Preparation method of high-strength and high-toughness paper-based material

Abstract

The application belongs to the technical field of papermaking, and particularly relates to a preparation method of high-strength and high-toughness paper-based material, and specifically comprises the following steps: putting paper pulp into a beater to beat the pulp, putting the pulp into a defibrator in batches to defibrate the pulp, and then beating the pulp into paper; preparing water-based polyurethane emulsion; putting dry paper into the water-based polyurethane emulsion for impregnation treatment; and putting the impregnated wet paper into a forced air drying oven for drying and solidification. Compared with the prior art, the preparation method of high-strength and high-toughness paper-based material of the application impregnates the dry paper with water-based polyurethane emulsion with positive electricity, realizes efficient filling of the polyurethane emulsion in the voids of the paper and mutual envelopment with the fibers, so as to achieve the effect of strengthening and toughening; the use of oxime chain extenders and double blocking agents enables a large number of active NCO groups to react with the hydroxyl groups on the paper fibers in the stage of solidification of the paper in the oven, so as to improve the tensile strength and elongation of the paper, and solve the problems of insufficient strength and stretchability of the existing products.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of papermaking, and particularly relates to a preparation method of high-strength and high-toughness paper-based material. BACKGROUND

[0002] Paper-based material has the characteristics of rich raw material reserves, recyclable and degradable products, and is widely used in people's daily production and life. However, the strength of ordinary paper mainly comes from the interaction of hydrogen bonds between fibers, which is formed during the formation, solidification and drying of paper. However, the bond energy of hydrogen bond between fibers is small, resulting in that the strength of paper is generally low. At the same time, cellulose is rich in hydrophilic hydroxyl groups and is extremely sensitive to water. In addition, paper is composed of randomly distributed fibers, and there are a large number of void structures, resulting in strong hydrophilicity. Its strength and toughness are difficult to meet the demand of high-grade packaging materials.

[0003] At present, there is a method of using polyurethane and other high molecular resin adhesives to impregnate decorative paper to improve the strength of the decorative paper in the prior art. However, due to the limitation of the synthesis structure of conventional polyurethane, the content of active isocyanate in it is very low, which leads to the fact that chemical cross-linking cannot be effectively formed between the isocyanate and the cellulose surface hydroxyl group in the paper compounding process. In addition, due to the diffusion and rearrangement limitation of molecular chain in the fiber void, the polyurethane component cannot form good dispersion in the paper during the polyurethane impregnation of the paper. The retention rate of polyurethane emulsion in the paper is very low, which further leads to the fact that polyurethane cannot efficiently fill the voids in the paper and cannot be wrapped with the paper fibers, thereby seriously affecting the toughening and strengthening effect of polyurethane on the paper. SUMMARY

[0004] The application provides a preparation method of high-strength and high-toughness paper-based material.

[0005] In order to achieve the above purpose, the technical scheme adopted by the application is as follows: a preparation method of high-strength and high-toughness paper-based material, which specifically comprises the following steps:

[0006] Step one, put the paper pulp slurry into a beater for beating, and control the beating degree of the paper pulp to be 17°SR-60°SR, then put the slurry into a defibrator in batches for defibration, and then beat into paper;

[0007] Step two, preparation of water-based polyurethane emulsion: polyisocyanate and oligomer polyol are added to the reaction vessel for stirring, and gradually heated to 80-100℃, after 1-3 hours of reaction, at least one dihydric alcohol compound is added, the reaction temperature is maintained at 80-100℃; After 3-5 hours of reaction, the temperature is lowered to 50-70℃, dimethylglyoxime or dimethyl ketone dioxime is added, and the reaction is carried out for 1-3 hours; The temperature is lowered to 40-60℃, an acid compound is added, the reaction is carried out for 0.5-1.5 hours, a ketone compound is added, and stirring is carried out for 0.5-1 hour; The reaction is poured out from the reaction vessel, deionized water is added for emulsification under a high-speed disperser, low-boiling-point substances are removed by distillation under reduced pressure, and a water-based polyurethane emulsion is prepared;

[0008] Step three, the dry paper sheet is immersed in the water-based polyurethane emulsion for treatment, and the immersion time is set to 0.5-3h;

[0009] Step four, the wet paper sheet after immersion is transferred to a blast drying oven for drying and curing for 2-4h.

