CN112094514A

CN112094514A - Water-based ceramic coating and preparation method thereof

Info

Publication number: CN112094514A
Application number: CN202010968287.2A
Authority: CN
Inventors: 陈钊聪; 张卫中
Original assignee: NANJING CHANGJIANG PAINT CO Ltd
Current assignee: NANJING CHANGJIANG PAINT CO Ltd
Priority date: 2020-09-15
Filing date: 2020-09-15
Publication date: 2020-12-18
Anticipated expiration: 2040-09-15
Also published as: CN112094514B

Abstract

The invention discloses a high-toughness water-based ceramic coating. The coating is a water-based, single-component and baking-drying product and consists of polyurethane modified nano ceramic emulsion, silicone resin emulsion, high-temperature-resistant pigment, filler, an auxiliary agent, a p-toluenesulfonic acid amine neutralized substance and water. The coating is convenient and fast to construct, has extremely low VOC emission in coating, has excellent flame retardance, heat resistance, corrosion medium shielding, bending resistance and impact resistance, and is an excellent choice for high-temperature-resistance, high-durability and anti-corrosion protective coating.

Description

Water-based ceramic coating and preparation method thereof

Technical Field

The invention relates to the technical field of coatings, in particular to a high-temperature-resistant, easily recoated, good corrosion medium shielding effect and bending-resistant water-based ceramic coating and a preparation method thereof.

Background

Ceramic coatings are a new class of coating materials based on organic-inorganic hybrid technology. The main structure of the paint is a covalent cross-linked inorganic (metal oxide, non-metal oxide and the like) network, so the paint has the incomparable performance advantages of high hardness, friction resistance, flame retardance, super weather resistance, low surface energy, chemical solvent resistance and the like compared with a plurality of traditional organic paints, and is an excellent choice for preparing special high-temperature-resistant and high-durability coatings.

The ceramic coating is mainly based on a sol-gel technical scheme, and the core components of the ceramic coating are silica sol and silane. Before curing, the components in the coating are present in the form of small molecules. After the curing process is started, the components are subjected to cross-linking among silanol hydroxyl groups, cross-linking between silanol and alkoxy, cross-linking between silanol and hydroxyl on the surface of a base material, cross-linking between silanol and hydroxyl on the surface of a pigment filler, and intermolecular coordination bond bonding, and finally cured to form a ceramic-like hard inorganic cross-linked network.

The appearance of the ceramic coating subverts the design concept of the traditional organic coating and brings possibility for realizing a plurality of coating functions. However, ceramic coatings based on the prior art also present a number of problems, such as:

(1) poor storage stability: since silane is easily hydrolyzed during storage and then condensed with silica sol, pigment and filler to form insoluble substances, manufacturers can only package silane, silica sol, pigment and filler in a two-component or three-component manner to improve the stability of the ceramic coating. Meanwhile, the shelf life of the product is shortened compared with that of the organic coating.

(2) The curing time is long, the pot life is short: the method comprises the following steps of (1) obtaining an ideal silanol prepolymer for reaction, promoting the ceramic coating to form a film uniformly, avoiding stress cracking, stirring and curing the ceramic coating for a long time before application, and generally lasting for 2-8 hours; the cured ceramic coating needs to be coated within several hours, otherwise, the product is gelatinized and loses the service performance. The complicated premixing process puts high requirements on equipment and process control of coating enterprises.

(3) Poor flexibility, no bending resistance, no impact resistance: since the ceramic coating is a highly cross-linked inorganic network (hardness up to 9H), the coating is highly brittle. In the coating process, a workpiece needs to be formed and then coated, otherwise, the ceramic coating is cracked and damaged due to small bending of the base material. Meanwhile, the coating needs to be used with extra care, and the coating can be damaged by collision and impact. In addition, the ceramic coating has high shrinkage and large internal stress in the curing process, so that the ceramic coating is not suitable for thick coating (the thickness of the coating film is generally less than 40 micrometers), or is easy to crack.

