Note: Descriptions are shown in the official language in which they were submitted.
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P07718 1
Le A 36 016-US
POLYURETHANE-POLYUREA DISPERSIONS
BACKGROUND OF THE INVENTION
Field of the Invention
The invention relates to polyurethane-polyurea dispersions, referred to below
as
PU dispersion, which contain aralkylamine-blocked isocyanate groups, and to
their preparation and use.
Description of the Related Art
In the coating of substrates, solvent-containing binders are increasingly
being
replaced by aqueous, environmentally friendly systems. An increasing role has
been played in particular by binders based on polyurethane-polyurea
dispersions,
owing to their excellent properties. Many areas of application are using 2K (2-
component) systems, which are generally composed of an OH-functional binder
and a polyisocyanate (blocked or not blocked). Furthermore, 1K (1-component)
self-crosslinking PU dispersions, which, as described for example in
US-A 4 387 181, possess blocked isocyanate groups and isocyanate-reactive
groups, are of great interest for many areas. The thermal treatment of the
systems
following application produces highly crosslinked coatings which, however,
exhibit little or no chemical crosslinking with the coated substrate. PU
dispersions
which, in contrast to this, possess blocked isocyanate groups and no
significant
amounts of isocyanate-reactive groups may be crosslinked, under thermal
loading,
with the substrate to which they have been applied or into which they have
been
incorporated. This type of what are referred to as post-crosslinkable PU
dispersions is described in, for example, DE-A 195 48 030.
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The principal compounds used fbr blocking isocyanates and polyisocyanates are
s-caprolactam, butanone oxirne, malonates, secondary amines, and triazole
derivatives and pyrazolce derivatives, as described in, for example,
EP-A 0 576 952, EP-A 0 566 953, EP-A 159 117, US-A 4 482 721, WO 97/12924
or EP-A 0 744 423 and also DE-A 195 48 030.
Secondary amine blocking agents, including aralkyl-substituted amines, are
known from, for example, EP-A 0 096 210. The use of such amines in aqueous
systems, particularly in post-crosslinkable PU dispersions, however, is not
known
from EP-A 0 096 210.
The preparation of aqueous post-crosslinkable PU dispersions normally involves
using prior art blocking agents such as, for example, c-caprolactam, and
butanone
oxime.
Whereas for post-crosslinkable PU dispersions possesssing s-caprolactarn-
blocked
isocyanate groups it is normal to employ baking temperatures around 160 C,
post-
crosslinkable PU dispersions for which butanone oxime has been used as the
blocking agent can be deblocked at temperatures lower by 10-20 C. At these
temperatures, however, the desired properties are no longer achieved in many
coatings. Furthermore, high deblocking temperatures or drying temperatures
often
cause unwanted thermal yellowing of the binders or coating. Moreover, these
deblocking temperatures are now considered too high, for reasons of cost, so
that
a demand has developed for post-crosslinkable PU dispersions containing
blocked
isocyanate groups which crosslink with a corresponding substrate at
temperatures
lower than in the case of butanone oxime.
A further disadvantage of prior art post-crosslinkable PU dispersions is the
low
hydrolysis stability in films and coatings.
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STV MA i OF THE INVENTION
The object of the present invention is therefore to provide post-crosslinkable
PU
dispersions containing isocyan.ate groups blocked with a blocking agent which
has
a significantly lower deblocking temperature as compared with the prior art
and,
furthermore, where coatings resulting from this coating composition have high
hydrolysis resistances.
It is now been found that PU dispersions possesssing aralkylamine-blocked
isocyanate groups meet the abovementioned profile of requirements.
The present invention provides post-crosslinkable aqueous PU dispersions
containing aralkylamine-blocked isocyanate groups composed of the following
components:
Al) polyisocyanates,
A2) polymeric polyols having average molar weights of 400 to 6 000,
A3) optionally mono- or polyalcohols or mono- or polyamines having average
molar weights of up to 400,
A4) at least one blocking agent, of which at least 20% by weight is composed
of aralkylamines,
and at least one compound selected from
A5) compounds which have at least one ionic or potentially ionic group and/or
A6) nonionically hydrophilicizing compounds, plus, where appropriate,
diluents, solvents and adjuvants.
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The dispersed polymer obtained from components Al) to A6) essentially no
longer contains any isocyanate-reactive groups.
DETAILED DESCRIPTION OF THE IN-VENTION
As used herein, unless otherwise expressly specified, all of the numerical
ranges,
amounts, values and percentages such as those for amounts of materials, times
and
temperatures of reaction, ratios oaf amounts, values for molecular weight, and
others in the following portion of the specification may be read as if
prefaced by
the word "about" even though the term "about" may not expressly appear with
the
value, amount or range.
