DE2260377A1 - Chemically resistant coatings for metal etc. - based on polyester resin, thermosetting acrylic resin and fluorine contg. vinyl polymer - Google Patents

Abstract

Coating compsns with good chemical resistance and excellent adhesion to metals etc., are based on (A) a thermosetting polyester whose alcohol component contains >80% prim. OH gps. and whose acid component contains >=1 aromatic and >=1 aliphatic carboxylic acid, (B) a thermosetting acrylic resin and (C) a (co)polymer of a fluorine-contg vinly monomer with >=2 F atoms. The compsns are generally made as dispersions in high boiling solvents and may be applied by spraying, brushing, dipping, powder coating, etc. and cured to colourless, elastic films at 130-350 degrees C.

Description

U E R Z U G S M I T T E L When applying chemically highly resistant Coatings based on fluorine-containing vinyl polymers on metallic substrates Adhesion difficulties arise depending on the coating material used on. There are particular difficulties z. B., polyvinylidene fluoride dispersion paints to be anchored on various metallic substrates in such a way that the "covers" well be liable.

It is known that polymerization products from vinylidene fluoride (CH2 = CF2) in combination with suitable synthetic resins that contain @olar groups, to be processed into adhesive coating materials. As such, Ftomo and Mixed polymers of different acrylic monomers, but also polyvinyl esters, polyvinyl dioxalanes, Polyethers, polyketones, polyamides and curable synthetic resins such as polyester, alkyd resins or the like.

Pei the known method must often before coating with polyvinylidene fluoride first an adhesion-promoting coating is applied to the substrate in order to to ensure perfect adhesion of the polyvinylidene coating to the substrate. The adhesion-promoting coating is generally only limited to resins which do not retain their adhesion-promoting properties even if they are repeatedly overbaked lose, e.g. P. epoxy resins.

According to another known method, mixtures of polyesters are made and polyvinylidene fluoride applied to metal substrates. This method However, it is limited to the fluidized bed sintering process.

The known coatings point to the various metallic substrates different adhesion properties. Ilinau comes that nan for every metal as a base a certain recipe must be worked out in order to achieve a satisfactory coating To maintain properties, in particular liability values.

According to the present invention, the difficulties have become the heretofore known process remedied by coating agent on the basis of a mixture, containing A) a thermosetting polyester resin, the alcohol component of which is a proportion of over 80% primary OH groups and its acid component at least one aromatic and contains at least one aliphatic carboxylic acid, B) a thermosetting acrylate resin and C) a Homo- and / or Slischpolymorisat of fluorine-containing vinyl monomers with up to two fluorine atoms.

Due to the polar groups present in the synthetic resins A and B, a strong interaction with the fluorine-containing polyolefins, e.g. B.

Polyvinylidene fluoride, and at the same time an intimate connection to Underlay achieved. The coating compositions according to the invention therefore have excellent properties Adhesion to various types of metallic substrates. When the polyester resin component A) If aromatic or only aliphatic carboxylic acid were contained, one would either Keep films that are too brittle or too soft.

Suitable polyester resins A) oind in particular those which contain free hydroxyl, Carboxyl or other suitable for crosslinking with thermosetting arylate resins reactive groups, e.g. B. blocked isocyanate groups or the like, contain, for example polyester with a hydroxyl number of at least 20, preferably 70 up to 130, and an SE number of at most 50, preferably 10 to 20.

The polyester resins can be saturated or unsaturated. Provided she contain predominantly saturated components, are at least trifunctional components present, for example at least trihydric alcohols and / or at least trihydric Carboxylic acids.

The acid components of polyester resins are aliphatic and aromatic Polycarboxylic acids such as o-, o- and terephthalic acid, pyromylitic acid, trimellitic acid, Succinic acid, adipic acid, azelaic acid, sebacic acid, dichlorosuccinic acid, Tetrahydrophthalic acid, tetrachlorophthalic acid, hexachloroendomethylene-tetrahydrophthalic acid, also maleic acid, fumaric acid, itaconic acid or the like. As alcohol components the polyester resins A are suitable, for. B. di- and triols, such as ethylene glycol, diethylene glycol, Triethylene glycol, 1,3-propanediol, 1,3-butanediol, 1,5-pentanediol, 2,2-dimethyl-1,3-propanediol, Glycerin - this, however, only in minor amounts -, trimethylolethane - or propane, cyclic alcohols such as dimethylolcyclohexane or the like, the Components are each present individually or in a mixture.

