Modified cellulose additive for coating and preparation method thereof

Abstract

The invention relates to a modified cellulose additive for a coating and a preparation method thereof. The preparation method comprises the following steps: preparing titanium dioxide sol; reacting hydroxyethyl cellulose with anhydride to obtain a modified cellulose dispersion liquid; titanium dioxide sol and the modified cellulose dispersion liquid are mixed to obtain composite dispersion liquid, and fluorine-containing and silicon-containing reactive monomers and methyl methacrylate are used as monomer pre-emulsion to be polymerized in the composite dispersion liquid. The surface of cellulose is grafted with chlorinated betaine to provide antibacterial and anti-fouling properties, the prepared nano titanium dioxide sol improves the ultraviolet shielding property, and the chlorinated betaine and the nano titanium dioxide sol can realize uniform physical mixing and adsorption through intermolecular hydrogen bond acting force, hydrogen bond interaction and the like; a hydrophobic monomer prepolymer is polymerized on the surface of a compound to form a core-shell structure, so that the compactness of the composite material is further improved, a polymer chain on the surface contains rich siloxane and can be effectively compounded with resin in a coating after being added into the coating, and a water dispersion emulsion form can be compatible with various water-based resin systems and is not easy to agglomerate.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of coating additives, in particular to a modified cellulose additive for coatings and a preparation method thereof. BACKGROUND

[0002] As a key material for protecting substrates, prolonging their service life and endowing them with specific functions, the development of coatings has always been closely related to the demand of mankind for continuously improving the performance of materials. From early natural oils and raw lacquer to modern synthetic resins (such as alkyd, acrylic, epoxy, and polyurethane), coating technology has undergone tremendous evolution. Among them, outdoor protective coatings need to be exposed to sunlight, rain, temperature changes, pollutants, and microorganisms for a long time, and their performance is subject to extremely high requirements.

[0003] Traditional outdoor coatings, such as acrylic coatings or alkyd resin coatings, mainly focus on providing basic decorative and certain weather resistance. However, they generally have the defect of insufficient durability: they are easily powdered and discolored under the action of ultraviolet light, the mechanical strength of the coating gradually decreases, and they are difficult to resist the penetration and adhesion of pollutants such as oil stains and acid rain, leading to appearance contamination and degradation of protective function. The introduction of functional additives can effectively endow the coating with oil resistance, corrosion resistance and other properties, but in order to make the outdoor coating have more properties, a large amount of additives need to be added, the introduction of a large amount of additives undoubtedly increases the cost, and the simultaneous use of multiple initiators also faces the problem of compatibility, which may lead to the deterioration of the mechanical and barrier properties of the coating. SUMMARY

[0004] In view of the deficiencies in the prior art, the present application is based on biological material cellulose to prepare an additive material for coatings, which can effectively improve the antibacterial corrosion resistance and durability of the material when added to the coating, avoiding the problem of phase separation caused by the simultaneous use of multiple functional additives.

[0005] To achieve the above-mentioned purpose, the present application provides the following technical solutions: A preparation method of a modified cellulose additive for coatings, comprising the following steps: S1, preparing titanium dioxide sol from tetrabutyl titanate; S2, first forming an acid anhydride intermediate from chloroacetic acid and trimethyl acetyl chloride; adding hydroxyethyl cellulose and deionized water into a reaction bottle, ultrasonic treatment for 30 min, adding the acid anhydride intermediate for room temperature reaction for 4-6 h; adding trimethylamine solution, heating to 60℃ for reaction for 3 h, cooling, and adjusting the pH to neutral to obtain a modified cellulose dispersion; S3, adding the titanium dioxide sol into the system of step S2, stirring for reaction for 4-8 h to obtain a composite dispersion; S4, the fluorine-containing reactive monomer and the silicon-containing reactive monomer are mixed with methyl methacrylate, deionized water and a reactive emulsifier are added, and high-speed shearing emulsification is performed for 15 min to form a monomer pre-emulsion; S5, the composite dispersion liquid of step S3 is heated to 70-80℃, one-third of the monomer pre-emulsion is added, an initiator ammonium persulfate is added, and reaction is performed for 30 min; the remaining monomer pre-emulsion is slowly added dropwise to the composite dispersion liquid, while the initiator ammonium persulfate is supplemented, and reaction is performed for 6 h; after cooling, the product is sieved and then dispersed in deionized water to obtain the product.

