CN111065694A

CN111065694A - Curable surface protective coating composition, process for its preparation and application to metal substrates and resulting coated metal substrates

Info

Publication number: CN111065694A
Application number: CN201880058325.1A
Authority: CN
Inventors: R.贾娜; C.希尔杰斯; I.拉马克里什南; K.穆鲁吉桑; W.哈特勒布
Original assignee: Momentive Performance Materials Inc
Current assignee: Momentive Performance Materials Inc
Priority date: 2017-07-31
Filing date: 2018-07-31
Publication date: 2020-04-24
Also published as: WO2019027991A1; MX2020001306A; JP2020529493A; KR20200079479A; EP3662024A1; JP7324186B2; BR112020002051A2

Abstract

Surface protective coating forming compositions exhibiting excellent shelf life (storage stability) and cured coating properties are obtained from trialkoxysilanes and metal oxide powders.

Description

Curable surface protective coating composition, process for its preparation and application to metal substrates and resulting coated metal substrates

Technical Field

The present invention relates to the field of surface protective coating compositions such as conversion and passivation coatings, and more particularly to curable coating compositions derived from alkoxysilanes and processes for coating metal substrates therewith.

Background

A large number of surface protective coating compositions have been developed over the years for application to a wide variety of surfaces as a means of imparting corrosion and/or abrasion resistant properties thereto. For example, chromium and heavy metal phosphate conversion coatings have been used to prepare metal surfaces prior to painting. However, increasing concerns over the toxicity of chromium and the polluting effects of chromates, phosphates and other heavy metals as industrial waste discharged into streams, rivers and other waterways have driven the search for alternatives to such metal coating compositions.

One type of surface protective coating composition that emerges from these efforts to develop non-chromium, non-phosphate, and non-heavy metal based metal coating compositions is derived from alkoxysilanes. Although curable coating compositions derived from alkoxysilanes continue to attract a high degree of interest in the metal industry, some of which have gained widespread commercial acceptance, there is still considerable room for improvement in one or more of their properties that continue to be of great importance to metal manufacturers and processors, such as, for example, the storage stability of uncured compositions, as well as the adhesion, flexibility, corrosion resistance, abrasion/wear resistance and optical transparency properties of cured compositions.

Disclosure of Invention

According to one aspect of the present invention, there is provided a curable surface protective coating forming composition for application to protect a surface of a substrate, such as one of: a metal, metal alloy, metallized part, metal or metallized part having one or more protective layers, said coating forming composition comprising:

(i) at least one alkoxysilane selected from the group consisting of formulas a and B:

(X-R¹)_aSi(R²)_b(OR³)_4-(a+b)formula A

(R³O)₃Si-R¹-Si(OR³)₃Formula B

Wherein:

x is an organic functional group, more specifically mercapto, acyloxy, glycidyloxy, epoxy, epoxycyclohexyl, epoxycyclohexylethyl, hydroxy, episulfide, acrylate, methacrylate, ureido, thiourea, vinyl, allyl, -NHCOOR⁴or-NHCOSR⁴Group (wherein R⁴Is a monovalent hydrocarbon group containing 1 to about 12 carbon atoms, more specifically 1 to about 8 carbon atoms), a thiocarbamate, a dithiocarbamate, an ether, a thioether, a disulfide, a trisulfide, a tetrasulfide, a pentasulfide, a hexasulfide, a polythioether, a xanthate, a tristhiocarbonate, a dithiocarbonate, or an isocyanato group, or wherein R is a monovalent hydrocarbon group containing 1 to about 12 carbon atoms, more specifically 1 to about 8 carbon atoms, or a substituted heterocyclic group, or a heterocyclic group³additional-Si (OR) as defined below³) A group;

each R¹Is a linear, branched or cyclic divalent organic group of 1 to about 12 carbon atoms, more specifically 1 to about 10 carbon atoms, and most specifically 1 to about 8 carbon atoms, such as a divalent hydrocarbon group, for example, methylene, ethylene, propylene, isopropylene, butylene, isobutylene, cyclohexylene, arylene, aralkylene or alkarylene as non-limiting examples, and which optionally contains one or more heteroatoms such as O, S and NR as non-limiting examples⁴Wherein R is⁴Is hydrogen or alkyl of 1 to 4 carbon atoms;

each R²An alkyl, aryl, alkaryl, or aryl group independently of 1 to about 16 carbon atoms, more specifically 1 to about 12 carbon atoms, and still more specifically 1 to 4 carbon atomsAlkyl, and which optionally comprises one or more halogen atoms, more particularly fluorine atoms;

each R³Alkyl groups independently of 1 to about 12 carbon atoms, more specifically 1 to about 8 carbon atoms, and still more specifically 1 to 4 carbon atoms;

subscript a is 0 or 1, subscript b is 0, 1, or 2, and a + b is 0, 1, or 2; and

when subscript a is 0 or 1, subscript b is 0, 1, or 2, and a + b is 2, the amount of alkoxysilane of formula a is from 0 to about 8 weight percent of the coating forming composition,

when a + b is 0, the amount of alkoxysilane of formula A is from 0 to about 15 weight percent of the coating forming composition,

wherein the combined amount of alkoxysilane of formula A and alkoxysilane of formula B in which subscript a is 0 or 1, subscript B is 0 or 1, and a + B is 1 is from about 8 to about 40 weight percent, and

the total amount of alkoxysilanes of formulas a and B does not exceed about 50, preferably about 45, more preferably about 40 weight percent of the coating-forming composition;

(ii) at least one metal oxide in particulate form in an amount of from about 5 to about 50 weight percent of the coating-forming composition;

(iii) at least one water-miscible organic solvent;

(iv) at least one acid hydrolysis catalyst;

(v) water; and

(vi) optionally at least one condensation catalyst,

the coating-forming composition has a viscosity in the range of about 3.0 to about 7.0cst, more specifically about 4.0 to about 5.5cst, and still more specifically about 4.5 to about 5.0cst at 25 ℃.

In the present invention, a glass-melting-measuring of glass by means of the Rolling Ball-melting-measuring by means of Hoeppler according to the DIN 53015 standard, equipped with a Haake DC10 temperature control unit and a Ball set 800-0182 (in particular, having a diameter of 15.598mm, a weight of 4.4282g and a weight of 2.229 g/cm)³Ball two of Density) 356-001 at 25 ℃.

In one embodiment of the invention, the at least one alkoxysilane (i) selected from the formulae a and B may also be a hydrolysis and condensation product thereof. Such product oligomers of alkoxysilane (i) are selected from formulas A and B, and the like. They are prepared by hydrolysis and condensation of an alkoxysilane (i) selected from the formulae A and B. That is, the alkoxysilyl group reacts with water, the corresponding alcohol is released, and then the resulting hydroxysilyl group condenses to form Si-O-Si (siloxane group). The resulting hydrolysis and condensation products or oligomers may be, for example, linear or cyclic polysiloxanes containing from 2 to 30 siloxy units, preferably from 2 to 10 siloxy units, and the remainder alkoxy groups. It will be appreciated that the same limitations as to the amount of alkoxysilane (i) apply to the corresponding oligomers derived from alkoxysilanes of formulae a and B, that is,

when subscript a is 0 or 1, subscript b is 0, 1, or 2, and a + b is 2, the amount of alkoxysilane of formula a is from 0 to about 25 wt% of the coating forming composition,

the combined amount of alkoxysilanes of formula a and B, where subscript a is 0 or 1, subscript B is 0 or 1, and a + B is 1, is from about 8 to about 40 weight percent of the coating-forming composition, and

the total amount of alkoxysilanes of formulas a and B does not exceed about 50, preferably about 45, more preferably about 40 weight percent of the coating-forming composition.

Specific preferred examples of such oligomers include especially oligomeric glycidoxypropyl-trimethoxysilane.

Further according to the present invention, there is also provided a process for forming the aforementioned curable surface protective coating forming composition, comprising:

a) cooling (chill) the mixture of alkoxysilane (i) and a portion of acid hydrolysis catalyst (iv);

b) adding metal oxide (ii) and water (v) to the refrigerated mixture of step (a);

c) (iv) adding the water-miscible organic solvent (iii) and the remaining acid hydrolysis catalyst (iv) to the mixture from step (b);

d) aging the mixture from step (c) under the following conditions: an elevated temperature for a period of time effective to provide a curable coating-forming composition having a viscosity in the range of from about 3.0 to about 7.0cStk, more specifically from about 4.0 to about 5.5cStk, and still more specifically from about 4.5 to about 5.0cStk at 25 ℃; and

e) optionally, a condensation catalyst (vi) is added at, during or after any of the preceding steps.

