Coatings containing caprolactone oligomer polyols
FIELD OF INVENTION 
     The present invention provides improved crosslinkable coatings that contain a polyol component which is a caprolactone oligomer containing a cycloaliphatic moiety. 
     BACKGROUND OF THE INVENTION 
     Most coatings are crosslinkable or thermosetting resins that cure by chemical reactions of the various components to form a crosslinked polymeric coating. Often one of the reactive components in the uncured coating is a polyol that reacts with other complimentary coating components to effect crosslinking. Reactive diluents offer one way to lower volatile organic content with star polymer blends and in blends with acrylic, fluoropolymer, or polyester polyols. It is desirable to have low viscosity reactive diluents that have low volatility but do not excessively lower the hardness of the cured coating. 
     Japanese Patent Application 61-200120 discloses a process for making lactone oligomers of various alcohols and polyols, and among the list of useful polyols are cyclohexanediol and cyclohexanedimethanol. A cyclohexanedimethanol-caprolactone oligomer is disclosed. There is no mention in this patent of the use of any of these compounds. In particular there is no mention of the caprolactone oligomers of cycloaliphatic polyols for use in coatings. 
     The use of caprolactone oligomer polyols derived from acyclic polyols has been recommended. See for example commercial booklet &#34;TONE Polyols&#34;, &#34;Serial No.&#34; F-49592, published 11/82 by Union Carbide Corp., Danbury, CT, which describes caprolactone oligomer polyols for use in coatings. These polyols are derived from acyclic polyols (believed to be diethylene glycol and/or trimethylol propane), and the presence of cyclic polyol residues in the oligomers is not mentioned. 
     It is the object of this invention to provide an improved polyol coating component that exhibits a good balance of properties in both the cured and uncured coatings. The caprolactone oligomer polyols containing cycloaliphatic moieties, disclosed herein as a coating component, in particular offer the advantages of relatively low viscosity coating, even when solvent levels are low, reasonably rapid curing, and good hardness of the cured coating. 
     SUMMARY OF THE INVENTION 
     The present invention comprises a crosslinkable coating composition, wherein a polyol component comprises a compound of the formula ##STR1## wherein: 
     R 1  is a covalent bond or alkylene containing 1, 2, 3 or 4 carbon atoms; 
     n is about 1 to about 4; 
     m is 2, 3 or 4; and 
     Q is a saturated carbocyclic ring containing 5 or 6 carbon atoms, or S-R 2  -T wherein S and T are each independently saturated carbocyclic rings containing 5 or 6 carbon atoms, and R 2  is a covalent bond or an alkylene group containing 1, 2, 3 or 4 carbon atoms; 
     provided that no more than one R 1  is bound to any carbocyclic carbon atom, and further provided that when Q is S-R 2  -T, each R 1  is bound to a carbon atom of the carbocyclic rings of S and T. 
     DETAILS OF THE INVENTION 
     This invention comprises improved crosslinkable coatings wherein the improvement is a &#34;polyol component&#34; which is an oligomer of caprolactone that includes a cycloaliphatic polyol moiety. Crosslinking coatings are well known to those skilled in the art, and are coatings, that during or after application, cure (crosslink), to form a crosslinked polymeric network which is the final coating. The coatings may cure with or without applied external heat. While some coatings contain only one type of functional group that either acts to crosslink the coating by itself or with components in the air (for example oxygen or moisture), it is common for crosslinkable coatings to contain two or more monomeric, oligomeric and/or polymeric compounds that contain complimentary reactive groups that will react with one another. If the coating is to crosslink, at least one of the functional groups should be present in a tri- (or higher) functional compound, and all other reactive groups should be present in di- (or higher) functional compounds. 
     In many types of coatings including those of the present invention, one of these complimentary reactive groups may be hydroxyl. The hydroxyl (alcohol) function is quite versatile, and may react with a variety of complimentary reactive groups also suitable for use in the present invention such as epoxy, carboxylic anhydride, isocyanate, ketoxime blocked isocyanate, carboxylic acid, urethane, and formaldehyde modified melamine. Preferred complimentary reactive groups are isocyanate and formaldehyde modified melamine resin, and isocyanate is especially preferred. These preferred complimentary groups are often included with (low molecular weight) polymers, such as styrenic or acrylic polymers. 
     Examples of coating formulations useful with the polyol component of this invention include those described U.S. Pat. Nos. 4,076,766, 5,003,004, and 4,816,500; in B. N. McBane, &#34;Automotive Coatings&#34;, Federation of Societies for Coating Technology, Philadelphia, 1987, p. 24 to 29; R. F. Storey and S. F. Thames, &#34;Proceeding of the Eighteenth Water-Borne, Higher Solids, and Powder Coatings Symposium&#34;, Feb. 6-8, 1991, obtainable from the Dept. of Polymer Science, University of Southern Mississippi; and H. F. Payne, &#34;Organic Coating Technology&#34;, Vol. I and II, John Wiley &amp; Sons, Inc., New York, 1954 and 1961; all of which are hereby incorporated by reference. 
