Steel Protective Coating Compositions, Methods of Their Manufacture, and Methods of Their Use

Abstract

Steel sheet coating compositions in which polymeric resin or ceramic properties are produced by admixing an aluminum coordinate complex and an aluminum resin, a polysilazane as a source of silicon, an organic solvent, an organic synthesis catalyst, and optionally a non-metallic, non-ionic, low-nucleophilic base. The admixed coating is applied to sheet steel prior to hot-stamping in order to inhibit surface formation of iron oxides and to improve steel sheet surface characteristics.

Claims

1. An oxidation-protective coating composition for steel sheets comprising: (a) an aromatic organic solvent; (b) at least one source of aluminum; (c) a silazane; and (d) an organic synthesis catalyst.

2. The composition as claimed in claim 1, wherein said aromatic organic solvent is selected from one or more compounds of the group consisting of 1,2-diethylbenzene, 1,3-diethylbenzene, 1,4-diethylbenzene, 1,2,3-trimethylbenzene, 1,2,4-trimethylbenzene, 1,3,5-trimethylbenzene, polyethylbenzene, bicyclo[4.4.0]deca-1,3,5,7,9-pentaene, 2-methylindole, and 2-phenylpropane.

3. The composition as claimed in claim 1, wherein said at least one source of aluminum is present in the form of an aluminum pigment.

4. The composition as claimed in claim 1, wherein said at least one source of aluminum is present in the form of a coordination complex of aluminum.

5. The composition as claimed in claim 4, wherein said aluminum coordination complex of aluminum is aluminum acetylacetonate.

6. The composition as claimed in claim 1, wherein said silazane is a polysilazane polymer resin comprising silicon and nitrogen.

7. The composition as claimed in claim 6, wherein said polysilazane is an organic polysilazane.

8. The composition as claimed in claim 6, wherein said polysilazane is an inorganic polysilazane.

9. The composition as claimed in claim 1, wherein said organic synthesis catalyst is an organohetercyclic compound.

10. The composition as claimed in claim 9, wherein said organoheterocyclic compound is an azepane.

11. The composition as claimed in claim 1, wherein said organic synthesis catalyst is 1,8-diazabicyclo[5.4.0]undec-7-ene.

12. The composition as claimed in claim 1, additionally comprising an organophosphorus compound.

13. The composition as claimed in claim 2, wherein said organophosphorus compound is a phosphazene.

14. The composition as claimed in claim 13, wherein said phosphazene is 2-tert-Butylimino-2-diethylamino-1,3-dimethylperhydro-1,3,2-diaza phosphorine.

15. The composition as claimed in claim 1, where said aromatic organic solvent is present in a w/w concentration of from 30% to 60%; said aluminum is present in a w/w concentration of from 5% to 25%; said silazane is present in a w/w concentration of from 20% to 60%; and said organic synthesis catalyst is present in a concentration of from 0.5% to 5%.

16. The composition as claimed in claim 1, where said aromatic organic solvent is present in a w/w concentration of from 40% to 50%; said aluminum is present in a w/w concentration of from 10% to 20%; said silazane is present in a w/w concentration of from 30% to 50%; and said organic synthesis catalyst is present in a concentration of from 1% to 4%.

17. The composition as claimed in claim 16, where said aromatic organic solvent is present in a w/w concentration of 44 to 45%; said aluminum is present in a w/w concentration of from 12% to 14%; said silazane is present in a w/w concentration of from 38% to 42%; and said organic synthesis catalyst is present in a w/w concentration of approximately 2%.

18. A method of protecting surfaces of carbon steel during high temperature stamping, comprising roller-coating the surfaces of the steel to be stamped with a coating composition as claimed in claim 1.

19. A method of making the steel oxidative-protective coating composition of claim 18, comprising the steps of (a) admixing said aromatic organic solvent, aluminum, silazane, and catalyst to a homogeneous consistency admixture; (b) calculating an amount of time needed to achieve a cure optimized rate of the admixture of step (a); (c) adjusting the amount of the catalyst of step (a) to an amount sufficient to obtain said cure optimized rate; and (d) applying the product of step (c) to a steel article in need of protection from oxidation, by applying said cure optimized admixture to said steel article prior to heat-stamping said steel article.

