Jae-hong YU. (25/2, 67-10 Chilsan-dong, Dongrae-gu 607-030 Pusan, KR)
Cho, Seong-mo (7/2 627-7 Munhyun 2-dong, Nam-gu 608-042 Pusan, Nam-gu 608-042 Pusan, KR)
Bae, Sang-sik (Haewoundae Whamok-Town 101-107, 1310 Chwa-dong, Haewoundae-gu 612-030 Pusan, KR)
Kim, Hyung-seoung (Hanil-Town 2nd, 64-1 Yangduk-dong, Hoewon-gu 630-490 Pusan, 204-1006, KR)
Lee, Jeong-sam (Neospot Apartment Bujune-dong, Pusanjin-gu 614-030 Pusan, 101-2606, KR)
Jae-hong YU. (25/2, 67-10 Chilsan-dong, Dongrae-gu 607-030 Pusan, KR)
Cho, Seong-mo (7/2 627-7 Munhyun 2-dong, Nam-gu 608-042 Pusan, Nam-gu 608-042 Pusan, KR)
Bae, Sang-sik (Haewoundae Whamok-Town 101-107, 1310 Chwa-dong, Haewoundae-gu 612-030 Pusan, KR)
Kim, Hyung-seoung (Hanil-Town 2nd, 64-1 Yangduk-dong, Hoewon-gu 630-490 Pusan, 204-1006, KR)
| 1. | An aqueous type polyurethane dispersion composition for a synthetic leather, comprisin: 100 parts by weight of an aqueous polyurethane dispersion obtained from a polyurethane of which the main chain is covalently bonded to anionic groups including a carboxyl group or a sulfonate group, or cationic groups including a tertiary amine group; 0.1 to 5 parts by weight of a water repellant; 0.1 to 8 parts by weight of an emulsifier; (). 1 to 1 part by weight of an antifoamer; and (), I to 5 parts by weight of an inorganic filler. |
| 2. | An aqueous polyurethanebased synthetic leather being characterized in that the synthetic leather is obtained by impregnating a composition comprising parts by weight of aqueous polyurethane dispersion, 0.1 to 5 parts weight of a water repellant. 0.1 to 8 parts by weight of an emulsifier. 0.1 to 1 part by weight of an antiformaer, and 0.1 to 5 parts by weight of an inorganic filler into a substrate, coating the foamed or defoamed composition on the substrate, and coagulating the coated substrate with a coagulating solution, wherein aqueous polyurethane dispersion is covalently bonded to anionic groups including carboxyl group of sulfonate group, or cationic groups including a tertiary amine group, wherein the coagulating solution is selected from the group consisting of an aqueous solution of various salts, a mixed solution of salt and acid, a mixed solution of salt and base, a mixed solution of acid and base. and mixtures thereof. |
| 3. | The aqueous polyurethanebaed synthetic leather as claimed in claim 2, wherein the water repellent is a fluorine or a silicone compound. |
| 4. | aqueous polyurethanebased synthetic leather as claimed in claim 2, wherein the emulsifier is selected from the group consisting of sodium bis(2 <BR> methylhexyl)sulfosuccinate, sodium laurylsulphate, sodium isopropyl<BR> naphthalene sulfonate, sodium bis(tridecyl)sulfosuccinate, n octadecyldisodium sulfosuccinate, octylphenoxypoly(ethyleneoxy)ethanol, trimethylnonyloxypoly(ethyleneoxy)ethanol. nonylphenoxypoly(ethylencoxy)ethanol, glyceryltrilate, ethylene glycol ethylene monostearate, sorbitanetriolate, sorbitanetristearate and mixture thereof. |
| 5. | The aqueous polyurethanebased synthetic leather as claimed in claim 2, wherein the antifoamer is a siliconbased aniifoamer. |
| 6. | The aqueous polyurethanebased synthetic leather as claimed in claim 2, wherein the inorganic lillcr is a powder selected from the group consisting of powders of modified silica, titanium oxide, alumina, ferric oxide, calcium oxide or magnesium oxide with an average diameter of around 1 µm, and mixtures thereof, The aqueous polyurethanebased synthetic leather as claimed in claim 2, wherein the coagulating solution is selected from the group consisting of an queous solution of various salts, a mixed solution of salt and acid, a mixed solution of saklt and base, a mixed solution of acid and base, and mixtures <BR> thereof,<BR> <BR> <BR> A method for preparing a synthetic leather from an aquous polyurethane<BR> dispersion, comprising the steps of: (a) preparing a coating composition comprising 100 parts by weight of an aqueous polyurethane dispersion, 0.1 to 5 pars by weight of a water repeflent, 0.1 to 8 parts by weight of an emulsifier, 0.1 to 1 part by weight of an antifoamer, and 0.1 to 5 parts by weight of an inorganic filler, and subjecting the ating composition to mechanical foaming or defoaming, wherein the <BR> (ICU : CItIS}17 ? \'LII'C'. 7rll'1' C11) l'IQ17 t'. lil, ? C0'1C17'lOllCCI fi0 rlIlI0I11C tl'LIaS including carboxyl group or sulfonate group, or cationic groups including a tertiary amine group : (b) impregnating the aqueous polyurethane dispersion composition into a substrate including a woven or nonwoven fabric : (c) coating the substrate obtained in step (b) with the aqueous polyurethane dispersion composition foamed or defoamed in step (a) : (d) coagulating the coated substrate with a coagulating solution selected from the group consisting of an aqueous solution of various salts, a mixed solution of salt and acid, a mixed solution of salt and base, a mixed solution of acid and base. and mixtures thereof; and (e) subjecting the coagulated substrate to a posttreatment including washing. |
BACKGROUND ART Genet-ally synthetic leathers are prepared from a polyurethane, which is excellent in chemical and physicla properties. inter alia, chemical resistance and softness.
U.S. Patent No. 3.208.875 discloses a method for preparing a synthetic leather internally provided with numerous closed cells and having a coagulated surface layer, ill which a solution of polyurethane in an orgnaic solvent is coated on a nonwoven fabric and the polyurethane-coated nonwoven fabric is the passed through a coagulation bath normally containing water as coagulating solution compatible with
the organic solvent used to dissolve the polyurethane but incompatible with the <BR> <BR> 7plPlt1'C1r111t'.. lt) lllr tlC () t'r1111C 0't'. 17t 111 : 1IC1 Itl 1'SOLIIOII CC) rllll tfl W<BR> <BR> CllZLIC'. C 1110 7 C1lLlltlll SOI111011 0 tlC : Ct) rl, ! llllf1011 7rll. IA11S 111 : tlOC. 10VW'I'. useses an excess of an organic solvent that is relatively toxic and has a high boiling point to cause environmental pollution.
