阅读说明：本技术 一种造纸增强剂的制备方法 (Preparation method of papermaking reinforcing agent ) 是由 马科 于 2020-07-08 设计创作，主要内容包括：本发明公开了一种造纸增强剂的制备方法,属于造纸助剂制备技术领域。本发明将秸秆渣用强碱液分解,过滤提取出含大量木质素的浸液,再用2,3-环氧丙基三甲基氯化铵阳离子化,调至中性,离心沉淀干燥得到阳离子分散剂,利用正磷酸盐的酯化,通过焦磷酸盐为中间体的反应,这两种正磷酸盐受热都会分解成焦磷酸盐,生成的焦磷酸盐再与淀粉轻基起反应得到淀粉磷酸酯,以淀粉磷酸酯为基体接枝丙烯酰胺单体,得到淀粉磷酸酯接枝物,发挥其协同作用,能有效提高纸张的湿强和干强；本发明中以秸秆渣为原料制备的阳离子分散剂为木质素阳离子化产物,木质素本身具有较大的空间结构,在造纸增强剂中会产生较大的空间位阻,提高造纸增强剂中颗粒的分散性能。(The invention discloses a preparation method of a papermaking reinforcing agent, and belongs to the technical field of preparation of papermaking additives. Decomposing straw residues with strong alkali liquor, filtering to extract an immersion liquid containing a large amount of lignin, cationizing with 2, 3-epoxypropyltrimethylammonium chloride, adjusting to be neutral, centrifugally precipitating and drying to obtain a cationic dispersant, reacting orthophosphate with the esterification of orthophosphate through the reaction of pyrophosphate as an intermediate, decomposing the two orthophosphates into pyrophosphate when being heated, reacting the generated pyrophosphate with starch light base to obtain starch phosphate, grafting acrylamide monomer with the starch phosphate as a matrix to obtain a starch phosphate graft, exerting the synergistic effect of the starch phosphate graft and effectively improving the wet strength and the dry strength of paper; according to the invention, the cationic dispersant prepared by taking the straw residues as the raw material is a lignin cationization product, and the lignin has a larger spatial structure, so that larger steric hindrance can be generated in the papermaking reinforcing agent, and the dispersion performance of particles in the papermaking reinforcing agent is improved.)

1. A preparation method of a papermaking reinforcing agent is characterized by comprising the following specific preparation steps:

adding the starch phosphate graft and deionized water into a stirring kettle, stirring to be homogeneous, adding a low-molecular-weight cross-linking material and a cationic dispersant, adjusting the pH to 5.5-6.0 by using an acetic acid solution with the mass fraction of 50%, and adding water for dilution to obtain a papermaking reinforcing agent;

the preparation method of the cationic dispersant comprises the following specific steps:

putting 40-50 parts by weight of straw residues and 100-120 parts by weight of a 30% sodium hydroxide solution into a water bath reaction kettle with a stirrer, heating in a water bath to 70-80 ℃, starting the stirrer, stirring for 3-5 hours, filtering to remove filter residues, adding 2, 3-epoxypropyltrimethylammonium chloride into filtrate, stirring for reaction for 20-25 min, regulating the filtrate to be neutral by using 95% glacial acetic acid, performing centrifugal treatment, washing precipitates obtained by centrifugation for 2-3 times by using water, then transferring the precipitates into an oven with the set temperature of 70-80 ℃, and drying for 4-5 hours to obtain a cationic dispersant;

the starch phosphate graft specifically comprises the following preparation steps:

(1) adding starch and 20 mass percent sodium dihydrogen phosphate solution into a beaker, stirring for 10-15 min at room temperature, adding urea, heating to 45-50 ℃ in a water bath, reacting for 3-4 h under heat preservation, filtering to remove filtrate, and drying the precipitate in an oven at a set temperature of 50-55 ℃ for 4-5 h to obtain starch phosphate;

(2) adding the starch phosphate and water into a three-neck flask of a condensation reflux device, heating the mixture to 50-60 ℃ in a water bath, stirring the mixture for 4-5 min at a constant temperature, adding an acrylamide monomer, adding an initiator, introducing nitrogen for protection, reacting the mixture for 1-2 h under a heat preservation condition, then pouring out a reaction solution, and air-drying the reaction solution at normal temperature to obtain a starch phosphate graft;

the preparation method of the low molecular weight cross-linked polymer comprises the following specific steps:

