Preparation method of environment-friendly modified glyoxal water repellent agent

Abstract

The invention provides a preparation method of an environment-friendly modified glyoxal water repellent agent, which comprises the following steps: purging and replacing air in a reaction kettle with nitrogen, adding a glyoxal aqueous solution into the reaction kettle, adjusting the pH value to 3-5 with an alkali solution, and then adding urea according to the molar ratio of glyoxal to urea of (1.0-2.0): 1, the reaction temperature of 40-75 DEG C and the reaction time of 1-2 hours; polyhydric alcohol is added into the obtained solution, the molar ratio of polyhydric alcohol to glyoxal is (1.0-1.5): 1, a reaction is conducted for 2-3 h at the temperature of 60-85 DEG C, and the modified glyoxal water repellent agent is obtained. The process is simple, the raw materials are cheap and easy to obtain, the reaction conditions are mild, the viscosity of the coating is moderate after the coating is applied, and the wet friction resistance, glossiness and smoothness of paper can be well improved in the papermaking coating process. Compared with a traditional water-resistant agent, the modified glyoxal water-resistant agent can better meet the performance requirement of paper, and the quality of the paper is improved.

Description

Technical Field

[0001] The invention relates to the technical field of papermaking coating water-repellent preparation, in particular to a method for preparing an environmentally friendly modified glyoxal water-repellent. Background Art

[0002] In the paper coating process, water repellent is usually used to improve the wet friction resistance, glossiness and smoothness of paper. Water repellent can reduce the water solubility of pigments and adhesives after drying and film formation, improve the wet friction resistance and pick strength of coated paper, effectively improve the printing performance of coated paper, and reduce hair loss and powder loss. Water repellents for paper coating are mainly modified melamine formaldehyde resin, polyamide polyurea epichlorohydrin and urea-formaldehyde resin, but they will release harmful formaldehyde and harmful substances AOX during production, use and storage.

[0003] Chinese patent CN102312395A discloses a method for preparing a papermaking water-repellent agent, which uses glyoxal to completely replace formaldehyde to synthesize glyoxal / urea resin, fundamentally solving the problem of formaldehyde in urea-formaldehyde resin, avoiding formaldehyde pollution, and having a significant water-repellent effect. However, when the glyoxal water-repellent agent is used in the papermaking coating process, the gloss and smoothness of the paper are poor. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide a method for preparing a modified glyoxal water repellent, which can solve the formaldehyde pollution in traditional water repellents and improve the glossiness and smoothness of coated paper.

[0005] The present invention is achieved by adopting the following technical solutions:

[0006] A method for preparing an environmentally friendly modified glyoxal water repellent comprises the following steps:

[0007] S1, using nitrogen to purge and replace the air in the reactor, adding a glyoxal aqueous solution into the reactor, adjusting the pH value to 3-5 with an alkaline solution, and then adding urea, the molar ratio of glyoxal to urea is 1.0-2.0:1, the reaction temperature is 40-75°C, and the reaction time is 1-2h;

[0008] S2, adding polyol to the solution obtained in step S1, wherein the molar ratio of the polyol to glyoxal is 1.0-1.5:1, and continuing the reaction at 60-85° C. for 2-3 hours to obtain the modified glyoxal water repellent.

[0009] The alkaline solution can be an alkaline solution commonly used in the art, such as at least one selected from sodium hydroxide aqueous solution, potassium hydroxide aqueous solution, calcium hydroxide aqueous solution, and ammonia water. The concentration of the alkaline solution is not limited and can be prepared according to actual needs, and its function is to adjust the pH value of glyoxal.

[0010] The polyol can be a trihydric alcohol, a tetrahydric alcohol, a pentahydric alcohol, or a hexahydric alcohol, preferably a C3-C6 polyhydric alcohol, such as glycerol, pentaerythritol, sorbitol, or xylitol, preferably glycerol.

[0011] Preferably, the molar ratio of glyoxal to urea is 1.2-1.8:1, more preferably 1.4-1.6:1, and most preferably 1.5:1.

[0012] Preferably, the molar ratio of polyol to glyoxal is 1.1-1.4:1, more preferably 1.2-1.3:1, and most preferably 1.2:1.

[0013] The preparation process of the present invention does not add formaldehyde and organic halides (AOX), eliminating the source of harm to human health. Urea and glyoxal undergo addition and polycondensation reactions, and then polyols are added for modification, thereby improving the performance of urea-glyoxal resin, improving the stability of the product, and helping to form a network structure with fibers, limiting the movement between fibers, preventing fiber swelling and water absorption, and improving wet friction resistance.

