Classifications

• • 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
  • C08G59/00—Polycondensates containing more than one epoxy group per molecule; Macromolecules obtained by polymerising compounds containing more than one epoxy group per molecule using curing agents or catalysts which react with the epoxy groups
  • C08G59/18—Macromolecules obtained by polymerising compounds containing more than one epoxy group per molecule using curing agents or catalysts which react with the epoxy groups ; e.g. general methods of curing
  • C08G59/20—Macromolecules obtained by polymerising compounds containing more than one epoxy group per molecule using curing agents or catalysts which react with the epoxy groups ; e.g. general methods of curing characterised by the epoxy compounds used
  • C08G59/32—Epoxy compounds containing three or more epoxy groups
  • C08G59/3209—Epoxy compounds containing three or more epoxy groups obtained by polymerisation of unsaturated mono-epoxy compounds
• • 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
  • C09D163/00—Coating compositions based on epoxy resins; Coating compositions based on derivatives of epoxy resins

Definitions

• the invention relates to acrylic coating resins for use as coatings for rigid substrates which have excellent heat resistance and high temperature performance.
• Glycidyl methacrylate (GMA) acrylic powder coatings were introduced in the coatings industry in the 1970s, and are useful as protective coatings for metal. These thermoset, decorative powder coatings have recently found significant application in the automotive industry as primer surfacers, wheel coatings and as black-out coatings for automobile trim.
• GMA is polymerized with other monomers such as acrylates, methacrylates and other unsaturated monomers such as styrene and its derivatives.
• the crosslinker is a saturated aliphatic dicarboxylic acid.
• GMA powder like other thermoset powder coatings is typically applied by electrostatic spraying, followed by curing at elevated temperature.
• Glycidyl methacrylate coatings are also available in solvent form and have application for coating metals and certain plastics, and are useful in industrial maintenance coatings.
• Conventional epoxy-functional (meth) acrylates such as glycidyl methacrylate, have high volatility and toxicity.
• a polyalicyclic acrylic acid ester derivative has been shown to be useful as a comonomer with an acrylic monomer in molding applications for optical materials.
• no formulations using polyalicyclic acrylic acid ester derivatives are known for solvent-borne or powder coatings .
• the invention is directed to a coating composition
• a coating composition comprising :
• - Ri is a residue of an alpha-beta ethylenically unsaturated carboxylic acid ;
• R 2 is an alkylene group having 1-4 carbons or an alkoxylene group having 1-4 carbons ; and n is an integer from 0 to 15 (which means n is 0 or an integer from 1 to 15) ;
• crosslinker (B) a crosslinker selected from the group of dicarboxylic acids and/or anhydrides or selected from the group of polyamides and/or polyamines. More particularly, the crosslinker (B) may be at least one dicarboxylic acid or anhydride or alternatively at least one compound selected from the group of polyamides and/or polyamines .
• the invention also includes compositions in a powder form, as well as solvent-borne coating resin compositions comprising a compound (A) of formula (I), a crosslinker (B) as defined above, and an organic solvent.
• the powder form and solvent-borne forms of the coating resin compositions may additionally contain comonomers such as acrylates, methacrylates and vinyl aromatic monomers, such as vinyl toluenes, styrene, styrene derivatives and the like, and mixtures of these co onomers .
• coating compositions may also contain dispersing aids, flow aids, pigments, catalysts and the like.
• the invention also comprises methods of coating substrates with the powder and solvent-borne compositions of the invention comprising the steps of a) applying said compositions to the substrate and b) curing the said compositions .
• the invention also comprises coated articles formed by coating substrates with the powder and solvent- borne compositions of the invention.
• the invention also includes composition wherein the copolymerizable alpha-beta ethylenically unsaturated epoxide compound (A) is an epoxide-containing (meth) acrylate ester of formula (II) :
• R 3 is a hydrogen or methyl group
• R 4 is an alkylene group of 1-4 carbons or an alkoxylene group of 1-4 carbons ; and n is an integer from 0 to 15.
• the invention further includes a method of coating a substrate comprising (a) applying a composition comprising a copolymerizable, alpha-beta ethylenically unsaturated epoxide compound, a dicarboxylic acid or anhydride and an organic solvent to a substrate, (b) causing the solvent to flash off the coated substrate ; and (c) exposing the coated substrate to an elevated temperature for a sufficient amount of time at the selected temperature to cure the coating.