20. An steel sheet for hot-stamping, comprising said steel sheet having at least one surface coated by a composition comprising: (a) an aromatic organic solvent; (b) a source of aluminum; (c) a silazane; and (d) an organic synthesis catalyst.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0029] The present invention in its varying embodiments will now be described more fully. This invention may, however, be embodied in many different forms and should not be construed as being limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those of ordinary skill in the art.

[0030] Although the detailed description of this Specification contains many specifics for the purposes of illustration, a person of ordinary skill in the art will appreciate that many variations and alterations to the following details are within the scope of the invention. Accordingly, the following embodiments of the invention are set forth without any loss or diminution of generality to, and without imposing limitations upon, the claimed invention.

[0031] As used herein, the word “exemplary” or “illustrative” means “serving as an example, instance, or illustration.” Any implementation described herein as “exemplary” or “illustrative” is not necessarily to be construed as preferred or advantageous over other implementations. All of the implementations described below are exemplary implementations provided to enable persons skilled in the art on how to make or use the embodiments of the disclosure and are not intended to limit the scope of the disclosure of the invention, which is defined solely by the claims.

[0032] Furthermore, in this detailed description, a person skilled in the art should note that quantitative qualifying terms such as “generally,” “substantially,” “mostly,” and other terms are used, in general, to mean that the referred-to object, characteristic, or quality constitutes a majority of the subject of the reference. The meaning of any of these terms is dependent upon the context within which it is used, and the meaning may be expressly modified.

[0033] Abbreviations, nomenclature, and technical & non-technical term definitions as used in these examples are as follows.

[0034] The phrase “a” or “an” in the context of an entity or moiety as used herein refers to one or more of that entity or moiety, as in for example. “a” compound refers to one or more compounds or at least one compound. As such, the terms “a” (or “an”), “one or more,” “at least one,” and “can or “and”, may be used interchangeably. The term “about” has its plain and ordinary meaning of “approximately.” Regarding metal ion ratios and dosing amounts, the qualifier “about” reflects the standard experimental error commonly used by those of ordinary skill in the chemistry, materials, and metallurgy arts. The terms “optional” or “optionally” as used herein means that a subsequently described event or circumstance may, but need not, occur and that the description includes instances where the event or circumstance occurs and instances in which it does not.

[0035] The term “mixing” or “efficient mixing” as used herein is not limited to the same compounding process; it involves all mixing methods in a manufacturing process.

[0036] The compositions of the present invention can be prepared readily according to the following examples or modifications thereof using readily available starting materials, reagents and conventional synthesis procedures. In these reactions, it is also possible to make use of variants which are themselves known to those of ordinary skill in this art, but these are not mentioned in greater detail.

[0037] The most preferred compositions and their constituent compounds of the invention are any or all of those specifically set forth in these examples. These compositions are not, however, to be construed as forming the only genus that is considered as the invention, and any combination of the compositions and constituent compounds or their moieties may itself form a genus. The following examples further illustrate details for the preparation and the quantitative and qualitative analysis of the compounds of the present invention. Those skilled in the art will readily understand that known variations of the conditions and processes of the following preparative procedures can be used to prepare these compounds. All temperatures are degrees Celsius unless noted otherwise.

[0038] Silazanes. Silicon-nitrogen compounds with alternating silicon- (“sila”) and nitrogen atoms (“aza”) are designated as silazanes. Simple examples of silazanes are disilazane H.sub.3Si—NH—SiH.sub.3 and hexamethyldisazane (H.sub.3C).sub.3Si—NH—Si(CH.sub.3).sub.3. If only one silicon atom is bound to the nitrogen atom, the materials are known as silylamines or aminosilanes (for example triethylsilylamine (H.sub.5C.sub.2).sub.3Si—NH.sub.2). If three silicon atoms are bound to each nitrogen atom, the materials are called silsesquiazanes. Small ring-shaped molecules with a basic network of Si—N are named cyclosilazanes (for example cyclotrisilazane [H.sub.2Si—NH].sub.3).

