Environment-friendly formaldehyde-free glue for plywood and preparation process thereof

Abstract

The invention provides environment-friendly formaldehyde-free glue for plywood and a preparation process of the environment-friendly formaldehyde-free glue. The environment-friendly formaldehyde-free glue for the plywood comprises the following components in parts by mass: 10-15 parts of polyvinyl alcohol, 60-85 parts of an epoxy resin compound, 2-7 parts of an organic curing agent, 5-12 parts of filler, 40-60 parts of a sodium silicate aqueous solution, 2-4 parts of a catalyst, 2-10 parts of a viscosity modifier, 0.01-1 part of inorganic salt and 1-5 parts of an organic stabilizer, the epoxy resin compound comprises modified epoxy resin, and the modified epoxy resin is prepared by reaction of epoxy resin and dimethyldichlorosilane. The environment-friendly formaldehyde-free glue for the plywood, which is prepared by using the components and the content provided by the invention, has good tensile shear strength and tensile strength, has high peel strength when being used for bonding boards, and still has high peel strength even if being placed in a high-humidity environment for a long time.

Description

Technical Field

[0001] The invention belongs to the field of adhesives, and in particular relates to an environmentally friendly formaldehyde-free glue for plywood and a preparation process thereof. Background Art

[0002] During the production and application of traditional plywood, the release of formaldehyde has been a problem that has troubled manufacturers and consumers. Since formaldehyde is widely considered to be one of the main sources of indoor air pollution, long-term exposure to formaldehyde not only poses a serious threat to human health, such as causing respiratory diseases, skin inflammation and even cancer, but also has an irreversible impact on the environment. Although there are plywood products claiming to be "formaldehyde-free" or "low formaldehyde" on the market, most of these products still use glue containing formaldehyde, but the formaldehyde content is reduced through technical means. Although these methods have reduced the problems caused by formaldehyde to a certain extent, they have not fundamentally solved the existence of formaldehyde and cannot completely eliminate the potential risks to the environment and human health.

[0003] In order to solve the formaldehyde problem from the source, the plywood industry has introduced the production technology of environmentally friendly glue, which not only effectively reduced the pollution to the environment, but also greatly reduced the emission of harmful substances in the traditional production process. However, most of the environmentally friendly glues on the market have a more complicated production process of formaldehyde-free glues and the required raw materials are more expensive, which leads to their prices being higher than traditional formaldehyde-containing glues, increasing the purchasing cost of consumers; a large number of researchers have studied for a long time and have obtained formaldehyde-free glues that perform well in environmental protection, but they are still inferior in terms of peel strength, waterproof durability, etc. For example, the patent with announcement number "CN104449411B" discloses an adhesive and its preparation method and its application in plant fiberboard or artificial board. By using sodium silicate aqueous solution, brine, nano-silica, filler, modifier, stabilizer and inorganic adhesive, the obtained adhesive has a higher peel strength, but the peel strength and waterproof durability are poor when the relative humidity of the air is high. Summary of the invention

[0004] The purpose of the present invention is to provide an environmentally friendly formaldehyde-free glue for plywood and a preparation process thereof, so as to solve the problem of poor peeling strength and waterproof durability when the relative humidity of the air is high, as mentioned in the above background technology.

[0005] To achieve the above-mentioned purpose, the present invention provides the following technical solutions: on the one hand, an environmentally friendly formaldehyde-free glue for plywood, the environmentally friendly formaldehyde-free glue for plywood comprising the following components in parts by weight: 10-15 parts of polyvinyl alcohol, 60-85 parts of epoxy resin compound, 2-7 parts of organic curing agent, 5-12 parts of filler, 40-60 parts of sodium silicate aqueous solution, 2-4 parts of catalyst, 2-10 parts of viscosity modifier, 0.01-1 parts of inorganic salt, and 1-5 parts of organic stabilizer; the epoxy resin compound comprises modified epoxy resin, and the modified epoxy resin is prepared by reacting epoxy resin and dimethyldichlorosilane.

