Modified gelatin / small molecule sugar-based composite wood adhesive and preparation method and application thereof

Abstract

The present invention relates to the field of adhesive technology, and specifically to a modified gelatin / small molecule sugar-based composite wood adhesive, a preparation method and an application thereof. The preparation method comprises: step S1, weighing gelatin in a container, and then adding deionized water to the container; placing the container containing gelatin and deionized water on a reactor, heating and stirring to obtain a gelatin glue solution; step S2, adding a small molecule sugar and a weak acidic substance to the gelatin glue solution, and then raising the temperature and stirring to react to obtain a modified gelatin / small molecule sugar-based composite wood adhesive. The raw materials used in the present invention are bio-friendly, green and non-toxic, widely available, do not use any reaction aids and organic reagents, have mild reaction conditions, do not require special conditions and equipment, have a simple preparation process, and are green and environmentally friendly. The method can not only meet the requirements of the current board making process, but also has a simple preparation process and low cost, and can achieve the purpose of being non-toxic, pollution-free, environmentally friendly, and having high economic benefits.

Description

Technical Field

[0001] The invention relates to the technical field of adhesives, and in particular to a modified gelatin / small molecule sugar-based composite wood adhesive and a preparation method and application thereof. Background Art

[0002] The adhesives currently used in the market mainly include three types of "trialdehyde glues", namely urea-formaldehyde, phenol-formaldehyde and melamine-formaldehyde. These adhesives, which are a mixture of formaldehyde and minerals, will release a large amount of formaldehyde and other harmful substances during production and use. Formaldehyde is a highly irritating colorless gas that has been confirmed by the World Health Organization as a carcinogen and teratogen, which seriously endangers human health. With the continuous improvement of people's living standards, the development of green and environmentally friendly wood adhesives has become the mainstream in today's world.

[0003] A large number of biomass raw materials have been used as environmentally friendly adhesives at home and abroad, including starch, tannic acid, lignin, plant protein, cellulose, etc. Among them, protein has been widely studied in the synthesis of adhesives due to its advantages such as low price, rich functional groups and wide sources. Although adhesives based on soy protein have made great progress, it is still necessary to develop adhesives with excellent performance from other protein resources.

[0004] Gelatin is a partially degraded form of collagen, which exists in large quantities in animal skin and bones. It is a linear polymer mainly composed of amino acids. It has good adhesion properties in solution and becomes a potential adhesive. When pure gelatin is used as an adhesive, its adhesion ability is poor, and the formed film is not resistant to water and has poor oxidation resistance.

[0005] However, the current chemical cross-linking method based on gelatin requires the introduction of organic solvents, which will cause certain harm to the environment. At the same time, the existing gelatin wood adhesives also have problems such as poor water resistance, high cost of modifiers, and complex improvement processes, which limit their industrial promotion and application. Summary of the invention

[0006] Aiming at the problems of poor water resistance of gelatin, high cost of modifier and complicated improvement process in the prior art, the present invention provides a preparation method of modified gelatin / small molecule sugar-based composite wood adhesive, wherein the preparation method uses gelatin, small molecule sugar, weak acidic substance and deionized water;

[0007] The preparation method comprises:

[0008] Step S1, weighing gelatin into a container, and then adding deionized water into the container; placing the container containing gelatin and deionized water on a reactor, heating and stirring to obtain a gelatin solution;

[0009] Step S2, adding small molecule sugar and weak acidic substance to the gelatin solution, and then raising the temperature and stirring to react to obtain a modified gelatin / small molecule sugar-based composite wood adhesive.

[0010] The technical principle of the present invention is: the present invention modifies gelatin by adding an appropriate amount of small molecule sugar and a small amount of weakly acidic substances to prepare a gelatin-based formaldehyde-free wood adhesive with good mechanical properties.

[0011] The reaction mechanism is: small molecule sugar is introduced into gelatin to form hydrogen bonds, citric acid or malic acid is cross-linked in gelatin / small molecule sugar by amidation and esterification, and the cross-linked structure can form hydrogen bonds within the wood molecules, between molecules and on the wood surface, thereby improving the water resistance of the adhesive.

[0012] Preferably, the mass ratio of the gelatin, the small molecule sugar and the weak acidic substance is 10:5-10:2.5-10.

[0013] Preferably, the gelatin is industrial gelatin.

[0014] Preferably, the small molecule sugar is sucrose or glucose. Sucrose is widely present in plants and is mainly derived from sugarcane, and is one of the important sugar sources. Sucrose is a common disaccharide with a high content and is widely used in the food industry. Sucrose small molecules have strong ductility, 8 hydroxyl groups, and 12 carbons, which can be used as adhesives.

