Note: Descriptions are shown in the official language in which they were submitted.
EeA3295232
AQUEOUS COATING COMPOSITIONS AND THEIR USE FOR THE
PREPARATION OF COATINGS THAT ARE PERMEABLE TO WATER VAPOR
BACKGROUND OF THE INVENTION
The invention relates to the coating of substrates,
in particular, flexible substrates such as textile sheets, with
agents obtained from (A) polyurethanes containing hydrophilic
groups and (B) an aqueous phase. The invention further relates
to the use of these agents for the preparation of coatings
which are permeable to water vapor. they term "polyurethanes"
as used in this invention includes polyurethane ureas.
Coatings that are highly permeable to water vapor
have in the past repeatedly been the object of investigations
l0 and developments for which they are particularly suitable, for
example, for the manufacture of high quality leather
substitutes or for the production of garments having high
wearing comfort.
Because immersion bath and evaporation coagulation,
incorporation, and subsequent washing out of water-soluble
salts, as well as perforation by means of high energy electron
beams, produce microchannels or microcavities in the coating
and thereby weaken the coating, it is of particular interest to
obtain coatings that are permeable to water vapor but which are
2p _ free from pores.
Most polyurethanes used for coating compositions are
dissolved or dispersed in organic solvents but the trend toward
using coating compositions containing little or no solvent
favors the use of aqueous coating systems. Polyurethanes that
are self-emulsifiable due to the presence of hydrophilic groups
and that can, therefore, be dispersed in water without the aid
of external emulsifiers are known. See German Patentschriften
RH0344
US
_ 2 _
2,446,440, 2,551,094,. 2,651,505, 2,651,506, and 2,659,617 and
German Offenlegungss<:hrift 2,816,815. An optimum combination
of dispersibility of the polyurethane in water with high
permeability to water vapor and sufficient water resistance of
the coatings, such a<.> is required for coating compositions used
for the preparation of water vapor permeable coatings, has,
however, not been available until now.
It has now surprisingly been found that coatings that
are highly permeable to water vapor and have very little
tendency to swell in water can be prepared by using, as coating
compositions, systems containing (A) polyurethanes that contain
ionic groups and polyethylene oxide units having defined
quantity and sequence length and (B) an aqueous phase.
SUMMARY OF THE INVENTION
The invention thus relates to coating compositions
comprising
(A) a polyurethane based on a polyisocyanate, a diol having an
average molecular weight of from 350 to 5000 (preferably
from 800 to 2500), and a chain lengthening agent having a
2o molecular weight of from 32 to 349, wherein said poly-
urethane (A) contains ionic groups in a quantity of from
0.1 to 75 milliequivalents (meq) (preferably from 0.5 to
40 meq) per 100 g of polyurethane (A) and 6 to 50~ by
weight (preferably 10 to 40%a by weight and more preferably
from 10 to 35% by weight), based on polyurethane (A), of
polyethylene oxide units -(CH2CH20)n- having a sequence
length n of from 2 to 50 (preferably from 2 to 25 and more
preferably from 3 to 12) incorporated into the main chain,
and
3o . (B) from 30 to 80% by weight, based on the sum of components
(A) and (B), of an aqueous phase.
DETAILED DESCRIPTION OF THE INVENTION
The term "'incorporated into the main chain" as used
in the context of this invention means that the polyethylene
oxide units do not form the end of a chain but are attached at
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both ends to radical<_;, each of which contains at least one
urethane or urea group. "Incorporated into the main chain" is
thus contrasted to the conventional concept of "terminally
positioned" or "laterally positioned".
The effect achievable with the coating compositions
according to the invention is very surprising because
polyurethanes which contain either the ionic groups alone or
the polyethylene oxide units of the type defined in the claims
alone do not, for practical purposes, have any permeability to
1o water vapor.
The polyurethanes described in German Patentschriften
2,551,094, 2,651,505" 2,651,506, and 2,659,617 and in German
Offenlegungsschrift x',816,815 contain polyethylene oxide units
in terminal positions and/or lateral positions and thus do not
i5 satisfy the requirements according to the present invention.
In the polwurethanes described in German Patent-
schrift 2,446,440, units of sulfonated diols that may contain
alkylene oxide units are incorporated into the main chain in
such a quantity that the polyurethanes have a sulfonate group
2o content of from 0.1 to 6fo by weight.
Polyesters are mentioned in German Patentschrift
2,446,440 (column 9) among the usual starting components for
the preparation of polyurethanes, admittedly without any
indication of the quantities. Only propoxylated or ether
25 group-free sulfonate diols are used in the examples. Polyether
polyols free from sulphonate groups are not used. German
Patentschrift 2,446,440, therefore, could not suggest that
particularly valuable products for coating compositions would
be obtained when both ionic groups and polyethylene oxide units
30 . having sequence lengths of from 2 to 50 are incorporated into
the polyurethanes in a quantity from above 6 to 50fo by weight.
German Patentschrift 2,446,440 does not mention water vapor
permeable coatings and, therefore, could not suggest using
polyurethane dispersions for the preparation of water vapor
35 permeable coatings.
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For the preparation of coatings that are permeable to
water vapor, it was necessary to overcome a prejudice insofar
as one skilled in the art would regard it as highly probable
that coatings based on polyurethanes that contain not only
ionic groups but in addition other hydrophilic groups (such as,
polyethylene oxide units) would not provide sufficient wet
resistance. Even with hindsight it still appears extremely
surprising that dispersibility of the palyurethanes in water
and high permeability to water vapor could be combined with
l0 good wet strength of the resulting coatings.
The polyurethanes (A) may be prepared in known
manner, either solvent-free or, preferably, in an organic
solvent.
Polyurethanes (A) are prepared from polyisocyanates
of the formula Q(NCO)2 in which Q stands for an aliphatic
hydrocarbon group having 4 to 12 carbon atoms, a cyclo-
aliphatic hydrocarbon group having 6 to 25 carbon atoms, an
aromatic hydrocarbon group having 6 to 15 carbon atoms, or an
araliphatic hydrocarbon group having 7 to 15 carbon atoms.
