ester bonds is introduced to replace a conventional cationic monomer, and a vinyl monomer AGE or GMA with epoxy groups is introduced to obtain the papermaking reinforcing agent.

The above prior art solutions have the following drawbacks: in the preparation process of initiating copolymerization of the amphoteric high-molecular multi-component copolymer, because reactivity ratios of a plurality of monomers of negative ions and positive ions are greatly different, the reaction system of the method is difficult to completely copolymerize, and the amphoteric high-molecular multi-component copolymer with the positive ions uniformly distributed in a high-polymer molecular structure cannot be obtained.

Disclosure of Invention

The problem to be solved by the invention is to provide a preparation method of a paper reinforcing agent aiming at the defects in the prior art, which achieves the purpose of complete copolymerization by stepwise copolymerization and controlling the crosslinking degree in the copolymerization process, and solves the problem that the reinforcing performance of the paper reinforcing agent is reduced due to uneven distribution of cations in the amphoteric high polymer multipolymer prepared by the prior method.

The above object of the present invention is achieved by the following technical solutions:

s1 takes a proper amount of deionized water, 65-75 parts of acrylamide monomer, 30-60 parts of cationic monomer, 1-10 parts of chain transfer agent, 0.5-1.0 part of cross-linking agent and 1-3 parts of peroxide initiator, and the raw materials are put into a storage container in turn under the stirring condition of 15-25r/min, then aerobic acid is used for adjusting the pH value to 2.7-3.0, and stirring is carried out for 10-15min, so as to obtain a reaction monomer with the raw material content of 15%; s2, preheating a copolymerization container to 60 ℃, putting a first part of reaction monomer and a first part of auxiliary agent into the copolymerization container under the stirring condition of 15-25r/min, heating to 65-70 ℃ under static normal pressure, gradually increasing the vacuum degree of the copolymerization container to 80 +/-2 Pa in the process, and carrying out copolymerization reaction for 2-3h when the temperature in the copolymerization container reaches 75 +/-2 ℃; s3, adding a second part of reaction monomer and a second part of auxiliary agent into a copolymerization container, continuously stirring for 5-10min, then removing vacuum of the copolymerization container by adopting nitrogen, pressurizing to 0.15 +/-0.02 MPa, and statically heating to 80-85 ℃ under normal pressure; in the process, 1-10 parts of azo initiator is dripped into the copolymerization container for 0.5-1.0h, and then the heat preservation reaction is continued at the temperature of 85 +/-2 ℃ to obtain polyacrylamide resin; s4 when the viscosity of the reactant in the copolymerization container reaches 8000 mPa.s, adding 1-10 parts of a terminator into the copolymerization container, and stopping the copolymerization reaction to obtain the paper reinforcing agent.

By adopting the technical scheme, on the basis of an acrylamide monomer and a cationic monomer, a proper chain transfer agent, a crosslinking agent, a peroxide initiator and an azo initiator are added to control the crosslinking degree in the copolymerization process, and a copolymerization monomer and an auxiliary agent are added in batches for stepwise copolymerization, so that the polyacrylamide resin content in the later stage of the copolymerization reaction is in a stable rising state, and a terminator is added to control the end point of the copolymerization reaction, further the reaction system of the method can be completely copolymerized, the polyacrylamide resin with cations uniformly distributed in a high polymer molecular structure can be obtained, the problem that the original paper reinforcing agent is easy to break in a molecular chain structure under the action of shearing force is directly solved, and the paper reinforcing agent with strong anti-interference capability, high crosslinking degree, good fluidity and excellent application performance is finally obtained.

Further, in S2, 100 parts of the reactive monomer and 40 parts of the auxiliary agent are divided into two parts in advance, and the weight ratio of the first part of the reactive monomer to the second part of the reactive monomer is (1-3): 1, the weight ratio of the first part of auxiliary agent to the second part of auxiliary agent is (1-4): 1. the copolymerization reaction is carried out at the proportion, and the polyacrylamide resin content and the reaction time have good linear relation at the later stage of the copolymerization reaction.

