Novel Polyketones

Of recent years, aromatic polyketones have generated widespread interest by reason of their resistance to thermal degradation. In large part, interest has focused on polyketones having the repeat unit ##SPC2##

(Here and in the claims, a six-membered ring signifies phenyl or phenylene, as the case may be). Following Bonner U.S. Pat. No. 3,065,205, polyketones having the above repeat unit may be prepared by Friedel-Crafts catalyzed polymerization of phosgene and diphenyl ether. The same repeat unit is additionally described in British Pat. No. 1,086,021 to M. E. B. Jones to obtain by polycondensation of diphenyl ether-4-carbonyl chloride, and from the reaction of diphenyl ether and diphenyl ether-4,4'-dicarbonyl chloride.

A number of patents which include reference to improved methods of making such polyketones have since issued. For example processes disclosed in U.S. Pat. Nos. 3,441,538 and 3,442,857 derive advantage by resort hydrogen dydrogen fluoride-enhanced boron trifluoride catalysis. Melt processable polymers characterized by that repeat unit are prepared in the copending, commonly assigned application of Klaus J. Dahl, Ser. No. 218,465, filed Jan. 17, 1972 now abandoned, where additional art is discussed.

Aromatic polyketones having other repeat units have been investigated to some extent. Melt processable polyketones having the repeat unit ##SPC3##

Are described in the copending, commonly assigned application of Klaus J. Dahl (Ser. No. 218,466, filed Jan. 17, 1972, now abandoned) as arising from, eg, HF/BF.sub.3 -catalyzed polymerization of biphenylyloxybenzoyl chloride. According to R. N. Johnson et al, G.B. Pat. No. 1,078,234 polymers having the repeat unit ##SPC4##

And melting at 350.degree.C arise from reaction of hydroquinone and 4,4'-difluorobenzophenone.

It would be of substantial advantage if aromatic polyketones having acceptable properties could be secured employing as reactants materials more commonly and cheaply available than those most often employed in past work. One known aromatic polyketone, that having the repeat unit ##SPC5##

Has been economically prepared by reaction of diphenyl ether and terephthaloyl chloride but Berr, in U.S. Pat. No. 3,516,966, reports that the HF/BF.sub.3 -catalyzed polymerization of those reactants affords melt-unstable product. Berr accordingly prepared copolyketone having a substantial content of isophtyaloyl residue, and reported the product as melt stable. In our hands the Berr process afforded polymer of satisfactory molecular weight, but compression molded slabs exhibited excessive gel content, indicative of a substantial degree of thermal crosslinking during melt processing. We have since determined that diphenyl ether is unstable in the HF/BF.sub.3 system under the conditions preferred by Berr, leading to side reactions of an as yet undefined but plainly problematic nature. Now, by judicious choice of reactants and process conditions, we have obtained through HF/BF.sub.3 -catalyzed polymerization novel and economic aromatic polyketones whose inherent viscosity is essentially unaffected by compression molding at 410.degree.C for 5 minutes at, eg, 10,000 psi.

According to this invention there are provided aromatic polyketones predominately comprised of the recurring structural unit ##SPC6##

wherein each of x, m and n are 0 or 1, p is an integer from 1 to 4, n is 0 where x is 1, and wherein when p is greater than 1, m is 1 and x is 0, the inherent viscosity of which polymers being essentially unaffected by compression molding at, eg, 410.degree.C for 5 minutes at 10,000 psi.

Representative coreactants useful in forming the homopolymers which are preferred in the practice of this invention are listed in the table which follows. Each is a known compound which is prepared from standard literature procedures.

In the case of the electrophilic reactant, the leaving group may be, albeit preferably is not, other than chlorine, eg, methoxy, hydroxy, etc. For the case where p is 2, 3 4, 4, any of the electrophilic coreactants may be employed with, respecitvely, tetra-, penta- or hexaphenylene ether. The former reactant is obtained by condensation of 2 moles of phenol with 1 mole of 4,4'-dibromodiphenylether. Pentaphenylene ether is secured by condensing 1,4-dibromobenzene (1 mole) and 2 moles of 4-hydroxydiphenylether, while the nucleophilic coreactant last-mentioned is readily afforded by condensation of 4,4'-dibromodiphenylether (1 mole) and 2 moles of 4-hydroxydiphenylether.

Preferably, essentially all of the repeat units of the polymer are identical. In such cases, the essentially para polymer may be expected to exhibit thermooxidative stability superior to polymers characterized by substantial meta linkage, like those arising where, eg, mixtures of terephthaloyl and isophthaloyl chloride are employed as electrophilic reactants. Of course, even where only terephthaloyl chloride or a like "para" reactant is employed, it is likely inevitable that a minor number, eg several percent, of the repeat units will contain isomeric linkages arising from attack of the electrophilic reactant on the growing polymer chain at positions other than para.