2o Examples of such preferred diisocyanates include tetramethylene
diisocyanate, hexamethylene diisocyanate, dodecamethylene
diisocyanate, 1,4-diisocyanatocyclohexane, 3-isocyanatomethyl-
3,3,5-trimethylcyclohexylisocyanate (isophorone diisocyanate),
4,4'-diisocyanatodicyclohexylmethane, 4,4'-diisocyanato-3,3'-
dimethyldicyclohexylmethane, 4,4'-diisocyanatodicyclo-
hexylpropane-(2,2), 1,4-diisocyanatobenzene, 2,4- or 2,6-
diisocyanatotoluene or mixtures of these isomers, 4,4'-, 2,4'-
or 2,2'-diisocyanatodiphenylmethane or mixtures of these
isomers, 4,4'-diisocyanatodiphenylpropane-(2,2), p-xylylene
3o diisocyanate and a,a,a',a'-tetramethyl-rn- or -p-xylylene
diisocyanate, and mixtures of these compounds.
The higher functional polyisocyanates known from
polyurethane chemistry and known modified polyisocyanates, such
as polyisocyanates containing carbodiimide groups, allophanate
groups, isocyanurate groups, urethane groups, and/or biuret
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groups, may, of tour.<>e, also be used as all or part of the
polyisocyanate component.
The reactants used for the polyisocyanates are mainly
polyhydroxyl compounds containing from 2 to 8 (preferably 2
or 3) hydroxyl groups per molecule and having a molecular
weight (average) of up to 5000 (preferably up to 2500). Both
low molecular weight polyhydroxyl compounds having molecular
weights of from 32 to 349 and relatively high molecular weight
polyhydroxyl compounds having average molecular weights of at
l0 _ least 350 (preferably at least 1000), such as those described
in detail in the above-mentioned publications, may be used.
Relatively high molecular weight polyhydroxyl
compounds include the hydroxypolyesters, hydroxypolyethers,
hydroxy-polythioethers, hydroxypolyacetals, hydroxypoly-
carbonates, and/or hydroxypolyester amides known in poly-
urethane chemistry, preferably those having average molecular
weights of from 600 to 4000 and most preferably those with
average molecular weights of from 800 to 2500. Polycarbonate
polyols, polyether polyols. and polyester polyols are
particularly preferred.
Components suitable for use in the synthesis of the
polyurethanes (A) for introducing polyethylene oxide units
include homopolyethylene glycols and ethylene oxide copoly-
ethers (preferably el:hylene oxide/propylene oxide mixed ethers)
containing hydroxyl end groups and having a block or random
distribution, provided that the ethylene oxide sequences
satisfy the requirements according to the invention. Among
these, polyether carbonates and polyether esters based on the
above-mentioned homopolyethylene glycols, ethylene oxide
. copolyethers or mixtures thereof with other polycarbonate-
forming or polyester-forming polyhydroxyl compounds are
preferred. If copolyethers or polyether carbonates or
polyether esters based on such copolyethers are used as
components for introducing the polyethylene oxide units into
the polyurethane (A) or its precursors, only those units which
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have the sequence lengths as claimed herein count as poly-
ethylene oxide sequences within the meaning of the invention,
while those polyethylene oxide sequences which have a sequence
length above or below the limits claimed are not included.
The optimum quantity of polyethylene oxide units in
polyurethane (A) depends to some extent on the sequence length
and follows the rule that if the sequence length is short the
quantity may be slightly greater and if the sequence length is
great the quantity may be slightly smaller. Thus with a
sequence length of Z, the quantity of these polyethylene oxide
units in polyurethane (A) may be up to 50fo by weight, whereas
if the sequence length is above 20, it is advisable to limit
the quantity of these polyethylene oxide units in polyurethane
(A) to 20% by weight.
Monofunctional polyethylene oxide alcohols (i.e.,
ethoxylated monohydric alcohols or ethoxylated phenols) may be
incorporated into polyurethane (A) in quantities of from 0.2 to
5% by weight, based on polyurethane (A), for assisting the
dispersing action. 1:f such monofunctional polyethylene oxide
2p alcohols are incorporated into polyurethane (A), the proportion
of ionic groups may be reduced but these monofunctional units
make hardly any contribution to the permeability of the
coatings to water vapor. The proportion of such monofunctional
polyethylene oxide units in polyurethane (A), based on the
total quantity of polyethylene oxide units incorporated, should
not exceed 30fo by weight and is preferably not more than 20~o by
weight (more preferably not more than l0fo by weight). Best
results are obtained when no monofunctional polyethylene oxide
units are incorporated.
Starting components which supply the polyethylene
oxide units for polyurethane (A) thus include mainly ethylene
oxide polyethers and ethylene oxide/propylene oxide mixed
polyethers having 2 o r 3 hydroxyl groups, but for the mixed
polyethers the predominant proportion by weight should be
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provided by ethylene oxide units. Pure ethylene oxide
polyethers are preferred.
The term "average molecular weights" in the context
of this invention denotes molecular weights determined as
number average molecular weights.
Compounds that are used in addition to the components
supplying the polyethylene oxide units defined in the claims
may be selected from t:he isocyanate-reactive compounds
conventionally used in polyurethane chemistry.
Polyhydroxyl components that are suitable as starting
materials for polyurethanes but which do not contain the
polyethylene oxide units according to the invention are
described below.
Suitable hydroxyl group-containing polycarbonates are
. obtainable by the reaction of carbonic acid derivatives such as
diphenylcarbonate or phosgene with diols. Suitable diols for
this purpose include ethylene glycol, 1,2- and 1,3-propanediol,
1,4- and 1,3-butanediol, 1,6-hexanediol, 1,8-octanediol,
neopentyl glycol, 1,4-bis(hydroxymethyl)cyclohexane, 2-methyl-
1,3-propanediol, 2,2,4-trimethyl-1,3-pentanediol, dipropylene
glycol, polypropylene glycols, dibutylene glycol, polybutylene
glycols, bisphenol A, and tetrabromobisphenol A. The diol
component preferably contains from 40 to 1009'o by weight of
hexanediol, preferably 1,6-hexanediol, and/or hexanediol
derivatives, preferably those containing ether or ester groups
in addition to OH end groups, for example, products obtained by
the reaction of 1 mol of hexanediol with at least 1 mol
(preferably 1 to 2 mol) of caprolactone according to the method
of German Auslegeschrift 1,770,245 or by the autoetherification
. of hexanediol to form di- or trihexylene glycol. The
preparation of such derivatives has been disclosed, for
example, in German Auslegeschrift 1,570,540. The polyether-
polycarbonate diols described in German Offenlegungsschrift
3,717,060 are also very suitable.
