CA1204347A - Vaporous amine catalyst spray method - Google Patents
Vaporous amine catalyst spray methodInfo
- Publication number
- CA1204347A CA1204347A CA000449250A CA449250A CA1204347A CA 1204347 A CA1204347 A CA 1204347A CA 000449250 A CA000449250 A CA 000449250A CA 449250 A CA449250 A CA 449250A CA 1204347 A CA1204347 A CA 1204347A
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- Canada
- Prior art keywords
- amine
- isocyanate
- vaporous
- carrier gas
- atomizing
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
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Classifications
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- 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
- C08G18/00—Polymeric products of isocyanates or isothiocyanates
- C08G18/06—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen
- C08G18/08—Processes
- C08G18/16—Catalysts
- C08G18/18—Catalysts containing secondary or tertiary amines or salts thereof
- C08G18/1891—Catalysts containing secondary or tertiary amines or salts thereof in vaporous state
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
- B05D—PROCESSES FOR APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
- B05D1/00—Processes for applying liquids or other fluent materials
- B05D1/02—Processes for applying liquids or other fluent materials performed by spraying
- B05D1/04—Processes for applying liquids or other fluent materials performed by spraying involving the use of an electrostatic field
-
- 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
- C08G18/00—Polymeric products of isocyanates or isothiocyanates
- C08G18/06—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen
- C08G18/08—Processes
- C08G18/0895—Manufacture of polymers by continuous processes
-
- 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
- C08G18/00—Polymeric products of isocyanates or isothiocyanates
- C08G18/06—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen
- C08G18/28—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen characterised by the compounds used containing active hydrogen
- C08G18/40—High-molecular-weight compounds
- C08G18/42—Polycondensates having carboxylic or carbonic ester groups in the main chain
- C08G18/4266—Polycondensates having carboxylic or carbonic ester groups in the main chain prepared from hydroxycarboxylic acids and/or lactones
- C08G18/4286—Polycondensates having carboxylic or carbonic ester groups in the main chain prepared from hydroxycarboxylic acids and/or lactones prepared from a combination of hydroxycarboxylic acids and/or lactones with polycarboxylic acids or ester forming derivatives thereof and polyhydroxy compounds
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- 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
- C09D175/00—Coating compositions based on polyureas or polyurethanes; Coating compositions based on derivatives of such polymers
- C09D175/04—Polyurethanes
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- Chemical & Material Sciences (AREA)
- Organic Chemistry (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Medicinal Chemistry (AREA)
- Polymers & Plastics (AREA)
- Health & Medical Sciences (AREA)
- Engineering & Computer Science (AREA)
- Materials Engineering (AREA)
- Life Sciences & Earth Sciences (AREA)
- Wood Science & Technology (AREA)
- Manufacturing & Machinery (AREA)
- Application Of Or Painting With Fluid Materials (AREA)
- Paints Or Removers (AREA)
- Polyurethanes Or Polyureas (AREA)
- Catalysts (AREA)
- Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)
Abstract
VAPOROUS AMINE CATALYST SPRAY METHOD
ABSTACT OF THE DISCLOSURE
Disclosed is a novel method for applying a film of a coating compostion in liquid form onto a substrate which applied film cures rapidly at room temperature without heat curing. The coating composition comprises an aromatic hydroxyl-functional compound and a multi-isocyanate cross-linking agent, optionally dispersed in a fugitive organic solvent therefor. The method comprises the steps of:
(a) forming an atomizing gas flow which comprises in intimate mixture of a carrier gas bearing a catalytic amount of a vaporous tertiary amine;
(b) atomizing said liquid coating composition with said vaporous catalytic amine-bearing atomizing carrier gas flow; and (c) directing said atomizate of step (b) onto said substrate to form said applied film.
ABSTACT OF THE DISCLOSURE
Disclosed is a novel method for applying a film of a coating compostion in liquid form onto a substrate which applied film cures rapidly at room temperature without heat curing. The coating composition comprises an aromatic hydroxyl-functional compound and a multi-isocyanate cross-linking agent, optionally dispersed in a fugitive organic solvent therefor. The method comprises the steps of:
(a) forming an atomizing gas flow which comprises in intimate mixture of a carrier gas bearing a catalytic amount of a vaporous tertiary amine;
(b) atomizing said liquid coating composition with said vaporous catalytic amine-bearing atomizing carrier gas flow; and (c) directing said atomizate of step (b) onto said substrate to form said applied film.
Description
1;~04347 VAPOROUS AMINE CATALYST SPRAY METHOD
Background of the lnvention .
The present invention relates to polyol polymers cured with multi-isocyan~te cross-linking agents ~nd more p~rticularly to such ~I system which is ~urable in the presence of vaporous tereiary smine cdtalyst wherein no curing chtlmber i8 required.
S Vapor permeation curable co~tings are a CldS~ of costings formulated from dromatic-hydroxyl functiondl polymers and multi-isocyandte cross-linlcing ~geneswherein an dpplied film thereof-is cured by exposure to a vaporous tertiary ~mine cat~lyst. In order to contain and h~ndle the vaporou~ tertiary amine c~ltalyst economicallp and safely, curing ch-lmbers, eg. U.S. Pat~. Nos. 3,851,402 ~nd 3,931,684, were developed. Such curing chambers typic~y are substantially empty rectangular boxes through which a conveyor bearing the co~ted substrate passes.
Provision is made for entrPnce and exit of vaporous tertiary amine, normally borne by an inert gas carrier such as nitrogen or carbon dioxide, for example, and me~n~ at the inlet and the outlet of the chdmber to enhance containment of the vaporous 15 tertiary amine catalyst within the chamber. The inlet ~nd outlet contdin mesns further restrict the entrance of oxygen into the chdmber bec~use oxygen can credte dn explosive condition with the vaporous tertiary amine catalyst. Cure of such COdtingS i5 SO tapid that no external source of heat is required. An apparent drawback of such curing chambers is the capital investment required and the amouAt 20 of space which such curing chambers occupy in the plant. For example, such chdmbers can range up to 40 or 5û feet or longer in order to ensure sufficient contact time between the cur~ble coated substr~te dnd vdporous amine atmosphere.Also, ch~mbers must be specidlly designed in order to handle large parts, eg.
~dutomotive parts, for curing. While such ch~mbers can be engineered, extra expense 25 in their manufacture, operation, and maintendnce is required.
One proffered dlternative to such vapor permeation curing chambers is the use of dual component spr~ying systems. For example, commerci~l spray equipment includes spray guns ~d~pted to spray liquid codting compositions which must be sepdrated from ~ source of catalyst. Such systems norm~lly employ a mixing he~ld30 or manifold which immediately preceeds the spray tip. Such delayed mixing in the sprdy process minirnizes the opportunity for the c talyst and coating composition to ~204347 prematurely geL Excellent discussions of such dual component or catalyst spraying can be found in the Finishing Handbook, Chapter 4, p.227 (1973); Volume 38, No. 6 (June, 1975); pp 48-55 (March, 197B); dnd Chapter 4, pp 195-230, especially page 223 (1981). The liquid c~talyst, optionally dispersed in solvent, i9 shown to be delivered S under pressure of air to the spray gun as is the liquid coating composition.
Another dual spray method involves the simultaneous sprdying from two spray nozzles of the liquid coating composition and cAtalyst component separately dS
proposed in U.S. Pat. No. 3,960,644. U.S. Pat. No. 3,049,439 provides a design for a spray gun wherein the accelerator or cat~lyst and resin are premixed within the 10 spray gun in an atomizing chsmber immediately prior to exiting from the gun. U.S.
Pat. No. 3,535,151 describes the selective addition of water und a thickener to a substantially dry liquid polyester resin in the spray gun as the polyester resin is being sprayed. U.S. Pat. No. 3,893,621 proposes a multi-nozzled spray gun which discharges an dirless spray of liquid promoted resin from d first pair of nozzles and 15 low pressure air ~tomized liquid caWyst from a second pair of nozzles wherein each atomized stream is mixed by intersection of each atomized stream exiting the sprdy gun immediately prior to deposition onto d substrate. U.S. Pat. No. 4,322,460 proposes to utilize a conventional tw~component sprdy nozzel with mixing of a polyester resin and a benzoyl peroxide catalyst dissolved in cyclohexanone in the 20 mixing head of the spray nozzle. U.S. Pat.No. 3,249,304 proposes to eliminate the possible polymerization of the catalyzed liquid resin within the mixing head of the spruy gun during periods when the gun is not being used by providing a solvent wash line which flushes the mixing chamber during periods when the codting composition dnd catalyst are not fed into the spray gun. U.S. Pat. No. 3,179,341 provides yet 25 ~nother design for the mixing head within the spray gun for multi-component systems which include d resln and catalyst therefor. U.S. Pat. No. 1,841,07~
intersects d spr~y of coagul~ble rubber and coagulunt vupor wherein the coagulable rubber streams dre created from two separ~te spray nozzles. Similarly, U.S. Pat.No. 2,249,205 takes two sep~rate spray guns ~nd intersects a streum of removable30 latex and atomized fluid coagul~nt which intermixed stredms then are applied to a substrate. U.S. Pat. No. 4,195,148 (and 4,234,445) utilizes a conventional internally mixed spray gun as described above for spraying a mixture of d polyurethane prepolymer and ~n isocyanate curative therefor.
As the Examples will demonstrate, the obvious choice of a conventional two-35 component mixing spray nozzle for use with vapor permeation curable coatings WllSunsatisfactory because the cutalyzed liquid codting composition gelled so r~pidly thdt the spr~y gun became suîficiently plugged and spraying ceased. Thus, d new method for utilizing spray applicdtion for vapor permeation curllble coatings WdS
required. The present invention is directed to such a novel spray method.
Broad Stdtement of the lnvention . . _ The present invention is a method for spplying a film of ~ liquid coating composition onto a substrate wherein the liquid co~ting composition comprises anarom~tic hydroxyl-bearing compound and a multi-isocyanate cross-linking agent, optionally dispersed in fugitive organic solvent therefor. The liquid codting composition cures rapidly at room temperature in the presence of a vaporous 10 tertidry amine catalyst without the necessity for curing heat being applied. The novel method of the present invention comprises forming un atomizing gas flow comprising an intimate mixture of an at~mizing grlS bearing a catalytic ~mount of a vaporous terti.lry amine; eltOmiZing said liquid coating composition with ~aid vaporous catalytic amine-beQring atomizing gas flow; and directing the atomizdte15 onto said substrate to form said applied film. The atomizing gas may be an inert gas or m~y be air (eg moleculdr oxygen). The temperature and pressure of the atomizing gas flow cQn be adjusted to provide the desired concentration of vaporous tertiary ~mine cat~lyst therein ~nd/or additional c~rrier gas can be added to such stream prior to the spray gun to ddjust the concentration of vllporous tertiary amine 20 c~ltalyst. aor~entional eleci:rostatic spra~ techniques also ~ be ~l,oye~.
Advantages of the present invention include the fact that a large7 cumbe~
some, and expensive curing chamber are not required for cure of the vapor permeation curable coatings without sacrifice of performance of the cured coatings.
