CN111285985A - Activated lignin modified phenolic resin wood adhesive and preparation method thereof - Google Patents
Activated lignin modified phenolic resin wood adhesive and preparation method thereof Download PDFInfo
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Abstract
The invention discloses a preparation method of an activated lignin modified phenolic resin wood adhesive, which comprises the following steps: mixing and stirring an alkali-urea aqueous solution and a lignin raw material to prepare a lignin pretreatment solution; the lignin pretreatment solution is mixed with phenol, a formaldehyde solution, an alkaline solution and a solvent, and the mixture is stirred and reacted to prepare the activated lignin modified phenolic resin wood adhesive. The method adopts the non-toxic environment-friendly alkali-urea aqueous solution which is simple and convenient to operate to degrade and activate the lignin, can be directly used for synthesizing the phenolic resin adhesive, has simple equipment, simple and effective process, steady and controllable reaction and high industrial feasibility, and can realize the simple and effective synthesis of the phenolic resin wood adhesive with excellent comprehensive performance and high lignin substitution under mild conditions.
Description
Technical Field
The invention belongs to the field of wood adhesive preparation, and particularly relates to an activated lignin modified phenolic resin wood adhesive and a preparation method thereof.
Background
The yield of the artificial boards in China accounts for 50-60% of the total yield of the global artificial boards, the total yield of the artificial boards in China in 2018 is 29909 ten thousand cubic meters, the yield is increased by 1.43% compared with the yield in 2017, and the yield is the top of the world artificial board production. The wood adhesive is used as a main raw material for producing the artificial board, the development and progress of the wood adhesive are important guarantees for ensuring various performance indexes of the artificial board, and more than 1500 million tons of wood adhesive are required to be consumed in China every year. As an important adhesive in the wood industry, the phenolic resin adhesive has the advantages of excellent water-resistant adhesive bonding performance, weather resistance, wear resistance, chemical corrosion resistance and the like, so that the phenolic resin adhesive is widely applied to the production of water-resistant and weather-resistant outdoor artificial boards such as reconstituted wood/reconstituted bamboo and the like. However, the raw materials of phenolic resin adhesives mainly depend on petroleum-based phenol, and the phenolic resin adhesives are high in toxicity and price, so that the prices of phenolic resins and bonded wooden products are high. Meanwhile, with the shortage of global fossil resources and the aggravation of environmental problems caused by the use of the fossil resources, the finding of a biomass polyphenol material with wide sources, low price and environmental protection to replace toxic petroleum-based phenol has become an important development trend for preparing modified phenolic resin wood adhesives with excellent performance, low price and environmental protection.
The lignin is a natural polyphenol polymer widely existing in plants, is widely distributed in nature and low in price, and has basic conditions and great potential for preparing biomass-based phenolic resin wood adhesives by substituting petroleum-based phenol. The lignin is an amorphous polymer formed by connecting p-hydroxyphenyl propanol, guaiacyl propanol and syringyl propanol through a C-C bond and a C-O-C bond, and accounts for about 30 percent of the total organic carbon in the biosphere. The lignin is used for modifying the phenolic resin wood adhesive, so that the production cost of the phenolic resin adhesive can be reduced, the biomass content in the phenolic resin adhesive is increased, the release amount of toxic and harmful substances in a phenolic resin adhesive system is reduced, and the high-value and high-efficiency utilization of the industrial waste lignin can be realized. However, the industrial lignin has a complex structure, a large molecular weight, a large steric hindrance and a few C-5 active sites, so that the reaction activity of the industrial lignin with formaldehyde is low, and finally, when the lignin-based phenolic resin adhesive is prepared, the substitution amount of the lignin for phenol is low, and the water-resistant adhesive bonding performance of the modified phenolic resin adhesive is poor, so that the application and development of the industrial lignin in actual industrial production are limited.
