Patent Application
20200024475
The present invention relates to coating compositions for coating a variety of substrates. In particular, the present invention relates to a coating composition that provides an abrasion resistant coating, such as for a hardcoat formulation.
Polymeric materials, particularly thermoplastics such as polycarbonate, are promising alternatives to glass for use as a structural material in a variety of applications, including automotive, transportation, and architectural glazing applications, where increased design freedom, weight savings, and improved safety features are in high demand. Plain polycarbonate substrates, however, are limited by their lack of abrasion, chemical, ultraviolet (UV), and weather resistance, and, therefore, need to be protected with optically transparent coatings that alleviate above limitations in the aforementioned applications.
Silicone hardcoats have been traditionally used to improve the abrasion resistance and UV resistance of various polymers including polycarbonate and acrylics. This enables the use of polycarbonates in a wide range of applications, including architectural glazing and automotive parts such as headlights.
The addition of a thermally curable silicone hardcoat generally imparts abrasion resistance to the polymeric substrate. The addition of organic or inorganic UV-absorbing materials in the silicone hardcoat layer can improve the weatherability of the polymeric substrate. However, over prolonged outdoor exposure, micro cracks start to form and coating failure occurs. Crack formation is an undesirable phenomena and it limits the coating's durability to protect the underlying substrate. There is a need to develop hard coats that provide improved abrasion and weathering performance to plastic substrates with improved crack resistance. There were different ways crack resistance in a coating has been sought to be improved. U.S. Pat. No. 7,857,905 describes a flexible thermal cure silicone hardcoat that is allegedly obtained with improved crack resistance. Others have described improving crack resistance by controlling thickness of coating, molecular weight of resin, crosslinking density, and thermal expansion coefficient (U.S. Publication No. 2012/0058347); controlling concentration of metal oxide particles (U.S. Publication No. 2013/0164539); or controlling the UV absorber, concentration of catalysts, and ratio of hydrolysable silyl groups in a coating (U.S. Publication No. 2007/0219298). U.S. Pat. No. 8,603,587 describes coating compositions with highly scratch-resistant coatings featuring high hardness in conjunction with very good weathering stability and crack resistance, even at coat thicknesses>40 um using different silane.
Provided herein is a coating composition suitable for forming a silicone hardcoat. The composition comprises a mixture of silanes as the base for forming the siloxanol resin. The combination of a component A with a component B as described herein provides a coating with good optical properties, adhesion, abrasion resistance, weatherability, and/or crack resistance as evaluated and understood with respect to various accepted test methods including, but not limited to, adhesion after water immersion, critical strain, abrasion, microindentation testing, etc.
In one aspect, provided is a composition comprising:
Component A of the formula (R1)dSi(OR2)4−d, wherein R1 is a C1-C3 monovalent hydrocarbon, R2 is a C1-C3 monovalent hydrocarbon or a hydrogen radical and d is 0, 1, or 2, and
Component B, is selected from the group consisting of Formula 1, Formula 2, or a combination thereof:
(R3)aSi(OR4)4−a Formula 1
(R5O)m(R6)nSi(R9)x(R10)y(R11)zSi(R8)s(OR7)p Formula 2
wherein R3 is chosen from a C5-C20 linear or branched alkyl radical, a C5-C20 fluoroalkyl, a mixture of hydrocarbon and fluorocarbon chain, C5-C20 linear or branched hydrocarbon chain containing thioester group, C6-C24 saturated or unsaturated linear or cyclic hydrocarbon chain containing amino group or urea group, R4 is C1-C20 monovalent hydrocarbon radical or a hydrogen radical; a is 0, 1 to 3;
R5 and R7 are independently chosen from a C1-C20 monovalent hydrocarbon radical or a hydrogen radical;
R6 and R8 are independently selected from a C1 to C3 monovalent hydrocarbon radical or a hydrogen radical; m and p are 1 to 3; n and s are 1 to 3 such that m+n is 3, and s+p is 3;
R9 is chosen from a C1-C24 divalent hydrocarbon radical;
R10 and R11 are independently chosen from C1 to C24 monovalent hydrocarbon radical;
x is 1 to 20, y is 0 to 20, and z is 0 to 20;
metal oxide particles;
UV absorber;
a catalyst; and
a solvent.
In one embodiment, component B is present in an amount of about 1 weight percent to about 60 weight percent based on the total weight of the component A and the component B.
The composition of any previous embodiment, wherein R3 of component B is chosen from pentyl, hexyl, heptyl, octyl, nonyl decyl, dodecyl, 3,3,3-triflurorpentyl, 3,3,3-triflurorhexyl, 3,3,3-trifluroheptyl, 3,3,3-triflurooctly, perfluoropentyl, pefluorohexyl, pefluoroheptyl, or perfluorohexyl.
The composition of any previous embodiment, wherein R4 is selected from methyl and ethyl.
The composition of any previous embodiment, wherein component B is chosen from a silane of Formula 2 having the formula 2a: (R5O)m(R6)nSi—Z—Si(R8)s(OR7)p 2a where Z is a C1-C24 bivalent hydrocarbon radical.
In one embodiment, the bivalent hydrocarbon radical Z is of the formula —R21—R23—R22— where R21 and R22 are independently C1-C6 bivalent hydrocarbon groups, and R23 is a C5-C10 bivalent cyclic group, which may be saturated, unsaturated, or aromatic.
The composition of any previous embodiment, wherein the component A is methyltrimethoxy silane.
The composition of any previous embodiment, wherein the metal oxide particles are present in an amount of from about 0.1 weight percent to about 50 weight percent. In one embodiment, the metal oxide particles are present in an amount of from about 0.5 weight percent to about 30 weight percent. In one embodiment, the metal oxide particles are present in an amount of from about 1 weight percent to about 20 weight percent based on the total weight of the composition.
