CN102977846B - Adhesive for plywood and method for preparing same - Google Patents

Abstract

The invention provides an adhesive for a plywood, prepared from the following raw materials according to parts by weight: 70-80 parts of dispersion medium, 20-35 parts of degreased soyabean protein powder, 0.5-3 parts of sodium carbonate, 2-6 parts of urea, 1-2 parts of complexing agent and 1-5 parts of enhancer. The adhesive provided by the invention has the characteristics that all the components have excellent mutual synergistic effect, a materials such as a metal salt is compounded with the soybean protein, and simultaneously, glutaraldehyde is taken as the enhancer so that the problem of poor water resistence of the common soybean protein adhesive is solved; therefore, the adhesive is capable of meeting the waterproof requirement of the adhesive for the plywood and guaranteeing the practical performance of the soybean protein adhesive; and the plywood prepared by using the adhesive provided by the invention is capable of meeting the international requirements of the class II plywood. Besides, the invention also provides a method for preparing the adhesive for the plywood; and the method is simple in process, convenient for operation and suitable for popularization and application.

Description

Adhesive for plywood and preparation method thereof

technical field

The invention relates to an adhesive and a preparation method thereof, in particular to an adhesive for preparing plywood and a preparation method thereof.

Background technique

Over the past 30 years, my country's wood-based panel production has grown rapidly. In 2010, the total output of my country's wood-based panels was 153.6 million cubic meters, accounting for about 50% of the world's weight, including 71.3966 million cubic meters of plywood and 16.5228 million cubic meters of blockboard. The total output of wood-based panels, plywood, furniture, and wood flooring has ranked first in the world for many years in a row.

The adhesives commonly used in the production of wood-based panels are formaldehyde-based synthetic resins, mainly urea-formaldehyde resins and their modified products. Although after years of hard work, the production level of wood-based panel adhesives in my country has been greatly improved, and the environmental protection characteristics of wood-based panels and their products have been greatly improved, but the wood-based panels and their products produced by many enterprises (furniture, wooden floors, indoor wood There is still a relatively serious formaldehyde release problem, which is the main source of formaldehyde pollution in indoor air pollution.

At present, there are mainly four methods to reduce formaldehyde emission from wood-based panels: 1) Use low molar ratio modified urea-formaldehyde resin adhesive; 2) Use other environmentally friendly adhesives; 3) Add formaldehyde scavenger to urea-formaldehyde resin adhesive for wood-based panels ; 4) Post-processing of wood-based panels. But all there are many defectives in these technical methods. For example: 1) Although the use of a low molar ratio modified urea-formaldehyde resin adhesive can effectively reduce the formaldehyde emission of wood-based panel products, the bonding strength of the product is often reduced, which cannot meet the requirements of use; and the curing time is prolonged and the production efficiency is reduced; 2) The use of other environmentally friendly adhesives, such as isocyanate adhesives, has led to a substantial increase in the production cost of wood-based panels, which is difficult for enterprises and users to accept; the wood-based panels prepared with ordinary protein adhesives have low bonding strength, and the wood-based panels are easy to open; 3) In artificial Adding formaldehyde scavenger to the urea-formaldehyde resin adhesive for boards can effectively reduce the release of free formaldehyde from wood-based panels, but it often reduces the bonding strength of wood-based panels; at the same time, the price of general formaldehyde scavenger is often much higher than that of urea-formaldehyde resin adhesives. Just improved product cost, reduced product competitiveness; 4) carry out post-processing to wood-based panel, disclose a kind of adopting ammonia gas vacuum method to prepare E1/EO level environment-friendly type wood-based panel in the invention patent application of CN1526528 as publication number Manufacturing process; the utility model patent with publication number CN2394770 discloses a treatment device for reducing formaldehyde emission from wood-based panels. These post-processing methods not only make the manufacturing process of wood-based panels complicated, but also require huge investment in post-processing equipment and significant production costs. improve. In summary, although the above measures can effectively reduce the release of free formaldehyde from wood-based panels, they cannot completely solve the problem of formaldehyde release, or cannot be popularized due to reasons such as high production costs.

