WO2013085788A1

WO2013085788A1 - Synergized flame retarded polyolefin polymer composition, article thereof, and method of making the same

Info

Publication number: WO2013085788A1
Application number: PCT/US2012/067022
Authority: WO
Inventors: Sergei V. Levchik; Paul MOY; Gerald R. Alessio; Garrett SHAWHAN; James Innes
Original assignee: Icl-Ip America Inc.
Priority date: 2011-12-09
Filing date: 2012-11-29
Publication date: 2013-06-13

Abstract

There is provided herein a flame retarded polyolefin polymer composition comprising a thermoplastic polyolefin polymer, an inorganic flame retardant and a calcium borate on an inorganic carrier. There is also provided a method for making a flame retarded polyolefin polymer composition comprising contacting at least one thermoplastic polyolefin polymer with at least one inorganic flame retardant and at least one calcium borate on an inorganic carrier and heating the mixture of thermoplastic polyolefin polymer, at least one inorganic flame retardant and at least one calcium borate on an inorganic carrier to above the melting temperature of the thermoplastic polyolefin polymer.

Description

SYNERGIZED FLAME RETARDED POLYOLEFIN POLYMER COMPOSITION. ARTICLE THEREOF. AND METHOD OF MAKING THE SAME

This application claims priority to U.S. provisional application number 61/658,687 filed on June 12, 2012 and also to U.S. Provisional application number 61/568,968 filed on December 9, 201 1.

FIELD OF THE INVENTION

The present invention relates to flame retardant compositions and more particularly to a combination of a mineral flame retardant and a synergist comprising a calcium borate on an inorganiccarrier. Such compositions are suitable for use with thermoplastic polyolefin polymers and more specifically for the manufacture of cable insulation and jackets, tubings, extruded film and/or sheets useful for construction and building materials, shipping pallets as well as molded automotive parts and electronic parts.

BACKGROUND OF THE INVENTION

Polyolefins are represented by two high volume thermoplastic polymers, polyethylene and polypropylene, as well as a large number of ethylene-propylene copolymers, and copolymers of other alkylene monomers. By varying the ratio of lower alkylene to higher alkylene co-monomer, a broad range of polymers, from thermoplastics to elastomers, can be produced. Similarly, ethylene can be copolymerized with vinyl acetate or ethyl acrylate, which combination reduces the crystallinity of the polyethylene and results in products having the characteristics of thermoplastic elastomers.

Polyolefin resin is widely used in the production of wire and cable jacketings, tubings, air ducts, thermal insulation systems, shipping pallets, computer cabinets, electrical appliances, interior household decorations, sockets for decorative lamps and automobile parts, among many other items. They are the polymers of choice due to their good processing characteristics, chemical resistance, weathering resistance, electrical properties and mechanical strength. One major disadvantage is that polyolefins are flammable. This has generated a growing demand for flame retarded polyolefins. For wire and cable applications, halogen-free flame retardant materials are desirable to provide both insulation and jacketing for cables in areas where it is necessary to avoid the generation of corrosive gases in the event of fire. Such areas where halogen- free cables are useful include underground transportation systems and tunnels,

communication centers, hotels, hospitals, schools, theaters and other such public spaces. Jacketing materials have to be highly flame retardant, have good heat resistance and good physical properties.

In recent years pallets of injection molded polymers have increasingly replaced traditional wood pallets. Such injection molded polymer pallets have numerous advantages over wooden pallets. For example, polymer pallets are capable of being molded in complex shapes which facilitate the shipping of numerous types of articles. Polymer pallets are also easy to clean, which encourages their reuse. However, the combustion of polymer pallets involves more heat compare to wood pallets. Thus, it is desirable to minimize the combustibility and heat release, and in turn, lower any potential flame spread of polymer based pallets. It is further desirable to provide pallets which mimic the behavior of wood pallets during combustion, and which are preferably improved with respect to combustion properties. It is also industry trend to switch to halogen-free pallets.

