Organic solvent-based retroreflective compositions for industrial spraying.

Abstract

The present invention relates to an organic solvent-based retroreflective ink, paint, or coating composition having a shear rate of 0.5 rpm, η1, between 0.2 and 8 Pa·s, and a shear rate of 20 rpm, η2, between 80 and 450 mPa·s, with the proviso that the second Brookfield viscosity, η2, is at least two times lower than the first Brookfield viscosity, η1, the composition consisting of 25-75 wt. % organic solvent; 1-85 wt. % spherical glass beads; 0.15-1.2 wt. % thickener; and 0-30 wt. % of one or more additional ingredients, based on the total weight of the composition; the Brookfield viscosities, η1 and η2, being measured using a #2 spindle at a temperature of 25° C. in a 600 ml beaker having a diameter of 8.25 cm.

Description

[Technical field]

[0001] [Field of the Invention] The present invention relates to an organic solvent-based retroreflective composition and to a method for its preparation. The present invention further relates to a method for coating a substrate with a retroreflective layer using said organic solvent-based retroreflective composition, and to substrates coated with a retroreflective layer obtainable by said method.

[0002] [Background of the invention] Retroreflective paints, inks and coatings are used in a variety of applications, such as to improve the visibility of road signs, road markers, fabrics, automobiles, etc., under low light conditions. Paints, inks and coatings are typically imparted with retroreflective properties by the addition of spherical glass beads having a particular refractive index. Retroreflection occurs through the tandem action of refraction of incident light through the top surface of the spherical glass bead, internal reflection from the lower inner surface of the spherical glass bead, and then refraction of the light as it exits the top surface of the spherical glass bead back in the direction from which it came.

[0003] WO 2004 / 017104 discloses a retroreflective composition comprising a thixotropic blend comprising retroreflective microspheres, a binder system, and at least two thixotropic agents in an amount of about 2 to about 5% by weight based on the retroreflective composition. The retroreflective composition is intended for use as a paint, ink, or coating and is applied to a substrate using an aerosol applicator with a propellant. Table 1 of WO 2004 / 017104 discloses typical and preferred amounts of the types of ingredients in the composition. Example 1 of WO 2004 / 017104 discloses a composition in which the solvent is an undefined aliphatic or aromatic naphtha, the solid resin granules are an undefined acrylic type, the first thixotropic agent is an undefined polyurea type, and the second thixotropic agent is an undefined calcium sulfonate complex. The composition of Example 1 has a viscosity between 9,000 and 30,000 cps at 0.5 rpm and between 600 and 1,900 cps at 20 rpm, measured at 25° C. using a Brookfield #3 spindle.

[0004] WO 00 / 42113 relates to retroreflective inks comprising microbeads in a liquid carrier medium. The inks are intended for screen printing onto fabrics. WO 00 / 42113 discloses that the viscosity of the screen printing inks is 10-30 Pa·s at room temperature as measured with a Brookfield viscometer using a #5 spindle rotating at 10 rpm. The inks disclosed in Tables 1-4 and 6 comprise water, a thickener and glass beads. The viscosity is 12.3-32 Pa·s at room temperature as measured with a Brookfield viscometer using a #5 spindle rotating at 10 rpm. Screen printing is a printing technique in which a mesh is used to transfer a paste-like ink onto a substrate, except in areas made impermeable to the ink by a sealing stencil. A blade or squeegee is moved across the screen to fill the open mesh openings with ink, and then a reverse stroke momentarily touches the screen to the substrate along the contact line. This causes the ink to wet the substrate and, when the screen rebounds after the blade has passed, the ink is drawn through the mesh openings. In general, as known to those skilled in the art of printing, the rheological properties of screen printing inks and inks for professional or industrial (high speed) spraying are fundamentally different due to the distinct techniques used to apply them to the substrate. Screen printing inks are not suitable for professional or industrial (high speed) spraying.

[0005] Developing a retroreflective composition that has good stability, sprayability, and results in good print or coating quality is a challenge because the rheology modifiers required to keep the retroreflective particles - such as spherical glass beads, which usually have a density substantially higher than that of the fluid carrier - from distributing homogeneously throughout the fluid carrier would adversely affect the rheological behavior during spraying.

[0006] There is a need for retroreflective inks, coatings and paints that are sufficiently stable that they can be easily applied to a variety of substrates, preferably using professional or industrial (high velocity) spraying, resulting in retroreflective layers or coatings with improved quality.

[0007] It is therefore an object of the present invention to provide a retroreflective composition that can be professionally or industrially applied to a variety of substrates as a paint, ink or coating, that can be applied to a substrate by spraying, such as professional or industrial (high velocity) spraying, and that has sufficient stability or shelf life.

[0008] It is a further object of the present invention to provide a retroreflective composition that can be professionally or industrially applied to a variety of substrates by spraying, such as professional or industrial (high velocity) spraying, as a paint, ink or coating, resulting in improved print or coating quality, e.g. good or improved uniformity or smoothness of the layer.

[0009] [Summary of the Invention] The present inventors have unexpectedly determined that one or more objectives can be met by using an organic solvent-based retroreflective composition that exhibits shear thinning behavior, having a lower viscosity at high shear rates and low concentrations of thickener, compared to prior art compositions.

[0010] Thus, in a first aspect, the invention provides an organic solvent based retroreflective ink, paint or coating composition having a η at a shear rate of 0.5 rpm between 0.2 and 8 Pa·s, and a η at a shear rate of 20 rpm between 80 and 450 mPa·s, provided that the second Brookfield viscosity η is at least two times lower than the first Brookfield viscosity η, based on the total weight of the composition: 25-75% by weight of organic solvent; 1-85% by weight of spherical glass beads having a median particle size D50, measured using laser diffraction, between 1 and 150 μm and a refractive index, measured at a wavelength λ of 589 nm, between 1.5 and 2.8; 0.15 to 1.2% by weight of a thickening agent; and 0-30% by weight of one or more further components; The Brookfield viscosities η1 and η2 are measured using a #2 spindle at a temperature of 25° C. in a 600 ml beaker having a diameter of 8.25 cm. Organic solvent based retroreflective ink, paint or coating compositions are provided.

[0011] The inventors have determined that this organic solvent-based retroreflective composition can be applied, for example, using professional or industrial (high velocity) spraying to a variety of substrates, resulting in a retroreflective coating layer having excellent print or coating quality.

[0012] The reduced amount of thickener and reduced viscosity at a shear rate of 20 rpm results in improved homogeneity and smoothness of the retroreflective layer, especially resulting in a layer with less "orange peel". The reduced amount of thickener reduces the viscosity not only at high shear rates (typical of spray conditions) but also at low shear rates (related to stability). The inventors have unexpectedly found that the reduced amount of thickener required to obtain improved homogeneity and smoothness of the retroreflective layer is still adequate to provide an organic solvent-based retroreflective ink, paint or coating composition with sufficient stability or shelf life.

[0013] In a second aspect, there is provided a process for the preparation of an organic solvent-based retroreflective ink, paint or coating composition as defined herein, comprising the steps of: (i) adding to a container an organic solvent, spherical glass beads as defined above, a thickening agent as defined above, and optionally one or more further ingredients as defined above; and (ii) stirring or homogenising the mixture obtained in step (i) preferably at a temperature between 15 and 70° C., preferably for a period of between 5 and 60 minutes.

[0014] In a third aspect, the present invention provides a method of coating a substrate with a retroreflective layer, the method comprising: a) providing a substrate; b) optionally applying a primer layer to the substrate of step (a); c) optionally, but not preferably, applying a colored base layer to the substrate of step (a) or the primer layer of step (b); d) spraying an organic solvent based retroreflective ink, paint or coating composition as defined hereinbefore onto the substrate of step (a) or onto the layer of step (b) or (c); e) drying and / or curing the substrate coated with the retroreflective layer obtained in step (d); and f) Optionally, coating the dried substrate coated with the retroreflective layer obtained in step (e) with one or more additional transparent coating layers, followed by drying and / or curing.

