Ecological quick-acting NC paint and preparation method thereof

Abstract

The invention relates to the technical field of coatings, in particular to ecological quick-acting NC paint and a preparation method thereof.The preparation method comprises the steps that nitrocellulose is soaked in part of a mixed solvent to be fully swelled; adding the swollen nitrocellulose and the residual mixed solvent into a reaction kettle, stirring and dissolving to form a transparent glue solution matrix; adding the mixed resin and acetylated citrate into the transparent glue solution matrix, and uniformly mixing to construct a resin system; adding a functional filler, a flatting agent, a defoaming agent, a dispersing agent and the like into the resin system, and dispersing at a high speed to obtain paint liquid; detecting the viscosity of the paint liquid by using a viscometer, and adjusting to construction viscosity according to a test result; and filtering with a 200-mesh filter screen, and filling into a sealed container to obtain the ecological quick-acting NC paint. The low-VOC solvent system and the bio-based resin system are adopted, VOC emission can be remarkably reduced, and harm to the environment and the human body is reduced; the DSP cross-linking agent endows the paint film with the self-repairing capability by utilizing the reversible fracture and recombination characteristics of the DSP cross-linking agent.

Description

Technical Field

[0001] The present invention relates to the technical field of coatings, and specifically to an ecological and fast-acting NC paint and a preparation method thereof. Background Art

[0002] NC paint, also known as nitrocellulose paint, is a volatile paint made with nitrocellulose as the main film-forming substance, combined with solvents, plasticizers, pigments and other additives.

[0003] Traditional NC paints have poor environmental friendliness and relatively high volatile organic compound (VOC) content, which is harmful to the environment and human health. However, compared with PU paints (polyurethane paints, cured by chemical reactions), UV paints (ultraviolet cured paints, requiring special equipment for curing), and water-based paints, due to its core advantages of "fast construction, easy repair, and controllable cost", it still occupies an important position in the fields of furniture, automobiles, construction, handicrafts, etc.

[0004] With the tightening of environmental protection regulations (such as the EU REACH regulation and the Chinese GB 18581-2020 standard) and the increasing demand of consumers for healthy and environmentally friendly products, NC paints are developing towards environmental protection, functionality, and high performance. Developing an NC paint with both ecological and high performance has become an urgent need in the industry. Summary of the Invention

[0005] In order to solve the problems existing in the prior art, on the one hand, the present invention provides an ecological and fast-acting NC paint, aiming to combine ecological properties and high performance, and specifically adopts the following solutions: An ecological and fast-acting NC paint contains the following raw materials in parts by mass: 30-50 parts of a mixed solvent, 20-30 parts of a mixed resin, 20-30 parts of nitrocellulose, 3-6 parts of acetylated citrate, 9-15 parts of a functional filler, 0.1-0.3 parts of a leveling agent, 0.2-0.4 parts of an antifoaming agent, 0.3-0.5 parts of a dispersant, 0.1-0.3 parts of an anti-settling agent, and 2-5 parts of a DSP cross-linking agent; the mixed resin is compounded from cashew shell oil-based epoxy resin and maleic resin in a mass ratio of 1-4:1-3; the mixed solvent is compounded from ethyl lactate and propylene glycol monomethyl ether in a mass ratio of 7:3.

[0006] Preferably, the functional filler is compounded from cellulose nanocrystals and montmorillonite in a mass ratio of 1:0.5-1.5.

[0007] Preferably, the leveling agent is BYK-333.

[0008] Preferably, the antifoaming agent is BYK-024.

[0009] Preferably, the dispersant is Disperbyk-190.

[0010] Preferably, the anti-settling agent is Aerosil R972.