[0014] The inventor unexpectedly found that after urea and glyoxal react, further adding polyols for modification, the modified glyoxal water repellent obtained can unexpectedly improve the smoothness and glossiness of coated paper. This may be because the water repellent modified by polyols can be combined with papermaking fillers to fill the gaps in the paper during coating, thereby improving the smoothness and glossiness. However, this effect is not positively correlated with the number of hydroxyl groups of the polyol. The inventor found that the use of triols for modification, especially propylene glycol, is better than tetrahydric alcohols to hexahydric alcohols in improving the smoothness and glossiness of coated paper, indicating that the more hydroxyl groups in the polyol, the better the modification effect. In addition, a series of water repellents were synthesized using different dialdehydes or using melamine instead of urea, but the above-mentioned effect of improving smoothness and glossiness was not found, which further deepened the unpredictability of the above-mentioned improvement of the present invention.

[0015] The invention has simple process, cheap and readily available raw materials, mild reaction conditions, moderate viscosity of the coating after application, and can well improve the wet friction resistance, glossiness and smoothness of paper in the papermaking coating process. Compared with the traditional water-repellent, the modified glyoxal water-repellent of the invention can better meet the performance requirements of paper and improve the quality of paper. DETAILED DESCRIPTION

[0016] 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.

[0017] The instruments or raw materials in the present invention without indicating the manufacturer are all conventional commercial instruments or raw materials.

[0018] Unless otherwise mentioned, the detection indicators involved in the embodiments of the present invention are detected by conventional detection methods in the art.

[0019] Among them, the smoothness, glossiness and printing glossiness of coated paper are measured in accordance with GB / T10335.2-2018.

[0020] Wet friction test method: Cut the test paper into the standard size required by the instrument, and use an electric friction tester for testing. The friction head is a standard wet friction white cloth. For one paper product to be tested, more than 20 paper samples need to be prepared. Adjust the number of frictions and test until the paper sample has no obvious skin lifting, fuzzing, or abrasion. The number of frictions is taken as the test value, which is called wet friction. In order to make the value more accurate, at least 3 paper samples are tested under the initial wet friction of the paper sample. If there is no obvious skin lifting, fuzzing, or abrasion, the wet friction can be determined as the final data value.

[0021] Example 1

[0022] The air in the reactor was replaced by nitrogen purge, 40 wt % glyoxal aqueous solution was added to the reactor, the pH value of the glyoxal aqueous solution was adjusted to 3.2 with 10 wt % sodium hydroxide aqueous solution, and urea was added after the adjustment, the molar ratio of glyoxal to urea was 1.5:1, the reaction temperature was 70° C., and the reaction time was 2 h;

[0023] Then, glycerol was added to the above solution, the molar ratio of glycerol to glyoxal was 1.2:1, and the reaction was continued at 80° C. for 3 h. After the reaction was completed, deionized water was added to adjust the solid content to 40%, thereby obtaining modified glyoxal water repellent E1.

[0024] Embodiment 2-4

[0025] Different polyols are used to replace the glycerol in Example 1, and other process conditions are the same as in Example 1. Example 2 uses pentaerythritol, Example 3 uses sorbitol, and Example 4 uses xylitol. The specific preparation process is as follows:

[0026] The air in the reactor was replaced by nitrogen purge, 40 wt % glyoxal aqueous solution was added to the reactor, the pH value of the glyoxal aqueous solution was adjusted to 3.2 with 10 wt % sodium hydroxide aqueous solution, and urea was added after the adjustment, the molar ratio of glyoxal to urea was 1.5:1, the reaction temperature was 70° C., and the reaction time was 2 h;

[0027] Then, polyol was added to the above solution, the molar ratio of polyol to glyoxal was 1.2:1, and the reaction was continued at 80°C for 3 hours. After the reaction was completed, deionized water was added to adjust the solid content to 40%, thereby obtaining modified glyoxal water repellent E2-E4.

[0028] Example 5

[0029] The air in the reactor was replaced by nitrogen purge, 40 wt % glyoxal aqueous solution was added into the reactor, the pH value of the glyoxal aqueous solution was adjusted to 5 with 10 wt % sodium hydroxide aqueous solution, and urea was added after the adjustment, the molar ratio of glyoxal to urea was 2:1, the reaction temperature was 75° C., and the reaction time was 1 h;

[0030] Then, glycerol was added to the above solution, the molar ratio of glycerol to glyoxal was 1.5:1, and the reaction was continued at 85° C. for 2 h. After the reaction was completed, deionized water was added to adjust the solid content to 40%, thereby obtaining modified glyoxal water repellent E5.

