WO2014168754A1

WO2014168754A1 - Flame retarded thermoplastic elastomer composition, process for making same and wire jacket

Info

Publication number: WO2014168754A1
Application number: PCT/US2014/031732
Authority: WO
Inventors: Sergei V. Levchik
Original assignee: Icl-Ip America Inc.
Priority date: 2013-04-08
Filing date: 2014-03-25
Publication date: 2014-10-16

Abstract

There is provided herein a flame retarded thermoplastic elastomer composition containing at least one thermoplastic elastomer and at least one metal phosphonate. There is also provided finished parts and articles e.g., such as wire and cable insulations, electrical and electronic equipment, car interior materials, and the like containing the flame retarded thermoplastic elastomer composition described herein.

Description

FLAME RETARDED THERMOPLASTIC ELASTOMER

COMPOSITION, PROCESS FOR MAKING SAME AND WIRE JACKET

FIELD OF THE INVENTION

The present invention relates to flame-retarded thermoplastic elastomer composition(s), preferably thermoplastic polyurethane (TPU) composition(s) useful for applications where high flame retardant performance is desirable, such as wire and cable applications, electrical and electronic equipment, car interior materials, and the like.

BACKGROUND OF THE INVENTION

Halogen-containing materials such as polyvinyl chloride (PVC) find widespread use in wire and cable applications. However due to end-of-life disposal and incineration issues there are efforts by some major consumer electronic producers to find viable alternatives to PVC. Thermoplastic elastomers are seen as a potential halogen-free replacement to PVC as thermoplastic elastomers and PVC are similar in many physical and mechanical aspects. Wire and cable applications, however, require flame retardancy. Adding flame retardants to thermoplastic elastomers often times degrades the desired physical and mechanical properties of the thermoplastic elastomer.

Thermoplastic elastomer (TPE) compositions based upon polyurethane or polyester elastomers are well known and are used in many industrial applications including wire and cable coverings, e.g., insulated wires and protective cable jackets. To be useful as a wire and cable covering, these polyurethane or polyester based elastomers must exhibit, among other things, good mechanical properties, e.g., good elasticity and tensile strength, extrudability and flame retardancy. These polyurethane and polyester type thermoplastic elastomers inherently possess good elasticity and mechanical strength, but they are not inherently flame retardant.

Accordingly, methods of providing flame resistance to such a thermoplastic elastomers have been developed, and especially, some methods of adding a flame resistant to a resin have been mainly used. Since the addition of a flame retardant may reduce physical properties of a thermoplastic elastomer, such as elongation at break, a resilient elastic force, elastic modulus, abrasion, etc., it is preferable to add the flame retardant to the resin in as small an amount as possible so as to minimize the reduction. Also, thermoplastic elastomers are decomposed into a low molecular weight molten material when they undergo combustion, thereby causing a flaming-drip. In this case, if a fire occurs, the flaming-drip may spread the fire. Therefore, reducing the occurrence of flaming-drip during combustion is one of many important things to be taken into account in developing a thermoplastic elastomers and more specifically thermoplastic

polyurethane (TPU) resins.

SUMMARY OF THE INVENTION

Accordingly, the present invention provides a flame retarded thermoplastic elastomer composition, which is highly self-extinguishable during combustion and can improve flame retardancy and decrease flaming-drips while maintaining suitable physical and mechanical properties of the underlying thermoplastic elastomer material.

More specifically the present invention is directed to a flame retarded

thermoplastic elastomer composition comprising at least one thermoplastic elastomer and at least one metal phosphonate. The flame retardant thermoplastic elastomer composition can further optionally contain one or more supplemental flame retardants, e.g. halogen- free flame retardants, such as aromatic phosphate ester, melamine or melamine salts, intumescent ammonium or amine phosphate, aluminum hydroxide or magnesium hydroxide and the like.

The flame retarded thermoplastic elastomer composition according to the present invention is safe in use due to its improved flame retardancy and reduction in flaming- drip. Thus, the flame retarded theremoplastic elastomer composition is expected to be very useful for use as a wire insulator, for use in electrical and electronic equipment, and for use in car interior materials, and other related applications.

