WO2014059594A1

WO2014059594A1 - Polyurethane and polyolefin based synthetic leathers having improved embossing characteristics

Info

Publication number: WO2014059594A1
Application number: PCT/CN2012/083017
Authority: WO
Inventors: Weichao GU; Ning Kang; Bo Liu; Yunfei YAN; Chao Zhang; Hongliang Zhang
Original assignee: Dow Global Technologies Llc
Priority date: 2012-10-16
Filing date: 2012-10-16
Publication date: 2014-04-24

Abstract

Disclosed herein are externally stabilized, poromeric, synthetic leathers having improved embossing characteristics that are made from a fabric that is optionally impregnated with a polymer resin, wherein the fabric is coated with a polymerized layer that was made from a frothed mixture comprising polyurethane dispersed in water (PUD), at least one surfactant, a thickener, and at least one polyolefin dispersed in water (POD). Methods of making said synthetic leathers are also disclosed.

Description

POLYURETHANE AND POLYOLEFIN BASED SYNTHETIC LEATHERS HAVING IMPROVED EMBOSSING CHARACTERISTICS

Background of the Invention

Currently, most polyurethane (PU) synthetic leathers are made using organic solvents, such as dimethylforrnarnide, methylethyl ketone (MEK) and toluene. These solvents vaporize during manufacture and post manufacturing, which leads to potential health issues for the manufacturing staff, the end users of the synthetic leather, and the environment. As a result, the European standard for the solvent PU based synthetic leather was changed to require less than 10 ppm DMF in the leather, Making such leathers is a challenge using organic solvent based methodologies. As a result, the use of solvent free or water borne PU (also known as polyurethane dispersion or PUD) has received attention, as it uses little, if any, organic solvent.

PUD is an aqueous emulsion of PU particles in water having high solid content, small particle size, and prolonged stability (up to six months or longer). When making synthetic leather using PUD, the following general method is used: 1) PUD is frothed 2) the frothed PUD is applied to a fabric, 3) the thickness of the frothed PUD is adjusted using methods known in the art, and 4) the now coated fabric is cured to form a synthetic leather having a poromeric layer. See U.S, Patent 7,306,825 for an example of this methodology.

Synthetic leather derived from PUD is similar to that made from PU and an organic solvent. It is breathable, and has good hand-feel. More importantly, the PUD synthetic leather is low in volatile organic compounds. However, some PUD based synthetic leathers, while having nice hand feeling, also have poor embossing characteristics. This is unfortunate, as embossable synthetic leathers are very desirable in the fashion industry. As a result of having poor embossing characteristics (among other reasons), the application of PUD based synthetic leather has been limited.

It would be advantageous to develop a PUD based synthetic leather that had improved embossing characteristics, reduced cost of preparation, or both.

Summary of the Invention

In one aspect, provided herein are synthetic leathers made from PUD comprising, in combination: a fabric that is optionally impregnated with a polymer resin, wherein the fabric is coated with a polymerized layer that was made from a frothed mixture comprising a polyurethane dispersion in a solvent comprising water (PUD), at least one surfactant, at least one thickener, and at least one polyolefin dispersed in a solvent that comprises water (POD).

In a second aspect, disclosed here are PUD based methods of making a poromeric synthetic leather, the methods comprising:

frothing a mixture comprising PUD, at least one polyolefin dispersed in a solvent that comprises water (POD), at least one surfactant, and at least one thickener;

applying the frothed mixture to a fabric that is optionally impregnated with a PU resin, thereby forming a coated fabric;

adjusting the thickness of the frothed PUD on the optionally impregnated fabric; and subjecting the coated fabric to drying conditions.

In a third aspect, disclosed here are PUD based methods of making poromeric leather having improved embossing characteristics, the methods comprising:

combining polyurethane dispersed in water, at least one polyolefin dispersed in water, at least one surfactant and at least one thickener to form a mixture;

frothing the mixture

adjusting the thickness of the frothed PUD on the optionally impregnated, coated fabric; and

subjecting the coated fabric to drying conditions.

In a fourth aspect, disclosed herein are PUD based synthetic leathers made according to the methods of the first, second, and third aspects.

The PUD based synthetic leathers disclosed herein are externally stabilized, i.e., they require the presence of at least one surfactant in the PUD containing mixture.

