Coated Particles and Methods of Making and Using the Same

Abstract

Improved silica based matting agents are disclosed. The matting agents are useful in waterborne coatings composition to provide exceptional properties to a wood based substrate. Films resulting on the coated substrate unexpectedly provide improved chemical resistance, thermal stress resistance, weather resistance, and/or film clarity to the surface of a wood substrate. Methods of making and using the matting agents are also disclosed.

Claims

1. A matting agent comprising coated silica particles, said coated silica articles comprising: silica particles having a particle surface; and greater than 30.0 weight percent (wt %), based on a total weight of said silica particles, of (i) one or more waxes, (ii) one or more polymers, or (iii) any combination of (i) and (ii) coated on said particle surface.

2. The matting agent of claim 1, wherein said silica particles comprise 31.0 wt % to about 50.0 wt %, based on a total weight of said silica particles, of (i) said one or more waxes, (ii) said one or more polymers, or (iii) any combination of (i) and (ii) on said particle surface.

3. The matting agent of claim 1, wherein said silica particles comprise from about 40.0 wt % to about 50.0 wt %, based on a total weight of said silica particles, of (i) said one or more waxes, (ii) said one or more polymers, or (iii) any combination of (i) and (ii) on said particle surface.

4. The matting agent of claim 1, wherein said silica particles comprise silica gel, precipitated silica or fumed silica particles.

5. The matting agent of claim 1, wherein said silica particles have a total pore volume of from about 0.30 cc/gm to about 2.20 cc/gm, as determined by Barrett-Joyner-Halenda (BJH) method, and a BET particle surface area of at least about 100 m.sup.2/g up to 1500 m.sup.2/g, or greater.

6. The matting agent of claim 5, wherein said silica particles have a total pore volume of from about 1.8 cc/gm to about 2.0 cc/gm, as determined by BJH method, and a BET particle surface area of at least about 200 m.sup.2/g up to 900 m.sup.2/g.

7-8. (canceled)

9. The matting agent of claim 1, wherein said coated silica particles have an average particle size of from about 1.0 micron (m) to about 50 m.

10. (canceled)

11. The matting agent of claim 1, wherein said coated particles comprise said one or more waxes.

12. The matting agent of 11, wherein said one or more waxes comprise a hydrocarbon wax, a paraffin wax, a polyethylene wax, a polypropylene wax, a plant wax, an animal wax, or any combination thereof.

13. The matting agent of claim 12, wherein said one or more waxes comprise a polyethylene wax, a polypropylene wax, or a combination thereof.

14. (canceled)

15. The matting agent of claim 1, wherein said coated particles comprise one or more polymers.

16. The matting agent of claims 15, wherein said one or more polymers comprise polydiene, vulcanized polydiene, polyacrylamide, polyvinyl polypyrrolidone, cellulose acetate butyrate, or any combination thereof.

17-18. (canceled)

19. The matting agent of claim 1, wherein said coated particles are free-flowing particles.

20. The matting agent of claim 1, when incorporated into a coating composition and applied onto a substrate, enables the coating composition to (i) form a film having a film clarity L* of less than 7.0 units as measured using a portable Spectro-Guide 45/0 colorimeter, and (ii) exhibit a water damage 24 hr L* of less than 5.0 units as measured using a portable Spectro-Guide 45/0 colorimeter.

21. (canceled)

22. The matting agent of claim 20, when incorporated into a coating composition and applied onto a substrate, enables the coating composition to exhibit a 50/50 water/ethanol damage 1 hr L* of less than 8.0 units as measured using a portable Spectro-Guide 45/0 colorimeter.

23. The matting agent of claim 22, when incorporated into a coating composition and applied onto a substrate, enables the coating composition to exhibit a 50/50 water/ethanol damage 4 hr L* of less than 16.0 units as measured using a portable Spectro-Guide 45/0 colorimeter.

24. The matting agent of claim 1, when incorporated into a coating composition and applied onto a substrate, enables the coating composition to exhibit (i) a film clarity L* of less than 7.0 units, (ii) a water damage 24 hr L* of less than 4.0 units, (iii) a 50/50 water/ethanol damage 1 hr L* of less than 8.0 units, and (iv) a 50/50 water/ethanol damage 4 hr L* of less than 10.0 units, all measured using a portable Spectro-Guide 45/0 colorimeter.

25. A method of preparing the matting agent of claim 1, said method comprising: contacting the porous silica particles with (i) the one or more waxes, (ii) the one or more polymers, or (iii) any combination of (i) and (ii) so as to form coated silica paricles; heat treating the coated silica particles at an elevated temperature for a heat treatment period of time; allowing the heat-treated coated particles to cool; and milling the heat-treated coated particles so as to result in a final particle size of less than about 100 m.

26-32. (canceled)

33. The method of claim 25, wherein the coated silica particles are heat treated at elevated temperature ranges from about 90 C. to about 140 C., and the heat treatment period of time ranges from about 1.0 hour (hr) to about 4.0 hr.

34-36. (canceled)

37. A coating composition comprising the matting agent of claim 1.

38. The coating composition of claim 37, wherein said composition comprises an aqueous composition.

39. A substrate coated with the coating composition of claim 37, wherein said substrate comprises a wood substrate.

40. (canceled)

41. A method of improving chemical resistance, thermal stress resistance, weather resistance, film clarity, or any combination thereof, of a waterborne composition applied to a wood substrate, said method comprising: incorporating the matting agent of claim 1 into the coating composition; applying the coating composition onto at least one surface of a wood substrate to form a coating; and drying the coating to form a film on at least one surface of the wood substrate.

42-45. (canceled)

46. The method of claim 41, wherein the film exhibits (i) a film clarity L* of less than 7.0 units, (ii) a water damage 24 hr L* of less than 4.0 units, (iii) a 50/50 water/ethanol damage 1 hr L* of less than 8.0 units, and (iv) a 50/50 water/ethanol damage 4 hr L* of less than 10.0 units, all measured using a portable Spectro-Guide 45/0 colorimeter.

Description

DETAILED DESCRIPTION

[0023] To promote an understanding of the principles of the present invention, descriptions of specific embodiments of the invention follow and specific language is used to describe the specific embodiments. It will nevertheless be understood that no limitation of the scope of the invention is intended by the use of specific language. Alterations, further modifications, and such further applications of the principles of the present invention discussed are contemplated as would normally occur to one ordinarily skilled in the art to which the invention pertains.