Still further, the present invention is directed a flame retarded article comprising a metal conductor and a coating on the metal conductor to provide an "insulated" wire capable of electrical transmission of low voltage telecommunication signals or for a wide range of electrical power transmission applications, wherein the coating on the metal conducter comprises the flame retarded thermoplastic elastomer composition described herein

DETAILED DESCRIPTION OF THE INVENTION

A "thermoplastic elastomer," as used herein, is a polymer that has the ability to be stretched beyond its original length and retract to substantially its original length when released and which softens when exposed to heat and returns to substantially its original condition when cooled to room temperature. The thermoplastic elastomers employed herein are not crosslinked, or are otherwise void of crosslinking. The thermoplastic elastomers employed herein are distinct from, and do not include, "thermosetting polymers" which solidify or "set" irreversibly when heated. Nonlimiting examples of suitable thermoplastic elastomers include thermoplastic polyurethane ("TPU"), thermoplastic polyester elastomer (TPEE), thermoplastic polyamide elastomer, and any combinations thereof.

A thermoplastic polyurethane elastomer, as used herein, is the reaction product of a polyisocyanate, one or more polymeric diol(s), and optionally one or more difunctional chain extender(s). The TPUs used in the present invention includes a hard segment and a soft segment. The hard segment is derived by a reaction of diisocyanate with a diol of a chain extender. The soft segment is derived by reaction of a polyol with diisocyanate, and the characteristic thereof depends on the kind of polyol.

The diisocyanate may be selected singly or in combination from the group including aromatic diisocyanate, aliphatic diisocyanate and cyclic aliphatic diisocyanate. The aromatic diisocyanate may include 1,4-phenylenediisocyanate;

2,4toluenediisocyanate, 2,6-toluenediisocyanate, or a mixture thereof; 2,2- methylenediphenylenediisocyanate, 2,4'-methylenediphenylenediisocyanate, or 4,4'- methylenediphenylenediisocyanate; and naphthalene diisocyanate. The aliphatic diisocyanate or cyclic aliphatic diisocyanate may include cyclohexane diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, etc.

The diol used as the chain extender may be used singly or in combination from the group including ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, 1,3-butanediol, l,4butanediol, 2-methylpentanediol, 1,5-pentanediol, 1,6- hexanediol, 1,4-cyclohexanediol, 1,4-cyclohexanedimethanol and neopentyl glycol.

The polyol may include polyester polyol, polyether polyol, etc. The polyester polyol is prepared by reacting at least one kind of dicarboxylic acid with at least one kind of diol. The dicarboxylic acid includes adipic acid, sebacic acid, suberic acid, methyladipic acid, glutaric acid, azelaic acid, etc., and the diol includes ethylene glycol, 1,3- or 1,2-propylene glycol, 1,4-butanediol, 2-methylpentanediol, 1,5-pentanediol, l,6hexanediol, etc. Also, cyclic carbonate, etc., such as ε-caprolactone, may be used for preparing polyester polyol. Especially, mainly used polyester polyol is poly(ethylene adipate), poly(l,4butylene adipate), or a mixture thereof, and also poly(8-caprolactone) is mainly used.

The polyether polyol is obtained by additional polymerization of alkylene oxide. Alkylene oxide that may be used in the present invention includes ethylene oxide, propylene oxide, butylene oxide, tetrahydrofuran, etc. Especially, mainly used polyether polyol includes poly (propylene oxide)glycol, poly(tetramethylene ether)glycol, or a mixture thereof.

Nonlimiting examples of some thermoplastic polyurethanes (TPUs) which may be employed herein include PELLETHANE™ available from the Lubrizol Corporation; ESTANE™ , TECOFLEX™ , CARBOTHANE™ , TECOPHILIC™ , TECOPLAST™ , and TECOTHANE™ , all available from Noveon; ELASTOGRAN™ and other thermoplastic polyurethanes available from BASF; and additional thermoplastic polyurethane materials available from Bayer, Huntsman, Lubrizol Corporation,

Merquinsa and other suppliers.

The TPUs useful in the practice of this invention are typically used in amounts ranging from about 20 wt% to about 90 wt% based on the weight of the composition. Preferably, the TPUs are used in an amount ranging from about 30 wt % to about 85 wt%, more preferably from about 40 wt % to about 75 wt% based on the total weight of the flame retarded thermoplastic polyurethane composition.

The metal phosphonate used herein can be a salt of alkyl alkylphosphonic acid or a salt of aryl alkylphosphonic acid. In one embodiment the salt of alkyl alkylphosphonic acid or salt of aryl alkylphosphonic acid can be such that the alkyl group and/or aryl group contains up to about 12 carbon atoms. In a further embodiment the metal phosphonate is represented by general formula (I):

where Me is a metal, n is equal to the valency of the metal and is an integer of from 1 to 4, specifically 2 or 3, R¹ is a linear or branched alkyl of up to about 12 carbon atoms, specifically from up to about 4 carbon atoms, R is a linear or branched alkyl of up to about 12 carbon atoms, specifically up to about 4 carbon atoms or a substituted aryl or an unsubstituted aryl of general formula (II):

where R is hydrogen, or a branched or linear alkyl of up to about 4 carbon atoms, or an -NH₂, -CN or -N0₂ group.

In one specific embodiment, R 1 and/or R 2 are each independently methyl or ethyl radicals.

Metals, i.e., Me of the above formula (I), include alkaline earth or transition metals such as the non-limiting group consisting of Ca, Mg, Zn, Al, Fe, Ni, Cr, Ti. The most specific metal is Al.

In one embodiment the metal phosphonate of the formula (I) is an aluminum salt of methyl methylphosphonic acid (AMMP), where Me is aluminum, R 1 and R 2 are both methyl and n=3. AMMP contains a high level (i.e., 26 weight percent) of active phosphorus. AMMP can be synthesized either by reacting methyl methylphosphonate with an aqueous solution of sodium hydroxide followed by precipitation with aluminum chloride, or by direct reaction of aluminum hydroxide with methyl methylphosphonate at about 180° C in a high shear mixer.

Specifically, the metal phosphonate is present in the flame retarded TPU composition in the range of from about 5 wt% to about 50 wt% and more specifically in the range of from about 10 wt% to about 40 wt% based on the total weight of the flame retarded thermoplastic elastomer composition. The flame retarded thermoplastic elastomer composition can further comprise an optional supplemental flame retardant selected from the group consisting of aromatic phosphate esters; melamine or melamine salts; intumescent ammonium or amine phosphates;

inorganic flame retardants, e.g., aluminum hydroxide and magnesium hydroxide; and, combinations thereof.

In one embodiment, it is beneficial to use one or more aromatic phosphate ester in the flame retarded thermoplastic elastomer composition because phosphate esters improve melt flow of the composition. In one embodiment, the aromatic phosphate ester is represented by the following formula (III):

O O

l h

R¹— O-P O-X-O-P -O—

n

O O

R² R

wherein R¹, R², R³ and R⁴ are each independently selected from an aryl group or alkyl substituted aryl group containing up to about 12 carbon atoms, X is an arylene or bisphenylene group containing from 6 to about 18 carbon atoms. The phosphate may be a low molecular weight phosphate such as a monophosphate wherein n is 0 and as such will typically have a molecular weight less than about 500. The phosphate may also contain an oligomeric phosphate wherein n has an average value of from 0 to 5 in which case the weight average molecular weight of the phosphate is at least about 500 and more specifically about 500 to about 2000. Alternatively, the phosphate can be a mixture of any of the phosphates described herein.

In the above formula (III) for the phosphates of the invention, the aryl groups may be aryl or an alkyl substituted aryl group (i.e. alkaryl group) containing up to about 12 carbon atoms. More specifically, the aryl groups are independently selected from phenyl, cresyl, xylyl, propylphenyl and butylphenyl groups. The arylene or bisphenylene group is derived from a dihydric compound and is more specifically resorcinol, hydroquinone or bisphenol-A. The aryl groups (R¹, R², R³ and R⁴) are more specifically phenyl. In the case of the oligomeric phosphates, the more specific aryl phosphate ester is hydroquinone bis(diphenyl phosphate) wherein n is from 1 to about 2, with diphosphate with n=l being the main component of the mixture, X is hydroquinone and each of the R groups is phenyl.

As stated above, a melamine or melamine salt can be included in the flame retarded thermoplastic elastomer composition as an optional supplemental flame retardant. Specifically, the melamine salts can be at least one compound selected from the group consisting of melamine phosphate, dimelamine phosphate, melamine

pyrophosphate, melamine polyphosphate, melamine borate, melamine cyanurate, melamine oxalate, melamine sulfate, melam or melem phosphate, melam or melem polyphosphate, melamine ammonium phosphate, melamine ammonium pyrophosphate, melamine ammonium polyphosphate, condensation products of melamine, e.g., melem melam, melon and higher condensation products of melamine; and, mixtures thereof.

In the preferred embodiment, melamine is preferably selected over melamine salts.

As stated above, ammonium or amine salts of phosphoric or pyrophosphoric or polyphosphoric acids can be can be included in the flame retarded thermoplastic elastomer composition as supplemental flame retardants. Example of such salts are ammonium polyphosphate, ethylenediamine phosphate, piperazine pyrophosphate and similar.

