MXPA99003743A - Aqueous coating system containing uretan (meta) - acrylate-isocyanates showing isocyanate groups and enduring by - Google Patents

Abstract

The invention relates to an aqueous coating system with which machinable and dried surfaces are produced by hardening the components containing groups (meta-acryloyl) The desired properties of the coatings obtained with it are achieved by crosslinking The components containing NCO groups with components containing active hydrogen The binder component shows both (meta) acryloyl groups and also free NCO groups and the coating obtained with the sample after curing provides sufficient strength even in unlit or poorly illuminated spots. The invention also relates to the use of these coating systems

Description

Aqueous coating system contains urethane (meta) - acrylate isocyanates and shows isocyanate groups and is UV hardened.

DESCRIPTION OF THE INVENTION: The invention relates to an aqueous coating system with which manipulated and dried surfaces are produced by means of UV curing of the components containing (meta) acryloyl groups. The desired properties of the coatings obtained therefrom are achieved by crosslinking the components containing NCO groups with components containing active hydrogen. The binder component shows both (meta) acryloyl groups and also free NCO groups. The coating obtained therefrom shows after curing a sufficient strength even in unlit or badly illuminated spots. The invention also relates to the use of these coating systems. The hardening of the coating systems showing (meta) acryloyl groups by means of radical polymerization initiated by UV is known and is technically established. It is one of the fastest hardening methods in coating technology. UV hardening lacquers, however, show disadvantages from all points of view, such as high volume shrinkage during curing, which can lead to adhesion problems. The high density of crosslinking inherent in the system leads to fragility, lack of REF: 30145 elasticity and lack of resistance to shock. In addition, the hardening of the coating systems showing UV-hardening (meta) acryloyl groups is linked to the availability of a sufficient irradiation dose of the corresponding wavelength. The poorly lit areas harden only on a small scale, which leads to sensible losses in surface resistance, and the unlit areas do not harden at all. Coatings based on aqueous binders containing active hydrogen atoms, preferably polyols and polyisocyanates are known (for example from EP-A 358 979) 'The technical properties of the coatings, such as adhesion, elasticity, strength Shock and stability against atmospheric agents can be varied over a wide range by means of the extensive selection of the members of the reaction. The hardening of the corresponding two-component polyurethane-based aqueous systems requires, however, compared to systems that harden by irradiation, a long period of time and preferably high temperatures. But they do not require UV light. Also known in the field of solvent-based lacquers are the combinations of the two types of hardening by UV irradiation and cross-linking of polyurethane, such as so-called systems (dual curing). A) Yes US Pat. No. 4,342,793 discloses curable resin compositions containing an irradiatable hardenable reactive diluent which are esters of low molecular mass of acrylic acid, a saturated polyol and a polyisocyanate. Hardening occurs by irradiation to polymerize the reactive diluent and then by thermal hardening for the formation of a polyurethane from the polyol and the polyisocyanate. The disadvantage of systems of this type is that the solvent content and thus the emission are relatively high. In addition, in the case of unfavorable irradiation, unreacted reactive diluent may remain in the hardened lacquer film. This can lead to problems, for example in case of contact of the skin with the lacquer film. In addition, the properties of the lacquer film, such as hardness and physical and chemical resistance, can be negatively influenced. The problem of the present invention then consists in making available a coating system based on aqueous binders and, by means of a UV curing, allowing a quick handling of the lacquered pieces, as well as by cross-linking components with active hydrogen atoms and showing NCO groups, preferably polyols, makes an appropriate profile of properties adjustable to the application and on the other hand makes possible a sufficient hardening even in the areas not illuminated or badly illuminated. Surprisingly, it has been found that in coating systems, which are essentially composed of urethanes (meta) acrylates with (meth) acryloyl groups and free NCO groups, polyisocyanates and aqueous polyols after UV curing, that