[0010] As a preferred, the oligomer polyol includes at least one of polyether diol, polyester diol, polyhexolactone diol, polycarbonate diol, polyethylene glycol adipate or polytetrahydrofuran ether.

[0011] As a preferred, the polyisocyanate includes at least one of toluene diisocyanate, isophorone diisocyanate, methane diisocyanate, 1,6-hexamethylene diisocyanate or dicyclohexyl methane diisocyanate.

[0012] As a preferred, the dihydric alcohol compound includes at least one of 1,4 butanediol, 1,6 hexanediol, 2,2-dimethylol butyric acid, 2,2-dimethylol propionic acid, 2,2-dimethylol propionic acid ammonium, nitrogen methyl diethanolamine, nitrogen ethyl diethanolamine, oleic acid diethanolamide.

[0013] As a preferred, the hydroxyl value of the oligomer polyol is 50-100mgKOH / g.

[0014] As a preferred, the acid compound is any one of sulfuric acid, hydrochloric acid, phosphoric acid, nitric acid, formic acid, acetic acid, oxalic acid, benzoic acid.

[0015] As a preferred, the ketone compound is any one of acetone or butanone.

[0016] As a preferred, the beating degree of the paper pulp is controlled to 30°SR.

[0017] As a preferred, the wet paper sheet is transferred to a blast drying oven for drying and curing at 105℃ for 2h.

[0018] As preferred, after the wet paper sheet is dried and solidified, the paper is subjected to tensile force, tensile strength and elongation detection by a tensile testing machine.

[0019] Compared with the prior art, the application has the advantages and positive effects that:

[0020] Compared with the prior art, the application has the advantages and positive effects that:

[0021] (1) In the preparation of the water-based polyurethane emulsion, the positive water-based polyurethane emulsion is prepared by regulating the emulsion particle size and surface charge distribution and adding a positively charged double blocking agent, and under the charge attraction, the polyurethane emulsion is filled in the paper gap and enveloped with the fiber, so that the reinforcing and toughening effects are achieved.

[0022] (2) The oxime chain extender is used in the application, so that the urethane groups in the polyurethane molecular chain are efficiently dissociated to form a large number of active NCO groups in the curing stage of the paper in the oven, and the groups can have a chemical cross-linking reaction with the hydroxyl groups on the paper fiber, so that the chemical link between the polyurethane molecules and the cellulose network is further enhanced, and the tensile strength and elongation of the paper are improved, and the problems of insufficient strength and elongation performance in the existing products are solved; and the double blocking agent is used in the application, so that the molecular chain growth point is not locked by using a single blocking agent, the growth of the polyurethane molecular chain is affected, and the polyurethane molecular chain enhances the fiber network of the paper. DETAILED DESCRIPTION

[0023] In order to more clearly understand the above-mentioned purposes, features and advantages of the application, the application will be further described below in combination with examples. In the following description, a large number of specific details are set forth in order to fully understand the application, but the application can also be implemented in other ways different from those described herein, therefore, the application is not limited to the specific examples disclosed in the following description.

[0024] The beating degree and the impregnation time can affect the absorption rate of the water-based polyurethane emulsion by the paper, and with the increase of the beating degree of the paper pulp fiber, the absorption rate of the water-based polyurethane emulsion by the paper shows a trend of first increasing and then decreasing, and through a limited number of experiments, it is known that the beating degree is controlled at 30 o SR can improve the absorption rate of the fiber to the polyurethane emulsion; with the extension of the impregnation time of the paper in the polyurethane emulsion, the absorption rate of the polyurethane shows a gradually increasing trend, and through a limited number of experiments, it is known that when the impregnation time reaches 2h, the absorption rate of the polyurethane can reach 30%, and when the impregnation time exceeds 2h, the absorption rate of the polyurethane changes little, therefore, the efficiency is the highest when the impregnation time of the paper is controlled at 2h.

[0025] Example 1

[0026] This embodiment of a method for preparing a high-strength, high-toughness paper-based material specifically includes the following steps:

[0027] Step 1: Weigh 30g of oven-dry pulp, add water to prepare a 10% wet pulp, and transfer it to a refiner for beating. Control the beating speed to maintain a freeness of 30. o SR; based on paper basis weight 100g / m 2 Weigh out a certain amount of pulp, add water and stir for 5 minutes, then pour it into a defragmenter for defragmentation. Adjust the speed of the defragmenter to 4000 r / min, and then use a Kaiser paper machine to form paper to obtain dry paper sheets.