[0024] It must be noted that as used herein and in the appended claims, the singular forms a, and, and the include plural referents unless the context clearly dictates otherwise. Thus, for example, reference to an oxide includes a plurality of such oxides and reference to oxide includes reference to one or more oxides and equivalents thereof known to those skilled in the art, and so forth.

[0025] About modifying, for example, the quantity of an ingredient in a coated particle and/or composition, concentrations, volumes, process temperatures, process times, recoveries or yields, flow rates, and like values, and ranges thereof, employed in describing the embodiments of the disclosure, refers to variation in the numerical quantity that may occur, for example, through typical measuring and handling procedures; through inadvertent error in these procedures; through differences in the ingredients used to carry out the methods; and like proximate considerations. The term about also encompasses amounts that differ due to aging of a formulation with a particular initial concentration or mixture, and amounts that differ due to mixing or processing a formulation with a particular initial concentration or mixture. Whether modified by the term about the claims appended hereto include equivalents.

[0026] The present invention is directed to improve silica based matting agents comprising silica particles having a particle surface; and greater than 30.0 weight percent (wt %), based on a total weight of the coated particles, of (i) one or more waxes, (ii) one or more polymers, or (iii) any combination of (i) and (ii) coated on the particle surface. Typically, (i) the one or more waxes, (ii) the one or more polymers, or (iii) any combination of (i) and (ii) is present on the particle surface in an amount up to about 40.0 wt %, based on a total weight of the coated particles, but the coated particles of the present invention may comprise any amount of (i) the one or more waxes, (ii) the one or more polymers, or (iii) any combination of (i) and (ii) up to about 50.0 wt % (or more), based on a total weight of the coated particles. In some exemplary embodiments, the coated particles comprise from greater than 30.0 wt % to about 50.0 wt % (or any value greater than 30.0 and 50.0 or less wt %, in increments of 0.1 wt %, for example, about 35.1 wt %, or any range of values between 30.0 and 50.0 wt %, in increments of 0.1 wt %, for example, from about 30.3 to about 37.8 wt %), based on a total weight of the coated particles, of (i) the one or more waxes, (ii) the one or more polymers, or (iii) any combination of (i) and (ii) on the particle surface. In some exemplary embodiments, the coated particles comprise from about 40.0 wt % to about 50.0 wt % (or any value between 40.0 and 50.0 wt %, in increments of 0.1 wt %, for example, about 40.1 wt %, or any range of values between 40.0 and 50.0 wt %, in increments of 0.1 wt %, for example, from about 40.3 to about 47.8 wt %), based on a total weight of the coated particles, of (i) the one or more waxes, (ii) the one or more polymers, or (iii) any combination of (i) and (ii) on the particle surface.

[0027] Suitable particulate silica useful to prepare the matting agents of the present invention includes, but is not limited to, silica gel, precipitated silica, fumed silica and colloidal silica. Suitable silica also includes, but is not limited to, ordered mesoporous silica prepared through an organic template (e.g., a surfactant) during the formation of silica particles, followed by a high temperature pyrolysis to burn off the organics. Particularly preferred silica particles comprise silica gel or precipitated silica particles.

[0028] Commercially available porous silica particles that are suitable for use in the present invention include, but are not limited to, porous inorganic particles available from W. R. Grace (Columbia, Md.) under the trade designation SYLOID such as SYLOID C807 silica gel particles and SYLOID MX106 precipitated silica particles.

[0029] In a preferred embodiment, the silica particles comprise silica having a purity of at least about 93.0% by weight SiO.sub.2, or at least about 93.5% by weight SiO.sub.2, at least about 94.0% by weight SiO.sub.2, at least about 95.0% by weight SiO.sub.2, at least about 96.0% by weight SiO.sub.2, at least about 97.0% by weight SiO.sub.2, or at least about 98.0% by weight SiO.sub.2 up to 100% by weight SiO.sub.2 based upon the total weight of the particle.

[0030] The silica particles may have a variety of different symmetrical, asymmetrical or irregular shapes, including chain, rod or lath shape. The particles may have different structures including amorphous or crystalline, etc. In a preferred embodiment, the silica particles are amorphous. The particles may include mixtures of particles comprising different compositions, sizes, shapes or physical structures, or that may be the same except for different surface treatments. Porosity of the particles may be intraparticle or interparticle in cases where smaller particles are agglomerated to form larger particles.

[0031] As used herein, the term crystalline means a solid material whose constituent atoms, molecules, or ions are arranged in an ordered pattern extending in all three directions, which may be measured by X-ray diffraction or differential scanning calorimetry. As used herein, the term amorphous means a solid material whose constituent atoms, molecules, or ions are arranged in a random, non-ordered pattern extending in all three directions, which may be determined by X-ray diffraction or differential scanning calorimetry.

[0032] As used herein, the term BET particle surface area is defined as meaning a particle surface area as measured by the Brunauer Emmet Teller (BET) nitrogen adsorption method.

[0033] As used herein, the phrase total pore volume refers to the average pore volume of a plurality of particles determined using the Barrett-Joyner-Halenda (BJH) nitrogen porosimetry as described in DIN 66134.

[0034] As used herein, the phrase particle size refers to median particle size (D50, which is a volume distribution with 50 volume percent of the particles are smaller than this number and 50 volume percent of the particles are bigger than this number in size) measured by dynamic light scattering when the particles are slurried in water or an organic solvent such as acetone or ethanol.

[0035] The porous silica particles used to form the matting agents of the present invention may have a total pore volume of at least 0.30 cc/g, from about 0.30 cc/gm to about 2.20 cc/gm (or any value greater than 0.40 cc/gm up to and including 2.20 cc/gm, in increments of 0.01 cc/gm, e.g., 0.62 cc/gm, or any range of values between greater than 0.40 cc/gm up to and including 2.20 cc/gm, in increments of 0.01 cc/gm, e.g., from about 1.50 cc/gm to about 2.20 cc/gm), as determined by BJH method. Typically, the porous silica particles used to form the matting agents of the present invention have a total pore volume of from about 1.8 cc/gm to about 2.00 cc/gm, as determined by BJH method.

[0036] The porous silica particles used to form the matting agents of the present invention may also have a BET particle surface area of at least about 100 m.sup.2/g up to 1500 m.sup.2/g (or any value greater than 100 m.sup.2/g up to and including 1500 m.sup.2/g, in increments of 1.0 m.sup.2/g, e.g., 453 m.sup.2/g, or any range of values between greater than 100 m.sup.2/g up to and including 1500 m.sup.2/g, in increments of 1.0 m.sup.2/g, e.g., from about 400 m.sup.2/g to about 444 m.sup.2/g), or greater. Typically, the porous silica particles have a BET particle surface area of at least about 100 m.sup.2/g up to 900 m.sup.2/g.