[0011] On the other hand, the present invention also provides a preparation method of an ecological quick-acting NC paint, comprising the following steps: 1) Cut the nitrocellulose into pieces and soak it in a part of the mixed solvent, and let it stand in a container to fully swell until there is no agglomeration; 2) Add the swollen nitrocellulose and the remaining mixed solvent to a reaction kettle, maintain the temperature at 30°C, and stir at a speed of 300 rpm until completely dissolved to form a transparent glue liquid matrix; 3) Keep the temperature at 30°C, add the mixed resin, acetylated citric acid ester and DSP crosslinking agent to the transparent glue liquid matrix, and stir at a speed of 600 rpm for 2 hours to ensure uniform mixing and construct a resin system; 4) Put the functional filler, leveling agent, defoaming agent, dispersant and anti-settling agent into the resin system, and disperse them evenly to obtain the paint liquid; 5) Detect the viscosity of the paint liquid with a viscometer and adjust it to the construction viscosity according to the test results; 6) After the viscosity of the paint liquid is adjusted, filter it through a 200-mesh filter screen and then fill it into a sealed container to obtain the ecological quick-acting NC paint.

[0012] Preferably, the target value of the viscosity of the paint liquid is 20 - 25 seconds for a cup No. 2 coating viscosity cup.

[0013] After adopting the above technical solutions, the beneficial effects of the present invention are as follows: The present invention adopts a low-VOC solvent system and a bio-based resin system, which can significantly reduce VOC emissions and reduce the harm to the environment and human body; the addition of the DSP crosslinking agent enables the paint film to form a denser and more stable coating structure during the drying process, further improving the comprehensive performance of the paint film; the DSP crosslinking agent endows the paint film with self-healing ability by utilizing its characteristics of reversible fracture and recombination. Detailed Description of the Invention

[0014] In order to make the purpose, technical solutions and advantages of the present invention clearer, the following further describes the present invention in detail with reference to specific embodiments. It should be understood that the specific embodiments described herein are only configured to explain the present invention and are not configured to limit the present invention. For those skilled in the art, the present invention can be implemented without some of these specific details. The following description of the embodiments is only for providing a better understanding of the present invention by showing examples of the present invention.

[0015] Example 1 This example provides a preparation method of an ecological quick-acting NC paint. The following are the specific preparation steps and technical details of this ecological quick-acting NC paint.

[0016] Step 1. Pretreatment of nitrocellulose Mix ethyl lactate and propylene glycol methyl ether in a mass ratio of 7:3 to prepare 30 parts of a mixed solvent, and reserve 30% of the total volume of the mixed solvent.

[0017] As the main solvent, ethyl lactate can effectively penetrate the molecular chains of nitrocellulose with its high polarity and bio-based characteristics, breaking hydrogen bonds and crystal regions, and its VOC content is much lower than that of traditional solvents (such as toluene and xylene). The compounding of ethyl lactate and propylene glycol methyl ether as a co-solvent takes into account solubility, evaporation rate, and environmental protection.

[0018] Weigh 20 parts (by mass) of nitrocellulose (nitrocellulose), cut it into pieces, soak it in the above 30% mixed solvent, place it in a container and let it stand still to fully swell until there is no caking.

[0019] Nitrocellulose is a long-chain polymer. It is difficult to dissolve quickly and uniformly when directly added to the solvent. Pretreatment can break the crystal region, promote subsequent uniform dissolution, and reduce the occurrence of caking.

[0020] Step 2. Preparation of adhesive solution Transfer the swollen nitrocellulose to a reaction kettle, and add the remaining 70% of the mixed solvent. Maintain the temperature at 30°C and stir at a speed of 300 rpm until completely dissolved to obtain a transparent adhesive solution matrix.

[0021] The molecular chains of the swollen nitrocellulose have been partially untangled, and high-shear stirring further promotes the diffusion of solvent molecules into the chain gaps to achieve molecular-level dispersion.

[0022] Step 3. Resin blending Maintain the temperature at 30°C, add 10 parts of CNSL (cashew nut shell liquid)-based epoxy resin, 10 parts of maleic resin, 3 parts of acetylated citric acid ester, and 2 parts of DSP cross-linking agent (dithiobis(succinimidyl propionate); CAS: 57757-57-0) to the transparent adhesive solution matrix, and stir at a speed of 600 rpm for 2 hours to ensure uniform mixing and construct a resin system.

