Patent Application
20180100069
The present invention relates to improved coating materials based on RMA systems, which cross-link with the aid of a classic Michael addition. The invention also relates to the coatings producible therefrom and to the coated components, in particular components for agricultural machinery and construction machinery, for example, parts of chassis, tools, or attachments.
Coating materials, which cross-link in a Michael addition reaction, are known. The coatings produced therefrom have high weathering stability and chemical resistances. The rapid curing of these coating materials is achieved by the use of high catalyst content, wherein, however, the processing time or the pot life of the coating material is strongly reduced.
Rapid curing is particularly advantageous primarily during the coating or painting of large components, such as chassis parts. However, due to the size and shape of the surfaces, a relatively long time is required for coating the entire component, so that the coating materials used must have long pot lives and long open times. In the following, pot life is designated as the time interval between mixing all components of a coating material and the time at which the cross-linking reaction in the coating material has progressed to the extent that the coating material may no longer be processed. In the following, open time is designated as the time interval in which a coating material film applied to a surface may be corrected without impairing the gradient properties.
During application of the coating material, the already coated areas must additionally be able to absorb the overspray that occurs during painting of the adjacent areas, without surface defects forming, for example, due to a poor progression. In the following, overspray is designated as material loss of the coating material caused during spray painting. The material loss may be caused by spraying past caused by an unfavourable orientation of the spray gun toward the workpiece or by strongly interrupted workpieces, like grids. Overspray may also occur due to coating material drops flowing off laterally from the workpiece surfaces. Overspray absorption is thereby the property of an applied coating material to absorb material from an overspray such that the desired smooth surface of the film or coating is retained.
After application of the coating material film or the coating material layer, a very fast drying or curing is desired for the coating. Forced drying at increased temperature is generally not possible for large components, as correspondingly large ovens would be required for this. Therefore, fast drying at room temperature is particularly desirable primarily for coating or painting very large components.
Binder systems cross-linking in a Michael addition, designated in the following as RMA systems, are known from EP 2374836 A1 and have a favourable ratio of pot life to drying time. The described binder systems show short drying times with long pot lives even at room temperature. Reference is thus specifically made to EP 2374836 A1 as a part of the description. The disadvantage of the known RMA systems is that the coating materials and coatings produced therefrom do not show the necessary and conventional properties.
It is therefore the object of the present invention to provide improved coating materials, coatings, and coating systems based on RMA systems which are particularly suitable for coating large components like chassis parts and tools of agricultural and construction machinery.
This problem is solved by coating materials for producing a coating according to the main claim. Additional embodiments are disclosed in the independent claims and subclaims, and in the description.
The coating materials according to the invention comprise an RMA system which has one or more CH acidic compounds A, one or more vinylogous carbonyl compounds B, and one or more catalysts C. In addition, they contain at least one or more light stabilizers, one or more pot life extenders, one or more open time extenders, one or more inorganic and/or organic pigments, and one or more corrosion protection agents.
In the following, the expression light stabilizer is understood to refer to additives and adjuvants that protect coatings from the influence of UV light, in particular prevent or at least significantly delay polymer degradation caused by UV radiation. The expression pot life extenders are understood to refer to additives and adjuvants which, as components of the ready to be used mixed coating material, delay the curing of the coating material prior to application. They evaporate during application so that the curing of the applied coating material is not affected, in particular, is not extended. The expression open time extenders is understood to refer to additives and adjuvants which also remain in the coating material even after application and delay curing for the coating. The expression corrosion protection agent is understood to refer to additives and adjuvants which prevent or at least delay corrosion of the metal at the interface of the metal substrate and the coating.
The coating materials according to the invention contain at least
wherein the indicated amounts respectively relate to the total amount of the coating material.
According to the invention, the compounds A and B are used in a molar ratio A:B of 0.5:1 through 2:1, preferably of 0.75:1 through 1.6:1, particularly preferably of 0.9:1 through 1.3:1, especially preferably of 0.95:1 through 1.1:1, wherein the molar amounts refer to the acidic protons of the compounds A and to the vinylogous carbonyl groups of the compounds B.