The solids content of the post-crosslinkable PU dispersions of the invention
can be
varied within limits of from 10 to 70% by weight. The post-crosslinkable PU
dispersions of the invention preferably contain a solids content of from 20 to
60%
by weight and with particular preference from 25 to 50% by weight. As a
proportion of the overall composition, the faction of organic solvents is
preferably less than 15% by weight, with particular preference less than 10%
by
weight and with very particular preference less than 5% by weight.
In the context of the invention, a potentially ionic group is a group which is
capable of forming an ionic group.
Preferably, the PU dispersions according to the invention contain 10 to 40% by
weight of Al), 30 to 90% by weight of A2), 0 to 30% by weight of A3) 1 to 20%
by weight of A4), 0 to 15% by weight of ionic or potentially ionic compounds
A5)
and 0 to 40% by weight of compounds A6), the sum of the components being
100% by weight.
More preferably, the PU dispersions according to the invention contain 10 to
30%
by weight of Al), 30 to 80% by weight of A2), 0 to 20% by weight of A3), 1 to
15% by weight of A4), 0 to 8% by weight of ionic or potentially ionic
compounds
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A5) and 0 to 35% by weight of compounds A6), the sum of the components being
100 /% by weight.
Most Preferably, the PU dispersions contain 15 to 30% by weight of Al), 30 to
70% by weight of A2), 0 to 10% by weight of A3), 1 to 10% by weight of A4) 0
to 8% by weight of ionic or potentially ionic compounds A5) and 5 to 30% by
weight of compounds A6), the sum of the components being 100% by weight.
Suitable diisocyanates (Al) are in principle those of the molecular weight
range
140 to 400, having aliphatically, cycloaliphatically, araliphatically and/or
aromatically bonded isocy anate groups, such as, for example, 1,4-diisocyanato-
butane, 1,6-diisocyanatohexane (HD1), 2-methyl-1,5-diisocyanatopentane, 1,5-
diisocyanato-2,2-dimethylpentane, 2,2,4- and 2,4,4-trimethyl-1,6-diiso-
cyanatohexane, 1,10-diisocyanatodecane, 1,3- and 1,4-diisocyanatocyclohexane,
1,3- and 1,4-bis-(isocyanatomethyl)-cyclohexane, 1-isocyanato-3,3,5-trimethyl-
5-
isocyanatomethylcyclohexane (isophorone diisocyanate, IP DI), 4,4'-
diisocyanato-
dicyclohexylmethane, 1.-isocyanato-l-methyl-4(3)-i.socyanatomethylcyclohexane,
bis-(isocyanatomethyl)-norbornane, 1,3- and 1,4-bis-(2-isocyanato-;prop-2-yl)-
benzene (TMXDI), 2,4- and 2,6-diisocyanatotoluene (TDI), 2,4'- and 4,4'-diiso-
cyanatodiphenylmethane, 1,5-diisocyanatonaphthalene or any desired mixtures of
such diisocyanates.
They are preferably polyisocyanates or polyisocyanate mixtures of said type
having exclusively aliphatically and/or cycloaliphatically bonded isocyanate
groups. Very particularly preferred starting components (Al) are
polyisocyanates
and polyisocyanate mixtures based on HDI, IPDI and/or 4,4'-diisocyanato-
dicyclohexylmethane.
Any desired polyisocyanates prepared by modification of simple aliphatic,
cycloaliphatic, araliphatic and/or aromatic diisocyanates, composed of at
least two
diisocyanates and having a uretdione, isocyanurate, urethane, allophanate,
biuret,
iminooxadiazinedione and/or oxadiazinetrione structure, as described, for
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example, in J. Prakt. Chern. 336 (1994), pages 185 - 200, are further suitable
as
polyisocyanates (Al).
At least 5%, preferably at least 10% and particularly preferably at least 15%
of the
isocyanate groups of the polyisocyanate (Al) of the PU dispersions according
to
the invention are in blocked form.
The polymeric polyols (A2) in the molar weight range from 400 to 6000 are the
customary ones as have long been used for polyurethanes and have an OH
functionality of at least 1.6 to 4, such as, for example, r olyacrylates,
polyesters,
polylactones, polyethers, polycarbonates, polyestercarbonates, polyacetals,
polyolefins and polysiloxanes. Polyols in a molar weight range from 600 to
2500
and having an OH functionality of 2 to 3 are preferred.
