CN110182833A - It is a kind of to be crosslinked the preparation method of houghite, water paint and preparation method thereof - Google Patents

Abstract

The invention provides a preparation method of a cross-linked hydrotalcite, a water-based coating and a preparation method thereof, belonging to the technical field of coatings. The preparation method of cross-linked hydrotalcite-like provided by the present invention comprises the following steps: mixing an aluminum source, a cross-linking agent and water, adjusting the pH value of the obtained mixed system to 5-9, and performing a chemical reaction to obtain a slurry; The slurry, the divalent metal ion source and the anion source are mixed, the pH value of the obtained mixed material is adjusted to 10-13, and then crystallized to obtain the cross-linked hydrotalcite. In the present invention, the aluminum source is reacted with sodium hydroxide to obtain aluminum hydroxide under the condition of weak acid or weak base, and the cross-linking agent reacts with the hydroxyl groups on the surface of the aluminum hydroxide, and at the same time cross-links with the hydroxyl groups on different hydrotalcite sheets, so that The hydrotalcite sheets are stacked and spliced in an orderly manner, and crystallized under strong alkali conditions. The prepared cross-linked hydrotalcite is dense, has large interlayer pores, large specific heat capacity, and good thermal insulation performance, which can significantly improve the thermal insulation performance and adhesion of coatings. Focus on.

Description

A preparation method of cross-linked hydrotalcite, water-based coating and preparation method thereof

technical field

The invention relates to the technical field of coatings, in particular to a preparation method of a crosslinked hydrotalcite, a water-based coating and a preparation method thereof.

Background technique

Hydrotalcite-like is a type of double metal hydroxide with a layered structure. It is alkaline, its composition and structure can be adjusted, and it has properties such as infrared absorption and ultraviolet blocking. Adding it to the coating can make the coating anti-corrosion, resistant Aging, weather resistance and certain heat insulation and other functions.

However, the traditional hydrotalcite-like has the following disadvantages: first, the hydrotalcite-like particles are small, the sheets are thin, the hiding power is poor, and the reflection effect on light is weak; The third is that the hydrotalcite-like surface has a high hydroxyl content, a large surface energy, and poor compatibility and adhesion with resins. Therefore, when traditional hydrotalcites are applied to thermal insulation coatings, there are defects such as unsatisfactory thermal insulation effect and poor adhesion, which lead to bubbling and peeling of the coating film, which restricts its popularization and application in thermal insulation coatings.

Chinese patent CN103318933A discloses a method for preparing surface-modified hydrotalcite compounds by using brucite. All raw materials are directly added at the same time without pretreatment, so that the synthesis and surface modification of hydrotalcite can be completed in one step; although this method significantly reduces the surface The production cost of modified hydrotalcite compounds simplifies the production process and shortens the production cycle, but the modified hydrotalcite prepared by this method only changes the hydrophilicity and hydrophobicity of the hydrotalcite surface (from hydrophilic to hydrophobic), thereby preventing crystallization The particles are agglomerated, and the hydrotalcite sheets are better dispersed, but the obtained hydrotalcite particles are small in size, loose, and have poor thermal insulation performance.

Contents of the invention

The object of the present invention is to provide a preparation method of cross-linked hydrotalcite, water-based coating and preparation method thereof. The cross-linked hydrotalcite prepared by the present invention is compact, has large interlayer pores, large specific heat capacity, and good heat insulation performance, and is compatible with Resin compatibility is good.

The water-based paint provided by the invention has good heat insulation performance, strong adhesion, long service life, safety and environmental protection; the preparation method is simple to operate and is suitable for industrial production.

In order to achieve the above-mentioned purpose of the invention, the present invention provides the following technical solutions:

The invention provides a kind of preparation method of cross-linked hydrotalcite, comprising the following steps:

Mix the aluminum source, cross-linking agent and water, adjust the pH value of the obtained mixed system to 5-9, and then carry out a chemical reaction to obtain a slurry;

The slurry, the divalent metal ion source and the anion source are mixed, the pH value of the obtained mixed material is adjusted to 10-13, and then crystallized to obtain the cross-linked hydrotalcite.

Preferably, the aluminum source includes one or more of aluminum nitrate, aluminum sulfate, aluminum chloride, sodium metaaluminate, aluminum hydroxide and aluminum oxide;

The crosslinking agent includes one or more of silane coupling agent, acrylic polymer and acrylic copolymer;

The source of divalent metal ions includes magnesium compounds and/or zinc compounds;

The source of anions includes soluble carbonates and/or soluble bicarbonates.

Preferably, the molar ratio of the aluminum source, crosslinking agent, divalent metal ion source and anion source is 1:(0.005-0.2):(1.5-4):(0.3-0.8).

Preferably, the temperature of the chemical reaction is 70-100° C., and the time is 2-8 hours.

Preferably, the crystallization temperature is 130-190° C., and the time is 12-20 hours.

The present invention also provides a water-based paint, including the cross-linked hydrotalcite prepared by the preparation method described in the above technical solution.

Preferably, the water-based paint is prepared from components comprising the following parts by weight:

25-40 parts of acrylic resin;

15-30 parts of cross-linked hydrotalcite;

15-30 parts of alkyd resin;

5-15 parts of titanium dioxide;

2 to 10 parts of barium sulfate;

0.1-2 parts of wetting agent;

0.1-2 parts of dispersant;

0.1 to 2 parts of defoamer;

0.1 to 2 parts of leveling agent;

0.1 to 2 parts of film-forming aids;

20-40 parts of water.

