U.S. patent number RE32,733 [Application Number 06/808,268] was granted by the patent office on 1988-08-16 for polymer/polyol compositions having improved combustion resistance.
This patent grant is currently assigned to Union Carbide Corporation. Invention is credited to Frank E. Critchfield, Edgar G. Shook, Donald W. Simroth.
United States Patent |
RE32,733 |
Simroth , et al. |
August 16, 1988 |
Polymer/polyol compositions having improved combustion
resistance
Abstract
A stable dispersion of a polymer in a polyol which imparts
improved combustion resistance to polyurethane foams prepared
therefrom wherein the polymer is a free-radical initiated copolymer
containing from about 0.5 to 75 weight percent, based on the
copolymer, of acrylonitrile and from about 25 to 99.5 weight
percent, based on the copolymer, of at least one other
polymerizible ethylenically unsaturated monomer and wherein the
copolymer is characterized by a crosslinking coefficient of less
than 55.
Inventors: |
Simroth; Donald W. (Charleston,
WV), Critchfield; Frank E. (S. Charleston, WV), Shook;
Edgar G. (S. Charleston, WV) |
Assignee: |
Union Carbide Corporation
(Danbury, CT)
|
Family
ID: |
27008306 |
Appl.
No.: |
06/808,268 |
Filed: |
December 12, 1985 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
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378651 |
May 18, 1982 |
|
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Reissue of: |
409177 |
Aug 18, 1982 |
04463107 |
Jul 31, 1984 |
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Current U.S.
Class: |
521/137; 524/310;
524/377; 524/760; 524/762 |
Current CPC
Class: |
C08F
283/06 (20130101); C08G 18/63 (20130101) |
Current International
Class: |
C08G
18/00 (20060101); C08F 283/06 (20060101); C08F
283/00 (20060101); C08G 18/63 (20060101); C08L
075/04 () |
Field of
Search: |
;521/137 ;252/182
;524/310,377,760,762 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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735010 |
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May 1966 |
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CA |
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785835 |
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May 1968 |
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CA |
|
503 |
|
Jul 1978 |
|
EP |
|
73588 |
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Jun 1976 |
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JP |
|
1477333 |
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Feb 1974 |
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GB |
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Primary Examiner: Welsh; Maurice J.
Attorney, Agent or Firm: Leuzzi; Paul W.
Parent Case Text
This application is a continuation-in-part of U.S. Ser. No. 378,651
filed May 18, 1982 and now abandoned.
Claims
We claim:
1. A stable dispersion of a polymer in a polyol, said dispersion
being useful in the preparation of polyurethane foams having
improved combustion resistance, wherein the polymer is a
.[.free-radical initiated.]. copolymer containing from about 0.5 to
.[.75.]. .Iadd.70 .Iaddend.weight percent, based on the copolymer,
of acrylonitrile and from about .[.25.]. .Iadd.30 .Iaddend.to 99.5
weight percent, based on the copolymer, of at least one other
polymerizable ethylenically unsaturated monomer.Iadd., with the
proviso that styrene is said other monomer when only one other
monomer is present, .Iaddend.and .[.wherein the.]. .Iadd.said
.Iaddend.copolymer .[.is.]. .Iadd.being .Iaddend.characterized by a
crosslinking coefficient of less than about 55.[...]..Iadd., and
being prepared by a free-radical catalyst initiated process carried
out in the presence of a chain transfer agent selected from the
group consisting of mercaptans, ketones, alcohols, aldehydes and
halogenated compounds at a temperature in excess of 100.degree. C.
.Iaddend.
2. The stable dispersion of claim 1 wherein the total amount of
polymer present in said dispersion is from about 5 to 50 weight
percent based on the weight of the dispersion.
3. The stable dispersion of claim 1 wherein the other polymerizable
ethylenically unsaturated monomers are selected from the group
consisting of styrene and its derivatives, acrylates,
methacrylates, nitrile derivatives, and vinyl acetate.
4. The stable dispersion of claim 1 wherein more than one other
polymerizable ethylenically unsaturated monomer is present in the
polymer.
5. The stable dispersion of claim 1 wherein at least one of the
other polymerizable ethylenically unsaturated monomers is
styrene.
6. The stable dispersion of claim 1 wherein the copolymer contains
from about 25 to .[.75.]. .Iadd.70 .Iaddend.weight percent, based
on the copolymer, of acrylonitrile.
7. The stable dispersion of claim 1 wherein the copolymer contains
from about 30 to 70 weight percent, based on the copolymer, of
acrylonitrile.
8. The stable dispersion of claims 1, 6 or 7 wherein the copolymer
is characterized by crosslinking coefficient of less than about
50.
9. The stable dispersion of claims 1, 6 or 7 wherein the copolymer
is characterized by a crosslinking coefficient of less than about
20.
10. The stable dispersion of claims 1, 6 or 7 wherein the copolymer
is characterized by a crosslinking coefficient of about zero (0).
.[.
11. The stable dispersion of claim 1 wherein the copolymer is
prepared by a free-radical catalyst initiated process carried out
at a temperature 100.degree. C. or higher..].
12. A process for preparing a polyurethane having improved
combustion resistance which comprises reacting a stable dispersion
of a polymer in a polyol with an organic polyisocyanate in the
presence of a catalyst to form such polyurethane wherein the stable
dispersion of a polymer in a polyol is the stable dispersion of
claim 1 either alone or in combination with other polyols and/or
other polymer/polyols.
13. The process of claim 12 wherein the polyurethane is a cellular
polyurethane and wherein a blowing agent is additionally present
during the reaction.
14. The process of claim 13 wherein there is additionally present a
foam stabilizer.
15. The process of claim 12 wherein the stable dispersion is the
stable dispersion of claim 6.
16. The process of claim 12 wherein the stable dispersion is the
stable dispersion of claim 7.
17. The process of claim 12 wherein the stable dispersion is the
stable dispersion of claim 8.
18. The process of claim 12 wherein the stable dispersion is the
stable dispersion of claim 9.
19. The process of claim 12 wherein the stable dispersion is the
stable dispersion of claim 10.
20. A polyurethane comprising the reaction product of claim 12.
21. A polyurethane comprising the reaction product of claim 15.
22. A polyurethane comprising the reaction product of claim 16.
23. A polyurethane comprising the reaction product of claim 17.
24. A polyurethane comprising the reaction product of claim 18.
25. A polyurethane comprising the reaction product of claim 19.
Description
BACKGROUND OF THE INVENTION
The instant invention relates to a novel class of stable
dispersions of a polymer in a polyol (hereinafter called
polymer/polyol compositions) which can react with organic
polyisocyanates to form polyurethane products having improved
combustion resistance. The invention also relates to novel
polyurethane products prepared from such polymer/polyol
compositions. Polymer/polyol compositions suitable for use in
producing polyurethane foams, elastomers, and the like, are known
materials. The basic patents in the field are U.S. Pat. Nos.
3,304,273, 3,383,351, U.S. Pat. No. Re. 28,715 and U.S. Pat. No.
Re. 29,118 to Stamberger. Such compositions can be produced by
polymerizing one or more olefinically unsaturated monomers
dissolved or dispersed in a polyol in the presence of a free
radical catalyst. Polymer/polyol compositions have the valuable
property of imparting to polyurethane foams and elastomers produced
therefrom higher load-bearing properties and modulus than are
provided by unmodified polyols.
Of the many applications known for polyurethane products derived
from polymer/polyol compositions, utility in the automotive
industry has ranked among the highest as urethane products were
employed in deep foam seating, energy-absorbing padding, moisture
resistant foam inside door panels, comfortable and grip-enhancing
steering wheel covers and flexible bumpers to name but a few.
However, with this application came the requirement that
polyurethane products for the automotive industry would have to
meet the Federal Motor Vehicle Safety Standard (FMVSS) No. 302, a
standard on the combustionability of the products.
The industry has attempted to meet this requirement through the
addition of small concentrations of flame retardants to the
polyurethane product or by adding to the polymer/polyol various
monomers which would impart greater combustion resistance to the
final polyurethane product. Unfortunately, most flame retardant
additives are not stable in polyurethane premixes and must
therefore be metered in as a separate stream to the foam machine
mixing head thereby creating the need for special equipment and
handling procedures. Additionally, the polymer/polyol compositions
containing monomers which improve the combustion resistance of the
finished product have proven to be either too costly to
commercialize or have special processing problems of their own,
such as dehydro-chlorination in the polymer/polyol derived from
vinylidene chloride. Accordingly, there continues to be a need for
improved polymer/polyol compositions which can impart greater
combustion resistance to the finished polyurethane product without
incurring the drawbacks previously encountered.
SUMMARY OF THE INVENTION
The present invention provides a stable dispersion of a polymer in
a polyol. The dispersion is generally useful in the preparation of
polyurethane foams and specifically useful in the preparation of
polyurethane foams having improved combustion resistance. The
polymer of the dispersion is a free-radical initiated copolymer
containing from about 0.5 to 75 weight percent, based on the
copolymer, of acrylonitrile and from about 25 to 99.5 weight
percent, based on the copolymer, of at least one other
polymerizible ethylenically unsaturated monomer and wherein the
copolymer is characterized by a crosslinking coefficient of less
than 55.
Additionally, the present invention provides a novel polyurethane
with improved combustion resistance where the polyurethane is
prepared by the reaction of an organic polyisocyanate and the
previously described stable dispersion of a polymer in a
polyol.
The discovery of the present invention provides a novel
polymer/polyol composition which is both stable and imparts to
polyurethanes prepared therefrom an increased resistance to
combustion over what was previously known in the polymer/polyol
art.
DETAILED DESCRIPTION OF THE INVENTION
It has now been discovered by the present inventors that the
combustion related deficiencies of polymer/polyol based
polyurethane foams are attributable to the structural properties of
the polymer employed in the polymer/polyol composition.
Experimental observation of the combustion process has revealed
that the source of the problem relative to polyurethane combustion
resides in the melt flow characteristics of the polymer employed in
the polymer/polyol composition. Analysis has indicated that due to
the degree of crosslinking and/or branching (hereinafter generally
referred to as the degree of crosslinking) the polymer does not
flow readily when exposed to an applied external heat source but
chars and emits combustible vapors under increasing temperature
rather than becoming fluid and flowing away from the heat source.
The degree of crosslinking and/or branching of the polymer refers
to the copolymer in the dispersed polymer particles and not to any
cross-linking between these discrete polymer particles nor between
these discrete polymer particles and the polyol both of which could
result in gelation.
The identification of the source of this problem has allowed for
the creation of a new polymer/polyol composition by control of
various parameters in the preparation of the stable dispersion of a
polymer in a polyol previously not identified as affecting the
combustion resistance of the finished polyurethane product.
In an effort to quantitatively determine the suitability of the
polymer structure in a stable dispersion of a polymer in a polyol a
simplified test was established that, when performed on the
dispersion, correlated to both the polymer's structure and to the
combustion resistance of the finished polyurethane product. As the
degree of crosslinking increases the solubility of the polymer in a
solvent decreases and the insoluble polymer acts to defract light
thereby reducing the amount of light transmitted through the
solution which in turn provides a relative measure of the degree of
crosslinking. The test consists of determining the light
transmission through a dispersion (or solution) of polymer/polyol
in dimethylformamide (DMF) such that one percent of the polymer is
present in the dispersion. This dispersion is transferred to one of
two matched 1 cm. transmission cells while the second matched cell
is filled with DMF (experimental analysis has indicated that the
influence of any polyol added to DMF is insignificant within the
bounds of normal statistical error and thus can be dispensed within
the control cell). A spectrophotometer, such as a Bausch and Lomb
Spectronic 710 Spectrophotomer, is calibrated to 100 percent
transmission for the transmission of light at 500 millimicrons wave
length throught the second, DMF-filled cell. After this calibration
the percent light transmission through the first,
polymer/polyol/DMF-filled cell is measured and referred to as LT
for light transmission.
A crosslinking coefficient (XLC) is then determined by subtracting
the light transmission from 100.
Experimentation has demonstrated that when the stable dispersion of
a polymer in a polyol has an XLC value of less than 55 improvement
in the combustion resistance of the resulting polyurethane becomes
apparant. It is preferred that the XLC value be 50 or less with
values 20 or less the more preferred and a value of about zero (0)
being the most preferred since it represents the least crosslinked
or branched polymer and thus the one with the greated melt
flow.
The discovery of the source of the problem gave rise to
identification of those processing variables which could be
adjusted to reduce the degree of crosslinking and/or number of
branches per polymer molecule in the stable dispersion of the
polymer in the polyol. These process variables include the catalyst
concentration, the residence time, the ratio of acrylonitrile to
the other polymerizable ethylenically unsaturated monomers and the
concentration of chain transfer agents. The process used in
producing the polymer/polyol compositions of this invention
involves polymerizing the monomers in the polyol while maintaining
a low monomer to polyol ratio throughout the reaction mixture
during the polymerization. Such low ratios are achieved by
employing process conditions that provide rapid conversion of
monomer to polymer. In practice, a low monomer to polyol ratio is
maintained, in the case of semi-batch and continuous operation, by
use of a free-radical polymerization catalyst, control of the
temperature and mixing conditions and, in the case of semi-batch
operation by slowly adding the monomers to the polyol. The mixing
conditions employed are those attained using a backmixed reactor
(e.g., a stirred flask or stirred autoclave). Such reactors keep
the reaction mixture relatively homogeneous and so prevent
localized high monomer to polyol ratios such as occur in certain
tubular reactors. However, tubular reactors can be employed if
modified so that increments of the monomer are added to various
stages.
The process variables identified above as influencing the degree of
crosslinking interact between themselves in such a manner that no
one individual variable has parameters which in and of themselves
are critical in attaining the necessary degree of crosslinking. In
other words, the selection of the level of any one variable depends
upon the levels selected for the remaining variables such that the
combination of variables results in a XLC value within the limits
defined as necessary to obtain the desired end product. Improvement
has been observed by increasing the catalyst concentration,
lowering the residence time, reducing the proportion of
acrylonitrile in the copolymer, increasing the concentration of a
chain transfer agent, or various combinations of the above.
Preferred ranges are indicated for each variable. Although
individual levels for each variable may be selected on the basis of
product needs or economic considerations, the overall combination
must result in the proper XLC value as determined by the test
procedure set forth above.
Control of residence time has been found useful in controlling the
degree of crosslinking. In a continuous operation to produce a
stable dispersion of a polymer in a polyol the residence time in
the first reactor has been found to substantially control the
degree of crosslinking in the polymer. By residence in a continuous
operation what is meant is that time calculated by dividing the
reactor's volume by the volumetric flow rate of the total feed to
the reactor. Residence times of from about one (1) minute to about
five (5) hours can be employed, preferably from ten (10) minutes to
two (2) hours.
In a semi-batch operation where the reactor can be partially
charged prior to initiating polymerization, the term residence time
refers to that period of time during which significant
polymerization between the acrylonitrile and the comonomer(s) is
occuring. Here, residence times of from about thirty (30) minutes
to about ten (10) hours are recommended.
The monomer feed insofar as it relates to the percent polymer in
the dispersion of polymer in the polyol is not limiting so long as
the final dispersion is stable and does not separate out upon
standing. In this regard, total polymer in the dispersion can range
from about 5 weight percent to up to or greater than about 50
weight percent.
The polymerization can also be carried out with an inert organic
solvent present. The only requirements in the selection of the
solvent is that it does not dissolve the polymer nor interfere with
the monomer's polymerization reaction. When an inert organic
solvent is used, it is generally removed from the reaction mixture
by conventional means before the polymer/polyol composition is used
to produce polyurethane foams.
The catalysts useful in producing polymer/polyol compositions in
accordance with this invention are the well known free radical type
vinyl polymerization catalysts for the formation of polymer
polyols, for example, peroxides, azo compounds such as
azobisisobutyronitrile, and mixtures thereof.
The catalyst concentration useful in controlling the degree of
crosslinking should range from about 0.1 to about 5.0 weight
percent based on the total feed to the reactor and preferably from
about 0.3 to about 1.0. Although, as mentioned above any
free-radical type vinyl polymerization catalyst can be used,
2,2'-azobis(isobutyronitrile) is preferred because is does not
increase the acid number of the product, does not impart an
objectionable odor to the product, and does not require special
handling, as compared to certain peroxide catalysts.
The temperature used in producing polymer/polyol compositions in
accordance with this invention is any temperature at which the
catalyst has a desireable rate of decomposition under the reaction
conditions. In the case of a continuous process, reaction
temperatures of greater than 100.degree. C. are preferred. The
maximum temperature used is not narrowly critical but should be
lower than the temperature at which significant decomposition of
the reactants or product occurs. By way of illustration,
2,2'-azobis(isobutyronitrile) has a preferred temperature range
from 105.degree. C. to 135.degree. C.
The prior art has suggested that temperatures at which the half
life of the catalyst is no longer than about six minutes is
desirable. Temperatures of typical catalysts with half lives of six
minutes are:
______________________________________ Catalyst Temperature
(.degree.C.) ______________________________________
Azobisisobutyronitrile 100.degree. C. Lauroyl Peroxide 100.degree.
C. Decanoyl Peroxide 100.degree. C. Benzoyl Peroxide 115.degree. C.
p-Chlorobenzoyl Peroxide 115.degree. C. t-Butyl Peroxyisobutyrate
115.degree. C. Acetyl Peroxide 105.degree. C. Propionyl Peroxide
102.degree. C. 2-t-Butylazo-2-cyanobutane 129.degree. C.
______________________________________
Of the monomers useful in the instant invention, acrylonitrile must
be present in an amount from about 0.5 to 75 weight percent, based
on the copolymers. The remaining 25 to 99.5 weight percent
comprises one or more polymerizible ethylenically unsaturated
monomers. Acrylonitrile is employed as a necessary monomer in this
invention because it forms polymer/polyol compositions that are
stable to phase separation and that produce polyurethane foams
having superior load bearing properties. Suitable comonomers
include styrene and its derivatives, acrylates, methacrylates,
nitrile derivatives such as methacrylonitrile, vinyl acetate, and
the like. For a more detailed list of suitable comonomers reference
is made to U.S. Pat. Nos. 3,931,092; 4,093,573; and the Stamberger
patents previously referred to.
It is preferred to employ styrene as the comonomer and in those
instances where a terpolymer is desired one of the comonomers is
preferably styrene. In controlling the degree of crosslinking it is
useful to maintain an acrylonitrile to comonomer or acrylonitrile
to termonomer ratio of from about 1:200 to 3:1 and preferably from
about 1:3 to 3:1 and most preferably from about 3:7 to about
7:3.
Finally, the addition of chain transfer agents to the
polymerization has been demonstrated to be useful in controlling
the degree of crosslinking. Chain transfer agents may be added in
an amount from about 0.1 to 10 weight percent or more based on the
total feed to the reactor and preferably from about 1 to 5 weight
percent. Suitable chain transfer agents include any material that
exhibits chain transfer activity. Useful classes of chain transfer
agents include mercaptans, ketones, alcohols, aldehydes,
halogenated compounds, benzene derivatives and the like. Chain
transfer agents selected from among such classes may be used alone
or in combination. The preferred chain transfer agent is
isopropanol due to its low toxicity, low odor, availability, cost
effectiveness and ease of removal.
It should be noted that in those instances where the chain transfer
agent exhibits strong chain transfer activity somewhat less than 10
weight percent should be employed otherwise the stability of the
dispersion could be adversely effected. Although the addition of
chain transfer agents in excess of 10 weight percent may be useful
in some instances such levels are not generally recommended. In
addition, the selection of parameters for the other processing
variables may be such that the inclusion of a chain transfer agent
may be dispensed with altogether.
Illustrative of the polyols useful in producing polymer/polyol
compositions in accordance with this invention are the
polyhydroxyalkanes, the polyoxyalkylene polyols, or the like. Among
the polyols which can be employed are those selected from one or
more of the following classes of compositions, alone or in
admixture, known to those skilled in the polyurethane art:
(a) Alkylene oxide adducts of polyhydroxyalkanes;
(b) Alkylene oxide adducts of non-reducing sugars and sugar
derivatives;
(c) Alkylene oxide adducts of phosphorus and polyphosphorus
acids;
(d) Alkylene oxide adducts of polyphenols;
(e) The polyols from natural oils such as castor oil, and the
like.
Illustrative alkylene oxide adducts of polyhydroxyalkanes include,
among others, the alkylene oxide adducts of ethylene glycol,
propylene glycol, 1,3-dihydroxypropane, 1,3-dihydroxybutane,
1,4-dihydroxybutane, 1,4-, 1,5-, and 1,6-dihydroxyhexane, 1,2-,
1,3-, 1,4-, 1,6-, and 1,8-dihydroxyoctane, 1,10-dihydroxydecane,
glycerol, 1,2,4-trihydroxybutane, 1,2,6-trihydroxyhexane,
1,1,1-trimethylolethane, 1,1,1-trimethylolpropane, pentaerthritol,
caprolactone, polycaprolactone, xylitol, arabitol, sorbitol,
mannitol, and the like. A preferred class of alkylene oxide adducts
of polyhydroxyalkanes are the ethylene oxide and propylene oxide
adducts of trihydroxyalkanes.
The polyols employed can have hydroxyl numbers which vary over a
wide range. In general, the hydroxyl numbers of the polyols
employed in the invention can range from about 20, and lower, to
about 150, and higher. The hydroxyl number is defined as the number
of milligrams of potassium hydroxide equivalent to the hydroxyl
content of one gram of polyol. The hydroxyl number can also be
defined by the equation: ##EQU1## where
OH=hydroxyl number of the polyol;
f=functionality, that is, a average number of hydroxyl groups per
molecule of polyol;
m.w.=molecular weight of the polyol.
The exact polyol employed depends upon the end-use of the
polyurethane product to be produced. The molecular weight or the
hydroxyl number is selected properly to result in flexible or
semi-flexible or rigid foams or elastomers when the polymer/polyol
produced from the polyol is converted to a polyurethane. The
polyols preferably possess a hydroxyl number of more than 150 for
rigid foams, from about 50 to about 150 for semi-flexible foams,
and from about 20 to about 70 for flexible foams. Such limits are
not intended to be restrictive, but are merely illustrative of the
large number of possible combinations of the above polyol
coreactants.
If desired, a polyol blend containing a small amount of a high
molecular weight polyol and a major amount of a low or a medium
molecular weight polyol can be used. Also, a polyol-polymer/polyol
blend containing a small amount of a polymer/polyol (prepared in a
high molecular weight polyol) and a major amount of a low or a
medium molecular weight polyol, as disclosed in U.S. Pat. No.
4,148,840, can be used as the polyol component.
The most preferred polyols employed in this invention include the
poly(oxypropylene)glycols, triols, higher functionality polyols and
any of these that are capped with ethylene oxide. These polyols
also include poly(oxypropyleneoxyethylene)polyols; however,
desirably, the oxyethylene content should comprise less than 80
percent of the total and preferably less than 60 percent. The
ethylene oxide, when used, can be incorporated in any fashion along
the polymer chain. Stated another way, the ethylene oxide can be
incorporated either in internal blocks, as terminal blocks, or may
be randomly distributed along the polymer chain. As is well known
in the art, the polyols that are most preferred herein contain
varying small amounts of unsaturation. As taught by Stamberger
(U.S. Pat. Nos. 3,304,273, 3,383,351, and U.S. Pat. No. Re.
28,715), unsaturation in itself does not affect in any adverse way
the formation of the polymer/polyol in accordance with the present
invention except in the case where the extent or type of
unsaturation is so high or effective as to result in a dispersion
of the polymer in a polyol that is gelled. Thus small amounts of
unsaturation can be incorporated into the polyol without departing
from the scope of the present invention.
The crude polymer/polyol compositions usually contain small amounts
of unreacted monomers. Such residual monomers can be converted to
additional polymer by employing either a multi-stage operation in a
continuous process or an extended cookout time in a semi-batch
process. In the event that there are small amounts of unreacted
monomer left, they can be removed by using a subsequent stripping
step.
In order to be commercially acceptable, a polymer/polyol
composition must have a reasonable degree of dispersion stability.
The stability should be sufficient to allow for relatively long
term storage without the loss of processability. The polymer/polyol
compositions must possess sufficiently small particles so that
filters, pumps, and similar components in reactors, foaming and/or
elastomer production equipment do not become plugged or fouled in
short periods of time. A stable dispersion of the polymer particles
in the polyol is of prime consideration in insuring that the
polymer/polyols can be processed in commercial production equipment
without the necessity of additional mixing to insure
homogeneity.
It has been recognized that the stability of polymer/polyols
requires the presence of a minor amount of a graft or addition
copolymer which is formed in situ from the polymer and the polyol.
It has been found recently that stability can be achieved also with
a preformed copolymeric stabilizer, as disclosed for example in
U.S. Pat. No. 4,242,249.
Stability has been achieved by employing a free-radical catalyst
and utilizing process conditions which promote rapid conversion of
monomer to polymer. In practice, a lower monomer to polyol ratio is
maintained by control of the reaction temperature and mixing
conditions in the case of a continuous or a semi-batch operation
and, in the case of a semi-batch operation, by slow addition of the
monomer to the polyol. A back-mixed reactor (e.g., a stirred flask
or a stirred autoclave) keeps the reaction mixture relatively
homogeneous and so prevents localized high monomer to polyol
ratios. The catalyst and temperature are chosen so that the
catalyst has a desirable rate of decomposition with respect to
residence time in the reactor for a continuous process or to the
feed time for a semi-batch process. The half-life of the catalyst
at the temperature utilized should be short compared to the time
the reactants are in the reaction zone.
Another factor known to affect stability is the molecular weight of
the polyol. Generally, the higher the molecular weight, the better
the dispersion stability. In case of low molecular weight polyols,
the dispersion stability can be improved by using either the polyol
blend technique as disclosed in U.S. Pat. No. 4,119,586 or the
polyol-polymer/polyol blend technique as disclosed in U.S. Pat. No.
4,148,840.
The invention also provides novel polyurethane products produced by
reacting: (a) a polymer/polyol composition of this invention or
mixtures thereof either alone or in combination with other polyols
and/or polymer/polyol compositions not of this invention and (b) an
organic polyisocyanate in the presence of (c) a catalyst. The
reaction can be performed in any suitable manner such as by the
prepolymer or one-shot technique. When the polyurethane is a foam,
the reaction mixture usually also contains a polyol such as the one
used to make the polymer/polyol, a blowing agent, and a foam
stabilizer.
The organic polyisocyanates that are useful in producing
polyurethanes in accordance with this invention are organic
compounds that contain at least two isocyanato groups. Such
compounds are well known in the art of producing polyurethane
foams. Suitable organic polyisocyanates include the hydrocarbon
diisocyanates, (e.g., the alkylene diisocyanates and the arylene
diisocyanates) as well as know triisocyanates and polymethylene
poly(phenylene isocyanates). As examples of suitable
polyisocyanates are 1,2-diisocyanatoethane, 1,4-diisocyanatobutane,
2,4-diisocyanatotoluene, 2,6-diisocyanatotoluene,
1,3-diisocyanato-o-xylene, 1,3-diisocyanato-m-xylene,
1,3-diisocyanato-p-xylene, 2,4-diisocyanato-1-chlorobenzene,
2,4-diisocyanato-1-nitrobenzene, 2,5-diisocyanato-1-nitrobenzene,
4,4'-diphenylmethylene diisocyanate; 3,3'-diphenylmethylene
diisocyanate; and polymethylene poly(phenyleneisocyanates) having
the formula: ##STR1## wherein x has an average value from 1.1 to 5
inclusive (preferably from 2.0 to 3.0). The preferred
polyisocyanate is about 80% of a mixture of 80% 2,4-tolylene
diisocyanate and 20% 2,6-tolylene diisocyanate and about 20% of a
polymeric isocyanate.
The catalysts that are useful in producing polyurethane in
accordance with this invention include: tertiary amines such as
bis(2,2'-dimethylaminoethyl)ether, trimethylamine, triethylamine,
N-methylmorpholine, N-ethylmorpholine, N,N-dimethylethanolamine,
N,N,N',N'-tetramethyl-1, 3-butanediamine, triethanolamine,
1,4-diazabicyclo[2.2.2.]octane, pyridine oxide, and the like and
organotin compounds such as dialkyltin salts of carboxylic acids,
e.g., dibutyltin diacetate, dibutyltin dilaurate, dibutyltin
maleate, dilauryltin diacetate, dioctyltin diacetate, and the like.
Similarly, there may be used a trialkyltin hydroxide, dialkyltin
oxide, dialkyltin dialkoxide, or dialkyltin dichloride. Examples of
these compounds include trimethyltin hydroxide, tributyltin
hydroxide, trioctyltin hydroxide, dibutyltin oxide, dioctyltin
dichloride, and the like. The catalysts are employed in small
amounts, for example, from about 0.001 percent to about 5 percent
based on weight of the reaction.
The blowing agents useful in producing polyurethane foams in
accordance with this invention include water and halogenated
hydrocarbons such as trichloromonofluoromethane,
dichlorodifluoromethane, dichloromonofluoromethane,
dichloromethane, trichloromethane, 1,1-dichloro-1-fluoroethane,
1,1,2-trichloro-1,2,2-trifluoromethane, hexafluorocyclobutane,
octafluorocyclobutane, and the like. Another class of blowing
agents include thermally-unstable compounds which liberate gases
upon heating, such as N,N'-dimethyl-N,N'-dinitrosoterephthalamide,
and the like. The generally preferred method of foaming for
producing flexible foams in the use of water or a combination of
water plus a fluorocarbon blowing agent such as
trichloromonofluoromethane. The quantity of blowing agent employed
will vary with factors such as the density desired in the foamed
product.
The foam stabilizers useful in producing polyurethane foams in
accordance with this invention include "hydrolyzable"
polysiloxane-polyoxyalkylene block copolymer such as the block
copolymers described in U.S. Pat. Nos. 2,834,748 and 2,917,480.
Another useful class of foam stabilizers includes the
"non-hydrolyzable" polysiloxane-polyoxyalkylene block copolymers
such as the block copolymers described in U.S. Pat. Nos. 3,505,377
and 3,686,254 and British Patent Specification No. 1,220,471. Yet
another useful class of foam stabilizers is composed of the
cyanonalkyl-polysilozanes, as described in U.S. Pat. No.
3,905,924.
Polyurethane products produced in accordance with this invention
are useful in the applications in which polyurethanes made from
conventional polymer/polyol compositions are employed. The
polymer/polyol compositions of this invention are particularly
useful in the production of high resiliency foams for use in arm
rests, mattresses, automobile seats and the like.
Whereas the exact scope of the instant invention is set forth in
the appended claims, the following specific examples illustrate
certain aspects of the present invention and, more particularly,
point out methods of evaluating the same. However, the examples are
set forth for illustration only and are not to be construed as
limitations on the present invention except as set forth in the
appended claims. All parts and percentages are by weight unless
otherwise specified.
POLYMER/POLYOL PREPARATION
The polymer/polyol compositions of the Examples were prepared
continuously in a tank reactor fitted with baffles and an impeller.
The feed components were pumped into the reactor continuously after
going through an inline mixer to assure complete mixing of the feed
components before entering the reactor. The internal temperature of
the reactor was controlled to within one degree Centrigrade. The
contents of the reactor were well mixed. The product flowed out of
the top of the reactor continuously through a back pressure
regulator that had been adjusted to give some positive back
pressure in the reactor. Portions of the crude product were vacuum
stripped at 2 millimeters absolute pressure and 120.degree. to
130.degree. C. for testing. Conversions were determined from
analysis of the amount of unreacted monomers present in the crude
product before stripping. In Examples 1-9, 18, and 24 the product
from the top of the reactor was further reacted in a second stage
to increase the conversion of monomer to polymer. All of the
polymer/polyols in the Examples were stable compositions.
As used in the Examples appearing below, the following
designations, symbols, terms and abbreviations have the indicated
meanings.
"Theoretical molecular weight" of a polyol denotes a number average
molecular weight calculated using equation (A) above based on the
functionality of the starter used to produce the polyol and the
experimentally determined hydroxyl number of the polyol.
"Triol" or "Diol" denotes the nominal functionality of a polyol
based on the functionality of the starter. Actual polyol
functionalities are somewhat lower (3 to 20% lower) than nominal
functionality because of the presence of some amount of lower
functionality material produced by side reactions. These side
reactions are more significant the higher molecular weight of the
polyol being produced.
Polyol I: A polyalkylene oxide triol produced from propylene and
ethylene oxides and glycerine and having theoretical number average
molecular weight of 5000. The alkylene oxide units are present
primarily in blocks and the primary OH content is about 75%. The
ethylene oxide is used to "cap" the triol. Based on its alkylene
oxide content, this triol contains 85 wt. % C.sub.3 H.sub.6 O and
15 wt. % C.sub.2 H.sub.4 O.
Polyol II: A polypropylene oxide triol produced from propylene
oxide and glycerine and having a theoretical number average
molecular weight of about 3,000.
Polyol III: A polyalkylene oxide triol, produced from propylene and
ethylene oxides and glycerine and having a theoretical number
average weight of 4800. The alkylene oxide units are present
primarily in blocks and the primary OH content is about 80%. The
ethylene oxide is used to "cap" the triol. Based on its alkylene
oxide content, this triol contains 83.5 wt. % C.sub.3 H.sub.6 O and
16.5 wt. % C.sub.2 H.sub.4 O.
Polyol IV: A polyalkylene oxide tetrol produced from propylene and
ethylene oxides and pentaerythritol and having a theoretical number
average weight of 8000. The alkylene oxide units are present
primarily in blocks and the primary OH content is about 82%. The
ethylene oxide is used to "cap" the polyol. Based on its alkylene
oxide content, this polyol contains 85 wt. % C.sub.3 H.sub.6 O and
15 wt. % C.sub.2 H.sub.4 O.
Polyol V: A polyalkylene oxide triol produced from propylene and
ethylene oxides and glycerine and having a theoretical number
average weight of 4300. The alkylene oxide units are present
primarily in blocks and the primary OH content is about 80%. The
ethylene oxide is used to "cap" the polyol. Based on its alkylene
oxide content, this polyol contains 83 wt. % C.sub.3 H.sub.6 O and
17 wt. % C.sub.2 H.sub.4 O.
Polyol VI: A polyalkylene oxide triol produced from propylene
oxide, ethylene oxide, allyl glycidyl ether, and glycerine and
having a theoretical number average weight of 4300. The alkylene
oxide units are present primarily in blocks and the primary OH
content is about 80%. The ethylene oxide is used to "cap" the
polyol. Based on its alkylene oxide content, this polyol contains
82 wt. % C.sub.3 H.sub.6 O, 17 wt. % C.sub.2 H.sub.4 O and 1 wt. %
allyl glycidyl ether.
Polyol VII: A mixture of high and low molecular weight polyols
formed in situ by coupling some of the polyol molecules of Polyol
VI with tolylene diisocyanate such that 0.635 wt. % tolylene
diisocyanate is reacted with 99.365 wt. % Polyol VI.
TABLE I
__________________________________________________________________________
Molded Foam Formulation Components Parts
__________________________________________________________________________
Polymer Polyol of Examples 100 Water 3.5 Catalyst A-1 0.1 Catalyst
33 0.36 Catalyst 12 0.005 Catalyst B 0.3 Silicone Surfactant 0.75
__________________________________________________________________________
80/20 Tolyene Diisocyanate/Polymeric Isocyanate (105 Index) Example
No. 1 2 3 4 5 6 7 8 9 10 11 12
__________________________________________________________________________
Reaction Temperature 125 127 125 145 135 126 145 125 127 125 125
130 .degree.C. Wt. % Catalyst (1) 0.43 0.33 0.72 0.35 0.37 0.35
0.35 0.74 0.75 0.75 0.75 0.58 in feed Wt. % Monomers 24.6 22.5 25.3
25.9 25.9 25.9 25.7 26.0 25.9 23.3 29.6 37.4 in feed Monomer Types
(4) A/S A/S A/S A/S A/S A/S A/S A/S A/S A/S A/S A/S Ratio of
Monomers 53/47 50/50 30/70 30/70 30/70 30/70 30/70 30/70 30/70
30/70 25/75 73/27 Polyol Type I I VII VII VII VII VII VII VII VI
VII I Residence Time (2), Min 58 52 79 29 21 12 12 21 20 12 12 12
Chain Transfer agent (6) 0 0 0 0 0 0 0 0 0 0 0 ISOP Wt. % CTA (5)
in feed 0 0 0 0 0 0 0 0 0 0 0 1.9 Monomer Conversion 95.6 94.2 93.0
91.6 91.5 89.6 87.8 92.4 95.1 86.6 88.5 93.5 (3), % XLC 97.1 98.2
96.4 93.3 87.7 33.1 60.1 49.5 56.8 1.3 0.8 19.6 Total Foam Burn
11.5+ 11.5+ 11.5+ 11.5+ 11.5+ 5.4 8.0 3.8 5.5 2.2 2.6 7.7 Length,
in. No. of Reactor stages 2 2 2 2 2 2 2 2 2 1 1 1
__________________________________________________________________________
Example No. 13 14 15 16 17 18 19 20 21 22 23 24
__________________________________________________________________________
Reaction Temperature 125 145 125 126 125 125 126 125 110 126 125
126 .degree.C. Wt. % Catalyst (1) 0.75 0.73 0.73 0.50 0.74 0.5 0.76
0.74 0.40 0.75 0.74 0.83 in feed Wt. % Monomers 24.6 25.3 26.9 26.3
26.0 22.5 23.2 23.1 19.7 22.8 25.5 22.6 in feed Monomer Types (4)
A/S A/S A/S/EA A/MMA A/AMS A/S A/S A/S A/S A/S A/S A/S Ratio of
Monomers 65/35 2/98 30/40/30 50/50 50/50 50/50 40/60 40/60 55/45
40/60 40/60 50/50 Polyol Type I V VII III III I III III II III IV I
Residence Time (2), Min 12 18 12 12 12 45 12 12 12 12 12 55 Chain
Transfer agent (6) ISOP 0 0 0 0 ISOP EB DDM ISOP THBA MEK ISOP Wt.
% CTA (5) in feed 2.0 0 0 0 0 5.0 2.0 1.0 0.8 2.0 2.0 2.1 Monomer
Conversion 91.4 81.9 88.5 83.7 73.9 93.6 90.4 88.8 84.1 88.2 91.6
96.1 (3). % XLC 8.8 0.9 1.0 7.7 0.6 1.1 1.8 0.9 0.6 0.6 2.6 29.8
Total Foam Burn 2.4 2.7 2.9 2.9 2.4 1.1 1.9 un- un- 1.2 2.2 2.1
Length, in. known known No. of Reactor stages 1 1 1 1 1 2 1 1 1 1 1
2
__________________________________________________________________________
(1) 2.2' azobis(isobutryonitrile) (2) first stage only (3) overall
conversion after last stage (4) A--Acrylonitrile S--Styrene
MMA--Methyl Methacrylate AMS--Alpha Methyl Styrene EA--Ethyl
Acrylate (5) CTA Chain Transfer Agent (6) ISOP--Isopropanol
EB--Ethyl Benzene DDM--Dodecyl Mercaptan
THBA--Tetrahydrobenzaldehyde MEK--Methyl Ethyl Ketone Note Example
14 was prepared by the teaching of U.S. Pat. No. 4,242,249 where
the added preformed stabilizer was a polyol 50/50
acrylonitrile/styrene copolymer adduct in the proportions of 3 1
and where the polyol contained 1 mole of methacrylate unsaturation
per mole of Polyol V and the stabilizer was used in an amount of
40% in the polyol fed to the reactor.
Catalyst A-1: A solution consisting of 70%
bis(2-dimethylaminoethyl)ether and 30% dipropyleneglycol.
Catalyst 33: A solution consisting of 33% triethylenediamine and
67% dipropyleneglycol.
Catalyst 12: Dibutyl tin dilaurate
Catalyst B: a mixture of 33%
dimethylamino-N,N-dimethyl-propionamide and 67% of a nonionic
surfactant.
Polyurethane Foam Preparation
Molded foams were prepared from the polymer/polyols of the Examples
by the following procedure using the proportions of components
shown in Table I. The polymer polyol, water, catalysts, and
surfactant were mixed in a one half gallon paper carton fitted with
a 4000 rpm mixer and baffles for 55 seconds. The isocyanate was
then added rapidly and mixing was resumed for an additional 5
seconds. The mixture is quickly poured into a waxed aluminum mold
which had been preheated to 50.degree.-60.degree. C. The mold was
then quickly closed and clamped. After two minutes, the mold was
placed in an oven at 121.degree. C. for 5 to 8 minutes. The foam
was then removed from the mold the post cured 30 minutes at
121.degree. C. After curing the foam specimens were cut and burned
per FMVSS-302. The total burn length reported was measured as the
distance from the foam edge nearest the flame to the point of
extinguishment.
* * * * *