Classifications

• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
  • H01B1/00—Conductors or conductive bodies characterised by the conductive materials; Selection of materials as conductors
  • H01B1/20—Conductive material dispersed in non-conductive organic material
  • H01B1/24—Conductive material dispersed in non-conductive organic material the conductive material comprising carbon-silicon compounds, carbon or silicon

Definitions

• This invention is directed to a primer composition and in particular to an electrically conductive and flexible primer composition.
• Primer compositions are well known in the art and are widely used in the manufacture of automobiles and truckes as shown in Simon U.S. Patent 4,232,090 issued Nov. 4, 1980.
• High solids polyester coating compositions also are well known as shown in Chang U.S. patent 3,994,851 issued Nov. 30, 1976.
• Polyester copolymers having linear and branched chains useful for coatings are shown in Sommerfeld et al U.S. Patent 4,442,269 issued April 10, 1984.
• none of these compositions meet the current needs of the automotive and truck manufacturing plants.
• a conductive, hard and flexible primer composition containing solvents and about 40-75% by weight of a film forming binder and pigments in a pigment to binder ratio of about 5:100 - 50:100; wherein the pigments comprise an electrically conductive carbon black pigment and the binder contains about
• the primer composition forms finishes that are hard, flexible and electrically conductive and have excellent adhesion to a variety of substrates such as cold roll steel, phosphatized steel, polyester reinforced fiber glass, reaction injection molded urethanes, partially crystalline polyamides and other plastic substrates and provides a surface to which conventional topcoats will adhere.
• substrates such as cold roll steel, phosphatized steel, polyester reinforced fiber glass, reaction injection molded urethanes, partially crystalline polyamides and other plastic substrates and provides a surface to which conventional topcoats will adhere.
• the primer is particularly useful on the aforementioned plastic substrates since the resulting finish is conductive and topcoats can be applied by electrostatic spraying which is currently being used by many auto and truck manufacturing facilities.
• Flexibility of the finish is determined by the mandrel bend test in which a panel coated with about 1.0 mil thick fully cured film of the coating decomposition is held at -18°C and then bent around a 1/2 inch diameter steel mandrel with the coated side of the panel facing outward. The coating should not break or crack.
• the coating composition is measured by a Sprayability Meter manufactured by Randsburg Electrocoating Corporation, Indianapolis, Indiana.
• the composition has a surface conductivity of at least 160 Randsburg units and preferably 165-350 Randsburg units.
• the primer composition has a film forming binder content of about 40-75% by weight and correspondingly about 25-60% by weight of a liquid carrier which usually is a solvent for the binder.
• the composition contains pigments in a pigment to binder weight ratio of about 5:100 - 50:100.
• the pigments must contain an electrically conductive pigment such as an electrically conductive carbon black pigment. Other pigments also can be used in the composition.
• the film forming binder of the composition contains about 50-80% by weight of a polyester copolymer and about 20-50% by weight of an alkylated melamine formaldehyde crosslinking agent.
• One highly preferred composition contains about 60-70% by weight of the polyester copolymer and 30-40% of the crosslinking agent are used and forms a high quality composition.
• the polyester copolymer used in the composition has a linear polyester segment with hydroxyl groups that has a hydroxyl number of about 15-300 and a number average molecular weight of about 300-3,000 and has branched polyester segments. These branched segments contain hydroxyl groups and have a hydroxyl number of about 175-300 and a number average molecular weight of about 500-2,000 and are attached to the linear segment by esterification of the hydroxyl groups of the the two segments with a diacid or an anhydride.
