LU85538A1 - PAINT COMPOSITIONS FOR METAL COATINGS - Google Patents

Description

PAINT COMPOSITIONS FOR METAL COATINGS.

The present invention relates to paint compositions for metallic coatings, and in particular to paint compositions having improved resistance to metallic marking.

The problem of metallic marking is a frequent and well-known phenomenon which occurs on the majority of metallic coatings.

Metallic marking is caused by the friction of a metallic object on the surface of the coating.

The colored trace which appears on the surface of the coating results from the transfer towards this surface of small quantities of metal or metal oxide because of the abrasion of the metal by the roughness present on the surface of the coating.

This phenomenon is easily highlighted for example by rubbing a coin or a ring on the metallic coating.

„This phenomenon is even more accentuated when using paints with a relatively low gloss.

Although this phenomenon is most often encountered on coated metal surfaces, it is well known that it also occurs when other types of substrates are used, such as for example glass, plastic.

It is also well known that the most important factor to consider is the state of dispersion of the pigment on the surface of the coating.

Thus, in order to remedy this drawback, it has already been proposed to incorporate into the coating a load of soft material, in the form of particles whose average dimensions are greater than those of the pigments used, so as to minimize the contact between metal and abrasive pigment. However, this type of additive tends to reduce the mechanical properties of the paint, and to limit the cooking techniques that can be used.

It has also been proposed to use a pigment / resin system such that the upper layer of the coating is free of pigment, or, which is equivalent, to apply the coating in two layers, the outer layer being free of pigment. However, this technique not only usually requires a double application, which results in loss of time, but moreover, this technique inevitably leads to obtaining glossy paints, which is not always desired.

It has also been proposed to use additives which are most often silicone-based, and which cause the appearance of a thin layer of lubricating material on the surface of the coating; The disadvantage of this type of product is that it considerably reduces the possibilities of printing or applying other coats of paint on this surface. In addition, it is well known that contamination of baking ovens with these silicone additives is extremely troublesome.

It would therefore be desirable to have paint compositions for metallic coatings which offer a markedly improved resistance to metallic marking, while having none of the drawbacks mentioned above.

The present invention relates to a composition of paints for metallic coatings, having improved resistance to metallic marking, and low gloss.

The present invention also relates to "", - 3 - paint compositions for metallic coatings having improved resistance to metallic marking while retaining its mechanical properties.

The subject of the present invention is also compositions of paints for metallic coatings having improved resistance to metallic marking, which can undergo heat treatment without having any drawbacks.

The paint composition of the present invention for metallic coatings, having improved resistance to metallic marking, comprising a polyester resin, a hardening agent, a diluent, pigments and additives, is characterized in that it additionally comprises a compound amine chosen from diamines, polyamines and those of general formula X - (CH,) - N ^ zn ^ E2 in which R ^ and R2 are identical or different radicals which can be hydrogen, alkyl radicals, substituted alkyls , - (Ct ^) - OH, aryls, substituted aryls, and where X is OH or the phenyl radical, and where n can take the values from 1 to 20.

The Applicant has now unexpectedly found that by adding an amino compound chosen from diamines, polyamines and those of general formula R.

X - (CH0) - N ^ Z Ώ \ R2 in which and R2 are identical or different radicals which can be hydrogen, alkyl radicals, substituted alkyls, - (CH2) - OH, aryls, substituted aryls, and where X is OH or the phenyl radical, and where n can take the values from 1 to 20, with a paint comprising a polyester resin, a hardener, pigments and possibly additives, the resistance to metallic marking of the coating obtained was considerably improved. from this painting.

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Among the amino compounds of the above general formula which can be used in the compositions of the invention, mention may in particular be made of alkanolamines such as, for example, monoethanolamine, dimethylethanolamine, diethylethanolamine, ethylethanolamine, diisopropyl- ethanolamine, butyldiethanolamine, methylethanolamine, methyldiethanolamine, ethyldiethanolamine, isopropylethanolamine, n-butylethanolamine, dimethylisopropanolamine, cyclohexyldiethanolamine, phenylethanolamine, N-cyanoethyl-N-hydroxyanoil tolyldiéthanola-mine, 1 'o-methoxyphenyldiéthanolamine.

In the case where X is the phenyl radical, it is preferred to use benzylamine.

As examples of diamines which can be used in the compositions of the invention, mention may be made of neopentane diamine, isophorone diamine.

As examples of polyamines, diethylenetriamine, triethylenetetramine, tetraethylene pentamine and the like are advantageously used.

