Patent Application
20150328927
1. Field of the Invention
This invention relates to the field of diffusion barriers and more specifically to the field of thin film barriers against diffusion of materials such as gas barriers for tires.
2. Background of the Invention
Diffusion barriers to gas and vapors are key components in a variety of applications, such as food packaging, flexible electronics, and tires. For instance, there is an increased need for improved barrier performance of tires. Conventional tires are typically composed of rubber and include an inner liner. Drawbacks to conventional tires include permeability of the inner liner. Such permeability may allow oxygen to migrate through the tire carcass to the steel belts, which may facilitate oxidation of the steel belts. Further drawbacks include inefficient air retention by which conventional tires may lose air pressure over a period of time and with use, which may increase rolling resistance of the tire.
Consequently, there is a need for improved diffusion barriers. There are also further needs for improved thin film barriers against fluid and solid diffusion. Moreover, there is a need for improved tires as well as increased air retention by tires.
These and other needs in the art are addressed in one embodiment by a method for producing a material diffusion barrier comprising a coating on an elastomeric substrate. The method includes exposing the elastomeric substrate to a cationic solution to produce a cationic layer on the elastomeric substrate. The cationic solution comprises a polymer, a colloidal particle, a nanoparticle, a salt, or any combinations thereof. The method also includes exposing the cationic layer to an anionic solution to produce an anionic layer on the cationic layer. The anionic solution comprises an anionic polymer, a second colloidal particle, a second salt, or any combinations thereof. The coating comprises a bilayer comprising the cationic layer and the anionic layer.
These and other needs in the art are addressed in another embodiment by a method for producing a material diffusion barrier comprising a coating on an elastomeric substrate. The method includes exposing the elastomeric substrate to an anionic solution to produce an anionic layer on the elastomeric substrate. The anionic solution comprises an anionic polymer, a colloidal particle, a salt, or any combinations thereof. The method also includes exposing the anionic layer to a cationic solution to produce a cationic layer on the anionic layer. The cationic solution comprises a polymer, a second colloidal particle, a nanoparticle, a second salt, or any combinations thereof. The coating comprises a bilayer comprising the cationic layer and the anionic layer.
In addition, these and other needs in the art are addressed in a further embodiment by a tire. The tire comprises an elastomeric substrate having a quadlayer. The quadlayer includes a first cationic layer. The first cationic layer includes a polymer, a colloidal particle, a nanoparticle, a salt, or any combinations thereof. The tire also includes a first anionic layer, wherein the first anionic layer comprises an anionic polymer, a second colloidal particle, a second salt, or any combinations thereof. The first cationic layer is disposed between the elastomeric substrate and the first anionic layer. The tire also includes a second cationic layer. The second cationic layer includes the polymer, the colloidal particle, the nanoparticle, the salt, or any combinations thereof. The first anionic layer is disposed between the first cationic layer and the second cationic layer. In addition, the tire includes a second anionic layer. The second anionic layer includes the anionic polymer, the second colloidal particle, the second salt, or any combinations thereof. The second cationic layer is disposed between the first anionic layer and the second anionic layer. Moreover, at least one of the first cationic layer, the first anionic layer, the second cationic layer, and the second anionic layer has a neutral charge.
The foregoing has outlined rather broadly the features and technical advantages of the present invention in order that the detailed description of the invention that follows may be better understood. Additional features and advantages of the invention will be described hereinafter that form the subject of the claims of the invention. It should be appreciated by those skilled in the art that the conception and the specific embodiments disclosed may be readily utilized as a basis for modifying or designing other embodiments for carrying out the same purposes of the present invention. It should also be realized by those skilled in the art that such equivalent embodiments do not depart from the spirit and scope of the invention as set forth in the appended claims.
For a detailed description of the preferred embodiments of the invention, reference will now be made to the accompanying drawings in which:
In an embodiment, a multilayer thin film coating method provides an elastomeric substrate with a diffusion retardant coating by alternately depositing positive (or neutral) and negative (or neutral) charged layers on the substrate. Each pair of positive and negative layers comprises a layer. In some embodiments, at least one layer is a neutral layer. It is to be understood that a neutral layer refers to a layer that does not have a charge. In embodiments, the multilayer thin film coating method produces any number of desired layers on substrates such as bilayers, trilayers, quadlayers, pentalayers, hexalayers, heptalayers, octalayers, and increasing layers. Without limitation, a plurality of layers may provide a desired retardant to transmission of material through the elastomeric substrate. The material may be any diffusible material. Without limitation, the diffusible material may be a solid, a fluid, or any combinations thereof. The fluid may be any diffusible fluid such as a liquid, a gas, or any combinations thereof, in an embodiment, the diffusible fluid is a gas.
The layers may have any desired thickness. In embodiments, each layer is between about 10 nanometers and about 2 micrometers thick, alternatively between about 10 nanometers and about 500 nanometers thick, and alternatively between about 50 nanometers and about 500 nanometers thick, and further alternatively between about 1 nanometers and about 100 nanometers thick.
