Basic substance suitable for production of the multilayer protective and/or decorative coat

BACKGROUND OF THE INVENTION 1. Field of the Invention The invention relates to a base material useful in applying protective and decorative coatings to surfaces, in particular to automotive body surfaces.

Especially in the automotive industry it is well known to use coating compositions containing coke pigments. These so-called "metallic paints" show different light reflectance depending on the viewing angle. In order to achieve the highest degree of this effect, the so-called "flip", great attention must be paid to the composition of the coating composition, both the resin-forming resin and the liquid medium. It may be difficult to design a single mass that meets the above requirement and at the same time exhibits a high degree of gloss after finishing, as is typically required for automobiles. For this reason, a process involving the application of two coatings has been proposed as one of the processes proposed for the production of metallic coatings.

The first coating to be applied by spraying onto the surface of the substrate is a metallic pigment containing primer. This coating is formulated to provide an optimum flip. A non-pigmented topcoat is again sprayed over the base coat to achieve the desired degree of gloss without modifying in any way the characteristics of the base coat.

The basic criterion for a successful two-layer metallysis system consisting of a base layer and a clear coating is that the base film coating must be able to withstand the solvents contained in the clear coating film forming material when the coating is applied. This is important in order to avoid breaking the metal pigment distribution and thus deteriorating the flip. In addition, it is highly desirable that the base coat has this property without having to undergo long intermediate drying or curing.

In known base coat systems, a clear coat in which both the base coat and the solvent-based cover coat, this requirement is achieved in most cases using an additive capable of imparting a gel-like character to the freshly formed base film. Cellulose acetobutyrate was used predominantly as this additive. The transition between the relatively low viscosity that the primer coating composition must have in the spray gun and this gel-like character is aided by the liquid diluent contained therein containing volatile components that preferentially evaporate during travel from the spray gun to the substrate.

In recent years, in order to prevent atmospheric pollution, considerable interest has been focused on coating compositions in which water is used as a diluent. A large number of such compositions have been proposed for use in the automotive industry. Until now, however, it has not been possible to successfully use aqueous compositions based on primers / clear coat systems. One factor that tends to hinder this achievement is the fact that it is extremely difficult to effectively evaporate the solvent from the primer between the spray gun and the substrate in a controlled manner, with the exception of the very costly humidity control in the spraying environment. It has now surprisingly been found that satisfactory aqueous-based coating compositions based on an aqueous dispersion of crosslinked polymeric microgel can be obtained.

The present invention provides a primer suitable for producing a multi-layered protective and / or decorative coating on a substrate surface comprising a film former, a volatile liquid medium therefor and pigment particles dispersed therein, characterized in that the film former and volatile liquid medium system. includes a dispersion of crosslinked microparticles of acrylic addition polymers in an aqueous medium having a diameter in the range of 0.01 to 10 μπι; they are insoluble in the aqueous medium used and are stable to coarse flocculation, the dispersion having a pseudoplastic or thixotropic character.

Crosslinked polymer microparticles can be formed of different types of polymer. Of particular interest in this application are acrylic addition polymers derived from one or more alkyl esters of acrylic or methacrylic acid, or mixtures thereof with other ethylenically unsaturated monomers. Suitable esters of acrylic or methacrylic acid are methyl methacrylate, ethyl methacrylate, propyl methacrylate, butyl methacrylate, ethyl acrylate, butyl acrylate and 2-ethylhexyl acrylate. Other suitable copolymerizable monomers include vinyl acetate, vinyl propionate, acrylonitrile, styrene, and vinyltoluene. Since the polymer is to be crosslinked, a minor amount of monomer that is polyfunctional can be added to the monomers from which the polymer is prepared due to polymerization, for example, ethylene glycol dimethacrylate, allyl methacrylate or divinylbenzene. Alternatively, minor amounts of two additional monomers bearing pairs of chemical groups may be added to these monomers, which may be reacted together either during or after the polymerization. Examples of such pairs of mutually reactive groups include an epoxy group and a carboxy group (for example, a glycidyl methacrylate-methacrylic acid system), an anhydride group and a hydroxy group or an isocyanate group and a hydroxy group.

The chemical composition and degree of crosslinking of the microparticulate polymer may be such that the polymer has a glass transition temperature Tg of either below room temperature, in which case the particles are rubbery, or higher than room temperature, then the particles are hard and glassy.

As already mentioned, the polymeric microparticles need to be dispersed in the matrix in a state that is stable to coarse flocculation, i.e. in a state where, even at low solids content, the dispersion contains few aggregates of a plurality of particles, if any some such aggregates. However, this does not exclude the possibility of a slight degree of flocculation of the particles, particularly at higher solids content. This condition can be achieved, for example, by steric stabilization, i. by forming a wall of chains of another polymer around the particles that are solvated by the aqueous coating material. Therefore, these strings have an advanced configuration. The term "solvated" in this context means that these polymer chains would actually be soluble in said aqueous medium if they formed independent molecules. However, since these chains are attached to the microparticles at one or more sites, the steric barrier remains permanently attached to the microparticles. The spherically stabilized polymer microparticles may conveniently be prepared by a process of dispersed polymerization of the respective monomers in an aqueous medium in the presence of a spherical stabilizer. The stabilizer is amphipathic in nature; it contains two basic ipolymer components with different properties in the molecule: one component is a polymer chain which is solvated by an aqueous medium and the other is a polymer chain which is not solvated by this medium and consequently anchors on polymeric microparticles which are by definition insoluble in aqueous environment. Suitable dispersion polymerization processes are described in British Patent Application Publication No. ICI No. 2,039,497A. The aqueous medium in which the polymerization is carried out consists of water mixed with a volatile organic co-solvent.

The mixture of water and co-solvent is capable of dissolving monomers, most or all of which would be substantially insoluble in water alone. These include the additional requirement that the polymerization be carried out at a temperature that is at least 10 degrees Celsius higher than the glass temperature of the polymer to be formed, and the requirement that no separate monomer phase should be present in the system at any time. The amphipathic steric stabilizer may be added to the polymerization mixture as a preformed substance, or may be formed in situ during polymerization from an aqueous-soluble polymer that is capable of copolymerizing with one of the polymerized monomers, or which may be grafted after hydrogen elimination. copolymerization with one of the polymerized monomers. The sterically stabilized dispersions of microparticles obtained by these processes are very suitable for the production of the base materials used according to the invention, since the organic co-solvent can be separated from them by distillation without compromising the stability of the dispersed phase to form a continuous phase product. exclusively with water.

