Environment-friendly pigment and preparation method thereof

Abstract

The application discloses an environment-friendly pigment and a preparation method thereof. The raw material components of the environment-friendly pigment include zinc oxide 15-25%, precipitated barium sulfate 20-30%, special calcium carbonate 25-35%, whitening and enhancing AB agent 11-23%, and high-performance dispersing agent 1-3%. The whitening and enhancing AB agent includes 8-15% of surface hydrophobic modified porous diatomite and 3-8% of cellulose nanocrystals. The preparation method comprises the following steps: firstly, pretreating the raw materials; then, preparing a dispersion phase; subsequently, compounding functional components; then, mixing base slurry; then, finely grinding the formed paste; and finally, adjusting and packaging the finished product. The application solves the problems of insufficient hiding power without titanium and poor mechanical capability of environment-friendly paint in the prior art.

Description

Technical Field

[0001] This invention relates to the field of environmentally friendly pigments, specifically to an environmentally friendly pigment and its preparation method. Background Technology

[0002] In the traditional pigment industry, titanium dioxide has long dominated the white pigment market due to its superior whiteness, hiding power, and chemical stability. However, its production process suffers from high energy consumption, high carbon emissions, and the environmental burden caused by the sulfuric acid process. With increasingly stringent global environmental regulations and a deepening of the concept of sustainable development, the development of high-performance, low-environmental-impact, and environmentally friendly alternative pigments has become an urgent need for the industry.

[0003] Existing environmentally friendly white pigment technologies mainly revolve around two paths: one is to modify or composite titanium dioxide to improve its utilization rate, such as using silica / alumina coating technology; the other is to develop titanium-free systems, using minerals such as zinc oxide, barium sulfate, and calcium carbonate as the core, and improving optical performance through particle size optimization, morphology control, and compounding techniques. However, the former still cannot get rid of its dependence on titanium resources, while the latter generally suffers from technical bottlenecks such as insufficient hiding power and poor mechanical properties of the coating film. In recent years, researchers have begun to explore structural white materials and biomimetic optical designs, attempting to achieve whitening effects through physical structure rather than chemical composition, but most of these efforts are still in the laboratory stage, facing challenges such as high cost, complex processes, and difficulties in large-scale production.

[0004] Therefore, it is essential to invent an environmentally friendly pigment and its preparation method. Summary of the Invention

[0005] The purpose of this invention is to provide an environmentally friendly pigment and its preparation method, which solves the problems of insufficient hiding power of titanium-free pigments and poor mechanical properties of environmentally friendly paints.

[0006] An environmentally friendly pigment and its preparation method are characterized in that the raw material components of the environmentally friendly pigment include: 15%-25% zinc oxide, 20%-30% precipitated barium sulfate, 25%-35% special calcium carbonate, 11%-23% whitening and strengthening agent, and 1%-3% high-performance dispersant.

[0007] Preferably, the whitening and strengthening AB agent comprises 8%-15% surface-hydrophobic modified porous diatomaceous earth and 3%-8% cellulose nanocrystals.

[0008] A method for preparing an environmentally friendly pigment is as follows: First, the raw materials are pretreated, including diatomaceous earth and cellulose nanocrystals being vacuum dried to a moisture content of less than 1%, and mineral fillers being dried and sieved. Then, a dispersed phase is prepared by using a dispersant to formulate a cellulose nanocrystal colloid and dispersing it at high speed. Next, functional components are compounded by adding diatomaceous earth and zinc oxide in stages while maintaining shear mixing. Then, the base slurry is mixed, and barium sulfate and calcium carbonate are added in stages and stirred. The resulting paste is finely ground using grinding beads in a three-stage grinding process to the desired fineness. Finally, the finished product is adjusted and packaged, and after adjusting the pH and viscosity, it is spray-dried to obtain the finished powder. Preferably, the surface-hydrophobic modified porous diatomaceous earth uses purified and calcined porous diatomaceous earth raw materials, and a silane coupling agent is used for wet or dry surface modification under suitable temperature and stirring conditions to ensure a uniform and stable hydrophobic film is formed on the surface of the diatomaceous earth particles. Finally, after drying and grinding, the surface-hydrophobic modified porous diatomaceous earth is obtained.

[0009] Preferably, the cellulose nanocrystals are made from natural cellulose, which is hydrolyzed with concentrated acid to remove the amorphous regions of the cellulose, retaining highly crystalline nanoscale rod-shaped crystals, and then purified by dialysis, high-pressure homogenization dispersion and spray drying.

