U.S. patent application number 11/058541 was filed with the patent office on 2005-08-04 for continuous preparation of thermoplastically processable polyurethanes.
Invention is credited to Brauer, Wolfgang, Heidingsfeld, Herbert, Peerlings, Henricus, Trabert, Ludwig.
Application Number | 20050171320 11/058541 |
Document ID | / |
Family ID | 30775454 |
Filed Date | 2005-08-04 |
United States Patent
Application |
20050171320 |
Kind Code |
A1 |
Brauer, Wolfgang ; et
al. |
August 4, 2005 |
Continuous preparation of thermoplastically processable
polyurethanes
Abstract
The present invention relates to a multi-stage process for the
continuous preparation of thermoplastically processable
polyurethanes with improved processing properties based on various
polyols
Inventors: |
Brauer, Wolfgang;
(Leverkusen, DE) ; Heidingsfeld, Herbert;
(Frechen, DE) ; Peerlings, Henricus; (Solingen,
DE) ; Trabert, Ludwig; (Krefeld, DE) |
Correspondence
Address: |
BAYER MATERIAL SCIENCE LLC
100 BAYER ROAD
PITTSBURGH
PA
15205
US
|
Family ID: |
30775454 |
Appl. No.: |
11/058541 |
Filed: |
February 15, 2005 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
11058541 |
Feb 15, 2005 |
|
|
|
10643856 |
Aug 19, 2003 |
|
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Current U.S.
Class: |
528/76 |
Current CPC
Class: |
C08G 18/10 20130101;
C08G 18/0895 20130101; C08G 18/10 20130101; C08G 18/388 20130101;
C08G 18/10 20130101; C08G 18/48 20130101; C08G 18/10 20130101; C08G
18/32 20130101 |
Class at
Publication: |
528/076 |
International
Class: |
C08G 018/30 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 21, 2002 |
DE |
10238112.7 |
Claims
1. A multi-stage process for the continuous preparation of
thermoplastically processable polyurethane elastomers (TPU) with
tensile strengths of >30 MPa (measured in accordance with EN ISO
527-3), comprising a) preparing a prepolymer I by reacting A) at
least one organic diisocyanate, with B) a polyol 1 having on
average at least 1.8 and not more than 3.0 Zerewitinoff-active
hydrogen atoms and a number-average molecular weight {overscore
(M)}.sub.n of 450 to 10,000; b) reacting said prepolymer I prepared
in a) with C) a polyol 2, which is different than polyol 1, wherein
said polyol 2 has on average at least 1.8 and not more than 3.0
Zerewitinoff-active hydrogen atoms and a number-average molecular
weight {overscore (M)}.sub.n of 60 to 10,000, to yield a prepolymer
II, wherein an equivalent ratio of NCO groups to the sum of
NCO-reactive groups of from 1.2:1 to 10:1 is established, based on
reaction components (A), (B) and (C); c) reacting, in a
high-viscosity reactor operating with a high shear energy, said
prepolymer II prepared in b) completely with: D) at least one low
molecular weight polyol or polyamine having on average at least 1.8
and not more than 3.0 Zerewitinoff-active hydrogen atoms and a
number-average molecular weight {overscore (M)}.sub.n of 60 to 400
as a chain lengthener; wherein steps a) to c) are optionally
carried out in the presence of F) catalysts, and optionally, with
the addition of E) 0 to 20 wt. %, based on the total amount of TPU,
of further auxiliary substances and additives, with the overall
equivalent ratio of NCO groups to the sum of NCO reactive groups
being from 0.9:1 to 1.2:1, based on the sum of all the reaction
components of steps a) to c), and wherein steps a) and b) are
carried out in separate reactors and step c) is carried out in a
separate reactor than steps a) and b.
2. The process of claim 1, wherein B) said polyol 1 and C) said
polyol 2, both of which contain Zerewitinoff-active hydrogen atoms,
are selected from the group consisting of (i) polyester-polyols,
(ii) polyether-polyols, (iii) polycarbonate-polyols, (iv) polyols
which contain nitrogen, phosphorus, sulfur and/or silicon atoms and
(v) mixtures thereof.
3. The process of claim 1, wherein D) said low molecular weight
polyols containing Zerewitinoff-active hydrogen atoms comprises
ethylene glycol, butanediol, hexanediol,
1,4di-(.beta.-hydroxyethyl)-hydroquinone, or
1,4-di(.beta.-hydroxyethyl)-bisphenol A.
4. The process of claim 1, wherein A) said organic diisocyanate
comprises an aromatic diisocyanate.
5. The process of claim 4, wherein said aromatic diisocyanate
comprises a diphenylmethane-diisocyanate isomer mixture having a
4,4'-diphenylmethane-diisocyanate content of >96 wt. %.
