Preparation method and spraying method of pulp molding high-permeability sizing agent

Abstract

The invention discloses a paper pulp molding high-permeability sizing agent preparation method, which specifically comprises: 1, carrying out anion modification on castor oil to obtain anion modified castor oil; step 2, carrying out alkylene oxide and cation modification on castor oil to obtain alkylene oxide-cation modified castor oil; step 3, modifying starch with phosphoric acid to obtain phosphoric acid modified starch; and 4, preparing the high-permeability sizing agent according to products obtained in the steps 1-3. The invention also discloses a spraying method of the sizing agent, and the sizing agent prepared by the invention solves the problem that the existing sizing agent has insufficient permeability to high-thickness paper, so that the performance of a paper pulp molded product is influenced.

Description

Technical Field

[0001] The invention belongs to the technical field of papermaking, and relates to a preparation method of a high-penetration sizing agent for pulp molding. The invention also relates to a spraying method of the high-penetration sizing agent for pulp molding. Background Art

[0002] Pulp molding is a three-dimensional papermaking technology that uses fiber as raw material and uses special molds on a molding machine to shape paper products of a certain shape. Pulp molded products need to be recyclable and degradable. In terms of application, the products need to meet the requirements of good shock resistance, cushioning, breathability, and anti-static properties. In addition, the introduction of functional additives can also achieve functions such as waterproofing and oil resistance. As a substitute for plastic, it can reduce the generation of white pollution and can be seen everywhere in life. So far, it has broad application prospects in the fields of electronic product packaging, daily chemical product packaging, and fresh food packaging.

[0003] It should be pointed out that the fatal weakness of today's pulp molded products is the lack of bearing capacity and structural strength. In order to improve these indicators, the thickness of the molded products has to be increased. At present, the minimum thickness of paper plastic products is 0.6mm, the maximum thickness can reach 1.5-2.0mm, and the thickness of the product is usually around 0.8-1.0mm. In order to increase the thickness of the product, paper plastic enterprises mainly use two methods. One method is to increase the amount of slurry, which not only increases the cost of the product, but also increases the difficulty of manufacturing; the other method is: surface sizing, such as people use surface sizing to improve the stiffness and mechanical properties of paper, but for pulp molding materials, its thickness is large, and the surface sizing agent is difficult to penetrate, making it difficult to improve the performance of pulp molded products. Summary of the invention

[0004] The purpose of the present invention is to provide a method for preparing a high-penetration sizing agent for pulp molding, which solves the problem that the existing sizing agent has insufficient permeability to high-thickness paper, thereby affecting the performance of pulp molded products.

[0005] Another object of the present invention is to provide a method for spraying a high-penetration sizing agent for pulp molding.

[0006] The first technical solution adopted by the present invention is a method for preparing a high-penetration sizing agent for pulp molding, which specifically comprises the following steps:

[0007] Step 1, anion-modifying castor oil to obtain anion-modified castor oil;

[0008] Step 2, performing alkylene oxide and cation modification on castor oil to obtain alkylene oxide-cation modified castor oil;

[0009] Step 3, modifying starch with phosphoric acid to obtain phosphoric acid-modified starch;

[0010] Step 4, preparing a high penetration sizing agent according to the products obtained in steps 1 to 3.

[0011] The first technical solution adopted by the present invention is also characterized in that:

[0012] The specific process of step 1 is:

[0013] 100-300 g of castor oil is added to a 250-500 mL round-bottom flask, 5-15 g of polyphosphoric acid is added dropwise in batches, and after the addition is completed, the reaction is continued at 100-160° C. for 30-60 minutes, and the mixture is cooled to room temperature; 10-30 g of sodium bicarbonate is added to the reaction solution in batches, and bubbles are generated at the beginning. After no bubbles are generated, unreacted sodium bicarbonate and by-products are filtered out, and the filtrate is collected to obtain anion-modified castor oil.

[0014] The specific process of step 2 is: take 100-300g of castor oil and 20-60g of 2,3-epoxypropyltrimethylammonium chloride, then add 0.2-0.6g of NaOH, react at room temperature for 30-60 minutes, add 20-60mL of acetic acid after the reaction to terminate the cation modification reaction; then add 0.2-0.6g of phosphoric acid and 50-150mL of hydrogen peroxide, heat to 50-80°C and react for 8-12h, after the reaction is completed, extract three times with 1000mL-3000mL of ethyl acetate to obtain epoxyalkyl-cation modified castor oil.

