Epoxy resin curatives and method using lactone-imidazole complexes
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is a continuation-in-part of Ser. No. 07/736,842 filed Jul. 29, 1991, for Epoxy Resin Curative And Method to W. Su and H. G. Waddill, now abandoned. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention relates to an improved method for curing epoxy resins and the resin product thus produced. The invention also relates to an epoxy resin and curative composition. 
     2. Description of Related Art 
     Epoxy resins constitute a broad class of polymeric materials having a wide range of physical properties. The resins are characterized by epoxide groups, which are cured by reaction with curing agents to provide cured epoxy resin compositions with various desirable properties. The most common epoxy resins are condensation products of epichlorohydrin and Bisphenol A. 
     Substituted imidazoles have been used as curing agents for epoxy resins. U.S. Pat. No. 4,931,528 to H. G. Waddill et al. discloses 1-isopropyl-2-methyl imidazole as an epoxy resin curative. 
     This patent teaches the desirability of making cured products from a substituted imidazole. The need for extending the working time of these compositions has become apparent in order to utilize the desirable properties of the imidazole curative for applications such as filament winding. 
     SUMMARY OF THE INVENTION 
     The invention comprises an epoxy resin composition comprising of epoxy resin and an effective curing amount of a curing agent. The curing agent comprises a lactone-imidazole complex. This complex is formed by mixing a selected lactone and a selected imidazole in a mole proportion of 1:5 to 5:1. 
     These compositions exhibit extended pot life (working time) over the imidazole used alone as a curing agent. This extended pot life makes the composition useful for applications such as filament windings. 
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The imidazole component of curative composition is 1,2-substituted or 1-substituted imidazole. The synthesis of these compounds is taught by U.S. Pat. No. 4,927,942 to G. P. Speranza et al. and in U.S. Pat. No. 4,921,969 to W. Su et al. both incorporated herein by reference in their entirety. These patent references teach that an imidazole is prepared by reacting a diamine with an organic acid to form an amide. For example, N-isopropylethylene diamine is reacted with acetic acid to form 1-isopropyl-2-methyl imidazoline. The amide containing reaction mixture is catalytically dehydrogenated to obtain the imidazole. The reaction mixture is then vacuum distilled to recover the imidazole product. 
     According to this method, a series of imidazoles were synthesized and identified, including: 
     1-isopropyl-2-methyl imidazole, 
     1-isopropyl-2-phenyl imidazole, 
     1-isopropyl-2-tolyl imidazole, 
     1,2-dimethyl imidazole, and 
     1-methyl imidazole. 
     The synthesis of lactones is well-known in the art. For example, U.S. Pat. Nos. 2,301,827 and 3,155,686 teach the preparation of lactones and are both incorporated herein by reference. In general, a lactone is an inner ester of a carboxylic acid. In a molecule comprising an aliphatic chain with carboxyl and hydroxy substitutes separated by 2 to 5 or more carbon atoms, a proton donor catalyzes the formation of the cyclic anhydride with the elimination of water. The reaction is generally represented as follows: ##STR1## wherein n ranges from 2 to 5 or more and R 1  is a hydrogen or alkyl radical of 1 to 18 carbon atoms or mixture thereof. 
     Suitable proton donors used include concentrated mineral acid such as sulfonic acid, perchloric acid and solid acid catalysts such as sulfonic acid ion exchange resins including sulfonic acid ion exchange resins. Organic acids such as p-toluene sulfonic acid hydrate have been used, as well as electron acceptors such as boron trifluoride and boron trifluoride etherate. The proton donor is provided in an amount to provide 1 to 2 moles of protons or electron acceptors per mole of carboxylic acid. 
     The lactonization reaction is carried out at a temperature of about 100° C. while removing water to maintain the reaction mixture essentially anhydrous. The reaction is continued under those conditions for sufficient time to effect the conversion of a substantial portion of reactant to lactone. It is convenient to follow the progression of the reaction by withdrawing samples during the reaction and subjecting them to infrared analysis. For example, the formation of 5 and 6 member ring lactone reaction products is shown by infrared analysis of the 5.66 and 5.78 micron regions. Thus, by utilizing the infrared analysis or correlated reaction times, the length of time to achieve the reaction product is determined. This time may range up to 5 hours. Experience has shown that catalyst concentration, and reaction temperature can be varied to produce essentially complete reaction in about 1 hour which is efficient and economic for a laboratory scale preparation. 
     The reaction mixture is diluted with a non-polar solvent to reduce its viscosity and filtered. The lactone is recovered by vacuum distillation, e.g., 80° C. and 2mm Hg pressure. 
     According to this method a number of lactones are synthesized including: 
     beta-butyrolactone, 
     gamma-butyrolactone, 
     epsilon-caprolactone, 
     gamma-caprolactone, 
     beta-propiolactone, 
     delta-valerolactone, 
     gamma-lactone, and 
     pantolactone. 
