Thermally stable, refractory thermoplastic polymer compositions for heat / fire spreading applications

Abstract

Thermally stable, fire resistant thermoplastic polymer compositions for heat / fire spreading applications are disclosed. A thermoplastic polymer composition includes a thermoplastic polymer and at least one ceramizable filler. The thermoplastic polymer composition may include additional additives. The thermoplastic polymer composition can be readily processed, is thermally stable, and retains its mechanical and insulating properties.

Description

Technical Field

[0001] The present invention relates to thermoplastic polymer compositions for heat / fire spreading applications. In particular, the present invention relates to thermoplastic polymer compositions comprising a thermoplastic polymer and at least one ceramifiable filler. The thermoplastic polymer composition may contain additional additives as desired. The resulting thermoplastic polymer composition is thermally stable, fire resistant, and maintains its insulating ability after exposure to heat or flame. Background Art

[0002] Many applications require that base materials withstand high heat and avoid the spread of fire. This is especially true for objects with electronic components that may experience thermal runaway. Thermal runaway is a process that is accelerated by increased temperature, which in turn releases energy and further increases the temperature. Thermal runaway can be associated with exothermic reactions or increased power flow and power dissipation. This risk is particularly present when lithium batteries are used in components. Thermal runaway leads to gas ejection, high temperatures, flames and smoke.

[0003] Ceramic materials can be used to prevent thermal runaway. However, ceramic materials are not flexible, low-cost or easy to manufacture. Therefore, a thermally stable, refractory material that can be easily manufactured and avoid these problems is needed. Preferably, the material is a polymer material with at least one ceramizable filler.

[0004] U.S. Patent No. 5,707,734 describes a polymer composite material with enhanced flame retardant behavior. The composite material comprises a polymer and glass fibers coated with fumed silica. The polymer can be selected from a wide variety of polymers including polybutylene, polyethylene terephthalate, polycarbonate, polyethylene, polypropylene, nylon, and mixtures of these polymers.

[0005] In the article "Flame Retardant Mechanism of Silica Gel / Silica" (Fire and Materials, Vol. 24, No. 6, 277-289, November / December 2000), Kashiwagi et al. studied various types of silica, silica gel, fumed silica, and fused silica in polypropylene and polyethylene oxide to determine their flame retardant effectiveness and mechanism. The fumed silica and silica gel used in this study accumulate near the polymer surface when subjected to flames, acting as a thermal barrier and a barrier to the transport of degradation products to the surface.

[0006] US Patent No. 6,774,159 B2 describes a composition having high resistance to the spread of fire. The composition comprises a base polymer and a fireproofing additive comprising a metal hydroxide. The composition avoids the problems associated with metal hydroxides, namely high viscosity and reduced mechanical properties.

[0007] US Patent Publication No. US2009 / 0326108A1 describes a halogen-free flame retardant thermoplastic polyurethane composition. The flame retardant thermoplastic polyurethane composite resin composition can improve the flame retardancy and flaming-drip of thermoplastic polyurethane resin by ideally forming char during combustion. The halogen-free flame retardant used is hypophosphite, diphosphite, dipentaerythritol, talc or melamine derivatives.

[0008] In the article "Influence of Fumed Silica on Flame-Retardant Properties of Ethylene VinylAcetate / Aluminum Hydroxide Composites," published in the Journal Qf Applied Polymer Science in 2010 (https: / / dpo.org / 10.1002 / app.33126), the authors describe the flammability and synergistic flame retardant effects of fumed silica. According to the authors' results, the addition of fumed silica improved the UL 94 rating of the composite. In addition, cone calorimeter testing showed that the addition of fumed silica significantly reduced the heat release rate of the composite when exposed to flames.

[0009] In a 2012 article, "Thermal Stability of High Density Polyethylene Fumed Silica Nanocomposites" (published in the Journal of Thermal Analysis and Calorimetry, Vol. 109, No. 2, August 2012), Dorigato et al. described how to prepare high-density polyethylene-based nanocomposites by melt mixing using surface-functionalized fumed silica nanoparticles. These materials were studied to determine their ability to improve mechanical properties and resist thermal degradation. Thermogravimetric analysis showed that the selected nanoparticles effectively increased the decomposition temperature and reduced the mass loss rate. The formation of a char-rich layer was responsible for limiting the diffusion of oxygen through the sample. Cone calorimeter testing demonstrated the effectiveness of the functionalized nanoparticles in delaying ignition time and reducing heat release rate values. The data showed that functionalized fumed silica nanoparticles can provide an effective way to enhance the flammability of polyolefins.