Likewise, the methods disclosed herein utilize externally stabilized PUDS.

The PUD based synthetic leathers disclosed herein may be used to make synthetic leather for any leather or synthetic leather applications. Particular examples include footwear, handbags, belts, purses, garments, furniture upholstery, automotive upholstery, and gloves.

Description of the Figures

Figure 1 is a picture of the cross section of the Control Sample synthetic leather, pre- embossment.

Figure 2 is a picture of the cross section of the synthetic leather of Sample 1, pre- embossment.

Figure 3 is a picture of the cross section of the synthetic leather of Sample 2, pre- embossment.

Figure 4 is a picture of the cross section of the synthetic leather of Sample 3, pre- embossment.

Figure 5 is a picture of the cross section of the synthetic leather of Sample 4, pre- embossment.

Figure 6 is a picture of the surface pattern of the Control Sample, post-embossment.

Figure 7 is a picture of the surface pattern of Sample 1, post-embossment.

Figure 8 is a picture of the surface pattern of Sample 2, post-embossment.

Figure 9 is a picture of the surface pattern of Sample 3, post-embossment.

Figure 10 is a picture of the surface pattern of Sample 4, post- embossment.

Detailed Description

As described above, in one aspect, disclosed herein are synthetic leathers comprising, in combination:

a fabric that is optionally impregnated with a polymer resin, wherein the fabric is coated with a polymerized layer that was made from a frothed mixture comprising a polyurethane dispersion in water, at least one polyolefin dispersed in water at least one surfactant, and at least a thickener.

In the leathers and methods of making the leathers disclosed herein, the weight percent of the polyolefin (POD) to the polyurethane is 1-50% when calculated using the following formula: (dry wt. of POD/ (dry wt. of POD+ dry wt. of PUD). More preferably, it is 5-40% or more preferably still 8-40%. Most preferably, it is 10-30 weight percent.

Typically, in the leathers and methods of making the leathers disclosed herein, the mixture comprising the PU and Polyolefin contains 0.1 to 99 % by weight PU (excluding the fabric). More preferably, the composition contains 50-95 % by weight PU. Even more preferably, the composition contains 70-90 % by weight PU. The composition also contains 99 to 0.1 % by weight Polyolefin; more preferably 50-5% weight Polyolefin, and still more preferably 30 -10 % by weight Polyolefin.

As used herein, a polyurethane dispersed in water is referred to as a PUD, while a polyolefin dispersed in water is referred to as a POD. When a polyurethane and/or polyolefin is dispersed in water, it is understood that the water optionally further comprises other, additional solvents, such as ketones, Cj-Ce alcohols, ethers, polyethers, DMF, dipropylene glycol dimethyl ether, and NMP. The water may contain one or more than one additional solvent. Preferably, these additional solvents comprise less 10 % by weight, based on the weight of the water and the additional solvent or solvents, More preferably they comprise less than 5% by weight. Still more preferably, it is less than 1% by weight. Most preferably, non-water solvents are not present in POD or PUD. And while deionized and/or distilled water may be used, it is not required. A preferred PUD is Syntegra 3000, which is an externally stabilized, high solid content MDI (methyl diphenyl diisocyanate) based waterborne polyurethane dispersion produced without the use of organic solvents, that is sold by The Dow Chemical Company.

In the leathers and methods of making the leathers disclosed herein, the POD has a solid content of at least 25% by weight. In one embodiment, the POD has a solid content that is at least 30% or more preferably at least 35%. More preferably still, the solid content is at least 40% or 45%.

As is known in the art, T_m is the melting point of the polymer; it is the temperature at which the polymer loses its orderly arrangement. In the leathers and methods disclosed herein, the polyolefin in the POD has a T_m of at least 50 °C. In one embodiment, the T_m is at least 60 °C; in still another, it is at least 70 °C. More preferably, the T_m is at least 80 °C. Still more preferably, it is at least 90 °C, and even more preferably, it is over 100 °C.

Without wishing to be bound to a theory, it is the inventors' belief that incorporating a higher T_m POD, i.e., the T_m is greater than 50 °C, into a synthetic leather increases the ability of the synthetic leather to retain any embossing that is applied to it because the polymer strands in the leather have little mobility when they are at a temperature lower than their T_m. Thus higher T_m PODS are more desirable than lower T_m PODs.

