Classifications

• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
  • C09D5/00—Coating compositions, e.g. paints, varnishes or lacquers, characterised by their physical nature or the effects produced; Filling pastes
  • C09D5/44—Coating compositions, e.g. paints, varnishes or lacquers, characterised by their physical nature or the effects produced; Filling pastes for electrophoretic applications
  • C09D5/4419—Coating compositions, e.g. paints, varnishes or lacquers, characterised by their physical nature or the effects produced; Filling pastes for electrophoretic applications with polymers obtained otherwise than by polymerisation reactions only involving carbon-to-carbon unsaturated bonds
• • 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
  • C09D179/00—Coating compositions based on macromolecular compounds obtained by reactions forming in the main chain of the macromolecule a linkage containing nitrogen, with or without oxygen, or carbon only, not provided for in groups C09D161/00 - C09D177/00
  • C09D179/04—Polycondensates having nitrogen-containing heterocyclic rings in the main chain; Polyhydrazides; Polyamide acids or similar polyimide precursors
  • C09D179/08—Polyimides; Polyester-imides; Polyamide-imides; Polyamide acids or similar polyimide precursors

Definitions

• the invention relates to polyetherimide fiber compositions, and especially relates to polyetherimide fiber compositions made via a cataphoretic electrodeposition process.
• Polyetherimide resins have been applied to substrates utilizing various techniques including anoinic electrodeposition.
• anionic, also known as anodic, electrodeposition chemically combines resin R with ion forming group, e.g., -COOH, to form acidic resin RCOOH, which reacts bases to form macro-ions RCOO- for anodic deposition.
• ion forming group e.g., -COOH
• RCOOH acidic resin
• Y + counter ions
• cathodic electrodeposition produces a product with no dissolution of the substrate, no staining, and better alkali resistance.
• This process employs the polycation, typically converting tertiary amines (NR3) to cations (NR4 + ) using aqueous acid and electrode reaction.
• R 3 N water insoluble oligomer
• HX external solubilizer
• R3NH + film forming macro-ions
• cathodic electrodeposition solves some of the problems of anodic electrodeposition, this process has not been commercially viable for polyetherimide compositions due to poor emulsion stability, limited storage abilities, solvent toxicity and irritating odor, and low throwing power, i.e., the ability of the coating to uniformly coat remote areas of a substrate with the desired thickness, resulting in limited consistent layer thickness.
• complex and hollow components are based upon thermoset materials, such as unsarurated polyesters and epoxy resins, having a high glass temperature because of the need for complete impregnation of the fibers in order to produce a substantially void-free composite, whereby complete impregnation is only attained with low viscosity polymers.
• thermoset materials such as unsarurated polyesters and epoxy resins
• these processes, the melt process, dry powder process, and solution process typically employ toxic or otherwise environmentally harmful chemicals or processes which require expensive secondary operations and long cycle times.
• the melt process comprises applying a molten thermoplastic material to the fibers by either using a cross-head extruder which feeds the molten material to a die directed through which the fibers pass, or the fibers pass through a molten material bath.
• Disadvantages of this process include fiber damage caused by the forces exerted on the fibers during processing and difficulty in impregnating in small quantities and in homogeneously impregnating tightly held fibers.
• the dry powder process comprises sintering very fine, low particle size thermoplastic material into the fibers. This process requires long cycle times and expensive secondary operations such as grinding procedures to obtain sufficiently small polymer particles.
• the fibers are impregnated with a low viscosity solution of the thermoplastic polymer.
• the volatilizing solvent which should be recycled, can form voids.
• thermoforming process such as vacuum/pressure molding, hydroforming, stamp forming, and autoclave forming, would then be employed to convert the fabricated pre-preg into complex shapes.
• the present invention relates to a cataphoretic electrodeposition process for forming polyetherimide coated fibers.