6-8. (canceled)
9. The process of claim 1, wherein step c) is carried out in a
multi-screw extruder.
Description
BACKGROUND OF THE INVENTION
[0001] The present invention relates to a multi-stage process for
the continuous preparation of thermoplastically processable
polyurethanes.
[0002] Thermoplastic polyurethanes (TPU) have been known for a long
time. They are of industrial importance because of the combination
of high-quality mechanical properties with the known advantages of
inexpensive thermoplastic processability. A wide range of variation
of the mechanical properties can be achieved by using various
chemical builder components. An overview of TPUs, their properties
and uses is given, for example, in Kunststoffe 68 (1978), pages 819
to 825 or in Kautschuk, Gummi, Kunststoffe 35 (1982), pages 568 to
584.
[0003] TPUs are built up from linear polyols, which are usually
polyester- or polyether-polyols, organic diisocyanates and
short-chain diols (i.e. chain lengtheners). A diversity of
combinations of properties can be established in a targeted manner
via the polyols. Catalysts can additionally be added to accelerate
the formation reaction. The builder components can be varied in
relatively wide molar ratios to establish the desired properties.
Molar ratios of polyols to chain lengtheners of 1:1 to 1:2 have
proved suitable. These result in products in the range from 70
Shore A to 75 Shore D.
[0004] Thermoplastically processable polyurethane elastomers can be
built up either stepwise (e.g. by prepolymer metering process), or
by simultaneous reaction of all the components in one stage (e.g.
by one-shot metering process).
[0005] TPUs can be prepared continuously or discontinuously. The
best known preparation processes are the belt process (see, for
example, GB-A 1 057 018) and the extruder process (see, for
example, DE-A 19 64 834, DE-A 23 02 564 and DE-A 20 59 570). In the
extruder process, the starting substances are metered into a screw
reactor, undergo polyaddition there and are converted into a
uniform granule form. The extruder process is comparatively simple,
but has the disadvantage that the homogeneity of the products
prepared in this manner is inadequate for many uses because the
mixing and reaction progress simultaneously. In addition, because
of the limited reaction space and the limited metering
possibilities, the variability in the targeted use of various
polyols is limited.
[0006] The two-stage process described in, for example, EP-A 0 571
828, in which the prepolymer is built up from a polyol and a
diisocyanate in a targeted manner in a tube reactor before the
extruder, provided an improvement in respect of a targeted and
controlled preparation of TPUs with improved processing properties.
The TPU formation is concluded in the subsequent extruder with the
addition of the chain lengthener. On the basis of the optimum
conditions in each process stage, TPUs can thus be prepared in a
targeted and controlled manner.
[0007] However, for many end-uses, it is not sufficient to use only
one polyol in preparing the TPU. Particular combinations of TPU
properties can be achieved by the simultaneous use of different
polyols. An example which may be mentioned is the combination of
polyester-polyols and polyether-polyols and the resulting
advantages. By addition of particular phosphorus-containing polyols
which can be built in, the flame resistance of the resultant TPU
can be improved without adversely influencing other properties.
[0008] If the sometimes chemically very different polyols are
reacted simultaneously by, e.g. the prepolymer process, or even
together with the chain lengthener by, e.g. the one-shot process,
with the diisocyanate in a continuous preparation process, tacky,
poorly processable TPUs are probably obtained due to the reaction
conditions no longer being optimum for all the starting
substances.
[0009] The object of the present invention was thus to provide an
economically favorable continuous process with which it is possible
to prepare readily processable, homogeneous, non-tacky TPUs in an
industrially simple manner.
[0010] Surprisingly, it has been possible to achieve this object by
a continuous multi-stage preparation process.
SUMMARY OF THE INVENTION
[0011] The present invention provides a multi-stage process for the
continuous preparation of thermoplastically processable
polyurethane elastomers (TPUs) with tensile strengths of >30 MPa
(measured in accordance with EN ISO 527-3). The present process
comprises:
[0012] a) preparing a prepolymer I by reacting
[0013] A) at least one organic diisocyanate, with
[0014] B) a polyol 1 having on average at least 1.8 and not more
than 3.0 Zerewitinoff-active hydrogen atoms and a number-average
molecular weight {overscore (M)}.sub.n of 450 to 10,000,
[0015] b) reacting said prepolymer I prepared in a) with
[0016] C) a polyol 2, which is different than polyol 1, said polyol
2 having on average at least 1.8 and not more than 3.0
Zerewitinoff-active hydrogen atoms and a number-average molecular
weight {overscore (M)}.sub.n of 60 to 10,000,
[0017] thereby yielding a prepolymer II, wherein an equivalent
ratio of NCO to the sum of NCO-reactive groups of from 1.2:1 to
10:1 is established, based on reaction components A), B) and
C);
[0018] c) reacting, in a high-viscosity reactor operating with a
high shear energy, said prepolymer II prepared in b), completely
with
[0019] D) at least one low molecular weight polyol or polyamine
having on average at least 1.8 and not more than 3.0
Zerewitinoff-active hydrogen atoms and a number-average molecular
weight {overscore (M)}.sub.n of 60 to 400 as a chain
lengthener,
[0020] wherein steps a) to c) are optionally carried out in the
presence of F) catalysts, and optionally with the addition of E)
from 0 to 20 wt. %, based on the total amount of TPU, of further
auxiliary substances and additives, and with the overall equivalent
ratio of NCO groups to the sum of NCO-reactive groups ranging from
0.9:1 to 1.2:1, based on the sum of all reaction components of
steps a) to c).
