High-temperature fast-curing starch-based adhesive for particleboards and preparation method thereof

Abstract

The present disclosure discloses a high-temperature fast-curing starch-based adhesive for particleboards and a preparation method thereof, belonging to the technical field of adhesive preparation. The low viscosity of the starch-based adhesive is ensured by selecting a crosslinking monomer which does not self-crosslink in a reaction process in the present disclosure, and a binary crosslinking agent matched with the crosslinking monomer is added before use to be quickly crosslinked with the crosslinking monomer at high temperature so as to ensure better thermosetting property and water resistance as well as faster curing speed of the starch-based adhesive at the same time, which meets the requirements of the particleboards for the adhesive, solves the problem of long curing time of the existing starch-based adhesives at high temperatures, further shortens the curing time of the starch-based adhesives to about 60 s, and improves the production efficiency of the particleboards.

Claims

1. A high-temperature fast-curing starch-based adhesive for particleboards, wherein the formula of the starch-based adhesive for the particleboards comprises: (in parts by mass) starch 150 parts water 250-500 parts concentrated hydrochloric acid 8-20 parts dilute nitric acid 8-13 parts a sodium hydroxide solution 25-40 parts an initiator 6-10 parts a crosslinking monomer 12-18 parts an emulsifier 2-5 parts a binary crosslinking agent 12-18 parts; and the initiator in the formula is cerium nitrate salt.

2. The starch-based adhesive for the particleboards according to claim 1, wherein the starch in the formula is any one or a combination of corn starch, waxy corn starch, tapioca starch, wheat starch, and potato starch.

3. The starch-based adhesive for the particleboards according to claim 1, wherein the emulsifier in the formula is disodium sulfosuccinate decyl polyoxyethylene (6) ether ester.

4. The starch-based adhesive for the particleboards according to claim 1, wherein the crosslinking monomer in the formula is one or a mixture of diacetone acrylamide and hydroxybutyl methacrylate.

5. The starch-based adhesive for the particleboards according to claim 1, wherein the binary crosslinking agent in the formula is one or a mixture of adipic dihydrazide and succinic dihydrazide.

6. The starch-based adhesive for the particleboards according to claim 1, wherein a preparation method of the starch-based adhesive for the particleboards comprises: (1) blending the starch and the water into starch slurry with a mass ratio of 30-50% on a dry basis of starch, and stirring evenly for later use; (2) heating the starch slurry obtained in step (1) up to 60? C., adding hydrochloric acid diluted to 0.8-1.2 mol/L for acid hydrolysis, and then adding the sodium hydroxide solution to adjust the pH of the starch slurry to pH 3-5; after the acid hydrolysis, adjusting the temperature of the starch slurry to 70-90? C., and pre-gelatinizing to obtain pre-gelatinized starch slurry; (3) taking the initiator that accounts for 30% to 60% of the total mass of the initiator and adding the dilute nitric acid to prepare an initiator solution; taking a certain mass of the emulsifier and adding water to prepare an emulsifier solution with a mass concentration of 2% to 6%; mixing the prepared emulsifier solution with 10-20 g of the crosslinking monomer, and then performing pre-emulsification by using a high-speed shearing machine to prepare a pre-emulsion; (4) adding all the initiator solution obtained in step (3) to the pre-gelatinized starch slurry obtained in step (2), and dropwise adding the pre-emulsion obtained in step (3) to the pre-gelatinized starch slurry obtained in step (2) at a constant speed; after the dropwise addition is completed, adding a reformulated initiator solution, where the reformulated initiator solution is prepared by adding the dilute nitric acid to the remaining initiator which accounts for 40% to 70% of the total mass of the initiator to formulate the initiator solution, and carrying out heat preservation again, so as to obtain a modified mixed emulsion system; and (5) cooling the modified mixed emulsion system obtained in step (4) to 30-50? C., adjusting the pH of the emulsion to pH 6-8, and evenly mixing with the binary crosslinking agent to obtain the starch-based adhesive.

7. The starch-based adhesive for the particleboards according to claim 6, wherein the acid hydrolysis time of step (2) is 2-4 hours.

8. The starch-based adhesive for the particleboards according to claim 6, wherein the pre-gelatinization time of step (2) is 30-60 minutes.

9. The starch-based adhesive for the particleboards according to claim 6, wherein the dropwise addition time of step (4) is controlled within 90-120 minutes.

10. Application of the high-temperature fast-curing starch-based adhesive for the particleboards according to claim 1 in hot-press bonding of the particleboards, plywood, fiberboard and wood blocks; and the application process is as follows: the high-temperature fast-curing starch-based adhesive and wood shavings are evenly mixed and paved, and is shaped by pressing under the conditions that the hot-pressing pressure is 3-11 MPa and the hot-pressing temperature is 130-180? C.

Description

DETAILED DESCRIPTION

(1) The present disclosure will be further illustrated below in conjunction with embodiments. It should be understood that these examples are only used for illustrative purposes and do not limit the protection scope of the present disclosure.