(4) Poor recoatability: because the surface energy of the ceramic coating is low and the ceramic coating is not easy to wet, the recoatability of the coating is poor. For unqualified products, the products can only be ground to a metal substrate and then reworked, which seriously affects the coating efficiency and cannot obtain a ceramic coating with high film thickness.

At present, ceramic paint is applied in the fields of non-stick pan, building curtain wall, subway locomotive, heat pipe, etc., and has gained certain market share. If the technical bottleneck can be overcome, the market of the ceramic coating can be greatly expanded.

Disclosure of Invention

The invention aims to provide the water-based ceramic coating which is suitable for the surfaces of metal and glass and has excellent flame retardance, heat resistance, corrosion medium shielding, bending resistance and impact resistance. The coating is a water-based, single-component and baking-drying product, is convenient to construct, has extremely low VOC (volatile organic compounds) emission in coating, and is an excellent choice for high-temperature-resistance, high-durability, anti-corrosion and protective coating.

The purpose of the invention can be realized by the following technical scheme:

a high-toughness water-based ceramic coating comprises the following components:

in some specific embodiments: the coating comprises the following components:

the technical scheme of the invention is as follows: the polyurethane modified nano ceramic emulsion is prepared by the following method:

s1: adding polyethylene glycol, polycarbonate diol and neopentyl glycol into an oxygen-removed reactor, heating to 100-150 ℃, and performing reduced pressure dehydration; cooling to below 50 ℃, adding acetone, and stirring to completely dissolve the materials; diluting hexamethylene diisocyanate and isophorone diisocyanate with acetone, and slowly dropping into a reactor; adding di-n-butyltin dilaurate, heating, refluxing, stirring and reacting for 3-4 h; cooling the system to below 40 ℃, adding organosilane, and stirring uniformly.

S2: slowly dripping the polyurethane prepolymer-silane mixed solution obtained in the step (1) into a mixed solution consisting of silica sol, ethylenediamine ethanesulfonic acid sodium salt and water; heating to 60-70 ℃, preserving heat for 1-3 h, and then removing acetone in the system under reduced pressure; and cooling and filtering to obtain the polyurethane modified nano ceramic emulsion with the nonvolatile content of 35-50%.

In some specific embodiments: the polyurethane modified nano ceramic emulsion comprises the following components:

in some preferred embodiments: the polyurethane modified nano ceramic emulsion comprises the following components:

in some specific embodiments: the polyurethane modified nano ceramic emulsion comprises the following components: the molar ratio of the hydroxyl component (polyethylene glycol, polycarbonate diol, neopentyl glycol) to the isocyanate component (hexamethylene diisocyanate, isophorone diisocyanate) is 1: 1.02 to 1.25; the polyethylene glycol is terminated by hydroxyl and has a molecular weight of 500-1000; the polycarbonate diol is prepared from Asahi chemical compounds T5650J and T5650E, and has a molecular weight of 500-800; the silica sol is hectorite HN3010 or HN3020 neutral silica sol.

In some specific embodiments: the polyurethane modified nano ceramic emulsion comprises the following components: the organosilane is phenyl triethoxysilane, dimethyl dimethoxysilane and N-aminoethyl-3-aminopropyl methyl dimethoxysilane, and the weight parts of the phenyl triethoxysilane, the dimethyl dimethoxysilane and the N-aminoethyl-3-aminopropyl methyl dimethoxysilane are 200-280 parts, 30-150 parts and 0.1-3 parts in sequence.

The high-toughness water-based ceramic coating comprises the following components in percentage by weight: the silicone resin emulsion is Wake MPF 52E or MP 50E; the filler is a mixture of whisker silicon and mica powder, and the mixing ratio of the whisker silicon to the mica powder is 1-3: 1.

The high-toughness water-based ceramic coating comprises the following components in percentage by weight: the wetting dispersant is a Pico BYK-190 dispersant; the defoaming agent is a Digao Foamex 810 defoaming agent; the corrosion inhibitor is Asconium 142 DA; the base material wetting agent is a digao Wet KL 245 base material wetting agent; the thickening agent is Heimax 299 thickening agent; the p-toluenesulfonate amine neutralizer is Zhanxin VXK 6395 or German WD-04, and the dispersant is BYK-190 dispersant.

