Preparation method of high-performance PAE wet strength agent

Abstract

The invention relates to a preparation method of a high-performance PAE wet strength agent, and belongs to the technical field of papermaking additives. The high-performance PAE wet strength agent is prepared from a self-made cross-linking agent, diethylenetriamine, a catalyst, deionized water and adipic acid as raw materials, the cross-linking agent is prepared by modifying epoxy chloropropane, the prepared cross-linking agent does not contain an organochlorine structure, the problem of organochlorine residues existing in the PAE wet strength agent can be thoroughly solved, and in addition, the PAE wet strength agent has the advantages that the preparation process is simple, and the production cost is low. Compared with a traditional wet strength agent, the cross-linking agent disclosed by the invention has the advantages that the curing temperature is lower, the damage of high temperature to a fiber structure can be effectively reduced, the flexibility of paper is reserved, and in addition, the cross-linking agent disclosed by the invention also has a pyridyl quaternary ammonium salt structure and can be combined in the paper to play a lasting antibacterial effect after pulp preparation and curing.

Description

Technical Field

[0001] The invention belongs to the technical field of papermaking additives, and in particular relates to a method for preparing a high-performance PAE wet strength agent. Background Art

[0002] Polyamide epichlorohydrin resin (PAE) is currently the most commonly used wet strength agent in the papermaking industry. Its mechanism of action is to form a three-dimensional network structure through a cross-linking reaction between the epoxy groups on the molecular chain and the hydroxyl groups in cellulose. At the same time, the cationic charge generates electrostatic adsorption with the fiber surface, thereby significantly improving the wet strength of the paper. PAE has a wide applicable pH range and can perform well in neutral to weakly alkaline environments. It has the advantage of low addition dosage and is widely used in the fields of household paper, packaging paper and specialty paper.

[0003] PAE wet strength agent needs to be dried and cured at a high temperature of over 100°C to achieve sufficient cross-linking. In the case of thin paper or papermaking pulp with poor heat resistance, such as straw pulp and waste paper pulp, high temperature may cause irreversible damage to the fiber structure in the paper, resulting in a decrease in the fiber polymerization degree, which in turn directly affects the mechanical strength and flexibility of the fiber. In addition, the preparation of PAE wet strength agent requires the use of cross-linking agent epichlorohydrin. These epichlorohydrins are difficult to fully consume during cross-linking and may produce organochlorine such as MCPD and DCP due to side reactions. These carcinogenic organochlorines migrate to the surface of the paper and will cause harm to the human body. To address the above shortcomings, the present invention modifies epichlorohydrin to prepare a method for preparing a high-performance PAE wet strength agent. Summary of the Invention

[0004] The object of the present invention is to provide a method for preparing a high-performance PAE wet strength agent, so as to solve the problems mentioned in the above background technology.

[0005] The purpose of the present invention can be achieved through the following technical solutions:

[0006] A method for preparing a high-performance PAE wet strength agent comprises the following steps:

[0007] The first step is to mix epichlorohydrin, a pyridine formaldehyde derivative, and anhydrous potassium carbonate in a three-necked flask, install a condenser and a thermometer, turn on magnetic stirring, and react at a temperature of 60-80°C for 4-8 hours. After the reaction is completed, cool to room temperature and filter to remove anhydrous potassium carbonate. Then, the filtrate is rotary evaporated to remove unreacted epichlorohydrin to obtain a crosslinker precursor;

[0008] In the second step, the cross-linking agent precursor, long-chain halogenated hydrocarbon, and acetonitrile are mixed in a three-necked flask, equipped with a condenser and a thermometer, and magnetic stirring is turned on. The reaction is carried out at a temperature of 20-80°C for 2-24 hours. After the reaction is completed, the solvent is removed by rotary evaporation, and the remaining solid is recrystallized with ethyl acetate to obtain a cross-linking agent;

