High-gloss formula of nitro gloss paint for pencils and preparation method of high-gloss formula

Abstract

The invention discloses a high-gloss formula of nitro gloss paint for pencils and a preparation method, and particularly relates to the field of paint gloss paint. The coating comprises the following components: 18-22 parts of nitrocellulose with a nitrogen content of 12%, 8-12 parts of organosilicon modified resin, 5-8 parts of a gloss enhancing auxiliary agent, 2-4 parts of rare earth doped functional particles, 1.5-2.5 parts of a leveling agent, 1.5-2 parts of a cross-linking agent, and 50-60 parts of a solvent. The preparation method comprises the following steps: dissolving nitrocellulose and organosilicon modified resin; adding a gloss enhancing aid and rare earth doped functional particles, and dispersing to form a rare earth ion-silica chain-resin oriented network; the rare earth doped functional particles are prepared by doping a silica network with rare earth ions Ce < 3 + > and Eu < 3 + > and introducing an amino functional group, and the glossiness, the adhesive force, the wear resistance and the stability of a paint film are remarkably improved through the oriented network.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of paint finish, in particular to a high gloss formula and preparation method of nitro finish for pencil. BACKGROUND

[0002] The technical field of paint and varnish includes various coating materials for the surface of objects, mainly used to change or improve the physical and chemical properties of the surface of objects. These coating materials are usually composed of solvents, resins, pigments, additives, etc., and are widely used in furniture, construction, automobiles, electronics and other industries. There are various types of paint and varnish, including anticorrosive paint, decorative paint, functional paint, etc. The core content of this technical field is how to optimize the formula of paint, improve its performance, enhance the adhesion, durability, glossiness and other characteristics of the coating, while reducing environmental pollution and harm to human health.

[0003] Traditional nitro finish uses nitrocellulose as the main film-forming material, combined with resin, plasticizer and solvent system to prepare. It has the advantages of fast drying and good workability, but the film layer is prone to micropores, insufficient gloss, poor adhesion and other problems. Although the addition of silicone resin, nano filler or photoinitiating system can improve the performance, there are still problems such as easy agglomeration of nano filler, difficult control of silicone chain segment orientation, mismatch of solvent evaporation rate in multi-stage drying, and low energy utilization rate of photoreaction system.

[0004] The invention of patent CN104744620B uses core-shell structure emulsion; organic / inorganic hybrid crosslinking to improve adhesion, weather resistance, self-cleaning property; does not use titanium dioxide to avoid polymer degradation, with a bacteria inhibition rate > 70%, suitable for building, bridge and other exterior walls.

[0005] The invention of patent CN115322674B uses polyurethane acrylic resin + pure acrylic resin to reduce shrinkage, active monomer to improve adhesion, and silane coupling agent to enhance glass adhesion, with high hardness 5H, high wear resistance and water boiling resistance.

[0006] The invention of patent CN112409888B modifies the epoxy-polyurethane water dispersion, combining the hardness of epoxy and the toughness of polyurethane, self-crosslinking emulsion to improve curing speed and film-forming property, filler system tungsten carbide and spodumene to enhance wear resistance and chemical resistance, water-based and environmentally friendly, with high gloss > 90GU.

[0007] The invention of patent CN105295633B fluorine-modified acrylate emulsion improves weather resistance and adhesion, pre-disperses matt paste to ensure uniformity of matt finish, fast drying, storage stability, and is suitable for various substrates.

[0008] According to the background and prior art, the most commonly used traditional nitro-based lacquer currently has the problems of limited gloss generally less than 85GU, poor surface flatness, weak scratch resistance and adhesion, and the like, and is prone to peeling after use for a period of time. If rare earth particles are added to the coating, they are prone to agglomeration and uneven dispersion, resulting in a decrease in transparency and unstable coating film performance. The compatibility of nitrocellulose and modified resin in an organic solvent system is poor, resulting in uneven film formation. Traditional nitro-based lacquer is widely used for wood finishing such as pencils, and is mainly dried by solvent evaporation. High volatile organic compound emissions and physical degradation such as brittleness and surface defects are prone to occur, which are caused by the chemical properties of the material itself.

[0009] Therefore, the present application provides a high-gloss nitro-based lacquer formula for pencils and a preparation method thereof. SUMMARY

[0010] The main purpose of the present application is to provide a high-gloss nitro-based lacquer formula for pencils and a preparation method thereof, which can effectively solve the problems of yellowing of the paint surface, low gloss, low wear resistance, and low adhesion.

