KR850000445B1 - Coating process - Google Patents

Abstract

A process for applying multilayer protective and/or decorative coatings on substrate surfaces comprises covering the surfaces with a primer contg. a film-forming agent, a volatile solvent and finely divided pigment, and applying a transparent top-coat compsn. contg. a film-forming polymer and volatile carrier solvent to produce a second polymer film covering the first film. The primer comprises an aq. dispersion of crosslinked polymer particles(dia. 0.01-10 microns), which are insoluble in the aq. medium but do not flocculate, such that the medium has a pseudo-plastic or thixotropic character. The process is esp. applicable to coating car bodies.

Description

How to Form a Multilayer Cover

The present invention relates to a method of applying protective and decorative coatings on a body surface, in particular on a vehicle body surface.

Particularly in the automobile industry, it is known to use coating compositions containing metal pigments, which are so-called "glamour metallic finishing agents" in which different light reflection actions are obtained by vision.

In order to maximize the "flip" tone effect, it is necessary to carefully prescribe the coating composition for the film-forming resin and the liquid medium. While satisfying this condition, it is difficult to obtain a high degree of gloss at the final finish usually desired in the automotive industry. For this reason, one of the proposed methods for obtaining a metallic luster finish is a two coat method, which contains a metal pigment and is formulated with a base coat prepared to provide the maximum "flip" effect. Is spray-coated on the surface of the gas and top-catted again without a pigment that gives high gloss without denaturing the coating properties on the base coat.

For a successful "base coat / clear coat" two-coat metallic gloss finish, the base coat coating should be applied during clearcoat coating so as not to interfere with the action of the metal pigment (and thus not impair the "flip" effect). It should be chemical resistant against clearcoat solvent. Moreover, it is desirable that the base coat film retain this property without the need for long-term intermediate drying or hardening operations.

Basecoat and clearcoat are used together as a medium for organic solvents and in known basecoat / clearcoat systems, the above requirement is, in most cases, by using additives that can impart gelling properties to the basecoat coating immediately after formation. And the additive used for this purpose is cellulose acetate butyrate.

The change from the relatively low viscosity of the basecoat composition required in the spray gun to this gel composition results in the liquid diluent of the composition being volatiles that are selectively lost by evaporation until reaching the gas from the spray gun. It is encouraged by inclusion in.

In order to avoid air pollution, the coating composition which uses water rather than the organic solvent as a diluent has been attracting attention recently. As such compositions have been proposed for a variety of uses in the automotive industry, the use of aqueous compositions as basecoat components in basecoat / clearcoat systems is not yet satisfactory. One of these reasons is that it is very difficult to selectively control evaporate the diluent of the base cord composition from the spray gun to the gas without controlling the ambient humidity of the spray zone at high cost. However, we were able to prepare a satisfactory aqueous basecoat composition based on crosslinked polymer microgels.

Accordingly, the present invention provides a method of coating a basecoat composition comprising (a) a film forming material (b) a volatile liquid medium for the material and (c) pigment particles dispersed in the liquid medium, and 2) 1) Forming a polymer coating on the surface of the substrate with the composition applied in step 3) adding to the base coat coating formed for a transparent top coat composition containing d) a film forming polymer and e) a volatile liquid carrier for the polymer. Forming a multi-layer protective film and / or decorative film on the surface of the gas by a process consisting of forming a second polymer film on the base coat film with the composition applied in step 3). ) And (b) have a diameter of 0.01-10 microns and are insoluble in aqueous media and stable to gross flocculation of crosslinked polymer particulates in aqueous media. Liquid and in the plastic (擬 塑性) or yaw, characterized by the supplied dispersion showing a modified (搖 變性), it provides a method for forming a multilayer coating film.

Crosslinked polymer particulates can be obtained from various types of polymers. Particularly interesting for this purpose are acrylic moieties obtained from one or two or more alkyl esters of acrylic acid or methacrylic acid, optionally with other ethylenically unsaturated monomers. Suitable acrylic or methacrylic esters include methyl methacrylate, ethyl methacrylate, methacrylic acid, propyl, butyl methacrylate, ethyl acrylate, butyl acrylate and 2-ethylhexyl acrylate. Suitable other copolymerizable monomers include vinyl acetate, vinyl propionate, acrylonitrile, styrene and vinyltoluene. Since the polymers must be crosslinked, monomers having multifunctionality for the polymerization, such as ethylene glycol dimethacrylate, allyl methacrylate or divinylbenzene, may be included in small proportions in the monomers providing the polymer. Alternatively, these monomers may be reacted with each other during or after polymerization such as epoxy and carboxyl groups (eg, in glycidyl methacrylate and methacrylic acid), anhydrides and hydroxyl groups or isocyanates and hydroxyl groups. It may comprise a small proportion of the other two monomers having a chemical group pair.

The chemical composition and crosslinking degree of the polymer microparticles may be such that they may have a Tg (glass-rubber transition temperature) below room temperature (in this case the microparticles are rubbery) or may have a Tg above room temperature (in this case the microparticles Hard glass state).

As mentioned above, the polymer microparticles in the basecoat composition need to be dispersed with little or no particle agglomerate, even when the dispersion contains a solid, i.e., even when the dispersion contains a solid, in particular a relatively high solid. In this case, even a slight amount of particle agglomeration is not a big mistake. This state is achieved by hanging the barriers of the different polymer chains around the polymer particles, for example by steric stabilization, ie, as a result of the solvation by the aqueous medium in the composition, resulting in an extended array of chains. Can be achieved. In this regard, the term "solvation" can be dissolved in the above-mentioned aqueous medium when the polymer chain in question is an independent molecule, but the polymer chain is attached to the polymer microparticles at one or more sites along its length. It means that the barrier remains permanently bound to the polymer microparticles. Such three-dimensionally stabilized polymer microparticles can be prepared by dispersing the appropriate monomer in an aqueous medium in the presence of a stereostable. This stabilizer is amphiphilic, which means that two essential polymer components having different properties in the molecule, i.e., polymer chain components solvated in this aqueous medium, and not solvated in this medium are aqueous media. It contains a polymer chain component that is fixed to the polymer fine particles insoluble in. Suitable dispersion polymerization processes are described in British Patent No. 7940088 (Application Publication No. 2039497A). The aqueous medium used for the polymerization consists of water mixed with a volatile organic auxiliary solvent, which can dissolve all or all of the monomers which are insoluble in water alone. In this polymerization method, it is necessary to perform so that a separation monomer phase may not exist at the temperature which is at least 10 degreeC higher than the glass transition temperature of the polymer which forms superposition | polymerization. Amphiphilic steric stabilizers can be grafted by monomers in situ during polymerization from polymers obtained as a preformed material that are added to the polymerization mixture or dissolved in an aqueous medium and copolymerized with polymerized seed monomer or dehydrogenated. The steric stabilized fine particle dispersion obtained by this method is very suitable for the preparation of the base-coat composition used in the present invention, by distilling from this dispersion to remove the organic auxiliary solvent without impairing the stability of the dispersed phase. This is because a product in which the continuous phase consists of complaints can be obtained.