(2) Determination of Adhesive Curing Time:

(3) 30 g of an adhesive and 0.5 g of a binary crosslinking agent were separately added into a beaker and mixed thoroughly. 2.0 g of the mixture in the beaker was transferred to a test tube. A stirring rod was inserted into the test tube. The test tube and stirring rod were placed in a beaker filled with boiling water, the stopwatch was immediately started and the sample began to cure under stirring. When the stirring rod could not be lifted, the stopwatch was stopped immediately, and the measured time represented the adhesive curing time. Each sample was subjected to three parallel experiments, and an average value was taken.

Example 1

(4) TABLE-US-00001 Formula (mass/g): corn starch 150 water 350 a 12 mol/L concentrated hydrochloric 18 acid solution a 10 mol/L sodium hydroxide solution 33 a 0.5 mol/L dilute nitric acid solution 10 ceric ammonium nitrate (an initiator) 8 disodium sulfosuccinate decyl 1.96 polyoxyethylene (6) ether ester (an emulsifier) diacetone acrylamide (a crosslinking 15 monomer) adipic dihydrazide (a binary crosslinking 15 agent)

(5) Technological Process: (1) the starch and the water were blended into starch slurry with a mass ratio of 45% on a dry basis of starch, and stirred evenly for later use; (2) the starch slurry obtained in step (1) was heated up to 60? C., 18 g of the 12 mol/L concentrated hydrochloric acid solution was diluted to 1 mol/L and then added into the starch slurry for acid hydrolysis, and the acid hydrolysis was carried out for 2.5 h; after that, the 10 mol/L sodium hydroxide solution was added to adjust pH to 4; the temperature of the acid-hydrolyzed starch slurry was adjusted to 80? C., and the reaction temperature was kept unchanged at 80? C. after pre-gelatinization for 40 min; (3) 4 g of the initiator was dissolved in 5 g of dilute nitric acid to prepare an initiator solution, 1.96 g of the emulsifier was dissolved in 24.8 g of water to prepare a 5% emulsifier solution, all 15 g of the crosslinking monomer was added to the emulsifier, and pre-emulsification was performed by using a high-speed shearing machine to prepare a pre-emulsion; (4) all the initiator solution obtained in step (3) was added to the pre-gelatinized starch slurry obtained in step (2), and the pre-emulsion was dripped into the reaction system obtained after pre-gelatinization in step (2) at a constant speed within 90 min; after the dropwise addition was completed, 4 g of the initiator was added again and dissolved in 5 g of the dilute nitric acid to prepare an initiator solution, and the reaction was carried out for 90 min to obtain a modified mixed emulsion system; (5) the modified mixed emulsion system obtained in step (4) was cooled to 50? C., and the pH of the emulsion was adjusted to 6, so that the starch-based adhesive was obtained; and (6) when in use, the obtained starch-based adhesive and the binary crosslinking agent were pre-mixed uniformly and then applied to hot-pressing of the particleboards.

(6) The product obtained in this example has a milky white and glossy appearance, and is lower in initial viscosity, which meets the use requirements of the particleboards. Referring to the method of Determination of adhesive curing time mentioned earlier, the adhesive curing time was determined to be 60 s.

(7) The thickness swelling rates of water absorption of the particleboards obtained by hot-pressing for 5 min at 170? C. and 11 MPa are 6%, which meets the requirement for P2 type particleboards in the national standard.

Example 2

(8) TABLE-US-00002 Formula (mass/g): corn starch 150 water 350 a 12 mol/L concentrated hydrochloric 18 acid solution a 10 mol/L sodium hydroxide solution 33 a 0.5 mol/L dilute nitric acid solution 10 ceric ammonium nitrate (an initiator) 8 disodium sulfosuccinate decyl 1.96 polyoxyethylene (6) ether ester (an emulsifier) diacetone acrylamide (a crosslinking 15 monomer) adipic dihydrazide (a binary crosslinking 15 agent)

(9) Technological Process:

(10) (1) the starch and the water were blended into starch slurry with a mass ratio of 45% on a dry basis of starch, and stirred evenly for later use;

(11) (2) the starch slurry obtained in step (1) was heated up to 60? C., 18 g of the 12 mol/L concentrated hydrochloric acid solution was diluted to 1 mol/L and then added into the starch slurry for acid hydrolysis, and the acid hydrolysis was carried out for 1 h; after that, the 10 mol/L sodium hydroxide solution was added to adjust pH to 4; the temperature of the acid-hydrolyzed starch slurry was adjusted to 80? C., and the reaction temperature was kept unchanged at 80? C. after pre-gelatinization for 40 min;

(12) (3) 4 g of the initiator was dissolved in 5 g of dilute nitric acid to prepare an initiator solution, 1.96 g of the emulsifier was dissolved in 24.8 g of water to prepare a 5% emulsifier solution, all 15 g of the crosslinking monomer was added to the emulsifier, and pre-emulsification was performed by using a high-speed shearing machine to prepare a pre-emulsion;