[0037] The uncoated silica particles of the present invention typically have an average particle size of from about 1.0 micron (m) to about 50 m (or any value between and including 1.0 m up to about 50 m, in increments of 0.1 m, e.g., 45.0 m, or any range of values between and including 1.0 m up to about 50 m, in increments of 0.1 m, e.g., from about 3.2 m to about 50.1 m). However, it should be understood that the coated particles of the present invention may have any average particle size depending on the use of the coated particles. In some embodiemnts, the coated particles of the present invention have an average particle size of from about 3.0 m to about 12.0 m. The matting agents of the present invention may comprise one or more waxes coated on the particle surface and within the pores of the porous silica particles. When present, the one or more waxes may comprise, but are not limited to, a hydrocarbon wax (i.e., a wax comprising relatively long alkyl chains, e.g., alkyl chains having 20 or more carbon atoms therein, with or without one or more various functional groups such as fatty acids, primary and secondary long chain alcohols, unsaturated bonds, aromatics, amides, ketones, and aldehydes), a paraffin wax (i.e., from 20-40 carbon atoms without additional functional groups), a polyethylene wax, a polypropylene wax, a plant wax such as a carnauba wax (i.e., Brazil wax), an animal wax such as bee wax, or any combination thereof.

[0038] Commercially available waxes that are suitable for use in the present invention include, but are not limited to, waxes available from Mitsui Chemicals, LLC (Osaka, Japan) under the trade designations Hi-WAX or EXCEREX waxes, waxes available from Honeywell Performance Additives (Morristown, N.J.) under the trade designations RHEOLUB waxes; and waxes available from TH.C.TROMM GmbH (Cologne, Germany) under the trade designations Polarwachs waxes.

[0039] In some embodiments, the matting agent comprise silica particles are coated with a polyethylene wax, a polypropylene wax, or a combination thereof. In some desired embodiments, the coating on the silica particles comprises a polyethylene wax having an average molecular weight of at least 2000. Such a relatively high molecular weight polyethylene wax is commercially available from TH.C.TROMM GmbH (Cologne, Germany) under the trade designations Polarwachs wax.

[0040] When present, the one or more waxes are typically present in an amount of greater than 30 wt %, based on a total weight of the matting agents. Preferably, the one or more waxes are present in an amount ranging from about 31.0 wt % to about 50.0 wt % (or any value between 31.0 and 50.0 wt %, in increments of 0.1 wt %, for example, about 35.1 wt %, or any range of values between 31.0 and 50.0 wt %, in increments of 0.1 wt %, for example, from about 31.3 to about 37.8 wt %), based on a total weight of the matting agents. In some embodiments, the one or more waxes are present in an amount ranging from about 40.0 wt % to about 50.0 wt % (or any value between 40.0 and 50.0 wt %, in increments of 0.1 wt %, for example, about 45.1 wt %, or any range of values between 40.0 and 50.0 wt %, in increments of 0.1 wt %, for example, from about 40.3 to about 47.8 wt %), based on a total weight of said matting agents.

[0041] In another embodiment of this invention, the matting agents of the present invention may comprise one or more polymers, alone or in combination with the above-described one or more waxes, on the particle surface and within the pores of the porous silica particles. When present, the one or more polymers may comprise, but are not limited to, one or more polymers comprising: a polydiene (e.g., polyisoprene, polybutadiene, or a combination thereof), a vulcanized polydiene, a polyacrylamide, a polyvinyl polypyrrolidone, a cellulose acetate butyrate, or any combination thereof. In some desired embodiments, the one or more polymers comprise a polydiene, a vulcanized polydiene, or any combination thereof.

[0042] Commercially available polymers that are suitable for use in the present invention include, but are not limited to, polymers available from Kuraray Co., LTD (Tokyo, Japan) under the trade designations KL-10 liquid rubber polymer (i.e., polyisoprene).

[0043] When present, the one or more polymers are typically present in an amount of greater than 30 wt %, based on a total weight of the matting agents. Preferably the amount of the one or more polymers ranges from about 31.0 wt % to about 50.0 wt % (or any value between 31.0 and 50.0 wt %, in increments of 0.1 wt %, for example, about 35.1 wt %, or any range of values between 31.0 and 50.0 wt %, in increments of 0.1 wt %, for example, from about 31.3 to about 37.8 wt %), based on a total weight of the coated particles. In some embodiments, the one or more polymers are present in an amount ranging from about 31.0 wt % to about 40.0 wt % (or any value between 31.0 and 40.0 wt %, in increments of 0.1 wt %, for example, about 31.0 wt %, or any range of values between 31.0 and 40.0 wt %, in increments of 0.1 wt %, for example, from about 31.3 to about 31.8 wt %), based on a total weight of the coated particles.

Method of Preparing

[0044] The matting agents of the present invention may be prepared by contacting the porous silica particles with (i) one or more waxes, (ii) one or more polymers, or (iii) any combination of (i) and (ii) so as to result in coated porous silica particles having a particle surface; and greater than 30.0 wt %, based on a total weight of the coated particles, of (i) the one or more waxes, (ii) the one or more polymers, or (iii) any combination of (i) and (ii) on the particle surface. Any conventional method may be used to contact the porous silica particles with (i) one or more waxes, (ii) one or more polymers, or (iii) any combination of (i) and (ii) so as to result in coated porous silica particles.

[0045] In some embodiments, the contacting step may be a wet process. The wet contacting process step may comprise dissolving (i) the one or more waxes, (ii) the one or more polymers, or (iii) any combination of (i) and (ii) in a solvent to form a solvent mixture; incorporating the porous silica particles into the solvent mixture; and removing or evaporating the solvent from the solvent mixture, to form coated silica particles.

[0046] The coated silica particles may thereafter be subjected to size reduction. Any known method of reducing the particle size may be used, and include, but are not limited to, a milling step such as ball mill or a mortar pestle grinding step. In one embodiment, the coated particles are subjected to a size reduction step, wherein the average particle size of the coated particles is reduced to a first average particle size of less than about 500 microns (m).