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The hydroxyll polycarbonates should be mainly linear
but may, if desired, tie slightly branched by the incorporation
of polyfunctional components, in particular, low molecular
weight polyols. Glycerol, trimethylolpropane, 1,2,6-hexane-
triol, 1,2,4-butanetriol, triroethylolpropane, pentaerythritol,
quinitol, mannitol and sorbitol, methyl glycoside, and
1,4,3,6-dianhydrohexitols, for example, are suitable for this
purpose.
Suitable po'iyether polyols include the polyethers
known in polyurethane chemistry, for example, the addition or
mixed addition compounds of tetrahydrofuran, styrene oxide,
propylene oxide, the butylene oxides, or epichlorohydrin
obtained by reaction with divalent starter molecules such as
water, the above-mentioned diols, or amines containing two NH
bonds, in particular, the addition or mixed addition compounds
of propylene oxide.
Examples of suitable polyester polyols include the
reaction products of polyvalent (preferably divalent) alcohols,
optionally together with trivalent alcohols, with polybasic
(preferably dibasic) carboxylic acids. Instead of using free
polycarboxylic acids, the corresponding polycarboxylic acid
anhydrides or corresponding polycarboxylic acid esters of lower
alcohols or mixtures thereof may be used for the preparation of
the polyesters. The polycarboxylic acids may be aliphatic,
cycloaliphatic, aromatic, and/or heterocyclic and may be
substituted (e. g., by halogen atoms) and/or unsaturated.
Examples of suitable polycarboxylic acids and derivatives
thereof include succinic acid, adipic acid, suberic acid,
azelaic acid, sebacic acid, phthalic acid, isophthalic acid,
trimellitic acid, phthalic acid anhydride, tetrahydrophthalic
acid anhydride, hexahydrophthalic acid anhydride, tetrachloro-
phthalic acid anhydride, endomethylene tetrahydrophthalic acid
anhydride, glutaric acid anhydride, malefic acid, malefic acid
anhydride, fumaric acid, dimeric and trimeric fatty acids such
as oleic acid optionally mixed with monomeric fatty acids,
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_ g _
terephthalic acid dimethyl ester and terephthalic acid
bis-glycol ester. Examples of suitable polyhydric alcohols
include ethylene glycol, 1,2- and 1,3-propanediol, 1,4- and
2,3-butanediol, 1,6-hexanediol, 1,8-octanediol, neopentyl
glycol, cyclohexanedimethanol, 1,4-bis(hydroxymethyl)cyclo-
hexane, 2-methyl-1,3-propanediol, glycerol, trimethylolpropane,
1,2,6-hexanetriol, 1,2,4-butanetriol, trimethylolethane,
pentaerythritol, quinitol, mannitol and sorbitol, methyl-
glycoside, diethylene glycol, triethylene glycol, tetraethylene
l0 glycol, dipropylene glycol, dibutylene glycol, and polybutylene
glycols.
Mixtures of the above-mentioned polyether polyols
with polycarbonate polyols and/or polyester polyols having
average molecular weights of from 1000 t.o 3000 and obtained
from adipic acid, 1,6-hexanediol, and neopentyl glycol are also
particularly preferred.
Further starting components for the preparation of
polyurethanes (A) are in particular chain lengthening agents
having molecular weights of from 32 to 299 and containing 1,4-
hydroxyl and/or amino groups.
Low molecular weight polyhydroxyl compounds ("chain
lengthening agents") include a wide variety of diols such as,
for example:
a) Alkane diols such as ethylene glycol, 1,2- and 1,3-
propanediol, 1,4-butanediol, 1,5-pentanediol, dimethyl-
1,3-propanediol, and 1,6-hexanediol;
b) Ether diols such as diethylene glycol, triethylene glycol,
or hydroquinone dihydroxyethyl ether;
c) Ester dials corresponding to the following general
. formulas:
HO-(CH2)x-CO-0-(CH2)y-OH and
HO-(CH2)x-0-CO-R-CO-0-(CH2)x-OH
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wherein
R denotes an alkylene or arylene group having 1 to 10
(preferably 2 to 6) carbon atoms,
x is from 2 to 6, and
y is from 3 to 5,
for example, b-hydroxybutyl-E-hydroxycaproic acid ester,
w-hydroxyhexyl-y-hydroxybutyric acid ester, adipic acid
f3-hydroxyethyl ester, and terephthalic acid bis(f3-hydroxyethyl)
ester.
Polyamines may also be used as chain lengthening
agents and are preferably aliphatic or cycloaliphatic diamines,
although trifunctional or higher functional polyamines may also
be included for producing a particular degree of branching.
Examples of suitable aliphatic polyamines include ethylene-
diamine, 1,2- and 1,3-propylenediamine, 1,4-tetramethylene-
diamine, 1,6-hexamethylenediamine, the isomeric mixture of
2,2,4- and 2,4,4-trimethylhexamethylenediamine, 2-methyl-
pentamethylenediamine, and bis(f3-aminoethyl)amine (diethylene-
triamine).
Suitable cycloaliphatic polyamines include
CH" CH2-NH2 CH3
NH2
C CH3
NH2 NH2
CH3 NH2
H2N NH2
NH2
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NH2
H2N CHI NHZ
NH2
CH3 CH3
H2N )-- CH2--i NH2
CH3 CH3
H2N ?-- CH2 NH2
CH3 CH3
Araliphatic: polyamines, such as, 1,3- and
1,4-xylylenediamine or a,a,a',a'-tetramethyl-1,3- and
-1,4-xylylenediamine may also be used as chain lengthening
agents for the preparation of polyurethanes (A).
