Efficient chlorine-free wet strength agent and preparation method thereof

Abstract

A preparation method of the high-efficiency chlorine-free wet strength agent comprises the following steps: mixing adipic acid and tetraethylenepentamine, and reacting at 155-175 DEG C for 6-8 hours to obtain prepolymer polyamide polyamine; diluting the prepolymer, adding ethylene glycol diglycidyl ether, heating to 30-45 DEG C, and preserving heat; adding epichlorohydrin to continue the heat preservation reaction, and adding acid to adjust the pH value of the system to 2-4 when the viscosity of the system is increased to 30-100 mPa.s; raising the temperature to 45-55 DEG C, adding a dechlorinating agent, and keeping the temperature; the high-efficiency chlorine-free wet strength agent for papermaking is prepared from adipic acid, tetraethylenepentamine, ethylene glycol diglycidyl ether and epichlorohydrin in a molar ratio of (0.5-1.2): (1-1.5): (0.2-1.0): (0.1-0.8) by adding deionized water to adjust the solid content, and the high-efficiency chlorine-free wet strength agent for papermaking is obtained. The prepared wet strength agent is chlorine-free and environment-friendly, can be used for food contact paper, is remarkably improved in retention and drainage aiding performance, shortens the curing time, and can greatly improve the wet strength, water resistance and folding strength of the paper.

Description

Technical Field

[0001] The invention relates to the technical field of papermaking wet strength agent preparation, in particular to a chlorine-free wet strength agent and a preparation method thereof. Background Art

[0002] Common wet strength agents include polyethyleneimine (PEI), urea-formaldehyde resin (UF), polyamide polyamine epichlorohydrin resin (PAE), etc., all of which have good wet strength effects. At present, the most widely used wet strength agent is polyamide polyamine epichlorohydrin resin, which is a water-soluble, cationic, thermosetting resin that does not contain formaldehyde polymers. It can be papered under neutral, slightly alkaline and acidic conditions, and has a wide range of pH values. PAE wet strength agent has a higher reinforcing effect on wood pulp than on grass waste paper. With the increase of beating degree, the surface area of ​​pulp fiber increases, the adsorption capacity of wet strength agent is greater, and the dry and wet strength of paper is correspondingly improved. It has a strong adsorption effect on negatively charged fillers, sizing agents and fine fibers, and has obvious retention and filtration effects in the papermaking process. The amount of addition depends on the wet strength requirements of the paper. Excessive addition will cause pulp flocculation, affecting the papermaking uniformity and the recycling of broken paper. It also improves the folding resistance, surface strength and transverse expansion rate of paper, and has a good effect on reducing wet paper breakage during paper machine operation.

[0003] Conventional PAE wet strength agents have a high chlorine content, mainly because during the synthesis process, epichlorohydrin undergoes a hydrolysis side reaction, producing a large amount of 3-chloro-1,2-propylene glycol (MCPD) and 1,3-dichloro-2-propanol (DCP), which limits the application of PAE wet strength agents in food contact paper. Currently, reducing the organic chlorine content and improving the wet strength effect are the main research directions for improving PAE wet strength agents.

[0004] Chinese patent CN101392478A discloses a method for preparing an epoxy cross-linked modified paper moistening agent, which uses a dibasic acid and a polyamine as raw materials to react to prepare a polyamide polyamine intermediate, takes a certain amount of the polyamide polyamine intermediate, epoxy resin and epichlorohydrin, reacts at a certain temperature until the product reaches a certain viscosity, and then adds acid to terminate the reaction to obtain an epoxy cross-linked modified paper moistening agent. This method can reduce the amount of epichlorohydrin used and reduce the organic chlorine content in the discharge; the product retention rate is greatly improved, which can not only improve the wet strength of the paper, but also increase the physical properties of the paper such as folding resistance, tensile strength and dry strength. However, the wet strength agent prepared by this method still contains organic chlorine, and its various properties as a paper wet strength agent need to be further improved. Summary of the invention

[0005] The technical problem to be solved by the present invention is to provide a chlorine-free, environmentally friendly, high moisturizing strength, short curing period type wet strength agent and a preparation method thereof, thereby overcoming the above-mentioned defects of the prior art.