To solve this problem a growing interest has been taken in the methods for preparing a synthetic leather using an aqueous polyurethane dispersions.
U. S. Patent No. 4. 171.391 discloses a method for preparing a synthetic leather using an aqueous plyurethane dispersions. This method is. however, undesirable since it has limit on controlling the structure of cells (e.g., size and density of cells) and utilises acetic acid as a coagulating solution whose unique spicy odor is not easy to remove but has to be separately removed from the final product. Moreover, the method takes too much timwe in coagulation that the productivity may be deteriorated.
Another method for preparing a synthetic leather with reduced complexity of the process, especially, reduced time for coagulation is disclosed in U.S. Patent No.
4.332,710, characterized by using a heat-coagulating agent tha tgenertates an acid by heat to promote coagulation. This method is disadvantageous in that the use of the heat-coagulating agent detyeriorates the storage stability of aqueous polyurethane dispersions U. S. Pathent No. 5.460.873 discloses still another method for preparing Lisynthetic leather using a physical foaming machine to cause production of cells under mechanical stirring at high speed. This method. however, involves some problems in that the opoen cells cover thew surface of the product. such product being inadequate for use as a synthetic leather due to its coarse surface, and that the conventional process of manufacturing the synthetic leather is unusable since the
method requires a separate drying faciiity.
Accordingly, there is still a need of a novel method for preparing a synthetic leather environment-friendly and excellent in propoerties and productivity.
DISCLOSURE OF THE INVENTION It is an object of the present invention to provide a aqueous polyurethane dispersion composition suitable for a synthetic leather.
It is another object of the present invention to provide a method for preparing a synthetic leather of good properties which is internally provided with numerous closed cells and almost destitute of opoen cells on the surface.
It is still another object of the present invention to provide a method for preparing a synthetic leather internally provided with cells of which the size, shape and distribution are controllable depending on the condition of the coagulation bath containing cdoagulation solution.
To achieve the objects of the present invention, there is provided an aqueous polyurethane dispersion composition for a synthetic leather, comprising: 100 parts by weight of an aqueous polyurethane dispersion, of which the main chain is covalently bonded to anionic groups including a carboxyl group or a sulfonate group, or cationic groups including a tertiuary amine group ; 0.1 to 5 parts by weight of a water repellant; owl to to 8 parts by weight of an emulsifier; 0.1 to 1 part by weight of an antifoamer; and 0.1 to 5 paorts by weight of an inorganic filler. in another aspect of the present in vention. there is provided aqueous polyurethane-based synthetic leather that is obtained by impregnating the composition comprising 100 parts by weight of an aqueous polyurethane dispersion.
0.1 to 5 parts by weight of a water repellant. 0.1 to 8 parts by weight of an emulsifier, 0. l to 1 part by weight of an antifoamer, and 0.1 to 5 parts by weight of an inorganic <BR> <BR> I (', I' 1I1t0 l ll3Stt'elt.'. riI7C/ (I' CUlilil,'7C', C (C'. (C7eiI21C'. C l7I' (lllll ( : C COI71701i1 () II OIl i7L substrate, and then coagulating the impregnated and/or coated substrate with a coagulating solution, wherein the aqueous polyurthane dispersion is obtained by dispersing a polyurethane in water of which the main chain is covalently bonded to anionic groups including carboxyl group or sulfonate group. or cationic groups including a tertiary7 amine group. Wherein the coagulation solution is selected from the group consisting of an aqueous solution of various salts, a mixed solution of salf and acid, a mixed solution of salt and base, a miuxed solution of acid and base, and mixtures thereof.
In further another aspect of the present ivvention. there is provided a method for preparing a synthetic leather from an aqueous polyurethane dispersions. <BR> <BR> <P>C01171'1111 1 : C ( ? S 0 : Cl) EIjrll'1114 tll CU111OS11C) 17 CO1711'15111 (U Lll' b" weight of an aqueous polyurethane dispersions, 0.1 to 5 parts by weight of a water repellent. 0. 1 to 8 parts by weight of an emulsifier. 0. 1 to 1 part by weight of an antifoamer. and 0.1 to 5 parts by weight of an inorganic filler, and subjecting the composition to mechanical foaming or defoaming, wherein aqueous polyurethane dispersions of which the main chain is covalently bonded to anionic groups including carboxyl group or sulfonate group, or cationic groups including a tertiary amine group; (b) impregnating the aqueous polyurethane dispersion composition into a substrate including a woven or nonwoven fabric; (c) coating the substrate obtained in step (b) with the foamed or defoamed composition in step (a); (d) coagulating the substrate obtained in step(c) with a coagulating solution selected from the group
consisting of an aqueous solution of various salts, a mixed solution of salt and acid, a mixed solution of salt and base, a mixed solution of acide and base, and mixtures <BR> Ilt'. l' : 0 ; f111C (G Lll, jt'C111 !..', Il CpBflllCj SLISfI'rlt t ( il 7 () 5-il'r1111C17 lllCLlC117r washing, and drying, etc.
BRIEF DESCRIPTION OF DRAWINGS Figures 1 to 19 present microscopic photograpohs showing enlarged cross sections of the synthetic leathers prepared in accordance with Examples 1 to 19 of the present invention.
BEST MODE FOR CARRYING OUT THE INVENTION An aqueous polyurethane dispersion composition for synthetic leather <BR> ZCCO1'C117 Lr7 17L t' ; C111 ll7\t'111017 : 011'1 ? I'ISC ; S n ali'S !' \c'1c411 U 111 lCllQllS polyurethane dispersion of which the main chain is covalentloy bonded to ainonic groups including carboxyl group of sulfonate group. or cationic groups including a tertiary amine group : 0.1 to 5 parts by weight of a water repellant; 0.1 to 8 parts by weight of an emulsifier; 0.1 to 1 part by weight of an antifoamer : and 0. 1 to 5 parts by weight of an inorganic filler.