[0015] In a fourth aspect, the present invention relates to a substrate coated with a retroreflective layer obtained or obtainable by the method for coating a substrate as defined herein.

[0016] definition The term "orange peel" as used herein refers to a speckled print defect characterized by a grainy image reminiscent of the texture of orange peel, caused by the failure of ink to bleed into a smooth film layer.

[0017] The term "shear thinning behavior" in the context of the organic solvent-based compositions of the present invention relates to the decrease in viscosity when the composition, initially in a static state, is subjected to a shear rate. [Brief description of the drawings]

[0018] [Figure 1a]1 depicts the smoothness / orange peel of retroreflective coatings prepared using compositions according to the invention and comparative compositions. [Figure 1b] 1 depicts the smoothness / orange peel of retroreflective coatings prepared using compositions according to the invention and comparative compositions. [Figure 1c] 1 depicts the smoothness / orange peel of retroreflective coatings prepared using compositions according to the invention and comparative compositions. [Figure 1d] 1 depicts the smoothness / orange peel of retroreflective coatings prepared using compositions according to the invention and comparative compositions. [Figure 1e] 1 depicts the smoothness / orange peel of retroreflective coatings prepared using compositions according to the invention and comparative compositions. [Figure 1f] 1 depicts the smoothness / orange peel of retroreflective coatings prepared using compositions according to the invention and comparative compositions. [Figure 1g] 1 depicts the smoothness / orange peel of retroreflective coatings prepared using compositions according to the invention and comparative compositions. [Figure 1h] 1 depicts the smoothness / orange peel of retroreflective coatings prepared using compositions according to the invention and comparative compositions. Detailed Description

[0019] In a first aspect, the invention provides an organic solvent based retroreflective ink, paint or coating composition having a η at a shear rate of 0.5 rpm between 0.2 and 8 Pa·s, and a η at a shear rate of 20 rpm between 80 and 450 mPa·s, with the proviso that the second Brookfield viscosity η is at least two times lower than the first Brookfield viscosity η, based on the total weight of the composition: 25-75% by weight of organic solvent; 1-85% by weight of spherical glass beads having a median particle size D50, measured using laser diffraction, between 1 and 150 μm and a refractive index, measured at a wavelength λ of 589 nm, between 1.5 and 2.8; 0.15 to 1.2% by weight of a thickening agent; and 0-30% by weight of one or more further components; Brookfield viscosities η1 and η2 are for organic solvent based retroreflective ink, paint or coating compositions measured using a #2 spindle at a temperature of 25° C. in a 600 ml beaker having a diameter of 8.25 cm.

[0020] In a highly preferred embodiment, a first aspect is an organic solvent based retroreflective ink, paint or coating composition having a η at a shear rate of 0.5 rpm between 0.2 and 8 Pa s, and a η at a shear rate of 20 rpm between 80 and 450 mPa s, with the proviso that the second Brookfield viscosity η is at least two times lower than the first Brookfield viscosity η, based on the total weight of the composition: 25-68% by weight of organic solvent; 20-70% by weight of spherical glass beads having a median particle size D50, measured using laser diffraction, between 5 and 150 μm and a refractive index, measured at a wavelength λ of 589 nm, between 1.5 and 2.8; 0.15 to 1.2% by weight of a thickening agent; and 0-30% by weight of one or more further components; Brookfield viscosities η1 and η2 refer to organic solvent based retroreflective ink, paint or coating compositions measured using a #2 spindle at a temperature of 25° C. in a 600 ml beaker having a diameter of 8.25 cm.

[0021] stability In a preferred embodiment, the organic solvent-based retroreflective ink, paint or coating composition is considered stable if it is stable for at least 12 hours, more preferably at least 1 day, even more preferably at least 2 days, at least 5 days, at least 10 days, at least 1 month, at least 2 months, at least 6 months, at least 1 year, at least 2 years, and no settling or separation can be observed by visual and tactile inspection. In a preferred embodiment, the organic solvent-based retroreflective ink, paint or coating composition is spray stable for at least 24 hours. A composition is considered spray stable if it can be sprayed without remixing.

[0022] Organic solvents The term "organic solvent" as used herein relates to an organic solvent or mixture of organic solvents (most preferably anhydrous) containing less than 3% water by weight, preferably less than 2% water by weight, more preferably less than 1% water by weight, even more preferably less than 0.5% water by weight.

[0023] Preferred organic solvents are selected from the group consisting of aliphatic and aromatic solvents, ketones, esters, glycoethers, alcohols, halogenated hydrocarbons, and combinations thereof.Highly preferred organic solvents are selected from the group consisting of xylene (mixture of isomers), toluene, ethylbenzene, naphtha, 1,2,4-trimethylbenzene, mesitylene, n-propylbenzene, isopentyl acetate, n-butyl acetate, (2-methoxymethylethoxy)propanol, 2-butoxyethyl acetate, 2-methylbutyl acetate, isobutanol, 1-butanol, 1-ethoxypropan-2-ol, 2,6-dimethyl-4-heptanone, 2-methoxy-1-methylethyl acetate, 4,6-dimethyl-heptan-2-one, 4-methyl-2-pentanone, 1-methoxy-2-propanol, 1-methoxy-2-propyl acetate, 2-(2-butoxyethoxy)ethanol, 2-butoxyethanol, 5-methylhexan-2-one, ethyl acetate, and combinations thereof.

[0024] In a highly preferred embodiment, the amount of organic solvent is from 25 to 68 weight percent, based on the total weight of the organic solvent-based retroreflective ink, coating, or paint composition.

[0025] In a preferred embodiment, the amount of organic solvent is from 27 to 65% by weight, more preferably from 30 to 60% by weight, and even more preferably from 35 to 58% by weight, based on the total weight of the organic solvent-based retroreflective ink, coating or paint composition.

[0026] In embodiments, the amount of organic solvent is 25-66%, 25-62%, 25-60%, 25-58%, or 25-56% by weight, based on the total weight of the organic solvent-based retroreflective ink, coating, or paint composition.

[0027] In other embodiments, the amount of organic solvent is 28-68%, 30-68%, 32-68%, 34-68%, 36-68%, 38-68%, or 40-68% by weight, based on the total weight of the organic solvent-based retroreflective ink, coating, or paint composition.

[0028] In still other embodiments, the amount of organic solvent is 28-75%, 30-75%, 32-75%, 34-75%, 36-75%, 38-75%, or 40-75% by weight, based on the total weight of the organic solvent-based retroreflective ink, coating, or paint composition.

[0029] Spherical Glass Beads As defined above, the refractive index of the spherical glass beads measured at a wavelength λ of 589 nm lies between 1.5 and 2.8.

[0030] In a preferred embodiment, the spherical glass beads are (a) between 2.0 and 2.8, preferably between 2.1 and 2.4; or (b) a refractive index, measured at a wavelength λ of 589 nm, between 1.7 and 2.1, preferably between 1.8 and 2.0;

[0031] In a preferred embodiment, the term "glass" in "spherical glass beads" as used herein refers to an amorphous, non-crystalline solid and transparent material made of oxides. In another embodiment, the term "glass" in "spherical glass beads" refers to a solid and transparent material made of oxides and containing some microcrystallinity. The refractive index of spherical glass beads is closely related to the density of glass, but the relationship is not linear. Due to the nature of glass, the density is approximately an additive function of its composition. The density of spherical glass beads with a refractive index between 1.5 and 2.8 is typically between 2.5 and 4.5 g / cm. 3 The value fluctuates between .

