WO2022144881A1

WO2022144881A1 - Polymeric flame retardants

Info

Publication number: WO2022144881A1
Application number: PCT/IL2021/051544
Authority: WO
Inventors: Eyal EDEN; Joseph Zilberman; Eran GLUZ; Elad HAKIMI
Original assignee: Bromine Compounds Ltd.
Priority date: 2020-12-30
Filing date: 2021-12-28
Publication date: 2022-07-07

Abstract

A bromine-phosphorus polymeric compound of the Formula (II) and its use as a flame-retardant in thermoplastics are described. A process for preparing the polymeric compound of Formula (II) by reacting brominated epoxy resins with X1X2P(=0)-OH or X3-0-PH (=0)(X4) is also described.

Description

POLYMERIC FLAME RETARDANTS

Field of the invention

The present invention provides novel bromine-phosphorus polymeric compounds , namely bromine-based polymers containing phosphinate groups , serving as highly ef ficient flame retardants in thermoplastic resins . The invention further provides fire retarded polymer compositions comprising said bromine-phosphorus polymers . The terms fire retardants and flame retardants are used herein synonymously .

Background of the invention

Brominated or phosphorus-based flame retardants are known to be highly ef fective and in many cases are the only options for reducing the fire risk of synthetic polymeric materials . However, the growing public and governmental scrutiny of chemicals , and particularly flame retardants , has increased over the years . The goal now is towards more sustainable flame retardants having a polymer nature . Polymeric flame retardants exhibit a superior environmental profile to that of non- polymeric molecules , because owing to their high molecular weight , they are less susceptible to migration once embedded (blended) in a plastic resin . In addition, thanks to their high molecular weight , polymeric compounds are not likely to penetrate through cell membranes of living tissue , and therefore do not pose a health hazard .

A variety of bromine-containing polymers are known in the art as flame retardants for thermoplastic resins . Unlike non- polymeric flame retardants which may migrate out of the thermoplastic polymer matrix leading to contamination of the environment and leaving the polymer unprotected in terms of fire resistance , polymeric flame retardants do not usually leach out or volatili ze during the service li fe of the resin . One known group of efficient polymeric flame retardants consists of brominated epoxy polymers of Formula (I) based on tetrabromobisphenol A:

Formula (I) wherein n is, for example, from 1 to 25, e.g., 2 to 20. Flame retardants of Formula (I) are available in the marketplace in the form of powders, with melting/sof tening points in the range of ~100 to 190°C, e.g., the F-2000 series from ICL-IP. End-capped brominated epoxy polymers, that is, where the terminal positions of the chains are occupied by brominated phenol (tribromophenol) are also known, as mentioned below.

Summary of the invention

We have now found that phosphorus can be incorporated into the terminus of brominated epoxy polymers of Formula (I) by a reaction with suitable reactants of Formulas (A) and (B) : Formula (A) : X⁴X²P (=0) -OH; and Formula (B) : X³-O-PH (=0) (X⁴ ) , (X¹ and X², X³ and X⁴ are defined below) .

The reaction can be carried out without a solvent/diluent ; it advances efficiently in the absence of a solvent, taking place in the molten state, e.g., by liquifying the starting material of Formula (I) and adding one or more reactants of Formulas (A) and (B) to the melt under stirring. On completion, the reaction mass is solidified, and the product is collected in a particulate form, for example, in the form of a powder or flakes . The reaction product is end-capped brominated epoxy polymer of

Formula (II) :

Formula (II) wherein n is an integer from 1 to 25, e.g., 2 to 20, and the terminal groups Ri and R2 contain a phosphorus atom at an oxidation state of +1, that is, each of Ri and R2 is independently selected from:

A) X¹X²P (=0) -0*- (the asterisk indicates that the oxygen atom is linked to the methylene group in the polymer of Formula II) , such that:

Al) X¹ and X² are independently selected from hydrogen and hydrocarbyl; or

A2 ) X¹ and X², when taken together with the phosphorus atom, form a five-membered or six-membered (optionally unsaturated) ring; or

B) X³-O-P* (=0) (X⁴)- (the asterisk indicates that the phosphorus atom is linked to the methylene group in the polymer of Formula (II) ) , such that X³ and X⁴, when taken together with the phosphorus atom, form a ring (e.g., sixmembered ring) containing phosphorus and oxygen atoms:

optionally fused to one or more aromatic rings. To prepare compounds of Formula II, variant A) , where one or both of R¹ and R² is X²X²P (=0) -0*-, the starting material of Formula (I) is reacted with the corresponding compound of Formula (A) X²X²P (=0) -OH . That is, a phosphinic acid or derivative thereof.

