Patent Application
20210380818
The invention relates to additives for coating compositions and, more specifically to a holistic binder systems that may serve as additive platforms for liquid and/or powder coating compositions.
Powder coating compositions are dry, free-flowing powders. In use, these powders are applied to a substrate (e.g., electrostatic spraying, fluidized bed coating, and/or hot flocking), which is then heated. This added energy causes the powder to melt, flow, and fuse into a continuous film. Advantageously, this procedure results in a robust film with good adhesion, while effectively eliminating the need to rely upon solvents (and particularly volatile organic compounds).
Generally speaking, powder compositions are primarily composed of polyurethanes, polyester, polyethylene, and epoxy, as well as various combinations thereof (e.g., epoxy-polyester, urethane-polyester, hydroxyl polyester, TGIC-polyester, TGIC-free polyester, acrylic, etc.), as base resin(s). Polyisocyanates, tryiglycidylisocyanurate (TGIC) and TGIC-free curatives may be included, and other additives, such as flow control agents, hardeners, catalysts, fillers, gloss control agents, pigments, and charge inhibitors may also be incorporated to enhance the characteristics of the blend as it is mixed, applied, and/or fused. In operation, the resins melt and fuse together, while the additives facilitate various underlying attributes during or after fusion, all with the goal of creating a chemically non-reactive, durable, and continuous coating wherever the composition is applied to the substrate. In some instances, the formulation may be created to allow the composition to be used as a solid, dry powder or, by suspending or otherwise mixing that powder certain types of liquid carriers, in a liquid form.
Conventional formulations often rely on additives to impart a specific function to the coating composition, such as wetting, flow characteristics (e.g., viscosity, etc.), surface hardness, or other traits. In these prior art compositions, a separate coating additive was required to impart just one of these functions, with the additive usually becoming effective upon curing within the composition during application. Prior to the invention disclosed below, multi-functional additives (i.e., one additive that was able to deliver several different characteristics/functions) were not believed to be feasible.
Because the base resins create the bulk of final chemical coatings (whether powder or liquid), it is generally thought to be desirable to maximize the amount of resin. In contrast, and especially to the extent that additives typically cost more and/or present unique formulation challenges in comparison to the base resins, additives tend to be used in their purest possible form but at the lowest possible levels while still delivering the desired attributes.
There are many problems that can arise during fusion or curing of a coating, including formation of surface defects or cracking, increased surface tension, increased taber abrasion, loss of color/gloss, impact fading, delayed curing, etc. As an example, one problem during fusion or curing of a coating is the formation of surface defects upon curing whereby surface tension creates irregularities which affect the flow of the fusing materials and results in “orange peel” (i.e., non-smooth appearance or finish after the composition solidifies). Another problem is the inability of a cured/fused coating to withstand mechanical actions such as rubbing, scraping and erosion can create irregularities and reduce the overall lifespan and utility of that coating. A still further problem relates to increased surface cracking due to lack of flexibility, causing the additive to fail both the ⅛th inch conical bend test and the OT bend test according to ASTM D4338-97.
The use of certain additives has been employed to address each of these problems. Examples of functional additives include flow control additives, such as homopolymers and copolymers of polyacrylates (e.g., esters of methacrylic and acrylic acids). Such additives can be provided in master batch dispersed on silica particles at an active level of up to 65 wt. % in the additive (or about 1.0 wt. % of the total composition), although additional leveling aids may be required (e.g., Resiflow P-67,Resiflow P-1200,Resiflow P-65Oxymelt A-2 (from Estron Chemical), Modaflow 2000 (from Allnex), and X-22 (Monsanto)).
A particular example of a flow control additive is U.S. Pat. No. 9,353,254, which is incorporated by reference and describes a powder coating flow aid relying on a polyethylene resin combined with a polyester hydroxyl resin. A polymeric curative, degassing agent, ricinoleic acid (i.e., 12-hydroxy-9-cis-octadecenoic acid), and glass flake are also used, and the flow aid is introduced to powder coating compositions by way of a silica carrier. The polyethylene is provided at between 3.1 to 9.5 wt. %, the polyester hydroxyl at 35 to 50 wt. %, the polymeric curative at 5.0 to 10.0 wt. %, the degassing agent at 0.25 to 2.0 wt. %, the ricinoleic acid at 0.5 to 3.0 wt. %, glass flakes at 20 to 50 wt. %, and the silica carrier being 0.5 to 5.0 wt. % of the flow aid's total weight.