This process is particularly preferred when the metal oxide (ii) is a colloidal suspension of at least one metal oxide selected from the group consisting of silica, alumina, titania, ceria, tin oxide, zirconia, antimony oxide, indium oxide, iron oxides, titania doped with iron oxides and or zirconia, and rare earth oxides, or when the metal oxide (ii) is selected from a mixture of alumina and silica.

Further in accordance with another embodiment of the present invention, there is also provided a process for forming the aforementioned curable surface protective coating forming composition, comprising:

a) cooling the mixture of metal oxide (ii) and acid hydrolysis catalyst (iv), preferably to a temperature of from about-20 ℃ to about 15 ℃, preferably from about-10 ℃ to about 10 ℃, more preferably from about 0 to about 10 ℃,

b) adding alkoxysilane (i) (or a mixture thereof) to the refrigerated mixture of step (b);

c) allowing the mixture obtained in step c) to warm to room temperature (about 25 ℃) (preferably by allowing it to reach room temperature for example overnight or less preferably by applying heat),

d) adding to the mixture obtained in step d) the at least one water miscible organic solvent (iii), and optionally a condensation catalyst (vi) and optionally one or more other optional components (vii), to obtain a composition having a viscosity in the range of from about 3.0 to about 7.0cst at 25 ℃. This process is particularly preferred when the metal oxide (ii) is selected from silica modified with alumina. For example, silicas modified with alumina particles such as

100S/45 (now: Levasil CS45-58P) (Akzo Nobel) and

a mixture of 200S/30 (now: Levasil CS30-516P) (Akzo Nobel) and acetic acid (iv) was stirred in the flask. The mixture is cooled to 0 to 10 ℃ while alkoxysilane (i) is added dropwise over a period of 20 to 50 minutes. The mixture was stirred while the solution was allowed to reach room temperature. The next day, a solvent (iii) such as an alcohol, a catalyst (vi) and a flow additive (vii) is added. The entire mixture was stirred for at least 15 minutes to obtain a coating-forming composition.

According to yet another aspect of the invention, a metal provided with a surface protective coating (i.e. a coating that imparts corrosion and/or wear resistance to the surface of the uncoated or pre-coated metal) is obtained by a coating process further comprising:

f) applying a coating of the aforementioned coating-forming composition to an uncoated or pre-coated surface of the metal;

g) (iv) removing at least a portion of the solvent (iii) from the applied coating of the coating-forming composition; and

h) the coating of the solvent-depleted coating-forming composition is cured to provide a corrosion-resistant and/or wear-resistant coating on the metal surface.

The curable coating-forming composition of the present invention possesses excellent storage stability and the cured surface protective coatings obtained therefrom tend to exhibit one or more functionally advantageous properties such as high levels of corrosion and abrasion resistance, adhesion to metal surfaces, flexibility (resistance to cracking or crazing due to metal bending), and acid and/or alkali resistance. Furthermore, the overall excellent optical clarity of the cured coatings herein allows the aesthetically appealing quality of the underlying substrate surface to be manifested in good effect.

Detailed Description

In the description and claims herein, the following terms and expressions should be understood to have the meanings indicated below.

The singular forms "a", "an" and "the" include plural referents unless the context clearly dictates otherwise, and reference to a particular numerical value includes at least that particular value.

Other than in the working examples, or where otherwise indicated, all numbers expressing quantities of materials, reaction conditions, durations, quantitative properties of materials, and so forth, recited in the specification and claims are to be understood as being modified in all instances by the term "about".

All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. The use of any and all examples, or exemplary language (e.g., ") such as") provided herein, is intended merely to better illuminate the invention and does not pose a limitation on the scope of the invention unless otherwise claimed.

No language in the specification should be construed as indicating any non-claimed element as essential to the practice of the invention.

As used herein, the terms "comprising," including, "" containing, "" characterized by, "and grammatical equivalents thereof are inclusive or open-ended terms that do not exclude additional unrecited elements or method steps, but are also to be understood to include the more limiting terms" consisting of … … "and" consisting essentially of … ….

Compositional percentages are given in weight percent unless otherwise indicated.

It should be understood that any numerical range recited herein includes all sub-ranges within that range and any combination of the endpoints of that range or sub-ranges.

It is also to be understood that any compound, material or substance that is specifically or implicitly disclosed in the specification and/or described in the claims as belonging to a group of structurally, compositionally and/or functionally related compounds, materials or substances includes individual representatives of the group and all combinations thereof.

The expression "coating-forming composition" will be understood to mean a composition which, although not a practical or useful coating composition per se, forms a high quality and effective thermal energy-cured surface protective coating after the treatment described in detail herein for application to a metal surface.

The term "metal" as used herein will be understood herein to apply to the metal itself, metal alloys, metalized parts, and metal or metalized parts provided with one or more non-metallic protective layers.

By "hydrolytic condensation" is meant that one or more silanes in the coating composition-forming mixture are first hydrolyzed and the hydrolysis products are subsequently subjected to a condensation reaction with themselves or with other hydrolyzed and/or unhydrolyzed components of the mixture.

A. Components of coating Forming compositions

Alkoxysilane (i)

The alkoxysilane (i) present in the coating-forming composition may be one or more dialkoxysilanes, trialkoxysilanes and/or tetraalkoxysilanes of formula a and/or one or more trialkoxysilanes of formula B as described above, provided that at least one such trialkoxysilane is included herein.

Examples of dialkoxysilanes of formula A include dimethyldimethoxysilane, diethyldiethoxysilane, diethyldimethoxysilane, 3-cyanopropylphenyldimethoxysilane, diphenyldimethoxysilane, diphenyldiethoxysilane, di (p-tolyl) dimethoxysilane, di (diethylamino) dimethoxysilane, di (hexamethyleneamino) dimethoxysilane, di (trimethylsilylmethyl) dimethoxysilane, vinylphenyldiethoxysilane, and the like, and mixtures thereof.

As noted above, alkoxysilanes, including dialkoxysilanes, also include hydrolysis and condensation products (oligomers) thereof.

Examples of trialkoxysilanes of formula A include methyltrimethoxysilane, methyltriethoxysilane, ethyltrimethoxysilane, ethyltriethoxysilane, ethyltripropoxysilane, n-propyltrimethoxysilane, n-propyltriethoxysilane, n-propyltripropoxysilane, n-propyltributoxysilane, n-butyltrimethoxysilane, isobutyltrimethoxysilane, n-pentyltrimethoxysilane, n-hexyltrimethoxysilane, isooctyltriethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, phenyltrimethoxysilane, phenyltriethoxysilane, octyltrimethoxysilane, trifluoropropyltrimethoxysilane, 3-aminopropyltrimethoxysilane, 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane, oligomers and mixtures thereof. Of these, methyltrimethoxysilane, octyltrimethoxysilane and glycidoxypropyltrimethoxysilane are particularly advantageous.

As noted above, alkoxysilanes, including trialkoxysilanes, also include hydrolysis and condensation products (oligomers) thereof.

Examples of tetraalkoxysilanes (i.e., tetraalkylorthosilicate) of formula a include tetramethoxysilane, dimethoxydiethoxysilane, tetraethoxysilane, methoxytriethoxysilane, tetrapropoxysilane, and the like, and mixtures thereof.

Examples of trialkoxysilanes of formula B include 1, 2-bis (trimethoxysilyl) ethane, 1, 2-bis (triethoxysilyl) ethane, bis (trimethoxysilylpropyl) disulfide, bis (triethoxysilylpropyl) disulfide, bis (trimethoxysilylpropyl) tetrasulfide, bis (triethoxysilylpropyl) tetrasulfide, bis (3-triethoxysilylpropyl) amine, bis (3-trimethoxysilylpropyl) amine, and the like, and mixtures thereof.

Metal oxide (ii)

The metal oxide component (ii) is typically provided in particulate form, e.g., approximately spherical or equiaxed particles, having an average particle size in the range of from about 5nm to about 500nm, more specifically from about 10 to about 200nm and still more specifically from about 10 to about 60 nm. The average particle size is determined in particular by small-angle laser light scattering (LALLS) using the full density theory (full Mie the) using a Mastersizer2000 or 3000 (Malvern Instruments).

The metal oxide (ii) is advantageously provided as an aqueous colloidal dispersion thereof, for example, an aqueous colloidal dispersion of a metal oxide such as silica, alumina, titania, ceria, tin oxide, zirconia, antimony oxide, indium oxide, iron oxide, titania doped with iron oxide and/or zirconia, rare earth oxides, and mixtures and composite oxides thereof. Alternatively, the metal oxide (ii) in powder form may be dispersed in the coating composition.