[0032] Oxides which can be used in the glass are oxides of silicon, boron, aluminum, sodium, barium, vanadium, titanium, lanthanum, strontium, zirconium, potassium, magnesium, iron, calcium, zinc, lithium, barium and lead. The spherical glass beads may contain various combinations of, for example, silica (SiO2), boron oxide (BO3), phosphorus pentoxide (PO5), vanadium pentoxide (VO5), arsenic trioxide (As2O3), germanium oxide (GeO2), calcium oxide (CaO), sodium oxide (Na2O), magnesium oxide (MgO), zinc oxide (ZnO), aluminum oxide (Al2O3), potassium oxide (KO), iron oxide (Fe2O3), lead oxide (PbO), barium oxide (BaO), barium titanate (BaTiO3), titanium oxide (TiO2), lithium oxide (Li2O), strontium oxide (SrO), lanthanum oxide (La2O3), and zirconium oxide (ZrO2). Silica and boron oxide generally have the lowest density. Glasses containing a large weight percentage of these oxides therefore generally result in glass beads with a low refractive index. The refractive index can be increased by the addition of oxides having a high molecular weight. Preferably, the spherical glass beads do not contain PbO.

[0033] Glass beads having a refractive index in the range of 1.5 to 2.51 and their composition in terms of oxides are disclosed in WO 2014 / 109564, which is incorporated herein by reference in its entirety. PbO-free transparent glass beads having a refractive index greater than 2.15 are disclosed in U.S. Pat. No. 4,082,427, which is incorporated herein by reference in its entirety.

[0034] The spherical glass beads may be colored spherical glass beads as long as they maintain transparency. Both colored spherical glass beads made of colored transparent glass and spherical glass beads with a concentric transparent colored coating are included in the present invention. The color may be a natural color brought about by the composition of oxides, or may be intentionally selected by adding a component with a specific color. Colored glass beads with high refractive index and high transparency are disclosed in WO2014 / 109564.

[0035] Thus, in embodiments, at least some of the spherical glass beads are made of a colored transparent glass and / or at least some of the spherical glass beads are coated with a concentric transparent colored coating.

[0036] The spherical glass beads have a median diameter D50 as measured by laser diffraction. The median diameter D50 is therefore the volume median based on the volume distribution. The median diameter D50 is the diameter below which half of the population of spherical glass beads falls. This volume median diameter is often referred to in the art as Dv50 or D v0.5 It is called.

[0037] In a highly preferred embodiment, the spherical glass beads have a median particle size D50, measured using laser diffraction, of between 5 and 150 μm.

[0038] In an embodiment, the spherical glass beads have a median particle size D50, measured using laser diffraction, between 25 and 100 μm, preferably between 30 and 75 μm, more preferably between 35 and 50 μm.

[0039] In a preferred embodiment, the spherical glass beads have a median particle size D50, measured using laser diffraction, of between 5 and 100 μm, for example between 5 and 75 μm, between 5 and 50 μm, between 5 and 45 μm, between 5 and 40 μm or between 5 and 35 μm.

[0040] In a highly preferred embodiment, the spherical glass beads have a median particle size D50, measured using laser diffraction, of between 1 and 100 μm, for example between 1 and 75 μm, between 1 and 50 μm, between 1 and 45 μm, between 1 and 40 μm, between 1 and 35 μm, between 1 and 30 μm, between 1 and 25 μm, between 1 and 20 μm, between 1 and 15 μm, or between 1 and 10 μm.

[0041] In yet another embodiment, the spherical glass beads have a median particle size D50, as measured using laser diffraction, between 25 and 150 μm, e.g., between 50 and 150 μm, between 75 and 150 μm, between 100 and 150 μm, between 110 and 150 μm, or between 115 and 150 μm.

[0042] The diameters D10 and D90 are often referred to in the art as Dv10 or D v0.1 and Dv90 or D v0.9 The D10 diameter is the diameter below which 10% of a population of spherical glass beads fall. Similarly, the D90 diameter is the diameter below which 90% of a population of spherical glass beads fall.

[0043] The span of the particle size distribution of spherical glass beads as measured by laser diffraction is defined as follows:

[0044]

number

[0045] In another embodiment, the spherical glass beads have a median particle size D50, measured using laser diffraction, between 15 and 100 μm, and a span between 0 and 1.9, such as between 0 and 1.5, between 0 and 1, between 0 and 0.5, between 0 and 0.2, or between 0 and 0.1.

[0046] In yet another embodiment, the spherical glass beads have a median particle size D50, measured using laser diffraction, between 30 and 75 μm, and a span between 0 and 1.9, such as between 0 and 1.5, between 0 and 1, between 0 and 0.5, between 0 and 0.2, or between 0 and 0.1.

[0047] In another preferred embodiment, the spherical glass beads have a median particle size D50, measured using laser diffraction, between 15 and 50 μm and a span between 0 and 1.9, such as between 0 and 1.5, between 0 and 1, between 0 and 0.5, between 0 and 0.2 or between 0 and 0.1.

[0048] In yet another preferred embodiment, the spherical glass beads have a median particle size D50, measured using laser diffraction, between 1 and 35 μm, and a span between 0 and 1.9, such as between 0 and 1.5, between 0 and 1, between 0 and 0.5, between 0 and 0.2, or between 0 and 0.1.

[0049] In yet another preferred embodiment, the spherical glass beads have a median particle size D50, measured using laser diffraction, between 5 and 35 μm, and a span between 0 and 1.9, such as between 0 and 1.5, between 0 and 1, between 0 and 0.5, between 0 and 0.2, or between 0 and 0.1.

[0050] In yet another preferred embodiment, the spherical glass beads have a median particle size D50, measured using laser diffraction, between 10 and 25 μm, and a span between 0 and 1.9, such as between 0 and 1.5, between 0 and 1, between 0 and 0.5, between 0 and 0.2, or between 0 and 0.1.

[0051] In yet another preferred embodiment, the spherical glass beads have a median particle size D50 measured using laser diffraction between 1 and 25 μm and a span between 0 and 1.9, such as between 0 and 1.5, between 0 and 1, between 0 and 0.5, between 0 and 0.2, or between 0 and 0.1.

[0052] In yet another preferred embodiment, the spherical glass beads have a median particle size D50, measured using laser diffraction, between 1 and 15 μm, and a span between 0 and 1.9, such as between 0 and 1.5, between 0 and 1, between 0 and 0.5, between 0 and 0.2, or between 0 and 0.1.

[0053] In yet another preferred embodiment, the spherical glass beads have a median particle size D50, measured using laser diffraction, between 1 and 10 μm, and a span between 0 and 1.9, such as between 0 and 1.5, between 0 and 1, between 0 and 0.5, between 0 and 0.2, or between 0 and 0.1.

[0054] As will be appreciated by those skilled in the art, span=0 corresponds to monodisperse spherical glass beads.

[0055] In a preferred embodiment, at least a portion of the spherical glass beads are hemispherically coated with a light reflective coating, preferably with a hemispherical aluminum coating (HAC). In another embodiment, at least a portion of the spherical glass beads are fluorochemically coated.

[0056] In a highly preferred embodiment, the amount of spherical glass beads is 20-70% by weight, based on the total weight of the organic solvent based retroreflective ink, coating or paint composition.

[0057] In a preferred embodiment, the amount of spherical glass beads is 23 to 68% by weight, more preferably 25 to 65% by weight, and even more preferably 28 to 63% by weight, based on the total weight of the organic solvent-based retroreflective ink, coating or paint composition.

[0058] In embodiments, the amount of spherical glass beads is 20-65%, 20-63%, 20-60%, 20-57%, 20-54%, 20-52%, or 20-50% by weight based on the total weight of the organic solvent-based retroreflective ink, coating, or paint composition.

[0059] In embodiments, the amount of spherical glass beads is 1-80%, 1-78%, 1-76%, 1-74%, 1-72%, 1-70%, or 1-68% by weight based on the total weight of the organic solvent based retroreflective ink, coating, or paint composition.

