RU2790437C2 - Dispersive coating - Google Patents

Abstract

FIELD: chemical industry.

SUBSTANCE: invention relates to the chemical industry and can be used in the manufacture of dispersed coatings with a metallic effect. The composition of the dispersion coating, preferably powder, includes: at least one hardener containing an epoxy group, for example, an epoxy resin; at least one polyester polymer; at least one amino alcohol with a molecular weight of 50-400 g/mol, containing 1-3 amino groups and 1-5 hydroxyl groups, in an amount of 0.1-10% of the total weight of the composition; and at least one metallic pigment containing Al, in an amount of 1-10% of the total mass of the composition. Amino alcohol can be selected from diethanolamine, ethanolamine, 2-amino-1-butanol, 2-amino-2-methyl-1-propanol, 2-amino-2-ethyl-1,3-propanediol, tris-(hydroxymethyl)-aminomethane, 2- amino-2-methyl-1,3-propanediol, monomethylaminoethanol, isopropylaminoethanol, tert-butylaminoethanol, ethylaminoethanol, n-butylaminoethanol, isopropanolamine, diisopropanolamine and mixtures thereof. To obtain this composition, a hardener, a polyester polymer and an amino alcohol are mixed. The mixture is extruded and a metallic pigment is added to the obtained particles. The composition is applied to the substrate by electrostatic spraying with optional subsequent curing of the resulting coating. The specified composition forms the top layer on the substrate.

EFFECT: increased resistance of the coating to color change due to fingerprints during operation or touch, increased corrosion resistance of the metallic pigment, improved dispersibility in the composition, exclusion of the upper transparent layer.

17 cl, 10 tbl

Description

The present invention relates to dispersed metallic effect coatings obtained using pigments such as aluminium. In particular, the present invention relates to the prevention of corrosion of said pigments in the resulting coating, as well as to the prevention of abrasions or fingerprints on said coating. Also, the present invention relates to the use of a dispersed coating for coating a substrate, as well as to a method for obtaining a dispersed coating, a method for curing said coating and its use. The dispersion coating according to the present invention preferably forms a top layer on the surface of the substrate.

Traditionally, coating powders are made by extruding a mixture of resins and curing agents (and standard additives, etc.) to obtain a homogeneous mixture, and then grinding the extrudate and screening the resulting product to obtain the desired particle size and particle size distribution. The powder is then electrosprayed onto a substrate, traditionally a metal substrate, and cured at high temperatures. The type of finish on the substrate is regulated by the introduction of additives.

Currently, there is a proliferation of powder coatings in the market for metal powder coatings that provide a metallic effect on the surface of the coated product. The metallic effect is obtained by introducing metallic pigments into the powder coating at the right time. However, these metallic pigments can be corroded by oxygen, moisture, etc. Corrosion can also be caused by contact with acids, bases and water. This violates the appearance and integrity of the coating. To prevent this problem, current practice is to use an additional clear coating layer, which is applied separately over the metallic effect coating to provide corrosion protection. However, the application of this additional coating is costly and time consuming, while consumers require a simpler solution that avoids the application of an additional clear coating. Reducing the coverage by one layer will significantly reduce the time and cost.

It has also been noted that these powder coating compositions containing metallic pigments can be disadvantageous due to non-uniformity if the metallic pigment is not properly distributed in the coating. Another problematic issue is scuffs or fingerprints on the resulting coating. To ensure an aesthetically ideal appearance, it is necessary to prevent the formation of such defects. Thus, there is a need for a particulate coating composition that addresses some or all of these problems.

The authors of the present invention solve this problem by introducing an amino alcohol into the powder coating. The present invention preferably relates to a polyester/epoxy powder coating composition containing metallic effect pigments such as aluminum powder or flakes and an amino alcohol. Surprisingly, it has been found that said powder coating composition can be applied as a single coat without the need for an additional top coat.

This formulation unexpectedly stabilizes the metallic pigment against corrosion, eg improves acid resistance, base resistance and water/moisture resistance. Due to this, the need for an upper transparent coating layer is leveled. The amino alcohol also contributes to the dispersibility of the metallic pigment in the powder coating composition. The coating according to the present invention is noticeably less susceptible to discoloration due to fingerprints during handling or touching.

The problem of corrosion of metallic pigments has been known in the past, and attempts have been made to solve this problem in various ways, but with limited success. In US 2009/0264575, the inventors propose a coating of metallic pigment particles. Ideally, said coating is based on epoxy and polyester resins, and is therefore compatible with the binder that normally forms the bulk of the film-forming coating. The idea is that immersing the metallic pigments in the epoxy/polyester resin prevents the pigment from corroding. Therefore, in essence, said document provides a coated metal particle for isolating the metal from air and moisture. The coated metal particle can be used as a concentrate in a powder coating to provide the desired amount of pigment. Some manufacturers even use a double coat technique, for example based on an inorganic/organic double coat such as a silica coat followed by an acrylate coat or a polyester/epoxy coat.

The coating of the metal particles improves the storage stability of the pigments, however, the corrosion resistance of said particles after application to the substrate is still not ideal. Therefore, while many metal particles are coated to provide longer shelf life prior to application, our experience is that these particles are still susceptible to oxidation after application. In addition, coating the particles is costly and time consuming.

CN 101225279 A discusses a composition designed to solve the problem of fingerprints. This composition uses epoxy resin, polyester resin, pigment, filler and aluminum flakes. The aluminum flakes are believed to improve flow characteristics, enhance abrasion and scratch resistance, and have a defoaming effect.

CN 103483979 A describes a powder coating composition containing aluminum flakes, an epoxy resin, a polyester resin and vinyl tris-(beta-methoxyethoxy)-silane as an adhesion promoter. This combination purportedly improves wear resistance, prevents scratching, and has a defoaming effect.

However, the possibility of using an amino alcohol in such powder coating compositions has never been considered before. Amino alcohol not only improves the aesthetic appearance, but also improves the dispersibility of the metallic pigment. In addition, the use of amino alcohol leads to an improvement in corrosion resistance. The most noticeable improvement is the resistance of the coating to acids or bases. Finally, moisture resistance can be improved.

Brief description of the invention

According to one aspect of the present invention, there is provided a particulate coating composition, preferably a powder coating composition, comprising:

(i) at least one curing agent, such as at least one compound containing an epoxy group;

(ii) at least one polyester polymer;

(iii) at least one amino alcohol; And

(iv) at least one metallic pigment.

According to another aspect of the present invention, there is provided a substrate coated with a particulate coating composition, preferably a powder coating composition, comprising:

(i) at least one curing agent, such as at least one compound containing an epoxy group;

(ii) at least one polyester polymer;

(iii) at least one amino alcohol; And

(iv) at least one metallic pigment.

According to another aspect of the present invention, there is provided a substrate coated with a primer layer and, on top of said primer layer, a layer of a dispersion coating composition, preferably a layer of a powder coating composition, comprising:

a particulate coating composition, preferably a powder coating composition, comprising:

(i) at least one curing agent, such as at least one compound containing an epoxy group;

(ii) at least one polyester polymer;

(iii) at least one amino alcohol; And

(iv) at least one metallic pigment.

