A method for preparing a phytate starch adhesive

Abstract

The application discloses a preparation method of phytate-esterified starch adhesive, and raw material formula of the preparation method is as follows in mass parts: 80-120 parts of corn starch, 120-180 parts of hydrochloric acid, 4-24 parts of an oxidizing agent, 3.2-4.8 parts of an initiator, 0.8-2.5 parts of sodium dodecyl sulfate, 0.8-12 parts of a grafting monomer, 4-6 parts of a crosslinking agent, 360-540 parts of deionized water, 8-12 parts of a drying catalyst, and proper amount of sodium hydroxide. The prepared starch adhesive has strong bonding capacity, good water resistance and excellent stability, and is not prone to mildew and deterioration during storage.

Description

Technical Field

[0001] This invention relates to a method for preparing a starch adhesive. Background Technology

[0002] The global adhesives and sealants market is growing rapidly, projected to reach $85.8 billion by 2026. Industries such as those manufacturing packaging, plywood, and wood composites for furniture, electronics, aerospace, and other technology products are driving this expansion. Petrochemical feedstocks are typically used as core ingredients in the production of formaldehyde, urea, and polyurethane, key components of many widely used adhesives. However, concerns about environmental pollution from oil spills, global warming, and fossil fuel consumption are prompting researchers to consider using biodegradable “green” materials as alternatives to petrochemical adhesive components. Natural resources form the basis for “green” raw materials for producing high-quality adhesives. Starch has advantages such as wide availability, low price, green and pollution-free nature, and ease of use. It is widely used as a synthetic raw material for environmentally friendly adhesives and has become an ideal alternative to traditional synthetic resin adhesives. Therefore, the preparation of green and environmentally friendly adhesives using renewable resources has attracted increasing attention. These green and environmentally friendly adhesives can be widely used for bonding paper, cartons, wallpaper, and wood panels. As a result, the performance requirements for modified starch adhesives are also increasing. Therefore, it is urgent to develop starch adhesives that meet the needs of various industries, such as fast drying, water resistance, high bonding strength, excellent stability, and environmental friendliness. Summary of the Invention

[0003] The technical problem to be solved by this invention is to prepare a starch adhesive with strong adhesion, good water resistance and excellent stability.

[0004] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0005] A method for preparing a plant acid-esterified starch adhesive, wherein the raw material formula, in parts by weight, is as follows:

[0006]

[0007]

[0008] The concentration of the hydrochloric acid is 0.4–0.6 mol / L;

[0009] The grafting monomer is one or two of N-isopropylacrylamide and ester monomers, wherein the ester monomer is vinyl acetate or methyl methacrylate.

[0010] The initiator is a redox system composed of ammonium persulfate and sodium bisulfite, and the mass ratio of ammonium persulfate to sodium bisulfite is 2:1 to 3:1;

[0011] The crosslinking agent is phytic acid;

[0012] The preparation method includes the following steps:

[0013] (1) Mix 80-120 parts of starch with 360-540 parts of water to form a starch solution, stir evenly, add 4-24 parts of oxidant, adjust the pH to 9-10 with an appropriate amount of NaOH, carry out the oxidation reaction for 0.5-2 hours, then add 120-180 parts of hydrochloric acid with a concentration of 0.4-0.6 mol / L to hydrolyze for 0.5-2 hours, wash, centrifuge, dry, grind to obtain oxidized acidified starch;

[0014] (2) Place the oxidized and acidified starch obtained in step (1) in a water bath at a temperature of 80-85℃ and gelatinize for 30-35 minutes to obtain a gelatinized starch solution.

[0015] (3) Reduce the temperature of the water bath in step (2) to 50-55℃, take 3.2-4.8 parts of initiator and dissolve them in a small amount of water (enough to dissolve the initiator) to prepare an initiator solution. Add the solution to the gelatinized starch solution and adjust the pH to 4-5 with NaOH. Dissolve 0.8-12 parts of graft monomer and 0.8-2.5 parts of sodium dodecyl sulfate in a small amount of water and slowly add them drop by drop to the gelatinized starch solution. After the addition is complete, continue the reaction for 1.3-3 hours. After the reaction is completed, the graft copolymerized modified starch slurry is obtained.

[0016] (4) Then add 4 to 6 parts of phytic acid as a crosslinking agent to the graft copolymerized starch slurry obtained in step (3) and react at 50 to 80°C for 1 to 3 hours;

[0017] (5) Finally, add 8-12 parts of drying agent to the reaction solution obtained in step (4). After the drying agent is fully dispersed, phytate-treated starch adhesive is obtained. If the obtained adhesive produces bubbles, add a certain amount of defoamer tributyl phosphate according to the amount of bubbles, not exceeding 0.5% of the starch mass.

[0018] Preferably, the oxidant is hydrogen peroxide.

[0019] Preferably, the oxidation reaction lasts for 1 hour.

[0020] Preferably, the concentration of the hydrochloric acid is 0.5 mol / L.

[0021] Preferably, the grafting monomer is one or two of N-isopropylacrylamide and ester monomers, wherein the ester monomer is vinyl acetate or methyl methacrylate, and the mass ratio of N-isopropylacrylamide to ester monomer is 25-50%:75-50%.

