CA2050914C

CA2050914C - Coating compound, process for making it and its use, especially for painting the outside of deep-drawn cans

Info

Publication number: CA2050914C
Application number: CA002050914A
Authority: CA
Inventors: Ludger Keweloh; Bernhard Koster; Siegfried Krause
Original assignee: BASF Lacke und Farben AG
Current assignee: PPG Industries Ohio Inc
Priority date: 1989-03-13
Filing date: 1990-02-21
Publication date: 1998-10-27
Anticipated expiration: 2010-02-21
Also published as: DK0462981T3; JPH04500230A; EP0462981A1; FI97391C; NO913591L; LTIP530A; LV10786A; MD777F2; RU2096434C1; AU5089590A; JPH06102764B2; DE3908104A1; BR9007223A; ATE105315T1; FI914291A0; NO913591D0; LT3331B; ES2056446T3; DE59005640D1; WO1990010678A1

Abstract

The present invention relates to coating compositions comprising a hydroxyl-containing, modified or unmodified polyester and/or a hydroxyl-containing epoxy resin and/or a hydroxyl-containing acrylate copolymer as well as a crosslinking agent reactive toward hydroxyl groups and a lubricant, wherein a wax paste D is used as lubricant, which paste comprises d1) 3 to 30% by weight of one or more polyolefin waxes and/or substituted polyolefin waxes d2) 0 to 25% by weight of one or more melamine-formaldehyde resins d3) 5 to 40% by weight of one or more acrylate resins having a hydroxyl value of 10 to 150 mg of KOH/g and a number average molecular weight of 2000 to 7000, and d4) 10 to 80% by weight of one or more organic solvents, the amounts by weight of the components d1 to d4 in each case totalling 100% by weight.
The invention furthermore relates to a process for the preparation of these coating compositions and to their use, in particular for exterior coating of deep-drawn cans.

Description

~05~14 _ -¦~ PAT 89 194 09.03.1989/fe (0503Z) BASF Lacke + Farben AG
Coatina composition, process for its preparation and use of the coatinq comPosition, in particular for exterior coatinq of deeP-drawn cans The present invention relates to coating composi-tions comprising a hydroxyl-containing, modified or unmodified polyester and/or a hydroxyl-containing epoxy resin and/or a hydroxyl-contAi~ing acrylate copolymer as well as a crosslinking agent reactive toward hydroxyl groups and a lubricant.
In addition, the invention relates to a process for the preparation of these coating compositions and to their use, in particular for exterior coating of deep-drawn cans.
Packing receptacles, for example cans, tubes, drums, buckets and the like which are often designated as packaging cont~iners, generally carry on their outside a coat of paint, the purpose of which is mainly decorative.
For this reason the basic requirements of suitable coating compositions are problem-free processing and blemish-free surfaces. The blemish-free decorative coat must, however, withstand the often extreme stresses encountered in the manufacture and use of the packaging containers (folding, flange formation, deformation, sterilization etc.).
Exterior coating of packaging containers usually consists of a multicoat system comprising a basecoat as 205091~

- 09.03.1989/fe (0503Z) the decoration carrier, a printed coat and, if appropriate, a colorless protective coat, the so-called silver varnish. Those basecoats which do not carry a protective coat as the exterior finish are subject to particularly severe demands. These basecoats are also known as non-varnish exterior paints.
Non-varnish exterior paints must be highly compatible with the subsequent print, i.e. they must be capable of accepting print satisfactorily, they must possess good adhesion and good resistance to condensa-tion. The resultant coatings must have a high gloss, i.e.
a degree of gloss (60~ reflection angle) > 80, they must possess high abrasion resistance and a smooth surface structure, i.e. one free from craters and the like.
Non-varnish exterior paints of this type are known (cf. for example Ullmanns Encyklopadie der technis-chen Chemie, 4th edition, 1978, volume 15, pp. 713-714).
Basic raw materials for these paints are modified alkyd resins, epoxy resins, epoxy resin esters, polyester resins and polyacrylate resins. These non-varnish exterior paints usually contain a lubricant, the purpose of which is to influence to a desired degree surface hardness of the resultant coating in order to achieve optimum abrasion resistance of the coatings coupled with good surface properties, high gloss and good print acceptability. In these known paints, carnauba waxes and readily volatile waxes, for example lanolin or beeswax, 20sa~l 09.03.1989/fe (0503Z) are used as lubricants.
However, problems arise when these known non-varnish exterior paints are employed in the coating of deep-drawn cans which are subject to very severe deforma-tion in their upper region. Even given such an extremelysevere deformation, it is essential to ensure that the paint film is undamaged. This requirement can only be met with coating compositions which give rise to flexible paint films. It is further essential to ensure that the resultant coatings withstand the extreme mechanical stresses encountered in can manufacture and filling. It means that the resultant paint films have high abrasion resistance and a correspondingly high degree of hardness, especially scratch hardness; this again requires the use of lubricants which are able to control to a desired degree the hardness of the paint surfaces. Examples of lubricants which ensure high scratch hardness are poly-ethylene, polypropylene and polytetrafluoroethylene waxes. These waxes, however, normally have a strong matting effect and are therefore unsuitable for use in paints for packaging containers made of sheet metal, since can manufacturers require glossy surfaces.
The basic object of the present invention has been to provide coating materials which are suitable as non-varnish exterior paints for the coating of deep-drawn cans. The resultant coatings should accordingly possess a smooth surface, a high degree of gloss, good print 2 0 ~
.