[0028] Step 2: Preparation of waterborne polyurethane emulsion: Add 20g of polytetrahydrofuran ether diol to a three-necked flask, heat to 120℃, evacuate to maintain a vacuum of less than 0.1MPa, dehydrate for 6 hours, and then lower the temperature to 25℃; add 15g of isophorone diisocyanate to the reaction vessel, heat and stir under nitrogen protection, raise the temperature to 90℃, and react for 3 hours; add 2g of N-methyldiethanolamine and 0.5g of 1,4-butanediol, react for 2 hours, lower the temperature to 60℃, add 3g of dimethylglyoxime, react for 3 hours, lower the temperature to 40℃, add 2.5g of acetic acid, react for 1 hour, add acetone and stir for 0.5 hours, then add deionized water and disperse and emulsify at 8000rpm, finally remove acetone by rotary evaporation to obtain a dioxime-based waterborne polyurethane emulsion;

[0029] Step 3: Transfer the dry paper sheet into a water-based polyurethane emulsion based on bisoxime for 2 hours.

[0030] Step 4: After impregnation, transfer the wet paper sheets into a forced-air drying oven and dry at 105°C for 4 hours to obtain impregnated paper.

[0031] The obtained paper was tested for tensile strength, tensile strength and elongation using a tensile testing machine. The tensile strength was measured to be 3.33 N / m and the elongation was 10%.

[0032] Example 2

[0033] This embodiment of a method for preparing a high-strength, high-toughness paper-based material specifically includes the following steps:

[0034] Step 1: Weigh 30g of oven-dry pulp, add water to prepare a 10% wet pulp, and transfer it to a refiner for beating. Control the beating speed to maintain a freeness of 30°SR; according to a paper basis weight of 100g / m³. 2 Weigh out a certain amount of pulp, add water and stir for 5 minutes, then pour it into a defragmenter for defragmentation. Adjust the speed of the defragmenter to 4000 r / min, and then use a Kaiser paper machine to form paper to obtain dry paper sheets.

[0035] Step 2: Preparation of waterborne polyurethane emulsion: Add 20g of polytetrahydrofuran ether diol to a three-necked flask, heat to 120℃, evacuate to maintain a vacuum of less than 0.1MPa, dehydrate for 6 hours, and then lower the temperature to 25℃; add 15g of isophorone diisocyanate to the reaction vessel, heat and stir under nitrogen protection, raise the temperature to 90℃, and react for 3 hours; add 2g of N-methyldiethanolamine and 0.5g of 1,4-butanediol, react for 2 hours, lower the temperature to 60℃, add 4.4g of dimethyl ketone dioxime, react for 3 hours, lower the temperature to 40℃, add 2.5g of acetic acid, react for 1 hour, add acetone and stir for 0.5 hours, then add deionized water and disperse and emulsify at 8000rpm, finally remove acetone by rotary evaporation to obtain a waterborne polyurethane emulsion based on dioxime groups;

[0036] Step 3: Transfer the dry paper sheet into a water-based polyurethane emulsion based on bisoxime for 2 hours.

[0037] Step 4: After impregnation, transfer the wet paper sheets into a forced-air drying oven and dry at 105°C for 4 hours to obtain impregnated paper.

[0038] The obtained paper was tested for tensile strength, tensile strength and elongation using a tensile testing machine. The tensile strength was measured to be 4.07 N / m and the elongation was 9%.

[0039] Comparative Example 1

[0040] This comparative example specifically includes the following steps:

[0041] Step 1: Weigh 30g of oven-dry pulp, add water to prepare a 10% wet pulp, and transfer it to a refiner for beating. Control the beating speed to maintain a freeness of 30. o SR; Weigh a certain amount of pulp according to a paper basis weight of 100 g / m2, add water and stir for 5 minutes, then pour it into a defragmenter for defragmentation. Adjust the speed of the defragmenter to 4000 r / min, and then use a Kaiser sheeter to form paper to obtain dry paper sheets.

