Gouache composition and preparation method thereof

Abstract

The gouache composition is characterized by comprising the following components: a binder, a dispersing agent, a thickening agent, a coloring agent, an inorganic filler, a wetting agent, a humectant, a defoaming agent and the balance of water, the binder is a non-reducing sugar, a sugar alcohol compound or a sugar alcohol polymer. The invention also discloses a preparation method of the gouache composition. The gouache composition disclosed by the invention has high aging resistance, high brightness and better dry-wet difference effect, and is suitable for professional art creation and occasions with higher requirements on quality of works.

Description

Technical Field

[0001] The present invention relates to a painting pigment, in particular to a gouache pigment and a preparation method of the gouache pigment. Background Art

[0002] Gouache, a water-based opaque pigment, is widely used in illustration, design, and education. Its unique hiding power and solubility are largely dependent on the pigment properties of the binder. The binder not only serves as a carrier for the pigment particles but also determines the pigment's brightness, tinting strength, drying speed, stability, and durability.

[0003] Existing gouache pigments often use natural colloids as binders, which suffer from low transparency and poor weather resistance. For example, see Chinese Invention Patent Application Publication No. 202411526889.7, "Method for Preparing a High-Solid, Low-Viscosity Peach Gum Solution for Gouache Pigments" (Application Publication No. CN119391003A). This document uses peach gum as a binder to produce a high-solid, low-viscosity peach gum solution, which has a good feel when used in gouache pigments. However, the treated peach gum still has a darker color, and the transmittance of a 40% peach gum aqueous solution is ≤75%.

[0004] With reference to the Chinese invention patent application with application number 201810263166.0, entitled "An Art Gouache Pigment Containing Nano-Components and Its Manufacturing Method" (application publication number CN108384300A), the application discloses an art gouache pigment containing nano-components made from epoxy resin-modified styrene-acrylic emulsion, epoxy acrylic resin, ascorbic acid, sodium citrate, tetrahydrophthalic anhydride, plant gum, wax, sodium dodecylbenzenesulfonate, tannate, fumed silica, nanofiller, colorant, fragrance, defoamer, wetting agent, preservative, and water. The pigment has high covering power, weather resistance, tinting power, and high temperature resistance, and dries quickly. After being placed in an outdoor environment or a high-temperature environment for a long time, its color difference changes very little, and it has very excellent stability. However, the gouache pigment with epoxy resin-modified styrene-acrylic emulsion and epoxy acrylic resin as binders has poor redissolubility after drying.

[0005] The solution prepared from natural peach gum is dark in color and it is difficult to achieve a color close to transparent. After being added to the gouache system, the non-transparent color of the peach gum itself will affect the color presentation of the color powder. In addition, after a long time, the color of the gouache pigment will darken due to the effects of light, oxygen, etc. In addition, the raw material of natural peach gum for preparing gouache binder is affected by moisture, temperature, light, etc., and the quality varies greatly between batches, and the color varies in depth. The peach gum picked directly from the tree needs to go through a series of operations such as soaking, degradation, and bleaching before it can be made into a more ideal peach gum solution to prepare gouache. The process is complicated, and the weather resistance of peach gum as a binder needs to be improved.

[0006] Generally speaking, moderately increasing the content of binder will make the color of gouache pigment more vivid, but it is difficult to prepare peach gum solution with higher concentration using ordinary equipment. On the one hand, peach gum absorbs a large amount of water during foaming, and it is difficult to stir the equipment. On the other hand, if pressurized, it is easy to cause uneven molecular weight distribution. At the same time, the viscosity of peach gum solution with higher concentration is already too high. When combined with a large amount of inorganic fillers and colorants, it will greatly affect the silky feel. Many gouache pigments on the market have large painting resistance. In fact, we hope to have a binder with high solubility, transparency and good weather resistance, so as to achieve more excellent performance expression of gouache pigments.

[0007] If you buy commercially available peach gum powder that can be dissolved directly, you should generally prepare a 30% concentration solution and add it to the gouache product system according to the formula amount. As the solid peach gum powder content increases in the formula system, the resistance of the prepared pigment will be very high, seriously affecting the painting effect. If the binder used has high solubility but low viscosity, it will provide more room for formula development and improve the overall performance of the pigment.

[0008] The current art market is in urgent need of a highly transparent and weather-resistant binder to mitigate the binder's inherent shortcomings of insufficient transparency and aging resistance, in order to produce gouache pigments with brighter colors and better weather resistance, which are particularly suitable for professional painting and long-term preservation needs. Summary of the Invention

[0009] The first technical problem to be solved by the present invention is to provide a gouache pigment composition with high light transmittance and excellent weather resistance in response to the above technical status quo.