In one embodiment, the leathers and methods of making the leathers disclosed herein contain a POD that was made from a monomer that comprises a C₂-C₁₀ alkylene. Preferably, the monomer makes a polyolefm that comprises a polyethylene. Examples of polyethylenes include low density polyethylene, a polyethylene-polypropylene copolymer, a polyethylene-polypropylene block copolymer, polyethylene-octene copolymer ,

polyethylene-octene block copolymer or a maleic anhydride - polyethylene graft copolymer. In one embodiment, said polyethylene and polyethylene copolymers have a Tm > 80 °C. In another embodiment, the POD further comprises an acrylic acid copolymer. While various acrylic acid copolymers are known in the art, preferred examples include ethylene acrylic acid copolymer and propylene acrylic acid copolymer, with the ethylene copolymer being preferred.

In one embodiment, the polyolefm in the POD is a C₂-Cjo polyolefm and the POD further comprises a C₂-Cio alkylene acrylic acid copolymer.

PODs are made by mixing a polyolefm, a surfactant and water. More specifically, melted polyolefm is mixed into water that contains ethylene acrylic acid copolymer and NaOH or (N,N-dimethylethanolamine (DMEA)), which react to form surfactant like products. The melted polyolefm droplets are then encapsulated by the surfactant like products, which stabilize the droplets in the water.

The leathers and methods of making the leathers disclosed herein, optionally further comprise an additive that is, a filler (such as wood fibers, CaC0₃, Si0₂, and Ti0₂) a flame retardant, a pigment, a flowing additive, hand feel additive, antioxidant, anti-UV additive, antistatic agent, antimicrobial agent, or combinations thereof. Wood fibers also include wood flour. In one embodiment, the leathers and methods require the presence of at least one of the aforementioned additives. The aforementioned fillers, when present, account for 0.1 -80 % by weight of the composition (excluding the fabric). More preferably, when present, the fillings account for 0.1 - 50 % by weight of the composition. Still more preferably, the fillers account of 0.1 - 30 % by weight of the composition. The non-filler additives, i.e., the aforementioned additives, not including the fillers, typically account for 0.01-30 % by weight of the composition. More preferably, the non-filler additives account for 0, 1-20 % by weight of the composition. Still more preferably, the non-filler additives account for 1-10 % by weight of the composition.

Examples of suitable surfactants used in the leathers and methods disclosed herein include, cationic, anionic, or nonionic surfactants. Suitable classes of surfactants include, but are not restricted to, sulfates of ethoxylated phenols such as poly(oxy-l,2-ethanediyl)-a- sulfo-co-(nonylphenoxy) ammonium salt; alkali metal fatty acid salts such as alkali metal oleates and stearates; polyoxyalkylene nonionics such as polyethylene oxide, polypropylene oxide, polybutylene oxide, and copolymers thereof; alcohol alkoxylates; ethoxylated fatty acid esters and alkylphenol ethoxylates; alkali metal lauryl sulfates; amine lauryl sulfates such as triethanolamine lauryl sulfate; quaternary ammonium surfactants; alkali metal alkylbenzene sulfonates such as branched and linear sodium dodecylbenzene sulfonates; amine alkyl benzene sulfonates such as triethanolamine dodecylbenzene sulfonate; anionic and nonionic fluorocarbon surfactants such as fiuorinated alkyl esters and alkali metal perfluoroalkyl sulfonates; organosilicon surfactants such as modified polydimethylsiloxanes; and alkali metal soaps of modified resins. Exemplary preferred surfactants include disodium octadecyl sulfosuccinimate, sodium dodecylbenzene sulfonate, sodium stearate and ammonium stearate.

In some embodiments, the mixture comprising PUD and POD comprises at least two surfactants. It is preferred for one of the surfactants to be amphoteric. Preferably, the amphoteric surfactant is a betaine such as cocamidopropyl betaine. In one embodiment, at least one surfactant is ammonium stearate, disodium octadecyl sulfosuccinimate or cocamidopropyl betaine.

In one preferred embodiment, the mixture that comprises PUD and POD contains at least two surfactants. While different combinations of surfactants may be used, in at least one preferred embodiment, the at least three surfactants are selected from the group consisting of ammonium stearate, disodium octadecyl sulfosuccinimate and

cocamidopropyl betaine.

