DE69320644T2 - ELECTROSTATIC COATING OF POLYMER OBJECTS AND METHOD FOR THE PRODUCTION THEREOF - Google Patents

Abstract

Polyurethane/polyurea polymers can be electrostatically painted without first being coated with a conductive primer. Disclosed is an improvement in a process for electrostatically painting polyurethane/polyurea polymers, the improvement being to prepare the polymer from a formulation including a non-volatile metal salt conductivity inducing material. The polymers painted by the process of the present invention can have physical properties and aesthetic properties substantially similar to those of otherwise identical polymers prepared without the non-volatile metal salt conductivity inducing materials of the present invention. The increased conductivity of the polymers can allow them to be charged with sufficient charge density to permit efficient paint transfer to the polymer surface. Also disclosed is a composition of at least two layers, one layer being an outer layer of electrostatically applied paint, and the other an inner layer of polyurethane/polyurea polymer.

Description

This invention relates to a method for electrostatically coating polymers. This invention particularly relates to the electrostatically coating polymers with urethane or urea groups.

It is well known that most coating or painting processes are unlikely to be 100 percent efficient. For example, when a coating or paint is sprayed onto an object, some of the paint or coating directed at the object may not deposit on the object. In even less efficient circumstances, the paint and the object may acquire a static charge of the same polarity, causing the paint to be partially repelled from the object. Another commonly observed application inefficiency is that the paint layer on a coated object may be of uneven thickness. Yet another commonly observed application inefficiency, particularly when spray coating objects with complex shapes, is that the paint may tend to move from the sprayer to the object to which it is to be applied in a relatively straight line and may not cover surfaces not directly accessible to the sprayer.

In application processes where a very high quality paint coating is required, such as the coating of automobile body panels, it is generally desirable to completely and evenly coat an object to be coated with a minimum amount of paint. This is due to several reasons. First, paint for such applications is often very expensive. Therefore, reducing paint usage offers the immediate benefit of reduced paint costs. Second, paint that does not deposit on the object being coated may be lost to the environment, and this loss may be environmentally undesirable. Therefore, reducing the amount of paint lost to the environment during a coating process reduces the cost of disposing of the lost paint solids and reduces emissions of paint solvents. Third, while a slightly too thick layer of paint on an object can sometimes be tolerated, a layer of paint that is too thin can more often not be tolerated. In addition to improving the appearance of an object, modern paints often play a critical role in protecting a coated object from its environment. For example, paint can protect metal objects from corrosion or protect plastic objects from degradation by ultraviolet radiation. Therefore, failure of coated objects due to areas of too thin paint on the objects can be avoided by applying the paint to objects where the paint layer is of a uniform and sufficient thickness.

To minimize the problems of inefficient coating, it is common practice when coating some materials to apply the paint electrostatically. Electrostatic coating creates a static electrical potential between paint and an object to be coated, causing the paint to be attracted to the object. As a result of this electrostatic attraction, less paint can be lost to the environment and the paint can be more evenly distributed over the object without the entire surface being directly accessible to the paint sprayer.

But electrostatically coating objects is not always free of difficulties. To electrostatically coat an object, an electrical potential must be created between the object to be coated and the paint to be applied to the object. If an object is either non-conductive or of very low conductivity, it cannot be efficiently electrostatically charged and therefore cannot be efficiently electrostatically coated.

One way to electrostatically coat polymers is to first make them more conductive by preparing the polymers from formulations that include conductive fillers. European Patent Application 0 363 103 to Suzuki et al. discloses preparing a thermoplastic polymer with 2 to 50 weight percent of a fibrous conductive filler, such as carbon fibers, metallic fibers, metallized glass fibers, metal-coated carbon fibers, and conductive potassium titanate whiskers. The polymer is etched and then electrostatically coated. However, adding such large amounts of fibrous fillers to a polymer can adversely affect both the physical properties of the polymer and the color coating. A separate etching step may also be undesirable.

JP II 2-180960 assigned to Kanto Auto Works discloses the manufacture of polyurethane substrates with improved conductivity. The polyurethanes of this document are made with ammonium salts such as n-alkyldimethyl ammonium sulfates. One difficulty with such additives is that they only increase conductivity when they are wetted. This could be a problem in a coating application located in an area where the ambient humidity is not constant. Alternatively, intentionally wetting objects prior to electrostatic coating could be time consuming and expensive.

Another means of electrostatically coating polymers is to first make them more conductive by applying conductive agents called "prepcoats". These prep coatings are conductive agents that adhere to the surface of the polymer. Such agents may include materials such as quaternary amines. A problem with such compounds is that they are often hydrophilic. In reaction injection molding (RIM) of polyurethanes, the adsorbed water can cause blemishes on the surfaces of the polymer. Hydrophilic layers can increase the tendency of articles to adsorb water prior to paint application, thus promoting the formation of blemishes and thus being undesirable for applications requiring high quality coatings.

EP-A-0 475 360 relates to a method for improving the electrical conductivity of a resin such as polyethylene, polypropylene, etc., ABS resin, acrylic resin, polyamide resin, polyvinyl chloride resin, polycarbonate resin, polyacetal resin and phenol resin, which comprises combining (A), a macromolecular compound obtained by cross-linking a polyether polyol, and (B), a soluble electrolyte salt, into a matrix resin. EP-A-0 443 767 relates to a method for producing an ionically conductive article, the method comprising the steps of: (a) providing an ionically conductive polymer; (b) forming a charging material comprising the ionically conductive polymer and a generally non-ionically conductive polymer; and (c) producing an ionically conductive article from the charging material.

Yet another solution to the problem of electrostatic coating of plastics is to first coat a plastic article with a conductive layer and then electrostatically apply paint to the coated article. For example, US Patent 5,071,593 to Takahashi et al. discloses the coating of problematic plastics such as polyacetal and polyesters with a conductive agent before electrostatic coating.

EP-A-0 309 286 relates to an electrically conductive composition for use for the electrostatic coating of a plastic article consisting of polyacetal resin, polyethylene terephthalate, polybutylene terephthalate and aromatic polyesters, the composition comprising (A) a polyurethane resin and (B) an electrically conductive inorganic fine powder and/or an electrically conductive organic substance.

However, coating an object with a conductive agent can be inefficient. It requires significant expenditures in additional coating equipment, additional process time to apply the conductive agent, additional process time to crosslink or cure the conductive agent, and expenditures for the cost of the conductive agent.

It is known in the art that polymers, particularly reaction injection molded polyurethane/polyurea polymers, are suitable materials for the manufacture of automotive parts such as, for example, instrument panels and interior and exterior panels. In order to coat articles made from such polymers and to produce a high quality paint finish as is required in modern automobile manufacturing practice, it is known to electrostatically coat these articles after first applying a conductive primer thereto. Known methods for electrostatically coating polymer articles comprise at least the steps of: (1) preparing an article to be coated from a polyurethane/polyurea polymer formulation; (2) coating this article with a conductive agent (or conductive primer); (3) applying an electrical charge of a first polarity to a paint; (4) applying an electrical charging the object of a second and opposite polarity (or merely charging either the paint or the object relative to earth while leaving the other neutral to earth); and (5) allowing the paint to flow from a coating device onto the object.

It would be desirable in the art to efficiently electrostatically coat polymers without having to pretreat the polymer by priming or pre-coating the polymer with a conductive material. It would also be desirable in the art to more efficiently electrostatically coat a polymer that has been primed or pre-coated with a conductive substance. It would be desirable in the art to produce a polymer with sufficient natural conductivity to efficiently electrostatically coat the polymer. It would be desirable in the art that the polymer to be coated not require any special treatment, such as wetting. It would also be desirable in the art that the coated polymer have a coated surface of sufficiently high quality and have sufficiently strong physical properties so that the polymer can be used in very demanding applications, such as the manufacture of automobiles. Finally, it would be desirable in the art if articles of dissimilar composition, e.g. B. metal and plastic, could be coated as a single unit, instead of coating them separately and then bonding them.