Alternatively, the dispersion of polymeric microparticles can be obtained by aqueous emulsion polymerization of suitable monomers. In this case, stability to flocculation is achieved by having electrically charged substances derived from a water-soluble ionogenic surfactant and / or a water-soluble ionizable polymerization initiator present on the particles. Such polymerization processes are extensively described in the literature.

Further, the polymeric microparticles can be produced by a non-aqueous dispersion monomer polymerization process, after which the resulting polymer is transferred to an aqueous medium. Such a procedure is described in British Patent Application Publication No. ICI No. 2,006,229A. In a first step of this process, a sterically stabilized dispersion is formed in a non-aqueous liquid of a polymer which is insoluble in both the non-aqueous liquid and water, using any of the processes known for making such dispersions, in a second step polymerizes in the presence of a spherical stabilizer one or more monomers from which a second polymer may be formed, which itself is soluble in the desired aqueous medium at a suitable pH and finally the resulting composite polymer microparticles are transferred from the non-aqueous medium to the aqueous medium.

The above discussion is directed to the case where the crosslinked polymer microparticles consist of addition polymers, which are the most suitable type of polymer for this purpose. However, it is also possible for the microparticles to be formed from a condensation type polymer, for example a polyester prepared from a polyhydric alcohol and a polybasic acid. Suitable polyhydric alcohols are ethylene glycol, ipropylene glycol, butylene glycol, 1,6-hexylene glycol, neopentyl glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, glycerol, trimethylopropane, trimethylolethane, pentaerythritol, dipentaerythritol, styreneerythritol, hexaneerythritol, hexaneerythritol, RJ 100 "), condensation products of trimethylolpropane with ethylene oxide or propylene oxide (such as the commercially available products referred to as "Niax" tritols). Suitable polycarboxylic acids are succinic acid (or its anhydride, adipic acid, azelaic acid, sebacic acid, maleic acid (or its anhydride), fumaric acid, muconic acid, itaconic acid, acid 248039 to phthalic acid (or its anhydride), isophthalic acid, terephthalic acid, trimellitic acid (or anhydride) and pyrornellitic acid (or anhydride thereof). Enhancement of the polycondensates is achieved by adding substances of greater functionality than 2 to the initial reaction mixture, although in this case it may be difficult to ensure that all molecules are actually crosslinked. This is because the polycondensation molecules are characterized by a broad molecular weight distribution compared to the addition polymer molecules.

The methods outlined above for the production of polymeric microparticles by polymerizing addition type monomers in an aqueous medium are generally not applicable to condensation type monomers, since water has an inhibitory effect on the condensation reaction. However, microparticles of condensation polymers can be readily prepared by non-aqueous dispersion polymerization according to the methods described in British Patents ICI Nos. 1,373,531, 1,440,794 and 1,419,199. These patents also disclose the production of crosslinked microparticles. These microparticles can then be dispersed in a non-aqueous medium by a second polymerization step, as described in British Patent Application Publication No. 2,006,229A cited above, after which the microparticles are transferred to a selected aqueous medium.

The term "aqueous medium" refers to either water alone or water mixed with a water-miscible organic liquid, such as methanol. The aqueous medium may also contain water-soluble substances added to adjust the pH of the matrix, as described in more detail below.

The pigment particles dispersed in the aqueous matrix of the matrix as defined above may have a size in the range of 1 to 50 μΐη and may be any pigments commonly used in coating compositions for substrates, such as inorganic pigments such as titanium dioxide , iron (III) oxide, chromium (III) oxide, lead chromate and carbon black, organic pigments such as phthalocyanine blue and phthalocynin green, carhazole violet, anthrapyrimidine yellow, phthavanthron yellow, isoindoline yellow, indathron blue, quinacridone violet and perylene red. For the purposes of the invention, the term pigment also includes conventional fillers and extenders such as talc or kaolin.

The invention is of particular importance in the case of primers containing metallic flakes as pigment, which are used for the production of bright metallic coatings, the so-called metalyses, mainly on the surface of car bodies. Particularly suitable metal pigments are aluminum flakes and copper bronze flakes. However, the invention also offers advantages when painting in permanent shades, as discussed in more detail below. Generally, pigments of any kind can be added to the matrix in an amount of from 2 to 100%, based on the total mass of the mass. When pigmenting with metallic pigments is used, their amount is preferably in the range of 5 to 30% by weight, based on the total weight of the mass.

These pigments, whether metallic or otherwise, can be blended into the matrix using known pigment dispersants which are suitable for use in aqueous systems.

The presence of the crosslinked polymeric microparticles in the primer coatings confers the desired ability of the film of the latter to withstand subsequent application of the coating coatings without disturbing the film or pigmentation, especially pigmentation by metallic pigments. Without the use of these microparticles, a satisfactory matrix / clear coating system cannot be produced.

In addition to this essential property, it is also desirable that the dispersion of insoluble microparticles be of a pseudoplastic or thixotropic nature. It is to be understood that the apparent viscosity of the dispersion varies according to the degree of shear stress to which the dispersion is exposed, in particular that the apparent viscosity under low shear conditions is higher than at high shear. The change in viscosity that occurs when the shear applied is changed may be immediate or may require a finite time interval, but is within the viscosity measurement time range. The reason why the dispersion on which the matrix is ​​based is required to have this character is most evident in the case where the matrix contains metallic flakes as pigment. In such a case, it is desirable that the total concentration of non-volatile solids present be relatively small. As a result, a substantial shrinkage of the base film can be achieved after application to the substrate and during drying, which results in the correct orientation of the metal flakes and an optimum flip effect. However, when the primer is to be applied to the substrate by spraying, it needs to have a sufficiently low viscosity to ensure efficient spraying in the spray gun. However, as soon as the mass hits the substrate, its viscosity should be high enough to prevent it from flowing, creating curtains or uneven distribution and uneven orientation of the metal flakes, even though the loss of water and other solvents by evaporation between the spray gun and the substrate is low (due to high ambient humidity).