The composition of any previous embodiment, wherein the metal oxide particles chosen from silica, zirconia, titania, alumina, ceria, tin oxide, zinc oxide, antimony oxide, or a combination of two or more thereof.
The composition of any previous embodiment, wherein the metal oxide particles have an average particle size of from about 1 nm to about 250 nm.
The composition of any previous embodiment, further comprising additives selected from an antioxidant, a thermal stabilizer, an adhesion promoter, filler, UV absorber, surfactant or a combination of two or more thereof.
The composition of any previous embodiment, wherein the solvent is chosen from an aliphatic alcohol, a glycol ether, a cycloaliphatic alcohol, an aliphatic ester, a cycloaliphatic ester, an aliphatic hydrocarbon, a cycloaliphatic hydrocarbon, an aromatic hydrocarbon, a halogenated aliphatic compound, a halogenated cycloaliphatic compound, a halogenated aromatic compound, an aliphatic ether, a cycloaliphatic ether, an amide solvents, a sulfoxide solvent, or a combination of two or more thereof.
The composition of any previous embodiment, wherein the catalyst is at least one member selected from the group consisting of tetra-n-butylammonium acetate, tetra-n-butylammonium formate, tetra-n-butylammonium benzoate, tetra-n-butylammonium-2-ethylhexanoate, tetra-n-butylammonium-p-ethylbenzoate, tetra-n-butylammonium propionate, and TBD-acetate (acetate of 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD)).
The composition of any previous embodiment, wherein the coating forming composition is applied to a substrate, said substrate selected from an acrylic polymer, a polyamide, a polyimide, an acrylonitrile-containing polymer, a polyvinyl halide, a polyolefin, a polycarbonate, or a copolycarbonate, a metal, a glass, or a combination of two or more thereof.
In another aspect, provided is an article comprising a substrate and a coating disposed on at least a portion of a surface of the substrate, wherein the coating is formed from a composition according to any previous embodiment.
In another aspect, provided is an article comprising a substrate and a coating composition covering at least a portion of said substrate, the coating composition comprising: Component A of the formula (R1)dSi(OR2)4−d, wherein R1 is a C1-C3 monovalent hydrocarbon, R2 is a C1-C3 monovalent hydrocarbon or a hydrogen radical and d is 0, 1, or 2, and
Component B is selected from the group consisting of Formula 1, Formula 2, or a combination thereof:
(R3)aSi(OR4)4−a Formula 1
(R5O)m(R6)nSi(R9)x(R10)y(R11)zSi(R8)s(OR7)p Formula 2
wherein R3 is chosen from a C5-C20 linear or branched alkyl radical, a C5-C20 fluoroalkyl, a mixture of hydrocarbon and fluorocarbon chain, C5-C20 linear or branched hydrocarbon chain containing thioester group, C6-C24 saturated or unsaturated linear or cyclic hydrocarbon chain containing amino group or urea group, R4 is C1-C20 monovalent hydrocarbon radical or a hydrogen radical; a is 0, 1 to 3;
R5 and R7 are independently chosen from a C1-C20 monovalent hydrocarbon radical or a hydrogen radical;
R6 and R8 are independently selected from a C1 to C3 monovalent hydrocarbon radical or a hydrogen radical; m and p are 1 to 3; n and s are 1 to 3 such that m+n is 3, and s+p is 3;
R9 is chosen from a C1-C24 divalent hydrocarbon radical;
R10 and R11 are independently chosen from C1 to C24 monovalent hydrocarbon radical;
x is 1 to 20, y is 0 to 20, and z is 0 to 20;
In one embodiment of the article, wherein component B is present in an amount of from about 1 weight percent to about 60 weight based on the total weight of the component A and the component B.
The article of any previous embodiment, wherein R3 is chosen from pentyl, hexyl, heptyl, octyl, nonyl decyl, dodecyl, 3,3,3-triflurorpentyl, 3,3,3-triflurorhexyl, 3,3,3-trifluroheptyl, 3,3,3-triflurooctyl, perfluoropentyl, pefluorohexyl, pefluoroheptyl, or perfluorohexyl.
The article of any previous embodiment, wherein R4 is selected from methyl and ethyl.
The article of any previous embodiment, wherein the component A is methyltrimethoxy silane.
The article of any previous embodiment, wherein the metal oxide particles are present in an amount of from about 0.1 weight percent to about 50 weight percent. In one embodiment, the metal oxide particles are present in an amount of from about 0.5 weight percent to about 30 weight percent. In one embodiment, the metal oxide particles are present in an amount of from about 1 weight percent to about 20 weight percent based on the total weight of the composition.
The article of any previous embodiment, wherein the metal oxide particles chosen from silica, zirconia, titania, alumina, ceria, tin oxide, zinc oxide, antimony oxide, or a combination of two or more thereof.
The article of any previous embodiment, wherein the metal oxide particles have an average particle size of from about 1 nm to about 250 nm.
The article of any previous embodiment, wherein the substrate is chosen from an acrylic polymer, a polyamide, a polyimide, an acrylonitrile-styrene copolymer, a styrene-acrylonitrile-butadiene terpolymer, a polyvinyl halide, a polyethylene, a polycarbonate, a copolycarbonate, a metal, a glass, or a combination of two or more thereof.
The article of any previous embodiment, wherein the coating composition is deposited on solid substrate by applying at least one coating deposition method selected from spray, dip, flow, spin.
The article of any previous embodiment, wherein the coating composition is cured. In one embodiment, optionally a primer coating is disposed between the coating composition and the substrate.