• the invention additionally comprises a coated article wherein a substrate is coated with the powder composition or the solvent-borne composition according to the claimed methods of the invention.
• Figure 1 shows a coating prepared by laying a powder of the invention on a phosphate-treated steel panel inside a 0.051 mm (2 mil) polyester film template to control coating thickness.
• the copolymerizable alpha-beta ethylenically unsaturated epoxide compounds are suitable for use in preparing solvent-borne and powder coatings compositions and more particularly in preparing acrylic solvent-borne and powder coatings compositions.
• the copolymerizable alpha-beta ethylenically unsaturated epoxide compounds suitable for use in the invention are those having the general formula (I) as defined above and can be crosslinked by a crosslinker selected from at least one dicarboxylic acid and/or anhydride or a crosslinker selected from at least one polyamide and/or polyamine, in an organic solvent for solvent-borne coating compositions.
• copolymerizable epoxide compounds (A) of formula (I) suitable for use in the invention are epoxy-containing (meth) acrylate esters having the formula (II) as defined above.
• the copolymerizable epoxide- containing (meth) acrylate esters of formula (II), suitable for use in the invention are (meth) acrylic esters of epoxidized dicyclopentadiene of formula (III) :
• the resin compositions of the invention include both solvent-borne resins and powder resins.
• the compositions are provided with at least one dicarboxylic acid and/or anhydride for crosslinking the composition.
• Solvent-borne compositions additionally comprise at least one organic solvent selected from the group consisting of alcohols, aromatic hydrocarbons, aliphatic hydrocarbons, and acetates.
• the powder and solvent-borne compositions of the invention may include other monomers which may be (co) polymerized and/or crosslinked with the copolymerizable alpha-beta ethylenically unsaturated epoxide compounds and more particularly with the epoxide- containing (meth) acrylate esters of the composition.
• the monomers suitable for use in the composition are acrylates, methacrylates, vinyl and vinyl aromatic monomers and their derivatives, such as styrene and styrene derivatives and the like, and mixtures of these monomers .
• Suitable acrylates, methacrylates, styrenes and styrene derivatives include, but are not limited to : vinyl monomers, such as vinyl acetate, styrene, vinyl toluenes, divinyl benzenes and the like ; acrylic and methacrylic esters, such as methyl (meth) acrylate, ethyl (meth) acrylate, glycidyl (meth) acrylate, isopropyl (meth) acrylate, n-butyl (meth) acrylate, isobutyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, 2- hydroxyethyl (meth) acrylate, ethylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, tetraethylene glycol di (meth) acrylate, glycerol di (meth) acrylate, glyce
• acrylates methacrylates and styrenes suitable for use in the invention, preferred are butyl acrylate, methyl methacrylate, vinyl toluenes and styrene, and the like.
• the comonomers are provided in an amount of about 30-90 wt based on the solids weight of the composition. Preferably, the comonomers are provided in an amount of about 50-80 wt% . Most preferably, the comonomers are provided in an amount of about 60-70 wt%.
• the copolymerizable alpha-beta ethylenically unsaturated epoxide compound and more particularly the epoxide-containing (meth) acrylate ester is provided in an amount of about 1-40 wt% based on the solids weight of the composition.
• the copolymerizable unsaturated epoxide-containing (meth) acrylic ester is provided in an amount of about 10-25 wt% and most preferably in an amount of about 15 wt% .
• the copolymerizable alpha-beta ethylenically unsaturated epoxide compound and more particularly the epoxide-containing (meth) acrylate monomer (ester) may be crosslinked with at least one dicarboxylic acid and/or anhydride.
• the dicarboxylic acids and anhydrides may generally be aliphatic dicarboxylic acids and anhydrides.
• the aliphatic dicarboxylic acids or anhydrides suitable for use in the present invention are not particularly restricted.
• Examples of the aliphatic dicarboxylic acids and anhydrides suitable for use in the invention include dodecanedioic acid, malonic acid, adipic acid, pimelic acid, suberic acid, azelaic acid, glutaric acid, sebacic acid, succinic acid, brassylic acid, dicarboxylic acids of the general formula COOH- (CH 2 ) p -COOH, wherein p is an integer of about 1-14, and the like.
• a preferred dicarboxylic acid is dodecanedioic acid.
