Patent Application
20160208045
The invention relates to a process for making a polymeric material and a polymeric material per se. Particularly, although not exclusively, the invention relates to a process for making polyetheretherketone (PEEK) and a novel PEEK per se.
PEEK polymers are known to have a range of outstanding properties, including excellent heat resistance, chemical resistance, dimensional stability and mechanical properties. They are utilised in a wide range of demanding applications, including, amongst others, aerospace, automotive, electronics, deep sea oil and gas, and nuclear industries, as well as being approved for a wide range of medical uses.
A number of companies currently manufacture PEEK polymers (including Evonik Industries, Solvay and Applicant), and currently all of these manufacturers rely on a nucleophilic reaction process (as disclosed generally in European Patent Publication EP1879) whereby 1,4-dihydroxybenzene (HQ) is reacted with 4,4′-difluorobenzophenone (BDF) at elevated temperature in the presence of a suitable high boiling solvent (typically diphenylsulfone or sulfolane) and typically in the presence of a carbonate base in order to promote the polymerisation reaction.
Alternative, electrophilic routes, to PEEK polymers are also possible (see for example European patents EP1263836B and EP1170318B) although such routes are believed not to be used to produce PEEK commercially.
There are a number of significant problems with the standard industrial nucleophilic process to PEEK polymers which will be well known to those skilled in the art and include:
It is an object of the preferred embodiments of the present invention to address at least some of the aforementioned problems.
In addition, commercially available PEEK has a Tg of 143° C. and a Tm of about 340° C.
For many applications, however, it is desirable to maintain relatively high Tg but lower the Tm so as to facilitate melt processing. It is an object of preferred embodiments of the invention to address this problem.
Furthermore, it is desirable for PEEK polymers produced to be as light in colour as possible, since darker polymers may be perceived to be of lower quality (e.g. as being relatively impure). Lighter coloured PEEK is generally preferred for applications where the aesthetics of the article are important. It is an object of preferred embodiments to address this problem.
According to a first aspect of the invention, there is provided a process for producing a polymeric material having a repeat unit of formula
the process comprising polycondensing a monomer of structure
Thus, in the process, monomers of structure II are polycondensed with one another to produce the polymeric material of formula I.
Said process is preferably carried out in the presence of one or more carbonates. The process is preferably carried out in the presence of alkali metal carbonate. Said process is preferably carried out in the presence of one or more carbonates which preferably include sodium carbonate, which may, optionally, be in combination with potassium carbonate.
The total mol % of carbonates used in the process (i.e. the total number of moles of carbonates used in the process divided by the total number of moles of hydroxy monomer(s) used (especially said monomer of structure II), expressed as a percentage) is suitably at least 100 mol %.
The total mol % of carbonates may be greater than 100 mol %. It may be less than 105 mol %.
The mol % of sodium carbonate used in the process (i.e. the moles of sodium carbonate used in the process divided by the moles of said monomer of structure II) may be at least 90 mol %, preferably at least 92 mol %, more preferably at least 95 mol %.
The total mol % of sodium carbonate and potassium carbonate used in the process (i.e. the sum of the moles of sodium carbonate and potassium carbonate used in the process divided by the moles of said monomer of structure II) is preferably at least 100 mol % and is, more preferably, greater than 100 mole %. It may be in the range 100 to 105 mol %.
The mol % of carbonates (which term is intended to encompass carbonate (CO32−) and bicarbonate (HCO3−)) other than sodium carbonate and potassium carbonate used in the process is preferably less than 5 mol %, more preferably less than 1 mol % (again related to the moles of said monomer of structure II).
Preferably, the only carbonates used in the process are sodium carbonate and potassium carbonate.
In the process, alkali metal fluoride (which suitably comprises sodium fluoride and may comprise both sodium fluoride and potassium fluoride when sodium and potassium carbonate are used in the process, as is preferred) is suitably produced as a bi-product of the polycondensation. The ratio of the total number of moles of alkali metal fluoride produced in the process divided by the number of moles of repeat units of formula I is suitably in the range 0.9 to 1.1 and is preferably about 1.
