A low-temperature curable chitosan adhesive, its preparation method and application

Abstract

The present invention relates to the technical field of biomass chitosan adhesives, and specifically, to a low-temperature curing chitosan adhesive, its preparation method and application. It includes the following steps: Step S1, prepare acidified hydroxyethyl cellulose; Step S2, weigh chitosan and the product after the completion of reaction in Step S11 at room temperature, add them to a beaker, add a certain amount of deionized water, and continuously stir at 85°C for 0.5 h; Step S3, weigh boron nitride at room temperature and add it to the product prepared in Step S2, and continuously stir at room temperature for 0.5 h to finally obtain the chitosan adhesive. The preparation method in the present invention prepares an adhesive by acidifying hydroxyethyl cellulose, chitosan and boron nitride, without the need for additional chemical drugs to modify chitosan.

Description

Technical Field

[0001] The present invention relates to the technical field of low-temperature curing chitosan adhesives using an "organic-inorganic hybridization" strategy. Specifically, it relates to a low-temperature curing chitosan adhesive using an "organic-inorganic hybridization" strategy, its preparation method and application. Background Art

[0002] Traditional petroleum-based adhesives have problems such as environmental pollution and health hazards. Currently, most adhesives in the industry are made from non-renewable petrochemical resources, such as tri-aldehyde adhesives. However, all three of these adhesives use formaldehyde as a raw material and will release formaldehyde during production and use, causing harm to the environment, which is contrary to the current demand for sustainable development. Biomass resources are considered potential substitutes for petroleum-based adhesives because of their green and renewable nature.

[0003] Chitosan is a polysaccharide extracted from the shells of crustaceans such as crab shells and shrimp shells. Its huge production capacity and low cost make it an ideal material for developing bio-based adhesives. However, chitosan has hydrophilicity, resulting in poor water resistance of chitosan adhesives, which limits their application in high-humidity environments. At the same time, the hot pressing temperature required for chitosan adhesives is relatively high and the durability is poor. Therefore, it is necessary to modify chitosan to improve its adhesive properties.

[0004] Although there are already some modification methods in the prior art. For example, some researchers have modified chitosan by cross-linking, graft copolymerization and other modification methods to change the internal or external structure of chitosan to improve its performance; however, these methods have complex processing procedures and increase costs, so they are easily limited in practical applications. Summary of the Invention

[0005] The present invention provides a preparation method of a low-temperature curing chitosan adhesive using an "organic-inorganic hybridization" strategy. The raw materials used are bio-based materials, and the obtained chitosan adhesive has high strength and good water resistance.

[0006] The technical solution of the present invention is as follows:

[0007] Step S1: Hydroxyethyl cellulose and maleic anhydride are heated in acetonitrile for an acidification reaction, and after the reaction ends, acidified hydroxyethyl cellulose is obtained;

[0008] Step S2: Chitosan and the acidified hydroxyethyl cellulose obtained in Step S1 are heated in water for modification to obtain a modified intermediate;

[0009] Step S3: Boron nitride is hybridized with the modified intermediate prepared in Step S2 to obtain the chitosan adhesive.

[0010] Preferably, in step S1, the mass ratio of hydroxyethyl cellulose to maleic anhydride is 1:1.5 - 2.5, more preferably 1:2;

[0011] The reaction temperature is 90 - 100 °C, more preferably 92 °C, and the reaction time is 20 - 30 h, more preferably 24 h.

[0012] Preferably, in step S2, the mass ratio of acidified hydroxyethyl cellulose to chitosan is 5:3 - 6, more preferably 5:4;

[0013] The reaction temperature is 80 - 90 °C, and the reaction time is 0.5 - 2.0 h.

[0014] Preferably, in step S3, the mass ratio of the modified intermediate obtained in step S2 to boron nitride is 30:0.5 - 1.5, more preferably 30:1;

[0015] The reaction temperature is 20 - 30 °C, more preferably room temperature, and the reaction time is 0.5 - 2.0 h, more preferably 0.5 h.

[0016] The present invention also provides a low-temperature curable chitosan adhesive using an "organic-inorganic hybrid" strategy, which is prepared by the above-mentioned preparation method of a low-temperature curable chitosan adhesive using an "organic-inorganic hybrid" strategy.

[0017] The present invention also provides an application of a low-temperature curable chitosan adhesive using an "organic-inorganic hybrid" strategy in the preparation of plywood, which is carried out based on the low-temperature curable chitosan adhesive obtained by the foregoing preparation method; and is applied to the preparation of a three-layer plywood; it specifically includes the following steps:

[0018] Step S1, drying

[0019] The poplar veneer is dried to a moisture content of less than 9%.

