Hydrophobic high heat optical acrylic copolymers
The invention relates to acrylic copolymers and terpolymers incorporating high Tg, hydrophobic (meth)acrylates that have high thermal stability and excellent optical properties. These copolymers are optically clear, and provide a copolymer having a Tg of 115-140 C, along with sufficiently high molecular weight. The copolymer is found to exhibit high heat resistance, high light transmission, low haze, low moisture uptake, excellent environmental stability, excellent high temperature thermal stability, and excellent mechanical properties, along with excellent UV resistance. The copolymer, or terpolymer may be used to form lighting pipes, thin wall parts, optical lenses, extruded films, (co-)extruded sheets/profiles, thermo-formable sheets, cast sheets, composites, etc.
1. A composition comprising a copolymer comprising:
a) from 0.1 to 10 weight percent monomer units comprising tert-butyl cyclohexyl methacrylate and 3,3,5-trimethylcyclohexyl(meth)acrylate, wherein said tert-butyl cyclohexyl methacrylate and 3,3,5-trimethylcyclohexyl(meth)acrylate monomer units have a trans/cis ratio of from 30/70 to 85/15;
b) at least 80 weight percent methylmethacrylate monomer units;
c) from 0 to 10 weight percent other monomer units copolymerizable with methylmethacrylate, wherein said other monomer units comprise from 0.01 to 10 weight percent of methacrylic acid;
wherein said copolymer has a Tg of from 116° C. to 140° C.
2. The composition of claim 1 , wherein said other monomer units further comprise from 0.01 to 25 weight percent of a high Tg comonomer, comprising at least one of acrylic acid, itaconic acid, alpha methyl styrene, maleic anhydride, maleimide, isobornyl methacrylate, norbornyl methacrylate, t-butyl methacrylate, cyclohexyl methacrylate, acrylamide and methacrylamide, and mixtures thereof.
3. The composition of claim 1 , further comprising 50 to 3500 ppm of antioxidant, based on the weight of the polymer solids.
4. The composition of claim 1 , wherein said copolymer has a weight average molecular weight of from 55,000 g/mole to 200,000 g/mole.
5. The composition of claim 1 , wherein said composition has a Total White Light Transmission (TWLT) of at least 91%, as measured on a 3.2 mm thick plaque, using ASTM method D1003.
6. The composition of claim 1 , wherein said copolymer has a refractive index of 1.47-1.50 at the wavelength of 589 nm.
7. The composition of claim 1 , further comprising from 5 to 95 weight percent of one or more compatible polymers based on the weight of the total polymer solids.
8. An article comprising the composition of claim 1 , wherein said article is a lighting pipe, thin wall parts, optical lens, extruded films, (co-)extruded sheet or profile, a thermo-formable sheet, a cast sheet, a composite, an LED/OLED optical component, a co-extruded profiles used in building and constructions or reflective signage.
9. The composition of claim 1 , wherein said copolymer has a melt flow rate measured at 230° C. under 3.8 kg from 1.4 g/10 minutes to 4.1 g/10 minutes.
10. The composition of claim 1 , wherein said composition has an optical haze of less than 2% as measured on a 3.2 mm thick plaque.
11. The composition of claim 1 , wherein said composition has a water absorption at 23° C. for 504 hours of from 1.229% to 1.400% by weight gain.
12. The composition of claim 1 , wherein said composition has an 85° C./85% RH high temperature/high humidity resistance without seeing crazing defects at the exposure time of from 240 hours to 470 hours.