• This process comprises: forming a polyetherimide emulsion, comprising the steps of: dispersing a polyetherimide resin in a solvent and a substantially water insoluble cosolvent, said polyetherimide resin having anhydride groups; reacting a ring opening agent with said anhydride groups, wherein amine groups are formed; neutralizing said amine groups with a neutralization agent to form a quaternized mixture; forming the polyetherimide emulsion by adding water to said quatemized mixture; inserting an anode into said emulsion; inserting fibers into said emulsion, wherein said fiber preform functions as a cathode; applying an electrical current to said emulsion; forming a polyetherimide cation; and reacting said polyetherimide cation at said cathode to form a polyetherimide species which coats said fibers.
• the fibers are cataphoretically coated in a polyetherimide emulsion which comprises, polyetherimide resin, a ring opening agent, a neutralization agent, a solvent, a cosolvent, and water.
• the coating process comprises dissolving the polyetherimide in solvent, adding the cosolvent, opening anhydride groups with the ring opening agent, quaternizing the amine groups with the neutralization agent, and finally adding water to form the aqueous polyetherimide emulsion.
• the fibers and an anode are then placed in the emulsion, a current is applied, and the polyetherimide reacts to coat the fibers.
• the emulsion comprises up to about 10 volume percent (vol%) polyetherimide resin, up to about 5 vol% ring opening agent, up to about 5 vol% neutralization agent, up to about 20 vol% solvent, and up to about 20 vol% cosolvent, balance water, with about 3 vol% to about 8 vol% polyetherimide resin, about 0.2 vol% to about 3 vol% ring opening agent, about 0.3 vol% to about 3.5 vol% neutralization agent, about 8 vol% to about 15 vol% solvent, and about 9 vol% to about 15 vol% cosolvent, balance water preferred, and about 4 vol% to about 7 vol% polyetherimide resin, about 0.5 vol% to about 1.5 vol% ring opening agent, about 0.5 vol% to about 2 vol% neutralization agent, about 10 vol% to about 13 vol% solvent, and about 10 vol% to about 12.5 vol% cosolvent, balance water especially preferred.
• Polyetherimide resins suitable for use as the polyetherimide resin component of the emulsion of the present invention are known compounds whose preparation and properties have been
• Patent Nos. 3,803,085 and 3,905,942 the respective disclosures of which are incorporated herein by reference.
• the polyetherimide resin component of the present invention contains from greater than 1 to 1000 or more, preferably from 10 to 1000, structural units of the formula (I):
• T is -O- or a group of the formula -O-Z-O- ;
• Z is a divalent radical selected from the group consisting of formulae (II):
• X is a member selected from the group consisting of divalent radicals of the formulae (III):
• R is a divalent organic radical selected from the group consisting of: (a) aromatic hydrocarbon radicals having from 6 to about 20 carbon atoms and halogenated derivatives thereof, (b) alkylene radicals having from 2 to about 20 carbon atoms, (c) cycloalkylene radicals having from 3 to about 20 carbon atoms, and (d) divalent radicals of the general formula (IV):
• y' is an integer from about 1 to about 5.
• the polyethermide resin may be a copolymer which, in addition to the etherimide units described above, further contains polyimide repeating units of the formula (VI):
• R is as previously defined for formula (I) and M is selected from the group consisting of formula (VII):
• Polyetherimide resins are made by known methods, such as, for example, those disclosed in U.S. Patent Nos. 3,847,867, 3,814,869, 3,850,885, 3,852,242 3,855,178 and 3,983,093, the disclosures of which are hereby incorporated herein by reference.
• the polyetherimide resin is made by the reaction of an aromatic bis(ether anhydride) of the formula (X):
• T and R are defined as described above in formula (I).
• the reactions can be carried out employing well-known solvents, for example, o- dichlorobenzene, m-cresol /toluene and the like to effect interaction between the anhydride of formula (X) and the diamine of formula (XI), at temperatures from about 100°C to about 250°C
• the polyethermide resin can be prepared by melt polymerization of aromatic bis(ether anhydride)s and diamines accomplished by heating a mixture of the ingredients at elevated temperatures with concurrent stirring.