     The polyol component of this invention comprises a caprolactone oligomer which has hydroxyl groups, and may be made by initiating caprolactone polymerization with a cyclic polyol. It is known in the art that alcohols (along with certain catalysts), including cyclic alcohols (see for example Japanese Patent Application 61-200120, supra), may be used to initiate the polymerization of caprolactone according to the overall equation: ##STR2## Generally the average degree of polymerization, z, will be the original molar ratio of caprolactone to ROH (or total hydroxyl groups present if ROH were a polyol), assuming the reaction was carried to completion. It is realized by those skilled in the art the product caprolactone oligomer or polymer will have a distribution of degrees of polymerization, z, and that z represents an arithmetic average of that distribution. A general reference for the polymerization of caprolactone is D. B. Johns et al., in K. J. Ivin and T. Saegusa, Ed., Elsevier Applied Science Publishers, Barking, Essex, England, 1984, p. 461-521, which is hereby incorporated by reference. 
     The specific polyol component of this invention has the formula ##STR3## wherein Q, R 1 , n and m are as defined above. Thus n, which is the average degree of polymerization of each caprolactone chain corresponds to z above. It is preferred that n is from about 1 to about 2. The symbol m represents the functionality (number of hydroxyl groups) of the polyol component, and is preferably 2. R 1  is a covalent bond or alkylene group that connects the caprolactone chain to the group Q, Q being a carbocyclic ring or the grouping S-R 2  -T, which also has carbocyclic rings. It is preferred that R 1  is a covalent bond or methylene (--CH 2  --). 
     When Q is a carbocyclic ring, preferably it is cyclohexylene, more preferably 1,4-cyclohexylene. When Q is S-R 2  -T it is preferred if R 2  is 2,2-propylene or methylene. It is also preferred if both S and T are each cyclohexylene, and more preferred if both S and T are 1,4-cyclohexylene. As stated above, any R 1  must be bound to a carbocyclic ring carbon atom (Q, S or T) and no more than one R 1  may be bound to any carbocyclic ring carbon atom. 
     Thus one skilled in the art will understand that to obtain the polyol component wherein Q is 1,4-cyclohexylene, R 1  is a covalent bond, n is two and m is two, one would react one mole of 1,4-cyclohexanediol with 4 moles of caprolactone. Similarly, to obtain the polyol component where Q is 1,4-cyclohexylene, R 1  is methylene, n is one and m is two, one would react one mole of 1,4-cyclohexanedimethanol with two moles of caprolactone; to obtain the polyol component where Q is S-R 2  -T and S and T are 1,4-cyclohexylene, R 2  is 2,2-propylene, R 1  is a covalent bond, n is 2.5 and m is 2, one would react one mole of 2,2-bis(4-hydroxycyclohexyl)propane with 5 moles of caprolactone. Other combinations will be evident to the art skilled, and preparations of polyol components are illustrated in Experiments 1 to 4 hereinafter. 
     The polyol component of the present invention may be used conventionally in coatings in which polyols are normally used. Thus the polyol component may be used as the sole polyol present or may be used in combination with other polyols. Compounds containing complimentary reactive groups will also be present when the coating is to be cured. Other conventional coating components, such as solvents, catalysts, retarders, pigments, leveling agents, gloss enhancing agents, etc., may also be present. 
     The polyol component of the present invention offers improvements over other polyols. One recent goal of those skilled in the coating art has been to reduce solvent content while maintaining coating quality. The polyol component herein has a relatively low viscosity, and many are liquids, distinct advantages towards lowering solvent content. It is preferred if the polyol component herein is a liquid at the lower of ambient or application temperature. Even if it is not a liquid, a mixture of the polyol components may be used to depress the melting point of the solid individual polyol(s), preferably below room or application temperature, whichever is lower. When compared to other polyols, such as caprolactone oligomers made from acyclic polyols (for example the &#34;Tone&#34;® polymer described above), the polyol component of the present invention often yields harder cured coatings, an advantage in some applications. In addition, the polyol component of the present invention has relatively low vapor pressure, resulting in lowered atmospheric emissions during application and curing. 
     The coatings of the present invention are useful in many applications, for example, coating metals (automobiles), for industrial finishes, and for coating hard plastics. 
     This invention further comprises the cured films which are made from the coating compositions that contain the polyol component of the invention. Cured coating compositions are compositions in which crosslinking has occurred by reaction of complimentary functional groups with each other. 
     In the following Experiments and Examples, Knoop Hardness is measured according to the method described in G. G. Sward,, &#34;Paint Testing Manual&#34;, 13th Ed., The American Society for Testing Materials, Philadelphia, 1972, p. 289 to 290, and bubble viscometers (and the methods associated with them) are described in the same reference, p. 197 to 199. 
     In the following Experiments and Examples, the following abbreviations are used: 
     CHDM - cyclohexanedimethanol 
     CL - ε-caprolactone 
     KHN - Knoop Hardness 
     Mn - number average molecular weight 
     OH#- hydroxyl number 
     Tg - glass transition temperature 
    
