U.S. patent application number 14/431533 was filed with the patent office on 2015-09-17 for polyurethane based synthetic leathers comprising nanoparticles and having improved peel strength.
This patent application is currently assigned to Dow Global Technologies LLC. The applicant listed for this patent is Dow Global Technologies LLC. Invention is credited to Weichao Gu, Ning Kang, Bo Liu, Yunfei Yan, Chao Zhang, Hong Liang Zhang.
Application Number | 20150259851 14/431533 |
Document ID | / |
Family ID | 50487424 |
Filed Date | 2015-09-17 |
United States Patent
Application |
20150259851 |
Kind Code |
A1 |
Gu; Weichao ; et
al. |
September 17, 2015 |
POLYURETHANE BASED SYNTHETIC LEATHERS COMPRISING NANOPARTICLES AND
HAVING IMPROVED PEEL STRENGTH
Abstract
Disclosed herein are methods of producing externally stabilized,
poromeric synthetic leathers having improved peel strength, the
methods comprising: preparing a prepolymer from a mixture
comprising at least one polyester polyol, at least one polyether
polyol, at least one isocyanate and optionally in a solvent; mixing
the prepolymer, water, and a first surfactant; optionally add a
second chain extender to form a PUD; preparing a mixture comprising
said PUD, at least one surfactant, and at least one thickener;
frothing said mixture; applying the frothed mixture to a fabric and
thereby forming a coated fabric; adjusting the thickness of the
frothed mixture on the coated fabric; drying the coated fabric.
Methods of improving the peel strength of poromeric synthetic
leathers are also disclosed. Externally stabilized synthetic
leathers having improved peel strength are also disclosed.
Inventors: |
Gu; Weichao; (Shanghai,
CN) ; Kang; Ning; (Qingdao, CN) ; Zhang; Hong
Liang; (Shanghai, CN) ; Yan; Yunfei;
(Shanghai, CN) ; Zhang; Chao; (Shanghai, CN)
; Liu; Bo; (Shanghai, CN) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Dow Global Technologies LLC |
Midland |
MI |
US |
|
|
Assignee: |
Dow Global Technologies LLC
Midland
MI
|
Family ID: |
50487424 |
Appl. No.: |
14/431533 |
Filed: |
October 16, 2012 |
PCT Filed: |
October 16, 2012 |
PCT NO: |
PCT/CN2012/083026 |
371 Date: |
March 26, 2015 |
Current U.S.
Class: |
428/304.4 ;
427/358 |
Current CPC
Class: |
D06N 3/146 20130101;
D06N 3/0006 20130101; D06N 3/123 20130101; D06N 3/0047 20130101;
D06N 3/0077 20130101; D06N 3/14 20130101; D06N 3/0088 20130101;
D06N 2211/28 20130101; Y10T 428/249953 20150401 |
International
Class: |
D06N 3/14 20060101
D06N003/14; D06N 3/12 20060101 D06N003/12; D06N 3/00 20060101
D06N003/00 |
Claims
1. Methods for producing externally stabilized, poromeric synthetic
leathers having improved peel strength, the methods comprising:
preparing a prepolymer from a mixture comprising at least one
polyester polyol, at least one polyether polyol, at least one
isocyanate and optionally in a solvent; mixing the prepolymer,
water, and a first surfactant; optionally add a second chain
extender to form a PUD; preparing a mixture comprising said PUD, at
least one surfactant, and at least one thickener; frothing said
mixture; applying the frothed mixture to a fabric and thereby
forming a coated fabric; adjusting the thickness of the frothed
mixture on the coated fabric; drying the coated fabric.
2. Methods of improving the peel strength of poromeric synthetic
leathers, the methods comprising: preparing a prepolymer from a
mixture comprising at least one polyester polyol, at least one
polyether polyol, at least one isocyanate and optionally in a
solvent; mixing the prepolymer, water, and a first surfactant;
optionally add a second chain extender to form a PUD; preparing a
mixture comprising said PUD, at least one surfactant, and at least
one thickener; frothing said mixture; applying the frothed mixture
to a fabric and thereby forming a coated fabric; adjusting the
thickness of the frothed mixture on the coated fabric; drying the
coated fabric.
3. Methods according to claim 1, wherein the fabric is a needled
cotton and polyester fiber hybrid woven fabric having short fibers
on the surface and is optionally impregnated with a polymer
resin.