The key point of preparing the lignin-based phenolic resin wood adhesive is to improve the reactivity of lignin and formaldehyde by activating the lignin by a chemical means. The traditional lignin activation method mainly comprises lignin phenolization, hydroxymethylation, demethoxylation, degradation modification and the like. For example, patent CN107337774B adopts phenolization strategy to improve lignin reaction activity, and the lignin modified phenolic resin adhesive is successfully prepared by quaternary synergistic copolymerization of lignin, formaldehyde and furfural. In the patent CN104910341B, microwave-CuO is adopted to degrade and modify lignin in the papermaking black liquor, and then the lignin is subjected to phenolization and hydroxymethylation activation modification to prepare the lignin modified phenolic resin adhesive with various performances meeting the requirements of the national standard (GB/T14732-. In the patent CN105754527A, the lignin is subjected to demethoxylation activation treatment under the protection of high temperature and nitrogen by in-situ generation of Lewis acid, and the performance index of the produced demethoxylation activated lignin modified phenolic resin wood adhesive meets the national standard requirement. However, lignin phenolization and hydroxymethylation modification cannot increase the number of active sites in lignin, lignin demethoxylation and degradation treatment generally requires high temperature, high pressure, a toxic catalyst or a volatile reagent, nitrogen protection or expensive instruments and equipment, and the like, and complex operations such as washing, filtering, centrifuging, drying and the like are required to recover lignin when the lignin modified phenolic resin adhesive is activated, so that secondary pollution is easily caused and the production cost is increased, thereby limiting the industrial application of the lignin. Therefore, the lignin is activated by adopting a simple, environment-friendly and low-cost modification strategy, the complex recovery process of the activated lignin is reduced, and the lignin-modified phenolic resin is the most important trend for preparing the environment-friendly green wood adhesive.
The alkali-urea aqueous solution is a solvent with low cost, no toxicity, environmental protection and simple and convenient operation, and can be used for dissolving cellulose and chitin. Researches find that the rapid dynamic self-assembly process between the small molecules in the alkali-urea aqueous solution and the cellulose or the chitin can promote the cellulose and the chitin to be dissolved at low temperature, and then a relatively stable inclusion compound at low temperature is formed through the action of hydrogen bonds. At present, the application of alkali-urea aqueous solution has been expanded to the dissolution of biomass materials such as starch, wheat straw, wood pulp, norway spruce wood chips and the like; previous studies have shown that aqueous alkali-urea solutions have the ability to dissolve lignin, however, there are few reports of direct degradation treatment of industrial lignin using alkali-lignin under mild conditions.
Disclosure of Invention
In order to solve the problems, the invention provides the activated lignin modified phenolic resin wood adhesive which is simple and convenient, green and environment-friendly and has strong industrial feasibility and the preparation method thereof.
In order to achieve the purpose, the technical scheme adopted by the invention is as follows:
a preparation method of an activated lignin modified phenolic resin wood adhesive comprises the following steps:
(1) mixing and stirring an alkali-urea aqueous solution and a lignin raw material to prepare a lignin pretreatment solution;
(2) the lignin pretreatment solution is mixed with phenol, a formaldehyde solution, an alkaline solution and a solvent, and the mixture is stirred and reacted to prepare the activated lignin modified phenolic resin wood adhesive.
Further, the mass ratio of the lignin raw material to the phenol in the lignin pretreatment solution is 1:9-7:3, the mass ratio of the lignin raw material to the alkali-urea aqueous solution is 2:5-4:5, the mass of the alkaline reagent in the alkali-urea aqueous solution accounts for 7% of the mass of the alkali-urea aqueous solution, and the mass ratio of the alkaline reagent in the alkali-urea aqueous solution to the urea is 7: 5-7: 15.
Further, the step of mixing and stirring the alkali-urea aqueous solution and the lignin raw material in the step (1) comprises the following steps: mixing and stirring an alkali-urea aqueous solution and a lignin raw material, standing the lignin/alkali-urea aqueous solution at the temperature of-20-60 ℃, and stirring the lignin/alkali-urea aqueous solution at room temperature to prepare the lignin pretreatment solution.
Further, the step (2) of mixing, stirring and reacting the lignin pretreatment solution with phenol, formaldehyde solution, alkaline solution and solvent comprises the following steps: mixing and stirring the lignin pretreatment solution, the phenol, the water and the first batch of formaldehyde solution for reaction, adding the alkaline solution and the formaldehyde solution for one or more times for stirring reaction, and adding the last batch of alkaline solution into the reaction mixture after the reaction.