[0021] Suitable organic diisocyanates to be used as component A)
include, for example, aliphatic, cycloaliphatic, araliphatic,
heterocyclic and aromatic diisocyanates, such as those which are
described in, for example, Justus Liebigs Annalen der Chemie, 562,
pages 75 to 136.
[0022] Specific examples which may be mentioned in detail include
aliphatic diisocyanates such as, for example,
hexamethylene-diisocyanate; cycloaliphatic diisocyanates such as,
for example, isophorone-diisocyanate, 1,4-cyclohexane-diisocyanate,
1-methyl-2,4- and -2,6-cyclohexane-diisocyanate and the
corresponding isomer mixtures, 4,4'-, 2,4'- and
2,2'-dicyclohexylmethane-diisocyanate and the corresponding isomer
mixtures; and aromatic diisocyanates such as, for example,
2,4-toluylene-diisocyanate, mixtures of 2,4- and
2,6-toluylene-diisocyanate, 4,4'-diphenylmethane-diisocyanate,
2,4'-diphenylmethane-diisocyanate and
2,2'-diphenylmethane-diisocyanate, mixtures of
2,4'-diphenylmethane-diisocyanate and 4,4'-diphenylmethane-di-
isocyanate, urethane-modified liquid
4,4'-diphenylmethane-diisocyanates and/or
2,4'-diphenylmethane-diisocyanates, 4,4'-diisocyanato-1,2-diphenyl-
-ethane and 1,5-naphthylene-diisocyanate.
Diphenylmethane-diisocyanate isomer mixtures with a
4,4'-diphenylmethane-diisocyanate content of greater than 96 wt. %
are preferably used, and 4,4'-diphenylmethane-diiso- cyanate and
1,5-naphthylene-diisocyanate are used in particular. The
diisocyanates mentioned above can be used individually or in the
form of mixtures with one another. They can also be used together
with up to 15 mol % (calculated for the total diisocyanate) of a
polyisocyanate, but polyisocyanate may be added at the most in an
amount such that a thermoplastically processable product is formed.
Examples of such polyisocyanates are
triphenylmethane-4,4',4"-triisocyanate and
polyphenyl-polymethylene-polyisocyanates.
[0023] The compounds suitable to be used as component B) in the
present invention include, preferably, polyester polyols, polyether
polyols or polycarbonate-polyols or polyols which contain nitrogen,
phosphorus, sulfur and/or silicon atoms, or mixtures of these.
Among the polyols which contain heteroatoms, phosphate-,
phosphonate- and phosphine oxide-containing polyols are
particularly preferred.
[0024] Linear hydroxyl-terminated polyols having on average from
about 1.8 to about 3.0 Zerewitinoff-active hydrogen atoms per
molecule, preferably from about 1.8 to about 2.2
Zerewitinoff-active hydrogen atoms per molecule, and having a
molecular weight of 450 to 10,000 g/mol are preferably employed as
component B) (i.e. polyol 1). These linear polyols often contain
small amounts of non-linear compounds as a result of their
production. Thus, these are also often referred to as
"substantially linear polyols".
[0025] Suitable polyether-diols for component B) of the present
invention can be prepared by, for example, reacting one or more
alkylene oxides having 2 to 4 carbon atoms in the alkylene radical
with a starter molecule which contains two active hydrogen atoms in
bonded form. Alkylene-oxides which may be mentioned include, for
example, ethylene oxide, 1,2-propylene oxide, epichlorohydrin,
1,2-butylene oxide and 2,3-butylene oxide. Ethylene oxide,
propylene oxide and mixtures of 1,2-propylene oxide and ethylene
oxide are preferably used. The alkylene oxides can be used
individually, alternately in succession or as mixtures. Possible
starter molecules include, for example: water, amino alcohols
including, for example, N-alkyl-diethanolamines such as, for
example, N-methyl-diethanolamine; and diols such as, for example,
ethylene glycol, 1,3-propylene glycol, 1,4-butanediol and
1,6-hexanediol. Mixtures of starter molecules can also optionally
be employed. Suitable polyether-polyols also include the
polymerization products of tetrahydrofuran which contain hydroxyl
groups. It is also possible to employ trifunctional polyethers in
amounts of 0 to 30 wt. %, based on the weight of the bifunctional
polyethers. The amount of trifunctional polyethers used is limited
to an amount which still results in a thermoplastically processable
product being formed. The substantially linear polyether-diols of
the present invention preferably have (number average) molecular
weights of 450 to 5,000 g/mol. They can be used either individually
or in the form of mixtures with one another.
