A preparation method of sizing starch for papermaking

Abstract

The present invention discloses a preparation method of sizing starch for papermaking, belonging to the surface sizing process of papermaking. The preparation method includes: toughening treatment, ball milling, preparation of filler, dilution, and enzymatic hydrolysis; for the ball milling, corn starch, polyethylene glycol 400, polyethyleneimine, and water are mixed and then ball milled; for the preparation of filler, calcium chloride dihydrate and water are mixed, ultrasonically oscillated at 15 - 40 °C, light calcium carbonate is added, and ultrasonically oscillated continuously, centrifuged, the precipitate is dried, then mixed with an aqueous solution of non-ionic polyacrylamide, stirred at 25 - 50 °C, centrifuged, the precipitate is dried, then mixed with an aqueous solution of polyethylene glycol 400, stirred at 15 - 40 °C, centrifuged, and the precipitate is dried; the enzymatic hydrolysis efficiency of the present invention is high, the water solubility of the sizing starch for papermaking prepared is good, the foam generated in the surface sizing system is less, the fluidity and permeability are strong, the improvement effect on the strength of the paper is good, and the influence on the whiteness of the paper is small.

Description

Technical Field

[0001] The present invention relates to a papermaking surface sizing process, and specifically to a method for preparing papermaking sizing starch. Background Art

[0002] The surface sizing technology is a technology that can improve the comprehensive performance of paper. It is to flow the surface sizing material onto the surface of paper fibers, and by increasing the intermolecular force and chemical bonding force between fibers, thereby affecting the surface performance, water resistance and mechanical properties of paper.

[0003] In the surface sizing process, the most commonly used surface sizing material is starch. Starch is a carbohydrate existing in corn, cassava, potatoes and other plants. Currently, the most commonly used starches are corn starch and cassava starch. Due to the large output and low price of corn starch, in order to reduce costs and increase efficiency, more and more paper mills use corn starch instead of cassava starch for the surface sizing process. However, compared with cassava starch, when using corn starch for surface sizing, there are the following disadvantages: First, compared with cassava starch, corn starch has a high amylose content and is more likely to retrograde and thicken after gelatinization, affecting the sizing effect; Second, compared with cassava starch, corn starch contains more insoluble substances such as proteins and lipids, which easily cause more screenings in the filter and starch storage tank, increase the pipeline pressure, and even enter the feeding system, causing the sizing rod to be clogged and affecting the stability of the system operation.

[0004] In addition, as a kind of natural starch, corn starch also has the problem of high viscosity, resulting in low fluidity when using corn starch for surface sizing, and it is also prone to gelation during use. Moreover, corn starch also has the problems of not being able to dissolve in cold water and poor film-forming property, which affects the application effect of corn starch in surface sizing.

[0005] Modified starch is to make up for the defects of natural starch by using methods such as biological modification, chemical modification, physical modification and composite modification, and to introduce new functions to meet the market demand. Modified starch includes enzymatically hydrolyzed starch, oxidized starch, esterified starch, etc. Among them, enzymatically hydrolyzed starch has good film-forming property and permeability and is widely used in the surface sizing process.

[0006] When applying enzymatically hydrolyzed starch to surface sizing, first dilute corn starch with water, add amylase for gelatinization, then inactivate the enzyme and dilute to obtain enzymatically hydrolyzed starch, i.e., papermaking sizing starch. Then mix the papermaking sizing starch with a surface sizing agent to obtain a surface sizing material, and then flow the surface sizing material onto the surface of paper fibers. However, there are the following problems in the above application: First, proteins and fats in corn starch will affect the surface sizing effect. Specifically, a high protein content will cause excessive foaming in the surface sizing system, and the foam is easily adhered to the surface of the tank to form deposits; fats are easily adhered to the surface of the tank along with the foam, resulting in the deterioration of the deposits. Second, the smaller the molecular weight of enzymatically hydrolyzed starch, the stronger its fluidity and permeability, but the smaller the molecular weight, the worse the effect of improving the strength of the paper. Third, the amylose content in corn starch is high, and amylose contains more α-1,6-glycosidic bonds, which will hinder the enzymatic hydrolysis of α-amylase, resulting in low enzymatic hydrolysis efficiency.

