Preparation method of PAE wet strength agent with low organochlorine small molecule content
By modifying epichlorohydrin to prepare cross-linking agents and chain extenders, the problems of organochlorine residues in PAE wet strength agents and paper brittleness were solved, and a PAE wet strength agent with low organochlorine content was achieved, which improved the dry and wet tensile strength and flexibility of paper.
Patent Information
- Application Number
- CN202510788891.X
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-06-13
- Publication Date
- 2025-09-16
AI Technical Summary
The organic chlorine produced during the preparation process of existing PAE wet strength agents is difficult to completely consume, causing health hazards. At the same time, the increased cross-linking degree leads to increased brittleness of paper, making it difficult to maintain high strength and toughness in a wet state.
The cross-linking agent is prepared by modifying epichlorohydrin, and a silane coupling agent is reacted with epichlorohydrin to generate a cross-linking agent that does not contain organic chlorine. The reaction sequence is adjusted to improve the conversion rate. The chain extender is synthesized by combining triethanolamine and 2-bromoethanol to modify the prepolymer, introducing flexible thioether bonds and siloxane structures to form stable chemical bonds.
It significantly reduces the organic chlorine content, improves the cross-linking degree and molecular chain flexibility of the PAE wet strength agent, enhances the dry and wet tensile strength and anti-swelling properties of the paper, while maintaining high toughness and improving the wet strength effect of the paper.
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Figure BDA0005447814140000071
Abstract
Description
Technical Field
[0001] The invention belongs to the technical field of papermaking additives, and in particular relates to a method for preparing a PAE wet strength agent with low organic chlorine small molecule content. 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] The preparation of PAE wet strength agent requires the use of a crosslinking agent, epichlorohydrin. Epichlorohydrin not only increases the crosslinking degree of the PAE wet strength agent but also forms azetidinium groups with nitrogen atoms in the PAE molecular chain. These groups attract the negatively charged cellulose and enhance the adsorption of the PAE wet strength agent to the fiber surface. However, these epichlorohydrins are difficult to fully consume during crosslinking, and may produce organochlorine due to side reactions, which is harmful to human health. To address the above technical deficiencies, the present invention prepares a crosslinking agent that does not contain organochlorine by partially modifying epichlorohydrin, and adjusts the reaction sequence to improve the conversion rate of epichlorohydrin, thereby providing a method for preparing a PAE wet strength agent with a low content of small molecules of organochlorine. Summary of the Invention
[0004] The object of the present invention is to provide a method for preparing a PAE wet strength agent with low organic chlorine small molecule content, 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 PAE wet strength agent with low organic chlorine small molecule content comprises the following steps:
[0007] S1. Epichlorohydrin, a silane coupling agent, anhydrous potassium carbonate, and anhydrous toluene 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 a temperature of 40-60° C. for 3-6 hours. After the reaction was completed, the mixture was cooled to room temperature and the solid was filtered out. The solvent was then removed by rotary evaporation to obtain a cross-linking agent.
[0008] S2. Mix triethanolamine, 2-bromoethanol, and acetonitrile in a three-necked flask, install a condenser and a thermometer, start magnetic stirring, and react at a temperature of 20-40°C for 4-8 hours. After the reaction is completed, the reaction solution is spin-dried to obtain a chain extender;
[0009] S3, diethylenetriamine, catalyst, and deionized water are mixed in a three-necked flask, a condenser and a thermometer are installed, and magnetic stirring is turned on. Adipic acid is then added to the three-necked flask in 2 to 4 batches. After the addition is completed, the mixture is reacted at a temperature of 130 to 160° C. for 1 to 2 hours. After that, the condenser is turned off, the stopper of the three-necked flask is opened to allow the water to fully evaporate, and a chain extender is added to the three-necked flask. The reaction is continued at this temperature for 3 to 4 hours to obtain the prepolymer PCC for standby use;
[0010] S4. Add the prepolymer PCC into a three-necked flask, start magnetic stirring, and add deionized water into the three-necked flask to adjust the solid content to 10-15%. Then, add epichlorohydrin into the three-necked flask and react at a temperature of 40-60°C for 20-30 minutes. Then, add a cross-linking agent into the three-necked flask, continue to keep warm and react for 1-2 hours, and then adjust the pH to 3-4 with acid to obtain a PAE wet strength agent with low organic chlorine small molecule content.
