CA1289696C - Hydroxyl-terminated polyepichlorohydrin polymers and derivatives thereof - Google Patents

Abstract

Abstract of the Disclosure Epichlorohydrin is polymerized in the presence of anhydrous stannic chloride catalyst and an alcohol initiator to produce a polyepichlorohydrin product comprising predominantly secondary hydroxyl-terminated polyepichlorohydrin polymer having low polydispersity, from which polyurethanes and azide derivatives can be made, polyurethanes prepared from such azide derivatives being useful as a binder for solid rocket propellants.

Description

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l 6~557-3065 HYDROXYL-TERMINATED POLYEPICHLOROHYDRIN
POLYM~RS AND DERIVATIV~S THEREOF
This invention relates ko hydroxyl-terminated polymers of epichlorohydrin and their preparation. A divisional applica-tion, divided out of the present parent application, has been ~ filed which divisional relates to azide derivati~e~ of said ; polymers. In another aspect, the invention of the parent appllaation relates to polyurethanes of said epichlorohydrin polymer~. In another aspect, the invention of the di.visional appli~ation relates to solld rocket propellants uslng as a binder - a polyurethane prepared from glycidyl azide polymers derived from , polyeplchlorohydrin.
t~ The acid-catalyzed (or cationic) ring-opening or ~ polymerization of epichlorohydrin in the presence of initiators , .
mainly hydroxyl-containing molecules, e.g., water or alcohols ~; (includiny polyols), to yield hydroxyl-terminated eplahlorohydrin derivativesr is known. U.S. Patent Nos. 4,340,749 (Patel), 4,391,970 (Okamoto) and 4,431,845 (Young, et al) describe some recent improvements. The first reference discloses tha reaction ` 20 of fluoroaliphatic alcohols with epiahlorohydrin, and use of stannic chloride as a catalyst, to prepare fluoroaliphatic, hydroxyl-terminated epichlorohydrins containing more than 25 wt.
carbon-bonded ~luorlne. The other two re~erences disalose polymerization of epiahlorohydrin in the presence of wa~er or a hydroxyl ~aterial (e.g. ethylene glycol) and a catalyst (in the ` Young et al patent, a fluorinated aaid and a polyvalent organo tin l; aompound suah as diphenyl-dibutyl tin). Other art ls U.S. Patent Nos. 2,327,053 (Marple et al) and 2,380,185 (Marple et a].) which ; ` ' ~ . , ,~ .
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la 60557-3065 disclose reacting epichlorohydrin with an excess of hydroxy compounds, such as isopropyl alcohol, in the presence of a ~etal halide, such as stannic chloride, to produce mono-adducts rather than polymers, When Xnown catalys~s are used in concentrations to provide complete conversion ~G !

