The copolymer provides a low moisture adsorption and enhanced hydrophobicity.

The copolymers of the invention have excellent optical properties, with a TWLT of at least 89%, preferably at least 91% and more preferably at least 92%; and an optical haze of less than 5%, preferably less than 4% and most preferably less than 2.5%.

In addition to the above properties, the copolymer of the invention has excellent environmental stability, and excellent mechanical properties, along with excellent UV resistance.

Blends of the high Tg copolymers of the invention with other polymers, and especially acrylic polymers is anticipated by the invention. The high Tg copolymers or terpolymers of the invention (with the refractive index of 1.47-1.50) are optically and physically compatible with many typical optical acrylic copolymers (with a refractive index of about 1.49) in their mixtures and/or combinations through melt processing/solution blends. The copolymer of the invention would typically be blended with other acrylic resins at 5 to 95 weight percent, preferably 5 to 75 weight percent, and more preferably at 10 to 60 weight percent of the total polymer solids.

Blends with other compatible polymers, in all ratios, are also anticipated by this invention. Especially useful compatible polymers for a blend include, but are not limited to, other poly(methyl methacrylate) copolymers such as pMMA-EA and PMMA-MA, poly(styrene-acrylonitrile, SAN), polyvinylidene fluoride, copolymers of vinylidene fluoride and hexafluoropropene, and polylactic acid.

Uses

The copolymers of the invention are thermoplastic, and can be easily shaped into sheets, films, light pipe and lenses

The excellent impact resistance, heat stability, high molecular weight, moisture resistance and optical properties, makes the copolymer of the invention especially useful for forming automotive front lenses and automotive black trim, capped stock layers for building and construction, light pipes, solar back sheets, films for digital printing, protection films for reflective signage, diffusing sheets and films for LED lighting applications, optical lenses, optical films for electronics, thermo-formable sheets, injection molded parts, composites, and others.

High heat acrylic films of the invention may be used in LED/OLED displays. If cost-effective OLED technologies are widely used to replace LED/LCD technologies, the number of optical polarizers for OLED may be reduced.

Within this specification embodiments have been described in a way which enables a clear and concise specification to be written, but it is intended and will be appreciated that embodiments may be variously combined or separated without parting from the invention. For example, it will be appreciated that all preferred features described herein are applicable to all aspects of the invention described herein.

EXAMPLES

Testing Methods:

Injection molded samples: In the testing below involving injection molded samples or plaques, the plaque sample size was molded at 45 mm (width)×67 mm (length)×3.2 mm (thickness).

Melt flow rate (MFR) measurement: Instron Ceast MF30 equipment was used for polymers in melt flow rate measurements. The die temperature was controlled at 230° C. while the loading cell weight was at 3.8 kg. The dried pellets were used near 20° C. below the T_gover 8 hours.

Gel permeation chromatography (GPC): Waters Alliance 2695 and Waters Differential Refractometer 2410 were used to make polymer molecular weight measurements. Columns were based on two PL Gel mixed C columns and a guard column (7.8 mm I.D.×30 cm, 5 μm). THF (HPLC grade) was selected as a solvent. Temperature was controlled at 35° C. Ten poly(methyl methacrylate) standards were used in the calibration, ranging in M_p(peak molecular weight) from 550 to 1,677,000 g/mole.

Differential scanning calorimetry (DSC): The glass transition temperatures of acrylic polymers were measured at a heating rate of 10° C./minutes in N₂using TA instruments Q2000 DSC, during the second heating. The first heating was used to heat the sample to 170° C. at a heating rate of 10° C./minute, then, the sample was cooled down to 0° C. at a cooling rate of 10° C./minute. The sample weight was controlled at 5-10 mg.

Thermogravimetry (TGA): The thermal decomposition temperatures of acrylic polymers were measured at a heating rate of 10° C./minute in N₂using TA instruments Q5000 TGA. The sample weight was controlled at 5-10 mg. The samples were pre-dried under a vacuum oven at 100° C. overnight.

Total light transmission: The total light transmission was measured from film and/or plaque samples in a transmission mode using Perkin Elmer Lambda 950 with a 150 mm integrating sphere. The selected UV/Vis wavelength range was from 200 nm to 800 nm in UV/Vis region.