The use of mineral fillers to provide flame retardancy to polyolefins has long been known. Metal hydroxides, especially aluminum hydroxides (such as for example ATH) and magnesium hydroxides (MDH), have been used as mineral fillers in this context. The metal hydroxides are used alone or in combination with each other.

The flame retardant action of metal hydroxides is based essentially on endothermic decomposition, release of water, a dilution effect of the polymer matrix and the formation of a solid metal oxide-carbonaceous layer of char, all of which lead to a certain degree of mechanical stabilization of the burning polymer. This can, for example, reduce or even completely prevent the production of burning drips. Furthermore, the encrusted char on the surface of the burning polymer acts as a "protective barrier" for the underlying polymer layers, which barrier may prevent the rapid propagation of combustion. Therefore, improvement of the quality of the char in terms of the absence of cracks and a uniform cohesive surface of the char is very important. SUMMARY OF THE INVENTION

According to the present invention there is provided in one embodiment a flame retarded polyolefin polymer composition comprising:

(a) a thermoplastic polyolefin polymer;

(b) an inorganic flame retardant; and,

(c) a calcium borate on an inorganic carrier.

The present invention provides a flame retarded polyolefin composition which is capable of forming extruded cable insulation jackets, sheets, films or molded parts, which are flame retardant and have a low heat-release rate and coherent uniform char. The subject flame retarded polyolefin polymer composition can be used in wires and cables, building construction applications, manufacturing of shipping pallets or for the production of electrical or electronic parts, appliances and automotive parts.

In another embodiment herein there is provided, in one embodiment, a method for making a flame retarded polyolefin polymer composition by contacting at least one thermoplastic polyolefin polymer, at least one inorganic flame retardant and at least one calcium borate on an inorganic carrier, and then heating the mixture to above the melting temperature of the thermoplastic polyolefin polymer.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

There is provided herein a flame retarded polyolefin polymer composition which is a mixture of the herein-described components (a), (b) and (c). The flame retarded polyolefin polymer composition herein can be used to produce articles such as extruded wire and cable insulation jackets, sheets, films or molded parts, building construction applications, manufacturing of shipping pallets or for the production of electrical or electronic parts, appliances and automotive parts, wherein these articles have improved electrical properties such as continuous tracking index, surface resistivity and volume resistivity and improved physical properties such as improved heat release rate over an identical composition which employs a calcium borate without a carrier, or more specifically without an inorganic carrier, e.g., wollastonite. A thermoplastic polyolefin resin of essentially any grade can be selected as the thermoplastic polyolefin polymer (a) herein according to the desired performance requirements such as formability and mechanical properties, including stiffness, heat resistance, and the like, of the resulting flame retarded polyolefin polymer composition.

The thermoplastic polyolefin polymer (a) is specifically at least one of a

polyethylene homopolymer, polyethylene copolymer, polypropylene homopolymer, and polypropylene copolymer.

In one embodiment, the thermoplastic polyolefin polymer (a) is at least one of a high-density polyethylene, a low-density polyethylene or a linear low-density

polyethylene. Amorphous, crystalline and elastomeric forms of polypropylene can be used as thermoplastic polyolefin polymer (a).

Some non-limiting examples of compounds that may be used as the thermoplastic polyolefin polymer (a) are low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), linear very low-density polyethylene (VLDPE), high-density polyethylene (HDPE), ethylene-methyl methacrylate (EMMA) copolymer, ethylene methyl acrylate (EMA) copolymer, ethylene ethyl acrylate (EEA) copolymer, ethylene butyl acrylate (EBA) copolymer, ethylene vinyl acetate (EVA) copolymer, ethylene glycidyl methacrylate copolymer, ethylene-butene-1 copolymer, ethylene-butene-hexene