[0060] In other embodiments, the amount of spherical glass beads is 22-70%, 24-70%, 26-70%, 27-70%, 28-70%, 29-70%, or 30-70% by weight, based on the total weight of the organic solvent based retroreflective ink, coating, or paint composition.

[0061] In still other embodiments, the amount of spherical glass beads is 2-85%, 5-85%, 8-85%, 10-85%, 12-85%, 14-85%, or 16-85% by weight, based on the total weight of the organic solvent based retroreflective ink, coating, or paint composition.

[0062] The particular application of the organic solvent-based retroreflective ink, coating or paint composition will determine the optimum refractive index of the spherical glass beads. If the composition is applied in a dry environment or onto a substrate that will exhibit retroreflectivity under dry conditions, and if the applied layer of retroreflective spherical glass beads is not coated with an additional layer, the refractive index of the spherical glass beads, measured at a wavelength λ of 589 nm, may be between 1.8 and 2.8.

[0063] In an embodiment, the organic solvent-based retroreflective ink, coating or paint composition defined herein comprises spherical glass beads having a refractive index, measured at a wavelength λ of 589 nm, between 1.8 and 2.0.

[0064] On the other hand, if the composition is to be applied in a wet environment or on a substrate that will exhibit retroreflectivity under wet conditions, or if the applied layer of retroreflective spherical glass beads is coated with one or more additional transparent layers, the refractive index of the spherical glass beads measured at a wavelength λ of 589 nm is preferably between 2.0 and 2.8, more preferably between 2.2 and 2.4. Compositions that will exhibit retroreflectivity under both dry and wet conditions, and if the applied layer of retroreflective spherical glass beads is coated with one or more additional transparent layers or is not coated, can include different types of glass beads having different refractive indices and, optionally, different sizes. In an embodiment, the organic solvent-based retroreflective ink, coating or paint composition defined herein includes spherical glass beads having a refractive index measured at a wavelength λ of 589 nm between 2.0 and 2.8, preferably between 2.2 and 2.4.

[0065] In another embodiment, the organic solvent-based retroreflective ink, coating or paint composition defined herein comprises at least two types of spherical glass beads, at least one type of spherical glass beads having a refractive index, measured at a wavelength λ of 589 nm, between 1.8 and less than 2.0, and at least one further type of spherical glass beads having a refractive index, measured at a wavelength λ of 589 nm, between 2.0 and 2.8.

[0066] Thickener The organic solvent-based retroreflective ink, coating or paint composition includes a thickener. Without wishing to be bound by any theory, it is believed that the thickener limits or reduces the settling and / or sedimentation of the spherical glass beads and optionally further particulate matter in the organic solvent-based retroreflective ink, coating or paint composition, so that the composition can be easily resuspended. Furthermore, while also not wishing to be bound by any theory, it is believed that the thickener provides the organic solvent-based retroreflective ink, coating or paint composition with shear thinning behavior.

[0067] In a preferred embodiment, the thickening agent comprises a mixture of different thickening agents.

[0068] Preferred examples of thickeners that can be used in the organic solvent based retroreflective ink, coating or paint compositions are selected from the group consisting of (modified) hydrogenated castor oil, clays, modified clays, calcium sulfonate complexes, organophilic phyllosilicates, silica gels, synthetic amorphous silicas, acrylic acid type gelling agents, modified cellulosic materials, polyurea dispersions, solutions of urea modified polyamides, polyurethane dispersions and combinations thereof.

[0069] Examples of modified clays include BENTONE® LT and BENTONE® 38 (Elementis Global). Examples of silica gels include HDK® N20 (Wacker Chemical Corporation) and AEROSIL® (Evonik). An example of an organophilic phyllosilicate is Claytone 40 (Byk). An example of a modified hydrogenated castor oil is Efka® RM 1900 (BASF). An example of a hydrogenated castor oil is Efka® RM 1920 (BASF). An example of a solution of a urea modified non-polar polyamide in isobutanol / monophenyl glycol is Rheobyk-431 (Byk). An example of a solution of a medium polar urea modified polyamide in isobutanol / solvent naphtha is Rheobyk-430 (Byk). An example of a synthetic amorphous silica is Zeothix® (Huber).

[0070] In a preferred embodiment, in the organic solvent based retroreflective ink, coating or paint composition, the two thickeners are more preferably Organophilic phyllosilicates and modified hydrogenated castor oil; or A calcium sulfonate complex and a polyurea dispersion are used.

[0071] In a preferred embodiment, the amount of thickener is from 0.20 to 1.18 wt. %, more preferably from 0.25 to 1.15 wt. %, and even more preferably from 0.30 to 1.10 wt. %, based on the total weight of the organic solvent-based retroreflective ink, coating or paint composition.

[0072] In embodiments, the amount of thickener is from 0.15 to 1.18 weight percent, from 0.15 to 1.15 weight percent, or from 0.15 to 1.10, based on the total weight of the organic solvent based retroreflective ink, coating, or paint composition.

[0073] In other embodiments, the amount of thickener is 0.20-1.20 wt%, 0.30-1.20 wt%, 0.40-1.20 wt%, 0.45-1.20 wt%, or 0.50-1.20 wt%, based on the total weight of the organic solvent-based retroreflective ink, coating, or paint composition.

[0074] The amount of organic solvent in an organic solvent-based retroreflective ink, coating or paint composition is specified independently. When the thickener is applied in the form of a dispersion in a solvent, for example, the amount of thickener defined above relates to the dry weight of the thickener.

[0075] Further ingredients As described above, the organic solvent-based retroreflective ink, paint or coating composition includes 0-30% by weight of one or more additional components. As will be recognized by those skilled in the art, the "additional" components are different from the other components defined in the organic solvent-based retroreflective ink, paint or coating composition. In other words, the additional components do not include spherical glass beads, thickeners and organic solvents.

[0076] In a preferred embodiment, the further component or components are selected from the group consisting of foam control agents, luminescent agents, UV absorbers, binders and resins, preservatives, dyes, pigments and cure initiators.

[0077] Binders and resins suitable for organic solvent-based compositions are generally known to those skilled in the art. The binder or resin may be radiation-curable. If the binder or resin is radiation-curable, the further component may include a curing initiator, such as a photoinitiator or a thermal initiator.

[0078] In an embodiment, the organic solvent based retroreflective ink, paint or coating composition comprises as part of one or more additional components synthetic pigment flakes having an average diameter between 5 and 50 μm, a thickness of less than 1 μm, and an aspect ratio (flake diameter / thickness) of at least 10, said synthetic pigment flakes being selected from (A), (B), (C) or a combination thereof: (A) metal or synthetic mica flakes, optionally coated with at least one layer of one or more components selected from the group consisting of metal oxides, metals, metal sulfides, titanium suboxides, titanium oxynitrides, FeO(OH), SiO2, B2O3, GeO2, MgF2, alloys, rare earth compounds, and optionally coated with an outer layer comprising one or more colorants and binders; (B) flakes comprising Al2O3, SiO2, glass, ceramic, graphite or mica platelets coated with at least one layer of one or more components selected from the group consisting of metal oxides, metals, metal sulfides, titanium suboxides, titanium oxynitrides, FeO(OH), SiO2, B2O3, GeO2, alloys, rare earth compounds, and optionally coated with an outer layer comprising one or more colorants and binders; (C) Flakes comprising Al2O3 platelets doped with one or more components selected from the group consisting of TiO2, ZrO2, SiO2, SnO2, In2O3, ZnO and iron oxides, coated with at least one layer of one or more components selected from the group consisting of metal oxides, metals, metal sulfides, titanium suboxides, titanium oxynitrides, FeO(OH), SiO2, B2O3, GeO2, alloys, rare earth compounds, and optionally coated with an outer layer comprising one or more colorants and binders.

[0079] The term "average diameter" refers to the median particle size D50 in the context of synthetic pigment flakes.

