Method for providing organic solvent-based compositions having retroreflective properties

Abstract

A method for providing a composition selected from the group consisting of organic solvent-based pastes, inks, paints, and coating formulations having retroreflective properties, comprising: a) providing an organic solvent-based paste, ink, paint, or coating formulation without retroreflective properties; b) providing a retroreflective organic solvent-based composition having the following composition composition, based on the total weight of the retroreflective organic solvent-based composition: 10-49.85 wt.% of an organic solvent; 50-85 wt.% of spherical glass beads having a laser diffraction diameter between 1 and 1500 μm. % of a thickener; and 0-10 wt.% of one or more further ingredients; c) mixing the organic solvent-based ink, paint or coating formulation without retroreflective properties of (a) with the retroreflective organic solvent-based composition of (b) in a weight ratio of between 30:70 and 70:30 to provide an organic solvent-based paste, ink, paint or coating formulation with retroreflective properties.

Description

Technical Field

[0001] The present invention relates to a method of providing a composition selected from the group consisting of organic solvent-based pastes, inks, paints, and coating formulations having retroreflective properties. The present invention further relates to such a method further comprising the step of applying the retroreflective composition to a substrate. Background Art

[0002] Retroreflection is used in a variety of applications. For example, it can improve the visibility of road signs, street signs, textiles, cars, etc. in dark conditions, or simply to improve their visual appearance. Road signs are often given retroreflective properties by adding spherical glass beads with a specific refractive index. Retroreflection occurs through the following sequential operation: incident light is refracted by passing through the upper surface of the spherical glass beads, undergoes internal reflection at the lower landing surface of the spherical glass beads, and then refracts when the light exits the upper surface of the spherical glass beads, returning to the direction from which the incident light came.

[0003] WO2004 / 017104A2 discloses retroreflective compositions comprising retroreflective microspheres, a binder system, and a thixotropic blend comprising at least two thixotropic agents in an amount of about 2 to about 5 wt. % based on the retroreflective composition. The retroreflective compositions are intended for use as paints, inks, and coatings and are applied to substrates using an aerosol applicator with a propellant.

[0004] WO 00 / 42113 A1 relates to a retroreflective ink comprising microbeads in a liquid carrier medium. The ink is intended for screen printing on textiles.

[0005] Organic solvent-based pastes, paints, inks, and coating formulations are commercially available from numerous suppliers in a variety of colors and / or customized for various applications. Each new application and modification of an organic solvent-based paste, paint, ink, or coating formulation, from lab sample to commercial product, requires a costly and time-consuming development process. Clearly, offering numerous products in different colors and / or for various applications requires large warehouses and extensive inventory to quickly respond to customer orders.

[0006] As explained above, adding retroreflective properties to paste, paint, ink, and coating formulations can be advantageous because it results in improved visibility and / or a more appealing visual appearance.

[0007] Developing retroreflective versions of already commercially available organic solvent-based pastes, paints, inks, and coating formulations also requires an expensive and time-consuming development process because the addition of additional components, including retroreflective spherical glass beads, should not significantly affect the processability of the existing paste, paint, ink, or coating formulation, let alone the properties of the paste, paint, ink, or coating formulation after drying or curing. Providing retroreflective pastes, paints, inks, and coating formulations in addition to those without retroreflective properties requires an even larger warehouse.

[0008] Therefore, there is a need for an effective method of providing organic solvent-based pastes, paints, inks and coating formulations on demand, that is, commercially available organic solvent-based pastes, paints, inks and coating formulations having retroreflective properties that do not materially alter the processability of the organic solvent-based paints, inks and coating formulations and do not materially affect the properties of the pastes, paints, inks or coating formulations after drying or curing.

[0009] As shown in the accompanying examples, the inventors have demonstrated that providing organic solvent-based pastes, paints, inks, and coating formulations with retroreflective properties cannot be accomplished by simply mixing the organic solvent-based pastes, paints, inks, or coating formulations with retroreflective spherical glass beads because this results in inhomogeneities, air entrapment, and / or instabilities with respect to the distribution of the spherical glass beads throughout the composition.

[0010] It is therefore an object of the present invention to provide an efficient method for providing organic solvent-based pastes, paints, inks and coating formulations having retroreflective properties that does not substantially alter the processability of the organic solvent-based pastes, paints, inks and coating formulations and does not deleteriously affect the properties of the pastes, paints, inks or coating formulations after drying or curing.

[0011] It is a further object of the present invention to provide an efficient method for providing organic solvent based pastes, paints, inks and coating formulations having retroreflective spherical glass beads that results in a uniform and stable distribution of the retroreflective spherical glass beads throughout the composition. Summary of the Invention

[0012] The inventors have unexpectedly demonstrated that one or more of these objectives can be met by mixing an organic solvent-based paste, paint, ink, or coating formulation without retroreflective properties with an organic solvent-based composition comprising retroreflective spherical glass beads and a thickener, the organic solvent-based composition having a first Brookfield viscosity, η2, between 5 and 350 Pa·s at a shear rate of 0.5 rpm and a second Brookfield viscosity, η3, between 100 and 5000 mPa·s at a shear rate of 20 rpm, with the proviso that η3 is at least 2 times lower than η2, wherein η2 and η3 are measured at a temperature of 20° C. using a #4 spindle, and optionally followed by the addition of additional thickener.

[0013] Thus, in a first aspect, the present invention relates to a method of providing a composition selected from the group consisting of organic solvent-based pastes, inks, paints and coating formulations having retroreflective properties, the method comprising the steps of:

[0014] a) providing an organic solvent based paste, ink, paint or coating formulation having no retroreflective properties, the organic solvent based paste, ink, paint or coating formulation having a Brookfield viscosity η1 at a shear rate of 0.5 rpm and at a temperature of 20° C. between:

[0015] 1 mPa·s, as measured in a 600 ml beaker with a diameter of 8.25 cm using a #1 spindle; and

[0016] 300 Pa·s, as measured in a 600 ml beaker with a diameter of 8.25 cm using a #5 spindle;

[0017] b) providing a retroreflective organic solvent-based composition having a first Brookfield viscosity, η2, between 5 and 350 Pa·s at a shear rate of 0.5 rpm and a second Brookfield viscosity, η3, between 100 and 5000 mPa·s at a shear rate of 20 rpm, with the proviso that η3 is at least 2 times lower than η2, wherein η2 and η3 are measured at a temperature of 20° C. in a 600 ml beaker having a diameter of 8.25 cm using a #4 spindle, and wherein the retroreflective organic solvent-based composition consists, based on the total weight of the retroreflective organic solvent-based composition:

[0018] 10-49.85 wt.% organic solvent;

[0019] 50-85 wt.% spherical glass beads having a median particle size D50 between 1 and 1500 μm as measured using laser diffraction, and a refractive index measured at a wavelength λ of 589 nm between 1.5 and 2.8;

[0020] 0.15-3.5 wt.% thickener; and

[0021] 0-10 wt.% of one or more further ingredients;

[0022] c) mixing the organic solvent-based ink, paint or coating formulation without retroreflective properties provided by step (a) with the retroreflective organic solvent-based composition provided by step (b) in a weight ratio of between 30:70 and 70:30 to provide an organic solvent-based paste, ink, paint or coating formulation with retroreflective properties;

[0023] d) optionally mixing the organic solvent-based paste, ink, paint or coating formulation having retroreflective properties obtained in step (c) with 0-4.5 wt.% of synthetic pigment flakes having an average diameter between 5 and 150 μm, a thickness of less than 1 μm, and an aspect ratio of at least 10, based on the total weight of the organic solvent-based paste, ink, paint or coating formulation having retroreflective properties obtained in step (c); and

[0024] e) optionally mixing the mixture obtained in step (c) or (d) with 0-3 wt.% of a thickener based on the total weight of the organic solvent-based paste, ink, paint or coating formulation having retroreflective properties obtained in step (c) or (d), respectively.