(13) (4) all the initiator solution obtained in step (3) was added to the pre-gelatinized starch slurry obtained in step (2), and the pre-emulsion was dripped into the reaction system obtained after pre-gelatinization in step (2) at a constant speed within 90 min; after the dropwise addition was completed, 4 g of the initiator was added again and dissolved in 5 g of the dilute nitric acid to prepare an initiator solution, and the reaction was carried out for 90 min to obtain a modified mixed emulsion system;

(14) (5) the modified mixed emulsion system obtained in step (4) was cooled to 50? C., and the pH of the emulsion was adjusted to 6, so that the starch-based adhesive was obtained; and

(15) (6) when in use, the obtained starch-based adhesive and the binary crosslinking agent were pre-mixed uniformly and then applied to hot-pressing of the particleboards.

(16) The product obtained in this example has a milky white appearance, and is poor in fluidity and higher in viscosity, which cannot meet the use requirements of the particleboards and has no application value.

Example 3

(17) TABLE-US-00003 Formula (mass/g): corn starch 150 water 350 a 12 mol/L concentrated hydrochloric 18 acid solution a 10 mol/L sodium hydroxide solution 33 a 0.5 mol/L dilute nitric acid solution 10 ceric ammonium nitrate (an initiator) 8 disodium sulfosuccinate decyl 1.96 polyoxyethylene (6) ether ester (an emulsifier) diacetone acrylamide (a crosslinking 15 monomer) adipic dihydrazide (a binary crosslinking 15 agent)

(18) Technological process:

(19) (1) the starch and the water were blended into starch slurry with a mass ratio of 45% on a dry basis of starch, and stirred evenly for later use;

(20) (2) the starch slurry obtained in step (1) was heated up to 60? C., 18 g of the 12 mol/L concentrated hydrochloric acid solution was diluted to 1 mol/L and then added into the starch slurry for acid hydrolysis, and the acid hydrolysis was carried out for 4 h; after that, the 10 mol/L sodium hydroxide solution was added to adjust pH to 4; the temperature of the acid-hydrolyzed starch slurry was adjusted to 80? C., and the reaction temperature was kept unchanged at 80? C. after pre-gelatinization for 40 min;

(21) (3) 4 g of the initiator was dissolved in 5 g of dilute nitric acid to prepare an initiator solution, 1.96 g of the emulsifier was dissolved in 24.8 g of water to prepare a 5% emulsifier solution, all 15 g of the crosslinking monomer was added to the emulsifier, and pre-emulsification was performed by using a high-speed shearing machine to prepare a pre-emulsion;

(22) (4) all the initiator solution obtained in step (3) was added to the pre-gelatinized starch slurry obtained in step (2), and the pre-emulsion was dripped into the reaction system obtained after pre-gelatinization in step (2) at a constant speed within 90 min; after the dropwise addition was completed, 4 g of the initiator was added again and dissolved in 5 g of the dilute nitric acid to prepare an initiator solution, and a thermal reaction was carried out for 90 min to obtain a crosslinked and modified mixed emulsion system;

(23) (5) the crosslinked and modified mixed emulsion system obtained in step (4) was cooled to 50? C., and the pH of the emulsion was adjusted to 6, so that the starch-based adhesive was obtained; and

(24) (6) when in use, the obtained starch-based adhesive and the binary crosslinking agent were pre-mixed uniformly and then applied to hot-pressing of the particleboards.

(25) The product obtained in this example has a milky white and glossy appearance, and is very low in initial viscosity. Referring to the method of Determination of adhesive curing time mentioned earlier, the adhesive curing time was determined to be 140 s; and after the adhesive was placed for a period of time, delamination occurred, which proved that the adhesive has no practical value.

(26) Examples 1, 2 and 3 are used to demonstrate the effect of acid hydrolysis time on the viscosity of the adhesive. From the above data, it can be seen that if the acid hydrolysis time is too short, the acid hydrolysis effect is poor, which leads to excessive viscosity and poor fluidity of the adhesive, and thus cannot meet the use requirements of the particleboards; and if the acid hydrolysis time is too long, so that the starch is excessively disintegrated, the reaction effect is poor, the curing time becomes longer, and the effect of rapid curing cannot be achieved.

Example 4

(27) TABLE-US-00004 Formula (mass/g): corn starch 150 water 350 a 12 mol/L concentrated hydrochloric 18 acid solution a 10 mol/L sodium hydroxide solution 33 a 0.5 mol/L dilute nitric acid solution 10 ceric ammonium nitrate (an initiator) 8 disodium sulfosuccinate decyl 1.96 polyoxyethylene (6) ether ester (an emulsifier) N-hydroxyethyl acrylamide (a 15 crosslinking monomer) adipic dihydrazide (a binary crosslinking 15 agent)