The surfactant or surfactants are sometimes used as a concentrate in water. Further, the surfactant(s) may be added to the PUD or the PUD may be added to the surfactant(s).

When the PUD and POD containing mixture comprises at least two surfactants, they may be added to the mixture simultaneously or one after the other. Alternatively, the PUD and POD mixture is added to a single surfactant, with the second surfactant being added later, or the PUD mixture is added to a mixture of the surfactants. If desired, more than two surfactants may be used, with three being preferred in at least one embodiment.

In an embodiment, at least one surfactant is ammonium stearate, disodium octadecyl sulfosuccinimate or cocamidopropyl betaine; and the dry weight percent of the POD is 10- 30%, when calculated using the following formula: (dry wt. of POD/ (dry wt. of POD + dry wt. of PUD). As previously mentioned, in one aspect, disclosed herein are methods of making a poromeric synthetic leather comprising:

frothing a mixture comprising PUD, at least one surfactant, and at least one polyolefin dispersed in a solvent the comprises water; and at least one thickener;

In another aspect, disclosed herein are methods of making poromeric leather having improved embossing characteristics, the methods comprising;

frothing the mixture

subjecting the coated fabric to drying conditions.

In one embodiment of the two aforementioned methods, the methods comprise frothing a mixture comprising PUD, POD, ammonium stearate, disodium octadecyl sulfosuccinimate, cocoamidopropyl betaine and an acrylic acid copolymer thickener;

coating an optionally impregnated fabric with the frothed mixture; adjusting the thickness of the frothed mixture on the fabric; and subjecting the coated fabric to drying conditions. In a further embodiment, the solids content of the frothed mixture is between 25 and 60% by weight. More preferably it is between 30 and 60% by weight, 35 and 60% by weight, 40 and 60% by weight, or 45 and 60% by weight. Most preferably, it is between 50 and 55% by weight.

Embossing is well known in the art as a method of producing raised and/or sunken patterns or designs in a material, such as a metal, leather or a synthetic material. Embossing is typically performed by heating a material (although, not always), contacting the material with at least one die, and then applying pressure so that the die presses into the material, for enough time to cause the pattern from the die to be transferred to the material. Pressure may be applied using a hand press, a pneumatic press, or any other method known in the art. If desired, two matching dies may be used, i.e., a male and a female die may be used.

Methods for embossing synthetic leathers are known in the art. Examples include the following. Heating the synthetic leather to 160-220 °C in an oven, and then embossing it using an embossing machine. This is an example of a discontinuous method that is often used in a laboratory setting. Alternatively, in an industrial setting, a continuous process is typically used. In such a process, the leather is heated by an oven or IR heater to aboutl 60- 220 °C, and then embossed using a patterned roller. The 160-220 °C temperature is typical for embossing the synthetic leathers disclosed herein. Of course, higher or lower temperature may be used. But if the temperature is too high, degradation of the synthetic leather will occur. And if the temperature is too low, the pattern embossed onto the synthetic leather will fade or even completely disappear. The ability to select the appropriate embossing temperature is known to those skilled in the art. Suitable embossing pressures can be from O.OlMPa to 20MPa (even higher), but more typically from 0.4 MPa to 5 MPa. The resulting product should keep the pattern on its surface.

In an embodiment of the aforementioned methods, the resulting poromeric, synthetic leather is embossed using methods well known in the art. The embossing pattern may be that of natural leather or any other desired pattern.

Thickeners are well known in the art and any thickener may be used in the leathers and methods disclosed herein. The thickener may be non-associative or associative. It may be a cellulose ether derivative, natural gum alkali swellable emulsion, a clay, an acid derivative, an acid copolymer, a urethane associate thickener (UAT), a polyether urea polyurethane (PEUPU), a polyether polyurethane (PEPU) or a hydrophobically modified ethoxylated urethane (HEUR). One preferred thickener is based on an acrylic acid copolymer, with ethylene acrylic acid copolymer being particularly preferred. Preferably, the thickener does not cause the PUD/POD containing mixture to become unstable. If desired, a combination of thickeners may be used. One preferred thickener is an acrylic acid copolymer (ACUSOL 81 OA, sold by The Dow Chemical Company).

Examples of thickeners include those that do not cause the dispersion to become unstable. More preferably, the rheological modifier is a water soluble thickener that is not ionized. Examples of useful thickeners include methyl cellulose ethers, alkali swellable thickeners (e.g., sodium or ammonium neutralized acrylic acid polymers), hydrophobically modified alkali swellable thickeners (e.g., hydrophobically modified acrylic acid copolymers) and associative thickeners (e.g., hydrophobically modified ethylene-oxide-based urethane block copolymers). Preferably the rheological modifier is a methylcellulose ether. The amount of thickener may be any useful amount. Typically the amount of thickener is at least about 0.1% to about 10% by weight of the total weight of the dispersion. Preferably the amount of thickener is between about 0.5% to about 7% by weight.

Examples of pigments, include Ti0₂, carbon black and other, known pigments.

Pigments are well known in the art and typically present in less than 20% by weight, based on the dried leather.

Examples of flame retardants that may be used in the leathers and methods disclosed herein include those typically used to give enhanced flame retardant properties to a typical latex foam. Such flame retardants include phosphonate esters, phosphate esters, halogenated phosphate esters or a combination thereof. Representative examples of phosphonate esters include dimethylphosphonate (DMMP) and diethyl ethylphosphonate (DEEP).

Representative examples of phosphates esters include triethyl phosphate and tricresyl phosphate. When used the phosphonate or phosphate ester flame retardants are present in the final foam at a level of from 0.5 to 30 percent by weight of the final foam.

Representative examples of halogenated phosphate esters include 2-chloroethanol phosphate (C₆Hi2Cl₂0₄P); 1 -chloro-2-propanol phosphate [tris(l-chloro-2-propyl) phosphate] (C₉H,₈C1₃04P) (TCPP); l,3-DichIoro-2-Propanol Phosphate (C₉H₁₅C1₆0₄P) also called tris(l,3-dichloro-2-propyl) phosphate; tri(2-chloroethyl) phosphate; tri (2,2- dichloroisopropyl) phosphate; tri (2,3-dibromopropyl) phosphate; tri(l,3- dichloropropyl)phosphate; tetrakis(2-chloroethyl)ethylene diphosphate; bis(2-chloroethyl) 2-chloroethylphosphonate; diphosphates [2-chloroethyl diphosphate]; tetrakis(2-chloroethyl) ethylenediphosphate; tris-(2-chloroethyl)-phosphate, tris-(2-chloropropyl)phosphate, tris- (2,3-dibromopropyl)-phosphate, tris(l,3-dichloropropyl)phosphate tetrakis (2-chloroethyl- ethylene diphosphate and tetrakis(2-chloro ethyl) ethyleneoxyethylenediphosphate. When used as a flame retardant, the halogenated phosphate ester will comprise 0.5 to 30 percent by weight of the final foam.

Dehydratable flame retardants, such as alkali silicates, zeolites or other hydrated phosphates, borosilicates or borates, alumina hydroxides, cyanuric acid derivatives, powdered melamine, graphites, mica, vermiculites, perlites, aluminohydrocalcite, hydromagnesite, thaumasite and wermlandite. A1₂0₃H₂0, and Alumina trihydrate, may also be used. The dehydratable flame retardant is generally added to the polyurethane dispersion in an amount of from 5 to 120 parts per 100 parts dispersion solids of the final Compound. Preferably the flame retardant is added in an amount from 10 to 100 parts per 100 parts dispersion solids of the final Compound. More preferably the flame retardant is added in an amount from 20 to 80 parts per 100 parts dispersion solids of the final Compound.

Examples of hand feel additives include organic silicon compounds. When present, the amount of hand feel additive is 0.1% to about 10% by weight of the total weight of the dispersion. Preferably the amount of hand feel additive is between about 0.5% to about 5% by weight. In another embodiment, it is less than 3 % by weight.

Antioxidants are known in the art and include polymeric hindered phenol resins.

In an embodiment according to any of the preceding aspects and/or embodiment(s), the synthetic leathers and methods described herein further comprise at least one additive that is C C0₃, Si0₂, wood fibers, Ti0₂, or combinations thereof.

In another embodiment of any of the previously described aspects and/or embodiments, the mixture further comprises at least one additive that is a flame retardant, a pigment, a flowing additive, hand feel additive, antioxidant, anti-UV additive, or combinations thereof. Typically, these additives comprise 0.01 to 10% by weight of the solid content. More preferably, these additives comprise 0.1-8% by weight (still more preferably, 2-5%) of the solid content.

In the above methods, the order of combining the PUD, POD, at least one surfactant and at least one thickener to form the mixture does not matter.

Frothing may be accomplished by any method known in the art. Examples include mechanical mixing, bubbling a gas into the mixture or a combination thereof.

Likewise, applying the frothed mixture to the fabric may also be accomplished by any method known in the art.

The synthetic leathers and methods described herein utilize a fabric that is coated with the mixture comprising PUD and POD. Many different fabrics that are known in the art may be used. The fabric may be woven or nonwoven. In one embodiment, the fabric is a woven fabric. The fabric may be made by any suitable method such as those known in the art. The fabric may be prepared from any suitable fibrous material, such as, but not limited to, synthetic fibrous materials and natural or semi synthetic fibrous materials and mixtures or blends thereof. Examples of synthetic fibrous materials include polyesters, polyamides, acrylics, polyolefms, polyvinyl chlorides, polyvinylidene chlorides, polyvinyl alcohols and blends or mixtures thereof. Examples of natural semi-synthetic fibrous materials include cotton, wool and hemp. Further examples include needled cotton and polyester fiber hybrid woven fabric.

In the leathers and methods disclosed herein, the fabric is optionally impregnated with a polymer resin. Acceptable resins include isocyanate containing resins, such as polyisocyanates, which are preferred. Examples of polyisocyanate include organic diisocyanates, and may be aromatic, aliphatic, or cycloaliphatic, or a combination thereof. Representative examples of suitable diisocyanates include 4,4'- diisocyanatodiphenylmethane, 2,4'-diisocyanatodiphenylmethane₅ isophorone diisocyanate, p-phenylene diisocyanate, 2,6 toluene diisocyanate, polyphenyl polymethylene

polyisocyanate, 1 ,3-bis(isocyanatomethyl)cyclohexane, 1 ,4-diisocyanatocyclohexane, hexamethylene diisocyanate, 1,5 -naphthalene diisocyanate, 3,3'-dimethyl-4,4'-biphenyl diisocyanate, 4,4'-diisocyanatodicyclohexylmethane, 2,4'-diisocyanatodicyclohexylmethane, and 2,4-toluene diisocyanate, or combinations thereof. More preferred diisocyanates are 4,4'-diisocyanatodicyclohexylmethane, 4,4'-diisocyanatodiphenylmethane, 2,4'- diisocyanatodi-cyclohexylmethane, and 2,4'-diisocyanatodiphenylmethane. Most preferred is 4,4'-diisocyanatodiphenylmethane (also known as 4₃4'-MDI) and 2,4'- diisocyanatodiphenylmethane (also known as 2,4'-MDI). The polyisocyanates may be purified or part of a mixture of polyisocyanates.

The impregnation of the fabric may be conducted by any suitable method known in the art. Examples include dipping, spraying or doctor blading. After impregnating, the impregnated textile may have excess resin removed to leave the desired amount of dispersion within the textile. Typically, this may be accomplished by passing the

impregnated textile through rubber rollers.

Generally, the impregnated fabric is impregnated with a resin in an organic solvent

(which makes a solution) or water (which makes a dispersion). Typical solvents include dimethylformamide (DMF), methylethyl ketone (MEK) and toluene, although other solvents will afford acceptable results. Generally, the organic solvent used to impregnate the fabric will contain 0.5-50% by weight of resin. More preferably, the organic solvent will contain 5-30% by weight of resin. Still more preferably, 15-25% by weight of resin.

Example of suitable resins include one or more PODs. The ability to prepare an impregnated fabric, using either a solution or a dispersion is well known in the art. The frothed mixture may be applied to the fabric using any suitable method known in the art. Examples include using a Labcoater type LTE-S (Werner Mathic AG).

Likewise, the thickness of the froth on the fabric can be adjusted using methods known in the art. Examples include using a doctor blade assembly.

