Patent Publication Number: US-2009226719-A1

Title: Composite material formulation

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of U.S. Provisional Application No. 61/034,039, filed Mar. 5, 2008. 
    
    
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
     Not Applicable 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to composite materials. More particularly it relates to fiber-reinforced epoxy resins. 
     2. Description of the Related Art including information disclosed under 37 CFR 1.97 and 1.98. 
     Curable resinous compositions are described in international application WO 2006/052253 published under the Patent Cooperation Treaty. The curable composition described in that patent publication may be hardened in the presence of a heat activated catalyst to render a scratch resistant hard surface. 
     Organometallic compositions and coating compositions are described in international application WO 2006/022899 published under the Patent Cooperation Treaty. Certain catalysts described therein include organometallic compositions according to the formula Metal(Amidine) 2 (Carboxylate) x  where x is the oxidation state of the metal. Examples include Zn(Lindax-1) 2 (acetate) 2 , Zn(Lindax-1) 2 (formate) 2  and Zn(Lindax-1) 2 (2-ethylhexanoate) 2  where Lindax-1 supplied by Lindau Chemicals Inc. is 1-(2-hydroxypropyl)imidazole. 
     BRIEF SUMMARY OF THE INVENTION 
     The system according to the present invention may be comprised of an epoxy resin, hardener and catalyst. One particular preferred system ratio is 1:1.64:0.005, respectively. The epoxy resin may be a tetrafunctional resin. The hardener may be a nadic methyl anhydride. One particularly preferred heat activated catalyst is 1-(2-hydroxypropyl) imidazole available from Lindau Chemicals, Inc. (Columbia, S.C.) under the brand name LINDAX 1. The amount of catalyst may be tailored to a certain desired pot life, oven cure and to promote polymer crosslinking at a faster rate. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING(S) 
         FIG. 1  is a differential scanning calorimeter (DSC) plot for a sample having a cure schedule of 11 hours at 140° F., 2 hours at 302° F. and 5 hours at 425° F. 
         FIG. 2  is a differential scanning calorimeter (DSC) plot for a sample having a cure schedule of 13 hours at 140° F., 2 hours at 302° F. and 5 hours at 425° F. 
         FIG. 3  is a differential thermo-mechanical analyzer plot of a sample prepared using a final cure period temperature of 425° F. 
         FIG. 4  is a differential scanning calorimeter plot for a sample cured at a final temperature of 425° F. 
         FIG. 5  is a differential scanning calorimeter plot for a sample cured at a final temperature of 450° F. 
         FIG. 6  is a differential scanning calorimeter plot for a sample cured at a final temperature of 475° F. 
         FIG. 7  is a differential thermo-mechanical analyzer plot of a sample prepared using a final cure period temperature of 325° F. 
         FIG. 8  is a thermo gravimetric analyzer plot for uncured material impregnated with resin and pulled through an orifice having a diameter of 0.054 inch. 
         FIG. 9  is a thermo gravimetric analyzer plot for uncured material impregnated with resin and pulled through an orifice having a diameter of 0.064 inch. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     A composite is a mixture or mechanical combination on a macro scale of two or more materials that are solid in the finished state, are mutually insoluble, and differ in chemical nature. One major type of composite material is reinforced plastics, principally comprised of glass fiber and a thermosetting resin. Other types of fibers such as carbon, boron, aluminum silicate, and silicon carbide may be used. 
     A composite system according to the present invention may be comprised of an epoxy resin, hardener and catalyst. One particular preferred system ratio is 1:1.64:0.005 respectively. The epoxy resin may be a tetrafunctional resin. The hardener may be a nadic methyl anhydride. One particularly preferred heat-activated catalyst is 1-(2-hydroxypropyl) imidazole available from the Lindau Company under the brand name LINDAX 1. 
     The amount of catalyst may be tailored to the desired pot life, oven cure and to promote polymer crosslinking at a faster rate. In a preferred embodiment, fiberglass rovings are impregnated with this resin system as the filament winding process takes place. During filament winding, the pot containing the resin mixture is preferably maintained at a temperature of about 110° F. to promote the flow of the system to better impregnate the fiberglass strands. Once the winding process is complete and the tubing has been fabricated, the system is cured at 140° F. for 12 hours, 302° F. for 2 hours and 425° F. for 5 hours. The process is then substantially complete. 
     One aspect of this new solution which differentiates it from prior solutions is the catalyst. Epoxy resin systems are usually two part systems, additives may be incorporated into the system to give the epoxy one or more special characteristics. In this system, the catalyst and the amount are critical. The catalyst in this case provides a faster cure, promoting a higher amount of crosslinking thereby enabling the product to have a higher glass transition temperature allowing it to be exposed to extreme environments where high temperatures and pressures are involved. 
     Table 1, below, shows the onset glass transition temperature (T g ) for various tested systems as determined by thermomechanical analysis using an expansion probe. The sample thickness is also shown in the table. The weight percent catalyst for Sample Nos. 3, 4 and 5 were 0.1, 1.0 and 0.5, respectively. Sample Nos. 1 and 2 represent resin/hardener systems of the prior art. Sample No. 5 represents the currently preferred system. 
     