4. Methods according to claim 1, wherein at least one surfactant is
ammonium stearate, disodium octadecyl sulfosuccinimate or
cocamidopropyl betaine.
5. Methods according to claim 1, wherein the mixture comprises at
least two surfactants.
6. Methods according to claim 1, wherein the mixture further
comprises at least one additive that is CaCO.sub.3, SiO.sub.2, wood
fibers, TiO.sub.2, a flame retardant, a pigment, a flowing
additive, handfeel additive, antioxidant, anti-UV additive, or
combinations thereof.
7. Methods according to claim 1, wherein the PUD has a solid
content of 30-65% by weight.
8. Methods according to claim 1, wherein the isocyanate comprises
isophorone diisocyanate; 4,4'-diisocyanatodiphenylmethane;
2,4'-diisocyanatodiphenylmethane, or combinations thereof.
9. Methods according to claim 1, wherein the polyester:polyether
ratio in the PUD is 1:0.5-4.
10. Methods according to claim 1, wherein the coated fabric is
dried/cured at a temperature of at least 30.degree. C. and no more
than 200.degree. C.
11. Methods according to claim 1, wherein the isocyanate comprised
methylenediphenyl diisocyanate, and at least one polyester polyol
has an Mn of 1000-2000.
12. Methods according to claim 1, wherein the thickening agent is
an acrylic acid copolymer.
13. Methods according to claim 1, wherein the PUD is mixed with at
least three surfactants that are independently selected from the
group consisting of disodium octadecyl sulfosuccinimate, sodium
dodecylbenzene sulfonate, sodium alpha olefin sulfonate, sodium
stearate, cocamidopropyl betaine, and ammonium stearate.
14. Methods according to claim 13, wherein the at least three
surfactants are ammonium stearate, disodium octadecyl
sulfosuccinimate and cocamidopropyl betaine, and are in the ratio
of 1:0.2-0.4:0.23-0.4.
15. A porometric synthetic leather made according to claim 15.
Description
BACKGROUND OF THE INVENTION
[0001] Currently, most polyurethane (PU) synthetic leathers are
made using organic solvents, such as dimethylformamide, 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.
[0002] 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. Pat. No. 7,306,825 for an example of this
methodology.
[0003] 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. Typically, the PUD in the PUD based
synthetic leather is made by combining a diisocyanate and a polyol.
The resulting product is then dispersed in water to make the PUD.
While such synthetic leathers have high solid content and nice hand
feel, they have poor peel strength. Thus, it would be advantageous
to develop a PUD based synthetic leather that had improved peel
strength performance.
SUMMARY OF THE INVENTION
[0004] In one aspect, disclosed herein are methods for producing
externally stabilized, poromeric synthetic leathers having improved
peel strength, the methods comprising:
[0005] preparing a prepolymer from a mixture comprising at least
one polyester polyol, at least one polyether polyol, at least one
isocyanate and optionally in a solvent;
[0006] mixing the prepolymer, water, and a first surfactant;
[0007] optionally add a second chain extender to form a PUD;
[0008] preparing a mixture comprising said PUD, at least one
surfactant, and at least one thickener;
[0009] frothing said mixture;
[0010] applying the frothed mixture to a fabric and thereby forming
a coated fabric;
[0011] adjusting the thickness of the frothed mixture on the coated
fabric;
[0012] drying the coated fabric.
[0013] In another aspect, disclosed herein are methods of improving
the peel strength of poromeric synthetic leathers, the methods
comprising:
[0014] preparing a prepolymer from a mixture comprising at least
one polyester polyol, at least one polyether polyol, at least one
isocyanate and optionally in a solvent;
[0015] mixing the prepolymer, water, and a first surfactant;
[0016] optionally add a second chain extender to form a PUD;
[0017] preparing a mixture comprising said PUD, at least one
surfactant, and at least one thickener;
[0018] frothing said mixture;
[0019] applying the frothed mixture to a fabric and thereby forming
a coated fabric;
[0020] adjusting the thickness of the frothed mixture on the coated
fabric;
[0021] drying the coated fabric.
[0022] In another aspect, poromeric, synthetic leathers having
improved peel strength made according to the aforementioned methods
are also disclosed herein.
