Hybrid epoxy-polyurethane water-based primer as well as preparation method and use method thereof

Abstract

Hybrid aqueous primer compositions, in particular hybrid epoxy-polyurethane aqueous primers, as well as methods for their production and their use are provided.

Description

[0001] Cross-references to related applications

[0002] This application relates to and claims priority to U.S. Provisional Application Serial No. 63 / 460,152, filed April 18, 2023, the entire contents of which are incorporated herein by reference. Technical Field

[0003] This invention relates to hybrid epoxy-polyurethane waterborne primer compositions, their production methods, and their application methods, particularly as primers for substrates containing metal surfaces. Background Technology

[0004] Environmental considerations, particularly the negative environmental impact of solvent-based coating solutions and, especially, the volatile organic compounds (VOCs) associated with them, have led to a growing demand for the development and use of waterborne coatings. Solvent-based primers are frequently used in vehicle repair, offering improved performance in areas such as corrosion protection. However, the VOCs associated with solvent-based primers are one of the key issues driving interest in switching to waterborne primers.

[0005] Low VOCs and zero emissions are significant advantages of waterborne coatings, driving the development of a wide variety of waterborne coating solutions. Much effort has been made to replace solvent-based primers with waterborne primers. However, past efforts have yielded unsatisfactory performance, particularly in the field of corrosion protection, thus limiting the use of waterborne primers, especially for vehicle repair and, more specifically, for coating other metal surfaces.

[0006] A primer is a paint or coating product that allows a topcoat to adhere to a surface better than when applied alone. Primers are designed to adhere to a surface and form a bonding layer that is better prepared to receive paint. Unlike paint, primers are generally not intended to serve as a durable outermost finish, but can be engineered to have improved filling and bonding properties with the underlying materials. Sometimes this is achieved through chemical methods, while other methods involve controlling the physical properties of the primer, such as its porosity, tackiness, and hygroscopicity. Summary of the Invention

[0007] Therefore, one object of the present invention is to provide a hybrid waterborne primer composition having a combination of properties that cannot be obtained with primers based on a single polymer.

[0008] Another object of the present invention is to provide a hybrid waterborne primer composition that can be applied to a substrate, particularly a metal substrate, without the need for an etching primer.

[0009] Another object of the present invention is to provide a hybrid waterborne primer composition that can be applied to a substrate, particularly a metal substrate, after an initial application of an etching primer, and which provides comparable or improved properties such as adhesion, corrosion resistance and hydrolysis resistance compared to conventional solvent-based primers used with etching primers.

[0010] Another object of the present invention is to provide a method for producing the hybrid waterborne primer compositions of the present invention, and methods of using them.

[0011] These and other objectives of the present invention, individually or in combination, have been achieved by discovering a hybrid primer comprising a crosslinked polymer network formed of epoxy resin, polyurethane dispersion and isocyanate-containing compounds.

[0012] Its production methods and its application methods in substrate coating, especially in metal substrate coating, are satisfied. Attached Figure Description

[0013] A more complete understanding of the invention and its many accompanying advantages will become readily apparent when considered in conjunction with the accompanying drawings, and by referring to the following detailed description, in which:

[0014] Figure 1 A schematic diagram of the reaction for preparing an exemplary embodiment of the hybrid epoxy-polyurethane waterborne primer of the present invention is provided.

[0015] Figure 2 A schematic diagram of the structure of some embodiments of the hybrid epoxy-polyurethane waterborne primer of the present invention is provided.

[0016] Figure 3A Photographs illustrating the corrosion resistance after a 20-day salt spray test between substrates coated with a conventional polyurethane solvent-based primer [(a) and (b)] and hybrid epoxy-polyurethane waterborne primers [(c) and (d)] of certain embodiments of the present invention.

[0017] Figure 3B Provided from Figure 3A The images are illustrations of the corrosion resistance performance, where the darker box-shaped values ​​are the control (a) and the lighter box-shaped values ​​are embodiments of the present invention (b).

[0018] Figure 4A This is another photographic illustration of the corrosion resistance after a 20-day salt spray test, compared to the hybrid epoxy-polyurethane waterborne primers of certain embodiments of the present invention [(c), (d), (e), and (f)], and to substrates [(a) and (b)] coated with a conventional polyurethane solvent-based primer.