The suitable polycarbonates having hydroxyl groups are obtainable by reacting
carbonic acid derivatives, for example dipnenyl carbonate, dimethyl carbonate
or
phosgene, with diols. Suitable such diols are, for example, ethylene glycol,
1,2-
and 1,3-propanediol, 1,3- and 1,4-butanediol, 1,6-hexanediol, 1,8-octanediol,
neopentylglycol, 1,4-bishydroxymethylcyclohexane, 2-methyl-1,3-propariediol,
2,2,4-trimethyl-1,3-pentanediol, dipropylene glycol, polypropylene glycols,
dibutylene glycol, polybutylene glycols, bisphenol A, tetrabromobisphenol A
and
lactone-modified diols. The diol component preferably contains 40 to 100% by
weight of hexanediol, preferably 1,6-hexanediol, and/or hexanediol
derivatives,
preferably those which have ether or ester groups in addition to terminal OH
groups, e.g. products which were obtained by reacting 1 mol of hexanediol with
at
least 1 mol, preferably 1 to 2 mol, of caprolactone according to DE--A 17 70
245
or by etherifying hexanediol with itself to give di- or trihexylene glycol.
The
preparation of such derivatives is disclosed, for example, in DE-A 15 70 540.
The
polyether-polycarbonatediols described in DE-A 37 17 060 can also be used.
The hydroxypolycarbonates should be substantially linear. However, they may
optionally be slightly branched by incorporation of polyfunctional components,
in
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particular low molecular weight polyols. For example, glycerol, trimethylol-
propane, 1,2,6-hexanetriol, 1,2,4-butanetriol, trimethylolpropane,
pentaerythritol,
quinitol, mannitol and sorbitol, menylglycoside and 1,3,4,6-dianhydrohexitols
are
suitable for this purpose.
Suitable polyetherpolyols are the polytetramethylene glycol polyethers which
are
known per se in polyurethane chemistry and can be prepared, for example, via
polymerization of tetrahydrofuran by cationic ring opening.
Other suitable polyetherpolyols are polyethers, such as, for example, the
polyols
prepared using initiator molecules from styrene oxide, propylene oxide,
butylene
oxides or epichlorohydrins, in particular ofpropylene oxide.
Suitable polyesterpolyols are, for example, reaction products of polyhydric,
preferably dihydric and optionally additionally trihydri.c, alcohols with
polybasic,
preferably dibasic, carboxylic acids. Instead of the free polycarboxylic
acids, it is
also possible to use corresponding polycarboxylic anhydrides or corresponding
polycarboxylic esters of lower alcohols or their mixtures for the preparation
of the
polyesters. The polycarboxylic acids may be aliphatic, cycloaliphat:ic,
aromatic
and/or heterocyclic and optionally substituted, for example by halogen atoms,
and/or unsaturated.
Monofunctional alcohols and monoamines are suitable components (.A3) for
terminating the polyurethane prepolymer. Preferred monoalcohols are aliphatic
monoalcohols having 1 to 18 C atoms, such as, for example, ethanol, n-butanol,
ethylene glycol monobutyl ether, 2-ethylhexanol, 1-octanol, 1-dodecanol or 1-
hexadecanol. Preferred monoamines are aliphatic monoamines, such as, for
example, diethylamine, dibutylamine, ethanolamine, N-methylethanolamine or
N,N-diethanolamine.
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Polyols, aminopolyols or polyan-lines having a molar weight of less than 400,
which. are described in large numbers in the corresponding literature, are
also
suitable as component (_A3).
Examples of preferred components (A3) Ere:
a) alkanediols, such as ethanediol, 1,2- and 1,3-propanediol, 1,4- and
2,3-butanediol, I,5-pentanediol, 1,3-dimethylpropanediol, 1,6-hexanediol,
neopentylglycol, cyclohexanedi.methanol and 2--m ethyl- 1,3 --propanediol,
b) etherdiols, such as diethylene diglycol, triethylene glycol or hydroquinone
dihydroxyethyl ether,
c) esterdiols of the general formulae (III) and (IV)
HO-(CH,,),-CO-O-(CH2)y-OH (III)
HO-(CH2),-O-CO-R-CO-O(CH2),-OH (IV)
in which
R is an alkylene or arylene radical having 1 to 10 C atoms, preferably
2 to 6 C atoms,
x is 2 to 6 and
y is 3 to 5,
such as, for example, S-hydroxyeuyl-e-hydroxycaproates,
co-hydroxyhexyl- y-hydroxybutyrates,13-hydroxyethyl adipate and
bis(B-hydroxy-ethyl) terephthalate, and
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d) polyarnines such as ethylenediamine, 1,2- and 1,3-dialninopropane,
1,4-diaminobuutane, 1,6-diaminohexane, isophoronediamine, isomer
mixture of 2,2,4- and 2,4,4-trimethy1hexa-methylenediamine, 2-methyl-
pentamethylenediamine, diethylene-triamine, 1,3- and 1,4-xylylene-
diamine, a,a,a',a'-tetramethyl-l,3- and -1,4-xylylenediamine and
4,4-diaminodicyclohexylmet?iane. Suitable diamines in the context of the
invention are also hydrazine, hydrazine hydrate and substituted hydrazines,
such as, for example, N-rethylhydrazi.ne, N,N'-dimethylhydrazine and
their homologues and acid dihydrazides, adipic acid, 3-methyiadipic acid,
sebacic acid, hydracrylic acid and terephthalic acid, semicarbazidoalkylene
hydrazides, such as, for example, 13-semicarbazidopropionic acid hydrazide
(e.g. DE-A 17 70 591), senicarbazidoalkylene-carbazine esters, such as,
for example, 2-semicarbazidoethylcarbazine ester (e.g. DE -A 19 18 504),
or aminosemicarbazide compounds, such as, for example, 13-aminoethyl
semicarbazido-carbonate e.g. D E-A 19 02 931).