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in a short reaction period, the product is t-ypically dark color.
Although the hydroxyl-terminated polyepichlorohydrin polyols prepared following the procedures described in some o~ the art produce polymer products which are useful in some applications, they generally contain undesirable amounts, e.g. up to 10 to 20 weight percent, of low molecular weight, non-hydroxyl functional, cyclic ether oligomers (comprising 2 or 4 epichlorohydrin units) as impuritles or by-products which increase in amount as the molecular weight o~ the polyepichlorohydrin product increases. The formation of cyclic oligomers is unfortunately characteristic of cationic ring-opening polymerizations of cyclic ethers (E.J. Geothals, Adv. Po]ym.
Sci.,23, 104 (1977)), and time-consuming frac~ionation or extraction of the products may have to be used if one desires to remove such impurities ~rom the polymeri~ate. Furthermore, prior art methods often result in polyepichlorohydrin polymer products having relatively high polydispersity (the ratio o~ weight average molecular weight, Mw, to number average molecular weight, Mw,), which means, for example, that polyurethanes prepared from such products generally will not have physical properties oE desired values.
Azide derivatives of hydroxyl-terminated polyepichlorohydrin polymers, i.e. glycidyl azide polymers prepared by reaction o such polyepichlorohydrins with inorganic azide, have been proposed in preparing energetic binders ~or solid propellants (see, for example, U.S. Patent Nos. 4,268,450 (Frankel et al) and 4,486,351 (Earl)). The presence of the oligomer impurities in the glycidyl azide polyol derivatives de~racts rom B' ~ . .
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. 2a 60557-3065 ; the physical properties of the propellent binders prepared from them. .
: The invention of the present parent application providesr in one a~pect~ a polyepichlorohydrin product having a number average molecular weight of at least 2000 and a : polydispersity of less than 1.2, said procluct comprlsing predominantly secondary hydroxyl-ter~inated polyepichlorohydrin polymer and essentially no non-hydroxyl functi.onal cyclic ether : oligo~err said product bei.ng made hy polymerizing epichlorohydrin ln the presence of anhydrous stannic chloride catalystr a strong ~ .
carboxylic acid co-catalyst, and an alcohol as an initiator.
The invention of the divisional application provides, ln one aspect, a normally liquid, polyglycidyl azide product having a ~;~ low polydispersity which is produced by reacting a polyepichlorohydrin product described a~ove with an inorganlc : azide r said polyglycidyl azide product comprlsin~ predominantly . secondary hydroxyl-terminated polyglycidyl a7.ide polymer.
The invention of the present parent application provides, in another aspect, a process for the preparation of the novel polyepichlorohydrin product defined above ';
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by the polymerization of epichlorohydrin in the presence of anhy-drous stannic chloride, SnC14, as a polymerization catalyst, and, as an initiator, an alcohol, preferably an organic polyol, which is unreactive with the catalyst, and a strong carboxylic acid (i.e., one having a PKa o less than about 2, preferably less than about 1) as a co-catalyst, such as trifluoroacetic acid or trichloroacetic acid. The polyepichlorohydrin polymer preferably has epichlorohydrin (or chloromethylethyleneoxy) units as essentially the only repeating units in the polymer and has a hydroxyl functionality, mainly or essentially in the form of -CH2CH~CH2Cl)OH, of up to 4 or more. The product is generally normally liquid and has a number average molecular weight, for example, of 2000 to 10,000 and a relatively narrow molecular weight distribution or low polydispersity, which is less than 1.2.
~he polyepichlorohydrin product contains only a relatively minor amount, e.g. less than 2 weight percent, per 1000 molecular weig'nt of product, of low molecular weight, non-hydroxyl functional, cyclic ether oligomers which generally have 2 or 4 epichlorohydrin units cyclized, or essentially none of such oligomer i said co-catalyst is used. And the product is light colored, e.g. with aGardner color of less than 2.
The polyglycidyl azide products of the divisional application deiined above are prepared by reactiny a polyepi-chlorohydrin product as defined above with an inorganic azide.
The process is outLined in the following equation where R(OH)m represents the initiator.

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3a 60557-30.65 O SnC14 nCH2CHCH2Cl + R(OH)m ~ R ¦O(CH2CHO)n~ +
(and preferably strong L CH2Cl Im carboxylic acid) minor amount (if any) of ollgomer.

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In ~he above equation, R is an organic ra~ical, e.g.
containing 1 to 20 carbon atoms, such as an aliphatic radical or aromatic radical or combination of such ra~icdls, which cdrl contain or be subs~ituted with moieties tl~at are unreactive with epichlorohydrin or desired product and do no~ adversely affect the polymerization or desired product, such as halo, oxy, carbonyl, or combinations of such moieties, e~g., e~ter. For exa~ple, R can be CH3-l ClC~l2CH2~' CH3CH2C~i2CH2-/ C6HsCH2-~ -CH2C6HloCH2_r -(CH2)x-w~lere x is 3-8, -CH(R")C~(R')- and -CH(R')CH2CH(R')- where R' is selected ~rom H and a lower alkyl, such as CH3-, C~l2Cl-, and C2~s-, and R'l is said lower alkyl, (CHC~20)XCH2CH2l0CH2fH)y~ where x ~ y is 1 to 20 CH2Cl C~2Ci ~C~l2C6H4CH2-/ and c~3c(c~2-)3. The subscript m i~ 1, 2, 3 or 4, and n is at least 2 and, where R has a molecular weight of less than 1000, n is a number such that the polyepichlorohydrin, i.e. poly(chloromethylethyleneoxy), portion of the product is the major portion of the product by weight, n generally being 2 to about 100.
Polyglycidyl azide polymer derivatives, described hereinafter, of the polyepichlorohydrin polymers can be represented by a forl~ula like "I" in the above equation excep~ that Cl is replaced by N3. Such derivatives will generally have approximately the same low polydispersity and low oligomer content as the polyepichlorohydrin precursor.
The strong carboxylic acid used as a co-catalyst generally increases the polymerization reaction rate a~
compared to the reaction rate obtained when it is not used, i.e~ when just the ~tannic chloride catalyst is used: for example~ the time for complete conversion at 65-70C of the ; epichlorohydrin i3 reduced from about 24 hours to 1 hour when the co-catalys~ is used with the ~tannic chloride.
The use of the co-catalyst with the stannic chloride also al1ows a lower amo~nt of stannic chloride catalyst to be ~, :

