UV curable putty composition for covering, filling and repairing substrate defects

Abstract

Provided are a radiation-curable putty composition and a method for repairing substrate defects using the composition. The radiation-curable putty composition comprises about 6-50 wt % of a UV-curable oligomer, about 4-25 wt % of a non-reactive oligomer, about 5-30 wt % of a UV-reactive monomer, an extender, about 3-10 wt % of fumed silica, a polyhydroxycarboxylic acid amide, and about 3-6 wt % of a photoinitiator, wherein the photoinitiator comprises a surface-curing photoinitiator and a fully-curing photoinitiator and wherein the putty composition has a solid content of about 99 wt % or more.

Description

Field of the Invention

[0001] The present invention relates to a putty composition for covering, filling and repairing gaps and defects of a substrate and a method for applying the putty composition to a substrate. The composition has improved dimensional stability and good workability and filling performance. The present invention also relates to a method for filling gaps and defects of a substrate with the putty composition, the use of the putty composition and a substrate treated with the putty composition. Background of the Invention

[0003] Fillers, such as render compositions and thick lacquers, are commonly used in the wood industry, particularly in the construction and furniture industries, to repair defects, damages or imperfections in wooden substrates such as holes, cracks, knots, scratches or scrapes, where, for example, drilling has been necessary during the manufacturing process, etc. Some of the challenges faced when applying fillers to substrates include shrinkage, difficulty in application, improper adhesion and incomplete curing.

[0004] Fillers all shrink to some extent. When the putty composition is cured, it often shrinks, thereby affecting the filling level and subsequently affecting the structural integrity and aesthetics of the wood substrate. Shrinkage may require additional processing steps, thereby reducing process efficiency.

[0005] Ease of application is also important when utilizing fillers. The filler should fill well even when applied quickly in an automated industrial production line.

[0006] Incomplete curing is another challenge encountered when applying render compositions, especially to defects in wood substrates having higher depth profiles.

[0007] The cured render composition should also provide good adhesion since it is typically coated with other layers of material such as primers, enamels, clearcoats, etc. It is beneficial for subsequent coatings to adhere properly to the cured render composition so that there is no flaking, cracking and the integrity and aesthetics of the final coated substrate is not affected.

[0008] Monomers are commonly used in putties to improve the sandability and viscosity of the composition. However, it has been observed that monomers also cause the putty to shrink upon curing. Therefore, there is a need for a putty that exhibits improved dimensional stability while maintaining acceptable sandability and viscosity for application to wood substrates.

[0009] Overview

[0010] The inventors surprisingly found that the combination of 99 wt% or greater solids content, low monomer weight percentage, and a combination including waxes (e.g., amides) and silica still allows good workability while maintaining better dimensional stability / less shrinkage. These improved properties make the putty better for repairing wood defects. The inventors also surprisingly found that including a non-UV curable component in the putty composition unexpectedly improves the adhesion of the cured putty composition, so that subsequent coatings can better adhere to the putty composition. This can eliminate the need for sanding the putty composition before applying subsequent coatings on it.

[0011] In addition, including a surface curing photoinitiator and a full curing photoinitiator improves the overall cure of the coating, especially when filling deeper voids in wood substrates. Improved cure is achieved using only one type of cure using ultraviolet (UV) light. The inventors surprisingly found that using a blend of a surface curing photoinitiator and a full curing photoinitiator in a weight ratio of 5:1-10:1 resulted in improved cure of the putty composition.

[0012] The putty composition of the present disclosure works particularly well when applied in an automated industrial production line, allowing for a faster, more cost-effective application. It has excellent filling properties when applied on an automated coating machine as opposed to manual application. After application, the cured material has excellent dimensional stability, sandability, and recoatability. Due to the improved recoatability, the putty composition can improve production efficiency by allowing the applicator to forgo the primer application step.

[0013] The inventors have discovered a novel putty composition, which, after curing, produces a putty coating having significantly improved dimensional stability, workability, filling property, recoatability and curing compared to known putty coatings.