Alternatively, polymer particulate dispersions can be obtained by aqueous emulsion polymerization of the appropriate monomers, in which case stabilization against agglomeration is carried out on the particulates with charge species obtained from water soluble ionizing surfactants and / or water soluble polymerization initiators. Obtained by being present. Such polymerization methods are widely described in the literature.

In addition, the polymer fine particles can be prepared by transferring the polymer obtained by the non-aqueous dispersion polymerization of the monomer to the aqueous medium. Such a process is described in British Patent No. 42557/77 (Application Publication No. 2006229A). This method comprises the first step of preparing a stereostabilizing dispersion in a non-aqueous liquid of a non-aqueous liquid and a water insoluble polymer by methods well known to those skilled in the art, a second polymer which is dissolved in the desired aqueous medium at a suitable pH. And a second step of polymerizing the resulting monomer in the dispersion obtained above in the presence of a steric stabilizer and transferring the resulting composite polymer fine particles from the non-aqueous medium to the aqueous medium.

All of the above descriptions relate to the case where the crosslinked polymer microparticles are from an additive polymer, which is the kind of polymer most suitable for the purposes of the present invention, but in another way, the polymer microparticles may be condensed polymers, for example, It is also possible to use polyesters prepared from alcohols and polycarboxylic acids. Suitable polyhydric alcohols for the production of polyester include ethylene glycol, propylene glycol, butylene glycol, 1: 6-hexylene glycol, neopentyl glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, glycerol, triethylolpropane, trimethyl Olethane, pentaerythritol, dipentaerythritol, tripentaerythritol, hexane triol, oligomers of styrene and allyl alcohol (e.g., commercially available from Monsanto Chemical Company in the designation of RJ 100), trimethylolpropane Condensation products of ethylene oxide or propylene oxide (products known as the "Niax" triol).

Suitable polycarboxylic acids include succinic acid (or anhydride thereof), adipic acid, azelaic acid, sebacic acid, maleic acid (or anhydride thereof), fumaric acid, muconic acid, itaconic acid, phthalic acid (or anhydride thereof), isophthalic acid, terephthalic acid, trimelli Butyric acid (or anhydride thereof) and pyromellitic acid (or anhydride thereof). These polymers obtain crosslinks by mixing two or more functions of materials in the starting composition, but in this case all molecular species actually cross because the molecularosis formed in the condensation polymerization is widely distributed as compared to the case of addition polymerization. It is difficult to combine.

The above-described method of producing polymer fine particles by polymerization in an aqueous medium of an addition type monomer is generally not applicable to condensation type monomers because of the inhibitory effect of water on the condensation reaction. However, the condensed polymer microparticles can be easily prepared by dispersion polymerization in a non-aqueous solute according to the methods described in the Applicants' British Patent Nos. 1373531, 1403794 and 1414199, and also a method of obtaining crosslinked fine particles. It is described in this specification. The polymer fine particles can be transferred to a selected aqueous medium after being introduced into the second polymerization stage of the process described in British Patent No. 42557/77 (Application Publication No. 2006229A) described above as dispersed in a non-aqueous medium.

"Aqueous medium" means a mixture of water or an organic liquid miscible with water, such as methanol, or water alone, and the aqueous medium also includes a water-soluble substance introduced for the purpose of adjusting the pH of the basecoat composition, as described below. This may be included.

The pigment particles dispersed in the aqueous medium of the basecoat composition as described above have a particle size in the range of 1-50 microns, and any pigments commonly used in surface coating compositions, namely titanium dioxide, iron oxide, chromium oxide, lead chromate and Inorganic pigments such as carbon black and organic pigments such as phthalocyanine blue, phthalocyanine green, carbazole violet, anthrapyridine yellow, flavantron yellow, isoindolin yellow, indanthrone blue, quinacridone biolet or perylene red Can be. The term "pigment" in the present invention is meant to include conventional fillers and extenders such as talc or kaolin.

The method of the invention is particularly suitable in the case of basecoat compositions containing metal powders, mainly for the purpose of forming a "glamor-metal" finishing coating on the vehicle body surface as described above, and particularly suitable as a metal powder pigment. And bronze powder. However, the present invention is also advantageous for forming an "unicolor" finish film as described below. Generally, pigments may be formulated in the basecoat composition in an amount of 2% -100% of the total weight of the composition. When using metal pigments, this is preferably 5% -30% of the total weight of the composition.

Such pigments, whether metallic or other materials, may be formulated in the basecoat composition in the presence of known pigment dispersants suitable for use in aqueous systems.

The presence of crosslinked polymer particulates in the basecoat composition does not interfere with the coating and does not interfere with the formulation of pigments (particularly metal pigments), which are essential for achieving the basecoat / clearcoat system, and continue to resist the application of the topcoat composition. To the coating obtained from this composition.

In addition to this essential requirement, the dispersion of insoluble fine particles, as described above, should contain external plasticity or thixotropy. This means that the viscosity of the dispersion can vary depending on the degree of shear applied to the dispersion, in particular, the viscosity is higher at low shear than at high shear. Viscosity changes that occur upon a change in applied shear may require a finite time interval that is instantaneous or within a time of viscosity measurement. The reason why this property is required in the dispersion based on the base coat composition is most evident when the basecoat composition contains a metal powder pigment, in which case the metal powder is contracted by shrinking the base coat film after application to the gas and during the drying operation. In order to secure the optimum flip effect by orienting correctly, it is preferable that the total concentration of the nonvolatile solids is relatively low. However, if the basecoat composition is spray coated onto a gas, the composition should have a viscosity low enough to atomize, but after reaching the gas, the composition will lose some water and other solvents as it evaporates between the spray gun and the gas. However, it must have a viscosity high enough to prevent the occurrence of "relaxation" of the coating or "sheariness" (uneven distribution and orientation) of the metal powder.