Generally, the amino compounds of the invention are used in an amount of from about 0.1 to about 3% by weight relative to the paint composition.

It is not advisable to use quantities lower than 0.1% by weight because the improvement in resistance to metallic marking decreases considerably.

On the other hand, the use of high percentages of these amino compounds does not significantly increase the resistance to metal marking. In addition, under these conditions, yellowing of the paint may appear, which constitutes one of the possible drawbacks which must be taken into account.

Preferably, the amino compounds are used in an amount of 0.3 to 1% by weight based on the paint composition.

It is understood that the amounts of amino compounds to be used depend on the compounds used. The amounts are generally easily determined by those skilled in the art.

It is also preferred to use amino compounds which are liquid at the temperature of use in order to facilitate the use of the composition.

The polyester used in the composition of the present invention is a saturated polyester having hydroxyl groups. Generally, the hydroxyl number of the polyesters used is between 15 and 200, and generally between 30 and 100.

Among the polyesters which can be used in the composition of the invention, mention may in particular be made of the condensation products of saturated diols and / or higher polyols with aromatic and / or cycloaliphatic dicarboxylic acids free of ethylenic unsaturation, and acids saturated aliphatic dicarboxyls.

Examples of diols which can be used to prepare the polyester include ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,2-butane diol, 1,3-butanediol, 1,4-butanediol, 2,2-dimethylpropane 1,3-diol, 1,6-hexanediol, 2-ethylhexane-1,3-diol, 1,2- cyclohexanediol, 1,4-cyclohexanediol, 1,2-bis (hydroxymethyl) -cyclohexane, 1,3-bis (hydroxymethyl) -cyclohexane, 1,4-bis (hydroxymethyl) -cyclohexane, x, 8 -bis (hydroxymethyl) -tricyclo [5.2.1.0] decanes where the values 3, 4 or 5 are assigned to x, diethylene glycol, triethylene glycol, triethylene glycol, dipropylene glycol and tripropylene glycol. The cycloaliphatic diols can be used in their cis or trans form or in the form of a mixture of the two isomers.

As examples of aromatic or cycloaliphatic dicarboxylic acids include phthalic, isophthalic, terephthalic, hexahydroterephthalic, tetrahydrophthalic, hexahydrophthalic, hexahydroisophta-lic, or endomethylene tetrahydrophthalic endoéthylène, hexachloro-endomethylene-tetrahydrophthalic anhydride or tetrabromo phthalic ft.

Cycloaliphatic dicarboxylic acids can be used in their cis or trans form or in the form of a mixture of the 2 isomers.

As examples of saturated aliphatic dicarboxylic acids, mention may be made of succinic, glutaric, adipic, suberic, sebacic, decanedicarboxylic, 2,2,4-tri-methyladipic acids. One can also use unsaturated dicarboxylic acids but in small amounts, such as for example the acids chosen from the group comprising maleic acid, fumaric acid, itaconic or citraconi-que.

In addition to the free dicarboxylic acids, it is also possible to use their lower alcohol esters such as, for example, dimethyl, diethyl or dipropyl esters. If the dicarboxylic acids form anhydrides, these can also be used, such as for example phthalic, hexahydrophthalic, tetrahydrophthalic, succinic, glutaric and maleic anhydrides.

The polyesters obtained from the compounds mentioned above, and used subsequently in the compositions of the invention generally have a molecular weight of between 240 and 4000.

Other types of polyesters can also be used in the compositions of the invention, in particular those constituted by hydroxylated alkyd resins.

As examples of alkyd resins, mention may be made of the reaction products of diols and / or polyols with aromatic, cycloaliphatic or aliphatic dicarboxylic acids, as well as with fatty acids.

The fatty acids which can be used are chosen from the group comprising caproic, caprylic, pelangonic, lauric, myristic, palmitic, arachidic, behenic, oleic, linoleic, linolenic acids, and their mixtures in the form of acids obtained from oils. natural oils such as flaxseed, castor oil, soybean, peanut or coconut oil.

Unsaturated carboxylic acids can also be used, but in small amounts. Synthetic fatty acids can also be used, such as for example 2-ethylhexylic, o (-alkylcarboxylic, isononic acids or mixtures of synthetic fatty acids having from 7 to 9 carbon atoms. Esters and natural oils of acids Free can also be used in the preparation of alkyd resins.

It is also possible to use, as polyesters, the products mentioned above and which contain a certain percentage of silicone fragments and which can be obtained according to techniques well known to those skilled in the art.

