WO2017013670A1 - A one component self-healing coating composition - Google Patents

A one component self-healing coating composition Download PDF

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Publication number
WO2017013670A1
WO2017013670A1 PCT/IN2015/000396 IN2015000396W WO2017013670A1 WO 2017013670 A1 WO2017013670 A1 WO 2017013670A1 IN 2015000396 W IN2015000396 W IN 2015000396W WO 2017013670 A1 WO2017013670 A1 WO 2017013670A1
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WIPO (PCT)
Prior art keywords
resin
coating composition
range
acid
anyone
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PCT/IN2015/000396
Other languages
French (fr)
Inventor
Girish MIRCHANDANI
Mohamed Askar PARAVAKKAL
Dayanand PUTHRAN
Sanjay DAS
Sisir Kumar Mandal
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Asian Paints Ltd.
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Publication of WO2017013670A1 publication Critical patent/WO2017013670A1/en

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    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
    • C08K3/00—Use of inorganic substances as compounding ingredients
    • C08K3/32—Phosphorus-containing compounds
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
    • C08G63/00—Macromolecular compounds obtained by reactions forming a carboxylic ester link in the main chain of the macromolecule
    • C08G63/66—Polyesters containing oxygen in the form of ether groups
    • C08G63/668—Polyesters containing oxygen in the form of ether groups derived from polycarboxylic acids and polyhydroxy compounds
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
    • C08L67/00—Compositions of polyesters obtained by reactions forming a carboxylic ester link in the main chain; Compositions of derivatives of such polymers
    • C08L67/04—Polyesters derived from hydroxycarboxylic acids, e.g. lactones
    • 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
    • C09D133/00—Coating compositions based on homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by only one carboxyl radical, or of salts, anhydrides, esters, amides, imides, or nitriles thereof; Coating compositions based on derivatives of such polymers
    • C09D133/04—Homopolymers or copolymers of esters
    • C09D133/06—Homopolymers or copolymers of esters of esters containing only carbon, hydrogen and oxygen, the oxygen atom being present only as part of the carboxyl radical
    • C09D133/062—Copolymers with monomers not covered by C09D133/06
    • C09D133/066—Copolymers with monomers not covered by C09D133/06 containing -OH groups
    • 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
    • C09D167/00—Coating compositions based on polyesters obtained by reactions forming a carboxylic ester link in the main chain; Coating compositions based on derivatives of such polymers
    • C09D167/02—Polyesters derived from dicarboxylic acids and dihydroxy compounds

Definitions

  • the present invention particularly provides for a coating composition suitable as clear/top coat that enables self-mending of nano/micro/macro scratches on the coating at ambient temperatures, increases the spray solid as well as imparts excellent appearance and good mechanical properties to the coating film wherein a method for forming multi!ayered coating films is also provided to meet varied end use and application including automotive use.
  • Aesthetics of automobile topcoats is of prime importance to the customers.
  • One approach is to make the coating extremely hard by incorporating nanoparticles such as alumina, zirconia and silica. However this is primarily a surface phenomenon.
  • the other approach is to make the coating with a self-healing capability.
  • Intrinsic self-healing commonly uses supramolecular polymers, oligomers which self heal via reversible hydrogen bonding or via dynamic covalent bonding.
  • Extrinsic self-healing commonly uses additives such as microcapsules filled with monomeric healing agents or microvascular networks that enable repeated self-healing and even healing of larger cracks via either foam generation or chemical reaction of healing agents.
  • the mechanism of healing involves use of healing agents with chemistries which differ from the chemistry of the base polymer and involves addition of additives such as microcapsules which may get damaged during preparation of the coating formulation thereby reducing the efficiency of self-healing. Further use of stimuli such as high temperature is commonly reported.
  • Patents JP 08127643 A and KR 142276 Bl is directed to the synthesis of thermosetting polymeric prepolymer which shows excellent shape-memory effect and also has excellent heat resistance, chemical resistance, transparency and coloring property.
  • Polyester resin composition contains at least one kind of dicarboxyiic acid component, at least one kind of diol component, and a component selected to have an unsaturated end group to help in crosslinking.
  • US20120322931 describes polyester which consists of low molecular weight polytrimethylene ether glycol (Mn 100 to 310) cross linked with isocyanate as antimicrobial coating composition.
  • CA 2723217 Al discloses a method to prepare a thermoplastic elastomer based on polyester which consist of one component from ethylene glycol, 1,3 propane diol etc.
  • US 20130184408 disclosure relates to a process of forming a polymer composition by the free radical polymerization of a monomer mixture in the presence of low molecular weight polytrimethylene ether glycol (Mn 120 to 490).
  • WO 2012133836 Al discloses a self-repajring coating film based on a fluorine-containing copolymer containing vinyl ether or a vinyl ester.
  • US 20040161538 Al discloses a multilayered coating composition using a polyester polyol/acrylic copolymer hybrid binder which can be cured with aminoplastic resins, free and blocked polyisocyanates. This prior art utilizes a hybrid polymer in the coating composition that is cured with isocyanate as the curing agent.
  • the primary object of the present invention is to provide for a coating composition preferably a clear coating composition, a synthesis method for manufacturing the same that would self heal and would be reparable even at ambient conditions and would provide for good mechanical hardness under baking conditions.
  • a coating composition having self-scratch healing characteristics comprising aminoplastic resin crosslinked polyester polyol resin comprising condensation product of carboxylic acids and polyols including one or more renewable polyalkylene glycols.
  • polyester polyol resin comprises polymeric condensation product having renewable polyalkylene glycols selected from anyone or more of cerenol, PT EG (polytetramethylene ether glycol) or polycaprolactone polyol in the polymer backbone.
  • said coating composition is provided wherein said polyester polyol resin comprises polymeric condensation product having renewable polyalkylene glycols selected from anyone or more of cerenol, PTMEG (polytetramethylene ether glycol) or polycaprolactone polyol in the polymer backbone.
  • said coating composition is provided wherein said polyester polyoi resin is a polyester polyoi resin blend comprising acrylic polyoi resin having at least one Veova monomer bonded to said acrylic polyoi.
  • said coating composition is provided wherein at least one Veova monomer in said acrylic polyoi resin is in amounts of 5- 20% by wt. of the coating composition preferably in the range of 10 to 18% by wt. for enhanced durability.
  • said coating composition is a clear composition and mechanically robust possessing self mending ability of nano/micro/ macro scratches under ambient conditions with gloss recovery after crockmeter testing of at least 40% to upto 200% ; has good mechanical hardness including scratch and pencil hardness of F-2H,Persoz hardness of at least 100 seconds under baking conditions; allows spraying for end use and application involving polyester polyoi resin at high solid content of 65-90% thus favouring a low VOC (volatile organic content) coating and enabling automotive use.
  • VOC volatile organic content
  • said polyester polyoi resin blend including acrylic polyoi resin has hydroxyl value in the range of 60-200 mg KOH/gm preferably 125-170 mg KOH/gm of said resins favouring desired mechanical properties and flexibility of a clear coat.
  • said polyester polyoi resin blend including acrylic polyoi resin has acid value of upto 30 mg KOH/g preferably upto 20 mg KOH/g and more preferably upto 10 mgKOH/gm of said resins favouring desired appearance and adhesiveness of the clear coat on the substrate.
  • a lower OH value below the OH value mentioned above does not provide for the desired mechanical properties of the coat and higher OH value while adding to higher cost leads to excessive curing of the. resin leading to the loss of flexibility of the coat without adding on to the characteristic mechanical hardness properties.
  • the acid value exceeds 30 mg KOH/g, appearance and adhesiveness of coating becomes unsatisfactory because of excessive curing and also affects the storage stability of the one component coating system.
  • the acid value is in the range of 0 to 10 mg KOH/g.'
  • a coating composition could be provided that advantageously confers intrinsic self-healing properties at ambient temperatures also when including renewable polyalkylene glycol such as cerenol in the backbone of the polyester polyol resin which when cross-linked with aminoplastic resins results into a mechanically robust coating that is having excellent scratch hardness and pencil hardness along with the self-healing property.
  • the coating composition involves a polymer that can be prepared using low solvent content thereby resulting into a low VOC coating which can be sprayed at a high solid content.
  • the polyester polyol may be used alone or may contain the acrylic polyol as a blend.
  • said coating composition comprises polyester polyol resin blend comprising polyester polyol and acrylic polyol in the ratio range of 30: 70-95: 5, preferably in the range 50: 50 by weight.
  • said coating composition is storage stable composition with storage stability of at least upto 30 days as a one component system free of viscosity pick up and gelation and free of toxic isocyanate.
  • a coating composition is provided comprising upto 20% of hyper-branched/ dendritic polyols facilitating spraying for end use and application at high solid content of 50 to 60%.
  • said coating composition is a film coating composition including multi film coatings of thickness in the range of 100 to 120 microns involving clear coat thickness of 30 to 40 microns and having self-scratch healing characteristics at ambient temperatures.
  • said coating composition comprises polyester polyol resin obtained of aliphatic, aromatic and/or cycloaliphatic polycarboxylic acids and polyols including polyalkylene glycols.
  • said polyester polyol comprises one or more polycarboxylic acids including succinic acid (or anhydride thereof), adipic acid, azeiaic acid, sebacic acid, phthaiic acid (or anhydride thereof), isophthalic acid, terephthalic acid, cyclohexane dicarboxylic acid, trimellitic acid (or anhydride thereof) and pyromellitic acid (or anhydride thereof) in the range of 40% to 60% of the polyester polyol by weight.
  • said polyester polyol comprises one or more polyol selected from ethylene glycol, propylene glycol, butylene glycol, 1,6-hexylene glycol, neopentyl glycol, glycerol, trimethylolpropane, trimethylolethane, pentaerythritol, dipentaerythritol, tripentaerythritol, hexanetriol including condensation products of trimethylolpropane and ethylene oxide or propylene oxide, in the range of 20% to 40% of the polyester polyol by weight.
  • said coating composition is provided wherein said acrylic polyol comprises vinyl monomers, more specifically esters of acrylic or methacrylic acid including acrylates of alkyl, cycloalkyl, or aryl acrylates and methacrylates and aromatic vinyl compounds including styrene or multifunctional acrylic monomers such as diacrylates or triacrylates.
  • said coating compositio is provided wherein said polyester polyol has molecular weight (Mn) in the range of 500 to 4000 g/mol and wherein the acrylic polyol has a theoretical Fox Tg in the range of -50 to +20 °C preferably Tg in the range of -15 to +15°C.
  • said acrylic polyol resin in the polyester polyol resin blend has molecular weight (Mn) in the range 500-4000 g/mol has solid levels in the range 65-90%and includes Veova 9 and Veova 10 monomer together with esters of Versatic acid.
  • a coating composition wherein said acrylic polyol comprises hydroxyl monomers including hydroxyalkyl acrylates and hydroxyalky methacrylates such as 2-hydroxyethyl acrylate, 2- hydroxypropyl acrylate, 3-hydroxypropyl acrylate, 4-hydroxybutyl acrylate, hydroxyhexyl acrylate, hydroxyoctyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxpropyl methacrylate, 2-hydroxypropyl methacrylate, 4-hydroxybutyl methacrylate, hydroxyhexyl methacrylate, hydroxyoctyl methacrylate, allyl and methally alcohol, butyl hydroxyethyl maleate and fumarate, butyl hydroxypropyl maleate and fumarate, including acetoacetate monomers such as acetoacetate ethyl methacrylate and also comprises ethylenically unsaturated acids including acrylic acid
  • said coating composition comprising solvent or mixture of solvents upto 30 percent of the ingredients of the composition and from 40 to 50% of the coating composition for spraying wherein said solvents include amyl acetate, toluene, ethyl acetate, butyl acetate, methoxy propyl acetate, acetone, methyl isobutyl ketone, methyl ethyl ketone, methyl amyl ketone, mineral spirits, ethylene glycol monoether acetates and other aliphatic, cycloaliphatic and aromatic hydrocarbons, such as xylene, esters, ethers, ketones, and other compatible solvents and reactive diluents of Cardura E10.