[0010] US Patent Publication No. US2015 / 0152222A1 describes a flame retardant thermoplastic polyurethane composition comprising a non-halogen flame retardant. The thermoplastic polyurethane composition can be used in various applications requiring high flame performance and low smoke performance as well as high tensile strength, such as wire and cable applications, film applications, and molding applications.

[0011] US Patent Publication No. US2015 / 0170789A1 describes a refractory composition. The refractory composition comprises at least one polymer and at least one ceramic material. The composition does not contain a material that produces significant ionic conductivity when melted below a threshold temperature, and substantially does not contain magnesium hydroxide Mg(OH)2.

[0012] In a 2019 article, “Synergistic Effects of Metal Hydroxides and Fumed Nanosilica as Fire Retardants for Polyethylene” (published in Flame Retardancy and Thermal Stability of Materials, 2: 30-48), Fredi et al. described the effects of aluminum / magnesium hydroxide microfillers and organically modified fumed silica nanoparticles on linear low-density polyethylene. The authors found that increased viscosity contributed to the synergistic effect between metal hydroxides and nanosilica. The authors concluded that metal hydroxides and fumed nanosilica enhanced the mechanical properties and fire resistance of polyethylene.

[0013] U.S. Patent No. 10,854,356 B2 describes a fire-resistant cable with a ceramizable layer. The applicant describes a composition based on a mixture of a specific thermoplastic ethylene polymer, silicon dioxide as a filler and hydrated magnesium silicate as a stabilizer. The composition can be used to manufacture a cable that has suitable mechanical properties when in service and effectively maintains the cable in service in the presence of fire and mechanical stress.

[0014] Even with all of these advances, there remains a need for thermoplastic polymer materials having improved fire spread resistance and thermal stability, which can be easily processed while still retaining the basic mechanical properties of the polymer. Summary of the invention

[0015] One embodiment is directed to a thermally stable, fire-resistant thermoplastic polymer composition comprising a thermoplastic polymer and at least one ceramizable filler.

[0016] One embodiment is directed to a method of forming a thermally stable, fire-resistant thermoplastic polymer comprising a thermoplastic polymer and at least one ceramizable filler.

[0017] Another embodiment is directed to the use of a thermally stable, fire-resistant thermoplastic polymer composition comprising a thermoplastic polymer and at least one ceramizable filler in an object that may be subjected to excessive heat or exposed to fire.

[0018] Yet another embodiment is directed to a battery enclosure made from a thermally stable, fire-resistant thermoplastic polymer comprising a polymer and at least one ceramizable filler.

[0019] Other features and advantages of the present invention will be apparent from the following more detailed description of the preferred embodiments, taken in conjunction with the accompanying drawings, which illustrate, by way of example, the principles of the invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 is a graph showing the temperature change over time at the top of a plate made from the polymer composition of the present invention when the bottom of the plate is exposed to flame. DETAILED DESCRIPTION

[0021] The description of the illustrative embodiments according to the principles of the present invention is intended to be interpreted with respect to the accompanying drawings, which should be considered as part of the entire written description. In the description of the embodiments of the present invention disclosed herein, any reference to direction or orientation is intended only for the convenience of description, and is not intended to limit the scope of the present invention in any way. Relative terms such as "lower", "higher", "horizontal", "vertical", "higher", "lower", "up", "down", "top" and "bottom" and their derivatives (e.g., "horizontally", "downwardly", "upwardly", etc.) should be interpreted as referring to the orientation as described at the time or as shown in the accompanying drawings discussed. These relative terms are only for the convenience of description, and do not require the device to be constructed or operated with a specific orientation, unless clearly indicated. Unless otherwise clearly described, terms such as "attachment", "fixation", "connection", "coupling", "interconnection", etc. refer to the relationship in which the structure is directly or indirectly fastened or attached to each other through an intermediate structure, and the two cases of movable or rigid attachment or association.

[0022] Furthermore, the features and benefits of the present invention are described with reference to preferred embodiments. Therefore, the present invention should be expressly not limited to such embodiments describing some possible non-limiting combinations of features that may exist alone or in other feature combinations, the scope of the present invention being defined by the appended claims.