The aralkylamines of component A4) correspond to the formula (V)
R (R3)x
HN M.
in which
RI, R2, R3 can be identical or different and denote hydrogen, C1-C4-alkyl, C6-
C10-
cycloalkyl, preferably hydrogen,
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R4 denote C,-C4-alkyl, C6-C10-eycloalkyl or C=-C14-aralkyl, preferably
methyl.,
ethyl, isopropyl and tert-butyl, particularly preferably ter?-butyl,
x represents the number 1, 2, 3, 4 or 5.
As an example of blocking agents A4) mention maybe made of the following:
N-methyl-, N-ethyl-, N-(iso)propyl-,N-n-butyl-, N-iso-butyl-, N-tert-butyl-
benzylamine or 1,1-dimethylbenzylamine.. N-alkyl-N-1,1-dirLlethylmethy1-
phenylamine, adducts of benzylamine with compounds having activated double
bonds such as malonates, N,N-dimethylaminopropylbenzylamine and other
unsubstituted or substituted benzylamines containing tertiary amino groups,
and/or dibenzylamine. It is of course also possible to use mixtures of these
amines
with one another and/or with other blocking agents. These are, for example,
alcohols, lactams, oximes, malonates, alkyl acetoacetates, triazoles, phenols,
imidazoles, pyrazoles, and amines, such as butanone oxime, diisopropylarnine,
1,2,4-triazole, dimethyl-1,2,4-triazole, imidazole, diethyl malonate, ethyl
acetoacetate, acetone oxime, 3,5-dimethylpyrazole, c-caprolactam or any
desired
mixtures of these blocking agents. Preference is given to using N-
aralkylamines
such as NT-(iso)propyl-, N-n-butyl, N-iso-butyl-, N-tert-butylbenzylamine as
blocking agent A4). A more preferred blocking agent A4) is N-tert-butylbenzyl-
amine.
Suitable ionic or potentially ionic compounds A5), which can be used as well
as
or instead of the nonionic compounds A6), are, for example, mono- and
dihydroxycarboxylic acids, mono- and diarninocarboxylic acids, mono- and
dihydroxysulfonic acids, mono- and diaminosulfonic acids and mono- and
dihydroxyphosphonic acids or mono- and diaminophosphonic acids and their
salts, such as dimethylolpropionic acid, hydroxypivalic acid, N-(2-
aininoethyl)-B-
alanine, 2-(2-amino-ethylamino)-ethanesulfonic acid, ethylenediamine-propane-
sulfonic or ethylenediamine-butanesulfonic acid, 1,2- or 1,3-propylene-diamine-
B-
ethylsulfonic acid, lysine, 3,5-diaminobenzoic acid, the hydrophilicizing
agent
according to Example 1 of EP-A 0 916 647 and its alkali metal and/or ammonium
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salts, the adduct of sodium bisulfate with but-2-ene-1,4-diol,
polyethersulfonate,
the propoxylated adduct of 2-butenediol and NaHSO3 (e.g. in DE-A 2 446 440,
pages 5-9, formula I-III), and building blocks, such as methyldiethanolamine,
which can be converted into cationic groups can be used as hydrophilic
components. Preferred ionic or potential ionic compounds AS) are those which
have carboxyl or carboxylate and/or sulfonate groups and/or ammonium groups.
Particularly preferred ionic compounds AS) are those which contain carboxyl
and/or sulfonate groups as ionic or potentially ionic groups, such as the
salts of N-
(2-aminoethyl)-13-alanine, 2-(2-aminoethy amino)ethanesulfonic acid, of the
hydrophilicizing agent according to Example I of EP-A 0 916 647 and of
dimethylolpropionic acid.
The hydroxy components among components (A2), (A3) and (A5) may contain
double bonds which may originate, for example, from long-chain aliphatic
carboxylic acids or fatty alcohols. Functionalization with olefinic double
bonds is
possible, for example, by the incorporation of allylic groups or of acrylic
acid or
methacrylic acid and their respective esters.