09.03.1989/fe (0503Z) acceptability, good abrasion resistance and high scratch hardness coupled with high film flexibility. In addition, the coating compositions should have a long shelf life, i.e. the resultant paint films should meet the above requirements in respect of their optical and mechanical properties even after the coating compositions have been stored for 3 months or longer.
Surprisingly, the object is achieved by a coating composition comprising a hydroxyl-containing, modified or unmodified polyester and/or a hydroxyl-containing epoxy resin and/or a hydroxyl-containing acrylate copolymer as well as a crosslinking agent reactive toward hydroxyl groups and a lubricant. The coating composition uses as lubricant a wax paste D which comprises d1) 3 to 30% by weight of one or more polyolefin waxes and/or substituted polyolefin waxes d2) 0 to 25% by weight of one or more melamine-formaldehyde resins d3) 5 to 40% by weight of one or more acrylate resins having a hydroxyl value of 10 to 150 mg of KOH/g and a number average molecular weight of 2000 to 7000, and d4) 10 to 80% by weight of one or more organic solvents, the amounts by weights of the components d1 to d4 in each case totalling 100% by weight.
The present invention furthermore relates to a process for the preparation of these coating compositions 20aO914 -_ - 5 - PAT 89 194 09.03.1989/fe (0503Z) and to the use of these coating compositions for coating packaging containers, in particular for exterior coating of deep-drawn cans.
Given the large number of known lubricants, it was surprising and could not be foreseen that it was precisely the use of the wax pastes according to the invention that gave rise to coating compositions which furnish paint films of a high degree of gloss, smooth surface, good paint acceptability and good abrasion resistance coupled with high flexibility, this excellent profile of properties remaining unchanged even after the coating compositions have been stored for two weeks or longer.
It is true that the product literature on the waxes employed in the coating compositions according to the invention recommends the use of these wax dispersions as lubricants in can coating compositions. However, coating compositions which - as recommended - have had these wax dispersions directly added to them, still suffer from the considerable drawbacks of being matt and having a short shelf life. Already after a two weeks' storage of the coating compositions, the resultant films manifest a distinct - and in can coating no longer acceptable - loss of gloss compared with films obtained with freshly prepared coating compositions. Moreover, these films do not have a smooth surface but one with many craters.

2 ~
-~ - 6 - PAT 89 194 09.03.1989/fe (0503Z) The indlvidual components of the coating compositions according to the invention are elucidated in greater detail in the text below.
The coating compositions comprise one or more hydroxyl-containing polymers as binders. These polymers may or may not contain other functional groups, for example carboxyl groups. These polymers (component A) are used in the coating compositions preferably in an amount of 10 to 60% by weight, based on the total weight of the components A to F.
These hydroxyl-containing polymers are chosen from the group of hydroxyl-cont~ining polyesters and/or hydroxyl-cont~ining acrylate-modified polyesters and/or hydroxyl-contA i n i ng epoxide-modified polyesters. If desired, they can also be used in combination with epoxy resins and/or hydroxyl-cont~i n i ng acrylate copolymers.
The most decisive criterion in the choice of suitable binder components should be that they should furnish, in combination with the crosslinking agent in question (component B), coatings of sufficient flexibility to withstand the mechanical stresses incurred in the defor-mation of coated cans without the paint films suffering cracking, tearing or similar damage.
The hydroxyl-containing polye~ters to be used as the component A are prepared by the usual process of esterifying aliphatic, cycloaliphatic and aromatic diols and/or polyols. The polyesters have typical hydroxyl 20~91~