[0009] Step 3: Add diethylenetriamine, catalyst and deionized water into a three-necked flask, install a condenser and a thermometer, turn on magnetic stirring, then add adipic acid into the three-necked flask in 2 to 4 batches, react at a temperature of 130 to 160° C. for 1 to 2 hours, then turn off the condenser and open the stopper of the three-necked flask to allow the water to fully evaporate, and continue to keep the temperature for 3 to 4 hours to obtain the prepolymer PCC for standby use;

[0010] Step 4: Add the prepolymer PCC into a three-necked flask, start magnetic stirring, and add deionized water to the three-necked flask to adjust the solid content to 10-15%. Then, add a cross-linking agent to the three-necked flask and react at a temperature of 40-60°C for 1-2 hours, then adjust the pH to 3-4 with acid to obtain a high-performance PAE wet strength agent.

[0011] Furthermore, the pyridinecarboxaldehyde derivative is one of 2-hydroxy-3-pyridinecarboxaldehyde and 4-hydroxy-3-pyridinecarboxaldehyde.

[0012] Furthermore, the long-chain halogenated hydrocarbon is one of dodecyl chloride, dodecyl bromide, tetradecyl chloride and tetradecyl bromide.

[0013] Furthermore, the catalyst is one of phosphoric acid and p-toluenesulfonic acid.

[0014] Furthermore, in the first step, the ratio of epichlorohydrin to pyridine formaldehyde derivative is 9.3-37.2:11.1-12.3 by mass.

[0015] Furthermore, in the second step, the ratio of the cross-linking agent precursor to the long-chain halogenated hydrocarbon is 15-18:20-32 in parts by mass.

[0016] Furthermore, in the third step, the usage ratio of diethylenetriamine, catalyst, deionized water and adipic acid is 92-114:1.8-3.8:10-40:131-161 in parts by mass.

[0017] Furthermore, in the fourth step, the ratio of the prepolymer PCC to the cross-linking agent is 11.5-18:20-30 by mass.

[0018] Beneficial effects of the present invention:

[0019] 1) The present invention uses epichlorohydrin and a pyridine carboxaldehyde derivative as raw materials, and utilizes the chlorine atoms of epichlorohydrin and the hydroxyl groups of the pyridine carboxaldehyde derivative to undergo a nucleophilic substitution reaction in an alkaline environment to obtain a crosslinking agent precursor. In the alkaline environment, the quaternary ammonium salt reaction will be inhibited. Subsequently, the crosslinking agent precursor and a long-chain halogenated hydrocarbon are used as raw materials, and the pyridine structure of the crosslinking agent precursor and the halogen atoms of the long-chain halogenated hydrocarbon undergo a quaternary ammonium salt reaction to obtain a crosslinking agent. After the epichlorohydrin is modified by the present invention, the crosslinking agent no longer contains organic chlorine, which can completely solve the problem of organic chlorine residues in PAE wet strength agents.

[0020] 2) The cross-linking agent of the present invention contains an epoxy structure and an aldehyde structure. When reacting with the prepolymer PCC, the epoxy group preferentially reacts with the active imine structure in the prepolymer PCC to obtain a PAE wet strength agent, and then ring-opens to obtain a hydroxyl structure. The remaining aldehyde group in the cross-linking agent can further undergo an acetal reaction with the hydroxyl group obtained by the ring-opening of the nearby epoxy group and the hydroxyl group in the cellulose, thereby increasing the cross-linking degree between the wet strength agent and the paper. Since the activation energy required for the acetal reaction between the aldehyde group and the hydroxyl group is less than the activation energy required for the substitution reaction between the halogen and the hydroxyl group, the wet strength agent of the present invention has a lower curing temperature than traditional wet strength agents, can effectively reduce the damage to the fiber structure caused by high temperature, and retain the flexibility of the paper.