In addition, Chinese application 200810032289.X discloses a new type of wood adhesive, which includes the following components: water: 100 parts by weight; raw material containing protein: 3-45 parts by weight; acidity regulator: 0.01-15 parts by weight; Group compound: 0.01 to 15 parts by weight; curing agent: 0.01 to 15 parts by weight; preservative: 0.01 to 15 parts by weight; viscosity modifier: 0 to 15 parts by weight; filler: 0 to 10 parts by weight; drier: 0 ~15 parts by weight. The novel wood adhesive hardly releases formaldehyde during production and use, and in addition, it has high water resistance. However, in the actual use process, it was found that due to its complex components and the lack of obvious synergistic effect between them, its stability and viscosity were not ideal, and its practicability was poor. Therefore, it is still necessary to propose an environmentally friendly soybean protein with excellent performance. adhesive.

Contents of the invention

The first purpose of the present invention is to provide a high-quality adhesive for plywood against various defects in the prior art, which does not contain formaldehyde and is an environmentally friendly adhesive for plywood.

The second object of the present invention is to provide a method for preparing the above-mentioned adhesive for plywood, the method is simple in process, convenient in operation and suitable for popularization and application.

To achieve the first purpose, the present invention adopts the following technical solutions:

An adhesive for plywood, wherein the adhesive is prepared in parts by weight from the following raw materials: 70-80 parts of dispersion medium, 20-35 parts of defatted soybean protein powder, 0.5-3 parts of sodium carbonate, 2 parts of urea -6 parts, 1-2 parts of complexing agent, 1-5 parts of reinforcing agent.

The above-mentioned adhesive is prepared with defatted soybean protein powder as the main body. As a renewable resource, soybean protein helps to solve the problem of exhaustion of synthetic fossil raw materials used in conventional plywood adhesives, and conforms to the principles of environmental protection and sustainable development. Moreover, soybean protein is rich in sources and can be stably produced in large quantities, which has great advantages.

The soybean protein adhesive is processed from defatted soybean protein powder, effectively utilizes soybean processing residues, comprehensively utilizes resources, saves production costs, and increases the added value of products.

Wherein, the above-mentioned defatted soybean protein powder, as a commonly used soybean processing residue, is understood and easily obtained by those skilled in the art, and the present invention is not particularly limited thereto.

Wherein, it is preferred that the adhesive includes, in parts by weight: 72-76 parts of dispersion medium, 25-30 parts of defatted soybean protein powder, 1-2.5 parts of sodium carbonate, 3-4 parts of urea, 1.2-1.8 parts of complexing agent, Enhancer 2-4 parts.

The aforementioned complexing agents at least include but are not limited to zinc chloride, copper sulfate and zirconium carbonate. Those skilled in the art can predict that under the premise of ensuring that the complexing agent contains zinc chloride, copper sulfate and zirconium carbonate, other effective complexing agents can be further added to realize the present invention, and the specific selection is determined by those skilled in the art. master.

In order to simplify the composition of the adhesive, the present invention preferably adopts a complexing agent containing only zinc chloride, copper sulfate and zirconium carbonate, and further finds that when the weight between zinc chloride, copper sulfate and zirconium carbonate in the complexing agent When the ratio is: 0.8-1.2: 0.5-1.5: 0.5-1.5, the complexation reaction can be better promoted, and finally high-quality adhesives can be obtained, among which zinc chloride, copper sulfate and carbonic acid in the complexing agent are more preferred The weight ratio of zirconium is: 0.9-1.0:0.8-1.2:0.8-1.2. When preparing the complexing agent, you only need to accurately weigh each formula, then grind it and mix it evenly.

In the present invention, a glyoxal solution with a mass concentration of 30-40% is used as a reinforcing agent, and the compounding of metal salt and other substances with soybean protein is used in the present invention, and the glyoxal reinforcing agent is used to solve the problem of poor water resistance of common soybean protein adhesives , can meet the water resistance requirements of the adhesive used for plywood, ensure the practical performance of the soy protein adhesive, and the plywood prepared by the adhesive of the present invention can meet the requirements of class II plywood in the national standard.

In the adhesive of the present invention, the dispersion medium is water, preferably demineralized water.

The invention treats the soy protein as an adhesive for plywood, does not contain free formaldehyde, does not have the problem of formaldehyde release in the glued plywood, and completely solves the problem of formaldehyde pollution in indoor air caused by artificial boards.

The inventor found in the actual research process that although other complexing agents and reinforcing agents commonly used in the prior art are used to replace the adhesive obtained by the auxiliary agent described in the present invention, or the soybean protein mucus without adding any auxiliary agent also has certain viscosity, but in It has been found in experimental tests that the stability and bonding strength of the above-mentioned adhesives are far from reaching the standard, and cannot be popularized in practical applications. However, due to the scientific and reasonable design of the components and dosages of the adhesive described in the present invention, they form the best synergistic effect with each other, so the water resistance, strength and stability of the adhesive are significantly improved.