09.03.1989/fe (0s03Z) values between 30 and 100 mg of KOH/g, preferably between 40 and 80 mg of KOH/g, and number average molecular weights between 3000 and 8000. Preferred mixtures are those comprising 0 to 20 parts of polyesters having hydroxyl values between 70 and 80 mg of KOH/g and 40 to 100 parts of polyesters having hydroxyl values of 50 to 100 mg of KOH/g. Examples of carboxylic acids suitable for the synthesis of the polyesters are phthalic acid, isophthalic acid, terephthalic acid, tetrahydrophthalic acid, hexahydrophthalic acid, adipic acid, azelaic acid, sebacic acid, maleic acid, glutaric acid and longer-chain, aliphatic or cycloaliphatic dicarboxylic acids, for example the dicarboxylic acids known as dimeric fatty acids. Commercial technical dimeric fatty acids generally contain at least 80% by weight of dimeric fatty acid as well as up to a maximum of 20% by weight of the trimers and up to 1% by weight of the monomers of the correspond-ing fatty acids. Isophthalic acid is preferably used as the acid component.
Examples of the alcohol component used in the preparation of the polyesters are ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, butanediols, pentanediols, neopentyl glycol, heYAnediols, 2-methylpen-tane-1,5-diol, 2-ethylbutane-1,4-diol, dimethylolcyclo-hexane, glycerol, trimethylolethane, trimethylolpropan~
and trimethylolbutane, pentaerythritol, dipentaerythri-tol, polycaprolactonediols, polycaprolactonetriols and 2 ~
_ - 8 - PAT 89 194 09.03.1989/fe (0503Z) others. Preferred alcohol components are hexane-1,6-diol, neopentyl glycol and trimethylolpropane.
Acrylate-modified polyesters, if desired also in combination with the polyesters just described and/or S other binder components, are additionally used as the component A. These acrylate-modified polyesters generally have hydroxyl values between 50 and 100 mg of KOH/g, preferably between 90 and 100 mg of KOH/g, and a number average molecular weight between 4000 and 6000. They may be prepared by a number of methods, for example by a direct incorporation of acrylate units in the synthesis of the polyesters. Thus, for example, acrylic and/or methacrylic acid as well as hydroxyalkyl acrylates and hydroxyalkyl methacrylates can be used at the same time as the acid or alcohol component in the preparation of the polyesters. The acrylate-modified polyesters are preferably prepared by acrylations of saturated and unsaturated polyesters. For example, hydroxyl-containing polyesters can be first reacted with (meth)acrylic acid and then polymerized in the presence of other unsaturated monomers. Unsaturated polyesters, for example those prepared using maleic and fumaric acid in the synthesis of the polyesters, may be also polymerized in conjunction with acrylic monomers.
Polyesters which are further suitable as binders are epoxide-modified polyesters having hydroxyl values between 30 and 100 mg of ROH/g, preferably between 40 and 20~914 09.03.1989/fe (0503Z) 60 mg of KOH/g.
Epoxide-modified polyesters are understood to be those polyesters which are combined with epoxy resins as part of the polyol component already in the preparation of polyesters. Since the epoxy resins always contain in addition to the terminal epoxide groups hydroxyl groups, they can replace a part of the polyalcohol in the syn-thesis of the polyesters. The proportion of epoxy resin in the epoxide-modified polyesters varies between 50 and 90% by weight, preferably 70 to 90% by weight of epoxy resin, based on the weight of the epoxide-modified polyester. Examples of suitable compounds are the poly-esters commercially available under the trade names of Uranox~ from DSM, Alftalat- and Resydrol- from Hoechst, Jagahyd from Jager (Dusseldorf) and Halwepox~ from Chemische Werke Huttens-Albatus.
Furthermore, the possibility exists to combine the polyester with an epoxy resin only at the stage of paint preparation. In such a case chemical reactions between these two systems occur only during the baking of a film prepared from these compositions. These systems comprising a mixture of polyester resin and epoxy resin have been found to be successful in practice. The incomplete compatibility of polyester and epoxy resins, frequently observed, is improved by the addition, for example, of an amino resin component. The combination of a polyester/epoxy resin with acrylate resins as the third 2~91~
_ - - 10 - PAT 89 194 09.03.1989/fe (0503Z) component is also possible. The mixing proportions of hydroxyl-contAining polyesters to epoxy resins are mostly in the range from 0 to 20 parts of epoxy resin per 100 parts of polyester. For the combination with the polyester epoxy resins of low to medium viscosity are preferably used, for example Epikote~ 1001, 824, 834 and 1004 from Shell Chemie. Acrylate copolymers which are suitable for use in the coating compositions have hyd-roxyl values of 10 to 150 mg of KOH/g and number average molecular weights of 2000 to 12,000. They can be prepared by polymerization of hydroxyl-containing monomers with suitable comonomers, using known methods. Examples of monomers contA i n ing a hydroxyl function are hydroxyalkyl acrylates and methacrylates or hydroxyalkyl esters of other unsaturated carboxylic acids as well as reaction products of acrylic and/or methacrylic acid with glycidyl compound~ and of hydroxyalkyl esters of unsaturated carboxylic acids with ~-caprolactone. Examples of suit-able monomers contAini~g a hydroxyl function are listed on pages 14 and 15 of this text. Examples of suitable comonomers are also given on these pages.
As the crosslinking agent (component B), the coating compositions according to the invention comprise one or more aminoplast resins and/or one or more blocked di- or polyisocyanates. The amount of crosslinking agent used is preferably 1 to 20% by weight, based on the weight of the components A to F.