[0025] The retroreflective organic solvent-based composition provided in step (b) consists primarily of an organic solvent and spherical glass beads. The inert spherical glass beads have little or no effect on organic solvent-based pastes, inks, paints, or coating formulations. Therefore, these systems are highly compatible with commercial organic solvent-based pastes, inks, paints, or coating formulations. Upon drying or curing, the organic solvent disappears from the paste, ink, paint, or coating formulation. The inventors have demonstrated that when the retroreflective organic solvent-based composition defined in step (b) is added in an appropriate amount and, if appropriate, a thickener, the workability of the organic solvent-based paste, paint, ink, or coating formulation provided in step (a) is substantially unchanged. Since the retroreflective spherical glass beads are added in the form of a sufficiently stable and uniform organic solvent-based composition as defined in step (b), they can be added to the organic solvent-based paste, ink, paint or coating formulation without retroreflective properties as defined in step (a) without air entrapment, thereby producing a sufficiently stable and uniform organic solvent-based paste, ink, paint or coating formulation with retroreflective properties.

[0026] definition

[0027] The term 'shear thinning behavior' in the context of the retroreflective organic solvent-based composition provided by step (b) of the process as defined herein refers to a reduction in viscosity when a composition initially in a stationary position is subjected to a shear rate. DETAILED DESCRIPTION

[0028] In a first aspect, the present invention relates to a method of providing a composition selected from the group consisting of organic solvent-based pastes, inks, paints, and coating formulations having retroreflective properties, the method comprising the steps of:

[0029] a) providing an organic solvent based paste, ink, paint or coating formulation having no retroreflective properties, the organic solvent based paste, ink, paint or coating formulation having a Brookfield viscosity η1 at a shear rate of 0.5 rpm and at a temperature of 20° C. between:

[0030] 1 mPa·s, measured in a 600 ml beaker with a diameter of 8.25 cm using a #1 spindle; and

[0031] 300 Pa·s, measured in a 600 ml beaker with a diameter of 8.25 cm using a #5 spindle;

[0032] b) providing a retroreflective organic solvent-based composition having a first Brookfield viscosity, η2, between 5 and 350 Pa·s at a shear rate of 0.5 rpm and a second Brookfield viscosity, η3, between 100 and 5000 mPa·s at a shear rate of 20 rpm, with the proviso that η3 is at least 2 times lower than η2, wherein η2 and η3 are measured at a temperature of 20° C. in a 600 ml beaker having a diameter of 8.25 cm using a #4 spindle, and wherein the retroreflective organic solvent-based composition consists, based on the total weight of the retroreflective organic solvent-based composition:

[0033] 10-49.85 wt.% organic solvent;

[0034] 50-85 wt.% spherical glass beads having a median particle size D50 between 1 and 1500 μm as measured using laser diffraction, and a refractive index measured at a wavelength λ of 589 nm between 1.5 and 2.8;

[0035] 0.15-3.5 wt.% thickener; and

[0036] 0-10 wt.% of one or more further ingredients;

[0037] c) mixing the organic solvent-based ink, paint or coating formulation without retroreflective properties provided by step (a) with the retroreflective organic solvent-based composition provided by step (b) in a weight ratio of between 30:70 and 70:30 to provide an organic solvent-based paste, ink, paint or coating formulation with retroreflective properties;

[0038] d) optionally mixing the organic solvent-based paste, ink, paint or coating formulation having retroreflective properties obtained in step (c) with 0-4.5 wt.% of synthetic pigment flakes having an average diameter between 5 and 150 μm, a thickness of less than 1 μm, and an aspect ratio of at least 10, based on the total weight of the organic solvent-based paste, ink, paint or coating formulation having retroreflective properties obtained in step (c); and

[0039] e) optionally mixing the mixture obtained in step (c) or (d) with 0-3 wt.% of a thickener based on the total weight of the organic solvent-based paste, ink, paint or coating formulation having retroreflective properties obtained in step (c) or (d), respectively.

[0040] In a very preferred embodiment, the first aspect relates to a method of providing a composition selected from the group consisting of organic solvent-based pastes, inks, paints and coating formulations having retroreflective properties, the method comprising the steps of:

[0041] a) providing an organic solvent based paste, ink, paint or coating formulation having no retroreflective properties, the organic solvent based paste, ink, paint or coating formulation having a Brookfield viscosity η1 at a shear rate of 0.5 rpm and at a temperature of 20° C. between:

[0042] 1 mPa·s, as measured in a 600 ml beaker with a diameter of 8.25 cm using a #1 spindle; and

[0043] 300 Pa·s, as measured in a 600 ml beaker with a diameter of 8.25 cm using a #5 spindle;

[0044] b) providing a retroreflective organic solvent-based composition having a first Brookfield viscosity, η2, between 5 and 350 Pa·s at a shear rate of 0.5 rpm and a second Brookfield viscosity, η3, between 100 and 5000 mPa·s at a shear rate of 20 rpm, with the proviso that η3 is at least 2 times lower than η2, wherein η2 and η3 are measured at a temperature of 20° C. in a 600 ml beaker having a diameter of 8.25 cm using a #4 spindle, and wherein the retroreflective organic solvent-based composition consists, based on the total weight of the retroreflective organic solvent-based composition:

[0045] 15-49.85 wt.% organic solvent;

[0046] 50-80 wt.% spherical glass beads having a median particle size D50 between 5 and 1500 μm as measured using laser diffraction, and a refractive index measured at a wavelength λ of 589 nm between 1.5 and 2.8;

[0047] 0.15-3.5 wt.% thickener; and

[0048] 0-10 wt.% of one or more further ingredients;

[0049] c) mixing the organic solvent-based ink, paint or coating formulation without retroreflective properties provided by step (a) with the retroreflective organic solvent-based composition provided by step (b) in a weight ratio of between 30:70 and 70:30 to provide an organic solvent-based paste, ink, paint or coating formulation with retroreflective properties;

[0050] d) optionally mixing the organic solvent-based paste, ink, paint or coating formulation having retroreflective properties obtained in step (c) with 0-4.5 wt.% of synthetic pigment flakes having an average diameter between 5 and 150 μm, a thickness of less than 1 μm, and an aspect ratio of at least 10, based on the total weight of the organic solvent-based paste, ink, paint or coating formulation having retroreflective properties obtained in step (c); and

[0051] e) optionally mixing the mixture obtained in step (c) or (d) with 0-3 wt.% of a thickener based on the total weight of the organic solvent-based paste, ink, paint or coating formulation having retroreflective properties obtained in step (c) or (d), respectively.

[0052] As will be appreciated by those skilled in the art, limited precipitation, (phase) separation and / or syneresis of the retroreflective organic solvent-based compositions provided by step (b) of the process defined herein is not a problem, as long as such compositions can be resuspended, for example, using simple stirring, in order to obtain a composition that remains homogeneous for a sufficient time to be processed (i.e., mixed with the organic solvent-based paste, ink, paint or coating formulation without retroreflective properties provided by step (a) of the process defined herein). Similarly, limited precipitation, (phase) separation and / or syneresis of the organic solvent-based paste, ink, paint or coating formulation with retroreflective properties provided by steps (c), (d) or (e) of the process defined herein is not a problem, as long as such compositions can be resuspended, for example, using simple stirring, in order to obtain a composition that remains stable and homogeneous for a sufficient time to be processed (i.e., applied to the substrate of interest).