The preferred metal oxide (ii) is aqueous colloidal silica. Aqueous dispersions of colloidal silica that may be advantageously utilized in the present invention include those having an average particle size in the range of from about 20 to about 150nm, and preferably from about 5 to about 30 nm. Such dispersions are known in the art and are commercially available, including, for example,

(Sigma Aldrich),

(Nissan Chemical), and

(Akzo Nobel) and

colloidal silica (Nalco Chemical Company),

(Akzo Nobel). Such dispersions are available in the form of both acidic and basic hydrogels.

Both acidic and basic colloidal silicas may be added to the coating-forming compositions of the present invention. Colloidal silica having a low alkali content may provide a more stable coating composition and may therefore be preferred. Particularly preferred colloidal silicas include

1034A (Nalco Chemical company) and

o40, Snowtex ST-033 and

OL-40(Nissan Chemical)，

AS40 and

HS 40(Sigma-Aldrich), Levasil 200/30 and

200S/30(now Levasil CS30-516P) (Akzo Nobel) and

A205(Cabot Corporation)。

if the metal oxide (ii) is as defined in paragraphs [0025] to [0028], the total amount of alkoxysilanes of formulae A and B preferably does not exceed about 40 wt% of the coating-forming composition.

In an embodiment of the coating-forming composition according to the invention, the metal oxide (ii) is selected from a mixture of alumina and silica. Preferably, the weight ratio of alumina to silica (Al) for the mixture₂O₃/SiO₂) From about 1:99 to about 99:1, preferably from about 5:95 to about 90:10, more preferably from about 5:95 to about 75: 25. Such mixtures are preferably prepared by mixing aqueous colloidal dispersions of alumina and silica. The use of a mixture of alumina and silica provides good adhesion to aluminum surfaces, very high wear resistance, good corrosion protection, heat resistance, and acid and alkali resistance.

In an embodiment of the coating forming composition according to the invention, the metal oxide (ii) is selected from silica modified with alumina. In one embodimentSuch silica modified with alumina may be silica, the surface of which has been modified with alumina. Therefore, such silica modified with alumina is sometimes referred to as Al₂O₃-SiO₂-core-shell particles. Further, in this embodiment, the metal oxide (ii) may be provided as an aqueous colloidal dispersion. Such silica or Al modified with alumina₂O₃-SiO₂The use of core-shell particles is particularly useful for protecting anodized aluminum parts on the exterior surface of automobiles, such as roof rails and trim parts, and provides high resistance to corrosion by high or low pH liquids, high scratch resistance and high heat resistance. The use of such silica modified with alumina in the coating-forming composition according to the present invention provides high scratch resistance under long-term high acidic environmental conditions. Examples of silicas modified with alumina include, for example, the Levasil-type, e.g., comprising Al with an average particle size of about 30nm₂O₃Of surface-modified silicon dioxide particles

100S/45 (currently: Levasil CS45-58P) dispersion (45% in water), and containing Al with an average particle size of about 17nm₂O₃Of surface-modified silicon dioxide particles

200S/30 (currently: Levasil CS30-516P) dispersion (30% in water) and a surface area of about 85m²/g(in

100S/45) and about 160m²/g(

200S/30)。

In embodiments where silica modified with alumina is used, a mixture comprising at least two silicas modified with aluminas having different average particle sizes may be used. For example, a mixture of two silicas modified with aluminas having different average particle sizes may be used, wherein the weight ratio of the alumina-modified silica having the smaller particle size (e.g., 10-25nm) is higher than the weight ratio of the alumina-modified silica having the larger particle size (e.g., 26-40nm), preferably the small/large ratio is from about 10:1 to about 1:2, preferably from about 10:1 to about 2: 1. This measurement provides a particularly high scratch resistance.

The amount of metal oxide (ii) added to the coating-forming compositions herein can generally vary from about 5 to about 50, more specifically from about 10 to about 40, and still more specifically from about 10 to about 30 weight percent, based on the weight of the composition.

(ii) Water-miscible organic solvent (iii)

Illustrative of the water-miscible solvent (iii) that may be added to the coating-forming composition of the present invention are alcohols such as methanol, ethanol, propanol, isopropanol, n-butanol, t-butanol, methoxypropanol, ethylene glycol, diethylene glycol butyl ether, and combinations thereof. Other water-miscible organic solvents such as acetone, methyl ethyl ketone, ethylene glycol monopropyl ether, and 2-butoxyethanol may also be utilized. Typically, these solvents are used in combination with water, which together with any water associated with the metal oxide (ii) and/or other components of the coating composition provides some or all of its water (v).

The total amount of water-miscible solvent (iii) present in the coating-forming composition can vary widely, for example, from about 10 to about 80, more specifically from about 10 to about 65, more specifically from about 10 to about 60 and still more specifically from about 10 to about 50 weight percent, based on the total weight thereof. When the coating-forming composition includes alumina-modified silica as the metal oxide (ii), the total amount of the water-miscible solvent (iii) present in the coating-forming composition can vary widely, for example, from about 40 to about 70, more specifically from about 50 to about 65 weight percent, based on the total weight thereof.

Acid hydrolysis catalyst (iv)

Any acid hydrolysis catalyst previously used for the hydrolysis of alkoxysilanes can be added to the coating-forming compositions herein. Illustrative acid hydrolysis catalysts (iv) include sulfuric acid, hydrochloric acid, acetic acid, propionic acid, 2-methylpropionic acid, butyric acid, valeric acid (valeric acid), caproic acid (caproic acid), 2-ethylhexanoic acid, enanthic acid (enanthic acid), caproic acid, caprylic acid (caprylic acid), oleic acid, linoleic acid, linolenic acid, cyclohexanecarboxylic acid, cyclohexylacetic acid, cyclohexenecarboxylic acid, benzoic acid, phenylacetic acid, malonic acid (malic acid), succinic acid (succinic acid), adipic acid (adipic acid), 2-butenedioic acid (maleic acid), lauric acid, stearic acid, myristic acid, palmitic acid, isononanoic acid, neodecanoic acid (pivalic acid), lauric acid, stearic acid, myristic acid, palmitic acid, isononanoic acid, amino acids, and mixtures thereof. The acid hydrolysis catalyst may be used undiluted or in the form of an aqueous solution.

The acid hydrolysis catalyst (iv) is present in the coating-forming composition of the invention in at least a catalytically effective amount, in most cases in an amount ranging from about 0.1 to about 5, more specifically from about 0.5 to about 4.5, and more specifically from about 2 to about 4 weight percent, based on the total weight of the coating-forming composition. In some embodiments, for example, when the coating-forming composition includes silica modified with alumina as the metal oxide (ii), the amount of the acid hydrolysis catalyst (iv) may also range from about 0.1 to about 2 wt%, based on the total weight of the coating-forming composition.

Water (v)

The water component of the coating-forming compositions herein is advantageously Deionized (DI) water. Some or even all of the total water present in the coating composition forming mixture may be added as part of one or more other components of the mixture, for example, an aqueous colloidal dispersion of the metal oxide (ii), the water-miscible solvent (iii), the acid hydrolysis catalyst (iv), the optional condensation catalyst (vi), and/or other optional components (vii) such as those described below.

The total amount of water (v) can vary within widely varying ranges, for example, from about 5 to about 40, more specifically from about 5 to about 30 and still more specifically from about 5 to about 15 weight percent based on the total weight of the coating-forming composition.

Optional condensation catalyst (vi)

Optional condensation catalyst (vi) catalyzes the condensation of the partially or fully hydrolyzed silane components (a) and (b) of the coating-forming compositions herein and thus acts as a curing catalyst.

Although the coating-forming composition may be cured in the absence of the optional condensation catalyst (vi), effective curing may require more severe conditions, such as application of elevated temperatures (thermal cure) and/or extended curing times, both of which may be undesirable from a cost and/or productivity standpoint. In addition to providing a more economical coating process, the use of optional condensation catalyst (vi) also generally results in improved shelf life of the coating-forming composition.

