WO2014096763A1 - Copolyesterimides of poly(alkylene terephthalate)s having high tg and high monomer content and film made therefrom - Google Patents
Copolyesterimides of poly(alkylene terephthalate)s having high tg and high monomer content and film made therefrom Download PDFInfo
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- WO2014096763A1 WO2014096763A1 PCT/GB2013/051527 GB2013051527W WO2014096763A1 WO 2014096763 A1 WO2014096763 A1 WO 2014096763A1 GB 2013051527 W GB2013051527 W GB 2013051527W WO 2014096763 A1 WO2014096763 A1 WO 2014096763A1
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
- C08G73/00—Macromolecular compounds obtained by reactions forming a linkage containing nitrogen with or without oxygen or carbon in the main chain of the macromolecule, not provided for in groups C08G12/00 - C08G71/00
- C08G73/06—Polycondensates having nitrogen-containing heterocyclic rings in the main chain of the macromolecule
- C08G73/10—Polyimides; Polyester-imides; Polyamide-imides; Polyamide acids or similar polyimide precursors
- C08G73/16—Polyester-imides
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
- C08L79/00—Compositions of macromolecular compounds obtained by reactions forming in the main chain of the macromolecule a linkage containing nitrogen with or without oxygen or carbon only, not provided for in groups C08L61/00 - C08L77/00
- C08L79/04—Polycondensates having nitrogen-containing heterocyclic rings in the main chain; Polyhydrazides; Polyamide acids or similar polyimide precursors
- C08L79/08—Polyimides; Polyester-imides; Polyamide-imides; Polyamide acids or similar polyimide precursors
Definitions
- the present invention is concerned with novel polyesters and films made therefrom, and methods for their synthesis.
- the present invention is concerned with novel copolymers of poly(alkylene terephthalate)s, particularly poly(ethylene terephthalate) (PET), which exhibit improved heat-resistance and thermo-mechanical stability.
- PET poly(ethylene terephthalate)
- T g glass transition temperature
- T m crystalline melting point
- degree of crystallinity degree of crystallinity
- the melt-processing temperature should be well below (for instance, at least about 20°C below) the decomposition temperature of the polymer.
- comonomers have been introduced into polymers in order to increase T g while retaining T m , but also resulting in convergence of the decomposition temperature and the T m , which leads to the production of degradation products in the melt.
- Many attempts have also been made to enhance the glass transition temperature of polyesters by the introduction of more rigid comonomers.
- such comonomers also disrupt the packing of the polymer chains in the crystal lattice, so that while the T g increases, the T m and degree of crystallinity typically both decrease as the proportion of comonomer increases, leading ultimately to amorphous materials.
- PET is a semi-crystalline copolymer having a glass transition temperature (T g ) of 78°C and a crystalline melting point of (T m ) of 260°C.
- T g glass transition temperature
- T m crystalline melting point of
- PEEK Poly ether ether ketone
- T g glass transition temperature
- T m crystalline melting point
- PEEK Poly ether ether ketone
- PEEK is one of the few examples of a high T g (approximately 143-146°C) semi-crystalline thermoplastic polymer, and has been used successfully in engineering and biomedical applications.
- PEEK is suitable only for certain types of articles; for instance, it is not suitable for the manufacture of biaxially oriented films.
- PEEK is also very expensive and has a high crystalline melting point (approximately 350°C).
- An object of the present invention is to provide polyesters which exhibit improved heat- resistance and thermo-mechanical stability.
- a further object of the present invention is to provide a thermoplastic polymer with high or increased T g but without increasing T m to a point where the polymer is no longer melt-processible under economic conditions (i.e. the polymer should remain melt-processible below about 320°C, preferably below about 300°C).
- a further object of the present invention is to provide semi-crystalline polyesters which exhibit high T g as well as high T m .
- a further object of the present invention is to increase the T g of a polyester without significantly decreasing its T m and/or its degree of crystallinity, and preferably without significantly decreasing its decomposition temperature.
- the term “without significantly decreasing the T m” means that the T m decreases by no more than 10%, preferably no more than 5%.
- the term “without significantly decreasing the degree of crystallinity” means that the polyester retains a degree of crystallinity which is commercially useful, preferably in the range of from about 10% to about 60%, preferably from about 20 to about 50%.
- a further object of the present invention is to provide a copolyester having a T g which is higher than the corresponding base polyester, without significantly decreasing its T m and/or its degree of crystallinity and preferably without significantly decreasing its decomposition temperature.
- a further object of the present invention is to provide a comonomer suitable for partial substitution of a monomer in a conventional polyester which increases the T g of said polyester without significantly decreasing its T m and/or its degree of crystallinity, and preferably without significantly decreasing its decomposition temperature.
- any increase in T m must not be so large that melt-processing becomes uneconomical and that the T m and decomposition temperature converge.
- the above-mentioned objects of the present invention have, as their underlying objective, the provision of copolyester articles made from a copolyester having a T g which is higher than the corresponding base polyester, without significantly increasing the T m to a point where the polymer is no longer melt-processible under economic conditions, particularly without significantly decreasing the degree of crystallinity of the copolyester article (in order to achieve acceptable thermo-mechanical properties), and preferably also without significantly decreasing the decomposition temperature of the copolyester.
- the term "copolyester” refers to a polymer which comprises ester linkages and which is derived from three or more types of comonomers.
- the term “corresponding base polyester” refers to a polymer which comprises ester linkages and which is derived from two types of comonomers comprising ester-forming functionalities, and which serves as a comparator for a copolyester which is derived from comonomers comprising the comonomers of the corresponding base polyester.
- a comonomer comprising ester-forming functionalities preferably possesses two ester- forming functionalities.
- the term "semi-crystalline" is intended to mean a degree of crystallinity of at least about 5% measured according to the test described herein, preferably at least about 10%, preferably at least about 15%, and preferably at least about 20%. Accordingly, the present invention provides a copolyester comprising repeating units derived from an aliphatic glycol, terephthalic acid, and the monomer of formula (I):
- the copolyesters according to the present invention are thermoplastic. Copolyesters and articles made therefrom as described herein exhibit semi-crystalline properties. The copolyesters according to the present invention can be readily obtained at high molecular weight.
- the copolyesters according to the present invention can be melt-processed below 320°C (preferably below 300°C) into tough, high strength articles.
- the copolyesters are also referred to herein as co(polyester-imide)s.
- the comonomer (I) constitutes a proportion of the glycol fraction of the copolyester.
- the comonomer (I) is present in amounts of no more than about 50 mol% of the glycol fraction of the copolyester, preferably no more than about 40 mol%, preferably no more than about 30 mol%, preferably no more than about 25 mol%, and in one embodiment no more than about 20 mol%, and in a further embodiment no more than about 15 mol%.
- the aliphatic glycol is preferably selected from C 2 , C 3 or C 4 aliphatic diols, more preferably from ethylene glycol, 1,3-propanediol and 1,4-butanediol, more preferably from ethylene glycol and 1,4-butanediol, and is most preferably ethylene glycol.
- the number of carbon atoms in the aliphatic glycol may be the same or different as the number (n) in the comonomer (I), but it is most preferably the same in order to retain crystallinity, particularly in order to retain crystallinity with increasing amounts of comonomer.
- n is as defined for formula (I);
- the group X is the carbon chain of said aliphatic glycol
- the copolyester may contain more than one type of aliphatic glycol, and/or more than one type of monomer of formula (I).
- the copolyester comprises a single type of aliphatic glycol.
- the copolyester comprises a single type of monomer of formula (I).
- the copolyester comprises a single type of aliphatic glycol, and a single type of monomer of formula (I).