[0042] Step 2: Preparation of waterborne polyurethane emulsion: Add 20g of polytetrahydrofuran ether diol to a three-necked flask, heat to 120℃, evacuate to maintain a vacuum of less than 0.1MPa, dehydrate for 6 hours, and then lower the temperature to 25℃; add 15g of isophorone diisocyanate to the reaction vessel, heat and stir under nitrogen protection, raise the temperature to 90℃, and react for 3 hours; add 2g of N-methyldiethanolamine and 0.5g of 1,4-butanediol, react for 2 hours, lower the temperature to 60℃, add 5.2g of diacetyl monooxime, react for 3 hours, lower the temperature to 40℃, add 2.5g of acetic acid, react for 1 hour, add acetone and stir for 0.5 hours, then add deionized water and disperse and emulsify at 8000rpm, finally remove acetone by rotary evaporation to obtain a waterborne polyurethane emulsion based on a monooxime group;

[0043] Step 3: Transfer the dry paper sheets into a water-based polyurethane emulsion based on monooxime for 2 hours.

[0044] Step 4: After impregnation, transfer the wet paper sheets into a forced-air drying oven and dry at 105°C for 4 hours to obtain impregnated paper.

[0045] The obtained paper was tested for tensile strength, tensile strength and elongation using a tensile testing machine. The tensile strength was measured to be 3 N / m and the elongation was 7%.

[0046] Comparative Example 2

[0047] This comparative example specifically includes the following steps:

[0048] Step 1: Weigh 30g of oven-dry pulp, add water to prepare a 10% wet pulp, and transfer it to a refiner for beating. Control the beating speed to maintain a freeness of 30. o SR; based on paper basis weight 100g / m 2 Weigh out a certain amount of pulp, add water and stir for 5 minutes, then pour it into a defragmenter for defragmentation. Adjust the speed of the defragmenter to 4000 r / min, and then use a Kaiser paper machine to form paper to obtain dry paper sheets.

[0049] Step 2: Preparation of waterborne polyurethane emulsion: Add 20g of polytetrahydrofuran ether diol to a three-necked flask, heat to 120℃, evacuate to maintain a vacuum level below 0.1MPa, dehydrate for 6 hours, and then lower the temperature to 25℃; add 15g of isophorone diisocyanate to the reaction vessel, heat and stir under nitrogen protection, raise the temperature to 90℃, and react for 3 hours; add 2g of N-methyldiethanolamine and 0.5g of 1,4-butanediol, react for 5 hours, lower the temperature to 40℃, add 2.5g of acetic acid, react for 1 hour, add acetone and stir for 0.5 hours, then add deionized water and disperse and emulsify at 8000rpm; finally, remove acetone by rotary evaporation to obtain an oxime-free waterborne polyurethane emulsion.

[0050] Step 3: Immerse the dry paper sheets in an oxime-free aqueous polyurethane emulsion for 2 hours.

[0051] Step 4: After impregnation, transfer the wet paper sheets into a forced-air drying oven and dry at 105°C for 4 hours to obtain impregnated paper.

[0052] The obtained paper was tested for tensile strength, tensile strength and elongation using a tensile testing machine. The tensile strength was measured to be 0.47 N / m and the elongation was 6%.

[0053] Table 1 compares the paper strength properties obtained from Examples 1 and 2 and Comparative Examples 1 and 2.

[0054] Table 1

[0055]

[0056] In preparing an aqueous polyurethane emulsion, this invention controls the particle size and surface charge distribution of the emulsion and adds a positively charged dual-end agent to obtain a positively charged aqueous polyurethane emulsion. Under the attraction of charges, the polyurethane emulsion achieves efficient filling of the voids in the paper and mutual encapsulation with the fibers, thereby achieving the effect of strengthening and toughening.

[0057] This invention employs oxime chain extenders. As can be seen from the data in Table 1 (Examples 1, 2, and Comparative Example 2), the tensile strength and elongation of this invention are significantly improved compared to using oxime-free aqueous polyurethane emulsions. The oxime chain extender used in this invention causes efficient dissociation of the urethane groups in the polyurethane molecular chain during the paper curing stage in the oven, forming a large number of active NCO groups. These groups can undergo chemical cross-linking reactions with the hydroxyl groups on the paper fibers, thereby further enhancing the chemical bond between the polyurethane molecules and the cellulose network, thus improving the tensile strength and elongation of the paper and solving the problems of insufficient strength and elongation in existing products.