     The lactone:imidazole complex is formed by mixing the lactone with the imidazole in the desired mole ratio, for example, 1:5 to 5:1. The preferred ratio is 1:2 to 3:1, most preferably 1:1 to 2:1. The mixing is conducted at room temperature with the spontaneous formation of the complex. For example, the lactone and imidazole are mixed with a mechanical mixer in a stainless steel resin pot at 20° C. to 25° C. (68° F. to 77° F.) for one-half to one minute. 
     In forming an epoxy resin product the lactone-imidazole complex curing agent is admixed in an effective curing amount with an epoxy resin. This can be accomplished by adding the epoxy resin to the curing agent in the same resin pot in which the lactone-imidazole complex was synthesized. The components are mixed by stirring until a homogeneous admixture is formed. This lactone-imidazole admixture has a slower reaction time than the imidazole-epoxy resin admixture. The pot life is therefore useful in applications which require an extended pot life, such as filament winding. 
     The curative agent is added to the formulation in an amount that achieves desired properties. The proper amount of curative to provide best properties is usually determined by the preparation of a number of samples which are tested to determine the composition with the most desirable physical characteristics. Typically, the physical property maximized is either the glass transition point (Tg) according to ASTM D-34I8 or the heat deflection temperature (HDT) according to ASTM D-648. 
     Curing may be accomplished at ambient conditions. For development of optimum achievable properties, however, curing at elevated temperature may be necessary. The curing temperature range acceptable in this invention is from about 60° C. to about 250° C. for about 1 to 36 hours. 
     The preferred epoxy base resin is a vicinal polyepoxide containing compound. Generally the vicinal polyepoxide containing compounds which are amine cured are organic materials having an average of at least 1.8 reactive 1,2-epoxy groups per molecule. These polyepoxide materials can be monomeric or polymeric, saturated or unsaturated, aliphatic, cycloaliphatic, aromatic or heterocyclic, and may be substituted if desired with other substituents besides the epoxy groups, e.g., hydroxyl groups, ether radicals, aromatic halogen atoms and the like. These vicinal polyepoxide containing compounds typically are of an epoxy equivalent weight of 150 to 250. Preferably the base resin, which has an epoxide equivalent weight of from 175 to 195, is derived from condensing epichlorohydrin with 2,2-bis(p-hydroxyphenyl propane) to form 2,2-bis[(p-2,3 epoxy propoxy)phenyl] propane, a derivative of bisphenol A. 
     Preferred polyepoxides are those of glycidyl ethers prepared by epoxidizing the corresponding allyl ethers or reacting, by known procedures, a molar excess of epichlorohydrin and an aromatic polyhydroxy compound, i.e., isopropylidene bisphenol, novolac, resorcinol, derivatives or aromatic amines, etc. The epoxy derivatives of methylene or isopropylidene bisphenols are especially preferred. 
     A widely used class of polyepoxides which are useful according to the present invention includes the resinous epoxy polyethers obtained by reacting an epihalohydrin, such as epichlorohydrin, and the like, with either a polyhydric phenol or a polyhydric alcohol. Typically the epoxy resins have an average of at least 1.8 reactive, 1,2-epoxy groups per molecule. An illustrative, but by no means exhaustive, listing of suitable dihydric phenols includes 4,4,-isopropylidene bisphenol, 
     2,4&#39;-dihydroxydiphenylethylmethane, 
     3,3&#39;-dihydroxydiphenyldiethylmethane, 
     3,4&#39;-dihydroxydiphenylmethylpropylmethane, 
     2,3&#39;-dihydroxydiphenylethylphenylmethane, 
     4,4&#39;-dihydroxydiphenylpropylphenylmethane, 
     4,4&#39;-dihydroxydiphenylbutylphenylmethane, 
     2,2&#39;-dihydroxydiphenylditolylmethane, 
     4,4&#39;-dihydroxydiphenyltolylmethylmethane and the like. 
     Other polyhydric phenols which may also be co-reacted with an epihalohydrin to provide these epoxy polyethers are such compounds as resorcinol, hydroquinone, substituted hydroquinones, e.g., methylhydroquinone, and the like. 
     Among the polyhydric alcohols which can be co-reacted with an epihalohydrin to provide these resinous epoxy polyethers are such compounds as ethylene glycol, propylene glycols, butylene glycols, pentane diols, bis-(4-hydroxycyclohexyl)dimethylmethane, 1,4-dimethylolbenzene, glycerol, 1,2,6-hexanetriol, trimethylolpropane, mannitol, sorbitol, erythritol, pentaerythritol, their dimers, trimers and higher polymers, e.g., polyethylene glycols, polypropylene glycols, triglycerol, dipentaerythritol and the like, polyallyl alcohol, polyhydric thioethers, such as 2,2&#39;-,3,3&#39;-tetrahydroxydipropylsulfide and the like, mercapto alcohols such as monothioglycerol, dithioglycerol and the like, polyhydric alcohol partial esters, such as monostearin, pentaerythritol monoacetate and the like, and halogenated polyhydric alcohols such as the monochlorohydrins of glycerol, sorbitol, pentaerythritol and the like. 
     Another class of polymeric polyepoxides which can be amine cured and are in accordance with the present invention includes the epoxy novolac resins obtained by reacting, preferably in the presence of a basic catalyst, e.g., sodium or potassium hydroxide, an epihalohydrin, such as epichlorohydrin, with the resinous condensate of an aldehyde, e.g., formaldehyde, and either a monohydric phenol, e.g., phenol itself, or a polyhydric phenol. Further details concerning the nature and preparation of these epoxy novolac resins can be obtained in Lee, H. and Neville, K., Handbook of Epoxy Resins, McGraw Hill Book Co., New York, 1967. 
    