Further, the step (2) of mixing, stirring and reacting the lignin pretreatment solution with phenol, formaldehyde solution, alkaline solution and solvent comprises the following steps:
step 2-1: mixing and stirring the lignin pretreatment solution, phenol, water and a first batch of formaldehyde solution at a stirring speed of 300-;
step 2-2: raising the temperature of the reaction mixture to 80-90 ℃, and stirring for reaction for 45-75 min;
step 2-3: adding a first batch of alkaline solution and a second batch of formaldehyde solution into the reaction mixture under the stirring state, and reacting for 45-75 min at the temperature of 80-90 ℃;
step 2-4: adding a second batch of alkaline solution and a third batch of formaldehyde solution into the reaction mixture under the stirring state, and reacting for 45-75 min at the temperature of 80-90 ℃;
step 2-5: and adding a third batch of alkaline solution into the reaction mixture under the stirring state, reacting for 10-30 min at 70-80 ℃, and then cooling the reaction mixture and discharging.
Further, in the step of mixing, stirring and reacting the lignin pretreatment solution with phenol, a formaldehyde solution, an alkaline solution and a solvent, the mass percentage of the total amount of the alkaline solution added to the lignin raw material and the total amount of the phenol is 5-15%, and the mass ratio of the alkaline solution added for three times is 1:1: 2.
Further, in the step of mixing, stirring and reacting the lignin pretreatment solution with phenol, a formaldehyde solution, an alkaline solution and a solvent, the mass of the added formaldehyde solution of the first batch is 40-50% of the total mass of the formaldehyde solution, the mass of the added formaldehyde solution of the second batch is 25-30% of the total mass of the formaldehyde solution, and the mass of the added formaldehyde solution of the third batch is 25-30% of the total mass of the formaldehyde solution.
Further, the alkaline reagent in the alkali-urea aqueous solution is one or more of sodium hydroxide, lithium hydroxide and potassium hydroxide, the lignin raw material is one or more of wheat straw alkali lignin, ethanol lignin, lignosulfonate or corncob alkali lignin, and the alkaline solution is one or more of barium hydroxide, potassium hydroxide and sodium hydroxide aqueous solution.
Further, in the step (1), the urea in the alkali-urea aqueous solution is partially or completely replaced by thiourea.
The activated lignin modified phenolic resin wood adhesive is prepared by the method.
Compared with the prior art, the invention has the remarkable advantages that:
(1) the lignin raw material is degraded and activated by the aqueous solution of alkali-urea, so that the molecular weight and the steric hindrance of the lignin can be effectively reduced, the number of lignin reaction active sites is increased to improve the reaction activity of the lignin, the raw material is wide and easy to obtain, the price is low, the activation process is simple and convenient, the activation condition is mild and controllable, the degradation and activation treatment of the lignin can be realized under the conditions of low temperature and normal pressure, the activation treatment effect is good, toxic/volatile catalysts or reagents are not needed, and nitrogen protection or expensive equipment and instruments are not needed;
(2) the lignin pretreatment solution prepared by taking an alkali-urea aqueous solution as an activating reagent does not need complex recovery processes such as washing, filtering, centrifuging, drying and the like, can be directly used for preparing the phenolic resin adhesive, and does not cause secondary pollution;
(3) the lignin pretreatment solution prepared by taking an alkali-urea aqueous solution as an activating reagent is directly used for preparing the phenolic resin adhesive, and an alkaline reagent, urea and water in the alkali-urea aqueous solution can be respectively used as a catalyst, a formaldehyde trapping agent and a solvent during the synthesis of the phenolic resin adhesive, so that the preparation method is simple and easy to control, and the industrial feasibility is high;
(4) the substitution amount of lignin to phenol in the activated lignin modified phenolic resin adhesive prepared by the method is 10-70%, the production cost of the phenolic resin wood adhesive is effectively reduced, and economic and environment-friendly high-value utilization of industrial waste gas lignin is effectively realized; the water-resistant bonding strength of the plywood prepared from the activated lignin modified phenolic resin wood adhesive meets the production requirement of I-type artificial boards, and the formaldehyde emission reaches the standard requirement of E0 level.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail with reference to the following embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
An activated lignin modified phenolic resin wood adhesive and a preparation method thereof, comprising the following steps:
step 1, activating lignin pretreatment by using an alkali-urea aqueous solution: mixing and stirring an alkaline reagent, urea and water to prepare an alkali-urea aqueous solution, stirring at the stirring speed of 500-; placing the lignin/alkali-urea aqueous solution at the temperature of-20-60 ℃ for 12-48h, and then stirring the lignin/alkali-urea aqueous solution at the room temperature with the stirring speed of 1000-2000r/min for 30-60 min, thereby obtaining the lignin pretreatment solution.