U.S. Pat. Nos. 7,494,636; 7,695,705; and 10,125,046 provide examples of conventional specialized silica-based materials that are specifically engineered for use as additives in coating compositions and/or polymers. Generally speaking, in contrast to the additives created using the inventive method described herein, these additives serve as simple fillers that only influence flow and rheological characteristics. Although some are characterized as “multifunctional” because surface modification of the silica by certain agents (e.g., silane coupling agents) imparts hydrophobicity or other desired qualities, they are not multifunctional in the sense that they do not address multiple deficiencies in a coating composition
Examples of additives that address a lack of durability and corrosion resistance include ultraviolet light absorbers, hindered-amine light stabilizers, inorganic fillers, and the like. More generally, these traits are thought to also be improved by having an overall thicker and/or more heavily cross-linked resin-based coating. Thus, these additives tend to promote more robust final coatings.
U.S. Pat. Nos. 6,835,458 and 6,987,144 provide examples of additives used in combination with various types of siloxanes. These additives are described as useful for such functions as mar and scratch resistance in coating compositions, but are not multifunctional.
Appearance additives, such as benzoin or Oxymelt A-4 (Estron Chemical), are believed to facilitate the escape of volatile components during curing. Such additives might also act as dispersants for the pigments, with a resulting improvement in the appearance (e.g., gloss, smoothness, etc.). An example of a dispersing appearance additive is Surfynol P-200 (Air Products).
U.S. Pat. No. 9,139,737 and European Patent 2821446B1 are merely conventional additives that address gloss and appearance issues by relying on nano- or micro-sized particles of silica-based compounds.
In contrast to the inventive method of preparing a multifunctional additive which is then provided to a silica carrier, U.S. Pat. No. 7,105,201 contemplates the fast heating of coating components (usually, base resins) prior to blending the composition in order to make heterogeneous “composite particles.” These composite particles require distinct glass transition temperatures, so as to allow the use of separate, individual resins that might not otherwise be easily co-processed. Small amounts (<0.2 wt. %) of nano-sized (˜20 nm) inorganic particles can be mixed with these composites in the event additional, “conventional” additives are to be introduced to the composition. As such, these composite particles are not additives within the conventional sense.
While U.S. Pat. No. 9,045,669 suggests the use of inorganic carriers in combination with a solid particle, dialkylethers to create an additive, the disclosed composition is indicated for use primarily with paints and lacquers (i.e., compositions relying upon organic or aqueous solvents). Further, only dialkylether is provided, with the possible amount relating to the surface area of the carrier, so that higher surface area carriers allow for higher loading by way of coating that surface with dialkylether.
Generalized examples of still other powder coatings and/or additives can be found in U.S. Pat. Nos. 4,007,299; 5,229,470; 5,721,052; 5,786,308; 5,997,944; 6,121,408; 6,825,258; 6,905,778; and 9,296,917. These disclosures are all incorporated by reference herein.
Still other non-additive based approaches for addressing final, finished coating irregularities exist. One means is to increase extruder temperature and mix times and, if employed, increasing the amount of additives. Another prevalent means to address defects without additives is to increase or decrease the film build or thickness, depending on the precise nature of the issue that must be addressed (e.g., improved corrosion resistance might require a thicker coating). Of course, some of these non-additive solutions are not satisfactory because they result in another undesired side effect known as “edge pulling.” Edge pulling is a condition in which the coating pulls away from the corners of the coated substrate resulting in incomplete formation of the finish.
Conventional additive solutions add cost owing to their reliance on various additional substances. Further, these additives may not be compatible with all coating platforms, and properly incorporating or introducing the additive into the formulation can present it own challenges. For example, the additive must provide an acceptable performance on the Hegman-type gage tests (e.g., ASTM D1210), which measure the fineness of dispersion of pigment vehicle systems, in order to be incorporated into liquid-based platforms.
