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Description  |
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BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to new, ionically modified PUR spreading pastes, to
their production and to their use for the production of coatings permeable
to water vapor on fabrics or leather substrates by the direct or transfer
method using the technique of evaporation coagulation.
2. Description of the Prior Art
Fabric or leather coatings highly permeable to water vapor are of
increasing interest, above all in the shoe and coating fields. The
advantage of coated materials such as these is that the clothing produced
from them on the one hand affords optimal protection, but on the other
hand allows bodily moisture to escape in the form of water vapor. These
properties are extremely valuable both from the physiological and hygiene
point of view and also from the point of view of wearing comfort.
An important process for producing microporous coatings permeable to water
vapor is the so-called bath coagulation process described, for example, in
DE-AS No. 1,270,276 and in DE-AS No. 1,769,277. In this process, a
substrate is coated with a polyurethane or polyurethane urea dissolved in
an organic solvent and the coated product is introduced into a bath of a
non-solvent (for example water) miscible with the solvent. Coagulation of
the polyurethane is obtained by extraction of the solvent by the
non-solvent.
The disadvantages of this process are that very large quantities of
non-solvent are required for the necessary complete removal of the solvent
and that the process is time-consuming. In addition, special, relatively
expensive apparatus are required for carrying out this process and also
for working up the solvent/non-solvent mixtures accumulating therein.
Accordingly, there have been no shortage of attempts to produce coatings
permeable to water vapor by the direct or transfer coating processes using
conventional fabric coating machines. Most of these attempts are based on
the so-called technique of evaporation coagulation. In principle, this
process is carried out by adding a certain quantity of a less volatile
non-solvent to a polymer dissolved in a volatile solvent and spreading the
resulting solution, dispersion or suspension onto a substrate. The coating
is dried by careful heating, during which the volatile solvent
preferentially evaporates first. The result is that the polymer coagulates
in the layer and, after final drying, shows a microporous structure. This
process is described, for example, in DE-PS No. 1,694,059. The
polyurethanes used therein are colloidally dissolved in volatile organic
solvents such as tetrahydrofuran or methylethylketone and mixed with
organic non-solvents having a higher evaporation index such as cleaning
spirit. A similar process is described in CH-PS No. 481, 971with the added
feature that water is included among the non-solvents mentioned therein
for addition to the polymer solutions. Another example of this approach is
the process according to DE-PS No. 2,004,276 which uses hydrophilic
polyurethanes based on aromatic diisocyanates which contain certain
proportions of polyoxyethylene compounds as synthesis components.
Solutions of these polyurethanes in certain organic solvents such as
methylethylketone are mixed with water as non-solvent and applied to a
substrate, after which the coating is coagulated by selective evaporation
and subsequently dried.
However, the above-mentioned processes based on the principle of
evaporation coagulation also have serious disadvantages. A major
disadvantage is that selective evaporation of the more volatile solvent
components is time-consuming and requires extremely precise temperature
control.
Accordingly, handling of the corresponding products in the coating machines
is complicated and, above all, only possible at low rates of travel.
Another serious disadvantage which applies in particular to the process
according to DE-PS No. 2,004,276 is that the polyurethane solutions or
suspensions described therein are difficult to process. Although they have
low solids contents, these products are highly viscous, even before the
addition of water which is made at the time of application. They are
described as "sludge-like suspensions" and show a pronounced tendency
towards premature drying with formation of gel particles and specks.
Therefore, they are difficult to handle.
Accordingly, an object of the present invention is to provide a process for
the production of coatings permeable to water vapor which may be carried
out by the direct or transfer method in conventional coating machines and
which does not have any of the disadvantages described in the foregoing.
This object is achieved by the process according to the invention which is
described in detail hereinafter. The invention is based on the surprising
observation that multi-phase, stable spreading pastes, which may be
processed surprisingly easily in conventional coating machines to form
microporous coatings, can be obtained from hydrophobic polyurethanes or
polyurethane ureas which are dissolved in organic solvents and contain
certain silicone, polyether, polyester or perfluorocarbon resin segments
and, in addition, contain incorporated groups convertible into salts by
the addition of certain quantities of water. The process according to the
invention has the advantage that the polyurethane solutions are low in
viscosity before addition of the water and, accordingly, are easy and safe
to handle by the operator who prepares the ready-to-use spreading pastes
shortly before application. In addition, the spreading pastes obtainable
by the process according to the invention and characterized by
incorporated salt-forming groups are distinguished by particularly good
stability in storage and are safe to process. Finally, the microporous
coatings obtained by the process according to the invention combine the
requisite high permeability to water vapor with good waterproof
properties.