[0006] As a further improvement, the epoxy resin composite is a composition of epoxy resin and modified epoxy resin.

[0007] As a further improvement, the organic stabilizer is prepared by reacting trimethylamine hydrochloride and a silane coupling agent.

[0008] As a further improvement, the mass ratio of the epoxy resin to the modified epoxy resin is 1:0.1-0.5.

[0009] As a further improvement, the filler is at least one of nano silicon dioxide, magnesium oxide and aluminum oxide.

[0010] As a further improvement, the catalyst is at least one of methyl acetate, ethyl acetate, and o-sulfonylbenzoimide.

[0011] As a further improvement, the organic curing agent is 2-ethyl-4-methylimidazole.

[0012] As a further improvement, the preparation method of the modified epoxy resin comprises the following steps:

[0013] The epoxy resin and the organic solvent are placed in a reaction kettle to be fully dissolved, and then dimethyldichlorosilane, a catalyst and an amine compound are added, and the temperature is raised to 45-60° C. to fully react. After the reaction is completed, the modified epoxy resin is purified to obtain the modified epoxy resin.

[0014] As a further improvement, the preparation method of the organic stabilizer comprises the following steps:

[0015] The silane coupling agent, trimethylamine hydrochloride and an organic solvent are placed in a reactor, heated to a suitable temperature, and then fully reacted. After the reaction is completed, the organic stabilizer is obtained by vacuum distillation, washing and drying.

[0016] As a further improvement, the filler includes but is not limited to nano silicon dioxide and talc.

[0017] As a further improvement, the viscosity regulator includes but is not limited to chitosan.

[0018] As a further improvement, the inorganic salt includes but is not limited to trisodium phosphate and magnesium chloride.

[0019] On the other hand, the present invention also provides a process for preparing an environmentally friendly formaldehyde-free glue for plywood, comprising the following steps:

[0020] (1) Stirring the polyvinyl alcohol and epoxy resin composite until mixed;

[0021] (2) adding an organic curing agent, a sodium silicate aqueous solution, a viscosity modifier, a filler, a catalyst, an inorganic salt, and an organic stabilizer to the mixture in step (1), and then mixing the mixture to remove bubbles to obtain an environmentally friendly formaldehyde-free glue for plywood.

[0022] Compared with the prior art, the beneficial effects of the present invention are: the environmentally friendly formaldehyde-free glue for plywood prepared using the components and contents provided in the present application has good tensile shear strength and tensile strength, and the prepared glue has high peel strength when used for bonding boards, and even when placed for a long time in a high humidity environment, it still has high peel strength and better bonding properties. DETAILED DESCRIPTION

[0023] The present invention will be described below in conjunction with specific embodiments. It should be noted that the following embodiments are examples of the present invention and are only used to illustrate the present invention, but not to limit the present invention. Other combinations and various modifications within the concept of the present invention may be performed without departing from the spirit or scope of the present invention.

[0024] In the following embodiments, except for modified epoxy resin A and organic stabilizer A, the other compound monomers and related reagents used can be purchased from the market. Among them, epoxy resin was purchased from Guangzhou Korina New Materials Co., Ltd., model EP CYD-128; sodium silicate aqueous solution was purchased from Sichuan Shunmei New Materials Co., Ltd.; polyvinyl alcohol was purchased from Guangzhou Xingchuangzhi New Materials Co., Ltd., model RS235; chitosan was purchased from Shaanxi Langde Biotechnology Co., Ltd., model A14511; nano-silica was purchased from Shanghai Zhenlishi Network Technology Co., Ltd., model Aerosil R972.

[0025] The preparation method of modified epoxy resin A comprises the following steps:

[0026] 50 g of epoxy resin and 27 mL of ethyl acetate were placed in a reaction kettle and fully dissolved at 40°C. Then, 2 g of dimethyldichlorosilane, 0.32 g of dibutyltin dilaurate and 12.5 g of triethylamine were added. The temperature was raised to 50°C and fully reacted. After reacting for 8 hours, the mixture was washed with deionized water 6 times and distilled under reduced pressure to obtain modified epoxy resin A.