Another issue with respect to existing functional additives is that they generally serve only one purpose—to address a single, discrete issue (e.g., existing irregularities prior to the addition of additive). In order to address multiple issues, multiple additives were required, and the increased mass/volume dedicated within the overall composition to multiple additives (or increased amounts of a single additive that lacks efficacy) means lost opportunities to maximize the formulation in other respects.
Ultimately, the failure to tackle the issue or issues addressed by additive(s) will result in rejection of the coated article for failure to comply with applicable coating standards set by ASTM. In turn, these rejections result in the coated articles being discarded and/or subject to costly reworking.
In view of the foregoing, a universal additive solution would be welcome. Such a solution would be based on a binder system platform that could be adjusted to address any number of the irregularities and problems identified herein.
A multi-functional additive platform is contemplated that may serve as any combination of a flow modifier, flexibility agent, wetting agent, curing agent, gloss control additive, mar/scratch resistance additive, impact resistance additive, and/or rheology modifier. The additive itself is a complete binder platform comprising certain types of resin(s) and/or other items such as curatives, hardeners, pigments, tetramethoxy glycoluril, waxes, catalysts and flow aids. The additive is associated with a carrier, such as a silica-based system, so as to simplify its introduction and use in conventional powder coating formulations wherein the additive is less than 1.5 wt. % of the total formulation (additive plus conventional powder formulation) and sometimes as little as 0.05 wt. %. Suitable carriers include (3-aminopropyl) trimethoxysilane (TMS), silicon dioxide (at 45 to 55% active levels), and/or the flow aid disclosed in U.S. Pat. No. 9,353,254.
While the binder systems herein appear as if they could serve as powder coating compositions in their own right, the inventors have discovered that the disclosed formulations can be incorporated into a wide range of different coating platforms without the need for conventional additives. Further, the additive created using the inventive method itself is not formulated to be—and, in numerous embodiments, simply cannot serve as—a distinct, stand-alone coating composition (e.g., some of the preferred curatives are not capable of adequately curing or hardening the resins of the binder system on their own). Instead, the binder system approach eliminates or greatly reduces the need for non-resin components, despite the fact that multiple resins and/or other optional additives, including hardeners, tetramethoxy glycoluril, pigments, waxes, catalyst, flow aids, degassing agents and gloss modifiers can be included in the additive to enhance its multifunctional properties.
Further reference is made to the appended claims and description below, all of which disclose elements of the invention. While specific embodiments are identified, it will be understood that elements from one described aspect may be combined with those from a separately identified aspect. In the same manner, a person of ordinary skill will have the requisite understanding of common processes, components, and methods, and this description is intended to encompass and disclose such common aspects even if they are not expressly identified herein.
Reference will now be made in detail to exemplary embodiments of the present invention. It is to be understood that other embodiments may be utilized and structural and functional changes may be made without departing from the respective scope of the invention. Moreover, features of the various embodiments may be combined or altered without departing from the scope of the invention. As such, the following description is presented by way of illustration only and should not limit in any way the various alternatives and modifications that may be made to the illustrated embodiments and still be within the spirit and scope of the invention.
Any elements described herein as singular can be pluralized (i.e., anything described as “one” can be more than one). Any species element of a genus element can have the characteristics or elements of any other species element of that genus. The described configurations, elements or complete assemblies and methods and their elements for carrying out the invention, and variations of aspects of the invention can be combined and modified with each other in any combination. As used herein, the words “example” and “exemplary” mean an instance, or illustration. The words “example” or “exemplary” do not indicate a key or preferred aspect or embodiment. The word “or” is intended to be inclusive rather an exclusive, unless context suggests otherwise. As an example, the phrase “A employs B or C,” includes any inclusive permutation (e.g., A employs B; A employs C; or A employs both B and C). As another matter, the articles “a” and “an” are generally intended to mean “one or more” unless context suggest otherwise.