[0007] For the first above-mentioned problem, the commonly used solution at present is to add polyamine salt protein inhibitors and defoamers. However, for protein inhibitors and defoamers, the protein inhibitor is a polyamine salt protein inhibitor, and the polyamine salt protein inhibitor can reduce the foam amount by chelating with proteins. However, the addition of polyamine salt protein inhibitors and defoamers will affect the whiteness of the paper. For the second above-mentioned problem, the commonly used solution at present is to toughen the starch. Specifically, before enzymatic hydrolysis, by heating and raising the temperature under a high moisture content, the fluidity of corn starch molecules is enhanced, thereby promoting cross-linking and recrystallization between amylose and amylopectin in corn starch, so as to improve the short-range orderliness and further increase the double helix degree of corn starch. It is more difficult for amylase to enter the double helix molecular structure of corn starch, so more higher molecular weight dextran molecules are retained in the enzymatically hydrolyzed starch, thereby enhancing the interaction between the enzymatically hydrolyzed starch and paper fibers and improving the strength of the paper. At the same time, the uncrosslinked and uncrystallized starch can be fully enzymatically hydrolyzed, thereby improving the fluidity of the enzymatically hydrolyzed starch, but reducing the water solubility of the enzymatically hydrolyzed starch. For the third above-mentioned problem, the commonly used solution at present is to add cofactors calcium lactate or calcium acetate. However, the cofactors calcium lactate or calcium acetate will chelate with hydroxyl groups, further reducing the water solubility of the enzymatically hydrolyzed starch. Summary of the Invention

[0008] Aiming at the deficiencies of the existing technology, the present invention provides a preparation method of papermaking sizing starch. In the preparation, the enzymatic hydrolysis efficiency is high, the water solubility of the prepared papermaking sizing starch is good, the foam generated in the surface sizing system is less, the fluidity and permeability are strong, the effect of improving the strength of the paper is good, and the influence on the whiteness of the paper is small.

[0009] To solve the above technical problems, the technical solutions adopted by the present invention are as follows:

[0010] A preparation method of sizing starch for papermaking, comprising: toughening treatment, ball milling, preparing filler, diluting, and enzymatic hydrolysis;

[0011] For the toughening treatment, mix corn starch and water, stir at a stirring speed of 50 - 100 rpm at 15 - 40 °C for 10 - 20 min, then raise the temperature to 60 - 65 °C, let stand for 23 - 25 h, centrifuge at a centrifugal speed of 3000 - 4000 rpm for 15 - 20 min, discard the supernatant, wash the precipitate with water 2 - 3 times, and dry at 40 - 50 °C to obtain the toughened starch;

[0012] In the toughening treatment, the mass ratio of corn starch to water is 340 - 360:1000 - 1050;

[0013] For the ball milling, add corn starch, polyethylene glycol 400, polyethyleneimine, and water into a ball mill for ball milling for 30 - 35 min to obtain a ball - milled material;

[0014] In the ball milling, the mass ratio of corn starch, polyethylene glycol 400, polyethyleneimine, and water is 100 - 105:4.5 - 5:2.3 - 2.5:500 - 550;

[0015] The molecular weight of the polyethyleneimine is 40000;

[0016] During the ball milling, the temperature is 15 - 40 °C, the rotation speed is 450 - 500 rpm, and the ball - to - material ratio is 25 - 30:1;

[0017] For the preparation of the filler, mix calcium chloride dihydrate and water, ultrasonically vibrate at 15 - 40 °C for 10 - 15 min, add light calcium carbonate, continue ultrasonically vibrating for 10 - 15 min, centrifuge at a centrifugal speed of 6000 - 7000 rpm for 15 - 20 min, discard the supernatant, dry the precipitate at 80 - 90 °C, then mix it with an aqueous solution of non - ionic polyacrylamide, stir at a stirring speed of 50 - 100 rpm at 25 - 50 °C for 1.5 - 2 h, centrifuge at a centrifugal speed of 6000 - 7000 rpm for 15 - 20 min, discard the supernatant, dry the precipitate at 120 - 140 °C, then mix it with an aqueous solution of polyethylene glycol 400, stir at a stirring speed of 50 - 100 rpm at 15 - 40 °C for 50 - 60 min, centrifuge at a centrifugal speed of 6000 - 7000 rpm for 15 - 20 min, discard the supernatant, and dry the precipitate at 120 - 140 °C to obtain the filler;