In addition, in order to achieve the second purpose, the present invention adopts the following technical solutions:

A kind of preparation method of above-mentioned adhesive, described method comprises the steps:

1) Add defatted soybean protein powder and sodium carbonate into the dispersion medium, stir evenly to obtain a mixture;

2) Add complexing agent to the mixture and stir evenly;

3) Continue to add the enhancer, stir evenly, and you are done.

In the preparation method of the present invention, the preferred step 1 is: adding sodium carbonate and defatted soy protein powder into the dispersion medium, stirring evenly, and keeping the temperature at 40-80° C. for 3-6 hours to obtain the mixture.

In the preparation method of the present invention, the preferred step 2 is: cooling the mixture to 25-35° C., adding a complexing agent and stirring evenly.

As a kind of best implementation mode of the present invention, described method comprises the steps:

1) Add sodium carbonate and defatted soy protein powder into the dispersion medium, stir evenly, and then keep warm at 45-70°C for 4-5 hours to obtain a mixture;

2) After cooling the mixture to 30-32°C, add complexing agent and stir evenly to make complexation reaction;

3) Continue to add the reinforcing agent and stir evenly to obtain the adhesive.

Adopt above-mentioned technical scheme, the present invention has the following advantages:

(1) The formaldehyde-free soy protein adhesive of the present invention is easy to use, and there is no need to modify the existing wood-based panel production equipment and process, so there is no need to increase equipment investment.

(2) The formaldehyde-free adhesive of the present invention is cheap. At present, the price of urea-formaldehyde resin adhesive with 50% solid content and low free formaldehyde content is 1800-2500 yuan/ton, the price of phenolic resin adhesive is 5000-6000 yuan/ton, the price of soybean protein adhesive (35% solid content) of the present invention At 1500-2000 yuan/ton, the price is far lower than that of phenolic resin adhesives and close to that of urea-formaldehyde resin adhesives. The adhesive prepared by the invention can replace the conventional formaldehyde-containing adhesive for plywood, and the total amount of glue used in the preparation of plywood remains unchanged, so the use cost is equivalent to that of urea-formaldehyde resin adhesive and far lower than the use cost of phenolic resin adhesive. Therefore, the soybean protein adhesive of the present invention has good application prospects.

Detailed ways

Example 1

1) Prepare materials according to the following weight ratio:

Among them, the complexing agent is a powder prepared by the School of Materials Science and Technology of Beijing Forestry University, which includes zinc chloride: 0.8 parts, copper sulfate: 0.5 parts, zirconium carbonate: 0.5 parts, and the above components are ground and mixed evenly; The enhancer is glyoxal solution with a mass concentration of 30%.

2) Add all the demineralized water, sodium carbonate, soybean protein powder and urea into the reaction kettle equipped with a stirrer, thermometer and condensing device, and stir evenly.

3) Heating to 45-47°C, keeping it warm for 3 hours to obtain a mixture.

4) Cool the mixture down to 30°C to make a uniform soy protein mucus.

5) Add a complexing agent to the soy protein mucus and stir evenly to make it undergo complexation reaction.

6) Continue to add the enhancer to it and stir evenly to obtain the soy protein adhesive. The performance and quality indicators of the adhesive obtained in this embodiment are shown in Table 1.

Example 2

1) Prepare materials according to the following weight ratio:

Among them, the complexing agent is a powder prepared by the School of Materials Science and Technology of Beijing Forestry University, including 1.2 parts of zinc chloride, 1.5 parts of copper sulfate, and 1.5 parts of zirconium carbonate. 30% glyoxal solution.

2) Add all the demineralized water, sodium carbonate, urea, soybean protein powder into the reaction kettle equipped with agitator, thermometer and condensing device, and stir evenly;

3) Heating to 40-42°C and reacting for 6 hours to obtain the mixture;

4) Cool the mixture down to 30°C to make a uniform soy protein mucus.

5) Add a complexing agent to the soy protein mucus and stir evenly to make it undergo complexation reaction.

6) Continue to add the enhancer to it and stir evenly to obtain the soy protein adhesive. The performance and quality indicators of the adhesive obtained in this embodiment are shown in Table 1.

Example 3

1) Prepare materials according to the following weight ratio:

Among them, the complexing agent is a powder prepared by the School of Materials Science and Technology, Beijing Forestry University, including the following components in weight proportions: 0.8 parts of zinc chloride, 1.5 parts of copper sulfate, and 1 part of zirconium carbonate, which are ground evenly and mixed Uniform; the enhancer is a solution of glyoxal with a mass concentration of 30%.