An illustrative example of a condensation catalyst (vi) that may optionally be present in the coating-forming composition herein is of the formula [ (C)₄H₉)₄N]⁺[OC(O)-R⁵]^-Tetrabutylammonium carboxylate of (4), wherein R⁵Selected from the group consisting of hydrogen, alkyl groups containing from 1 to about 8 carbon atoms, and aromatic groups containing from about 6 to about 20 carbon atoms. In a preferred embodiment, R⁵Is a group containing about 1 to 4 carbon atoms, such as methyl, ethyl, propyl, isopropyl, butyl or isobutyl. The aforementioned tetrabutylammonium carboxylates are somewhat milder in their catalytic action compared to the more active types of condensation catalysts (v), such as mineral acids and alkali metal hydroxides, and tend to optimize the shelf life of the coating-forming compositions containing them. Exemplary tetrabutylammonium carboxylate condensation catalysts of the foregoing formula are tetra-n-butylammonium acetate (TBAA), tetra-n-butylammonium formate, tetra-n-butylammonium benzoate, tetra-n-butylammonium 2-ethylhexanoate, tetra-n-butylammonium p-ethylbenzoate, and tetra-n-butylammonium propionate. Preferred condensation catalysts in terms of effectiveness and suitability with respect to the present invention are tetrabutylammonium carboxylate, tetra-n-butylammonium acetate (TBAA), tetra-n-butylammonium formate, tetra-n-butylammonium benzoate, tetra-n-butylammonium 2-ethylhexanoate, tetra-n-butylammonium p-ethylbenzoate, and tetra-n-butylammonium propionate, tetramethylammonium acetate, tetramethylammonium benzoate, tetrahexylammonium acetate, dimethylammonium formate (dimethylammonium form), dimethylammonium acetate, tetramethylammonium carboxylate, tetramethylammonium 2-ethylhexanoate, benzyltrimethylammonium acetate, tetraethylammonium acetate, tetraisopropylammonium acetate, triethylmethylammonium acetateAmmonium, diethanoldimethylammonium acetate, monoethanoltrimethylammonium acetate, ethyltriphenylphosphonium acetate, TBD acetate (1,5, 7-triazabicyclo [4.4.0]]Dec-5-ene (TBD)), and combinations of two or more thereof.

Among the aforementioned tetrabutylammonium carboxylate condensation catalysts, tetra-n-butylammonium acetate and tetra-n-butylammonium formate are generally preferred, and tetra-n-butylammonium acetate is more preferred.

When utilized, the condensation catalyst (vi) in the coating-forming compositions herein can be present in at least a catalytically effective amount, for example, from about 0.0001 to about 1 weight percent, based on the total weight of the composition.

Other optional Components (vii)

One or more other optional components (vii) are suitable for inclusion in the coating-forming compositions herein.

For example, the coating-forming composition may also include one or more surfactants to act as leveling agents or flow additives. Examples of suitable surfactants include fluorinated surfactants such as

(3M) Silicone polyethers such as

And

(Momentive Performance Materials, Inc.), and silicone surface additives such as polyether modified silicones, for example BYK-302(BYK Chemie USA). The coating compositions herein may also include UV absorbers such as benzotriazoles, benzophenones, dibenzylcatechol. Preferred UV absorbers are those capable of co-condensation with silanes, specific examples of which include 4- [ gamma- (trimethoxysilyl) propoxy]-2-hydroxybenzophenone, 4- [ gamma- (triethoxysilyl) propoxy]-2-hydroxybenzophenone and 4, 6-dibenzoyl-2- (3-triethoxysilylpropyl) resorcinol. When using the preferred UV absorbers capable of co-condensing with silanes, it is important that the coating composition be cured by the application of thermal energy theretoSufficient mixing to co-condense the UV absorber with other reactive species prior to its application to the metal surface. The co-condensed UV absorber prevents coating performance loss that can be caused by leaching of free UV absorber to the environment during weathering.

The coating-forming compositions herein also include one or more antioxidants such as hindered phenols (e.g., a hindered phenol)

1010(Ciba Specialty Chemicals), dyes (e.g., methylene green, methylene blue, etc.), fillers such as titanium dioxide, zinc phosphate, barite, aluminum flake, etc., and plasticizers such as dibutyl phthalate.

B. Formation of a coating-forming composition.

In the formation of the heat-curable coating composition of the present invention, a mixture of alkoxysilane (i) and a portion of acid hydrolysis catalyst (iv) is cooled, followed by addition of the remaining portion of acid hydrolysis catalyst (iv) and aging of the resulting mixture under predetermined conditions as follows: elevated temperature and for a period of time that results in a thermally cured composition having a viscosity in the following range: about 3.0 to about 7.0cStk, more specifically about 4.0 to about 5.5cStk in another embodiment and still more specifically about 4.5 to about 5.0cStk in yet another embodiment.

Refrigeration can be effected, for example, by using an ice bath, an ice/NaCl mixture or a dry ice/isopropanol mixture. More specifically, alkoxysilane (i) and acid hydrolysis catalyst (iv) were placed in a glass bottle and then placed in an ice bath to refrigerate the mixture while monitoring the temperature by an external thermometer. The chilling of the mixture of alkoxysilane (i) and acid hydrolysis catalyst (iv) is preferably carried out to a temperature of from about-20 ℃ to about 15 ℃, preferably from about-10 ℃ to about 10 ℃, more preferably from about 0 to about 10 ℃.

In the first stage of the process of forming the thermal energy cured coating compositions herein, a mixture of the trialkoxysilane of formula a and/or B, optionally the dialkoxysilane of formula a and/or the tetraalkoxysilane, and about 10 to about 40% of the total amount of the acid hydrolysis catalyst (iv) is chilled to a temperature in the range of about-20 ℃ to about 15 ℃, and preferably about-10 ℃ to about 10 ℃. While in refrigerated conditions, the metal oxide (ii) such as aqueous colloidal silica is slowly added to the mixture.

After the metal oxide (ii) is added and stirring is continued for a period of about 2 to about 10 days, and more specifically about 5 to about 8 days, the refrigerated mixture is allowed to increase in temperature to or about ambient temperature, for example about 20 ℃ to about 30 ℃. During this constant stirring, the alkoxysilane component (i) of the mixture undergoes an initial stage of hydrolysis, followed by condensation of the resulting hydrolysate.

When the metal oxide (ii) is selected from silica modified with alumina, these formulations are preferably cooled for several hours/overnight, for example from about 2 to about 10 hours.

In the second stage of the process of forming the thermally-cured coating compositions herein, the water-miscible solvent (iii) and the remaining acid hydrolysis catalyst (iv) are added to the now ambient-temperature reaction medium and under continuous stirring for a period of time, for example, from about 5 to about 24 and more specifically from about 8 to about 15 hours, during which further hydrolysis of the silane and/or partial hydrolysate and condensation of the hydrolysate so formed occurs.

When the metal oxide (ii) is selected from silica modified with alumina, it is preferable to add the whole amount of the acid hydrolysis catalyst (iv) directly from the beginning so that no acid hydrolysis catalyst (iv) is added at this time.

The addition of part of the acid hydrolysis catalyst (iv) in the first stage and the addition of the remaining acid hydrolysis catalyst (iv) in the second stage results in a curable coating composition in the above-mentioned viscosity range. The hydrolysis and condensation reaction rates depend on the concentration of the acid hydrolysis catalyst (iv) and the pH of the reaction mixture. The final pH of the reaction mixture is advantageously maintained at about 2 to about 7, and more specifically about 4 to about 6. Acid hydrolysis catalyst (iv) was added in two stages in order to maintain the pH at each stage. The acid hydrolysis catalyst (iv) is added, for example, dropwise to the initial portion in such a manner as to prevent aggregation and precipitation of the metal oxide particles (ii), thereby subjecting the alkoxysilane component (i) to hydrolysis and functionalizing the metal oxide particles (ii). With silanization of the metal oxide particles (ii), the pH of the mixture will reach almost neutral.

A pH range of about 3 to about 4, for example about 3.5 to about 3.8, is generally obtained without additional pH adjustment when the metal oxide (ii) is selected from silica modified with alumina.

The acid hydrolysis catalyst (iv) may be added in a second stage to maintain the final pH of the mixture such that condensation of the silanol is controlled and gel formation is hindered, thereby providing a relatively long shelf life, e.g., the coating forming composition comprises less than about 5, preferably less than about 2 and more preferably less than about 1 weight percent gel of its total weight after storage at ambient temperature for not less than about 15 days, more specifically not less than about 20 days and still more specifically not less than about 30 days. Storage at temperatures in the range of about 0 to about 15c, preferably about 5 to about 10c, may be suitable in some embodiments.

If utilized, the optional condensation catalyst (vi) may be added in at least a catalytically effective amount at, during or after steps (a) - (d) of preparing the curable coating composition. The amount of optional condensation catalyst (v) can vary widely, for example from about 0.01 to about 0.5, and more specifically from about 0.05 to about 0.2 weight percent based on the total weight of the coating-forming composition.

The optimum amount of residual silanol is obtained by accelerating the condensation reaction during aging as described more fully below. Once the desired viscosity level is obtained, the curable coating composition can be applied to a desired substrate to produce a uniform, transparent and hard coating thereon (steel wool abrasion resistance test with a 1kg load, as described in table 5 below).

After this additional hydrolysis period, optional condensation catalyst (v) and one or more other optional components (vii) may be added to the reaction mixture, advantageously with continuous stirring for an additional period of time, for example from about 1 to about 24 hours. The resulting reaction mixture is now ready for aging.