[0047] Once reduced in size, the coated silica particles are desirably heat treated at an elevated temperature for a heat treatment period of time. Typically, the elevated temperature is from about 90 C. to about 140 C. (or any value between 90 C. up to and including 140 C., in increments of 1.0 C., for example, about 100 C., or any range of values between 90 C. up to and including 140 C., in increments of 1.0 C., for example, from about 91.0 C. to about 102.0 C.). Typically, the heat treatment period of time ranges from about 1.0 hour (hr) to about 4.0 hr (or any value between 1.0 hr up to and including 4.0 hr, in increments of 1.0 minute, for example, about 1.0 hr and 9 minutes, or any range of values between 1.0 hr up to and including 4.0 hr, in increments of 1.0 minute, for example, from about 1.0 hr and 9 minutes to about 2.0 hr and 5 minutes).

[0048] In one exemplary embodiment in which one or more wax coatings are present, the elevated temperature of the heat treatment step ranges from about 100 C. to about 130 C., and the heat treatment period of time ranges from about 1.0 hr to about 1.5 hr. In another exemplary embodiment in which one or more polymers are present, the elevated temperature of the heat treatment step ranges from about 90 C. to about 100 C., and the heat treatment period of time ranges from about 2.5 hr to about 3.5 hr.

[0049] Following any heat treatment step, the heat-treated coated silica particles are allowed to cool. Once cooled, the heat-treated particles may optionally be further reduced in size so as to result in a fmal particle size of less than about 100 m (or any value less than about 100 m, in increments of 1.0 m, for example, about 45.0 m, or any range of values between about 1.0 m up to and including 100 m, in increments of 1.0 m, for example, from about 4.0 m to about 6.7 m). As discussed above, any known method of reducing particle size may be used. In one exemplary embodiment, a milling step may be utilized so as to result in coated particles having a final particle size of less than about 45.0 m.

[0050] In other exemplary embodiments, the contacting step may not involve any solvent and therefore be a dry process. In one embodiment, the dry process may comprise melting (i) the one or more waxes, (ii) the one or more polymers, or (iii) any combination of (i) and (ii) to form a liquid coating; and incorporating the porous silica particles into the liquid coating. In yet other embodiments, the dry process may comprise simultaneously contacting and mixing (a)(i) the one or more waxes, (ii) the one or more polymers, or (iii) any combination of (i) and (ii), and (b) the porous silica particles in a conventional mixer such as a ribbon blender, a Henschel mixer, a fluid energy mill (FEM) or a micronizing jet mill at high temperature (i.e., a temperature that melts any waxes and/or polymers if needed). In these embodiments, the heating and particle size reduction steps are combined and additional particle size reduction may or may not be necessary.

[0051] In some exemplary embodiments, the crosslinking of polymer coated silica particles are desirable for even better stability and properties. In another exemplary embodiment, the crosslinking comprises a vulcanization step. In methods that comprise a vulcanization step, elemental sulfur, a vulcanization promoter, or both, may be added to the one or more polymers during the contacting step. Suitable vulcanization promoters for use in the present invention include, but are not limited to, elemental sulfur, and butyl zimate.

Coating Compositions

[0052] The matting agents of present invention are useful to prepare coating compositions comprising aqueous suspensions or dispersions of the herein-described matting agents. In a preferred embodiment, the coating composition is a waterborne coating composition.

[0053] The coating compositions comprise the disclosed coated silica products in addition to various other ingredients used in coating compositions. Examples of other ingredients that can be present in the compositions include an aqueous binder resin, such as a self crosslinking modified acrylic copolymers emulsion or a LATEX acrylic binder Neocryl KX12, a coalescent solvent such as dipropylene glycol n-butyl ether (DOWANOL PDnB). The composition may or may not contain color pigments such as organic pigments. When the composition contains a color pigment, a dispersant may be included in the formulation. When the composition contains no color pigment, the composition is called clear coat. Clear coats are preferred in wood coating as natural color and grain structure of wood, such as, teak, cherry, oak, walnut, mahogany and rose wood, is highly prized in applications, such as, furniture and wood carvings.

[0054] The balance of the composition is typically water. Other diluents can also be included aside from water, such as aliphatics, aromatics, alcohols, ketones, white spirit, petroleum distillate, esters, glycol ethers, low-molecular weight synthetic resins, and the like. Environmentally friendly diluents, such as water, are preferred.

[0055] Other miscellaneous additives can also be included in the compositions, including without limitation, additives to modify surface tension, improve flow properties, improve finished appearance, increase wet edge, improve pigment stability, impart antifreeze properties, control foaming, control skinning, etc. Further additives that can be included in the compositions include without limitation catalysts, thickeners, stabilizers, emulsifiers, texturizers, adhesion promoters, UV stabilizers, de-glossing agents, biocides to fight bacterial growth, and the like. Oil can be included as a rheology agent, gloss modifier and protective agent that will reduce damage to the coating that would otherwise result from forming processes and from degrative elements in the service environment of the coated materials.

[0056] The coating compositions of the present invention typically comprise (I) from about 1.0 wt % up to about 99.0 wt % (or any value between 1.0 wt % up to and including 99.0 wt %, in increments of 0.1 wt %, for example, about 5.1 wt %, or any range of values between 1.0 wt % up to and including 99.0 wt %, in increments of 0.1 wt %, for example, from about 1.3 to about 4.8 wt %) of the matting agents, and (II) from about 99.0 wt % to about 1.0 wt % (or any value between 99.0 wt % to and including 1.0 wt %, in increments of 0.1 wt %, for example, about 95.1 wt %, or any range of values between 99.0 wt % to and including 1.0 wt %, in increments of 0.1 wt %, for example, from about 98.3 to about 94.8 wt %) of one or more additional components, both component (I) and (II) being based on a total weight of the coating composition.

Use

[0057] The present invention is even further directed to the use of the matting agents in various coating applications/processes. When used as a matting agent in coating compositions, the herein-described coated silica particles provide one or more improved properties such as improved chemical resistance, improved thermal stress resistance, improved weather resistance, improved film clarity, or any combination thereof in the final coating.

[0058] In a preferred embodiment, the matting agents of the invention are useful in methods of improving chemical resistance, thermal stress resistance, weather resistance, and/or film clarity of a coating composition applied to a substrate. In a particularly preferred embodiment, the substrate is a wood subtrate. In one desired embodiment, a wood substrate is treated with an aqueous coating composition thereof, wherein the coating composition comprises the matting agents of the invention on a surface of the wood substrate. Other substrates which may be coated with coating compositions in accordance with the present invention include, but are not limited to, leather, plastics (e.g.,vinyl), metal (e.g., coil) or metal alloys, cement or concrete or other industrial finishes.

