CA2047678A1 - Linear polyurethane elastomer compositions and use of modified diisocyanates for preparing same - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE

Linear polyurethane elastomers of a polyol component, at least two extender components, and a diisocyanate compound are prepared by reacting the diisocyanate compound with one of the extender components to form a modified diisocyanate component having a functionality of about 2 prior to reacting this modified component with the other components of the elastomer. A
preferred polyol component includes a mixture of a polycarbonate polyol and a polyether polyol. These new elastomers possess a unique combination of hydrolytic stability, toughners, and flexibility and can be processed at lower temperatures compared to elastomers prepared from similar compositions wherein the isocyanate compound is not modified.

Description

~0 40/11309 Pcr/~lsso/ol477 ~0~767~

LINEAR POLYIJRETHANE ELAST02~1ER COMPOSITIONS AND
USE OF MODIFIED DIISOCYANATES FOR PREPARING SAME

Technical Field The present invention relates to the preparation of linear ~hermoplastic polyurethane elastomers of a polyol component, at least one extenlder component, and a diisocyanate compound by initially reartiny the diisocyanate compound with the extendex to form a modified diisocyanate component prior to reac~ing this component with ~he polyol component and other extenders, if any.

Backqround Art In today's market, polyurethane elastomers are utilized in a wide array of products and applications, including producing industrial coated fabrics. For the latter, these polyurethanes are generally linear polymers exhibiting elastomeric characteristics of high tensile strength and elongation.
These linear polyurethanes are quite varied in their final properties as a result of the large number of permutations that can be applied to the three main components that are used in their manufacture. These components are polyols, polyisocyanates, and one or more extenders (generally diols). Some examples of these compounds are: polyether, polyester, polycaprolactone, polycarbonate, and polybutadiene polyols; toluene diisocyanate, 4,4'-diphenylmethane diisocyanate, cyclohexane diisocyanate, isophorone diisocyanate, naphthalene diisocyanate: xylene diisocyanate, hexane diisocyanate, and hydrogenated 4,4'-diphenylmethane diisocyanate; and 1,4-butanediol, 1,6-hexanediol~ and 1,3-butanediol extenders.
Typically, polyurethane elastomers which are considered top of the line with respect to performance, include, for example, polytetramethylene glycol (polyether) polyurethanes and poly(butane adipates or hexane adipates) ester w090/ll309 2 ~ ~ 7 6 7 ~ PCT~usgo/ol~7 polyurethanes. of these polymer~, the polyether polyurethanes exhibit good hydrolytic stability and low temperature properties but are generally poor for fuel resistance and oxidation resistance, while the polyester polyurethanes are tough with good abrasion resistance, oxidation resistance ~nd fuel resistance, but not particularly resistant to hydrolysis. Still, at the present time the polyesters are generally considered to represent the best compromise of physical properties and chemical resistance of the various polyurethanes.
There are also a few polyurethanes based on polycarbonate polyols in the market. It is well known ~hat these polycarbonate polyurethanes have very good hydrolytic stability and generally have good to very good resistance to other de~radation forces; however, th~y ars ùsually too hard, rigid and brittle for use in industrial coated fzbrics.
Currently, high performance coated fabrics are based on polyester polyurethanes in order to meet the specifications currently in effect, but resistance to hydrolysis remains their weak point and represents a problem for these products. Thus, there is a desire ~or improved hydrolytic stability in a number of applications. A polyurethane having improved hydrolytic properties and sufficient elastomeric character to be useful in the manufacturing of industrial coated fabrics is also desirable and needed.
It is known from Japanesa Patent Specification Sho(61)-76275 that polyurethane elastomers can be produced from a diol mixture of a polycarbonate diol and a polyoxytetramethylene glycol, and/or a polydimethyl siloxane glycol: an organic diisocyanate and a chain extension compound. Practical Example 4 of Table I lists a porous polyurethane fil~ formed from an 80/20 mixture of polycarbon~te diol and polyoxytetra methylene glycol; 4,4'-diphenyl methane diisocyanate and 1,4-butylene glycol, while Practical Example 1 illustrates a film formed from a WO ~/11309 2 0 ~ 4~ 6 7 8 Pcr/~s~/ol4~7 50/25/25 mixture of polycarbonate diol/polyoxytetra methylene glycol/polydimethylsiloxane glycol; 4,4'-diphenyl methane diisocyanate and ethylene glycol. ~hes~ porous films can be used in the manufacture of arti~ioial leather or suede articles.
Also, Japanese Patent Specification Sho(61)-151235 discloses the preparation of aliphatic polycar~onate polyols from various mixtures of dialkyl carbonates and glycols.
These polyols are described as ha~ing low color adhesion and smooth reactivity with isocyanates. Neither reference suggests that these ~aterials can be used as or in the production of polyurethane elastomers for industrial coated fabrics.
A wide variety of organic isocyanate and polyisocyanate compounds are available for use in the preparation of polyurethane elastomers. The particular isocyanate is selected to facilitate preparation of the polyurethane for the intended application. Generally, isocyanates which are liquid at room temperature are prepared for ease of handling.
Diphenyl methane diisocyanate ("MDI") is a solid diisocyanate which is available on a commercial scale and consists primarily of the 4,4' isomer with a small amount of the 2,4' isomer. These isomers are both solids at room temperature, having melting points of 42 and 36 C, respectively. Other isomers, such as the 2,2' isomer, are also solid at room temperature.
~ o convert solid MDI into a form which is more desirable for use in thP preparation of polyurethanes, the prior art teaches that a liquid MDI cs~position can be prepared, for example, by partially reacting solid MDI with a glycol, diol or other polyol. Generally, about 10 to 35%
of the isocyanate groups are reacted with the polyol. A
number of U.S. patents illustrate this concept, including U.S. Patents 3,883,571, 4,115,429~ 4,118,411, 4,22g,347,