  • solvents include amyl acetate, toluene, ethyl acetate, butyl acetate, methoxy propyl acetate, acetone, methyl isobutyl ketone, methyl ethyl ketone, methyl amy
  • said coating composition comprising cross-linkers involving anyone or more of aminoplastic resins including melamine formaldehyde having an imino group, methyl/butyl mixed alkylated melamine resin containing high imino groups, methylated melamine resin containing high imino groups or butylated melamine resin containing high imino groups and formaldehyde, benzoguanamine formaldehyde, urea wherein the solid content of said melamine resin is in the range of 70-100 percent by weight.
  • aminoplastic resins including melamine formaldehyde having an imino group, methyl/butyl mixed alkylated melamine resin containing high imino groups, methylated melamine resin containing high imino groups or butylated melamine resin containing high imino groups and formaldehyde, benzoguanamine formaldehyde, urea wherein the solid content of said melamine resin is in the range of 70-100 percent by weight.
  • said coating composition comprises rheology modifiers, flow leveling additives, defoamers, wetting agents, sag control agents, nanoparticles, nanoadditives, dispersing agents, antimicrobial additives & curing catalysts.
  • a process for the preparation of coating composition comprising a. providing a polyester polyol resin comprising condensationproduct of carboxylic acids and polyols including one or more renewable polyalkylene glycols with or without acrylic polyol resin with at least one Veova monomer in the backbone; and b. combining thus obtained polyester resins with aminoplastic resin based crosslinking agent and obtaining therefrom said scratch-healing coating composition.
  • said coating composition wherein said polyester polyol resin comprises polymeric condensation product having renewable polyalkylene glycolsselected from anyone or more cerenol, PTMEG (polytetramethylene ether glycol) or pplycaprolactone polyol in the polymer backbone and wherein saidpolyester polyol resin has hydroxyl value in the range of 60-200 mg KOH/gm preferably 125-170 mg KOH/gm favouring a clear coat with the desired mechanical properties and flexibility.
  • said at least one Vepva monomer in the backbone of said acrylic polyol is used in amounts of 5-20% by wt. of the coating composition preferably in the range of 10 to 18% by wt.
  • polyester polyol resin used with or without acrylic polyol resin also have predetermined hydroxyl values in the range of 60-200 mg KOH/gm preferably 125-170 mg KOH/gm prior to crosslinking and curing with aminoplastic resin.
  • said process for the preparation of coating composition comprises providing said anyone or more polyalkylene glycols in the backbone of said polymer including Cerenol in the polyester polyol of molecular weight (Mn) in the range of 500 to 3000 g/mol with a hydroxyl number of 37 to 224mgKOH/g in the range of 1% to 20 % preferably in the range of 2 to 14% and more preferably in the range of 4 to 10% of the polyester polyol by weight; polycaprolactone polyols of molecular weight (Mn) in the range of400 to 2000 g/mol and hydroxyl value ranging from 56 to 280 mgKOH/g in the range of 1% to 20 % preferably in the range of 2 to 14% and more preferably in the range of 4 to 10% of the polyester polyol by weight;PTMEG of molecular weight (Mn) in the range of250 to 3000 g/mol and hydroxyl value ranging from 40 to 500 mgKOH
  • the ratio of polyester resin blend including acrylic polyol to aminoplastic resin used is in the range of 60/40 to 90/10 by weight on solid basis.
  • a self scratch healing coated substrate comprising ⁇ said substrate coated with a top surface coat of aminoplastic resin crosslinked polyester polyol resin comprising condensation product of carboxylic acids and polyols including one or more renewable polyalkylene glycols with or without acrylic polyol resin having at least one Veova monomer in the backbone.
  • said self scratch healing coated substrate comprises multilayer coated substrates comprising , a. at least one base/ color coat applied on different substrates as base materials; and. b. at least one said self scratch -healing clear coating composition for forming a top coat.
  • said method for obtaining self scratch healing coated substrate is obtained following the steps of a. providing base/color coating composition on an undercoated/ uncoated base material as at least one coat; b. providing said self scratch -healing clear coating as at least one coat as a top coating by wet on wet application method; c. baking at 125 to 150 °C for 25 to 30 minutes and obtaining a multilayered coating film therefrom.
  • said application method for forming the multilayered coating film on base materials including coatings to be coated includes spray application, airless spray, bell applicator, dip.
  • said substrates as base materials includes metals such as iron, aluminum, copper or alloys thereof, inorganic materials such as glass etc., resins such as polyethylene resin, polypropylene resin, ethylene-vinyl acetate copolymer resin, polyamide resin, acrylic resin, vinylidene chloride resin, polycarbonate resin, polyurethane resin, epoxy resin, etc., plastic materials such as various FRPs (fiber reinforced polymer), natural materials such as woods, synthetic materials.
  • thermosetting composition comprising polyester poiyol resin comprising condensation product of carboxylic acids and polyols including one or more renewable polyalkylene glycols conferring self- healing attributes.
  • said polyester poiyol resin comprises polymeric condensation product including said renewable polyalkylene glycols in the polymer backbone and has selective hydroxyl value in the range of 60-200 mg KOH/gm preferably 125-170 mg KOH/gm to favour desired mechanical properties and flexibility when cross-linked.
  • Figure la and b illustrates stereo microscope images of coated panels at different times after crock-meter testing at time 0 hrs and at time 24 hrs at ambient temperatures respectively.
  • the present invention particularly provides a coating composition having self-scratch healing/self-reparable characteristics comprising aminoplastic resin crosslinked polyester poiyol resin comprising condensation product of carboxylic acids and polyols including one or more renewable polyalkylene glycols.
  • a synthesis method for manufacturing said coating composition involving melamine cured shape memory polyester or polyester/acrylic blend coating films is provided wherein, by specifying the thermosetting composition and cross linking agent of the said polyester or polyester/acrylic blend coating resin, clear coat film having excellent self-mending ability under ambient conditions and good mechanical hardness under baking conditions could be provided.
  • a self-healing one component clear coat composition is thus provided characterized in that: a) A thermosetting component prepared from polyacids, polyols and anyone or more of pol alkylene glycols such as cerenol which is incorporated into the backbone of the polymer. Cerenol used in the reaction has Mn in the range of 500 to 3000 g/mol.
  • the thermosetting component is prepared from of Veova monomer incorporated acrylic that is incorporated into the backbone of the polymer. The acrylic polyol can be blended with the polyester polyol or the polyester polyol may be used alone.
  • thermosetting component comprising a mixture of polyacids, polyols and polyalkylene glycols selected from anyone or more of cerenol, PTMEG (polytetramethylene ether glycol) or polycaprolactone polyol present in the polymer backbone.
  • the natural renewable Cerenol is incorporated into the backbone of the polymer and is cured with aminoplastic resins as the crosslinker.
  • the polymer composition is prepared using a blend of the above mentioned polyester polyol resin with an acrylic polyol comprising acrylic monomers and Veova based monomers in the backbone of said acrylic polyol polymer.
  • thermosetting clear coating composition is a coating composition comprising a polyester polyol which contains Cerenol in reacted form or a blend of the polyester polyol with an acrylic polyol which contains Veova in reacted form, a melamine resin containing an imino/methyl/butyl/mixed alkyl group and other flow leveling additives or rheology modifiers, wherein a ratio of polyester or polyester/acrylic blend resin to melamine formaldehyde resin is adjusted to be in the range of 60/40 to 90/10 so as to maintain optimized mechanical properties and to provide an excellent appearance and durability to the coating after baking.
  • a resin which is a condensation product of polyalcohol with polycarboxylic acid is used as the polyester resin.
  • These resins contain free hydroxyl and carboxyl groups in a predetermined proportion which allow reactions with melamine ' cross-linking agent to provide for the desired characteristics.
  • Polyalcohols suitable for manufacturing polyester resins include ethylene glycol, propylene glycol, butylene glycol, 1,6-hexylene glycol, neopentyl glycol, glycerol, trimethylolpropane, trimethylolethane, pentaerythritol, dipentaerythritol, tripentaerythritol, hexanetriol and condensation products of trimethylolpropane and ethylene oxide or propylene oxide, polycaprolactone and poly tetrahydrofuran.
  • carboxylic acids include succinic acid (or anhydride thereof), adipic acid, azelaic acid, sebacic acid, phthalic acid (or anhydride thereof), isophthalic acid, terephthalic acid, cyclohexanedicarboxylic acid, trimellitic acid (or anhydride thereof) and pyromellitic acid (or anhydride thereof) .
  • a resin which is a product of addition polymerization by free radical or controlled radical polymerization of unsaturation containing vinyl or acrylic monomers is used as the acrylic resin.
  • These resins contain free hydroxyl and carboxyl groups in a predetermined proportion which allow reactions with a standard cross-linking agent.
  • the acrylic resin consists of vinyl monomers, more specifically esters of acrylic or methacrylic acid.
  • Typical acrylates may include alkyl, cycloalkyl, or aryl acrylates and methacrylates.
  • useful acrylate monomers are methyl methacrylate, butyl acrylate, n-butyl methacrylate, lauryl methacrylate, 2-ethylhexyl methacrylate, isobomyl methacrylate, and cyclohexyl methacrylate.
  • Another type of vinyl monomer that may be included are the aromatic vinyl compounds such as styrene. Further multifunctional acrylic monomers such as diacrylates or triacrylates may also be used.
  • the acrylic resin can have a theoretical Fox Tg in the range of -50 to +20 °C.
  • the preferable Tg is in the range of -15 to + 15°C.
  • Hydroxyl containing monomers suitable for manufacturing acrylic resins include hydroxyalky acrylates and hydroxyalky methacrylates such as 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 3-hydroxypropyl acrylate, 4-hydroxybutyl acrylate, hydroxyhexyl acrylate, hydroxyoctyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxpropyl methacrylate, 2- hydroxypropyl methacrylate, 4-hydroxybutyl methacrylate, hydroxyhexyl methacrylate, hydroxyoctyl methacrylate, allyl and methally alcohol, butyl hydroxyethyl maleate and fumarate, butyl hydroxypropyl maleate and fumarate, and the like.
  • the preferred hydroxy containing monomers are hydroxyl ethyl methacrylate and hydroxyl propyl methacrylate.
  • Acetoacetate monomers which undergo crosslinking with aminoplastic resins may also be used such as acetoacetate ethyl methacrylate.
  • Further examples of crosslinkable monomers are the ethylenically unsaturated acids such as acrylic acid, methacrylic acid, ethacrylic acid, crotonic acid, isocrotonic acid, cinnamic acid, maleic acid, fumaric acid, aconitic acid, citraconic acid, mesaconic acid, itaconic acid and glutaconic acid.
  • Coating composition of the present invention is characterized in that the amount of Cerenol has a specific range of values between 1% to 20% preferably in the range of 2 to 14% and more preferably in the range of 4 to 10%. In contrast, when the percentage exceeds 20, appearance of the clear coating become excellent but the nail hardness would become insufficient.
  • the number average molecular weight of the Cerenol is 500 to 3000.
  • Cerenol is a biodegradable polyol and chemically it is a polyether diol. It contains renewably sourced 1, 3-propanediol derived from corn.
  • Cerenol H650, Cerenol H1000, Cerenol H2400 are some of the grades available under the said trade names commercially from DuPont. Bio based polypropane diols which may also be used are available under the trade name of P03G are obtained from Allessa .
  • Polytetramethylene ether glycol is derived from the polymerization of tetrahydrofuran and is available commercially from BASF under the trade name PolyTHF. Various grades such as PolyTHF 650, 1000 or 2000 can be used. Polycaprolactone polyols are available commercially from Perstop under the trade name Capa. Various grades such as Capa 2043, 2085, 2200, 2100 etc. can be used. Cerenol, PTMEG and Polycaprolactone polyols may be used as a mixture or individually in the polyester backbone. Coating composition of the present invention is characterized in that the amount of Veova has a specific range of values between 5% to 20 % and preferably in the range of 10 to 18%.
  • Veova monomers are the vinyl esters of Versatic acid and are based on Neodecanoic acid.
  • Veova 9 and Veova 10 are some of the grades , available commercially from Momentive. Veova 10 with a Tg of -3 °C is preferred.
  • the polyester and acrylic resin preferably has a number-average molecular weight, in the range of 500-4000 g/mol, a hydroxyl value in the range of 60-200 mg KOH/g, and an acid value in the range of 0-30 mg KOH/g.