Further, the acrylamide monomer is acrylamide, methacrylamide or a derivative thereof; the cationic monomer is ethylene amine, allyl amine, methacryloyloxyethyl trimethyl ammonium chloride, methacryloyloxypropyl trimethyl ammonium chloride, dimethyl diallyl ammonium chloride, dimethylaminoethyl methacrylate or dimethylamino propyl methacrylamide. Acrylamide is preferably used as the acrylamide monomer and dimethyldiallylammonium chloride as the cationic monomer.

Further, the chain transfer agent is sodium pantetheine sulfonate, sodium allyl sulfonate, ethanolamine, sodium formate or sodium phosphate; the cross-linking agent is N, N-dimethylacrylamide, N-diallyl acrylamide and vinyl toluene. It is preferred to use sodium pantetheine sulfonate as chain transfer agent and N, N-diallylacrylamide as crosslinking agent.

Further, the peroxide initiator is persulfate/sodium bisulfite; the azo initiator is azobisisobutyronitrile, azobis (2-methylpropionamidine), 2-azo-bis (2-amidinopropane) hydrochloride, 1- ((cyano-1-methylethyl) azo) formamide, dimethyl 2, 2' -azobisisobutyrate or azobis (N-aminoethyl) butylamidine; the terminator is sodium sulfite or sodium bisulfite. Ammonium persulfate, potassium persulfate or sodium persulfate/and sodium bisulfite are preferably used as the peroxide initiator, 2, 2-azo-bis (2-amidinopropane) hydrochloride as the azo initiator, and sodium sulfite as the terminator. The peroxide initiators are used as the initiators in the early stage of the copolymerization reaction, and the azo initiators are used as the initiators in the later stage of the copolymerization reaction, so that the copolymerization rate in the later stage of the copolymerization reaction is improved, the residues of acrylamide monomers and cationic monomers are reduced, and the performance of the paper reinforcing agent is greatly improved.

Further, the organic acid is sulfuric acid, formic acid or maleic acid. Formic acid is preferably used as the aerobic acid to adjust the pH.

Further, the auxiliary agent is prepared by taking 15-25 parts of aluminide, 4-6 parts of viscosity regulator, 1.5-2.0 parts of bulking agent, 1-2 parts of cosolvent and 0.1-1.0 part of antioxidant, sequentially putting the raw materials into a storage container under the stirring condition of 15-25r/min, adding 40 parts of deionized water, and continuously stirring for 10-15min to obtain the auxiliary agent.

Specifically, the aluminide is aluminum sulfate, aluminum chloride, aluminum acetate or aluminum myristate. Aluminum myristate is preferably used as aluminide. Aluminum ions in the aluminum myristate can be used as a special structural auxiliary agent, and the aluminum ions react with the polyacrylamide resin to generate an interpenetrating network structure, so that the cation density and the distribution uniformity of the copolymer are improved, and the paper reinforcing agent has better anti-interference capability.

Specifically, the viscosity modifier comprises a cellulose ether; the bulking agent comprises gaseous aluminum oxide; the cosolvent is N, N-dimethylacetamide and acetone in a volume ratio of 1: 1. Firstly, the cosolvent can promote the dissolution and mixing of all components in the raw material of the paper strengthening agent, and the water solubility of the paper strengthening agent is improved; then the high molecular structure of the cellulose ether can adsorb redundant deionized water and form a spatial three-dimensional network structure, so that the workability of the paper reinforcing agent is improved, and the polyacrylamide resin has a stable structure and is not easy to break; finally, the positive electricity tendency of the paper reinforcing agent is enhanced by the gas-phase aluminum oxide, the looseness of the paper reinforcing agent is favorably improved, and the oxidation reaction among partial raw materials is preliminarily inhibited, so that the acrylamide monomer and the cationic monomer are more uniformly dispersed, and the polyacrylamide resin with the cations uniformly distributed in the molecular structure of the high polymer is obtained.

