GB2237810A - Aromatic polyetherketones - Google Patents

Abstract

A melt-crystallisable aromatic polyetherketone comprises 2, 6-napthylene units either alone or together with other divalent aromatic units connected to one another by -O-, -S-, or -CO- linkages, the other units being selected from 1,4- phenylene, 4,4'-biphenylene, 4,4''-terphenylene, and polyaromatic residues comprised by 1,4-phenylene units linked by -0-, -S-, -CO-, -SO2-, and/or -CH2-. The polymer is crystallisable from the melt or upon annealing, and preferably exhibits a glass transition temperature of at least 165 DEG C.

Description

Aromatic Polymers This invention relates to aromatic polymers.

Aromatic polyetherketones are known, useful polymers which have been produced by a variety of methods. The methods are usually based on two reaction types, namely nucleophilic aromatic substitution (eg the polycondensation of activated aryl fluorides with phenoxides to produce ether linkages) and electrophilic aromatic substitution (eg the polycondensation of acid chlorides or carboxylic acids with aryl ethers to produce ketone linkages). Examples of such methods have recently been reviewed by M J Mullins and E P Woo, J Macromolecular Science Rev. Macromol Chem Phys, C27 (2), 313, 1987.

Such polymers are usually crystalline, have relative high glass transition (Tg's) and melting temperatures (Tm's) and exhibit a variety of useful properties such as excellent electrical insulating and mechanical properties at high temperatures and high strength, toughness and resistance to fire and chemicals. Two particular polymers, ie polyetherketone (PEK), Tg - 165 C, having the repeating unit: -O-Ph-CO-Phand polyetheretherketone (PEEK), Tg - 1440C, having the repeat unit: -O-Ph-O-Ph-CO-Phwherein Ph is 1,4-phenylene, have been commercially exploited.

Other useful polymers are continuously being sought. One possible class of polyetherketones is that containing naphthalene residues.

US-A-4786694 relates to the formation of crystalline oligomers which are then coupled using multi-ring units to form polymers. The patent generically discloses inter alia oligomers containing naphthalene residues. However, it has been found by other workers that polymers containing naphthalene residues are amorphous and are not readily melt crystallisable. For example, amorphous polymers based on 2,6-bis (fluorobenzoyl)naphthalene with 9, 9-bis (4-hydroxyphenyl )fluorene or 2,2'-bis(4-hydroxyphenyl)propane were amorphous and not melt crystallisable were disclosed by P M Hergenrother et al, Polymer, February, 1988, Vol 29.

The Applicant has surprisingly found that certain polyetherketones containing a repeating unit of formula I

ie 2,6-naphthylene, are crystalline or are at least crystallisable from the melt or upon annealing and exhibit Tg's at least as good as those of PEK and PEEK if not better.

Thus, according to the present invention, a melt-crystallisable aromatic polyetherketone comprises 2,6-naphthylene units either alone or together with other diva lent aromatic units connected to one another by -O-, -S- or -CO- linkages, the other units being selected from 1,4phenylene, 4,4' biphenylene, 4,4' '-terphenylene, and polyaromatic residues comprised by 1,4-phenylene units linked by -O-, -S-, -CO-, -502-, andlor -CB2-, the amount of linkages other than -CO- or -0- when present being insufficient to substantially affect the crystalline character of the polymer.

Preferably, polymers according to the invention have a reduced viscosity (RV) of at least 0.3, more particularly at least 0.8, and especially at least 1.0, determined using 1.Og of polymer in looms of 98X sulphuric acid at 250C.

Preferably, polymers according to the invention are tough, ie the polymers can be creased without breaking.

Polymers according to the invention are crystallisable from the melt or upon annealing. Preferably, the polymers are crystallisable when cooled at a rate of at least O.50Cmin-1, more particularly at least 100C-1 and, more particularly, at least l50Cmin-1; or when annealed between Tg and Tm for less than 2 hours and, more particularly, for less than 1 hour.

Polymers according to the invention also exhibit enhanced Tg's compared to the Tg's of PEK and PEEK. Preferred polymers exhibit Tg's of at least 1650C.