2D5~

09.03.1989/fe (0503Z) The aminoplast resins generally are the known, usually etherified, melamine-aldehyde and/or benzoguan-amine-aldehyde reaction products. The corresponding formaldehyde reaction products are preferably used.
Compatibility of the resins with other film formers and solvents is affected by the chain length of the etherifi-cation alcohol and the degree of etherification.
Principal etherification components are n-butanol and isobutanol.
Benzoguanamine-formaldehyde resins are preferably used, since, compared with melamine resins, they give rise to flexible coatings.
Blocked di- and polyisocyanates are used either in conjunction with the aminoplast resins or as the sole crosslinking agent. Suitable isocyanate components are aliphatic, cycloaliphatic and aromatic di- and polyiso-cyanates, for example trimethylene diisocyanate, tetramethylene diisocyanate, pentamethylene diisocyanate, hexamethylene diisocyanate, hexamethoxy diisocyanate, trimethylhexamethylene 1,6-diisocyanate and tris-hexamethylene triisocyanate; 1,3-cyclopentane diiso-cyanate, 1,4-cycloheYAne diisocyanate, 1,2-cyclohexane diisocyanate and isophorone diisocyanate as well as 2,4-and 2,6-toluylene diisocyanate and mixtures thereof, 4,4'-diphenylmethane diisocyanate, m-phenylene diiso-cyanate, p-phenylene diisocyanate, 4,4'-diphenyl diiso-cyanate, 1,5-naphthalene diisocyanate, 1,4-naphthalene 2~a9~4 09.03.1989/fe (0503Z) diisocyanate, 4,4'-toluidine diisocyanate and xylylene diisocyanate as well as substituted aromatic systems, for example dianisidine diisocyanates, 4,4'-diphenyl ether diisocyanates or chlorodiphenylene diisocyanates and higher-functional aromatic isocyanates, for example 1,3,5-triisocyanatobenzene, 4,4',4 -triisocyanatotri-phenylmethane, 2,4,6-triisocyanatotoluene and 4,4'-diphenyldimethylmethane 2,2',5,5'-tetraisocyanate.
Hexamethoxy diisocyanate is preferably used.
Butoxime and malonic esters are suitable blocking agents for the isocyanates.
The coating materials according to the invention furthermore comprise one or more organic solvents, preferably in amounts of 20 to 70% by weight, based on the total weight of the components A to F. The optimum solvent content in each case depends especially on the method of application (spraying, dipping and the like) and can be simply determined by an average person skilled in the art by a few routine experiments.
Suitable solvents are aliphatic, cycloaliphatic and aromatic hydrocarbons, esters, ethers and ketones, for example xylene, various petroleum ethers, tetralin, decalin, Solvent Naphtha-, various grades of Solvesso~, various grades of Shellsol~, butyl glycol, ethylene glycol dibutyl ether, ethylene glycol diethyl ether, diethylene glycol dimethyl ether, methyl ethyl ketone, methyl n-amyl ketone, diethyl ketone, ethyl butyl ketone, diisopropyl - - 13 - ~ ~S 0 9 1 4 ketone, diisobutyl ketone, acetylacetone, methyl scetate, ethyl acetate, propyl acetate, butyl acetate, amyl acetate, methyl glycol acetate, ethyl glycol acetate and butyl diglycol acetate.
As an essential part of the invention, the coating compositions contain as lubricant for the purpose of controlling the hardness of the coatings a wax paste D which compri~es d1) 3 to 30% by weight, preferably 6 to 15% by weight, of one or more polyolefin waxes and/or substituted polyolefin waxes d2) 0 to 25% by weight, preferably 0 to 10% by weight, of one or more melamine-formaldehyde resins d3) 5 to 40% by weight, preferably 5 to 30% by weight, of one or more acrylate resin~ having a hydroxyl value of 10 to 150 mg of KOH/g and a number average molecular weight of 2000 to 7000, and d4) 10 to 80% by weight of one or more organic solvents, the amounts by weight of the components d1 to d~ in each case totalling 100% by weight.
Polyethylene and/or polypropylene and/or poly-tetrafluoroethylene waxe~ are preferably used, the polyethylene waxes beLng particularly preferred.
Examples of suitable waxes (component dl) are the polytetrafluoroethylene waxe~ commercially available under the trade name "SST3" from Shamrock Chemicals and "Polyfluo 190" and ~'Polyfluo 400'" from Floridienne Trade-mark '''~'A

~;J5391 4 Polymers, as well as the polyethylene waxes distributed by Lanco under the trade name 'PE 1500", also the poly-propylene waxes "PP 1362 ~" and 'CP 1481 8 F" from Lanco as well as mixtures of polyethylene and polytetrafluoro-ethylene waxes such as the commercial products "TF 1780"
and 'TF 177~" from Lanco, "MP 26~ and "MP 611" from Micro Powders, as well as a variety of other waxes, for example the commercial product '447-A" from Luba-Paint.
The wax or a dispersion of the wax in organic solvents, for example the various grades of Shellsol6 and/or Solvesso~, is processed to a wax paste by homogeni-zing the components d1 to d3 together with some of the component d4. The viscosity of the wax paste is adjusted by the addition of further solvents in such a manner that further processing of the wax paste with the aid of stirrer mills, bead mills, ~and mill~ and the like is possible.
The acrylate re~ins which are suitable for the preparation of the wax paste are low-molecular (number average molecular weight 2000 to 7000), they wet the wax well and they react rapidly with the crosslinking agents B employed under the baking conditions. They have hydroxyl values between 10 and 150 mg of KOH/g, pre-ferably 20 to 120 mg of KOH/g. They can be prepared by copolymerizing hydroxyl-containing monomers with other ethylenically unsaturated compounds.
Examples of monomer8 cont A ining a hydroxyl Trade-mark . ~ ~ 27293-54 2~5091~

~ ~ 09.03.1989/fe (0503Z) function are hydroxyalkyl acrylates and methacrylates, for example hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate, hydroxybutyl (meth)acrylate as well as the corresponding hydroxyalkyl crotonates, isocrotonates, itaconates, maleates and fumarates.
The reaction products of acrylic or methacrylic acid with the glycidyl ester of a carboxylic acid con-taining a tertiary ~ carbon atom or the reaction products of the glycidyl ester of an ~,~-ethylenically unsaturated carboxylic acid with a tertiary aliphatic carboxylic acid may be employed in part as the hydroxyalkyl esters of ~,~-ethylenically unsaturated carboxylic acids. Further-more, the reaction products of one mole of hydroxyethyl acrylate and/or hydroxyethyl methacrylate with on average 2 moles of ~-caprolactone may be employed in part.
Other suitable ethylenically unsaturated monomers are the alkyl acrylates and methacrylates, for example methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, tert.-butyl acrylate, isopropyl acrylate, isobutyl acrylate, pentyl acrylate, isoamyl acrylate, hexyl acrylate, 2-ethylhexyl acrylate, octyl acrylate, 3,5,5-trimethylhexyl acrylate, decyl acrylate, dodecyl acrylate, hexadecyl acrylate, octadecyl acrylate, octa-decenyl acrylate and the corresponding methacrylates.
Other monomers may be used, provided they do not cause undesirable properties of the copolymer. Examples of suitable acrylate resins are the resins available under - 16 - ~ ~ ~0 9 I r the trade names Synthalat~ from Synthopol, Setalux~, from Akzo, Synthacryl~ from Hoechst and Uracron~ from DSM.
The non-plasticlzed, isobutyl-etherlfled melamlne-formaldehyde resln commerclally avallable under the trade name "Maprenal MF 800 " from Casella AG ls partlcularly preferred as the component d2.
Examples of sultable solvents (component d4) are the solvents llsted on pages 12 and 13 of thls text. They are lncorporated lnto the wax paste ln amounts of 10 to 80% by welght, the amount used belng chosen ln each case such that lt leads to good further processablllty of the wax paste, for example ln stlrrer mllls, bead mllls and sand mllls.
It ls preferred that the wax paste ls employed in the coatlng composltlons ln an amount of 0.8 to 8.0% by welght, based on the total welght of the components A to F.
Wlth lncreaslng concentratlon of the wax paste ln the coatlng composltlons, surface sllp and scratch reslstance of the resultant coatlng lncreases, whlle prlnt acceptablllty decreases. However, slnce the plgments whlch may be contained ln the coatlng composltion exerclse an lnfluence on the surface sllp and scratch reslstance of the resultant coating, the preferred amounts of the wax paste wlll ln each case depend on whether plgmented or non-plgmented systems are belng considered. Thus, the wax paste ls used ln plgmented coatlng composltlons, preferably ln amounts of 1.5 to 3% by welght, based on ~, ~ ,.

