Water-resistant polyvinyl acetate adhesive as well as preparation method and application thereof

Abstract

The water-resistant polyvinyl acetate adhesive is prepared from the following raw materials in parts by weight: 230 to 270 parts of vinyl acetate, 8 to 12 parts of an initiator, 23 to 28 parts of polyvinyl alcohol, 0.8 to 1.2 parts of an emulsifier, 2.2 to 2.6 parts of a cross-linking agent and 50 to 80 parts of a modifier. Acrylic acid is added into the polyvinyl acetate adhesive for modification, so that the water resistance and temperature resistance of the polyvinyl acetate adhesive can be improved. And polyvinyl alcohol with different viscosities is added into the polyvinyl acetate adhesive, so that the polyvinyl acetate adhesive with proper viscosity can be obtained, and the viscosity and permeation cohesiveness of the polyvinyl acetate adhesive in the shaving board are good. Meanwhile, the viscosity and the initial viscosity of the polyvinyl acetate adhesive are optimized, and the strength of the formed plate blank is improved. And a continuous and uniform thin layer is formed on the surface of the large shaving board, so that moisture-proof and water-resistant performance and board surface glossiness can be improved.

Description

Technical Field

[0001] The present invention relates to the field of adhesives, and specifically relates to a water-resistant polyvinyl acetate adhesive, a preparation method thereof, and an application thereof. Background Art

[0002] Traditional particleboards often use adhesives with high formaldehyde content, and their environmental protection performance is not high. Currently, isocyanate adhesives are often used, but when isocyanate adhesives are applied to the surface of particleboards, they are prone to sticking to steel belts and have a high failure rate. Using polyvinyl acetate adhesives to replace isocyanate adhesives in particleboards can reduce the failure rate and improve production efficiency. However, traditional polyvinyl acetate adhesives have poor water resistance and temperature resistance, and have poor moisture-proof performance in the fields of wood products, furniture, building materials, etc. Therefore, it is crucial to develop a water-resistant, temperature-resistant, and high-viscosity polyvinyl acetate adhesive.

[0003] Chinese invention patent CN116515426A discloses a formaldehyde-free adhesive, a preparation method thereof, an application thereof, and an application method. The present invention uses a mixed type of active monomers to carry out copolymerization reaction to form an acrylate-modified polyvinyl acetate emulsion type thermosetting adhesive. Using this acrylate-modified polyvinyl acetate emulsion type thermosetting adhesive system to form a formaldehyde-free adhesive has the characteristics of fire prevention, flame retardancy, water resistance, and moisture resistance, but its application performance in particleboards is not good. Chinese invention patent CN105111975A discloses a preparation method of a modified polyvinyl acetate emulsion adhesive and its product. Through chemical copolymerization modification, using modified monomers to copolymerize with vinyl acetate, determining the optimal copolymerization raw material ratio and copolymerization process conditions to obtain an ideal copolymer emulsion adhesive, improving the water resistance and cold resistance of the polyvinyl acetate emulsion adhesive and broadening its application range, but the water resistance is still not good. Summary of the Invention

[0004] In order to develop a water-resistant, temperature-resistant, and high-viscosity polyvinyl acetate adhesive, a first aspect of the present invention provides a water-resistant polyvinyl acetate adhesive. The preparation raw materials include, by weight: 230-270 parts of vinyl acetate, 8-12 parts of initiator, 23-28 parts of polyvinyl alcohol, 0.8-1.2 parts of emulsifier, 2.2-2.6 parts of crosslinking agent, and 50-80 parts of modifier.

[0005] As an embodiment, the polyvinyl alcohol includes polyvinyl alcohol A and polyvinyl alcohol B, and the weight ratio of polyvinyl alcohol A to polyvinyl alcohol B is (8-10):(13-16).

[0006] As an embodiment, the degree of alcoholysis of polyvinyl alcohol A is 85-90%; the degree of alcoholysis of polyvinyl alcohol B is 95-99%.

[0007] As an embodiment, the degree of alcoholysis of the polyvinyl alcohol A is 88%; the degree of alcoholysis of the polyvinyl alcohol B is 99%.