[0011] To achieve the above-mentioned purpose, the technical scheme adopted by the present application is as follows: A nitro-based lacquer for pencils comprises the following components by weight: 18-22 parts of nitrocellulose with a nitrogen content of 12%, 8-12 parts of silicone-modified resin, 5-8 parts of gloss-enhancing additives, 2-4 parts of rare earth-doped functional particles, 1.5-2.5 parts of leveling agents, 1.5-2 parts of cross-linking agents, and 50-60 parts of solvents. The rare earth-doped functional particles are Ce / Eu-doped SiO2 nanoparticles modified by 3-aminopropyltriethoxysilane under the action of a catalyst, wherein the molar ratio of Ce to Eu is 1.5-3:1, and the particle size is 30-90 nm.

[0012] Preferably, the solvents are obtained by mixing 25-35% of cyclohexanone methyl ether and 4-methyl-2-pentanone, 15-25% of dipropylene glycol methyl ether, 10-20% of 3-ethoxypropyl acetate, and 20-30% of tert-butyl acetate, and stirring for 30-60 minutes at 20-30°C.

[0013] The mass ratio of the two components in the cyclohexanone methyl ether and 4-methyl-2-pentanone mixture is 4:6.

[0014] More preferably, the percentages of the components in the solvent system are mass percentages, and the total of the four solvent components is 100%.

[0015] The present application also discloses a method for preparing a nitro-based lacquer for pencils, comprising the following steps: S1: Dissolve the nitrocellulose with a nitrogen content of 12% and the silicone-modified resin in a solvent to form a transparent base liquid under the condition of 550-650 rpm in a reaction kettle; S2: adding gloss enhancer and rare earth doped functional particles into the transparent base liquid prepared in S1, increasing the speed to 750-850 rpm, and dispersing for 50-70 min; S3: decreasing the speed to 200-300 rpm, adding leveling agent, isocyanate crosslinking agent and catalyst, stirring at 25-40 DEG C for 10-20 min to perform chemical bonding, vacuum degassing for 5-15 min, and filtering to obtain the nitro gloss paint for pencil.

[0016] Preferably, the chemical bonding is to make the amino group on the surface of the rare earth doped functional particles interact with the resin and crosslinking agent components through coordination, hydrogen bonding and van der Waals force under the condition of 25-40 DEG C, to form a silicon-oxygen network mainly composed of Si-O-Si bonds, and to generate a directional network structure of rare earth ion-silicon-oxygen chain-resin.

[0017] Preferably, the gloss enhancer is silicone leveling gloss agent, acrylic gloss promoter, polyurethane modified leveling agent or fluorocarbon modified gloss agent.

[0018] Preferably, the preparation process of the rare earth doped functional particles is as follows: S2-1: adding tetraethoxysilane 7-9 parts, ethanol 75-85 parts and deionized water 8-12 parts into a reactor in sequence, adding ammonia water to adjust pH to 9.0, and stirring at 350-450 rpm for 30-45 min to obtain a transparent precursor sol; S2-2: dissolving cerium nitrate 0.4-0.6 parts and europium nitrate 0.2-0.4 parts in 15-25 parts of ethanol, and adding the transparent precursor sol to stir for 10-18 min; S2-3: stirring at 35-45 DEG C for 50-70 min, and standing for 8-14 h to obtain a rare earth doped transparent sol, and adding 3-aminopropyl triethoxysilane 0.8-1.2 parts to react for 1.5-2.5 h; S2-4: vacuum drying at 55-65 DEG C for 6-10 h, and crushing to obtain the rare earth doped functional particles with a particle size of 30-90 nm.

[0019] More preferably, the adding in sequence is to add in sequence according to the polarity from large to small.

[0020] Preferably, the leveling agent is one of polyether modified silicone oil, fluorocarbon surface additive and acrylic leveling agent.

[0021] Preferably, the catalyst is organotin octanoate 0.05-0.1 parts by weight.

[0022] Compared with the prior art, the application has the following beneficial effects: 1. The present application constructs a rare earth ion-silicon chain-resin directional synergistic network structure by rare earth doped functional particles and silicone modified resin to improve the light reflection of paint film to form a smooth surface layer, improve the anti-ultraviolet reaction performance of paint film, the adhesion of gloss paint and color stability, so that the product can maintain high gloss appearance for a long time in outdoor or high temperature environment, has anti-yellowing and fluorescent function, and improves the decoration.