[0021] 3) The cross-linking agent of the present invention contains a pyridyl quaternary ammonium salt structure. After pulping and maturation, the wet strength agent combined with the paper can also exert a lasting antibacterial effect, which has good prospects in the fields of household paper and medical paper. DETAILED DESCRIPTION

[0022] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts shall fall within the scope of protection of the present invention.

[0023] Example 1: A method for preparing a high-performance PAE wet strength agent, comprising the following steps:

[0024] The first step is to mix 9.3 parts of epichlorohydrin, 11.1 parts of 2-hydroxy-3-pyridinecarboxaldehyde, and 21 parts of anhydrous potassium carbonate in a three-necked flask, install a condenser and a thermometer, turn on magnetic stirring, and react at a temperature of 60°C for 8 hours. After the reaction is completed, cool to room temperature and filter to remove anhydrous potassium carbonate. Then, the filtrate is rotary evaporated to remove unreacted epichlorohydrin to obtain a crosslinker precursor;

[0025] Step 2: 15 parts of a cross-linking agent precursor, 20 parts of dodecyl chloride, and 60 parts of acetonitrile were mixed in a three-necked flask, equipped with a condenser and a thermometer, and magnetic stirring was turned on. The mixture was reacted at 20°C for 24 hours. After the reaction was completed, the solvent was removed by rotary evaporation, and the remaining solid was recrystallized from ethyl acetate to obtain a cross-linking agent.

[0026] The third step, by weight, 92 parts of diethylenetriamine, 1.8 parts of catalyst, and 10 parts of deionized water were added to a three-necked flask, a condenser and a thermometer were installed, and magnetic stirring was turned on. Then, 131 parts of adipic acid were added to the three-necked flask in two batches, each batch adding 65.5 parts. After the addition was completed, the reaction was carried out at a temperature of 130°C for 2 hours, and then the condensed water was turned off and the stopper of the three-necked flask was opened to fully evaporate the water. The reaction was continued for 4 hours to obtain the prepolymer PCC for standby use;

[0027] Step 4: Add 11.5 parts of prepolymer PCC into a three-necked flask by mass, turn on magnetic stirring, and add deionized water to the three-necked flask to adjust the solid content to 10%. Then, add 20 parts of cross-linking agent to the three-necked flask and react at a temperature of 40°C for 2 hours. After that, adjust the pH to 3 with acid to obtain a high-performance PAE wet strength agent.

[0028] Example 2: A method for preparing a high-performance PAE wet strength agent, comprising the following steps:

[0029] The first step is to mix 18.6 parts of epichlorohydrin, 11.5 parts of 2-hydroxy-3-pyridinecarboxaldehyde, and 26 parts of anhydrous potassium carbonate in a three-necked flask, install a condenser and a thermometer, turn on magnetic stirring, and react at a temperature of 67°C for 7 hours. After the reaction is completed, cool to room temperature and filter to remove anhydrous potassium carbonate. Then, the filtrate is rotary evaporated to remove unreacted epichlorohydrin to obtain a crosslinker precursor;

[0030] Step 2: 16 parts of a cross-linking agent precursor, 24 parts of dodecyl bromide, and 120 parts of acetonitrile were mixed in a three-necked flask, equipped with a condenser and a thermometer, and magnetic stirring was turned on. The reaction was carried out at 40°C for 18 hours. After the reaction was completed, the solvent was removed by rotary evaporation, and the remaining solid was recrystallized from ethyl acetate to obtain a cross-linking agent;

[0031] The third step, by weight, 100 parts of diethylenetriamine, 2.5 parts of phosphoric acid, and 20 parts of deionized water were added to a three-necked flask, a condenser and a thermometer were installed, and magnetic stirring was turned on. Then, 141 parts of adipic acid were added to the three-necked flask in 3 batches, each batch adding 47 parts. After the addition was completed, the reaction was carried out at a temperature of 140°C for 1.33 hours. After that, the condensed water was turned off and the stopper of the three-necked flask was opened to fully evaporate the water. The reaction was continued at this temperature for 3.33 hours to obtain the prepolymer PCC for standby use;

[0032] Step 4: Add 13.6 parts of prepolymer PCC into a three-necked flask by mass, turn on magnetic stirring, and add deionized water to the three-necked flask to adjust the solid content to 11.6%. Then, add 23 parts of cross-linking agent to the three-necked flask and react at a temperature of 47°C for 1.33 hours. After that, adjust the pH to 3.5 with acid to obtain a high-performance PAE wet strength agent.