terpolymer, ethylene propylene diene terpolymer (EPDM), ethylene-octene copolymer (EOR), ethylene copolymerized polypropylene (random PP or block PP), ethylene propylene (EPR) copolymer, poly-4-methyl-pentene-l, maleic anhydride grafted low- density polyethylene, hydrogenated styrene-butadiene (H-SBR) copolymer, maleic anhydride grafted linear low-density polyethylene, maleic anhydride grafted linear very low-density polyethylene, copolymers of ethylene and a-olefin with a carbon number of 4 to 20, ethylene-styrene copolymer, maleic anhydride grafted ethylene-styrene copolymer, maleic anhydride grafted ethylene-methyl acrylate copolymer, maleic anhydride grafted ethylene-vinyl acetate copolymer, ethylene-maleic anhydride copolymer, ethylene-ethyl acrylate-maleic anhydride terpolymer, and ethylene-propylene-butene-1 terpolymer including butene-1. These compounds may be used individually as the thermoplastic polyolefin polymer (a). Alternatively, two or more types of them may be blended as thermoplastic polyolefin polymer (a). Some non-limiting examples of the copolymers which can be used as the thermoplastic polyolefin polymer (a) are at least one of ethylene-vinyl acetate (EVA); ethylene-propylene rubber (EPR); ethylene-propylene-diene-monomer rubber (EPDM); and copolymers of ethylene and propylene with butene-1, pentene-1, 3-methylbutene-l, 4- methylpentene-1, octene-1 and mixtures thereof.

The thermoplastic polyolefin polymer (a) used herein can be any thermoplastic polyolefin resin, but most specifically, can be an ethylene vinyl acetate containing 25-90% by weight ethylene and 10-75% by weight vinyl acetate, a linear low density polyethylene (LLDPE), a low density polyethylene (LDPE), a very low density polyethylene (VLDPE), a high density polyethylene (HDPE), and mixtures thereof.

The thermoplastic polyolefin polymer (a) is specifically applied in pellet form having a melting point in the range of from about 150°C to about 250° Celsius (C), more specifically, from about 175° C to about 230° C. The thermoplastic polyolefm polymer (a) specifically has a specific gravity in the range of from about 0.85 to about 1.2 and most more specifically from about 0.90 to about 1.0. The most specific thermoplastic polyolefin polymer (a) has a melt flow rate in the range of from about 0.2 g/10 min. to about 30 g/10 min., and more specifically, from about 1 g/10 min. to about 12 g/10 min.

The thermoplastic polyolefin polymer (a) may also optionally be reinforced or filled.

It will be understood herein that the term "filler" as used herein with regard to thermoplastic polyolefin polymer (a) is a different component from the inorganic flame retardant (b) described elsewhere herein.

Suitable fillers for thermoplastic polyolefin polymer (a) include typical

reinforcing and non-reinforcing fillers such as precipitated and fumed silicas, ground quartz, diatomaceous earth, ground limestone, ground felspar, mica, expanded mica, precipitated calcium carbonate, etc.

The term "reinforcing" with respect to fillers generally refers to fillers of small size and high surface area, for example mean particle sizes of about 0.1 μηι or less, and specific surface areas (BET) of 50 m²/g or higher, while non-reinforcing fillers, which are more specifically used herein, have larger particles sizes, e.g. 1 μπι to 100 μι^η,

specifically 1 μηι to 20 μηι. Suitable fibrous fillers which can be used as fillers for the thermoplastic polyolefin polymer (a) are typically short or long glass fibers. Other fibrous

reinforcement such as aramid fiber, carbon fiber, boron nitride fiber, etc., may also be used as filler for thermoplastic polyolefin polymer (a), however, such materials are generally more expensive than glass fibers.

In another embodiment of this invention the flame retarded polyolefin polymer composition herein can further optionally contain nanofiller as filler for thermoplastic polyolefin polymer (a), for example organically treated clay or carbon nanotubes.

The polyolefin polymer (a) is specifically present in the flame retarded polyolefin polymer composition in an amount of from about 20 wt. % to about 90 wt. %, more specifically from about 30 wt. % to about 85 wt. % based on the total weight of the flame retarded polyolefin polymer composition.