[0023] 2. The topcoat of the present application dopes Ce 3+ / Eu 3+ into the silicon-oxygen network structure, Ce 3+ absorbs ultraviolet rays to achieve energy transfer between Ce 4+ and Ce 3+ , alleviates oxidative degradation and prolongs the service life of the coating, and Eu 3+ itself has color, which can effectively observe the microscopic changes of the paint surface and the changes of the paint layer when combined with the self-repairing primer.

[0024] 3. The present application uses isocyanate crosslinking agent in combination with silicone resin, accelerates the surface drying and drying speed of paint film, and improves industrial efficiency through precise metering directional network, synergistic effect of optimized solvent system and crosslinking reaction kinetics. BRIEF DESCRIPTION OF DRAWINGS

[0025] Figure 1 The present application is a flowchart; DETAILED DESCRIPTION

[0026] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following will briefly introduce the drawings needed in the embodiment description. Obviously, the drawings in the following description are only some examples or embodiments of the present application, and for those skilled in the art, the present application can also be applied to other similar scenarios without creating labor. Unless it is obvious from the language environment or otherwise stated, the same reference numbers in the figures represent the same structure or operation.

[0027] A high-gloss formula and preparation method of nitro gloss paint for pencils, a flowchart of which is shown in Figure 1 , comprising the following steps: S1: 25-35% cyclohexanone methyl ether + 4-methyl-2-pentanone mixed components, 15-25% dipropylene glycol methyl ether, 10-20% 3-ethoxypropyl acetate, 20-30% t-butyl acetate are added into the reaction kettle in turn, stirring is started, the stirring speed is increased to 550-650 rpm, and then 12% nitrogen-containing nitrocellulose is slowly added under the condition that the addition rate is less than 50 g / min, the solution is dissolved completely until it is clear and free of particles, then silicone modified resin is added and stirring is continued for 30-60 minutes to form a transparent base solution.

[0028] The solvent system has the characteristics of multi-boiling point and gradient evaporation, which ensures that the film layer drying process is smooth and the stress distribution is uniform. Cyclohexanone methyl ether has strong solubility but high boiling point and slow evaporation, and 4-methyl-2-pentanone has strong solubility but moderate evaporation rate, so that the curves of solubility and drying speed are smooth and controllable.

[0029] S2: The transparent base liquid prepared in S1 is transferred into a dispersion kettle, 5-8 parts of gloss enhancing aid is added, the rare earth doped functional particles are dispersed with a small amount of solvent for 5-10 min, and at the same time the rotating speed is increased to 750-850 rpm, and dispersed for 50-70 min. After dispersion, check whether there is agglomeration with a 200 mesh screen. The dispersed sample is placed for 10 min and does not separate, which is qualified. In this step, the rare earth particles and the amino group on the surface of the siloxane chain form a coordination effect, the gloss enhancing aid migrates to the interface of the rare earth-siloxane chain, reduces the surface tension, and forms a stable transparent dispersion system, providing reaction sites for subsequent crosslinking reaction.

[0030] The rare earth doped particles are prepared by dissolving cerium nitrate 0.4-0.6 parts and europium nitrate 0.2-0.4 parts in 15-25 parts of ethanol, stirring for 10-18 min, then slowly adding to the sol system, maintaining the reaction temperature at 35-45℃, continuing to stir for 50-70 min, and reacting for 8-14 h to obtain a rare earth doped silica sol.

[0031] 0.8-1.2 parts of aminopropyltriethoxysilane is added to the system, and the reaction is carried out at constant temperature for 1.5-2.5 h to form an amino layer on the surface of the microparticles, improve the interfacial bonding energy with the resin, and vacuum dry at 55-65℃ for 6-10 h. The particle size is controlled at 30-90 nm to obtain rare earth doped functional particles. The rare earth ions are embedded in the framework through the Si-O-Ce / Eu reaction bond, reducing agglomeration.

[0032] S3: The mixed liquid of S2 is reduced to 200-300 rpm, 1.5-2.5 parts of leveling agent, 1.5-2 parts of crosslinking agent, and 0.05-0.1 parts of catalyst are added, stirred uniformly, and then placed for 5 min. The system is pumped into a vacuum tank, the vacuum degree is maintained at -0.085 MPa, degassed for 10 min, filtered, and a pencil nitro varnish is obtained. It is stored in airtight explosion-proof barrel and stored in the dark.