Another advantage is the flexibility provided by the novel vaporous amine catdlyst 25 spray method to Hpply coatings to a variety of p rts which are unsuitable or impractical for curing in a chamber. Another advantdge is that the speed of cure of the applied film is rapid and substantially equivalent to the speed of cure obtained within a curing chamber. Yet another advantage which will become dpparent in theExamples is that the novel vaporous amine catalyst spray method provides the 30 lbility to utilize multi-isocyandte curing agents containing only or predominating in ~liph~tic isocy~nate which class of isocyandtes have heretofore not been recom-mended for use in vapor permeation curable coatings. These and other ~dv~ntages will become readily app~rent to those skilled in the art based upon the disclosure cont~ined herein.
1~434'7 Detailed Descriytion of the Invention A unique achievement of the novel vaporous amine cdtslyst spray method of the present invention is the lack of intensive c~pitAl investment required to implement the invention compared to convention~ vapor permeation curable tech 5 nology utilizing a curing chamber. Thdt is, the equipment required for the novel vaporous ~mine cat~lyst spr~y method include an dmine generator, d conventional single component spray gun, a conventional paint sprdy booth or hood, dnd conventional amine scrubbing equipment. Except for the spray gun and spray booth, the remaining equipment is required in practicing conventional vdpor permedtion 10 curable coating~ with a curing chdmber. The spray gun and spray booth, however, are conventional and normally found within plants that have conventional coating~
lines. The coatings need not be altered in formulation, but for perhaps a viscosity adjustment, for use in the novel vaporous amine cat~lyst spray method disclosed herein. Thus, the invention easily can be adapted to and implemented in paint spray 15 line~ of current commercidl design. As will become more readily apparent 2rom the following discussion and Examples, the coated parts can be readily handled within a short period of time following coating, eg. 5-15 minutes, which means that shorter lines can be tolertlted in the plant. Moreover, as the Examples will demonstrate, if mild forced-air heating is applied to the coated substrates, solvent removal from the 20 films will be dccelerated and curing times dramaticaUy decreased.
Referring to the liquid coating compositions which may be used in the vaporous amine catslyst spray method of the present invention, virtually ~ny vapor permeation curable coatlng formulation can be cured according to the novel method of the present invention. Typical vapor perlDeation curable coatings formuldtions 25 compri~e an aromati~hydroxyl functional polymer or resin, a multi-isocyandte curing agent which conventionally contains significant aromdtic isocyanate content, and optionally a fugitive organic solvent therefor. With respect to the aromatichydroxyl-cont~ining polymer or resin, U.S. Patent No. 3,409,579 discloBe~ d binder composition of a phenol-dldehyde resin (including resole, novolac, and resitole), 30 which preferably is ~ benzylic ether or polyether phenol resin, a liquid poly-isocyanate, and d tertiary amine curing dgent (which mdy be in vaporous form) dispersed in an organic solvent. U.S. Patent No. 3,676,392 disclose3 d resin composition in dn organic solvent composed of a polyether phenol or a methylol-terminated phenolic (resole) resin, a liquid polyisocyan~te, and a basic curing agent.
35 U.S. Patent No. 3,429,84R discloses a composition like that in U.S. Patent No.
3,409,579 with the addition of a silane thereto.
34~ 1 1 U.S. Patent No. 3,789,044 is directed to a curable composition composed of a polyepoxide resin capped with hydroxybenzoic acid, a polyisocyanate, and a tertiary amine which may be in gaseous form. U.S. Patent No. 3,822,226 discloses d cur~ble composition composed of a phenol reacted wi~h ~n unsaturated material selected 5 from unsaturated fatty acids, oils, fatty acid esters, butadiene homopolymers,butadiene copolymers, alcohols, /md acids; a polyisocyRnate; und a tertiary amine which may be in gaseous form. U.S. Patent No. 3,836,491 discloses a curable composition composed of a hydroxy functional polymer (eg., polyester, acrylic, polyether, etc.) capped with hydroxybenzoic acid, a polyisocyanate, and a tertiary 10 amine which may be in gaseous form. British Patent No. 1,369,351 is directed to a resinous composition which is curable by exposure to vaporous amine or upon contact ~vith a liquid amine wherein the composition comprises a polyisocyandte and a hydroxy or epoxy compound which has been capped with a diphenolic acid. British Patent No. 1,351,881 modifies a polyhydroxy, polyepoxy, or polycarboxyl resin with 15 the reaction product of a phenol and an aldehyde which modified resin contains free phenolic hydroxyl grou~s which then can be reacted with a polyisocyanate in the presence of a liquid or gaseous tertiary amine for obtaining cros~-linking and curing of the composition. Much of the material in the foregoing references is discussed in paper entitled "Vapor Permeation Curing", FATIPEC Congress, 11, 1972, pp 335-342.
U.S. Patent No. 2,967,117 shows d coating composed of d polyhydroxy polyester and a polyisocyanate which is cured in the presence of a gaseous tertiary amine. U.S. Patent No. 4,267,239 proposes to react para-hydroxybenzoic acid withan alkyd resin and cure the product with an isocyanate curing agent, optionally with a vaporous tertiary amine cdt~lyst. U.S. Patent No. 4,298,658 proposes an alkyd 25 resin modified with 2,6-dimethylol-p-cresol which is cured with an isocyQnate curing agent, optionally with a vaporous tertiary amine.
More recent and presently preferred aromatic hydroxyl-functional polymers, though, include U.S. Pats. Nos. 4,343,839; 4,3~5,039; and 4,374,167 which disclose polyester resin coatings especially adapted for flexible substrates and which 30 comprises an aromatic hydroxyl-functional condensation product, a multi-isocyanate curing agent, a volatile organic solvent therefor, and a unique mar-resisting agent of an organic compound physically incompatible in the coating composition and having an effective chain length of at least about 12 carbon atoms. U.S. Pat. No. 4,374,181 discloses coatings especially adapted for reaction injection molded ~RIM) urethane 3S parts which is composed of an aromatic hydroxyl functional condensation product comprising a linear aliphatic dibasic acid, a linear aliphatic glycol, and a combina-tion of a linear aliphatic glycol and aromatic dicarboxylic acid, and a phenol-c~pping 12~43~7 agent~ wherein molecular weight dnd equivAlent weight L~re closely controlled. Amulti-isocyanate curing ~gent and voldtile orgdnie solvent dre included in the coating composition. U.S. Pat. No. 4,331,782 discloses d hydroxybenzoic acid-epoxy adduct for c~pping polyester resins idedlly suited for vdpor permedtion curable 5 coating compositions. U.S. Pat. No. 4,343,924 proposes a stsbilized phenol-function~ll condensdtion product of a phenol-aldehyde re~ction product bearing aplurality of methylol dnd phenol groups, and a polyol, polycarboxylic dcid, or polyepoxide, wherein the condensation product is reacted with a selective trdns-methylolating agent for substantially transforming residual methylol groups into10 non-active hydrogen groups. The stabilized phenol-functionQl condensation product is combined with a multi-isocyan~te cross-linking ~gent, and an organic solvent therefor for vdpor permeation curing. U.S. Pat. No. 4,366,193 discloses the use of dn aromatic hydroxyl-functional compound comprising substituted or unsubstituted1,2-dihydroxybenzene or derivatives thereof for vapor permeation curdble codtings.
15 U.S. Pat. No. 4,368,222 discloses the uniqueness of utilizing vdpor permeation curable co~ltings for surface-porous substrdtes of fibrou~-reinforced molding com-pounds (eg. SMC) for minimizing surfdce irnperfections in the cured codting.
U.S. Patent 4,396,647 discloses the use.of trihydroxy diphenyl for vapor permeation curingO
It will be dppreciated thdt additionel aromatic-hydroxyl polymers dnd resins can be ut.lized in forming v~por permedtion curable codting compositions for use in the novel vaporous amine c~t~lyst spr~y method disclosed herein. So long as the polyol is curdble with a multi-isocyanate curing agent in the presence of a vdporous tertiary dmine ~nd is spr~yable (i.e. sufficiently liquid on its own, by he~ting, or by 25 dispesing in a solvent), such polyol is suitable for use in the present invention.
Multi-isocyandte cross-linking ~Igents cross link with the dromdtic hydroxyl groups of the resulting adduct-capped polymer under the influence of a vaporous~tertiary amine to form urethane linkages and to cure the codting. Aromdtic isocyandtes are preferred in order to obtain the desired rapid redction in the 30 presence of the vaporous tertiary amine catalysts ~t room temperdture. For high performance codtings, initial color as well as the discoloration due to sunlight can ---be minimized by including at least a moderate lf-vel of aliphatic isocyanate content in the curing agent. Of course, polymeric isocyanates are employed in order to reduce toxic vapors of iSoCyandte monomers. Further, dlcohol-modified dnd other 35 modified isocyandte compositions find utility in the invention. Multi-isocyandtes preferably will have from about 2-4 isocydnate groups per molecule for use in the coating composition of the present invention. SuitaMe multi-isocyanates for use in the present invention include, for example, hexamethylene diisocyanate, 4,4'-toluene diisocyanate (TDI), diphenylmethane diisocy~nate (MDI~, polymethyl polyphenyl 5 isocyanate (Polymeric MDI or PAPI), m- and p- phenylene diisocyan~tes, bitolylene diisocyanate, triphenylmethane triisocyanate, tris-(4-isocyandtophenyl) thiophos-phate, cyclohexane diisocyanate (CHDI), bis-(isocyanatomethyl) cyclohexane (H6XDI), dicyclohexylmeth~me diisocyunate t~l2MDI), trimethylhexane diisocyan-ate, dimer ucid diisocyan~te (DDI), dicyclohexylmethane diisocyanste, and dimethyl 10 derivatives thereof, trimethyl hexamethylene diisocyanate, lysine diisocyan~te and its methyl ester, isophorone diisocyQnate, methyl cyclohexane diisocyanate, 1,5-napthslene diisocyanate, triphenyl methane triisocyanate, xylylene diisocyanate and methyl and hydrogenQted derivatives thereof, polymethylene polyphenyl isocyanates, chlorophenylene-2,4-diisocyanate, and the like and mixtures thereof. Aromatic and 15 aliphatic poly-isocyanate dimers, trimers, oligomers, polymers (including biuret and isocyanurate derivatives), ~nd isocyanQte functional prepolymers often are available as preformed packages and such packages are suitable for use in the present invention also.
The ratio of aromatic hydroxyl equivalents from the phenol-functional com-20 pound to the isocyanate equivalents of the multi-isocyanate cross-linking egent should preferdbly be greater than 1:1 and can range on up to about 1:2. The precise intended applicetion of the coating composition often will dictate this ratio orisocyanate index. At high cross-linking densities or isocyanate equivàlents, harder but relatively inflexible films sre produced while ut lower cross-llnking densities or 25 isocyanate equivalents flexibility of the fllms increases. Optimizing the particular property or combination of properties desired can be determined as those skilled in this art will appreciate.