SUMMARY OF THE INVENTION
The present invention is directed to optionally pigmented spreading pastes
containing polyurethane plastics for the production of coatings permeable
to water vapor on fabric or leather substrates by the direct or transfer
method based on the principle of evaporation coagulation, characterized in
that the spreading pastes are multiphase mixtures of
(A) about 5 to 50% by weight of hydrophobic polyurethanes and/or
polyurethane ureas which contain about 0.01 to 0.5% by weight, preferably
about 0.05 to 0.25% by weight, of chemically incorporated groups
convertible into salts wherein least a portion of the groups, preferably
0.01-0.4% by weight, are present in salt form and about 1 to 30% by weight
of synthesis components containing at least two terminal and/or lateral
NCO-reactive groups based on silicone resins, atomatic hydroxypolyethers
aromatic hydroxypolyesters, perfluorocarbon resins or mixtures thereof,
(B) 0 to about 30% by weight of hydrophobic polyurethanes and/or
polyurethane ureas which contain about 0.01 to 0.5% by weight, preferably
about 0.05 to 0.25% by weight of chemically incorporated groups
convertible into salts wherein at least a portion of the groups are
present in salt form and which are synthesized without the special
synthesis components mentioned under (A).
(C) about 5 to 50% by weight of organic solvents for (A) and (B)
(D) 0 to about 40% by weight of organic non-solvents for (A) and (B),
(E) 0 to about 5% by weight of crosslinking agents or hydrophobicizing
agents and
(F) about 10 to 70% of water.
The present invention is additionally directed to a process for preparing
the spreading pastes by mixing solutions of the polyurethanes or
polyurethane ureas (A) and, optionally, (B) in the organic solvents (C)
(which may optionally contain the organic non-solvents (D) and component
(E)), with water (F) after conversion of at least a portion of the groups
capable of salt formation into salt form.
The present invention is also directed to the use of the spreading pastes
in the form of mixtures of components (A) to (F) having the quantitative
and qualitative composition indicated above for the production of coatings
permeable to water vapor on fabric or leather substrates by the direct or
transfer method based on the principle of evaporation coagulation.
DETAILED DESCRIPTION OF THE INVENTION
The polyurethanes or polyurethane ureas (A) are polyadducts obtainable in
known manner from polyisocyanates and compounds containing active hydrogen
atoms. However, the principal characteristic of these polymers if (1)
their content of about 0.01 to 0.5% by weight, preferably about 0.05 to
0.2% by weight, of groups convertible into salts such as carboxylic acid
and/or sulfonic acid groups, or tertiary amino groups and (2) their
content of silicone resins, aromatic hydroxypolyethers, aromatic
hydroxypolyesters and/or perfluorocarbon resins.
Starting materials for producing the polyurethanes or polyurethane ureas
(A) include:
1. organic polyisocyanates, preferably diisocyanates corresponding to the
formula Q(NCO).sub.2 where Q is an aliphatic hydrocarbon radical
containing 4 to 12 carbon atoms, a cycloaliphatic hydrocarbon radical
containing 6 to 25 carbon atoms, an aromatic hydrocarbon radical
containing 6 to 15 carbon atoms or an araliphatic hydrocarbon radical
containing 7 to 15 carbon atoms.
Examples of preferred diisocyanates include tetramethylene diisocyanate,
hexamethylene diisocyanate, 1,4-diisocyanatocyclohexane,
3-isocyanato-methyl-3,5,5-trimethylcyclohexylisocyanate (isophorone
diisocyanate), 4,4'-diisocyanatodicyclohexylmethane,
4,4'-diisocyanato-3,3'-dimethyldicyclohexylmethane,
4,4'-diisocyanatodicyclohexylpropane(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 diisocyanate,
.alpha.,.alpha.,.alpha.',.alpha.'-tetramethyl-m- or -p-xylylene
diisocyanate and mixtures of these compounds.
Particularly preferred diisocyanates (at least 50 mole % of all
diisocyanates) are isophorone diisocyanate and
4,4'-diisocyanatodicyclohexylmethane.