[0011] Furthermore, the silane coupling agent is one of KH-580 and KH-590.
[0012] Furthermore, the catalyst is p-toluenesulfonic acid.
[0013] Furthermore, the mass ratio of epichlorohydrin, silane coupling agent, anhydrous potassium carbonate and anhydrous toluene in S1 is 9.3-18.6:19-39:14-28:40-50.
[0014] Furthermore, the mass ratio of triethanolamine, 2-bromoethanol and acetonitrile in S2 is 11.2-14.8:12.5-15.5:40-100.
[0015] Furthermore, the mass ratio of diethylenetriamine, catalyst, deionized water, adipic acid and chain extender in S3 is 103-125:2.2-3.4:10-40:176-220:12-20.
[0016] Furthermore, the mass ratio of prepolymer PCC, epichlorohydrin and cross-linking agent in S4 is 25-31:3.6-4.8:14.4-16.8.
[0017] Beneficial effects of the present invention:
[0018] 1) The present invention partially modifies epichlorohydrin and utilizes a nucleophilic substitution reaction between the mercapto group in the silane coupling agent and the chlorine atom in the epichlorohydrin to obtain a crosslinking agent. By modifying epichlorohydrin, the crosslinking agent obtained by the present invention no longer contains organic chlorine. By adjusting the addition order, the unmodified epichlorohydrin can preferentially participate in the crosslinking reaction, thereby effectively improving the conversion rate of epichlorohydrin and significantly reducing the organic chlorine content in the final product.
[0019] 2) The cross-linking agent of the present invention contains epoxy groups and siloxane structures. When preparing the PAE wet strength agent, the epoxy groups in the cross-linking agent preferentially react with the imine structures in the prepolymer PCC. The remaining siloxane structures in the cross-linking agent can further react with the hydroxyl groups obtained by ring-opening of cellulose and nearby epoxy groups after hydrolysis to form stable chemical bonds by dehydration condensation. The cross-linking agent of the present invention can replace the cross-linking effect of the original cross-linking agent epichlorohydrin in the PAE wet strength agent, thereby reducing the amount of epichlorohydrin used.
[0020] 3) The present invention synthesizes tetrakis(2-hydroxyethyl)ammonium bromide from triethanolamine and 2-bromoethanol and then uses the resultant as a chain extender to modify the prepolymer PCC. This not only increases the crosslinking degree of the PAE molecular chain, enabling the PAE molecular chain to form a denser network structure, effectively resisting the penetration of water molecules, improving the wet strength effect of the PAE wet strength agent, and increasing the dry and wet tensile strength and swelling resistance of paper treated with the PAE wet strength agent, but also increases the charge density of the PAE molecular chain, making up for the molecular chain charge density defect caused by partial replacement of epichlorohydrin, and ensuring the adsorption retention rate of the PAE wet strength agent on the fiber surface.
[0021] 4) Increasing the crosslinking degree of the PAE molecular chain can improve the dry and wet tensile strength of the treated paper, but it also increases the brittleness of the paper. The crosslinking agent of the present invention introduces flexible thioether bonds and siloxanes to improve the flexibility of the molecular chain and suppress the effect of increased crosslinking on the brittleness of the paper. The two can play a synergistic role. The crosslinked structure provides rigid support, and the flexible chain segments disperse external stress, achieving a "combination of rigidity and flexibility", so that the paper treated with the PAE wet strength agent can have both high strength and high toughness in the wet state. DETAILED DESCRIPTION
[0022] It should be understood that the expression "one or more of" includes individually each of the items recited after the expression and various combinations of two or more of the recited items, unless otherwise apparent from the context and usage. The expression "and / or" in conjunction with three or more recited items should be understood to have the same meaning, unless otherwise apparent from the context.
[0023] The terms "comprising", "having" or "containing", including their grammatical synonyms, should generally be understood as open and non-restrictive, e.g., not excluding other unrecited elements or steps, unless otherwise specifically stated or understood from the context.
[0024] It should be understood that the order of steps or the order in which certain actions are performed are not important as long as the present invention remains operable. Additionally, two or more steps or actions may be performed simultaneously.
[0025] The use of any and all examples or exemplary language, such as "such as" or "including," herein is intended merely to better illustrate the invention and does not limit the scope of the invention unless otherwise claimed. No language in this specification should be construed as indicating any non-claimed element as essential to the practice of the invention.
[0026] Example 1: A method for preparing a PAE wet strength agent with low organic chlorine small molecule content, comprising the following steps:
[0027] S1. Mix 9.3 parts of epichlorohydrin, 19 parts of silane coupling agent KH-590, 14 parts of anhydrous potassium carbonate, and 40 parts of anhydrous toluene in a three-necked flask, install a condenser and a thermometer, turn on magnetic stirring, and react at 40°C for 6 hours. After the reaction is completed, cool to room temperature and filter to remove the solid, then rotary evaporate to remove the solvent to obtain a cross-linking agent;
[0028] S2. Mix 11.2 parts of triethanolamine, 12.5 parts of 2-bromoethanol, and 40 parts of acetonitrile in a three-necked flask, install a condenser and a thermometer, turn on magnetic stirring, and react at 20°C for 8 hours. After the reaction is completed, the reaction solution is spin-dried to obtain a chain extender;
[0029] S3. By weight, 103 parts of diethylenetriamine, 2.2 parts of p-toluenesulfonic acid, and 10 parts of deionized water were mixed in a three-necked flask, a condenser and a thermometer were installed, and magnetic stirring was turned on. Then, a total of 176 parts of adipic acid were added to the three-necked flask in two batches, 88 parts in each batch. After the addition was completed, the reaction was carried out at a temperature of 130° C. for 2 hours. After that, the condensed water was turned off, the stopper of the three-necked flask was opened to fully evaporate the water, and 12 parts of a chain extender were added to the three-necked flask. The reaction was continued at this temperature for 4 hours to obtain a prepolymer PCC for standby use;
[0030] S4. Add 25 parts of prepolymer PCC into a three-necked flask by mass, start magnetic stirring, and add deionized water to the three-necked flask to adjust the solid content to 10%. Then, add 3.6 parts of epichlorohydrin to the three-necked flask and react at a temperature of 40°C for 30 minutes. Then, add 16.8 parts of a cross-linking agent to the three-necked flask, continue to keep the reaction warm for 2 hours, and then adjust the pH to 3 with acid to obtain a PAE wet strength agent with low organic chlorine small molecule content.
[0031] Example 2: A method for preparing a PAE wet strength agent with low organic chlorine small molecule content, comprising the following steps:
[0032] S1. Mix 14 parts of epichlorohydrin, 29 parts of silane coupling agent KH-580, 21 parts of anhydrous potassium carbonate, and 45 parts of anhydrous toluene in a three-necked flask, install a condenser and a thermometer, turn on magnetic stirring, and react at 50°C for 4.5 hours. After the reaction is completed, cool to room temperature and filter to remove the solid, then rotary evaporate to remove the solvent to obtain a cross-linking agent;
[0033] S2. Mix 13 parts of triethanolamine, 14 parts of 2-bromoethanol, and 70 parts of acetonitrile in a three-necked flask, install a condenser and a thermometer, turn on magnetic stirring, and react at 30°C for 6 hours. After the reaction is completed, the reaction solution is spin-dried to obtain a chain extender;
[0034] S3, by mass, 114 parts of diethylenetriamine, 2.8 parts of p-toluenesulfonic acid, and 25 parts of deionized water were mixed in a three-necked flask, a condenser and a thermometer were installed, and magnetic stirring was turned on. Then, 198 parts of adipic acid were added to the three-necked flask in 3 batches, 66 parts in each batch, and the reaction was carried out at a temperature of 145 ° C for 1.5 hours. After that, the condensed water was turned off, the stopper of the three-necked flask was opened to fully evaporate the water, and 16 parts of a chain extender were added to the three-necked flask, and the reaction was continued at this temperature for 3.5 hours to obtain a prepolymer PCC for standby use;
[0035] S4. Add 28 parts of prepolymer PCC into a three-necked flask by mass, start magnetic stirring, and add deionized water to the three-necked flask to adjust the solid content to 12.5%. Then, add 4.2 parts of epichlorohydrin to the three-necked flask and react at a temperature of 50°C for 25 minutes. Then, add 15.6 parts of a cross-linking agent to the three-necked flask, continue to keep the reaction warm for 1.5 hours, and then adjust the pH to 3.5 with acid to obtain a PAE wet strength agent with low organic chlorine small molecule content.
[0036] Example 3: A method for preparing a PAE wet strength agent with low organic chlorine small molecule content, comprising the following steps:
[0037] S1. Mix 18.6 parts of epichlorohydrin, 39 parts of silane coupling agent KH-580, 28 parts of anhydrous potassium carbonate, and 50 parts of anhydrous toluene in a three-necked flask, install a condenser and a thermometer, turn on magnetic stirring, and react at 60°C for 3 hours. After the reaction is completed, cool to room temperature and filter to remove the solid, then rotary evaporate to remove the solvent to obtain a cross-linking agent;
[0038] S2. Mix 14.8 parts of triethanolamine, 15.5 parts of 2-bromoethanol, and 100 parts of acetonitrile in a three-necked flask, install a condenser and a thermometer, turn on magnetic stirring, and react at 40°C for 4 hours. After the reaction is completed, the reaction solution is spin-dried to obtain a chain extender;
[0039] S3, by mass, 125 parts of diethylenetriamine, 3.4 parts of p-toluenesulfonic acid, and 40 parts of deionized water were mixed in a three-necked flask, a condenser and a thermometer were installed, and magnetic stirring was turned on. Then, 220 parts of adipic acid were added to the three-necked flask in 4 batches, 55 parts in each batch, and the reaction was carried out at a temperature of 160° C. for 1 hour. After that, the condensed water was turned off, the stopper of the three-necked flask was opened to fully evaporate the water, and 20 parts of a chain extender were added to the three-necked flask. The reaction was continued at this temperature for 3 hours to obtain a prepolymer PCC for standby use;
[0040] S4. Add 31 parts of prepolymer PCC into a three-necked flask by mass, start magnetic stirring, and add deionized water to the three-necked flask to adjust the solid content to 15%. Then, add 4.8 parts of epichlorohydrin to the three-necked flask and react at a temperature of 60°C for 20 minutes. Then, add 14.4 parts of a cross-linking agent to the three-necked flask, continue to keep the temperature and react for 1 hour, and then adjust the pH to 4 with acid to obtain a PAE wet strength agent with low organic chlorine small molecule content.
[0041] Comparative Example 1: The cross-linking agent of the present invention is replaced by an equal amount of epichlorohydrin, and the prepolymer PCC is not modified by using a chain extender. The remaining raw materials and preparation steps are the same as those of Comparative Example 3.
[0042] Comparative Example 2: This comparative example is a commercially available low-chlorine PAE wet strength agent.
[0043] Experimental Example 1: The performance of the PAE wet strength agents with low organic chlorine content in Examples 1 to 3 and Comparative Example 1 and the commercially available PAE wet strength agent in Comparative Example 2 were tested separately. 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.