Preferably, the dispersant includes a nonionic surfactant.

The present invention also provides the preparation method of the water-based paint described in the above technical scheme, comprising the following steps:

Mixing cross-linked hydrotalcite, titanium dioxide and barium sulfate and then grinding to obtain mixed powder;

mixing the mixed powder with acrylic resin, part of water, wetting agent, and dispersant to obtain the first slurry;

mixing the first slurry with an alkyd resin to obtain a second slurry;

The second slurry, film-forming aid, defoamer, leveling agent and remaining water are mixed to obtain a water-based paint.

Preferably, the particle size of the mixed powder is 0.1-15 μm;

The part of water accounts for 40-70wt% of the total water consumption.

The invention provides a preparation method of cross-linked hydrotalcite, comprising the following steps: mixing an aluminum source, a cross-linking agent and water, adjusting the pH value of the obtained mixed system to 5-9, and performing a chemical reaction to obtain a slurry; The slurry, the divalent metal ion source and the anion source are mixed, the pH value of the obtained mixed material is adjusted to 10-13, and then crystallized to obtain the cross-linked hydrotalcite. The crosslinking agent used in the present invention can simultaneously crosslink with the hydroxyl groups on different hydrotalcite sheets under weak acid and weak alkali conditions, so that the hydrotalcite sheets can be stacked and spliced in an orderly manner, and it is easier to generate and form hydrotalcite sheets under strong alkali conditions. Crystallization, the obtained hydrotalcite-like particles are large, dense, opaque, and have strong hiding power, which can significantly improve the reflectivity of the coating film, reflect most of the heat, and have good heat insulation performance; the surface of cross-linked hydrotalcite-like The active groups in the uncrosslinked crosslinking agent can further condense with the active groups of acrylic resin, alkyd resin and paint substrate, which can significantly improve the compatibility of crosslinked hydrotalcites with acrylic resin and alkyd resin . Moreover, the gap between the cross-linked hydrotalcite-like layers prepared by the present invention is large, which can effectively reduce the heat transfer rate; the crystallization water between the cross-linked hydrotalcite-like layers has a large specific heat capacity, which can greatly reduce the heating rate of the coating film; The nature of barrier can block the transfer of heat, has good heat insulation performance, and has good compatibility with acrylic resin and alkyd resin.

The present invention also provides a water-based paint, wherein the cross-linked hydrotalcite has the advantages of compactness, opacity, and strong hiding power, and can significantly improve the reflectivity of the coating film and reflect most of the heat; the cross-linked hydrotalcite It has the property of infrared blocking, which can block the transfer of heat; the interlayer gap of cross-linked hydrotalcite can effectively reduce the heat transfer speed; the crystallization water between the cross-linked hydrotalcite layers has a large specific heat capacity, which greatly reduces the coating film. The temperature rise rate, thereby significantly improving the thermal insulation performance of the coating. At the same time, the active groups of the cross-linking agent that have not cross-linked on the surface of the cross-linked hydrotalcite can further condense with the active groups contained in the substrate coated with acrylic resin, alkyd resin and paint, which significantly improves the performance of the cross-linked hydrotalcite. The compatibility with the resin and the adhesion of the paint avoid problems such as bubbling, peeling, and skinning of the paint during use, and the service life is long. Moreover, the water-based paint provided by the present invention uses water as a dispersant, which effectively reduces VOC emissions, conforms to the concept of green chemistry, and is safe and environmentally friendly.

The invention provides the preparation method of the water-based paint, which is simple in operation and suitable for large-scale production.

Description of drawings

Fig. 1 is the XRD pattern of hydrotalcite and cross-linked hydrotalcite-like, wherein, A represents comparative example 1, and B represents embodiment 1;

Fig. 2 is the SEM figure of hydrotalcite and cross-linked hydrotalcite-like, wherein, A represents comparative example 1, and B represents embodiment 1;

Fig. 3 is a comparison chart of diffuse reflectance of different coated plates, wherein, A represents a blank plate, B represents comparative example 2, C represents embodiment 4, and D represents embodiment 5;

Figure 4 is a comparison chart of the thermal insulation properties of different coatings, where A represents a blank board, B represents Comparative Example 2, C represents Example 4, and D represents Example 5.

Detailed ways

The invention provides a kind of preparation method of cross-linked hydrotalcite, comprising the following steps:

Mix the aluminum source, cross-linking agent and water, adjust the pH value of the obtained mixed system to 5-9, and then carry out a chemical reaction to obtain a slurry;

The slurry, the divalent metal ion source and the anion source are mixed, the pH value of the obtained mixed material is adjusted to 10-13, and then crystallized to obtain the cross-linked hydrotalcite.

In the present invention, unless otherwise specified, all raw material components are commercially available products well known to those skilled in the art.