It is of course also possible to use the higher polyisocyanates known per
se in polyurethane chemistry or even modified polyisocyanates known per
se, for example polyisocyanates containing carbodiimide groups,
allophanate groups, isocyanurate groups, urethane groups and/or biuret
groups, in the process according to the invention.
2. Water-insoluble polyhydroxyl compounds of the type known per se in
polyurethane chemistry having molecular weights of 400 to about 10,000
preferably about 600 to 5000, and melting points below about 60.degree.
C., preferably below 45.degree. C. The corresponding dihydroxy compounds
are preferably used. Compounds having a functionality of 3 or higher in
the context of the isocyanate polyaddition reaction may be used in small
quantities to obtain a certain degree of branching. Tri-functional or
higher polyisocyanates may also be used for the same purpose, as mentioned
above. The polyhydroxyl compounds preferably are based on predominantly
aliphatic synthesis components.
Preferred hydroxyl compounds are the hydroxypolyesters, hydroxypolyethers,
hydroxypolythioethers, hydroxypolycarbonates and/or hydroxypolyester
amides known per se in polyurethane chemistry.
The polyesters containing hydroxyl groups which may be used in accordance
with the invention include reaction products of polyhydric, preferably
dihydric and, optionally, also trihydric alcohols with polybasic,
preferably dibasic carboxylic acids. Instead of using the free
polycarboxylic acids, it is also possible to use the corresponding
polycarboxylic acid anhydrides, corresponding polycarboxylic acid esters
of lower alcohols or mixtures thereof for producing the polyesters.
The polycarboxylic acids are preferably aliphatic and/or cycloaliphatic and
may optionally be substituted, for example by halogen atoms, and/or
unsaturated. Examples of suitable polycarboxylic acids include succinic
acid, adipic acid, suberic acid, azelaic acid, sebacic acid,
tetrahydrophthalic acid anhydride, endomethylene tetrahydrophthalic acid
anhydride, glutaric acid anhydride, maleic acid, maleic acid anhydride,
fumaric acid and dimeric and trimeric fatty acids (such as oleic acid,
optionally in admixture with monomeric fatty acids). Suitable polyhydric
alcohols include ethylene glycol, 1,2- and 1,3-propane diol, 1,4- and
1,3-butane diol, 1,6-hexane diol, 1,8-octane diol, neopentyl glycol,
1,4-bis-hydroxymethyl cyclohexane, 2-methyl-1,3-propane diol,
2,2,4-trimethyl-1,3-pentane diol, glycerol, trimethylol propane,
1,2,6-hexane triol, 1,2,4-butane triol, trimethylol ethane,
pentaerythritol, quinitol, mannitol, sorbitol, methyl glycoside,
1,4,3,6-dianhydrohexitols, diethylene glycol, dipropylene glycol,
polypropylene glycols, dibutylene glycol and polybutylene glycols.
The polyesters may contain terminal carboxyl groups. Polyesters of
lactones, for example .epsilon.-caprolactone, or hydroxy-carboxylic acids,
for example .epsilon.-hydroxycaproic acid, may also be used.
The polyethers preferably containing two hydroxyl groups suitable for use
in accordance with the invention are also known per se. They may be
obtained, for example, by the polymerization of tetrahydrofuran and/or
epoxides (such as ethylene oxide, propylene oxide, butylene oxide, styrene
oxide or epichlorohydrin) on their own (for example in the presence of
boron trifluoride) or by the addition of these epoxides, optionally in
admixture or successively, onto starter compounds containing reactive
hydrogen atoms such as alcohols and amines (for example water, ethylene
glycol or propylene glycol). In order to guarantee the crucial
characteristic of hydrophobicity of the polyurethane (urea)s according to
the invention, the polyethers used as synthesis components should only
contain at least so many ethylene oxide units that the resulting
polyurethanes or polyurethane ureas contain less than about 2% by weight
of oxyethylene segments --CH.sub.2 --CH.sub.2 --O--. Polyethers free from
ethylene oxide are preferably used for producing the polymers according to
the invention.
