Quick-drying long-activation-period environment-friendly formaldehyde-free water-based adhesive for thickening two-component technical veneer and preparation method of quick-drying long-activation-period environment-friendly formaldehyde-free water-based adhesive

Abstract

The invention provides quick-drying and long-activation-period environment-friendly formaldehyde-free water-based adhesive for thickening two-component technical veneers and a preparation method of the quick-drying and long-activation-period environment-friendly formaldehyde-free water-based adhesive, and mainly relates to a thickening process in the field of woodworking furniture. The quick-drying and long-service-time two-component technical veneer thickening environment-friendly formaldehyde-free water-based adhesive is prepared from a self-made high-solid low-viscosity acrylate copolymer polymer, a small-particle-size ethylene-vinyl acetate copolymer, modified polymerized MDI and a catalyst. The adhesive prepared by the invention has the advantages of long activation period, high final bonding strength, good breaking effect on a base material, invisible adhesive film, and no cracking of sliced veneer and thick veneer. And the process time of an application end can be obviously shortened (the cold pressing time is shortened, and the mold replacement is accelerated), the glue consumption is reduced, and the production efficiency of customers is effectively improved.

Description

Technical Field

[0001] The invention belongs to the technical field of adhesives, and in particular relates to a quick-drying, long-activation-period two-component technological veneer thickening environmentally friendly formaldehyde-free water-based adhesive and a preparation method thereof. Background Art

[0002] Background introduction of related technology: In the field of wood processing technology, technological wood is a new type of decorative material, whose main features are clear texture, bright colors and high ornamental value. However, during the production process, technological wood is prone to cracking, fluffing, and anti-sticking due to its thin slice thickness, which not only affects its aesthetics but also reduces its service life. In the field of adhesive chemistry, traditional urea-formaldehyde glue is widely used in wood bonding because of its low price and high bonding strength. However, urea-formaldehyde glue releases formaldehyde during production and use, causing harm to the environment and human health. In the field of environmental protection engineering, with the increasingly stringent environmental protection regulations, the application of traditional urea-formaldehyde glue and other formaldehyde-containing adhesives has been greatly restricted. Therefore, the development of a formaldehyde-free, environmentally friendly technological wood thickening adhesive has become an urgent need in the current market.

[0003] Solutions of existing technologies: Existing solutions mainly involve removing formaldehyde from glue by replacing the formula of urea-formaldehyde glue. However, this method cannot fundamentally solve the problem, because the formaldehyde in urea-formaldehyde glue comes from the reaction between urea and formaldehyde, which is inevitable.

[0004] Problems with existing technologies: The problems with existing technologies in this field are mainly as follows: 1) Traditional urea-formaldehyde glue cannot slice thin veneers, mainly because the hardness of urea-formaldehyde glue is too high, which makes the veneer easy to tear during the slice process; 2) During the production process, urea-formaldehyde glue releases formaldehyde, which is harmful to the environment and human health. 3) Although existing formaldehyde-free adhesives can solve the formaldehyde pollution problem, their bonding strength often cannot meet actual needs, and the price is high, which is not conducive to large-scale application. 4) Water-based adhesives dry slowly, and some dense woods need to be cured for more than half a month. Summary of the invention

[0005] The purpose of the present invention is to provide a quick-drying, long-activation-period two-component technological veneer thickening environmentally friendly formaldehyde-free water-based adhesive and a preparation method thereof in view of the deficiencies of the prior art.

[0006] The objective of the present invention is achieved through the following technical solutions:

[0007] In the first aspect, the present invention provides a quick-drying, long-activation-period two-component technological veneer thickened environmentally friendly formaldehyde-free water-based adhesive, wherein the quick-drying, long-activation-period two-component technological veneer thickened environmentally friendly formaldehyde-free water-based adhesive is prepared from component A and component B in a mass ratio of 100:8; wherein component A is prepared from the following raw materials in parts by weight: 30 to 100 parts of ethylene-vinyl acetate copolymer emulsion, 0 to 70 parts of acrylate copolymer emulsion, 0.2 to 0.5 parts of defoaming agent, 0.1 to 0.5 parts of catalyst and 2 to 5 parts of mildewproofing agent; component B is a curing agent.

