Preparation method of papermaking sizing starch

Abstract

The invention discloses a preparation method of papermaking sizing starch, and belongs to a papermaking surface sizing process, the preparation method comprises the following steps: toughening treatment, ball milling, filler preparation, dilution and enzymolysis; in the step of ball milling, corn starch, polyethylene glycol 400, polyethyleneimine and water are mixed and then subjected to ball milling; the preparation of the filler comprises the following steps: mixing calcium chloride dihydrate and water, carrying out ultrasonic oscillation at 15-40 DEG C, adding light calcium carbonate, continuously carrying out ultrasonic oscillation and centrifugation, drying a precipitate, mixing with a nonionic polyacrylamide aqueous solution, stirring and centrifuging at 25-50 DEG C, drying the precipitate, mixing with a polyethylene glycol 400 aqueous solution, stirring and centrifuging at 15-40 DEG C, and drying the precipitate; the enzymolysis efficiency is high, the prepared papermaking sizing starch is good in water solubility, few in foam generated in a surface sizing system, high in flowability and permeability, good in effect of improving the strength of paper and small in influence on the whiteness of the paper.

Description

Technical Field

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

[0002] Surface sizing technology is a technology that can improve the comprehensive performance of paper. It is a process in which the surface sizing material flows into the surface of paper fibers, increasing the intermolecular force and chemical bonding force between fibers, thereby affecting the surface performance, water resistance and mechanical properties of the paper.

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

[0004] In addition, corn starch, as a kind of natural starch, has the problem of high viscosity, which leads to low fluidity when using corn starch for surface sizing. It is also easy to gel when used. In addition, corn starch cannot be dissolved in cold water and has poor film-forming properties, which affects the application effect of corn starch in surface sizing.

[0005] Modified starch is a product that uses biological modification, chemical modification, physical modification and composite modification methods to make up for the defects of natural starch and introduce new functions to meet market demand. Modified starch includes enzymatic starch, oxidized starch, esterified starch, etc. Among them, enzymatic starch has good film-forming and permeability and is widely used in surface sizing.

[0006] When enzymatic starch is applied to surface sizing, corn starch is first diluted with water, and then amylase is added for gelatinization. Then, the enzyme is inactivated and diluted to obtain enzymatic starch, i.e., paper sizing starch. Then, the paper sizing starch is mixed with a surface sizing agent to obtain a surface sizing material, and then the surface sizing material is flowed into the surface of paper fibers. However, there are the following problems in the above application: First, the protein and fat in corn starch will affect the surface sizing effect. Specifically, high protein content will lead to excessive foam in the surface sizing system, and the foam is easy to adhere to the surface of the tank to form sediment; fat is easy to adhere to the surface of the tank with the foam, causing the sediment to deteriorate; second, the smaller the molecular weight of enzymatic starch, the stronger the fluidity and permeability, but the smaller the molecular weight, the worse the effect of improving the strength of paper; third, corn starch has a high content of amylose, 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 problem mentioned above, the commonly used solution is to add polyamine salt protein inhibitors and defoamers, but the protein inhibitors and defoamers are polyamine salt protein inhibitors. Polyamine salt protein inhibitors can reduce the amount of foam by chelating with proteins, but the addition of polyamine salt protein inhibitors and defoamers will affect the whiteness of the paper; for the second problem mentioned above, the commonly used solution is to toughen the starch, specifically, before enzymatic hydrolysis, the fluidity of corn starch molecules is enhanced by heating at a high moisture content, thereby promoting cross-linking and recrystallization between amylose and amylopectin in corn starch. , thereby improving the short-range order and further improving the double helix degree of corn starch. It is difficult for amylase to enter the double helix molecular structure of corn starch, thereby retaining more high molecular weight glucan molecules in the enzymatic starch, thereby enhancing the interaction between the enzymatic starch and paper fibers and improving the strength of the paper. At the same time, the uncross-linked and crystallized starch can be fully enzymatically hydrolyzed, thereby improving the fluidity of the enzymatic starch, but reducing the water solubility of the enzymatic starch. For the third problem mentioned above, the commonly used solution is to add cofactors calcium lactate or calcium acetate, but the cofactors calcium lactate or calcium acetate will chelate with the hydroxyl groups, further reducing the water solubility of the enzymatic starch. Summary of the invention

[0008] In view of the shortcomings of the prior art, the present invention provides a method for preparing paper sizing starch. During the preparation, the enzymatic hydrolysis efficiency is high, the prepared paper sizing starch has good water solubility, less foam is generated in the surface sizing system, the fluidity and permeability are strong, the effect of improving the strength of paper is good, and the influence on the whiteness of paper is small.