Suitable inorganic flame retardants (b) are known in the art, e.g., metal hydroxides. Specific, inorganic flame retardants (b) include the non-limiting examples of magnesium hydroxide (Mg(OH)₂) (MDH), alumina trihydrate (Al(OH)₃) (ATH), boehmite, hydro tal cite, basic magnesium carbonate, calcium aluminate hydrate, talc, clay and combinations thereof. Of these types of inorganic flame retardants (b), aluminum hydroxide is the most specifically used because of its relatively low cost and high flame retardant efficiency. Magnesium hydroxide also has good flame retardant efficiency and is thermally stable.

The most specific inorganic flame retardant (b) for use in the flame retardant polyolefin polymer composition for shipping pallets is MDH, which is widely available from synthetic sources such as precipitation from brines. It is also available from natural sources, such as crushed minerals, for example, brucite. Precipitated magnesium hydroxide is widely available, for example from ICL-IP America, and from other sources. ATH is also available from numerous sources.

From the viewpoint of mechanical properties, ease of dispersion and flame retardancy, the above inorganic flame retardants (b) are the more specific for use when the average particle diameter of the inorganic flame retardant (b) is 10 μπι or less and when the ratio of coarse particles with a particle diameter of 25 μιη or more is 10% or less to the total inorganic flame retardant. It is also possible to increase the water resistance of the inorganic flame retardants (b) by treating the surfaces of these particles, using a fatty acid, fatty acid metal salt, silane coupling agent, titanate coupling agent, acrylate resin, phenol resin, cationic or nonionic water-soluble resin, or the like, according to the usual manner.

The inorganic flame retardant (b) specifically makes up from about 10 wt. % to about 65 wt. % based on the total weight of the flame retarded polyolefin polymer composition and more specifically from about 15 wt. % to about 60 wt. % based on the total weight of the flame retarded polyolefin polymer composition, e.g., based on the polymer components, inorganic flame retardant and calcium borate on an inorganic carrier.

It will be understood herein in one embodiment that the inorganic carrier herein is such that it supports, i.e., serves as a vehicle for, the calcium borate and exists together with the calcium borate and can be made by methods known in the art for making supported substances. In one non-limiting embodiment herein the carrier for the calcium borate is different from the flame retardant (b) used herein and/or different from the filler described above which may be incorporated into the thermoplastic polyolefin polymer (a). In another embodiment herein, the carrier for the calcium borate can be the same as the flame retardant (b) used herein and/or the same as the filler described above which may be incorporated into the thermoplastic polyolefin polymer (a), provided that the carrier exists only in conjunction with the calcium borate, i.e., only as a support for the calcium borate in that it has been formed as one component and is used as such in the flame retardant polyolefin polymer composition herein.

In one non-limiting embodiment the inorganic carrier for the calcium borate is wollastonite.

In one embodiment, the calcium borate on an inorganic carrier (c) can comprise any known inorganic filler material as the inorganic carrier. Some non-limiting examples of inorganic filler material which may function as the inorganic carrier are alumina trihydrate, natural calcium carbonate, precipitated calcium carbonate, calcium sulphate, carbon black, carbon fibers, clay, cristobalite, diatomaceous earth, dolomite, feldspar, graphite, glass beads, glass fibers, kaolin, magnesium carbonate, magnesium hydroxide, metal powders or fibers, mica muscouite, mica phlogopite, natural silica, synthetic silica, nepheline-syenite, talc, whiskers, wollastonite, and combinations thereof. The calcium borate on an inorganic carrier, (e.g., a wollastonite carrier), which is used herein, can in one embodiment be manufactured by the reaction of lime with boric acid in the presence of an inorganic carrier, (e.g., wollastonite), in a water suspension, with subsequent drying, milling and sieving. More specifically, the calcium borate on an inorganic carrier (c) is such that the particles of calcium borate on an inorganic carrier (c) have a mean particle size (d₅₀) of from about 1 micron to about 15 microns and 99 weight percent of the total amount of particles of calcium borate on an inorganic carrier have a diameter (d₉₉) of less than about 50 microns, and more specifically, a d₅o of from about 2 microns to about 10 microns and a d₉₉ of less than about 25 microns.

In another embodiment the inorganic carrier is synthetic calcium silicate having a d₅o of from about 0.5 microns to about 3 microns. Such calcium silicates are available for example from Evonik, Europe or Shreji, China.