[0008] Furthermore, the glass transition temperature of the ethylene-vinyl acetate copolymer emulsion is -30 to -10°C.

[0009] Furthermore, the viscosity of the acrylic copolymer emulsion is 6 to 8 Pa.s.

[0010] Furthermore, the acrylic ester copolymer emulsion is prepared by the following method:

[0011] The seed emulsion polymerization method is adopted. In the first step, polymer particles with an emulsion particle size of 0.2-0.4 μm are prepared as seeds. In the second step, pre-emulsified butyl acrylate, polyvinyl acetate and BPO initiator are added to the seed emulsion system, and the aqueous phase is controlled to contain no or very little free emulsifier to inhibit the generation of new particles, so that the added monomers continue to polymerize on the seeds and the particles grow, thereby achieving the purpose of increasing the particle size and controlling the particle distribution; at the same time, silicone-modified acrylic resin is added for grafting during the continued polymerization process to give the colloid better strength and initial adhesion.

[0012] Furthermore, the curing agent is one of polymeric MDI and modified polymeric MDI, or a mixture of the two in any ratio.

[0013] Furthermore, the modified polymeric MDI is prepared by the following method:

[0014] First add 20-40g PEG400 to the reaction bottle, heat to 100°C, dehydrate for 2h under vacuum of -0.1MPa, cool to 70°C, add 150-250g MDI for open reaction, control the temperature at 75°C±2°C, when the NCO content reaches 24-30%, add 5-10g TMP for chain extension, react at 75°C±2°C for 1h to obtain modified polymeric MDI.

[0015] Furthermore, the mildew preventer is an isothiazolinone mildew preventer.

[0016] In a second aspect, the present invention provides a method for preparing a quick-drying, long-activation-period two-component technological veneer thickening environmentally friendly formaldehyde-free water-based adhesive, which comprises the following steps, measured in parts by weight:

[0017] (1) Preparation of component A:

[0018] Mix 50-70 parts of ethylene-vinyl acetate copolymer emulsion and 30-50 parts of acrylate copolymer emulsion, stir thoroughly for 30-50 minutes, add 2-5 parts of mildew inhibitor and stir thoroughly for 30-60 minutes, then add 0.1-0.5 parts of catalyst and 0.2-0.5 parts of defoamer and stir for 10 minutes, then vacuum for 30 minutes, and discharge to obtain component A;

[0019] (2) Mixing of components A and B: The prepared component A and component B are uniformly mixed in a mass ratio of 100:8 to obtain a quick-drying, long-activation-period two-component technological veneer thickening environmentally friendly formaldehyde-free water-based adhesive.

[0020] The beneficial effects of the present invention are:

[0021] 1) The raw materials used in the preparation process of the present invention do not contain formaldehyde and have good bonding strength, which can meet the needs of slicing thin and thick veneers, while avoiding the release of formaldehyde in the production process, which causes harm to the environment and human health;

[0022] 2) The modified polymeric MDI used in the present invention can increase the drying and curing speed of the film and shorten the process time of the technical veneer production;

[0023] 3) The viscosity range of the present invention is 1500-3000cps, and the amount of glue applied can be arbitrarily controlled. It can be used for any wood without the problem of slow cold pressing and the film being too thick to affect the drying speed;

[0024] 4) The adhesive of the present invention uses a relatively soft VAE emulsion and a relatively hard self-polymerized acrylic copolymer emulsion mixed in proportion, and the obtained adhesive film has moderate hardness and softness after drying, so that the thickened wood of the technical wood will not crack, the planed veneer will not be fuzzy, burr-free, and non-sticky. Both thin and thick veneers can be planed, and the production quality rate reaches 90%, which is much higher than the existing technology, thereby improving production efficiency, reducing production costs, and improving the aesthetics and service life of the product. DETAILED DESCRIPTION