[0010] Preferably, the raw material pretreatment involves placing surface-hydrophobically modified porous diatomaceous earth and cellulose nanocrystals in an 80°C vacuum drying oven for 4 hours to ensure a moisture content of less than 1%, thus eliminating the impact of adsorbed moisture during storage on dispersion stability. Zinc oxide, precipitated barium sulfate, and special calcium carbonate are treated in a 105°C forced-air drying oven for 2 hours to prevent agglomeration due to deliquescence in subsequent processes. All raw materials must pass through a 200-mesh sieve to ensure the absence of hard agglomerates, laying the foundation for subsequent fine dispersion. Preferably, the dispersed phase is prepared in a high-speed disperser equipped with a variable frequency control system. First, 60% of the formulation amount of deionized water is added, and a high-performance dispersant is slowly injected at 500 rpm, and stirred continuously for 5 minutes to ensure complete dissolution. Then, dry cellulose nanocrystal powder is evenly sprinkled onto the liquid surface in three batches. Each time it is added, the rotation speed is stepped up to 2000 rpm and maintained for 10 minutes until a uniform, transparent nanocolloidal dispersed phase with obvious Tyndall effect is formed. Preferably, the functional component compounding is carried out in a high-speed disperser at a shear rate of 2000 rpm, by sequentially adding pretreated surface-hydrophobic modified porous diatomaceous earth and zinc oxide through a negative pressure suction system. Each raw material is added at 5-minute intervals, and after addition, high-speed dispersion is continued for 15 minutes. The fluid shear force allows the open structure of the porous diatomaceous earth to initially intertwine with the cellulose nanocrystal network, forming a composite matrix system with both light scattering and antibacterial functions. Preferably, the main mixing process involves adjusting the disperser speed to 1500 rpm and adding precipitated barium sulfate and special calcium carbonate at a uniform speed via a metering conveyor belt, with the total feeding time controlled within 25 minutes. A cyclical pattern of adding materials first, then wetting, and finally dispersing is adopted, with a 1-minute pause after every 10% of raw materials is added to allow the particles to be fully wetted, ultimately forming a uniform paste-like material without dry powder lumps. Preferably, the pre-dispersed material is transferred to a rod-pin type nano-sand mill and loaded with zirconia ceramic grinding beads with a particle size of 0.3 mm, achieving a filling rate of 75%. Under circulating water cooling conditions of 8-10℃, three-stage series grinding is performed at a speed of 2800 rpm, with a residence time of 12 minutes per stage. The outlet material is tested by a laser particle size analyzer to ensure that D90 ≤ 2 μm, and the final fineness is measured to be ≥ 6.5 by a scraper fineness gauge. Preferably, the final adjustment and packaging of the finished product involves final adjustment of the ground slurry in a low-speed mixing tank: first, the pH is precisely adjusted to 8.8±0.2 using a 10% ammonia solution, and then 0.2% thickener is added according to the rheological curve to stabilize the rotational viscosity at 2100±100 cP. After filtration through a 500-mesh vibrating screen, it can be packaged as a slurry product or sent to a spray drying tower to obtain a powder product with excellent flowability.

[0011] Preferably, by incorporating composite oxides composed of different metal ions, such as cobalt blue, chrome green, iron oxide red, and titanium yellow, and utilizing their stable crystal structure and color-growth mechanism, highly weather-resistant and environmentally friendly colored coatings covering the full spectrum of red, yellow, blue, and green can be prepared. For example, adding cobalt aluminum spinel blue can produce a high-temperature resistant, non-migrating royal blue; adding rutile titanium nickel yellow can produce a bright and stable lemon yellow. These pigments are non-toxic, have strong lightfastness, and are suitable for outdoor architectural and industrial coatings.

[0012] Preferably, eco-friendly special color effects can be created by adding plant / mineral-based natural pigments and structural color-forming materials. By compounding plant-extracted pigments, such as indigo, curcumin, and sodium copper chlorophyllin, or mineral natural pigments, such as lapis lazuli blue and ochre red, and combining them with structural color-forming materials, such as mica-based pearlescent powder and cellulose photonic crystals, low-environmental-impact colored coatings with natural textures and biodegradable properties can be developed. For example, adding modified mica titanium pearlescent powder can produce an angle-dependent color effect; combining it with the self-assembled photonic structure of cellulose nanocrystals can produce iridescence or specific structural colors. This approach is particularly suitable for children's paints, artistic paints, and high-end eco-friendly decorative applications.

[0013] Compared with the prior art, the beneficial effects of the present invention are as follows: The formulation of this invention uses surface-hydrophobically modified porous diatomaceous earth. Through its natural multi-level pore structure and surface hydrophobic modification technology, a stable microscopic optical scattering network is constructed in the coating, which can significantly improve the dry hiding power and whiteness of the pigment and compensate for the optical shortcomings of the titanium-free system. At the same time, the hydrophobic surface enhances the compatibility with the resin, which not only improves the water resistance and impermeability of the paint film, but its pore structure also gives the coating a continuous humidity regulation function and can optimize the thixotropy and storage stability of the coating system.

[0014] The formulation of this invention uses cellulose nanocrystals. As a bio-based nanomaterial, the cellulose nanocrystals form an intertwined reinforcing network skeleton in the paint film, which greatly improves the tensile strength, crack resistance and wear resistance of the coating, giving the paint film both high hardness and flexibility. Its nanoscale fiber structure can effectively fill microscopic defects, improve the density and surface smoothness of the coating, and as a green additive, it can reduce the carbon footprint of the product and meet the requirements of high-end environmental certification.

[0015] This invention incorporates composite metal oxides, which exhibit color development through a stable spinel or rutile crystal structure, endowing the coating with superior weather resistance and chemical stability: color difference ΔE < 1.5 under strong ultraviolet radiation, and acid and alkali resistance exceeding level 5, maintaining vibrant color over a long period. Its non-toxic and environmentally friendly properties, along with high-temperature stability, make it suitable for high-end applications such as exterior wall coatings, industrial corrosion protection, and children's toys, achieving a balance between safety and performance.

[0016] This invention incorporates plant- and mineral-based natural pigments and structural color-forming materials. The combination of these pigments creates an eco-friendly aesthetic: plant pigments provide biodegradable, soft hues, while mica pearlescent powder generates a dynamic iridescent effect through multi-layer interference, giving the coating an angle-dependent, flowing luster. Simultaneously, the self-assembly structure of cellulose photonic crystals allows for precise control of specific wavelength reflections, forming an environmentally friendly structural color-forming coating that balances visual artistry with zero heavy metal emissions, meeting the needs of high-end interior decoration and sustainable design. Detailed Implementation

[0017] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0018] An environmentally friendly pigment and its preparation method are characterized in that the raw material components of the environmentally friendly pigment include: 15%-25% zinc oxide, 20%-30% precipitated barium sulfate, 25%-35% special calcium carbonate, 11%-23% whitening and reinforcing AB agent, and 1%-3% high-performance dispersant.

[0019] Preferably, the whitening and strengthening AB agent comprises 8%-15% surface-hydrophobic modified porous diatomaceous earth and 3%-8% cellulose nanocrystals.

[0020] The preparation method of an environmentally friendly pigment is as follows: S101: First, the raw materials are pretreated; S102: Subsequently, the dispersed phase is prepared; S103: Next, functional component compounding is carried out; S104: Then the base slurry is mixed in the main mixture; S105: Finely grind the formed paste; S106: Finally, adjust and package the finished product; Preferably, the surface-hydrophobic modified porous diatomaceous earth uses purified and calcined porous diatomaceous earth raw materials, and uses a silane coupling agent to carry out wet or dry surface modification treatment under suitable temperature and stirring conditions to ensure that a stable hydrophobic film is uniformly formed on the surface of the diatomaceous earth particles. Finally, after drying and grinding, the surface-hydrophobic modified porous diatomaceous earth can be obtained.

[0021] Preferably, the cellulose nanocrystals are made from natural cellulose, which is hydrolyzed with concentrated acid to remove the amorphous regions of the cellulose, retaining highly crystalline nanoscale rod-shaped crystals, and then purified by dialysis, high-pressure homogenization dispersion and spray drying.

[0022] Preferably, the raw material pretreatment involves drying the surface-hydrophobically modified porous diatomaceous earth and cellulose nanocrystals in an 80°C oven for 4 hours to ensure that the moisture content is less than 1%; zinc oxide, precipitated barium sulfate, and special calcium carbonate are dried at 105°C for 2 hours for later use. Preferably, the dispersed phase is prepared by adding deionized water and a high-performance dispersant in a high-speed disperser at 500 rpm, slowly adding dried cellulose nanocrystals, increasing the speed to 2000 rpm and continuing for 15 minutes to form a uniform and transparent nanocolloidal dispersed phase. Preferably, the functional component compounding is carried out by adding dry surface hydrophobic modified porous diatomaceous earth and zinc oxide sequentially to the dispersed phase while maintaining a high speed of 2000 rpm in a high-speed disperser, and continuing to disperse for 10 minutes after each addition of raw material to form a basic slurry with porous structure and antibacterial function. Preferably, the main mixing process involves gradually adding precipitated barium sulfate and special calcium carbonate to a high-speed disperser after adjusting it to 1500 rpm, controlling the feeding speed to prevent clumping, and continuing to disperse for 20 minutes after all the materials have been added to form a uniform paste. Preferably, fine grinding involves transferring the paste to a zirconia bead mill and grinding it three times at a speed of 3000 rpm, until the fineness is measured to be ≥6.5 on the scraper fineness gauge. Preferably, the finished product adjustment and packaging involves adjusting the pH of the ground slurry to 8.5-9.0, controlling the viscosity at 2000±200 cP using a rotational viscometer, filtering it through a 200-mesh sieve, and then sealing it in drums or spray drying it into powder. Example

[0023] An environmentally friendly pigment uses the following proportions of raw materials: 25% zinc oxide, 30% precipitated barium sulfate, 24% special calcium carbonate, 15% surface hydrophobic modified porous diatomaceous earth, 3% cellulose nanocrystals, and 3% high-performance dispersant.

[0024] After production according to the processing steps in this case, the low cellulose nanocrystal content means that the nano-reinforcing effect of the paint film is limited, and its crack resistance, toughness, and abrasion resistance may not be significantly improved. The overall mechanical properties of the paint film are closer to those of traditional mineral coatings. The product is suitable for applications with extremely high requirements for hiding power and workability, but with general requirements for paint film hardness and abrasion resistance, such as ordinary interior walls. Example

[0025] An environmentally friendly pigment uses the following proportions of raw materials: 20% zinc oxide, 30% precipitated barium sulfate, 24% special calcium carbonate, 15% surface hydrophobic modified porous diatomaceous earth, 8% cellulose nanocrystals, and 3% high-performance dispersant.

[0026] After production according to the processing steps in this case, the high amount of surface hydrophobic modified porous diatomaceous earth provides excellent covering and construction performance. At the same time, the high amount of cellulose nanocrystals constructs a dense nanofiber network, which can greatly improve the tensile strength, crack resistance and surface density of the coating film. However, this formula has the highest cost and the system viscosity is extremely high, which places extremely stringent requirements on the dispersion process and additives, making the preparation very challenging. Example

[0027] 1. An environmentally friendly pigment uses the following proportions of raw materials: zinc oxide 25%, precipitated barium sulfate 30%, special calcium carbonate 31%, surface hydrophobic modified porous diatomaceous earth 8%, cellulose nanocrystals 3%, and high-performance dispersant 3%.

[0028] 2. After production according to the processing steps in this case, the proportion of both key innovative materials used is reduced, and the product performance will be highly dependent on traditional zinc oxide and precipitated barium sulfate. The improvement in hiding power is limited, and the film performance may not differ much from the basic formulation, but costs are controlled. Example

[0029] An environmentally friendly pigment uses the following proportions of raw materials: 25% zinc oxide, 30% precipitated barium sulfate, 26% special calcium carbonate, 8% surface hydrophobic modified porous diatomaceous earth, 8% cellulose nanocrystals, and 3% high-performance dispersant.

[0030] After production according to the processing steps in this case, the high content of cellulose nanocrystals will give the paint film excellent toughness, hardness and unique texture, but the low surface hydrophobic modified porous diatomaceous earth will limit its structural whitening effect and workability improvement, and the slurry viscosity is high and the fluidity is poor. Example

[0031] An environmentally friendly pigment uses the following proportions of raw materials: 20% zinc oxide, 25% precipitated barium sulfate, 35% special calcium carbonate, 12% surface hydrophobic modified porous diatomaceous earth, 5% cellulose nanocrystals, and 3% high-performance dispersant.

[0032] After production according to the processing steps in this case, 12% of the surface-modified hydrophobic porous diatomaceous earth generates highly efficient light scattering. Combined with the intrinsic masking effect of zinc oxide, it surpasses traditional titanium-free formulations and approaches the level of low-titanium dioxide coatings. 5% of cellulose nanocrystals form a fiber network in the paint film, which increases the tensile strength of the coating by more than 50% and the wear resistance by 40%, while maintaining excellent flexibility. The surface-modified hydrophobic porous diatomaceous earth prevents sedimentation and improves anti-sagging properties. The cellulose nanocrystals and dispersants work together to achieve zero hard sedimentation and storage stability of more than 12 months.

[0033] This formulation achieves the optimal solution in five dimensions of performance: coverage, strength, construction, environmental protection, and cost by precisely controlling the synergistic effect of structural scattering and nano-enhancement.

[0034] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. An environmentally friendly pigment, characterized in that, The environmentally friendly pigment raw material composition includes: zinc oxide 15% - 25%, precipitated barium sulfate 20% - 30%, special calcium carbonate 25% - 35%, whitening and reinforcing AB agent 11% - 23%, and high-performance dispersant 1% - 3%.

2. The environmentally friendly pigment as described in claim 1, characterized in that, The whitening and strengthening AB agent comprises 8%-15% surface-hydrophobic modified porous diatomaceous earth and 3%-8% cellulose nanocrystals.

3. The preparation method of the environmentally friendly pigment as described in claim 1 is as follows: First, the raw materials are pretreated, including diatomaceous earth and cellulose nanocrystals being vacuum dried to a moisture content of less than 1%, and mineral fillers being dried and sieved; then, a dispersed phase is prepared by using a dispersant to prepare cellulose nanocrystal colloids and dispersing them at high speed; next, functional components are compounded by adding diatomaceous earth and zinc oxide in stages while maintaining shear mixing; then, the basic slurry is mixed in bulk, and barium sulfate and calcium carbonate are added in stages and stirred; the formed paste is finely ground by three-stage grinding with grinding beads to the required fineness; finally, the finished product is adjusted and packaged, and after adjusting the pH and viscosity, it is spray-dried to obtain the finished powder.

4. The surface-hydrophobic modified porous diatomaceous earth as described in claim 2 uses purified and calcined porous diatomaceous earth raw materials, and uses a silane coupling agent to carry out wet or dry surface modification treatment under suitable temperature and stirring conditions to ensure that a stable hydrophobic film is uniformly formed on the surface of the diatomaceous earth particles. Finally, after drying and grinding, the surface-hydrophobic modified porous diatomaceous earth can be obtained.

5. The cellulose nanocrystals as described in claim 2 are made from natural cellulose, by removing the amorphous regions of cellulose through concentrated acid hydrolysis, retaining highly crystalline nanoscale rod-shaped crystals, and then obtaining them through steps such as dialysis purification, high-pressure homogenization dispersion and spray drying.

6. The method for preparing the environmentally friendly pigment as described in claim 3, characterized in that, The raw material pretreatment involves drying surface-hydrophobically modified porous diatomaceous earth and cellulose nanocrystals in an 80°C oven for 4 hours to ensure a moisture content of less than 1%; zinc oxide, precipitated barium sulfate, and special calcium carbonate are dried at 105°C for 2 hours for later use. The dispersed phase preparation involves adding deionized water and a high-performance dispersant to a high-speed disperser at 500 rpm, slowly adding dried cellulose nanocrystals, increasing the speed to 2000 rpm and continuing for 15 minutes to form a uniform and transparent nanocolloidal dispersed phase. The aforementioned functional component composite is prepared by adding dry, surface-hydrophobic modified porous diatomaceous earth and zinc oxide sequentially to the dispersed phase while maintaining a high-speed disperser at a speed of 2000 rpm. Each addition of raw material is dispersed for 10 minutes to form a basic slurry with a porous structure and antibacterial function. The main mixing process involves gradually adding precipitated barium sulfate and special calcium carbonate to a high-speed disperser after adjusting it to 1500 rpm, controlling the feeding speed to prevent clumping, and continuing to disperse for 20 minutes after all the materials have been added to form a uniform paste. The fine grinding process involves transferring the paste to a zirconia bead mill and grinding it three times at a speed of 3000 rpm, until the fineness is measured to be ≥6.5 on the scraper fineness gauge. The finished product adjustment and packaging involves adjusting the pH of the ground slurry to 8.5-9.0, controlling the viscosity at 2000±200 cP using a rotational viscometer, filtering it through a 200-mesh sieve, and then sealing it in drums or spray drying it into powder.

7. The method for preparing the environmentally friendly pigment as described in claim 1, characterized in that, By incorporating metal ions into composite oxides and utilizing their stable crystal structure and color-developing mechanism, it is possible to prepare high-weather-resistant and environmentally friendly colored coatings with a full spectrum of colors.

8. The method for preparing the environmentally friendly pigment as described in claim 1, characterized in that, By compounding plant-extracted pigments or natural mineral color powders and combining them with structural color-generating materials, it is possible to develop low-environmental-impact colored coatings with natural texture and biodegradable properties.