A method for preparing aging-resistant rice paper by secondary sizing using a medium / alkaline sizing agent

Abstract

The invention provides a method for preparing aging-resistant cooked rice paper by secondary sizing with a neutral / alkaline sizing agent, belonging to the technical field of rice paper manufacturing. The method combines in-slurry sizing with surface sizing, specifically performing in-slurry sizing of AKD before adding a dispersant, carambola vine juice, so as to reduce the negative influence of anionic substances on the dispersion or adsorption of AKD in the slurry and impart excellent water resistance to the rice paper; and performing surface sizing with a neutral / alkaline surface sizing liquid during paper baking or after paper forming, coating the surface of the rice paper with a film to fill pores, and simultaneously enhancing the bonding force between fibers, thereby compensating for the defect that AKD sizing cannot improve the mechanical properties of the rice paper.

Description

Technical Field

[0001] The invention belongs to the technical field of rice paper manufacturing, and specifically discloses a method for preparing aging-resistant cooked rice paper by secondary sizing with a medium / alkaline sizing agent. Background Art

[0002] Xuan paper, a representative of traditional Chinese calligraphy and painting paper, bears the witness of countless works of art and is a vital component of China's fine traditional culture. Depending on the processing method, Xuan paper can be divided into two categories: raw Xuan paper and cooked Xuan paper. Unprocessed Xuan paper is called raw Xuan paper, which is lyophilic and easily absorbs water and ink. Xuan paper that has been treated with sizing is called cooked Xuan paper, which has a certain degree of lyophobicity on the surface, resisting the rapid diffusion and penetration of water and ink. Cooked Xuan paper currently sold on the market is generally made by applying rosin to the raw Xuan paper, then applying sizing with alum water or by adding rosin to alum water, and then hanging it to dry.

[0003] Xuan paper holds immense artistic and cultural value, and therefore demands high durability. However, alum hydrolysis produces acid, and rosin, also an acidic sizing agent, accelerates the aging of the paper, hindering its long-term preservation. After prolonged storage, alum-sizing can leak through the paper, impacting its performance and reducing its value. Furthermore, the drag-dye sizing method is prone to paper breakage, limiting the choice of high-viscosity sizing agents. Summary of the Invention

[0004] The present invention provides a method for preparing aging-resistant rice paper by secondary sizing with a medium / alkaline sizing agent, so as to overcome the problem that the acidic rosin / alum sizing system accelerates the aging of the rice paper and the disadvantage that the drag-dye sizing method is prone to paper breakage.

[0005] The above-mentioned method for preparing aging-resistant rice paper by secondary sizing with a medium / alkaline sizing agent comprises the following steps:

[0006] S1, preparing Xuan paper pulp;

[0007] S2, while dispensing water according to the conventional papermaking process for Xuan paper in national standard GB / T 18739-2008, the pH value of the AKD emulsion is adjusted to 7.5 using sodium carbonate, and the AKD emulsion is added to the Xuan paper pulp at a mass fraction of 0.6-1.0% based on the absolute dry mass of the Xuan paper pulp, and stirred to apply size;

[0008] S3, add carambola vine juice, stir evenly and then pick up the paper;

[0009] S4, pressing;

[0010] S5, baking the paper. During or after the baking step, a neutral / alkaline surface sizing solution is evenly applied to the surface of the Xuan paper. After the surface sizing agent is dried, the cooked Xuan paper is obtained.

[0011] The medium / alkaline surface sizing liquid is prepared by adding water to a surface sizing agent with a mass fraction of 1 to 4%, adjusting the pH value to 7.0 to 10.5 with a pH regulator, and stirring the mixture to obtain a liquid.

[0012] In step S1, the celtis chinensis bark pulp and the paddy rice straw pulp are added into a pulp decompressor at a mass ratio of 6:4, and water is added to the pulp at a pulp concentration of 0.2% and the pulp is decompressed. After the decomposition is completed, Xuan paper pulp is obtained.

[0013] In step S2, the cationic AKD emulsion with a solid content of 15% is diluted 10 times with water, and the pH value of the diluted AKD emulsion is adjusted using a 10% sodium carbonate solution.

[0014] In step S3, the carambola vine juice is calculated to be 12-18% of the absolute dry mass of the Xuan paper pulp.

[0015] In step S3, 34g / m 2 The pulp mass was quantitatively calculated and a wet paper web simulating rice paper was prepared using a Kaiser paper former.

[0016] In step S4, a paper sheet press is used to press the wet paper web at a pressure of 400 kPa for 5 minutes to simulate the pressing of rice paper.

