Organic silicon modified water-based carbon dioxide-based polyurethane bamboo and wood coating and preparation method thereof

Abstract

The invention discloses an organic silicon modified water-based carbon dioxide-based polyurethane bamboo wood coating and a preparation method thereof. The coating is prepared from the following raw materials: 70 to 170 parts of carbon dioxide-based polyol, 5 to 15 parts of hydroxyl MQ silicon resin, 25 to 60 parts of diisocyanate compound, 0.2 to 0.5 part of organic tin, 2 to 8 parts of N-methyldiethanolamine, 2 to 5 parts of dihydric alcohol containing side chain alkyl, 2 to 10 parts of neutralizer and 60 to 180 parts of acetone. The carbon dioxide-based polyol is used as a raw material, the hydroxyl MQ silicon resin component is introduced, the hydroxyl MQ silicon resin is doped into a resin system, and the water resistance and the mechanical property of the water-based carbon dioxide-based polyurethane resin are improved by utilizing the hydrophobicity and the high mechanical strength of the hydroxyl MQ silicon resin and the good compatibility of the hydroxyl MQ silicon resin and the polyurethane resin; therefore, the waterborne polyurethane bamboo and wood coating with water resistance and high mechanical strength is obtained.

Description

Technical Field

[0001] This invention relates to waterborne polyurethane coatings, specifically to an organosilicon-modified waterborne carbon dioxide-based polyurethane bamboo and wood coating and its preparation method. Background Technology

[0002] As an environmentally friendly alternative to traditional solvent-based polyurethane, waterborne polyurethane (WPU), with its water-based dispersion medium, effectively reduces the emission of volatile organic compounds (VOCs) and has become a research hotspot in the wood coatings industry, especially for children's room decoration. However, dispersing polyurethane with a hydrophobic backbone in water requires the introduction of hydrophilic groups, which to some extent affects the water resistance of polyurethane. Therefore, how to further improve the water resistance and mechanical properties of waterborne polyurethane while maintaining its environmentally friendly characteristics has become a research focus.

[0003] Carbon dioxide-based polyols (PPCs) are a novel, inexpensive, and high-performance environmentally friendly polyol. Polyurethane coatings made from PPCs generally outperform those made from conventional polyester or polyether polyols, exhibiting better hydrolysis resistance and thus showing broad application prospects. However, the water resistance and mechanical properties of waterborne polyurethane coatings made from PPCs require further improvement.

[0004] MQ silicone resin, an organic-inorganic hybrid polysiloxane with a unique bilayer structure, consists of an inner layer of highly cross-linked tetrafunctional siloxane units, similar in chemical structure to SiO2, while the inorganic core is encapsulated by an outer layer composed of monofunctional siloxane segments. This gives it the dual characteristics of a hydrophobic framework and an inorganic core, offering the possibility of improving the water resistance and mechanical properties of waterborne polyurethanes. However, the organic part of MQ silicone resin (trimethylsiloxane) is a typical low-polarity, hydrophobic group, while waterborne resins rely on hydrophilic groups for water dispersion. The polarity mismatch at the molecular scale makes mutual wetting and bonding difficult. Furthermore, the number of silanol groups (Si-OH) on the surface of MQ silicone resin that can form hydrogen bonds is usually small and their reactivity varies, further weakening its ability to interact with the abundant polar groups in waterborne resins. This results in poor compatibility between silicone and waterborne resins, affecting their modification effect. Summary of the Invention

[0005] To address the above problems, this invention provides an organosilicon-modified waterborne carbon dioxide-based polyurethane bamboo and wood coating and its preparation method. This carbon dioxide-based waterborne polyurethane has the advantages of strong water resistance and high mechanical strength.

[0006] To achieve the above objectives, the present invention provides an organosilicon-modified waterborne carbon dioxide-based polyurethane bamboo and wood coating, which is prepared by weight from the following materials: 70-170 parts of carbon dioxide-based polyol, 5-15 parts of hydroxyl MQ silicone resin, 25-60 parts of diisocyanate compound, 0.2-0.5 parts of organotin, 2-8 parts of N-methyldiethanolamine, 2-5 parts of alkyl diol containing side chains, 2-10 parts of neutralizing agent, and 60-180 parts of acetone; wherein the carbon dioxide-based polyol is a carbon dioxide-based polycarbonate polyol polymerized from carbon dioxide and epoxide, with a number average molecular weight of 1000-3000, a carbonate content of 40%-60%, and a hydroxyl value of 40-60 mgKOH / g.