The elastomeric substrate comprises material having viscoelasticity. Any desirable elastomeric substrate may be coated with the multilayer thin film coating method. In an embodiment, the elastomeric substrate is synthetic rubber, natural rubber, or any combinations thereof. In embodiments, the elastomeric substrate includes natural rubber. Without limitation, examples of suitable elastomeric substrates include polyisoprene, polybutadiene, polychloroprene, butadiene-styrene copolymers, acrylonitrilebutadiene copolymers, ethylenepropylene-diene rubbers, polysulfide rubber, nitrile rubber, silicone, polyurethane, butyl rubber, or any combinations thereof. In some embodiments, the rubber comprises a carbon black filled natural rubber formulation vulcanized with sulfur.
The negative charged (anionic) layers comprise layerable materials. In some embodiments, the layerable materials are neutral and provide an anionic layer that has a neutral charge. In embodiments, one or more anionic layers are neutral. Without limitation, layerable materials with a neutral charge increase elasticity of the diffusion resistant coating. The layerable materials include anionic polymers, colloidal particles, salts, or any combinations thereof. In an embodiment, the layerable materials comprise an anionic polymer, a colloidal particle, or any combinations thereof and at least one salt. Without being limited by theory, layerable materials comprising an anionic polymer, a colloidal particle, or any combinations thereof and at least one salt may weaken the bonds and may improve elasticity. Without limitation, examples of suitable anionic polymers include polystyrene sulfonate, polymethacrylic acid, polyacrylic acid, poly(acrylic acid, sodium salt), polyanetholesulfonic acid sodium salt, poly(vinylsulfonic acid, sodium salt), or any combinations thereof. In addition, without limitation, colloidal particles include organic and/or inorganic materials. Further, without limitation, examples of colloidal particles include clays, colloidal silica, inorganic hydroxides, silicon based polymers, polyoligomeric silsesquioxane, carbon nanotubes, graphene, or any combinations thereof. Any type of clay suitable for use in an anionic solution may be used. Without limitation, examples of suitable clays include sodium montmorillonite, hectorite, saponite, Wyoming bentonite, vermiculite, halloysite, or any combinations thereof. In an embodiment, the clay is vermiculite. In some embodiments, the clay is sodium montmorillonite. Any inorganic hydroxide that may provide retardancy to gas or vapor transmission may be used. In an embodiment, the inorganic hydroxide includes aluminum hydroxide, magnesium hydroxide, or any combinations thereof. The salts may include any salts suitable for use with the multilayer thin film coating method. In an embodiment, the salts include salts from the Hofmeister series of anions. In embodiments, the salts include salts from the ions CO32−, F−, SO42−, H2PO42−, C2H3O2−, Cl−, NO3−, Br−, Cl03−, I−, ClO4−, SCN−, S2O32−, or any combinations thereof. In an embodiment, the salt includes the ion Cl−. The salts are of a concentration from about 1 millimolar in solution to about 10 millimolar in solution, alternatively from about 5 millimolar in solution to about 10 millimolar in solution, alternatively from about 1 millimolar in solution to about 100 millimolar in solution, and further alternatively from about 0.1 millimolar in solution to about 100 millimolar in solution.
The positive charge (cationic) layers comprise cationic materials. In some embodiments, one or more cationic layers are neutral. The cationic materials comprise polymers, colloidal particles, nanoparticles, salts, or any combinations thereof. In an embodiment, the cationic materials comprise a polymer, a colloidal particle, a nanoparticle, or any combinations thereof and at least one salt. Without being limited by theory, cationic materials comprising a polymer, a colloidal particle, a nanoparticle, or any combinations thereof and at least one salt may weaken bonds and may improve elasticity. The polymers include cationic polymers, polymers with hydrogen bonding, or any combinations thereof. Without limitation, examples of suitable cationic polymers include branched polyethylenimine, linear polyethylenimine, cationic polyacrylamide, cationic poly diallyldimethylammonium chloride, poly(allyl amine), poly(allyl amine) hydrochloride, poly(vinyl amine), poly(acrylamide-co-diallyldimethylamnmnium chloride), or any combinations thereof. Without limitation, examples of suitable polymers with hydrogen bonding include polyethylene oxide, polyglycidol, polypropylene oxide, poly(vinyl methyl ether), polyvinyl alcohol, polyvinylpyrrolidone, polyallylamine, branched polyethylenimine, linear polyethylenimine, poly(acrylic acid), poly(methacrylic acid), copolymers thereof, or any combinations thereof. In an embodiment, a cationic material includes polyethylene oxide, polyglycidol, or any combinations thereof. In some embodiments, the cationic material is polyethylene oxide. In an embodiments, the cationic material is polyglycidol. In embodiments, the polymers with hydrogen bonding are neutral polymers. In addition, without limitation, colloidal particles include organic and/or inorganic materials. Further, without limitation, examples of colloidal particles include clays, layered double hydroxides, inorganic hydroxides, silicon based polymers, polyoligomeric silsesquioxane, carbon nanotubes, graphene, or any combinations thereof. Without limitation, examples of suitable layered double hydroxides include hydrotalcite, magnesium LDH, aluminum LDH, or any combinations thereof. The salts may include any salts suitable for use with the multilayer thin film coating method. In an embodiment, the salts include salts from the Hofmeister series of cations. In embodiments, the salts include salts from the ions NH4+, K+, Na+, Li+, Mg2+, Ca2+, Rb+, Cs+, N(CH3)4+, or any combinations thereof. In embodiments, the salts include salts from the ions K+, Na+, or any combinations thereof. In an embodiment, the salts include salts from the ion K+. In other embodiments, the salts include salts from the ion Na+. Embodiments include the salt comprising NaCl, KCl, or any combinations thereof. In some embodiments, the salt comprises NaCl. In other embodiments, the salt comprises KCl. The salts are of a concentration from about 1 millimolar in solution to about 10 millimolar in solution, alternatively from about 5 millimolar in solution to about 10 millimolar in solution, and alternatively from about 1 millimolar in solution to about 100 millimolar in solution.