[0053] As demonstrated in the accompanying examples, the retroreflective organic solvent-based composition provided by step (b) of the process defined herein and the organic solvent-based paste, ink, paint or coating formulation having retroreflective properties provided by step (c), (d) or (e) of the process defined herein remain stable and homogeneous for a sufficient period of time to facilitate their processing.

[0054] In step (c), the organic solvent-based paste, ink, paint or coating formulation provided in step (a) is preferably mixed with the retroreflective organic solvent-based composition provided in step (b) in a weight ratio of between 60:40 and 40:60, more preferably between 45:55 and 55:45.

[0055] In a preferred embodiment, the method as defined herein further comprises the step of applying the organic solvent-based paste, ink, paint or coating formulation having retroreflective properties obtained in step (c), (d) or (e) to a substrate using screen printing, curtain coating, spray coating or spray painting.

[0056] In a preferred embodiment, steps (c), (d), and (e) are performed under stirring at a temperature between 15 and 30° C. Stirring is preferably performed at a low shear rate to avoid entrapment of air bubbles. In another preferred embodiment, step (c) comprises adding the retroreflective organic solvent-based composition provided in step (b) to the organic solvent-based paste, ink, paint, or coating formulation provided in step (a) that does not have retroreflective properties.

[0057] The synthetic pigment flakes added in optional step (d) are preferably selected from synthetic pigment flakes as defined herein under 'further ingredients'.

[0058] organic solvents

[0059] The term 'organic solvent' as used herein relates to an organic solvent or mixture of organic solvents comprising less than 3 wt.% water, preferably less than 2 wt.% water, more preferably less than 1 wt.% water, even more preferably less than 0.5 wt.% water, most preferably no water.

[0060] Preferably, the organic solvent is selected from the group consisting of aliphatic and aromatic solvents, ketones, esters, sugar ethers, alcohols, halogenated hydrocarbons, and combinations thereof. Very preferably, the organic solvent is selected from the group consisting of xylene (mixture of isomers), toluene, ethylbenzene, naphtha, 1,2,4-trimethylbenzene, mesitylene, n-propylbenzene, isoamyl 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.

[0061] In a very preferred embodiment, the amount of organic solvent is 15-49.85 wt. %, based on the total weight of the retroreflective organic solvent-based composition provided in step (b).

[0062] In a preferred embodiment, the amount of the organic solvent is 20-45 wt.%, more preferably 25-40 wt.%, even more preferably 28-35 wt.%, based on the total weight of the retroreflective organic solvent-based composition provided in step (b).

[0063] In embodiments, the amount of organic solvent is 15-48 wt.%, 15-45 wt.%, 15-42 wt.%, 15-40 wt.%, or 15-38 wt.%, based on the total weight of the retroreflective organic solvent-based composition provided in step (b).

[0064] In embodiments, the amount of organic solvent is 10-48 wt.%, 10-45 wt.%, 10-42 wt.%, 10-40 wt.% or 10-38 wt.% based on the total weight of the retroreflective organic solvent-based composition provided in step (b).

[0065] In other embodiments, the amount of organic solvent is 20-49.85 wt.%, 24-49.85 wt.%, 26-49.85 wt.%, 28-49.85 wt.%, 29-49.85 wt.%, or 30-49.85 wt.%, based on the total weight of the retroreflective organic solvent-based composition provided in step (b).

[0066] Spherical glass beads

[0067] As defined above, the refractive index of the spherical glass beads measured at a wavelength λ of 589 nm is between 1.5 and 2.8.

[0068] In a preferred embodiment, the spherical glass beads have a refractive index measured at a wavelength λ of 589 nm between:

[0069] (a) between 2.0 and 2.8, preferably between 2.1 and 2.4; or

[0070] (b) between 1.7 and 2.1, preferably between 1.8 and 2.0.

[0071] In preferred embodiments, the term "glass" as used herein in "spherical glass beads" refers to an amorphous, non-crystalline solid and transparent material made of oxides. In other embodiments, the term "glass" as used herein 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 the glass, but this relationship is not linear. Due to the nature of glass, the density is approximately an additive function of its composition. Spherical glass beads with a refractive index between 1.5 and 2.8 typically have a density between 2.5 and 4.5 g / cm 3 Changes between.

[0072] Oxides that can be used in the glass include oxides of silicon, boron, aluminum, sodium, barium, vanadium, titanium, lanthanum, strontium, zirconium, potassium, magnesium, iron, calcium, zinc, lithium, barium, and lead. Spherical glass beads may, for example, comprise various combinations of silica (SiO2), boron oxide (BO3), phosphorus pentoxide (PO5), vanadium pentoxide (VO5), arsenic trioxide (AsO3), 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. Therefore, glasses containing a larger weight percentage of these oxides generally produce glass beads with a low refractive index. The refractive index can be increased by adding oxides with higher molecular weights. Preferably, the spherical glass beads do not contain PbO.

[0073] Glass beads with a refractive index in the range of 1.5-2.51 and their oxide compositions are disclosed in WO2014 / 109564A1, which is incorporated herein by reference in its entirety. PbO-free transparent glass beads with a refractive index above 2.15 are disclosed in US4,082,427, which is incorporated herein by reference in its entirety.

[0074] The spherical glass beads may be colored, as long as they remain transparent. The present invention encompasses colored spherical glass beads made from colored transparent glass and spherical glass beads having a concentric transparent colored coating. The color may be a natural color resulting from the composition of the oxides or may be purposefully selected by adding a component having a specific color. Colored glass beads with a high refractive index and high transparency are disclosed in WO 2014 / 109564 A1.

[0075] Therefore, in one embodiment, at least a portion of the spherical glass beads are spherical glass beads made of colored transparent glass and / or at least a portion of the spherical glass beads have a concentric transparent colored coating.

[0076] The spherical glass beads have a median particle size D50 as measured using laser diffraction. Thus, the median particle size D50 is the volume median based on the volume distribution. The median particle size D50 is the diameter below which half of the population of spherical glass beads is located. This volume median particle size is often referred to in the art as Dv50 or D v0.5 .

[0077] In a very preferred embodiment, the spherical glass beads have a median particle size D50, as measured using laser diffraction, between 5 and 1500 μm.

[0078] In one embodiment, the spherical glass beads have a median particle size D50 as measured using laser diffraction between 25 and 100 μm, preferably between 30 and 75 μm, more preferably between 35 and 50 μm.

[0079] In a preferred embodiment, the spherical glass beads have a median particle size D50 as measured using laser diffraction between 5 and 100 μm, such as 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.

[0080] In a preferred embodiment, the spherical glass beads have a median particle size D50 as measured using laser diffraction between 1 and 100 μm, such as 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.

[0081] In another embodiment, the spherical glass beads have a median particle size D50 as measured using laser diffraction between 25 and 150 μm, such as 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.

[0082] In yet another embodiment, the spherical glass beads have a median particle size D50 as measured using laser diffraction between 5 and 1400 μm, such as between 5 and 1200 μm, between 5 and 1000 μm, between 5 and 800 μm, between 5 and 500 μm, or between 5 and 300 μm.

[0083] In another embodiment, the spherical glass beads have a median particle size D50 as measured using laser diffraction between 1 and 1400 μm, such as between 1 and 1200 μm, between 1 and 1000 μm, between 1 and 800 μm, between 1 and 500 μm, or between 1 and 300 μm.

[0084] Diameters D10 and D90 are commonly 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 the population of spherical glass beads fall. Similarly, the D90 diameter is the diameter below which 90% of the population of spherical glass beads fall.