2~91 jl -- 09.03.1989/fe (0503Z) the total weight of the components A to F, while in non-pigmented systems the amount of the added wax paste is between 3 and 6% by weight, based on the total weight of the components A to F. However, the optimum amount of wax paste to be used for each purpose can be determined by a few routine experiments.
As already stated, the coating compositions may be used in the form of clearcoats, varnishes and top-coats. The pigment content is correspondingly between 0 and 35% by weight, based on the total weight of the components A to F. Suitable pigments are both organic and inorganic pigments, for example titanium dioxide, various iron oxide pigments and diacrylides.
In addition, the coating compositions may also comprise 0 to 1% by weight, based on the total weight of the components A to F, of auxiliaries and additives, for example flow control agents (for example high-molecular acrylates), wetting agents (for example high-molecular acrylates) and antifoams (for example silicone oil).
If appropriate, 0 to 15% by weight, based on the total weight of the coating composition, of fillers, for example talc, mica, kaolin, chalk, quartz powder, ground shale, barium sulfate, various silicic acids, silicates, glass fibers, organic fibers and the like, may also be added to the coating compositions.
The preparation of the coating compositions according to the invention is carried out in the usual 2 ~

-~- 09.03.1989/fe (0503Z) manner by mixing the components. It follows, that if a component is not a liquid, it must first be dissolved in a solvent and this solution is mixed with the other components. The incorporation of the wax paste is carried out in such a manner that it is incorporated in the coating composition as the last component by being added to the other components with stirring, particular atten-tion being paid to maintaining the temperature of the mixture below the melting point of the wax in order to prevent, for example, any possible recrystallization processes of the wax on cooling. The incorporation of the pigments E generally takes place by grinding the pigments with one of the binders and admixing the remaining components. As mentioned above, the wax paste D is preferably incorporated as the last component.
The coating compositions according to the inven-tion are cured in a temperature range of 180 to 235~C
(object temperature, metal peak temperature) during a period of 5 to 90 seconds. These coating compositions can be applied to a substrate as a film by spraying, flow-coating, dipping, rolling, blade-coating or brushing, the film being subsequently cured to form a strongly adhering coating. The coating compositions are preferably utilized for exterior coating of sheet metal packaging containers, especially deep-drawn cans for beverages. The application and curing of the coating compositions is in that case performed on a painting plant customary for the packaging 2~91~

09.03.1989/fe (0503Z) industry.
The amount of the coating compositions applied depends on the particular end use. If the coating com-positions are utilized for exterior coating of sheet metal packaging containers, the film thickness of the cured films is generally 5 to 20 ~m.
Suitable substrates are in particular sheet metal packaging containers, for example cans, buckets, drums, tubes, glass closures and two-part deep-drawn beverage cans, particularly preferred being deep-drawn beverage cans made of a great variety of materials, for example aluminum, black plate, tin plate and various ferrous alloys which may or may not be coated with a passivation coat based on nickel, chromium and zinc compounds. The coating compositions according to the invention may of course also be applied to other substrate~.
The coating compositions according to the inven-tion have the advantage of the resultant paint films having a high degree of gloss, a smooth surface, good print acceptability and good abrasion resistance coupled with high flexibility. As regards application in prac-tice, the good shelf life of the coating compositions is especially noteworthy.
The examples below elucidate the invention in _5 greater detail. All parts and percentages are parts and percentages by weight, unless expressly stated otherwise.

