Method of producing flexible laminates
A method of producing a flexible laminate and a flexible laminate produced by the method are provided. The method involves laminating flexible substrates with a urethane adhesive and allowing the urethane adhesive to cure. The urethane adhesive comprises at least one polyisocyanate, at least one polyfunctional curative, at least one metal based catalyst and a catalyst blocking agent. The catalyst blocking agent allows for improved control of the curing rate of the urethane adhesive in the flexible laminate. The curing rate of the urethane adhesive can be controlled with heat or actinic radiation or both. The method allows for faster and more economical production of flexible laminates.
1 . A method of producing a flexible laminate comprising:
(a) applying a urethane adhesive to at least one of at least two flexible substrates wherein the at least two flexible substrates may be the same or different materials;
(b) laminating the at least two flexible substrates with the urethane adhesive between the substrates to form a flexible laminate and
(c) allowing the urethane adhesive to cure forming a flexible laminate wherein the urethane adhesive comprises at least one polyisocyanate, at least one polyfunctional curative, a metallic based catalyst and at least one catalyst blocking agent wherein the at least one catalyst blocking agent comprises a mercapto compound or a polyphenol with adjacent hydroxyl groups or both.
2 . The method of producing a flexible laminate as claimed in claim 1 , wherein the flexible laminate is heated to accelerate the curing of the urethane adhesive.
3 . The method of producing a flexible laminate as claimed in claim 1 , wherein the catalyst blocking agent comprises a mercapto compound or a mixture of a mercapto compound and a polyphenol with adjacent hydroxyl groups and wherein the urethane adhesive further comprises an olefinic compound.
4 . The method of producing a flexible laminate as claimed in claim 3 , wherein the flexible laminate is exposed to actinic radiation or e-beam radiation to accelerate the curing of the urethane adhesive.
5 . The method of producing a flexible laminate as claimed in claim 1 , wherein the at least two flexible substrates are selected from the group consisting of polyethylene (PE) sheet, polypropylene (PP) sheet, PE/PP sheet oriented PP, metalized PET, mono-axially oriented PP nylon sheet, polyester sheet, mylar sheet, styrenic sheet, polycarbonate sheet, acrylic sheet, acetal sheet, Delrine® sheet, Lexan® sheet, Lucite® sheet, Micarta® sheet, Perspex® sheet, Plexiglas® sheet, Acrylite® sheet, PET sheets, ABS sheet, PVC sheet, PTFE sheet, HIPS sheet, EVOH sheet and PP/EVOH sheet.
6 . The method of producing a flexible laminate as claimed in claim 1 , wherein the at least one polyisocyanate is selected from the group consisting hexamethylene diisocyanate, hexamethylene diisocyanate trimer, tetramethylxylylene diisocyanate, 4,4′-toluene diisocyanate (TDI), diphenylmethane diisocyanate (MDI), polymethyl polphenyl isocyanate (Polymeric MDI or PAPI), m- and p-phenylene diisocyanates, bitolylene diisocyanate, triphenylmethane triisocyanate, tris-(4-isocyanatophenyl)thiophosphate, cyclohexane diisocyanate (CHDI), bis-(isocyanatomethyl)cyclohexane (H 6 XDI), dicyclohexylmethane diisocyanate (H 12 MDI), trimethylhexane diisocyanate, dimer acid diisocyanate (DDI), dicyclohexylmethane diisocyanate, and dimethyl derivatives thereof, trimethyl hexamethylene diisocyanate, lysine diisocyanate and its methyl ester, isophorone diisocyanate, methyl cyclohexane diisocyanate, methylenedicyclohexane diisocyanate, isophorone diisocyanate, 1,5-naphthalene diisocyanate, triphenyl methane triisocyanate, xylylene diisocyanate and methyl and hydrogenated derivatives thereof, polymethylene polyphenyl isocyanates, chlorophenylene-2,4-diisocyanate and mixtures thereof.
7 . The method of producing a flexible laminate as claimed in claim 1 , the at least one polyfunctional curative is selected from the group consisting of hydroxypolyesters, hydroxypolyethers, hydroxypolythioesters, hydroxypolyacetals, hydroxypolycarbonates, dimeric fatty alcohols, esteramides, polyetherpolyols, polyesterpolyols, polycarbonatepolyols, ethylene glycol, triethylene glycol, tetraethylene glycol, 1,2- and 1,3-propanediol, 1,4- and 1,3-butanediol, 1,6-hexanediol, 1,8-octanediol, neopentyl glycol, 1,4-bis-(hydroxymethyl)-cyclohexane, bis-(hydroxymethyl)-(tricycle-[5.2.1.0 2.6 ]-decane or 1,4-bis-(2-hydroxyethoxy)-benzene, 2-methyl-1,3-propanediol, 2,2,4-trimethylpentanediol, 2-ethyl-1,3-hexanediol, dipropylene glycol, polypropylene glycols, dibutylene glycol, polybutylene glycols, bisphenol A, tetra-bromobisphenol A, glycerol, trimethylolpropane, 1,2,6-hexanetriol, 1,2,4-butanetriol, pentaerythritol, quinitol, mannitol, sorbitol, methylglycoside 1,4:3,6-dianhydrohexitol and mixtures thereof.
8 . The method of producing a flexible laminate as claimed in claim 1 , wherein the metallic based catalyst is selected from the group consisting of dibutyltindilaurate, stannous acetate, stannic oxide, stannous octoate, dibutyltin dioctoate, tin mercaptides, stannous citrate, stannous oxylate, stannous chloride, stannic chloride, tetra-phenyl tin, tetra-butyl tin, tri-n-butyl tin acetate, di-alkyl tin dicarboxylates, dimethyl tin dichloride, bismuth tricarboxylates, bismuth nitrate, bismuth halides, bismuth sulfide, basic bismuth dicarboxylates and mixtures thereof.
9 . The method of producing a flexible laminate as claimed in claim 1 , wherein when the urethane adhesive comprises a mercapto compound as a catalyst blocking agent, the mercapto compound is selected from the group consisting of trimethylol propane tri-(3-mercapto propionate), pentaerythritol tetra-(3-mercapto propionate), glycol di-(3-mercapto propionate), glycol dimercapto acetate, trimethylol propane trithioglycolate, mercapto diethyl ether, ethane dithiol, thiolactic acid, mercapto propionic acid and esters thereof, thiophenol, thio acetic acid, 2-mercapto ethanol, 1,4-butanedithiol, 2,3-dimercapto propanol, toluene-3,4-dithiol, alpha,alpha′-dimercapto-para-xylene, thiosalicylic acid, mercapto acetic acid, dodecane dithiol, didodecane dithiol, di-thio phenol, di-para-chlorothiophenol, dimercapto benzothiazole, 3,4-dimercapto toluene, allyl mercaptan, benzyl mercaptan, 1,6-hexane dithiol, 1-octane thiol, para-thiocresol, 2,3,5,6-tetrafluorothiophenol, cyclohexyl mercaptan, methylthioglycolate, various mercapto pyridines, dithioerythritol, 6-ethoxy-2-mercaptobenzothiazole, d-limonene dimercaptan γ-mercapto silane, and mixtures thereof.
10 . The method of producing a flexible laminate as claimed in claim 1 , wherein when the urethane adhesive comprises a polyphenol with adjacent hydroxy groups as a catalyst blocking agent, the polyphenol with adjacent hydroxyl groups is selected from the group consisting of catechol, pyrogallol, 3-methoxy catechol, a catechol derivative as shown in formula I
where R′ is a divalent organic group and mixtures thereof.
11 . The method of producing a flexible laminate as claimed in claim 3 , wherein the olefinic compound is selected from the group consisting of diallyl phthalate, acrylic acid, methacrylic acid alkyl acrylate, alkyl methacrylate, acrylamide and mixtures thereof.
12 . The method of producing a flexible laminate as claimed in claim 1 , wherein the at least two flexible substrates with the urethane adhesive between the substrates are married by passing through a nip point between two rolls where pressure is applied and wherein one or both of the two rolls are optionally heated.
13 . The method of producing a flexible laminate as claimed in claim 4 , wherein the at least two flexible substrates with the urethane adhesive between the substrates are married by passing through a nip point between two rolls where pressure is applied, wherein one or both of the two rolls are optionally heated and wherein the at least two flexible substrates with the urethane adhesive between the substrates is exposed to actinic radiation prior to passing through the nip point.
14 . The method of producing a flexible laminate as claimed in claim 1 , wherein at least one of the at least two flexible substrates contains print.
15 . The method of producing a flexible laminate as claimed in claim 14 , wherein the at least one of the at least two flexible substrates contains print that is printed by a least one printing method selected from the group consisting of a water-based method, a solvent-based method and radiation-based method.
16 . The method of producing a flexible laminate as claimed in claim 1 , wherein the urethane adhesive is applied to at least one smooth roll laminating head and then transferred the at least one of the at least two flexible substrates.
17 . A flexible laminate material manufactured by the method of producing a flexible laminate as claimed in claim 1 .
18 . The method of producing a flexible laminate as claimed in claim 1 , wherein the urethane adhesive further comprises a solvent.
19 . The method of producing a flexible laminate as claimed in claim 18 , wherein the solvent is selected from the group consisting of a ketone, MEK, MIBK, an aromatic solvent, toluene, xylene, an aliphatic solvent, hexane, cyclohexane, an ester, ethyl acetate, THF and mixtures thereof.
20 . The method of producing a flexible laminate as claimed in claim 1 , wherein the urethane adhesive further comprises a tertiary amine.
21 . The method of producing a flexible laminate as claimed in claim 20 , wherein the tertiary amine is triethylamine, dimethylethylamine, tetramethylethylenediamine, trimethylamine, tributylamine, dimethylbenzylamine, dimethylcyclohexylamine, dimethylethanolamine, diethylethanolamine, triethanolamine, pyridine, 4-phenylpropylpyridine, 2,4,6-collidine, quinoline, tripropylamine, isoquinoline, N-ethylmorpholine, triethylenediamine and mixtures therof.
22 . The method of producing a flexible laminate as claimed in claim 1 , wherein the flexible laminate is plastic coated with silicon oxide or aluminum oxide.
23 . The method of producing a flexible laminate as claimed in claim 1 , wherein the metallic based catalyst is based on at least one metal selected from the group consisting of tin, bismuth, germanium, cobalt and manganese.