The molar ratio of the aromatic to the aliphatic carboxylic acids in the polyester resin it is generally 5: 1 to 1: 4, preferably 3: 1 to 1: 3.

The hydroxyl groups of the alcohol component are advantageous at least 90%, expediently z @ at least 95% primary. Those alcohols are particularly preferred which contain only primary hydroxyl groups.

Suitable blocked isocyanate components of the polyester resins are, for. B.

Adducts of aromatic isocyanates and phenols or acetoacetic esters, Malonic ester, from isocyanates1 trimethylolpropane and phenol or one from 2,4-diisocyanato-toluene and uretdione group-containing prepared trialkyl or alkylarylphosphine Diisocyanate.

Coating agents with such polyester resins are particularly advantageous A containing an aromatic acid component, preferably those containing at least 15% by weight, based on the polyester resin, of an aromatic poly, preferably Contain dicarboxylic acid.

Component A can also be modified with fatty acids or fats. Then it generally contains up to 25% by weight, based on the total resin, preferably saturated fatty acids such as caproic acid, 2-ethylhexanoic acid, pelargonic acid, capric acid, lauric acid, myristic acid and branched fatty acids such as isooctanoic acid or isonanoic acid, the fatty acids resulting from the refining of fats and oils, such as the so-called "lead fatty acids ", @ Cyclohexanmonocarbonsäure.

Suitable thermosetting acrylate resins 13 are, for. 8. Homosexual or

Copolymers of acrylic monomers that are reactive in the polymer Form side groups, such as hydroxyl, epoxy and / or carboxyl groups, preferably but methylol resp.

Methylol ether groups. Such resins can be self-crosslinking - i. H. heat-curable or externally crosslinking without the addition of a hardener - d. H. with the help of hardenable - be.

The self-crosslinking acrylate resins contain as an essential component N-methylolamide groups attached to acrylic resp.

Methacrylic acid and / or maleic, fumaric and / or itaconic acid are bound, or etherification products thereof with Al @ anols with up to 8 carbon atoms in the alkyl group.

Instead of or together with the alkylolamide groups, they can also hydroxyalkyl esters of the abovementioned carboxylic acids, whose ester groups 2 to 18, preferably 2 to 4 carbon atoms. Possible are e.g. B. the Hydroxyethyl 3-bz @ 2-hydroxypropyl and 4-hydroxybutyl esters, such as hydroxyethyl acrylate, methacrylate, 2-hydroxyproylacrylate, methacrylate and 4-hydroxybutyl acrylate and methacrylate and the half esters or diesters of the aforementioned dicarboxylic acids with polyhydric alcohols, preferably with adjacent OH groups. However, is for the self-crosslinking resins the embodiment mentioned first with the alkylolamide groups To be preferred because they bring the optimal properties and hardening these resins are easier to achieve. The self-crosslinking and the externally crosslinking Acrylic resins generally contain more than others Component still Alkyl esters of acrylic or methacrylic acid with 1 to 18, preferably 1 to 8, carbon atoms in the alkyl radical and optionally other polymerizable monomers, such as styrene or similar. In many cases, the acrylate resins contain by polymerisation of free ~, ß-olefinically unsaturated mono- and / or polycarboxylic acids or partial esters of such polycarboxylic acids free carboxyl groups, where the acid number in the Is usually a maximum of 50.

The self-crosslinking acrylate resins can also under the action be networked by Hartern.

The externally crosslinking acrylate resins differ from the self-crosslinking ones in that they do not contain any alkylolamide groups. For the hardening one will therefore usually use an additional substance, preferably an amine resin.