The methods require drying or otherwise treating/curing the coated fabric (i.e., the optionally impregnated fabric that is coated with the frothed mixture) so that the synthetic leather forms. Suitable drying conditions include subjecting the froth coated fabric to 1) a constant temperature until dry, 2) a temperature gradient wherein the temperature changes over time, or 3) a multistep drying regime where the temperature is held for a set amount of time and then changed to a different temperature, which is then held for a set amount of time (3, 4, 5, or more drying steps may also be used). The drying times for each step may be the same or different. Typical drying times are from a few seconds up to one hour. One example of a suitable drying protocol is to subject the froth covered, optionally impregnated fabric to a temperature of 80-105 °C for 4-10 minutes and then to a temperature of 165-175 °C for 3-10 minutes. During the drying process, the water evaporates and the polyolefin sets (which may include melting of at least some of the material coated onto the fabric) and thereby forms the final coating. The drying process should not cause decomposition of any of the synthetic leather components.

Typically, the drying is performed in an oven at atmospheric pressure, but it can be performed at pressures above or below atmospheric pressure.

Experimental Procedures:

Table 1 POD formulations and properties

MAH graft PE

(maleic anhydride AMPLYFI GPv

1 15 - - - 80% grafted with 209, Dow

polyethylene)

Ethylene Acrylic Acid PRIMACOR

77.2 20% 20% 20% 20% Copolymer 59801, Dow

Additives: The additives percentage related to the acid groups in Ethylene Acrylic Acid Copolymer.

NaOH - - 80% 80% - -

N,N-

Dimethvlethanol amine Huntsman - - - 120% 120% (DMEA)

Note: The PODs were made from above formulations by the DOW Bluewave technology. The solid contents of all POD samples were 50%. The Ethylene Acrylic Acid Copolymer was a surfactant working with NaOH or DMEA. The NaOH or DMEA content was related to the acid groups in Ethylene Acrylic Acid Copolymer.

Preparation of poromeric, synthetic leather:

Control Sample: PUD (Syntegra 3000, Dow) based poromeric layer preparation

Preparation of the frothed mixture: A mixture comprising PUD (which had a solids content of 50-55 percent by weight), ammonium stearate (STANFAX 320, Para-chem), disodium octadecyl sulfosuccinimate (STANFAX 318, Para-chem), cocamidopropyl betaine (STANFAX 590, Para-chem) and acrylic acid copolymer thickener (ACUSOL 81 OA, Dow) was frothed using a Model 2MT1A foam machine (E.T. OAKES Corp.) run at lOOOrpm. The thickened PUD viscosity was controlled to ISOOOcp to 28000cp, and the wet froth density was about 0.50-0.85g cm³. The details of the control PUD formulation appear below in Table 2.

Coating the frothed mixture onto a fabric: The frothed layer was applied to a fabric that was attached to a pin frame, using a Labcoater type LTE-S (Werner Mathic AG). The doctor knife was positioned at 1.8-2.5mm between the roller and knife (including resin and fabric). The frothed dispersion was dispersed and the doctor bladed to foam a coating of frothed PUD on the fabric. The coated fabric was then placed in an oven at 100°C for 6min, which was then heated to 170°C in 5min to form the synthetic leather having a poromeric layer.

Samples 1-4 were made using a method analogous to that used to make the Control sample, except that some of the PUD was replaced with POD, as described in Table 2.

Table 2 PUD/POD poromeric layer's formulation

Procedure of poromeric layer embossing:

The poromeric synthetic leather was placed in a 170°C (or 190°C) oven heated for lOmin, and then pressed (1-lOMPa) for 3seconds in a cool press machine.

Figures 1-5 show that POD containing synthetic leathers (Figures 2-5) have similar structures to non-POD containing synthetic leathers (Figure 1, control), Thus, adding POD does not fundamentally change the structure of the synthetic leather.

Figures 6 (control) and 7-10 (POD containing synthetic leathers) show the results of synthetic leathers that were embossed as described above and then heated to 90 ° C in an oven for 5 hours, in order to simulate the effects of aging. As can be seen, the pattern embossed in the control sample has "relaxed," is difficult to discern and is not acceptable. In contrast, the POD containing synthetic leathers have maintained the embossed pattern, and are acceptable.

Claims

WHAT IS CLAIMED IS:

1. A poromeric synthetic leather comprising, in combination:

a fabric that is optionally impregnated with a polymer resin, wherein the fabric is coated with a polymerized layer that was made from a frothed mixture comprising a polyurethane dispersion in water (PUD), at least one polyolefm dispersed in water (POD) at least one surfactant, and at least one thickener.

2. Leathers according to claim 1 , wherein the weight percent of the polyolefm dispersed in water (POD) to the polyurethane in water (PUD) is 5-40%, when calculated using the following formula: (dry weight of POD/( dry weight of POD + dry weight of PUD).

3. Leathers according to any one of claims 1 - 2, wherein the polyolefm in the POD is a C₂-C io polyolefm.

4. Leathers according to any one of claims 1 - 3, wherein the polyolefm dispersed in water has a solid content of at least 40%.

5. Leathers according to any one of claims 1 - 4, wherein the polyolefm in the POD has a T_m of at least 50 °C.

6. Leathers according to any one of claims 1 - 5, wherein the polyolefm in the POD comprises a polyethylene or its copolymer.

7. Leathers according to claim 6, wherein the polyethylene is low density polyethylene, a polyethylene-polypropylene copolymer, polyethylene-octene copolymer, a polyethylene- polypropylene block copolymer, polyethylene-octene block copolymer or a maleic anhydride - polyethylene graft copolymer; wherein said polyethylene and the polyethylene copolymers have a T_m >80 °C.

8. Leathers according to any one of claims 1 - 7, wherein the mixture further comprises at least one additive that is a filler that is wood fibers, CaC0₃, Si0_2j or Ti0_2; a flame retardant, a pigment, a flowing additive, hand feel additive, antioxidant, anti-UV additive, antistatic agent, antimicrobial agent, or combinations thereof.

9. Leathers according to any one of claims 1 - 8, wherein the PUD and POD containing mixture comprises at least two surfactants.

10. Leathers according to claims 1 - 9, wherein at least one surfactant is ammonium stearate, disodium octadecyl sulfosuccinimate or cocamidopropyl betaine; and the weight percent of the POD to the PUD is 10-30%, when calculated using the following formula: (dry wt. of POD/( dry wt. of POD + dry wt. of PUD).

11. Methods of making a poromeric synthetic leather comprising:

frothing a mixture comprising polyurethane dispersed in water (PUD), at least one surfactant, at least one polyolefin dispersed in water (POD); and at least one thickener; applying the frothed mixture to a fabric that is optionally impregnated with a PU resin, thereby forming a coated fabric;

12. Methods of making poromeric leather having improved embossing characteristics, the methods comprising:

combining polyurethane dispersed in water (PUD) at least one polyolefin dispersed in water (POD), at least one surfactant and at least one thickener to form a mixture;

frothing the mixture

subjecting the coated fabric to drying conditions.

13. Methods according to claims 11 or 12, wherein the weight percent of the POD to the PUD is 15-30%, when calculated using the following formula: (dry wt. of POD/( dry wt. of POD + dry wt. of PUD).

14. Methods according to any one of claims 11 - 13, wherein the fabric is a woven or non-woven fabric.

15. Methods according to any one of claims 1 1 - 14, wherein the POD has a solid content of at least 30%.

16. Methods according to any one of claims 11 - 15, wherein the polyolefin in the polyolefin dispersion has a Tm of at least 80 °C.

17. Methods according to any one of claims 11 - 16, wherein the polyolefin dispersion comprises a C₂-Cio alkylene and acrylic acid copolymer and further comprises a

polyethylene.

18. Methods according to claim 17, wherein the polyethylene is low density

polyethylene, a polyethylene-polypropylene copolymer, a polyethylene-polypropylene block copolymer, polyethylene-octene copolymer , polyethylene-octene block copolymer or a maleic anhydride - polyethylene graft copolymer, wherein said polyethylene and the polyethylene copolymers have a Tm >80 °C.

1 . Leathers according to any one of claims 1 - 10, wherein the mixture further comprises at least one additive that is, wood fibers, CaC0₃, Si0₂, Ti0₂, a flame retardant, a pigment, a flowing additive, hand feel additive, antioxidant, anti-UV additive, or combinations thereof and wherein the mixture comprises at least two surfactants that are selected from the group of ammonium stearate, disodium octadecyl sulfosuccinimate or cocamidopropyl betaine.