[0014] The present invention relates in a first aspect to a putty composition comprising about 6-50 wt % of a UV-curable oligomer, about 4-25 wt % of a non-reactive oligomer, about 5-30 wt % of a UV-reactive monomer, an extender, about 3-10 wt % of fumed silica, a polyhydroxycarboxylic acid amide and about 3-6 wt % of a photoinitiator, wherein the photoinitiator comprises a surface-curing photoinitiator and a fully-curing photoinitiator and wherein the putty composition has a solid content of about 99 wt % or greater.

[0015] In an exemplary embodiment, the weight ratio of the surface curing photoinitiator to the full curing photoinitiator is 5: 1 to 10: 1. In another embodiment, the surface curing photoinitiator may include cyclohexyl phenyl ketone and / or the full curing photoinitiator may include benzoylphosphine oxide.

[0016] In another exemplary embodiment, the UV curable oligomer of the putty composition is selected from aliphatic or aromatic urethanes, epoxy or polyester acrylates and mixtures thereof. In another embodiment, the UV curable oligomer has an acrylate functionality equal to or greater than 2. In some embodiments, the UV oligomer has 3-4 reactive groups.

[0017] In another exemplary embodiment, the UV reactive monomer is selected from trimethylolpropane triacrylate (TMPTA), neopentyl glycol diacrylate (NPGDA), dipropylene glycol diacrylate (DPGDA), tripropylene glycol diacrylate (TRPDGA), trimethylolpropane triacrylate (TMPTA), trimethylolpropane trimethacrylate (TMPTMA), pentaerythritol triacrylate (PETA) and mixtures thereof. In another embodiment, the monomer has a functionality of 2-4.

[0018] In another embodiment, the extender is selected from the group consisting of talc, gypsum, calcium carbonate, wollastonite, barium sulfate, and mixtures thereof. In additional embodiments, the extender is present in an amount of about 5-30 wt % based on the weight of the putty composition.

[0019] In another embodiment, the weight ratio of polyhydroxycarboxamide to fumed silica is from 1:10 to 1:4.

[0020] Another aspect of the present invention provides a method for repairing defects or flaws in a substrate, comprising the steps of: a) providing the substrate, b) applying a putty composition according to the first aspect of the present invention to the substrate and c) curing the putty composition with UV radiation. The method may further comprise the steps of: d) applying a primer on the substrate and e) applying an enamel on the primed substrate. In another embodiment, the method may further comprise sanding the substrate after curing step c) and before step d).

[0021] Another aspect of the present invention provides a substrate fully or partially coated with the putty composition according to the first aspect of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] A complete understanding of the invention can be obtained from the following description of certain embodiments of the invention when read in conjunction with the accompanying drawings, in which:

[0024] Figure 1 The output images of each step of the coating process described in Example 1. DETAILED DESCRIPTION OF THE INVENTION

[0026] The following description of the preferred embodiment is merely exemplary in nature and is in no way intended to limit the invention, its application, or uses.

[0027] Unless expressly stated otherwise, all numbers used herein, such as those expressing values, ranges, amounts or percentages, may be read as if preceded by the word "about", even if this term does not expressly appear.

[0028] As used herein, the singular forms "a", "an", and "the" include plural references unless the context clearly dictates otherwise. For example, although "a" peeling layer, "a" support platform, "an" overflow nozzle are mentioned herein, combinations of (a plurality of) these components may be used in the present invention.

[0029] As used herein, "plurality" means two or more.

[0030] As used herein, the terms "comprising" and "consisting of" are synonymous with "including" or "containing" and are inclusive or open-ended and do not exclude additional unrecited members, elements, or method steps. If used, the phrase "consisting of is closed and excludes all additional elements. Furthermore, the phrase "consisting essentially of excludes additional material elements but allows for the inclusion of non-material elements that do not significantly change the nature of the invention.

[0031] When any numerical range is mentioned, such range should be understood to include every number and / or fraction between the minimum and maximum values ​​of the range. For example, the range of "1-10" is intended to include all sub-ranges between (and including) the minimum value of 1 and the maximum value of 10, i.e., having a minimum value equal to or greater than 1 and a maximum value equal to or less than 10. When expressing amounts, concentrations, sizes and other parameters in the form of ranges, preferred ranges, upper limits, lower limits or preferred upper and lower limits, it should be understood that any range that can be obtained by combining any upper limit or preferred value with any lower limit or preferred value is also specifically disclosed, regardless of whether the resulting range is clearly mentioned in the context.