2 ~

~ 09.03.1989/fe to503Z) Preparation of wax paste 1 1.4 parts of a commercial 20% polyethylene wax dispersion (commercial product ~CERAFAK 178~ from CERA
CHEMIE B.V., 7400 AM DhVh~-l'h'~, Netherlands), 0.3 parts of a commercial 72% solution in isobutanol of a non-plasticized, isobutyl-etherified melamine-formaldehyde resin (commercial product "Maprenal~ MF 800" from Casella AG, Hoechst Group) and 0.5 parts of a commercial solution (60% in xylene/butyl acetate 9 : 1) of a low-molecular acrylate resin (hydroxyl value 45 mg of KOH/g, based on solid resin) are processed with cooling to a homogeneous wax paste using a stirrer mill.
Preparation of wax paste 2 1.4 parts of the 20% polyethylene wax dispersion described above ("CERAFAR 178" from CERA CHEMIE B.V.) and 0.5 parts of a commercial solution (60% in xylene/butyl acetate 9 : 1) of an acrylate resin (hydroxyl value 45 mg of KOH/g, based on solid resin) are processed with cooling to a homogeneous wax paste using a stirrer mill.
Preparation of wax pastes 3 to 10 95.4 parts of the commercial waxes listed in Table 1, 200 parts of Solvesso- 150, 120 parts of a 72%
solution in isobutanol of a non-plasticized, isobutyl-etherified melamine-formaldehyde resin (commercial product ~Maprenal~ MF 800" from Casella AG) and 270 parts of a commercial solution (60% in xylene/butyl acetate 9 : 1) of a low-molecular acrylate resin (hydroxyl value 2 ~

09.03.1989/fe (0503Z) 45 mg of ROH/g, based on solid resin) are processed with cooling to a homogeneous wax paste using a bead mill.
Preparation of wax disPersion 11 95.4 parts of a commercial mixture of polyethy-lene/polytetrafluoroethylene waxes (commercial product ~MP 26" from Micro Powders) and 200 parts of Solvesso~ 150 are processed with cooling to a homogeneous wax disper-sion using a bead mill.
Preparation of wax dispersion 12 95.4 parts of a commercial mixture of polyethy-lene/polytetrafluoroethylene waxes (commercial product "MP 611" from Micro Powders) and 200 parts of Solvesso~
150 are processed with cooling to a homogeneous wax dispersion using a bead mill.
Example 1 27.0 parts of titanium dioxide of rutile type and 28.5 parts of a commercial solution of an acrylated polyester (polyester/acrylate resin 1 : 1, acid value 45-50 mg of ROH/g, hydroxyl value 80 to 100 mg of KOH/g calculated on the solid resin, solvent Solvesso~ 150, butyl glycol) are ground using a dissolver to a fineness of 7-10 ~m. 3.2 parts of a solution (60% of solid resin, 32% of Solvesso- 150, 8% of butyl glycol) of a saturated polyester based on isophthalic acid, dimeric fatty acid, hexanediol, neopentyl glycol and trimethylolpropane having an acid value below 10 mg of KOH/g and a hydroxyl value of 76 mg of ROH/g, 7.6 parts of a commercial 70%

2 ~3 5 ~

09.03.1989/fe (0s03Z) solution of an epoxide-modified alkyd resin (acid value 40-60 mg of KOH/g, based on solid resin), 7.6 parts of a Table 1: Waxes employed in the pastes Paste Wax 3 SST 3, polytetrafluoroethylene wax from Shamrock Chemicals 4 TF 1780, polytetrafluoroethylene/polyethylene wax from Lanco (Bremen) TF 1778, polytetrafluoroethylene/polyethylene wax from Lanco (Bremen) 6 Polyfluo 190, polytetrafluoroethylene wax from Floridienne Polymers 7 Polyfluo 400, polytetrafluoroethylene wax from Floridienne Polymers 8 MP 26, polytetrafluoroethylene/polyethylene wax from Nicro Powders 9 MP 611, polytetrafluoroethylene/polyethylene wax from Micro Powders PE 1500, polyethylene wax from Lanco (Bremen) 2 ~

09.03.1989/fe (0503Z) 75% solution in xylene of an epoxy resin based on bisphe-nol A (epoxide equivalent weight 450-500 g), 6.5 parts of an 82-86% solution in n-butanol of a benzoguanamine resin etherified with n-butanol, 4.2 parts of hexamethoxy diisocyante blocked with butoxime, 10 parts of butyl diglycol acetate and 3.2 parts of butyl glycol are then added with mixing. 2.2 parts of the wax paste 1 are then incorporated into this mixture with stirring, care being taken that the temperature does not rise above 35~C. The coating composition 1 prepared in this manner is applied to a tin plate panel E 2.8/2.8 by blade-coating (dry film thickness 15 ~m) and is baked for 1 minute at 200~C in a circulating air oven. The degree of gloss (60~) and tendency to cratering of the resultant coating are assessed. The test results are listed in Table 2.
To assess shelf life, the coating composition 1 was stored for two weeks at room temperature prior to being applied. It was then likewise applied to a tin plate panel E 2.8/2.8 by blade-coating (dry film thick-ness 15 ~m) and baked for 1 minute at 200~C in a circu-lating air oven. The degree of gloss (60~) and tendency to cratering of the resultant coating are likewise examined. The results are given in Table 2.
To test the abrasion properties, the coating composition 1 is also applied to the exterior of DWI
(drawn and wall-ironed) beverage cans with the aid of painting machinery customary in the packaging industry 2!3~314 09.03.1989/fe (0503Z) (dry film thickness 10 ~m) and baked for 1 minute at 200~C. The cured coating is then overprinted with a decoration using commercial printing inks.
The upper part of the beverage can overprinted in this manner is then narrowed using known customary machinery (from the internal diameter of the upper part of the cans of 67 mm to an internal diameter of the upper part of the cans of 57 mm) - the so-called spin-spin necking deformation -, about 1000 cans being deformed per minute. These narrowed cans showed no abrasion phenomena during the printing and deformation despite the high mechanical stresses.
Comparison Example 1 A coating composition Cl is prepared in the same manner as used in Example 1, except that instead of 2.2 parts of the wax paste 1 1.4 parts of the commercial 20% polyethylene wax dispersion (commercial product "CERAFAR 178" from CERA CHEMIE B.V.) - described in Example 1 for wax paste 1 - are incorporated in the coating composition Cl.
In the same manner as used in Example 1, this coating composition Cl is stored for two weeks imme-diately after preparation and is then applied at room temperature to tin plate panel E 2.8/2.8 (dry film thickness 15 ~m) and baked for 1 minute at 200~C. The degree of gloss (60~) and tendency to cratering of the resultant coating are examined. The test results are ~ 09.03.1989/fe (0503Z) given in Table 2.
The abrasion properties of the coatings prepared using the coating composition C1 are tested in the same manner as in Example 1, in that the coating composition C1 is applied to DWI beverage cans and baked, the cans are then overprinted and in the upper part narrowed from an internal diameter of 67 mm to an internal diameter of 57 mm. The number of cans deformed per minute is also 1000. In this case the cans deformed in this manner likewise showed no abrasion phenomena.
Example 2 A coating composition 2 is prepared in the same manner as used in Example 1, except that instead of 2.2 parts of the wax paste 1 1.9 parts of the wax paste 2 are incorporated. The coating composition 2 is applied to a tin plate panel E 2.8/2.8 and the resultant coating is cured and tested as described in Example 1. The test results are given in Table 2.
The abrasion properties are tested in the same manner as used in Example 1 and no abrasion phenomena of the deformed cans were noted.
Examples 3 to 10 The coating compositions 3 to 10 are prepared in the same manner as used in Example 1, except that instead of 2.2 parts of the wax paste 1 2.5 parts of the wax pastes 3 to 10 are incorporated. The coating compositions are applied, cured and tested as described in Example 1.