Furthermore, the PU dispersions according to the invention may contain
nonionically hydrophilicizing compounds (A6), e.g. polyoxyalkylene ethers
having at least one hydroxyl or amino group. These polyethers contain a
proportion of 30% by weight to 100% by weight of building blocks which are
derived from ethylene oxide. Suitable poly: theis include linear polyethers
having
a functionality of between 1 and 3, but also compounds of the general formula
(VI)
R3
Ho, 2 ___OH (-VI h,
R R
in which
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R' and RZ, independently of one another, each denote a divalent aliphatic,
cycloaliphatic or aromatic radical having 1 to 18 C atoms which
may be interrupted by oxygen and/or nitrogen atoms and
R3 represents a non-hydroxyl-terminated polyester or preferably
polyether. R3 eparticularly preferably represents an alkoxy-
terminated polyethylene oxide radical.
Nonionicaly hydrophilicizing compounds A6) include, for example, monohydric
polyalkylene oxide polyether alcohols which contain on average from 5 to 70,
preferably from 7 to 55, ethylene oxide units per molecule, such as are
available in
conventional manner by alkoxylation of suitable initiating molecules (e.g. in
Ullmanns Encyclopadie der technischen Chemie, 4th edition, volume 19, Verlag
Chemie, Weinheirn pp. 31-38). Examples of suitable initiating molecules are
saturated monoalcohols such as methanol, ethanol, n-propanol, isopropanol, n-
butanol, isobutanol, sec-butanol, the isomers pentanols, hexanols, octanols
and
nonanols, n-decanol, n-dodecanol, n-tetradecanol, n-hexadecanol, n-
octadecanol,
cyclohexanol, the isomeric methylcyclohexanols or hydroxymethylcyclohexan, 3-
ethyl-3-hydroxymethyloxetane, or tetrahydrofurfuryl alcohol; diethylene glycol
monoalcohol ethers such as, for example, diethylene glycol monobutyl ether;
unsaturated alcohols such as allyl alcohol, 1,1-dimethyl allyl alcohol or
oleyl
alcohol, aromatic alcohols such as phenol, the isomeric cresols or methoxy-
phenols, araliphatic alcohols such as benzyi alcohol, anisyl alcohol or
cinnamyl
alcohol; secondary monoamines such as dimethylamirie, diethylamine, dipropy-
lamine, diisopropylamine, dibutylamine, bis-(2-ethylhexyl)-amine, N-methyl-
and
N-ethylcyclohexylamine or dicyclohexylamine and also heterocyclic secondary
amines such as morpholine, pyrrolidine, piperidine or !H-pyrazole.
Preferred initiating molecules are saturated monoalcohols and also diethylene
glycol monoalkyl ethers. Particular preference is given to using diethylene
glycol
monobutyl ether as initiating molecule.
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Alkylene oxides particularly suitable for the alkoxylation reaction are
ethylene
oxide and propylene oxide, which may be used in any order or else in a mixture
for the alkoxylation reaction.
The polyalkylene oxide polyether alcohols are either pure polyethylene oxide
polyethers or mixed polyalkylene oxide polyethers at least 30 mol% preferably
at
least 40 mol% of whose alkylene oxide units consist of ethylene oxide units.
Preferred nonionic compounds are mono functional mixed polyalkylene oxide
polyethers which contain at least 40 mol.% of ethylene oxide units and not
more
than 60 mol% of propylene oxide units.
For hydrophilicizing the post-crosslinkable PU dispersions of the invention it
is
also possible to use combinations of ionic (AS) and nonionic (A6) hydro-
philicizing agents. In this case it is preferred to use combinations of
anionic (AS)
and nonionic (A6) hydrophilicizing agents. Overall, for the preparation of the
post-crosslinkable PU dispersions of the invention, preference is given to the
exclusive use of nonionic hydrophilicizing agents A6).
The aqueous polyurethane dispersions of the invention are prepared in the
manner
known from the prior art, as summarized, for example, by D. Dieterich in a
review
article [D. Dieterich, Prog. Org. Coatings 9, 281 (1981)]. The polyisocyanate
component Al) is reacted to completion with components A2) and/or A3) and/or
A6), blocking agents A4) and low molecu')ar weight chain extenders A3) and/or
A5) to give a polyurethane, where appropriate with the use of a solvent which
can
be separated off again later. Suitable solvents are the customary paint
solvents
known per se, such as, for example, ethyl acetate, butyl acetate, 1-
methoxyprop-2-
yl acetate, 3-methoxy-n-butyl acetate, acetone, 2-butanone, 4-methyl-2-
pentanone,
cyclohexanone, toluene, xylene, chlorobenzene, mineral spirit, mixtures which
contain in particular relatively highly substituted arornatics, as are
commercially
available, for example, under the names Solvent Naphtha, Solvesso (Exxon
Chemicals, Houston, USA), Cypar (Shel'i Chemicals, Eschborn, DE), Cyclo Sol
(Shell Chemicals, Eschborn, DE), Tolu Solo (Shell Chemicals, Eschborn, DE),
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Shellsol (Shell Chemicals, Eschborn, DE), carbonic acid esters, such as
dimethyl
carbonate, diethyl carbonate, 1,2-ethylene carbonate and 1,2-propylene
carbonate,
lactones, such as B-propiolactone, y-butyrolactone, s-caprolactone and c-
methyl-
caprolactone, propylene glycol diacetate, diethylene glycol dimethyl ether,
dipropylene glycol dimethyl ether, diethylone glycol ethyl and butyl ether
acetate,
N-methylpyrrolidone and ~T methylcapr olactam, or any desired mixtures of such
solvents. Preferred solvents are acetone, 2--butanone and N-methylpyrrol done.
Acetone is particularly preferred.
In a further step, groups capable of neutralization are then optionally
converted
into the salt form and transferred to the aqueous phase. Depending on the
degree
of neutralization and content of ionic (T-roups, the dispersion may be made
very
finely divided so that it virtually has the appearance of a solution, but very
coarse-
particled formulations are also possible and are likewise sufficiently stable.
However, mean particle sizes of less than 300 rim are preferred since these
improve the emulsification of a polyisocyanate and hence the quality of the
coating film.
Preferably, the polyol components A2), A3) and A6) and also the blocking agent
A4) are introduced initially and reacted with the polyisocyanates Al.
Thereafter
any further hydroxy-functional components A3) are added and the reaction
mixture is reacted to give a polyurethane prepolymer, without addition of
solvent.
The prepolymer is dispersed by adding water. Then any amino-functional
components A3) and/or A5) are added in the form, for example, of an aqueous
solution.
The solids content of the post-crosslinkable PU dispersions of the invention
can be
varied within limits from 10 to 70% by weight. The post-crosslinkable PU
dispersions of the invention preferably contain a solids content of from 20 to
60%
by weight and with particular preference from 25 to 50/ by weight. As a
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proportion of the overall composition, the fraction of solvents is preferably
less
than 15% by weight, with more preference less than 10% by weight and with most
preference less than 5% by weight.
The PU dispersions of the invention can be employed in combination with
suitable
reaction. partners containing isocyanate-reactive groups: for example, aqueous
binders, such as polyurethane dispersions and/or polyacrylate dispersions
and/or
their mixtures or hybrids. Further suitable reaction partners include low
molecular
weight amines, which can be processed in solution in water to give heat-
crosslinkable coating compositions which can be processed from the aqueous
phase. Furthermore, the PU dispersions of the invention may also be
incorporated
into 1K binders such as, for example, polyurethane dispersions and/or
polyacrylate dispersions and also polyurethane-polyacrylate hybrid
dispersions.
The post-crosslinkable PU dispersions of the invention may also be used
without
the addition of a further reaction partner, for the purpose, for example, of
coating
or sizing or impregnating substrates containing hydrogen atoms which are
reactive
towards isocyanate groups.
The invention likewise provides for the use of the PU dispersions of the
invention
in paints and coating compositions. Post-crosslinkable polyurethane-polyurea
dispersions may thus be added to formulations to produce sizes.
The post-crosslinkable PU dispersions of the invention are used either alone
or in
combination with other aqueous binders for the preparation of coating
compositions. Such aqueous binders maybe composed, for example, of polyester,
polyacrylate, polybutadiene, polyvinyl acetate, polyepoxide or other
polyurethane
polymers. Also possible is the combination with radiation-curable binders, as
described in, for example, EP-A-0 753 531.
The post-crosslinkable PU dispersions of the invention are used preferably as
binders in coatings and adhesives. Coatings based on the compositions of the
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invention may be applied to any desired substrates, examples being metal,
wood,
glass.. glass fibres, carbon fibers, stone, ceramic, minerals, concrete, hard
and
- Iexible plastics of a wide variety of kinds, woven and non-woven textiles,
leather,
paper, hard fibres, straw and bitumen, which may where appropriate have been
provided with customary primers prior to coating. Preferred substrates are
glass
fibres, carbon fibres, metals, textiles and leather. One particularly
preferred
substrate is the glass fibre.
The post-crosslinkable PU dispersions of the invention can be used as such or
in
combination with the auxiliaries and additives known from coating technology,
such as, for example, nonionic and/or anionic thickeners, fillers, pigments,
waxes,
hand agents, dyes, solvents, levelling agents and crosslinkers for the
production of
coatings.
The application of the coating materials can be effected by known methods, for
example by brushing, pouring, knife coating, spraying, rolling or immersion..
The
coating film can be dried at room temperature or elevated temperature, but
also by
baking at up to 200 C.
The PU dispersions of the invention are storable and transportable and can be
processed at any desired later point in time. Depending on the chosen chemical
composition of the polyurethane, coatings having different properties are
obtained. Thus, soft tacky coats and thermoplastic and elastorneric products
having a wide range of hardnesses up to glass-hard thermosetting plastics can
be
obtained.
Preference is also given to the use of the post-crosslinkable PU dispersions
of the
invention in or as sizes, especially glass fibre sizes. Post-crosslinkable
polyurethane-polyurea dispersions thus may be added to formulations to produce
sizes.
The PU dispersions of the invention can be used in the sizes alone or
preferably
with other binders such as, for example, polyacrylate dispersions,
polyurethane-
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polyacrylate hybrid dispersions, polyvinyl ether or polyvinyl ester
dispersions,
polystyrene or polyacrylonitrile dispersions, also in combination with
crosslinkers
such as blocked polyisocyanates (crosslinkers) and amino crosslinker resins
such
as, for example, melamine. resins.
Furthermore, it is possible to add further crosslinkers prior to application.
Crosslinkers suitable for this purpose are preferably hydrophilic or
hydrophilicized polyisocyanate crosslinkers.
For the preparation of the sizes, the post-crosslinkable PU dispersions of the
invention are generally used as binder component and crosslinker component and
may comprise further components such as emulsifiers, further film-forming
resins,
adhesion promoters, lubricants and auxiliaries such as wetting agents or
antistats.
The adhesion promoters, lubricants and auxiliaries, the process for the
preparation
of the sizes and the process for sizing glass fibers and the subsequent
processing
of the glass fibers are known and are described, for example, in I.L.
Loewenstein,
"The Manufacturing Technology of Continous Glass Fibres", Elsevier Scientific
Publishing Corp., Amsterdam, London, New York, 1983.
The present invention also provides glass Fibres sized with a size comprising
the
PU dispersions of the invention.
Both the known glass types used for glass filament manufacture, such as E, A,
C
and S glass, and the other products known per se from glass fiber
manufacturers
are suitable for the sized glass fibres. Among said glass types for the
production of
continuous glass filaments, the E glass fibers, owing to their freedom from
alkali,
high tensile strength and high modulus of elasticity, are the most important
for
reinforcing plastics.
As matrix polymers it is possible to use a large number of thermoplastics and
thermosetting polymers. Examples of suitable thermoplastic polymers include
the
following: polyolefins such as polyethylene or polypropylene, polyvinyl
chloride,
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addition polymers such as styrene/acrylonitrile copolymers, ABS, polymeth-
acrylate or polyoxymethylene, aromatic and/or aliphatic polyamides such as
polyamide 6 or polyamide 6,6, polycondensates, such as polycarbonate,
polyethylene terephthalate, liquid-crystalline polyaryl esters, polyarylene
oxide,
polysulfone, polyarylene sulfide, polyaryl sulfone, polyether sulfone,
polyaryl
ethers or polyether ketone or polyadducts such as polyurethanes. Examples that
may be mentioned of suitable thermosetting polymers include the following:
epoxy resins, unsaturated polyester resins, phenolic resins, amine resins,
polyurethane resins, polyisocyanurates, epoxide/isocyanurate combination
resins,
furan resins, cyanurate resins and bismaleimide resins.
EXAMPLES
The mechanical properties of post-crosslinkable PU dispersions are determined
on
free films produced as follows:
A film applicator consisting of two polished rolls which can be set an exact
distance apart has a release paper inserted into it ahead of the back roll.
The
distance between the paper and the front roll was adjusted using a feeler
gange.
This distance corresponds to the wet film thickness of the resulting coating,
and
can be adjusted to the desired add-on of each coat. Coating can also be
carried out
consecutively in two or more coats. To apply the individual coats, the
products
(aqueous formulations are adjusted to a viscosity of 4500 mPa s beforehand by
adding ammonia/polyacrylic acid) were poured onto the nip between the paper
and the front roll, the release paper was pulled away vertically downwards,
and
the corresponding film was formed on the paper. Where two or more coats were
to
be applied, each individual coat was dried and the paper was reinserted.
The 100% modulus was determined in accordance with DIN 53504 on films
> 100 m thick.
The average particle sizes (the numerical average is stated) of the PU
dispersions
were determined by means of laser correlation spectroscopy (instrument:
Malvern
Zetasizer*1000, Malver Inst. Limited).
*trade-mark
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Film storage under hydrolysis conditions takes place in accordance with
DIN EN 12280-3. The mechanical properties of these film samples are determined
after 24 hours storage under standard conditions (20 C and 65% humidity) in
accordance with DIN 53504.
Example 1 (inventive).