(28) Technological Process: (1) the starch and the water were blended into starch slurry with a mass ratio of 45% on a dry basis of starch, and stirred evenly for later use; (2) the starch slurry obtained in step (1) was heated up to 60? C., 18 g of the 12 mol/L concentrated hydrochloric acid solution was diluted to 1 mol/L and then added into the starch slurry for acid hydrolysis, and the acid hydrolysis was carried out for 2.5 h; after that, the 10 mol/L sodium hydroxide solution was added to adjust pH to 4; the temperature of the acid-hydrolyzed starch slurry was adjusted to 80? C., and the reaction temperature was kept unchanged at 80? C. after pre-gelatinization for 40 min; (3) 4 g of the initiator was dissolved in 5 g of dilute nitric acid to prepare an initiator solution, 1.96 g of the emulsifier was dissolved in 24.8 g of water to prepare a 5% emulsifier solution, all 15 g of the crosslinking monomer was added to the emulsifier, and pre-emulsification was performed by using a high-speed shearing machine to prepare a pre-emulsion; (4) all the initiator solution obtained in step (3) was added to the pre-gelatinized starch slurry obtained in step (2), and the pre-emulsion was dripped into the reaction system obtained after pre-gelatinization in step (2) at a constant speed within 90 min; after the dropwise addition was completed, 4 g of the initiator was added again and dissolved in 5 g of the dilute nitric acid to prepare an initiator solution, and the reaction was carried out for 90 min to obtain a modified mixed emulsion system; (5) the modified mixed emulsion system obtained in step (4) was cooled to 50? C., and the pH of the emulsion was adjusted to 6, so that the starch-based adhesive was obtained; and (6) when in use, the obtained starch-based adhesive and the binary crosslinking agent were pre-mixed uniformly and then applied to hot-pressing of the particleboards.

(29) The product obtained in this example has a milky white and glossy appearance, and is lower in initial viscosity, which meets the use requirements of the particleboards. Referring to the method of Determination of adhesive curing time mentioned earlier, the adhesive curing time was determined to be 150 s.

(30) The thickness swelling rates of water absorption of the particleboards obtained by hot-pressing for 5 min at 170? C. and 11 MPa are 15%, which does not meet the requirement for P2 type particleboards in the national standard.

(31) Examples 1 and 4 are used to demonstrate the effect of the crosslinking monomer on the adhesive curing time. From the above data, the significance analysis shows that the adhesive prepared from the diacetone acrylamide is shorter in curing time when being used in combination with the adipic dihydrazide, which can meet the rapid curing requirement of the particleboard adhesive, while the adhesive prepared from N-hydroxyethyl acrylamide is longer in curing time and low in curing efficiency when being used in combination with the adipic dihydrazide, which cannot meet the demand for the particleboard adhesive.

Example 5

(32) TABLE-US-00005 Formula (mass/g): corn starch 150 water 350 a 12 mol/L concentrated hydrochloric 18 acid solution a 10 mol/L sodium hydroxide solution 33 a 0.5 mol/L dilute nitric acid solution 10 ceric ammonium nitrate (an initiator) 8 disodium sulfosuccinate decyl 1.96 polyoxyethylene (6) ether ester (an emulsifier) diacetone acrylamide (a crosslinking 15 monomer)

(33) Technological Process: (1) the starch and the water were blended into starch slurry with a mass ratio of 45% on a dry basis of starch, and stirred evenly for later use; (2) the starch slurry obtained in step (1) was heated up to 60? C., 18 g of the 12 mol/L concentrated hydrochloric acid solution was diluted to 1 mol/L and then added into the starch slurry for acid hydrolysis, and the acid hydrolysis was carried out for 2.5 h; after that, the 10 mol/L sodium hydroxide solution was added to adjust pH to 4; the temperature of the acid-hydrolyzed starch slurry was adjusted to 80? C., and the reaction temperature was kept unchanged at 80? C. after pre-gelatinization for 40 min; (3) 4 g of the initiator was dissolved in 5 g of dilute nitric acid to prepare an initiator solution, 1.96 g of the emulsifier was dissolved in 24.8 g of water to prepare a 5% emulsifier solution, all 15 g of the crosslinking monomer was added to the emulsifier, and pre-emulsification was performed by using a high-speed shearing machine to prepare a pre-emulsion; (4) all the initiator solution obtained in step (3) was added to the pre-gelatinized starch slurry obtained in step (2), and the pre-emulsion was dripped into the reaction system obtained after pre-gelatinization in step (2) at a constant speed within 90 min; after the dropwise addition was completed, 4 g of the initiator was added again and dissolved in 5 g of the dilute nitric acid to prepare an initiator solution, and the reaction was carried out for 90 min to obtain a modified mixed emulsion system; (5) the modified mixed emulsion system obtained in step (4) was cooled to 50? C., and the pH of the emulsion was adjusted to 6, so that the starch-based adhesive was obtained; and

(34) The product obtained in this example has a milky white and glossy appearance, and is lower in initial viscosity, which meets the use requirements of the particleboards. The curing time is determined by referring to the above-mentioned method of Determination of adhesive curing time without adding a binary crosslinking agent, and the obtained adhesive cannot be cured and thus is not available.