Step 2, synthesizing a phenolic resin wood adhesive: the phenol is activated into phenol anions under the alkaline condition, which is favorable for the smooth synthesis reaction, so the method of the invention activates the phenol in advance. Under the condition of 40 ℃ (the temperature is lower than the melting point of phenol), the lignin pretreatment solution, the phenol, the water and the first formaldehyde solution are mixed and stirred at the stirring speed of 300-. The stirring speed influences the performance of the lignin-based phenolic resin adhesive, and when the stirring speed is lower than 300r/min, lignin cannot be fully dissolved, so that the adhesive bonding strength of the adhesive is reduced; when the stirring speed is higher than 500r/min, excessive energy is consumed, and the production cost is increased.
And 3, raising the temperature of the reaction mixture to 80-90 ℃, and stirring for reaction for 45-75 min. The reaction temperature affects the synthesis reaction rate of the phenolic resin adhesive, and when the reaction temperature is lower than 80 ℃, the reaction is too slow and takes longer; when the reaction temperature is higher than 90 ℃, the reaction and heat release are rapid, the reaction process is difficult to control, and the molecular weight distribution of the product is not uniform.
And 4, adding the first batch of alkaline solution and the second batch of formaldehyde solution into the reaction mixture under the stirring state, and reacting for 45-75 min at the temperature of 80-90 ℃. The pH value of the reaction system influences the reaction synthesis rate, and when the pH value of the reaction system is too low, the reaction speed is slowed down, and the production efficiency is reduced; when the pH value of the reaction system is too high, the reaction speed is too high, so that the reaction process is difficult to control, and simultaneously, the formaldehyde is subjected to the Cannizzaro decomposition reaction, the molar ratio of the system is influenced, and the performance of the synthetic adhesive is reduced; for this purpose, the alkaline solution is added in three portions to control the pH value of the reaction system.
And 5, adding a second batch of alkaline solution and a third batch of formaldehyde solution into the reaction mixture under a stirring state, reacting for 45-75 min at the temperature of 80-90 ℃, wherein the adding frequency of formaldehyde influences the effective amount of formaldehyde in the synthetic adhesive, and adding formaldehyde in three batches can effectively slow down the reaction heat release, so that the reaction is easy to control, and the free phenol content in the synthetic adhesive is reduced.
And 6, adding a third batch of alkaline solution into the reaction mixture under the stirring state, reacting for 10-30 min at 70-80 ℃, then quickly cooling the reaction mixture to 40 ℃, and discharging.
Wherein the mass ratio of the lignin raw material to the phenol in the lignin pretreatment solution is controlled to be 1:9-7: 3; adding three batches of alkaline solution in a mass ratio of 1:1: 2; adding alkaline solution into the three batches of alkaline solution, wherein the mass percentage of the total amount of the alkaline solution in the lignin raw material and the phenol is 5-15%; the addition of water ensures that the solid content of the phenolic resin adhesive system is 40-50%; because the industrial lignin has a complex structure, contains certain impurities and is not easy to calculate the molar ratio of the raw materials, the molar ratio of the formaldehyde solution to the phenol and the lignin raw materials is controlled to be 2.0-2.3 according to the calculation that 1 equivalent of the lignin raw material is equal to 0.4-0.5 equivalent of the phenol; the mass of the first batch of formaldehyde solution is 40-50% of the total mass of the formaldehyde solution, the mass of the second batch of formaldehyde solution is 25-30% of the total mass of the formaldehyde solution, and the mass of the third batch of formaldehyde solution is 25-30% of the total mass of the formaldehyde solution.