[0019] Figure 4BProvided from Figure 4A The photographs illustrate the corrosion resistance performance of the conventional 2K polyurethane solvent-based primer (a), the hybrid epoxy-polyurethane primer of the present invention containing 30% epoxy resin (b), and the hybrid epoxy-polyurethane primer of the present invention containing 50% epoxy resin (c). Detailed Implementation

[0020] This invention relates to hybrid epoxy-polyurethane waterborne primers, methods for preparing these primers, and their use as coatings on substrates, particularly metal substrates. The hybrid epoxy-polyurethane waterborne primers of this invention can be used alone as a primer applied directly to a substrate (or, in some embodiments, directly to metal or "DTM"), or in combination with surface treatments (such as etching primers or other chemical surface treatments) on the substrate to be coated, so that the substrate surface can better receive and adhere the hybrid epoxy-polyurethane waterborne primer of this invention.

[0021] In the context of this invention, the term "hybrid primer" includes, but is not limited to, semi-interpenetrating and fully interpenetrating crosslinked networks of two polymer types, blends of two different polymer types that have been chemically bonded directly or via a binder, chemically bonded crosslinked networks of two polymer types, crosslinked networks of one polymer type that has been chemically modified by a compound, etc., wherein the chemically modified polymer type can then form its own crosslinked network after being bonded to the original crosslinked network.

[0022] In the context of this invention, the term "aqueous" is intended to mean that the polymer component is in an aqueous medium and the VOC is less than 250 g / L. In some embodiments, waterborne coatings offer one or more of the following advantages:

[0023] • Low toxicity and low flammability due to low VOC levels and low HAP emissions

[0024] • Lower cost than solvent-based coatings, and in most cases requires no additives, thinners, or hardeners.

[0025] • Less paint is needed to cover the same surface area compared to using solvent-based paint solutions.

[0026] • Spray guns can be easily cleaned with water or water-based solutions, and do not require paint thinner, acetone, or methyl acetate (making them more environmentally friendly and safer for users).

[0027] • Furthermore, the drying time of water-based primers is shorter than that of solvent-based primers, and the drying time for sanding is close to that of solvent-based primers.

[0028] • For safety reasons, there are no special requirements for the storage of water-based primers and the disposal of waste water-based primers.

[0029] The term "comprising" and its variations are not intended to be limiting when they appear in the specification and claims.

[0030] The range of values ​​expressed using endpoints includes all values ​​contained within that range (for example, 1 to 5 includes 1, 1.5, 2, 2.75, 3, 3.80, 4, 5, etc.).

[0031] As used herein, the terms “comprising,” “having,” “with,” or variations thereof are intended to be inclusive in a manner similar to the term “comprising.” The singular forms “a,” “an,” and “the” include multiple referents unless the context clearly indicates otherwise. Furthermore, the terms “a,” “an,” “the,” “at least one,” and “one or more” are used interchangeably. Thus, for example, a coating composition containing “one” additive means that the coating composition may contain “one or more” additives. As used throughout this specification and claims, approximate language may be applied to modify quantitative expressions that can be permissibly varied without causing a change in the essential function associated with them. Therefore, values ​​modified by terms such as “about” are not limited to the specified precise values. In some cases, approximate language may correspond to the precision of the instrument used to measure the value. Moreover, unless otherwise specifically stated, the use of terms “first,” “second,” etc., does not indicate order or importance, but rather the terms “first,” “second,” etc., are used to distinguish one element from another.

[0032] As used herein, the terms “may” and “may be” indicate a possibility of occurring within a set of conditions; possessing the specified attribute, characteristic, or function; and / or qualifying another verb by expressing one or more of the performance, capability, or possibility associated with a qualified verb. Therefore, the use of “may” and “may be” indicates that the modified term is clearly appropriate, capable, or suitable for the indicated capability, function, or use, while taking into account that in some cases the modified term may sometimes be inappropriate, incapable, or unsuitable. For example, in some cases an event or capability may be anticipated, while in others it may not occur—this distinction is captured by the terms “may” and “may be.”

[0033] In the specification and claims, reference will be made to several terms having the following meanings. The singular forms “a,” “an,” and “the” include multiple referents unless the context clearly indicates otherwise. As used throughout the specification and claims, approximate language may be applied to modify quantitative expressions that can be permissibly varied without causing a change in the essential function associated with them. Thus, values ​​modified by terms such as “about” are not limited to the specified precise values. In some cases, approximate language may correspond to the precision of the instrument used to measure the value. Furthermore, unless otherwise specifically stated, the use of terms such as “first,” “second,” etc., does not indicate order or importance, but rather the terms “first,” “second,” etc., are used to distinguish one element from another.