[0006] Further, the specific process of step S1 is as follows: 10-20 parts by weight of tetrabutyl titanate is stirred and mixed with anhydrous ethanol in a volume ratio of 1:4, and 1-3 parts by weight of acetylacetone is added to form solution A; 3-10 parts of glacial acetic acid is mixed with 50-100 parts by weight of a 20% ethanol solution to form solution B, solution B is added dropwise to solution A, and stirring is continued until a clear and transparent titanium dioxide sol is obtained; the product is left to stand overnight for use.

[0007] Further, the preparation process of the acid anhydride intermediate is as follows: Chloroacetic acid, triethylamine and DMF are added to a reaction bottle, stirred and mixed uniformly, and a solution of trimethylacetyl chloride in DMF is added dropwise, stirring is performed for 2-8 h, reaction is completed, the precipitate is removed by filtration, and the filtrate is the acid anhydride intermediate.

[0008] Further, the mass ratio of the hydroxyethyl cellulose to the acid anhydride intermediate is 1:0.5-2.

[0009] Further, in step S4, the amount ratio of the titanium dioxide sol to the modified cellulose dispersion liquid, in terms of solid content, is 1-3 g:5 g.

[0010] Further, in step S4, the fluorine-containing reactive monomer is selected from one or more of trifluoroethyl methacrylate, hexafluorobutyl methacrylate, dodecafluoroheptyl acrylate and perfluorohexylethyl methacrylate; the silicon-containing reactive monomer is selected from one or more of γ-methacryloyloxypropyl trimethoxysilane, vinyl triethoxysilane and vinyl trimethoxysilane; and the reactive emulsifier is one or more of allyloxy hydroxypropyl sodium sulfonate, vinyl sodium sulfonate and m-styrene sodium sulfonate.

[0011] Further, in step S4, the molar ratio of the fluorine-containing reactive monomer, the silicon-containing reactive monomer, methyl methacrylate and the reactive emulsifier is 1-3:0.5-1.5:5-10:0.5-1.

[0012] Furthermore, in step S5, the ratio of the composite dispersion to the monomer preemulsion is recorded as 5~15:10~20 based on their solid content.

[0013] The present invention further provides a modified cellulose additive for coatings prepared by the above preparation method.

[0014] Compared with existing technologies, the beneficial effects of this invention are as follows: This invention focuses on the preparation of an additive that can be added to outdoor coatings to improve their antifouling, anticorrosive, and aging resistance by using natural polymer material cellulose and inorganic material titanium dioxide; by grafting chlorinated betaine onto the surface of cellulose to provide antibacterial and antifouling properties, and by preparing nano-titanium dioxide sol to improve ultraviolet shielding, the two can achieve uniform physical mixing and adsorption through intermolecular hydrogen bonding forces and hydrogen bond interactions; then, a hydrophobic monomer prepolymer composed of fluorine-containing reactive monomers, silicon-containing reactive monomers, and methyl methacrylate polymerizes on the surface of the composite to form a core-shell structure, further improving the density of the composite material; since the polymer chains on the surface contain abundant siloxanes, adding it to the coating can effectively combine with the resin in the coating, and the water-dispersible emulsion form is compatible with various water-based resin systems, is not prone to agglomeration, and the introduction of an additive can bring functions such as aging resistance, antibacterial and antifouling properties, avoiding the use of excessively multifunctional additives. Detailed Implementation

[0015] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. 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 skilled in the art without creative effort are within the scope of protection of the present invention.