Polyethers modified by vinyl polymers of the type obtained, for example, by
the polymerization of styrene or acrylonitrile in the presence of
polyethers (U.S. Pat. Nos. 3,383,351, 3,304,273, 3,523,093, 3,110,695;
DE-PS No. 1,152,526) are also suitable. The higher functionality
polyethers which may also be used are similarly formed by the alkoxylation
of higher functionality starter molecules such as ammonia, ethanolamine,
ethylene diamine, trimethylol propane, glycerol or sucrose.
Among the polythioethers, reference is made in particular to the
condensates of thiodiglycol on its own and/or with other glycols,
dicarboxylic acids, formaldehyde, amino-carboxylic acids or aminoalcohols.
Depending on the coreactants, the products are polythiomixed ethers,
polythioether esters or polythioether ester amides.
Suitable polycarbonates containing hydroxyl groups include those known per
se which may be obtained, for example, by reaction of diols such as
1,3-propane diol, 1,4-butane diol and/or 1,6-hexane diol, with phosgene or
diarylcarbonates such as diphenylcarbonate.
The polyester amides and polyamides include the predominantly linear
condensates obtained from polybasic, saturated and unsaturated carboxylic
acids or their anhydrides and polyhydric, saturated and unsaturated
aminoalcohols, diamines, polyamines and mixtures thereof. Polyhydroxyl
compounds containing urethane or urea groups may also be used.
Representatives of the above-mentioned polyisocyanate and hydroxy compounds
suitable for use in the process according to the invention are described,
for example in High Polymers, Vol. XVI, "Polyurethanes, Chemistry and
Technology" by Saunders-Frisch, Interscience Publishers, New York/London,
Vol. I, 1962, pages 32-42 and pages 44-54 and Vol. II, 1964, pages 5-6 and
198-199 and also in Kunststoff-Handbuch, Vol. VII, Vieweg-Hochtlen,
Carl-Hanser-Verlag, Munich, 1966, for example on pages 45 to 71.
3. Compounds containing groups convertible into salts such as carboxylic
acid and/or sulfonic acid groups, or tertiary amino groups. These
compounds preferably have a molecular weight of about 120 to 399 and are
incorporated into the polyurethanes according to the invention in the form
of compounds containing primary and/or secondary hydroxyl and/or amino
groups. Examples include dimethylolpropionic acid, tartaric
acid, bis-(.beta.-hydroxyethoxy)-benzoic acids, alkoxylation
products of amino acids (such as bis-(.beta.-hydroxyethyl)-amino-acetic
acid, bis-(.beta.-hydroxypropyl)-aminocaproic acid and
bis-(.beta.-hydroxyethyl)-aminobenzoic acids), lysine, 3,5-diaminobenzoic
acid, 2,5-diaminophenoxyacetic acid, reaction products of diamines with
chloroacetic acid (such as bis-(.beta.-aminomethyl)-glycine), reaction
products of diamines with acrylic acids (such as
2-aminoethyl-.beta.-aminopropionic acid,
4-aminohexyl-.beta.-aminopropionic acid and
aminoisophoryl-.beta.-aminopropionic acid), reaction products of amino
acids with acrylonitrile followed by hydrogenation of the nitrile groups
(such as bis-(.gamma.-aminopropyl)-glycine,
bis(.gamma.-aminopropyl)-aminobutyric acid,
bis(.gamma.-aminopropyl)-4-amino-benzoic acid and
bis(.gamma.-aminopropyl)-4-aminocyclohexane-1-carboxylic acid), disulfonic
acids (such as 1,4-butane sulfonic acid and alkoxylation products
thereof), alkoxylation products of aminosulfonic acids (such as
bis-(.beta.-hydroxyethyl)taurine and
bis-(.beta.-hydroxypropyl)-4-aminobenzene sulfonic acid), diaminosulfonic
acids (based on reaction products of diamines with .beta.-chloroethane
sulfonic acid (such as .beta.-aminoethyl taurine, 4-aminobutyl taurine and
bis-(.gamma.-aminopropyl)-taurine), and aromatic diaminosulfonic acids
(such as flavonic acid, 4,4'-diaminodibenzyl-2,2'-disulfonic acid,
2,6-diaminotoluene-4-sulfonic acid).
Salt formation of the carboxylic and/or sulfonic acids and/or acids of
phosphorus may be carried out using bases such as the hydroxides of the
alkali metals, but is preferably carried out using ammonia, tertiary
amines (such as triethylamine, tripropylamine, triethanolamine and
tripropanolamine), alkylmorpholines (such as N-methylmorpholine),
triethylene diamine, dimethylbenzylamines etc.
