Abstract:
A coating 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. Specifically provided is a lining for the interior of steel drums and pails, which lining has very low levels of volatile organic compounds, while still having superior hardness and flexibility. The coating and drum-lining made from the coating is essentially a water-base, thereby effectively eliminating the problem of VOC-emission. The 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-based polyester-resin coating is a water-base phenolic coating.

Description:
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.3823Materials (PEI-A)           (TOFA)                P.E.300                      P.E.74/18                            3712NPF__________________________________________________________________________Timellitic     200-300           200-300                168    86   355Anhydride (TMA)Isophthalic     --    --   655   323   --Acid (IPA)Adipic Acid     --    --   192    94    90Neopentyl 300-500           300-400                685   169   450ClycolPelargonic Acid     200-300           --   --    --    198Tall Oil  --    356  --    --    --Fatty AcidGlycidyl Ester     --    --   --    399   --of VersaticAcid 1__________________________________________________________________________ 
    
     The preferred formulation for each is as follows: 
     
         __________________________________________________________________________Resin Formulations     Parts by Weight     P.E.3823           P.E.3823Materials (PEI-A)           (TOFA)                P.E.300                      P.E.74/18                            3712NPF__________________________________________________________________________Timellitic     291   240  168    86   355Anhydride(TMA)Isophthalic     --    --   655   323   --Acid (IPA)Adipic Acid     --    --   192    94    90Neopentyl 419   346  685   169   450ClycolPelargonic     239   --   --    --    198AcidTall Oil  --    356  --    --    --Fatty AcidGlycidyl  --    --   --    399   --Ester ofVersaticAcid 1     1116  1080 1700  1071  1093Less water     116    80  200    71    93of reactionYield     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       8.002.  Isophthalic acid, IPA-99                 52.1        2.003.  Trimellitic anhydride, TMA                 53.4        1.774.  Tall oil fatty acid,                 134.2       3.00    Acintol FA-15.  Trimellitic anhydride, TMA                 37.1        1.23                 407.4    Less water of esterification                 -32.4    Yield at 36 A.N.  375.06.  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             35-37Viscosity, Gardner-Holdt             Z4Color, Gardner    5-7NVM, %            75Volatile          75Density, 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__________________________________________________________________________      Parts by Weight      P.E.3823            P.E.3823Materials  (PELA)            (TOFA)                  P.E.300                        P.E.74/18                              3712NPF__________________________________________________________________________Coating Formulation2 Dimethyl 40-80 40-80 40-80 40-80 40-80amino ethanolCrosslinker-      200-400            200-400                  200-400                        200-400                              200-400Hexamethoxy-methylmelamineDistilled  2000-3000            2000-3000                  2000-3000                        2000--3000                              2000-3000Water__________________________________________________________________________ 
    
     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__________________________________________________________________________      Parts by Weight      P.E.3823            P.E.3823Materials  (PELA)            (TOFA)                  P.E.300                        P.E.74/18                              3712NPF__________________________________________________________________________Solution PropertiesResin/Cross-      50/80 50/80 50/80 50/80 50/80linkerRatio      10/30 10/30 10/30 10/30 10/30Water/Solvent       50/100             50/100                   50/100                         50/100                               50/100Ratio      10/20 10/20 10/20 10/20 10/20NVM-%      25-45 25-45 25-45 25-45 25-45Initial Ph 7.5 +/-            7.5 +/-                  7.5 +/-                        7.5 +/-                              7.5 +/-      1     1     1     1     1Viscosity 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__________________________________________________________________________      Parts by Weight      P.E.3823            P.E.3823Materials  (PELA)            (TOFA)                  P.E.300                        P.E.74/18                              3712NPF__________________________________________________________________________Coating Formulation2 Dimethyl 60    60    60    60    60amino ethanolCrosslinker-      280   280   280   280   280HexamethoxyMethyl MelamineDistilled  2450  2450  2450  2450  2450Water      3790  3790  3790  3790  3790__________________________________________________________________________ 
    
     The properties exhibited by the coating formulation on Table 4, is as shown in Table 5, hereinbeolow. 
     
                                           TABLE 5__________________________________________________________________________      Parts by Weight      P.E.3823            P.E.3823Materials  (PELA)            (TOFA)                  P.E.300                        P.E.74/18                              3712NPF__________________________________________________________________________Solution PropertiesResin/Cross-      80/20 80/20 80/20 80/20 80/20linker RatioWater/Solvent      86/14 86/14 86/14 86/14 86/14RatioNVM-%      30-33 30-33 30-33 30-33 30-33Initial Ph 7.5 +/-            7.5 +/-                  7.5 +/-                        7.5 +/-                              7.5 +/-      1     1     1     1     1Viscosity Zahn      100 +/-            100 +/-                  100 +/-                        100 +/-                              100 +/-Cup #2 seconds      10    10    10    10    10__________________________________________________________________________ 
    
     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__________________________________________________________________________EVALUATION RESULTSApplication:    Dip CoatSubstrate:    Cold Rolled SteelFilm Thickness:    .5 mil, averageCure Schedule:    PolyEnviro systems, 30 minutes at 350° F.    Solvent system, 15 minutes at 395° F.Chemical testing:    Spot testing at room temperature covered by watchglassRatings: Visual evaluation No change = 0, very slight = 1, slight = 2,    moderate = 3,    considerable = 4, severe = 5       P.E.3823              P.E.3823Materials   (PELA) (TOFA)  P.E.300  P.E.74/18                                        3712NPFhours exposure       24         48 72              24                48 72 24 48 72 24 48 72 24 48 72 24 48 72__________________________________________________________________________10% Sodium Chloride       0 0  0 0 0  0  0  0  1  0  0  1  0  0  0  0  0  010% Hydrochloric Acid       0 0  0 0 0  2  2  3-4                            5  0  0  2-3                                        3  5  5  0  0  1-210% Sulfuric Acid       0 0  0 0 0  0  0  2  4-5                               0  0  0  0  0  4  0  0  0-110% Acetic Acid       0 0  0 0 0  0  0  1  1-2                               2-3                                  3-4                                     5  1-2                                           3  5  3  5  510% Phosphoric Acid       0 0  0 0 0  0  0  1-2                            2-3                               0  0  1  0  0  1  0  1-2                                                       410% Sodium Hydroxide       0 0  0 0 0  0  0  0  1  2-3                                  5  5  0  0  1  5  5  510% Ethanol 0 0  0 0 0  0  0  0  0  0  0  1  0  0  0  0  0  1Distilled Water       0 0  0 0 0  0  0  0  0  0  0  0  0  0  0  0  0  0Calcium 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__________________________________________________________________________ 
    
     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______________________________________APPEARANCE:      Yellowish-white viscous liquidSPECIFIC GRAVITY:            1.15 + 0.05DENSITY:         8.98 lbs/galVISCOSITY:       50-60 sec. (Zohn cup #2)pH:              8.5 ± 0.5______________________________________ 
    
     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/galB.  TOTAL VOLATILES:    65 wgt per centC.  WATER CONTENT:      58.5 wgt per centD.  ORGANIC VOLATILE:   6.5 wgt per centE.  NONVOLATILE CONTENT:                   35 wgt per centG.  VOC CONTENT:        1.17 lbs/gal (less water).______________________________________ 
    
     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 --         20.0-40.02-Dimethyl Amino         0.5-1.5   1.0-3.0    1.0-4.0EthanolCrosslinker   3.0-8.0    5.0-12.0HexamethoxyMethyl MelaminePolsolv EB    1.0-3.0   2.0-6.0    1.0-6.0Distilled water         55.5-70.5 44.0-72.0  45.0-77.0Crosslinker DER 331         --        --         1.0-5.0______________________________________Draw down on phosphatized steel carbon plate. Bake @ 450° F.for 10 minutes.PROPERTIES OFBAKED FILMFilm Hardness hard      very hard  softMEK Rubs      50        100+       10Adhesion      good      excellent  marginalAppearance    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         --        28P.E. 3823 PELA         31.4      --         30.22-Dimethyl Amino         1.2       2.8        1.2EthanolCrosslinker Cymel         6.0       9.4Polsolv EB    2.4       3.7Distilled water         59.0      56.1       60.5Crosslinker 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           6.0-15.0Deionized H.sub.2            20.0-30.0Butyl Cellosolve 2.0-4.0P.E. 2392        30.0-50.0P.E. 3823 TOFA   2.0-4.0Deionized H.sub.2 O            20.0-40.0PropertiesPH = 8.0 +/- 1.0Viscosity = 85 +/- 10 Seconds Zohn&#39;s Cup #2______________________________________ 
    
     The preferred formulation for this fourth product is as follows: 
     
         ______________________________________          P.E. 20______________________________________PKHW-35          12Deionized H.sub.2 O            25Butyl Cellosolve  3P.E. 2392        46P.E. 3823 TOFA    3Deionized H.sub.2 O            11            100PropertiesPH = 8.0 +/- 1.0Viscosity = 85 +/- 10 Seconds Zohn&#39;s Cup #2______________________________________ 
    
     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.