[0026] Suitable polyester-diols to be used as component B) in the
present invention can be prepared, for example, from dicarboxylic
acids having 2 to 12 carbon atoms, preferably 4 to 6 carbon atoms,
and polyhydric alcohols. Suitable dicarboxylic acids include, for
example: aliphatic dicarboxylic acids, such as succinic acid,
glutaric acid, adipic acid, suberic acid, azelaic acid and sebacic
acid, and aromatic dicarboxylic acids, such as phthalic acid,
isophthalic acid and terephthalic acid. The dicarboxylic acids can
be used individually or as mixtures, e.g. in the form of a
succinic, glutaric and adipic acid mixture. For the preparation of
the polyester-diols it may be advantageous, where appropriate, to
use the corresponding dicarboxylic acid derivatives, such as
carboxylic acid diesters having 1 to 4 carbon atoms in the alcohol
radical, carboxylic acid anhydrides or carboxylic acid chlorides,
instead of the dicarboxylic acids. Examples of suitable polyhydric
alcohols include glycols having 2 to 10, preferably 2 to 6 carbon
atoms, such as, for example, ethylene glycol, diethylene glycol,
1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,10-decanediol,
2,2-dimethyl-1,3-propanediol, 1,3-propanediol and dipropylene
glycol. The polyhydric alcohols can be used by themselves or
optionally as a mixture with one another, depending on the desired
properties. Compounds which are also suitable for use as component
B) include esters of carbonic acid with the diols mentioned above,
and particularly those diols having 4 to 6 carbon atoms, such as
1,4-butanediol and/or 1,6-hexanediol, condensation products of
.omega.-hydroxycarboxylic acids, such as .omega.-hydroxycaproic
acid, and preferably polymerization products of lactones such as,
for example, .omega.-caprolactones which are optionally
substituted. Polyester-diols which are preferably used include
ethanediol polyadipates, 1,4-butanediol polyadipates,
ethanediol-1,4-butanediol polyadipates,
1,6-hexanediol-neopentylglycol polyadipates,
1,6-hexanediol-1,4-butanedio- l polyadipates and polycaprolactones.
These polyester-diols preferably have (umber average) molecular
weights of 450 to 5,000 g/mol, and can be used individually or in
the form of mixtures with one another.
[0027] Linear hydroxyl-terminated polyols having on average 1.8 to
3.0 Zerewitinoff-active hydrogen atoms per molecule and having a
molecular weight of 60 to 10,000 g/mol are also employed as
component C) (polyol 2) in accordance with the present invention.
The previously mentioned compounds which are described as being
suitable for component B) can be used, with the proviso that polyol
2 is different than polyol 1.
[0028] Polyester-polyols, polyether-polyols and
polycarbonate-polyols or mixtures of these compounds having a
(number average) molecular weight of 100 to 5,000 g/mol and having
on average 1.8 to 2.2 Zerewitinoff-active hydrogen atoms per
molecule are particularly preferred as polyol (2).
[0029] Specific polyols which contain heteroatoms such as, for
example, nitrogen-, phosphorus-, silicon- or sulfur-containing
polyols can preferably also be employed. Phosphate-, phosphonate-
or phosphine oxide-containing polyols having a molecular weight of
100 to 5,000 g/mol and having on average 1.8 to 2.2
Zerewitinoff-active hydrogen atoms per molecule are particularly
preferred.
[0030] Compounds which are preferably employed as a phosphate are
those which correspond to the general formula (I) 1
[0031] wherein:
[0032] R.sup.1 and R.sup.2: may be the same or different, and each
independently represents a hydrogen atom, a branched or unbranched
alkyl radicals having 1 to 24 carbon atoms, a substituted or
unsubstituted aryl radical having 6 to 20 carbon atoms, a
substituted or unsubstituted aralkyl radical having 6 to 30 carbon
atoms, or a substituted or unsubstituted alkaryl radical having 6
to 30 carbon atoms;
[0033] R.sup.3, R.sup.4 and R.sup.5: may be the same or different,
and each independently represents a branched or unbranched alkylene
radical having 1 to 24 carbon atoms, a substituted or unsubstituted
arylene radical having 6 to 20 carbon atoms, a substituted or
unsubstituted aralkylene radical having 6 to 30 carbon atoms, or a
substituted or unsubstituted alkarylene radical having 6 to 30
carbon atoms; and
[0034] n: represents a number from 0 to 100.
