WO1998029492A1

WO1998029492A1 - Flame resistant nylon elastomers

Info

Publication number: WO1998029492A1
Application number: PCT/US1998/001122
Authority: WO
Inventors: Lawrence A. Acquarulo; Charles J. O'neil
Original assignee: Acquarulo Lawrence A
Priority date: 1997-01-03
Filing date: 1998-01-05
Publication date: 1998-07-09
Also published as: JP2001507746A; CA2277081A1; EP0950076A4; EP0950076A1

Abstract

A flame retardant nylon elastomer composition comprising a nylon elastomer and an effective amount of the following ingredients in mixture thereof: (1) a flame-retardant comprising a halogenated aromatic compound; (2) antimony oxide; and (3) a particulate inorganic compound. The nylon elastomers are characterized with a UL 94 V-0 rating, and an increased limiting oxygen index.

Description

Flame Resistant Nylon Elastomers Polyamide materials are used in the form of fibers, and they have also become important as specialty thermoplastics for use in engineering applications. The fiber forming polyamides are often referred to as nylons. Aliphatic polyamides such as nylon-6,6 is a linear polymer and thus thermoplastic, and crystalline, and of high melting point. Aliphatic nylons tend to have good mechanical properties, including good abrasion resistance, in addition to having some measure of flexibility in spite of their high crystallinity and high melting points. With regards to the preparation of nylons with enhanced flexibility, thermoplastic polyamides of the elastomeric type have been more recently prepared, which may be considered as polyamide analogues of the somewhat older and more fully established polyester rubbers. The commercial polymers consist of polyether blocks separated by polyamide blocks. The polyether blocks may be based upon polyethylene glycol, polypropylene glycol, or polytetramethylene ether glycol. The polyamides are usually based upon nylon- 11 but may be based upon nylons 6 of nylon-6,6 or even a copolymer such as nylon-6/nylon-l 1. A wide range of block polyamides have been offered by ATOCHEM under the trade name PEBAX®. Such resins vary in the type of polyether, the nature of the polyamide block and the ratio of polyether to polyamide blocks. The polymers range in hardness from Shore A 60 to Shore D72 which is broader than for the thermoplastic polyester and thermoplastic polyurethane rubbers. Melting range is also dependent on the particular composition, and varies between 140 - 215 °C. With regard to nylons in general, and as with many other plastics materials, there have been substantial efforts to improve resistance to burning; i.e., one of the long-standing problems with nylons is that they are flammable. Halogen compounds synergised by zinc oxide or zinc borate have been used to improve flame resistance, including compounds containing red phosphorous. The halongens and phosphorous formulations tend to darken the nylon's color and this has led to halogen- and phosphorous-free grades of light color. A recent review of issued U.S. Patents illustrates how the search for improved flame resistant polyamides has progressed to the point where even today, specific formulations are still being explored to improve flame resistance characteristics. For example, in U.S. Patent No. 5,543,452, there is disclosed a flame-resistant polyamide resin comprising a blend of a polyamide or a blend of a polyamide with another polymer and a flame retardant comprising a brominated styrene or styrene derivative polymer having acid anhydride groups and a flame retardant comprising a brominated polystyrene. In U.S. Patent No. 5,476,887 there is disclosed a flame retardant polyamide composition consisting of a copolymer of polyamide-6,6 and at least one other monomer selected from the group consisting of a dicarboxylic acid of 7-14 carbon atoms, m-benzenedicarboxylic acid, o-benzenedicarboxylic acid, and p-benzenedicarboxylic acid said copolymer having a melting point below 250 °C and 10-20% by weight of melamine based on the weight of the composition. In U.S. Patent 5,466,741 there is disclosed a polyamide-based composition, suited for molding into a variety of shaped articles, containing an effective amount of red phosphorous and a corrossion/migration-reducing amount of at least one zinc compound selected from amongst zinc oxide, zinc sulfide and an oxygen-containing zinc salt, e.g., zinc borate. In U.S. Patent No. 5,438,084 there is disclosed a flame retardant polyamide composition containing 100 parts by weight of an aliphatic polyamide- containing resin, 2-50 parts by weight of magnesium hydroxide, 1 to 15 parts by weight of red phosphorous and 0.1 to 5 parts by weight of an epoxy resin. In U.S. Patent No. 5,378,750 there is disclosed a flame-resistant molding composition consisting of thermoplastic, partially crystalline polyamide and 40-60% by weight, based upon weight of a molding composition, of magnesium hydroxide and optionally one or more reinforcing materials, an elastomer, and processing additives. U.S. Patent No. 5,412,014 discloses a fire retardant resin composition, which rely upon a free-flowing silicone polymer powder, said powder having an average particle size of 1 to 1000 microns and being prepared by mixing a polydiorganosiloxane with a silica filler along with a phosphorous-based fire retardant compound, wherein the mixing occurs via single screw extrusion. The resultant resin composition is said to provide a significant improvement in fire retardancy but does not exhibit the severe deterioration of impact resistance incurred when the resin is modified with only phosphorous-based fire retardant. In U.S. Patent No. 5,391 ,594, the free-flowing silicon powder composition is described as a flame retardant in a variety of thermoplastic resins, including nylons. Accordingly, what