Further, the alkaline reagent in the alkali-urea aqueous solution is one or more of sodium hydroxide, lithium hydroxide and potassium hydroxide, and preferably sodium hydroxide;
further, in the step 1, the mass of the alkaline reagent in the alkaline-urea aqueous solution accounts for 7% of the mass of the alkaline-urea aqueous solution, the mass ratio of the alkaline reagent to the urea is controlled to be 7: 5-7: 15, and the mass ratio of the alkaline reagent to the urea is preferably 7: 12;
further, in the step 1, the mass ratio of the lignin raw material to the alkali-urea aqueous solution is 2:5-4:5, preferably the mass ratio of the lignin raw material to the alkali-urea aqueous solution is 3: 5;
further, in the step 1, the lignin raw material is one or more of wheat straw alkali lignin, ethanol lignin, lignosulfonate and corncob alkali lignin.
Further, in the step 2, the stirring time is 5-15 min, preferably 10 min;
further, in the steps 2-6, the stirring rate is 300-500r/min, preferably 400 r/min.
Further, in the step 2-5, the formaldehyde solution is a commercially available 35% -37% formaldehyde solution;
further, in step 4-6, the alkaline solution is one or more of barium hydroxide, potassium hydroxide and sodium hydroxide aqueous solution, preferably sodium hydroxide aqueous solution;
further, in step 4-6, the solubility of the alkaline solution is 50%, and the mass percentage of the total amount of the alkaline solution added in the three batches in the total amount of the lignin raw material and the phenol is 5% -15%, preferably 6% -10%.
Further, in step 1, the urea in the alkali-urea aqueous solution is partially or completely replaced with thiourea.
The alkaline reagent in the alkaline-urea aqueous solution used in the following examples is one or more of sodium hydroxide, lithium hydroxide and potassium hydroxide, and the urea can be partially or completely replaced by thiourea; the lignin raw material is one or more of wheat straw alkali lignin, ethanol lignin, lignosulfonate and corncob alkali lignin sold in the market, and the lignin raw material does not need to be purified; in the examples, 35% to 37% of formaldehyde solution was used, and phenol was a commercially available analytical reagent; the alkaline solution is one or more of barium hydroxide, potassium hydroxide and sodium hydroxide aqueous solution with the concentration of 50%; the mass ratio of the lignin raw material to the phenol in the lignin pretreatment solution is controlled to be 1:9-7:3, namely the substitution amount of the lignin raw material to the phenol is 10-70%.
Example 1
1) Taking 7g of sodium hydroxide, 12g of urea and 81g of water, putting the mixture in a 250ml conical flask, and stirring the mixture for 10min at 500 r/min; adding 60g of sodium lignosulphonate into the sodium hydroxide-urea aqueous solution, and stirring for 40min at 1000 r/min; placing sodium lignosulfonate/sodium hydroxide-urea aqueous solution at-16 ℃ for 24h, and then thawing the sodium lignosulfonate/sodium hydroxide-urea aqueous solution at room temperature; stirring the unfrozen sodium lignosulfonate/sodium hydroxide-urea aqueous solution at the room temperature at the rotating speed of 1000r/min for 30min to obtain sodium lignosulfonate pretreatment solution;
2) mixing 123.2g of sodium lignosulfonate pretreatment solution, 108g of phenol and 100.8g of formaldehyde solution at 40 ℃, and stirring for 10min at the stirring speed of 300 r/min;
3) raising the temperature of the reaction mixture to 90 ℃, and stirring for reaction for 60 min;
4) adding 10g of sodium hydroxide solution and 72.6g of formaldehyde solution into the reaction mixture under the stirring state, and reacting for 60min at 90 ℃;
5) to the reaction mixture were added 10g of sodium hydroxide solution and 72.6g of formaldehyde solution under stirring, and reacted at 90 ℃ for 60 min.
6) Under the stirring state, 20g of sodium hydroxide solution is added into the reaction mixture, the reaction is carried out for 30min at 70 ℃, and then the reaction mixture is quickly cooled to 40 ℃ for discharging.
The prepared activated lignin modified phenolic resin adhesive is used for pressing three-layer poplar plywood, the performance of the three-layer poplar plywood is tested, and the test results are listed in table 1.
Example 2
1) Taking 7g of lithium hydroxide, 12g of urea and 81g of water, and stirring for 10min at 500r/min in a 250ml conical flask; adding 60g of sodium lignin sulfonate into the lithium hydroxide-urea aqueous solution, and stirring for 40min at 1000 r/min; placing sodium lignosulfonate/lithium hydroxide-urea aqueous solution at 0 ℃ for 24 hours, and then thawing the sodium lignosulfonate/lithium hydroxide-urea aqueous solution at room temperature; stirring the unfrozen sodium lignosulfonate/lithium hydroxide-urea aqueous solution at the room temperature at the rotating speed of 1000r/min for 60min to obtain sodium lignosulfonate pretreatment solution;
2) mixing 123.2g of sodium lignosulfonate pretreatment solution, 108g of phenol and 100.8g of formaldehyde solution at 40 ℃, and stirring for 10min at the stirring speed of 300 r/min;
3) raising the temperature of the reaction mixture to 90 ℃, and stirring for reaction for 60 min;
4) adding 10g of sodium hydroxide solution and 72.6g of formaldehyde solution into the reaction mixture under the stirring state, and reacting for 60min at 90 ℃;
5) to the reaction mixture were added 10g of sodium hydroxide solution and 72.6g of formaldehyde solution under stirring, and reacted at 90 ℃ for 60 min.
6) Under the stirring state, 20g of sodium hydroxide solution is added into the reaction mixture, the reaction is carried out for 30min at 70 ℃, and then the reaction mixture is quickly cooled to 40 ℃ for discharging.
The prepared activated lignin modified phenolic resin adhesive is used for pressing three-layer poplar plywood, the performance of the three-layer poplar plywood is tested, and the test results are listed in table 1.
Example 3
1) Taking 7g of sodium hydroxide, 12g of thiourea and 81g of water in a 250ml conical flask, and stirring for 10min at 500 r/min; adding 60g of ethanol lignin into the sodium hydroxide-thiourea aqueous solution, and stirring for 40min at 1000 r/min; placing the ethanol lignin/sodium hydroxide-thiourea aqueous solution at 25 ℃ for 24h, and then stirring the ethanol lignin/sodium hydroxide-thiourea aqueous solution at room temperature at the rotating speed of 1000r/min for 60min to obtain an ethanol lignin pretreatment solution;
2) mixing 123.2g of ethanol lignin pretreatment liquid, 108g of phenol and 100.8g of formaldehyde solution at 40 ℃, and stirring for 10min at the stirring speed of 300 r/min;
3) raising the temperature of the reaction mixture to 90 ℃, and stirring for reaction for 60 min;
4) adding 10g of sodium hydroxide solution and 72.6g of formaldehyde solution into the reaction mixture under the stirring state, and reacting for 60min at 90 ℃;
5) to the reaction mixture were added 10g of sodium hydroxide solution and 72.6g of formaldehyde solution under stirring, and reacted at 90 ℃ for 60 min.
6) Under the stirring state, 20g of sodium hydroxide solution is added into the reaction mixture, the reaction is carried out for 30min at 70 ℃, and then the reaction mixture is quickly cooled to 40 ℃ for discharging.
The prepared activated lignin modified phenolic resin adhesive is used for pressing three-layer poplar plywood, the performance of the three-layer poplar plywood is tested, and the test results are listed in table 1.
Example 4
1) Taking 7g of potassium hydroxide, 12g of urea and 81g of water in a 250ml conical flask, and stirring for 10min at 500 r/min; adding 60g of ethanol lignin into the potassium hydroxide-urea aqueous solution, and stirring for 40min at 1000 r/min; standing the ethanol lignin/potassium hydroxide-urea aqueous solution at 50 ℃ for 24h, and then stirring the ethanol lignin/potassium hydroxide-urea aqueous solution at room temperature at the rotating speed of 1000r/min for 60min to obtain an ethanol lignin pretreatment solution;
2) mixing 123.2g of ethanol lignin pretreatment liquid, 108g of phenol and 100.8g of formaldehyde solution at 40 ℃, and stirring for 10min at the stirring speed of 300 r/min;
3) raising the temperature of the reaction mixture to 90 ℃, and stirring for reaction for 60 min;
4) adding 10g of sodium hydroxide solution and 72.6g of formaldehyde solution into the reaction mixture under the stirring state, and reacting for 60min at 90 ℃;
5) to the reaction mixture were added 10g of sodium hydroxide solution and 72.6g of formaldehyde solution under stirring, and reacted at 90 ℃ for 60 min.
6) Under the stirring state, 20g of sodium hydroxide solution is added into the reaction mixture, the reaction is carried out for 30min at 70 ℃, and then the reaction mixture is quickly cooled to 40 ℃ for discharging.
The prepared activated lignin modified phenolic resin adhesive is used for pressing three-layer poplar plywood, the performance of the three-layer poplar plywood is tested, and the test results are listed in table 1.
Comparative example 1
1) Taking 60g of sodium lignosulfonate and 100g of water in a 250ml conical flask, and stirring at the rotating speed of 1000r/min for 60min at room temperature to obtain sodium lignosulfonate pretreatment liquid;
2) mixing 123.2g of sodium lignosulfonate pretreatment solution, 108g of phenol and 100.8g of formaldehyde solution at 40 ℃, and stirring for 10min at the stirring speed of 300 r/min;
3) raising the temperature of the reaction mixture to 90 ℃, and stirring for reaction for 60 min;
4) adding 11.4g of sodium hydroxide solution and 72.6g of formaldehyde solution into the reaction mixture under the stirring state, and reacting for 60min at 90 ℃;
5) to the reaction mixture were added 11.4g of sodium hydroxide solution and 72.6g of formaldehyde solution under stirring, and reacted at 90 ℃ for 60 min.
6) Under the stirring state, 22.8g of sodium hydroxide solution is added into the reaction mixture, the reaction is carried out for 30min at 70 ℃, and then the reaction mixture is quickly cooled to 40 ℃ for discharging.
The prepared activated lignin modified phenolic resin adhesive is used for pressing three-layer poplar plywood, the performance of the three-layer poplar plywood is tested, and the test results are listed in table 1.
Table 1 comparison table of properties of lignin modified phenolic resin wood adhesive and three-layer poplar plywood prepared by using the same
Preparing a three-layer poplar plywood: the glue application amount of the poplar veneer is 250-300 g/m2(double-sided gluing) and hot-pressing at 130 deg.C under 1.0MPa for 70 s/mm.
From the comparison between the above four examples and comparative example 1, it can be seen that the adhesive prepared by using the alkali-urea aqueous solution or the alkali-thiourea aqueous solution is superior to the adhesive prepared without using the urea aqueous solution or the alkali-thiourea aqueous solution in three indexes of gel time, bonding strength and formaldehyde emission.
Detection of the phenolic resin wood adhesive: the water-resistant adhesive strength is tested according to the detection standard of the I-type artificial board in the national standard GB/T9846-2015; the formaldehyde emission is tested according to the dryer method detection standard in the national standard GB/T17657-2013.
The method adopts the alkali-urea aqueous solution to degrade the activated lignin to prepare the phenolic resin wood adhesive modified by the degraded activated lignin, has simple equipment, simple and effective process, stable and controllable reaction and high industrialization feasibility, can realize the simple and effective synthesis of the phenolic resin wood adhesive with excellent comprehensive performance and high lignin substitution amount under mild conditions, and has important economic and social significance for realizing the high-value utilization of the industrial waste lignin.
The foregoing illustrates and describes the principles, general features, and advantages of the present invention. It will be understood by those skilled in the art that the present invention is not limited to the embodiments described above, which are described in the specification and illustrated only to illustrate the principle of the present invention, but that various changes and modifications may be made therein without departing from the spirit and scope of the present invention, which fall within the scope of the invention as claimed. The scope of the invention is defined by the appended claims and equivalents thereof.
Claims (10)
1. The preparation method of the activated lignin modified phenolic resin wood adhesive is characterized by comprising the following steps:
(1) mixing and stirring an alkali-urea aqueous solution and a lignin raw material to prepare a lignin pretreatment solution;
(2) the lignin pretreatment solution is mixed with phenol, a formaldehyde solution, an alkaline solution and a solvent, and the mixture is stirred and reacted to prepare the activated lignin modified phenolic resin wood adhesive.
2. The preparation method of the activated lignin modified phenolic resin wood adhesive according to claim 1, wherein the mass ratio of the lignin raw material to the phenol in the lignin pretreatment solution is 1:9-7:3, the mass ratio of the lignin raw material to the alkali-urea aqueous solution is 2:5-4:5, the mass of the alkaline reagent in the alkali-urea aqueous solution accounts for 7% of the mass of the alkali-urea aqueous solution, and the mass ratio of the alkaline reagent to the urea in the alkali-urea aqueous solution is 7: 5-7: 15.
3. The preparation method of the activated lignin modified phenolic resin wood adhesive according to claim 1, wherein the mixing and stirring step of the alkali-urea aqueous solution and the lignin raw material in the step (1) comprises: mixing and stirring an alkali-urea aqueous solution and a lignin raw material, standing the lignin/alkali-urea aqueous solution at the temperature of-20-60 ℃, and stirring the lignin/alkali-urea aqueous solution at room temperature to prepare the lignin pretreatment solution.
4. The preparation method of the activated lignin modified phenolic resin wood adhesive according to claim 1, wherein the step (2) of mixing, stirring and reacting the lignin pretreatment solution with phenol, formaldehyde solution, alkaline solution and solvent comprises the following steps: mixing and stirring the lignin pretreatment solution, the phenol, the water and the first batch of formaldehyde solution for reaction, adding the alkaline solution and the formaldehyde solution for one or more times for stirring reaction, and adding the last batch of alkaline solution into the reaction mixture after the reaction.
5. The preparation method of the activated lignin modified phenolic resin wood adhesive according to claim 1, wherein the step (2) of mixing, stirring and reacting the lignin pretreatment solution with phenol, formaldehyde solution, alkaline solution and solvent comprises the following steps:
step 2-1: mixing and stirring the lignin pretreatment solution, phenol, water and a first batch of formaldehyde solution at a stirring speed of 300-;
step 2-2: raising the temperature of the reaction mixture to 80-90 ℃, and stirring for reaction for 45-75 min;
step 2-3: adding a first batch of alkaline solution and a second batch of formaldehyde solution into the reaction mixture under the stirring state, and reacting for 45-75 min at the temperature of 80-90 ℃;
step 2-4: adding a second batch of alkaline solution and a third batch of formaldehyde solution into the reaction mixture under the stirring state, and reacting for 45-75 min at the temperature of 80-90 ℃;
step 2-5: and adding a third batch of alkaline solution into the reaction mixture under the stirring state, reacting for 10-30 min at 70-80 ℃, and then cooling the reaction mixture and discharging.
6. The preparation method of the activated lignin modified phenolic resin wood adhesive according to claim 5, wherein in the step of mixing, stirring and reacting the lignin pretreatment solution with phenol, formaldehyde solution, alkaline solution and solvent, the mass percentage of the total amount of the alkaline solution added to the lignin raw material and the phenol is 5% -15%, and the mass ratio of the alkaline solution added in three times is 1:1: 2.
7. The preparation method of the activated lignin modified phenolic resin wood adhesive according to claim 6, wherein in the step of mixing, stirring and reacting the lignin pretreatment solution with phenol, formaldehyde solution, alkaline solution and solvent, the formaldehyde solution is added to the first batch by mass at 40-50% of the total mass of the formaldehyde solution, the formaldehyde solution is added to the second batch by mass at 25-30% of the total mass of the formaldehyde solution, and the formaldehyde solution is added to the third batch by mass at 25-30% of the total mass of the formaldehyde solution.
8. The method for preparing the activated lignin modified phenolic resin wood adhesive according to claim 7, wherein the alkaline reagent in the alkali-urea aqueous solution is one or more of sodium hydroxide, lithium hydroxide and potassium hydroxide, the lignin raw material is one or more of wheat straw alkali lignin, ethanol lignin, lignosulfonate and corncob alkali lignin, and the alkaline solution is one or more of barium hydroxide, potassium hydroxide and sodium hydroxide aqueous solution.
9. The method for preparing the activated lignin modified phenolic resin wood adhesive according to any one of claims 1 to 8, wherein the urea in the alkali-urea aqueous solution in the step (1) is partially or completely replaced by thiourea.
10. The activated lignin modified phenolic resin wood adhesive is characterized by being prepared by the method in any one of steps 1-9.
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| CN114456754A (en) * | 2022-03-28 | 2022-05-10 | 石河子大学 | Biomass-based phenolic resin adhesive and preparation method thereof |
| CN114456754B (en) * | 2022-03-28 | 2023-05-12 | 石河子大学 | Biomass-based phenolic resin adhesive and preparation method thereof |
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