Classifications

• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
  • C09D5/00—Coating compositions, e.g. paints, varnishes or lacquers, characterised by their physical nature or the effects produced; Filling pastes
  • C09D5/04—Thixotropic paints
• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
  • C09D7/00—Features of coating compositions, not provided for in group C09D5/00; Processes for incorporating ingredients in coating compositions
  • C09D7/40—Additives
  • C09D7/42—Gloss-reducing agents

Definitions

• This invention pertains to a matt, thixotiopic paint formulation and a method of pioducing such a paint formulation
• a paint formulation desirably possesses additional properties, such as a certain degree of thixotropy, in order to enhance its utility for a variety of applications
• Thixotropy is a characteristic of a paint formulation that i
• Silica an inoiganic material having silicon dioxide (S ⁇ O 2 ) as a basic sti uctuial unit, is useful in a wide va ⁇ ety of commercial applications Silica exists in a va ⁇ ety of molecular forms, which include, for example, monomers, dimeis, oligomers, cyclic forms, and polymers
• silica can be amorphous, crystalline, hydrated, solvated, or dry, and can exist in a variety of particulate and aggtegated states
• Amorphous silica can be formed by molecular precipitation, foi example, by cooling a supersaturated solution, concentrating an undersatuiated solution, or by careful hydrolysis of a solution of a labile silica precursor, such as a S ⁇ Cl , esters of silica, S ⁇ (OR) , and the like, to provide a supei saturated solution of S ⁇ (OH) 4 , from which precipitates amorphous silica
• a labile silica precursor such as a S ⁇ Cl , esters of silica, S ⁇ (OR) , and the like
• silica usually sand
• silica can be vaporized at about 2000 °C and cooled to foim anhydrous amorphous silica particles
• silica can be sublimed at about 1500 °C in the presence of a reducing agent (e g , coke) to form SiO, which can be oxidized to form particulate silica
• a reducing agent e g , coke
• Other methods of pioducing fumed silica include, for example, oxidation of SiCl 4 at high temperatures or burning SiCl in the presence of methane or hydrogen.
• Silica solutions exhibit polymerization behavior, resulting in the increase of Si- O-Si bonds and decrease of Si-OH bonds.
• amorphous silica dissolves (and/or depolymerizes), forming Si(OH) 4 , which undergoes polymerization to form discrete particles with internal Si-O-Si bonds and external Si-OH bonds on the particle surface.
• the polymeric silica particles thus formed will further associate to give chains and networks comprising the individual particles.
• sol refers to a dispersion of discrete, colloidal particles, for example, of amorphous silica in an aqueous medium. If the sol is stable, a sol does not gel or settle even after several years of storage, and may contain up to about 50 wt.% silica and particle sizes up to 300 nm, although particles larger than about 70 nm settle slowly depending on the viscosity of the medium.
• a silica sol can be formed, for example, by growing particles to a certain size in a weakly alkaline solution, or by addition of dilute acid to a solution of sodium silicate (e.g., Na 2 SiO 3 ) with rapid mixing, until the pH drops to about 8-10, followed by removal of Na + (e.g., by ion-exchange resin or electrodialysis).
• Silica sols depending upon the type of silica, the particle size, and the nature of the particles, can be destabilized to form gels under mildly acidic to strongly acidic conditions.
• the term "gel” refers to a coherent, rigid, continuous three-dimensional network of colloidal particles.
• Silica gels can be produced by the aggregation of colloidal silica particles (typically under acidic conditions when neutralizing salts are absent) to form a three dimensional gel microstructure. Whether a gel will form under a particular set of conditions, however, can depend on the silica properties, such as, for example, particle size and the nature of the particle surface.
• the term "hydrogel” refers to a gel in which the pores (spaces within the gel microstructure) are filled with water.
• the term “alcogel” refers to a gel in which the pores are filled with an alcohol.
• a low density xerogel known as an "aerogel” is formed.
• Silica aerogels may have very unusual and highly desirable properties such as, for example, optical transparency, extremely low density, and unprecedented low thermal conductivity. See Herrmann et al., Journal of Non-Crystalline Solids, 186, 380-387 (1995).
• Synthetic silicas such as the micronized silica xerogels and precipitates used as matting agents, typically are hydrophilic, owing to the silanol groups present on the surface of the silica particles.
• Patent 5,221,337 discloses that the modification of silica with an organic polyol compound can lead to a matting agent which has practically no negative effect on the thixotropy of a paint formulation. This approach, however, remains problematic, as the addition of both a thixotropic additive and a matting agent can lead to undesirable interactions in a paint formulation.