The solvent or vehicle for the coating composition is a volatile organic solventmixture which preferably includes ketones and esters for minimizing viscosity of the 30 composition. Some aromatic solvents may be necessary and typically are a part of the volatiles in commercial isocyanate polymers. For the polyol resin, suitable solvents include, for example, methyl ethyl ketone, acetone, methyl isobutyl ketone, ethylene glycol monoethyl ether acetate tsold under the trademark Cellosolve acetate) and the like. Some solvents can be too volatile so that mixtures may be35 preferred. For the polyisocy nate, conventional commercially available solvents therefor include toluene, xylene, Cellosolve acetate (Cellosolve is a registered 34~7 trademark and Cellosolve ncetate is ethylene glycol monoethyl ether acetate), and the like. Such arom~tic solvents are quite compatible with the preferred ketone and ester solvents for the polyester resin when the two package3 are mixed together in the pot. Sufficient solvent usually is added in order to bring the non-volatile solids 5 content to the coating composition down to about 50-80% by weight for achieving a practical spray application viscosity, depending upon pigmentation. It should benoted that the effective non-volatile solids content of the coating composition can be increased by incorporation of a rel~tively low or non-volatile (high boiling) ester plasticizer which is retained for the most part in the cured film. Suitable such ester 10 plasticizers include, for example, dibutyl phthlate, di(2-ethylhexyl) phthlate 1DOP], and the like. The proportion of ester plasticizer should not exceed about 5-10% by weight, otherwise loss of m~r resistdnce can occur.
It will be appreciated that additional solvent often may be required in order toachieve an dppropriate viscosity for spray of the coating composition according to 15 the precepts of the present invention. The precise viscosity required of the coating composition most often will be dictllted by the particular manufacturer's brand of spray equipment utilized, though application onto vertically disposed parts, forexample, may ulter the viscosity requirements of the coating composition in order to prevent the running and dripping of the coating composition.
As to the performance requirements which are met by the co~ting composi-tion, it should be noted the coating composition, polyol resin and isocyanate cross-linking agent, h~ve ll minimum pot liIe of at least 4 hours in ~n open pot and generally the pot life exceeds 8 hours and can range up to 18 hours and more. Such long pot lives means that refilling the pot at the plant during shifts generally is not 25 required. Moreover, the pot life of the coating composition in a closed cont~iner generdlly exceeds one month. After storage of the coating composition, the stored composition can be cut to application viscosity with suit/~ble solvent and such composition retains all of the excellent performance characteristics which it initidlly possessed.
Additional ingredients which suitably can be incorporated into the coating composition of the present invention include tinctoridl pigments, plasticizers, flatting agents, flow leveling agents, and a wide variety of conventional paint additiYes.
It should be added that a co~lting composition (eg. polyol, multi-isocyanate 35 cross-linker and optional solvent) is suitable for use in the present invention if it can be tr~nsported or conveyed through lines to the spray nozzle and thence atomized 12~434~7 g with the vaporous amine catalyst atomizing gas stre~m. Most often, this trdnsldtes into the codting composition being liquid. For present purposes, d liquid codting composition comprehends a coating composition which is liquid at room temper~-ture, can be made liquid for spraying by hedting, or is made liquid by dispersing in S solvent for spraying. Any manner by which the co~ting composition cun be liquefied or rendered liquid for sprsying by atomization is suitable for use in the present invention providing that the vupor permedtion cure chemistry is mdintained.
The vaporous amine cutulyst will be a tertiary amine such ~, for example, triethyl amine, dimethyl ethyl amine, cyclohexyl dimethyl amine, methyl diethyl 10 amine, dnd the like. The proportion of vaporous ~mine c~talyst may range from as low as a percent or less on up ~o six percent or more. It should be cautioned that higher levels of amine catalyst are not recommended where air or sources of moleculdr oxygen are present ~s explosive mixtures msy result. The tertiary amine catalyst is in vaporous form in a carrier gas which may be inert, such as nitrogen or 15 carbon dioxide, or may be in flir, or mixtures thereof. It will be dpprecidted that depending upon the carrier gas and the particular tertiary amine catdlyst of choice, that certain minimum temperatures and pressures of the atomizing gas stre~m mustbe maintained in order to ensure th~t the amine catalyst remains vdporous and does not condense in any lines. Mdintenance of the tertidry amine catdlyst in vapor 20 phsse, though, is within the skill of routine engineering.
As to the type of eguipment required to generate the vdporous amine and deliver the vuporous amine in carrier gas, a variety of amine vapor generators are commercially manufdctured and most often utilized with the cold box process in the foundry industry. Various types of dmine generators in common use include the 25 liquid injector type and the vaporizer type. The injector type amine generator forces liquid amine into a stream of fast-moving carrier gas, either compressed air or inert gas such as dry C02 or N2. The turbulent c~rrier stre,3m evaporates thevolatile amine and transports it to the spr~y gun. The amine catalyst is forced into the carrier gas line by one of two mechanisms. The first mechanism is d calibrated 30 piston operating aguinst check or diverter valves. The second method is d pressurized amine holding tunk wfiich delivers amine for a pre-set length of time.
The vuporizer type of amine generator sccomplishes the gasification of the aminecdtalyst either by bubbling carrier gas through a deep bath of liquid amine (bubbler type), or by heating (boiling) the dmine prior to blending with the carrier gas 35 (proportioner type). All of the dcceptable commercial generator types and variations thereof have the dbility to deliver vaporous umine in u short period of :~L20434~
time and can be suitably modified to provide a sufficient volume typically utilizing an accumulator for providing surge capacity as required for extended periods of demand on the amine generator system. Of course, all lines will be steam traced or otherwise heated in order to ensure that the vaporou~ amine cutalyst does not 5 condense in any of the lines. Also, the amine generators and accumulators mostoften will be heated for the same purpose. A representative amine vapor generator used in the foundry core industry is shown in U.S. Pat. No. 4,05~,886.
From the amine generator or accumulator, the atomizing gas flow bearing catalytic vaporous tertiary amine will be tr~msported, preferably through stenm 10 traced or heated piping, to the Qpray gun. Nominally any conventionul or unconventional spray gun for spraying of liquid coating or paint composition can be used according to the precepts of the present invention. The atomizing gas flow bearing vuporous tertiary amine will be the atomizing gas which will atomize theliquid coating composition in convention~ f~shion through the spray gun. Most 15 often the atomizing ga~ now will be heated to a temperature sufficient to ensure that the vaporous tertiary amine remains in its vapor phase. It also is possible to preheat the liquid co~lting composition for ensuring appropriate viscosity for sprsying and/or to achieve special effects. Because tertiary amine is being exh~usted from the spray gun, ~afety and environmental precaution dictates that 20 operation of the vsporous amine catalyst spray gun be conducted in a conventional paint spray booth or paint spray hood. Such paint ~pray booths are so convention~l that no further description of them need be detailed here. It is to be noted that the spray booth exhaust can be vented to the atomosphere or the amine can be sent to a conventional scrubbing system, typically using an acid such QS sulfuric acid or 25 phosphoric acid, or otherwise disposed of in conventional fashion.
Because of the unique intimate contact between the vaporous tertiary amine from the atomizing gas flow and the atomized liquid coating composition, thick-nesses of the coating composition on substrates can become quite thick and full cure still achieved. This is to be contrasted with conventional vapor permeation cure30 technology utilizing d vapor cure chamber wherein extremely thin films must be cured in order to ensure complete diffusion of the vaporous amine through the film thickness. Film thicknesses of 10 to 15 mils or more (dry), however, can be successfully applied and cured dccording to the vaporous amine catalyst spray method of the present invention. The coated part can be permitted to air dry at 35 ambient indoor temperature and rapid curing will take place. Norm-qlly, shorter lines at the plant will be required because the codting becomes tack-free in such d i~O43~'7 short time. Moreover, convention~l b~lking ovens dre no longer required. The speed of cure, however, cdn be ~cceler~ted even more by ~ugmenting the solvent being expelled from the applied film. Such solvent expulsion c~m be augmented or enhdnced by post-conditioning most reddily tlccomplished by thermdl medns. Thdt 5 is, the v~poroua amine cdt~llyst spr~y-applied coating on the substrate can beexposed to low to moderate he~t (eg. ~bout 50-150C desirably, for ~ short time, eg.
about 1-5 minutes desirdbly). Of course, incre~lsed hetlting temper-~tures usually medn shorter treatment time~ and vice versa. Such hedt conditioning or treatmentis practiced under conditions fllr short of those (eg. time and ternper~ture) necessary 10 for hedt curing an isocydn~te/polyol coating, especially since no c~t~yst i5 ddded during such thermal conditioning.
The following Exdmples show how the present invention c~n be practiced but should not be construed aS limiting. In thi~ applicdtion~ dll percent~ges and proportions dre by weight and ~11 units ~re in the metric system, unless otherwise 15 expressly indicated.
IN THE EXAMPLES
In the Ex~mples, the novel vapor permeation cure sprdy method employed a DeVilbiss~nodel MBC 510-36EX siphon spray gun (1.778 mm orifdce, 10~12 cc/min 20 rated nOw rdte, gas consumption of 3.07 L/sec dt 2.1 kg/cm2 pressure, fdn spray pdttern, DeVilbiss Company, Toledo, Ohio 43692). The dir input of the sprdy gun was connected to a heated accumulator maintained at ~ temperature of dbout 38C
(100F). The dccumuldtor contained nitrogen bearing 2.7% triethyldmine (TEA) catalyst vapor held at a totdl pressure of about 4.2 kg/cm2 (60 psi).
The TEA nitrogen stream was generated by an dmine generdtor composed of a 190 L (50 gal) tdnk cont~lining 114 L (30 gal.) of liquid TEA (38C and 1.4 kg~cm23.
the tank w~s fitted with a 7.62 cm (3 in.) diarneter pdcked (152.5 cm of Koch Sulzer dense p~cking) column fitted with d spray nozzle and conventional rnist elimindtor.
Liquid TEA WdS pumped dt d ra~e of dbout 3.8 L/min. to the sprdy nozzle which 30 sprdyed the liquid TEA down onto the packing. Nitrogen WdS buboled through the column to gredter than 95% sdturdtion dnd sent to the accumulator. - The dmine generdtor is detailed further in dttorney's docket ASH 4469 of Maher L. Mansour.Compdrdtive spray tests dlso were conducted wherein the liquid codting cornposition WdS mixed with liquid triethylamine c~talyst in the mixing head of a 35 DeVilbiss model ~BC 510-AV601-FX siphon spray gun hdving d MBC 444 FX fluid * Trademark .~
1~043~
needle (1.067 mm orifdce, 10-30 cc/min rated flow rate, ~ir consumption of 3.07 L/sec at 2.1 kg/cm pressure). Air was delivered to the spray gun at
Background of the lnvention .
The present invention relates to polyol polymers cured with multi-isocyan~te cross-linking agents ~nd more p~rticularly to such ~I system which is ~urable in the presence of vaporous tereiary smine cdtalyst wherein no curing chtlmber i8 required.
S Vapor permeation curable co~tings are a CldS~ of costings formulated from dromatic-hydroxyl functiondl polymers and multi-isocyandte cross-linlcing ~geneswherein an dpplied film thereof-is cured by exposure to a vaporous tertiary ~mine cat~lyst. In order to contain and h~ndle the vaporou~ tertiary amine c~ltalyst economicallp and safely, curing ch-lmbers, eg. U.S. Pat~. Nos. 3,851,402 ~nd 3,931,684, were developed. Such curing chambers typic~y are substantially empty rectangular boxes through which a conveyor bearing the co~ted substrate passes.
