CN116285827A - Single Ning Jijiao adhesive and preparation method and application thereof - Google Patents

Abstract

The invention belongs to the technical field of artificial boards, and particularly relates to a single Ning Jijiao adhesive and a preparation method and application thereof. The invention provides a preparation method of a single Ning Jijiao adhesive, which comprises the following steps: mixing a cross-linking agent, tannin and water to obtain the tannin-based adhesive; the cross-linking agent is polybasic acid and/or anhydride substance. The tannin-based adhesive prepared by taking the polyacid and/or anhydride substances as the cross-linking agent has the advantages of safety and innocuity. The tannin-based adhesive provided by the invention has the advantages of simple preparation method, low cost and easiness in realizing industrial production. When the tannin-based adhesive provided by the invention is used for preparing the artificial board, the cross-linking agent and tannin are subjected to esterification reaction in the hot pressing process, so that a three-dimensional network cross-linking structure is formed, and the bonding strength is improved.

Description

Single Ning Jijiao adhesive and preparation method and application thereof

Technical Field

The invention belongs to the technical field of artificial boards, and particularly relates to a single Ning Jijiao adhesive and a preparation method and application thereof.

Background

In order to alleviate the contradiction between supply and demand of wood, the artificial board industry has been rapidly developed. The artificial board is made up of wood or other non-wood plant through mechanical processing, separating to obtain unit materials, and adhering adhesive and other additives. Wherein, the adhesive plays a vital role in the artificial board production process. The traditional wood adhesives are mainly phenolic resin, urea-formaldehyde resin and melamine formaldehyde resin. The adhesives release a large amount of harmful volatile organic compounds such as formaldehyde in the preparation and application processes, so that serious environmental problems are caused and the human health is influenced. Therefore, in recent years, development of aldehyde-free adhesives has attracted great attention. Because biomass materials are renewable and environmentally friendly, they become the main raw materials for preparing aldehyde-free adhesives, such as lignin, tannins, proteins, starches, and the like. Wherein, tannin is a natural polyphenol, can be used as a wood adhesive by partially or completely replacing phenolic substances in phenolic resin, and has the advantages of low price, huge reserve, reproducibility, degradability, safety, no toxicity and the like. The most common method for preparing tannin based adhesives is to use formaldehyde as a crosslinking agent. In the method, tannin can react with formaldehyde through polycondensation reaction to form a tannin-based adhesive, however, when formaldehyde is used as a cross-linking agent, the reaction rate of the reaction of the tannin and the cross-linking agent is not easy to control, so that the fluidity and the reactivity of the obtained adhesive are poor, and the prepared tannin-based adhesive has low bonding strength and water resistance, and is difficult to meet the industrial production requirement of wood.

At present, the problem of poor bonding strength and water resistance of the tannin-based adhesive is solved, and a method of modifying tannin and adding other cross-linking agents is mainly adopted. The method for adding other cross-linking agents is most commonly used, and the cross-linking agents with longer molecular chains can be used for replacing formaldehyde with short molecular chains, so that further modification or sizing is facilitated, and the mainly used cross-linking agents comprise urea-diethylenetriamine polyamide, glyoxal, epoxy resin, furfural-glyoxal, epichlorohydrin, polyurethane and the like; however, the above methods have the common problem of complex process, and the crosslinking agent used in the method has toxicity or has an insignificant effect on improving the gluing performance, which is unfavorable for production and use.

Disclosure of Invention

In view of the above, the invention provides a single Ning Jijiao adhesive, a preparation method and application thereof, and the tannin-based adhesive provided by the invention is safe and nontoxic and has higher bonding strength to plates.

In order to solve the technical problems, the invention provides a preparation method of a single Ning Jijiao adhesive, which comprises the following steps:

mixing a cross-linking agent, tannin and water to obtain the tannin-based adhesive;

the cross-linking agent is polybasic acid and/or anhydride substance.

Preferably, the polyacid includes one or more of maleic acid, tartaric acid, oxalic acid, malonic acid, adipic acid, succinic acid, malic acid, citric acid, itaconic acid, and citraconic acid.

Preferably, the acid anhydride comprises one or more of maleic anhydride, itaconic anhydride, citraconic anhydride, succinic anhydride and adipic anhydride.

Preferably, the mass ratio of the cross-linking agent to the tannin is 0-3:1; and the amount of the crosslinking agent is not 0.

Preferably, the mass ratio of the tannin to the water is 1:0.2-5.