[0034] The term "aqueous composition" or dispersion as used herein means particles dispersed in an aqueous medium. An "aqueous medium" as used herein refers to a continuous phase comprising at least 50% by weight of water, wherein the remaining composition of the aqueous medium comprises particles and water-miscible compounds, such as alcohols, glycols, glycol ethers, glycol esters, etc.

[0035] In the context of this invention, the term "dispersion" refers to a mixture of a dispersible polymer and a carrier. The term "dispersion" includes, but is not limited to, the term "solution".

[0036] The terms "preferred" and "ideally" refer to embodiments of the invention that provide certain benefits in certain circumstances. However, other embodiments may also be preferred in the same or other circumstances. Furthermore, the description of one or more preferred embodiments does not imply that other embodiments are unavailable, and is not intended to exclude other embodiments from the scope of the invention.

[0037] As used in this article, the term “structural unit” (also known as a polymeric unit) for naming monomers refers to the residue of the monomer after polymerization, or the monomer in its polymerized form.

[0038] Unless otherwise indicated herein or clearly contradicted by the context, all methods described herein may be performed in any suitable order. The use of language (e.g., “such as”) in any examples or descriptions provided herein is intended to illustrate the invention and not to limit its scope. Any statements herein regarding the nature or benefits of the invention or preferred embodiments are not intended to be limiting. The invention includes all modifications and equivalents of the subject matter described herein as permitted by applicable law. Furthermore, unless otherwise indicated herein or clearly contradicted by the context, the invention covers any combination of the foregoing elements in all possible variations. Descriptions of any references or patent claims herein, even if marked “prior,” are not intended to constitute a concession by such references or patents to prior art. Unclaimed language should not be considered to limit the scope of the invention. Any statement or suggestion herein that certain features constitute part of the claimed invention, unless reflected in the appended claims, is not intended to be limiting. The marking of a patent number on any product or the identification of a patent number in connection with any service should not be construed as indicating that all embodiments described herein are incorporated into such product or service.

[0039] Epoxy resins are well-known as high-performance materials in various architectural and metallic coating applications, offering a combination of chemical resistance, adhesion, corrosion resistance, mechanical strength, and high flexibility in some cases. On the other hand, polyurethane has been proven to react rapidly with isocyanates in short bursts and possess improved coating properties, such as a wide range of hardness, abrasion and impact resistance, flexibility, and strong adhesion. Both epoxy and polyurethane waterborne primers are commercially available for use in the automotive repair field. However, epoxy waterborne primers alone exhibit some weaknesses, as long drying times are undesirable in rapid coating processes, and epoxy primers do not sand as well as polyurethane primers. The sanding performance of rigid epoxy resins is a disadvantage, as it is difficult to achieve a smooth surface with a high optical appearance, especially when cured at room temperature. Another significant disadvantage is the long drying time caused by the slow reaction rate between epoxy resin and amine curing agents, as most customers prefer rapid drying.

[0040] Polyurethane (PU) dispersions are PU resins dispersed in water, producing a unique combination of toughness, mechanical properties, and durability not typically achievable in other polymer chemistry. These resins are used on a wide range of surfaces and applications, including wood, metal, plastics, masonry, and textiles. Meanwhile, water-based polyurethane dispersions used in the manufacture of adhesives exhibit excellent performance in terms of heat resistance, rapid drying, durable bond strength, and sprayability. Despite the many advantages of waterborne polyurethanes, the porous structure within the coating resulting from the reaction of isocyanates with water can reduce the stability of polyurethane-formed coatings. Furthermore, polyurethane primers exhibit poor adhesion to steel, necessitating the application of an etching primer to the substrate first, increasing the number of steps in the coating process and leading to increased process and raw material costs.

[0041] Therefore, there is a need for a primer that can combine the chemical resistance, adhesion, corrosion resistance, mechanical strength, and high flexibility of epoxy primers with the short drying time, hardness, abrasion resistance, impact resistance, and adhesive properties of polyurethane primers.

[0042] Therefore, one embodiment of the present invention provides a hybrid epoxy-polyurethane waterborne primer that provides this desired combination of properties. The hybrid epoxy-polyurethane waterborne primer of the present invention is obtained by blending an epoxy resin and a waterborne polyurethane dispersion with an isocyanate compound. The reactions between the polyurethane dispersion and the isocyanate, and between the epoxy resin and the isocyanate, respectively produce the following... Figure 1 and Figure 2 The two crosslinking networks shown are crosslinked together by isocyanate as a curing agent, thereby significantly improving the adhesion and mechanical strength of the film. The hybrid epoxy-polyurethane waterborne primer of the embodiments of the present invention provides one or more of the following advantages:

[0043] • Reduced drying time through rapid reaction of polyurethane dispersion and isocyanate.