For example, for subvariant Al) , phosphinic acid of Formula (IV) may be used:

Formula (IV) wherein X¹ and X² are independently selected from hydrogen, aryl, alkyl aryl, aryl alkyl, hydroxy alkyl, allyl or a linear or branched alkyl group containing from 1 to 6 carbon atoms, such as from methyl, ethyl, propyl, isopropyl, n-butyl, t- butyl, isobutyl, n-pentyl or n-hexyl, and preferably methyl or ethyl, more preferably X¹ and X² both being ethyl, thereby arriving at compounds of Formula II in which one or both of Ri and R2 is the moiety of Formula (III) :

Formula (III)

For example, for subvariant A2 ) , cyclic phosphinic acids of Formula (VI) [derived from phospholene phosphinic acids; also known as 1-hydroxy-phospholene-l-oxides ] may be used (X¹ and X² are taken together with the phosphorus atom, to form a fivemembered, optionally monounsaturated ring) :

Formula (VI) wherein the dashed line indicates a double bond located between the carbon atom at position 3 and one of the carbon atoms at positions 2 and 4 provided that each of the two ring carbon atoms which are not part of the double bond are each bonded to one of the two hydrogen atoms shown in the structural Formula (VI) ;

R¹, R², R³ and R⁴ are independently selected from H, a linear or branched alkyl group containing from 1 to 4 carbon atoms, preferably methyl or ethyl; thereby arriving at compounds of Formula II in which one or both of Ri and R2 is the moiety of Formula (V) :

To prepare compounds of Formula (II) , variant B) , where one or both of R¹ and R² is X³-O-P* (=0) (X⁴)-, such that X³ and X⁴, when taken together with the phosphorus atom, form a six-membered ring containing phosphorus and oxygen atoms, fused with one or more aromatic ring(s) , the starting material of Formula (I) is reacted with the corresponding compound of Formula (B) , namely, X³-O-PH(=O) (X⁴) , such as, for example, 10-Dihydro-9- oxa-10-phosphaphenanthrene 10-oxide (DOPO) of Formula (VIII) :

Formula (VIII) preferably in the presence of quaternary ammonium or phosphonium salt catalyst, thereby arriving at compounds of Formula II in which one or both of Ri and R2 is the moiety of Formula (VI I ) :

Formula (VII)

Thus, more specifically, the invention provides processes for the preparation of the novel bromine-phosphorus polymeric compounds of Formula (II) having one or two phosphinate functionalities - by the reaction of tetrabromobisphenol A based brominated epoxy polymers of Formula (I) with phosphinic acids of Formula (IV) , phospholene phosphinic acids of Formula (VI) (also named 1-hydroxy-phospholene-l-oxides ) or 9,10- Dihydro-9-oxa-10-phosphaphenanthrene 10-oxide (DOPO) of Formula (VIII) , or with a mixture of two or more phosphinic acids, or with a mixture of a phosphinic acid and DOPO (Formula (VIII) ) .

The present invention further provides fire retarded thermoplastic compositions comprising said novel brominephosphorus polymeric compounds which can be used either individually or in admixture with one another. Detailed Description of Preferred Embodiments

The brominated epoxy polymers of Formula (I) used as starting materials in the preparation of the novel flame retardants of Formula (II) are commercial products known as the F-2000 series produced by ICL-IP (Dead Sea Bromine) . These starting materials can be prepared by methods known in the art (for example, EP 467364) , by reacting tetrabromobisphenol A with epichlorohydrin, optionally in an inert solvent such as toluene or methyl isobutyl ketone, in the presence of a base (e.g., an aqueous solution of sodium hydroxide) under heating. Following phase separation, the organic phase, which contains the product, is washed with water to remove residual salts therefrom and the product is finally recovered by removing the organic solvent.

Low and medium molecular weight brominated epoxy resins of Formula (I) , with weight average molecular weight of 1500 to 12000, e.g., 1500 - 5000 (e.g., 2000 - 4000, specifically 2500 3500) can be used as starting materials in the present invention. One suitable starting material available on the marketplace is F-2016 from ICL-IP, with molecular weight of about 3000-3500, e.g., around 3200. Low molecular weight brominated epoxy resins of Formula (I) such as F-2016 are liquefiable at a temperature in the range of 100 to 180°C and are applicable to a solvent-free reaction with the phosphorus containing reactants (A) and (B) , affording, on solidification, readily manageable end-capped polymers recovered in a particulate form. It is noteworthy that in contrast, a solvent-free reaction of phosphinic acid with the monomer, i.e., diglycidyl ether of tetrabromobisphenol A:

results in a sticky, difficult to handle solid. The reaction of the brominated epoxy polymers of Formula (I) according to variant (A) of the invention, namely, with phosphinic acids of the formula X¹X²P (=0) -OH, is preferably carried out without any solvent and any catalyst.

Suitable phosphinic acids include, inter alia, hypophosphorous acid (phosphinic acid H3PO2) , alkylphosphonous acids such as for example methyl, ethyl, propyl, butyl, hydroxyethyl phosphonous acids, dialkyl phosphinic acids such as for example methylethyl phosphinic acid, diethyl phosphinic acid, di-n-butyl phosphinic acid, di-isobutyl phosphinic acid and 1- hydroxy-phospholene-l-oxides of Formula (VI) , described, e.g., in WO 99/07715; for example, at least one of the following isomers, or an equally proportioned mixture thereof (from 40 : 60 to 60:40) :

The reaction of the brominated epoxy polymers of Formula (I) according to variant B of the invention, namely, with the cyclic compounds X³-O-PH(=O) (X⁴) , such as DOPO, is carried out in the presence of a quaternary ammonium, and preferably in the presence of a more thermally stable quaternary phosphonium salt catalyst, without an organic solvent.