In embodiments, the positive (or neutral) and negative layers are deposited on the elastomeric substrate by any suitable method. Embodiments include depositing the positive (or neutral) and negative layers on the elastomeric substrate by any suitable liquid deposition method. Without limitation, examples of suitable methods include bath coating, spray coating, slot coating, spin coating, curtain coating, gravure coating, reverse roll coating, knife over roll (i.e., gap) coating, metering (Meyer) rod coating, air knife coating, or any combinations thereof. Bath coating includes immersion or dip. In an embodiment, the positive (or neutral) and negative layers are deposited by bath. In other embodiments, the positive and negative layers are deposited by spray.
In embodiments, the multilayer thin film coating method provides two pairs of anionic and cationic layers, which two pairs comprise a quadlayer. In embodiments, the multilayer thin film coating methods provides one of the anionic layers and/or one of the cationic layers as a neutral layer. Embodiments include the multilayer thin film coating method producing a plurality of quadlayers on an elastomeric substrate.
In embodiments, after formation of first cationic layer 25, the multilayer thin film coating method includes removing elastomeric substrate 5 with the produced first cationic layer 25 from the cationic mixture and then exposing elastomeric substrate 5 with first cationic layer 25 to anionic molecules in an anionic mixture to produce first anionic layer 30 on first cationic layer 25. The anionic mixture contains first layer layerable materials 1S. The first layer layerable materials 15 are negatively charged and/or neutral. Without limitation, the positive or neutral first cationic layer 25 attracts the anionic molecules to form the cationic (or neutral)-anionic pair of first cationic layer 25 and first anionic layer 30. The anionic mixture includes an aqueous solution of first layer layerable materials 15. In an embodiment, first layer layerable materials 15 comprise polyacrylic acid. The aqueous solution may be prepared by any suitable method. In embodiments, the aqueous solution includes first layer layerable materials 15 and water. First layer layerable materials 15 may also be dissolved in a mixed solvent, in which one of the solvents is water and the other solvent is miscible with water (e.g., ethanol, methanol, and the like). Combinations of anionic polymers and colloidal particles may be present in the aqueous solution. Any suitable water may be used. In embodiments, the water is deionized water. In some embodiments, the aqueous solution may include from about 0.05 wt. % first layer layerable materials 15 to about 1.50 wt. % first layer layerable materials 15, alternatively from about 0.01 wt. % first layer layerable materials 15 to about 2.00 wt. % first layer layerable materials 15, and further alternatively from about 0.001 wt. % first layer layerable materials 15 to about 20.0 wt. % first layer layerable materials 15. In embodiments, elastomeric substrate 5 with first cationic layer 25 may be exposed to the anionic mixture for any suitable period of time to produce first anionic layer 30. In embodiments, elastomeric substrate 5 with first cationic layer 25 is exposed to the anionic mixture from about 1 second to about 20 minutes, alternatively from about 1 second to about 200 seconds, and alternatively from about 10 seconds to about 200 seconds, and further alternatively from about instantaneous to about 1.200 seconds, and alternatively from about 1 second to about 5 seconds, and alternatively from about 4 seconds to about 6 seconds, and further alternatively about 5 seconds. In an embodiment, elastomeric substrate 5 with first cationic layer 25 is exposed to the anionic mixture from about 4 seconds to about 6 seconds. Without limitation, the exposure time of elastomeric substrate 5 with first cationic layer 25 to the anionic mixture and the concentration of first layer layerable materials 15 in the anionic mixture affect the thickness of the first anionic layer 30. For instance, the higher the concentration of first layer layerable materials 15 and the longer the exposure time, the thicker the first anionic layer 30 produced by the multilayer thin film coating method.
