CN1884418A - Amino resin binding agent for preparing superstrong water-tight bamboo-wood sheet and sheet production process - Google Patents

Abstract

The invention provides a kind of amino resin adhesive for the production of ultra-strong, water-resistant bamboo and wood boards and the processing and post-treatment technology of the boards. The technical scheme adopted is to synthesize urea-formaldehyde resins in a strong acid system, so that the urea-formaldehyde resin molecules have a large amount of The active branched chain structure; before sizing, add an appropriate amount of high-efficiency latent cross-linking agent to the adhesive, and the board will release compounds with active groups during the heating or placing process. Cross-linking between molecules and between urea-formaldehyde resin molecules and wood fibers, thereby improving the bonding strength and water resistance of the boards; the bamboo and wood boards produced by using the technology of the present invention have high mechanical strength and excellent water resistance and weather resistance , also has the characteristics of low cost and simple process; it is suitable for the production of bamboo and wood panels that require high water resistance.

Description

Amino resin adhesive for super water-resistant bamboo and wood board preparation and board processing technology

Technical field:

The invention belongs to the processing field of bamboo and wood boards, is an amino resin adhesive produced by using aldehydes and amino compounds, and is used for the production, processing and post-treatment technology of super strong and water-resistant bamboo and wood boards; it can be applied to plywood, fine wood Production and processing of wood-based panels such as wood boards, particle boards, and fiberboards; it can also be used for molding and processing of straw fiber boards.

Background technique:

In the production and processing technology of water-resistant bamboo and wood panels, such as: building formwork, container floor, vehicle board, reinforced composite wood flooring, etc., some adhesives with high water resistance have been used at home and abroad, such as: phenolic resin, polyurethane, melamine Formaldehyde resin, etc. During the processing of the board, these adhesives can cross-link with the wood fiber to form a network structure, thereby improving the water resistance of the board. However, the use of these adhesives generally has problems such as high cost and consumption of a large amount of petrochemical resources. At the same time, a large amount of toxic chemical raw materials such as phenol, isocyanate, and melamine are used in the synthesis of adhesives, which not only pollutes the environment, but also causes great harm to production personnel. Therefore, there is an urgent need to develop new adhesives and sheet processing technologies with low cost, low pollution, high strength, and good water resistance.

Urea-formaldehyde resin adhesive has the characteristics of good bonding strength, colorless, and low cost, and has always been the preferred adhesive in the wood processing industry. But, the strength of urea-formaldehyde resin adhesive is on the low side, and water resistance is poor, has limited its application on the production of water resistance bamboo, wood board. Therefore, urea-formaldehyde resin-based adhesives are not currently used at home and abroad when producing this type of board.

If appropriate technology can be adopted to improve the comprehensive performance of urea-formaldehyde resin, so that it has considerable strength and can achieve good water resistance, then the problem of high cost of water-resistant bamboo and wood board adhesives and large consumption of petrochemical resources can be solved. question.

Invention content:

The invention provides a production technology, board processing and post-treatment technology of an amino resin-based adhesive used in the production of super-strong, water-resistant bamboo and wood boards.

The present invention achieves the purpose of improving the bonding ability and water resistance of the urea-formaldehyde resin adhesive to wood through the design and mutual cooperation of the production technology, glue mixing technology and plate post-treatment technology of the urea-formaldehyde resin adhesive; the specifically adopted technical scheme is: (1) Synthesize urea-formaldehyde resin in a strong acid system, so that the urea-formaldehyde resin molecule has a large number of active branched chain structures; (2) Add an appropriate amount of high-efficiency latent cross-linking agent to the adhesive before sizing, and the board will be heated or placed During the process, compounds with active groups are released, and these compounds act as crosslinks between urea-formaldehyde resin molecules and between urea-formaldehyde resin molecules and wood fibers during the curing process, thereby improving the bonding strength and water resistance of the board; (3) Use the process of pre-pressing-hot pressing, or pre-pressing-heating (or placing at room temperature) for aging; (4) After the board is formed, use alkaline materials to treat the board to improve the physical and chemical structure of the adhesive layer and further improve the overall quality of the board. performance.

The bamboo and wood boards processed and produced by the technology of the invention have the characteristics of low cost, high strength, super water resistance and simple process; they are suitable for the production and processing of bamboo and wood boards requiring high water resistance and the production and processing of straw fiber boards.