Example 6

(35) TABLE-US-00006 Formula (mass/g): corn starch 150 water 350 a 12 mol/L concentrated hydrochloric 18 acid solution a 10 mol/L sodium hydroxide solution 33 a 0.5 mol/L dilute nitric acid solution 10 ceric ammonium nitrate (an initiator) 8 disodium sulfosuccinate decyl 1.96 polyoxyethylene (6) ether ester (an emulsifier) diacetone acrylamide (a crosslinking 15 monomer) ammonium chloride (a binary 15 crosslinking agent)

(36) Technological Process: (1) the starch and the water were blended into starch slurry with a mass ratio of 45% on a dry basis of starch, and stirred evenly for later use; (2) the starch slurry obtained in step (1) was heated up to 60? C., 18 g of the 12 mol/L concentrated hydrochloric acid solution was diluted to 1 mol/L and then added into the starch slurry for acid hydrolysis, and the acid hydrolysis was carried out for 2.5 h; after that, the 10 mol/L sodium hydroxide solution was added to adjust pH to 4; the temperature of the acid-hydrolyzed starch slurry was adjusted to 80? C., and the reaction temperature was kept unchanged at 80? C. after pre-gelatinization for 40 min; (3) 4 g of the initiator was dissolved in 5 g of dilute nitric acid to prepare an initiator solution, 1.96 g of the emulsifier was dissolved in 24.8 g of water to prepare a 5% emulsifier solution, all 15 g of the crosslinking monomer was added to the emulsifier, and pre-emulsification was performed by using a high-speed shearing machine to prepare a pre-emulsion; (4) all the initiator solution obtained in step (3) was added to the pre-gelatinized starch slurry obtained in step (2), and the pre-emulsion was dripped into the reaction system obtained after pre-gelatinization in step (2) at a constant speed within 90 min; after the dropwise addition was completed, 4 g of the initiator was added again and dissolved in 5 g of the dilute nitric acid to prepare an initiator solution, and the reaction was carried out for 90 min to obtain a modified mixed emulsion system; (5) the modified mixed emulsion system obtained in step (4) was cooled to 50? C., and the pH of the emulsion was adjusted to 6, so that the starch-based adhesive was obtained; and (6) when in use, the obtained starch-based adhesive and the binary crosslinking agent were pre-mixed uniformly and then applied to hot-pressing of the particleboards.

(37) The product obtained in this example has a milky white and glossy appearance, and is lower in initial viscosity, which meets the use requirements of the particleboards. The curing time is determined by referring to the above-mentioned method of Determination of adhesive curing time, and the obtained adhesive cannot be cured.

(38) Examples 1, 5 and 6 are used to demonstrate the effect of the binary crosslinking agent on the adhesive curing time. From the above data, the significance analysis shows that the adhesive can be quickly cured after the addition of the binary crosslinking agent, while the adhesive without the binary crosslinking agent or added with other binary crosslinking agents cannot be cured completely, and thus cannot be applied to the particleboards.

Example 7

(39) TABLE-US-00007 Formula (mass/g): corn starch 150 water 350 a 12 mol/L concentrated hydrochloric 18 acid solution a 10 mol/L sodium hydroxide solution 33 a 0.5 mol/L dilute nitric acid solution 10 ceric ammonium nitrate (an initiator) 8 disodium sulfosuccinate decyl 1.96 polyoxyethylene (6) ether ester (an emulsifier) diacetone acrylamide (a crosslinking 15 monomer) adipic dihydrazide (a binary crosslinking 15 agent)

(40) Technological Process:

(41) (1) the starch and the water were blended into starch slurry with a mass ratio of 45% on a dry basis of starch, and stirred evenly for later use;

(42) (2) the starch slurry obtained in step (1) was heated up to 60? C., 18 g of the 12 mol/L concentrated hydrochloric acid solution was diluted to 1 mol/L and then added into the starch slurry for acid hydrolysis, and the acid hydrolysis was carried out for 2.5 h; after that, the 10 mol/L sodium hydroxide solution was added to adjust pH to 4; the temperature of the acid-hydrolyzed starch slurry was adjusted to 80? C., and the acid-hydrolyzed starch slurry was pre-gelatinized for 40 min and then cooled to 70? C. for reacting;

(43) (3) 4 g of the initiator was dissolved in 5 g of dilute nitric acid to prepare an initiator solution, 1.96 g of the emulsifier was dissolved in 24.8 g of water to prepare a 5% emulsifier solution, all 15 g of the crosslinking monomer was added to the emulsifier, and pre-emulsification was performed by using a high-speed shearing machine to prepare a pre-emulsion;

(44) (4) all the initiator solution obtained in step (3) was added to the pre-gelatinized starch slurry obtained in step (2), and the pre-emulsion was dripped into the reaction system obtained after pre-gelatinization in step (2) at a constant speed within 90 min; after the dropwise addition was completed, 4 g of the initiator was added again and dissolved in 5 g of the dilute nitric acid to prepare an initiator solution, and the reaction was carried out for 90 min to obtain a modified mixed emulsion system;

(45) (5) the crosslinked and modified mixed emulsion system obtained in step (4) was cooled to 50? C., and the pH of the emulsion was adjusted to 6, so that the starch-based adhesive was obtained; and

(46) (6) when in use, the obtained starch-based adhesive and the binary crosslinking agent were pre-mixed uniformly and then applied to hot-pressing of the particleboards.