In embodiments as further shown in
In embodiments, after formation of the second cationic layer 35, the multilayer thin film coating method includes removing elastomeric substrate 5 with the produced first cationic layer 25, first anionic layer 30, and second cationic layer 35 from the cationic mixture and then exposing elastomeric substrate 5 with first cationic layer 25, first anionic layer 30, and second cationic layer 35 to anionic molecules in an anionic mixture to produce second anionic layer 40 on second cationic layer 35. The anionic mixture contains second layer layerable materials 70. Without limitation, the positive or neutral second cationic layer 35 attracts the anionic molecules to form the cationic (or neutral)-anionic pair of second cationic layer 35 and second anionic layer 40. The anionic mixture includes an aqueous solution of second layer layerable materials 70. In an embodiment, second layer layerable materials 70 comprise clay. Embodiments include the clay comprising sodium montmorillonite. The aqueous solution may be prepared by any suitable method. In embodiments, the aqueous solution includes second layer layerable materials 70 and water. Second layer layerable materials 70 may also be dissolved in a mixed solvent, in which one of the solvents is water and the other solvent is miscible with water (e.g., ethanol, methanol, and the like). Combinations of anionic polymers and colloidal particles may be present in the aqueous solution. Any suitable water may be used. In embodiments, the water is deionized water. In some embodiments, the aqueous solution may include from about 0.05 wt. % second layer layerable materials 70 to about 1.50 wt. % second layer layerable materials 70, alternatively from about 0.01 wt. % second layer layerable materials 70 to about 2.00 wt. % second layer layerable materials 70, and further alternatively from about 0.001 wt. % second layer layerable materials 70 to about 20.0 wt. % second layer layerable materials 70. In embodiments, elastomeric substrate 5 with first cationic layer 25, first anionic layer 30, and second cationic layer 35 may be exposed to the anionic mixture for any suitable period of time to produce second anionic layer 40. In embodiments, elastomeric substrate 5 with first cationic layer 25, first anionic layer 30, and second cationic layer 35 is exposed to the anionic mixture from about 1 second to about 20 minutes, alternatively from about 1 second to about 200 seconds, and alternatively from about 10 seconds to about 200 seconds, and further alternatively from about instantaneous to about 1,200 seconds, and alternatively from about 1 second to about 5 seconds, and alternatively from about 4 seconds to about 6 seconds, and further alternatively about 5 seconds. In an embodiment, elastomeric substrate 5 with first cationic layer 25, first anionic layer 30, and second cationic layer 35 is exposed to the anionic mixture from about 4 seconds to about 6 seconds. Quadlayer 10 is therefore produced on elastomeric substrate 5. In embodiments as shown in
In an embodiment as shown in
In such embodiments shown in
Embodiments shown in
In further embodiments as shown in
In embodiments, the cationic mixture includes an aqueous solution of first primer layer materials 60. The aqueous solution may be prepared by any suitable method. In embodiments, the aqueous solution includes first primer layer materials 60 and water. In other embodiments, first primer layer materials 60 may be dissolved in a mixed solvent, in which one of the solvents is water and the other solvent is miscible with water (e.g., water, methanol, and the like). The solution may also contain colloidal particles in combination with polymers or alone, if positively charged. Any suitable water may be used. In embodiments, the water is deionized water. In some embodiments, the aqueous solution may include from about 0.1 wt. % first primer layer materials 60 to about 1.0 wt. % first primer layer materials 60, and alternatively may include from about 0.05 wt. % first primer layer materials 60 to about 1.50 wt. % first primer layer materials 60, alternatively from about 0.01 wt. % first primer layer materials 60 to about 2.00 wt. % first primer layer materials 60, and further alternatively from about 0.001 wt. % first primer layer materials 60 to about 20.0 wt. % first primer layer materials 60. In an embodiments, the aqueous solution may include from about 0.1 wt. % first primer layer materials 60 to about 1.0 wt. % first primer layer materials 60. In embodiments, elastomeric substrate 5 may be exposed to the cationic mixture for any suitable period of time to produce first primer layer 80. In embodiments, elastomeric substrate 5 is exposed to the cationic mixture from about 1 second to about 20 minutes, alternatively from about 1 second to about 200 seconds, and alternatively from about 10 seconds to about 200 seconds, and further alternatively from about instantaneous to about 1.200 seconds, and alternatively from about 1 second to about 5 seconds, and alternatively from about 4 seconds to about 6 seconds, and further alternatively about 5 seconds. In an embodiment, elastomeric substrate 5 is exposed to the cationic mixture from about 4 seconds to about 6 seconds.
In embodiments as shown in
In embodiments as shown in
Embodiments include the multilayer thin film coating method providing a coated elastomeric substrate 5 having a gas transmission rate between about 0.005 cc/(m2*day*atm) and about 5,000 cc/(m2*day*atm), alternatively between about 0.005 cc/(m2*day*atm) and about 1,000 cc/(m2*day*atm), and alternatively between about 0.03 cc/(m2*day*atm) and about 100 cc/(m2*day*atm), further alternatively between about 0.3 cc/(m2*day*atm) and about 100 cc/(m2*day*atm), and further alternatively between about 3 cc/(m2*day*atm) and about 30 cc/(m2*day*atm).
It is to be understood that the multilayer thin film coating method is not limited to exposure to a cationic mixture followed by an anionic mixture. In embodiments in which elastomeric substrate 5 is positively charged or neutral, the multilayer thin film coating method includes exposing elastomeric substrate 5 to the anionic mixture followed by exposure to the cationic mixture. In such embodiment (not illustrated), first anionic layer 30 is deposited on elastomeric substrate 5 with first cationic layer 25 deposited on first anionic layer 30, and second anionic layer 40 is deposited on first cationic layer 25 followed by second cationic layer 35 deposited on second anionic layer 40 to produce quadlayer 10 with the steps repeated until coating 65 has the desired thickness. In embodiments in which elastomeric substrate 5 has a neutral charge, the multilayer thin film coating method may include beginning with exposure to the cationic mixture followed by exposure to the anionic mixture or may include beginning with exposure to the anionic mixture followed by exposure to the cationic mixture.