[0023] CNSL (cashew nut shell liquid)-based epoxy resin contains a long-chain phenolic structure, which can improve the flexibility and thermal stability of the resin system and has good compatibility with nitrocellulose. As a bio-based resin, CNSL is derived from agricultural waste and has renewable properties compared to petroleum-based epoxy resins. Maleic resin has good compatibility with nitrocellulose and can improve the hardness of the paint film. The compounding of CNSL-based epoxy resin and maleic resin provides an adjustable compounding ratio, which can balance hardness and flexibility to meet the needs of different substrates.

[0024] As a bio-based plasticizer, acetylated citrate can reduce the viscosity of the system and improve processability. The DSP cross-linking agent can introduce disulfide bonds, which can form a covalent cross-linking network with the functional groups in the resin system during the film curing process, endowing the film with high mechanical strength. Under thermal stimulation, the disulfide bonds break and are re-oxidized to achieve the reconstruction of the cross-linking network, realizing the self-repair of micro-scratches on the film and maintaining the long-term beauty of the film.

[0025] Step 4: Functionalization of fillers Put 6 parts of cellulose nanocrystals, 3 parts of montmorillonite, 0.3 part of Disperbyk-190 and 0.1 part of Aerosil R972 into the resin system, disperse at a high speed of 1200 rpm for 15 minutes, then add 0.1 part of BYK-333 and 0.2 part of BYK-024, and stir at a speed of 600 rpm for 30 minutes to obtain the paint solution.

[0026] Cellulose nanocrystals are rod-shaped crystal materials with a relatively high aspect ratio. Interlaced cellulose nanocrystals can form a three-dimensional network structure, significantly enhancing the mechanical strength of the film. Montmorillonite is a layered silicate that can extend the gas diffusion path and reduce the oxygen transmission rate of the film. The three-dimensional network of cellulose nanocrystals and the lamellar structure of montmorillonite produce a synergistic strengthening effect: the three-dimensional network of cellulose nanocrystals forms and embeds into the interlayer domain of montmorillonite, enhancing the impact toughness through mechanical occlusion and stress dispersion; the montmorillonite lamellae disperse external stress and inhibit crack propagation, while the three-dimensional network bears the main load to achieve the balance of rigidity and toughness.

[0027] Disperbyk-190 is a high molecular weight copolymer dispersant containing anchoring groups, which can inhibit the agglomeration of particulate components (such as cellulose nanocrystals and montmorillonite). Aerosil R972 is a hydrophilic fumed silica, which can inhibit the sedimentation of particulate components. BYK-024 is a polyether silicone copolymer, which can achieve efficient defoaming by destroying the elasticity of the bubble film (reducing the surface viscosity) and preventing bubble recombination.

[0028] BYK-333 is a polyether-modified polydimethylsiloxane leveling agent, which can improve the leveling property of the film. After the coating is applied, BYK-333 quickly migrates to the gas-liquid interface to form a uniform molecular layer, avoiding sudden changes in surface tension caused by the solvent evaporation gradient, thereby inhibiting the formation of defects such as orange peel.

[0029] Step 5: Detection and formulation Use a Tu-2 cup viscometer (NK-2 viscosity cup) to measure the time required for the paint solution to flow from the full cup to the break point at 25°C. The target value is 20 - 25 seconds, and repeat 3 times and take the average value. Adjust the viscosity to the target construction viscosity by solvent addition method or adjusting the resin system according to the test results.

[0030] If it is greater than 25 seconds, it means the viscosity is high, which may lead to poor leveling of the paint film, pinholes and other defects. Add mixed solvent according to the original formula ratio (ethyl lactate: propylene glycol methyl ether according to the mass ratio = 7:3), then stir at a low speed of 500 rpm for 20 minutes, let it stand for 15 minutes and then re-measure the viscosity.

[0031] If it is less than 20 seconds, it means that the viscosity is low, which may cause sagging, insufficient hiding power and other problems. Add CNSL-based epoxy resin, stir at a low speed of 500 rpm for 20 minutes, let it stand for 15 minutes and then re-measure the viscosity.

[0032] Step 6: Packaging After the viscosity of the paint liquid is adjusted, it is filtered through a 200-mesh filter and then filled into a sealed container to obtain an ecological quick-acting NC paint.

[0033] Example 2 A method for preparing an ecological quick-acting NC paint comprises the following steps: 1) Take 30% of the total volume of 35 parts of mixed solvent, weigh 25 parts of nitrocellulose, cut it into pieces and soak it in the above mixed solvent, and let it stand in a container to allow it to fully swell until there are no lumps; 2) Transfer the swollen nitrocellulose to a reactor, add the remaining 70% of the mixed solvent, maintain the temperature at 30°C, and stir at 300 rpm until it is completely dissolved to obtain a transparent glue matrix; 3) Maintaining the temperature at 30°C, add 15 parts of CNSL-based epoxy resin, 10 parts of maleic acid resin, 5 parts of acetylated citrate and 4 parts of DSP crosslinker to the transparent glue base, stir at 600 rpm for 2 hours to ensure uniform mixing, and construct a resin system; 4) 6 parts of cellulose nanocrystals, 6 parts of montmorillonite, 0.35 parts of Disperbyk-190 and 0.2 parts of AerosilR972 were added to the resin system, dispersed at a high speed of 1200 rpm for 15 minutes, and then 0.2 parts of BYK-333 and 0.3 parts of BYK-024 were added, and stirred at a speed of 600 rpm for 30 minutes to obtain a paint solution; 5) Use a viscometer to test the viscosity of the paint liquid and adjust the viscosity to the target construction viscosity based on the test results; 6) After the viscosity of the paint liquid is adjusted, it is filtered through a 200-mesh filter and then filled into a sealed container to obtain an ecological quick-acting NC paint.

[0034] Example 3 A method for preparing an ecological quick-acting NC paint comprises the following steps: 1) Take 30% of the total volume of 50 parts of the mixed solvent, weigh 30 parts of nitrocellulose, cut it into pieces and soak it in the above mixed solvent, and let it stand in a container to allow it to fully swell until there are no lumps; 2) Transfer the swollen nitrocellulose to a reaction kettle, add the remaining 70% of the mixed solvent, maintain the temperature at 30°C, and stir at a speed of 300 rpm until completely dissolved to obtain a transparent adhesive liquid matrix; 3) Keep the temperature at 30°C, add 16 parts of CNSL-based epoxy resin, 12 parts of maleic resin, 6 parts of acetylated citric acid ester, and 5 parts of DSP cross-linking agent to the transparent adhesive liquid matrix, and stir at a speed of 600 rpm for 2 hours to ensure uniform mixing and construct a resin system; 4) Put 6 parts of cellulose nanocrystals, 9 parts of montmorillonite, 0.5 part of Disperbyk-190, and 0.3 part of Aerosil R972 into the resin system, disperse at a high speed of 1200 rpm for 15 minutes, then add 0.3 part of BYK-333 and 0.4 part of BYK-024, and stir at a speed of 600 rpm for 30 minutes to obtain a paint solution; 5) Detect the viscosity of the paint solution with a viscometer and adjust the viscosity to the target construction viscosity according to the test results; 6) After the viscosity of the paint solution is adjusted, filter it through a 200-mesh filter screen and then fill it into a sealed container to obtain an ecological fast-acting NC paint.

[0035] Example 4 A preparation method of an ecological fast-acting NC paint includes the following steps: 1) Take 30% of the total volume of 30 parts of the mixed solvent, weigh 20 parts of nitrocellulose, cut it into pieces and soak it in the above-mentioned mixed solvent, and let it stand in a container to fully swell until there is no caking; 2) Transfer the swollen nitrocellulose to a reaction kettle, add the remaining 70% of the mixed solvent, maintain the temperature at 30°C, and stir at a speed of 300 rpm until completely dissolved to obtain a transparent adhesive liquid matrix; 3) Keep the temperature at 30°C, add 5 parts of CNSL-based epoxy resin, 15 parts of maleic resin, 3 parts of acetylated citric acid ester, and 2 parts of DSP cross-linking agent to the transparent adhesive liquid matrix, and stir at a speed of 600 rpm for 2 hours to ensure uniform mixing and construct a resin system; 4) Put 6 parts of cellulose nanocrystals, 3 parts of montmorillonite, 0.3 part of Disperbyk-190, and 0.1 part of Aerosil R972 into the resin system, disperse at a high speed of 1200 rpm for 15 minutes, then add 0.1 part of BYK-333 and 0.2 part of BYK-024, and stir at a speed of 600 rpm for 30 minutes to obtain a paint solution; 5) Detect the viscosity of the paint solution with a viscometer and adjust the viscosity to the target construction viscosity according to the test results; 6) After the viscosity of the paint solution is adjusted, filter it through a 200-mesh filter screen and then fill it into a sealed container to obtain an ecological fast-acting NC paint.

[0036] Example 5 A preparation method of an ecological quick-acting NC paint, comprising the following steps: 1) Take 30% of the total volume of 50 parts of the mixed solvent, weigh 20 parts of nitrocellulose, cut it into pieces and soak it in the above-mentioned mixed solvent, and let it stand in a container to fully swell until there is no agglomeration; 2) Transfer the swollen nitrocellulose to a reaction kettle, add the remaining 70% of the mixed solvent, maintain the temperature at 30°C, and stir at a speed of 300 rpm until completely dissolved to obtain a transparent glue liquid matrix; 3) Keep the temperature at 30°C, add 20 parts of CNSL-based epoxy resin, 10 parts of maleic resin, 3 parts of acetylated citrate ester and 2 parts of DSP cross-linking agent to the transparent glue liquid matrix, and stir at a speed of 600 rpm for 2 hours to ensure uniform mixing and construct a resin system; 4) Put 6 parts of cellulose nanocrystals, 3 parts of montmorillonite, 0.3 parts of Disperbyk-190 and 0.1 part of Aerosil R972 into the resin system, disperse at a high speed of 1200 rpm for 15 minutes, then add 0.1 part of BYK-333 and 0.2 part of BYK-024, and stir at a speed of 600 rpm for 30 minutes to obtain a paint liquid; 5) Detect the viscosity of the paint liquid with a viscometer and adjust the viscosity to the target construction viscosity according to the test results; 6) After the viscosity of the paint liquid is adjusted, filter it through a 200-mesh filter screen and then fill it into a sealed container to obtain the ecological quick-acting NC paint.

[0037] Example 6 A preparation method of an ecological quick-acting NC paint, comprising the following steps: 1) Take 30% of the total volume of 50 parts of the mixed solvent, weigh 25 parts of nitrocellulose, cut it into pieces and soak it in the above-mentioned mixed solvent, and let it stand in a container to fully swell until there is no agglomeration; 2) Transfer the swollen nitrocellulose to a reaction kettle, add the remaining 70% of the mixed solvent, maintain the temperature at 30°C, and stir at a speed of 300 rpm until completely dissolved to obtain a transparent glue liquid matrix; 3) Keep the temperature at 30°C, add 24 parts of CNSL-based epoxy resin, 6 parts of maleic resin, 3 parts of acetylated citrate ester and 2 parts of DSP cross-linking agent to the transparent glue liquid matrix, and stir at a speed of 600 rpm for 2 hours to ensure uniform mixing and construct a resin system; 4) Put 6 parts of cellulose nanocrystals, 9 parts of montmorillonite, 0.3 parts of Disperbyk-190 and 0.1 part of Aerosil R972 into the resin system, disperse at a high speed of 1200 rpm for 15 minutes, then add 0.1 part of BYK-333 and 0.2 part of BYK-024, and stir at a speed of 600 rpm for 30 minutes to obtain a paint liquid; 5) Detect the viscosity of the paint solution with a viscometer and adjust the viscosity to the target construction viscosity according to the test results; 6) After the viscosity of the paint solution is adjusted, filter it through a 200-mesh filter screen and then fill it into a sealed container to obtain the ecological fast-acting NC paint.