[0039] Polysilazanes. Polysilazanes are silazane polymers consisting of both large chains and rings showing a range of molecular masses. Polysilazanes are a class of polymers in which silicon and nitrogen atoms alternate to form the basic backbone. Polysilazanes are a preferred category of silazanes utilized in the present invention. A polymer with the general formula (CH.sub.3).sub.3Si—NH—[(CH.sub.3).sub.2Si—NH].sub.n—Si(CH.sub.3).sub.3 is designated as poly(dimethylsilazane). According to the IUPAC rules for the designation of linear organic polymers, the compound would actually be named poly[aza(dimethylsilylene)], and according to the preliminary rules for inorganic macromolecules catena-poly[(dimethylsilicon)-m-aza]. By “polysilazane” is meant any oligomeric or polymeric composition comprising a plurality of Si—N repeat units. By “oligomer” is meant any molecule or chemical compound which comprises several repeat units, generally from about 2 to 10 repeat units. “Polymer”, as used herein, means a molecule or compound which comprises a large number of repeat units, generally greater than about 10 repeat units. Since each silicon atom is bound to two separate nitrogen atoms and each nitrogen atom to two silicon atoms, both chains and rings of the formula [R.sup.1R.sup.2Si—NR.sup.3] may occur, where R.sup.1-R.sup.2 can be hydrogen atoms or organic substituents. If all substituents R are H atoms, then the polymer is designated as perhydropolysilazane, polyperhydridosilazane, or inorganic polysilazane ([H.sub.2Si—NH].sub.n). If hydrocarbon substituents are bound to the silicon atoms, the polymers are designated as organopolysilazanes. The synthesis of polyorganosilazanes was first described in 1964 by Kriger and Rochow. C. R. Kruger. E. G. Rochow, J. Polym. Sci. Vol. A2, 1964, 3179-3189, the disclosure of which is incorporated herein by reference. By reacting ammonia with chlorosilanes (ammonolysis), trimeric or tetrameric cyclosilazanes were formed initially and further reacted at high temperatures with a catalyst to yield higher molecular weight polymers. Ammonolysis of chlorosilanes still represents an important synthetic pathway to polysilazanes, but it is not a preferred method of preparation of the polysilazines of the present invention. In the 1960s, the first attempts to transform organosilicon polymers into quasi-ceramic materials were described..sup.[2] At this time, suitable (“pre-ceramic”) polymers heated to 1000° C. or higher were shown to split off organic groups and hydrogen and, in the process, the molecular network is rearranged to form amorphous inorganic materials. Using polymer derived ceramics (PDCs), alternative embodiments of the invention are disclosed here, especially in the area of high-performance, i.e. high temperature and/or work-hardened steel materials. The most important pre-ceramic polymers in the production of PDCs are polysilanes [R.sup.1R.sup.2Si—R.sup.1R.sup.2Si].sub.n, polycarbosilanes [R.sup.1R.sup.2Si—CH.sub.2]. polysiloxanes [R.sup.1R.sup.2Si—O].sub.n and polysilazanes [R1R2Si—NR3].sub.n. In polysilazanes, each silicon atom is bound to two nitrogen atoms and each nitrogen atom to at least two silicon atoms (three bonds to silicon atoms are also possible). If all remaining bonds are with hydrogen atoms, the result is perhydropolysilazane [H.sub.2Si—NH].sub.n. In organopolysilazanes, at least one organic substituent is bound to the silicon atom. The amount and type of organic substituents have a predominant influence on the macro-molecular structure of polysilazanes.

[0040] Polysilazanes are colorless to pale yellow liquids or solid materials. Conditional of manufacturing, the liquids often contain dissolved ammonia that can be detected by smell, though this is not a preferred embodiment of the present invention and ammonia-free or lowered ammonia preparations are preferred. The average molecular weight can range from a few thousand to approximately 100,000 g/mol while the density normally lies around 1 g/cm.sup.3. The state of aggregation and the viscosity are both dependent on the molecular mass and the molecular macrostructure. Solid polysilazanes are produced by chemical conversion of the liquid materials (crosslinking of smaller molecules). The solid materials can be fusible or unmeltable and can be soluble or insoluble in organic solvents. Sometimes, polysilazane solids behave as thermosetting polymers, but in some cases, thermoplastic processing is possible. After the synthesis, an aging process frequently takes place in which dissolved ammonia plays an important role. The R.sub.3Si—NH.sub.2 groups resulting from the ammonolysis reaction form silazane units by splitting off ammonia. If ammonia cannot escape, the silazane units can be split again into R.sub.3Si—NH.sub.2 groups. Therefore, frequent venting of ammonia can lead to an increase in preferred molecular mass. The most preferred forms of polysilzanes used in the invention are of reduced ammonia content or ammonia free. Also, functional groups that are not bound directly into the polymer backbone can react under suitable conditions (for example Si—H with N—H groups) and increase crosslinking of the rings and chains. An increase in molecular weight can also be observed during storage at higher temperatures or in sunlight.