The mole ratio of repeating unit I to said other units is at least 1:99, and is preferably in the range 10:90 to 90:10, more particularly in the range 20:80 to 80:20. Preferred polymers according to the invention contain between 20 and 60 mole X of repeating unit I.

The other repeating units may include units containing linkages other than -CO- and -0- provided the essentially crystalline character of the polymers according to the invention is not lost. Preferably, the proportion of units containing such linkages is not more than 25Z, and more particularly not more than 20I.

Examples of other repeating units additional to those listed above are: - -Ph-O-Ph -Ph-CO-Ph -Ph-S02-Ph -Ph-CH2-Ph -Ph-O-Ph-CO-Ph-O-Ph -Ph-O-Ph-S02-Ph-O-Ph-.

Polymers according to the invention are thus particularly useful for applications which require resistance to solvents and to high temperatures.

Polymers in accordance with the invention can be melt processed into shaped articles, including films and insulating coatings on electrical conductors or used as matrices in composites. They can be used in applications for which polyetherketones and/or polyethersulphones have been proposed previously. In particular they may be used for those applications which require a combination of one or more of good electrical insulating properties, good resistance to a wide range of chemicals, retention of mechanical properties up to high temperature, good resistance to burning and the emission of low proportions of toxic fumes and with low smoke density on burning. Films whether undrawn, uniaxially-drawn or biaxially-drawn are especially useful when made of these polymers.

Whilst for many applications the polymers of the invention may be used with few if any additives, other than stabilisers, additives may be incorporated for example inorganic and organic fibrous fillers such as of glass, carbon or polyparaphenylene terephthalamide; organic fillers such as polysulphones, polyketones, polyimides, polyesters and polytetrafluoroethylene at various levels of compatibility; and inorganic fillers such as graphite, boron nitride, mica, talc and vermiculite; nucleating agents; and stabilisers such as phosphates and combinations thereof.

Typically the total content of additives is 0.1 to 80Z, especially at most 70Z by weight of the total composition. The composition can contain for example 5 to 30Z by weight of boron nitride; or at least 20Z by weight of short glass or carbon fibre; or 50 to 70Z especially about 60Z, by volume of continuous glass or carbon fibre; or a mixture of a fluorine-containing polymer, graphite and an organic or inorganic fibrous filler and the total proportion of these additives is preferably 20 to 50Z by weight of the total composition.

The composition may be made by mixing the polymer with the additives for example by particle or melt blending. More specifically the polymeric material, in the form of dry powder or granules, can be mixed with the additives using a technique such as tumble blending or high speed mixing. The blend thus obtained may be extruded into a lace which is chopped to give granules. The granules can be subjected to a forming operation, for example injection moulding or extrusion, to give a shaped article.

Alternatively the composition may be film, foil, powder or granules of the polymer with or without particulate additives, laminated with a fibrous filler in the form of mats or cloths.

Alternatively a composition containing fibrous filler may be obtained by passing essentially continuous fibre, for example glass or carbon fibre, through molten polymer or a mixture containing it in a dissolved or finely dispersed state. The product obtained is a fibre coated with polymer and may be used alone, or together with other materials, for example a further quantity of the polymer, to form a shaped -article. The production of compositions by this technique is described in more detail in EP-A 56703, 102158 an 102159.

Polymers according to the present invention can be conveniently made either by an electrophilic reaction in the presence of an acid capable of activating the condensation reaction or by a nucleophilic reaction in the presence of a base.

The invention will now be illustrated by reference to the following Examples.

Example 1 11.128g (0.05lmole) of 4,4'-difluorobenzophenone, 46g of diphenylsulphone and 8.009g (0.050mole) of 2,6-dihydroxynaphthalene were weighed into a 250ml flask which was purged with nitrogen and then immersed in a heated oil bath at 16O0C. When the contents of the flask were fluid, they were stirred and 5.003g (0.050mole) of sieved ( < 250p) anhydrous sodium carbonate was slowly added thereto followed by 0.138g (0.OOlmole) of sieved anhydrous potassium carbonate. The temperature of the reaction mixture was then raised to 1950C for one hour, then to 2700C for one hour and then to 3200C for two hours following which 0.2g (0.001mole) of 4,4'-difluorobenzophenone was then added to the mixture.