[0027] The preparation method of organic stabilizer A comprises the following steps:

[0028] 50 g of silane coupling agent KH560, 20 g of trimethylamine hydrochloride and 35 mL of anhydrous ethanol were placed in a reactor, heated to 70°C, and fully reacted. After reacting for 6 hours, the mixture was distilled under reduced pressure, washed with petroleum ether 4 times, and dried at 35°C for 2 hours to obtain an organic stabilizer A.

[0029] The preparation process of the environmentally friendly formaldehyde-free glue for plywood prepared in Examples 1-5 and Comparative Examples 1-2 comprises the following steps:

[0030] (1) Stirring the polyvinyl alcohol and epoxy resin composite until uniformly mixed at a stirring speed of 50 r / min;

[0031] (2) adding an organic curing agent, a sodium silicate aqueous solution, a viscosity modifier, a filler, a catalyst, an inorganic salt, and an organic stabilizer to the mixture in step (1), and then mixing and removing bubbles to obtain an environmentally friendly formaldehyde-free glue for plywood, wherein the mixing speed is 50 r / min.

[0032] The components required in Examples 1-5 and Comparative Examples 1-2 and the contents of each component are shown in Table 1-2:

[0033] Table 1

[0034]

[0035]

[0036] Table 2

[0037]

[0038]

[0039] The plywood obtained in Examples 1-5 and Comparative Examples 1-2 was tested for tensile shear strength and tensile strength using environmentally friendly formaldehyde-free glue (wherein, when testing tensile shear strength and tensile strength, the test machine used was Shimadzu AGS-J series electronic testing machine), and the test method was as follows:

[0040] Tensile shear strength: tested according to GB / T 7124-1986 standard;

[0041] Tensile strength: tested according to GB / T 528-1998 standard;

[0042] When the plywood obtained in Examples 1-5 and Comparative Examples 1-2 was bonded with environmentally friendly formaldehyde-free glue, a peel strength test was performed. The test method is as follows:

[0043] Peel strength test: According to GB / T 17657-1999 standard, the peel strength test of three-layer poplar board is as follows: The three-layer poplar board is obtained by gluing, cold pressing and hot pressing, among which the glue coating amount is 340g / m 2 (Double-sided), after gluing, cold press at 1.2MPa for 60min, and then hot press, hot pressing conditions: temperature is 112℃, pressure is 1MPa, hot pressing time is 60s / mm; the three-layer poplar board after hot pressing is sawn into type A specimens, and then placed in an environment with a temperature of 23℃ and a relative air humidity of 90%RH for 1 day and 30 days respectively. The type A specimens are first soaked in 63℃ hot water for 3 hours, and then placed in a 63℃ drying oven for 3h, and after cooling to room temperature, tested with a RGT-10 microcomputer-controlled electronic universal testing machine.

[0044] The test results are shown in Table 3, as follows:

[0045] Table 3

[0046]

[0047]

[0048] From the comparison between Example 1 and Comparative Example 1, it can be seen that the use of the modified epoxy resin can produce an environmentally friendly formaldehyde-free glue for plywood with good tensile shear strength and tensile strength, and when the glue is used for bonding boards, it still has high peel strength and good bonding properties even when placed for a long time in a high humidity environment;

[0049] From the comparison between Example 1 and Comparative Example 2, it can be seen that the use of the organic stabilizer provided in the present application, when the plywood is used for bonding the board with the environmentally friendly formaldehyde-free glue, still has high peel strength when placed for a long time in a high humidity environment, and the tensile shear strength and tensile strength of the obtained glue are also improved to a certain extent;

[0050] By comparing Example 1 with Examples 4-5, it can be seen that when the mass ratio of the epoxy resin and the modified epoxy resin provided by the present application is within an appropriate range, the tensile shear strength and tensile strength of the environmentally friendly formaldehyde-free glue for plywood prepared are better, and when the prepared glue is used for bonding boards, it has a higher peel strength even when placed for a long time in a high humidity environment;

[0051] In summary, the environmentally friendly formaldehyde-free glue for plywood prepared using the components and contents provided in this application has good tensile shear strength and tensile strength, and the prepared glue has high peel strength when used for bonding boards, and still has high peel strength even when placed for a long time in a high humidity environment, thereby having better bonding properties.