(1) adding 20-25 parts by weight of chitosan and 40-50 parts by weight of 2% acetic acid solution into a four-neck flask, stirring for 4-5 min, adding 30-35 parts by weight of 30% formaldehyde aqueous solution and 40-45 parts by weight of polyacrylamide, heating to 60-80 ℃, and reacting for 2-3 h to obtain a cross-linked substance;

(2) dialyzing the cross-linked product with distilled water to obtain a dialyzed reaction product, placing the dialyzed reaction product in a rotary evaporator, carrying out rotary evaporation at the rotating speed of 80-90 r/min for 20-25 min to obtain a rotary evaporation product, and then carrying out freeze drying at the temperature of-40 to-20 ℃ for 30-35 min to obtain the low-molecular-weight cross-linked product.

2. The method for preparing a papermaking reinforcing agent according to claim 1, wherein: the papermaking reinforcing agent comprises the main components in the specific preparation steps of 40-50 parts by weight of starch phosphate graft, 30-40 parts by weight of low molecular weight cross-linking material and 20-25 parts by weight of cationic dispersant.

3. The method for preparing a papermaking reinforcing agent according to claim 1, wherein: the viscosity of the papermaking reinforcing agent obtained after the papermaking reinforcing agent is diluted by water in the specific preparation step is 100-120 mPa & s.

4. The method for preparing a papermaking reinforcing agent according to claim 1, wherein: in the specific preparation step of the cationic dispersant, the addition amount of 2, 3-epoxypropyltrimethylammonium chloride is 4-5% of the mass of the filtrate.

5. The method for preparing a papermaking reinforcing agent according to claim 1, wherein: the starch phosphate graft is prepared by the following raw materials in part by weight in the step (1), wherein the raw materials comprise 40-45 parts of starch, 60-70 parts of sodium dihydrogen phosphate solution with the mass fraction of 20% and 5-10 parts of urea.

6. The method for preparing a papermaking reinforcing agent according to claim 1, wherein: the starch phosphate graft specifically comprises, in the step (2), 5-6 parts of starch phosphate, 100-110 parts of water, 10-15 parts of acrylamide monomer and 4-5 parts of initiator by weight.

7. The method for preparing a papermaking reinforcing agent according to claim 1, wherein: the initiator in the specific preparation step (2) of the starch phosphate graft is obtained by dissolving 1g of ammonium ceric nitrate in 50mL of nitric acid solution with the concentration of 1 mol/L.

8. The method for preparing a papermaking reinforcing agent according to claim 1, wherein: the polyacrylamide in the specific preparation step (1) of the low molecular weight cross-linked substance is preferably anionic polyacrylamide.

9. The method for preparing a papermaking reinforcing agent according to claim 1, wherein: the molecular weight cut-off of the low molecular weight cross-linking substance is controlled to be below 500KD in the dialysis process in the specific preparation step (2).

Technical Field

The invention discloses a preparation method of a papermaking reinforcing agent, and belongs to the technical field of preparation of papermaking additives.

Background

The paper-making industry in China is in a high-speed development stage, and because of the shortage of wood resources in China, the paper-making industry currently adopts grass and waste paper to recycle pulp and make paper. However, the use of grass and waste paper raw materials and fillers can cause strength loss, and the use of paper reinforcing agents can solve these problems in order to meet the demand of people for high-grade paper. The paper strengthening agent is a fine chemical for strengthening the strength of paper and paperboard, and is mainly used in the paper production process to improve the strength and tear resistance of paper made of straw pulp and waste paper.

The reinforcing agents can be divided into dry-strengthening agents and wet-strengthening agents according to different effects, wherein the dry-strengthening agents and the wet-strengthening agents belong to internal reinforcing agents, and the reinforcing mechanisms of the internal reinforcing agents are different.

