Process for preparing temporary protective coatings

The invention relates to a method for the production of temporary Protective covers on the burnt - on outer varnish layer Motor vehicle painting. The protective coatings are used to protect the lacquer surface of Motor vehicles, in particular new vehicles, for example during Assembly, transport and storage. They can be used after As film-like film can easily be removed again.

Aqueous coating agents for the purpose of temporary protection of high quality Goods are known. For example, new motor vehicles will be used during Storage and transport with such protective lacquers. The Protective lacquers are easily removable from the object, for example By washing with appropriate cleaning solutions or leaving them Can be peeled off as a film, which is generally disposed of by incineration becomes. Temporary aqueous protective varnishes which can be peeled off in film form after use are known. These are, for example, aqueous coating compositions On the basis of copolymers containing comonomers, such as (meth) acrylonitrile Or (meth) acrylamide. After use the formed Coverings as a film are stripped off and burnt, leaving it to release Toxic gases. Further examples are aqueous coating compositions The basis of copolymers which contain comonomers with Amino acid transfer into anionic groups. The amines volatilize as the coating layers are dried.

WO 90 08 165 discloses aqueous protective lacquers which, after fulfillment Of their protective function as film-like film. Its field of application is the temporary protection of the most diverse Building parts before building-type pollution during construction work. The Aqueous protective lacquers contain a polymer dispersion as a binder, The acrylate resins, polyvinyl alcohol, ethene / vinyl acetate copolymers, and the like Copolymers of vinyl and acrylic monomers, each either alone or In any mixture. JP-A-57 121 067 relates to a coating agent for protecting Waterproof layers against the bleeding of tar. The Coating agent is based on ethylene / vinyl acetate copolymers and Acrylic resins. The object of the invention is to provide a method for Preparation of temporary protective coatings from aqueous film Removable coating agents for the protection and preservation of Motor vehicles. The coating compositions used should be as few as possible Volatile organic substances Requirements in the motor vehicle industry, namely Paint surface of new vehicles during assembly, transport and transport Storage against contamination, formation of water spots and etching, For example by acid rain.

The object is achieved by providing a method for Preparation of temporary protective coatings by application of an aqueous Coating agent on a substrate, characterized in that: An aqueous coating agent, which is used as a binder in the form of a binder aqueous polymer dispersions<sl><li>A) from 50 to 90% by weight of one or more thermoplastic copolymers At least one C 2 -C 4 -olefin and at least one vinyl ester By weight of a C 2 -C 11 -monocarboxylic acid, where olefin (s) and vinyl ester in the Weight ratio of 10: 90 to 40:60 and are common At least 80% by weight of the copolymer,</li><li>B) from 10 to 50% by weight of one or more thermoplastics (Meth) acrylic copolymers which are free from comonomers with nitrile- And amide groups and at least 50% by weight (Meth) acrylic esters of C1-C18 alcohols, and</li><li>C) from 0 to 30% by weight of one or more of A) and B) copolymers,</li></sl>The% by weight each being based on the resin solid body and on 100% by weight, and wherein the substrate used is a Burnt-on outer lacquer layer of a motor vehicle lacquer.

