A preparation method of modified lignin wet strength agent
By grafting copolymerization of hydroxymethylated modified lignin with polyamide epoxy resin, a modified lignin wet strength agent was prepared, which solved the problem of high cost of existing papermaking wet strength agents and achieved high quality and low price wet strength properties.
Patent Information
- Application Number
- CN202411986656.5
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-12-31
- Publication Date
- 2025-04-08
AI Technical Summary
The existing paper-making wet strength agents are costly and it is difficult to achieve high-quality, low-cost wet strength properties.
A modified lignin wet strength agent was prepared by graft copolymerization of hydroxymethylated modified lignin with polyamide epoxy resin. The method includes mixing the modified lignin with the polyamide epoxy resin in a certain proportion, adjusting the pH value and reacting at a suitable temperature to obtain a lignin modified wet strength agent.
It realizes a low-cost and excellent performance lignin modified wet strength agent, effectively utilizes renewable resources and reduces papermaking costs.
Abstract
Description
Technical Field
[0001] The invention relates to the field of papermaking chemicals, and in particular to a method for preparing a modified lignin wet strength agent. Background Art
[0002] After ordinary paper and paperboard are soaked in water, their mechanical strength only retains 4-10% of the dry strength. If you want to give them a certain wet strength performance, you need to add a wet strength agent during the papermaking process or post-processing process to achieve the desired effect. However, the wet strength agents currently used are expensive, which leads to an increase in paper costs. Therefore, it is imperative to develop high-quality and low-cost papermaking wet strength agents.
[0003] Lignin is the second largest natural polymer material in nature after cellulose in quantity. It is a natural polymer material with a three-dimensional network structure. Its molecular structure is mainly composed of three phenylpropane structural units: syringylpropane (S), guaiacylpropane (G), and p-hydroxyphenylpropane (H). There are a large number of benzene ring structures in the structure, and it contains polar groups such as hydroxyl, carbonyl, and carboxyl, which provides a theoretical basis for its further functionalization. However, in the actual functionalization process, lignin has a large steric hindrance and few reactive sites, resulting in low reactivity and difficulty in effective functionalization. In order to improve the reactivity of lignin, it is necessary to modify lignin. The modification methods mainly include hydroxymethylation, phenolization, and demethylation. Among them, the hydroxymethylation method introduces hydroxymethyl groups into the lignin structure and is one of the most widely used methods.
[0004] Polyamide epoxy resin (PAE) is a widely used wet strength agent with good performance. It has active amino and hydroxymethyl groups in its structure. The present invention aims to prepare a new wet strength agent by graft copolymerizing hydroxymethylated lignin with polyamide epoxy resin, thereby effectively utilizing one of the renewable resources of lignin and reducing the cost of the wet strength agent. Summary of the invention
[0005] After the lignin of the invention is modified by hydroxymethylation, it has higher reaction activity, and after being grafted and copolymerized with PAE, a lignin modified wet strength agent with low cost and excellent performance is prepared.
[0006] The present invention is specifically implemented in the following manner.
[0007] A method for preparing a modified lignin wet strength agent, specifically comprising mixing a polyamide epoxy resin and a hydroxymethylated modified lignin in a certain proportion, adjusting the pH value of the system to 4.0-7.0, reacting at a certain temperature for a certain time, and cooling to obtain a lignin modified wet strength agent;
[0008] The ratio of the polyamide epoxy resin to the hydroxymethylated modified lignin is 1:(0.3-0.6).
[0009] Preferably, the pH value of the system is 4.0-8.0; the reaction temperature is 40-70° C.; and the reaction time is 1-5 hours.
[0010] Preferably, the preparation steps of the polyamide epoxy resin include: mixing a dicarboxylic acid, polyethylene polyamine, a polyacid with a functionality ≥ 3 and a catalyst, heating to 160-190° C. for reaction for 2-6 hours, adding dilution water after sufficient reaction, and diluting the polymer to a solid content of 45-60%; adding epichlorohydrin dropwise to the polymer solution obtained in the previous step at room temperature for 40-60 minutes, reacting at 30-40° C. for 30-60 minutes, reacting at 45-50° C. for 60-90 minutes, and heating to 65-70° C.; when the viscosity reaches 40-100 cps, adding a terminating acid to terminate the reaction, adjusting the pH to 2-5, and obtaining the polyamide epoxy resin.
[0011] More preferably, the weight proportions of the raw materials of the polyamide epoxy resin are as follows: 4-6 parts of dicarboxylic acid, 3-5 parts of polyethylene polyamine, 0.01-0.2 parts of polyacid, 0.01-0.15 parts of catalyst, 4-5 parts of epichlorohydrin, and 0.5-1.5 parts of terminating acid.