According to another aspect of the present invention, there is provided a substrate coated with a dispersion coating composition, or a substrate coated with a primer layer and over said primer layer with a layer of a dispersion coating composition, as described herein, said powder coating composition being cured.

Preferably, said particulate coating composition forms a top layer on the substrate.

According to another aspect of the present invention, a kit is provided comprising:

a first composition containing at least one curing agent, such as at least one compound containing an epoxy group, at least one polyester polymer and at least one amino alcohol; And

a second composition containing at least one metallic pigment.

According to another aspect of the present invention, a process is provided for preparing a dispersion coating composition, preferably a powder coating composition, comprising mixing at least one curing agent, such as at least one compound containing an epoxy group, at least one polyester polymer and at least one amino alcohol with the formation of a mixture;

extruding the resulting mixture to form particles;

introducing at least one metallic pigment to form a dispersed powder coating.

According to another aspect of the present invention, there is provided a product obtainable by the method described above.

According to another aspect of the present invention, a method is provided for coating a substrate with the above-described particulate coating, for example using electrostatic spraying, comprising applying said particulate coating to said substrate, for example using electrostatic spraying, and optionally curing the resulting coating.

According to another aspect of the present invention, a method is provided for coating a substrate with a dispersion coating composition, preferably a powder coating composition, comprising mixing at least one curing agent, such as at least one compound containing an epoxy group, at least one polyester polymer and at least one amino alcohol to form a mixture;

extruding the resulting mixture to form particles;

introducing at least one metallic pigment to form a dispersed powder coating;

applying said particulate coating to said substrate, for example using electrostatic spraying, and optionally curing the resulting coating.

According to another aspect of the present invention, the use of an amino alcohol is provided for preventing corrosion of a metallic pigment contained in a powder coating composition containing at least one hardener, such as at least one epoxy group-containing compound, at least one polyester polymer, and at least one metallic pigment.

Preferably, the proposed coating is a top layer. Thus, no more coating should be applied over the coating according to the present invention.

Detailed description of the invention

The present invention relates to a particulate coating composition, such as a powder coating composition, which can be used to coat a substrate. The particulate coating composition must contain at least four components: at least one hardener such as at least one compound containing an epoxy group, at least one polyester polymer, at least one amino alcohol, and at least one metallic pigment. The particulate coating composition of the present invention is preferably used as a top coat on a substrate, which may or may not be provided with a primer layer. The term "top coat" means that no further coats are applied over the particulate coat according to the present invention.

It is believed that the amino alcohol, among other things, prevents corrosion of the metallic pigment in the coating, thus eliminating the need for a clear topcoat over the coating layer. Thus, the amino alcohol can help prevent damage to the coating by acids, bases and water. The amino alcohol also aids in the dispersion of the metallic pigment in the dispersed coating. The amino alcohol helps to prevent aesthetic discolouration of the coating, for example by fingerprints or other contact with human skin, or by abrasion.

The particulate composition according to the present invention can preferably be obtained by mixing two particulate, preferably powder compositions. The particulate composition containing the amino alcohol can be mixed with the particulate composition containing the metallic pigment.

Complex polyester polymer

The coating composition according to the present invention contains at least one reactive polyester polymer. The term reactive means that the polyester polymer must contain functional groups capable of reacting with the functional groups of the curing agent to cure the coating. Suitable functional groups contained in the polyester include carboxyl groups, ester groups, isocyanate groups and hydroxyl functional groups. Ideally, the polyester is hard. Further preferably, the polyester is a carboxylated or hydroxylated polyester, in particular a saturated carboxylated polyester resin or a saturated hydroxylated polyester resin. Most preferably, the polyester is a carboxylated polyester resin and therefore contains a plurality of COOH pendant groups.

Thus, the polyester polymer is preferably a solid resin containing a plurality of free carboxyl groups or hydroxyl groups. Preferably the polyester polymer has a T _c in excess of 40°C, more preferably in excess of 50°C.

Ideally, the polyester resin has an acid number (AN). Most preferred are polyester resins with an acid number (AN) in the range of 20-80 mg KOH/g, such as 30-70 mg KOH/g, preferably 40-60 mg KOH/g. Particularly preferred are resins with an AN in the range of 55-68 mg KOH/g or 60-70 mg KOH/g.

More preferably, the polyester polymer is an acid-functional polyester, in particular having the above CN.

Therefore, the polyester resin preferably contains a plurality of carboxyl groups. These groups must be able to react with the hardener, ideally with epoxy groups, and therefore must be available for interaction. This means that carboxyl groups must represent side groups in the molecule. In addition, this powder coating component according to the present invention is a polymer, for example, obtained by polymerization of monomers, at least one of which contains a carboxyl group.

A mixture of polyester polymers or a single polyester polymer can be used.

The use of carboxy-functional polyesters is preferred, especially those referred to as 50/50 type resins or 80/20 type resins (i.e., which use 80 wt. % of 20% carboxyl-functional polyester). mass containing epoxy groups of the connection binder). The values of CF and EEM should preferably correspond to each other. For example, the AN of a 50/50 type resin can be 60 to 80 mg KOH/g. Resins referred to as 80/20 type resins will have lower ANs such as 20 to 40 mg KOH/g.

The monomers used to prepare the polyesters according to the present invention may be based on terephthalic acid, isophthalic acid, for example together with glycols such as neopentyl glycol.

Alternatively, the polyester may contain OH functional groups. The hydroxyl value is preferably about 50-300 mg KOH/g.

Another alternative may be unsaturated polyesters. They can be cured using peroxide initiators. The term "unsaturated polyesters" means the presence of many unsaturated bonds in the side chains of the polyester, for example, introduced through (meth)acrylate. Unsaturated polyesters suitable for the present invention are amorphous or crystalline. Crystalline unsaturated polyesters are described in WO 2011/138431 A1 and WO 2011/138432 A1. These materials can be cured with peroxides, optionally in combination with infrared or radiation, or with UV curing photoinitiators. In this case, the hardener is the initiator.

The polyester polymer preferably has an Mw of at least 1000, more preferably at least 2000. The upper limit of Mw may be 10000. Preferred Mw values are 2000-6000, preferably 2500 to 5000, such as about 3000. Molecular weights are determined using gel permeation chromatography (GPC) with polystyrene standards.

Such resins are well known in the art and are sold under trademarks such as Uralac by DSM and Crylcoat by Allnex.

Hardener

Also necessary is at least one hardener. The hardeners interact with the polyester polymer during the curing reaction to provide a film coating on the substrate.

Preferably, the hardener is an epoxy group-containing compound such as an epoxy resin. It is also possible to use a variety of epoxy group-containing compounds.

The epoxy group-containing compound is preferably an epoxy resin. Ideally, it is a solid resin containing one or more epoxy groups. Suitable resins are also well known in the art and are well known commercially. The epoxy-containing compound includes TGIC (triglycidyl isocyanurate), Araldite PT 910/PT912, bisphenol A resins, novolac resins, modified novolac resins, 4,4'-isopropylidenediphenol epichlorohydrin (bisphenol F) resins, glycidyl methacrylates (GMA) and etc.

In one preferred embodiment, the epoxy resin is TGIC, Araldite PT 910/PT912, bisphenol A resins, modified novolac resins or 4,4'-isopropylidene diphenol epichlorohydrin (bisphenol F) resins. Thus, in one embodiment, the use of glycidyl methacrylate (GMA) or glycidyl methacrylates (GMA) is excluded altogether. Particularly preferred is a bisphenol A resin.