In still another aspect, provided is a method for forming an article with a coating. The method comprises applying a coating composition in accordance with any previous aspect or embodiment to a surface of a substrate.
In yet another aspect, provide is a method of forming a coating composition comprising mixing the materials employed in the composition of any previous aspect or embodiment.
These and other aspects and embodiments are further understood with respect to the drawings and detailed description.
The accompanying drawings illustrate various systems, apparatuses, devices and related methods, in which like reference characters refer to like parts throughout, and in which:
Reference will now be made to exemplary embodiments, examples of which are illustrated in the accompanying drawings. It is to be understood that other embodiments may be utilized and structural and functional changes may be made. Moreover, features of the various embodiments may be combined or altered. 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. In this disclosure, numerous specific details provide a thorough understanding of the subject disclosure. It should be understood that aspects of this disclosure may be practiced with other embodiments not necessarily including all aspects described herein, etc.
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 than 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.
Provided is a coating composition that may form a coating with one or more desirable properties including, but no limited to, optical properties, adhesion, abrasion resistance, weatherability, and/or crack resistance. The composition is a siloxanol based resin comprising a component A, a component B, metal oxide particles, a catalyst, a solvent and optionally UV absorber. In particular, the combination of the component A and the component B have been found to provide coatings formed from the composition with improved crack resistance compared to compositions employing the component A alone.
The component A may be chosen from an organoalkoxysilane of the formula (R1)dSi(OR2)4−d, wherein R1 is a C1-C3 monovalent hydrocarbon radical, preferably a C1-C3 alkyl radical, more preferably a methyl or ethyl group. R2 is an R1 or a hydrogen radical and d is 0, 1 to 2. Particularly suitable organoalkoxysilanes include organoalkoxysilanes, for example, methyltrimethoxysilane, methyltriethoxysilane, or a mixture thereof, which can form a partial condensate. Additional organoalkoxysilanes include, but are not limited to, tetraethoxysilane, ethyltriethoxysilane, diethyldiethoxysilane, tetramethoxysilane, dimethyldimethoxysilane, ethyltriethoxysilane, propyltriethoxysilane, etc. It will be appreciated that the component A may be provided by one type of silane, or two or more different silanes.
The component A may be present in an amount of from about 5 weight percent to about 99.9 weight percent, about 10 weight percent to about 90 weight percent, even from about 20 weight percent to about 80 weight percent, based on the total weight of the total silane composition. Here as elsewhere in the specification and claims, numerical values may be combined to form new and non-specified ranges.
The component B may be present in an amount of from about 5 weight percent to about 90 weight percent, about 10 weight percent to about 60 weight percent, even from about 10 weight percent to about 30 weight percent, based on the total weight of the total silane composition. Here as elsewhere in the specification and claims, numerical values may be combined to form new and non-specified ranges.
The Component B is selected from the group consisting of at least one of formula 1 or 2:
(R3)aSi(OR4)4−a Formula 1
(R5O)m(R6)nSi(R9)x(R10)y(R11)zSi(R8)s(OR7)p Formula 2
wherein R3 is chosen from a C5-C20 linear or branched alkyl radical, a C5-C20 fluoroalkyl, a mixture of hydrocarbon and fluorocarbon chain, C5-C20 linear or branched hydrocarbon chain containing thioester group, C6-C24 saturated or unsaturated linear or cyclic hydrocarbon chain containing amino group or urea group, R4 is C1-C20 monovalent hydrocarbon radical or a hydrogen radical; a is 0, 1 to 3;
R5 and R7 are independently chosen from a C1-C20 monovalent hydrocarbon radical or a hydrogen radical;
R6 and R8 are independently selected from a C1 to C3 monovalent hydrocarbon radical or a hydrogen radical; m and p are 1 to 3; n and s are 1 to 3 such that m+n is 3, and s+p is 3;
R9 is chosen from a C1-C24 divalent hydrocarbon radical;
R10 and R11 are independently chosen from C1 to C24 monovalent hydrocarbon radical;
x is 1 to 20, y is 0 to 20, and z is 0 to 20.
In one embodiment, the component B is chosen from Formula 1. The thioester containing groups may be chosen from those of the formula —R12—S—C(O)—R13, where R12 is a C1-C12 linear or branched bivalent hydrocarbon group and R13 is a C1-C12 monovalent hydrocarbon group. The amino containing hydrocarbons may be chosen from those of the formula —R14—N(R15)—R16 where R14 is chosen from a C1-C12 bivalent hydrocarbon group, R15 is chosen from hydrogen or a C1-C12 monovalent hydrocarbon group, R16 is chosen from hydrogen or a C1-C12 monovalent hydrocarbon group, or R14 and R16 are taken to form a 5-12 membered ring. The urea containing hydrocarbons may be chosen from those of the formula —R17—N(R18)—C(O)—N(R19)R20, where R17 is chosen from a C1-C12 bivalent hydrocarbon group, R18, R19, and R20 are independently chosen from hydrogen and a C1-C12 bivalent hydrocarbon group, or R17 and R20 are taken to form a 5-12 membered ring.
When R3 is a fluoroalkyl, the fluoroalkyl group may have one or more fluorinated alkyl groups, and in embodiments may be a perfluoroalkyl group. Examples of suitable R3 groups include, but are not limited to, pentyl, hexyl, heptyl, octyl, nonyl decyl, dodecyl, 3,3,3-triflurorpentyl, 3,3,3-triflurorhexyl, 3,3,3-trifluroheptyl, 3,3,3-triflurooctly, perfluoropentyl, pefluorohexyl, pefluoroheptyl, perfluorohexyl, etc.