[0022] Preferably, the initiator is a redox system composed of ammonium persulfate and sodium bisulfite, and the mass ratio of ammonium persulfate to sodium bisulfite is 3:1.

[0023] Preferably, the drying agent is one or more of zeolite powder, sodium montmorillonite, light calcium carbonate, and ultrafine kaolin.

[0024] Preferably, 0.8-12 parts of graft monomer and 0.8-2.5 parts of sodium dodecyl sulfate are completely dissolved in a small amount of water and then added dropwise to the gelatinized starch solution at a rate not exceeding 2 drops / min. If the dropping rate is too fast, it will reduce the stability of the polymerization reaction, and the high monomer concentration will easily lead to self-polymerization, resulting in a lower grafting rate and poor film-forming properties and water resistance of the resulting adhesive.

[0025] As a preferred embodiment, the raw material formula, in parts by weight, is as follows:

[0026]

[0027] The concentration of the hydrochloric acid is 0.5 mol / L;

[0028] The oxidant is hydrogen peroxide;

[0029] The grafting monomer is one or two of N-isopropylacrylamide and ester monomers, wherein the ester monomer is vinyl acetate or methyl methacrylate, and the mass ratio of N-isopropylacrylamide to ester monomer is 25-50%:75-50%.

[0030] The initiator is a redox system composed of ammonium persulfate and sodium bisulfite, and the mass ratio of ammonium persulfate to sodium bisulfite is 3:1;

[0031] The crosslinking agent is phytic acid;

[0032] The drying agent is one or more of zeolite powder, sodium montmorillonite, light calcium carbonate, and ultrafine kaolin.

[0033] As a further preferred option, the raw material formulation, in parts by weight, is as follows:

[0034]

[0035]

[0036] Compared with existing technologies, the beneficial effects of this invention are as follows: This invention first oxidizes and acid-hydrolyzes natural starch. Oxidation modification adds carboxyl and aldehyde groups to the starch molecular chain, providing more possibilities for subsequent modification. Acid hydrolysis increases the crystallinity of starch and the solid content of starch adhesives while also reducing viscosity. Because starch hydroxyl groups readily form hydrogen bonds with water, the cohesive force between the hydroxyl groups on starch molecules and water molecules is much greater than their adhesive effect with the adhesive material. The hydrophilicity of natural starch makes forming waterproof adhesives challenging. This invention selects N-isopropylacrylamide and ester monomers with strong hydrophobic groups as grafting monomers. Grafting acrylic monomers with hydrophobic groups onto natural starch chains can improve its bonding strength and water resistance to a certain extent. This invention also selects phytic acid as a crosslinking agent. Because phytic acid contains phosphate groups, it can crosslink with the hydroxyl groups in starch molecules. The crosslinking effect is much stronger than hydrogen bonding, requiring more water molecules to break the crosslinking bond, thus improving the stability of the starch adhesive. Crosslinking agents can further enhance the grafting reaction and form chemical bonds, ultimately improving the bonding strength and stability of the starch adhesive. Finally, the addition of a drying agent not only improves the thermal stability of the adhesive but also significantly increases its drying speed. The resulting starch adhesive exhibits strong adhesive ability, good water resistance, and excellent stability, and is not prone to mold or deterioration during storage. Attached Figure Description

[0037] Figure 1 This is a comparison chart of the bonding strength of the adhesive prepared in the embodiments and comparative examples of the present invention and a commercially available brand adhesive;

[0038] Figure 2 This is a comparison chart of the water resistance time of the adhesive prepared in the embodiments and comparative examples of the present invention and a commercially available brand adhesive;

[0039] Figure 3 This is a comparison chart of the water loss rate of the adhesive prepared in the embodiments and comparative examples of the present invention and the commercially available brand adhesive;

[0040] Figure 4 This is the infrared spectrum of the starch adhesive prepared in Example 3 of the present invention;

[0041] Figure 5 This is a SEM image of the starch adhesive prepared in Example 3 of the present invention. Detailed Implementation Plan

[0042] The technical solution of the present invention will be further described below through specific embodiments, but the scope of protection of the present invention is not limited thereto:

[0043] Unless otherwise specified in the embodiments of this invention, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be obtained through conventional technical means or commercially available.

[0044] Example 1:

[0045] The ingredients, by weight, include 100 parts corn starch, 150 parts HCl (0.5 mol / L), 400 parts water, 20 parts hydrogen peroxide, appropriate amount of sodium hydroxide, 4 parts ammonium persulfate-sodium bisulfite, 1 part sodium dodecyl sulfate, 2.5 parts N-isopropylacrylamide, 7.5 parts vinyl acetate, 4 parts phytic acid, 10 parts montmorillonite, and appropriate amount of defoamer.