[0015] The specific process of step 3 is:

[0016] Step 3.1, take 100-300 g of starch, add 300-900 g of deionized water, and stir evenly to obtain starch milk;

[0017] Step 3.2, using NaOH solution to adjust the pH of the starch milk to 10-11, then add 0.5-1.5g of polyphosphoric acid, and fully react at 60-90°C for 2-6h. After the reaction, adjust the pH to 5-6, wash repeatedly with 500-1500mL of deionized water for 3 times, filter to obtain a filter cake, dry the filter cake under vacuum at 45-90°C overnight, and then sieve through a pore size sieve to obtain a phosphoric acid-modified starch with a particle size of 20-50um.

[0018] The specific process of step 4 is: take 30-90g of the anionic modified castor oil prepared in step 1, 30-90g of the alkylene oxide-cationic modified castor oil prepared in step 2, and 100-300g of the phosphoric acid modified starch prepared in step 3, add them into 1-3L of deionized water in sequence, stir at 45-90°C for 30min, and obtain a translucent sizing agent.

[0019] The viscosity of the sizing agent prepared in step 4 is 100-500 centipoise.

[0020] The second technical solution adopted by the present invention is a method for spraying a high-penetration sizing agent for pulp molding. The specific process is as follows: add the sizing agent to the spraying instrument, take 20cmx20cm of 0.8-1.6mm thick pulp molding base paper, the spraying interval is 30-60mm, the nozzle height is 100-200mm, the spraying thickness is 10-20um, and the sprayed paper sample is placed in a constant temperature box and dried at 45-90℃ for 3-6h.

[0021] The beneficial effect of the present invention is that the present invention uses green and environmentally friendly biomass castor oil as a raw material to prepare a high-permeability surface sizing agent, which solves the problem of insufficient permeability of spray sizing and sizing agents for high-thickness paper. A surface spray sizing process is selected. The high-permeability sizing agent is used to improve the mechanical performance indicators such as stiffness and strength of pulp molding, and the thickness-increasing method is abandoned to improve the strength and stiffness. The adhesion and antistatic properties of the sizing agent to the pulp molding surface are improved, and a chemical bond is established between the sizing agent and the fiber, that is, the surface sizing agent is stable in pulp molding, which can reduce or avoid the dissolution and migration of pulp molding sizing agent components. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is a curve diagram showing the relationship between the apparent viscosity and shear rate of the high-penetration surface sizing agent prepared in Example 1 of the method for preparing the high-penetration sizing agent for pulp molding of the present invention. DETAILED DESCRIPTION

[0023] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments.

[0024] The preparation method of the pulp molding high-penetration sizing agent of the present invention specifically comprises the following steps:

[0025] Step 1, anionic modification of castor oil, the specific process is:

[0026] Take 100-300g of castor oil, add it into a 250-500mL round-bottom flask, add 5-15g of polyphosphoric acid in batches (add over 10 minutes, 0.5-1.5g per minute), continue to react at 100-160°C for 30-60min after the addition is completed, and add excess sodium bicarbonate 10-30g (add in 10 times, 1-3g each time) to the reaction solution after cooling to room temperature, bubbles begin to be generated, and after no bubbles are generated, filter out unreacted sodium bicarbonate and by-product sodium phosphate (inorganic salt), collect the filtrate, and obtain anion-modified castor oil.

[0027] Step 2, alkylene oxide and cationic modification of castor oil, the specific process is:

[0028] Take 100-300g of castor oil and 20-60g of 2,3-epoxypropyltrimethylammonium chloride, then add 0.2-0.6g of NaOH. React at room temperature for 30-60 minutes. After the reaction is completed, add 20-60mL of acetic acid to terminate the cation modification reaction, further add 0.2-0.6g of phosphoric acid and 50-150mL of hydrogen peroxide, heat to 50-80℃ and react for 8-12h. After the reaction is completed, extract three times with 1000mL-3000mL of ethyl acetate to obtain epoxyalkyl-cation modified castor oil.

