DE2260377B2 - COATING AGENT BASED ON A MIXTURE OF POLYESTER RESIN, ACRYLATE AND FLUOROUS POLYMERIZES - Google Patents

Description

When applying chemically highly resistant coatings based on fluorine-containing vinyl polymers Difficulties arise on metallic substrates depending on the coating material used in liability. There are particular difficulties z. B., polyvinylidene fluoride dispersion paints on various to anchor metallic bases in such a way that the coatings adhere well.

It is known. Polymerization products from vinylidene fluoride

(CH ₂ = CF ₂ )

coating materials to be adhered in combination with suitable synthetic resins containing polar groups to process. As such, homopolymers and copolymers of various acrylic monomers, but also polyvinyl esters, polyvinyl dioxalanes, polyethers, polyketones, polyamides and curable ones Synthetic resins such as polyester, alkyd resins or the like are called.

In the known processes, a coating with polyvinylidene fluoride must often first be carried out Adhesion-promoting coating can be applied to the substrate to ensure proper adhesion of the Polyvinylidene coating to ensure the substrate. The adhesion promoting coating is in generally only limited to those resins that have their adhesion promoting properties even after repeated overburning Do not lose properties, e.g. B. epoxy resins.

Another known method involves using mixtures of polyesters and polyvinylidene fluoride Metal supports applied. However, this process is limited to the fluidized bed sintering process

The known coatings show different adhesion properties on the various metallic substrates. In addition, a specific recipe is worked out for each metal as a base must in order to obtain satisfactory technical paint properties, in particular adhesion values.

Coating agent based on a vinylidene fluoride polymer and an aldehyde-modified, optionally etherified, copolymer of an unsaturated one Acid amide and at least one other monomer are known. These mixtures can optionally also contains additional resins, e.g. polyester, such as glycerol phthalic acid ester a

A selection of the polyesters is not made here. The known coating agents therefore show in some respects iacktechnische properties that are not suitable for the intended use.

According to a further publication, the etherified copolymers mentioned above are used in a mixture with a vinyl fluoride polymer and additional resins, but without the addition of polyester.

Furthermore, in a publication are thermosetting mixtures of a modified, optionally etherified acrylic copolymer described. Polyester can also be used in addition. However, this publication contains no reference to fluorine-containing polymers.

In accordance with the present invention, the difficulties of the previously known methods are now addressed remedied by a coating agent based on a mixture consisting of

A) a thermosetting polyester resin, its alcohol component a proportion of over 80% primary OH groups and its acid component at least one aromatic and at least contains an aliphatic carboxylic acid,

B) a thermosetting acrylate resin and

C) a homo- and / or mixed polymer of fluorine-containing vinyl monomers with up to two Fluoromatics and optionally

D) usual additives.

The polar groups present in the synthetic resins A) and B) result in a strong interaction with the fluorine-containing polyolefins, e.g. B. polyvinylidene fluoride, and at the same time an intimate connection to Backing achieved The coating compositions according to the invention therefore exhibit excellent adhesion various metallic substrates. If the polyester resin component A) is aromatic or only would contain aliphatic carboxylic acids, the result would be either too brittle or too soft films.

Suitable polyester resins A) are in particular those which are free hydroxyl, carboxyl or other for crosslinking with thermosetting acrylate resins suitable reactive groups, e.g. B. blocked isocyanate groups or the like, for example polyester with a hydroxyl number of at least 20, preferably 70 to 130, and an acid number of at most 50, preferably 10 to 20. The polyester resins can be saturated or unsaturated. If they contain predominantly saturated components, are at least trifunctional components are present,

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for example at least trihydric alcohols and / or at least trihydric carboxylic acids. The acidic components of the polyester resins are aliphatic and aromatic polycarboxylic acids, such as o-, tsoond terephthalic acid, pyromethic acid, trimeilitic acid, succinic acid, adipic acid, azelaic acid, sebacic acid, dichlorobuccinic acid, tetrahydrophthalic acid, furthermore, tetrachlorophthalic acid, italicosilicic acid, or the like. As the alcohol component (j _he polyester resins A suitable propanediol 2,2-dimethyl-13-z. B. di- and triols, such as ethylene glycol, diethylene glycol, triethylene glycol, propanediol-1,3, 1,3-butanediol, 1,5-Pentandioi, Glycerol - but only in minor amounts -, trimethylolethane or trimethylolpropane, cyclic alcohols such as dimethylolcyclohexane or the like, the components being present individually or as a mixture.

