GB2508601A

GB2508601A - Flame Retardant Composition

Info

Publication number: GB2508601A
Application number: GB1221774.1A
Authority: GB
Inventors: John Williams
Original assignee: William Blythe Ltd
Current assignee: William Blythe Ltd
Priority date: 2012-12-04
Filing date: 2012-12-04
Publication date: 2014-06-11

Abstract

The present invention relates to flame retardant additives suitable for use with polyamides, such as polyamide suitable for use in packaging electronics components. The flame retardant composition comprises nylon (e.g. nylon 6 or nylon 6,6), zinc stannate and brominated polymer (especially brominated polyacrylate).

Description

Flame Retardant Composition The present invention relates to flame retardant additives suitable for use with polyamides, such as polyamide suitable for use in packaging Electronics components. In particular the present invention relates to flame retardant additives for polyamides which avoid the use of antimony and hence can provide antimony free Flame retarded polyamide.

Background

Aliphatic polyamides such as Nylon 6 and Nylon 66 are widely used for engineering plastics because they have good heat resistance, good chemical resistance, high stiffness, good abrasion resistance and good moldability. For applications such as the manufacture of electric and electronic appliances the polyamide composition is required to meet flame retardant standards as well as application specific standards relating to mechanical properties and stability.

There are two main approaches to developing a polyamide composition that meets the flame retardant performance standards that apply to specific end uses such as electronics: Using a source of halogen as the primary flame retardant species Using agents other than halogens (e.g. Phosphorus derivatives) as the primary flame retardant species In both approaches secondary additives are used to optimize and customize the performance of the composition to match the end application; for example to boost flame retardant activity, improve heat stability or to preserve key mechanical properties.

The selection of polymer additives is governed by several factors in addition to their designated function, for example: The polymer additives must have low toxicity, or eco-toxicity effects so that the final polyamide compositions meets the requirements of regulatory directives that govern the end application. For example the RoHS, WEE and ELV requirements The secondary additives must also have no detrimental effect on the function of the other polymer additives contained in the engineering polyamide composition.

Since flame retardant additives do not necessarily contribute other benefits to a composition the level of incorporation is preferably optimised and a level of incorporation low.

Flame retarded polyamide compositions containing a source of halogen as the primary flame retardant active agent has been based on bromine derivatives. Many disclosures are available of such compositions such as CN102382459 which discloses a polyamide carrier flame-retarding master batch and a preparation method. The master batch includes, by weight, 15 to 36 parts of polycaprolactam (Nylon 6), 48 to 63 parts of primary fire retardant, 16 to 21 parts of secondary fire retardant, and 0.4 to 0.6 parts of oxidation inhibitor. The primary flame retardant being deca-bromine di-phenylethane. This document also evidences the standard industry measurement for flat flame retardants in the form of the Underwriter's Laboratory test (UL-94) which classifies retardants as V-2, V-i or V-0 in increasing order of effectiveness, or if not effective does not classify. Further, whilst this disclosure indicates the production of a masterbatch as a precursor additive for a final product at temperatures required to produce masterbatch, which requires next revision process to melt the nylon starts to initiate flame retardant activity and therefore compounding 1 additives together prior to exclusion processing is the conventional method of incorporating such additives.

Regulatory developments, as well as processing conditions such as temperature profiles, have also defined the most suitable brominated derivatives as polymeric compounds. Such materials as brominated polystyrene, brominated polyacrylate and brominated epoxy polymer are known for use as primary flame retardants. The thermal ability of these compounds generally precludes the use in a pre-prepared masterbatch.

As a further example, JP5230360 discloses a FLAME RETARDANT RESIN COMPOSITION including 1-pts.wt. brominated polystyrene, 1-40 pts.wt. brominated benzyl polyacrylate, as the primary flame retardants compounded with polyphenylene ether resin and 90-10 pts.wt. polyamide resin, for example nylon. The composition, typical of such compositions also comprises 1-30 pts.wt. of an antimony compound as a secondary flame retardant.