In the process, carbon dioxide is suitably produced as a bi-product of the polycondensation. The ratio of the total number of moles of carbon dioxide produced in the process divided by the number of moles of repeat units of formula I is suitably in the range 0.9 to 1.1, and is preferably about 1
Said polymeric material having a repeat unit of formula I may include at least 90 mol %, suitably at least 95 mol %, preferably at least 98 mol %, especially at least 99 mol % of repeat units of formula I.
Said polymeric material having a repeat unit of formula I may include at least 90 wt %, suitably at least 95 wt %, preferably at least 98 wt % of repeat units of formula I.
Said polymeric material having a repeat unit of formula I preferably includes fluorine moieties at its ends. Preferably at least 90% (more preferably about 100%) of the number of end groups in said polymeric material comprise fluorine atoms.
In the process, the ratio of the number of moles of monomer of formula II divided by the total number of moles of monomers used in the process is preferably in the range 0.90 to 1, more preferably in the range 0.95 to 1, especially in the range 0.98 to 1. When said ratio is not equal to 1, the process may include introducing an additional monomer into the process. Said additional monomer preferably does not include an hydroxyl moiety. Said additional monomer preferably includes at least two halogen atoms, especially two fluorine atoms. Said additional monomer is preferably a difluoro-compound. It is preferably arranged to react with and replace the OH moieties of monomer of formula II. It is preferably arranged to end-cap the polymeric material formed in the process. As a result, ends of the polymeric material of formula I suitably include fluorine atoms which suitably help to stabilise the polymeric material.
In the process, it is preferred that no hydroxyl group-containing monomer is used other than said monomer of structure II. Said process preferably does not comprise use of a hydroquinone.
Said additional monomer preferably includes one or more phenyl moieties. Said additional monomer suitably includes at least one phenyl moiety, substituted in the 4-position, suitably with a fluorine atom. Said additional monomer may include two phenyl moieties. In this case, preferably both of said two phenyl moieties are substituted by fluorine atoms, suitably in the 4-positions. Said two phenyl moieties may be separated by a ketone moiety. Said additional monomer is preferably 4,4′-difluorobenzophenone.
Said process suitably include polycondensing 95 to 100 wt % (preferably 97.5 to 99.5 wt %) of said monomer of structure II in the presence of 0 to 5 wt % (preferably 0.5 to 2.5 wt %) of said additional monomer.
In a preferred embodiment, said process is carried out in the presence of a solvent (which is suitably a polar aprotic organic solvent). Advantageously, the ratio of the total number of moles of monomers used in the process divided by the total number of moles of solvent may be greater than 0.3, suitably greater than 0.4. The ratio may be in the range 0.1 to 0.8, for example in the range 0.3 to 0.6.
Said solvent may be of formula
where W is a direct link, an oxygen atom or two hydrogen atoms (one attached to each benzene ring) and Z and Z′, which may be the same or different, are hydrogen atoms or phenyl groups. Examples of such aromatic sulphones include diphenylsulphone, dibenzothiophen dioxide, phenoxanthin dioxide and 4-phenylsulphonyl biphenyl. Diphenylsulphone is a preferred solvent.
The process is preferably carried out under substantially anhydrous conditions. In the process, the compound of formula II is suitably contacted with carbonate of the type described in the presence of said solvent, especially diphenylsulphone. Polymerisation is suitably effected at a temperature within the range 150° C. to 400° C. In the process, the reactants are suitably heated up to a maximum temperature which may be greater than 300° C., for example in the range 300° C. to 350° C. The process may be carried out without holding the temperature at any temperature less than 300° C. Heat up, to a temperature in excess of 300° C., may be substantially continuous.
Advantageously, preferably no blanket of inert gas (e.g. N2) is introduced and/or used in the process, for example to minimise oxidation. The process may be carried out under ambient atmospheric conditions.