[0032] The terms "preferred", "preferably", "desirably", and "particularly" and their synonyms are generally used herein to refer to embodiments of the present invention that may provide particular benefits under certain circumstances. However, the listing of one or more preferred, desirable or particular embodiments does not mean that other embodiments are not useful and is not intended to exclude those other embodiments from the scope of the present invention.

[0033] As used herein, "putty" refers to a very thick, viscous, dough-like liquid material that hardens after curing and can be used to fill and repair substrate imperfections.

[0034] The term "UV" as applied to radiation curable resins and coating compositions is intended to mean ultraviolet (UV).

[0035] As used herein, "oligomer" refers to a polymer having a molecular weight of 500 or greater.

[0036] As used herein, "non-reactive oligomer" refers to an oligomer that does not have UV reactive groups.

[0037] As used herein, the term "substrate" refers to the parent material or base material to which the coating is applied. For example, the substrate may include solid wood, wood composites (including without limitation plywood, medium density fiberboard (MDF), and wood flour-containing composites), fiberglass-thermoset composites, PVC, plastics, and other non-cellulose substrates.

[0038] As used herein, "curing" and like terms refer to the process of hardening or drying a material to form a coating on a substrate.

[0039] All percentages, ratios and proportions used herein are given on a weight basis unless otherwise specified.

[0040] The present invention relates to a radiation curable putty composition for covering, filling and repairing wood defects in a production environment as a preparatory step before finishing the wood. It was surprisingly found that reducing the amount of monomer in the putty composition and including a combination of wax and silica allows good workability while reducing shrinkage. It was also surprisingly found that including a non-reactive oligomer in the putty composition improves adhesion. The inventors also surprisingly found that including both a surface curing photoinitiator and a full curing photoinitiator resulted in a more thoroughly and evenly cured putty composition.

[0041] The radiation curable putty composition according to one aspect of the present invention may comprise:

[0042] about 6-50 wt. % UV-curable oligomer;

[0043] about 4-25 wt. % non-reactive oligomers;

[0044] about 5-30 wt % UV reactive monomer;

[0045] Bulking agent;

[0046] about 3-10 wt. % fumed silica;

[0047] Polyhydroxycarboxylic acid amides; and

[0048] about 3-6 wt % of a photoinitiator, the photoinitiator comprising a surface curing photoinitiator and a full curing photoinitiator; and

[0049] The putty composition has a solid content of 99 wt % or more.

[0050] The UV curable oligomer of the putty composition may include aliphatic or aromatic urethane, epoxy or polyester acrylate. In certain embodiments, the UV curable oligomer may be modified bisphenol A epoxy diacrylate, amine modified polyether acrylate, aliphatic epoxy modified acrylate oligomer, aliphatic polyester urethane diacrylate oligomer and mixtures thereof. The UV curable oligomer has UV reactive groups. The functionality of the UV curable oligomer is equal to or greater than 2. In some embodiments, the UV curable oligomer has 3-4 reactive groups. If the functionality of the UV curable oligomer is too high, the putty composition may become too brittle.

[0051] The putty composition may include about 6-50 weight % of the UV curable oligomer based on the weight of the putty composition. In another embodiment, the putty composition includes about 6-40 weight % of the UV curable oligomer. In yet another embodiment, the putty composition includes about 20-40 weight % of the UV curable oligomer. In another embodiment, the putty composition includes about 10 weight % of the UV curable oligomer based on the weight of the putty composition.

[0052] The putty composition of the present invention further comprises a non-reactive oligomer. The non-reactive oligomer may be an acrylic resin, a vinyl resin, a nitrocellulose resin or a mixture thereof. The non-reactive oligomer should provide a non-stick film before UV curing.

[0053] The putty composition may include about 4-25 weight % of non-reactive oligomers based on the weight of the putty composition. In another embodiment, the putty composition may include about 12-20 weight % of non-reactive oligomers based on the weight of the putty composition. Non-reactive oligomers affect the adhesive properties of the putty composition. The inventors found that if the amount of non-reactive oligomers is too low, the coating applied on the cured putty composition cannot adhere well to the surface of the cured putty composition. It was also found that if the amount of non-reactive oligomers is too high, the putty composition becomes too sticky and cannot be handled.