[0012] More preferably, the polyacid is citric acid.
[0013] More preferably, the dicarboxylic acid includes one or more of oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, terephthalic acid, maleic acid, and fumaric acid.
[0014] More preferably, the polyethylene polyamine includes one or more of diethylenetriamine, triethylenetetramine and tetraethylenepentamine.
[0015] More preferably, the catalyst includes one or more of sulfuric acid, hydrochloric acid, phosphoric acid, p-toluenesulfonic acid, macroporous cation exchange resin, and Lewis acid.
[0016] More preferably, the terminating acid includes one or more of sulfuric acid, hydrochloric acid, acetic acid, and phosphoric acid.
[0017] Preferably, the preparation step of the hydroxymethylated modified lignin includes: adding lignin, formaldehyde solution and solid alkali into a hydrothermal reactor, stirring evenly, sealing the reactor, and then heating to a specific temperature, reacting for a certain time, cooling to room temperature, collecting the product, washing, filtering and drying to obtain hydroxymethylated modified lignin.
[0018] More preferably, the lignin is alkali lignin;
[0019] More preferably, the solid base comprises sodium hydroxide and / or potassium hydroxide.
[0020] More preferably, the mass concentration of the formaldehyde solution is 37%.
[0021] More preferably, the ratio of the lignin, the formaldehyde solution and the solid alkali is 1:(0.25-0.75):(0.01-0.06).
[0022] More preferably, the reaction temperature is 80-130° C., and the reaction time is 60-180 min.
[0023] More preferably, the washing solvent is water.
[0024] Beneficial effects of the present invention: The lignin used in the present invention is a by-product of the caustic soda pulping process in the papermaking process, which is usually directly discharged into the nature as combustion or waste, causing environmental pollution. The hydroxymethylated modified lignin turns the papermaking by-product alkali lignin into treasure, and is grafted and copolymerized with polyamide epichlorohydrin (PAE) to become a papermaking additive, thereby realizing the high-value utilization of alkali lignin. DETAILED DESCRIPTION
[0025] The present invention is further described below by way of examples, but the present invention is not limited to the scope of the examples. The experimental methods in the following examples without specifying specific conditions are carried out according to conventional methods and conditions, or selected according to the product specifications. The reagents and raw materials used in all the examples of the present invention are commercially available.
[0026] Example 1
[0027] A method for preparing a modified lignin wet strength agent, specifically comprising:
[0028] (1) Preparation of polyamide epoxy resin: 132 g of bottom water, 260 g of adipic acid and 1.5 g of citric acid were added to a reaction kettle, stirring was started, 180 g of diethylenetriamine was slowly added under stirring, stirring and reacting for 1 hour, 1.5 g of concentrated sulfuric acid as a catalyst was added, stirring and reacting for another 1 hour, then the temperature was continued to be raised to 165° C. and reacting for 5 hours, after the water output reached the designed amount, dilution water was added to dilute the polymer to a solid content of 50%; 160 g of the polymer solution was taken, 400 g of water was added, stirring was uniformly followed by slowly dropping 45 g of epichlorohydrin for 40 min, after the dropwise addition was completed, the reaction was carried out at 30° C. for 60 min, at 45° C. for 90 min, then the temperature was raised to 65° C., when the viscosity of the reaction solution reached 40 cps, 50% dilute sulfuric acid was added to terminate the reaction, and the pH value was adjusted to 3.7 to obtain polyamide epoxy resin;
[0029] (2) Preparation of hydroxymethylated modified lignin: 12 g of wheat straw alkali lignin, 0.12 g of solid sodium hydroxide, and 3.0 g of 37% formaldehyde solution were added to a hydrothermal reactor, stirred evenly, and the reactor was sealed, and then the temperature was raised to 80°C and kept for 180 min. After cooling to room temperature, the product was washed, filtered, and dried to obtain hydroxymethylated lignin;
[0030] (3) Preparation of modified lignin wet strength agent: 100 g of the polyamide epoxy resin obtained in step (1) and 30 g of the hydroxymethylated lignin obtained in step (2) were mixed uniformly, the pH value of the system was adjusted to 4.0, the temperature was raised to 40° C., the reaction was kept at this temperature for 5 hours, and then the temperature was lowered to obtain a lignin modified wet strength agent.