[0009] In order to solve the above technical problems, the technical solution adopted by the present invention is as follows: A method for preparing papermaking sizing starch, comprising: toughening treatment, ball milling, preparing filler, diluting, and enzymolysis; The toughening treatment comprises mixing corn starch and water, stirring at 15-40° C. at a stirring speed of 50-100 rpm for 10-20 min, then heating to 60-65° C., standing for 23-25 ​​h, centrifuging at a centrifugal speed of 3000-4000 rpm for 15-20 min, discarding the supernatant, washing the precipitate with water for 2-3 times, and drying at 40-50° C. to obtain toughened starch; In the toughening treatment, the mass ratio of corn starch to water is 340-360:1000-1050; The ball milling comprises adding corn starch, polyethylene glycol 400, polyethyleneimine and water into a ball mill for ball milling for 30-35 minutes 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 molecular weight of the polyethyleneimine is 40000; 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. for 10-15 minutes, adding light calcium carbonate, continuing ultrasonically shaking for 10-15 minutes, centrifuging at a centrifugal speed of 6000-7000 rpm for 15-20 minutes, discarding the supernatant, drying the precipitate at 80-90° C., mixing it with a non-ionic polyacrylamide aqueous solution, and stirring it at 25-50° C. at a stirring speed of 50-100 rpm for 1.5-2 h, centrifuging at a centrifugal speed of 6000-7000 rpm for 15-20 min, discarding the supernatant, drying the precipitate at 120-140° C., mixing with a polyethylene glycol 400 aqueous solution, stirring at a stirring speed of 50-100 rpm at 15-40° C. for 50-60 min, centrifuging at a centrifugal speed of 6000-7000 rpm for 15-20 min, discarding the supernatant, and drying the precipitate at 120-140° C. to obtain a filler; 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 20-30kHz; The dilution is to dilute the α-amylase by 200-300 times using 50-60° C. water to obtain an α-amylase dilution solution; In the dilution, the enzyme activity of the α-amylase is 4000 U / g; The enzymolysis comprises mixing the toughened starch, ball mill, filler and water, stirring at 15-40° C. at a stirring speed of 100-400 rpm for 10-20 min, adding α-amylase dilution, stirring for 10-20 min, keeping warm at 60-70° C. for 10-12 min, keeping warm at 90-95° C. for 14-15 min, and keeping warm at 120° C. for 5-6 min to obtain papermaking sizing starch, and storing the papermaking sizing starch at 80-85° C. for standby use; 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.