[0054] The putty composition comprises a monomer. The monomer has an acrylate backbone that makes it UV reactive. The monomer may be 1,6-hexanediol diacrylate (HDDA), tripropylene glycol diacrylate (TPGDA), dipropylene glycol diacrylate (DPGDA), tripropylene glycol diacrylate (TRPDGA), trimethylolpropane triacrylate (TMPTA), trimethylolpropane trimethacrylate (TMPTMA) or pentaerythritol triacrylate (PETA) and mixtures thereof. The monomer has a functionality of 2-4. The putty composition may comprise a monomer greater than about 5% by weight and up to about 30% by weight based on the weight of the putty composition.

[0055] In one embodiment, a blend of UV reactive monomers and non-reactive oligomers may be used, such as an acrylic polymer diluted at about 50 wt % with a 1 / 1 weight ratio of reactive diluents 1,6-hexanediol diacrylate (HDDA) and tripropylene glycol diacrylate (TPGDA).

[0056] The putty composition of the present invention also includes an extender. The extender can be a mineral or other inorganic extender, such as talc, calcium carbonate, wollastonite, barium sulfate, calcium carbonate, other similar materials and mixtures thereof. In some embodiments, the extender is present in an amount of about 5-30 weight % based on the weight of the putty composition. In other embodiments, the extender is present in an amount of about 5-20 weight % or about 5-10 weight % based on the weight of the putty composition. For indoor applications, higher extender dosages improve the sanding properties of the cured putty composition. For outdoor applications, lower extender dosages improve the weathering resistance of the cured putty composition.

[0057] The putty composition of the present invention further comprises polyhydroxycarboxylic acid amide.

[0058] The putty composition of the present invention also contains fumed silica. This component is used to control viscosity. Fumed silica is also known as pyrogenic silica because it is produced in a flame. Fumed silica is present in an amount of about 3-10% by weight based on the weight of the putty composition.

[0059] In some embodiments, the polyhydroxycarboxylic acid amide is present in an amount of about 10-25% by weight based on the fumed silica weight content. In other embodiments, the polyhydroxycarboxylic acid amide is present in an amount of about 15-20% by weight based on the fumed silica content. The inventors have found that maintaining the ratio of polyhydroxycarboxylic acid amide to fumed silica within this range keeps the viscosity at an ideal level for easy application.

[0060] The putty composition of the present invention comprises a surface curing photoinitiator and a full curing photoinitiator. In some embodiments, these two types of photoinitiators can be used as a blend. The blend of photoinitiators can be present in an amount of about 3-6 weight % based on the weight of the putty composition. The blend can include a weight ratio of the surface curing photoinitiator to the full curing photoinitiator in the range of about 10:1-5:1.

[0061] The surface curing photoinitiator may belong to the class of cyclohexyl phenyl ketones. For example, the surface curing photoinitiator may be 1-hydroxycyclohexyl phenyl ketone, such as cyclohexyl phenyl ketone available from IGM. 184 photoinitiator. In another embodiment, the surface curing photoinitiator can be 2-hydroxy-2-methylpropiophenone such as 1173 or methyl phenylglyoxylate such as MBF were purchased from IGM.

[0062] The full-cure photoinitiator may belong to the class of benzoylphosphine oxides. For example, the full-cure photoinitiator may be bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide, such as available from IGM 819. In another embodiment, the full cure photoinitiator can be diphenyl (2,4,6-trimethylbenzoyl) phosphine oxide available from IGM.

[0063] The combination of surface cure and full cure photoinitiator results in a more thorough cure, which is particularly beneficial when the applied putty composition has a greater depth profile, such as when filling deep surface defects in wood substrates. In some embodiments, the cured putty compositions of the present disclosure achieve a degree of cure of greater than 99%.

[0064] The putty composition of the present invention may further comprise additives such as defoamers or deaerators, dispersants and / or wetting agents known to those skilled in the art.

[0065] Methods and Administration

[0066] The putty composition of the present disclosure can be applied to solid wood, wood composites (including without limitation plywood, medium density fiberboard (MDF) and wood powder-containing composites), fiberglass-thermosetting composites, PVC, plastics and other non-cellulose substrates. It can be used on substrates for windows, flooring and outdoor molding applications. The putty composition can be applied to a tie coat to improve the adhesion of the putty composition to the substrate.

