DE3320615A1 - Use of alkyl-substituted 2,4-hydroxybenzophenones for stabilising baking finishes - Google Patents

Abstract

The use of alkyl-substituted 2,4-dihydroxybenzophenones, optionally in combination with further stabilisers, for stabilising baking (stoving) finishes (coatings, paints, enamels, lacquers), in particular compounds of the formula <IMAGE> in which R is C3-C12-alkyl, and R1 is hydrogen or C1-C8-alkyl.

Description

Use of alkyl-substituted 2,4-dihydroxybenzophenones for

Stabilizing stoving finishes It is known that stoving finishes, especially to stabilize car paintwork with light stabilizers. It was now found that selected benzophenone compounds are suitable for this purpose are.

The present invention particularly relates to the use of alkyl-substituted 2,4-dihydroxybenzophenones, optionally in combination with other stabilizers to stabilize stoving varnishes.

In particular, the invention relates to the use of compounds of the formula where R is alkyl (C312) and R1 is hydrogen or alkyl (C18), for stabilizing stoving coatings.

R is preferably branched alkyl such as isopropyl, secondary or tert. Butyl, branched amyl such as iso-amyl or a mixture of isomers such as e.g. of dodecyl, preferably tert. Butyl.

R1 preferably denotes hydrogen or alkyl (C1,2) in the 2'-position, preferably hydrogen.

Most preferred is the compound 2,4-dihydroxy-4'-tert-butylbenzophenone. The compounds of the formula (I) are known or can be prepared according to known per se Methods are made.

The preferred use of the compounds of formula (I) is Stabilization of vehicle paintwork, preferably two-layer paintwork, preferably of metallized paintwork. This makes their usability noticeable elevated.

All stoving lacquers can be used as lacquers. Such will be preferred "Burned in" at over 100 ° C in order to obtain optimal properties.

In particular, they are in combination with the said light stabilizers Paints (so-called wet paints) preferred which contain as binders: combinations made from oil-modified polyester resins (oil alkyd resins) and melamine-formaldehyde resins or combinations of externally crosslinking polyacrylate resins and melamine-formaldehyde resins or combinations of saturated polyesters and melamine-formaldehyde resins or self-crosslinking polyacrylic resins or also polyacrylate resins with polymerized Styrene. In addition, two-component acrylic resin varnishes are also available acrylate resin containing hydroxyl groups and aliphatic or aromatic isocyanates in question, as well as thermoplastic polyacrylate resins. Two-component polyurethane resin lacquers should also be mentioned consisting of polyester resins and / or polyether resins containing hydroxyl groups, hardened with aliphatic or aromatic isocyanates. For metallize paints have the thermoplastic polyacrylate resins or externally crosslinking resins are particularly important Polyacrylate resins in combination with 3utanol-etherified melamine resins as well Polyacrylate resins containing hydroxyl groups, hardened with aliphatic isocyanates. as well The powder coatings known per se come into consideration, which are e.g. Compound (I) were treated.

External crosslinking polyacrylate resins are described, for example, in H. Kittel, Textbook of paints and coatings, Berlin, Vol. I, Part 2, page 712 or also in US-P 3,062,763.

The compounds according to the invention and their above-mentioned mixtures can also be used in the presence of other additives. Such are known per se and describe e.g. in DGS 2 606 358. These belong, for example, to the group of UV absorbers and light stabilizers like that 2- (2'-hydroxyphenyl) benzotriazoles, 2-hydroxybenzophenones, 2,2,6,6-tetraalkylpiperidine compounds, salicylates, cinnamic acid esters, Esters of optionally substituted benzoic acids, oxalic anilides. A preferred one Use is the combination of the compounds of the formula (I) with 2,2,6,6-tetramethylpiperidine compounds.

The addition of the compound of formula (I) to the varnish can be in any Stage of paint production take place, in solid or dissolved form in one suitable solvents, such as xylene or toluene, in a concentration of approx. 10% by weight.

By adding 0.02 - 5% by weight of UV stabilizer, primarily 0.2-2% by weight according to formula (I) to the liquid stoving enamels can also the light and weather fastness of organic pigments in the cured stoving finishes significantly increased, the tendency to form hairline cracks in two-layer coatings the weathering can be significantly reduced and the gloss retention can be significantly improved.

Surprisingly, this is also evident in the case of metallized paintwork, as well as excellent long-term stabilization of the clearcoat film of two-layer metallized paintwork with regard to hairline cracking and gloss retention.

The stabilization of two-layer metallized paintwork, as usual Used in the automotive industry, either by adding it to the base coat and / or by adding to the clearcoat.

Adding it to the clearcoat alone already shows a considerable improvement the weathering stability.