• the invention is predicated, at least in part, on the surprising discovery that a silica-based matting agent can be utilized which contributes thixotropy to a paint formulation, and does not spoil the effect of other additives used to optimize the paint formulation.
• the invention provides a matt, thixotropic paint formulation comprising a resin system and a matting agent.
• the matting agent comprises a hydrophobic metal oxide, which has a surface moiety (i.e., one or more surface moieties) selected from the group consisting of trimethyl silyl, vinyl dimethyl silyl, acryl dimethyl silyl, and dimethyl silyl.
• the paint formulation is characterized by having thixotropic properties such that it does not sag at a notch height of about 75 ⁇ m when measured with an anti-sag meter after application to a substrate.
• the invention also provides a method of producing such a paint formulation.
• the invention further provides a substrate having a surface coated with the matt, thixotropic paint formulation of the invention.
• the invention provides a matt, thixotropic paint formulation comprising (a) a resin system, and (b) a matting agent comprising a hydrophobic metal oxide, wherein the metal oxide has a surface moiety (i.e., one or more surface moieties) selected from the group consisting of trimethyl silyl, vinyl dimethyl silyl, acryl dimethyl silyl, and dimethyl silyl, and wherein the formulation, after application to a substrate, does not sag at a notch height of about 75 ⁇ m when measured with an anti-sag meter.
• a matting agent comprising a hydrophobic metal oxide, wherein the metal oxide has a surface moiety (i.e., one or more surface moieties) selected from the group consisting of trimethyl silyl, vinyl dimethyl silyl, acryl dimethyl silyl, and dimethyl silyl
• the resin system can comprise any suitable resin.
• the resin can be any resin, many of which are known by those of skill in the art, suitable for use in a paint formulation. Suitable resins include, for example, alkyds, acrylics, epoxies, urethanes, polyesters, cellulosics, and mixtures and precursors thereof.
• the resin comprises at least one acrylic or at least one alkyd.
• Suitable acrylic resins for use in the paint formulation include those known as WORLEE CRYL A 1220 (E.H. Worlee & Co., Germany). More preferably, the resin comprises at least one alkyd.
• any suitable amount of resin can be present in the paint formulation.
• the resin can be present in the paint formulation in an amount of about 10-95 wt.%.
• the resin is present in the paint formulation in an amount of about 20-75 wt.%, more preferably in an amount of about 25-50 wt.%.
• the matting agent used in conjunction with the invention generally comprises a hydrophobic metal oxide.
• Any suitable metal oxide can be used in the context of the invention. Suitable metal oxides include silica, alumina, titania, zirconia, ceria, magnesia, and mixtures thereof, with silica being particularly prefei ⁇ ed.
• the metal oxide is typically characterized as being pyrogenic (i.e., fumed), precipitated, an aerogel, or a xerogel, with an aerogel being particularly preferred.
• aerogel refers to a high-porosity, substantially amorphous, organic or inorganic gel where the pore liquid has been replaced with air.
• the aerogel comprises silica and is prepared by modifying the surface of a hydrogel with a silylating agent and drying the surface-modified gel.
• the silica aerogel produced by this process may be partially or completely hydrophobic depending on the degree and type of silylation.
• the silica aerogels disclosed in WO 98/23366 are especially desirable as the metal oxide in the paint formulation of the invention.
• the metal oxide By treating the metal oxide with a silylating agent, the metal oxide exhibits a hydrophobic character. Indeed, the silylating agent imparts to the surface of the metal oxide particles a silyl moiety. Any suitable silyl moiety may be bonded to the metal oxide in the context of the invention to obtain the effect.
• Suitable silyl moieties are derived, for example, from compounds (e.g., silylating agents) of the following general formulae: R 3 Si-O-SiR 3 (I)
• R 3 Si-N(H)-SiR 3 (H) wherein the radicals R are identical or different and are each hydrogen or a nonreactive, organic, linear, branched, cyclic, saturated or unsaturated, aromatic or heteroaroinatic radical, preferably -Cis alkyl or C 6 -C
• Equally suitable silyl moieties can be derived from silanes of the formulae R' .
• n 1-4
• R 1 and R 2 are identical or different and are each hydrogen or a nonreactive, organic, linear, branched, cyclic, saturated or unsaturated, aromatic or heteroaromatic radical, preferably a Ci-Cj . alkyl or C 6 -C ⁇ 4 aryl, and more preferably a C ⁇ -C 6 alkyl, cyclohexyl, or phenyl.
• the radicals also can contain halogen substituents, such as fluorine or chlorine.
