Polyester-resin coating and drum liner made therefrom
This is a continuation of co-pending application Ser. No. 08/018,070 filed on Feb. 16, 1993, now abandoned. 
    
    
     BACKGROUND OF THE INVENTION 
     The present invention is directed to a coating made from a polyester resin, and to a liner for drums made from the polyester resin coating. 
     Steel drums, or pails, such as 55-gallon drums and 5-gallon pails, often require an interior protective lining in order to protect the contents in the drum. Currently-used protective liners contain primarily organic solvent bases. An example of such an organic solvent base liner, which is extensively used, is an epoxy/phenolic coating, such as &#34;Sterilkote&#34; produced by Russell-Stanley Corp., of Woodbridge, N.J. The problem with the conventional, organic solvent base, protective drum-linings is that they are high in volatile organic compound (VOC). Standards set by the Environmental Protection Agency (EPA), enacted to reduce solvent emissions, require that no more than 4.3 pounds of VOC per gallon of coating may be used for drum and pail interior, protective linings. While some currently-sold organic solvent base drum-linings do meet such strict EPA requirements, a lining that provides even lower VOC&#39;s would be highly advantageous. Such a low VOC lining should also be inert to reaction with all of the many corrosive materials packaged in steel drums and pails, in order to prevent contamination, and needs to have a low enough viscosity, in order to allow it to be sprayed, or otherwise, applied to the interior of a drum or pail, by conventional application-techniques, as well as being sufficiently hard and flexible, in order to serve as a drum-lining. The present invention provides a new drum or pail interior lining that has low VOC levels, yet also provides lining-qualities superior in performance to conventionally-used solvent-based linings. 
     SUMMARY OF THE INVENTION 
     It is the primary objective of the present invention to provide a novel coating or protective covering that may be used in all environments where a protective coating is applied to a metal, such as for use in coating coils, for coating the interior of cans or beverage containers, and as well as for a host of other uses where protective coatings and films are applied to a metal. 
     It is the primary objective of the present invention to specifically provide a lining for the interior of steel drums and pails which has very low levels of volatile organic compounds, which incorporates the novel coating of the invention therein, which drum-lining has superior hardness and flexibility, as well as other superior properties necessary for a steel-drum lining, as compared to conventional steel-drum linings. 
     It is an object of the present invention to provide such a novel coating and such a novel steel-drum lining which are mostly contain a water-base rather than an organic solvent base, thereby effectively eliminating the problem of VOC-emissions. 
     The novel coating of the invention for use in all metal-coating environments is made from a water-base polyester-resin, and the steel-drum lining made from this water-base polyester-resin coating is a water-base phenolic coating. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention will be more readily understood with reference to the accompanying drawing, wherein: 
     FIG. 1 is a graph showing the test results comparing drum-lining coatings of the present invention compared to conventional solvent-base, phenolic coatings. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The novel coating of the invention for use in all environments where metal is coated, such as in beverage cans or tins, coils, etc., is a water-base polyester resin. According to the invention, the coating is made from a water soluble polyester and cross-linked with melamine type organic resin which contains less than ten percent of organic solvent. The polyester resin is formulated from one of five different formulations, as set forth in Table 1 hereinbelow. 
     
                                           TABLE I                                 
__________________________________________________________________________
Resin Formulations                                                        
          Parts by Weight                                                 
          P.E.3823                                                        
                P.E.3823                                                  
Materials (PEI-A)                                                         
                (TOFA)                                                    
                     P.E.300                                              
                           P.E.74/18                                      
                                 3712NPF                                  
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Timellitic                                                                
          200-300                                                         
                200-300                                                   
                     168    86   355                                      
Anhydride (TMA)                                                           
Isophthalic                                                               
          --    --   655   323   --                                       
Acid (IPA)                                                                
Adipic Acid                                                               
          --    --   192    94    90                                      
Neopentyl 300-500                                                         
                300-400                                                   
                     685   169   450                                      
Clycol                                                                    
Pelargonic Acid                                                           
          200-300                                                         
                --   --    --    198                                      
Tall Oil  --    356  --    --    --                                       
Fatty Acid                                                                
Glycidyl Ester                                                            
          --    --   --    399   --                                       
of Versatic                                                               
Acid 1                                                                    
__________________________________________________________________________
 