[0080] As will be appreciated by those skilled in the art, the term "synthetic" in "synthetic pigment flakes" means that the pigment flakes are not naturally occurring pigment flakes, but rather are chemically manufactured pigment flakes or chemically / physically engineered naturally occurring pigment flakes. One advantage of using synthetic pigment flakes is that they have a very smooth surface, which can result in increased reflectivity.

[0081] The term "flake" or "platelet" as used herein refers to a pigment shape having a large surface area and a small thickness. Typically, flakes or platelets are characterized by their "aspect ratio", which is defined as the largest dimension (i.e., the largest diameter of the surface divided by the smallest dimension (i.e., the thickness)). Synthetic pigment flakes as used herein have an aspect ratio of at least 10, preferably at least 15, and more preferably at least 20.

[0082] In a preferred embodiment, the average diameter of the synthetic flakes is between 6 and 45 μm, more preferably between 7 and 35 μm, even more preferably between 8 and 25 μm, still more preferably between 9 and 20 μm, and most preferably between 10 and 16 μm.

[0083] In a preferred embodiment, the thickness of the synthetic flakes is between 10 nm and 800 nm, more preferably between 15 nm and 600 nm. In another preferred embodiment, the thickness of the synthetic flakes is between 10 and 200 nm, more preferably between 10 and 150 nm, even more preferably between 10 and 100 nm, and even more preferably between 10 and 50 nm.

[0084] In embodiments, the amount of one or more additional components is 0-25 wt%, 0-20 wt%, 0-15 wt%, 0-12 wt%, 0-10 wt%, 0-8 wt%, 0-6 wt%, or 0-5 wt%, based on the total weight of the organic solvent-based retroreflective ink, paint, or coating composition.

[0085] In other embodiments, the amount of one or more additional components is from 0.1 to 23 wt %, from 0.5 to 17 wt %, or from 1 to 15 wt %, based on the total weight of the organic solvent-based retroreflective ink, paint, or coating composition.

[0086] The amount of organic solvent in the organic solvent-based retroreflective ink, paint or coating composition is specified independently. If the one or more further components are applied, for example, in the form of a solution, suspension or dispersion in a solvent, the amount of the one or more further components defined above relates to the dry weight, i.e. the solvent-free weight of the one or more further components.

[0087] Rheological behavior An organic solvent-based retroreflective ink, paint or coating composition has shear thinning behavior, which means that the viscosity of the composition decreases when the static / stable state is disturbed by subjecting it to a certain increased shear rate.

[0088] As defined above, the organic solvent-based retroreflective ink, paint or coating composition defined herein has a η1 at a shear rate of 0.5 rpm between 0.2 and 8 Pa·s, and a η2 at a shear rate of 20 rpm between 80 and 450 mPa·s, provided that the second Brookfield viscosity η2 is at least two times lower than the first Brookfield viscosity η1, as measured in a 600 ml beaker having a diameter of 8.25 cm using a #2 spindle at a temperature of 25° C.

[0089] In a preferred embodiment, η1 is between 0.25 and 5 Pa·s and η2 is between 100 and 425 mPa·s, provided that η2 is at least two times lower than η1. In another preferred embodiment, η1 is between 0.26 and 2.5 Pa·s and η2 is between 110 and 400 mPa·s, provided that η2 is at least two times lower than η1. In yet another preferred embodiment, η1 is between 0.27 and 2 Pa·s and η2 is between 120 and 350 mPa·s, provided that η2 is at least two times lower than η1.

[0090] The first viscosity η1 of the organic solvent-based retroreflective ink, paint or coating composition, determined at a shear rate of 0.5 rpm, is sufficient to keep the spherical glass beads and any optional additional particulate materials in suspension for a sufficiently long period of time. A shear rate of 20 rpm is typical for (industrial) spray conditions at which the organic solvent-based retroreflective ink, paint or coating composition can be applied to a substrate. The second viscosity η2 is sufficiently low to provide an organic solvent-based retroreflective ink, paint or coating composition that can be easily sprayed.

[0091] In a preferred embodiment, the organic solvent-based retroreflective ink, paint or coating composition defined herein has a third Brookfield viscosity η3 at a shear rate of 10 rpm, measured using a #5 spindle at a temperature of 25° C. in a 600 ml beaker having a diameter of 8.25 cm, of less than 1.5 Pa s, more preferably less than 1.3 Pa s, even more preferably less than 1.1 Pa s, such as less than 1.0 Pa s, less than 0.8 Pa s, or less than 0.6 Pa s.

[0092] In another preferred embodiment, the organic solvent-based retroreflective ink, paint or coating composition defined herein has an η4 at a shear rate of 0.5 rpm between 0.25 and 5 Pa·s, and an η5 at a shear rate of 20 rpm between 80 and 450 mPa·s, measured with a #3 spindle at a temperature of 25° C. in a 600 ml beaker having a diameter of 8.25 cm, provided that the fifth Brookfield viscosity η5 is at least two times lower than the fourth Brookfield viscosity η4.

[0093] In yet another preferred embodiment, the organic solvent-based retroreflective ink, paint or coating composition defined herein has an η4 at a shear rate of 0.5 rpm of between 0.30 and 3 Pa·s, and an η5 at a shear rate of 20 rpm of between 100 and 425 mPa·s, measured with a #3 spindle at a temperature of 25° C. in a 600 ml beaker having a diameter of 8.25 cm, provided that the fifth Brookfield viscosity η5 is at least two times lower than the fourth Brookfield viscosity η4.

[0094] In yet another preferred embodiment, the organic solvent-based retroreflective ink, paint or coating composition defined herein has an η4 at a shear rate of 0.5 rpm between 0.35 and 2.5 Pa·s, and an η5 at a shear rate of 20 rpm between 110 and 400 mPa·s, provided that the fifth Brookfield viscosity η5 is at least two times lower than the fourth Brookfield viscosity η4.

[0095] Method for preparing organic solvent-based retroreflective ink, paint or coating compositions Generally speaking, the components of the organic solvent-based retroreflective ink, coating or paint composition can be added in any order, however, it is preferred to add the thickener at the end of the process, at least after the spherical glass beads have been added to the organic solvent, since it becomes more difficult to distribute the components homogeneously in the thickened composition.

[0096] In a preferred embodiment, the thickener is added after mixing the organic solvent and the spherical glass beads. In another preferred embodiment, the thickener is added after mixing the organic solvent, the spherical glass beads, and any additional ingredients. To avoid the inclusion of air bubbles in the organic solvent-based retroreflective ink, coating, or paint composition, stirring or homogenization is preferably performed at a low shear rate.

[0097] In a second aspect, there is provided a process for the preparation of an organic solvent-based retroreflective ink, coating or paint composition as defined herein, comprising the steps of: (i) adding to a container an organic solvent, spherical glass beads as defined above, a thickening agent as defined above and optionally one or more further ingredients as defined above; and (ii) stirring or homogenising the mixture obtained in step (i) preferably at a temperature between 15 and 70° C., preferably for a period between 5 and 60 minutes.

[0098] However, the addition of different components may also be accomplished at different stages of the process. Thus, in embodiments, there is provided a process for the preparation of an organic solvent-based retroreflective ink, coating or paint composition as defined herein, said process comprising: (i) adding to a vessel an organic solvent, spherical glass beads as defined above, at least a portion of a thickening agent as defined above, and optionally a portion of one or more further ingredients as defined above; (ii) stirring or homogenizing the mixture obtained in step (i) at a temperature preferably between 15 and 70° C., for a period preferably between 5 and 60 minutes; (iii) adding at least a portion of one or more further ingredients as defined above to the composition obtained in step (ii) or (iii), optionally adding a portion of a thickening agent as defined above, and optionally adding an organic solvent; and (iv) stirring or homogenizing the mixture obtained in step (iii) at a temperature preferably between 15 and 70° C., for a period preferably between 5 and 60 minutes.

[0099] In embodiments, the time between carrying out steps (i) and (ii) on the one hand, and steps (iii) and (iv) on the other hand, may be several days or months, or even longer.

[0100] The method for preparing an organic solvent-based retroreflective ink, coating or paint composition may also include the production of an intermediate organic solvent-based retroreflective ink, coating or paint composition having the composition and properties defined above, followed by adding and mixing another composition to obtain the final organic solvent-based retroreflective ink, coating or paint composition, provided that the final organic solvent-based retroreflective ink, coating or paint composition still has the composition and properties defined above.

[0101] Consequently, in embodiments, there is provided a method for the preparation of an organic solvent based retroreflective ink, coating or paint composition as defined herein, said method comprising: (i) adding to a container an organic solvent, spherical glass beads as defined above, at least a portion of the thickening agent as defined above and optionally a portion of one or more further ingredients as defined above; (ii) stirring or homogenizing the mixture obtained in step (i), preferably at a temperature between 15 and 70° C., for a period of preferably between 5 and 60 minutes, to obtain an intermediate organic solvent-based retroreflective ink, coating or paint composition having the composition and properties of the organic solvent-based retroreflective ink, coating or paint composition defined hereinbefore; (iii) adding at least a portion of one or more further ingredients as defined above to the intermediate organic solvent-based retroreflective ink, coating or paint composition obtained in step (ii), optionally adding a portion of a thickener as defined above, and optionally adding an organic solvent; and (iv) stirring or homogenizing the mixture obtained in step (iii) at a temperature preferably between 15 and 70° C., for a period preferably between 5 and 60 minutes, to obtain the organic solvent-based retroreflective ink, coating or paint composition.

[0102] In embodiments, the time between carrying out steps (i) and (ii) on the one hand, and steps (iii) and (iv) on the other hand, may be several days or months, or even longer.

[0103] Method for coating a substrate In a third aspect, the invention relates to a method of coating a substrate with a retroreflective layer, said method comprising: a) providing a substrate; b) optionally applying a primer layer to the substrate of step (a); c) optionally, but not preferably, applying a colored base layer to the substrate of step (a) or the primer layer of step (b); d) spraying an organic solvent based retroreflective ink, coating or paint composition as defined hereinbefore onto the substrate of step (a) or onto the layer of step (b) or (c); e) drying and / or curing the substrate coated with the retroreflective layer obtained in step (d); and f) Optionally, coating the dried substrate coated with the retroreflective layer obtained in step (e) with one or more additional transparent coating layers, followed by drying and / or curing.

[0104] Step (d) of spraying the organic solvent-based retroreflective ink, coating or paint composition can include spraying a single layer in one step, or multiple layers on top of each other in subsequent spraying steps. Subsequent layers are preferably applied "wet-on-wet", meaning that the subsequent layer is applied on a previous layer from which at least some to substantially all of the organic solvent has evaporated, but which has not (fully) cured. This means that even if the subsequent layer is applied "wet-on-wet", an intermediate drying step is applied between the application of the subsequent layer.

[0105] Interlayer drying is typically accomplished at a temperature between 20 and 30° C. for about 2 to 15 minutes.

[0106] It is also possible to thoroughly dry and / or cure a layer before applying a subsequent layer. Thorough drying and / or curing of a layer is typically accomplished at a temperature of about 60° C. for about 20 minutes, or at a temperature of about 20° C. for 30 minutes in air. It is within the skill of one of ordinary skill in the art to select suitable drying conditions.

[0107] In an embodiment, step (d) includes spraying multiple layers, for example 2, 3, 4 or 5 layers.

[0108] In an embodiment, step (d) includes n subsequent spraying steps resulting in n layers, where an xth layer is applied at least partially over an x-1th layer, where x is an integer between 2 and n, and where n is an integer between 2 and 5.

[0109] In a preferred embodiment, the organic solvent-based retroreflective ink, coating or paint composition is applied to the substrate 1m in step (d). 2 More preferably, the amount is 100 to 800 g per m 2 It is applied in an amount of 100 to 400 g per area.

[0110] In an embodiment, step (b) is not performed. In a highly preferred embodiment, step (c) is not performed.

[0111] The geometry of the substrate to be coated is not limited in any way, so long as it can be coated by spraying, i.e., droplets of the organic solvent-based retroreflective ink, coating, or paint composition can reach the surface of the substrate. In an embodiment, the substrate is flat. In another embodiment, the substrate is curved. In a further embodiment, the substrate includes flat and curved portions.

[0112] The inventors have established that organic solvent-based retroreflective ink, coating or paint compositions can be applied, for example, using professional or industrial (high speed) spraying to a variety of substrates to result in retroreflective coating layers having excellent print or coating qualities, such as uniformity and retroreflectivity at wide angles. These results can also be obtained when the organic solvent-based retroreflective ink, coating or paint composition is applied to the surface of a vertically positioned substrate, and even when the substrate surface is sprayed from below.

[0113] When the retroreflective coating layer is provided with one or more further transparent coating layers (i.e., step (f) of the method for coating a substrate defined above is performed), a retroreflective layer with high smoothness and improved cleanability is obtained.

[0114] In a preferred embodiment, the substrate is selected from fabric, leather, metal, concrete, rubber, plastic, carbon fiber, and combinations thereof. Fabric as used herein includes woven or knitted textile fabrics such as cotton, polyester, nylon, silk, wool, viscose, and acrylic.

[0115] Regardless of the type of material from which the substrate is made, the substrate may be selected from the group consisting of apparel, traffic signs, automobile chassis or bodies, bicycle frames, roads, pavements, and guardrails.

[0116] The substrate on which the retroreflective coating according to the present invention is applied may be provided with one or more additional transparent coating layers in step (f). These one or more additional transparent coating layers may serve to protect the retroreflective layer against abrasion and / or moisture. Furthermore, they may be used to provide the substrate coated with the retroreflective layer with a particular matte or shiny / glossy appearance. The one or more additional transparent coating layers may be colored. The one or more additional transparent coating layers applied in the optional step (f) may include a liquid coating layer, a powder coating layer, or a combination thereof, which is subsequently cured or dried.

[0117] If one or more additional transparent coating layers are applied to the layer of organic solvent-based retroreflective ink, coating or paint composition in step (f), this layer of organic solvent-based retroreflective ink, coating or paint composition is usually not fully cured, and it is within the skill of the art to select suitable drying conditions.

[0118] The spraying in step (c) is preferably accomplished using curtain coating, a spray gun, a high speed rotary bell, a high speed rotating disk, or using a spray can containing a propellant. In a preferred embodiment, the spraying is accomplished without the use of a propellant.

[0119] In a fourth aspect, the present invention relates to a substrate coated with a retroreflective layer obtained or obtainable by the method defined above. The substrate coated with the retroreflective layer can have a matt or shiny appearance.

[0120] In a preferred embodiment, a substrate coated with a retroreflective layer, preferably coated with one or more further transparent coating layers (i.e. step (e) of the method of coating a substrate defined above is performed) exhibits retroreflection of the retroreflective layer at any angle between 0 and 80°, for example between 0 and 78°, between 0 and 75°, between 0 and 70°, between 0 and 65°, between 0 and 60°, between 0 and 55°, between 0 and 50°, between 0 and 45° and between 0 and 40° from the normal of the coated substrate. This retroreflection of the retroreflective layer is determined by directing a beam of a torch at the retroreflective layer, with the line of sight of the eye substantially coinciding with the beam of the torch, and visually determining whether retroreflection is observed. The experiment starts at an angle of 0 from the normal of the coated substrate, after which the angle is gradually increased until retroreflection is no longer discernible.

[0121] Thus, the invention has been described with reference to certain specific embodiments discussed above, it being recognized that these embodiments are susceptible to various modifications and alternative forms known to those skilled in the art.