[0059] Generally, the method of utilizing a matting agent in a coating composition in accordance with the invention comprises incorporating the inventive matting agents into the coating composition, preferably an aqueous coating composition, prior to applying the coating composition onto the substrate. The typical incorporation step includes mixing or dispersing the matting agents into the formulation. The method of applying the coating composition to a substrate includes brushing, rolling, air spraying, or drawdowning or other possible methods. As discussed further in the examples below, incorporation of the matting agent of the current invention into a coating composition (e.g., a wood substrate coating composition) and subsequent application of the coating composition, provide the coated films with improved chemical resistance, improved thermal stress resistance, improved weather resistance, and/or improved film clarity, when compared to known coatings/films that do not contain the matting agents of the present invention. For example, in some embodiments, a coating composition comprising the matting agents results in a clear coated film on a substrate, and the film exhibits a film clarity L* of less than 7.0 units (or any value less than 7.0 units, in increments of 0.1 units, for example, 2.4 units, or any range of values less than 7.0 units, in increments of 0.1 units, for example, from about 1.2 units to about 2.4 units) as measured using a portable Spectro-Guide 45/0 colorimeter and the method described in the examples below.

[0060] In some embodiments, a coating composition comprising the matting agents of the invention results in a coated film on a substrate, and the film exhibits a water damage 24 hr L* of less than 5.0 units (or any value less than 5.0 units, in increments of 0.1 units, for example, 2.4 units, or any range of values less than 5.0 units, in increments of 0.1 units, for example, from about 1.2 units to about 2.4 units) as measured using a portable Spectro-Guide 45/0 colorimeter and the method described in the examples below.

[0061] In some embodiments, a coating composition comprising the inventive matting agents results in a coated film on a substrate, and the film exhibits a 50/50 water/ethanol damage 1 hr L* of less than 8.0 units (or any value less than 5.0 units, in increments of 0.1 units, for example, 2.4 units, or any range of values less than 5.0 units, in increments of 0.1 units, for example, from about 1.2 units to about 2.4 units) as measured using a portable Spectro-Guide 45/0 colorimeter and the method described in the examples below.

[0062] In some embodiments, a coating composition comprising the herein-described coated particles results in a coated film on a substrate, and the film exhibits a 50/50 water/ethanol damage 4 hr L* of less than 16.0 units (or any value less than 16.0 units, in increments of 0.1 units, for example, 12.4 units, or any range of values less than 16.0 units, in increments of 0.1 units, for example, from about 10.2 units to about 12.4 units) as measured using a portable Spectro-Guide 45/0 colorimeter and the method described in the examples below.

[0063] In some desired embodiments, a coating composition comprising the herein-described coated particles results in a coated film on a substrate, and the film exhibits (i) a film clarity L* of less than 7.0 units (or any value less than 7.0 units, in increments of 0.1 units, for example, 2.4 units, or any range of values less than 7.0 units, in increments of 0.1 units, for example, from about 1.2 units to about 2.4 units), (ii) exhibits a water damage 24 hr AL* of less than 4.0 units (or any value less than 4.0 units, in increments of 0.1 units, for example, 2.4 units, or any range of values less than 4.0 units, in increments of 0.1 units, for example, from about 1.2 units to about 2.4 units), (iii) a 50/50 water/ethanol damage 1 hr L* of less than 8.0 units (or any value less than 5.0 units, in increments of 0.1 units, for example, 2.4 units, or any range of values less than 5.0 units, in increments of 0.1 units, for example, from about 1.2 units to about 2.4 units), and (iv) a 50/50 water/ethanol damage 4 hr L* of less than 10.0 units (or any value less than 10.0 units, in increments of 0.1 units, for example, 8.4 units, or any range of values less than 10.0 units, in increments of 0.1 units, for example, from about 7.2 units to about 7.4 units), all measured using a portable Spectro-Guide 45/0 colorimeter and the method described in the examples below.

[0064] While not wishing to be bound by any particular theory, it is hypothesized that the improved properties of chemical/thermal stress resistance exhibited by the improved matting agents, and resulting films, may be due to one or more of the following factors: 1) reduction of particle shrinkage during drying; 2) improved adhesion between matting particle and the latex; 3) ability for wax/organic coating to better flow and fill in cracks as they form; 4) reduced stress on the latex-particle interface due to the softening of the latex in the region surrounding the particle, and 5) diffusion of the latex into the pores of the film, thereby reducing penetration of water and ethanol into the film.

[0065] It should be understood that although the above-described coated particles, methods and uses are described as comprising one or more components or steps, the above-described coated particles, methods and uses may comprise, consists of, or consist essentially of any of the above-described components or steps of the coated particles, methods and uses. Consequently, where the present invention, or a portion thereof, has been described with an open-ended term such as comprising, it should be readily understood that (unless otherwise stated) the description of the present invention, or the portion thereof, should also be interpreted to describe the present invention, or a portion thereof, using the terms consisting essentially of or consisting of or variations thereof as discussed below.

[0066] As used herein, the terms comprises, comprising, includes, including, has, having, contains, containing, characterized by or any other variation thereof, are intended to encompass a non-exclusive inclusion, subject to any limitation explicitly indicated otherwise, of the recited components. For example, a coated particle, method and/or use that comprises a list of elements (e.g., components or steps) is not necessarily limited to only those elements (or components or steps), but may include other elements (or components or steps) not expressly listed or inherent to the particle, method and/or use.

[0067] As used herein, the transitional phrases consists of and consisting of exclude any element, step, or component not specified. For example, consists of or consisting of used in a claim would limit the claim to the components, materials or steps specifically recited in the claim except for impurities ordinarily associated therewith (i.e., impurities within a given component). When the phrase consists of or consisting of appears in a clause of the body of a claim, rather than immediately following the preamble, the phrase consists of or consisting of limits only the elements (or components or steps) set forth in that clause; other elements (or components) are not excluded from the claim as a whole.

[0068] As used herein, the transitional phrases consists essentially of and consisting essentially of are used to define coated particles, methods and/or uses that include materials, steps, features, components, or elements, in addition to those literally disclosed, provided that these additional materials, steps, features, components, or elements do not materially affect the basic and novel characteristic(s) of the claimed invention. The term consisting essentially of occupies a middle ground between comprising and consisting of.

[0069] The present invention is further illustrated by the following examples, which are not to be construed in any way as imposing limitations upon the scope thereof. On the contrary, it is to be clearly understood that resort may be had to various other embodiments, modifications, and equivalents thereof which, after reading the description herein, may suggest themselves to those skilled in the art without departing from the spirit of the present invention and/or the scope of the appended claims.