Haze: Optical haze of clear film and/or plaque samples was measured using BYK HazeGard Plus under ASTM method D1003.

Tensile strength and elongation: The tensile strength, modulus and elongation of the tensile bars was evaluated using Instron Model 4202 at the crosshead speed of 5 mm/minute using ASTM D638 method after being preconditioned at 23° C./48 hours. The tensile was at 6″ in length while the width was at 0.50″. The sample thickness was at 0.125″.

Refractive index: Refractive index of the polymer film was measured at three different wavelengths of 402 nm, 518 nm, and 636.5 nm using an optical prism coupler Metricon 2010 from Metricon Inc while the refractive index was calculated at a selected wavelength of 589 nm.

NMR: Samples were prepared by dissolving 200 mg of pellets in ˜4 ml CDCl₃in separate 10 mm NMR tubes for ¹³C NMR. The ¹H spectra were acquired on the Bruker AV III HD 500 (11.07 T) spectrometer with a 5 mm ¹H/¹⁹F/¹³C TXO probe at 25° C. before and after derivatization of MAA. The ¹³C spectra were acquired on the Bruker AV 400 (9.4 T) with a 10 mm BBO probe at 50° C.

Vicat softening temperatures: The samples were tested in Instron HV6M under 10N and 50N external forces using ASTM method D1525. The sample heating rate was controlled at the speed of 50° C./hour. The injection molded samples were annealed at ˜20 C below the Tg value for 16 hours and were kept in a desiccator oven before testing.

Water absorption: The injection molded samples were immersed in a D. I. water bath (23° C.) using ASTM method D570. The water absorption value was measured based on the weight gain while the sample surfaces were cleaned up with dry tissues.

Water haze: The injection molded plaque samples were immersed in a D. I. water bath at a selected temperature such as 60° C. The plaque sample size was molded at 45 mm (width)×67 mm (length)×3.2 mm (thickness). The water haze was measured with a BYK HazeGard after the water on the sample surfaces was cleaned up with dry tissues.

Notched Izod impact: Notched Izod impact strength or resistance was measured using ASTM D256 method with a 1.0 J impact hammer at 21° C./50% relative humidity. The notched Izod bars were injection-molded at the size of 10.2 mm (width)×100 mm (long)×3.2 mm (thick).

pMMA-Co-Tert-Butyl Cyclohexyl Methacrylate

Example 1 (Comparative, MW1805 with no impact modifier, Tg=119° C.). This example demonstrates the preparation of a high molecular weight copolymer of methyl methacrylate and tert-butyl cyclohexyl methacrylate, containing 73% trans/27% cis isomer ratio). 98,660 parts of methyl methacrylate and 1,000 parts of tert-butyl cyclohexyl methacrylate were charged in to a reaction vessel near 0° C. under N₂with a mechanical stirring speed of 100 rpm. In addition, Luperox® 531 (from Arkema) was used as an initiator at a level of 16 parts while 320 parts of n-dodecyl mercaptan (n-DDM from Aldrich) was used as a chain transfer agent. The polymerization reaction occurred at 160° C. for 6 hours. When the conversion reached near 50%, the residual monomers were removed through a venting system. The resulting polymer was passed through a single-screw extruder at a die temperature of 235° C. while the barrel temperatures were at 230-250° C. The melt stream went through a water bath before the pelletization. Then the polymer was pelletized into 3-4 mm long resin pellets and dried at 100° C. in a desiccator oven for 8 hours. The melt flow rate of the polymer was measured to be 2.1 g/10 minutes at 230° C. under 3.8 kg. The refractive index of the resulting polymer was measured at 1.491 at 589 nm.

The resulting polymer was confirmed using ¹H NMR to possess the composition of pMMA/tert-butyl cyclohexyl methacrylate (99.1/0.9 w/w). The syndiotacticity of the copolymer was determined at 50% from the chemical shift of 44.5 ppm using ¹³C NMR while the isotaticity and atacticity were measured at 8% and 42% from 45.5 ppm and 45.0 ppm. The glass transition temperature of the resin was measured to be 119° C. in N₂using DSC at the heating rate of 10° C./minute while the Vicat temperature was detected at 120° C. under 10N. The weight average molecular weight Mw of the resin was measured as being 105,000 g/mole using GPC along with a Mw/Mn (polydispersity) value of 1.8. The light transmission from a 3.2 mm plaque was measured to be 92.1% at 560 nm using Lambda 950 while the haze was measured to be 0.6% at 3.2 mm thickness, using a hazemeter (Haze Gard Plus from BYK). The tensile modulus of the test sample was 3.2 GPa while the tensile strength was 77 MPa, along with a tensile elongation of 9.5%. Water absorption was measured at 1.26% by weight gain percentage. Notched Izod impact strength was measured at 2.1 kJ/m².