After a further 30 minutes, the flask was removed from the oil bath and cooled. The resultant product was milled, leached firstly with acetone and then hot water and the resultant white polymer was dried.

The polymer had an RV of 1.21, a Tg of 174 C and a Tm of 332"C. A compression-moulded (3900C, 24.6MPa) film of the polymer quenched from 3900C could be creased through 1800 without fracture. After annealing at 2600C for one hour, the film was opaque and highly crystalline and was still creasable.

A portion of the film was melted on the hot stage of a polarising microscope under a nitrogen blanket. The stage was then cooled at various rates from 4000C to 1900C and the sample was observed continuously between crossed polarisers. The temperature (Tn) at which birefringent spherulites first appeared was noted. On reaching 1900C, the sample was removed and assessed visually for opalescence as a further indication of crystallinity. The results are given in Table I.

TABLE I COOLING RATE (OClmin) Tn (OC) OPALESCENCE 20 240 NOT DETECTED 10 260 DENSE 5 280 OPAQUE The onset of birefringence is a more sensitive way of detecting melt-crystallisation than is the use of DSC since the latter technique did not detect endotherms until the cooling rate exceeded 200cumin.

Example 2 tComnarative) Using the method described in Example 1, a polymer was made with 2,7-dihydroxynaphthalene instead of 2,6-dihydroxynaphthalene. This polymer had an RV of 0.94 and a Tg of 1620C. The polymer was amorphous as made and remained so on annealing at 2000C for 30 minutes.

Using the optical method described in Example 1, and using a cooling rate of 5 C/min, neither birefringence nor opalescence could be detected in the polymer. The polymer thus failed to crystallise to any detectable degree from the melt.

lg of the polymer was completely soluble in l-chloronaphthalene at 2600C. The solution was cooled to 1200C at a rate of 1OClmin.

Crystallisation did not occur and no solids were recovered on filtration at 1200C. Indeed, crystallisation was not apparent at this slow cooling rate until haze started to develop slowly at 640C. The solution was further cooled to room temperature and the crystalline product was filtered off, washed with cold l-chloronaphthalene followed by acetone and was then vacuum dried at 1200C. At least 80Z of the original polymer was recovered and it was found to be highly crystalline with a melting point of 2700C.

The polymer was of relatively high molecular weight and did not crystallise to any extent on slow cooling from the melt; nor did it crystallise rapidly from hot l-chloronaphthalene at 2400C. This behaviour is quite different to that reported by Kritcheldorf et al, Polymer, Vol 25, August 1984 who mentioned it as a crude reaction product (no molecular weight data given) having a Tg of 152-1540C and rapid rates of crystallisation both from the melt and from l-chloronaphthalene at 2400C.

Example 3 tComparative) The synthesis of Example 2 was repeated but using potassium carbonate as the sole base, which resulted in a polymer of IV 0.37dlg-1 indicating a relatively low molecular weight. The polymer failed to give tough films on compression moulding confirming that it was of relatively low molecular weight. DSC examination of the polymer gave a Tg of 160"C. A very tiny amount of crystallinity was present in the polymer as made as evidenced by endotherms at 2530C and 384"C on the DSC trace but the crystallinity could not be recovered upon cooling from the melt. For example, a sample of the polymer cooled from the melt at 0.50cumin failed to exhibit a crystallisation exotherm and remained essentially amorphous.Similarly, a specimen quenched from 4000C failed to crystallise after annealing at 2000C for 30 minutes.

A solution was prepared in l-chloronaphthalene and behaved exactly as described in Example 2 except that crystallisation was not observed until below 300C. On this occassion, at least 86Z recovery was noted.

The Tm was again found to be 2700C.

This behaviour of different molecular weight material was again different to that reported by Kricheldorf et al.

Example 4 (Comparative) Using the method described in Example 1, a polymer was made with 1, 4-dihydroxynaphthalene instead of 2.6-dihydroxynaphthalene, Decomposition and discoloration was apparent during this synthesis and an amorphous, acetone-soluble product was obtained.