[0033] Example 3: A method for preparing a high-performance PAE wet strength agent, comprising the following steps:

[0034] The first step is to mix 27.9 parts of epichlorohydrin, 11.9 parts of 4-hydroxy-3-pyridinecarboxaldehyde, and 31 parts of anhydrous potassium carbonate in a three-necked flask, install a condenser and a thermometer, turn on magnetic stirring, and react at a temperature of 74°C for 5 hours. After the reaction is completed, cool to room temperature and filter to remove anhydrous potassium carbonate. Then, the filtrate is rotary evaporated to remove unreacted epichlorohydrin to obtain a crosslinker precursor;

[0035] Step 2: 17 parts of a cross-linking agent precursor, 28 parts of tetradecyl chloride, and 180 parts of acetonitrile were mixed in a three-necked flask, equipped with a condenser and a thermometer, and magnetic stirring was turned on. The mixture was reacted at 60°C for 6 hours. After the reaction was completed, the solvent was removed by rotary evaporation, and the remaining solid was recrystallized from ethyl acetate to obtain a cross-linking agent.

[0036] The third step, by mass, 106 parts of diethylenetriamine, 3.1 parts of p-toluenesulfonic acid, and 30 parts of deionized water were added to a three-necked flask, a condenser and a thermometer were installed, and magnetic stirring was turned on. Then, 151 parts of adipic acid were added to the three-necked flask in 4 batches, each batch adding 37.75 parts. After the addition was completed, the reaction was carried out at a temperature of 150°C for 1.67 hours. After that, the condensed water was turned off and the stopper of the three-necked flask was opened to fully evaporate the water. The reaction was continued at this temperature for 3.67 hours to obtain the prepolymer PCC for standby use;

[0037] Step 4: Add 15.8 parts of prepolymer PCC into a three-necked flask by mass, turn on magnetic stirring, and add deionized water to the three-necked flask to adjust the solid content to 13.3%. Then, add 27 parts of cross-linking agent to the three-necked flask and react at a temperature of 53°C for 1.67 hours. After that, adjust the pH to 4 with acid to obtain a high-performance PAE wet strength agent.

[0038] Example 4: A method for preparing a high-performance PAE wet strength agent, comprising the following steps:

[0039] The first step is to mix 37.2 parts of epichlorohydrin, 12.3 parts of 4-hydroxy-3-pyridinecarboxaldehyde, and 36 parts of anhydrous potassium carbonate in a three-necked flask, install a condenser and a thermometer, turn on magnetic stirring, and react at a temperature of 80°C for 4 hours. After the reaction is completed, cool to room temperature and filter to remove anhydrous potassium carbonate. Then, the filtrate is rotary evaporated to remove unreacted epichlorohydrin to obtain a crosslinker precursor;

[0040] Step 2: 18 parts of a cross-linking agent precursor, 32 parts of tetradecyl bromide, and 240 parts of acetonitrile were mixed in a three-necked flask, equipped with a condenser and a thermometer, and magnetic stirring was turned on. The mixture was reacted at 80°C for 2 hours. After the reaction was completed, the solvent was removed by rotary evaporation, and the remaining solid was recrystallized from ethyl acetate to obtain a cross-linking agent.