    
     EXAMPLE 1 
     Lactone-imidazole complexes were prepared by mixing the imidazole with the lactone at room temperature. The imidazoles used were a follows: 
     
         ______________________________________                                    
1-isopropyl-2-methyl imidazole                                            
                         (IPMI)                                           
1-isopropyl-2-phenyl imidazole                                            
                         (IPPI)                                           
1-isopropyl-2 o-tolyl imidazole                                           
                         (IPTI)                                           
1,2-dimethyl imidazole   (DMI)                                            
1-methyl imidazole       (MI)                                             
______________________________________                                    
 
    
     The complexes prepared are listed here: 
     
         ______________________________________                                    
                          mole ratio                                      
lactone          imidazole                                                
                          lactone:imidazole                               
______________________________________                                    
a. beta-butyrolactone                                                     
                 IPMI     1:1                                             
b. gamma-butyrolactone                                                    
                 IPMI     1:1                                             
c. beta-butyrolactone                                                     
                 IPMI     2:1                                             
d. gamma-butyrolactone                                                    
                 IPMI     2:1                                             
e. epsilon-caprolactone                                                   
                 IPMI     1:1                                             
f. gamma-caprolactone                                                     
                 IPMI     1:1                                             
g. epsilon-caprolactone                                                   
                 IPMI     2:1                                             
h. gamma-butyrolactone                                                    
                 IPPI     1:1                                             
i. epsilon-caprolactone                                                   
                 IPPI     1:1                                             
j. gamma-butyrolactone                                                    
                 IPPI     1:1                                             
k. epsilon-caprolactone                                                   
                 IPPI     1:1                                             
l. epsilon-caprolactone                                                   
                 DMI      1:1                                             
m. epsilon-caprolactone                                                   
                 MI       1:1                                             
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     The beta-butyrolactone/1-isopropyl-2-methyl imidazole complex was confirmed by C 13  NMR spectroscopy. The results were consistent with a complex formed between the carbonyl carbon of beta-butyrolactone and the one pair of electrons of 1-isopropyl-2-methyl imidazole. 
     These lactone-imidazole complexes were reacted with a liquid epoxy resin of 185 to 192 equivalent epoxy weight (EEW). 
     EXAMPLE 2 
     Reactivity of 1-isopropyl-2-methyl imidazole - lactone complexes with epoxy resin 
     