Preferably, the mixing is performed under stirring conditions, wherein the stirring temperature is 45-55 ℃, and the stirring time is 4-6 min.

The invention also provides the tannin-based adhesive prepared by the preparation method of the technical scheme, wherein the dry bonding strength of the tannin-based adhesive is 0.7-1.6 MPa, and the wet bonding strength of the tannin-based adhesive is 0.73-1.53 MPa.

The invention also provides application of the tannin-based adhesive in the artificial composite board.

Preferably, the preparation method of the artificial composite board comprises the following steps:

performing first gluing on any surface of the bottom plate and the panel, performing second gluing on the two surfaces of the core plate, and laminating according to the sequence of the bottom plate, the core plate and the panel to obtain a composite plate blank; the surface of the base plate and the surface of the panel glue are directly contacted with the core plate;

and hot-pressing the composite board blank to obtain the artificial composite board.

Preferably, the temperature of the hot pressing is 140-220 ℃, the time of the hot pressing is more than or equal to 3min, and the pressure of the hot pressing is more than or equal to 0.5MPa.

The invention provides a preparation method of a single Ning Jijiao adhesive, which comprises the following steps: mixing a cross-linking agent, tannin and water to obtain the tannin-based adhesive; the cross-linking agent is polybasic acid and/or anhydride substance. The tannin-based adhesive prepared by taking the polyacid and/or anhydride substances as the cross-linking agent has the advantages of safety and innocuity. The tannin-based adhesive provided by the invention has the advantages of simple preparation method, low cost and easiness in realizing industrial production. When the tannin-based adhesive provided by the invention is used for preparing the artificial board, the cross-linking agent and tannin are subjected to esterification reaction in the hot pressing process, so that a three-dimensional network cross-linking structure is formed, and the bonding strength is improved.

Detailed Description

The invention provides a preparation method of a single Ning Jijiao adhesive, which comprises the following steps:

and mixing the cross-linking agent, tannin and water to obtain the tannin-based adhesive.

In the present invention, all the preparation materials are commercially available products well known to those skilled in the art unless specified otherwise.

In the present invention, the crosslinking agent is a polybasic acid and/or an acid anhydride, preferably a polybasic acid or an acid anhydride, and more preferably a polybasic acid. In the present invention, the polybasic acid preferably includes one or more of maleic acid, tartaric acid, oxalic acid, malonic acid, adipic acid, succinic acid, malic acid, citric acid, itaconic acid and citraconic acid, more preferably maleic acid or citric acid. In the present invention, when the polybasic acid is two or more of the specific acids, the ratio of the specific acids is not particularly limited, and any ratio may be used.

In the present invention, the acid anhydride substance preferably includes one or more of maleic anhydride, itaconic anhydride, citraconic anhydride, succinic anhydride and adipic anhydride, more preferably maleic anhydride or citraconic anhydride. In the present invention, when the acid anhydride is two or more of the above specific acid anhydrides, the ratio of the specific acid anhydrides is not particularly limited, and any ratio may be used.

In the present invention, when the crosslinking agent is a polybasic acid and an acid anhydride substance, the ratio of the specific polybasic acid and acid anhydride is not particularly limited, and any ratio is adopted.

In the present invention, the water is preferably deionized water.

In the present invention, the mass ratio of the crosslinking agent to the tannin is preferably 0 to 3:1, more preferably 0.3 to 1.8:1, still more preferably 0.5 to 1:1, and most preferably 0.6 to 0.8:1; the amount of the crosslinking agent is not 0.

The present invention defines that the mass ratio of the crosslinking agent and the tannin within the above-mentioned range facilitates the formation of the crosslinking agent and the tannin in a three-dimensional crosslinked structure.

In the present invention, the mass ratio of the tannin to the water is preferably 1:0.2 to 5, more preferably 1:0.2 to 2.5, still more preferably 1:0.5 to 2, and most preferably 1:1.6 to 1.8.

In the present invention, the mixing is preferably performed under stirring, and the temperature of the stirring is preferably 45 to 55 ℃, more preferably 48 to 50 ℃; the stirring time is preferably 4 to 6 minutes, more preferably 5 minutes. The invention has no special requirement on the stirring rotation speed, and can be uniformly mixed.

In the present invention, the mixed solution preferably further comprises: cooling the mixed system; the temperature after cooling is preferably 20 to 35 ℃, more preferably 25 to 30 ℃. The cooling mode is not particularly required, and the cooling mode is adopted in the conventional mode in the field.

