Processes for enhancing flame retardance and chemical resistance of polymers

Patent metadata

Field	Value
Publication number	US-9758616-B2
Application number	US-201514607399-A
Country	US
Kind code	B2
Filing date	Jan 28, 2015
Priority date	Dec 20, 2012
Publication date	Sep 12, 2017
Grant date	Sep 12, 2017

Abstract

Processes for increasing the chemical resistance of a surface of a formed article are disclosed. The formed article is produced from a polymeric composition comprising a photoactive additive containing photoactive groups derived from a monofunctional benzophenone. The surface of the formed article is then exposed to ultraviolet light to cause crosslinking of the photoactive additive and produce a crosslinked surface. The crosslinking enhances the chemical resistance of the surface. Various means for controlling the depth of the crosslinking are also discussed.

First claim

The invention claimed is:

1. A method for forming a cross-linked polycarbonate article, comprising:
providing a composition that comprises:
a cross-linkable polycarbonate resin having endcaps derived from a monohydroxybenzophenone, a weight average molecular weight (Mw) from 15,000 to 30,000 and a polydispersity index (PDI) from 3.0 to 4.0 as measured by GPC using a UV detector and polycarbonate standards, and a monohydroxybenzophenone-derived endcap content from 3.0 to 4.5 wt %;
optionally one or more additional polycarbonate base resins different from the cross-linkable polycarbonate resin; and
a flame retardant;
wherein the monohydroxybenzophenone-derived endcap content of the composition is between 1.2 wt % and 4 wt %, and wherein the composition has a melt flow rate (MFR) of 7 to 20 g/10 min measured at 300° C./1.2 kg/360 sec dwell;

forming an article from the composition; and
exposing the formed article to UV radiation from a UV radiation source for a time sufficient to form the cross-linked polycarbonate article;
wherein the cross-linked polycarbonate article has a gel layer of at least 5 microns thickness as measured by optical microscopy, and wherein the molded article after exposure to UV radiation has a pFTP(V1) of at least 0.95 at 1.2 mm thickness after aging for 7 days at 70° C.

2. The method of claim 1 , wherein the UV radiation source is a metal halide doped mercury lamp, an electrodeless D-bulb, an electrodeless H-bulb, an electrodeless V-bulb, a Xenon Arc lamp, or a UVA (320-390 nm) light emitting diode (LED).

3. The method of claim 1 , wherein the UV radiation source is a metal halide doped mercury lamp or an electrodeless D-bulb.

4. The method of claim 3 , wherein the molded article is exposed to UV radiation from a metal halide doped mercury lamp providing at least 12 J/cm 2 of UVA as measured using an EIT PowerPuck.

5. The method of claim 3 , wherein the molded article is exposed to UV radiation from a metal halide doped mercury lamp providing at least 35.9 J/cm 2 of UVA as measured using an EIT PowerPuck.

6. The method of claim 3 , wherein the molded article is exposed to UV radiation from a metal halide doped mercury lamp providing at least 59.9 J/cm 2 of UVA as measured using an EIT PowerPuck.

7. The method of claim 1 , wherein the molded article is exposed to filtered UV radiation using a 280 nm long pass filter.

8. The method of claim 1 , wherein the molded article is exposed to filtered UV radiation using a 320 nm long pass filter.

9. The method of claim 1 , wherein the article is formed by injection molding.

10. A method for preparing an injection-molded article having low yellowness and high chemical resistance, comprising:
receiving a composition that comprises:
a cross-linkable polycarbonate resin having endcaps derived from a monohydroxybenzophenone, a weight average molecular weight (Mw) from 15,000 to 30,000 and a polydispersity index (PDI) from 3.0 to 4.0 as measured by GPC using a UV detector and polycarbonate standards, and a monohydroxybenzophenone-derived endcap content from 3.0 to 4.5 wt %;
optionally one or more additional polycarbonate base resins different from the cross-linkable polycarbonate resin; and
optionally a flame retardant;
wherein the composition has a melt flow rate (MFR) of 7 g/10 min or higher, measured at 300° C./1.2 kg/360 sec dwell;

injection-molding the composition to a molded article; and
exposing the molded article to a selected UV light range and a selected dosage of UV radiation to obtain the injection-molded article, wherein the injection molded article has a yellowness index (YI) of 15 or less at 3.2 mm thickness when measured at least 48 hours after UV exposure, and has a % retention of 85% or greater at 3.2 mm thickness in a tensile elongation at break test using the ASTM D638 Type I method at 50 mm/min after exposure to acetone under 1.0% strain at 23° C.

11. The method of claim 10 , wherein the injection molded article has a pFTP(V1) of at least 0.70 at 1.2 mm thickness after aging for 7 days at 70° C.

12. The method of claim 10 , wherein the injection molded article has a YI of 8 or less.

13. The method of claim 10 , wherein the composition has a melt flow rate (MFR) of 7 to 20 g/10 min.

14. The method of claim 10 , wherein the composition comprises Rimar salt flame retardant, and the injection molded article has a pFTP(V1) of at least 0.70 at 1.2 mm thickness after aging for 7 days at 70° C.

15. The method of claim 10 , wherein the composition comprises Rimar salt flame retardant, and the injection molded article has a pFTP(V1) of at least 0.90 at 1.2 mm thickness after aging for 7 days at 70° C.

16. The method of claim 10 , wherein the composition comprises Rimar salt flame retardant, and the injection molded article has a pFTP(V0) of at least 0.60 at 1.2 mm thickness after aging for 7 days at 70° C.

17. A composition, comprising:
a cross-linkable polycarbonate resin having endcaps derived from a monohydroxybenzophenone and a weight average molecular weight (Mw) from 15,000 to 30,000 and a polydispersity index (PDI) from 3.0 to 4.0 as measured by GPC using a UV detector and polycarbonate standards;
optionally one or more additional polycarbonate base resins different from the cross-linkable polycarbonate resin; and
a flame retardant;
wherein the composition comprises at least 45 wt % of the cross-linkable polycarbonate resin, wherein the monohydroxybenzophenone-derived endcap content of the composition is between 1.2 wt % and 4 wt %, wherein the composition has a melt flow rate (MFR) of 7 to 20 g/10 min measured at 300° C./1.2 kg/360 sec dwell, and wherein an article formed from the composition has a light transmission (% T), of 85% or greater at 3.2 mm thickness.

18. A molded article formed from the composition of claim 17 , wherein after irradiation with UV light, the article has (a) a light transmission (% T) of 75% or greater at 3.2 mm thickness, and (b) either:
(i) a gel layer of at least 8 microns thickness as measured by optical microscopy; or
(ii) an increase in Mw of at least 30% as measured by GPC using a UV detector and polycarbonate standards.

19. The molded article of claim 18 , wherein the article has a pFTP(V1) of at least 0.95 at 1.2 mm thickness after aging for 7 days at 70° C.

20. The molded article of claim 18 , wherein the article has a delta yellowness index (YI) value of 12 or less at 3.2 mm thickness measured at least 48 hours after UV exposure.

21. The molded article of claim 18 , wherein the article has a pFTP(V0) of at least 0.6 at 1.2 mm thickness.

22. The molded article of claim 18 , wherein the article has a % retention of 85% or greater at 3.2 mm thickness in a tensile elongation at break test using the ASTM 0638 Type I method at 50 mm/min after exposure to acetone under 1% strain at 23° C.

23. The molded article of claim 22 , wherein the article has a delta yellowness index (YI) of less than 12 at 3.2 mm thickness measured at least 48 hours after UV exposure.

24. The molded article of claim 22 , wherein the article has a pFTP(V1) of at least 0.95 at 1.2 mm thickness after aging for 7 days at 70° C.

25. The molded article of claim 18 , wherein the article has a % retention of 90% or greater at 3.2 mm thickness in a tensile elongation at break test using the ASTM D638 Type I method at 50 mm/min after exposure to acetone under 1% strain at 23° C.

26. The molded article of

Assignees

• Sabic Global Technologies Bv

Inventors

• Morizur Jean-Francois
• Sybert Paul Dean
• Flores Amanda Marie
• Johnson Peter
• Frazee Andrew
• Evans Thomas L

Classifications

• C08G67/00

  Macromolecular compounds obtained by reactions forming in the main chain of the macromolecule a linkage containing oxygen or oxygen and carbon, not provided for in groups C08G2/00 - C08G65/00 · CPC title

• B29C35/0805

  using electromagnetic radiation · CPC title

• C08L2205/025

  containing two or more polymers of the same hierarchy C08L, and differing only in parameters such as density, comonomer content, molecular weight, structure · CPC title

• C08K5/549

  containing silicon in a ring · CPC title

• B29K2069/00

  Use of PC, i.e. polycarbonates {or derivatives thereof}, as moulding material · CPC title