In embodiments (not shown), quadlayers 10 may have one or more than one cationic layer (i.e., first cationic layer 25, second cationic layer 35, cationic layers in primer layer 45) comprised of more than one type of cationic materials. In an embodiment (not shown), quadlayers 10 may have one or more than one anionic layer (i.e., first anionic layer 30, second anionic layer 40, anionic layers in primer layer 45) comprised of more than one type of anionic material. In some embodiments, one or more cationic layers are comprised of the same materials, and/or one or more of the anionic layers are comprised of the same anionic materials. It is to be understood that coating 65 is not limited to one layerable material but may include more than one layerable material and/or more than one cationic material.
It is to be understood that the multilayer thin film coating method for preparing an elastomeric substrate 5 with coating 65 having bilayers 50 is not limited to exposure to a cationic mixture followed by an anionic mixture. In embodiments in which elastomeric substrate 5 is positively charged, the multilayer thin film coating method includes exposing elastomeric substrate 5 to the anionic mixture followed by exposure to the cationic mixture. In such embodiment (not illustrated), anionic layer 100 is deposited on elastomeric substrate 5 with cationic layer 95 deposited on anionic layer 100 to produce bilayer 50 with the steps repeated until coating 65 has the desired thickness. In embodiments in which elastomeric substrate 5 has a neutral charge, the multilayer thin film coating method may include beginning with exposure to the cationic mixture followed by exposure to the anionic mixture or may include beginning with exposure to the anionic mixture followed by exposure to the cationic mixture.
It is to be further understood that coating 65 is not limited to one layerable material 110 and/or one cationic material 105 but may include more than one layerable material 110 and/or more than one cationic material 105. The different layerable materials 110 may be disposed on the same anionic layer 100, alternating anionic layers 100, or in layers of bilayers 50 (i.e., or in layers of trilayers or increasing numbers of layers). The different cationic materials 105 may be disposed on the same cationic layer 95, alternating cationic layers 95, or in layers of bilayers 50 (i.e., or in layers of trilayers or increasing numbers of layers). For instance, in embodiments as illustrated in
It is to be understood that the multilayer thin film coating method produces coatings 65 of trilayers, pentalayers, and increasing numbers of layers by the embodiments disclosed above for bilayers 50 and quadlayers 10. It is to be understood that coating 65 is not limited to only a plurality of bilayers 50, trilayers, quadlayers 10, pentalayers, hexalayers, heptalayers, octalayers, or increasing numbers of layers. In embodiments, coating 65 may have any combination of such layers.
In some embodiments in which coating 65 comprises trilayers, the trilayers comprise a first cationic layer comprising polyethylenimine, a second cationic layer comprising polyethylene oxide or polyglycidol, and an anionic layer comprising clay. In such an embodiment, the second cationic layer is disposed between the first cationic layer and the anionic layer. In another embodiment in which coating 65 comprises trilayers, the trilayers comprise a first cationic layer comprising polyethylenimine, an anionic layer comprising clay, and a second cationic layer comprising polyethylene oxide or polyglycidol. In such an embodiment, the anionic layer is disposed between the first cationic layer and the second cationic layer. In some embodiments in which coating 65 comprises trilayers, the trilayers comprise a cationic layer comprising polyethylene oxide or polyglycidol, a first anionic layer comprising polyacrylic acid or polymethacrylic acid, and a second anionic layer comprising sodium montmorillonite. In such an embodiment, the first anionic layer is disposed between the cationic layer and the second anionic layer.
In some embodiments, the multilayer thin film coating method includes rinsing elastomeric substrate 5 between each (or alternatively more than one) exposure step (i.e., after the step of exposing to a cationic mixture or step of exposing to an anionic mixture). For instance, after elastomeric substrate 5 is removed from exposure to the cationic mixture, elastomeric substrate 5 with first cationic layer 25 is rinsed and then exposed to an anionic mixture. In some embodiments, quadlayer 10 is rinsed before exposure to the same or another cationic and/or anionic mixture. In an embodiment, coating 65 is rinsed. The rinsing is accomplished by any rinsing liquid suitable for removing all or a portion of ionic liquid from elastomeric substrate 5 and any layer. In embodiments, the rinsing liquid includes deionized water, methanol, or any combinations thereof. In an embodiment, the rinsing liquid is deionized water. A layer may be rinsed for any suitable period of time to remove all or a portion of the ionic liquid. In an embodiment, a layer is rinsed for a period of time from about 5 seconds to about 5 minutes. In some embodiments, a layer is rinsed after a portion of the exposure steps.