Specifically, the antioxidant is pentaerythritol tetrakis [ β - (3, 5-di-tert-butyl-4-hydroxyphenyl) propionate ], tris [2, 4-di-tert-butylphenyl ] phosphite, 2-thiobis (4-methyl-6-tert-butylphenol) or octadecanol [ β - (3, 5-di-tert-butyl-4-hydroxyphenyl) propionate ]. Tetrakis- [ beta- (3, 5-di-tert-butyl-4-hydroxyphenyl) propanoic acid ] pentaerythritol ester is preferably used as antioxidant. Because the color of the paper reinforcing agent product is greatly influenced by the copolymerization reaction time, the oxidation reaction among part of raw materials is further carried out all the time by adopting the antioxidant, thereby being beneficial to avoiding oxidative discoloration and improving the product quality.

In conclusion, the beneficial technical effects of the invention are as follows: on the basis of acrylamide monomers and cationic monomers, proper chain transfer agents, crosslinking agents, peroxide initiators and azo initiators are added to control the crosslinking degree in the copolymerization process, and copolymerization monomers and auxiliaries are added in batches to carry out fractional copolymerization, so that the paper reinforcing agent with strong anti-interference capability, high crosslinking degree, good fluidity, uniform distribution of cations in molecular structures in the copolymer and excellent application performance is finally obtained.

Detailed Description

In order to make the technical means, the creation features, the achievement purposes and the functions of the invention clearer and easier to understand, the invention is further described in the following with the specific embodiments.

Examples

Example 1: the invention discloses a preparation method of a paper reinforcing agent, which comprises the following steps,

s1, preparing a reaction monomer, taking a proper amount of deionized water, 65 parts of acrylamide monomer, 40 parts of cationic monomer, 5 parts of chain transfer agent, 0.5 part of cross-linking agent and 3 parts of peroxide initiator, putting the raw materials into a storage container in sequence under the stirring condition of 15r/min, then adjusting the pH value to 2.7 by using aerobic acid, and stirring for 10min to obtain the reaction monomer with the raw material content of 15%; dividing 100 parts of reaction monomers into two parts, wherein the weight ratio of the first part of reaction monomers to the second part of reaction monomers is 2: 1;

s2, preparing an auxiliary agent, namely taking 20 parts of aluminide, 6 parts of viscosity regulator, 1.5 parts of bulking agent, 1.0 part of cosolvent and 1.0 part of antioxidant, sequentially putting the raw materials into a storage container under the stirring condition of 15r/min, adding the raw materials into the storage container to 40 parts by using deionized water, and continuously stirring for 10min to obtain the auxiliary agent; dividing 40 parts of auxiliary agent into two parts, wherein the weight ratio of the first part of auxiliary agent to the second part of auxiliary agent is 2: 1;

s3 copolymerization, namely preheating a copolymerization container to 60 +/-2 ℃, putting a first part of reaction monomer and a first part of auxiliary agent into the copolymerization container under the stirring condition of 15r/min, heating to 65 ℃ under static normal pressure, gradually increasing the vacuum degree of the copolymerization container to 80 +/-2 Pa in the process, enabling the temperature in the copolymerization container to reach 75 +/-2 ℃, carrying out copolymerization for 3 hours, then putting a second part of reaction monomer and a second part of auxiliary agent into the copolymerization container, continuously stirring for 10 minutes, removing vacuum of the copolymerization container by adopting nitrogen, pressurizing to 0.15 +/-0.02 MPa, and heating to 85 ℃ under static normal pressure; in the process, 5 parts of azo initiator is dripped into the copolymerization container for 0.7h, and then the heat preservation reaction is continued under the condition of 85 +/-2 ℃ to obtain polyacrylamide resin;

s4 when the viscosity of the reactant in the copolymerization container reaches 8000 mPa.s, adding 8 parts of terminator into the copolymerization container, stopping the copolymerization reaction, removing nitrogen, adding a proper amount of deionized water, adjusting the content of polyacrylamide resin to be 15%, cooling to below 25 ℃, filtering with a 100-mesh filter screen, discharging to obtain the paper reinforcing agent.