[0025] In order to make the purpose, technical scheme and advantages of the present invention more clear, the present invention is further described in detail in combination with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention, rather than all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0026] The invention provides a quick-drying, long-activation-period two-component technological veneer thickening environmentally friendly formaldehyde-free water-based adhesive. The quick-drying, long-activation-period two-component technological veneer thickening environmentally friendly formaldehyde-free water-based adhesive is prepared from component A and component B in a mass ratio of 100:8; wherein component A is prepared from the following raw materials in parts by weight: 30 to 100 parts of ethylene-vinyl acetate copolymer emulsion, 0 to 70 parts of acrylate copolymer emulsion, 0.2 to 0.5 parts of defoaming agent, 0.1 to 0.5 parts of catalyst and 2 to 5 parts of mildewproofing agent; component B is a curing agent.

[0027] The glass transition temperature of the ethylene-vinyl acetate copolymer emulsion is -30 to -10°C.

[0028] The viscosity of the acrylic copolymer emulsion is 6-8 Pa.s.

[0029] The acrylic ester copolymer emulsion is prepared by the following method:

[0030] The seed emulsion polymerization method is adopted. In the first step, polymer particles with an emulsion particle size of 0.2-0.4 μm are prepared as seeds. In the second step, pre-emulsified butyl acrylate, polyvinyl acetate and BPO initiator are added to the seed emulsion system, and the aqueous phase is controlled to contain no or very little free emulsifier to inhibit the generation of new particles, so that the added monomers continue to polymerize on the seeds and the particles grow, thereby achieving the purpose of increasing the particle size and controlling the particle distribution; at the same time, silicone-modified acrylic resin is added for grafting during the continued polymerization process to give the colloid better strength and initial adhesion.

[0031] The curing agent is one of polymeric MDI and modified polymeric MDI or a mixture of the two in any proportion.

[0032] The modified polymeric MDI is prepared by the following method:

[0033] First add 20-40g PEG400 to the reaction bottle, heat to 100°C, dehydrate for 2h under vacuum of -0.1MPa, cool to 70°C, add 150-250g MDI for open reaction, control the temperature at 75°C±2°C, when the NCO content reaches 24-30%, add 5-10g TMP for chain extension, react at 75°C±2°C for 1h to obtain modified polymeric MDI.

[0034] The mildew preventer is an isothiazolinone mildew preventer.

[0035] A method for preparing a quick-drying, long-activation-period two-component technological veneer thickening environmentally friendly formaldehyde-free water-based adhesive, measured by weight, comprising the following steps:

[0036] (1) Preparation of component A:

[0037] Mix 50-70 parts of ethylene-vinyl acetate copolymer emulsion and 30-50 parts of acrylate copolymer emulsion, stir thoroughly for 30-50 minutes, add 2-5 parts of mildew inhibitor and stir thoroughly for 30-60 minutes, then add 0.1-0.5 parts of catalyst and 0.2-0.5 parts of defoamer and stir for 10 minutes, then vacuum for 30 minutes, and discharge to obtain component A;

[0038] (2) Mixing of components A and B: The prepared component A and component B are uniformly mixed in a mass ratio of 100:8 to obtain a quick-drying, long-activation-period two-component technological veneer thickening environmentally friendly formaldehyde-free water-based adhesive.

[0039] Compared with the prior art, this technical solution mainly solves the following problems:

[0040] 1) The technical problem that traditional urea-formaldehyde glue cannot slice veneer;

[0041] 2) During the production process, urea-formaldehyde glue will release formaldehyde, which will cause harm to the environment and human health;

[0042] 3) While ensuring environmental protection, the bonding performance is optimized to meet customers' large-scale applications.

[0043] 4) The problem of insufficient universality of adhesives for the production of different substrates of technological veneer during application is solved.