[0023] The PUD based synthetic leathers disclosed herein are
externally stabilized, i.e., they require the presence of at least
one surfactant that does not react with the PUD. Likewise, the
methods disclosed herein utilize externally stabilized PUDs.
[0024] 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
[0025] FIG. 1 is a picture of the cross section of a polyester
polyol free synthetic leather, where the coated fabric has long
fibers (Control 1).
[0026] FIG. 2 is a picture of the cross section of a polyester
polyol free synthetic leather, where the coated fabric has short
fibers (Control 2).
[0027] FIG. 3 is a picture of the cross section of a polyester
polyol containing synthetic leather, where the coated fabric has
long fibers (Example 1).
[0028] FIG. 4 is a picture of the cross section of a polyester
polyol containing synthetic leather, where the coated fabric has
short fibers (Example 2).
DETAILED DESCRIPTION
[0029] The methods and leathers disclosed herein require the
incorporation of at least one polyester polyol, at least one
polyether polyol and at least one isocyanate into the PUD.
[0030] Polyester polyols, are compounds that have an ester
containing backbone and further comprise at least two OH groups.
They are typically made from aliphatic organic dicarboxylic acids
with 2 to 12 carbons, preferably aliphatic dicarboxylic acids with
4 to 6 carbons, and multivalent alcohols, preferably diols, with 2
to 12 carbons. Examples of aliphatic dicarboxylic acids include
succinic acid, glutaric acid, adipic acid, suberic acid, azelaic
acid, sebacic acid, decanedicarboxylic acid, maleic acid, fumaric
acid, phthalic acid, isophthalic acid, and terephthalic acid. The
corresponding dicarboxylic acid derivatives may also be used such
as dicarboxylic acid mono- or di-esters of alcohols with 1 to 4
carbons, or dicarboxylic acid anhydrides. Examples of divalent and
multivalent alcohols, especially diols, include ethanediol,
diethylene glycol, glycerine and trimethylolpropanes or mixtures of
at least two of these diols. Polyester polyols derived from
vegetable oils (natural oil polyols or NOPs) may also be used.
[0031] Polyether polyols are compounds that have an ether backbone
and further comprise at least two OH groups. Polyether polyols are
commonly made by reacting monomeric compounds (either alone or in
combination), such as glycerine (a triol), pentaerythritol (a
tetraol), ethylene glycol (a diol), diethylene glycol (a diol of
the formula: HOCH.sub.2CH.sub.2OCH.sub.2CH.sub.2OH), and/or sucrose
with ethylene oxide, propylene oxide and/or butylene oxide in the
presence of an initiator and/or a catalyst. Suitable initiators
include aliphatic and aromatic amines, such as monoethanolamine,
vicinal toluenediamines, ethylenediamines, and propylenediamine.
Useful catalysts include strong bases, such as NaOH, or KOH, and
double metal cyanide catalysts, such as zinc
hexacyanocobalt-t-butanol complex. Common polyether polyols include
polyethylene glycol (PEG), polypropylene glycol, and
poly(tetramethlene ether)glycol.
[0032] The use of a strong base catalyst to make a polyether polyol
often causes the polyether polyol to be too basic, which has a
detrimental effect on the aforementioned prepolymer. Consequently,
it is often necessary to treat the polyether polyol with a
scavenger compound, which reacts with the residual base and makes
the prepolymer more acidic. Suitable scavenger compounds include
benzoyl chloride, and 85% phosphoric acid, with benzoyl chloride
being preferred. Typically, adding aqueous acids introduces excess
water into the prepolymer, which will react with the isocyanate and
adversely impact the resulting leather. The inventors typically use
a scavenger compound to adjust the net controlled polymerization
rate of the mixture to be lower than -10. ASTM D 6437-05
corresponds to the CPR procedure.
[0033] The isocyanates used herein contain at least two isocyanate
groups and include organic diisocyanates, which may be aromatic,
aliphatic, or cycloaliphatic, or a combination thereof.
Representative examples of suitable diisocyanates include
4,4'-diisocyanatodiphenylmethane, 2,4'-diisocyanatodiphenylmethane,
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'-diisocyanatodicyclohexylmethane, and
2,4'-diisocyanatodiphenylmethane. Most preferred are isophorone
diisocyanate; 4,4'-diisocyanatodiphenylmethane (also known as
4,4'-MDI); and 2,4'-diisocyanatodiphenylmethane (also known as
2,4'-MDI). The isocyanates may be purified or part of a mixture of
one or more isocyanates. If an isocyanate is a solid, it may be
melted and/or dissolved in a solvent before it is reacted with the
at least one polyester polyol and the at least one polyether
polyol.