The process may be carried out in a receptacle and, advantageously, the receptacle may be run fuller than in prior art processes for production of said polymeric material because only half the amount of carbon dioxide is produced compared to prior art processes. In the process the maximum amount of liquid in the receptacle during the process may fill at least 80%, preferably at least 85% of the volume of the receptacle. Said volume may be less than 95%.
The polymeric material of the first aspect preferably has a Tm of less than 340° C. It may have a Tg in the range 142 to 144° C. Said polymeric material of the first aspect may include any of the preferred features described according to the second embodiment.
According to a second aspect of the invention, there is provided a polymeric material which comprises a repeat unit of formula I, wherein said polymeric material has a Tm of less than 340° C. and a Tg in the range 142 to 144° C.
Preferred features of the polymeric material of the first and second aspects are described below.
Preferably, the only repeat units in said polymeric material of formula I are repeat units which include phenyl moieties (especially unsubstituted phenyl moieties), ether moieties and ketone moieties. Preferably, the only repeat units in said polymeric material of formula I are repeat units which comprise unsubstituted phenyl moieties separated by ether or ketone moieties. In said repeat units, preferably the ratio of the number of ether moieties divided by the number of ketone moieties is 2; and the ratio of the sum of the number of ether moieties and ketone moieties divided by the number of phenyl moieties is 1.
Said polymeric material having a repeat unit of formula I may include at least 90 mol %, suitably at least 95 mol %, preferably at least 98 mol %, especially at least 99 mol % of repeat units of formula I.
Said polymeric material having a repeat unit of formula I may include at least 90 wt %, suitably at least 95 wt %, preferably at least 98 wt % of repeat units of formula I.
Said polymeric material having a repeat unit of formula I preferably includes fluorine moieties at its ends. Preferably at least 90% (more preferably at least 99%, especially about 100%) of the number of end groups in said polymeric material comprise fluorine atoms.
Said polymeric material may have a Tm (assessed as described hereinafter) of less than 339° C., suitably less than 338° C., preferably less than 337° C. The Tm may be in the range 332° C. to 339° C., suitably in the range 333° C. to 337° C.
The difference (Tm−Tg) between the Tm and Tg of said polymeric material may be in the range 189-195° C.
In a preferred embodiment, said polymeric material has a Tg in the range 142° C.-144° C., a Tm in the range 333° C. to 337° C. and the difference between the Tm and Tg is in the range 189° C. to 195° C.
Said polymeric material may have a crystallinity measured as described hereinafter of at least 25%. Crystallinity may be less than 38%.
Said polymeric material suitably has a melt viscosity (MV) of at least 0.06 kNsm−2, preferably has a MV of at least 0.08 kNsm−2, more preferably at least 0.085 kNsm−2, especially at least 0.09 kNsm−2. MV of said polymer material is suitably measured using capillary rheometry operating at 400° C. at a shear rate of 1000s−1 using a tungsten carbide die, 0.5 mm×3.175 mm. Said polymer material may have a MV of less than 1.00 kNsm−2, suitably less than 0.8 kNsm−2.
Said polymeric material may have a tensile strength, measured in accordance with ISO527 of at least 40 MPa, preferably at least 60 MPa, more preferably at least 80 MPa. The tensile strength is preferably in the range 80-110 MPa, more preferably in the range 80-100 MPa.
Said polymeric material may have a flexural strength, measured in accordance with ISO178 of at least 130 MPa. The flexural strength is preferably in the range 135-180 MPa, more preferably in the range 140-150 MPa.
Said polymeric material may have a flexural modulus, measured in accordance with ISO178 of at least 2 GPa, preferably at least 3GPa. The flexural modulus is preferably in the range 3.0-4.5 GPa, more preferably in the range 3.0-4.0 GPa.
Said polymeric material may be in the form of pellets or granules, wherein the pellets or granules include at least 95wt %, preferably at least 99wt %, especially about 100 wt % of said polymeric material. Pellets or granules may have a maximum dimension of less than 10 mm, preferably less than 7.5 mm, more preferably less than 5.0 mm.
Said polymeric material suitably has L*, assessed as described hereinafter, of at least 65, preferably at least 66, more preferably at least 67. The L* may be less than 78. In some embodiments, it may be less than 75. L* is suitably in the range 66 to 782.