As noted above, the inventors endeavored to create a multi-functional binder system which could serve as an additive to simultaneously address issues and irregularities such as surface tension, surface cracking, delayed curing, loss of gloss/color, taber abrasion, impact fading, etc. These added benefits could include a lower viscosity during the curing process (whether for powder or liquid applied coatings), improved mar and scratch resistance for the final fused/cured coating, improved flexibility, improved surface tension, improved weathering resistance, increased curing mechanism, improved slip resistance, improved impact fading, improved substrate wetting and increased flow in surface rheology with minimal effect on the gloss of the final, fused/cured coating.
Specific examples of binder system platforms according to the invention are included in Tables 1 through 4 below. While these are provided as discrete formulations, these may be selectively combined, reordered, or omitted to form still other combinations and permutations, all of which form separate aspects of the invention.
As previously stated, while the binder system disclosed herein nominally includes components that are common to conventional coatings, the ancillary components (i.e., the non-resin components, such as anti-corrosion pigments, curative/hardeners, degassing agents, anti-oxidants, and the like) are not necessarily selected so as to make the flow modifier a viable, stand-alone finished coating composition in its own right. That is, while the additives appear to have the same constituents as a conventional, finished powder coating, it is irrelevant whether these components would themselves be useful as a coating. Indeed, the curatives proposed for some embodiments do not sufficiently act as curatives for the disclosed resins of the binder system.
Instead, the binder systems are formulated to be combined with a separate stand-alone coating composition and to deliver the desired effects with respect to surface tension, viscosity, flow, etc. as that finished coating composition (including the additives created using the inventive method) cures. This holistic approach to formulating an additive—by considering a combination of resins and ancillary components that deliver a synergistic effect—is, in the inventors' view, a stark departure from previous additives. Whereas past additives identified one or two chemicals as “active” or important contributors to its efficacy—with the additive itself then formulated to maximize the amount(s) of those active ingredients, the disclosed aspects of this invention acknowledge the significance of providing an entire binder system that itself melts and integrates with finished coating composition to which it is added and, eventually, cured.
Further, by relying on a carrier system, the additives created using the inventive method can be integrated seamlessly during the curing process. That is, the micronized additive(s) (i.e, particle sizes between 100 nanometers and 5 microns) can be introduced to the finished coating composition by way of an inert carrier that will simply become part of the final, cured coating. Further, when delivered on a carrier system, the finished coating's storage life is increased and its handling is simplified. In this manner, the inventors refer to the binder system additives as a “platform” through which any number of goals or aims to improve coatings can be achieved (of course, in conventional coatings, these goals or aims were only fulfilled by separate and discrete components, many of which were introduced in pure form and at significant cost).
Thus, one aspect of the disclosed formulations is that the amounts of each multi-functional additive component are selected relative to ratio of multi-functional additive to the carrier system. That is, the additive adheres to the silica carrier in known amounts, so that the combination additive-carrier is provided to the finished coating composition at the relatively low weight percentages contemplated herein. Further, given the aforementioned synergistic effects of the constituents of the additive, the relative (or “stoichiometric”) amounts of the constituents and the carrier system are important to the efficacy of the final additive.
In some aspects, the multifunctional additive, after initial extrusion and grinding, can be added at 55 wt. % or greater in comparison to the silica carrier. That is, the weight ratio of extruded additive to silica is 55:45 or more. In other aspects, ratios of 5:95, 10:90; 15:85; 20:80; 25:75; 30:70; 35:65; 40:60; and 45:55 are contemplated. Carriers of particular interest include (3-aminopropyl) trimethoxysilane and/or a silicone dioxide-precipitated amorphous silicate (45-55% active). The flow aid disclosed in U.S. Pat. No. 9,353,254 (which includes polyethylene resin, polyester hydroxyl resin, polymeric curative(s), degassing agent, ricinoleic acid, and glass flake) has also proven to serve as a useful carrier in its own right.