• the silyl moiety is a trimethyl silyl, a vinyl dimethyl silyl, an acryl dimethyl silyl, or a dimethyl silyl.
• the metal oxide can be characterized by having a degree of hydrophobicity.
• degree of hydrophobicity refers to the ratio by volume of methanol in a methanol-water mixture that wets the metal oxide, thereby loaning a homogeneous suspension.
• the metal oxide preferably is characterized by a degree of hydrophobicity of at least about 40%.
• the degree of hydrophobicity desirably is as high as possible inasmuch as a higher degree of hydrophobicity generally provides an improved thixotropic effect.
• the contact between the metal oxide particles and the silylating agent can be achieved by any suitable means.
• a silylating agent can be sprayed onto the metal oxide particles before being mixed with a carrier. It is preferred, however, that the contact between metal oxide particles and a silylating agent comprise adding at least one silylating agent to a metal oxide in a suitable carrier or solvent (e.g., water).
• a suitable carrier or solvent e.g., water
• a solution of a silylating agent in water can be added to an aqueous mixture of a metal oxide.
• the relative ratio of the total amount of silylating agent to the total amount of metal oxide must be high enough so that a sufficient amount of the metal oxide particles contact the silylating agent. Therefore, the metal oxide can be present in the paint fo ⁇ nulation in an amount of about 0.1-30 wt.%, preferably about 0.2-25 wt.%, and most preferably about 0.5-15 wt.%.
• the thixotropy of the paint formulation can be measured by any technique known in the art.
• the thixotropy is typically measured with an anti-sag meter, such as, for example, the Type 419 or the equivalent Leneta sag- resistance applicator (Erichsen GmbH, Germany).
• an anti-sag meter such as, for example, the Type 419 or the equivalent Leneta sag- resistance applicator (Erichsen GmbH, Germany).
• a paint fo ⁇ nulation is applied to a substrate and drawn downwards by an applicator.
• the applicator comprises various notch heights along its length, typically ranging from 25-300 ⁇ m. When paint is drawn over the substrate by the applicator, stripes of paint are formed on the substrate with increasing thicknesses corresponding to the respective notch heights on the applicator.
• Paint formulations of the present invention are characterized as being resistant to sagging at a notch height of about 75 ⁇ m, which is recognized in practice as indicating non-sagging/non-dripping behavior. It will be understood that as the thixotropy of a paint increases so too will the maximum notch height at which sagging is not detected.
• the paint formulation of the invention after application to a substrate, will also be characterized by providing a matt finish to the substrate.
• the paint formulation can be characterized by a 60 ° gloss level of 50 gloss units or less (as measured by a BYK-Gardner gloss meter). More preferably the paint formulation is characterized by a 60 ° gloss level of 40 gloss units or less (e.g., 30 gloss units or less).
• Matt surfaces are desirable for many applications. For example, the reduced glare of surfaces in schools, hospitals, and universities offers less chance of visual distraction, and concentration is better in such environments. Such finishes also demonstrate less tendency to become unsightly as time progresses, as small scratches and imperfections are less obvious than on gloss surfaces.
• the metal oxide will be in the fo ⁇ n of discrete individual particles, of an aggregated or non-aggregated state.
• the metal oxide particles can have any suitable diameter. Generally, the metal oxide has a median particle diameter of about 1-15 ⁇ m. It is preferred, however, for the metal oxide to have a median particle diameter of about 2-10 ⁇ m. Alternatively, the particles can initially be larger (e.g., about 5 mm) and subsequently broken down to the desired size during the manufacture of the paint formulation.
• the metal oxide can have any suitable surface area. Generally, the metal oxide has a surface area of at least about 100 m 2 /g, preferably at least about 200 m 2 /g, and most preferably at least about 300 m 2 /g. hi certain embodiments, it is suitable for the metal oxide
• the surface area of the metal oxide will not exceed 900 m /g and will be about 100-900 m 2 /g.
• the surface area of the metal oxide can be measured by any suitable method known in the art. Typically, the surface area of the metal oxide is dete ⁇ nined by the method of S. Brunauer, P.H. Emmet, and I. Teller. J Am. Chemical Society, 60, 309 (1938), which is commonly referred to as the BET method.
• the metal oxide also can have any suitable tap density, such as about 0.01-0.2 g/cm . To measure the tap density, a known mass of the dry powder is transferred to a 10 cm 3 graduated cylinder and tapped 40 times by hand.
• the metal oxide can have any suitable porosity. Typically the metal oxide has a porosity of about 50% or more, preferably about 70% or more, and most preferably about 80%o or more, since it is known that higher porosity leads to more effective matting.