Suitable incorporable tertiary amines convertible into salts include
N-alkyl dialkanolamines (such as N-methyl diethanolamine, N-ethyl
dipropanolamine, N-benzyl diethanolamine, N-cyclohexyl diethanolamine and
N-phenyl dipropanolamine) and N-alkyldiamines (such as N-methyldipropylene
triamine).
Salt formation is carried out using quaternizing agents and/or acids such
as dimethylsulfate, benzylchloride, p-toluene sulfonic acid methyl ester,
phosphoric acid, acetic acid, glycolic acid, lactic acid, tartaric acid,
benzoic acid, hydroxybenzoic acid and citric acid.
The compounds 3 are incorporated in (A) in amounts sufficient to provide
about 0.01 to 0.5% by weight, preferably from 0.05 to 0.25% by weight,
based on (A), of groups convertible into salts.
4. Compounds having a functionality of at least two in the isocyanate
addition reaction selected from silicone resins, aromatic
hydroxypolyethers, aromatic hydroxypolyesters and perfluorocarbon resins.
More particularly, the compounds include:
(a) compounds containing polysiloxane segments which have at least two
terminal and/or lateral isocyanate-reactive groups and molecular weights
of 194 to about 20,000, preferably 194 to about 10,000, most preferably
about 300 to 3,000. Difunctional polysiloxanes containing organofunctional
terminal groups are preferably used. These compounds contain structural
units having the formula, --O--Si(R).sub.2 --, wherein R is a C.sub.1
-C.sub.4 alkyl radical or a phenyl radical, but preferably a methyl
radical.
Organofunctional, linear polysiloxanes suitable for use as starting
material in accordance with the invention are described, for example, in
DE-AS Nos. 1,114,632, 1,190,176, 1,248,287, 2,543,638 or in DE-OS Nos.
2,356,692, 2,445,648, 2,363,452, 2,427,273 or 2,558,523. The
organofunctional terminal groups are preferably aliphatic hydrocarbon
radicals containing a hydroxyl, carboxyl, mercapto or primary or secondary
amino group and, optionally, heteroatoms such as oxygen. Preferred
carbofunctional groups include primary and secondary hydroxyl groups and
also secondary amino groups. Starting compounds terminated by primary
hydroxyl groups are particularly preferred. The organofunctional compounds
may be present in the starting materials, for example, in the form of the
following carbo-functional radicals:
##STR1##
The organofunctional polysiloxanes contain at least 1 and preferably from 3
to 30 structural units corresponding to the formula --O--Si(R).sub.2 --
and a molecular weight of 194 to about 20,000, preferably about 300 to
3000.
According to the invention, particularly preferred starting compounds are
hydroxymethyl polydimethyl siloxanes corresponding to the following
general formula
##STR2##
which may be obtained in known manner, for example by the process
according to DE-AS No. 1,236,505.
(b) Hydroxy-functional polyethers which are produced by alkoxylation of
aromatic compounds containing at least two phenolic hydroxyl groups which
contain less than 10% by weight of oxyethylene segments, --CH.sub.2
--CH.sub.2 --O--, and which have molecular weights of about 26 to 3000,
preferably about 300 to 2000. Difunctional polyethers of this type are
preferably used. Compounds containing at least two phenolic hydroxyl
groups which are suitable for use in the production of the aromatic
polyethers used in accordance with the invention include hydroquinone,
isomeric naphthalene diols, but preferably diols corresponding to the
formula
##STR3##
wherein X represents one of the difunctional radicals --S--, --O--,
--SO.sub.2 --, --CO-- or --C(R.sub.1 R.sub.2)--, wherein R.sub.1 and
R.sub.2 may be the same or different and represent hydrogen or C.sub.1
-C.sub.4 alkyl radicals together form an aliphatic ring containing 5 or 6
carbon atoms. Diols in which X represents --C(R).sub.2 -- are particularly
preferred and those in which X represents --C(CH.sub.3).sub.2 -- are most
preferred. The aromatic hydroxy-polyethers suitable for use in accordance
with the invention are produced in known manner by polyaddition of cyclic
ethers onto the aromatic polyols mentioned above. Suitable cyclic ethers
include ethylene oxide, propylene oxide, butylene | | |