According to a third aspect of the invention, there is provided a pack comprising a polymeric material as described herein.
Said pack may include at least 1 kg, suitably at least 5 kg, preferably at least 10 kg, more preferably at least 14 kg of material of which at least a part is made up of said polymeric material. Said pack may include 1000 kg or less, preferably 500 kg or less of said material. Preferred packs include 10 to 500 kg of said material.
Said pack may include at least 1 kg, suitably at least 5 kg, preferably at least 10 kg, more preferably at least 14 kg of a said polymeric material. Said pack may include 1000 kg or less, preferably 500 kg or less of said polymeric material. Preferred packs include 10 to 500 kg of a said polymeric material.
Polymeric material in said pack may be in powder or granular form.
Said pack may comprise packaging material (which is intended to be discarded or re-used) and a desired material (which suitably comprises said polymeric material). Said packaging material preferably substantially fully encloses said desired material. Said packaging material may comprise a first receptacle, for example a flexible receptacle such as a plastics bag in which said desired material is arranged. The first receptacle may be contained within a second receptacle for example in a box such as a cardboard box.
Any feature of any aspect of any invention or embodiment described herein may be combined with any feature of any aspect of any other invention or embodiment described herein mutatis mutandis.
Specific embodiments of the invention will now be described, by way of example, with reference to the accompanying figures, in which:
The following materials are referred to hereinafter:
4-fluoro-4′-(4-hydroxyphenoxy) benzophenone synthesised as described in Example 4, referred to as “FHPB”.
In general terms the preparation of polyetheretherketone (PEEK) may be undertaken by polycondensation of a single monomer (4-fluoro-4′-(4-hydroxyphenoxy) benzophenone) in diphenylsulphone (DPS) solvent and in the presence of sodium carbonate and potassium carbonate as summarized in the scheme below.
A small amount of 4,4′-difluorobenzophenone (BDF) may be included in the polymerisation mixture (or may be added during the polymerisation) to control the rate of polymerisation, act as an end stopper and/or to ensure the PEEK polymer is fluorine ended.
Compared to the process described in EP1879 which involves polycondensation of BDF and hydroquinone (HQ), use of the single monomer may be advantageous for at least the following reasons:
Further details on the process are provided below.
DPS (132.0 g, 0.616 mol), FHPB (92.49 g, 0.300 mol) and BDF (0.87 g, 0.004 mol) were charged to a 500 ml flange flask equipped with an anchor type agitator, overhead stirrer, gas inlet and air condenser. After inerting with nitrogen, (a step which is not required but which was included so as to be comparative with Example 3), the mixture was heated to 160° C. with stirring at 70 rpm. Sodium carbonate (15.98 g, 0.151 mol) and potassium carbonate (0.42 g, 0.003 mol) was slowly added and the resulting mixture heated at 1° C./min to 310° C. The polymerisation mixture was maintained at 310° C. until the desired torque rise was reached. At this point the molten toffee was poured into a foil tray, allowed to cool, milled and washed with 2 litres of acetone and then with warm water at a temperature of 40-50° C. until the conductivity of the waste water was <2 μS. The resulting polymer powder was dried in an air oven for 12 hours at 120° C.
In this comparative example, PEEK was prepared using the sodium salt of FHPB as illustrated in the scheme below.
FHPB was reacted with an equimolar amount of sodium hydroxide to produce the sodium salt which could then be polymerised in DPS without any further sodium carbonate.
In the process, DPS (132.0 g, 0.616 mol) was charged to a 500 ml flange flask equipped with an anchor type agitator, overhead stirrer, gas inlet and air condenser. After inerting with nitrogen the mixture was heated to 290° C. with stirring at 70 rpm. The FHPB sodium salt (99.08 g, 0.300 mol) was added over 10 minutes whilst maintaining the contents temperature at 290-300° C. When the addition was complete potassium carbonate (0.42 g, 0.003 mol) and BDF (0.87 g, 0.004 mol) were added. The resulting mixture was heated to 310° C. and maintained at this temperature until the desired torque rise was reached. If required, further potassium carbonate (0.21 g, 0.002 moles) was added to increase the rate of polymerisation. At this point the molten toffee was poured into a foil tray, allowed to cool, milled and washed with 2 litres of acetone and then with warm water at a temperature of 40-50° C. until the conductivity of the waste water was <2 μS. The resulting polymer powder was dried in an air oven for 12 hours at 120° C.
DPS (132.0 g, 0.616 mol), HQ (33.03 g, 0.300 mol) and BDF (66.33 g, 0.304 mol) were charged to a 500 ml flange flask equipped with an anchor type agitator, overhead stirrer, gas inlet and air condenser. After inerting with nitrogen the mixture was heated to 160° C. with stirring at 70 rpm. When the mixture was molten, sodium carbonate (31.96 g, 0.302 mol) and potassium carbonate (0.83 g, 0.006 mol) was slowly added and the resulting mixture heated at 1° C./min to 310° C. The polymerisation mixture was maintained at 310° C. until the desired torque rise was reached. The reaction mixture was then poured into a foil tray, allowed to cool, milled and washed with 2 litres of acetone and then with warm water at a temperature of 60-70° C. until the conductivity of the waste water was <2 μS. The resulting polymer powder was dried in an air oven at 120° C.
Aluminium chloride (333.35 g, 2.5 mol) and 1,2-dichlorobenzene (650 ml) and were charged to a nitrogen inerted 1 L jacketed reactor flask equipped with anchor style agitator, overhead stirrer, temperature probe, addition funnel and a condenser with an outlet to a caustic scrubber.
The reaction was heated to 60° C. and 4-phenoxyphenol (186.21 g, 1.0 mol) was added portion wise. When the addition was complete 4-fluorobenzoylchloride (158.56 g, (1.0 mol) was added drop-wise over 120 minutes. The reaction mixture was heated at 1° C./min to 90° C. and maintained at this temperature for 60 minutes.
The brown coloured solution was then carefully quenched onto stirred cold water and the biphasic mixture was allowed to exotherm to 90° C. in order to solubilise the monomer in the organic phase. The aqueous phase was removed and the organic phase washed with demineralised water (3×500ml) to remove aluminium salts and excess acidity.
The organic phase was cooled at 1 ° C./min to 0° C. and the crystalline solid filtered off and washed with 60/80 petroleum ether (400 ml).
The crude product was dissolved in hot toluene (5 ml per 1 g of product), stirred with activated carbon (2% w/w) and then hot filtered to remove the carbon. The clear yellow filtrate was slowly cooled to 0° C., filtered, washed with toluene (200 ml), 60/80 petroleum ether (400 ml) and dried under vacuum at 60° C. The product was 99.98% pure and had a melting point of 142.3° C.
Assessments and results for Examples 1, 2 and 3 are detailed and discussed below. Note that references to “standard PEEK” and “standard PEEK process” refer to PEEK made as described in Example 3.
The Heat of Fusion for melting (ΔHm) was obtained by connecting the two points at which the melting endotherm deviates from the relatively straight baseline. The integrated area under the endotherm as a function of time yields the enthalpy (mJ) of the melting transition: the mass normalised heat of fusion is calculated by dividing the enthalpy by the mass of the specimen (J/g). The level of crystallisation (%) is determined by dividing the Heat of Fusion of the specimen by the Heat of Fusion of a totally crystalline polymer, which for polyetheretherketone is 130 J/g.
Results for polymers produced (referred to as Examples 1a, 1b and 1c) made as described in Example 1 are provided in Table 1.
The peak melting point value for commercially available PEEK made using a standard PEEK process is approximately 340° C. Thus, the Example 1 process leads, advantageously, to a lower Tm (of approximately 335° C.).
| Number | Date | Country | Kind |
|---|---|---|---|
| 1317183.0 | Sep 2013 | GB | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/GB2014/052818 | 9/26/2014 | WO | 00 |