[0058] Meanwhile, the data from Examples 1, 2 and Comparative Example 1 show that the aqueous polyurethane emulsions based on bisoxime groups prepared by dual end-capping agents in Examples 1 and 2 of this invention have a certain degree of improvement in tensile strength and elongation compared with the aqueous polyurethane emulsion based on monooxime groups prepared by single end-capping agent in Comparative Example 1.

[0059] This invention employs a dual end-capping agent, avoiding the use of a single end-capping agent that locks the molecular chain growth points, affecting the growth of polyurethane molecular chains and thus impacting the polyurethane molecular chains' ability to reinforce the paper fiber network. This further ensures the improvement of the paper's tensile strength and elongation.

[0060] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any other way. Any person skilled in the art may make changes or modifications to the above-disclosed technical content to create equivalent embodiments that can be applied to other fields. However, any simple modifications or equivalent changes made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the protection scope of the present invention.

Claims

1. A method for preparing a high-strength, high-toughness paper-based material, characterized in that, The preparation method specifically includes the following steps: Step 1: Put the pulp into a pulping machine for pulping. The pulp beating degree is controlled at 17°SR-60°SR. Then, put the pulp into a desoldering machine in batches for desoldering, and then form it into paper. Step 2: Preparation of waterborne polyurethane emulsion: Polyisocyanates and oligomeric polyols are added to a reaction vessel and stirred. The temperature is gradually increased to 80-100℃. After reacting for 1-3 hours, diol compounds and alkanolamine compounds are added, maintaining the reaction temperature at 80-100℃. After reacting for 3-5 hours, the temperature is lowered to 50-70℃, and dimethyl ketone oxime or dimethyl ketone dioxime is added, reacting for 1-3 hours. The temperature is then lowered to 40-60℃, and acid compounds are added, reacting for 0.5-1.5 hours. Ketone compounds are added, and the mixture is stirred for 0.5-1 hour. The reactants are then poured out of the reaction vessel, and deionized water is added for emulsification using a high-speed disperser. Low-boiling-point substances are removed by vacuum distillation to obtain the waterborne polyurethane emulsion. The diol compounds are selected from at least one of 1,4-butanediol and 1,6-hexanediol; the alkanolamine compounds are selected from at least one of N-methyldiethanolamine and N-ethyldiethanolamine. Step 3: Immerse the dry paper sheets in an aqueous polyurethane emulsion for 0.5-3 hours. Step 4: Transfer the impregnated wet paper sheets into a forced-air drying oven to dry and cure for 2-4 hours.

2. The method for preparing high-strength and high-toughness paper-based material according to claim 1, characterized in that, The oligomeric polyols include at least one of polyether diols, polyester diols, polycaprolactone diols, polycarbonate diols, polyethylene adipate, or polytetrahydrofuran ether.

3. The method for preparing high-strength and high-toughness paper-based material according to claim 1, characterized in that, The polyisocyanate includes at least one of toluene diisocyanate, isophorone diisocyanate, methane diisocyanate, 1,6-hexamethylene diisocyanate, or dicyclohexylmethane diisocyanate.

4. The method for preparing high-strength and high-toughness paper-based material according to claim 2, characterized in that, The hydroxyl value of the oligomeric polyol is 50-100 mg KOH / g.

5. The method for preparing high-strength and high-toughness paper-based material according to claim 1, characterized in that, The acidic compound is any one of sulfuric acid, hydrochloric acid, phosphoric acid, nitric acid, formic acid, acetic acid, oxalic acid, and benzoic acid.

6. The method for preparing high-strength and high-toughness paper-based material according to claim 1, characterized in that, The ketone compound is either acetone or butanone.

7. The method for preparing high-strength and high-toughness paper-based material according to claim 1, characterized in that, The pulp beating degree is controlled at 30°SR.

8. The method for preparing high-strength and high-toughness paper-based material according to claim 1, characterized in that, The wet paper sheets were transferred to a forced-air drying oven and dried and cured at 105°C for 2 hours.

9. The method for preparing high-strength and high-toughness paper-based material according to claim 1, characterized in that, After the wet paper sheet is dried and cured, the paper is tested for tensile strength, tensile strength and elongation using a tensile testing machine.

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