• the dicarboxylic acid is provided in an amount sufficient to crosslink the copolymerizable alpha-beta ethylenically unsaturated epoxide compound and preferably the epoxide-containing (meth) acrylate monomer.
• the dicarboxylic acids or anhydrides are present in an amount of 5-25 wt% based on the weight of the composition.
• the dicarboxylic acids or anhydrides are added in an amount of 5-15 wt%.
• the dicarboxylic acids or anhydrides are provided in an amount of 10 wt%.
• the solvent-borne coating resin compositions of the invention are provided in organic solvents.
• the organic solvents useful in the invention as solvents for the solvent-borne coating resins compositions will depend largely on the application for which the coating resin composition will be applied.
• Examples of the solvents which may be used in the invention include organic alcohols, aliphatic hydrocarbons, aromatic hydrocarbons, such as benzene, xylene, toluene, and the like, acetates such as butyl acetate, ethyl acetate, and the like, and mixtures thereof.
• xylene and butyl acetate and mixtures thereof are preferred.
• the solvent-borne coating resin compositions of the invention may also include pigments, such as titanium dioxide (Ti0 2 ) and the like ; dispersing acids, such as Anti-Terra U Dispersing Aid, and the like ; and catalysts, such as p-toluenesulfonic acid catalyst (p-TSA) and the like.
• pigments such as titanium dioxide (Ti0 2 ) and the like
• dispersing acids such as Anti-Terra U Dispersing Aid, and the like
• catalysts such as p-toluenesulfonic acid catalyst (p-TSA) and the like.
• a solvent-borne coating resin composition containing the copolymerizable alpha-beta ethylenically unsaturated epoxide compound, more preferably the epoxide-containing (meth) acrylate ester monomer and optionally, a comonomer, such as acrylate, methacrylate and/or styrene, is blended with a dicarboxylic acid or anhydride in a solvent.
• the composition may contain other additives such as pigments, dispersing aids, and catalysts.
• the substrate to be coated is coated with the solvent-borne coating resin composition.
• the solvent is allowed to flash off, and the coating on the coated substrate is allowed to cure by exposing the coated substrate to elevated temperature.
• the elevated temperature is about 100-300°C for 1 minute to 2 hours.
• the temperature is about 150-250°C for 10 minutes to 1 hour and most preferably at about 200°C.
• the polymerization or curing time depends on the precise formulation and the temperature at which polymerization is allowed to proceed. For embodiments exposed to a temperature of about 200 °C, the polymerization time may be from about 15 minutes to about 1 hour. Generally, the polymerization time will be about 30 minutes.
• the powder coating resins compositions of the invention may be prepared for use in coating substrates for high-temperature curing.
• the powder coating compositions comprise the copolymerizable alpha-beta ethylenically unsaturated epoxide compounds which preferably may be epoxide-containing (meth) acrylate ester monomers, dry-blended with a dicarboxylic acid or anhydride, and optionally, a comonomer, such as acrylates, methacrylates, and/or styrenes.
• the composition may also include pigments, such as titanium dioxide (Ti0 2 ) and the like ; flow promoting agents, such as Modaflow Flow Aid, and the like ; and catalysts, such as p-TSA (p-toluene sulfonic acid), and the like.
• Pigments, such as titanium dioxide, when added are typically provided in an amount of about 0 to 30 wt% .
• Catalysts which promote more rapid curing, are generally added in an amount of about 0 to 0.02 wt%.
• the blended composition may be ground to a selected particle size. Particle size is selected based on the application, but typical particle size is about 5-100 ⁇ m.
• the powder coating resin compositions may be applied to a substrate to be coated by any known means, such as by corona discharge or triboelectric charging, and the like, at an elevated temperature, such as in a forced air oven.
• curing takes place at an elevated temperature, such as 60-250°C.
• the cure is achieved at a temperature of about 100-200°C. Most preferably, the temperature is about 150°C. It will be understood by persons skilled in the art that the temperature of the cure may be adjusted based on the precise composition of the resin and the time required for curing. Some adjustment for these factors will be easily achieved by modifying the conditions of the cure depending on the desired cure dynamics.
• the unsaturated alpha- beta ethylenically unsaturated epoxide compounds may be used as a comonomer for coatings that can be crosslinked with polyamides and/or polyamines at ambient temperature or at elevated temperatures.