Suitable quaternary ammonium salt catalysts are triethylbenzyl ammonium bromide, tetrabutyl ammonium bromide and tributylbenzyl ammonium chloride. Especially suitable quaternary phosphonium salt catalysts are tetrabutyl phosphonium bromide and ethyltriphenyl phosphonium acetate. An effective amount of a quaternary salt catalyst is employed in the range of 0.2 to 1.5% by weight, and preferably from 0.3 to 0.6% by weight, based on the total quantity of the reagents. The amount of a single phosphinic acid, or a mixture of di f ferent phosphinic acids , or a mixture of a phosphinic acid and DOPO used in the reaction with brominated epoxy polymers is preferably expressed in a molar ratio between the phosphinic acid or DOPO and the brominated epoxy polymer . Thus , the molar ratio in such cases is in a range of about 0 . 5 to 2 mol phosphinic acid or DOPO per 1 mol brominated epoxy polymer that is calculated based on weight average molecular weight of the polymer . Preferably this molar ratio is from about 1 . 8 to about 2 .

Using a molar ratio between the phosphorus-containing reactant and the brominated epoxy polymer below 0 . 5 is inexpedient due to the very low phosphorus content in the product , which can hardly be ef ficient in terms of flame retardancy .

An excess of phosphorus-containing reactant above 2 mol per 1 mol brominated epoxy polymer having two epoxy end groups according to Formula ( I ) is expected to result in residual unreacted phosphinic acid or DOPO . The phosphinic acids and DOPO are relatively volatile compounds . Thus , their presence in free form in bromine-phosphorus flame retardants of the invention will result in their partial evaporation or sublimation during the extrusion or molding processes of making fire retarded thermoplastic compositions comprising said bromine-phosphorus flame retardants . Such evaporation or sublimation of the free phosphinic acids or DOPO are undesirable as far as safety and health considerations are concerned . In addition, the residual free phosphinic acids possessing strong acidity will cause corrosion of the equipment employed in the extrusion or molding processes .

The bromine-phosphorus polymeric flame retardants of the present invention have a typical bromine content of about 35- 50% by weight and a typical phosphorus content of about 0.8- 7.5% by weight. The compound of Formula (II) obtained by reacting brominated epoxy polymer F-2016 having weight average molecular weight of 3200 with diethyl phosphinic acid taken in an amount of 2 mol per 1 mol brominated epoxy polymer contains 45-49% (e.g., 48.3%) bromine and 1.5 to 2.0% (e.g., 1.7%) phosphorus .

Said reactions are carried out at a temperature of between 160 and 210°C, and preferably between 170 and 200°C, depending on the softening range of the brominated epoxy polymer. Applying a temperature lower than 160°C resulted in a low conversion of the reagents mainly due to a very high viscosity of the polymer. On the other hand, applying a temperature higher than 210°C is not advisable since at such temperatures discoloration of the reaction mixture takes place and undesirable decomposition products may be formed. When the reaction is finished the reaction mass is cooled down to solidify, and crushed/milled to collect a particulate product which may be purified by reprecipitation, if desired.

The present invention provides novel polymeric brominephosphorus compounds possessing highly satisfactory flame retarding characteristics, having good compatibility with the thermoplastic resins such as polyesters, polyamides, styrenic resins and polyolefins, and imparting excellent UV stability to those thermoplastic resins. The invention further provides polymeric compositions containing the said novel brominephosphorus compounds that exhibit excellent fire retardancy.

In the experimental work reported below, the performance of the novel phosphorus-containing, end-capped brominated epoxy polymers of Formula (II) was studied in some thermoplastics and compared to commercial flame retardants of Formula (I) , i.e., the "parent" compound and analogues thereof, and also to commercial end-capped brominated epoxy polymers, that is, where the terminal positions of the chains are occupied by brominated phenol (i.e., tribromophenol) , having the following structure :

Formula (IB)

Flame retardants of Formula (IB) are commercially available as the F-3000 series from ICL-IP. Table 1 summarizes the main characteristics of the polymeric flame retardants which were tested in the studies reported below:

Table 1

The polymeric flame retardants tabulated in Table 1 were tested in thermoplastics in comparative studies when applied at equal bromine strength, i.e., bromine concentrations in formulations were the same (bromine concentration is calculated by multiplying the bromine content of a given flame retardant (see Table I) by the amount of the flame retardant added to the polymeric composition (i.e., concentration of the FR in the formulation) ) .