[0041] With contact to water or moisture, polysilazanes decompose more or less quickly. Water molecules attack the silicon atom and the Si—N bond is cleaved. The R.sub.3Si—NH—SiR.sub.3 forms R.sub.3Si—NH.sub.2 and HO—SiR.sub.3 which can further react (condensation) to form R.sub.3Si—O—SiR.sub.3 (siloxanes). The rate of the reaction with water (or other OH containing materials like alcohols) depends on the molecular structure of the polysilazanes and the substituents. Perhydropolysilazane [H.sub.2Si—NH].sub.n will decompose very quickly and exothermically with contact to water while polysilazanes with large substituents react very slowly. Polysilazanes are not vaporizable because of strong intermolecular forces. Heating polysilazanes results in crosslinking to form higher molecular weight polymers. At temperatures of 100-300° C. further crosslinking of the molecules takes place with evolution of hydrogen and ammonia. If the polysilazane contains further functional groups such as vinyl units, additional reactions can take place. In general, liquid materials will be converted to solids as the temperature increases. At 400-700° C., the organic groups decompose with the evolution of small hydrocarbon molecules, ammonia and hydrogen which are preferably vented off. Between 700 and 1200° C., a highly preferred three-dimensional amorphous network develops containing Si, C and N (“SiCN ceramics”) with a density of ca. 2 g/cm.sup.3. A further temperature increase can result in crystallization of the amorphous material and the formation of silicon nitride, silicon carbide and carbon. This so-called pyrolysis of the polysilazanes produces preferred ceramic materials from low-viscosity liquids with very high yield (up to 90%). Due to the organic groups that are often used to give good polymer processability, preferred ceramic yield is normally in the range of 60-80%. For a long time polysilazanes have been synthesized and characterized, and their great potential for many applications was acknowledged. However, up to now, very few products have been developed into a marketable commodity.

[0042] The most preferred polysilazane used in a most preferred embodiment of the invention is a commercially available product called Durazane® 1800, available from Merck KGaA of Darmstadt, Germany. This polysilazane is a liquid phase, low-viscosity, solvent-free organic polysilazane resin having the industrial properties of being a coating binder and a polymeric ceramic precursor. Durazane® 1800 exhibits good adhesion, good hardness, hydrophobicity, and good barrier properties. When used as a polymeric ceramic precursor, it yields a preferred pyrolyzed ceramic material that shows excellent high temperature stability, being able to endure peak temperatures of up to 1000° C., which is well within the range of temperatures encountered in the hot-stamping process. It has a high ceramic yield of 80 to 90%, depending on the atmosphere used. Its applications are in the field of high temperature coatings for the protection of metals against corrosion in industrial applications, in the formulation of non-stick high temperature coatings for rollers or molds, and for the infiltration of porous preforms and resin transfer moldings. Durazane 1800 exhibits the following properties:

[0043] Dry film thickness: 8-10 μm.

[0044] Non-cured temperature stability: up to 350-400° C.

[0045] Pencil Hardness: up to 5H (DIN EN ISO 15184).

[0046] Indentation Hardness (DIN EN ISO 14577-1).

[0047] Radical Initiator DCP cured for 2 h @ 150° C.: 60-65 MPa.

[0048] Radical Initiator LP cured for 2 h @ 130° C.: 185-200 MPa.

[0049] Contact angle water: 90-96°.

[0050] Contact angle oil: 42-44°.

[0051] Surface energy: 24-26 mN/m.

[0052] Polar part: 2-3 mN/m.

[0053] Dispersive part: 22-23 mN/m.

[0054] Adhesion by cross cut: 0 (DIN EN ISO 2409:2013, where 0=excellent, 5=no adhesion).

[0055] Cured temperature stability: up to 1000° C.

[0056] Appearance: clear to trace hazy liquid.