This retention of external plasticity is expressed by the value of eta _a (appearance viscosity force) at the selected value D (shear speed 1 / sec). In the case of the metal pigment-containing basecoat composition used in the present invention, when a solid substance having a nonvolatile content of 30% by weight or less is contained, the value of η _a is 0.5 pore or less at a shear rate of 10000 1 / sec and a D value of 1.0 1 / sec. It is preferable that it is 20 poses or more. More preferably, the base coat composition has _a ? _A value of 0.25 or less at D = 10000 1 / sec and 40 or more at D = 1.0 1 / sec. "Integral color", which contains a pigment other than the metal powder for the base coat composition, η _a value of D = 10000 1 / on the second one Powys or less, and straight in the D = 1.0 1 / sec to gradation at least 5 Powys, more Preferably it is less than 0.7 pose at 10000 1 / s and more than 10 poses at D = 1.0 1 / s. However, due to unexpected plasticity or thixotropy, the 2-3 selected viscosity / point data cannot be determined completely and accurately and depends on the number of viscometric methods used. Thus, the values recited above are not intended as limitations to ensure the advantages of the present invention, but rather as listed as appropriate indicators, the degree of plasticity required for each dispersion or basecoat composition obtained therefrom. Or whether thixotropy can be readily determined by a simple test by one skilled in the art.

There are many ways to impart plasticity or thixotropy to the basecoat composition. In some cases, no special means is required, for example, when polymer microparticles are prepared by the method described in the above-mentioned British Patent Application No. 42557/77 (Application No. 2006229A). In this method, firstly, polymer fine particles are prepared by non-aqueous acid polymerization of an appropriate monomer and crosslinked to a degree that can be dissolved at a suitable pH in a hydrophilic medium forming a final dispersion by polymerization of a separate monomer. To produce a hydrophilic second polymer. However, when these two non-aqueous polymerization stage products are transferred to the aqueous medium, the second polymer is not completely dissolved in the aqueous medium, and much of this remains bound to the polymer fine particles, whereby the fine particles remain in the aqueous medium. The conjugated polymer may be an aqueous acid solution showing stabilization or thixotropy while being stabilized with a dispersion in water. Other monomers suitable for use in the second polymerization step include, for example, hydroxyalkyl esters of acrylic or methacrylic acid, monoacrylic or mono methacrylic esters of polyglycols such as polyethylene glycol, polyglycol monovinylethers, or vinylpy Ralidone and the like, which may optionally include a mixture with non-hydrophilic monomers such as methyl methacrylate, butyl acrylate, vinyl acetate or small proportions of styrene. In addition, the solubility required in the aqueous medium is achieved using acrylic acid esters containing basic groups as main monomer components, such as dimethylaminoethyl methacrylate or diethylaminoethyl methacrylate, wherein the basic groups are dissolved in the aqueous medium. In the form of a salt by reaction with a suitable acid, such as lactic acid.

The second polymer may also be derived from a comonomer containing a polymerizable carboxylic acid such as acrylic acid or methacrylic acid, which may be dissolved in an aqueous medium in which a base such as dimethylamino ethanol is dissolved. Thus, in general, the second polymer may be nonionic, anionic or cationic.

When the polymer microparticles are prepared by the aqueous emulsion polymerization method well known in the art, the second polymer which is water soluble in nature is provided with a monomer which provides a polymer comprising an acid salt former capable of providing water solubility in the presence of the polymer microparticles, It may be prepared by polymerization in the same aqueous medium. Thus suitable polymerizable carboxylic acids, such as acrylic acid or methacrylic acid, are hydrophilic monomers, such as hydroxyethyl methacrylate or hydroxypropylmethacryl, which provide, if necessary, a non-hydrophilic monomer such as methyl methacrylate and a water insoluble monopolymer. The rates can be used together as a consumption rate.

When the polymer microparticles are prepared by dispersion polymerization in an aqueous medium as described in the specification of British Patent Application No. 7940088 (Application No. 2039297A) to which the present application is applied, the second water-soluble polymer may be a suitable monomer and water-soluble salt derivative as described above. Basic monomers such as dimethylaminoethyl methacrylate obtained can be preferably prepared by polymerizing again in the same medium.

A water soluble (not entirely water soluble) polymer produced in the original position in the presence of the polymer microparticles by the above method cannot impart the desired plasticity to the basecoat composition, but a suitable polymer composition is selected, for example, as described above. Viscosity can be obtained at different shear rates or by simple test methods such as applying the composition to a gas.

Instead of or in addition to producing a suitable water soluble polymer in its original position, such polymer may be added to the aqueous acidic solution of the polymer microparticles as a preformed discrete component.

Suitable polymers for this purpose can significantly increase the viscosity of the composition when dissolved in an aqueous medium at low concentrations. For example, well-known thickeners used in coating compositions based on aqueous polymer tartex may be added, but not all of these thickeners are suitable for this purpose, and some thickeners may have the desired plasticity in the composition to which they are added. Do not grant. In other cases, when dissolved alone in an aqueous medium, thickeners that do not exhibit isomers can impart plasticity to the dispersion of the microparticles by the interaction between the polymer microparticles (for example, by hydrogen bonding or the action of a polar group). There is also. A commercially available thickener deemed most suitable is the "Acrysol" ASE60 sold by Rohm & Haas ("Acrysol" is a registered trademark).

Thus, the water soluble polymer that is combined with the polymer microparticles or added to the microdispersion to impart plasticity or thixotropy to the particulate dispersion should be uncrosslinked, but the polymer may be in crosslinkable form if necessary. have. That is, the polymer may contain chemically reactive groups and thereby crosslink the basecoat composition, preferably the topcoat composition, after application to the substrate in the presence of an optionally added crosslinker. For example, the polymer may contain reactive groups derived from hydroxyl or carboxyl group-containing monomers as described above and may be crosslinked in the presence of amino resins, such as methylated melamine-formaldehyde condensates, that are soluble in an aqueous medium.