In addition to polyester, the composition contains an organic diluent with a boiling point of between 100 and 310 ° C. As examples of diluents, mention may be made of the aromatic hydrocarbons sold under the name of Solvesso 100, 150 or 200, or also the glycol ethers and their acetates, isophorone or their mixtures.

The hardener used in the composition of the present invention is a polyester crosslinking agent used. As examples of suitable crosslinking agents, mention may be made of amino resins containing etherified N-methylol or N-methylol groups, such as those which can generally be obtained by reaction between an aldehyde, for example formaldehyde, with compounds containing amino or acid groups such as melamine, urea, N, N'-ethylene-urea, dicyandiamide or benzo-guanamine, and mixtures thereof. The preparation of such compounds is notably described in Houben-Weyl, Methoden der organischen Chemie, Vol. 14/2 pp. 319-371 (1963)

It is preferable that the compounds mentioned above are partially or completely etherified with alcohols containing from 1 to 6 carbon atoms, such as for example methanol, ethanol, n-propanol, isopropanol, n- butanol, isobutanol, amyl alcohol, hexanol or mixtures of these alcohols.

As particularly suitable examples, mention may be made of melamine methylol comprising from 4 to 6 methylol groups per molecule of melamine and of which at least 3 methylol groups are etherified with methanol, ethanol, propanol or butanol, or condensation products of Ν, Ν'-ethylene diurea with formaldehyde, etherified with butanol.

However, it is preferred to use a hexa-alkoxymethyl melamine, the alkoxy groups of which contain from 1 to 4 carbon atoms.

It is also possible to use other crosslinking agents, alone or in admixture with the compounds defined above. It is thus possible to use the blocked or non-blocked isocyanurate compounds, or the aliphatic, cycloaliphatic or aromatic di-, tri- or polyisocyanates, blocked or unblocked.

Examples of suitable isocyanates that may be mentioned are hexamethylene diisocyanate, 2,2,4-trimethyl 1,6-hexane diisocyanate, isophorone diisocyanate, the addition product of a 1,4-butane molecule diol and two molecules of isophorone diisocyanate, the addition product of one molecule of 1,4-butane diol and two molecules of hexamethylene diisocyanate, dicyclohexyl methane-4,4'-diisocyanate, xylylene diisocyanate, 1 , 3,5-trimethyl (2,4-ü-diisocyanato-methyl benzene, toluene diisocyanate, diphenyl methane-4,4'-diisocyanate, the adduct of 3 molecules of hexamethylene diisocyanate and 1 molecule of water , the adduct of one molecule of trimethylolpropane and three molecules of isophorone diisocyanate or toluene diisocyanate, and the adduct of one molecule of pentaerythritol and four molecules of hexamethylene diisocyanate.To block the isocyanate compound or isocyanurate, any suitable blocking agent can be used.

To produce the final coating on the metal substrate, the hydroxylated polyester and the hardener are subjected to a heat treatment which most often requires the presence of a catalyst suitable for the polyester-hardener combination used.

The paint compositions of the invention also contain pigments such as those generally used in the paint industry; most often, metal oxides such as TiC> 2 and the like are used.

The paint compositions of the invention may also contain other additives such as spreading agents, matting agents and the like well known to those skilled in the art.

To produce the composition of the invention, a polyester and a hardener are mixed in proportions such that the polyester / hardener ratio is between 50/50 and 95/5.

The pigments, generally T1O2, and the usual additives are dispersed in this mixture. The pigment / polyester + hardener weight ratio is between 0.1 and 2.

The composition also contains an organic solvent or a mixture of solvents of the hydroxylated polyester, having a boiling point of between 100 and 310 ° C. The amount of solvent used is generally between 20 and 70% by weight based on the paint composition.

The amino compound of the invention is added to this mixture in the proportions of 0.1 to 3% by weight on the paint.

This paint is applied by methods known to those skilled in the art, in particular by means of brushes, rollers, a spray gun or even a soaking bath on metallic substrates, pretreated or not, such as iron, steel, aluminum, tinned iron and the like.

Then, the metal substrate thus coated is subjected to a heat treatment according to known techniques.

The gloss of the coatings thus obtained is measured at 60 ° according to the Gardner method.

By low gloss coatings, we must understand those characterized by a value less than 50% according to the Gardner scale.

The following examples are given in order to better illustrate the compositions of the invention, but without limiting the scope thereof.

