CA2242132A1 - One component polyurea coating - Google Patents

Abstract

A new one-component polyurea coating composition which is curable at ambient temperature and comprises, a quasi-prepolymer isocyanate, having an NCO
content of about 7 to about 30, a polyamine resin component in the form of a Schiff base blocked amine dispersed throughout the isocyanate, and said composition being formulated at an index between about 100 to 160, and wherein the composition is moisture insensitive, and no catalyst is required to effectuate curing.

Description

ONE COMPONENT POLYUREA COATING

This application is a continuation in part of applicant's copending U.S.
provisional application, Serial No. 60/056,212, filed August 21, 1997.

B~ck~round Of The Invention This invention broadly relates to a new one component polyurea coating system. There are several pertinent differences between this invention and prior art coatings that are important: (1) This invention is truly amine cured (urea linkages) and is moisture initi~ted only. Existing systems typically have been full prepolymers comprised of polyisocyanates and polyols which react to form urethane linkages. The excess NCO
content of the full prepolymers are typically in the range of 3.0 to 4Ø The final cure is accomplished by reaction with atmospheric moisture which does form urea linkages as follows: the moisture (water) reacts slowly with the isocyanate (3-4 NCO content) to forrn carbamic acid, which then quickly dissociates to forrn an amine, which can then react with isocyanate to form urea linkages. The percentage of urea linkage is low since the prepolymer contains urethane linkages. Typical moisture cure elastomer systems require a catalyst. In this invention no catalysts are required. However, a catalyst can be used if desired. An important advantage of this invention is that these systems are extremely moisture insensitive. They do not liberate CO2 with exposure to atmospheric moisture caused by reaction of the isocyanate and water. Atmospheric moisture reacts with the complexed Schiff bases, decomposing them into their constituent amines, which, in turn react rapidly with the isocyanate. Atmospheric moisture-isocyanate-carbamic acid reaction - 1 - 2~00-o l 003 proceeds very slowly and is essentially eliminated by the much more aggressive moisture-Schiff base reaction. As a result, the coatings of this invention will cure without detriment, regardless of high moisture content. Existing moisture cured urethanes do liberate CO2 gas as a by-product. That gas must have time to migrate to the coating surface and escape in order to have as a solid polymer and not have reduced density due to entrapped cellular. (2) This invention works well with quasi-prepolymers having NCO
contents of 8 and higher, i.e., all of the way to "one-shot" non-prepolymerized isocyanates having NCO content of around 30. Existing earlier systems typically were based upon full prepolymers (polyurethane linkages) having NCO contents of around 3.0 to 4Ø
Applicant's new composition with high NCO content permits fast, low viscosity systems, and can be sprayed at 100% solids with no solvents required. This invention is based on an NCO content of about 7 to 30, preferred NCO content of 9 to 18, and most preferred NCO content of 10 to 16. (3) Existing earlier moisture cured systems typically were forrn~ ted at an index of about 200, whereas this invention utilizes a much lower index.
Broadly it should be an index of about 100 to 160, preferably an index of 100 to 140, and most preferably an index of about 105 to 130.

Description Of The Invention Broadly stated this invention involves a new one-component polyurea coating composition which is curable at ambient temperature and comprises, (a) a quasi-prepolymer isocyanate, having an NCO content of about 7 to about 30, (b) a polyamine resin component in the form of a Schiff base blocked amine dispersed throughout the isocyanate, said composition being formulated at an index between about 100 to 160.
When a diamine is used as the polyamine resin, the diamine may be de~med as a polyoxyalkylene (li~min~. One group of appropriate polyoxyalkylene ~i~mines that may be used are those sold by Huntsm~n Corporation as JEFFAMINE~ D-Series products having the formula:

H2N-CI H-CH2- [-O-CI H2-CH],r-NH2 R' R' wherein R' independently represents hydrogen or methyl and x is a number having an average value of about 1 to about 60.
Representative products having this structural formula include polyoxypropylene diamines with the structure above where x has the following values:

x = 2 to 3 for JEFFAMINE~ D-230 x = 5 to 6 for JEFFAMINE~ D-400 x = ~ 33 for JEFFAMINE~ D-2000 and x = ~ 60 for JEFFAMINE~ D-4000 This invention works equally well with the polyoxyalkylene amines in conjunction with both aromatic and cycloaliphatic diamine cross-linkers. Diethyltoluene diamine (DETDA or ETHACURE~9 l00) and Di(methylthioether)toluene diamine (ETHACURE~ 300) are examples of aromatic based materials, while isophorone diamine (VESTANAT~ IPD), 1,4-diaminocyclohexane and 1,2-diaminocyclohexane are examples of cycloaliphatic (li~min~s. Combinations of high and low molecular weight difunctional and trifunctional polyoxyalkylene amines (JEFFAMINE~9 D-230, D-400, D-2000, D-4000, T-403, T-3000 and T-5000) can also be used alone. It has been discovered that combinations of (li~min~s and triamines are also usable.
When a triamine is used as the polyamine resin, the triamine may be defined as a polyoxyalkylene triamine. One group of such triamines is shown by the formula:

H2C-(O-CH2- ~Cl H)l-NH2 R' H-f-(O-CH2-CI H)y-NH2 H2C-(O-CH2- ICH)z~NH2 (where -- x + y+ z = 3~70) And, x + y + z = ~40-50 for JEFFAMINE T-3000;
x + y + z = ~ 70-80 for JEFFAMINE T-5000 For T-403 (Hnn~m,-n Triamine 403) x + y + z = 5.3 H2C-(O-CH2- ICH)r-NH, R' CH3-CH2- I (O_CH2_Cl H)y~NH2 H2C-(O- CH2- CH) - NH2 In order to further illustrate the invention, the following examples are provided. It is to be understood, however, that the examples are for illustrative purposes and are not intended to be limiting of the scope of the invention as set forth in the subjoined claims.

I~XAMPI,E I
Coating system was prepared by blending 100 parts of "A" component quasi-prepolymer A 444 (see Glossary description hereinafter) with 133 parts of "B" component which was prepared by addition reaction of isobutyraldehyde to the two ~ mines and one triamine to produce a Schiff base (complexed, blocked amine). The water liberated in that reaction was stripped by vacuum azeotropic distillation. Balance of the "B" formula was then added and blended into the anhydrous Schiff base.
Following is the "B" formula for example I coating system (in parts by weight) (see Glossary, which appears later herein, for description of chemicals used).

JEFFAMINE~ D-2000 48.46 JEFFAMINE~ T-5000 12.46 ETHACURE~9 100 16.00 ISOBUTYRALDEHYDE 17.00 PIGMENT 25.00 BAYLITH~ L PASTE 12.00 SILQUEST~9 A 187 (from O.S.I. Co.) 0.50 BYK~9 A501 0.50 BYK~9 320 0.75 METACURE~ T-12 1.00 TOTAL 133.67 Viscosity of the resulting coating system was four hundred fifty centipoise at room temperature (75~F). Several 3 x 6 inch steel panels were brush coated to a thickness of approximately .005 inches. The coatings were allowed to cure by atmospheric moisture. The surfaces became dry to touch in seventy five minutes and hard overnight.

Example II coating system "B" component was prepared by the same method as example I coating system "B" component described above. Example III through example XV coating system "B" components were formulated using the commercially available Schiff bases itemized below on the following pages.
There are advantages of preparing proprietary Schiff bases. A full and continuous range of blocked amine equivalent weight products is possible by complexing different ratios of the various molecular weight polyoxyalkylene amines and low molecular weight aromatic or aliphatic amine cross-linkers with isobutyraldehyde.
Properly formulated combinations will function as single curatives that produce desired properties in cured elastomers, handling, processing, curing profiles and cured product physical properties can be maximized with various amine component combinations.
Currently, there are a very limited number of Schiff bases commercially available. They all have similar, low equivalent weights. Formulating concessions are required when using them that are not necessary when high equivalent weight versions are incorporated. They do, however, work when properly incorporated as is demonstrated by the example formulas herein.

The following tabulated examples were all prepared according to this invention.
Polyurea One-Component (2 K) Co~ting EXAMPLES II III IV V VI VII VIII IX X
Isocyanate A Component POLYARMOR0 A444 IOO. --- --- 140. 140. 115.115. lOO. ---POLYARMOR0 CF-60 A --- lOO. IOO. --- --- --- --- --- ---MONDUR0 ML --- --- --- --- --- --- --- --- lOO.
Resin B Component VESTAMIN0 A-139 --- 30.3 30.3 49.7 49.7 49.749.7 32.72 112.DESMOPHEN0 XP-7069E --- --- --- --- --- --- --- --- ---JEFFOX0 PPG 2000 --- 30.3 30.3 10.85 9.85 13.312.6 --- ---JEFFAMINE0 D-2000 48.75 --- --- --- --- --- --- --- ---ETHACURE0 lOO 17.93 --- --- --- --- --- --- --- ---UNILINK0 4200 2.25 --- --- --- --- --- --- --- ---PIGMENT 25. 25. 25. 25. 25. 25. 25. 9.8 ---BAYLITH0 L PASTE 12. 11.65 11.15 12.7 12.7 --- 12.7 --- ---BAYLITH0 L POWDER --- --- --- --- --- 12. --- --- ---SILQUEST A-187 0.5 0.5 0.5 0.5 0 5 --- --- ---BYK0 A501 0.5 0.5 0.5 0.5 0.5 0.75 BYK0 052 --- --- --- --- --- --- --- 0.75 BYK0 320 0.75 0.75 0.75 0.75 0.75 --- --JEFFCAT0 DMDEE --- --- 1.5 --- l.O --- --- --- ---METACURE0 T-12 0.5 l.O --- --- --- --- --- --- ---PTSI ---ISOBUTYRALDEHYDE 17.0 --- --- --- --- --- -- --- ---~ 7 - 2200-01003 The following tabulated examples were all prepared according to this invention.
Polyurea One-Component (2 K) Coating EXAMPLES XI XII XIII XIV XV
Isocyanate A Component POLYARMOR0 A444 --- --- 140. --- ---POLYARMOR0 CF-60 A --- IOO. --- --- ---POLYARMOR0 A-490 l lO. --- --- 140. ---VESTANAT0 IPDI --- --- --- --- lOO .

Resin B Component VESTAMIN0 A-139 --- --- --- --- lOO.
DESMOPHEN0 XP-7069E --- 34.4 56.4 --- ---DESMOPHEN0 XP-7076 112.3 --- --- --- ---DESMOPHEN0 XP-7071 E --- --- --- 33.2 ---JEFFOX0 PPG 2000 --- 26.2 9.85 10.85 ---ETHACURE0 lOO --- --- ---PIGMENT --- 25. 25. 25. ---BAYLITH0 L PASTE --- 11.65 12.7 12. ---SILQUEST A-187 --- 0.5 0.5 0.5 ---BYK0 A501 1.04 0.5 0.5 0.5 ---BYK0 052 1.04 --- --- ---BYK0 320 --- 0.75 0.75 0.75 JEFFCAT0 DMDEE --- --- I .O --METACURE0 T-12 --- I.O --- l .O ---PTSI --- --- --- ---ISOBUTYRALDEHYDE --- -- --- --- ---Coated specimens were made on 3 x 6 inch steel panels for each of the fifteen example formulas. A small batch of each formulas was produced and brush applied to the steel panels to a thickness of approximately .005 inches. All of the batches and specimens were made during the same day, thus providing common curing conditions for each formula.

Temperature during the trial was 70~F and relative humidity was 40%. Tack free time along with general observations were recorded for each formula. The information is tabulated below.

TACK FREE
FORMULA TIME (min.) OBSERVATIONS
Decent film. Smooth. Relatively short pot life.
II 54 Excellent film. Low elongation. Not brittle.
III 40 Excellent film. High elongation. Pot life > 8 hours.
IV -- Cured well. Slightly brittle. Epoxy-like.
V 42 Brushed very well. Good film. Pot life > 8 hours.
VI 18 High gloss. Good film.
VII 50 Pot life > 8 hours.
VIII 45 Cured well. Surface rough and pitted.
IX 20 Good film.
X 25 Good film. Smooth. Fairly brittle. Epoxy-like.
XI 38 Some exotherm on blending. Slightly milky film. Smooth.
XII 38 Quite brittle. Smooth.
XIII 34 Good film. Smooth. Brushed well.
XIV 40 Good film. Smooth. High gloss.
XV 38 Good film. Slightly brittle. Epoxy-like.

~ 9 - 2200-01003 Description Of Quasi-Prepolymers (Parts By Weight) POLYARMOR~ CF-60A 444A 462A 490A
Modified MDI 60.0 Liquid Uretonimine-modified Methylene Diisocyanate (MDI) 49 4 44 0 Isopllorone Diisocyanate 45 .0 2000 MW Polypropylene Glycol 40.6 40.0 56.0 Polyoxyalkylene Diamine 45 .0 Propylene Carbonate 10.0 10.0 Totals 100.0100.0 100.0 100.0 GLOSSARY
POLYARMOR~ CF-60 A An aliphatic quasi-prepolymer available from Visuron Technologies, Inc. (Bay City, Michigan).
POLYARMOR~ A-444 An aromatic quasi-prepolymer available from Visuron Technologies, Inc. (Bay City, Michigan).
POLYARMOR~9 A-462 An aromatic quasi-prepolymer available from Visuron Technologies, Inc. (Bay City, Michigan).
POLYARMOR~ A-490 An aromatic quasi-prepolymer available from Visuron Technologies, Inc. (Bay City, Michigan).
VESTANAT~ IPDI Isophorone diisocyanate available from Huls America Co.
VESTAMIN~ A-139 A Schiff Base available from Huls America Co.
~ESMOPHEN~ XP-7069E A Schiff Base available from Bayer Co.
~ESMOrIIl~N~ Xr-7071E A Scllit'f Base available from Bayer Co.
~ESMOPHENa~ XP-7076E A Schiff Base available from Bayer Co.
MONDUR~ ML A liquid uretonimine-modified methylene diisocyanate product available from Bayer Co.
JEFFAMINE~ D-2000 An amine-terminated polyoxypropylene diol of 2000molecular weight available from H lntcm:~n Corporation.
JEFFAMINE~ T-5000 An amine-terminated polyoxypropylene triol of 5000 molecular weight available from Hnnt~m~n Corporation.
JEFFOX'~9 PPG-2000 A propylene glycol product have a molecular weight of 2000 from Hunt~m~n Corporation.
ETHACUREX 100 A diethyltolunediamine product from Albemarle Co.
UNILINK~ 4200 An N, N'-Bis(alkyl)methylenetli"niline product from UOP, Inc.
BAYLITH~ L PASTE A molecular sieve in paste form available from Bayer Co.

BAYLITH~ L POWDER A molecular sieve in powder form available from Bayer Co.
SILQUEST~ A-187 Gamrna-Glycidoxypropyltrimethoxy silane. Coupling Agent. Available from O.S.I. Specialties, Inc.
BYK~ A501 Silicone free defoamer from BYK Chemie Co.
BYKQ9 052 Silicone free defoamer from BYK Chemie Co.
BYK~9 320 Silicone free defoamer from BYK Chemie Co.
JEFFCAT~ DMDEE Dimorpholino-dethylether. Amine catalyst for moisture cure. Available from Huntsman Corporation.
METACURE~T-12 Dibutyltindilaurate. Gellation catalyst. Available from Air Products Co.
PTSI p-Toluenesulfonylisocyanate. Monofunctionalmoisture scavenger. A product of VanChem, Inc.
JEFFSOL~9 PC Propylene carbonate available Hunstman Corporation.
ISOBUTYRALDEHYDE Available from Eastman Chemical Co.

Pi~nents Ti-Pure3 R-900 Titanium dioxide available from E.I. du Pont de Nemours, Co.
RAVEN~ 1020 Carbon black available from Columbia Chemicals Co.
Pigment Dispersions Pigments of various colors dispersed in high molecular weight polyol. Available from Plasticolors, Inc.

The volumetric ratio of the "A" isocyanate component and "B" resin component as shown in the examples above should be from about 75 to 25 or reverse;
more preferably 60 to 40 or reverse; most preferably 50:50.

- l 2 - 2200-o l 003 Extended shelf life studies of several versions of example formula III ("A"
and "B" components blended) have been made. It has been observed that the viscosity of the coating in sealed, nitrogen blanketed containers has not increased materially. The curing profile, appearance and physical properties of coated specimens is about the same after 90 days as for freshly blended material and coated samples. Accordingly, it is believed that coatings of this invention will be suitable for true one component, single container (lK) shipment and delivery. (lK = one component).
Studies have been made to accelerate the cure profile of the coatings made under this invention. It has been found that "tack-free time" can be dramatically reduced by exposure to increased humidity. As seen with the example formulas, tack-free time ranging from about thirty to seventy five minutes were achieved at 70~F/40% relative humidity. Separate trials using example formula III coated specimens were exposed to the following conditions: Water mist over the coating at room temperature decreased tack-free time by about 50%, misting with water at 120~F deceased the tack-free time by about 66%
and, finally placing coated specimens of Formula III in atmospheric steam at 150-175~F
resulted in tack-free times as low as sixty seconds. While the extremely fast sixty second tack-free samples exhibited some deterioration, slightly slower three minute tack-free samples were quite good and ten minute tack-free samples were excellent. The benefits are highly advantageous for production coating applications where line speed matched curing profiles are necessary. Similarly, the benefits are highly advantageous for contracting coating applications where turn around and return to use time can be reduced.
These accelerated techniques are not possible with prior moisture cured urethanes.

- 1 3 - 2200-o 1 003 presence of the excess moisture and resulting faster cure rate previously resulted in substantial coating deterioration in the form of bubbles, blisters and pinholes.
The information herein is provided to describe an important embodiment of the one component polyurea technology of this invention. Polyurea is increasingly being used as a concrete floor sealant coating to compete with epoxy, urethanes and other current offerings. Warehouse, shop, office mechanical room and aircraft hanger floors are examples of where such coatings can be highly useful. Interior floor sealing applications such as these are specified primarily to provide attractive floors, seal the concrete against wear and concrete dust, preclude moisture and chemical cont~min~nt intrusion, provide markings such as pedestrian aisle perimeters, and to allow for periodic washing for cleanliness.
Similarly, the coatings of this invention are highly useful in parking deck coating applications. Parking decks are seal coated to protect against weather deterioration, primarily to prohibit intrusion of water and chlorides into the concrete.
They are sealed with an aggregate course included in the upper layer to enhance the wearability of the surface against vehicular tire wear and pedestrian scuffing. Primary reasons for polyurea use are: Quick turn-around and return to use, durability of the cured coating, and cost competitiveness.
Plural component polyurea, however, is substantially limited for the above uses, especially for inside applications, due to the overspray that is a by-product of the high pressure, high velocity material discharge from the spray gun. Fume and misting containment requirements are extensive. Masking and isolation wall preparations generally exceed the actual coating timing. Frequently, such operations are unacceptable, such as in a hospital environment where the fugitive odors and misting are prohibitive.
Exterior installations, such as parking deck coatings are also plagued with overspray, which becomes airborne and coats automobiles and structures. Meticulous attention needs to be given to the wind conditions and direction with corresponding screening utilized. Experience on many jobs with contractors has proven that adequate protection is only seldomly used.
Several approaches have been attempted in the past to overcome these prior problems and difficulties. (1) Topcoat the polyurea seal coat with epoxy. Poor solution since epoxy is not color-fast. It is also brittle and is well known for cracking and crazing.
(2) Topcoat the polyurea seal coat with commercial moisture cured pigmented urethane or clearcoat. The urethanes are color-fast, have decent elongation, but also have solvents and have not been very well received by end users. The solvents generate unacceptable fumes.
(3) Several end users have tried to topcoat aromatic polyurea seal coat with aliphatic polyurea. There are, however, serious deficiencies: The overspray and fumes are still present; cleaning the spray machine and hoses and the changeover from aromatic to aliphatic is very time consuming and expensive, and; the logistics of when and at what stage of the job to changeover are highly problematical.
This new one component polyurea of this invention solves all of the above over coating problems. (1) It has sufficient working time. It can be brush, roller, squeegee or spray applied. When airless sprayed, the overspray is minim:~l. When coated out by the other methods the overspray is totally elimin~ted. The odors emitted are - 1 5 - 2200-o 1 003 reasonable regardless of tlle application metho(l. (2) For interior applications, the base sealing coat could be non-spray applied one component aromatic polyurea. Upon sufficient cure, that could be followed with the topcoat of aliphatic one component, also by non-spray methods. (3) For exterior applications (and those interior permitting) the seal coat could be plural component aromatic polyurea sprayed followed within minutes with the one component aliphatic airless sprayed from a separate pump by another operator (including aggregate, if required). The topcoat could either be pigmented of clearcoat which provides depth.
The spectrum of suitable embodiments for the coatings of this invention is very large. These coatings are ideal as protective barriers for steel engineering structures such as buildings, storage tanks and bridges as well as for mobile vessels like ship hulls, railcars~ trucks and automobiles and civil engineering -- road marking coatings. They are also excellent sealants for all types of masonry surfaces in addition to flooring cited above.
Also, wood sealing is very cost effective and provides protection and aesthetic value in al types of applications.
While it will be apparent that the preferred embodiments of the invention disclosed above are well calculated to fulfill the objects, benefits and advantages of the invention, it will be appreciated that the invention is susceptible to modification, variation and change without departing from the proper scope or fair meaning of the subjoined claims.

- 1 6 - 2200-o 1 003

Claims (18)

1. A new one-component polyurea coating composition which is curable at ambient temperature and comprises, (A) a quasi-prepolymer isocyanate, having an NCO content of about 7 to about 30, (B) a polyamine resin component in the form of a Schiff base blocked amine dispersed throughout the isocyanate, said composition being formulated at an index between about 100 to 160, and wherein the composition is moisture insensitive.

2. The composition of claim 1 wherein, no catalyst is required to effectuate curing.

3. The composition of claim 2 wherein, said NCO content is about 9 to about 18, said index is between about 100 to about 140.

4. The composition of claim 1 wherein, said NCO content is about 10 to about 16, said index is between about 105 to about 130.

5. The composition of claim 1 wherein, said NCO content is about 9 to about 18, said index is between about 100 to about 140, and said polyamine resin component contains one or more products having the formula:

wherein R' independently represents hydrogen or methyl, and x is a number having an average value of about 1 to about 60.

6. The composition of claim 1 wherein, said NCO content is about 9 to about 18, said index is between about 100 to about 140, and said polyamine resin component contains one or more products having the formula:

where, x+y+z = 3.0 to 70, and wherein R' independently represents hydrogen or methyl, and x is a number having an average value of about 1 to about 60.

7. The composition of claim 1 wherein, said NCO content is about 9 to about 18, said index is between about 100 to about 140, and wherein the composition is moisture insensitive, and a coating applied from the composition will cure without detriment regardless of possible high moisture content.

8. The composition of claim 1 wherein, said NCO content is about 9 to about 18, said index is between about 100 to about 140, and the polyamine resin component is a polyoxyalkylene amine useable in conjunction with either an aromatic or cycloaliphatic diamine cross-linker.

9. The composition of claim 1 wherein, said NCO content is about 9 to about 18, said index is between about 100 to about 140, and wherein said polyamine resin component is a combination of high and low molecular weight difunctional and trifunctional polyoxyalkylene amines.

10. The composition of claim 3 wherein, said composition has a pot life of at least 3 hours to about 24 hours.

11. The composition of claim 1 wherein, said NCO content is about 9 to about 18, said index is between about 100 to about 140, and a combination of diamines and triamines is used for the polyamine resin component.

12. The composition of claim 1 wherein, said NCO content is about 9 to about 18, said index is between about 100 to about 140, and the volumetric ratio of the A component to the B component is within the range of about 75:25 to about 25:75.

13. The composition of claim 1 wherein, said NCO content is about 9 to about 18, said index is between about 100 to about 140, and the volumetric ratio of the A component to the B component is within the range of about 60:40 to about 40:60.

14. The composition of claim 1 wherein, said NCO content is about 9 to about 18, said index is between about 100 to about 140, and the volumetric ratio of the A component to the B component is about 50:50.

15. The composition of claim 13 wherein, said composition after application is tack free within 20 to 60 minutes.

16. The composition of claim 1 wherein, said NCO content is about 9 to about 18, said index is between about 100 to about 140, and the composition is suitable for one component single container shipment.

17. The composition of claim 1 wherein, said NCO content is about 9 to about 18, said index is between about 100 to about 140, and wherein a coating applied from the composition is tack-free within about one to three minutes.

18. The composition of claim 14 wherein, said composition after application is tack free within 20 to 60 minutes.