In an embodiment, the multilayer thin film coating method includes rinsing elastomeric substrate 5 having coating 65 with a salt solution after a desired exposure step (i.e., after the step of exposure to a cationic mixture or an anionic mixture). For instance, after coating 65 is formed on elastomeric substrate 5, elastomeric substrate 5 having coating 65 is rinsed in the salt solution. Rinsing with the salt solution may be before and/or after rinsing with the rinsing liquid (i.e., deionized water). In an embodiment, elastomeric substrate 5 having coating 65 is rinsed with the salt solution before rinsing with the rinsing liquid. The salts may include any salts suitable for use with the multilayer thin film coating method. In an embodiment in which the outer layer of coating 65 is neutral or negative (i.e., the anionic layer, second anionic layer, third anionic layer, etc., which depends upon whether coating 65 is a bilayer, trilayer, quadlayer, etc.), the salts include salts from the Hofmeister series of anions. In embodiments, the salts include salts from the ions CO32−, F−, SO42−, H2PO42−, C2H3O2−, Cl−, NO3−, Br−, Cl03−, I−, ClO4−, SCN−, S2O32−, or any combinations thereof. In an embodiment, the salt includes the ion Cl−. The salts are of a concentration from about 1 millimolar in solution to about 10 millimolar in solution, alternatively from about 5 millimolar in solution to about 10 millimolar in solution, alternatively from about 1 millimolar in solution to about 100 millimolar in solution, and further alternatively from about 0.1 millimolar in solution to about 100 millimolar in solution. In an embodiment in which the outer layer of coating 65 is neutral or positive (i.e., the cationic layer, second cationic layer, third cationic layer, etc., which depends upon whether coating 65 is a bilayer, trilayer, quadlayer, etc.), the salts include salts from the Hofmeister series of cations. In embodiments, the salts include salts from the ions NH4+, K+, Na+, Li+, Mg2+, Ca+, Rb+, Cs+, N(CH3)4+, or any combinations thereof. In embodiments, the salts include salts from the ions K+, Na+, or any combinations thereof. In an embodiment, the salts include salts from the ion K+. In other embodiments, the salts include salts from the ion Na+. Embodiments include the salt comprising NaCl, KCl, or any combinations thereof. In some embodiments, the salt comprises NaCl. In other embodiments, the salt comprises KCl. The salts are of a concentration from about 1 millimolar in solution to about 10 millimolar in solution, alternatively from about 5 millimolar in solution to about 10 millimolar in solution, and alternatively from about 1 millimolar in solution to about 100 millimolar in solution. In alternative embodiments, the multilayer thin film coating method includes rinsing one or more layers with a salt solution during the deposition process of producing coating 65. In some alternative embodiments, rinsing one or more of the layers with a salt solution is accomplished with the same or different salt solutions.
In embodiments, the multilayer thin film coating method includes drying elastomeric substrate 5 between each (or alternatively more than one) exposure step (i.e., step of exposing to cationic mixture or step of exposing to anionic mixture). For instance, after elastomeric substrate 5 is removed from exposure to the cationic mixture, elastomeric substrate 5 with first cationic layer 25 is dried and then exposed to an anionic mixture. In some embodiments, quadlayer 10 is dried before exposure to the same or another cationic and/or anionic mixture. In an embodiment, coating 65 is dried. The drying is accomplished by applying a drying gas to elastomeric substrate 5. The drying gas may include any gas suitable for removing all or a portion of liquid from elastomeric substrate 5. In embodiments, the drying gas includes air, nitrogen, or any combinations thereof. In an embodiment, the drying gas is air. In some embodiments, the air is filtered air. The drying may be accomplished for any suitable period of time to remove all or a portion of the liquid from a layer (i.e., quadlayer 10) and/or coating 65. In an embodiment, the drying is for a period of time from about 5 seconds to about 500 seconds. In an embodiment in which the multilayer thin film coating method includes rinsing after an exposure step, the layer is dried after rinsing and before exposure to the next exposure step. In alternative embodiments, drying includes applying a heat source to the layer (i.e., quadlayer 10) and/or coating 65. For instance, in an embodiment, elastomeric substrate 5 is disposed in an oven for a time sufficient to remove all or a portion of the liquid from a layer. In some embodiments, drying is not performed until all layers have been deposited, as a final step before use.
In some embodiments (not illustrated), the thin film coating method includes coating 65 comprising additives. In embodiments, the additives may be mixed in anionic mixtures with layerable materials. For instance, the thin film coating method includes mixing the additives with the layerable materials in the aqueous solution, includes mixing the additives with the cationic materials in the aqueous solution, or any combinations thereof. In some embodiments, coating 65 has a layer or layers of additives. The additives may be used for any desirable purpose. For instance, additives may be used for protection of elastomeric substrate 5 against ultraviolet light or for abrasion resistance. For ultraviolet light protection, any negatively charged material suitable for protection against ultraviolet light and for use in coating 65 may be used. In an embodiment, examples of suitable additives for ultraviolet protection include titanium dioxide, clay, or any combinations thereof. In embodiments, the additive is titanium dioxide. Any clay suitable for ultraviolet protection may be used. In an embodiment, the clay is vermiculite. For abrasion resistance, any additive suitable for abrasion resistance and for use in coating 65 may be used. In embodiments, examples of suitable additives for abrasion resistance include crosslinkers. Any crosslinker suitable for use with an elastomer may be used. In an embodiment, the crosslinker may be any chemical that reacts with any matter in coating 65. Without limitation, examples of crosslinkers include bromoalkanes, aldehydes, carbodiimides, amine active esters, or any combinations thereof. In embodiments, the aldehydes include glutaraldehyde, di-aldehyde, or any combinations thereof. In an embodiment, the aldehydes include glutaraldehyde. In an embodiment, the carbodiimide is 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide (EDC). Embodiments include the amine reactive esters including N-hydroxysuccinimide esters, imidoesters, or any combinations thereof. The crosslinkers may be used to crosslink the anionic layers and/or cationic layers (i.e., to one another or to themselves). In some embodiments, the additives are added in a separate exposure (i.e., separate bath, spray, or the like) from the exposure that provided coating 65.