[0038] Perform performance measurements on the ecological fast-acting NC paints prepared in Examples 1-6, and the results are shown in the following table.

[0039]

[0040] The VOC (volatile organic compound) content of the ecological fast-acting NC paint is reduced to ≤350 g / L, which is better than the 600-700 g / L of traditional nitro paints. Excessive use of CNSL-based epoxy resin will improve the flexibility of the paint film, so the paint film hardness of Example 6 is the lowest. Increasing the dosage of maleic resin will significantly increase the hardness, supplemented with montmorillonite and cellulose nanocrystals, so the hardness is the highest.

[0041] According to the above embodiments of the present invention, these embodiments do not describe all the details in detail, nor do they limit the invention to only the specific embodiments. Obviously, many modifications and variations can be made according to the above description. These embodiments are selected and specifically described in this specification to better explain the principles and practical applications of the present invention, so that those skilled in the art can make good use of the present invention and its modified use based on the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims

1. An ecological and fast-acting NC paint, characterized in that, The invention comprises the following raw materials in parts by weight: 30 to 50 parts of a mixed solvent, 20 to 30 parts of a mixed resin, 20 to 30 parts of nitrocellulose, 3 to 6 parts of acetylated citrate, 9 to 15 parts of a functional filler, 0.1 to 0.3 parts of a leveling agent, 0.2 to 0.4 parts of a defoaming agent, 0.3 to 0.5 parts of a dispersant, 0.1 to 0.3 parts of an anti-settling agent and 2 to 5 parts of a DSP cross-linking agent; The mixed resin is compounded by cashew nut shell oil-based epoxy resin and maleic acid resin in a mass ratio of 1-4:1-3; the mixed solvent is compounded by ethyl lactate and propylene glycol methyl ether in a mass ratio of 7:

3.

2. The ecological fast-acting NC paint according to claim 1, characterized in that: The functional filler is compounded with cellulose nanocrystals and montmorillonite in a mass ratio of 1:0.5-1.

5.

3. The ecological quick-acting NC paint according to claim 1, characterized in that: The leveling agent is BYK-333.

4. The ecological quick-acting NC paint according to claim 1, characterized in that: The defoamer is BYK-024.

5. The ecological quick-acting NC paint according to claim 1, characterized in that: The dispersant is Disperbyk-190.

6. The ecological quick-acting NC paint according to claim 1, characterized in that: The anti-settling agent is Aerosil R972.

7. A preparation method of the ecological quick-acting NC paint as described in claim 1, characterized in that, The steps include: 1) Cut the nitrocellulose into pieces and soak them in part of the mixed solvent. Let it stand in a container to allow it to fully swell until there are no lumps. 2) Add the swollen nitrocellulose and the remaining mixed solvent into the reactor, maintain the temperature at 30°C, and stir at 300 rpm until completely dissolved to form a transparent glue matrix; 3) Maintaining the temperature at 30°C, add the mixed resin, acetylated citrate and DSP crosslinker to the transparent glue base, stir at 600 rpm for 2 hours to ensure uniform mixing and build the resin system; 4) Add functional fillers, leveling agents, defoamers, dispersants and anti-settling agents into the resin system and disperse them evenly to obtain a paint solution; 5) Use a viscometer to test the viscosity of the paint and adjust it to the construction viscosity based on the test results; 6) After the viscosity of the paint liquid is adjusted, it is filtered through a 200-mesh filter and then filled into a sealed container to obtain an ecological quick-acting NC paint.

8. The preparation method of the ecological quick-acting NC paint according to claim 7, characterized in that: The target value for the viscosity of the paint solution is 20-25 seconds to apply 2 cups.

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