[0057] Color: Colorless to trace yellow.

[0058] Density @25° C.: 0.950-1.050 g/cm3 (ISO 2811-1).

[0059] Viscosity @20° C.: 10-40 cP.

[0060] Conditions of use:

[0061] Pretreatment:

[0062] Grease and dust/particle free surface of substrates are required.

[0063] Sandblasting of metal substrates is preferred.

[0064] Curing conditions:

[0065] Optimally cured with radical initiators, which allows a reduction of the curing temperature or time (for example 2 h/150° C. with addition of 0.5-2 wt.-% dicumylperoxide [DCP] or 2 h/130° C. with addition of 0.5-2 wt.-% Luperox531M80 [LP]).

[0066] Non catalytic curing: 250° C. for 0.5 h; 180° C. for 3-4 h.

[0067] Pyrolysis:

[0068] Pyrolysis takes place at temperatures >500° C.

[0069] Dilution/Formulation:

[0070] Dilution: Dilution is possible with organic solvents such as alkanes (e.g. heptane, isoalkanes), esters (e.g. ethyl acetate, butyl acetate, propylene glycol, methyl ether acetate), ethers (e.g. THF, di-n butyl ether), aromates (e.g. toluene, xylene) or ketones (e.g. methyl ethyl ketone). The resin reacts in the presence of water, water vapor or alcohols therefore it is important to use above mentioned solvents with lowest possible water content.

[0071] Formulation: Durazane® 1800 may be blended with multiple alternative embodiment coating components, including organic pigments, pigment preparations, metal powders (zinc, aluminum), ceramic powders to increase the ceramic properties of the final admixture (e.g. silicon nitride, boron carbide, aluminum oxide, boron nitride, or silicon nitride) and many alternative co-binders and additives.

[0072] Aluminum. Aluminum Pigment as a Source. The preferred metal constituent of the invention is the metal aluminum. In a most preferred embodiment, aluminum is sourced from the use of a suitable aluminum pigment. The most preferred aluminum pigment used in a most preferred embodiment of the invention is a commercially available product called STAPA Hydrolan 501, available from the Eckart division of Altana corporation, of Hartenstein, Germany. STAPA Hydrolan 501 is the most preferred embodiment of the STAPA® Hydrolan line of non-leafing, aluminum pigments. It is used in general industrial, automotive and accessories coatings. STAPA IL HYDROLAN 501, material number 005332, is an aluminum paste, more specifically a pigment paste of flaky aluminum powder produced of pure aluminum with an inorganic coating. Properties that characterize all aluminum pigments for waterborne systems in the HYDROLAN® line of aluminum pigments are that these silica encapsulated pigments are very shear-stable, and that they are off-gassing resistant. The specific gravity is 1.4 kg/l. The solvent used is isopropanol (IL) and the preparation includes miscellaneous lubricants and additives. The pigment composition is aluminum app. 53%.

[0073] Powder Characteristics:

TABLE-US-00001 TI00004 pigment content/non-volatile 58.0-62.0% TI00004 volatile content 38.0-42.0% TI00005 sieving <63 μm 99.9-100.0% TI00009 D 10  7.0-11.0 micrometers TI00009 D 50 22.0-28.0 micrometers TI00009 D 90 44.0-52.0 micrometers

[0074] Aluminum acetylacetonate. Aluminum acetylacetonate (aluminum 2,4-pentanedionate), also referred to as Al(acac).sub.3, is a preferred aluminum coordination complex with formula Al(C.sub.5H.sub.7O.sub.2).sub.3, molecular weight 324.31 g/mol, CAS number 13963-57-0. This aluminum coordination complex with three acetylacetone ligands is used as a precursor in the preparation of aluminum oxide films. The molecule has D.sub.3 symmetry, being isomorphous with other octahedral tris(acetylacetonate)s. Aluminum acetylacetonate may additionally be used to prepare transparent superhydrophobic boehmite and silica films by sublimation, to deposit aluminum oxide films by chemical vapor deposition, to deposit aluminum oxide films by chemical vapor deposition, and as a catalyst. Acetylacetonates are coordination complexes derived from acetylacetone and metal salts, most often salts of transition metals, and most preferably aluminum. These compounds allow many metal ions to be soluble in organic solvent, in contrast to most metal salts. This allows them to be used as catalyst precursors and reagents in reactions which occur in organic phase in chemical synthesis. Acetylacetonates are also frequently used as shift reagents in nuclear magnetic resonance (NMR) spectroscopy, a research and analysis technique that exploits magnetic properties of atomic nuclei to provide detailed information about a chemical substance. Aluminum acetylacetonate is commercially available from Sigman-Aldrich of St. Louis, Mo.