[0044] Compared with the existing technology, the beneficial effects of this technical solution are as follows:

[0045] 1) The adhesive of the present invention can be used for planing thin and thick veneers, and has a good bonding effect on dense wood, which solves the problem that traditional urea-formaldehyde adhesive cannot plane thin veneers and improves the utilization rate of wood.

[0046] 2) The adhesive of the present invention is formaldehyde-free and has excellent environmental protection performance, thus avoiding the harm to the environment and human health caused by the release of formaldehyde during the production and use of traditional urea-formaldehyde adhesives.

[0047] 3) The finished board bonded by the adhesive of the present invention does not crack during each manufacturing process, and the veneer does not fluff, has no burrs, and does not stick back, thereby improving the aesthetics and service life of the product.

[0048] 4) High cost performance, conducive to large-scale application, effectively improving the production efficiency of the client and reducing production costs.

[0049] Example 1

[0050] The preparation of component A, in parts by weight, comprises the following steps:

[0051] (1) According to the formula, 60 parts of ethylene-vinyl acetate copolymer emulsion (VAE emulsion), 35 parts of acrylate copolymer emulsion, 0.5 parts of silicone defoamer, 0.5 parts of polyurethane catalyst T-12 and 4 parts of isothiazolinone mildew inhibitor were weighed.

[0052] (2) Pour the weighed VAE emulsion and acrylate copolymer emulsion into a stirring tank and stir for 30 minutes.

[0053] (3) After stirring, add the weighed isothiazolinone mildew inhibitor into the stirring tank and stir for 30 minutes.

[0054] (4) Continue to add the weighed organosilicon defoamer and polyurethane catalyst T-12 to the stirring tank and stir for 10 minutes; then extract at a vacuum degree of -0.1 MPa for 30 minutes.

[0055] (5) Stop stirring and take out the product A1.

[0056] Example 2

[0057] The preparation of component A, in parts by weight, comprises the following steps:

[0058] (1) According to the formula, 30 parts of ethylene-vinyl acetate copolymer emulsion (VAE emulsion), 65 parts of acrylate copolymer emulsion, 0.5 parts of silicone defoamer, 0.5 parts of polyurethane catalyst T-12 and 4 parts of isothiazolinone mildew inhibitor were weighed.

[0059] (2) Pour the weighed VAE emulsion and acrylate copolymer emulsion into a stirring tank and stir for 30 minutes.

[0060] (3) After stirring, add the weighed isothiazolinone mildew inhibitor into the stirring tank and stir for 30 minutes.

[0061] (4) Continue to add the weighed organosilicon defoamer and polyurethane catalyst T-12 to the stirring tank and stir for 10 minutes; then extract at a vacuum degree of -0.1 MPa for 30 minutes.

[0062] (5) Stop stirring and take out the product A2.

[0063] Example 3

[0064] The preparation of component A, in parts by weight, comprises the following steps:

[0065] (1) According to the formula, 60 parts of ethylene-vinyl acetate copolymer emulsion (VAE emulsion), 35 parts of acrylate copolymer emulsion, 0.5 parts of silicone defoaming agent and 4 parts of isothiazolinone mildew inhibitor were weighed.

[0066] (2) Pour the weighed VAE emulsion and acrylate copolymer emulsion into a stirring tank and stir for 30 minutes.

[0067] (3) After stirring, add the weighed mildew inhibitor into the stirring tank and stir for 30 minutes.

[0068] (4) Continue to add the weighed defoaming agent into the stirring tank and stir for 10 minutes; then extract at a vacuum degree of -0.1 MPa for 30 minutes.

[0069] (5) Stop stirring and take out the product A3.

[0070] Example 4

[0071] The preparation of component A, in parts by weight, comprises the following steps:

[0072] (1) According to the formula, 95 parts of ethylene-vinyl acetate copolymer emulsion (VAE emulsion), 0.5 parts of silicone defoamer, 0.5 parts of polyurethane catalyst T-12 and 4 parts of isothiazolinone mildew inhibitor were weighed.