[0044] • Improve the flexibility of epoxy resin through flexible polyurethane

[0045] • Increased chemical and thermal stability through epoxy resins

[0046] • No etching primer is required (but you may wish to use one).

[0047] • Improved sanding performance through the film formed by epoxy primer

[0048] • The membrane has better corrosion resistance.

[0049] Therefore, in some embodiments of the present invention, a hybrid primer is provided comprising a cross-linked polymer network formed of an epoxy resin, a polyurethane dispersion and an isocyanate-containing compound.

[0050] Epoxy resins include, but are not limited to, epoxy resins formed from epichlorohydrin and one or more bisphenol compounds. The one or more bisphenol compounds can be any suitable bisphenol compound and can be selected based on the desired final properties from the epoxy resin portion of the hybrid primer.

[0051] In some embodiments, the bisphenol compound includes, but is not limited to, one or more compounds selected from the following:

[0052] structural name CAS Bisphenol A 80-05-7 Bisphenol AP 1571-75-1 Bisphenol AF 1478-61-1 Bisphenol B 77-40-7 Bisphenol BP 1844-01-5 Bisphenol C 79-97-0 Bisphenol C 2 14868-03-2 Bisphenol E 2081-08-5 Bisphenol F 620-92-8 Bisphenol G 127-54-8 Bisphenol M 13595-25-0 Bisphenol S 80-09-1 Bisphenol P 2167-51-3 Bisphenol pH 24038-68-4 Bisphenol TMC 129188-99-4 Bisphenol Z 843-55-0 Dinitrobisphenol A 5329-21-5 Tetrabromobisphenol A 79-94-7

[0053] Preferably, the one or more bisphenol compounds are selected from the group consisting of bisphenol A, bisphenol B, bisphenol E, bisphenol F and bisphenol AF.

[0054] Curing (or crosslinking) of epoxy resins can be achieved by reacting the epoxy resin with itself (homogenization) or by forming copolymers with multifunctional curing agents or hardeners. This curing is responsible for the qualities of the material, such as durability, versatility, and adhesion. Any desired molecule containing reactive hydrogen can be used to react with the epoxy groups of the epoxy resin. Common types of hardeners used with epoxy resins include amines, acids, acid anhydrides, phenols, alcohols, and thiols. These have a relative reactivity in roughly the following order (lowest first): phenol < acid anhydride < aromatic amine < alicyclic amine < aliphatic amine < thiol.

[0055] While some epoxy resin / hardener combinations will cure at ambient temperature, others may require heating. Sometimes the temperature is increased gradually to control the curing rate and prevent excessive heat buildup from the exothermic reaction.

[0056] Curing agents that exhibit low or limited reactivity at ambient temperature but react with epoxy resin at high temperatures are called latent curing agents. When using latent curing agents, the epoxy resin and curing agent can be mixed and stored for a period of time before use, which is advantageous for many industrial processes.

[0057] The epoxy curing reaction can also be accelerated by adding a small amount of accelerator. Tertiary amines, carboxylic acids, and alcohols (especially phenols) are effective accelerators.

[0058] The polyurethane dispersions of these embodiments of hybrid primers are aqueous dispersions (or aqueous dispersions) of polyurethane, preferably formed from one of aliphatic or aromatic diisocyanates, one or more diols or polyols, a catalyst, and optionally one or more additives selected from the group consisting of chain extenders and crosslinking agents conventional in polyurethane chemistry.

[0059] In some embodiments, the polyurethane dispersion comprises one or more hydroxyl and / or carboxyl functional groups that react with one or both of the isocyanate-containing compound and the epoxy resin to allow the formation of a crosslinked network of the hybrid primer of these embodiments.

[0060] The isocyanate-containing compounds used in these embodiments can be any isocyanate compound that reacts with either (and preferably both) epoxy resins and polyurethane dispersions, and can preferably be diisocyanates or polyisocyanates. Examples of such isocyanate-containing compounds include, but are not limited to, compounds containing aliphatic isocyanates and compounds containing aromatic isocyanates, which can be blocked or unblocked isocyanates, and specific examples include, but are not limited to, hexamethylene diisocyanate (HDI), isophorone diisocyanate (IPDI), 4,4'-diisocyanate dicyclohexylmethane (HMDI), and tetramethylxylenylidene diisocyanate (TMXDI) and their blocked derivatives.