[0033] During the reaction, the amino groups on the surface of the rare earth doped functional particles can physically adsorb, form hydrogen bonds and local coordination with the components of the resin or crosslinking agent, forming a Si-O-Si-based silicon-oxygen network; at the same time, the isocyanate groups react with the amine groups and hydroxyl groups in the system to form urea bonds -NH-CO-NH- and carbamate bonds -NH-CO-O-, respectively, thereby further enhancing the chemical crosslinking and interfacial bonding between the rare earth ions, the silicon-oxygen chain and the resin, the catalyst catalyzes the crosslinking of the crosslinking agent and the hydroxyl resin, the rare earth ions promote the ordering of the silicon-oxygen chain, forming a directional light reflection interface, and vacuum degassing ensures that the paint film is bubble-free, improving the gloss of the mirror surface. The network can significantly improve the compactness and gloss of the paint film during formation, and improve adhesion and weather resistance.

[0034] At a catalyst temperature of 25-40°C, -NH, -OH, -Si-OH can adduct or condense with -NCO, or hydrolyze-condense to form a -Si-O-Si- network. When the catalyst or temperature is insufficient, it is mainly physical dispersion + hydrogen bonding or van der Waals force, and the gloss and adhesion are also improved.

[0035] The organosilicon modified resin has a hydroxyl value of 40-120 mg KOH·g -1 or a hydrolyzable silane end group content of 0.2-1.5 mmol·g -1， The network crosslinking amount formed is determined by titration to ensure that the prepared paint has the superior performance described in the present application. The isocyanate crosslinking agent is preferably an aliphatic polyisocyanate or its trimer, with an NCO mass fraction of 18-24%. Under the condition of NCO: active -H = 0.9-1.1, and under the catalysis of organotin octanoate, the resin is mainly hydrolyzable silane end groups, Si-OR:H2O = 1:1-3 is added and hydrolyzed under the catalysis of acid or amine, and then condensed to form a -Si-O-Si- network.

[0036] The rare earth ion-silicon-oxygen chain-resin directional network is an optional working condition, and its formation depends on the crosslinked body system and working conditions. When the chemical reaction is not triggered, the particles or resins are physically oriented and interfacially strengthened through hydrogen bonding and van der Waals forces, and not all conditions necessarily form covalent crosslinked structures.

[0037] Example 1 S1: Add 25% cyclohexanone methyl ether + 4-methyl-2-pentanone mixed components, 15% dipropylene glycol methyl ether, 10% 3-ethoxypropyl acetate, 20% t-butyl acetate to the reaction kettle in turn, start stirring, and slowly add nitrocellulose with a nitrogen content of 12% under the condition of stirring at a speed of 550 rpm, control the addition rate to be less than 50 g / min, dissolve completely until the solution is clear and free of particles, then add organosilicon modified resin and continue stirring for 30 minutes to form a transparent base solution.

[0038] S2: The transparent base solution prepared in S1 was transferred into a dispersion kettle, 5 parts of gloss enhancer was added, and the rare earth doped functional particles were dispersed using a small amount of solvent for 5 min, while the rotation speed was increased to 750 rpm, and dispersed for 50-70 min. After the dispersion was completed, a mixed solution was obtained.

[0039] Preparation of rare earth doped particles: 0.4 parts of cerium nitrate and 0.2 parts of europium nitrate were dissolved in 15 parts of ethanol, and after stirring for 10 min, they were slowly added dropwise into the sol system, the reaction temperature was maintained at 35°C, and after continuous stirring for 50 min, the reaction was carried out for 8 h to obtain a rare earth doped silica sol.

[0040] 0.8 parts of aminopropyltriethoxysilane was added to the system, and constant temperature reaction was carried out for 1.5 h to form an amino layer on the surface of the microparticles, improve the interfacial bonding energy with the resin, and vacuum drying was carried out at 55°C for 6 h. The particle size was controlled to 30 nm to obtain rare earth doped functional particles.

[0041] S3: The rotation speed of the mixed solution of S2 was reduced to 200 rpm, 1.5 parts of a leveling agent, 1.5 parts of a crosslinking agent, and 0.05 parts of a catalyst were added, and after stirring uniformly, it was left for 5 min. The system was pumped into a vacuum tank, the vacuum degree was maintained at -0.085 MPa, degassing was carried out for 10 min, and filtration was carried out to obtain a pencil nitro varnish, which was stored in a sealed explosion-proof bucket and stored in the dark.