The fluorine-containing polymers C) are in particular those made from fluorine-containing polymers Vinyl monomers with up to 2 fluorine atoms, such as 1-fluoroethylene (polyvinyl fluoride) and l, l-difluoroethylene (polyvinylidene fluoride). You can following the various procedures polymerization technology, such as suspension or emulsion polymerization have been. Their fluorine content is generally between about 30, preferably between about 40 and about 60 weight percent. Component C is usually in the form of a solid, 2.B. Powder.

The quantitative ratio of the acrylic resin component to the polyester resin component in the coating compositions according to the invention is generally in the range of 5: 1 up to 1: 5, preferably 2: 1 to 1: 2. The proportion of the sum of the components (A. + B) to component C can vary from 9: 1 to 1: 9, preferably 3: 1 to 1: 3. According to a preferred embodiment, the coating agents according to the invention contain 2 to 25, preferably 3 to 20 parts by weight of component A, 2 to 25, preferably 3 to 20% by weight of component B and 1 to 65, preferably 8 to 50% by weight of component C, each based on Fostharz. The total proportion of the three binders should together not more than 60, preferably not more than 50% by weight of the Coating means amount.

The coating agent can also contain other Ilarzo, e.g. B. those which form elastic films or have a crosslinking effect under the curing conditions and which in general do not have a detrimental effect on the lacquered properties of the coating, e.g. B. in terms of color, weather resistance or the like, cause. For example, amine resins with methylol or methylol ether groups can be added as a crosslinking special component in certain cases, especially when used of thermosetting, externally crosslinking acrylate resins. As amine resins are z. B. urea-formaldehyde resin, Benzoguan - @@ in-formaldehyde resin sowi @ their Etherification products, but preferably melamine-formaldehyde resin, especially hexamethoxymethylmelamine, called.

Because of the low solubility of component C, this is invented.

coating compositions according to the invention generally as a dispersion in higher-boiling polar organic solvent, e.g. B. those with boiling points of 150 to 300 ° C, such as dimethyl phthalate, ethylene glycol monomethyl, ethyl, butyl ether, or their @ssigester, diethylene glycol monoethyl, butyl ether, propylene glycol carbonate, butyrolactone, Diacotonic alcohol or the like. These can be used to control the viscosity Solvents with a lower proportion of low-boiling solvents, the can also be polar, such as @ ethyl ethyl ketone, liethyl isobutyl ketone, acetone, toluene, Mixtures of aliphatic and aromatic hydrocarbons with boiling points of 150 to 2200 G (known under the trade name "Solvesso"), or the like blend. The said solvent should therefore be higher-boiling so that it When the coating is stoved, it remains in the coating until a homogeneous film is formed.

The application of the coating agent can be carried out in a conventional manner, e.g. B.

by spraying, dipping, flooding, brushing, rolling or powder coating take place.

The coating agents according to the invention can also contain conventional additives, such as dyes, pigments, fillers, plasticizers, stabilizers, wetting agents, dispersing agents, Anti-settling agents, leveling agents, contained in the usual quantities.

The use of dyes and pigments comes especially then into consideration when the coating compositions according to the invention are used as paints will. The ratio of binder (solids) to the total amount is then advantageous of pigment in the range from 8: 1 to 1: 1, preferably 5: 1 to 3: 1. As dyes or pigments are those that reduce the thermal load when the Survive coatings undamaged, e.g. titanium dioxide, graphite, zinc chromate, Strontium chromate, chromium oxide, zinc sulfide, nickel titanium yellow, chromium titanium yellow, cadmium yellow, Cadmium red, ultramarine blue, @isenoxydrot, @isenoxydschwarz, phthalocyanine complexes, Naphthol red or the like. It is irrelevant whether the coloring pigments are used are organic or inorganic in nature.

Suitable materials are z. T5. Talc, mica, kaolin, quartz metal, Barium sulfate, asbestos flour, slate flour or the like, suitable anti-settling agents are z. B. finely divided silica, bentonite, colloidal silicates or the like.

The "coatings can be at elevated temperature, preferably under certain circumstances Solidify or harden up to 350 ° C, or above 130 ° C, whereby the stoving time Strongly on the baking conditions, such as the temperature, the type of substrate, the Oven dimensions as well as the composition of the coating or solvent dependent is.