Provision is made for entrPnce and exit of vaporous tertiary amine, normally borne by an inert gas carrier such as nitrogen or carbon dioxide, for example, and me~n~ at the inlet and the outlet of the chdmber to enhance containment of the vaporous 15 tertiary amine catalyst within the chamber. The inlet ~nd outlet contdin mesns further restrict the entrance of oxygen into the chdmber bec~use oxygen can credte dn explosive condition with the vaporous tertiary amine catalyst. Cure of such COdtingS i5 SO tapid that no external source of heat is required. An apparent drawback of such curing chambers is the capital investment required and the amouAt 20 of space which such curing chambers occupy in the plant. For example, such chdmbers can range up to 40 or 5û feet or longer in order to ensure sufficient contact time between the cur~ble coated substr~te dnd vdporous amine atmosphere.Also, ch~mbers must be specidlly designed in order to handle large parts, eg.
~dutomotive parts, for curing. While such ch~mbers can be engineered, extra expense 25 in their manufacture, operation, and maintendnce is required.
One proffered dlternative to such vapor permeation curing chambers is the use of dual component spr~ying systems. For example, commerci~l spray equipment includes spray guns ~d~pted to spray liquid codting compositions which must be sepdrated from ~ source of catalyst. Such systems norm~lly employ a mixing he~ld30 or manifold which immediately preceeds the spray tip. Such delayed mixing in the sprdy process minirnizes the opportunity for the c talyst and coating composition to ~204347 prematurely geL Excellent discussions of such dual component or catalyst spraying can be found in the Finishing Handbook, Chapter 4, p.227 (1973); Volume 38, No. 6 (June, 1975); pp 48-55 (March, 197B); dnd Chapter 4, pp 195-230, especially page 223 (1981). The liquid c~talyst, optionally dispersed in solvent, i9 shown to be delivered S under pressure of air to the spray gun as is the liquid coating composition.
Another dual spray method involves the simultaneous sprdying from two spray nozzles of the liquid coating composition and cAtalyst component separately dS
proposed in U.S. Pat. No. 3,960,644. U.S. Pat. No. 3,049,439 provides a design for a spray gun wherein the accelerator or cat~lyst and resin are premixed within the 10 spray gun in an atomizing chsmber immediately prior to exiting from the gun. U.S.
Pat. No. 3,535,151 describes the selective addition of water und a thickener to a substantially dry liquid polyester resin in the spray gun as the polyester resin is being sprayed. U.S. Pat. No. 3,893,621 proposes a multi-nozzled spray gun which discharges an dirless spray of liquid promoted resin from d first pair of nozzles and 15 low pressure air ~tomized liquid caWyst from a second pair of nozzles wherein each atomized stream is mixed by intersection of each atomized stream exiting the sprdy gun immediately prior to deposition onto d substrate. U.S. Pat. No. 4,322,460 proposes to utilize a conventional tw~component sprdy nozzel with mixing of a polyester resin and a benzoyl peroxide catalyst dissolved in cyclohexanone in the 20 mixing head of the spray nozzle. U.S. Pat.No. 3,249,304 proposes to eliminate the possible polymerization of the catalyzed liquid resin within the mixing head of the spruy gun during periods when the gun is not being used by providing a solvent wash line which flushes the mixing chamber during periods when the codting composition dnd catalyst are not fed into the spray gun. U.S. Pat. No. 3,179,341 provides yet 25 ~nother design for the mixing head within the spray gun for multi-component systems which include d resln and catalyst therefor. U.S. Pat. No. 1,841,07~
intersects d spr~y of coagul~ble rubber and coagulunt vupor wherein the coagulable rubber streams dre created from two separ~te spray nozzles. Similarly, U.S. Pat.No. 2,249,205 takes two sep~rate spray guns ~nd intersects a streum of removable30 latex and atomized fluid coagul~nt which intermixed stredms then are applied to a substrate. U.S. Pat. No. 4,195,148 (and 4,234,445) utilizes a conventional internally mixed spray gun as described above for spraying a mixture of d polyurethane prepolymer and ~n isocyanate curative therefor.
As the Examples will demonstrate, the obvious choice of a conventional two-35 component mixing spray nozzle for use with vapor permeation curable coatings WllSunsatisfactory because the cutalyzed liquid codting composition gelled so r~pidly thdt the spr~y gun became suîficiently plugged and spraying ceased. Thus, d new method for utilizing spray applicdtion for vapor permeation curllble coatings WdS
required. The present invention is directed to such a novel spray method.
Broad Stdtement of the lnvention . . _ The present invention is a method for spplying a film of ~ liquid coating composition onto a substrate wherein the liquid co~ting composition comprises anarom~tic hydroxyl-bearing compound and a multi-isocyanate cross-linking agent, optionally dispersed in fugitive organic solvent therefor. The liquid codting composition cures rapidly at room temperature in the presence of a vaporous 10 tertidry amine catalyst without the necessity for curing heat being applied. The novel method of the present invention comprises forming un atomizing gas flow comprising an intimate mixture of an at~mizing grlS bearing a catalytic ~mount of a vaporous terti.lry amine; eltOmiZing said liquid coating composition with ~aid vaporous catalytic amine-beQring atomizing gas flow; and directing the atomizdte15 onto said substrate to form said applied film. The atomizing gas may be an inert gas or m~y be air (eg moleculdr oxygen). The temperature and pressure of the atomizing gas flow cQn be adjusted to provide the desired concentration of vaporous tertiary ~mine cat~lyst therein ~nd/or additional c~rrier gas can be added to such stream prior to the spray gun to ddjust the concentration of vllporous tertiary amine 20 c~ltalyst. aor~entional eleci:rostatic spra~ techniques also ~ be ~l,oye~.
Advantages of the present invention include the fact that a large7 cumbe~
some, and expensive curing chamber are not required for cure of the vapor permeation curable coatings without sacrifice of performance of the cured coatings.
Another advantage is the flexibility provided by the novel vaporous amine catdlyst 25 spray method to Hpply coatings to a variety of p rts which are unsuitable or impractical for curing in a chamber. Another advantdge is that the speed of cure of the applied film is rapid and substantially equivalent to the speed of cure obtained within a curing chamber. Yet another advantage which will become dpparent in theExamples is that the novel vaporous amine catalyst spray method provides the 30 lbility to utilize multi-isocyandte curing agents containing only or predominating in ~liph~tic isocy~nate which class of isocyandtes have heretofore not been recom-mended for use in vapor permeation curable coatings. These and other ~dv~ntages will become readily app~rent to those skilled in the art based upon the disclosure cont~ined herein.
1~434'7 Detailed Descriytion of the Invention A unique achievement of the novel vaporous amine cdtslyst spray method of the present invention is the lack of intensive c~pitAl investment required to implement the invention compared to convention~ vapor permeation curable tech 5 nology utilizing a curing chamber. Thdt is, the equipment required for the novel vaporous ~mine cat~lyst spr~y method include an dmine generator, d conventional single component spray gun, a conventional paint sprdy booth or hood, dnd conventional amine scrubbing equipment. Except for the spray gun and spray booth, the remaining equipment is required in practicing conventional vdpor permedtion 10 curable coating~ with a curing chdmber. The spray gun and spray booth, however, are conventional and normally found within plants that have conventional coating~
lines. The coatings need not be altered in formulation, but for perhaps a viscosity adjustment, for use in the novel vaporous amine cat~lyst spray method disclosed herein. Thus, the invention easily can be adapted to and implemented in paint spray 15 line~ of current commercidl design. As will become more readily apparent 2rom the following discussion and Examples, the coated parts can be readily handled within a short period of time following coating, eg. 5-15 minutes, which means that shorter lines can be tolertlted in the plant. Moreover, as the Examples will demonstrate, if mild forced-air heating is applied to the coated substrates, solvent removal from the 20 films will be dccelerated and curing times dramaticaUy decreased.
Referring to the liquid coating compositions which may be used in the vaporous amine catslyst spray method of the present invention, virtually ~ny vapor permeation curable coatlng formulation can be cured according to the novel method of the present invention. Typical vapor perlDeation curable coatings formuldtions 25 compri~e an aromati~hydroxyl functional polymer or resin, a multi-isocyandte curing agent which conventionally contains significant aromdtic isocyanate content, and optionally a fugitive organic solvent therefor. With respect to the aromatichydroxyl-cont~ining polymer or resin, U.S. Patent No. 3,409,579 discloBe~ d binder composition of a phenol-dldehyde resin (including resole, novolac, and resitole), 30 which preferably is ~ benzylic ether or polyether phenol resin, a liquid poly-isocyanate, and d tertiary amine curing dgent (which mdy be in vaporous form) dispersed in an organic solvent. U.S. Patent No. 3,676,392 disclose3 d resin composition in dn organic solvent composed of a polyether phenol or a methylol-terminated phenolic (resole) resin, a liquid polyisocyan~te, and a basic curing agent.
35 U.S. Patent No. 3,429,84R discloses a composition like that in U.S. Patent No.
3,409,579 with the addition of a silane thereto.
34~ 1 1 U.S. Patent No. 3,789,044 is directed to a curable composition composed of a polyepoxide resin capped with hydroxybenzoic acid, a polyisocyanate, and a tertiary amine which may be in gaseous form. U.S. Patent No. 3,822,226 discloses d cur~ble composition composed of a phenol reacted wi~h ~n unsaturated material selected 5 from unsaturated fatty acids, oils, fatty acid esters, butadiene homopolymers,butadiene copolymers, alcohols, /md acids; a polyisocyRnate; und a tertiary amine which may be in gaseous form. U.S. Patent No. 3,836,491 discloses a curable composition composed of a hydroxy functional polymer (eg., polyester, acrylic, polyether, etc.) capped with hydroxybenzoic acid, a polyisocyanate, and a tertiary 10 amine which may be in gaseous form. British Patent No. 1,369,351 is directed to a resinous composition which is curable by exposure to vaporous amine or upon contact ~vith a liquid amine wherein the composition comprises a polyisocyandte and a hydroxy or epoxy compound which has been capped with a diphenolic acid. British Patent No. 1,351,881 modifies a polyhydroxy, polyepoxy, or polycarboxyl resin with 15 the reaction product of a phenol and an aldehyde which modified resin contains free phenolic hydroxyl grou~s which then can be reacted with a polyisocyanate in the presence of a liquid or gaseous tertiary amine for obtaining cros~-linking and curing of the composition. Much of the material in the foregoing references is discussed in paper entitled "Vapor Permeation Curing", FATIPEC Congress, 11, 1972, pp 335-342.
U.S. Patent No. 2,967,117 shows d coating composed of d polyhydroxy polyester and a polyisocyanate which is cured in the presence of a gaseous tertiary amine. U.S. Patent No. 4,267,239 proposes to react para-hydroxybenzoic acid withan alkyd resin and cure the product with an isocyanate curing agent, optionally with a vaporous tertiary amine cdt~lyst. U.S. Patent No. 4,298,658 proposes an alkyd 25 resin modified with 2,6-dimethylol-p-cresol which is cured with an isocyQnate curing agent, optionally with a vaporous tertiary amine.