[0031] Example 6

[0032] The air in the reactor was replaced by nitrogen purge, 40 wt % glyoxal aqueous solution was added into the reactor, the pH value of the glyoxal aqueous solution was adjusted to 3 with 10 wt % sodium hydroxide aqueous solution, urea was added after the adjustment, the molar ratio of glyoxal to urea was 1:1, the reaction temperature was 40° C., and the reaction time was 2 h;

[0033] Then, glycerol was added to the above solution, the molar ratio of glycerol to glyoxal was 1:1, and the reaction was continued at 60° C. for 3 h. After the reaction was completed, deionized water was added to adjust the solid content to 40%, thereby obtaining modified glyoxal water repellent E6.

[0034] Example 7

[0035] The air in the reactor was replaced by nitrogen purge, 40 wt % glyoxal aqueous solution was added to the reactor, the pH value of the glyoxal aqueous solution was adjusted to 4 with 10 wt % sodium hydroxide aqueous solution, and urea was added after the adjustment, the molar ratio of glyoxal to urea was 1.7:1, the reaction temperature was 60° C., and the reaction time was 1.5 h;

[0036] Then, glycerol was added to the above solution, the molar ratio of glycerol to glyoxal was 1.3:1, and the reaction was continued at 75° C. for 2.5 hours. After the reaction was completed, deionized water was added to adjust the solid content to 40%, thereby obtaining modified glyoxal water repellent E7.

[0037] Comparative Example 1

[0038] Prepared according to the method of Example 4 of Chinese Patent CN102312395A:

[0039] 1. Add 90% of glyoxal according to the molar ratio of glyoxal to urea of ​​1.5:1, at which pH = 2.0; adjust pH = 5.6 with 10% NaOH aqueous solution.

[0040] 2. Add urea required for the reaction and heat to promote dissolution.

[0041] 3. When the temperature rises to 30°C, stop heating, wait for the reaction to automatically rise to 50°C, start timing, and keep the temperature constant for 3 hours.

[0042] 4. After 3 hours, add the remaining glyoxal. At this time, the pH value has no significant change and is still around 5. Keep the reaction at constant temperature for 2 hours.

[0043] 5. After the reaction is completed, stop heating, add an appropriate amount of reaction water, and then add 0.2% ammonium persulfate and 1% sodium hypochlorite by total mass.

[0044] 6. After the solution is uniform, stop stirring to obtain water repellent D1.

[0045] Comparative Example 2

[0046] Prepared according to the method of Example 11 of Chinese patent CN109235129A: at 80°C, take a 40wt% aqueous solution of glyoxal containing 14 parts of glyoxal and 9 parts of aluminum sulfate, add them to a 70wt% aqueous solution of sorbitol containing 24.5 parts of sorbitol, react for 4 hours under stirring, add 30 parts of water, cool to 40°C, adjust the pH to 4 with a NaOH aqueous solution, and obtain a water repellent D2.

[0047] Comparative Example 3

[0048] Glutaraldehyde was used to replace glyoxal in Example 1, and other process conditions were basically the same as those in Example 1. The specific preparation method is as follows:

[0049] The air in the reactor was replaced by nitrogen purge, 20 wt % glutaraldehyde aqueous solution was added into the reactor, the pH value of the glutaraldehyde aqueous solution was adjusted to 5 with 10 wt % sodium hydroxide aqueous solution, and urea was added after the adjustment, the molar ratio of glutaraldehyde to urea was 1.5:1, the reaction temperature was 70° C., and the reaction time was 2 h;

[0050] Then, glycerol was added to the above solution, the molar ratio of glycerol to glutaraldehyde was 1.2:1, and the reaction was continued at 80° C. for 3 h. After the reaction was completed, deionized water was added to adjust the solid content to 40%, thereby obtaining water repellent D3.

[0051] Comparative Example 4

[0052] Melamine was used to replace the urea in Example 1, and other process conditions were the same as those in Example 1. The specific preparation method is as follows:

[0053] The air in the reactor was replaced by purging with nitrogen, 40 wt % glyoxal aqueous solution was added into the reactor, the pH value of the glyoxal aqueous solution was adjusted to 3.2 with 10 wt % sodium hydroxide aqueous solution, and melamine was added after the adjustment, the molar ratio of glyoxal to melamine was 1.5:1, the reaction temperature was 70° C., and the reaction time was 2 h;

[0054] Then, glycerol was added to the above solution, the molar ratio of glycerol to glyoxal was 1.2:1, and the reaction was continued at 80° C. for 3 h. After the reaction was completed, deionized water was added to adjust the solid content to 40%, thereby obtaining water repellent D4.