It is also desirable to improve the processability of the flame retarded polyolefin polymer composition by improving resin flow by treating the surfaces of the calcium borate on an inorganic carrier (c) particles, using a fatty acid or fatty acid metal salt or the like, according to the usual manner. In one embodiment, the calcium borate on an inorganic carrier (c) is surface treated with stearic acid.

Specifically, the calcium borate on an inorganic carrier (c) is present in the flame retarded polyolefin polymer composition in an amount from about 2 wt. % to about 35 wt. % and more specifically in the range from about 3 wt. % to 15 wt. % based on the total weight of the flame retarded polyolefin polymer composition.

The flame retarded polyolefin polymer composition described herein can comprise (a) thermoplastic polyolefin polymer, (b) inorganic flame retardant and calcium borate on an inorganic carrier (c). Specifically, the inorganic flame retardant (b) is present in an amount of from 25 wt. % to about 60 wt. % of the total weight of the flame retarded polyolefin polymer composition. More specifically, the calcium borate on an inorganic carrier (c) is present in an amount of from about 2 wt. % to about 35 wt. % based on the total weight of the flame retarded polyolefin polymer composition. More specifically, the flame retardant package of inorganic flame retardant (b) plus calcium borate on an inorganic carrier (c) are present in an amount of from about 20 wt. % to about 65 wt. % based on the total weight of the flame retarded polyolefin polymer composition. In one embodiment, the flame retarded polyolefin polymer composition is in the absence of halogen.

In one further embodiment the flame retarded polyolefin polymer composition can optionally, further contain common additives, including for example, coupling agents, antioxidants, ultraviolet and light stabilizers, UV screeners, UV absorbers, e.g., titanium dioxide (for UV resistance and to give a white color to the product), UV processing aids e.g., zinc stearate, heat stabilizers, dispersing agents, lubricants and combinations thereof.

Additional flame retardant ingredients can also be used in the flame retarded polyolefin polymer composition herein. These additional flame retardant ingredients include both organic and inorganic retardants. Organic flame retardants include numerous conventional nitrogenous organic compounds such as but not limited to ureas, derivatized ureas, urea and/or melamine/formaldehyde condensates, cyanurates and isocyanurates, melamine derivatives, carbamates, etc. Inorganic flame retardants include various metal carbonates, metal bicarbonates, metal oxides, metal phosphates and ammonium phosphates. Hydrated inorganic compounds which serve as water generators are also useful herein.

High charring agents such as pentaerythritol, sugars and starches may also be useful in the flame retarded polyolefin polymer composition herein, as well as

expandable fillers such as expandable mica or graphite. Expanded products such as expanded mica and expanded graphite may also be useful in minor amounts, i.e. amounts which can be incorporated without overly lowering the density and affecting the physical characteristics of the thermoplastic polyolefin polymer (a). Glass or ceramic

microspheres may also be useful.

In one embodiment herein, the flame retarded polyolefin polymer composition herein can further optionally incorporate an auxiliary solid phosphate ester. The role of the phosphate ester is to improve the resin flow and provide additional flame retardancy. The solid phosphate ester is preferably an aromatic phosphate or bisphosphate.

In one embodiment herein, the polyolefin polymer composition of this invention will show a significant decrease in the heat release rate as measured in the cone calorimeter test. It is believed that the flame retarded polyolefin polymer composition herein has reduced heat release and thus, a higher probability of passing the UL 2335 "Fire Tests of Storage Pallets" or ASTM E-84 "Standard Test Method for Surface Burning Characteristics of Building Materials" compared to flame retardant compositions that do not contain calcium borate on an inorganic carrier component (c). Another important characteristic of the flame retarded polyolefin polymer composition herein is that it shows improved integrity of the char obtained in the cone calorimeter test.