[0029] Step 3, phosphoric acid modification of starch, the specific process is:

[0030] Take 100-300g of starch, add 300-900g of deionized water, stir evenly to obtain starch milk, adjust the pH of the starch milk to 10-11 with NaOH solution, add 0.5-1.5g of polyphosphoric acid, and fully react at 60-90°C for 2-6h. After the reaction, adjust the pH to 5-6, wash repeatedly with 500-1500mL of deionized water for 3 times, filter to obtain a filter cake, dry the filter cake under vacuum at 45-90°C overnight, pass through 50um and 20um aperture sieves, and sieve to obtain phosphoric acid-modified starch with a particle size of 20-50um.

[0031] Step 4, preparation of high penetration sizing agent, the specific process is as follows:

[0032] Take 30-90g of anion-modified castor oil, 30-90g of alkylene oxide-cation-modified castor oil, and 100-300g of phosphoric acid-modified starch, add them successively into 1-3L of deionized water, stir at 45-90°C for 30min, and obtain a translucent sizing agent with a viscosity of 100-500 centipoise.

[0033] The invention discloses a method for spraying a pulp molding high-penetration sizing agent on a pulp molding surface. The specific process is as follows: adding the high-penetration sizing agent prepared in step 4 to a spraying instrument, taking a 0.8-1.6 mm thick pulp molding base paper 20 cm x 20 cm, spraying with a spacing of 30-60 mm, a nozzle height of 100-200 mm, and a spraying thickness of 10-20 um. Put the sprayed paper sample into a thermostat and dry it at 45-90° C. for 3-6 hours.

[0034] Example 1 (Surface sizing of 1.2 mm pulp molding base paper)

[0035] Step 1, anionic modification of castor oil, the specific process is:

[0036] Take 100g of castor oil, add it to a 250mL round-bottom flask, add 5g of polyphosphoric acid in batches (add it over 10 minutes, 0.5g per minute), continue to react at 100°C for 30min after the addition is completed, and add an excess of 10g of sodium bicarbonate (added in 10 times, 1g each time) to the reaction solution after cooling to room temperature. Bubbles begin to be generated. After no bubbles are generated, filter out the unreacted sodium bicarbonate and the by-product sodium phosphate, collect the filtrate, and obtain anion-modified castor oil.

[0037] Step 2, alkylene oxide and cationic modification of castor oil, the specific process is:

[0038] Take 100g of castor oil and 20g of 2,3-epoxypropyltrimethylammonium chloride, then add 0.2g of NaOH. React at room temperature for 30 minutes. After the reaction is completed, add 20mL of acetic acid to terminate the cationic modification reaction, further add 0.2g of phosphoric acid and 50mL of hydrogen peroxide, and heat to 50℃ for 8h. After the reaction is completed, extract three times with 1000mL of ethyl acetate to obtain epoxyalkyl-cation-modified castor oil.

[0039] Step 3, phosphoric acid modification of starch, the specific process is:

[0040] Take 100g of starch, add 300g of deionized water, stir evenly to obtain starch milk, adjust the pH of the starch milk to 10 with NaOH solution, add 0.5g of polyphosphoric acid, and fully react at 60°C for 2h. After the reaction, adjust the pH to 5, wash repeatedly with 500mL of deionized water 3 times, filter to obtain a filter cake, dry the filter cake at 45°C under vacuum overnight, pass through 50um and 20um aperture sieves, and sieve to obtain phosphoric acid-modified starch with a particle size of 20-50um.

[0041] Step 4, preparation of high penetration sizing agent, the specific process is as follows:

[0042] Take 30 g of anion-modified castor oil, 30 g of alkylene oxide-cation-modified castor oil, and 100 g of phosphoric acid-modified starch, add them into 1 L of deionized water successively, stir at 45° C. for 30 min, and obtain a translucent sizing agent with a viscosity of 100 centipoise.

[0043] Spraying sizing on the surface of pulp molding: Add the high-penetration sizing agent prepared in step 4 to the spraying instrument, take 1.2mm thick pulp molding base paper 20cmx20cm, spray spacing 30mm, nozzle height 100mm, spray thickness 10um. Put the sprayed paper sample into a constant temperature box and dry it at 45℃ for 3h.