An aqueous polyurethane-based synthetic leather according to the poresent invention is prepared by impregnating a substrate with a composition comprising parts by weight of the aqueous polyurehane dispersion of which the main chain is covalently bonded to anionic group sincluding carboxyl group or sulfonale group, or cationic groups including a tertiary amine group, 0.1 to 5 parts by weigtht of a water repellant, 0. to 8 parts by weight of an emulsifier. 0.1 to 1 part by weigtht of an
antifoamer. and 0.1 to 5 parts by weight of an inorganic filler, coating the foamed or <BR> <BR> <BR> <BR> <BR> t. Qr111l1, C CbIllCISILIClII OI , a : SLSISl'lC. VSlC Cpeiia. lil 11 ('. Ct) lCj SUlWl'lte ; Vll a coagulating solution selected from the group consisting of an aqueous solution of various salts. a mixed solution of salt and acid. a mixed solution of salt and base, a mixed sotution of acid and base. and mixtures thereof.
The anionic or cartionic polyurethane dispersion is an aqueous polyurethane dispersion of which the main chain is covalently bonded to anionic groups including carboy) group or sulfonate group. or cationic groups including a tertiary amine group, as disclosed in U.S. Patent Nos. 2.968.575 and 4.171.391 that are incorporated herein by reference. That is. the aqueous polyurethane dispersion is obtained by a method in which an aqueous dispersion type polyisocyanate including an ionic charged group to allô\ self-emulsification is prepared by the condensation reaction between isocyanate. diol. polyol. and ionic chain extender. dispersed in water. and <BR> <BR> <BR> <BR> <BR> L11C11 1.) C ; C : i : Ct U j'111C'. 1'1Z1L1C) tl 1LC110I1 L1S111, ? 1 la0y°Ml1"lS4ll trSJ C111S41 O\tilC : 1'. 1 isocyanate as used in preparation of the polyisocyanate includes aromatic or aliphatic diisocyanates and a mixture thereof. Specifically, the isocyanate is selected from the group consisting of tolylene-2,4-diisocyanate, tolylene-2,6-diisocyanate. meta- phenylene diisocyanate. biphenylene-4,4'-diisocyanate. methylenebis(4-phenyl diisocyanate), 4-chloro-1,3-phenylene diisocyanate. naphthalene-1.5- diisocyanate, tetramethylene-1.4- diisocyanate, hexamethylene 1,6- diisocyanate, decamethylene- 1.10- diisocyanate. cyclohexylene-1,4- diisocyanate. methylenebis(4-cyclohexyl isocyanate)), tetrahydronaphthylene diisocyannate. isophoron diisocyanate. 4. <BR> <BR> <BR> <BR> <BR> methylenebis(cyclohexyl isocyanate) and mixtures thereof. The isocyanate is preferably hexamethylene-1.6-diisocyanate. isophoron diisocyanate, cyclohexylene
1.4-diisocyanate. or 4. 4'-methy) enebis (cyciohexyi isocyanate).
Examples of the polyol as used in preparation of the polyisocyanate include a polyester polyol or a polyether polyol. The polyester polyol is usually obtained by condensation reaction between a dicarboxylic acid compound and a diol compound.
Examples of the dicarboxylic acid compound as used herein include succinic acid. glutaric acid, adipic acid, suberic acid, azelanic acid, sebacic acid, dodecane dicarboxylic acid. hexahydrophthalic acid, isophthalic acid, terephthalic acid. ortho- phthahe acid. tetrachlorophthalic acid, 1.5-naphthalene dicarboxylic acid. fumaric acid, maleic acid, itaconic acid. citraconic acid, mesaconic acid, and tetrahydrophthalic acid. Examples of the diol compound as used herein include ethyleneglycol. propyleneglycol. 1,3-propanediol. 1,3-butanediol. 1,4-butanediol. 1.5- pentanediol. 1.6-hexanediol. neopentylglycol. diethyleneglycol. dipropyleneglycol. triethyleneglycol. tetraethyleneglycol. dibutyleneglycol. 2-methyl-1.3-pentanediol.
2.2.4-trimethyl-1,3-pentanediol. and 1.4-cyclohexanedimethanol. The customary example of the suitable polyether polyol include polyethyleneglycol. polypropyleneglycol. and polytetramethyleneglycol. The molecular weight of the polvol is in the range from 400 to 10. 000 and preferably from 400 to 3. 000. The ionic chain extender for self-emulsification of the polyisocyanate can be either an anionic cllain extender or a cationic chain extender. The suitable anionic chain extender as used herein is a compound containing a carboxyl group or a sulfonate group. such as 2,4-diamino-5-methylbenzenesulfonic acid and 2.2-dimethylolpropionic acid. The suitable cationic chain extender as used herein is a tertiary amine diol or diamine ilsound, such as methyldiethanolamine. the amount of the ionic chain extender is in the range of 1 to 25 wt.% and preferably 1.5 to 5 wt.% based on the total weight of
the polyurethane. A neutralizing agent is used to convert the anionic or cationic groups covatentty bonded to the main chain of the potyurethanc to a sa) t in order to increase dispersability in water for self-emulsification. Examples of the neutralizing agent for an anionic polyurethane include trimethylamine, triethylamine, triisopropylamine, tributylamine, N,N-dimethylcyclohexyl. N,N-dimethylaniline. N- methylmorphorine. N-methylpiperazine. N-methylpyrrolidine. and n- methylpiperidine. Examples of the neutralizing agent for a cationic polyurethane include acids such as phosphoric acid and acetic acid. The amount of the neutralizing agent is stoichiometrically more than 80% based on the ionic group. the isocyanate and the polyol are reacted with each other at a mole ratio of 1.1:1 to 4:1 to form the polyisocyanate. The polyisocyanate dispersed in water is reacted with a chain extender for post-polymerization. The suitable chain extender as used herin is polyamines. the example of which include hydrazine. ethylenediamine. piperazine. diethylenetriamine. triethylenetetramine, tetraethylenepentamine, pentaethylenehexamine. N,N,N'-tris(2-aminoethyl)amine, N-(2- piperazinoethyl) etlylenediaminc :. N. N'-bis (2-aminoethyl) piperazine. N, N. N'-tris (2- aminoethyt)ethylenediamine. N-[N-(2-aminoethyl)-2-aminoethyl]-N'-(2- aminoethyl)piperazine. N-(2-aminoethyl)-N'-(2-piperazinoethyl)ethylenediamine, N,N-bis(2-aminoethyl)-N-(2-piperazinoethyl)amine. N,N-bis(2- piperazinoethyl)amine, guanidine, melamine. N-(2-aminoethyl)-1,3-propanediamine, 3,3'-diaminobenzidine. 2,4,6-triaminopyridine, dipropylenetriamine, tetrapropylenepentamine. tripropylenetetramien, N.N-bis(6-aminohexyl)amine. N,N'- <BR> <BR> <BR> bis(3-aminopropyl)ethylenediamine, 2,4-bis(4'-aminobenzyl)aniline. 1,4-<BR> <BR> <BR> <BR> <BR> <BR> butanediamine. 1,6-hexanediamine, 1.8-octanediamine. 1,10-decanediamine. 2-
methylpentamethylenediamine. 1,12-dodecanediamine. isophorondiamine (or 1- amino-3-aminomethyl-3,5,5-trimethyl-cyclohexane), and bis(4- aminocyclohexyl)methane (or bis(aminocyclohexane-4-yl)-methane).
Thus obtained is the aqueous polyurethane dispersion, which has preperably a solid resin content of 20 to 50% and more preferably 20 to 30%. and a particle size of 50 to 200 nm. the aqueous polyurethane dispersions is commerciauy available. fhe aqueous polyurethane dispersion composition for ysnthetic leather preferably has a viscosity of 500 to 5.00 cps and more preferably 1.000 to 3.000 cps for being used as an impregnating composition; or preferably has a viscosity of 5.000 to 15.000 cps and more preferably 5.000 to 10.000 cps for being used as a coating composition. For the control of the viscosity, a thickening agent commercially available. such as as urethane, acryl, or cellulose-based thickening agent The water repellent as used herein is a fluorine compound or a silicon compound. which are commercially available as well known to those skilled in the art. and the specific example of the water repellent include Zonyl (e.g., 8412TM or RNTM) supplied by Ciba-Geggy Co., Scotch guard (e.g., FC255TM or fc214-230tm) supplied by M Co.. and Frelloll (e. (}. 8070TM or 8787TM) supplied by Dupon Co. The water repellent enhances water repellent property and water resistance and aids formation of tile cells in the synthetic leather thus obtained. If the amount of the water repellent is less than t). 1 part bv weight. the synthetic leather obtained has a significant deterioration of water resistance and water repellent property. An excess of the water repellent more than 5 parts by weight has undesirable effects on the synthetic leather. such as deterioration in mechanical properties. texture and appearance (e.g., greasiness).
The @ emulsifier as used herein is an anionic or non-ionic emulsifier and preferably selected from the group consisting of sodium bis(2- ethylhexyl)sulfosuccinate, sodium laurylsulphate, sodium isopropyl naphthalene sulfonate. sodium bis(tridecyl)sulfosuccinate. n-octadecyldisodium sulfosuccinate. <BR> <BR> <P>OC'17t : 11 (a\I701' ( : 17' ; I10' : I1w1110, l'I171C'tlI1Q11VIQ\V' (011't'. tll'IC''I7t ; 0\yC : tl1e11101. nonylphenoxypoly(ethyleneoxy)ethanol, glyceryltriolate, ethylene glycol ethylene monostearate. sorbitanetriolate. sorbitanetristearate and mixtures thereof. The emulsifier has a function of aiding formation of cells in the coating layer in the preparation of the synthetic leather. If the amount of the emulsifier is less than 0.1 part by weight. the cells in the synthetic leather may crash during the drying step. <BR> <BR> lll E111 t'1Ct'$xD 71.'i'. 117L1si1'l" 11101'C.'lElll c 7M1'1S '\1' 117t. tylt'y"177'lC't'17 : 1' lrlS<BR> <BR> Il : s11l'ce \\ W'1 c L'1'iICV al7t rl Ct'Ll : l'lUl'ellt, l1 D flC 1111t ? 1117111f l : C \1'. 11 thlt synthetic leather being dried.
The antifoamer as used herein is a sihcon-based antifoamer. preferabiy in combination with lipophilic particles (e.g., polyurea) in order to enhance the dispersability and antifoaming characteristic of the silicon oil. An example of the suitable antifoamer is an organically modified polysiloxane. which is comlllercialln available as we)) known to those skilled in the art. The antifoamer prevents the formation such as small crater on the surface of synthetic leather and controls the number and size of the internal cells in the synthetic leather. Less than 0.1 part by weight of the antifoamer deteriorates the antifoaming effect and makes it hard to control the number and size of the cells in the coating layer. whereas an excess of the antifoamer more than 8 parts by weight deteriorates the mechanical properties of the complete synthetic leather and inhibits formation of cells in the synthetic leather. as a
result,of which the softness of the synthetic feather is deteriorated.
'the inorganic filler as used herein is a commercially available inorgaic filler. the example of which is a powder of modified silica. litanium oxide, alumina, ferric oxide, calcium oxide or magnesium oxide with an average diameter of around 1 µm. and mixtures thereof. An amount of the inorganic filler less than 0.1 part by weight deteriorates the abrasion resistance and prevents formation of cells in the coating layer, whereas an excess of the inorganic filler greater than 5 parts by weight deteriorates the softness of the synthetic leather.
The aqueous polyurethane resin composition according to the present invention as obtained by mixing additives including water-repellent, emulsifier, antifoamer and inorganic filler with an acueous polyurethane dispersion is impregnated into a substrate. mechanically foamed or defoamed and then coated on the substrate. Subsequently. the coated substrate is coagualted with a coagulating solution, which is selected from the group consisting of an aqueous solution of various salts, a mixed solution of salt and acid, a mixed solution of salt and base, a mixed solution of acid and base, and mixtures thereof.
The mechanical foaming step is effected with a known stirring machine called "mechanical stirrer". The defoaming step is also effected with a commercially available pressure container operating under vacuum. The mechanical stirrer and the pressure container are both well known to those skilled in the art.
The impregnation prior to the coating step and the coating of the aqueous polyurethane dispersion compsition on the substrate are achieved by a known method such as dipping or glazing coating (e.g., embossing coating), which is well known to those skilled in the art.
The coagulating solution as used herein is preferably selected for the group consisting of an aqueous solution of varius salts, a mixed solution of salt and acid, a mixed solution of salt and base, a mixed solution of acid and base. and mixtures thereof. Examples of the salts contained in the aqueous solution of salts as a coagulating oslution include: (a) all general salts including sodium chloride (NaCl), silver chloride (AgCl), silver bromide (AgBr), silver iodide (Agl), silver chromate (AgCrO4), barium carbonate (BaCO3), barium fluoride (BaF2), calcium carbonate (CaCO3), mercury chloride (PbCl2), magnesium carbonate (MgCO3), lead chloride (PbCl2), silver nitrate (AgNO3), copper sulfate (CuSO4), copper chloride (CuCl2), and Icacl sulfate (PbSO4); (b) sodium chloride, potassium chloride, calcium chloride, sodium sulfate and calcium sulfate, which are obtained by neutralization between a acid acid (e. g., hydrochloric acid, sulfuric acid, phosphoric acid, nitric acid, hydrogen bromide, hydrogen iodide, nitrous acid, hypochlorous acid, etc.) and a strong base (e.g., sodium hydroxide, potassium hydroxide, calcium hydroxide. magnesium hydroxide, ammonia, etc.): (c) ammonium chloride, ammonium sulfate, ammonium bromide and sodium carbonate, which are obtained by neutralization between a strong acid as defined above and a weak base including almost all water soluble amines : (d) CH3COONa, CH3CH2COONa, CH3 COOK and C, H5Na, which are obtained by neutralization between a strong base as defined above and a weak acid (e.g., fluoric acid, hydrogen sulfide, carbonic acid, sodium carbonate, carboxylic acids such as CH3COOH and CH3CH2COOH; and (e) CH3COONH4 and CH3CH2COONH1, which are obtained by neutralization between a weak acid and a weak base as defined above. The coagulating solution may have a pH value variable depending on the type and amount of the salt used therein and preferably controlled
in tile range from 3 to I 1. The pH value of the coagulating solution can be controlled by adding an acid or base to the aqeous solution of the salt. or regulating the equivalent weight of the acid and base used in the preparation of the aqueous solution of the satt.
The temperature of the coagulating solution in the coagulation bath is preferably in the range of 10 to 50 °C.
Following the coagulation step. the substrate is subjected to a post-treatment including washing, drying, embossing, buffing and weight reducing to produce the complete synthetic leather, the post-treatment method being well known to those skilled in the art.
The method for preparing a synthetic leather from an aqueous polyurethane dispersion according to the present invention includes the steps of: (a) preparing a coating osition comprisin@ g 100 parts by weight of an aqueous polyurethane dispersion. 0. l to si parts by weight of a water repellent, 0.1 to 8 parts by weight of an emulsifier, 0.1 to 1 part by weight of an antifoamer, and 0.1 to 5 parts by weight of an inorganic filler, and subjecting the coating composition to mechanical foaming or deforaming, wherein aqueous polyurethane dispersion is covalentlybonded to anionic groups including carboxyl group or sulfonate group, or cationic groups including a tertiary amine group; (b)impregnating the aqueouspolyurethane dispersion composition into a substrate including a woven or nonwoven fabric; (c) coating the substrate obtained in step (b) with the polyurethane dispersion foamed or defoamed in <BR> <BR> step (a); (d) coagulating the coated substrate with a coagulating solution selected<BR> <BR> fro the the group consisting of an aqueous solution of various salts, a mixed slution of salt and acid, a mixed solution of salt and base, a mixed solution of acid and base, and
mixtures thereof', and (e) subjecting the coagulated substrate to a post-treatment including washing, and drying, etc.
In the step (a) of preparing the coating composition, the above-described <BR> <BR> lCllh : l) lIS a01)'LI1'1111N. CIS ? I'Slt) 11 IS 11'll\C : C Vrll riCCjIIVC SLIC7 W V'c ('I' I'h'. 71 : (11. emulsifier, antifoamer and inorganic filler and the mixture is subjected to a mechanical foaming of defoaming step. The foamed or defoamed coating <BR> <BR> C0117QS11C11 1S y7 ? I1C t0 tllC : Sll ? tl'1 1C17 1111111ClafiC : yr ltll'S2J) 7) V i llpWl1 coating method and passed through a coagulation bath containing the coagulating solution in the subsequent coagulation step, allowing the polyurethane dispersion to bee coagulated into a synthetic leather. The thickness of the coating is in the range of <BR> <BR> C). ' () i 117117. I 1 llCsll ('S C) 17 (.' Ce1t1I7, 1S CSS t2ct7 . tI2Il7. '1C.'lc'itlI'tl'C'_1'O the synthetic leather is too thin to provide the properties peculiar to the leather. On the <BR> <BR> Olf.'1'7illlt. 1P. llClllt'SS 0 : 011111, 1 41''. e11L1' 1r111 J 1111 CCll01z1tC f'. I"071 : I'115 t the synthetic leather.
In the step (b) of preparing the substrate, the aqueous polyurethane dispersion is mixed with additives such as water repellentk, emulsifier, antifoamer and inorganci filler, and the mixture is thickened with a thickening agent to have a viscosity of 500 to 5,000 cps and preferaby 1,000 to 3,000 cps. The mixture is then impregnated into a woven or nonwoven fabric, which is applied to the subsequent coating step. The impregnation rate is in the range of 5 to 90% and preferably 5 to 50% based on the tot weight of the woven or nonwoven fabric. An impregnation rate of less than 5% deteriorates the mechnaical properties of the synthetic leather including tensile <BR> <BR> SI'Cllll U111 tlt'tlSlf) Il I'ltrlllt'. 11C1'15 t111 1117a1' ! 1111U11 I'llC : l\CCIClll4 t) Ci> deteriorates the softness of the synthetic leather,
According to the present invention, the coagulation step (d) controls the shape, size and density of cells eepending on the type, pH value and concentration of the aqueous solution of the salt to prevent formation such as small craters on the surface. which allows production of a synthetic leather with good properties such as coating property.
The coagulating solution can be an aqueous solution of any general salt including silver chlorider, silver bromide, silver iodide, silver chromate, barium carbonate, barium fluoride, calcium carbonate, mercury chloride, magnesium carbonate, lead chloride, silver nitrate, copper sulfate. copper chloride and lead sulfate. l coagulating solution can also be an aqueous solution of salts including sodium chloride, potassium chloride, calcium chloride, sodium sulfate and calcium sulfate, which are obtained by neutralization between a strong acid (e.g., hydrochloric acid. sulfuric acid, phosphoric acid, nitric acid hydrogen bromide, hydrogen iodide, nitrous acid, hypochlorous acid, etc.) and a strong base (e. g.- sodium hydroxide. potassium hydroxide, calcium hydroxide, magnesium hydroxide, ammonia, etc.), The coagulating solution can also be an aqueous solution os salts including ammonium chloride, ammonium sulftate, ammonium bromide and sodium carbonate, which are obtained by neutrazliation between a strong acid (e.g., hydrochloric acid, sulfuric acid. phosphoric acid, nitric acid, hydrogen bromide, hydrogen iodide, nitrous acid, hypochlorous acid, etc) and a weak base including almost all water soluble amines.
The coagulating solution can also be an aqueous solution of salts including CH3COONa, CH3CH2COONa, CH3COOK and C6H5Na, which are obtained by
neutratixation between a strong base (e.g., sodium hydroxide, potassium hydroxide. calcium hydroxide, magnesium hydroxide, ammonia,etc.) and a weak acid (e.g., fluoric acid, hydrogen sulfide, carbonic acid, sodium carbonate, carboxylic acids such as CH3COOH and CH3CH2COOH.
The coagulating solution can also be an aqueous solution of salts including CH3COONH4 and CH3CH2COONH4, which are obtained by neutralization between a weak acid (e.g., fluoric acid, hydrogen sulfide, carbonic acid. sodium carbonate. carboxylic acids such as CH3COOH and CH3CH2COOH and a weak base including almost all water soluble amines.
Besides, the coagulating solution can be a mixed aqueous solution obtained by adding an acid or base to the aqueous solution of the salt, or regulating the equivalent weight of the acid and base used in the preparation of the aqueous solution of the salt.
In the coagulation step (d), the salt content in the coagulation solution is preferably in the range of 5 to 50 wt.% and more preferably in the range of 20 to 40 wt.% ofo The salt content of less than 5 wt.% causs the cells crashedduring the drying step. whereas the salt conent of greater than 50 wt.% involves a problem in the washing step. In controlling the pH value of the coagulating solution with an addition of an acid or base to the aqueous solution of the sail. the pH vaiue is preferabfy in the range of 3 to 11 and moe preferably in the range of 4 to 10. For example. the pH value of the coagulating solution is in the range of 3 to 7 for an ainionic plyurehane dispersion and 7 to 11 for a catinoinic polyurehtnae dispoersion. IF the pH value of the coagulation solution is less than 3 for the anionic polyurethane dispersion or greater than 11 for the catinoic polyurethane dispersion, the cells are scarely formed in the synthetic leather.
Hereinafter. the present invention will be described in detail by way of the following examples, which are not intended to limit the scopeof the present invention.
Example 1 A coating composition and an impregnating composition were prepared at the composition ratio shown in Tables 1 and 2.
Table l Material parts by wight Aqueouspolyurehane dispersion 100 Thickening agent 3 (Acrysol RM-825 from Rohm & Hass Inc.) Antifoamer 0.3 (BYKI-022 from BYK-chemy Inc.0 Inorganic filler 0.15 (Nipsi E-170 from Nippon Silica Inc.) Waterrepellent 3 (Neosilk SDB from Dadedong Inc.0 Emulsifler 0.2 (ammoniumstearate)
*Aqueous plyurethane dispersion is available from nanopol Inc., in Korea by the trade name NPL-5000(solid contents 25% by weight, ion contents 3.5%/solid by weight, anionic polyurethne emulsion).
Table 2 Material Parts by weight Aqueous polyurethane dispersion 100 Thickening agent 0.2 (Acrysol RM-825 from Rohm & Hass Inc.) Antifomaer 0.2 9BK-024 from BYK-chemy Inc.) Inorganicfiller 0.05 (Nipsil E-170 from Nippon Silica Inc.) Water repellent 5 (Neosilk SDB from daedong Inc.) Emulsilfer 0.1 (ammonium stearate)
*aqeuous polyurethane dispersion is available from Nanopol Inc., in Korea byy the trade name NPL-5200(solid contents 25% by weigt, ion contents 1.8%/solid by weignht, anionic polyurehane emulsion).
Thehe coating composition prepared according to Table 1 was defoamed with a pressure container and coated on a nonwoven Fabric which was previousty dipped in the impregnating composition as prepared according to Table 2. using a glazing coating for an embossing process. The coated nonwoven fabric was immersed in a cogaulation bath containing a coagulating solution for 5 minutes. Here, the coagulating solution was obtained by adding ammonia (NH3) to 30 wt.% of an aqeuous solution of phosphoric acid and controlld to have a pH value of 4. Removed from the coagulation bath, the coated nonwoven fabric was washed and dried to obtain a synthetic leather.
FIG. 1 presents a microscopic photograph showing an enlarged cross section of the synthetic leather. As i saparent from FIG. 1, numerous closed cells are uniformly
provided in the synthetic leather and the surface of the synthetic leather become smooth.
Example 2 A coating composition was prepared at the composition ratio shown in Table 3 Table 3 Material Parts by weight Aqueous polyurethan e dispersion 100 Thickening agent 3 (Acrysol RM-825 from Rohm & Hass Inc.) Antifomaer 0.1 (BYK-022 from BYK-chemy Inc.) Inorganic filler 0.15 (Nipsil HD from Nippon Silica Inc.) Water repellent 3 CVersill3 from Daedong Inc.) Emnlsifier 0. 2 (ammoniumstearate)
*Aqeuous polyurethane dispersion is available from Nanopol Inc., in Korea by the trade name NPL-5100)solid contents 25% by weight, ion contentw 2.5%/solid by weight, anionic polyurethane emulsion).
The coating composition prepared according to table 3 was foamed with a foamer to have uniform open cells and coated on a nonwoven fabric which was dipped in the impregnating composition prepared in Example 1. The coated nonwoven fabric was immersed in a coagulation bath containing a coagulating solution for 5 minutes. Here, the coagulating solution was obtained by adding
ammonia (NH3) to 30 wt.% of an aqueous solution of phosphoric acid and controlled to have a pH value of 4. Removed from the coagulation bath, the coated nonwoven fabric was washed and dried to obtain a synthetic leather, FIG. 2 presents a microscopic photograph showing an enlarged cross section of the synthetic leather. As is apparent from FIG. 2, numerous closed cells are uniformly provided in the synthetic leather and the surface of the synthetic leather become smooth.
Examp) e 3 AnAn impregnating composition was prepared at the composition ratio shown in Table 4.
Table 4 Material Parts by weight Aqueous polyurethane dispersion 100 Illc,) (Acrysol RM-825 from Rohm & Hass Inc.) Antifoamer 0.2 (BYK-022 from BYK-chemy Inc.) Inorganic filler 0.15 (Nipsil HD from Nippon Silica Inc.) Water repellent 5 (Versill @ from Daedong Inc.) Emulsifier 0.2 (ammonium stearate) * Aqueous polyurethane dispersion is available from Nanopol Inc., in Korea by the trade name NPL-5300(solid contents 25% by weight. ion contents 2%/solid by weight, anionic polyurethane emulsion.
The impregnating composition prepared according to Table 4 was <BR> <BR> <BR> <BR> <BR> <BR> 1177)pI'C,'. ! IlrltCC IIltO l Sll () I1'lllll :I11011V0'C : Il ll'IC j'01'SLICtC'.-l « : '111 : tIC ICalli'. l- WllOll a coating step. and the impregnated nonwoven fabric was heated and passed between pressure rollers to provide an impregnation rate of 45% with respect to the nonwoven fabric. The impregnated nonwoven fabric was immersed in a coagulation bath containing a coagulating solution for 5 minutes. Here, the coagulating solution was obtained by adding ammonia (NH3) to 30 wt.% of an aqueous solution of phosphoric acid and controlled to have a pH value of 4. Removed from the coagulation bath, the coated nonwoven fabric was washed and dried to obtain a synthetic leather. FIG. 3 presents a microscopic photograph showing an enlarged cross section of the synthetic leather. As is apparent from FIG. 3. the polyurethane resin is uniformed distributed over the nonwoven fabric other than the surface and has a space from the fiber unit to <BR> <BR> <BR> <BR> <BR> ) 1'C) VICI LIIICiC'11 SOrLllc : S E117C lI111C'SS LO 1 LICt',-11 « W'17L1c'LIC t', ililll' 01'SLICC.<BR> <BR> <BR> <BR> <BR> <BR> <BR> <BR> lLsaml)4 The procedures were performed to obtain a synthetic leather in the same manner as described in Example I excepting that 10 wt.% of an aqueous solution of sodium chloride was used as a coagulating solution. FIG. 4 presents a microscopic photograph showing an cnlarged cross section of the synthetic leather. As shown in FIG. 4 the use of sodium chloride in the coagulating solution caused an increase in formation of the cell-frce region.
Exampfc 5 The procedures were performed to obtain a synthetic leather in the same manner as described in Example 1 excepting that 20 wt.% of an aqueous solution of sodium chloride was used as a coagulating solution. FIG. 5 presents a microscopic photograph showing an enlarged corss section of the synthetic leather. As shown in FIG. 5, an increased concentration of the aqueous sodium chloride solution used as a coagulating solution caused an increase in formation of the cell-free region.
Example 6 A coating composition and an impregnating composition were prepared at the composition ratio shown in Tables 5 and 6.
T, i b I e Material parts by weight Aqueous polyurethane dispersion 100 Thickening agent 3 (Aerysol RM-825 from Rohm & Hass Inc.0 Antifoamer 0.3 (BYK-022 from BYK-chemy Inc.) Inorganic filler 0.15 (Nipsil E-170 from Nippon Silican Inc.) Water repellent 3 (Neosilk SDB from Daedong Inc.)
* Aqueous polyurethane dispersion is a cationic polyurethane emulsion having solid contents 25% by weight and ion contents 10%/solid by weight.
Table 6 Material parts by weight Aqueouspolyurethane dispersion* 100 Thickening agent 0.2 (Acrysol RM-825 from Rohm & Hass Inc.) Antifoamer 0.2 (BYK-024 from BYK-chemy Inc.) Inorganic filler 0.05 (Nipsil E-170 from Nippon Silica Inc.) Water repellent 5 (Neosilk SDB from Daedong Inc.)
* Aqueous polyurethane dispersion is a cationic polyurethane emulsion having solid contents 25% by weight and ion contents 10%/solid by weight.
The coating composition prepared according to Table 5 was defoamed with a defoamer and coated on a nonwoven fabric which was previously dipped in the impregnating composition as prepared according to Table 6, using a glazing coating for an embossing process. The coated nonwoven fabric was immersed in a coagulation bath containing a coagulating solution for 5 minutes, Here, the coagulating solution was obtained by mixing a 20% aqueous mixed solution of nitric acid with potassium hydroxide at the mole ratio of 1:1. Removed from the coagulation bath. the coated nonwoven fabric was washed and dried to obtain a synthetic leather. FIG. 6 presents a microscopic photograph showing an chlarged cross section of the synthetic leather. As is apparent from FIG. 6, the cationic polyurethane resin emulsion is also coagulated by the action of salt to produce the synthetic leather.
Example 7 The procedures were performed to obtain a synthetic) leather in the same manner as described in Example 6 excepting that a 30% aqueous mixed solution of nitric acid and potassium hydroxide at the mole ratio of 1:1 was used as a coagulating solution. F ! G. 7 presents a microscopic photograph showing an enlarged cross section off the synthetic leather. As shown in FIG. 7, an increased concentration of the aqueous solution of the salt reduced the number of porous cells to almost zero.
Example 8 The procedures were performed to obtain a synthetic leather in the same manner as described in Example 1 excepting that a 20% aqueous mixed solution of nitric acid and ammonia at the mole ratio of 1:1 was used as a coagulating solution.
FIG. 8 presents a microscopic phtograph showing an enlarged cross section of the synthetic leather, As shown in FIG. 8. the cells had a more apparent cylindrical form relative to those of Example 1, That is. the shape of the cells can be varicd depending on the type of the salt used in the coagulating solution.
Example 9 The procedures were performed to obtain a synthetic leather in the same manner as described in Example 1 excepting that a 30% aqueous mixed solution of nitric acid and ammonia at the mole ratio of 1:1 was used as a coagulating solution.
FIG. 9 presents a microscopic phtograph showing an enlarged cross section of the synthetic leather. As shown in FIG. 9, an increased content of the salt in the coagulation solution allowed a production of the cell-free synthetic leather. This demonstrates that the content of the salt is an important factor in controlling the shap3 of the cet) s.