The preparation method of the water-based ceramic coating comprises the following steps:

s1: dispersing water, high-temperature resistant pigment, filler, fumed silica, wetting dispersant, defoamer and corrosion inhibitor at high speed under stirring until the mixture is uniform and free of powder balls and caking; then the slurry is transferred to a grinding device and ground until the fineness of the slurry is less than 40 mu m.

S2: adding the polyurethane modified nano ceramic emulsion, the silicone resin emulsion, the base material wetting agent and the p-toluenesulfonate amine neutralized substance into the slurry obtained in the step S1, and uniformly stirring; adding a thickening agent, adjusting the viscosity of the system to 70-120 KU, and filtering to obtain the water-based ceramic coating.

The invention has the beneficial effects that:

firstly, the invention innovatively discloses a silane coating technology based on nonionic/anionic polyurethane as a carrier. The organosilane and condensation products thereof are coated by macromolecular micelles formed by the aqueous polyurethane prepolymer, the ethylenediamine ethanesulfonic acid sodium salt, the aminosilane and the water chain extension, so that the silane reaction is prevented from advancing, and the single-component aqueous ceramic coating which can be stably stored for more than 15 months is obtained. When the coating is applied, the drying of the coating causes a deformation of the micelle structure. At the same time, the heating may intensify the movement of the polyurethane segment. At this point, the silane will release and induce a crosslinking film-forming process.

Secondly, the invention designs a composite toughened water-based ceramic coating based on silicone resin/polyurethane/mica, and the coating has excellent shock resistance, bending resistance and corrosion medium shielding performance. Polyurethane, a silicone resin chain segment and flaky mica in proper proportion are introduced to serve as buffer micro-areas, so that the shrinkage stress generated in the curing process of the ceramic coating is greatly reduced, the brittle connection of an inorganic network is improved, the bending resistance and the impact resistance are improved, and thick coating cracking is avoided. In addition, the introduced organic components can also improve the compactness of the coating, improve the water vapor barrier effect and improve the corrosion protection performance.

Again, the ternary silane system "phenyltriethoxysilane, dimethyldimethoxysilane and N-aminoethyl-3-aminopropylmethyldimethoxysilane" was used. The N-aminoethyl-3-aminopropylmethyldimethoxysilane can be grafted to a polyurethane main chain at the chain extension stage of a polyurethane prepolymer, so that a stable bridging structure is formed between a polyurethane chain segment and an inorganic phase, the coating strength is improved, and the toughening effect of the polyurethane chain segment is improved. On the basis, phenyltriethoxysilane and dimethyldimethoxysilane with different reactivity are selected, so that the initial curing is accelerated, and the excessive shrinkage stress can be avoided.

Fourthly, a p-toluene sulfonic acid amine neutralization substance is innovatively selected as a catalyst for the cross-linking and film forming of the ceramic coating. The p-toluenesulfonic acid amine neutralized substance has high room temperature stability, and can be decomposed at 100-140 ℃ to release p-toluenesulfonic acid. The introduction of the closed catalyst ensures the stability of the liquid coating at room temperature, reduces the curing temperature of the traditional baking ceramic coating from 200-280 ℃ to about 120 ℃, and effectively reduces the coating energy consumption.

Finally, a pure water-based material scheme is selected, so that the VOC emission of the ceramic coating can be reduced to below 20g/L, and the re-upgrading of safety and environmental protection is realized.

The water-based ceramic coating disclosed by the invention is flame-retardant, heat-resistant, efficient in corrosion medium shielding, bending-resistant and impact-resistant, and is an excellent choice for high-temperature-resistant and high-durability corrosion protection coating.