Component A) of the aqueous coating agent is one Aqueous polymer dispersion based on a thermoplastic copolymer At least one C 2 -C 4 -olefin and at least one vinyl ester of a C2-C11 monocarboxylic acid, wherein Olefin (s) and vinyl ester in a 10:90 to 40:60 weight ratio And together at least 80% by weight of the Thermoplastic copolymers. Examples of C 2 -C 4 -olefins Are ethene, propene, butene-1, butene-2, isobutene, preference being given to ethene. Examples of preferred vinyl esters are vinyl acetate, vinyl propionate And vinyl versatate, particularly preferred is vinyl acetate. Both Versatates which can be used are vinyl esters of the Versatic acids. Versatic acids are commercial products of the company Shell for strong Branched, saturated monocarboxylic acids with longer alkyl side chains And tertiary carboxyl groups. These are the Versatic acids To C-5 to C-11 alkanoic acids. Olefin (s) and vinyl ester are present in the Thermoplastic copolymers of component A) in a 10: 90 to 40 : 60 weight ratio, preferably the weight ratio From olefin (s) to vinyl ester (s) between 15: 85 and 30: 70 Copolymers can contain from 0 to 20% by weight of C 2 -C 4 -olefins and vinyl esters A C 2 -C 11 monocarboxylic acid different olefinically unsaturated Monomers in copolymerized form. Preferred are nitrile and Comonomers containing amide groups are excluded. Preference is also given Water-soluble comonomers and neutralization into ionic groups For example, comonomers having transferable groups (Meth) acrylic acid. If acidic comonomers are present in the copolymer Of component A) are contained, this is only slight Amount of the case corresponding to an acid number of the copolymer of the Component A) of, for example, below 10, preferably below 5 mg KOH / g. The amounts in a proportion of up to 20% by weight, If appropriate, comonomers besides the olefinic Unsaturated double bond no other functional group, such as For example epoxide groups, hydroxyl groups and alkoxysilane groups, on. In particular, such comonomers are avoided Due to their functionality (s) alone or in combination with Other comonomers to an internal crosslinking of the copolymer of the Component A) or to a crosslinking between the copolymer of the Component A), the (meth) acrylic copolymer of component B) and / or The copolymer of component C). (Meth) acrylic As also in the following, methacrylic and acrylic. Examples of im Copolymers of component A) Other functional groups besides the olefinically unsaturated Double bond are alkyl esters, such as fumaric acid dialkyl esters, Maleic acid dialkyl esters, for example with C 1 -C 6 -alkyl such as methyl, Ethyl, propyl, butyl, isopropyl, isobutyl, tertiary butyl or hexyl, Vinylaromatics, such as styrene, vinyltoluene, but in particular (Meth) acrylic acid esters of C1-C18 monoalcohols, such as, for example, Methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, Butyl (meth) acrylate, isopropyl (meth) acrylate, isobutyl (meth) acrylate, Tert-butyl (meth) acrylate, hexyl (meth) acrylate, cyclohexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, 3,5,5-trimethylhexyl (meth) acrylate, Dodecyl (meth) acrylate, hexadecyl (meth) acrylate, octadecyl (meth) acrylate, Lauryl (meth) acrylate, isobornyl (meth) acrylate. Preferred are the Copolymers of the aqueous polymer dispersion A) exclusively from C 2 -C 4 -olefin (s) And vinylester (s) of a C2-C11 monocarboxylic acid. Particular preference is given to ethene / vinyl acetate copolymers. The glass transition temperature, determined according to DIN 53 765, of the Thermoplastic copolymers of component A) is preferred Between 0 and 30 ° C, more preferably between 5 and 20 ° C. The Preparation of the aqueous polymer dispersion A) is preferably carried out Emulsion polymerization. Particularly preferred as component A) Preferred ethene / vinyl acetate emulsion copolymers are concerned For example, products which are commercially available (see Karsten, Lacquer raw material tables, Curt R. Vincentz Verlag, Hanover, 1992, 9. Edition, chapter 9.2.2, page 301).