  • the molecular weight is further preferably in the range of 600-2000 g/mol.
  • the hydroxy! group value is less than 60, the mechanical properties of coating becomes insufficient. In contrast, when the value exceeds 200, curing becomes excessive and film is no more flexible. Further preferably, the value is in the range of 125-170 mg KOH/g.
  • the acid value exceeds 30, appearance and adhesiveness of coating becomes unsatisfactory because of excessive curing.
  • the high acid value also affects the storage stability of the one component coating system. Further preferably, the acid value is in the range of 0 to 10 mg KOH/g.
  • esterification cataiyst can be employed in the synthesis to promote reaction.
  • Tin catalysts or titanium catalysts are preferred.
  • the esterification catalyst is present from about 0.001 to about 0.1 percent by weight, based on the total weight of the polyester polyol.
  • suitable catalysts include, but are not limited to, acids such , as sulfuric acid, phosphoric acid, para-toluene sulfonic acid, organotin compounds such dibutyl tin-(IV) dilaurate, and titanium compounds such as titanium (IV) isoproproxide, hydrated monobutyltin oxide, dibutyltin oxide, or titanium (IV) butoxide (titanium tetrabutoxide, TBT).
  • the reaction mixture comprises from about 25 to about 800 ppm of the esterification catalyst.
  • the free radical polymerization used to form the acrylicpolyol backbone is preferably carried out using conventional techniques, such as by heating the monomers in the presence of a free radical polymerization initiator, typically, tertiary butyl perbenzoate, tertiary butyl peroctoate, cumene hydroperoxide, benzoyl peroxide, di-tertiary butylperoxide, di-cumene peroxide, methyl ethyl ketone peroxide or similar peroxy compounds, or an azo compound such as azobisisobutyronitrile is employed.
  • a free radical polymerization initiator typically, tertiary butyl perbenzoate, tertiary butyl peroctoate, cumene hydroperoxide, benzoyl peroxide, di-tertiary butylperoxide, di-cumene peroxide, methyl ethyl ketone peroxide or similar peroxy compounds, or an azo compound such
  • the amount of free radical polymerization initiator can be varied depending upon the desired molecular weight but 0.05-8 percent by weight based on the weight of total polymerizable monomers is typical. A preferred range is from 0.05 to 4 percent by weight. A mixture of two or more initiators may be used.
  • polymerization is preferably continued until the resulting resinous polyol has the desired molecular weight, but still sufficiently low viscosity for use in the coating composition of the present invention.
  • aminoplastic resins such as melamine formaldehyde containing an imino group
  • the melamine resin can be a methyl/butyl mixed alkylated melamine resin containing high imino groups, methylated melamine resin containing high imino groups or butylated melamine resin containing high imino groups.
  • thesolid content of the melamine resin is in the range of 70-100 percent by weight.
  • Cymel 323, Cymel 325, Cymei 1130 and Cymel U 65 are some examples ofaminoplastic resins from Allnex.
  • aminoplastic resins are aldehyde condensation products of melamine, urea, benzoguanamine, or a similar compound.
  • the aldehyde employed is formaldehyde, although useful products can be made from other aldehydes, such as acetaldehyde, crotonaldehyde, acrolein, benzaldehyde, furfural, and others.
  • Condensation products of melamine or urea are the most common and are preferred, but products of other amines and amides in which at least one amine group is present can also be employed.
  • Other crosslinking agents can also be used, such as urea formaldehyde, benzoguanamine formaldehyde or compatible mixtures of any of the forgoing crosslinkers.
  • acid catalysts such as p-toluene sulfonic acid, dodecylbenzene sulfonic acid, amineblocked alkylated benzene sulfonic acids, phosphoric acids etc are used to enhance the cross linking reaction between the polyester polyol/ acrylic polyol and the melamine formaldehyde resin.
  • acid catalysts such as p-toluene sulfonic acid, dodecylbenzene sulfonic acid, amineblocked alkylated benzene sulfonic acids, phosphoric acids etc are used to enhance the cross linking reaction between the polyester polyol/ acrylic polyol and the melamine formaldehyde resin.
  • Contents of the polyol (polyester or polyester/acrylic blend) and the cross-linking agent are 60-90 percent by weight for the polyol and 10-40 percent by weight for the cross-linking agent, preferably 65-85 percent by weight for the former and 15-35 percent by weight for the latter.
  • content of the cross-linking agent is less than 10 percent by weight (when the content of polyol exceeds 90 percent by weight)
  • cross-linking in the coating may not be sufficient.
  • the content of the cross-linking agent exceeds 40 percent by weight when the content of the polyol is less than 60 percent by weight, not only the storage stability of the coating composition is reduced but also the curing speed thereof is enhanced, so that the appearance of coating may become deteriorated.
  • An amount of blending, a blending ratio and an amount of added components in the present specification represent an amount calculated as solid mass unless otherwise specified.
  • the polyester polyol may be used independently or as a blend with the acrylic polyol.
  • the ratio of the acrylic polyol to the polyester polyol is in the ratio range of 30:70-95:5, preferably in the range 50: 50 by weight.
  • Hyperbranched or dendritic polyols may be added to the formulation in the range of 1 to 20% to further facilitate application at high solids.
  • the hyperbranched polyol can be, for example, a polyester polyol or polyether polyol, or any multi-hydroxy functionalized molecule.
  • a hyperbranched polymer is a polymer that is highly branched, and which contains multiple end groups, such as, in the case of a polyol, multiple hydroxyl end groups.
  • the hyperbranched oligomer/polymer can advantageously have a dendritic structure, i.e., a branching, treelike structure in which chains radiate out from a central atom or cluster of atoms.
  • a dendritic structure i.e., a branching, treelike structure in which chains radiate out from a central atom or cluster of atoms.
  • Boltorn H20 and Boltor H30 are examples of dendritic hyperbranched polyester polyols available from Perstorp.
  • nanoadditives may be added in the formulation to enhance the properties such as scratch resistance, abrasion resistance, mechanical properties, appearance, gloss and gloss retention after crockmeter testing.
  • Such additives are not limited to nano silica, nano alumina, nano zirconia, nano titania, nano zinc oxide, nano clay, single walled and multi walled carbon nanotubes, graphene, various nano fibers etc.
  • the clear coating composition may appropriately contain, besides the aforementioned components, sedimentation preventives (suspending agents) such as polyamide wax which is a lubricant dispersion of aliphatic amide, and polyethylene wax which is a colloidal dispersion comprising polyethylene oxide as the main ingredient, polyurea dispersion (which is a dispersion of polyurea particles in acrylic polyol) as anti-sagging agent, ultraviolet ray absorbent, antioxidant, leveling agent, surface adjusting agent such as silicone and organic polymers, thickening agent, antifoaming agent, lubricant, cross linking polymer particles (microgel), etc.
  • sedimentation preventives such as polyamide wax which is a lubricant dispersion of aliphatic amide, and polyethylene wax which is a colloidal dispersion comprising polyethylene oxide as the main ingredient, polyurea dispersion (which is a dispersion of polyurea particles in acrylic polyol) as anti-sagging agent, ultraviolet ray absorbent, antioxidant, leveling agent,
  • the present invention facilitates the formulation to be sprayed at a high application solid content of 50 to 60% thereby leading to improved productivity, coverage and lower impact on the environment compared to low to medium solid systems which are sprayed at 30 to 45% application solids.
  • a solvent is preferably used as the liquid reaction medium and for spraying the coating formulation.
  • the solvent can be used at from 0 percent to 30 percent of the total reaction mixture and from 40 to 50% of the total spray coating formulation.
  • Typical solvents used are the following : amyl acetate, toluene, ethyl acetate, butyl acetate, methoxy propyl acetate, acetone, methyl isobutyl ketone, methyl ethyl ketone, methyl amyl ketone, mineral spirits, ethylene glycol monoether acetates and other aliphatic, cycloaiiphatic and aromatic hydrocarbons, such as xylene, esters, ethers, ketones, and other compatible solvents are conveniently used.
  • a method for forming multilayered coating films according to the present invention is a method wherein a color coating film is made on a previously undercoated base material, followed by a formation of a clear/top coating film to provide multilayered coating films.
  • the substrate to be coated is an automobile body or parts thereof, it is preferable that an undercoating film has been previously formed on the substrate by the electrodeposition coating method, etc. after the process of chemical treatment.
  • resins as a major component of electrodeposition coat used in the electrodeposition coating are liquid rubbers (those having epoxy resin as a structural skeleton such as maleic acid resin, maleic acid polybutadiene resin, and aminoplastic-epoxy polybutadiene resin, etc.) such as drying oil or polybutadiene, etc., resins having the fatty acid esters of resinous polyols as the main structural skeleton, etc.
  • the electrodeposition coating resin is acidic resin
  • bases such as ammonia, amines, inorganic alkalis, etc. prior to its dissolution or dispersion in water.
  • acids such as acetic acid, boric acid, phosphoric acid, etc. prior to its dissolution or dispersion in water.
  • cross linking agents such as melamine resin, blocked polyisocyanate, additives such as pigments, solvents, etc. may be appropriately combined. It is desirable that electrodeposition coating film is so arranged that the coating film usually becomes 10-40 microns thick after baking.
  • the multilayered coating films can be formed on a variety of base materials to be coated.
  • examples of specific coating base materials are metals such as iron, aluminum, copper or alloys thereof, inorganic materials such as glassetc, resins such as polyethylene resin, polypropylene resin, ethylene-vinyl acetate copolymer resin, polyamide resin, acrylic resin, vinylidene chloride resin, polycarbonate resin, polyurethane resin, epoxy resin, etc., plastic materials such as various FRPs, etc., in addition, natural materials such as woods, fibrous materials (paper, fabrics, etc.) or synthetic materials, etc.
  • the base materials to be coated on which undercoating film has been formed by chemical treatment or undercoating, etc. may be sometimes referred to as base materials to be coated.
  • the under coating/primer film is baked at 120 to 150 °C for 25 to 45 minutes and the dry film thickness could be 30 to 40 micro meter.
  • a color coating composition is applied to the base materials to be coated to build an intermediate coating film.
  • the intermediate coating may be applied onto the undercoating film in wet-on-dry manner.
  • a typical pigmented color coating composition includes pigment, a film forming binder which can be a polyurethane, an acrylourethane, an acrylic polymer or a silane polymer, and a crosslinking agent such as, an aminoplastic, an alkylated melamine formaldehyde crosslinking agent or a polyisocyanate crosslinking agent.
  • the base coating composition can be solvent or water borne and can be in the form of a dispersion or a solution.
  • pigments used in the color coating composition include metallic flake pigments, such as aluminum flake or pearl flake pigments.
  • the clear/top coat of the present invention is then applied on color coating film in wet on wet manner.
  • the color and clear coating film is baked together at 125-150° C for a predetermined time to build a glossy clear top coating film.
  • the coating composition displays a gloss recovery over a period of a few minutes to a several hours under ambient conditions depending on the temperature.
  • the gloss recovery is from 5% to 200% dependent on the composition.
  • the clear coating composition displays a pencil hardness of F-2H, a Persoz hardness of greater than 100 seconds, gloss recovery after crockmeter testing of greater than 40% while exhibiting the property of self-healing.
  • the color coating film DFT (dry film thickness) is preferably 15 to 25 microns and the clear coating DFT is 30 to 40 microns.
  • Example 1 The present invention is more specifically described below with reference to examples, but should not be construed being limited thereto.
  • Example 1
  • TMP trimethylpropane
  • PG glycol neopentyl glycol
  • dibutyltin dilaurate catalyst 0.05% of the total weight
  • Polyester polyol resins were prepared as described in example 1 as shown in Table 1.
  • Example 10 Preparation of Clear Coating Composition:
  • a cold rolled steel plate (0.8 mm thick) having vertical and horizontal surfaces was degreased, chemically modified using a zinc phosphate treatment agent and subjected to electrodeposition with a cationic electrodeposition coating so as to achieve a DFT of 25 microns. Then, after baking at 160° C for 30 minutes, a primer coating composition was air- sprayed so as to achieve a DFT of 30 microns, which was baked at 140° C for 30 minutes to form a primer coating film.
