Ecological fast-acting NC paint and preparation method thereof

Abstract

The present invention relates to the field of coating technology, and specifically to an ecological fast-acting NC paint and a preparation method thereof, the preparation method comprising: soaking nitrocellulose in a portion of a mixed solvent to fully swell it; adding the swollen nitrocellulose and the remaining mixed solvent into a reactor, stirring and dissolving them to form a transparent glue liquid matrix; adding a mixed resin and acetylated citrate to the transparent glue liquid matrix, mixing them evenly, and constructing a resin system; adding functional fillers, leveling agents, defoamers, dispersants, etc. into the resin system, dispersing them at high speed, and obtaining a paint liquid; detecting the viscosity of the paint liquid with a viscometer, and adjusting it to a construction viscosity based on the test results; filtering through a 200-mesh filter, and then filling the paint into a sealed container to obtain an ecological fast-acting NC paint. The present invention adopts a low-VOC solvent system and a bio-based resin system, which can significantly reduce VOC emissions and reduce harm to the environment and human body; the DSP cross-linking agent, by utilizing its reversible fracture and recombination properties, imparts the paint film with self-repairing capabilities.

Description

Technical Field

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

[0002] NC paint, whose full name is nitrocellulose lacquer, is a volatile paint made with nitrocellulose (nitrocellulose cotton) as the main film-forming substance, combined with solvents, plasticizers, pigments and other additives.

[0003] Traditional NC paints are less environmentally friendly, with high levels of volatile organic compounds (VOCs), which are harmful to the environment and human health. However, compared to PU paints (polyurethane paints, which cure via chemical reactions), UV paints (ultraviolet-curing paints, which require specialized equipment for curing), and water-based paints, NC paints still hold a significant position in the furniture, automotive, construction, and handicraft industries, thanks to their core advantages of rapid application, ease of repair, and manageable costs.

[0004] With stricter environmental regulations (such as the EU REACH regulation and China's GB 18581-2020 standard) and growing consumer demand for healthy and environmentally friendly products, NC coatings are developing towards environmental friendliness, functionality, and high performance. Developing an NC coating that combines ecological and high performance has become an urgent industry need. Summary of the Invention

[0005] In order to solve the problems existing in the prior art, the present invention provides an ecological fast-acting NC paint, which aims to combine ecological properties with high performance, and specifically adopts the following solutions:

[0006] An ecological fast-acting NC paint comprises 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 a defoamer, 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 prepared by compounding cashew nut shell oil-based epoxy resin and maleic acid resin in a mass ratio of 1-4:1-3; and the mixed solvent is prepared by compounding ethyl lactate and propylene glycol methyl ether in a mass ratio of 7:3.

[0007] Preferably, the functional filler is compounded by cellulose nanocrystals and montmorillonite in a mass ratio of 1:0.5 to 1.5.

[0008] Preferably, the leveling agent is BYK-333.

[0009] Preferably, the defoaming agent is BYK-024.

[0010] Preferably, the dispersant is Disperbyk-190.

[0011] Preferably, the anti-settling agent is Aerosil R972.

[0012] On the other hand, the present invention also provides a method for preparing an ecological fast-acting NC paint, comprising the following steps:

[0013] 1) Cut the nitrocellulose into small pieces and soak them in part of the mixed solvent. Let it stand in a container until it fully swells and there are no lumps.

[0014] 2) Add the swollen nitrocellulose and the remaining mixed solvent to the reactor, maintain the temperature at 30°C, and stir at 300 rpm until completely dissolved to form a transparent glue matrix;

[0015] 3) Maintaining the temperature at 30°C, add the mixed resin, acetylated citrate, and DSP crosslinker to the transparent adhesive matrix and stir at 600 rpm for 2 hours to ensure uniform mixing and build the resin system;

[0016] 4) Add functional fillers, leveling agents, defoaming agents, dispersants and anti-settling agents into the resin system and disperse them evenly to obtain a paint solution;

[0017] 5) Use a viscometer to test the viscosity of the paint and adjust it to the construction viscosity based on the test results;

[0018] 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 the ecological fast-acting NC paint.

[0019] Preferably, the target value of the paint viscosity is 20-25 seconds to apply 2 cups.

[0020] After adopting the above technical solution, the beneficial effects of the present invention are:

[0021] The present invention adopts a low-VOC solvent system and a bio-based resin system, which can significantly reduce VOC emissions and reduce harm to the environment and human body; the addition of DSP cross-linking agent enables the paint film to form a denser and more stable coating structure during the drying process, further improving the overall performance of the paint film; the DSP cross-linking agent uses its reversible fracture and recombination properties to give the paint film self-repairing ability. DETAILED DESCRIPTION

[0022] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with 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 the need for some of these specific details. The following description of the embodiments is merely to provide a better understanding of the present invention by illustrating examples of the present invention.

[0023] Example 1

[0024] This embodiment provides a method for preparing an ecological fast-acting NC paint. The following are the specific preparation steps and technical details of the ecological fast-acting NC paint.

[0025] Step 1: Nitrocellulose pretreatment

[0026] Ethyl lactate and propylene glycol methyl ether were mixed in a mass ratio of 7:3 to prepare 30 parts of a mixed solvent, and 30% of the total volume of the mixed solvent was taken for standby use.

[0027] Ethyl lactate, the primary solvent, possesses high polarity and bio-based properties, effectively penetrating nitrocellulose molecular chains, disrupting hydrogen bonds and crystalline regions. Its VOC content is significantly lower than that of traditional solvents such as toluene and xylene. Ethyl lactate is combined with propylene glycol monomethyl ether as a co-solvent, achieving a balanced balance of solvency, volatility, and environmental performance.

[0028] Weigh 20 parts (by mass) of nitrocellulose (nitrocellulose cotton), chop it into pieces, soak it in the above 30% mixed solvent, and place it in a container and let it stand until it fully swells without lumps.

[0029] Nitrocellulose is a long-chain high molecular polymer that is difficult to dissolve quickly and evenly when added directly to the solvent. Pretreatment can destroy the crystalline area, promote subsequent uniform dissolution, and reduce the occurrence of agglomeration.

[0030] Step 2: Preparation of glue

[0031] The swollen nitrocellulose was transferred to a reactor, and the remaining 70% of the mixed solvent was added. The temperature was maintained at 30° C. and stirred at 300 rpm until the mixture was completely dissolved to obtain a transparent glue matrix.

[0032] The nitrocellulose molecular chains have been partially disentangled after swelling, and high shear stirring further promotes the diffusion of solvent molecules into the gaps between the chains, achieving molecular-level dispersion.

[0033] Step 3: Resin blending

[0034] Maintaining the temperature at 30°C, add 10 parts of CNSL (cashew nut shell liquid)-based epoxy resin, 10 parts of maleic acid resin, 3 parts of acetylated citrate, and 2 parts of DSP crosslinker (disulfide bissuccinimidyl propionate; CAS: 57757-57-0) to the transparent adhesive matrix and stir at 600 rpm for 2 hours to ensure uniform mixing to construct the resin system.

[0035] CNSL (cashew nut shell liquid)-based epoxy resins contain long-chain phenolic structures, which improve the flexibility and thermal stability of the resin system and have good compatibility with nitrocellulose. As a bio-based resin, CNSL is derived from agricultural waste and is more renewable than petroleum-based epoxy resins. Maleic acid resins are also highly compatible with nitrocellulose and can improve film hardness. Compounding CNSL-based epoxy resins with maleic acid resins allows for adjustable blending ratios to balance hardness and flexibility, tailored to the needs of different substrates.