More recent and presently preferred aromatic hydroxyl-functional polymers, though, include U.S. Pats. Nos. 4,343,839; 4,3~5,039; and 4,374,167 which disclose polyester resin coatings especially adapted for flexible substrates and which 30 comprises an aromatic hydroxyl-functional condensation product, a multi-isocyanate curing agent, a volatile organic solvent therefor, and a unique mar-resisting agent of an organic compound physically incompatible in the coating composition and having an effective chain length of at least about 12 carbon atoms. U.S. Pat. No. 4,374,181 discloses coatings especially adapted for reaction injection molded ~RIM) urethane 3S parts which is composed of an aromatic hydroxyl functional condensation product comprising a linear aliphatic dibasic acid, a linear aliphatic glycol, and a combina-tion of a linear aliphatic glycol and aromatic dicarboxylic acid, and a phenol-c~pping 12~43~7 agent~ wherein molecular weight dnd equivAlent weight L~re closely controlled. Amulti-isocyanate curing ~gent and voldtile orgdnie solvent dre included in the coating composition. U.S. Pat. No. 4,331,782 discloses d hydroxybenzoic acid-epoxy adduct for c~pping polyester resins idedlly suited for vdpor permedtion curable 5 coating compositions. U.S. Pat. No. 4,343,924 proposes a stsbilized phenol-function~ll condensdtion product of a phenol-aldehyde re~ction product bearing aplurality of methylol dnd phenol groups, and a polyol, polycarboxylic dcid, or polyepoxide, wherein the condensation product is reacted with a selective trdns-methylolating agent for substantially transforming residual methylol groups into10 non-active hydrogen groups. The stabilized phenol-functionQl condensation product is combined with a multi-isocyan~te cross-linking ~gent, and an organic solvent therefor for vdpor permeation curing. U.S. Pat. No. 4,366,193 discloses the use of dn aromatic hydroxyl-functional compound comprising substituted or unsubstituted1,2-dihydroxybenzene or derivatives thereof for vapor permeation curdble codtings.
15 U.S. Pat. No. 4,368,222 discloses the uniqueness of utilizing vdpor permeation curable co~ltings for surface-porous substrdtes of fibrou~-reinforced molding com-pounds (eg. SMC) for minimizing surfdce irnperfections in the cured codting.
U.S. Patent 4,396,647 discloses the use.of trihydroxy diphenyl for vapor permeation curingO
It will be dppreciated thdt additionel aromatic-hydroxyl polymers dnd resins can be ut.lized in forming v~por permedtion curable codting compositions for use in the novel vaporous amine c~t~lyst spr~y method disclosed herein. So long as the polyol is curdble with a multi-isocyanate curing agent in the presence of a vdporous tertiary dmine ~nd is spr~yable (i.e. sufficiently liquid on its own, by he~ting, or by 25 dispesing in a solvent), such polyol is suitable for use in the present invention.
Multi-isocyandte cross-linking ~Igents cross link with the dromdtic hydroxyl groups of the resulting adduct-capped polymer under the influence of a vaporous~tertiary amine to form urethane linkages and to cure the codting. Aromdtic isocyandtes are preferred in order to obtain the desired rapid redction in the 30 presence of the vaporous tertiary amine catalysts ~t room temperdture. For high performance codtings, initial color as well as the discoloration due to sunlight can ---be minimized by including at least a moderate lf-vel of aliphatic isocyanate content in the curing agent. Of course, polymeric isocyanates are employed in order to reduce toxic vapors of iSoCyandte monomers. Further, dlcohol-modified dnd other 35 modified isocyandte compositions find utility in the invention. Multi-isocyandtes preferably will have from about 2-4 isocydnate groups per molecule for use in the coating composition of the present invention. SuitaMe multi-isocyanates for use in the present invention include, for example, hexamethylene diisocyanate, 4,4'-toluene diisocyanate (TDI), diphenylmethane diisocy~nate (MDI~, polymethyl polyphenyl 5 isocyanate (Polymeric MDI or PAPI), m- and p- phenylene diisocyan~tes, bitolylene diisocyanate, triphenylmethane triisocyanate, tris-(4-isocyandtophenyl) thiophos-phate, cyclohexane diisocyanate (CHDI), bis-(isocyanatomethyl) cyclohexane (H6XDI), dicyclohexylmeth~me diisocyunate t~l2MDI), trimethylhexane diisocyan-ate, dimer ucid diisocyan~te (DDI), dicyclohexylmethane diisocyanste, and dimethyl 10 derivatives thereof, trimethyl hexamethylene diisocyanate, lysine diisocyan~te and its methyl ester, isophorone diisocyQnate, methyl cyclohexane diisocyanate, 1,5-napthslene diisocyanate, triphenyl methane triisocyanate, xylylene diisocyanate and methyl and hydrogenQted derivatives thereof, polymethylene polyphenyl isocyanates, chlorophenylene-2,4-diisocyanate, and the like and mixtures thereof. Aromatic and 15 aliphatic poly-isocyanate dimers, trimers, oligomers, polymers (including biuret and isocyanurate derivatives), ~nd isocyanQte functional prepolymers often are available as preformed packages and such packages are suitable for use in the present invention also.
The ratio of aromatic hydroxyl equivalents from the phenol-functional com-20 pound to the isocyanate equivalents of the multi-isocyanate cross-linking egent should preferdbly be greater than 1:1 and can range on up to about 1:2. The precise intended applicetion of the coating composition often will dictate this ratio orisocyanate index. At high cross-linking densities or isocyanate equivàlents, harder but relatively inflexible films sre produced while ut lower cross-llnking densities or 25 isocyanate equivalents flexibility of the fllms increases. Optimizing the particular property or combination of properties desired can be determined as those skilled in this art will appreciate.
The solvent or vehicle for the coating composition is a volatile organic solventmixture which preferably includes ketones and esters for minimizing viscosity of the 30 composition. Some aromatic solvents may be necessary and typically are a part of the volatiles in commercial isocyanate polymers. For the polyol resin, suitable solvents include, for example, methyl ethyl ketone, acetone, methyl isobutyl ketone, ethylene glycol monoethyl ether acetate tsold under the trademark Cellosolve acetate) and the like. Some solvents can be too volatile so that mixtures may be35 preferred. For the polyisocy nate, conventional commercially available solvents therefor include toluene, xylene, Cellosolve acetate (Cellosolve is a registered 34~7 trademark and Cellosolve ncetate is ethylene glycol monoethyl ether acetate), and the like. Such arom~tic solvents are quite compatible with the preferred ketone and ester solvents for the polyester resin when the two package3 are mixed together in the pot. Sufficient solvent usually is added in order to bring the non-volatile solids 5 content to the coating composition down to about 50-80% by weight for achieving a practical spray application viscosity, depending upon pigmentation. It should benoted that the effective non-volatile solids content of the coating composition can be increased by incorporation of a rel~tively low or non-volatile (high boiling) ester plasticizer which is retained for the most part in the cured film. Suitable such ester 10 plasticizers include, for example, dibutyl phthlate, di(2-ethylhexyl) phthlate 1DOP], and the like. The proportion of ester plasticizer should not exceed about 5-10% by weight, otherwise loss of m~r resistdnce can occur.
It will be appreciated that additional solvent often may be required in order toachieve an dppropriate viscosity for spray of the coating composition according to 15 the precepts of the present invention. The precise viscosity required of the coating composition most often will be dictllted by the particular manufacturer's brand of spray equipment utilized, though application onto vertically disposed parts, forexample, may ulter the viscosity requirements of the coating composition in order to prevent the running and dripping of the coating composition.
As to the performance requirements which are met by the co~ting composi-tion, it should be noted the coating composition, polyol resin and isocyanate cross-linking agent, h~ve ll minimum pot liIe of at least 4 hours in ~n open pot and generally the pot life exceeds 8 hours and can range up to 18 hours and more. Such long pot lives means that refilling the pot at the plant during shifts generally is not 25 required. Moreover, the pot life of the coating composition in a closed cont~iner generdlly exceeds one month. After storage of the coating composition, the stored composition can be cut to application viscosity with suit/~ble solvent and such composition retains all of the excellent performance characteristics which it initidlly possessed.
Additional ingredients which suitably can be incorporated into the coating composition of the present invention include tinctoridl pigments, plasticizers, flatting agents, flow leveling agents, and a wide variety of conventional paint additiYes.
It should be added that a co~lting composition (eg. polyol, multi-isocyanate 35 cross-linker and optional solvent) is suitable for use in the present invention if it can be tr~nsported or conveyed through lines to the spray nozzle and thence atomized 12~434~7 g with the vaporous amine catalyst atomizing gas stre~m. Most often, this trdnsldtes into the codting composition being liquid. For present purposes, d liquid codting composition comprehends a coating composition which is liquid at room temper~-ture, can be made liquid for spraying by hedting, or is made liquid by dispersing in S solvent for spraying. Any manner by which the co~ting composition cun be liquefied or rendered liquid for sprsying by atomization is suitable for use in the present invention providing that the vupor permedtion cure chemistry is mdintained.
The vaporous amine cutulyst will be a tertiary amine such ~, for example, triethyl amine, dimethyl ethyl amine, cyclohexyl dimethyl amine, methyl diethyl 10 amine, dnd the like. The proportion of vaporous ~mine c~talyst may range from as low as a percent or less on up ~o six percent or more. It should be cautioned that higher levels of amine catalyst are not recommended where air or sources of moleculdr oxygen are present ~s explosive mixtures msy result. The tertiary amine catalyst is in vaporous form in a carrier gas which may be inert, such as nitrogen or 15 carbon dioxide, or may be in flir, or mixtures thereof. It will be dpprecidted that depending upon the carrier gas and the particular tertiary amine catdlyst of choice, that certain minimum temperatures and pressures of the atomizing gas stre~m mustbe maintained in order to ensure th~t the amine catalyst remains vdporous and does not condense in any lines. Mdintenance of the tertidry amine catdlyst in vapor 20 phsse, though, is within the skill of routine engineering.
As to the type of eguipment required to generate the vdporous amine and deliver the vuporous amine in carrier gas, a variety of amine vapor generators are commercially manufdctured and most often utilized with the cold box process in the foundry industry. Various types of dmine generators in common use include the 25 liquid injector type and the vaporizer type. The injector type amine generator forces liquid amine into a stream of fast-moving carrier gas, either compressed air or inert gas such as dry C02 or N2. The turbulent c~rrier stre,3m evaporates thevolatile amine and transports it to the spr~y gun. The amine catalyst is forced into the carrier gas line by one of two mechanisms. The first mechanism is d calibrated 30 piston operating aguinst check or diverter valves. The second method is d pressurized amine holding tunk wfiich delivers amine for a pre-set length of time.
The vuporizer type of amine generator sccomplishes the gasification of the aminecdtalyst either by bubbling carrier gas through a deep bath of liquid amine (bubbler type), or by heating (boiling) the dmine prior to blending with the carrier gas 35 (proportioner type). All of the dcceptable commercial generator types and variations thereof have the dbility to deliver vaporous umine in u short period of :~L20434~
time and can be suitably modified to provide a sufficient volume typically utilizing an accumulator for providing surge capacity as required for extended periods of demand on the amine generator system. Of course, all lines will be steam traced or otherwise heated in order to ensure that the vaporou~ amine cutalyst does not 5 condense in any of the lines. Also, the amine generators and accumulators mostoften will be heated for the same purpose. A representative amine vapor generator used in the foundry core industry is shown in U.S. Pat. No. 4,05~,886.
From the amine generator or accumulator, the atomizing gas flow bearing catalytic vaporous tertiary amine will be tr~msported, preferably through stenm 10 traced or heated piping, to the Qpray gun. Nominally any conventionul or unconventional spray gun for spraying of liquid coating or paint composition can be used according to the precepts of the present invention. The atomizing gas flow bearing vuporous tertiary amine will be the atomizing gas which will atomize theliquid coating composition in convention~ f~shion through the spray gun. Most 15 often the atomizing ga~ now will be heated to a temperature sufficient to ensure that the vaporous tertiary amine remains in its vapor phase. It also is possible to preheat the liquid co~lting composition for ensuring appropriate viscosity for sprsying and/or to achieve special effects. Because tertiary amine is being exh~usted from the spray gun, ~afety and environmental precaution dictates that 20 operation of the vsporous amine catalyst spray gun be conducted in a conventional paint spray booth or paint spray hood. Such paint ~pray booths are so convention~l that no further description of them need be detailed here. It is to be noted that the spray booth exhaust can be vented to the atomosphere or the amine can be sent to a conventional scrubbing system, typically using an acid such QS sulfuric acid or 25 phosphoric acid, or otherwise disposed of in conventional fashion.
Because of the unique intimate contact between the vaporous tertiary amine from the atomizing gas flow and the atomized liquid coating composition, thick-nesses of the coating composition on substrates can become quite thick and full cure still achieved. This is to be contrasted with conventional vapor permeation cure30 technology utilizing d vapor cure chamber wherein extremely thin films must be cured in order to ensure complete diffusion of the vaporous amine through the film thickness. Film thicknesses of 10 to 15 mils or more (dry), however, can be successfully applied and cured dccording to the vaporous amine catalyst spray method of the present invention. The coated part can be permitted to air dry at 35 ambient indoor temperature and rapid curing will take place. Norm-qlly, shorter lines at the plant will be required because the codting becomes tack-free in such d i~O43~'7 short time. Moreover, convention~l b~lking ovens dre no longer required. The speed of cure, however, cdn be ~cceler~ted even more by ~ugmenting the solvent being expelled from the applied film. Such solvent expulsion c~m be augmented or enhdnced by post-conditioning most reddily tlccomplished by thermdl medns. Thdt 5 is, the v~poroua amine cdt~llyst spr~y-applied coating on the substrate can beexposed to low to moderate he~t (eg. ~bout 50-150C desirably, for ~ short time, eg.
about 1-5 minutes desirdbly). Of course, incre~lsed hetlting temper-~tures usually medn shorter treatment time~ and vice versa. Such hedt conditioning or treatmentis practiced under conditions fllr short of those (eg. time and ternper~ture) necessary 10 for hedt curing an isocydn~te/polyol coating, especially since no c~t~yst i5 ddded during such thermal conditioning.
The following Exdmples show how the present invention c~n be practiced but should not be construed aS limiting. In thi~ applicdtion~ dll percent~ges and proportions dre by weight and ~11 units ~re in the metric system, unless otherwise 15 expressly indicated.
IN THE EXAMPLES
In the Ex~mples, the novel vapor permeation cure sprdy method employed a DeVilbiss~nodel MBC 510-36EX siphon spray gun (1.778 mm orifdce, 10~12 cc/min 20 rated nOw rdte, gas consumption of 3.07 L/sec dt 2.1 kg/cm2 pressure, fdn spray pdttern, DeVilbiss Company, Toledo, Ohio 43692). The dir input of the sprdy gun was connected to a heated accumulator maintained at ~ temperature of dbout 38C
(100F). The dccumuldtor contained nitrogen bearing 2.7% triethyldmine (TEA) catalyst vapor held at a totdl pressure of about 4.2 kg/cm2 (60 psi).
The TEA nitrogen stream was generated by an dmine generdtor composed of a 190 L (50 gal) tdnk cont~lining 114 L (30 gal.) of liquid TEA (38C and 1.4 kg~cm23.
the tank w~s fitted with a 7.62 cm (3 in.) diarneter pdcked (152.5 cm of Koch Sulzer dense p~cking) column fitted with d spray nozzle and conventional rnist elimindtor.
Liquid TEA WdS pumped dt d ra~e of dbout 3.8 L/min. to the sprdy nozzle which 30 sprdyed the liquid TEA down onto the packing. Nitrogen WdS buboled through the column to gredter than 95% sdturdtion dnd sent to the accumulator. - The dmine generdtor is detailed further in dttorney's docket ASH 4469 of Maher L. Mansour.Compdrdtive spray tests dlso were conducted wherein the liquid codting cornposition WdS mixed with liquid triethylamine c~talyst in the mixing head of a 35 DeVilbiss model ~BC 510-AV601-FX siphon spray gun hdving d MBC 444 FX fluid * Trademark .~
1~043~
needle (1.067 mm orifdce, 10-30 cc/min rated flow rate, ~ir consumption of 3.07 L/sec at 2.1 kg/cm pressure). Air was delivered to the spray gun at
2.1 kg/cm2 (30 psi) and 3% triethyl~mine catalyst in MEK solvent W8S delivered ~t 1.4 kg/cm2 (20 psi). A ball v~ve permitted precise control over entry of the test 5 catalyst solution into the mixing head of the spr~ly gun. The mixture of liquid codting composition dnd catalyst solution gelled so r~pidly in the mixing hedd that extreme caution h~d to be used. Thus, only 2 panels could be sprayed dt ~ time followed by immediate solvent flushing. Also, a blue dye WA9 added to the cdtdlyst solution so that delivery of the cat~yst through the baU vL~lve could be confirmed 10 visuully. Both spray guns dppeared to deliver equ~l consumption of applied coating composition based on the visudl appearance of the spray fan generdted by edch gun.
Also, the solvent amount in pdck sprayed formuIatoins wa~ approximately the same.
All ev~uations were conducted on Bonderite 37 steel p~nels and all spraynig was conducted under d Igbor~tory sprdy booth with exhaust. During all sprdy testing 15 of the novel spray method, no amine odor WdS detected by operating personnel outside the spray booth hood.
The liquid codting composition WdS formulated from 500 parts by weight of- the dromdtic hydroxyl-terminated polyester of Example 1 of U.S. Pdts. Nos. 4,374,167;
20 4,343,839, or 4,365,039 and 350 parts by weight of isocyanate no. 1004 which WdS dn equal weight mixture of Mondur~HC isocyandte ~tetrafunctional reaction product of hexamethylene diisocyandte dnd toluene diisocyan~lte, 11.5% NCO content, equivalent weight of 365, 60% solids in Cellosolve*acetdte/xylene, Mobdy Chemical Compe~ny, Pittsburgh, PA.) and Desmodur* L-2291A isocyandte (dliphdtic poly-25 functional isocyanate of the hexamethylene diisocyandte biuret type, Mobay Chemical Company). The resinous mixture was cut with ~dditional MIBK (methyl isobutyl ketone) solvent to achieve a spr~y viscosity of 20 sec. in a #4 Ford cup (this- -viscosity was maintdined in dll examples). This codting composition hds been shown to possess d pot life in excess of 48 hours in an open pot.
Two pdnels each were coated by the novel vaporous catslyst sprPy method and the convention.ll liquid cdtdlyst spray method. The panels were permitted to dir dry ~t dmbient indoor room temperature and then evaluated with the following results.
*Trademarks ' ~`:.;~..
Also, the solvent amount in pdck sprayed formuIatoins wa~ approximately the same.
All ev~uations were conducted on Bonderite 37 steel p~nels and all spraynig was conducted under d Igbor~tory sprdy booth with exhaust. During all sprdy testing 15 of the novel spray method, no amine odor WdS detected by operating personnel outside the spray booth hood.
The liquid codting composition WdS formulated from 500 parts by weight of- the dromdtic hydroxyl-terminated polyester of Example 1 of U.S. Pdts. Nos. 4,374,167;
20 4,343,839, or 4,365,039 and 350 parts by weight of isocyanate no. 1004 which WdS dn equal weight mixture of Mondur~HC isocyandte ~tetrafunctional reaction product of hexamethylene diisocyandte dnd toluene diisocyan~lte, 11.5% NCO content, equivalent weight of 365, 60% solids in Cellosolve*acetdte/xylene, Mobdy Chemical Compe~ny, Pittsburgh, PA.) and Desmodur* L-2291A isocyandte (dliphdtic poly-25 functional isocyanate of the hexamethylene diisocyandte biuret type, Mobay Chemical Company). The resinous mixture was cut with ~dditional MIBK (methyl isobutyl ketone) solvent to achieve a spr~y viscosity of 20 sec. in a #4 Ford cup (this- -viscosity was maintdined in dll examples). This codting composition hds been shown to possess d pot life in excess of 48 hours in an open pot.
Two pdnels each were coated by the novel vaporous catslyst sprPy method and the convention.ll liquid cdtdlyst spray method. The panels were permitted to dir dry ~t dmbient indoor room temperature and then evaluated with the following results.
*Trademarks ' ~`:.;~..
3~7 Panel Time (min) ~ilm Thickness MEK Double No. Set to Touch(l) Print Free(2) (mils) Rubs at 1 hr.
5 Vaporous Catalvst Spray 1 - 2 6 0.5 80 2 2 5 0.6 110 Liquid Catalyst Spray 3 4 15 0 . 5 22 10 4 3 12 0.4 13 . __ (1)Coating removed by finger placed on coated panel with light to moderate pressure (2)Finger print emboss on coating by finger placed on panel with 15 light to moderate pre~sure The abov~tabul~ted results demonstrate that the novel vaporous catdlyst spr~y method produced a codting which cured much more rapidly than did the conventional liquid catalyst spray method. Coatings lines in commercial plants can be shortened because the coated panels can be handled shortly after coating.
20 Moreover, curing heat is not required. After 24 hours, ~11 co~ting~ possessed in exce~s of 500 MEK double rubs. Thus, the ultimate properties appear comparable.
In this Example the vaporous catPlyst spray coated panels were subjected to post-cure treatment light heating to incresse solvent expulsion from the films. The 25 coating composition of claim 1 (isocyan~te index of 1.1:1) was sprayed with the following results.
Panel Film Thickness Post-Heating MEK DouMe Rubs 30 No. (mils3 at 1 hr.
0. 5 None 68 2 0.5 1 min. at 66C77 3 O.S 2 min. at 66C120
5 Vaporous Catalvst Spray 1 - 2 6 0.5 80 2 2 5 0.6 110 Liquid Catalyst Spray 3 4 15 0 . 5 22 10 4 3 12 0.4 13 . __ (1)Coating removed by finger placed on coated panel with light to moderate pressure (2)Finger print emboss on coating by finger placed on panel with 15 light to moderate pre~sure The abov~tabul~ted results demonstrate that the novel vaporous catdlyst spr~y method produced a codting which cured much more rapidly than did the conventional liquid catalyst spray method. Coatings lines in commercial plants can be shortened because the coated panels can be handled shortly after coating.