2) Add all the demineralized water, sodium carbonate, urea and soybean protein powder into the reaction kettle equipped with agitator, thermometer and condensing device, and stir evenly.

3) Heating to 68-70°C and reacting for 5 hours to obtain a mixture.

4) Cool the mixture down to 30°C to make a uniform soy protein mucus.

5) Add a complexing agent to the soy protein mucus and stir evenly to make it undergo complexation reaction.

6) Continue to add the enhancer to it and stir evenly to obtain the soy protein adhesive. The performance and quality indicators of the adhesive obtained in this embodiment are shown in Table 1.

Example 4

1) Prepare materials according to the following weight ratio:

Among them, the complexing agent is a powder prepared by the School of Materials Science and Technology of Beijing Forestry University, including 1 part of zinc chloride, 1 part of copper sulfate, and 1 part of zirconium carbonate, which are ground and mixed evenly; the reinforcing agent is a mass concentration of 40% glyoxal solution.

2) Add all the demineralized water, sodium carbonate, urea, soybean protein powder into the reaction kettle equipped with agitator, thermometer and condensing device, and stir evenly;

3) Heating to 78-80°C and reacting for 4 hours to obtain the mixture;

4) Cool the mixture down to 25°C to make a uniform soy protein mucus.

5) Add a complexing agent to the soy protein mucus and stir evenly to make it undergo complexation reaction.

6) Continue to add the enhancer to it and stir evenly to obtain the soy protein adhesive. The performance and quality indicators of the adhesive obtained in this embodiment are shown in Table 1.

Example 5

1) Prepare materials according to the following weight ratio:

Among them, the complexing agent is a powder prepared by the School of Materials Science and Technology, Beijing Forestry University, including the following components in weight proportions: 0.8 parts of zinc chloride, 1.2 parts of copper sulfate, and 1.2 parts of zirconium carbonate, which are ground evenly and mixed Uniform; the enhancer is a solution of glyoxal with a mass concentration of 35%.

2) Add all the demineralized water, sodium carbonate, urea and soybean protein powder into the reaction kettle equipped with agitator, thermometer and condensing device, and stir evenly.

3) Heating to 58-60°C and reacting for 3.5 hours to obtain a mixture.

4) Cool down the mixture to 35°C to make a uniform soy protein mucus.

5) Add a complexing agent to the soy protein mucus and stir evenly to make it undergo complexation reaction.

6) Continue to add the enhancer to it and stir evenly to obtain the soy protein adhesive.

The performance and quality indicators of the adhesive obtained in this embodiment are shown in Table 1.

The performance index of table 1 soybean protein adhesive

In order to verify the performance of the adhesive described in the present invention, the inventor further carried out a series of experiments. Due to space limitations, only the most representative data are listed here.

Test example 1

In this test example, the products of Examples 1-3 of the present invention and Comparative Examples 1-6 were used to manufacture three-layer plywood of 450×450 mm.

in:

Comparative examples 1-3: using the soy protein mucus obtained in step 4 in Examples 1-3 as the adhesive respectively;

Comparative Example 4: Compared with Example 1 of the present invention, the only difference is that no complexing agent is added in this example.

Comparative Example 5: Compared with Example 1 of the present invention, the only difference is that no enhancer is added in this example.

Comparative example 6: Example 7 of Chinese application 200810032289.X (wood adhesive prepared mainly from defatted soybean meal powder and soybean protein isolate)

Poplar veneer: dry to 8-12% moisture content; thickness 1.6mm;

The veneer adhesive used the products of Examples 1-3 of the present invention and the products of Comparative Examples 1-6.

Plywood is prepared according to the normal process as follows:

Glue sizing: Glue is applied on both sides of the core board, and the amount of glue applied is 220-300g/m ² .

Aging method and time: closed aging, 10-30 minutes.

Pre-compression pressure and time: pre-compression for 30 minutes, pressure 0.8MPa.

Hot pressing pressure: 1.2MPa, hot pressing temperature is 120-130°C, hot pressing time is 70s/mm.

According to the test method of GB/T17657-1999 "Physical and Chemical Properties of Wood-based Panels and Decorated Wood-based Panels", the performance test of the produced plywood products is carried out. The test results are shown in Table 2.