[0041] The third step, by mass, 114 parts of diethylenetriamine, 3.8 parts of p-toluenesulfonic acid, and 40 parts of deionized water were added to a three-necked flask, a condenser and a thermometer were installed, and magnetic stirring was turned on. Then, 161 parts of adipic acid were added to the three-necked flask in 4 batches, each batch adding 40.25 parts. After the addition was completed, the reaction was carried out at a temperature of 160°C for 1 hour, and then the condensed water was turned off and the stopper of the three-necked flask was opened to fully evaporate the water. The reaction was continued for 3 hours to obtain the prepolymer PCC for standby use;

[0042] Step 4: Add 18 parts of prepolymer PCC into a three-necked flask by mass, turn on magnetic stirring, and add deionized water to the three-necked flask to adjust the solid content to 15%. Then, add 30 parts of cross-linking agent to the three-necked flask and react at a temperature of 60°C for 1 hour, then adjust the pH to 4 with acid to obtain a high-performance PAE wet strength agent.

[0043] Comparative Example 1: The cross-linking agent of the present invention is replaced by conventional epichlorohydrin, and a method for preparing a high-performance PAE wet strength agent comprises the following steps:

[0044] The first step is to add 114 parts of diethylenetriamine, 3.8 parts of p-toluenesulfonic acid, and 40 parts of deionized water into a three-necked flask by mass, install a condenser and a thermometer, turn on the magnetic stirring, and then add 161 parts of adipic acid to the three-necked flask in 4 batches, each batch adding 40.25 parts. After the addition is completed, react at a temperature of 160°C for 1 hour, then turn off the condensation water and open the stopper of the three-necked flask to fully evaporate the water, and continue to keep warm for 3 hours to obtain the prepolymer PCC for standby use;

[0045] In the second step, 18 parts of prepolymer PCC were added to a three-necked flask by mass, magnetic stirring was turned on, and deionized water was added to the three-necked flask to adjust the solid content to 15%. Then, 30 parts of epichlorohydrin were added to the three-necked flask and reacted at a temperature of 60°C for 1 hour. After that, the pH was adjusted to 4 with acid to obtain a high-performance PAE wet strength agent.

[0046] Comparative Example 2: This comparative example is a commercially available low-chlorine PAE wet strength agent.

[0047] Experimental Example 1: The high-performance PAE wet strength agents in Examples 1 to 4 and Comparative Example 1 and the commercially available PAE wet strength agent in Comparative Example 2 were tested for performance. The organic chlorine (MCPD: 3-chloro-1,2-propylene glycol, DCP: 1,3-dichloro-2-propanol) content of each component wet strength agent was analyzed by HPLC. The calculation results are shown in Table 1.

[0048] Experimental Example 2: The pulp used is straw pulp and bamboo pulp, and the ratio of straw pulp to bamboo pulp is 7:3. The pulp is mixed and beaten, and the beating degree is 35°SR. After beating, water is added to dilute it to 1.5%, and then the wet strength agents of each component in Examples 1 to 4 and Comparative Examples 1 to 2 are added. According to the national standard papermaking method, the aging temperature is 80°C, and a semi-automatic paper former is used to form the paper. Then, the dry tensile strength is tested with reference to the national standard GB / T12914-2008 "Determination of tensile strength of paper and paperboard", and the wet tensile strength is tested with reference to the national standard GB / T465.2-2008 "Determination of tensile strength of paper and paperboard after immersion in water". The test results are shown in Table 1.

[0049]

[0050] As can be seen from Table 1, the high-performance PAE wet strength agent of the present invention in Examples 1 to 4 has an organic chlorine content of 0, which completely solves the problem of organic chlorine residue in PAE wet strength agents. In addition, in low-temperature aging scenarios, the wet strength agent of the present invention has a better effect than commercially available PAE wet strength agents, and has good application prospects in the field of papermaking pulp with poor heat resistance, such as waste paper pulp, straw pulp, and bamboo pulp.