EXAMPLES

[0070] The following examples describe (i) processes in accordance with the present invention for preparing coated particles, and (ii) the evaluation of the coated particles in coating compositions.

Example 1

Formation of Silica Particles Coated with Wax (Wet Method)

[0071] 2.5-10 grams of wax were dissolved in 60-100 ml of toluene with heating. 10 g of SYLOID C807 silica particles were mixed with the wax solution. The mixture was left in a crystallizing dish in a well ventilated fume hood overnight to allow all of the solvent to evaporate. The dried residue was subjected to mortar pestle to allow all the particles to pass a 500 m screen. The screened particles were then subsequently heated at 130 C. for 1 hour. After drying, the particles were cooled down and the particle size was further reduced with an analytical mill to enable the particles to pass a 45 m screen. The screened particles were suitable for use, as is, directly in, for example, a paint formulation.

Example 2

Formation of Silica Particles Coated with Polyisoprene Utilizing a Vulcanization Step (Wet Method)

[0072] 4.3 grams of polyisoprene (10 kD MW, mostly trans-, KL-10, commercially available from Kuraray) were dissolved in 60 ml of toluene. 0.24 g of elemental sulfur and 0.12 g of butyl zimate (commercially available from Vanderbilt Chemicals, LLC) were added to the solution and mixed well. 10 g of SYLOID C807 silica particles were mixed with the solution. The mixture was left in a crystallizing dish in a well ventilated fume hood overnight to allow all of the solvent to evaporate. The dried residue was then subjected to mortar pestle to allow all the particles to pass a 500 m screen. The screened particles were subsequently heated at 95 C. for 3 hours. After that, the particles were cooled down and the particle size was further reduced with an analytical mill to enable most of the particles to pass a 45 m screen. The screened particles were suitable for use, as is, directly in, for example, a paint formulation.

Example 3

Formation of Silica Particles Coated with Polyisoprene Without Utilizing a Vulcanization Step (Wet Method)

[0073] 7.0 grams of polyisoprene (10 kD MW, mostly trans-, KL-10, commercially available from Kuraray) were dissolved in 60 ml of toluene. 10 g of SYLOID C807 silica particles was mixed with the solution. The mixture was left in a crystallizing dish in a well ventilated fume hood overnight to allow all of the solvent to evaporate. The dried residue was then subjected to mortar pestle to allow all of the particles to pass a 500 m screen. The screened particles were subsequently heated at 70 C. for 3 hours. After that, the particles were cooled down and the particle size was further reduced with an analytical mill to enable most of the particles to pass a 45 m screen. The screened particles were suitable for use, as is, directly in, for example, a paint formulation.

Example 4

Formation of Silica Particles Coated with Wax with Melting and Mixing (Dry Method)

[0074] 4 kg of SYLOID C807 silica particles were mixed with 4 kg of POLARWACHS N481 polyethylene wax under nitrogen in a 10L Henscher Mixer. The mixer was heated to 120 C. for 2 hours. The mixture was mixed with 3000 rpm for 2 hours. The sample was then cooled down to room temperature.

Example 5

Formation of Silica Particles Coated with Wax with Melting and Milling (Dry Method)

[0075] 4 kg of silica gel (30 m particle size, 2 cc/g pore volume) particles were mixed with 4 kg of POLARWACHS N481 polyethylene wax under nitrogen in a 10 L Henscher Mixer. The mixer was heated to 120 C. for 2 hours. The mixture was mixed with 3000 rpm for 2 hours. The sample was then cooled down to room temperature, and the composite was subjected to a fluid energy mill under nitrogen to bring the particle size down to 9 um (median particle size).

Example 6

Formation of a Stock Solution for Testing of Coating Compositions

[0076] The components listed in Table 1 below were combined as described below to form a stock solution for testing coating compositions as discussed below.

TABLE-US-00001 TABLE 1 Stock Solution For Testing of Coating Compositions Weight Raw Material Supplier (g) Comments NEOCRYL KX12 DSM 77.43 Acrylic Emulsion Deionized Water 11.07 DOWANOL PDnB Dow Chemical 8.85 Coalescent BYK 024 BYK 0.55 Defoamer SURFYNOL 104E Air Products 1.11 Wetting and Defoamer RHEOLATE 299 Elementis 0.22 Rheolate BYK 346 BYK 0.77

[0077] 77.43 grams (g) of NEOCRYL KX12 and 5.53 g of deionized water were mixed in a first container. 8.85 g of DOWANOL PDnB and 5.54 g of deionized water were mixed in a second container. Then, the contents of the second container were slowly poured into the first container. The mixture was dispersed at 1500 rpm for 15 minutes using a DISPERMAT disperser from Gardner Company (Pompano Beach, Fla.) with a 30 mm wide blade.

[0078] 0.55 g of BYK 024, 1.11 g of SURFYNOL 104E and 0.22 g of RHEOLATE 299 were added to the mixture in the first container. The mixture was then dispersed at 2500 rpm for 10 minutes using the DISPERMAT disperser.

[0079] 0.77 g of BYK 346 was added to the mixture in the first container. The mixture was then dispersed at 1000 rpm for 5 minutes using the DISPERMAT disperser. The resulting mixture then was used as a stock solution, capable of being stored for up to 1 month.

Example 7

Formation of Coating Compositions Comprising a Matting Agent and the Stock Solution

[0080] Coating compositions comprising a matting agent and the stock solution of Example 6 were prepared as follows. After a given amount of matting agent was added into a given amount of stock solution formed in Example 3 above, the resulting mixture was dispersed at 2500 rpm for 30 min using the DISPERMAT disperser, and then allowed to sit overnight at room temperature.

[0081] Drawdowns for testing each coating composition were carried out the second day (i.e., the day after making a given coating composition) using the drawdown procedure described below.

[0082] Drawdown Procedure and Drawdown Cards

[0083] Drawdowns were carried out with a wire wound lab rod from Gardner Company with wire size of 40. With this size, the wet film thickness was about 100 m. The draw down plates used were 219286 mm.sup.2 plain black charts from Leneta Company, Inc. (Mahwah, N.J.). The procedure for each drawdown was as follows: [0084] 1. In a dust free clean room, a blank drawdown plate was placed on a vacuum holder. [0085] 2. Using a pipette, about 2-5 ml of a well-mixed coating composition sample was positioned on and near the top of a sample sheet. [0086] 3. The ends of the drawdown rod were immediately grasped. Using the thumbs of both hands to keep the rod from bowing or bending away from the sample, the drawdown rod was drawn down through the liquid pool, spreading and metering the fluid across the sample sheet. After a given drawdown was made, the drawdown rod was immersed in a cleaning tray after use. [0087] 4. After the drawdown, the drawdown samples were left at room temperature for at least four days to allow complete drying of the coated layer. [0088] 5. After the coated drawdown plate was dry, chemical resistance, film clarity, matting efficiency and cold check tests were carried out using the procedures below.