The molar ratio of the aromatic to the aliphatic carboxylic acids in the polyester resin is generally from 5: 1 to 1: 4. preferably 3: 1 to 1: 3.
The hydroxyl groups of the alcohol component are advantageously at least 90%. expediently at least 95% primary. Those alcohols which exclusively contain primary hydroxyl groups are particularly preferred.

Suitable blocked isocyanate components of the polyester resins are, for. B. Adducts from aromatic Isocyanates and phenols or acetoacetic esters, malonic esters. from isocyanates, trimethylolpropane and phenol or from 2,4-diisocyanatotoluene and trialkyl or Diisocyanate containing uretdione groups made from alkylarylphosphine.

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

Component A can also be modified with fatty acids or fatty oils. Then it contains im generally 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 ones Fatty acids, such as isooctanoic acid or isonanoic acid, are used in the refining of fats and oils produced fatty acids, such as the so-called "first run fatty acids", also cyclohexane monocarboxylic acid.

Suitable thermosetting acrylate resins B are, for. B. homopolymers or copolymers of acrylic monomers, which form reactive side groups in the polymer, such as hydroxyl, epoxy and / or carboxyl groups, preferably however, methylol or methylol ether groups. Such resins can be self-crosslinking - i. H. thermosetting without the addition of a hardener - or externally crosslinking - d. H. with the participation of a Hardener hardenable - be.

The self-crosslinking acrylate resins contain N-methylolamide groups as an essential component are bound to acrylic or methacrylic acid and / or maleic, fumaric and / or itaconic acid, or Etherification products of these with alkali> len with up to 8 C 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 are 2 to 18, preferably 2 to 4 Have carbon atoms. Possible issues are e.g. B.

35 the hydroxyethyl 3- or 2-hydroxypropyl and 4-hydroxybutyl esters, such as hydroxyethyl acrylate, methacrylate, 2-hydroxypropyl acrylate, methacrylate and 4-hydroxybutyl acrylate and methacrylate and the half esters or diesters of the aforementioned dicarboxylic acids with polyhydric alcohols, preferably with neighboring OH groups. However, for the self-crosslinking resins, the first-mentioned embodiment with the alkylolamide groups is to be preferred because they bring the optimal properties with them and the curing of these resins is easier to achieve Methacrylic acid with 1 to 18, preferably 1 to 8, carbon atoms in the alkyl radical and optionally further polymerizable monomers, such as styrene or the like. The acrylate resins often contain free carboxyl groups as a result of the polymerisation of free α-olefinically unsaturated mono- and / or polycarboxylic acids or partial esters of such polycarboxylic acids, the acid number generally being a maximum of 50.

The self-crosslinking acrylate resins can also be crosslinked under the action of hard materials.

The externally crosslinking acrylate resins differ from the self-crosslinking ones in that they do not have any Contain alkylolamide groups. An additional substance is therefore usually used for hardening, preferably use an amine resin.

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

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('5 The proportion of the acrylic resin component to The polyester resin component in the coating compositions according to the invention is generally in the range from 5: 1 to 1: 5, preferably 2: 1 to 1: 2. The proportion of the sum of the components (A + B) for component C can vary from 9: 1 to 1: 9, preferably 3: 1 to 1: 3. After a In a preferred embodiment, the coating agents according to the invention contain 2 to 25, preferably 3 up to 20% 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. in each case based on solid resin. Of the The total proportion of the three binders together should not be more than 60, preferably not more than 50 % By weight of the coating agent.