[0010] Compared with the prior art, the present invention has the following beneficial effects: (1) The method for preparing paper sizing starch of the present invention comprises combining the toughened starch with a ball milling material, wherein the ball milling material is a combination of ball-milled corn starch, polyethylene glycol 400, and polyethylene imine. During the ball milling, the short-range order of the starch is reduced and the solubility is increased. The polyethylene glycol 400 and polyethylene imine can also be combined with the starch through intermolecular forces, thereby facilitating the insertion of α-amylase in enzymatic hydrolysis and the progress of enzymatic hydrolysis. The hydroxyl groups in the polyethylene glycol 400 and the amino groups in the polyethylene imine also have electrostatic attraction with the polar amino acid residues in the amylase. Thus, it is more conducive to the adsorption and enzymolysis of α-amylase, further improving the enzymolysis efficiency and the permeability of the prepared paper sizing starch. Polyethylene glycol 400 and polyethylene imine can also promote the dispersion of 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, thereby ensuring that the prepared paper sizing starch generates less foam in the surface sizing system. In addition, polyethylene glycol 400 and polyethylene imine can also promote the film formation of higher molecular weight dextran molecules, thereby improving the strength of paper. (2) The preparation method of the papermaking sizing starch of the present invention comprises adding a filler during the preparation process. When preparing the filler, light calcium carbonate is first mixed with a calcium ion solution and then subjected to ultrasonic vibration to promote the dispersion of the light calcium carbonate and the adsorption of calcium ions, thereby obtaining light calcium carbonate adsorbing calcium ions. The light calcium carbonate adsorbing calcium ions is then mixed with a non-ionic polyacrylamide aqueous solution. The calcium ions can promote the adsorption of the light calcium carbonate on the non-ionic polyacrylamide, thereby obtaining light calcium carbonate adsorbing calcium ions and non-ionic polyacrylamide. Finally, the light calcium carbonate is mixed with polyethylene glycol 400. The polyethylene glycol 400 is adsorbed on the light calcium carbonate. The outermost layer is a filler. The polyethylene glycol 400 in the outermost layer can improve the dispersibility 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 fix α-amylase and promote enzymolysis, thereby improving the enzymolysis 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, but because polyacrylamide is prone to generate bubbles during stirring, the defoaming effect of the filler is general. In addition, the filler can also promote film formation and play a filling role, thereby improving the strength and whiteness of the paper. (3) The preparation method of the papermaking sizing starch of the present invention has high enzymatic hydrolysis efficiency and strong permeability of the prepared papermaking sizing starch. During enzymatic hydrolysis, the papermaking sizing starch is kept warm at 60-70°C for 10-12 minutes and at 90-95°C for 14-15 minutes. The prepared papermaking sizing starch is applied to offset paper and the sizing amount is controlled to be 2.5 g / m 2 After that, the Cobb value (60s) can reach 26-28g / m 2 ; (4) The papermaking sizing starch prepared by the present invention has good water solubility, and the content of 325-mesh sieve residue is 0.0041-0.0057%; (5) The paper sizing starch prepared by the present invention generates less foam in the surface sizing system. The paper sizing starch prepared by the present invention is stirred at a stirring speed of 200 rpm for 5 minutes and then left to stand for 1 minute without bubbles. (6) The papermaking sizing starch prepared by the present invention has strong fluidity and a viscosity of 25.5-27.1 mPa•s; (7) The papermaking sizing starch prepared by the present invention has a good effect on improving the strength of paper. The prepared papermaking sizing starch is applied to offset paper, and the sizing amount is controlled to be 2.5 g / m 2 After that, the printing surface strength is 2.6-2.9m / s; (8) The papermaking sizing starch prepared by the present invention has little effect on the whiteness of paper. The prepared papermaking sizing starch is applied to offset paper, and the sizing amount is controlled to be 2.5 g / m 2 After that, the whiteness is 84.6-86.5%. DETAILED DESCRIPTION

[0011] In order to have a clearer understanding of the technical features, purposes and effects of the present invention, the specific implementation methods of the present invention are now described.

[0012] The corn starch used in the examples was from the same manufacturer and the same production batch, and had an amylose content of 27.7 wt %.

[0013] Example 1 A method for preparing papermaking sizing starch is as follows: 1. Toughening treatment: 340 g corn starch and 1000 g water were mixed, stirred at 15°C at a stirring speed of 50 rpm for 10 min, then heated to 60°C, allowed to stand for 23 h, centrifuged at a centrifugal speed of 3000 rpm for 15 min, the supernatant was discarded, the precipitate was washed twice with water, and dried at 40°C to obtain toughened starch; 2. Ball milling: add 100g corn starch, 4.5g polyethylene glycol 400, 2.3g polyethyleneimine and 500g water into a ball mill for ball milling. The temperature during ball milling is controlled at 15°C, the rotation speed is 450rpm, the ball-to-material ratio is 25:1, and the ball milling is performed for 30min to obtain a ball mill material. The molecular weight of the polyethyleneimine is 40000; 3. Prepare filler: 10g calcium chloride dihydrate and 900g water are mixed, ultrasonically vibrated at a frequency of 20kHz for 10min at 15°C, 40g light calcium carbonate is added, ultrasonically vibrated for 10min, centrifuged at a centrifugal speed of 6000rpm for 15min, the supernatant is discarded, the precipitate is dried at 80°C, mixed with 5000g non-ionic polyacrylamide aqueous solution, stirred at a stirring speed of 50rpm at 25°C for 1.5h, centrifuged at a centrifugal speed of 6000rpm for 15min, the supernatant is discarded, the precipitate is dried at 120°C, mixed with 1000g polyethylene glycol 400 aqueous solution, stirred at a stirring speed of 50rpm at 15°C for 50min, centrifuged at a centrifugal speed of 6000rpm for 15min, the supernatant is discarded, and the precipitate is dried at 120°C to obtain filler; 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%; 4. Dilution: dilute the α-amylase 200 times with 50°C water to obtain α-amylase dilution solution; The enzyme activity of the α-amylase is 4000 U / g; 5. Enzymolysis: Mix 325 g toughened starch, 580 g ball mill, 37 g filler and 350 g water, stir at 15°C at 100 rpm for 10 min, add 28 g α-amylase dilution, continue stirring for 10 min, keep warm at 60°C for 10 min, keep warm at 90°C for 14 min, and keep warm at 120°C for 5 min to obtain paper sizing starch, which is stored at 80°C for standby use.

