IR reflective elements made of impact-resistance plastic, and a process for their production
A process for the production of a translucent, IR-reflective plastic element, consisting entirely or at least in part of an impact-resistant, thermoplastic plastic, containing IR-reflective particles made of a lamellar-shaped carrier pigments coated with a metal oxide and the plastic element made therefrom.
1. An element, comprising:
a low viscosity thermoplastic plastic;
from 0.01 to 2 wt. % of IR-reflective particles comprising at least one lamellar-shaped carrier pigment coated with a metal oxide; and
an impact modified polymethyl methacrylate comprising a polymethyl methacrylate matrix and an agent to modify impact resistance;
wherein
a hail impact test rating of the element is at least 4J according to SIA V280, and
the element is obtained by a process comprising:
mixing the IR-reflective particles with a melt of the low-viscosity thermoplastic plastic at a temperature of at least 280° C. in a pressure-free, non-shearing zone of a twin-screw extruder to form a pre-mixture comprising from 5 to 40 wt. % of the IR-reflective particles;
extruding the pre-mixture;
converting the pre-mixture to a granulate or a melt;
mixing the granulate or melt of the premixture with a granulate or a melt of the impact modified polymethyl methacrylate to form a mixture;
extruding or co-extruding the mixture with another melt of a thermoplastic plastic into an extrudate having a desired shape; and
cooling said extrudate to obtain the element
wherein a melt viscosity of the low viscosity thermoplastic plastic is 20 to 80% lower than a melt viscosity of the matrix polymethyl methacrylate at a temperature at which the mixture is extruded or co-extruded.
2. The element according to claim 1 , wherein the hail impact test rating of the element is at least 4.5 J according to SIA V280.
3. The element according to claim 1 , wherein the hail impact test rating of the element is at least 5 J according to SIA V280.
4. The element according to claim 1 , wherein the wt. % of the IR-reflective particles is from 0.1 to 2 wt. %.
5. The element according to claim 1 , wherein the IR reflective pigment is a pearl-luster pigment having a diameter of from 20 to 100 μm.
6. The element according to claim 5 , wherein the carrier pigment is coated with an alternating layer of TiO 2 /Si O 2 /Ti O 2 .
7. The element according to claim 6 , wherein a total thickness of the alternating layer is from 150 to 300 nm.
8. The element according to claim 1 , further comprising a white pigment.
9. The plastic element according to claim 8 , wherein an amount of the white pigment is from 0.5 to 5 wt. %.
10. The element according to claim 1 , wherein the element is a flat sheet or a hollow element.
11. The element according to claim 1 , wherein the element is a multi-web plate.
12. The plastic element according to claim 1 , wherein the element is a double-web plate.
13. The element according to claim 1 , wherein the element is a co-extruded flange of a multi-web plate.
14. The element according to claim 1 , wherein the carrier pigment is coated with alternating layers of metal oxide.
15. The element according to claim 1 , wherein the carrier pigment is coated with alternating layers of metal oxide; and
a difference of the index of refraction between two alternating layers is at least 0.1.
16. The element according to claim 1 , wherein the carrier pigment is coated with a layer of metal oxide having a thickness of 90 to 150 nm.