Transparently coated polycarbonate component, its production and use

Abstract

The present invention relates to a multilayer construction containing a support or frame composed of a nontransparent polymer as layer c) and a transparent layer b) based on a thermoplastic polymer having a solar transmittance TDS of more than 20%, determined in accordance with ISO 13837:2008 at a layer thickness of 4 mm, and a siloxane-based protective layer a) which is applied to layer c) and layer b), wherein the siloxane layer a) is selectively postcured in selected regions by means of ultrashort-wave UV radiation, and to a method for selective surface treatment.

Claims

1. A multilayer construction, comprising: a) a siloxane-based protective layer; b) a transparent layer based on a thermoplastic polymer having a first surface and an opposing second surface, wherein the siloxane-based protective layer is disposed on the first surface; and c) a carrier or frame layer of a nontransparent polymer, disposed on and covering only a portion of the second surface, with a remaining portion not covered forming in plan view a region of the transparent layer having a solar transmittance T.sub.DS of greater than 20% (determined according to ISO 13837:2008 at a layer thickness of 4 mm), wherein the siloxane-based protective layer is post-cured using ultrashortwave UV radiation only in the region where the solar transmittance is greater than 20%, not overlapping with the carrier or frame in plan view.

2. The multilayer construction as claimed in claim 1, wherein the transparent layer is transparent in the visible wavelength range, meaning a light transmission of at least 80% (determined according to ASTM 1003:2011/ISO 13468:2006; reported in % and with illuminant D65/10°).

3. The multilayer construction as claimed in claim 1, wherein the transparent layer is transparent in the IR wavelength range meaning an average transmittance of at least 10% in the range between 750 nm and 2500 nm (determined according to ISO 13468-2:2006) and a light transmission less than 1% in the range between 380 nm and 780 nm (determined according to ISO 13468:2006, with illuminant D65/10°).

4. The multilayer construction as claimed in claim 1, wherein the thermoplastic polymer of the transparent layer is selected from at least one of the group consisting of polycarbonate, copolycarbonate, polyester carbonate, polystyrene, styrene copolymers, aromatic polyesters, polyethylene terephthalate, PET-cyclohexanedimethanol copolymer, polyethylene naphthalate, polybutylene terephthalate, polyamide, cyclic polyolefin, poly- or copolyacrylate, poly- or copolymethacrylate, poly- or copolymethyl methacrylate, polystyrene-acrylonitrile copolymer, and thermoplastic polyurethane.

5. The multilayer construction as claimed in claim 4, wherein the thermoplastic polymer of wherein the thermoplastic polymers of the transparent layer is selected from group consisting of polycarbonate, copolycarbonate, polyester carbonate, aromatic polyesters, and polymethylmethylacrylate.

6. The multilayer construction as claimed in claim 5, wherein the thermoplastic polymer of the transparent layer is polycarbonate.

7. The multilayer construction as claimed in claim 1, wherein the haze value of the transparent layer is less than 3% (measured according to ASTM 1003:2011).

8. The multilayer construction as claimed in claim 1, wherein the carrier or frame is along at least a portion of the peripheral edge of the second surface of the transparent layer.

9. The multilayer construction as claimed in claim 8, wherein the nontransparent polymer is a black polymer blend.

10. The multilayer construction as claimed in claim 9, wherein the black polymer blend is a polycarbonate blend.

11. The multilayer construction as claimed in claim 10, wherein the solar transmittance T.sub.DS of carrier or frame is less than 1%.

12. The multilayer construction as claimed in claim 1, wherein the ultrashortwave UV radiation comprises a radiation dose of 200 to 2100 mJ/cm.sup.2.

13. The multilayer construction as claimed in claim 1, wherein the siloxane-based layer contains organosilicon compounds of formula:
R.sub.nSiX.sub.4-n,  (I) and/or partial condensates thereof, wherein R is identical or different and represents a linear or branched, saturated or mono- or polyunsaturated or aromatic hydrocarbon X is identical or different and represents hydrolyzable groups or hydroxyl groups, and n is 0, 1, 2, or 3.

14. The multilayer construction as claimed in claim 13, wherein in formula (I) R represents saturated, branched or unbranched alkyl radicals having 1 to 20 carbon atoms and/or represents mono- or polyunsaturated branched or unbranched alkenyl radicals having 2 to 20 carbon atoms or aromatic groups having 6 to 12 carbon atoms, X represents a C1- to C4-alkoxy group and n is 1 or 2.

15. The multilayer construction as claimed in claim 1, wherein the protective layer comprises a topcoat layer a primer layer, wherein the primer layer is arranged between the topcoat layer and the transparent layer.