[0035] Compounds which are preferably employed as a phosphonate are
those which correspond to the general formula (II) 2
[0036] wherein:
[0037] R.sup.1 and R.sup.2: may be the same or different, and each
independently represents a branched or unbranched alkylene radical
having 1 to 24 carbon atoms, a substituted or unsubstituted arylene
radical having 6 to 20 carbon atoms, a substituted or unsubstituted
aralkylene radical having 6 to 30 carbon atoms, or a substituted or
unsubstituted alkarylene radical having 6 to 30 carbon atoms;
[0038] R.sup.3: represents a hydrogen atom, a branched or
unbranched alkyl radical having 1 to 24 carbon atoms, a substituted
or unsubstituted aryl radical having 6 to 20 carbon atoms, a
substituted or unsubstituted aralkyl radical having 6 to 30 carbon
atoms, or a substituted or unsubstituted alkaryl radical having 6
to 30 carbon atoms; and
[0039] x and y: each independently represents a number of from 1 to
50, preferably from 2 to 40.
[0040] Compounds which can also preferably be employed as a
phosphonate are those which correspond to the general formula (III)
3
[0041] wherein:
[0042] R.sup.1 and R.sup.2: may be the same or different, and each
independently represents a hydrogen atom, a branched or unbranched
alkyl radical having 1 to 24 carbon atoms, a substituted or
unsubstituted aryl radical having 6 to 20 carbon atoms, a
substituted or unsubstituted aralkyl radical having 6 to 30 carbon
atoms or a substituted or unsubstituted alkaryl radical having 6 to
30 carbon atoms;
[0043] R.sup.3 represents a branched or unbranched alkylene radical
having 1 to 24 carbon atoms, a substituted or unsubstituted arylene
radical having 6 to 20 carbon atoms, a substituted or unsubstituted
aralkylene radical having 6 to 30 carbon atoms, or a substituted or
unsubstituted alkarylene radical having 6 to 30 carbon atoms;
and
[0044] R.sup.4 and R.sup.5 may be the same or different, and each
independently represents a branched or unbranched alkylene radical
having 1 to 24 carbon atoms, a substituted or unsubstituted arylene
radical having 6 to 20 carbon atoms, a substituted or unsubstituted
aralkylene radical having 6 to 30 carbon atoms, or a substituted or
unsubstituted alkarylene radical having 6 to 30 carbon atoms.
[0045] Compounds which are preferably employed as a phosphine oxide
are those which correspond to the general formula (IV): 4
[0046] wherein:
[0047] R.sup.1 represents a hydrogen atom, a branched or unbranched
alkyl radical having 1 to 24 carbon atoms, a substituted or
unsubstituted aryl radical having 6 to 20 carbon atoms, a
substituted or unsubstituted aralkyl radical having 6 to 30 carbon
atoms, or a substituted or unsubstituted alkaryl radical having 6
to 30 carbon atoms; and
[0048] R.sup.2 and R.sup.3 may be the same or different, and each
independently represents a branched or unbranched alkylene radical
having 1 to 24 carbon atoms, a substituted or unsubstituted arylene
radical having 6 to 20 carbon atoms, a substituted or unsubstituted
aralkylene radical having 6 to 30 carbon atoms, or a substituted or
unsubstituted alkarylene radical having 6 to 30 carbon atoms.
[0049] Chain-lengthening agents suitable for use as component D)
which are employed in the present invention include low molecular
weight polyols or polyamines having on average 1.8 to 3.0
Zerewitinoff-active hydrogen atoms per molecule and a (number
average) molecular weight of 60 to 400 g/mol. These low molecular
weight compounds preferably include aliphatic diols having 2 to 14
carbon atoms such as, for example, ethanediol, 1,6-hexanediol,
diethylene glycol, dipropylene glycol and, in particular,
1,4-butanediol. However, diesters of terephthalic acid with glycols
having 2 to 4 carbon atoms, such as e.g. terephthalic acid
bis-ethylene glycol or terephthalic acid bis-1,4-butanediol;
hydroxyalkylene ethers of hydroquinone, such as e.g.
1,4-di(.beta.-hydroxyethyl)-hydroquinone; ethoxylated bisphenols,
such as e.g. 1,4-di(.beta.-hydroxyethyl)-bispheno- l A;
(cyclo)aliphatic diamines, such as e.g. isophoronediamine,
ethylenediamine, 1,2-propylene-diamine, 1,3-propylenediamine,
N-methyl-propylene-1,3-diamine and N,N'-dimethyl-ethylenediamine;
and aromatic diamines, such as e.g. 2,4-toluylenediamine and
2,6-toluylenediamine, 3,5-diethyl-2,4-toluylenediamine or
3,5-diethyl-2,6-toluylenediamine, and primary mono-, di-, tri-
and/or tetraalkyl-substituted 4,4'-diaiminodiphenylmethanes, are
also suitable. Mixtures of the abovementioned chain lengtheners can
also be employed. In addition, relatively small amounts of triols
can also be added.