In the method herein, the thermoplastic polyolefin polymer (a), the inorganic flame retardant (b), the calcium borate on an inorganic carrier (c) and any other components, are contacted, e.g., in the desired quantities, and then the mixture is heated to a temperature above the melting point of the thermoplastic polyolefin polymer (a). The heating and blending can be done in either order, however, in the more specific embodiment, these processes are conducted simultaneously. The mixing may be conducted in any suitable equipment including a batch mixer, Banbury mixer, single or twin screw extruder, ribbon blender, injection molding machine, two-roll mill or the like.

In one embodiment the inorganic flame retardant (b) and the calcium borate on an inorganic carrier (c) are added in the powder form and then compounded into the thermoplastic polyolefin polymer (a) by a known method.

In another embodiment herein the inorganic flame retardant (b) and the calcium borate on an inorganic carrier (c) are premixed together, optionally with a binding agent, and granulated into concentrates in order to improve handling and decrease dusting, and then subsequently added to the thermoplastic polyolefin polymer (a).

In another specific embodiment herein, the flame retarded polyolefin polymer composition herein can be further cross-linked in order to improve the dimensional stability. Techniques of cross-linking polyolefins are well known in the art with the most common being free-radical cross-linking, radiation cross-linking or moisture-cure cross- linking using alkoxysilyl-grafted polyolefin. Cross-linked polyolefins can be used in the production of cable jackets and tubing.

In another embodiment there is provided a method for producing insulation or jackets, tubes, films, sheets, shipping pallets or injection-molded polyolefin parts, which comprises contacting the at least one thermoplastic polyolefin polymer (a) with at least one inorganic flame retardant (b) and at least one calcium borate on an inorganic carrier (c), such as those described herein, and heating the mixture to above the melting temperature of the thermoplastic polyolefm polymer (a) and then forming cable insulation or jackets or tubes or sheets or shipping pallets or injection-molded polyolefm parts therefrom.

The invention herein further comprises a cable insulation or jacket comprising the flame retarded polyolefm polymer composition described herein.

The invention herein also comprises extruded polyolefm sheets or injection molded parts, e.g., molded automotive parts or molded electronic parts which comprise the flame retarded polyolefm polymer composition described herein.

The invention herein further comprises an extruded or injection molded shipping pallet which comprises the flame retarded polyolefm polymer composition described herein.

The following examples are used to illustrate the present invention.

EXAMPLES

Example 1

285 gallons of cold city water (about 50 - 70 degrees F) were added to a 1000 gallon stainless steel reactor. This was followed by addition of 262 lbs of hydrated lime, Ca(OH)₂, 1000 lbs of wollastonite (calcium metasilica, NY AD M1250, ex. Nyco) and 430 lbs of boric acid. The mixture was suspended and mixed for at least 10 minutes to complete the reaction. The temperature in the reactor increased to about 90-120 degrees F. The slurry of the product was then pumped to a surge tank and then it was pumped through a wet milling system 35 U Palla followed by M60 Sweco vibrating mills (1/2 inch ceramic cylindrical media). The wet-milled product was pumped into a steam heated drum dryer operating at 190 - 240 degrees F and was then conveyed by a hot air line with the end temperature setup at about 310 degrees F. At the final stage the dried product went through a ACM60 grinding mill further decreasing the particle size to d₅₀ < 7 micron and d₉₉ < 25 micron. The final product was packaged into bags.

Examples 2 and 3 (cable jacketing formulation)

A list of the materials used in these examples is as follows:

(a) - Ethylene-vinyl acetate copolymer, Elvax 265, ex. DuPont (EVA)

(b) - Magnesium hydroxide, FR-20-120D-S7, ex. ICL-IP America Inc. (MDH) (c) - Calcium borate on wollastonite carrier as produced in Example 1.

Compounding of the EVA compositions was performed in a Brabender Intel li-Torque bowl mixer with a chamber volume of 60 cm³ at 190° C with a blade speed of 60 rpm and a mixing duration of 5 minutes. Test specimens, 10x10x3 cm, were prepared by compression molding using a Wabash hydraulic press at 220° C, using a force of 4 tons, for 4 min. The EVA compositions were tested in a Stanton Redcroft Cone calorimeter at 50 kW/m², according to the AST E 1354 test method. The results of the Cone calorimeter test are shown in Table 1.

Table 1

'HRR- heat release rate

As reported in Table 1 , the replacement of 5 wt. % of magnesium hydroxide with calcium borate on a silicate carrier resulted in prolongation of time of ignition and a decrease of heat release rate and the peak of the heat release rate. Furtliermore, the char left after the cone experiment in Example 3 looked different from the char of Comparative Example 2. The char from Examplet 3 was black, which is indicative of involvement of the polymer (EVA) in the charring. Furthermore the surface of the char of example 3 was smooth and had significantly less cracks than the char from Comparative example 2.

Example 4

In order to improve processability (resin flow) of the compositions the component (c) calcium borate on wollastonite carrier synergist was treated with stearic acid. 2.3 kg of calcium borate on wollastonite carrier of Example 1 and 34.5 g of stearic acid (99 % Cig) were placed into laboratory Henschel high intensity mixer. The temperature of the batch was brought up to 100 degrees Celsius by operating the mixer which allowed the stearic acid to combine with the surface of the calcium borate on wollastonite carrier. The effectiveness of the coating was checked by mixing a small sample of coated calcium borate on wollastonite carrier with water and assessing if the particles floated on top of the water.

Example 5

Example 4 was repeated, but the amount of stearic acid was increased to 69 g.

Examples 6-15

A list of the materials used in these examples is as follows:

(a) - Ethylene-vinyl acetate copolymer, Elvax 265, ex. DuPont (EVA)

(b) - Magnesium hydroxide, FR-20-120D-S10, ex. ICL-IP (MDH)

(ci) - Calcium borate on wollastonite carrier as produced in Example 1.

(c₂) - Calcium borate on wollastonite carrier as produced in Example 4.

(C3) - Calcium borate on wollastonite carrier as produced in Example 5.

The compounding was performed in a similar manner to that done in Examples 2 and 3 but using Brabender Rheology Software to measure the peak and normalized viscosity. Once the instrument was calibrated, the loading peak was displayed after forcing the premixed components into the auxiliary chute/ram assembly and maximum shear resulted. The "normalized" viscosity was seen after all the components were homogenized and the shear rate had leveled to a consistent range. The results of the rheology measurements and cone calorimeter data are shown in Table 2. As it is seen from rheology data of the stearic acid surface treated calcium borate on silicate carrier

(Examples 10-15), such helped decrease the peak and also normalized viscosity. This was understood to demonstrate that these formulations show better resin flow properties during processing. Table 2.

'HRR- heat release rate

Examples 16-18 (shipping pallets formulation')

Examples 2 and 3 were repeated with the difference that high impact polypropylene copolymer ASI Polypropylene 1404-01, ex. A. Schulman was used instead of EVA. In addition to the Cone calorimeter measurements, a Limiting Oxygen Index (LOI) flammability test was performed on 3.2x125 mm bars according to ASTM D 2863 using a Stanton Redcroft FTA Flammability Apparatus. Notched Izod impact strength was measured according to ASTM D 256 using a Pendulum type Monitor Impact Tester, TMI - Model 43-02-01. Heat Deflection Temperature (HDT) was measured according to ASTM D 648 using Automatic Deflection Tester Tinius Olsen Model DS-5.

The results of the Cone calorimeter test are shown in Table 3.

Table 3

aHRR- heat release rate

PP copolymer - polypropylene copolymer

As in is seen from the Table 3 replacement of 5 wt. % MDH with 5 wt. % calcium borate (from example 3) results in increase of LOI and decrease in heat release rate. Even taking into consideration that the amount of PP copolymer doesn't change the total heat also decreases. These are indications of the synergistic effect between MDH and calcium borate.

While the process of 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 embodiment disclosed as the best mode contemplated for carrying out the process of the invention but that the invention will include all embodiments falling within the scope of the appended claims.

Claims

Claims:

1. A flame retarded polyolefin polymer composition comprising a thermoplastic polyolefin polymer, an inorganic flame retardant and a calcium borate on an inorganic carrier .