According to the invention, the catalysts C and compounds A are used in a molar ratio C:A of 0.8:1 through 2.5:1, particularly 1.1:1 through 1.9:1, particularly preferably 1.3:1 through 1.7:1, wherein the molar amounts refer to the cation X+of catalyst C and the acidic protons of the compounds A.
Suitable CH acidic compounds A are compounds with the general Formula I
Furthermore, the —C(═O)—Y and/or —C(═O)—Y′ groups from Formula I may be replaced by CN— or aryl groups.
According to the invention, malonic acid esters, acetoacetic acid esters, or mixtures thereof are preferably used. Malonic acid esters are particularly preferred with oligomer and polymer substituents, for example, based on polyesters, polyurethanes, polyacrylates, epoxy resins, polyamides, or polycarbonates. Malonic acid esters are particularly preferred with oligomer and polymer substituents based on polyesters, polyurethanes, and/or polycarbonates. The acetoacetic acid esters used preferably contain oligomer and polymer substituents, for example, based on polyalcohols, polyvinyl alcohols, epoxy resins, hydroxy-functional polyethers, polyesters, or polyacrylates. Acetoacetic acid esters are particularly preferred with oligomer and polymer substituents based on polyesters and/or polyacrylates. Compounds are more particularly preferred selected from the group containing malonic acid esters with oligomer and polymer substituents based on polyesters, which are obtained from the reaction of at least malonic acid, malonic acid dimethyl ester, and/or malonic acid diethyl ester with hexahydrophthalic acid and/or its anhydride and neopentyl glycol, and acetoacetic acid esters with oligomer and polymer substituents based on polyesters, which are obtained from the reaction of at least acetoacetic acid, acetoacetic acid methyl ester, and/or acetoacetic acid ethyl ester with hexahydrophthalic acid and/or its anhydride and neopentyl glycol.
Suitable vinylogous carbonyl compounds B are, for example, acrylates and/or maleates, in particular unsaturated acryloyl-functional compounds. According to the invention, acrylesters are preferred that are made from compounds containing 1 through 20 carbon atoms and at least 2, preferably 2 through 6 hydroxyl groups. According to the invention, polyesters are additionally preferred that are obtained from reacting maleic acid, fumaric acid, and/or itaconic acid, or anhydrides thereof with di- or polyvalent hydroxyl compounds which may contain a monovalent hydroxyl- or carboxyl compound. Resins are additionally preferred, like polyesters, polyurethanes, polyethers, and/or alkyd resins which correspondingly contain activated unsaturated groups, for example, urethane acrylates, polyether acrylates, polyfunctional polyacrylates, polyalkylmaleates, and polyacrylates that are obtained from the reaction of acrylic acid with epoxy resins. According to the invention, butanediol diacrylate, hexanediol diacrylate, trimethylolpropane triacrylate, entaerythritol tetraacrylate, di (trimethylolpropane) tetraacrylate, dipentaerythritol hexaacrylate, dipropylene glycol diacrylate, and tripropylene glycol diacrylate are particularly preferred.
Suitable latent-basic compounds for the catalysts C are, for example, substituted carboxylic acid salts of Formula II:
According to the invention, R is preferably an alkyl group or an aralkyl group, particularly preferably an alkyl group with 1 through 4 carbon atoms. The carbonate group and the cation X+ may also additionally be present on a molecule with the corresponding structure. Furthermore, R′ is preferably an alkyl group, particularly preferably an alkyl group with 1 through 4 carbon atoms, particularly preferably with 3 through 4 carbon atoms. According to the invention, ammonium and/or phosphonium carbonate are preferably used. Suitable ammonium carbonates are, for example, tetrahexylammonium methyl carbonate, tetrahexylammonium hydrogen carbonate, tetradecanyl trihexylammonium methyl carbonate, tetradecylammonium methyl carbonate, tetrabutylammonium methyl carbonate, tetrabutylammonium ethyl carbonate, tetrabutylammonium hydrogen carbonate, tetrapropylammonium methyl carbonate, tetrapropylammonium ethyl carbonate, tetrapropylammonium hydrogen carbonate, benzyltrimethylammonium methyl carbonate, trihexylmethylammonium methyl carbonate, or trioctylmethylammonium methyl carbonate. Tetrabutylammonium methyl carbonate, tetrabutylammonium ethyl carbonate, tetrabutylammonium hydrogen carbonate, tetrapropylammonium methyl carbonate, tetrapropylammonium ethyl carbonate, tetrapropylammonium hydrogen carbonate, and mixtures thereof are particularly preferably used.
Suitable light stabilizers are radical scavengers like sterically inhibited aliphatic amines, e.g., based on substituted 2,2,6,6-tetramethylpiperidines, UV absorbers like 2-hydroxyphenyl benzotriazoles, 2-hydroxybenzophenones, 2-hydroxyphenyltriazines, or oxalanilides, and quenchers like organic nickel compounds and peroxide decomposers like thioethers or phosphites. Radical scavengers, for example, sterically inhibited aliphatic amines based on substituted 2,2,6,6-tetramethylpiperidines, and/or UV absorbers, for example, 2-hydroxyphenyl benzotriazoles, 2-hydroxybenzophenones, 2-hydroxyphenyltriazines, and oxalanilides are preferably used. Substituted 2,2,6,6-tetramethylpiperidines, 2-hydroxyphenyltriazines, 2-hydroxybenzophenones, and mixtures thereof are particularly preferably used.
Suitable pot life extenders are short-chain alcohols which have an evaporation number below 35, preferably below 20. Alcohols are particularly suited which have up to 6, preferably up to 4, particularly up to 3 carbon atoms. Thus, for example, methanol, ethanol, n-propanol, i-propanol, n-butanol, i-butanol, and mixtures thereof may be used according to the invention.
Suitable open time extenders are basic NH-functional compounds with a pKa value between 4 and 14. Succinimides, 1,2,4,-triazoles, 1,2,3,-benzotriazoles, 5,5-diphenylhydantoins, hydantoins, (RS)-3-ethyl-3-methylpyrrolidine-2,5-dione, and mixtures thereof are preferred. Succinimides, 1,2,4,-triazoles, 1,2,3,-benzotriazoles, and mixtures thereof are particularly preferred.
Suitable inorganic pigments are, for example, titanium dioxide, iron oxides, chromium oxides, chromium titanates, bismuth vanadate, cobalt blue, and carbon blacks. Titanium dioxide, iron oxides, and carbon blacks are preferred inorganic pigments. Suitable organic pigments are, for example, pigment yellow 151, pigment yellow 213, pigment yellow 83, pigment orange 67, pigment orange 62, pigment orange 36, pigment red 170, pigment violet 19, pigment violet 23, pigment blue 15:3, pigment blue 15:6, pigment green 7. Preferred pigments are pigment yellow 151, pigment orange 67, pigment red 170, pigment violet 19, pigment blue 15:3, pigment green 7.
Suitable corrosion protection agents are tannin derivatives, basic sulfonates, nitrocarboxylates, like aminocarboxylate, and zinc salts of organic nitric acids, like zinc-nitroisophthalate, or zinc salts of cyanuric acid. Additional suitable corrosion protection agents are anti-corrosive pigments, like iron mica, aluminium pigments, or talc, and active pigments which cause electrochemical passivation of the metal surface, like phosphates, borates, silicates, molybdates, or chromates. According to the invention, active pigments, for example, phosphates with zinc-, aluminium-, magnesium-, zirconium-, and strontium cations, and hybrid forms thereof, are preferred. Aluminium magnesium phosphates, aluminium zinc phosphates, and aluminium strontium phosphates are particularly preferred.
In another embodiment of the present invention, additional additives and adjuvants may be added to the coating materials, like dispersing additives, fillers, and/or matting agents, in order to improve the required properties of the coating material and/or of the coating.
The coating materials according to the invention may thereby contain up to 25, preferably 0.00001 through 8, particularly preferably 0.00001 through 5 wt. % dispersing additives, wherein the indicated amounts respectively relate to the total amount of coating material. Suitable dispersing agents are, for example, high molecular weight block copolymers with pigment affinic groups, highly branched polyester or acrylate polyester copolymers with pigment affinic groups. Preferably used dispersing additives are high molecular weight block copolymers with pigment affinic groups.
The coating materials according to the invention may additionally contain up to 60, preferably 0.00001 through 40, particularly preferably 10 through 30 wt. % fillers, wherein the indicated amounts respectively relate to the total amount of the coating material. Suitable fillers are, for example, carbonates like chalk, limestone, calcite, precipitated calcium carbonate, dolomite or barium carbonate, sulphates like barite, barium sulphate, or calcium sulphate, fibres from melts of glass or basalts, glass powder, glass beads, and slags. The preferred fillers used are barium sulphate and/or calcium carbonate.
The coating materials according to the invention may additionally contain up to 30, preferably 0.00001 through 20, particularly preferably 0.00001 through 10 wt. % matting agents, wherein the indicated amounts respectively relate to the total amount of the coating material. The expression matting agent is understood to refer to additives and adjuvants that reduce the gloss of a coating or generate a matte gloss. Matting agents generate the surface structure necessary for this in the coating without affecting other features and properties. Suitable matting agents are, for example, micronized amorphous silicas, like silica gels or precipitated silicas, micronized and precipitated waxes, like polyethylene waxes, polypropylene waxes, polyamide waxes, or PTFE waxes, and also micronized polymers, like urea aldehyde resin. Preferred matting agents used are micronized and precipitated polyethylene waxes, polypropylene waxes, polyamide waxes, PTFE waxes, and micronized urea aldehyde resin.
In another embodiment according to the invention, the coating materials contain up to 50, preferably 0.00001 through 30, particularly preferably 0.00001 through 20 wt. % aprotic solvents, wherein the indicated amounts respectively relate to the total amount of the coating material. The expression aprotic solvents is understood in the following to refer to solvents that contain no ionisable protons in the molecule. Suitable aprotic solvents are, for example, aliphatic hydrocarbons, cycloaliphatic hydrocarbons, aromatic hydrocarbons, ketones, esters, ethers, ether esters, in particular, ethylacetate, butyl acetate, acetone, n-butanone, methyl isobutyl ketone, methoxypropyl acetate, and dimethyl sulfoxide. Preferably used solvents are ethylacetate, butyl acetate, acetone, n-butanone, methyl isobutyl ketone, methoxypropyl acetate, and mixtures thereof.
The compounds used as catalysts C according to the invention are latent bases, as the carbonate according to Formula II is in equilibrium with its disassociation products, carbon dioxide and the corresponding hydroxide- or alkoxy base. As long as carbon monoxide may not escape from the system, the equilibrium lies more strongly in favour of the carbonate. Only when a carbon dioxide is removed, and thus a sufficient amount of base is present, does the cross-linking begin with the aid of the Michael addition. During storage of the coating materials according to the invention in closed containers, from which carbon dioxide may not escape, the coating material according to the invention may be basically formulated as a single component system. The shelf life may, however, be increased if the individual components of the coating material according to the invention are formulated in multicomponent systems. Thus, for example, a catalyst component, which contains the catalysts C, is only mixed shortly before processing with the binder components, which contain the CH acidic compounds A and the vinylogous carbonyl compounds B.
According to the invention, the CH acidic compounds A and the vinylogous carbonyl compounds B may be contained in a binder component together with the light stabilizers, open time extenders, and pot life extenders used. This binder component may additionally contain pigments, fillers, corrosion protection agents, and additionally other additives like solvents. The catalysts C and, if necessary, other solvents and pot life extenders may be contained in a catalyst component. In one preferred embodiment, the CH acidic compounds A may be present in a first binder component, the vinylogous carbonyl compounds B in a second binder component, and the catalysts C in a catalyst component. In one such three-component system, the CH acidic compounds A are contained in the first binder component, together with the open time extenders and light stabilizers. If necessary, this first binder component may additionally contain pigments, fillers, and corrosion protection agents, and additional additives. The vinylogous carbonyl compounds B are preferably contained in the second binder component. Furthermore, the second binder component may also contain pigments, fillers, corrosion protection agents, and additional additives. The catalysts C are contained in the catalyst component. Furthermore, the catalyst component may contain solvents and pot life extenders.
It is known that the addition of additional components, which are customary for producing a coating, reduces the shelf life of RMA systems. The coating materials according to the invention with their particular selection of light stabilizers, open time extenders, pot life extenders, pigments, corrosion protection agents, dispersing agents, functional fillers, matting agents, and aprotic solvents have an unexpectedly high shelf life in comparison to previously known coating materials based on RMA systems.
Furthermore, the properties of coatings, which are produced from coating materials based on RMA systems, are strongly compromised by the presence of other components of the coating material, in contrast to coatings which are produced from coating materials based on conventional binders, for example, epoxy resins or polyurethanes. It has been surprisingly demonstrated that the coating materials according to the invention result in coatings which have properties necessary for use for components of construction and agricultural machinery, in particular mechanical stabilities, even at high coating thicknesses, and corrosion resistance.
In one particularly preferred embodiment, the coating materials according to the invention contain at least:
wherein the indicated amounts respectively relate to the total amount of the coating material.
The coating materials according to the invention have a surprisingly higher shelf life in comparison to previously known RMA coating materials and RMA coatings. They also show improved drying behaviour. Coatings obtained from the coating materials according to the invention additionally have an improved light stability, in particular less yellowing and higher gloss retention.
The coating materials according to the invention have pot lives greater than or equal to 1 hour, preferably greater than or equal to 2 hours, particularly preferably between 2 and 4 hours. The pot life is generally determined via the flow time from a flow cup. The end of the pot life is determined as the point at which the flow time shows double the value of the starting flow time. The testing method is described below in detail in the Examples. Furthermore, the coating materials according to the invention demonstrate open times of greater than or equal to 15 minutes, preferably greater than or equal to 20 minutes, particularly preferably greater than or equal to 25 minutes. In addition to the long pot lives and open times, the coating materials according to the invention surprisingly demonstrate an unusually broad climate window in which they may be processed without deterioration. They are processable, for example, at temperatures up to 45° C. and at relative air humidity of up to 99%. In addition, they demonstrate a long overspray absorption, for example, over a time interval of more than 25 minutes.
In contrast to conventionally used coating materials based on polyurethane, the coating materials according to the invention have significantly reduced drying times. In one preferred embodiment, the coating materials according to the invention are used to produce a coating on substrates, for example, metals, plastic materials, or fibre composite materials. Metals are particularly suited, for example, steels and iron alloys, aluminium, and aluminium alloys. The component surfaces to be coated may be provided with a primer, for example, the conventional primers known to the person skilled in the art based on epoxy resins or polyurethanes. Furthermore, they may be pre-treated as is conventional and familiar to the person skilled in the art. Preferred pre-treatments are iron phosphating, zinc phosphating, conversion layers based on manganese, zirconium, or silicon compounds, sand blasting, galvanizing, or electro-dip priming. Particularly preferred pre-treatments are conversion layers based on manganese, zirconium, or silicon compounds. The coatings according to the invention also demonstrate a good adhesion to pre-treated substrates. They additionally have a high anti-corrosion effect.
The coatings according to the invention also demonstrate optically flawless surfaces even at high coating thicknesses. They may have dry coating thicknesses between 80 and 150 μm. The application of the coating materials according to the invention may be carried out within a large coating thickness interval without compromising the surface quality of the coating. The coating materials according to the invention and coatings are thus less sensitive with respect to overlayer thicknesses, which may occur during the application, e.g., due to an unfavourable geometry of the substrate.
Due to their properties, the coating materials according to the invention may be used in particular for the production of single-layer lacquers. They are additionally suited for use for coating large components, in particular for coating large area components made of metal, for example, chassis for construction and agricultural machinery.
The present invention also relates to a method for coating components. The method according to the invention thereby comprises the steps: (a) applying the coating material according to the invention to a surface of a substrate, and (b) curing the applied coating material for 0.5 through 12, preferably 0.5 through 6, particularly preferably 0.5 through 4 hours at temperatures between 5 and 50, preferably 15 and 40, particularly preferably 20 and 35° C.
The coating materials according to the invention have an above-average solids content and correspondingly contain low proportions of volatile organic substances, for example, solvents. The solids content is defined as the proportion by mass of a coating material that remains as residue after 30 minutes during evaporation at 105° C. Essentially, the solids generally comprise binders, non-volatile additives, pigments, and fillers. The solids content of the coating materials according to the invention lie between 65 and 95, preferably 70 and 90, particularly preferably between 75 and 85 wt. %, relative to the total weight of the coating materials.
Conventionally, rough and matte surfaces are obtained using conventional spraying methods in the case of processing of coating materials with high solids content. In contrast, the coating materials according to the invention also yield surprising high-quality surfaces even during an application by means of hydraulic very high pressure spraying (airless), airless spraying with air support (airmix), and pneumatic spraying or compressed air spraying. All spraying methods may thereby be used, including electrostatically supported.
In another embodiment of the method, all components of the coating material used are mixed prior to application. The mixing may thereby be carried out manually or by machine.
As the coating materials according to the invention may be cured at room temperature, they are primarily suited for coating large components, as they are used, for example, to build agricultural and construction machinery. They may, for example, be used for coating chassis parts, roofs, doors, chassis cladding, lattice masts, jibs, grippers, blades, cutters, or ploughshares.
The production of the coating materials is carried out according to coating technology standards, which are known and familiar to the person skilled in the art. The catalyst solution used in Example Recipe 1 is produced in that 42.8 g diethyl carbonate and 26.1 g i-propanol are added to a solution of 17.1 g tetra butyl ammonium hydroxide in 14 g water.
To evaluate the shelf life of the coating materials, the pot life and the drying time of Example Recipe 1 were determined. Samples were thereby tested or used to produce a coating after 1 day of storage at 23° C., after 28 days of storage at 40° C., and after 1 year of storage at 20 through 23° C. respectively.
Determination of pot life: The pot life is determined using a flow cup. In this method, a liquid is filled into a cup with a defined volume, which has a defined nozzle in its bottom. The coating material runs out through the nozzle, wherein the time from the discharge of the liquid jet up until the liquid jet breaks off is measured as the flow time. All preparations and measurements are carried out at a temperature of 23° C. Initially, all components of the coating material are mixed and the flow time of the mixture is immediately measured (initial flow time). The measurement is repeated at regular intervals. The end of the pot life is reached when the flow time is double the initial flow time.
Determination of drying time: To determine the drying time, a drying time recorder, a drying time measurement device from BYK Gardner, is used. For this purpose, the coating material to be examined is uniformly applied on glass strips with the aid of a film drawer. The glass strips are subsequently laid in a linear recorder. Needles are then applied to the coating and drawn across the drying film at a defined, constant speed. A characteristic drying image of the coating is thereby created, in which the individual time segments show the different curing states: flow or open time, initial trace, film tearing, and surface track. The curing of the coating material thereby begins at the end of the open time, i.e., at the point at which the track etched by the needle remains visible in the applied film. It ends with the surface track, i.e., at the time at which the needle no longer leaves a visible track in the applied film.
The quality of the coatings which are produced from the differently stored coating materials from Example Recipe 1 was also examined to determine shelf life of the coating material. Gloss and corrosion resistance were determined for this purpose. Samples were used to produce a coating after 1 day of storage at 23° C., after 28 days of storage at 40° C., and after 1 year of storage at 20 through 23° C. respectively. To produce the sample bodies, Example Recipe 1 was applied to treated steel plates using cup guns and cured at room temperature. As a pre-treatment, the steel plates were provided with a silane conversion layer.
Determination of surface gloss: The gloss of the coating surface is determined as a reflectometer value. The reflectometer value of a sample is defined as the ratio of the light beams reflected by the sample surface and a glass surface with a refractive index of 1,567 in the mirror direction. The measurement values are determined with the aid of a conventional refractometer at an angle of 60°.
Determination of corrosion resistance: Salt spray tests were carried out to evaluate the corrosion resistance. For this purpose, the coatings of the sample bodies were cut with cross shapes down to the metal surface. The sample bodies were subsequently exposed in a spray chamber to a salt spray mist made from a 5% salt solution with a pH value between 6.5 and 7.2 over a time period of 500 hours at 35±2° C. Afterwards, the sample bodies were rinsed with clear water and subsequently conditioned at room temperature for 1 hour. The damage from infiltration is evaluated. For this purpose, the loose parts of the coating are carefully removed at the cuts. In each case, the broadest area of delamination is determined and indicated in millimetres.
As the table shows, the coating materials according to the invention have a high shelf life. After longer storage at increased temperatures, the coating materials themselves do not demonstrate a deterioration in their processability. The coatings produced therefrom also show no impairment to their properties.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2015 105 983.5 | Apr 2015 | DE | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/DE2016/000165 | 4/20/2016 | WO | 00 |