[0042] Example 2 S1: 35% cyclohexanone methyl ether + 4-methyl-2-pentanone mixed components, 25% dipropylene glycol methyl ether, 20% 3-ethoxypropyl acetate, and 30% t-butyl acetate were sequentially added to a reaction kettle, and stirring was started. The rotation speed was increased to 650 rpm, and nitrocellulose with a nitrogen content of 12% was slowly added at a rate of less than 50 g / min. After complete dissolution, the solution was clear and particle-free. Then, a silicone modified resin was added, and stirring was continued for 60 min to form a transparent base solution.

[0043] S2: The transparent base solution prepared in S1 was transferred into a dispersion kettle, 5 parts of gloss enhancer was added, and the rare earth doped functional particles were dispersed using a small amount of solvent for 5 min, while the rotation speed was increased to 750 rpm, and dispersed for 50-70 min. After the dispersion was completed, a mixed solution was obtained.

[0044] Preparation of rare earth doped particles: 0.6 parts of cerium nitrate and 0.4 parts of europium nitrate were dissolved in 25 parts of ethanol, and after stirring for 18 min, they were slowly added dropwise into the sol system, the reaction temperature was maintained at 42°C, and after continuous stirring for 70 min, the reaction was carried out for 14 h to obtain a rare earth doped silica sol.

[0045] Amino propyl triethoxysilane 1.2 parts was added into the system, and the reaction was kept constant temperature for 2.5 hours to form an amino layer on the surface of the microparticles, so as to improve the interfacial bonding energy with the resin. The microparticles were dried under vacuum at 65°C for 10 hours, and then crushed to control the particle size at 90 nm to obtain the rare earth doped functional particles.

[0046] S3: The mixed solution of S2 was reduced to 300 rpm, 2.5 parts of leveling agent, 2 parts of crosslinking agent, and 0.1 part of catalyst were added, and after stirring uniformly, it was placed for 5 minutes. The system was pumped into a vacuum tank, and the vacuum degree was maintained at -0.085 MPa for 10 minutes for degassing. Filtration was performed to obtain a nitro gloss paint for pencils, which was stored in a sealed explosion-proof bucket and kept away from light.

[0047] Example 3 S1: 30% cyclohexanone methyl ether + 4-methyl-2-pentanone mixed components, 20% dipropylene glycol methyl ether, 15% 3-ethoxypropyl acetate, and 25% tert-butyl acetate were sequentially added to a reaction kettle, and stirring was started at a speed of 600 rpm. Nitrocellulose with a nitrogen content of 12% was slowly added under the condition of controlling the addition rate to be less than 50 g / min. After complete dissolution to form a clear solution without particles, silicone modified resin was added and stirring was continued for 45 minutes to form a transparent base solution.

[0048] S2: The transparent base solution prepared in S1 was transferred to a dispersion kettle, 7 parts of gloss enhancer was added, and the rare earth doped functional particles were dispersed with a small amount of solvent for 7 minutes while the rotation speed was increased to 700 rpm. Dispersion was performed for 60 minutes, and after dispersion was completed, a mixed solution was obtained.

[0049] Preparation of rare earth doped particles: Cerium nitrate 0.5 parts and europium nitrate 0.3 parts were dissolved in 20 parts of ethanol, and after stirring for 14 minutes, they were slowly added dropwise into the sol system. The reaction temperature was maintained at 40°C, and stirring was continued for 60 minutes. After 11 hours of reaction, a rare earth doped silica sol was obtained.

[0050] Amino propyl triethoxysilane 1.0 parts was added into the system, and the reaction was kept constant temperature for 2.0 hours to form an amino layer on the surface of the microparticles, so as to improve the interfacial bonding energy with the resin. The microparticles were dried under vacuum at 60°C for 8 hours, and then crushed to control the particle size at 60 nm to obtain the rare earth doped functional particles.

[0051] S3: The mixed solution of S2 was reduced to 250 rpm, 2.0 parts of leveling agent, 1.7 parts of crosslinking agent, and 0.07 part of catalyst were added, and after stirring uniformly, it was placed for 5 minutes. The system was pumped into a vacuum tank, and the vacuum degree was maintained at -0.085 MPa for 10 minutes for degassing. Filtration was performed to obtain a nitro gloss paint for pencils, which was stored in a sealed explosion-proof bucket and kept away from light.