[0075] Solvents. Preferred solvents used in admixing the compositions of the invention are organic aromatic solvents. The most preferred organic aromatic solvent is commercially available as Hi Sol 15, which is itself a mixture of the organic aromatic solvents diethylbenzene, 1,2-diethylbenzene, 1,3-diethylbenzene, 1,4-diethylbenzene, 1,2,3-trimethylbenzene, 1,2,4-Trimethylbenzene or 1,3,5-trimethylbenzene, polyethylbenzene, aka solvent naphtha, naphthalene, 2-methylindole, and cumene.

[0076] Catalysts. The addition of a suitable catalyst confers the advantage of achieving a customized or preferred drying time or curing time of the coating on the selected steel article. Target drying time or curing time may be achieved, reduced, or increased through selection of the catalyst and adjustment of the amount of the selected catalyst in the admixture. Typically, in the industrial setting the goal will be to reduce drying time and thereby accelerate the entire coating operation. The most preferred catalyst for use in the invention admixture is diazabicycloundecene, 1,8-Diazabicyclo[5.4.0]undec-7-ene, CAS 6674-22-2. This catalyst is commonly used in organic synthesis as a catalyst, a complexing ligand, a non-nucleophilic base, and as a protecting agent if needed during organic synthesis. The most preferred amount of this catalyst is in the range of 0.5 to 5.0% by weight, with the operator having the freedom to adjust the concentration of catalyst upward or downward to optimize the drying time or the cure time of the coating composition.

[0077] Bases. The most highly preferred base to use in the admixture of the invention is BEMP-phosphazene (2-tert-Butylimino-2-diethylamino-1,3-dimethylperhydro-1,3,2-diaza phosphorine), CAS 98015-45-3. This base is a member of the family of phosphazene bases. Phosphazenes refer to classes of organophosphorus compounds featuring phosphorus (V) with a double bond between P and N, for example phosphazenes having the formula RN═P(NR.sub.2).sub.3. Phosphazene bases are strong, uncharged bases that are non-metallic, non-ionic and low nucleophilic bases. They are stronger bases than regular amine or amidine bases.

[0078] Protonation takes place at the doubly bonded nitrogen atom. Properties of phosphazene bases include the ability to generate in situ highly reactive “naked” anions, e.g. for alkylation reactions or for spectroscopic investigations; that they are applicable in reactions where ionic bases cause solubility problems; that they are useful in reactions where ionic bases are sensitive towards oxidation or acylation: and that they are useful in reactions where ionic bases result in Lewis-acid catalyzed side reactions, for example in aldol reactions, epoxide-opening, hydride shifts, elimination of alkoxide, and polyanion-formation. The addition of a suitable phosphorous base compound confers the additional advantage of achieving a further customized or preferred drying time or curing time of the coating on the selected steel article. Target drying time or curing time may be achieved, reduced, or increased through selection of the phosphorous base and adjustment of the amount of the selected phosphorous base in the admixture.

[0079] Methods of Application. The application of the curable protective coating compositions of the present invention may take place by using the application methods known in the prior art such as bar coating, air-knife coating, roll coating, spray coating and dip coating. In those cases in which flat substrates are to be coated, the application preferably takes place in the roller application method. If a substrate is a coil shape, for example a steel coil is to be coated, a pretreatment for Si-based passivation on the steel coil may be applied prior to the application of the coating composition on the substrate. The curable protective coating composition can be applied by roller application onto the steel surface after the steel is manufactured in a steel manufacturing mill, or can be applied by spraying or another suitable dispersive process onto the steel surface at a hot-stamping site. The post-application cured coating polymeric, pre-ceramic, or ceramic product of the invention can also provide corrosion protection to the steel during storage and transfer between two industrial sites. The coating composition can be cured by flashing off at room temperature or by accelerated curing at an elevated temperature, in which case temperatures of preferably up to 300° C. may be employed for the drying and curing of the coating.