• Any suitable ca ⁇ ier e.g., solvent
• a carrier is used to facilitate the application of the resin and metal oxide onto the surface of a suitable substrate. Suitable earners include inorganic carriers such as water, as well as organic carriers such as hydrocarbons, alcohols, ketones, esters, ethers, aroinatics, alkanes, and mixtures thereof. Any suitable concentration of carrier can be present in the paint fo ⁇ nulation, such as up to about 80 wt.%.
• the paint fomiulation can further comprise at least one thixotropic additive.
• the matting agent i.e., silyl-treated metal oxide
• a thixotropic additive can be included in the fomiulation to further enhance the thixotropy of the paint fo ⁇ nulation.
• Suitable thixotropic additives included, for example, chemically treated fumed silica, organically modified clay, modified alkyds, and the like.
• the thixotropic additive is based on an alkyd with an amide- or urethane-modified alkyd being particularly preferred.
• the thixotropic additive can be present in the paint fomiulation in an amount of about 0.5-5 wt.%, or, particularly in the case of modified resins, up to 50 wt.%.
• the paint formulation can further comprise any of a variety of other additives that are known in the art to be suitable for incorporation into a paint fomiulation.
• Suitable additives can include, for example, cationic surfactants, anionic surfactants (e.g., long-chain alkylbenzene sulfonate salts and long-chain, preferably branched chain, alkylsulfosuccinate esters), nonionic surfactants (e.g., polyalkylene oxide ethers of long-chain, preferably branched-chain, alkyl group-containing phenols, polyalkylene oxide ethers of long-chain alkyl alcohols, and fluorinated surfactants), hardeners (e.g., active halogen compounds, vinylsulfone compounds, aziridine compounds, epoxy compounds, acryloyl compounds, isocyanate compounds, etc.), pigment dispersants, thickeners, flowabi ty improvers, antifoamers (e.g., octyl alcohol, silicone-based antifoamers, etc.), foam inhibitors, releasing agents, foaming agents, penetrants, coloring dye
• Additional pigments other than the metal oxide can be present in the paint formulation.
• Such pigments include, for example, calcium carbonate, clays, aluminum silicates, urea-formaldehyde fillers, and the like, as well as other hydrophilic matting agents.
• Suitable pigments include alumina (e.g., alumina sols, colloidal alumina, cationic aluminum oxide or hydrates thereof, pseudoboehmite, etc.), magnesium silicate, magnesium carbonate, kaolin, talc, calcium sulfate, barium sulfate, titanium dioxide, zinc oxide, zinc sulfide, zinc carbonate, satin white, diatomaceous earth, calcium silicate, aluminum hydroxide, lithopone, zeolite, hydrated halloycite, magnesium hydroxide, polyolefins (e.g., polystyrene, polyethylene, polypropylene, etc.), plastics (e.g., acrylic), urea resin, and melamine resin.
• any conventional colored pigments may be used.
• Such pigments include the Sico-Flush pigments available from BASF AG, Ludwigshafen, Germany.
• a number of other additives can be present in the paint fomiulation and are particularly contemplated for use in a water-based paint fomiulation.
• a coalescing agent for example, a coalescing agent, a flow additive, a defoamer, a surfactant, a rust inhibitor and a pH regulator are all suitable additives which can be incorporated, if desired.
• a coalescing agent can be present to promote the softening of the resin during drying of the components of the paint fo ⁇ nulation, and such materials are well known.
• a coalescing agent is BUTYL CELLOSOLVE (ARCO Chemical Company, Newtown Square, Pennsylvania). Any suitable concentration of coalescing agent can be present in the paint fomiulation, such as about 1 -35 wt.%.
• a flow additive can be present to promote the wetting of the substrate by the paint formulation and the leveling of the paint formulation.
• a typical flow additive is DISBERBYK 301 (BYK-Chemie, Germany). Any suitable concentration of flow additive can be present in the paint fo ⁇ nulation, such as about 0.5-4 wt.%.
• a defoamer can be present to reduce the presence of bubbles in the paint fomiulation upon mixing of the components. Any suitable defoamer can be used in the paint fomiulation of the invention.
• One preferred defoamer is DISBERBYK 035 (BYK- Chemie, Gennany). Any suitable concentration of defoamer can be present in the paint fomiulation, such as about 0.01-3 wt.%.
• a surfactant can be utilized to reduce the surface tension of the paint fomiulation.
• Any suitable surfactant can be used in the paint fomiulation of the invention.
• One preferred surfactant is SURFYNOL 104 BC (Air Products & Chemicals, Inc.). Any suitable concentration of surfactant can be present in the paint fomiulation, such as about 0.01-3 wt.%.