In S1, the acrylamide monomer is acrylamide, methacrylamide, or a derivative thereof; acrylamide is preferably used as the acrylamide monomer.

The cationic monomer is ethylene amine, allyl amine, methacryloyloxyethyl trimethyl ammonium chloride, methacryloyloxypropyl trimethyl ammonium chloride, dimethyl diallyl ammonium chloride, dimethylaminoethyl methacrylate or dimethylamino propyl methacrylamide; dimethyldiallylammonium chloride is preferably used as cationic monomer.

The chain transfer agent is sodium pantetheine sulfonate, sodium allylsulfonate, ethanolamine, sodium formate or sodium phosphate; sodium pantetheinesulfonate is preferably used as a chain transfer agent.

The cross-linking agent is N, N-dimethylacrylamide, N-diallyl acrylamide and vinyl toluene; n, N-diallylacrylamide is preferably used as crosslinking agent.

The peroxide initiator is persulfate/sodium bisulfite; the persulfate may be ammonium, potassium or sodium persulfate, with sodium persulfate and sodium bisulfite being preferred as the peroxide initiator

The organic acid is sulfuric acid, formic acid or maleic acid; formic acid is preferably used as the aerobic acid to adjust the pH.

In S2, the aluminide is aluminum sulfate, aluminum chloride, aluminum acetate, or aluminum myristate; aluminum myristate is preferably used as aluminide.

The viscosity modifier comprises a cellulose ether.

The bulking agent comprises a gas phase alumina.

The cosolvent is N, N-dimethylacetamide and acetone in a volume ratio of 1: 1.

The antioxidant is tetra [ beta- (3, 5-di-tert-butyl-4-hydroxyphenyl) propionic acid ] pentaerythritol ester, tri [2, 4-di-tert-butylphenyl ] phosphite, 2-thiobis (4-methyl-6-tert-butylphenol) or [ beta- (3, 5-di-tert-butyl-4-hydroxyphenyl) propionic acid ] octadecanol; tetrakis- [ beta- (3, 5-di-tert-butyl-4-hydroxyphenyl) propanoic acid ] pentaerythritol ester is preferably used as antioxidant.

In S3, the azo initiator is azobisisobutyronitrile, azobis (2-methylpropionamidine), 2-azo-bis (2-amidinopropane) hydrochloride, 1- ((cyano-1-methylethyl) azo) formamide, dimethyl 2, 2' -azobisisobutyrate or azobis (N-aminoethyl) butylamidine; 2, 2-azo-bis (2-amidinopropane) hydrochloride is preferably used as azo initiator.

In S4, the terminator is sodium sulfite or sodium bisulfite; sodium sulfite is preferably used as a terminator.

Example 2: the invention discloses a preparation method of a paper reinforcing agent, which comprises the following steps,

s1, preparing a reaction monomer, taking a proper amount of deionized water, 75 parts of acrylamide monomer, 45 parts of cationic monomer, 1 part of chain transfer agent, 1.0 part of cross-linking agent and 2 parts of peroxide initiator, sequentially putting the raw materials into a storage container under the stirring condition of 25r/min, then adjusting the pH value to 2.8 by using aerobic acid, and stirring for 12min to obtain the reaction monomer with the raw material content of 15%; dividing 100 parts of reaction monomers into two parts, wherein the weight ratio of the first part of reaction monomers to the second part of reaction monomers is 3: 1;