[0008] As an embodiment, the polyvinyl alcohol A is polyvinyl alcohol 1788, and the polyvinyl alcohol B is polyvinyl alcohol 1799.

[0009] As an embodiment, the weight ratio of the polyvinyl alcohol 1788 to the polyvinyl alcohol 1799 is 10:15.

[0010] As an embodiment, the emulsifier is alkylphenol polyoxyethylene, and the number of ethoxy groups in the alkylphenol polyoxyethylene is 7 - 15.

[0011] As an embodiment, the number of ethoxy groups in the alkylphenol polyoxyethylene is 10.

[0012] As an embodiment, the modifier includes at least one of corn starch, chitosan, silicone, acrylic acid, or melamine.

[0013] As an embodiment, the modifier is acrylic acid.

[0014] During the experiment, the inventors found that the polyvinyl acetate adhesive has technical problems such as poor water resistance, heat resistance, and low viscosity, resulting in the waterproof performance of the particleboard not meeting the requirements. The inventors added acrylic acid modification to the polyvinyl acetate adhesive, which can improve the water resistance and temperature resistance of the polyvinyl acetate adhesive. The reason may be that the polyvinyl acetate adhesive modified with acrylic acid interacts with N - hydroxymethyl acrylamide, which can increase the cross - link density of the cross - linked network, thereby improving the water resistance and temperature resistance of the polyvinyl acetate adhesive.

[0015] The inventors further found during the experiment that adding polyvinyl alcohol with different degrees of alcoholysis to the polyvinyl acetate adhesive can obtain a polyvinyl acetate adhesive with appropriate viscosity, and it has good viscosity and penetration adhesion in the particleboard. The reason may be that using polyvinyl alcohol with different degrees of alcoholysis can obtain an appropriate viscosity, and it can be dissolved into the polyvinyl acetate adhesive at an appropriate temperature, uniformly dispersed in the polyvinyl acetate adhesive system, achieving good initial adhesion performance and improving the structural strength after the slab is formed.

[0016] As an embodiment, the initiator includes at least one of ammonium persulfate, potassium persulfate, benzoyl peroxide, sodium persulfate, or hydrogen peroxide.

[0017] As an embodiment, the initiator is ammonium persulfate.

[0018] As an embodiment, the crosslinking agent includes at least one of N-methylolacrylamide, N-butoxymethylacrylamide, N-isobutoxymethylacrylamide, N,N-methylenebisacrylamide, and pentaerythritol triacrylate.

[0019] As an embodiment, the crosslinking agent is N-methylolacrylamide.

[0020] As an embodiment, the raw materials for preparing the water-resistant polyvinyl acetate adhesive further include, by weight: 8-11 parts of ethanol, 0.4-0.8 parts of neutralizing agent, 0.8-1.2 parts of preservative, 0.5-1 part of defoaming agent, 350-380 parts of water, and 17-21 parts of plasticizer.

[0021] As an embodiment, the neutralizing agent is sodium bicarbonate.

[0022] As an embodiment, the plasticizer includes, but is not limited to, dibutyl phthalate.

[0023] As an embodiment, the preservative includes, but is not limited to, sodium benzoate.

[0024] The second aspect of the present invention provides a method for preparing a water-resistant polyvinyl acetate adhesive, comprising the following steps:

[0025] S1: Mix water and polyvinyl alcohol and stir, heat up to 88-92 °C, and dissolve;

[0026] S2: Cool down to 50-70 °C, add an emulsifier and 1 / 3 of the total amount of initiator;

[0027] S3: Heat up to 70-80 °C, add a crosslinking agent, dropwise add 10-15 wt% of vinyl acetate within 30 min. When there is no liquid reflux, maintain at 70-75 °C, dropwise add the remaining vinyl acetate, and finish dropping within 4-5 h. During this period, add 1 / 3 of the total amount of initiator in equal batches and slowly dropwise every 15 min. After the vinyl acetate is dropped, stir for 10 min, start to heat up to 85-95 °C, dropwise add 1 / 3 of the total amount of initiator, and carry out a constant temperature reaction for 20-40 min, then cool down to 40-50 °C;

[0028] S4: Add ethanol, neutralizing agent, preservative, and plasticizer, stir for 20-40 min, then add a modifier for emulsification, stir for 15-25 min, and then add a defoaming agent, stir for 5-15 min to obtain the water-resistant polyvinyl acetate adhesive.