For component B) of the aqueous coating composition used Is an aqueous polymer dispersion based on a Thermoplastic (meth) acrylic copolymers which do not contain any comonomers Nitrile and amide groups and which is at least 50% by weight (Meth) acrylic esters of Cl-C18 alcohols. examples for (Meth) acrylic acid esters of C1-C18 monoalcohols Methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, Butyl (meth) acrylate, isopropyl (meth) acrylate, isobutyl (meth) acrylate, Tert-butyl (meth) acrylate, hexyl (meth) acrylate, cyclohexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, 3,5,5-trimethylhexyl (meth) acrylate, Dodecyl (meth) acrylate, hexadecyl (meth) acrylate, octadecyl (meth) acrylate, Lauryl (meth) acrylate, isobornyl (meth) acrylate. The thermoplastic (Meth) acrylic copolymers of component B) can be from 0 to 50% by weight of (Meth) acrylic acid esters of C1-C18 alcohols, olefinic Unsaturated monomers in copolymerized form, wherein Nitrile and amide groups are excluded. Preference is also given to water-soluble comonomers and by neutralization Comonomers which can be converted into ionic groups, For example (meth) acrylic acid. If acid comonomers In the (meth) acrylic copolymer of component B), this is In a small quantity of the case, corresponding to an acid number (Meth) acrylic copolymers of component B) of, for example, less than 10, Preferably less than 5 mg KOH / g. They preferably have a proportion by weight Up to 50% by weight, if appropriate, of the comonomers present Olefinically unsaturated double bond no further functional Group such as epoxide groups, hydroxyl groups, and the like Alkoxysilane groups. In particular, such comonomers are used Which, owing to their functionality (s), can be used alone or in Combination with other comonomers to an internal networking of the (Meth) acrylic copolymers of component B) or to a crosslinking Between the (meth) acrylic copolymer of component B) and the (meth) Copolymers of component (s) A) and / or C). Examples For (meth) acrylic copolymers of component (B) Contained comonomers without further functional groups besides the Olefinically unsaturated double bond are alkyl esters such as Fumaric acid dialkyl esters, maleic acid dialkyl esters, for example with C 1 -C 6 -alkyl, Such as methyl, ethyl, propyl, butyl, isopropyl, isobutyl, Tertiary butyl, hexyl, vinylaromatics such as styrene, vinyltoluene or Vinyl esters of a C2-C11 monocarboxylic acid, such as vinyl acetate, vinyl propionate And versatic acid vinyl ester. Preference is given to the (meth) acrylic copolymers Of the aqueous polymer dispersion B) exclusively from (Meth) acrylic esters of Cl-C18 alcohols. The after Glass transition temperature of the thermoplastic (Meth) acrylic copolymers of component B) is between 0 and 30 ° C., Preferably between 5 and 20 ° C. The preparation of the aqueous (Meth) acrylic copolymer dispersion B) is preferably carried out Emulsion polymerization. The (meth) acrylic copolymer dispersions B) For example, products which are commercially available (cf. Karsten, Lackrohstofftabellen, Curt R. Vincentz Publisher, Hannover, 1992, 9th Edition, Chapter 13.6.1, page 363).

In the case of component C) of the aqueous coating composition used according to the invention It is polymer dispersions different from A) and B) With the same limitations with respect to the monomer selection As in the case of the copolymers of component A) and the (Meth) acrylic copolymers of component B), ie, monomers with nitrile and Amide groups are preferably excluded. Preference is also given Water-soluble monomers and by neutralization into ionic groups Monomers which can be converted, for example (Meth) acrylic acid. If acidic monomers in the copolymer Of component C) are present, this is only a small one Amount of the case corresponding to an acid number of the copolymer of the Component C) of, for example, below 10, preferably below 5 mg KOH / g. Preference is also not given to monomers which, in addition to the Olefinically unsaturated double bond is another functional group Such as, for example, epoxy groups, hydroxyl groups and Alkoxysilane groups. In particular, such monomers are avoided Due to their functionality (s) alone or in combination with Other comonomers to an internal crosslinking of the copolymer of the Component C) or to a crosslinking between the copolymer of the Component C), the copolymer of component A) and / or the component A) (Meth) acrylic copolymers of component B).

In a preferred embodiment, the thermoplastic Copolymers of component A) and / or the copolymers of component C) Free from comonomers with nitrile and amide groups. There will be Aqueous coating compositions are obtained which additionally have the advantage that, That the films obtained after use are only very soluble in the combustion Little or no toxic gases.

Components A), B) and C) are used in a resin solids ratio of 50 To 90 parts of A): 10 to 50 parts of B): 0 to 30 parts of C) Whereby the parts add up to 100 parts. Preference is given to Component C) are dispensed with and only the components A) and B) in the Resin solids ratio 50 to 90 parts A): 10 to 50 parts B), Preferably from 55 to 85 parts of A): 15 to 45 parts of B).

A desired, but generally not necessary PH adjustment of the generally weakly acidic mixtures of the components A), B) and, if desired, C) can be carried out by means of organic or Inorganic bases, such as, for example, ammonia, Alkali metal carbonates, alkali metal hydroxides, amines, amino alcohols. The Inorganic bases are preferred.