[0044] Example 2 (Surface sizing of 1.6 mm pulp molding base paper)

[0045] Step 1, anionic modification of castor oil, the specific process is:

[0046] Take 100g of castor oil, add it to a 250mL round-bottom flask, add 5g of polyphosphoric acid in batches (add it over 10 minutes, 0.5g per minute), continue to react at 100°C for 30min after the addition is completed, and add an excess of 10g of sodium bicarbonate (added in 10 times, 1g each time) to the reaction solution after cooling to room temperature. Bubbles begin to be generated. After no bubbles are generated, filter out the unreacted sodium bicarbonate and the by-product sodium phosphate, collect the filtrate, and obtain anion-modified castor oil.

[0047] Step 2, alkylene oxide and cationic modification of castor oil, the specific process is:

[0048] Take 100g of castor oil and 20g of 2,3-epoxypropyltrimethylammonium chloride, then add 0.2g of NaOH. React at room temperature for 30 minutes. After the reaction is completed, add 20mL of acetic acid to terminate the cationic modification reaction, further add 0.2g of phosphoric acid and 50mL of hydrogen peroxide, and heat to 50℃ for 8h. After the reaction is completed, extract three times with 1000mL of ethyl acetate to obtain epoxyalkyl-cation-modified castor oil.

[0049] Step 3, phosphoric acid modification of starch, the specific process is:

[0050] Take 100g of starch, add 300g of deionized water, stir evenly to obtain starch milk, adjust the pH of the starch milk to 10 with NaOH solution, add 0.5g of polyphosphoric acid, and fully react at 60°C for 2h. After the reaction, adjust the pH to 5, wash repeatedly with 500mL of deionized water 3 times, filter to obtain a filter cake, dry the filter cake under vacuum at 45°C overnight, pass through 50um and 20um aperture sieves, and sieve to obtain phosphoric acid-modified starch with a particle size of 20-50um.

[0051] Step 4, preparation of high penetration sizing agent, the specific process is as follows:

[0052] Take 30 g of anion-modified castor oil, 30 g of alkylene oxide-cation-modified castor oil, and 100 g of phosphoric acid-modified starch, add them into 1 L of deionized water successively, stir at 45° C. for 30 min, and obtain a translucent sizing agent with a viscosity of 100 centipoise.

[0053] Spraying sizing on the surface of pulp molding: Add the high-penetration sizing agent prepared in step 4 to the spraying instrument, take 20cmx20cm of 1.6mm thick pulp molding base paper, spray with a spacing of 30mm, a nozzle height of 100mm, and a spray thickness of 10um. Put the sprayed paper sample in a constant temperature box and dry it at 45℃ for 3h.

[0054] Comparative Example 1 (Castor oil was not modified, and castor oil was directly added, which could not be evenly mixed)

[0055] Step 1, take 100g of starch, add 300g of deionized water, stir evenly to obtain starch milk, adjust the pH to 10 with NaOH solution, add 0.5g of polyphosphoric acid, and fully react at 60°C for 2h. After the reaction, adjust the pH to 5, wash repeatedly with 5000mL of deionized water for 3 times, filter to obtain a filter cake, dry the filter cake under vacuum at 45°C overnight, pass through 50um and 20um aperture sieves respectively, and sieve to obtain phosphoric acid-modified starch with a particle size of 20-50um.

[0056] Step 2, take 60g of castor oil and 100g of phosphoric acid-modified starch, add them into 1L of deionized water successively, stir at 45°C for 30min, and it is found that the mixture cannot be mixed and oil and water are separated into layers.

[0057] Comparative Example 2 (sulfonated dioctyl sodium succinate was used to replace anion-modified castor oil, which failed to penetrate effectively and had poor stiffness and tensile strength)

[0058] Step 1: Take 100g of castor oil and 20g of 2,3-epoxypropyltrimethylammonium chloride, then add 0.2g of NaOH. React at room temperature for 30 minutes. After the reaction is completed, add 20mL of acetic acid to terminate the cation modification reaction, further add 0.2g of phosphoric acid and 50mL of hydrogen peroxide, and heat to 50°C for 8h. After the reaction is completed, extract three times with 1000mL of ethyl acetate to obtain epoxyalkyl-cation modified castor oil.

[0059] Step 2, take 100g of starch, add 300g of deionized water, stir evenly to obtain starch milk, adjust the pH to 10 with NaOH solution, add 0.5g of polyphosphoric acid, and fully react at 60°C for 2h. After the reaction, adjust the pH to 5, wash repeatedly with 500mL of deionized water for 3 times, filter to obtain a filter cake, dry the filter cake under vacuum at 45°C overnight, pass through 50um and 20um aperture sieves, and sieve to obtain phosphoric acid-modified starch with a particle size of 20-50um.