s2, preparing an assistant, namely taking 15 parts of aluminide, 4 parts of viscosity regulator, 1.7 parts of bulking agent, 1.5 parts of cosolvent and 0.5 part of antioxidant, sequentially putting the raw materials into a storage container under the stirring condition of 25r/min, adding the raw materials into the storage container to 40 parts by using deionized water, and continuously stirring for 12min to obtain the assistant; dividing 40 parts of auxiliary agent into two parts, wherein the weight ratio of the first part of auxiliary agent to the second part of auxiliary agent is 4: 1;

s3 copolymerization, namely preheating a copolymerization container to 60 +/-2 ℃, putting a first part of reaction monomer and a first part of auxiliary agent into the copolymerization container under the stirring condition of 25r/min, heating to 66 ℃ under static normal pressure, gradually increasing the vacuum degree of the copolymerization container to 80 +/-2 Pa in the process, enabling the temperature in the copolymerization container to reach 75 +/-2 ℃, carrying out copolymerization for 2.8h, then putting a second part of reaction monomer and a second part of auxiliary agent into the copolymerization container, continuously stirring for 7min, removing vacuum of the copolymerization container by adopting nitrogen, pressurizing to 0.15 +/-0.02 MPa, and heating to 84 ℃ under static normal pressure; in the process, 1 part of azo initiator is dripped into a copolymerization container for 0.5h, and then the heat preservation reaction is continued under the condition of 85 +/-2 ℃ to obtain polyacrylamide resin;

s4, when the viscosity of the reactant in the copolymerization container reaches 8000 mPa.s, adding 5 parts of a terminator into the copolymerization container, stopping the copolymerization reaction, removing nitrogen, adding a proper amount of deionized water, adjusting the content of the polyacrylamide resin to be 15%, cooling to below 25 ℃, filtering by using a 100-mesh filter screen, discharging, and thus obtaining the paper reinforcing agent.

Example 3: the invention discloses a preparation method of a paper reinforcing agent, which comprises the following steps,

s1, preparing a reaction monomer, taking a proper amount of deionized water, 70 parts of acrylamide monomer, 50 parts of cationic monomer, 3 parts of chain transfer agent, 0.7 part of cross-linking agent and 1 part of peroxide initiator, sequentially putting the raw materials into a storage container under the stirring condition of 20r/min, then adjusting the pH value to 3.0 by using aerobic acid, and stirring for 15min to obtain the reaction monomer with the raw material content of 15%; dividing 100 parts of reaction monomers into two parts, wherein the weight ratio of the first part of reaction monomers to the second part of reaction monomers is 1: 1;

s2, preparing an assistant, namely taking 25 parts of aluminide, 5 parts of viscosity regulator, 2.0 parts of bulking agent, 2.0 parts of cosolvent and 0.4 part of antioxidant, sequentially putting the raw materials into a storage container under the stirring condition of 20r/min, adding the raw materials into the storage container to 40 parts by using deionized water, and continuously stirring for 15min to obtain the assistant; dividing 40 parts of auxiliary agent into two parts, wherein the weight ratio of the first part of auxiliary agent to the second part of auxiliary agent is 3: 1;

s3 copolymerization, namely preheating a copolymerization container to 60 +/-2 ℃, putting a first part of reaction monomer and a first part of auxiliary agent into the copolymerization container under the stirring condition of 20r/min, heating to 67 ℃ under static normal pressure, gradually increasing the vacuum degree of the copolymerization container to 80 +/-2 Pa in the process, enabling the temperature in the copolymerization container to reach 75 +/-2 ℃, carrying out copolymerization for 2.3h, then putting a second part of reaction monomer and a second part of auxiliary agent into the copolymerization container, continuously stirring for 6min, removing vacuum of the copolymerization container by adopting nitrogen, pressurizing to 0.15 +/-0.02 MPa, and heating to 82 ℃ under static normal pressure; in the process, 3 parts of azo initiator is dripped into the copolymerization container for 0.8h, and then the heat preservation reaction is continued under the condition of 85 +/-2 ℃ to obtain polyacrylamide resin;

s4 when the viscosity of the reactant in the copolymerization container reaches 8000 mPa.s, adding 1 part of terminator into the copolymerization container, stopping the copolymerization reaction, removing nitrogen, adding a proper amount of deionized water, adjusting the content of polyacrylamide resin to be 15%, cooling to below 25 ℃, filtering with a 100-mesh filter screen, discharging to obtain the paper reinforcing agent.

Example 4: the invention discloses a preparation method of a paper reinforcing agent, which comprises the following steps,

s1, preparing a reaction monomer, taking a proper amount of deionized water, 75 parts of acrylamide monomer, 30 parts of cationic monomer, 10 parts of chain transfer agent, 0.5 part of cross-linking agent and 2 parts of peroxide initiator, sequentially putting the raw materials into a storage container under the stirring condition of 15r/min, then adjusting the pH value to 2.9 by using aerobic acid, and stirring for 13min to obtain the reaction monomer with the raw material content of 15%; dividing 100 parts of reaction monomers into two parts, wherein the weight ratio of the first part of reaction monomers to the second part of reaction monomers is 2: 1;

s2, preparing an auxiliary agent, namely taking 20 parts of aluminide, 6 parts of viscosity regulator, 1.8 parts of bulking agent, 1.7 parts of cosolvent and 0.1 part of antioxidant, sequentially putting the raw materials into a storage container under the stirring condition of 15r/min, adding the raw materials into the storage container to 40 parts by using deionized water, and continuously stirring for 13min to obtain the auxiliary agent; dividing 40 parts of auxiliary agent into two parts, wherein the weight ratio of the first part of auxiliary agent to the second part of auxiliary agent is 1: 1;

s3 copolymerization, namely preheating a copolymerization container to 60 +/-2 ℃, putting a first part of reaction monomer and a first part of auxiliary agent into the copolymerization container under the stirring condition of 15r/min, heating to 68 ℃ under static normal pressure, gradually increasing the vacuum degree of the copolymerization container to 80 +/-2 Pa in the process, enabling the temperature in the copolymerization container to reach 75 +/-2 ℃, carrying out copolymerization for 2.5h, then putting a second part of reaction monomer and a second part of auxiliary agent into the copolymerization container, continuously stirring for 6min, removing vacuum of the copolymerization container by adopting nitrogen, pressurizing to 0.15 +/-0.02 MPa, and heating to 83 ℃ under static normal pressure; in the process, 10 parts of azo initiator is dripped into the copolymerization container for 0.5h, and then the heat preservation reaction is continued under the condition of 85 +/-2 ℃ to obtain polyacrylamide resin;

s4 when the viscosity of the reactant in the copolymerization container reaches 8000 mPa.s, adding 3 parts of terminator into the copolymerization container, stopping the copolymerization reaction, removing nitrogen, adding a proper amount of deionized water, adjusting the content of polyacrylamide resin to be 15%, cooling to below 25 ℃, filtering with a 100-mesh filter screen, discharging to obtain the paper reinforcing agent.

Example 5: the invention discloses a preparation method of a paper reinforcing agent, which comprises the following steps,

s1, preparing a reaction monomer, taking a proper amount of deionized water, 65 parts of acrylamide monomer, 60 parts of cationic monomer, 7 parts of chain transfer agent, 0.8 part of cross-linking agent and 3 parts of peroxide initiator, putting the raw materials into a storage container in sequence under the stirring condition of 25r/min, then adjusting the pH value to 2.8 by using aerobic acid, and stirring for 10min to obtain the reaction monomer with the raw material content of 15%; dividing 100 parts of reaction monomers into two parts, wherein the weight ratio of the first part of reaction monomers to the second part of reaction monomers is 3: 1;