One aspect of the present invention is a method for coating crosslinked or cured polymers containing urea and/or urethane groups, comprising the steps of: (A) preparing a crosslinked or cured polymer from a polymer formulation comprising (1) materials comprising or forming urea groups, urethane groups or mixtures thereof, and (2) a non-volatile A conductivity-inducing metal salt material, wherein the polymer becomes conductive only by incorporation of the conductivity-inducing, non-volatile metal salt material into the polymer, and (B) coating the polymer, wherein the polymer is electrostatically coated.

Another aspect of the present invention is a method for electrostatically coating a crosslinked or cured polymer containing urea and/or urethane groups, wherein the polymer is formed into a shaped article, coated with a conductive preparatory substance, and then electrostatically coated, wherein the polymer is prepared from a polymer formulation comprising (1) materials comprising or forming urea groups, urethane groups, or mixtures thereof, and (2) a conductivity-inducing non-volatile metal salt material.

Yet another aspect of the present invention is an electrostatically coated article comprising at least two layers, wherein a first layer is a layer of polymer prepared from a polymer formulation comprising (1) materials comprising or forming urea groups, urethane groups, or mixtures thereof, and (2) a conductivity inducing, non-volatile metal salt material, wherein the polymer becomes conductive only by incorporation of the conductivity inducing, non-volatile metal salt material into the polymer, and a second layer, wherein the second layer is a paint layer wherein the polymer is electrostatically coated.

The present invention is an improvement on known processes for electrostatically coating polymers. This improvement comprises preparing an article to be coated from a polymer formulation comprising (1) materials comprising or forming urea and/or urethane groups and (2) a conductivity-inducing, non-volatile metal salt material. The resulting Polymers can be electrostatically coated without the use of a conductive primer or other precoat.

In the process of the present invention, a cured polymer is coated. For the purposes of the present invention, the cured polymer is one in which the reaction to produce the polymer is substantially complete and the polymer is in a solid and preferably rigid form. Even more preferably, the polymer is in a form suitable for coating. For example, the polymer may be in the form of an automobile body panel, quarter panel, or instrument panel.

The conductivity inducing materials of the present invention are non-volatile metal salts. As the salt, the conductivity inducing materials of the present invention have both a cation and an anion. The cation of the salt can be a cation of any metal that forms an ionizable salt with one or more anions, including Li, Be, Na, Mg, Al, K, Ca, Ga, Ge, Cu, Zn, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Rb, Sr, In, Sn, Sb, Y, Zr, Nb, Mo, Ru, Rh, Pd, Ag, Cd, Cs, Ba, TI, Pb, Bi, Hf, Ta, W, Re, Os, Ir, Pt, Au, Hg and the lanthanide series of the periodic table of elements. Preferably, the cation is a cation of an alkali metal (Li, Na, K, Rb, Cs), an alkaline earth metal (Ca, Ba, Sr), Co, Ni, Fe, Cu, Cd, Zn, Sn, Al or Ag; more preferably, the cation is a cation of an alkaline earth or alkali metal; even more preferably, the cation is a monovalent cation, particularly an alkali metal cation; and most preferably, the cation is a cation of Li, Na, K or mixtures thereof. The non-volatile metal salt cations of the present invention can be selected from the group comprising the cations of Li, Na, K and mixtures thereof.

The conductivity inducing non-volatile metal salt materials of the present invention are salts of certain anions having the above One group of preferred non-volatile metal salts are fluoroalkyl sulfonic acid salts. The fluoroalkyl sulfonic acid anion (fluoroalkyl sulfonate) is suitably any fluoroalkyl sulfonic acid anion compatible with a particular composition in which it is used. Advantageously, preferred fluoroalkyl sulfonates have from one to twenty carbon atoms and are either straight chain, branched or cyclic. Fluoroalkyl sulfonates are sulfonate anions having a fluorine-substituted alkyl group, i.e. fluorine atoms bonded to the carbon atoms of the alkyl groups. The alkyl groups optionally also have hydrogen atoms and/or other halogen atoms bonded to the carbon atoms. Preferably, at least 25 percent, more preferably 75 percent (by number) of the non-carbon atoms bonded to the carbon atoms of the fluoroalkyl groups are halogen, preferably fluorine. More preferably, the fluoroalkyl groups are perhaloalkyl groups, i.e. alkyl groups having only halogen substitution. Suitable halogens include fluorine, chlorine, bromine and iodine, preferably fluorine and chlorine. Suitable perhaloalkyl sulfonic acid anions include, for example, C₂H₂F₃SO₃⊃min; (Tresylate), C2 HF4 SO3- , C2 HClF3 SO3- , C3 H2 F5 SO3- , C4 H2 F7 SO3- , C5 H2 F9 SO3- supmin;, C7 ClF14 SO3- , C8 Cl2 H2 F13 SO3- , C20 ClHF39 SO3- .

The fluoroalkyl groups are most preferably perfluoroalkyl groups. Exemplary perfluoroalkyl sulfonic acid anions include, for example, CF₃SO₃- (triflate), C₂F₅SO₃⁻, C₃F₇SO⁻⁴, C₄F₆SO⁻⁴ (nonaflate), C₅F₁₁₁SO₃⁻, C₆F₁₃SO₃⁻, C₇F₁₅SO₃⁻, C₈F₁₇₁SO₃⁻, C₆F₁₅SO₃⁻, C₆F₁₅SO₃⁻, C₆F₁₅SO₃⁻, isomers thereof and mixtures thereof. The salts of the perfluoroalkyl sulfonates preferably have 1 to 20, more preferably 1 to 10 carbon atoms for reasons of availability and compatibility with polymers.

Other non-volatile metal salts may also be used as conductivity inducing materials to prepare the formulations of the present invention. The anion of such salts is known to those skilled in the art by properties such as pi-bonding, electron-withdrawing groups such as halogen atoms, and the possibility of resonance structures. The anion is preferably a relatively large, polyatomic anion with substituents such as phenyl groups, sulfur atoms and phosphorus atoms that can accept and delocalize an electron charge; more preferably the anion has more than one, more preferably at least 4, most preferably at least 5 non-metallic atoms.

Non-metallic atoms are generally understood to mean those selected from the group comprising boron, carbon, silicon, phosphorus, arsenic, oxygen, sulfur, selenium, tellurium, fluorine, chlorine, bromine, iodine and astatine. Preferred non-metallic atoms are boron, phosphorus, sulfur, fluorine and carbon in aromatic groups; sulfur and carbon in aromatic groups are more preferred. The anion is preferably monovalent. The anion is more preferably the conjugate base of an inorganic acid having one or more delocalizable electrons, e.g. a fluoroalkylsulfonate or a tetraorganoboron ion. Such anions include, for example, NO₃⁻, SCN⁻, SO₄²⁻; HSO₄⁻, SO₃²⁻, PX₆⁻, HSO₃⁻, CNSO₃⁻, XSO₃⁻, wherein X is a halogen, SXSO₃⁻, where X is a hydrogen or an anion, ClO₄⁻, PO₄³⁻, H₂PO₄⁻, HPO₄²⁻; PO₃³⁻, HPO₃²⁻, H₂PO₃⁻, especially tetraalkyl and tetraaryl boron ions and non-alkyl or non-aryl substituted sulfone ions.