In embodiments, R4 is a C1-C4 hydrocarbon radical. Particularly suitable hydrocarbon radical groups include alkyl groups. Non-limiting examples of suitable alkyl groups include, for example, a methyl or ethyl. In one embodiment, the component B is chosen from Formula 1, a is 1, and R4 is methyl or ethyl.
In embodiments, the component B may be of the Formula 1 and chosen from, pentyltrimethoxysilane, hexyltrimethoxysilane, heptyltrimethoxysilane, octyltrimethoxysilane, nonyltrimethoxysilane, decyltrimethoxysilane, dodecyltrimethoxysilane, pentyltriethoxysilane, hexyltriethoxysilane, heptyltriethoxysilane, octyltriethoxysilane, nonyltriethoxysilane, decyltriethoxysilane, dodecyltriethoxysilane, pentyltripropoxysilane, hexyltripropoxysilane, heptyltripropoxysilane, octyltripropoxysilane, nonyltripropoxysilane, decyltripropoxysilane, dodecyltripropoxysilane, etc. It will be appreciated that the component B may be provided by a single type of silane or a mixture of two or more silanes.
In embodiments, the component B is chosen from a silane of Formula 2. The silane of Formula 2 may also be described by the formula 2a:
(R5O)m(R6)nSi—Z—Si(R8)s(OR7)p Formula 2
where Z is a C1-C24 bivalent hydrocarbon radical. The bivalent hydrocarbon radical Z as well as those of R9—R11 may be a linear or branched hydrocarbon and may optionally contain a cyclic group within the hydrocarbon chain. In one embodiment, Z may be represented as —R21—R23—R22 where R21 and R22 are independently C1-C6 bivalent hydrocarbon groups, and R23 is a C5-C10 bivalent cyclic group which may be saturated, unsaturated, or aromatic. In one embodiment, R23 is chosen from a bivalent cyclopentane, cyclohexane, cycloheptane, cyclooctane, cyclononane, cyclopentadiene, cyclopentene, cyclohexene, cycloheptene, cyclooctene, or benzene.
In embodiments, R5 and R7 are independently chosen from a C1-C4 hydrocarbon radical. Particularly suitable hydrocarbon radical groups include alkyl groups. Non-limiting examples of suitable alkyl groups include, for example, a methyl or ethyl.
Non-limiting examples of compounds from which the component B may be chosen include:
The component B may be present in an amount of from about 1 weight percent to about 60 weight percent based on the total weight of the component A and the component B. Here as elsewhere in the specification and claims, numerical values may be combined to form new and non-specified ranges.
It will be appreciated that the component B may be chosen from two or more different suitable organofunctional silanes. In one embodiment, the composition comprises two or more organofunctional silanes of the type of Formula 1. In one embodiment, the composition comprises two or more organofunctional silanes of the type of Formula 2. In one embodiment, the composition comprises one or more silanes of the type of Formula 1 and one or more silanes of the type of Formula 2.
The composition further comprises metal oxide particles. The metal particles used in the composition of the invention are not particularly limited. Generally, the metal particles will be metal oxide particles. Suitable examples include, but are not limited to, silica, zirconia, titania, alumina, ceria, or a combination of two or more thereof. In one embodiment, the metal oxide nanoparticles are silica nanoparticles.
The size of the metal oxide particles may be selected as desired for a particular purpose or intended application. In embodiments, the metal oxide particles are nanosized particles. Nanoparticles may have dimensions in the range of one to about 500 nanometers. For clear coat applications, the particles should have a size below a certain limit such that it will not scatter light passing through the coating. Particles with dimensions less than λ/2 do not scatter light of X, where X is the wavelength of light, and will not disrupt the transparency of the matrix in which they are incorporated. In embodiments, the metal particles have a diameter of 190 nanometers or less. In other embodiments, the metal particles have a diameter of from about 1 nm to about 190 nm; from about 5 nm to about 175 nm; from greater than 15 nm to about 150 nm; or from about 20 nm to about 100 nm. Here as elsewhere in the specification and claims, numerical values may be combined to form new and non-specified ranges.
In one embodiment, the metal oxide comprises silica (SiO2) particles. Generally, any colloidal silica can be used. Examples of suitable colloidal silica include, but are not limited to, fumed colloidal silica and precipitated colloidal silica. Particularly suitable colloidal silicas are those that are available in an aqueous medium. Colloidal silicas in an aqueous medium are usually available in a stabilized form, such as those stabilized with sodium ion, ammonia, or an aluminum ion. The colloidal silica may have particle diameters of from 5 to 250 nanometers, more specifically 10 to 150 nanometers, from 15 to 100 nanometers, even from 20 to 85 nanometers. Here as elsewhere in the specification and claims, numerical values may be combined to form new and non-specified ranges. Using relatively large colloidal silica particles has been found to provide a composition with excellent shelf life stability.
In one embodiment, the particle diameters for the metal oxide particles (including, e.g., colloidal silica) are determined in accordance with ASTM E2490-09 (2015), Standard Guide for Measurement of Particle Size Distribution of Nanomaterials in Suspension by Dynamic Light Scattering (DLS).
Colloidal silica is known in the art and commercially available. Dispersions include, for example, those under the trademarks of LUDOX® AS-40 (Sigma Aldrich), SNOWTEX® (Nissan Chemical), BINDZIL® (Akzo Nobel) and NALCO® 1034A (Nalco Chemical Company).
The composition also comprises a solvent. The solvent is not particularly limited. In one embodiment, the solvent may be chosen from an aliphatic alcohol, a glycol ether, a cycloaliphatic alcohol, an aliphatic ester, a cycloaliphatic ester, an aliphatic hydrocarbon, a cycloaliphatic hydrocarbon, an aromatic hydrocarbon, a halogenated aliphatic compound, a halogenated cycloaliphatic compound, a halogenated aromatic compound, an aliphatic ether, a cycloaliphatic ether, an amide solvents, a sulfoxide solvent, or a combination of two or more thereof. Examples of suitable solvents include, but are not limited to, alcohols, such as methanol, ethanol, propanol, isopropanol, n-butanol, tert-butanol, methoxypropanol, ethylene glycol, diethylene glycol butyl ether, or combinations thereof. Other polar organic solvents such as acetone, methyl ethyl ketone, ethylene glycol monopropyl ether, and 2-butoxy ethanol, can also be utilized. In embodiments, the solvent used is one or more selected from 1-methoxy-2-propanol, diacetone alcohol (DAA), acetyl acetone, cyclohexanone, methoxypropylacetate, ketones, glycol ether, or mixtures of two or more thereof. The amount of solvent in the composition ranges preferably from about 25 wt. % to about 85 wt. %, more preferably from about 40 wt. % to about 80 wt. %, and most preferably from about 50 wt. % to about 75 wt. %, all based on the total weight of the composition. The composition may also comprise a catalyst. The catalyst is not particularly limited and any suitable catalyst for curing the coating composition can be used.
The catalyst is at least one member selected from the group consisting of tetra-n-butylammonium acetate, tetra-n-butylammonium formate, tetra-n-butylammonium benzoate, tetra-n-butylammonium-2-ethylhexanoate, tetra-n-butylammonium-p-ethylbenzoate, tetra-n-butylammonium propionate and TBD-acetate (acetate salt of 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD)).
The catalyst can be added to the coating formulation as desired for a particular purpose or intended application. Generally, the catalyst should be added in an amount that will not affect or impair the physical properties of the coating, but in a sufficient amount effective to catalyze the curing reaction. In one embodiment, the catalyst is provided in an amount ranging from 1 ppm to about 75 ppm; from about 10 ppm to about 70 ppm; even from about 20 ppm to about 60 ppm. Here, as elsewhere in the specification and claims, numerical values may be combined to form new and non-specified ranges. The “ppm” value of the catalyst may be defined as parts per million.
Other additives such as hindered amine light stabilizers, antioxidants, dyes, flow modifiers and leveling agents or surface lubricants can be used in the topcoat. Other colloidal metal oxides can be present at up to about 10% by weight of the aqueous/organic solvent borne siloxanol resin/colloidal silica dispersion and can include metal oxides such as, antimony oxide, cerium oxide, aluminum oxide, zinc oxide, and titanium dioxide. Additional organic UV absorbers may be used.
The UV absorbers can also be chosen from a combination of inorganic UV absorbers and organic UV absorbers. Examples of suitable organic UV absorbers include but are not limited to, those capable of co-condensing with silanes. Such UV absorbers are disclosed in U.S. Pat. Nos. 4,863,520, 4,374,674, 4,680,232, and 5,391,795 which are herein incorporated by reference in their entireties. Specific examples include 4-[gamma-(trimethoxysilyl) propoxyl]-2-hydroxy benzophenone and 4-[gamma-(triethoxysilyl) propoxyl]-2-hydroxy benzophenone and 4,6-dibenzoyl-2-(3-triethoxysilylpropyl) resorcinol. When the UV absorbers that are capable of co-condensing with silanes are used, the UV absorber should co-condenses with other reacting species by thoroughly mixing the coating composition before applying it to a substrate. Co-condensing the UV absorber prevents coating performance loss caused by the leaching of free UV absorbers to the environment during weathering.
The catalyst can be added to the coating composition directly or can be dissolved in a solvent or other suitable carrier. The solvent may be a polar solvent such as methanol, ethanol, n-butanol, t-butanol, n-octanol, n-decanol, 1-methoxy-2-propanol, isopropyl alcohol, ethylene glycol, tetrahydrofuran, dioxane, bis(2-methoxyethyl)ether, 1,2-dimethoxyethane, acetonitrile, benzonitrile, methylethyl ketone, dimethylformamide (DMF), dimethyl sulfoxide (DMSO), N-methylpyrrolidinone (NMP), and propylene carbonate.
The coating compositions may include other materials or additives to provide the coating with desired properties for a particular purpose or intended application. For example, the primer composition may also include other additives such as hindered amine light stabilizers, antioxidants, dyes, flow modifiers, and leveling agents. The composition of the invention can also include surfactants as leveling agents. Examples of suitable surfactants include, but are not limited to, surfactants such as silicone polyethers under the designation Silwet® and CoatOSil® available from Momentive Performance Materials, Inc. of Albany, N.Y., FLUORAD™ from 3M Company of St. Paul, Minn., and polyether-polysiloxane copolymers such as BYK®-331 manufactured by BYK®-Chemie. Suitable antioxidants include, but are not limited to, hindered phenols (e.g. IRGANOX® 1010 from Ciba Specialty Chemicals).
The compositions described herein may be employed as a coating for a substrate of interest. The coating may be cured to form a hardcoat top coat. The coating may be applied to a portion of a surface of the substrate or the entire surface of a substrate to be coated. Examples of suitable substrates include, but are not limited to, organic polymeric materials such as acrylic polymers, e.g., poly(methylmethacrylate), polyamides, polyimides, acrylonitrile-styrene copolymer, styrene-acrylonitrile-butadiene terpolymers, polyvinyl chloride, polyethylene, polycarbonates, copolycarbonates, high-heat polycarbonates, metal, glass, a combination of two or more thereof, and any other suitable material.
The coating composition can be applied to a substrate with or without the aid of a primer material. The primer material may be chosen from any material suitable for facilitating adhesion of the topcoat material to the substrate. The primer material is not particularly limited, and may be chosen from any suitable primer material. In one embodiment, the primer is chosen from homo and copolymers of alkyl acrylates, polyurethanes, polycarbonates, polyvinylpyrrolidone, polyvinylbutyrals, poly(ethylene terephthalate), poly(butylene terephthalate), or a combination of two or more thereof. In one embodiment, the primer may be polymethylmethacrylate.
In one embodiment, a primer layer is applied to the substrate prior to applying the coating composition. The primer may be coated onto a substrate by flow coat, dip coat, spin coat, spray coat, or any other methods known to a person skilled in the field, it is allowed to dry by removal of any solvents, for example by evaporation, thereby leaving a dry coating. The primer may subsequently be cured. Additionally, a topcoat (e.g., a hardcoat layer) may be applied on top of the dried primer layer by flow coat, dip coat, spin coat or any other methods known to a person skilled in the field. Optionally, a topcoat layer may be directly applied to the substrate without a primer layer.
In an embodiment, the coated substrates have a critical strain in the range of about 1 percent to about 10 percent, about 1.5 percent to about 7 percent, even from about 2 percent to about 5 percent, as measured at 3-10 micron coating thickness. Here as elsewhere in the specification and claims, numerical values may be combined to form new and non-specified ranges.
The following examples illustrate embodiments of materials in accordance with the disclosed technology. The examples are intended to illustrate embodiments of the disclosed technology, and are not intended to limit the claims or disclosure to such specific embodiments.
A small glass bottle was charged with acetic acid (2.71 g) and methyl trimethoxy silane (MTMS, 35.21 g), the mixture was then chilled in an ice bath. A mixture of silica (LUDOX® AS-40, 14.16 g) and water was then added over approximately 20 minutes to the chilled mixture of silane and acetic acid mixture. The mixture heated slightly due to the exothermic reaction of the silane hydrolysis and was allowed to stir over several hours while it cooled back to room temperature. Next, a mixture of IPA (Isopropyl alcohol) and n-BuOH (n-Butanol) was added and mixed for approximately 30 minutes. 4,6-dibenzoyl-2-(3-triethoxysilylpropyl) resorcinol (SDBR) was then added to the hydrolysis mixture (2.82 g, 32% SDBR in 1-methoxy-2-proanol solution) and stirring was continued until the SDBR was dispersed. The reaction mixture was allowed to stir and mix for another day. A 40% solution of tetrabutylammonium acetate (TBAA) in water (0.1 g) and BYK® 302 (0.05 g) were added. The formulation was then aged sufficiently before being applied as top coat.
A small glass bottle was charged with acetic acid (2.71 g) and MTMS (33.45 g) and n-butyl trimethoxy silane (1.76 g), the mixture was then chilled in an ice bath. A mixture of silica (LUDOX® AS-40, 14.16 g) and water was then added over approximately 20 minutes to the chilled mixture of silane and acetic acid mixture. The mixture heated slightly due to the exothermic reaction of the silane hydrolysis and was allowed to stir over several hours while it cooled back to room temperature. Next a mixture of IPA (Isopropyl alcohol) and n-BuOH (n-Butanol) was added and mixed for approximately 30 minutes. SDBR was then added to the hydrolysis mixture (2.82 g, 32% SDBR in 1-methoxy-2-proanol solution) and stirring was continued until the SDBR was dispersed. The reaction mixture was allowed to stir and mix for another day. A 40% solution of TBAA in water (0.1 g) and BYK® 302 (0.05 g) were added. The formulation was then aged sufficiently before being applied as top coat.
A small glass bottle was charged with acetic acid (2.71 g) and MTMS (31.69 g) and 3,3,3-trifluoropropyl trimethoxy silane (3.52 g), the mixture was then chilled in an ice bath. A mixture of silica (LUDOX® AS-40, 14.16 g) and water was then added over approximately 20 minutes to the chilled mixture of silane and acetic acid mixture. The mixture heated slightly due to the exothermic reaction of the silane hydrolysis and was allowed to stir over several hours while it cooled back to room temperature. Next a mixture of IPA (Isopropyl alcohol) and n-BuOH (n-Butanol) was added and mixed for approximately 30 minutes. SDBR was then added to the hydrolysis mixture (2.82 g, 32% SDBR in 1-methoxy-2-proanol solution) and stirring was continued until the SDBR was dispersed. The reaction mixture was allowed to stir and mix for another day. A 40% solution of TBAA in water (0.1 g) and BYK® 302 (0.05 g) were added. The formulation was then aged sufficiently before being applied as top coat.
A cerium oxide-siloxanol hydrolysate was prepared by charging 22.41 g of the cerium oxide sol (Sigma Aldrich, 20 Wt % solids, 2.5 wt % acetic acid stabilized, aqueous) to an Erlenmeyer flask and 20.96 g of MTMS was then added to the chilled cerium oxide sol over 20 minutes. The mixture heated slightly due to the exothermic reaction of the silane hydrolysis and was allowed to stir over several hours while it cooled back to room temperature. The hydrolysate was then diluted by adding 19 g of n-Butanol. The hydrolysate was aged by allowing it to stand for three days at room temperature.
A colloidal silica-siloxanol hydrolysate was prepared by charging 27.64 g of colloidal silica sol (Nalco 1034A, 34.7 Wt % solids, aqueous) to an Erlenmeyer flask and 13.58 g of MTMS was then added to the chilled SiO2 sol over 20 minutes while stirring the mixture. The mixture heated slightly due to the exothermic reaction of the silane hydrolysis and was allowed to stir over several hours while it cooled back to room temperature. The hydrolysate was then diluted by adding 30 g of iso-propanol. The hydrolysate was aged by allowing it to stand for three days at room temperature.
The cerium oxide containing hydrolysate and colloidal silica containing hydrolysate were then combined and stirred to completely mix them. 39 g of n-Butanol was added to 130 g of the ceria-silica hydrolysate mixture. The mixture was stripped of ˜41 g of the solvent by vacuum distillation at 50 mbar and 70° C. The pH of the formulation was then adjusted to 5.1 by adding NH3 solution. To the CeO2/SiO2 siloxanol hydrolysate mixture was then added 0.3 g of 10% solution of flow control agent BYK® 302 polyether modified polydimethylsiloxane. The solid content of the formulation was measure to be 24.71%. Finally, 0.062 g of 1, 5, 7-Triazabicyclo[4.4.0]dec-5-ene was added as a cure catalyst to the formulation. The formulation was sufficiently aged prior to use as top coat.
A small glass bottle was charged with acetic acid (2.71 g) and methyl trimethoxy silane (30.18 g, MTMS). A mixture of silica (18.67 g, LUDOX® AS-40 40) and water was added to the chilled mixture of silane with acetic acid over approximately 20 minutes. The mixture was allowed to stir over several hours while cooled back to room temperature. Next a mixture of IPA (Isopropyl alcohol) and n-BuOH (n-Butanol) was added and mixed for approximately 30 minutes. Silanated hydroxybenzophenone (2.76 g, SHBP) was added after that and continued to mix. The reaction mixture was allowed to stir and mix for another day. A 40% solution of TBAA in water (0.09 g) and BYK® 302 (0.12 g) and acrylic polyol (0.88 g) were added. This formulation was aged sufficiently before being applied as top coat.
A small glass bottle was charged with acetic acid (2.71 g) and MTMS (31.69 g) and Octyl triethoxy silane (3.52 g, Silquest™ A-137 from Momentive Performance Materials Inc.), the mixture was then chilled in an ice bath. A mixture of silica (LUDOX® AS-40, 14.16 g) and water was then added over approximately 20 minutes to the chilled mixture of silane/acetic acid mixture. The mixture heated slightly due to the exothermic reaction of the silane hydrolysis and it cooled back was allowed to stir over several hours while it cooled back down to room temperature. Next a mixture of IPA (Isopropyl alcohol) and n-BuOH (n-Butanol) was added and mixed for approximately 30 minutes. SDBR was then added to the hydrolysis mixture (2.82 g, 32% SDBR in 1-methoxy-2-proanol solution) and stirring was continued until the SDBR was dispersed. The reaction mixture was allowed to stir and mix for another day. A 40% solution of TBAA in water (0.1 g) and BYK® 302 (0.05 g) were added. The formulation was then aged sufficiently before being applied as top coat.
Examples 2-3 were prepared using a similar procedure as described with respect to Example 1 by varying the ratio of MTMS and Octyl triethoxy silane
Example 4-5 were prepared using a similar procedure as described with respect to Example 1, except that Dodecyl triethoxy silane was used in place of Octyl triethoxy silane.
Example 6 was prepared using a similar procedure as described with respect to Example 1, except that part of MTMS was replaced with tetraethoxy silane, and Dodecyl triethoxy silane was used in place of Octyl triethoxy silane.
Example 7 was prepared using a similar procedure as described with respect to Example 1, except that 1,8-Bis (Triethoxy silyl) Octane was used in place of Octyl triethoxy silane.
Example 8 was prepared using a similar procedure as described with respect to Example 1, except that Nonafluorohexyl trimethoxysilane was used in place of Octyl triethoxy silane.
A cerium oxide-siloxanol hydrolysate was prepared by charging 22.41 g of the cerium oxide sol (Sigma Aldrich, 20 Wt % solids, 2.5 wt % acetic acid stabilized, aqueous) to an Erlenmeyer flask and 18.89 g of MTMS was then added to the chilled cerium oxide sol over 20 minutes. 1.73 g of Octyl triethoxysilane (Silquest™ A137, Momentive Performance Materials Pvt. Ltd) was added in drops after the addition of MTMS. The mixture heated slightly due to the exothermic reaction of the silane hydrolysis and was allowed to stir over several hours while it cooled back to room temperature. The hydrolysate was then diluted by adding 19 g of n-Butanol. The hydrolysate was aged by allowing it to stand for three days at room temperature.
A colloidal silica-siloxanol hydrolysate was prepared by charging 27.64 g of colloidal silica sol (Nalco® 1034A, 34.7 Wt % solids, aqueous) to an Erlenmeyer flask and 13.58 g of MTMS was then added to chilled SiO2 sol over 20 minutes. 1.24 g of Octyl triethoxysilane (A137, Momentive Performance Materials Pvt. Ltd) was added in drops after the addition of MTMS. The mixture heated slightly due to the exothermic reaction of the silane hydrolysis and was allowed to stir over several hours while it cooled back to room temperature. The hydrolysate was then diluted by adding 30 g of iso-propanol. The hydrolysate was aged by allowing it to stand for three days at room temperature.
The cerium oxide containing hydrolysate and colloidal silica containing hydrolysate were then combined and stirred to completely mix them. 37 g of n-Butanol was added to 130 g of the ceria-silica hydrolysate mixture. The mixture was stripped off 36.45 g of the solvent by vacuum distillation at 50 mbar and 70° C. to get 127.89 g of formulation. The pH of the formulation was then adjusted to 5.1 by adding NH3 solution. To the CeO2/SiO2 siloxanol hydrolysate mixture was then added 0.4 g of 1% solution of flow control agent BYK® 302 polyether modified polydimethylsiloxane. The solid content of the formulation was measure to be 21.99%. Finally, 0.059 g of 1,5,7-Triazabicyclo[4.4.0]dec-5-ene was added as a cure catalyst to the formulation. The formulation was then aged sufficiently before being applied as top coat.
A small glass bottle was charged with acetic acid (2.71 g) and methyl trimethoxy silane (24.14 g, MTMS) and Octyl triethoxy silane (6.04 g, Silquest™ A-137 from Momentive Performance Materials Inc.). A mixture of silica (18.67 g, LUDOX® AS-40) and water was added to the chilled mixture of silane with acetic acid over approximately 20 minutes. The mixture was allowed to stir over several hours while cooling back to room temperature. Next the mixture of alcohol solvent was added and mixed for approximately 30 minutes. Silylated hydroxybenzophenone (2.76 g, SHBP) was added after that and continued to mix. TBAA (0.09 g) and BYK® 302 (0.12 g) and acrylic polyol (0.88 g) were added. This formulation was aged sufficiently before being applied as top coat.
Coating formulations prepared in Comparative example 5 and example 10 were applied directly on polymeric substrate.
Tables 1 provides formulations for the coating compositions.
Preparation of Primer Formulation
Primer formulations were prepared by mixing a Polymethyl methacrylate PMMA, solvent and a flow control agent. The PMMA solutions were prepared by dissolving PMMA resin (7 gm) in 93 g of a mixture of 1-methoxy-2-propanol (85 wt. %) and diacetone alcohol (15 wt. %) at 50 deg C. in a glass bottle for >17 hrs. BYK® 331 (0.03%) flow additive was added to the above mixture. This primer solution was used for coating on polycarbonate.
Preparation of Coated Polycarbonate Panels
Silicone coating formulations in Table 1 were coated on polycarbonate plates according to the following procedure. Polycarbonate (PC) plaques (6×6×0.3 cm) were cleaned with a stream of N2 gas to remove any dust particles adhering to the surface followed by rinsing of the surface with isopropanol. The plates were then allowed to dry inside the fume hood for 20 minutes. The primer solutions were then applied to the PC plates by flow coating. The solvent in the primer coating solutions were allowed to flash off in the fume hood for approximately 20 minutes (22° C., 37% RH) and then put in an oven for 125° C. for 45 minutes. After cooling to room temperature, the primed PC plates were then flow coated with the silicone coating solution. After drying for approximately 20 minutes (22° C., 37% RH), the coated plates were placed in a preheated circulated air oven at 130° C. for 45 minutes.
Measurement of Coating Properties
The optical characteristics (Transmission and Haze) were measured using a BYK Gardner haze guard instrument. Measurements were made according to ASTM D 1003.
Coating should have transmittance value of more than >85% and haze should be <1. Adhesion was measured using a cross hatch adhesion test according to ASTM D3200/D3359.
The adhesion is rated on a scale of 5B-0B, with 5B indicative of the highest adhesion. Adhesion after water immersion was done by immersing the coated PC plates in 65° C. water followed by cross hatch adhesion test at different time intervals.
Steel wool abrasion tests were performed by rubbing grade 0000 steel wool under a weight of 1 Kg on the surface of the coated substrate. The initial haze (Hi) of the coated sample was measured prior to steel wool abrasion then again after rubbing back and forth 5 times (Hf). The ΔHaze (ΔH) was calculated as, ΔH=Hf−Hi.
Taber abrasion testing was done in accordance with ASTM D1003 and D1044, haze measurements were made using a BYK haze-gard, ΔH values at 500 cycles were recorded. A minimum of four specimens of each experimental sample were tested, the average ΔH(500) is reported.
Critical Strain Measurement:
Testing was performed on an Instron model #5565, run in tensile mode, with a crosshead speed of 5 mm/min. Critical strain measurements were obtained through the use of a non-contact digital extensometer with video capture and playback. The extensometer was capable of recording precise measurements of the strain experienced by the sample under load and correlating the video frames to the instantaneous strain on the sample. A critical strain value was obtained by reviewing the video playback of the test once completed to identify the strain at which the cracks began to propagate beyond a nominal distance of 1 mm. Critical strain was reported as measured at 3-10 micron coating thickness. The critical strain values have been reported with a standard deviation of 5 percent.
Nanoindentation Testing:
A Hysitron TI950 Triboindenter with Berkovich tip was used for all nanomechanical measurements reported here. Quasi-static testing was performed to measure the Young's modulus (E) of the coatings. Quasi-static nanoindentation testing was done to obtain reduced modulus values for all of the samples. The nano-DMA experiment was built from a standard frequency sweep program with frequency range from 10-200 Hz. Indents were spaced 10 microns apart. The contact depth was targeted to 5.0±0.1% of total coating thickness. Dynamic testing by nano-DMA was performed to measure the storage modulus (E′), loss modulus (E″) and tangent delta values (E″/E′) of the coatings. High loss modulus and tangent delta values indicate the improved ability of the coating to dissipate energy.
Properties of the coatings are measured for all the new formulation and presented in Table 2. The coatings maintain very good optical clarity and adhesion with the addition of the component Bs. By introducing the component B with the longer chain (e.g., SILQUEST™ A-137 silane) the percent strain to failure is improved by >50% as shown in
4-5.8
To understand the effect of microstructure on these newly developed coating, formulations from Example 1 and 2 were aged under different condition, which reflects the degree of cross-linking in the cured material. Coating properties of these aged formulations were evaluated. All these formulations were stable. Different properties of the coatings are presented in Tables 5 and 6.
Mechanical properties of all these coatings were evaluated and aspects are shown in
While the above description contains many specifics, these specifics should not be construed as limitations on the scope of the invention, but merely as exemplifications of preferred embodiments thereof. Those skilled in the art may envision many other possible variations that are within the scope and spirit of the invention as defined by the claims appended hereto.