(47) The product obtained in this example has a milky white and glossy appearance, and is lower in initial viscosity, which meets the use requirements of the particleboards. Referring to the method of Determination of adhesive curing time mentioned earlier, the adhesive curing time was determined to be 90 s.

(48) The thickness swelling rates of water absorption of the particleboards obtained by hot-pressing for 5 min at 170? C. and 11 MPa are 10%, which exceeds 8% and thus does not meet the requirement for P2 type particleboards in the national standard.

Example 8

(49) TABLE-US-00008 Formula (mass/g): corn starch 150 water 350 a 12 mol/L concentrated hydrochloric 24 acid solution a 10 mol/L sodium hydroxide solution 33 a 0.5 mol/L dilute nitric acid solution 10 ceric ammonium nitrate (an initiator) 8 disodium sulfosuccinate decyl 1.96 polyoxyethylene (6) ether ester (an emulsifier) diacetone acrylamide (a crosslinking 15 monomer) adipic dihydrazide (a binary crosslinking 15 agent)

(50) Technological Process: (1) the starch and the water were blended into starch slurry with a mass ratio of 45% on a dry basis of starch, and stirred evenly for later use; (2) the starch slurry obtained in step (1) was heated up to 60? C., 24 g of the 12 mol/L concentrated hydrochloric acid solution was diluted to 1.5 mol/L and then added into the starch slurry for acid hydrolysis, and the acid hydrolysis was carried out for 2.5 h; after that, the 10 mol/L sodium hydroxide solution was added to adjust pH to 4; the temperature of the acid-hydrolyzed starch slurry was adjusted to 80? C., and the reaction temperature was kept unchanged at 80? C. after pre-gelatinization for 40 min; (3) 4 g of the initiator was dissolved in 5 g of dilute nitric acid to prepare an initiator solution, 1.96 g of the emulsifier was dissolved in 24.8 g of water to prepare a 5% emulsifier solution, all 15 g of the crosslinking monomer was added to the emulsifier, and pre-emulsification was performed by using a high-speed shearing machine to prepare a pre-emulsion; (4) all the initiator solution obtained in step (3) was added to the pre-gelatinized starch slurry obtained in step (2), and the pre-emulsion was dripped into the reaction system obtained after pre-gelatinization in step (2) at a constant speed within 90 min; after the dropwise addition was completed, 4 g of the initiator was added again and dissolved in 5 g of the dilute nitric acid to prepare an initiator solution, and there action was carried out for 90 min to obtain a modified mixed emulsion system; (5) the modified mixed emulsion system obtained in step (4) was cooled to 50? C., and the pH of the emulsion was adjusted to 6, so that the starch-based adhesive was obtained; and (6) when in use, the obtained starch-based adhesive and the binary crosslinking agent were pre-mixed uniformly and then applied to hot-pressing of the particleboards.

(51) The product obtained in this example has a slurry y white and glossy appearance, and is lower in initial viscosity, which meets the use requirements of the particleboards. Referring to the method of Determination of adhesive curing time mentioned earlier, the adhesive curing time was determined to be 100 s; and after the adhesive was placed for a period of time, delamination occurred, which proved that the adhesive has no practical value.

(52) Examples 1, 7, and 8 are used to demonstrate the effect of the reaction conditions on the adhesive curing time. From the above data, the significance analysis shows that if the reaction temperature is too low, the grafting efficiency of the monomer will be affected, resulting in prolonged curing time, while too high acid hydrolysis concentration will lead to excessive disintegration, so as to reduce the reaction efficiency and further cause a phenomenon of delamination. Therefore, the optimal reaction conditions are a hydrochloric acid concentration of 1 mol/L and a reaction temperature of 80? C.

Example 9

(53) TABLE-US-00009 Formula (mass/g): corn starch 150 water 350 a 12 mol/L concentrated hydrochloric 18 acid solution a 10 mol/L sodium hydroxide solution 33 a 0.5 mol/L dilute nitric acid solution 10 ceric ammonium nitrate (an initiator) 8 disodium sulfosuccinate decyl 1.96 polyoxyethylene (6) ether ester (an emulsifier) hydroxybutyl methacrylate (a 15 crosslinking monomer) succinic dihydrazide (a binary 15 crosslinking agent)

(54) Technological Process:

(55) (1) the starch and the water were blended into starch slurry with a mass ratio of 45% on a dry basis of starch, and stirred evenly for later use;