According to the preparation method provided by the invention, nontoxic polyacid and/or anhydride substances are used as the cross-linking agent, so that the use safety of the adhesive is improved, and the pollution to the environment is reduced; meanwhile, the preparation method provided by the invention is simple and easy to operate, and is convenient for industrial production.

The invention also provides the tannin-based adhesive prepared by the preparation method according to the technical scheme, wherein the dry bonding strength of the tannin-based adhesive is 0.7-1.6 MPa, preferably 0.8-1.3 MPa; the wet bonding strength of the tannin-based adhesive is 0.73-1.53 MPa, preferably 0.8-1.3 MPa.

The invention also provides application of the tannin-based adhesive in the artificial composite board. In the present invention, the method for preparing the artificial composite board preferably comprises the following steps:

performing first gluing on any surface of the bottom plate and the panel, performing second gluing on the two surfaces of the core plate, and laminating according to the sequence of the bottom plate, the core plate and the panel to obtain a composite plate blank; the surface of the base plate and the surface of the panel glue are directly contacted with the core plate;

and hot-pressing the composite board blank to obtain the artificial composite board.

The invention carries out first sizing on any surface of a bottom plate and a panel, carries out second sizing on two surfaces of a core plate, and stacks the bottom plate, the core plate and the panel in sequence to obtain a composite board blank; the surface of the base plate and the face plate glued is in direct contact with the core plate. The invention has no special requirements on the bottom plate, the core plate and the face plate, and can be realized by adopting plates which are conventional in the field. In the embodiment of the invention, the bottom plate, the core plate and the face plate are fast-growing poplar boards with the thickness of 1.5mm and the water content of 8-10%. In the present invention, the first sizing amount and the second sizing amount are independently preferably 280 to 320g/m ² More preferably 290 to 300g/m ² . The number of layers of the core plate is not particularly limited, and the number of layers of the core plate is limited according to actual needs.

After the composite board blank is obtained, the composite board blank is hot-pressed to obtain the artificial composite board. In the present invention, the temperature of the hot pressing is preferably 140 to 220 ℃, more preferably 180 to 200 ℃; the time of the hot pressing is preferably 3 minutes or more, more preferably 3 to 7 minutes, still more preferably 4 to 6 minutes; the pressure of the hot pressing is preferably 0.5MPa or more, more preferably 0.5 to 1MPa, still more preferably 0.7 to 1MPa.

In the invention, the cross-linking agent in the tannin-based adhesive and tannin undergo esterification reaction under the hot-pressing condition to form a three-dimensional cross-linked structure. The invention limits the temperature, pressure and time of hot pressing in the above range, can better control the degree of esterification reaction, is favorable for forming a stable three-dimensional cross-linked structure and improves the bonding strength.

The technical solutions provided by the present invention are described in detail below in conjunction with examples for further illustrating the present invention, but they should not be construed as limiting the scope of the present invention.

Example 1

40g of tannin, 24g of maleic acid and 64g of deionized water are stirred for 5min at 50 ℃, and cooled to 25 ℃ to obtain the tannin-based adhesive.

Example 2

40g of tannin, 40g of maleic acid and 80g of deionized water are stirred for 5min at 50 ℃, and cooled to 25 ℃ to obtain the tannin-based adhesive.

Example 3

40g of tannin, 32g of maleic acid and 72g of deionized water are stirred for 5min at 50 ℃, and cooled to 25 ℃ to obtain the tannin-based adhesive.

Example 4

40g of tannin, 24g of citric acid and 64g of deionized water are stirred at 50 ℃ for 5min to obtain the tannin-based adhesive.

Example 5

40g of tannin, 40g of citric acid and 80g of deionized water are stirred at 50 ℃ for 5min to obtain the tannin-based adhesive.

Example 6

40g of tannin, 32g of citric acid and 72g of deionized water are stirred at 50 ℃ for 5min to obtain the tannin-based adhesive.

Comparative example 1

40g of tannin was dissolved in 40g of deionized water at 50℃to obtain an aqueous tannin solution.

Comparative example 2

After 40g of tannin and 40g of deionized water are uniformly mixed, 2g of formaldehyde is added, and Shan Ningjiao adhesive is obtained after full mixing.