2 0 ~ 7 6 7 8 PCT/l~S~/01477 4,490,300, 4,490,301, 4,539,156, 4,539,157 and 4,539,158.
Such liquid diisocyanates are stated as beiny useful for forming polyurethanes for a wide variety of applications.
None of these modified diisocy~nate compositions have, however, been utilized to prepare linear thermopla~tic polyurethane elas~omPr~ whic~h have lower temperature processing characteristics clD~pared to similar compositions prepared from solid MDI.

Summary o~ the Invantion The invention relates t~ improvements in the preparation of a linear the~moplastic polyurethane elastomer composition prepared from a polyol component, a diisocyanate compound, and first and second extender components. The processing temperature of the polyurethane is lowered by initially reacting the diisocyanate compound with the ~irst extender in a molar ratio of above 2:1 to form a modified diisocyanate component having a functionality of about 2 prior to reacting the modified diisocyanate component with the polyol and second sxtender components. Thus, a linear thermoplastic polyurethane elastomer composition is formed which has lower temperature processing characteristics compared to similar compositions wherein the diisocyanate compound is not modified.
The pslyol component may be a polyether polyol, polycarbonate polyol, polycaprolactone polyol, polyester polyol, polybutadiene polyol or mixturas thereof, and the first extender component is generally a polyol or amine compound having a molecular weight of less than about 500.
Preferably the first extender component comprises a diol.
Also, the second extender component is included for optimum results.
Generally, between about 10 to 30% by weight of the diisocyanate compound is modified so that the modified diisocyanate component has an NCO content of between about w~ ~/ll~9 2 0 ~ 7 6 7 8 PCT~S90~01477 14 and 33%, and preferably between about 20 and 26~. The most advantageous diisocyanate compound is one that primarily oomprises 4,4'-diphenyl methane diisocyanate, with the first extender component being ~ polyol or amine compound having a molecular weight between about 60 and 250, 6uch a~ 1,4-butane dlol, tripropylene glycol, dipropylene glycol, propylene glycol, ethylen~ glycol, 1,6-hexane diol, 1,3-butane diol, neopentyl glycol, ethylene diamine or mixtures thereoP.
The present invention also relates to a l$near thermoplastic polyurethane elastomer compositions comprising a mixture of a polycarbonate polyol and a polyether polyol;
a diisocyanate compound; and first and second extenders.
The diisocyanate compound is initially reacted with one of the extenders in a molar ratio of above 2:1 60 as to form a modified diisocyanate component having a functionality of about 2 prior to reaction with the other components. This modified diisocyanate component provides relatively low tamperature processing properties to the composition, whereas the polyol mixture provides superior hydrolytic stability and low temperature flexibility to the composition.
Preferably, the first extender component is a polyol or amine compound having a molecular weight of lass than about 500, such as a diol, while the diisocyanate compound primarily comprises 4,4'-diphenyl methane diisocyanate.
Advantageously, the first ex~ender component is a polyol or amine compound having a molecular weight between about 60 and 250, such as 1,4-butane diol, tripropylene glycol, dipropylene glycol, propylene glycol, ethylenQ glycol, 1,6-hexane diol, 1,3-butane diol, neopentyl glycol, ethylene dia~ine or mixtures thereof.
Generally, the polyether polyol and polycarbonate polyol are present in a relative amount of between 2:1 to 1:8. When the first extender is 1,4-butanediol and the WO ~/ll309 2 ~ ~ 7 ~ PCT/~S~/~1477 second extender i5 tripropylene glycol, and when between about lo to 30% by weight o~ the dii.~ocyanate compound is modified~ the modified diisocyanate compo~ent has an NCo content of between about 14 and 33~, preferably between about 20 and 26~. A~ter ~odifying the dii~ocyanate, the modified ~at~ri~l is reacted with the o~her compon~nts. The overall NCO/OH ratio of th~ entire composi~ion is between about 0.95 and 1.05/l.

Detailed Description _~ the_I~vention One preferred embodiment of this invention relates to a polyurethane elastomer based on a mixture of polycarbonate and polyether polyols, a modified diisocyanate component formed by reacting a diisocyanate compound with a low molecular waight extender such as tripropylene glycol, and a second extender of 1,4-butanediol. The modified diisocyanate and the second extender ena~le the polymer to have low temperature processing properties compared to those wherein the diisocyanate is not modified. This polymer also has hydrolytic stability which is vastly superior to conventional polyester polyurethanes. This polymer also has elastomeric characteristics and other physical properties which render it suitable for use in coated fabric manufacturing processes and resultant products produced therefrom.
In this embodiment, the polyether polyol and polycarbonate polyol can be used in any relative amounts provided that each are present in the co~position. It has been found convenient to use a polyether polyol:
polycarbonate polyol ratio in the range o~ between 2.1 to 1:8.
Instead of tripropylene glycol and 1,4-butanediol, other low molecular weight extender~ ca~ be used.
Generally, polyols having a ~olecular weight o~ between about 60 and 500 (and preferably less than 250) have been WO ~/1l~n PCT/US~J01477 2~767~

found to be advantageous, although amines ~uch as ethylene diamine can also be used. Specific polyols include diols such as 1,3-butanediol, ethylene glycol, tripropylene glycol, dipropylene glycoI, propylene glycol, and neopentyl glycol, triols ~uch as trimethyol propane, as well as mixtures of these component~, can ~ u~ed.
Any dii~ocyanate co~pouncl i8 ~uitable with those based on 4,4'-diphenyl methane diisocyanate being preferred.
Toulene diisocyanate, naphthalene diisocyanate, isophorone diisocyanate, xylene diisocyanate and cyclohexane diisocyanate can also be used, if desirsd, but these compounds are generally more expensive or slower reacting.
Such diisocyanate compounds are converted to a modified diisocyanate component as previously described.
The relative amount of modified diisocyanate to polyol ranges from above 2:1 to 20:1, and preferably between about 2.5:1 and 8:1. The second extender compound is included in an amount to achieve a final NCO:OH ratio of between about 0.95 to 1.05/1. The Examples illustrate preferred ratios of componen~s for use in the preparation of linear polyurethanes in accordance with this invention.
Another preferred embodiment of the invention relates to the manufacture of any type of polyurethane elastomer prepared from the modified diisocyanate component to significantly lower the temperature re~uirements for processing the polyurethane on heat processing equipment, i.e., calenders, extruders, injection molding apparatus, etc. This modification includes reacting diisocyanate compound with 2 low molecular weight extender (i.e., polyol or amine compound, to form a ~odi~ied diisocyanate component, prior to preparing the polyurethane with the other components.
The term "MDI" will be used throughout this application to designate diisocyanate compounds primarily based on 4,4'-diphenyl methane diisocyanate which are preferred for use in this invention. Also, the term "liquid MDI" will be .

., WO90/11309 2 0 4 7 6 7 ~ P~T/US~/01~77 used to designate an e~sentially difunctional m~dified MDI
component prepared ~rom tha reaction of a low ~olecular weight polyol with an ~DI compound to ~orm a modified diisocyanate composition which i5 liquid at room temperature.
The low molecular weight extender used to ~odi~y the diisocyanate compound generally includes diols, triols or amines having 2 mol~cular w~ight b~low about 500, but any polyol which enables the diiEocyanate compound to possess a functionality of about 2 and an NC0 content of between about 14 and 33%, preferably between 20 and 26S, after modi~ication, would be acceptable.
In this e~bodiment, Pssentially any polyol component can be used for reaction with the liquid MDI component, including polyether, polyester, polycaprolactone, polycarbonate or polybutadiane polyols or mixtures thereof.
As noted above, a preferred polyol component is mixture of a polyether polyol and ~olycarbonate polyol.
It is also possible to add additional extenders to such compositions, these extenders also beins a polyol or amine compound, preferably one of relatively low molecular weight (i.e., less than about 500). It is also possible to utilize unsaturated polyols as extenders, such as low molecular weight diols which include one or more double bonds.
However, any conventional ~xtender known to those skilled in the art can be used, depending upon the results desired.
Thus, the present invention demonstrates how various polycarbonate and polyether polyols, modified diisocyanate components and extenders may be blended over a wide range to allow the design of polyurethane poly~ers having different physical characteristics and properties. This ma~es it possible to custom design a polymer for a particular application.
There are several different types of modified ~DIs presently on the market, but the types suitable for use in this invent:ion are essentially difunctional. The preferred WO ~/ll309 PCT/~'S~/0147, ~7~i78 g liquid MDI components are made by rea~ting an MDI compound with a small amount of a diol such as tripropylene glycol or a mixture of diols. The material resulting from this slight extension of the MDI compound is a liguid at room temperature while, as noted above, the original MDI compound is a solid at ~uch te~peratures. Thi~ makss the liquid MDI
substantially easier to handle and process, while retaining generally equivalent performallce to the unmodified M~I
compound.
Representative modified liquid MDI components which are suitable and preferred or use in ~he present invention are disclosed in U.S. Patents 3,883,571, ~,115,429, 4,118,411, 4,229,347, 4,490,300, 4,490,301, 4,539,156, 4,539,157, and 4,539,158: all these components are essentially difunctional and are obtained as the reaction product of MDI. With a diol or polyol having a molecular weight below about 500. To the extent necessary to understand this component of the inventive compositions, these patents are expressly incorporated herein by reference thereto. Those isocya~ates having a functionality which is much greater than two are not particularly suitable for use in this invention, since they promote crosslinking rather than linearity in the resultant polyurethane polymer. The functionality of these compounds should be above 1.9 but below 2.2, with the preferred modified diisocyanate components being those having a ~unctionally of approximately 2 so as to ~acilitate the preparation of linear polyurethanes.
In the production of polyurethanes, it is generally known to utilize one of two different manufacturing processes. In one ~ethod, known as the i'one-shot" approach, all hydroxyl bearing components (i.e., polyols and extender diols) are combined as a mixture, to which is added an isocyanate component in essentially stoichiometric quantities to form the final product. The second method contemplates the formation of a prepolymer by reacting WO90/11309 2 ~ 4 ~ ~ ~ 8 PCT/US~/01477 excess isocyanate with one or more high molecul~r wei~ht hydroxyl bearing components, followed by th~ reaction of this prepolymer with the extender to form he final product.
As noted abova, the use of th~ modified diisocyanate components of this inventiDn enables a polyur~than~ having lower temperature proce~sing characteristics to be achieved.
The temperature difference can be as great ~s 30 to 40F
below that of a correspondin~ formulation wherein the diisocyanata compound is not modified. However, greater temperature reductions are achieved when the polyurethane is manufactured in a specific manner.
For example, if the polyurethanes o the invention are made by the conventional "one shot" technique, a slight reductio~ on the order of about 3-4 degrees is obtained:
this representing only about 10% of the maximum reduction which could be achieved. Similarly, if solid MDI is used to prepare an isocyanate prepolymer with the high ~olecular weiyht polyol prior to reacting this prepolymer with the mixed extenders, a temperature reduction of about 4-5 degrees (i.e., about 15% of the maximum) is achieved.
Substantial reductions in the temperature processability of the resulting polyurethane can be achieved by following one of the following methods Qf manufacture.
In one version, the isocyanate is pre~reacted with one of the extenders to form a ~odified isocyanat~ component prior to reaction with a mixture of the high molecular weight polyol and other extenders. This enables a temperature reduction of about 20 to 25 degrees to be achieved (i.e., about 60% of the optimum~. Finally, tha optimum temperature reduction is achieved by sequentially reacting the modified isocyanate compon~nt first with ths hi~h ~olecular wei~ht polyol followed by reaction with th~ second extender. As noted above, ~ temperature reduction o~ 30 to 40 degrees is possible, with the formation of a clear polyurethane polymer.