[0006] The present invention is achieved by adopting the following technical solutions:

[0007] A method for preparing a high-efficiency chlorine-free wet strength agent comprises the following steps:

[0008] S1, mixing adipic acid and tetraethylenepentamine, reacting at 155-175°C for 6-8h to obtain a prepolymer polyamide polyamine;

[0009] S2. Dilute the prepolymer to a certain solid content, add ethylene glycol diglycidyl ether, and heat to 30-45°C for insulation;

[0010] S3, add epichlorohydrin and appropriate amount of water, continue to keep warm and react, when the viscosity of the system rises to 30-100mPa·s, add acid to adjust the pH of the system to 2-4;

[0011] S4, raise the temperature to 45-55°C, add dechlorinating agent, and keep warm;

[0012] S5, adding deionized water to adjust the solid content to obtain a high-efficiency chlorine-free wet strength agent for papermaking;

[0013] Wherein, the molar ratio of adipic acid, tetraethylenepentamine, ethylene glycol diglycidyl ether and epichlorohydrin is (0.5-1.2):(1-1.5):(0.2-1.0):(0.1-0.8).

[0014] The inventor unexpectedly found that the polyamide polyamine prepolymer was prepared by using tetraethylene pentamine and adipic acid, and then ethylene glycol diglycidyl ether was added for reaction, and finally epichlorohydrin was added to form a modified PAE wet strength agent, which unexpectedly can greatly improve the retention and drainage performance, and greatly improve the paper properties such as wet strength, water resistance and folding resistance of paper. The principle is not very clear, but it is speculated that it may be because the wet strength agent prepared by the present invention has a highly branched structure, which makes it easy to adsorb on the fiber surface. The retention performance is well improved when used alone. The cross-linked network formed between molecules and within molecules improves the bonding strength between paper fibers, which can greatly improve the wet strength, water resistance and folding resistance of paper. The inventor further found that replacing tetraethylene pentamine with conventional diethylene triamine, or replacing ethylene glycol diglycidyl ether with epoxy resin, does not significantly improve the paper properties such as wet strength, water resistance and folding resistance of paper. It is speculated that the unexpected synergistic effect is produced by the joint participation of tetraethylene pentamine and ethylene glycol diglycidyl ether in the reaction. Based on the above findings, the present invention is completed.

[0015] Preferably, the molar ratio of adipic acid, tetraethylenepentamine, ethylene glycol diglycidyl ether and epichlorohydrin is (0.6-1.1):(1.05-1.35):(0.4-0.9):(0.3-0.6).

[0016] More preferably, the molar ratio of adipic acid, tetraethylenepentamine, ethylene glycol diglycidyl ether and epichlorohydrin is 1:(1.25-1.45):(0.8-0.9):(0.5-0.6).

[0017] Preferably, in step S2, the insulation time is 0.5-3h.

[0018] The dechlorinating agent is selected from at least one of sodium thiosulfate, sodium bisulfite and sodium sulfite. The molar ratio of the dechlorinating agent to epichlorohydrin is (1-8): (0.03-0.4).

[0019] Preferably, the molar ratio of the dechlorinating agent to epichlorohydrin is (3-6):(0.1-0.3).

[0020] More preferably, the molar ratio of the dechlorinating agent to epichlorohydrin is (4.5-5.5):(0.15-0.25).

[0021] In step S3, the acid may be an acid commonly used in the art, such as hydrochloric acid, sulfuric acid, acetic acid, or acetic acid.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] 1. The wet strength agent prepared by the present invention is chlorine-free and environmentally friendly and can be used for paper in contact with food;

[0024] 2. The wet strength agent prepared by the present invention greatly improves the retention and drainage properties and shortens the aging period;

[0025] 3. The wet strength agent prepared by the present invention can greatly improve the wet strength, water resistance and folding resistance of paper. DETAILED DESCRIPTION

[0026] The following description is used to disclose the present invention so that those skilled in the art can implement the present invention. The preferred embodiments described below are only used as examples, but are not used to limit the scope of the present invention. Those skilled in the art can think of other obvious variations. The basic principles of the present invention defined in the following description can be applied to other embodiments, variations, improvements, equivalent solutions, and other technical solutions that do not deviate from the spirit and scope of the present invention.