Example 1 a) Hydroxylated Polyester

Commercial polyester DYNAPOL LH 818 (Dynamit Nobel) was used; it is a saturated polyester resin (in 50% solution in a mixture of aromatics) characterized by a hydroxyl number less than 20, an acid number less than 3, a density at 20 ° C equal to 3 1.053 g / cm, a flash point of 67 ° C, a viscosity at 20 ° C between 4000 and 5000 mPa.s, and a color index according to Gardner (ASTM D-1544) less than 3.

b) Preparation of the composition

A paint was prepared containing, by weight: 22.9 parts of polyester as described above, 4.1 parts of commercial hexamethoxymethyl melamine, as hardening agent, 23.8 parts of titanium dioxide, 46.3 parts of diluent ( mixture 1/1 Solvesso 150 / butyl-diglycol) 0.5 part of para-toluenesulfonic acid, as catalyst for the curing reaction, 4.1 parts of a matting agent (sold by the company GRACE under the name of SYLOID 74 ), and 0.3 part of dimethyl ethanolamine (or 2-dimethylamino ethanol).

This paint was applied to a 0.75 mm thick galvanized steel plate and subjected to a; heat treatment by passing through an oven at 340 ° C for 55 seconds. The peak metal temperature was 232 ° C. The gloss of the coating thus obtained was 42%.

No standard method to evaluate the metallic marking being developed and accepted in the coating industry, we used, in this example as in the following ones, the subjective test consisting in rubbing the edge of a coin on the coating. No trace was observed with the composition of the present example. Comparative_Example 1 A

Example 1 was repeated, omitting to introduce dimethyl ethanolamine into the paint composition. The coating obtained had a gloss of 40% and showed traces of pronounced metallic marking.

Comparative_Example 1 B

Example 1 was repeated, replacing dimethyl ethanolamine with an equal weight of pyridine. The coating thus obtained had a gloss of 33% and exhibited traces of pronounced metallic marking.

Example 2

Example 1 was repeated, except that the amount of matting agent was increased to 8.1 parts by weight. The coating obtained, which was not sensitive to metallic marking, had a gloss of 22%.

Comparative_Example 2 A

Example 2 was repeated, except that omission was made to introduce dimethyl ethanolamine into the composition of

painting. An 18% gloss coating was obtained which was particularly sensitive to metallic marking. Examples 3 to H

Example 1 was repeated, except that the quantity and / or the nature of the agent improving the resistance to metallic marking was modified. The experimental conditions and the results are given in the following table. In order to facilitate the measurement of the metallic marking, an arbitrary scale has been defined, in which the following coefficients represent: 0 and 1 = pronounced metallic marking; 2 and 3 =

Claims (7)

1. Paint composition for metallic coatings, having improved resistance to metallic marking, comprising a polyester resin, a hardening agent, a diluent, pigments and additives, characterized in that it additionally comprises an amino compound chosen from diamines, polyamines and those of general formula (I), and their mixtures X - (CH,) - N ^ 1 (I) znv, R2 ~ 1 - in which and R2 are identical or different radicals, which can be l hydrogen, alkyl radicals, substituted alkyls, - (CH2) n-OH, aryls, substituted aryls, and where X is OH or the phenyl radical, and where n can take the values from 1 to 20. 2. Paint composition for metallic coatings according to claim 1, characterized in that it comprises the amino compound in an amount of between approximately 0.1 - and approximately 3% and preferably between approximately 0.3 and 1% by weight based on the total weight of the composition. 3. A paint composition for metallic coatings according to any one of claims 1 and 2, characterized in that among the diamines used, neopentane diamine is taken. 4. Paint composition for metallic coatings according to any one of claims 1 and 2, characterized in that the polyamines used are chosen from diethylenetriamine, triethylenetetramine, tetra-ethylenepentamine and their mixtures. 5. Paint composition for metallic coatings according to “any one of claims 1 and 2, characterized in that the amino compounds of general formula (I) / Ri X - (CH,) - N (I) δ n \ R2 are preferably ethanolamine, 2-dimethylamino ethanol, benzyl amine and mixtures thereof. 6. Paint composition for metallic coatings having improved resistance to metallic marking, comprising a polyester resin, a polyester hardener chosen from amino resins containing etherified N-methylol or N-methylol groups, a diluent whose boiling point is between 100 and 310 ° C, pigments in a pigment / resin weight ratio '- 14 - polyester + hardener between 0.1 and 1, characterized in that it also comprises an amino compound at a rate of approximately 0 , 1 to about 3% by weight based on the total composition, the latter being chosen from the group comprising monoethanolamine, 2-dimethylamino ethanol, benzyl amine, diethylenetriamine, neopen-tane diamine and their mixtures. 7. Metallic surfaces coated with a paint, the composition of which is described in any one of claims 1 to 6. / i