[0050] Although it is possible, at least theoretically, to use the
same compound as polyol 2 and as chain lengthening agent, these
compounds are different in actual use.
[0051] Conventional monofunctional compounds can furthermore also
be employed in small amounts, e.g. as chain terminators or mold
release aids. Examples which may be mentioned are alcohols, such as
octanol and stearyl alcohol, or amines, such as butylamine and
stearylamine.
[0052] To prepare the TPUs of the present invention, the builder
components, optionally in the presence of catalysts, auxiliary
substances and/or additives, are preferably reacted in amounts such
that the equivalent ratio of NCO groups from A) to the sum of
NCO-reactive groups, in particular the OH (and/or NH) groups of the
low molecular weight compounds D) and the polyols B) and C), is
from 0.9:1.0 to 1.2:1.0, and preferably from 0.95:1.0 to
1.10:1.0.
[0053] Suitable catalysts to be used as component F) in the present
invention include the conventional tertiary amine catalysts known
from the prior art. Examples of suitable catalysts include tertiary
amine compounds such as, for example, triethylamine,
dimethylcyclohexylamine, N-methylmorpholine,
N,N'-dimethyl-piperazine, 2-(dimethylamino-ethoxy)-et- hanol,
diazabicyclo-(2,2,2)-octane and the like, and, in particular,
organometallic compounds, such as titanic acid esters, iron
compounds or tin compounds, e.g. tin diacetate, tin dioctoate, tin
dilaurate or the tin-dialkyl salts of aliphatic carboxylic acids,
such as dibutyltin diacetate or dibutyltin, dilaurate or the like.
Preferred catalysts are organometallic compounds, in particular
titanic acid esters and compounds of iron and/or tin.
[0054] In addition to the TPU components and the catalysts,
auxiliary substances and/or additives, referred to here as
component E), may be present in amounts of up to 20 wt. %, based on
the total weight of the TPU. These auxiliary substances and/or
additives can be dissolved in one of the TPU components, preferably
in component B), or they may also optionally be metered in, after
the reaction has taken place, in a subsequent mixing unit such as,
e.g. an extruder.
[0055] Examples of these auxiliary substances and/or additives
which may be mentioned include lubricants, such as fatty acid
esters, metal soaps thereof, fatty acid amides, fatty acid
ester-amides and silicone compounds, antiblocking agents,
inhibitors, stabilizers against hydrolysis, light, heat and
discoloration, flameproofing agents, dyestuffs, pigments, inorganic
and/or organic fillers and reinforcing agents. Reinforcing agents
include, in particular, fibrous reinforcing substances, such as
e.g. inorganic fibers, which are prepared according to the prior
art and can also be charged with a size. Further details of the
auxiliary substances and additives mentioned can be found in the
technical literature, for example, in the monograph by J. H.
Saunders and K. C. Frisch "High Polymers", volume XVI,
Polyurethane, part 1 and 2, Verlag Interscience Publishers 1962 and
1964, the Taschenbuch fur Kunststoff-Additive by R. Gchter and H.
Muller (Hanser Verlag Munich 1990) or in DE-A 29 01 774, the
disclosure of which is herein incorporated by reference.
[0056] Further additives which can be incorporated into the TPU are
thermoplastics such as, for example, polycarbonates and
acrylonitrile/butadiene/styrene terpolymers, and in particular,
ABS. Other elastomers, such as rubber, ethylene/vinyl acetate
copolymers, styrene/butadiene copolymers and other TPUs, can also
be used. Furthermore, commercially available plasticizers, such as
phosphates, phthalates, adipates, sebacates and alkylsulfonic acid
esters, are also suitable for incorporation.
[0057] The preparation process according to the invention is
preferably carried out as follows.
[0058] The components A) and B) in step a) are mixed continuously
at temperatures above their melting point, preferably at
temperatures of 50 to 220.degree. C., and reacted to form
prepolymer I. This stage is preferably carried out in a mixing unit
with a high shear energy. For example, a mixing head or a
high-speed tubular mixer, a nozzle or a static mixer can be used.
Static mixers which can be employed include those which are
disclosed in, Chem.-Ing. Techn. 52, no. 4, page 285 to 291, and in
"Mischen von Kunststoff und Kautschukprodukten", VDI-Verlag,
Dusseldorf 1993, the disclosures of which are herein incorporated
by reference. SMX static mixers from Sulzer -may be mentioned by
way of example.
[0059] In another embodiment, a tube can also be used as the
reactor for the reaction.