[0031] Example 2
[0032] A method for preparing a modified lignin wet strength agent, specifically comprising:
[0033] (1) Preparation of polyamide epoxy resin: 100 g of bottom water, 250 g of adipic acid and 1.5 g of citric acid were added to a reaction kettle, stirring was started, 181 g of diethylenetriamine was slowly added under stirring, stirring and reacting for 1 hour, 1.2 g of concentrated sulfuric acid as a catalyst was added, stirring and reacting for another 1 hour, then the temperature was continued to be raised to 170° C. (the reaction temperature was set according to actual needs) and reacted for 4 hours. After the water output reached the designed amount, dilution water was added to dilute the polymer to a solid content of 50%; 200 g of the polymer solution was taken, 400 g of water was added, and after stirring evenly, 64 g of epichlorohydrin was added, and the dropwise addition time was 60 min. After the dropwise addition was completed, the reaction was carried out at 40° C. for 30 min, at 50° C. for 60 min, and then the temperature was raised to 70° C. When the viscosity of the reaction solution reached 70 cps, 50% dilute sulfuric acid was added to terminate the reaction, and acid was added to adjust the pH to 3.5 to obtain polyamide epoxy resin;
[0034] (2) Preparation of hydroxymethylated modified lignin: 12 g of wheat straw alkali lignin, 0.42 g of solid sodium hydroxide, and 3.0 g of 37% formaldehyde solution were added to a hydrothermal reactor, and the mixture was evenly reduced by half. The reactor was sealed, and then the temperature was raised to 100°C and kept for 120 min. After cooling to room temperature, the product was washed with water, filtered, and dried to obtain hydroxymethylated lignin;
[0035] (3) Preparation of modified lignin wet strength agent: 100 g of the polyamide epoxy resin obtained in step (1) and 40 g of the hydroxymethylated lignin obtained in step (2) were mixed uniformly, the pH value of the system was adjusted to 6.0, the temperature was raised to 50° C., the reaction was kept at this temperature for 3 hours, and then the temperature was lowered to obtain a lignin modified wet strength agent.
[0036] Example 3
[0037] A method for preparing a modified lignin wet strength agent, specifically comprising:
[0038] (1) Preparation of polyamide epoxy resin: 80 g of bottom water, 146 g of adipic acid and 1.0 g of citric acid were added to a reaction kettle, stirring was started, 103 g of diethylenetriamine was slowly added under stirring, stirring and reacting for 1 hour, 1.0 g of concentrated sulfuric acid as a catalyst was added, stirring and reacting for another 1 hour, and then the temperature was continued to be raised to 190° C. (the reaction temperature was set according to actual needs) and reacted for 2 hours. After the water output reached the designed amount, dilution water was added to dilute the polymer to a solid content of 50%; 200 g of the polymer solution was taken, 400 g of water was added, and after stirring evenly, 56 g of epichlorohydrin was added, and the addition time was 50 min. After the addition was completed, the reaction was carried out at 35° C. for 45 min, and at 47° C. for 75 min, and then the temperature was raised to 67° C. When the viscosity of the reaction solution reached 100 cps, 50% dilute sulfuric acid was added to terminate the reaction, and an acid or base was added to adjust the pH to 4.0 to obtain a polyamide epoxy resin;
[0039] (2) Preparation of hydroxymethylated modified lignin: 12 g of wheat straw alkali lignin, 0.6 g of solid sodium hydroxide, and 6.0 g of 37% formaldehyde solution were added to a hydrothermal reactor, and the mixture was evenly reduced by half. The reactor was sealed, and then the temperature was raised to 180°C and kept for 60 min. After cooling to room temperature, the product was washed, filtered, and dried to obtain hydroxymethylated lignin;
[0040] (3) Preparation of modified lignin wet strength agent: 100 g of the polyamide epoxy resin obtained in step (1) and 60 g of the hydroxymethylated lignin obtained in step (2) were mixed uniformly, the pH value of the system was adjusted to 8.0, and then the temperature was raised to 60° C., kept warm for reaction for 1 hour, and then cooled to obtain a lignin modified wet strength agent.
[0041] Comparative Example 1
[0042] Compared with Example 1, the only difference is that the hydroxymethylated modified lignin is replaced by unmodified lignin.
[0043] Comparative Example 2
[0044] Compared with Example 1, the only difference is that sodium lignin sulfonate is used to replace the hydroxymethylated modified lignin.