[0055] Comparative Example 5

[0056] Glutaraldehyde was used to replace glyoxal in Example 1, melamine was used to replace urea, and other process conditions were basically the same as those in Example 1. The specific preparation method is as follows:

[0057] The air in the reactor was replaced by purging with nitrogen, a 20 wt % glutaraldehyde aqueous solution was added to the reactor, and the pH value of the glutaraldehyde aqueous solution was adjusted to 5 with a 10 wt % sodium hydroxide aqueous solution. After the adjustment, melamine was added, and the molar ratio of glutaraldehyde to melamine was 1.5:1. The reaction temperature was 70° C. and the reaction time was 2 h.

[0058] Then, glycerol was added to the above solution, with a molar ratio of glycerol to glutaraldehyde of 1.2:1, and the reaction was continued at 80° C. for 3 h. After the reaction was completed, deionized water was added to adjust the solid content to 40%, thereby obtaining water repellent D5.

[0059] Application Examples

[0060] Use water repellent E1-E7, D1-D5 to prepare the coating according to the following formula:

[0061] 95 grade heavy calcium carbonate 300g,

[0062] 98 grade light calcium carbonate 100g,

[0063] Brazilian porcelain clay 100g,

[0064] Propylene styrene latex (dry weight) 50g,

[0065] Water repellent (dry weight) 2g,

[0066] Add appropriate amount of deionized water to adjust the coating weight solid content to 65%.

[0067] Experimental process:

[0068] 1) Add 95-grade heavy calcium carbonate, 98-grade light calcium carbonate, Brazilian porcelain clay and appropriate amount of deionized water into a high-speed disperser, stir evenly and disperse at high speed for 20-30 minutes until the fineness is qualified, add latex and water repellent at low speed, stir evenly, discharge and filter with a 100-mesh sieve;

[0069] 2) Spread the prepared coating with a 10# coating rod at 75g / m 2 Coated on coated paper, coating amount 15g / m 2 ,spare.

[0070] 3) Coating and calendering conditions: Take the above coated paper samples and use a small calender to hard calender twice (0.3Mpa, 85°C) for later use. Use the national standard method to test the coating performance of paper; judgment standard: the greater the smoothness and glossiness, the better the effect. The specific test results are shown in Table 1:

[0071] Table 1 Performance test indicators of different coated paper samples

[0072]

[0073] It can be seen from the above application results that the water repellent prepared by Examples 1-7 of the present invention, when applied to papermaking coatings for coated paper, can significantly improve the smoothness and glossiness of the coated paper, compared with the comparative example.

[0074] 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 an environmentally friendly modified glyoxal water repellent, characterized in that: The following steps are involved: S1, using nitrogen to purge and replace the air in the reactor, adding a glyoxal aqueous solution into the reactor, adjusting the pH value to 3-5 with an alkaline solution, and then adding urea, the molar ratio of glyoxal to urea is 1.0-2.0:1, the reaction temperature is 40-75°C, and the reaction time is 1-2h; S2, adding polyol to the solution obtained in step S1, wherein the molar ratio of the polyol to glyoxal is 1.0-1.5:1, and continuing the reaction at 60-85° C. for 2-3 hours to obtain the modified glyoxal water repellent.

2. The method according to claim 1, characterized in that The polyol is selected from C3-C6 polyols.

3. The method according to claim 2, characterized in that The polyol is a trihydric alcohol, a tetrahydric alcohol, a pentahydric alcohol or a hexahydric alcohol.

4. The method according to claim 1, characterized in that The polyol is selected from at least one of glycerol, pentaerythritol, sorbitol and xylitol.

5. The method according to claim 1, characterized in that The polyol is glycerol.

6. The method according to claim 1, characterized in that The molar ratio of glyoxal to urea is 1.2-1.8:

1.

7. The method according to claim 1, characterized in that The molar ratio of glyoxal to urea is 1.4-1.6:

1.

8. The method according to claim 1, characterized in that The molar ratio of polyol to glyoxal is 1.1-1.4:

1.

9. The method according to claim 1, characterized in that The molar ratio of polyol to glyoxal is 1.2-1.3:

1.

10. The method according to claim 1, characterized in that The following steps are involved: S1, using nitrogen to purge and replace the air in the reactor, adding a glyoxal aqueous solution into the reactor, adjusting the pH value to 3-5 with an alkaline solution, and then adding urea, the molar ratio of glyoxal to urea is 1.5:1, the reaction temperature is 40-75°C, and the reaction time is 1-2h; S2, adding glycerol to the solution obtained in step S1, wherein the molar ratio of glycerol to glyoxal is 1.2:1, and continuing the reaction at 60-85° C. for 2-3 hours to obtain the modified glyoxal water repellent.

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