[0080] Preferably, the curable protective coating composition is cured under a temperature 100° C. to 300° C. for a polymeric coating or of 300 to 1000° C. for a ceramic coating. Accelerated curing by means for example of IR radiation, forced-air drying, UV irradiation or electron beam curing may also be useful. The coating can be applied not only to flat substrates but also to coils which are passing through a cold and/or hot forming step, or else the coating can be applied to substrates which have already undergone cold forming.

[0081] The coating composition according to the present invention may be applied in so called “direct” or “indirect” hot forming/stamping processes. In an indirect process of hot stamping, a flat substrate coated with the protective coating composition is sequentially pre-stamped, heated and then hot stamped. In a direct process, the coated flat substrate is first heated and then hot stamped.

[0082] The present coating composition is suitable particularly for the surface coating of a substrate whose surface is composed at least partly of steel. The coating composition is intended in particular for the surface coating of substrates made of carbon steel, and is suitable preferentially for the surface coating of a high-strength steel substrate which, following the surface coating, is subjected to a hot forming operation or hot stamping process, in particular to hot forming at temperatures between 800° C. and about 1000° C., preferably at between about 880° C. and about 970° C. These types of steels are, for example, duplex steels alloyed with chromium, nickel, and manganese, and boron-manganese steels.

[0083] In addition, it is possible where appropriate to add commercially customary wetting/dispersion agents, thickeners, setting agents, rheological agents, leveling agents, defoamers, hardness improving agents, lubricants and coating film modifiers or the like, all according to product performance parameters chosen through the skills of the ordinary practitioner in the art of chemistry, chemical engineering, materials science, or metallurgy, to achieve specified properties of the coating or of the coated product. Suitable examples of coating film modifiers are cellulosic materials, such as cellulose esters and cellulose ethers; homopolymers or copolymers from styrene, vinylidene chloride, vinyl chloride, alkyl acrylate, alkyl methacrylate, acrylamide, methacrylamide, acrylonitrile, methacrylonitrile, vinyl ether, and vinyl acetate monomers; polyesters or copolyesters; polyurethanes or polyurethane acrylates; epoxy resins; polyvinylpyrrolidone; polytetrafluoromethylene, polyphenyl, polyphenylene, polyimide and polytetrafluoroethylene. The compounds of the present invention can be prepared readily according to the following Examples or modifications thereof using readily available starting materials, reagents and conventional synthesis procedures. In these reactions, it is also possible to make use of variants which are themselves known to those of ordinary skill in this art, but these are not mentioned in greater detail.

[0084] The most preferred compounds of the invention are any or all of those specifically set forth in these Examples. These compounds are not, however, to be construed as forming the only genus that is considered as the invention, and any combination of the compounds or their moieties may itself form a genus. The following examples further illustrate details for the preparation, application, quantitative analysis and qualitative analysis of the compounds of the coatings of the present invention. Those skilled in the art will readily understand that known variations of the conditions and processes of the following preparative procedures can be used to prepare these compounds. All temperatures are degrees Celsius unless noted otherwise.

Example 1

[0085] Into a suitably sized mixing vessel were added 445 pounds of Hi Sol 15 Aromatic 150 organic solvent, 145 pounds of Hydrolan Aluminium 501 aluminum pigment, 389.45 pounds of Durazane 1800 Polysilizane, and 20.55 pounds of 1,8-diazabicycloundecene catalyst, which were then mixed under medium speed agitation until a lump free, smooth, and homogeneous mixture was achieved; estimated curing time of the admixture was adjusted by titrating the admixture with the addition of aluminum acetylacetonate and adding 2-tert-butylimino-2-diethylamino-1,3-dimethylperhydro-1,3,2-diazaphosphorine base. The resulting mixture was analyzed and found to not exceed 6.5 hegman cure to 350 f pmt for 30 seconds to a hardness of 2 h min at 0.4 mils dry film thickness.