Aging of the aforementioned coating composition forming mixture may be carried out at elevated temperatures for a period of time which has been empirically determined to result in a viscosity in the aforementioned range of about 3.0 to about 7.0 cst.

When the metal oxide (ii) is selected from silica modified with alumina, no aging is generally required.

Achieving such viscosities results in curable coating compositions having good to excellent cured coating properties. Lower viscosity can lead to reduced coating film hardness and post-curing, which can occur upon continuous exposure of the coating. Higher viscosities can lead to cracking of the coating film under curing and subsequent exposure conditions.

For many coating composition forming blends, viscosities in the range of about 3.0 to about 7.0cst can be obtained by: the coating-forming mixture is heated in an oven to a temperature of about 25 to about 100 ℃ for about 30 minutes to about 1 day, more specifically at a temperature of about 25 to about 75 ℃ for about 30 minutes to about 5 days and still more specifically at a temperature of 25 to about 50 ℃ for about 3 to about 10 days. The hydrolyzable silane containing hydroxyl groups is partially hydrolyzed when less than an equivalent of water reacts with the hydrolyzable silyl group. When the percent hydrolysis is in the range of about 1 to about 94%, the hydroxyl-containing hydrolyzable silane is considered to be partially hydrolyzed. When the percent hydrolysis is in the range of about 95 to about 100%, the hydroxyl-containing hydrolyzable silane is considered to be fully hydrolyzed. The partially hydrolyzed hydrolyzable silanes containing hydroxyl groups have better stability in aqueous solution because R¹The O-Si groups terminate the polymerization reaction of the silanol condensation and maintain a lower average molecular weight oligomeric component derived from the hydroxyl-containing hydrolyzable silane. The lower average molecular weight oligomeric component adsorbs more uniformly on the metal substrate resulting in better adhesion.

C. Coating application and curing procedure

The coating-forming compositions of the present invention, with or without further added solvent, will typically have a solids content of from about 10 to about 50, more specifically from about 15 to about 40, and still more specifically from about 20 to about 30, weight percent. The pH of the coating composition will often range from about 3 to about 7 and more specifically from about 4 to about 6.

When the metal oxide (ii) is selected from silica modified with alumina, the pH of the coating composition will often be in the range of about 3 to about 4, for example about 3.5 to about 3.8.

The curable coating composition can be applied to a metal substrate with or without a primer and preferably without a primer.

Suitable metals include steel, stainless steel, aluminum, anodized aluminum, magnesium, copper, bronze, various alloys of these metals, and the like, with anodized aluminum being a particularly desirable substrate due to its inherent corrosion resistance properties and strength to weight ratio.

The coating-forming composition may be applied to the metal or other substrate using any conventional or other known technique such as spraying, brushing, and flow coating. Drop coating is also possible. The thickness of the wet, i.e., freshly applied, coating can vary over a fairly broad range, such as from about 10 to about 150, more specifically from about 20 to about 100, and still more specifically from about 40 to about 80 microns. Such a thickness of the coating so applied, upon drying, will provide a cured coating having a thickness corresponding in the range of about 3 to 30, more specifically about 5 to about 20, and still more specifically about 10 to about 15 microns.

When the metal oxide (ii) is selected from silica modified with alumina, the dry coating thickness (DFT) is typically adjusted to be from about 2 to about 10 microns, preferably from about 3 to about 7 microns.

As the coating dries, the solvent (iii) and any other readily volatile substances will evaporate and the applied coating will become tack-free to the touch for a brief period of time, for example around 15-30 minutes, at which point the coating/film can be considered to be ready for curing advantageously using conventional or other known thermal curing procedures, the operating requirements of which are well known in the art. For example, thermally accelerated curing may be carried out at a temperature in the range of about 80 to about 200 ℃ for a period of about 30 to about 90 minutes to provide a cured, optically clear, hard protective coating on the base metal.

The cured coating obtained from the coating composition of the present invention may be in direct contact with the metal surface, may act as the sole coating therein, may be superimposed on one or more other coatings and/or may itself possess one or more other coatings superimposed thereon. In addition to imparting corrosion and/or abrasion resistance properties to its metal substrate, the cured coating composition may also serve as an aesthetic coating, in which case it will constitute the sole or outermost coating on the metal substrate.

The advantages of the coating-forming composition of the present invention over known alkoxysilane-based coating-forming compositions are not only the former's excellent storage stability, believed attributable to the specific combination of starting components and their amounts and the unique process of obtaining the coating-forming composition, particularly its independent cooling, separate addition of hydrolysis catalysts and aging steps, but also its ease of application to various metals and metallized surfaces and the reliable uniform nature of the cured coating.

As indicated previously, the cured coating compositions of the present invention exhibit excellent properties, including a high level of adhesion to metal surfaces, corrosion resistance, flexibility (resistance to cracking or crazing), abrasion/wear resistance, and optical transparency, the latter being particularly sought after where the cured coating composition is intended to additionally serve as a decorative coating.

Examples

Comparative example 1

Comparative example 1 illustrates a curable coating-forming composition prepared according to Burger et al, U.S. Pat. No.6,695,904, and applied to anodized aluminum panels 15cm long, 4cm wide and 4mm thick.

A mixture of 62.0g of methyltrimethoxysilane, 18.1g of tetraethoxysilane and 23.13g of aqueous colloidal silica (40% by weight suspension) was prepared, to which 1.3g of 37% by weight sulfuric acid as acid hydrolysis catalyst was added dropwise at-5 ℃. The mixture was continuously stirred at 20 ℃ for 1 hour to provide a coating composition. Within a few hours, the reaction mixture had gelled. However, after 1 hour, the mixture was attempted to be flow coated onto an anodized aluminum substrate to a uniform thickness of about 10-15 microns at a temperature of 23 ℃ and 40% RH. After a drain time (flash-off time) of 25 minutes to evaporate the flow coating volatiles, the coating was cured at 130 ℃ for 1 hour.

The resulting cured coating was opaque, exhibited extensive cracking and had delaminated, indicating little if any adhesion to the underlying anodized aluminum surface.

A sample of the coating composition aged at 50 ℃ for 24 hours had completely gelled, and a sample of the coating composition held at about 23 ℃ had completely gelled within 24 to 48 hours. The viscosity of the coating composition cannot be measured due to its instability.

Examples 1 to 15 (use of colloidal silica as the metal oxide (ii))

Examples 1-15 illustrate the preparation of coating-forming compositions of the present invention and their performance as cured coatings on anodized aluminum panels 15cm long, 4cm wide and 4mm thick and stainless steel panels 15cm long, 10cm wide and 1mm thick.

The starting components of the curable coating-forming compositions of examples 1-15 are listed in table 1 below:

table 1: starting material

The general procedure for forming the curable coating-forming compositions of examples 1-15 is described in table 2 below:

table 2: preparation procedure

Curable coating-forming compositions of examples 1-15 were prepared from the indicated mixtures set forth in table 3 below using the starting materials listed in table 1 and the general preparation procedure described in table 2:

table 3: curable coating-forming composition

A glass-melt by Means of a glass-melt by Means of the glass-melt by Means of the Hoeppler standard according to DIN 53015, equipped with a Haake DC10 temperature control unit and a Ball group 800-0182 (in particular having a 15.598mm diameter, a 4.4282g weight and 2.229 g/cm)³Sphere two of density) the Hoeppler falling ball viscometer model 356-001 measures the viscosity of the coating forming compositions of examples 1, 3 and 15 at 25 c as shown in table 4 below.

Table 4: viscosity of the curable coating-forming composition

Examples	Viscosity, cStk
		1	4.9936
3	4.8850
		15	4.8678

The general procedure for applying the curable coating-forming compositions of examples 1-15 to anodized aluminum and stainless steel panels and curing the coating thereon was as follows:

coating procedure

Application of a coating layer having a thickness of approximately 10 microns may be performed by any suitable means, such as by drop coating, flow coating or spray coating. Drop coating is used to apply a layer of approximately 10 microns thick of the coating-forming composition to an anodized aluminum plate and flow coating is used to apply a coating of this thickness to a stainless steel plate.

Curing procedure

After the coating was applied to the anodized aluminum and stainless steel substrate, the volatiles were allowed to evaporate at about 23 deg.C, resulting in a non-tacky coating layer in about 25 minutes. The coated panels were then baked in a hot air oven at 130 ℃ for 45-60 minutes to produce a fully cured, transparent hard coat on the metal surface.