  • Table 2 Formulation (in parts by weight) and properties of multi-film coating formed using polyester polyol resins.
  • a coating film was formed by a method for forming multilayered coating films according to this invention, wherein, while achieving the property of self- healing, appearance of coating film and mechanical properties of the final coating were excellent.
  • the clear coating composition of the present invention is isocyanate free, can be applied at a higher solid content and the coating composition has a satisfactory storage stability as a one component system as indicated by no viscosity pickup under ambient conditions over a period of 30 days.
  • Figure 1 shows stereo microscope images of the scratches created by the crockmeter test ( 10 cycles) immediately after testing at time 0 hrs and at time 24 hrs at ambient temperatures respectively, wherein after 24 hrs the scratches are seen to diminish.
  • a low molecular weight acrylic polyol solution is prepared by charging the following ingredients of Table 3 into a polymerization vessel equipped with a thermometer, reflux condenser, stirrer, addition funnel and a heating mantle. Table 3.
  • Portion 1 is charged to polymerization vessel and heated to its reflux temperature (144 degree C). The constituents are under constant stirring in the polymerization vessel during the entire process. Portion 2 is premixed and added drop wise into the vessel at a rate of 0.4 parts per minute over 190 minute period while the resulting, reaction mixture is held at its reflux temperature. Portion 3 is added as a chaser catalyst after 45 minutes of addition of portion 2 and the reaction at reflux temperature is continued for another 90 minutes to react all the free monomers. Heating is stopped and reaction mass is cooled to room temperature under stirring. The resin thus obtained is diluted to 75% solid, Gardner viscosity (25 deg C) U-V, hydroxyl value of 130 and Mn of 3500 g/mol.
  • Example 12 Synthesis of acrylic polyol in accordance with Example 11 was performed without Veova monomer as per the ingredients of Table 4 below.
  • Example 13 Synthesis of acrylic polyol in accordance with Example 11 was performed without Veova monomer as per the ingredients of Table 5 below.
  • Example 14 Formulation (in parts by weight) and properties of multi-film coating formed using a blend of acrylic polyols as per (Examples 11- 13) and polyester polyol resins ( Example 2) are tabulated below in Table 6.
  • a coati ng film was formed using a blend of a polyester and acrylic polyol by a method for formi ng muitilayered coating films according to the present invention, wherei n, it was found that while achieving the property of self-healing, appearance of coating film and mechanical properties of the final coating were excellent only for the blend under SI. No. 1 in Table 6 above.
  • the coating composition that advantageously confers intrinsic self-healing properties at ambient temperatures also when including renewable polya!kylene glycol such as cerenol in the backbone of the polyester polyol resin, which when cross-linked with aminoplastic resins results into a mechanically robust coating having excellent scratch hardness and pencil hardness along with the self-healing property.
  • the coating composition involves a polymer that can be prepared using low solvent content thereby resulting into a low VOC coating which can be sprayed at a high solid content.
  • the polyester polyol may be used alone or may contain the acrylic polyol as a blend providing for the desired characteristics of the coat.

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Abstract

A coating composition having self-scratch healing characteristics comprising aminoplastic resin cross-linked polyester polyol resin comprising one or more renewable polyalkylene glycols is provided. A synthesis method for manufacturing said coating composition involving melamine cured shape memory polyester or polyester/acrylic blend coating films is provided wherein, by specifying the thermosetting composition and cross linking agent of the said polyester or polyester/acrylic blend coating resin, clear coat film having excellent self-mending ability under ambient conditions and good mechanical hardness under baking conditions is provided.

Description

TITLE: A ONE COMPONENT SELF-HEALING COATING COMPOSITION
Field of the invention
The present invention particularly provides for a coating composition suitable as clear/top coat that enables self-mending of nano/micro/macro scratches on the coating at ambient temperatures, increases the spray solid as well as imparts excellent appearance and good mechanical properties to the coating film wherein a method for forming multi!ayered coating films is also provided to meet varied end use and application including automotive use.
Background Art Aesthetics of automobile topcoats is of prime importance to the customers. There are mainly two approaches to improve the mechanical properties (abrasion and scratch resistance) of the coatings. One approach is to make the coating extremely hard by incorporating nanoparticles such as alumina, zirconia and silica. However this is primarily a surface phenomenon. The other approach is to make the coating with a self-healing capability.
Self-healing is reported via two approaches, intrinsic and extrinsic self-healing. Intrinsic self-healing commonly uses supramolecular polymers, oligomers which self heal via reversible hydrogen bonding or via dynamic covalent bonding. Extrinsic self-healing commonly uses additives such as microcapsules filled with monomeric healing agents or microvascular networks that enable repeated self-healing and even healing of larger cracks via either foam generation or chemical reaction of healing agents.
However, the mechanism of healing involves use of healing agents with chemistries which differ from the chemistry of the base polymer and involves addition of additives such as microcapsules which may get damaged during preparation of the coating formulation thereby reducing the efficiency of self-healing. Further use of stimuli such as high temperature is commonly reported.
Most commonly automotive topcoats belong to polyester aminoplast, acrylic aminoplast or isocyanate cured polyurethane coatings. In the field of automotive coatings, there is a keen demand for the development of a coating composition which would be self-reparable at low temperature, be free of toxic isocyanates, and have an improved coverage with a high solid content, have excellent mechanical properties and display excellent aesthetics. State of the art literature commonly uses polyurethane chemistry to prepare self-healing coatings (reversible hydrogen bonding), Examples are JP 2013049839 A, US 20090062453 Al, JP 2010260979 A.
Another approach used in literature is the addition of nanoparticles to the coating formulation to give a gloss . recovery for polyurethane coatings. Examples are US 8664298 Bl, Narendra et al Polymer Letters (2012), 6(1), 26-40.
Inclusion of molecules such as cyclobutanediol, polycaprolactone, etc in the resin composition render self-healing properties to the applied coating film. These systems are cross-linked with isocyanate and may need external stimuli to repair the coating film defects. Reference may be drawn to extracts of 247th ACS National Meeting & Exposition, Dallas, TX, United States, March 16-20, 2014 (2014), POLY-223, Yelena N et al Journal of Materials Science (2013), 48(24), 8588-8595, Erika D Rodriguez et al International SAMPE Technical Conference (2010), 42, a56/l-a56/6.
Patents JP 08127643 A and KR 142276 Bl is directed to the synthesis of thermosetting polymeric prepolymer which shows excellent shape-memory effect and also has excellent heat resistance, chemical resistance, transparency and coloring property. Polyester resin composition contains at least one kind of dicarboxyiic acid component, at least one kind of diol component, and a component selected to have an unsaturated end group to help in crosslinking. US20120322931 describes polyester which consists of low molecular weight polytrimethylene ether glycol (Mn 100 to 310) cross linked with isocyanate as antimicrobial coating composition.
CA 2723217 Al discloses a method to prepare a thermoplastic elastomer based on polyester which consist of one component from ethylene glycol, 1,3 propane diol etc. US 20130184408 disclosure relates to a process of forming a polymer composition by the free radical polymerization of a monomer mixture in the presence of low molecular weight polytrimethylene ether glycol (Mn 120 to 490).
WO 2012133836 Al discloses a self-repajring coating film based on a fluorine-containing copolymer containing vinyl ether or a vinyl ester. US 20040161538 Al discloses a multilayered coating composition using a polyester polyol/acrylic copolymer hybrid binder which can be cured with aminoplastic resins, free and blocked polyisocyanates. This prior art utilizes a hybrid polymer in the coating composition that is cured with isocyanate as the curing agent.
However, while it is apparent that there exists few coating compositions that have shape memory effect there is still a need in the art to explore coating compositions with improved self healing property/ self-reparable characteristics even at ambient temperatures even in being free of toxic isocyanates. It is also a need in the art to provide for said coating compositions with improved coverage with a high solid content together with excellent mechanical properties that would display excellent aesthetics and would be manufactured involving facile method of preparations suitable for diverse end use and application including automotive use.
Objects of the invention
Thus the primary object of the present invention is to provide for a coating composition preferably a clear coating composition, a synthesis method for manufacturing the same that would self heal and would be reparable even at ambient conditions and would provide for good mechanical hardness under baking conditions.
It is another object of the present invention to provide for a coating composition involving a a shape memory polyester melamine or polyester/acrylic melamine coating films comprising renewable polyols wherein, based on a specific thermosetting composition comprising polyester or polyester/acrylic and cross linking agent of melamine for said thermosetting composition, clear coat film having excellent self-mending ability under ambient conditions and good mechanical hardness under baking conditions would be achieved. It is yet another object of the present invention to provide for a low temperature self- healing coating composition that would be suitable for automotive use and would ensure a satisfactory finished appearance as well as improved film properties.
It is another object of the present invention to provide for isocyanate free, stable, one- package coating composition that would be sprayable at high solid content and can be used as top coating or intermediate coating in automotive finishing processes. It is a further object of the present invention to provide for a self-healing coating composition with intrinsic self healing characteristics not dependent on nanoparticle or microcapsule additives.
It is another object of the present invention to provide for a melamine crosslinked thermosetting composition that would not require any component from the unsaturated molecules whereby the synthesis methodology of said coating composition would be simple and industrially facile and economical and in not involving any unsaturated functionality would not require any inhibitor or special care to prevent the premature polymerization.
In is yet another object of the present invention to provide for the present polyester resin composition comprising renewable cerenol in the backbone of the said polyester resin that would impart the desired self-healing characteristics.
Other objects and advantages of the present invention will become apparent as per the following summary and the detailed description of the invention below.
Summary of the invention
Thus it is a basic aspect of the present invention to provide for a coating composition having self-scratch healing characteristics comprising aminoplastic resin crosslinked polyester polyol resin comprising condensation product of carboxylic acids and polyols including one or more renewable polyalkylene glycols.
Preferably said coating composition is provided wherein said polyester polyol resin comprises polymeric condensation product having renewable polyalkylene glycols selected from anyone or more of cerenol, PT EG (polytetramethylene ether glycol) or polycaprolactone polyol in the polymer backbone.
According to another preferred aspect of the present invention said coating composition is provided wherein said polyester polyol resin comprises polymeric condensation product having renewable polyalkylene glycols selected from anyone or more of cerenol, PTMEG (polytetramethylene ether glycol) or polycaprolactone polyol in the polymer backbone. According to yet another preferred aspect of the present invention said coating composition is provided wherein said polyester polyoi resin is a polyester polyoi resin blend comprising acrylic polyoi resin having at least one Veova monomer bonded to said acrylic polyoi.
According to another preferred aspect of the present invention said coating composition is provided wherein at least one Veova monomer in said acrylic polyoi resin is in amounts of 5- 20% by wt. of the coating composition preferably in the range of 10 to 18% by wt. for enhanced durability.
Advantageously said coating composition is a clear composition and mechanically robust possessing self mending ability of nano/micro/ macro scratches under ambient conditions with gloss recovery after crockmeter testing of at least 40% to upto 200% ; has good mechanical hardness including scratch and pencil hardness of F-2H,Persoz hardness of at least 100 seconds under baking conditions; allows spraying for end use and application involving polyester polyoi resin at high solid content of 65-90% thus favouring a low VOC (volatile organic content) coating and enabling automotive use. Preferably in said coating composition said polyester polyoi resin blend including acrylic polyoi resin has hydroxyl value in the range of 60-200 mg KOH/gm preferably 125-170 mg KOH/gm of said resins favouring desired mechanical properties and flexibility of a clear coat.
More preferably in said coating composition said polyester polyoi resin blend including acrylic polyoi resin has acid value of upto 30 mg KOH/g preferably upto 20 mg KOH/g and more preferably upto 10 mgKOH/gm of said resins favouring desired appearance and adhesiveness of the clear coat on the substrate.
It is thus a surprising finding of the present invention that when the polyalkylene glycols including the renewable polyalkylene glycols (selected from anyone or more PTMEG, Cerenol, polycaprolactone polyoi) having flexible bifunctional linear segment, different molecular weight, chain length, OH value, Tg, reactivity, when incorporated in the backbone of the polyester polyoi resin that is subsequently cured with aminoplastic resin enables achievement of self-healing properties.