[0016] Furthermore, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0017] Example 1: A modified cellulose additive for coatings S1. Mix 15 parts by weight of tetrabutyl titanate and anhydrous ethanol at a volume ratio of 1:4, and add 2 parts by weight of acetylacetone to form solution A. Mix 5 parts of glacial acetic acid with 80 parts by weight of 20% ethanol solution to form solution B. Add solution B dropwise to solution A and stir continuously until a clear and transparent titanium dioxide sol is obtained. Let it stand overnight for later use.

[0018] S2. Add 2g chloroacetic acid, 3ml triethylamine and 20ml DMF to the reaction flask, stir and mix well, add 2.5g trimethylacetyl chloride DMF solution dropwise, stir for 2~8 hours until the reaction is complete, filter to remove the precipitate, the filtrate is the acid anhydride intermediate, for later use. Add 10g of hydroxyethyl cellulose and 100ml of deionized water to a reaction flask, sonicate for 30min, add 2g of acid anhydride intermediate and react at room temperature for 4-6h; add 10ml of 33% trimethylamine aqueous solution, heat to 60℃ and react for 3h, cool down and adjust pH to neutral to obtain modified cellulose dispersion. S3. Add titanium dioxide sol to the system in step S2 at a mass ratio of 1:5 for solute, stir and react for 4-8 hours to obtain a composite dispersion, remove part of the solvent by rotary evaporation to obtain a composite dispersion with a solid content of 20-40 wt%. S4. Mix 3 mmol of perfluorohexyl ethyl methacrylate and 1.5 mmol of γ-methacryloyloxypropyltrimethoxysilane with 10 mmol of methyl methacrylate, add 30 ml of deionized water and 1 mmol of sodium vinyl sulfonate, and emulsify at high speed for 15 min to form a monomer pre-emulsion. S5. Heat 30 ml of the composite dispersion from step S3 to 70-80°C, add one-third of the monomer preemulsion, add 0.1 g of initiator ammonium persulfate, and react for 30 min. Slowly add the remaining monomer preemulsion to the composite dispersion, while adding 0.2 g of initiator ammonium persulfate, and keep the reaction at the temperature for 6 h. Cool down, sieve, and redisperse in deionized water to obtain a 20 wt% dispersion.

[0019] Example 2: S1. Mix 15 parts by weight of tetrabutyl titanate and anhydrous ethanol at a volume ratio of 1:4, and add 2 parts by weight of acetylacetone to form solution A. Mix 5 parts of glacial acetic acid with 80 parts by weight of 20% ethanol solution to form solution B. Add solution B dropwise to solution A and stir continuously until a clear and transparent titanium dioxide sol is obtained. Let it stand overnight for later use.

[0020] S2. Add 2g chloroacetic acid, 3ml triethylamine and 20ml DMF to the reaction flask, stir and mix well, add 2.5g trimethylacetyl chloride DMF solution dropwise, stir for 2~8 hours until the reaction is complete, filter to remove the precipitate, the filtrate is the acid anhydride intermediate, for later use. Add 10g of hydroxyethyl cellulose and 100ml of deionized water to a reaction flask, sonicate for 30min, add 2g of acid anhydride intermediate and react at room temperature for 4-6h; add 10ml of 33% trimethylamine aqueous solution, heat to 60℃ and react for 3h, cool down and adjust pH to neutral to obtain modified cellulose dispersion. S3. Add titanium dioxide sol to the system of step S2 according to the mass ratio of solute 3:5, stir and react for 4-8 hours, remove part of the solvent by rotary evaporation, and obtain a composite dispersion with a solid content of 20-40 wt%. S4, 3 mmol of trifluoroethyl methacrylate and 1.5 mmol of vinyl triethoxysilane were mixed with 10 mmol of methyl methacrylate, 30 ml of deionized water and 1 mmol of sodium allyloxy hydroxypropyl sulfonate were added, and high-speed shearing emulsification was performed for 15 min to form a monomer pre-emulsion; S5, the composite dispersion liquid of step S3 was heated to 70-80℃, one third of the monomer pre-emulsion was added, initiator ammonium persulfate was added, and reaction was performed for 30 min; the remaining monomer pre-emulsion was slowly added to the composite dispersion liquid while supplementing the initiator ammonium persulfate, and incubation reaction was performed for 6 h; after cooling, the product was sieved and then dispersed in deionized water to obtain a 20 wt% dispersion liquid.