Example 5 Using the method described in Example 1, a polymer was made using a reaction mixture consisting of 9.496g (0.0255mole) of 2,6-bis (4-fluorobenzoyl)naphthalene, 2.753g (0.025mole) of hydroquinone, 23.7g of diphenylsulphone, 2.650g (0.025mole) of sodium carbonate and 0.069g (0.0005mole) of potassium carbonate. During polycondensation, crystallisation occurred at 3000C followed by remelting at 320at.

The resultant polymer had an RV of 0.34, a Tg of 169"C and a Tm of 3820C. The polymer was highly crystalline as made and crystallised readily from the melt when cooled at 200Cmin-1 from 4000C. The film was not creasable.

Example 6 Example 5 was repeated but using 4.018g (0.025mole) of 2,6-dihydroxynaphthalene instead of the hydroquinone.

The resultant polymer had an RV of 0.87, a Tg of 187"C and a Tm of 3790C. The polymer was highly crystalline as made. A small amount of crystallinity was apparent upon cooling at 2O0Cmin-1 from 4400C. A tough amorphous film quenched from 4400C became highly crystalline upon annealing for one hour at 3250C. The film was not creasable but was very stiff.

Example 7 Example 5 was repeated but using 4.656g (0.025mole) of 4,4'dihydroxy biphenyl instead of the hydroquinone.

The resultant polymer had an RV of 0.80, a Tg of 19200 and a Tm of 42500. The polymer was crystalline as made. The polymer crystallised well upon cooling at 200Cmin-1 from 46000. The film was creasable when amorphous but not so when crystalline.

ExamPle 8 Example 1 was repeated but using 21.135g (0.051mole) of 4,4, -bis (4-fluorobenzoyl)diphenylethe4r.

The resultant polymer had an RV of 1.36, a Tg of 17100 and two Tm's of 3230C and 3680C, respectively. A tough, transparent, ie amorphous, film was made by quenching from the melt at 380 C. The quenched film was annealed for one hour at 2400C to give an opaque, ivory-coloured tough film, ie crystalline and creasable.

Claims (11)

1. A melt-crystallisable aromatic polyetherketone comprising 2,6-naphthylene units either alone or together with other divalent aromatic units connected to one another by -O-, -S- or -CO- linkages, the other units being selected from 1,4- phenylene, 4,4'-biphenylene, 4,4''-terphenylene, and polyaromatic residues comprised by 1,4-phenylene units linked by -O-, -S-, -CO-, -S02-, and/or -CH2-, the amount of linkages other than -CO- or -0- when present being insufficient to substantially affect the crystalline character of the polymer.

2. A polyetherketone according to claim 1 which has a reduced viscosity of at least 0.3, more particularly at least 0.8, and especially at least 1.0, determined using l.Og of polymer in lOOml of 98Z sulphuric acid at 250C.

3. A polyetherketone according to claim 1 or claim 2 which is tough.

4. A polyetherketone according to any one of the preceding claims which is crystallisable from the melt or upon annealing.

5. A polyetherketone according to claim 5 which is crystallisable when cooled at a rate of at least O.SoCmin-l, more particularly at least 10 C-1 and, more particularly, at least l50Cmin-1; or when annealed between Tg and Tm for less than 2 hours and, more particularly, for less than 1 hour.

6. A polyetherketone according to any one of the preceding claims which exhibits a Tg of at least 1650C.

7. A polyetherketone according to any one of the preceding claims wherein the mole ratio of repeating unit I to said other units is at least 1:99, and is preferably in the range 10:90 to 90:10, more particularly in the range 20:80 to 80:20.

8. A polyetherketone according to any one of the preceding claims which contains between 20 and 60 mole Z of repeating unit I.

9. A polymer composition comprising a polyetherketone according to any one of claims 1 to 8 and at least one component selected from stabilisers, organic fillers and inorganic fillers.

10. A shaped article of a polyetherketone according to any one of claims 1 to 8 or of a composition according to claim 9.

11. A polyetherketone according to claim 1 substantially as hereinbefore described with reference to the Examples.