[0060] Step 3, take 30g of sodium salt of dioctyl sulfonate succinate, 30g of alkylene oxide-cationic modified castor oil, and 100g of phosphoric acid-modified starch, add them into 1L of deionized water successively, stir at 45°C for 30min, and obtain a sizing agent with a viscosity of 100 centipoise.

[0061] Spraying sizing on the surface of pulp molding: Add the sizing agent prepared in step 3 to the spraying instrument, take 1.2mm thick pulp molding base paper 20cmx20cm, spray spacing 30mm, nozzle height 100mm, spray thickness 10um. Put the sprayed paper sample into a constant temperature box and dry it at 45℃ for 3h.

[0062] Comparative Example 3 (Castor oil was not epoxy-modified and had poor internal binding energy)

[0063] Step 1, take 100g of castor oil, add it to a 250mL round-bottom flask, add 5g of polyphosphoric acid in batches (add it over 10 minutes, 0.5g per minute), continue to react at 100°C for 30min after the addition is completed, and add an excess of 10g of sodium bicarbonate (added in 10 times, 1g each time) to the reaction solution after cooling to room temperature, and bubbles begin to be generated. After no bubbles are generated, filter out the unreacted sodium bicarbonate and the by-product sodium phosphate, collect the filtrate, and obtain anion-modified castor oil.

[0064] Step 2, take 100g of castor oil and 20g of 2,3-epoxypropyltrimethylammonium chloride, then add 0.2g of NaOH. React at room temperature for 30 minutes, and after the reaction is completed, add 20mL of acetic acid to terminate the cation modification reaction. After the reaction is completed, extract three times with 1000mL of ethyl acetate to obtain cation-modified castor oil.

[0065] Step 3, take 100g of starch, add 300g of deionized water, stir evenly to obtain starch milk, adjust the pH to 10 with NaOH solution, add 0.5g of polyphosphoric acid, and fully react at 60°C for 2h. After the reaction, adjust the pH to 5, wash repeatedly with 500mL of deionized water for 3 times, filter to obtain a filter cake, dry the filter cake under vacuum at 45°C overnight, pass through 50um and 20um aperture sieves, and sieve to obtain phosphoric acid-modified starch with a particle size of 20-50um.

[0066] Step 4, take 30g of anion-modified castor oil, 30g of cation-modified castor oil, and 100g of phosphoric acid-modified starch, add them into 1L of deionized water successively, stir at 45°C for 30min, and obtain a translucent sizing agent with a viscosity of 100 centipoise.

[0067] Spray sizing on the surface of pulp molding: Add the sizing agent prepared in step 4 to the spraying instrument, take 1.2mm thick pulp molding base paper 20cmx20cm, spray spacing 30mm, nozzle height 100mm, spray thickness 10um. Put the sprayed paper sample into a constant temperature box and dry it at 45℃ for 3h.

[0068] Comparative Example 4 (phosphoric acid-modified starch was replaced with quaternary ammonium salt cationic starch, and the stiffness, tensile strength and internal binding energy were poor)

[0069] Step 1, take 100g of castor oil, add it to a 250mL round-bottom flask, add 5g of polyphosphoric acid in batches (add it over 10 minutes, 0.5g per minute), continue to react at 100°C for 30min after the addition is completed, and add an excess of 10g of sodium bicarbonate (added in 10 times, 1g each time) to the reaction solution after cooling to room temperature, and bubbles begin to be generated. After no bubbles are generated, filter out the unreacted sodium bicarbonate and the by-product sodium phosphate, collect the filtrate, and obtain anion-modified castor oil.

[0070] Step 2, take 100g of castor oil and 20g of 2,3-epoxypropyltrimethylammonium chloride, then add 0.2g of NaOH. React at room temperature for 30 minutes, add 20mL of acetic acid after the reaction to terminate the cation modification reaction, further add 0.2g of phosphoric acid and 50mL of hydrogen peroxide, heat to 50°C and react for 8h. After the reaction, extract three times with 1000mL of ethyl acetate to obtain epoxyalkyl-cation modified castor oil.

[0071] Step 3, take 30g of anion-modified castor oil, 30g of alkylene oxide-cation-modified castor oil, and 100g of quaternary ammonium salt cationic starch, add them into 1L of deionized water successively, stir at 45°C for 30min, and obtain a translucent sizing agent with a viscosity of 100 centipoise.