[0089] Gloss (Matting Efficiency), Film Clarity and Chemical Resistance Measurement and Test Methods:

[0090] A portable Micro-TRI-Gloss meter (from BYK-Gardner USA, Columbia, Md.) was used for film gloss reading. 60 gloss values were measured and reported.

[0091] For film clarity and chemical damage check, a portable Spectro-Guide 45/0 colorimeter (also from BYK-Gardner) was used. The L* values were obtained by readings of the colorimeter on a given coated film. On the card with black background, unmatted stock solution (from Example 6) gave an L* value of around 7.9. The addition of a matting agent (e.g., silica) in the stock solution made the film whiter (i.e., resulting in a higher L* value) and the film clarity matted film was defined as the difference between the new L* value and the L* value from the film formed out of the stock solution containing no matting agent.

[0092] Chemical Resistance test methods used were similar to European standard specifications EN 12720/DIM 68861-1. Resistances towards deionized water and 50/50 ethanol in water were tested. The test were carried out as follows [0093] 1. Circles (1 inch in diameter) were cut out of a Fisherbrand filter paper. [0094] 2. Circles were soaked in either water or 50/50 ethanol/water for 30 seconds. [0095] 3. Each soaked circle was placed onto a dried drawdown card, and then covered with a weighing boat to prevent evaporation. [0096] 4. After a certain amount of time (i.e., 24 hours for water test, and 1 hour and 4 hours for the 50/50 ethanol in water), the weighing boat and paper were removed. [0097] 5. A white mark in the contact area developed over time, and after overnight, the L* values were measured using the Spectro-Guide 45/0 colorimeter. [0098] 6. The chemical damage (inversely proportional to the chemical resistance) was defined as the difference between the L* value of the white mark (i.e., the largest reading out of at least three readings) and the background of the film. The percentage of change was also calculated.

[0099] Cold Check Test

[0100] This test was designed to simulate weather change and relative humidity change, which affects water resistance of and water penetration into a given coating. The test was carried out by allowing a dried drawdown card to go through the following environment for 5 cycles: a relative humidity=95% for a first phase at 20 C. for 1 hour, and a second phase at 50 C. for 1 hour, then repeated for a total of 5 cycles. After these cycles, the L* values were measured using the Spectro-Guide 45/0 colorimeter and were compared against the values before these cycles.

Example 8

Formation of Coated Particles of the Invention

[0101] Sample coated particles were prepared using the materials shown in Table 2 below. The first nine samples was prepared using the procedures outlined in Example 1 above. Sample 10 was prepared using the procedures outlined in Example 4, and Sample 11 was prepared using the procedures outlined in Example 5.

TABLE-US-00002 TABLE 2 oated Particle Sample Formulations Wax/Silica Coated Amounts Particle Starting (in grams) Sample Silica Silica Particle (% Total Number Particles Source Wax Wax Source Organic) 1 SYLOID W. R. Grace POLARWACHS TH. C. TROMM 2.5/10 C807 silica (Columbia, MD) N481 polyethylene GmbH (20%) gel wax 2 SYLOID W. R. Grace POLARWACHS TH. C. TROMM 4.3/10 C807 silica (Columbia, MD) N481 polyethylene GmbH (30%) gel wax 3 SYLOID W. R. Grace POLARWACHS TH. C. TROMM 7.0/10 C807 silica (Columbia, MD) N481 polyethylene GmbH (40%) gel wax 4 SYLOID W. R. Grace POLARWACHS TH. C. TROMM 10.0/10 C807 silica (Columbia, MD) N481 polyethylene GmbH ((50%) gel wax 5 SYLOID W. R. Grace POLARWACHS TH. C. TROMM 7.0/10 MX106 (Columbia, MD) N481 polyethylene GmbH (40%) precipitated wax silica 6 SYLOID W. R. Grace POLARWACHS TH. C. TROMM 7.0/10 MX106 (Columbia, MD) N481 polyethylene GmbH (40%) precipitated wax 7 silica W. R. Grace Carnauba wax Aldrich 7.0/10 (Columbia, MD) (40%) 8 SYLOID W. R. Grace NP 506 Mitsui 7.0/10 MX106 (Columbia, MD) polypropylene wax (San Jose, CA) (40%) precipitated 9 ACEMATT Evonik POLARWACHS TH. C. TROMM 7.0/10 TS100 fumed (Essen, N481 polyethylene GmbH (40%) silica Germany) wax (Cologne, Germany) 10 SYLOID W. R. Grace POLARWACHS TH. C. TROMM 5 kg/5 kg C807 silica (Columbia, MD) N481 polyethylene GmbH (50%) gel wax 11 Large particle W. R. Grace POLARWACHS TH. C. TROMM 5 kg/5 kg size silica gel (Columbia, MD) N481 polyethylene GmbH (50%) wax

Example 9

Comparative Particles

[0102] Comparative particles shown in Table 3 below were used as received without further modification.

TABLE-US-00003 TABLE 3 Comparative Sample Particles Comparative Particle Sample Number Comparative Matting Agent Comp 1 SYLOID C807 silica gel Comp 2 SYLOID MX106 precipitated silica Comp 3 ACEMATT TS100 fumed silica Comp 4 Fumed silica + organic (TS100 + CERAFLOUR 920) Comp 5 Fumed silica + wax (TS100 + CERAFLOUR 929)

[0103] In Table 3, in Comparative Example 4, the organic used was CERAFLOUR 920, which is a urea-formaldehyde based organic matting agent, and the wax used in Comparative Example 5 was CERAFLOUR 929, which is a micronized polyethylene wax based organic matting agent. Both of these were commercially available from BYK-Chemie GmbH (Wesen, Germany). In both Comparative Examples 4 and 5, mixtures of the pure silica and organic matting agents (physical blends of the two types of matting agents) were used in the paint formulations.