The coating agent can also contain other resins, e.g. B. those under the curing conditions Form elastic films or have a crosslinking effect and which generally have no adverse effect on the paint properties of the coating, e.g. B. in terms of color, weather resistance or the like, cause. An addition of amine resins with methylol or methylol ether groups can act as a crosslinking agent active component in certain cases, especially when using heat curable foreign-linked / terminated acrylate resins are appropriate. As amine resins, for. B. urea formaldehyde

'resin, benzoguanamine-formaldehyde resin and their Etherification products, but preferably melamine-formaldebyd resin, especially hexamethoxymethylmel-, amine, called

• a. Due to the low solubility of component (C erfindungsgemälie the Oberzugsmittel is usually as a dispersion in high-boiling polar organic solvent, for. Example, those having boiling points of 150 to 300 ⁰ C, such as dimethyl phthalate, ethylene glycol monomethyl, ethyl, -butyläther , or their ethyl acetate, diethylene glycol monoethyl, butyl ether, propylene glycol carbonate, butyrolactone, diacetone alcohol, etc. To control the viscosity, these solvents can be mixed with a smaller proportion of low-boiling solvents, which can also be polar, such as methyl ethyl ketone, methyl isobutyl ketone, acetone, toluene, mixtures (known under the trade designation "Soivesso") blend of aliphatic and aromatic hydrocarbons having boiling points of 150 to 220 ⁰ C, or the like. the above-mentioned solvents is therefore to be higher boiling to make it as long as remaining during baking of the coating in the coating, to 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. To brush, Rolling or powder coating take place.

The coating compositions according to the invention can also Customary additives such as dyes, pigments, fillers, plasticizers, stabilizers. Wetting agents, dispersing agents. Anti-settling agents, leveling fluids, in the usual amounts included.

The use of dyes and pigments comes into consideration especially if the Coating agents according to the invention can be used as a paint color. The ratio is then advantageous Binder (solids) to the total amount of pigment in the range from 8: 1 to 1: 1, preferably 5: 1 up to 3: 1. Suitable dyes or pigments are those that reduce the thermal load during curing 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, iron oxide red, Iron oxide black, phthalocyanine complexes, naphthol red or the like. It is without It matters whether the coloring pigments are organic or inorganic in nature.

Suitable fillers are e.g. B. talc, mica, kaolin, quartz flour, barium sulfate, asbestos flour, slate flour or the like, suitable anti-settling agents are e.g. B. finely divided silica, bentonite, colloidal silicates or similar.

The coatings can be at elevated temperature, preferably above 130 ° C, under some circumstances up to 35O ⁰ C, solidify or cure, with the baking time greatly that of the baking conditions such as the temperature, the nature of the substrate, the furnace dimensions and composition Coating · or solvent is dependent.

Suitable substrates for the coating compositions according to the invention are, for. B. earthenware, ceramics, glass, Plastic, but preferably metal such as iron, zinc, Copper, aluminum. Steel, brass, bronze or the like. The I documents can still go through mechanical and / or chemical pretreatment has been made more adhesive or corrosion resistant be. However, the coating compositions according to the invention adhere excellently to a wide variety of metal substrates without bonding primer or intermediate layer. The good adhesion of these single-layer paintwork corresponds to the values GTOA to GTIA 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 resistance to yellowing and weather resistance.

The coating compositions according to the invention are for the production of clear or pigmented coatings

ίο or coatings can be used in many ways, in particular for lining and cladding objects that come with aggressive media or with atmospheric media Influences come into contact, for household appliances, machines, vehicle parts, components for electrical engineering Purposes as well as for thermally stressed objects.

Due to their favorable properties, the coating compositions according to the invention are excellent for single-layer painting, preferably using the continuous coil coating process suitable. Such pre-coated sheets can be subsequently drawn by deep drawing, folding, profiling, Embossing or the like without any significant impairment of the other favorable properties

deformable. The adhesive coating layer can remain unchanged, but it can also be used as an intermediate layer, thus serve as a base for further coatings, which in turn consist of the same or another usual Coating material can exist.