The testing of the coated metal sheets was performed as described in table 5 below:

table 5: testing of coated panels

Coating performance data are given in tables 6-9 below:

table 6: coating performance on anodized aluminum substrates

Table 7: coating performance on unpolished bulk aluminum substrates

Examples	Appearance of the coating	Initial adhesion	Wear of steel wire	Heat resistance
					1	Clear/smooth/glossy	Through 5B	By passing	By passing
10	Clear/smooth/glossy	Through 5B	By passing	By passing

Table 8: coating properties on stainless steel substrates

Examples	Appearance of the coating	Initial adhesion	Wear of steel wire	Heat resistance
					1	Clear/smooth/glossy	Through 5B	By passing	By passing

Table 9: corrosion performance on anodized aluminum substrates

Examples	Moisture resistance, 240hr	NSS tolerance, 480hr	CASS test, 48hr
				1	By passing	By passing	By passing

Examples 16-25 (using a mixture of silica and alumina particles as metal oxide (ii)) table-10: starting material

TABLE-11: examples 16 to 25

(all numbers refer to wt%, based on the total composition)

The coating formulation was prepared by any of the following procedures:

one-pot procedure (One-pot procedure) for coating formulation:

acetic acid and trialkoxysilane were charged into glass bottles. After cooling the reaction mixture to 0 ℃ in an ice bath, the mixture of silica nanoparticles and water was added dropwise to the refrigerated mixture of silane and acetic acid while maintaining the temperature below 10 ℃. The mixture was then allowed to stir for approximately 1-2 hours. The alumina nanoparticle dispersion was then added to the mixture and allowed to stir for an additional approximately 12-14 hours while the solution temperature was slowly raised to room temperature. The alcohol and remaining acetic acid were then added and stirred for approximately 12 hours, followed by the TBAA catalyst and flow additive. Thereafter, the formulation was aged in a hot air oven at 50 ℃ for approximately 5 days before being coated on the metal surface.

Two-pot procedure (Two-pot procedure) for coating formulation:

in this method, a coating solution may be prepared by separately reacting an alkoxysilane and different nanoparticles. This method may be a preferred option over a one pot procedure for compositions where the nanoparticles have a tendency to settle in the formulation. However, this method can generally be used for coating compositions having any ratio of two different nanoparticles. In this method, acetic acid and trialkoxysilane are charged into a glass bottle. After cooling the reaction mixture to 0 ℃ in an ice bath, the mixture of silica nanoparticles and water was added dropwise to the refrigerated mixture of silane and acetic acid while maintaining the temperature below 10 ℃. The mixture was then allowed to stir for approximately 16 hours while the solution temperature was slowly raised to room temperature. In another glass bottle, a portion of the alkoxysilane (preferably 1:1 weight percent silane and nanoparticles) and nanoparticles (alumina) were mixed together and kept under stirring at room temperature for approximately 16 hours. Thereafter, the two solutions were mixed together at room temperature and kept under stirring for 1-2 hours. Then, the alcohol and the remaining acetic acid were added and stirred for approximately 12 hours, followed by the TBAA catalyst and flow additive. Thereafter, the formulation was aged in a hot air oven at 50 ℃ for approximately 5 days before being coated on the metal surface.

General procedure for coating on metal surfaces:

the coating composition is a thermally cured single layer optically clear protective coating that is applied directly on the anodized aluminum surface. The application of a thin layer of coating of roughly 10 microns in thickness is achieved by drop/flow/spray coating. After coating on the aluminum substrate, the volatiles were volatilized at ambient conditions (approximately 20-25 ℃, 40 ± 10% RH) and a non-stick coating formed in 25-30 minutes. After solvent drainage, the coated panels were baked in a hot air oven at 130-200 ℃ for 30-60 minutes to obtain a fully cured transparent hard coating on the metal surface.

Test methods (examples 16 to 25):

appearance of the coating: this test was performed by visual inspection. To pass, the coating must be smooth, glossy, optically clear, and free of any coating defects.

Initial adhesion: cross hatch adhesion tests were performed according to standard procedure ASTM D3359. To be acceptable, all coatings must pass 5B.

Abrasion resistance test by Crockmeter (Crockmeter): this test was conducted by an AATCC Crockmeter CM-5 instrument using a 5CM x 5CM green rubbing cloth (from Atlas) for 10 cycles (1 cycle ═ back and forth rubbing); distance: 100 mm; force: 9N (automatic application). To pass this test, the surface should not have any visible scratches after testing.

Heat resistance: the coated panels were kept in a hot air oven at 160 ℃ for 24 hours. By pass, there should be no loss of adhesion, delamination or cracking.

And (3) testing the hydrochloric acid resistance: the coated plate was immersed in a hydrochloric acid (HCl) solution at pH 1.0 for 10 minutes. After exposure, the plates were removed from the solution, washed with DI water and dried under ambient conditions. By passing, there should be no softening, loss of adhesion, delamination, cracking or corrosion of the coating film.

Alkali resistance test: the coated plate was immersed in a sodium hydroxide buffer solution at pH 13.5 for 10 minutes. The buffer solution was prepared by mixing the appropriate amounts by weight of sodium hydroxide, sodium phosphate dodecahydrate, sodium chloride, and deionized water. After exposure, the plates were removed from the solution, washed with DI water and dried under ambient conditions. By passing, there should be no softening, loss of adhesion, delamination, cracking or corrosion of the coating film.

And (3) sulfuric acid resistance test: the coated panels were immersed in H at pH 2.1₂SO₄In solution for 5 days. After exposure, the plates were removed from the solution, washed with DI water and dried under ambient conditions. By passing, there should be no softening, loss of adhesion, delamination, cracking or corrosion of the coating film.

Corrosion resistance test-Kesternich test (acid rain simulation): this test was carried out according to DIN 50017 up to three cycles. By passing, the coating should not exhibit any softening, delamination, loss of adhesion, change in visual appearance, or any other coating defects.

Table 12: test results examples 16 to 25

And (3) corrosion resistance testing: kesternich test (acid rain simulation)

Examples 19, 23, 24 and 25 were subjected to the Kesternich test and all passed the test.

As these tests demonstrate, the inventive compositions of examples 16-25 comprising silica and alumina particles all provided good coating properties such as adhesion, abrasion resistance and pH tolerance tests (HCl and NaOH buffer). In particular, the examples also provide very good results for scratch resistance, pH resistance tests including sulfuric acid resistance and in the Kesternich test.

Examples 26 to 30 (Al)₂O₃-SiO₂Core-shell particles as metal oxide (ii))

Table 13: starting material

TABLE-14: examples 26 to 30

(all numbers refer to wt-%, based on the total composition)

Preparation of the coating composition

A mixture of core-shell particles Levasil 100S/45 and Levasil 200S/30 and acetic acid was stirred in the flask. The mixture is cooled to 0-10 ℃ while the silane is added dropwise over a period of 20-50 minutes. The mixture was stirred while the solution was brought to room temperature. The next day, alcohol, catalyst and flow additive were added. The entire mixture was stirred for at least 15 minutes.

Coating procedure

After preparation, the clear coating composition is applied directly on the anodized aluminum in a layer thickness of 2 to 8 μm. Application of the coating composition is achieved by drop/flow coating or spraying. After coating the anodized aluminum substrate, the solvent drain-off takes 2-20 minutes to obtain a non-stick coating layer. The coated substrate is then cured in a hot air oven at 130 ℃ to 200 ℃ for 30 minutes to 2 hours to obtain complete cure.

Table 15: test results examples 26 to 30

The following tests and test procedures have been performed on anodized aluminum parts.

SO converted from DIN50018-2,0S₂Laboratory testing: 0.67 wt.% SO₂The solution was placed in a 5L bottle, which was placed in a water bath at 40 ℃. The coated sample is placed with the lower part into the solution and the upper part subjected to SO₂An atmosphere. According to this test protocol, the coating should not change optically after five days.

Alkali resistance according to TL 182: there was no change in appearance after the following test series on the same assembly over a temperature range of 23 ℃ to 35 ℃:

a) 10 back-and-forth rubs with a 1kg load

b) Immersing in a pH 1 solution (0.1M hydrochloric acid) for 10 minutes

c) Rinsed in water and dried

d) Aging at 40 ℃ for 1 hour, and then continuing the test sequence without cooling (step)

e) Immersed in a solution of pH 13.5 (12.7g caustic soda, 4.64g sodium phosphate dodecahydrate, 0.33g sodium chloride; all dissolved in 1 liter of water) for 10 minutes

48 hours salt spray test, according to DIN EN ISO 9227(CASS test).

The following table summarizes the results from the different coating compositions

Watch 15

Examples	SO₂Laboratory testing	Kesternich test	Alkali resistance	CASS test
					26	Line of	Line of	Line of	Line of
27	Line of	-	-	-
					28	Line of	-	-	-
29	Line of	Line of	Line of	Line of
					30	Line of	Line of	Line of	Line of

While the invention has been described with reference to specific embodiments thereof, it is evident that many changes, modifications and variations can be made without departing from the inventive concept disclosed herein. Accordingly, it is intended to embrace all such changes, modifications, and variations that fall within the spirit and broad scope of the appended claims.