Example 2

[0086] Into a suitably sized mixing vessel were added 444 pounds of Hi Sol 15 Aromatic 150 organic solvent, 120 pounds of Hydrolan Aluminium 501 aluminum pigment, 415 pounds of Durazane 1800 Polysilizane, and 20.55 pounds of 1,8-diazabicycloundecene catalyst, which were then mixed under medium speed agitation until a lump free, smooth, and homogeneous mixture was achieved; estimated curing time of the admixture was adjusted by titrating the admixture with the addition of aluminum acetylacetonate and adding and 2-tert-butylimino-2-diethylamino-1,3-dimethylperhydro-1,3,2-diazaphosphorine base. The resulting mixture was analyzed and found to not exceed 6.5 hegman cure to 350 f pmt for 30 seconds to a hardness of 2 h min at 0.4 mils dry film thickness.

Example 3

[0087] Into a suitably sized mixing vessel were added 404.9 pounds of Hi Sol 15 Aromatic 150 organic solvent, 255.4 pounds of Hydrolan Aluminium 501 aluminum pigment, 349.7 pounds of AW Hawthore Polysilizane, and Indopol as needed to achieve a desired admixture flow, which were then mixed under medium speed agitation until a lump free, smooth, and homogeneous mixture was achieved The resulting mixture was analyzed was found to not exceed 6.5 hegman cure to 350 f pmt for 30 seconds to a hardness of 2 h min at 0.4 mils dry film thickness.

Example 4

[0088] Into a suitably sized mixing vessel are added 444 pounds of Hi Sol 15 Aromatic 150 organic solvent, 175 pounds of Hydrolan Aluminium 501 aluminum pigment, 300 pounds of Durazane 1800 Polysilizane, and 15 pounds of 1,8-diazabicycloundecene catalyst, which is then mixed under medium speed agitation until a lump free, smooth, and homogeneous mixture was achieved; estimated curing time of the admixture is adjusted by titrating the admixture with the addition of aluminum acetylacetonate and adding and 2-tert-butylimino-2-diethylamino-1,3-dimethylperhydro-1,3,2-diazaphosphorine base. The resulting mixture should show analysis of not to exceed 6.5 hegman cure to 350 f pmt for 30 seconds to a hardness of 2 h min at 0.4 mils dry film thickness.

Example 5

[0089] Into a suitably sized mixing vessel are added 444 pounds of Hi Sol 15 Aromatic 150 organic solvent, 175 pounds of Hydrolan Aluminium 501 aluminum pigment, 500 pounds of Durazane 1800 Polysilizane, and 15 pounds of 1,8-diazabicycloundecene catalyst, which is then mixed under medium speed agitation until a lump free, smooth, and homogeneous mixture is achieved; estimated curing time of the admixture is adjusted by titrating the admixture with the addition of aluminum acetylacetonate and adding and 2-tert-butylimino-2-diethylamino-1,3-dimethylperhydro-1,3,2-diazaphosphorine base. The resulting mixture should show analysis of not to exceed 6.5 hegman cure to 350 f pmt for 30 seconds to a hardness of 2 h min at 0.4 mils dry film thickness.

[0090] Ordinarily skilled inorganic and organic chemists and chemical engineers may modify the compositional embodiments within the specifications' teachings according to methods well known to those of ordinary skill in the arts, to provide numerous preferred alternative embodiments for a particular physico/chemical/material/structural set of desired performance parameters of coated sheet steel articles, without rendering such embodiments unstable or compromising their advantageous manufacturing characteristics.

[0091] While the above description contains a great deal of specificity, these should not be construed as limitations on the scope of any embodiment, but as exemplifications of the presented embodiments thereof. Many other alternative embodiments and variations are possible within the teachings of the various embodiments. While the invention has been described with reference to exemplary embodiments, it will be understood by those skilled in the art that various changes may be made, and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention will not be limited to the particular embodiments expressly disclosed as the best mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the appended claims. Moreover, unless the text specifically reads otherwise, the use of the terms first, second, and so forth do not denote any order or hierarchy of importance, but rather the terms first, second, and so forth are used to distinguish one disclosed element from another. Furthermore, the use of the terms a, an, etc. do not denote a limitation of quantity, but rather denote the presence of at least one of the referenced items.

[0092] While the invention has been described, exemplified, and illustrated in reference to certain preferred embodiments thereof, those skilled in the art will appreciate that various changes, modifications, and substitutions can be made therein without departing from the spirit and scope of the invention.

[0093] It is intended, therefore that the invention be limited only by the scope of the claims which follow, and that such claims be interpreted as broadly as is reasonable.