       
         
           
               
               
             
               
                   
                 TABLE 1 
               
             
            
               
                   
                   
               
               
                   
                 Sample ID 
               
            
           
           
               
               
               
               
               
               
            
               
                   
                 CY179/L25 
                 L290/25 
                 721/25/0.1 
                 721/25/1.0 
                 721/25/0.5 
               
            
           
           
               
               
            
               
                   
                 Sample No. 
               
            
           
           
               
               
               
               
               
               
            
               
                   
                 1 
                 2 
                 3 
                 4 
                 5 
               
               
                   
                   
               
            
           
           
               
               
               
               
               
               
            
               
                 Thick- 
                 3.77 mm 
                 1.40 mm 
                 2.77 mm 
                 2.04 mm 
                 3.03 mm 
               
               
                 ness 
               
               
                 Onset 
                 218.0° C. 
                 223.0° C. 
                 204.0° C. 
                 223.4° C. 
                 295.0° C. 
               
               
                 Temp 
               
               
                   
               
            
           
         
       
     
     Table 2, below, shows the transition temperatures of various resin/hardener systems without a catalyst. MY721/A5200 is a resin/hardener system from Huntsman Corporation (Basel, Switzerland) that utilizes an amine-based hardener. MY721/A917 is another resin/hardener system from Huntsman Corporation that utilizes an amine-based hardener. “Pure G-14” is an epoxy resin system of the prior art that has an anhydride-based hardener. “Blend G-13” is a bis A epoxy system having a cyclo aliphatic hardener. 
     
       
         
           
               
               
               
               
             
               
                 TABLE 2 
               
               
                   
               
               
                   
                 Transition 
                 Transition 
                   
               
               
                 Resin/Hardener 
                 1° C. 
                 2° C. 
               
               
                 (ratio) 
                 (° F.) 
                 (° F.) 
                 Observation 
               
               
                   
               
             
            
               
                 Lindoxy 
                 192.6 
                 Not 
                 Transition 1 is strong so it can 
               
               
                 190/Lindride 25 
                 (378.7) 
                 observed 
                 be considered the T g   
               
               
                 (1:1.25) 
               
               
                 Lindoxy 
                 219.5 
                 Not 
                 Transition 1 is strong so it can 
               
               
                 290/Lindride 25 
                 (427.1) 
                 observed 
                 be considered the T g . Other 
               
               
                 (1:1) 
                   
                   
                 transitions too small to take into 
               
               
                   
                   
                   
                 account. 
               
               
                 MY721/A5200 
                 204.3 
                 Not 
                 Transition 1 is strong so it can 
               
               
                 (1:0.40) 
                 (399.7) 
                 observed 
                 be considered the T g . 
               
               
                   
                   
                   
                 Unlike 10/30 samples, only one 
               
               
                   
                   
                   
                 clear transition observed. 
               
               
                 MY721/A917 
                 217.2 
                 Not 
                 Unlike 10/30 sample, sample 
               
               
                 (1:1.41) 
                 (423.0) 
                 observed 
                 showed lower amount of un- 
               
               
                   
                   
                   
                 cured material on only one clear 
               
               
                   
                   
                   
                 transition. 
               
               
                 MY721/Lindride 
                 220.8 
                 Not 
                 Shows a unique transition and 
               
               
                 25 
                 (429.4) 
                 observed 
                 almost 20° F. higher as compared 
               
               
                 (1:1.64) 
                   
                   
                 to sample with only 0.4 ratio of 
               
               
                   
                   
                   
                 Lindride 25 
               
               
                 Pure G-14 
                 217.1 
                 Not 
                 Transition 1 is strong so it can 
               
               
                   
                 (422.8) 
                 observed 
                 be considered the T g   
               
               
                 Blend G-13 
                 216.4 
                 Not 
                 Transition 1 is strong so it can 
               
               
                   
                 (421.5) 
                 observed 
                 be considered the T g   
               
               
                   
               
            
           
         
       
     
     Samples having differing initial cure times are compared in  FIGS. 1 and 2 . The sample of  FIG. 1  had a cure schedule of 11 hours at 140° F., 2 hours at 302° F. and 5 hours at 425° F. The sample of  FIG. 2  had a cure schedule of 13 hours at 140° F., 2 hours at 302° F. and 5 hours at 425° F. 
     Samples having differing final cure temperatures are compared in  FIGS. 4 ,  5  and  6 . The sample of  FIG. 4  was cured at a final temperature of 425° F. The sample of  FIG. 5  was cured at a final temperature of 450° F. The sample of  FIG. 6  was cured at a final temperature of 475° F. 
     The glass transition temperature of an organic polymer may be determined by differential scanning calorimetry (or DSC), a thermoanalytical technique in which the difference in the amount of heat required to increase the temperature of a sample and reference are measured as a function of temperature.  FIGS. 1 ,  2 ,  4 ,  5  and  6  are DSC plots. Another technique for determining T g  is differential thermo-mechanical analysis.  FIGS. 3 and 7  are differential thermo-mechanical analyzer plots of selected samples. 
     In  FIG. 3 , Curve B is E′ in dynes per cm 2 , Curve D is E″ in dynes per cm 2 , Curve A is delta L in millimeters and Curve D is tangent delta. In  FIG. 7 , Curve F is E′ in dynes per cm 2 , Curve G is E″ in dynes per cm 2 , Curve E is delta L in millimeters and Curve H is tangent delta. Lines A and E on the charts depicted in  FIGS. 3 and 7 , respectively, represent the coefficient of linear expansion. Lines B and F represent E′, the elastic or storage component of the complex modulus E*. Lines D and G represent E″, the viscous or loss component of the complex modulus. E′ and E″ are related to the complex modulus by the Pythagorean theorem: (E*)E 2 =(E′)E 2 +(E″)E 2 . Lines C and H are the tangent of delta, (tan δ), which is E″/E′. It is a measure of elasticity. By way of example, tire treads have a low tan δ, about 0.25, while butyl shock absorbers have a high tan δ. The peak in the tan delta line can be interpreted as the glass transition. The T g  can be interpreted from either the E′ or E″ curve using the intersection of slopes. This may be advantageous when the tangent delta peak is not very clear or occurs out of the test range. In the charts reproduced in  FIGS. 3  and  7 , the slope intersects of E′ where used since the peak of tan delta occurs to the far right of, or off the chart. Both the glass transition, and the stability of E′ and E″ over the tested temperature range are figures of merit for the material tested. 
     Another aspect of the invention is the processing and the cure schedule. Filament winding with a tetrafunctional epoxy resin is unique in itself due to the epoxy&#39;s viscosity. 
     For one, particular preferred embodiment, a resin-impregnated fiber will have between about 30% and about 35% resin, by weight, in the “wet” condition—i.e., prior to curing.  FIG. 8  is a thermo gravimetric analyzer plot for material impregnated with resin and pulled through an orifice having a diameter of 0.054 inch. The sample size was 14.1890 mg. A nitrogen purge was used as the temperature was ramped from room temperature to 600° C. An air purge was used from 600 to 1000° C. 
       FIG. 9  is a thermo gravimetric analyzer plot for material impregnated with resin and pulled through an orifice having a diameter of 0.064 inch. The sample size was 17.2820 mg. A nitrogen purge was used as the temperature was ramped from room temperature to 600° C. An air purge was used from 600 to 1000° C. It can be seen that the 0.064 inch diameter orifice (or “nib”) comes closer to producing material in the desired range of about 30 to 35% resin. 
     One particular application of the method of the invention is the production of composite bridge plugs. A bridge plug is a downhole tool that is located and set to isolate the lower part of a wellbore. Bridge plugs may be permanent or retrievable, enabling the lower wellbore to be permanently sealed from production or temporarily isolated from a treatment conducted on an upper zone. Often, bridge plugs are removed from a well bore by drilling them out. Bridge plugs fabricated predominately from steel or similar hard metals are difficult to drill out, often requiring several replacements of the drill bit during the removal operation. Bridge plugs fabricated using synthetic polymer materials are relatively easy to remove by drilling, but frequently lack the strength required to obtain a reliable set. It has been found that a bridge plug fabricated using fiberglass impregnated with a resin composition according to the present invention, wound on a mandrel and cured as hereinabove described has the requisite strength but can easily be drilled out of the wellbore after it has been set. 
     Although the invention has been described in detail with reference to certain preferred embodiments, variations and modifications exist within the scope and spirit of the invention as described and defined in the following claims.