- the copolyesters may contain minor amounts of other glycols and in a preferred embodiment such other glycols constitute no more than 10 mol%, preferably no more than 5 mol%, preferably no more than 1 mol% of the total glycol fraction, but in order to maximise performance it is preferred that the glycol fraction consists of comonomer (I) and said aliphatic glycol(s) described above.
- the copolyesters of the present invention may contain minor amounts (preferably no more than 10 mol%, preferably no more than 5 mol%, preferably no more than 1 mol% of the total acid fraction) of one or more other dicarboxylic acids (preferably aromatic dicarboxylic acids), for instance including naphthalene-dicarboxylic acid (such as 2,6- naphthalenedicarboxylic acid), isophthalic acid, 4,4'-diphenyldicarboxylic acid, 1,4- cyclohexane dimethanol and 1,6-hexanediol.
- dicarboxylic acids preferably aromatic dicarboxylic acids
- naphthalene-dicarboxylic acid such as 2,6- naphthalenedicarboxylic acid
- isophthalic acid 4,4'-diphenyldicarboxylic acid
- 1,4- cyclohexane dimethanol 1,6-hexanediol.
- copolyesters of the present invention contain minor amounts of an aromatic dicarboxylic acid other than terephthalic acid
- said aromatic dicarboxylic acid other than terephthalic acid is selected from aromatic dicarboxylic acids other than naphthalene-dicarboxylic acids.
- the acid fraction of the copolyesters of the present invention consists of terephthalic acid.
- the copolyester of the present invention preferably contains only aliphatic glycol, terephthalic acid and the monomer of formula (I) defined hereinabove.
- copolyesters of the present invention can be synthesised according to conventional techniques for the manufacture of polyester materials by condensation or ester interchange, typically at temperatures up to about 310°C.
- Polycondensation may include a solid phase polymerisation stage.
- the solid phase polymerisation may be carried out in a fluidised bed, e.g. fluidised with nitrogen, or in a vacuum fluidised bed, using a rotary vacuum drier.
- Suitable solid phase polymerisation techniques are disclosed in, for example, EP-A-0419400 the disclosure of which is incorporated herein by reference.
- the aliphatic glycol is reacted with the terephthalic acid to form a bis(hydroxyalkyl)-terephthalate, which is then reacted with the monomer (I) in the desired molar ratios under conditions of elevated temperature and pressure in the presence of a catalyst, as exemplified in Scheme (1) below.
- Suitable solvents include mixtures of DMAc and toluene.
- Water by-product is suitably removed from the reaction zone during the course of the reaction, for instance by azeotropic distillation. Further steps in the synthetic and isolation procedure typically comprise:
- the copolyesters of the present invention are suitable for use in applications requiring improved heat-resistance and/or thermo-mechanical performance.
- the copolyesters of the present invention can be used in film form or fibre form or in moulding compositions.
- incorporation of the specific co-monomer (I) into a terephthalate polyester not only increases the T g substantially but does so without significant detriment to the crystallinity of articles made therefrom. This is achieved without significantly increasing the T m .
- Articles made from the copolyesters described herein exhibit semi-crystalline properties.
- Such articles comprise the copolyesters of the present invention wherein the comonomer (I) is present in amounts of from greater than 10 mol% to no more than about 50 mol% of the glycol fraction of the copolyester, as described hereinabove, and in a preferred embodiment from about 20 mol% to about 45 mol%.
- a fibre or moulding composition or moulded article comprising a copolyester comprising repeating units derived from an aliphatic glycol, terephthalic acid, and the monomer of formula (I) defined hereinabove, wherein the comonomer (I) is present in amounts of greater than 10 mol% of the glycol fraction of the copolyester.
- the fibre, moulding composition or moulded article may be produced according to conventional techniques in the art.
- the copolyesters of the present invention are also suitable for film manufacture.
- Biaxially oriented films in particular are useful as base films for magnetic recording media, particularly magnetic recording media required to exhibit reduced track deviation in order to permit narrow but stable track pitch and allow recording of higher density or capacity of information, for instance magnetic recording media suitable as server backup/data storage, such as the LTO (Linear Tape Open) format.
- LTO Linear Tape Open
- copolyesters of the present invention are also suitable for the manufacture of film (preferably biaxially oriented film) for use in electronic and opto-electronic devices (particularly wherein the film is required to be flexible) where thermo-mechanically stable backplanes are critical during fabrication of the finished product, for instance in the manufacture of electroluminescent (EL) display devices (particularly organic light emitting display (OLED) devices), electrophoretic displays (e-paper), photovoltaic (PV) cells and semiconductor devices (such as organic field effect transistors, thin film transistors and integrated circuits generally), particularly flexible such devices.
- EL electroluminescent
- OLED organic light emitting display
- e-paper electrophoretic displays
- PV photovoltaic
- semiconductor devices such as organic field effect transistors, thin film transistors and integrated circuits generally
- a film comprising a copolyester comprising repeating units derived from an aliphatic glycol, terephthalic acid, and the monomer of formula (I) defined hereinabove, wherein the comonomer (I) is present in amounts of greater than 10 mol% of the glycol fraction of the copolyester.
- the film is preferably an oriented film, preferably a biaxially oriented film.
- Said copolyester is preferably the major component of the film, and makes up at least 50%, preferably at least 65%, preferably at least 80%, preferably at least 90%, and preferably at least 95% by weight of the total weight of the film.
- Said copolyester is suitably the only polyester used in the film.
- Formation of the film may be effected by conventional extrusion techniques well-known in the art.
- the process comprises the steps of extruding a layer of molten polymer at a temperature within an appropriate temperature range, for instance in a range of from about 280 to about 300°C, quenching the extrudate and orienting the quenched extrudate.
- Orientation may be effected by any process known in the art for producing an oriented film, for example a tubular or flat film process.
- Biaxial orientation is effected by drawing in two mutually perpendicular directions in the plane of the film to achieve a satisfactory combination of mechanical and physical properties.
- simultaneous biaxial orientation may be effected by extruding a thermoplastics polyester tube which is subsequently quenched, reheated and then expanded by internal gas pressure to induce transverse orientation, and withdrawn at a rate which will induce longitudinal orientation.
- the film-forming polyester is extruded through a slot die and rapidly quenched upon a chilled casting drum to ensure that the polyester is quenched to the amorphous state.
- Orientation is then effected by stretching the quenched extrudate in at least one direction at a temperature above the glass transition temperature of the polyester.
- Sequential orientation may be effected by stretching a flat, quenched extrudate firstly in one direction, usually the longitudinal direction, i.e.
- Stretching is generally effected so that the dimension of the oriented film is from 2 to 5, more preferably 2.5 to 4.5 times its original dimension in the or each direction of stretching.
- stretching is effected at temperatures higher than the T g of the polyester, preferably about 15 °C higher than the T g .
- Greater draw ratios may be used if orientation in only one direction is required. It is not necessary to stretch equally in the machine and transverse directions although this is preferred if balanced properties are desired.
- a stretched film may be, and preferably is, dimensionally stabilised by heat-setting under dimensional support at a temperature above the glass transition temperature of the polyester but below the melting temperature thereof, to induce the desired crystallisation of the polyester.
- TD transverse direction
- Toe-in can involve dimensional shrinkage of the order 2 to 4% but an analogous dimensional relaxation in the process or machine direction (MD) is difficult to achieve since low line tensions are required and film control and winding becomes problematic.
- the actual heat-set temperature and time will vary depending on the composition of the film and its desired final thermal shrinkage but should not be selected so as to substantially degrade the toughness properties of the film such as tear resistance.