[0034] The PUDs disclosed herein are made by reacting at least one
polyester polyol at least one polyether polyol and at least one
isocyanate, optionally in a solvent (wherein the solvent does not
or minimally reacts with the isocyanate). This affords a
prepolymer, which is then added to a mixture comprising a solvent
that is comprised of water, at least one surfactant, and at least
one chain extender. The mixture may be stirred or mixed using
methods known in the art. The resulting polyurethane dispersion
(PUD) has a "milk-like" appearance. The polyester polyol to the
polyether ratio in the PUD is 0.1-99 polyester polyol to 99.9-1
polyether polyol. More preferably, the ratio is 30-70 polyester
polyol to 70-30 polyether polyol. The polyester:polyether ratio in
the PUD is 1:0.5-4:0. More preferably the ratio is 1:0.5-2.5.
[0035] Typically, the ratio of the polyol mixture to the isocyanate
is 85:15 to 55:45. More preferably, the ratio is 75:25 to
65:35.
[0036] As will be appreciated by those skilled in the art, the
order of mixing the aforementioned reagents may be changed.
[0037] As used herein, a polyurethane dispersed in water is
referred to as a PUD. When a polyurethane is dispersed in water, it
is understood that the water optionally further comprises other,
additional solvents, such as ketones, C.sub.1-C.sub.6 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 PUD. And while
deionized and/or distilled water may be used, it is not
required.
[0038] The leathers and methods of making the leathers disclosed
herein, optionally further comprise an additive that is a; fillers
(such as wood fibers, CaCO.sub.3, SiO.sub.2, and TiO.sub.2), a
flame retardant, a pigment, a flowing additive, handfeel additive,
antioxidant, anti-UV additive, antistatic agent, antimicrobial
agent, or combinations thereof. Wood fibers also include wood
floor. In one embodiment, the leathers and methods require the
presence of at least one of the aforementioned additives.
[0039] The aforementioned fillers, when present, account for
0.1-50% by weight of the composition (excluding the fabric). More
preferably, when present, the fillings account for 0.1-40% by
weight of the composition. Still more preferably, the fillers
account for 0.1-30% by weight of the composition.
[0040] The non-filler additives, i.e., the aforementioned
additives, not including the fillers, typically account for
0.01-20% by weight of the composition. More preferably, the
non-filler additives account for 0.1-10% by weight of the
composition. Still more preferably, the non-filler additives
account for 1-5% by weight of the composition. Flowing additives,
handfeel additives, antioxidants, anti-UV additives, antistatic
agents, and antimicrobial agents are typically comprise less than
5% by weight of the composition. The additives may be added to the
polyester polyol modified PUD, to the mixture comprising the
polyester polyol modified PUD or combinations thereof.
[0041] 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-1,2-ethanediyl)-.alpha.-sulfo-.omega.-(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
fluorinated alkyl esters and alkali metal perfluoroalkyl
sulfonates; organosilicon surfactants such as modified
polydimethylsiloxanes; and alkali metal soaps of modified resins.
Exemplary surfactants include disodium octadecyl sulfosuccinimate,
sodium dodecylbenzene sulfonate, sodium alpha olefin sulfonate,
sodium stearate, cocamidopropyl betaine, and ammonium stearate.
Typically the total amount of surfactant used is less than 10%,
based on the total weight of the dried synthetic leather. When the
surfactant is mixed with the PUD, it is used to stabilize the air
bubbles in the frothed PUD. The surfactant or surfactants are
sometimes used as a concentrate in water. When two or more
surfactants are being used, they may be added to the mixture
simultaneously or one after the other.
[0042] At least one thickener is added to the PUD before it is
frothed. 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 (which is sold
by The Dow Chemical Company as ACUSOL 810A) being particularly
preferred. Preferably, the thickener does not cause the PUD
containing mixture to become unstable. If desired, a combination of
thickeners may be used.
[0043] 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.