For the purposes of the present invention, the term non-volatile metal salt is further defined to exclude those salts that are incompatible with or undesirable for formulations for polymers containing urethane and/or urea groups. For example, the non-volatile metal salt anion of the present invention is not a SCH anion, since the salts of these anions can cause handling problems due to viscosity increase in polyurea formulations. SCH⊃min; anions are also known to be present in some Polyurethane formulations. This property can cause handling problems in some coating applications. In contrast, non-volatile metal salts having good compatibility with formulations for polymers with urethane and/or urea groups are included and are preferred. For example, tetraphenylboron and hexafluorophosphate anions are particularly preferred as conductivity inducing materials for the present invention because of their good compatibility and handling properties. Mixtures of non-volatile metal salts of the present invention can also be used to practice the present invention. Most preferably, the non-volatile metal salts of the present invention are salts wherein the non-volatile metal salt anion is selected from the group comprising a perfluoroalkyl sulfonate, a tetraphenylboron anion, a hexafluorophosphate anion, or mixtures thereof.

The amount of conductivity inducing material included in the polyurethane/polyurea formulations of the present invention varies with the polymer. In the technique of the present invention, sufficient conductivity enhancing material is included in the formulation to make the material sufficiently conductive to permit efficient electrostatic coating. A relatively non-conductive polymer may require more conductivity inducing material than a relatively more conductive polymer. In general, the amount of conductivity inducing material added to an electrostatically coated polymer formulation suitable for preparing polyurethane/polyurea polymers is preferably from 0.02 percent to 1.5 percent, more preferably from 0.05 percent to 1.0 percent, and even more preferably from 0.10 to 0.75 percent.

The non-volatile conductivity-inducing metal salt materials of the present invention are preferably those which, when incorporated in a polymer formulation will result in a polymer having physical properties substantially similar to those of polymers prepared without the non-volatile conductivity inducing metal salt materials but otherwise identical. The physical properties relevant here are those properties which determine whether the polymer is suitable for the application for which it is intended. For example, one such property is aesthetic appearance. If a non-volatile metal salt results in an undesirable appearance in a polymer at the minimum concentration necessary to efficiently coat the polymer, it is not a preferred conductivity inducing material of the present invention. Other physical properties which are often useful in determining whether a polymer is suitable for applications in which electrostatic coating is often performed include: flex modulus, tear strength, and tensile strength. For purposes of the present invention, two polymers have substantially similar physical properties if the values for these properties are within 15 percent, preferably within 12 percent, and most preferably within 10 percent of each other. In some cases, the non-volatile metal salts of the present invention can interact with the polymers into which they are incorporated to actually improve some polymer physical properties.

The polymers of the present invention can be electrostatically coated with the same efficiency as a control steel coated under similar conditions. The efficiency of the coating process is determined by measuring the amount of paint deposited on the article during the electrostatic coating process. For the purposes of the present invention, the term "efficiently electrostatically coated" is defined as the condition wherein the same thickness of paint is deposited on a polymer article as on a steel object when electrostatically coated under the same or substantially similar conditions.

The process of the present invention can be used for polymers that are conductive only by incorporating conductivity-inducing, non-volatile metal salt materials of the present invention. For the purposes of the present invention, the term "conductive" is defined by electrical conductivity sufficient for efficient electrostatic coating. The term "efficiently electrostatically coated" is used as defined in the immediately preceding paragraph.

The polymers of the present invention have urea groups, urethane groups, and mixtures thereof. That is, the polymers can be made from materials that comprise or react to form only polyurethane or polyurea groups, or the polymers of the present invention can be made from materials that comprise or react to form both polyurethane and polyurea groups. Other polymer linkages can also be formed in the technique of the present invention. For example, a polymer can be made with polyurethane, polyurea, and isocyanurate groups.

The polymers of the present invention can also be polymer blends and specialty elastomer polymers. For example, a polyurethane of the present invention can be blended with another polymer such as, for example, an acrylonitrile-butadiene-styrene polymer and then electrostatically coated. Other miscible polymers suitable for the present invention include, but are not limited to, nylon, polyethylene terephthalate and polyacrylate. Specialty elastomers can be made from polymers of the present invention with materials such as epoxy resins and polycarbonate resins. The network polymers can be made by mixing one or more Monomers are incorporated into the formulations of the present invention so that the materials form a co-continuous or phase-separated in situ polymer network. Preferably, the urea/urethane group-containing polymers are the major component of multipolymer compositions of the present invention.

The polymers of the present invention can be either thermoplastic or thermosetting. Polyurethanes are prepared from formulations comprising both a polyisocyanate and a polyalcohol. Polyureas are prepared from formulations comprising both a polyisocyanate and a polyamine. The polyurethane/polyurea polymers are often prepared from formulations comprising a polyisocyanate and both a polyalcohol and a polyamine.

In the technique of the present invention, the polyisocyanate formulation component may advantageously be selected from organic polyisocyanates, modified polyisocyanates, isocyanate-based prepolymers and mixtures thereof. These may include aliphatic or cycloaliphatic isocyanates, but aromatic and especially multifunctional aromatic isocyanates are preferred. Preferred are 2,4- and 2,6-toluene diisocyanates and the corresponding isomeric mixtures; 4,4'-, 2,4'- and 2,2'-diphenylmethane diisocyanates and the corresponding isomeric mixtures; mixtures of 4,4'-, 2,4'-, and 2,2'-diphenylmethane diisocyanates and polyphenyl-polymethylene polyisocyanates (PMDI); and mixtures of PMDI and toluene diisocyanates. Also suitable for the present invention are aliphatic and cycloaliphatic isocyanate compounds such as 1,6-hexamethylene diisocyanate; 1-isocyanato-3,5,5-trimethyl-1-3-isocyanatomethylcyclohexane; 2,4- and 2,6-hexahydrotoluene diisocyanate, as well as the corresponding isomeric mixtures; 4,4'-, 2,2'- and 2,4'-dicyclohexylmethane diisocyanate, as well as the corresponding isomeric mixtures.

Also advantageously used for the polyisocyanate component are so-called modified multifunctional isocyanates, i.e. products obtained by chemical reactions of the above diisocyanates and/or polyisocyanates. Examples include polyisocyanates containing esters, ureas, biurets, allophanates and preferably carbodiimides and/or uretonimines; diisocyanates or polyisocyanates containing isocyanurate and/or urethane groups. Liquid polyisocyanates containing carbodiimide groups, uretonimine groups and/or isocyanurate rings with isocyanate group (NCO) contents of 10 to 40 percent by weight, more preferably 20 to 35 percent by weight, can also be used. These include, for example: B. Polyisocyanates based on 4,4'-, 2,4'- and/or 2,2'-diphenylmethane diisocyanate and the corresponding isomeric mixtures, 2,4- and/or 2,6-toluene diisocyanate and the corresponding isomeric mixtures, 4,4'-, 2,4'- and 2,2'- diphenylmethane diisocyanate and the corresponding isomeric mixtures; Mixtures of diphenylmethane diisocyanates and PMDI and mixtures of toluene diisocyanates and PMDI and/or diphenylmethane diisocyanates.