20 Moreover, curing heat is not required. After 24 hours, ~11 co~ting~ possessed in exce~s of 500 MEK double rubs. Thus, the ultimate properties appear comparable.
In this Example the vaporous catPlyst spray coated panels were subjected to post-cure treatment light heating to incresse solvent expulsion from the films. The 25 coating composition of claim 1 (isocyan~te index of 1.1:1) was sprayed with the following results.
Panel Film Thickness Post-Heating MEK DouMe Rubs 30 No. (mils3 at 1 hr.
0. 5 None 68 2 0.5 1 min. at 66C77 3 O.S 2 min. at 66C120
4 0.5 5 min. at 66C442 The post-he~ting conditions are quite insufficient in time ~nd temperature to cure the coatings, yet these results do demonstrate that the degree of cure is 1~434'7 improved by such heating. It is believed that gredter amounts of solvent in the film~
is expelled by the post-cure thermdl tre~tment; thus, the improvement in film propertles. These results me~n thdt coatings lines cdn be shortened even more byimplementdtion of the post-cure therm~ tre~tment. After 5 minute~, the film
is expelled by the post-cure thermdl tre~tment; thus, the improvement in film propertles. These results me~n thdt coatings lines cdn be shortened even more byimplementdtion of the post-cure therm~ tre~tment. After 5 minute~, the film
5 properties appro~ch their ultimgte. Note that ~I panels were handleable dfter the thermal treatment ~md the air-dry (no heat) p~mel was print-free in 5-6 minutes ~fter coating.
The following liquid co~lting compositions were formulated (pbw is p~rts by weight):
Formulation I
Polyol 1415(1) 500 pbw Adipic acid 7 moles 1,4-But~ne diol 6 moles Trimethylolpropane 2 moles Diphenolic acid 2 moles Mondur CB-60 Isocyan~te(2) 445 pbw MIBK 90 pbw .
20 (l)Resin 514 in Exdmple 1 of U.S. Pat. No. 4,368,222 (2)Arom~tic isocydnate (NCO equivdlent of 10.0 to 11.0) compound, Mobay Chemical Company Pormulation 2 Polyol 51400-9A(3) 760 pbw Dimethyl terephthdlate 1 mole 1,4-Butane diol 8 moles Azelaic acid 6 moles Diphenolic acid 2 moles Isocyandte 1004 350 pbw MIBK 180 pbw . . _ . . . _ (3)Resin 120 in Example 1 of U.S. Pat.No. 4~374,181 with dimethyl terephthdldte repldcing terephthdlic acid.
i4347 Formulation 3 Polyol 51400-12(4) 760 pbw 2-Hydroxyethyl methacrylate 2 moles Styrene 2 moles Butyl acrylate 4 moles 2-Ethyl hexyl acrylate 2 moles Butyl methacrylHte 4 moles Diphenolic acid 2 moles Isocyanate 1004 - 350 pbw MIBK 200 pbw (4)Diphenolic acid reacted in second stage after ~11 other 15 ingredients reacted in first stage reaction.
Formulation 4 Polyol 51400-12 760 pbw IsocyQnate KL5-2444(5) 231 pbw MIBK 150 pbw (5)Isocyanate KL5-244 is an aliphatic isocyanate of hexamethylene diisocyanate (NCt) content 20%, 90% solid~ in Cellosolve acetate, equivalent weight of 2103, Moblly Chemical Company.
Each of the formulations was applied by the novel vaporous catslyst spray method ~nd by the liquid catalys~ spray method with the following results.
::~2~ 347 Film Set to Eormulation Thicknes~ Touch Print-Pree MEK Double Rubs No. (mils) (min) (min)1 Hr.24 Hr~.
Vaporous Catalyst S~ay 1 0.5 9 l5 S00+>1000 2 0 . 5 10 27 150> S00 3 0.4 4 6 10 55 4 0.4 20 70 6 175 Liquid Cat~lyst Ser y 10 1 0.5 10 15 285> 1000 2 0.4 12 30 12> S00 3 0 . ~ 5 12 25 55 0 . 4 25 90 3 40 Severell import~nt observations can be made based on the above-tabulated data. The coatings generally were set to $he touch ~md print free in shorter time~
for the novel vaporous cat~yst spray method, except for formulatiQn 3 (which results &re not consistent with all other tests). MEK rubs also generally were greater one hour after application of the coating by the vaporous catalyst spray20 method.
The most remarkable results, however, are for formulation 4 which contained only aliph~tic isocyanate cross-linking agent. Gener~l teachings in vapor permea-tion curable technology are that ~iphatic isocyanate~ will not cure completely in the presence of vaporous tertiary amine cat~lysts or will cure so slowly to muke25 their use undesirable. 8y the novel vaporouq catalyst spray method, however, remarkable cure Wlls achieved ~s evidenced by the 175 MEK rubs 24 hours after application of the coatings. For the first time use of only aliphatic or pre-dominantly ~liphatic multi-isocyanate cross-linking agents in vapor permeation cure coatings appears practical. The acute differences between v~proous amine and 30 liquid amine catalysts is clearly evident.
In order to demonstrate the ability of the novel spray method to provide very thick cured codtings, the polyol polyester of Example 1 (cut in MlBK to 70% solids r~ther than cut in Cellosolve acetate) and isocyanate 1004 cross-linking agent were 35 cut in MIBK to the required spray viscosity. The first panel was sprayed to a dry 12~3~7 -~7-film thickness of 8 mils and the second sprayed to a d~y film thickness of 15 mils.
Both panels were set to touch in 3 minutes and were print free in 5 minutes. (The room wss opened to the outdoors for these tests and it was a dry, warm day. The warmer climate may have resulted in faster drying times compared to the thinner 5 films in the other exsmples).
Each film was sdjudged to be non-blocking and h~mdleable in 20-30 minutes.
Within 72 hours from application, eQch film was fully-cured and tightly bound to the substrste. Thus, the intense expected skinning of the applied films did not suppress cure through the thickness of the ~ilm nor inter~ere with solvent expulsion from the 10 film. That such thick film~ c~n be fully cured by vapor permeation cure means is yet ~mother unique achievement of the present invention.
The following liquid co~lting compositions were formulated (pbw is p~rts by weight):
Formulation I
Polyol 1415(1) 500 pbw Adipic acid 7 moles 1,4-But~ne diol 6 moles Trimethylolpropane 2 moles Diphenolic acid 2 moles Mondur CB-60 Isocyan~te(2) 445 pbw MIBK 90 pbw .
20 (l)Resin 514 in Exdmple 1 of U.S. Pat. No. 4,368,222 (2)Arom~tic isocydnate (NCO equivdlent of 10.0 to 11.0) compound, Mobay Chemical Company Pormulation 2 Polyol 51400-9A(3) 760 pbw Dimethyl terephthdlate 1 mole 1,4-Butane diol 8 moles Azelaic acid 6 moles Diphenolic acid 2 moles Isocyandte 1004 350 pbw MIBK 180 pbw . . _ . . . _ (3)Resin 120 in Example 1 of U.S. Pat.No. 4~374,181 with dimethyl terephthdldte repldcing terephthdlic acid.
i4347 Formulation 3 Polyol 51400-12(4) 760 pbw 2-Hydroxyethyl methacrylate 2 moles Styrene 2 moles Butyl acrylate 4 moles 2-Ethyl hexyl acrylate 2 moles Butyl methacrylHte 4 moles Diphenolic acid 2 moles Isocyanate 1004 - 350 pbw MIBK 200 pbw (4)Diphenolic acid reacted in second stage after ~11 other 15 ingredients reacted in first stage reaction.
Formulation 4 Polyol 51400-12 760 pbw IsocyQnate KL5-2444(5) 231 pbw MIBK 150 pbw (5)Isocyanate KL5-244 is an aliphatic isocyanate of hexamethylene diisocyanate (NCt) content 20%, 90% solid~ in Cellosolve acetate, equivalent weight of 2103, Moblly Chemical Company.
Each of the formulations was applied by the novel vaporous catslyst spray method ~nd by the liquid catalys~ spray method with the following results.
::~2~ 347 Film Set to Eormulation Thicknes~ Touch Print-Pree MEK Double Rubs No. (mils) (min) (min)1 Hr.24 Hr~.
Vaporous Catalyst S~ay 1 0.5 9 l5 S00+>1000 2 0 . 5 10 27 150> S00 3 0.4 4 6 10 55 4 0.4 20 70 6 175 Liquid Cat~lyst Ser y 10 1 0.5 10 15 285> 1000 2 0.4 12 30 12> S00 3 0 . ~ 5 12 25 55 0 . 4 25 90 3 40 Severell import~nt observations can be made based on the above-tabulated data. The coatings generally were set to $he touch ~md print free in shorter time~
for the novel vaporous cat~yst spray method, except for formulatiQn 3 (which results &re not consistent with all other tests). MEK rubs also generally were greater one hour after application of the coating by the vaporous catalyst spray20 method.
The most remarkable results, however, are for formulation 4 which contained only aliph~tic isocyanate cross-linking agent. Gener~l teachings in vapor permea-tion curable technology are that ~iphatic isocyanate~ will not cure completely in the presence of vaporous tertiary amine cat~lysts or will cure so slowly to muke25 their use undesirable. 8y the novel vaporouq catalyst spray method, however, remarkable cure Wlls achieved ~s evidenced by the 175 MEK rubs 24 hours after application of the coatings. For the first time use of only aliphatic or pre-dominantly ~liphatic multi-isocyanate cross-linking agents in vapor permeation cure coatings appears practical. The acute differences between v~proous amine and 30 liquid amine catalysts is clearly evident.
In order to demonstrate the ability of the novel spray method to provide very thick cured codtings, the polyol polyester of Example 1 (cut in MlBK to 70% solids r~ther than cut in Cellosolve acetate) and isocyanate 1004 cross-linking agent were 35 cut in MIBK to the required spray viscosity. The first panel was sprayed to a dry 12~3~7 -~7-film thickness of 8 mils and the second sprayed to a d~y film thickness of 15 mils.
Both panels were set to touch in 3 minutes and were print free in 5 minutes. (The room wss opened to the outdoors for these tests and it was a dry, warm day. The warmer climate may have resulted in faster drying times compared to the thinner 5 films in the other exsmples).
Each film was sdjudged to be non-blocking and h~mdleable in 20-30 minutes.
Within 72 hours from application, eQch film was fully-cured and tightly bound to the substrste. Thus, the intense expected skinning of the applied films did not suppress cure through the thickness of the ~ilm nor inter~ere with solvent expulsion from the 10 film. That such thick film~ c~n be fully cured by vapor permeation cure means is yet ~mother unique achievement of the present invention.
Claims (20)
1. A method for applying onto a substrate a film of a coating composition in liquid form and which comprises an aromatic hydroxyl-functional compound and a multi-isocyanate cross-linking agent, wherein said applied film is curable rapidly at room temperature, which comprises:
(a) forming an atomizing gas flow which comprises an intimate mixture of a carrier gas bearing a catalytic amount of a vaporous tertiary amine;
(b) atomizing said liquid costing composition with said vaporous cata-lytic amine-bearing atomizing carrier gas flow; and (c) directing said atomizate of step (b) onto said substrate to form said applied film.