~ ~ ~s ~

- 09.03.1989/fe (0s03Z) The test results are given in Table 2.
Abrasion properties were tested likewise in the same manner as described in Example 1 and no abrasion phenomena of the deformed cans were noted.
Example 11 A coating composition 11 is prepared in the same manner as used in Example 1, except that no titanium dioxide is added (clearcoat) and instead of 2.2 parts of the wax paste 1 4.4 parts of the wax paste 1 are added.
The coating composition 12 is applied to a tin plate panel E 2.8/2.8, cured and tested in the same manner as described in Example 1. The test results are given in Table 2.
Abrasion properties were tested in the same manner as used in Example 1 and no abrasion phenomena of the deformed cans were noted.
Comparison ExamPles 2 to 3 The coating compositions C2 and C3 are prepared in the same manner as used in Example 1, except that instead of 2.2 parts of the wax paste 1 1.0 parts of the wax dispersion 11 and 12 respectively are incorporated.
The coating compositions are applied, cured and tested in the same manner as described in Example 1. The test results are given in Table 2.
Abrasion properties were likewise tested as described in Example 1 and no abrasion phenomena of the deformed cans were noted.

2~a~v~ 4 ~ 09.03.1989/fe (0503Z) C- ,~rison Example 4 A coating composition C4 is prepared in the same manner as used in Example 11, except that instead of 4.4 parts of the wax paste 1 2.8 parts of the commercial 20% polyethylene wax dispersion (commercial product "CERAFAR 178" from CERA CHEMIE B.V.) - as described in Example 1 for the wax paste 1 - are incorporated in the coating composition C4.
In the same manner as used in Example 1, this coating composition C4 is stored for two weeks imme-diately after preparation and is then applied at room temperature to a tin plate panel E 2.8/2.8 (dry film thickness 15 ~m) and baked for 1 minute at 200~C. The degree of gloss (60~) and ten~ency to cratering of the resultant coating are examined. The test results are given in Table 2.
In the same manner as used in Example 1, abrasion properties of the coatings prepared using the coating composition C4 are examined in that the coating composi-tion C4 is applied to DWI beverage cans and baked, thecans are then overprinted and narrowed in their upper part from an internal diameter of 67 mm to an ternal diameter of 57 mm. The number of deformed cans per minute is likewise 1000. Also in thi~ ca~e the deformed cans showed no abrasion phenomena.
ReY to symbols used in Table 2:
a: The coating compositions are applied immediately 2~SD~

~ 09.03.1989/fe (0503Z) after their preparation.
b: The coating compositions are first stored for two weeks immediately after their preparation and only then applied.
c: Tendency to cratering was assessed visually: O = no cratering, 5 = pronounced cratering.
d: Measured on the Erichsen scratch hardness instrument model 239/2, bearing load 6 N.

20~0~

09 . 03 .1989/fe ( O 5 0 3 Z ) un s un ~j ~
O ~ ~O ~ O
~r 7~ ~ ~ ~ ~ ~ ~ ~ I I N
~ ~a A ~ A ~ A
U ,C

-I~.~ OOOOOOOOOOOOu~
~r S
u 3 u c . ~ ~
~, r ~ O O O O O O O O O O O O O ~ ~ ~
,~
r ~~
~ ~ n ~O R
a~
U~ ~
~S ~OOOOOOOOOOOOOO
_ ~rl ~
~ 3 ~ v l v l v l v m ~ O
_I o ~O a a~ ~ ~oooooooooo~ooo U S
O ~;
un _ ~,~ _ ~ 3 r ~ A
E~
~-a~ ~

E~ X ~ o ~

Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. Coating compositions comprising a hydroxyl-containing, modified or unmodified polyester or a hydroxyl-containing epoxy resin or a hydroxyl-containing acrylate copolymer as well as a crosslinking agent reactive towards hydroxyl groups and a lubricant, wherein a wax paste D is used as lubricant, which paste D comprises d1) 3 to 30% by weight of one or more polyolefin waxes or substituted polyolefin waxes d2) 0 to 25% by weight of one or more melamine-formaldehyde resins d3) 5 to 40% by weight of one or more acrylate resins having a hydroxyl value of 10 to 150 mg of KOH/g and a number average molecular weight of 2000 to 7000, and d4) 10 to 80% by weight of one or more organic solvents, the amounts by weight of the components d1 to d4 in each case totalling 100% by weight.