[0020] Step S2, sizing:

[0021] The two sides of the dried poplar veneer are coated with the colloid, and the colloid is prepared by the above-mentioned preparation method; the single-sided sizing amount is 160 g / m 2 ; after sizing, there is no need to wait for the glue to dry;

[0022] Step S3, assembling the billet

[0023] The sized poplar veneers are arranged and combined in a way perpendicular to the grain to form a billet of a predetermined shape and size;

[0024] Step S4, hot pressing

[0025] Put the product after assembling the blanks into a hot press for pressing. The hot pressing temperature is 30 - 160°C, the hot pressing pressure is 1.5 MPa, and the hot pressing time is 6 min - 24 h.

[0026] Compared with the prior art, the present invention has the following remarkable improvements:

[0027] (1) The present invention uses chitosan as the main raw material for preparing the adhesive. Chitosan is a polysaccharide extracted from the shells of crustaceans. Compared with petrochemical raw materials, it has low cost, is renewable and pollution-free. Moreover, there is no need to use additional chemicals to modify chitosan, and the operation is simple and the cost is low. Therefore, the present invention conforms to the trend of sustainable development and the mainstream development needs of adhesives in the future.

[0028] (2) In the present invention, the reaction conditions of the whole reaction process are relatively mild, the requirements for the reaction device are low, and the situation of high hot pressing temperature of chitosan-based adhesives is solved, which is conducive to the popularization in actual production and application.

[0029] (3) In the present invention, there is no need to use additional chemicals to modify chitosan, the requirements for reaction raw materials are low, and the safety and stability of the reaction are improved, and there are few limitations in actual applications.

[0030] (4) The adhesive performance of the chitosan adhesive prepared by the preparation method in the present invention is relatively excellent. Even when the hot pressing temperature is 60°C, the dry strength of the plywood is 2.14 MPa, and the strength after soaking in 63°C hot water and 93°C hot water is above 0.7 MPa, which can meet the standards of actual applications and has good application prospects.

[0031] Generally speaking, in the present invention, the raw material cost of the preparation method is low and relatively safe, the reaction conditions are mild, the requirements for reaction equipment are low, the hot pressing temperature is low, and at the same time, a final product with better adhesive performance can be obtained. The main raw material of this adhesive comes from biomass, avoiding the use of formaldehyde; it can also reduce the production cost of the adhesive, improve the environmental protection performance of the board, reduce environmental pollution, and is conducive to promoting the rational development and utilization of renewable resources; it has good prospects for actual application in production. Description of the Drawings

[0032] Figure 1 It is the schematic diagram of the preparation reaction principle of acidified hydroxyethyl cellulose;

[0033] Figure 2 It is the schematic diagram of the reaction principle of acidified hydroxyethyl cellulose and chitosan;

[0034] Figure 3 It is the schematic diagram of the principle of the preparation of the adhesive of the present invention. Detailed Embodiments

[0035] To further understand the content of the present invention, the present invention will be described in detail in conjunction with embodiments. It should be understood that the embodiments are only for explaining the present invention rather than limiting it.

[0036] Example 1

[0037] This example provides a preparation method of a low-temperature curable chitosan adhesive using an "organic-inorganic hybrid" strategy, and the preparation is carried out according to the following method:

[0038] (1) Heat 6 grams of hydroxyethyl cellulose and 12 grams of maleic anhydride in acetonitrile for an acidification reaction at a reaction temperature of 92 °C. After the reaction, acidified hydroxyethyl cellulose is obtained;

[0039] (2) Weigh 5 grams of acidified hydroxyethyl cellulose and 3 grams of chitosan at room temperature and add them to the reactor;

[0040] (3) Add deionized water according to a solid content of 15%, heat to 85 °C and continuously stir and react for 0.5 h;

[0041] (4) Cool the product obtained after the reaction in step (2) to room temperature, add 1 g of boron nitride and continue to continuously stir for 0.5 h, and then cool to room temperature to obtain the prepared low-temperature curable chitosan adhesive using an "organic-inorganic hybrid" strategy;

[0042] (5) Dry the poplar veneer to a moisture content of less than 9%. Coat the two sides of the dried poplar veneer with the colloid. Arrange and combine the veneers coated with the colloid in a vertical grain pattern to form a blank with a predetermined shape and size. Put the assembled product into a hot press for pressing. The hot pressing temperature is 160 °C and the hot pressing time is 6 min to obtain a sample plywood.

[0043] Example 2

[0044] This example provides a preparation method of a low-temperature curable chitosan adhesive using an "organic-inorganic hybrid" strategy, and the preparation is carried out according to the following method:

[0045] (1) Heat 6 grams of hydroxyethyl cellulose and 12 grams of maleic anhydride in acetonitrile for an acidification reaction at a reaction temperature of 92 °C. After the reaction, acidified hydroxyethyl cellulose is obtained;

[0046] (2) Weigh 5 grams of acidified hydroxyethyl cellulose and 4 grams of chitosan at room temperature and add them to the reactor;

[0047] (3) Add deionized water according to a solid content of 15%, heat to 85 °C and continuously stir and react for 0.5 h;

[0048] (4) Cool the product obtained after the reaction in step (2) to room temperature, add 1 g of boron nitride and continue continuous stirring for 0.5 h, then cool to room temperature to obtain the prepared low-temperature curable chitosan adhesive with the "organic-inorganic hybrid" strategy;

[0049] (5) Dry the poplar veneer to a moisture content of less than 9%, coat the two sides of the dried poplar veneer with the colloid, arrange and combine the veneers coated with the colloid in a vertical grain manner to form a blank with a predetermined shape and size, and put the blanked product into a hot press for pressing. The hot pressing temperature is 160 °C and the hot pressing time is 6 min to obtain a sample plywood.

[0050] Example 3

[0051] This example provides a preparation method of a low-temperature curable chitosan adhesive with the "organic-inorganic hybrid" strategy, which is prepared according to the following method:

[0052] (1) Heat 6 g of hydroxyethyl cellulose and 12 g of maleic anhydride in acetonitrile for acidification reaction at a reaction temperature of 92 °C to obtain acidified hydroxyethyl cellulose after the reaction;

[0053] (2) Weigh 5 g of acidified hydroxyethyl cellulose and 5 g of chitosan at room temperature and add them to the reactor;

[0054] (3) Add deionized water according to a solid content of 15%, raise the temperature to 85 °C and continuously stir and react for 0.5 h;

[0055] (4) Cool the product obtained after the reaction in step (2) to room temperature, add 1 g of boron nitride and continue continuous stirring for 0.5 h, then cool to room temperature to obtain the prepared low-temperature curable chitosan adhesive with the "organic-inorganic hybrid" strategy;

[0056] (5) Dry the poplar veneer to a moisture content of less than 9%, coat the two sides of the dried poplar veneer with the colloid, arrange and combine the veneers coated with the colloid in a vertical grain manner to form a blank with a predetermined shape and size, and put the blanked product into a hot press for pressing. The hot pressing temperature is 160 °C and the hot pressing time is 6 min to obtain a sample plywood.

[0057] Example 4

[0058] This example provides a preparation method of a low-temperature curable chitosan adhesive with the "organic-inorganic hybrid" strategy, which is prepared according to the following method:

[0059] (1) Heat 6 g of hydroxyethyl cellulose and 12 g of maleic anhydride in acetonitrile for acidification reaction at a reaction temperature of 92 °C to obtain acidified hydroxyethyl cellulose after the reaction;

[0060] (2) Weigh 5 g of acidified hydroxyethyl cellulose and 4 g of chitosan at room temperature and add them to the reactor;

[0061] (3) Add deionized water according to a solid content of 15%, heat up to 85 °C and continuously stir and react for 0.5 h;

[0062] (4) Cool the product obtained after the reaction in step (2) to room temperature, add 2 g of boron nitride and continue to continuously stir for 0.5 h, then cool to room temperature to obtain the prepared low-temperature curable chitosan adhesive with an "organic-inorganic hybrid" strategy;

[0063] (5) Dry the poplar veneer to a moisture content of less than 9%, coat both sides of the dried poplar veneer with the colloid, arrange and combine the veneers coated with the colloid in a way perpendicular to the grain to form a blank with a predetermined shape and size, put the grouped product into a hot press for pressing, the hot pressing temperature is 160 °C, and the hot pressing time is 6 min to obtain the sample plywood.

[0064] Example 5

[0065] This example provides a preparation method of a low-temperature curable chitosan adhesive with an "organic-inorganic hybrid" strategy, which is prepared according to the following method:

[0066] (1) Heat 6 g of hydroxyethyl cellulose and 12 g of maleic anhydride in acetonitrile for acidification reaction, the reaction temperature is 92 °C, and after the reaction, acidified hydroxyethyl cellulose is obtained;

[0067] (2) Weigh 5 g of acidified hydroxyethyl cellulose and 4 g of chitosan at room temperature and add them to the reactor;

[0068] (3) Add deionized water according to a solid content of 15%, heat up to 85 °C and continuously stir and react for 0.5 h;

[0069] (4) Cool the product obtained after the reaction in step (2) to room temperature, add 3 g of boron nitride and continue to continuously stir for 0.5 h, then cool to room temperature to obtain the prepared low-temperature curable chitosan adhesive with an "organic-inorganic hybrid" strategy.

[0070] (5) Dry the poplar veneer to a moisture content of less than 9%, coat both sides of the dried poplar veneer with the colloid, arrange and combine the veneers coated with the colloid in a way perpendicular to the grain to form a blank with a predetermined shape and size, put the grouped product into a hot press for pressing, the hot pressing temperature is 160 °C, and the hot pressing time is 6 min to obtain the sample plywood.

[0071] The test of the bonding strength is carried out according to the relevant requirements in the national standard GB / T17657-2013. First, the sample plywood is sawn into the same size (100mm×25mm), grooved, and the area of the adhesive layer is 25mm×25mm. They are respectively soaked in a water bath at 63±3℃ and 93±3℃ for 3 hours, taken out and placed at room temperature for ten minutes, and then the bonding strength test is carried out using an electronic universal testing machine. The test results are shown in Table 1:

[0072] Table 1 Performance of plywood prepared with different adhesives

[0073]

[0074] The above embodiments are the preferred embodiments of the present invention, but the embodiments of the present invention are not limited by the above embodiments. Any other substitutions, changes, combinations, and simplifications made without departing from the essence and principle of the present invention are included in the protection scope of the present invention.

Claims

1. A preparation method of a low-temperature curable chitosan adhesive, characterized in that, It includes the following steps: Step S1: Hydroxyethyl cellulose and maleic anhydride are heated in acetonitrile for an acidification reaction. After the reaction ends, acidified hydroxyethyl cellulose is obtained; Step S2: Chitosan and the acidified hydroxyethyl cellulose obtained in Step S1 are heated in water for modification to obtain a modified intermediate; Step S3: Boron nitride is hybridized with the modified intermediate prepared in Step S2 to obtain the chitosan adhesive; In Step S1, the mass ratio of hydroxyethyl cellulose to maleic anhydride is 1:1.5 - 2.5; The reaction temperature is 90 - 100 °C, and the reaction time is 20 - 30 h.

2. The preparation method of the low-temperature curable chitosan adhesive according to claim 1, characterized in that: In Step S2, the mass ratio of acidified hydroxyethyl cellulose to chitosan is 5:3 - 6; The reaction temperature is 80 - 90 °C, and the reaction time is 0.5 - 2.0 h.

3. The preparation method of the low-temperature curable chitosan adhesive according to claim 1, characterized in that: In Step S3, the mass ratio of the modified intermediate obtained in Step S2 to boron nitride is 30:0.5 - 1.5; The reaction temperature is 20 - 30 °C, and the reaction time is 0.5 - 2.0 h.

4. A low-temperature curable chitosan adhesive, characterized in that: It is prepared by the preparation method described in any one of Claims 1 - 3.

5. Application of the low-temperature curing chitosan adhesive as described in Claim 4 in the preparation of plywood.

6. Use of the low-temperature curable chitosan adhesive according to claim 5 in the preparation of plywood, characterized in that, It includes the following steps: Step A: Drying Poplar veneer is dried to a moisture content of less than 9%; Step B: Glue application: The two sides of the dried poplar veneer are coated with a colloid, and the colloid is the low-temperature curing chitosan adhesive described in 5; Step C: Laminating The glue-coated poplar veneers are arranged and combined in a way perpendicular to the grain to form a blank with a predetermined shape and size; Step D: Hot pressing The product after laminating is put into a hot press for pressing to obtain the plywood.

7. Use of the low-temperature curable chitosan adhesive according to claim 6 in the preparation of plywood, characterized in that, In step B, the single-sided glue application amount is 150 to 170 g / m 2 ; After applying the glue, there is no need to wait for the glue to dry.

8. Use of the low-temperature curable chitosan adhesive according to claim 7 in the preparation of plywood, characterized in that, In Step D, the hot pressing temperature is 30 - 160 °C, the hot pressing pressure is 1.0 - 2.0 MPa, and the hot pressing time is 6 min - 24 h.

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