Hydrazine, hydrazine hydrate, and substituted
hydrazines are also to be regarded as diamines for the purpose
of this invention. Examples include methyl hydrazine, N,N'-
dimethyl hydrazine and their homologues, and acid dihydrazides
such as carbodihydrazide, oxalic acid dihydrazide, the
dihydrazides of malonic acid, succinic acid, glutaric acid,
adipic acid, f3-methyladipic acid, sebacic acid, hydracrylic
?0 acid and terephthalic acid, semicarbazido-alkylene hydrazides
such as f3-semicarbazidopropionic acid hydrazide (German
Offenlegungsschrift 1.,770,591), semicarbazido alkylene carbazic
esters such as 2-semicarbazidoethyl carbazic ester (German
Offenlegungsschrift 1.,918,504), or aminosemicarbazide compounds
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such as (3-aminomethylsemicarbazido carbonate (German Offen-
legungsschrift 1,902,931).
Ionic groups for the polyurethanes (A) include alkali
metal and ammonium carboxylate and sulfonate groups and
ammonium groups. Suitable components for introducing these
ionic groups into the polyurethanes (A) include dihydroxy-
carboxylic acids, diaminocarboxylic acids, dihydroxysulfonic,
acids and diaminoalkylsulfonic acids and their salts, for
example, dimethylolpropionic acid, ethylenediamino-Q-ethyl-
lo sulfonic acid, ethylenediamino-propyl- or -butyl-sulfonic acid,
1,2- or 1,3-propylenediamine-(3-ethylsulfonic acid, lysine,
3,5-diaminobenzoic, acid and their alkali metal and/or ammonium
salts, as well as the adduct of sodium bisulfite with 2-butene-
1,4-diol.
1s The preferred components used for introducing the
ionic groups into polyurethanes (A) include, in particular, the
aliphatic diols containing sulfonate graups according to German
Offenlegungsschrift 2,446,440 that correspond to the following
formula
HO-[iH-CH2-0]n-CH2-CH2- H-CH2-[0-CH2-~H]m-OH
R 03M R
wherein
R denotes hydrogen or an organic group having 1 to 8 carbon
atoms,
m and n independently represent the numbers 1 to 10, and
M denotes ammonium or the cation of an alkali metal.
Examples of (potentially) cationic starting
components include diols having tertiary amino groups, such as
N-methyl-diethanolamine and its protonation or alkylation
3o products.
The components used for introducing the ionic groups
into polyurethanes (A) may in general be cationic and/or
anionic hydrophilic difunctional starting components of the
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type described for the preparation of aqueous polyurethane
dispersions, such as, for example, dihydroxyl compounds,
diamines, or diisocya.nates containing (potentially) ionic
groups.
The aqueous phase (B) consists for the most part of
water but may also contain organic auxiliary solvents.
Preferred organic auxiliary solvents include, for example,
amides such as N,N-dimethylformamide, N,N-dimethylacetamide,
amd N-methylpyrrolidone; ketones, such as, methyl ethyl ketone,
1o diacetone alcohol, and cyclohexanone; ethers such as ethylene
glycol monomethyl-, monoethyl-, and monobutyl ethers and the
corresponding ethers of diethylene glycol, and propylene glycol
monomethyl- and monobutyl ether; and esters such as propylene
glycol diacetate and dipropylene glycol methyl ether acetate.
The quantity of organic auxiliary solvents is preferably up to
20fo by weight (preferably up to 10% by weight), based on the
total amount of aqueous phase (B).
Polyurethane (A) that is obtained as a solvent-free melt
or in the form of a solution after its preparation may then be
2o converted into an aqueous dispersion by mixing with water and
optionally thereafter distilling off any auxiliary solvent.
Polyurethanes (A) may in principle be converted into
aqueous dispersions by any known process, for example, by
dispersion without the aid of solubilizing agents, for example,
by mixing the solvent;-free polyurethane with water in apparatus
capable of producing high shearing gradients, by using very
small quantities of organic solvents for plasticizing the
polyurethanes in the same apparatus, or by using non-mechanical
dispersing agents such as extremely high frequency sound waves.
. On the other hand, simple mixing apparatus, such as stirrer
vessels or so-called throughflow mixers, may be used since
polyurethane (A) is <.;elf-dispersible.
The dispersions may be mixed with other anionic or
non-ionic dispersions., for example, with polyvinyl acetate or
with polyethylene, polystyrene, polybutadiene, polyvinyl
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chloride, polyacrylate, or copolymer dispersions. Known
emulsifiers that are not chemically fixed, preferably ionic
emulsifiers of this type, may also be added but are, of course,
not necessary.
Fillers, plasticizers, pigments, carbon black and
silica sols, and dispersions of aluminum, clay, or asbestos may
also be incorporated in the dispersion.
Certain properties of the coatings prepared according
to the invention, such as the handle or the surface smoothness,
may be modified by means of oligomeric compounds with molecular
weights of from 300 to 6000 (preferably from 500 to 1500)
containing polysiloxane segments and having at least two
isocyanate reactive groups. Difunctional polysiloxanes
containing organofunctional end groups are preferably used.
Such compounds have structural units of the formula -0-Si(R)2-
wherein R represents a C1-C4 alkyl group or a phenyl group
(preferably a methyl group).
The aqueous coating compositions according to the
invention are stable and suitable for storage and transport and
2o may be worked up at any later time. The properties of coatings
obtained can be varied according to the selected chemical
composition and the urethane group content. Thus, soft, sticky
layers and thermoplastic or rubbery elastic products with
various degrees of hardness up to glass-hard duroplasts may be
obtained. The hydrophilic character of the products may also
vary within certain limits. The elastic products may be
thermoplastically processed at elevated temperatures, for
example, at from 100 to 180°C, provided they are not chemically
cross-linked.
30. The coating compositions according to the invention
are suitable for coating or dressing and impregnating woven and
non-woven textiles, leather, paper, hard fibres, straw, and
paper-type materials. For this purpose, the dispersions or
pastes are preferably applied to a porous support which
subsequently remains bonded to the finished product, for
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example, woven or non-woven textiles or fiber mats, felts or
non-woven webs or pape r webs, foam sheets, or split leather,
which bring about instant solidification of the coating due to
the suction effect of such substrates. The resultant product
is subsequently dried at elevated temperature and, optionally,
pressed. Drying may also be carried out on smooth, porous, or
non-porous materials, such as metal, glass, paper, cardboard,
ceramic material, steel sheeting, silicone rubber, or aluminum
foil. The finished sheet structure is subsequently lifted off
and used as such or applied to a substrate by the reversal
process entailing gluing, flame backing, or calendering.