[0029] As an embodiment, the particleboard includes a particleboard surface layer and a particleboard core layer.

[0030] As an implementation method, the sizing of the surface layer of the particleboard includes the polyvinyl acetate adhesive and the MDI adhesive prepared by the present invention.

[0031] As an implementation method, the sizing amount of the polyvinyl acetate adhesive prepared by the present invention is 1 - 5 kg / m 3 , and the sizing amount of the MDI adhesive on the surface layer of the particleboard is 5 - 10 kg / m 3 .

[0032] Compared with the prior art, the present invention has the following beneficial effects:

[0033] (1) For the water - resistant polyvinyl acetate adhesive of the present invention, adding acrylic acid modification to the polyvinyl acetate adhesive can improve the water resistance and temperature resistance of the polyvinyl acetate adhesive.

[0034] (2) For the water - resistant polyvinyl acetate adhesive of the present invention, adding polyvinyl alcohol with different degrees of alcoholysis to the polyvinyl acetate adhesive can obtain a polyvinyl acetate adhesive with appropriate viscosity, and it has good viscosity and penetration bonding property in the particleboard.

[0035] (3) For the water - resistant polyvinyl acetate adhesive of the present invention, when the weight ratio of polyvinyl alcohol 1788 and polyvinyl alcohol 1799 is (8 - 10):(13 - 16), it can optimize the viscosity and initial tackiness of the polyvinyl acetate adhesive and improve the strength of the formed board blank.

[0036] (4) For the water - resistant polyvinyl acetate adhesive of the present invention, a continuous and uniform thin layer can be formed on the surface of large flakes through physical and chemical bonding, which can synergistically improve the moisture - proof and water - resistant performance and the gloss of the board surface.

[0037] (5) For the water - resistant polyvinyl acetate adhesive of the present invention, in synergistic action with the MDI adhesive, when applied to the surface layer of the particleboard, it can reduce the hot - pressing sticking - board failure, greatly reduce the sizing cost, and synergistically improve the environmental protection performance. Specific implementation method

[0038] The polyvinyl alcohol 1788 is purchased from Guangzhou Suixin Chemical Co., Ltd., with the brand number 1788;

[0039] The polyvinyl alcohol 1799 is purchased from Guangzhou Suixin Chemical Co., Ltd., with the brand number 1799;

[0040] The defoaming agent is purchased from Guangzhou Zhongwan New Materials Co., Ltd., with the brand number W - 810.

[0041] Example 1

[0042] A water-resistant polyvinyl acetate adhesive, the preparation raw materials in parts by weight include: 253 parts of vinyl acetate, 9 parts of initiator, 25 parts of polyvinyl alcohol, 1.1 parts of emulsifier, 2.6 parts of crosslinking agent, 70 parts of modifier, 11 parts of ethanol, 0.5 part of neutralizing agent, 0.9 part of preservative, 0.75 part of defoaming agent, 375 parts of water, and 19 parts of plasticizer.

[0043] The polyvinyl alcohol includes polyvinyl alcohol A and polyvinyl alcohol B. The polyvinyl alcohol A is polyvinyl alcohol 1788 with a degree of alcoholysis of 88%, and the polyvinyl alcohol B is polyvinyl alcohol 1799 with a degree of alcoholysis of 99%. The weight ratio of polyvinyl alcohol A to polyvinyl alcohol B is 10:15.

[0044] The emulsifier is OP-10.

[0045] The initiator is ammonium persulfate. The crosslinking agent is N-methylolacrylamide.

[0046] The neutralizing agent is sodium bicarbonate. The plasticizer is dibutyl phthalate. The preservative is sodium benzoate.