Example 10

Formation of Specific Coating Compositions

[0104] Matting agent-containing coating compositions were prepared using the coated particles of the present invention of Example 8 and the comparative sample particles of Example 9. Each matting agent-containing coating composition was prepared using the procedure described in Example 7 above. After formation, each matting agent-containing coating composition was drawdown using the draw-down procedure described hereinabove. After drying, each of the resulting films was evaluated for gloss, film clarity and chemical resistance according to the methods described above. Table 4 below summarizes the results.

TABLE-US-00004 TABLE 4 Test Results For Coatings Containing Coated Particle Samples and Comparative Particle Samples Water 50/50 50/50 Damage Damage Damage % 24 hr 1 hr 4 hr Coating Matting Film (L*) (L*) (L*) Sample agent in 60 Clarity (% (% (% Number Coating Gloss (L*) Change) Change) Change) 1 3.75 12.1 6.46 6.8 14.4 15.2 (47%) (100%) (106%) 2 4.30 11.6 6.35 4.7 10.9 11.2 (33%) (76%) (78%) 3 5.00 12.9 6.00 3.1 6.8 8.4 (22%) (49%) (61%) 4 6.00 14.1 5.97 1.1 0.2 3.7 (8%) (1%) (27%) 5 5.00 13.1 6.50 2.6 11.4 11.6 (18%) (79%) (80%) 6 5.00 14.0 6.22 1.6 n/a 9.0 (11%) (63%) 7 5.00 17.8 4.41 1.2 11.0 9.8 (10%) (89%) (79%) 8 5.00 13.6 6.21 1.1 9.4 11.6 (7%) (66%) (8%) 9 5.00 12.3 5.55 5.0 1.9 6.5 (37%) (14%) (49%) 10 6.00 14.1 5.3 0.8 2.1 4.7 (6%) (16%) (35%) 11 6.00 12.6 4.7 0.7 1.4 4.2 (6%) (11%) (34%) Comp 1 3.00 12.7 7.59 10.7 19.2 20.0 (69%) (124%) (129%) Comp 2 3.00 8.4 7.69 7.2 n/a 18.2 (46%) (117%) Comp 3 3.00 13.6 5.65 17.2 12.8 24.2 (127%) (94%) (179%) Comp 4 4.00 10.7 7.16 16.6 10.1 19.5 (2 + 2) (110%) (67%) (129%) Comp 5 5.00 10.0 6.95 11.8 9.4 18.4 (2.5 + 2.5) (79%) (64%) (124%)

[0105] As shown in Table 4 above, all wax coated matting agents of the present invention exhibited improved chemical resistance when compared to that obtained from the comparative samples. In samples 1-4 and comparative sample 1, as the wax level increased, the chemical resistance increased as represented by lower L* values.

[0106] Also, when compared to Sample 9 and Comparative Samples 4, 5, wax coating resulted in much better chemical resistance than simple physical blending of the silica with organic based matting agents.

[0107] Table 5 below shows the improvement of the Cold Check properties of coatings formed using the coated particles of the present invention using the Cold Check test method described hereinabove.

TABLE-US-00005 TABLE 5 Cold Check Test Results Coating Loading Change in L* Values Sample Number (g + 100 g Stock) Initial After 5 Cycles % Change 6 5.00 15.5 15.5 0% Comp 2 3.00 15.6 21.9 41%

[0108] As shown, with a wax coating, significant reduction (0% change vs. 41% change) of whiteness was obtained.

Example 11

Formation of Additional Specific Coating Compositions

[0109] Two additional matting agent-containing coating compositions were prepared using (i) polyisoprene coated silica (4.3 g of polyisopyrene and 10 g of SYLOID C807 silica gel particles with vulcanization) formed using the procedure described in Example 2 above, (ii) polyisoprene coated silica (7.0 g of polyisopyrene and 10 g of SYLOID C807 silica gel particles without vulcanization) formed using the procedure described in Example 3 above, and (iii) Comparative particles designated Comp 1 above. Each matting agent-containing coating composition was prepared using the procedure described in Example 7 above. After formation, each matting agent-containing coating composition was drawdown using the draw-down procedure described hereinabove. After drying, each of the resulting films was evaluated for gloss, film clarity and chemical resistance according to the methods described above. Table 6 below summarizes the results.

TABLE-US-00006 TABLE 6 Test Results For Coating Samples 12-13 and Comparative Coating Sample 1 Water 50/50 50/50 Coating Loading Film Damage Damage Damage Sample Particle Sample (g + 100 g 60 Clarity 24 hr (L*) 1 hr (L*) 4 hr (L*) Number Information Stock) Gloss (L*) (% Change) (% Change) (% Change) 12 30% Organic, 4.00 14.4 6.37 3.2 7.8 9.5 with (22%) (55%) (67%) Vulcanization 13 40% Organic, 6.00 12.5 7.24 3.2 1.8 6.2 without (21%) (12%) (41%) Vulcanization Comp 1 Unmodified 3.00 12.7 7.59 10.7 19.2 20.0 Silica (69%) (124%) (129%)

[0110] As shown in Table 6 above, polyisoprene coated silica particles (with or without vulcanization) also provided significant chemical resistance improvement compared to unmodified silica particles.

[0111] While the invention has been described with a limited number of embodiments, these specific embodiments are not intended to limit the scope of the invention as otherwise described and claimed herein. It may be evident to those of ordinary skill in the art upon review of the exemplary embodiments herein that further modifications, equivalents, and variations are possible. All parts and percentages in the examples, as well as in the remainder of the specification, are by weight unless otherwise specified. Further, any range of numbers recited in the specification or claims, such as that representing a particular set of properties, units of measure, conditions, physical states or percentages, is intended to literally incorporate expressly herein by reference or otherwise, any number falling within such range, including any subset of numbers within any range so recited. For example, whenever a numerical range with a lower limit, R.sub.L, and an upper limit R.sub.U, is disclosed, any number R falling within the range is specifically disclosed. In particular, the following numbers R within the range are specifically disclosed: R=R.sub.L+k(R.sub.UR.sub.L), where k is a variable ranging from 1% to 100% with a 1% increment, e.g., k is 1%, 2%, 3%, 4%, 5% . . . 50%, 51%, 52% . . . 95%, 96%, 97%, 98%, 99%, or 100%. Moreover, any numerical range represented by any two values of R, as calculated above is also specifically disclosed. Any modifications of the invention, in addition to those shown and described herein, will become apparent to those skilled in the art from the foregoing description and accompanying drawings. Such modifications are intended to fall within the scope of the appended claims. All publications cited herein are incorporated by reference in their entirety.