WO2001098398A1

WO2001098398A1 - Flame-retarded polyamides

Info

Publication number: WO2001098398A1
Application number: PCT/IL2001/000567
Authority: WO
Inventors: Evgenya Reznik-Vaks; Yoav Bar Yaakov; Pierre Georlette
Original assignee: Bromine Compounds Ltd
Current assignee: Bromine Compounds Ltd
Priority date: 2000-06-22
Filing date: 2001-06-21
Publication date: 2001-12-27
Anticipated expiration: 2002-12-22
Also published as: IL136965A0; WO2001098398A9; AU2001266302A1

Abstract

Flame retarded polyamide compositions, which comprise a combination of organic halogenated flame retardants and at least one inorganic filler, such as magnesium hydroxide, and which does not comprise antimony trioxide. The compositions may comprise a combination of organic chlorinated flame retardants and at least one inorganic filler, or of organic brominated flame retardants and at least one inorganic filler.

Description

FLAME-RETARDED POLYAMIDES

Field of the Invention

This application relates to the production of polyamide compositions that are flame-retarded to a high degree without containing antimony trioxide.

Background of the Invention

Antimony trioxide is commonly used as a synergist for halogen containing fire retardants in polymers. Other compounds of heavy metals are also used for this purpose. However, none of these fire retardants are harmless from the ecological viewpoint, and it is desirable to dispense with them.

European Patent Application 0 736 566 A2, which corresponds to USP 5,674,931, discloses a flame-retarded thermoplastic resin composition which comprises, besides the base thermoplastic resin, inorganic fillers and a flame -retarding amount of an acid pyrophosphate, the cation of which is a metal selected from among alkali and alkali-earth metals. The base thermoplastic resins disclosed are polyesters.

European Patent Application EP 0 736 567 A2, corresponding to USP 5,554,674, discloses a similar composition wherein, however, the inorganic filler is not comprised, and which comprises a halogenated flame retardant. The thermoplastic resins of the composition are, or comprise, polyester resins. The organic flame retardants particularly suggested are brominated aromatic polycarbonates.

Markezich, R.L. et al., in an article entitled "Use of a Chlorinated Flame Retardant in Combination with Other Flame Retardants", disclose the flame retarding of polyolefins using a mixture of a chlorinated flame retardants and inorganic salts such as magnesium hydroxide. Said mixture is said to show a synergistic effect. Sb₂O3 is also added in some such mixtures. The chlorinated flame retardant is Dechlorane Plus®, the Diels-Alder diadduct of hexachlorcyclopentadiene and 1,5-cyclooctadiene.

European Patent Application EP 855,421 described flame retarded resin molding compositions with enhanced electrical properties, that comprise a polyamide, a halogenated flame retardant, a fiber glass and/or mineral filler, and pyro/polyphosphate, and optionally glass fibers or an olefinic polymer. A nylon 66 composition according to this application had a UL-94 rating V-l.

None of the prior art flame retardant compositions is completely satisfactory for the flame retardation of polyamides. For instance, a V-0 rating is not achieved, and or Sb θ3 is present in the flame retardants, which is undesirable.

It is therefore a purpose of this invention to provide a flame retardation of polyamides (hereinafter PA) without the use of undesirable components, particularly heavy metal compounds, and more particularly antimony trioxide. The polyamides that are particularly considered are PA46 which is poly-tetramethylene adipamide, PA66 which is poly-hexamethylene adipamide, PA6 which is polycaprolactam or polycaproamide, Pll which is poly(ll-aminoundecanoamide), P12 which is polydodecanolactam or polylaurolactam, and blends of the above, such as PA6/PA66.

It is a further purpose of this invention to provide flame-retarded polyamide compositions which are reinforced with mineral additives.

It is a further purpose of this invention to provide flame-retarded polyamide compositions which are reinforced with glass or carbon fibers. It is a further purpose of this invention to provide polyamide compositions, that are flame-retarded without the use of antimony trioxide and which have a high level of flame retardancy according to the well known standards in practice. A good review of said standards is given in the book "International Plastics Flammability Handbook- 2^nd edition," by Jurgen Troitzsch, published by Hanser in 1990.

It is a still further purpose of this invention to provide polyamide compositions that are class N-0 and V-l according to the standard UL-94 and/or have LOI (Limited Oxygen Index) values higher than 35.

Other purposes and advantages of the invention will appear as the description proceeds.