[0047] A preparation method of a water-resistant polyvinyl acetate adhesive, comprising the following steps:

[0048] S1: Mix and stir water and polyvinyl alcohol, heat up to 90 °C and dissolve.

[0049] S2: Cool down to 60 °C, add the emulsifier and 1 / 3 of the total amount of the initiator.

[0050] S3: Heat up to 75 °C, add the crosslinking agent, dropwise add 35 parts by weight of vinyl acetate within 30 min. When there is no liquid reflux, maintain 75 °C, dropwise add the remaining vinyl acetate, and finish dropping within 5 h. During this period, add 1 / 3 of the total amount of the initiator in equal batches slowly every 15 min. After the vinyl acetate is dropped, stir for 10 min, start to heat up to 90 °C, dropwise add 1 / 3 of the total amount of the initiator, and keep the temperature constant for reaction for 30 min, then cool down to 45 °C.

[0051] S4: Add ethanol, neutralizing agent, preservative and plasticizer, stir for 30 min, then add the modifier for emulsification, stir for 20 min, and then add the defoaming agent and stir for 10 min to obtain the water-resistant polyvinyl acetate adhesive.

[0052] Example 2

[0053] A water-resistant polyvinyl acetate adhesive, the preparation raw materials in parts by weight include: 253 parts of vinyl acetate, 6 parts of initiator, 25 parts of polyvinyl alcohol, 1.1 parts of emulsifier, 3 parts of crosslinking agent, 70 parts of modifier, 11 parts of ethanol, 0.5 part of neutralizing agent, 0.9 part of preservative, 0.75 g of defoaming agent, 375 parts of water, and 19 parts of plasticizer.

[0054] The polyvinyl alcohol includes polyvinyl alcohol A and polyvinyl alcohol B. The polyvinyl alcohol A is polyvinyl alcohol 1788 with a degree of alcoholysis of 88%, and the polyvinyl alcohol B is polyvinyl alcohol 1799 with a degree of alcoholysis of 99%. The weight ratio of polyvinyl alcohol A to polyvinyl alcohol B is 10:10.

[0055] The emulsifier is OP-10.

[0056] The initiator is ammonium persulfate. The crosslinking agent is N-methylolacrylamide.

[0057] The neutralizing agent is sodium bicarbonate. The plasticizer is dibutyl phthalate. The preservative is sodium benzoate.

[0058] A preparation method of a water-resistant polyvinyl acetate adhesive includes the following steps:

[0059] S1: Mix water and polyvinyl alcohol and stir, heat up to 90 °C and dissolve;

[0060] S2: Cool down to 60 °C, add the emulsifier and 1 / 3 of the total amount of the initiator;

[0061] S3: Heat up to 75 °C, add the crosslinking agent, dropwise add 35 parts by weight of vinyl acetate within 30 min. When there is no liquid reflux, keep at 75 °C, dropwise add the remaining vinyl acetate, and finish dropping within 5 h. During this period, add 1 / 3 of the total amount of the initiator in equal batches and slowly every 15 min. After the vinyl acetate is dropped, stir for 10 min, start to heat up to 90 °C, dropwise add 1 / 3 of the total amount of the initiator, and keep the temperature constant for reaction for 30 min, then cool down to 45 °C; S4: Add ethanol, the neutralizing agent, the preservative and the plasticizer, stir for 30 min, add the modifier for emulsification, stir for 20 min, add the defoaming agent, and stir for 10 min to obtain the water-resistant polyvinyl acetate adhesive.

[0062] Example 3

[0063] A water-resistant polyvinyl acetate adhesive, the preparation raw materials include, by weight: 253 parts of vinyl acetate, 9 parts of initiator, 25 parts of polyvinyl alcohol, 1.1 parts of emulsifier, 2.6 parts of crosslinking agent, 45 parts of modifier, 11 parts of ethanol, 0.5 part of neutralizing agent, 0.9 part of preservative, 0.75 part of defoaming agent, 375 parts of water, and 19 parts of plasticizer.