    
     EXPERIMENT 1 
     1,4-Cyclohexanedimethanol with 2 Moles of 
     Caprolactone 
     A 3 L round bottom flask was fitted with a reflux condenser. The stirrer was a stainless steel anchor driven by an air motor with gear reduction. A thermocouple was used to measure temperature of the reactants. The following were charged to the reaction flask: 
     
         ______________________________________                                    
Wt.         Component                                                     
______________________________________                                    
432.6 g.    1,4-cyclohexanedimethanol, (Eastman                           
            Chemical Products, Inc.,                                      
            Kingsport, Tennessee                                          
            CHDM-D Glycol)                                                
684.9 g.    ε-caprolactone Tone ® Monomer                     
            EC HP, from Union Carbide Corp.,                              
            Danbury, Connecticut                                          
 1.5 g.     10% solution of dibutyl tin                                   
            dilaurate in Xylene                                           
______________________________________                                    
 
    
     The above components were heated to 150° C. and held at 150° to 160° C. for 4 hours. Gas chromatography showed that all the caprolactone had been consumed. The product had a viscosity of 7.5 Stokes at 23° C. 
     EXPERIMENT 2 
     1,4-Cyclohexanedimethanol with other 
     Ratios of Caprolactone 
     Using a procedure similar to that for Experiment 1, various ratios of 1,4-cyclohexanedimethanol were reacted with ε-caprolactone. Table 1 gives the ratio of moles to viscosity and amount of unreacted cyclohexanedimethanol. 
     
                       TABLE 1                                                     
______________________________________                                    
              Stokes                                                      
Reactant Ratio*                                                           
              Viscosity                                                   
                       Residual 1.4-CHDM**                                
______________________________________                                    
  1/1         10.7     25                                                 
1.5/1         9.3      14                                                 
  2/1         8.2       7                                                 
2.5/1         6.9      --                                                 
3.0/1         6.9      --                                                 
______________________________________                                    
 *Ratio of caprolactone to 1,4cyclohexanedimethanol                       
 **Wt % cyclohexanedimethanol in the product                              
 
    
     EXPERIMENT 3 
     Hydrogenated Bisphenol-A (HPBA) with Caprolactone 
     Using a procedure similar to that for Experiment 1, various ratios of HBPA were reacted with ε-caprolactone. Table 2 gives the ratio of moles to viscosity. 
     