As stated above, inorganic flame retardants can be included in the flame retarded thermoplastic elastomer composition as supplemental flame retardants. Specific, preferred inorganic flame retardant include magnesium hydroxide (Mg(OH)2), aluminum hydroxide (Al(OH)₃), boehmite, basic magnesium carbonate, calcium aluminate hydrate and the like.

The supplemental flame retardant (e.g., supplemental halogen-free flame retardant) will be present in the flame retarded TPU composition in an amount from about 1 to about 25 weight percent, more specifically from about 2 to about 15 weight percent based on the total weight of the flame retarded thermoplastic elastomer composition.

The flame retarded thermoplastic elastomer composition herein can have a flame retardancy rating of HB, V-2, V-l, V-0 and 5VA according to UL-94 protocol. In one embodiment the flame retarded thermoplastic elastomer composition can have a flame retardancy rating of at least V-l or V-0 as is required in most electronic applications.

Additives may be used to modify the properties of the flame retarded

thermoplastic elastomer composition used in the practice of this disclosure. Additives may be included in the conventional amounts as already known in the art and literature. Usually additives are used to provide specific desired properties to the polyurethanes such as various antioxidants, ultraviolet inhibitors, waxes, thickening agents and fillers. When fillers are used, they may be either organic or inorganic, but are generally inorganic such as clay, talc, calcium carbonate, silica and the like. Also, fibrous additives, such as glass or carbon fiber, may be added to impart certain properties.

The method of blending the components of the flame retarded thermoplastic elastomer composition herein is not critical and can be carried out by conventional techniques. One convenient method comprises blending the thermoplastic elastomer (e.g., TPU), the metal phosphonate and optionally supplemental halogen-free flame retardant in a powder or granular form, extruding the blend and compounding the extruded blend into pellets or other suitable shapes. In order to improve handling and avoid dusting the metal phosphonate can be pre-compounded with the thermoplastic elastomer as a masterbatch in the form of pellets. If supplemental flame retardant aromatic phosphate ester is used as a liquid, it is fed into the extruder using liquid feeding equipment, e.g. metering pumps. Alternatively, the metal phosphonate can be dispersed in the aromatic phosphate ester using high shear mixer and fed into the extruder using liquid feeding equipment.

In one embodiment of this invention an article is provided which includes a metal conductor and a coating on this metal conductor (e.g. wherein the coating comprises the flame retarded thermoplastic elastomer composition described herein) to provide an "insulated" wire capable of electrical transmission of low voltage telecommunication signals or for a wide range of electrical power transmission applications. In one embodiment the article comprises the flame retarded thermoplastic elastomer

composition described herein. In one embodiment the article is a wire insulator, e.g, a wire insulator which comprises the flame retarded thermoplastic elastomer composition described herein. In one embodiment such a wire insulator can be used in electrical and electronic equipment, and for use in car interior materials, and other related applications Nonlimiting examples of suitable coated metal conductors include flexible wiring such as flexible wiring for consumer electronics, a power cable, a power charger wire for cell phones and/or computers, computer data cords, power cords, appliance wiring material, and consumer electronic accessory cords or the like.

There is also provided herein a process of making a flame retarded thermoplastic elastomer composition comprising contacting at least one thermoplastic elastomer and at least one metal phosphonate. Further there is provided a flame retarded thermoplastic elastomer made by the process, an article comprising the flame retarded thermoplastic elastomer, and a wire insulator which is the article.

The following examples are used to illustrate the present invention.

EXAMPLES

In order to prepare samples of flame retarded polycarbonate composition that illustrate the invention, the following procedures have been used.

Materials.

ai - Polyether type TPU Elastogran 1180a, ex. BASF)

bi - Aluminum methyl methylphosphonate, AMMP ex. ICL-IP

ci - Hydroquinone bis(diphenyl phosphate), HDP ex. ICL-IP

c₂ - Melamine, grade 003, ex. DSM

c₃ -Melamine Phosphate, Fyrol MP ex. Akzo Nobel

c₄ - Proprietary Intumescent FR, FR2100J, Amfine

c₅ - Aluminum hydroxide, HT-980, ex. R.J. Marshall

Compounding

The pellets of TPU, AMMP and supplemental flame retardants were weighted on a semi analytical scale with consequent manual mixing in plastic bags. The mixtures were introduced into the main feeding port of the extruder. The compounding was performed on Brabender Plasti-Corder PL-2000 twin screw extruder at 170-200 °C at 90 rpm. The extruded strands were cooled in a tray filled with water and ice and pelletized by cutting. The compounded pellets were dried in a circulating air oven over night at 80°C. Compression molding.