[0018] In the preparation of the filler, the mass ratio of calcium chloride dihydrate, water, light calcium carbonate, non-ionic polyacrylamide aqueous solution, and polyethylene glycol 400 aqueous solution is 10 - 11:900 - 1000:40 - 45:5000 - 5500:1000 - 1200;

[0019] The average particle size of the light calcium carbonate is 1 μm;

[0020] In the non-ionic polyacrylamide aqueous solution, the concentration of non-ionic polyacrylamide is 0.5 wt%, and the molecular weight of non-ionic polyacrylamide is 8 million;

[0021] The concentration of the polyethylene glycol 400 aqueous solution is 2 wt%;

[0022] The frequency of the ultrasonic oscillation is 20 - 30 kHz;

[0023] For the dilution, α-amylase is diluted 200 - 300 times with water at 50 - 60 °C to obtain an α-amylase dilution;

[0024] In the dilution, the enzyme activity of the α-amylase is 4000 U / g;

[0025] For the enzymatic hydrolysis, after mixing the toughened starch, ball milling abrasive, filler, and water, it is stirred at a stirring speed of 100 - 400 rpm at 15 - 40 °C for 10 - 20 min, then the α-amylase dilution is added and stirring continues for 10 - 20 min. It is kept warm at 60 - 70 °C for 10 - 12 min, at 90 - 95 °C for 14 - 15 min, and at 120 °C for 5 - 6 min to obtain papermaking sizing starch, which is stored at 80 - 85 °C for later use;

[0026] In the enzymatic hydrolysis, the mass ratio of the toughened starch, ball milling abrasive, filler, water, and α-amylase dilution is 325 - 340:580 - 600:37 - 40:350 - 380:28 - 30.

[0027] Compared with the prior art, the beneficial effects of the present invention are:

[0028] (1)The preparation method of the paper sizing starch of the present invention combines the toughened starch with a ball-milling abrasive during the preparation. The ball-milling abrasive is a combination of ball-milled corn starch, polyethylene glycol 400, and polyethyleneimine. During ball-milling, the short-range order of the starch decreases and its solubility increases. Polyethylene glycol 400 and polyethyleneimine can also bind to the starch through intermolecular forces, which is beneficial for the insertion of α-amylase and the progress of enzymatic hydrolysis. There is also an electrostatic attraction between the hydroxyl groups in polyethylene glycol 400 and the amino groups in polyethyleneimine and the polar amino acid residues in the amylase, which is more conducive to the adsorption and enzymatic hydrolysis of α-amylase, further improving the enzymatic hydrolysis efficiency and the permeability of the prepared paper sizing starch. Polyethylene glycol 400 and polyethyleneimine can also promote the dispersion of the toughened starch, thereby improving the water solubility and fluidity of the prepared paper sizing starch. Polyethylene glycol 400 can also reduce the surface tension of the liquid, ensuring that less foam is generated in the surface sizing system of the prepared paper sizing starch. In addition, polyethylene glycol 400 and polyethyleneimine can also promote the film formation of higher molecular weight dextran molecules, thereby improving the strength of the paper;

[0029] (2)The preparation method of the paper sizing starch of the present invention adds a filler during the preparation. When preparing the filler, first, light calcium carbonate is mixed with a calcium ion solution and then ultrasonically vibrated to promote the dispersion of light calcium carbonate and its adsorption of calcium ions, thereby obtaining light calcium carbonate adsorbed with calcium ions. Then, the light calcium carbonate adsorbed with calcium ions is mixed with an aqueous solution of non-ionic polyacrylamide. Calcium ions can promote the adsorption of non-ionic polyacrylamide by light calcium carbonate, obtaining light calcium carbonate adsorbed with calcium ions and non-ionic polyacrylamide. Finally, it is mixed with polyethylene glycol 400. Polyethylene glycol 400 is adsorbed on the outermost layer of light calcium carbonate to obtain the filler. The outermost polyethylene glycol 400 can improve the dispersion of light calcium carbonate in water, thereby improving the water solubility and fluidity of the prepared paper sizing starch. At the same time, the calcium ions and non-ionic polyacrylamide in the filler can also immobilize α-amylase and promote enzymatic hydrolysis, thereby improving the enzymatic hydrolysis efficiency and the permeability of the prepared paper sizing starch. The polyethylene glycol on the surface of the filler can also play a defoaming role. However, since polyacrylamide is prone to generate bubbles during stirring, the defoaming effect of the filler is generally average. In addition, the filler can also promote film formation and play a filling role, thereby improving the strength and whiteness of the paper;