[0072] Spray sizing on the surface of pulp molding: Add the sizing agent prepared in step 3 to the spraying instrument, take 1.2mm thick pulp molding base paper 20cmx20cm, spray spacing 30mm, nozzle height 100mm, spray thickness 10 u m. Place the sprayed paper sample in a constant temperature box and dry it at 45℃ for 3h.

[0073] Table 1 below is a performance comparison of 1.2 mm pulp molding base paper and Example 1, and Table 2 below is a performance comparison result of pulp molding products obtained after the products prepared in Example 1 and Comparative Examples 1-4 were sprayed onto a thick pulp molding surface:

[0074] Table 1

[0075] 1.2mm thick base paper Example 1 <![CDATA[Stiffness ( mN *m)]]> 115 225 <![CDATA[Tensile strength ( kN / m)]]> 4.1 5.6 <![CDATA[Internal bond strength (J / m 2 )]]> 120 210

[0076] Table 3

[0077]

[0078]

[0079] Results and Discussion

[0080] like Figure 1 As shown, the high penetration sizing agent prepared in Example 1 was tested for rheological properties and found that as the shear rate increased, the viscosity became smaller and smaller, showing shear thinning properties, and was suitable for use through a spraying process. The initial raw materials used for the high penetration surface sizing agent were castor oil and starch, both of which are renewable green and environmentally friendly materials, and the solvent used was deionized water to avoid the release of VOC.

[0081] As shown in Table 1, the comparison of the 1.2 mm thick pulp molding base paper before and after surface sizing revealed that the performance indicators such as stiffness, tensile strength and internal bonding strength in Example 1 were significantly improved, indicating that the sizing agent can effectively penetrate into the 1.2 mm thick pulp molding material.

[0082] As shown in Table 2, in Comparative Example 1, castor oil was used directly. Since deionized water was used as the solvent, water and oil were not miscible, and stratification occurred, and the spraying process of the pulp molding base paper could not be completed.

[0083] In Comparative Example 2, sodium sulfonated dioctyl succinate is a traditional penetrant and cannot penetrate effectively. In addition, sodium sulfonated dioctyl succinate cannot cooperate with alkylene oxide-cation-modified castor oil, and its penetration capacity is limited. Compared with Example 1, the stiffness and tensile strength are significantly reduced.

[0084] In Comparative Example 3, the cationic modified castor oil was not epoxidized, which resulted in the cationic modified castor oil being unable to form chemical bonds with the base paper fibers after entering the pulp molding. In contrast, in Example 1, the cationic castor oil contained epoxy bonds and could undergo a ring-opening reaction with the base paper fibers.

[0085] In Comparative Example 4, the phosphate-modified starch was replaced with a quaternary ammonium salt cationic starch. Since the starch component is the main component of the sizing agent, the quaternary ammonium salt cationic starch cannot form chemical bonds with the base paper fibers, and performance indicators such as stiffness, tensile strength and internal bonding strength are all reduced.

[0086] Table 3 below is a performance comparison between the 1.6 mm pulp molding base paper and Example 2:

[0087] Table 3

[0088] 1.6mm thick base paper Example 2 <![CDATA[Stiffness( mN *m)]]> 128 230 <![CDATA[Tensile strength ( kN / m)]]> 4.6 5.8 <![CDATA[Internal bond strength (J / m 2 )]]> 137 216

[0089] Generally, the thickness of pulp molding base paper is between 0.8-1.6 mm. Although a relatively thick pulp molding base paper of 1.2 mm is used in Example 1, the prepared sizing agent can effectively penetrate to improve the paper performance. As shown in Table 3, the developed sizing agent can also efficiently penetrate to improve the mechanical properties of the base paper using pulp molding base paper of 1.6 mm. In particular, compared with Example 1, the stiffness, tensile strength and internal bonding strength are further improved.

[0090] Example 3

[0091] Step 1, anionic modification of castor oil, the specific process is:

[0092] Take 200g of castor oil, add it to a 400mL round-bottom flask, add 10g of polyphosphoric acid in batches (add over 10 minutes, 1g per minute), continue to react at 130°C for 50min after the addition is completed, cool to room temperature, add an excess of 20g of sodium bicarbonate (added in 10 times, 2g each time) to the reaction solution, bubbles begin to be generated, and after no bubbles are generated, filter out the unreacted sodium bicarbonate and the by-product sodium phosphate, collect the filtrate, and obtain anion-modified castor oil.