More generally, the invention comprises copolyketones, eg, those predominately comprised of a single repeat unit conforming to the structural formula last depicted. Among suitable candidates for copolymerization may be mentioned the following nucleophilic coreactants:

phosgene

carbonyl difluoride

isophthaloyl chloride

benzene-1,4-di(sulfonyl chloride)

benzene-1,3-di(sulfonyl chloride)

2-chlorobenzene-1,4-disulfonyl chloride

thio-bis(4,4'-benzoyl chloride)

oxy-bis(4,4'-benzene sulfonyl chloride)

benzophenone-4,4'-di(carbonyl chloride)

oxy-bis(3,3'-benzoyl chloride)

thio-bis(3,3'-benzene sulfonyl chloride)

oxy-bis(3,3'-benzene sulfonyl chloride)

diphenyl-3,3'-di(carbonyl chloride)

carbonyl-bis(3,3'-benzoyl chloride)

sulfonyl-bis(4,4'-benzoyl chloride)

sulfonyl-bis(3,3'-benzoyl chloride)

sulfonyl-bis(3,4'-benzoyl chloride)

thio-bis(3,4'-benzoyl chloride)

diphenyl-3,4'-di(carbonyl chloride)

oxy-bis[4,4'-(2-chlorobenzoyl chloride)]

naphthalene-1,6-di(carbonyl chloride)

naphthalene-1,5-di(carbonyl chloride)

naphthalene-2,6-di(carbonyl chloride)

naphthalene-1,5-di(sulfonyl chloride)

oxy-bis[7,7'-naphthalene-2,2'-di(carbonyl chloride)]

thio-bis[8,8'-naphthalene-1,1'di(carbonyl chloride)]

7,7'-binaphthyl-2,2'-di(carbonyl chloride)

diphenyl-4,4'-di(carbonyl chloride)

carbonyl-bis[7,7'-naphthalene-2,2'-di(carbonyl chloride)]

sulfonyl-bis[6,6'-naphthalene-2,2'-di(carbonyl chloride)]

dibenzofuran-2,7-di(carbonyl chloride)

Parentheticaly, our preferred process conditions may be employed in the formation of homopolymers, many of them novel, from the above-listed coreactants. Where the copolyketone coreactant is more than binuclear the copolyketone should, by preference, contain at least about 70%, most preferably at least about 80% repeat units answering to the generic structure last depicted.

In a further embodiment of the invention we prepare linear, crystalline melt-stable polymers predominantely and, most preferably, essentially comprised of the repeat unit ##SPC7##

wherein the moieties of structure ##SPC8##

are, for each repeat unit, independently selected from the group consisting of para and meta, x and m being as earlier defined. Preferably, up to 50% of the ##SPC9##

moieties are meta, most preferably from about 10% to about 50%. Such polymers are prepared just as in the case of all-para polymers, save that some or all of the electrophilic terephthaloyl chloride reactant is replaced by is phthaloyl chloride. The use of mixed terephthaloyl and isophthaloyl chlorides permits variation of the melt temperature between 271.degree. and 360.degree.C for the system ##SPC10##

copolymers of this type may confer greater latitude in extrusion temperatures and afford improved compatibility for blending with other resins to obtain special effects, such as plasticization. Additional advantages which may accrue from this deviation from an all-para polymer system include changes in crystallization behavior and attendant effects on stress corrosion in fluids, or at elevated temperatures.

Preferably the polymers of the invention exhibit inherent viscosity of at least about 0.4, more preferably from about 0.5 to about 2.0, and most preferably from about 0.7 to 1.5. Molecular weight may be controlled by capping, as taught in the aforesaid application of Dahl, Ser. No. 136,236, the disclosure of which is incorporated herein by reference. Preferred capping agents contain a ketonic linkage, eg, 4-phenoxybenzophenone.

In preparing the polymers of the invention by the preferred procedure, equal molar amounts of nucleophilic and electrophilic (dichloride) coreactants are combined, optionally with minor amounts of monofunctional capping agent, and sufficient anhydrous HF added to form, at 0.degree.C, a 10% wt. solution. At -20.degree.C to 10.degree.C, preferably 0.degree.C, after first allowing all HCI to evolve, BF.sub.3 is added under 30 psi pressure, the material permitted to react for about 6 hours, and the polymerization mixture then diluted with SO.sub.2 or additional HF to form a solution containing about 5% wt. solids. Recovery is by spray drying or precipitation in a Waring blendor into H.sub.2 O (room temperature) or methanol (-78.degree.C). Fluorine and boron content of the resulting product is reduced by water wash and the material then dried at 150.degree.C and 20 mm Hg for 3-5 hours. All reactions are performed in transition metal-free environs.

In the following examples of preferred embodiments of the invention, all parts and percentages are by weight and all temperatures in centigrade degrees unless otherwise indicated.