Table 2 Formaldehyde emission and bonding strength of glued plywood

The above-mentioned test results show that the formaldehyde emission of the plywood manufactured by the formaldehyde-free soybean protein adhesive of the present invention is very low (for the release of formaldehyde from the wood body), and the bonding strength of the plywood is above 1.10MPa, reaching the standard of Class II plywood in the national standard (poplar wood≥ 0.70MPa). In addition, the experimental results of Comparative Examples 1-5 show that changing the composition of reinforcing agent or complexing agent, or without adding reinforcing agent and complexing agent, the bonding strength of the obtained adhesive is far from the standard, and cannot be used in practice. . The experimental results of Comparative Example 6 show that the bonding strength of the adhesive obtained in the present invention is significantly better than that of the prior art.

Test example 2

In this test example, stability tests were carried out on the products of Examples 1-3 of the present invention and Comparative Examples 1-6 respectively.

in:

Comparative example 1-3: using the soy protein mucus in embodiment 1-3 as adhesive;

Comparative Example 4: Compared with Example 1 of the present invention, the only difference is that no complexing agent is added in this example.

Comparative Example 5: Compared with Example 1 of the present invention, the only difference is that no enhancer is added in this example.

Comparative example 6: Example 7 of Chinese application 200810032289.X (wood adhesive prepared mainly from defatted soybean meal powder and soybean protein isolate)

Test method: Refer to GB-T 14074-2006 wood adhesive and its resin test method to detect the stability of the adhesive and the change of the viscosity of the adhesive.

Test results: within 5 days of the experimental test, the appearance and viscosity of the adhesives in Examples 1-3 did not change significantly, while Comparative Examples 1-6 all had varying degrees of water precipitation, and the viscosity also decreased significantly. Among them, Comparative Example 1 -3 is the most obvious, followed by Comparative Example 4-6.

The above test results show that the stability of the adhesive obtained by the present invention is significantly better than other soybean protein adhesives.

Although the present invention has been described in detail with general descriptions and specific embodiments above, it is obvious to those skilled in the art that some modifications or improvements can be made on the basis of the present invention. Therefore, the modifications or improvements made on the basis of not departing from the spirit of the present invention all belong to the protection scope of the present invention.

Claims (9)

1. An adhesive for plywood, characterized in that: the adhesive is prepared in parts by weight from raw materials comprising the following proportions: 70-80 parts of dispersion medium, 20-35 parts of defatted soybean protein powder, 0.5 parts of sodium carbonate -3 parts, 2-6 parts of urea, 1-2 parts of complexing agent, 1-5 parts of enhancer, the enhancer is glyoxal solution with a mass concentration of 30-40%. 2. The adhesive according to claim 1, characterized in that: the adhesive is prepared in parts by weight from raw materials comprising the following proportions: 72-76 parts of dispersion medium, 25-30 parts of defatted soybean protein powder, Sodium carbonate 1-2.5 parts, urea 3-4 parts, complexing agent 1.2-1.8 parts, enhancer 2-4 parts. 3. The adhesive according to claim 1 or 2, characterized in that the complexing agent comprises at least zinc chloride, copper sulfate and zirconium carbonate. 4. The adhesive according to claim 3, characterized in that: the weight ratio between zinc chloride, copper sulfate and zirconium carbonate in the complexing agent is: 0.8-1.2:0.5-1.5:0.5-1.5 . 5. The adhesive according to claim 1, characterized in that: the dispersion medium is demineralized water. 6. a preparation method of the adhesive described in any one of claims 1-5, said method comprising the steps of: 1) adding defatted soybean protein powder, urea and sodium carbonate into the dispersion medium, stirring evenly to obtain a mixture; 2) Add complexing agent in the mixture, stir evenly; 3) Continue to add the enhancer, stir evenly, and you get it. 7. The preparation method according to claim 6, characterized in that: said step 1 is: adding sodium carbonate and defatted soy protein powder into the dispersion medium, stirring evenly and then incubating at 40-80°C for 3-6 hours to obtain mixture. 8. The preparation method according to claim 6, characterized in that: said step 2 is: cooling the mixture to 25-35°C, adding complexing agent and stirring evenly. 9. preparation method according to claim 6, is characterized in that: described method comprises the steps: 1) Add sodium carbonate, urea and defatted soy protein powder into the dispersion medium, stir evenly, and then keep warm at 45-70°C for 4-5 hours to obtain a mixture; 2) After the mixture is cooled to 30-32°C, a complexing agent is added and stirred evenly; 3) Continue to add the reinforcing agent and stir evenly to obtain the adhesive.