In some embodiments, the pH of the anionic and/or cationic solution is adjusted. Without being limited by theory, reducing the pH of the cationic solution reduces growth of coating 65. Further, without being limited by theory, the coating 65 growth may be reduced because the cationic solution may have a high charge density at lowered pH values, which may cause the polymer backbone to repel itself into a flattened state. In some embodiments, the pH is increased to increase the coating 65 growth and produce a thicker coating 65. Without being limited by theory, a lower charge density in the cationic mixture provides an increased coiled polymer. The pH may be adjusted by any suitable means such as by adding an acid or base. In an embodiment, the pH of an anionic solution is between about 0 and about 14, alternatively between about 1 and about 7, and alternatively between about 1 and about 3, and further alternatively about 3. Embodiments include the pH of a cationic solution that is between about 0 and about 14, alternatively between about 3 and about 12, and alternatively about 3.
The exposure steps in the anionic and cationic mixtures may occur at any suitable temperature. In an embodiment, the exposure steps occur at ambient temperatures.
In some embodiments, coating 65 is optically transparent.
In an embodiment, elastomeric substrates 5 may comprise a portion or all of the rubber portions of a tire. In such an embodiment, coating 65 may provide a barrier that limits gas (i.e., oxygen), vapor, and/or chemicals to pass through the tire. Elastomeric substrates 5 with coating 65 may be used for any suitable portions of a tire such as, without limitation, the carcass, the innerliner, and the like. In an embodiment, the carcass of a tire comprises elastomeric substrate 5 with coating 65.
To further illustrate various illustrative embodiments of the present invention, the following examples are provided.
Natural sodium montmorillonite (MMT) (CLOISITE® NA+, which is a registered trademark of Southern Clay Products, Inc.) clay was used as received. Individual MMT platelets had a negative surface charge in deionized water, reported density of 2.86 g/cm3, thickness of 1 nm, and a nominal aspect ratio (l/d)≧200. Branched polyethylenimine (PEI) (Mw=25,000 g/mol and Mn=10,000 g/mol) and polyacrylic acid (PAA) (35 wt. % in water, Mw=100,000 g/mol) were purchased from Sigma-Aldrich (Milwaukee, Wis.) and used as received. Polyethylene oxide (PEO) (Mw=4,000,000 g/mol) was purchased from Polysciences, Inc. (Warrington, Pa.). 500 μm thick, single-side-polished, silicon wafers were purchased from University Wafer (South Boston, Mass.) and used as reflective substrates for film growth characterization via ellipsometry.
Film Preparation.
All film deposition mixtures were prepared using 18.2MΩ deionized water, from a DIRECT-Q® 5 Ultrapure Water System, and rolled for one day (24 h) to achieve homogeneity. DIRECT-Q® is a registered trademark of Millipore Corporation. Prior to deposition, the pH of 0.1 wt. % aqueous solutions of PEI were altered to 10 or 3 using 1.0 M HCl, the pH of 0.1 wt. % aqueous solutions of PEO were altered to 3 using 1.0 M HCl, the pi of 0.2 wt. % aqueous solutions of PAA were altered to 3 using 1.0 M HCl, and the pH of 2.0 wt. % aqueous suspensions of MMT were altered to 3 using 1.0 M HCl. Silicon wafers were piranha treated for 30 minutes prior to rinsing with water, acetone, water again and finally dried with filtered air prior to deposition. Elastomeric substrates were rinsed with deionized water, immersed in a 40 wt. % propanol in water bath at 40° C. for 5 minutes, rinsed with RT 40 wt. % propanol in water, rinsed with deionized water, dried with filtered air, and plasma cleaned for 5 minutes on each side. Each appropriately treated substrate was then dipped into the PEI solution at pH 10 for 5 minutes, rinsed with deionized water, and dried with filtered air. The same procedure was followed when the substrate was next dipped into the PAA solution. Once this initial bilayer was deposited, the above procedure was repeated when the substrate was dipped into the PEO solution, then the PAA solution, then the PEI solution at pH 3, and finally the MMT suspension, using 5 second dip times for polymer solutions and using one minute dip times for the MMT suspension, until the desired number of quadlayers of PEO/PAA/PEI/MMT were achieved. All films were prepared using a home-built robotic dipping system.
Film Characterization
Film thickness was measured every one to five quadlayers (on silicon wafers) using an ALPHA-SE® ellipsometer, ALPHA-SE is a registered trademark of J. A. Woollam Co., Inc. OTR testing was performed by Mocon, Inc. in accordance with ASTM D-3985, using an Oxtran 2/21 ML instrument at 0% RH.
From the results,
Cationic branched polyethylenimine (PEI) (Mw=25.000 g/mol and Mn=10,000 g/mol) and anionic poly(acrylic acid) (PAA) (Mw=100,000 g/mol) were purchased from Sigma-Aldrich (Milwaukee, Wis.). Poly(ethylene oxide) (PEO) (Mw=4,000,000 g/mol) was purchased from Polysciences, Inc. (Warrington, Pa.). The pH of aqueous solutions containing 0.1 wt. % PEI, 0.2 wt. % PAA, or 0.1 wt. % PEO was adjusted to 3 using 1 M HCl prior to film assembly. Southern Clay Products, Inc. (Gonzales, Tex.) supplied natural, untreated montmorillonite (MMT) (CLOISITE® NA+). This clay had a cationic exchange capacity of 0.926 meq/g and was negatively-charged in deionized water. MMT platelets had a density of 2.86 g/cm3, diameter of 10-1000 nm and thickness of 1 nm. A natural vermiculite (VMT) (MICROLITE® 963++) clay dispersion containing no clay particles greater than 45 microns was used. MICROLITE® is a registered trademark of W.R. Grace & Co.-Conn. The pH of the aqueous suspension containing 1 wt. % clay (either MMT or VMT) was also adjusted to 3 using a 1 M HCl prior to film assembly. Before deposition, mini-tire and certain butyl rubber plaques were treated using a BD-20C Corona Treater (Electro-Technic Products, Inc., Chicago), which created a negative surface charge. A 5 minute 1M HNO3 treatment was also employed for certain butyl rubber plaques and then compared with other methods. Carcass rubber films were rinsed with deionized water, bathed in 40 wt. % N-Propanol (NP) at 40° C. for 5 min, rinsed with NP and again with water before being dried with filtered air. Carcass rubber films rinsed only with deionized water were also prepared as references.
All films created for oxygen transmission rate testing were sent to Mocon, Inc. (Minneapolis, Minn.) and tested in accordance with ASTM D-3985,13 using an Oxtran 2/21 ML instrument. OTR testing was done at 40° C. and 0% RH, unless otherwise specified. Thickness of films was measured on silicon wafers using a Reflectometer (Filmetrics F20-UV). Thin film topography was imaged using a JEOL JSM-7500F FE-SEM.
Dip coatings on carcass rubber plaques were prepared using home-built robotic dipping systems. The surface of rubber plaques were cleaned by plasma using a Diener Electronic ATTO plasma system (purchased from Thierry Corporation, Detroit, Mich.) at 25 W for 5 minutes. The deposition time for PE/PAA primer layer was 5 minutes, and the time was reduced to 1 minute for regular quadlayer deposition. Rinsing and drying were carried out between depositions. A spraying study was carried out on a modified spraying robot from Svaya Nanotechnologies. The spray deposition time for primer layer was 10 seconds, which was followed by a 5 seconds pause. The time was reduced to 3 seconds for regular quadlayer deposition, which was followed by a 3 seconds pause between layers. There was a 10 seconds rinse and a 5 seconds pause between depositions. No drying was applied until the end.
Dip coating of a mini-tire was performed using several buckets. The dipping time for a primer layer on the mini-tire was 5 minutes. The deposition time for all the other layers was set at 1 minute. The mini-tire was immediately rinsed with de-ionized water and dunked three times after each deposition, but not dried.
Layer-by-layer assembly of a stretchable gas barrier film that was comprised of quadlayers of polyethylene oxide (PEO), poly(acrylic acid) (PAA), branched polyethylenimine (PEI), and clay were deposited onto rubber to improve the gas barrier performance. To optimize the coating process and gas barrier property, effects of primer layer pH, clay type, propanol rinsing, water rinsing, and stretching on gas barrier were studied, with the results summarized in Table 1. Deposition of PEI/PAA primer layer ensured good adhesion between the coating and rubber plaque. Unstretched film was prepared with a pH 3 PEI primer that exhibited an almost unnoticeable increase in OTR relative to pH 10 (from 11.2 to 11.9), and the same may be observed for stretched samples (from 51.5 to 53.4). It was concluded that the pH of primer layer PEI solution may be set at pH 3 to reduce consumption of solution and simplify the coating process.
The effect of applying propanol rinsing before assembly was also studied, and it was found that removal of propanol rinsing not only simplified the coating process, but also improved the gas barrier (see Table 1). The optimal MMT solution concentration was determined to be 1% to prevent embrittlement of the coating due to excessive deposition of clay. The optimized recipe for a stretchy coating was PEO/PAA/PEI/1% MMT QLs with a pH 3 PEI/PAA primer layer on rubber plaques without propanol rinsing.
The solutions used for 20 bilayers of PAA/PEO film were 0.1 wt. % polyethylenimine (PEI) (natural pH), deionized water (natural pH), 0.1 wt. % polyacrylic acid (PAA) (pH 3), 0.1 wt. % polyethylene oxide (PEO) (pH 3), and deionized water (pH 3). The assembly procedure included step 1 with a rubber plaque rinsed with deionized water, dried with compressed air, and then plasma treated for 5 minutes. In step 2, the rubber plaque was dipped into 0.1 wt. % PEI solution for 30 minutes, rinsed with deionized water (natural pH) and then dried with compressed air. In step 3, the rubber plaque was dipped into 0.1 wt. % PAA solution for 1 minute. In step 4, the rubber plaque was dip-rinsed in deionized water (pH3) for 3 times, and the rinse time was 20 seconds each. In step 5, the rubber plaque was dipped into 0.1 wt. % PEO solution for 1 minute. In step 6, the rubber plaque was dip-rinsed in deionized water (pH3) for 3 times, and the rinse time was 20 seconds each. Steps 4 to 6 were repeated 20 times to obtain a 20 bilayer PAA/PEO film. The results are shown below in Table 2.
Although the present invention and its advantages have been described in detail, it should be understood that various changes, substitutions and alterations may be made herein without departing from the spirit and scope of the invention as defined by the appended claims.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/US13/78376 | 12/30/2013 | WO | 00 |
| Number | Date | Country | |
|---|---|---|---|
| 61746623 | Dec 2012 | US |