[0007] Preferably, the material further includes 50 to 160 parts of water, so that the solid content of the coating is 40% to 60%.

[0008] Preferably, the diisocyanate compound is selected from one or more of toluene diisocyanate, diphenylmethane diisocyanate, 1,6-hexamethylene diisocyanate, isophorone diisocyanate, and 4,4-dicyclohexylmethane diisocyanate.

[0009] Preferably, the organotin is selected from one or more of dibutyltin dilaurate, stannous octoate, and dibutyltin diacetate.

[0010] Preferably, the side-chain alkyl diol is selected from one or more of neopentyl glycol, 1,3-butanediol, 1,4-butanediol, 3-methyl-1,5-pentanediol, 2,4-diethyl-1,5-pentanediol, 2-butyl-2-ethyl-1,3-propanediol, and 2-methyl-1,8-octanediol.

[0011] Preferably, the neutralizing agent is selected from one or more of glacial acetic acid, citric acid, tannic acid, caffeic acid, and malic acid.

[0012] A second aspect of this invention provides a method for preparing the above-mentioned organosilicon-modified waterborne carbon dioxide-based polyurethane bamboo and wood coating, which includes the following steps: S1. According to the formula, the carbon dioxide-based polyol, hydroxyl MQ silicone resin, diisocyanate and organotin are subjected to 60~120℃ for 1~4 hours to obtain the first intermediate; S2. The first intermediate, acetone and N-methyldiethanolamine are reacted at 10~35°C for 20~120 minutes to obtain the second intermediate; S3. The second intermediate, the side-chain alkyl diol, water and neutralizing agent are reacted at 30~50℃ for 20~40 minutes to obtain the organosilicon-modified waterborne carbon dioxide-based polyurethane resin.

[0013] Specifically, in step S1, the preparation method of the hydroxyl MQ silicone resin is as follows: 15-30 parts of hexamethyldisiloxane (MM), 90-180 parts of tetraethyl orthosilicate (TEOS) and 20-40 parts of tetramethyldisiloxane (HMM) are reacted at 50-70°C in an acidic environment for 1-4 hours to synthesize Si-H bonded MQ silicone resin (HMQ). Subsequently, 60-120 parts of Si-H bonded MQ silicone resin and 8-20 parts of 2-(allyloxy)ethanol are subjected to a hydrosilylation reaction at 50-70°C under nitrogen protection for 6-12 hours to obtain hydroxyl MQ silicone resin (MQ-OH).

[0014] A third aspect of the present invention provides the application of the above-described coating in the preparation of bamboo and wood materials.

[0015] Through the above technical solution, the present invention achieves the following beneficial effects: This invention utilizes carbon dioxide-based polyols as raw materials, which are distinct from traditional petrochemical-based polyol materials. Prepared using carbon dioxide gas, these polyols contain a large number of carbonate bonds, exhibiting good mechanical properties and low cost. Large-scale production can effectively utilize gaseous carbon dioxide, which is of great significance for energy conservation and emission reduction. Furthermore, a hydroxyl MQ silicone resin component is introduced into this waterborne resin system. By doping the hydroxyl MQ silicone resin into the resin system, its hydrophobicity, high mechanical strength, and good compatibility with polyurethane resin are utilized to improve the water resistance and mechanical properties of the waterborne carbon dioxide-based polyurethane resin. This results in a waterborne polyurethane bamboo and wood coating with water resistance and high mechanical strength. Detailed Implementation

[0016] The specific embodiments of the present invention will be described in detail below with reference to examples. It should be understood that the specific embodiments described herein are for illustration and explanation only and are not intended to limit the present invention.

[0017] Example 1 The preparation method of hydroxyl MQ silicone resin is as follows: 15 parts of hexamethyldisiloxane (MM), 90 parts of tetraethyl orthosilicate (TEOS) and 20 parts of tetramethyldisiloxane (HMM) are reacted at 50°C in an acidic environment for 4 hours to synthesize Si-H bonded MQ silicone resin (HMQ). Subsequently, 60 parts of Si-H bonded MQ silicone resin and 8 parts of 2-(allyloxy)ethanol are subjected to hydrosilylation reaction at 50°C under nitrogen protection for 12 hours to obtain hydroxyl MQ silicone resin (MQ-OH).