Metallized coatings according to the invention can be in many colors and can also be made in light pastel tones.

Example 1 Use in car topcoat.

Lacquer build-up Structure of the two-layer metallized lacquer from a base lacquer (base coat) and a clear coat (top coat) according to the following composition.

I. Basecoat Consisting of (GT = parts by weight): 15.00 GT commercial polyacrylate resin, externally crosslinking (Viacryl SC 344, Vianova, Vienna) (Delivery form 50% in xylene / butanol 4: 1) according to the definition of DIN 53'186 2.61 parts by weight commercially available butanol-etherified melamine resin, moderately reactive, delivery form 72% in isobutanol vMaprenal MF 800, Casella) produced by polycondensation from 1 mol of melamine with 3-6 moles of formaldehyde, etherified with 3-6 moles of butanol according to the definition of DIN 53'187 0.77 part by weight n-butanol 0.26 part by weight colloidal silica 6.70 part by weight xylene 51.75 part by weight cellulose acetobutyrate solution, 20% (composition see below) 3.85 GT aluminum paste, not floating (non leafing), commercial form 65% in alkyl glycol acetate according to the definition of DIN 55'923 13.54 parts by weight of butyl acetate 5.15 parts by weight of ethyl glycocoacetate 0.37 parts by weight of Byketol OK (leveling agent, Mixture of high-boiling aromatics, ketones and esters, boiling range 160-185 "C; 100.00 GT Cellulose acetobutyrate solution 20.00 pbw cellulose acetobutyrate Acetyl content approx. 13.6% butyryl contains 38.7% hydroxyl content 1.25% viscosity in Poise (d Pa. S), 20% strength in acetone: 2.0 10.00 parts by weight n-butanol 35.00 parts by weight xylene 35.00 parts by weight Butyl acetate 100.00 GT II. Clear lacquer (top coat) consisting of 80.00 GT polyacrylate resin (analogous to base coat) 13.90 pbw melamine resin (similar to base coat) 4.10 pbw n-butanol 2.00 GT Byketol OK (analogue to base coat) 100.00 GT Execution: Paint structure base coat I colored additionally with 0.3 GT copper phthalocyanine blue C.I. Pigment Blue 15: 1, applied by spraying, layer thickness approx. 25 p (without UV stabilizer).

Overpainted (spray application, after the base coat has dried) a) with clear lacquer according to II, containing 25 µ layer thickness, b) with clear lacquer according to II additionally 1 GT of the compound 2,4-dihydroxy-4'-tert. butylbenzophenone, 25 p layer thickness, a) and b) burned in for 30 minutes 14,000.

Weathered for 1 year in Florida, inclination 5 ° to the south.

Sheets according to example b) achieve a significantly better rating than those according to example a).

Example 2 A clear lacquer layer is applied to the base lacquer according to Example 1 / I (top coat) according to Example 1 / II, which contains 2% of the compound of the formula 2,4-dihydroxy-4'-tert.-butylbenzophenone contains applied with a spray apparatus in 20 to 30 u layer thickness. The so The films obtained are artificially exposed in a UV device (UVCON from Atlas). Excellent results are obtained.

Example 3 Films produced according to Example 2 are 3 Thermally stressed for hours at 140 "C. By reflectance measurement between 290 and 380 nm it is found that the compound 2,4-dihydroxy-4'ert-butylbenzophenone is still completely present or is non-volatile under these conditions.

Claims (8)

Use of alkyl-substituted 2,4-hydroxybenzophenones for stabilization of stove-enamelling claims 1. Use of alkyl-substituted 2,4-dihydroxybenzophenones, optionally in combination with other stabilizers to stabilize Stove enamelling. 2. Use according to claim 1 of compounds of the formula where R is alkyl (C3-12) and R1 is hydrogen or alkyl (C1.8), for stabilizing stoving finishes. 3. Use according to claims 1 and 2 of the compound of Formula (I) in which R is tert-butyl and R1 is hydrogen. 4. Use according to claims 1-3 in combination with 2,2,6,6-tetramethylpiperidine compounds 5. Use according to claims 1-4 for stabilizing vehicle paintwork, preferably two-coat finishes, preferably metallized finishes. 6. Use according to claims 1-5 in concentrations of 0.02-5% by weight, preferably 0.2-2% by weight in liquid stoving enamels. 7. Liquid stoving enamel, containing 0.02-5% by weight, preferably 0.2-2% by weight of an alkyl-substituted 2,4-dihydroxybenzophenone. 8. Cured stoving enamel containing 0.02-5% by weight, preferably 0.02-2% by weight of an alkyl-substituted 2,4-dihydroxybenzophenone.