16. The multilayer construction as claimed in claim 15, wherein the topcoat layer comprises a polysiloxane-based topcoat comprising: i. at least one UV-absorber selected from the group consisting of benzophones, resorcinols, 2-(2-hydroxyphenol)benzotriazoles, hydroxphenyl-s-triazines, cyanoacrylates, and oxalanilides, and optionally a UV-inhibitor from the group of sterically hindered amines; and ii. at least one combination of an organomodified silane with a silica sol.

17. A process for making the multilayer construction as claimed in claim 1, wherein the transparent layer and carrier or frame are formed by a two-component injection molding process.

18. A process for treating the siloxane-based protective layer of the multilayer construction as claimed in claim 1, wherein ultrashortwave UV radiation is generated via excimer lamp or excimer laser.

19. A process for surface treating a multilayer construction, wherein the multilayer construction comprises: a) a siloxane-based protective layer; b) a transparent layer based on a thermoplastic polymer having a first surface and an opposing second surface, wherein the siloxane-based protective layer is disposed on the first surface; and c) a carrier or frame layer of a nontransparent polymer, disposed on and covering only a portion of the second surface, with a remaining portion not covered forming in plan view a region of the transparent layer having a solar transmittance T.sub.DS of greater than 20% (determined according to ISO 13837:2008 at a layer thickness of 4 mm), wherein the step of surface treating comprises post-curing the siloxane-based protective layer using ultrashortwave UV radiation only in the region where the solar transmittance is greater than 20%, not overlapping with the carrier or frame in plan view.

20. The process for surface treating a multilayer construction as claimed in claim 19, wherein the ultrashortwave UV radiation dose is in the range of 700 to 1400 mJ/cm.sup.2, generated by an excimer lamp or laser.

Description

(1) Layer c may be applied atop layer b) by processes known to those skilled in the art. Multicomponent injection molding, adhesive bonding or lacquering are suitable in particular.

(2) FIG. 1 describes a multilayer construction according to the invention provided with a siloxane-based layer a) which is applied above layer b) and an optional further layer c) and which is selectively post-cured in the region characterized by layer b). In this representation layer c) represents a frame.

(3) FIG. 2 represents a multilayer construction composed of 2 layers, wherein the siloxane-based layer a) in turn consists of a topcoat layer at and a primer layer a2, and the substrate layer b).

EXAMPLES

(4) The invention is hereinbelow more particularly described with reference to working examples, the methods of determination described here being used for all corresponding parameters in the present invention description unless otherwise stated.

(5) The experiments which follow relate to layer constructions composed of the layers a and b, wherein layer h is chosen such that T.sub.DS varies.

(6) Siloxane-Based Protective Layer a)

(7) Primer for layer a2: Silfort SHP470 FT 2050 is a primer having a solids content of 9% by weight, a specific density of 0.94-0.96 g/cm3 at 20° C. and a viscosity at 25° C. of 75 to 95 MPa s based on 1-methoxy-2-propanol as solvent. The product is available from Momentive Performance Materials GmbH, Leverkusen.

(8) Topcoat for layer a1: Silfort AS4700 is a thermally curing siloxane-based topcoat containing isopropanol, n-butanol and methanol as solvent, having a solids content of 25% by weight, a specific density of 0.92 g/cm3 at 20° C. and a viscosity measured at 25° C. of 3-7 MPa s. The product is available from Momentive Performance Materials GmbH, Leverkusen.

(9) Application was performed manually. The liquid primer or topcoat solution for forming the layers was poured over the sheet in the longitudinal direction starting from the upper edge of the small-scale part while simultaneously passing the starting point of the lacquer on the sheet from left to right over the sheet width. After a flash-off time of 30 minutes at 23° C. the coated sheets hanging vertically on a clamp were subsequently cured at 130° C. for 60 minutes. Following the application of the primer layer a2 the topcoat material was applied analogously as the topcoat layer at and, after a 30-minute flash-off time at 23° C., was cured at 130° C. for 60 minutes.

(10) The layer thickness of the layers a1 and a2 was determined by white light interferometry (for example by means of a white light interferometer from Eta Optic; ETA-SST).