Dry strength agents are fine chemicals used to improve the bonding between fibers to increase the physical strength (tensile strength, tear strength, burst strength, etc.) of paper without affecting its wet strength. In general, polymers which are soluble in water and which carry hydrogen bonds are suitable as dry strength aids. In fact, wood fibers contain hemicellulose, a natural dry strength agent. The hydrogen bonding and electrostatic adsorption between fibers are the reasons for the dry strength of paper, and particularly, the hydrogen bonding points are many, the bonding force is strong, and the dry strength is mainly caused. Common dry strength agents are starch derivatives (about 95% of the total amount), mainly cationic starch, amphoteric starch, and the like. The starch used in the paper industry is mostly modified starch, and the amount of the starch is almost 80-90% of the total amount of the paper-making chemicals.

The mechanical strength of paper and paperboard is almost completely lost after being soaked in water, and generally only 4-10% of the dry paper strength can be maintained, while some special papers such as photographic base paper, blueprint base paper, military ground paper, banknote paper and the like not only have certain dry strength requirements, but also still can maintain certain mechanical strength and characteristics after being soaked in water, and therefore, a wet strength agent is required to be added to improve the wet strength of the paper. Wet strength is the ability of paper to retain some mechanical strength and properties after it has been saturated with water. After the wet strength agent is added, the wet strength of the paper can reach 20-40% of the original dry strength.

The polyethyleneimine is the cationic wet strength agent which is most applied and has a well-known effect at present, and the molecular chain of the polyethyleneimine contains a plurality of cationic groups, so that the polyethyleneimine can generate strong electrostatic adsorption with hydroxyl on cellulose to form a secondary valence crosslinking network.

At present, most of papermaking reinforcing agents on the market have single function, for example, modified starch can only be used for dry strength agents; high molecular polymers such as polyethyleneimine, urea-formaldehyde resin, melamine-formaldehyde resin and the like are used for the wet strength agent, and most of the high molecular polymers are toxic and are not suitable for being used in large quantities. The requirement of having both dry strength and wet strength cannot be met.

The aqueous solution polymerization process is simple, the polymerization yield is high, the environmental pollution is less, and the method is the preferred method for preparing the organic polymer. Aqueous solution polymerization has many advantages, but also has many disadvantages, and it is difficult to prepare a high-molecular-weight polymer having a high solid content. The utilization rate is low, the liquid product has high viscosity and poor fluidity, and the problems can be effectively solved by inverse emulsion, inverse suspension, precipitation polymerization and the like. However, the use of a large amount of organic solvent causes problems such as pollution and production cost, and the water solubility of the product is poor, which makes the use of the product very difficult.

Therefore, the invention of a papermaking reinforcing agent which has dry strength and wet strength and good fluidity is necessary for the technical field of preparation of papermaking additives.

Disclosure of Invention

The invention mainly solves the technical problem, and provides a preparation method of a papermaking reinforcing agent aiming at the defects that the conventional papermaking reinforcing agent is difficult to have double functions of a dry reinforcing agent and a wet reinforcing agent, solid particles in a reinforcing agent liquid product have poor water solubility and low utilization rate, and the liquid product has high viscosity and poor liquidity.

In order to solve the technical problems, the technical scheme adopted by the invention is as follows:

the preparation method of the papermaking reinforcing agent comprises the following steps:

adding the starch phosphate graft and deionized water into a stirring kettle, stirring to be homogeneous, adding a low-molecular-weight cross-linking material and a cationic dispersant, adjusting the pH to 5.5-6.0 by using an acetic acid solution with the mass fraction of 50%, and adding water for dilution to obtain a papermaking reinforcing agent;

the preparation method of the cationic dispersant comprises the following specific steps:

putting 40-50 parts by weight of straw residues and 100-120 parts by weight of a 30% sodium hydroxide solution into a water bath reaction kettle with a stirrer, heating in a water bath to 70-80 ℃, starting the stirrer, stirring for 3-5 hours, filtering to remove filter residues, adding 2, 3-epoxypropyltrimethylammonium chloride into filtrate, stirring for reaction for 20-25 min, regulating the filtrate to be neutral by using 95% glacial acetic acid, performing centrifugal treatment, washing precipitates obtained by centrifugation for 2-3 times by using water, then transferring the precipitates into an oven with the set temperature of 70-80 ℃, and drying for 4-5 hours to obtain a cationic dispersant;

the starch phosphate graft specifically comprises the following preparation steps:

(1) adding starch and 20 mass percent sodium dihydrogen phosphate solution into a beaker, stirring for 10-15 min at room temperature, adding urea, heating to 45-50 ℃ in a water bath, reacting for 3-4 h under heat preservation, filtering to remove filtrate, and drying the precipitate in an oven at a set temperature of 50-55 ℃ for 4-5 h to obtain starch phosphate;

(2) adding the starch phosphate and water into a three-neck flask of a condensation reflux device, heating the mixture to 50-60 ℃ in a water bath, stirring the mixture for 4-5 min at a constant temperature, adding an acrylamide monomer, adding an initiator, introducing nitrogen for protection, reacting the mixture for 1-2 h under a heat preservation condition, then pouring out a reaction solution, and air-drying the reaction solution at normal temperature to obtain a starch phosphate graft;

the preparation method of the low molecular weight cross-linked polymer comprises the following specific steps:

(1) adding 20-25 parts by weight of chitosan and 40-50 parts by weight of 2% acetic acid solution into a four-neck flask, stirring for 4-5 min, adding 30-35 parts by weight of 30% formaldehyde aqueous solution and 40-45 parts by weight of polyacrylamide, heating to 60-80 ℃, and reacting for 2-3 h to obtain a cross-linked substance;

(2) dialyzing the cross-linked product with distilled water to obtain a dialyzed reaction product, placing the dialyzed reaction product in a rotary evaporator, carrying out rotary evaporation at the rotating speed of 80-90 r/min for 20-25 min to obtain a rotary evaporation product, and then carrying out freeze drying at the temperature of-40 to-20 ℃ for 30-35 min to obtain the low-molecular-weight cross-linked product.

The papermaking reinforcing agent comprises the main components in the specific preparation steps of 40-50 parts by weight of starch phosphate graft, 30-40 parts by weight of low molecular weight cross-linking material and 20-25 parts by weight of cationic dispersant.

The viscosity of the papermaking reinforcing agent obtained after the papermaking reinforcing agent is diluted by water in the specific preparation step is 100-120 mPa & s.

In the specific preparation step of the cationic dispersant, the addition amount of 2, 3-epoxypropyltrimethylammonium chloride is 4-5% of the mass of the filtrate.

The starch phosphate graft is prepared by the following raw materials in part by weight in the step (1), wherein the raw materials comprise 40-45 parts of starch, 60-70 parts of sodium dihydrogen phosphate solution with the mass fraction of 20% and 5-10 parts of urea.

The starch phosphate graft specifically comprises, in the step (2), 5-6 parts of starch phosphate, 100-110 parts of water, 10-15 parts of acrylamide monomer and 4-5 parts of initiator by weight.

The initiator in the specific preparation step (2) of the starch phosphate graft is obtained by dissolving 1g of ammonium ceric nitrate in 50mL of nitric acid solution with the concentration of 1 mol/L.

The polyacrylamide in the specific preparation step (1) of the low molecular weight cross-linked substance is preferably anionic polyacrylamide.

The molecular weight cut-off of the low molecular weight cross-linking substance is controlled to be below 500KD in the dialysis process in the specific preparation step (2).

The invention has the beneficial effects that:

(1) the invention decomposes straw residue with strong alkali liquor, extracts immersion liquid containing a large amount of lignin by filtration, then carries out cationization with 2, 3-epoxypropyl trimethyl ammonium chloride, adjusts to be neutral, carries out centrifugal precipitation and drying to obtain cationic dispersant,

the method comprises the steps of utilizing esterification of orthophosphate, reacting through pyrophosphate as an intermediate, decomposing the orthophosphate into the pyrophosphate when the orthophosphate is heated, reacting the generated pyrophosphate with a starch light base to obtain starch phosphate, grafting an acrylamide monomer by using the starch phosphate as a matrix to obtain a starch phosphate graft, crosslinking anionic polyacrylamide and chitosan through a Mannich reaction principle to obtain a crosslinked substance, dialyzing to intercept the low-molecular-weight crosslinked substance, wherein the crosslinked substance is chitosan-anionic polyacrylamide, organically combining the reinforcement property of polyacrylamide and the reinforcement property of chitosan to play a synergistic effect, and effectively improving the wet strength of paper, and the starch phosphate graft belongs to a starch cationic derivative and can effectively improve the dry strength of the paper;