2. The coating composition as claimed in claim 1, wherein the coating composition comprises A) 10 to 60% by weight of one or more hydroxyl-containing, modified or unmodified polyesters or epoxy resins or acrylate copolymers B) 1 to 20% by weight of one more aminoplast resins and/or one or more blocked diisocyanates or poly-isocyanates C) 20 to 70% by weight of one or more organic solvents D) 0.8 to 8.0% by weight of the wax paste D
E) 0 to 35% by weight of one or more pigments and F) 0 to 1% by weight of other auxiliaries and additives, the amounts by weight of the components A to F in each case totalling 100% by weight.

3. The coating composition as claimed in claims 1 or 2, wherein the wax paste D comprises d1) 6 to 15% by weight of one or more polyolefin waxes and/or substituted polyolefin waxes d2) 0 to 10% by weight of one or more melamine-formaldehyde resins d3) 5 to 40% by weight of one or more acrylate resins having a hydroxyl value of 10 to 150 mg of KOH/g and a number average molecular weight of 2000 to 7000, and d4) 10 to 80% by weight of one or more organic solvents, the amounts by weight of the components d1 to d4 in each case totalling 100% by weight.

4. The coating composition as claimed in claim 1, 2 or 3, wherein the coating composition comprises no pigments and 3.0 to 6.0% by weight of the wax paste D.

5. The coating composition as claimed in claim 1, 2, 3 or 4, wherein the coating composition comprises 15 to 35% by weight of pigment and 1.5 to 3.0% by weight of the wax paste D.

6. The coating composition as claimed in any one of claims 1 to 5, wherein the wax paste D comprises as the component d1 one or more polyethylene waxes or polypropylene waxes or polytetrafluoroethylene waxes.

7. The coating composition as claimed in any one of claims 1 to 6, wherein the wax paste D as the component d1 comprises one or more polyethylene waxes.

8. The coating composition according to any one of claims 1 to 7 wherein the wax paste D is present in an amount from 0.8 to 8.0% by weight.

9. Process for the preparation of a coating composition comprising a hydroxyl-containing, modified or unmodified polyester or a hydroxyl-containing epoxy resin or a hydroxyl-containing acrylate copolymer as well as a crosslinking agent reactive toward hydroxyl groups and a lubricant, the individual components being thoroughly mixed with one another, wherein a wax paste D is used as lubricant, which paste comprises d1) 3 to 30% by weight of one or more polyolefin waxes and/or substituted polyolefin waxes d2) 0 to 25% by weight of one or more melamine-formaldehyde resins d3) 5 to 40% by weight of one or more acrylate resins having a hydroxyl value of 10 to 150 mg of KOH/g and a number average molecular weight of 2000 to 7000, and d4) 10 to 80% by weight of one or more organic solvents, the amounts by weight of the components d1 to d4 in each case totalling 100% by weight.

10. The process as claimed in claim 9, wherein the coating composition comprises A) 10 to 60% by weight of one or more hydroxyl-containing, modified or unmodified polyesters or epoxy resins or acrylate copolymers B) 1 to 20% by weight of one more aminoplast resins and/or one or more blocked diisocyanates or polyisocyanates C) 20 to 70% by weight of one or more organic solvents D) 0.8 to 8.0% by weight of the wax paste D
E) 0 to 35% by weight of one or more pigments and F) 0 to 1% by weight of other auxiliaries and additives, the amounts by weight of the components A to F in each case totalllng 100% by weight.

11. The process as claimed in claims 9 or 10, wherein the wax paste D comprises d1) 6 to 15% by weight of one or more polyolefin waxes and/or substituted polyolefin waxes d2) 0 to 10% by weight of one or more melamine-formaldehyde resins d3) 5 to 40% by weight of one or more acrylate resins having a hydroxyl value of 10 to 150 mg of KOH/g and a number average molecular weight of 2000 to 7000, and d4) 10 to 80% by weight of one or more organic solvents, the amounts by weight of the components d1 to d4 in each case totalling 100% by weight.

12. The process as claimed in claim 9, 10 or 11, wherein the coating composition comprises no pigments and 3.0 to 6.0%
by weight of the wax paste D.

13. The process as claimed in claim 9, 10, 11 or 12, wherein the coating composition comprises 15 to 35% by weight of pigment and 1.5 to 3.0% by weight of the wax paste D.

14. The process as claimed in any one of claims 9 to 13, wherein the wax paste D comprises as the component d1 one or more polyethylene waxes or polypropylene waxes or polytetrafluoroethylene waxes.

15. The process as claimed in any one of claims 9 to 14, wherein the wax paste D as the component d1 comprises one or more polyethylene waxes.

16. The process as claimed in any one of claims 9 to 15 wherein the wax paste D is present in an amount from 0.8 to 8.0% by weight.

17. Use of the coating compositions as claimed in any one of claims 1 to 8 for coating packaging containers.

18. Use of the coating compositions as claimed in any one of claims 1 to 8 as non-varnish exterior paint for the coating of deep-drawn cans.