[0010] The second technical problem to be solved by the present invention is to provide a method for preparing a gouache pigment composition with high light transmittance and excellent weather resistance in response to the above-mentioned technical status quo.

[0011] The technical solution adopted by the present invention to solve the above-mentioned first technical problem is: a gouache pigment composition, characterized by comprising the following components and their weight ratios:

[0012] Binder 10-45%;

[0013] Dispersant 0.5-5%;

[0014] Thickener 0.1-10%;

[0015] Colorant 5-30%;

[0016] Inorganic filler 5-25%;

[0017] Wetting agent 0.5% to 5%;

[0018] Moisturizer 1% to 4%;

[0019] Defoaming agent 0.1% to 1%;

[0020] Bactericidal preservative 0.15% to 0.4%;

[0021] The balance is water;

[0022] The binder is non-reducing sugar, sugar alcohol compound or sugar alcohol polymer.

[0023] The non-reducing sugar is at least one of trehalose, isomaltulose, fructooligosaccharides, galacto-oligosaccharides, isomaltooligosaccharides, sulfobutyl-β-cyclodextrin, and hydroxypropyl-β-cyclodextrin. Polysaccharides such as galacto-oligosaccharides and malto-oligosaccharides have extremely poor reactivity of the reducing chain ends. These oligosaccharides can be obtained by polymerizing carbohydrate monomers or by hydrolyzing high-polymer sugars such as starch and cellulose under acidic conditions.

[0024] The sugar alcohol compound is at least one of xylitol, sorbitol, erythritol and maltitol.

[0025] Preferably, the sugar alcohol compound comprises the following components and their weight ratios:

[0026] Xylitol 1;

[0027] Sorbitol 0.5~1:2.

[0028] The sugar alcohol polymer is at least one of xylitol polymer, sorbitol polymer, erythritol polymer or maltitol polymer, and the polymerization degree of the sugar alcohol polymer is 2-10.

[0029] The dispersant is at least one of sodium polyacrylate, modified polycarboxylate or phosphate dispersants.

[0030] The colorant is at least one of an inorganic pigment, an organic pigment or a dye.

[0031] The inorganic filler is at least one of barium sulfate, aluminum hydroxide, magnesium hydroxide, magnesium silicate, aluminum silicate, aluminum oxide, and wollastonite. The inorganic filler has a particle size of 1 to 10 μm and has been surface-modified with a silane coupling agent in an amount of 0.5 to 2% by weight of the filler. The inorganic filler is surface-treated with a silane coupling agent (KH-550) to enhance interfacial bonding with the carbohydrate binder and reduce cracking in the dry film (crack density is reduced by 50%).

[0032] Good gouache pigments require small differences in wetness and dryness, dark colors that are dark and do not turn gray after drying, and bright colors that are bright and have good covering power. Therefore, the selection of inorganic fillers is very important. On the one hand, after entering the system, a certain amount of addition is required to ensure the thickness brought by the filler, and the amount added should not be too little. Gouache requires a uniform matte texture. In particular, different powders have different effects on wetness and dryness, and the density also varies greatly. It is necessary to comprehensively consider the density of the finished pigment, the wetness and dryness difference effect, the matte effect, etc.

[0033] The wetting agent is at least one of an anionic wetting agent, a nonionic wetting agent, or a silicone wetting agent. Gouache systems require a high dosage of toner and filler, and some colors require multiple toners. The addition of a wetting agent effectively improves color compatibility and pigment wettability, enhancing the uniformity and color development of the entire gouache paint surface and reducing color floating and blooming in some colors.

[0034] The moisturizing agent is at least one of glycerin and PEG 400. Because the amount and type of each color powder added vary, it is desirable for the various gouache pigments to have similar drying speeds overall when making gouache pigments. Furthermore, in most cases, gouache pigments are designed to be left exposed for a long time until the painting is completed, although they can be sprayed with water after drying. Therefore, a moisturizing agent is essential when formulating the pigments, taking into account the drying speeds of the various colors and the moisturizing effect of the pigments during use.

[0035] The defoamer is at least one of a mineral oil defoamer and a silicone defoamer. The defoamer can eliminate bubbles generated during the preparation and use process to a certain extent, improve the stability and appearance quality of the product, and improve floating color, floating, and smoothness.

[0036] Wetting agents can reduce the surface tension of the pigment surface and improve the dispersibility and wettability of the pigment.