                       TABLE 2                                                     
______________________________________                                    
Reactant Ratio*                                                           
              Centipoise Viscosity**                                      
______________________________________                                    
2.0/1         30,200                                                      
2.5/1         14,240                                                      
3.0/1          7,920                                                      
4.0/1          4,920                                                      
______________________________________                                    
 *Ratio of caprolactone to HBPA                                           
 **Brookfield Viscometer, #6 spindle                                      
 
    
     EXPERIMENT 4 
     Preparation of a Adduct of 1,4 Cyclohexaneddiol 
     Using a procedure similar to that for Experiment 1, 1 mole of 1,4-cyclohexane diol (Quinitol®, from Eastman Chemical Products, Inc., Kingsport, Tennessee) was reacted with 2 moles of caprolactone in a reaction vessel to yield the desired titled adduct. 
     EXPERIMENT 5 
     Preparation of an Adduct of 1.6-Hexanediol 
     (a noncarbocyclic diol) 
     One mole of 1,6-hexanediol was reacted with 2 moles of caprolactone by a procedure similar to that for Experiment 1 to yield the titled product. 
     The product had a viscosity of 2.3 stokes. 
     EXPERIMENT 6 
     Description of Methacrylate Star Polymer 
     Used for Blending 
     This star polymer was designed to have good compatibility with the oligomer of Example 1 while also giving cured films with high refractive index for superior gloss. It has the following composition: 
     
         ______________________________________                                    
Component              Wt. % in Star                                      
______________________________________                                    
End Group*             1.66                                               
Ethyleneglycol dimethacrylate (EDGMA)                                     
                       5.02                                               
Methyl methacrylate (MMA)                                                 
                       44.34                                              
Benzyl methacrylate (Benzyl MA)                                           
                       44.34                                              
2-Hydroxyethyl methacrylate (HEMA)                                        
                       4.64                                               
______________________________________                                    
 *Contains a hydroxyl group from the initiator that was used.             
 
    
     The star polymer was prepared by the methods described in U.S. Pat. No. 5,003,004 and in J. A. Simms, Rubber Chemistry and Technology, Vol. 64, pp. 139-151 (1991), each of which is herein incorporated by reference. 
     The design was for 7500 Mn arms and a 2/1 core to arm mole ratio. Each arm would have an average of 3.83 hydroxyls. Calculated OH# was 27.1 for the star solids. The xylene polymer solution containing this star had a nonvolatile content of 53.7% and a viscosity of 5500 centipoise. 
     DESCRIPTION OF OTHER POLYMERS USED FOR BLENDING 
     Lumiflon® 916, a hydroxyl containing copolymer of trifluorochloroethylene, alkyl vinyl ether and 4-hydroxybutyl vinyl ether of about 6000 number average molecular weight and 90 hydroxyl number was purchased from ICI America, Wilmington, Delaware, as a 65% solution in xylene. 
     Styrene Acrylic copolymer &#34;A&#34; is a 45° C. Tg linear polymer of about 2500 Mn. It has the wt. % composition styrene/n-butyl methacrylate/n-butyl acrylate/hydroxypropyl acrylate (15/30/17/38), and was prepared at E. I. du Pont de Nemours and Company, Wilmington, Delaware. 
     Styrene Acrylic copolymer &#34;B&#34; is a 85° C. Tg linear polymer of about 5000 Mn. It has the wt. % composition styrene/i-butyl methacrylate/methyl methacrylate/hydroxyethyl methacrylate 15/45/20/20, and was prepared at E. I. du Pont de Nemours and Company, Wilmington, Delaware. 
     Crosslinking Agents 
     Desmodur® N-3390, a 90% nonvolatile content isocyanate functional isocyanurate was purchased from the Mobay Company, Pittsburgh, Pennsylvania. Its isocyanate content was 5.13 milliequivalents of NCO per gram of solids. 
     CYMEL® 1133, an butylated/methylated melamine/formaldehyde resin was purchased from American Cyanamide, Wayne, New Jersey. 
     EXAMPLE 1 
     Isocyanate Crosslinked Coatings using Oligomer of 
     Experiment 1 with Styrene/Acrylic Copolymer &#34;B&#34; 
     The oligomer of Experiment 1 was reacted with copolymer B of Experiment 6 in the presence of the crosslinking agent isocyanate. Table 3 shows the non-volatile content of the coating blends. The isocyanate crosslinked was used at a concentration to give 1.05 NCO groups to 1 OH group. 
     For sample #2 of Table 3, Copolymer B (22.89 g) as a 59.8% solution in xylene was mixed with 6.0 g of the oligomer of Experiment 1, 1.2 g acetyl acetone (a volatile retarder for the catalyst), 0.06 g of a 10% solution of dibutyl tin dilaurate in propylene glycol monomethyl ether acetate, and 12.46 g of propylene glycol monomethyl ether acetate. Just before use the above blend was mixed with 11.93 g of Desmodur N 3390. This solution contained 55% nonvolatile content. It should be used within about 4 hours. In this instance a coating knife with a 7 mil gap was used to apply a film which when dry was 2.0 mils thick. The remaining samples were prepared in an analogous manner. 
     