[0044] Chain extenders are bifuncational or polyfuncational, low
molecular weight (typically weighing from 18 up to 500 g/mol)
compounds that contain at least two active hydrogen containing
groups. Any chain extender known to be useful to those of ordinary
skill in the art of preparing polyurethanes can be used in the
leathers and methods disclosed herein. Examples of chain extenders
include diols, polyols, diamines, polyamines, hydrazides, acid
hydrazides, and water. Of these, amine containing chain extenders
and water are preferred. Furthermore, one or a combination of chain
extenders may be used. For example, the chain extender may be mixed
with or otherwise contain water.
[0045] Examples of chain extenders include water, piperazine,
2-methylpiperazine; 2,5-dimethylpiperazine; 1,2-diaminopropane;
1,3-diaminopropane; 1,4-diaminobutane; 1,6-diaminohexane,
isophorone diamine, mixtures of isomers of 2,2,4- and
2,4,4-trimethyl hexamethylene diamine, 2-methyl pentamethylene
diamine, diethylene triamine, dipropylenetriamine,
triethylenetetramine, 1,3- and 1,4-xylylene diamine,
a,a,a',a'-tetramethyl-1,3- and -1,4-xylylene diamine and
4,4'-dicyclohexylmethanediamine,
3,3'-dimethyl-4,4'-dicyclohexylmethanediamine,
1,2-cyclohexanediamine, 1,4-cyclohexanediamine, dimethylethylene
diamine, hydrazine or adipic acid dihydrazide ethylene glycol;
aminoethylethanolamine (AEEA); aminopropylethanolamine,
aminohexylethanolamine; aminoethylpropanolamine,
aminopropylpropanolamine, aminohexylpropanolamine; cyclohexane
dimethanol; ethanolamine; diethanolamine; piperazine, JEFFAMINE
D-230 (a polyether with two amino terminating groups, having a
molecular weight of approximately 230 that is sold by the Huntsman
Co.), methyldiethanolamine; phenyldiethanolamine;
diethyltoluenediamine, dimethylthiotoluenediamine and
trimethylolpropane. Particularly preferred chain extenders include
water, AEEA, piperazine and 1,4-diaminobutane.
[0046] Examples of pigments, include TiO.sub.2, 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.
[0047] 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.
[0048] Representative examples of halogenated phosphate esters
include 2-chloroethanol phosphate
(C.sub.6H.sub.12Cl.sub.2O.sub.4P); 1-chloro-2-propanol phosphate
[tris(1-chloro-2-propyl)phosphate]
(C.sub.9H.sub.18Cl.sub.3O.sub.4P) (TCPP); 1,3-Dichloro-2-Propanol
Phosphate (C.sub.9H.sub.15Cl.sub.6O.sub.4P) also called
tris(1,3-dichloro-2-propyl)phosphate; tri(2-chloroethyl)phosphate;
tri(2,2-dichloroisopropyl)phosphate;
tri(2,3-dibromopropyl)phosphate; tri(1,3-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(1,3-dichloropropyl)phosphate tetrakis(2-chloroethyl-ethylene
diphosphate and
tetrakis(2-chloroethyl)ethyleneoxyethylenediphosphate. When used as
a flame retardant, the halogenated phosphate ester will comprise
0.5 to 30 percent by weight of the final foam.
[0049] 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.
Al.sub.2O.sub.3H.sub.2O, and Alumina trihydrate, may also be
used.
[0050] 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.
[0051] 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.
[0052] Antioxidants are known in the art and include polymeric
hindered phenol resins.
[0053] 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 CaCO.sub.3,
SiO.sub.2, wood fibers, TiO.sub.2, or combinations thereof.
[0054] 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.
[0055] 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.
[0056] Likewise, applying the frothed mixture to the fabric may
also be accomplished by any method known in the art.
[0057] The synthetic leathers and methods described herein utilize
a fabric that is coated with the frothed mixture. 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 non-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, polyacrylics, polyolefins,
polyvinyl chlorides, polyvinylidene chlorides, polyvinyl alcohols
and blends or mixtures thereof. Examples of natural semi-synthetic
fibrous materials include cotton, wool and hemp.
[0058] One preferred fabric is needled cotton and polyester fiber
hybrid woven fabric having short fibers (less than 1 mm) on the
surface.
[0059] Another preferred fabric is needled cotton and polyester
fiber hybrid woven fabric having long (greater than 3 mm) fibers on
the surface.
