Patent Application: US-75643996-A

Abstract:
hide / leather - polymer composite materials are provided by the impregnation of polymer systems into interstitial void spaces in the collagen fiber network of the hide / leather precursors , providing a broad spectrum of composite materials possessing a wide variety of bulk mechanical properties . preferably , the polymer systems employed in the inventive composites are bismaleimides , when high modulus , strength and flexural modulus are desired , and siloxane - based polymers , when elastomeric bulk properties are desired .

Description:
the following examples set forth preferred embodiments and techniques for the formation of polymer system hide / leather composite materials , as well as test results demonstrating various desirable properties of the composite materials . it is to be understood , however , that these examples are presented by way of illustration only and nothing therein should be taken as a limitation upon the overall scope of the invention . this example demonstrates that the instant invention could be practiced using polymer systems which generate gaseous by - products having the potential of creating undesirable void spaces in the finished composite product and the properties to be expected from formation of a composite with hide and an elastomer . 1 . after cutting from chrome - tanned cowhide ( unfinished leather ) to the desired size , the sample was weighed and then soaked in tetrahydrofuran ( thf ) as a solvent for approximately 2 hours . 2 . the amount of reactants were calculated so that the total mass of the polymer was equal to 50 % of the mass of the dry hide . the bis - benzene : dms molar ratio was 1 : 1 . 3 . since the bis - benzene is a crystalline solid , it was necessary to dissolve the bis - benzene in the solvent , in this case thf . the leather was soaked in this solution for 30 minutes . the dms then was diluted with thf at an approximate dms : thf volume ratio of 1 : 5 . both the leather and dms solution were cooled in an ice bath . the leather then was placed in the dms solution at ice bath conditions ; this system was left to react for 1 hour . during this portion of the impregnation process , ph paper was placed over the leather to confirm reaction . 4 . if a non - pressed sample was desired , the leather was placed in a vacuum oven overnight to dry after step 3 . if a pressed sample was desired , the leather was bagged and placed in the hot press for 8 hours at 30 ° c . and a pressure of 200 psi . 5 . after pressing , the sample was placed in the vacuum oven overnight to evaporate any excess solvent . based upon a visual inspection , the composite material produced in this example did not possess appreciable void spaces created by the generation of hcl gas . this example demonstrates that stage - wise impregnation could be satisfactorily used in the practice of the instant invention to impregnate high viscosity , high molecular weight precursors . 1 . after cutting to the desired size , the hide was weighed and soaked in tetrahydrofuran ( thf ) solvent for approximately 2 hours . 2 . for the initial psx batch , the mass of the psx prepolymer corresponding to 50 % of the mass of the dry hide . although the molar ratio had to be maintained at 1 : 1 for the calculations , only the amount of psx needed to be calculated . 3 . the amount of psx calculated in step 2 was measured out and diluted by about 50 % in thf . next , the leather was soaked in this solution for 2 hours . 4 . for the final baths , a psx : dry hide mass ratio of 1 . 5 : 1 was desired . the amount of psx required for the final bath was diluted with thf by approximately 50 %. the hide then was transferred to this bath and allowed to soak for 2 hours . 5 . the amount of mdi calculated for the final bath was dissolved in thf . then , both the hide and this mdi solution were placed in an ice bath to cool . eventually , the final psx and mdi solutions were combined ; and , the leather was soaked in this solution while still in an ice bath for another 2 hours . 