WO go~1 t309 P~T/l,IS90/01'177 ~7678 Again, MDI, modified as di5clo~ed herein, is the most advantageous diisocyanate for US2 in preparing the polyurethanes of this invention, although the othar isocyanates mentioned above c:an instead b~ used, if desired.
When light stability in a cl~!ar product i~ desirsd, an isophorone diisocyanate can be used to achieve better results than MDI. For a lower co~t isocyanate component, toluene diisocyanat~ (nTDIn) can be used, but it i8 less re~ctive than MDI. Thu~, when TDI i8 u~ed, ~ine extenders, rather than polyol or di~l extenders, 6hould bæ used. One skilled in the art can select the best co~bination of ingredients for any particular formulation.
These linear polyureth~ne elastomers are preferably made using a two step solution polymerization techniqueO
Predried toluene, dimethyl formamide and the isocyanate are charged to a 3000 ml reactor (in some cases a 15,000 ml reactor was u-~ed). A given weight of polyol(s), the amount needed to achieve the desired prepolymer NCO/OH value, is dissolved in additional dry toluene. The reactor is then prepurged with dry nitrogen and maintained under a posi~ive low pressure of dry nitrogen for the ~ull reaction time.
The isocyanate containing solution is preheated to 65-75DC (depending on anticipated exotherm~, and the solution of polyols is slowly added by a continuous stream (over one-half hour) to the reactor. The temperature is allowed to rise to 80-~O~C (depending on system) and is maintained at this temperature for an additional two hours.
The desired extender diol is preweighed and dissolved in dry dimethyl formamide. The rea¢tor is coolad to 60-65C
and two 7-lO gram samples of ~he reac~ion ~ixture are removed and analyzed ~or NCO conte~t. The diDl is then charged to the reactor, and the te~perature raised (partly by the exotherm of extension) to 85-90-C and maintained at this temperature ~or two hours. A sample o~ the polymer is dried and an IR spectrum was run. If free NCO is detected in the spectrum, the reaction is continued for another hour.

wo ~J11309 2 ~ ~ ~ 6 7 ~ P~T/US90/01~7~

~ e reaction solution is then allowed to cool to room tempera~ure overnight and stored in a container until it can be tested. All mixtures were designed to yield a solution of 30S by weight of polymer dissolved in a 60/40 mixture of toluene~DMF.
This solution cooking te~chnique provides an easy way of making this polymer, but it is difficult to evaluate the physical properties of such ~,olutions. Thus, the solution collected from an individual cook is ~pread coated onto rele~se paper and dried at 300~F to remove the solvent.
This film c~n then be strippe!d from the paper and used to conduct various physical property tests.

A. Modulus, Tensile Strenqth, and Elongation One gram of cadmium stearate was added to 200 grams of dried polymer and intimately mixad on a two roll rubber mill. A 0.040 inch slab of polymer was removed from tha mill and was u~ed to make tensile specimens. This was done by pressing the slab between two polished plates in a heated Wabash press for 15 minutes at sufficient temperature and pressure to yield a 0.010 - 0.014 inch film. Temperatures and pr~ssures varied depending upon the particular formulation. The press was cooled to roo~ temperature and the film was removad ~rom between the plates. From this film, five samples wer~ cut in the size of one inch by six inches. These were then tested on an Instron and averages sf 100% modulus, 200% moduius, tensile strength, and elongation were calculated from the test results. The temperature for the milling and pressing operations were observed and found to be related to formulation ch~nges.

B. Toluene Swell ~ wo pieces, one inch by two inches, of the pressed film wera immersed in toluene for 24 hours. Measure~ents of volume by displacement of alcohol before and after toluene immersion were used to calculate volume swell.

WO ~11~9 2 ~ ~ 7 ~ 7 8 PCT/~'~90/~l477 C. Flow TemPerature and Flow Rate A three to five gram sample of polymer wa~ finely chopped and used to determine the ~emperature at which the polymer would flow at a measurable rate and to determine the rate itself on a Kayness, Inc. extrusion plastometer ~odel D-0051. A measurable rate wa~ defined a greater than 0.15 grams per 10 ~inutes. Thu3 at t2mperatures below ~he flow temperature, neither fusion of the polymer nor flow greater than 0.15 grams i5 achieved. The ~low rate i5 defined as the number of grams extruded from the barrel of the plastometer in a period of ten minutes.

D. Brookfield Viscosity Fifteen grams of polymer were dissolved in 85 grams of dry dimethyl formamide and warmed to 30 d~grees C~ntigrade in a constant temperature bath overnight in a closed waterproof container. The viscosity was then measured on a Brookfield viscometer as quickly as possible after removing from the bath. Viscosity data is reported in cps.

E. Glass Transition Temperature (Tq) Several polymer slabs, including a known control, were measured for Tg. This work was done by two techniques, mechanical spectroscopy which measures the change in physical properties due to passing through the glass transition temperature and DSC (differential scanning calorimetry) which measures the second order transition defined as glass transition te~perature.
The improvements and advantages associated with the lin~ar polyurethane polymers developed in this invention are illustrated below in the Examples.

Examples The scope o~ the invention is further described in connection with the ~ollowing examples which are set forth for the sole purpose of illustrating the preferred W090/ll309 2 0 ~ 7 ~; 7 ~ PCT/US~/01~77 smbodiments of the invention and which are not to be construed as limiting the scope of the invention in any manner. In these examples, all parts given are by weight unless otherwise specified.

The specific preferred chemicals utilized in the examples are listed below as follows:

W090/11309 ~ 7 ~ PCTI~SgO/Ot477 POLYOLS
0ll Equiv, Supplier Identity TYpe Nu~ber Wt.

~G Industries Duracarb 120aliphatic carbonate 131.0 423.
PPG Industries Duracarb 122alipl~atic carbonate 95.0 590.0 PPG Industries Duracarb 124aliphatic carbonate 58.0 967.2 QC Chemicals Polymeg 1000 PTMEG ether 111.9 50103 QC Chemicals Polymeg 2000 P1'MEG ether 55.7 1007.2 Whitco Chemical Form-re~ 44-112 ester 113.3 495.1 ISOCY~NATES

Equiv.
Supplier Identity Type % NCO Wt.
.

ICI Rubinate 4~ MDI 33.5 125.0 ICI Rubinate LF-179 liquid MDI 23.0 1~2.5 Mobay Corp. Mondur PF liquid MDI 22.9 183.4 B~SF Lupranate MP-102 liquid MDI 23.0 182.5 Dow Chemical Isonate 181 liquid MDI 23.0 182.5 EXTE~DER DIOLS

Supplier Identity Equivalent Weiqht B~SF 1,4-butanediol 45 Dow Chemical tripropylene glycol 96 .

WO90/11309 2 0 4 7 6 7 8 PCT/US~/01~77 Examples l-l2 Table I (A&B) illustrates the erfect that modified liquid MDI components have on flow ~emperature o~ various polyurethanes compared to those made from the corresponding unmodified MDI compound. The talble li~ts six polyurethanes mada with various polyols, including ~ome mixtures of polyols.
Each two examples represent a polyurethane made from liquid MDI
and its analog made fro~ th~ corr~sponding MDI unmodified, solid component. As shown in ~e table, the percent hard segment is equivalent in each cc~mparison. Examples l, 3, 5, 7, 9 and ll are in accordance with the present invention, while Examples 2, 4, 6, 8, lO and 12 are included for comparison. In all cases, the liquid MDI polymer has a lower flow temperature than its solid MDI analog. Flow temperature is that temperature at which a measurable flow is first observed when tested on an extrusion plastometer.
Since flow temperature is a measure of the temperature at which the polymer may be processed on calendering and extrusion equipment, the use of the liquid MDI
components allows the making of polymers which process at lower temperatures, and therefore are easier to process and manufacture into articles such as calendered sheets for coated fabrics. The results demonstrate that all experimental polymers made with liquid MDI components exhibited lower milling temperatures than those of their solid MDI analogs.
Although Table I illustrates polyurethanes made with polyether, polyester, and polycarbonate polyols, it would be expected that this improvement would be present regardless of the specific type o~ polyol used.

Examples 13-16 The section on chemicals lists four commercially available liquid ~DI components and describes how they are produced. Table II (A&B) demonstrates that these four isocyanates are essentially equivalent in their ability to ~0 ~/ll309 2 0 4 7 6 7 8 PCT/~S~/01~77 ~16-Examplas 1-12 Table I (A&B) illustrates the effect that modified liquid MDI components have on f]ow temperature of various polyurethanes compared to those made from the corresponding unmodified MDI compound. The table list~ six polyurethanes made with variou~ polyols, including ~ome ~ixtures of polyols.
Each two examples represent a polyurethane made from liquid ~DI
and i~s analog made from the corresponding MDI unmodified, solid componen~. As shown in ~l¢ table, the percent hard segment is eguivalent in each comparison. Examples 1, 3, 5, 7, 9 and 11 are in accordance with the present invention, while Examples 2, 4, 6, 8, 10 and 12 are included for co~parison. In all cases, the liquid MDI polymer has a lower flow temperature than its solid MDI analog. Flow temperature is that temperature at which a measurable flow is first observed when tested on an extrusion plastometer.
Since flow temp~rature is a measure of the temperature at which the polymer may be processed on calendering and extrusion equipment, the use of the liquid MDI
components allows the making of polymers which process at lower temperatures, and therefore are easier to process and manufacture into articles such as calendered sheets ~or coated fabrics. ~he results demonstrate that all experimental polymers made with liquid MDI components exhibited lower milling temperatures than those of their solid MDI analogs.
Although Table I illustrates polyurethanes made with polyether, polyester, and polycarbonate polyols, it would be expected that this improve~ent would be present regardless of the specific type of polyol used.

Examples 13-16 The section on chemicals lists four commercially available liquid MDI components and describes how they are produced. Table II (A~B) demonstrates that these four isocyanates are essentially equivalent in their ability to W~ gO/I 1309 2 0 ~ 7 ~i 7 ~ PCr/~S90~0147~

~odify the flow temperatures and therefore the p~oc~ssing temperatures of polyurethanes made from them. Any one of these four preferred isocyanates may be employed in the development of low temperature processable ,polyurethanes~ As noted above, a wide variety of difunctional i~ocyanates which are ~odified by reaction with low molecular lweight polyols would ~lso be suitable for use in this invention.

Examples 17-22 Table III (A&B~ compares ~polycarbonate polyurethanes made from liquid MDI components against those made with solid MDI
components. Examples 17-19 are in accordance with the invention, while Ex~mples 20-22 are comparative. It can be seen from the data that polyurethane polymers made using liquid MDI exhibit better physical properties, particularly tensile strength, compared to those made with solid MDI. Flow temperatures were not specifically measured on the liquid MDI
polymers, but processing on the mill was found to be significantly better than for polymers made with the comparable unmodified, solid MDI compounds.
It should al o be noted that the use of liguid MDI allows the production of polyurethane elastomers having a higher percent hard segment. This is advantageous because in general the urethane linkages are much more stable to various degradation forces (i.e. hydrolysis, oxidation, etc.) than are ether, ester or other bonds in the polyol ~ackbone.

Examples 23-38 Polyurethane elastomers made from an aliphatic polycarbonate polyol, liquid MDI and 1,4-butanediol were prepared as shown in Table III, ~xamples 17-19. A mixture of polycarbonate polyols was used in Example 38 of table IV.
Excellent physical properties, particularly tensile strength and elongation, were achieved in these formulations. Upon further analysis of the tensile curves, it was observed that these polymers were more plastic than elastomeric in character.

wO ~/11309 2 0 ~ 7 ~ 7 ~ PCT/US~/01~77 Thus, these polymers could be described as hard and tough with a high yield val~e as illustrated by the lO0~ modulus values.
However, evaluation of ~ilms of the polycarbonate based polyurethane polymers exhibited poor cold crack properties.
To improve low temperature~ properties without sacrificing the properti~s of the polycarbonate backbone, a copolyol was introduced into the system, ~s ~hown in ~xa~ples 23-37 of Tables IV (A & B). ~ polytetramethylene glycol ("PTMGI') polyol was found to have ~h~ compatibility with the specific polycarbonate polyols used, with the ~olecular weight of lO00 and 2000 each found to be suitable.
From Table IV (B), it i5 observed that physical properties, i.e. modulus, elongation, tensile strength, and toluene swell are affected by percent weight secondary and by percent hard sPgment. Thus, as the percent of secondary polyol (PTMG polyether~ is increased, (or the polycarbonate is decreased), modulus decreases and the polymer becomes more elastomeric than plaetic. Also as the percent hard segment decreases, the modulus decreases but toluene swell (a measure of solvent resistance) increases. From this information, one skilled in the art can select the optimum combinations for the desired final product.
Two different molecular weight polyethers were evaluated. The results tend to indicate that change in properties is mainly related to the percent (by weight) of secondary polyol rather than to the molecular weight of the PTMG polyol. It is also observed that there is some lowering of tensile strength at higher percent secondary polyol, but at a weight ratio of primary/secondary polyol of greater than or equal to one, this is not significant. Increased ~olecular weight of these polymers can also be used to counteract this effect.

w~ 1309 2 0 ~ 7 6 ~ ~ PCT/~'S~/0147~

Examples 39 and 40 The ability to custom design a polymer to ~eet various physical requirements is suggested by the results of Table V.
It is al~o possible to improve low temperature properties.
Table V (A&B) compares two ~ormulations which are similar with the exception of the introduction of 20S PTMG polyether polyol into the polymer (Example 40)~ Again the change~ in physical properties can be observed.
The Tg of the formulations of these ex~mples was determined by mechanical spectrometry ~M.S.) and differential scanning calorimetry (DSC) to be as follows~

Polymer M.S. DSC
of Example Tq ( C) Tg ( C) 39 50.9-56.0 21 30.9 11 Thus the mixture of the PTNG polyether polyol with the polycar~onate polyol resulted in a significant lowering of the Tg (in degrees Centigrade). Thus, this polyol mixture increases the cold cracking and low temperature impact properties of the resulting linear polyurethane polymer.

Examples 41-45: Table VI (A~B) illustrates the reproducibility of the invention by listing several formulations which were made at different times on different days.

Examples 46-48 As described above, most o~ the elastomers of the Examples were made using a solution polymerization technique and then dried for testing and experimental use. This technique is not a 6uitable process for use in commercial manufacturing, and other methods of polymerization can be used.
One is to mix together the polyol(s) and diol(s) and then feed this stream with a stream of isocyanate to an intensive mixer.
The two streams when mixed are heat2d to initiate wo ~/11309 2 0 4 7 ~ 7 8 PCT/~'S90/01477 polymerization and extruded as a polymer (one ~hot). Another approach is to first make prepolymers from the polyol(s) using an excess of isocyanate and then to extend this material with the diol(s) in the presence of hQat. Two experiments were conducted in an attempt to simu]Late and evaluate these two approaches. In both cases, the formula o~ Example 40 was used.
The one-shot experiment was conducted by weighing the polyols and diol into a plastic container and mixing w811 under nitrogen. The appropriate ~mount o~ LF-179 was then added, mixed well, capped under nitrogen and placed in an oven at 9OC
overnight. The prepolymer approach was conducted by mixing the polyols thoroughly with an excess of isocyanate (per formula), followed by capping and heating for two hours at 85C. After removing the sample from the oven, an appropriate amount of diol was added, quickly mixed, capped and returned to a 9OC
oven overnight.
Table VII (A&B) gives a comparison of a solution cook to a one-shot and a prepolymer cook. In all cases, flow temperature is still lower than a comparable unmodified MDI
polymer and physical properties are very similar. Working these polymers on a rubber mill indicates that the prepolymer approach may actually yield a lower temperature processing polymer than the one-sho~ approach. Also, the prepolymer approach provides a much clearer polymer which is a sign of better uniformity and compatibility. Therefore the prepolymer approach is preferred although the one-shot approach will indeed yield acceptable polymer~ and, it is seen that a new linear polyurethane elastomers useful for a wide variety of application can be prepared.
While it i5 apparent that the invention herein disclosed is well calculated to fulfill the objects above stated, it will be appreciated that numerous modifications and embodiments may be devised by those skilled in the art, and it is intended that the appended claims cover all such modifications and embodiments as fall within the true spirit and scope of the present invention.

2 0 ~ 7 6 7 8 TABLE l(A) FQRMULATIONS

ISOCYA- PRlMARY SECONDARY EQUIV WEIG~IT PREPOL FINAE
EXAMPLE NATE _POLYOL POLYOL RATIO RATIO_ NCO/OH _ NCO~Oli 1 LF-179 DU~ACARB 120 POLYMEC 2000 2.410 1.0~5 2,503 0.981 2 HDI DURACARB 120 POLYMEG 2000 2.410 1.025 3.340 0.980

3 LF-179 DVRACARB 120 POLYMEC 2000 3.565 1.516 2.600 0.950

4 MDI DVRACARB 120 POLYMEG 2000 3.565 1.516 1.478 0.950 LF-179 POLYMEG 1000 _ _ 2.377 0.950 6 MDI POLYMEG 1000 _ _ 3.171 0.950 7 LF-179 DURACARB 122 POLYMEG 2000 3.546 2.079 3.163 0.950 8 MDI DURACARB 122 POLYMEG 2000 3.546 2.079 4.220 0.951 9 LF-179 DURACARB 124 POLYMEG 2000 1.575 1.512 4.471 0.950 MDI DURACARB 124 POLYMEG 2000 1.575 1.513 1.517 0.950 11 LF-179 FORM-REZ 1.970 0.980 12 MDI FORM REZ _ 2 S33 0 980 oess: 1. Equivalene ~nd wei~ht ratio refer to ehe ratlo of prlmary ~o secondnry polysl by equivalents or ~elght, respectively.
2. Each formulat~on coneains 1,4-butane diol as an ~xtender ln nn amount necessary to ~chleve the final NCO/O}I ratlo.

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ISOCYA- PRIMARY SECONDARY EQUIV UEIGHT PREPOL FI~AL
EXAMPLE NATE POLYOL POLYOL RATIO _ RATIO NCO/OH NCO~OII
13 LF-179 DURACARB 120 POLYMEG ZOOO 3.681 1.565 2.618 0.952 14 ISO.181 DURACARB 120 POLYMEG 2000 3.558 1.512 2.606 0.951 15 MP-102 DURACARB 120 POLYMEG 2000 3.558 1.512 2.606 0.951 16 MON PF DURACARB 120 POLYMEG 2000 3.558 1.512 2.606 0.950 otes: 1. Equlvalent snd welght ratlo refer to the ratlo of prlmary to secondary polyol by equivalents or welght, respectively.
2. Esch formulation cont~ins 1,4-butane dlol as an extender in an amount necessary to achleve the final NCO/OH ratlo.

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ISOCYA- PRIMARY SECONDARY EQUIV WEICHT PREPOL FINAL
EXAMPLE NATE POLYOLPOLYOL RATIO RATIO NCO/OH NCO/OH
23 LF-179 DURACARB 120 POLYMEG 1000 B.9~8 7.677 2.480 0.977 24 LF-179 DURACARB 120 POLYMEG 2000 8.996 3.949 2.480 0.977 LF-179 DURACARB 120 POLYMEG 1000 3.995 3.412 2.479 0 977 26 LF-179 DURACARB 120 POLYMEG lOOO 2.999 2.562 2.475 0.980 27 LF-179 DURACARB 120 POLYMEG 1000 2.999 2.562 2.475 0.980 28 LF-179 DURACARB 120 POLYMEG 1000 2.327 1.988 2.481 0.977 29 LF-179 DURACARB 120 POLYMEG lOOO 2.334 1.993 2.099 0.980 LF-179 DURACARB 120 POLYMEG 1000 1.498 1.280 2.478 0.977 31 LF-179 DURACARB 120 POLYMEG 2000 2.410 1;025 2.826 0.983 32 LF-179 DURACARB 120 POLYMEG 1000 0.999 0.853 2.478 0.977 33 LF-179 DURACARB 120 POLYMEG 2000 2.333 1.025 2.481 0.977 36 LF-179 DURACARB 120 POLYMEG 2000 2.333 1.025 2.481 0.977 LF-179 DURACARB 120 POLYMEG 2000 2.410 1.025 2.503 0.981 36 LF-179 DURACARB 120 POLYMEG 2000 2.410 1.025 2.120 0.984 37 LF-179 DURAC~RB 120 POLYMEG 2000 1.032 0.439 2.520 0.9~3 38 LF-179 DURACARB 120 DURACARB 122 1.000 0.725 2.475 0.990 Notes: 1. Equivalent and weight ratio refer to the ratio of primary to secondary polyol by equivalents or wel~ht, rcspectively.
2. Esch formulation contains 1,4-bueane diol as an extender in an amount necessary to achieve the final NCO/OH ratio.

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ISOCYA- PRIMARY SECONDARY EQUIV UEI~HT PREPOL FIN~L
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ISOCYA- PRIHARY SECONDM Y EQUIV WElGHT PREPOL FIN~L
XAMPLE NATE _ POLYOLPOLYOL RATIO RATIO NCO/OH NCO/OII
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Claims (20)

What is claimed is:

1. In the preparation of a linear thermoplastic polyurethane elastomer composition from a polyol component, a diisocyanate compound, and first and second extender components, the improvement which comprises lowering the processing temperature of said polyurethane by reacting the diisocyanate compound with said first extender in a molar ratio of above 2:1 to form a modified diisocyanate component having a functionality of about 2 prior to reacting the modified diisocyanate component with the polyol and second extender components, thus forming a linear thermoplastic polyurethane elastomer composition having lower temperature processing characteristics compared to similar compositions wherein the diisocyanate compound is not modified.

2. The composition of claim 1 wherein the polyol component is a polyether polyol, polycarbonate polyol, polycaprolactone polyol, polyester polyol, polybutadiene polyol or mixtures thereof.

3. The composition of claim 1 wherein the first extender component is a polyol or amine compound having a molecular weight of less than about 500.

4. The composition of claim 3 wherein the first extender component comprises a diol.

5. The composition of claim 1 wherein the second extender component is a polyol or amine compound having a molecular weight of less than bout 500 and which is different from said first extender component.

6. The composition of claim 1 wherein between about 10 to 30% by weight of the diisocyanate compound is modified so that the modified diisocyanate component has an NCO
content of between about 14 and 33%.

7. The composition of claim 6 wherein the NCO
content of the modified diisocyanate component is between about 20 and 26%.

8. Tha composition of claim 1 wherein the diisocyanate compound primarily comprises 4,4'-diphenyl methane diisocyanate.

9. The compoeition of claim 1 wherein the first extender component is a polyol having a molecular weight between about 60 and 250.

10. The composition of claim 1 wherein the first extender component is 1,4-butane diol, tripropylene glycol, dipropylene glycol, propylene glycol, ethylene glycol, 1,6-hexane diol, 1,3-butane diol, neopentyl glycol, ethylene diamine or mixtures thereof.

11. A linear thermoplastic polyurethane elastomer composition comprising:
a polycarbonate polyol;
a polyether polyol;
a diisocyanate compound;
a first extender component; and a second extender component;
wherein the diisocyanate compound is initially reacted with one of the extender components in a molar ratio of above 2:1 so as to form a modified diisocyanate component having a functionality of about 2 prior to reaction with the other components to provide relatively low temperature processing properties to the composition, whereas the polyol component provides superior hydrolytic stability and low temperature flexibility properties to the composition.

12. The composition of claim 11 wherein the first extender component is a polyol or amine compound having a molecular weight of less than about 500.

13. The composition of claim 12 wherein the first extender component comprises a diol.

14. The composition of claim 11 wherein the diisocyanate compound primarily comprises 4,4'-diphenyl methane diisocyanate.

15. The composition of claim 11 wherein the first extender component is a polyol having a molecular weight between about 60 and 250.

16. The composition of claim 11 wherein at least one of the extender components comprises 1,4-butane diol, tripropylene glycol, dipropylene glycol, propylene glycol, ethylene glycol, 1,6-hexane diol, 1,3-butane diol, neopentyl glycol, ethylene diamine or mixtures thereof.

17. The composition of claim 11 wherein the polyether polyol and polycarbonate polyol are present in the polyol component in a relative amount of between 2:1 to 1:8.

18. The composition of claim 11 wherein one extender component comprises 1,4-butanediol and the other extender component comprises tripropylene glycol.

19. The composition of claim 11 wherein between about 10 to 30% by weight of the diisocyanate compound is modified so that the modified diisocyanate component has an NCO content of between about 14 and 33%.

20. The composition of claim 19 wherein the NCO
content of the modified diisocyanate component is between about 20 and 26%.