[0061] If desired, any suitable isocyanate blocking agent may be used, including but not limited to sodium bisulfite, diethyl malonate, 3,5-dimethylpyrazole, methyl ethyl ketone oxime (MEKO), phenol, or caprolactam.

[0062] These same isocyanate-containing compounds, especially diisocyanates and polyisocyanates, can also be isocyanates of polyurethanes used to prepare polyurethane dispersions.

[0063] Figure 3A and Figure 3B The corrosion resistance of a hybrid epoxy-polyurethane waterborne primer of the present invention, without the use of an etching primer, is demonstrated compared to a conventional 2K polyurethane solvent-based control primer. The hybrid epoxy-polyurethane waterborne primer of the present invention was sprayed onto a cold-rolled steel substrate without the use of an etching primer, and a conventional 2K polyurethane solvent-based control primer was sprayed onto a cold-rolled steel substrate previously treated with an etching primer. A base coat was then applied to each of these substrates, followed by a clear coat.

[0064] Prior to salt spray chamber testing, the properties of the control primer and the primer of the present invention were measured on cold-rolled steel substrates, as well as the properties of each of the entire set of layers (including the primer layer and the clear coat). The results are shown in Table 1 below:

[0065] Table 1

[0066]

[0067] The coated substrates were tested in a salt spray chamber (according to ASTM B117) for 20 days, and areas of delamination and corrosion damage were examined. The results showed that the delamination and corrosion of the 2K polyurethane solvent-based control primer (a) (with an etch primer) and the hybrid epoxy-polyurethane waterborne primer of the present invention (b) (without an etch primer) were very similar. Figure 3B As shown.

[0068] Substrates coated with the hybrid epoxy-polyurethane waterborne primer of the present invention without an etch primer exhibit substantially the same characteristics as those coated with a conventional 2K polyurethane solvent-based control primer with an etch primer, except that the substrate coated with the hybrid epoxy-polyurethane waterborne primer without an etch primer shows a slightly lower image distinctness (DOI) (86.6) compared to the substrate coated with a conventional 2K polyurethane solvent-based control primer with an etch primer (96.5). Due to the presence of hydroxyl groups on the epoxy resin of the hybrid primer of the present invention, the coating using the hybrid primer of the present invention exhibits enhanced adhesion strength compared to conventional polyurethane.

[0069] The performance of the hybrid epoxy-polyurethane waterborne primer of the present invention was further evaluated by humidity chamber testing (GM14729). The results showed that the performance of the hybrid epoxy-polyurethane waterborne primer of the present invention was not significantly different from that of conventional polyurethane.

[0070] The hybrid epoxy-polyurethane waterborne primer of the present invention was further tested by first applying an etching primer (solvent-based epoxy resin) coated on a cold-rolled steel substrate, and then coating it with the hybrid epoxy-polyurethane waterborne primer of the present invention embodiment. Then, each panel was coated with a base coat, followed by a clear coat. Figure 4A and Figure 4B The following are examples of hybrid epoxy-polyurethane waterborne primers (30% epoxy resin content by weight) used in the presence of an etching primer. Figure 4B (b) in the middle; Figure 4A (c) and (d) in the content of 50% epoxy resin Figure 4B (c) in the middle; Figure 4A (e) and (f) in the figure) are coated substrates and, in the case of an etch primer, are conventional 2K polyurethane solvent-based control primers. Figure 4B (a) in the middle; Figure 4AThe corrosion resistance results of the substrates coated in (a) and (b) are shown. It is evident that the corrosion resistance of the hybrid epoxy-polyurethane primer is superior to that of the conventional polyurethane solvent-based control primer when using an etch primer. The use of the etch primer significantly increases the adhesion strength of the hybrid epoxy-polyurethane waterborne primer of the present invention. Since the hybrid primer of the present invention provides comparable adhesion characteristics without the use of an etch primer, the introduction of an epoxy resin-based etch primer increases the adhesion strength between the hybrid primer of the present invention and the cold-rolled steel substrate. Therefore, the corrosion resistance is increased due to the strong adhesion of the hybrid primer of the present invention to the substrate.