The invention mixes the aluminum source, the cross-linking agent and water, adjusts the pH value of the obtained mixed system to 5-9, and performs chemical reaction to obtain the slurry. In the present invention, the alkali used to adjust the pH value of the resulting mixed system to 5-9 preferably includes solid sodium hydroxide or sodium hydroxide solution. In the present invention, the type of the chemical reaction is related to the type of crosslinking agent, and the type of crosslinking agent is different, and the chemical reactions that take place are also different, and the chemical reaction includes hydrolysis and self-condensation of the crosslinking agent (such as silane coupling agent) Reaction; aluminum source reacts with sodium hydroxide to form aluminum hydroxide; cross-linking agent reacts with the hydroxyl group of aluminum hydroxide; cross-linking agent hydrolysis, self-condensation product reacts with the hydroxyl group of aluminum hydroxide, etc.

Under the condition of pH value of 5-9, it can ensure that the aluminum source reacts with sodium hydroxide to obtain aluminum hydroxide, and the cross-linking reaction between the cross-linking agent and different hydrotalcite layers is mainly due to the carboxyl group, hydroxyl group and water The hydroxyl groups on the surface of talc react, and the activity of the hydroxyl groups on the surface of hydrotalcite is the main factor leading to the success of crosslinking. Under weak acid and weak alkaline conditions, the crosslinking agent is more likely to react with the hydroxyl groups on the surface of aluminum hydroxide; if the pH If the value is too large, the aluminum hydroxide will dissolve and cannot react with the cross-linking agent, and the activity of hydroxyl groups on the surface of the laminate will decrease significantly after the formation of hydrotalcite, and the cross-linking agent will not be able to react with the hydroxyl groups on different layers at the same time. A cross-linked hydrotalcite was obtained.

In the present invention, the aluminum source preferably includes one or more of aluminum nitrate, aluminum sulfate, aluminum chloride, sodium metaaluminate, aluminum hydroxide and aluminum oxide, more preferably includes aluminum nitrate, aluminum sulfate , aluminum chloride, sodium metaaluminate, aluminum hydroxide or aluminum oxide, most preferably comprising aluminum nitrate, aluminum chloride or aluminum hydroxide.

In the present invention, the crosslinking agent preferably includes one or more of silane coupling agents, acrylic polymers and acrylic copolymers, more preferably includes silane coupling agents, acrylic polymers or acrylic copolymers substances, most preferably silane coupling agents. In the present invention, the silane coupling agent preferably includes tetraethoxysilane, ethyltrimethoxysilane, ethyltriethoxysilane, vinyltriethoxysilane, vinyltrimethoxysilane, methyl Triethoxysilane, methyltrimethoxysilane or propyltriethoxysilane; the acrylic polymer preferably comprises sodium polyacrylate or sodium polymethacrylate; the acrylic copolymer preferably comprises acrylic- Maleic acid copolymer, acrylic acid-maleic anhydride copolymer, acrylic acid-butyl acrylate copolymer, acrylic acid-ethyl acrylate copolymer. The cross-linking agent used in the present invention can simultaneously cross-link with the hydroxyl groups on different hydrotalcite sheets, so that the hydrotalcite sheets are stacked and spliced in an orderly manner, and the obtained cross-linked hydrotalcites are dense, opaque, and have strong hiding power, and can Significantly improve the reflectivity of the coating film and improve the heat insulation effect of the coating; at the same time, the non-crosslinked silanol on the surface of the crosslinked hydrotalcite can further condense with the active groups of the resin and the substrate, which significantly improves the crosslinked hydrotalcite. The compatibility of hydrotalcite and resin and the adhesion of paint avoid problems such as bubbling, shedding, and skinning of the paint during use, and prolong the service life of the paint.

In the present invention, the mixing of the aluminum source, cross-linking agent and water is preferably carried out under stirring conditions; the present invention has no special limitation on the speed and time of the stirring, as long as the mixing is uniform, specifically the stirring speed Preferably it is 200-800 rpm, more preferably 230-750 rpm; the stirring time is preferably 1-30 min, more preferably 5-20 min. In the present invention, the mixing temperature is preferably 70-100°C, more preferably 80-90°C.

In the present invention, the concentration of the sodium hydroxide solution is preferably 2.5-4.0 mol/L, more preferably 2.6-3.5 mol/L. In the present invention, the chemical reaction is preferably carried out under stirring conditions, and the stirring speed of the chemical reaction is preferably the same as that during mixing. In the present invention, the temperature of the chemical reaction is preferably 70-100° C., more preferably 80-90° C.; the time of the chemical reaction is preferably 2-8 hours, more preferably 3-6 hours.

After the slurry is obtained, the present invention mixes the slurry, the divalent metal ion source and the anion source, adjusts the pH value of the obtained mixed material to 10-13, and crystallizes to obtain the cross-linked hydrotalcite. In the present invention, the slurry and the divalent metal ion source first generate hydrotalcite-like nuclei under strong alkali conditions (pH value is 10-13), and the hydrotalcite-like nuclei are further crystallized to obtain cross-linked hydrotalcite-like nuclei. In the present invention, hydrotalcites are easier to generate and crystallize under strong alkali conditions, and at lower pH, it is difficult to form crystal nuclei, and the crystal growth rate is slower, and it takes a long time to crystallize to obtain a higher crystallinity. Good hydrotalcite. . In the present invention, the source of divalent metal ions includes one or more of magnesium compounds, zinc compounds and anion sources; wherein, the magnesium compounds preferably include magnesium chloride, magnesium nitrate, magnesium sulfate, magnesium hydroxide and oxide One or more in magnesium; Described zinc compound preferably comprises one or more in zinc chloride, zinc nitrate, zinc sulfate, zinc hydroxide and zinc oxide; The effect of described magnesium compound and zinc compound is to provide Metal elements required to cross-link hydrotalcite-like. In the present invention, the anion source preferably includes soluble carbonate and/or soluble bicarbonate, more preferably includes one of sodium carbonate, potassium carbonate, ammonium carbonate, sodium bicarbonate, potassium bicarbonate and ammonium bicarbonate or several, most preferably sodium carbonate, potassium carbonate or ammonium carbonate, the anion source provides the interlayer anions required for the cross-linked hydrotalcite, and also plays a role in adjusting the pH value.