[0085] The span of the particle size distribution of spherical glass beads as measured by laser diffraction is defined by:

[0086]

[0087] In another embodiment, the spherical glass beads have a median particle size D50 between 15 and 100 μm as measured using laser diffraction 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.

[0088] In another embodiment, the spherical glass beads have a median particle size D50 between 30 and 75 μm as measured using laser diffraction 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.

[0089] In another embodiment, the spherical glass beads have a median particle size D50 between 15 and 50 μm as measured using laser diffraction 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.

[0090] In another embodiment, the spherical glass beads have a median particle size D50 between 5 and 35 μm as measured using laser diffraction 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.

[0091] In another embodiment, the spherical glass beads have a median particle size D50 between 1 and 35 μm as measured using laser diffraction 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.

[0092] In another embodiment, the spherical glass beads have a median particle size D50 between 10 and 25 μm as measured using laser diffraction 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.

[0093] In another embodiment, the spherical glass beads have a median particle size D50 between 1 and 25 μm as measured using laser diffraction 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.

[0094] In another embodiment, the spherical glass beads have a median particle size D50 between 1 and 15 μm as measured using laser diffraction 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.

[0095] In another embodiment, the spherical glass beads have a median particle size D50 between 1 and 10 μm as measured using laser diffraction 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.

[0096] As understood by those skilled in the art, span = 0 corresponds to monodisperse spherical glass beads.

[0097] In a preferred embodiment, at least a portion of the spherical glass beads are hemispherically coated with a light reflecting coating, preferably a hemispherical aluminium coating (HAC). In another embodiment, at least a portion of the spherical glass beads are fluorochemically coated.

[0098] The specific application of the organic solvent-based ink, coating, or paint composition having retroreflective properties provided in step (c), (d), or (e) determines the most preferred refractive index of the spherical glass beads used in the retroreflective organic solvent-based composition provided in step (b). If the composition is applied in a dry environment or applied to a substrate that exhibits retroreflective properties in a dry condition and wherein the applied layer of retroreflective spherical glass beads is not coated with another layer, the refractive index of the spherical glass beads measured at a wavelength λ of 589 nm can be between 1.8 and 2.8.

[0099] In one embodiment, the retroreflective organic solvent-based composition provided in step (b) and the organic solvent-based ink, coating or paint composition having retroreflective properties provided in step (c), (d) or (e) comprise spherical glass beads having a refractive index between 1.8 and 2.0 measured at a wavelength λ of 589 nm.

[0100] If, on the other hand, the composition is applied in a wet environment or applied to a substrate that exhibits retroreflective reflectivity under wet conditions, or the applied layer of retroreflective spherical glass beads is coated with one or more further 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. The composition that exhibits retroreflective reflectivity under dry and wet conditions and in which the applied layer of retroreflective spherical glass beads is coated with or not coated with one or more further transparent layers may comprise different types of glass beads having different refractive indices and, optionally, different sizes. In one embodiment, the retroreflective organic solvent-based composition provided in step (b) and the organic solvent-based ink, coating, or paint composition having retroreflective properties provided in step (c), (d), or (e) comprise spherical glass beads having a refractive index measured at a wavelength λ of 589 nm of between 2.0 and 2.8, preferably between 2.2 and 2.4.

[0101] In another embodiment, the retroreflective organic solvent-based composition provided in step (b) and the organic solvent-based ink, coating or paint composition having retroreflective properties provided in step (c), (d) or (e) comprise at least two types of spherical glass beads, wherein at least one type of spherical glass beads has a refractive index of between 1.8 and less than 2.0 measured at a wavelength λ of 589 nm and at least another type of spherical glass beads has a refractive index of between 2.0 and 2.8 measured at a wavelength λ of 589 nm.

[0102] In a very preferred embodiment, the amount of spherical glass beads is 50-80 wt.%, based on the total weight of the retroreflective organic solvent-based composition provided in step (b).

[0103] In a preferred embodiment, the amount of the spherical glass beads is 53-75 wt.%, more preferably 58-72 wt.%, even more preferably 60-70 wt.%, based on the total weight of the retroreflective organic solvent-based composition provided in step (b).

[0104] In an embodiment, the amount of spherical glass beads is 50-78 wt.%, 50-75 wt.%, 50-73 wt.%, 50-72 wt.%, 50-71 wt.%, 50-70 wt.% or 50-69 wt.% based on the total weight of the retroreflective organic solvent-based composition provided in step (b).

[0105] In other embodiments, the amount of spherical glass beads is 52-80 wt.%, 54-80 wt.%, 56-80 wt.%, 57-80 wt.%, 58-80 wt.%, 59-80 wt.%, or 60-80 wt.%, based on the total weight of the retroreflective organic solvent-based composition provided in step (b).

[0106] In other embodiments, the amount of spherical glass beads is 52-85 wt.%, 54-85 wt.%, 56-85 wt.%, 57-85 wt.%, 58-85 wt.%, 59-85 wt.%, or 60-85 wt.%, based on the total weight of the retroreflective organic solvent-based composition provided in step (b).

[0107] thickener

[0108] The retroreflective organic solvent-based composition provided in step (b) of the method as defined herein comprises a thickener. This may be, optionally, the same thickener applied in step (e). As used herein, the term thickener may also refer to a combination of one or more thickeners. Thus, thickener and thickeners are used and have the same meaning unless otherwise indicated.

[0109] In one embodiment, a single thickener is used in the retroreflective organic solvent-based composition provided in step (b). In another embodiment, a single thickener is used in step (e).

[0110] In preferred embodiments, the thickener encompasses a mixture of different thickeners. In one embodiment, a mixture of different thickeners is used in the retroreflective organic solvent-based composition provided in step (b). In another embodiment, a mixture of different thickeners is used in step (e).

[0111] In embodiments, the thickener applied in step (e) is the same thickener applied to the retroreflective organic solvent-based composition provided in step (b). In other embodiments, the thickener applied in step (e) is different from the thickener applied to the retroreflective organic solvent-based composition provided in step (b).

[0112] As will be appreciated by those skilled in the art, the organic solvent-based paste, ink, paint, or coating formulation without retroreflective properties provided in step (a) may also include a thickener. If present, this thickener may be the same as or different from the thickener applied in step (b) and / or the thickener applied in step (e).

[0113] Without wishing to be bound by any theory, it is believed that the thickener limits or reduces the sedimentation and / or precipitation of the spherical glass beads and, if appropriate, further particulate matter in the retroreflective organic solvent-based composition provided in step (b) and the final organic solvent-based paste, ink, paint, or coating formulation having retroreflective properties provided in step (c), (d), or (e), so that these compositions can be easily resuspended. Additionally, without wishing to be bound by any theory, it is believed that the thickener provides shear-thinning behavior to the retroreflective organic solvent-based composition provided in step (b).

[0114] In a preferred embodiment, the amount of the thickener in the retroreflective organic solvent-based composition provided in step (b) is 0.20-3.0 wt.%, more preferably 0.25-2.5 wt.%, and even more preferably 0.30-2.1 wt.%, based on the total weight of the retroreflective organic solvent-based composition provided in step (b).

[0115] In an embodiment, the amount of the thickener in the retroreflective organic solvent-based composition provided in step (b) is 0.15-2.5 wt.%, 0.15-2.0 wt.%, 0.15-1.75 wt.%, 0.15-1.5 wt.% or 0.15-1.3 wt.%, based on the total weight of the retroreflective organic solvent-based composition provided in step (b).

[0116] In other embodiments, the amount of thickener in the retroreflective organic solvent-based composition provided in step (b) is 0.20-3.50 wt.%, 0.30-3.50 wt.%, 0.40-3.50 wt.%, 0.50-3.50 wt.%, 0.60-3.50 wt.%, 0.70-3.50 wt.% or 0.80-3.50 wt.%, based on the total weight of the retroreflective organic solvent-based composition provided in step (b).

