High functionality polyesters and coatings comprising the same

Abstract

A polyester prepared by free radical polymerization of an unsaturated polyester prepolymer, wherein the polymerization occurs primarily by reaction of the unsaturation of said prepolymer is disclosed. Coatings comprising the same are also disclosed, as are substrates coated at least in part with such coating.

Claims

1. A process for preparing an ungelled crosslinkable polyester resin comprising: (a) reacting a polycarboxylic acid with a polyol to form an unsaturated polyester prepolymer in which the unsaturation is along the backbone of the unsaturated polyester prepolymer and wherein the unsaturated polyester prepolymer has terminal acid and/or hydroxyl functional groups, a hydroxyl value ranging from 2 to 500 mg KOH/gm and/or an acid value ranging from 1 to 400 mg KOH/gm; and (b) subjecting the unsaturated polyester prepolymer to thermally induced free radical polymerization via the points of unsaturation along the unsaturated polyester prepolymer backbone to form the ungelled crosslinkable polyester resin that has a higher weight average molecular weight than the unsaturated polyester prepolymer such that the weight average molecular weight ratio of the ungelled crosslinkable polyester resin to the unsaturated polyester prepolymer is at least 1.2 and the hydroxyl value and the acid value of the ungelled crosslinkable polyester resin is in the same range as those of the prepolymer.

2. The process of claim 1 in which the unsaturated polyester prepolymer comprises one or more unsaturated polyester prepolymers.

3. The process of claim 2 in which the unsaturated polyester prepolymer comprises a mixture of different unsaturated polyester prepolymers.

4. The process of claim 1 in which the polycarboxylic acid is unsaturated.

5. The process of claim 4 in which the polycarboxylic acid comprises maleic, fumaric and/or itaconic acid and/or the esters and/or the anhydrides thereof.

6. The process of claim 1 wherein the number average functionality of unsaturation is from 0.1 to 5.0.

7. The process of claim 1 wherein the thermally induced free radical polymerization conditions are by heating the unsaturated polyester prepolymer in a diluent comprising an organic solvent and/or water to a temperature of 50 to 150 C. in the presence of a free radical initiator.

8. The process of claim 1 in which the unsaturated polyester prepolymer component has a number average molecular weight of 150 to 5000.

9. The process of claim 1 in which the ungelled crosslinkable polyester resin has a weight average molecular weight of at least 15,000 and a functionality of at least 100 mg KOH/gm.

10. The process of claim 1 in which the ungelled crosslinkable polyester resin has a weight average molecular weight of 1000-7,000,000.

Description

EXAMPLES

(1) The following examples are intended to illustrate the invention and should not be construed as limiting the invention in any way.

Example 1 Preparation of Unsaturated Polyester Prepolymers

(2) Four different unsaturated polycondensation prepolymers according to the present invention were prepared. The reaction compositions used in preparing the unsaturated polyester prepolymers are as shown in Table 1 below. Dibutyl tin oxide was used to promote esterification and, in some prepolymers, a small amount of a free radical inhibitor, methylhydroquinone (MEHQ), was added to extend the usable shelf life of the unsaturated polyester prepolymers thus formed.

(3) TABLE-US-00001 TABLE 1 Prepolymer Prepolymer A Prepolymer B Prepolymer C Prepolymer D Wt Wt Wt Wt Prepolymer E Prepolymer F Monomers Ratios Ratios Ratios Ratios Wt Ratios Wt Ratios MEG 5.77 6.87 4.53 1,2 PD 0.99 1.02 1.16 1,3 BD 25.78 26.60 36.62 29.70 35.37 24.67 TMP 12.21 12.55 4.6 3.48 TPA 25.66 26.54 27.42 IPA 25.66 26.54 7.69 17.98 13.77 18.50 CHDA 43.53 33.28 44.80 MAN 6.74 22.52 3.02 10.71 4.02 AA 9.7 DBTO 0.024 0.025 0.025 0.2 0.1 MEHQ 0.02 0.009 0.032 0.012 SnCl.sub.2 0.15 Let down butyl butyl butyl xylene xylene Butyl glycol/ solvent glycol glycol glycol propylene glycol mono methyl ether 1/1 Final resin 74% 74% 74% 70% 70% 71% solids

(4) In Table 1 above, MEG is monxethylene glycol; 1,2 PD is 1,2-propan diol; 1,3 BD is 1,3 butane diol; TMP is trimethylolpropane; TPA is terephthalic acid; IPA is isophthalic acid; CHDA is 1,4-cyclohexane dicarboxylic acid; MAN is maleic anhydride. AA is adipic acid; DBTO is dibutyl tin oxide; MEHQ is methyl hydroquinone; and SnCl.sub.2 is stannous chloride.

