A PROCESS FOR PRODUCING SHAPED ARTICLES OF A POLYMER COMPOSITION CONTAINING A POLYAMIDE, HALOGEN-FREE FLAME RETARDANT AND GLASS FIBERS

Abstract

The invention relates to a process for producing shaped articles comprising the steps of: compounding a polymer composition (A) containing a polyamide, a halogen-free melamine based flame retardant and at most 15 wt. % of glass fibers into pellets, compounding a polymer composition (B) containing a polyamide, more than 15 wt. % of glass fibers, and not containing halogen-free melamine based flame retardant into pellets, producing a mixture comprising the pellets of polymer composition (A) and (B), molding the mixture comprising the pellets of polymer composition (A) and (B) into shaped articles.

Claims

1. A process for producing shaped articles comprising the steps of: compounding a polymer composition (A) containing a polyamide, a halogen-free melamine based flame retardant and at most 15 wt. % of glass fibers into pellets, compounding a polymer composition (B) containing a polyamide, more than 15 wt. % of glass fibers, and not containing halogen-free melamine based flame retardant into pellets, producing a mixture comprising the pellets of polymer composition (A) and (B), molding the mixture comprising the pellets of polymer composition (A) and (B) into shaped articles.

2. Process according to claim 1, wherein the mixture comprises 50-90 wt. % of pellets of polymer composition (A) en 50-10 wt. % of pellets of polymer composition (B).

3. Process according to claim 1, wherein the polyamide used in the polymer composition (A) and (B) has a melting point below 260 C. (measured by DSC, according to ISO 11357-1:1997 under nitrogen atmosphere (purge 50ml/min) using a heating and cooling rate of 20 K/min).

4. Process according to claim 1, wherein as polyamide PA-6 or PA-66 is used.

5. Process according to claim 1, wherein the polymer composition (A) contains 15-30 wt. % halogen-free melamine based flame retardant.

6. Process according to claim 1, wherein the halogen-free melamine based flame retardant in polymer composition (A) is phosphorous-free.

7. Process according to claim 1, wherein the halogen-free melamine based flame retardant is chosen from the group of melamine, melamine cyanurate, melam, melem and mixtures thereof.

8. Process according to claim 1, wherein the polymer compositions (A) and/or (B) contain one or more further flame retardants.

9. Process according to claim 1, wherein the output of the kneader while producing the polymer compositions (A) and/or (B) is more than 100 kg/hour.

10. Process according to claim 1, wherein the ratio of the length as well as the ratio of the width or diameter of the pellets of polymer composition (A) and of the pellets of polymer composition (B) is between 0.5 and 1.5.

11. Process according to claim 1, wherein the ratio of the length as well as the ratio of the width or diameter of the pellets of polymer composition (A) and of the pellets of polymer composition (B) between 0.8 and 1.2.

12. Mixture of pellets comprising the pellets of polymer composition (A) and (B) as defined in claim 1.

Description

EXAMPLES

Ingredients:

[0048] PA6: Akulon K122 from DSM
Glass fiber: 173X-11p from 3B fiberglass
Flame retardant: melamine cyanurate MC50 from BASF
Flame retardant: Exolit OP1311 from Clariant
Mold release agent: ethylene-bis-stearamide (Acrawax C) from Lonza

Experimental.

[0049] All compositions were compounded on a 40 mm co-rotating twin screw extruder (Berstorff ZE40/48UTS). The polymer, flame retardants and mold release agent were added to the feed opening of the extruder, the glass fibers were dosed downstream to the extruder, where the polymer was in the molten state. The pellets were mixed in a tumble dryer. The final pellet mixtures were molded into various test samples for property testing using an Engel 75A injection moulding machine: [0050] 80801.5 mm plaques for GWIT testing. [0051] 1.5 mm UL94V specimen for the vertical burning test [0052] ISO 527-1A specimen for tensile testing.
GWIT tests were conducted in accordance with IEC60695-2-13, tensile tests were done in accordance with ISO527 and vertical burning tests were conducted in accordance to UL 94V.
Table 1 gives an overview of the experiments performed.

TABLE-US-00001 TABLE 1 experiments performed CE-A CE-B (A) (B) E1 PA6 56.8 44.3 46.4 39.34 glass-fiber 25 25 10 60 MRA 0.2 0.2 0.66 MeCy 12.5 17.9 OP1311 18 18 25.7 (A) 70 (B) 30 strand integrity OK foamed OK OK tensile modulus [Mpa] 9000 x 11000 tensile strenght [Mpa] 130 x 115 eab [%] 2 x 2 GWIT @ 1.5 mm [ C.] 775 x 825 UL 94V @ 1.5 mm V0 x V0
Comparative experiment A and B.

[0053] In comparative experiment A (CE-A) the polymer composition does not contain any melamine cyanurate, but different flame retardants. It shows that the flame retardant is thermally sufficiently stable to survive the processing of glass filled PA6 on a twin screw extruder. The material can be pelletized and is usable for injection-molding to transform it into shaped articles. However the GWIT levels are below 800 C. and therefor do not fulfill the requirements.

[0054] Comparative experiment B (CE-B) proves that when Melamine cyanurate is added to the formulation of CE-A the material can no longer be pelletized due to massive degradation of the melamine cyanurate resulting in foaming of the extruded strand. Such material cannot be used for injection-molding.

Example I

[0055] A composition (A) containing a high amount of the flame retardants, among which the melamine cyanurate and a small amount of glass fibers is produced that can be stranded into good quality pellets. Further a highly glass fiber filled composition (B) is produced, which does not contain flame retardant. Also this composition was easily be stranded into good quality pellets. See further table 1 (A) and (B).

[0056] The two compositions (A) and (B) were mixed in a 30:70 ratio to obtain the final granulate mixture that was injection molded into the test samples articles. Compared to CE-A this sample has better GWIT ratings and compared to CE-B this route allows for the production of shaped articles by injection molding.