[0067] In certain aspects, the putty compositions of the present disclosure have a remarkably thick and smooth consistency, which allows them to be applied to complex shaped wooden surfaces using a negative mold.

[0068] The putty composition can be applied at a rate of less than 75 grams per square meter. The putty composition can also be applied at a rate of about 20-30 grams per square meter. The putty composition can be applied using UV plaster equipment.

[0069] The putty composition can be cured using a UV processor. The curing process can be done using a mercury or gallium UV arc lamp. The energy requirement is 350-450 mj / cm 2 The cured putty composition can be recoated with conventional waterborne styrene-acrylic latex, waterborne polyurethane or polyvinyl alcohol based coatings, primers and enamels.

[0070] The putty composition, when cured, can be applied without additional surface preparation or if sanding is required, the cured paste has excellent sanding characteristics.

[0071] The following examples illustrate the present invention and are not intended to limit the scope of the invention in any way. In view of the present disclosure, those skilled in the art should appreciate that many changes can be made to the specific embodiments disclosed without departing from the scope of the invention and still obtain similar or similar results. Example

[0072] The following list shows some of the raw materials and ingredients used in the following examples. Alternative materials or suppliers may be substituted as would be appreciated by one skilled in the art.

[0073] Table 1

[0074]

[0075]

[0076] Example 1 (the present invention—indoor application)

[0077] The formulations shown in Example 1 in Table 2 below are thoroughly blended, carefully grinding all inorganics into the resin matrix so that they are fully wetted and incorporated using conventional methods in the art. The material is loaded into the slot of a dedicated automated plaster machine for application. A die suitable for the profile to be coated (in this case, a rectangular profile) is selected and the machine is run. The setting on the machine is 150-220fpm, the UV curing power is 350-450MJ and the residence time is 1-2 seconds. Approximately 35-55 grams per square meter of the putty composition is applied to a board 12 inches wide by 16 inches long by 1 inch thick and having at least one visible seam.

[0078] After curing, the section was lightly sanded with a 220-320 sanding belt and a styrene-acrylic latex primer was applied at a rate of 100-120 g / m2. The material was dried for 30-40 seconds and then cured at 65°C for 120 seconds. A styrene-acrylic based waterborne enamel was then applied at a rate of 90-100 g / m2 (gsm), dried for 90 seconds and cured at 60°C for 180 seconds. Figure 1 The images in show the output of each step of the process.

[0079] Figure 1 The order in which the board specimens with visible seams were coated at each step of the process is shown, from left to right: 1) bare wood board, 2) board coated with the putty composition of Example 1, 3) board coated with the putty composition of Example 1 and primer, 4) board coated with the putty composition of Example 1, primer and enamel. Figure 1 It was shown that with a 100-120 gsm primer coat, the panel seams were no longer noticeable, indicating less shrinkage than is common. Shrinkage was determined visually.

[0080] Example 1 is a sandable putty composition for interior use, and therefore has a higher amount of calcium carbonate.

[0081] Table 2

[0082]

[0083] Example 2 (the present invention—outdoor application)

[0084] The formulation shown in Example 2 in Table 2 was thoroughly blended, carefully grinding all inorganics into the resin matrix to fully wet and incorporate them using conventional methods in the art. The material was loaded into the tank of a dedicated automated plaster machine (purchased from Stiles Machinery of Greensboro North Carolina) for application. A die suitable for the section to be coated (in this case a rectangular section) was selected and the machine was run. The settings on the machine were 100-200 fpm, UV curing power was 350-450 MJ and residence time was 1-2 seconds. Approximately 35-55 grams per square meter of putty was applied to a board 12 inches wide by 16 inches long by 1 inch thick and having at least one visible seam.

[0085] After curing, the section was lightly sanded with a 220-320 sanding belt and a styrene-acrylic latex primer was applied at a rate of 100-120 g / m2. The material was dried for 30-40 seconds and then cured at 65°C for 120 seconds. A styrene-acrylic based waterborne enamel was then applied at a rate of 90-100 g / m2, dried for 90 seconds and cured at 60°C for 180 seconds.