Claims

1. A coating-forming composition comprising:

(i) at least one alkoxysilane or hydrolysis and condensation product thereof selected from the group consisting of formulas a and B:

(X-R¹)_aSi(R²)_b(OR³)_4-(a+b)formula A

(R³O)₃Si-R¹-Si(OR³)₃Formula B

Wherein:

x is an organic functional group;

each R¹Is a linear, branched or cyclic divalent organic group of 1 to about 12 carbon atoms optionally containing one or more heteroatoms;

each R²Independently an alkyl, aryl, alkaryl, or aralkyl group of from 1 to about 16 carbon atoms optionally containing one or more halogen atoms;

each R³Independently an alkyl group of from 1 to about 12 carbon atoms;

subscript a is 0 or 1, subscript b is 0, 1, or 2, and a + b is 0, 1, or 2; and

wherein the combined amount of alkoxysilane of formula a and alkoxysilane of formula B where subscript a is 0 or 1, subscript B is 0 or 1 and a + B is 1 is from about 8 to about 40 weight percent of the coating forming composition, and

wherein the total amount of alkoxysilanes of formulae a and B does not exceed about 50 wt% of the coating-forming composition;

(iii) at least one water-miscible organic solvent;

(iv) at least one acid hydrolysis catalyst;

(v) water; and

(vi) optionally at least one condensation catalyst,

the coating-forming composition has a viscosity in the range of about 3.0 to about 7.0cStk at 25 ℃.

2. The coating-forming composition of claim 1, wherein the total amount of alkoxysilanes of formulas a and B does not exceed about 45 wt% of the coating-forming composition.

3. The coating-forming composition of claim 1, wherein the total amount of alkoxysilanes of formulas a and B is no more than about 40 wt% of the coating-forming composition.

4. The coating-forming composition of any one of claims 1-3, wherein in the alkoxysilane of formula A, a is 1 and the organofunctional group X is mercapto, acyloxy, glycidoxy, epoxy, epoxycyclohexyl, epoxycyclohexylethyl, hydroxy, episulfide, acrylate, methacrylate, ureido, thioureido, vinyl, allyl, wherein R is⁴NHCOOR being a monovalent hydrocarbon radical comprising 1 to about 12 carbon atoms⁴or-NHCOSR⁴A group, a thiocarbamate, a dithiocarbamate, an ether, a thioether, a disulfide, a trisulfide, a tetrasulfide, a pentasulfide, a hexasulfide, a polythioether, a xanthate, a tristhiocarbonate, a dithiocarbonate, or an isocyanurate group, or wherein R is a hydrogen atom³Is further-Si (OR) as defined before³) A group.

5. The coating-forming composition of any one of claims 1-4, wherein in the alkoxysilane of formula B, R is¹Is a divalent hydrocarbon group comprising at least one heteroatom selected from: o, S and NR⁴Wherein R is⁴Is hydrogen or alkyl of 1 to about 4 carbon atoms.

6. The coating-forming composition of any one of claims 1-5, wherein the at least one alkoxysilane (i) is selected from at least one member of the group consisting of: trialkoxysilanes of formula a in which subscript a is 0 or 1, subscript B is 0 or 1 and a + B is 1, trialkoxysilanes of formula B, and mixtures of trialkoxysilanes of formula a and B.

7. The coating-forming composition of any one of claims 1-6, comprising an alkoxysilane (i) selected from at least one member of the group consisting of: dialkoxysilanes of formula a wherein subscript a is 0 or 1, subscript B is 0, 1 or 2 and a + B is 2, tetraalkoxysilanes of formula B wherein subscripts a and B are each 0, and mixtures of dialkoxysilanes and tetraalkoxysilanes of formulae a and B.

8. The coating-forming composition of any one of claims 1-7, wherein the trialkoxysilane of formula A is at least one member selected from the group consisting of: methyltrimethoxysilane, methyltriethoxysilane, ethyltrimethoxysilane, ethyltriethoxysilane, ethyltripropoxysilane, n-propyltrimethoxysilane, n-propyltriethoxysilane, n-propyltripropoxysilane, n-propyltributoxysilane, n-butyltrimethoxysilane, isobutyltrimethoxysilane, n-pentyltrimethoxysilane, n-hexyltrimethoxysilane, isooctyltriethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, phenyltrimethoxysilane, phenyltriethoxysilane, octyltrimethoxysilane, trifluoropropyltrimethoxysilane, 3-aminopropyltrimethoxysilane, 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, 3-glycidoxypropyltrimethoxysilane and 3-glycidoxypropyltriethoxysilane, and wherein the trialkoxysilane of formula B is at least one member selected from the group consisting of: 1, 2-bis (trimethoxysilyl) ethane, 1, 2-bis (triethoxysilyl) ethane, bis (trimethoxysilylpropyl) disulfide, bis (triethoxysilylpropyl) disulfide, bis (trimethoxysilylpropyl) tetrasulfide, bis (triethoxysilylpropyl) tetrasulfide, bis (3-triethoxysilylpropyl) amine and bis (3-trimethoxysilylpropyl) amine.

9. The coating-forming composition of any one of claims 1-8, wherein the metal oxide (ii) is a colloidal suspension of at least one metal oxide selected from the group consisting of: silicon dioxide, aluminum oxide, titanium dioxide, cerium dioxide, tin oxide, zirconium dioxide, antimony oxide, indium oxide, iron oxides, titanium dioxide doped with iron oxides and/or zirconium dioxide, and rare earth oxides.

10. The coating-forming composition of any one of claims 1-9, wherein the metal oxide (ii) is selected from a mixture of alumina and silica.

11. The coating-forming composition of any one of claims 1-10, wherein the metal oxide (ii) is selected from a mixture of alumina and silica, wherein the mixture has a weight ratio of alumina to silica (Al) of the mixture₂O₃/SiO₂) Is 1:99 to 99:1, preferably 5:95 to 90:10, more preferably 5:95 to 75: 25.

12. The coating-forming composition of any one of claims 1-8, wherein the metal oxide (ii) is selected from silica modified with alumina.

13. The coating-forming composition according to any one of claims 1 to 12, wherein the water-miscible solvent (iii) is at least one member selected from the group consisting of: alcohols, glycols, glycol ethers, and ketones.

14. The coating-forming composition according to any one of claims 1-13, wherein the at least one acid hydrolysis catalyst (iv) is at least one member selected from the group consisting of: sulfuric acid, hydrochloric acid, acetic acid, propionic acid, 2-methylpropionic acid, butyric acid, valeric acid (valeric acid), caproic acid (caproic acid), 2-ethylhexanoic acid, enanthic acid (enanthic acid), caproic acid, caprylic acid (caprylic acid), oleic acid, linoleic acid, cyclohexanecarboxylic acid, cyclohexylacetic acid, cyclohexene carboxylic acid, benzoic acid, phenylacetic acid, malonic acid (malic acid), succinic acid (succinic acid), adipic acid (adipic acid), 2-butenedioic acid (maleic acid), lauric acid, stearic acid, myristic acid, palmitic acid, isononanoic acid, neodecanoic acid, and amino acids, and wherein the coating-forming composition further comprises at least one condensation catalyst (vi) selected from the group consisting of the formula [ (C acid, propionic acid, 2-methylprop₄H₉)₄N]⁺[OC(O)-R⁵]^-Tetrabutylammonium carboxylate of (4), wherein R⁵Selected from the group consisting of hydrogen, alkyl groups containing from 1 to about 8 carbon atoms, and aromatic groups containing from about 6 to about 20 carbon atoms.

15. The coating-forming composition of any one of claims 1-14, wherein condensation catalyst (vi) is at least one member selected from the group consisting of: tetra-n-butylammonium acetate, tetra-n-butylammonium formate, tetra-n-butylammonium benzoate, tetra-n-butylammonium 2-ethylhexanoate, tetra-n-butylammonium p-ethylbenzoate, tetra-n-butylammonium propionate, and TBD-acetate (1,5, 7-triazabicyclo [4.4.0] dec-5-ene (TBD)).

16. The coating-forming composition of any one of claims 1-15 having a viscosity in the range of about 4.0 to about 5.5cst at 25 ℃.