[0044] Experimental Example 2: The pulp used is softwood pulp and hardwood pulp, and the mass ratio of softwood pulp to hardwood pulp is 1:1. The pulp is mixed and beaten, and the beating degree is 40°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 3 and Comparative Examples 1 to 2 are added. According to the national standard papermaking method, the aging temperature is 100°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 / T 12914-2008 "Determination of tensile strength of paper and paperboard", and the wet tensile strength is tested with reference to the national standard GB / T 465.2-2008 "Determination of tensile strength of paper and paperboard after immersion in water". The test results are shown in Table 1.
[0045] Table 1
[0046]
[0047] As can be seen from Table 1, the organic chlorine content in the PAE wet strength agent prepared by the preparation method of the present invention is significantly reduced, and the wet strength agent has stronger dry and wet tensile strength after curing.
[0048] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.
Claims
1. A method for preparing a PAE wet strength agent with low organic chlorine small molecule content, characterized in that: The following steps are involved: Preparation of cross-linking agent and chain extender: epichlorohydrin and silane coupling agent undergo nucleophilic substitution reaction under alkaline conditions to obtain cross-linking agent, and then triethanolamine and 2-bromoethanol undergo quaternary ammonium salt reaction to obtain chain extender; Preparation of prepolymer PCC: After uniformly mixing diethylenetriamine, a catalyst, and deionized water, adipic acid is added to the system, followed by reaction at a temperature of 130-160°C for 1-2 hours. After that, the reaction vessel is unsealed, a chain extender is added to the system, and the temperature is controlled at 130-160°C to continue the reaction to obtain prepolymer PCC; Preparation of PAE wet strength agent: Use deionized water to adjust the solid content of prepolymer PCC to 10-15%, then add epichlorohydrin to the system, react at a temperature of 40-60°C for a period of time, add a crosslinker to the system and continue to keep the temperature for a period of time. After the reaction is completed, adjust the pH of the system to 3-4 to obtain a PAE wet strength agent with low organic chlorine small molecule content.
2. The method for preparing a PAE wet strength agent with low organic chlorine small molecule content according to claim 1, characterized in that: The silane coupling agent is one of KH-580 and KH-590.
3. The method for preparing a PAE wet strength agent with low organic chlorine small molecule content according to claim 1, characterized in that: The catalyst is p-toluenesulfonic acid.
4. The method for preparing a PAE wet strength agent with low organic chlorine small molecule content according to claim 1, characterized in that: The mass ratio of epichlorohydrin to silane coupling agent is 9.3-18.6:19-39.
5. The method for preparing a PAE wet strength agent with low organic chlorine small molecule content according to claim 1, characterized in that: The mass ratio of triethanolamine to 2-bromoethanol is 11.2-14.8:12.5-15.
5.
6. The method for preparing a PAE wet strength agent with low organic chlorine small molecule content according to claim 1, characterized in that: The mass ratio of diethylenetriamine, catalyst, deionized water, adipic acid and chain extender is 103-125:2.2-3.4:10-40:175-219:12-20.
7. The method for preparing a PAE wet strength agent with low organic chlorine small molecule content according to claim 1, characterized in that: The mass ratio of prepolymer PCC, epichlorohydrin and cross-linking agent is 25-31:3.6-4.8:14.4-16.
8.
8. The method for preparing a PAE wet strength agent with low organic chlorine small molecule content according to claim 1, characterized in that: When preparing PAE wet strength agent, the reaction time after adding epichlorohydrin is 20 to 30 minutes.
9. The method for preparing a PAE wet strength agent with low organic chlorine small molecule content according to claim 1, characterized in that: When preparing PAE wet strength agent, the reaction time after adding the cross-linking agent is 1 to 2 hours.
10. The method for preparing a PAE wet strength agent with low organic chlorine small molecule content according to claim 1, characterized in that: When preparing prepolymer PCC, adipic acid is added in 2 to 4 batches.