[0037] In order to make the carbohydrate binder have better viscosity and performance, the present invention uses a thickener to dynamically match the viscosity of the binder. The binder and the thickener meet one of the following requirements:

[0038] The first type has an average molecular weight of 800 Da or less, and the thickener is added in an amount of 3-10%. The thickener is at least one of fumed silica, bentonite, and attapulgite. Fumed silica can make the product more bulky and achieve a lower density for the same volume, effectively improving water distribution and reducing product costs. Bentonite also helps with shaping, but adding too much can significantly affect the color of the system.

[0039] The second type is that the average molecular weight of the binder is greater than 800Da, the addition amount of the thickener is 0.1-3%, and the thickener is at least one of sodium carboxymethyl cellulose, hydroxypropyl methylcellulose, hydroxyethyl cellulose, carbomer, and alkali swelling thickener.

[0040] The gouache pigment composition also includes the following components and their weight ratios: 0.15% to 0.4% bactericidal preservative. The bactericidal preservative can prevent the gouache pigment from becoming moldy and deteriorating during storage and use, thereby extending the shelf life of the product. The bactericidal preservative includes the following components and their weight ratios:

[0041] 5-chloro-2-methyl-4-isothiazolin-3-one 0.01% to 0.06%;

[0042] 2-Methyl-4-isothiazolin-3-one 0.03-0.1%;

[0043] 1,2-Benzisothiazoline-3-one 0.03% to 0.15%;

[0044] Octylisothiazolinone 0.04%~0.1%.

[0045] 5-Chloro-2-methyl-4-isothiazolin-3-one (CIT) and 2-methyl-4-isothiazolin-3-one (MIT) are isothiazolinones. Isothiazolinones kill microorganisms by breaking the bonds between bacterial and algal proteins. Upon contact with microorganisms, isothiazolinones rapidly and irreversibly inhibit their growth, leading to cell death. Therefore, they have a strong inhibitory and bactericidal effect on common bacteria, fungi, and algae.

[0046] 1,2-Benzisothiazolin-3-one (BIT) is broad-spectrum and highly effective: BIT fungicides effectively kill a wide range of bacteria, fungi, molds, and yeasts, including common microorganisms such as Escherichia coli and Bacillus. They exhibit broad-spectrum and long-lasting bactericidal activity, achieving significant antibacterial effects even at relatively low concentrations.

[0047] Strong chemical stability: BIT fungicides remain unchanged for one year when stored at -2°C to 50°C, allowing them to maintain good bactericidal effects in a variety of environmental conditions. Wide range of applications: They can be used in a pH range of 2 to 14 and are suitable for high temperature and strong alkaline environments.

[0048] Octylisothiazolinone (OIT) has the following advantages: Broad-spectrum bactericidal effect: OIT fungicides are highly effective in killing a wide range of bacteria, fungi, and yeasts, demonstrating broad-spectrum bactericidal properties. Strong stability: Stable under strong ultraviolet light and acid rain conditions, and not easily decomposed. Convenient operation: Easy to operate, can be added at any process, and has a wide pH range (5 to 9). Significant mildew control: Excellent mildew control, significantly superior to traditional mildew inhibitors. Good thermal stability: Uniform dispersion, thermal stability, non-flammability, and easy to transport and use.

[0049] The addition of OIT can also enhance the product's dry film mildew resistance, because gouache paint is often used in a square cup such as an 80ml cup and is dipped in with a paintbrush. If left open, the surface will lose water, requiring a certain dry film mildew resistance. This is especially true for colors prone to mildew, such as crimson, black, and ultramarine. After adding color powder to these gouache paints, some of the color powders, due to their porous structure, easily absorb the bactericidal preservatives, weakening the system's antiseptic and antiseptic effects. Through extensive testing, it has been found that the above four ingredients can be combined in an appropriate proportion to effectively reduce the risk of mildew and at an appropriate cost, rather than drastically increasing the content of the four substances. In particular, when some fungicides are added in large amounts, their heat resistance is poor and they are prone to yellowing over time. The appropriate proportion can ensure the antiseptic and mildew resistance while keeping the cost under control, and it is also less likely to cause yellowing due to the addition of some fungicides.

[0050] The technical solution adopted by the present invention to solve the above second technical problem is: a method for preparing a gouache pigment composition, characterized in that it comprises the following steps

[0051] ① Mix the binder, dispersant, wetting agent, moisturizer, bactericide and preservative, defoamer with water, heat to 50-70℃ and stir to dissolve;

[0052] ② Add colorant and inorganic filler, stir evenly, pour into grinding equipment, and disperse to a fineness of ≤40μm;

[0053] ③Add thickener;

[0054] ④ After further grinding, the fineness reaches ≤40 μm to obtain a gouache pigment composition.

[0055] Furthermore, in step ①, a bactericidal preservative is added in a weight ratio of 0.15% to 0.4%.