[0093] Step 2, alkylene oxide and cationic modification of castor oil, the specific process is:

[0094] Take 200g of castor oil and 40g of 2,3-epoxypropyltrimethylammonium chloride, then add 0.4g of NaOH. React at room temperature for 40 minutes. After the reaction is completed, add 40mL of acetic acid to terminate the cationic modification reaction. Further add 0.4g of phosphoric acid and 100mL of hydrogen peroxide, heat to 70℃ and react for 10h. After the reaction is completed, extract three times with 2000mL of ethyl acetate to obtain epoxyalkyl-cation-modified castor oil.

[0095] Step 3, phosphoric acid modification of starch, the specific process is:

[0096] Take 200g of starch, add 600g of deionized water, stir evenly to obtain starch milk, adjust the pH of the starch milk to 10 with NaOH solution, add 1.0g of polyphosphoric acid, and fully react at 70°C for 4h. After the reaction, adjust the pH to 5, wash repeatedly with 1000mL of deionized water 3 times, filter to obtain a filter cake, dry the filter cake at 60°C under vacuum overnight, pass through 50um and 20um aperture sieves, and sieve to obtain phosphoric acid-modified starch with a particle size of 20-50um.

[0097] Step 4, preparation of high penetration sizing agent, the specific process is as follows:

[0098] Take 60 g of anion-modified castor oil, 60 g of alkylene oxide-cation-modified castor oil, and 200 g of phosphoric acid-modified starch, add them into 2 L of deionized water successively, stir at 60° C. for 30 min, and obtain a translucent sizing agent with a viscosity of 200 centipoise.

[0099] Spraying sizing on the surface of pulp molding: Add the high-penetration sizing agent prepared in step 4 to the spraying instrument, take 1.6mm thick pulp molding base paper 20cmx20cm, spray spacing 50mm, nozzle height 150mm, spray thickness 15um. Put the sprayed paper sample into a constant temperature box and dry it at 60℃ for 4h.

[0100] Example 4

[0101] Step 1, anionic modification of castor oil, the specific process is:

[0102] Take 300g of castor oil, add it to a 500mL round-bottom flask, add 15g of polyphosphoric acid in batches (add over 10 minutes, 1.5g per minute), continue to react at 160°C for 60min after the addition is completed, and add an excess of 30g of sodium bicarbonate (added in 10 times, 3g each time) to the reaction solution after cooling to room temperature. Bubbles begin to be generated. After no bubbles are generated, filter out the unreacted sodium bicarbonate and the by-product sodium phosphate, collect the filtrate, and obtain anion-modified castor oil.

[0103] Step 2, alkylene oxide and cationic modification of castor oil, the specific process is:

[0104] Take 300g of castor oil and 60g of 2,3-epoxypropyltrimethylammonium chloride, then add 0.6g of NaOH. React at room temperature for 60 minutes. After the reaction is completed, add 60mL of acetic acid to terminate the cationic modification reaction, further add 0.6g of phosphoric acid and 150mL of hydrogen peroxide, heat to 80℃ and react for 12h. After the reaction is completed, extract three times with 3000mL of ethyl acetate to obtain epoxyalkyl-cation-modified castor oil.

[0105] Step 3, phosphoric acid modification of starch, the specific process is:

[0106] Take 300g of starch, add 900g of deionized water, stir evenly to obtain starch milk, adjust the pH of the starch milk to 11 with NaOH solution, add 1.5g of polyphosphoric acid, and fully react at 90°C for 6h. After the reaction, adjust the pH to 6, wash repeatedly with 1500mL of deionized water 3 times, filter to obtain a filter cake, dry the filter cake at 90°C under vacuum overnight, pass through 50um and 20um aperture sieves, and sieve to obtain phosphoric acid-modified starch with a particle size of 20-50um.

[0107] Step 4, preparation of high penetration sizing agent, the specific process is as follows:

[0108] Take 90 g of anion-modified castor oil, 90 g of alkylene oxide-cation-modified castor oil, and 300 g of phosphoric acid-modified starch, add them into 3 L of deionized water successively, stir at 90° C. for 30 min, and obtain a translucent sizing agent with a viscosity of 500 centipoise.