[0117] In a preferred embodiment, the mixture obtained in step (c) or (d) is mixed in step (e) with 0-2.5 wt.%, 0-2.0 wt.%, 0-1.8 wt.%, 0-1.6 wt.%, 0-1.5 wt.%, 0-1.4 wt.% or 0-1.3 wt.% of a thickener, based on the total weight of the organic solvent-based paste, ink, paint or coating formulation having retroreflective properties obtained in step (c) or (d), respectively.

[0118] In another preferred embodiment, the mixture obtained in step (c) or (d) is mixed in step (e) with 0.1-3.0 wt.%, 0.2-3.0 wt.%, 0.3-3.0 wt.%, 0.4-3.0 wt.%, or 0.5-3.0 wt.% of a thickener, based on the total weight of the organic solvent-based paste, ink, paint or coating formulation having retroreflective properties obtained in step (c) or (d), respectively.

[0119] Preferred examples of thickeners that can be used in the retroreflective organic solvent-based composition provided in step (b) and / or step (e) are selected from the group consisting of: (modified) hydrogenated castor oil, clay, modified clay, calcium sulfonate complexes, organophilic phyllosilicates, silica gels, synthetic amorphous silica, acrylic type gelling agents, modified cellulosic materials, polyurea dispersions, solutions of urea-modified polyamides, polyurethane dispersions, and combinations thereof.

[0120] Examples of modified clays include LT and 38 (Elementis Global). Examples of silica gel include N20 (Wacker Chemical Corporation) and (Evonik). An example of an organophilic phyllosilicate is Claytone 40 (Byk). An example of a modified hydrogenated castor oil is RM 1900 (BASF). An example of hydrogenated castor oil is RM 1920 (BASF). An example of a solution of a urea-modified nonpolar 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 95(Huber).

[0121] In a preferred embodiment, two thickeners are used in the retroreflective organic solvent-based composition provided in step (b) and / or step (e), more preferably:

[0122] Organophilic phyllosilicates and modified hydrogenated castor oil; or

[0123] Calcium sulfonate complex and polyurea dispersion.

[0124] The amount of organic solvent in the retroreflective organic solvent-based composition provided in step (b) is independently specified. If the thickener is applied, for example, in the form of a dispersion in a solvent, the amount of thickener defined in the context of step (b) relates to the dry weight of the thickener. If, in step (e), the thickener is applied, for example, in the form of a dispersion in a solvent, the amount of thickener defined in the context of step (e) relates to the dry weight.

[0125] Further ingredients

[0126] As described above, the retroreflective organic solvent-based composition provided in step (b) comprises 0-10 wt.% of one or more further ingredients. As those skilled in the art will appreciate, the 'further' ingredients are distinct from the other ingredients defined in the retroreflective organic solvent-based composition provided in step (b). In other words, the further ingredients do not include spherical glass beads, a thickener, or an organic solvent.

[0127] In one embodiment, the one or more further ingredients are selected from the group consisting of foam control agents, preservatives, dyes, curing initiators, luminescent agents such as phosphors and fluorescent agents, pigments, UV absorbers, binders and resins.

[0128] Suitable binders and resins 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, further ingredients may include a curing initiator, such as a photoinitiator or a thermal initiator.

[0129] In one embodiment, the one or more further ingredients do not include any of dyes, pigments, binders, resins and curing initiators.

[0130] In a preferred embodiment, the one or more further ingredients do not include any of a binder, a resin and a curing initiator.

[0131] In one embodiment, the retroreflective organic solvent-based composition provided in step (b) comprises, as part of one or more further ingredients, synthetic pigment flakes having an average diameter between 5 and 150 μm, a thickness less than 1 μm, and an aspect ratio (flake diameter / thickness) of at least 10, wherein the synthetic pigment flakes are selected from (A), (B), (C), or a combination thereof:

[0132] (A) Metal flakes 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, metal alloys, rare earth compounds, and optionally coated with an outer layer comprising one or more colorants and a binder;

[0133] (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, metal alloys, rare earth compounds, and optionally coated with an outer layer comprising one or more colorants and a binder;

[0134] (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 oxide, coated with at least one layer of one or more components selected from the group consisting of metal oxides, metals, metal sulfides, low-valent titanium oxides, titanium oxynitrides, FeO(OH), SiO2, B2O3, GeO2, metal alloys, rare earth compounds, and optionally coated with an outer layer comprising one or more colorants and a binder.

[0135] In the case of synthetic pigment flakes, the term 'average diameter' refers to the median particle size D50.

[0136] As those skilled in the art will appreciate, 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 treated naturally occurring pigment flakes. One advantage of using synthetic pigment flakes is that they can be produced with very smooth surfaces, thereby increasing their reflective properties.

[0137] As used herein, the term 'flake' or 'platelet' refers to a pigment shape having a large surface area and a small thickness. Typically, a flake or platelet is characterized by its 'aspect ratio,' defined as the largest dimension, i.e., the maximum diameter of the surface, divided by the smallest dimension, i.e., the thickness. As used herein, synthetic pigment flakes have an aspect ratio of at least 10, preferably at least 15, and more preferably at least 20.

[0138] In a preferred embodiment, the synthetic flakes have an average diameter of 6-45 μm, more preferably 7-35 μm, even more preferably 8-25 μm, still more preferably 9-20 μm, and most preferably 10-16 μm.

[0139] 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, still more preferably between 10 and 50 nm.

[0140] In an embodiment, the amount of one or more further ingredients in the retroreflective organic solvent-based composition provided in step (b) is 0-8.0 wt.%, 0-6.0 wt.%, 0-4.0 wt.%, 0-3.0 wt.%, 0-2.5 wt.%, 0-2.0 wt.%, 0-1.5 wt.%, 0-1.0 wt.% or 0-0.5 wt.%, based on the total weight of the retroreflective organic solvent-based composition provided in step (b).

[0141] In other embodiments, the amount of one or more further ingredients in the retroreflective organic solvent-based composition provided in step (b) is 0.01-10 wt.%, 0.02-10 wt.%, 0.04-10 wt.%, 0.08-10 wt.%, 0.15-10 wt.%, 0.25-10 wt.%, 0.35-10 wt.%, 0.45-10 wt.% or 0.55-10 wt.%, based on the total weight of the retroreflective organic solvent-based composition provided in step (b).

[0142] The amount of organic solvent in the retroreflective organic solvent-based composition provided in step (b) is independently specified. If the one or more further ingredients are applied, for example, in the form of a solution, suspension or dispersion in a solvent, the amount of the one or more further ingredients defined above relates to the dry weight of the one or more further ingredients, that is, the weight without solvent.

[0143] Rheological behavior

[0144] The viscosity as measured and defined herein is the so-called Brookfield viscosity. As known to those skilled in the art, the Brookfield viscosity of different compositions may require measurement using different standardized spindles. Compositions with very low viscosities are typically determined using spindle #1, while compositions with high viscosities are typically determined using spindle #5. Compositions with intermediate viscosities may be determined using spindles #2, #3, or #4.

[0145] The viscosity of the organic solvent-based paste, ink, paint or coating formulation without retroreflective properties provided by step (a) of the method as defined herein can vary from very low values ​​to high values. This is why the lower limit of the Brookfield viscosity range is determined using spindle #1 and the upper value is determined using spindle #5.