Prepolymers with NCO contents of 5 to 40 percent by weight, more preferably 15 to 30 percent by weight, are also suitable. These prepolymers are prepared by the reaction of the di- and/or polyisocyanates with materials comprising diols, triols, but they can also be prepared with multivalent active hydrogen compounds such as di- and triamines and di- and trithiols. Individual examples are aromatic polyisocyanates with urethane groups, preferably with NCO contents of 5 to 40 percent by weight, more preferably 20 to 35 percent by weight, which are obtained by the reaction of diisocyanates and/or polyisocyanates with, for example, low molecular weight diols, triols, oxyalkylene glycols, dioxyalkylene glycols or polyoxyalkylene glycols with molecular weights of up to 800. These polyols can be used individually or in mixtures as di- and/or polyoxyalkylene glycols. For example, diethylene glycols, dipropylene glycols, Polyoxyethylene glycols, polyoxypropylene glycols and polyoxypropylene polyoxyethylene glycols can be used.

Particularly suitable for the present invention are: (i) polyisocyanates with an NCO content of 8 to 40 percent by weight, which contain carbodiimide groups and/or urethane groups, from 4,4'- diphenylmethane diisocyanate or a mixture of 4,4'- and 2,4'-diphenylmethane diisocyanates; (ii) prepolymers with NCO groups with an NCO content of 20 to 35 percent by weight, based on the weight of the prepolymer, which are prepared by the reaction of polyoxyalkylene polyols with a functionality of preferably 2 to 4 and a molecular weight of 800 to 15,000 with 4,4'-diphenylmethane diisocyanate or with a mixture of 4,4'- and 2,4'-diphenylmethane diisocyanates and mixtures of (i) and (ii); and (iii) 2,4- and 2,6-toluene diisocyanate and the corresponding isomeric mixtures. PMDI in any of its forms may also be used and is preferred. In this case it preferably has an equivalent weight between 125 and 300, more preferably from 130 to 175, and a functionality average of greater than 2. More preferably a functionality average of 2.5 to 3.5. The viscosity of the polyisocyanate component is preferably from 25 to 5,000 centipoise (cps) (0.025 to 5 Pas), but values of from 100 to 1,000 cps (0.1 to 1 Pa·s) at 25°C are preferred for ease of processing. Similar viscosities are preferred where alternative polyisocyanate components are selected.

In the technique of the present invention, a polyalcohol formulation component may advantageously be selected from the following classes of compositions, alone or as a mixture: (a) alkylene oxide adducts of polyhydroxyalkanes; (b) alkylene oxide adducts of non-reducing sugars and sugar derivatives; (c) alkylene oxide adducts of phosphorus and phosphoric acids; and (d) alkylene oxide adducts of polyphenols. These types of polyols are referred to herein as "base polyols." ("base polyols"). Examples of alkylene oxide adducts of polyhydroxyalkanes suitable herein are adducts of ethylene glycol, propylene glycol, 1,3-dihydroxypropane, 1,4-dihydroxybutane and 1,6-dihydroxyhexane, glycerin, 1,2,4-trihydroxybutane, 1,2,6-trihydroxyhexane, 1,1,1-trimethylolethane, 1,1,1-trimethylolpropane, pentaerythritol, polycaprolactone, xylitol, arabitol, sorbitol and mannitol. Preferred herein as alkylene oxide adducts of polyhydroxyalkanes are the ethylene oxide adducts of trihydroxyalkanes. Other suitable adducts include ethylenediamine, glycerin, ammonia, 1,2,3,4-tetrahydroxybutane, fructose and sucrose.

Also preferred are poly(oxypropylene) glycols, triols, tetrols, pentols and hexols and any of these having ethylene oxide capping. These polyols also include poly(oxypropyleneoxyethylene) polyols. The oxyethylene content should preferably be less than 80 weight percent of the total weight and more preferably less than 40 weight percent. If the ethylene oxide is used, it can be incorporated in any manner along the polymer chain, e.g. as internal blocks, terminal blocks or randomly distributed blocks or in any combination thereof.

Another preferred class of polyols are "copolymer polyols," which are base polyols with stably dispersed polymers such as acrylonitrile-styrene copolymers. The preparation of these copolymer polyols can be from reaction mixtures comprising a variety of other materials including, for example, catalysts such as azobisisobutyronitrile; copolymer polyol stabilizers; and chain transfer agents such as isopropanol.

Polyisocyanate polyaddition compounds containing active hydrogen (PIPA) are also suitable for the preparation of formulations of the present invention. PIPA compounds are typically the reaction products of TDI and triethanolamine. A process for preparing PIPA compounds can be found, for example, in US Patent 4,374,209, which was granted to Rowlands.

Polyester polyols can be used to prepare the polymers of the present invention. For example, polyols prepared from caprolactone are suitable. Polyols prepared from butanediol and adipic acid can also be used. Any suitable polyester known to one skilled in the art of preparing polyurethanes and polyureas can be used in the present invention.

Low molecular weight diols and triols can also be used to prepare the polymers of the present invention. Ethylene glycol is particularly suitable, but other similar compounds can also be used. Propylene glycol, diethylene glycol are also suitable for use in the present invention.

In the technique of the present invention, the polyamine formulation components can be selected from the group comprising polyamines and amine-terminated polyols. Polyamines preferred for preparing the polyurethane/polyurea formulations of the present invention include the known low molecular weight isocyanate-reactive compounds such as aromatic polyamines, particularly diamines, having molecular weights of less than 800, preferably less than 500.

Preferred compounds containing amine groups include the sterically hindered aromatic diamines which contain at least one linear or branched alkyl substituent in the ortho position to the first amino group and at least one, preferably two, linear or branched alkyl substituents with at least one, preferably one to three carbon atoms in the ortho position to the second amino group contain. Diese aromatischen Diamine umfassen 1-Methyl-3,5-diethyl-2,4- diaminobenzol, 1-Methyl-3,5-diethyl-2,6-diaminobenzol, 1,3,5-Trimethyl- 2,4-diaminobenzol, 1-Methyl-5-t-butyl-2,4-diaminobenzol, 1-Methyl-5-tbutyl-2,6-diaminonbenzol, 1,3,5-Triethyl-2,4-diaminobenzol, 1-Methyl-5-tbutyl-2,4-diaminobenzol, 1-Methyl-5-t-butyl-2,6-diaminobenzol, 1,3,5- Triethyl-2,4-diaminobenzol, 3,5,3'-5'-Tetraethyl-4,4'- diaminodiphenylmethan, 3,5,3',5'-Tetraisopropyl-4,4'- diaminodiphenylmethane, 3,5-diethyl-3'-5'-diisopropyl-4,4'-diaminodiphenylmethane, 3,3'-diethyl-5,5'-diisopropyl-4,4'-diaminodiphenylmethane, 1-methyl-2,6-diamino-4-isopropylbenzene and mixtures of the above diamines. Most preferred are mixtures of 1-methyl-3,5-diethyl-2,4-diaminobenzene and 1-methyl-3,5-diethyl-2,6-diaminobenzene in a weight ratio between 50:50 to 85:15, preferably 65:35 to 80:20.

Unhindered aromatic polyamines can be used with the sterically hindered chain extenders and include 2,4- and/or 2,6-diaminotoluene, 2,4'- and/or 4,4'-diaminophenylmethane, 1,2'- and 1,4-phenylenediamine, naphthalene-1,5-diamine and triphenylmethane-4,4',4"-triamine. The difunctional and polyfunctional aromatic amine compounds can also contain exclusively or partially secondary amino groups, such as 4,4'-di-(methylamino)-diphenylmethane or 1-methyl-2-methylamino-4-aminobenzene. Liquid mixtures of polyphenyl-polymethylene polyamines of the type obtained by condensing aniline with formaldehyde are also suitable.

In general, the non-sterically hindered aromatic diamines and polyamines are too reactive to provide sufficient processing time in the preparation of polymers such as RSG polyurethanes and polyureas. Accordingly, these diamines and polyamines should be used in combination with one or more of the sterically hindered diamines mentioned above. An exception to this is the case of methylenediorthochloroaniline. This particular diamine is a suitable material for the preparation of RSG polyurethane/polyureas, although it is not sterically hindered.