leads to dry and manipulable lacquer films, the cross-linking by means of the NCO reaction proceeds completely and leads to surfaces of high chemical and mechanical resistance. On the other hand, in the case of a poor lighting situation and a certain density of residual double bonds, the cross-linking through the reaction of the NCOs and with it a minimum level of indispensable resistance is guaranteed. This was all the more surprising since it had been assumed that the two reaction processes interfere with one another and the rapid polymerization initiated by UV "freezes" the slower NCO reaction, that is, the reaction of the NCO groups with components that contain active hydrogen, does not pass completely. The subject of the invention are coating systems with a) a urethane (meta) acrylate showing groups (meta) acryloyl and, where appropriate, free isocyanate groups, b) where appropriate another polyisocyanate c) a UV initiator initiating radical polymerization and d) one or more aqueous binders containing carbon atoms. active hydrogen The present two-component coating system is preferably manufactured, the component I) preferably containing the components ((a) plus (b)) and the second component II) the components ((c) + (d)). To achieve better properties for the coating technique, the components I and / or II can also contain e) a UV absorber with an absorption range up to 390 nm maximum and f) a HALS stabilizer, g) usual lacquer additives h) catalysts for the acceleration of the reaction of the NCO and j) inert co-solvents in the sense of crosslinking. Component I) and Component II) are combined in such a way that a ratio of NCO groups to reactive NCO groups is adjusted from 2 to 1 to 0.5 to 1, preferably from 1.5 to 1 to 0.8 to 1, especially preferred from 1.3 to 1 to 1 to 1- The compounds according to a) are obtained from mono-alcohols which show (meta) acryloyl groups and di- or polyisocyanates. The processes for the preparation of urethane (meta) acrylics are basically known and described (for example in DE-A 1 644 798, DE-A 2 115 373, DE-A 2 737 406). For urethan (meta) acrylates according to the invention, the ratio of NCO groups to OH groups is preferably from 1 to 0.2 to 1 to 1, preferably from 1 to 0.2 to 1 to 0.8 equiv. , especially preferred from 1 to 0.3 to 1 to 0.6 equiv. Among the mono-alcohols that show (meta) acryloyl groups, it is necessary to understand both the esters of acrylic or meta-acrylic acid showing a free hydroxyl group, with di-alcohols such as for example 2-hydroxyethyl-, 2-or 3-hydroxypropyl - or 2-, 3-, or 4- hydroxybutyl- (meta) acrylate as well as the mixtures that are desired from compounds of this type. Furthermore, monoalcohols are also contemplated which show (meta) acryloyl groups or transformation products consisting essentially of alcohols of this type, which are obtained by means of esterification of n-functional alcohols with (meta) acrylic acid, and can be used as alcohols also mixtures of different alcohols so that n means a whole or fractional number as a statistical average, of more than 2 to 4 and preferably 3, and used per mole of the mentioned alcohols of (n -0.8) up to (n - 1,2), preferably (n - 1) moles of (meta) acrylic acid. Examples of these compounds or product mixtures are the conversion products of i) glycerin, trimethylolpropane and / or pentaerythritol, low molecular weight alkoxylation products of alcohols of this type, such as, for example, ethoxylated or propoxylated trimethylolpropane. as, for example, the addition product of ethylene to trimethylolpropane oxide of an OH number of 550 or of the desired mixtures of this type of at least trifunctional alcohols with dialcohols such as for example ethylene glycol or propylene glycol with ii) (meta) acrylic acid in said molar ratio. These compounds have an average molecular weight Mn of 116 to 1000, preferably of 116 to 750, and particularly preferably of 116 to 158. In order to obtain the urethane (meta) acrylates a) according to the invention, basically all the diols are suitable. or polyisocyanates, such as bute thiocyanate hexamethylene diisocyanate (HDI), l-isocyanato-3, 3, 5-trimethyl-5-isocyanatomethyl-cyclohexane (IPDI) and / or bis (isocyanatocyclohexyl) -methane or other aliphatic diisocyanates or mixtures of these diisocyanates or "lacquer polyisocyanates" based on these diisocyanates. The term "lacquer polyisocyanates" based on these diisocyanates is to be understood as the derivatives of these diisocyanates which contain known biuret, urethane, uretdione and / or isocyanurate groups. The processes for obtaining "lacquer polyisocyanates" of this type are described, for example, in US Pat. No. 3,124. 605, 3 358 010, 3 903 126, 3 903 127, 3 975 622 or 4 324 879.