- a heat set temperature of about 150 to 245°C is generally desirable, preferably no higher than about 200°C, preferably no higher than about 190°C, preferably less than 180°C. After heat-setting the film is typically quenched rapidly in order induce the desired crystallinity of the polyester.
- the film may be further stabilized through use of an in-line relaxation stage.
- the relaxation treatment can be performed off-line.
- the film is heated at a temperature lower than that of the heat-setting stage, and with a much reduced MD and TD tension.
- the tension experienced by the film is a low tension and typically less than 5 kg/m, preferably less than 3.5 kg/m, more preferably in the range of from 1 to about 2.5 kg/m, and typically in the range of 1.5 to 2 kg/m of film width.
- the reduction in film speed (and therefore the strain relaxation) is typically in the range 0 to 2.5%, preferably 0.5 to 2.0%. There is no increase in the transverse dimension of the film during the heat-stabilisation step.
- the temperature to be used for the heat stabilisation step can vary depending on the desired combination of properties from the final film, with a higher temperature giving better, i.e. lower, residual shrinkage properties.
- a temperature of 135 to 250°C is generally desirable, preferably 150 to 230 °C, more preferably 170 to 200 °C.
- the duration of heating will depend on the temperature used but is typically in the range of 10 to 40 seconds, with a duration of 20 to 30 seconds being preferred.
- This heat stabilisation process can be carried out by a variety of methods, including flat and vertical configurations and either "off-line” as a separate process step or "in-line” as a continuation of the film manufacturing process. Film thus processed will exhibit a smaller thermal shrinkage than that produced in the absence of such post heat-setting relaxation.
- the film may further comprise any other additive conventionally employed in the manufacture of polyester films.
- agents such as anti-oxidants, UV-absorbers, hydrolysis stabilisers, cross-linking agents, dyes, fillers, pigments, voiding agents, lubricants, radical scavengers, thermal stabilisers, flame retardants and inhibitors, antiblocking agents, surface active agents, slip aids, gloss improvers, prodegradents, viscosity modifiers and dispersion stabilisers may be incorporated as appropriate.
- agents such as anti-oxidants, UV-absorbers, hydrolysis stabilisers, cross-linking agents, dyes, fillers, pigments, voiding agents, lubricants, radical scavengers, thermal stabilisers, flame retardants and inhibitors, antiblocking agents, surface active agents, slip aids, gloss improvers, prodegradents, viscosity modifiers and dispersion stabilisers may be incorporated as appropriate.
- Such components may be introduced into the polymer in
- the films may, in particular, comprise a particulate filler which can improve handling and windability during manufacture, and can be used to modulate optical properties.
- the particulate filler may, for example, be a particulate inorganic filler (e.g.
- metal or metalloid oxides such as alumina, titania, talc and silica (especially precipitated or diatomaceous silica and silica gels), calcined china clay and alkaline metal salts, such as the carbonates and sulphates of calcium and barium).
- the thickness of the film can be in the range of from about 1 to about 500 ⁇ , typically no more than about 250 ⁇ , and typically no more than about 150 ⁇ .
- the thickness of the multilayer film is suitably in the range of from about 1 to about 10 ⁇ , more preferably from about 2 to about 10 ⁇ , more preferably from about 2 to about 7 ⁇ , more preferably from about 3 to about 7 ⁇ , and in one embodiment from about 4 to about 6 ⁇ .
- the thickness of the multilayer film is typically in the range of from about 5 to about 350 ⁇ , preferably no more than about 250 ⁇ , and in one embodiment no more than about 100 ⁇ , and in a further embodiment no more than about 50 ⁇ , and typically at least 12 ⁇ , more typically at least about 20 ⁇ .
- an electronic or optoelectronic device comprising the film (particularly the biaxially oriented film) described herein, particularly electronic or opto-electronic devices such as electroluminescent (EL) display devices (particularly organic light emitting display (OLED) devices), electrophoretic displays (e-paper), photovoltaic (PV) cells and semiconductor devices (such as organic field effect transistors, thin film transistors and integrated circuits generally), particularly flexible such devices.
- EL electroluminescent
- OLED organic light emitting display
- e-paper electrophoretic displays
- PV photovoltaic
- semiconductor devices such as organic field effect transistors, thin film transistors and integrated circuits generally
- the magnetic recording medium includes, for example, linear track system data storage tapes such as QIC or DLT, and, SDLT or LTO of a further higher capacity type.
- the dimensional change of the base film due to the temperature/humidity change is small, and so a magnetic recording medium suitable to high density and high capacity causing less track deviation can be provided even when the track pitch is narrowed in order to ensure the high capacity of the tape.
- the sample (4-6 mg) was heated from 20°C to 300°C at a rate of 20°C/min, held at 300°C for 5 minutes, and then cooled to 20°C at a rate of 20°C/min, and then heated from 20°C to 350°C at 10°C/min.
- the thermal properties were recorded on the second heating scan.
- T g was taken as the extrapolated onset temperature of the glass transition observed on the DSC scan (heat flow (W/g) against temperature (°C)), as described in ASTM E1356-98.
- T cc and T m were taken from the DSC scan as the temperature at which peak heat flow was observed in the respective transitions.
- AH m is the theoretical enthalpy of fusion of a 100% crystalline PET polymer (140 J/g) as defined in the literature (B. Wunderlich, Macromolecular Physics, Academic Press, New York, (1976)).
- the degree of crystallinity is measured for samples which have been annealed at 200°C for 2 hours.
- the annealing of the sample was conducted during a DSC heating cycle.
- the full heating cycle for these crystallinity measurements was as follows:
- the thermal properties were recorded on the final heating scan.
- Inherent viscosity (ii) Inherent viscosity (r
- Tlinh ln[(t 2 /ti)/c]
- 4,4'-biphthalic dianhydride (5.65 g, 19.20 mmol), ethanolamine (2.4 ml, 39.37 mmol), DMAc (40 ml) and toluene (35 ml) were charged to a 250 ml round bottom flask and heated to 130 °C overnight.
- Dean-Stark apparatus was used to azeotropically distill off the water by-product.
- the hot reaction mixture was then added to water (-400 ml) upon which a white precipitate formed. This was then stirred for 6 hours, filtered, washed with water (2 x 40 ml) and MeOH (2 x 40 ml) and dried in a vacuum oven at 100 °C overnight.
- Example 2 Synthesis of a copolymer of PET containing 5 mol% of monomer 1
- Example 2 The procedure of Example 2 was repeated in a similar manner to synthesise copolymers of PET containing about 25mol% (Example 3) and about 42m ol% (Example 4) of monomer 1.
- the copolymers were analysed by MR and found to contain 24.99mol% and 42.1 1mol% of monomer 1, respectively.
- the (non-annealed) polymer samples of both Examples 3 and 4 were amorphous.
- control sample is pure PET, synthesised in accordance with the procedure described for Example 2 but without the inclusion of N,N'-bis-(2-hydroxyethyl)-4,4'- biphthalimide, and with a 1-hour reaction time.
- the polymer of Example 2 was then melt-pressed to form a thin, tough film (approx. 0.5 mm thick; approx. 2-3mm wide and approx. 2 cm long) which could be oriented by hot- drawing to at least six times its original extension.
- Biaxially oriented films were manufactured from the copolymers of Examples 3 and 4, and from the PET homopolymer control.
- Each polymer was fed to an extruder (single screw; screw speed approx. 80rpm) at a temperature in the range of 275 to 300°C.
- a cast film was produced, which was electrostatically pinned and threaded around the casting drum and over the top of the forward draw onto a scrap winder. Once settled, cast samples are collected at a range of casting drum speeds (2, 3 and 5 m ⁇ min) to give a range of thicknesses.
- the cast films are subsequently drawn using a Long Stretcher (supplied by T.M. Long Co., Somerville, New Jersey).
- the Long Sretcher comprises a hydraulically operated stretching head mounted inside a heated oven with a liftable lid.
- the operation of the stretching mechanism is based upon the relative motion of two pairs of draw bars (one fixed and one moveable, mounted normally to one another).
- the draw bars are attached to hydraulic rams which control the amount (draw ratio) and speed (draw rate) of the imposed stretching.
- On each draw bar are mounted pneumatic sample clips attached to a pantograph system.
- a sample loading system is used to position samples within the pneumatic clips.
- a cast sample cut to a specific size (l l . lxl 1.1cm) is located symmetrically on a vacuum plate attached to the end of an arm. The arm is run into the oven and the sample lowered so that it is between the clips. The clips are closed using nitrogen pressure to hold the film and the loading arm withdrawn.
- the oven is heated to a specified temperature by two plate-heaters.
- the lid is lowered and air heaters rapidly bring the sample up to a specified temperature.
- After a suitable preheat time (30 seconds), the draw is manually initiated by the operator.
- a draw rate of approximately 2.54cm/second was used.
- Simultaneous biaxial draw in perpendicular directions is used in these examples.
- Table 2 The processing conditions are given in Table 2 below.
- the films produced on the Long Stretcher are then crystallised using the Laboratory Crystallisation Rig and held at specified temperatures for specified times (as presented in Tables 3, 4 and 5 below).
- samples are clamped in a frame which is dropped pneumatically and held between heated platens for a specific time before being rapidly quenched by dropping into iced water.
- the density of the film samples was measured using a calibrated calcium nitrate/water density column controlled at a constant 23°C using a water jacket. Crystallinity of all film samples was calculated using known values for PET density and crystallinity, on the basis of the following literature data:
- the PET control film exhibited a crystallinity of 14.94% for the non-heat-set biaxially oriented film, and this increased to about 50% after additional crystallisation during heat-setting. At 240°C the film samples started to melt during crystallisation. Table 4: PETcoBPDI-25 film
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Abstract
A copolyester comprising repeating units derived from an aliphatic glycol, terephthalic acid, and the monomer of formula (I): wherein n = 2, 3 or 4, wherein comonomer (I) constitutes a proportion of the glycol fraction of the copolyester, and wherein the comonomer (I) is present in amounts of greater than 10 mol% of the glycol fraction of the copolyester, and films and articles made therefrom.
Description
COPOLYESTERIMIDES OF POLY(ALKYLENE TEREPHTHAL ATE) S HAVING HIGH TG AND HIGH MONOMER CONTENT AND FILM MADE THEREFROM
The present invention is concerned with novel polyesters and films made therefrom, and methods for their synthesis. In particular, the present invention is concerned with novel copolymers of poly(alkylene terephthalate)s, particularly poly(ethylene terephthalate) (PET), which exhibit improved heat-resistance and thermo-mechanical stability.
The glass transition temperature (Tg), crystalline melting point (Tm) and degree of crystallinity are key parameters in determining the thermo-mechanical properties of polyesters. Previous studies have succeeded in increasing the Tg of thermoplastic polymers, primarily homopolymers, but this has typically been accompanied by a corresponding increase in the Tm. Such increases in Tm can be disadvantageous because a thermoplastic polymer should also remain melt-processible (for instance in an extruder), and should preferably remain so under economic conditions (for instance, below about 320°C, preferably below about 300°C, which allows the use of conventional extrusion equipment). At higher processing temperatures, polymer extrusion requires expensive specialist equipment and a great deal of energy, and typically also results in degradation products. The melt-processing temperature should be well below (for instance, at least about 20°C below) the decomposition temperature of the polymer. In some cases, comonomers have been introduced into polymers in order to increase Tg while retaining Tm, but also resulting in convergence of the decomposition temperature and the Tm, which leads to the production of degradation products in the melt. Many attempts have also been made to enhance the glass transition temperature of polyesters by the introduction of more rigid comonomers. However, such comonomers also disrupt the packing of the polymer chains in the crystal lattice, so that while the Tg increases, the Tm and degree of crystallinity typically both decrease as the proportion of comonomer increases, leading ultimately to amorphous materials. In order to fabricate articles from polymeric materials, it is often critical that the polymer exhibit crystallinity to achieve articles with acceptable thermo-mechanical properties.
PET is a semi-crystalline copolymer having a glass transition temperature (Tg) of 78°C and a crystalline melting point of (Tm) of 260°C. Many attempts have been made to enhance the Tg of PET by the introduction of more rigid comonomers. Poly ether ether ketone (PEEK) is one of the few examples of a high Tg (approximately 143-146°C) semi-crystalline thermoplastic polymer, and has been used successfully in engineering and biomedical applications. However, PEEK is suitable only for certain types of articles; for instance, it is not suitable for the manufacture of biaxially oriented films. PEEK is also very expensive and has a high crystalline melting point (approximately 350°C).
An object of the present invention is to provide polyesters which exhibit improved heat- resistance and thermo-mechanical stability. A further object of the present invention is to provide a thermoplastic polymer with high or increased Tg but without increasing Tm to a point where the polymer is no longer melt-processible under economic conditions (i.e. the polymer should remain melt-processible below about 320°C, preferably below about 300°C). A further object of the present invention is to provide semi-crystalline polyesters which exhibit high Tg as well as high Tm. A further object of the present invention is to increase the Tg of a polyester without significantly decreasing its Tm and/or its degree of crystallinity, and preferably without significantly decreasing its decomposition temperature.
As used herein, the term "without significantly decreasing the Tm" means that the Tm decreases by no more than 10%, preferably no more than 5%. As used herein, the term "without significantly decreasing the degree of crystallinity", means that the polyester retains a degree of crystallinity which is commercially useful, preferably in the range of from about 10% to about 60%, preferably from about 20 to about 50%. A further object of the present invention is to provide a copolyester having a Tg which is higher than the corresponding base polyester, without significantly decreasing its Tm
and/or its degree of crystallinity and preferably without significantly decreasing its decomposition temperature.
A further object of the present invention is to provide a comonomer suitable for partial substitution of a monomer in a conventional polyester which increases the Tg of said polyester without significantly decreasing its Tm and/or its degree of crystallinity, and preferably without significantly decreasing its decomposition temperature.
While the objects of the invention do not exclude an increase in Tm, any increase in Tm must not be so large that melt-processing becomes uneconomical and that the Tm and decomposition temperature converge.
The above-mentioned objects of the present invention have, as their underlying objective, the provision of copolyester articles made from a copolyester having a Tg which is higher than the corresponding base polyester, without significantly increasing the Tm to a point where the polymer is no longer melt-processible under economic conditions, particularly without significantly decreasing the degree of crystallinity of the copolyester article (in order to achieve acceptable thermo-mechanical properties), and preferably also without significantly decreasing the decomposition temperature of the copolyester.
As used herein, the term "copolyester" refers to a polymer which comprises ester linkages and which is derived from three or more types of comonomers. As used herein, the term "corresponding base polyester" refers to a polymer which comprises ester linkages and which is derived from two types of comonomers comprising ester-forming functionalities, and which serves as a comparator for a copolyester which is derived from comonomers comprising the comonomers of the corresponding base polyester. A comonomer comprising ester-forming functionalities preferably possesses two ester- forming functionalities.
As used herein, the term "semi-crystalline" is intended to mean a degree of crystallinity of at least about 5% measured according to the test described herein, preferably at least about 10%, preferably at least about 15%, and preferably at least about 20%. Accordingly, the present invention provides a copolyester comprising repeating units derived from an aliphatic glycol, terephthalic acid, and the monomer of formula (I):
(I)
wherein n = 2, 3 or 4, and preferably wherein n = 2, and wherein the comonomer (I) is present in amounts of greater than 10 mol% of the glycol fraction of the copolyester.
Surprisingly, the present inventors have now found that incorporation of the specific comonomer (I) into a terephthalate polyester not only increases the Tg substantially but does so without significant detriment to the crystallinity of articles made therefrom. This is achieved without significantly increasing the Tm. The copolyesters according to the present invention are thermoplastic. Copolyesters and articles made therefrom as described herein exhibit semi-crystalline properties. The copolyesters according to the present invention can be readily obtained at high molecular weight. The copolyesters according to the present invention can be melt-processed below 320°C (preferably below 300°C) into tough, high strength articles. The copolyesters are also referred to herein as co(polyester-imide)s.
The comonomer (I) constitutes a proportion of the glycol fraction of the copolyester. Preferably, the comonomer (I) is present in amounts of no more than about 50 mol% of the glycol fraction of the copolyester, preferably no more than about 40 mol%, preferably no more than about 30 mol%, preferably no more than about 25 mol%, and in one embodiment no more than about 20 mol%, and in a further embodiment no more than about 15 mol%.
The aliphatic glycol is preferably selected from C2, C3 or C4 aliphatic diols, more preferably from ethylene glycol, 1,3-propanediol and 1,4-butanediol, more preferably from ethylene glycol and 1,4-butanediol, and is most preferably ethylene glycol. The number of carbon atoms in the aliphatic glycol may be the same or different as the number (n) in the comonomer (I), but it is most preferably the same in order to retain crystallinity, particularly in order to retain crystallinity with increasing amounts of comonomer. Thus, the aliphatic glycol preferably has the formula HO(CH2)mOH, where m = n.
In one embodiment, the aliphatic glycol is 1,4-butanediol and n = 4. In a preferred embodiment, the aliphatic glycol is ethylene glycol and n = 2.
The co olyesters can be described by formula (II) below:
(Π)
wherein:
n is as defined for formula (I);
the group X is the carbon chain of said aliphatic glycol;
and p and q are the molar fractions of the aliphatic glycol-containing repeating ester units and the monomer (I)-containing repeating ester units, respectively, i.e. q is greater than 10 and no more than 50, and p = 100-q . In one embodiment, the copolyester may contain more than one type of aliphatic glycol, and/or more than one type of monomer of formula (I). Preferably, however, the copolyester comprises a single type of aliphatic glycol. Preferably, the copolyester comprises a single type of monomer of formula (I). Preferably, the copolyester comprises a single type of aliphatic glycol, and a single type of monomer of formula (I).
The copolyesters may contain minor amounts of other glycols and in a preferred embodiment such other glycols constitute no more than 10 mol%, preferably no more than 5 mol%, preferably no more than 1 mol% of the total glycol fraction, but in order to maximise performance it is preferred that the glycol fraction consists of comonomer (I) and said aliphatic glycol(s) described above.
The copolyesters of the present invention may contain minor amounts (preferably no more than 10 mol%, preferably no more than 5 mol%, preferably no more than 1 mol% of the total acid fraction) of one or more other dicarboxylic acids (preferably aromatic dicarboxylic acids), for instance including naphthalene-dicarboxylic acid (such as 2,6- naphthalenedicarboxylic acid), isophthalic acid, 4,4'-diphenyldicarboxylic acid, 1,4- cyclohexane dimethanol and 1,6-hexanediol. Where the copolyesters of the present invention contain minor amounts of an aromatic dicarboxylic acid other than terephthalic acid, in one embodiment said aromatic dicarboxylic acid other than terephthalic acid is selected from aromatic dicarboxylic acids other than naphthalene-dicarboxylic acids. Preferably, however, the acid fraction of the copolyesters of the present invention consists of terephthalic acid.
Thus, the copolyester of the present invention preferably contains only aliphatic glycol, terephthalic acid and the monomer of formula (I) defined hereinabove.
The copolyesters of the present invention can be synthesised according to conventional techniques for the manufacture of polyester materials by condensation or ester interchange, typically at temperatures up to about 310°C. Polycondensation may include a solid phase polymerisation stage. The solid phase polymerisation may be carried out in a fluidised bed, e.g. fluidised with nitrogen, or in a vacuum fluidised bed, using a rotary vacuum drier. Suitable solid phase polymerisation techniques are disclosed in, for example, EP-A-0419400 the disclosure of which is incorporated herein by reference. In one embodiment, the aliphatic glycol is reacted with the terephthalic acid to form a bis(hydroxyalkyl)-terephthalate, which is then reacted with the monomer (I) in the desired molar ratios under conditions of elevated temperature and pressure in the presence of a catalyst, as exemplified in Scheme (1) below.
A method of synthesis for the compound of formula (I) comprises the step of contacting 4,4'-biphthalic anhydride (also known as 3,3',4,4'-biphenyl tetracarboxylic dianhydride (BPDA)) and an alkanolamine of formula HO(CH2)n H2 (wherein n = 2, 3 or 4) in a solvent and heating the mixture (preferably to a temperature in the range of from about 110 to about 140°C, for a period in the range of from about 6 to about 15 hours). Suitable solvents include mixtures of DMAc and toluene. Water by-product is suitably removed from the reaction zone during the course of the reaction, for instance by azeotropic distillation. Further steps in the synthetic and isolation procedure typically comprise:
(i) after the heating step, adding the hot reaction mixture to an approximately equal volume of water, which is then stirred, filtered, washed (for instance with water and then with methanol) and dried;
(ii) boiling the dried solid material in water to remove residual solvent, then filtering hot, washing with methanol, and dried.
The copolyesters of the present invention are suitable for use in applications requiring improved heat-resistance and/or thermo-mechanical performance. The copolyesters of the present invention can be used in film form or fibre form or in moulding compositions. Surprisingly, the present inventors have found that incorporation of the specific co-monomer (I) into a terephthalate polyester not only increases the Tg substantially but does so without significant detriment to the crystallinity of articles made therefrom. This is achieved without significantly increasing the Tm. Articles made from the copolyesters described herein exhibit semi-crystalline properties. Such articles (particularly oriented films) comprise the copolyesters of the present invention wherein the comonomer (I) is present in amounts of from greater than 10 mol% to no more than about 50 mol% of the glycol fraction of the copolyester, as described hereinabove, and in a preferred embodiment from about 20 mol% to about 45 mol%.
According to a further aspect of the invention, there is provided a fibre or moulding composition or moulded article comprising a copolyester comprising repeating units derived from an aliphatic glycol, terephthalic acid, and the monomer of formula (I) defined hereinabove, wherein the comonomer (I) is present in amounts of greater than 10
mol% of the glycol fraction of the copolyester. The fibre, moulding composition or moulded article may be produced according to conventional techniques in the art.
The copolyesters of the present invention are also suitable for film manufacture. Biaxially oriented films in particular are useful as base films for magnetic recording media, particularly magnetic recording media required to exhibit reduced track deviation in order to permit narrow but stable track pitch and allow recording of higher density or capacity of information, for instance magnetic recording media suitable as server backup/data storage, such as the LTO (Linear Tape Open) format. The copolyesters of the present invention are also suitable for the manufacture of film (preferably biaxially oriented film) for use in electronic and opto-electronic devices (particularly wherein the film is required to be flexible) where thermo-mechanically stable backplanes are critical during fabrication of the finished product, for instance in the manufacture of electroluminescent (EL) display devices (particularly organic light emitting display (OLED) devices), electrophoretic displays (e-paper), photovoltaic (PV) cells and semiconductor devices (such as organic field effect transistors, thin film transistors and integrated circuits generally), particularly flexible such devices.
According to a further aspect of the present invention, there is provided a film comprising a copolyester comprising repeating units derived from an aliphatic glycol, terephthalic acid, and the monomer of formula (I) defined hereinabove, wherein the comonomer (I) is present in amounts of greater than 10 mol% of the glycol fraction of the copolyester. The film is preferably an oriented film, preferably a biaxially oriented film. Said copolyester is preferably the major component of the film, and makes up at least 50%, preferably at least 65%, preferably at least 80%, preferably at least 90%, and preferably at least 95% by weight of the total weight of the film. Said copolyester is suitably the only polyester used in the film.
Formation of the film may be effected by conventional extrusion techniques well-known in the art. In general terms the process comprises the steps of extruding a layer of molten polymer at a temperature within an appropriate temperature range, for instance in a range of from about 280 to about 300°C, quenching the extrudate and orienting the quenched extrudate. Orientation may be effected by any process known in the art for producing an
oriented film, for example a tubular or flat film process. Biaxial orientation is effected by drawing in two mutually perpendicular directions in the plane of the film to achieve a satisfactory combination of mechanical and physical properties. In a tubular process, simultaneous biaxial orientation may be effected by extruding a thermoplastics polyester tube which is subsequently quenched, reheated and then expanded by internal gas pressure to induce transverse orientation, and withdrawn at a rate which will induce longitudinal orientation. In the preferred flat film process, the film-forming polyester is extruded through a slot die and rapidly quenched upon a chilled casting drum to ensure that the polyester is quenched to the amorphous state. Orientation is then effected by stretching the quenched extrudate in at least one direction at a temperature above the glass transition temperature of the polyester. Sequential orientation may be effected by stretching a flat, quenched extrudate firstly in one direction, usually the longitudinal direction, i.e. the forward direction through the film stretching machine, and then in the transverse direction. Forward stretching of the extrudate is conveniently effected over a set of rotating rolls or between two pairs of nip rolls, transverse stretching then being effected in a stenter apparatus. Stretching is generally effected so that the dimension of the oriented film is from 2 to 5, more preferably 2.5 to 4.5 times its original dimension in the or each direction of stretching. Typically, stretching is effected at temperatures higher than the Tg of the polyester, preferably about 15 °C higher than the Tg. Greater draw ratios (for example, up to about 8 times) may be used if orientation in only one direction is required. It is not necessary to stretch equally in the machine and transverse directions although this is preferred if balanced properties are desired.
A stretched film may be, and preferably is, dimensionally stabilised by heat-setting under dimensional support at a temperature above the glass transition temperature of the polyester but below the melting temperature thereof, to induce the desired crystallisation of the polyester. During the heat-setting, a small amount of dimensional relaxation may be performed in the transverse direction (TD) by a procedure known as "toe-in". Toe-in can involve dimensional shrinkage of the order 2 to 4% but an analogous dimensional relaxation in the process or machine direction (MD) is difficult to achieve since low line tensions are required and film control and winding becomes problematic. The actual heat-set temperature and time will vary depending on the composition of the film and its desired final thermal shrinkage but should not be selected so as to substantially degrade
the toughness properties of the film such as tear resistance. Within these constraints, a heat set temperature of about 150 to 245°C is generally desirable, preferably no higher than about 200°C, preferably no higher than about 190°C, preferably less than 180°C. After heat-setting the film is typically quenched rapidly in order induce the desired crystallinity of the polyester.
In one embodiment, the film may be further stabilized through use of an in-line relaxation stage. Alternatively the relaxation treatment can be performed off-line. In this additional step, the film is heated at a temperature lower than that of the heat-setting stage, and with a much reduced MD and TD tension. The tension experienced by the film is a low tension and typically less than 5 kg/m, preferably less than 3.5 kg/m, more preferably in the range of from 1 to about 2.5 kg/m, and typically in the range of 1.5 to 2 kg/m of film width. For a relaxation process which controls the film speed, the reduction in film speed (and therefore the strain relaxation) is typically in the range 0 to 2.5%, preferably 0.5 to 2.0%. There is no increase in the transverse dimension of the film during the heat-stabilisation step. The temperature to be used for the heat stabilisation step can vary depending on the desired combination of properties from the final film, with a higher temperature giving better, i.e. lower, residual shrinkage properties. A temperature of 135 to 250°C is generally desirable, preferably 150 to 230 °C, more preferably 170 to 200 °C. The duration of heating will depend on the temperature used but is typically in the range of 10 to 40 seconds, with a duration of 20 to 30 seconds being preferred. This heat stabilisation process can be carried out by a variety of methods, including flat and vertical configurations and either "off-line" as a separate process step or "in-line" as a continuation of the film manufacturing process. Film thus processed will exhibit a smaller thermal shrinkage than that produced in the absence of such post heat-setting relaxation.
The film may further comprise any other additive conventionally employed in the manufacture of polyester films. Thus, agents such as anti-oxidants, UV-absorbers, hydrolysis stabilisers, cross-linking agents, dyes, fillers, pigments, voiding agents, lubricants, radical scavengers, thermal stabilisers, flame retardants and inhibitors, antiblocking agents, surface active agents, slip aids, gloss improvers, prodegradents, viscosity modifiers and dispersion stabilisers may be incorporated as appropriate. Such
components may be introduced into the polymer in a conventional manner. For example, by mixing with the monomeric reactants from which the film-forming polymer is derived, or the components may be mixed with the polymer by tumble or dry blending or by compounding in an extruder, followed by cooling and, usually, comminution into granules or chips. Masterbatching technology may also be employed. The film may, in particular, comprise a particulate filler which can improve handling and windability during manufacture, and can be used to modulate optical properties. The particulate filler may, for example, be a particulate inorganic filler (e.g. metal or metalloid oxides, such as alumina, titania, talc and silica (especially precipitated or diatomaceous silica and silica gels), calcined china clay and alkaline metal salts, such as the carbonates and sulphates of calcium and barium).
The thickness of the film can be in the range of from about 1 to about 500 μπι, typically no more than about 250 μπι, and typically no more than about 150 μπι. Particularly where the film of the present invention is for use in magnetic recording media, the thickness of the multilayer film is suitably in the range of from about 1 to about 10 μπι, more preferably from about 2 to about 10 μηι, more preferably from about 2 to about 7 μηι, more preferably from about 3 to about 7 μπι, and in one embodiment from about 4 to about 6 μπι. Where the film is to be used as a layer in electronic and display devices as described herein, the thickness of the multilayer film is typically in the range of from about 5 to about 350 μπι, preferably no more than about 250 μπι, and in one embodiment no more than about 100 μπι, and in a further embodiment no more than about 50 μπι, and typically at least 12μπι, more typically at least about 20 μπι. According to a further aspect of the invention, there is provided an electronic or optoelectronic device comprising the film (particularly the biaxially oriented film) described herein, particularly electronic or opto-electronic devices such as electroluminescent (EL) display devices (particularly organic light emitting display (OLED) devices), electrophoretic displays (e-paper), photovoltaic (PV) cells and semiconductor devices (such as organic field effect transistors, thin film transistors and integrated circuits generally), particularly flexible such devices.
According to a further aspect of the invention, there is provided a magnetic recording medium comprising the film (particularly the biaxially oriented film) described herein as a base film and further comprising a magnetic layer on one surface thereof. The magnetic recording medium includes, for example, linear track system data storage tapes such as QIC or DLT, and, SDLT or LTO of a further higher capacity type. The dimensional change of the base film due to the temperature/humidity change is small, and so a magnetic recording medium suitable to high density and high capacity causing less track deviation can be provided even when the track pitch is narrowed in order to ensure the high capacity of the tape.
The following test methods were used to characterise the properties of the novel compounds disclosed herein.
(i) Glass transition temperature (Tg); temperature of cold crystallisation (Tcc), crystalline melting point (Tm) and degree of crystallinity (Xc) were measured by differential scanning calorimetry (DSC) using a Universal V4.5A machine (TA Instruments) according to the following test method and otherwise according to the method described in ASTM E1356-98. The sample was maintained under an atmosphere of dry nitrogen for the duration of the scan (approx. 1.5 to 3 hours). The sample (4-6 mg) was heated from 20°C to 300°C at a rate of 20°C/min, held at 300°C for 5 minutes, and then cooled to 20°C at a rate of 20°C/min, and then heated from 20°C to 350°C at 10°C/min. The thermal properties were recorded on the second heating scan.
The value of Tg was taken as the extrapolated onset temperature of the glass transition observed on the DSC scan (heat flow (W/g) against temperature (°C)), as described in ASTM E1356-98.
The values of Tcc and Tm were taken from the DSC scan as the temperature at which peak heat flow was observed in the respective transitions.
The degree of crystallinity (Xc) was calculated according to the equation:
Xc = AHm/AHm °
wherein:
AHm = experimental enthalpy of fusion calculated from the integral of the melting endotherm;
AHm = theoretical enthalpy of fusion of the corresponding poly(alkylene- terephthalate) homopolymer (i.e. without the co-monomer of formula (I)) at 100 % crystallinity. Thus, for copoly esters of the present invention comprising repeating units derived from ethylene glycol, terephthalic acid and the co-monomer of formula (I), AHm is the theoretical enthalpy of fusion of a 100% crystalline PET polymer (140 J/g) as defined in the literature (B. Wunderlich, Macromolecular Physics, Academic Press, New York, (1976)).
Herein, the degree of crystallinity is measured for samples which have been annealed at 200°C for 2 hours. The annealing of the sample was conducted during a DSC heating cycle. The full heating cycle for these crystallinity measurements was as follows:
(i) Heated from 20 to 300°C at 20°C/min
(ii) Held at 300°C for 5 minutes
(iii) Cooled to 20°C at 20°C/min
(iv) Heated to 200°C at 20°C/min
(v) Held at 200°C for 120 min
(vi) Cooled to 20°C
(vii) Heated from 20 to 400°C at 10°C/min.
The thermal properties were recorded on the final heating scan.
(ii) Inherent viscosity (r|inh) was determined at 25 °C for 0.1 % w/v solutions of the polymer in CHCI3/TFA (2: 1) using a Schott-Gerate CT-52 auto-viscometer, with capillary No. 53103. Inherent viscosities were calculated as:
Tlinh = ln[(t2/ti)/c]
wherein:
r|inh = Inherent Viscosity (dL/g)
ti = Flow time of solvent (s)
t2 = Flow time of the polymer solution (s)
c = Concentration of the polymer (g/dL)
The invention is further illustrated by the following examples. It will be appreciated that the examples are for illustrative purposes only and are not intended to limit the invention
as described above. Modification of detail may be made without departing from scope of the invention.
EXAMPLES
A reaction scheme to prepare copolyesters of the present invention is in Scheme 1.
Scheme 1. Synthesis of comonomer 1 and its copolymerisation with bis(hydroxy ethyl terephthalate) to give a family of co(polyester-imide)s (2) (where z in Scheme 1 is the degree of polymerisation of the overall copolymer).
Example 1: Synthesis of N,N'-bis-(2-hydroxyethyl)-4,4 '-biphthalimide (monomer 1)
4,4'-biphthalic dianhydride (5.65 g, 19.20 mmol), ethanolamine (2.4 ml, 39.37 mmol), DMAc (40 ml) and toluene (35 ml) were charged to a 250 ml round bottom flask and heated to 130 °C overnight. Dean-Stark apparatus was used to azeotropically distill off the water by-product. The hot reaction mixture was then added to water (-400 ml) upon which a white precipitate formed. This was then stirred for 6 hours, filtered, washed with water (2 x 40 ml) and MeOH (2 x 40 ml) and dried in a vacuum oven at 100 °C overnight. Residual solvent was removed as the product was boiled in water (40 ml) for 4 hours then filtered hot, washed with MeOH (2 x 25 ml), filtered and dried in a vacuum oven at 80 °C overnight. The isolated product was a white powder. (6.21 g, 81 %), m.p. (DSC) 286 °C, 1H NMR (400 MHz, DMSO) δ (ppm) 8.22 (m, 4Hb+c), 7.97 (d, J = 8.16 Hz, 2Ha), 4.85 (t, J = 11.96 Hz, 2Hf), 3.67 (t, J = 11.28 Hz, 4Hd), 3.59 (m, 4Hf), 13C NMR (400 MHz, DMSO) 167.48 (C7+8), 144.00 (Ci), 137.17 (C6), 132.75 (C4), 131.42(C3), 123.53 (C5), 121.68 (C2), 57.90 (C9), 40.42 (C10), IR: 3445, 2944, 1763, 1684, 1384, 1011, 739 cm"1.
Example 2: Synthesis of a copolymer of PET containing 5 mol% of monomer 1
Bis-(2-hydroxyethyl)terephthalate (4.7513 g, 18.70 mmol), N,N'-bis-(2-hydroxyethyl)- 4,4'-biphthalimide (0.3743 g, 0.98 mmol) and Sb203 (1.5 mg, 5.1xl0"3 mmol) were charged to a Schlenk tube fitted with a rubber sealed stirrer guide and a glass stirrer rod. The reaction mixture was heated to 200°C over 30 minutes by use of a tube furnace under an inert nitrogen atmosphere and held at that temperature for 10 minutes. A stirring rate of 300 rpm was applied via a mechanical stirrer and the reaction mixture was heated to 290 °C over 45 min. A vacuum of 0.5 torr was applied and the temperature was maintained for 30 min where the melt became increasingly more viscous. After this time nitrogen was purged through the system, the stirrer was removed and the mixture was allowed to cool. The reaction tube was cut and the glass tubing containing the polymer was broken up. The polymer was dissolved away from the glass and the stirrer in a solution of CHC13/TFA (2: 1) (-50 ml) and the glass was filtered off. The pale yellow solution was concentrated in vacuo to -10-15 ml and added dropwise into MeOH (-120 ml). The white polymer beads were filtered, washed with MeOH (2 x 15 ml) and dried in a vacuum oven overnight. Tg = 87 °C, Tcc = 163 °C, Tm = 242 °C, AHm = 31 Jg"1,
ηίιΛ = 0.53 dLg"1. The product was fully soluble in chloroform/trifluoroacetic acid and in hexafluoropropan-2-ol.
Examples 3 and 4
The procedure of Example 2 was repeated in a similar manner to synthesise copolymers of PET containing about 25mol% (Example 3) and about 42m ol% (Example 4) of monomer 1. The copolymers were analysed by MR and found to contain 24.99mol% and 42.1 1mol% of monomer 1, respectively. The (non-annealed) polymer samples of both Examples 3 and 4 were amorphous.
The experimental data for the Examples are summarised in Table 1 below.
Table 1
n/m: not measured
The control sample is pure PET, synthesised in accordance with the procedure described for Example 2 but without the inclusion of N,N'-bis-(2-hydroxyethyl)-4,4'- biphthalimide, and with a 1-hour reaction time. The polymer of Example 2 was then melt-pressed to form a thin, tough film (approx. 0.5 mm thick; approx. 2-3mm wide and approx. 2 cm long) which could be oriented by hot- drawing to at least six times its original extension.
Biaxially oriented films were manufactured from the copolymers of Examples 3 and 4, and from the PET homopolymer control.
Each polymer was fed to an extruder (single screw; screw speed approx. 80rpm) at a temperature in the range of 275 to 300°C. A cast film was produced, which was
electrostatically pinned and threaded around the casting drum and over the top of the forward draw onto a scrap winder. Once settled, cast samples are collected at a range of casting drum speeds (2, 3 and 5 m\min) to give a range of thicknesses. The cast films are subsequently drawn using a Long Stretcher (supplied by T.M. Long Co., Somerville, New Jersey). The Long Sretcher comprises a hydraulically operated stretching head mounted inside a heated oven with a liftable lid. The operation of the stretching mechanism is based upon the relative motion of two pairs of draw bars (one fixed and one moveable, mounted normally to one another). The draw bars are attached to hydraulic rams which control the amount (draw ratio) and speed (draw rate) of the imposed stretching. On each draw bar are mounted pneumatic sample clips attached to a pantograph system. A sample loading system is used to position samples within the pneumatic clips. A cast sample cut to a specific size (l l . lxl 1.1cm) is located symmetrically on a vacuum plate attached to the end of an arm. The arm is run into the oven and the sample lowered so that it is between the clips. The clips are closed using nitrogen pressure to hold the film and the loading arm withdrawn. The oven is heated to a specified temperature by two plate-heaters. The lid is lowered and air heaters rapidly bring the sample up to a specified temperature. After a suitable preheat time (30 seconds), the draw is manually initiated by the operator. A draw rate of approximately 2.54cm/second was used. Simultaneous biaxial draw in perpendicular directions is used in these examples. The processing conditions are given in Table 2 below.
Table 2
The films produced on the Long Stretcher are then crystallised using the Laboratory Crystallisation Rig and held at specified temperatures for specified times (as presented in Tables 3, 4 and 5 below). In this equipment, samples are clamped in a frame which is dropped pneumatically and held between heated platens for a specific time before being rapidly quenched by dropping into iced water.
The density of the film samples was measured using a calibrated calcium nitrate/water density column controlled at a constant 23°C using a water jacket. Crystallinity of all film samples was calculated using known values for PET density and crystallinity, on the basis of the following literature data:
Density of 0% crystallinity PET = 1.335g/cm3
Density of 100% crystallinity PET = 1.455 g/cm3
The density and crystallinity results for the films are shown in Tables 3, 4 and 5 below. Table 3: PET control film
The PET control film exhibited a crystallinity of 14.94% for the non-heat-set biaxially oriented film, and this increased to about 50% after additional crystallisation during heat-setting. At 240°C the film samples started to melt during crystallisation.
Table 4: PETcoBPDI-25 film
Table 5: PETcoBPDI-42 film
The data in Tables 4 and 5 demonstrate that the copolymers of the present invention can, surprisingly, be manufactured into crystalline biaxially oriented films under typical stenter conditions used on a conventional film-line, and that films manufactured in this way exhibit excellent crystallinity.
With the higher amounts of comonomer present in Examples 3 and 4, the manufacture of biaxially oriented crystalline films is suitably conducted at relatively lower heat-set (crystallisation) temperatures in the stenter. The inventors also observe that heat-setting did not significantly increase the crystallinity in the biaxially oriented films, indicating that the crystallinity of these films is primarily induced by the stretching operations.
Claims
1. A copolyester comprising repeating units derived from an aliphatic glycol, terephthalic acid, and the monomer of formula (I):
(I)
wherein n = 2, 3 or 4, wherein comonomer (I) constitutes a proportion of the glycol fraction of the copolyester, and wherein the comonomer (I) is present in amounts of greater than 10 mol% of the glycol fraction of the copolyester.
2. A co olyester according to claim 1 which has formula (II):
wherein:
n = 2, 3 or 4;
the group X is the carbon chain of said aliphatic glycol; and
p and q are the molar fractions of the aliphatic glycol-containing repeating ester units and the monomer (I)-containing repeating ester units, respectively.
3. A copolyester according to any preceding claim wherein the monomer (I) is present in a range of no more than about 50 mol% of the glycol fraction of the copolyester.
4. A copolyester according to any preceding claim wherein the monomer (I) is present in a range of no more than about 20 mol% of the glycol fraction of the copolyester.
5. A copolyester according to any preceding claim wherein the aliphatic glycol is selected from C2, C3 or C4 aliphatic diols.
6. A copolyester according to any preceding claim wherein the aliphatic glycol is ethylene glycol.
7. A copolyester according to any preceding claim wherein the number of carbon atoms in the aliphatic glycol is the same as the number (n) in comonomer (I).
8. A copolyester according to any preceding claim wherein n = 2.
9. A polyester film, particularly an oriented film, particularly a biaxially oriented film comprising a copolyester according to any of claims 1 to 8.
10. A fibre or moulding composition or moulded article comprising a copolyester according to any of claims 1 to 8.
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Cited By (4)
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---|---|---|---|---|
US9422399B2 (en) | 2013-06-18 | 2016-08-23 | Dupont Teijin Films U.S. Limited Partnership | Copolyesterimides derived from N,N′-bis-(hydroxyalkyl)-3,3′,4,4′-diphenylsulfonetetracarboxylic diimide and films made therefrom |
US9637588B2 (en) | 2013-10-07 | 2017-05-02 | Dupont Teijin Films U.S. Limited Partnership | Copolyesterimides derived from aromatic dicarboxylic acids and aliphatic glycols and films made therefrom |
US10450411B2 (en) | 2014-06-20 | 2019-10-22 | Dupont Teijin Films U.S. Limited Partnership | Copolyesterimides comprising bis(2-hydroxyalkyl)-2,2′-(1,4-phenylene)bis(1,3-dioxoisoindoline-5-carboxylate) and articles made therefrom |
WO2020228260A1 (en) * | 2019-05-15 | 2020-11-19 | 宁波市医疗中心李惠利医院 | Medical copolyester and preparation method therefor |
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US9840590B2 (en) | 2013-06-18 | 2017-12-12 | Dupont Teijin Films U.S. Limited Partnership | Copolyesterimides derived from N,N′-bis-(hydroxyalkyl)-benzophenone-3,3′,4,4′-tetracarboxylic diimide and films made therefrom |
US10377862B2 (en) | 2013-06-18 | 2019-08-13 | Dupont Teijin Films U.S. Limited Partnership | Copolyesterimides derived from N,N′-bis-(hydroxyalkyl)-benzophenone-3,3′,4,4′-tetracarboxylic diimide and films made therefrom |
US9637588B2 (en) | 2013-10-07 | 2017-05-02 | Dupont Teijin Films U.S. Limited Partnership | Copolyesterimides derived from aromatic dicarboxylic acids and aliphatic glycols and films made therefrom |
US10450411B2 (en) | 2014-06-20 | 2019-10-22 | Dupont Teijin Films U.S. Limited Partnership | Copolyesterimides comprising bis(2-hydroxyalkyl)-2,2′-(1,4-phenylene)bis(1,3-dioxoisoindoline-5-carboxylate) and articles made therefrom |
WO2020228260A1 (en) * | 2019-05-15 | 2020-11-19 | 宁波市医疗中心李惠利医院 | Medical copolyester and preparation method therefor |
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