[0060] 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 contain at least two isocyanate groups) were discussed
above.
[0061] 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.
[0062] 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.
[0063] If the fabric is impregnated with a resin in an organic
solvent, then 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.
[0064] 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).
[0065] 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.
[0066] 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 that is at least 80.degree. C. and no more than
250.degree. C. More preferably, the optionally impregnated fabric
is heated to a temperature of 80-105.degree. C. for 4-10 minutes
and then to a temperature of 165-175.degree. 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.
[0067] Typically, the drying is performed in an oven at atmospheric
pressure, but it can be performed at pressures above or below
atmospheric pressure.
[0068] In one embodiment, the polyester polyol modified PUD, the
filler or fillers, and the other additives comprise 0.1-99.9% by
weight of the total composition. More preferably, they comprise
60-99.9% by weight of the total composition. Still more preferably,
70-99.9% by weight of the total composition.
General Procedure for the Preparation of PUD Based, Poromeric
Synthetic Leather
Preparation of the Prepolymer:
[0069] Put at least one isocyanate resin into the reactor. If a
resin is a solid, heat it until it is melted.
[0070] Combine the polyols in a separate reaction vessel. If the
polyol mixture is a solid at ambient temperature, heat the polyol
mixture to a temperature higher than the mixture's melting point.
Adjust the net-controlled polymerization rate (CPR) to be lower
than -10 using a scavenger compound, such as benzoyl chloride.
Combine the polyol mixture and the isocyanate(s). Stir and heat the
combined mixture. Test the NCO % periodically using ASTM method
ASTM D 2572-87. When the desired NCO content is reached, reduce the
temperature of the reaction mixture.
Preparation of the Polyurethane Dispersion (PUD):
[0071] The prepolymer (from above) was placed in a plastic jar. The
jar was secured and a Cowles blade was inserted into the prepolymer
such that the blade is just covered. At least one surfactant is
added to the prepolymer, with mixing at 3000 rpm. Cold
(.about.5.degree. C.) deionized water (DI water) is slowly added to
the mixture. Gradually, the water-in-oil emulsion is converted into
an oil-in-water dispersion. A solution of chain extender in DI
water is slowly fed into the dispersion, the final dispersion is
allowed to degas under ambient condition with random stirring.
Experimental Procedures
[0072] The following three PUDs were used in the examples.
TABLE-US-00001 TABLE 1 PUD type Type PUD 1 PUD 2 PUD 3 Materials
Syntegra 3000 Polyester polyol Polyester polyol containing PUD
containing PUD Company Dow Synthesis Synthesis Solid content/%
50-55 50-55 50-55 Polyester/ 0/70/30 22.6/47.4/30 41/29/30
Polyether/ Isocyanate Ratio Particle Size/.mu.m 0.3 1.9 0.8
[0073] Note: PUD 1 is the control because it does not contain any
polyester polyol. PUDs 2 and 3 contain polyester polyol and were
made according to the methods described herein. The polyester in
PUD 2 was Bester 127 (a polyester polyol having an Mn of about
2,000, sold by The Dow Chemical Company), and the polyester in PUD
3 was Bester 48 (a polyester polyol product with an Mn=1000, sold
by The Dow Chemical Company). The polyethers in all these three
PUDs were mainly VORANOL 9287A (a 2000 molecular weight, 12 percent
ethylene oxide capped diol stabilized with alkyldiphenylamine, a
product of The Dow Chemical Company) with some small dosage
polyether resins (Mn=approximately 2000, sold by The Dow Chemical
Company) and CARBOWAX.TM. Methoxy polyethylene Glycol (MPEG) 1000
(from The Dow Chemical Company) mixture. The isocyanate was
4,4'-Methylenediphenyl diisocyanate (MDI) from Huntsman.
[0074] The following two fabrics were used in the examples
below.
TABLE-US-00002 TABLE 2 Fabric type Impregnated with Type
Description Resin? Fabric 1 Needled cotton and polyester fiber No
hybrid woven having long (>3 mm) fibers on the surface fabric
Fabric 2 Needled cotton and polyester fiber No hybrid woven fabric
with shorter fibers (<=1.2 mm) on the surface
[0075] Preparation of the Control Samples:
[0076] A poromeric layer of the synthetic leather was made using
frothed PUD. The frothing PUD dispersion had a solids content of
50-55 percent by weight with 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 810A, Dow). The thickened
PUD viscosity was controlled to 13,000 cp to 28,000 cp. The
detailed PUD formulations appear in Table 3.