• melt polymerizations employ temperatures between about 200°C and 400°C. Chain stoppers and branching agents may also be employed in the reaction.
• aromatic bis(ether anhydride)s of formula (X) include: 2,2-bis(4-(3,4-dicarboxyphenoxy)phenyl)propane dianhydride; 4,4'- bis(3,4-dicarboxyphenoxy)diphenyl ether dianhydride; 4,4'-bis(3,4-dicarbo- xyphenoxy)diphenyl sulfide dianhydride; 4,4'-bis(3,4-dicarboxyphenoxy) benzophenone dianhydride; 4,4'-bis(3,4-dicarboxyphenoxy)diphenyl sulfone dianhydride; 2,2-bis([4-(2,3-dicarboxyphenoxy)phenyl]propane dianhydride; 4,4'-bis(2,3-dicarboxyphenoxy)diphenyl ether dianhydride; 4,4'-bis(2,3- dicarboxyphenoxy)diphenyl sulfide dianhydride; 4,4'-bis(
• a dianhydride such as pyromellitic anhydride
• bis(ether anhydride) is used in combination with the bis(ether anhydride).
• the bis(ether anhydride)s can be prepared by the hydrolysis, followed by dehydration, of the reaction product of a nitro substituted phenyl dinitrile with a metal salt of dihydric phenol compound in the presence of a dipolar, aprotic solvent.
• Suitable organic diamines of formula (XI) include, for example: m- phenylenediamine; p-phenylenediamine; 4,4'-diaminodiphenylpropane, 4,4'- diaminodiphenylmethane (commonly named 4,4'-methylenedianiline); 4,4'- diaminodiphenyl sulfide; 4,4'-diaminodiphenyl sulfone; 4,4'-diaminodiphenyl ether (commonly named 4,4'-oxydianiline); 1,5-diaminonaphthalene; 3,3- dimethylbenzidine; 3,3-dimethoxybenzidine; 2,4-bis(beta-amino-t-butyl) toluene; bis(p-beta-amino-t-butylphenyl)ether; bis(p-beta-methyl-o- aminophenyl) benzene; l,
• Illustrative of a particularly preferred polyetherimide resin falling within the scope of formula (I) is one comprising repeating units wherein R is paraphenylene, metaphenylene, or mixtures of paraphenylene and metaphenylene and T is a group of the formula -O-Z-O- wherein Z has the formula (XIV):
• the polyetherimide resin may be a copolymer, a siloxane polyetherimide copolymer made by condensation of 2,2-bis(2,3- dicarboxy phenoxy phenol)propane dianhydride with metaphenylene diamine and an aminopropyl-terminated D 10 polydimethylsiloxane, containing 34 weight percent (wt%) structural units derived from the polydimethylsiloxane and having a molecular weight of about 60,000 grams per mole (g/mole).
• useful polyetherimide resins have an intrinsic viscosity [ ⁇ ] greater than about 0.2 deciliters per gram, preferably of from about 0.35 to about 0.7 deciliters per gram measured in m-cresol at 25°C.
• the polyetherimide resin of the present invention has a weight average molecular weight of from about 10,000 to about 150,000 g/mole, as measured by gel permeation chromatography, using a polystyrene standard.
• the polyetherimide resin is dissolved in a solvent capable of dissolving that particular polyetherimide resin.
• a solvent capable of dissolving that particular polyetherimide resin is an organic solvent such as N-methylpyrolidone.
• organic solvent such as N-methylpyrolidone.
• Other conventional solvents capable of dissolving the polyetherimide resin can alternatively be employed.
• the cosolvent should be a solvent for polyetherimide, be a liquid at a temperature of 0°C, should be misible with the solvent over a large temperature range, i.e., up to about 150°C, with up to 250°C preferred, and produce a ratio of solvent /cosolvent in the deposited coating of less than about 1.
• the cosolvent should be insoluble or only slightly soluble in water, preferably a solubility in water below about 5.5 grams per liter (g/1), in order to improve the emulsion stability and to obtain high throwing power properties (i.e. a mean voltage approaching zero, or a mean voltage of about zero) and to reduce water content in the deposited layers.