Three-layer plywood was prepared using the adhesives prepared in examples 1 to 6 and comparative examples 1 and 2, respectively, according to the following method:

preparing plywood by taking 3 fast-growing poplar boards with the thickness of 1.5mm and the water content of 8-10% as raw materials; optionally two poplar boards were at either surface according to 300g/m ² Is used as a bottom plate and a panel respectively; both surfaces of the remaining poplar board were subjected to a treatment of 300g/m ² Sizing the core board; laminating according to the sequence of the bottom plate, the core plate and the panel, wherein the glue applying surfaces in the bottom plate and the panel are directly contacted with the core plate to obtain a composite plate blank;

and (3) hot-pressing the composite board blank for 4min under the conditions of 180 ℃ and 0.7MPa to obtain the three-layer plywood.

The dry bonding strength and the wet bonding strength of the three-layer plywood are tested according to the related method in GB/T17657-2013 method for testing the physical and chemical properties of the artificial boards and the veneer artificial boards. The wet strength sample treatment method comprises the following steps: the three-layer plywood is placed in hot water with the temperature of 63+/-3 ℃ for soaking for 3 hours, a three-layer plywood sample is taken out after soaking, and the three-layer plywood sample is tested within half an hour, and the test results are shown in table 1:

table 1 three-layer plywood dry and wet bond strength three-dimensional network structure

Examples	Dry glue strength (MPa)	Wet bond strength (MPa)
			Example 1	1.11±0.08	0.93±0.12
Example 2	1.43±0.16	1.14±0.14
			Example 3	0.76±0.03	0.83±0.08
Example 4	0.88±0.02	0.81±0.07
			Example 5	1.27±0.01	1.40±0.13
Example 6	0.91±0.08	1.01±0.08
			Comparative example 1	0.50±0.04	——
Comparative example 2	0.55±0.02	0.48±0.09

As shown in Table 1, the dry bonding strength of the tannin-based adhesive is 0.76-1.43 MPa, the wet bonding strength is 0.81-1.40 MPa, and the dry bonding strength exceeds the requirements of the national standard II type board by 0.1-0.7 MPa, which indicates that the tannin-based adhesive prepared by the preparation method provided by the invention has good bonding strength, and the composite board prepared by the tannin-based adhesive provided by the invention has good mechanical property and water resistance.

Although the foregoing embodiments have been described in some, but not all, embodiments of the invention, it should be understood that other embodiments may be devised in accordance with the present embodiments without departing from the spirit and scope of the invention.

Claims (10)

1. A method for preparing a single Ning Jijiao adhesive, comprising the following steps:

mixing a cross-linking agent, tannin and water to obtain the tannin-based adhesive;

the cross-linking agent is polybasic acid and/or anhydride substance.

2. The method of claim 1, wherein the polyacid comprises one or more of maleic acid, tartaric acid, oxalic acid, malonic acid, adipic acid, succinic acid, malic acid, citric acid, itaconic acid, and citraconic acid.

3. The method of claim 1, wherein the anhydride comprises one or more of maleic anhydride, itaconic anhydride, citraconic anhydride, succinic anhydride, and adipic anhydride.

4. A method according to any one of claims 1 to 3, wherein the mass ratio of the cross-linking agent to the tannin is 0 to 3:1; and the amount of the crosslinking agent is not 0.

5. The method of claim 1, wherein the mass ratio of tannins to water is 1:0.2-5.

6. The method according to claim 1, wherein the mixing is performed under stirring at a temperature of 45 to 55 ℃ for a time of 4 to 6min.

7. The tannin based adhesive prepared by the preparation method according to any one of claims 1 to 6, wherein the dry bonding strength of the tannin based adhesive is 0.7 to 1.6MPa, and the wet bonding strength of the tannin based adhesive is 0.73 to 1.53MPa.

8. The use of the tannin-based adhesive of claim 7 in an artificial composite board.

9. The use according to claim 8, wherein the method of manufacturing the artificial composite board comprises the steps of:

performing first gluing on any surface of the bottom plate and the panel, performing second gluing on the two surfaces of the core plate, and laminating according to the sequence of the bottom plate, the core plate and the panel to obtain a composite plate blank; the surface of the base plate and the surface of the panel glue are directly contacted with the core plate;

and hot-pressing the composite board blank to obtain the artificial composite board.

10. The use according to claim 9, wherein the hot pressing temperature is 140 to 220 ℃, the time of the hot pressing is 3min or more, and the pressure of the hot pressing is 0.5MPa or more.