• the polyester copolymer has a number average molecular weight of about 800 - 3,500 and a hydroxyl number of about 50 - 170.
• the linear segment is formed from a straignt chain diol and a dicarboxylic acid.
• Typical diols that are useful have from 2-10 carbon atoms and are for example ethylene glycol, propylene glycol, butane diol, pentane diol, neopentyl glycol, hexane diol, octane diol, Esterdiol 204 (a commercial diol produced by Union Carbide) and the like.
• Preferred diols are neopentyl glycol and 1,6 hexane diol since these diols form high quality polyesters.
• Typical dicarboxylic acids that can be used are aromatic acids such as a phthalic acid, orthophthalic acid, isophthalic acid, and aliphatic acids such as adipic acid, azelaic acid and the like.
• the branched segment is formed from a straight chain diol, a branched chain polyol and a dicarboxylic acid.
• the above straight chain diols and dicarboxylic acids are used.
• Typical branched chain polyols that can be used are trimethylol propane, triethylol propane, pentaerythritol and the like.
• the linear and branched segments are attached by esterification of the hydroxyl groups of each segment with a diacid or an anhydride.
• the aforementioned acids can be used but preferably an anhydride is used.
• Typical anhydrides are orthophthalic anhydride, succinic anhydride, glutaric anhydride and the like.
• One preferred polyester copolymer has a linear chain segment of a polyester of neopentyl glycol, hexane diol, isophthalic acid and azelaic acid and branched chain segments of a polyester of neopentyl glycol, trimethylol propane, isophthalic acid and azelaic acid and are esterified with orthophthalic anhydride.
• the molar ratio of linear chain segment/anhydride/branched chain segment is 1/1/1 and the copolymer has a number average molecular weight of about 800 - 1,500 and a hydroxyl number of 125-155.
• polyester segments and polyester copolymer are prepared by conventional esterification procedures in which the components are charged into a polymerization vessel with solvents and usually a esterification catalyst and heated to about 100-200°C. for about 30 minutes to 5 hours with removal of water that is formed during the process.
• the crosslinking agent used in the composition is an alkylated melamine formaldehyde crosslinking resin. Typically, these resins have 1-8 carbon atoms in the alkyl group. Methylated melamine formaldehyde resins such as “Cymel”380 and methylated melamine formaldehyde resins containing methoxymethyl imino groups such as “Cymel”325 are preferred to form a high quality primer.
• One preferred combination is a blend of 40-40% by weight of "Cymel”380 and correspondingly about 60-40% by weight of "Cymel”325.
• the composition contains carbon black pigments that are electrically conductive such as a conductive furnace black pigment.
• One preferred pigment is a Vulcan XC-72-R furnace black pigment that does not have a surface treatment.
• Other pigments can be used in the composition provided that the conductivity remains at least 160 Ransburg units.
• Typical pigments that can be used are filler pigments such as talc, china clay, barytes, carbonates, silicates, metallic oxides such as titanium dioxide, zinc oxide and iron oxide and organic colored pigments and dyes.
• the pigments can be introduced into the primer composition by first forming a mill base with the polyester copolymer or with another compatible polymer or dispersant by conventional techniques such as sand grinding, ball milling, attritor grinding or two roll milling.
• the mill base is blended with other constituents used in the composition.
• any of the conventional solvents or blends of solvents can be used to form the primer composition provided that the selection of solvents is such that the polymeric binder constituents are compatible and give a high quality primer.
• the composition can contain about 0.01-2% by weight, based on the weight of the binder, of ultraviolet light stabilizers which term includes ultraviolet light absorbers, screeners and quenchers.
• ultraviolet light stabilizers include benzophenones, triazines, triazols, benzoates, hindered amines and blends of thereof.