[0017] In step S5, the surface sizing agent is one of gelatin, sodium alginate, carboxymethyl cellulose, and polyvinyl alcohol.

[0018] In step S5, the pH regulator is one of sodium carbonate solution, sodium propionate solution, calcium propionate solution, calcium hydroxide solution, or a mixture of sodium carbonate solution and sodium propionate solution, or a mixture of calcium propionate solution and calcium hydroxide solution.

[0019] The pH regulator is prepared by mixing 10% sodium carbonate solution and 10% sodium propionate solution in a mass ratio of 1:1, and by mixing 10% calcium propionate solution and saturated calcium hydroxide solution in a mass ratio of 1:1.

[0020] In step S5, a flat plate dryer is used to simulate the baking of rice paper;

[0021] Separate the wet paper web after pressing, brush it flat on the drying plate of the flat dryer for the first drying, then brush the medium / alkaline surface sizing liquid evenly on the paper surface, perform the second drying and then peel it off to obtain cooked rice paper; or,

[0022] Separate the wet paper webs after pressing, brush them flatly on the drying plate of the flat dryer, peel them off after drying, then evenly apply the medium / alkaline surface sizing liquid on both sides of the paper, hang them up to air dry, and you will get the cooked rice paper.

[0023] Compared with the prior art, the present invention has the following beneficial effects.

[0024] 1. The present invention adopts medium / alkaline sizing instead of acidic rosin / alum sizing, which reduces the introduction of acidic substances and improves the aging resistance of cooked rice paper.

[0025] 2. The present invention adopts a method combining in-slurry sizing with surface sizing, specifically, in-slurry sizing of AKD is performed before adding the dispersant carambola vine juice, thereby reducing the negative influence of anionic substances on the dispersion or adsorption of AKD in the slurry. In-slurry sizing of AKD can significantly improve the water resistance of Xuan paper after high-temperature drying, giving Xuan paper excellent water resistance. Surface sizing with a medium / alkaline surface sizing liquid is performed during paper baking, and a film is coated on the surface of the Xuan paper to fill the pores, while enhancing the bonding force between fibers, thereby compensating for the shortcoming that AKD sizing cannot improve the mechanical properties of Xuan paper, avoiding the problem of paper breakage caused by high-viscosity surface sizing agents when the paper is dragged and sizing is hung to dry, and increasing the diversity of surface sizing agents.

[0026] 3. The present invention adopts calcium propionate and sodium propionate to adjust the pH value, and at the same time has antibacterial and mildew-proof effects, which can reduce the microbial erosion during the storage of cooked rice paper. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the specific embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0028] Figure 1 These are pictures of the cooked rice paper samples prepared in Examples 1 to 4. DETAILED DESCRIPTION

[0029] The present invention is described in detail below with reference to the following examples: A Kaeser paper former, a paper press, and a flat dryer were used to simulate the steps of scooping, pressing, and baking Xuan paper.

[0030] Example 1

[0031] This embodiment provides a method for preparing aging-resistant cooked rice paper by secondary sizing with a medium / alkaline sizing agent. The surface sizing agent used is sodium alginate, and the pH regulator is prepared by mixing 10% sodium carbonate solution and 10% sodium propionate solution in a mass ratio of 1:1. 15g of sodium alginate is added to 1000g of cold water in small amounts and multiple times while stirring until completely dissolved. The pH value is adjusted to 10.5 using the pH regulator, and the mixture is stirred evenly to obtain a sodium alginate solution for use. The method comprises the following steps:

[0032] (1) Add appropriate amount of celtis sinensis bark pulp and paddy straw pulp in a mass ratio of 6:4 into the pulp deflaker, add water to a pulp concentration of 0.2% and deflake for 10,000 revolutions. After deflaking, pour into the pulp barrel for later use;

[0033] (2) Dilute the 15% solid content cationic AKD emulsion 10 times with water, adjust the pH value of the diluted AKD emulsion to 7.5 with 10% sodium carbonate solution, add it into the pulp barrel at a mass fraction of 0.8% of the absolute dry mass of Xuan paper pulp, and stir thoroughly for 5 minutes;

[0034] (3) Add the prepared carambola vine juice into the pulp barrel at 18% of the absolute dry mass of Xuan paper pulp, stir thoroughly for 5 minutes, and scoop out with a pulp cup at 34g / m 2 Quantitatively calculate the mass of pulp and use a Kaiser paper former to prepare a wet paper web;

[0035] (4) Pressing the stacked wet paper webs in a paper press at a pressure of 400 kPa for 5 minutes;

[0036] (5) Separate the wet paper web after pressing, brush it flatly on the drying plate of the flat dryer with a bristle brush, dry it at 70℃ for 2 minutes, and then use a wool brush to evenly brush the sodium alginate solution on the surface of the paper. After drying for 4 minutes, peel it off to obtain the cooked rice paper.