[0060] The reaction to form prepolymer I in step a) should
substantially be brought to complete conversion (with respect to
polyol 1). Preferably, more than 85 mol % of the polyol employed
should be reacted in this stage. The reaction temperatures should
be above 100.degree. C., preferably between 120.degree. C. and
250.degree. C. For the continuously operating process the volume of
the reactor is such that, in interaction with the reaction
temperature and throughput, the required conversion is ensured.
[0061] Preferably, in step b), component B) (i.e. polyol 2) which
is preheated to above its melting point, is mixed continuously into
prepolymer I with a high shear energy and the mixture allowed to
react to yield prepolymer II. The above mentioned reactors can also
be used for this stage. A reactor separated from stage a) is
preferably used for this stage.
[0062] In addition, for step b), the volume of the reactor is such
that, in interaction with the reaction temperature and the
throughput, a conversion of greater than 85 mol % of the amount of
polyol 2 employed is ensured.
[0063] In a particular embodiment, this stage can also be carried
out in a first part of a multi-screw extruder (e.g. a twin-screw
extruder ZSK).
[0064] Adding together all the reaction components, i.e. components
A), B) and C), of steps a) and b), an equivalent ratio of NCO
groups to the sum of NCO-reactive groups of 1.2:1 to 10:1 is
preferably established.
[0065] In step c), the prepolymer II is preferably mixed
continuously with the low molecular weight polyol or polyamine as
the chain lengthener, and allowed to react to yield the TPU in a
high-viscosity reactor.
[0066] Component D), the chain lengthener, is preferably mixed in
using a mixing unit which operates with a high shear energy.
Examples of such units which may be mentioned include a mixing
head, a static mixer, a nozzle or a multi-screw extruder. The
mixing and the reaction of the components of this stage are
preferably carried out in a multi-screw extruder (e.g. in a
twin-screw kneader ZSK) after step b).
[0067] Reaction step c) is preferably carried out in a reactor
which differs from the reactor used in steps a) and b) (different
type of reactor).
[0068] The temperatures of the extruder housing are selected such
that the reaction components are brought to complete conversion,
and the possible incorporation of the above mentioned auxiliary
substances or the optional components can be carried out with the
highest possible protection of the product.
[0069] At the end of the extruder the product is granulated.
Readily processable granules are obtained.
[0070] The TPU prepared by the process according to the invention
can be processed to injection-molded articles and to homogeneous
extruded articles.
[0071] The invention is to be illustrated in more detail with the
aid of the following examples.
EXAMPLES
[0072] The following recipe was used- in the working examples.
[0073] TPU recipe:
1 Polyol 1: Terathane .RTM. 1000 52.3 parts by wt. Polyol 2: Exolit
.RTM. OP 560 5.5 parts by wt. Chain lengthener: Butane-1,4-diol 6.2
parts by wt. Isocyanate: 4,4'-MDI 35.1 parts by wt. Additives:
Licowax .RTM. C 0.4 part by wt. Irganox .RTM. 1010 0.5 part by wt.
Tin dioctoate 0.011 part by wt. Terathane .RTM. 1000: Polyether
having a number average molecular weight of M.sub.n of 1,000 g/mol;
a commercial product of Du Pont de Nemours Isocyanate:
Diphenylmethane-4,4'-diisocyan- ate, commercially available from
Bayer AG Exolit .RTM. OP 560: Flameproofing agent based on
diol-phosphonate having a number average molecular weight of
M.sub.n of 300, commercially available from Clariant GmbH Irganox
.RTM. 1010 Tetrakis(methylene-(3,5-di-tert-butyl
4-hydroxycinnamate))-methane, commercially available from Ciba
Specialty Chemicals Inc. Licowax .RTM. C Ethylene-bis-stearylamide,
commercially available from Clariant
Example 1 (comparison)
[0074] (ZSK One-Shot Process)
[0075] Polyol 1, in which tin dioctoate was dissolved as a
catalyst, was heated to 200.degree. C. and metered continuously by
means of a gear pump into the first housing of a ZSK 53 (twin-screw
extruder from Werner/Pfleiderer).
[0076] Polyol 2 premixed with the butane-1,4-diol (60.degree. C.),
and 4,4'-diphenylmethane-diisocyanate (Desmodur.RTM. 44M)
(60.degree. C.) and Licowax.RTM. C were metered continuously into
the same housing, i.e. the first housing of the ZSK 53. The ZSK was
heated up to 220 to 230.degree. C. (housings 1 to 8). The last 4
housings were cooled. The speed of the screw was 290 rpm.
[0077] At the end of the screw the hot melt was taken off as a
strand, cooled in a water-bath and granulated.