These pseudoplastic properties are often documented by reporting the apparent viscosity values ​​η a in Pa.s at the selected shear rate D [s].^-1]. In the case of the metallic pigment base materials used according to the invention, this value should be 248039 t and y with a non-volatile solids content below 30% by weight, preferably less than 0.05 Pa. s at shear rate D = 10 000 s-¹ with more than 2 Pa. s at value D - 1 s'¹. Even more preferably, the matrix has a value of 77a less than 0.025 Pa. s at D = 10,000 s^-1 and more than 4 Pa. s at D '== 1.0 s¹. In the case of primers dyed to permanent shades with pigments other than metal flakes, the preferred value is 73a, again at a solids content below 30 ° / 0 below 0 Pa. s at D = - 10,000 s^_] and more than 1.0 Pa. s at D = 1.0 s^_1. However, it is in the nature of pseudoplastic or thioxotropic behavior that it is not possible to fully and precisely define the selected viscosity / shear stress data. Much depends on the viscosity measurement method actually used. Therefore, the above values ​​cannot be considered as strict limits to be observed in order to achieve the appropriate effects of the invention. Rather, this is an approximate guide and one of ordinary skill in the art can readily determine, by simple practical tests, whether a particular dispersion or a matrix formed therefrom has a sufficient degree of pseudoplasticity or thioxotropy.

There are various ways in which the base dispersion can be given a pseudoplastic or thioxotropic character. In some cases, no special measures are required. This may be the case, for example, when the microparticles were prepared as described above in British Patent Application Publication No. 2,006,229A. In this process, the polymeric microparticles are first prepared by dispersing polymerization of suitable monomers in a non-aqueous medium and then polymerizing other monomers to produce a second substantially non-crosslinked polymer having hydrophilic character, which means that it is inherently soluble in aqueous solution at a suitable pH. the environment in which the resulting dispersion is to be formed.

In fact, not all of the second polymer dissolves in the aqueous medium when the product obtained by the two-step polymerization in the non-aqueous medium is transferred to the aqueous medium. Much of the second polymer remains associated with the polymeric microparticles, and the microparticles are thereby stabilized in dispersion in an aqueous medium. This associated polymer can simultaneously impart pseudoplastic or thioxotropic properties to the aqueous dispersion. Other monomers suitable for the second stage of polymerization are, for example, hydroxyalkyl esters of acrylic or methacrylic acid, monoesters of acrylic or methacrylic acid and polyglycol, such as polyethylene glycol, monovinyl ether of such polyglycol, or vinylpyrrolidone, optionally in admixture with minor amounts of nonhydrophilic , vinyl acetate or styrene.

Alternatively or additionally, the desired aqueous solubility may be achieved by using an acrylic ester containing basic groups, such as dimethylaminoethyl methacrylate or diethylaminoethyl methacrylate as the major monomer component. These groups are then converted to salt groups by reaction with a suitable acid, for example lactic acid, dissolved in an aqueous medium. The second polymer may further be derived from comonomers comprising a substantial amount of a polymerizable carboxylic acid, such as acrylic acid or methacrylic acid, in which case the polymer may be soluble in an aqueous medium containing a dissolved base, such as dimethylaminoethanol. Thus, in general, the second polymer may be nonionic, anionic or cationic in nature.

When the polymeric microparticles have been produced by a known aqueous emulsion polymerization process, the second inherently water-soluble polymer can be produced by further polymerization in the same aqueous medium and in the presence of microparticles. The monomers used are monomers capable of providing a polymer which contains acidic salt-forming groups which can impart water solubility to the polymer. Thus, suitable monomers are polymerizable carboxylic acids such as acrylic or methacrylic acid, optionally together with minor proportions of non-hydrophilic monomers, such as methyl methacrylate, as well as hydrophilic monomers, which provide water-insoluble homopolymers, for example hydroxyethyl methacrylate with hydroxypropyl methacrylate.

If the polymeric microparticles have been produced by the aqueous dispersion polymerization process described in the above-cited British Patent Application No. 2,039,497A, the second water-soluble polymer may conveniently be formed by further polymerization in the same medium. Suitable monomers are those mentioned in the preceding paragraph and also basic monomers, such as dimethylaminoethyl methacrylate, from which water-soluble salts can be formed.

Not all water-soluble polymers produced in situ in the presence of microparticles by any of the methods described above can impart the desired pseudoplastic properties to the primer coatings. A suitable polymer composition can be obtained by simple testing in which, for example, the viscosity is measured at selected shear rates, or in which the compositions are actually applied to the substrate.

Instead of preparing a suitable water-soluble polymer in situ, the polymer may be added as a preformed separate component to the aqueous dispersion of microparticles. Suitable polymers are those which, when dissolved in an aqueous medium even at low concentrations, cause a significant increase in the viscosity of the mass. For example, one or more thickeners which are well known and used in aqueous polymer latex based coatings may be added. However, not all thickeners are suitable for this purpose since some of them are unable to impart the necessary pseudoplastic properties to the materials to which they are added. On the other hand, some thickeners which, when dissolved by themselves in an aqueous medium, do not possess these properties, can impart these properties to the dispersion of microparticles, through interactions between them and microparticles (for example, via hydrogen bridges or polar group interactions). One commercially available thickener which has proven to be very suitable is the "Acrysol" ASE 60 (Rohm and Hass).

It follows from the foregoing that any inherently water-soluble polymer that is associated with the polymer particles or which is added to the microparticle dispersion to impart pseudoplastic or thiioxotropic properties to the dispersion must be non-crosslinked in nature; however, such a polymer may, if desired, be of the crosslinkable type. That is, it may contain chemically reactive groups by means of which it may be crosslinked to the application of the base material, preferably also the topcoat. Optionally, the crosslinking may be carried out by means of an added crosslinker. Thus, as already shown, the polymer may contain hydroxyl or carboxyl groups derived from monomers bearing these groups and these groups may be used for subsequent crosslinking. using an amino resin such as a methylated melamine-formaldehyde condensate that is soluble in an aqueous medium.

It follows from the foregoing description that the primer coating composition may consist solely of polymeric microparticles, pigment particles, an aqueous medium in which both groups of particles are dispersed, and an inherently water-soluble polymer that imparts pseudoplastic properties to the mass. This is true, but it is much more preferred that the composition also comprises a film-forming polymer which is soluble in an aqueous medium. The presence of the film-forming polymer ensures that after application of the matrix to the substrate and evaporation of the aqueous medium, a substance is present on the substrate that can coalesce and fill the voids between the microparticles to form a coherent sufficiently integrated film in the second step of the process. In fact, part of the inherently water-soluble polymer that is present in the mass to impart pseudoplastic or thioxotropic properties can fulfill this function. Considering that the amount of such poly12mer required for this purpose is usually low, it may be appropriate to supplement it with one or more other water-soluble film forming agents which are added to the mass. These substances may optionally be chemically reactive with the components already present. Thus, the composition may contain oligonieric substances which, upon application of the composition, can be converted to high molecular weight products, but which in themselves do not significantly contribute to the viscosity of the composition prior to application. Examples of such compounds are low volatility diols such as 2-ethyl-1,3-hexanediol, low molecular weight propylene glycols, low molecular weight adducts of ethylene oxide with divalent or trivalent alcohols such as neopentyl glycol, bisphenol A, cyclohexanedimethanol, glycerol and trimethylolpropane such as NNN2 NMetrakis- (β-hydroxyethyl) adipamide and cyclic amides and esters such as ε-caprolactam and ε-caprolactone. If these substances are not sufficiently soluble in pure water, they should be soluble in an aqueous medium containing water together with an organic liquid that is miscible with water. Each of these oligomeric materials can be converted to a high molecular weight polymer upon application of the matrix to the substrate by utilizing their hydroxyl groups or other reactive groups to form linkages using a polyfunctional reagent also present in the mass. Particularly suitable for this purpose are aqueous resins which are soluble in the aqueous medium of the mass, in particular melamine-condensation condensates such as hexa (alkoxymethyl) melamines and their low molecular weight condensates.

Instead of containing the constituents of the film-forming polymer when applied to the substrate, the primer may comprise a preformed water-soluble acrylic polymer that does not impart pseudoplastic properties to the mass, or may contain dispersed particles of a non-crosslinked polymer that are stabilized by a similar in a manner such as crosslinked microparticles present. Each of these alternative components may optionally contain functional groups, such as hydroxylic acids, through which, after application of the mass to the substrate, it may be crosslinked using a crosslinker, for example an amino resin.

The proportions of the amounts of the various constituents of the matrix may vary within wide limits, and the optimum proportions of each individual system are often best determined experimentally, but some general principles may serve as a guide. Particular consideration should be given to the fact that when the amount of polymeric microparticles is too high in relation to the other film-forming substances present in the mass, the mass does not contain sufficient material to fill the gaps between the particles. In such a case, following the application of the clear coating, the coating has a tendency to fall (drop) into the gaps of the base film, resulting in a loss of gloss. On the other hand, if the microparticle content is too low, the particles may not impart the desired degree of resistance to attack by the solvent contained in the clear coating coating to the base film. To some extent, a lower amount of microparticles can be compensated in this direction by allowing the base film to dry for longer before applying the clear coating, but thereby reducing one of the main advantages to be obtained in the process of the invention. The satisfactory microparticle content is usually in the range of from 5 to 80% by weight based on the total non-volatile content of the matrix.

However, the optimum microparticle content depends to some extent on whether the pigment present in the matrix is ​​metallic or non-metallic. For materials containing metallic pigments. a microparticle content range of 40 to 75% by weight based on the above base is preferred. Using conventional color fast pigments, the preferred range of microparticle content is somewhat lower, i. 10 up to 50% by weight, based on the aforementioned base, since higher amounts of these pigments are usually required to achieve a suitable opacity at a sufficiently low film thickness. By reducing the amount of microparticles, too high a volume fraction of the total amount of dispersed substances that could result in the formation of a porous base film can be avoided. Applying the opaque transparent coating to such a porous film could cause the coating coating to leak into the base coating, resulting in poor gloss of the cover film.

As regards the thickener or second polymer which imparts pseudo-plastic properties to the mass, it can generally be stated as a guide that their amount in the matrix may vary from 0.3 to 50% by weight, based on the total non-volatile matter content of the matter. The amount of other film-forming agents present in the mass may range from 0 to 30% by weight. and when a cross-linking agent such as an amino resin is present, the amount may also be up to 30% by weight based on the total non-volatile content of the matrix. In addition, the matrix may optionally contain a catalyst by crosslinking to be carried out after application of the matrix to the substrate. The catalyst may be a water-soluble acidic compound such as p-toluenesulfonic acid, orthophosphoric acid, maleic acid or other strong carboxylic acid such as tetrachlorophthalic acid. Instead of the acid, the volatile amine volatile salts of such acids can also be used.

The base coatings according to the invention are suitable for use in a process for the production of a multi-layered protective and / or decorative coating on the surface of the substrate, which is the subject of U.S. Pat. No. 226,427. Details relating to the application of a primer to the substrate and further processing of the deposited film are set forth in this patent.

Since the base compositions of the present invention are aqueous based compositions, they have the advantage of eliminating or substantially reducing the disadvantages associated with atmospheric pollution inherent in solvent based compositions. Their main significance is that a short time after application to the substrate suffices to dry them, yet it is achieved that there is no tendency to mix the base coat with the topcoat or to dissolve the base film with the topcoat when applying the topcoat to the base film. If the inventive bases are used in the production of so-called metallics, these advantages are achieved without sacrificing the good orientation of the metal pigments. In the case of so-called. The base film undergoes to a much lesser extent the effect of blistering compared to water-based coatings that do not contain polymeric microparticles.

The invention is illustrated by the following examples in which parts and percentages are always intended to be parts and percentages by weight. The examples are illustrative only, but do not limit the scope of the invention in any way. The apparent viscosity values ​​of & gt; base masses were determined in the examples using two different instruments. -Qa values ​​at shear rate of 10,000 s^_1 were measured using a cone and plate viscometer modified to measure viscosity ranging from 0 to 0.2 Pa. s at the specified shear rate. This device is described in the Journal of Oil and Color Chemists¹ Association, July 1966, in an article by CH Monk and manufactured by Research Equipment (London) Limited.

Values ​​r, a at shear rate 1,0 s ”¹ were measured using a concentric cylinder viscometer, "Theomat 30" with "A" cup and weight. Each sample was subjected to a shear rate of 660 s^_1until a constant shear stress was reached and immediately thereafter the shear rate was changed to 1.0 sec.^_1, the shear stress was measured and the viscosity was calculated from these data. The Rheomat 30 is manufactured by Contraves AG in Zurich.

He did

AND.

Preparation of dispersion of polymer microparticles in aliphatic hydrocarbon

A reactor equipped with a stirrer, a thermometer, a reflux condenser and a monomer feed device for the returned distillate was charged with 35.429 parts of heptane. The heptane was heated to reflux (95-96 ° C) and a mixture of the following ingredients was added:

methyl methacrylate 5.425 parts, azodiisobutyronitrile 0.420 parts graft copolymer stabilizer (33% solution described below) 1.984 parts

The reactor contents are maintained at reflux temperature for 30 minutes to form a & quot; seeded & quot; polymer dispersion and then the following mixture of components is added to the returned distillate. The mixture was added at a constant rate for 3 hours.

methyl methacrylate 25,000 parts allyl methacrylate 0.775¹ azodiisobutyronitrile 0.338 part graft copolymer stabilizer (33% solution described below) 5.316 parts

After the addition was complete, the reactor contents were maintained at reflux for an additional hour, 12.874 parts of heptane were added and the mixture was again heated to reflux. A preformed mixture of the following composition is introduced into the returning distillate for 1 hour at a constant rate:

<td>methyl methacrylate</td><td> 3,883</td><td>part</td>

<td>butyl acrylate</td><td> 3,066</td><td>part</td>

<td>hydroxyethyl acrylate</td><td> 2,044</td><td>part</td>

<td>acrylic acid</td><td> 1,226</td><td>part</td>

<td>azodiisobutyronitrile</td><td> 0,071</td><td>part</td>

<td>graft copolymer as a stabi-</td><td></td><td></td>

<td>(33% solution described)</td><td></td><td></td>

<td>further)</td><td> 2,149</td><td>part</td>

After the entire amount of this mixture was added, the reaction mixture was kept at reflux temperature for 1 hour. A stable dispersion of crosslinked polymeric microparticles is obtained having a total non-volatile solids content of 43.5 to 44.5% and a non-volatile solids content insoluble in any polar solvent (so-called gel content) of 34.5 to 35%.

The graft copolymer stabilizer used in the above process was prepared as follows: 12-hydroxystearic acid was autocondensed to an acid value of about 31-34 mg KOH / g (equivalent to a molecular weight of 1650 to 1800 J) and then treated with an equivalent amount of glycidyl methacrylate. The resulting unsaturated ester is copolymerized in a weight ratio of 2: 1 with a mixture of methyl methacrylate and acrylic acid in a weight ratio of 95: 5. The copolymer was used as a 33% solution in a mixture of ethyl acetate (11.60%), toluene (14.44%), an aliphatic hydrocarbon boiling point 98 to 122 ° C (61.29%) and an aliphatic hydrocarbon boiling point 138 to 165 ° C (12.67%).

B.

Conversion of polymeric microparticles into an aqueous dispersion

To a reactor equipped with a stirrer, a thermometer, and a device for removing the volatile solvent by distillation is charged demineralized water 72.308 parts butoxyethanol 10.332 parts dimethylaminoethanol 0.552 parts

The reactor contents were heated to 100 ° C and 46.497 parts of the microparticle dispersion from step A were introduced into the reactor at a rate such that the heptane contained in the dispersion was removed by distillation without significant concentration in the reactor. The time required for this operation is about 2 hours. 29 to 30 parts of a distillate consisting mainly of heptane and some water are separated.

The product obtained is a stable aqueous dispersion of polymeric microparticles having a nonvolatile solids content of 20-22% and a pH of 7.2-7.5.

C.

Preparation of aluminum pigment concentrate

An aluminum paste (metal content% J 5.8 parts butoxyethanol 2.9 parts) was introduced into a stirred mixing vessel

The ingredients were mixed together for 15 minutes, then 2.9 parts of butoxyethanol were added at a constant rate for 30 minutes, and the mixture was further stirred for 1 hour. Then add 4_;84 After stirring for an additional hour, 1.93 parts of hexamethoxymethylmelamine and 0.97 parts of butoxyethanol were added and the mixture was stirred for an additional hour.

D.

Preparation of the base coat

The following components are mixed together for 1 hour: aluminum concentrate from Step C 19.34 parts of microparticle dispersion from Step B 79.61 parts of hexamethoxymethylmelamine 0.46 parts dimethylaminoethanol salt of p-toluenesulfonic acid, 10% solution in demineralized water 3.47 parts

The base material thus obtained has the following characteristics:

Solids content:

27,2 %

Apparent viscosity -zja:

0_;35 Bye . s at shear rate D 1 s^_l

-0,006 Pa. s at shear rate D —- 10,000 s'¹

Preparation of acrylic polymer for clear coating

In a reactor equipped with a stirrer, a thermometer, and a reflux condenser, 22.260 parts xylene aromatic hydrocarbon boiling point 190 to 210 ° C 10,000 parts was charged.

The mixture is heated to reflux (142-146 ° C) and a preformed mixture of the following composition is added over 3 hours:

styrene ethyl acrylate 2-ethylhexyl acrylate hydroxyethyl acrylate acrylic acid cumene hydroperoxide

21,49 díl

4.51 part

13.75 parts 10.05 parts 0.49 parts 1.41 parts

The reactants were maintained at reflux for an additional 2 hours and then isobutyl alcohol xylene was added

12.72 parts 3.32 parts

A clear polymer solution is obtained having a solids content of 50%.

F.

Preparation of a clear solvent-based coating material

The following components shall be mixed together:

polymer solution from step E 53.3 parts butyl melamine ormaldehyde resin in the form of 67% solution in butanol 26.5 parts dipentene 5.0 parts polymer improving flow properties in the form of 10% solution in xylene 0.1 part isobutyl alcohol 2.0 part xylene 13 1 part

A clear solution is obtained with a solids content of 44.4%. Its viscosity is 40 s (British standard cup B4 at 25 ° C).

G.

Application of the base coat and clear cover coat to the substrate

The metal plate is coated with primer, then leveled, then sprayed with two coatings of the metallic pigment described in Step D (used without further dilution) at 22 ° C and 39% RH. Between the two coatings, allow the first coat to dry for 2 minutes. The feed rate to the spray gun is 400 ml / min.

After not applying the second base coat, the board is blown at 25 ° C with air and then two clear coatings described in step F are applied to them. (The clear coat is diluted with xylene to viscosity 45 and according to British standard using a cup before application. B 3 at 25 ° C, J The second top coat is applied to the wet first coat, allowing the first coat to dry for only 2 minutes between the two coatings. ^CC.

The resulting silvery metallic coating has an excellent "flip", pigment orientation is good, and the coating looks like the highest flip coatings made using fully solvent-based coating systems. The gloss and adhesion between coatings is good and there is no leakage of the clear coating composition into the base coat.

Example 2

The metal plate is coated with primer, then leveled, then sprayed with two primer coatings containing the metallic pigment described in Step D of Example 1 (used without further dilution) at 25 ° C and 58% RH . Between the two coatings, allow the first coat to dry for 2 minutes. The feed rate of the duty of the cutting gun is 400 ml / min.

After applying the second base coat, the board is dried at 35 to 42 degrees Celsius for 10 minutes and then two clear coatings described in step F of Example 1 are applied. (The clear coat is diluted with xylene to a viscosity of 45 sec before application. British standards using cup B3 at 25 ^C,C.) The second topcoat is applied to the wet first coat; between the two coatings, the first coat is allowed to dry only for 2 minutes. After a final three-minute drying time, the plate is baked for 30 minutes at 125 to 130^CC.

The coating thus obtained has the same excellent properties as the coating described in the example

1.

Example 1

AND.

Preparation of an aqueous dispersion of polymeric microparticles

The following mixtures of substances are prepared:

(1) monomer mixture

<td>methyl methacrylate</td><td> 18,350</td><td>part</td>

<td>allylmethacrylate</td><td> 1,340</td><td>part</td>

<td>styrene</td><td> 4.700</td><td>part</td>

<td>butyl acrylate</td><td> 18,800</td><td>part</td>

<td>methacrylic acid</td><td> 1,410</td><td>part</td>

<td>primary octylmercaptan</td><td> 0,159</td><td>part</td>

<td>ammonium salt of adduct sulfate</td><td></td><td></td>

<td>nonylphenol and 5 moles</td><td></td><td></td>

<td>ethylene oxide</td><td> 0,185</td><td>part</td>

(2) ammonium persulfate initiator solution 0.130 parts deaineralized water 4.010 parts (3) methyl methacrylate surfactant solution 20.000 parts nonylphenol adduct sulfate salt and 5 moles ethylene oxide 20,000 parts

To a reactor equipped with a stirrer, a thermometer. a reflux condenser and a device for the controlled introduction of two separate liquid feedstocks shall be declared:

deraineralized water 47.641 parts surfactant solution (3) 0.100 parts

The batch is heated to 80 to 85 ° C, then 2000 parts of monomer mixture (1) are added and the resulting mixture is maintained at 80 to 85 ° C for 15 minutes. Then, 1.068 parts of the initiator solution (2) is added and the reaction mixture is kept at the same temperature for 20 minutes. Then, at constant speed, add within 5 hours:

monomer mixture (1) 42.944 parts hydroxysopropyl methacrylate 2.350 parts

During the same five-hour period, 3.672 parts of the initiator solution were fed separately into the reactor at a constant rate. The reaction mixture is kept at 80-83 ° C for 1 hour and then cooled to room temperature. A stable aqueous dispersion of crosslinked polymeric microparticles is obtained. The dispersion contains 49.6% solids and the content of non-volatile solids insoluble in any organic solvent is 44.5%.

B.

Preparation of the base coat

The mixture (4J

2.563 parts of a commercially available thickener known as Acrysol ASE 60 (Rohm and Hass Co.) was mixed with a sufficient amount of a 25% solution of dimethylaminoethanol in demineralized water to adjust the pH to 7.65. Additional demineralized water was then added to give a total weight of 23.956 parts.

Mixture (5j

A mixture of 29.299 parts of the microparticle dispersion from step A and 18.614 parts of demineralized water was adjusted to pH 7.65 by the addition of a sufficient 25% solution of dimethylaminoethanol in demineralized water. Then 23.956 parts of the mixture (4) prepared as described above are mixed into the resulting mixture.

The running mixer shall be filled with:

aluminum paste (metal content 65%) 3.133 parts

2-butoxyethanol 15,193 parts

The batch is stirred for 15 minutes, then:

hexamethoxymethylmelamine 3,696 parts polypropylene glycol (average molecular weight 400) 2,464 parts and stirring was continued for an additional hour. Then a mixture of (5) 71.869 parts demineralized water 1.623 parts was added and the mixture was stirred for an additional hour. The base material thus obtained has the following characteristics:

solids content:

205 percent

Apparent viscosity -qa:

3.46 Pa. s at shear rate D = 1 s¹0,042 Pa. with D - 10 000 s "¹

C.

Preparation of acrylic polymer for clear coating material

A reactor equipped with a stirrer, a thermometer, and a reflux condenser was charged with 42.20 parts of isopropyl alcohol. Isopropyl alcohol is heated to reflux (84 ° C) and then the following mixture of substances is added at a constant rate over 3 hours:

<td>methyl methacrylate</td><td> 19,85</td><td>part</td>

<td>butyl acrylate</td><td> 24,80</td><td>part</td>

<td>hydroxyethyl methacrylate</td><td> 2,48</td><td>part</td>

<td>acrylic acid</td><td> 2,48</td><td>part</td>

<td>isopropyl alcohol</td><td> 7,45</td><td>part</td>

<td>benzyl peroxide (60% paste in</td><td></td><td></td>

<td>dimethylf talátu)</td><td> 0,64</td><td>part</td>

<td>The reactants maintain DC</td><td>another 2 ho</td><td>diny</td>

at reflux temperature. A polymer solution containing 50^C/ o solids. 28.87 parts of isopropyl alcohol are removed from the solution by direct distillation and 1.86 parts of dimethylaminoethanol are added to the residue with stirring, followed by 80.35 parts of demineralized water. Distillation of the azeotropic mixture of isopropyl alcohol and water is then continued until a temperature of 96-98 ° C is reached, and the distillate is replaced by the addition of demineralized water. The total amount of separated distillate is 118.83 parts and the total amount of additionally added demineralized water is 114.65 parts. An aqueous acrylic polymer solution was obtained containing 33.5% solids.

D.

Preparation of a clear, water-based coating material.

The following are mixed together: polymer solution from step C 75.16 parts hexamethoxymethylmelamine 6.29 parts butoxyethanol 12.26 parts demineralizing water 5.50 parts dimethylaminoethanol salt p-toluenesulfonic acid (pH 7.6) 0.79 parts

The clear coating thus obtained contains 31.5% solids and has a viscosity of 0.05 Pa. with.

E.

Application of the base coat and clear cover coat to the substrate

The metal plate is prepared with a primer, then a leveling coat is applied and then the three coatings of the metallic pigment primer described in step B are sprayed on. The coatings are used without further dilution and sprayed at 25 ° C and relative temperature. humidity 51 ° / o. The second coating is applied 1 minute after application of the first coating, the feed rate to the spray gun being 400 ml / min.

After the third primer is applied, the board is dried at 35-42 for 10 minutes ^CC. Three coatings of the clear coating composition described in step D are then applied. The coatings are applied without. intermediate drying into the wet prior coating, since there is a delay of 2 minutes between the individual coatings, and after a third coat, a delay of 3 minutes. Then the plate is first heated to 70^CC and finally fired at 150 ° C for 30 minutes ^CC.

The resulting coating has an excellent flip, the pigment orientation is good, and the coating is similar in appearance to coatings with the highest degree of flip made using fully solvent-based coating systems. The gloss and adhesion between coatings is good and there is no leakage of the clear coating composition into the base coat.

Example 4

AND.

Preparation of an aqueous dispersion of polymeric microparticles

A reactor equipped with a stirrer, a thermometer, a reflux condenser and a device for the controlled introduction of two separate liquid charges is charged with:

<td>demineralized water</td><td>28,030 díl</td>

<td>and then the preformed mixture</td><td>containing</td>

<td>methyl methacrylate ammonium salt of adduct sulfate</td><td>0,029 díl</td>

<td>nonylphenol and 5 moles of ethylene oxide</td><td>0,029 díl</td>

<td>The contents of the reactor are stirred</td><td>warms up to</td>

<td>80 to 85 ° C and a mixture of the following components is added beforehand:</td><td>ready</td>

<td>butyl acrylate</td><td>0,069 díl</td>

<td>methyl methacrylate</td><td>0,069 díl</td>

The reaction mixture is maintained at 80-85 ° C for 15 minutes and then a mixture of demineralized water of 0.67 part ammonium persulfate 0.021 part is added.

The reactor contents were maintained at 80-85 ° C for a further 20 minutes, and then a preformed butylacrylate mixture of 10.75 parts by weight of methyl methacrylate, 10.189 parts of allyl methacrylate, 0.686 parts of ammonium salt of nonylphenol adduct, and 5 moles of ethylene oxide was added. part

A solution of 0.037 parts of ammonium persulfate in 4.985 parts of demineralized water was simultaneously introduced into the reactor at a constant rate over the same three-hour period.

After the addition of the above two batches, the reactor contents were maintained at 80-85 ° C for 1 hour. Then 34.716 parts of demineralized water are added, the temperature is brought back to 80 to 85 ° C and the following pre-prepared mixture is added to the mixture at a constant rate over 1 hour:

<td>methacrylic acid</td><td> 0,950</td><td>part</td>

<td>butyl acrylate</td><td> 2,035</td><td>part</td>

<td>hydroxyethyl acrylate</td><td> 1,357</td><td>part</td>

<td>methyl methacrylate</td><td> 0,950</td><td>part</td>

<td>ammonium salt of adduct sulfate</td><td></td><td></td>

<td>nonylphenol and 5 moles</td><td></td><td></td>

<td>ethylene oxide</td><td> 0,028</td><td>part</td>

A solution of 0.019 parts of ammonium persulfate and 0.016 parts of sodium borate in 0.59 parts of demineralized water was also fed into the reactor at a constant rate over the same one hour period.

After addition of the above two batches, the temperature of the reaction mixture was maintained at 80-85 ° C for an additional hour. The mixture was then cooled rapidly. A stable aqueous dispersion of polymeric microparticles is obtained. The dispersion has a total non-volatile solids content of 30% and a non-volatile solids content insoluble in organic solvents of 27%.

B.

Preparation of the base coat

The pH of the dispersion obtained in Step A was adjusted to 8.0 by addition of dimethylaminoethanol and 54.15 parts of this dispersion were introduced into a mixer. The following substances are then added to the blender in the following order:

demineralized water 18.91 parts butoxyethanol 8.12 parts aluminum pigment concentrate described in Example 1 (C) 18.02 parts

The mixture was stirred for 1 hour. A primer is obtained with the following properties:

Solids content:

25.8 percent

Apparent viscosity Tja:

0.20 Pa. s at shear rate D - 1 s^-1

0,02 Pa. s at shear rate D = 10 000 s^-1

C.

Application of primer and clear coating to substrate

Two primers containing the metallic pigment described in step B (without further dilution) at 22 ° C and a relative humidity of 39% are sprayed onto the metal plate prepared with primer and leveling coating. The coating composition described in step F of Example 1 is then applied as the coating material. The procedure for applying both the primer and the clear coating material is otherwise identical to that described in Example 1, step G.

The results obtained are similar to those obtained in Example 1, step G. Comparative Example A

AND.