[0037] Example 2

[0038] This embodiment provides a method for preparing aging-resistant cooked rice paper by secondary sizing with a neutral / alkaline sizing agent. The surface sizing agent used is carboxymethyl cellulose, and the pH regulator is prepared by mixing 10% calcium propionate solution and saturated calcium hydroxide solution in a mass ratio of 1:1. 20g of carboxymethyl cellulose is added to 1000g of cold water in small amounts and multiple times while stirring until completely dissolved. The pH value is adjusted to 8.5 using the pH regulator, and the mixture is stirred evenly to obtain a carboxymethyl cellulose solution for later use. The method comprises the following steps:

[0039] (1) Add appropriate amount of celtis sinensis bark pulp and paddy straw pulp in a mass ratio of 6:4 into the pulp deflaker, add water to a pulp concentration of 0.2% and deflake for 10,000 revolutions. After deflaking, pour into the pulp barrel for later use;

[0040] (2) Dilute the 15% solid content cationic AKD emulsion 10 times with water, adjust the pH value of the diluted AKD emulsion to 7.5 with 10% sodium carbonate solution, add it into the pulp barrel at a mass fraction of 0.8% of the absolute dry mass of Xuan paper pulp, and stir thoroughly for 5 minutes;

[0041] (3) Add the prepared carambola vine juice into the pulp barrel at 18% of the absolute dry mass of Xuan paper pulp, stir thoroughly for 5 minutes, and scoop out with a pulp cup at 34g / m2 Quantitatively calculate the mass of pulp and use a Kaiser paper former to prepare a wet paper web;

[0042] (4) Pressing the stacked wet paper webs in a paper press at a pressure of 400 kPa for 5 minutes;

[0043] (5) Separate the wet paper web after pressing, brush it flatly on the drying plate of the flat dryer with a bristle brush, dry it at 70℃ for 2 minutes, and then use a wool brush to evenly brush the carboxymethyl cellulose solution on the surface of the paper. After drying for 4 minutes, peel it off to obtain the cooked rice paper.

[0044] Example 3

[0045] This embodiment provides a method for preparing aging-resistant cooked rice paper by secondary sizing with a neutral / alkaline sizing agent. The surface sizing agent used is gelatin, and the pH regulator is prepared by mixing 10% calcium propionate solution and saturated calcium hydroxide solution in a mass ratio of 1:1. 30g of gelatin is soaked in 1000g of cold water and stirred for 10 minutes. The mixture is then heated to 60°C and stirred until the gelatin is completely dissolved. After cooling to room temperature, the pH value is adjusted to 7.0 using a pH regulator, and the mixture is stirred evenly to obtain a gelatin solution for later use. The method comprises the following steps:

[0046] (1) Add appropriate amount of celtis sinensis bark pulp and paddy straw pulp in a mass ratio of 6:4 into the pulp deflaker, add water to a pulp concentration of 0.2% and deflake for 10,000 revolutions. After deflaking, pour into the pulp barrel for later use;

[0047] (2) Dilute the 15% solid content cationic AKD emulsion 10 times with water, adjust the pH value of the diluted AKD emulsion to 7.5 with 10% sodium carbonate solution, add it into the pulp barrel at a mass fraction of 0.6% of the absolute dry mass of Xuan paper pulp, and stir thoroughly for 5 minutes;

[0048] (3) Add the prepared carambola vine juice into the pulp barrel at 12% of the absolute dry mass of Xuan paper pulp, stir thoroughly for 5 minutes, and scoop out with a pulp cup at 34g / m 2 Quantitatively calculate the mass of pulp and use a Kaiser paper former to prepare a wet paper web;

[0049] (4) Pressing the stacked wet paper webs in a paper press at a pressure of 400 kPa for 5 minutes;

[0050] (5) Separate the wet paper web after pressing, brush it flatly onto the drying plate of a flat dryer with a bristle brush, dry it at 70°C for 6 minutes, and then peel it off to form paper;

[0051] (6) Use a wool brush to evenly apply the gelatin solution on both sides of the paper, and hang it up to air dry to obtain the cooked rice paper.