Application by the reversal process may be carried out at any
time.
The coating composition may be applied to the
substrate by direct spread coating using coating knives,
rollers, or wire coaters. It is customary to apply several
coats in succession, preferably in two coats, so that the total
thickness of the coating composed of undercoat and top coats)
amounts to 10-100 ~cm (preferably 20-60 ~cm) .
The undercoat may also be a paste which dries to form
a microporous layer, as described in German Offenlegungsschrift
2,020,153.
The top coat that is subsequently applied protects
the entire combination of layers against mechanical stress and
abrasion.
Application of the coating combination composed of
undercoat and top coat may also be carried out by the so-called
reversal process, in which the top coat is first applied to a
separating support and dried, and, after application of a
second undercoat or bonding coat, the textile substrate is
lightly pressed into 'the still moist layer. After drying, a
firmly bonded combination of coating and substrate is obtained.
This bonded comination is detached from the separating support
and is substantially .similar in its structure to the direct
coating product described above.
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The coating compositions according to the invention
give rise to coatings in which the permeability to water vapor
has surprisingly little dependence upon the thickness of the
layer over a wide range of layer thicknesses. The coatings do
not swell noticeably in water.
The coatings, which are exceptionally permeable to
water vapor and absolutely resistant to drops, may also be
prepared from aqueous dispersions containing pigments and/or
dyes. Hydrophobicizing agents such as fluorocarbon resins,
1o waxes, and oils may also be added, provided they do not unduly
impair the permeability to water vapor. Cross-linking
additives that undergo a reaction on their own or with
polyurethane (A) only in the finished coating, generally by the
action of heat, may also be used. Examples of such compounds
include (partially) etherified melamine formaldehyde resins
(e.g., hexamethylol melamine) and polyisocyanates that are
optionally blocked and have 3 or more isocyanate groups (e. g.,
based on tris(isocyanatohexyl)isocyanurate and tris(isocyanato-
hexyl)biuret).
2o The invention further relates to the use of the
coating compositions according to the invention for the
preparation of water vapor permeable coatings, in particular,
on flexible substratE~s, such as textiles, leather, paper, and
the like.
The following examples further illustrate details for
the preparation and use of the compositions of this invention.
The invention, which is set forth in the foregoing disclosure,
is not to be limited either in spirit or scope by these
examples. Those ski'Iled in the art will readily understand
that known variations of the conditions and processes of the
following preparative procedures can be used to prepare these
compositions. Unless otherwise noted, all temperatures are
degrees Celsius and all parts and percentages are parts by
weight and percentages by weight, respectively.
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EXAMPLES
Starting materials used in the Examples:
Diol I: Polycarbonate of 1,6-hexanediol and tetra-
ethylene glycol (molar ratio 1:1), OH
number 56, molecular weight 2000, ethylene
oxide ("EOX") content 49%
Diol II: Polycarbonate of 1,6-hexanediol and tetra-
ethylene glycol (molar ratio 2:5), OH
number 82, molecular weight 1370, EOX
content 65%
l0 EOX polyether III: Monofunctional polyethylene glycol, OH
number 25, molecular weight. 2250
Diol sulfonate IV: Product of addition of NaHS03 to
propoxylated butene-1,4-diol, OH number
approximately 260, molecular weight 425
Diaminosulfonate V: H2N-CH2CH2-NH-CH2CH2-S03Na
Methods of measurement
The permeabilities to water vapor ("WVP") were
determined by the methods set out in publication DS 2109 TM1 of
British Textile Technology Group, Manchester, England.
The water resistance ("WR") was determined according
to DIN 53,886.
The resistance to drops was determined by subjecting
the upper surface of the coating to the action of water drops
(1 minute). If no pustular changes occur on the surface, the
coating is described as "absolutely drop resistant".
Example 1 Preparation of an aromatic polyurethane dispersion
for water-vapor permeable layers.
Formulation:
247.2 g diol I
15.2 g EOX polyether III
18.0 g diol sulfonate IV
200 g acetone
84.6 g 4,4'-diphenylmethane diisocyanate
17.0 g hexane-1,6-diisocyanate
Mo3955
- 18 -
18.0 g acetone azine
600.0 g desalted water
387 g of solid substance contained 10.9 meq of
S03Na/100 g and 31.3% by weight of EOX in the main chain.
Method:
The acetone and mixture of the two diisocyanates were
stirred into the mixture of components I, III, and IV that had
been dehydrated at 120°C, and the mixture was left to react
under reflux until the isocyanate value was constant. After
the temperature dropped to 40°C, the acetone azine was stirred
into the isocyanate prepolymer solution. The water was then
introduced with vigorous stirring, the resulting dispersion was
stirred for a further 2 hours, and the acetone was distilled
off.
A film weighing 68 g/m2 was prepared to determine the
permeability to water vapor (WVP). For this purpose, 100 g of
the dispersion were adjusted to a suitable viscosity for spread
coating using 1% of a polyacrylic acid thickener after
adjustment of the pH to 8 with concentrated ammonia. The water
vapor permeability was 15,700 g/m2d.
A film weighing 56 g/m2 prepared for comparison from
a polyurethane dispersion that had been prepared from a
formulation containing a polycarbonate of 1,6-hexanediol with
molecular weight 2000 instead of diol I but which otherwise had
the same composition had a permeability to water vapor of only
800 g/m2d. The solid substance contained 10.9 meq S03Na/100 g
and 0% EOX in the main chain.
Example 2 Preparation of an aliphatic polyurethane dispersion
for water-vapor permeable layers.