• a rust inhibitor can be added to the paint fomiulation.
• a variety of rust inhibitors are suitable in the context of the invention
• One piefe ⁇ ed rust inhibitoi is ammonium benzoate
• Any suitable concentration of rust inhibitoi can be present in the paint fomiulation, such as about 0 01-2 wt %
• a pH regulatoi can be ptesent to control the pH of the paint fomiulation
• the pH of the paint formulation is maintained in a range generally suitable foi paint formulations, particulaily in the context of the substrate intended to be coated with the fomiulation
• Any suitable pH legulator can be used in the paint formulation of the invention
• the pH can be regulated via the addition of an acid (e g , mineial acid, acidic cation exchange resin, etc ) or a base (e g , an alkali metal hydroxide, basic amon exchange resin, etc )
• an acid e g , mineial acid, acidic cation exchange resin, etc
• a base e g , an alkali metal hydroxide, basic amon exchange resin, etc
• One preferred pH regulator is ammonium hydioxide
• Any suitable concentration of pH regulator can be present in the paint fomiulation, such as about 1-4 wt %
• the invention also piovides a method of producing a matt, thixotropic paint fomiulation composing (a) providing a hydrophobic metal oxide, wherein the metal oxide has a suiface moiety (I e , one or more surface moieties) selected from the group consisting of tnmethyl silyl, vinyl dimethyl silyl, acryl dimethyl silyl, and dimethyl silyl, and wherein the fomiulation, after application to a substrate, does not sag at a notch height of about 75 ⁇ m when measured with an anti-sag meter, and (b) mixing the metal oxide with a resin to form the paint formulation
• the resin and metal oxide can be mixed together with a suitable carrier
• the resin, hydrophobic metal oxide, carrier, and paint fomiulation characteristics are described above with respect to the inventive paint fomiulation Other possible components of the paint formulation similarly aie described above [0041]
• the invention also encompasses a substrate having a surface coated with the paint fo
• a substrate can be heated with the paint formulation by any suitable technique
• the paint formulation can be applied to the substrate by airless and electrostatic spray, brushing, dip, flowcoat, and roller coating
• one coating of the paint fomiulation of the invention can be sufficient to impart a des ⁇ ed effect to a substrate (e g , a matt finish)
• more than one coating of a paint fo ⁇ nulation can be applied, which can be the same or different hi addition
• the flexibility and adhesion of the coating desirably is sufficient to permit later fo ⁇ uing of the substrate into parts for vanous manufacturing operations
• a paint fo ⁇ nulation of the invention was prepared by mixing the components in their respective amounts as set forth in the Table below.
• the matting agent used was a hydrophobic (i.e., silyl-treated) silica aerogel having a surface area of about 690 m " /g, a median particle size of about 7.6 ⁇ m, and a tap density of about 0.04 g/cm .
• Preferred embodiments of this invention are desc ⁇ bed heiein, including the best mode known to the inventors for carrying out the invention Of couise, variations of those preferred embodiments will become apparent to those of ordinary skill in the art upon reading the foiegoing desciiption The inventois expect skilled artisans to employ such variations as appiopnate, and the inventors intend foi the invention to be practiced otheiwise than as specifically described herein Accoidingly, this invention includes all modifications and equivalents of the subject matter recited in the claims appended hereto as pe ⁇ nitted by applicable law Moreover, any combination of the above-described elements in all possible va ⁇ ations thereof is encompassed by the invention unless otherwise indicated herein oi otheiwise clearly contradicted by context

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• Chemical & Material Sciences (AREA)
• Life Sciences & Earth Sciences (AREA)
• Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• Wood Science & Technology (AREA)
• Organic Chemistry (AREA)
• Paints Or Removers (AREA)
• Compositions Of Macromolecular Compounds (AREA)

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• 2002
  • 2002-03-08 WO PCT/US2002/007250 patent/WO2002074868A1/en not_active Ceased
  • 2002-03-08 JP JP2002573865A patent/JP4225466B2/ja not_active Expired - Fee Related
  • 2002-03-08 CN CNB028097084A patent/CN1263809C/zh not_active Expired - Fee Related
  • 2002-03-08 US US10/094,391 patent/US6720368B2/en not_active Expired - Lifetime
  • 2002-03-08 EP EP02717597A patent/EP1368439B1/en not_active Expired - Lifetime
  • 2002-03-08 AT AT02717597T patent/ATE542863T1/de active
  • 2002-03-08 CA CA002440986A patent/CA2440986A1/en not_active Abandoned

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