[0071] The performance of substrates coated with the hybrid epoxy-polyurethane waterborne primer of the present invention was also tested before and after humidity chamber testing, compared with those coated with a conventional 2K polyurethane solvent-based control primer. After humidity chamber testing at room temperature for one hour or 24 hours, poor adhesion strength was observed in the substrates coated with the conventional polyurethane control primer, while the substrates coated with the hybrid epoxy-polyurethane waterborne primer of the present invention achieved improved adhesion strength, particularly when the epoxy resin content in the hybrid waterborne primer was about 30% by weight. Therefore, in embodiments of the hybrid epoxy-polyurethane waterborne primer of the present invention, the epoxy resin content is preferably 20% to 40% by weight relative to the total amount of primer, more preferably 25% to 35% by weight relative to the total amount of primer.

[0072] The enhanced film durability was also evaluated using a stone impact resistance test (GMW 14700). It was found that the hybrid epoxy-polyurethane waterborne primer of the present invention provides improved durability compared to conventional 2K polyurethane solvent-based primers. This improved durability can be attributed to the rigid structure of the epoxy resin.

[0073] A further comparison was made between a conventional 2K polyurethane solvent-based primer control and an embodiment of the hybrid epoxy-polyurethane waterborne primer of the present invention (where the NCO / OH equivalent ratio is increased to 1.5 and the composition contains different amounts of organic solvent (30%, 50%, and 100%)). For the embodiment of the hybrid primer of the present invention, no significant changes in properties were found, except for reduced chemical resistance at higher organic solvent levels in the hybrid primer. The hybrid primer using organic solvents was found to have higher gloss and DOI properties compared to panels with lower NCO / OH equivalent ratios. While not wishing to be bound by any particular theory or mechanism of action, this improvement in gloss and DOI is believed to be due to the ability to generate a denser cross-linked network, resulting in a smoother surface.

[0074] Typically, coatings degrade when exposed to high humidity and high temperature environments. The performance of panels coated with the hybrid primer of this invention, which has a higher NCO to OH equivalent weight ratio, in terms of degradation resistance was evaluated by exposing them to a humidity chamber for 4 days. In terms of gloss 20 and DOI, the optical appearance of the panels was similar to those compared to those with conventional 2K polyurethane primers. Some samples also showed better gloss 20 and DOI after humidity testing. While again, it is undesirable to be bound by any particular theory or mechanism of action, this is believed to be attributable to the more stable structure produced by the hybrid primer of this invention.

[0075] Measurements of adhesion loss of the coating on the panel before and after exposure to the humidity chamber showed no significant difference in adhesion strength loss between the control primer and the hybrid primer of the present invention.

[0076] The corrosion resistance of various panels (conventional 2K polyurethane control primer and the hybrid primer of the present invention with different levels of organic solvents from 0% to 100%) was tested using a salt spray chamber test. No significant difference in corrosion magnitude was found between the control and the embodiments of the present invention. However, it was found that the amount of delamination in panels using the hybrid primer of the present invention increased with increasing amounts of organic solvents present.

[0077] The measurements of various characteristics were performed as follows:

[0078] Chemical resistance of primer - To test the chemical resistance of the primer, a panel coated with etched primer and base coat was rubbed with a hammer covered with three layers of fiber paper soaked in MEK solvent. According to ASTM D5402-19, the chemical resistance specification for the MEK test is more than 300 cycles without dissolution of the surface and no exposure of the steel surface.

[0079] Adhesion strength - The adhesion strength of the coating / film is evaluated according to ASTM D3359 by cross-cut test. The failure mode of the coating / film is also assessed based on observations of the coating / film peeled off from the tape and substrate. The test assesses the adhesion strength of each layer of coating / film by removing pressure-sensitive adhesive tape adhered to the cross-cut film.

[0080] Impact resistance - Evaluate the impact resistance of coatings / films applied to panels according to ASTM D5420. Data are repeated twice, and both the coated and uncoated sides are tested and recorded as direct impact strength and indirect impact strength.

[0081] Conical mandrel bending - The flexibility of the coating / film is evaluated by bending a tapered mandrel according to ASTM D522.

[0082] Stone impact resistance test- Membrane durability is measured according to GM 14729.

[0083] Optical appearance - The optical appearance of the coating / film is evaluated by gloss retention (20-degree gloss) and DOI retention (Wavescan).

[0084] Humidity chamber - Following GM 14729, the panel with edges was placed in a humidity chamber at approximately 30°C for 4 days. After removing the panel from the chamber, it was dried with fiber paper and exposed to room temperature for 1 hour and 24 hours. The coating / film was then measured to determine gloss (20 degrees), DOI, and grid.

[0085] Salt spray chamber - According to ASTM B117, panels with edge-painted surfaces and a central scratch are placed in a salt spray chamber at approximately 30°C for 20 days. The panels are washed with hot water, and any loose coating / film is removed with a metal scraper after removal from the chamber. The size of the delamination and the area of ​​corrosion are measured, and the average of ten measurement points is taken.

