CA2125225A1 - Rapid curing polyurethane composition useful as a coating or sealant - Google Patents

Abstract

RAPID CURING POLYURETHANE COMPOSITION
USEFUL AS A COATING OR SEALANT
ABSTRACT OF THE DISCLOSURE
A storage-stable, rapid curing one-component polyurethane composition useful as a sealant or coating is made with an isocyanate prepolymer having an isocyanate group content of from about 4 to about 6% and a molecular weight of from about 1400 to about 2100, an oxazolidine and optionally a catalyst.
The prepolymer used is the reaction product of toluene diisocyanate, a polytetramethylene ether glycol having a molecular weight of from about 500 to about 1500 and a diol having a molecular weight of from about 50 to about 200. This composition is useful as a coating or sealant for porous substrates, particularly wood-based products such as wood composites and flake board.

Description

212~2?,~.3 Mo3966 RAPID CURING POLYURETHANE COMPOSITION
USEFUL AS A COATING OR SEALANT
BACKGROUND OF THE INVENTION
The present invention relates to a system, particularly a one-component system, wh;ch cures at ambient temperature to form a polyurethane composition useful as a coating or sealant.
Coating and sealant compositions based upon polyurethanes and polyureas are known. Such compositions are typically available as either one-component or two-component systems.
lo U.S. Patent 5,126,421, for example, discloses a two-component system in which an isocyanate prepolymer is cured with a system composed of an oxazolidine moisture scavenger and a hydroxyl curing agent. The hydroxyl curing agent is preferably a polyhydric polyol such as ethylene glycol, butanediol, a polyether polyol, or a polyester polyol. The curing system is added to the isocyanate prepolymer shortly before it is to be applied to a substrate and allowed to cure at ambient temperature. -Two-component systems, such as that disclosed in U.S. -Patent 5,126,421, avoid the storage stability problems encountered with one-component systems. However, two-component systems are not as easy to use as one-component systems.
One-component coating systems are disadvantageous in that they employ aromatic polyisocyanate prepolymers. After such systems are applied to a substrate, the skin which forms reduces the amount of atmospheric moisture available to complete the curing reaction and thus slows the curing process.
Taub et al reported in their paper, "Polyfunctional Isocyanate-Oxazolidine Resins" which was presented at the Water-Borne & Higher Solids Coatings Symposium in February 1989 that storage-stable one-component urethane coatings could be prepared by reacting aliphatic diisocyanate prepolymers with N-2-hydroxyethyl oxazolidines. Taub et al also reported that aromatic isocyanate prepolymers did not produce storage stable 35376LM~368 ,,- . ; : ~ , ,: , i,. . ,. , - . :

i one-component urethane coatings. Aliphatic isocyanate-based systems such as those disclosed by Taub et al are, however, disadvantageous in that they have extremely slow cure times and "; are too expensive for most automated wood coatings production , 5 lines.
A one-component system which is easy to use, cures within , short per;ods of time and is storage stable would therefore be ~ particularly advantageous.

It is an object of the present invention to provide a storage-stable, one-component system which cures within a short `ZZ period of time.
It is another object of the present invention to provide a coating material which is moisture resistant.
¦ 15 It is a further object of the present invention to provide a process for coating a substrate in which the coating material -dries within minutes of its application.
It also an object of the present invention to provide coated materials~particularly coated wood materials,which are sufficiently moisture resistant to be useful in construction ; - -~applications.
These and other objects which will be apparent to those skilled in the art are accomplished by a system composed of a toluene diisocyanate prepolymer having a molecular weight of from about 1400 to about 2100 and an isocyanate group content of from about 4 to about 6% and an oxazolidine. It is preferred that an acid anhydride also be included in this system.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is a graph illustrating the results of the stability studies done at room temperature on the formulations of the present invention described in Examples 1-5.
Figure 2 is a graph illustrating the results of stability studies done at 60C on the formulations of the present invention described in Examples 1-5.
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Figure 3 is a graph illustrating the results of stability studies done on the formulations described ;n Examples 6-10.
Figure 4 is a graph illustrating the results of the stability studies done at room temperature on the formulations described in Examples 11 and 12.
DETAILED DESCRIPTION OF THE PRESENT INVENTION
The present invention relates to a one-component, fast curing, storage-stable system which is made up of a prepolymer of toluene diisocyanate and an oxazolidine having a molecular lo weight of from about 1400 to about 2100 and an isocyanate group content of from about 4 to about 6%. An acid anhydride catalyst is also preferably included in the system. The present invention also relates to a process for producing coatings and sealants from this system and to substrates coated n with this system. The systems of the present invention are useful for coating and sealing porous substrates such as wood, ~ ~
wood composites and flake board. ~ - -Isocyanate prepolymers are known. The toluene diisocyanate prepolymers of the present invention may be formed in accordance with any of the procedures known to those in the art. These prepolymers are preferably formed by reacting toluene diisocyanate with relatively high molecular weight polyhydroxyl compounds, particularly polyether polyols, and a low molecular weight glycols in amounts such that the resultant prepolymer will have an isocyanate group content of from about 4.0 to about 6.0 at 100% solids. Isocyanate to hydro~yl group ~-ratios of from about 1.5 to about 2.0 are generally appropriate. The most preferred high molecular weight polyether polyols for use in the production of the prepolymers of the present invention are the polytetramethylene ether glycols haYing molecular weights of from about 500 to about 1500, preferably about 1000. These polyether polyols are commercially available under names such as Polymeg and Terathane.

Mo3966 ^` ~12~225 The low molecular weight hydroxyl group containing compounds included in the materials used to produce the toluene diisocyanate prepolymers useful in the present invention generally have a molecular weight of from about 50 to about 200. Low molecular weight diols such as ethylene glycol and 1,3-butanediol are particularly preferred. These hydroxyl compounds are generally used in amounts of from about 1.0% to about 5.0%, based on the weight of high molecular weight polyol in the prepolymer forming reaction mixture. The low molecular lo weight diols have been found to be particularly advantageous because they reduce the amount of residual monomeric toluene diisocyanate in the product prepolymer.
Any of the known oxazolidines may be used in the compositions of the present invention. These oxazolidines may contain one or more oxazolidine structures. Appropriate oxazolid;nes are described, for example, in U.S. Patents 5,189,176 and 4,00~601. The oxzol;d;ne may also be obta;ned from polymers or oligomers having inherent oxazolidine functionalit;es. Suitable monocyclic oxazolidines are represented by the formula CH2 CIH2 '`~

C

Rl R2 ;.:

in which R represents an oligomeric or polymeric chain containing at least one carbon atom which chain may be substituted, R1 represents hydrogen, an aliphatic or aromatic group, and R2 represents hydrogen, an aliphatic or aromatic group.
Su;table bis-oxazolidines are represented by the formula Mo3966 , ~ ' . ,., ~ , , ' ~:

2 ~ 2 ~ 2 2 ~;

C C

S ~

Io in which R represents an oligomeric or polymeric chain, R1 represents H, aliphatic or aromatic group, and R2 represents H, aliphatic or aromatic group.
The monocyclic oxazolidine in which R represents an ethoxy group, R1 represents a methyl group, and R2 represents a methyl group is preferred.
The bis-oxazolidine which is a blend of the reaction products of oxazolidinylethanol and hexamethylene diisocyanate and oxazolidinylethanol and isophorone diisocyanate is most preferred.
The oxazolidine is generally included in the systems of -~
the present invention in an amount of from about 1% to about 30% by weight, preferably, frnm about 11.5% to about 26.6% by weight, based on the total weight of the system.
Curing of the systems of the present invention is promoted by including an acid anhydride catalyst in the system. Use of such catalyst is therefore preferred. Any of the known acid 3o anhydrides may be used. It has been found, however, that acid anhydrides of dicarboxylic acids are particularly useful. An example of a preferred acid anhydride suitable for use in the systems of the present invention is methylhexahydrophthalic Mo3966 ~` 2~22~

anhydrid~ such as that which is commercially available under the name Lekutherm Hardener M.
The acid anhydride is generally present in the systems of the present invention in an amount of from about 0.1% to about 1.2% by weight, preferably from about 0.01 to about 0.1% by weight, based on the total weight of the system.
Materials which may optionally be included in the systems of the present invention include any of the known fillers, organic solvents, drying agents, surface-active additives, lo anti-foaming agents, pigments, dyes, UV stabilizers, plasticizers, bacteriostatic and fungistatic substances. Known catalysts for the polyurethane forming reaction may also optionally be included. It has been found, however, that the tin catalysts which are commonly used in urethane-forming reactions, significantly reduce the storage stability of the one component systems of the present invention. Tin catalysts should not therefore generally be included in the systems of the present invention.
These optional materials preferably have a low water content (i.e., a water content of less than 0.0~% by weightJ or -~
be treated to remove as much of the water present as is possible prior to use in the systems of the present invention.
Fillers which are useful in the systems of the present invention include: silicate-containing minerals such as antigorite, serpentine, hornblends, amphibiles, chrysotile, talc, mica, and kieselguhr; metal oxides such as kaolin, aluminum oxides, titanium oxides, and iron oxides; metal salts such as chalk and barium sulfate; inorganic pigments such as cadmium sulfide and zinc sulfide; glass; asbestos powder; and carbon fibers. The filler which is commercially available under the name Nytal 400 is particularly preferred.
Organic solvents useful in the systems of the present invention are those having water content of no more than 0.05%
by weight.

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In preparing the systems of the present invent;on, it is preferred that the polyol, particularly where that polyol is a polyether polyol, be treated to remove water present therein.
Such water may, for example, be removed by adding a water scavenger to the polyether prior to use of the polyol in preparing the toluene diisocyanate prepolymer. The oxazolidines useful in the present invention are examples of suitable moisture scavengers. Where an oxazolidine is added to a polyol having a high initial water content, it may be necessary to increase the total amount of oxazolidine used in the production of the one-component systems of the present invention.
It is also preferred that any additives to be used in the system of the present invention which contain more than a trace amount of wa$er, be treated to remove as much of that moisture as possible prior to use in the one-component system. `~
The systems of the present invention are generally storage stable at ambient temperature for at least 3 months.
The systems of the present invention may be used as coatings or sealants on virtually any porous substrate. These systems are particularly advantageous as coatings for composite wood substrates such as lateral strand lumber products, wood flake board products and wood flooring materials. These coatings are typically from 3 to 30 mils thick, preferably from 2~ about 8 to about 20 mils.
The systems of the present invention may be applied to a substrate by any of the techniques known to those in the art.
For example, by brushing it on the substrate or by roll coating. The length of time necessary to completely cure, will, of course, depend upon the thickness of the coating and the temperature and amount of moisture present in the atmosphere surrounding the coated substrate. For example, a coated substrate which is exposed to steam would be expected to cure at a much faster rate than a coated substrate exposed to average atmospheric conditions.
Mo3966 2 1 2 ~ ! . 2 3 Having thus described our invention, the following Examples are given as being illustrative thereof. All parts and percentages given in these Examples are parts by weight and percentages by weight, unless otherwise indicated.
EXAMPLES
In the Examples which follow, the storage stability of the one-component system was determined by measuring the viscosity increase in samples over time. Each material for which the storage stability was to be determined was placed in 15 two-ounce glass jars, each of which was tightly sealed. At pre-determined intervals, the viscosity of the contents of an unopened jar was determined using a Haake Rotoviscometer.
Storage stability determinations were made for samples stored at 25C+ 4C and 60C + 2C.
The following materials were used in making the systems and coatings described in the Examples which follow:
PREPOLYMER A: Formed by reacting toluene diisocyanate which is commercially available from Miles Inc. under the name Mondur TDS, benzoyl chloride, the polytetramethylene glycol which is commercially available under the name Polymeg 1000 and 1,3-butanediol. This prepolymer had an NCO content of 5.1% and a viscosity of 19,500 mPa.s at 25C.
PREPOLYMER B: aliphatic polyisocyanate based on isophorone diisocyanate and dissolved in the organic solvent which is commercially available under the name Aromatic 100.
PREPOLYMER C: an aliphatic/aromatic polyisocyanate copolymer based on toluene diisocyanate and hexamethylene diisocyanate and dissolved in n-butyl acetate.
OXAZOLIDINE: ~he bis-oxazolidine which is a blend of the reaction products of oxazolidinylethanol and hexamethylene diisocyanate and oxazolidinylethanol and isophorone diisocyanate.

Mo3966 2 ~ 2 ~ 2 ~ -3 SOLVENT A: Aromatic organic solvent having a flash point above 150F which is commercially available under the name Aromatic 150.
SOLVENT B: Aromatic organic solvent which is commercially ava;iable under the name Aromatic 100. -FILLER: The material which is commercially available Nytal having a water content of no more than 0.02%.
STABILIZER: Benzoyl Chloride. -ANHYDRIDE: The fatty acid anhydride which is commercially lo available under the name Hardener M from Bayer AG, Germany.
DHCD: Dicyclohexylcarbodiimide.
TIN CATALYST: The tin catalyst which is commercially available under the designation T-12 from Air Products.

40 grams of PREPOLYMER A were combined with 6.87 grams of OXAZOLIDINE. The resultant system had an initial viscosity at room temperature of 1401 mPa.s. After storage for seven days this system had a viscosity at room temperature of 1558 mPa.s.
After 25 days at room temperature the viscosity of the system had increased to 1794 mPa.s. These results at room temperature are presented graphically in Figure 1.
This system was also stored at 60~C and the viscosity measured at this temperature over a period of 14 days. After 1 2~ day the viscosity had increased from 1401 to 1721 mPa.s. After 6 days the viscosity was measured at 2193 mPa.s. At day 14, the system gelled. These results at 60C are presented -graphically in Figure 2.
~XAMPLE 2 40 grams of PREPOLYMER A were combined with 6.87 grams ;~
OXAZOLIDINE and 0.05 grams of ANHYDRIDE (0.1% of the total system). The resultant system had an initial viscosity of 1454 mPa.s at room temperature. After storage for seven days at -~
room temperature, the viscosity had increased to 1595 mPa.s.
After 25 days, the viscosity was 1903 mPa.s at room ; - -~
Mo3966 :

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.~ , . , -- 2 ~ 2 ~3 - l o -temperature. These results are presented graphically in Fiyure 1.
The viscosity increase of this system after storage at 60C was also studied. The viscosity of these samples increased from 1454 mPa.s (initial viscosity) to 1740 mPa.s (1 day) to 235~ mPa.s (6 days) to 4186 mPa.s (14 days). After 21 days~ the system gelled. These results are graphically presented in Figure 2.

lo 40 grams of PREPOLYMER A were combined with 6.87 grams OXAZOLIDINE and 0.14 grams of ANHYDRIDE (0.3% total system).
The viscosity of this system at room temperature and at 60C
was then studied.
At 25C, the viscosity increased from 1419 mPa.s (initial) to 1613 mPa.s (7 days) to 1957 mPa.s (25 days). These results are graphically presented in Figure 1.
After storage at 60C, the viscosity increased from 1419 mPa.s (initial) to 1758 mPa.s (1 day) to 2643 mPa.s (6 days) to 5400 mPa.s (14 days) to 11635 mPa.s (21 days). The sys~em gelled after 42 days. These results are graphically presented in Figure 2.
EXAMPLE 4 -~
40 grams of PREPOLYMER A were combined with 6.87 grams of -~
OXAZOLIDINE and 0.28 grams of ANHYDRIDE (0.6% of total system).
The viscosity increase of th;s system after storage at room temperature and at 60C was studied.
At 25C, the viscosity increased from 1450 mPa.s (initial) to 1631 mPa.s (7 days) to 2084 mPa.s (25 days). These results are graphically presented in Figure 1.
After storage at 60~C, the viscosity of the system increased from 1450 mPa.s (initial) to 1703 mPa.s (1 day) to 2944 mPa.s (6 days) to 8192 mPa.s (14 days) to 16583 mPa.s (21 days). The system gelled after 42 days. These results are graphically presented in Figure 2.

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40.0 grams of PREPOLYMER A were combined with 6.87 grams of OXAZOLIDINE and 0.56 grams of ANHYDRIDE ~1.2% total system).
The viscosity increase of this system after storage at room temperature and at 60C was studied.
After storage at room temperature, the viscosity increased from 1468 mPa.s (initial) to 1685 mPa.s (7 days) to 2820 mPa.s (25 days). These results are graphically presented in Figure 1.
After storage at 60C, the viscosity of the system increased from 1468 mPa.s (initial) to 1757 mPa.s (1 day) to 4530 mPa.s (6 days) to 18470 mPa.s (14 days). The system gelled after 42 days. These results are presented graphically in Figure 2.

640.1 grams of PREPOLYMER A were combined with 110 grams of OXAZOLIDINE and 2.25 grams of DHCD. The viscosity increase during storage at room temperature and at 60C was studied.
After storage at room temperature, the viscosity of the system increased from 1558 mPa.s (initial) to 1631 mPa.s (3 days). The viscosity remained constant 1631 mPa.s up to day 7 when measurement was discontinued.
After storage at 60C, the viscosity of this system increased from 1558 mPa.s (initial) to 1738 mPa.s (1 day) to 2110 mPa.s (3 days) to 2936 mPa.s (7 days). These results are graphically presented in Figure 3.
EXAMPLE 7 -~
640.1 grams of PREPOLYMER A were combined with 110 grams of OXAZOLIDINE, 2.25 grams DHCD, and 1.13 grams of ANHYDRIDE. ~ -The viscosity increase of this system during storage over a period of 7 days at room temperature and 15 days at 60C was -~
studied.
After storage at room temperature, the viscosity increased from 1540 mPa.s (initial) to 1685 mPa.s (3 days) to 1812 mPa.s (7 days)-Mo3966 l . ~ .. .. .. .. .

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2 1 2 ~ ? 2 ~

After storage at 60C, the viscosity of the system increased from 1540 mPa.s (initial) to 1921 mPa.s (1 day) to 2556 mPa.s (3 days) to 2972 mPa.s (7 days) to 6800 mPa.s (15 days). These results are graphically presented in Figure 3.

640 grams of PREPOLYMER A were combined with 110 grams of OXAZOLIDINE, 2.25 grams DHCD, and 2.26 grams of ANHYDRIDE. The viscosity increase of this system during storage over a period of 7 days at room temperature and 15 days at 60C was studied.
Io After storage at room temperature, the viscosity of the system increased from 1596 mPa.s (initial) to 1776 mPa.s ~3 days) to 1862 mPa.s (7 days).
After storage at 60C, the viscosity of the system increased from 1596 mPa.s (initial) to 2120 mPa.s (1 day) to 2430 mPa.s (3 days) to 2972 mPa.s (7 days) tp 5900 mPa.s (15 days). These results are graphically presented in Figure 3.

640.1 grams of PREPOLYMER A were comb;ned with 110 grams of OXAZOLIDINE, 2.25 grams DHCD and 1.13 grams of TIN CATALYST.
The viscosity increase of this system during storage over a period of 7 days at room temperature and at 60C was studied.
After storage at room temperature, the viscosity of the system increased from 1649 mPa.s (initial) to 1685 mPa.s (3 days). The viscosity remained at 1685 mPa.s until measurement was discontinued after 7 days.
After storage at 60C, the viscosity of the system increased from 1649 mPa.s (initial) to 3026 mPa.s (1 day). The system was very nearly gelled after 3 days and had completely gelled after 7 days. These results are graphically presented in Figure 3.

640.1 grams of PREPOLYMER A were combined with 110 grams of OXAZOLIDINE, 2.25 grams of DHCD, and 2.26 grams of TIN
CATALYST. The viscosity increase of this system during storage Mo3966 .. .. ~

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over a period of 7 days at room temperature and at 60C was studied.
After storage at room temperature, the viscosity of the system increased from 1669 mPa.s (initial) to 1827 mPa.s ~3 days). A decreased viscosity of 1776 mPa.s was measured after 7 days.
After storage at 60C, the viscosity of the system increased from 1669 mPa.s (initial) to 3407 mPa.s (1 day). The system had very nearly gelled after 3 days and was completely gelled after 7 days. These results are graphically presented in Figure 3.
EXAMPLE~
469.2 yrams of PREPOLYMER A, 80.6 grams of OXAZOLIDINE, 0.6 grams of ANHYDRIDE, and 77.0 grams of the rutile anatase pigment which is commercially available from Dupont under the designation R-960 were combined. The increase in viscosity of this composition over a period of 60 days at room temperature --~
was studied. The increase in viscosity of the system over a period of 35 days when stored at 60~C was also studied.
After storage at room temperature, the viscosity of the system remained 2936 mPa.s through the first day, The viscosity increased from 3583 mPa.s (3 days) to 3969 mPa.s (7 days) to 4225 mPa.s (28 days) to 5350 mPa.s (60 days). These results are shown graphically in Figure 4.
After storage at 60C, the viscosity of the system increased from 2936 mPa.s (initial) to 5057 mPa.s (1 day) to 5534 mPa.s (3 days) to 7231 mPa.s (7 days) to 20219 mPa.s (14 days) to 152,630 mPa.s (28 days). The system had very nearly gelled after 35 days.

469.2 grams of PREPOLYMER A, 80.6 grams of OXA70LIDINE, 0.6 grams of ANHYDRIDE, and 77.0 grams of the rutile anatase pigment which is commercially available from Bayer AG under the designation R-FK-2 were combined. The increase in viscosity of Mo3966 ,. . . . .

-` 2 1 2 ~ 2 2 ~

the system when stored at room temperature and at 60C was measured.
After storage at room temperature, the viscosity of the system increased from 2954 mPa.s (initial) to 2972 mPa.s (1 day) to 3045 mPa.s (7 days~ to 3306 mPa.s (28 days). These results are presented graphically in Figure 4.
After storage at 60C, the viscosity of the system increased from 2954 mPa.s (initial) to 3353 mPa.s (1 day) to 4204 mPa.s (3 days) to 4929 mPa.s (7 days) to 14,24~ mPa.s ~14 days) to 23,946 mPa.s (21 days) to 49,440 mPa.s (28 days) to 90,740 mPa.s (35 days).

A one-component elastomeric topcoat was prepared from a mixture of 1000 grams of PREPOLYMER A, 199.56 grams of SOLVENT
B and 360.64 grams of titanium dioxide which mixture was let down with 199.56 grams of SOLVENT B, 24.31 grams of light stabilizers specifically, those which are commercially ava;lable under the names Tinuvin 292 and 1130, 6.01 grams of the stabilizer which is commercially available under the name Irganox 1010 in 10% xylene, 3.61 grams ANHYDRIDE and 202.14 OXAZOLIDINE. The resultant system had a solids content of 79.7% by weight. The tensile strength and elongation (determined in accordance with ASTM D-412) were 3060 psi (failure) and 380% (ultimate), respectively.

A one-component elastomeric coating composition useful for roofing applications was made by grinding 1000 9 of PREPOLYMER
A, 211.2 grams of SOLYENT B, 240.42 grams pure titanium dioxide [R-902], 180.32 grams decabromo diphenyl oxide (fine rehydrant 3o available from Great Lakes under the designation DE-83R and 60.11 grams antimony tr;ox;de and then lett;ng down th;s mixture with 211.20 grams of SOLVENT B, 24.21 grams of light stabilizers, specifically, those which are commercially available under the names Tinuvin 292 and 1130, 6.01 grams of the stabilizer which is commercially available under the name Mo3966 - ~--- 2 ~ 2 ~ ~ ~t3 Irganox 1010, 3.61 grams of ANHYDRIDE and 202.11 grams of OXAZOLIDINE. The resultant composition had a solids content of 80% by weight.

A one-component coating composition was prepared by -combining 56.9 grams of PREPOLYMER A, 2~.7 grams of SOLVENT A, 8.7 grams FILLER~ 0.2 grams ANHYDRIDE and 11.5 grams of OXAZOLIDINE.
This coating was then applied by brush to the edges of lo panels of wood composite panel which had been preconditioned at 160F/100% for 10 minutes and placed in an oven/humidity chamber for 5 minutes. This material effectively coated and protected the treated edges.
EXAMPLE 16 ~ -A one-component coating composition was prepared by ;~
combining 55.5 grams of PREPOLYMER A, 2.7 grams of PREPOLYMER
B, 8.5 grams of FILLER~ 11.2 grams of OXAZOLIDINE and 22.1 grams of SOLVENT A. -This composition was then applied by brush to the edges of -~
panels of wood composite panel which had been preconditioned at 160~F/100% for 10 minutes at thicknesses of 30 mils and 3 mils and placed in an oven/humidity chamber for 5 minutes to cure.
At either thickness, this coating effectively protected the treated edges and resisted swelling.

Mo3966 - ~ 2 ~ 2 3 ~ 2 5 Three different formulations were prepared by combining the listed materials in the amounts indicated in the following Table 1:

MATERIAL/SA~PLE A B C

PREPOLYMER A (grams) 56.9 55.4 PREPOLYMER B (grams) 2.7 PREPOLYMER C (grams) 63.4 ORGANIC SOLVENT A (grams) 22.722.1 FILLER (grams) 8.7 8.5 9.7 OXAZOLIDINE (grams) 11.5 11.2 26.6 ANHYDRIDE (grams) 0.2 0.19 0.2 Each of these formulations was applied by brush to preconditioned panels of flake board (160F/100% for lO
minutes) in an amount to seal and fill the flake board. The coated panels were then placed in an oven/humidity chamber for 5 minutes.
Moisture penetration and edge swell of the coated panels were determined in accordance with ANSI (American National Institute)/KCMA (Kitchen Cabinet Manufacturers Association) A 161.1-1990 Test Method No. 10 for detergent and water resistance with the exception that weight gain and swell were determined after 48 hours rather than 24 hours.
The panels coated with Sample C had an 83% weight gain (Edge Soak Test) and a 16% edge swell. The panels coated with Samples A and B had weight gains of from about 5 to 7% (Edge Soak Test) and from about 1-2% edge swell.

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Three different formulations were made with the materials listed in Table 2 below in the amounts indicated.

MATERIAL/SAMPLE A B C
PREPOLYMER A (grams) 56.9 55.48 PREPOLYMER B (grams) 2.7 PREPOLYMER C (grams) 63.4 ORGANIC SOLVENT A (grams) 22.7 22.1 FILLER (grams) 8.7 8.5 9.7 OXAZOLIDINE (grams) 11.5 11.2 26.6 ANHYDRIDE (grams) 0.2 0.19 0.2 Each of these formulations was applied by brush to -~
preconditioned panels of flake board (160Ft100% for 10 minutes) in an amount sufficient to seal and fill the flake board. The coated panels were then placed in an oven/humidity chamber for 5 minutes.
The degree of swelling and weight gain were determined using the same method as was used in Example 17 for one side overlaid oriented strandboard (Table 3) and for two side overlaid oriented strandboard (Tables 4 and 5) treated with formulations A and B. Panels coated with Formulation C
exhibited undesirably high swelling and weight gains.

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Table 3 Sponge Test Results of Moisture Penetration and Edge Swell of One Side Overlaid Oriented Strandboard.
Sample A B
Property Sealed Not Seal Sealed Not Seal Edge Swell 0.0108 0.1982 0.0093 0.1859 After 75 hours (inches) Percent 1.59 29.18 1.38 27.92 Edge Swell After 75 hours Weight 2.81 41.97 2.57 41.81 Gain After 75 hours (grams) Percent 1.91 17.63 1.15 18.56 Weight Gain After 75 hours _ 0 Note: percent swell and weight gain based on original thickness and weight of the sample.

0 .

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Table 4: Sponge Test Results of Moisture Penetration and Edge Swell of Two Side Overlaid Oriented Strandboard.
Sample A B
Propertv Sealed Not Sealed Sealed Not Sealed Edge Swell 0.0133 0.1092 0.0095 0.1215 After 75 hours (inches) Percent 1.81 14.94 1.29 16.55 -Edge Swell lo After 75 hours Weight 3.16 22.89 2.32 24.54 Gain After 75 hours (grams) Percent 1.31 9.39 0.9631 10.09 Weight Gain After 75 hours : :.
Note: percent swell and weight gain based on original thickness and weight of the sample.
Table 5: Modified ASTM Water Absorption and Thickness Swell Test Results for Two Side Overlaid Oriented Strandboard With Edges Sealed.
Propertv Sam~le A SamPle B
Edge Swell After 1000.0570 0.0418 hours (inches) Percent Edge Swell of 7.80 5.59 original th;ckness after 100 hours Weight 6ain After 46.35 25.27 100 hours (grams) Percent Weight Gain20.09 9.66 of the original weight after 100 hours Mo3966 - -'' :

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Although the invention has been described in detail in the foregoing for the purpose of illustration, it is to be understood that such detail is solely for that purpose and that variations can be made therein by those skilled in the art without departing from the spirit and scope of the invention except as it may be limited by the claims.

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Claims (11)

1. A storage-stable, rapid curing one-component polyurethane composition useful as a sealant or coating comprising:
a) an isocyanate prepolymer having an NCO group content of from about 4 to about 6% and a molecular weight of from about 1400 to 2100 which is the reaction product of toluene diisocyanate, a polytetramethylene ether glycol having a molecular weight of from about 500 to about 1500 and a diol having a molecular weight of from about 50 to about 200, and b) an oxazolidine represented by one of the following formulae I or II

in which R represents an organic group having at least one carbon atom, R1 represents hydrogen, an aliphatic or aromatic group, and R2 represents hydrogen, an aliphatic or aromatic group and optionally, c) a catalyst.

2. The composition of Claim 1 in which in the oxazolidine b) is represented by formula I in which R represents an ethoxy group, R1 represents a methyl group, and R2 represents a methyl group.

3. The composition of Claim 1 in which the oxazolidine b) is present in an amount of from about 1 to about 30%, based on the total amount of a), b) and any c) which is present.

4. The composition of Claim 1 in which the catalyst c) is present and c) is an acid dianhydride.

5. The composition of Claim 1 in which an organic solvent having a water content of less than 0.05% by weight is present.

6. The composition of Claim 1 in which a filler having a water content of less than 0.05% by weight is included.

7. The composition of Claim 1 in which the catalyst c) is a dianhydride of a dicarboxylic acid and that catalyst is included in an amount of from about 0.1% to about 0.3% by weight, based on the total weight of components a), b) and any c) which is present.

8. A process for coating a porous substrate comprising applying to a porous substrate a one-component coating composition comprising:
a) an isocyanate prepolymer having an isocyanate content of from about 4 to about 6% and a molecular weight of from about 1400 to about 2100 which is the reaction product of toluene diisocyanate and a polytetra-methylene polyether glycol having a molecular weight of from about 500 to about 1500, and a diol having a molecular weight of from about 50 to about 200, b) an oxazolidine, and c) an acid anhydride catalyst in a thickness of from about 3 to about 30 and allowing the coated substrate to cure.

9. The process of Claim 8 in which the prepolymer is formed from a polytetramethylene polyether glycol having a molecular weight of about 1000, the oxazolidine is represented by formula II and the catalyst is the anhydride of a dicarboxylic acid.

10. A coated substrate which is the product of the process of Claim 8 which is characterized by good moisture resistance.

11. The coated substrate of Claim 10 in which the substrate is a wood-based substrate.