[0030] (3)The preparation method of the paper sizing starch of the present invention has a high enzymatic hydrolysis efficiency and the prepared paper sizing starch has strong permeability. During enzymatic hydrolysis, it is kept at 60 - 70 °C for 10 - 12 min and at 90 - 95 °C for 14 - 15 min. The prepared paper sizing starch is applied to double-sided offset paper, and the sizing amount is controlled to be 2.5 g / m 2 After that, the Cobb value (60 s) can reach 26 - 28 g / m 2;

[0031] (4) The water-soluble sizing starch for papermaking prepared by the present invention is good, and the residue content on a 325-mesh sieve is 0.0041 - 0.0057%;

[0032] (5) The sizing starch for papermaking prepared by the present invention produces less foam in the surface sizing system. Stir the sizing starch for papermaking prepared by the present invention at a stirring speed of 200 rpm for 5 min, and then let it stand for 1 min, and there are no bubbles;

[0033] (6) The sizing starch for papermaking prepared by the present invention has strong fluidity and a viscosity of 25.5 - 27.1 mPa•s;

[0034] (7) The sizing starch for papermaking prepared by the present invention has a good effect on improving the strength of paper. Apply the prepared sizing starch for papermaking to double-sided offset paper and control the sizing amount to be 2.5 g / m 2 After that, the printing surface strength is 2.6 - 2.9 m / s;

[0035] (8) The sizing starch for papermaking prepared by the present invention has little influence on the whiteness of paper. Apply the prepared sizing starch for papermaking to double-sided offset paper and control the sizing amount to be 2.5 g / m 2 After that, the whiteness is 84.6 - 86.5%. Specific Embodiments

[0036] In order to have a clearer understanding of the technical features, objectives, and effects of the present invention, the specific embodiments of the present invention are now described.

[0037] The corn starch used in the examples is from the same manufacturer and the same production batch, and the amylose content is 27.7 wt%.

[0038] Example 1

[0039] A method for preparing sizing starch for papermaking is as follows:

[0040] 1. Toughening treatment: Mix 340 g of corn starch and 1000 g of water, stir at a stirring speed of 50 rpm at 15°C for 10 min, then heat up to 60°C, let it stand for 23 h, centrifuge at a centrifugal speed of 3000 rpm for 15 min, discard the supernatant, wash the precipitate with water twice, and dry it at 40°C to obtain the starch after toughening treatment;

[0041] 2. Ball milling: Add 100 g of corn starch, 4.5 g of polyethylene glycol 400, 2.3 g of polyethyleneimine, and 500 g of water to a ball mill for ball milling. Control the temperature during ball milling to be 15°C, the rotation speed to be 450 rpm, the ball-to-material ratio to be 25:1, and ball mill for 30 min to obtain the ball-milled material;

[0042] The molecular weight of the polyethyleneimine is 40,000;

[0043] 3. Preparation of the filler: Mix 10 g of calcium chloride dihydrate and 900 g of water, ultrasonically vibrate at a frequency of 20 kHz for 10 min at 15 °C, add 40 g of light calcium carbonate, continue ultrasonically vibrating for 10 min, centrifuge at a speed of 6000 rpm for 15 min, discard the supernatant, dry the precipitate at 80 °C, then mix it with 5000 g of an aqueous solution of non-ionic polyacrylamide, stir at a speed of 50 rpm for 1.5 h at 25 °C, centrifuge at a speed of 6000 rpm for 15 min, discard the supernatant, dry the precipitate at 120 °C, then mix it with 1000 g of an aqueous solution of polyethylene glycol 400, stir at a speed of 50 rpm for 50 min at 15 °C, centrifuge at a speed of 6000 rpm for 15 min, discard the supernatant, dry the precipitate at 120 °C to obtain the filler;

[0044] The average particle size of the light calcium carbonate is 1 μm;

[0045] The concentration of non-ionic polyacrylamide in the aqueous solution of non-ionic polyacrylamide is 0.5 wt%, and the molecular weight of non-ionic polyacrylamide is 8 million;

[0046] The concentration of the aqueous solution of polyethylene glycol 400 is 2 wt%;

[0047] 4. Dilution: Dilute α-amylase 200 times with water at 50 °C to obtain an α-amylase dilution;

[0048] The enzyme activity of the α-amylase is 4000 U / g;

[0049] 5. Enzymolysis: Mix 325 g of toughened starch, 580 g of ball-milling abrasive, 37 g of filler, and 350 g of water, stir at a speed of 100 rpm for 10 min at 15 °C, add 28 g of the α-amylase dilution, continue stirring for 10 min, keep warm at 60 °C for 10 min, keep warm at 90 °C for 14 min, keep warm at 120 °C for 5 min to obtain paper sizing starch, and store the paper sizing starch at 80 °C for later use.