         __________________________________________________________________________
                   6501-65D                                               
                        6713-1B                                           
                             6713-11C                                     
                                  6713-2A                                 
                                       6713-12B                           
                                            6713-14B                      
                                                 6713-20D                 
__________________________________________________________________________
Formulation - parts by weight                                             
Liquid epoxy resin (EEW 185-192)                                          
                   100  100  100  100  100  100  100                      
1-Isopropyl-2-methylimidazole (IPMI)                                      
                   2    --   --   --   --   --   --                       
IPMI-beta-Butyrolactone Complex                                           
1:1 molar          --   3    --   --   --   --   --                       
1:2 molar          --   --   3    --   --   --   --                       
IPMI-gamma-Butyrolactone Complex                                          
1:1 molar          --   --   --   2    --   --   --                       
1:2 molar          --   --   --   --   2    --   --                       
IPMI-epsilon-Caprolactone Complex                                         
1:1 molar          --   --   --   --   --   2    --                       
1:2 molar          --   --   --   --   --   --   4                        
Reactivity                                                                
Time to double viscosity                                                  
                   ˜16                                              
                        ˜28                                         
                             ˜32                                    
                                   ˜24                              
                                       ˜28                          
                                            ˜22                     
                                                 ˜20                
(centipoise) @ 23° C., hrs.                                        
Gel time, mins. @ 80° C.                                           
                   38.5 48.5 78.3 84.6 69.8 68.7 46.7                     
(100 g. mass) 120° C.                                              
                   14.0 12.6 16.0 15.0 15.6 19.4 14.7                     
150° C.     8.0  7.4  8.8  10.6 8.5  20.3 8.82                     
__________________________________________________________________________
 
    
     Each of the IPMI lactone complexes were less reactive toward an epoxy resin than was IPMI alone. Viscosity increase was slowed with the lactone complexes thus extending functional working temperature for these formulations. Gel times at a low temperature (80° C.), a temperature to low for complete curing of these formulations, were also longer for the systems cured with the lactone complexes. However, at higher temperatures (120° C. and 150° C.), reaction with the complexes was rapid and much like that of the IPMI curing reactions. Thus, use of the lactone complexes results in a more stable curing system at normal ambient temperatures but allows rapid curing at temperatures required to achieve complete reaction. 
     EXAMPLE 3 
     Properties of epoxy resins cured with 1-isopropyl-2-methyl imidazole - lactone complexes 
     
         __________________________________________________________________________
Formulation - parts by weight                                             
                   6501-65D                                               
                        6713-1B                                           
                             6713-11C                                     
                                  6713-2A                                 
                                       6713-12B                           
                                            6713-14B                      
                                                 6713-20D                 
__________________________________________________________________________
Liquid epoxy resin (EEW 185-192)                                          
                   100  100  100  100  100  100  100                      
1-Isopropyl-2-methylimidazole (IPMI)                                      
                   2    --   --   --   --   --   --                       
IPMI-beta-Butyrolactone Complex                                           
1:1 molar          --   3    --   --   --   --   --                       
1:2 molar          --   --   3    --   --   --   --                       
IPMI-gamma-Butyrolactone Complex                                          
1:1 molar          --   --   --   2    --   --   --                       
1:2 molar          --   --   --   --   2    --   --                       
IPMI-epsilon-Caprolactone Complex                                         
1:1 molar          --   --   --   --   --   2    --                       
1:2 molar          --   --   --   --   --   --   4                        
__________________________________________________________________________
Properties: Cured 1/8-inch Casting                                        
cured: 2 hrs 100° C., 4 hrs. 210° C.                        
                   6657-99D                                               
                        6713-1B                                           
                             6713-11C                                     
                                  6713-2A                                 
                                       6713-12B                           
                                            6713-14B                      
                                                 6713-20D                 
__________________________________________________________________________
Shore D hardness, 0-10 sec.                                               
                   88-87                                                  
                        90-87                                             
                             91-89                                        
                                  88-86                                   
                                       90-88                              
                                            94-91                         
                                                 93-90                    
HDT, °C., 284 psi                                                  
                   195.1                                                  
                        188.5                                             
                             182.4                                        
                                  241.8                                   
                                       162.3                              
                                            160.3                         
                                                 172.5                    
Izod impact strength, ft-lb/in                                            
                   0.06 0.08 0.04 0.04 0.03 0.05 0.03                     
Tensile strength, psi                                                     
                    2700                                                  
                         4800                                             
                              4200                                        
                                   3900                                   
                                        4000                              
                                             2400                         
                                                  2900                    
Tensile modulus, psi                                                      
                   415000                                                 
                        398000                                            
                             387000                                       
                                  430000                                  
                                       366000                             
                                            549000                        
                                                 521000                   
Elongation at break, %                                                    
                   0.7  1.5  1.2  1.0  1.1  0.6  0.8                      
Flexural strength, psi                                                    
                    7400                                                  
                         7200                                             
                              5800                                        
                                   8600                                   
                                        9500                              
                                             10000                        
                                                  9500                    
Flexural modulus, psi                                                     
                   357500                                                 
                        349500                                            
                             362000                                       
                                  374000                                  
                                       387000                             
                                            417000                        
                                                 363000                   
% wt. gain, 24-hr water boil                                              
                   1.20 1.34 1.46 1.33 0.96 0.95 1.40                     
3-hr acetone boil  0.00 0.02 0.13 0.09 0.05 0.11 0.18                     
Compression strength, psi                                                 
at yield            14900                                                 
                         14600                                            
                              14700                                       
                                   15600                                  
                                        15200                             
                                             14900                        
                                                  14500                   
at failure          27300                                                 
                          23000                                           
                              22000                                       
                                   28300                                  
                                        24800                             
                                             27400                        
                                                  27100                   
% compression at yield                                                    
                   12.7 13.5 12.7 13.2 12.2 12.6 12.2                     
at failure         28.9 28.1 25.8 31.2 28.5 30.4 30.7                     
Modulus, psi       199000                                                 
                        187700                                            
                             194600                                       
                                  199600                                  
                                       202900                             
                                            216000                        
                                                 200100                   
__________________________________________________________________________
 