Preparation of silvery metal base without microparticles

The blender is mixed with stirring:

aluminum paste (metal content 65% j 6.0 part

2-butoxyethanol 18.7 parts

The batch is stirred for 30 minutes, then hexamethoxymethylmelamine (4.3 parts) polypropylene glycol (average molecular weight) is added.

400) 2.9 parts and the mixture was further stirred for 1 hour. It is then added with stirring over 30 minutes

51.2 parts of an aqueous acrylic polymer dispersion having a solids content of 33.5%, prepared as described in Example 5C below, and then 16.9 parts of demineralized water.

In this way, a matrix is ​​obtained having the same ratio of pigment to binder, the same ratio of hexamethoxymethylmelamine to total non-volatile matter content and a very similar apparent viscosity value ηβ at D = 10,000 s^_1 The apparent viscosity of the microparticle-free coating composition at high shear rate indicates that the composition is suitable for spray application to a substrate. Its apparent viscosity at low shear rate D = 1 s^_1 however, it is only about 0.1 Pa.s, indicating that the composition has weak pseudoplastic or thioxotropic properties.

The primer is applied to the slab and a clear acrylic overcoat is applied to the primer as described in Example 1G. The composition of the clear opaque coating corresponds to that of Example IE and F. The silvery metallic coating thus obtained has a very low "flip" and shows traces of inhomogeneous pigment distribution and orientation. In addition, blisters form on the coating during firing.

Examples 1-4 illustrate the application of the method of the invention in the production of metallic coating 248039 coatings. The following example illustrates its application to coatings pigmented with conventional colourfast pigments.

Example 5

AND.

Preparation of the white pigment friction base

In a ball mill, the following ingredients are ground for 16 hours:

titanium dioxide, as a pigment of 31.3 parts

2-butoxyethanol 18.9 parts demineralized water 18.9 parts dimethylaminoethanol 0.2 parts hexamethoxymethylmelamine 7.7 parts

The resulting friction base having a particle size below 0.5 μΐη is then diluted with 11.6 parts of 2-butoxyethanol and 11.6 parts of demineralized water.

B.

Preparation of friction base of blue pigment

The following ingredients are milled together in a ball mill for 16 hours:

phthalocyanine blue pigment 12.9 parts

2-hutoxyethanol 23.8 parts demineralized water 23.8 parts dimethylaminoethanol 0.2 parts hexamethoxymethylmelamine 9.7 parts

The resulting friction base having a particle size below 0.5 µm is then diluted with 14.8 parts of 2-butoxyethanol and 14.8 parts of demineralized water.

C.

Preparation of an aqueous solution of acrylic polymer

The following ingredients are mixed together:

methyl methacrylate 19.9 parts butyl acrylate 24.8 parts hydroxyethyl methacrylate 2.5 parts acrylic acid 2.5 parts isopropyl alcohol 7 4 parts benzoyl peroxide 0.7 parts

Mixture 15.0 parts of the above mixture a

42.2 parts of isopropyl alcohol are introduced into a flask equipped with a stirrer, a thermometer, a reflux condenser and a rate-controlled liquid addition device. The contents of the flask were heated to reflux (84 ° C) and the remainder of the above mixture (42.8 parts) was introduced into the flask at a constant rate over 3 hours. The reaction mixture was refluxed for a further 2 hours to give a polymer solution containing 5.0% solids. 1.8 parts of dimethylaminoethanol are then added to the solution, the mixture is again heated to reflux, the reflux condenser is made to descending, and a total of 33 parts of distillate are distilled off over 10 hours and 85.0 parts of demineralized water are added. The aqueous acrylic polymer solution finally obtained contains 33.5% solids.

D.

Preparation of blue primer

The following components are mixed in the following order:

white pigment fraction described in paragraph A 52.25 parts blue pigment fraction described in paragraph B 8.39 parts microparticle dispersion described in Example 1 B 14.62 parts acrylic polymer solution described in paragraph G 24.33 parts

10% aqueous solution of p-toluenesulfonic acid neutralized to pH 7.6 by addition of dimethylaminoethanol 0.41 part

The resulting primer has a viscosity of 1.6 Pa. s at shear rate of 1 s ”¹ and 0.053 Pa. s at a shear rate of 10,000 s^_1.

E.

Application of the base coat and clear cover coat to the substrate

The metal plate is coated with a primer primer, a leveling compound and two coats of the blue primer described in paragraph D. The blue coats used without further dilution are sprayed onto the surface at 22 ° C and 39% relative humidity, with a lag between the two coats. 2 minutes. After application of the second primer, the board is blown with air at 25 ° C and then two coats of the clearcoat described in Example 1F are applied. The clear coating is diluted with xylene to a viscosity of 45 s measured in accordance with the British standard in cup B 3 at 25 ° C prior to spraying. A second coating of the coating is applied to the still wet first coating, since the delay between the first and second application is 2 minutes. After application of the second coating, the coating is allowed to dry for 3 minutes and then the plate is baked for 30 minutes at 125 to 130 ° C.

The resulting coating has good opacity and gloss, and no clear coating material flows into the base film.

Comparative example

AND.

Preparation of a blue primer without polymer microparticles

The following components are mixed together, in that order:

white pigment fraction described in Example 5 A 54.8 parts blue pigment fraction described in Example 5 B 8.8 parts hexamethoxymethylmelamine 0.3 part acrylic polymer solution described in Example 5 C 35.7 parts

A 101% aqueous solution of p-toluenesulfonic acid neutralized to pH 7.6 by addition of 0.4 parts dimethylaminoethanol

The resulting matrix has a viscosity of 0.1 Pa. s at a shear rate of 1 s^-1 and 0.083 Pa.s at a shear rate of 10,000 s^_1, ie it has a very weak pseudoplastic or thioxotropic character.

B.

Application of the base coat and clear coat to the substrate

The procedure of Example 5E is repeated except that the primer described in paragraph A above is used in place of the primer described in Example 5. In this case, significant blistering of the base coat is observed, i.e. air entrained in the base coat. separates in the form of bubbles that deform the surface of the film and damage its smooth appearance. In addition, a delay of more than 3 minutes must be used between the application of the second coat of primer and the first coat of clearcoat, since otherwise the clear coating material disrupts the base film, which has a detrimental effect on the resulting board appearance.