[0056] Compared with existing technologies, the advantages of this invention lie in: using non-reducing sugars, sugar alcohol compounds, or sugar alcohol polymers as the core binder, regulating the thickener dosage through molecular weight classification, and combining modified inorganic fillers to enhance the mechanical properties of the coating. The gouache pigment composition of this invention exhibits high aging resistance, high brightness, and a good wet-dry effect, making it suitable for professional art creation and applications requiring high-quality artwork.

[0057] Non-reducing sugars, sugar alcohol compounds or sugar alcohol polymers. These substances have stable chemical structures, no free aldehyde or ketone groups, cannot directly undergo reduction reactions with oxidants such as Fehling's reagent and Tollens reagent, and are difficult to dehydrate and decompose at high temperatures. Moreover, this type of binder has high purity and high solubility in water (greater than 30g / 100ml), and the transparency of its aqueous solution is higher than that of natural gum. The transmittance of 30% aqueous solution of the binder is ≥95% (wavelength 600nm); after irradiation with a xenon lamp (0.55W / m 2 After 20 hours, ΔE≤2.0 with no powdering, indicating excellent weather resistance. No VOC emissions are emitted during the preparation process. BRIEF DESCRIPTION OF THE DRAWINGS

[0058] Figure 1 This is a photograph of the coating film of the oligofructose-based gouache pigment (red) prepared in Example 3.

[0059] Figure 2 This is a photo of the coating film of the traditional peach gum-based pigment (red) prepared in Comparative Example 1.

[0060] Figure 3 These are photos of 30% binder aqueous solutions in various examples and comparative examples. Figure 4 This is a photo of a traditional crimson paint I unpacked and dipped a brush in in the paint, leaving it in the studio for a week. Figure 5 In order to directly pick up the mold with a palette knife, a photo of the mold being placed as a whole on the surface of the deep red gouache paint in Example 6. Figure 6 for Figure 5 Photos taken a week later. Figure 7 This is a photo of the gouache paint brush painting obtained in Example 7. Figure 8 This is a photo of the gouache paint brush painting obtained in Comparative Example 4. DETAILED DESCRIPTION

[0061] The present invention will be described in further detail below with reference to the accompanying drawings and embodiments.

[0062] Example 1: Xylooligosaccharide-based gouache pigment (low molecular weight binder)

[0063] Binder synthesis: Hemicellulose was depolymerized in 0.7 mol / L hydrochloric acid at 90°C for 60 min to obtain a xylooligosaccharide solution with an average molecular weight of 600, which was then dried into powder.

[0064] Formula: Xylooligosaccharides (30%), Fenghong bentonite SMP-HV2 (5%), sodium polyacrylate (2%), ultramarine (10%), modified kaolin (10%), Hemmings AP 7010 defoamer 0.5%, glycerin 2%, Dow 407 wetting agent 1%, bactericidal preservative 0.18% (CIT 0.03%, BIT 0.05%, MIT 0.06%, OIT 0.04%), water (39.62%).

[0065] preparation:

[0066] (1) Take 30g of oligoxylose, dissolve it in 70g of water, and test the light transmittance;

[0067] (2) Add 30 parts of oligoxylose to 39.62g of water and dissolve it at 60℃. Then add the formulated amount of glycerol, sodium polyacrylate, AP 7010, 407 wetting agent, and bactericidal preservative. Stir well and stir at a speed of 500-1000R / min.

[0068] (3) Add the formulated amount of ultramarine and kaolin, stir evenly, and grind with three rollers until the fineness is within 40 μm;

[0069] (4) After adding bentonite, continue grinding to reach the required state and conduct aging resistance test.

[0070] Performance: After testing, the transmittance of 30% binder aqueous solution is 96.5% (600nm); the ΔE of gouache paint dry film after UV aging is 1.35.

[0071] Example 2: Fructose-psicose eutectic binder (polymeric sugar)

[0072] Preparation of eutectic: Fructose and psicose were melt-mixed in a molar ratio of 1:2 and cooled to -20°C for crystallization.

[0073] Formula: eutectic binder (30%), Ashland hydroxyethyl cellulose 250HBR (0.6%), San Nopco 5020 dispersant (1.5%), phthalocyanine blue (10%), talc (8%), Hemmings AP 7015 defoamer 0.6%, BASF PEG 4003%, Dow 405 wetting agent 1%, bactericidal preservative 0.2% (CIT 0.02%, BIT 0.12%, MIT 0.06%, OIT 0.04%), water (45.1%).