[0086] One embodiment of applying the hybrid primer of the present invention involves spraying a solution of the hybrid epoxy-polyurethane waterborne primer of the present invention onto a cold-rolled steel substrate, with or without the application of an etching primer. After drying overnight at room temperature (23°C) and normal humidity (~50%), the resulting coating is sanded using 400# and 600# sandpaper, respectively. Finally, an acrylic base coat and a clear coat are sprayed onto the film and dried at room temperature.

[0087] Hybrid epoxy-polyurethane waterborne primers of some embodiments of the present invention can be prepared by any desired method in which the epoxy resin and polyurethane dispersion become a crosslinked network, including but not limited to: blending the epoxy resin, polyurethane dispersion and isocyanate-containing compound in an aqueous medium at a temperature and time sufficient to cause a reaction between the epoxy resin, polyurethane dispersion and isocyanate-containing compound to form a crosslinked network.

[0088] In one method of preparing the hybrid primer of the present invention, an epoxy waterborne primer optionally comprising one or more solvents, additives, pigments, or corrosion inhibitors is prepared by: combining optional components and mixing to achieve complete dispersion, such as, for example, by stirring with a dispersion disc for one hour, then adding an epoxy latex to the mixture, and subsequently cooling the resulting composition to room temperature. A polyurethane dispersion or latex is prepared by: combining one or more optional solvents, additives, pigments, and corrosion inhibitors (as needed), and preferably mixing the resulting composition using a dispersion disc. After mixing, a polyurethane dispersion is added, and the resulting mixture is stirred and cooled.

[0089] The resulting epoxy waterborne primer and polyurethane dispersion are combined with an isocyanate-containing compound, optionally with one or more pigments, solvents and additives, and the resulting composition is further stirred to allow for reaction between the epoxy resin, polyurethane and isocyanate-containing compound to provide a crosslinked network of the hybrid primer of the embodiments of the present invention.

[0090] While the embodiments discussed herein involve the hybrid waterborne primers discussed above, these embodiments are intended to be illustrative only and are not intended to limit the applicability of these embodiments to those discussed only herein.

[0091] The above description illustrates only several possible embodiments of various aspects of the invention, and equivalent changes and / or modifications will occur to those skilled in the art upon reading and understanding this specification and the accompanying drawings. Furthermore, while a particular feature of the invention has been disclosed with respect to only one of several embodiments, this feature may be combined with one or more other features of other embodiments, as may be desired and advantageous for any given or particular application.

[0092] The following are some non-limiting examples of embodiments of the present invention:

[0093] Implementation Scheme 1. A hybrid primer comprising a cross-linked polymer network formed of an epoxy resin, a polyurethane dispersion and an isocyanate-containing compound.

[0094] Implementation Scheme 2. The hybrid primer according to Implementation Scheme 1, wherein the polyurethane dispersion comprises hydroxyl and carboxyl functional groups that react with one or both of the isocyanate-containing compound and the epoxy resin.

[0095] Implementation Scheme 3. A hybrid primer according to any one of Implementation Scheme 1 or 2, wherein the polyurethane dispersion comprises a polyurethane formed from one of an aliphatic diisocyanate or an aromatic diisocyanate, one or more diols or polyols, a catalyst, and optionally one or more additives selected from the group consisting of chain extenders and crosslinking agents.

[0096] Implementation Scheme 4. A hybrid primer according to any one of Implementation Schemes 1 to 3, wherein the epoxy resin is formed from units derived from epichlorohydrin and one or more bisphenol compounds.

[0097] Implementation Scheme 5. The hybrid primer according to Implementation Scheme 4, wherein the one or more bisphenol compounds are selected from the group consisting of bisphenol A, bisphenol B, bisphenol E, bisphenol F and bisphenol AF.

[0098] Implementation Scheme 6. A hybrid primer according to any one of Implementation Schemes 1 to 5, wherein the isocyanate-containing compound is an aliphatic isocyanate-containing compound or an aromatic isocyanate-containing compound, either of which can be blocked or unblocked.

[0099] Implementation Scheme 7. A hybrid primer according to any one of Implementation Schemes 1 to 6, wherein the isocyanate-containing compound is a water-dispersible aromatic or aliphatic polyisocyanate.