Detailed ways

Amino resin adhesive of the present invention is made by following method:

(1) Synthesis of urea-formaldehyde resin-based adhesive:

Firstly, under the conditions of a temperature of 20-100°C and a pH value of 1-7, the aldehyde raw material and the amino compound are polymerized in a molar ratio of (8-1):1, and the reaction time is controlled at 5-120 minutes; Then, with sodium hydroxide, sodium carbonate, the aqueous solution of potassium hydroxide or potassium carbonate, the pH value of reaction medium is adjusted to 7～10; Add the amino compound that is (0.1～2): 1 with aldehyde raw material molar ratio; Simultaneously Add phenolic materials with a molar ratio of (0-1.0):1 to aldehyde raw materials; control the reaction time until the turbidity point occurs, adjust the pH value to 8.0-8.5, stop the reaction; cool down to below 40°C, and discharge.

The aldehyde raw materials used can be: one or more compounds in formaldehyde, trioxane and paraformaldehyde, and urea-formaldehyde resin concentrate can also be used; the amino compounds used are: urea, thiourea and melamine One or two or more substances; the phenolic materials used are: phenol, resorcinol, tannin or other polyphenols; in order to better control the production cost of amino resin adhesives, it is best to use formaldehyde, urea and phenol as raw material.

Synthesis steps: First, formaldehyde and urea are mixed with (8-1):1 , preferably (5 ~ 2): 1 molar ratio to carry out polymerization reaction, the reaction time is controlled at 5 ~ 120min, preferably 10 ~ 40min then, with sodium hydroxide, sodium carbonate, potassium hydroxide or potassium carbonate etc. The aqueous solution adjusts the pH value of the reaction medium to 7-10, preferably to 7-8; add urea with a molar ratio of (0.1-2):1, preferably (0.3-1):1 to formaldehyde; simultaneously add The molar ratio to formaldehyde is (0-1.0): 1, preferably (0.1-0.5): 1 phenol; control the reaction time until the turbidity point occurs (1ml of the reaction solution is dropped into water at 20°C and appears cloudy), Adjust the pH value to 8.0-8.5, stop the reaction; cool down to below 40°C, and discharge.

Below is a kind of concrete example of implementing the present invention, but the present invention is not limited to this example:

Add 1000Kg of formaldehyde with a mass concentration of 37% in the reaction kettle, adjust the pH=7.0~7.5; start stirring, raise the temperature, and control the temperature at 50°C; add 211.5Kg of urea, after the dissolution is complete, adjust the pH=3.0, and control the reaction time for 15 Minutes; after the reaction, adjust the pH=7.0~8.0, add 370Kg urea, add 10Kg phenol after dissolving; raise the temperature to 80°C, control the pH value of the reaction medium to 7.0~8.0; react until the turbidity point appears, the viscosity is about 200~400mPa .s; adjust the pH value = 8.0 to 8.5, cool down to below 40°C, and discharge.

The following is another specific embodiment of the present invention, but the present invention is not limited to this example:

First, under the conditions of temperature 70°C and pH value 2-3, formaldehyde and urea are polymerized at a molar ratio of 3:1, and the reaction time is controlled at 40 minutes; then, sodium hydroxide, sodium carbonate, hydrogen Aqueous solutions of potassium oxide or potassium carbonate etc. adjust the pH value of the reaction medium to 7-8; add urea with a molar ratio of 0.8:1 to formaldehyde; simultaneously add phenol with a molar ratio of 0.4:1 to formaldehyde; control the reaction time until When the turbidity point appears (1ml of the reaction liquid is dripped into 20°C water and appears cloudy), adjust the pH value to 8.0-8.5, stop the reaction; cool down to below 40°C, and discharge.

(2) Bonding process

Add 100Kg of the adhesive of the present invention into the glue mixing machine, and then add 1-70Kg of active fillers, such as: flour, wood flour, bean flour, bark powder, peanut shell powder, etc.; fully stir until completely uniform, and adjust the glue 0.1<pH<7.0, preferably 1.0<pH<6.0, and then add 0.01-20% of the urea-formaldehyde resin mass percentage, preferably 0.1-5% urethane crosslinking agent, its molecular formula is:

Wherein: R ₁ is phenyl, tolyl, naphthyl, alkyl etc.;

R ₂ is a phenol group, an alcohol group, an imine group and the like.