In the present invention, the molar ratio of the aluminum source, crosslinking agent, divalent metal ion source and anion source is preferably 1:(0.005～0.2):(1.5～4):(0.3～0.8), more preferably 1:(0.005-0.15):(2-4):(0.4-0.7), most preferably 1:(0.005-0.15):(2-3.7):(0.4-0.6). In the present invention, the amount of the anion source is preferably calculated by the amount of anions. In the present invention, there is no special limitation on the amount of water used, and the amount of water well known in the art can be used. Specifically, the amount ratio of aluminum source: water is 1 mol: (800-2500) mL. In the present invention, the amount of raw materials is controlled within the above range, which is beneficial to improving the cross-linking degree between the hydrotalcite-like layers, and further improving the performance of the cross-linking hydrotalcite-like.

In the present invention, the mixing of the slurry, the divalent metal ion source and the anion source is preferably carried out under stirring conditions, and the stirring speed is preferably 200-800rpm, more preferably 230-750rpm; the stirring The time is preferably 1 to 30 minutes, more preferably 5 to 20 minutes. In the present invention, the pH value of the obtained mixed material is adjusted to 10-13, preferably the pH value is adjusted to 11-12. In the present invention, the alkali used to adjust the pH value preferably includes sodium hydroxide solid or sodium hydroxide solution; in the present invention, the concentration of the sodium hydroxide solution is preferably 2.5-4.0mol/L, more preferably 2.6- 3.5mol/L. In the present invention, the crystallization temperature is preferably 130-190° C., more preferably 140-180° C.; the crystallization time is preferably 12-20 hours, more preferably 14-18 hours. In the present invention, controlling the crystallization conditions can ensure more complete hydrotalcite crystal growth and improve the crystallinity of the hydrotalcite.

In the present invention, the cooling preferably further includes cooling the obtained system, separating solid and liquid, and then drying and pulverizing the obtained filter cake to obtain a cross-linked hydrotalcite-like. The present invention has no special limitation on the cooling method and cooling rate, and the cooling method and cooling rate known in the art can be adopted. In the present invention, the method of solid-liquid separation is not particularly limited, and a solid-liquid separation method well known in the art can be used, such as filtration. In the present invention, the drying temperature is preferably 80-150° C., more preferably 100-120° C.; the drying time is preferably 4-16 hours, more preferably 5-12 hours. In the present invention, the particle size of the crushed cross-linked hydrotalcite is preferably 3-15 μm.

The present invention also provides a water-based paint, including the cross-linked hydrotalcite prepared by the preparation method described in the above technical solution.

In the present invention, the water-based coating is preferably prepared from the following components by weight: 25-40 parts of acrylic resin; 15-30 parts of alkyd resin; 15-30 parts of cross-linked hydrotalcite; 5 parts of titanium dioxide ～15 parts; 2～10 parts of barium sulfate; 0.1～2 parts of wetting agent; 0.1～2 parts of dispersant; 0.1～2 parts of defoamer; 0.1～2 parts of leveling agent; ; 20-40 parts of water.

In the present invention, the raw materials for preparing the water-based paint include 25-40 parts, preferably 30-40 parts, of acrylic resin in parts by weight. In the present invention, the acrylic resin preferably includes a hydroxy acrylic resin, more preferably a water-based hydroxy acrylic resin.

In the present invention, based on the parts by weight of the acrylic resin, the raw materials for preparing the water-based paint include 15-30 parts of alkyd resin, preferably 20-30 parts, more preferably 20-25 parts. In the present invention, after the alkyd resin is cured to form a film, it is glossy and tough, has strong adhesion, and has good wear resistance, weather resistance and insulation, etc., which improves the adhesion and service life of the coating.

In the present invention, based on the parts by weight of the acrylic resin, the raw materials for preparing the water-based paint include 15-30 parts of cross-linked hydrotalcite, preferably 15-25 parts, more preferably 20-25 parts. In the present invention, the surface of the cross-linked hydrotalcite contains active groups that have not undergone cross-linking reactions, such as silanol, which can condense with active groups contained in acrylic resins and alkyd resins, significantly improving the cross-linking effect. The compatibility of the hydrotalcite-like resin and the adhesion of the paint make the paint avoid problems such as bubbling, peeling, and skinning during use, and prolong the service life.

In the present invention, based on the parts by weight of the acrylic resin, the raw materials for preparing the water-based paint include 5-15 parts of titanium dioxide, preferably 6-13 parts, more preferably 8-12 parts. In the present invention, the titanium dioxide has a good ultraviolet shielding effect and strong adhesion, and can work together with other components to improve the adhesion and heat insulation performance of the paint and prolong the service life.