Polyurethane catalysts may also be suitably used in the present invention. The catalyst is preferably incorporated into the formulation in an appropriate amount to enhance the rate of reaction between the isocyanate groups of the composition of the present invention and a hydroxyl reacting species. Although a wide variety of materials are known to be suitable for this purpose, the most commonly used and preferred catalysts are the tertiary amine catalysts and the organotin catalysts.

Examples of tertiary amine catalysts include, for example, triethylenediamine, N-methylmorpholine, N-ethylmorpholine, diethylethanolamine, N-cocomorpholine, 1-methyl-4-dimethylaminoethylpiperazine, 3-methoxy-N-dimethylpropylamine, N,N-diethyl-3-diethylaminopropylamine and dimethylbenzylamine. Tertiary amine catalysts are also advantageously used in an amount of 0.01 to 2 percent by weight of the polyol formulation.

Examples of organotin catalysts include dimethyltin dilaurate, dibutyltin dilaurate, dioctyltin dilaurate and stannous octoate. Other examples of effective catalysts include those taught, for example, in US Patent No. 2,846,408. Preferably, the organotin catalyst is used in an amount of from 0.001 to 0.5 weight percent of the polyol formulation.

Catalysts which promote the formation of isocyanurate groups can also be used in the present invention. Suitable catalysts for use in the present invention include such as those mentioned in Saunders and Frisch, Polyurethanes. Chemistry and Technology in High Polymers Volume XVI, pages 94-97 (1962). Such catalysts are referred to herein as trimerization catalysts. Examples of these catalysts include aliphatic and aromatic tertiary amine compounds, organometallic compounds, alkali metal salts of carboxylic acids, phenols and symmetrical triazine derivatives. Preferred trimerization catalysts are potassium salts of carboxylic acids such as potassium octoate and tertiary amines such as, for example, 2,4,6-tris-(dimethylaminomethyl)-phenol.

The process of the present invention may include an additional step of molding the polymer into an article prior to painting. RMG, as discussed above, is a preferred method of making an article. Injection molding of thermoplastics is also a preferred means of making an article. Polymer molding may also be used in the process of the present invention, as may blow molding, extrusion molding and compression molding. An advantage of the present invention is that the articles so molded may be adhered to metal articles and both may be coated as a unit.

In addition to the above formulation components, the polyurethane/polyurea formulations of the present invention may also comprise materials known to those skilled in the art as useful for preparing polyurethane/polyurea polymers. Included in these materials are additives such as fillers, mold release agents, pigments, blowing agents, surfactants and flame retardants. Specifically excluded are other conductive fillers. The polymers of the present invention are in the absence of the conductivity inducing, non-volatile metal salt materials of the present Invention is not sufficiently conductive to be efficiently electrostatically coated.

The formulation components of the formulations of the present invention can be brought together in any manner known to be suitable to those skilled in the art of preparing polyurethane/polyurea polymers to form a polymer. A preferred means of forming the polyurethane/polyurea polymers of the present invention is by reaction injection molding (RIM). The preparation of RIM polymers is well known in the art, but generally involves the steps of introducing at least two streams of mutually reactive materials through a mixer into a mold wherein the materials polymerize to yield a molded polymer article.

In addition to the advantage of being paint coatable without the use of a conductive primer, the polymers of the present invention can be molded with fewer defects due to molding defects or webbing defects. Small polymer particles that remain in the mold after a molded article is removed from the mold are known as webbing (molding defect). Because the polymers of the present invention are comparatively more conductive than otherwise identical polymers made without conductivity inducing materials, they are less subject to static attraction to the mold and can be removed more easily. Therefore, the webbing particles are not as likely to remain and become an imperfection on the surface of the next article to be molded.

In the technique of the present invention, cured polymers are electrostatically coated. For the purpose of the present invention, the electrostatic coating comprises at least the steps of: (1) charging an article to be coated with an electrical charge, (2) charging a paint with an electrical charge of the opposite polarity to that of the article, or at least grounding the paint relative to the charged article, and (3) dispensing the paint from an electrostatic coating apparatus onto the article. It is also possible, and even more routine in some industries, to charge the paint and ground the article to be coated. Any means and apparatus known to those skilled in the art to be suitable for electrostatic coating can be used in the process of the present invention. For example, an apparatus such as a BINKS MODEL 85* can be used to electrostatically coat the cured polymers of the present invention (*BINKS MODEL 85 is a trade designation of Binks Manufacturing Company).

While the present invention may be practiced with liquid paints, such a narrow interpretation of the term "paint" is not intended. For the purposes of the present invention, the material that can be "applied" to an article by the method of the present invention includes any material that can be electrostatically deposited on an article. These materials include, but are not limited to, liquid pigment paints, liquid transparent paints (also known as clear coats), powder pigments, powder coatings, conductive coatings such as primers and prep coats. These materials may be used neat or solvent-based, water-based, or both solvent and water-based. For example, as in the case of powders, the materials may also be applied as a solid. The process of electrostatic coating also includes the process of electrodeposition, wherein the article is immersed in the material while an electrostatic potential is maintained between the article and the material applied thereto. rather than applying the material to the object in an aerosol.

A preferred embodiment of the present invention is an electrostatically coated article comprising at least two layers, wherein a first layer is a polymer layer made from a polymer formulation comprising (1) materials comprising or forming urea groups, urethane groups, or mixtures thereof, and (2) a conductivity inducing, non-volatile metal salt material, and a second layer, wherein the second layer is a layer of electrostatically applied paint, wherein (a) the polymer can be efficiently electrostatically coated, and (b) the polymer is conductive only by incorporation of the conductivity inducing, non-volatile metal salt material into the polymer. While the present invention is suitable for electrostatically coating articles not pretreated or coated with a conductive material, i.e. that the two layers are contiguous, the present invention can also be used to advantage to make articles with a third layer interposed between the electrostatically applied paint and the polymer. The third layer can be a non-conductive or a conductive coating. The non-volatile metal salts of the present invention increase the bulk conductivity of polymers made therewith. Surface coatings of a polymer with a conductive material increase surface conductivity but have little effect on bulk conductivity. It is believed that surface conductivity alone is not efficient in charging an article to be electrostatically coated. Therefore, the method of the present invention can be used to efficiently coat a polymer coated with a non-conductive layer or even a polymer coated with a conductive pre-coating, such as a conductive primer or prep coat.

The process of the present invention can be advantageous in comparison to conventional processes for electrostatic coating of polymers for several reasons. One of these reasons is that a very small amount of material is added to a polymer which both imparts sufficient conductivity to allow efficient electrostatic coating but does not significantly reduce the physical properties of the polymer. The non-volatile metallic salts of the present invention can be selected to be compatible with the polymer formulation in which they are incorporated. Alternatively, the salts can be mixed with a compatibilizer. If a compatibilizer is used, it should be selected so that it does not impart undesirable properties to the polymer and that it does not reduce the physical properties of the polymer. For example, n-methyl-2-pyrrolidone can be used to compatibilize a non-volatile salt of the present invention and yet not cause a significant reduction in the physical properties of the polymer produced therewith.

The following examples and comparative examples are intended to illustrate the present invention. These examples and comparative examples are not intended to limit the claims of the present invention and should not be interpreted as such.