[0015] Preferably, the weak acidic substance is citric acid or malic acid. Citric acid is a natural organic acid widely found in fruits, and contains three carboxyl groups and one hydroxyl group in its molecule. Citric acid has the characteristics of being non-toxic, environmentally friendly, and highly reactive, and can be used as an ideal gelatin crosslinking agent.

[0016] Preferably, the heating and stirring in step S1 is carried out at a temperature of 40-50° C., a heating time of 30-60 min, and a stirring speed of 280-400 rpm / min.

[0017] Preferably, the mass fraction of the gelatin solution is 20-30%.

[0018] Preferably, the mass ratio of the gelatin, small molecule sugar, weak acidic substance and deionized water is 10:5-10:2.5-10:23-40.

[0019] Preferably, the elevated temperature in step S2 is 60-90° C.; the stirring in step S2 is performed at a stirring speed of 280-400 rpm / min, and the reaction time is 3 hours.

[0020] The present invention also provides a modified gelatin / small molecule sugar-based composite wood adhesive, which is prepared based on the preparation method of the modified gelatin / small molecule sugar-based composite wood adhesive.

[0021] The present invention also provides an application of a modified gelatin / small molecule sugar-based composite wood adhesive, which is prepared based on the modified gelatin / small molecule sugar-based composite wood adhesive obtained by the preparation method and applied to the production of plywood.

[0022] Compared with the prior art, the present invention has the following significant improvements:

[0023] (1) The small molecule sugar (sucrose or glucose) and weak acidic substance (citric acid or malic acid) used in the preparation method of the present invention are green and non-toxic, widely available, and low in cost. In addition, the preparation method of the present invention does not require the introduction of any reaction aids and organic reagents, and has better bio-friendliness.

[0024] (2) The reaction conditions of the preparation method of the present invention are mild, no special conditions and equipment are required, the preparation process is simple, and the requirements for the reactor are low, which is conducive to actual production and application, and the prospects for promotion and application are very good.

[0025] (3) The modified gelatin / small molecule sugar-based composite wood adhesive prepared by the present invention has the characteristics of strong bonding force, green environmental protection, health and harmlessness, and excellent water resistance when used as a wood adhesive. It performs excellently in dry shear strength, warm water shear strength and boiling water shear strength. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a reaction mechanism diagram of the preparation method of the modified gelatin / small molecule sugar-based composite wood adhesive in the present invention. DETAILED DESCRIPTION

[0027] The present invention is further described below by way of examples. It should be understood that these examples are explanations and examples of the present invention and are not intended to limit the scope of the present invention in any form.

[0028] Example 1

[0029] The modified gelatin / small molecule sugar-based composite wood adhesive is prepared as follows:

[0030] Weigh 6 g of gelatin into a 100 ml round-bottom flask, add 18 g of deionized water, place it on a reactor, heat at 40 °C and stir at 300 rpm / min for 30 min to obtain a gelatin solution with a mass fraction of 25%. Then add 6 g of sucrose and 1.5 g of citric acid to the round-bottom flask and increase the temperature to 60 °C. Stir and react for 3 h to obtain a modified gelatin / small molecule sugar-based composite wood adhesive.

[0031] Example 2

[0032] The modified gelatin / small molecule sugar-based composite wood adhesive is prepared as follows:

[0033] Weigh 7.2 g of gelatin into a 100 ml round-bottom flask, add 21.6 g of deionized water, place it on a reactor, heat at 50 °C and stir at 300 rpm / min for 30 min to obtain a gelatin solution with a mass fraction of 25%. Then add 7.2 g of sucrose and 3.6 g of citric acid to the round-bottom flask and increase the temperature to 70 °C. Stir and react for 3 h to obtain a modified gelatin / small molecule sugar-based composite wood adhesive.

[0034] Example 3

[0035] The modified gelatin / small molecule sugar-based composite wood adhesive is prepared as follows:

[0036] Weigh 8.4 g of gelatin into a 100 ml round-bottom flask, add 25.2 g of deionized water, place it on a reactor, heat at 40 ° C and stir at 300 rpm / min for 30 min to obtain a gelatin solution with a mass fraction of 25%. Then add 8.4 g of sucrose and 8.4 g of citric acid to the round-bottom flask and increase the temperature to 80 ° C. Stir and react for 3 hours to obtain a modified gelatin / small molecule sugar-based composite wood adhesive.

[0037] Comparative Example 4

[0038] The modified gelatin / small molecule sugar-based composite wood adhesive is prepared as follows:

[0039] Weigh 6.6 g of gelatin into a 100 ml round-bottom flask, add 19.8 g of deionized water, place it on a reactor, heat at 45 °C and stir at 300 rpm / min for 30 min to obtain a gelatin solution with a mass fraction of 25%. Then add 3.3 g of sucrose and 3.3 g of citric acid to the round-bottom flask and increase the temperature to 80 °C. Stir and react for 3 h to obtain a modified gelatin / small molecule sugar-based composite wood adhesive.

[0040] Comparative Example 5

[0041] The modified gelatin / small molecule sugar-based composite wood adhesive is prepared as follows:

[0042] Weigh 3 g of gelatin into a 100 ml round-bottom flask, add 9 g of deionized water, place it on a reactor, heat at 40 °C and stir at 300 rpm / min for 30 min to obtain a gelatin solution with a mass fraction of 25%. Then, add 6 g of sucrose and 3 g of citric acid to the round-bottom flask and increase the temperature to 90 °C. Stir and react for 3 h to obtain a modified gelatin / small molecule sugar-based composite wood adhesive.

[0043] Example 6

[0044] The modified gelatin / small molecule sugar-based composite wood adhesive is prepared as follows:

[0045] Weigh 6 g of gelatin into a 100 ml round-bottom flask, add 18 g of deionized water, place it on a reactor, heat at 40 °C and stir at 300 rpm / min for 30 min to obtain a gelatin solution with a mass fraction of 25%. Then, add 6 g of sucrose and 3 g of malic acid to the round-bottom flask and increase the temperature to 80 °C. Stir and react for 3 h to obtain a modified gelatin / small molecule sugar-based composite wood adhesive.

[0046] Example 7

[0047] The modified gelatin / small molecule sugar-based composite wood adhesive is prepared as follows:

[0048] Weigh 6.67 g of gelatin into a 100 ml round-bottom flask, add 20 g of deionized water, place it on a reactor, heat at 50 °C and stir at 300 rpm / min for 60 min to obtain a gelatin solution with a mass fraction of 25%. Then add 6.67 g of glucose and 6.67 g of citric acid to the round-bottom flask and increase the temperature to 80 °C. Stir and react for 3 h to obtain a modified gelatin / small molecule sugar-based composite wood adhesive.

[0049] Example 8

[0050] The modified gelatin / small molecule sugar-based composite wood adhesive is prepared as follows:

[0051] Weigh 12.9 g of gelatin into a 100 ml round-bottom flask, add 38.7 g of deionized water, place it on a reactor, heat at 50 °C and stir at 300 rpm / min for 30 min to obtain a gelatin solution with a mass fraction of 25%. Then add 12.9 g of glucose and 12.9 g of malic acid to the round-bottom flask and increase the temperature to 80 °C. Stir and react for 3 h to obtain a modified gelatin / small molecule sugar-based composite wood adhesive.

[0052] Example 9

[0053] The modified gelatin / small molecule sugar-based composite wood adhesive is prepared as follows:

[0054] Weigh 6 g of gelatin into a 100 ml round-bottom flask, add 18 g of deionized water, place it on a reactor, heat at 50 °C and stir at 300 rpm / min for 60 min to obtain a gelatin solution with a mass fraction of 25%. Then, add 6 g of glucose and 3 g of malic acid to the round-bottom flask and increase the temperature to 80 °C. Stir and react for 3 h to obtain a modified gelatin / small molecule sugar-based composite wood adhesive.

[0055] Example 10

[0056] The modified gelatin / small molecule sugar-based composite wood adhesive is prepared as follows:

[0057] Weigh 9.9 g of gelatin into a 100 ml round-bottom flask, add 29.7 g of deionized water, place it on a reactor, heat at 50 °C and stir at 300 rpm / min for 60 min to obtain a gelatin solution with a mass fraction of 25%. Then add 4.95 g of glucose and 4.95 g of malic acid to the round-bottom flask and increase the temperature to 80 °C. Stir and react for 3 h to obtain a modified gelatin / small molecule sugar-based composite wood adhesive.

[0058] Comparative Example 11

[0059] The modified gelatin / small molecule sugar-based composite wood adhesive is prepared as follows:

[0060] Weigh 6 g of gelatin into a 100 ml round-bottom flask, add 14 g of deionized water, place it on a reactor, heat at 50 °C and stir at 300 rpm / min for 60 min to obtain a gelatin solution with a mass fraction of 30%. Then add 6 g of glucose and 3 g of malic acid to the round-bottom flask and increase the temperature to 80 °C. Stir and react for 3 h to obtain a modified gelatin / small molecule sugar composite wood adhesive.

[0061] Comparative Example 12

[0062] The modified gelatin / small molecule sugar-based composite wood adhesive is prepared as follows:

[0063] Weigh 6 g of gelatin into a 100 ml round-bottom flask, add 24 g of deionized water, place it on a reactor, heat at 40 °C and stir at 300 rpm / min for 60 min to obtain a gelatin solution with a mass fraction of 20%. Then, add 6 g of glucose and 3 g of malic acid to the round-bottom flask and increase the temperature to 90 °C. Stir and react for 3 h to obtain a modified gelatin / small molecule sugar-based composite wood adhesive.

[0064] Based on the above examples and comparative examples, in order to verify the performance characteristics of the modified gelatin / small molecule sugar-based composite wood adhesive, the following tests were performed:

[0065] The modified gelatin / small molecule sugar-based composite wood adhesive prepared in each embodiment and comparative example was used to press a three-layer plywood with a poplar veneer having a thickness of 2 mm. The physical and mechanical properties of the board were tested according to the requirements of the national standard GB / T 17657-2013 "Test methods for physical and chemical properties of artificial boards and veneer artificial boards", and the water resistance of the board was mainly tested. The specific steps are as follows: the synthesized modified gelatin / small molecule sugar-based composite wood adhesive was applied at a glue amount of 320 g / m 2Double-sided glue was applied on a single-layer poplar board, the hot pressing temperature was 200℃, and the hot pressing lasted for 6 minutes. Then the board was cut into 36 specimens and divided into 3 parts to test their dry strength, wet strength (immerse the specimens in 63℃ water for 3 hours), water resistance (immerse the specimens in boiling water for 3 hours), etc. The test results are shown in the following table:

[0066]

[0067] According to the strength measured in each embodiment, it was found through screening that when the mass ratio of the reactants is: gelatin: sucrose: citric acid = 10:10:5, gelatin: glucose: malic acid = 10:5:5, the reaction temperature is 80°C, and the reaction time is 3h, the corresponding modified gelatin / small molecule sugar-based composite wood adhesive has the best performance.

[0068] According to the water resistance requirements of GB / T 9846-2015 "Ordinary Plywood" for plywood, various performance data of the modified gelatin / small molecule sugar-based composite wood adhesive of the present invention are higher than the national standard requirements.

[0069] It is easy to understand that those skilled in the art can combine, split, reorganize, etc. the embodiments of the present application to obtain other embodiments based on one or several embodiments provided in the present application, and these embodiments do not exceed the protection scope of the present application.

[0070] The present invention and its implementation methods are described schematically above, and the description is not restrictive. The embodiments shown in the embodiments are only part of the implementation methods of the present invention, and the actual structure is not limited thereto. Therefore, if a person skilled in the art is inspired by the embodiments and designs a structure and an implementation method similar to the technical solution without creativity without departing from the purpose of the invention, they should all fall within the protection scope of the present invention.

Claims

1. A method for preparing a modified gelatin / small molecule sugar-based composite wood adhesive, characterized in that: The preparation method is carried out by using gelatin, small molecule sugar, weak acidic substance and deionized water; The preparation method comprises: Step S1, weighing gelatin into a container, and then adding deionized water into the container; placing the container containing gelatin and deionized water on a reactor, heating and stirring to obtain a gelatin solution; Step S2, adding small molecule sugar and weak acidic substance to the gelatin solution, then raising the temperature and stirring to obtain a modified gelatin / small molecule sugar-based composite wood adhesive; The mass ratio of the gelatin, small molecule sugar and weak acidic substance is 10:5-10:2.5-10; The small molecule sugar is sucrose or glucose; The weak acidic substance is citric acid or malic acid; When the small molecule sugar is sucrose and the weak acid substance is citric acid, the mass ratio of gelatin, sucrose and citric acid is 10:10:5; When the small molecule sugar is glucose and the weak acid substance is malic acid, the mass ratio of gelatin, glucose and malic acid is 10:5:5; The heating and stirring in step S1 is carried out at a temperature of 40-50° C., a heating time of 30-60 min, and a stirring speed of 280-400 rpm / min; The mass fraction of the gelatin solution is 20-30%; The mass ratio of the gelatin, small molecule sugar, weak acidic substance and deionized water is 10:5-10:2.5-10:23-40; The elevated temperature in step S2 is 60-90° C.; the stirring in step S2 is performed at a stirring speed of 280-400 rpm / min, and the reaction time is 3 hours.

2. Modified gelatin / small molecule sugar-based composite wood adhesive, characterized in that: The modified gelatin / small molecule sugar-based composite wood adhesive is prepared based on the preparation method of claim 1.

3. Application of modified gelatin / small molecule sugar-based composite wood adhesive, characterized in that: The modified gelatin / small molecule sugar-based composite wood adhesive obtained by the preparation method according to claim 1 is prepared and applied to the production of plywood.

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