Formulation:
129.7 g polycarbonate from 1,6-hexanediol, OH number 56,
molecular weight 2000
114.0 g diol I
82.6 g dihydroxypolypropylene glycol, OH number 56,
molecular weight 2000
Mo3955
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5.0 g dimethylolpropionic acid
59.5 g hexane-1,6-diisocyanate
2.2 g ethylenediamine
1.4 g hydrazine hydrate
5.6 g diaminosulfonate V
700.0 g acetone
600.0 g water
400 g of solid substance contained 7.4 meq S03Na/100
g and 149 by weight EOX in the main chain.
Method:
Polycarbonate, diol I, and dihydroxypolypropylene
glycol were dehydrated under vacuum at 105°C for 1 hour.
Dimethylolpropionic acid was added at 100°C and hexane-
diisocyanate was added at 80°C. After 3 hours at 95°C, the
resultant prepolymer was dissolved in acetone. The mixture of
chain lengthening agents comprising ethylene diamine, hydrazine
hydrate, and diaminosulfonate V dissolved in 120 g of water was
added dropwise at 50°C. The remaining quantity (480 g) of
water was then stirred in. After continuous stirring for 2 1/2
2o hours at 40°C, the acetone was removed by distillation. A
stable 40% dispersion was obtained.
To determine the permeability to water vapor, a film
weighing 53 g/m2 was prepared after thickening as in Example 1.
The WVP was 9500 g/m2d.
A comparison film prepared from a polyurethane
dispersion which instead of containing Diol I contained a
larger quantity, corresponding to the molar quantity, of a
polycarbonate of 1,6-hexanediol having a molecular weight of
2000 but which otherwise had the same composition had a
. permeability to water' vapor of only 900 g/m2d in a film having
a thickness corresponding to 58 g/m2. The solid substance
contained 7.4 meq S03Na/100 g and 0f° EOX in the main chain.
Mo3955
2°- 2109178
Transfer coating:
The dispersion described in Example 1 together with a
polyacrylic acid thickener was applied to a commercial
separating paper (Transcote* VEM CIS of S.D. Warren Company) by
means of a roller applicator with built-in coating knife so
that a film of 25 g/m2 was obtained after drying at 80 to
150'C.
Spread coating paste:
100 parts 40% PUR dispersion from Example 1
l0 1 part polyacrylic acid thickener
5 parts aqueous pigment preparation adjusted to pH 8
with ammonia
A spread coating paste prepared analogously from the
polyurethane dispersion of Example 2 (without pigment
preparation) was applied as bonding layer to the dried film.
After lamination of a cotton fabric weighing about 140 g/m2 and
drying of the whole arrangement of layers at 80 to 140'C, the
water-vapor permeable .article obtained had a total weight of
200 g/m2 and the coating composed of top coat and bonding coat
2p weighed 60 g/m2.
The soft article, which has a pleasant handle, has a
water vapor permeability of 6600 g/m2d and a water resistance
of 2000 mm.
A transfer article of analogous structure prepared
from the comparison dispersions described in Examples 1 and 2
without diol I has a water vapor permeability of 750 g/m2d in a
coating weighing 60 g/m2.
Example 3 Preparation of an aliphatic polyurethane dispersion
for water vapor permeable layers.
. Formulation:
245.5 g diol I
75.5 g dihydroxypolypropylene glycol, OH number 56,
molecular weight 2000
12.7 g EOX polyether III
3..1 g neopentyl glycol
*trade-mark
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- 21 -
54.0 g hexane diis:ocyanate
2.3 g ethylene diamine
1.4 g hydrazine hydrate
4.7 g diaminosulfonate V
700.0 g acetone
600.0 g water
400 g solid substance contained 6.2 meq S03Na/100 g
and 30.0% by weight E:OX in the main chain.
Method:
1o A 40~ dispersion was prepared analogously to Example
2. To determine the permeability to water vapor, the
dispersion was thickened as in Example 1 and a film weighing 57
g/m2 was produced. The water vapor permeability was 3600
9/m2d.
A comparison film produced from a polyurethane
dispersion which instead of containing diol I contained a
polycarbonate of 1,6-hexanediol of molecular weight 2000 but
was otherwise identical in composition had a water vapor
permeability of only 750 g/m2d when the film thickness was 59
g/m2.
Transfer coating:
A spread coating paste prepared from the dispersion
of Example 3 was applied as bonding layer to the top coat
described in Example 2 using a method analogous to that
. described in Example 2, and the layers were laminated at 140°C
with the cotton fabric also described in Example 2. The
coating composition composed of top coat and bonding coat
weighed 60 g/m2. The water vapor permeability of the article
was 6300 g/m2d at 2000 mm water resistance.
Example 4 Preparation of an aliphatic polyurethane dispersion
for WVP layers.
Formulation:
131.4 g polycarbonate of hexane-1,6-diol, OH number 56,
molecular weight 2000
116.8 g diol I
Mo3955
21091'78
_ 22 _
19.7 g EOX polyether III
6.2 g dimethylolpropionic acid
10.5 g 1,4-butanediol
44.2 g hexane-1,6-diisocyanate
58.3 g isophorone diisocyanate
3.5 g ethylene diamine
2.2 g hydrazine hydrate
7.2 g diaminosulfonate V
700.0 g acetone
lo~ 600.0 g water
400 g solid substance contaied 9.5 meq S03Na and
14.3 by EOX in the main chain.
Method:
A 40% polyurethane dispersion was prepared from these
components analogously to Example 2 by the acetone process.
To determine the permeability to water vapor, a film
weighing 52 g/m2 was prepared after thickening of the
dispersion with 3.0 g of a 30% solution of poly-N-vinyl-
pyrrolidone. The water vapor permeability was 11,300 g/m2d.
A comparison film from a polyurethane dispersion
analogous to that of Example 4 in which Diol I had been
replaced by the equimolar quantity of hexanediol polycarbonate
had a water vapor permeability of 1500 g/m2d in a film weighing
48 g/m2. The solid substance contained 9.5 meq S03Na and 0%
EOX in the main chain.