EXAMPLE 1

A polyurethane/polyurea polymer was prepared by reacting an isocyanate prepolymer (A side) and a polyol-diamine blend (B side) using a reaction injection molding apparatus to produce elastomer sheets measuring 17.5 inches (44.4 cm) x 10.0 inches (25.4 cm) x 0.063 inches (0.16 cm). The reaction injection molding apparatus parameters are shown in Table 1 below. The polyurethane/polyurea polymer formulation consisted of two components. The first component was a soft segment prepolymer based on Methylene diphenyl diisocyanate, the prepolymer being made from a polyether polyol sold commercially as SPECTRIM 50A* (*SPECTRIM 50A is a trade name of Dow Chemical Company). The second component was a mixed active hydrogen-containing component based on a polyether polyol and diethyltoluene diamine sold commercially as SPECTRIM 50B* (*SPECTRIM 50B is a trade name of Dow Chemical Company). 0.164 percent of the total polymer weight of a sodium perfluoroalkyl sulfonic acid salt was incorporated into the SPECTRIM 50B component, the SPECTRIM 50B component and the sodium perfluoroalkyl sulfonic acid salt, FLUORAD FC-98*, were mixed and placed in a container of the RSG device (*FLUORAD FC-98 is a trade name of 3M and is a mixture of potassium perfluorocyclohexyl alkyl sulfonates). The SPECTRIM 50A was also placed in a container of the RSG device. Panels were prepared by molding and post-curing.

The panels were washed using a five-step procedure comprising the steps of rinsing in ISW 32* for 60 seconds, rinsing in deionized water for 30 seconds, rinsing in ISW 33** for 30 seconds, rinsing in deionized water for 30 seconds, rinsing in deionized water for 15 seconds (*ISW-32 is a trade name of Dussois Chemicals Corp. and is a phosphoric acid based detergent; **ISW-33 is a trade name of Dussois Chemicals Corp. and is a phosphoric acid based paint application conditioner). The panels were then dried.

Paint was applied to the plaques by first weighing the plaques on an analytical balance (original plaque weight, OP weight) and then applying them to a curved metal support with an 8.6 inch (21.8 cm) radius. The support was then applied to a conveyor system moving at 320 inches per minute (8.13 m/minute). The distance the panels were moved during paint application was 20 inches (50.8 cm). The panels were coated using a BINKS MODEL 85* gun with a 0.046 inch (1.24 mm) orifice equipped with an E63PB~ air cap and D63B~' fluid tip (*BINKS MODEL 85, E63PB and D63B are trade names of Binks Manufacturing Company). The optimum conditions for coating a metal specimen to 1.4 mil (0.036 mm) were 50 psi (345 mPa) air atomization pressure and 8 psi (55.2 mPa) cup pressure. The gun was indexed below 3 inches (7.62 cm) for each of the 6 passes per coat of paint. The applied voltage was 70 to 75 kilovolts at a current of 40 to 45 microamperes. The paint used was PPG CBC8554* thinned with isobutyl acetate to achieve a spray viscosity of 22 seconds using a Fisher #2 cup (*PPG CBC8554 is a trade name of PPG Industries, Inc.). After a first coat of paint was applied, the paint was allowed to flash off for 1.5 minutes and then a second coat of paint was applied.

After the panels were paint coated, the paint transfer efficiency was measured by allowing the coated panels to flash off for five minutes and then curing the panels in a ventilated oven at 260ºF (127ºC) for 45 minutes. The panels were allowed to cool at room temperature for 30 minutes and then re-weighed on an analytical balance (final plaque weight (FP)). The throughput of the spray gun was determined by stopping the air flow and weighing the amount of paint accumulated in one minute. The percent weight solids in the paint (WT solids) was determined by flashing off the solvent from 5 to 10 grams of paint, curing at 120ºC for one hour and determining the difference in weight using a balance. The paint spray time (PST) (paint spray time]) was 44.4 seconds. The paint transfer efficiency was determined by the following formula:

and shown in Table 2 below.

COMPARISON EXAMPLE 2

A polyurethane/polyurea polymer was prepared, color coated and tested in a manner substantially identical to Example 1, except that the formulation did not contain FLUORAD FC-98 in place of 0.164 percent FLUORAD FC-98. The results are shown in Table 2 below. TABLE 1 Reaction Injection Molding Parameters TABLE 2

*FC-98 is a trade name of 3M and is a mixture of potassium perfluorocyclohexyl alkyl sulfonates.

EXAMPLE 3

A polyurethane/polyurea polymer was prepared in a manner substantially identical to Example 1, except that the formulation comprised 0.761 percent FLUORAD FC-98 instead of 0.164 percent FLUORAD FC-98. The panels were tested for physical properties. The results are presented in Table 3 below.

EXAMPLE 4

A polyurethane/polyurea polymer was prepared and tested in a manner substantially identical to Example 3, except that the formulation comprised 0.200 percent FLUORAD FC-98 instead of 0.761 percent FLUORAD FC-98. The results are presented in Table 3.

COMPARISON EXAMPLE 5

A polyurethane/polyurea polymer was prepared and tested in a manner substantially identical to Example 3, except that the formulation did not contain FLUORAD FC-98 in place of 0.761 percent FLUORAD FC-98. The results are presented in Table 3. TABLE 3

*FC-98 is a trade name of 3M and is a mixture of potassium perfluorocyclohexyl alkyl sulfonates.

1 ASTM-D-638-89, Test Method for Tensile Properties of Plastics

2 ASTM-D-790-86, Test Method for Flexural Properties of Unreinforced and Reinforced Plastics and Electrical Insulating Materials

3 ASTM-D-624-86, Test Method for Rubber Properties -- Tear Resistance

4 ASTM-D-3796-85, Method for Testing Microcellular Urethanes - - High Temperature Sag

5 ASTM-D-256-88, Test Method for Impact Strength of Plastics and Electrical Insulating Materials

6 ASTM-D-2240--86, Test Method for Rubber Properties - Durometer Hardness

7 ASTM-D-570-81, Test method for water absorption of plastics

EXAMPLES 6 TO 18 AND COMPARATIVE EXAMPLES 19 TO 24

Polymers were prepared with the non-volatile metal salts of the present invention. The additives detailed in Table 4A-4C below were mixed with the polymer formulations and then injection molded or reaction injection molded into articles suitable for color coating. A white base coat (CBC9753) was applied with a SPRAYMATION MODEL 31 01 60* automatic aperture sprayer. The specified conditions for the aperture spray system are:

- 850"/minute (2.16 m/minute) gun traverse speed;

- 2" (5.1 cm) spray gun index with 50% fan overlap;

- 40 psig (276 kPa) air atomization pressure

- BINKS MODEL 80A* electrostatic spray gun, including a 63B fluid tip, N63 air cap and a 111-1271 fluid needle;

- BINKS MODEL 111-3800, 0-100 kilovolt power supply;

- Distance between gun and part 10" (25.4 cm);

- Number of coatings = 2;

- Number of gun passes per coating = 8; and

- 80 kilovolts.

(*BINKS MODEL 80A and BINKS MODEL 111-3800 are trade names of Binks Manufacturing Company, SPRAYMATION MODEL 31 01 60 is a trade name of Spraymation Equipment Company) The process conditions used during the application and the specific paint preparation conditions are shown below. Paint coated panels were cured in an electric air circulation oven after paint application. The paints used were Pittsburgh Paint and Glass (PPG) paints. The paints had the following properties:

*PPG and CBC9753 are trademarks of Pittsburgh Paint and Glass

CALIBRATION:

Calibration was performed on bare steel apertures measuring 0.032 x 4 x 12 inches (0.81 mm x 10.2 cm x 30.48 cm). Calibration was performed by coating the apertures with paint while the electrostatics were off. The target film thickness of the steel calibration aperture was 0.8 mils +/- 0.1 mils (0.02 +/- 0.0025 mm). With few exceptions, the target film thickness was achieved using a 6 PSIG kettle pressure.

PANEL HOLDER AND GROUNDING:

The standard metal fascia support rods on the SPRAYMATION were replaced with fiberglass rods of the same dimensions. The frame cross members were replaced with oak, which was glued in place with epoxy.

Aluminum plates (2) measuring 4 x 6 x 1/4 inches (10.2 x 15.2 x 0.64 cm) were mounted 1 inch (2.54 cm) apart on the top oak cross board with wooden screws. A metal bolt was mounted smoothly on the surface of the metal plates. The bolt was centered on the plate and protruded from the back where it served as a grounding point. A grounding wire was attached with a nut and washer. The ground had a resistivity of 0.15 ohms.

EARTHING TEST:

Grounding testing was performed using a WOODHEAD MODEL 7040* Grounding Circuit Impedance Tester (**WOODHEAD MODEL 7040 is a trade designation of the Daniel Woodhead Company).

TEST APPLICATION:

Test samples were placed so that half of the sample was backed by a grounded aluminum plate and half was unreinforced. The test samples were held in place by clamping them to the outer edge (left part on the left side, right part on the right side) on the aluminum plate using the conductive metal clamp (≥ 0.15 ohm resistivity). This ensured that the plastic objects were grounded.

Since the aluminum plates were 4 inches (10.2 cm) wide and 6 inches (15.2 cm) long, the optimal part size was 4 inches (10.2 cm) wide and 12 inches (30.5 cm) long, so that half of the part was back reinforced and the other half was unreinforced. Some of the parts were 10 inches (25.4 cm) long, in In this case, 5 inches (12.7 cm) of the parts were backed with aluminum and 5 inches (12.7 cm) were not.

Many of the parts were only 5 inches (12.7 cm) long. In this case, 2 parts that were 5 inches (12.7 cm) long were clamped together to conduct the experiment. A 4 inch (10.2 cm) wide by 2.5 inch (6.4 cm) long by 1/4 inch (0.64 cm) thick non-conductive modified polyurethane panel was taped to the back of the aluminum plate. The metal clamp used to hold the parts in place was centered over the interface between the aluminum plate and the polyurethane. Half of the clamp was on each of the 5 inch (12.7 cm) long parts. Masking tape was used to cover any exposed aluminum.

FILM THICKNESS:

Film thickness was measured on the steel panels using an ELCOMETER 245 portable film thickness meter (*ELCOMETER 245 is a trading name of Elcometer Instruments Ltd.). Film thickness was measured visually on the plastic panels. A piece of the paint coated substrate was cut from the paint coated plastic substrate using a razor knife. The piece was placed on a flat cutting surface with the paint coated side down. A cross section was cut through the plastic and paint layers. The cross section was placed on a microscope slide. Paint thickness was measured at a magnification of 200x using a graduated eyepiece. On the 12 inch (30.5 cm) long panels, film thickness measurements were taken at 2 (5.1 cm) and 4 (12.7) inches from the top of the aluminum backed half of the test panels. On the 5-inch (12.7 cm) long panels that were clamped together and the 10-inch (25.4 cm) long panels, film thickness measurements were taken at 1.5 (3.81 cm) inches from the top of the aluminum-backed half of the test panel. They were measured at 3.5 inches (8.9 cm) below the metal backing on all samples.

COLOR WRAPPING:

The extent to which the paint wraps the part rather than simply migrating in a straight line from the sprayer to the part being coated was also measured. This is a subjective measurement known as paint wrap, which is obtained by comparing a sample to both an electrostatically coated steel control and a similarly coated steel control except that the electrostatic power was turned off during paint coating. These parts have paint wrap values of excellent and nonexistent, respectively. The hierarchy of paint wrap values is:

excellent > good > average > > poor > none.

The results are listed in Tables 4A-4C below. TABLE 4A TABLE 4B TABLE 4C

A SPECTRiM50S is a polyurethane/polyurea polymer prepared by blending two commercially available components (SPECTRIM 50S is a trade name of Dow Chemical Company). The first component was a soft segment prepolymer based on methyl diphenyl diisocyanate, the prepolymer being prepared from a polyether polyol sold commercially as SPECTRIM 50A* (*SPECTRIM 50A is a trade name of Dow Chemical Company). The second component was a blended active hydrogen-containing component based on a polyether polyol and diethyltoluenediamine sold commercially as SPECTRIM 50B* (~"SPECTRIM 50B is a trade name of Dow Chemical Company). The articles were prepared by reaction injection molding processes.

B FC-98 is a mixture of potassium perfluorocyclohexyl alkyl sulfonates available from 3M. FC-98 is a trade name of 3M.

C SPECTRIM 25 is a polyurethane/polyurea polymer prepared by blending two commercially available components (SPECTRIM 25 is a trade name of Dow Chemical Company). The first component was a soft segment prepolymer based on a methylene diphenyl diisocyanate, the prepolymer being prepared from a polyether polyol sold commercially as SPECTRIM 25A* (*SPECTRIM 25A is a trade name of Dow Chemical Company). The second component was a blended active hydrogen-containing component based on a polyether polyol and diethyltoluenediamine sold commercially as SPECTRIM 25B* (*SPECTRIM 25B is a trade name of Dow Chemical Company). The articles were prepared by reaction injection molding.

D SPECTRIM HF85 is a polyurethane/polyurea polymer prepared by blending two commercially available components (SPECTRIM HF85 is a trade name of Dow Chemical Company). The first component was a soft segment prepolymer based on methylene diphenyl diisocyanate, the prepolymer being prepared from a polyether polyol sold commercially as SPECTRIM HF85A* (*SPECTRIM HF85A is a trade name of Dow Chemical Company). The second component was a blended active hydrogen-containing component based on an aminated polyether polyol sold commercially as SPECTRIM HF8SB* (*SPECTRIM HF85B is a trade name of Dow Chemical Company). The articles were prepared by reaction injection molding.

E TPU is a thermoplastic urethane based on methylene diphenyl diisocyanate and a polyester polyol, which is sold commercially as PELLETHANE 2354-65D by the Dow Chemical Company. PELLETHANE 2354-65D is a trade name of the Dow Chemical Company. The additive was mixed into the liquid precursors used to make TPU. The articles were manufactured by injection molding.

F DEHYQUAT C is lauryl pyridinium chloride and is a trade name of Henkel Corporation.

EXAMPLES 25, 27-29 AND COMPARATIVE EXAMPLES 26 AND 30

Polyurethane/polyurea sheet samples were prepared using the polymers and non-volatile metal salts shown in Table 5 (*SPECTRIM 50S is a trade name of Dow Chemical Company). The sheets were prepared by mixing the non-volatile metal salts with the B-side of the formulation and reaction injection molding the sheets. The samples were tested for physical properties and the results are presented below in Table 5. TABLE 5

1SPECTRIM 50S is a polyurethane/polyurea polymer prepared by blending two commercially available components (SPECTRIM 50S is a trade name of Dow Chemical Company). The first component was a soft segment prepolymer based on methylene diphenyl diisocyanate, the prepolymer being prepared from a polyether polyol sold commercially as SPECTRIM 50A* (*SPECTRIM 50A is a trade name of Dow Chemical Company). The second component was a blended active hydrogen-containing component based on a polyether polyol and diethyltoluenediamine sold commercially as SPECTRIM 50B* (*SPECTRIM 50B is a trade name of Dow Chemical Company). The articles were prepared by reaction injection molding.

² SPECTRIM 25 is a polyurethane/polyurea polymer prepared by blending two commercially available components (SPECTRIM 25 is a trade name of Dow Chemical Company). The first component was a soft segment prepolymer based on methylene diphenyl diisocyanate, the prepolymer being prepared from a polyether polyol sold commercially as SPECTRIM 25A* (SPECTRIM 25A is a trade name of Dow Chemical Company). The second component was a blended active hydrogen-containing component based on a polyether polyol and diethyltoluenediamine sold commercially as SPECTRIM 25B* ('*SPECTRIM 25B is a trade name of Dow Chemical Company). The articles were prepared by reaction injection molding.

³ FC-98 is a mixture of potassium perfluorocyclohexyl alkyl sulfonates available from 3M. FC-98 is a trade name of 3M.

&sup4; Lithium trifluoromethanesulfonate.

A ASTM D-790-86, Test Method for Flexural Properties of Unreinforced and Reinforced Plastics and Electrical Insulating Materials.

B ASTM D-792-86, Test Method for Relative Density and Density of Plastics by Displacement.

C ASTM-D-624-86, Test Method for Rubber Properties -- Tear Strength. ASTM-D-638-89, Test Method for Tensile Properties of Plastics.

EXAMPLE 31 AND COMPARATIVE EXAMPLES 32-36

Panel samples were prepared using the polymers and additives as shown in Table 6 below. The panels were powder coated and using the following procedure:

POWDER COATING APPLICATION EQUIPMENT

A clear powder coating was applied to test panels using an electrostatic powder coating applicator from Nordson NPE CC8 Model 246152H* electrostatically applied. The coating gun was mounted on an ECLIPSE MODEL 50-6528 aperture sprayer using a rack speed of 300 inches/minute (762 cm/minute), a gun-to-part distance of 10 inches (25.4 cm), and a gun index of 3 inches (7.6 cm). The following conditions were held constant on the powder coater:

- Atomizing air = 20 PSIG (138 kPa)

- Vortex 0.2 PSIG (1.3 kPa) input

- Flow rate 30 PSIG (207 kPa)

- 90 kilovolts electrostatic potential.

SAMPLE MOUNTING AND GROUNDING

The samples were mounted with a ground clamp on a corrugated cardboard holder made by gluing together 4 12.5" L x 1.75" W x 0.125" inch pieces (31.75 cm L x 4.45 cm W x 3.18 mm). The holder was screwed onto the Eclipse support bar. The ground wire was attached to the top of the test pieces.

POWDER COATING AND FORMULATION

The powder coating was applied in one coat and then cured at 325ºF (163ºC) for 15 minutes.

The powder coating formulation consisted of the following components by weight: DER 662UH* 100 parts, EPON P-108** 4 parts, RESI FLOW P-67*** 1 part. (* DER 662UH is a trade name of Dow Chemical Company, ** EPON P-108 is a trade name of Shell Chemical Company, ***RESIFLOW P-67 is a trade name of Esrton Chemical Company).

The compound was mixed on a Buss Condux PLK-46 extruder at a kneading rate of 200 revolutions per minute at 70ºF (21ºC).

The extrudate was ground to powder using a Micropul Bantam mill using a 0.013 inch herringbone screen. The powder was sieved through a 150 mesh screen. TABLE 6

ASPECTRIM HF85 is a polyurethane/polyurea polymer made by blending two commercially available components (SPECTRIM HF85 is a trade name of the Dow Chemical Company).

The first component was a soft segment prepolymer based on methylene diphenyl diisocyanate, the prepolymer being prepared with a polyether polyol sold commercially as SPECTRIM HF85A* (*SPECTRIM HF85A is a trade name of the Dow Chemical Company). The second component was a blended active hydrogen-containing component based on an aminated polyether polyol sold commercially as SPECTRIM HF85B* (*SPECTRIM HF85B is a trade name of the Dow Chemical Company). The articles were prepared by reaction injection molding. B GTX is NORYL GTX 910-A~, an engineering thermoplastic based on a blend of polydimethylphenylene oxide and nylon available from General Electric Company (*NORYL GTX 910-A is a trade name of the General Electric Company). The additive is first mixed with the plastic in high concentration to form a concentrate. This concentrate is then mixed with untreated plastic in a ratio to achieve the specified concentration. Articles were molded by injection molding. C FC-98 is a mixture of potassium perfluorocyclohexyl alkyl sulfonates, available from 3M. FC-98 is a trade name of 3M.

Claims (17)

1. A method for coating cross-linked polymers containing urea and/or urethane groups, comprising the steps: (A) preparing a crosslinked polymer from a polymer formulation comprising (1) materials comprising or forming urea groups, urethane groups, or mixtures thereof, and (2) a non-volatile, conductivity-inducing metal salt material, wherein the polymer becomes conductive only by the incorporation of the non-volatile, conductivity-inducing metal salt materials into the polymer, and (B) coating the polymer, wherein the polymer is electrostatically coated. 2. The method of claim 1 further comprising a step of forming the polymer into a shaped article before it is coated. 3. A process according to claim 2, wherein the polymer is formed into a shaped article by injection molding or reaction injection molding. 4. The method of claim 3, wherein the polymer is formed into a shaped article by reaction injection molding. 5. The process of claim 1, wherein the non-volatile metal salt contains a cation selected from the group consisting of cations of Li, Na, K and mixtures thereof. 6. The method of claim 5, wherein the non-volatile metal salt contains an anion selected from the group consisting of a perfluoroalkyl sulfonate, a tetraphenylboron anion, a hexafluorophosphate anion, and mixtures thereof. 7. The process of claim 1 wherein the non-volatile metal salt is present in the polymer formulation at 0.02 to 1.5 percent. 8. A method for electrostatically coating a crosslinked polymer containing urea and/or urethane groups, wherein the polymer is formed into a shaped article, coated with a conductive preparatory substance and then electrostatically coated, wherein the polymer is prepared from a polymer formulation comprising (1) Materials comprising or forming urea groups, urethane groups or mixtures thereof, and (2) a non-volatile, conductivity-inducing metal salt material. 9. An electrostatically coated article comprising at least two layers, wherein a first layer is a polymer layer made from a polymer formulation comprising (1) Materials comprising or forming urea groups, urethane groups or mixtures thereof, and (2) a non-volatile conductivity-inducing metal salt material, wherein the polymer becomes conductive only by the incorporation of the non-volatile conductivity-inducing metal salt materials into the polymer, and a second layer, wherein the second layer is a coating layer wherein the polymer is electrostatically coated. 10. The electrostatically coated article of claim 9, wherein the non-volatile metal salt contains a cation selected from the group consisting of cations of Li, Na, K, and mixtures thereof. 11. The electrostatically coated article of claim 10, wherein the non-volatile metal salt contains an anion selected from the group comprising a perfluoroalkyl sulfonate, a tetraphenylboronic anion, a hexafluorophosphate anion, and mixtures thereof. 12. The electrostatically coated article of claim 9, wherein the non-volatile metal salt is present in the polymer at 0.02 to 1.5 percent. 13. The electrostatically coated article of claim 9, wherein the electrostatically applied coating layer and the polymer layer are adjacent to each other. 14. The electrostatically coated article of claim 9, wherein the article comprises an additional layer disposed between the electrostatically applied coating layer and the polymer layer. 15. The electrostatically coated article of claim 14, wherein the additional layer is a conductive primer or a conductive precoat. 16. The electrostatically coated article of claim 9, wherein the polymer is an article formed by injection molding or reaction injection molding. 17. The electrostatically coated article of claim 16, wherein the polymer is an article formed by reaction injection molding.