As described above, it can be seen that the basecoat composition is composed of polymer microparticles, pigment particles, an aqueous medium in which these two particles are dispersed, and a water-soluble polymer imparting plasticity to the composition. However, the composition is a film-forming polymer soluble in an aqueous medium so that it can be coalesced after application to a gas and evaporation of the aqueous medium to fill the space between the polymer microparticles and form an appropriately integrated adhesion coating in two steps of the process of the invention. It is preferable to contain. This action can be achieved by some of the water-soluble polymers present in the composition for the purpose of imparting plasticity or fibrillation, as described above, but since the proportion of this polymer required for this purpose is generally small, Or it is preferred to supplement by incorporating two or more other water soluble film formers, which may optionally react with components already present in the composition. For example, the composition may contain an oligomeric-phase material which may be converted to a high molecular weight product after being coated but which by itself does not contribute significantly to the viscosity of the composition before coating.

Materials that can be used for this purpose include low volatile diols such as 2-ethyl-1,3-hexanediol, low molecular weight polypropylene glycol, ethylene oxide and neopentyl glycol, bisphenol A, cyclohexanedimethanol, glycerol and Low molecular weight adducts with dihydric or trihydric alcohols such as trimethylolpropane, β-hydroxy alkylamides such as N, N, N ', N'-tetrakis- (β-hydroxyethyl) adipamide, mention may be made of cycleamides and esters such as ε-caprolactam and ε-caprolactone and the like.

Although these materials are not soluble in pure water, they must be dissolved in an aqueous medium consisting of water and organic liquid which can be miscible with water as described above. All these oligomeric materials can be converted to high molecular weight polymers by the application of the basecoat composition to a gas and then by combining the hydroxyl groups or other reactive groups in the materials with the multifunctional reactants present in the composition. Particularly useful materials for this purpose are amino resins which are soluble in the aqueous medium of the composition, for example melamine formaldehyde condensates such as hexa (alkoxymethyl) melamine and their molecular weight condensates.

The basecoat composition may contain a preformed, water-soluble acrylic polymer that does not impart plasticity thereto, instead of containing components that produce a film-forming polymer after being applied to a gas, or in the same form as the crosslinked polymer microparticles in the composition. The non-crosslinked particles stabilized with may be contained in a dispersed state. This counterpart may contain functional groups, such as hydroxyl groups, if necessary and may be crosslinked by a crosslinker such as an amino resin after application to the gas in the composition.

The relative proportions of the various components of the basecoat composition can vary widely, and the optimum ratio in each system is best determined by testing in many cases, but general indicators are described below.

In particular, if the proportion of polymer microparticles is too high for the other film forming materials in the above-mentioned composition, the foreign matter is not sufficient to fill the space between the polymer microparticles and therefore the composition precipitates in the basecoat coating upon application of the clearcoat and as a result Gloss is lost.

In contrast, if the proportion of the polymer fine particles is too low, it is not possible to give the basecoat composition protection against erosion by solvents present in the clearcoat composition. In this regard, relatively low polymer particulate concentrations can be compensated to some extent by lengthening the flash drying time of the basecoat coating prior to application of the clear code, but this reduces one of the major benefits obtained by the present invention.

In general, satisfactory proportions of polymer particulates may range from 5-80% by weight of the total nonvolatile content of the basecoat composition. However, the optimum ratio depends to some extent on whether the pigment present in the basecoat composition is metallic or nonmetallic. The preferred particulate content in the case of metallic pigment-containing compositions is 40-75% by weight, based on the same nonvolatile content. In the case of "monochromatic" compositions, the particulate content is relatively low, for example 10-50% by weight, based on the same volatiles, since the pigment ratio required to achieve adequate opacity with a relatively thin film thickness is higher than usual. Avoiding excessively high total volume fractions of the dispersion while reducing the particulate fraction. An excessively high total volume ratio results in the formation of a porous basecoat coating, which can sink and cause poor gloss.

As a general condition, the proportion of thickeners or plasticizers used in the composition ranges from 0.3-50% by weight of the total nonvolatile components, the amount of other film-forming materials is 0-30% by weight, When the same crosslinker is present, the amount thereof may be 30% by weight or less of the total nonvolatile content of the basecoat composition. If desired, the basecoat composition may contain a catalyst for the crosslinking reaction that is required to occur after applying the composition to the gas. The catalyst may be a water soluble acidic compound such as p-toluene, sulfonic acid, orthophosphoric acid, maleic acid or other strong carboxylic acids such as tetrachlorophthalic acid or salts of diacids with volatile aminos (heat labile).

Although the type of the film forming polymer component of the topcoat composition used in step (3) of the method of the present invention is not limited, generally, a film forming polymer in a thermosetting or thermoplastic form may be used. Suitable types of polymers may be derived from one or two or more ethylenically unsaturated monomers. Particularly useful polymers are those of the acryl-based moiety which is well used in the manufacture of paints in the automobile industry, that is, alkyl ester polymers of one or two or more (optionally in combination with other ethylenically unsaturated monomers) of acrylic acid or methacrylic acid or air. It is coalescing. Suitable acrylic esters include methyl methacrylate, ethyl methacrylate, propyl methacrylic acid, butyl methacrylate, ethyl acrylate, buryl acrylate, 2-ethylhexyl acrylate, and the like. Other suitable copolymerizable monomers include vinyl acetate, propionic acid, acrylonitrile, styrene and vinyltoluene. If an acrylic polymer in the form of a thermoset crosslink is desired, additionally suitable functional monomers to be used include acrylic acid, hydroxyethyl acrylate, hydroxyethyl methacrylate, 2-hydroxypropyl acrylate, 2-hydroxypropyl meta Acrylates, N- (alkoxymethyl) acrylamides and N- (alkoxymethyl) methacrylamides, and the like (where the alkoxy groups may be, for example, butoxy groups), glycidyl acrylate and glycidyl methacrylateyl Can be. In this case the topcoat composition is a crosslinker such as a diisocyanate, diepoxide or in particular a nitrogen-containing resin, ie a condensate with nitrogen containing compounds such as formaldehyde and urea, thiourea, melamine or benzoguanamine or lower alkyl of this condensate. Ethers, where the alkali groups have 1-4 carbon atoms. Particularly suitable crosslinkers are melamine formaldehyde condensates in which a substantial proportion of methylol groups are etherified by reaction with butanol.

The topcoat composition may be formulated with a suitable catalyst for use in the crosslinking reaction between the acrylic polymer and the crosslinker such as acid-reactive compounds such as acidic butyl maleate, butyl acid phosphate or p-toluenesulfonic acid. Alternatively, this catalysis may be provided by mixing free acid groups in the acrylic polymer, such as using acrylic acid as a comonomer in preparing the polymer.

The topcoat polymer may be present in solution or in a stable powder phase in the volatile liquid carrier of the topcoat composition, that is, the liquid carrier may be a solvent or a non-solvent for the topcoat composition. If the liquid carrier is a solvent, it consists of any organic liquid or mixture of organic liquids commonly used as a solvent of the polymer in the coating composition, such as aliphatic hydrocarbons such as hexane or heptane, aromatic hydrocarbons such as toluene or xylene, and mainly aliphatic compounds. But various aromatic boiling petroleum oils, esters such as butyl acetate, ethylene glycol diester or 2-ethoxyethyl acetate, ketones such as acetone or methyl isobutyl ketone, and alcohols such as butyl alcohol. have. The liquid or liquid mixture actually used as the liquid carrier depends on the type of topcoat polymer which allows the polymer to be dissolved in the liquid carrier, according to known principles in the field of coatings.

If the liquid carrier is an organic nonsolvent, it tends to have a lower polarity than the solvents described above, and the petroleum fraction with a low content of one or two or more aliphatic hydrocarbons, such as hexane, heptane or aliphatic compounds, has a high polarity as described above. Can be used in admixture with a liquid of the present invention, provided that the topcoat composition can be a non-aqueous polymer dispersion, provided that the mixture is a non-solvent of the topcoat polymer, which is usually a dispersion in which the polymer particles are not solvated by the liquid. Stereo-stabilized dispersions stabilized by block or graft copolymers containing polymer phase components bound to the polymer, The method by which such dispersions can be prepared is described in the patent specification and other documents, for example, in the United Kingdom patent. No. 941305; 1052241; 1122397; and 1231614 and "Dispersion polymerisation in organic Media" K. E It is extensively described in the publication by J. Barrett (John wiley and sons, 1975).

Alternatively, the topcoat composition may be based on water, such as the base composition, in which case the topcoat polymer may be in solution or in a stable dispersion in the aqueous medium. In the case of dispersions, these are steric sterically stabilized, for example, as prepared by the aqueous acid polymerization process as described in the above-mentioned British Patent Application No. 7940088, or as produced by known aqueous oil and polymerization processes, for example. It can be charged stabilized. Unlike the polymer microparticles of the basecoat composition, the topcoat polymer can always be in thermoset form and can therefore be crosslinked after application to the gas and optionally in the presence of a crosslinker.

Usually, the topcoat composition should be actually colorless to the extent that the pigmentation effect due to the basecoat does not change significantly, but in some cases it would be desirable to impart transparent coloring to the topcoat composition when the basecoat contains a metallic pigment. It may be desirable.

In the first operation step of the method of the present invention, the basecoat composition is applied to the gas surface, and may be prepared in advance or treated by a conventional method in the art. Particularly interesting gases in the present invention are metals such as steel or aluminum commonly used in automobile body construction, but other materials such as glass, ceramics, wood and plastics can also be subjected to the final curing of the multilayer coating. It can be used if it can withstand the temperature. After application of the basecoat composition, a polymer coating is formed on the gas surface. If desired, this can be achieved by heating the gas and the coating composition to volatilize the water and organic liquid diluent present, but when the composition contains a thermosetting film-forming substance, a heating temperature is used to crosslink the basecoat coating. It is also a technology falling within the scope of the present invention. However, the particular gum of the present invention is such that the topcoat composition can be applied to the basecoat coating without the topcoat composition being mixed with or dissolved in the basecoat coating (which prevents the metal pigment from oriented correctly, for example). A short drying time of is sufficient so that an optimum "flip" effect can be achieved. In each case, the appropriate drying conditions depend on the ambient humidity, but in general, a drying time of 1-5 minutes at a temperature of 15 ° -80 ° C is suitable to prevent mixing of the two coatings. At the same time, since the base coat coating is appropriately wetted by the top coat tongue, satisfactory adhesion between the coatings is obtained.

After applying the topcoat composition to the basecoat coating, the coated gas heating or curing operation is carried out to thereby volatilize the volatile liquid carrier of the topcoat, and optionally the film forming material of the topcoat and / or the basecoat to In the presence of crosslinking. This heating or curing operation is usually performed at a temperature of 100-140 ° C., but may be used if necessary to activate the crosslinking mechanism at temperatures lower than this.

In carrying out the process of the present invention, the basecoat and topcoat compositions may be applied to the substrate in a conventional manner such as brushing, spraying, dipping or perfusion, but the best results are obtained for the inhibition of pigments, in particular metal pigment orientation and gloss. It is desirable to apply a spray coating because it can be lost. Known spray processes, such as compressed air spray, electrostatic spray, hot spray and air spray, can be used for the application of the composition, and the light method and the automatic method are also suitable.

The film thickness of the basecoat coating is preferably 12.7 µ-38.1 µm and the thickness of the top coat 25.4 µ-76.2 µm (both after drying), and in relation to the "lammer-methyl" finishing agent, The advantage is that using an aqueous basecoat composition provides a basecoat / clearcoat system that eliminates or significantly reduces the crystallization of air pollution without interfering with the desired orientation control of the metal pigments. With regard to "integral" finishes, control of fuel orientation is not critical but provides the advantage that the basecoat coating is not hindered by the application of the following topcoat composition and the basecoat coating is aqueous Receives less "popping / 'action than coatings.

The present invention will be described in detail based on the following examples. Parts and percentages in the examples are by weight. In these examples, the viscosity value ηa of the bottom coating composition was measured using two different instruments. The value of? A at the 10,0001 / sec delivery rate was measured by an ICI cone plate viscometer, set to measure the 0-2.0 poise viscosity range at this delivery rate. The device is described in a paper by C. H. Monk of the July 1966 issue of the Journal of the Oil and Color Chemist's Association and manufactured by Resesrch Equipment (London).

The ηa value at 1.0 1 / sec shear rate was measured using a “Rheomat 30” concentric cylinder viscometer with an 'A' cup and bob, with each sample weighing up to 660 1 / sec until a constant shear stress could be read. After running at the shear rate, the shear rate was immediately converted to 1.0 1 / sec and the shear stress was measured and the viscosity was calculated from these data. "Rheomat 30" (Rh eomat is a registered trademark) is a product of Contrares AG (Zurich).

Example 1

A. Preparation of Polymeric Fine Particle Dispersions in Aliphatic Hydrocarbons

35429 parts of hexane was charged to a reactor equipped with a stirrer, a thermometer, a reflux condenser, and a means for adding a monomer to the reflux, and heated to a reflux temperature (95-96 ° C.) and the following mixed components were added.

Methyl methacrylate 5.425 parts Graft copolymer stabilizer 1.984 parts

0.420 parts of azodiisobutyronitrile (33% solution as described below)

The contents of the reactor were allowed to stand at reflux for 30 minutes to form a polymer dispersion, and then to the resultant reflux, a premix was added over a period of 3 hours at a constant rate.

Methyl methacrylate 25.000 parts Graft copolymer stabilizer 5.316 parts

0.755 parts of allyl methacrylate (33% solution as described below)

0.338 parts of azodiisobutyronitrile

After the addition was completed, the contents of the reactor were allowed to stand at reflux again for 1 hour, and then 12.874 parts of heptane were added and reflux was performed again. The reflux effluent was passed during this reaction, and then the premix was fed at a constant rate over 1 hour.

Methyl methacrylate 3.883 parts Azodiisobutyronitrile 0.071 parts

Butyl acrylate 3.066 parts Graft copolymer stabilizer 2.149 parts

2.044 parts of hydroxyethyl acrylate (33% solution as described below)

1.226 parts of acrylic acid

After the feed was completed, the reaction mixture was kept at reflux for 1 hour. A stable dispersion of crosslinked polymer fine particles having a total nonvolatile solids content of 43.5-44.5% and insoluble in polar solvents (ie gel content) of 34.5-35% is obtained.

The graft copolymer stabilizer used in the process is obtained as follows. The 12-hydroxy-stearic acid was self-condensed until an acid value of about 31-34 mg KOH / g (corresponding to a molecular weight of 1650-1800) and then reacted with the same amount of glycidyl methacrylate. The obtained unsaturated ester was copolymerized in the ratio of 2: 1 by the mixture of methyl methacrylate and acrylic acid of 95: 5 ratio. The obtained copolymer was used as a 33% solution in a mixture of 11.60% ethyl acetate, 14.44% toluene, 61.29% aliphatic hydrocarbon at boiling point 98-122 ° C and 12.67% aliphatic hydrocarbon at boiling point 138-165 ° C.

B. Transfer of Polymer Particles to Dispersions in Aqueous Medium

The following materials were injected into a reactor equipped with a stirrer, thermometer and means for removing volatiles by distillation:

Deionized water 72.308 parts Dimethylaminoethanol 0.529 part

Butoxyethanol 10.332 parts

The reactor contents are heated to 100 ° C. and 46.497 parts of the particulate dispersion obtained from step A are fed at a rate such that heptane in this dispersion can be distilled off without significantly increasing the component concentration in the reactor. The time required to do this is about 2 hours, and the amount of effluent, consisting mainly of heptane and a small amount of water, is 29-30 parts.

The product was a stable aqueous acid solution of polymer microparticles having a non-volatile solids content of 20-22% and a pH of 7.2-7.5.

C. Preparation of Aluminum Pigment Thickener

An aluminum paste (5.8 parts of 65% of metal content and 2.9 parts of butoxyethanol) was charged to a stirred mixing vessel. These components were stirred for 15 minutes, and then 2.9 parts were charged. These components were stirred for 15 minutes and stirred for another 1 hour. Part of hexamethoxymethylmelamine was added and stirred for 1 hour, and finally 1.93 parts of hexamethoxy methyl melamine and 0.97 part of butoxy-ethanol were added and the mixture was stirred for another hour.

D. Preparation of Basecoat Compositions

The components were stirred together for 1 hour. The obtained basecoat composition had the following properties.

Solid content: 27.2

Viscosity ηa: 35 Poses at D = 1 1 / sec shear rate

D = 10,000 0.06 poses at 1 / sec shear rate

E. Preparation of Acryl Polymers for Clearcoat Compositions

In a vessel equipped with a stirrer, a thermometer and a reflux condenser, the following were charged:

Xylene 22.260

10.000 parts of aromatic hydrocarbons (boiling point 190-210 ℃)

The mixture was heated to reflux (142-146 ° C.) and the next premixed components were added at a fixed rate for at least 3 hours.

The reaction was again kept at reflux for 2 hours and then added.

Isobutyl alcohol 12.72 parts

Xylene Part 3.32

The clear polymer solution thus obtained has a solids content of 50%.

F. Preparation of Solvent-Based Clearcoat Compositions

The following ingredients were mixed together.

A clear solution of 44.4% solids was obtained. It had a viscosity of 40 seconds (measured with 4 cups of B.S.B at 25 ° C).

G. Application of Basecoat and Topcoat to Gas

The metal panel treated with primer and surfer was sprayed twice without diluting the metal pigment-containing basecoat composition obtained in step D. Flash-off was performed for 2 minutes between two applications. The spray effluent with the spray gun was 400 ml / min.

After two coatings, air at 25 ° C. was vented to the panel and the clearcoat composition obtained in step F was applied twice by wet method, i.e. diluted with xylene to a viscosity of 45 seconds (measured with 3 cups of BSB at 25 ° C.). . After two minutes of flash-off between two applications and three minutes of flash-off, the panels were stowed at 125-130 ° C. for 30 minutes.

The resulting silver metallic coating showed an excellent "flip" effect and was coronally correlated with the highest flipping effect obtained from the complete solvent-based coating without any loosening. The gloss and internal adhesion were also good and the collier coat did not sink in the basecoat.

Example 2

The metal panel treated with the primer and the surfacer was sprayed twice at a temperature of 25 ° C. and a relative humidity of 58% without diluting the metal pigment-containing basecoat composition in Step D of Example 1 again. The flash-off for 2 minutes was performed between two coatings. The outflow rate of the paint from the spray gun was 400 ml / min.

After application twice, the panel was dried at 35-42 ° C. for 10 minutes and then the clearcoat composition obtained in step F of Example 1 was diluted with viscosity of 45 seconds (measured with 3 cups of BSB at 25 ° C.) in xylene. It was applied twice in a wet manner. After two minutes of flash-off between two applications, the panels were dried at 125-1300 ° C. for 30 minutes.

The obtained coating had the same excellent properties as those obtained in Example 1.

A. Preparation of Aqueous Acid Solution of Polymer Fine Particles

The following premixes were prepared:

(i) monomer premixes

(ii) initiator solution

Ammonium Persulfate 0.130part

Distilled water 4.010 parts

(iii) surfactant solution

20.000 parts of methyl methacrylate

20.000 parts of ammonium salt of sulfate of (nonylphenol + 5 mol ethylene oxide)

The following were charged to a reactor equipped with a stirrer, a thermometer, a reflux condenser and a device for controlling the introduction of the two-liquid feed, respectively.

47.641 parts of deionized water

Surfactant solution (iii) 0.100 parts

The charge was heated to 80-85 ° C. and then 2,000 parts of monomer mixture (i) were added and held at 80-85 ° C. for 15 minutes. 1.068 parts of initiator solution (ii) was added and the reaction mixture was kept at the same temperature for 20 minutes. The following premix was fed at a constant rate over 5 hours.

Monomer premix (i) 42.944 parts

2.350 parts of hydroxyisopropyl methacrylate

Over the same 5 hours, 3.672 parts of initiator solution (ii) were individually fed at a constant rate. The reaction mixture was kept at 80-85 ° C. for 1 hour and then cooled to room temperature to obtain a stable aqueous dispersion of crosslinked polymer particulates. The dispersion had a total solids content of 46.6% and a nonvolatile solids content that was insoluble in 44.5% organic solvents.

B. Preparation of Basecoat Compositions

Preliminary mixture (iv)

The pH was adjusted to 7.65 by stirring with 2.563 parts of a commercial thickener known as "Acrysol" ASE 60 ("Acrysol" is a registered trademark of Rohm & Hass Company) with 25% solution of dimethylaminoethanol in deionized water. Again deionized water was added to 23.956 parts.

Premix (v)

A mixture of 29.999 parts of the particulate dispersion obtained in step A and 18.614 parts of deionized water was adjusted to pH 7.65 by adding a 25% solution of dimethylamino ethanol in deionized water. It was mixed with 23.956 parts of the above premix (iv). Charged the following to the stirred mixture.

5.133 parts of aluminum paste (metal content, 65%)

2-butoxyethanol 15.193 parts

The contents were stirred for 15 minutes and the following was added.

Hexamethoxymethylmelamine 3.696parts

2.464 parts of polypropylene glycol (average molecular weight 400)

Stirring was continued for 1 hour and the following was added.

Premix (v) 71.869 parts

1.623 parts of deionized water

Stirring was continued for 1 hour. The obtained basecoat composition had the following properties.

Solid content: 20.5%

Viscosity ηa: 34.6 Poses at D = 1 1 / sec shear rate

0.42 Poses at D = 10.000 1 / sec

C. Preparation of Acrylic Polymers for Clearcoat Compositions

42.30 parts of isopropanol were charged to a reactor equipped with a stirrer, a thermometer and a reflux condenser. It was heated to reflux (84 ° C.) and the following premix was added at a constant rate over 3 hours.

The reaction mass was kept at reflux for another 2 hours. A 50% solids polymer solution was obtained. It was distilled directly to remove 28.87 parts of isopropane, and 1.89 parts of dimethylaminoethanol and 80.35 parts of deionized water were added to the residue with stirring. The distillation of the azeotropic mixture of isopropanol and water was continued to a temperature of 96-98 ° C. and the total amount of deionized water corresponding to the distillate was 114.65 parts. Thus, an aqueous solution of an acrylic polymer having a solids content of 33.5% was obtained.

D. Preparation of Aqueous Clearcoat Composition

The following ingredients were mixed:

A clearcoat composition was thus obtained having a viscosity of 31.5% solids and a viscosity of 0.5 poise.

E. Application of Basecoat and Clearcoat to Gases

The metal panel treated with the fryer and the surfacer is sprayed three times at 25 ° C. and 51% relative humidity, without diluting the metal pigment-containing basecoat composition obtained in step B again. The fresh-off was performed for 1 minute between each application | coating. The extraction rate of the paint by the spray gun was 400 ml / min.

On three applications, the panel was dried at 35-42 ° C. for 10 minutes and the clearcoat composition obtained in step D was coated three times in a wet manner. The flash-off was performed for 2 minutes between each application, and after various flash-offs for 3 minutes, the panel was preheated at 70 ° C. and dried at 150 ° C. for 30 minutes.

The coating thus obtained showed a flip effect and was free of "relaxation" and was identical in appearance to the top finish obtained from metallic application based on complete solvent. The gloss and inner coating adhesion was excellent and the clearcoat did not sink in the basecoat.

Example 4

29.030 parts of deionized water were added to a reactor equipped with a stirrer, a thermometer reflux condenser, and a device for respectively controlling the introduction of the two-liquid feed, and then the following premix was added.

0.029 parts of methyl methacrylate

0.029 part of ammonium salt of the sulfate of (nonyl phenol + 5 mol ethylene oxide)

The reactor contents were heated with stirring to 80-85 ° C. and the following premixes were added:

Butyl acrylate 0.069parts

Methyl methacrylate 0.069 parts

The reaction mixture was kept at 80-85 ° C. and the next mixture was added.

Deionized Water 0.67part

Ammonium Persulfate 0.021parts

The reactor contents were held for another 20 minutes at 80-85 ° C. and the following premixed components were fed to the reactor over a period of 3 hours at constant rate.

At the same time a solution of 0.037 parts of ammonium persulfate in 4.985 parts of deionized water was fed to the reactor over a period of 3 hours.

After completion of the feed, the reactor contents were maintained at 80-85 ° C. for 1 hour. 34.716 parts of deionized water was added and the temperature was maintained at 80-85 ° C. and the next premix was added at constant rate over 1 hour.

At the same time a solution of 0.019 parts of ammonium sulfate and 0.016 parts of sodium borate in 0.596 parts of distilled water was added to the reactor at a constant rate over 1 hour. After completion of the feed, the temperature was maintained at 80-85 ° C. for 1 hour and quickly cooled to obtain a stable aqueous dispersion of polymer fine particles. The dispersion had a total of nonvolatile solids of 30% and the nonvolatile solids insoluble in the organic solvent was 27%.

B. Preparation of Basecoat Compositions

The dispersion obtained in step A was adjusted to pH 8.0 by addition of dimethylamino ethanol and 54.15 parts thereof were charged to the mixer. The following ingredients were added in the order described.