Example 10 The procedures were performed to obtain a synthetic leather in the same manner as described in Example 1 excepting that a 20% aqueous mixed solution of phosphoric acid and potassium hydroxide at the mole ratio of 1:1 was used as a coagulating solution. FIG. 10 presents a microscopic photograph showing an enlarged cross section of the synthetic leather, Compared to Example t. this exampte used potassium hydroxide as a base in phosphoric acid instead of ammonia and showed that the shape of the cells can be varied depending on the type of the salt. The use of potassium hydroxide entirely reduced the uniformity of the cells but increased the sizc oi'tllc cells.
Example 11 The procedures were performed to obtain a synthetic leather in the same manner as described in Example 1 excepting that a 30% aqueous mixed solution of phsophoric acid and potassium hydroxide at the mole ratio of 1 : 1 was used as a coagulating solution. FIG. 11 presents a microscopic photograph showing an enlarged cross section of the synthetic leather, As shown in FIG. 11, an increased content of the sa) t in the coagulating solution caused an increase in formation of the ceH-free region.
Example 12 The procedures were performed to obtain a synthetic leather in the same manner as described in Example 1 excepting that a 20% aqueous mixed solution of phosphoric acid and tributylamine at the mole ratio of 1:1 was used as a coagulating solution. FIG. 12 presents a microscopic photograph showing an enlarged cross section of the synthetic leather. Compared to Example 1, this example used
tributylamine as a base in phosphoric acid instead of ammonia and showed that the shape of the cells can be varied depending on the type of the salt. The use of tribulylmoine entirety reduced the uniformity of the cells but increased the size of the <BR> <BR> cel Is.<BR> <BR> <P> Ewmple 13 'the procedures were performed to obtain a synthetic leather in the same manner as described in Example 1 excepting that a 30% aqueous mixed solution of phosphoric acid and tributylamine at the mole ratio of 1:1 was used as a coagulating solution. FIG. 13 presents a microscopic photograph showing an enlarged cross section of the synthetic leather. As shown in FIG. 13, an increased content of the salt in the coagulating solution caused an increase in formation of a cell-free region and reduced the thickness of the surface coating.
Example t4 The procedures were performed to obtain a synthetic leather in the same manner as described in Example 1 excepting that 10 wt.% of an aqueous sodium chloride solution was mixed with 30 wt.% of aqueous phosphoric acid solution to provide a coagulating solution having a controlled pH value of 5. FIG. 14 presents a microscopic photograph showing an enlarged cross section of the synthetic leather.
Example 1t The procedures were performed to obtain a synthetic leather in the same manner as descirbed in Example 1 excepting that 20 wt.% of an aqueous sodium chloride solution was mixed with 30 wt.% of aqueous phosphoric acid solution to provide a coagulating solution having a controlled pH value of 5, FIG. 15 presents a liiicl.oscopic photograph showing an enlarged cross section of the synthetic leather. In
regard to Examples 14 and 15, a decreased pH value of the coagulating solution, i.e., acidification caused an increase in formation of the cell-free synthetic leather.
Example t6 The procedures were performed to obtain a synthetic leather in the smae manner as described in Exmple 1 excepting that 10 wt.% of an aqueous sodium chloride solution was mixed with 30 wt.% of aqueous potassium hydroxide solution to provide a coagulating solution having a controlled pH value of 10. FIG. 16 presents a microscopic photograph showing an enlarged cross secton of the synthetic leather.
Example 17 The procedures were performed to obtain a synthetic leather in the same manner as described in Example 1 excepting that 20 wt.% of an aqueous sodium chloride solution was mixed withi 30 wt.% of aqueous potassium hydroxide solution to rovide a coagulating solution having a contrlled pH value of 10. FIG. 17 presents a microscopic photograph showing an enlarged cross section of the synthetic leather. In regard to Examples 16 and 17, and increased pH value of the coagulating solution, i.e., alkalization caused a sharp increase in the size of the cells. <BR> <BR> <P> Example 18<BR> <BR> . j7L'l'C : CLlI't VL1' l'. I'01'illf : t C Obe1111 l SV'111EtIC etll'111 lt : Slilll ; manner as described in Example 1 excepting that 20 wt.% of an aqueous phosphoric acid solution was mixed with ammonia to provide a coagulating solution having a controlled pH value of 4, FIG. 18 presens a microscopic photograph showing an enlarged cross section of the synthetic leather.
Example 19 The edures were erformed to obtain a synthetic leather in the same manner as described in Example 1 excepting that 30 wt.% of an aqueous phosphoric acid solution was mixed with ammonia to provide a coagulating solution having a controlled pH value of 4. FIG. 19 presents a microscopic photogrpah showing an enlarged cross section of the synthetic leather. In regard to Examples 18 and 19. the use of a mixed solution of acid and base instead of the solution of salt also provided numerous and uniform cells as in Example 1.
As described in the preceding examples, the present invention provides synthetic leathers prepared in various forms, That is, as shown in FIGS. 1 and 2, the synthetic leather is internally provided with closed cells of which the size and distribution are uniformly controllable, and thus feels smooth with good texture, It is also shown in Fig. 3 that the present invention provides a suede-like synthetic leather with sufficient softness and bulkiness in which thei polyurethane resin is uniformly distributed all over the nonwoven fabric other than the surface layer. As is apparent from FIG. 4 to 1 I. the use of various coagu) ating sotutions anow's a control oF the shape, size and density of cells and thereby effectively provides a synthetic leather of varous qualities. According to these figures, the synthetic leather may have targe- diameter cells with a very low density as wet) as those having a very small size. The density and size of the cells have an effect mainly on the texture and softness of the synthetic leather obtained so that the present invention provides a synthetic leather of various properties and makes it possible toi prepare a synthetic leather of desired properties.
Consequently, the present invention provides a environment-friendly method for preparing a synthetic leather with excellent properties and high productivity, and a <BR> <BR> 5'177C.'1C CEltl'I'r) tlllll : C tlt ; l'ly', jl 111V ('. Illll7 lISC) ) 1'0°1CE5 a lllh'. 111C1C () I' effectively preparing a synthetic leather of various qualities in which the shape, size and density ou'celles are controllable depending on the coagulating solution.
It Is to be noted that like reference numerals denote the same components in <BR> <BR> Il : Cl'rl"lIlS, rlllC rl Ck'. cll2Cl CC'. SCI'l7t1p11 0 (', 11L''I'WV' 110VI1 ILlllCl017 elIlC Stl'IICIII"'0 the present invention will be avoided lest it should obscure the subject matter of the present invention.