• Table 1 shows the immisibility point and coupling coefficient of the cosolvent for a 20 ml N-methylpyrrolidone-water (50/50) mixture with the coupling coefficient expressed as the amount of mixture divided by the amount of cosolvent necessary to obtain a heterogeneous mixture.
• the cosolvent additionally has a coupling coefficient of about 3.7 or greater in N-methylpyrolidone.
• Possible cosol vents include, but are not limited to, aromatic ethers, ketones, etherketones, arylallyl ketones, arylalkylketones, aryletheralcohols, ketones, phenols, and ether containing solvents, among others, with methyl phenyl ether (anisole) and 2-methoxy phenyl acetone preferred.
• the stability of the emulsion correlates to the water solubility of the cosolvent; higher water solubility cosolvent produces a lower stability of the emulsion or incomplete emulsification.
• Table 4 illustrates the effect of cosolvent on final amperage (current at the end of the coating period) and the time necessary to approach zero.
• the anhydride groups of the polyetherimide are opened using a ring opening agent.
• This ring opening agent can be any compound capable of ring opening the imide groups of the polyetherimide, with amines preferred. These amines are secondary or tertiary amines which are misible with water, and have sufficiently high boiling points to avoid volatilization under standard preparation and storage conditions (i.e. about 1 atmosphere and 25°C), with a boiling point above about 90°C preferred and a boiling point above about 110°C especially preferred. Preferably these amines additionally have hydrophilic groups, such as alcoholic groups. N-methylpiperazine is preferred, with 2-(l- piperazinyl)ethanol (HEP) especially preferred because they produce high polyetherimide yields, efficiently react with polyetherimide, and excess thereof is easily removed during curing of the polyetherimide coating.
• HEP 2-(l- piperazinyl)ethanol
• the ring opening agent reacts with the anhydride groups of the polyetherimide to form functionalized amine-acid groups.
• the amine groups are quaternized using a neutralization agent.
• Neutralization agents include acids having a sufficient acid strength to attain the desired quaternization.
• Possible neutralization agents include, but are not limited to, mono-acids having an acid strength K a of about IO' 5 or greater.
• Other acids can be employed however additional acid groups on the neutralization agent reduces the stability of the emulsion.
• lactic acid or glycolic acid is employed because the strong solvation of the counter ion of these acids induces an improved hydrophilic character resulting in migration to the water/solvent/cosolvent interphase, providing thereby a stable emulsion.
• Tables 5 and 6 show the improved stability yields of the emulsion and subsequently deposited coating when using lactic acid or glycolic acid as the neutralization agent.
• the preparation of the emulsion of the present invention is normally achieved by combining the components under conditions suitable for the formation of an emulsion. Suitable conditions include, for example, solution blending or melt mixing in single or twin screw type extruders, mixing bowl, screw extruders are often preferred due to their more intensive mixing or similar mixing devices which can apply a shear to the components. Twin capability over single screw extruders. It is often advantageous to apply a vacuum to the melt through at least one vent port in the extruder to remove volatile impurities in the composition.
• a polyetherimide resin under an inert atmosphere (i.e. nitrogen, argon, or another), a polyetherimide resin is preferably dissolved in a mixture of solvent and cosolvent, while heating the mixture. Although this process can be accomplished at room temperature (RT), heating the mixture is preferred in order to facilitate dissolution of the polyetherimide.
• a ring opening agent is dissolved in a cosolvent and mixed into the dissolution. The dissolution is then preferably heated to a sufficient temperature, for a sufficient period of time to react the ring opening agent with the desired amount of anhydride groups of the polyetherimide to form amine groups.
• the desired amount of anhydride groups reacted with the ring opening agent is based upon the particular application, with reaction of substantially all of the anhydride groups possible, between about 50% and about 80% preferred, and about 60% to about 75% especially preferred.
• a mixture of cosolvent and neutralization agent is added to quaternize the amine groups.