128.8 g of the polyether Desmophen 3603 Z (Bayer AG, DE, difunctional
polyether based on propylene oxide with an average molar weight of 2000
(CHZ = 56)), 25.6 g Polyether L 400 (Bayer AG, DE, difunctional polyether
based on propylene oxide with an average molar weight of 561 (OHZ = 200)),
86.4 g Polyether LB 25 (Bayer AG, DE, rr==.onofunctional polyether based on
ethylene oxide/propylene oxide with an average molar weight of 2250 (CHZ =
25)) and 21.5 g N-tert-butylbenzylamine are introduced into a vessel and
heated to
70 C. Then 100.01 g Desmodur W (Bayer AG, DE) are added over the course of
5 minutes. The subsequent stirring time at 75 C is 45 minutes. Following the
addition of 5.2 g trimethylolpropane the reaction mixture is stirred at 75 C
until
the theoretical NCO value has been reached and is then cooled to 60 C.
Dispersing is carried out by adding 527.0 g water (20 C) over the course of 10
minutes. Immediately after dispersion, a solution of 1.70 g of hydrazine
monohydrate, 10.2 g of isophoronediamine and 178.6 g of water at 40 C is added
over the course of 5 minutes. The subsequent stirring time at 40 C is 3 hours.
This
gives a storage-stable aqueous PU dispersion containing blocked isocyanate
groups which has a solids content of 33.0%.
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Example 2 (comparative)
128.8 g of the polyether Desmophen 3600 Z (Bayer AG, DE, difunetional.
polyether based on propylene oxide with an average molar weight of 2000
(OHZ = 56)), 25.6 g polyether L 400 (Bayer AG, DE, difunctional polyether
based on propylene oxide with an average molar weight of 561 (OHZ = 200)),
86.4 g polyether LB 25 (Bayer AG, DE, monofunctional polyether based on
ethylene oxide/propylene oxide with an average molar weight of 2250
(OHZ = 25)) and 14.9 g s-Caprolactam are introduced into a vessel and heated
to
70 C. Then 100.01 g Desmodur W (Bayer AG, DE) are added over the course of
5 minutes and the reaction mixture is heated to 100 C. The subsequent stirring
time at 100 C is 45 minutes. Following- the addition of 5.2 g
trimethylolpropane
the reaction mixture is stirred at 100 C until the theoretical NCO value has
been
reached and is then cooled to 60 C. Dispersing is carried out by adding 527.0
g
water (20 C) over the course of 10 minutes. Immediately after dispersion, a
solution of 1.70 g of hydrazine monohydrate, 10.2 g of isophoronediamnine and
178.6 g of water at 40 C is added over the course of 5 minutes. The subsequent
stirring time at 40 C is 3 hours. This gives a storage-stable aqueous pU
dispersion
containing blocked isocyanate groups which has a solids content of 34.6%.
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Table 1: Results of the mechanical properties of free films produced from
examples 1 and 2
Example I Example 2
(inventive) eorn aratiive
Blocking agent Tert-but lbenz famine 1 Caprolactam
Average article size 169 am 180 nin
Drying conditions 10 min, 125 C 10 min, 125 C
Tensile test: 0 value
100% modulus [MPa] 2.2 1.1
Tensile strength [MPa] 2.9 1.1
Elongation at break [%] 190 130
Tensile test after 7 d of hydrolysis
Tensile strength [MPa] 4.0 I has run
Elongation at break [%] 200 has run
Tensile test after 2 weeks of hydrolysis
Tensile strength [MPa] 4.0 has nun
Elongation at break [%] 260 has ran
Tensile test after 4 weeks of hydrolysis
Tensile strength [MPa] 4.3 has run
Elongation at break [%] 130 has nun
Tensile test after 6 weeks of hydrolysis
Tensile strength [MPa] 4.3 has run
Elongation at break i% 120 has nun
Tensile test after 8 weeks of hydrolysis
Tensile strength [MPa] 3.9 has run
Elongation at break [%] 130 has run
The results shown in table 1 demonstrate that with the use of the inventive
PUT
dispersion from example I a substantially higher hydrolysis resistance is
achieved
than with the prior art PU dispersion (example 2). Furthermore, it is evident
from
the tensile strength and elongation at break that, with the dispersion from
example
1, significantly higher mechanical properties are obtained after a drying time
of
minutes at 125 C on account of the lower deblocking temperature of the
10 blocking agent N-tert-butylbenzylamine, as compared with dispersion from
example 2, which contains a prior art blocking agent (caprolactam).
Although the invention has been described in detail in the foregoing for the
purpose
of illustration, it is to be understood that such detail is solely for that
purpose and that
variations can be made therein by those skilled in the art without departing
from the
spirit and scope of the invention except as it may be limited by the claims.