                                           TABLE 3                                 
__________________________________________________________________________
Sample                                                                    
     % Copolymer                                                          
             % Des                                                        
                 % CHDM                                                   
                       PHR  Viscosity,                                    
#    &#34;B&#34;     3390                                                         
                 Adduct.sup.a                                             
                       DBTDL.sup.b                                        
                            Stokes.sup.c                                  
                                 Hardness.sup.d                           
__________________________________________________________________________
1    76.06   23.94                                                        
                    0.00                                                  
                       0.02 1.40 12.00                                    
2    44.19   35.81                                                        
                 20    0.02 0.411                                         
                                 9.72                                     
3    28.26   41.75                                                        
                 30    0.02 0.182                                         
                                 5.47                                     
4    12.32   47.68                                                        
                 40    0.02 0.103                                         
                                 1.56                                     
__________________________________________________________________________
 .sup.a Of Experiment 1                                                   
 .sup.b Parts per 100 parts of coating polymers of dibutyl tin dilaurate  
 catalyst for isocyanate/polyol reaction                                  
 .sup.c Polymers were thinned with monomethyl ether of propyleneglycol    
 acetate and xylene to 55% nonvolatile content by weight                  
 .sup.d Cast with a 7 mil coating knife, baked 30 minutes at 121° C
 and held 2 weeks at 23° C. Measured as Knoop hardness number.     
 
    
     This showed the ability of the oligomer to reduce the viscosity while maintaining the same nonvolatile content. This allowed the solution to be sprayed at 55% nonvolatile when as little as 20% oligomer was added. Hardness was still in a useful range to 40% oligomer content. 
     EXAMPLE 2 
     Isocyanate Crosslinked Coatings using Oligomer of 
     Experiment 1 with Styrene/Acrylic Copolymer &#34;A&#34; 
     Coating blends were prepared from the oligomer of Experiment 1 and copolymer B of Experiment 6 using the procedure described in Example 1. Table 4 shows the non-volatile content of the coating blends. The isocyanate crosslinked was used at a concentration to give 1.05 NCO groups to 1 OH group. 
     
                                           TABLE 4                                 
__________________________________________________________________________
Sample                                                                    
     % Copolymer                                                          
             % Des                                                        
                 % CHDM                                                   
                       PHR  Viscosity,                                    
#    &#34;A&#34;     3390                                                         
                 Adduct.sup.a                                             
                       DBTDL.sup.b                                        
                            Stokes.sup.c                                  
                                 Hardness.sup.d                           
__________________________________________________________________________
1    62.59   37.41                                                        
                    0.00                                                  
                       0.02 0.41 10.50                                    
2    36.37   43.64                                                        
                 20    0.02 0.182                                         
                                 6.34                                     
3    23.25   46.75                                                        
                 30    0.02 0.163                                         
                                 3.65                                     
4    10.14   49.86                                                        
                 40    0.02 0.103                                         
                                 1.62                                     
__________________________________________________________________________
 .sup.a Of Experiment 1                                                   
 .sup.b Parts per 100 parts of coating polymers of dibutyl tin dilaurate  
 catalyst for isocyanate/polyol reaction                                  
 .sup.c Polymers were thinned with monomethyl ether of propyleneglycol    
 acetate and xylene to 55% nonvolatile by weight                          
 .sup.d Cast with a 7 mil coating knife, baked 30 minutes at 121° C
 and held 2 weeks at 23° C. The hardness was measured as Knoop     
 hardness number                                                          
 
    
     Although the viscosity of the styrene/acrylic polyol was lower in this instance, there was still a major reduction in viscosity with the addition of the caprolactone/1,4-CHDM adduct. The hardness remained in a useful range. 
     EXAMPLE 3 
     Isocyanate Crosslinked Coatings using Oligomer 
     of Experiment 3 with Styrene/Acrylic Copolymer &#34;A&#34; 
     Coating blends were prepared from the oligomer of Experiment 3 and copolymer A of Experiment 6 using the procedure described in Example 1. In this experiment the 2/1 adduct of caprolactone and hydrogentate bisphenol-A was used. For clarity the compositions are shown on the basis of nonvolatile content. The isocyanate crosslinker was used at a concentration to give 1.05 NCO groups to 1 OH group. 
     
                                           TABLE 5                                 
__________________________________________________________________________
Sample                                                                    
     % Copolymer                                                          
             % Des                                                        
                 % HBPA                                                   
                       PHR  Viscosity,                                    
#    &#34;A&#34;     3390                                                         
                 Adduct.sup.a                                             
                       DBTDL.sup.b                                        
                            Stokes.sup.c                                  
                                 Hardness.sup.d                           
__________________________________________________________________________
1    62.59   37.41                                                        
                    0.00                                                  
                       0.02 0.41  10.50                                   
2    39.13   40.87                                                        
                 20    0.02 0.321                                         
                                 10.3                                     
3    27.4    42.6                                                         
                 30    0.02 0.201                                         
                                 10.9                                     
4    15.67   44.33                                                        
                 40    0.02 0.182                                         
                                  9.88                                    
__________________________________________________________________________
 .sup.a Of Experiment 3                                                   
 .sup.b Parts per 100 parts of coating polymers of dibutyl tin dilaurate  
 catalyst for isocyanate/polyol reaction                                  
 .sup.c Polymers were thinned with monomethyl ether of propyleneglycol    
 acetate and xylene to 55% nonvolatile by weight                          
 .sup.d Cast with a 7 mil coating knife, baked 30 minutes at 121° C
 and held 2 weeks at 23° C. The hardness was measured as Knoop     
 hardness number                                                          
 
    
     This experiment showed that this adduct caused essentially no reduction in hardness while producing a substantial reduction in viscosity. 
     EXAMPLE 4 
     Isocyanate Crosslinked Coatings using the Oligomers of 
     Experiment 3 with Styrene/Acrylic Copolymer &#34;A&#34; 
     A coating was prepared from the oligomers of Experiment 3 with copolymer A of Experiment 6 using the procedure of Example 1. In this experiment oligomers with different ratios of caprolactone to hydrogenated bisphenol-A were compared. The compositions were compared at 30% oligomer content. For clarity the compositions are shown on the basis of nonvolatile content. The isocyanate crosslinked was used at a concentration to give 1.05 NCO groups to 1 OH group. 
     
                                           TABLE 6                                 
__________________________________________________________________________
Sample                                                                    
     % Copolymer                                                          
             % Des                                                        
                 CL to PHR  Viscosity,                                    
#    &#34;A&#34;     3390                                                         
                 HBPA.sup.a                                               
                       DBTDL.sup.b                                        
                            Stokes.sup.c                                  
                                 Hardness.sup.d                           
__________________________________________________________________________
1    27.4    42.6                                                         
                 2 to 1                                                   
                       0.02 0.201                                         
                                 10.9                                     
2    30.63   39.37                                                        
                 3 to 1                                                   
                       0.02 0.271                                         
                                 8.41                                     
3    32.78   37.22                                                        
                 4 to 1                                                   
                       0.02 0.271                                         
                                 4.87                                     
__________________________________________________________________________
The following experiment shows that an oligomer made with                 
1,6-hexanediol, a noncyclic diol gives very soft films                    
4    21.64   48.36                                                        
                 2 to 1                                                   
                       0.02 0.144                                         
                                 &lt;0.5                                     
__________________________________________________________________________
 .sup.a Adducts described in Experiment 3                                 
 .sup.b Parts per 100 parts of coating polymers of dibutyl tin dilaurate  
 catalyst for isocyanate/polyol reaction                                  
 .sup.c Polymers were thinned with monomethyl ether of propyleneglycol    
 acetate and xylene                                                       
 .sup.d Baked 30 minutes at 121° C. and held 2 weeks at 23° 
 C.                                                                       
 
    
     EXAMPLE 5 
     Coating Blend Studies With Methacrylate Star Polymer 
     The 1,4-cyclohexane dimethanol adduct of Experiment 1 was used to prepare coating blends as described in Example 1. Excellent film clarity and gloss were obtained with the 27 OH# star with equal parts and benzyl methacrylate in the arms described above. Different amounts of star were used to change the hardness of the blend coating as shown in the following Table 7. 
     
                       TABLE 7                                                     
______________________________________                                    
Sam-                                                                      
ple  % Star  % Des   % CHDM  PHR    Viscosity,                            
                                           Hard-                          
#    Pol.    3390    Adduct.sup.a                                         
                             DBTDL.sup.b                                  
                                    Stokes.sup.c                          
                                           ness.sup.d                     
______________________________________                                    
1    35      36.47   28.53   0.02   0.85   2.94                           
2    30      38.90   31.10   0.02   0.65   2.23                           
3    25      41.34   33.66   0.02   0.21   1.48                           
______________________________________                                    
 .sup.a Of Experiment 1                                                   
 .sup.b Parts per 100 parts of coating polymers of dibutyl tin dilaurate  
 catalyst for isocyanate/polyol reaction                                  
 .sup.c Polymers were thinned to 60% by weight with methyl namyl ketone an
 xylene                                                                   
 .sup.d Films were cast with a 7 mil knife, and allowed to cure for 1 mont
 at 25° C. The Knoop hardness was then determined                  
 
    
     These blends had the important advantage of becoming dust resistant in about 90 minutes. Coatings with high application solids do not usually show this characteristic. 
     EXAMPLE 6 
     Spraying of the Oligomer-containing Coatings 
     at 60% Solids 
     The following 30% star composition was spray applied at 60% solids, the solids produced when Part I was combined with Part II, each as defined below. Initial viscosity was 33 sec. in a #2 Zahn cup. It increased to 36.5 seconds in 1 hour. Hardness at room temperature reached 0.5 KHN in 4 hours, and increased to about 2 KHN overnight. Final hardness was about 5.5-6. These measurements were made on 2 mil films applied to glass. 
     
         ______________________________________                                    
Wt. Used   Component         Solids                                       
______________________________________                                    
Part I:                                                                   
56.11      Methacrylate Star 30                                           
31.10      Adduct(Exp. 1)    31.1                                         
 4.0       Acetyl Acetone                                                 
 0.20      DBTDL,.sup.a 10% in MEPGA.sup.b                                
                              0.02                                        
32.05      MAK.sup.c                                                      
 0.19      BYK-323.sup.d      0.1                                         
           (Part I is 49.5% solids)                                       
Part II:                                                                  
43.23      Des N-3390        38.9                                         
______________________________________                                    
 .sup.a DBTDL is dibutyl tin dilaurate, the catalyst for the isocyanate   
 crosslinking reaction                                                    
 .sup.b MEPGA is a solvent, monomethyl ether of propyleneglycol acetate   
 .sup.c MAK is methyl namyl ketone                                        
 .sup.d BYK325 is a surface tension control agent purchased from BykChemie
 USA, 524 S. Cherry Street, Wallingford, Connecticut, 06492.              
 
    
     This high solids clear was compared to a high quality commercially available isocyanate crosslinked clear in the following Table 8. 
     
                       TABLE 8                                                     
______________________________________                                    
Test Results    Control  Above Composition                                
______________________________________                                    
% Solids        38.3     60.0                                             
Viscosity, initial                                                        
                  .144    .65                                             
Viscosity, 2 hrs.                                                         
                  .182   1.29                                             
Viscosity, 4 hrs.                                                         
                  .321   2.50                                             
Cotton free time, min.sup.a                                               
                60       60                                               
Film Thickness  1.8      1.9                                              
KHN, 4 hrs.      0.30    0.68                                             
KHN, 24 hrs.    4.3      1.78                                             
KHN, 2 hrs, 80° C.                                                 
                11.5     4.0                                              
20° Gloss, Baked                                                   
                95       91                                               
______________________________________                                    
 Note that the experimental coating can be applied at much higher solids  
 than the control while still rapidly developing hardness. The coatings ha
 essentially the same gloss, thus both had a very attractive appearance.  
 .sup.aThe cotton free time was determined by dropping a cotton ball on th
 film at 5 minute intervals until the cotton no longer left fibers on the 
 surface.                                                                 
 
    
     EXAMPLE 7 
     Fluoropolymer Clear Toughened with Experiment 1 Adduct 
     Coating blends of Lumaflon® 916 reactive chlorotrifluoroethylene/vinyl ether polymer (35%), diol oligomer of Experiment 1 and Desmodur® 3390 isocyanate crosslinker (39.5%) were prepared as in Example 1. A chemically resistant, damage resistant, &lt;3.5 lb/gallon of solvent clear was produced. 
     
                       TABLE 9                                                     
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Sam- %                                                                    
ple  Lumi-   % Des   % CHDM  PHR    Viscosity,                            
                                           Hard-                          
#    flon ®                                                           
             3390    Adduct.sup.a                                         
                             DBTDL.sup.b                                  
                                    Stokes.sup.c                          
                                           ness.sup.d                     
______________________________________                                    
1    25      43.10   31.90   0.10   0.62   2.45                           
2    35      39.50   25.50   0.10   0.93   4.74                           
3    45      35.80   19.20   0.10   1.65   6.71                           
______________________________________                                    
 .sup.a Of Experiment 1                                                   
 .sup.b Parts per 100 parts of coating polymers of dibutyl tin dilaurate  
 catalyst for isocyanate/polyol reaction extend the mix life              
 .sup.c Polymers were thinned to 60% by weight with methyl ether of       
 propyleneglycol acetate and xylene                                       
 .sup.d Films were cast with a 10 mil knife, and baked for 2 hours at     
 121° C. The Knoop hardness was then determined                    
 
    
     When these coatings were applied on 28 gauge steel they passed 160 inch/pounds of direct impact without damage. This showed these materials to have a very good hardness/flexibility balance. 
     EXAMPLE 8 
     Fluoropolymer Clear with Oligomer 
     Crosslinked with Melamine Resin 
     Other crosslinking agents that react with hydroxyl groups were used with the oligomers of the present invention. The following Table 10 data shows that viscosity was reduced with very little sacrifice in hardness by using oligomer in a melamine resin crosslinked blend. The blends had good impact resistance and were resistant to 10% sulfuric acid up to 60° C. in a test simulating resistance to acid rain. In addition, the use of oligomer of the present invention, which was substantially cheaper than the fluoropolymer, provided a more economical coating. 
     
                       TABLE 10                                                    
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Sample                                                                    
      Lumiflon ®                                                      
                % CHDM    Cymel ®                                     
                                 Viscosity                                
                                        Hard-                             
#     916       Adduct.sup.a                                              
                          1133.sup.b                                      
                                 Stokes.sup.c                             
                                        ness.sup.d                        
______________________________________                                    
1     80                  20     5.5    11.2                              
2     65        15        20     2.85   10.5                              
3     55        25        20     1.92    9.58                             
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 .sup.a Of Experiment 1                                                   
 .sup.b 1 part of dodecylbenzene sulfonic acid was added to 100 parts of  
 coating as a crosslinking catalyst                                       
 .sup.c Polymers were thinned to 55% by weight with methyl ether of       
 propylene glycol acetate and xylene                                      
 .sup.d Films were cast with a 7 mil knife, and baked 30 minutes at       
 121° C. The Knoop hardness was then determined                    
 
    
     Although preferred embodiments of the invention have been described hereinabove, it is to be understood that there is no intention to limit the invention to the precise constructions herein disclosed, and it is to be further understood that the right is reserved to all changes coming within the scope of the invention as defined by the appended claims.