Detailed Description

The invention is further illustrated by the following examples, without limiting the scope of the invention:

the preparation steps of the water-based ceramic coatings of the examples 1-3 and the comparative examples 1-5 are as follows (the material ratio is shown in table 1, and the test results are shown in table 2):

(1) preparing polyurethane modified nano ceramic emulsion:

adding polyethylene glycol, polycarbonate diol and neopentyl glycol into an oxygen-removed reactor, heating to 100-150 ℃ (100 ℃ in example 1, 120 ℃ in example 2 and 150 ℃ in example 3), and dehydrating under reduced pressure; cooling to below 50 ℃, adding acetone, and stirring to completely dissolve the materials; diluting hexamethylene diisocyanate and isophorone diisocyanate with acetone, and slowly dropping into a reactor; adding di-n-butyltin dilaurate, heating, refluxing and stirring for reaction for 3-4 h (3 h for example 1, 3.5h for example 2 and 4h for example 3); cooling to below 40 deg.C, adding phenyltriethoxysilane, dimethyldimethoxysilane and N-aminoethyl-3-aminopropylmethyldimethoxysilane, and stirring.

Slowly dripping the obtained polyurethane prepolymer-silane mixed solution into a mixed solution consisting of silica sol, ethylenediamine ethanesulfonic acid sodium salt and water; heating to 60-70 ℃ (60 ℃ in example 1, 65 ℃ in example 2 and 70 ℃ in example 3), keeping the temperature for 2h, and then removing the acetone in the system under reduced pressure; and cooling and filtering to obtain the polyurethane modified nano ceramic emulsion with the nonvolatile content of 35-50%.

(2) Preparing the water-based ceramic paint:

dispersing water, copper-chromium black, crystal whisker silicon, mica powder, gas-phase silicon dioxide, a wetting dispersant, a defoaming agent and a corrosion inhibitor at high speed under stirring until the mixture is uniform and has no powder agglomerates and no caking; then the slurry is transferred to a grinding device and ground until the fineness of the slurry is less than 40 mu m.

Adding the polyurethane modified nano ceramic emulsion, the silicone resin emulsion, the base material wetting agent and the p-toluenesulfonate amine neutralized substance into the ground slurry, and uniformly stirring; adding a thickening agent, adjusting the viscosity of the system to 70-120 KU, and filtering to obtain the water-based ceramic coating.

(3) Preparing a ceramic coating:

and adding 10-15% of water into the obtained water-based ceramic coating for dilution, and then coating by adopting air spraying. The coated workpiece is placed for 15min at room temperature, then transferred into an oven, and gradually heated to 140 ℃. Keeping the temperature for 30min, taking out the workpiece, and cooling at room temperature.

TABLE 1 addition amount (g) of materials in examples 1 to 3 and comparative examples 1 to 5

TABLE 2 Main technical indices of the aqueous ceramic coating

Note:^[1]the heat resistance test temperature is 500 ℃, and the test time is 24 h.

Test results show that the water-based ceramic paint with excellent storage stability, impact resistance, bending resistance, butanone resistance and corrosion resistance is obtained in the examples 1 to 3. Meanwhile, the coating has stable mechanical property after heat resistance, good impact resistance and adhesive force performance and no obvious color change.

It can be seen from comparative examples 1-3 that the ratio of silicone resin to ceramic emulsion (12: 52, 6: 55, 10: 58 for examples 1, 2, and 3, respectively) has a large effect on the mechanical properties of the coating. The silicone resin has high proportion, and the indexes of the bending property, the impact resistance and the coatable film thickness of the coating are better, but the hardness and the temperature resistance limit are reduced. If the silicone resin is completely removed (e.g., comparative example 1), the coating loses toughness and is easily cracked. Meanwhile, the shielding effect of the corrosive medium is also reduced, and the salt spray resistance is reduced.

In addition to the proportions of the organic components, the type of organic component is also very important. In experiments, the silicon resin is adopted for toughening, so that the silicon resin can participate in curing and film forming to obtain a compact protective coating, and the heat resistance of a system can not be obviously damaged. If the silicone resin is replaced by other organic resin, such as silicone acrylic emulsion (comparative example 2), although a certain toughening effect is achieved, the temperature resistance limit of the coating is greatly reduced, and the impact resistance after heat resistance is lost. In addition, since the silicone-acrylic emulsion and the inorganic component cannot form a stable covalent network, significant microphase separation exists in the coating, the compactness is reduced, and the salt spray resistance is reduced.