[0036] Acetylated citrate, a bio-based plasticizer, reduces system viscosity and improves processability. DSP crosslinkers introduce disulfide bonds, forming a covalent crosslinking network with functional groups in the resin system during the film curing process, imparting high mechanical strength to the film. Under thermal stimulation, the disulfide bonds break and reoxidize, reconstructing the crosslinking network and enabling self-repair of micro-scratches in the film, maintaining long-term film aesthetics.

[0037] Step 4: Filler functionalization

[0038] 6 parts of cellulose nanocrystals, 3 parts of montmorillonite, 0.3 parts of Disperbyk-190 and 0.1 parts of Aerosil R972 were added to the resin system and dispersed at a high speed of 1200 rpm for 15 minutes. Subsequently, 0.1 parts of BYK-333 and 0.2 parts of BYK-024 were added and stirred at a speed of 600 rpm for 30 minutes to obtain a paint solution.

[0039] Cellulose nanocrystals are rod-shaped crystalline materials with a high aspect ratio. The interlaced cellulose nanocrystals can form a three-dimensional network structure, significantly improving the mechanical strength of the paint film. Montmorillonite is a layered silicate that can extend the gas diffusion path and reduce the oxygen permeability of the paint film. The three-dimensional network of cellulose nanocrystals and the lamellar structure of montmorillonite produce a synergistic reinforcement effect: the cellulose nanocrystals form a three-dimensional network embedded in the interlayer domain of montmorillonite, improving impact toughness and stress dispersion through mechanical interlocking: the montmorillonite lamellar layers disperse external stress and inhibit crack propagation, while the three-dimensional network bears the primary load, achieving a balance between rigidity and toughness.

[0040] Disperbyk-190, a high-molecular-weight copolymer dispersant containing anchoring groups, inhibits the agglomeration of particulate components (e.g., cellulose nanoparticles and montmorillonite). Aerosil R972, a hydrophilic fumed silica, inhibits the sedimentation of particulate components. BYK-024, a polyether siloxane copolymer, achieves efficient defoaming by disrupting the elasticity of the cell membrane (reducing surface viscosity) and preventing cell reorganization.

[0041] BYK-333 is a polyether-modified polydimethylsiloxane-based leveling agent that improves film leveling. After coating application, BYK-333 rapidly migrates to the air-liquid interface, forming a uniform molecular layer. This prevents sudden changes in surface tension caused by solvent evaporation gradients, thereby suppressing the formation of defects such as orange peel.

[0042] Step 5: Testing and deployment

[0043] Use a Tu-2 cup viscometer (NK-2 viscosity cup) at 25°C to measure the time it takes for the paint to flow from a full cup to the breaking point. Target a value of 20-25 seconds. Repeat three times and take the average. Based on the test results, adjust the viscosity to the target application viscosity by adding solvent or adjusting the resin system.

[0044] If it is greater than 25 seconds, it means the viscosity is high, which may lead to defects such as poor leveling of the paint film and pinholes. 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.

[0045] If the viscosity is less than 20 seconds, it indicates low viscosity, which can easily lead to problems such as sagging and insufficient hiding power. Add CNSL-based epoxy resin and stir at 500 rpm for 20 minutes. Let it stand for 15 minutes and then re-measure the viscosity.

[0046] Step 6: Packaging

[0047] 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 the ecological fast-acting NC paint.

[0048] Example 2

[0049] A method for preparing an ecological fast-acting NC paint comprises the following steps:

[0050] 1) Take 30% of the total volume of 35 parts of mixed solvent, weigh 25 parts of nitrocellulose, cut it into pieces, soak it in the mixed solvent, and let it stand in a container to allow it to fully swell until there are no lumps;

[0051] 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 completely dissolved to obtain a transparent glue matrix;

[0052] 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 adhesive matrix and stir at 600 rpm for 2 hours to ensure uniform mixing to form a resin system.

[0053] 4) Add 6 parts of cellulose nanocrystals, 6 parts of montmorillonite, 0.35 parts of Disperbyk-190, and 0.2 parts of Aerosil R972 into the resin system and disperse at 1200 rpm for 15 minutes. Then, add 0.2 parts of BYK-333 and 0.3 parts of BYK-024 and stir at 600 rpm for 30 minutes to obtain a paint solution.

[0054] 5) Use a viscometer to test the viscosity of the paint liquid and adjust the viscosity to the target application viscosity based on the test results;

[0055] 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 the ecological fast-acting NC paint.

[0056] Example 3

[0057] A method for preparing an ecological fast-acting NC paint comprises the following steps:

[0058] 1) Take 30% of the total volume of 50 parts of mixed solvent, weigh 30 parts of nitrocellulose, cut it into pieces and soak it in the mixed solvent. Let it stand in a container to allow it to fully swell until there are no lumps.

[0059] 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 completely dissolved to obtain a transparent glue matrix;

[0060] 3) Maintaining the temperature at 30°C, add 16 parts of CNSL-based epoxy resin, 12 parts of maleic acid resin, 6 parts of acetylated citrate, and 5 parts of DSP crosslinker to the transparent adhesive matrix and stir at 600 rpm for 2 hours to ensure uniform mixing to form a resin system.

[0061] 4) Add 6 parts of cellulose nanocrystals, 9 parts of montmorillonite, 0.5 parts of Disperbyk-190, and 0.3 parts of Aerosil R972 to the resin system and disperse at 1200 rpm for 15 minutes. Then, add 0.3 parts of BYK-333 and 0.4 parts of BYK-024 and stir at 600 rpm for 30 minutes to obtain a paint solution.

[0062] 5) Use a viscometer to test the viscosity of the paint liquid and adjust the viscosity to the target application viscosity based on the test results;

[0063] 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 the ecological fast-acting NC paint.

[0064] Example 4

[0065] A method for preparing an ecological fast-acting NC paint comprises the following steps:

[0066] 1) Take 30% of the total volume of 30 parts of mixed solvent, weigh 20 parts of nitrocellulose, cut it into pieces, soak it in the mixed solvent, and let it stand in a container to allow it to fully swell until there are no lumps;

[0067] 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 completely dissolved to obtain a transparent glue matrix;

[0068] 3) Maintaining the temperature at 30°C, add 5 parts of CNSL-based epoxy resin, 15 parts of maleic acid resin, 3 parts of acetylated citrate, and 2 parts of DSP crosslinker to the transparent adhesive matrix and stir at 600 rpm for 2 hours to ensure uniform mixing to form a resin system.

[0069] 4) Add 6 parts of cellulose nanocrystals, 3 parts of montmorillonite, 0.3 parts of Disperbyk-190, and 0.1 parts of Aerosil R972 to the resin system and disperse at 1200 rpm for 15 minutes. Then, add 0.1 parts of BYK-333 and 0.2 parts of BYK-024 and stir at 600 rpm for 30 minutes to obtain a paint solution.

[0070] 5) Use a viscometer to test the viscosity of the paint liquid and adjust the viscosity to the target application viscosity based on the test results;

[0071] 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 the ecological fast-acting NC paint.

[0072] Example 5

[0073] A method for preparing an ecological fast-acting NC paint comprises the following steps:

[0074] 1) Take 30% of the total volume of 50 parts of mixed solvent, weigh 20 parts of nitrocellulose, cut it into pieces and soak it in the mixed solvent. Let it stand in a container to allow it to fully swell until there are no lumps.

[0075] 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 completely dissolved to obtain a transparent glue matrix;

[0076] 3) Maintaining the temperature at 30°C, add 20 parts of CNSL-based epoxy resin, 10 parts of maleic acid resin, 3 parts of acetylated citrate, and 2 parts of DSP crosslinker to the transparent adhesive matrix and stir at 600 rpm for 2 hours to ensure uniform mixing to form a resin system.

[0077] 4) Add 6 parts of cellulose nanocrystals, 3 parts of montmorillonite, 0.3 parts of Disperbyk-190, and 0.1 parts of Aerosil R972 to the resin system and disperse at 1200 rpm for 15 minutes. Then, add 0.1 parts of BYK-333 and 0.2 parts of BYK-024 and stir at 600 rpm for 30 minutes to obtain a paint solution.