[0074] preparation:

[0075] (1) Take 30g of eutectic binder, dissolve it in 70g of water, and test the transmittance;

[0076] (2) Add 30 parts of eutectic binder to 45.1g of water. After dissolving fully, add the formulated amount of PEG 400, 5020 dispersants, AP 7015, 407 wetting agents, and bactericidal preservatives. Stir well and stir at a speed of 500-1000R / min.

[0077] (3) Add the formulated amount of phthalocyanine blue and talcum powder, stir evenly, and grind with three rollers until the fineness is within 40 μm;

[0078] (4) After adding hydroxyethyl cellulose, continue grinding to reach the required state and conduct aging resistance test.

[0079] Performance: After testing, the transmittance of 30% binder aqueous solution is 97% (600nm); the ΔE of gouache paint dry film after UV aging is 1.7.

[0080] Example 3: Fructooligosaccharide-based gouache pigment (high molecular weight binder)

[0081] Binder Synthesis: Using sucrose as the raw material, β-fructofuranosidase catalyzes the transfer of the fructose group from sucrose to another sucrose molecule, forming oligofructose. Gel chromatography analysis indicates the average molecular weight of the oligofructose is 2000. Dry and set aside.

[0082] Formula: Fructooligosaccharides (18%), Ashland hydroxyethylcellulose 250HBR (0.4%), San Nopco SN-5040 dispersant (1.5%), 254 red powder (10%), precipitated barium sulfate (10%), Hemmings AP 7010 defoamer 0.6%, glycerin 4%, Clariant 407 wetting agent 1%, bactericidal preservative 0.2% (CIT 0.01%, BI T 0.1%, MIT 0.05%, OIT 0.04%), water (54.3%).

[0083] preparation:

[0084] (1) Take 30g of oligofructose, dissolve it in 70g of water, and test the light transmittance;

[0085] (2) Add 18 parts of oligofructose to 54.3g of water. After dissolving fully, add the formulated amount of PEG 400, 5040 dispersants, AP 7015, 407 wetting agents, and bactericidal preservatives. Stir well and stir at a speed of 500-1000R / min.

[0086] (3) Add the formulated amount of red powder and barium sulfate, stir evenly, and grind with three rollers until the fineness is within 40 μm;

[0087] (4) After adding hydroxyethyl cellulose, continue grinding to reach the required state and conduct aging resistance test.

[0088] Performance: After testing, the transmittance of 30% binder aqueous solution is 95.5% (600nm); the ΔE of gouache paint dry film after UV aging is 1.4.

[0089] Example 4: Erythritol-based gouache pigment

[0090] Formula: erythritol (40%), Fenghong BP-188B (3%), DuPont 902+ titanium dioxide (10%), precipitated barium sulfate (10%), San Nopco SN-5040 dispersant (1.2%), Hemmings AP 7015 defoamer 0.6%, glycerin 3%, Clariant 407 wetting agent 1%, bactericidal preservative 0.2% (CIT 0.01%, BIT 0.1%, MIT 0.05%, OIT 0.04%), water (31%).

[0091] preparation:

[0092] (1) Take 30g of erythritol, dissolve it in 70g of water, and test the transmittance;

[0093] (2) Add 40 parts of low erythritol to 31g of water. After dissolving fully, add the formulated amount of glycerin, 5040 dispersant, AP 7015, 407 wetting agent, and bactericidal preservative. Stir well and stir at a speed of 500-1000R / min.

[0094] (3) Add the formulated amount of titanium dioxide and barium sulfate, stir evenly, and grind with three rollers until the fineness is within 40 μm;

[0095] (4) After adding bentonite, continue grinding to reach the required state and conduct aging resistance test.

[0096] Performance: After testing, the transmittance of 30% binder aqueous solution is 97% (600nm); the ΔE of gouache paint dry film after UV aging is 0.88.

[0097] Example 5: Hydroxypropyl-β-cyclodextrin-based gouache pigment

[0098] Formula: Hydroxypropyl-β-cyclodextrin (30%, molecular weight approximately 1500Da), ASE-60 (1%), sun-fast yellow 10G color powder (6%), precipitated barium sulfate (8%), Xufeng calcium carbonate 6018 10%, San Nopco 5020 dispersant (1.5%), Hemmings AP7010 defoamer 0.8%, glycerin 4%, Dow 405 wetting agent 1%, bactericidal preservative 0.18% (CIT 0.03%, BIT 0.05%, MIT 0.06%, OIT 0.04%), water (37.52%).

[0099] preparation:

[0100] (1) Take 30g of hydroxypropyl-β-cyclodextrin, dissolve it in 70g of water, and test the transmittance;

[0101] (2) Add 30 parts of hydroxypropyl-β-cyclodextrin to 37.52g of water. After dissolving fully, add the formulated amount of glycerin, 5020 dispersant, AP 7010, 405 wetting agent, and bactericidal preservative. Stir well and stir at a speed of 500-1000R / min.

[0102] (3) Add the formulated amount of color powder, precipitated barium sulfate, and calcium carbonate, stir evenly, and grind with three rollers until the fineness is within 40 μm;

[0103] (4) After adjusting the pH value to 8-8.5, add ASE-60 to thicken the mixture to the required state and conduct aging resistance test.

[0104] Performance: After testing, the transmittance of 30% binder aqueous solution is 98.3% (600nm); the ΔE of gouache paint dry film after UV aging is 1.3.

[0105] Comparative Example 1: Traditional peach gum-based pigment

[0106] Formula (1): Commercially available peach gum powder (30%) and water (70%) were used to prepare a 30% solution (compared with Examples 1-5 for transparency).

[0107] Formula (2) and Example 3 differ in the type of binder, but have the same amount of binder added, the same amount of other substances added, and the same preparation. The color vividness and aging test results are compared;

[0108] Combine Figure 1 and Figure 2 As shown, the red pigment prepared in Example 3 and the red pigment prepared in the comparative example can be found by comparison. Figure 1 The red color of comparative example 1 is more vivid, while the bright red of comparative example 1 is darker. The selected toner 254 red is a red toner with a yellowish hue. The peach gum solution itself will affect the presentation of the toner because it is dark.

[0109] Results: The test showed that the transmittance of 30% peach gum aqueous solution was 62% (600nm); the ΔE of gouache paint dry film after UV aging was 4.2.

[0110] Comparative Example 2: Emulsion-based pigment

[0111] Formula (1): VAE707 emulsion (30%), water (70%), prepared at a concentration of 30% (compared with Examples 1-5 for transparency).

[0112] Formula (2) and Example 5 have the same content of other substances except for the binder. However, the performance of the pigment made with acrylic emulsion and gouache pigment is quite different.

[0113] The main problem is that after being left out in the open at room temperature, the surface of the emulsion-based pigment will form a continuous film after it is completely dry. This film is usually non-resolvable, which is not conducive to the use of the pigment by dipping (the pigment surface has formed a film, which is not easy to dip the pen. Sugar substances used as binders can overcome this problem). Under normal circumstances, after being placed for a certain period of time, the pigment can still be easily dipped. It is usually necessary to reduce the amount of emulsion used, which can easily cause the disadvantage of a large difference in the wetness and dryness of the pigment. In addition, the painted pigment cannot be redissolved and modified on the sketch paper or drawing board after it is completely dry. In addition, the drying speed of the acrylic emulsion system is slower than that of the gouache system, requiring the painter to have good pigment control ability.

[0114] Results: After testing, the transmittance of 30% emulsion was 12% (600nm); the ΔE of gouache paint dry film after UV aging was 1.2.

[0115] Test method:

[0116] Light transmittance: Prepare a 30% aqueous solution of the compounded or synthetic gouache binder, place the aqueous solution in a quartz cuvette (1 cm optical path), and measure the light transmittance at 600 nm using an Ocean Optics USB2000+ fiber optic spectrometer.

[0117] UV Weathering Resistance: 6.0 g of the prepared gouache pigment was placed in a mold with a 50 mm diameter groove. The paint was evenly spread and dried to form a dry film. The dry film was then aged in a UV aging chamber. A colorimeter was used to measure the color change of the dry film using the CIELAB formula under natural light or other equivalent conditions. The color difference formula is ΔE = √[(ΔL)² + (Δa)² + (Δb)²], where ΔL = L² - L¹, Δa = a² - a¹, and Δb = b² - b¹.

[0118] Combine Figure 3As shown, a to g correspond to Examples 1 to 5 and Comparative Examples 1 to 2, respectively. In terms of the transparency of the binder emphasized in this application, the five examples all perform very well, and are significantly optimized compared to natural gum; in terms of weather resistance, Example 4 has the best weather resistance, because erythritol has no aldehyde or ketone groups at all, and its structure is very stable, which is also reflected in laboratory experiments, but the disadvantage is that the bonding force is slightly poor. Combined with the transparency and weather resistance of the binder, and considering the film-forming properties and glossiness of gouache pigments, Examples 3 and 5 perform the best, because both examples are oligomers of sugars with appropriate molecular weights. If the molecular weight is too high, the viscosity of the aqueous solution increases and the solubility decreases, which is not conducive to the production of gouache pigments). Combined with the viscosity regulator, the performance and glossiness are better.

[0119] As can be seen from the viscosity data in the table below, the viscosity comparison at 30% in the examples shows that the viscosities in each example are still relatively suitable. (Higher concentrations with lower viscosities can meet requirements such as a better feel, the addition of more toner to enhance pigment vividness, and the addition of more inorganic fillers to achieve better coverage.)

[0120] The viscosity of the 30% binder aqueous solution of the embodiment and the comparative example is as follows (using 0# rotor, 60R / min) when tested using the NDJ-8S rotational viscometer of Shanghai Shangpu Instrument Equipment Co., Ltd.

[0121]

[0122] Example 6, crimson gouache pigment, component ratio: xylo-oligosaccharide 17%, Hemmings AP 7010 defoamer 0.4%, San Nopco 5040 dispersant 1%, rose lake 3.13%, Lithol Rubine 3.52%, red iron oxide 4.69%, precipitated barium sulfate 7.82%, Xufeng calcium carbonate 6018 7.85%, silicon dioxide 0.8%, Dow 407 wetting agent 1%, PEG 400 2%, Fenghong bentonite SMP-HV2 8.7%, fungicide 0.2% (5-chloro-2-methyl-4-isothiazolin-3-one (CIT) 0.04%, 1,2-benzisothiazolin-3-one (BIT) 0.05%, 2-methyl-4-isothiazolin-3-one (MIT) 0.06%, octylisothiazolinone (OIT) 0.05%), water 41.89%, preparation method refers to Example 1.

[0123] A more stringent method is to use the following methods: first, the cultured mold is not diluted; second, the number of mold species is increased to four, the mold is picked up directly with a palette knife, and the mold is placed on the paint surface to observe its growth. Figure 4 As shown, 1 in the figure is Paecilomyces variotii, 2 is Alternaria alternata, 3 is Aspergillus flavus, and 4 is Aspergillus niger.

[0124] In a constant temperature and humidity environment of 28℃*90% humidity, after one week, it was found that none of the four types of molds expanded, and even the original molds were eliminated by the fungicide preservatives in the pigment system, such as Figure 5 shown.

[0125] Comparative Example 3, crimson gouache pigment, component ratio: xylo-oligosaccharide 17%, Hemmings AP 7010 defoamer 0.4%, San Nopco 5040 dispersant 1%, rose lake 3.13%, Lithol Rubine 3.52%, red iron oxide 4.69%, precipitated barium sulfate 7.82%, Xufeng calcium carbonate 6018 7.85%, silicon dioxide 0.8%, Dow 407 wetting agent 1%, PEG 400 2%, Fenghong bentonite SMP-HV2 8.7%, bactericidal preservative 0.43% (5-chloro-2-methyl-4-isothiazolin-3-one (CIT) 0.12%, 1,2-benzisothiazolin-3-one (BIT) 0.13%, 2-methyl-4-isothiazolin-3-one (MIT) 0.16%, octylisothiazolinone (OIT) 0.02%), water 41.66%. The components of Comparative Example 3 are different from those of Example 6 except for the content of bactericidal preservative and water, while the contents of other substances are the same. The preparation method is similar to Example 1.

[0126] After opening the package of the crimson gouache of Comparative Example 3, dip a brush into the solution containing Aspergillus flavus, then use an inoculating loop to gently scrape off the cultured mold, taking care not to scrape off the PDA culture medium, cover a sterile container with two layers of sterilized gauze, filter the washed mold and set aside, dip a brush into the solution (the mold concentration is greater than 10 6 cfu / ml), shake the brush lightly to allow the mold solution to spread on the paint surface. After placing the paint, leave it at room temperature for a week. If obvious mold growth is found on the surface, such as Figure 6 Preparation of aflatoxin solution: Take the cultured aflatoxin culture medium and pour 15 ml of sterile sodium chloride and Tween 80 mixed solution (250 ml of sodium chloride + 0.1 g of Tween 80 solution and stir evenly).

[0127] The test results show that although the amount of fungicide added in Example 6 is reduced, the effect is very good. The appropriate combination of fungicides can effectively improve the problem of mold, rather than saying that the larger the amount added, the better.

[0128] Example 7, Plain gouache pigment, component ratio: 15% xylo-oligosaccharide, 0.4% Hemmings AP 7010 defoamer, 1% San Nopco 5040 dispersant, 11% iron blue powder, 12% aluminum silicate (left picture) (12% ground calcium carbonate (right picture), 1% Dow 407 wetting agent, 3% glycerin, 5% Fenghong bentonite SMP-HV2, 0.2% fungicide (0.04% 5-chloro-2-methyl-4-isothiazolin-3-one (CIT), 0.05% 1,2-benzisothiazolin-3-one (BIT), 0.06% 2-methyl-4-isothiazolin-3-one (MIT), 0.05% octylisothiazolinone (OIT),), 51.4% water. Preparation method: Refer to Example 1.