In the present invention, based on the parts by weight of the acrylic resin, the raw materials for preparing the water-based paint include 2-10 parts of barium sulfate, preferably 3-9 parts, more preferably 4-8 parts. In the present invention, the barium sulfate has low oil absorption, high density, granular or spherical structure, good filling performance, and works synergistically with other components to improve the hiding rate of the coating and the strength of the coating film.

In the present invention, based on the parts by weight of the acrylic resin, the raw materials for preparing the water-based paint include 0.1-2 parts of wetting agent, preferably 0.5-2 parts, more preferably 0.5-1.5 parts. The present invention has no special limitation on the wetting agent, and wetting agents well-known in the art can be used, such as Germany Corning PE-100, TRITON wetting agent X-405, SN-5040 or SN-5027. In the present invention, the wetting agent works together with other components to change the surface tension and permeability of the paint, better wetting the substrate, and improve the adhesion of the paint; meanwhile, it can also assist in dispersion and Aids in dust-repelling action and avoids delamination of paint.

In the present invention, based on the parts by weight of the acrylic resin, the raw materials for preparing the water-based paint include 0.1-2 parts of dispersant, preferably 0.5-2 parts, more preferably 0.5-1.5 parts. In the present invention, the dispersant preferably includes a nonionic surfactant, more preferably SURFYNOL 440, Dow CF-10, SN-5040, SN-5027, German BYK BYK-191 or German BYK BYK-2010 .

In the present invention, based on the parts by weight of the acrylic resin, the raw materials for preparing the water-based paint include 0.1-2 parts of defoamer, preferably 0.5-2 parts, more preferably 0.5-1.5 parts. The present invention has no special limitation on the defoamer, and the defoamer well-known in the art can be used, such as Yoshida J0404, MONENG-2311, Clariant C740 from Switzerland or BASF 2190 from Germany. In the present invention, the defoaming agent can eliminate the foam generated during the production and coating process of the coating, which is beneficial to improving the smoothness of the coating film.

In the present invention, based on the parts by weight of the acrylic resin, the raw materials for preparing the water-based paint include 0.1-2 parts of leveling agent, preferably 0.5-2 parts, more preferably 0.5-1.5 parts. In the present invention, the leveling agent is preferably Rohm and Haas RM-2020, TEGO450 or BYK-346. In the present invention, the leveling agent can promote the coating to form a flat, smooth and uniform coating film during the drying and film forming process, which is beneficial to reduce the surface tension of the coating film and improve the wetting of the coating base material. wet capacity.

In the present invention, based on the parts by weight of the acrylic resin, the raw materials for preparing the water-based paint include 0.1-2 parts of film-forming aids, preferably 0.5-2 parts, more preferably 0.5-1.5 parts. In the present invention, the film-forming aid is not particularly limited, and the film-forming aid well-known in the art can be used, such as propylene glycol phenyl ether, ester alcohol dodeca, dipropylene glycol butyl ether or tripropylene glycol butyl ether. In the present invention, the titanium dioxide and barium sulfate pigments and fillers can form stable complexes with pigments and fillers under the action of film-forming aids, thereby improving the heat insulation effect and adhesion of the coating.

In the present invention, based on the parts by weight of the acrylic resin, the raw materials for preparing the water-based paint include 20-40 parts of water, more preferably 25-40 parts, more preferably 25-35 parts. In the present invention, the water is preferably deionized water. The invention uses water as the dispersion medium, and compared with other organic solvent dispersion mediums, effectively reduces VOC emission, conforms to the concept of green chemistry, and is safe and environment-friendly.

The present invention also provides the method for preparing the water-based paint described in the above-mentioned technical scheme, comprising the following steps:

mixing cross-linked hydrotalcite, titanium dioxide and barium sulfate to obtain a mixed powder;

mixing the mixed powder with water-based hydroxyacrylic resin, part of water, wetting agent and dispersant to obtain the first slurry;

mixing the first slurry with an alkyd resin to obtain a second slurry;

The second slurry, film-forming aid, defoamer, leveling agent and remaining water are mixed to obtain a water-based paint.

The invention mixes cross-linked hydrotalcite, titanium dioxide and barium sulfate to obtain mixed powder. In the present invention, the mixing is preferably carried out under stirring conditions, and the stirring speed is preferably 1800-2400rpm, more preferably 2100-2300rpm; the present invention has no special limitation on the stirring time, which can ensure that the materials are mixed evenly That's it. In the present invention, the particle size of the ground mixed powder is preferably ≤15 μm. The invention mixes the cross-linked hydrotalcite, titanium dioxide and barium sulfate fillers and then grinds them to a suitable fineness, which is beneficial to the uniform dispersion of the powder in the resin, and also saves the slurry grinding process and simplifies the operation steps.

After the mixed powder is obtained, the present invention mixes the mixed powder with water-based hydroxyacrylic resin, part of water, wetting agent and dispersant to obtain the first slurry. In the present invention, the mixing is preferably carried out under stirring conditions, the stirring speed is preferably 400-800rpm, more preferably 550-650rpm; the stirring time is preferably 10-120min, more preferably 20-90min . In the present invention, the part of water preferably accounts for 40-70 wt%, more preferably 45-65 wt%, most preferably 50-65 wt% of the total amount of water used.