[0051] Experimental Example 3: Referring to the national standard "GB / T 42702-2023 Determination of antibacterial properties of paper, paperboard and paper products", the antibacterial rates of the finished paper obtained in Experimental Example 2 with the wet strength agents of Examples 1 to 4 added against Staphylococcus aureus and Escherichia coli were tested. The finished paper with the wet strength agent of Comparative Example 1 was used as the control group. The test results are shown in Table 2.

[0052] project Staphylococcus aureus inhibition rate / % Escherichia coli inhibition rate / % Example 1 99.1 99.2 Example 2 99.2 99.4 Example 3 99.9 99.9 Example 4 99.9 99.9

[0053] As can be seen from Table 2, the high-performance PAE wet strength agent of the present invention in Examples 1 to 4 can provide good antibacterial performance after entering the paper through the pulp supply system, and has good prospects in the fields of household paper and medical paper.

[0054] The above is a detailed introduction to the preparation method of a high-performance PAE wet strength agent provided by the present invention. Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A method for preparing a high-performance PAE wet strength agent, characterized in that: The following steps are involved: Preparation of a cross-linking agent: epichlorohydrin and a pyridine formaldehyde derivative are reacted under alkaline conditions to obtain a cross-linking agent precursor, and the obtained cross-linking agent precursor is then reacted with a long-chain halogenated hydrocarbon to form a quaternary ammonium salt to obtain a cross-linking agent; Preparation of high-performance PAE wet strength agent: deionized water is added to adjust the solid content of prepolymer PCC to 10-15%, then a crosslinking agent is added to the system and the temperature is controlled at 40-60°C for reaction for 1-2 hours, and then the pH of the system is adjusted to 3-4 to obtain a high-performance PAE wet strength agent.

2. The method for preparing a high-performance PAE wet strength agent according to claim 1, characterized in that: The pyridinecarboxaldehyde derivative is one of 2-hydroxy-3-pyridinecarboxaldehyde and 4-hydroxy-3-pyridinecarboxaldehyde.

3. The method for preparing a high-performance PAE wet strength agent according to claim 1, characterized in that: The long-chain halogenated hydrocarbon is one of dodecyl chloride, dodecyl bromide, tetradecyl chloride and tetradecyl bromide.

4. The method for preparing a high-performance PAE wet strength agent according to claim 1, characterized in that: In the step of preparing the cross-linking agent, the usage ratio of epichlorohydrin and pyridine formaldehyde derivative is 9.3-37.2:11.1-12.3 by mass.

5. The method for preparing a high-performance PAE wet strength agent according to claim 1, characterized in that: In the step of preparing the cross-linking agent, the ratio of the cross-linking agent precursor to the long-chain halogenated hydrocarbon is 15-18:20-32 by mass.

6. The method for preparing a high-performance PAE wet strength agent according to claim 1, characterized in that: In terms of mass fractions, the usage ratio of the prepolymer PCC to the crosslinking agent in the step of preparing the high-performance PAE wet strength agent is 11.5-18:20-30.

7. The method for preparing a high-performance PAE wet strength agent according to claim 1, characterized in that: The prepolymer PCC is prepared by the following steps: After diethylenetriamine, catalyst and deionized water are evenly mixed, adipic acid is added to the system and reacted at a temperature of 130-160°C for 1-2 hours. After that, the container seal is removed and the temperature is controlled at 130-160°C to continue the reaction to obtain prepolymer PCC for use.

8. The method for preparing a high-performance PAE wet strength agent according to claim 1 or claim 7, characterized in that: The catalyst is one of phosphoric acid and p-toluenesulfonic acid.

9. The method for preparing a high-performance PAE wet strength agent according to claim 1 or claim 7, characterized in that: Calculated by mass, the usage ratio of diethylenetriamine, catalyst, deionized water and adipic acid in the step of preparing prepolymer PCC is 92-114:1.8-3.8:10-40:131-161.

10. The method for preparing a high-performance PAE wet strength agent according to claim 1 or claim 7, wherein when preparing the prepolymer PCC, the adipic acid is added in 2 to 4 batches.

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