FLAME RETARDANT STYRENE POLYMER COMPOSITION AND PROCESS FOR RECYCLING STYRENE POLYMER-CONTAINING SCRAP

Abstract

The present invention provides a flame-retardant styrene polymer composition comprising an organic bromine compound, zinc stearate and calcium stearate, the use for preparing styrene polymer films or foams and a process for recycling of styrene polymer-containing scrap.

Claims

1.-12. (canceled)

13. Flame-retardant styrene polymer composition comprising 300 to 15,000 ppm bromine, 10 to 1000 ppm zinc, and 10 to 1000 ppm calcium.

14. Flame-retardant styrene polymer composition according to claim 13, wherein bromine is present as organic bromine compound, zinc is present as zinc stearate, and calcium is present as calcium stearate.

15. Flame-retardant styrene polymer composition according to claim 13, comprising a) 70 to 99 wt.-% of styrene polymer (SP) b) 0.5 to 3 wt.-% of an organic bromine compound as flame-retardant (FR) c) 0.01 to 1 wt.-% of zinc stearate, d) 0.01 to 1.5 wt.-% of calcium stearate, and e) 0 to 24.5 wt.-% additives (A), selected from. acid scavengers, stabilizers, flame retardant synergists, athermanous compounds, blowing agents or mixtures therefrom.

16. Flame-retardant styrene polymer composition according to claim 13, wherein the weight ratio of Ca:Zn is in the range from 7:1 to 1:7.

17. Flame-retardant styrene polymer composition according to claim 13, wherein the weight ratio of Br:Zn is in the range from 10:1 to 300:1.

18. Flame-retardant styrene polymer composition according to claim 13, wherein the weight ratio of Ca:Zn is in the range from 5:1 to 1:5 and the weight ratio of Br:Zn is in the range from 20:1 to 250:1.

19. Flame-retardant styrene polymer composition according to claim 13, wherein the flame retardant is selected from brominated styrene-butadiene-block copolymer pentabromomonochlorocyclohexane, pentabromophenyl allyl ether, tetrabromobisphenol A bis (2,3-dibromo-2-methylpropyl ether), tetrabromobisphenol A bis (2,3-dibromopropyl ether), or the bis(allyl) ether of tetrabromobisphenol A or mixtures therefrom.

20. A process for recycling of styrene polymer-containing scrap comprising the steps: a) determining the content of bromine, zinc and calcium of the styrene polymer-containing scrap b) mechanically crushing the styrene polymer-containing scrap to pieces, c) adding organic bromine compound, calcium stearate and optionally zinc stearate in amounts to obtain a flame-retardant styrene polymer composition according to claim 13, d) melting and extruding the mixture from step c) e) optionally impregnating the melt obtained in step d) with a blowing agent, and f) extruding and granulating the melt obtained in step d) or step e) or extruding and expanding the melt obtained in step e) with foaming.

21. A process for producing a flame-retardant styrene-polymer composition according to claim 13, wherein calcium-stearate is added together with pieces of styrene polymer-containing scrap before melting the flame-retardant styrene-polymer composition.

22. A process for producing expandable styrene polymers or extruded styrene polymer foam comprising the steps of preparing a melt of a flame-retardant composition according to claim 13 and impregnating the melt with a blowing agent.

23. Use of the flame-retardant composition according to claim 13 for preparing styrene polymer films or foams.

24. Extruded styrene polymer foam (XPS) or expandable styrene polymer (EPS) comprising the flame-retardant styrene polymer composition according to claim 13.

Description

EXAMPLES

[0066] Hereinafter, the present invention is described in more detail and specifically with reference to the Examples, which however are not intended to limit the present invention.

[0067] Raw Materials: [0068] PS: Zn-stearate free polystyrene (PS 153 from Ineos Styrolution) [0069] Zn-stearate: Ligastar ZN 101 from Peter Greven [0070] Ca-stearate: Ligastar CA 800 from Peter Greven [0071] FR 3000 Emerald Innovation 3000 (brominated styrene-butadiene copolymer) from Lanxess [0072] SR-130 Pyroguard SR-130 from DKS Co. Ltd. [0073] DHT dihydro talcite (Hycite 713 from BASF) [0074] GMS glycerine mono stearate Dimodan HR 75 B from Danisco [0075] MD 1024 Irganox MD 1024 (steric hindered phenol) from BASF

Examples 1-4 and Comparative Examples C1-C6

[0076] Preparation of Polymer Blends.

[0077] Polystyrene blends were prepared by premixing 100 parts per weight of polystyrene PS with the amount (parts per weight per 100 parts of PS) of flame-retardant, Zn-stearate and stabilizer as listed in Table 1 and adding the premix into the feeding section of a twin-screw extruder ZSK 25 (Coperion). The extruder had a L/D (length to diameter) ratio of 32 and was operated at a speed of 200 rpm and a throughput of 10 kg/h. The loading unit was cooled with water. All other zones were adjusted to a temperature of 180° C. The melt leaving at the nozzle head was cooled in a water bath and then granulated.

[0078] The granules were dried in an air-circulated oven. The results of the inspection before and after tempering in a drying cabinet at 220° degrees Celsius for 10 minutes are summarized in Table 1.

[0079] Preparation of Foamed Films

[0080] Flame-retardant properties of the polymer blends were tested with foam films prepared from the granulated blends. 10 g of the blended granules were dissolved in 35 g of dichloromethane with 1.66 g of pentane S (80 wt.-% n-pentane, 20 wt.-% isopentane). The solution was poured into an aluminum bowl and the solvent let be evaporated. After 5 hours the polymer film was taken out and foamed with water vapor for 1.5 minutes. The obtained polymer films were tempered in a drying cabinet at 70° degrees Celsius for 24 hours.

[0081] The foamed films sheets were exposed to the flame of a propane gas burner and the time measured till the extinction of the flame. The results are summarized in table 1.

TABLE-US-00001 TABLE 1 Composition, visual inspection and burning test with foamed films Visual inspection Visual inspection Burning Flame retardant Zn-stearate Stabilizer before tempering after tempering time Example [wt.-%] [wt.-%] [wt.-%] step step [sec] 1 1.5 (FR 3000) 0.1 0.05 (Ca-Stearat) clear Some black points 5 2 1.5 (FR 3000) 0.1 0.1 (Ca-Stearat) clear clear 3 3 1.5 (FR 3000) 0.1 0.2 (Ca-Stearat) clear clear 3 4 1.5 (SR-130)  0.1 0.1 (Ca-Stearat) clear clear 5 C1 1.5 (FR 3000) — — clear Partially black 4 C2 1.5 (FR 3000) 0.1 — grey black 7 C3 1.5 (FR 3000) 0.1 0.1 (MD 1024) clear black 4 C4 1.5 (FR 3000) 0.1 0.2 (MD 1024) clear Mostly black 3 C5 1.5 (FR 3000) 0.1 0.1 (DHT) clear black 14 C6 1.5 (FR 3000) 0.1 0.1 (GMS) clear black 15