(56) (2) the starch slurry obtained in step (1) was heated up to 60? C., 18 g of the 12 mol/L concentrated hydrochloric acid solution was diluted to 1 mol/L and then added into the starch slurry for acid hydrolysis, and the acid hydrolysis was carried out for 2.5 h; after that, the 10 mol/L sodium hydroxide solution was added to adjust pH to 4; the temperature of the acid-hydrolyzed starch slurry was adjusted to 80? C., and the reaction temperature was kept unchanged at 80? C. after pre-gelatinization for 40 min;

(57) (3) 4 g of the initiator was dissolved in 5 g of dilute nitric acid to prepare an initiator solution, 1.96 g of the emulsifier was dissolved in 24.8 g of water to prepare a 5% emulsifier solution, all 15 g of the crosslinking monomer was added to the emulsifier, and pre-emulsification was performed by using a high-speed shearing machine to prepare a pre-emulsion;

(58) (4) all the initiator solution obtained in step (3) was added to the pre-gelatinized starch slurry obtained in step (2), and the pre-emulsion was dripped into the reaction system obtained after pre-gelatinization in step (2) at a constant speed within 90 min; after the dropwise addition was completed, 4 g of the initiator was added again and dissolved in 5 g of the dilute nitric acid to prepare an initiator solution, and the reaction was carried out for 90 min to obtain a modified mixed emulsion system;

(59) (5) the modified mixed emulsion system obtained in step (4) was cooled to 50? C., and the pH of the emulsion was adjusted to 6, so that the starch-based adhesive was obtained; and

(60) (6) when in use, the obtained starch-based adhesive and the binary crosslinking agent were pre-mixed uniformly and then applied to hot-pressing of the particleboards.

(61) The product obtained in this example has a milky white and glossy appearance, and is lower in initial viscosity, which meets the use requirements of the particleboards. Referring to the method of Determination of adhesive curing time mentioned earlier, the adhesive curing time was determined to be 65 s.

(62) The thickness swelling rates of water absorption of the particleboards obtained by hot-pressing for 5 min at 170? C. and 11 MPa are 7%, which meets the requirement for P2 type particleboards in the national standard.

Example 10

(63) TABLE-US-00010 Formula (mass/g): corn starch 150 water 350 a 12 mol/L concentrated hydrochloric 18 acid solution a 10 mol/L sodium hydroxide solution 33 ammonium persulfate (an initiator) 1.21 disodium sulfosuccinate decyl 1.96 polyoxyethylene (6) ether ester (an emulsifier) diacetone acrylamide (a crosslinking 15 monomer) adipic dihydrazide (a binary crosslinking 15 agent)

(64) Technological Process: (1) the starch and the water were blended into starch slurry with a mass ratio of 45% on a dry basis of starch, and stirred evenly for later use; (2) the starch slurry obtained in step (1) was heated up to 60? C., 18 g of the 12 mol/L concentrated hydrochloric acid solution was diluted to 1 mol/L and then added into the starch slurry for acid hydrolysis, and the acid hydrolysis was carried out for 2 h; after that, the 10 mol/L sodium hydroxide solution was added to adjust pH to 4; the temperature of the acid-hydrolyzed starch slurry was adjusted to 80? C., and the reaction temperature was kept unchanged at 80? C. after pre-gelatinization for 30 min; (3) 0.91 g of the initiator was dissolved in 35 g of water to prepare an initiator solution, and 1.96 g of the emulsifier was dissolved in 24.8 g of water to prepare a 5% emulsifier solution; (4) all the solution obtained in step (3) was added to the pre-gelatinized starch slurry obtained in step (2), and the crosslinking monomer was dripped into the reaction system obtained after pre-gelatinization in step (2) at a constant speed within 105 min; after the dropwise addition was completed, 10 g of the initiator solution with a mass concentration of 3% was added, and the reaction was carried out for 105 min to obtain a modified mixed emulsion system; (5) the modified mixed emulsion system obtained in step (4) was cooled to 50? C., and the pH of the emulsion was adjusted to 5, so that the starch-based adhesive was obtained; and (6) when in use, the obtained starch-based adhesive and the binary crosslinking agent were pre-mixed uniformly and then applied to hot-pressing of the particleboards.

(65) The product obtained in this example has a milky white and glossy appearance, and is lower in initial viscosity, which meets the use requirements of the particleboards. Referring to the method of Determination of adhesive curing time mentioned earlier, the adhesive curing time was determined to be 120 s.

(66) The thickness swelling rates of water absorption of the particleboards obtained by hot-pressing for 5 min at 170? C. and 11 MPa are 10%, which does not meet the requirement for P2 type particleboards in the national standard.