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~ 5-u~ed, e.g. to about 1~3 the amount. And the use of the co-cataly~t, whi~h~3peeds up the reaction rate, ~till generally re3ults in a hydroxyl-terminated polyepichloro-hydrin reaction product o light color, e.g~ a Gardner color of leqs than 2, and low polydispersity, and with lower amounts, if any, of the cyclic ether oligomers as compared to when the stannic chloride is u~ed a~ the only ca ta l y~ t.
i The initiator~ used in the proces~
l!O ~*$~ are tho~e which are unreac~ive with the qtannic chloride. Representative illu~trative initiators which can be u~ed include monohydric aliphatic alcohol~, such as CH30H~ C2H50H, (CH3)2CHOH~ CH3(C~12)30H, ClC2T340H, and C133(Cf12)l6C1120~1, monohydric cycloaliphatic alcohol~, such a~ C6HllCH20H, polyhydric aliphatic alcohol~, such as CH2(cH2oH)2l HOCH2CH(c~13)0Hl C2H4(CH2H)2' HOCH2CH(CH2Cl)OH, and C~3CH(OH)C2H40H, aromatic alcohols, such a~ C6~sCH20H, and polyhydric cycloaliphatic alcohols, quch a~

,fCH2CH2 C1~2CH2 and the hydroxyl-containing organic compounds dLsclosed in said U.S. Patent No. 2,327,053 which are unreactive with ~tannic chloride.
Initiators which are polymeric in nature can also be used, ~uch a~ a low molecular weight hydroxyl-~unctional polyepichlorohydrin, hydro~yl-functional poly(ethylenetere-phthalate), hydroxyl-functional perfluoropoly~oxyalkylene), ~uch as HOCH2CF~O~CF20)~CF2CF20)yCF2CH20H~
hydroxyl functional poly~oxyethylene), and hydroxyl-functional poly~oxypropylene). Other hydroxyl-containing organic monomeric or polymeric material8 which can be u~ed are those disclo~ed in ~aid U.S. Patent ~o. 4~43l,845 which are unreactive wi~h ~tannic chloride. Fluoroaliphatic , :

- 6 - 60~57-3065 alcohols which can be used are t'~ose suc'h as 17S02~(c2H5)cH2cE~2OH ~nd C8F17S02N(CH2CH2OH)2~ and those dis-closed in said U.S. Patent No. 4,340,749 which are unreactive with stannic chloride.
Mixtures of such initiators also can be used.
The applicability of an alcohol or hydroxyl-containing oryanic material as an initiator can be simply determined by mix-ing 1 part oE an'hydrous stannic chloride with 5 to 10 parts of the hydroxyl material in about 30 parts of L,2-dichloroethane solvent, heating the resulting mixture, e.g. 70C for 1 hoùr, and observing whether an irreversible reaction occurs, for example by evidence of a precipitate or evolution of hydrogen chloride. If no such reaction occurs, the hydroxyl material can be used as an initia-tor. l~aterials which have been found to be so reactive, and thus not suitable as an initiator, include ethylene glycol.
Where the stannic chloride is used in the process with-out the co-catalyst, 1,4-butane diol is not a preferred initiator since the use of the diol results in appreciable amounts of oli-gomer (see Example 5).
By controlling t'he proportions of epichlorohydrin to initiator, it is possible to limit the degree o poly~erization and, conse~uentlyl t'he ~olecular weight oE the polyepic'hlorohydrin product. Thus, t'he molar ratio of epichlorohydrin to hydroxyl group in t'he initiator may be in the range of about 2:1 to 100:1.
The stannic~ chloride catalyst employed in the process is a hydroly~abLe compound in the presence of water. Furthermore, its catalytic activity is considerably impaired w'hen it i5 in a hydrolyzed condition and larger amounts of such catalyst are ~7 - 7 - 60557~3065 required to effec-t the polymerization reaction when the reactants contain appreciable amounts oF water as compared to when they are substantially dry. Also, the hydrogen chloride liberated by the hydrolysis of the stannic chloride may combine with the epichloro-hydrin to form chlorohydrin by-products which may undesirably act as initiators. It is therefore preferable that the reactants used in the process be in substantially anhydrous condition.
The amount of stannic chloride catalyst to be used in the process wi~hout the co-catalyst is that amount sufficient to result in generally substantially quantitative or preferably essentially complete conversion of the epichlorohydrin to the polyepichlorbhydrin product, and the amount of stannic chloride to be used will depend on the desired molecular weight of- such product. Generally, for a product having a desired molecular weight of about 2000, such amount of stannic chloride will be about 0.5 to 1 weight percent of the polymerization reaction mixture; for a product with a molecular weight of 4000, such amount of stannic chloride will be about 1 to 2 weight percent;
and for a product with a molecular weight of 1000, ~uch amount 20 will be about 0.25 to 0.5 weight percent.
As discussed above, the process employs a strong carbo-xylic acid as a co-catalyst. Where such co-catalysts are used, l,~-butane diol can be used as initiators without resulting in the ~ormation of appreciable amounts of the cyclic oligomer.
Generally, the strong carboxylic acid co-catalyst used are those having a PKa of less than 2 and preferably less than 1, as determined, for example, by the method described by ~ .
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W. Huber, "Titration in i~onaqueous Solvents," Academic Press, ~ew York, N.Y., 196'7, p. 215. A class of such acid co-catalysts can be represen-ted by the formula R-CXY-CQOH, where X and Y are in-dependently selected from the group consisting of chlorine and fluorine, and R is hydrogen, fluorine, chlorine, or a moie-ty which is electron-withdrawing (relative to hydrogen), e.g. -C2Fs and -C6Hs, and does not adversely affect the polymerization.
Representative co-cataLyst (and thèir PKa values) include tri-fluoroacetic acid (0.23), trichloroacetic acid (0.66), and di-chloroacetic acid (1.25).
The a~ount of co-catalyst used is that which, -together with the stannic chloride catalyst, is sufficient to minimize the formation of the cyclic ether oligomeric by-products. Such amount generally will also, as compared to using the stannic chloride as -the sole catalyst, increase the reaction rate and permit use of less stannic chloride. Generally, the molar ratio of stannic chloride to co-catalyst will be 1:0.5 to 1:10, preferably 1:3 to 1:5, higher amounts of the co-catalyst in these ranges acting significantly as an initiator and thus influencing the molecular weight o~ the polyepichlorohydrin product.
The process can be carried out in the presence of a solvent or inert diLuent, for example where the alcohol inikiator is a solid, suitable solvents for this purpose representakively including 1,2-dichloroethanel benæene, toLuene, methylene c'hloride, and carbon tetrachloride. The caka~yst(s) can be added to the reackion vessel containing the initiator and solvent and the epichlorohydrin can be then incrementally added. Prior to 9~ . .