    
     Properties of epoxy cures with imidazole lactone complexes were not substantially different from those of cures with IPMI alone. Generally, slightly lowered HDT values were noted (one higher HDT; with 1:1 molar beta-butyrolactone complex) and slightly greater susceptibility to moisture (boiling water) and chemical attack (boiling acetone). This was not found in all cases. Other physical properties were either improved or were unaffected. 
     EXAMPLE 4A 
     Reactivity of 1-isopropyl-2-phenyl imidazole - lactone complexes 
     
         ______________________________________                                    
                6501-66A                                                  
                       6713-21C 6713-22B                                  
______________________________________                                    
Formulation - parts by weight                                             
Liquid epoxy resin                                                        
                  100      100      100                                   
(EEW 185-192)                                                             
1-Isopropyl-2-phenylimidazole                                             
                  2        --       --                                    
(IPPI)                                                                    
IPPI-beta-Butyrolactone                                                   
                  --       3        --                                    
Complex (1:1 molar)                                                       
IPPI-gamma-Caprolactone                                                   
                  --       --       2                                     
Complex (1:1 molar)                                                       
Reactivity:                                                               
Time to double viscosity @                                                
                  ˜45                                               
                           ˜47                                      
                                    ˜51                             
23° C., hrs.                                                       
Gel time, mins. @ 80°C.                                            
                  80.8     80.7     120.4                                 
(100 g. mass) 120° C.                                              
                  33.9     19.0     32.4                                  
150° C.    15.2     9.5      26.9                                  
______________________________________                                    
 
    
     EXAMPLE 4B 
     Epoxy Resins Cured with 1-isopropyl-2-phenyl imidazole - lactone complexes 
     
         ______________________________________                                    
                6501-4C                                                   
                       6713-21C 6713-22B                                  
______________________________________                                    
Formulation - parts by weight                                             
Liquid epoxy resin                                                        
                  100      100      100                                   
(EEW 185-192)                                                             
1-Isopropyl-2-phenylimidazole                                             
                  2        --       --                                    
(IPPI)                                                                    
IPPI-beta-Butyrolactone                                                   
                  --       3        --                                    
Complex (1:1 molar)                                                       
IPPI-gamma-Caprolactone                                                   
                  --       --       2                                     
Complex (1:1 molar)                                                       
Properties: Cured 1/8-inch                                                
Casting                                                                   
cured: 2 hrs 100° C.,                                              
4 hrs. 210° C.                                                     
Shore D hardness, 0-10 sec.                                               
                  91-90    91-89    90-88                                 
HDT, °C., 284 psi                                                  
                  261.6    223.5    200.7                                 
Izod impact strength, ft-lb/in                                            
                  0.14     0.04     0.05                                  
Tensile strength, psi                                                     
                   2800     3400     4200                                 
Tensile modulus, psi                                                      
                  471000   489000   437000                                
Elongation at break, %                                                    
                  0.6      0.9      1.2                                   
Flexural strength, psi                                                    
                   5000     6350     8950                                 
Flexural modulus, psi                                                     
                  387000   395000   372500                                
% wt. gain, 24-hr water boil                                              
                  1.16     1.35     1.44                                  
3-hr acetone boil 0.01     0.20     0.00                                  
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     Differences in reactivity of imidazole (IPPI) and IPPI lactone complexes were slight, in contrast to the results with IPMI lactone complexes. Physical properties were much like those obtained with IPMI complexes. 
     EXAMPLE 5 
     Reactivity of 1-methyl imidazole and 1-isopropyl imidazole - lactone complexes 
     