[0014] Example 2 A method for preparing papermaking sizing starch is as follows: 1. Toughening treatment: 345 g corn starch and 1020 g water were mixed, stirred at 80 rpm for 15 min at 20 ° C, then heated to 62 ° C, allowed to stand for 24 h, centrifuged at 3500 rpm for 18 min, the supernatant was discarded, the precipitate was washed twice with water, and dried at 45 ° C to obtain toughened starch; 2. Ball milling: 102 g corn starch, 4.7 g polyethylene glycol 400, 2.4 g polyethyleneimine, and 510 g water were added into a ball mill for ball milling. The temperature during ball milling was controlled at 20 ° C, the rotation speed was 450 rpm, the ball-to-material ratio was 28:1, and the ball milling was performed for 32 min to obtain a ball mill material. The molecular weight of the polyethyleneimine is 40000; 3. Prepare filler: 10.5g calcium chloride dihydrate and 920g water are mixed, ultrasonically vibrated at a frequency of 25kHz for 12min at 20°C, 42g light calcium carbonate is added, ultrasonically vibrated for 12min, centrifuged at a centrifugal speed of 6500rpm for 17min, the supernatant is discarded, the precipitate is dried at 85°C, mixed with 5100g non-ionic polyacrylamide aqueous solution, stirred at a stirring speed of 80rpm for 1.5h at 30°C, centrifuged at a centrifugal speed of 6500rpm for 17min, the supernatant is discarded, the precipitate is dried at 130°C, mixed with 1100g polyethylene glycol 400 aqueous solution, stirred at a stirring speed of 80rpm for 55min at 20°C, centrifuged at a centrifugal speed of 6500rpm for 18min, the supernatant is discarded, and the precipitate is dried at 130°C to obtain filler; 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%; 4. Dilution: dilute the α-amylase 250 times with 55°C water to obtain α-amylase dilution solution; The enzyme activity of the α-amylase is 4000 U / g; 5. Enzymolysis: Mix 330 g toughened starch, 590 g ball mill, 38 g filler and 360 g water, stir at 20°C at 200 rpm for 15 min, add 29 g α-amylase dilution, continue stirring for 15 min, keep warm at 65°C for 10 min, keep warm at 92°C for 14 min, and keep warm at 120°C for 5 min to obtain paper sizing starch, which is stored at 82°C for standby use.

[0015] Example 3 A method for preparing papermaking sizing starch is as follows: 1. Toughening treatment: 355 g corn starch and 1040 g water were mixed, stirred at 30°C at a stirring speed of 100 rpm for 18 min, then heated to 65°C, allowed to stand for 24.5 h, centrifuged at a centrifugal speed of 4000 rpm for 18 min, the supernatant was discarded, the precipitate was washed 3 times with water, and dried at 50°C to obtain toughened starch; 2. Ball milling: 104 g corn starch, 4.8 g polyethylene glycol 400, 2.5 g polyethyleneimine, and 540 g water were added into a ball mill for ball milling. The temperature during ball milling was controlled at 30 ° C, the rotation speed was 500 rpm, the ball-to-material ratio was 28:1, and the ball milling was performed for 35 min to obtain a ball mill material. The molecular weight of the polyethyleneimine is 40000; 3. Prepare filler: 10.5g calcium chloride dihydrate and 980g water are mixed, ultrasonically vibrated at a frequency of 25kHz for 14min at 30°C, 43g light calcium carbonate is added, ultrasonically vibrated for 14min, centrifuged at a centrifugal speed of 7000rpm for 20min, the supernatant is discarded, the precipitate is dried at 85°C, mixed with 5400g non-ionic polyacrylamide aqueous solution, stirred at a stirring speed of 100rpm for 2h at 40°C, centrifuged at a centrifugal speed of 7000rpm for 20min, the supernatant is discarded, the precipitate is dried at 140°C, mixed with 1150g polyethylene glycol 400 aqueous solution, stirred at a stirring speed of 100rpm for 60min at 30°C, centrifuged at a centrifugal speed of 6500rpm for 20min, the supernatant is discarded, and the precipitate is dried at 140°C to obtain filler; 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%; 4. Dilution: dilute the α-amylase 250 times with 55°C water to obtain α-amylase dilution solution; The enzyme activity of the α-amylase is 4000 U / g; 5. Enzymolysis: Mix 335 g of toughened starch, 595 g of ball mill, 39 g of filler and 375 g of water, stir at 30°C at 300 rpm for 20 min, add 30 g of 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 paper sizing starch, which is stored at 85°C for standby use.

[0016] Example 4 A method for preparing papermaking sizing starch is as follows: 1. Toughening treatment: 360 g corn starch and 1050 g water were mixed, stirred at 40°C at a stirring speed of 100 rpm for 20 min, then heated to 65°C, allowed to stand for 25 h, centrifuged at a centrifugal speed of 4000 rpm for 20 min, the supernatant was discarded, the precipitate was washed 3 times with water, and dried at 50°C to obtain toughened starch; 2. Ball milling: add 105g corn starch, 5g polyethylene glycol 400, 2.5g polyethyleneimine and 550g water into a ball mill for ball milling. The temperature during ball milling is controlled at 40°C, the speed is 500rpm, the ball-to-material ratio is 30:1, and the ball milling is performed for 35min to obtain a ball mill material. The molecular weight of the polyethyleneimine is 40000; 3. Prepare filler: 11g calcium chloride dihydrate and 1000g water are mixed, ultrasonically vibrated at a frequency of 30kHz for 15min at 40°C, 45g light calcium carbonate is added, ultrasonically vibrated for 15min, centrifuged at a centrifugal speed of 7000rpm for 20min, the supernatant is discarded, the precipitate is dried at 90°C, mixed with 5500g non-ionic polyacrylamide aqueous solution, stirred at a stirring speed of 100rpm for 2h at 50°C, centrifuged at a centrifugal speed of 7000rpm for 20min, the supernatant is discarded, the precipitate is dried at 140°C, mixed with 1200g polyethylene glycol 400 aqueous solution, stirred at a stirring speed of 100rpm for 60min at 40°C, centrifuged at a centrifugal speed of 7000rpm for 20min, the supernatant is discarded, and the precipitate is dried at 140°C to obtain filler; 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%; 4. Dilution: dilute the α-amylase 300 times with 60°C water to obtain α-amylase dilution solution; The enzyme activity of the α-amylase is 4000 U / g; 5. Enzymolysis: Mix 340 g toughened starch, 600 g ball mill, 40 g filler and 380 g water, stir at 40°C at 400 rpm for 20 min, add 30 g α-amylase dilution, continue stirring for 20 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 paper sizing starch, which is stored at 85°C for standby use.

[0017] Comparative Example 1 A method for preparing papermaking sizing starch is the same as Example 3, and the only difference from Example 3 is that the second step of ball milling is omitted; the addition of ball mill material is omitted in the fifth step of enzymatic hydrolysis, and the amount of water added in the fifth step of enzymatic hydrolysis is changed from 375g to 678g.

[0018] Comparative Example 2 A method for preparing papermaking sizing starch is the same as Example 3, and the only difference from Example 3 is that the third step of preparing fillers is omitted; and the addition of fillers is omitted in the fifth step of enzymatic hydrolysis.

[0019] Comparative Example 3 A method for preparing papermaking sizing starch is the same as comparative example 1, and 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, and the fifth step of the enzymatic hydrolysis step is specifically changed to: 335 g of toughened starch, 595 g of ball mill material, 39 g of filler and 375 g of water were mixed, stirred at 30°C at a stirring speed of 300 rpm for 20 min, 30 g of α-amylase dilution was added, stirring was continued for 18 min, and the mixture was kept warm at 70°C for 18 min, at 95°C for 21 min, and at 120°C for 6 min to obtain papermaking sizing starch.

[0020] Comparative Example 4 A method for preparing papermaking sizing starch is the same as Comparative Example 2, and the only difference from Comparative Example 2 is that 0.1 g of calcium acetate is additionally added in the fifth enzymatic hydrolysis step, and the fifth enzymatic hydrolysis step is specifically changed to: 335 g of toughened starch, 595 g of ball mill, 39 g of filler, 0.1 g of calcium acetate and 375 g of water were mixed, stirred at 30°C at a stirring speed of 300 rpm for 20 min, 30 g of α-amylase dilution was added, stirring was continued for 18 min, and the mixture was kept warm at 70°C for 12 min, at 95°C for 15 min, and at 120°C for 6 min to obtain papermaking sizing starch.

[0021] Performance Test 1 The 325 mesh residue content of the papermaking sizing starch prepared in Examples 1-4 and Comparative Examples 1-4 was tested, and the test results are as follows:

[0022] It can be seen from the above performance test results that the 325-mesh sieve residue content of the papermaking sizing starch prepared in Examples 1-4 is relatively low, indicating that the addition of ball mill and filler can reduce the 325-mesh sieve residue content.

[0023] Performance Test 2 The papermaking sizing starch prepared in Examples 1-4 and Comparative Examples 1-4 was stirred at 23° C. at a stirring speed of 200 rpm for 5 min, and then allowed to stand for 1 min to observe whether there were bubbles. The observation results were as follows:

[0024] It can be seen from the above performance test results that the papermaking sizing starch prepared in Examples 1-4 and Comparative Examples 2 and 4 has a strong defoaming ability, indicating that the addition of ball mill can play a defoaming role.

[0025] Performance Test 3 The viscosity of the papermaking sizing starch prepared in Examples 1-4 and Comparative Examples 1-4 was tested at 23°C, and the test results are as follows:

[0026] It can be seen from the above performance test results that the viscosity of the papermaking sizing starch prepared in Examples 1-4 is low, indicating that the addition of ball mill and filler can improve fluidity.

[0027] Performance Test 4 The papermaking sizing starch prepared in Examples 1-4 and Comparative Examples 1-4 were respectively mixed with a cationic styrene acrylic surface sizing agent at a mass ratio of 10:1, stirred at 23° C. at a stirring speed of 100 rpm for 5 min, and then water was added to adjust the solid content to 20% to obtain a surface sizing material; The cationic styrene acrylic surface sizing agent used was from the same manufacturer and the same production batch, with a solid content of 30%; Take the unsizing paper from the workshop, the weight is 80g / m 2 , the surface sizing materials prepared from the papermaking sizing starches of Examples 1-4 and Comparative Examples 1-4 were used for surface sizing, and the sizing amount was 2.5 g / m 2 After drying and calendering, the whiteness, Cobb value and printing surface strength of the offset paper were tested. The test results are as follows:

[0028] It can be seen from the above performance test results that after the paper sizing starch prepared in Examples 1-4 and Comparative Examples 1-4 is applied to offset paper, compared with the paper sizing starch prepared in Comparative Examples 1-4, the paper sizing starch prepared in Examples 1-4 can better improve the whiteness, Cobb value and printing surface strength of the offset paper.

[0029] Unless otherwise specified, all percentages used in the present invention are by mass.

[0030] Finally, it should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art can still modify the technical solutions described in the aforementioned embodiments or replace some of the technical features therein by equivalents. Any modification, equivalent replacement, improvement, 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 ball milling comprises mixing corn starch, polyethylene glycol 400, polyethylene imine and water and then ball milling to obtain a ball mill material; 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 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: The toughening treatment comprises mixing corn starch and water, stirring at 15-40° C., then heating to 60-65° C., standing, centrifuging, washing and drying the precipitate to obtain toughened starch.

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

4. The method for preparing paper sizing starch according to claim 1, characterized in that: 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 molecular weight of the polyethyleneimine is 40000; The temperature during ball milling is 15-40° C., the rotation speed is 450-500 rpm, and the ball-to-material ratio is 25-30:

1.

5. 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.

6. The method for preparing papermaking sizing starch according to claim 1, characterized in that: The dilution uses 50-60° C. water to dilute the α-amylase by 200-300 times to obtain an α-amylase dilution solution.

7. The method for preparing papermaking sizing starch according to claim 6, characterized in that: In the dilution, the enzyme activity of the α-amylase is 4000 U / g.

8. The method for preparing paper 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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