[0018] The preparation method of organosilicon-modified waterborne carbon dioxide-based polyurethane resin is as follows: 100 parts of carbon dioxide-based polyol (number average molecular weight 2000, carbonate content 50%, hydroxyl value 50 mg KOH / g) are dehydrated under vacuum at 100℃ for 2 hours. 10 parts of hydroxyl MQ silicone resin, 50 parts of isophorone diisocyanate, and 0.5 parts of dibutyltin dilaurate are reacted under nitrogen protection at 60℃ for 4 hours to obtain the first intermediate. 180 parts of acetone and 8 parts of N-methyldiethanolamine are added to the first intermediate at 35℃ and reacted for 20 minutes to obtain the second intermediate. The temperature is raised to 40℃, and 5 parts of 1,4-butanediol, 150 parts of water, and 5 parts of glacial acetic acid are added to the second intermediate and reacted for 30 minutes to obtain the organosilicon-modified waterborne carbon dioxide-based polyurethane resin.

[0019] Example 2 The preparation method of hydroxyl MQ silicone resin is as follows: 30 parts of hexamethyldisiloxane (MM), 180 parts of tetraethyl orthosilicate (TEOS) and 40 parts of tetramethyldisiloxane (HMM) are reacted at 70°C in an acidic environment for 1 hour to synthesize Si-H bonded MQ silicone resin (HMQ). Subsequently, 120 parts of Si-H bonded MQ silicone resin and 20 parts of 2-(allyloxy)ethanol are subjected to hydrosilylation reaction at 70°C under nitrogen protection for 6 hours to obtain hydroxyl MQ silicone resin (MQ-OH).

[0020] The preparation method of organosilicon-modified waterborne carbon dioxide-based polyurethane resin is as follows: 170 parts of carbon dioxide-based polyol (number average molecular weight 3000, carbonate content 60%, hydroxyl value 60mgKOH / g) are dehydrated under vacuum at 100℃ for 2 hours. 15 parts of hydroxyl MQ silicone resin, 60 parts of toluene diisocyanate, and 0.2 parts of dibutyltin dilaurate are reacted under nitrogen protection at 100℃ for 3 hours to obtain the first intermediate. 160 parts of acetone and 6 parts of N-methyldiethanolamine are added to the first intermediate at 25℃ and reacted for 60 minutes to obtain the second intermediate. The temperature is raised to 50℃, and 5 parts of neopentyl glycol, 160 parts of water, and 2 parts of citric acid are added to the second intermediate and reacted for 40 minutes to obtain the organosilicon-modified waterborne carbon dioxide-based polyurethane resin.

[0021] Example 3 The preparation method of hydroxyl MQ silicone resin is as follows: 20 parts of hexamethyldisiloxane (MM), 120 parts of tetraethyl orthosilicate (TEOS) and 30 parts of tetramethyldisiloxane (HMM) are reacted at 60°C in an acidic environment for 3 hours to synthesize Si-H bonded MQ silicone resin (HMQ). Subsequently, 90 parts of Si-H bonded MQ silicone resin and 15 parts of 2-(allyloxy)ethanol are subjected to hydrosilylation reaction at 60°C under nitrogen protection for 8 hours to obtain hydroxyl MQ silicone resin (MQ-OH).

[0022] The preparation method of organosilicon-modified waterborne carbon dioxide-based polyurethane resin is as follows: 70 parts of carbon dioxide-based polyol (number average molecular weight 1000, carbonate content 40%, hydroxyl value 40 mg KOH / g) are dehydrated under vacuum at 100℃ for 2 hours. 5 parts of hydroxyl MQ silicone resin, 25 parts of diphenylmethane diisocyanate, and 0.3 parts of stannous octoate are reacted at 120℃ under nitrogen protection for 1 hour to obtain the first intermediate. 60 parts of acetone and 2 parts of N-methyldiethanolamine are added to the first intermediate at 10℃ and reacted for 120 minutes to obtain the second intermediate. The temperature is raised to 30℃, and 2 parts of 3-methyl-1,5-pentanediol, 50 parts of water, and 10 parts of tannic acid are added to the second intermediate and reacted for 20 minutes to obtain the organosilicon-modified waterborne carbon dioxide-based polyurethane resin.

[0023] Comparative Example 1 The other conditions are the same as in Example 1, except that hydroxyl MQ silicone resin was not added.

[0024] Comparative Example 2 The other conditions are the same as in Example 1, except that the hydroxyl MQ silicone resin is replaced with MQ silicone resin.