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- 8a - 60557-3065 addinq the epichlorohydrin, and during its addition and the ensuing reaction, the reaction vessel is heated or cooled to a desired polymerization temperature, e.g. abou-t 0C to llODC, preferably 65 to 75C. The polymeri7ation reaction is conducted under anhydrous conditions and to that end a slow, dry nitrogen gas purge of t'he reaction vessel can be used. The reaction pressure is generaLly the autogenous pressure but superatmospheric pressures can be used, e.g. up to 10 atmosp'heres, w'here the more voLatile initiators are used.
Generally, completion of t'he reaction will be indicated by the cessation of the reaction exotherm and the leveling-off of the viscosity increase of the reaction mixture. Completion of the reaction can be verified by ~ .

.. . - . ~ . .. -......... . ~ , , ~ea~uring the weights of reaction mixture samples before and after they are heated to remove volatile materialA.
The resulting ~econdary hydroxyl-terminated polyepichlorohydrin product can be recovered by subjecting the reaction product mixture to reduced pressure to re~ove ~olvent and volatile material, e~g. unreacted epichlorohydrin, adding further 301vent~ and then extracting the non-volatile material with an extracting agent, such as aqueous organic Qolvent, e.g. alcohol such a~ methanol or a ketone such as acetone, containing a~monium hydroxide, or preferably a chelating agent for tin such as the tetrasodiu~ salt of ethylenedinitrilotetra-acetic acid, used in an amount of about 5 to 10 percent in excess of the equivalent amount neces~ary to complex with the stannic chloride and neutralize the acid co-catalyst ~if present)~ The resulting two phase~ are separated, the heavier phase containing the desired polyepichlorohydrin product and the other phase being the aqueous organic ~olvent containing the chelating agent and catalysts. The product pha~e can be washed ~everal additional time~ with aqueous organic ~olventO The washed product can be ~tripped under reduced pre~ure.
The recovered polyepichlorohydrin product typically has a Gardner color of less than 2 and i9 lighter in color than the crude product. Such light-colored product is advantageous in that it indicates to a purchaRer of it that it i~ of high purity and it can be used in application~ (e.g. optics) where such light color is a requirement.
The conversion of the epichlorohydrin to the desired secondary hydroxyl-terminated polyepichlorohydrin product by the procesq 4~ t~ i~n i9 generally ~ub~tantlally quantitative and u~ually at least 95 percent based on the epichlorohydrin reactant, and typically 98 to 100 percent when the co-catalyst i~ used with the stannic chlorid~. The amount of the cyclic oligomer by-product is a minor arount o:~ the polyel yr hlorohydr ~ n produc c, generally ' - ' ' ~ .