Transfer coating:
The polyurethane dispersion which had been thickened
with poly-N-vinylpyrrolidone as described above was used for
producing a top coat as in Example 2 after it had been
. pigmented. The spread coating paste described in Example 3 was
used as bonding coat. The textile substrate used was a mixed
fabric of cotton/polyester weighing 100 g/m2. The coating
composed of top coat and bonding coat weighed 53 g/m2. The
water vapor permeability was 6900 g/m2d. When the bonding coat
paste was used as a so-called beaten foam dispersion, unit
Mo3955
21Q9~~8
- 23 -
weight 500 g/1, the water vapor permeability was 7500 g/m2d
when the total layer weighed 55 g/m2 and the water resistance
was 2000 mm.
When the comparison dispersion mentioned in Example 4
was used as top coat and the comparison dispersion mentioned in
Example 3 was used as bonding coat, the water vapor
permeability values were 900 g/m2d (compact) and 1150 g/m2d
(foamed).
Example 5 Preparation of an aliphatic polyurethane dispersion
for water vapor permeable layers.
Formulation:
74.3 g 1,6-hexanediol polyadipate, OH number 133, molecular
weight 840
132.2 g diol II
27.3 g diol sulfonate IV
6.5 g trimethylolpropane
33.8 g N-methylpyrrolidone
118.0 g dicyclohexylmethane-4,4'-diisocyanate
21.5 g hexane-1,6-~diisocyanate
20.2 9 acetone azine
545.0 g desalted water
386 g of solid substance contained 16.7 meq S03Na/100
g and 22.3% by weight EOX in the main chain.
Method:
Trimethylolpropane, N-methylpyrrolidone, and the two
isocyanates were stirred at 70'C into the mixture of polyester
and components II and IV, which had been dehydrated at 100'C.
The mixture was allowed to react at 80°C until the NCO value
was constant. After cooling to 75'C, the acetone azine was
stirred into the isocyanate prepolymer melt. The water was
then introduced with vigorous stirring and the resultant
dispersion continued to be stirred for a further 3 hours. The
polyurethane dispersion was adjusted to a spread coating
viscosity (8000 mPa.s/25°C) with a polyacrylic acid thickener
Mo3955
~1091'~8
- 24 -
at pH 8 as in Example 1. The film weighing 56 g/m2 thus
produced had a water vapor permeability of 13,800 g/m2d.
The comparison film obtained from a polyurethane
dispersion analogous to that of Example 5 but with the diol II
content replaced by the equimolar quantity of hexanediol
polyadipate had a water vapor permeabiity of only 400 g/m2 in a
film weighing 52 g/m2. The solid substance (1040 g) contained
19.2 meq S03Na/100 g and 0% by weight EOX in the main chain.
Transfer coating:
1o The dispersions described in Examples 2 and 5 were
applied to a commercial separating paper (Transcote VEM C1S of
S.D. Warren Company) in a ratio by weight of 1:1 together with
a polyacrylic acid thickener, using a roller coating device
with coating knife cut in, to produce a film which weighed 25
9/m2 after drying at 80 to 150°C.
Spread coating paste:
50 parts 40% polyurethane dispersion of Example 2
50 parts 40% polyurethane dispersion of Example 5
1 part polyacrylic acid thickener
5 parts aqueous pigment preparation adjusted to pH 8 with
ammonia
A spread coating paste prepared analogously from the
polyurethane dispersion of Example 2 (without pigment
preparation) was applied as bonding layer to the dried film.
After lamination with a cotton fabric weighing about 140 g/m2
and drying of the whole arrangement of layers at 80 to 140°C,
the water vapor permeable article obtained had a total weight
of 200 g/m2 with the coatings (top coat and bonding coat)
weighing 60 g/m2.
The article, which was soft and pleasant to handle,
had a permeability to water vapor of 10,600 g/m2d with a water
resistance of 2000 mm WR.
When the amount of coating was varied from 50 g/m2 to
75 g/m2, the permeabilities to water vapor were equally high
with water resistance values of 2000 mm WR.
Mo3955
21091 78
- 25 -
A transfer article produced from the comparison
dispersions described in Examples 2 and 5 but without diol I or
diol II and analogous in structure had a water vapor
permeability of 1750 g,~m2 in a coating weighing 60 g/m2.
A further increase in permeability to water vapor can
be obtained by using a foamed bonding coat instead of the
compact bonding coat of Example 2.
A spread coating foam paste was applied to the dried
film of top coat in layers of 40 to 50 g/m2.
Foam spread coating paste (mechanical foaming):
100 parts 409: polyurethane dispersion of Example 2
2.0 parts STOKAL* SR foamant (Stockhausen)
0.8 parts STOKAL* STA foam stabilizer (Stockhausen)
1.5 part MIROX* AM thickener (Stockhausen)
. X parts ammonia to adjust to pH 8-9
Weight per litre: about 500 g/1
After lamination with a cotton fabric weighing about
140 g/m2 and drying of the arrangement of coatings at 80 to
140'C, the water vapor permeable article obtained had a total
weight of 220 g/m2 and the layer composed of top coat and
foamed bonding coat weighed 80 g/m2.
The soft article, which had a very pleasant handle,
had a water-vapor permeability of 13,500 g/m2d at 2000 rtm WR.
When sub,)ected to discrete water droplets, the
coatings were absolutely resistant to drops and exhibited
hardly any swelling 1n water.
Example 6 Preparation of an aliphatic polyurethane dispersion
for WVP layers.
Formulation:
30.. 258.0 g polyadipate of 1,6-hexanediol/neopentyl glycol (molar
ratio 65:35), OH number 66, molecular weight 1700
69.2 g diol II
60.0 g hexane-1,6-diisocyanate
2.4 g ethylene diamine
10.0 g diaminosulfonate V
*trade-mark
Mo3955
~1U9~'~8
- 26 -
70.0 g acetone
600.0 g water
400 g of solid substance contained 13.1 meq/100 g and
11.2~o by weight EOX in the main chain.
Method:
A 40% dispersion was prepared by the acetone process
analogously to Example 2. The permeability to water vapor of a
film weighing 63 g/m2 was 4400 g/m2d.
A film obtained from a dispersion in which the diol
to II content had been replaced by the equimolar quantity of a
polyadipate of 1,6-hexanediol/neopentyl glycol had a water
vapor permeability of 800 g/m2d (weight of film 54 g/m2). The
solid substance (417 g} contained 12.6 meq/100 g and O~o by
weight EOX in the main chain.