(a) forming an atomizing gas flow which comprises an intimate mixture of a carrier gas bearing a catalytic amount of a vaporous tertiary amine;
(b) atomizing said liquid costing composition with said vaporous cata-lytic amine-bearing atomizing carrier gas flow; and (c) directing said atomizate of step (b) onto said substrate to form said applied film.
2. The method of claim 1 wherein said coating composition additionally comprises a volatile organic solvent.
3. The method of claim 1 wherein said aromatic hydroxyl-functional compound is resinous or polymeric.
4. The method of claim 1 wherein said carrier gas is air.
5. The method of claim 1 wherein said carrier gas is an inert gas.
6. The method of claim 5 wherein said intert carrier gas comprises nitrogen or carbon dioxide.
7. The method of claim 1 wherein said carrier gas is a mixture of air and an inert gas.
8. The method of claim 1 wherein said atomizing gas flow is at a sufficient temperature and pressure to prevent said catalytic amine from condensing from its vaporous state.
9. The method of claim 1 wherein said coated substrate is subjected to a thermal conditioning step comprising maintaining said cured film at a temperature of between about 50° and 150° for a time ranging from between about 1 and 5 minutes.
10. The method of claim 1 wherein said atomizate of step (b) is directed onto said substrate to form a cured film ranging up to about 15 mils in thickness.
11. The method of claim 1 wherein said multi-isocyanate cross-linking agent is polymeric.
12. The method of claim 1 wherein said multi-isocyanate cross-linking agent is an aromatic multi-isocyanate, an aliphatic multi-isocyanate, or mixtures thereof.
13. The method of claim 11 wherein said multi-isocyanate cross-linking agent is an aromatic multi-isocyanate, an aliphatic multi-isocyanate, or mixtures thereof.
14. The method of claim 1 wherein the ratio of aromatic hydroxyl equivalents of said aromatic hydroxyl-functional compound to the isocyanate equivalents of said multi-isocyanate cross-linking agent range from between about 1:1 and 1:2.
15. The method of claim 2 wherein said solvent comprises a ketone, a carboxylic acid ester, an aromatic solvent, or mixtures thereof.
16. The method of claim 1 wherein said vaporous tertiary amine catalyst is selected from the group consisting of triethyl amine, dimethyl ethyl amine, cyclohexyl dimethyl amine, methyl diethyl amine, and mixtures thereof.
17. A method for applying onto a substrate a film of a coating composition in liquid form and which comprises an aromatic hydroxyl-functional resin, a polymeric multi-isocyanate cross-linking agent, and a volatile organic solvent, wherein said applied film is curable rapidly at room temperature, which comprises:
(a) forming an atomizing gas flow which comprises an intimate mixture of a carrier gas bearing a catalytic amount of a vaporous tertiary amine;
(b) atomizing said liquid coating composition with said vaporous catalytic amine-bearing atomizing carrier gas flow; and (c) directing said atomizate of step (b) onto said substrate to form said applied film.
(a) forming an atomizing gas flow which comprises an intimate mixture of a carrier gas bearing a catalytic amount of a vaporous tertiary amine;
(b) atomizing said liquid coating composition with said vaporous catalytic amine-bearing atomizing carrier gas flow; and (c) directing said atomizate of step (b) onto said substrate to form said applied film.
18. The method of claim 17 wherein said carrier gas comprises nitrogen or carbon dioxide.
19. The method of claim 17 wherein said vaporous tertiary amine catalyst is selected from the group consisting of triethyl amine, dimethyl ethyl amine, cyclohexyl dimethyl amine, and methyl diethyl amine.
20. The method of claim 17 wherein said polymeric multi-isocyanate cross-linking agent comprises between about 10 and 80% by weight of an aromatic multi-isocyanate and between about 90 and 25% by weight of an aliphatic multi-isocyanate.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US47415683A | 1983-03-10 | 1983-03-10 | |
| US06/474,156 | 1983-03-10 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1204347A true CA1204347A (en) | 1986-05-13 |
Family
ID=23882401
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000449250A Expired CA1204347A (en) | 1983-03-10 | 1984-03-09 | Vaporous amine catalyst spray method |
Country Status (16)
| Country | Link |
|---|---|
| JP (1) | JPS59170153A (en) |
| KR (1) | KR860001663B1 (en) |
| AT (1) | AT393635B (en) |
| AU (1) | AU550637B2 (en) |
| BE (1) | BE899061A (en) |
| BR (1) | BR8401022A (en) |
| CA (1) | CA1204347A (en) |
| DE (1) | DE3408773C2 (en) |
| ES (1) | ES8506773A1 (en) |
| FR (1) | FR2542221B1 (en) |
| GB (1) | GB2136441B (en) |
| IT (1) | IT1175454B (en) |
| MX (1) | MX163394B (en) |
| NL (1) | NL193722C (en) |
| SE (1) | SE458176B (en) |
| ZA (1) | ZA841329B (en) |
Families Citing this family (12)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| AU614753B2 (en) * | 1982-12-31 | 1991-09-12 | Ashland Oil, Inc. | Vaporous amine catalyst spray method |
| GB2176197B (en) * | 1985-05-31 | 1989-10-25 | Ashland Oil Inc | Vapour permeation curable coatings comprising polymercapto compounds and polyisocyanate curing agents |
| US4672000A (en) * | 1985-05-31 | 1987-06-09 | Ashland Oil, Inc. | Vapor permeation curable coatings comprising poly(nitro alcohol) resins and multi-isocyanate curing agents |
| US4677029A (en) * | 1985-11-21 | 1987-06-30 | Akzo America Inc. | Vapor-phase cure of coating compositions containing an aliphatic polyisocyanate and a tertiary amine polyahl |
| DE3544451C1 (en) * | 1985-12-16 | 1987-01-15 | Ashland Suedchemie Kernfest | Process for producing a water-permeable coating on granular, water-soluble substances and its application |
| JPS62191060A (en) * | 1986-02-18 | 1987-08-21 | Mitsui Toatsu Chem Inc | Foam coating apparatus |
| JPS62244476A (en) * | 1986-04-16 | 1987-10-24 | Shinto Paint Co Ltd | Improved method for anticorrosion painting of metal cast and forged product |
| JPH0732895B2 (en) * | 1986-05-15 | 1995-04-12 | 日産自動車株式会社 | How to apply urethane resin paint |
| NZ221309A (en) * | 1986-08-19 | 1989-12-21 | Antonio Sola | Separation of vapor and liquid components of a chemical agent introduced to a compressed air supply system |
| CA1324857C (en) * | 1987-01-12 | 1993-11-30 | Gary M. Carlson | Stabilized moisture curable polyurethane coatings |
| JPH0638946B2 (en) * | 1988-04-20 | 1994-05-25 | 日産自動車株式会社 | How to apply urethane resin paint |
| US8455608B2 (en) * | 2010-02-26 | 2013-06-04 | Basf Se | Catalyzed pellet heat treatment for thermoplastic polyurethanes |
Family Cites Families (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3049439A (en) * | 1960-04-11 | 1962-08-14 | Wald Ind Inc | Internal mix catalyst type spray gun and process employing same |
| CA1005943A (en) * | 1971-01-26 | 1977-02-22 | David D. Taft | Compositions based on diphenolic-type acid capped materials and polyisocyanate and a process for curing same |
| US4195148A (en) * | 1978-07-12 | 1980-03-25 | Uniroyal, Inc. | Polyurethane spray composition containing lactone viscosity modifier |
| US4343839A (en) * | 1980-12-15 | 1982-08-10 | Ashland Oil, Inc. | Vapor permeation curable polyester resin coating compositions for flexible substrates |
| US4368222A (en) * | 1981-06-05 | 1983-01-11 | Ashland Oil, Inc. | Vapor permeation curable coatings for surface-porous substrates |
| US4374181A (en) * | 1981-09-14 | 1983-02-15 | Ashland Oil, Inc. | Vapor permeation curable coatings for reaction injection molded parts |
-
1984
- 1984-02-22 GB GB08404620A patent/GB2136441B/en not_active Expired
- 1984-02-23 ZA ZA841329A patent/ZA841329B/en unknown
- 1984-03-02 BR BR8401022A patent/BR8401022A/en not_active IP Right Cessation
- 1984-03-02 BE BE212490A patent/BE899061A/en not_active IP Right Cessation
- 1984-03-08 FR FR8403588A patent/FR2542221B1/en not_active Expired
- 1984-03-08 NL NL8400754A patent/NL193722C/en not_active IP Right Cessation
- 1984-03-08 SE SE8401298A patent/SE458176B/en not_active IP Right Cessation
- 1984-03-08 MX MX200602A patent/MX163394B/en unknown
- 1984-03-09 IT IT19991/84A patent/IT1175454B/en active
- 1984-03-09 DE DE3408773A patent/DE3408773C2/en not_active Expired
- 1984-03-09 AT AT0080184A patent/AT393635B/en not_active IP Right Cessation
- 1984-03-09 ES ES530490A patent/ES8506773A1/en not_active Expired
- 1984-03-09 JP JP59044209A patent/JPS59170153A/en active Granted
- 1984-03-09 AU AU25447/84A patent/AU550637B2/en not_active Ceased
- 1984-03-09 CA CA000449250A patent/CA1204347A/en not_active Expired
- 1984-03-09 KR KR1019840001202A patent/KR860001663B1/en not_active IP Right Cessation
Also Published As
| Publication number | Publication date |
|---|---|
| KR860001663B1 (en) | 1986-10-16 |
| KR840007978A (en) | 1984-12-12 |
| BR8401022A (en) | 1984-10-16 |
| SE458176B (en) | 1989-03-06 |
| ZA841329B (en) | 1984-10-31 |
| AU550637B2 (en) | 1986-03-27 |
| SE8401298L (en) | 1984-09-11 |
| DE3408773C2 (en) | 1986-11-20 |
| ES530490A0 (en) | 1985-08-01 |
| JPS59170153A (en) | 1984-09-26 |
| MX163394B (en) | 1992-05-08 |
| ES8506773A1 (en) | 1985-08-01 |
| GB8404620D0 (en) | 1984-03-28 |
| FR2542221B1 (en) | 1988-11-18 |
| IT1175454B (en) | 1987-07-01 |
| JPH0150343B2 (en) | 1989-10-30 |
| DE3408773A1 (en) | 1984-09-13 |
| AU2544784A (en) | 1984-09-13 |
| IT8419991A0 (en) | 1984-03-09 |
| NL8400754A (en) | 1984-10-01 |
| SE8401298D0 (en) | 1984-03-08 |
| AT393635B (en) | 1991-11-25 |
| BE899061A (en) | 1984-07-02 |
| GB2136441A (en) | 1984-09-19 |
| GB2136441B (en) | 1986-06-18 |
| NL193722B (en) | 2000-04-03 |
| FR2542221A1 (en) | 1984-09-14 |
| ATA80184A (en) | 1991-05-15 |
| NL193722C (en) | 2000-08-04 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |