U.S. patent application number 10/085913 was filed with the patent office on 2002-06-27 for continuous process for preparing a polyurethane latex.
Invention is credited to Jakubowski, James J., Pate, James E. III, Willkomm, Wayne R..
Application Number | 20020082342 10/085913 |
Document ID | / |
Family ID | 21904172 |
Filed Date | 2002-06-27 |
United States Patent
Application |
20020082342 |
Kind Code |
A1 |
Jakubowski, James J. ; et
al. |
June 27, 2002 |
Continuous process for preparing a polyurethane latex
Abstract
A polyurethane/urea/thiourea latex having a narrow molecular
weight polydispersity and sub-micron particle size can be prepared
by first preparing a high internal phase ratio (HIPR) emulsion of a
polyurethane/urea/thiourea prepolymer, then contacting the emulsion
with a chain-extending reagent under such conditions to form the
polymer latex.
Inventors: |
Jakubowski, James J.;
(Midland, MI) ; Willkomm, Wayne R.; (Lake Jackson,
TX) ; Pate, James E. III; (Sanford, MI) |
Correspondence
Address: |
THE DOW CHEMICAL COMPANY
INTELLECTUAL PROPERTY SECTION
P. O. BOX 1967
MIDLAND
MI
48641-1967
US
|
Family ID: |
21904172 |
Appl. No.: |
10/085913 |
Filed: |
February 27, 2002 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10085913 |
Feb 27, 2002 |
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09631072 |
Aug 2, 2000 |
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09631072 |
Aug 2, 2000 |
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09320803 |
May 27, 1999 |
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09320803 |
May 27, 1999 |
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09040027 |
Mar 17, 1998 |
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5959027 |
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60039194 |
Mar 17, 1997 |
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Current U.S.
Class: |
524/589 |
Current CPC
Class: |
C08G 18/283 20130101;
C08G 18/0866 20130101; C08G 18/10 20130101; C08G 18/10 20130101;
C08G 18/3246 20130101 |
Class at
Publication: |
524/589 |
International
Class: |
C08K 003/00 |
Claims
What is claimed is:
1. A composition comprising a polyurethane latex having a mean
volume average particle size of not greater than about 1 micron and
a solids content of at least 45 percent by weight, wherein the
polyurethane latex contains the following units: 3where R and R'
are each aromatic.
2. The composition of claim 1, wherein the polyurethane latex
contains units formed from 4,4'-diisocyanatodiphenylmethane or
2,4'-diisocyanatodiphenylmethane or a combination thereof.
3. The composition of claim 1, wherein the polyurethane latex has a
solids content of not less than 50 percent by weight based on the
total weight of the latex.
4. The composition of claim 3, wherein the latex has a solids
content of not less than 55 percent by weight based on the total
weight of the latex and has a volume average particle size of not
greater than 0.5 micron and a polydispersity of not greater than
1.5.
5. The composition of claim 1, wherein the polyurethane latex has a
mean volume average particle size of not greater than about 0.5
micron.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This Application is a divisional application of U.S. patent
application Ser. No. 09/631,072 filed Aug. 2, 2000, which is a
continuation of U.S. patent application Ser. No. 09/320,803 filed
May 27, 1999, which is a divisional of U.S. patent application Ser.
No. 09/040,027 filed Mar. 17, 1998, which claims the benefit of
U.S. Provisional Application Serial No. 60/039,194 filed Mar. 17,
1997 all of which are hereby incorporated by reference.
BACKGROUND OF THE INVENTION
[0002] This invention relates to polyurethane/urea/thiourea latexes
prepared from a high internal phase ratio emulsion of a
urethane/urea/thiourea prepolymer.
[0003] Polyurethane/urea/thiourea latexes are generally prepared by
chain extending the reaction product of an organic diisocyanate and
an organic compound having two active hydrogen atoms such as
polyalkylene ether glycols, poly(alkylene ether-alkylene thioether)
glycols, alkyd resins, polyesters and polyester amides. The
diisocyanate is used in stoichiometric excess so that the reaction
product, also referred to as a polyurethane/urea/thiourea
prepolymer, is isocyanate terminated. The prepolymer is typically
prepared in the presence of a solvent. Examples of polyurethane
prepolymer preparations are described in U.S. Pat. Nos. 3,178,310,
3,919,173, 4,442,259, 4,444,976, and 4,742,095, inter alia.
[0004] U.S. Pat. No. 3,294,724 discloses the preparation of a
film-forming urethane latex by chain extending the
isocyanate-terminated prepolymer with a piperazine compound. First,
the prepolymer is prepared by reacting a polyalkylene ether glycol
with a diisocyanate. A prepolymer emulsion is then formed,
whereupon a piperazine compound dissolved in cold water is added to
the emulsion with stirring to form a stable chain-extended latex. A
solvent such as toluene or cyclohexanone is used either in the step
to form the prepolymer or in the chain extension step.
[0005] The solids content of a typical polyurethane latex tends to
be in the range of about 30 to 40 weight percent. For example, U.S.
Pat. No. 4,742,095 describes the preparation of a polyurethane
latex having a solids content of as high as 41 weight percent. To
minimize transport costs and drying times, it is desirable to
prepare a polyurethane latex that maximizes solids content without
having to resort to additional concentration means such as
evaporation of water.
[0006] It would be advantageous to prepare a
polyurethane/urea/thiourea latex in the substantial absence of any
ancillary organic solvents. It would be further advantageous to
prepare such a latex with controlled particle size and a narrow
particle size distribution. Finally, it would be desirable to
prepare a polyurethane latex that has a solids content of at least
45 percent by weight. Such a latex would be particularly useful as
a carpet backing.
SUMMARY OF THE INVENTION
[0007] In one aspect, the present invention is a process for
preparing a polyurethane/urea/thiourea latex comprising the steps
of: a) forming by a continuous process a high internal phase ratio
(HIPR) emulsion of a polyurethane/urea/thiourea prepolymer in the
presence of water and an emulsifying and stabilizing amount of a
surfactant; and b) contacting the high internal phase ratio
emulsion with a chain-extending reagent under such conditions to
form the polyurethane/urea/thiourea latex; wherein the prepolymer
is prepared by contacting a high molecular weight organic compound
having at least two active hydrogen atoms with sufficient
polyisocyanate, and under such conditions to ensure that the
prepolymer is terminated with at least two isocyanate groups.
[0008] In another aspect, the present invention is a process for
preparing a polyurethane/urea/thiourea latex comprising the steps
of: a) continuously merging into a disperser and in the presence of
an emulsifying and stabilizing amount of a surfactant, an aqueous
stream having a flow rate R.sub.1 and a polyurethane/urea/thiourea
prepolymer stream having a flow rate R.sub.2; b) mixing the merged
streams with a sufficient amount of shear to form a high internal
phase ratio emulsion; and c) mixing the high internal phase ratio
emulsion with water and a chain-extending reagent to form a
polyurethane/urea/thiourea latex; wherein R.sub.2:R.sub.1 is such
that the polydispersity of the HIPR emulsion is not greater than
about 3 or the volume average particle size is not greater than
about 2 microns.
[0009] In another aspect, the present invention is a continuous
process for preparing a polyurethane/urea/thiourea latex comprising
the steps of: a) merging a stream containing a stoichiometric
excess of a polyisocyanate with a stream containing a high
molecular weight organic compound having at least two active
hydrogen atoms into a static or an active mixer under such
conditions to form a polyurethane prepolymer that is terminated
with at least two end groups; b) forming an emulsion of the
prepolymer by merging a stream containing the prepolymer with a
stream containing water and in the presence of an emulsifying and
stabilizing amount of a surfactant; and c) contacting a stream of
the emulsion with a stream of a chain-extending reagent under such
conditions to form a polyurethane/urea/thiourea latex.
[0010] In another aspect, the present invention is a
polyurethane/urea/thiourea latex having a solids content of not
less than 45 percent by weight, based on the total weight of the
latex.
BRIEF DESCRIPTION OF THE DRAWING
[0011] FIG. 1 is a profile of the particle size and polydispersity
of an HIPR emulsion as a function of the urethane prepolymer to
water flow rates used to prepare the emulsion. The emulsion is
stabilized with linear sodium dodecylbenzene sulfonate.
DETAILED DESCRIPTION OF THE INVENTION
[0012] The polyurethane/urea/thiourea latex of the present
invention can be prepared by reacting a polyurethane/urea/thiourea
prepolymer with a chain-extending reagent in an aqueous medium and
in the presence of a stabilizing amount of a surfactant. The
polyurethane/urea/thiourea prepolymer can be prepared by any
suitable method such as those well known in the art. The prepolymer
is advantageously prepared by contacting a high molecular weight
organic compound having at least two active hydrogen atoms with
sufficient polyisocyanate, and under such conditions to ensure that
the prepolymer is terminated with at least two isocyanate
groups.
[0013] The polyisocyanate is preferably an organic diisocyanate,
and may be aromatic, aliphatic, or cycloaliphatic, or a combination
thereof. Representative examples of diisocyanates suitable for the
preparation of the prepolymer include those disclosed in U.S. Pat.
No. 3,294,724, column 1, lines 55 to 72, and column 2, lines 1 to
9, incorporated herein by reference, as well as U.S. Pat. No.
3,410,817, column 2, lines 62 to 72, and column 3, lines 1 to 24,
also incorporated herein by reference. Preferred diisocyanates
include 4,4'-diisocyanatodiphenylmethane,
2,4'-diisocyanatodiphenylmethane, isophorone diisocyanate,
p-phenylene diisocyanate, 2,6 toluene diisocyanate, polyphenyl
polymethylene polyisocyanate, 1,3-bis(isocyanatomethyl)cyclohexane,
1,4-diisocyanatocyclohexane, hexamethylene diisocyanate,
1,5-naphthalene diisocyanate, 3,3'-dimethyl-4,4'-biphenyl
diisocyanate, 4,4'-diisocyanatodicyclohexylmethane,
2,4'-diisocyanatodicyclohexylmethan- e, and 2,4-toluene
diisocyanate, or combinations thereof. More preferred diisocyanates
are 4,4'-diisocyanatodicyclohexylmethane,
4,4'-diisocyanatodiphenylmethane,
2,4'-diisocyanatodi-cyclohexylmethane, and
2,4'-diisocyanatodiphenylmethane. Most preferred is
4,4'-diisocyanatodiphenylmethane and
2,4'-diisocyanatodiphenylmethane.
[0014] As used herein, the term "active hydrogen group" refers to a
group that reacts with an isocyanate group to form a urea group, a
thiourea group, or a urethane group as illustrated by the general
reaction: 1
[0015] where X is O, S, NH, or N, and R and R' are connecting
groups which may be aliphatic, aromatic, or cycloaliphatic, or
combinations thereof. The high molecular weight organic compound
with at least two active hydrogen atoms has a molecular weight of
not less than 500 Daltons.
[0016] The high molecular weight organic compound having at least
two active hydrogen atoms may be a polyol, a polyamine, a
polythiol, or a compound containing combinations of amines, thiols,
and ethers. Preferably, the high molecular weight organic compound
having at least two active hydrogen atoms is a diol, a diamine, a
dithiol, an alcohol-amine, a thiol-amine, or an alcohol-thiol, and
has a weight average molecular weight of not less than 500.
Preferably, the high molecular weight organic compound having at
least two active hydrogen atoms is a polyalkylene glycol ether or
thioether or polyester polyol or polythiol having the general
formula: 2
[0017] where each R is independently an alkylene radical; R' is an
alkylene or an arylene radical; each X is independently S or O,
preferably O; n is a positive integer; and n' is a non-negative
integer, with the proviso that n and n' are sufficiently large that
the compound has a weight average molecular weight of not less than
about 500 Daltons, more preferably not less than about 750 Daltons,
and most preferably not less than about 1000 Daltons. Preferably,
the weight average molecular weight of the polyalkylene glycol is
not greater than about 20,000 Daltons, more preferably not greater
than about 10,000 Daltons, more preferably not greater than about
5000 Daltons, and most preferably not greater than about 3000
Daltons. The polyalkylene ether glycols and polyester polyols are
preferred. Representative examples of polyalkylene ether glycols
are polyethylene ether glycols, poly-1,2-propylene ether glycols,
polytetramethylene ether glycols, poly-1,2-dimethylethylene ether
glycols, poly-1,2-butylene ether glycol, and polydecamethylene
ether glycols. Preferred polyester polyols include polybutylene
adipate and polyethylene terephthalate.
[0018] A small amount of a low molecular compound with at least two
active hydrogen atoms may be added along with to the high molecular
weight organic compound having at least two active hydrogen atoms
to increase the tensile strength of the resulting polymer. The
molecular weight of the low molecular compound having at least two
active hydrogen atoms is in the range of from about 62 Daltons to
about 400 Daltons, and includes diols, dithiols, diamines, alcohol
amines, alcohol thiols, and amine thiols. Diols including
diethylene glycol, ethylene glycol, and dipropylene glycol are
preferred. The amount of low molecular weight organic compound is
preferably added in a sufficient amount to advantageously increase
the tensile strength of the resulting polymer. More preferably, the
amount of low molecular organic compound having at least two active
hydrogen atoms is not less than 0.5 weight percent, most preferably
not less than 1 weight percent based on the weight of the total
compounds having active hydrogen atoms; and more preferably not
greater than 10 weight percent, most preferably not greater than 5
weight percent based on the weight of the total compounds having
active hydrogen atoms.
[0019] Preferably, the NCO:XH ratio, where X is O or S, preferably
O, is not less than 1.1:1, more preferably not less than 1.2:1, and
preferably not greater than 5:1.
[0020] The polyurethane prepolymer can be prepared by a batch or a
continuous process by methods such as those well known in the art.
For example, a stoichiometric excess of a diisocyanate and a polyol
can be introduced in separate streams into a static or an active
mixer, preferably in the presence of an activating amount of an
organotin catalyst such as stannous octoate, and at a temperature
suitable for controlled reaction of the reagents, typically from
about 40.degree. C. to about 100.degree. C. The reaction is carried
to substantial completion in a plug flow reactor to form the
prepolymer. Upon substantial completion of the reaction, the
temperature of the prepolymer may be adjusted for the formation of
the HIPR emulsion.
[0021] The HIPR emulsion can be prepared by any suitable method
such as those well known in the art. (See, for example, U.S. Pat.
No. 5,539,021, column 1, lines 9 to 45, which teachings are
incorporated herein by reference.) In the process of the present
invention, the temperature at which the HIPR emulsion is prepared
is not critical; however, it may be desirable in some instances to
prepare the emulsion at subambient temperatures, because water
slowly reacts with diisocyanate groups to form amines and CO.sub.2,
and it may be advantageous to suppress premature reaction of water
and the prepolymer. Furthermore, the preferred temperature for
preparing the HIPR emulsion is dependent on the residence time,
that is, the time between the formation of the HIPR emulsion and
the contact of the emulsion with the chain-extending reagent. In
general, the shorter the residence time, the greater the
flexibility in selection of temperature is.
[0022] In a preferred method of preparing the HIPR emulsion, a
flowing stream containing the prepolymer is merged with a flowing
stream containing water with sufficient shear to form the HIPR
emulsion. An emulsifying and stabilizing amount of a surfactant is
also present, either in the stream containing the prepolymer, in
the stream containing the water, or in a separate stream. The
relative rates of the stream containing the prepolymer (R.sub.2)
and the stream containing the water (R.sub.1) are preferably such
that the polydispersity of the HIPR emulsion (the ratio of the
volume average diameter and the number average diameter of the
particles or droplets, or D.sub.65/D.sub.n) is not greater than
about 5, more preferably not greater than about 3, more preferably
not greater than about 2, more preferably not greater than about
1.5, and most preferably not greater than about 1.3; or the volume
average particle size is not greater than about 2 microns, more
preferably not greater than about 1 micron, more preferably not
greater than about 0.5 micron, and most preferably not greater than
about 0.3 micron. Furthermore, it is preferred that the HIPR
emulsion be prepared in a continuous process without phase
inversion or stepwise distribution of an internal phase into an
external phase.
[0023] The surfactant is sometimes used as a concentrate in water.
In this case, a stream containing the surfactant is advantageously
first merged with a stream containing the prepolymer to form a
prepolymer/surfactant mixture. Although an HIPR emulsion can be
prepared in this single step, it is preferred that a stream
containing the prepolymer and the surfactant be merged with a water
stream to dilute the surfactant and to create an HIPR emulsion.
[0024] Referring to FIG. 1, the profile of the polydispersity and
volume average particle size of the HIPR emulsion prepolymer
prepared with 1 percent RHODACAL.TM. LDS-22 surfactant (sodium
dodecylbenzene sulfonate, a trademark of Rhone Polenc) is
illustrated. The region where the oil:water feed rate ratio
(R.sub.2:R.sub.1) is in the range of about 5:1 to about 9.2:1
represents the preferred operating range of R.sub.2:R.sub.1for the
given prepolymer (prepared by reacting 30 weight percent of a 50:50
mixture of 4,4'-diisocyanatodiphenylmethane and
2,4'-diisocyanatodiphenylmethane with 70 weight percent of a
polypropylene oxide diol having a weight average molecular weight
of about 2000), and the type and amount of surfactant used.
[0025] When the HIPR emulsion is prepared using 3 percent by weight
DeSULF.TM. TLS-40 surfactant (active ingredient is triethanolamine
lauryl sulfate, a trademark of DeForest Enterprise, Inc.), the
preferred R.sub.2:R.sub.1 is from about 5:1 to about 8:1. When the
surfactant is 3 percent by weight DeSULF.TM. DBS-60T surfactant
(active ingredient is triethanolamine dodecylbenzene sulfonate, a
trademark of DeForest Enterprise, Inc.) the preferred
R.sub.2:R.sub.1 is from about 3.5:1 to about 6:1.
[0026] An external surfactant, which may be cationic, anionic, or
nonionic, is preferably used to prepare the HIPR emulsion. Suitable
classes of surfactants include, but are not restricted to, sulfates
of ethoxylated phenols such as
poly(oxy-1,2-ethanediyl).alpha.-sulfo-.omega.- (nonylphenoxy)
ammonium salt; alkali metal fatty acid salts such as alkali metal
oleates and stearates; polyoxyalkylene nonionics such as
polyethylene oxide, polypropylene oxide, polybutylene oxide, and
copolymers thereof; alcohol alkoxylates; ethoxylated fatty acid
esters and alkylphenol ethoxylates; alkali metal lauryl sulfates;
amine lauryl sulfates such as triethanolamine lauryl sulfate;
quaternary ammonium surfactants; alkali metal alkylbenzene
sulfonates such as branched and linear sodium dodecylbenzene
sulfonates; amine alkyl benzene sulfonates such as triethanolamine
dodecylbenzene sulfonate; anionic and nonionic fluorocarbon
surfactants such as fluorinated alkyl esters and alkali metal
perfluoroalkyl sulfonates; organosilicon surfactants such as
modified polydimethylsiloxanes; and alkali metal soaps of modified
resins. If the prepolymer is self-emulsifying by inclusion of
emulsifying nonionic, cationic, or anionic groups, then an external
surfactant may or may not be necessary.
[0027] Generally, higher surfactant concentrations result in
smaller diameter particles, but surfactant concentrations that are
too high tend to deleteriously affect the properties of products
such as films prepared from the HIPR emulsion. A person of ordinary
skill in the art can readily determine the appropriate surfactant
concentration for the particular end use.
[0028] Although it is possible to first dissolve the prepolymer in
a solvent for the prepolymer prior to forming the HIPR emulsion, it
is preferred to prepare the HIPR emulsion in the substantial
absence of a solvent, more preferably in the absence of a solvent.
As used herein, the term "in the substantial absence of a solvent"
means that a solvent for the prepolymer represents not more than 10
weight percent, preferably not more than 5 weight percent, more
preferably not more than 1 weight percent, and most preferably not
more than 0.1 weight percent of the HIPR emulsion based on the
weight of the prepolymer and the solvent.
[0029] The inclusion of a solvent often adds an unnecessary expense
to the manufacture of the end-use product. Moreover, solvent
removal, when necessary to obtain acceptable physical properties of
the product, is also an expensive as well as a time-consuming step.
Thus, a preferred process of the present invention represents an
advance in the art of the preparation of urethane latexes.
[0030] A polyurethane/urea/thiourea polymer is prepared by
contacting the HIPR emulsion of the prepolymer with a
chain-extending reagent, which is a compound that contains
functional groups that react with isocyanate groups to form
urethane, urea, or thiourea groups. Chain-extending reagents are
well known in the art.
[0031] The HIPR emulsion is preferably first diluted with
sufficient water to form a prepolymer latex having a disperse phase
to aqueous phase ratio that is less than about 3:1. Although water
can be used as a chain-extending agent, other chain-extending
agents are preferred for building of molecular weight. Therefore,
it is preferred that the prepolymer latex be contacted with the
preferred chain-extending reagent before substantial reaction takes
place between water and the prepolymer. Preferred chain-extending
reagents include aliphatic, cycloaliphatic, aromatic polyamines,
and alcohol amines. More preferred chain-extending reagents are
alcohol monoamines such as monoethanol amine and diethanol amine,
and diamines including hydrazine, ethylene diamine,
propylene-1,2-diamine, propylene-1,3-diamine,
tetramethylenediamine, hexamethylenediamine,
4,4'-dimethylamino-3,3'-dimethyl-diphenylmethane,
4,4'-diamino-diphenylmethane, 2,4-diaminotoluene,
2,6-diaminotoluene, aminoethylethanolamine, and piperazine.
Water-soluble diamines are most preferred. Piperazine is an example
of a most-preferred chain-extending agent.
[0032] The chain-extending reagent is preferably the limiting
reagent because it is desirable to avoid residual chain-extending
reagent, particularly diamine, in the final latex. Thus, in a
preferred method of preparing the polyurethane/urea/thiourea latex,
an aqueous solution of a diamine is contacted with a stoichiometric
excess of a latex of the prepolymer (that is, a stoichiometric
excess of isocyanate groups). After the diamine is substantially
completely reacted, the resultant latex is preferably allowed to
stand for a sufficiently long time so that the remaining isocyanate
groups react with the water. The preferred latex is a
polyurethane/urea latex having a volume average particle size of
not greater than about 1 micron, more preferably not greater than
about 0.5 micron, and most preferably not greater than about 0.4
micron, with a polydispersity that is preferably not greater than
about 2, more preferably not greater than about 1.5, and most
preferably not greater than about 1.3.
[0033] It has been surprisingly discovered that the volume average
particle size and polydispersity of a final
polyurethane/urea/thiourea latex prepared from an HIPR emulsion of
a polyurethane/urea/thiourea prepolymer by the process of the
present invention is generally less than the particle size and
polydispersity of a polyurethane/urea/thiourea latex not prepared
from an HIPR emulsion of a polyurethane/urea/thiourea prepolymer,
for a given surfactant, and at a given concentration of the
surfactant.
[0034] It is further surprising that a polyurethane latex with high
solids content that is at least 45 percent by weight, preferably at
least 50 percent by weight, more preferably at least 55 percent by
weight, based on the weight of the latex, can be prepared by the
process of the present invention. This high solids latex can be
prepared without resorting to costly removal of water from a more
dilute latex.
[0035] The polyurethane/urea/thiourea latexes of the present
invention are useful for applications for latexes with controlled
particle size and narrow size distributions are especially
important. Such applications include films, floor coatings, and
adhesives, especially for carpet-backing applications.
[0036] The following examples are for illustrative purposes only
and are not intended to limit the scope of this invention. All
percentages are in weight percent unless otherwise stated.
EXAMPLE 1
[0037] A urethane/urea prepolymer was prepared by reacting 70
percent by weight of a poly(propylene oxide) polyol VORANOL.TM.
2120 polyol (a trademark of The Dow Chemical Company) with 30
percent by weight of ISONATE.TM. 50 MDI (a trademark of The Dow
Chemical Company; a 50:50 mixture of
4,4'-diisocyanatodiphenylmethane and 2,4'-diisocyanatodiphenyl-
methane). The following processes were carried out at 10.degree. C.
The prepolymer was fed continuously at a rate of 31.4 g/minute
through a 1/2-inch (1.25 cm) stainless-steel tube fitted to one arm
of a T. A 20-percent aqueous solution of a sodium dodecylbenzene
sulfonate (RHODACAL.TM. DS-10, a trademark of Rhone Polenc) was fed
continuously at a rate of 4.7 g/minute through a 1/8-inch (0.31 cm)
stainless-steel tubing fitted to the other arm of the T. The two
streams were combined and passed through a static mixer to form a
non-emulsified blend. The blend was then fed into a 1/2-inch (1.25
cm) stainless-steel tube fitted to one arm of a T attached to the
input of a 70-mL centrifugal pump. Concurrently, water was pumped
through a 1/8-inch (0.31 cm) tetrafluoroethylene tubing fitted to
the other arm of the T, at the rate of 3.0 g/minute. The two
streams were merged and mixed together under shear in the
centrifugal pump operating at 650 rpm to form an HIPR emulsion.
[0038] The HIPR emulsion was diluted in a second centrifugal pump
by feeding the emulsion into a 1/2-inch (1.25 cm) stainless-steel
tube fitted to one arm of a T attached to a centrifugal pump.
Concurrently, water was pumped at a rate of 10 g/minute through
1/4-inch (0.63 cm) tetrafluoroethylene tubing fitted to the other
arm of the T. The two streams were mixed with the centrifugal pump
operating at 900 rpm.
[0039] Chain extension was accomplished in a third centrifugal pump
by feeding the diluted emulsion into a 1/2-inch (1.25 cm)
stainless-steel tube fitted to an arm of a T that was attached to
the input of a centrifugal pump. Concurrently, a 4.2 percent
aqueous solution of piperazine was pumped at a constant rate of
22.0 g/minute through a 1/4-inch (0.63 cm) tetrafluoroethylene tube
fitted to the other arm of the T. The two streams were mixed in the
centrifugal pump operating at 650 rpm. The product was collected
and allowed to stand overnight to allow water to react with the
remaining isocyanate groups. The resulting stable
poly(urethanelurea) latex was found to have a solids content of
47.1 percent by weight, a volume average particle size of 0.342
micron, and a polydispersity of 1.2, as measured by a Coulter LS
230 particle size analyzer.
EXAMPLE 2
[0040] The prepolymer was prepared by combining VORANOL.TM. 5287
polyol (63.35 percent by weight, a trademark of The Dow Chemical
Company), ISONATE.TM. 50 MDI (33.3 percent by weight), diethylene
glycol (1.35 percent by weight), and polyethylene oxide monol
having a molecular weight of 950. The following processes were
conducted at ambient temperature (19.degree. C.).
[0041] The prepolymer was fed continuously at rate of 32.1 g/minute
through a first arm fitted to a first T. DeSULF.TM. DBS-60T
surfactant (a 60 percent aqueous solution of triethanolamine
dodecylbenzene sulfonate, a trademark of DeForest Enterprises,
Inc.) was fed at a rate of 1.61 g/minute through a first arm of a
second T, and merged with a water stream flowing at a rate of 5.5
g/minute through the second arm of the second T. The prepolymer
stream and the water/surfactant stream were merged at the first T
and passed through a static mixer and then fed to the input port of
a IKA-SD 41 SUPER-DISPAX.TM. dispersing instrument (a trademark of
IKA-WORKS, Inc.), which was a rotor/stator device that was operated
at 1200 rpm.
[0042] The ratios of feeds into the dispersing instrument were 81.9
percent prepolymer, 4.1 percent surfactant solution, and 14.0
percent water. The HIPR emulsion formed in the dispersing
instrument had a volume average particle size of 0.265 micron and a
polydispersity of 3.1, as measured by a Coulter LS130 particle size
analyzer.
[0043] Chain extension was accomplished in a LIGHTNIN.TM. model
0.025 LB in-line blender (a trademark of GREEY/LIGHTNIN). The HIPR
emulsion from the dispersing instrument was fed into a first arm
attached to a third T and merged with an aqueous stream fed through
a second arm of the third T at the rate of 5.1 g/minute. The output
of the combined streams was fed into one arm of a fourth T, which
was attached to the input of the in-line blender. Concurrently, a
10 percent aqueous piperazine solution was pumped at a constant
rate of 18.0 g/minute (0.75 equivalents, based on the isocyanate
groups of the prepolymer) through the other arm of the fourth T.
The two streams were mixed in the in-line blender operating at 1500
rpm. The product was collected and allowed to stand overnight to
allow water to react with the remaining isocyanate groups. The
resulting stable poly(urethane/urea) latex was found to have a
solids content of 56.0 percent by weight, a volume average particle
size of 0.256 micron, and a polydispersity of 3.5, as measured by a
Coulter LS 230 particle size analyzer.
EXAMPLE 3
[0044] The same general procedure used to prepare the latex from
Example 2 was repeated. In this example, the surfactant was
DeSULF.TM. LTS-40 surfactant (a 40 percent aqueous solution of
triethanolamine lauryl sulfate, a trademark of Deforest
Enterprises, Inc.) and the flow rates were prepolymer, 32.0
g/minute; surfactant, 2.4 g/minute; and water, 3.5 g/minute. The
ratios of the components that were fed into the disperser were
prepolymer, 84.4 percent; surfactant solution, 6.3 percent; and
water, 9.2 percent. The HIPR emulsion had a volume average particle
size of 0.182 micron and a polydispersity of 1.6, as measured by a
Coulter LS130 particle size analyzer.
[0045] The aqueous stream used to dilute the HIPR emulsion was
flowed at a rate of 4.6 g/minute, and the piperazine solution was
pumped at a rate of 17.9 g/minute. The final poly(urethane/urea)
latex was found to have a solids content of 57.0 percent by weight,
a volume average particle size of 0.188 micron, and a
polydispersity of 1.9.
* * * * *