[0050] Example 2

[0051] A method for preparing paper sizing starch is as follows:

[0052] 1. Toughening treatment: Mix 345 g of corn starch and 1020 g of water, stir at a stirring speed of 80 rpm at 20 °C for 15 min, then heat up to 62 °C, let stand for 24 h, centrifuge at a centrifugal speed of 3500 rpm for 18 min, discard the supernatant, wash the precipitate twice with water, and dry at 45 °C to obtain the toughened starch;

[0053] 2. Ball milling: Add 102 g of corn starch, 4.7 g of polyethylene glycol 400, 2.4 g of polyethyleneimine, and 510 g of water to a ball mill for ball milling. Control the temperature during ball milling at 20 °C, the rotation speed at 450 rpm, the ball-to-material ratio at 28:1, and ball mill for 32 min to obtain the ball-milled material;

[0054] The molecular weight of the polyethyleneimine is 40000;

[0055] 3. Preparation of filler: Mix 10.5 g of calcium chloride dihydrate and 920 g of water, ultrasonically vibrate at a frequency of 25 kHz at 20 °C for 12 min, add 42 g of light calcium carbonate, continue ultrasonically vibrate for 12 min, centrifuge at a centrifugal speed of 6500 rpm for 17 min, discard the supernatant, dry the precipitate at 85 °C, then mix it with 5100 g of an aqueous solution of non-ionic polyacrylamide, stir at a stirring speed of 80 rpm at 30 °C for 1.5 h, centrifuge at a centrifugal speed of 6500 rpm for 17 min, discard the supernatant, dry the precipitate at 130 °C, then mix it with 1100 g of an aqueous solution of polyethylene glycol 400, stir at a stirring speed of 80 rpm at 20 °C for 55 min, centrifuge at a centrifugal speed of 6500 rpm for 18 min, discard the supernatant, and dry the precipitate at 130 °C to obtain the filler;

[0056] The average particle size of the light calcium carbonate is 1 μm;

[0057] The concentration of non-ionic polyacrylamide in the aqueous solution of non-ionic polyacrylamide is 0.5 wt%, and the molecular weight of non-ionic polyacrylamide is 8 million;

[0058] The concentration of the aqueous solution of polyethylene glycol 400 is 2 wt%;

[0059] 4. Dilution: Dilute α-amylase 250 times with water at 55 °C to obtain the α-amylase dilution;

[0060] The enzyme activity of the α-amylase is 4000 U / g;

[0061] 5. Enzymatic hydrolysis: Mix 330 g of toughened starch, 590 g of ball-milled material, 38 g of filler, and 360 g of water. Stir at a speed of 200 rpm for 15 min at 20°C, add 29 g of α-amylase dilution, continue stirring for 15 min, keep at 65°C for 10 min, keep at 92°C for 14 min, and keep at 120°C for 5 min to obtain paper sizing starch. Store the paper sizing starch at 82°C for later use.

[0062] Example 3

[0063] A preparation method of paper sizing starch is as follows:

[0064] 1. Toughening treatment: Mix 355 g of corn starch and 1040 g of water, stir at a speed of 100 rpm for 18 min at 30°C, then heat up to 65°C, let stand for 24.5 h, centrifuge at a speed of 4000 rpm for 18 min, discard the supernatant, wash the precipitate with water 3 times, and dry at 50°C to obtain toughened starch.

[0065] 2. Ball milling: Add 104 g of corn starch, 4.8 g of polyethylene glycol 400, 2.5 g of polyethyleneimine, and 540 g of water into a ball mill for ball milling. Control the temperature during ball milling at 30°C, the rotation speed at 500 rpm, and the ball-to-material ratio at 28:1. Ball mill for 35 min to obtain ball-milled material.

[0066] The molecular weight of the polyethyleneimine is 40000.