[0077] The PUD was frothed using a Model 2MT1A foam machine (E.T.
OAKES Corp.) run at 1000 rpm. The wet froth density of the PUD was
about 0.50-0.85 g/cm.sup.3. A Labcoater type LTE-S (Werner Mathic
AG) was used to apply the frothed PUD to a fabric that was attached
to pin frame. The doctor knife was positioned at 1.8-2.5 mm 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.degree. C. for 6-10 min, which was then heated to
170.degree. C. in about 5 min. to form the synthetic leather having
a poromeric layer.
TABLE-US-00003 TABLE 3 PUD poromeric layer formulation Items
Control 1 Control 2 Materials Weight/g Weight/g Fabric type Fabric
1 Fabric 2 PUD 1 (Syntegra 3000) 1000 1200 Stanfax 320 40.0 48.0
Stanfax 590 11.3 13.5 Stanfax 318 13.1 15.6 Acusol 810A 60.0 79.4
Viscosity/cp 17900 23300 Foam density/(g/cm.sup.3) 0.748 0.690
[0078] Preparation of the Experimental Examples
[0079] The polyester polyol modified PUD based leathers were made
essentially according to the methods described above for the
control samples. The key difference being the use of the
formulations and fabrics in Table 4 replacing those in Table 3.
TABLE-US-00004 TABLE 4 Polyester modified PUD poromeric layer
formulation Sample 1 Sample 2 Materials Weight (g) Weight (g)
Fabric type Fabric 1 Fabric 2 PUD 2 1000 -- PUD 3 -- 750 Stanfax
320 (ammonium stearate) 40.0 30.2 Stanfax 590 (cocamidopropyl
betaine) 11.3 10 Stanfax 318 (disodium octadecyl 13.1 9.5
sulfosuccinimate) Acusol 810A (acrylic acid copolymer) 76.5 77.3
Viscosity (cp) 17500 17200 Foam density (g/cm.sup.3) 0.781
0.622
[0080] Peel Strength Test:
[0081] Peel strength tests were conducted according to the GB/T
8949-2008 Chinese Standard. Briefly, the synthetic leather was cut
into two 15 cm.times.12 cm leather sheets. Then these two leather
sheets were glued together using a suitable adhesive, but about 5
cm (in the length direction) was not treated with adhesive. The two
pieces were pressed with a 5 Kg steel plate, dried and cured over
24 hours. The bonded sheet was cut along the length-wise into four
15 cm.times.3 cm samples. These four samples were tested using an
Instron machine with a speed of 200 cm/min.
[0082] PUD Viscosity Measurement
[0083] Bulk viscosities of the thickened PUD before frothing were
measured using a Brookfield viscometer with a 20 rpm #6
spindle.
[0084] Results of Leather Peel Strength:
TABLE-US-00005 TABLE 5 Peel strength of the poromeric layer samples
Items Control 1 Control 2 Sample 1 Sample 2 Peel strength/(N/(3
cm)) 28 46 52 90 Fabric Fabric 1 Fabric 2 Fabric 1 Fabric 2
[0085] The peel strength increased from 28 N/(3 cm) (Control 1) to
46 N/(3 cm) (Control 2) by changing from a fabric having long
fibers on the surface to a fabric having short fibers on the
surface. Replacing the PUDs in Control samples 1 and 2 with
polyester polyol modified PUD (Sample 1 and 2) afforded synthetic
leathers having significantly improved peel strengths, relative to
PUDs that do not contain any polyester polyol modified PUD.
[0086] Comparing Control 1 to Sample 1 shows the polyester polyol
modified PUD has a peel strength that is 85% higher than the
corresponding non-modified PUD. Likewise, Sample 2 has a peel
strength that is 96% higher than the corresponding non-modified
PUD
[0087] FIG. 1 (Control 1) and 3 (Example 1), both are cross
sections of synthetic leathers on fabrics having long fibers, and
they have similar structures. Thus, Example 1, while having
superior properties relative to Control 1, has a similar overall
structure. The same applies for FIG. 2 (Control 2) and 4 (Example
2), but the fabrics contain short fibers.
* * * * *