The usual pre-pressing-high-temperature hot-pressing process conditions can be used for plate processing, and the usual sizing method and sizing amount can be used; the hot-pressing temperature used is 80-230°C; the pressure is: 0.5-3.0MPa; hot-pressing Time: 5~120min;

Or use the process of pre-pressing-heating (or standing at room temperature) to process the plate. Using this process can save energy and time-consuming hot-pressing procedures, reduce energy consumption, and improve production efficiency. The specific implementation method is to use the above-mentioned compounding method and common sizing method and sizing amount. Firstly, pre-pressing is carried out at a pressure of 0.5-3.0Mpa; the temperature is 0-230°C, preferably at room temperature; the pre-pressing time can be any period of time, but the best is 20-40min. Then, the pre-pressed board can be used for aging at a temperature of 0-200°C, preferably at room temperature, and the aging time can be any period of time, preferably 48 hours.

(3) post-treatment process

In order to further improve the comprehensive performance of the board, after the board is formed, the board is post-treated. The specific method is to use alkaline gas, liquid or solid to carry out alkaline treatment on the board. The characteristic is that it can significantly improve the urea-formaldehyde resin. The physical and chemical properties of the material improve the strength, water resistance and weather resistance of the board; the alkaline materials used include: sodium carbonate, sodium hydroxide, potassium carbonate, potassium hydroxide, calcium hydroxide, barium hydroxide, magnesium hydroxide , ammonia water, ammonia gas, ammonium carbonate, ammonium bicarbonate, urea, methylamine, ethylamine, ethylenediamine, diethylamine, triethylamine, diethanolamine, triethanolamine and other compounds; a single above compound can be used, or Use the original solution of their mixture or their aqueous solution; its main feature is that the pH value of their aqueous solution is greater than 7; when the alkaline material used is gas, use the alkaline gas in a closed container to process the plate Cyclic pressurized fumigation treatment; when the alkaline material used is liquid or its aqueous solution, the method of immersing the plate in the alkaline solution is used for treatment, or the plate is hot-pressed after soaking, or it can be heated in a closed container Fumigate the board after vaporizing the solid or liquid alkaline material; the best effect can be achieved by using the circulating gas or liquid during treatment; at the same time, in order to increase the treatment effect, a certain amount of additives are added to the fumigation gas or soaking liquid, such as: Penetrant (surfactant); the closed container and liquid processing container used can adopt all available closed environments; the processing time can be any time period greater than 0 hours, preferably 0.5 to 4.0 hours; the processing temperature range can be -50-250°C, preferably -10-60°C; the treatment pressure is 0-200 atmospheres, preferably 1-5 atmospheres; after the alkali treatment process is completed, the plate can be dried by any possible method. The dried board is the finished product.

Product technical indicators, using this patented technology to produce water-resistant panels (take the 28cm thick container floor as an example), according to relevant national standards, the performance of plywood can reach:

(1) Dry bonding strength: The water-resistant sheet produced by this patented technology (taking a 28cm-thick container floor as an example) is rolled back and forth 9 times by a 7.5-ton truck without deformation.

(2) Water resistance: use the water-resistant sheet produced by this patented technology (take the container floor with a thickness of 28cm as an example), boil it in boiling water for 4 hours, dry it in an oven at (63±3)°C for 20 hours, and then boil it in boiling water for 4 hours. hours, the residual strength is greater than 3.0MPa.

Or after continuous boiling in boiling water for 72 hours, after drying in an oven at (63±3)°C for 20 hours, the residual strength is greater than 3.0MPa.

(3) Formaldehyde emission: in line with E1 standard.

Claims (8)

1. An amino resin adhesive for the preparation of super-strong water-resistant bamboo and wood boards is characterized in that it is prepared by synthesizing urea-formaldehyde resin under a strong acid system, so that the urea-formaldehyde resin molecule has a large amount of active branched chain structures. 2. According to claim 1, the amino resin adhesive for the preparation of super-strong water-resistant bamboo and wood panels is characterized in that it is made by the following method: Firstly, under the conditions of a temperature of 20-100°C and a pH value of 1-7, the aldehyde raw material and the amino compound are polymerized in a molar ratio of (8-1):1, and the reaction time is controlled at 5-120 minutes; Then, with sodium hydroxide, sodium carbonate, the aqueous solution of potassium hydroxide or potassium carbonate, the pH value of reaction medium is adjusted to 7～10; Add the amino compound that is (0.1～2): 1 with aldehyde raw material molar ratio; Simultaneously Add phenolic materials with a molar ratio of (0-1.0):1 to aldehyde raw materials; control the reaction time until the turbidity point occurs, adjust the pH value to 8.0-8.5, stop the reaction; cool down to below 40°C, and discharge. 3. According to claim 2, the amino resin adhesive for preparing super-strong water-resistant bamboo and wood panels is characterized in that it is made by the following method: Firstly, under the conditions of a temperature of 60-90°C and a pH value of 2-3, the aldehyde raw material and the amino compound are polymerized in a molar ratio of (5-2):1, and the reaction time is controlled within 10-40 minutes; Then, with sodium hydroxide, sodium carbonate, the aqueous solution of potassium hydroxide or potassium carbonate, the pH value of the reaction medium is adjusted to 7～8; Add the amino compound that is (0.3～1): 1 with the aldehyde raw material molar ratio; Simultaneously Add phenolic materials with a molar ratio of (0.1-0.5):1 to aldehyde raw materials; control the reaction time until the turbidity point occurs, adjust the pH value to 8.0-8.5, stop the reaction; cool down to below 40°C, and discharge. 4. The amino resin adhesive for preparing super-strong water-resistant bamboo and wood boards according to claim 3, wherein the aldehyde raw material can be one or more of formaldehyde, paraformaldehyde and paraformaldehyde , can also use urea-formaldehyde resin to concentrate the liquid; the amino compound is one or more of urea, thiourea and melamine; the phenolic material is phenol, resorcinol, tannin or other polyphenols . 5. The amino resin adhesive for preparing super water-resistant bamboo and wood boards according to claim 4, characterized in that said aldehyde raw material is formaldehyde; said amino compound is urea; and said phenolic material is phenol. 6. A processing technology for preparing super-strong water-resistant bamboo and wood panels with amino resin adhesive as claimed in claim 1, the processing technology is as follows: Put 100Kg of the above-mentioned adhesive into the glue mixing machine, then add 1-70Kg of active filler, fully stir until it is completely uniform, adjust the glue solution to 0.1<pH<7.0, and then add a cross-linking agent accounting for 0.01-20% of the mass percentage of urea-formaldehyde resin , Use the usual process conditions for plate processing, use the usual sizing method and sizing amount, the hot pressing temperature used is 80-230°C; the pressure is 0.5-3.0MPa; the amount of sizing on one side is 100-600g/m ² ; The hot pressing time is 5-120 minutes; Or use the pre-pressing-heating aging process to process the board, use the above-mentioned glue compounding method and the usual sizing method and sizing amount; first implement the pre-pressing, at a pressure of 0.5-3.0Mpa; the temperature is 0-230°C, It is best at room temperature; the pre-pressing time can be any time period, but it is preferably 20-40 minutes; then, the plate after pre-pressing can be used at a temperature of 0-100 ° C, and it is best to leave it at room temperature for aging. The curing time can be any period of time, preferably 48 hours; Subsequent treatment process: Alkaline treatment of the board with alkaline gas, liquid or solid can significantly improve the physical and chemical properties of the urea-formaldehyde resin material, improve the strength, water resistance and weather resistance of the board, and the pH value of their aqueous solution is greater than 7; when the alkali used When the alkaline material is gas, use the alkaline gas in a closed container to carry out cyclic pressure fumigation treatment on the plate; when the alkaline material used is liquid or its aqueous solution, soak the plate in the alkaline solution. method, or heat-press the board after soaking, or fumigate the board after vaporizing solid or liquid alkaline materials in a closed container; at the same time, in order to increase the treatment effect, add a certain amount of Auxiliary, after the alkali treatment process is completed, the board can be dried by any possible method, and the dried board is the finished product. 7. The processing technology for preparing super water-resistant bamboo and wood boards according to claim 10, characterized in that the active fillers are flour, wood flour, bean flour, bark powder and peanut shell powder; The joint agent is 0.01-20% carbamate compound, and its molecular formula is:

Wherein: R ₁ is phenyl, tolyl, naphthyl, alkyl etc.; R ₂ is a phenol group, an alcohol group, an imine group and the like. 8. The processing technology for preparing super water-resistant bamboo and wood boards according to claim 10, characterized in that said alkaline materials are sodium carbonate, sodium hydroxide, potassium carbonate, potassium hydroxide, calcium hydroxide, hydrogen Stock solutions of barium oxide, magnesium hydroxide, ammonia water, ammonia gas, ammonium carbonate, ammonium bicarbonate, urea, methylamine, ethylamine, ethylenediamine, diethylamine, triethylamine, diethanolamine, triethanolamine compounds or their Aqueous solution; the above compounds can be used alone, or the aqueous solution of a mixture of two or more of them can be used, and the pH value of the aqueous solution is greater than 7; the best effect can be achieved by using circulating gas or liquid during treatment.