[0073] (2) Pour the weighed VAE emulsion and acrylate copolymer emulsion into a stirring tank and stir for 30 minutes.

[0074] (3) After stirring, add the weighed isothiazolinone mildew inhibitor into the stirring tank and stir for 30 minutes.

[0075] (4) Continue to add the weighed organosilicon defoamer and polyurethane catalyst T-12 to the stirring tank and stir for 10 minutes; then extract at a vacuum degree of -0.1 MPa for 30 minutes.

[0076] (5) Stop stirring and take out the product A4.

[0077] The four A components prepared in Examples 1 to 4 were used in combination with 10% Suprasec 1051 (B1), Suprasec 2085 (B2), and modified polymeric MDI (B3) at a mass ratio of 100:8, and the following performance tests were performed. The performance test results are shown in Table 1.

[0078] Activation period test: Seal the curing agent and component A separately in advance and place them in a constant temperature and humidity chamber at 35°C and 60% humidity for 4 hours. Take out the curing agent and component A from the constant temperature environment, and mix component A with the curing agent at a mass ratio of 100:8. Stir them thoroughly until they are uniform, place them in a constant temperature and humidity chamber, and test the viscosity changes over time. If the viscosity increases sharply during the test and does not have good coating properties, it is considered to be unusable and has exceeded the activation period.

[0079] Peeling degree test: Taking walnut and poplar substrates with poor water permeability as an example: double-sided glue application, control the glue application amount to 80g / m 2 , pressure 1000mPa, cold pressing at room temperature for 4h, after unloading the pressure, curing for 24h at a temperature of 25℃ and a humidity of 60%, and then performing a peeling test. If the substrate is damaged, the bonding performance to the substrate is good.

[0080] Drying speed test: Use 25*50mm beech wood blocks, control the glue coating area to 25*25mm, put 5 in each group, put them in the fixture and apply a force of 41N, and test the compressive shear strength of pressurization for 20min, 40min, 60min, 90min, and 120min respectively. If the strength reaches 5MPa or above after 60min of pressurization, it is judged that the drying speed is fast. If the pressurization time is 120min to reach 5MPa or above, the drying speed is medium. If the strength does not reach 5MPa after 120min of pressurization, the drying speed is slow.

[0081] Yield test: Taking the walnut substrate with poor water permeability as an example: double-sided glue application, control the glue application amount to 80g / m 2 , apply glue 30 sheets, pressure 1000mPa, cold press at room temperature for 4h, after unloading the pressure, cure for 48 hours at temperature 25℃ and humidity 60%, and then conduct cutting test to observe the cracking rate of veneer after cutting. If the cracking rate is less than 10%, the yield rate is high.

[0082] Bonding strength test: Take beech wood strips as an example, select two seamless beech wood strips as a group, apply glue evenly on both sides, pressurize with a clamp, use an 81N torque wrench to apply pressure, cold press for 16 hours at 25℃ and 30% humidity, remove the clamp to make a sample for compression shear strength test, and test the compression shear strength. Under the same pressurization time, the higher the strength, the better the bonding strength.

[0083] Formaldehyde content: Use the rotary evaporation method to test the formaldehyde content. If it is greater than 0.05g / kg, it means the formaldehyde content exceeds the standard.

[0084] Table 1: Performance test results

[0085]

[0086]

[0087] Based on the above test data, the introduction of modified polymeric MDI can effectively improve the comprehensive performance of the product. The prepared colloid has high initial strength, high later adhesion, high yield rate, and good thermal stability. It can dry quickly for both ordinary substrates and impermeable substrates, providing higher bonding strength.

[0088] Based on the above test data, the introduction of modified polymeric MDI can effectively improve the comprehensive performance of the product. The prepared colloid has high initial strength, high later adhesion, high yield rate, and good thermal stability. It can dry quickly for both ordinary substrates and impermeable substrates, providing higher bonding strength.