[0086] The joints of the panels coated with the putty composition of Example 2 were no longer noticeable, indicating less shrinkage than is common. Shrinkage was determined visually. Unlike Example 1, the exterior coating of Example 2 did not require sanding prior to application of subsequent coatings.

[0087] Table 3

[0088]

[0089] In the same manner as in Examples 1 and 2, putty compositions of Examples 3 to 5 below were prepared.

[0090] Example 3 (Comparative—without non-reactive acrylic oligomer)

[0091] The cured putty composition of Example 3 in Table 3 cannot be painted with a waterborne paint unless the putty composition is sanded prior to application of the waterborne paint (to allow for a mechanical bond between the putty and the paint).

[0092] Example 4 (Comparative—Non-Reactive Acrylic Oligomer Outside the Claimed Range)

[0093] The cured putty composition of Example 4 in Table 3 was too viscous after UV curing (probably due to the large amount of non-reactive acrylic oligomer) and could not be handled.

[0094] Example 5 (Comparative—One Photoinitiator Only)

[0095] The cured putty composition of Example 5 in Table 3 was physically dry when it came out of the UV light oven, but had no adhesion due to lack of full cure or excessive surface cure in portions with greater depth profiles or when the coating was applied heavily due to the size of the wood defects.

[0096] In view of the foregoing description and examples, it will be apparent to a person skilled in the art that equivalent modifications may be made thereto without departing from the scope of the claims.

Claims

1. A putty composition comprising: about 6-50 wt. % UV-curable oligomer; about 4-25 wt. % non-reactive oligomers; about 5-30 wt % UV reactive monomer; Bulking agent; about 3-10 wt. % fumed silica; Polyhydroxycarboxylic acid amides; and about 3-6 wt % of a photoinitiator, the photoinitiator comprising a surface curing photoinitiator and a full curing photoinitiator; and wherein the putty composition has a solid content of about 99 wt % or greater, The non-reactive oligomer is acrylic resin, vinyl resin, nitrocellulose resin and a mixture thereof.

2. The putty composition of claim 1, wherein the weight ratio of the surface curing photoinitiator to the full curing photoinitiator is about 5:1-10:

1.

3. The putty composition of claim 1 or 2, wherein the surface curing photoinitiator comprises cyclohexyl phenyl ketone and the full curing photoinitiator comprises benzoyl phosphine oxide.

4. The putty composition according to any one of the preceding claims, wherein the UV curable oligomer is selected from aliphatic or aromatic urethanes, epoxy or polyester acrylates and mixtures thereof.

5. The putty composition according to any one of the preceding claims, wherein the UV curable oligomer has a functionality equal to or greater than 2.

6. The putty composition according to any one of the preceding claims, wherein the monomer is selected from trimethylolpropane triacrylate (TMPTA), neopentyl glycol diacrylate (NPGDA), dipropylene glycol diacrylate (DPGDA), tripropylene glycol diacrylate (TRPDGA), trimethylolpropane triacrylate (TMPTA), trimethylolpropane trimethacrylate (TMPTMA), pentaerythritol triacrylate (PETA) and mixtures thereof.

7. The putty composition according to any one of the preceding claims, wherein the UV reactive monomer has a functionality of 2-4.

8. A putty composition according to any one of the preceding claims, wherein the extender is selected from the group consisting of talc, gypsum, calcium carbonate, wollastonite, barium sulfate and mixtures thereof.

9. The putty composition according to any one of the preceding claims, wherein the extender is present in an amount of about 5-30 wt % based on the weight of the putty composition.

10. The putty composition according to any one of the preceding claims, wherein the weight ratio of polyhydroxycarboxylic acid amide to fumed silica is 1:10 to 1:

4.

11. Methods for repairing substrate defects, including: a) providing the substrate; b) applying a putty composition according to any one of the preceding claims to the substrate; and c) curing the putty composition with UV radiation.

12. The method of claim 11, further comprising: d) applying a primer to the substrate, and e) applying an enamel paint on the primed substrate.

13. The method of claim 12, further comprising sanding the substrate after curing step c) and before step d).

14. A substrate fully or partially coated with a putty composition according to any one of claims 1 to 10.

Images