A 50 ml. polychlorotrifluoroethylene tube was charged with 1.2984g (4.95 mmoles) of 1,4-diphenoxybenzene, 1.0049g (4.95 mmoles) of terephthaloyl chloride, 0.0027g (0.01 mmoles) of 4-phenoxybenzophenone (capping agent) and a stir bar. To this mixture was slowly added 20 ml of anhydrous hydrogen fluoride. The tube was then connected to a polychlorotrifluoroethylene vacuum line (Toho Kasei Co. Ltd., Osaka, Japan) and purged with nitrogen while cooling to 0.degree.C. Boron trifluoride gas was admitted and the reaction mixture was held at 30 psi pressure for 6 hr. to give a viscous orange-red solution. Excess boron trifluoride was purged from the reaction system, the polymer solution was diluted with anhydrous hydrogen fluoride, and then poured into rapidly stirred, cold (-78.degree.) methanol. The resultant polymer precipitate was filtered and washed with water and methanol, followed by drying at 180-200 /20 mm Hg to yield colorless, fluffy material, which was annealed at 230.degree. for 20 minutes. Inherent viscosity before and after compression molding, elemental composition and physical characteristics of the polymer are set out, respectively, in Table II - IV, infra. In the case of this and the following Examples, compression molding at 410.degree. for 5 minutes at a pressure of 10,000 psi afforded nearly colorless, flexible slabs. It is particularly noteworthy that in every case inherent viscosity was essentially unaffected by compression molding. This also held true when, in related work, diphenyl ether and terephthaloyl chloride were reacted by the foregoing procedure to afford polymer having the repeat unit ##SPC11##

In the latter case inherent viscosity of the powder was 0.53 and that of the slab 0.49. All inherent viscosities are mean values obtained according to the method of Sorenson et al., Preparative Methods of Polymer Chemistry, Interscience (1968) p. 44 [0.1 g. polymer in 100 ml. soln. of concentrated H.sub.2 SO.sub.4 at 25.degree.C]. Melting points were determined with a Perkin Elmer Differential Scanning calorimeter.

The additional polymers listed in Table 1 were prepared following the procedure of Example 1 and their properties determined as set out in Tables II - IV. In the case of Example 5 no melt point was determined, though the material is estimated to melt at a temperature within the range 300.degree.-350.degree.C.

Anhydrous hydrogen fluoride was saturated with boron trifluoride at -23.degree. and 30 psi pressure for 4 hr. A 50-ml reaction tube was charged with 1.3050 g (4.975 mmoles) of 1,4-diphenoxybenzene, 1.0151 g (5mmoles) of isophthaloyl chloride, 0.0137 g (1 mole %) of p-phenoxybenzophenone and a stir bar. To this mixture was added slowly 10 ml of the cold (-78.degree.) boron trifluoride saturated hydrogen fluoride solution, and the reaction tube was connected to the vacuum line. A boron trifluoride pressure of 30 psi was applied and the polymerization was allowed to proceed at 0.degree. for 16 hr. to give a viscous, orange solution. Excess boron trifluoride was purged from the reaction system, the polymer solution was diluted with hydrogen fluoride and then poured into rapidly stirred, cold (0.degree.) water. The resultant polymer precipitate was filtered and washed with water, followed by drying at 150.degree./20 mm Hg to yield colorless, fluffy material. The material showed an inherent viscosity of 1.36. Compression molding at 400.degree. for 5 min produced a flexible slab of inherent viscosity of 1.37. Differential scanning colorimetry indicated a glass transition temperature of 153.degree. and a crystalline melting temperature of 271.degree. (scan rate: 20 /min) Thermogravimetric analysis in air showed a 10% weight loss at 600 (scan rate: 20.degree./min). Molecular spectroscopy revealed the following data which are consistent with a linear polymer of repeating unit: ##SPC12##

infrared (film cast from hydrogen fluoride): 1655cm.sup..sup.-1 [ketone link], 1235 cm.sup..sup.-1 [ether link]; ultraviolet (conc. sulfuric acid) max., 407nm (.epsilon., 4.8 .times. 10.sup.4); nuclear magnetic resonance (ClCF.sub.2 -COCF.sub.2 Cl.sup.. D.sub.2 O/CDCl) = 1:1): , ppm: 7.18 (doublet, 4H, J = 9 Hz), 7.28 (singlet, 4H), [protons in ortho position to ether linkage]; 7.82 (singlet, 3H), 8.08 (doublet, 4H J = 9 Hz), 8.18 (singlet, 1H) [protons in proximity of ketone linkages].

The experiment detailed in the preceding example was repeated, but mixtures of terephthaloyl chloride and isophthaloyl chloride were used. Acid chloride ratios employed and data of polymer characterization are shown in Table 5 attached.

The products of this invention are film and fiber-forming polymers suitable for use in electrical insulation, as by melt extrusion over wires cables, and the like. Preferred polymers are crystalline materials melting at a temperature in the range 340.degree.-404.degree.C. Those in which carbonyl moieties are present in number greater than ether oxygen may be expected to crystallize substantially more quickly than, eg, poly (benzophenone ether), holding out the promise that the post-annealing step commonly practiced with extrudates of the latter polymer can be eliminated without adversely affecting properties such as tensile strength and resistance to scrap abrasion and environmental stress corrosion. Polymers prepared according to this invention whose melt points are on the order of 400.degree.C or higher, when employed in electrical insulation, are advantaged thereby in resisting loss of insulative integrity through inadvertent contact with soldering irons.