After the first slurry is obtained, the present invention mixes the first slurry with an alkyd resin to obtain a second slurry. In the present invention, the mixing is preferably carried out under stirring conditions, the stirring speed is preferably 1900-2500rpm, more preferably 2100-2400rpm; the stirring time is preferably 20-150min, more preferably 30-120min .

After obtaining the second slurry, the present invention mixes the second slurry, film-forming aid, defoamer, leveling agent and remaining water to obtain the water-based paint.

In the present invention, the remaining water preferably accounts for 30-60 wt%, more preferably 35-45 wt%, of the total amount of water used. In the present invention, the remaining water preferably corresponds to the part of water, that is, the total amount of the part of water and the remaining water is preferably 100%. In the present invention, there is no special limitation on the speed and time of the mixing, as long as the well-known mixing methods in the art can be used to ensure that the materials are evenly mixed.

In the present invention, the cross-linked hydrotalcite has a certain hydrophobicity, and titanium dioxide and barium sulfate have a certain hydrophilicity. Wetting agents and dispersants are added to make the cross-linked hydrotalcite fully wet and reduce the first slurry The viscosity of the material is conducive to its dispersion in the resin. The carboxyl group in the acrylic resin can interact with the uncrosslinked active groups in the crosslinked hydrotalcite to improve the compatibility between the crosslinked hydrotalcite and the resin. Mixing the obtained first slurry with an alkyd resin can improve the fullness, gloss, hardness, solvent resistance, weather resistance and yellowing resistance of the coating. Coalescing agent has greater cohesion to the emulsion, and it needs to be added after the cross-linked hydrotalcite, titanium dioxide and barium sulfate are fully dispersed, otherwise it will affect the dispersion of the mixed powder of titanium dioxide and barium sulfate. The defoamer can effectively eliminate the foam generated by rapid stirring during the dispersion of pigments and fillers, and at the same time suppress the foam generated by the leveling agent added later. The leveling agent can effectively reduce the surface tension of the coating, improve the permeability of the coating, increase the coatability, and make the coating uniform. However, the leveling agent is composed of surfactants and is prone to generate a large amount of foam. To join, to prevent rapid stirring and produce foam. In the present invention, by controlling the above-mentioned feeding sequence, the obtained coating has good heat insulation performance and strong adhesion, and the problems of bubbling, shedding, and skinning will not occur during use, and the service life is long; and the coating of the present invention uses water as the dispersion Medium, effectively reducing VOC emissions, in line with the concept of green chemistry, safe and environmentally friendly.

The technical solutions in the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Apparently, the described embodiments are only some of the embodiments of the present invention, but not all of them. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without making creative efforts belong to the protection scope of the present invention.

Example 1

Fully mix 187.6g of aluminum nitrate, 13.6g of ethyltriethoxysilane and 1000mL of deionized water at 80°C, adjust the pH value to 9.0 with sodium hydroxide, stir and reflux for 3 hours to obtain a slurry;

Mix the slurry, 256.4g of magnesium nitrate and 31.8g of sodium carbonate well, adjust the pH value to 11 with sodium hydroxide, crystallize at 160°C for 14h, cool and filter to obtain a filter cake, and place the resulting filter cake at 120 It is dried at ℃ for 10 h, and then pulverized to obtain a cross-linked hydrotalcite.

Example 2

Fully mix 187.6g of aluminum nitrate, 10.2g of octyltriethoxysilane and 1000mL of deionized water at 80°C, adjust the pH value to 8.5 with sodium hydroxide, stir and reflux for 5 hours, and obtain a slurry;

Mix the slurry, 205.1g of magnesium nitrate, 59.5g of zinc nitrate and 25.2g of sodium carbonate well, adjust the pH value to 12 with sodium hydroxide, crystallize at 140°C for 18 hours, cool and filter to obtain a filter cake, The resulting filter cake was dried at 120° C. for 10 h, and then pulverized to obtain a cross-linked hydrotalcite.

Example 3

Mix 39.0 g of aluminum hydroxide, 6.8 g of octyltrimethoxysilane and 1000 mL of deionized water at 90°C, adjust the pH to 8.0 with sodium hydroxide, stir and reflux for 6 hours to obtain a slurry;

The slurry, 40.3g of magnesium oxide and 31.8g of sodium carbonate were mixed well, and the pH value was adjusted to 11 with sodium hydroxide, crystallized at 180°C for 15h, cooled and filtered to obtain a filter cake, which was obtained at 120 It is dried at ℃ for 10 h, and then pulverized to obtain a cross-linked hydrotalcite.

Comparative example 1

Fully mix 187.6g of aluminum nitrate and 1000mL of deionized water at 80°C, adjust the pH value to 9.0 with sodium hydroxide, stir and reflux for 3 hours to obtain a slurry;

Mix the slurry, 256.4g of magnesium nitrate and 31.8g of sodium carbonate well, and adjust the pH value to 11 with sodium hydroxide, crystallize at 160°C for 14h, cool, and filter to obtain a filter cake. Drying under conditions for 10h, and then pulverized to obtain hydrotalcite-like.