• the amount of neutralization agent utilized is based upon the desired amount of amine groups to quaternize. For example, to quaternize 50 vol.% of the amine groups, a 50 vol.% aqueous solution of the neutralization agent is mixed into the dissolution. Preferably, up to about 75% or more of the amine groups are quatemized, with about 42% to about 55% especially preferred.
• sufficient water preferably demineralized water, is added to attain the desired percentage of polyetherimide in aqueous emulsion.
• solvent can be utilized in conjunction with or instead of the cosolvent so long as the solventicosolvent ratio is maintained below about 1; at ratios above about 1 the emulsion becomes unstable.
• the fibers can be impregnated with the emulsion utilizing a cataphoretic electrodeposition process.
• the fibers can be woven or non-woven fabrics, unidirectional tapes, random fiber sheets, among others having any length or diameter desired to form the particular component.
• Possible fibers include any conductive fiber compatible with the emulsion, including coated fibers, with glass fibers, carbon fibers, and mixtures thereof preferred, such as a metal coated glass fiber /fabric.
• Possible coatings include conductive coatings such as metal coatings, including, but are not limited to, nickel, iron, steel, copper, and others, and alloys thereof.
• Pretreatment of the fibers improves coating adhesion and therefore the mechanical properties of the final composite and facilitates homogeneous thickness of the wetted layers.
• Possible pretreatments include, but are not limited to, pretreating the fibers with good solvents for the polyetherimide, such as N-methylpyrrolidone and chloroform, among others.
• One possible pretreatment method comprises rinsing or soaking the fibers in the solvent.
• Impregnation of the fibers with the polyetherimide aqueous emulsion then comprises inserting an anode, i.e.
• the voltage can be up to about 100 volts (V), with about 20 V to about 60 V preferred.
• V volts
• the voltage applied directly effected the yield and the wetting /impregnation quality.
• the impregnated fabric was rinsed, such as with de-ionized water or other inert liquid, to remove any organic substances which may be present.
• the polyetherimide can be cured at elevated temperatures.
• the temperature should be sufficient to cure the polyetherimide within the cure period, while not adversely effecting the fibers. Typically, the temperature is between about 250°C and 300°C for up to about 30 minutes, with about 15 minutes to about 20 minutes preferred.
• amine groups were quatemized via stirring 19.9 g cosolvent and an equal molar amount of a 50% aqueous solution of the neutralization agent (i.e., 4.2 g. of a 50% aqueous solution of glycolic acid) into 100 g of the polymer solution.
• a 6 wt% polyetherimide aqueous emulsion was then formed by slowly adding 259.9 g of demineralized water to the quatemized solution.
• Electrodeposition of the polyetherimide aqueous emulsion comprised inserting a stainless steel rod (anode) and carbon fiber fabric (cathode) into the emulsion, and applying a voltage. After deposition process, the impregnated fabric was rinsed with de- ionized water and cured at elevated temperatures, between about 250°C and 300°C for 15 to 20 minutes.
• Tables 9 and 10 show improved stability and yields of the emulsion and subsequently deposited coating using HEP as the ring opening agent compared to a standard ring opening agent (N-methylpiperazine (NMP)).
• NMP N-methylpiperazine
• Table 11 shows the solvent and water content of the polyetherimide coatings.
• the solvent:cosolvent ratio is below 1, with a low water content.
• Low amounts of water result in improved throwing power, as the conductivity of the polyetherimide coating decreases, while a low solventicosolvent ratio indicates a preference of cosolvent deposition, thereby readily enabling the production of improved coatings since the cosolvent more readily volatilizes during cure of the coating, producing a substantially uniform, adherent coating.
• Table 12 shows typical mechanical properties of carbon fiber polyetherimide composites (each composite comprises 50 vol% fibers and 50 vol% polyetherimide formed by laminating 26 woven fabric layers) made by the cataphoretic electrodeposition process described in the above example.
• the fiber polyetherimide composite of the present invention enables simplified, inexpensive environmentally friendly production of complex geometry fiber reinforced components having good mechanical properties.

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