Test specimens for UL-94 testing were cut from 1.6 mm thick slabs compression molded using a Wabash hydraulic press. Test specimens for tensile properties testing were cut from 3.2 mm thick slabs molded using the same press.

Test methods.

Before testing specimens were conditioned at 23°C for 168 hours.

Vertical flammability test - UL-94 V protocol, specimen thickness 1.6 was used for the flammability tests.

Tensile properties were measured according ASTM D638 using an Instron material testing machine.

Shore A hardness was measured according ASTM D2240 using a hand held device. Examples 1-9 and Comparative Examples C.l -6

Table 1 shows the formulations and combustion performances according to the UL-94 test and physical properties of the flame retarded TPU compositions. As it is seen in Example 4, a TPU composition containing 35 wt. % AMMP gave a non-dripping V-0 rating showing at the same time the highest Shore A hardness and highest modulus and keeping a good elongation at break.

Table 6 Formulations combustion and physical properties of flame retarded TPU compositions

* BD: Burning Drip; D: Dripping; N: No Dripping; BTC: Burn To the Clamp.

While the invention has been described with reference to certain embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiments disclosed as the best mode contemplated for carrying out this invention but that the invention will include all embodiments falling within the scope of the appended claims.

Claims

1. A flame retarded thermoplastic elastomer composition comprising at least one thermoplastic elastomer and at least one metal phosphonate.

2. The flame retarded thermoplastic elastomer composition of Claim 1 where the elastomer is selected from the group thermoplastic polyurethane, thermoplastic polyester elastomer, thermoplastic polyamide elastomer, and any combination thereof.

3. The flame retarded thermoplastic elastomer composition of Claim 2 where the thermoplastic elastomer is thermoplastic polyurethane.

4. The flame retarded thermoplastic elastomer composition of Claim 1 where the metal phosphonate is represented by general formula (I):

where Me is a metal, n is equal to the valency of the metal and is an integer of from 1 to

4, R 1 is a linear or branched alkyl group containing up to about 12 carbon atoms, R 2 is a linear or branched alkyl group containing up to about 12 carbon atoms, or a substituted aryl or an unsubstituted aryl of general formula (II):

where R is hydrogen, or a linear or bra inncchheedd aallkkyyll ccoontaining up to about 4 carbon atoms, or a -NH₂, -CN or -N0₂ group.

5. The flame retarded thermoplastic elastomer composition of claim 4 where the metal phosphonate is aluminum methyl methylphosphonate.

6. The flame retarded thermoplastic elastomer composition of Claim 1 further comprising a supplemental flame retardant selected from the group consisting of aromatic phosphate esters, melamine or melamine salts, intumescent ammonium or amine phosphates, aluminum hydroxide, magnesium hydroxide and combinations thereof.

7. The flame retarded thermoplastic elastomer composition of Claim 6 where the

wherein R¹, R², R³ and R⁴ are each independently selected from group or alkyl substituted aryl group containing up to about 12 carbon atoms, X is an arylene or bisphenylene group containing from 6 to about 18 carbon atoms, wherein n is from 0 to 5.

8. The flame retarded thermoplastic elastomer composition of Claim 1 where the thermoplastic elastomer is present in the amount of from about 20 to about 90 wt. % and the metal phosphonate is present in the amount of from about 5 wt% to about 50 wt% based on the total weight of the flame retarded thermoplastic elastomer composition.

9. The flame retarded thermoplastic elastomer composition of Claim 1 where the thermoplastic elastomer is present in the amount of from about 40 to about 75wt. % and the metal phosphonate is present in the amount of from about 10 wt% to about 40 wt% based on the total weight of the flame retarded thermoplastic elastomer composition.

10. The flame retarded thermoplastic elastomer composition of Claim 6 where the supplemental flame retardant is present in an amount of from about 1 to about 25 wt% based on the total weight of the composition.

11. An article comprising the flame retarded thermoplastic elastomer composition of Claim 1.

12. A wire insulator comprising the flame retarded thermoplastic elastomer composition of Claim 1.

13. A process of making a flame retarded thermoplastic elastomer composition comprising contacting at least one thermoplastic elastomer and at least one metal phosphonate.

14. A flame retarded thermoplastic elastomer made by the process of Claim 13.

15. An article comprising the flame retarded thermoplastic elastomer of Claim 14.

16. The article of Claim 15, wherein the article is a wire insulator.