[0045] Implementation Effect
[0046] 400SR softwood pulp and 350SR hardwood pulp were mixed in a mass ratio of 1:1 and beaten to 370SR. The wet strength agent described in the comparative example and Examples 1-3 was added, and the specific addition amount was 120 kg / t paper. The papermaking basis weight was 50 g / m 2. The blank sample is a sample without any wet strength agent. After being made into sheets by a LABTECH 73-62 semi-automatic paper former, the sheets were pressed by a LABTECH 73-50 standard paper press, dried on a paper fast dryer, and aged in an oven at 105°C for 15 minutes to balance the moisture, and then the dry and wet strength of the paper samples were tested. The results are shown in the following table, in which the application performance of the present invention is better than that of the wet strength agent shown in the comparative example.
[0047] Table 1 Physical indexes of paper samples (temperature / humidity, 25°C / 40%)
[0048] Wet strength agent type Dry tensile strength (kN / m) Wet tensile strength (kN / m) Wet strength retention % (wet / dry) Blank 1.698 0.067 3.9 Example 1 3.263 1.761 53.9 Example 2 3.356 1.972 58.7 Example 3 3.369 1.991 59.0 Comparative Example 1 2.100 0.084 7.95 Comparative Example 2 3.002 1.341 44.67
[0049] The above shows and describes the basic principles, main features and advantages of the present invention. It should be understood by those skilled in the art that the present invention is not limited by the above embodiments. The above embodiments and descriptions are only for explaining the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, which fall within the scope of the present invention to be protected. The scope of the present invention to be protected is defined by the attached claims and their equivalents.
Claims
1. A method for preparing a modified lignin wet strength agent, characterized in that: After mixing polyamide epoxy resin and hydroxymethyl modified lignin in a certain proportion, adjusting the pH value of the system to 4.0-7.0, then reacting at a certain temperature for a certain time, and cooling to obtain the modified lignin wet strength agent of the present invention; The ratio of the polyamide epoxy resin to the hydroxymethylated modified lignin is 1:(0.3-0.6).
2. The method for preparing a modified lignin wet strength agent according to claim 1, characterized in that: The pH value of the system is between 4.0 and 8.0; The reaction temperature is 40-70°C; The reaction time is 1-5 hours.
3. The method for preparing a modified lignin wet strength agent according to claim 1, characterized in that: The preparation steps of the polyamide epoxy resin include: mixing dicarboxylic acid, polyethylene polyamine, polyacid with functionality ≥3 and catalyst, heating to 160-190° C. for reaction for 2-6 hours, adding dilution water after sufficient reaction, and diluting the polymer to a solid content of 45-60%; dripping epichlorohydrin into the polymer solution obtained in the previous step at room temperature for 40-60 minutes, reacting at 30-40° C. for 30-60 minutes, reacting at 45-50° C. for 60-90 minutes, and heating to 65-70° C.; when the viscosity reaches 40-100 cps, adding terminating acid to terminate the reaction, adjusting the pH to 2-5, and obtaining the polyamide epoxy resin.
4. The method for preparing a polyamide epoxy resin according to claim 3, wherein: The weight proportions of the raw materials are as follows: 4-6 parts of dicarboxylic acid, 3-5 parts of polyethylene polyamine, 0.01-0.2 parts of polyacid, 0.01-0.15 parts of catalyst, 4-5 parts of epichlorohydrin, and 0.5-1.5 parts of terminating acid.
5. The method for preparing a polyamide epoxy resin according to claim 3, wherein: The dicarboxylic acid includes one or more of oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, terephthalic acid, maleic acid, and fumaric acid; The polyethylene polyamine includes one or more of diethylenetriamine, triethylenetetramine, and tetraethylenepentamine; The polyacid is citric acid; The catalyst includes one or more of sulfuric acid, hydrochloric acid, phosphoric acid, p-toluenesulfonic acid, macroporous cation exchange resin, and Lewis acid; The terminating acid includes one or more of sulfuric acid, hydrochloric acid, acetic acid, and phosphoric acid.
6. The method for preparing a modified lignin wet strength agent according to claim 1, characterized in that: The preparation steps of the hydroxymethylated modified lignin include: adding lignin, formaldehyde solution and solid alkali into a hydrothermal reactor, stirring evenly, sealing the reactor, heating to a specific temperature, reacting for a certain time, cooling to room temperature, collecting the product, washing, filtering and drying to obtain the hydroxymethylated modified lignin.
7. The method for preparing hydroxymethylated modified lignin according to claim 6, characterized in that: The lignin is alkali lignin; The solid alkali comprises sodium hydroxide and / or potassium hydroxide; The mass concentration of the formaldehyde solution is 37%; The ratio of the lignin, the formaldehyde solution and the solid alkali is 1:(0.25-0.75):(0.01-0.06); The reaction temperature is 80-130°C and the reaction time is 60-180min; The washing solvent is water.