[0052] Example 4 S1: 26% cyclohexanone methyl ether + 4-methyl-2-pentanone mixed components, 16% dipropylene glycol methyl ether, 11% 3-ethoxypropyl acetate, 21% t-butyl acetate were sequentially added to the reaction kettle, and stirring was started at a speed of 560 rpm. Nitrocellulose with a nitrogen content of 12% was slowly added under the condition that the addition rate was less than 50 g / min, and the solution was completely dissolved until it was clear and free of particles. Then, a silicone modified resin was added, and stirring was continued for 31 minutes to form a transparent base solution.

[0053] S2: The transparent base solution prepared in S1 was transferred to a dispersion kettle, 6 parts of a gloss-enhancing aid was added, and rare earth doped functional particles were dispersed using a small amount of solvent for 6 minutes while the rotation speed was increased to 755 rpm. Dispersion was carried out for 51 minutes, and after dispersion was completed, a mixed solution was obtained.

[0054] Preparation of rare earth doped particles: Cerium nitrate 0.56 parts and europium nitrate 0.3 parts were dissolved in 16 parts of ethanol, and after stirring for 11 minutes, they were slowly added dropwise to the sol system. The reaction temperature was maintained at 36°C, and stirring was continued for 51 minutes, and then the reaction was carried out for 9 hours to obtain a rare earth doped silica sol.

[0055] Ammonia propyl triethoxysilane 0.9 parts was added to the system, and constant temperature reaction was carried out for 1.6 hours to form an amino layer on the surface of the microparticles, improve the interfacial bonding energy with the resin, and vacuum drying was carried out at 56°C for 7 hours. The particle size was controlled to 31 nm after crushing, and rare earth doped functional particles were obtained.

[0056] S3: The mixed solution of S2 was reduced to a speed of 210 rpm, 1.6 parts of a leveling agent, 1.6 parts of a crosslinking agent, and 0.06 parts of a catalyst were added, and after stirring uniformly, it was left to stand for 5 minutes. The system was pumped into a vacuum tank, the vacuum degree was maintained at -0.085 MPa, and degassing was carried out for 10 minutes. Filtration was carried out to obtain a lead pencil nitro varnish, which was stored in a sealed explosion-proof bucket and kept in the dark.

[0057] Example 5 S1: 34% cyclohexanone methyl ether + 4-methyl-2-pentanone mixed components, 24% dipropylene glycol methyl ether, 19% 3-ethoxypropyl acetate, and 21% t-butyl acetate were sequentially added to the reaction kettle, and stirring was started at a speed of 555 rpm. Nitrocellulose with a nitrogen content of 12% was slowly added under the condition that the addition rate was less than 50 g / min, and the solution was completely dissolved until it was clear and free of particles. Then, a silicone modified resin was added, and stirring was continued for 59 minutes to form a transparent base solution.

[0058] S2: The transparent base solution prepared in S1 was transferred to a dispersion kettle, 7 parts of a gloss-enhancing aid was added, and rare earth doped functional particles were dispersed using a small amount of solvent for 9 minutes while the rotation speed was increased to 845 rpm. Dispersion was carried out for 65 minutes, and after dispersion was completed, a mixed solution was obtained.

[0059] Preparation of rare earth doped particles: 0.5 parts of cerium nitrate and 0.3 parts of europium nitrate were dissolved in 24 parts of ethanol, and after stirring for 17 min, they were slowly added dropwise into the sol system, the reaction temperature was maintained at 44°C, and the stirring was continued for 69 min, and then the reaction was carried out for 13 h, to obtain a rare earth doped silica sol.

[0060] 1.1 parts of aminopropyltriethoxysilane were added into the system, and the reaction was carried out at constant temperature for 2.4 h, so as to form an amino layer on the surface of the microparticles and improve the interfacial bonding energy with the resin, and then the system was dried under vacuum at 64°C for 9 h, and the particle size was controlled to be 89 nm by crushing, to obtain the rare earth doped functional particles.

[0061] S3: the stirring speed of the mixed solution of S2 was reduced to 290 rpm, 2.4 parts of a leveling agent, 1.9 parts of a crosslinking agent and 0.95 parts of a catalyst were added, and after uniform stirring, the system was left to stand for 5 min, and then the system was pumped into a vacuum tank, and the vacuum degree was maintained at -0.085 MPa for 10 min, and then filtration was carried out, to obtain a nitro paint for pencil, which was stored in a sealed explosion-proof bucket and kept away from light.