[0052] Example 4

[0053] This embodiment provides a method for preparing aging-resistant cooked rice paper by secondary sizing with a neutral / alkaline sizing agent. The surface sizing agent used is polyvinyl alcohol, and the pH regulator is prepared by mixing 10% calcium propionate solution and saturated calcium hydroxide solution in a mass ratio of 1:1. 40g of polyvinyl alcohol is soaked in 1000g of cold water and heated to 95°C. The mixture is stirred continuously until the polyvinyl alcohol is completely dissolved. After cooling to room temperature, the pH value is adjusted to 7.5 using the pH regulator. The mixture is stirred evenly to obtain a polyvinyl alcohol solution for later use. The method comprises the following steps:

[0054] (1) Add appropriate amount of celtis sinensis bark pulp and paddy straw pulp in a mass ratio of 6:4 into the pulp deflaker, add water to a pulp concentration of 0.2% and deflake for 10,000 revolutions. After deflaking, pour into the pulp barrel for later use;

[0055] (2) Dilute the 15% solid content cationic AKD emulsion 10 times with water, adjust the pH value of the diluted AKD emulsion to 7.5 with 10% sodium carbonate solution, add it into the pulp barrel at a mass fraction of 1.0% of the absolute dry mass of Xuan paper pulp, and stir thoroughly for 5 minutes;

[0056] (3) Add the prepared carambola vine juice into the pulp barrel at 12% of the absolute dry mass of Xuan paper pulp, stir thoroughly for 5 minutes, and scoop out with a pulp cup at 34g / m 2 Quantitatively calculate the mass of pulp and use a Kaiser paper former to prepare a wet paper web;

[0057] (4) Pressing the stacked wet paper webs in a paper press at a pressure of 400 kPa for 5 minutes;

[0058] (5) Separate the wet paper web after pressing, brush it flatly onto the drying plate of a flat dryer with a bristle brush, dry it at 70°C for 6 minutes, and then peel it off to form paper;

[0059] (6) Use a wool brush to evenly apply the polyvinyl alcohol solution on both sides of the paper, and hang it to air dry to obtain the cooked rice paper.

[0060] Example 5

[0061] In this example, the cooked rice paper prepared in Examples 1 to 4 was subjected to the following tests. Before the tests, the paper samples were equilibrated under the conditions specified in GB / T10739-2002 for more than 4 hours:

[0062] (1) Use an analytical balance to weigh the paper sample. The difference between the sized paper sample and the unsized paper sample is the sizing amount.

[0063] (2) Use a surface contact angle tester to measure the average water contact angle and ink contact angle of the paper sample within 10 seconds;

[0064] (3) Measure the pH value of the cold water extract of the paper sample according to GB / T 1545-2008;

[0065] (4) Measure the alkali reserve of paper samples according to GB / T 24998-2010;

[0066] (5) Measure the tensile strength of paper samples according to GB / T 22898-2008.

[0067] The test results are shown in the following table:

[0068]

[0069] The test results show that the water contact angle and ink contact angle of the rice paper produced by the secondary sizing method of the present invention both reach above 90°. The contact angles of Examples 1 and 2 reach or even exceed those of commercially available rice paper sized with traditional rosin / alum sizing. The pH values ​​of the rice paper produced by the present invention are higher than those of commercially available rice paper sized with traditional rosin / alum sizing, falling within the reference pH value of 7.5 to 10.0 for high-durability paper specified in GB / T 24422-2009 and GB / T 24423-2009. The alkali reserve of the rice paper produced by the present invention is higher than that of commercially available rice paper sized with traditional rosin / alum sizing, falling within the reference alkali reserve of ≥0.4 mol / kg specified in GB / T 24422-2009 and GB / T 24423-2009 for high-durability paper. The tensile strength of the rice paper produced by the present invention is generally between that of commercially available rice paper sized with traditional rosin / alum sizing.

[0070] Use a brush dipped in Yidege Chinese ink to repeatedly brush the rice paper produced by the present invention for 8 times. After the ink is dry, the effect on the front and back of the paper sample is as follows: Figure 1 As shown (the upper left is Example 4, the upper right is Example 2, the lower left is Example 1, and the lower right is Example 3): the ink on the front of the paper sample is clear and the ink color is rich; there is no ink penetration on the back of the paper sample.