[0025] Performance testing Using poplar wood as the substrate, a waterborne polyurethane coating (the resin prepared in Examples 1-3 and Comparative Examples 1-2, 120 g / m³) was sprayed on. 2 The cured film was then pre-cured at 80 °C for 2 h and cured at 150 °C for 6 h to prepare coated wood samples. Hydrophobicity test: The water contact angle was measured using a contact angle meter; three samples were tested each time, and the average value was taken. Adhesion test: According to national standard GB / T 13912-2020, the adhesion strength was tested by pulling the coating layer off the wood. Pencil hardness test: According to standard GB / T 6739-2022, a pencil with a hardness of 6 H to 6 B was used for hardness testing. Tensile property test: The cured film was subjected to a tensile test at a stretching speed of 20 mm / min. The cured film was made from a dumbbell-shaped mold with a gauge length of 10 mm, a width of 2 mm, and a thickness of 1 mm.

[0026] The test results are as follows:

[0027] The data on water contact angles show that the embodiments of the present invention and Comparative Example 2 have high water contact angles, exceeding 90°. The reason why the MQ silicone resin in these waterborne resins enhances the hydrophobicity of the waterborne coatings lies in its three-in-one function of "structure-migration-shielding": the methyl group provides inherent hydrophobicity, forming a dense hydrophobic top layer on the coating surface, creating micro-roughness and effectively covering the internal hydrophilic components. In contrast, the waterborne resin without MQ silicone resin (Comparative Example 1) has a poor water contact angle because it introduces a large number of hydrophilic groups, resulting in a poor water contact angle. The polar hydroxyl groups in the hydroxyl MQ silicone resin have good affinity with the waterborne polyurethane (WPU) segments, allowing them to be more uniformly dispersed in the system during the coating film formation process. During water evaporation and film curing, the hydrophobic siloxane segments (-Si-O-Si-) in the silicone resin migrate and accumulate more orderly and stably on the coating surface, forming a dense low surface energy layer. Furthermore, hydroxyl groups can act as "anchor points," binding with WPU through hydrogen bonds or chemical reactions to prevent macroscopic phase separation or excessive internal migration of the silicone resin during storage or film formation, thereby ensuring the stability and effective presence of hydrophobic components on the surface. Traditional MQ silicone resin (Comparative Example 2) lacks strong polar groups, has poor compatibility with WPU, and is prone to aggregation or uneven migration during film formation, resulting in potentially incomplete and unstable hydrophobic surfaces. Therefore, its contact angle is lower than that of the embodiments of this invention.

[0028] The adhesion data shows that the embodiments of the present invention and Comparative Example 2 exhibit high adhesion. The MQ silicone resin enhances the adhesion of waterborne coatings not through simple physical mixing, but by forming chemical bonds with the substrate through its reactive functional groups. Simultaneously, it acts as a modulus transition layer and stress buffer layer, fundamentally optimizing and strengthening the interface between the coating and the substrate. The adhesion of the embodiments of the present invention is higher than that of Comparative Example 2 because the hydroxyl groups of the MQ silicone resin can participate in chemical reactions during the WPU curing process (such as reacting with -NCO groups) or form chemical bonds or strong hydrogen bonds with polar groups on the substrate surface. This establishes a stronger "bridge" between the waterborne polyurethane matrix, the silicone resin modifier, and the substrate, further enhancing the interfacial bonding force.

[0029] As can be seen from the pencil hardness data, the embodiments of the present invention and Comparative Example 2 have higher pencil hardness, mainly because the rigid inorganic siloxane nanoframework of MQ silicone resin is uniformly dispersed in the organic polymer matrix as a reinforcing phase, which effectively improves the resistance to plastic deformation and the density of the coating surface, thus exhibiting higher pencil hardness.