(5) The above prepolymers were prepared as described below:

(6) Prepolymer A A. Charge to reactor 1,3 BD, 1,2 PG, TMP, TPA, IPA & DBTO catalyst B. Heat to a maximum temperature of 240 C. under nitrogen sparge and process to an acid value of less than 10 for resin clarity. Maintain max head temperature of packed column at 102 C. to minimize glycol losses. C. Cool to 140 C. and sample for hydroxyl value. Adjust hydroxyl value to 178 net with 1,3 BD. Process in glycol adjustment at 180 C. for 2 hours. D. Cool to 140 C. and charge AA Reheat to distillation with max reactor temperature of 170 C. for final acid value of 40-42. E. Cool to 110 C. and charge thinning solvent butyl glycol.

(7) Prepolymer B A. Charge to reactor 1,3 BD, 1,2 PG, TMP, TPA, IPA & DBTO catalyst. B. Heat to a maximum temperature of 240 C. under nitrogen sparge and process to an acid value of less than 10 for resin clarity. Maintain max head temperature of packed column at 102 C. to minimize glycol losses. C. Cool to 140 C. and sample for hydroxyl value. Adjust hydroxyl value to 176 net with 1,3 BD. Process in glycol adjustment at 180 C. for 2 hours. D. Cool to 140 C. and charge MAN. Reheat to distillation with max reactor temperature of 160 C. for final acid value of 40-42. E. Cool to 110 C. and charge thinning solvent, butyl glycol, containing MEHQ inhibitor.

(8) Prepolymer C A. Charge to reactor 1,3 BD, 1,2 PG, TMP, TPA, IPA & DBTO catalyst. B. Heat to a maximum temperature of 240 C. under nitrogen sparge and process to an acid value of less than 10 for resin clarity. Maintain max head temperature of packed column at 102 C. to minimize glycol losses. C. Cool to 140 C. and charge MAN. Reheat to distillation with max reactor temperature of 200 C. for an acid value of 60-70. D. Cool to 120 C. and sample for hydroxyl value. Adjust hydroxyl value to 40 net with 1,3 BD. Process in glycol adjustment at 120 C. for 2 hours. E. Reheat to distillation with max reactor temperature of 200 C. for final acid value of 40-42. F. Cool to 110 C. and charge thinning solvent butyl glycol.

(9) Prepolymer D & E A. Charge to reactor 1,3 BD, MEG, CHDA, IPA, MAN, MEHQ & DBTO in order. B. Heat to a maximum temperature of 200 C. under nitrogen sparge and process to clarity (acid value approx 40-50). C. Cool reactor to 180 C. and sample for hydroxyl value. Adjust hydroxyl value with 1,3 BD as required (Polymer D target OHV 40-42, Polymer E target OHV 150-153). D. Reheat to 195-200 C. and establish azeotropic distillation with the careful addition of xylene. E. Process to final acid value target of 1-3. F. Cool to 135 C. and thin with xylene solvent.

(10) Prepolymer F A. Charge to reactor 1,3 BD, MEG, TMP, IPA, CHDA (43% of charge) & SnCl.sub.2 catalyst. B. Heat to a maximum temperature of 230 C. under nitrogen sparge and process to an acid value of less than 10 for resin clarity. Maintain max head temperature of packed column at 102 C. to minimize glycol losses. C. Cool to 140 C. and charge MeHQ, CHDA (57% of charge), MAN. Reheat to distillation with max reactor temperature of 200 C. process to acid value of 70-80. D. Cool to 120 C. and sample for hydroxyl value. Adjust hydroxyl value to 34.7 net with 1,3 BD. Process in glycol adjustment at 140 C. for 2 hours. E. Reheat to distillation, 195-200 C. establish azeotropic distillation with the careful addition of xylene. Process to final acid value of 45-50. F. Cool to 110 C. and charge thinning solvent butyl glycol and propylene glycol mono methyl ether.

(11) TABLE-US-00002 TABLE 2 (Calculated parameters) Gross Tg Resin Code Type OHV AV Mn Maleic/Chain ( C.) Prepolymer A Branched 118 42 1095 57.4 Prepolymer B Branched 118 42 1109 0.86 70 Prepolymer C Branched 82 42 1092 2.81 63.8 Prepolymer D Linear 33 2 2500 0.9 66 Prepolymer E Linear 150 2 726 0.9 60.5 Prepolymer F Branched 15.3 50 2304 1.08 65

(12) In Table 2 above, OHV is gross hydroxyl value (mg potassium hydroxide/g of prepolymer); AV is acid value (mg potassium hydroxide/g of prepolymer); Mn is number average molecular weight; maleic/chain is the average number of double bonds per unsaturated polyester prepolymer chain; and Tg is the glass transition temperature.

(13) Acid value was determined as follows. The sample was dissolved in a suitable solvent(s). Standard solvents were DMF or a 3/1 mixture of xylene/methyl proxitol. Indicators used were thymol phthalein for DMF solvent & Phenol phthalein for xylene/methyl proxitol. The resin solution was titrated against 0.1N alcoholic KOH for end point.

(14) Hydroxyl value was determined as follows. Resin samples were dissolved in a hydroxyl free solvent and an accurately known, but stoichmetric excess of acetic anhydride dissolved in butyl acetate was added. The solutions were then heated to allow the acetic anhydride to react with any hydroxyl groups in the resin. The remaining excess of acetic anhydride was then hydrolyzed using pyridine & water. Blank titrations were carried out with no resin sample. The blanks and resin solution samples were titrated against methanolic KOH to determine the net hydroxyl value.

Example 2 Preparation of Polyesters by Free Radical Polymerization of the Unsaturated Polyester Prepolymers

(15) Using the unsaturated polyester prepolymers of Example 1, polyesters were prepared by free radical polymerization of the chains of the unsaturated polyester prepolymers via their double bonds. Unless specified otherwise, the free radical polymerization step in the following examples was performed under stirring at 100 C., with a nitrogen purge, using tert-butyl-peroxy-2-ethylhexanoate as the free radical initiator which has a calculated half-life of 22.9 minutes at 100 C. Reaction mixture was held at temperature for 5 hours after initiator addition. Tests were conducted on the resulting polyesters and the tests and the results obtained are discussed below.

(16) (a) Slightly Branched Polyester with a Calculated Maleic Functionality/Prepolymer Chain of <1

(17) The free radical polymerization was conducted using two different approaches, the first involving the addition of a single shot of the free radical initiator and the second involving the addition of multiple shots of the initiator at intervals during the progress of the polymerization.

(18) (i) Initiator Added as a Single Shot

(19) A series of polyester resins was prepared by adding a 50% solution of initiator in butyl glycol to a 50% solution of the branched polyester Prepolymer B in butyl glycol at 0.1, 0.2, 0.3 and 0.9:1 molar ratios of initiator radical:maleic double bond (R*CC). The polyester resins produced as a result were coded Polyester 1, Polyester 2, Polyester 3 and Polyester 4 (which gelled) respectively.

(20) During each resin preparation, samples were taken for gel permeation chromatography (GPC) analysis, both at 1 hour after the initiator addition and at the end of the process.

(21) (ii) Multiple Shots of Initiator

(22) Polyester 5 was prepared by adding a 50% solution of initiator in butyl glycol to a 50% solution of the branched Prepolymer B (see Tables 1 and 2 above) in butyl glycol at a total ratio of initiator:maleic double bond of 0.5:1 R*:CC but, instead of adding all the initiator in one go, the initiator was divided into five equal amounts of 0.1:1 R*:CC, with a one hour interval between each initiator addition. Resin samples were taken 1 hour after each initiator addition for GPC analysis. These samples were labeled Polyester 5a, 5b, 5c, 5d and 5e respectively.

(23) (iii) Control Polymers

(24) Two control polymers were also prepared for GPC comparison:

(25) Polyester 6: A 50% solution of Prepolymer B in butyl glycol was heated to 100 C. and held for three hours without initiator.

(26) Polyester 7: A 50% solution in butyl glycol of Prepolymer A, a saturated polyester resin having a similar calculated number average molecular weight Mn, OHV and AV as Prepolymer B, was heated to 100 C. and a 50% butyl glycol solution of the equivalent amount of initiator (0.3:1) as in the preparation of Polyester 5c in Example 2(a)(ii) above was added in 3 separate shots at hourly intervals.

(27) (b) Higher Maleic Functionality/Chain

(28) To investigate the influence of higher maleic functionality per chain, Polyester 8 was prepared using the slightly branched polyester Prepolymer C at a 0.1:1 R*:CC ratio under the same conditions used in Example 2(a), but with a process solids value of 60%. The polymer began to gel within 10 minutes after the initiator was added.

(29) A second polymer Polyester 9 was prepared under the same conditions, but by adding a single shot of initiator at a significantly reduced R*:CC ratio of 0.003:1 to the Prepolymer C; a sample was taken for GPC at 2 hours after the addition of initiator. Two further additions of initiator at intervals of 2 hours at a 0.006:1 R*:CC ratio were made and samples taken 2 hours after each addition. The samples collected were labeled Polyester 9a, 9b and 9c respectively.

(30) (c) Linear Polyesters with Different Starting Molecular Weights

(31) To investigate the effect of the starting polyester chain length, the following resins were prepared, at 0.1:1 R*:CC ratio using the same conditions as in Example 2(a) (i) and as solvent a mixture of xylene and butyl glycol, for GPC analysis:

(32) Polyester 10using Prepolymer D, calculated Mn 2500

(33) Polyester 11using Prepolymer E, calculated Mn 726

(34) (d) Different Process Temperature and Different Types of Initiator

(35) To verify that the free radical polymerization can be carried out at different process temperatures and with different types of initiators, the following resins were also prepared using Prepolymer D (see Tables 1 and 2 above) at 0.1:1 R*:CC ratio and then analyzed by GPC:

(36) Polyester 12: polymerization reaction at 100 C., initiator tert-butyl-peroxy-2-ethylhexanoate, calculated initiator half-life 22.9 minutes, total amount of initiator added in three equal portions at 2 hour intervals, sample taken 2 hours after final addition.

(37) Polyester 13: polymerization reaction at 120 C., initiator tert-butyl-peroxy-2-ethylhexanoate, calculated initiator half-life 2.95 minutes, total amount of initiator added in three equal portions at 2 hour intervals, sample taken 2 hours after final addition.

(38) Polyester 14: polymerization reaction at 80 C., initiator tert-butyl-peroxy-2-ethylhexanoate, calculated initiator half-life 223.6 minutes. Due to the much longer initiator half-life initiator added in one portion, after initiator addition the resin was held at 80 C. for 8 hours and sampled.

(39) Polyester 15: polymerization reaction at 135 C., using tert-butyl peroxybenzoate as the initiator, calculated initiator half-life 13.0 minutes, total amount of initiator added in three equal portions at 2 hour intervals, sample taken 2 hours after final addition.

(40) Polyester 16: polymerization reaction at 100 C., using dibenzoyl peroxide as the initiator, calculated initiator half-life 22.3 minutes, total amount of initiator added in three equal portions at 2 hour intervals, sample taken 2 hours after final addition.

(41) (e) Polyester Prepared in an Aqueous Mixture

(42) To verify that the free radical polymerization can be carried out in aqueous mixtures, the following resin was prepared using Prepolymer F (see Tables 1&2 above). Prepolymer F solution (43.2 gm) was mixed with dimethylaminoethanol (2.4 gm), then water (54.4 gm) was added and the resulting mixture used in the polymerization. Polymerization was carried out at 0.1:1 R*:CC ratio with initiator tort-butyl-peroxy-2-ethylhexanoate, polymerization reaction at 90 C., calculated initiator half-life 69.4 minutes, total amount of initiator added in 1 hour feed, held at 90 C. for 2 hours after end of addition. Samples were taken at 15 minute intervals during the feed and then at 1 hour and 2 hours after the feed. Details of these samples, 17a, 17b, 17c, 17d, 17e and 17 f are given in Table 3 below and all show evidence of increase in molecular weight from the starting prepolymer.

(43) The weight average molecular weights Mw were determined by GPC (referenced to polystyrene) for the polymers prepared in Examples 2(a) to 2(d) above. The Mw increase factor compared to the respective starting prepolymers was calculated. These results are tabulated in Table 3 below.

(44) TABLE-US-00003 TABLE 3 Total Comments on n Mw Resins R*: CC samples Mw increase Prepolymer B Starting PE 2684 Polyester 1 0.1 Single addition 3761 1.4 Polyester 2 0.2 Single addition 5616 2.09 Polyester 3 0.3 Single addition 11,180 4.17 Polyester 5a 0.1 1.sup.st shot 3,359 1.25 Polyester 5b 0.2 2.sup.nd shot 5,019 1.87 Polyester 5c 0.3 3.sup.rd shot 9,680 3.61 Polyester 5d 0.4 4.sup.th shot 35,140 13.09 Polyester 5e 0.5 5.sup.th shot 239,600 89.27 Prepolymer C Starting PE 8,545 Polyester 9a 0.003 1.sup.st shot 19,690 2.3 Polyester 9b 0.009 2.sup.nd shot 72,490 8.48 Polyester 9c 0.015 3.sup.rd shot 3,403,000 398.24 Prepolymer D Starting PE 3,322 Polyester 10 0.1 Single addition 11,220 3.38 Prepolymer E Starting PE 928 Polyester 11 0.1 Single addition 3,590 3.87 Prepolymer B Starting PE 2,684 Polyester 6 0 No initiator 2,691 No change Prepolymer A Starting PE 3,118 Polyester 7 0.3 No maleic 3,118 No change Prepolymer D.sub.(note 1) Starting PE 2,380 Polyester 13 0.1 120 C. 4,999 2.10 Polyester 12 0.1 100 C. 4,762 2.00 Polyester 14 0.1 80 C. 3,588 1.51 Polyester 15 0.1 135 C. 8,572 3.60 Polyester 16 0.1 100 C. 6,001 2.52 Prepolymer F Starting PE 12900 Polyester 17a 0.025 15 mins feed 13870 1.08 Polyester 17b 0.05 30 mins feed 22050 1.71 Polyester 17c 0.075 45 mins feed 38280 2.97 Polyester 17d 0.1 At end feed 76750 5.95 Polyester 17e 0.1 1 hour hold 218500 16.94 Polyester 17f 0.1 2 hour hold 195200 15.13 Note .sub.1Prepolymer D is second batch of Prepolymer D

(45) As confirmation that the free radical polymerization process did not affect the other functional groups, hydroxy and carboxy, the hydroxyl and acid values of Polyester 12 (0.1:1 R*:CC) were compared against the starting unsaturated polyester Prepolymer D. The results, given in mg KOH/g of resin, are as follows:

(46) TABLE-US-00004 Net OHV AV Gross OHV Prepolymer D 40.2 2.1 42.3 Polyester 12 40.0 2.5 42.5
The results show that there was no reduction in hydroxyl value after free radical polymerization, but there was a slight increase in acid value. However, gas chromatography of polyester polymerized with higher levels of tert-butyl peroxy-2-ethylhexanoate had shown the presence oft-butanol and 2-ethyl hexanoic acid in the final polymer. The slight increase in acid value of Polyester 12 is more likely to be due to the formation of 2-ethyl hexanoic acid from the tert-butyl peroxy-2-ethylhexanoate during the process rather than a change in carboxyl groups on the prepolymer.

(47) The GPC results set out in Table 3 above confirm that the addition of free radical initiators to unsaturated polyester prepolymers according to the present invention results in the preparation of polyesters having a significant increase in weight average molecular weight Mw compared to the starting prepolymer. In conjunction with the fact demonstrated above, that other functional groups on the prepolymer remain relatively unaffected, free radical polymerization of unsaturated polyester prepolymers as described in this invention will enable polyesters with a combination of average functionality and molecular weight to be achieved that has not been previously attainable by other conventional methods. The starting prepolymer can be linear, branched, have different starting molecular weight (chain length) and have different numbers of double bonds per chain, to give different resulting polyesters according to the present invention and m all cases an increased molecular weight is observed. Also the weight average molecular weight Mw increase can be achieved using different types of fire radical initiators and at different temperatures.

(48) There were no changes in the weight average molecular weight Mw of the two control resins, Polyester 6 (without initiator) and Polyester 7 (without double bonds in the starting polyester prepolymer), which indicates that the polymerization is specific to the unsaturated groups in the starting polyester prepolymer in the presence of a free radical initiator and not a face of the process conditions.

(49) The weight average molecular weight Mw increased with increasing levels of initiator, irrespective of whether the initiator was added in a single addition or added in multiple shots. However, excessively high initiator levels can lead to resin gellation, as demonstrated in Polyester 4 (0.9:1 R*:CC ratio). Also, the higher average number of 2.81 double bonds per chain Prepolymer C needed significantly less initiator to reach a weight average molecular weight Mw almost to the point of gellation (see Polyester 9). This suggests that the weight average molecular weight Mw increase can also be influenced by the average number of double bonds per prepolymer chain.

Example 3 Testing of Resins for Packaging Coatings

(50) Some of the free radical polymerized polyesters prepared in Examples 2(a) to 2(d) above, together with the respective starting polyester prepolymers, were reacted with BAKELITE 6520LB, an alkylated phenol/formaldehyde resin (functionality 3) and BAKELITE 7081LB, an unalkylated o-cresol/formaldehyde resin (difunctional), at different levels of the phenolic resins and with different levels of phosphoric acid catalyst to give a range of coating formulations according to the present invention. The amounts of resin and phosphoric acid catalyst used and the solvent employed are given in the results reported below.

(51) The coating formulations thus prepared were applied by a wire bar coater onto 0.22 mm tinplate panels and cured in a laboratory box oven. The chosen cure time and temperature ranges were from 4 to 12 minutes and 160 to 200 C. respectively, with a center point of 8 minutes and 180 C.

(52) The cured panels of the different samples were subjected to the following tests commonly used to assess packaging coatings:

(53) Methylethyl ketone (MEK) rubsfor cure and chemical resistance comparison.

(54) Wedge Bendsto check bending flexibility, film integrity & film network.

(55) Box Drawto compare mechanical deformation.

(56) Sterilization(90 min at 121 C. in water & steam).

(57) MEK rubs: a panel of the cured film is rubbed back and forth in a linear direction (counted as 1 double rub) using a piece of cotton wool soaked in MEK until the coating has been removed or readied 200 double rubs. The number of double rubs is recorded.

(58) Wedge Bend: a 10 cm long4 cm wide strip of coated panel is formed into a U-shape on a 6 mm metal bar, the U-shaped piece is then placed into a tapered recess and a 2 kg metal weight is dropped onto the test piece from a height of 60 cm to form a wedge shape. After immersion in an acidified copper sulphate solution for 2 minutes, the test piece is rinsed in tap water and visually assessed for any cracking. The length of film along the bend without cracking is recorded as a percentage of the total length of the test piece.

(59) Box draw: a coated panel is placed in a stamping press to produce a small square box (21 mm in depth). The corners of the box is visually assess for any coating breakdown. The result is recorded as an average of the depth of draw without breakdown.

(60) Sterilization: a coated panel is placed in a lidded container part filled with tap water with half of the panel immersed and half of the panel above the water line. The container is then placed inside an autoclave and heated to the described temperature and duration. The coating is assessed for any film defects and graded from 0-10 (0=no defects, 10=severe coating breakdown).

(61) To assess the potential use of the free radical polymerized resin formulations in water-based coatings, Polyester 2, Polyester 3 and the starting Prepolymer B were neutralized with different amounts of dimethylethanolamine and diluted with deionized water.

(62) Packaging Coatings Test Results

(63) Tests were performed on the following three resins: Prepolymer B (starting polyester prepolymer), Polyester 2 (0.2:1 R*:CC) and Polyester 5 (0.5:1 R*:CC) (see Tables 1 to 3 above) to measure the performance of polyesters of the present invention obtained by the free radical polymerization of the starting polyester prepolymer as measured against said starting polyester prepolymer. The tests conducted involved crosslinking of the polyesters with two alternative phenolic resins, coating of the resulting formulations on a test substrate, curing of the coating formulations and then comparing performance of the coatings using standard industry techniques.

(64) (a) Response to Catalysis

(65) Catalyst used: Phosphoric acidin millimoles per 100 g resin solids (mmol phr)

(66) Cure conditions: 8 minutes at 180 C.

(67) Substrate: 0.22 mm 2.8/2.8 tin-plated steel

(68) Film weight: 5-6 grams/m.sup.2 (gsm)

(69) Phenolic resins: BAKELITE 6520LB (functionality 3)

(70) BAKELITE 7081LB (functionality=2)
Phenolic level: 6520LB 25.5% of total binder solids 78081LB 19.3% of total binder solids
Tests: MEK double rubsnumber of rubs before film removal. Wedge Bend% of the coating without any fracture.
The results are as shown in Table 4 & 5.

(71) TABLE-US-00005 TABLE 4 Catalyst MEK With BAKELITE 6520LB mmol phr double rubs Wedge Bend Prepolymer Sample B-1 0 10 44% B Sample B-2 1 6 26% Sample B-3 5 20 76% Sample B-4 10 20 72% Polyester 2 Sample 2-1 0 14 72% Sample 2-2 1 23 75% Sample 2-3 5 118 83% Sample 2-4 10 200 73% Polyester 5 Sample 5-1 0 45 74% Sample 5-2 1 75 85% Sample 5-3 5 200 84% Sample 5-4 10 200 89%

(72) TABLE-US-00006 TABLE 5 Catalyst MEK With BAKELITE 7081LB mmol phr double rubs Wedge Bend Prepolymer Sample B-5 0 1 0% B Sample B-6 1 1 0% Sample B-7 5 5 66% Sample B-8 10 5 0% Polyester 2 Sample 2-5 0 1 0% Sample 2-6 1 2 0% Sample 2-7 5 18 78% Sample 2-8 10 10 9% Polyester 5 Sample 5-5 0 5 0% Sample 5-6 1 40 69% Sample 5-7 5 40 88% Sample 5-8 10 60 86%
Further tests were also conducted using differing amount of phenolic resin.
Catalyst used: 5 mmol phr Phosphoric acid
Cure, condition: 8 minutes at 180 C.
Substrate: 0.22 mm 2.8/2.8 tin plated steel
Film weight: 5-6 gsm
Phenolic resins: BAKELITE 6520LB (functionality 3) BAKELITE 7081LB (functionality=2)
Tests: MEK double rubsnumber of rubs before film removal. Wedge Bend% of the coating without any fracture. Box Drawmm passed (maximum draw 21 mm)
The results are shown in Table 6 and 7.

(73) TABLE-US-00007 TABLE 6 6520LB MEK % on double Wedge Box Draw With 5 mmol catalyst phr solids rubs Bend (mm) Prepolymer Sample B-9 0 1 0% 5.8 B Sample B-10 14.6 14 81% 7.3 Sample B-11 25.5 20 76% 4.5 Sample B-12 40.6 200 75% 2.8 Sample B-13 50.6 200 64% 2 Polyester 2 Sample 2-9 0 1 0% 5.9 Sample 2-10 14.6 56 77% 7.6 Sample 2-11 25.5 118 83% 4.9 Sample 2-12 40.6 200 72% 2.5 Sample 2-13 50.6 200 62% 1.4 Polyester 5 Sample 5-9 0 3 0% 11.0 Sample 5-10 14.6 200 90% 8.0 Sample 5-11 25.5 200 94% 5.0 Sample 5-12 40.6 200 77% 3.0 Sample 5-13 50.6 200 68% 3.0

(74) TABLE-US-00008 TABLE 7 7081LB MEK % on double Wedge Box Draw With 5 mmol catalyst phr solids rubs Bend (mm) Prepolymer Sample B-14 0 1 0% 5.8 B Sample B-15 10.7 1 0% 8 Sample B-16 19.3 5 66% 6.3 Sample B-17 32.4 20 73% 8.5 Sample B-18 41.8 15 58% 8.3 Polyester 2 Sample 2-14 0 1 0% 5.9 Sample 2-15 10.7 2 1% 6.1 Sample 2-16 19.3 18 78% 5.8 Sample 2-17 32.4 24 76% 7.5 Sample 2-18 41.8 36 63% 8.1 Polyester 5 Sample 5-14 0 3 0% 11.0 Sample 5-15 10.7 50 81% 10.0 Sample 5-16 19.3 40 88% 9.0 Sample 5-17 32.4 63 79% 9.0 Sample 5-18 41.8 95 68% 8.0

(75) It is clear from the MEK rub and Wedge Bend test results as shown in Tables 4 and 5 that cure and bending flexibility, which is indicative of the extent of the film network, significantly improves as the molecular weight and the functionality/chain of the resin increases.

(76) For the coatings obtained from the highest molecular weight Polyester 5 with the poly-functional phenolic, due to the increase in functionality/chain in the enhanced molecular weight polyesters of the present invention, a lower level of phenolic crosslinker is needed to achieve the improvement in film network (see Table 6).

(77) The Box Draw flexibility of the coating obtained with the difunctional phenolic crosslinker and the same polyester is also noticeably better than that obtained with the difunctional phenolic and the lower molecular weight polyester Prepolymer 2 (see Table 7).

(78) (b) Sterilization Resistance (90 Minutes/121 C. in Tap Water)

(79) Catalyst used: 5 mmol phr Phosphoric acid

(80) Cure condition: 4-12 minutes at 160-200 C.

(81) Substrate: 0.22 mm 2.8/2.8 tin plated steel

(82) Phenolic resins: BAKELITE 6520LB (functionality 3)

(83) BAKELITE 7081LB (functionality=2)

(84) The samples that gave the highest Wedge Bend results from each polyester resin above were coated and cured for different times and at different temperatures. The coated panels were placed in a Kilner jar, with the lower half of the panel immersed in tap water and the upper half of the panel above the water-line, and sterilized in an autoclave.

(85) Tests: 90 minutes at 121 C. in tap water

(86) Visual inspection of panel exposed to vapor and immersed 0=no defects, 10=Complete film breakdown
Tested Resins:
Prepolymer B: With 14.6% 6520LB (Sample B-10) With 32.4% 7081LB (Sample B-17)
Polyester 2: With 25.5% 6520LB (Sample 2-11) With 19.3% 7081LB (Sample 2-16)
Polyester 5: With 25.5% 6520LB (Sample 5-11) With 19.3% 7081LB (Sample 5-16)
The results are shown in Tables 8 and 9

(87) TABLE-US-00009 TABLE 8 Water sterilization Coating cure (90 min./121 C.) With BAKELITE 6520LB conditions Vapor Immersed Prepolymer Sample B-10 4 min./160 C. 9 9 B 12 min./160 C. 3 2 8 min./180 C. 3 3 4 min./200 C. 3 0 12 min./200 C. 3 3 Polyester 2 Sample 2-11 4 min./160 C. 3 3 12 min./160 C. 2 3 8 min./180 C. 3 0 4 min./200 C. 3 3 12 min./200 C. 3 0 Polyester 5 Sample 5-11 4 min./160 C. 9 2 12 min./160 C. 2.5 2.5 8 min./180 C. 2.5 0 4 min./200 C. 2 0 12 min./200 C. 0 0

(88) TABLE-US-00010 TABLE 9 Water sterilization Coating cure (90 min./121 C.) With BAKELITE 7081LB conditions Vapor Immersed Prepolymer Sample B-17 4 min./160 C. 8.75 9 B 12 min./160 C. 3 3 8 min./180 C. 2 3 4 min./200 C. 3 3 12 min./200 C. 2 0 Polyester 2 Sample 2-16 4 min./160 C. 5 9.25 12 min./160 C. 3 3 8 min./180 C. 2 0 4 min./200 C. 3 3 12 min./200 C. 3 3 Polyester 5 Sample 5-16 4 min./160 C. 2 0 12 min./160 C. 2 2 8 min./180 C. 2 0 4 min./200 C. 3 0 12 min./200 C. 2 2

(89) The highest molecular weight and functionality/chain resin Polyester 5 gave a noticeable improvement in performance in the immersed phase. Curing at 12 minutes/200 C. with the poly-functional phenolic actually passed the sterilization test whereas the lower molecular weight resin formed with the polyester prepolymer either failed in the steam phase or the immersed phase.

(90) (c) Conversion to a Water-Based Polyester

(91) Prepolymer B, Polyester 2 and Polyester 5 all have a calculated AV of 42. The starting Prepolymer B needed 70% neutralization with dimethylethanolamine to produce a clear solution in deionized water. The high molecular weight polyesters of the invention, Polyester 2 and Polyester 5, however, only required 50% neutralization to achieve a clear solution when diluted with the same amount of deionized water. This further confirms that the number of acid groups/chain has been increased as a result of the radical polymerization.

(92) Whereas particular embodiments of this invention have been described above for purposes of illustration, it will be evident to those skilled in the art that numerous variations of the details of the present invention may be made without departing from the invention as defined in the appended claims.