CA1336469C

CA1336469C - Storage-stable hydrocurable oxazolidine-isocyanate compositions

Info

Publication number: CA1336469C
Application number: CA000573010A
Authority: CA
Inventors: John J. Theodore
Original assignee: Minnesota Mining and Manufacturing Co
Current assignee: 3M Co
Priority date: 1988-07-26
Filing date: 1988-07-26
Publication date: 1995-07-25
Anticipated expiration: 2012-07-25
Also published as: JPH0255715A; AU611706B2; AU2032488A

Abstract

A one-part, storage-stable moisture-curable composition useful as an adhesive, coating and sealant comprising a urethane oxazolidine and an aromatic polyfunctional isocyanate. The urethane oxazolidine can have structures such as:

Description

1 33 6 4 69 42352 CAN lA

STORAGE-STABLE HYDROCURABLE
S OXAZOLIDINE-ISOCYANATE COMPOS I TI ONS

Technical Field This invention relates to one-part, storage-stable, 10 moisture-curable adhesive, coating, and sealant compositions comprising a defined oxazolidine and a polyfunctional aromatic isocyanate.

Background Art Moisture-curable, isocyanate terminated, urethane prepolymers have long been used in formulating adhesive, coating and sealant products. The reactions of such compounds with atmospheric moisture are often catalyzed by addition of tertiary amines or tin salts to increase the cure rate. A
20 by-product of the reaction is carbon dioxide, which when generated in sufficient quantity, can create voids in the cured polymer. As one way to overcome this problem, oxazolidine compounds have been utilized as curing agents or co-reactants. (See, e.g., U.S. Patent Nos. 3,661,923, 25 3,743,626, 4,138,545, and 4,002,601).
The use of oxazolidine compounds in one-component, moisture curable urethane compositions has generally been limited to systems using aliphatic isocyanates. (See, e.g., U.S. Patent Nos. 3,912,691, 4,024,117, 4,381,388 and 30 4,417,102.) The art has taught that the storage life of systems which include aromatic polyisocyanates is very brief.
(See U.S. Patent No. 4,118,376, for example.) The use of blends of aromatic isocyanates and oxazolidines is stated to be "not attractive if long pot-life of the blend is required"
35 in Journal of Coatings Technology, 49, 65, 1977, and to "offer only one or two days of pot-life", Preprints of 1 33646q Division of Orqanic Coatinqs and Plastics, 167th Meeting of the American Chemical Society, April 1974, page 739.
Storage-stability, or pot-life, of six months or greater is desirable, and a composition having such a pot-life would be considered storage-stable. However, the use of aliphatic isocyanates to attain same is not desirable because of typically slow cure times and considerable expense.
It is therefore desirable to provide a storage stable, moisture curable composition which utilizes an aromatic isocyanate.

SummarY of the Invention It has surprisingly been found that aromatic isocyanate compounds can be used in combination with certain types of oxazolidine compounds to produce storage-stable, hydrocurable, one-part compositions useful as adhesives, coating or sealants. The storage-stable, hydrocurable, one-part composition of the present invention comprises a urethane oxazolidine and an aromatic polyfunctional isocyanate or isocyanate prepolymer. The urethane oxazolidine is preferably a urethane bisoxazolidine.

Detailed Description of the Invention The urethane oxazolidine compounds of the invention may be any organic compound having at least one, and preferably two or three, groups of the following formula:

2a 60557-3476 Rl~
=C=N- R~ -O-C-NH- R5 - R2 R3 n wherein:

_3_ l 336469 Rl represents an aliphatic hydrocarbon group having from 2 to 6, preferably 2 or 3, carbon atoms;
R2 and R3 may be the same or different and represent hydrogen, aliphatic hydrocarbon groups having 1 to 4 carbon atoms, cyclo-aliphatic hydrocarbon groups having 5 to 7 carbon atoms, or aromatic hydrocarbon groups having 6 to 10 carbon atoms or, together with the ring carbon atom, they may represent a five-membered ring. R2 and R3 are preferably the same or different groups and are hydrogen or aliphatic hydrocarbon groups having from 1 to 4 carbon atoms, R4 represents an aliphatic hydrocarbon group having from 2 to 6 carbon atoms;
R5 represents a group which is obtained by removal of the isocyanate groups from an organic isocyanate, preferably a di- or tri-isocyanate; and n represents an integer of from 1 to 6, preferably 2 or 3.
Such oxazolidines have been described, for example, in U.S. Patent No. 4,002,601 and numerous examples are 25 provided therein.
Hydrolytic ring opening of these oxazolidines results in the formation of one hydroxyl group and one secondary amino group per oxazolidine ring so that even oxazolidines having only a single oxazolidine ring are 30 converted by reaction with water into compounds which are difunctional for the purpose of the isocyanate addition reaction. However, it is preferred to use urethane oxazolidines containing two oxazolidine rings (bisoxazolidine) for greater cross-link density in the final , _ cured product, such as in particular N,N'-bis-[(2-isopropyl-1,3-oxazolidin-3-yl)-ethoxycarbonyl]-1,6-diaminohexane.
A suitable commercially available urethane bisoxazolidine i8 "Hardner OZ", baæed on aliphatic poly(amino-alcohol), commercially available from Hobay Chemical Corporation.
It is theorized that these oxazolidines are capable of providing the desired pot-life because they are non-acidic, free acids being capable of promoting the opening of the oxazolidine ring prematurely.
Any organic aromatic polyisocyanates may be used for the preparation of the prepolymers, with isocyanate groups such as diphenylmethane-2,4'-diisocyanate and/or 4,4'-diisocyanate;
tolylene-2,4-diisocyanate and -2,6-diisocyanate and mixtures of these isomers being exemplary. Other examples include:
naphthylene-1,5-diisocyanate; triphenylmethane-4,4',4"-triisocyanate; phenylene-1,3-diisocyanate and -1,4-diisocyanate;
dimethyl-3,3'-biphenylene-4,4'-diisocyanate;
diphenylisopropylidine-4,4'-diisocyanate; biphenylene diisocyanate; xylylene-1,3-diisocyanate and -1,4-diisocyanate.
A list of useful commercially available polyisocyanates is found in the ~Encyclopedia of Chemical Technology," Kirk-Othmer, 2nd Ed., Vol. 12, pp. 46-47, Interscience Pub., N.Y. (1967). Preferable isocyanates include diphenylmethane-4,4'-diisocyanate (MDI) and tolylene-2,4-diisocyanate/tolylene-2,6-diisocyanate (TDI) and mixtures of these isomers.

* Trade-mark ~ _ 1 336469 Also, isocyanate-functional derivative(s) of MDI and TDI may be used, such as liquid mixtures of the isocyanate functional derivative with melting point modifiers (e.g., mixtures of MDI with polycarbodiimide adducts such as "Isonate 143L", commercially available from the Upjohn Co., and *

"Mondur CD", commercially available from Mobay Chemical Corp.);
polymeric diphenylmethane diisocyanates (e.g., "PAPI", and the series "PAPI 20" through "PAPI 901", commercially available from the Upjohn Co., "Mondur MR", "Mondur HRS", and "Mondur MRS-10", commercially available from Mobay Chemical Corp., and "Rubinate Mn, commercially available from Rubicon Chemicals, Inc.); and blocked isocyanate compounds formed by reacting aromatic isocyanates or the above-described isocyanate-functional derivatives with blocking agents such as ketoximes and the like. Such blocked isocyanate compounds will, for convenience, be regarded herein as isocyanate-functional derivatives of MDI or TDI.
Suitable polyols for use in this invention include polytetramethylene oxide glycols, ethylene oxide-terminated polypropylene oxide polyols, polypropylene oxide polyols, polyethylene oxide polyols, hydroxy-terminated polybutadienes, aliphatic glycols, polyester polyols (e.g., polyacrylate polyols or polycaprolactone polyols), fatty alcohols, and triglycerides (e.g., castor oil) such as are described in U.S. Patent No.
4,511,626. Mixtures of polyols can also be used.
Because of their hydrolytic stability in the cured * Trade-mark _- 5a 1 336469 60557-3476 compositions of the invention, preferred classeæ of polyols are polypropylene oxide polyols, ethylene oxide-terminated polypropylene oxide polyols, and polytetramethylene oxide glycols, particularly those having a number averaqe molecular weight from about 500 to 6000. Suitable commercially available polytetramethylene oxide glycols include the "QO Polymeg R 650, 1000, or 2000 series, commercially available from Quaker Oats Co., and "Terathane " 650, 1000, or 2000 serie~, commercially available from E.I. du Pont de Nemours & Co., Inc. Suitable commercially available polypropylene oxide polyols include the ~ ~ * ~
"Niax " series "PPG" , "LHT" , and "LHG" commercially available from Union Carbide Corp. Ethylene oxide terminated polypropylene oxide polyols are commercially available as the "Poly G" series, available from Olin Chemicals.
The equivalent ratio of oxazolidine to isocyanate preferably should be from about 0.1 to about 1.2 to 1Ø

* Trade-Mark -6- l 336469 -Decreasing quantities of oxazolidine reduce the effectiveness of carbon dioxide suppression, while increasing quantities result in excess unreacted oxazolidine, which can lead to a reduction in strength of the cured composition, excessive 5 tackiness and a gummy consistency, all undesirable characteristics.
The compositions of the invention can contain other ingredients or adjuvants if desired. For example, extenders or reinforcing fillers (e.g., carbon black, metal oxides such 10 as zinc oxide, and minerals such as talc, clays, silica, silicates, and the like) may be included to impart particular characteristics to the composition.
Plasticizers such as partially hydrogenated terphenyls (e.g., ~HB-40 , commercially available from 15Monsanto Corp.), alkylsulfonic ester of phenol (e.g., "Mesamol ~, commercially available from Mobay Chemical Corp.), dioctyl phthalate, dibutyl phthalate, diisodecyl phthalate, or tri-cresyl phosphate can also be employed in the compositions of the invention.
Solvents such as toluene, xylene, methyl ethyl ketone, acetone, ethyl acetate, mineral spirits and VM and P
naphtha and other suitable materials free of isocyanate-reactive moieties can be employed in the compositions of the invention.
In addition, the compositions can contain antioxidants, pigments, W absorbers, adhesion promoters (e.g., silanes such as mercapto silanes or aminosilanes or tackifying resins such as terpenephenolics), drying agents (e.g., molecular sieves such as sodium aluminum silicate or 30desicants such as zeolite) and the like.
The prepolymers of the invention are made using conventional methods. Typically, they are prepared by reacting an excess of one or more polyisocyanates with one or more polyols to produce a prepolymer having residual 35isocyanate functionality.

r ~ d~ ~

~7~ l 336469 The compositions of the invention when properly compounded have utility as adhesives, coatings, and sealants and can be applied to a variety of articles and substrates, such as articles or substrates of glass, metal, plastic, 5 wood, leather, masonary, textiles, and the like. They find particular utility where low shrinkage, void free compositions are required such as sealing concrete joints.
The invention is further described by the following non-limiting examples wherein all parts are by weight unless 10 otherwise specified.

Example 1 A composition of the invention was prepared by adding to a reaction vessel, fitted with a nitrogen inlet and 15 a thermometer, 16.49 parts (13.2 NCO equivalents) of flake MDI, 21.06 parts (1.0 OH equivalent) polypropylene oxide polyol ("Niax LHT-28", Union Carbide). Mixing was started and the mixture was heated to 60C. Then, 52.45 parts (5.2 OH
equivalents) polytetramethylene ether glycol, MW 2000 20 ("Polymeg 2000", Quaker Oats Co.) and 10.0 parts partially hydrogenated terphenyl ("HB-40", Monsanto Corp.) were added.
The mixture was held at 60C for 3 hours then cooled to about 55C and stored in a sealed container.
A :~To 535 parts of this prepolymer were added, under 7 25 nitrogen and with stirring, 50 parts fumed silica (nCab-O-Sil~
TS-720", Cabot Corp ), 40 parts titanium dioxide, 160 parts -talc ("Mistron RCS , Cyprus Industrial Minerals Co.), 7.5 parts gamma-mercaptopropyltrimethoxy silane ("Silane A-189~
Union Carbide), 100 parts alkylsulphonic ester of phenol 30 ("Mesamoll", Mobay Chemical Corp.), 47.3 parts urethane bisoxazolidine ("Hardner OZ", Mobay Chemical Corp.), and 20 parts toluene. The resultant product was transfered to conventional plastic caulking cartridges. The sealant was dispensible using a manual caulking gun, and in the plastic 35 containers, the composition maintained a caulkable viscosity in excess of six months when stored at about 25C.
d~ -r~

_ 1 336469 Example 2 A composition of the invention was prepared by adding to a reaction vessel fitted with a nitrogen inlet, 5 stirrer and thermometer, 10.72 parts (19.7 NCO equivalents) of an 80:20 mixture of tolylene-2,4-diisocyanate and tolylene-2,6-diisocyanate and 9.99 parts toluene, 21.03 parts (3.3 OH equivalents) polypropylene oxide glycol, MW 2000, ("Niax Polyol PPG-2025", Union Carbide) and 58.19 parts (6.6 10 OH equivalents) polypropylene oxide polyol ("Niax LHT-42", Union Carbide) with stirring. The reaction mixture was slowly heated to about 80C and held there for about 3 hours then cooled to about 52C. Then, 0.07 part dibutyltin d~laurate was added and mixing and cooling continued for about 1 hour.
15 The resultant prepolymer was stored in a sealed container.
To 45.6 parts of this prepolymer were added, under nitrogen and with stirring, 2.7 parts titanium dioxide; 2.7 parts zinc*oxide; 20.7 parts talc; 0.06 part carbon black ' ("Raven 410", Cities S~rvice Co.); 8.3 parts terpenephenolic 20 resin (nPiccofyn A-135~, Hercules); 1.9 parts fumed silica;
2.0 parts urethane bisoxazolidine; 1.1 parts silane containing primer (prepared by mixing 1610 g. biuret of hexamethylene diisocyanate ("Desmodur N-75", Mobay Chemical Co.), 427 g. silane and 1.3 g. dimethylpiperazine in a three 25 liter four inlet resin flask equipped with mechanical stirrer, reflux condenser, and nitrogen supply, for two hours at 80C with stirring), and 15.2 parts 1-methoxy-2-acetoxy propane.
This composition was applied as a sealant to 30 concrete. The composition was poured into a gap of 1.5 cm between blocks, 15 1/2 cm x 5 1/2 cm x 5 cm, of aggregate concrete. The composition was cured at 25C, 50% R.H. for 7 days, followed by 2 days at 49C. The cured sealant was relatively free of voids when cut open and inspected.

~tra de - n~ar Example 3 and Comparative Examples 1-3 These examples illustrate the storage stability of the compositions of the invention utilizing a urethane bisoxazolidine versus the same prepolymer catalyzed with 5 conventional urethane catalysts such as amines and tin salts.
Using the prepolymer of Example 1, four one-part moisture curable compositions were prepared and evaluated.
Example 3 was prepared with 8.54 parts of "Hardner OZ".
Comparative Example 1 was prepared with 0.2 part of "Niax 10 A-99" (a tertiary amine catalyst, commercially available from Union Carbide Corp.). In Comparative Examples 2 and 3, 0.8 part and 0.1 part respectively of dibutyltin dilaurate (DBTDL) were added. Set out below in Tables 1-4 are the viscosity measurements after containers of samples had been 15 exposed to various temperatures. Measurements in centipoises (cps) were taken with a Brookfield RVF viscometer using a #6 spindle and speed of 4 RPM with sample temperature at about 23C.

Example 3 ~ prepolymer + 8.54 parts Hardner OZ
Comparative Example 1 ~ prepolymer + O.2 part NIAX A-99 Comparative Example 2 - prepolymer + 0.8 part DBTDL
Comparative Example 3 - prepolymer + 0.1 part DBTDL

-lo- 1 336469 Table 1 - 24C Viscosity (cps) Comp. Comp. Comp.
Ex. 3 Ex. 1 Ex. 2 Ex. 3 Initial 48,750 50,00050,000 50,000 1 week 51,250 55,00061,250 50,000 2 weeks 51,250 51,87575,625 52,500 3 weeks S0,000 50,00096,250 53,750 4 weeks 52,500 52,500143,750 51,200 5 weeks 55,000 55,000231,250 53,750 6 weeks 51,250 53,750375,000 57,500 7 weeks 56,250 57,500 >500,000 56,250 8 weeks 67,500 67,500 gelled 18 weeks 77,500 77,500 75,000 1 year 130,000 120,000 165,000 Table 2 - 38C Viscosity (cps) Comp. Comp. Comp.
Ex. 3 Ex. 1 Ex. 2 Ex. 3 Initial 48,750 50,000 50,000 50,000 1 week 56,250 56,250 161,250 55,000 2 weeks 61,250 61,250 >500,000 62,500 3 weeks 62,50062,500 gelled 67,500 25 4 weeks 78,75072,500 70,000 5 weeks 88,75077,500 82,500 6 weeks 85,00087,500 93,750 7 weeks 98,750102,500 107,S00 8 weeks 122,500 136,250 30 18 weeks 310,000 >500,000 470,000 ~ Table 3 - 49C Viscosity (cps) Comp. Comp. Comp.
Ex. 3 Ex. 1 Ex. 2 Ex. 3 5 Initial 48,750 50,00050,000 50,000 1 week 67,500 65,00078,750 65,000 2 weeks 86,250 68,750297,500 83,750 3 weeks 112,000 75,000gelled 100,000 4 weeks 140,000 91,250 112,500 10 5 weeks180,000 172,500 162,500 6 weeks193,750 375,000 185,000 7 weeks235,000 >500,000 250,000 8 weeks290,000 gelled 18 weeks >500,00 gelled Table 4 - 60C Viscosity (cps) Comp. Comp. Comp.
Ex. 3 Ex. 1 Ex. 2 Ex. 3 20 Initial48,750 50,000 50,000 50,000 1 week 82,500 72,500 gelled 88,750 2 weeks210,000 131,250 181,250 3 weeks 375,000 gelled 390,000 4 weeks >500,000 >500,000 25 5 weeks gelled gelled 6 weeks 7 weeks 8 weeks 18 weeks The composition of the invention, Example 3, performed better than or as well as Comparative Examples 1-3 at all temperatures tested. Furthermore, Comparative Examples 1-3 all produced undesirable CO2 gas, which will not allow 35 formation of a void-free coating.

-12- l 336469 Comparative Example 4 This comparative example illustrates the decreased storage stability of compositions utilizing an adipate-based bisoxazolidine.
A moisture curable composition was prepared and evaluated as in Example 3 using the prepolymer of Example 1 and 6.83 parts (1 equivalent) of an adipate-based bisoxazolidine ("QM-1007", commercially available from Rohm and Haas Co.). Viscosity measurements are set out in Table 5 10 below.

Table 5 - Viscosity (cps) 15 Initial 82,500 85,00082,500 82,500 24 hr. 81,250 87,500131,250 158,750 1 week 88,750 131,250132,500 315,000 2 weeks 98,750 126,250178,750 >500,000 3 weeks 100,000 141,250265,000 gelled 20 4 weeks 123,750 158,250352,000 5 weeks112,500 170,000395,000 6 weeks135,000 180,000485,000 7 weeks140,000 235,000>500,000 11 weeks270,000 gelled This example appears to support the theory tha~ a bisoxazolidine capable of containing free acid exhibits decreased storage stability.

Claims

1. A storage-stable, hydrocurable, one-part composition comprising a urethane oxazolidine and an aromatic polyfunctional isocyanate or aromatic isocyanate prepolymer.

2. The composition of claim 1 wherein said urethane oxazolidine has the structural formula:

wherein:
R1 represents an aliphatic hydrocarbon group having from 2 to 6, carbon atoms;
R2 and R3 may be the same or different and represent hydrogen, aliphatic hydrocarbon groups having 1 to 4 carbon atoms, cycloaliphatic hydrocarbon groups having 5 to 7 carbon atoms, or aromatic hydrocarbon groups having 6 to 10 carbon atoms or, together with the ring carbon atom, they may represent a five-membered ring, R4 represents an aliphatic hydrocarbon group having from 2 to 6 carbon atoms;
R5 represents a group which is obtained by removal of the isocyanate groups from an organic isocyanate; and n represents an integer of from 1 to 6.

3. A composition according to claim 2 wherein R1 is a hydrocarbon group having from 2 to 3 carbon atoms, R2 and R3 are the same or different groups and are hydrogen or an aliphatic hydrocarbon group having from 1 to 4 carbon atoms, R5 represents a group which is obtained by removal of the isocyanate groups from an organic di- or tri- isocyanate and n is an integer of 2 or 3.

4. The composition of claim 1 wherein said urethane oxazolidine is a urethane bisoxazolidine.

5. The composition of claim 1 wherein the equivalent ratio of said oxazolidine to said isocyanate is between about 0.1 and 1.2 to 1Ø

6. The composition of claim 5 wherein said equivalent ratio of said oxazolidine to said isocyanate is between about 0.25 and 1.0 to 1Ø

7. A polymeric urethane material formed by contacting a composition according to claim 1 with water.

8. The polymeric urethane material of claim 7 wherein said oxazolidine is a bisoxazolidine.

9. An article of manufacture comprising a substrate having a coating of said polymeric urethane material of claim 7 on at least a portion thereof.