It is also possible to use aromatic polyisocyanates, for example "lacquer polyisocyanates" based on 2,4-diisocyanato-toluene or their technical mixtures with 2,6-diisocyanato-toluene or based on 4,4'-diisocyanato-diphenyl- methane or its mixtures with its isomers and / or its higher homologs. Of course, it is also basically possible to use the desired mixtures of the polyisocyanates mentioned by way of example. In order to make possible a better incorporation of the urethan (meta) acrylates a) to the aqueous binders d), hydrophilized polyisocyanates can also be used, either alone or in a mixture with the non-hydrophilized polyisocyanates described above. The hydrophilization can be carried out, for example, cationically, anionically or non-ionically, by means of internal or external emulsifiers such as polyethers. Polyisocyanates of this type are described, for example, in the documents of patents EP-A 443 138, EP-A 469 389, EP-A 486 881, EP-A 510 438, EP-A 540 985, EP-A 645 410, EP-A 697 424 or EP-A 728 785. The described addition reaction can be accelerated in a manner known per se by means of suitable catalysts, such as, for example, tin octoate, dibutyltin dilaurate or tertiary amines. It is possible to stabilize the resulting urethane (meta) acrylate, which optionally contains free NCO groups, against premature polymerization by means of the addition of suitable inhibitors, such as, for example, phenols, hydroquinones, and quinones, for example. 2, 5-diterc-butylquinone. These inhibitors are added in amounts of in each case 0.001 to 0.3% by weight during or in connection with manufacturing. The products a) can be obtained, where appropriate, in inert solvents in the sense of manufacture and subsequent application, which can be considered as cosolvents i). As other polyisocyanates as said component b) to be used where appropriate, all polyisocyanates which can be used also for obtaining the urethane (meta) acrylates can be used. Preferred are hydrophilicized or non-hydrophilic aliphatic "lacquer polyisocyanates" based on HDI, IPDI or bis (isocyanato-cyclohexyl) urethane or mixtures of these "lacquer polyisocyanates". For the reduction of the viscosity, the component I may optionally additionally contain reactive diluents curable by irradiation as esters of the acrylic acid of low molecular mass. The ratio of the (meta) acryloyl groups of components a) to the sum of the free isocyanate groups of components a) and b) is between 0.2 to 5.0 equiv. and 5 to 0.2 equiv., preferably between 0.5 to 2.0 equiv. and 2.0 to 0.5 equiv. The UV initiators corresponding to ac) can be 2-hydroxy in 1-ketones such as for example 1-hydroxycyclohexylphenyl ketone, benzylacetals such as benzyldimethylacetal, acylphosphine oxides such as, for example, bis (2-4) oxide. 6-trimethylbenzoyl) -phenylphosphine, benzophenone and its derivatives or mixtures of the different types of UV initiators. As component d), all the aqueous resin dispersions customary in two-component polyurethane coating technology can also be used. Resins of this type and the process for obtaining these resins are known from the literature. Thus, the resins can be constructed, for example, from the class of polyesters, polyacrylates, polyurethanes, polyureas, polycarbonates or polyethers. It is also possible to use hybrid dispersions at will or mixtures of different dispersions ad libitum. In general, the resins have hydroxy or amino functionality. But also in exceptional cases it is possible to use non-functional dispersions as a binder component. It is also possible, but not preferred, the use of resin dispersions which together with the hydroxy- and amino functions additionally contain unsaturated functions, suitable for UV curing. For the weathering stability of the hardened lacquer coating, a UV absorber e) can be added with an absorption range up to 390 nm maximum and a HALS stabilizer. Suitable UV absorbers of the triphenyltriazine type, for example Tinuvin® 400 (Ciba) or of the oxalic acid dianilide type, for example, Sanduvor "3206 (Clariant).

UV absorbers are preferably added in amounts of. in each case 0.5 to 3.5% based on the solid binder. Suitable HALS stabilizers f) are the commercially available types such as Tinuvin® 292 or Tinuvin® 123 (Ciba) or Sanduvor® 3058 (Clariant). These HALS stabilizers are preferably added in amounts of 0.5% to 2.5% based on the solid binder. Examples of lacquer additives g) include leveling agents, air removal agents, defoamers, thickeners and thixotropic agents. In given cases, catalysts h) can also be added for the acceleration of the crosslinking reaction of the polyurethane. All known catalysts of two-component polyurethane technology are suitable, such as, for example, tin octoate, dibutyltin-dilaurate or tertiary amines. The hardener component I shows at 23 ° C in general a viscosity of 50 to 10,000, preferably 50 to 2000 mPas (D = 40). If required, the polyisocyanates can be mixed with small amounts of inert solvents to lower the viscosity to a value within the aforementioned ranges. The amount of such solvents is, however, at most, such that in the coating compositions according to the invention finally obtained, a maximum of 20% by weight appears, preferably 10% by weight, of solvent, also entering into the calculations the solvent still existing in the case of the resin dispersions d). Suitable solvents are, for example, aliphatic or aromatic hydrocarbons, such as xylene, toluene, solvent naphtha or for example N-methyl-pyrrolidone, diethylene glycol dimethyl ether, acetone, methyl ethyl ketone, methyl isobutyl ketone, ethyl acetate, butyl acetate, methoxypropyl acetate. or mixtures of these or other inert solvents. To obtain the aqueous binder combination, the hardening component I is emulsified in the aqueous resin component II. At the same time, the required processing viscosity is adjusted. In many cases simple emulsification techniques are sufficient, for example with a mechanical stirrer or often also a simple mixture of the two components by hand to achieve coatings with very good properties. However, it is also possible to use mixing techniques with higher shear energy, such as, for example, jet dispersion, as described in Farbe & Lack, 102/3, 1996, p. 88-100. The coating can be obtained by the most different projection methods, such as, for example, pressurized, airless or electrostatic spray processes using one or two component projection equipment, but also by means of brush application, roller , cylinders or squeegee.

The drying and hardening of the coating is preferably carried out by means of 1. Removal of the air from the water and, where appropriate, of the co-solvents added at room temperature or, where appropriate, at a higher temperature, preferably at 100 ° C. 2. UV curing, the mercury irradiators of high or medium pressure usual in the market are suitable. These irradiators can be provided with other elements and preferably show a power of 80 to 240 w / cm of lamp length. 3. Subsequent crosslinking of the NCO-containing components with the ingredients containing active hydrogen atoms. This can be carried out at room temperature or forced at a higher temperature, advantageously up to 150 ° C at the most. The invention also relates to the use of coating systems for obtaining coatings on substrates and more different materials, such as wood, metals, plastics, etc. Preferably, the coating systems for the coating of body parts are used. Examples All data in% refer to weight. The viscosity measurements were made in a cone and plate viscometer according to DIN 53019 to D = 40. The mentioned commercial names are even when not expressly indicated, registered trademarks. Binders used containing active hydrogen atoms Binder A Aqueous dispersion of polyacrylate, free of cosolvent based on methyl methacrylate, butylacrylate, butyl methacrylate, styrene, hydroxypropyl methacrylate and acrylic acid, di-tert-butyl peroxide as initiator and dimethylethanolamine as a neutralizing agent. The solids content is around 50% for a viscosity of about 500 mPa.s (23 ° C, D = 40). The acid number is about 12 mg of KOH / g of substance, the content of OH 2.2%, the pH approx. 7.9. Binder B Aqueous dispersion of urethane-modified polyester, free of co-solvent based on trimethylolpropane, neopentyl glycol, 1,6-hexanediol, cyclohexanedimethanol-1,4-hexahydrophthalic acid anhydride, adipic acid, dimethylolpropionic acid and isophorone diisocyanate as well as dimethylethanolamine as a neutralizing agent . The solids content is around 42% for a viscosity of about 1000 mPa. s (23 ° C, D = 40). The acid number is about 8 mg of KOH / g of substance, the content of OH 1.5%, the pH approx. 8.4 Obtaining urethan (meta) acrylates according to the invention Example 1 In a tank with stirring, equipped with element thermal, drip regulator, reflux condenser, gas supply and gas evacuation, 1268.7 g of an HDI isocyanurate with 23% NCO content, 0.96 g of dibutyltin dilaurate and 1.92 g are dosed. of 2,6-di-tert-butylcresone. Three times the volume of the tank, air per hour and six times the volume of the nitrogen tank per hour is passed under agitation. It is heated to 50 ° C and from 50 ° C, 266.8 g of hydroxyethyl acrylate are added dropwise in such a way that the temperature rises with the exothermic reaction to a maximum of 60 ° C. After the complete addition of the hydroxyethyl acrylate, duration of about 6 to 8 hours, stirring is continued for another hour at 60 ° C: A urethane-acrylate solution with an NCO content of 11.5 is produced Example 2 In a tank with stirring, equipped with a thermal element, drip regulator, reflux condenser, gas supply and gas evacuation, 1268.7 g of an HDI isocyanurate with 23% NCO content, 519 are dosed. 4 g of methoxypropyl acetate, 0.96 g of dibutyltin dilaurate and 1.92 g of 2,6-di-tert-butylcresol. Three times the volume of the air tank per hour and six times the volume of the nitrogen tank per hour are passed under agitation. It is heated to 50 ° C and from 50 ° C 806 g of hydroxyethyl acrylate are added dropwise in such a way that the temperature rises with the exothermic reaction to a maximum of 60 ° C.

After the complete addition of the hydroxyethyl acrylate, lasting about 6 to 8 hours, stirring is continued for a further hour at 60 ° C. A urethane acrylate solution without free NCO groups is produced. Obtaining, application and testing of coating systems. The NCO / OH ratio is l / l. Example 3 Component 2 132.6 parts of aqueous polyacrylate dispersion, 46% in water / solvent naphtha 100 / 2- butoxyethanol, neutralized with dimethylethanolamine 44, 6: 6, 5: 1, 6: 1, 5 with an OH content about 4.5% based on the solid resin (Bayhidrol® VP LS 2271, Bayer AG). 145.9 parts of aqueous dispersion of urethane-modified polyester, 42% in water / N-methylpyrrolidone, neutralized with dimethylethanolamine 54: 3: 1 with an OH content of about 3.8% based on the solid resin (Bayhydrol.RTM. VP LS 2231, Bayer AG). 65.4 parts of water Component 1 151.9 parts of urethane acrylate according to example 1 83.9 parts of solvent naphtha 100/2 -butoxyethanol 4/1 11.1 parts of Tinuvin® 1130 (Ciba), 50% in butyl diglycol acetate .5 parts of Tinuvin® 292 (Ciba), 50% in ethyl acetate. butyl diglycol 1.8 parts of BYK 345R (Byk) 1.8 parts of BYK 333R (Byk) in 25% water 3.5 parts of Irgacure 184R (Ciba) 50% in hexanediol diacrylate The two components are mixed in a homogeneous by means of a jet dispersion of nozzles according to DE-A 19510651 with a nozzle of 0.1 mm in diameter at 50 bar, and is applied with a commercially available spray gun on a hot plate. metal pre-coated with a two-component polyurethane lacquer, pigmented, so as to result in a film thickness of about 120 g / cm 2. The drying of the wet coating is carried out by means of 5 minutes of aeration at room temperature, 10 min. pre-drying at 80 ° C, followed by UV hardening (1 m / min band speed, 1 high pressure Hg irradiator of .80 / cm, 10 cm irradiation distance). At room temperature, the resulting hardness was tested according to Konig by means of pendulum damping, and resistance to solvents after 1 hour, 1 day and after 7 days. The results are shown in table 1. Example 4 Component 2: 129.7 parts binder A 144.5 parts binder B 91.6 parts water Component 1.- Same as component 2 of example 3, but instead of 83.9 parts of solvent naphtha 100/2-butoxyethanol 4 / 1, 63.7 parts of methoxypropyl acetate.

The mixing, application, drying, and testing of the lacquer is carried out as in example 3. Example 5 Component 2: 98.0 parts binder A 96.5 parts water Component 1: _72, 7 parts urethanocrylate of example 1 96.0 parts urethane acrylate Example 2 81.1 parts methoxypropyl acetate 6, 7 parts Sanduvor "3206 (Clariant) 80% in xylene 2, 7 parts BYKR 306 (Byk) 10, 9 parts Irgacure" 185 (Ciba) 50% in hexanediol diacrylate mixing, application, drying, and testing of the lacquer is carried out as in example 3. Example 6 (comparison) Component 2: 176.6 parts polyacrylate dispersion of example 3 194.3 parts dispersion of urethane-modified polyester of example 3 55.7 parts _water Component 1 110.3 parts VP LS 2025/1 demodor (Bayer) NCO content 23% 42, 9 parts solvent naphtha 100/2 -butoxyethanol 4 / 1 11, 1 part Tinuvin® 1130 (Ciba), 50% in butyl diglycol acetate 5,5 parts Tinuvin® 292 (Ciba) 50% in butyl diglycol acetate 1, 8 parts BYKR 345 (Byk) 1, 8 parts - BYKR 333 (Byk) The mixing, application, drying, and testing of the lacquer is carried out as in Example 3. Results Example 3 4 5 6 Amortig of pendulum "After 1 hour 31 30 104 6 After 24 hours 74 77 134 14 After 168 hours 129 128 146 85 Resist. to solvents 2) After 24 hours 2234 1134 0024 4455 After 168 hours 0023 0023 0003 1135 ? in s according to Konig) 5 minutes acting time of xylene / methoxypropyl acetate / ethyl acetate / acetone 0 = unchanged 5 = dissolved / destroyed It is noted that in relation to this date, the best method known to the applicant to carry out the aforementioned invention, is the conventional one for the manufacture of the objects or products to which it refers.

Claims (5)

2. Having described the invention as above, it is drafted as tm > The following items are included in the following lists: 1. Coating systems characterized by containing a) a urethane (meta) acrylate showing groups (meta) acryloyl and, where appropriate, free isocyanate groups, b) where appropriate another polyisocyanate, c) a UV initiator initiating radical polymerization and d) one or more aqueous binders containing one or more active hydrogen atoms. Urethane (meta) acrylate a) according to claim 1, obtained from mono-alcohols showing (meta) acryloyl groups and polyfunctional isocyanates, characterized in that the ratio of the NCO groups to the groups
3. OH is 1: 0.2 equiv. up to 1: 0.8 equiv. 3. Coating system according to claim 1, characterized in that the binder containing active hydrogen atoms is a polyol.
4. 4. Coating system according to claim 1, characterized in that the ratio of the (meta) acryloyl groups of component a) to the sum of the free isocyanate groups of components a) and b) is between 0.5: 2, 0 equiv. and 2.0: 0.5 equiv.
5. 5. Coating systems according to claim 1, characterized in that an absorbent is contained in UV with an absorption range up to 390 nm. Coating system according to claim 1, characterized in that an HALS amine is contained. Use of coating systems to obtain coatings. Use of coating systems for the lacquering of body parts.