Flame-retardant mixture

Details Flame-retardant mixture Flame-retardant mixture

2002-03-21

2003-10-07

Sanders, Kriellion A. (Department: 1714)

Synthetic resins or natural rubbers -- part of the class 520 ser

Synthetic resins

Processes of preparing a desired or intentional composition...

C524S115000, C524S414000

Reexamination Certificate

active

06630526

ABSTRACT:

The invention relates to a flame-retardant mixture comprising:
a) a polymer composition
b) a phosphorus-containing compound
c) a triazine flame retardant, the weight ratio of a, b en c lying between 94:1:5 and 35:30:35.
Such a mixture is known from WO 99/02606, in which the melamine condensation products melam or melem are used as the flame retardant in polyamide or polyester compositions.
The disadvantage of using melam or melem as the flame retardant is that its flame-retardant effect is insufficient for a number of applications.
The aim of the invention, now, is to provide a flame-retardant mixture whose flame-retardant properties are better than those of a mixture containing melam or melem as the flame retardant.
This aim is achieved by providing a flame-retardant mixture wherein the triazine flame retardant comprises at least:
c1) 1-95 wt. % melem,
c2) 0.01-25 wt. % melam,
c3) 0.01-20 wt. % melamine,
c4) 0.1-95 wt. % higher condensation products of melamine and/or melem, the wt. % being understood to be relative to the total of c1) up to and including c4) and together amounting to 100%, and the concentration of volatile components in the flame retardant being at most 5 wt. %. The mixture according to the invention shows a substantially shorter burning time in the UL 94 vertical burning test than the known mixture.
The flame-retardant mixture according to the invention comprises:
a) a polymer composition
b) a phosphorus-containing compound
c) a triazine flame retardant, the weight ratio of a, b and c lying between 94:1:5 and 35:30:35, and the triazine flame retardant comprising at least:
c1) 1-95 wt. % melem,
c2) 0.01-25 wt. % melam,
c3) 0.01-20 wt. % melamine,
c4) 0.1-95 wt. % higher condensation products of melamine and/or melem, the wt. % being understood to be relative to the total of c1) up to and including c4) and together amounting to 100%, and the concentration of volatile components in the flame retardant being at most 5 wt. %.
The polymer composition contains at least a polymer, and may in addition to polymer also comprise reinforcing agents and/or fillers and/or compounds with a synergistic effect with respect to the flame-retardant composition and/or other flame-retardant components than those according to the invention and also the usual additives, for example thermal and UV stabilisers, mould release agents, flow-promoting agents, softeners, lubricants, dispersing agents, colourants and/or pigments, in amounts commonly used for these additives, providing the properties are not adversely affected.
Polymers that are suitable for use in the flame-retardant mixture according to the invention are polymers that require heat-resistant flame retardants such as polyamides, polyimides, polyesters, polycarbonates, polymers containing styrene, epoxy resins, unsaturated polyester resins, polyurethanes and mixtures and blends of these materials. Examples of polyamides are polyamides and copolyamides that are derived from diamines and dicarboxylic acids and/or from aminocarboxylic acids or the corresponding lactams, such as polyamide 4, polyamide 6, polyamide 6/6, 6/10, 6/9, 6/12, 4/6, 66/6, 6/66, polyamide 11, polyamide 12, partially aromatic (co)polyamides, for example polyamides based on an aromatic diamine and adipic acid; polyamides prepared from an alkylenediamine and iso- and/or terephthalic acid and copolyamides thereof, copolyether amides, copolyester amide, etc. Examples of polyesters are polyesters derived from dicarboxylic acids and dialcohols and/or from hydroxycarboxylic acids or the corresponding lactones such as polyethylene terephthalate, polybutylene terephthalate, poly-1,4-dimethylolcyclohexane terephthalate, polyhydroxybenzoates, polycaprolactone and copolyesters thereof, copolyether esters, etc. Examples of polymers containing styrene are polystyrene, acrylonitrile-styrene copolymer, acrylonitrile-styrene-butadiene copolymers and mixtures hereof.
As the polymer, the flame-retardant mixture preferably contains polyesters such as polyethylene terephthalate and/or polybutylene terephthalate, polybutylene terephthalate being especially preferable, or polyamides, with polyamide 6, polyamide 6,6, polyamide 4,6 or mixtures of the aforementioned polyamides being especially preferable.
If reinforcing agents and/or fillers are used in the polymer composition, their concentration may vary within a wide range and this concentration is partly determined by the level of mechanical properties desired. In general the concentration of reinforcing agents will not amount to more than 50 wt. % of the total of the flame-retardant mixture according to the invention. Preferably a reinforced flame-retardant mixture will contain 5-50 wt. % reinforcing agents, more preferably 15-45 wt. %. Examples of reinforcing agents are mica, clay, talc, glass fibres, aramide fibres and carbon fibres. Different reinforcing agents may be combined. Glass fibres are however preferable.
The flame-retardant properties of the flame-retardant mixture according to the invention may be enhanced by the presence of a compound with a synergistic effect with respect to the flame-retardant composition, such as a charforming compound, optionally combined with a catalyst promoting the formation of char in the polymer composition. In general the concentration of the triazine flame retardant may consequently be lower.
In principle, all the known substances that are capable of enhancing the flame-retardant properties of flame-retardant polymer compositions by means of char formation caused by the fire are suitable for use as the charforming compound. Examples of this are phenolic resins, epoxy resins, polyurethanes, novolak resins, melamine resins, alkyd resins, allyl resins, unsaturated polyester resins, silicone resins, urethane resins, acrylate resins, polyphenylene ether, polycarbonate, polyvinyl alcohol, poly(ethylene covinyl), starch, glucose and compounds containing at least two hydroxyl groups. Examples of compounds containing at least two hydroxyl groups are alcohols containing at least two hydroxyl groups, for example pentaerythritol, dipentaerythritol, tripentaerythritol and mixtures hereof. The concentration in the total of the flame-retardant mixture of the charforming compound that is synergistic with respect to the triazine flame retardant generally lies between 0 and 30 wt. %, preferably between 1 and 20 wt. %.
Metal salts of tungstic acid, a complex oxide acid of tungsten and a metalloid, salts of tin oxide, ammonium sulphamate and/or its dimer may for example be used as the catalyst promoting char formation. Metal salts of tungstic acid are preferably alkali metal salts of tungstic acid and in particular sodium tungstate. A complex oxide acid of tungsten and a metalloid is understood to be a complex acid oxide that is formed by a metalloid such as silicon or phosphorus and tungsten such as silicotungstic acid or phosphotungstic acid. The amount of catalyst promoting char formation that is used in the total of the flame-retardant mixture is 0.1-5 wt. %, preferably 0.1-2.5 wt. %.
The flame-retardant properties of the flame-retardant mixture according to the invention may be further enhanced if the polymer composition comprises one or more other flame-retardant components. In principle, all the know flame retardants are suitable for use as the other flame-retardant component. Examples are antimony oxides, such as antimony trioxide, in combination with halogen compounds; alkaline earth metal oxides, for example zinc oxide, magnesium oxide; other metal oxides, for example alumina, silica, iron oxide and manganese oxide; metal hydroxides, for example magnesium hydroxide and aluminium hydroxide; nanocomposites; clay such as montmorillonite clay and kaolin clay; treated clay such as clay treated with primary ammonium compounds or with quarternary ammonium compounds or with melamine or with melamine condensation products or with phosphorus-containing compounds; silicon-containing compounds such as silicates, organosilicon compounds, aromatic organosilicon compounds and silanes; metal borates, for exam

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