Suitable substrates for the coating compositions according to the invention are z. P. earthenware, ceramics, glass, plastic, preferably, but metal, such as iron, Zinc, copper, aluminum, steel, brass, pronze or the like. The documents mechanical and / or chemical pretreatment can make them more adhesive or have been made more resistant to corrosion. However, the coating compositions according to the invention adhere excellent on a wide variety of metal substrates without an adhesive primer hzw. Intermediate layer. The good adhesion of this one-coat paintwork corresponds the values GT OA to GT 1A according to the test specifications in accordance with DIN 53 151. In addition these "coatings can be shaped very well, have a high gloss, excellent Yellowing resistance and weather resistance.

The coating agents according to the invention are for the production of clear or pigmented coverings or coatings can be used in a variety of ways, especially for lining and cladding objects that have been exposed to aggressive media or come into contact with atmospheric influences, for household appliances, Machinery, Vehicle parts, components for electrotechnical purposes as well as for thermally stressed Objects.

Because of their favorable properties, the are according to the invention Coating agent excellent for one-coat painting, preferably after Process of continuous strip coating (coil goating) is suitable. Like that pre-coated sheets can be subsequently drawn by deep drawing, folding, profiling, Embossing or the like without significant impairment of the remaining favorable Properties deformable. The adhesive coating layer can remain unchanged, However, it can also be used as an intermediate layer, i.e. as a base for further top-ups which in turn consist of the same or a different customary coating material can exist.

The coating agents according to the invention are produced by Mix components A, B and C, with components A and B mostly as resin solutions in organic solvents, component C, such as polyvinylidene fluoride, as a solid, z. B. in dispersion, but mostly in powder form. It recommends to particularly intensive grinding, z. F. in. The ball mill, to pay attention. the Components A, R and C and any additives such as pigment, filler or the like including any additional resin that may be present, can be used in any order be added before grinding. The grinding or dispersing of the component C can for example take place together with component A or B or with both. A dispersion of component C in a solution or dispersion at least one of the components A and B is possible. The amine resin, if present is expediently added after dispersing.

In the following examples, parts are parts by weight. In the examples 1 to 4, a solvent mixture A is used for the roller application, which consists of 25 parts of dimethyl phthalate, 25 parts of diethylene glycol monoethyl ether, 25 parts of acetic acid (@ - ethoxyethyl) ester and 25 parts of 3,5-trimethylcyclohexon-2-one-1, a solvent mixture for spray application B from 10 parts of dimethyl phthalate, 40 parts of 5,5-trimethylcyclohexen-2-one-1, 25 parts @ ethyl ethyl ketone, 10 parts @ ssigsäure- (2-ethoxy-ethyl) -ester and 15 parts @ ssigsäure-butyl-ester used.

Examples 1) In a mixture of 303 g of polyvinylidene fluoride, 70 g of thermosetting Polyester resin from 39.8 parts by weight of tsophthalic acid, 20.4 g parts by weight of sebacic acid, 28.4 parts by weight of 2,2-dimethyl-1,3-propanediol and 11.4 parts by weight of trimethyleipropane, 30.5 g of heat-curable acrylate resin from 56.7 parts @ethacrylic acid, 60.7 parts acrylic acid, 308.5 parts of n-butoxymethyl methacrylamide, 96.5 parts of @ -butoxymethyl acrylamide, 130.6 Parts of 4-hydroxybutyl methacrylate, 87.5 parts of 2-hydroxypropyl acrylate and 259.5 parts Styrene, and 596 g of the solvent mixture S is on a pad of 0.3 Up to 0.5 mm thick tinplate by spraying in one layer @ wet film thickness applied from 50 to 150 µm and cured at 1800 C for 15 minutes.

@an receives a colorless, well-adhering and elastic coating.