Example 2 (MW1805 copolymer with 40% impact modifier with Tg=−117° C.). This example demonstrates the preparation of a high molecular weight copolymer of methyl methacrylate and tert-butyl cyclohexyl methacrylate (containing 73% trans/27% cis isomer) 99.1/0.9, along with a commercial core-shell acrylic impact modifier (40% MPD85T from Altuglas).

High Tg hydrophobic acrylic resins (Tg=119° C.) were compounded with core-shell impact modifiers having a particle size of 250-300 nm to form impact acrylic resins using a twin-screw extruder with the compounding speed of 50 lbs/hour at a die temperature of 230° C. UV stabilizer was also added into the formulation through pre-blending in the compounding. The compounded acrylic pellets were cut through a water bath at ambient temperature and dried at 100° C.

TABLE 1

Example 2
Suppliers
Amount (parts)

Acrylic copolymer
Arkema
5885

Core Shell Impact Modifier
Arkema
4000

Tinuvin ® 234
BASF
100

Irganox ® 1010
BASF
10

Irgafos ® 126
BASF
5

The melt flow rate of the resulting polymer was measured to be 0.8 g/10 minutes at 230° C. under 3.8 kg. The refractive index of the resulting polymer was measured at 1.491 at 589 nm. The glass transition temperature of the resin was measured to be 117° C. in N₂using DSC at the heating rate of 10° C./minute while the Vicat temperature was detected at 117° C. under 10N. The weight average molecular weight Mw of the resin was measured as being 105,000 g/mole using GPC along with a Mw/Mn (polydispersity) value of 1.8. The light transmission from a 180 um film was measured to be 92.2% at 560 nm using Lambda 950 while the haze was measured to be 2.5% at 3.2 mm using a hazemeter (Haze Gard Plus from BYK). The tensile modulus of the test sample was 2.0 GPa while the tensile strength was 47 MPa, along with a tensile elongation of 64%. Water absorption was measured at 1.45% by weight gain percentage. Notched Izod impact strength was measured at 4.5 kJ/m².

Example 3 (MW1806 copolymer with 40% impact modifier plus 5% Nanostrength® MS50 with Tg=˜116° C.). This example demonstrates the preparation of a high molecular weight copolymer MW1806 of methyl methacrylate and tert-butyl cyclohexyl methacrylate (containing 73% trans/27% cis isomer)-97.5/2.5, along with the commercial core-shell acrylic impact modifier (40% MPD85T from Altuglas) and 5% Nanostrength® MS50 (from Arkema). The weight average molecular weight Mw of the resin was measured as being 100,000 g/mole using GPC along with a Mw/Mn (polydispersity) value of 1.8.

TABLE 2

Example 3
Suppliers
Amount (parts)

Acrylic MW1806
Arkema
5485

Core Shell Impact Modifier
Arkema
4000

Nanostrength ® M550
Arkema
500

Irganox ® 1010
BASF
10

Irgafos ® 126
BASF
5

High Tg hydrophobic acrylic resins (Tg=118° C.) made at Arkema were compounded with core-shell impact modifiers having a particle size of 250-300 nm to form impact acrylic resins using a twin-screw extruder with the compounding speed of 50 lbs/hour at a die temperature of 210° C. UV stabilizer was also added into the formulation through pre-blending in the compounding. The compounded acrylic pellets were cut through a water bath at ambient temperature and dried at 100° C.

The melt flow rate of the resulting polymer was measured to be 0.9 g/10 minutes at 230° C. under 3.8 kg. The refractive index of the resulting polymer was measured at 1.491 at 589 nm. The glass transition temperature of the resin was measured to be 116° C. in N₂using DSC at the heating rate of 10° C./minute while the Vicat temperature was detected at 117° C. under 10N. The weight average molecular weight Mw of the resin was measured as being 100,000 g/mole using GPC along with a Mw/Mn (polydispersity) value of 1.8. The light transmission from a 170 um film was measured to be 92.3% at 560 nm using Lambda 950 while the haze was measured to be 2.4% at 3.2 mm thickness, using a hazemeter (Haze Gard Plus from BYK). The tensile modulus of the test sample was 1.8 GPa while the tensile strength was 43 MPa, along with a tensile elongation of 78%. Water absorption was measured at 1.43% by weight gain percentage. Notched Izod impact strength was measured at 3.4 kJ/m².

Example 4 (MW1806 copolymer with 40% impact modifier with Tg=˜116° C.). This example demonstrates the preparation of a high molecular weight copolymer MW1806 of methyl methacrylate and tert-butyl cyclohexyl methacrylate (SR218 from Sartomer, containing 73% trans/27% cis isomer)-97.5/2.5, along with the commercial core-shell acrylic impact modifier (40% MPD85T from Altuglas). The weight average molecular weight Mw of the resin was measured as being 100,000 g/mole using GPC along with a Mw/Mn (polydispersity) value of 1.8.

TABLE 3

Example 4
Suppliers
Amount (parts)

Acrylic MW1806
Arkema
5885

Core Shell Impact Modifier
Arkema
4000

Tinuvin ® 234
BASF
100

Irganox ® 1010
BASF
10

Irgafos ® 126
BASF
5

High Tg hydrophobic acrylic resins (MW1806, Tg=118° C.) made at Arkema were compounded with core-shell impact modifiers having a particle size of 250-300 nm to form impact acrylic resins using a twin-screw extruder with the compounding speed of 50 lbs/hour at a die temperature of 210° C. UV stabilizer was also added into the formulation through pre-blending in the compounding. The compounded acrylic pellets were cut through a water bath at ambient temperature and dried at 100° C.

The melt flow rate of the resulting polymer was measured to be 0.75 g/10 minutes at 230° C. under 3.8 kg. The refractive index of the resulting polymer was measured at 1.491 at 589 nm. The glass transition temperature of the resin was measured to be 116° C. in N₂using DSC at the heating rate of 10° C./minute while the Vicat temperature was detected at 118° C. under 10N.

The light transmission from a 180 um film was measured to be 92.3% at 560 nm using Lambda 950 while the haze was measured to be 2.5% at 3.2 mm thickness, using a hazemeter (Haze Gard Plus from BYK). The tensile modulus of the test sample was 1.8 GPa while the tensile strength was 46 MPa, along with a tensile elongation of 64%. Water absorption was measured at 1.44% by weight gain percentage. Notched Izod impact strength was measured at 4.4 kJ/m².

Example 5 (MW1806 copolymer with 45% impact modifier with Tg=˜115° C.). This example demonstrates the preparation of a high molecular weight copolymer MW1806 of methyl methacrylate and tert-butyl cyclohexyl methacrylate (SR218 from Sartomer, containing 73% trans/27% cis isomer)-97.5/2.5, along with the commercial core-shell acrylic impact modifier (45% MPD85T from Altuglas). The weight average molecular weight Mw of the resin was measured as being 100,000 g/mole using GPC along with a Mw/Mn (polydispersity) value of 1.8.

TABLE 4

Example 5
Suppliers
Amount (parts)

Acrylic MW1806
Arkema
5485

Core Shell Impact Modifier
Arkema
4500

Tinuvin ® 234
BASF
100

Irganox ® 1010
BASF
10

Irgafos ® 126
BASF
5

High Tg hydrophobic acrylic resins (MW1806, Tg=118° C.) made at Arkema were compounded with core-shell impact modifiers having a particle size of 250-300 nm to form impact acrylic resins using a twin-screw extruder with the compounding speed of 50 lbs/hour at a die temperature of 210° C. UV stabilizer was also added into the formulation through pre-blending in the compounding. The compounded acrylic pellets were cut through a water bath at ambient temperature and dried at 100° C.

The melt flow rate of the resulting polymer was measured to be 0.75 g/10 minutes at 230° C. under 3.8 kg. The refractive index of the resulting polymer was measured at 1.491 at 589 nm. The glass transition temperature of the resin was measured to be 115° C. in N₂using DSC at the heating rate of 10° C./minute while the Vicat temperature was detected at 116° C. under 10N.