6 . subsequently , the hide was placed in a vacuum oven at 60 ° c . overnight to dry . after drying , the final product was placed in the hot press for 2 hours at 100 ° c . and a pressure of 275 psi . this example demonstrates that the instant invention could be practiced using polymer systems precursors normally requiring relatively high cure temperatures ( substantially in excess of 200 ° c .) with the assistance of catalysts . 1 . ten grams of bmi was dissolved in 30 to 50 ml of dimethylformamide . 4 , 4 &# 39 ;- diaminodiphenylmethane ( ddm ) was added to this solution such that the molar ratio of bmi - to - ddm was 1 . 3 : 1 . 1 , 4 - diazabicyclo - 2 , 2 , 2 !- octane ( dabco ) was added to this solution to achieve a catalyst concentration of 0 . 4 wt %. 2 . samples of chrome - tanned cowhide were placed in the solution above , and held at ambient temperature for a period of 1 to 2 days . 3 . upon removal from the solution , the impregnated hide sample was placed on a piece of aluminum foil to permit evaporation of the solvent at ambient conditions . 4 . the sample was placed in a vacuum oven for one hour at a vacuum in the range of - 25 to - 30 kpa and a temperature of 100 ° c . to remove residual solvent . the operating conditions were chosen to facilitate removal of the solvent but to minimize any cure of the resin during this time . 5 . the sample then was heated in a hot press at 100 ° to 120 ° c . and at a pressure of 8 . 6 psig for 2 hours . 6 . the temperature of the hot press was increased to 150 ° c . for 12 hours at the previous pressure . 7 . the system temperature was reduced to 49 ° c . while maintaining a system pressure of 8 . 6 psig for 1 hour . 8 . at that point , the temperature was returned to ambient while the system pressure was maintained . once the system returned to ambient temperature , the pressure was released and the sample removed . this example demonstrates that commercially popular polymer systems and curing agents could be used in the practice of the instant invention . 1 . the sample of chrome - tanned hide to be utilized was presoaked to acetone for several or up to 20 hours . 2 . subsequent to soaking , the tanned hide was allowed to dry at ambient conditions . 3 . the presoaked , dried hide samples were dried further at 90 ° to 100 ° c . and at a vacuum less than - 90 kpa for 3 to 4 hours . the samples were weighed and their areas recorded after drying . 4 . ten grams of bismaleimide ( bmi ) monomer was dissolved in 25 to 40 mol of 1 , 4 - dioxane . jeffamine d - 230 ( texaco chemical co .) was added to this solution such that the molar ratio of bmi - to - jeffamine was 1 . 0 : 1 . 0 . 5 . the samples of chrome - tanned cowhide prepared in steps 1 and 2 were placed in this solution of reagents , and held at ambient temperature , for 1 to 2 days . 6 . upon removal from the solution , the impregnated hide sample was placed on a piece of aluminum foil to permit evaporation of the solvent at ambient conditions . 7 . the sample was placed in a vacuum oven at a room temperature for several hours at a vacuum less than - 50 kpa to remove residual solvent . the vacuum was reduced to the - 70 to - 80 kpa range for an additional 24 to 36 hours . the intent was to minimize any cure of the resin during solvent removal . 8 . the sample then was heated in a hot press according to the temperature and pressure schedule below : a . ( completion of impregnation ) 90 ° to 95 ° c . at 2 . 3 psig for 1 hour b . ( curing of polymer system precursors ) 150 ° c . at 2 . 3 psig for 4 hours c . ( curing of polymer system precursors ) 160 ° c . at 3 . 8 psig for 24 hours d . ( controlled cooling to prevent warping ) 49 ° c . at 3 . 8 psig for 1 hour 9 . the temperature was returned to ambient while the system pressure was maintained . once the system returned to ambient temperature , the pressure was released and the sample removed . a summary of mechanical properties associated with hide / leather alone and the hide / leather polymer composite materials are presented in tables 1 and 2 . table 1______________________________________summary of mechanical propertiesof the hlp materials described herein resin up - young &# 39 ; s tensile breaking take modulus strength strengthsample ( wt %) ( mpa ) ( mpa ) ( mpa ) ______________________________________hide / leather alone not ( 2 . 4 ) (. 9 ) (. 9 )( unpressed ) applicable 46 . 7 23 . 4 23 . 4hide / leather alone not 266 . 9 16 . 8 16 . 5 ( pressed ) applicableunpressed ( 30 . 5 ) ( 3 . 2 ) ( 3 . 2 ) hide / leather - dms - 23 % 244 . 5 19 . 9 19 . 9bis - benzenecompositepressed hide / leather - ( 36 . 8 ) ( 3 . 7 ) ( 3 . 7 ) dms - bis - benzene 17 % 297 . 4 21 . 79 21 . 8compositehide / leather - siloxane - 28 % 449 . 6 32 . 76 31 . 7ureabismaleimide - ddm not 6028 24 . 3 24 . 3 applicablehide / leather - bismalei - ( 951 ) ( 4 . 4 ) ( 8 . 4 ) mide - ddm 27 % 2550 . 19 . 4 16 . 6bismaleimide - jeffamine not ( 6 . 3 ) ( 4 . 7 ) applicable 9346 . 62 . 8 60 . 3hide / leather - bismalei - ( 907 ) ( 3 . 8 ) ( 3 . 8 ) mide - jeffamine 36 % 3371 39 . 2 39 . 2______________________________________ * standard deviations are included in parentheses when applicable . table 2__________________________________________________________________________summary of mechanical propertiesof the hlp materials described herein energy yield percent to break izod impact strength elongation point datasample ( mpa ) at break ( joules ) ( ft - lb . sub . f / in ) __________________________________________________________________________hide / leather alone ( 3 . 64 ) ( 2 . 5 ) not appli -( unpressed ) 1 . 56 44 . 3 17 . 5 cablehide / leather alone 0 . 452 41 . 2 14 . 22 not appli -( pressed ) cableunpressed not 32 . 8 ( 3 . 5 ) nothide / leather - dms - available 12 . 5 applicablebis - benzenecompositepressed hide / leather - not ( 6 . 4 ) ( 4 . 3 ) notdms - bis - benzene available 27 . 9 12 . 3 applicablecompositehide / leather - siloxane - not 77 . 4 21 . 00 noturea available applicablebismaleimide - ddm 8 . 6 2 . 5 0 . 20 1 . 0hide / leather - ( 2 . 4 ) (. 286 ) (. 012 ) 1 . 9bismaleimide - ddm 13 . 5 2 . 0 0 . 125bismaleimide - jeffamine ( 2 . 2 ) (. 77 ) (. 09 ) 1 . 3 6 . 8 7 . 4 0 . 59hide / leather - ( 5 . 6 ) (. 2 ) (. 078 ) 4 . 1bismaleimide - jeffamine 19 . 1 2 . 3 0 . 370__________________________________________________________________________ the results obtained in the examples presented in tables 1 and 2 demonstrate that new composite materials may be synthesized according to the instant invention which possess improved mechanical properties . the tensile strength , breaking strength , and young &# 39 ; s modulus of composite system using relatively brittle polymers resemble those of the polymer systems alone , while the notch toughness and impact resistance ( both of which are based upon izod impact data ) are enhanced by formation of the composite material . when the polymer systems of interest are rigid or brittle in nature , the resulting composite material possesses improved notch strength ( based upon izod impact data ) and vibration dampening ( based upon interpretation of dma data presented in fig1 - 4 ) characteristics when compared to the polymer system alone . in each example , 1 - 4 , the impregnated leather was visually inspected and each sample was found to be fully impregnated . full impregnation of leather was also demonstrated by data appearing in fig6 and 7 . fig6 and 7 present two spectra acquired via energy dispersive spectroscopy ( eds ) on a scanning electron microscope . this particular technique obtains chemical information about the sample from the energies of x - rays emitted during exposure of the sample to an electron beam ( in this case , generated by the scanning electron microscope ). the chemical information is specific to that region of the sample exposed to the electron beam ; i . e ., it can give chemical information about the small area of the sample . the eds data presented in fig6 and 7 were obtained from a cross - section of a siloxane - urea - hide sample at both the surface ( fig7 ) and at the center of the sample ( fig6 ). the only source for the silicon is the polymeric material impregnated into the leather . the obvious presence of silicon at the center of the sample is clear evidence that the siloxane - urea polymer is present throughout the leather ; thus demonstrating that full impregnation was achieved . as used herein , &# 34 ; fully impregnated &# 34 ; means that the interstitial void spaces between the collagen fibers existing throughout the entire thickness of the collagen fiber network of the hide / leather have been substantially filled with the polymer system precursor solution during impregnation . upon curing , the precursors form a polymer matrix which is laced inextricably throughout the collagen fiber network of the hide / leather . in this sense , the hide / leather is said to be fully impregnated with the polymer system . thus , the combined bulk properties of the hlp composite material ( e . g ., toughness , strength , modulus ) are substantially different than the bulk properties of either the hide / leather or a cured polymer system alone . for instance , a bulk property associated with leather useful for shoe uppers is that such leather has the capability of absorbing and permeating vapor from perspiration . when fully impregnated with a polymer system of the instant inventions ( such as bismaleimides or siloxane - based polymers ), this bulk property is markedly reduced in the resulting hlp composite . it will be appreciated , however , that the hlp composite of the instant invention will possess many other very beneficial properties ( as previously discussed ). it will also be appreciated , however , that comparatively small regions of the hide / leather composite may exist as voids ( less than about 10 % total volume of void spaces existing between the pretreated , unimpregnated hide / leather ) without reducing the extent to which the hlp bulk properties are improved over those of the hide / leather or polymer system individually . for example , the hide / leather may have small , very dense regions which will not permit impregnation . consequently , when it is stated herein that the hide / leather is fully impregnated , it is also meant that if interstitial void regions exist in the composite collagen network that lack the presence of polymer , such deficiency is not sufficient to materially modify the extent to which the natural properties of the hide / leather or polymer system are changed in the hlp composite . the incorporation of an elastomeric or tough polymer into the composite material provides improved elastomeric behavior of the composite material whose properties are intermediate between those of the polymer and the hide / leather . other properties such as tear resistance may be significantly enhanced by the presence of the hide . for example , incorporating a siloxane - urea polymer into the hide / leather produces a sample with the following changes in properties when compared to the hide / leather itself : 1 . the low temperature (& lt ;- 100 ° c .) flexural modulus of the composite material ( based upon interpretation of dma data presented in fig1 - 4 ) is approximately 10 times higher than that of the hide / leather alone . 2 . after prolonged exposure to ambient conditions , the flexibility of the hide / leather increases with the incorporation of the siloxane - urea polymer . 3 . the percent strain at break of the material increases from approximately 40 % for the hide / leather alone to over 100 % for the hide / leather polymer composite material based on siloxane - urea polymers . the hide / leather polymer composite materials also possess the advantage that they may be formed with properties which approach or exceed those of the polymer alone without being as expensive as the polymer system . in particular , the results developed in the examples demonstrate the ability of the composite to retain many of the properties of the polymer system at polymer system concentrations as low as 30wt %. the instant invention should not be viewed as limited to the specific examples discussed . the instant invention may be practiced so long as : 1 . the monomers , prepolymers or resin systems selected are capable of impregnation into hide or leather before significant polymerization can occur ; and in addition , polymer systems used in the practice of the instant invention may be those where polymerization proceeds via condensation reaction mechanisms , as well as via addition reaction mechanisms . in the latter respect , such addition reactions may be initiated by techniques such as gamma - ray irradiation or the addition of an initiator or catalyst . the dma data disclosed herein was collected on a perkin - elmer dma system 7 with a 3 - point flexural and a compression accessory . terms relating to dynamic mechanical measurements on plastics , as used herein , should be construed in accordance with astm standard test procedure d 4092 - 83a , &# 34 ; standard definitions and descriptions of terms relating to dynamic mechanical measurements on plastics .&# 34 ; ______________________________________chrome - tanned leather that has been tanned with chromiumleather compounds but which has not been dyed or fat liquoured ( see t . c . thorstensen , practical leather technology ( r . e . krieger publishing co ., malabar , fl 1985 ) p . 320 ) hide the pelt of a large animal , such as a cow , horse , sheep , pig , etc . ; often used inter - changeably with skin ( see t . c . thorstensen , practical leather technology ( r . e . krieger publishing co ., malabar , fl 1985 ) p . 320 ) hide / leather used in situations when hide , leather , or any product intermediate in the processing of the hide to finished leather ( such as chrome - tanned leather ) is appropriate to the discussionhlp composite abbreviation used herein for a composite material prepared from hide / leather and a polymer systemleather hides or skins that have been tannedpolymer a high molecular weight compound prepared from lower molecular weight precursors ( including monomer reactants , prepolymers or resins ); usage herein will imply that the material will have been reacted to a form typical of its engineering applicationsprepolymer partially polymerized systems which are still capable of liquid flowresin a partially polymerized substance that typically exhibits tackiness which can be subsequently reacted to form the final polymeric material , is capable of flow at elevated temperature , and typically can be dispersed in an appropriate solvent______________________________________ ______________________________________bis - benzene 1 , 4 - bis ( dimethylhydrosilyl ) benzenebmi 1 , 1 &# 39 ;- ( methylenedi - 1 , 4 - phenylene ) bismaleimide ( also known as n , n &# 39 ;- bismaleimide - diphenyl methane ) dabco 1 , 4 - diazabicyclo 2 , 2 , 2 !- octaneddm 4 , 4 &# 39 ;- diaminodiphenylmethane ( also known as 4 , 4 &# 39 ;- methylene dianiline ) 15 . dms dimethyldichlorosilanejeffamine any of a series of polyoxypropyleneamines commercially available as part of the &# 34 ; jeffamine &# 34 ; series . in the development effort described herein it specifically refers to jeffamine d - 230 ( having a molecular weight of approximately 230 g / mole ) mdi 4 , 4 &# 39 ;- diphenylmethane diisocyanatepsx aminopropyldimethyl - terminated polydimethyl - siloxane ( huls america , number averaged molecular weight of about 2500 ; undiluted viscosity of about 50 centipoise ) ______________________________________ bay , h ., g . eckert , and w . bergold , &# 34 ; waterproofing of leather , pelts or leather substitutes with siloxanes ,&# 34 ; fed . rep . ger . patent 3 , 800 , 629 ( 20 jul . 1989 ). buechler , p . r ., p . l . kronick , and f . schlonick , &# 34 ; radiation polymerized graft copolymers for leather ,&# 34 ; in renewable - resource materials ( c . e . carraher , jr . and l . h . sperling , eds .) ( plenum press , new york , 1986 ) pp . 251 - 258 . feairheller , s . h ., a . h . korn , e . h . harris , e . m . filchione , and m . m taylor , u . s . pat . no . 