The platforms contemplated herein can be cured 10 min. @ 375° F. or 20 min. @ 350° F., using a convection oven such as laboratory oven (e.g., Blue M made in White Deer, Pa.). The multi-functional additive is then milled or ground to a particle size that is appropriate for powder coating applications, with micronized sizes being most ideal when a carrier system is used. In this manner, as little as 0.5 to 150 grams of additive per 1000 grams of finished coating powder can be effective when blending a finished powder coating composition, post extrusion (of the finished coating composition), according to certain aspects of the invention. Alternatively, as noted above, 0.05 to 1.5 wt. % of the multi-functional additive can be blended and extruded with/as part of the finished coating composition.
At ambient temperature and pressure, the components forming the additive extrudate are admixed in a tumbler for 40-55 minutes or a high speed mixer for 45-50 seconds until fully blended. The admixed material is then placed in the extruder hopper via the screw mechanism at 300 RPM to the extruder dye, preferably with three temperature zones at a feed rate of 400 g/min. Any suitable extruder utilizing a single or twin screw mechanism may be used to form an extrusion product. The zone settings may be, respectively 60/60/100° C. The extrusion sheet product is then ground into particles (e.g., via a Retch mill grinder or coffee grinder) for 1-5 minutes at ambient temperature and pressure to form a powder having a most or substantially all of the particles preferably between about 30 to 50 μm in size.
The silica carrier is then blended with the particulates of this additive extrudate. This may occur via a high speed system (e.g., Henschel) for a period of time sufficient to further micronize the components and adhere them to the carrier.
In identifying appropriate resins for the multi-functional additive (selected from one more of the groups of epoxy, epoxy-polyester, hydroxyl polyester, acrylic, TGIC polyester and TGIC-free polyester), alternatives can be identified so long as they have the same chemical composition and similar characteristics, such as the viscosity, Tg temperature, differential scanning calorimetry, and Hegman gage test, as the exemplary grades of material identified herein.
Coating platforms appropriate for the multifunctional additives made according to this invention preferably include a conventional thermosetting powder coating resin material selected from one or more of the groups of epoxy, epoxy-polyester, hydroxyl polyester, acrylic, TGIC polyester and TGIC-free polyester resins. Conventional additives, such as hardeners, tetramethoxy glycoluril, pigments, waxes, catalysts, flow aids, degassing agents and gloss modifiers may be included, although many of these additives will be unnecessary in view of the multifunctional hardness composition's capabilities. In these cases, only about 0.5% to about 1.5% by weight of a finished powder coating platform will be comprised of the multifunctional additive.
Representative and suitable epoxy resins include Kukdo Epoxy resin KD-242H. KD-242H, is a bisphenol-A type solid epoxy resin which has excellent flow characteristics. KD-242H has an epoxy equivalent weight specification of 660-720 (g/eq), a softening point of about 85 to 95° C., and a melt viscosity of specification of about 2200 to 2800 cps at 150° C. Suitable hardeners include Kukdo KD-410J, Epikure 101 and Dyhard 100.
Dow Chemical's D.E.R 663U is a solid epoxy resin and is a standard medium molecular weight epoxy resin for powder coating applications. The resin has an epoxy equivalent weight specification of 730-820 (g/eq), a softening point specification of 92°−102° C. and a melt viscosity specification of 2000-4000 cps at 150° C. Suitable hardeners include Kukdo KD-401, KD-41, KD-410J, Epikure 101 and Dyhard 100.
Representative examples of epoxy-polyester resins useful in one embodiment include: Crylcoat 2401-2 and Crylcoat 2471-4 from Allnex; SP-100 and SP-400 from Sun Polymers; and Rucote 102, 106, and Rucote 118 from Stepan Company. The table below shows one example of a multifunctional hardness composition formulation in accordance with one embodiment of the invention (column 2) and approximated weight ranges covering other embodiments of the invention.
The multifunctional additives herein can be added to liquid as well as powder coating formulations. The formulation may be combined with liquids such as water (preferably de-ionized and/or distilled), acetone, methyl-ethyl ketone (butanone), ethanol, and other, similar common industrial solvents, as well as combinations thereof. When the multifunctional hardness composition is combined with such a liquid carrier, the formulation volatilizes after the initial coating.