[0046] Prepare a starch solution by mixing 100 parts starch with 400 parts water, stir well, add 20 parts H2O2, adjust the pH to 9-10 with an appropriate amount of NaOH, react for 2 hours, add 150 parts 0.5mol / L HCl for acid hydrolysis for 1 hour, wash, centrifuge, dry, grind to obtain oxidized acidified starch. The temperature of the oxidized and acidified starch was adjusted to 80-85℃, and gelatinization was carried out for 30 minutes. The reaction temperature was set to 50℃. Four parts of a redox initiator, ammonium persulfate-sodium bisulfite (mass ratio 3:1), were dissolved in a small amount of water to prepare an initiator solution, which was then added to the oxidized and acidified starch. The pH was adjusted to 4-5 with an appropriate amount of NaOH. 2.5 parts of N-isopropylacrylamide and 7.5 parts of vinyl acetate were dissolved in a small amount of water, and 1 part of sodium dodecyl sulfate was added. After complete dissolution, the solution was added to the gelatinized starch solution at a rate of 2 drops / min. The reaction was allowed to proceed for 1.5 hours after the addition was complete. After the reaction was completed, a graft copolymerized modified starch slurry was obtained. Subsequently, 4 parts of phytic acid were added as a crosslinking agent, and the reaction was carried out at 50℃ for 2 hours. Finally, 10 parts of montmorillonite, a drying agent, were added. After the drying agent was fully dispersed for 1 hour, stirring was stopped to obtain the prepared starch adhesive sample. If bubbles were generated, a certain amount of defoamer, tributyl phosphate (not exceeding 0.5% of the starch mass), was added depending on the amount of bubbles.

[0047] The test method for starch adhesive samples is as follows:

[0048] 1. Bond strength determination

[0049] The test was performed according to the method specified in the national standard GB / T 17517-1998 "Test Method for Compression Shear Strength of Adhesives for Wood and Timber".

[0050] 2. Water resistance test

[0051] Take two wooden blocks, each 1cm thick, 2cm wide, and 3cm long. On the surface of one of the wooden blocks (6cm... 2Apply 0.5g of adhesive, then glue another wooden block onto it, apply pressure of 3MPa for 6 hours, remove the pressure, and let it stand at room temperature for 24 hours. Place the sample in a 60℃ constant temperature water bath and observe whether it delaminates, and record the delamination time.

[0052] 3. Stability Test

[0053] The prepared sample was stored in a 500ml covered container and placed in a dry, light-protected environment at (23±2)℃. The sample was observed periodically (24h) to check for gelation or delamination (either of these two phenomena indicates that the adhesive has lost its stability). The time of gelation or delamination was recorded.

[0054] 4. Drying speed test

[0055] Take two 25cm pieces 2 Two pieces of corrugated paper of the same size were weighed and recorded as W0. Then, after applying the sample adhesive, they were immediately overlapped and bonded together, and the weight was recorded as W1. Simultaneously, two more pieces of corrugated paper of the same size were weighed and recorded as W2. Both were placed in the same environment at (23±2)℃, and their weights were recorded after 30 minutes as W1 and W2, respectively. 11 W 12 Then, both were placed in a 60℃ oven and dried for 24 hours. Their weights after drying were weighed and recorded as W. 01 W 02 The formula for calculating the water loss rate at 30 minutes is:

[0056]

[0057] The test results are as follows:

[0058] The product obtained in this embodiment is a pale yellow viscous liquid with a bonding strength of 5.207 MPa, a water resistance time of 79 min, and a water loss rate of 61.8%. However, the product will exhibit gelation after 14 days, so the storage time is 14 days.

[0059] Example 2:

[0060] The ingredients, by weight, include 100 parts corn starch, 150 parts HCl (0.5 mol / L), 450 parts water, 20 parts hydrogen peroxide, appropriate amount of sodium hydroxide, 4 parts ammonium persulfate-sodium bisulfite, 1 part sodium dodecyl sulfate, 2.5 parts N-isopropylacrylamide, 7.5 parts vinyl acetate, 4 parts phytic acid, 10 parts montmorillonite, and appropriate amount of defoamer.

[0061] Prepare a starch solution by mixing 100 parts starch with 450 parts water, stir well, add 20 parts H2O2, adjust the pH to 9-10 with an appropriate amount of NaOH, react for 2 hours, add 150 parts 0.5mol / L HCl for acid hydrolysis for 1 hour, wash, centrifuge, dry, grind and obtain oxidized acidified starch. The temperature of the starch slurry was adjusted to 80-85℃, and gelatinization was carried out for 30 minutes. The reaction temperature was set to 50℃. A redox initiator, ammonium persulfate-sodium bisulfite, with a mass ratio of 3:1 was dissolved in a small amount of water to prepare an initiator solution, which was then added to the gelatinized starch. The pH was adjusted to 4-5 with an appropriate amount of NaOH. 2.5 parts of N-isopropylacrylamide and 7.5 parts of vinyl acetate were dissolved in a small amount of water, and 1 part of sodium dodecyl sulfate was added. After complete dissolution, the solution was added to the gelatinized starch solution at a rate of 2 drops / min, and the reaction was carried out for 1.5 hours. After the reaction was completed, a graft copolymerized modified starch slurry was obtained. Subsequently, 4 parts of phytic acid were added as a crosslinking agent, and the reaction was carried out at 50℃ for 2 hours. Finally, 10 parts of montmorillonite drier were added, and stirring was stopped after the drier was fully dispersed for 1 hour to obtain the prepared starch adhesive sample.

[0062] The testing method for the starch adhesive sample was the same as in Example 1, and the test results are as follows:

[0063] The product obtained in this embodiment is a pale yellow viscous liquid. Compared with Example 1, the product obtained in Example 2 has better fluidity, and its bonding strength is 6.777 MPa, water resistance time is 103 min, water loss rate is 58.7%, and storage time is 90 days or even longer.