[0146] In a preferred embodiment of the organic solvent based paste, ink, paint or coating formulation without retroreflective properties, the organic solvent based paste, ink, paint or coating formulation has a Brookfield viscosity η1 at a shear rate of 0.5 rpm and at a temperature of 20° C. between:

[0147] 5 mPa·s, more preferably 10 mPa·s, as measured in a 600 ml beaker having a diameter of 8.25 cm using a #1 spindle; and

[0148] • 280 Pa·s, more preferably 250 Pa·s, as measured in a 600 ml beaker with a diameter of 8.25 cm using a #5 spindle.

[0149] The retroreflective organic solvent-based composition provided by step (b) of the method as defined herein exhibits shear-thinning behavior.

[0150] In a preferred embodiment, the retroreflective organic solvent-based composition provided in step (b) has a first Brookfield viscosity η2 between 8 and 325 Pa·s at a shear rate of 0.5 rpm and a second Brookfield viscosity η3 between 110 and 4000 mPa·s at a shear rate of 20 rpm, with the proviso that η3 is at least 4 times lower than η2, wherein η2 and η3 are measured at a temperature of 20° C. in a 600 ml beaker having a diameter of 8.25 cm using a #4 spindle.

[0151] In another preferred embodiment, the retroreflective organic solvent-based composition provided in step (b) has a first Brookfield viscosity η2 between 10 and 310 Pa·s at a shear rate of 0.5 rpm and a second Brookfield viscosity η3 between 125 and 4000 mPa·s at a shear rate of 20 rpm, with the limitation that η3 is at least 5 times lower than η2, wherein η2 and η3 are measured at a temperature of 20° C. in a 600 ml beaker with a diameter of 8.25 cm using a #4 spindle.

[0152] In another embodiment, the retroreflective organic solvent-based composition provided in step (b) has a first Brookfield viscosity, η2, between 5 and 350 Pa·s at a shear rate of 0.5 rpm and a second Brookfield viscosity, η3, between 100 and 5000 mPa·s at a shear rate of 20 rpm, with the proviso that η3 is at least 30, 50, 60, 70, or 80 times lower than η2, wherein η2 and η3 are measured at a temperature of 20° C. in a 600 ml beaker having a diameter of 8.25 cm using a #4 spindle.

[0153] In another embodiment, the retroreflective organic solvent-based composition provided in step (b) has a first Brookfield viscosity, η2, between 5 and 25 Pa·s at a shear rate of 0.5 rpm and a second Brookfield viscosity, η3, between 100 and 5000 mPa·s at a shear rate of 20 rpm, with the proviso that η3 is at least 2, 3, 4, or 5 times lower than η2, wherein η2 and η3 are measured at a temperature of 20° C. in a 600 ml beaker having a diameter of 8.25 cm using a #4 spindle.

[0154] Process for preparing retroreflective organic solvent-based compositions

[0155] The retroreflective organic solvent-based composition provided in step (b) can be prepared as follows. Generally speaking, the ingredients of the retroreflective organic solvent-based 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 are added to the organic solvent, because in a thickened composition, it is more difficult to uniformly distribute the ingredients.

[0156] In one embodiment, the retroreflective organic solvent-based composition provided in step (b) is prepared by:

[0157] (i) adding an organic solvent, spherical glass beads as defined above, a thickener as defined above and optionally one or more further ingredients as defined above to a container; and

[0158] (ii) stirring or homogenizing the mixture obtained in step (i), preferably at a temperature between 15 and 70° C., for a time preferably between 5 and 60 minutes.

[0159] In a preferred embodiment, the thickener is added after the mixture of the organic solvent and the spherical glass beads has been stirred or homogenized. In another preferred embodiment, the thickener is added after the mixture of the organic solvent, the spherical glass beads, and any further ingredients has been stirred or homogenized. The stirring or homogenization is preferably performed at a low shear rate to avoid entrainment of air bubbles.

[0160] Thus, the present invention has been described with reference to certain embodiments discussed above. It should be appreciated that these embodiments are susceptible to various modifications and alternative forms that will be apparent to those skilled in the art.

[0161] Furthermore, for a proper understanding of this document and its claims, it should be understood that the verb 'to comprise' and its conjugations are used in their non-limiting sense to mean that items following the word are included, but items not specifically mentioned are not excluded. Furthermore, referring to a component by the indefinite article 'a' does not exclude the possibility that more than one of the component is present, unless the context clearly requires that only one component be present. Thus, the indefinite article 'a' or 'an' generally means 'at least one'.

[0162] Examples

[0163] Measuring solution viscosity

[0164] Viscosity using Brookfield DV2T viscometer, at a temperature of 20°C, using different standardized spindles (#1, #2, #3, #4 and #5; obtained from Brookfield LV-1, LV-2, LV-3, LV-4, and LV-5) were measured according to the operating instructions. The measurements were performed in a 600 ml low-profile Griffin beaker with a flat bottom and 8.25 cm diameter without protective legs. Before measuring the viscosity, the sample was brought to a temperature of 20°C and homogenized using stirring.

[0165] Example 1

[0166] Three retroreflective organic solvent-based compositions (compositions provided according to step (b) of the process of the present invention) were prepared by adding the ingredients in the following order to a container (3.5 liters) at ambient temperature (-20°C) and using Dispermill Orange line 18 / 186:

[0167] (1) Add organic solvent and start stirring at 500 rpm;

[0168] (2) Add glass beads while mixing at 500 rpm for at least 5 minutes;

[0169] (3) while mixing at 1300 rpm, add the first thickener for at least 5 minutes and slowly increase the rpm to 2000 rpm without introducing air bubbles;

[0170] (4) adding further thickener as appropriate and continuing stirring at 1800 rpm for at least 45 minutes and, if necessary, further slowly increasing the rpm without introducing air bubbles; and

[0171] (5) On the second day, after the thickener has finally set, the composition is stirred at about 2300 rpm for 15 minutes.

[0172] The amounts of the different ingredients are listed in Table 1. The following ingredients were used.

[0173] Spherical glass beads:

[0174] '(AA)' microscopic glass beads (RI 2.2), obtained from Jianxi Sunflex Light Retroreflective Material Co., Ltd., 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 mass of about 4.5 g / cm 3 These spherical glass beads contain TiO2, BaO, ZnO and CaO.

[0175] '(BB)' microscopic glass beads (RI 2.2, HAC), obtained from Jianxi Sunflex Light Retroreflective Material Co., Ltd., hemispherical aluminum-coated glass beads having a refractive index of about 2.2 measured at a wavelength λ of 589 nm, a median particle size D50 of 40.37 μm, a D10 diameter of 37.32 μm, and a D90 diameter of 44.11 μm as measured using laser diffraction, and a mass of about 4.5 g / cm 3 These spherical glass beads contain TiO2, BaO, ZnO and CaO.

[0176] organic solvents

[0177] Syrox S8000 diluent (Axalta), a mixture of organic solvents including 5-methylhexan-2-one, n-butyl acetate, 2,6-dimethylheptan-4-one, and 4,6-dimethylheptan-2-one

[0178] OK Thinner (Gamma, the Netherlands)

[0179] Cromax XB383 standard diluent (Axalta), containing a mixture of organic solvents such as xylene, ethylbenzene, naphtha, 1,2,4-trimethylbenzene, mesitylene, n-propylbenzene, isoamyl acetate, n-butyl acetate, 2-methylbutyl acetate, and 4-methyl-2-pentanone

[0180] thickener

[0181] · RM 1920, available from BASF, hydrogenated castor oil, finely powdered, thickener

[0182] Claytone 40, available from Byk, organophilic phyllosilicate, thickener

[0183] Table 1: Composition of Retroreflective Organic Solvent-Based Compositions

[0184]

[0185] Example 2

[0186] The stability of the three retroreflective organic solvent-based compositions given in Table 1 was determined by visual and tactile inspection to see whether the samples exhibited sedimentation, syneresis, or separation (phase or other) just before resuspension and whether the samples exhibited sedimentation, syneresis, or separation (phase or other) directly after the mixture was resuspensed. Additionally, it was determined whether the samples remained stable and homogeneous for a sufficient period of time after resuspension.