Figure 1 is the XRD patterns of hydrotalcite-like and cross-linked hydrotalcite-like, wherein, A represents Comparative Example 1, and B represents Example 1. It can be seen from Figure 1 that the structure of the cross-linked hydrotalcite-like prepared in Example 1 and the uncross-linked hydrotalcite-like prepared in Comparative Example 1 are consistent, indicating that the cross-linking agent does not enter the interlayer of the hydrotalcite, but the cross-linking agent Interaction with the surface of hydrotalcite.

2 is a SEM image of hydrotalcite-like and cross-linked hydrotalcite-like, wherein, A represents Comparative Example 1, and B represents Example 1. As can be seen from Figure 2, the morphology of the uncrosslinked hydrotalcite prepared in Comparative Example 1 is flaky hexagonal, and the stacking between the layers is disordered; while the crosslinked hydrotalcite prepared in Example 1 is under the action of a crosslinking agent Different hydrotalcite layers are spliced and stacked in an orderly manner, and the layers are stacked in an orderly manner to form a dense "block".

Comparative example 2

Mix 187.6g of aluminum nitrate, 256.4g of magnesium nitrate, 31.8g of sodium carbonate, 13.6g of ethyltriethoxysilane and 1000mL of deionized water at 80°C and adjust the pH to 11 with sodium hydroxide to obtain a slurry in Crystallize at 160°C for 14 hours, cool and filter to obtain a filter cake, dry the obtained filter cake at 120°C for 10 hours, and then pulverize to obtain modified hydrotalcite.

test case 1

According to HG-T 3820-2013 synthetic hydrotalcite analysis method, the whiteness, laser average particle size (D50), laser average particle size (D90) and specific surface area of the prepared cross-linked hydrotalcite were tested. The test results are shown in Table 1 .

Table 1 Cross-linked hydrotalcite-like performance test results

It can be seen from Table 1 that the cross-linked hydrotalcite-like laser average particle size (D50) is greater than 6.5 μm, and the laser average particle size (D50) is greater than 1.0 μm, which is significantly larger than that of uncross-linked hydrotalcite-like and surface-modified hydrotalcite-like The average particle size of the laser shows that under the action of the cross-linking agent, different hydrotalcite layers are spliced and stacked in an orderly manner, and the particle size of the cross-linked hydrotalcite is significantly increased; the specific surface area of the cross-linked hydrotalcite is less than 2.5 m ² /g, while the specific surface areas of uncrosslinked hydrotalcite-like and surface-modified hydrotalcite-like are both larger than 18.0m ² /g, indicating that the cross-linked hydrotalcite-like layers prepared by the preparation method provided by the present invention are stacked orderly , Dense.

Example 4

In parts by weight, 30 parts of the cross-linked hydrotalcite prepared in Example 1, 10 parts of titanium dioxide and 5 parts of barium sulfate were fully mixed, and ground to a particle size of less than 15 μm to obtain a mixed powder;

Stir and mix the mixed powder, 30 parts of water-based hydroxyacrylic resin, 25 parts of deionized water, 1 part of wetting agent and 1 part of dispersing agent at a speed of 600 rpm to obtain the first slurry;

Stir and mix the first slurry and 20 parts of alkyd resin at a speed of 2300 rpm to obtain the second slurry;

The second slurry, 1 part of defoamer, 2 parts of film-forming aid, 1 part of leveling agent and 15 parts of deionized water were fully stirred evenly to obtain a water-based coating.

Example 5

In parts by weight, 30 parts of the cross-linked hydrotalcite prepared in Example 2, 7.5 parts of titanium dioxide and 7.5 parts of barium sulfate were fully mixed, and ground to a particle size of less than 15 μm to obtain a mixed powder;

Stir and mix the mixed powder, 40 parts of water-based hydroxyacrylic resin, 25 parts of deionized water, 1 part of wetting agent and 1 part of dispersing agent at a speed of 600 rpm to obtain the first slurry;

Stir and mix the first slurry and 15 parts of alkyd resin at a speed of 2300 rpm to obtain the second slurry;

The second slurry, 1 part of defoamer, 2 parts of film-forming aid, 1 part of leveling agent and 10 parts of deionization were fully stirred evenly to obtain a water-based coating.

Example 6

In parts by weight, 30 parts of the cross-linked hydrotalcite prepared in Example 3, 5 parts of titanium dioxide and 10 parts of barium sulfate were fully mixed, and ground to a particle size of less than 15 μm to obtain a mixed powder;

The mixed powder, 35 parts of water-based hydroxyl acrylic resin, 20 parts of deionized water, 1 part of wetting agent and 1 part of dispersant, 15 parts of alkyd resin, 1 part of defoamer, 2 parts of film-forming aid, 1 part of leveling agent and 20 parts of deionized water are fully stirred evenly to obtain a water-based coating.

Comparative example 3

In parts by weight, 30 parts of hydrotalcite prepared in Comparative Example 1, 10 parts of titanium dioxide and 5 parts of barium sulfate were fully mixed, and ground to a particle size of less than 15 μm to obtain a mixed powder;

Stir and mix the mixed powder, 30 parts of water-based hydroxyacrylic resin, 25 parts of deionized water, 1 part of wetting agent and 1 part of dispersing agent at a speed of 600 rpm to obtain the first slurry;

Stir and mix the first slurry and 20 parts of alkyd resin at a speed of 2300 rpm to obtain the second slurry;

The second slurry, 1 part of defoamer, 2 parts of film-forming aid, 1 part of leveling agent and 15 parts of deionized water were fully stirred evenly to obtain a water-based coating.