Significantly it was found that based on the selective OH value in the range of 60-200 mg KOH/gm preferably 125-170 mg KOH/gm & acid value of the resin of upto 30 mg KOH/g preferably upto 20 mg KOH/g and more preferably upto 10 mg KOH/gm the desired crosslinking density, stability, mechanical properties, appearance and adhesiveness of the coating composition could be attained, that is very useful industrially.
A lower OH value below the OH value mentioned above does not provide for the desired mechanical properties of the coat and higher OH value while adding to higher cost leads to excessive curing of the. resin leading to the loss of flexibility of the coat without adding on to the characteristic mechanical hardness properties.
More preferably when the acid value exceeds 30 mg KOH/g, appearance and adhesiveness of coating becomes unsatisfactory because of excessive curing and also affects the storage stability of the one component coating system. Further preferably, the acid value is in the range of 0 to 10 mg KOH/g.'
Further it is a special finding of the present invention that only when veova containing acrylic polyol resin is blended with the polyester polyol resin, the blend after being crosslinked with the aminoplastic resin helps retain the self healing property of the polyester polyol resin which other acrylic polyols in combination fails to retain. The industrial usefulness of the polyester polyol resin thus increases manifold as the acrylics provide for higher durability at lower cost compared to polyesters making the blend a further industrially useful material.
Thus surprisingly a coating composition could be provided that advantageously confers intrinsic self-healing properties at ambient temperatures also when including renewable polyalkylene glycol such as cerenol in the backbone of the polyester polyol resin which when cross-linked with aminoplastic resins results into a mechanically robust coating that is having excellent scratch hardness and pencil hardness along with the self-healing property. In addition the coating composition involves a polymer that can be prepared using low solvent content thereby resulting into a low VOC coating which can be sprayed at a high solid content. The polyester polyol may be used alone or may contain the acrylic polyol as a blend.
Preferably said coating composition comprises polyester polyol resin blend comprising polyester polyol and acrylic polyol in the ratio range of 30: 70-95: 5, preferably in the range 50: 50 by weight. Advantageously, said coating composition is storage stable composition with storage stability of at least upto 30 days as a one component system free of viscosity pick up and gelation and free of toxic isocyanate. According to another preferred aspect of the present invention a coating composition is provided comprising upto 20% of hyper-branched/ dendritic polyols facilitating spraying for end use and application at high solid content of 50 to 60%.
Preferably, said coating composition is a film coating composition including multi film coatings of thickness in the range of 100 to 120 microns involving clear coat thickness of 30 to 40 microns and having self-scratch healing characteristics at ambient temperatures.
According to another preferred aspect of the present invention said coating composition comprises polyester polyol resin obtained of aliphatic, aromatic and/or cycloaliphatic polycarboxylic acids and polyols including polyalkylene glycols. According to yet another preferred aspect of the present invention a coating composition is provided wherein said polyester polyol comprises one or more polycarboxylic acids including succinic acid (or anhydride thereof), adipic acid, azeiaic acid, sebacic acid, phthaiic acid (or anhydride thereof), isophthalic acid, terephthalic acid, cyclohexane dicarboxylic acid, trimellitic acid (or anhydride thereof) and pyromellitic acid (or anhydride thereof) in the range of 40% to 60% of the polyester polyol by weight.
According to another preferred aspect of the present invention in said coating composition said polyester polyol comprises one or more polyol selected from ethylene glycol, propylene glycol, butylene glycol, 1,6-hexylene glycol, neopentyl glycol, glycerol, trimethylolpropane, trimethylolethane, pentaerythritol, dipentaerythritol, tripentaerythritol, hexanetriol including condensation products of trimethylolpropane and ethylene oxide or propylene oxide, in the range of 20% to 40% of the polyester polyol by weight.
According to yet another preferred aspect of the present invention said coating composition is provided wherein said acrylic polyol comprises vinyl monomers, more specifically esters of acrylic or methacrylic acid including acrylates of alkyl, cycloalkyl, or aryl acrylates and methacrylates and aromatic vinyl compounds including styrene or multifunctional acrylic monomers such as diacrylates or triacrylates.
According to yet another preferred aspect of the present invention said coating compositio is provided wherein said polyester polyol has molecular weight (Mn) in the range of 500 to 4000 g/mol and wherein the acrylic polyol has a theoretical Fox Tg in the range of -50 to +20 °C preferably Tg in the range of -15 to +15°C. Preferably in said coating composition said acrylic polyol resin in the polyester polyol resin blend has molecular weight (Mn) in the range 500-4000 g/mol has solid levels in the range 65-90%and includes Veova 9 and Veova 10 monomer together with esters of Versatic acid.
According to another preferred aspect of the present invention there is provided a coating composition wherein said acrylic polyol comprises hydroxyl monomers including hydroxyalkyl acrylates and hydroxyalky methacrylates such as 2-hydroxyethyl acrylate, 2- hydroxypropyl acrylate, 3-hydroxypropyl acrylate, 4-hydroxybutyl acrylate, hydroxyhexyl acrylate, hydroxyoctyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxpropyl methacrylate, 2-hydroxypropyl methacrylate, 4-hydroxybutyl methacrylate, hydroxyhexyl methacrylate, hydroxyoctyl methacrylate, allyl and methally alcohol, butyl hydroxyethyl maleate and fumarate, butyl hydroxypropyl maleate and fumarate, including acetoacetate monomers such as acetoacetate ethyl methacrylate and also comprises ethylenically unsaturated acids including acrylic acid, methacrylic acid, ethacrylic acid, crotonic acid, isocrotonic acid, cinnamic acid, maleic acid, fumaric acid, aconitic acid, citraconic acid, mesaconic acid, itaconic acid and glutaconic acid .
According to yet another preferred aspect of the present invention there is provided said coating composition comprising solvent or mixture of solvents upto 30 percent of the ingredients of the composition and from 40 to 50% of the coating composition for spraying wherein said solvents include amyl acetate, toluene, ethyl acetate, butyl acetate, methoxy propyl acetate, acetone, methyl isobutyl ketone, methyl ethyl ketone, methyl amyl ketone, mineral spirits, ethylene glycol monoether acetates and other aliphatic, cycloaliphatic and aromatic hydrocarbons, such as xylene, esters, ethers, ketones, and other compatible solvents and reactive diluents of Cardura E10.
According to another preferred aspect of the present invention there is provided said coating composition comprising cross-linkers involving anyone or more of aminoplastic resins including melamine formaldehyde having an imino group, methyl/butyl mixed alkylated melamine resin containing high imino groups, methylated melamine resin containing high imino groups or butylated melamine resin containing high imino groups and formaldehyde, benzoguanamine formaldehyde, urea wherein the solid content of said melamine resin is in the range of 70-100 percent by weight.
Preferably said coating composition comprises rheology modifiers, flow leveling additives, defoamers, wetting agents, sag control agents, nanoparticles, nanoadditives, dispersing agents, antimicrobial additives & curing catalysts. According to another aspect of the present invention there is provided a process for the preparation of coating composition comprising a. providing a polyester polyol resin comprising condensationproduct of carboxylic acids and polyols including one or more renewable polyalkylene glycols with or without acrylic polyol resin with at least one Veova monomer in the backbone; and b. combining thus obtained polyester resins with aminoplastic resin based crosslinking agent and obtaining therefrom said scratch-healing coating composition.
According to yet another preferred aspect of the present invention there is provided said coating composition wherein said polyester polyol resin comprises polymeric condensation product having renewable polyalkylene glycolsselected from anyone or more cerenol, PTMEG (polytetramethylene ether glycol) or pplycaprolactone polyol in the polymer backbone and wherein saidpolyester polyol resin has hydroxyl value in the range of 60-200 mg KOH/gm preferably 125-170 mg KOH/gm favouring a clear coat with the desired mechanical properties and flexibility. Preferably in said process for the preparation of coating composition said at least one Vepva monomer in the backbone of said acrylic polyol is used in amounts of 5-20% by wt. of the coating composition preferably in the range of 10 to 18% by wt.
More preferably said process for the preparation of coating composition is provided wherein said polyester polyol resin used with or without acrylic polyol resin also have predetermined hydroxyl values in the range of 60-200 mg KOH/gm preferably 125-170 mg KOH/gm prior to crosslinking and curing with aminoplastic resin.
According to another preferred aspect of the present invention there is provided said process for the preparation of coating composition comprises providing said anyone or more polyalkylene glycols in the backbone of said polymer including Cerenol in the polyester polyol of molecular weight (Mn) in the range of 500 to 3000 g/mol with a hydroxyl number of 37 to 224mgKOH/g in the range of 1% to 20 % preferably in the range of 2 to 14% and more preferably in the range of 4 to 10% of the polyester polyol by weight; polycaprolactone polyols of molecular weight (Mn) in the range of400 to 2000 g/mol and hydroxyl value ranging from 56 to 280 mgKOH/g in the range of 1% to 20 % preferably in the range of 2 to 14% and more preferably in the range of 4 to 10% of the polyester polyol by weight;PTMEG of molecular weight (Mn) in the range of250 to 3000 g/mol and hydroxyl value ranging from 40 to 500 mgKOH/g in the range of 1% to 20 % preferably in the range of 2 to 14% and more preferably in the range of 4 to 10% of the polyester polyol by weight.
According to another preferred aspect of the present invention there is provided a process for the preparation of coating composition wherein the ratio of polyester resin blend including acrylic polyol to aminoplastic resin used is in the range of 60/40 to 90/10 by weight on solid basis.
According to another aspect of the present invention there is provided a self scratch healing coated substrate comprising · said substrate coated with a top surface coat of aminoplastic resin crosslinked polyester polyol resin comprising condensation product of carboxylic acids and polyols including one or more renewable polyalkylene glycols with or without acrylic polyol resin having at least one Veova monomer in the backbone.
Preferably, said self scratch healing coated substrate comprises multilayer coated substrates comprising , a. at least one base/ color coat applied on different substrates as base materials; and. b. at least one said self scratch -healing clear coating composition for forming a top coat.
More preferably said method for obtaining self scratch healing coated substrate is obtained following the steps of a. providing base/color coating composition on an undercoated/ uncoated base material as at least one coat; b. providing said self scratch -healing clear coating as at least one coat as a top coating by wet on wet application method; c. baking at 125 to 150 °C for 25 to 30 minutes and obtaining a multilayered coating film therefrom.
Preferably a method is provided wherein said application method for forming the multilayered coating film on base materials including coatings to be coated includes spray application, airless spray, bell applicator, dip. According to another preferred aspect of the present invention there is provided said method wherein said substrates as base materials includes metals such as iron, aluminum, copper or alloys thereof, inorganic materials such as glass etc., resins such as polyethylene resin, polypropylene resin, ethylene-vinyl acetate copolymer resin, polyamide resin, acrylic resin, vinylidene chloride resin, polycarbonate resin, polyurethane resin, epoxy resin, etc., plastic materials such as various FRPs (fiber reinforced polymer), natural materials such as woods, synthetic materials.
According to another aspect of the present invention there is provided a thermosetting composition comprising polyester poiyol resin comprising condensation product of carboxylic acids and polyols including one or more renewable polyalkylene glycols conferring self- healing attributes. 1
Preferably in said thermosetting composition said polyester poiyol resin comprises polymeric condensation product including said renewable polyalkylene glycols in the polymer backbone and has selective hydroxyl value in the range of 60-200 mg KOH/gm preferably 125-170 mg KOH/gm to favour desired mechanical properties and flexibility when cross-linked.
Brief description of figures
Figure la and b: illustrates stereo microscope images of coated panels at different times after crock-meter testing at time 0 hrs and at time 24 hrs at ambient temperatures respectively.
Detailed description of the invention
As discussed hereinbefore the present invention particularly provides a coating composition having self-scratch healing/self-reparable characteristics comprising aminoplastic resin crosslinked polyester poiyol resin comprising condensation product of carboxylic acids and polyols including one or more renewable polyalkylene glycols. A synthesis method for manufacturing said coating composition involving melamine cured shape memory polyester or polyester/acrylic blend coating films is provided wherein, by specifying the thermosetting composition and cross linking agent of the said polyester or polyester/acrylic blend coating resin, clear coat film having excellent self-mending ability under ambient conditions and good mechanical hardness under baking conditions could be provided.