[0122] Moreover, for the proper understanding of this specification and its claims, it should be understood that the verb "comprise" and its conjugations are used in an open-ended sense to mean that the items following the word are included, but items not specifically mentioned are not excluded. Furthermore, the reference of an element with the indefinite article "a" or "an" does not exclude the possibility that there are more than one of that element, unless the context clearly dictates that there is only one of that element. Thus, the indefinite article "a" or "an" generally means "at least one." EXAMPLES

[0123] Protocol Viscosity Measurement The viscosity was measured using a Brookfield Ametek® DV2T viscometer at a temperature of 25° C. using different standardized spindles (#2, #3 and #5; LV-2, LV-3 and LV-5, obtained from Brookfield Ametek®) according to the operating instructions. The measurements were carried out in flat-bottomed 600 ml Griffin beakers with a diameter of 8.25 cm and without protective feet. Before measuring the viscosity, the samples were brought to a temperature of 25° C. and homogenized using stirring.

[0124] Example 1 Four compositions according to the invention (samples 2, 4, 5 and 7) and four comparative compositions (samples 1, 3, 6 and 8) were prepared on a kg scale. The following ingredients were used:

[0125] Spherical glass beads: Micro glass beads (RI 2.2), having a refractive index of about 2.2 measured at a wavelength λ of 589 nm, a median particle size D50 of 26.56 μm, a D10 diameter of 19.77 μm and a D90 diameter of 32.41 μm as measured using laser diffraction, and a particle size of about 4.5 g / cm 3 The spherical glass beads were obtained from Jianxi Sunflex Light Retroreflective Material Co, Ltd. and had a specific gravity of 1.0 to 1.05%. These spherical glass beads contain TiO2, BaO, CaO, SiO2, and ZnO.

[0126] Micro glass beads (RI 1.9, HAC) obtained from Jianxi Sunflex Light Retroreflective Material Co, Ltd., had a refractive index of about 1.9 measured at a wavelength λ of 589 nm, a median particle size D50 of 38.22 μm, a D10 diameter of 34.86 μm, and a D90 diameter of 43.04 μm, as measured using laser diffraction, and a weight average particle size (g / cm) of about 4.2 g / cm 3 Hemispherical aluminum coated glass beads having a specific gravity of 1. These spherical glass beads contain TiO2, BaO, SiO2, CaO and Al2O3.

[0127] Organic solvents The solvent portion of Chromax XB165 Centari 6000 Low Emission Binder (Axalta), a mixture of organic solvents including xylene, toluene, ethylbenzene, isopentyl acetate, n-butyl acetate, isobutanol, and 2-methoxy-1-methylethyl acetate Mixtures of organic solvents, such as xylene, ethylbenzene, naphtha, 1,2,4-trimethylbenzene, mesitylene, n-propylbenzene, isopentyl acetate, n-butyl acetate, 2-methylbutyl acetate, and 4-methyl-2-pentanone, Chromax XB383 (Axalta) Chromax AU370 / Imron® 700 polyurethane thinner (Axalta), contains xylene, ethyl acetate, n-butyl acetate, ethylbenzene, isopentyl acetate, 2-methylbutyl acetate, and toluene Avatar T-4500 (obtained from Global Refinish Trading Center, Cyprus), containing acrylate thinner, dimethylbenzene (mixture of isomers), n-butyl acetate, 1-methoxy-2-propyl acetate, ethylbenzene, and 2-(2-butoxyethoxy)ethanol. Butyl glycol, the solvent portion of Aquamet® CP-BG / 8500 / 60 obtained from Schlenk Metallic Pigments GmbH

[0128] Further ingredients Chromax XB165 Centari 6000 Low Emission Binder binder Solid part of Aquamet® CP-BG / 8500 / 60, silica-coated aluminum flakes with an average diameter of about 16 μm and a thickness of <1 μm obtained from Schlenk Metallic Pigments GmbH. Xylarlic® T61-10 WNT Micro Silver, coated aluminum oxide flakes obtained from Merck KGaA, with an average diameter between 8 and 14 μm and a thickness of <1 μm.

[0129] Thickener Efka® RM 1900, obtained from BASF, modified hydrogenated castor oil, fine powder, thickener Efka® RM 1920, obtained from BASF, hydrogenated castor oil, fine powder, thickener

[0130] Claytone 40, an organophilic phyllosilicate from Byk, a thickener Four compositions according to the invention (Samples 2, 4, 5 and 7), and four comparative compositions (Samples 1, 3, 6 and 8) were prepared by adding the ingredients to a vessel (3.5 liters) in the following order: (1) adding an organic solvent, e.g., Avatar T-4500, at room temperature (about 20° C.) and starting stirring at 500 rpm; (2) adding glass beads at room temperature (about 20° C.) while mixing at 500 rpm for at least 5 minutes; (3) adding a first thickener, e.g., Claytone 40, at room temperature (about 20° C.) while mixing at 1300 rpm for at least 5 minutes, slowly increasing the rpm to 2000 rpm without introducing air bubbles; (4) adding further thickener, e.g. Efuka® RM 1900 and / or Efuka® RM 1920, followed by stirring for at least 45 minutes at 1800 rpm and, if necessary, slowly increasing the rpm without introducing air bubbles; (5) adding additional ingredients, such as Chromax XB165 and pigment flakes, while mixing at 2000 rpm and continuing mixing at 2000 rpm for at least 15 minutes; and (6) Optionally, additional thickener is added, followed by stirring at about 1800 rpm for an additional 15 minutes.

[0131] The amounts of the different ingredients are listed in Table 1.

[0132] [Table 1] TIFF2024524825000003.tif226149

[0133] Using the protocol defined above, the viscosities of the compositions in Table 1 were measured using a Brookfield Viscometer with a #5 spindle rotating at 10 rpm at a temperature of 25° C., a Brookfield Viscometer with a #3 spindle rotating at 0.5 and 20 rpm at a temperature of 25° C., and a #2 spindle rotating at 0.5 and 20 rpm at a temperature of 25° C. The results are shown in Tables 2, 3, and 4. As shown in Tables 3 and 4, the organic solvent-based retroreflective ink, coating, or paint compositions according to the invention and the comparative compositions exhibit shear thinning behavior.

[0134] [Table 2]

[0135] The resulting Brookfield viscosities of the compositions according to the invention, measured using a #5 spindle rotating at 10 rpm, are therefore between 480 and 840 mPa·s, much lower than the lower values ​​required for screen printing (inks) as disclosed in WO 00 / 42113.

[0136] [Table 3]

[0137] The resulting Brookfield viscosities of the compositions according to the invention, measured using a #3 spindle rotating at 0.5 and 20 rpm, are therefore between 0.48 and 1.44 Pa·s and between 126 and 378 mPa·s, respectively, which are much lower than the lower values ​​specified in WO 2004 / 017104.

[0138] [Table 4]

[0139] The stability of the compositions in Table 1 was determined by visual and tactile inspection of the samples to see if they exhibited settling, syneresis, or separation (phase or otherwise) after certain times after resuspension. See Table 5.

[0140] [Table 5]

[0141] Example 2 The compositions in Table 1 of Example 1 were sprayed onto a flat greyish metal test plate (10.5×14.9 cm, 154.2 cm) with a vertical black bar (0.3 cm wide) using a spray gun (DeVILBISS HVLP, DV1-C1 Plus) equipped with a 1.3 mm nozzle. 2 The coating was applied at room temperature (approximately 20°C) over the entire surface of a metal test plate (having an effective surface area of ​​1000 mm). The spray gun was positioned 30 cm away from the metal test plate and a pressure of 1.9 bar was applied. One layer was applied. The layer was dried and cured in air at a temperature of approximately 20°C for 30 minutes. The weight of the dried and cured coating layer [g / m 2 ] was calculated (see Table 6).

[0142] [Table 6]

[0143] After drying, the coating quality was visually inspected: the overall (away from center) retroreflectivity and maximum angle of retroreflection [°] of both the comparative example and the example according to the invention were considered to be good.