Summary of the Invention

The polyamide compositions according to the invention are flame-retarded with a combination of organic halogenated flame retardants and fillers as described below in more detail. In a preferred form of the invention, the halogen is bromine or chlorine, but preferably bromine. In a preferred form of the invention, the fillers are inorganic (mineral) fillers, chosen from the group consisting of silicates, carbonates, talc or magnesium hydroxides. The most preferred filler is talc or magnesium hydroxide including its natural forms (brucite and huntite).

The preferred content of the aforesaid additives in the plastic formulations are as follows:

Halogen content from 2 to 20 wt% and preferably between 3 and 16 wt% Filler content from 5 to 40 wt% and preferably between 7 and 30 wt%. In a preferred form of the invention, the polyamides are reinforced with fibers, e.g., with up to about 30 wt%, preferably 5-30 wt%, of glass fibers or carbon fibers.

The organic halogenated flame retardants have high processing stability that permits them to be processed with polyamides, and are chosen preferably from among the group consisting of:

Decabromodiphenyl alkane and its derivatives (e.g. S-8010 produced by

Albemarle)

Brominated trimethylphenyl indan (e.g. FR-1808 produced by Dead Sea

Bromine Group (DSBG))

High molecular weight brominated epoxy or phenoxy resin (e.g. F-2400 produced by DSBG)

Decabromodiphenyl oxide (e.g. FR-1210 produced by DSBG)

Poly(pentabromobenzyl acrylate) (e.g. FR-1025 produced by DSBG)

Brominated polystyrene (e.g. Pyro-check 68 produced by Ferro)

Poly(dibromostyrene) (e.g. PDBS-80 produced by Great Lakes Chemicals)

Poly(dibromophenylene oxide) (e.g. PO-64P produced by Great Lakes

Chemicals)

Chlorinated cycloaliphatic compound, such as Dodecachloropentacyclooctadeca-7,15 diene (e.g. Dechlorane Plus produced by Occidental Chemicals), and their blends.

"FR" means flame retardant, but when referred to a composition, it means flame retarded. Flame retardant synergists other than antimony-based compounds, such as zinc borates, zinc sulfides and iron oxides, may be used. The inorganic fillers may be chosen from the family of silicates, talc, carbonates, magnesium hydroxide and their blends. They are preferably surface treated to improve their processing, and the thermomechanical properties of the final objects obtained with the plastic compositions of the invention. The preferred fillers are talc or magnesium hydroxide including its natural forms (brucite and huntite).

It is recommended to use a surface treatment of the filler(s) with coupling agents and the coupling agents most suitable for such surface treatments for polyamides are chosen in the family of silanes. In some cases, the use of another coupling agent is more cost-efficient. Surface treatment agents that are recommended are, for instance:

- Silanes (e.g., gamma-aminopropyltriethoxysilane), N-beta-(aminoethyl)-gamma-aminopropyl-trimethoxysilane, beta-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 3-chloropropyl-trimethoxysilane, vinyltriacetoxysilane, etc.

- Derivatives of fatty acids or polymeric fatty acids

- Various combinations of materials mentioned above;

- Derivatives of phosphorous & phosphoric acid and organic compounds containing phosphorous;

- Type of organic titanates, organic zirconates, organic aluminates or silicates coupling agents.

In the compositions, additives that are commonly used in nylon compositions can be added. Such additives include heat stabilizers, lubricants, antioxidants, nucleating agents, pigments, processing aids, impact modifiers, compatabilizers such as maleic modified polyolefins, UN stabilizers, mold release, anti-dripping agents (such as fluorinated polymers, polyphenylene sulphone, etc). An example of antioxidant, heat stabilizer is Irganox B-1171, manufactured by Ciba-Geigy, which is a blend including multifunctional, nitrogen-containing hindered phenol. Examples of lubricants are calcium stearate and Ν,Ν'-ethylene bisstear amide, produced, this latter, by Lonza under the trade name Acrawax C. The polyamide compositions of the invention can be prepared in accordance with the rules known to those skilled in the art. For instance, all the ingredients (including the flame retardants) are compounded in a suitable processor, preferably a twin screw extruder. By "compounding" is meant herein that the polyamides are heated to melt them and intimately mixed with the other ingredient so as to obtain a substantially homogeneous mass. Afterwards, the compounded' composition is used to produce finished articles, for instance by injection molding, extrusion of profiles or calendering, in a substantially conventional way. In all other respects, the conditions of compounding in the extruder and the molding conditions are as usual in the art, and need not be described, because they are the same as for any composition of the corresponding basic polyamides.