A self-healing one component clear coat composition is thus provided characterized in that: a) A thermosetting component prepared from polyacids, polyols and anyone or more of pol alkylene glycols such as cerenol which is incorporated into the backbone of the polymer. Cerenol used in the reaction has Mn in the range of 500 to 3000 g/mol. Alternatively, the thermosetting component is prepared from of Veova monomer incorporated acrylic that is incorporated into the backbone of the polymer. The acrylic polyol can be blended with the polyester polyol or the polyester polyol may be used alone. b) And a curing agent from the class of aminoplastic resins which is preferably reactive without the presence of acid catalyst wherein the ratio of polyester or polyester/ acrylic resin to aminoplastic resin is adjusted to be in the range of 60/40 to 90/10 A thermosetting component is thus provided comprising a mixture of polyacids, polyols and polyalkylene glycols selected from anyone or more of cerenol, PTMEG (polytetramethylene ether glycol) or polycaprolactone polyol present in the polymer backbone. The natural renewable Cerenol is incorporated into the backbone of the polymer and is cured with aminoplastic resins as the crosslinker. Alternately, the polymer composition is prepared using a blend of the above mentioned polyester polyol resin with an acrylic polyol comprising acrylic monomers and Veova based monomers in the backbone of said acrylic polyol polymer.
Clear/Top Coating Composition One embodiment of a thermosetting clear coating composition according to the present invention is a coating composition comprising a polyester polyol which contains Cerenol in reacted form or a blend of the polyester polyol with an acrylic polyol which contains Veova in reacted form, a melamine resin containing an imino/methyl/butyl/mixed alkyl group and other flow leveling additives or rheology modifiers, wherein a ratio of polyester or polyester/acrylic blend resin to melamine formaldehyde resin is adjusted to be in the range of 60/40 to 90/10 so as to maintain optimized mechanical properties and to provide an excellent appearance and durability to the coating after baking.
A resin which is a condensation product of polyalcohol with polycarboxylic acid is used as the polyester resin. These resins contain free hydroxyl and carboxyl groups in a predetermined proportion which allow reactions with melamine' cross-linking agent to provide for the desired characteristics. Polyalcohols suitable for manufacturing polyester resins include ethylene glycol, propylene glycol, butylene glycol, 1,6-hexylene glycol, neopentyl glycol, glycerol, trimethylolpropane, trimethylolethane, pentaerythritol, dipentaerythritol, tripentaerythritol, hexanetriol and condensation products of trimethylolpropane and ethylene oxide or propylene oxide, polycaprolactone and poly tetrahydrofuran.
Appropriate carboxylic acids include succinic acid (or anhydride thereof), adipic acid, azelaic acid, sebacic acid, phthalic acid (or anhydride thereof), isophthalic acid, terephthalic acid, cyclohexanedicarboxylic acid, trimellitic acid (or anhydride thereof) and pyromellitic acid (or anhydride thereof) .
A resin which is a product of addition polymerization by free radical or controlled radical polymerization of unsaturation containing vinyl or acrylic monomers is used as the acrylic resin. These resins contain free hydroxyl and carboxyl groups in a predetermined proportion which allow reactions with a standard cross-linking agent.
The acrylic resin consists of vinyl monomers, more specifically esters of acrylic or methacrylic acid. Typical acrylates may include alkyl, cycloalkyl, or aryl acrylates and methacrylates. Examples of useful acrylate monomers are methyl methacrylate, butyl acrylate, n-butyl methacrylate, lauryl methacrylate, 2-ethylhexyl methacrylate, isobomyl methacrylate, and cyclohexyl methacrylate. Another type of vinyl monomer that may be included are the aromatic vinyl compounds such as styrene. Further multifunctional acrylic monomers such as diacrylates or triacrylates may also be used. The acrylic resin can have a theoretical Fox Tg in the range of -50 to +20 °C. The preferable Tg is in the range of -15 to + 15°C. Hydroxyl containing monomers suitable for manufacturing acrylic resins include hydroxyalky acrylates and hydroxyalky methacrylates such as 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 3-hydroxypropyl acrylate, 4-hydroxybutyl acrylate, hydroxyhexyl acrylate, hydroxyoctyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxpropyl methacrylate, 2- hydroxypropyl methacrylate, 4-hydroxybutyl methacrylate, hydroxyhexyl methacrylate, hydroxyoctyl methacrylate, allyl and methally alcohol, butyl hydroxyethyl maleate and fumarate, butyl hydroxypropyl maleate and fumarate, and the like. The preferred hydroxy containing monomers are hydroxyl ethyl methacrylate and hydroxyl propyl methacrylate. Acetoacetate monomers which undergo crosslinking with aminoplastic resins may also be used such as acetoacetate ethyl methacrylate. Further examples of crosslinkable monomers are the ethylenically unsaturated acids such as acrylic acid, methacrylic acid, ethacrylic acid, crotonic acid, isocrotonic acid, cinnamic acid, maleic acid, fumaric acid, aconitic acid, citraconic acid, mesaconic acid, itaconic acid and glutaconic acid.
Coating composition of the present invention is characterized in that the amount of Cerenol has a specific range of values between 1% to 20% preferably in the range of 2 to 14% and more preferably in the range of 4 to 10%. In contrast, when the percentage exceeds 20, appearance of the clear coating become excellent but the nail hardness would become insufficient. The number average molecular weight of the Cerenol is 500 to 3000. Cerenol is a biodegradable polyol and chemically it is a polyether diol. It contains renewably sourced 1, 3-propanediol derived from corn. Cerenol H650, Cerenol H1000, Cerenol H2400 are some of the grades available under the said trade names commercially from DuPont. Bio based polypropane diols which may also be used are available under the trade name of P03G are obtained from Allessa .
Polytetramethylene ether glycol (PTMEG) is derived from the polymerization of tetrahydrofuran and is available commercially from BASF under the trade name PolyTHF. Various grades such as PolyTHF 650, 1000 or 2000 can be used. Polycaprolactone polyols are available commercially from Perstop under the trade name Capa. Various grades such as Capa 2043, 2085, 2200, 2100 etc. can be used. Cerenol, PTMEG and Polycaprolactone polyols may be used as a mixture or individually in the polyester backbone. Coating composition of the present invention is characterized in that the amount of Veova has a specific range of values between 5% to 20 % and preferably in the range of 10 to 18%. In contrast, when the percentage is low the self-healing property diminishes.Veova monomers are the vinyl esters of Versatic acid and are based on Neodecanoic acid. Veova 9 and Veova 10 are some of the grades , available commercially from Momentive. Veova 10 with a Tg of -3 °C is preferred.
The polyester and acrylic resin preferably has a number-average molecular weight, in the range of 500-4000 g/mol, a hydroxyl value in the range of 60-200 mg KOH/g, and an acid value in the range of 0-30 mg KOH/g. When the number-average molecular weight is out of the range, functions and appearance of coatings may become unsatisfactory. The molecular weight is further preferably in the range of 600-2000 g/mol. When the hydroxy! group value is less than 60, the mechanical properties of coating becomes insufficient. In contrast, when the value exceeds 200, curing becomes excessive and film is no more flexible. Further preferably, the value is in the range of 125-170 mg KOH/g. When the acid value exceeds 30, appearance and adhesiveness of coating becomes unsatisfactory because of excessive curing. The high acid value also affects the storage stability of the one component coating system. Further preferably, the acid value is in the range of 0 to 10 mg KOH/g.
Small amounts of esterification cataiyst can be employed in the synthesis to promote reaction. Tin catalysts or titanium catalysts are preferred. Typically, the esterification catalyst is present from about 0.001 to about 0.1 percent by weight, based on the total weight of the polyester polyol. Examples of suitable catalysts include, but are not limited to, acids such , as sulfuric acid, phosphoric acid, para-toluene sulfonic acid, organotin compounds such dibutyl tin-(IV) dilaurate, and titanium compounds such as titanium (IV) isoproproxide, hydrated monobutyltin oxide, dibutyltin oxide, or titanium (IV) butoxide (titanium tetrabutoxide, TBT). Preferably, the reaction mixture comprises from about 25 to about 800 ppm of the esterification catalyst.
The free radical polymerization used to form the acrylicpolyol backbone is preferably carried out using conventional techniques, such as by heating the monomers in the presence of a free radical polymerization initiator, typically, tertiary butyl perbenzoate, tertiary butyl peroctoate, cumene hydroperoxide, benzoyl peroxide, di-tertiary butylperoxide, di-cumene peroxide, methyl ethyl ketone peroxide or similar peroxy compounds, or an azo compound such as azobisisobutyronitrile is employed. The amount of free radical polymerization initiator can be varied depending upon the desired molecular weight but 0.05-8 percent by weight based on the weight of total polymerizable monomers is typical. A preferred range is from 0.05 to 4 percent by weight. A mixture of two or more initiators may be used.
In any of the processes described above, polymerization is preferably continued until the resulting resinous polyol has the desired molecular weight, but still sufficiently low viscosity for use in the coating composition of the present invention.
As a cross-linking agent used in the clear coating composition, aminoplastic resins such as melamine formaldehyde containing an imino group is used. The melamine resin can be a methyl/butyl mixed alkylated melamine resin containing high imino groups, methylated melamine resin containing high imino groups or butylated melamine resin containing high imino groups. Further preferably, thesolid content of the melamine resin is in the range of 70-100 percent by weight. Cymel 323, Cymel 325, Cymei 1130 and Cymel U 65 are some examples ofaminoplastic resins from Allnex.In general, aminoplastic resins are aldehyde condensation products of melamine, urea, benzoguanamine, or a similar compound. Usually, the aldehyde employed is formaldehyde, although useful products can be made from other aldehydes, such as acetaldehyde, crotonaldehyde, acrolein, benzaldehyde, furfural, and others. Condensation products of melamine or urea are the most common and are preferred, but products of other amines and amides in which at least one amine group is present can also be employed. Other crosslinking agents can also be used, such as urea formaldehyde, benzoguanamine formaldehyde or compatible mixtures of any of the forgoing crosslinkers.
Conventionally acid catalysts such as p-toluene sulfonic acid, dodecylbenzene sulfonic acid, amineblocked alkylated benzene sulfonic acids, phosphoric acids etc are used to enhance the cross linking reaction between the polyester polyol/ acrylic polyol and the melamine formaldehyde resin. In the present invention it is preferred, to carry out the curing in absence of acid catalyst.
Contents of the polyol (polyester or polyester/acrylic blend) and the cross-linking agent are 60-90 percent by weight for the polyol and 10-40 percent by weight for the cross-linking agent, preferably 65-85 percent by weight for the former and 15-35 percent by weight for the latter. When the content of the cross-linking agent is less than 10 percent by weight (when the content of polyol exceeds 90 percent by weight), cross-linking in the coating may not be sufficient. On the other hand, when the content of the cross-linking agent exceeds 40 percent by weight (when the content of the polyol is less than 60 percent by weight), not only the storage stability of the coating composition is reduced but also the curing speed thereof is enhanced, so that the appearance of coating may become deteriorated. An amount of blending, a blending ratio and an amount of added components in the present specification represent an amount calculated as solid mass unless otherwise specified.
The polyester polyol may be used independently or as a blend with the acrylic polyol. The ratio of the acrylic polyol to the polyester polyol is in the ratio range of 30:70-95:5, preferably in the range 50: 50 by weight. Hyperbranched or dendritic polyols may be added to the formulation in the range of 1 to 20% to further facilitate application at high solids. The hyperbranched polyol can be, for example, a polyester polyol or polyether polyol, or any multi-hydroxy functionalized molecule. A hyperbranched polymer is a polymer that is highly branched, and which contains multiple end groups, such as, in the case of a polyol, multiple hydroxyl end groups. The hyperbranched oligomer/polymer can advantageously have a dendritic structure, i.e., a branching, treelike structure in which chains radiate out from a central atom or cluster of atoms. Boltorn H20 and Boltor H30 are examples of dendritic hyperbranched polyester polyols available from Perstorp.