[0067] 3. Preparation of filler: Mix 10.5 g of calcium chloride dihydrate and 980 g of water, ultrasonically vibrate at a frequency of 25 kHz for 14 min at 30°C, add 43 g of light calcium carbonate, continue ultrasonically vibrating for 14 min, centrifuge at a speed of 7000 rpm for 20 min, discard the supernatant, dry the precipitate at 85°C, then mix it with 5400 g of non-ionic polyacrylamide aqueous solution, stir at a speed of 100 rpm for 2 h at 40°C, centrifuge at a speed of 7000 rpm for 20 min, discard the supernatant, dry the precipitate at 140°C, then mix it with 1150 g of polyethylene glycol 400 aqueous solution, stir at a speed of 100 rpm for 60 min at 30°C, centrifuge at a speed of 6500 rpm for 20 min, discard the supernatant, and dry the precipitate at 140°C to obtain filler.

[0068] The average particle size of the light calcium carbonate is 1 μm.

[0069] The concentration of non-ionic polyacrylamide in the non-ionic polyacrylamide aqueous solution is 0.5 wt%, and the molecular weight of non-ionic polyacrylamide is 8 million.

[0070] The concentration of the polyethylene glycol 400 aqueous solution is 2 wt%.

[0071] 4. Dilution: Dilute α-amylase 250 times with water at 55 °C to obtain an α-amylase dilution.

[0072] The enzyme activity of the α-amylase is 4000 U / g.

[0073] 5. Enzymolysis: Mix 335 g of the toughened starch, 595 g of the ball-milled material, 39 g of the filler, and 375 g of water, stir at a stirring speed of 300 rpm at 30 °C for 20 min, add 30 g of the α-amylase dilution, continue stirring for 18 min, keep warm at 70 °C for 12 min, keep warm at 95 °C for 14 min, and keep warm at 120 °C for 6 min to obtain papermaking sizing starch, and store the papermaking sizing starch at 85 °C for use.

[0074] Example 4

[0075] A method for preparing papermaking sizing starch is as follows:

[0076] 1. Toughening treatment: Mix 360 g of corn starch and 1050 g of water, stir at a stirring speed of 100 rpm at 40 °C for 20 min, then heat up to 65 °C, stand for 25 h, centrifuge at a centrifugation speed of 4000 rpm for 20 min, discard the supernatant, wash the precipitate 3 times with water, and dry at 50 °C to obtain the toughened starch.

[0077] 2. Ball milling: Add 105 g of corn starch, 5 g of polyethylene glycol 400, 2.5 g of polyethyleneimine, and 550 g of water to a ball mill for ball milling, control the temperature during ball milling at 40 °C, the rotation speed at 500 rpm, the ball-to-material ratio at 30:1, and ball mill for 35 min to obtain the ball-milled material.

[0078] The molecular weight of the polyethyleneimine is 40000.

[0079] 3. Preparation of filler: Mix 11 g of calcium chloride dihydrate with 1000 g of water, ultrasonically oscillate at a frequency of 30 kHz for 15 min at 40°C, add 45 g of light calcium carbonate, continue ultrasonically oscillating for 15 min, centrifuge at a speed of 7000 rpm for 20 min, discard the supernatant, dry the precipitate at 90°C, then mix it with 5500 g of non-ionic polyacrylamide aqueous solution, stir at a speed of 100 rpm at 50°C for 2 h, centrifuge at a speed of 7000 rpm for 20 min, discard the supernatant, dry the precipitate at 140°C, and then mix it with 1200 g of polyethylene glycol 400 aqueous solution, stir at a speed of 100 rpm at 40°C for 60 min, centrifuge at a speed of 7000 rpm for 20 min, discard the supernatant, and dry the precipitate at 140°C to obtain the filler;

[0080] The average particle size of the light calcium carbonate is 1 μm;

[0081] The concentration of non-ionic polyacrylamide in the non-ionic polyacrylamide aqueous solution is 0.5 wt%, and the molecular weight of non-ionic polyacrylamide is 8 million;

[0082] The concentration of the polyethylene glycol 400 aqueous solution is 2 wt%;

[0083] 4. Dilution: Dilute α-amylase 300 times with water at 60°C to obtain an α-amylase dilution;

[0084] The enzyme activity of the α-amylase is 4000 U / g;

[0085] 5. Enzymatic hydrolysis: Mix 340 g of toughened starch, 600 g of ball-milled material, 40 g of filler, and 380 g of water, stir at a speed of 400 rpm at 40°C for 20 min, add 30 g of α-amylase dilution, continue stirring for 20 min, keep at 70°C for 12 min, keep at 95°C for 15 min, keep at 120°C for 6 min to obtain papermaking sizing starch, and store the papermaking sizing starch at 85°C for use.