[0064] The polyvinyl alcohol includes polyvinyl alcohol A and polyvinyl alcohol B. The polyvinyl alcohol A is polyvinyl alcohol 1788 with a degree of alcoholysis of 88%, and the polyvinyl alcohol B is polyvinyl alcohol 1799 with a degree of alcoholysis of 99%. The weight ratio of polyvinyl alcohol A to polyvinyl alcohol B is 5:5.

[0065] The emulsifier is OP-10.

[0066] The initiator is ammonium persulfate. The crosslinking agent is N-methylolacrylamide.

[0067] The neutralizing agent is sodium bicarbonate. The plasticizer is dibutyl phthalate. The preservative is sodium benzoate.

[0068] A preparation method of a water-resistant polyvinyl acetate adhesive, comprising the following steps:

[0069] S1: Mix water and polyvinyl alcohol and stir, heat up to 90 °C and dissolve;

[0070] S2: Cool down to 60 °C, add the emulsifier and 1 / 3 of the total amount of the initiator;

[0071] S3: Heat up to 75 °C, add the crosslinking agent, dropwise add 35 parts by weight of vinyl acetate within 30 min. When there is no liquid reflux, keep at 75 °C, dropwise add the remaining vinyl acetate, and finish dropping within 5 h. During this period, add 1 / 3 of the total amount of the initiator in batches slowly every 15 min on average. After the vinyl acetate is added dropwise, stir for 10 min, start to heat up to 90 °C, dropwise add 1 / 3 of the total amount of the initiator, and keep the temperature constant for reaction for 30 min, then cool down to 45 °C;

[0072] S4: Add ethanol, neutralizing agent, preservative and plasticizer, stir for 30 min, then add the modifier for emulsification, stir for 20 min, then add the defoaming agent and stir for 10 min to obtain the water-resistant polyvinyl acetate adhesive.

[0073] Performance test

[0074] The particleboard includes a particleboard surface layer and a particleboard core layer. The specific structure of the particleboard is particleboard surface layer + particleboard core layer + particleboard surface layer, and the weight ratio is 20:60:20. The density of the particleboard is 650 kg / m 3 , and the thickness of the particleboard is 15 mm.

[0075] Apply the polyvinyl acetate adhesive and MDI adhesive prepared by the present invention to the particleboard surface layer. The sizing amount of the polyvinyl acetate adhesive is 4 kg / m 3 , and the sizing amount of the MDI adhesive on the particleboard surface layer is 6 kg / m 3 . The polyvinyl acetate adhesive and the MDI adhesive are output and atomized for sizing in different pipelines.

[0076] The particleboard core layer uses MDI adhesive, and the sizing amount is 11 kg / m 3 .

[0077] The particleboard is formed by assembling the particleboard surface layer + particleboard core layer + particleboard surface layer, pre-pressing, hot-pressing (using a three-stage hot-pressing process with a hot-pressing temperature of 185 °C, the first stage: pressure 18.0 MPa, time 0.1 min; the second stage: pressure 6.5 MPa, time 2 min; the third stage: pressure 9.0 MPa, time 0.6 min), cooling, and trimming. Physical and mechanical property tests were carried out on it, and the results are shown in Table 1.

[0078] 1. Density: The density was tested according to the method in 4.2 of GB / T 17657-2022.

[0079] 2. Internal bond strength: The internal bond strength was tested according to the method in 4.11 of GB / T 17657-2022.

[0080] 3. Modulus of rupture: The modulus of rupture was tested according to the method in 4.7 of GB / T 17657-2022.

[0081] 4. Elastic modulus: The elastic modulus was tested according to the method in 4.7 of GB / T 17657-2022.

[0082] 5. Surface bond strength: The surface bond strength was tested according to the method in 4.15 of GB / T 17657-2022.

[0083] 6. Internal bond strength after boiling in water: The internal bond strength after boiling in water was tested according to the method in 4.13 of GB / T 17657-2022.

[0084] 7. Thickness swelling rate after water absorption: The thickness swelling rate after water absorption was tested according to the method in 4.4 of GB / T 17657-2022.

[0085] 8. Moisture content: The moisture content was tested according to the method in 4.3 of GB / T 17657-2022.