Various nanoadditives may be added in the formulation to enhance the properties such as scratch resistance, abrasion resistance, mechanical properties, appearance, gloss and gloss retention after crockmeter testing. Such additives are not limited to nano silica, nano alumina, nano zirconia, nano titania, nano zinc oxide, nano clay, single walled and multi walled carbon nanotubes, graphene, various nano fibers etc.
The clear coating composition may appropriately contain, besides the aforementioned components, sedimentation preventives (suspending agents) such as polyamide wax which is a lubricant dispersion of aliphatic amide, and polyethylene wax which is a colloidal dispersion comprising polyethylene oxide as the main ingredient, polyurea dispersion (which is a dispersion of polyurea particles in acrylic polyol) as anti-sagging agent, ultraviolet ray absorbent, antioxidant, leveling agent, surface adjusting agent such as silicone and organic polymers, thickening agent, antifoaming agent, lubricant, cross linking polymer particles (microgel), etc. These additives may be usually combined in less than 10 to 25 parts by weight per 100 parts by weight of the resins and cross-linking agent in total to improve the performances of the coating.
The present invention facilitates the formulation to be sprayed at a high application solid content of 50 to 60% thereby leading to improved productivity, coverage and lower impact on the environment compared to low to medium solid systems which are sprayed at 30 to 45% application solids.
A solvent is preferably used as the liquid reaction medium and for spraying the coating formulation. The solvent can be used at from 0 percent to 30 percent of the total reaction mixture and from 40 to 50% of the total spray coating formulation. Typical solvents used are the following : amyl acetate, toluene, ethyl acetate, butyl acetate, methoxy propyl acetate, acetone, methyl isobutyl ketone, methyl ethyl ketone, methyl amyl ketone, mineral spirits, ethylene glycol monoether acetates and other aliphatic, cycloaiiphatic and aromatic hydrocarbons, such as xylene, esters, ethers, ketones, and other compatible solvents are conveniently used. Reactive diluents such as Cardura E10 may also be used. A method for forming multilayered coating films according to the present invention is a method wherein a color coating film is made on a previously undercoated base material, followed by a formation of a clear/top coating film to provide multilayered coating films.
In the case where the substrate to be coated is an automobile body or parts thereof, it is preferable that an undercoating film has been previously formed on the substrate by the electrodeposition coating method, etc. after the process of chemical treatment. Examples of resins as a major component of electrodeposition coat used in the electrodeposition coating are liquid rubbers (those having epoxy resin as a structural skeleton such as maleic acid resin, maleic acid polybutadiene resin, and aminoplastic-epoxy polybutadiene resin, etc.) such as drying oil or polybutadiene, etc., resins having the fatty acid esters of resinous polyols as the main structural skeleton, etc. In the case where the electrodeposition coating resin is acidic resin, it is preferable to neutralize it with bases such as ammonia, amines, inorganic alkalis, etc. prior to its dissolution or dispersion in water. And, when the resin is basic, it is preferable to neutralize it with acids such as acetic acid, boric acid, phosphoric acid, etc. prior to its dissolution or dispersion in water. Into the electrodeposition coating, cross linking agents such as melamine resin, blocked polyisocyanate, additives such as pigments, solvents, etc. may be appropriately combined. It is desirable that electrodeposition coating film is so arranged that the coating film usually becomes 10-40 microns thick after baking. The multilayered coating films can be formed on a variety of base materials to be coated. In this case, examples of specific coating base materials are metals such as iron, aluminum, copper or alloys thereof, inorganic materials such as glassetc, resins such as polyethylene resin, polypropylene resin, ethylene-vinyl acetate copolymer resin, polyamide resin, acrylic resin, vinylidene chloride resin, polycarbonate resin, polyurethane resin, epoxy resin, etc., plastic materials such as various FRPs, etc., in addition, natural materials such as woods, fibrous materials (paper, fabrics, etc.) or synthetic materials, etc. In this specification, the base materials to be coated on which undercoating film has been formed by chemical treatment or undercoating, etc. may be sometimes referred to as base materials to be coated. The under coating/primer film is baked at 120 to 150 °C for 25 to 45 minutes and the dry film thickness could be 30 to 40 micro meter.
A color coating composition is applied to the base materials to be coated to build an intermediate coating film. In the case where the base materials to be coated have been undercoated with undercoating, etc., the intermediate coating may be applied onto the undercoating film in wet-on-dry manner. A typical pigmented color coating composition includes pigment, a film forming binder which can be a polyurethane, an acrylourethane, an acrylic polymer or a silane polymer, and a crosslinking agent such as, an aminoplastic, an alkylated melamine formaldehyde crosslinking agent or a polyisocyanate crosslinking agent. The base coating composition can be solvent or water borne and can be in the form of a dispersion or a solution. Generally, pigments used in the color coating composition include metallic flake pigments, such as aluminum flake or pearl flake pigments.
The clear/top coat of the present invention is then applied on color coating film in wet on wet manner. The color and clear coating film is baked together at 125-150° C for a predetermined time to build a glossy clear top coating film. The coating composition displays a gloss recovery over a period of a few minutes to a several hours under ambient conditions depending on the temperature. The gloss recovery is from 5% to 200% dependent on the composition.
The clear coating composition displays a pencil hardness of F-2H, a Persoz hardness of greater than 100 seconds, gloss recovery after crockmeter testing of greater than 40% while exhibiting the property of self-healing.
There is no limitation in the method for forming the multilayered coating film on base materials to be coated and can be by spray application, airless spray, bell applicator, dip method, etc. The color coating film DFT (dry film thickness) is preferably 15 to 25 microns and the clear coating DFT is 30 to 40 microns.
Examples
The present invention is more specifically described below with reference to examples, but should not be construed being limited thereto. Example 1
Manufacturing of Polyester Resin
In a 1-liter flask equipped with a stirrer, nitrogen inlet pipe, temperature controller, condenser and decanter were placed trimethylpropane (TMP) (0.050 moles), neopentyl glycol ( PG glycol) (0.3664 moles) and dibutyltin dilaurate catalyst (0.05% of the total weight), and the mixture was dissolved by heating it to 80-100° C. Stirring was initiated at the point that it became possible and 1,4-cyclohexane dicarboxylic acid (1,4 CHDA) (0.1893 moles), isophthalic acid (IPA) (0.0611 moles) and adipic acid (0.0784 moles) were further added to the mixture, and the reaction temperature was elevated to 180°C after the addition of 4% of the total weight of xylene into the mixture. When the water of reaction began to be produced, the reaction temperature was raised to 210° C over a period of 2 hours at a constant rate. On attaining, 210° C, the reaction was continued at that temperature for 4 more hours to reach the acid value of 5 mg KOH/g. After cooling, the resin is diluted to 75% solid with 1 : 1 mixture of xylene to butyl acetate. The resin thus obtained is having the acid value of 5 and hydroxyl value of 162.
Example 2-9
Polyester polyol resins were prepared as described in example 1 as shown in Table 1. Example 10: Preparation of Clear Coating Composition:
As shown in Table 1, a number of polyester resins were prepared, combined with cross- linking agents, rheology additives and flow-leveling additives in proportions specified in Table 2, mixed under stirring with organic solvents (butanol/xylene/ethyl carbitol =35/35/30 by weight) using a stirrer until the viscosity suitable for coating is reached to obtain clear coating compositions 2-9.
Preparation of Base Materials to be Coated :
A cold rolled steel plate (0.8 mm thick) having vertical and horizontal surfaces was degreased, chemically modified using a zinc phosphate treatment agent and subjected to electrodeposition with a cationic electrodeposition coating so as to achieve a DFT of 25 microns. Then, after baking at 160° C for 30 minutes, a primer coating composition was air- sprayed so as to achieve a DFT of 30 microns, which was baked at 140° C for 30 minutes to form a primer coating film.
Top Coating Film :
On the primer applied base material a color coat was air sprayed to make a dried coating film thickness of 20 microns and allowed to stand for 10 minutes. The clear coating composition was then air sprayed by wet on wet method to make a dried coating thickness of 30 microns and 10 minutes flash of time was given before baking at 140° C for 30 minutes. The coating was allowed to dry for 24 hours under ambient conditions after which the properties were tested. Table 1. Examples of polyester polyol resins synthesized .
* 2-methyl 1, 3 propane diol
**Polycaroplactone polyol from Perstop
***Polytetrahydrofuran from BASF
Figure imgf000023_0001
Table 2 : Formulation (in parts by weight) and properties of multi-film coating formed using polyester polyol resins.
Figure imgf000024_0001
As shown in Table 2, a coating film was formed by a method for forming multilayered coating films according to this invention, wherein, while achieving the property of self- healing, appearance of coating film and mechanical properties of the final coating were excellent. Furthermore, the clear coating composition of the present invention is isocyanate free, can be applied at a higher solid content and the coating composition has a satisfactory storage stability as a one component system as indicated by no viscosity pickup under ambient conditions over a period of 30 days. Figure 1 shows stereo microscope images of the scratches created by the crockmeter test ( 10 cycles) immediately after testing at time 0 hrs and at time 24 hrs at ambient temperatures respectively, wherein after 24 hrs the scratches are seen to diminish.
Example 11 : Synthesis of acrylic polyol
A low molecular weight acrylic polyol solution is prepared by charging the following ingredients of Table 3 into a polymerization vessel equipped with a thermometer, reflux condenser, stirrer, addition funnel and a heating mantle. Table 3. Example of acrylic polyol resin synthesized involving Veova monomer.
Figure imgf000025_0001
Portion 1 is charged to polymerization vessel and heated to its reflux temperature (144 degree C). The constituents are under constant stirring in the polymerization vessel during the entire process. Portion 2 is premixed and added drop wise into the vessel at a rate of 0.4 parts per minute over 190 minute period while the resulting, reaction mixture is held at its reflux temperature. Portion 3 is added as a chaser catalyst after 45 minutes of addition of portion 2 and the reaction at reflux temperature is continued for another 90 minutes to react all the free monomers. Heating is stopped and reaction mass is cooled to room temperature under stirring. The resin thus obtained is diluted to 75% solid, Gardner viscosity (25 deg C) U-V, hydroxyl value of 130 and Mn of 3500 g/mol.
Example 12 : Synthesis of acrylic polyol in accordance with Example 11 was performed without Veova monomer as per the ingredients of Table 4 below.
Table 4. Example of acrylic polyol resin synthesized without Veova monomer
Figure imgf000026_0001
Example 13 : Synthesis of acrylic polyol in accordance with Example 11 was performed without Veova monomer as per the ingredients of Table 5 below.
Table 5. Example of acrylic polyol resin synthesized without Veova monomer
Figure imgf000026_0002
Ditertiary amyl peroxide 0.6
O-xylene 2
Total 100
Example 14 : Formulation (in parts by weight) and properties of multi-film coating formed using a blend of acrylic polyols as per (Examples 11- 13) and polyester polyol resins ( Example 2) are tabulated below in Table 6.
Table 6 :
Figure imgf000027_0001
As seen i n Table 6, a coati ng film was formed using a blend of a polyester and acrylic polyol by a method for formi ng muitilayered coating films according to the present invention, wherei n, it was found that while achieving the property of self-healing, appearance of coating film and mechanical properties of the final coating were excellent only for the blend under SI. No. 1 in Table 6 above. Table 6 thus clearly demonstrates that the polyester polyol resin of the present invention (Example 2) only when blended with veova based acrylic polyol resin and is finally cross-linked and cured with aminoplastic resin retains the property of self-healing, which property of self-healing could not be retained with other acrylic resins minus veova monomers as per Examples 12 and 13 when present in combination with the polyester polyol resin of Example 2.
It is thus possible by way of the present advancement to provide for a coating composition that advantageously confers intrinsic self-healing properties at ambient temperatures also when including renewable polya!kylene glycol such as cerenol in the backbone of the polyester polyol resin, which when cross-linked with aminoplastic resins results into a mechanically robust coating having excellent scratch hardness and pencil hardness along with the self-healing property. In addition the coating composition involves a polymer that can be prepared using low solvent content thereby resulting into a low VOC coating which can be sprayed at a high solid content. The polyester polyol may be used alone or may contain the acrylic polyol as a blend providing for the desired characteristics of the coat.