17. The coating-forming composition of any one of claims 1-11 and 13-16, obtained from a process comprising:

a) cooling the mixture of alkoxysilane (i) and acid hydrolysis catalyst (iv);

b) adding metal oxide (ii) and water (vi) to the refrigerated mixture of step (a);

c) (iv) adding a water miscible solvent (iii) and additional acid hydrolysis catalyst (iv) to the mixture from step (b);

d) aging the mixture from step (c) under the following conditions: an elevated temperature for a period of time determined to provide a curable coating-forming composition having a viscosity in the range of about 3.0 to about 7.0cStk at 25 ℃; and

e) optionally adding a condensation catalyst (vi) at, during or after any of the preceding steps.

18. The coating-forming composition of claim 17, wherein the metal oxide (ii) is as defined in claim 9 or 10.

19. The coating-forming composition of any one of claims 1-8 or 11-16, obtained by a process comprising:

a) chilling the mixture of metal oxide (ii) and acid hydrolysis catalyst (iv), preferably to a temperature of from about-20 ℃ to about 15 ℃, preferably from about-10 ℃ to about 10 ℃, more preferably from about 0 to about 10 ℃;

b) adding alkoxysilane (i) to the refrigerated mixture of step (b);

c) bringing the mixture obtained in step c) to room temperature (about 25 ℃),

d) adding to the mixture obtained in step d) the at least one water miscible organic solvent (iii), and optionally a condensation catalyst (vi) and optionally one or more optional components (vii), to obtain a composition having a viscosity in the range of about 3.0 to about 7.0cst at 25 ℃.

20. The coating-forming composition of claim 19, wherein the metal oxide (ii) is as defined in claim 12.

21. The coating-forming composition of any one of claims 17-20 having a viscosity of about 4.0 to about 5.5cst at 25 ℃.

22. The coating-forming composition of any one of claims 17-21, wherein the alkoxysilane (i) is at least one member selected from the group consisting of: trialkoxysilanes of formula a in which subscript a is 0 or 1, subscript B is 0 or 1 and a + B is 1, trialkoxysilanes of formula B, and mixtures of trialkoxysilanes of formula a and B.

23. The coating-forming composition of any one of claims 17-21, wherein the alkoxysilane (i) is at least one member selected from the group consisting of: dialkoxysilanes of formula a wherein subscript a is 0 or 1, subscript B is 0, 1 or 2 and a + B is 2, tetraalkoxysilanes of formula B wherein subscripts a and B are each 0, and mixtures thereof.

24. The coating-forming composition of any one of claims 17-22, wherein the trialkoxysilane of formula a is at least one member selected from the group consisting of: methyltrimethoxysilane, methyltriethoxysilane, ethyltrimethoxysilane, ethyltriethoxysilane, ethyltripropoxysilane, n-propyltrimethoxysilane, n-propyltriethoxysilane, n-propyltripropoxysilane, n-propyltributoxysilane, n-butyltrimethoxysilane, isobutyltrimethoxysilane, n-pentyltrimethoxysilane, n-hexyltrimethoxysilane, isooctyltriethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, phenyltrimethoxysilane, phenyltriethoxysilane, octyltrimethoxysilane, trifluoropropyltrimethoxysilane, 3-aminopropyltrimethoxysilane, 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, 3-glycidoxypropyltrimethoxysilane and 3-glycidoxypropyltriethoxysilane, and wherein the trialkoxysilane of formula B is at least one member selected from the group consisting of: 1, 2-bis (trimethoxysilyl) ethane, 1, 2-bis (triethoxysilyl) ethane, bis (trimethoxysilylpropyl) disulfide, bis (triethoxysilylpropyl) disulfide, bis (trimethoxysilylpropyl) tetrasulfide, bis (triethoxysilylpropyl) tetrasulfide, bis (3-triethoxysilylpropyl) amine and bis (3-trimethoxysilylpropyl) amine.

25. The coating-forming composition of any one of claims 17-18, wherein the metal oxide (ii) is at least one member selected from an aqueous colloidal suspension of at least one metal oxide selected from silica, alumina, titania, ceria, tin oxide, zirconia, antimony oxide, indium oxide, iron oxide, titania doped with iron and or zirconia, and rare earth oxides, wherein the water-miscible solvent (iii) is at least one member selected from alcohols, glycols, glycol ethers, and ketones, wherein the acid hydrolysis catalyst (iv) is at least one or more members selected from the group consisting of: sulfuric acid, hydrochloric acid, acetic acid, propionic acid, 2-methylpropionic acid, butyric acid, valeric acid (valeric acid), caproic acid (caproic acid), 2-ethylhexanoic acid, heptanoic acid (enanthic acid), caproic acid, caprylic acid (caprylic acid), oleic acid, linoleic acid, linolenic acid, cyclohexanecarboxylic acidAcid, cyclohexylacetic acid, cyclohexene carboxylic acid, benzoic acid, phenylacetic acid, malonic acid (malic acid), succinic acid (succinic acid), adipic acid (adipic acid), 2-butenedioic acid (maleic acid), lauric acid, stearic acid, myristic acid, palmitic acid, isononanoic acid, neodecanoic acid, lauric acid, stearic acid, myristic acid, palmitic acid, isononanoic acid, and amino acid, and wherein the coating-forming composition further comprises at least one condensation catalyst (vi) selected from the group consisting of: formula [ (C)₄H₉)₄N]⁺[OC(O)-R⁵]^-Tetrabutylammonium carboxylate of (4), wherein R⁵Selected from the group consisting of hydrogen, alkyl groups containing from 1 to about 8 carbon atoms, and aromatic groups containing from about 6 to about 20 carbon atoms.

26. The coating-forming composition of any one of claims 19-20, wherein the metal oxide (ii) is selected from silica modified with alumina, wherein the water-miscible solvent (iii) is at least one member selected from the group consisting of alcohols, glycols, glycol ethers, and ketones, wherein the acid hydrolysis catalyst (iv) is at least one or more members selected from the group consisting of: sulfuric acid, hydrochloric acid, acetic acid, propionic acid, 2-methylpropionic acid, butyric acid, valeric acid (valeric acid), caproic acid (caproic acid), 2-ethylhexanoic acid, enanthic acid (enanthic acid), caproic acid, caprylic acid (caprylic acid), oleic acid, linoleic acid, linolenic acid, cyclohexanecarboxylic acid, cyclohexylacetic acid, cyclohexene carboxylic acid, benzoic acid, phenylacetic acid, malonic acid (malic acid), succinic acid (succinic acid), adipic acid (adipic acid), 2-butenedioic acid (maleic acid), lauric acid, stearic acid, myristic acid, palmitic acid, isononanoic acid, neodecanoic acid, lauric acid, stearic acid, myristic acid, palmitic acid, isononanoic acid, and amino acids, and wherein the coating-forming composition further comprises at least one condensation catalyst (vi) selected from the group consisting of: formula [ (C)₄H₉)₄N]⁺[OC(O)-R⁵]^-Tetrabutylammonium carboxylate of (4), wherein R⁵Selected from the group consisting of hydrogen, alkyl groups containing from 1 to about 8 carbon atoms, and aromatic groups containing from about 6 to about 20 carbon atoms.

27. The coating-forming composition of any one of claims 17-18, wherein in step (a), the mixture is chilled to a temperature of about-20 ℃ to about 15 ℃.

28. The coating-forming composition of any of claims 17-18, wherein in step (a), the mixture comprises about 10 to about 50 wt% of the total amount of acid hydrolysis catalyst (iv), with the remainder of acid hydrolysis catalyst (iv) added in step (c).

29. The coating-forming composition of any of claims 17-18, wherein in step (e), the mixture from step (d) is aged at a temperature of about 20 ℃ to about 100 ℃ for a period of about 1 to about 60 days.

30. A process for coating a surface of a metal to impart corrosion and/or wear resistant properties thereto, comprising applying a coating-forming composition according to any one of claims 1 to 29 to an uncoated or pre-coated surface of the metal for which corrosion and/or wear resistance is desired and curing the applied coating-forming composition to provide a corrosion and/or wear resistant coating thereon.

31. A process according to claim 30, wherein the coating-forming composition is applied to a surface of anodized aluminum, bulk aluminum, magnesium, steel, copper, bronze or alloys thereof, a metallized surface or a metal provided with at least one protective layer.

32. A process for coating a surface of a metal to impart corrosion and/or wear resistant properties thereto, comprising applying a coating-forming composition obtained by a process according to any one of claims 17 to 26 to an uncoated or pre-coated surface of the metal for which corrosion and/or wear resistance is desired and allowing the applied coating-forming composition to cure to provide a corrosion and/or wear resistant coating thereon.

33. A process according to claim 32, wherein the coating-forming composition is applied to a surface, a metallised surface or a metal part provided with at least one protective layer of anodized aluminium, bulk aluminium, magnesium, steel, copper, bronze or alloys thereof.

34. A coated metal surface comprising a corrosion and/or wear resistant coating prepared by the process of claim 30.