Example 11

(67) TABLE-US-00011 Formula (mass/g): corn starch 150 water 350 a 12 mol/L concentrated hydrochloric 18 acid solution a 10 mol/L sodium hydroxide solution 33 ammonium persulfate (an initiator) 1.21 sodium dodecyl sulfonate (an 1.96 emulsifier) diacetone acrylamide (a crosslinking 15 monomer) adipic dihydrazide (a binary crosslinking 15 agent)

(68) Technological Process: (1) the starch and the water were blended into starch slurry with a mass ratio of 45% on a dry basis of starch, and stirred evenly for later use; (2) the starch slurry obtained in step (1) was heated up to 60? C., 18 g of the 12 mol/L concentrated hydrochloric acid solution was diluted to 1 mol/L and then added into the starch slurry for acid hydrolysis, and the acid hydrolysis was carried out for 2 h; after that, the 10 mol/L sodium hydroxide solution was added to adjust pH to 4; the temperature of the acid-hydrolyzed starch slurry was adjusted to 80? C., and the reaction temperature was kept unchanged at 80? C. after pre-gelatinization for 30 min; (3) 0.91 g of the initiator was dissolved in 35 g of water to prepare an initiator solution, and 1.96 g of the emulsifier was dissolved in 24.8 g of water to prepare a 5% emulsifier solution; (4) all the solution obtained in step (3) was added to the pre-gelatinized starch slurry obtained in step (2), and the crosslinking monomer was dripped into the reaction system obtained after pre-gelatinization in step (2) at a constant speed within 105 min; after the dropwise addition was completed, 10 g of the initiator solution with a mass concentration of 3% was added, and there action was carried out for 105 min to obtain a modified mixed emulsion system; (5) the modified mixed emulsion system obtained in step (4) was cooled to 50? C., and the pH of the emulsion was adjusted to 5, so that the starch-based adhesive was obtained; and (6) when in use, the obtained starch-based adhesive and the binary crosslinking agent were pre-mixed uniformly and then applied to hot-pressing of the particleboards.

(69) The product obtained in this example has a milky white and glossy appearance, and is lower in initial viscosity, which meets the use requirements of the particleboards. Referring to the method of Determination of adhesive curing time mentioned earlier, the adhesive curing time was determined to be 130 s.

(70) The thickness swelling rates of water absorption of the particleboards obtained by hot-pressing for 5 min at 170? C. and 11 MPa are 12%, which does not meet the requirement for P2 type particleboards in the national standard.

Example 12

(71) TABLE-US-00012 Formula (mass/g): corn starch 150 water 350 a 12 mol/L concentrated hydrochloric 18 acid solution a 10 mol/L sodium hydroxide solution 33 a 0.5 mol/L dilute nitric acid solution 10 ceric ammonium nitrate (an initiator) 8 sodium dodecyl sulfonate (an 1.96 emulsifier) diacetone acrylamide (a crosslinking 15 monomer) adipic dihydrazide (a binary crosslinking 15 agent)

(72) Technological Process: (1) the starch and the water were blended into starch slurry with a mass ratio of 45% on a dry basis of starch, and stirred evenly for later use; (2) the starch slurry obtained in step (1) was heated up to 60? C., 18 g of the 12 mol/L concentrated hydrochloric acid solution was diluted to 1 mol/L and then added into the starch slurry for acid hydrolysis, and the acid hydrolysis was carried out for 2.5 h; after that, the 10 mol/L sodium hydroxide solution was added to adjust pH to 4; the temperature of the acid-hydrolyzed starch slurry was adjusted to 80? C., and the reaction temperature was kept unchanged at 80? C. after pre-gelatinization for 40 min; (3) 4 g of the initiator was dissolved in 5 g of dilute nitric acid to prepare an initiator solution, 1.96 g of the emulsifier was dissolved in 24.8 g of water to prepare a 5% emulsifier solution, all 15 g of the crosslinking monomer was added to the emulsifier, and pre-emulsification was performed by using a high-speed shearing machine to prepare a pre-emulsion; (4) all the initiator solution obtained in step (3) was added to the pre-gelatinized starch slurry obtained in step (2), and the pre-emulsion was dripped into the reaction system obtained after pre-gelatinization in step (2) at a constant speed within 90 min; after the dropwise addition was completed, 4 g of the initiator was added again and dissolved in 5 g of the dilute nitric acid to prepare an initiator solution, and the reaction was carried out for 90 min to obtain a modified mixed emulsion system; (5) the modified mixed emulsion system obtained in step (4) was cooled to 50? C., and the pH of the emulsion was adjusted to 6, so that the starch-based adhesive was obtained; and (6) when in use, the obtained starch-based adhesive and the binary crosslinking agent were pre-mixed uniformly and then applied to hot-pressing of the particleboards.

(73) The product obtained in this example has a slurry y white and glossy appearance, and is lower in initial viscosity, which meets the use requirements of the particleboards.

(74) Referring to the method of Determination of adhesive curing time mentioned earlier, the adhesive curing time was determined to be 110 s.

(75) The thickness swelling rates of water absorption of the particleboards obtained by hot-pressing for 5 min at 170? C. and 11 MPa are 9%, which does not meet the requirement for P2 type particleboards in the national standard.

(76) Although the present disclosure has been disclosed as above with preferred examples, it is not intended to limit the present disclosure. Anyone familiar with this technology can make various changes and modifications without departing from the spirit and scope of the present disclosure. Therefore, the scope of protection of the present disclosure shall be subject to those defined content in the Claims.