Most preferred are solid epoxy resins with an epoxy equivalent weight (EEM) in the range of 300-2000. such resins are often described by "type". Resins of types 2, 2.5, 3, 4 and modified novolac resins are suitable for the present invention. Type 2 resins can have EEM=550-700, eg Epikote 1002 resin, Epikote 3022-FCA resin. Type 2.5 resins may have EEM=600-750, e.g. Araldite GT 6450. Type 3 resins may have EEM=700-850, e.g. Epikote 3003 resin, Araldite GT 7004. Epikote 1055 resin. Modified novolak resins may include Epikote 2017 or Araldite GT 7255 resin.

Especially preferred is the use of an epoxy resin with an EEM of 730 to 840 (such as type 3).

As an alternative to epoxy resins, the present invention also contemplates the use of other hardeners such as hydroxyalkylamide hardeners and polyisocyanate hardeners such as the uretdione type or caprolactam blocked isocyanates (eg isophorone diisocyanate). In particular, polyisocyanate hardeners are preferably used with hydroxyl-functional polyester resins to form polyurethanes. Hydroxyalkylamide hardeners can be used with carboxyl-functional polyester resins. Particularly preferred is the use of hydroxyalkylamide hardeners such as Primid XL-552, available from Ems Primid.

Another alternative to a curing agent is simply a peroxide, if the polymer is an unsaturated polyester and can undergo a curing reaction between its molecules when initiated with the peroxide.

Note that the hardener and polyester must interact to cure the coating. Therefore, it is preferable to mix these components in such a ratio that the reactive groups, for example carboxyl, in the polyester and, for example, the epoxy groups in the hardener, are within ±25% of the stoichiometric ratio. More preferred is the ratio of carboxyl to epoxide within ±10% of the stoichiometric ratio. Most preferred is the ratio of carboxyl to epoxide within ±5% of the stoichiometric ratio.

One skilled in the art will recognize that some of the additives discussed below may contain carboxyl groups. When calculating the ratio of EEM to CN, the contribution made by any carboxyl groups in standard additives used in powder coating should be taken into account.

It should be noted that this calculation is based on the total number of carboxyl and epoxy groups present. If the compounds contain many carboxyl or epoxy groups, this should be taken into account in these calculations, although this is a common procedure for an experienced chemist.

In the present specification, the combination of hardener and polyester resin is referred to as a binder system. Ideally, the present invention utilizes a hybrid epoxy-carboxyl-functional polyester binder system. These systems are well known in the art. It is within the scope of the present invention to use a pure polyester binder when the binder is an unsaturated polyester that can be cured with an epoxide.

So, polyester can be from 50 to 97% of the mass. relative to the binder, preferably 60-96% of the mass. regarding the binder. The hardener may be from 3 to 50, preferably from 3 to 40% of the mass. regarding the binder. The amount of polyester polymer will therefore be close to or greater than the amount of hardener compound. When used as a binder unsaturated polyester polymer can be almost 100% of the mass. relative to the binder, with a small addition of initiating hardener.

The amount of binder in the powder coating according to the present invention can be from 40 to 99% by weight, preferably from 50 to 95% by weight.

metallic pigment

The particulate coating according to the present invention contains a metallic pigment. The purpose of the metallic pigment is to provide a metallic color effect on the coated substrate. Such coatings are used to coat household appliances, furniture, building components, tools, vehicles, and so on, to provide a metallic effect coating.

Any metallic pigment can be used in the present invention as long as said metallic pigment is susceptible to corrosion. The present invention relates, inter alia, to a method for reducing or preventing corrosion of a metallic pigment. Therefore, it is obvious that the pigment in question should preferably be a pigment that can be corroded.

The metal in question is typically a transition metal (groups 3 to 12 of the periodic table), Al, or Sn. The pigment may also be an alloy. Ideally, the pigment contains an elemental metal or alloy rather than a salt (eg oxide) or ionic form. It should be noted that many powder coatings contain titanium dioxide and other metal salts as fillers. Titanium dioxide is a white, non-corrosive powder and is not a metallic pigment. The metallic pigment must be capable of providing a metallic effect in the resulting coating.

The metallic pigment is usually used in the form of flakes or particles, it may contain aluminum or an aluminum alloy, or another metal or alloy such as stainless steel, copper, tin, bronze or brass (gold is usually too expensive), and can be used to provide various metallic effects, including those known as "glossy" or "shiny" finishes. A combination of two or more different metallic pigments may be used.

It is advantageous when the metallic pigment is aluminum or an aluminum alloy. "Foiling" or "non-foiling" systems can be used. In the foil-forming system, aluminum flakes are oriented with respect to each other to form a continuous layer on or near the surface of the applied coating film, forming an opaque silver finish,

Non-foiling aluminum pigments, which are able to orientate themselves within the coating film, provide aesthetic characteristics quite different from foil-forming aluminum pigments. They have the unique ability to provide "flop", polychromatic and sparkling effects. "Flop effect" is the ability to change color when viewed from different angles. This ability is directly related to the orientation of the flakes in the film.

The metal pigment(s) are usually included in the powder coating composition after extrusion or other homogenization process (hereinafter referred to as "after mixing"). One form of post-mixing process involves dry mixing, and any available dry mixing process may be used. Pigments can be added before or after milling, for example at the particle screening stage. However, in theory, metallic pigments can be added at various stages of the manufacturing process, for example, a portion before grinding and a portion before screening. One of skill in the art would be able to devise ways to introduce pigment into a powder coating. In one possible embodiment, the pigments are added during the pre-mixing stage, i. e. before extrusion. Products advertised as "Powdersafe" or "Powdersafe-02" are suitable for direct extrusion. The use of said pigments forms an additional aspect of the present invention.

According to another aspect of the present invention, a method is provided for preparing a dispersion coating composition, preferably a powder coating composition, comprising mixing at least one hardener, such as at least one compound containing an epoxy group, at least one polyester polymer, at least one metallic a pigment and at least one amino alcohol to form a mixture;

extruding the resulting mixture and, optionally, grinding and/or grinding to obtain a dispersed powder coating.

In particular, the pigment and the powder coating may be "bonded". The bonding method should be understood as a method of mixing a powder coating and a metallic pigment in which the pigment particles are physically bonded to the powder coating particles by heating the mixture to the glass transition temperature of the powder coating. In this way, the adhesion of metal pigments to the surface of the powder coating particles is ensured.

A range of hammer and other textured metallic finishes can be obtained by applying, in addition to the metallic pigment, a suitable hammer or other texture additive.

The metallic pigment may be a coated or uncoated material. Examples of coated materials include pigments coated with silica or other inert inorganic material for greater chemical resistance and durability. Alternatively, the pigment may be coated with a polymeric material for a similar purpose, such as an acrylic, PTFE, or thermoset plastic material, or may be placed in a polymer or plasticizer carrier compatible with the film-forming binder of the powder coating composition, such as a polyester/epoxy coating. Another possibility is to coat the metal pigment with a coloring agent, such as a metal oxide pigment, such as, for example, iron oxide, to provide certain color effects. The use of silica-coated metal pigments is preferred to improve the stability of the particles both during storage and during subsequent coating. Double-coated particles (eg, using an inorganic and then an organic coating) are acceptable but less desirable because their metallic effect is reduced. It may also be possible to use a silane as a metal pigment adhesive to bond the coating layer to the particle.