The results reported below reveal the surprising compatibility of the bromine-phosphorus polymers of the invention in polyester and styrene-containing polymers and the greatly improved ultraviolet (UV) light stability demonstrated by thermoplastic formulations flame retarded with the brominephosphorus polymers of Formula II, compared with formulations based on the structurally similar comparative (commercial) flame retardants. The ability of a plastic material to resist deterioration of its electrical, mechanical, and optical properties caused by exposure to light, heat, and water can be very significant for many applications. UV light stability measurements reported herein were performed according to ASTM D4329 with UVA-340 lamps, intended to induce property changes associated with end-use conditions, namely, the effects of ultraviolet solar irradiance.

Another advantage displayed by the flame retardants of the invention is seen in reduced flammability of thin parts. The flammability characteristics of plastic materials are usually quantifiable according to a method specified by Underwriter Laboratories standard UL 94, where an open flame is applied to the lowermost edge of a vertically mounted test specimen made of the tested polymer formulation. The specimens used in the UL 94 test method vary in thickness (typical thicknesses are ~3.2 mm, ~1.6 mm, ~0.8 mm and ~0.4 mm) . During the test, various features of the flammability of the test specimens are recorded. Then, according to the classification requirements, the polymer formulation is assigned with either V-0, V-l or V- 2 rating at the measured thickness of the test specimen. Polymer formulation assigned with the V-0 rating is the least flammable. In the UL-94 burning test, the thinner the specimens are, the longer the burning time. Therefore, the requirements of UL 94 V-0 rating for thin test specimens (e.g., 0.8 or 0.4 mm thick samples) are not easily met.

However, the flame retardants of the present invention achieve the goal at reasonable bromine concentrations, at which the "parent" compound is less successful.

Thus, the phosphorus-containing end-capped brominated epoxy resins of the invention are useful as flame retardant agents in a flammable material. Accordingly, another aspect of the present invention is a flame-retarded composition which comprises a flammable material and the novel polymer of the invention. For example, the bromine-containing polymers of the invention can be used to reduce the flammability of acrylonitrile-butadiene-styrene (ABS) and polyesters, e.g., poly ( 1 , 4-butylene terephthalate) (PBT) , including grades reinforced with glass-fibers (PBT/GF) .

A flame-retarded composition of the invention comprises an effective flame-retarding amount of the novel phosphorus- containing end-capped brominated epoxy of the invention, e.g., the compounds of Formula II. The concentration the flame retardant of Formula II in the plastic formulation is adjusted to obtain a bromine concentration of least 5 %, e.g., from 5 to 10% (by weight, based on the total weight of the flame-retarded plastic composition) . Recalling that the bromine content of the compounds of Formula II is in the range of 45 to 50% by weight bromine, their loading in the thermoplastic composition is expected to vary from ~10 to 20% by weight, based on the total weight of the flame-retarded plastic composition. Other conventional additives may also be included in the plastic composition. For example, an inorganic compound (typically a metal oxide) that enhances the action of brominated flame retardants. A preferred example of a suitable inorganic compound, which is generally considered as an "inorganic synergist", is antimony oxide, e.g., antimony trioxide (Sb20s, ATO) . The ratio between the weight concentrations of bromine and ATO in the compositions of the invention is, for example, from 4:1 to 1.5:1 (bromine: ATO) , e.g., weight ratio of 2.5:1 to 1.5:1.

The compositions according to the present invention also include one or more anti-dripping agents such as polytetrafluoroethylene (abbreviated PTFE) in a preferred amount between 0.1 and 1.0 wt%, more preferably between 0.15 and 0.7 wt%, based on the total weight of the composition. PTFE is described, for example, in US 6,503,988.

Apart from the thermoplastic, the flame retardant of Formula II, a synergist (e.g., ATO) , and an anti-dripping agent (e.g., PTFE) , the composition of this invention may further contain conventional additives, such as processing aids, antioxidants (e.g., hindered phenol type) , lubricants, UV stabilizers, thermal stabilizers, pigments, dyes and the like. The total concentration of these auxiliary additives is typically not more than 3 % by weight. For example, Irganox® B225, consisting of an equally proportioned mixture by weight of tris (2, 4- ditert-butylphenyl ) phosphite and pentaerythritol tetrakis[3- [3, 5-di-tert-butyl-4-hydroxyphenyl] propionate, and Irganox® 1010 (pentaerythritol tetrakis [ 3- [ 3 , 5-di-tert-butyl-4- hydroxyphenyl ] propionate ) .

ABS compositions of the invention preferably comprise not less than 50 wt% ABS (relative to the total weight of the formulation) , e.g., from 50 to 85 wt% ABS, generally from 70 to 80 wt% ABS. The term ABS refers in the context of the present invention to copolymers and terpolymers that include the structural units corresponding to (optionally substituted) styrene, acrylonitrile and butadiene, regardless of the composition and method of production of said polymers. Characteristics and compositions of ABS are described, for example, in the Encyclopedia of Polymer Science and Engineering, Volume 16, pages 72-74 (1985) . ABS with MFI between 1 and 50 g/10 min (measured according to ISO 1133 at 220°C/10 kg) can be used.