The isocyanate-terminated polyurethane prepolymer is obtained by reasonably controlling the molar ratio of the hydroxyl component to the isocyanate component, and silane is embedded by virtue of chain extension, so that the stability of the single-component ceramic coating is very important. Comparative example 3 the amount of hexamethylene diisocyanate was reduced to increase the molar ratio of the hydroxyl component to the isocyanate component from 1:1.04 to 1: 0.95. The polyurethane prepolymer obtained in the process is hydroxyl-terminated, does not have the capability of chain extension under water and amine, and cannot form a macromolecular micelle coated with silane. The test result shows that the storage stability of the silane is obviously reduced because the coating of the comparative example 3 is not coated by the chain extension, and the coating begins to deteriorate and block after being stored for 3 days.

The invention also has the innovation point that the bisaminosilane is selected to participate in chain extension, and the bonding strength of the polyurethane and the inorganic network is improved. Comparative example 4 removed the aminosilane involved in chain extension, which resulted in the polyurethane segment not forming a stable covalent link with the inorganic phase. The test results show that the toughening effect of the coating of the comparative example 4 is reduced, and the salt spray resistance is also slightly reduced.

In order to obtain better salt spray resistance, the liquid corrosion inhibitor is selected for passivating the base material. Comparative example 5 removed the added 142DA corrosion inhibitor. The test result shows that the salt fog resistance of the coating is obviously reduced, and the adhesive force is also slightly reduced.

Claims

1. A high-toughness water-based ceramic coating is characterized in that: the coating comprises the following components:

2. the aqueous ceramic coating of claim 1, characterized in that: the coating comprises the following components:

3. the aqueous ceramic coating according to claim 1 or 2, wherein the polyurethane modified nano ceramic emulsion is prepared by the following method:

4. The aqueous ceramic coating of claim 3, characterized in that:

5. the aqueous ceramic coating of claim 4, characterized in that:

6. the aqueous ceramic coating of claim 4, characterized in that: the polyethylene glycol is terminated by hydroxyl and has a molecular weight of 500-1000; the polycarbonate diol is Asahi chemical synthesized T5650J or T5650E polycarbonate diol, and the molecular weight is 500-800; the silica sol is hectorite HN3010 or HN3020 neutral silica sol;

preferably: the hydroxyl component is polyethylene glycol, polycarbonate diol and neopentyl glycol, and the isocyanate component is hexamethylene diisocyanate and isophorone diisocyanate; the molar ratio of the hydroxyl component to the isocyanate component is 1: 1.02 to 1.25;

7. the aqueous ceramic coating of claim 4, characterized in that: the organosilane is phenyl triethoxysilane, dimethyl dimethoxysilane and N-aminoethyl-3-aminopropyl methyl dimethoxysilane, and the weight parts of the phenyl triethoxysilane, the dimethyl dimethoxysilane and the N-aminoethyl-3-aminopropyl methyl dimethoxysilane are 200-280 parts, 30-150 parts and 0.1-3 parts in sequence.

8. The aqueous ceramic coating according to claim 1, wherein the silicone emulsion is wacker MPF 52E or MP 50E; the filler is a mixture of whisker silicon and mica powder, and the mixing ratio of the whisker silicon to the mica powder is 1-3: 1.

9. The aqueous ceramic coating of claim 1, wherein the wetting dispersant is a BYK-190 dispersant; the defoaming agent is a Digao Foamex 810 defoaming agent; the corrosion inhibitor is Asconium 142 DA; the base material wetting agent is a digao Wet KL 245 base material wetting agent; the thickening agent is Heimax 299 thickening agent; the p-toluenesulfonate amine neutralizer is Zhanxin VXK 6395 or German WD-04; the dispersant is BYK-190 dispersant.

10. A method for preparing the aqueous ceramic paint according to claim 1, characterized in that: the method comprises the following steps: