Chrome-free leather retanning

Abstract

A method for forming chrome-free retanned leather including: (a) contacting wet white (chrome-free tanned hide) with a retanning mixture comprising from 2% to 15%, by solids weight, based on the wet weight of the wet white, of an amphoteric polymer composition comprising amine functional units and acid functional units; and (b) applying a polymeric overcoat containing an acrylic copolymer with one or more metal transition elements, with a thickness of no greater than 100 microns, to the retanned wet white, is provided. The present invention also provides a chrome-free retanned leather formed by the method.

Claims

1. A method for forming chrome-free retanned leather comprising: (a) preparing a chrome-free tanned leather hide; (b) contacting the chrome-free tanned leather with a retanning mixture comprising from 2% to 15%, by solids weight, based on the wet weight of the chrome-free tanned leather hide, of an amphoteric polymer composition comprising amine functional units and acid functional units; and (c) applying a polymeric overcoat containing an acrylic copolymer with one or more metal transition elements, with a thickness of no greater than 100 microns, to the retanned leather wherein the polymeric overcoat further comprises polyurethane.

2. The method of claim 1 wherein the composition used to prepare a chrome-free tanned leather hide comprises glutaraldehyde.

3. The method of claim 1 wherein the amphoteric polymer composition comprises at least 10%, based on the dry weight of the polymer composition, of one or more amine functional monomers, in polymerizable form; and at least 10%, based on the dry weight of the polymer composition, of one or more acid functional monomers, in polymerizable form.

4. The method of claim 1 wherein the amphoteric polymer composition has a weight average molecular weight (Mw) of 15,000 or less, as determined by size exclusion chromatography; and has no more than 25%, by weight based on the dry weight of the polymer composition, of an oligomer having a weight average molecular weight (Mw) of 1000 or less, as determined by size exclusion chromatography.

5. The method of claim 1 wherein the acrylic copolymer of the polymeric overcoat contains phosphorus acid monomer units copolymerized therein.

6. The method of claim 5 wherein the phosphorus acid monomer units are in the range of greater than 0 to 5% by weight of the acrylic copolymer.

7. The method of claim 1 wherein the metal transition element in the polymeric overcoat is zinc.

8. The method of claim 1 wherein the polymeric overcoat further comprises from 5 to 20% by weight based on the solid content of the polymeric overcoat, of organic, solid spherical particle beads with a particle size of 3 to 10 microns, as measured using a Disc Centrifuge Photosedimentometer.

9. A chrome-free retanned leather formed by the method of claim 1.

10. A method for forming chrome-free retanned leather comprising: (a) preparing a chrome-free tanned leather hide; (b) contacting the chrome-free tanned leather with a retanning mixture comprising from 2% to 15%, by solids weight, based on the wet weight of the chrome-free tanned leather hide, of an amphoteric polymer composition comprising amine functional units and acid functional units; and (c) applying a polymeric overcoat containing an acrylic copolymer with one or more metal transition elements, with a thickness of no greater than 100 microns, to the retanned leather wherein the acrylic copolymer of the polymeric overcoat contains phosphorus acid monomer units copolymerized therein.

11. The method of claim 10 wherein the phosphorus acid monomer units are in the range of greater than 0 to 5% by weight of the acrylic copolymer.

12. The method of claim 10 wherein the metal transition element in the polymeric overcoat is zinc.

13. The method of claim 10 wherein the composition used to prepare a chrome- free tanned leather hide comprises glutaraldehyde.

14. The method of claim 10 wherein the amphoteric polymer composition comprises at least 10%, based on the dry weight of the polymer composition, of one or more amine functional monomers, in polymerizable form; and at least 10%, based on the dry weight of the polymer composition, of one or more acid functional monomers, in polymerizable form.

15. The method of claim 1 wherein the polymeric overcoat further comprises from 5 to 20% by weight based on the solid content of the polymeric overcoat, of organic, solid spherical particle beads with a particle size of 3 to 10 microns, as measured using a Disc Centrifuge Photosedimentometer.

16. A method for forming chrome-free retanned leather comprising: (a) preparing a chrome-free tanned leather hide; (b) contacting the chrome-free tanned leather with a retanning mixture comprising from 2% to 15%, by solids weight, based on the wet weight of the chrome-free tanned leather hide, of an amphoteric polymer composition comprising amine functional units and acid functional units; and (c) applying a polymeric overcoat containing an acrylic copolymer with one or more metal transition elements, with a thickness of no greater than 100 microns, to the retanned leather, wherein the polymeric overcoat further comprises from 5 to 20% by weight based on the solid content of the polymeric overcoat, of organic, solid spherical particle beads with a particle size of 3 to 10 microns, as measured using a Disc Centrifuge Photosedimentometer.

17. The method of claim 16 wherein the metal transition element in the polymeric overcoat is zinc.

18. The method of claim 16 wherein the composition used to prepare a chrome- free tanned leather hide comprises glutaraldehyde.

19. The method of claim 16 wherein the amphoteric polymer composition comprises at least 10%, based on the dry weight of the polymer composition, of one or more amine functional monomers, in polymerizable form; and at least 10%, based on the dry weight of the polymer composition, of one or more acid functional monomers, in polymerizable form.

20. The method of claim 16 wherein the amphoteric polymer composition has a weight average molecular weight (Mw) of 15,000 or less, as determined by size exclusion chromatography; and has no more than 25%, by weight based on the dry weight of the polymer composition, of an oligomer having a weight average molecular weight (Mw) of 1000 or less, as determined by size exclusion chromatography.

Description

EXAMPLES

(1) TABLE-US-00001 TABLE 1 Product names that are used in the Examples. Product Name Description Company Euderm Nappa Soft S Soft anti-tack agent and Lanxess GmbH, Leverkusen, filler DE Euderm Duller SN-02 Matting agent Lanxess GmbH, Leverkusen, DE Euderm Black BN black Pigment Lanxess GmbH, Leverkusen, DE Bayderm PR MX Aqueous Polyurethane Lanxess GmbH, Leverkusen, dispersion DE ACRYSOL RM-1020 Hydrophobically modified The Dow Chemical Company Ethylene Oxide Urethane rheology modifier Leukotan 970 Acrylic syntan The Dow Chemical Company Baykanol AN2-C Wetting agent Lanxess GmbH, Leverkusen, DE Oxalic Acid Dihydrate pH regulator Sinopharm Chemical Reagent Co., Ltd. Tanigan PAK Neutralizing and buffering Lanxess GmbH, Leverkusen, material DE Sodium formate Neutralizing and buffering Sinopharm Chemical dihydrate material Reagent Co., Ltd. Sodium bicarbonate Neutralizing and buffering Shanghai Hongguang material Chemical Co., Ltd. Tanigan BN Retanning replacement Lanxess GmbH, Leverkusen, syntan DE Tara Vegetable tannage Lanxess GmbH, Leverkusen, DE Tanigan F Syntan Lanxess GmbH, Leverkusen, DE Baygenal Blank TD Dyestuff Lanxess GmbH, Leverkusen, DE Levotan L Softening and filling Lanxess GmbH, Leverkusen, polymer DE Eureka 950R Fat Liquor; Altas Refinery Inc. Formic acid (HCOOH) pH regulator Sinopharm Chemical Reagent Co., Ltd. VAZO 52 Azo radical initiator Dupont Bruggolite FF6 Reductant Brueggemann Chemical

(2) Test/Evaluation Methods:

(3) (1) Softness (BLC) testing method is ISO 17235-2002: Leather—Physical and mechanical tests—Determination of softness.

(4) (2) Softness (handling) and fullness, softness and fullness of crusts were ranked by manual handling/feeling. Same criterion was implemented for their evaluation, i.e., higher rank number correlates to higher degree of performance, meaning that Rank 6 is the highest level of performance (the softest and the fullest).

(5) (3) Thickness (%) of crusted were tested and calculated step by step. Thickness test method is ISO2589-2002. The thickness data of the tanned stocks before treating process were measured and recorded as Thickness (1), the thickness data of the crusts after treating process were measured and recorded as Thickness (2). Then the thickness (%) was calculated as below formula:
Thickness (%)=(Thickness (2)−Thickness (1))/Thickness(1)×100

(6) (4) Dye intensity represents the shade/intensity of color especially on leather surface, which was ranked as number 1-6. A number 6 means the deepest color of leathers in the same trial. A higher number shows deeper color.

(7) Application of basecoat onto the leather substrates:

(8) Leather swatches (11.3×3.5 cm) of each of the leather substrate preparations were aligned in a side to side fashion and attached to a single 12″×12″ (0.0929 m.sup.2) mylar sheet using double sided tape with the grain side of the leather facing away from the mylar sheet. Basecoat was spray applied to the leather to achieve a dry add-on of 32.3-53.8 dry grams basecoat per square meter of leather. The leather was dried in a 90° C. oven for at least 4 minutes.

(9) Evaluation of Coated Leather:

(10) The coated leather was visually assessed for evenness of appearance and rated on a relative scale of 1 to 10 depending on how even the coating appeared on the leather substrate. A low rating indicates a less even distribution of coating. The coated leather was assessed for naturalness using a sterio scope at 10× magnification and rated on a relative scale of 1 to 10 depending on how natural the grain structure was retained after coating. A low rating indicates a less natural appearance of the coated substrate.

(11) Adhesion Testing:

(12) 1.4×11 cm pieces were cut from base coated leather. A layer of glue (Super Glue Gel, The Gorilla Company, Cincinnati, Ohio) was applied to the basecoat side of the leather and a 1×10 cm PVC strip (Model STD 112P1, SATRA TECHNOLOGY, Northhamptonshire, United Kingdom) was placed onto the wet glue. A 2228 gram weight was applied to the leather/pvc article and after 3 hours adhesion of the basecoat to the PVC strip was placed into an Adhesion of Finish Tester (SATRA Model STD112) and weight was applied to the leather until adhesion of coating to leather failed. A higher weight value indicates improved adhesion of finish to leather.

AP Example 1: Synthesis of Amphoteric Polymer Composition

(13) (45DMAEMA/30MAA/25MMA), MW 2K-10K

(14) Ethanol (300 g) was charged to a 3-L reactor and heated to 70° C. An initiator solution of VAZO 52 (2,2′-Azobis(2,4-dimethylvaleronitrile), 5.25 g in 47.25 g ethanol) was charged to the reactor. Immediately after initiator addition a monomer mix containing ethanol (167.87 g), methacrylic acid (157.5 g), methyl methacrylate (131.25 g), N,N-dimethylaminoethyl methacrylate (236.25 g), 2-mercaptoethanol (21.00 g) was fed to the reactor over 60 minutes. When the monomer mix feed was complete it was rinsed to the reactor with ethanol (31.50 g). After rinsing the solution was held for 30 min at 70° C. then heated to 78° C. At 78° C. a solution of VAZO 52 (1.05 g in 9.45 g ethanol) was charged to the reactor and the solution was held for 1 h. After the hold the solution was cooled to 70° C. To the reactor at 70° C. was added hydrogen peroxide (35% in water, 3.75 g), ammonium hydroxide (29% in water, 22.50 g) and water (975 g). The resulting solution was transferred to a separate vessel where the ethanol was removed under vacuum. The resulting ethanol free solution had a solids content of 40.6% and pH of 7.2.

(15) Leather Processing

(16) The stocks, purchased from tannery, were treated by glutaraldehyde, and then were used to evaluate the selected samples retanning performance. The tanned leather stocks were re-weighted. All weights were based on the weight of the leather stock (100% means a weight equal to the weight of the stock in the drum). All chemical addition percentages refer to their weight% based on the weight of the leather stock, unless specially stated. 1) The tanned stock was offere with 300% float, 0.6% Baykanol AN2-C and 0.6% oxalic acid at 35° C. The stock was tumbled at least for 120 minutes until it was totally wet back (the water inside the stock was saturated and the stock became soft). The float pH was measured and the drum was drained. 2) The stock and an added 100% float were neutralized with 2.0% Tanigan PAK, 1.0% sodium formate for 20 minutes, and then added 1.5-1.75% sodium bicarbonate. The mixture was then drummed for at least 2 hours. The stock cross-section was checked to make sure the stocks were neutralized totally. The pH of the neutralization float was monitored and maintained in the range of 5.0-5.5 by offering sodium bicarbonate to the leather in 0.5% and/or 0.25% portions per addition as needed. 3) The drum was drained and the stocks were washed with 300% float at 35° C. for 5 minutes. 4) The drum temperature was raised to 40° C. and an added 100% float into the drum. The comparative samples of Blank (no retanning agent) and commercial product of Leukotan 970 were added as 6% solids weight. As comparison, the selected samples were added as 2%, 4%, 6% and 8% solids weight (the added solids weight of sample was based on the stock weight), drummed for 90-120 minutes. 5) 3% Tanigan BN and 6% Tara were added into the drum to treat the stocks for 20-60 minutes, and then 2% Tanigan F and 3% Baygenal Blank TD (dyestuff) were offered to the stock at 40° C. for 30-60 minutes. 6) The drum temperature was raised to 50° C. and an added 50% float into the drum. 3% Levotan L was added and treated the stocks for 20 minutes and 5% Eureka 950R was offered to the stock for 60-90 minutes. 7) Formic acid was added to the contents of the retanning drum at a level of 0.5 weight % formic acid (85% active concentration). The formic acid was added as 10-25% into the drum to lower the float pH to less than 3.6, continually drummed for 10-30 minutes at room temperature. 8) The treated stock was horsed overnight. On the following day, it was hung on the toggle to be dried.

(17) The frame-dried treated stock (called crust) was adjusted its moisture content to 16-19% by spraying it uniformly with water and sealing it in a plastic bag for 4-24 hours (called conditioning). The resulting conditioned leather was then mechanically softened by a process called staking to provide the suitable leather samples for further testing or evaluation.

(18) Retanning Formulation

(19) The below retanning formulation was used to create retanning Examples 2-5 and retanning Comparative Examples A and B according to the process steps described above.

(20) RT Comparative A utilizes no retanning agent, called as “blank.”

(21) RT Comparative B utilizes commercial product Leukotan 970.

(22) RT Example 2 utilizes 2 wt. % of AP Example 1 as the polymer.

(23) RT Example 3 utilizes 4 wt. % of AP Example 1 as the polymer.

(24) RT Example 4 utilizes 6 wt. % of AP Example 1 as the polymer.

(25) RT Example 5 utilizes 8 wt. % of AP Example 1 as the polymer.

(26) TABLE-US-00002 TABLE 2 Retanning formulations and steps Process Wt. % Chemical Min REMARKS Strips Strips Thickness: Stock Glutaraldehyde tanned leather 1.4-1.6 mm Weight (gram) Refloat 300 water@35° C. 0.6 Baykanol AN2-C 120 0.6 Oxalic acid O/N pH 3.70 drain 100 water@35° C. 2 Tanigan PAK 1 Sodium formate•2H.sub.2O 20 0.5 Sodium bicarbonate 0.5 Sodium bicarbonate 120 Check, drain Wash 300 water@35° C. Retan 100 water@40° C. 120 6 RT Comparative A 6 RT Comparative B 2/4/6/8 RT Examples 2-5 respectively 3 Tanigan BN 20 6 Tara 2 Tanigan F 60 3 Baygenal Blank TD Add 50 water@50° C. 3 Levotan L 20 5 Eureka 950R 60 10-25 10% HCOOH @RT 30 pH < 3.6, drain Wash 300 Water@25° C. 5 Wash 300 Water@25° C. 5

(27) After applying the retanning formulation above to the chrome-free glutaraldehyde tanned leather, a visual and testing assessment was conducted and the results are shown below.

(28) TABLE-US-00003 TABLE 3 Retanned Leather Assessment Softness Softness Thickness Dye Sample (BLC) (handling) (%) Fullness Intensity RT Comp A 2.6 2.8 18.6 3.3 3.0 RT Comp B 2.8 3.0 20.0 3.3 3.0 RT Ex. 2 2.7 3.1 19.7 3.8 3.5 RT Ex. 3 2.6 2.9 21.8 3.5 4.0 RT Ex. 4 2.3 2.5 22.0 3.8 4.0 RT Ex. 5 2.1 2.0 20.7 4.0 4.0

(29) Higher rank, better performance—(1 worst-6 best).

(30) The retanned leathers of Table 3 are also referred to as Crusts 1-6 respectively, which are used in later examples.

(31) Results show that leathers containing greater than 2% of an amphoteric retanning polymer provided leathers with better thickness, fullness, dye value than the controls of an acrylic acid polymer and the blank. The leathers containing lower than 4% of an amphotric retanning polymer provided leathers with similar softness to the controls, but a bit of less softness than the controls when applied in an amount greater than 4%.

POLYMERIC OVERCOAT EXAMPLES

(32) Base polymers (BP) are used to prepare polymeric overcoat formulations.

BP Example 6: Preparation of 90(94.5BA/3.3AA/2.2PEM)//10MAA Emulsion Polymer with Zinc

(33) A 4-necked round bottom flask equipped with a mechanical stirrer and reflux condenser was charged with DI water (732.4 g) and heated to 45° C. A first monomer emulsion containing DI water (92.8 g), Sodium lauryl sulfate (24.8 g, 28% active), Sodium dodecylbenzene sulfonate (25.6 g, 22.5% active), butyl acrylate (550.0 g), acrylic acid (19.4 g) and phosphoethyl methacrylate (12.5 g) was prepared separately. The entire monomer emulsion was added and rinsed to the reactor and then sequentially were added solutions of iron sulfate (0.004 g in 4.3 g water), ammonium persulfate (0.41 g in 6 g water) and Lykopon/sodium hydroxide (0.68 g/0.12 g in 14 g water) at which time an exotherm to 87° C. was observed. After the reaction peaked the contents were cooled to 65° C. and then methyl methacrylate (61.6 g) was charged to the reactor. Solutions of t-butylhydroperoxide (0.28 g in 4 g water) and sodium sulfoxylate formaldehyde (0.18 g in 12 g water) were added and an exotherm to 63° C. was observed. Additional solutions of t-butylhydroperoxide (0.92 g in 21.6 g water) and sodium sulfoxylate formaldehyde (0.62 g in 21.6 g water) were added to reduce residual monomers. Ammonium hydroxide (1.54 g) was added to the reactor. A slurry made from DI water (34 g) and zinc oxide (9.86 g) was added over 15 minutes. The reactor contents were held at 40° C. for 1 h then additional ammonium hydroxide (15 g) was added. The resulting emulsion had a solids content of 34.4% and a pH of 8.9.

BP Comparative Example C: Preparation of 80(94.1BA/3.4AA/2.5PEM)//20MAA Emulsion Polymer without Zinc

(34) A 4-necked round bottom flask equipped with a mechanical stirrer and reflux condenser was charged with DI water (757.5 g) and heated to 35° C. A first monomer emulsion containing DI water (200.9 g), Sodium lauryl sulfate (23.2 g, 28% active), Sodium dodecylbenzene sulfonate (23.3 g, 22.5% active), butyl acrylate (598.45 g), acrylic acid (21.75 g) and phosphoethyl methacrylate (16 g) was prepared separately. A portion of the monomer emulsion (216.5 g) was added to the reactor and then sequentially were added solutions of iron sulfate (0.01 g in 2.5 g water), ammonium persulfate (0.16 g in 15 g water) and Lykopon (0.31 g in 15 g water) at which time an exotherm to 56° C. was observed. After the reaction peaked the contents were cooled to 46° C. and the remainder of the monomer emulsion added quickly. To this mixture were added additional solutions of ammonium persulfate (0.46 g in 15 g water) and Lykopon (0.78 g in 15 g water) and the reaction exothermed to 79° C. After this reaction, residual monomers were reduced by adding solutions of t-butylhydroperoxide (0.35 g in 5 g water) and sodium formaldehyde sulfoxylate (0.18 g in 15 g water). The reaction contents were cooled to 64° C. and then methyl methacrylate (155 g) was charged to the reactor. Solutions of t-butylhydroperoxide (0.71 g in 10 g water) and Bruggolite FF6 (0.54 g in 20 g water) were added and an exotherm to 74° C. was observed. Additional solutions of t-butylhydroperoxide (1.17 g in 20 g water) and FF6 (1.02 g in 22.5 g water) were added to reduce residual monomers. A solution made from DI water (187.5 g), sodium lauryl sulfate (85.1 g, 28% active) and triethylamine (21.4 g) was added over 45 minutes. The resulting emulsion had a solids content of 34.6% and a pH of 7.2.

(35) BP Comparative D is an 80(96.5BA/3.5AA)//20MMA multistage emulsion polymer without zinc added. BP Example 7 is a 90(96.5BA/3.5AA)//10MMA multistage emulsion polymer with zinc added in the same amount as in BP Example 6. The use of “//” denotes a multistage polymerization process.

(36) Preparation of Polymeric Overcoat Formulations:

(37) Into a 250 milliliter plastic paint container 68 grams of water, 32 grams of EUDERM Nappa soft s, 60 Grams of EUDERM SN-02, 40 grams of EUDERM Black BN, a total of 200 grams of binder dispersion(s) and ACRYSOL RM-1020 were sequential added, with mixing using a 3 prong mixing blade, to obtain a #2 zahn cup viscosity of at least 15 seconds. In one formulation (example x) 30 grams of acrylic bead dispersion was added after the binder was added. The basecoat formulations were passed through a 125 μm filter prior to spray application.

(38) Application of Polymeric Overcoat (Basecoat) onto the Leather Substrates:

(39) Leather swatches (11.3×3.5 cm) of each of the leather substrate preparations were aligned in a side to side fashion and attached to a single 12″×12″ (0.0929 m.sup.2) mylar sheet using double sided tape with the grain side of the leather facing away from the mylar sheet. Basecoat was spray applied to the leather to achieve a dry add-on of 32.3-53.8 dry grams basecoat per square meter of leather. The leather was dried in a 90° C. oven for at least 4 minutes.

(40) TABLE-US-00004 TABLE 4 K-values pf Polymer Bead (multiple stage 4.5 micron acrylic bead) K(0) full compression Ratio of Material K(10), N/m2) (N/m2) K0/K10 Polymer Bead 1.20E+10 4.12E+10 3.43 Polymer bead sample was evaluated using a compression rate of 0.79 gram-force/sec

(41) TABLE-US-00005 TABLE 5 Polymeric overcoat formulations (PO Form) PO PO Comparative PO PO Comparative Form 1 Form 2 PO Form 3 Form 4 Form 5 PO Form 6 Product PUD + AC + Zn PUD + AC PUD + AC + Zn + AC + PEM AC + Zn AC + Zn + PEM bead Water 68 68 68 68 68 68 Euderm 32 32 32 32 32 32 Nappa Soft S Euderm 60 60 60 60 60 60 Duller SN-02 Black 40 40 40 40 40 40 BN BP 200 Comp C BP 120 Comp D BP Ex 7 120 200 120 BP Ex 6 200 Bayderm 80 0 80 80 bottom PR MX 4.5 30 micron acrylic bead (32% solids emul.) RM-1020 4.8 3.5 7.8 3.7 3.8 8.0 Total 404.8 403.5 407.8 433.7 403.8 408 PUD—polyurethane dispersion, AC—acrylic emulsion polymer, PEM—phosphoethyl methacrylate in the AC, Zn—zinc, bead—acrylic bead

(42) TABLE-US-00006 TABLE 6 Visual assessment of coated leather for Naturalness after apply PO PO Comp PO PO PO Comp PO Crust Crust type Form 1 Form 2 Form 3 Form 4 Form 5 Form 6 1 blank 5 9 7 5 — — 2 6% Leukotan 970 3 4 3 3 — — 3 2% Ex 1 6 4 3 6 — — 4 4% Ex 1 7 7 4 8 — — 5 6% Ex 1 7 5 3 8 8 — 5 6% Ex 1 — — — — — 3 6 8% Ex 1 7 5 3 8 — — Assessment for “naturalness” 1-10, 1 = covered and 10 = natural
Results show that leathers containing 2% or greater of an amphoteric retanning polymer over coated with a basecoat coating of an acrylic polymer containing zinc provides improved natural appearances as compared to controls containing an anionic retanning polymer.

(43) TABLE-US-00007 TABLE 7 Visual assessment of coated leather for even appearance after applying basecoat PO PO Comp PO PO PO Comp PO Crust Crust type Form 1 Form 2 Form 3 Form 4 Form 5 Form 6 1 Blank 2 2 2 2 — — 2 6% Leukotan 970 6 6 6 6 — — 3 2% Ex 1 7 7 7 7 — — 4 4% Ex 1 8 8 8 8 — — 5 6% Ex 1 8 8 8 8 8 — 5 6% Ex 1 — — — — — 6 6 8% Ex 1 8 8 8 8 — — Visual Even-ness assessment: 1-10 1 = poor and not an even distribution of coating across area (deeper penetration-dryer) and 10 = very even distribution of coating over the leather article.
Results show that leathers containing 2% or greater of an amphoteric retanning polymer over coated with a basecoat provide improved natural appearance than a comparative control containing an anionic retanning polymer and significantly better than a comparative control that contains no retanning polymer.

(44) TABLE-US-00008 TABLE 8 Dry adhesion of coating to crust (coatings on crust 5) PO Form 2 PO Form 5 Comp PO Form 6 Weight force at 1350 1837 967 adhesion failure (grams) Standard Deviation 215 153 208 (grams)