Antimony compounds have been used as synergists to improve the overall activity. Antimony compounds can be used as synergists for bromine-based primary flame retardant systems; however their toxicity and eco-toxicity characteristics are disadvantageous for polyamide compositions that are required to meet the highest standards set by industrial governing bodies, original equipment manufacturers and the consumer.

The above bromine-antimony compositions have proven generally effective and are known in a wide range of compositions both of bromine compound and antimony compound, mixed in various compositions across a range of polyamides the purposes of flame retardancy. As mentioned previously it is desirable to incorporate low levels and provide high weight effectiveness, including on grounds of cost, and hence much effort has been put into optimising compositions since effectiveness does not appear to be a simple function of bromine level or antimony level. This is not surprising since the complex chemistry during a thermal degradation reaction will depend upon the nature of the substrate, such as polyamides, even the type of polyamides as well as the specific delivery mechanism for the primary and secondary flame retardants.

Many other classes of claim retardant are known to the skilled person for the above are most

relevant to the present disclosure.

Another class of claim retardant having low toxicity and a better environmental profile than antimony compounds is zinc stannate (ZnSnO4). This material is known for use in polyvinyl chloride, epoxy resins and has occasionally been disclosed for use with polyamides.

An objective of the present invention is to provide an antimony free or at least antimony reduced flame retardant composition for use with polyamides. The present invention also addresses the problem of providing an optimum composition for flame retardancy so as to provide high weight effectiveness for any additive. The consequential problem of accurate delivery of high weight effectiveness flame retardants in a compounding and extrusion process is also addressed.

The present invention provides and improved or alternative flame retardancy composition and additive suitable for providing such a composition.

The present invention in its various embodiments is as set out in the appended claims.

Experimental Flame retarded, glass-filled (30%) Polyamide 66 compounds were manufactured using three types of brominated polymer as the primary flame retardant; using Flamtard S as the synergist. The composition of each of the ten experimental compounds is reproduced in Table 1.

Table 1: Composition of Flame Retarded, Glass-Filled Polyamide 66 Compounds Run No. Polyamide 66' Glass Fibre2 Stabilizers' Br Polymer4a Flamtard S5 1 69.4 30.0 0.6 0 0 2 46.9 30.0 0.6 22.5 0 3 46.9 30.0 0.6 15.7 6.8 4 46.9 30.0 0.6 19.1 3.4 Polyamide 661 Glass Fibre2 Stabilizers' Br Polymer4b Flamtard 5 46.9 30.0 0.6 22.5 0 6 46.9 30.0 0.6 15.6 6.9 7 46.9 30.0 0.6 19.05 3.45 Polyamide 661 Glass Fibre2 Stabilizers' Br Polymer4° Flamtard 5 8 46.9 30.0 0.6 22.5 0 9 46.9 30.0 0.6 17.1 5.4 46.9 30.0 0.6 19.8 2.7 1Polyamide 66 = Durethan A30 S (Lanxess) CS 7628 [diameter = 10 micron, length = 4 mm] (Lanxess) Irganox 1098 (BASF), Irgafos 168 (BASF) Caesit AV/PA (Baerlocher) 4aFR 803P (ICL), 4bFR 1025 (ICL), 4CF 2400 (ICL) 5William Blythe Ltd Each of the test compounds was manufactured using a twin-screw extruder (Leistritz MIC 27 GL/44D), operated at between 260 and 270°C and a screw speed of 300 rpm; giving a throughput of 4 kg / hr. Each test compound was converted into a standard test bar (127.5 mm x 12.7 mm x 1.6 mm) by injection moulding, according to UL-94 specification.

Flame Retardant Raw Materials Brominated polymeric flame retardant FR 803P (ICL Industrial Products) is Brominated Polystyrene (Molecular Weight: 600,000), belonging to the chemical family of Polyhalogenated Aromatic Polymers.

Brominated polymeric flame retardant FR-1025 (ICL Industrial Products) has the chemical name 2-Propenoic acid, (2,3,4,5,6-bromophenymethyl ester, homopolymer, and also belongs to the chemical family of Polyhalogenated Aromatic Polymers.

Brominated polymeric flame retardant F-2400 ((ICL Industrial Products) is a brominated epoxy polymer.

Flamtard S is the trade name used by William Blythe Limited for Zinc Stannate (CAS No.: 12036-37-2).

Results The flame retardant performance of each experimental formulation was evaluated according to the flame retardant standard UL-94 (Underwriter's Laboratory, USA). The gradation of flame retardant performance is divided into "V" ratings, as illustrated below: V-0 = burning stops within lOs on a vertical sample (non-flaming drips permitted) V-i = burning stops within 30s on a vertical sample (non-flaming drips permitted) V-2 = burning stops within 30s on a vertical sample (flaming drips permitted)

S

The performance of each flame retardant and combination of flame retardants is reported in Table 2, below: Table 2: Flame Retardant Performance of Glass-Filled Polyamide 66 Compounds (Nylon 6,6) Flame Retardant Run 1 Run 2 Run 3 Run 4 Run S Run 6 Run 7 Run 8 Run 9 Run 10 FR-803P1 0 22.5 15.7 19.1 0 0 U 0 0 0 FR-10252 0 0 0 0 22.5 15.6 19.05 0 0 0 FR-24003 0 0 0 0 0 0 U 22.5 17.1 19.8 Flamtard S 0 0 6.8 3.4 0 6.9 3.45 0 5.4 2.7 UL-94 Result nc. V-2 nc V-V V-2 V-0 V-0 V-2 n.c. n.c.

1 FR-803P = brominated polystyrene 2 FR-1025 = brominated polyacrylate as poly pentabromobenzyl acrylate, CAS #59447-57-3 F 2400 = brominated epoxy polymer + n.c. = not classified, i.e. fail.

* Results (5 x repeats) showed 2 x V-i and 3 x n.c.

The brominated polymeric flame retardant compounds were shown to behave effectively for the retardation of flame, each achieving the rating of "V-2" according to the Underwriter's Laboratory test (UL-94). However, none of these products reached the best "V-0" rating.

Whilst maintaining the total additive concentration at 22.5% (i.e. Brominated Polymer + Flamtard 5) in the test compound it was found that Flamtard Shad a beneficial effect on the flame retardant performance. For example, the maximum flame retardant rating of V-0 was achieved when Flamtard S was combined with Brominated Polyacrylate (FR-1025), as reported in Run 6 and Run 7.

Conclusion

Flamtard S acts synergistically with brominated polyacrylate; improving the flame retardant performance from "V-2" (by UL-94 evaluation), for the brominated polyacrylate alone, to the maximum rating of "V-0" for combinations of Flamtard S(6.9 and 3.45%) and brominated polyacrylate (15.6 and 19.05%) at the same total additive concentration of 22.5%.

Claims

Claims, 1. A flame retarded nylon composition, the composition comprising: nylon; zinc stannate; and brominated polymer.
2. The composition of claim 1 wherein the brominated polymer is selected from one or more of: brominated polystyrene; brominated polyacrylate; and brominated epoxy polymer.
3. The composition of claim 2 wherein the polymer is poly pentabromobenzyl acrylate, or poly pentabromobenzyl methacrylate.
4. The composition of any preceding claim, wherein the weight ratio of brominated polymer to zinc stannate is from 10:1 to 1:2.
5. The composition of claim 2 wherein the weight ratio of brominated polymer to zinc stannate is from 8:1 to 3:1.
6. The composition of any preceding claim, wherein the zinc stannate is in powder form of particle size of less than 5jim d3'2 as determined by laser light scattering particle size analysis.
7. The composition of claim 2 wherein the zinc stannate particle size is in the range 1.4 and 2.2 jim.
8. The composition of any proceeding claim, wherein the nylon is nylon 6 or nylon 6,6.
9. The composition of any preceding claim, wherein the weight of the brominated polymer and zinc stannate is from 0.2 to 1 times the weight of glass fibre incorporated into the composition 9. A method of preparing a flame retarded nylon composition comprising and mixing zinc stannate with brominated polymer to form a homogeneous masterbatch and then incorporating the masterbatch with nylon and, optionally, fibreglass, in an exclusion apparatus to form a flame retarded article.
10. The method of claim 9 wherein the masterbatch comprises from 10 to 20% nylon.