[0144] The maximum angle of retroreflection [°] is determined by directing the beam of a torch at the retroreflective layer so that the line of sight of the eye is substantially coincident with the beam of the torch and visually determining whether retroreflection is observed. The experiment starts at an angle of 0 normal to the coated substrate, and then the angle is gradually increased until retroreflection is no longer discernible.

[0145] The smoothness or "orange peel" of the coating layer was evaluated by directing light through a grating under an angle onto the surface of the coating layer and observing the sharpness of the image of the grating reflected by the surface of the coating layer: the sharper the image of the grating reflected by the surface of the coating layer, the smoother the surface and the less orange peel there is.

[0146] In Figs. 1a-1h, the results are presented in the order of Comparative Example 1, Example 2, Comparative Example 3, Examples 4 and 5, Comparative Example 6, Example 7 and Comparative Example 8. As can be clearly seen in Figs. 1a-1h, the examples according to the invention have a much smoother surface than the corresponding comparative examples, i.e., less orange peel. In this respect, the results of Comparative Example 1 (Fig. 1a) should be compared with Example 2 (Fig. 1b), the results of Comparative Example 3 (Fig. 1c) should be compared with Example 4 (Fig. 1d), the results of Comparative Example 6 (Fig. 1f) should be compared with Example 5 (Fig. 1e), and the results of Comparative Example 8 (Fig. 1h) should be compared with Example 7 (Fig. 1g). All of the examples according to the invention have a much lower Brookfield viscosity using a #2 spindle at about 25 °C and 20 rpm than the corresponding comparative examples.

Claims

1. An organic solvent based retroreflective ink, paint or coating composition having a second Brookfield viscosity η ２ is the first Brookfield viscosity η １ η at a shear rate of 0.5 rpm between 0.2 and 8 Pa s, provided that the η is at least 2 times lower than １ , and η at a shear rate of 20 rpm between 80 and 450 mPa·s ２ Based on the total weight of the composition, 25 to 75% by weight of an organic solvent; 1-74% by weight of spherical glass beads having a median particle size D50, measured by means of laser diffraction, between 1 and 150 μm and a refractive index, measured at a wavelength λ of 589 nm, between 1.5 and 2.8; 0.15 to 1.2% by weight of a thickening agent; and 0-30% by weight of one or more further components; The Brookfield viscosity η １ and η ２ is an organic solvent based retroreflective ink, paint or coating composition measured using a #2 spindle at a temperature of 25° C. in a 600 ml beaker having a diameter of 8.25 cm.

2. Based on the total weight of the composition, 25 to 68% by weight of an organic solvent; 20-70% by weight of spherical glass beads having a median particle size D50, measured by means of laser diffraction, between 5 and 150 μm and a refractive index, measured at a wavelength λ of 589 nm, between 1.5 and 2.8; 0.15 to 1.2% by weight of a thickening agent; and 10. The organic solvent-based retroreflective ink, paint or coating composition of claim 1, which comprises 0-30% by weight of one or more additional components.

3. η ２ η １ η １ is between 0.25 and 5 Pa s, and η ２ is between 100 and 425 mPa·s, preferably η ２ η １ η １ is between 0.26 and 2.5 Pa s, and η ２ is between 110 and 400 mPa·s, more preferably η ２ η １ η １ is between 0.27 and 2 Pa s, and η ２ 2. The organic solvent based retroreflective ink, paint or coating composition of claim 1, wherein the viscosity is between 120 and 350 mPa.s.

4. The fifth Brookfield viscosity η measured using a #3 spindle at a temperature of 25° C. in a 600 ml beaker having a diameter of 8.25 cm. ５ is the fourth Brookfield viscosity η ４ η at a shear rate of 0.5 rpm between 0.25 and 5 Pa s, provided that η is at least 2 times lower than ４ , and η at a shear rate of 20 rpm between 80 and 450 mPa·s ５ 2. The organic solvent based retroreflective ink, paint or coating composition of claim 1, having

5. The spherical glass beads are (i) between 2.0 and 2.8, preferably between 2.1 and 2.4; or 2. The organic solvent-based retroreflective ink, paint or coating composition of claim 1, having (ii) a refractive index measured at a wavelength λ of 589 nm of between 1.7 and 2.1, preferably between 1.8 and 2.

0.

6. 2. The organic solvent based retroreflective ink, paint or coating composition of claim 1, wherein the spherical glass beads have a median particle size D50 measured using laser diffraction of between 1 and 100 μm, between 1 and 75 μm, between 1 and 50 μm, between 1 and 45 μm, between 1 and 40 μm, or between 1 and 35 μm.

7. 2. The organic solvent based retroreflective ink, paint or coating composition of claim 1, wherein the spherical glass beads have a median particle size D50 measured using laser diffraction of between 5 and 100 μm, between 5 and 75 μm, between 5 and 50 μm, between 5 and 45 μm, between 5 and 40 μm, or between 5 and 35 μm.

8. 10. The organic solvent based retroreflective ink, paint or coating composition of claim 1, wherein at least a portion of the spherical glass beads are hemispherically coated with an aluminum coating.

9. 2. The organic solvent-based retroreflective ink, paint or coating composition of claim 1, wherein the organic solvent is selected from the group consisting of aliphatic and aromatic solvents, ketones, esters, glycoethers, alcohols, halogenated hydrocarbons and combinations thereof.

10. 2. The organic solvent based retroreflective ink, paint or coating composition of claim 1, wherein the thickening agent is selected from the group consisting of (modified) hydrogenated castor oil, clays, modified clays, sulfonate calcium complexes, organophilic phyllosilicates, silica gels, synthetic amorphous silicas, acrylic acid type gelling agents, modified cellulosic materials, polyurea dispersions, solutions of urea modified polyamides, polyurethane dispersions and combinations thereof.

11. 2. The organic solvent-based retroreflective ink, paint, or coating composition of claim 1 comprising 0.20 to 1.18 wt. %, preferably 0.25 to 1.15 wt. %, more preferably 0.30 to 1.10 wt. % of a thickener, based on the total weight of the organic solvent-based retroreflective ink, paint, or coating composition.

12. 2. The organic solvent based retroreflective ink, paint or coating composition of claim 1, wherein the one or more further components are selected from the group consisting of foam control agents, luminescent agents, UV absorbers, binders and resins, preservatives, dyes and curing initiators.

13. A process for the preparation of an organic solvent-based retroreflective ink, coating or paint composition according to any one of claims 1 to 12, comprising the steps of: (i) adding the organic solvent, the spherical glass beads, the thickening agent, and optionally the one or more additional ingredients to a container; and (ii) stirring or homogenising the mixture obtained in step (i) preferably at a temperature between 15 and 70° C., preferably for a period between 5 and 60 minutes.

14. 1. A method of coating a substrate with a retroreflective layer, comprising: a) providing a substrate; b) optionally applying a primer layer to the substrate of step (a); c) optionally applying a colored base layer to the substrate of step (a) or to the primer layer of step (b); d) spraying the organic solvent-based retroreflective ink, paint or coating composition of any one of claims 1 to 12 onto the substrate of step (a) or the layer of step (b) or (c); e) drying and / or curing the substrate coated with the retroreflective layer obtained in step (d); and f) optionally coating the dry substrate coated with the retroreflective layer obtained in step (e) with one or more further transparent coating layers, followed by drying and / or curing.

15. 15. The method of claim 14, wherein the organic solvent-based retroreflective ink, paint or coating composition is sprayed onto the substrate in step (d) using curtain coating, using a spray gun, a high speed rotary bell, a high speed rotating disk, or using a spray can containing a propellant.

16. 15. The method of claim 14, wherein step (d) comprises n subsequent spraying steps resulting in n layers, where an xth layer is applied at least partially over an x-1th layer, where x is an integer between 2 and n, and n is an integer between 2 and 5.

17. A substrate coated with a retroreflective layer obtainable by the method of claim 14.

Images