Example 2 (comparison)
[0078] (ZSK Prepolymer Metering Process)
[0079] This experiment was carried out analogously to Example 1,
except that polyol 2 and the butane-1,4-diol were metered into
housing 7 of the ZSK, instead of into housing 1 as above.
Example 3 (comparison)
[0080] (Two-Stage Process)
[0081] This experiment was carried out analogously to Example 1,
except that polyol 1 and the MDI were metered continuously into a
static mixer of a static mixer zone of 3.times. DN 20 (SMX from
Sulzer). This static mixer zone led directly into housing 1 of the
ZSK. The remaining components were mixed and/or metered as in
Example 1.
Example 4 (according to the invention)
[0082] (Multi-Stage Prepolymer Metering Process)
[0083] This experiment was carried out analogously to Example 3,
except that the continuous addition and reaction of polyol 2 was
carried out in a reactor consisting of a DN 18 static mixer and a
tube (length-diameter ratio: 80). This reactor was mounted directly
after the static mixer zone from Example 3 and led directly into
housing 1 of the ZSK. The remaining components were mixed and/or
metered as in Example 3.
[0084] The results of the product testing are shown in the
table.
[0085] Measurement of the MVR Values (MVR=Melt Volume Rate)
[0086] The MVR value of the granules was measured in accordance
with ISO 1133 with a weight of 10 kg.
[0087] Production of the Injection-Molded Articles
[0088] The particular TPU granules from Examples 1 to 4 were melted
(melt temperature approx. 230.degree. C.) in an injection molding
machine D 60 (32 screw from Mannesmann) and shaped into sheets (125
mm.times.50 mm.times.2 mm).
[0089] Tube Extrusion
[0090] The particular TPU granules from Examples 3 and 4 were
melted (metering 3 kg/h; 230 to 195.degree. C.) in a single-screw
extruder 30/25D (Plasticorder PL 2000-6 from Brabender) and
extruded to a tube through a tube die.
[0091] Mechanical Testing at Room Temperature
[0092] The modulus at 100% elongation and the tear strength were
measured on the injection-molded test specimens in accordance with
DIN 53 405.
[0093] Determination of the Flameproofing Properties:
[0094] The flameproofing properties were determined in accordance
with UL94 V at a thickness of the test specimen of 3 mm (described
in Underwriters Laboratories Inc. Standard of Safety, "Test
for-Flammability of Plastic Materials for Parts in Devices and
Appliances", p. 14 et seq., Northbrook 1998 and J. Triotzsch,
"International Plastics Flammability Handbook", p. 346 et seq.,
Hanser Verlag, Munich 1990).
[0095] In this test a V 0 rating means non-burning dripping. A
product with this rating is therefore designated as
flame-resistant. A V 2 rating means burning dripping, i.e. absence
of flame resistance.
2 Results: Reactor: Static Metering of MVR 100% Tear UL 94 Mixer
Metering Metering Chain Metering 200.degree. C. Modulus strength
test Tube Example Extruder of polyol 1 of polyol 2 Lengthener D OF
MDI Granules 10 kg [MPa] [MPa] (3 mm) extrusion 1* ZSK 53 hous. 1
hous. 1 hous. 1 ZSK hous. 1 tacky 20 6.7 39 V 2 ZSK ZSK ZSK 2* ZSK
53 hous. 1 hous. 7 hous. 7 ZSK hous. 1 very 42 ZSK ZSK ZSK tacky;
cannot be processed 3* 3 .times. DN20/ 1st DN20 hous. 1 hous. 1 ZSK
1st DN20 tacky 25 6.2 47 V 0 inhomogeneous ZSK 53 ZSK extrudate 4*
3 .times. DN20/ 1st DN20 1st DN18 hous. 1 ZSK 1st DN20 not tacky, 7
6.7 48 V 0 homogeneous 1 .times. DN18/ readily extrudate tube/
granulated ZSK 53 *comparison example not according to the
invention hous. = housing ZSK 53 = (twin-screw kneader from
Werner/Pfleiderer) 3 .times. DN20 = static mixer of three DN20
static mixers from Sulzer 1 .times. DN18 = one static mixer DN18
from Sulzer
[0096] The TPU granules prepared by the one-shot process (Example
1) were tacky and achieved a rating of only V2 in the flame test.
Tackiness of granules makes their further processing and their
handling (e.g. conveying, transfer to containers etc.)
difficult.
[0097] The products prepared by the ZSK prepolymer process were so
severely tacky that it was not possible to process them (Example
2).
[0098] The TPU products prepared by the two-stage prepolymer
process (Example 3) were also tacky. Inhomogeneous extruded tubes
were obtained by processing.
[0099] The granules prepared by the multi-stage process according
to the invention (Example 4), on the other hand, were not tacky and
could be processed very readily to TPU articles (e.g. extruded
tubes) with excellent TPU properties.
[0100] 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.
* * * * *