[0089] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A quick-drying, long-activation-period two-component technological veneer thickening environmentally friendly formaldehyde-free water-based adhesive, characterized in that: The quick-drying, long-activation-period two-component technological veneer thickening environmentally friendly formaldehyde-free water-based adhesive is prepared from component A and component B in a mass ratio of 100:8; wherein component A is prepared from the following raw materials in parts by weight: 30 to 100 parts of ethylene-vinyl acetate copolymer emulsion, 0 to 70 parts of acrylate copolymer emulsion, 0.2 to 0.5 parts of defoaming agent, 0 to 0.5 parts of catalyst and 2 to 5 parts of mildewproofing agent; component B is a curing agent.

2. A quick-drying, long-activation-period two-component technological veneer thickening environmentally friendly formaldehyde-free water-based adhesive according to claim 1, characterized in that: The glass transition temperature of the ethylene-vinyl acetate copolymer emulsion is -30 to -10°C.

3. The quick-drying, long-activation-period two-component technological veneer thickening environmentally friendly formaldehyde-free water-based adhesive according to claim 1, characterized in that: The viscosity of the acrylic copolymer emulsion is 6-8 Pa.s.

4. The quick-drying, long-activation-period two-component technological veneer thickening environmentally friendly formaldehyde-free water-based adhesive according to claim 3, characterized in that: The acrylic ester copolymer emulsion is prepared by the following method: The seed emulsion polymerization method is adopted. In the first step, polymer particles with an emulsion particle size of 0.2-0.4 μm are prepared as seeds. In the second step, pre-emulsified butyl acrylate, polyvinyl acetate and BPO initiator are added to the seed emulsion system, and the aqueous phase is controlled to contain no or very little free emulsifier to inhibit the generation of new particles, so that the added monomers continue to polymerize on the seeds and the particles grow, thereby achieving the purpose of increasing the particle size and controlling the particle distribution; at the same time, silicone-modified acrylic resin is added for grafting during the continued polymerization process to give the colloid better strength and initial adhesion.

5. The quick-drying, long-activation-period two-component technological veneer thickening environmentally friendly formaldehyde-free water-based adhesive according to claim 1, characterized in that: The curing agent is one of polymeric MDI and modified polymeric MDI or a mixture of the two in any proportion.

6. The quick-drying, long-activation-period two-component technological veneer thickening environmentally friendly formaldehyde-free water-based adhesive according to claim 5, characterized in that: The modified polymeric MDI is prepared by the following method: First add 20-40g PEG400 to the reaction bottle, heat to 100°C, dehydrate for 2h under vacuum of -0.1MPa, cool to 70°C, add 150-250g MDI for open reaction, control the temperature at 75°C±2°C, when the NCO content reaches 24-30%, add 5-10g TMP for chain extension, react at 75°C±2°C for 1h to obtain modified polymeric MDI.

7. The quick-drying, long-activation-period two-component technological veneer thickening environmentally friendly formaldehyde-free water-based adhesive according to claim 1, characterized in that: The mildew preventer is an isothiazolinone mildew preventer.

8. A method for preparing the quick-drying, long-activation-period two-component technological veneer thickening environmentally friendly formaldehyde-free water-based adhesive as claimed in claim 1, characterized in that: By weight, the method comprises the following steps: (1) Preparation of component A: Mix 50-70 parts of ethylene-vinyl acetate copolymer emulsion and 30-50 parts of acrylate copolymer emulsion, stir thoroughly for 30-50 minutes, add 2-5 parts of mildew inhibitor and stir thoroughly for 30-60 minutes, then add 0.1-0.5 parts of catalyst and 0.2-0.5 parts of defoamer and stir for 10 minutes, then vacuum for 30 minutes, and discharge to obtain component A; (2) Mixing of components A and B: The prepared component A and component B are uniformly mixed in a mass ratio of 100:8 to obtain a quick-drying, long-activation-period two-component technological veneer thickening environmentally friendly formaldehyde-free water-based adhesive.

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