[0086] Comparative Example 1

[0087] A method for preparing papermaking sizing starch is the same as that in Example 3. The only difference from Example 3 is: omitting the second step of ball-milling; omitting the addition of ball-milled material in the fifth step of enzymatic hydrolysis, and changing the addition amount of water in the fifth step of enzymatic hydrolysis from 375 g to 678 g.

[0088] Comparative Example 2

[0089] A preparation method of sizing starch for papermaking, which is the same as Example 3. The only difference from Example 3 is that the third step of preparing the filler is omitted; the addition of the filler is omitted in the fifth step of the enzymatic hydrolysis step.

[0090] Comparative Example 3

[0091] A preparation method of sizing starch for papermaking, which is the same as Comparative Example 1. The only difference from Comparative Example 1 is that the enzymatic hydrolysis time in the fifth step of the enzymatic hydrolysis step is multiplied by 1.5 times. Specifically, the fifth step of the enzymatic hydrolysis step is changed to:

[0092] Mix 335 g of toughened starch, 595 g of ball-milled material, 39 g of filler, and 375 g of water, stir at a stirring speed of 300 rpm at 30 °C for 20 min, add 30 g of α-amylase dilution solution, continue stirring for 18 min, keep warm at 70 °C for 18 min, keep warm at 95 °C for 21 min, and keep warm at 120 °C for 6 min to obtain sizing starch for papermaking.

[0093] Comparative Example 4

[0094] A preparation method of sizing starch for papermaking, which is the same as Comparative Example 2. The only difference from Comparative Example 2 is that 0.1 g of calcium acetate is additionally added in the fifth step of the enzymatic hydrolysis step. Specifically, the fifth step of the enzymatic hydrolysis step is changed to:

[0095] Mix 335 g of toughened starch, 595 g of ball-milled material, 39 g of filler, 0.1 g of calcium acetate, and 375 g of water, stir at a stirring speed of 300 rpm at 30 °C for 20 min, add 30 g of α-amylase dilution solution, continue stirring for 18 min, keep warm at 70 °C for 12 min, keep warm at 95 °C for 15 min, and keep warm at 120 °C for 6 min to obtain sizing starch for papermaking.

[0096] Performance Test 1

[0097] Test the 325-mesh residue content of the sizing starch for papermaking prepared in Examples 1-4 and Comparative Examples 1-4. The test results are as follows:

[0098]

[0099] It can be seen from the above performance test results that the 325-mesh residue content of the sizing starch for papermaking prepared in Examples 1-4 is relatively low, indicating that the addition of both the ball-milled material and the filler can reduce the 325-mesh residue content.

[0100] Performance Test 2

[0101] Stir the papermaking sizing starches prepared in Examples 1-4 and Comparative Examples 1-4 at a stirring speed of 200 rpm at 23°C for 5 min, then let it stand for 1 min, and observe whether there are still bubbles. The observation results are as follows:

[0102]

[0103] From the above performance test results, it can be seen that the papermaking sizing starches prepared in Examples 1-4 and Comparative Examples 2 and 4 have strong defoaming ability, indicating that the addition of ball mill materials can play a defoaming role.

[0104] Performance Test 3

[0105] Test the viscosities of the papermaking sizing starches prepared in Examples 1-4 and Comparative Examples 1-4 at 23°C. The test results are as follows:

[0106]

[0107] From the above performance test results, it can be seen that the papermaking sizing starches prepared in Examples 1-4 have low viscosities, indicating that the addition of ball mill materials and fillers can play a role in improving fluidity.