15 Example 7 Preparation of an aliphatic polyurethane dispersion
for WVP layers.
Formulation:
239.0 g diol I
14.7 g EOX polyether III
20 17.4 g diolsulfonate IV
111.5 g dicyclohexylmethane-4,4'-diisocyanate
17.4 g acetone azine
600.0 g desalted water
388 g of solid substance contained 10.6 meq S03Na/100
25 g and 30.2% by weight EOX in the main chain.
Method:
A 40~o dispersion was prepared by the acetone azine
process analogously to Example 5.
A film weighing 56 g/m2 had a WVP value of 6900 g/m2.
3o A film obtained from a polyurethane dispersion
containing, instead of diol I, the equimolar quantity of a
polyadipate of 1,6-hexanediol/neopentyl glycol (molar ratio
65:35), molecular weight 2000, and otherwise having the same
composition had a water vapor permeability of only 1200 g/m2d
Mo3955
~1091~8
_ 27 _
in a film weighing 60 g/m2. The solid substance (388 g)
contained 10.6 meq S03Na/100 g and 0% EOX in the main chain.
Example 8 Preparation of an aliphatic polyurethane dispersion
for WVP 1 ayers .
Formulation:
260.6 g diethylene glycol polyadipate, OH number 45,
molecular
weight 2500
66.7 g dihydroxypolypropylene glycol, OH number 56,
1o molecular weight 2000
11.3 g EOX polyether III
3.6 g dimethylolpropionic acid
50.4 g hexane-1,6-diisocyanate
2.0 g ethylenediamine
1.3 g hydrazine hydrate
4.1 g diaminosulfonate V
700.0 g acetone
600.0 g water
400g of solid substance contained 5.4 meq S03Na/100 g
2o and 26% by weight EOX in the main chain.
Method:
A 40% dispersion was prepared by the acetone process
analogously to Example 2.
A film prepared from the dispersion which had been
thickened as in Example 1 had a water vapor permeability of
3600 g/m2d in a film weighing 56 g/m2.
When the diethylene glycol polyadipate in this
Example was replaced by the equimolar quantity of 1,6-hexane-
diol polycarbonate (molecular weight 2000), the film produced
. from this dispersion, weighing 58 g/m2, had a permeability to
water vapor of 900 g/m2d. The solid substance (348 g)
contained 6.2 meq S03,Na/100 g and 0% EOX in the main chain.
Example 9 Preparation of an aliphatic polyurethane dispersion.
Formulation:
131.4 g hexane-1,6-diol polycarbonate, OH number 56,
Mo3955
~~Q~~~g
_ 28 _
molecular weight 2000
116.8 g polycarbonate from triethylene glycol, OH number 56,
molecular weight 2000
19.7 g EOX polyether III
6.2 g dimethylolpropionic acid
10.5 g 1,4-butanediol
44.2 g hexane-1,6-diisocyanate
58.3 g isophorone ~diisocyanate
3.5 g ethylene diamine
lo- 2.2 g hydrazine hydrate
7.2 g diaminosulf~onate V
750.0 g acetone
600.0 g water
400 g of solid substance contained 9.5 meq S03Na/100
g and 22% by weight EOX in the main chain.
Method:
A 40%a dispersion was prepared analogously to Example
2 by the acetone process.
A film produced from a dispersion which had been
2o thickened as in Example 1 and weighed 54 g/m2 had a
permeability to water vapor of 10,500 g/m2d.
When the polycarbonate of triethylene glycol was
replaced by the equimolar quantity of the polycarbonate of
hexane-1,6-diol, the film obtained from this dispersion had a
water vapor permeability of 1500 g/m2d when the weight was 48
g/m2. The solid substance X400 g) contained 9.5 meq S03Na/100
g and 0% EOX in the main chain.
Example 10 Preparation of an aliphatic polyurethane dispersion
far WNP layers.
3o Formulation:
60.9 g polycarbonate of 1,6-hexanediol, OH number 56,
molecular weight 2000
207.1 g diol I
6.5 g dimethylolpropionic acid
11.0 g 1,4-butanediol
Mo3955
~109I'~8
_ 29 _
43.5 g hexane-1,6-diisocyanate
57.5 g isophorone diisocyanate
3.7 g ethylene diamine
3.3 g hydrazine hydrate
7.5 g diaminosulfonate V
700.0 g acetone
600.0 g water
400 g of solid substance contained 9.9 meq S03Na/100
g and 25.4% by weight EOX in the main chain.
Method:
A 40% polyurethane dispersion was prepared from these
components by the acetone process as in Example 2.
To determine the permeability to water vapor, a film
weighing 52 g/m2 was prepared from the dispersion after it had
been thickened with 3.0 g of a 30% solution of poly-N-vinyl
pyrrolidone. The water vapor permeability was 12,300 g/m2d.
A comparison film produced from a polyurethane
dispersion analogously to Example 10 without containing diol I
but containing the equimolar quantity of the polycarbonate of
2o hexanediol and having otherwise the identical composition had a
water vapor permeability of 1500 g/m2d in a film weighing 48
9/m2-
Transfer coating:
The polyurethane dispersion which had been thickened
with poly-N-vinylpyrrolidone as above was used for producing a
top coat after it had been pigmented as in Example 2. The
spread coating paste described in Example 2 was used as bonding
coat. The textile substrate used was a mixed fabric of
cotton/polyester weighing 100 g/m2. The coating composed of
. top coat and bonding coat weighed 53 g/m2. The water vapor
permeability was 11,100 g/m2d. When the bonding coat paste was
used as a so-called beaten foam dispersion with a unit weight
of 500 g/1, the water vapor permeability of the whole coating
weighing 55 9/m2 was 14,500 g/m2d.
Mo3955
21091'8
- 30 -
The coatings. from all the examples according to the
invention were resistant to drops and showed hardly any
swelling in water.
When the comparison dispersion mentioned in Example
10 was used as top coat and the comparison dispersion mentioned
in Example 2 was used as bonding coat, the water vapor
permeability values were 800 g/m2d (compact) and 950 g/m2d
(foamed).
Mo3955