less than 2 weight percent per 1000 molecular weight of product and, in the case where the co-catalyst is used with the stannic chloride, less than 0.5 weight percent per lO00 molecular weight of product.
The secondary hydroxyl-terminated polyepichlorohydrin products can be reacted with chain extension agents or cross-linking agents, such as polyfunctional compounds reactive with hydroxyl groups. For example, the products can be reacted with polyisocyanates, e.y., p-phenylene diisocyanate, 2,4- and/or 2,6-tolylene diisocyanates, in a conventional urethane reaction (e.g.,see said U.~. Patent Nos. 4,340,749 and 4,405,497) to form elasto-meric polyurethanes useful as foams for upholstery, auto~obile bumpers, and high performance coatings, or reac-ted with tertiary amines to form water-soluble polymeric quaternary salts used as plating bath additivesO
The polyepichlorohydrin products can also ~e reacted in a conventional manner with inorganic or metal azides, such as sodium azide, to fornl normally liquid, secondary hydroxyl-terminated polyglycidyl azide polymers used as energetic binders or plasticizers for solid gun propellants, for example by the procedures described in U.S. Patent ~os. 4,268,450 (Frankel et al), 4,288,262 (Flanagan), 4,379,894 tFrankel et al), and 4,486,351 (Earl).
The low content of the cyclic oligomer by-product in the polyepichlorohydrin product i9 advantageously carried over to the derivatives thereof, such as polyglycidyl azide polymer derivative product, together with the relatively low polydispersity property, ~r ~ ~ .

, :' ' - ll - 60557-3065 thu~ the derivatives will have mechanical or physical properties which enhance their use, e.g. as energekic propellant binders or plasticizers.
In using the polyglycidyl aæide polymer derivative products for use in solid rocket propellants, they can be mixed with an optional liquid plasticizer and then with solid particu-late oxidizer, polyisocyanate curing agent, optional other fuel components, bonding ayents, processing aids, burn rate catalysts, cure catalysts, carbon black, and combustion stabilizers. The propellant ingredients can be blended in a slow speed, high-shear mixer until all the solid particles are wetted by the li~uids in the system, the mixing optionally being carried out under vacuum to remove trapped air. The polyisocyanate curing agent is then added. An additional short mixing cycle is completed. The viscous, uncured propellant slurry can be transferred into a prepared rocket motor casing. The filled casing can then be slow-; ly heated to the appropriate cure temperature (generally 55 to 80C) and held at that temperature until the urethane reaction has taken place and the liquid binder precursor is converted to a solid, elastomeric polyurethane matrix providing mechanical inte-grity, environmental protection, and a controlled burning surface to the resulting solid propellant. Such propellants can be used in aircraft starter cartridges and ducted rocket `boosters, and as low signature propellants, minimum smoke propellant, and gun propellants.
E'urther ~etails on the preparation of the above-described polyurethanes and their use as binders for solid rocket :. ~ .

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- lla - 60557-3065 propellants will be omitted in the interest of brevity, since the steps in prepariny them are well-known, e.g. see U.S. Patent No. 3,642,705 ~Zollinyer).
Objects and advan-tages are illustrated in the following examples.
Example l :
To a 5-L, 3-neck flask equipped with an electric heating mantLe, stirrer, thermometer, condenser, addition funnel, and gas inlet tube was added 273 g l,2-dichloroethane solvent and 75.5 g .1,4-bis(hydroxymethyl)cyclohexane initiator. A slow, dry nitrogen gas purge was started and . . .
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, , maintained throughout the reaction and ~olvent ~tripping operation. To the well-qtirred ~olution heated to 65C waq added, by mea~ of a ~yringe, 15 9 ~tannic chloride. The heat~ng mantle was removed and 2,652 g epichlorohydrin wa3 added with stirring over a two-hour period while maintaining the reaction temperature at 65-70C by controlling the rate of addition and the u~e of a water-ice bath. After the addition wa~ complete, the reaction ~ixture was s~irred at 65 to 70~C for an additional 24 hours~ A
small~ weighed ~ample of the reaction mixture was heated for l hour at 105C in a vented oven to remove volatile material, and the heated sample then weighed, the difference in weights indicating 98% conversion of epichlorohydrin to hydroxyl-terminated polyepichlorohydrin product. Solvents and volatile material~ were re~oved at 65C under reduced pre~ure ~5 torr) over a six-hour periodO A small product ~ample (lA) was removed for analy~i~. The remainder of the crude product wa~ dissolved in 600 g 1,2-dichloroethane, and 1500 g of a lO~ aqueous ~ethanol ~olution containing 30 g of ethylenedinitrilo-~ tetraacetic acid, te~rasodium salt, added, and the mixture ; ~tirred vigorou~ly for two hours at 60C. The mixture was ~ cooled to room temperature and the lower pha~e of the two ; liqu~d phases was ~eparated and extracted with 1500 9 10%
aqueous methanol at 60~C~ The pha~es were separated as before and the lower phase extracted again with 1500 9 of 10% aqueou~ methanol at 60C. The lower phase, which ~eparated, wa~ stripped of ~olvent and volatiles at 5 torr over a six-hour period to yield 2122 9 of the purified, liquid polyepichlorohydrin diol having the following ~tructure;