The coating composition used according to the invention can, in addition to the Binder components A), B) and, if desired, C) further non-reactive Additives in varnish-like amounts. examples are Light stabilizers, flow control agents, protective colloids, emulsifiers, Plasticizers, defoamers, biocides, release agents, dyes or else Pigments in opaque or non-covering quantities, For example for marking purposes and in particular Rheology-controlling and / or thickening agents. examples for The latter being present in amounts ranging from 0.1 to 5% by weight, preferably 0.5 To 3% by weight, based on the solid resin content, in the inventive Coating agents, are highly disperse silicic acid, Inorganic layer silicates, water - soluble cellulose ethers such as Hydroxyethylcellulose, methylcellulose, carboxymethylcellulose, and the like Synthetic polymers with ionic and / or associative Groups such as polyvinyl alcohol, poly (meth) acrylic acid, Polyvinylpyrrolidone or else hydrophobically modified ethoxylated Polyurethanes or polyacrylates.

Silicones are preferred in the aqueous coating composition used according to the invention Avoided.

The aqueous coating agent has, if desired, By the addition of deionized water, relatively high Solids content of, for example, 30 to 60% by weight, preferably 40 to 55% by weight, , A possible content of, for example, a coalescing aid Containing organic water-thinnable solvent By weight, preferably below 5% by weight, preferably below 2% by weight, based on Resin solid. The novel compounds according to the invention are particularly preferred Aqueous coating agent is not an organic solvent.

The aqueous coating compositions used according to the invention are used as temporary Protective covers are applied to high quality goods. Application of the So produced, can be carried out in the customary manner, For example by roller coating or by brushing By spraying or casting. The drying of Coatings can be applied in a wide range Temperature range, for example, between 20 and 80 ° C. The Coating agents are suitable for coatings based on A plurality of substrates such as wood, Textiles, plastics, glass, ceramics and in particular metal and plastic Painted metals. Preference is given to a closed, non-crosslinked, Tack-free protective coating. Preferably, the aqueous Coating composition in a dry-film thickness of 30 to 100 μm, Preferably between 40 and 80 μm.

A preferred embodiment is the application of the Coating composition in which it is applied by spraying or spraying Casting in a dry film thickness of 30 to 100 μm is preferred Between 40 and 80 μm on the baked outer varnish layer of a Automotive paint layer injected and at temperatures Between 20 and 80 ° C to form a closed, non-crosslinked, Tack-free protective coating. A special advantage of the Aqueous coating agent is that with Even with application with only one order, especially in only A high dry film thickness. Of the Coating can be as foil-like after fulfilling its protective function Film removed without special measures from the object to be protected and Subsequently, without signifying an environmental hazard, or By combustion, for example, without releasing toxic gases Be disposed of.

The aqueous coating compositions prepared from the aqueous coating compositions used according to the invention Coating layers are characterized by one of the requirements Protection. They protect the paint surface of the Protecting objects reliably against ante- rations due to environmental influences, For example acid rain, and are thus particularly suitable as Temporary coatings for new vehicles.

example 1

19 parts of a 50% strength by weight aqueous copolymer dispersion Acrylic acid esters having a glass transition temperature of 12 ° C. (determined According to DIN 53 765) is mixed with 3 parts of a commercially available release agent mixed. Thereafter, 78 parts of a 53% strength by weight aqueous solution are added, with vigorous stirring Aqueous ethene / vinyl acetate copolymer dispersion with a Glass transition temperature of 13 ° C. (determined according to DIN 53 765). The aqueous coating composition thus prepared having a viscosity according to DIN 53211-4 of 32 seconds is set to 50 μm dry layer thickness With a typical car series lacquer construction (consisting of priming, Filler, basecoat and outer clearcoat) By spraying. 10 minutes drying at 80 ° C (Oven temperature) provides a closed, silk mat Protective coating, which after cooling without special measures as Like film can be peeled off from the clear lacquer surface. In the test With 36% strength sulfuric acid at 65 ° C., Protective coating provided before a first, optically Perceptible damage is at least 30 minutes longer than The unprotected clear lacquer surface.

Example 2

20 parts of the coating composition from Example 1 are introduced and the mixture is added The dissolver with a portion of a commercially available polyurethane associative thickener (Borchigel L 75 N, 54%) were added and the mixture was stirred With further 80 parts of the coating composition from Example 1 Completed. The viscosity according to DIN 53211-4 is 90 seconds.