[0078] 5) Use a viscometer to test the viscosity of the paint liquid and adjust the viscosity to the target application viscosity based on the test results;

[0079] 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 the ecological fast-acting NC paint.

[0080] Example 6

[0081] A method for preparing an ecological fast-acting NC paint comprises the following steps:

[0082] 1) Take 30% of the total volume of 50 parts of mixed solvent, weigh 25 parts of nitrocellulose, cut it into pieces and soak it in the mixed solvent. Let it stand in a container to allow it to fully swell until there are no lumps;

[0083] 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 completely dissolved to obtain a transparent glue matrix;

[0084] 3) Maintaining the temperature at 30°C, add 24 parts of CNSL-based epoxy resin, 6 parts of maleic acid resin, 3 parts of acetylated citrate, and 2 parts of DSP crosslinker to the transparent adhesive matrix and stir at 600 rpm for 2 hours to ensure uniform mixing to form a resin system.

[0085] 4) Add 6 parts of cellulose nanocrystals, 9 parts of montmorillonite, 0.3 parts of Disperbyk-190, and 0.1 parts of Aerosil R972 to the resin system and disperse at 1200 rpm for 15 minutes. Then, add 0.1 parts of BYK-333 and 0.2 parts of BYK-024 and stir at 600 rpm for 30 minutes to obtain a paint solution.

[0086] 5) Use a viscometer to test the viscosity of the paint liquid and adjust the viscosity to the target application viscosity based on the test results;

[0087] 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 the ecological fast-acting NC paint.

[0088] The performance of the ecological fast-acting NC paint prepared in Examples 1-6 was measured, and the structures are shown in the following table.

[0089]

[0090] The VOC (volatile organic compound) content of the eco-friendly fast-acting NC paint is reduced to ≤350g / L, surpassing the 600-700g / L of traditional nitrocellulose lacquer. Excessive use of CNSL-based epoxy resin increases the film's flexibility, resulting in the lowest film hardness in Example 6. Increasing the amount of maleic acid resin significantly increases hardness, and combined with montmorillonite and cellulose nanocrystals, the film achieves the highest hardness.

[0091] While the embodiments of the present invention are described above, these embodiments do not exhaustively describe all details, nor do they limit the present invention to specific embodiments. Clearly, many modifications and variations can be made based on the above description. This specification selects and specifically describes these embodiments in order to better explain the principles and practical applications of the present invention, thereby enabling those skilled in the art to make good use of the present invention and its modifications and uses. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. An ecological fast-acting NC paint, characterized in that: The invention comprises the following raw materials in parts by weight: 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 a defoaming 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 prepared by compounding cashew nut shell oil-based epoxy resin and maleic acid resin in a mass ratio of 1-4:1-3; the mixed solvent is prepared by compounding ethyl lactate and propylene glycol methyl ether in a mass ratio of 7:3; the functional filler is prepared by compounding cellulose nanocrystals and montmorillonite in a mass ratio of 1:0.5-1.5; and the DSP cross-linking agent is dithiobissuccinimidyl propionate.

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

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

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

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

6. A method for preparing the ecological fast-acting NC paint according to claim 1, characterized in that: The steps include: 1) Cut the nitrocellulose into small pieces and soak them in part of the mixed solvent. Let it stand in a container until it fully swells and there are no lumps. 2) Add the swollen nitrocellulose and the remaining mixed solvent to 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 adhesive matrix and stir at 600 rpm for 2 hours to ensure uniform mixing and build the resin system; 4) Add functional fillers, leveling agents, defoaming agents, 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 the ecological fast-acting NC paint.

7. The method for preparing the ecological fast-acting NC paint according to claim 6, characterized in that: The target value for the paint viscosity is 20-25 seconds to apply 2 cups.

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