s2, preparing an assistant, namely taking 15 parts of aluminide, 5 parts of viscosity regulator, 1.6 parts of bulking agent, 1.3 parts of cosolvent and 0.8 part of antioxidant, sequentially putting the raw materials into a storage container under the stirring condition of 25r/min, adding the raw materials into the storage container to 40 parts by using deionized water, and continuously stirring for 10min to obtain the assistant; dividing 40 parts of auxiliary agent into two parts, wherein the weight ratio of the first part of auxiliary agent to the second part of auxiliary agent is 3: 1;

s3 copolymerization, namely preheating a copolymerization container to 60 +/-2 ℃, putting a first part of reaction monomer and a first part of auxiliary agent into the copolymerization container under the stirring condition of 25r/min, heating to 70 ℃ under static normal pressure, gradually increasing the vacuum degree of the copolymerization container to 80 +/-2 Pa in the process, enabling the temperature in the copolymerization container to reach 75 +/-2 ℃, carrying out copolymerization for 2.0h, then putting a second part of reaction monomer and a second part of auxiliary agent into the copolymerization container, continuously stirring for 5min, removing vacuum of the copolymerization container by adopting nitrogen, pressurizing to 0.15 +/-0.02 MPa, and heating to 80 ℃ under static normal pressure; in the process, 7 parts of azo initiator is dripped into the copolymerization container for 1.0h, and then the heat preservation reaction is continued under the condition of 85 +/-2 ℃ to obtain polyacrylamide resin;

s4 when the viscosity of the reactant in the copolymerization container reaches 8000 mPa.s, adding 10 parts of terminator into the copolymerization container, stopping the copolymerization reaction, removing nitrogen, adding a proper amount of deionized water, adjusting the content of polyacrylamide resin to be 15%, cooling to below 25 ℃, filtering with a 100-mesh filter screen, discharging to obtain the paper reinforcing agent.

Performance test

The paper reinforcing agents obtained in examples 1 to 5 above were sheeted as follows, and the physical properties of the finished paper were tested.

Taking national waste paper pulp of a core layer provided by a certain factory, setting the quantitative quantity of paper as 120 g/square meter, using a KFR semi-automatic sheet making machine in the whole sheet making process, sequentially adding 2.5kg of cationic starch and 3kg of AKD neutral sizing agent in the sheet making process, adding 20kg and 40kg of self-product, diluting 1.2kg of aluminum sulfate (the using amount is equal to absolute dry fiber) with off-web white water, drying the paper sheet in a drum dryer at 105 ℃, keeping the temperature and humidity for 24 hours after drying, and testing the basis weight and the bursting strength of the finished paper sheet. The burst index was measured in GB/T13024-2003 "determination of paper burst", and the basis weight and burst data of the paper are shown in Table 1.

TABLE 1

As can be seen from Table 1, the paper strength additive prepared by the method of the present invention, based on acrylamide monomers and cationic monomers, the crosslinking degree in the copolymerization process is controlled by adding proper chain transfer agent, crosslinking agent, peroxide initiator and azo initiator, and the copolymerization is carried out step by adding copolymerization monomer and auxiliary agent in batches, so that the polyacrylamide resin content in the later stage of copolymerization reaction is in a stable rising state, then adding a terminating agent to control the end point of copolymerization reaction, further, the reaction system of the method can be completely copolymerized, the polyacrylamide resin with cations uniformly distributed in the molecular structure of the high polymer can be obtained, the problem that the molecular chain structure is easy to break when the original paper reinforcing agent is subjected to shearing force is directly solved, and the method has the advantages of strong anti-interference capability, high crosslinking degree, good fluidity and excellent application performance.

Finally, the above embodiments are only for illustrating the technical solutions of the present invention and not for limiting, although the present invention has been described in detail with reference to the preferred embodiments, it should be understood by those skilled in the art that modifications or equivalent substitutions may be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all of them should be covered in the claims of the present invention.