Claims

We Claim:
- 1. A coating composition having self-scratch healing characteristics comprising aminopiastic resin crosslinked polyester polyol resin comprising condensation product of carboxylic acids and polyols including one or more renewable polyalkylene glycols.
2. A coating composition as claimed in claim 1 wherein said polyester polyol resin comprises polymeric condensation product having renewable polyalkylene glycols selected from anyone or more of cerenol, PTMEG (polytetramethylerie ether glycol) or polycaprolactone polyol in the polymer backbone.
3. A coating composition as claimed in anyone of preceding claims 1 or 2 wherein said polyester polyol resin is a polyester polyol resin blend comprising acrylic polyol resin having at least one Veova monomer bonded to said acrylic polyol.
4. A coating composition as claimed in claim 3 wherein at least one Veova monomer in said acrylic polyol resin is in amounts of 5-20% by wt. of the coating composition preferably in the range of 10 to 18% by wt. for enhanced durability.
5. A coating composition as claimed in anyone of the preceding claims 1-4 which is a clear composition and mechanically robust possessing self mending ability of nano/micro/ macro scratches under ambient conditions with gloss recovery after crockmeter testing of at least 40% to upto 200% ; has good mechanical hardness including scratch and pencil hardness of F-2H,Persoz hardness of at least 100 seconds under baking conditions; allows spraying for end use and application involving polyester polyol resin at high solid content of 65-90% thus favouring a low VOC (volatile organic content) coating and enabling automotive use.
6. A coating composition as claimed in anyone of the preceding claims 1-5 wherein said polyester polyol resin blend including acrylic polyol resin has hydroxyl value in the range of 60-200 mg KOH/gm preferably 125-170 mg KOH/gm of said resins favouring desired mechanical properties and flexibility of a clear coat.
7. A coating composition as claimed in anyone of the preceding claims 1-6 wherein said polyester polyol resin blend including acrylic polyol resin has acid value of upto 30 mg KOH/g preferably upto 20 mg KOH/g and more preferably upto 10 mgKOH/gm of said resins favouring desired appearance and adhesiveness of the clear coat on the substrate.
8. A coating composition as claimed in anyone of the preceding claims 1-7 comprising polyester polyol resin blend comprising polyester polyol and acrylic polyol in the ratio range of 30 : 70-95: 5, preferably in the range 50 : 50 by weight.
9. A coating composition as claimed in anyone of the preceding claims 1-8 which is storage stable composition with storage stability of at least upto 30 days as a one component system free of viscosity pick up and gelation and free of toxic isocyanate
10. A coating composition as claimed in anyone of the preceding claims 1-9 comprising upto 20% of hyper-branched/ dendritic polyols facilitating spraying for end use and application at high solid content of 50 to 60% .
11. A coating composition as claimed in anyone of the preceding claims 1-10 as film coating composition including multi film coatings of thickness in the range of 100 to 120 microns involving clear coat thickness of 30 to 40 microns and having self-scratch healing characteristics at ambient temperatures.
12. A coating composition as claimed in anyone of the preceding claims 1- 11 comprising polyester polyol resin obtained of aliphatic, aromatic and/or cycioaliphatic polycarboxylic acids and polyols including polyalkylene glycols.
13. A coating composition as claimed in anyone of the preceding claims 1-12 wherein said polyester polyol comprises one or more polycarboxylic acids including succinic acid (or anhydride thereof), adipic acid, azelaic acid, sebacic acid, phthalic acid (or anhydride thereof), isophthalic acid, terephthalic acid, cyclohexane dicarboxyiic acid, trimellitic acid (or anhydride thereof) and pyromellitic acid (or anhydride thereof) in the range of 40% to 60% of the polyester polyol by weight.
14. A coating composition as claimed in anyone of the preceding claims 1-13 wherein said polyester polyol comprises one or more polyol selected from ethylene glycol, propylene glycol, butylene glycol, 1,6-hexylene glycol, neopentyl glycol, glycerol, trimethylolpropane, trimethylolethane, pentaerythritol, dipentaerythritol, tripentaerythritol, hexanetriol including condensation products of trimethylolpropane and ethylene oxide or propylene oxide, in the range of 20% to 40% of the polyester polyol by weight.
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15. A coating composition as claimed in anyone of the preceding claims 1-14 wherein said acrylic polyol comprises vinyl monomers, more specifically esters of acrylic or methacrylic acid including acrylates of alkyl, cycloalky!, or aryl acrylates and methacrylates and aromatic vinyl compounds including styrene or multifunctional acrylic monomers such as diacrylates or triacrylates.
16. A coating composition as claimed in anyone of the preceding claims 1-15 wherein said polyester polyol has molecular weight( n) in the range of 500 to 4000 g/mol and wherein the acrylic polyol has a theoretical Fox Tg in the range of -50 to +20 °C preferably Tg in the range of - 15 to + 15°C.
17. A coating composition as claimed in anyone of the preceding claims 1-16 wherein said acrylic polyol resin in the polyester polyol resin blend has molecular weight (Mn) in the range 500-4000 g/mol has solid levels in the range 65-90%and includes Veova 9 and Veoya 10 monomer together with esters of Versatic acid.
18. A coating composition as claimed in anyone of the preceding claims 1-17 wherein said acrylic polyol comprises hydroxy! monomers including · hydroxyalkyl acrylates and hydroxyalky methacrylates such as 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 3- hydroxypropyl acrylate, 4-hydroxybutyl acrylate, hydroxyhexyl acrylate, hydroxyoctyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxpropyl methacrylate, 2-hydroxypropyl methacrylate, 4-hydroxybutyl methacrylate, hydroxyhexyl methacrylate, hydroxyoctyl methacrylate, allyl and methally alcohol, butyl hydroxyethyl maleate and fumarate, butyl hydroxypropyl maleate and fumarate, including acetoacetate monomers such as acetoacetate ethyl methacrylate and also comprises ethylenically unsaturated acids including acrylic acid, methacrylic acid, ethacrylic acid, crotonic acid, isocrotonic acid, cinnamic acid, maleic acid, fumaric acid, aconitic acid, citraconic acid, mesaconic acid, itaconic acid and glutaconic acid.
19. A coating composition as claimed in anyone of the preceding claims 1-18 comprising solvent or mixture of solvents upto 30 percent of the ingredients of the composition and from 40 to 50% of the coating composition for spraying wherein said solvents include amyl acetate, toluene, ethyl acetate, butyl acetate, methoxy propyl acetate, acetone, methyl isobutyl ketone, methyl ethyl ketone, methyl amyl ketone, mineral spirits, ethylene glycol monoether acetates and other aliphatic, cycloaliphatic and aromatic hydrocarbons, such as xylene, esters, ethers, ketones, and other compatible solvents and reactive diluents of Cardura E10.
20. A coating composition as claimed in anyone of the preceding claims 1-19 comprising cross-linkers involving anyone or more of aminoplastic resins including melamine formaldehyde having an imino group, methyl/butyl mixed alkylated melamine resin containing high imino groups, methylated melamine resin containing high imino groups or butylated melamine resin containing high imino groups and formaldehyde, benzoguanamine formaldehyde, urea wherein the solid content of said melamine resin is in the range of 70- 100 percent by weight.
21. A coating composition as claimed in anyone of the preceding claims 1-20 comprising rheology modifiers, flow leveling additives, defoamers, wetting agents, sag control agents, nanoparticles, nanoadditives, dispersing agents, antimicrobial additives and curing catalysts.
22. A process for the preparation of coating composition as claimed in anyone of the preceding claims 1-21 comprising
a. providing a polyester polyol resin comprising condensationproduct of carboxylic acids and polyols including one or more renewable polyalkylene glycols with or without acrylic polyol resin with at least one Veova monomer in the backbone; and b. combining thus obtained polyester resins with aminoplastic resin based crosslinking agent and obtaining therefrom said scratch-healing coating composition.
23. A process as claimed in claim 22 wherein said polyester polyol resin comprises polymeric condensation product having renewable polyalkylene glycolsselected from anyone or more cerenol, PTMEG (polytetramethylene ether glycol) or polycaprolactonepolyol in the polymer backbone and wherein saidpolyester polyol resin has hydroxyl value in the range of 60-200 mg KOH/gm preferably 125-170 mg KOH/gm favouring a clear coat with the desired mechanical properties and flexibility.
24. A process for the preparation of coating composition as claimed in anyone of the preceding claims 22-23 wherein said at least one Veova monomer in the backbone of said acrylic polyol is used in amounts of 5-20% by wt. of the coating composition preferably in the range of 10 to 18% by wt.
25. A process for the preparation of coating composition as claimed in anyone of the preceding claims 22-24 wherein said polyester polyol resin used with or without acrylic polyol resin also have predetermined hydroxyl values in the range of 60-200 mg KOH/gm preferably 125-170 mg KOH/gm prior to crosslinking and curing with aminoplastic resin.
26. A process for the preparation of coating composition as claimed in anyone of the preceding claims 22-25 comprising providing said anyone or more polyalkylene glycols in the backbone of said polymer including Cerenolin the polyester polyol of molecular weight (Mn) in the range of 500 to 3000 g/mol with a hydroxyl number of 37 to 224 mgKOH/g in the range of 1% to 20 % preferably in the range of 2 to 14% and more preferably in the range of 4 to 10% of the polyester polyol by weight; polycaprolactone polyols of molecular weight (Mn) in the range of400 to 2000 g/mol and hydroxyl value ranging from 56 to 280 mgKOH/g in the range of 1% to 20 % preferably in the range of 2 to 14% and more preferably in the range of 4 to 10% of the polyester polyol by weight; PTMEG of molecular weight (Mn) in the range of250 to 3000 g/mol and hydroxyl value ranging from 40 to 500 mgKOH/g in the range of 1% to 20 % preferably in the range of 2 to 14% and more preferably in the range of 4 to 10% of the polyester polyol by weight.
27. A process for the preparation of coating composition as claimed in anyone of the preceding claims 22-26 wherein the ratio of polyester resin blend including acrylic polyol to aminoplastic resin used is in the range of 60/40 to 90/10 by weight on solid basis.
28. A self scratch healing coated substrate comprising
said substrate coated with a top surface coat of aminoplastic resin crossiinked polyester polyol resin comprising condensationproduct of carboxylic acids and polyols including one or more renewable polyalkylene glycols with or without acrylic polyol resin having at least one Veova monomer in the backbone.
29. A self scratch healing coated substrate as claimed in claim 28 comprising multilayer coated substrates comprising
a. at least one base/ color coat applied on different substrates as base materials; and.
b. at least one said self scratch -healing clear coating composition as claimed claims 1-21 for forming a top coat;
30. A method for obtaining self scratch healing coated substrate as claimed in anyone of claims 28 or 29 following the steps of
a. providing base/color coating composition on an undercoated/ uncoated base material as at least one coat;
b. providing said self scratch -healing clear coating as at least one coat as a top coating by wet on wet application method;
c. baking at 125 to 150 °C for 25 to 30 minutes and obtaining a multilayered coating film therefrom.
31. A method as claimed in claim 30 wherein said application method for forming the multilayered coating film on base materials including coatings to be coated includes spray application, airless spray, bell applicator, dip.
32. A method as claimed in anyone of claims 30 or 31 wherein said substrates as base materials includes metals such as iron, aluminum, copper or alloys thereof, inorganic materials such as glass etc., resins such as polyethylene resin, polypropylene resin, ethylene-vinyl acetate copolymer resin, polyamide resin, acrylic resin, vinylidene chloride resin, polycarbonate resin, polyurethane resin, epoxy resin, etc., plastic materials such as various FRPs (fiber reinforced polymer), natural materials such as woods, synthetic materials.
33. A thermosetting composition comprising polyester polyol resin comprising condensation product of carboxylic acids and polyols including one or more renewable polyalkylene glycols conferring self-healing attributes.
34. A thermosetting composition as claimed in claim 33 wherein said polyester polyol resin comprises polymeric condensation product including said renewable polyalkylene glycols in the polymer backbone and has selective hydroxyl value in the range of 60-200 mg KOH/gm preferably 125-170 mg KOH/gm to favour desired mechanical properties and flexibility when cross-linked.
PCT/IN2015/000396 2015-07-23 2015-10-19 A one component self-healing coating composition WO2017013670A1 (en)

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