[0108] Performance Test 4

[0109] Respectively mix the papermaking sizing starches prepared in Examples 1-4 and Comparative Examples 1-4 with a cationic styrene-acrylic surface sizing agent in a mass ratio of 10:1, stir at a stirring speed of 100 rpm at 23°C for 5 min, and then add water to adjust the solid content to 20% to obtain surface sizing materials;

[0110] The cationic styrene-acrylic surface sizing agent used is from the same manufacturer and the same production batch, and the solid content is 30%;

[0111] Take un-surface-sized double-sided offset paper of the same production batch from the workshop, with a grammage of 80 g / m 2 , and respectively use the surface sizing materials prepared from the papermaking sizing starches of Examples 1-4 and Comparative Examples 1-4 for surface sizing, with a sizing amount of 2.5 g / m 2 , and then after drying treatment and calendering treatment, test the whiteness, Cobb value, and printing surface strength of the double-sided offset paper. The test results are as follows:

[0112]

[0113] From the above performance test results, it can be seen that after applying the papermaking sizing starches prepared in Examples 1-4 and Comparative Examples 1-4 to the double-sided offset paper, compared with the papermaking sizing starches prepared in Comparative Examples 1-4, the papermaking sizing starches prepared in Examples 1-4 can better improve the whiteness, Cobb value, and printing surface strength of the double-sided offset paper.

[0114] Unless otherwise specified, the percentages used in the present invention are all mass percentages.

[0115] Finally, it should be noted that the above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or perform equivalent replacements for some of the technical features. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for preparing papermaking sizing starch, characterized in that: include: Toughening treatment, ball milling, filler preparation, dilution, enzymatic hydrolysis; The toughening treatment comprises mixing corn starch and water, stirring at 15-40° C., then heating to 60-65° C., standing for 23-25 ​​hours, centrifuging, washing and drying the precipitate, and obtaining toughened starch; The ball milling comprises mixing corn starch, polyethylene glycol 400, polyethylene imine and water and then ball milling to obtain a ball mill material; In the ball mill, the mass ratio of corn starch, polyethylene glycol 400, polyethyleneimine and water is 100-105:4.5-5:2.3-2.5:500-550; The temperature during ball milling is 15-40°C, the rotation speed is 450-500rpm, and the ball-to-material ratio is 25-30:1; The filler is prepared by mixing calcium chloride dihydrate and water, ultrasonically shaking at 15-40° C., adding light calcium carbonate, continuing ultrasonic shaking, centrifuging, drying the precipitate, mixing it with a non-ionic polyacrylamide aqueous solution, stirring at 25-50° C., centrifuging, drying the precipitate, mixing it with a polyethylene glycol 400 aqueous solution, stirring at 15-40° C., centrifuging, and drying the precipitate to obtain the filler; The dilution is to dilute the α-amylase 200-300 times with water at 50-60° C. to obtain an α-amylase dilution solution; The enzymolysis comprises mixing the toughened starch, ball mill, filler and water, stirring at 15-40° C., adding α-amylase dilution, continuing stirring, keeping warm at 60-70° C. for 10-12 minutes, keeping warm at 90-95° C. for 14-15 minutes, and keeping warm at 120° C. for 5-6 minutes to obtain papermaking sizing starch.

2. The method for preparing paper sizing starch according to claim 1, characterized in that: In the toughening treatment, the mass ratio of corn starch to water is 340-360:1000-1050.

3. The method for preparing paper sizing starch according to claim 1, characterized in that: In the ball milling, the molecular weight of the polyethyleneimine is 40,000.

4. The method for preparing paper sizing starch according to claim 1, characterized in that: In the preparation of the filler, the mass ratio of calcium chloride dihydrate, water, light calcium carbonate, non-ionic polyacrylamide aqueous solution, and polyethylene glycol 400 aqueous solution is 10-11:900-1000:40-45:5000-5500:1000-1200; The average particle size of the light calcium carbonate is 1 μm; The concentration of nonionic polyacrylamide in the nonionic polyacrylamide aqueous solution is 0.5wt%, and the molecular weight of the nonionic polyacrylamide is 8 million; The concentration of the polyethylene glycol 400 aqueous solution is 2wt%; The frequency of the ultrasonic oscillation is 20-30 kHz.

5. The method for preparing paper sizing starch according to claim 1, characterized in that: In the dilution, the enzyme activity of the α-amylase is 4000 U / g.

6. The method for preparing papermaking sizing starch according to claim 1, characterized in that: In the enzymolysis, the mass ratio of the toughened starch, the ball mill, the filler, water, and the α-amylase dilution is 325-340:580-600:37-40:350-380:28-30; In the enzymatic hydrolysis, after the papermaking sizing starch is prepared, the papermaking sizing starch is stored at 80-85° C. for later use.

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