[0064] Example 3:

[0065] The ingredients, by weight, include 100 parts corn starch, 150 parts HCl (0.5 mol / L), 450 parts water, 20 parts hydrogen peroxide, appropriate amount of sodium hydroxide, 4 parts ammonium persulfate-sodium bisulfite, 1 part sodium dodecyl sulfate, 5 parts N-isopropylacrylamide, 5 parts vinyl acetate, 4 parts phytic acid, 10 parts montmorillonite, and appropriate amount of defoamer.

[0066] 100 parts starch and 450 parts water were mixed to form a starch solution, stirred evenly, and 20% (by weight of starch) of H2O2 was added. The pH was adjusted to 9-10 with an appropriate amount of NaOH. After reacting for 2 hours, 0.5 mol / L HCl was added for acid hydrolysis for 1 hour. After washing, centrifugation, drying, and grinding, oxidized acidified starch was obtained. The temperature of the starch slurry was adjusted to 80-85℃, and gelatinization was carried out for 30 minutes. The reaction temperature was set to 50℃. A redox initiator of ammonium persulfate-sodium bisulfite in a mass ratio of 3:1 was dissolved in a small amount of water to prepare an initiator solution, which was added to the gelatinized starch. The pH was adjusted to 4-5 with an appropriate amount of NaOH. 5 parts of N-isopropylacrylamide and 5 parts of vinyl acetate were dissolved in a small amount of water, and 1 part of sodium dodecyl sulfate was added. After complete dissolution, the solution was added to the gelatinized starch solution at a rate of 2 drops / min. The reaction was carried out for 1.5 hours. After the reaction, a graft copolymerized modified starch slurry was obtained. Subsequently, 4 parts of phytic acid were added as a crosslinking agent, and the reaction was carried out at 50℃ for 2 hours.

[0067] Finally, add 10 parts of montmorillonite drying agent, and stop stirring after the drying agent has been fully dispersed for 1 hour to obtain the prepared starch adhesive sample.

[0068] The testing method for the starch adhesive sample was the same as in Example 1, and the test results are as follows:

[0069] The product obtained in this embodiment is a pale yellow viscous liquid with a bonding strength of 4.137 MPa, a water resistance time of 124 min, a water loss rate of 64.5%, and a storage time of 90 days or even longer.

[0070] The chemical composition and microstructure of the starch adhesive sample prepared in Example 3 were analyzed, and the results are as follows: Figure 4 and Figure 5 As shown.

[0071] like Figure 4 As shown, 3387cm -1 The broad peak at 1640 cm⁻¹ is attributed to the OH stretching vibration of the glucose unit. -1 The absorption at this point is attributed to the superposition of carbonyl and amide groups, proving that vinyl acetate and N-isopropylacrylamide were successfully grafted onto starch, 1154 cm⁻¹. -1 and 1028cm -1 The absorption peak at 1560 cm⁻¹ originates from the superposition of CO stretching vibrations, C₂C₃ and OH bending vibrations in starch, and COC stretching vibrations of glycosidic bonds. -1 This corresponds to the bending vibration of the NH bond, at 1272 cm⁻¹. -1 The absorption peak at 963 cm⁻¹ corresponds to the stretching vibrations of the CN and NH bonds. -1 The peak at this point likely corresponds to the characteristic absorption peak of POC, indicating that phytic acid and starch have successfully crosslinked.

[0072] like Figure 5 As shown, there are a few scaly synapses on the surface of the adhesive film, and no cracks were found on the surface of the adhesive film, so the surface of the adhesive film is relatively smooth. This phenomenon may be due to the cross-linking effect of phytic acid, which successfully combines with the hydroxyl groups on the starch molecules to form a denser structure. This is also an important factor that can improve the bonding strength and water resistance of starch adhesives.

[0073] Example 4:

[0074] The ingredients, by weight, include 100 parts corn starch, 150 parts HCl (0.5 mol / L), 450 parts water, 20 parts hydrogen peroxide, appropriate amount of sodium hydroxide, 4 parts ammonium persulfate-sodium bisulfite, 2 parts sodium dodecyl sulfate, 5 parts N-isopropylacrylamide, 5 parts vinyl acetate, 4 parts phytic acid, 10 parts montmorillonite, and appropriate amount of defoamer.

[0075] 100 parts of starch were mixed with water to form a starch solution, stirred evenly, and 20% (by weight of starch) of H2O2 was added. The pH was adjusted to 9-10 with an appropriate amount of NaOH. After reacting for 2 hours, 0.5 mol / L HCl was added for acid hydrolysis for 1 hour. After washing, centrifugation, drying, and grinding, oxidized acidified starch was obtained. The temperature of the starch slurry was adjusted to 80-85℃, and gelatinization was carried out for 30 minutes. The reaction temperature was set to 50℃. A redox initiator of ammonium persulfate-sodium bisulfite in a mass ratio of 3:1 was dissolved in a small amount of water to prepare an initiator solution, which was added to the gelatinized starch. The pH was adjusted to 4-5 with an appropriate amount of NaOH. 5 parts of N-isopropylacrylamide and 5 parts of vinyl acetate were dissolved in a small amount of water, and 2 parts of sodium dodecyl sulfate were added. After complete dissolution, the solution was added to the gelatinized starch solution at a rate of 2 drops / min. The reaction was carried out for 1.5 hours. After the reaction, a graft copolymerized modified starch slurry was obtained. Subsequently, 4 parts of phytic acid were added as a crosslinking agent, and the reaction was carried out at 50℃ for 2 hours.