[0086] Table 1

[0087]

[0088]

[0089] In Example 1 and 2, the viscosity regulation and water and heat resistance enhancement technology of polyvinyl acetate adhesives, and the technology of applying polyvinyl acetate and MDI in batches and multiple times were used to exert the synergistic effect of polyvinyl acetate and MDI, creating a water-soluble high heat and water resistant polyvinyl acetate adhesive with appropriate viscosity and initial tack, achieving a large amount of substitution of MDI for sizing the surface particles of particleboard, improving the strength of the formed board blank, reducing the trouble of sticking to the hot press, greatly reducing the sizing cost, and synergistically improving the environmental performance.

Claims

1. A water-resistant polyvinyl acetate adhesive, characterized in that: The raw materials prepared include, by weight: 230-270 parts of vinyl acetate, 8-12 parts of initiator, 23-28 parts of polyvinyl alcohol, 0.8-1.2 parts of emulsifier, 2.2-2.6 parts of crosslinking agent and 50-80 parts of modifier.

2. The water-resistant polyvinyl acetate adhesive according to claim 1, characterized in that: The polyvinyl alcohol comprises polyvinyl alcohol A and polyvinyl alcohol B, and the weight ratio of the polyvinyl alcohol A to the polyvinyl alcohol B is (8-10):(13-16).

3. The water-resistant polyvinyl acetate adhesive according to claim 1, characterized in that: The alcoholysis degree of the polyvinyl alcohol is 85-99%.

4. The water-resistant polyvinyl acetate adhesive according to claim 1, characterized in that: The emulsifier is alkylphenol polyoxyethylene, and the number of ethoxy groups in the alkylphenol polyoxyethylene is 7-15.

5. The water-resistant polyvinyl acetate adhesive according to claim 1, characterized in that: The modifier includes at least one of corn starch, chitosan, silicone, acrylic acid or melamine.

6. The water-resistant polyvinyl acetate adhesive according to claim 1, characterized in that: The initiator includes at least one of ammonium persulfate, potassium persulfate, benzoyl peroxide, sodium persulfate or hydrogen peroxide.

7. The water-resistant polyvinyl acetate adhesive according to claim 1, characterized in that: The crosslinking agent includes at least one of N-hydroxymethyl acrylamide, N-butoxymethyl acrylamide, N-isobutoxymethyl acrylamide, N,N-methylenebisacrylamide, and pentaerythritol triacrylate.

8. The water-resistant polyvinyl acetate adhesive according to claim 1, characterized in that: The raw materials for preparing the water-resistant polyvinyl acetate adhesive further include, by weight: 8-11 parts of ethanol, 0.4-0.8 parts of a neutralizer, 0.8-1.2 parts of a preservative, 0.5-1 parts of a defoaming agent, 350-380 parts of water and 17-21 parts of a plasticizer.

9. A method for preparing the water-resistant polyvinyl acetate adhesive according to claim 8, characterized in that: The following steps are involved: S1: Mix water and polyvinyl alcohol and stir, raise the temperature to 88-92°C to dissolve; S2: Cool down to 50-70°C, add emulsifier and 1 / 3 of the total initiator; S3: Raise the temperature to 70-80°C, add a crosslinking agent, and drop 10-15wt% of vinyl acetate within 30 minutes. When there is no liquid reflux, maintain 70-75°C, drop the remaining vinyl acetate, and drip it within 4-5 hours. During this period, slowly drop 1 / 3 of the total amount of initiator in batches every 15 minutes. After the vinyl acetate is added, stir for 10 minutes, start to raise the temperature to 85-95°C, drop 1 / 3 of the total amount of initiator, and react at a constant temperature for 20-40 minutes, and then cool to 40-50°C; S4: Add ethanol, neutralizer, preservative and plasticizer, stir for 20-40 minutes, add modifier for emulsification, stir for 15-25 minutes, add defoamer, stir for 5-15 minutes, and obtain water-resistant polyvinyl acetate adhesive.

10. An application of the water-resistant polyvinyl acetate adhesive according to claim 8, characterized in that: Used in the surface particles of particleboard.

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