H~fHCH2 )nC~2{}Cll2(cH2fH) nH
CH2Cl CH2Cl The molecular weight of the purified polyepichlorohydrin product was calculated to be 5200, , ~: ~

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based on the epichlorohydrin used. The molecular weight found was about 4000 (determined from equivalent weight by titration with phenyl isocyanate). Oligomer content of this purified polymer determined by gel permeation chromatography was 2.7 wt.~ compared with 4.7 wt.% for the crude product (sample lA above before purification).
Examples 2-7 Additional preparations of polyepichlorohydrin diol products, comprising liquid polyepichlorohydrin diols having structures within the scope of formula I, supra, where m is 2, were made following the yeneral procedure of Example 1 and utiliz-ing catalyst/ initiator systems. The reagents employed and the molecular weights and cyclic oligomer content of the resulting products are shown in Table 1 below together with that of Example 1. Comparative Examples C-l to C-5, employing prior art catalyst and initiators, are also included in Table 1.
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' , The lower "found" molecular weights for the diol product~ are believed due to small amount~ of water (present in the epichlorohydrin monomer) which acts a~ an additional initiator and thus contribute~ to the lower "found" molecular weight value~
Table 1 show~ the decrea~ed amount of oligomer C j obtained u5ing the SnC14 cataly~t ~-rh~ ~e~oR~
compared with a prior art catalyst sy~tem; thi~ i~ shown by comparing product~ of ~imilar molecular weight~, viz~ Ex. 2 vs~ C-4, Ex. 6 vs. C-5, Ex. 3 vs. C-2, and Ex. 4 V9~ C 3.

Example 8 A. To a ~lask equipped as in ~xample 1 wa~ added 40 9 1,2-dichloroethane, 7.2 9 1,4~bis(hydroxymethyl)cyclo-hexane, and 4.0 ml of a 1,2-dichloroethane ~olution containing 0.84 9 SnC14 and 1.74 9 CF3COOH co-catalyst. To this ~tirred solution wa~ added 222.7 9 of epichlorohydrin over a 35-minute period and the temperature was maintained at 65-70C by cooling the flask. During the addition, the solution turned from clear to pink to blue and finally to a dark purple color. After an additional 30 min. of stirring at 65-70C, the reaction mixture was cooled to room temperature and a small sample (Al) wa~ removed for analysis. The re~ainder of the reaction mixture was extracted with 100 g of a 10% aqueous methanol solution containing 2 g of the sodium salt of ethylenedinitrilo-tetraacetic acid and 0.5 g of concentrated aqueous NH40H, the extraction cau~ing dissipation of the purple colorO
The re~ulting light-colored, organic phase wa~ extracted with two 100 g portions of 10% aqueouq methanol solution and then ~tripped o solvent and volatiles at 65-70C and 5 torr over a 4-hour period to yield the liquid hydroxyl-terminated polyepichlorohydrin (A2) comprising polymer haYing a structure like that shown in Example 1.
; B. The above reaction was repeated except the CF3COOH wa~ omitted. At the end of the addition of epichlorohydrin, a considerable amount of it remained ,.
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~17-unreacted, so heating at 65C wa~ contin~ed for a total of 23 hours. After cooling to room temperature, a sample of the reaction ~ixture ~Bl) wa~ removed for analy~is. The remainder of the reaction mixture was extracted a~ above except that NE]40H waq omitted in the fir~t extrac~ion. The wa~hed organic pha~e was s~ripped of ~olvent a~ above to yield the liquid hydroxyl-terminated polyepichlorohydrin (B2) pro~uct compri~ing polymer haviny the 3tructure shown in Example 1.
Analy~is o~ the above polymeric products are summarized in Table 2.

~Iydroxyl Oligomer equivalent Poly content, Product weight Mb Mbdispersity~ wt.