The invention specifically provides ABS composition comprising: from 65 to 85% by weight of ABS (e.g., from 70 to 80%) ; from 10 to 20% by weight of flame retardant of Formula (II) (e.g., from 12 to 18 %) ; from 2 to 7% by weight antimony trioxide (e.g., from 3 to 7%) ; and from 0.1 to 1.0% by weight PTFE (e.g., from 0.1 to 0.5% by weight) .

Turning now to polyester compositions of the invention, these contain not less than 10% by weight, e.g., from 20 to 70% by weight and preferably from 20 to 60% by weight of a thermoplastic polyester (e.g., 35-55%) , i.e., polyesters of the classes based on: aromatic dicarboxylic acids and aliphatic dihydroxy compounds; and aromatic dicarboxylic acids and aromatic dihydroxy compounds.

Of the former class, preferred are linear polyesters obtained from terephthalic acid, isophthalic acid and 2, 6 naphathalenedicarboxylic acid, wherein the aliphatic dihydroxy compound is a diol having from 2 to 6 carbon atoms, such as 1 , 2-ethanediol , 1 , 3-propanediol , 1 , 4-butanediol , 1, 6- hexanediol, 1 , 4-hexanediol , and mixtures thereof. Particularly preferred are polyalkylene terephthalates derived from alkanediols having from 2 to 6 carbon atoms. Among these, especially preferred are polyethylene terephthalate (PET) and polybutylene terephthalate (PBT) . Copolymers and/or polyblends available in the market for many linear polyesters are also contemplated for use in the invention. Additional details regarding suitable polyesters can be found in US 6,503,969 and US 8,188,172. PBT is available from various manufacturers, e.g., BASF and Ticona. For example, the melt flow index of the PBT (MFI; ISO 1133 250°C/2.16 kg) may vary from 25 g/10 min to 50 g/10 min, e.g., from 20 to 35 g/10 min or from 35 to 50 g/10 min .

Polyester compositions of the invention preferably comprise a reinforcing filler, especially glass fibers, which are usually pre-coated by manufacturers in order to improve their compatibility with the polymer in question (e.g., polyester in the present case) . For example, the major constituents of glass fibers applied for reinforcing polyester intended for use in electrical devices are alumino-borosilicates ; such type of glass in known as E-glass. The glass fibers comprise filaments with diameter in the range from Ip to 30p, and are applied in the form of chopped strands with length in the range from 2 to 10 mm, e.g., from 3 to 4.5 mm. The concentration of the glass fibers is usually from 5% to 40% by weight, e.g., from 10% to 40% by weight, preferably at least 20% by weight, e.g., from 20 to 35% by weight, in particular from 25 to 35% by weight and especially from 27 to 33% by weight, i.e., around 30% by weight, based on the total weight of the composition.

The invention specifically provides a composition comprising: from 30 to 60% by weight of a polyester (e.g., 45-55%) , namely, polyalkylene terephthalate, and especially polybutylene terephthalate (PBT) ; from 20 to 35% by weight of a reinforcing filler, e.g., glass fibers (e.g., 25-35% and especially 27-33%) ; from 10 to 20% by weight of flame retardant of Formula (II) (e.g., from 11 to 15 %) ; from 2 to 7% by weight antimony trioxide (e.g., from 3 to 5%) ; and from 0.1 to 1.0% by weight PTFE (e.g., 0.3 to 0.7% by weight) .

The preparation of the thermoplastic compositions of the invention may be carried out using different methods known in the art. For example, the compositions are produced by meltmixing the components, e.g., in a co-kneader or twin-screw extruder, wherein the mixing temperature is, e.g., in the range from 200 to 250°C. In some formulations it is possible to feed all the ingredients to the extrusion throat together, but in other cases, such as for PBT/GF, it is generally preferred to first dry-mix some of the components, and then to introduce the dry blend into the main feed port of the extruder, with one or more of the ingredients being added downstream. For example, PBT, flame retardant of Formula II, and one or more of the conventional additives are dry blended and the blend is fed to the extruder throat, followed by the addition of glass fibers downstream. Process parameters such as barrel temperature, melt temperature and screw speed are described in more detail in the examples that follow.

The resultant extrudates are comminuted into pellets. The dried pellets are suitable for feed to an article shaping process, injection molding, extrusion molding, compression molding, optionally followed by another shaping method. Articles molded from the compositions form another aspect of the invention. Examples

Methods

³¹P NMR spectra were recorded in CDCI3 on a Bruker Avance III 500MHz spectrometer.

Example 1 (variant Al)

Reaction of brominated epoxy polymer and (C2H5) 2P (O) OH

A 2 liter reactor, equipped with a mechanical stirrer and a thermometer was charged with brominated epoxy polymer F-2016 with MW 3200 (960 g) and heated to 140°C until the F-2016 had fully melted. Further diethyl phosphinic acid (DEFA; 73.2 g, 0.6 mol) , was added and the reaction mixture was heated at 180°C for 1 hour until the diethyl phosphinic acid conversion was complete (confirmed by ³¹P-NMR) . After the reaction was finished, the product was poured onto an aluminum plate. 1030 g of the bromine-phosphorus polymer of Formula (II) with bromine content of 48.3% and phosphorus content of 1.7% was obtained. The product was milled resulting in a white to off- white powder. ³¹P NMR (Chloroform-d, ppm) 5 64.8 and 65.3 (main peaks) .

Example 2 (variant B)

Reaction of brominated epoxy polymer and DOPO

A 2 liter reactor, equipped with a mechanical stirrer and a thermometer was charged with brominated epoxy polymer F-2016 with MW 3200 (900 g) and heated to 140°C until the F-2016 had fully melted. Further DOPO (121 g, 0.56 mol) and tetrabutyl phosphonium bromide catalyst (2.2 g) were added. The reaction was accompanied by an exotherm and the temperature rose to 215°C. The reaction mixture was cooled to 190°C and kept at this temperature for 1 hour until the DOPO conversion was complete (confirmed by ³¹P-NMR) . After the reaction was finished, the product was poured onto an aluminum plate. The bromine-phosphorus polymer of Formula (II) with bromine content of 45.8% and phosphorus content of 1.7% was obtained. Subsequent milling of the product afforded an off-white powder. ³¹P NMR (Chloroform-d, ppm) 5 10.90 and 12.1 (main peaks) .

Example 3 (variant Al)

Reaction of brominated epoxy polymer and ( (CH3) 2CH-CH2) 2P (O) OH

A 1 liter reactor, equipped with a mechanical stirrer and a thermometer was charged with brominated epoxy polymer F-2016 with MW 3200 (640 g) and heated to 140°C until the F-2016 had fully melted. Further di-isobutyl phosphinic acid (71 g) was added and the reaction mixture was heated at 170°C for 1 hour until the di-isobutyl phosphinic acid conversion was complete (confirmed by ³¹P-NMR) . After the reaction was finished, the product was poured onto an aluminum plate. The brominephosphorus polymer of Formula (II) with bromine content of 46.8% and phosphorus content of 1.7% was obtained. Subsequent milling of the product afforded a white to off-white powder. 3¹P NMR (Chloroform-d, ppm) 5 61.18 and 61.25 (main peaks) .

Example 4 (variant A2)

Reaction of brominated epoxy polymer and a mixture consisting of

A 1 liter reactor, equipped with a mechanical stirrer and a thermometer was charged with brominated epoxy polymer F-2016 with Mw 3200 (640 g) and heated to 140°C until the F-2016 had fully melted. Further an isomeric mixture composed of 55% 1- hydroxy-3-methyl-3-phospholene-l-oxide and 45% l-hydroxy-3- methyl-2-phospholene-l-oxide (52 g) was added and the reaction mixture was heated at 170°C for 1 hour until the phospholene phosphinic acids conversion was complete (confirmed by ³¹P- NMR) . After the reaction was finished, the product was poured onto an aluminum plate. The bromine-phosphorus polymer of Formula (IT) with bromine content of 48% and phosphorus content of 1.8% was obtained. Subsequent milling of the product afforded an off-white powder. ³¹P NMR (Chloroform-d, ppm) 5 78.2-75.3 (multiple peaks) .

Example 5 (comparative)

Reaction of non -polymeric F-2200 and (C2H5) 2P (O) OH

A 1 liter reactor, equipped with a mechanical stirrer and a thermometer was charged with diglycidyl ether of tetrabromobisphenol A F-2200 with MW 700 (830 g) , DEPA (283.5 g, 2.3 mol) , and the mixture was heated at 185°C for 1 hour until the diethyl phosphinic acid conversion was complete (confirmed by ³¹P-NMR) . After the reaction was finished, the product was poured onto an aluminum plate. 1110 g of the bromine-phosphorus non-polymeric compound with bromine content of 35.6% and phosphorus content of 6.6% was obtained in the form of a sticky, difficult to handle, solid. ³¹P NMR (121 MHz, Chlorof orm-d, ppm) 5 64.37 and 64.74 (main peaks) .

Examples 6-7 (comparative) and Examples 8-9 (of the invention)

V-0 rated PBT/GF formulations

In this set of examples, the end-capped brominated epoxy polymer of Example 1 was tested in PBT/GF, to evaluate its ability to reduce the flammability of PBT/GF across the acceptable test thickness range (i.e., measured at test specimens down to 0.4 mm) , vis-a-vis a commercial brominated epoxy resin.

Preparation

PBT (Ultradur® 4520 from BASF) and additives (with the exception of the brominated FR and glass fibers) were premixed and the blend was fed via Feeder no. 1 into the main port of a twin-screw co-rotating extruder ZE25 with L/D=32 (Berstorff) . The brominated FR was fed via Feeder no. 2 to the extruder main port. The glass fibers (PPG 3786) were added downstream, via Feeder no. 3 to the fifth zone of the barrel through a lateral feeder. Operating parameters of the extruder were as follows :

Barrel temperature (from feed end to discharge end) : 220°C, 240°C, 245°C, 250°C, 260°C, 270°C, 270°C, die - 275°C.

Screw rotation speed: 350 rpm

Feeding rate: 12 kg/hour.

The strands produced were pelletized in a pelletizer 750/3 from Accrapak Systems Ltd. The resultant pellets were dried in a circulating air oven (Heraeus Instruments) at 80°C for 3 hours. The dried pellets were injection molded into test specimens (1.6, 0.8 and 0.4 mm thick) using Allrounder 500-150 from Arburg, which operated with Ti (feeding) = 240°C, T2=250°C, T3=260°C, T4=265^OC, TS (nozzle)= 270°C; mold temperature of 70 °C; injection pressure = 1000 bar; holding pressure = 850 bar; back pressure = 10 bar; holding time = 10 s; cooling time 15 s; mold closing force = 500 kN; and injection speed = 25 cm³/s .

The test specimens were conditioned at 23°C for one week and then subjected to the test set out below.

Flammability test

A direct flame test was carried out according to the Underwriters-Laboratories standard UL 94 in a gas methane operated flammability hood, applying the vertical burn on the 1.6, 0.8, and 0.4 mm thick test specimens. The compositions and test results are tabulated in Table 2 . The calculated concentrations of bromine , antimony trioxide and phosphorus in the compositions are also set out in Table I I ( antimony trioxide used was a 80% masterbatch, MO 112 from Kaf rit , IL ) .

Table 2

It is seen that in the case of F-2100 the presence of (bromine=6-7 % /Sb2O3=3-4 % ) in PBT/GF can only achieve UL 94 rating of V-2 , whereas an equal bromine/Sb203 loading in the case of the flame retardant of Example 1 conferred better levels of flame retardancy to PBT/GF, i . e . , V- 0 rating was achieved across the entire thickness range test , including the thinner test specimen .

Examples 10 - 12 (comparative) and 13 (of the invention) V-0 rated ABS formulations

In the next set of Examples , the performance of the flame retardant of Example 1 was studied in ABS and compared to a few commercial brominated epoxy and end-capped brominated epoxy resins. Flame retardancy, mechanical and physical properties and UV light stability were measured. The compositions and test results are tabulated in Table 3.

Preparation

ABS (Magnum™ 3404) and additives were premixed and the blend was fed via Feeder no. 1 into the main port of a twin-screw co-rotating extruder ZE25 with L/D=32 (Berstorff) . Operating parameters of the extruder were as follows:

Barrel temperature (from feed end to discharge end) : 190°C, 200°C, 210°C, 220°C, 220°C, 225°C, 230°C, die - 240°C.

Screw rotation speed: 350 rpm

Feeding rate: 12 kg/hour.

The strands produced were pelletized in a pelletizer 750/3 from Accrapak Systems Ltd. The resultant pellets were dried in a circulating air oven (Heraeus Instruments) at 80°C for 3 hours. The dried pellets were injection molded into test specimens (1.6 mm thick) using Allrounder 500-150 which operated with Ti (feeding)= 210°C, T2=215°C, T3=220°C, T4=225°C, Ts (nozzle) = 230°C; mold temperature of 35°C; injection pressure = 1300 bar; holding pressure = 700 bar; back pressure = 50 bar; holding time = 11 s; cooling time 9 s; mold closing force= 500 kN; and injection speed = 35 cm³/s .

The 1.6 mm thick test specimens were conditioned at 23°C for one week and then subjected to the tests set out below to determine their properties.

Flammability test

A direct flame test was carried out according to the Underwriters-Laboratories standard UL 94 in a gas methane operated flammability hood, applying the vertical burn on the 1.6 mm thick test specimens. Mechanical test

Tensile strength was measured according to ASTM D638 using Zwick Z 010 material testing machine ( type 2 dumbbells were used, with a speed test of 50 mm/min) .

Physical test

Melt flow index was measured with Gottfert MI-3 , according to ASTM D 1238 at 220°c / 5 Kg [ g/ l Omin] .

UV light stability test

The instrument used was Atlas 2000 . Measurements were performed according to ASTM D4329 with UVA-340 lamps .

The compositions and test results are tabulated in Table 3 . The calculated concentrations of bromine and antimony trioxide in the compositions are also set out in Table 3 ( antimony trioxide used was a 80% masterbatch, MO 112 from Kafrit , IL ) .

Table 3

The results indicate that all four flame retardants passed the UL 94V-0/1.6 mm test (the flame retardant of Example 1 met the challenge with a calculated bromine loading of 8.7% by weight) . It is also seen that the flame retardant of Example 1 and commercial brominated epoxy resins were roughly comparable in terms of mechanical and physical properties. However, ABS formulation which contained the flame retardant of Example 1 (Example 13) was significantly more stable against UV light irradiation, exhibiting less color change when exposed to UV light than comparative ABS formulations.

Claims

1. A bromine-phosphorus polymeric compound of the Formula (II) :

Formula (II) wherein n is an integer from 1 to about 25, and Ri and R2 are independently selected from (A) and (B) :

A) X⁴X²P (=0) -0*- (the asterisk indicates that the oxygen atom is linked to the methylene group in the polymer of Formula II) , such that:

Al) X¹ and X² are independently selected from hydrogen and hydrocarbyl; or

A2 ) X¹ and X², when taken together with the phosphorus atom, form a five-membered or six-membered (optionally unsaturated) ring; and

B) X³-O-P* (=0) (X⁴)- (the asterisk indicates that the phosphorus atom is linked to the methylene group in the polymer of Formula (II) ) , such that X³ and X⁴, when taken together with the phosphorus atom, form a ring containing phosphorus and oxygen atoms:

optionally fused to one or more aromatic rings.

26 2) A bromine-phosphorus polymeric compound of Formula (II) according to claim 1, wherein Ri and R2 are independently X²X²P (=0) -0*-, wherein Xi and X2 are independently selected from hydrogen and hydrocarbyl .

3) A bromine-phosphorus polymeric compound of Formula (II) according to claim 2, wherein X¹X²P (=0) -0*- is a group of formula (III) :

Formula (III) wherein X¹ and X² are independently selected from hydrogen, aryl, alkyl aryl, aryl alkyl, hydroxy alkyl, allyl or a linear or branched alkyl group containing from 1 to 6 carbon atoms.

4) A bromine-phosphorus polymeric compound of Formula (II) according to claim 3, wherein X¹ and X² are independently selected from a linear or branched alkyl group containing from 1 to 6 carbon atoms .

5) A bromine-phosphorus polymeric compound of Formula (II) according to claim 4, wherein X¹ and X² are both ethyl, or both isobutyl .

6) A bromine-phosphorus polymeric compound of Formula (II) according to claim 1, wherein Ri and R2 are independently X²X²P (=0) -0*-, wherein X¹ and X² are taken together with the phosphorus atom to form a five-membered or six-membered

(optionally unsaturated) ring. 7) A bromine-phosphorus polymeric compound of Formula (II) according to claim 6, wherein X⁴X²P (=0) -0*- is a group of Formula (V) :

Formula (V) wherein the dashed line indicates a double bond located between the carbon atom at position 3 and one of the carbon atoms at positions 2 and 4 provided that each of the two ring carbon atoms which are not part of the double bond are each bonded to one of the two hydrogen atoms shown in the structural Formula (V) , and R¹, R², R³ and R⁴ are independently selected from hydrogen, a linear or branched alkyl group containing from 1 to 4 carbon atoms.

8) A bromine-phosphorus polymeric compound of Formula (II) according to claim 7, wherein the group of Formula (V) is selected from

and a mixture thereof.

9) A bromine-phosphorus polymeric compound of Formula (II) according to claim 1, wherein Ri and R2 are independently X³-O-P* (=0) (X⁴)-, and X³ and X⁴ are taken together with the phosphorus atom to form a ring containing phosphorus and oxygen atoms :

fused to one or more aromatic rings.

10) A bromine-phosphorus polymeric compound of Formula (II) according to claim 9, wherein X³-O-P* (=0) (X⁴)- is a group of Formula (VII)

Formula (VII)

11) A process for preparing a bromine-phosphorus polymeric compound of Formula (II) as defined in claim 1, comprising reacting a brominated epoxy resin of Formula (I) :

Formula (I) wherein n is from 1 to about 25, with a reactant, or a mixture of reactants, selected from the group consisting of:

A) X²X²P (=0) -OH, such that:

Al) X¹ and X² are independently selected from hydrogen and hydrocarbyl; or

29 A2 ) X¹ and X², when taken together with the phosphorus atom, form a five-membered or six-membered (optionally unsaturated) ring; and

B) X³-O-PH(=O) (X⁴) , such that X³ and X⁴, when taken together with the phosphorus atom, form a ring containing phosphorus and oxygen atoms :

optionally fused to one or more aromatic rings.

12) A process according to claim 11, wherein the reaction is devoid of a solvent/diluent .

13) A process according to claim 12, comprising melting a brominated epoxy resin of Formula (I) :

Formula (I) adding one or more reactants of formulas (A) and (B) to the melt under stirring, completing the reaction and solidifying the reaction mass to recover the product of Formula (II) .

14) A process according to claim 13, comprising collecting the product of Formula (II) in a particulate form.

15) A flame-retarded composition, comprising a flammable material and the polymer of Formula (II) as defined in any one of claims 1 to 10. 16) A flame-retarded composition according to claim 15, wherein the flammable material is a thermoplastic selected from the group consisting of polyesters and styrene-containing polymers.

17) A flame-retarded composition according to claim 16, comprising : from 65 to 85% by weight of acrylonitrile-butadiene-styrene ; from 10 to 20% by weight of flame retardant of Formula (II) ; from 2 to 7% by weight of antimony trioxide; and from 0.1 to 1.0% by weight PTFE.

18) A flame retarded composition according to claim 16, comprising : from 30 to 60% by weight of polyalkylene terephthalate; from 20 to 35% by weight of a reinforcing filler; from 10 to 20% by weight of flame retardant of Formula (II) ; from 2 to 7% by weight of antimony trioxide; and from 0.1 to 1.0% by weight PTFE.

19) A composition according to any one of claims 15 to 18, wherein the polymer of Formula II is as defined in claim 5.