Further, coating compositions having the binder system platform (i.e., multifunctional) additive can be applied on various substrate types such as plastic, metal, aluminum, wood, concrete, paper, cloth, stucco and a host of other materials to act as a coating. Additional, exemplary resins and additives, suitable for such coating compositions, as disclosed in any the references identified herein are also incorporated by reference. Still other components that may be mixed into or formed as part of the extruded powder.
Unless specifically noted, all tests and measurements are conducted in ambient conditions according to commonly accepted measurement protocols (e.g., such as those regularly published by ASTM International) and relying upon commercially available instruments according to the manufacturer-recommended operating procedures and conditions. Specific tests and regimens identified in the military and other specifications noted above may be particularly informative in characterizing the performance of coatings contemplated herein, including ASTM B117, D476 (type III or IV), D522, D523, D1849, D2794, D2805, D3271, D3335, D3359, D3363, D3451, D3723, D4060, D5767, D7027, D7187, E308, E1331, G90, G154, and G171. Unless noted to the contrary (explicitly or within the context of a given disclosure), all measurements are in grams and all percentages are based upon weight percentages.
Unless otherwise stated, all percentages stated herein are weight percentages based on the total powder coating composition or, in the context of the multifunctional additive component itself, the composition of the additive.
In addition to the disclosures of the applications invoked in the priority claim, additional aspects of the invention are provided in the tables below. The percentages cited are with respect to the total mass/weight of the formulation for the additive to be extruded, prior to mixing that extrudate with the silica carrier and/or introduction of the silica-carried additive into a final fusion powder coating composition. Further, these weight percentages may be adjusted appropriately within the stated ranges, such that the specific example provided for each additive should not be deemed as limiting.
With reference to the tables below, representative examples of polyester hydroxyl resins useful in some embodiments of the multifunctional hardness composition include: Crylcoat 2401-2 and Crylcoat 2471-4 from Allnex; SP-100 and SP-400 from Sun Polymers; and Rucote 102, 108 and Rucote 121 from Stepan Company.
Representative curatives useful in one embodiment include, Crelan NI2 blocked cycloaliphatic polyisocynate, Dow Chemical TGIC, (triglycidyllisocyanurate), Epikure 101 Imidazole Adduct, Epikure P-108 DICY Imidazole Adduct, aliphatic and cycloaliphatic amine multifunctional hardness composition from Momentive Industries and phenolic hardener DEH84 from Dow Chemical.
In the tables below, exemplary acrylic resins case be selected from
Although the embodiments of this disclosure have been disclosed, it is to be understood that the present disclosure is not to be limited to just the described embodiments, but that the embodiments described herein are capable of numerous rearrangements, modifications and substitutions without departing from the scope of the claims hereafter. It is, of course, not possible to describe every conceivable combination of components or methodologies for purposes of describing the present specification, but one of ordinary skill in the art may recognize that many further combinations and permutations of the present specification are possible. Furthermore, to the extent that the term “includes” is used in either the detailed description or the claims, such term is intended to be inclusive in a manner similar to the term “comprising” as “comprising” is interpreted when employed as a transitional word in a claim. The claims as follows are intended to include all modifications and alterations insofar as they come within the scope of the claims or the equivalent thereof.
This application is a continuation of International Application No. PCT/US2019/067436 filed on Dec. 19, 2019 which claims priority to the following co-pending United States patent applications (referenced by serial number and filing date), all of which are incorporated by reference and all of which include as inventors the individuals identified as inventors in this case: 62/781,869 filed on Dec. 19, 2018;62/802,235 filed on Feb. 7, 2019;Ser. No. 16/225,451 filed on Dec. 19, 2018;Ser. No. 16/225,416 filed on Dec. 19, 2018; andSer. No. 16/225,381 filed on Dec. 19, 2018.
| Number | Date | Country | |
|---|---|---|---|
| 62781869 | Dec 2018 | US | |
| 62802235 | Feb 2019 | US |
| Number | Date | Country | |
|---|---|---|---|
| Parent | PCT/US2019/067436 | Dec 2019 | US |
| Child | 17351710 | US | |
| Parent | 16225451 | Dec 2018 | US |
| Child | PCT/US2019/067436 | US |