[0030] The tensile strength data shows that the embodiments of the present invention and Comparative Example 2 exhibit high tensile strength, mainly due to the reactive MQ resin acting as a multifunctional crosslinking point, forming strong chemical bonds with the matrix resin to construct a three-dimensional network with high cohesive strength. Its rigid inorganic framework, acting as nano-reinforcing particles, is uniformly dispersed in the matrix, effectively transferring and dispersing tensile stress. Due to the strong chemical bonding brought about by the hydroxyl groups, when the coating is subjected to tensile stress, the stress can be efficiently transferred from the flexible WPU segments to the rigid MQ siloxane core. The siloxane core, acting as dispersed "reinforcing points," can uniformly disperse local stress throughout the polymer network, avoiding early fracture caused by stress concentration. The tensile strength of the embodiments of the present invention is higher than that of Comparative Example 2 because the hydroxyl MQ silicone resin forms a molecular-level organic-inorganic hybrid material with WPU through chemical bonds. This structure combines the flexibility of the organic phase with the rigidity of the inorganic phase, achieving an excellent synergistic reinforcement effect, the so-called "nanocomposite reinforcement." The weak interface between the MQ silicone resin and the matrix makes the interface prone to becoming the initiation point and propagation path of microcracks under stress, leading to material failure at lower stress levels.

[0031] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solution of the present invention, and these simple modifications all fall within the protection scope of the present invention.

[0032] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present invention will not describe the various possible combinations separately.

[0033] Furthermore, various different embodiments of the present invention can be combined in any way, as long as they do not violate the spirit of the present invention, they should also be regarded as the content disclosed by the present invention.

Claims

1. A silicone-modified aqueous carbon dioxide-based polyurethane bamboo wood coating, characterized by, The coating is prepared by 70-170 parts by weight of carbon dioxide-based polyol, 5-15 parts of hydroxyl MQ silicone resin, 25-60 parts of diisocyanate compound, 0.2-0.5 parts of organic tin, 2-8 parts of N-methyl diethanolamine, 2-5 parts of side chain alkyl diol, 2-10 parts of neutralizing agent, and 60-180 parts of acetone; wherein the carbon dioxide-based polyol is a carbon dioxide-based polycarbonate polyol polymerized from carbon dioxide and epoxide, with a number average molecular weight of 1000-3000, a carbonate mass content of 40%-60%, and a hydroxyl value of 40-60 mgKOH / g.

2. The coating of claim 1, wherein, The materials further include 50-160 parts of water, so that the solid content of the coating is 40%-60%.

3. The coating of claim 1, wherein, The diisocyanate compound is selected from one or more of toluene diisocyanate, diphenylmethane diisocyanate, 1,6-hexamethylene diisocyanate, isophorone diisocyanate, and 4,4-dicyclohexylmethane diisocyanate.

4. The coating of claim 1, wherein, The organic tin is selected from one or more of dibutyltin dilaurate, stannous octoate, and dibutyltin diacetate.

5. The coating of claim 1, wherein, The side chain alkyl diol is selected from one or more of neopentyl glycol, 1,3-butanediol, 1,4-butanediol, 3-methyl-1,5-pentanediol, 2,4-diethyl-1,5-pentanediol, 2-butyl-2-ethyl-1,3-propanediol, and 2-methyl-1,8-octanediol.

6. The coating of claim 1, wherein, The neutralizing agent is selected from one or more of glacial acetic acid, citric acid, tannic acid, caffeic acid, and malic acid.

7. A process for the preparation of silicone-modified aqueous carbon dioxide-based polyurethane bamboo wood coating according to any one of claims 1 to 6, characterized in that, The method comprises the following steps: S1. According to the ratio, the carbon dioxide-based polyol, hydroxyl MQ silicone resin, diisocyanate, and organic tin are reacted at 60-120°C for 1-4 hours to obtain a first intermediate; S2. The first intermediate, acetone, and N-methyl diethanolamine are reacted at 10-35°C for 20-120 minutes to obtain a second intermediate; S3. The second intermediate, side chain alkyl diol, water, and neutralizing agent are reacted at 30-50°C for 20-40 minutes to obtain the silicone-modified aqueous carbon dioxide-based polyurethane resin.

8. The method of claim 7, wherein, In step S1, the hydroxyl MQ silicone resin is prepared by reacting 15-30 parts of hexamethyldisiloxane, 90-180 parts of tetraethyl orthosilicate, and 20-40 parts of tetramethyldisiloxane at 50-70°C in an acidic environment for 1-4 hours to synthesize Si-H bonded MQ silicone resin, and then performing a silicon hydride reaction on 60-120 parts of the Si-H bonded MQ silicone resin and 8-20 parts of 2-(allyloxy)ethanol at 50-70°C under nitrogen protection for 6-12 hours to obtain the hydroxyl MQ silicone resin.

9. Use of the coating of any one of claims 1-6 or the coating prepared by the method of claim 7 or 8 in the preparation of bamboo wood materials.

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