2. The flame retarded polyolefin polymer composition of Claim 1 wherein the thermoplastic polyolefin polymer is at least one of a polyethylene homopolymer, polyethylene copolymer, polypropylene homopolymer and polypropylene copolymer.

3. The flame retarded polyolefin polymer composition of Claim 1 wherein the thermoplastic polyolefin polymer is at least one of an ethylene- vinyl acetate copolymer (EVA); ethylene-propylene rubber (EPR); ethylene-propylene-diene-monomer rubber (EPDM); and copolymers of ethylene and propylene with butene-1 , pentene-1, 3- methylbutene- 1 , 4-methylpentene-l, octane- 1, and mixtures thereof.

4. The flame retarded polyolefin polymer composition of Claim 1 wherein the inorganic flame retardant is a metal hydroxide.

5. The flame retarded polyolefin polymer composition of Claim 1 wherein the inorganic flame retardant is selected from the group consisting of aluminum hydroxide, magnesium hydroxide, magnesium basic carbonate, hydrotalcite, calcium aluminate hydrate and combinations thereof.

6. The flame retarded polyolefin polymer composition of Claim 1 wherein the inorganic carrier is selected from the group consisting of alumina trihydrate, natural calcium carbonate, precipitated calcium carbonate, calcium sulphate, carbon black, carbon fibers, clay, cristobalite, diatomaceous earth, dolomite, feldspar, graphite, glass beads, glass fibers, kaolin, magnesium carbonate, magnesium hydroxide, metal powders or fibers, mica muscouite, mica phlogopite, natural silica, synthetic silica, nepheline-syenite, talc, whiskers, wollastonite, and combinations thereof.

7. The flame retarded polyolefin polymer composition of Claim 1 wherein the inorganic carrier is wollastonite.

8. The flame retarded polyolefin polymer composition of Claim 1 wherein the calcium borate on an inorganic carrier is calcium borate on a wollastonite carrier in particulate form such that the particles of calcium borate on wollastonite have a median diameter (d₅₀) of from 2 microns to about 10 microns and 99 weight percent of the particles based on the total weight of calcium borate on a wollastonite carrier particles have a diameter (dw) of less than 25 microns.

9. The flame retarded polyolefin polymer composition of Claim 1 wherein the calcium borate on an inorganic carrier is surface treated with a fatty acid or a fatty acid salt.

10. The flame retarded polyolefin polymer composition of Claim 1 wherein the inorganic flame retardant is present in an amount of from about 10 weight percent to about 65 weight percent of the total weight of the flame retarded polyolefin polymer

composition.

1 1. The flame retarded polyolefin polymer composition of Claim 1 wherein the inorganic flame retardant is present in an amount of from about 15 weight percent to about 60 weight percent of the total weight of the flame retarded polyolefin polymer

composition.

12. The flame retarded polyolefin polymer composition of Claim 1 wherein the calcium borate on an inorganic carrier is present in an amount of from about 2 weight percent to about 35 weight percent of the total weight of the flame retarded polyolefin polymer composition.

13. The flame retarded polyolefin polymer composition of Claim 1 wherein the calcium borate on an inorganic carrier is present in an amount of from 3 weight percent to about 15 weight percent of the total weight of the flame retarded polyolefin polymer composition.

14. An article selected from the group consisting of tubing, extruded film or sheets, molded automotive parts or molded electronic parts comprising the flame retarded polyolefin polymer composition of Claim 1.

15. A cable insulation or jacket comprising the flame retarded polyolefin polymer composition of Claim 1.

16. A flame retarded shipping pallet comprising the flame retarded polyolefin polymer composition of Claim 1.

17. A method of making a flame retarded polyolefin polymer composition comprising: contacting at least one thermoplastic polyolefin polymer with at least one inorganic flame retardant and at least one calcium borate on an inorganic carrier;

heating the mixture of thermoplastic polyolefin polymer, at least one inorganic flame retardant and at least one calcium borate on an inorganic carrier to above the melting temperature of the thermoplastic polyolefin polymer.