Comparative example 4

In parts by weight, 30 parts of the cross-linked hydrotalcite prepared in Example 1, 10 parts of titanium dioxide, and 5 parts of barium sulfate were fully mixed, and ground to a particle size of 15 μm to obtain a mixed powder;

The mixed powder, 30 parts of water-based hydroxyacrylic resin, 40 parts of deionized water, 1 part of wetting agent, 1 part of dispersant, 20 parts of alkyd resin, 1 part of defoamer, 2 parts of film-forming aid, 1 part of leveling agent is fully stirred evenly to obtain water-based paint.

test case 2

Prepare the coating film according to the method of national standard GB/T1765-1979, and test the heat insulation performance of the coating according to the method of GB/T25261-2018 "reflective heat insulation coating for buildings"; the test results are shown in Table 2, and the diffuse reflection comparison chart of the coated board is shown in image 3.

The performance test result of table 2 waterborne coating

It can be seen from Table 2 that the coating added with cross-linked hydrotalcite has good construction and water resistance, and the bond strength and heat insulation performance are significantly improved.

Figure 3 is a comparison chart of diffuse reflectance of different coated boards, where A represents a blank board, B represents Comparative Example 2, C represents Example 4, and D represents Example 5. It can be seen from Figure 3 that the addition of cross-linked hydrotalcite significantly improves the diffuse reflectance of the coating film.

Figure 4 shows a comparison chart of the thermal insulation properties of different coatings, where A represents a blank board, B represents Comparative Example 2, C represents Example 4, and D represents Example 5. It can be seen from Figure 4 that the insulation temperature difference of the coating prepared by adding uncrosslinked hydrotalcite is only 3.0°C, while that of the coating prepared by adding crosslinked hydrotalcite is 26.9 and 26.6°C respectively , indicating that the cross-linked hydrotalcite significantly improves the thermal insulation performance of the coating, and the water-based coating provided by the invention has excellent thermal insulation performance.

The above is only a preferred embodiment of the present invention, it should be pointed out that, for those of ordinary skill in the art, without departing from the principle of the present invention, some improvements and modifications can also be made, and these improvements and modifications can also be made. It should be regarded as the protection scope of the present invention.

Claims (10)

1. a preparation method of cross-linked hydrotalcite, is characterized in that, comprises the following steps: Mix the aluminum source, cross-linking agent and water, adjust the pH value of the obtained mixed system to 5-9, and then carry out a chemical reaction to obtain a slurry; The slurry, the divalent metal ion source and the anion source are mixed, the pH value of the obtained mixed material is adjusted to 10-13, and then crystallized to obtain the cross-linked hydrotalcite. 2. preparation method according to claim 1, is characterized in that, described aluminum source comprises one or more in aluminum nitrate, aluminum sulfate, aluminum chloride, sodium metaaluminate, aluminum hydroxide and aluminum oxide kind; The crosslinking agent includes one or more of silane coupling agent, acrylic polymer and acrylic copolymer; The source of divalent metal ions includes magnesium compounds and/or zinc compounds; The source of anions includes soluble carbonates and/or soluble bicarbonates. 3. The preparation method according to claim 1, characterized in that, the molar ratio of the aluminum source, crosslinking agent, divalent metal ion source and anion source is 1:(0.005～0.2):(1.5～4) :(0.3～0.8). 4. The preparation method according to claim 1, characterized in that, the temperature of the chemical reaction is 70-100° C., and the time is 2-8 hours. 5. The preparation method according to claim 1, characterized in that, the crystallization temperature is 130-190° C., and the time is 12-20 hours. 6. A water-based paint, characterized in that it comprises the cross-linked hydrotalcite prepared by the preparation method according to any one of claims 1-5. 7. water-based paint according to claim 6, is characterized in that, is prepared by comprising the component of following weight part: 25-40 parts of acrylic resin; 15-30 parts of cross-linked hydrotalcite; 15-30 parts of alkyd resin; 5-15 parts of titanium dioxide; 2 to 10 parts of barium sulfate; 0.1-2 parts of wetting agent; 0.1-2 parts of dispersant; 0.1 to 2 parts of defoamer; 0.1 to 2 parts of leveling agent; 0.1 to 2 parts of film-forming aids; 20-40 parts of water. 8. The water-based paint according to claim 7, wherein the dispersant comprises a nonionic surfactant. 9. The preparation method of the water-based paint according to any one of claims 6 to 8, characterized in that, comprising the following steps: Mixing cross-linked hydrotalcite, titanium dioxide and barium sulfate and then grinding to obtain mixed powder; mixing the mixed powder with acrylic resin, part of water, wetting agent, and dispersant to obtain the first slurry; mixing the first slurry with an alkyd resin to obtain a second slurry; The second slurry, film-forming aid, defoamer, leveling agent and remaining water are mixed to obtain a water-based paint. 10. The preparation method according to claim 9, characterized in that, the particle size of the mixed powder is 0.1-15 μm; The part of water accounts for 40-70wt% of the total water consumption.