[0062] Comparative Example 1 In S2, no rare earth doped particles were used, and the remaining steps were the same as in Example 1.

[0063] Comparative Example 2 In S3, no crosslinking agent was added, and only a basic nitro paint was prepared, and the remaining steps were the same as in Example 1. In S1, no organic silicon modified resin was used, and only a common nitro paint resin was used, and the remaining steps were the same as in Example 1.

[0064] Comparative Example 4 In S1, the solvent system was randomly poured, and the order of pouring according to the polarity was not used, and the remaining steps were the same as in Example 1.

[0065] The nitro paint for pencil prepared in the above Examples 1 to 5 and Comparative Examples 1 to 4 was subjected to performance testing.

[0066] 1. Appearance and color detection According to GB / T9754 "Determination of 60° mirror gloss of color paint and varnish", the prepared paint was coated on the surface of a flat wood piece in two coats, and the thickness was 30 to 40 μm, and the paint was naturally dried for 24 h, and then a 60° gloss meter was used to closely contact the paint surface, and three different positions of each sample were tested, and the readings were recorded, and the average value was calculated, and the unit was GU.

[0067] 2. Drying performance detection Reference GB / T1728 "Determination of Drying Time of Paint and Varnish", film is prepared on standard glass plate with draw coater, thickness 100 μm, placed in 24℃ environment, timing from film preparation completion, every 5 min, measure the flagpole, can touch with finger or glass rod, record the time to reach dry to touch, continue to place, every 10 min, measure the time to dry to handle, every sample is repeated 3 times, take the average value.

[0068] 3. Abrasion resistance test Reference GB / T1768 "Determination of Abrasion Resistance of Paint and Varnish Film", uniformly paint on the plane of wood bar with thickness greater than 5 mm, ensure complete drying of the coating, install the experiment on the abrasion tester, contact surface of the grinding wheel, set 500g per grinding wheel, set 500rpm, clean the residual powder, weigh the mass of the sample before and after grinding.

[0069] 4. Adhesion test Reference GB / T9286-2021 Cross-cut test method, paint sample plate is adjusted for at least 16 hours under the condition of temperature 23±2℃, relative humidity 50±5%, use cutting tools, draw 6 parallel cuts on the coating at uniform speed and appropriate pressure, rotate the sample plate by 90° to draw the same number of cuts vertically on the original cuts to form a grid pattern, center the adhesive tape on the grid area, smooth with fingers, ensure good contact between the adhesive tape and the coating without bubbles, within 5-10 seconds, tear off the adhesive tape at an angle as close to 60° as possible, quickly and smoothly, under good lighting conditions, carefully observe the peeling of the coating in the grid area with a visual magnifying glass, Compare with the grading diagram in the standard to determine the adhesion grade.

[0070] Abrasion loss (mg / 100 turns) = (m1-m2) x 100 / N, N is the number of test turns.

[0071] The sample test results of examples 1-5 and comparative examples 1-3 are shown in Table 1: Table 1: Comparison of performance test results of examples and comparative examples The gloss of the embodiments of the present application is all ≥95 GU, which is much higher than that of the comparative examples. The gloss of comparative example 1 significantly decreases to 82 GU due to the lack of rare earth, which proves that the rare earth doped functional particles are the core to achieve ultra-high gloss. The mechanism lies in that the energy level transition of Ce 3＋ / Eu 3＋ ions releases heat energy in the film forming process, which promotes the directional arrangement of resin molecules, thereby forming a smoother mirror surface reflection layer, which also embodies that the directional network can absorb heat energy to form a smoother paint surface.

[0072] The lowest gloss of Comparative Example 3 indicates that the surface arrangement of the silicone segment under light induction can affect the gloss, and the micro-flatness of the paint film surface decreases, and the high gloss performance of the examples is the result of the synergistic effect of the rare earth energy level transition and the surface arrangement of the silicone.

[0073] The test data show that the present application successfully solves the problems of insufficient gloss, poor wear resistance and weak adhesion of traditional nitro-based light paint, the gloss of the nitro-based light paint of the present application is increased to ≥95GU, the abrasion is reduced by more than 50, and the adhesion reaches 1st level reaction.