Detailed Description of Preferred Embodiments

The following examples are intended to illustrate, but not limit, the invention. The materials used in the examples are listed in Table I.

The general procedure involved compounding of polyamide granules with flame retardant (FR) components (halogenated FRs and magnesium hydroxide) and other additives, as required. GF means glass fiber. GFR indicates glass fiber reinforced compositions.

Before compounding, granules of polyamide were dried at 80°C in vacuum. Compounding was performed in Berstorff ZE25 co-rotating extruder L/D=32 with open vent. The regime of compounding is set forth in Table II. Feeding was performed by K-SFS24 gravimetric feeding system ex. K-Tron International. Polymer was fed from the granule's feeder. All other powder additives were mixed manually in plastic bags and were fed from a gravimetric powder's feeder.

The polymer and the powder mixture were fed into the main feeding port of the extruder. Glass fibers were introduced to the 5^th section of the extruder via lateral feeder.

Strands of PA compositions were pelletized in the pelletizer 750/3 ex. Accrapak Systems Limited. The produced pellets were dried in the vacuum oven at 80°C for 24 hours.

Evaluation of moisture of the pellets was performed by Metier LP-15 Infrared Dryer (examples 1-7) or by Karl Fisher test with ovens (examples 8-12). Moisture before injection molding was less than 0.2%.

Injection molding was performed in an Allrounder 500 - 150 — 320 S ex. Arburg injection machine. The injection molding regimes are given in Table Ha. Test methods and equipment used in the Examples are summarized in Table III.

Flammability was tested according to test UL-94 and LOI. Before testing, specimens were conditioned at 70° in a circulating air oven for .7 days. Other properties were tested on the molded specimens which were conditioned in silica-filled dry dessiccator at 23°C ± 2°C for a minimum of two weeks before testing, to prevent the influence of water absorption on all mechanical properties.

Examples 1 and 2.

Compositions of formulations and results of tests are set forth in Table IV. These examples demonstrate the surprising achievement of a stronger flame retardancy for glass fiber reinforced polyamide 66 (GFR PA 66) having V-0 rating and higher LOI without antimony trioxide, by using the combination of FR-1808 (brominated trimethylphenyl indan) and surface treated magnesium hydroxide. Another advantage of said composition is the higher Tracking Index (CTI). Moreover it is shown that compositions without antimonj*- trioxide have higher* Notched Izod Impact.

Examples 3-6.

Composition of formulations and results of tests are set forth in Table V. These examples demonstrate the possibility of obtaining formulations of glass fiber reinforced polyamide 66 (GFR PA66) having V-0 rating, high LOI and CTI, with a combination of brominated flame retardant (Br-FR) and magnesium hydroxide without antimony trioxide.

Example 7.

In this example, polyamide 66 with no glass fiber was used. V-0 rating and high LOI value was also obtained. The content of formulation and results of flammability tests are set forth in Table VI.

Examples 8-9.

Table VII is a comparison between Example 8 according to the invention (without antimony trioxide) and Example 9 according to the prior art (with antimony trioxide). Example 8 illustrates the surprising improvement of most properties, such as better flame retardancy (the UL-94 rating is V-0 and the LOI is 57.5), while Example 9 is only rated V-l and its LOI is only 35-38. Better CTI and impact properties are also obtained by Example 8 according to the invention.

Examples 8, 10-12. .

The composition of the formulations and the results of tests are set forth in Table VII. These examples demonstrate the possibility of obtaining formulations of glass fiber reinforced polyamide 6 (GFR PA6) having V-0 rating, high LOI, high CTI value and good mechanical properties, with a combination of brominated flame retardant (Br-FR) and magnesium hydroxide without antimony trioxide.

Table I. Materials used in t.b-P diW βg

Table II. Regimes of Compounding for FR-PAs

Table Ha. Regimes of Iniection Molding for FR-PAs

Table III: Test method and equipment used in the Examples

Table IV: Examples using GFR PAββ

Table V: Examples using GFR PA66

Table VI: Example using PAββ

Table VII: Examples using GFR PA-β

While examples illustrative of the invention have been given, it will b understood that the invention can be carried out with many variations modifications and adaptations, without departing from its spirit o- exceeding the scope of the claims.

Claims

1. Flame retarded polyamide compositions; which comprise a combination of organic halogenated flame retardants and at least one inorganie filler and which does not comprise antimony trioxide.

2. Compositions according to claim 1, which comprise a combination of organic chlorinated flame retardants and at least one inorganic filler.

3. Compositions according to claim 1, which comprise a combination of organic brominated flame retardants and at least one inorganic filler.

4. Compositions according to any one of claims 1 to 3, wherein the inorganic filler is magnesium hydroxide.

5. Compositions according to claim 1, wherein the organic halogenated compounds have high processing stability that permits them to be processed with polyamides.

6. Compositions according to claim 1, wherein the organic halogenated compounds are chosen from among the group consisting of decabromodiphenyl alkane and its derivatives (e.g. S-80^'10), brominated trimethylphenyl indan (e.g. FR-1808), poly(pentabromobenzylacrylate) (e.g. FR-1025), brominated epoxy or phenoxy resin with molecular weight 20,000-70,000 (e.g. F-2400), brominated polystyrene (e.g. Pyro-check 68), decabromodiphenyl oxide (e.g. FR-1210), poly(dibromostyrene) (e.g. PDBS-80), poly(dibromophenylene oxide) (e.g. PO-64P) and dodecachloropentacyclooctadeca-7,15 diene (e.g. Dechlorane Plus).

7. Compositions according to claim 1, wherein the organic halogenated compound is dodecachloropentacyclooctadeca-7J5 diene (e.g. Dechlorane Plus).

8. Compositions according to claim 1, wherein the organic halogenated compound is brominated trimethylphenyl indan (e.g. FR-1808).

9. Compositions according to claims 1 to 5, wherein the halogen content is between 2 and 20 wt%.

10. Compositions according to claim 9, wherein the halogen content is between 3 and 16 wt%.

11. Compositions according to any one of claims 1 to 5, comprising between 5 and 40 wt% of inorganic filler.

12. Compositions according to claim 11, comprising between 7 and 30 wt% of inorganic filler.

13. Compositions according to any one of claims 1 to 5, wherein the inorganic filler, has been surface treated with coupling agents.

14. Compositions according to claim 13, wherein the coupling agent is aminosilane.

15. Compositions according to claim 1, further comprising additives chosen from the group consisting of heat stabilizers, lubricants, antioxidants, nucleating agents, pigments, processing aids, impact modifiers, compatabilizers, UV stabilizers, mold release, anti-dripping agents, and flame retardant synergists other than antimony trioxide.

16. Compositions according to claim 15, wherein the antidripping agents are chosen from among fluorinated polymers and polyphenylene sulphone.

17. Composition according to claim 1 , wherein the inorganic filler is talc.

18. Composition according to claim 1 , wherein the inorganic filler is magnesium carbonate.

19. Composition according to claim 1 , wherein the inorganic filler is huntite.

20. Composition according to claim 1 , wherein the inorganic filler is brucite.

21. Compositions according to claim 1, reinforced with fiber.

22. Compositions according to claim 21, wherein the fiber is glass fiber.

23. Composition according to claim 21, wherein the fiber reinforcement is comprised between 5 and 30 wt%.

24. Process for making flame retarded polyamide compositions according to claim 1, which comprises the steps of mixing all the ingredients and compounding them together.

25. Process according to claim 24, wherein all the ingredients are compounded with the organic brominated flame retardants and magnesium hydroxide in a twin screw extruder.

26. Use of organic brominated flame retardants, chosen from among the group consisting of decabromodiphenyl alkane and its derivatives (e.g. S-8010), brominated trimethylphenyl indan (e..g. FR-1808), poly(pentabromobenzylacrylate) (e..g. FR-1025), brominated epoxy or phenoxy resin with molecular weight 20,000-70,000 (e..g. F-2400), brominated polystyrene (e.g. Pyro-check 68), decabromodiphenyl oxide (e.g. FR-1210), poly(dibromostyrene) (e.g. PDBS-80), poly(dibromophenylene oxide (e.g. PO-64P) and dodecachloropentacyclooctadeca-7,15 diene (e.g. Dechlorane Plus), together with inorganic fillers in the manufacture of flame retarded polyamide compositions, substantially as described and exemplified.

27. Use according to claim 26, wherein the organic halogenated compound is dodecachloropentacyclooctadeca-7,15 diene (e.g. Dechlorane Plus).

28. Use according to claim 26, wherein the organic halogenated compound is brominated trimethylphenyl indan (e.g. FR-1808).