Al -~ 1842 2~011 r 19 0 Bl -- 1861 26561.42 4~3 B2 1870 1963 25951~32 208 ._ .
a Determined by phenyl isocyanate titration.
b Determined by gel permeation ~h~
(polypropylene glycol ~tandard) c MW/Mn ~!e~
Example 8~ wa~ repeated except that twice the quantlty of initiator ~14.4 g) and one-hal the amount of catalyst ~olution (2.0 ml) were employed. The epichlorohydrin addition took 1 hour the dark purple color of the reaction mixture changed to a pale yellow near the end of the addition. Sample~ of the polyepichlorohydrin product taken after reaction ~Ex. 9-lJ and after extraction and stripping (Ex. 9-2) were analyzed. The results are summarized in Table 3.
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- 18 - ~0557-3065 Hydroxyl Oligomer equivalent Poly- content, Examp:Le weight Mn Mwdispersity wt. %

9-1 -- 1420 15531.094 0 9-2 910 1~2 160~1.096 0 Examples 10-19 These examples describe the results of employing various dihydroxy ini-tiators with the tin te~rachloride/trifluoroacetic acid catalyst system in polymerizing epichlorohydrin (in 25 g 1,2 dichloroethane) following the general procedure of Example 8A. In each example, the reaction was carried out by adding the epichlorohydrin over a 30-min. period and at 70C for 1 hr. The reactants, amounts, approximate conversion, and product analyses ~ 10 are summarized in Table 4. The liquid diol polymers of each example had structures faLling within the scope of formula I, supra.

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effective as 1,4-bi~(hydroxymethyl)cyclohexane (Example 10) a~ initiator~ in the polymerization of epichlorohydrin in high yield~ to a polyepichlorohydrin product free of oligomer and having a low polydisper~ityO However, under t~e ~ame reaction conditions, u~ing ethylene glycol instead of ~uch initiators, a low yield (18%) of polyepichloro-hydrin product resulted~

Example 14 This example de~cribes the preparation of a nominally 4000 molecular weight polyepichlorohydrin product following the general procedu~e of Example 8A employing 60 g l,2-dichloroethane, 3.3 g 1,4-bis(hydroxymethyl)cyclo hexane, 7 ml of a 1,2-dichloroethane ~olution containing 1047 9 tin tetrachloride, 3.05 9 trifluoroacetic acid, and 213 g of epichlorohydrin. The reaction time wa8 105 hour~
; at 70~C (98~ conver~ion). The reaction mixture was ;~ extracted with an aqueous methanol 301ution as in Example 8A and the polyepichlorohydrin product wa~ i~olated and upon being analyzed the hydroxyl eqUiY~ wt. found to be 1770, Mn wa9 2010, ~w was 2550, and polydispersity was 1.27. There wa~ little if any oligomer in the product a~
indicated by gel perm~ation chromatography ~no more than about 1% in any case). Proton nmr of the product indicated about 7% primary hydroxyl groups due to ~ome polymer chains being initiated by trifluoroacetic acid which wa~ later removed in the i~olation procedure.

Example lS
3~ Thi3 example de~cribe~ the preparation o~ a low molecular weight polyepichlorohydrin havin~ only one hydroxyl group at the end of each polymer chain by ~ing a monohydroxy initiator molecule, The procedure followed was that of Examples 11-13, employing 25 g 1~2-dichloroethane, 40.3 g 2-chloroethanol initiator, 3 ml of a .

1,2-dichloro~tha~e solution containing 0.63 g tin tetrachloride and 1.36 g trifluoroacetic acid, and 210 g of epichlorohydrin. The reaction conditions were 1 hour at 70~C (97~ conver~ion). The reaction mixture was extracted with 100 g of a 20% aqueous methanol ~olution containing 4 9 of ethylenedinitrilotetraacetic acid, tetra~odium salt.
The liquid polyepichlorohydrin product comprises a Inono-secondary hydroxyl-terminated polyepichlorohydrin polymer having a structure falling within the scope of formula I, supra, where m i9 1. The product wa~ isolated and analysis ~howecl the hydroxyl equiv. wt. was 650, ~n was 430~ Mw was 480, and polydispersity was 1.11. There was no oligomer indicated by gel permeation chromatography.