The mixture was stirred for 1 hour to obtain a basecoat composition having the following properties.

Solid content: 25.8%

Viscosity ηa: 20 Poses at D = 1 1 / sec shear rate

D = 10,000 0.2 poses at 1 / sec shear rate

C. Application of Basecoats and Clearcoats to Gases

The metal panel treated with the fryer and the surfacer is sprayed twice at a temperature of 22 ° C. and a relative humidity of 39 without diluting the metal pigment-containing basecoat composition obtained in step B again.

The clearcoat composition was applied as described in step F of Example 1. Application of the basecoat and clearcoat composition is the same as in step G of Example 1.

The same results as described in step G of Example 1 were obtained.

Comparative Example A

A. Preparation of a negative metallic basecoat containing no polymer particulates

6.0 parts of aluminum paste (65% of metal content) and 18.7 parts of 2-butoxyethanol were charged to the stirring mixer. The contents were stirred for 30 minutes and the following was added.

Hexamethoxymethyl melamine 4.3part

2.9 parts of polypropylene glycol (average molecular weight 400)

Stirring was continued for another hour. 51.2 parts of an aqueous acrylic polymer solution of 33.5% solids described in Example 5 (C) were added over 30 minutes with stirring and 16.9 parts of deionized water was added.

The resulting basecoat composition has the same pigment: binder ratio as the basecoat composition described in Example 1 of the present invention, i.e. the ratio of the same hexamethoxy methylmelamine to total inert content, and a viscosity η _a value even at a similar D = 10,000 1 / sec. 0.3 poise). Viscosities at high interruptions of compositions containing no polymer particulates show that they are suitable for spray application to gases, but at low shear rates (ie D = 1 1 / sec) the viscosity is only about 1.0 poise It has been found that the composition merely shows some plasticity or thixotropy.

This basecoat composition is apply | coated to a panel, and the acrylic clearcoat composition of Example 1 (E) and (F) is apply | coated on this in the same way as Example 1 (G). The silver metallic coating thus obtained shows a very poor "flip" effect and no "relaxation" is present and "flips" during the drying process.

Example 1-4 relates to the production of a "glamorous-metallic" finish coating film, but the following example describes the "integral color" finish coating film.

Example 5

A. Preparation of White Mill Base Pigments

The following ingredients were ground together for 16 hours at base.

The resulting millbase pigment having a particle size of 0.5 microns or less was diluted with 11.6 parts 2-butoxyethanol and 11.6 parts deionized water.

B. Preparation of Blue Millbase Pigments

The following ingredients were ground together in a ball mill for 16 hours.

The resulting millbase pigment having a particle size of 0.5 microns or less was diluted with 14.8 parts 2-butoxyethanol and 14.8 parts deionized water.

C. Preparation of Acrylic Polymer Aqueous Solution

The following ingredients were mixed.

A mixture of 15.0 parts of the mixture and 42.2 parts of isoprotanol was charged to a flask equipped with a stirrer, thermometer, reflux condenser, and a device for controlling the addition of liquid feed. The contents of the flask were heated to reflux (84 ° C.) and the residue (42.8 parts) of the mixture was added at constant rate over 3 hours. The reaction mixture was heated at reflux for another 2 hours to give a 51.0% solids content and a polymer solution. 1.8 parts of dimethylamino ethanol was added to the solution, and the resulting mixture was reheated to reflux, the condenser was readjusted, and the effluent was removed while adding 85.0 parts of deionized water, and a total of 33.0 parts were removed for 10 hours. The finally obtained acrylic polymer aqueous solution had a solids content of 33.5%.

D. Preparation of Blue Basecoat Compositions

The following components were mixed in the order described.

The obtained basecoat composition showed a viscosity of 16.0 poses at D = 1.0 1 / sec shear rate and 0.53 poses at D = 10000 1 / sec omnispeed.

E. Application of Basecoat and Clearcoat to Gases

The metal panel treated with the fryer and the surfacer is sprayed twice at a temperature of 22 ° C. and a relative humidity of 39% without diluting the blue basecoat composition obtained in step D above.

The flash-off was performed for 2 minutes between two coatings. After application twice, the panel was infused with 25 ° C. air, and the wet coat was diluted with a clearcoat composition as described in Example 1 (F) to xylene for 45 seconds (measured with 3 cups of BSB at 25 ° C.). Apply twice. The flash-off was performed for 2 minutes between two coatings, and the panel was dried at 125-130 ° C for 30 minutes after the flash-off was performed for the last 3 minutes. It had good opacity and gloss obtained so that the clearcoat did not grow in the basecoat.

Comparative Example B

A. Preparation of Blue Basecoat Composition Free of Polymer Fine Particles

The following components were mixed in the order described.

The obtained basecoat composition D = 1.0 exhibited a viscosity of 1.0 poise at a shear rate of 1 / sec, and a viscosity of 0.83 poise at a shear rate of D = 10000 1 / sec. That is, it showed little plasticity or thixotropy.

B. Application of Basecoat and Topcoat to Gases

The procedure of Example 5 (E) was repeated except that the basecoat composition of (A) was used instead of the basecoat composition of Example 5 (D). In this case, significant "popping" is observed in the basecoat, that is, the air that accompanies the basecoat is separated into bubbles, which results in deformation of the coating surface and damage of the flat appearance.

Furthermore, if the time is not given more than three minutes from two application of the base coat to one application of the clear coat, the base coat is damaged by the clear coat and adversely affects the finish appearance of the panel.

Claims (1)

a base coat composition comprising (a) a film forming material, (b) a liquid medium volatile to the material and (c) pigment particles dispersed in the liquid medium, is applied to the gas surface, and in this step The coated composition forms a polymer coating on the gas surface, and the basecoat film formed thereon is a transparent top coat composition containing (d) a film forming polymer and (e) a liquid carrier volatile for the polymer. Forming a multilayer protective film and / or a decorative film on the surface of the gas by a process consisting of forming a second polymer film on the basecoat film with the applied composition after application to ) And (b) have a diameter of 0.01-10 microns and are in dispersion in an aqueous medium of crosslinked polymer microparticles that are insoluble in aqueous media and are stable against gross flocculation. St. method of forming a multilayer coating characterized in that provided by the (擬 塑性) or a dispersion showing a thixotropic (搖 變性).