(11) Substrate Layer b Substrate 1: Visually transparent sheet made of polycarbonate having an MVR of about 12 cm.sup.3/(10 min) measured at 300° C. at a loading of 1.2 kg (according to ISO 1133-1:2012-03) from Covestro Deutschland AG. Substrate 2: Visually nontransparent sheet made of polycarbonate from Covestro Deutschland AG having an MVR of about 12 cm.sup.3/10 min measured at 300° C. at a loading of L2 kg (according to ISO 1133-1:2012-03); based on bisphenol A and terminated with phenol. The material contains 0.1% by weight of Macrolex Green 5B (1,4-bis(tolylamino)anthraquinone; anthraquinone dye; Solvent Green 3; Color index 61565) from Lanxess AG and 0.1% by weight of Macrolex Violet 3R (anthraquinone dye; Solvent Violet 36; Color index number 61102) from Lanxess AG. The polycarbonate has a light transmission in the VIS range of the spectrum (380 to 780 nm) of about 0%. Substrate 3: Visually nontransparent sheet made of polycarbonate from Covestro Deutschland AG having an MVR of about 12 cm.sup.3/10 min measured at 300° C. at a loading of 1.2 kg (according to ISO 1133-1:2012-03); based on bisphenol A and terminated with phenol. The material contains 0.16% by weight of carbon black and has a light transmission in the VIS range of the spectrum (380 to 780 nm) of 0%.

(12) The sheets were produced by the injection molding process and had a thickness of 4 mm.

(13) The light transmission in the VIS region of the spectrum (380 to 780 nm, transmittance T.sub.VIS) of the sheets was determined according to DIN ISO 13468-2; 2006 (D65, 10′, layer thickness of specimen sheet: 4 mm).

(14) The direct solar transmittance T.sub.DS of the substrate material was determined at a layer thickness of 4 mm according to ISO 13837:2008. The transmission measurements were performed using a Perkin Elmer Lambda 950 spectrophotometer with a photometer sphere. All values were determined in the course of measurement with wavelengths of 320 nm to 2500 nm inclusive where AX is 5 nm.

(15) The average IR transmittance is to be understood as meaning the arithmetic average of the transmittance in the wavelength range of 780 to 2500 nm which is determined at a layer thickness of 4 mm according to ISO 13468-2:2006.

(16) TABLE-US-00002 TABLE 2 Transmission data for the substrate materials Average IR transmittance Thickness T.sub.VIS (%) T.sub.DS (%) (%) Substrate 1 4 mm 88 59 56 Substrate 2 4 mm 0 37.4 56 Substrate 3 4 mm 0 ≤1 ≤1

(17) Selective Surface Treatment using Excimer Lamp

(18) Post-curing was performed with an excimer lamp (Xe lamp, emitted wavelength 172 nm) with different radiation doses achieved via different irradiation times of the coated substrates. The irradiation apparatus used was the L-VUV-UV laboratory apparatus from IOT.

(19) The abrasion/scratch resistance of the non-post-treated/excimer-lamp-post-treated coated substrates 1 to 3 was determined by means of the Taber abrasion test according to ASTM 1044 (2008 version). Depending on whether the substrate was transparent or dark-colored, scratching was determined by measuring haze or gloss before and after the Taber abrasion test.

(20) Haze measured according to the standard ASTM 1003 (2011 version). ΔHaze is determined according to the following formula:
ΔHaze=Haze.sub.(initial value)−Haze.sub.(value after Taber)

(21) For the nontransparent sheets, gloss was measured. Gloss is measured according to the standard DIN EN ISO 2813 at an angle of 20°. Agloss is determined according to the following formula:

(22) $\Delta \mathrm{gloss}=\frac{\mathrm{Value}\left(\mathrm{after}\mathrm{test}\right)-\mathrm{Value}\left(\mathrm{before}\mathrm{test}\right)}{\mathrm{Value}\left(\mathrm{before}\mathrm{test}\right)}\times 100\%$

(23) The smaller ΔHaze/gloss, the more resistant the tested surface to externally induced abrasion.

(24) TABLE-US-00003 TABLE 3 Layer thicknesses of the protective layer a (cf. FIG. 2) Ex. 1 to 3 Ex. 4 to 6 (μm) (μm) Primer layer a.sub.2 1.0-1.4 1.8-3.0 Siloxane-based 3.0-4.0 7.0-9.0 topcoat layer a.sub.1

(25) Weathering of the Samples

(26) The coated sheets were subjected to an accelerated weathering test in an Atlas Ci 5000 Weatherometer with an irradiation strength of 0.75 W/m.sup.2/nm at 340 nm and a drying/rain cycle of 102: 18 minutes (referred to hereinbelow as ASTM G155 mod.).

(27) The coated substrates were weathered for 2200 hours.

(28) Evaluation of the samples after performing the weathering as per the method ASTAI G155 mod was carried out according to scores 1 to 3, wherein:

(29) 1=no damage to coating,

(30) 2=light damage to coating in the form of clouding or light cracking,

(31) 3=severe damage to coating in the form of cracking or delamination of the lacquer layer.

Inventive Example 1

(32) Substrate 1 combined with primer layer a2 in a layer thickness range of 1.8 to 2.2 μm and siloxane-based topcoat layer a.sub.1 in a layer thickness range of 5.5 to 6.5 μm. This was followed by post-curing using excimer lamps with a wavelength of 172 nm and different radiation doses. ΔHaze was determined after 1000 cycles of the Taber test. The non-irradiated sample served as a reference.

(33) TABLE-US-00004 Weathering Radiation dose(mJ/cm.sup.2) ΔHaze (%) (score 1-3) No weathering reference 2.6 1  700 (inventive) 1.4 1 1400 (inventive) 1.3 1 2200 (comparison) 1.0 3

Inventive Example 2

(34) Substrate 2 combined with primer layer a2 in a layer thickness range of 1.8 to 2.2 μm and siloxane-based topcoat layer a.sub.1 in a layer thickness range of 5.5 to 6.5 μm. This was followed by post-curing using excimer lamps with a wavelength of 172 nm and different radiation doses. ΔGloss was determined after 1000 cycles of the Taber test.

(35) TABLE-US-00005 Radiation dose (mJ/cm.sup.2) ΔGloss Weathering (score 1-3) No irradiation 4.9 1  700 2.5 1 1400 2.5 2 2200 2.4 3

Comparative Example 3

(36) Substrate 3 combined with primer layer a2 in a layer thickness range of 1.8 to 2.2 μm and siloxane-based topcoat layer a1 in a layer thickness range of 5.5 to 6.5 μm. This was followed by post-curing using excimer lamps with a wavelength of 172 nm and different radiation doses. ΔGloss was determined after 1000 cycles of the Taber test.

(37) TABLE-US-00006 Radiation dose (mJ/cm.sup.2) ΔGloss Weathering (score 1-3) No irradiation 6.7 1  700 3.2 3 1400 2.5 3 2200 2.4 3

Inventive Example 4

(38) Substrate 1 combined with primer layer a2 in a layer thickness range of 2.6 to 3.0 μm and siloxane-based topcoat layer a1 in a layer thickness range of 7.7 to 9.0 μm. This was followed by post-curing using excimer lamps with a wavelength of 172 nm and different radiation doses. ΔHaze was determined after 1000 cycles of the Taber test.

(39) TABLE-US-00007 Weathering Radiation dose (mJ/cm.sup.2) ΔHaze (%) (score 1-3) No irradiation 2.6 1  700 1.4 1 1400 1.3 1 2200 1.0 3

Inventive Example 5

(40) Substrate 2 combined with primer layer a.sub.2 in a layer thickness range of 2.6 to 3.0 μm and siloxane-based topcoat layer a.sub.1 in a layer thickness range of 7.7 to 9.0 μm. This was followed by post-curing using excimer lamps with a wavelength of 172 nm and different radiation doses. ΔHaze was determined after 1000 cycles of the Taber test.

(41) TABLE-US-00008 Radiation dose (mJ/cm.sup.2) ΔGloss Weathering (score 1-3) No irradiation 4.1 1  700 2.0 1 1400 1.8 1 2200 1.3 3

Comparative Example 6

(42) Substrate 3 combined with primer layer a2 in a layer thickness range of 2.6 to 3.0 μm and siloxane-based topcoat layer a1 in a layer thickness range of 7.7 to 9.0 μm. This was followed by post-curing using excimer lamps with a wavelength of 172 nm and different radiation doses. ΔGloss was determined after 1000 cycles of the Taber test.

(43) TABLE-US-00009 Radiation dose (mJ/cm.sup.2) ΔGloss Weathering (score 1-3) No irradiation 6.7 1  700 3.8 2 1400 2.5 3 2200 2.3 3

(44) It is clearly apparent that irradiation and radiation dose can bring about a reduction in haze value or in gloss after 1000 cycles of Taber irrespective of the substrate. It was further found that as a function of the T.sub.DS weathering has a significant influence on the surface quality of the protective layer a in the overall construction. Thus, constructions where T.sub.DS is <1% (substrate 3) suffer premature weathering failure (comparative examples 3 and 6). This effect tends to be increasingly severe with increasing radiation dose. It can be concluded from this result that in multi-ply constructions which as a result of the presence of a layer C in the construction have regions having a T.sub.DS of <1% and regions having a T.sub.DS of >20% a selective surface curing using excimer radiation should only be carried out in the regions having a T.sub.DS of >20%. This ensures that the regions having a T.sub.DS<1% do not suffer premature weathering failure. I.e. in the case of parts having for example a black edge, only the layer construction a) and b) may be irradiated.