(2) the cationic dispersant prepared by taking straw residues as a raw material is a lignin cationization product, the lignin has a larger spatial structure, and can generate larger steric hindrance in a papermaking reinforcing agent, so that the improvement of the dispersion performance of particles in the papermaking reinforcing agent is facilitated, the liquid of the papermaking reinforcing agent is kept at uniform density and has good fluidity, the water solubility of solid particles can be improved by the anion of the prepared chitosan-anionic polyacrylamide cross-linked polymer, the viscosity of the reinforcing agent can be greatly reduced by the cross-linked polymer with low molecular weight, although the starch derivative is esterified, part of hydroxyl sites do not participate in the reaction, the starch derivative can also be dispersed in aqueous liquid, the utilization rate and the fluidity of the reinforcing agent liquid are improved, and the starch derivative has a wide application prospect.

Detailed Description

Putting 40-50 parts by weight of straw residues and 100-120 parts by weight of a 30% sodium hydroxide solution into a water bath reaction kettle with a stirrer, heating in a water bath to 70-80 ℃, starting the stirrer, stirring for 3-5 hours, filtering to remove filter residues, adding 4-5% by weight of 2, 3-epoxypropyltrimethylammonium chloride into the filtrate, stirring and reacting for 20-25 minutes, regulating the filtrate to be neutral by using 95% by weight of glacial acetic acid, centrifuging, washing the precipitate obtained by centrifuging for 2-3 times by using water, then transferring the precipitate into a drying oven with the set temperature of 70-80 ℃, and drying for 4-5 hours to obtain a cationic dispersant for later use; adding 40-45 parts of starch and 60-70 parts of 20% sodium dihydrogen phosphate solution into a beaker according to parts by weight, stirring for 10-15 min at room temperature, adding 5-10 parts of urea, heating to 45-50 ℃ in a water bath, reacting for 3-4 h at a constant temperature, filtering to remove filtrate, and drying the precipitate in an oven at a set temperature of 50-55 ℃ for 4-5 h to obtain starch phosphate; adding 5-6 parts of starch phosphate and 100-110 parts of water into a three-neck flask of a condensation reflux device according to parts by weight, heating the mixture in a water bath to 50-60 ℃, stirring the mixture at a constant temperature for 4-5 min, adding 10-15 parts of acrylamide monomer, adding an initiator, introducing nitrogen for protection, reacting the mixture after heat preservation for 1-2 h, then discharging a reaction solution, and drying the reaction solution at normal temperature to obtain a starch phosphate graft for later use, wherein the initiator is obtained by dissolving 1g of ammonium ceric nitrate in 50mL of nitric acid solution with the concentration of 1 mol/L. Adding 20-25 parts by weight of chitosan and 40-50 parts by weight of 2% acetic acid solution into a four-neck flask, stirring for 4-5 min, adding 30-35 parts by weight of 30% formaldehyde aqueous solution and 40-45 parts by weight of anionic polyacrylamide, heating to 60-80 ℃, and reacting for 2-3 h to obtain a cross-linked substance; dialyzing the cross-linked substance with distilled water, controlling the cut-off molecular weight to be below 500KD to obtain a dialyzed reaction product, placing the dialyzed reaction product in a rotary evaporator, carrying out rotary evaporation at the rotating speed of 80-90 r/min for 20-25 min to obtain a rotary evaporation product, and then carrying out freeze drying at the temperature of-40 to-20 ℃ for 30-35 min to obtain a low-molecular-weight cross-linked substance; adding 40-50 parts by weight of standby starch phosphate graft and 400-500 parts by weight of deionized water into a stirring kettle, stirring to a homogeneous phase, adding 30-40 parts by weight of the low molecular weight cross-linking material and 20-25 parts by weight of standby cationic dispersant, adjusting the pH to 5.5-6.0 by using an acetic acid solution with the mass fraction of 50%, and adding water to dilute until the viscosity is 100-120 mPa · s to obtain the papermaking reinforcing agent.