[0100] Implementation Scheme 8. A hybrid primer according to any one of Implementation Schemes 1 to 6, wherein the isocyanate-containing compound is selected from the group consisting of hexamethylene diisocyanate (HDI), isophorone diisocyanate (IPDI), 4,4'-diisocyanate dicyclohexylmethane (HMDI), tetramethylxylenylidene diisocyanate (TMXDI), and their blocked derivatives.

[0101] Implementation Scheme 9. A water-based hybrid primer composition comprising a hybrid primer according to any one of Implementation Schemes 1 to 8 in an aqueous medium.

[0102] Implementation Scheme 10. A method for preparing a hybrid primer according to any one of Implementation Schemes 1 to 8, the method comprising:

[0103] The epoxy resin, the polyurethane dispersion, and the isocyanate-containing compound are blended in an aqueous medium at a temperature and time sufficient to induce a reaction between the epoxy resin, the polyurethane dispersion, and the isocyanate-containing compound to form the crosslinked network.

[0104] Based on the foregoing teachings, additional modifications and variations of the invention are possible. Therefore, it should be understood that, within the scope of the appended claims, the invention can be practiced in ways other than those specifically described herein.

Claims

1. A hybrid primer comprising a cross-linked polymer network formed of an epoxy resin, a polyurethane dispersion, and an isocyanate-containing compound.

2. The hybrid primer according to claim 1, wherein the polyurethane dispersion comprises hydroxyl and carboxyl functional groups that react with one or both of the isocyanate-containing compound and the epoxy resin.

3. The hybrid primer according to claim 1, wherein the polyurethane dispersion comprises a polyurethane formed from one of an aliphatic diisocyanate or an aromatic diisocyanate, one or more diols or polyols, a catalyst, and optionally one or more additives selected from the group consisting of chain extenders and crosslinking agents.

4. The hybrid primer according to claim 1, wherein the epoxy resin is formed from units derived from epichlorohydrin and one or more bisphenol compounds.

5. The hybrid primer according to claim 4, wherein the one or more bisphenol compounds are selected from the group consisting of bisphenol A, bisphenol B, bisphenol E, bisphenol F and bisphenol AF.

6. The hybrid primer according to claim 1, wherein the isocyanate-containing compound is an aliphatic isocyanate-containing compound or an aromatic isocyanate-containing compound, either of which can be blocked or unblocked.

7. The hybrid primer according to claim 1, wherein the isocyanate-containing compound is a water-dispersible aromatic or aliphatic polyisocyanate.

8. The hybrid primer according to claim 1, wherein the isocyanate-containing compound is selected from the group consisting of hexamethylene diisocyanate (HDI), isophorone diisocyanate (IPDI), 4,4'-diisocyanate dicyclohexylmethane (HMDI), tetramethylxylenyl diisocyanate (TMXDI), and their blocked derivatives.

9. A water-based hybrid primer composition, said water-based hybrid primer composition comprising, in an aqueous medium, the hybrid primer according to claim 1.

10. A method for preparing the hybrid primer according to claim 1, the method comprising: The epoxy resin, the polyurethane dispersion, and the isocyanate-containing compound are blended in an aqueous medium at a temperature and time sufficient to induce a reaction between the epoxy resin, the polyurethane dispersion, and the isocyanate-containing compound to form the crosslinked network.

11. The method of claim 10, wherein the polyurethane dispersion comprises hydroxyl and carboxyl functional groups that react with one or both of the isocyanate-containing compound and the epoxy resin.

12. The method of claim 10, wherein the polyurethane dispersion comprises a polyurethane formed from one of an aliphatic or aromatic diisocyanate, one or more diols or polyols, a catalyst, and optionally one or more additives selected from the group consisting of chain extenders and crosslinking agents.

13. The method of claim 10, wherein the epoxy resin is formed from units derived from epichlorohydrin and one or more bisphenol compounds.

14. The method of claim 13, wherein the one or more bisphenol compounds are selected from the group consisting of bisphenol A, bisphenol B, bisphenol E, bisphenol F and bisphenol AF.

15. The method of claim 10, wherein the isocyanate-containing compound is an aliphatic isocyanate-containing compound or an aromatic isocyanate-containing compound, either of which may be blocked or unblocked.

16. The method of claim 10, wherein the isocyanate-containing compound is a water-dispersible aromatic or aliphatic polyisocyanate.

17. The method of claim 10, wherein the isocyanate-containing compound is selected from the group consisting of hexamethylene diisocyanate (HDI), isophorone diisocyanate (IPDI), 4,4'-diisocyanate dicyclohexylmethane (HMDI), tetramethylxylenyl diisocyanate (TMXDI), and their blocked derivatives.

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