2) A mixture consisting of 89.4 g polyvinylidene fluoride, 80 g thermosetting polyester resin made from 36.4 parts of terephthalic acid, 11.1 parts of ethylene glycol, 16 parts of 2,2-dimethyl-1,3-propanediol, 13.1 parts of trimethylolpropane, 8.2 parts Pelargonic acid and 15.2 parts maleic anhydride, 136 g thermosetting acrylate resin from 27.2 parts of acrylic acid, 35 parts of methacrylic acid, 250.7 parts of 2-hydroxypropyl acrylate, 241 parts of 4-hydroxybutyl methacrylate, 219.6 parts of butyl methacrylate and 226.5 parts of styrene, 89.4 parts of talc and 555 g of solvent mixture A are through Rolling on sheet steel with a layer thickness of about 50 to 100 µm wet film thickness applied and cured for 10 minutes at 190 ° C. On the hardened coating layer Another 100 pin thick layer of baking varnish is added to the base one alkyd resin modified with a nondrying fatty acid and one partially Melamine resin etherified with butanol (mixing ratio 7: 3) by spraying applied and cured for 30 minutes at 140 ° C. A varnish with excellent Liability, perfect @ surface and good @ lastishness.

3) A mixture is applied to a base made of a phosphated steel hole from 187.6 g of polyvinylidene fluoride, 7 g of heat-curable polyester resin according to the example 2.60 g of thermosetting acrylate resin according to Example 1, 57 g of titanium dioxide, 31 g of talc and 591 g of the solvent mixture A by rolling in a layer thickness (wet film thickness) applied from 50 to 100 µm and cured for 6 minutes at 195 ° C. @ to the hardened The coating layer is still another coating agent, consisting of 185 g Polyvinyl fluoride, 85 g of thermosetting polyester resin according to Example 1, 84 g of thermosetting Acrylate resin according to Example 1, 90 g of titanium dioxide and 556 g of the solvent mixture B applied by spraying with a wet film thickness of 50 to 150 μm and 2 minutes Cured for a long time at 240 ° C in a convection oven. You get a well-adhering, shiny, elastic and corrosion-resistant coating with perfect adhesion on the pad.

4) On a base made of 0.5 to 0.8 mm thick aluminum sheet a mixture of 167.4 g polyvinylidene fluoride, 73.7 g thermosetting polyester resin according to Example 1, 93.7 g of thermosetting acrylate resin according to Example 1, 83.5 g of titanium dioxide and 582 g of the solvent mixture A by rolling in a wet film thickness of 50 to 100 µm applied and cured at 230 ° C for 3 minutes. One holds an @lastic, shiny and corrosion-resistant coating with perfect adhesion to the base, which can be subsequently deformed without damage by deep drawing, folding or the like is.

Comparative experiments to Example 4 a) The procedure is as in the example 4, but with a polyester resin containing the same acids in the same amount as after Example 1, but instead of the alcohols mentioned there now 32.1 parts by weight Contains glycerine.

b) The procedure is as in Example 4, but with a polyester resin, which consists exclusively of 56.2 parts by weight of isophthalic acid and 31.9 parts by weight @ Consists of glycerin.

The coating compositions of the two comparative tests are as in the example 4 applied to a base made of aluminum sheet and hardened.

Test results of the comparative experiments 1. Tensile bond strength The according to Example 4 and the comparative experiments a) and b) produced coated aluminum plates are treated as follows: A so-called cross-cut is applied in the cover, the depth of which extends to the diotall. Thereupon the sample is at the interface stretched. nnnn is a pressure-sensitive adhesive strip on the stretched grid interface pressed on and quickly withdrawn from the sample. Sticks when the strip is peeled off the coating on the adhesive strip instead of on the plate, the adhesion is poor. If the coating cannot be peeled off from the aluminum backing at all, so this shows excellent adhesion.

2. Flexibility The following are used to determine the flexibility Example 4 coated panels bent at an angle of 1800 C co that is the uborsuz is on the outside (so-called "T-bend test").

3. Heat resistance To test the heat resistance, in each case 3 samples of the coated panels at different temperatures and times hardened, namely 3 minutes at 230 ° C, 2 minutes at 2700 and 1 minute at 3000 C. These bake conditions become approximately those for continuous coil coating conditions required by single-layer painting (= so-called "coil coating process") reproduced.

4. Yellowing resistance The yellowing resistance is given to the same Probon determined in which the heat resistance is determined. Dio investigation takes place visually, with the following assessment: no change in the white tone = excellent light yellow color æ medium strong yellow color = bad In The following table summarizes the test results of the comparative tests.

Table property sample @ i n b r e n n b e d i n g u n s e n 3 Min./230 ° C 2 min./270 ° C 1 min./300 ° C Dehn-Haft- 4 excellent excellent excellent strength a (comparison 3 medium bad bad b (comparison) bad bad poor flexibility 3 excellent excellent average a (comparison) poor bad bad b (comparison) bad bad bad yellowing 3 excellent excellent excellent resistance a (comparison) medium poor poor b (comparison) bad bad bad; -from the table it can be seen that the inventive Coating agents at stoving temperatures of 230 - 3000 C their excellent flexibility, Maintain tensile strength and resistance to yellowing. So it occurs too at firing temperatures of 270 and 3000 C under the specified conditions none Yellowing on.

In contrast, the comparative samples a, show their polyester component A) Only aromatic and aliphatic carboxylic acids, but with an alcohol component has only 66 ß prim.ron hydroxyl groups, after curing at 230 ° C a reduction tensile strength, resistance to yellowing, and poor flexibility. At even higher stoving temperatures, there is a further decrease in the properties on.

The samples b, their polyester resin component f) exclusively from an aromatic acid and exclusively from glycerine with only 66 :: primary Hydroxyl groups already show at the stoving temperature of 2300 G even worse properties, which are retained even at higher firing temperatures will.

Claims (13)

Claims 1. Coating agent based on a mixture containing A) a thermosetting polyester resin, the alcohol component of which is more than 80 % primary OH group and its acid component at least one aromatic and Contains at least one aliphatic carboxylic acid, B) a thermosetting acrylate resin and C) a homo- and / or mixed polymer of fluorine-containing vinyl monomers with up to 2 fluorine atoms. 2. Coating agent according to claim 1, characterized in that the @ narrow ratio of component A) to component B) in the range from 5: 1 to 1: r, preferably 2: 1 to 1: 2. 3. çbersugsmlttcl according to claim 1 or 2, characterized in that that the weight ratio of the sum of components (A + B) to component C) in Range from 9: 1 to, preferably 3: 1 to 1: 3. 4. Coating agent according to Claims 1 to 3, characterized in that that the component A) is a polyester with an OII number of at least 20, preferably 70 to 130, and an acid number of at most 50, preferably 10 to 20, is. 5. Coating agent according to claims 1 to li, characterized in that that in component A) the molar ratio of the aromatic to the aliphatic acidic 5; 1 to 1: 4, preferably 3: 1 to 1: 3. G. Coating agent according to Claims 1 to 5, characterized in that that component N) is at least 15% by weight, based on the polyester resin, of aromatic Contains polycarboxylic acids, preferably dicarboxylic acids. 7. Coating agent according to Claims 1 to G, characterized in that that the hydroxyl groups of the alcohol component in the polyester resin A) to at least 90, preferably at least 95% are primary. 8. Coating agent according to Claims 1 to 7, characterized in that that component A) is up to 25% by weight, based on the total resin, preferably Contains saturated fatty acids built in. 9. Coating agent according to Claims 1 to 8, characterized in that that component B) α, @ - @ thylenically unsaturated carboxamide groups, preferably copolymerized acrylic or methacrylic alkylolamide with optionally etherified alkylol groups containing up to 8 carbon atoms. 10. Coating agent according to Claims 1 to 9, characterized in that that component B) polymerized hydroxyalkyl esters α, ßäthylenisch unsaturated Carboxylic acids, preferably the acrylic or. Methacrylic acid. 11. coating agent @ l according to claims 1 to 10, characterized in that that component B) contains free carboxyl groups. 12. Ubersugsmittel according to claims 1 to 11, characterized in that that it is in the form of a dispersion, preferably in a higher boiling polar organic Solvent. 13. Use of the coating agent according to claims 1 to 12 for the Production of coatings, especially for single-layer painting, preferably after continuous coil coating.