The coating compositions according to the invention are produced by mixing components A, B and C, with components A and B mostly as resin solutions in organic solvents, the Component C, such as polyvinylidene fluoride, as a solid, e.g. B. in dispersion, but mostly in powder form, are present. It is advisable to use particularly intensive grinding, e.g. B. in the ball mill, too respect, think highly of. Components A, B and C and any additives such as pigments, fillers or the like including any additional resin that may be present, can be used in any order prior to milling can be added. The grinding or dispersing of component C can, for example, together with Component A or B or both. Also dispersing component C in a solution or dispersion of at least one of components A and B is possible. Any existing Amine resin is expediently added after dispersing.

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

example 1

A mixture of 303 g polyvinylidene fluoride, 70 g thermosetting polyester resin from 39.8 parts by weight Isophthalic acid, 20.4 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 trimethylolpropane. 30.5 g of thermosetting Acrylate resin from 56.7 parts of methacrylic acid. 60.7

Parts of acrylic acid, 308.5 parts of N-butoxymethyl methacrylamide, 96.5 parts of N-butoxymethyl acrylamide, 130.6 parts of 4-hydroxybutyl methacrylate, 87.5 parts of 2-hydroxypropyl acrylate and 259.5 parts of styrene, and 596 g of the solvent mixture B is added to a backing of 0.3 μΐη applied to 0.5 mm thick tinplate by spraying in a layer thickness wet film thickness of 50 to 150 and 15 minutes cured at 18O ⁰ C for. A colorless, well adhering and elastic coating is obtained.

Example 2

Mine mixture, consisting of 89.4 g polyvinylidene fluoride. 80 g of hardenable polyester resin composed of 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 of pelargonic acid and 15.2 parts of maleic anhydride. 186 g of thermosetting acrylate resin made from 27.2 parts of acrylic acid and 35 parts of methacrylic acid. 250.7 parts of 2-hydroxypropyl acrylate, 241 parts of 4-hydric xybutyl methacrylate. 219.6 parts of Bun methacrylate and 226.5 parts of styrene. 89.4 parts of talc and 555 g of solvent mixture A are applied by rolling onto sheet steel in a layer thickness of about 50 to 100 μm wet film thickness and cured at 190 ° C. for 10 minutes. Is applied to the cured coating layer is still a further 100 μιτι thick layer of stoving lacquer to d ~ r based on a modified with a mchttrocknenden fatty acid alkyd resin and partly of a butanol-etherified melamine resin (mixing ratio 7: 3) applied by spraying, and 30 minutes at 14O ⁰ C hardened. The result is a lacquer with excellent adhesion, a perfect surface and good elasticity.

Example 3

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A mixture of 187.6 g of polyvinylidene fluoride, 73 g of thermosetting polyester resin according to 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 solvent mixture A is rolled onto a substrate made of phosphated sheet steel. Wet film thickness) of 50 bh 100 µm and cured for δ minutes at 195 ° C. Another coating agent, consisting of 185 g of 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 solvent mixture B is applied to the cured coating layer by spraying with a wet film thickness of 50 to 150 μm applied for 2 minutes at 240 ⁰ C in the burn-in forced air oven cured to give a guthaftenden, glossy, elastic, and corrosion resistant coating with a perfect adhesion to the substrate.

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Example 4

A mixture of 167.4 g is placed on a base made of 0.5 to 0.8 mm thick aluminum sheet Polyvinylidene fluoride. 73.7 g of 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 des Solvent mixture A applied by rolling in a wet film thickness of 50 to 100 μm and for 3 minutes cured at 230 ° C. An elastic, glossy and corrosion-resistant coating is obtained flawless adhesion to the substrate without damage from deep drawing, folding or the like is subsequently deformable.

Comparative experiments to Example 4

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

b) The procedure is as in Example 4, but with a polyester resin consisting exclusively of 56.2 Parts by weight isophthalic acid and 31.9 parts by weight glycerol.

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

Test results of the comparison tests
l. tensile adhesion

The coated aluminum plates produced according to example 4 and comparative experiments a) and b) are treated as follows: A so-called cross-cut is made in the coating, the depth of which is up to on the metal reaches. The sample is then stretched at the interface. Then a pressure sensitive one Adhesive tape pressed onto the stretched grid interface and quickly peeled off the sample. Sticks when the strip is peeled off the coating is on the adhesive strip rather than the plate, the adhesive strength is bad. If the coating cannot be peeled off from the aluminum base at all, this is evidence of excellent adhesion.

2. Flexibility

To determine the flexibility, the plates coated as in Example 4 are bent at an angle bent by 180 ° so that the cover is on the outside (so-called "T-bend test").

3. Heat resistance

To test the heat resistance, 3 samples of the coated panels are cured at different temperatures and times, namely 3 minutes at 230 ° C. 2 minutes at 270 ° C and 1 minute at 300 ⁰ C. With these baking conditions are as those for the continuous strip-coat coating by (= so-called. "Coil coating process"'reproduced conditions required.

4. Resistance to yellowing

The yellowing resistance is determined on the same samples on which the heat resistance is determined. The determination is done visually, where the following assessment applies:

no change in the shade of white = excellent light yellow color = medium

strong yellowing = bad

The test results of the comparative tests are summarized in the table below.

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Tabel 9 sample 22 60 377 in 1 min / 300 ^r C properties Ψ 10 excellent i 4th bad Tensile strength a (comparison) Stoving conditions bad I. b (comparison) 3 min./230 ° C 2 min / 270 ^c C middle 4th excellent excellent bad 1 flexibility a (comparison) middle bad bad I. b (comparison) bad bad excellent I. 4th excellent excellent bad I ₁ Resistance to yellowing a (comparison) bad bad bad I '■■■■' b (comparison) bad bad excellent excellent 1 middle bad S. bad bad

From the table it follows that the erfindungsgeir, ..- SEN coating agent at baking temperatures of 230-300 ⁰ C retain their excellent flexibility, Dehnhaftfestigkeit and yellowing resistance. Even at stoving temperatures of 270 and 300 ^° C. under the specified conditions, there is no yellowing.

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

The samples b. whose polyester resin component A) is composed exclusively of an aromatic acid and exclusively of glycerol with only 66% primary hydroxyl groups, show ^{even worse properties at the stoving temperature of 230 °} C., which are retained even at higher stoving temperatures.

Example 5

On a pad of 0.3-0.8 mm thick galvanized iron sheet, a mixture of 180 g of polyvinyl

fluoride, 53.7 g of thermosetting polyester resin according to Example 1, 73.7 g of thermosetting acrylate resin according to Example 1, 75 g of red iron oxide, 25 g of talc and 592.6 g of the solvent mixture A applied by rolling in a wet film thickness of 100-150 μ and 5 Cured at 250 ^° C. for minutes. An elastic and corrosion-resistant coating with perfect adhesion to the substrate is obtained.

Example 6

A mixture of 194.6 g of a copolymer of vinyl fluoride and vinylidene fluoride (fluorine content 51-52% by weight), 69 g of heat-curable polyester resin according to Example 2.64 is placed on a base of 0.3-0.5 mm thick aluminum sheet pretreated with chromosulfuric acid g of thermosetting acrylate resin according to Example 1, 30 g of chromium oxide, 27 g of titanium dioxide, 18 g of talc, 13 g of barium sulfate, Ig finely divided silica and 583.4 g of the solvent mixture A applied by rollers with a layer thickness (wet film thickness) of about 100 μ and 3 minutes cured ^{at 260 °} C. for a long time. An elastic and corrosion-resistant coating with very good adhesion to the substrate is obtained.

Claims (5)

Patent claims: 1. Coating agent based on a mixture of polyester resin, acrylic and fluorine-containing polymers, characterized in that the mixture consists of A) a thermosetting polyester resin, the alcohol component of which is an Amei! from above 80% primary OH groups and their 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 and optionally D) usual additives
consists. 2. coating means according to claim 1, characterized in that the quantitative ratio of Component A) to component B) is in the range from 5: 1 to 1: 5 3. Coating agent according to Claims 1 and 2, characterized in that component A) contains at least 15% by weight, based on the polyester resin, of aromatic polycarboxylic acids. 4. Coating agent according to Claims 1 to 3, characterized in that it is in the form of a Dispersion is present in a higher-boiling polar organic solvent. 5. Use of the coating agent according to claims 1 to 4 for the production of coatings for single-layer painting, preferably after continuous coil coating.