• These compositions may also include other comonomers such as acrylates, methacrylates and vinyl or vinyl aromatic monomers, such as vinyl toluenes, styrene and styrene derivatives.
• the unsaturated epoxide compound or more particularly the epoxide-containing (meth) acrylate ester is present in an amount of about 1-60 wt% based on the weight of the composition.
• the unsaturated epoxide compound or epoxide-containing (meth) acrylate ester is present in an amount of about 10-40 wt% and most preferably is present in an amount of about 15-25 wt%.
• the polyamides and/or polyamines in this embodiment may be present in an amount of about 5-50 wt% based on the weight of the composition.
• the polyamides and/or polyamines are present in an amount of about 10-40 wt% and most preferably in an amount of about 15-25 wt%.
• Suitable polyamides and/or polyamines include, but are not limited to : ethyleneamines, propyleneamines, higher alkyleneamines, Mannich Bases, amines from adducts of amines with epoxy, adducts with acrylonitrile, ketimines, arylaliphatic amines, alicyclic aliphatic amines, cycloaliphatic amines, unsaturated fatty acid derivatives of alkylene amines and the like.
• ethyleneamines such as diethylenetriamine and triethylenetetraamine .
• the aforementioned acrylates, methacrylates, vinyl aromatic monomers, such as vinyl toluenes, styrene and styrene derivatives may be provided in an amount of about 1-60 wt% based on the solids weight of the composition.
• these comonomers are provided in an amount of about 10-40 wt% and most preferably in an amount of about 15-25 wt% .
• additives of this embodiment may include pigments and dispersing aids as described in the previous embodiments .
• compositions containing polyamines and/or polyamides may be cured at ambient temperature or at elevated temperature. Suitable temperatures are from about 25° to about 150°C.
• the unsaturated epoxide compounds or more particularly the epoxide-containing (meth) acrylate esters are blended with the polyamines and/or polyamides and are crosslinked at ambient temperature to about 150 °C.
• Coating resins compositions may also be prepared to include a UV initiator and a cationic photoinitiator for crosslinking in a hybrid cure system with ultraviolet light and heat. These coating compositions may include at least one UV initiator and/or at least one cationic photoinitiator . Cationic curing provides a high rate of curing.
• the cationic initiators suitable for use in the invention include sulfonium and iodonium salts.
• sulfonium and iodonium salts upon exposure to ultraviolet light, decompose to yield an acid catalyst.
• cationic initiators include diaryliodonium hexafluoro- antimonate, triarylsulfonium hexafluoroantimonate, triarylsulfonium hexafluorophosphate, cyclopentadiene hexafluorophosphate and the like.
• the cationic photoinitiator is typically present in an amount of about 0.5 to 1 wt%.
• UV light is applied, which partially cures the compositions. Exposure to elevated temperatures completes the curing process.
• UV initiators include benzoin ethers, benzil ketals, acetophenones, phosphine oxide, and benzophenone, as well as others known in the art.
• the alpha-beta ethylenically unsaturated epoxide compound or preferably the epoxide-containing (meth) acrylate ester is blended with other cycloaliphatic monomers, a UV initiator (e.g., benzophenone) and a cationic photoinitiator.
• the composition is formed into a powder, which is applied to the substrate.
• the coating is partially cured by exposure to UV light by any conventional method, and cure is completed by applying heat (such as in a forced air oven) at temperatures of about 40-80°C, preferably about SO- 70°C, and most preferably at about 60°C.
• the copolymerizable alpha-beta ethylenically unsaturated epoxide compounds or preferably the epoxide- containing (meth) acrylate esters of the invention confer a significant advantage over conventional epoxy-functional (meth) acrylate esters, such as glycidyl methacrylate.
• Viscosity was measured with a Brookfield LVT viscometer. Percent volatiles was measured according to ASTM D2369, which measures weight loss after 1 hour at 110°C. Glass transition temperature was measured by differential scanning calorimetry (DSC) in which a specimen was cured with 0.5 wt% Vazo 67 at 100°C for 3 hours. Autopolymerization was also measured by DSC.
• resins were prepared and evaluated by several tests : 60° Gloss was measured using a Micro-Triglossmeter from Byk-Gardner ; Pencil Hardness, Reverse Impact and Cross-Hatch Adhesion were each measured by ASTM methods ; and the MEK double rub method was used to measure Solvent Resistance.