3 , 843 , 320 ( 1974 ). friese , h . h ., and w . prinz , &# 34 ; waterproofing of fashion leathers ,&# 34 ; leder - haeutemarkt 38 ( 32 ), 5 - 6 , 8 - 10 ( 1986 ). harris , e . h ., m . m taylor , and s . h . feairheller , j . am . leather chem . assoc . 67 , 111 ( 1972 ). jordan , e . f ., jr ., b . artymyshyn , a . l . everett , m . v . hannigan , and s . h . feairheller , &# 34 ; polymer - leather composites . i . process and location study for the deposition of selected acrylate monomers by polymerization into chrome - tanned cattlehide ,&# 34 ; j . appl . polym . sci . 25 , 2621 - 2647 ( 1980 ). jordan , e . f ., jr ., and s . h . feairheller , &# 34 ; polymer - leather composites . ii . kinetics of the deposition of selected acrylate monomers by polymerization into chrome - tanned cattlehide ,&# 34 ; j . appl . polym . sci . 25 , 2755 - 2776 ( 1980 ). jordan , e . f ., jr ., b . artymyshyn , m . v . hanningan , r . j . carroll , and s . h . feairheller , &# 34 ; polymer - leather composites v . preparative methods , kinetics , morphology , and mechanical properties of selected acrylate polymer - leather composite materials ,&# 34 ; in polymer applications of renewable - resource materials ( polymer science and technology , vol . 17 ) ( c . e . carraher , jr . and l . h . sperling , eds .) ( plenum press , new york , 1983 ) pp . 407 - 452 . khananashvili , l . m ., sh . v . pichkhadze , m . d . mikhailov , et al ., &# 34 ; composition for waterproofing leather ,&# 34 ; soviet patent 1 , 244 , 182 a1 ( 15 july 1986 ). korasteleva , z . k ., &# 34 ; new methods for leather treatment !,&# 34 ; kozh .- obuvn . prom - st . 20 ( 10 ), 20 - 21 ( 1978 ). korn , a . h ., s . h . feairheller , and e . m . filachione , j . am . leather chem . assoc . 67 , 111 ( 1974 ). kronick , p . l ., b . artymyshyn , p . r . buechler , and w . wise , &# 34 ; viscoelasticity of calf hide impregnated with radiation - polymerized polyhydroxyethyl methacrylate ,: in renewable - resource materials ( c . e . carraher , jr . and l . h . sperling , eds .) 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( to rohm and haas co . ), belg . patent 637 , 052 . neher , m . b . and v . b . vely ( to titekote corp . ), u . s . pat . no . 3 , 066 , 997 ( dec . 4 , 1962 ). nikka chemical industry and shimizu chemical k . k ., &# 34 ; treatment of leather ,&# 34 ; japanese patent 58 , 080 , 400 a2 ( 14 may 1983 ). radzynkiewicz , r ., and m . mikula , &# 34 ; studies on the use of polish silicones . part i . waterproofing of upper leathers with silicones in solvents ,&# 34 ; przegl . skorzany 31 ( 10 ), 308 - 312 ( 1976 ). rao , k . p ., k . t . joseph , and y . nayudamma , &# 34 ; characterization of the collagen - vinyl graft copolymers prepared by the ceric ion method . ii . infrared spectra and electron microscopy ,&# 34 ; j . appl . polymer sci ., 16 , 975 - 0986 ( 1972 ). rao , k . p ., k . t . joseph , and y . nayudamma , &# 34 ; characterization of the collagen - vinyl graft copolymers prepared by the ceric ion method . i . solution properties ,&# 34 ; j . appl . polymer sci ., a - 1 , 9 , 3199 - 3212 ( 1971 ). zakharova , s . v ., l . v . slobodskikh , m . b . mikhailov , and l . k . tsivinskaya , &# 34 ; oligomeric organotitanium compounds in compositions for water - repellency treatment of leathers ,&# 34 ; kozh .- obuvn . prom - st ., 25 - 27 ( 1992 ). zurabyan , k . m ., v . i . sidorov , m . i . filimonova , et al ., &# 34 ; use of ethyl silicate and still residues from its production for the waterproofing of leather ,&# 34 ; kozh .- obuvn . prom - st , 37 - 39 ( 1984 ). zurabyan , k . m ., k . s . pushchevaya , l . v . slobodskskh , et al ., &# 34 ; rendering suede leather for shoe uppers water - repellent ,&# 34 ; soviet patent 922 , 148 al ( 23 apr . 1982 ). zurabyan , k . m ., v . v . nepomnina , l . v . slobodskskh , et al ., &# 34 ; waterproofing of leather with organosilicon compounds ,&# 34 ; kozarstvi 30 ( 10 ), 296 - 297 ( 1980 ).