[0052] The above implementation modes are only for illustrating the technical concept and features of the present invention, and their purpose is to enable people familiar with this technology to understand the content of the present invention and implement it, and they cannot be used to limit the protection scope of the present invention. Any equivalent changes or modifications made according to the spirit of the present invention should be included in the protection scope of the present invention.

Claims

1. An environmentally friendly formaldehyde-free glue for plywood, characterized in that: The environmentally friendly formaldehyde-free glue for plywood comprises the following components in parts by weight: 10-15 parts of polyvinyl alcohol, 60-85 parts of epoxy resin compound, 2-7 parts of organic curing agent, 5-12 parts of filler, 40-60 parts of sodium silicate aqueous solution, 2-4 parts of catalyst, 2-10 parts of viscosity modifier, 0.01-1 parts of inorganic salt, and 1-5 parts of organic stabilizer; The epoxy resin compound comprises a modified epoxy resin, and the modified epoxy resin is prepared by reacting an epoxy resin with dimethyldichlorosilane.

2. The environmentally friendly formaldehyde-free glue for plywood according to claim 1, characterized in that: The epoxy resin composite is a composition of epoxy resin and modified epoxy resin.

3. The environmentally friendly formaldehyde-free glue for plywood according to claim 1, characterized in that: The organic stabilizer is prepared by reacting trimethylamine hydrochloride and a silane coupling agent.

4. The environmentally friendly formaldehyde-free glue for plywood according to claim 2, characterized in that: The mass ratio of the epoxy resin to the modified epoxy resin is 1:0.1-0.

5.

5. The environmentally friendly formaldehyde-free glue for plywood according to claim 1, characterized in that: The filler is at least one of nano silicon dioxide, magnesium oxide and aluminum oxide.

6. The environmentally friendly formaldehyde-free glue for plywood according to claim 1, characterized in that: The catalyst is at least one of methyl acetate, ethyl acetate and o-sulfonylbenzoimide.

7. The environmentally friendly formaldehyde-free glue for plywood according to claim 6, characterized in that: The organic curing agent is 2-ethyl-4-methylimidazole.

8. The environmentally friendly formaldehyde-free glue for plywood according to claim 1, characterized in that: The preparation method of the modified epoxy resin comprises the following steps: The epoxy resin and the organic solvent are placed in a reaction kettle to be fully dissolved, and then dimethyldichlorosilane, a catalyst and an amine compound are added, and the temperature is raised to 45-60° C. to fully react. After the reaction is completed, the modified epoxy resin is purified to obtain the modified epoxy resin.

9. The environmentally friendly formaldehyde-free glue for plywood according to claim 3, characterized in that: The preparation method of the organic stabilizer comprises the following steps: The silane coupling agent, trimethylamine hydrochloride and an organic solvent are placed in a reactor, heated to a suitable temperature, and then fully reacted. After the reaction is completed, the organic stabilizer is obtained by vacuum distillation, washing and drying.

10. A process for preparing an environmentally friendly formaldehyde-free glue for plywood according to any one of claims 1 to 9, characterized in that: The following steps are involved: (1) Stirring the polyvinyl alcohol and epoxy resin composite until mixed; (2) adding an organic curing agent, a sodium silicate aqueous solution, a viscosity modifier, a filler, a catalyst, an inorganic salt, and an organic stabilizer to the mixture in step (1), and then mixing the mixture to remove bubbles to obtain an environmentally friendly formaldehyde-free glue for plywood.

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