[0021] Comparative Example 1: S1, a reaction bottle was added with 2 g of chloroacetic acid, 3 ml of triethylamine and 20 ml of DMF, and the mixture was stirred and mixed uniformly, a DMF solution of 2.5 g of trimethylacetyl chloride was added dropwise, stirring was performed for 2-8 h, reaction was completed, the precipitate was removed by filtration, and the filtrate was an anhydride intermediate which was prepared for use; A reaction bottle was added with 10 g of hydroxyethyl cellulose and 100 ml of deionized water, and ultrasonic treatment was performed for 30 min, 2 g of the anhydride intermediate was added, and reaction was performed at room temperature for 4-6 h; 10 ml of 33% trimethylamine aqueous solution was added, the temperature was raised to 60℃, and reaction was performed for 3 h, the temperature was lowered, and the pH was adjusted to neutral to obtain a modified cellulose dispersion liquid; S2, 3 mmol of perfluorohexyl ethyl methacrylate and 1.5 mmol of γ-methacryloyloxy propyl trimethoxysilane were mixed with 10 mmol of methyl methacrylate, 30 ml of deionized water and 1 mmol of sodium vinyl sulfonate were added, and high-speed shearing emulsification was performed for 15 min to form a monomer pre-emulsion; S3, the modified cellulose dispersion liquid was heated to 70-80℃, one third of the monomer pre-emulsion was added, initiator ammonium persulfate was added, and reaction was performed for 30 min; the remaining monomer pre-emulsion was slowly added to the composite dispersion liquid while supplementing the initiator ammonium persulfate, and incubation reaction was performed for 6 h; after cooling, the product was sieved and then dispersed in deionized water to obtain a 20 wt% dispersion liquid.

[0022] Comparative Example 2: S1, a reaction bottle was added with chloroacetic acid, triethylamine and DMF, and the mixture was stirred and mixed uniformly, a DMF solution of trimethylacetyl chloride was added dropwise, stirring was performed for 2-8 h, reaction was completed, the precipitate was removed by filtration, and the filtrate was an anhydride intermediate which was prepared for use; A reaction bottle was added with hydroxyethyl cellulose and deionized water, and ultrasonic treatment was performed for 30 min, the anhydride intermediate was added, and reaction was performed at room temperature for 4-6 h; trimethylamine solution was added, the temperature was raised to 60℃, and reaction was performed for 3 h, the temperature was lowered, and the pH was adjusted to neutral to obtain a modified cellulose dispersion liquid; S2, adding titanium dioxide powder into the modified cellulose dispersion solution, stirring for 4-8h to obtain a composite dispersion solution; concentrating to obtain a 20wt% dispersion solution.

[0023] Examples 1-2 and Comparative Examples 1-2 were added to the water-based acrylic paint at an amount of 10wt%, and the paint was observed for stratification and other phenomena. The paint was applied to wood to form a paint film, and the paint film performance was tested.

[0024] Mildew resistance: GB / T 21866-2008.

[0025] Water resistance: the surface state of the paint film was observed after immersion in deionized water for 7 days.

[0026] Weather resistance: the paint film state after 500h of testing using a QUV accelerated aging instrument.

[0027] Table 1 Comparative Example 1 did not add titanium dioxide, and was added to the water-based acrylic paint, still having good compatibility, but the paint film formed had poor mildew resistance, and the water resistance and weather resistance were also decreased compared to Examples 1 and 2. Comparative Example 2 used ordinary titanium dioxide powder mixed with modified cellulose, and did not form a core-shell structure by surface polymerization, and the poor stability of the additive itself led to poor mixing with the paint, and after standing, there was stratification and sedimentation, the mildew resistance was better than Comparative Example 1, but the poor compatibility with the paint led to poor water resistance and weather resistance.

[0028] Although the embodiments of the present application have been disclosed as above, it is not limited to the application listed in the specification and the embodiments, and can be fully applied to various fields suitable for the present application, and additional modifications can be easily realized by those skilled in the art, and therefore the present application is not limited to specific details, but is within the general concept defined by the claims and the equivalent scope.

Claims

1. A method for preparing a modified cellulose additive for paints, characterized by, Comprising the following steps: S1, preparation of titanium dioxide sol by tetrabutyl titanate; S2, first form acid anhydride intermediate with chloroacetic acid and trimethyl acetyl chloride; add hydroxyethyl cellulose and deionized water in the reaction bottle, ultrasonic treatment for 30 min, add acid anhydride intermediate, react at room temperature for 4-6 h; add trimethylamine solution, heat to 60℃ for 3 h, cool down, adjust pH to neutral, get modified cellulose dispersion; S3, add titanium dioxide sol to the system of step S2, stir for 4-8 h, get composite dispersion; S4, mix fluorine-containing reactive monomer and silicon-containing reactive monomer with methyl methacrylate, add deionized water and reactive emulsifier, high-speed shear emulsification for 15 min, form monomer pre-emulsion; S5, heat the composite dispersion of step S3 to 70-80℃, add one third of the monomer pre-emulsion, add initiator ammonium persulfate, react for 30 min; slowly drop the remaining monomer pre-emulsion into the composite dispersion, add initiator ammonium persulfate at the same time, keep warm for 6 h; cool down, sieve, then disperse in deionized water.

2. The method for producing a modified cellulose additive for paints according to claim 1, characterized by, The specific process of step S1 is: Stir 10-20 parts by weight of tetrabutyl titanate with anhydrous ethanol according to volume ratio 1:4, add 1-3 parts by weight of acetylacetone to form solution A; Mix 3-10 parts of glacial acetic acid with 50-100 parts by weight of 20% ethanol solution to form solution B, drop solution B into solution A, continue to stir until clear and transparent titanium dioxide sol is obtained; stand overnight for aging.

3. The method for producing a modified cellulose additive for paints according to claim 1, characterized by, The preparation process of the acid anhydride intermediate is: Add chloroacetic acid, triethylamine and DMF in the reaction bottle, stir and mix uniformly, drop in the DMF solution of trimethyl acetyl chloride, stir for 2-8 h, reaction is completed, remove the precipitate by filtration, the filtrate is the acid anhydride intermediate.

4. The method for producing a modified cellulose additive for paints according to claim 1, characterized by, The mass ratio of hydroxyethyl cellulose to acid anhydride intermediate is 1:0.5-2.

5. The method of producing a modified cellulose additive for paints according to claim 1, characterized by, In step S4, the dosage ratio of titanium dioxide sol to modified cellulose dispersion is 1-3 g:5 g in terms of solid content.

6. The method of producing a modified cellulose additive for paints according to claim 1, characterized by, In step S4, the fluorine-containing reactive monomer is selected from one or more of trifluoroethyl methacrylate, hexafluorobutyl methacrylate, dodecafluoroheptyl acrylate, and perfluorohexylethyl methacrylate; the silicon-containing reactive monomer is selected from one or more of γ-methacryloyloxypropyl trimethoxysilane, vinyl triethoxysilane, and vinyl trimethoxysilane; the reactive emulsifier is one or more of allyloxy hydroxypropyl sulfonic acid sodium, vinyl sulfonic acid sodium, and m-styrene sulfonic acid sodium.

7. The method of producing a modified cellulose additive for paints according to claim 1, characterized by, In step S4, the molar ratio of fluorine-containing reactive monomer, silicon-containing reactive monomer, methyl methacrylate, and reactive emulsifier is 1-3:0.5-1.5:5-10:0.5-1.

8. The method of producing a modified cellulose additive for paints according to claim 1, characterized by, In step S5, the dosage ratio of composite dispersion to monomer pre-emulsion is 5-15:10-20 in terms of solid content.

9. A modified cellulose additive for paint prepared by the preparation method of any one of claims 1-8.

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