[0129] like Figure 7 As shown, after painting with the gouache paint brush obtained in the final embodiment, it can be seen that the picture is relatively uniform, the picture has no obvious shades, and the sense of depth is good.

[0130] Comparative Example 4, Plain gouache pigment, component ratio: xylo-oligosaccharide 15%, Hemmings AP 7010 defoamer 0.4%, San Nopco 5040 dispersant 1%, iron blue powder 11%, ground calcium carbonate 12%, Dow 407 wetting agent 1%, glycerin 3%, Fenghong bentonite SMP-HV2 5%, fungicide 0.2% (5-chloro-2-methyl-4-isothiazolin-3-one (CIT) 0.04%, 1,2-benzisothiazolin-3-one (BIT) 0.05%, 2-methyl-4-isothiazolin-3-one (MIT) 0.06%, octylisothiazolinone (OIT) 0.05%), water 51.4%. The components of Comparative Example 4 are different from those of Example 7 except that ground calcium carbonate replaces aluminum silicate. The preparation method is similar to that of Example 1.

[0131] like Figure 8 As shown, after painting with the gouache paint brush obtained in the final embodiment, it can be seen that the sense of depth is poor, resulting in an unnatural transition in the areas where light painting is desired.

Claims

1. A gouache pigment composition, characterized in that It includes the following components and their weight ratios: Binder 10-45%; Dispersant 0.5-5%; Thickener 0.1-10%; Colorant 5-30%; Inorganic filler 5-25%; Wetting agent 0.5% to 5%; Moisturizer 1% to 4%; Defoaming agent 0.1% to 1%; Bactericidal preservative 0.15% to 0.4%; The balance is water; The binder is non-reducing sugar, sugar alcohol compound or sugar alcohol polymer.

2. Gouache paint composition according to claim 1, characterized in that The non-reducing sugar is at least one of trehalose, isomaltulose, fructooligosaccharide, galacto-oligosaccharide, isomaltulose, sulfobutyl-β-cyclodextrin and hydroxypropyl-β-cyclodextrin.

3. Gouache paint composition according to claim 1, characterized in that The sugar alcohol compound is at least one of xylitol, sorbitol, erythritol and maltitol.

4. gouache pigment composition according to claim 3, characterized in that The sugar alcohol compound includes the following components and their weight ratios: Xylitol 1; Sorbitol 0.5~1:

2.

5. Gouache paint composition according to claim 1, characterized in that The sugar alcohol polymer is at least one of xylitol polymer, sorbitol polymer, erythritol polymer or maltitol polymer, and the polymerization degree of the sugar alcohol polymer is 2-10.

6. Gouache paint composition according to claim 1, characterized in that The inorganic filler is at least one of barium sulfate, aluminum hydroxide, magnesium hydroxide, magnesium silicate, aluminum silicate, aluminum oxide, and wollastonite.

7. The gouache pigment composition according to claim 6, characterized in that The particle size of the inorganic filler is 1-10 μm. The surface of the inorganic filler is modified by a silane coupling agent, and the amount of the silane coupling agent is 0.5-2% of the weight of the filler.

8. The gouache pigment composition according to claim 1, characterized in that The binder and thickener meet one of the following requirements: The first type, wherein the average molecular weight of the binder is ≤800Da, the addition amount of the thickener is 3-10%, and the thickener is at least one of fumed silica, bentonite, and attapulgite; The second type is that the average molecular weight of the binder is greater than 800Da, the addition amount of the thickener is 0.1-3%, and the thickener is at least one of sodium carboxymethyl cellulose, hydroxypropyl methylcellulose, hydroxyethyl cellulose, carbomer, and alkali swelling thickener.

9. The gouache pigment composition according to claim 1, characterized in that The bactericidal preservative comprises the following components and their weight ratios: 5-chloro-2-methyl-4-isothiazolin-3-one 0.01% to 0.06%; 2-Methyl-4-isothiazolin-3-one 0.03-0.1%; 1,2-Benzisothiazoline-3-one 0.03% to 0.15%; Octylisothiazolinone 0.04%~0.1%.

10. A method for preparing the gouache pigment composition according to any one of claims 1 to 9, characterized in that Includes the following steps ① Mix the binder, dispersant, wetting agent, moisturizer, defoamer, bactericide and preservative with water, heat to 50-70℃ and stir to dissolve; ② Add colorant and inorganic filler, stir evenly, pour into grinding equipment, and disperse to a fineness of ≤40μm; ③Add thickener; ④ After further grinding, the fineness reaches ≤40 μm to obtain a gouache pigment composition.

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