• the first set of examples demonstrates the invention in use as a solvent-borne coating.
• An acrylic terpolymer was prepared by combining 6.17 moles of butyl acrylate, 1.14 moles methyl methacrylate and 1.0 moles of dicyclopentadiene methacrylate epoxide in solution at 100 - 120 °C using an azonitrile initiator. The resulting terpolymer had an epoxide equivalent weight of approximately 1200.
• the terpolymer coating resin prepared was formulated into a solvent-borne acrylic white enamel coating, as shown in Table 2, by mixing with Ti0 2 , dispersing aid, solvent and pTSA catalyst on an air-driven high shear mixer. Dodecanedioic acid was added and the mixture was mixed in a laboratory 3-roll mill.
• a drawdown was prepared on chrome-treated aluminium panel using a # 10 wire wound drawdown rod for testing coating properties.
• the panel sat at 25°C for 30 minutes to allow the solvent to flash off.
• the panel was then baked in a forced air oven at 200°C for 1 hour.
• the panel was subjected to the following tests : 60° Gloss was measured using a micro-triglossmeter from Byk-Gardner. Solvent Resistance was measured using the MEK double rub method, in which a paper towel is saturated with MEK solvent and is wiped back and forth across the surface of the film coating with nominal pressure. One wipe back and forth constitues a double-rub. Reverse Impact, Pencil Hardness and Cross-Hatch Adhesion were measured following the ASTM method. The results are shown in Table 2.
• An acrylic terpolymer was prepared by combining 6.8 moles of butyl acrylate, 1.25 moles methyl methacrylate and 1.0 mole of glycidyl methacrylate in solution at 100 - 120°C using an azonitrile initiator. The resulting terpolymer had an epoxide equivalent weight of approximately 1200.
• the terpolymer coating resin prepared was formulated into a solvent-borne acrylic white enamel coating, as shown in Table 2, by mixing with Ti0 2 , dispersing aid, solvent and p-toluenesulfonic acid catalyst (p-TSA catalyst) on an air-driven high shear mixer. Dodecanedioic acid was added and the mixture was mixed in a laboratory 3-roll mill.
• a drawdown was prepared on chrome-treated aluminium panel using a # 10 wire wound drawdown rod for testing coating properties.
• the panel sat at 25°C for 30 minutes to allow the solvent to flash off.
• the panel was then baked in a forced air oven at 200°C for 1 hour.
• the second set of examples demonstrates the use of the invention as an acrylic powder coating.
• An acrylic powder coating resin was prepared by combining 1.0 moles of butyl acrylate, 3.25 moles of methyl methacrylate and 4.24 moles of styrene and 1.06 moles of dicyclopentadiene methacrylate epoxide.
• the resulting tetrapolymer coating resin was formulated into an acrylic powder coating formulation, as shown in Table 3, by dry blending with the Ti0 2 , p-TSA catalyst, dodecanedioic acid and a Modaflow agent in a one pint epoxy-lined aluminium can on a shaker for 10 minutes. The formulation was then ground to fine particles using a mortar and pestle.
• the coating was prepared in the laboratory by laying the powder on a phosphate-treated steel panel inside of a 0.051 mm (2 mil) polyester film template to control coating thickness as shown in Figure 1.
• a second phosphate-treated steel panel was placed on top of the template and then the coating was cured in a hydraulic press at 150°C for 20 minutes under 2 metric tons of pressure.
• An acrylic powder coating resin was prepared by combining 1.0 moles of butyl acrylate, 3.25 moles methyl methacrylate, and 4.24 moles of styrene, and 1.06 moles of glycidyl methacrylate.
• the resulting tetrapolymer coating resin was formulated into an acrylic powder coating formulation, as shown in Table 3, by dry blending with the Ti0 2 , p-TSA catalyst, dodecanedioic acid and a Modaflow agent in a one pint epoxy-lined aluminium can on a shaker for 10 minutes. The formulation was then ground to fine particles using a mortar and pestle.
• the coating was prepared in the laboratory by laying the powder on a phosphate-treated steel panel inside of a 0.051 mm (2 mil) polyester film template to control coating thickness as shown in Figure 1.
• a second phosphate-treated steel panel was placed on top of the template and then the coating was cured in a hydraulic press at 150 °C for 20 minutes under 2 metric tons of pressure.

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