    
     The preferred formulation for each is as follows: 
     
         __________________________________________________________________________
Resin Formulations                                                        
          Parts by Weight                                                 
          P.E.3823                                                        
                P.E.3823                                                  
Materials (PEI-A)                                                         
                (TOFA)                                                    
                     P.E.300                                              
                           P.E.74/18                                      
                                 3712NPF                                  
__________________________________________________________________________
Timellitic                                                                
          291   240  168    86   355                                      
Anhydride                                                                 
(TMA)                                                                     
Isophthalic                                                               
          --    --   655   323   --                                       
Acid (IPA)                                                                
Adipic Acid                                                               
          --    --   192    94    90                                      
Neopentyl 419   346  685   169   450                                      
Clycol                                                                    
Pelargonic                                                                
          239   --   --    --    198                                      
Acid                                                                      
Tall Oil  --    356  --    --    --                                       
Fatty Acid                                                                
Glycidyl  --    --   --    399   --                                       
Ester of                                                                  
Versatic                                                                  
Acid 1                                                                    
          1116  1080 1700  1071  1093                                     
Less water                                                                
          116    80  200    71    93                                      
of reaction                                                               
Yield     1000  1000 1500  1000  1000                                     
                     -500                                                 
                     1000                                                 
__________________________________________________________________________
 
    
     Of these five formulations, the first two, P.E. 3823 (PELA--Pelargonic Acid) and P.E. (TOFA--Tall Oil Fatty Acid) provide the most superior characteristics for use in a coating. 
     The ingredients of each polyester resin shown above is cooked, in a conventional manner, known to those skilled in the art. For example, for producing P.E. 3823 (TOFA type), the following pilot kettle batch is a preferred manner of cooking: 
     Batch Size: 375 pound yield (solid), 500 pounds at 75% NVM 
     
         ______________________________________                                    
Material          Weight (lbs.)                                           
                              Mole Ratio                                  
______________________________________                                    
1.  Neopentyl glycol, NPG                                                 
                      130.6       8.00                                    
2.  Isophthalic acid, IPA-99                                              
                      52.1        2.00                                    
3.  Trimellitic anhydride, TMA                                            
                      53.4        1.77                                    
4.  Tall oil fatty acid,                                                  
                      134.2       3.00                                    
    Acintol FA-1                                                          
5.  Trimellitic anhydride, TMA                                            
                      37.1        1.23                                    
                      407.4                                               
    Less water of esterification                                          
                      -32.4                                               
    Yield at 36 A.N.  375.0                                               
6.  Ethylene glycol mono                                                  
                      125.0                                               
    butyl ether                                                           
                      500.0       Total at                                
                                  75% NVM                                 
______________________________________                                    
 
    
     Processing Procedure: 
     1. Charge neopentyl glycol, isophthalic acid, and first state trimellitic anhydride to reactor equipped with agitator, inert gas sparge and steam heated partial condenser. 
     2. Slowly heat the materials, begin agitation at about 90° C.(2000° F.) and continue heating to a maximum temperature 232°-238° C. (450°-460° F.) while maintaining a maximum overhead temperature of 102° C. (215° F.). Use 5-10 lb. steam on the partial condenser to help maintain overhead temperature. 
     3. Hold for an acid number of less than 10. 
     4. Cool to 200° C. (390° F.), charge tall oil fatty acid, and then reheat to 220°-227° C.(430°-440° F.). 
     5. Hold for an acid number of less than 10 and a viscosity at 80% NVM in ethylene glycol mono butyl ether of T+ (Gardner-Holdt). 
     6. Cool to 200° C. (390° F.), add final stage trimellitic anhydride, and reheat to 205°-210° C. (400°-410° F.). Alternately, cool to 121° C. (250° F.), and hold overnight with 10 pound steam on kettle jacket. Then reheat to 177° C. (350° F.), add final stage trimellitic anhydride, and continue heating to 205°-210° C. (400°-410° F.). 
     7. Hold for an acid number of 42-44. 
     8. Cool to 177°-160° C. (350°-320° F.) and hold for an acid number of 35-37. 
     9. Thin in the kettle with ethylene glycol mono butyl ether to 75% NVM. 
     10. Package in a lined drum with excess in five gallon pails. 
     11. Determine final properties of polymer as follows: 
     
         ______________________________________                                    
                Specification                                             
______________________________________                                    
Acid number, solids                                                       
                  35-37                                                   
Viscosity, Gardner-Holdt                                                  
                  Z4                                                      
Color, Gardner    5-7                                                     
NVM, %            75                                                      
Volatile          75                                                      
Density, lb./gal. Ethylene glycol mono butly                              
                  ether                                                   
______________________________________                                    
 
    
     The coating itself is formed by mixing the respective polyester resin cooked as above, according to the formulation shown in Table 2, hereinbelow. 
     
                                           TABLE 2                                 
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           Parts by Weight                                                
           P.E.3823                                                       
                 P.E.3823                                                 
Materials  (PELA)                                                         
                 (TOFA)                                                   
                       P.E.300                                            
                             P.E.74/18                                    
                                   3712NPF                                
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Coating Formulation                                                       
2 Dimethyl 40-80 40-80 40-80 40-80 40-80                                  
amino ethanol                                                             
Crosslinker-                                                              
           200-400                                                        
                 200-400                                                  
                       200-400                                            
                             200-400                                      
                                   200-400                                
Hexamethoxy-                                                              
methylmelamine                                                            
Distilled  2000-3000                                                      
                 2000-3000                                                
                       2000-3000                                          
                             2000--3000                                   
                                   2000-3000                              
Water                                                                     
__________________________________________________________________________
 
    
     Theoretically, following chemical cross-linking, reaction will occur with Methoxy methyl functionality of Hexamethoxy methyl melamine. ##STR1## 
     The properties exhibited by each coating are shown in Table 3, hereinbelow. 
     
                                           TABLE 3                                 
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           Parts by Weight                                                
           P.E.3823                                                       
                 P.E.3823                                                 
Materials  (PELA)                                                         
                 (TOFA)                                                   
                       P.E.300                                            
                             P.E.74/18                                    
                                   3712NPF                                
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Solution Properties                                                       
Resin/Cross-                                                              
           50/80 50/80 50/80 50/80 50/80                                  
linker                                                                    
Ratio      10/30 10/30 10/30 10/30 10/30                                  
Water/Solvent                                                             
            50/100                                                        
                  50/100                                                  
                        50/100                                            
                              50/100                                      
                                    50/100                                
Ratio      10/20 10/20 10/20 10/20 10/20                                  
NVM-%      25-45 25-45 25-45 25-45 25-45                                  
Initial Ph 7.5 +/-                                                        
                 7.5 +/-                                                  
                       7.5 +/-                                            
                             7.5 +/-                                      
                                   7.5 +/-                                
           1     1     1     1     1                                      
Viscosity Zahn                                                            
           100 +/-                                                        
                 100 +/-                                                  
                       100 +/-                                            
                             100 +/-                                      
                                   100 +/-                                
Cup#2 seconds                                                             
           30    30    30    30    30                                     
__________________________________________________________________________
 
    
     The preferred coating formulation is as shown in Table 4, hereinbelow. 
     
                                           TABLE 4                                 
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           Parts by Weight                                                
           P.E.3823                                                       
                 P.E.3823                                                 
Materials  (PELA)                                                         
                 (TOFA)                                                   
                       P.E.300                                            
                             P.E.74/18                                    
                                   3712NPF                                
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Coating Formulation                                                       
2 Dimethyl 60    60    60    60    60                                     
amino ethanol                                                             
Crosslinker-                                                              
           280   280   280   280   280                                    
Hexamethoxy                                                               
Methyl Melamine                                                           
Distilled  2450  2450  2450  2450  2450                                   
Water                                                                     
           3790  3790  3790  3790  3790                                   
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     The properties exhibited by the coating formulation on Table 4, is as shown in Table 5, hereinbeolow. 
     
                                           TABLE 5                                 
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           Parts by Weight                                                
           P.E.3823                                                       
                 P.E.3823                                                 
Materials  (PELA)                                                         
                 (TOFA)                                                   
                       P.E.300                                            
                             P.E.74/18                                    
                                   3712NPF                                
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Solution Properties                                                       
Resin/Cross-                                                              
           80/20 80/20 80/20 80/20 80/20                                  
linker Ratio                                                              
Water/Solvent                                                             
           86/14 86/14 86/14 86/14 86/14                                  
Ratio                                                                     
NVM-%      30-33 30-33 30-33 30-33 30-33                                  
Initial Ph 7.5 +/-                                                        
                 7.5 +/-                                                  
                       7.5 +/-                                            
                             7.5 +/-                                      
                                   7.5 +/-                                
           1     1     1     1     1                                      
Viscosity Zahn                                                            
           100 +/-                                                        
                 100 +/-                                                  
                       100 +/-                                            
                             100 +/-                                      
                                   100 +/-                                
Cup #2 seconds                                                            
           10    10    10    10    10                                     
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     A comparison of the final polyester coatings to each other after having been subjected to conventional testing techniques, as well as their comparison to a conventional solvent-based coating, is shown in table 6 hereinbelow. 
     
                                           TABLE 6                                 
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EVALUATION RESULTS                                                        
Application:                                                              
         Dip Coat                                                         
Substrate:                                                                
         Cold Rolled Steel                                                
Film Thickness:                                                           
         .5 mil, average                                                  
Cure Schedule:                                                            
         PolyEnviro systems, 30 minutes at 350° F.                 
         Solvent system, 15 minutes at 395° F.                     
Chemical testing:                                                         
         Spot testing at room temperature covered by watchglass           
Ratings: Visual evaluation No change = 0, very slight = 1, slight = 2,    
         moderate = 3,                                                    
         considerable = 4, severe = 5                                     
            P.E.3823                                                      
                   P.E.3823                                               
Materials   (PELA) (TOFA)  P.E.300  P.E.74/18                             
                                             3712NPF                      
hours exposure                                                            
            24                                                            
              48 72                                                       
                   24                                                     
                     48 72 24 48 72 24 48 72 24 48 72 24 48 72            
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10% Sodium Chloride                                                       
            0 0  0 0 0  0  0  0  1  0  0  1  0  0  0  0  0  0             
10% Hydrochloric Acid                                                     
            0 0  0 0 0  2  2  3-4                                         
                                 5  0  0  2-3                             
                                             3  5  5  0  0  1-2           
10% Sulfuric Acid                                                         
            0 0  0 0 0  0  0  2  4-5                                      
                                    0  0  0  0  0  4  0  0  0-1           
10% Acetic Acid                                                           
            0 0  0 0 0  0  0  1  1-2                                      
                                    2-3                                   
                                       3-4                                
                                          5  1-2                          
                                                3  5  3  5  5             
10% Phosphoric Acid                                                       
            0 0  0 0 0  0  0  1-2                                         
                                 2-3                                      
                                    0  0  1  0  0  1  0  1-2              
                                                            4             
10% Sodium Hydroxide                                                      
            0 0  0 0 0  0  0  0  1  2-3                                   
                                       5  5  0  0  1  5  5  5             
10% Ethanol 0 0  0 0 0  0  0  0  0  0  0  1  0  0  0  0  0  1             
Distilled Water                                                           
            0 0  0 0 0  0  0  0  0  0  0  0  0  0  0  0  0  0             
Calcium Hypochlorite.sup.2                                                
            0 1-2                                                         
                 3 0 1-2                                                  
                        3-4                                               
                           0  1-2                                         
                                 1-2                                      
                                    0  2  3-4                             
                                             0  1-2                       
                                                   2-3                    
                                                      0  1-2              
                                                            3-4           
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     The above table shows the superior properties of each of the water-base polyester resin coatings as compared to a conventional solvent-based coating, as well as the superiority of the P.E. 3823 (TOFA) as compared to the other polyester resin coatings of the invention, with regards to being inert to the corrosive materials shown. 
     The water soluble, organic coating P.E. 3823 (TOFA) contains less than ten percent of organic solvent, and can be applied to a metal substrate by rollcoating, spraying or dipping. Typical properties of the P.E. 3823 (TOFA) are shown in Table 7: 
     
                       TABLE 7                                                     
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APPEARANCE:      Yellowish-white viscous liquid                           
SPECIFIC GRAVITY:                                                         
                 1.15 + 0.05                                              
DENSITY:         8.98 lbs/gal                                             
VISCOSITY:       50-60 sec. (Zohn cup #2)                                 
pH:              8.5 ± 0.5                                             
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     The recommended application of the P.E. 3823 (TOFA) is to adjust the proper viscosity by adding distilled water for suitable application. Also baking cycle can be adjusted at the required film weight. The product is typically packaged in 55 gallon steel drums. Storage requirements are such that it is be to be stored in combustible liquid storage area. Storage should be away from heat, ignition sources and open flame in accordance with applicable federal, state or local regulations. The container should be kept closed, and the product should not be allowed to freeze. 
     One very important, and critical, characteristic of all of the water-base polyester coatings of the invention is the low level of volatile organic compound (VOC). For P.E. 3823: 
     
         ______________________________________                                    
VOC DATA SHEET                                                            
______________________________________                                    
A.  COATING SP. GRAVITY:                                                  
                        1.15 + 0.05                                       
    Density:            8.95 lbs/gal                                      
B.  TOTAL VOLATILES:    65 wgt per cent                                   
C.  WATER CONTENT:      58.5 wgt per cent                                 
D.  ORGANIC VOLATILE:   6.5 wgt per cent                                  
E.  NONVOLATILE CONTENT:                                                  
                        35 wgt per cent                                   
G.  VOC CONTENT:        1.17 lbs/gal (less water).                        
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     As can be seen, the 1.17 lbs./gal is considerably below the 4.3 lbs./gal. requirement set by the EPA, as discussed above, as is also considerably less than presently-used, low-level VOC, primarily organic solvent base, steel-drum linings. 
     Each of the novel, water-base phenolic drum-lining compounds of the invention uses the novel P.E. 3823 (TOFA) or P.E. 3823 (PELA) as one of its main ingredients. Shown in Table 9 are formulations, by weight-percentage, of three such novel drum-lining compounds, each of which includes one of the P.E. 3823 (TOFA) or P.E. 3823 (PELA), a phenolic, and a crosslinking agent; also shown are the properties of the baked film. 
     
                       TABLE 8                                                     
______________________________________                                    
            P.E. 5  P.E. 10    P.E. 15                                    
______________________________________                                    
P.E. 3823 TOFA                                                            
              --        20.0-35.0  --                                     
P.E. 3823 PELA                                                            
              25.0-32.0 --         20.0-40.0                              
2-Dimethyl Amino                                                          
              0.5-1.5   1.0-3.0    1.0-4.0                                
Ethanol                                                                   
Crosslinker   3.0-8.0    5.0-12.0                                         
Hexamethoxy                                                               
Methyl Melamine                                                           
Polsolv EB    1.0-3.0   2.0-6.0    1.0-6.0                                
Distilled water                                                           
              55.5-70.5 44.0-72.0  45.0-77.0                              
Crosslinker DER 331                                                       
              --        --         1.0-5.0                                
______________________________________                                    
Draw down on phosphatized steel carbon plate. Bake @ 450° F.       
for 10 minutes.                                                           
PROPERTIES OF                                                             
BAKED FILM                                                                
Film Hardness hard      very hard  soft                                   
MEK Rubs      50        100+       10                                     
Adhesion      good      excellent  marginal                               
Appearance    yellowish yellowish  whitish                                
______________________________________                                    
 
    
     The preferred formulation is as shown in Table 9: 
     
                       TABLE 9                                                     
______________________________________                                    
            P.E. 5  P.E. 10    P.E. 15                                    
______________________________________                                    
P.E. 3823 TOFA                                                            
              --        28                                                
P.E. 3823 PELA                                                            
              31.4      --         30.2                                   
2-Dimethyl Amino                                                          
              1.2       2.8        1.2                                    
Ethanol                                                                   
Crosslinker Cymel                                                         
              6.0       9.4                                               
Polsolv EB    2.4       3.7                                               
Distilled water                                                           
              59.0      56.1       60.5                                   
Crosslinker DER 331                                                       
              --        --         2.3                                    
______________________________________                                    
 Draw down on phosphatized steel carbon plate. Bake @ 450° F. for 1
 minutes.                                                                 
 
    
     The fourth, and preferred, novel, water-base phenolic drum-lining compound of the invention uses the novel P.E. 3823 (TOFA) only, and has the formulation, by weight-percentage, as shown in Table 10, hereinbelow; also shown are the properties. 
     
                       TABLE 10                                                    
______________________________________                                    
               P.E. 20                                                    
______________________________________                                    
PKHW-35           6.0-15.0                                                
Deionized H.sub.2                                                         
                 20.0-30.0                                                
Butyl Cellosolve 2.0-4.0                                                  
P.E. 2392        30.0-50.0                                                
P.E. 3823 TOFA   2.0-4.0                                                  
Deionized H.sub.2 O                                                       
                 20.0-40.0                                                
Properties                                                                
PH = 8.0 +/- 1.0                                                          
Viscosity = 85 +/- 10 Seconds Zohn&#39;s Cup #2                               
______________________________________                                    
 
    
     The preferred formulation for this fourth product is as follows: 
     
         ______________________________________                                    
               P.E. 20                                                    
______________________________________                                    
PKHW-35          12                                                       
Deionized H.sub.2 O                                                       
                 25                                                       
Butyl Cellosolve  3                                                       
P.E. 2392        46                                                       
P.E. 3823 TOFA    3                                                       
Deionized H.sub.2 O                                                       
                 11                                                       
                 100                                                      
Properties                                                                
PH = 8.0 +/- 1.0                                                          
Viscosity = 85 +/- 10 Seconds Zohn&#39;s Cup #2                               
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     The element P.E. 2392 is a unique, proprietary, commercially- available phenolic resin made and sold by Poly Enviro Laboratory, Inc. of Alsip, Ill. 
     FIG. 1 shows the hardness properties of the water-base phenolic-resin drum-lining coatings of the present invention in comparison to the conventional solvent-base, phenolic drum-lining coatings. The results shown are for reverse-impact tests, and the bars 10,10&#39; shown in black are for a conventional solvent-base, phenolic drum-lining coating, while the first cross-hatched bars 20, 20&#39; are for the P20 water-base phenolic-resin drum-lining coating of the present invention detailed in Table 10, above, while the third cross-hatched bars 30, 30&#39; are for a combination of the 0.5 mil thick outer layer of P20 coating compound over an inner, 0.5 mil thick layer of P10 coating compound detailed in Table 10, above. The measured values on the ordinate axis are lbs./sq.in. The first set of bar graphs 10, 20, 30 are for coatings on non-phosphatized steel, while the bar graphs 10&#39;, 20&#39;, and 30&#39; are for coatings on phosphatized steel. As can be readily seen, not only do the water-base, phenolic-resin, drum-lining coatings of the invention provide very low levels of VOC, but, also, at least the preferred P20 compound of Table 6 provides superior hardness as compared to the conventional, solvent-based phenolic coatings for drum linings. 
     While a specific embodiment of the invention has been shown and described, it is to be understood that numerous changes and modifications may be made therein without departing from the scope, spirit and intent of the invention as set forth in the appended claims.