[0027] The instruments or raw materials in the present invention without indicating the manufacturer are all conventional commercial instruments or raw materials.

[0028] Unless otherwise mentioned, the detection indicators involved in the embodiments of the present invention are detected by conventional detection methods in the art.

[0029] Example 1

[0030] Step (1): 10 parts by weight of adipic acid and 20 parts by weight of tetraethylenepentamine are mixed, and reacted at 165° C. for 6 hours to obtain a prepolymer polyamide polyamine;

[0031] Step (2): diluting the prepolymer to a solid content of about 30%, adding 8 parts by weight of ethylene glycol diglycidyl ether, heating to 30° C., and keeping the temperature for 1 hour;

[0032] Step (3): adding 7 parts by weight of deionized water and 3.5 parts by weight of epichlorohydrin, continuing the reaction at a heat preservation temperature, and when the viscosity of the system rises to 30 mPa·s, adding acetic acid to adjust the pH of the system to 3.0;

[0033] Step (4): raising the temperature to 50° C., adding 0.25 parts by weight of sodium bisulfite, and keeping the temperature for 1 hour;

[0034] Step (5): adding deionized water to adjust the solid content to about 12.5%, thereby obtaining a highly efficient chlorine-free wet strength agent for papermaking.

[0035] Example 2

[0036] Step (1): 12 parts by weight of adipic acid and 23 parts by weight of tetraethylenepentamine are mixed, and reacted at 170° C. for 6.5 hours to obtain a prepolymer polyamide polyamine;

[0037] Step (2): diluting the prepolymer to a solid content of about 35%, adding 10 parts by weight of ethylene glycol diglycidyl ether, heating to 30° C., and keeping the temperature for 1.5 h;

[0038] Step (3): adding 8 parts by weight of deionized water and 4 parts by weight of epichlorohydrin, continuing the reaction at a heat preservation temperature, and when the viscosity of the system rises to 30 mPa·s, adding acetic acid to adjust the pH of the system to 3.0;

[0039] Step (4): heating to 50° C., adding 0.28 parts by weight of sodium sulfite, and keeping warm for 1 hour;

[0040] Step (5): adding deionized water to adjust the solid content to about 12.5%, thereby obtaining a highly efficient chlorine-free wet strength agent for papermaking.

[0041] Example 3

[0042] Step (1): 13 parts by weight of adipic acid and 24 parts by weight of tetraethylenepentamine are mixed, and reacted at 170° C. for 7.5 hours to obtain a prepolymer polyamide polyamine;

[0043] Step (2): diluting the prepolymer to a solid content of about 40%, adding 13 parts by weight of ethylene glycol diglycidyl ether, raising the temperature to 35° C., and keeping the temperature for 2.5 hours;

[0044] Step (3): adding 9 parts by weight of deionized water and 4.5 parts by weight of epichlorohydrin, continuing the heat-keeping reaction, and when the viscosity of the system rises to 35 mPa·s, adding acetic acid to adjust the pH of the system to 2.8;

[0045] Step (4): heating to 55° C., adding 0.3 parts by weight of sodium thiosulfate, and keeping warm for 1 hour;

[0046] Step (5): adding deionized water to adjust the solid content to about 12.5%, thereby obtaining a highly efficient chlorine-free wet strength agent for papermaking.

[0047] Example 4

[0048] Step (1): 15 parts by weight of adipic acid and 25 parts by weight of tetraethylenepentamine are mixed, and reacted at 170° C. for 8 hours to obtain a prepolymer polyamide polyamine;

[0049] Step (2): diluting the prepolymer to a solid content of about 40%, adding 15 parts by weight of ethylene glycol diglycidyl ether, raising the temperature to 35° C., and keeping the temperature for 3 hours;

[0050] Step (3): adding 10 parts by weight of deionized water and 5 parts by weight of epichlorohydrin, continuing the reaction at a heat preservation temperature, and when the viscosity of the system rises to 35 mPa·s, adding acetic acid to adjust the pH of the system to 2.5;

[0051] Step (4): heating to 55° C., adding 0.35 parts by weight of sodium thiosulfate, and keeping warm for 1 hour;

[0052] Step (5): adding deionized water to adjust the solid content to about 12.5%, thereby obtaining a highly efficient chlorine-free wet strength agent for papermaking.

[0053] Comparative Example 1

[0054] The conventional method is used to prepare the polyamide polyamine epichlorohydrin resin wet strength agent, and the specific process is as follows:

[0055] Step (1): 15 parts by weight of adipic acid and 11 parts by weight of diethylenetriamine are mixed, and reacted at 170° C. for 8 hours to obtain a prepolymer polyamide polyamine;

[0056] Step (2): diluting the prepolymer to a solid content of about 40%, adding 13 parts by weight of epichlorohydrin, and continuing the reaction at a heat preservation temperature. When the viscosity of the system rises to 35 mPa·s, adding acetic acid to adjust the system pH to 2.5;

[0057] Step (3): adding deionized water to adjust the solid content to about 12.5% ​​to obtain a polyamide polyamine epichlorohydrin resin wet strength agent.

[0058] Comparative Example 2

[0059] Without adding epichlorohydrin, the other processes are similar to those in Example 4, and the specific process is as follows:

[0060] Step (1): 15 parts by weight of adipic acid and 25 parts by weight of tetraethylenepentamine are mixed, and reacted at 170° C. for 8 hours to obtain a prepolymer polyamide polyamine;

[0061] Step (2): dilute the prepolymer to a solid content of about 40%, add 15 parts by weight of ethylene glycol diglycidyl ether, raise the temperature to 35° C., keep the temperature for 3 hours, and add acetic acid to adjust the system pH to 2.5;

[0062] Step (3): heating to 55° C., adding 0.35 parts by weight of sodium thiosulfate, and keeping warm for 1 hour;

[0063] Step (4): adding deionized water to adjust the solid content to about 12.5%, thereby obtaining a highly efficient chlorine-free wet strength agent for papermaking.

[0064] Comparative Example 3

[0065] The same amount of diethylenetriamine was used to replace tetraethylenepentamine, and epoxy resin E-20 was used to replace ethylene glycol diglycidyl ether. The other steps were the same as those in Example 4. The specific process is as follows:

[0066] Step (1): 15 parts by weight of adipic acid and 25 parts by weight of diethylenetriamine are mixed, and reacted at 170° C. for 8 hours to obtain a prepolymer polyamide polyamine;

[0067] Step (2): dilute the prepolymer to a solid content of about 40%, add 15 parts by weight of epoxy resin E-20, raise the temperature to 35° C., and keep warm for 3 hours;

[0068] Step (3): adding 10 parts by weight of deionized water and 5 parts by weight of epichlorohydrin, continuing the reaction at a heat preservation temperature, and when the viscosity of the system rises to 35 mPa·s, adding acetic acid to adjust the pH of the system to 2.5;

[0069] Step (4): heating to 55° C., adding 0.35 parts by weight of sodium thiosulfate, and keeping warm for 1 hour;

[0070] Step (5): adding deionized water to adjust the solid content to about 12.5%, thereby obtaining a highly efficient chlorine-free wet strength agent for papermaking.

[0071] Comparative Example 4

[0072] The same amount of diethylenetriamine was used to replace tetraethylenepentamine, and the other steps were the same as in Example 4. The specific process is as follows:

[0073] Step (1): 15 parts by weight of adipic acid and 25 parts by weight of diethylenetriamine are mixed, and reacted at 170° C. for 8 hours to obtain a prepolymer polyamide polyamine;

[0074] Step (2): diluting the prepolymer to a solid content of about 40%, adding 15 parts by weight of ethylene glycol diglycidyl ether, raising the temperature to 35° C., and keeping the temperature for 3 hours;

[0075] Step (3): adding 10 parts by weight of deionized water and 5 parts by weight of epichlorohydrin, continuing the reaction at a heat preservation temperature, and when the viscosity of the system rises to 35 mPa·s, adding acetic acid to adjust the pH of the system to 2.5;

[0076] Step (4): heating to 55° C., adding 0.35 parts by weight of sodium thiosulfate, and keeping warm for 1 hour;

[0077] Step (5): adding deionized water to adjust the solid content to about 12.5%, thereby obtaining a highly efficient chlorine-free wet strength agent for papermaking.

[0078] Comparative Example 5

[0079] The same amount of epoxy resin E-20 was used to replace ethylene glycol diglycidyl ether, and the other steps were the same as in Example 4. The specific process is as follows:

[0080] Step (1): 15 parts by weight of adipic acid and 25 parts by weight of tetraethylenepentamine are mixed, and reacted at 170° C. for 8 hours to obtain a prepolymer polyamide polyamine;

[0081] Step (2): dilute the prepolymer to a solid content of about 40%, add 15 parts by weight of epoxy resin E-20, raise the temperature to 35° C., and keep the temperature for 3 hours;

[0082] Step (3): adding 10 parts by weight of deionized water and 5 parts by weight of epichlorohydrin, continuing the reaction at a heat preservation temperature, and when the viscosity of the system rises to 35 mPa·s, adding acetic acid to adjust the pH of the system to 2.5;

[0083] Step (4): heating to 55° C., adding 0.35 parts by weight of sodium thiosulfate, and keeping warm for 1 hour;

[0084] Step (5): adding deionized water to adjust the solid content to about 12.5%, thereby obtaining a highly efficient chlorine-free wet strength agent for papermaking.

[0085] Chloropropanol was detected by GC / MS (Agilent 7890B-7000C) triple quadrupole gas chromatography-mass spectrometry, and the chromatographic column was Agilent HP-5 chromatographic column. The test results of organic chlorine content are shown in Table 1.

[0086] Table 1 Sample organic chlorine content test data

[0087]

[0088] Application Examples

[0089] Unbleached kraft pulp was used, wherein the ratio of coniferous wood pulp to hardwood wood pulp was 5:5, and the beating degree was 38°SR. The filler addition amount was 15%, the retention agent dosage was 400ppm, the pulp concentration was diluted to 1.0% (mass percentage) with tap water, the wet strength agent addition amount was 1% (absolute dry weight of wet strength agent / absolute dry weight percentage of pulp), and the wet strength agent prepared in the above examples was added and stirred for 1 minute. The paper weight was 120g / m 2 The retention rate is compared based on the quantitative analysis of the hand sheets, and the water filterability is compared based on the beating degree of various pulps. Then, the dry tensile strength and wet tensile strength are tested according to GB / T2914-2008 and GB / T465.2-2008, and the ratio of wet / dry tensile index is calculated. For test data, see Table 2 for the test results of pulp and paper indicators after adding wet strength agent.

[0090] Table 2 Paper sample wet strength performance test data

[0091]

[0092] It can be seen from the experimental results that the chlorine-free wet strength agent prepared by the present invention has a chloropropanol content of 0, and the comparative example 1 adopts a conventional PAE synthesis method, and the chloropropanol content is 3562ppm. The detection results are shown in Table 1.

[0093] The paper basis weight of the blank sample in Table 2 is 120.0 g / m 2 The paper weight of the comparative example is 124.1-126.2g / m 2 The paper weights of Examples 1-4 are significantly higher than those of the blank sample and the comparative example, and can reach up to 128.5 g / m 2 This indicates that the wet strength agent of the present invention has excellent retention of the slurry, increases the utilization rate of the slurry, and can significantly improve the retention and filtration performance.

[0094] The beating degrees of Examples 1-4 in Table 2 are below 37.1°SR, with the lowest reaching 36.2°SR, which is lower than the beating degrees of the blank sample and the comparative example, indicating that the wet strength agent of the present invention has better water filtration performance for the slurry.

[0095] The tensile strength of Examples 1-4 in Table 2 is between 1.15-1.29 KN / m, which is significantly higher than the blank sample and the comparative example. The dry tensile coefficient and wet tensile coefficient of Examples 1-4 are also significantly higher than the blank sample and the comparative example, indicating that the wet strength agent of the present invention has better dry strength performance and wet strength performance.

[0096] The wet / dry ratios of Examples 1-4 in Table 2 are all above 23.68%, the comparative example is between 13.03% and 21.43%, and the blank sample paper is only 4.39%, indicating that the wet enhancement effect of the present invention is better and the maturation period is greatly shortened.

[0097] It can be further seen from the data in Table 2 that replacing tetraethylene pentamine with diethylene triamine or replacing ethylene glycol diglycidyl ether with epoxy resin does not significantly improve paper properties such as wet strength, water resistance and folding resistance, indicating that the joint reaction of tetraethylene pentamine and ethylene glycol diglycidyl ether produces an important synergistic effect.

[0098] It should be understood by those skilled in the art that the above embodiments are only examples and do not limit the present invention. The purpose of the present invention has been fully and effectively achieved. The functional and structural principles of the present invention have been demonstrated and explained in the embodiments, and the embodiments of the present invention may be deformed or modified in any way without departing from the principles.

Claims

1. A method for preparing a high-efficiency chlorine-free wet strength agent, characterized in that: The steps include: S1, mixing adipic acid and tetraethylenepentamine, reacting at 155-175°C for 6-8h to obtain a prepolymer polyamide polyamine; S2. Dilute the prepolymer to a certain solid content, add ethylene glycol diglycidyl ether, and heat to 30-45°C for insulation; S3, add epichlorohydrin and appropriate amount of water, continue to keep warm and react, when the viscosity of the system rises to 30-100mPa·s, add acid to adjust the pH of the system to 2-4; S4, raise the temperature to 45-55°C, add dechlorinating agent, and keep warm; S5, adding deionized water to adjust the solid content to obtain a high-efficiency chlorine-free wet strength agent for papermaking; Wherein, the molar ratio of adipic acid, tetraethylenepentamine, ethylene glycol diglycidyl ether and epichlorohydrin is (0.5-1.2):(1-1.5):(0.2-1.0):(0.1-0.8).

2. The method according to claim 1, characterized in that The molar ratio of adipic acid, tetraethylenepentamine, ethylene glycol diglycidyl ether and epichlorohydrin is (0.6-1.1):(1.05-1.35):(0.4-0.9):(0.3-0.6).

3. The method according to claim 1, characterized in that The molar ratio of adipic acid, tetraethylenepentamine, ethylene glycol diglycidyl ether and epichlorohydrin is 1:(1.25-1.45):(0.8-0.9):(0.5-0.6).

4. The method according to claim 1, characterized in that In step S2, the insulation time is 0.5-3h.

5. The method according to claim 1, characterized in that The dechlorinating agent is selected from at least one of sodium thiosulfate, sodium bisulfite and sodium sulfite.

6. The method according to claim 1, characterized in that The molar ratio of the dechlorinating agent to epichlorohydrin is (1-8):(0.03-0.4).

7. The method according to claim 1, characterized in that The molar ratio of the dechlorinating agent to epichlorohydrin is (3-6):(0.1-0.3).

8. The method according to claim 1, characterized in that The molar ratio of the dechlorinating agent to epichlorohydrin is (4.5-5.5):(0.15-0.25).

9. The method according to claim 1, characterized in that In step S3, the acid is selected from at least one of hydrochloric acid, sulfuric acid, acetic acid, and acetic acid.

10. A high-efficiency chlorine-free wet strength agent prepared according to the method of claims 1-9.

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