Thia example describe the preparation of the glycidyl azide poly~er derivative of a polyepichlorohydrin pro~uct of-tr~r~
One hundred grams o~ the polyepichlorohydrin product prepared like that of Example 2, di~solved in 100 g of dimethylsulfoxide (DMSo), was added to a stirred ~lurry of 100 g of sodium azide in 230 9 of DMSO. The mixture was heated to 80C and maintained at that temperature for 24 ~ houra and decanted from the precipitated salts into an ; equal volume of cold water. The decanted mixture was heated to 80C and stirred or 2 hours, the phases allowed to ~eparate, the aqueous phase discarded, and the water washing repeated twice more. Then 120 9 of 1,2-dichloroethane wa~ added to the wa~hed product and the resulting solution was washed three times with 600 9 portions o water. The separate~ organic phase was ~tripped at 40-50C and 5 torr with a slow N2 purge ~or 6 hours, to yield a hydroxyl-terminated polyglycidyl azide polymer product having the ~tructure H(oclHcH2)nocH2 { > CH20(CH2cHO)nH

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About 1 ml o the above azide polymer product wa3 placed in a deflagrating spoon and held ju~t above a ~unsen burner flame, whereupon it rapidly (in a matter o~ a few second3) disappeared in a red-glowing fireball with a "woof" 30und. This shows that the product is energe~ic and indicates that it would be u3eful in preparing a E~olyurethane hinder for solid rocket propellant~.

Exam~le 17 The- polyepichlorohydrin product (10.6 g) of Example 2 was mixed at room tem~erature with 2 g of a polyisocyanate~ DESMODUR N-100~ and 1 drop of a urethane cataly3t, dibutyltin dilaurate. The mixture gelled to yield a polyurethane elaetomer.
A 3ample of the polyurethane ela~tomer immersed in heptane in a closed bottle did not appear to gain weight over a period of month3, showing that it could be u~ed to form solvent resi~tant article~, ~uch as floor covering~, gasket~, and hoses.
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~ Example 18 The polyglycidyl azide polymer product of Example 16 (11 9) wa3 mixed at room temperature with 2 g of D~SMODUR ~-100, and 4 drops of dibutyltin dilaurate. The curable mixture gelled in 137 minutes to yield a polyurethane elaqtomer. A small piece of the cured elastomer wa3 held with tweezers ju~t above the flame of a burning wooden match, whereupon it partially vaporized wi thou t charrirlg: the evolved vaporq extinguished the ~lame. Thi~ indicates the utility of the ela~tomer as an energetic binder for solid rocket propellant3.
A film coating of the curable mixture in 1,2~dichloroethane wa3 preparPd and allowed to cure upon standing. The re.sulting cured coa~ing could be removed by hot air from an electric heat qun 8ub~tantially without damaging the polyester film ~ubstrate upon which the ~ ~r~e ~'~

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curable mixture wa~ ca3t. This ~how~ the polyurethane elastomer i8 useful a8 a thermally relea~able coating.

Variou~ modifications and alteration~ of this invention will become apparent to those ~killed in the art without departing from the scope and spirit of this inventionO

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Claims (12)

1. A polyepichlorohydrin product having a number average molecular weight of a least 2000 and a polydispersity of less than 1.2, said product comprising predominantly secondary hydroxyl-terminated polyepichlorohydrin polymer and essentially no non-hydroxyl functional cyclic ether oligomer, said product being made by polymerizing epichlorohydrin in the presence of anhydrous stannic chloride catalyst, a strong carboxylic acid co-catalyst, and an alcohol as an initiator.

2. The product of claim 1 wherein said product is normally liquid, has a Gardner color of less than 2, and said polyepichlorohydrin polymer is represented by the formula where R is an organic radical, m is 1 to 4, and n is at least 2.

3. The product of claim 2 where R has 1 to 20 carbon atoms and is an aliphatic radical, cycloaliphatic radical, an aromatic radical, or combination of such radicals, m is 2, and n is 2 to 100 .

4. The product of claim 2 where R is -CH?and m is 2.

5. The product of claim 2 wherein R is -(CH2)3-,-(CH2)4-, or -CH2CH(CH3)-, and m is 2.

6. The product of claim 2 wherein R is ClCH2CH2- and m is 1.

7. The product of claim 1 wherein said polyepichlorohydrin polymer has repeating units consisting of chloromethylethyleneoxy units.

8. Elastomeric polyurethane comprising the reaction product of the polyepichlorohydrin product of claim 1 and polyisocyanate.

9. A process for the preparation of the polyepichlorohydrin product of claim 1, which comprises polymerizing epichlorohydrin in the presence of anhydrous stannic chloride catalyst, a strong carboxylic acid co-catalyst and an alcohol as an initiator.

10. The process according to claim 9 wherein the product of the process is extracted with an aqueous organia solvent solution containing a chelating agent for tin, separating the resulting two phases, and recovering the polyepichlorohydrin product from the heavier phase.

11. The process according to claim 10 wherein said chelating agent is the tetrasodium salt of ethylenedinitrilotetraacetic acid.

12. The process according to claim 9 wherein said strong carboxylic acid has a PKa of less than about 2, as a co-catalyst.