[0074] The above shows and describes the basic principles and main features of the present application and the advantages of the present application. Those skilled in the art should understand that the present application is not limited to the above examples, and the above examples and descriptions in the specification are only to illustrate the principles of the present application, and various changes and improvements can be made without departing from the spirit and scope of the present application, and these changes and improvements all fall within the scope of the claimed present application. The scope of protection of the present application is defined by the appended claims and their equivalents.

Claims

1. A nitrocellulose varnish for pencils, characterized in that, The composition comprises the following components by weight: 18-22 parts nitrocellulose with a nitrogen content of 12%, 8-12 parts organosilicon modified resin, 5-8 parts gloss-enhancing agent, 2-4 parts rare earth-doped functional particles, 1.5-2.5 parts leveling agent, 1.5-2 parts isocyanate crosslinking agent, and 50-60 parts solvent. The rare earth-doped functional particles are Ce / Eu-doped SiO2 nanoparticles modified with 3-aminopropyltriethoxysilane under the action of a catalyst, wherein the molar ratio of Ce to Eu is 1.5-3:1 and the particle size is 30-90 nm.

2. The nitrocellulose varnish for pencils according to claim 1, characterized in that, The solvent is obtained by mixing 25-35% cyclohexanone methyl ether and 4-methyl-2-pentanone, 15-25% dipropylene glycol methyl ether, 10-20% ethyl 3-ethoxypropionate, and 20-30% tert-butyl acetate, and stirring at 20-30°C for 30-60 minutes. The mass ratio of the cyclohexanone methyl ether and 4-methyl-2-pentanone mixture is 4:

6.

3. A method for preparing the nitrocellulose varnish for pencils according to any one of claims 1 to 2, characterized in that, Includes the following steps: S1: Nitrocellulose with a nitrogen content of 12% and organosilicon-modified resin are dissolved in a solvent in a reactor at 550-650 rpm to form a transparent base liquid; S2: Add gloss-enhancing agent and rare earth-doped functional particles to the transparent base liquid prepared in S1, increase the speed to 750-850 rpm, and disperse for 50-70 min; S3: Reduce the speed to 200~300rpm, add leveling agent, isocyanate crosslinking agent and catalyst, mix at 25~40℃ for 10~20min for chemical bonding, degas under vacuum for 5~15min, and filter to obtain nitrocellulose varnish for pencils.

4. The method for preparing nitrocellulose varnish for pencils according to claim 3, characterized in that, The chemical bonding described in step S3 involves using a catalyst at 25–40°C to allow the amino groups on the surface of the rare earth-doped functional particles to interact with the resin and crosslinking agent components through coordination, hydrogen bonding, and van der Waals forces, forming a silicon-oxygen network dominated by Si-O-Si bonds, thus generating a directional network structure of rare earth ions-silicon-oxygen chains-resin.

5. The method for preparing nitrocellulose varnish for pencils according to claim 3, characterized in that, The gloss-enhancing additives mentioned in step S2 are silicone leveling gloss agents, acrylic gloss accelerators, polyurethane modified leveling agents, and fluorocarbon modified gloss agents.

6. The method for preparing nitrocellulose varnish for pencils according to claim 3, characterized in that, The preparation process of the rare earth-doped functional particles in step S2 is as follows: S2-1: Add 7-9 parts of tetraethoxysilane, 75-85 parts of ethanol, and 8-12 parts of deionized water to the reactor in sequence, add ammonia water to adjust the pH to 9.0, and stir at 350-450 rpm for 30-45 min to obtain a transparent precursor sol. S2-2: Dissolve 0.4-0.6 parts of cerium nitrate and 0.2-0.4 parts of europium nitrate in 15-25 parts of ethanol, add to a transparent precursor sol, and stir for 10-18 minutes; S2-3: Stir at 35-45℃ for 50-70 min, let stand for 8-14 h to obtain rare earth doped transparent sol, add 0.8-1.2 parts of 3-aminopropyltriethoxysilane and react for 1.5-2.5 h; S2-4: Vacuum drying at 55~65℃ for 6~10h, followed by pulverization to obtain rare earth-doped functional particles with a particle size of 30~90nm.

7. The method for preparing nitrocellulose varnish for pencils according to claim 3, characterized in that, The leveling agent mentioned in step S3 is one of polyether modified silicone oil, fluorocarbon surface additive, or acrylic leveling agent.

8. The method for preparing nitrocellulose varnish for pencils according to claim 3, characterized in that, The catalyst mentioned in step S3 is 0.05 to 0.1 parts by weight of organotin octanoate.

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