• the primer composition can be applied to a flexible or rigid substrate by conventional techniques such as spraying, electrostatic spraying, dipping, brushing, flowcoating and the like. As mentioned above the preferred method as electrostatic spraying. After application, the composition is baked at about 100-200°C for about 5-45 minutes tor form a primer coating layer about 0.1-2.0 mils thick. Generally the primer layer is about 0.5-1.5 mils thick. Conventional solvent borne or water borne acrylic enamels or lacquers, acrylic polyurethane coatings, polyesterurethane coatings, alkyd enamels and the like can be applied and then baked to form a durable automotive or truck finish on the substrate.
• a polyester solution is prepared by charging the following constituents into a polymerization vessel equipped with a mechanical stirrer, an electric heating mantle, a nitrogen inlet tube, a water separator, a thermometer, an addition funnel and a water cooled reflux condenser:
• Portion 1 is charged into the polymerization vessel and with stirring heated to 125-150°C for about 1 hour.
• Portion 2 is then added and water is distilled off at a temperature of about 220-225°C.
• Portion 3 is added and then Portion 4 is added and the composition is cooled to room temperature.
• the resulting polyester solution has a solids content of about 80% and the polyester has a hydroxyl number of about 120-150 and a number average molecular weight of about 1,200 and has a molar ratio of branched polyester/orthophthalic anhydride/linear polyester of 1:1:1.
• a mill base is prepared by charging the following constituents into a sand mill and grinding to a 0.5 mil fineness: Parts by weight Polyester solution (prepared above) 40.01 "Cymel” 380 (80% solids of a polymeric methylated melamine formaldehyde resin in isobutanol) 15.60 Conductive carbon black pigment (Vulcan XC-72-R conductive furnace black without a surface treatment) 6.20 Diisobutyl ketone 26.73 Methyl ethyl ketone 11.46 Total 100.00
• a coating composition was prepared by blending together the following constituents: Parts by Weight Mill base (prepared above) 56.08 "Resiflow” (50% solution of an acrylic terpolymer flow control agent in “Solvesso”100) 0.26 "Syloid” 378 (flatting agent of synthetic silica having a partical size of 3-5 microns) 0.97 Polyester solution (prepared above) 13.89 "Cymel”325 (80% solids in isobutanol of a methylated melamine formaldehyde resin having methoxymethyl imino functionality and a degree of polymerization of 2.3) 6.38 UV screener (10% solution of "Tinuvin” 900 2-[2-hydroxy-3,5-di(1,1-dimethyl(benzyl)phenyl]-2H-benzotriazole in xylene) 1.89 Ethylene glycol monobutyl ether acetate 14.38 Butanol 8.04 Total 101.89
• the resulting primer composition has a solids content of 46.5%, pigment/binder ratio of 13.5/100 and is black in color.
• the primer was reduced to a spray viscosity of 35" measured with a No.2 Fisher cup at 25°C with methyl amyl ketone and sprayed onto a cold roll steel panel, a phosphatized steel panel, a fiber glass reinforced polyester panel, a reaction injection molded urethane panel and a partially crystalline polyamide panel.
• the steel panels were baked for 30 minutes at about 125°C and the remaining panels were baked at 120°C for about 30 minutes.
• the panels had had a black color,a dry film thickness of about 0.8 mils and a gloss measured at 60°C of about 30.
• the coatings on the panels had the following properties: mar resistance - good adhesion - good sandability - good knife scrape resistance - good solvent resistance - 75 double rubs (1:1 ratio p-naphtha/isopropanol) conductivity - >165 Randsburg Units humidity resistance 96 hour at 38°C/100% rel. humidity - 101 dry crosshatch and tape adhesion - 101 mandrel bend 180° (-18°C) - 52 (-29°C) - 42 Rating system 1 0 - 10, 10 - best, 0 - worst Rating system 2 0- 5, 5 - best, 0 - worst

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• Physics & Mathematics (AREA)
• Chemical & Material Sciences (AREA)
• Dispersion Chemistry (AREA)
• Spectroscopy & Molecular Physics (AREA)
• Paints Or Removers (AREA)
• Application Of Or Painting With Fluid Materials (AREA)

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Cited By (6)

Citations (2)

• 1988
  • 1988-02-18 CA CA000559228A patent/CA1320779C/en not_active Expired - Fee Related
  • 1988-02-19 EP EP88102427A patent/EP0328711A1/de not_active Ceased

Patent Citations (2)

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