[0076] Finally, add 10 parts of montmorillonite drying agent, and stop stirring after the drying agent has been fully dispersed for 1 hour to obtain the prepared starch adhesive sample.

[0077] The testing method for the starch adhesive sample was the same as in Example 1, and the test results are as follows:

[0078] The product obtained in this embodiment is a pale yellow viscous liquid with a bonding strength of 4.338 MPa, a water resistance time of 105 min, a water loss rate of 65.6%, and a storage time of 90 days or even longer.

[0079] Comparative Example 1:

[0080] The ingredients, by weight, include 100 parts corn starch, 150 parts HCl (0.5 mol / L), 450 parts water, 20 parts hydrogen peroxide, appropriate amount of sodium hydroxide, 4 parts ammonium persulfate-sodium bisulfite, 1 part sodium dodecyl sulfate, 4 parts phytic acid, 10 parts montmorillonite, and appropriate amount of defoamer.

[0081] 100 parts of starch were mixed with water to form a starch solution, stirred evenly, and 20% (by weight of starch) of H2O2 was added. The pH was adjusted to 9-10 with an appropriate amount of NaOH. After reacting for 2 hours, 0.5 mol / L HCl was added for acid hydrolysis for 1 hour. After washing, centrifugation, drying, and grinding, oxidized and acidified starch was obtained. The temperature of the starch slurry was adjusted to 80-85℃, and gelatinization was carried out for 30 minutes. The reaction temperature was set to 50℃. A redox initiator of ammonium persulfate-sodium bisulfite in a mass ratio of 3:1 was dissolved in a small amount of water to prepare an initiator solution, which was added to the gelatinized starch. The pH was adjusted to 4-5 with an appropriate amount of NaOH, and 1 part of sodium dodecyl sulfate was dissolved in a small amount of water and added to the gelatinized starch solution at a rate of 2 drops / min. Then, 4 parts of phytic acid were added as a crosslinking agent, and the reaction was carried out at 50℃ for 2 hours. Finally, 10 parts of montmorillonite drier were added, and stirring was stopped after the drier was fully dispersed for 1 hour to obtain the prepared starch adhesive sample.

[0082] The testing method for the starch adhesive sample was the same as in Example 1, and the test results are as follows:

[0083] The product obtained in this embodiment is a pale yellow viscous liquid. The product has a bonding strength of 2.713 MPa, a water resistance time of 12 min, and a water loss rate of 52.3%. Without the addition of graft monomers, the product's bonding strength and water resistance are both poor, and the storage time is 30 days.

[0084] Comparative Example 2:

[0085] The ingredients, by weight, include 100 parts corn starch, 150 parts HCl (0.5 mol / L), 450 parts water, 20 parts hydrogen peroxide, appropriate amount of sodium hydroxide, 4 parts ammonium persulfate-sodium bisulfite, 1 part sodium dodecyl sulfate, 5 parts N-isopropylacrylamide, 10 parts vinyl acetate, 4 parts phytic acid, 10 parts montmorillonite, and appropriate amount of defoamer.

[0086] 100 parts of starch were mixed with water to prepare a starch solution, stirred evenly, and 20% (by weight of starch) of H2O2 was added. The pH was adjusted to 9-10 with an appropriate amount of NaOH. After reacting for 2 hours, 0.5 mol / L HCl was added for acid hydrolysis for 1 hour. After washing, centrifugation, drying, and grinding, oxidized acidified starch was obtained. The temperature of the starch slurry was adjusted to 80-85℃, and gelatinization was carried out for 30 minutes. The reaction temperature was set to 50℃. A redox initiator of ammonium persulfate-sodium bisulfite in a mass ratio of 3:1 was dissolved in a small amount of water to prepare an initiator solution, which was added to the gelatinized starch. The pH was adjusted to 4-5 with an appropriate amount of NaOH. 5 parts of N-isopropylacrylamide and 10 parts of vinyl acetate were dissolved in a small amount of water, and 1 part of sodium dodecyl sulfate was added. After complete dissolution, the solution was added to the gelatinized starch solution at a rate of 2 drops / min. The reaction was carried out for 1.5 hours. After the reaction, a graft copolymerized modified starch slurry was obtained. Subsequently, 4 parts of phytic acid were added as a crosslinking agent, and the reaction was carried out at 50℃ for 2 hours.

[0087] Finally, add 10 parts of montmorillonite drying agent, and stop stirring after the drying agent has been fully dispersed for 1 hour to obtain the prepared starch adhesive sample.

[0088] The testing method for the starch adhesive sample was the same as in Example 1, and the test results are as follows:

[0089] The product obtained in this embodiment is a pale yellow viscous liquid with a bonding strength of 2.673 MPa, a water resistance time of 22 min, a water loss rate of 50.6%, and a storage time of 3 days.

[0090] Comparative Example 3:

[0091] The ingredients, by weight, include 100 parts corn starch, 150 parts HCl (0.5 mol / L), 450 parts water, 20 parts hydrogen peroxide, appropriate amount of sodium hydroxide, 4 parts ammonium persulfate-sodium bisulfite, 1 part sodium dodecyl sulfate, 5 parts N-isopropylacrylamide, 5 parts vinyl acetate, 10 parts montmorillonite, and appropriate amount of defoamer.

[0092] Prepare a starch solution by mixing 100 parts of starch with water and stirring until homogeneous. Add 20% H2O2 by weight of starch and adjust the pH to 9-10 with an appropriate amount of NaOH. After reacting for 2 hours, add 0.5 mol / L HCl to hydrolyze for 1 hour. After washing, centrifuging, drying, and grinding, obtain oxidized acidified starch. The temperature of the starch slurry was adjusted to 80-85℃, and gelatinization was carried out for 30 minutes. The reaction temperature was set to 50℃. A redox initiator, ammonium persulfate-sodium bisulfite, with a mass ratio of 3:1 was dissolved in a small amount of water to prepare an initiator solution, which was then added to the gelatinized starch. The pH was adjusted to 4-5 with an appropriate amount of NaOH. Five parts of N-isopropylacrylamide and five parts of vinyl acetate were dissolved in a small amount of water, and one part of sodium dodecyl sulfate was added. After complete dissolution, the solution was added to the gelatinized starch solution at a rate of 2 drops / min. The reaction was carried out for 1.5 hours. After the reaction was completed, a graft copolymerized modified starch slurry was obtained. Finally, 10 parts of montmorillonite drier were added. After the drier was fully dispersed for 1 hour, stirring was stopped to obtain the prepared starch adhesive sample.

[0093] The testing method for the starch adhesive sample was the same as in Example 1, and the test results are as follows:

[0094] The product obtained in this embodiment is a pale yellow viscous liquid. The product has a bonding strength of 0.827 MPa, a water resistance time of 15 min, and a water loss rate of 63.3%. That is, the bonding strength and water resistance are very poor when no crosslinking agent is added. The storage time is 1 day.

[0095] Comparative Example 4:

[0096] The ingredients, by weight, include 100 parts corn starch, 150 parts HCl (0.5 mol / L), 450 parts water, 20 parts hydrogen peroxide, appropriate amount of sodium hydroxide, 4 parts ammonium persulfate-sodium bisulfite, 1 part sodium dodecyl sulfate, 5 parts N-isopropylacrylamide, 5 parts vinyl acetate, 8 parts phytic acid, 10 parts montmorillonite, and appropriate amount of defoamer.

[0097] 100 parts of starch were mixed with water to prepare a starch solution, stirred evenly, and 20% (by weight of starch) of H2O2 was added. The pH was adjusted to 9-10 with an appropriate amount of NaOH. After reacting for 2 hours, 0.5 mol / L HCl was added for acid hydrolysis for 1 hour. After washing, centrifugation, drying, and grinding, oxidized and acidified starch was obtained. The temperature of the starch slurry was adjusted to 80-85℃, and gelatinization was carried out for 30 minutes. The reaction temperature was set to 50℃. A redox initiator of ammonium persulfate-sodium bisulfite in a mass ratio of 3:1 was dissolved in a small amount of water to prepare an initiator solution, which was added to the gelatinized starch. The pH was adjusted to 4-5 with an appropriate amount of NaOH. 5 parts of N-isopropylacrylamide and 5 parts of vinyl acetate were dissolved in a small amount of water, and 1 part of sodium dodecyl sulfate was added. After complete dissolution, the solution was added to the gelatinized starch solution at a rate of 2 drops / min. The reaction was carried out for 1.5 hours. After the reaction, a graft copolymerized modified starch slurry was obtained. Subsequently, 8 parts of phytic acid were added as a crosslinking agent, and the reaction was carried out at 50℃ for 2 hours.

[0098] Finally, add 10 parts of montmorillonite drying agent, and stop stirring after the drying agent has been fully dispersed for 1 hour to obtain the prepared starch adhesive sample.

[0099] The testing method for the starch adhesive sample was the same as in Example 1, and the test results are as follows:

[0100] The product obtained in this embodiment is also pale yellow in appearance and is very viscous. After being left for several hours, the product gels, and the storage time is 1 day (storage time less than 1 day is counted as 1 day). Therefore, this product has no commercial application value, and other properties do not need to be investigated.

[0101] Comparative Example 5:

[0102] The ingredients, by weight, include 100 parts corn starch, 150 parts HCl (0.5 mol / L), 450 parts water, 20 parts hydrogen peroxide, appropriate amount of sodium hydroxide, 4 parts ammonium persulfate-sodium bisulfite, 1 part sodium dodecyl sulfate, 10 parts N-isopropylacrylamide, 4 parts phytic acid, 10 parts montmorillonite, and appropriate amount of defoamer.

[0103] Prepare a starch solution by mixing 100 parts of starch with water and stirring until homogeneous. Add 20% H2O2 by weight of starch and adjust the pH to 9-10 with an appropriate amount of NaOH. After reacting for 2 hours, add 0.5 mol / L HCl to hydrolyze for 1 hour. After washing, centrifuging, drying, and grinding, obtain oxidized acidified starch. The temperature of the starch slurry was adjusted to 80-85℃, and gelatinization was carried out for 30 minutes. The reaction temperature was set to 50℃. A redox initiator, ammonium persulfate-sodium bisulfite, with a mass ratio of 3:1 was dissolved in a small amount of water to prepare an initiator solution, which was then added to the gelatinized starch. The pH was adjusted to 4-5 with an appropriate amount of NaOH. Ten parts of N-isopropylacrylamide were dissolved in a small amount of water, and one part of sodium dodecyl sulfate was added. After complete dissolution, the solution was added to the gelatinized starch solution at a rate of 2 drops / min. The reaction was carried out for 1.5 hours. After the reaction was completed, a graft copolymerized modified starch slurry was obtained. Then, four parts of phytic acid were added as a crosslinking agent, and the reaction was carried out at 50℃ for 2 hours. Finally, ten parts of montmorillonite drier were added. After the drier was fully dispersed for 1 hour, stirring was stopped to obtain the prepared starch adhesive sample.

[0104] The testing method for the starch adhesive sample was the same as in Example 1, and the test results are as follows:

[0105] The product obtained in this embodiment is a pale yellow viscous liquid with a bonding strength of 4.098 MPa, a water resistance time of 70 min, a water loss rate of 60.2%, and a storage time of 7 days.

[0106] Comparative Example 6:

[0107] The ingredients, by weight, include 100 parts corn starch, 150 parts HCl (0.5 mol / L), 450 parts water, 20 parts hydrogen peroxide, appropriate amount of sodium hydroxide, 4 parts ammonium persulfate-sodium bisulfite, 1 part sodium dodecyl sulfate, 10 parts vinyl acetate, 4 parts phytic acid, 10 parts montmorillonite, and appropriate amount of defoamer.

[0108] Prepare a starch solution by mixing 100 parts of starch with water and stirring until homogeneous. Add 20% H2O2 by weight of starch and adjust the pH to 9-10 with an appropriate amount of NaOH. After reacting for 2 hours, add 0.5 mol / L HCl to hydrolyze for 1 hour. After washing, centrifuging, drying, and grinding, obtain oxidized acidified starch. The temperature of the starch slurry was adjusted to 80-85℃, and gelatinization was carried out for 30 minutes. The reaction temperature was set to 50℃. A redox initiator, ammonium persulfate-sodium bisulfite, with a mass ratio of 3:1 was dissolved in a small amount of water to prepare an initiator solution, which was then added to the gelatinized starch. The pH was adjusted to 4-5 with an appropriate amount of NaOH. Ten parts of vinyl acetate were dissolved in a small amount of water, and one part of sodium dodecyl sulfate was added. After complete dissolution, the solution was added to the gelatinized starch solution at a rate of 2 drops / min. The reaction was carried out for 1.5 hours. After the reaction was completed, a graft copolymerized modified starch slurry was obtained. Then, four parts of phytic acid were added as a crosslinking agent, and the reaction was carried out at 50℃ for 2 hours. Finally, ten parts of montmorillonite drier were added. After the drier was fully dispersed for 1 hour, stirring was stopped to obtain the prepared starch adhesive sample.

[0109] The testing method for the starch adhesive sample was the same as in Example 1, and the test results are as follows:

[0110] The product obtained in this embodiment is a pale yellow viscous liquid with a bonding strength of 4.427 MPa, a water resistance time of 76 min, a water loss rate of 59.5%, and a storage time of 7 days.

[0111] Comparative Example 7

[0112] Commercially available brand starch adhesives were tested using the same method as in Example 1. The test results are as follows: the bonding strength was 5.946 MPa, the water resistance time was 80 min, the water loss rate was 65.3%, and the storage time was 14 days.

[0113] Finally, the properties of the samples prepared in the above examples and comparative examples were compared with those of commercially available brand-name starch adhesives, and the results are as follows: Figure 1-3 As shown.

[0114] The above experimental results show that the starch adhesive prepared in Example 3 has the best overall performance. Next, the chemical composition of the starch adhesive sample prepared in Example 3 will be analyzed. Figure 4 ) and microstructure ( Figure 5 ) to conduct analysis.

[0115] like Figure 4 As shown, 3387cm -1 The broad peak at 1640 cm⁻¹ is attributed to the OH stretching vibration of the glucose unit. -1 The absorption at this point is attributed to the superposition of carbonyl and amide groups, proving that vinyl acetate and N-isopropylacrylamide were successfully grafted onto starch, 1154 cm⁻¹. -1and 1028cm -1 The absorption peak at 1560 cm⁻¹ originates from the superposition of CO stretching vibrations, C₂C₃ and OH bending vibrations in starch, and COC stretching vibrations of glycosidic bonds. -1 This corresponds to the bending vibration of the NH bond, at 1272 cm⁻¹. -1 The absorption peak at 963 cm⁻¹ corresponds to the stretching vibrations of the CN and NH bonds. -1 The peak at this point likely corresponds to the characteristic absorption peak of POC, indicating that phytic acid and starch have successfully crosslinked.

[0116] Through observation Figure 5 The adhesive film surface has a few scaly synapses, and no cracks were found on the adhesive film surface, so the adhesive film surface is relatively smooth. This phenomenon may be due to the cross-linking effect of phytic acid, which successfully combines with the hydroxyl groups on the starch molecules to form a denser structure. This is also an important factor that can improve the bonding strength and water resistance of starch adhesives.

[0117] In summary, the starch adhesive prepared by this invention has a simple process, fast drying speed, good water resistance, high bonding strength, and excellent stability. Most of its properties are superior to those of commercially available brand adhesives, and it can meet the bonding needs of paper, cardboard boxes, wallpaper, and wood panels.

Claims

1. A method for preparing a plant acid-esterified starch adhesive, characterized in that: The raw material formulation for the preparation method, in parts by mass, is as follows: 80-120 parts corn starch 120-180 parts hydrochloric acid 4-24 parts of oxidant Initiator 3.2-4.8 parts Sodium dodecyl sulfate 0.8-2.5 parts 0.8-12 parts of graft monomer 4-6 parts of crosslinking agent 360-540 parts deionized water 8-12 parts of drying agent Sodium hydroxide (appropriate amount) The concentration of the hydrochloric acid is 0.4~0.6 mol / L; The grafting monomer is a combination of N-isopropylacrylamide and an ester monomer, wherein the ester monomer is vinyl acetate or methyl methacrylate; and the mass ratio of N-isopropylacrylamide to the ester monomer is 25-50%:75-50%. The initiator is a redox system composed of ammonium persulfate and sodium bisulfite, and the mass ratio of ammonium persulfate to sodium bisulfite is 2:1 to 3:1; The crosslinking agent is phytic acid; The preparation method includes the following steps: (1) Mix 80-120 parts of corn starch with 360-540 parts of water to form a starch solution, stir evenly, add 4-24 parts of oxidant, adjust the pH to 9-10 with an appropriate amount of NaOH, carry out the oxidation reaction for 0.5-2h, then add 120-180 parts of hydrochloric acid with a concentration of 0.4-0.6mol / L to hydrolyze for 0.5-2h, wash, centrifuge, dry, grind to obtain oxidized acidified starch; (2) Place the oxidized and acidified starch obtained in step (1) in a water bath at a temperature of 80~85℃ and gelatinize for 30~35 minutes to obtain a gelatinized starch solution; (3) Reduce the temperature of the water bath in step (2) to 50~55℃, take 3.2-4.8 parts of initiator and dissolve them in a small amount of water to prepare an initiator solution and add it to the gelatinized starch solution. Adjust the pH to 4~5 with NaOH. After completely dissolving 0.8-12 parts of graft monomer and 0.8-2.5 parts of sodium dodecyl sulfate in a small amount of water, slowly add them drop by drop to the gelatinized starch solution. After the drop is finished, continue the reaction for 1.3~3h. After the reaction is completed, the graft copolymerized modified starch slurry is obtained. (4) Then add 4-6 parts of phytic acid as a crosslinking agent to the graft copolymerized starch slurry obtained in step (3) and react at 50-80℃ for 1-3 hours; (5) Finally, add 8-12 parts of drying agent to the reaction solution obtained in step (4), and obtain phytate esterified starch adhesive after the drying agent is fully dispersed.

2. The preparation method according to claim 1, characterized in that: If the resulting adhesive produces bubbles, add a certain amount of defoamer tributyl phosphate, depending on the amount of bubbles. The amount added should not exceed 0.5% of the starch mass.

3. The preparation method according to claim 1 or 2, characterized in that: The oxidant is hydrogen peroxide.

4. The preparation method according to claim 1 or 2, characterized in that: The concentration of the hydrochloric acid is 0.5 mol / L.

5. The preparation method according to claim 1 or 2, characterized in that: The initiator is a redox system composed of ammonium persulfate and sodium bisulfite, and the mass ratio of ammonium persulfate to sodium bisulfite is 3:

1.

6. The preparation method according to claim 1 or 2, characterized in that: The drying agent is one or more of zeolite powder, sodium montmorillonite, light calcium carbonate, and ultrafine kaolin.

7. The preparation method according to claim 1 or 2, characterized in that: Dissolve 0.8-12 parts of graft monomer and 0.8-2.5 parts of sodium dodecyl sulfate completely in a small amount of water, and then add them dropwise to the gelatinized starch solution at a rate not exceeding 2 drops / min.

8. The preparation method according to claim 1 or 2, characterized in that: The raw material formula, in parts by weight, is as follows: 100 parts cornstarch 150 parts hydrochloric acid 20 parts of oxidant 4 parts of initiator 1-2 parts of sodium dodecyl sulfate 10 graft monomers 4 parts crosslinking agent 400-450 parts deionized water 8-12 parts of drying agent The concentration of the hydrochloric acid is 0.5 mol / L; The oxidant is hydrogen peroxide; The grafting monomer is a combination of N-isopropylacrylamide and an ester monomer, wherein the ester monomer is vinyl acetate or methyl methacrylate, and the mass ratio of N-isopropylacrylamide to the ester monomer is 25-50%:75-50%. The initiator is a redox system composed of ammonium persulfate and sodium bisulfite, and the mass ratio of ammonium persulfate to sodium bisulfite is 3:1; The crosslinking agent is phytic acid; The drying agent is one or more of zeolite powder, sodium montmorillonite, light calcium carbonate, and ultrafine kaolin.

9. The preparation method according to claim 8, characterized in that: The raw material formula, in parts by weight, is as follows: 100 parts corn starch 150 parts hydrochloric acid 20 parts of oxidant 4 parts of initiator 1 part sodium dodecyl sulfate 10 graft monomers 4 parts crosslinking agent 450 parts deionized water 10 parts of drying agent.

Images