Ideally, the particles do not carry an organic coating. Ideally, the particles do not bear an oligomeric or polymeric coating.

The total proportion of metallic pigment(s) included in the coating composition may vary from 0.1 to 10% by weight (relative to the weight of the coating composition), for example, from 0.4 to 8% by weight, preferably from 0.5 to 5 % by weight, typically 1 to 4% by weight. The values given refer to the actual weight of the particles, which may or may not be coated.

The particle size d50 of the metallic pigment can vary in the range of 3-50 µm. Typically, the particle size d50 is 10-30 µm. Ideally, the average particle size d50 is at least 10 µm. Particle size can be measured with a Malvern device giving the result as a d50 value. D50 is the median mass diameter (MMD). MMD is defined as the average particle diameter by weight.

Amino alcohol

The amino alcohol according to the present invention is a compound containing at least one hydroxyl group and at least one primary, secondary or tertiary amino group. Salts of these compounds can also be used. Preferably, the amino alcohol according to the present invention is formed only by the elements C, H, O and N. Preferably, primary or secondary amino alcohols are used.

In general, amino alcohols that can be used according to the present invention include compounds of the following formulas:

NH ₂ R ¹ ,

where R ¹ represents a linear or branched alkyl group containing from 1 to 10 carbon atoms, preferably from 2 to 8 carbon atoms, and more preferably from 2 to 4 carbon atoms, which contains at least one hydroxyl group; And

NHR ¹ R ² ,

where R ¹ is a linear or branched alkyl group containing 1 to 10 carbon atoms, preferably 2 to 8 carbon atoms, and more preferably 2 to 4 carbon atoms, or a linear or branched alkyl group containing 1 to 10 carbon atoms carbon, preferably from 2 to 8 carbon atoms, and more preferably from 2 to 4 carbon atoms, containing at least one primary hydroxyl group, and R ² is a linear or branched alkyl group containing from 1 to 10 carbon atoms, preferably from 2 to 8 carbon atoms, and more preferably 2 to 4 carbon atoms, containing at least one hydroxyl group.

It is also possible to use a mixture of these amino alcohols. Preferably, the hydroxyl group in said formula is primary, i.e. formed with the carbon atom to which it is attached, the group -CH ₂ -OH.

Amino alcohols used according to the present invention may be in liquid or solid form. One of ordinary skill in the art is well aware of techniques that can be used to incorporate liquid amino alcohols into a powder mixture. For example, prior to incorporating the liquid amino alcohols into the powder coating mixture of the present invention, the liquid amino alcohols may be absorbed onto an inert carrier such as silica.

Preferably the amino alcohols of the present invention include, without limitation, diethanolamines, ethanolamines, 2-amino-1-butanol, 2-amino-2-methyl-1-propanols, 2-amino-2-ethyl-1,3-propanediols, tris- (hydroxymethyl)-aminomethanes, 2-amino-2-methyl-1,3-propanediols, monomethylaminoethanols, isopropylaminoethanols, tert-butylaminoethanols, ethylaminoethanols, n-butylaminoethanols, isopropanolamines, diisopropanolamines and mixtures of these compounds. More preferably, the alkanolamines of the present invention are diethanolamines, tris(hydroxymethyl)aminomethanes, and mixtures of these compounds.

Preferably, the amino alcohol used in the present invention will have a molecular weight of less than 500 g/mol, such as 50 to 400 g/mol, such as 75 to 350 g/mol.

The amino alcohol may contain 1 to 3 amino groups, preferably 1 to 2 amino groups, preferably 1 amino group. Preferably, the amine functional group contains an NH bond, i. e. represents a primary or secondary amino group, in particular primary (-NH ₂ ).

The amino alcohol may contain one hydroxyl group or from 2 to 5 hydroxyl groups, such as 2 or 3 hydroxyl groups.

Ideally, the amino alcohol contains one amino group, ideally a primary amine, and 2 or more, such as 3 hydroxyl groups.

Preferred amino alcohols are tris-(hydroxymethyl)-aminomethane (THAM) and diethanolamine. Therefore, possible amino alcohols include:

ethanolamine

2-(methylamino)-ethanol

3-amino-1-propanol

amino-2-propanol

DL-Alaninol

3-amino-1,2-propanediol

serinol (C ₃ H ₉ NO ₂ )

1,3-diamino-2-propanol

1-amino-2-methyl-2-propanol

1-methoxy-2-propylamine

2-(ethylamino)-ethanol

2-amino-1-butanol

2-amino-2-methyl-1-propanol

2-amino-2-methyl-1-propanol

2-dimethylaminoethanol

3-methoxypropylamine

3-methylamine-1-propanol

4-amino-1-butanol

2-(2-aminoethoxy)-ethanol

3-methylamino-1,2-propanediol

diethanolamine

tris-(hydroxymethyl)-aminomethane

N-(2-hydroxyethyl)-ethylenediamine

meso-1,4-diamino-2,3-butanediol

trans-2-aminocyclopentanol hydrochloride

1-dimethylamino-2-propanol

2-(isopropylamino)-ethanol

2-(propylamino)-ethanol

2-amino-3-methyl-1-butanol

3-dimethylamino-1-propanol

3-ethoxypropylamine

5-amino-1-pentanol

2-amino-1-pentanol

3-(dimethylamino)-1,2-propanediol

N-methyldiethanolamine

2-(3-aminopropylamino)-ethanol

1-amino-1-cyclopentanemethanol

trans-2-aminocyclohexanol

trans-4-aminocyclohexanol

2-(butylamino)-ethanol

2-(diethylamino)-ethanol

2-(tert-butylamino)-ethanol

2-dimethylamino-2-methylpropanol

4-(dimethylamino)-1-butanol

6-amino-1-hexanol

2-amino-1-hexanol

bis-(2-hydroxypropyl)-amine

N-ethyldiethanolamine

triethanolamine

N,N'-bis-(2-hydroxyethyl)-ethylenediamine

3-diethylamino-1-propanol

3-(diethylamino)-1,2-propanediol

1,3-bis-(dimethylamino)-2-propanol

2-{[2-(dimethylamino)-ethyl]-methylamino}-ethanol

2-(diisopropylamino)-ethanol

N-butyldiethanolamine

N-tert-butyldiethanolamine; And

2-(dibutylamino)-ethanol.

The amount of amino alcohol in the composition according to the present invention may be from 0.1 to 10% by weight, such as from 0.2 to 5% by weight, preferably from 0.2 to 4% by weight, for example, from 0.2 to 3% wt.

According to another aspect of the present invention, there is provided a particulate coating composition, preferably a powder coating composition, comprising:

(i) at least one hardener;

(ii) at least one polyester polymer, and the components (i) and (ii) together comprise from 40 to 99% of the mass. from the composition of the coating;

(iii) from 0.1 to 10% of the mass. at least one amino alcohol; And

(iv) from 0.1 to 10% of the mass. at least one metallic pigment.

Also according to the present invention, a substrate is provided, on which the specified dispersed coating is applied.

Preferably, the amino alcohol is from 0.3 to 5% of the mass. from the composition of the coating, such as from 0.3 to 3% of the mass.

Silane

The powder coating composition according to the present invention may also contain at least one silane. The inventors of the present invention have found that the problem of corrosion of metal pigments can be solved by introducing a silane into the powder coating composition.

Such a silane should not be a coating on the metal particle or act as an adhesive in the metal particle. It is located separately. By "located separately" in the present description means that the silane is not applied as a coating on the metallic pigment.

The silanes used generally have a low Mw, such as less than 400 g/mol. Suitable silanes have the general formula (I) or (II)

where z is an integer from 1 to 3,

where y is an integer from 1 to 2,

R is a hydrocarbyl group containing from 1 to 12 C atoms, optionally containing an ether or amine linker,

R ¹ is a hydrocarbyl group containing 1 to 12 C atoms;

Y is a functional group associated with R, which can react with the corresponding functional groups of the curing agent; And

each X is independently a halogen group or an alkoxy group.

As functional groups Y, one can mention isocyanate, epoxy, amine, hydroxyl, carboxyl, acrylate or methacrylate groups. The Y group may be linked to any part of the R chain. It will be appreciated that if the Y group is an epoxy group, R will contain at least two carbon atoms to allow the formation of an epoxy ring system.

It is particularly preferred if Y represents an amino group or an epoxy group. Preferred amino groups are NH ₂ groups.

It is particularly preferred if X is an alkoxy group such as a C1-6 alkoxy group, in particular a methoxy or ethoxy group. It is also particularly preferred if two or three alkoxy groups are present. That is, ideally z is 2 or 3, especially 3. Index y is preferably 2.

R ¹ is preferably C _1-4 alkyl such as methyl.

R is a hydrocarbyl group containing up to 12 carbon atoms. It may contain an alkylene chain or a combination of an alkylene chain and rings such as phenyl or cyclohexyl rings. The term "optionally contains an ether or amine linker" means that the carbon chain can be interrupted by a -O- or -NH- group in the chain, for example, to form a silane such as [3-(2,3-epoxypropoxy)-propyl ]-trimethoxysilane: H ₂ COCHCH ₂ OCH ₂ CH ₂ CH ₂ Si(OCH ₃ ) ₃ . Preferably, the Y group is not linked to a carbon atom linked to a linker such as -O- or -NH-.

R may therefore be (C ₆ H ₅ )-NH-(CH ₂ ) ₃ - or Ph-NH-(CH ₂ ) ₃ - or (C ₆ H ₅ )-(CH ₂ ) ₃ and so on.

R is preferably an unsubstituted (excluding Y, of course) straight chain alkyl chain containing from 2 to 8 C atoms and optionally containing an ether or amine linker.

Therefore, preferably the silane has the general formula corresponding to the structure (III)

where z' is an integer from 2 to 3, R' is an unsubstituted straight chain alkyl chain containing 2 to 8 C atoms and optionally containing an ether or amine linker, Y' is an amine or epoxy functional group linked with a group R', and X' represents an alkoxy group.

Examples of such silanes are the many products available from Degussa in Rheinfelden and sold under the brand name Dynasylan(R)D, the Silquest(R) silanes from OSi Specialties, and the GENOSIL(R) silanes from Wacker.

Specific examples include methacryloxypropyltrimethoxysilane (Dynasylan MEMO, Silquest A-174NT), 3-mercaptopropyltri(methoxy)ethoxysilane (Dynasylan MTMO or 3201; Silquest A-189), 3-glycidoxypropyltrimethoxysilane (Dynasylan GLYMO, Silquest A-187), tris-(3- trimethoxysilylpropyl)-isocyanurate (Silquest Y-11597), gamma-mercaptopropyltrimethoxysilane (Silquest A-189), beta-(3,4-epoxycyclohexyl)-ethyltrimethoxysilane (Silquest A-186), gamma-isocyanatopropyltrimethoxysilane (Silquest A-Link 35, Genosil GF40), (methacryloxymethyl)-trimethoxysilane (Genosil XL 33), (isocyanatomethyl)-trimethoxysilane (Genosil XL 43), aminopropyltrimethoxysilane (Dynasylan AMMO; Silquest A-1110), aminopropyltriethoxysilane (Dynasylan AMEO) or N-(2-aminoethyl)- 3-aminopropyltrimethoxysilane (Dynasylan DAMO, Silquest A-1120), or N-(2-aminoethyl)-3-aminopropyltriethoxysilane, triamino-functional trimethoxysilane (Silquest A-1130), bis-(gamma-trimethoxysilylpropyl)-amine (Silquest A-1170) , N-ethyl-gamma-aminoisobutyltrimethox ysilane (Silquest A-Link 15), N-phenyl-gamma-aminopropyltrimethoxysilane (Silquest Y-9669), 4-amino-3,3-dimethylbutyltrimethoxysilane (Silquest Y-11637), (N-cyclohexylaminomethyl)-triethoxysilane (Genosil XL 926 ), (N-phenylaminomethyl)-trimethoxysilane (Genosil XL 973), Deolink Epoxy TE and Deolink Amino TE (D.O.G Deutsche Oelfabrik), and mixtures of these compounds.

Other specific examples of silanes of interest include

3-aminopropyltriethoxysilane,

3-aminopropyltrimethoxysilane,

N-(aminoethyl)-aminopropyltrimethoxysilane H ₂ NCH ₂ CH ₂ NHCH ₂ CH ₂ CH ₂ Si(OCH ₃ ) ₃ ,

3-aminopropylmethyldiethoxysilane,

3-(2-aminoethylamino)-propylmethyldimethoxysilane

(H ₂ NCH ₂ CH ₂ NHCH ₂ CH ₂ CH ₂ SiCH ₃ (OCH ₃ ) ₂ ),

[3-(2,3-epoxypropoxy)-propyl]-triethoxysilane

(H ₂ COCHCH ₂ OCH ₂ CH ₂ CH ₂ Si (OCH ₂ CH ₃ ) ₃ ,

[3-(2,3-epoxypropoxy)-propyl]-trimethoxysilane (H ₂ COCHCH ₂ OCH ₂ CH ₂ CH ₂ Si(OCH ₃ ) ₃ ).

Especially preferred is the use of silanes ([3-(2,3-epoxypropoxy)-propyl]-triethoxysilane or 3-aminopropyltriethoxysilane. A mixture of silanes can also be used.

separately from said metallic pigment.

The amount of silane contained in the powder coating may generally be from 0.1 to 10% by mass, preferably from 0.2 to 6% by mass, more preferably from 0.4 to 3% by mass. from the total mass, ideally, from 0.6 to 3% of the mass.

The silane may be applied to the carrier or may be applied in its original form (or as part of a solution). The use of carriers simplifies the introduction of the silane because the silane can be introduced as a solid rather than as a liquid. So, you can use silane materials in which 50% of the mass. is the carrier material and 50% of the mass. makes up silane. It is understood that the amount of silane given above for the powder coating as a whole refers to the "pure" silane and does not take into account the weight of the support material. When using a carrier, the person skilled in the art must take the weight of the carrier into account accordingly.

According to another aspect of the present invention, there is provided a particulate coating composition, preferably a powder coating composition, comprising:

(i) at least one curing agent, such as at least one compound containing an epoxy group,

(ii) at least one polyester polymer,

(iii) no at least one amino alcohol;

(iv) at least one metallic pigment; And

(v) at least one silane.

Also according to the present invention, a substrate is provided, on which the specified dispersed coating is applied.

Production

Preferably the polyester polymer, hardener and amino alcohol are premixed and extruded. The extrusion conditions are known and in general the extrusion will be carried out at a low temperature to avoid premature curing.

The ingredients can be mixed and extruded to form particles, as is known in the art, and the resulting particles can then be milled to form a powder. Metallic pigments can be added after extrusion or, using the above Powdersafe technology, they can also be added before extrusion. Metallic pigments and particulate coatings can be bonded together in a manner in which the pigment and the particulate coating are mixed and heated to the glass transition temperature of the particulate coating. Thus, the adhesion of metal pigments to the surface of the particles of the dispersed coating is ensured.

Pigments can be added before or after grinding, preferably after. After milling, screening can be applied to maximize the uniformity of the particle size distribution.

To ensure uniformity before extrusion, the components of the mixture should be well mixed. Preferably, the temperature of the extrudate does not exceed 140°C to prevent premature curing.

The extruded granulates can be milled with all types of conventional mills and the resulting particles classified by a chosen method to isolate the particle size most suitable for use as a powder. The particle size distribution d50 for the powder coating composition may be from 10 to 120 µm, with the preferred particle size d50 in the range from 15 to 75 µm, preferably at least 20 or 25 µm, preferably not more than 50 µm, more specifically from 20 up to 45 microns. In general, particle size can be determined using a Malvern particle size analyzer.

Additives

It should also be appreciated that the particulate coatings of the present invention may contain a wide range of industry standard additives. Additives used include gloss modifiers, scratch-resisting agents, pigments (non-corrosive metallic and non-metallic pigments), fillers, degassing agents, flow agents, waxes, antioxidants, optical brighteners, and surface modification agents. These additives together can be up to about 60% of the mass. powder coating, for example, up to 40% wt., ideally, up to 20% wt., such as up to 10% wt. relative to the weight of the coating. Additives can be 2% of the mass. or less by weight of the dispersed coating, in particular if there is also a primer layer.

Fillers include micronized minerals. Pigments of interest include organic pigments and inorganic pigments such as carbon black.

In particular, pigments and fillers can be up to 50% of the mass. relative to the weight of the coating, such as up to 40% of the mass. of the total mass, preferably 2.0-20% of the mass. These numbers include the metallic pigment discussed in detail above.

Other additives can be from 0.1 to 15% of the mass. relative to the total weight of the powder coating, such as from 0.5 to 15 wt. -%, preferably from 0.7 to 10 wt. -%, in particular, from 1 to 8 wt.%. It should be taken into account that the powder coating according to the present invention must be dry and free from water and other volatile organic solvents.

Stabilizing additive

The inventors of the present invention have also found that the incorporation of certain stabilizing additives into the particulate coating according to the present invention leads to a significant improvement in properties, such as a synergistic improvement. In particular, the presence of a stabilizing additive makes it possible to maintain gloss for a much longer period of time and improves acid resistance (ΔL) and moisture resistance (ΔE).

The stabilizing additive may contain at least one silicate material selected from the group consisting of: (a) materials obtained by mixing or preferably reacting silica or silicate with a trivalent metal compound; and (b) natural or synthetic metal silicates,

Preferably, the stabilizing additive also includes an oxide selected from zinc oxide, magnesium oxide or silica, preferably zinc oxide, which can be included in an amount of from 2 to 30% by weight of the total weight of the stabilizing additive, preferably at least 5%, 10% or 15% by weight, more specifically not exceeding 20% or 25% by weight.

The preferred trivalent metal in embodiment (a) is chromium, iron or aluminum, in particular aluminum. In embodiment (b), a trivalent metal silicate is advantageously used.

The trivalent metal compound may, for example, be a phosphate (preferably mono- or dihydrogen phosphate), fluoride, fluorosilicate, chloride, sulfate or alkanecarboxylate. Aluminum phosphates or sulfates are preferred.

The silicon dioxide in embodiment (a) is predominantly amorphous silicon dioxide or a precursor thereof.

Examples of natural metal silicates for use in embodiment (b) are china clay and bentonite.

As an indication of the relative proportions of silicon dioxide and trivalent metal compound in embodiment (a), the ratio of silicon to trivalent metal atom may be, for example, from 1.5 to 30:1, preferably at least 1.5:1, 2 .5:1 or 3.5:1, preferably not more than 20:1, 15:1 or 10:1. In general, the same silicon:metal atom ratios also apply to embodiment (b), in particular if the metal silicate is a trivalent metal silicate.

Other classes of materials that can be used as a stabilizing additive include those based on or containing phosphates or borates, generally a metal phosphate or borate. The phosphate is preferably an orthophosphate, but may also be an acid phosphate or a polyphosphate.

Thus, for example, another stabilizing additive that can be used contains dicalcium phosphate dihydrate, such as the material "Budit 222" supplied by Budenheim Chemische Fabrik. Also worth mentioning is dimagnesium phosphate trihydrate, such as the materials "Budit 229" and "Budit 246" (Budenheim Chemische Fabrik).

The stabilizing agent may be, for example, zinc phosphate: (a) zinc phosphate di- or tetrahydrate; (b) spheroidal zinc phosphate as a crystalline phase mixed with an amorphous phase containing Fe(II) phosphate and Fe(III) phosphate; (c) zinc molybdate modified zinc phosphate rendered organophilic by surface treatment.

Other materials considered as stabilizing additives include: (i) alkaline earth metal hydrogen phosphates together with alkaline earth metal carbonates, optionally also including one or more additives selected from fluorosilicates, fluorobrates, alkali and alkaline earth metal fluorides;

(ii) mixtures of magnesium hydrogen phosphate and calcium hydrogen phosphate;

(iii) polyphosphates and acidic polyphosphates, including ammonium polyphosphates; modified hydrates of strontium-aluminum polyphosphates; hydrates of zinc-aluminum polyphosphates; modified zinc-calcium-aluminum phosphate-silicate hydrates; and modified hydrates of calcium silicate polyphosphates;

(iv) orthophosphate hydrates, including modified zinc-calcium-strontium orthophosphate silicate hydrates; modified zinc-aluminum orthophosphate hydrates; organically processed hydrates of basic zinc orthophosphates; modified hydrates of basic zinc-molybdenum orthophosphates or hydrates of basic zinc-silicate phosphates, respectively;

(v) phosphosilicates such as, for example, potassium-strontium-zinc phosphosilicate, calcium phosphosilicate and zinc-aluminum phosphosilicate;

(vi) organophosphonates, including metal organophosphonates, such as, for example, salts of a multivalent metal cation and an organic phosphonic acid containing at least two phosphonic acid groups, for example, calcium etidronate (1-hydroxyethane-1,1-diphosphonic acid monocalcium salt dihydrate ). Further information regarding these materials can be found in GB 2121419 A.

(vii) barium metaborate monohydrate;

(viii) zinc salts of organic nitro compounds;

(ix) zinc oxide/cinnamic acid combinations; And

(x) molybdates, including basic molybdates such as, for example, zinc molybdates) and calcium-zinc molybdate complexes containing a calcium-zinc molybdate complex compound on a calcium carbonate core.

In a particularly preferred embodiment, the stabilizing additive is a metal phosphate such as a transition metal, alkali metal or alkaline earth metal phosphate, in particular an alkaline earth metal phosphate such as dicalcium phosphate dihydrate. The amount of stabilizing additive can be from 0.25 to 3.0 wt. -%, such as from 0.25 to 2.0 wt. The authors of the present invention have found that the combination of a stabilizing additive and an amino alcohol can lead to a synergistic improvement in properties. In particular, the combination of dicalcium phosphate dihydrate and THAM leads to synergy.

The present inventors have shown that the combination of small amounts of THAM, such as 0.25 to 1.5 wt%, with small amounts of dicalcium phosphate dihydrate, such as 0.25 to 1.5 wt%, results in synergy.

According to another aspect of the present invention, there is provided a particulate coating composition, preferably a powder coating composition, comprising:

(i) at least one curing agent, such as at least one compound containing an epoxy group,

(ii) at least one polyester polymer,

(iii) at least one amino alcohol;

(iv) at least one metallic pigment; And

(v) at least one stabilizing additive, such as a metal phosphate additive, in particular dicalcium phosphate dihydrate.

The stabilizing additives used in accordance with the present invention may be incorporated by intimate mixing with the other constituent(s) of the composition, prior to extrusion or other homogenization process, and/or may be introduced during said process.

Alternatively, the additive(s) of the present invention may be incorporated into the coating composition by any available method after mixing as described above in connection with the incorporation of metallic pigment(s).

Application to substrates

The dispersion coating of the present invention can be applied to a substrate using any conventional powder coating method such as spraying, eg electrostatically. Triboelectric atomizers can also be used. Coating techniques are well known in the art and will be readily understood by one of skill in the art. The coating composition can be applied as a single coat or applied over a primer layer to form a top coat. In any embodiment, it is preferred that the coating according to the present invention form a top coat applicable to any substrate. Thus, the coating according to the present invention may function simultaneously as a primer and a topcoat, or may be applied over a conventional primer.

substrate

The substrate to which the dispersion coatings of the present invention are applied can be any substrate such as metal substrate (steel, galvanized steel, aluminium), wood, MDF, HDF, plywood, fibreboard, particle board, plastic, glass, ceramics, graphite-filled composite materials and so on. Substrates for indoor or outdoor use are included.

Coated products include household appliances, building components, furniture, vehicles, supplies and implements, and so on.

The object to be coated may be coated with a primer layer, although this is not essential. Zinc, a zinc-free powder, or a corrosion-inhibiting liquid primer can be used in the primer layer. Typical epoxy and epoxy/polyester primers contain 0-85% wt. zinc.

Powder coatings according to the present invention form a top coat on any substrate. That is, no additional coating layer is required to be applied over it. Therefore, the substrates may comprise a primer layer and a topcoat layer containing the powder composition of the present invention, or simply comprise a topcoat of the present invention, without a base coat of primer.

Curing

After powder coating is applied to the substrate, the coating must be cured. The coated substrate can be cured in a traditional convection oven or in a combined IR/convection oven. You can also use induction heating. The use of a convection/induction oven or even a convection/induction/IR oven is also contemplated. Thermal curing is preferred.

If heat is applied during curing, the temperature should preferably be in the range of 100 to 250°C, for example 150 to 200°C.

The powder coating of the present invention can be cured using short curing cycles, such as 15 minutes or less.

The powder coating is preferably free-flowing during the curing operation, resulting in smooth, even finishes.

The film thickness of the cured coating is preferably 20 to 200 microns, such as 30 to 120 microns, in particular 40 to 100 microns.

It is a feature of the present invention that the powder coating of the present invention does not corrode. The lack of corrosion also shows up in good color retention and little change in gloss. Therefore, the coating is preferably resistant to acids, bases and water.

It should be noted that the coating must also provide an acceptable metallic effect. The main purpose of the coatings according to the present invention is to provide a metallic paint effect on the coated substrate. The coatings according to the present invention also provide a good metallic effect while reducing corrosion. Ideally, coatings have a "fresh paint" effect. A fresh paint effect is achieved with a minimum difference between the two gloss measurements at 20° and 60°. Preferably, the value of the gloss difference measured at these angles is 50 or less.

Below, the present invention will be described with reference to the following non-limiting examples.

Analysis Methods

Film thickness: Measured according to ISO 2178.

Gloss: Measured according to ISO 2813 at measurement angles of 60° or 20°.

EEM: Measured according to ASTM D-1652

Acid number (AN): Measured according to ASTM D974

Color changes, ΔL and ΔE, were measured on a Largo Coloreye 3000 instrument.

Examples - common protocols

Getting the powder:

The ingredients (except the metallic pigment) were dry mixed in a high speed mixer to ensure sufficient dispersion of the powder premix. The preblend was then placed into a Theyson TSK 20-24 twin screw extruder and extruded under the following conditions: 30 degrees feed, 50 degrees melt, 100 degrees mix and disperse, 100 degrees head, 500 rpm, torque moment 60-65.

The extruded material was fed onto cooled rollers and passed through a crusher, crushing the cooled material into flakes. Then the crushed flakes were fed into the mill. The extruded pieces were milled and sieved through a 125 µm rotary sieve to obtain a particle size distribution (PSD) (d ₅₀ ) of 25-50 µm (determined on a Malvern particle size analyzer).

The resulting powder was then carefully mixed with the metallic pigment.

Applying the powder to the substrate

The powder was applied to cold rolled phosphated stainless steel panels using a standard corona spray gun.

Film curing

The powder coated substrates were cured by conventional heat transfer by convection using a conventional Heraeus tabletop oven.

Curing was carried out at a target temperature of 180°C. The curing time at the target temperature was 10 minutes.

Examples:

Examples according to the present invention were prepared based on the powder coating composition described in Table 1. 1.5% of the mass. standard aluminum powder Special PCR 901 was injected after the extruder. All other components were premixed and extruded.

Typical film thickness 50-100 µm

Table 1 lists the components for each of the examples:

Test results

Fingerprint resistance

A person's fingers were pressed against the coated surface to leave a fingerprint on the surface. Coatings containing amino alcohol were less susceptible to discoloration from fingerprints when handled or touched, and were easier to remove with paper tissue. The following scale was used to evaluate the performance related to fingerprint resistance.

F1 = strong fingerprints that are difficult to remove

F2 = Pronounced fingerprints that are difficult to remove

F3 = obvious fingerprints that are fairly easy to remove

F4 = low-visibility fingerprints that are easy to remove

F5 = no visible fingerprints

Coatings were also evaluated for appearance. The smallest difference between gloss measured at 20° and gloss measured at 60° was defined as "freshly colored appearance". A difference of 50 or less was taken as a sign of "freshly colored appearance".

Appearance A: Cloudy, metallic pigment agglomeration

Appearance B: Freshly colored appearance, no metallic pigment agglomeration

Acid resistance

The panels were covered on both sides. Half of the panel was immersed in a 5% HCl solution for a given time. The difference in darkness, ΔL, before and after the test described the corrosion of the panels. Panels with high corrosion resistance had a low absolute value of ΔL, while panels highly susceptible to corrosion had high absolute values of ΔL.

The coatings containing the amino alcohol showed little change in darkness. For TNAM, the characteristics increased with an increase in the content of TNAM.

Alkali resistance

1 cm ² of Whatman 597 filter paper was immersed in 1% NaOH solution and immediately placed on the coated panels. The time to visible darkening was recorded.

Coatings containing amino alcohol take longer to develop corrosion from NaOH solution. This characteristic also increased with an increase in the amount of the additive.

Moisture resistance

Carried out a corrosion test/humidity test according to ISO 6270-2. The coatings were exposed to a constant humidity (CH) condensing atmosphere. The temperature was 40±3°C, the relative humidity was about 100% with condensation on the test specimens. The gloss and color were measured before and after the test.

The color difference, ΔE, described the corrosion of the panels. Panels with high corrosion performance had a low ΔE value, and panels highly susceptible to corrosion had high ΔE values. This characteristic also increased with an increase in the amount of the additive.

* complete destruction

Adhesion

A multi-blade cutting device with 6 cutting blades, according to ISO 2409, was used to obtain cross-cuts on the coating, with a cutting speed of 2-5 cm/sec. Then, a 5 mm Eriksen test was performed in the center of the notches and adhesive tape (3M No#250) was pressed against the lattice structure. Then the tape was removed and the classification was performed from Gt0 to Gt5. Gt0 indicates that no part of the coverage has been removed, while Gt5 describes that the coverage has been completely removed. Coatings according to the present invention had better adhesion to the surface.

The introduction of a stabilizing additive and amino alcohol.

Other examples according to the present invention were obtained based on the composition of the powder coating described in Table 7. 1.5% of the mass. standard aluminum powder Special PCR 901 was injected after the extruder. All other components were premixed and extruded.

Table 7 lists the components for each of the examples:

Tris-(hydroxymethyl)-aminomethane (THAM) and/or calcium hydrogen phosphate dihydrate CaHPO ₄ were added to the components from the above Comparative Example 1. Added quantities are shown in Table 8 below, in % wt. relative to the above composition of equation 1. Coatings were applied to the panels and cured as described above. The coating thickness ranged from 50 to 100 microns.

The resulting coatings were tested for moisture resistance, alkali resistance and fingerprint resistance by the methods described above.

Discussion

It is clearly seen that the combination of THAM and CaHPO ₄ gives an improvement in moisture (corrosion), alkali resistance and fingerprint resistance tests.

Claims (28)

1. A particulate coating composition, preferably a powder coating composition, comprising: (i) at least one hardener such as at least one compound containing an epoxy group, (ii) at least one polyester polymer, (iii) at least one amino alcohol having a molecular weight of 50 to 400 g/mol and containing 1 to 3 amino groups and 1 to 5 hydroxyl groups; And (iv) at least one metallic pigment containing Al. 2. Coating composition according to claim 1, characterized in that said metallic pigment is uncoated or coated with silicon dioxide. 3. The composition of the coating according to any one of paragraphs. 1, 2, characterized in that these components (i) and (ii) together constitute from 40 to 99% of the mass. from the total weight of the coating composition. 4. The composition of the coating according to any one of paragraphs. 1-3, characterized in that the specified metallic pigment is from 0.1 to 10% wt., preferably from 0.2 to 4% of the mass. from the total weight of the coating composition. 5. Coating composition according to any one of paragraphs. 1-4, characterized in that the specified amino alcohol is from 0.1 to 10 wt. -%, preferably from 0.3 to 5% of the mass. from the total weight of the coating composition. 6. Coating composition according to any one of paragraphs. 1-5, characterized in that said at least one amino alcohol has the formula: NH ₂ R ¹ , where R ¹ represents a linear or branched alkyl group containing from 1 to 10 carbon atoms, preferably from 2 to 8 carbon atoms and more preferably from 2 to 4 carbon atoms, which contains at least one hydroxyl group; or NHR ¹ R ² , where R ¹ is a linear or branched alkyl group containing 1 to 10 carbon atoms, preferably 2 to 8 carbon atoms, and more preferably 2 to 4 carbon atoms, or a linear or branched alkyl group containing 1 to 10 carbon atoms carbon, preferably from 2 to 8 carbon atoms, and more preferably from 2 to 4 carbon atoms, containing at least one primary hydroxyl group, and R ² is a linear or branched alkyl group containing from 1 to 10 carbon atoms, preferably from 2 to 8 carbon atoms, and more preferably 2 to 4 carbon atoms, containing at least one hydroxyl group; or mixtures thereof. 7. Coating composition according to claim 6, characterized in that said at least one amino alcohol is selected from diethanolamine, ethanolamine, 2-amino-1-butanol, 2-amino-2-methyl-1-propanol, 2-amino-2 -ethyl-1,3-propanediol, tris-(hydroxymethyl)-aminomethane, 2-amino-2-methyl-1,3-propanediol, monomethylaminoethanol, isopropylaminoethanol, tert-butylaminoethanol, ethylaminoethanol, n-butylaminoethanol, isopropanolamine, diisopropanolamine and their mixtures. 8. Coating composition according to any one of paragraphs. 1-7, characterized in that said amino alcohol is tris-(hydroxymethyl)-aminomethane (THAM) or diethanolamine. 9. Coating composition according to any one of paragraphs. 1-8, characterized in that said hardener is an epoxy resin. 10. Coating composition according to any one of paragraphs. 1-9, additionally containing at least one silane. 11. The composition of the coating according to any one of paragraphs. 1-10, additionally containing a stabilizing additive, preferably a metal phosphate. 12. The composition of the coating according to any one of paragraphs. 1-11, additionally containing CaHPO ₄ . 13. Substrate coated with a particulate coating composition according to any one of paragraphs. 1-12, wherein preferably said particulate coating composition forms a top layer on the substrate. 14. Substrate coated with a particulate coating composition according to any one of paragraphs. 1-12, wherein said particulate coating composition is cured, or a substrate coated with a primer layer and, on top of it, a particulate coating composition layer according to any one of paragraphs. 1-12, wherein said particulate coating composition is cured. 15. The method of obtaining the composition of the dispersed coating according to any one of paragraphs. 1-12, preferably powder coating compositions comprising mixing at least one curing agent, such as at least one compound containing an epoxy group, at least one polyester polymer and at least one amino alcohol to obtain a mixture; extruding the resulting mixture to obtain particles; adding at least one metallic pigment to obtain a dispersed powder coating. 16. The method of applying to the substrate a dispersed coating according to any one of paragraphs. 1-12, for example, using electrostatic spraying, which includes applying the specified dispersion coating on the specified substrate, for example, using electrostatic spraying, and optionally curing the resulting coating. 17. Use of an amino alcohol having a molecular weight of 50 to 400 g/mol and containing 1 to 3 amino groups and 1 to 5 hydroxyl groups to prevent corrosion of a metallic pigment contained in a powder coating composition containing at least one hardener , such as at least one compound containing an epoxy group, at least one polyester polymer and at least one metallic pigment containing Al.