[0187] As is understood by those skilled in the art, limited sedimentation, (phase) separation and / or syneresis of the retroreflective organic solvent-based compositions provided in step (b) of the process according to the present invention is not a problem, as long as such compositions can be resuspended, for example using simple stirring, in order to obtain a composition that remains stable and homogeneous long enough to be processed (i.e., mixed with the organic solvent-based paste, ink, paint or coating formulation without retroreflective properties provided in step (a) of the process according to the present invention).

[0188] Resuspension was performed by vigorous mechanical stirring for 5 minutes using an overhead stirrer (without introducing air bubbles). The results of stability measurements immediately before and after resuspension are listed in Table 2a. Table 2a lists the sedimentation, syneresis and 'air bubble / lump' values ​​determined according to the classification given in Table 2b.

[0189] Table 2a: Stability results

[0190]

[0191] Table 2b: Stability Classification

[0192] Sedimentation classification # Severe precipitation / unresuspendable 1 Moderate sedimentation / difficult resuspension 2 Mild sedimentation / easy resuspension 3 No precipitation / uniform 4 Sedimentation classification # Severe syneresis 1 Moderate syneresis 2 Mild syneresis 3 No syneresis 4 Bubble / Agglomerate Classification # Unmixed glass lumps 1 bubble 2 No bubbles - no lumps 3

[0193] The Brookfield viscosities of the three retroreflective organic solvent-based compositions given in Table 1 (provided in step (b) of the process according to the present invention) were determined according to the protocol defined above using spindle #4 at 0.5 rpm and 20 rpm. The results are presented in Table 2c. The three retroreflective organic solvent-based compositions exhibited shear thinning behavior.

[0194] Table 2c: Brookfield viscosity using spindle #4 at approximately 20°C

[0195] sample Viscosity at 0.5 rpm [Pa·s] Viscosity at 20 rpm [mPa·s] T00980 300.0 3500 T00994 14.40 2790 T01039 13.20 150

[0196] Example 3

[0197] The three retroreflective organic solvent-based compositions of Example 1 (provided in step (b) of the process according to the present invention) were used to prepare five different compositions selected from the group consisting of organic solvent-based pastes, inks, paints or coating formulations having retroreflective properties.

[0198] The three retroreflective organic solvent-based compositions of Example 1 (provided in step (b) of the process according to the present invention) were mixed with several commercial products without retroreflective properties listed in Table 3 (provided in step (a) of the process according to the present invention). The viscosities of the commercial products are also shown in Table 3.

[0199] Table 3: Commercial products without retroreflective properties

[0200]

[0201] (§) Brookfield viscosity was measured according to the protocol as defined herein before using spindle #2 at 0.5 rpm.

[0202] (§§) Brookfield viscosity was measured according to the protocol as defined herein before using spindle #3 at 0.5 rpm.

[0203] (§§§) Brookfield viscosity was measured according to the protocol as defined herein before using spindle #5 at 0.5 rpm.

[0204] (§§§§)Undetermined.

[0205] (*) Cromax Verkehrsblau is a mixture of 42.15 wt.% XB155 Centari 6000 Low Emission Binder (Axalta), 5.47 wt.% XB165 Centari 6000 Low Emission Binder (Axalta), 29.91 wt.% Cromax AM28 Centari Mastertint Fast blue HS (Axalta), 12.76 wt.% Cromax AM1 Centari Mastertint White HS (Axalta), 7.59 wt.% Cromax AM27 Centari Mastertint Blue (Axalta) and 2.13 wt.% Cromax AM30 Centari Mastertint Fast Green HS (Axalta).

[0206] (**) A mixture of 75 wt.% Q550 Autobase Plus MM and 25 wt.% Q065 Autobase Plus MM.

[0207] When necessary, additional thickener (selected from the thickeners listed in Example 1) was added.

[0208] Five compositions selected from the group consisting of organic solvent-based pastes, inks, paints or coating formulations having retroreflective properties were prepared by adding the ingredients to a 600 ml beaker at ambient temperature (-20°C) in the following order and using a Dispermill Orange - line 18 / 186:

[0209] (1) Add an organic solvent-based paste, ink, paint, or coating formulation (Table 3) without retroreflective properties to a beaker and begin stirring;

[0210] (2) Add the retroreflective organic solvent-based composition (Table 1) to the beaker and continue stirring at 700-1500 rpm for about 10 minutes;

[0211] (3) When adding additional thickener, extend the stirring at about 1800 rpm for an additional 15 minutes with each addition; and

[0212] (4) On the second day, after the thickener has finally set, the composition is stirred at about 1800-2500 rpm for 15 minutes.

[0213] The amounts of the different ingredients in the resulting organic solvent-based paste, ink, paint or coating formulation having retroreflective properties (provided in step (c) or (e) of the process according to the present invention) are listed in Table 4.

[0214] Table 4: Composition of organic solvent-based paste, ink, paint or coating formulations having retroreflective properties

[0215]

[0216] The stability of five different compositions selected from the group consisting of organic solvent-based pastes, inks, paints or coating formulations having retroreflective properties (provided in step (c) or (e) of the process according to the present invention) was determined by visual and tactile inspection of whether the samples exhibited sedimentation, syneresis or separation (phase or other) just before resuspension and whether the samples exhibited sedimentation, syneresis or separation (phase or other) directly after resuspension of the mixture. In addition, it was determined whether the samples remained stable and homogeneous for a sufficiently long period of time after resuspension.

[0217] As is understood by those skilled in the art, limited sedimentation, (phase) separation and / or syneresis of organic solvent-based paste, ink, paint or coating formulations having retroreflective properties (provided in step (c) or (e) of the process according to the invention) is not a problem, as long as such compositions can be resuspended, for example using simple stirring, in order to obtain a composition that remains stable and homogeneous for a long enough time to process it, i.e. to apply it to the substrate of interest.

[0218] Resuspension was performed by vigorous mechanical stirring for 5 minutes using an overhead stirrer (without introducing air bubbles). The results of stability measurements immediately before and after resuspension are listed in Table 5. Table 5 lists the sedimentation, syneresis and 'air bubble / agglomeration' values ​​determined according to the classification given in Table 2b.

[0219] Table 5: Stability results

[0220]

[0221] Example 4

[0222] Five different compositions selected from the group consisting of organic solvent-based pastes, inks, paints or coating formulations having retroreflective properties disclosed in Table 4 were applied using the corresponding 'Application Methods' disclosed in Table 3 for the corresponding 'Uses' disclosed in Table 3, thereby producing visually appealing coated substrates having retroreflective properties.

[0223] Comparative Examples

[0224] Five comparative retroreflective compositions were prepared by directly mixing a composition selected from the group consisting of an organic solvent-based paste, ink, paint, or coating formulation (as defined in Example 3) with spherical glass beads as defined in Example 1. The comparative retroreflective compositions were prepared as follows. A commercial organic solvent-based paste, ink, paint, or coating formulation without retroreflective properties was placed in a beaker. The spherical glass beads were then added and then thoroughly mixed using a Dispermill Orange-Line 18 / 186 at 1000-2100 rpm for 7-10 minutes. The process was performed at ambient temperature (~20°C). The amounts of the different ingredients in the resulting comparative compositions are listed in Table 6.