         ______________________________________                                    
           6713-41A                                                       
                  6713-40C 6501-66A 6713-31B                              
______________________________________                                    
Formulation -                                                             
parts by weight                                                           
Liquid epoxy resin                                                        
             100      100      100    100                                 
(EEW 185-192)                                                             
1-Methylimidazole                                                         
             1        --       --     --                                  
(MI)                                                                      
MI-epsilon-Capro-                                                         
             --       3        --     --                                  
lactone Complex                                                           
(1:1 molar)                                                               
1-Isopropyl-2-o-Toly-                                                     
             --       --       2      --                                  
limidazole (IPTI)                                                         
IPTI-epsilon-Capro-                                                       
             --       --       --     2                                   
lactone Complex                                                           
(1:1 molar)                                                               
Reactivity:                                                               
Time to double vis-                                                       
             ˜24                                                    
                      ˜22                                           
                               ˜45                                  
                                      ˜46                           
cosity @ 23° C., hrs.                                              
Gel time, mins. @                                                         
80° C.                                                             
             45.7     41.9     80.8   80.4                                
120° C.                                                            
             15.0     13.0     33.9   18.1                                
150° C.                                                            
             8.7      7.6      15.2   9.2                                 
______________________________________                                    
Properties - Cured                                                        
1/2-inch Casting                                                          
cured: 2 hrs 100° C.,                                              
4 hrs. 210°C.                                                      
             6713-41A 6713-40C 6501-46A                                   
                                      6713-31B                            
______________________________________                                    
Shore D hardness,                                                         
             90-88    90-88    90-89  90-89                               
0-10 sec.                                                                 
HDT, °C., 264 psi                                                  
             171.0    179.6    244.1  241.7                               
Izod impact strength,                                                     
             0.02     0.02     0.12   0.04                                
ft-lb/in                                                                  
Tensile strength, psi                                                     
              4500     4100     3800   3450                               
Tensile modulus, psi                                                      
             399000   402000   380500 434000                              
Elongation at break,                                                      
             1.4      1.2      1.1    1.0                                 
Flexural strength,                                                        
              6700     6500     4400   7000                               
psi                                                                       
Flexural modulus,                                                         
             383500   376000   372000 376000                              
psi                                                                       
% wt. gain,                                                               
24-hr water boil                                                          
             1.39     1.62     1.19   1.38                                
3-hr acetone boil                                                         
             0.20     0.22     0.04   0.08                                
Compression strength,                                                     
psi                                                                       
at yield      15000    14600   --     --                                  
at failure    28800    22000   --     --                                  
% compression                                                             
at yield     12.4     13.6     --     --                                  
at failure   32.9     26.4     --     --                                  
Modulus, psi 202000   192000                                              
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     Results are like those of Example 3. Only small differences were found in reactivity of imidazoles versus imidazole lactone complexes. Physical properties of imidazole-lactone complexes were similar to those obtained with substituted imidazoles in Examples 3 and 4. 
     
                       TABLE OF TEST METHODS                                       
______________________________________                                    
Gel Time (minutes)     ASTM D-2471-71                                     
Shore D-Hardness 0-10 seconds                                             
                       ASTM D-2240                                        
Elongation at Break (%)                                                   
                       ASTM D-638                                         
Heat Deflection Temperature (HDT)                                         
                       ASTM D-648                                         
(°C., 264 psi/66 psi)                                              
Izod impact Strength (ft lbs/in)                                          
                       ASTM D-256                                         
Tensile strength (psi) ASTM D-638                                         
Tensile Modulus (psi)  ASTM D-638                                         
Flexural Strength (psi)                                                   
                       ASTM D-790                                         
Flexural Modulus (psi) ASTM D-790                                         
Compression Strength at Yield;                                            
                       ASTM D-695                                         
at Failure (psi)                                                          
Modulus (psi)                                                             
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     While particular embodiments of the invention have been described, it will be understood, of course, that the invention is not limited thereto since many modifications may be made, and it is, therefore, contemplated to cover by the appended claims any such modification as fall within the true spirit and scope of the invention.