[0071] In summary, the rice paper prepared by secondary sizing with a medium / alkaline sizing agent provided by the present invention has hydrophobicity, writing quality, and tensile strength comparable to commercially available rice paper sizing with traditional rosin / alum sizing. Furthermore, the pH value and alkali reserve are both higher than those of commercially available rice paper sizing with traditional rosin / alum sizing, meeting the requirements of relevant national standards for high-durability paper. The method provided by the present invention features diverse and easily accessible sizing materials, a simple sizing process, and excellent sizing results, and has considerable application prospects in the field of calligraphy and painting papers such as rice paper.

[0072] 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 aging-resistant rice paper by secondary sizing with a medium / alkaline sizing agent, characterized in that: The steps include: S1, preparing Xuan paper pulp; S2, adjusting the pH value of the AKD emulsion to 7.5 using sodium carbonate, adding the emulsion to the Xuan paper pulp at a mass fraction of 0.6-1.0% of the absolute dry mass of the Xuan paper pulp and stirring to apply size; S3, add carambola vine juice, stir evenly and then pick up the paper; S4, pressing; S5, baking the paper. During or after the baking step, a neutral / alkaline surface sizing solution is evenly applied to the surface of the Xuan paper. After the surface sizing agent is dried, the cooked Xuan paper is obtained. The neutral / alkaline surface sizing liquid is prepared by mixing a surface sizing agent with water to a mass fraction of 1 to 4%, adjusting the pH value to 7.0 to 10.5 using a pH regulator, and stirring the mixture to obtain a liquid; The surface sizing agent is one of gelatin, sodium alginate, carboxymethyl cellulose and polyvinyl alcohol.

2. The method for preparing aging-resistant cooked rice paper by secondary sizing with a neutral / alkaline sizing agent according to claim 1, characterized in that: In step S1, the celtis chinensis bark pulp and the paddy rice straw pulp are added into a pulp decompressor at a mass ratio of 6:4, and water is added to the pulp at a pulp concentration of 0.2% and the pulp is decompressed. After the decomposition is completed, Xuan paper pulp is obtained.

3. The method for preparing aging-resistant cooked rice paper by secondary sizing with a neutral / alkaline sizing agent according to claim 1, characterized in that: In step S2, the cationic AKD emulsion with a solid content of 15% is diluted 10 times with water, and the pH value of the diluted AKD emulsion is adjusted using a 10% sodium carbonate solution.

4. The method for preparing aging-resistant cooked rice paper by secondary sizing with a neutral / alkaline sizing agent according to claim 1, characterized in that: In step S3, the carambola vine juice is calculated as 12-18% of the absolute dry mass of the Xuan paper pulp.

5. The method for preparing aging-resistant cooked rice paper by secondary sizing with a neutral / alkaline sizing agent according to claim 4, characterized in that: In step S3, 34g / m 2 The pulp mass was quantitatively calculated and a wet paper web simulating rice paper was prepared using a Kaiser paper former.

6. The method for preparing aging-resistant cooked rice paper by secondary sizing with a neutral / alkaline sizing agent according to claim 1, characterized in that: In step S4, a paper sheet press is used to press the wet paper web at a pressure of 400 kPa for 5 minutes to simulate the pressing of rice paper.

7. The method for preparing aging-resistant cooked rice paper by secondary sizing with a neutral / alkaline sizing agent according to claim 1, characterized in that: In step S5, the pH regulator is one of sodium carbonate solution, sodium propionate solution, calcium propionate solution, calcium hydroxide solution, or a mixture of sodium carbonate solution and sodium propionate solution, or a mixture of calcium propionate solution and calcium hydroxide solution.

8. The method for preparing aging-resistant cooked rice paper by secondary sizing with a neutral / alkaline sizing agent according to claim 7, characterized in that: The pH regulator is prepared by mixing 10% sodium carbonate solution and 10% sodium propionate solution in a mass ratio of 1:1, or the pH regulator is prepared by mixing 10% calcium propionate solution and saturated calcium hydroxide solution in a mass ratio of 1:

1.

9. The method for preparing aging-resistant cooked rice paper by secondary sizing with a neutral / alkaline sizing agent according to claim 1, 7 or 8, characterized in that: In step S5, a flat plate dryer is used to simulate the baking of rice paper; Separate the wet paper web after pressing, brush it flat on the drying plate of the flat dryer for the first drying, then brush the medium / alkaline surface sizing liquid evenly on the paper surface, perform the second drying and then peel it off to obtain cooked rice paper; or, Separate the wet paper webs after pressing, brush them flatly on the drying plate of the flat dryer, peel them off after drying, then evenly apply the medium / alkaline surface sizing liquid on both sides of the paper, hang them up to air dry, and you will get the cooked rice paper.

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