the above review of recent technology reveals is that there has been and remains a continuous effort to refine the various flame retardant formulations to improve the resistance of nylons to burning. Furthermore, with respect to the nylon elastomers noted above, until now, it has remained unknown how one could modify such resins in order to produce a nylon elastomer that would have improved resistance to burning, and meet or exceed what is known as a " V-0" rating. A " V-0" rating is a rating developed by Underwriters Laboratories, known as the UL94 test, in which 0.64 cm thick samples are held in vertical position and lit by a Bunsen burner at the bottom end thereof. The material is then rated according to performance. A "V-0" rating is one in which no test specimens burn longer than 10 seconds after removal from the flame, where no test specimens exhibit flaming drip that ignites dry surgical cotton placed 30.5 cm below the test specimen, and one in which no afterglow persists for longer than 30 seconds. Accordingly, it is an object of this invention to develop a new flame retardant system to impart flame retardancy to nylon elastomer materials, such as PEBAX®, that would additionally allow for the nylon elastomer to be characterized with a UL 94 V-0 rating. It is also an object of this invention, to provide in a nylon elastomer material, a combination of flame retardant additives/components, characterized in that the flame retardant components act in a synergistic manner to provide a flame resistant nylon elastomer resin, of improved limiting oxygen index, which does not drip, and in which additives/components do not have a significant effect on the nylon's elastomeric properties. A flame resistant elastomeric polyamide resin composition comprising a elastomeric polyamide and a flame retardant comprising a halogenated aromatic compound, antimony oxide, and a powdered inorganic resin modifier. Expressed in method form, the present invention comprises dispersing in a nylon elastomer a flame retardant comprising a halogentated aromatic compound, antimony oxide and a particulate inorganic compound, wherein for each part by weight of nylon elastomer to be modified, the dispersion contains about 0.5 parts of halogenated aromatic compund, 0.3 parts antimony oxide, 0.1 part of particulate inorganic compound, and the remainder, anti-oxidant. The present invention, in a preferred embodiment, comprises about 50 % (wt.) of an elastomeric nylon, about 25 % (wt.) of a brominated aromatic compound, about 15-20% of antimony oxide, and about 5% of a powdered inorganic filler or an inorganic polymer resin. Stated another way, for each part of nylon elastomer to be modified, the elastomeric nylon preferably contains about 0.5 parts of brominated aromatic compound, 0.3 parts of antimony oxide, and 0.1 parts of a particulate inorganic compound, and optionally, a small amount of antioxidant. The elastomeric polyamides which have been rendered flame-retardant preferably include those resins sold by ATOCHEM Inc. under the tradename PEBAX®. Accordingly, such nylon elastomers range in hardness from Shore A 60 to Shore D 72. It can therfore be appreciated that when durometer hardness values increases (which represent an increase in polyamide over polyether segment concentration) the overall amount of flame retardant system as disclosed herein can be reduced. For example, at durometer hardness values of Shore D 72, the overall amount of flame retardant in the system can be reduced to a total of about 40 % (wt). The preferred aromatic brominated flame retardants which have been found suitable include SAYTEX® 102E, which is available from Albemarle Corporation. SAYTEX® 102E is described as a high purity grade of deca- bromodiphenyl oxide, of molecular formula C,₂OBr₁₀ containing a high level of aromatic bromine. Also preferred as an aromatic bromine flame retardant is SAYTEX BT- 93 W®, which is again available from Albemarle. SAYTEX BT-93W® is described as an aromatic bromine with an imide structure, of molecular formula of C₁₈H₄O4N₂Br₈. The preferred antimony oxide is antimony trioxide TMS, which is available from Anzon Inc. Antimony trioxide TMS contains 99% antimony oxide as Sb₂O₃ along with other elemental inorganic ingredients. The preferred particulate inorganic compounds include Dow Corning Si powder resin modifiers which are 100 percent active, free-flowing, silicone powders. They are available in several grades with varying types of organic reactivities (none, epoxy, methacrylate and amine). Particularly preferred and as disclosed herein, Dow Corning 4-7081 was employed, which is a resin modifier designed for methacrylate type materials. Finally, in accordance with the present invention, it is preferred to incorporate in the flame retardant composition a small amount of an antioxidant. Preferred antioxidants include IRGANOX® 1010, which is available from Ciba- Geigy, which is sold as a high performance solid antioxidant. In addition, IRGAFOS® 168 can be employed, which is also available from Ciba-Geigy Corporation. As noted above, when the above basic and preferred formulations are herein employed, a flame-retardant elastomeric nylon composition is obtained, that is specifically characterized as having a UL 94 V-0 rating. In addition, the limiting oxygen index (LOI) is seen to improve. For example, the LOI of ummodified PEBAX 3533 was measured to be less than 0.15. When such PEBAX is combined at 50 %(wt.) with 25% SAYTEX BT-93 W® and 15-18 % (wt.) of antimony oxide, along with about 5.0 % (wt.) of powdered silicon and 1-2% of an antioxidant, the LOI was measured on a 0.32 cm thick sample to be 0.27-0.28. Examples The following table describes the various formulations illustrative of the present invention:

TABLE 1

Sample Number

Component IΔ IB 2A 2B 2C 3A 3JB 4A 4B

Pebax 3533 680 680 568 508 508 498 498 468 468

Irganox

B215 15 15 15 02 02 — — —

Irganox

1010 05 05 05 — - 02 02 02 02

Melamine

Cyanurate 30 — — — — — — — —

Pyronil 45 45

Pyrocheck LM 135

Sb₂0₃ 120 162 19 20 20 23 23

Dechlorane

+25 25 23

Talc 7

Saytech 102E (DE83R)

19 25 25 25

BT-93W

25 25

Dow Corning

In connection with Table I, note the following: Pyronil 45 is a brominated flame-retardant available from ATOMCHEM, containing about 45% bromine. Pyrocheck LM is also a brominated flame retardant, as is DE-83R (Great Lakes Inc.). Dechlorane 25 is a chlorinated flamed retardant. The following results were obtained with regards to the above formulations. Samples 1 A and IB both failed to obtain a V-0 rating due to dripping and ignition of cotton on 0.64 cm samples. Sample 2A failed to obtain a V-0 rating due to slight dripping. Sample 2B showed flame retardant blooming to the surface making the surface chalky in appearance. Sample 2C obtained a V-0 rating along with a limiting oxygen index of 0.25-0.26. Samples 3 A and 3B similarly obtained a V-0 rating, with a limiting oxygen index in 3 A of 0.26 and in 3B of 0.27. Finally, samples 4A and 4B both achieved a V-0 rating at 0.64 cm thickness, and sample 4A had an oxygen index of 0.27 and 4B was measured at

Claims

I claim: L A flame retardant nylon elastomer composition comprising a nylon elastomer and the following ingredients in mixture therof: (1) a flame-retardant comprising a halogenated aromatic compound; (2) antimony oxide; and (3) a particulate inorganic compound. 2. The composition of claim 1, wherein for each part by weight of nylon, there is about 0.5 parts of halogenated aromatic compound, 0.3 parts antimony oxide, and 0.1 parts of particulate inorganic compound. 3. The composition of claim 1, further containing an antioxidant. 4. The composition of claim 1 characterized by one or more of the following features: (a) wherein the nylon elastomer is a nylon block copolymer comprising an aliphatic polyamide block and a polyether block; (b) wherein the nylon elastomer has a hardness range of about Shore A60 to Shore D72; and (c) wherein the nylon elastomer comprises about 50% (wt.) of the flame retardant composition. 5. The composition of claim 1, wherein the halogenated aromatic compound is a brominated compound containing aromatic functionality. 6. The composition of claim 1, wherein the particulate inorganic compound contains powdered silicon. 7. The composition of claim 1, characterized by one or more of the following features: (1) said composition exhibits a UL94 V-O rating; and (b) the LOI of the flame-retarded nylon elastomer is increased over the nylon elastomer prior to mixing with said flame-retardant ingredients. 8. A flame retardant nylon elastomer composition comprising about 50 % (wt.) of a nylon elastomer and the following ingredients in mixture therof: (1) about 25 % (wt.) of a flame-retardant comprising a brominated aromatic compound; (2) about 15-20% (wt.) of antimony oxide; and (3) about 5% (wt.) of a particulate inorganic compound containing silicon. 9. A method for imparting fire retardancy to a nylon elastomer comprising the steps of dispersing in said nylon elastomer the following phosphorous-free ingredients: (1) a flame-retardant comprising a halogenated aromatic compound; (2) antimony oxide; and (3) a particulate inorganic compound. 10. The method of claim 9, wherein for each part by weight of nylon elastomer to be modified, the dispersion contains about 0.5 parts of halogenated aromatic compound, 0.1 part of particulate inorganic compound, and 0.3 parts of antimony oxide.