[0225] Table 6: Composition of comparative compositions

[0226]

[0227] The stability of the five comparative retroreflective compositions was evaluated seven days after manufacture. Table 7 lists the sedimentation, syneresis, and 'bubble / lump' values ​​for the five comparative retroreflective compositions, as determined according to the classifications given in Table 2b. The results demonstrate that the samples exhibit moderate to severe sedimentation to the point where they are either unresuspendable (samples T01236, T01237, and T01240) or barely resuspendable (T01238 and T01239). In addition, sample T01239 exhibits both bubbles and lumps.

[0228] Table 7: Stability results

[0229] sample T01236 T01237 T01238 T01239 T01240 precipitation 1 1 2 2 1 Syneresis 4 4 4 4 4 Bubbles / lumps 3 3 3 2&1 3

Claims

1. A method of providing a composition selected from the group consisting of organic solvent-based pastes, inks, paints, and coating formulations having retroreflective properties, the method comprising the steps of: a) providing an organic solvent based paste, ink, paint or coating formulation having no retroreflective properties, the organic solvent based paste, ink, paint or coating formulation having a Brookfield viscosity η1 at a shear rate of 0.5 rpm and at a temperature of 20° C. between: 1 mPa·s, as measured in a 600 ml beaker with a diameter of 8.25 cm using a #1 spindle; and 300 Pa·s, as measured in a 600 ml beaker with a diameter of 8.25 cm using a #5 spindle; b) providing a retroreflective organic solvent-based composition having a first Brookfield viscosity η2 between 5 and 350 Pa·s at a shear rate of 0.5 rpm and a second Brookfield viscosity η3 between 100 and 5000 mPa·s at a shear rate of 20 rpm, with the constraint that η3 ≤ 0.5·η2, wherein η2 and η3 are measured at a temperature of 20° C. in a 600 ml beaker having a diameter of 8.25 cm using a #4 spindle, and Wherein, based on the total weight of the retroreflective organic solvent-based composition, the retroreflective organic solvent-based composition consists of: 10-49.85 wt.% organic solvent; 50-85 wt.% of spherical glass beads having a median particle size D50 between 1 and 1500 μm as measured using laser diffraction, and a refractive index measured at a wavelength λ of 589 nm between 1.5 and 2.8; 0.15-3.5 wt.% thickener; and 0-10 wt.% of one or more further ingredients; c) mixing the organic solvent-based ink, paint or coating formulation without retroreflective properties provided by step (a) with the retroreflective organic solvent-based composition provided by step (b) in a weight ratio of between 30:70 and 70:30 to provide an organic solvent-based paste, ink, paint or coating formulation with retroreflective properties; d) optionally mixing the organic solvent-based paste, ink, paint or coating formulation having retroreflective properties obtained in step (c) with 0-4.5 wt.% of synthetic pigment flakes having an average diameter between 5 and 150 μm, a thickness of less than 1 μm, and an aspect ratio of at least 10, based on the total weight of the organic solvent-based paste, ink, paint or coating formulation having retroreflective properties obtained in step (c); and e) optionally mixing the mixture obtained in step (c) or (d) with 0-3 wt.% of a thickener based on the total weight of the organic solvent-based paste, ink, paint or coating formulation having retroreflective properties obtained in step (c) or (d), respectively.

2. The method of claim 1, wherein the retroreflective organic solvent-based composition provided in step (b) consists of: 15-49.85 wt.% organic solvent; 50-80 wt.% spherical glass beads having a median particle size D50 between 5 and 1500 μm as measured using laser diffraction, and a refractive index measured at a wavelength λ of 589 nm between 1.5 and 2.8; 0.15-3.5 wt.% thickener; and 0-10 wt.% of one or more further ingredients.

3. The method of claim 1 or 2, wherein the retroreflective organic solvent-based composition provided in step (b) has a first Brookfield viscosity η2 between 8 and 325 Pa·s at a shear rate of 0.5 rpm and a second Brookfield viscosity η3 between 110 and 4000 mPa·s at a shear rate of 20 rpm, with the constraint that η3 ≤ 0.25·η2, wherein η2 and η3 are measured at a temperature of 20° C. in a 600 ml beaker having a diameter of 8.25 cm using a #4 spindle.

4. The method of claim 1 , wherein the organic solvent-based paste, ink, paint or coating formulation without retroreflective properties provided in step (a) has a Brookfield viscosity η1 at a shear rate of 0.5 rpm and a temperature of 20° C. between: 5 mPa·s, as measured in a 600 ml beaker with a diameter of 8.25 cm using a #1 spindle; and • 280 Pa·s, as measured in a 600 ml beaker with a diameter of 8.25 cm using a #5 spindle.

5. The method of claim 1 , wherein the spherical glass beads in the retroreflective organic solvent-based composition provided in step (b) have a refractive index measured at a wavelength λ of 589 nm between: (i) 2.0 and 2.8; or (ii) 1.7 and 2.

1.

6. The method of claim 1, wherein the spherical glass beads in the retroreflective organic solvent-based composition provided in step (b) have a median particle size D50 between 1 and 100 μm as measured using laser diffraction.

7. The method of claim 1, wherein the spherical glass beads in the retroreflective organic solvent-based composition provided in step (b) have a median particle size D50 between 5 and 100 μm as measured using laser diffraction.

8. The method of claim 1, wherein at least a portion of the spherical glass beads in the retroreflective organic solvent-based composition provided in step (b) are hemispherically coated with an aluminum coating.

9. The method of claim 1, wherein the organic solvent in the retroreflective organic solvent-based composition provided in step (b) is selected from the group consisting of aliphatic and aromatic solvents, ketones, esters, sugar ethers, alcohols, halogenated hydrocarbons, and combinations thereof.

10. The method of claim 1 , wherein the thickening agent in the retroreflective organic solvent-based composition provided in step (b) is selected from the group consisting of hydrogenated castor oil, modified hydrogenated castor oil, clay, modified clay, calcium sulfonate complex, organophilic phyllosilicate, silica gel, synthetic amorphous silica, acrylic type gelling agents, modified cellulosic materials, polyurea dispersions, solutions of urea-modified polyamides, polyurethane dispersions, and combinations thereof.

11. The method of claim 1, wherein the amount of the thickener in the retroreflective organic solvent-based composition provided in step (b) is 0.20-3.0 wt. % based on the total weight of the retroreflective organic solvent-based composition provided in step (b).

12. The method of claim 1, wherein the one or more further ingredients in the retroreflective organic solvent-based composition provided in step (b) are selected from the group consisting of foam control agents, preservatives, dyes, curing initiators, luminescent agents, pigments, UV absorbers, binders, and resins.

13. The method of claim 1, wherein steps (c), (d) and / or (e) are performed at a temperature between 15 and 30°C with stirring.

14. The method of claim 1, wherein step (c) comprises adding the retroreflective organic solvent-based composition provided in step (b) to the organic solvent-based paste, ink, paint, or coating formulation without retroreflective properties provided in step (a).

15. The method of claim 1 , wherein in step (c), the organic solvent-based paste, ink, paint or coating formulation without retroreflective properties provided in step (a) and the retroreflective organic solvent-based composition provided in step (b) are mixed in a weight ratio of between 40:60 and 60:

40.

16. The method of claim 1 , wherein in step (e), the mixture obtained in step (c) or (d) is mixed with 0-2.5 wt.% of a thickener, based on the total weight of the organic solvent-based paste, ink, paint or coating formulation having retroreflective properties obtained in step (c) or (d), respectively.

17. The method of claim 1 , further comprising the step of applying the organic solvent-based paste, ink, paint or coating formulation having retroreflective properties obtained in step (c), (d) or (e) to a substrate using screen printing, curtain coating, spray coating or spray painting.

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