[0109] Spraying sizing on pulp molding surface: Add the high penetration sizing agent prepared in step 4 to the spraying instrument, take 20cmx20cm of 0.8mm thick pulp molding base paper, spray spacing of 60mm, nozzle height of 200mm, spray thickness of 20um. Put the sprayed paper sample into a constant temperature box and dry it at 90℃ for 6h.

[0110] The present invention abandons the method of improving the strength of pulp molding by using traditional polymer PVA, polyacrylamide and other sizing agents, avoiding the problem of difficult fiber recycling. A green and environmentally friendly castor oil high-penetration surface sizing agent is constructed, and its spray sizing is realized, which improves the stiffness of pulp molding and achieves anti-static.

Claims

1. A method for preparing a high-penetration sizing agent for pulp molding, characterized in that: The specific steps include: Step 1, anion-modifying castor oil to obtain anion-modified castor oil; Step 2, performing alkylene oxide and cation modification on castor oil to obtain alkylene oxide-cation modified castor oil; Step 3, modifying starch with phosphoric acid to obtain phosphoric acid-modified starch; Step 4, preparing a high penetration sizing agent according to the products obtained in steps 1 to 3.

2. The method for preparing a pulp molding high penetration sizing agent according to claim 1, characterized in that: The specific process of step 1 is as follows: 100-300 g of castor oil is added to a 250-500 mL round-bottom flask, 5-15 g of polyphosphoric acid is added dropwise in batches, and after the addition is completed, the reaction is continued at 100-160° C. for 30-60 minutes, and the mixture is cooled to room temperature; 10-30 g of sodium bicarbonate is added to the reaction solution in batches, and bubbles are generated at the beginning. After no bubbles are generated, unreacted sodium bicarbonate and by-products are filtered out, and the filtrate is collected to obtain anion-modified castor oil.

3. The method for preparing a pulp molding high penetration sizing agent according to claim 2, characterized in that: The specific process of step 2 is: taking 100-300g of castor oil and 20-60g of 2,3-epoxypropyltrimethylammonium chloride, adding 0.2-0.6g of NaOH, reacting at room temperature for 30-60 minutes, adding 20-60mL of acetic acid after the reaction to terminate the cation modification reaction; then adding 0.2-0.6g of phosphoric acid and 50-150mL of hydrogen peroxide, heating to 50-80°C for reaction for 8-12h, and after the reaction, extracting three times with 1000mL-3000mL of ethyl acetate to obtain epoxyalkyl-cation modified castor oil.

4. The method for preparing a pulp molding high penetration sizing agent according to claim 3, characterized in that: The specific process of step 3 is as follows: Step 3.1, take 100-300 g of starch, add 300-900 g of deionized water, and stir evenly to obtain starch milk; Step 3.2, using NaOH solution to adjust the pH of the starch milk to 10-11, then add 0.5-1.5g of polyphosphoric acid, and fully react at 60-90°C for 2-6h. After the reaction, adjust the pH to 5-6, wash repeatedly with 500-1500mL of deionized water for 3 times, filter to obtain a filter cake, dry the filter cake under vacuum at 45-90°C overnight, and then sieve through a pore size sieve to obtain a phosphoric acid-modified starch with a particle size of 20-50um.

5. The method for preparing a pulp molding high penetration sizing agent according to claim 4, characterized in that: The specific process of step 4 is: take 30-90g of anionic modified castor oil prepared in step 1, 30-90g of alkylene oxide-cationic modified castor oil prepared in step 2, and 100-300g of phosphoric acid modified starch prepared in step 3, add them into 1-3L of deionized water in sequence, stir at 45-90°C for 30min, and obtain a translucent sizing agent.

6. The method for preparing a high-penetration sizing agent for pulp molding according to claim 5, characterized in that: The viscosity of the sizing agent prepared in step 4 is 100-500 centipoise.

7. A method for spraying a high-penetration sizing agent for pulp molding, characterized in that: The specific process is as follows: add the sizing agent into the spraying instrument, take 0.8-1.6mm thick pulp molding base paper 20cmx20cm, spray spacing 30-60mm, nozzle height 100-200mm, spray thickness 10-20um, put the sprayed paper sample into a constant temperature box, and dry it at 45-90℃ for 3-6h.

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