[0023] The thermally stable, fire-resistant composition comprises a thermoplastic polymer and at least one ceramizable filler, and optionally other additives. The thermoplastic polymer used in the composition can be a thermoplastic polymer, a cross-linked thermoplastic polymer, or a mixture thereof.

[0024] Thermoplastic polymers may be amorphous or semi-crystalline. Examples of suitable thermoplastic polymers include, but are not limited to: (i) polyolefins (PO), such as polyethylene (PE), polypropylene (PP), polybutene, ethylene propylene rubber (EPR), polyethylene oxide (POE), cyclic olefin copolymers (COC), or combinations thereof; (ii) styrene polymers, such as polystyrene (PS), acrylonitrile butadiene styrene (ABS), styrene acrylonitrile (SAN), styrene butadiene rubber (SBR or HIPS), poly (α-methyl styrene), styrene maleic anhydride (SMA), styrene-butadiene copolymers (SBC) (such as styrene-butadiene-styrene copolymers (SBS) and styrene-ethylene / butadiene-styrene copolymers (SEBS)), styrene-ethylene / propylene-styrene copolymers (SEPS), styrene butadiene latex (SBL), ethylene propylene diene monomer (EPDM) modified SAN and / or acrylic elastomers (e.g., PS-SBR copolymers), or combinations thereof; (iii) thermoplastic polyurethanes (TPU) other than those described above; (iv) polyamides, such as polyamide 6 (PA6), polyamide 6,6 (PA66), polyamide 1,1 (PA11), polyamide 1,2 (PA12), copolyamide (COPA), or combinations thereof; (v) acrylic polymers, such as polymethyl acrylate, polymethyl methacrylate, methyl methacrylate styrene (MS) copolymer, or combinations thereof; (vi) polyvinyl chloride (PVC), chlorinated polyvinyl chloride (CPVC), or combinations thereof; (vii) polyoxymethylene, such as polycondensate (viii) polyesters, such as polyethylene terephthalate (PET), polybutylene terephthalate (PBT), copolyesters including polyether-ester block copolymers and / or polyester elastomers (COPE), such as glycol-modified polyethylene terephthalate (PETG), polylactic acid (PLA), polyglycolic acid (PGA), copolymers of PLA and PGA, or combinations thereof; (ix) polycarbonate (PC), polyphenylene sulfide (PPS), polyphenylene oxide (PPO); or combinations thereof.

[0025] Other non-limiting examples of commercially used thermoplastic polymers include: poly(vinyl halide), polyvinyl alcohol, polynitriles, polyacetals, polyimides, polyaryl ketones, polyether ketones, polyhydroxyalkanoates, polycaprolactones, polysulfones, polyphenylene oxides, polyacetates, liquid crystal polymers, fluoropolymers, ionomers, thermoplastic elastomers, copolymers of any one of them, and combinations of any two or more of them.

[0026] Non-limiting examples of specific commercial thermoplastic polymers include: acrylonitrile butadiene styrene (ABS), polymethyl methacrylate (PMMA), cellulose acetate, cyclic olefin copolymer (COC), ethylene vinyl acetate (EVA), ethylene vinyl alcohol (EVOH), polytetrafluoroethane (PTFE), ionomers, polyoxymethylene (POM or acetal), polyacrylonitrile (PAN), polyamide 6, polyamide 6,6, polyamide-imide (PAI), polyaryletherketone (PAEK), polybutadiene (PBD), polybutylene (PB), polybutylene terephthalate (PBT), polycaprolactone (PCL), polychlorotrifluoroethylene (PCTFE), polyethylene terephthalate (PET ), polycyclohexanedimethylene terephthalate (PCT), polycarbonate (PC), polyhydroxybutyrate (PHB), polyethylene (PE), polyetheretherketone (PEEK), polyetherketoneketone (PEKK), polyetherimide (PEI), polyethersulfone (PES), chlorinated polyethylene (CPE), polyimide (PI), polylactic acid (PLA), polymethylpentene (PMP), polyphenylene oxide (PPO), polyphenylene sulfide (PPS), polyphthalamide (PPA), polypropylene (PP), polysulfone (PSU), polytrimethylene terephthalate (PTT), polyurethane (PU), polyvinyl acetate (PVA), polyvinyl chloride (PVC), polyvinylidene chloride (PVDC) and styrene-acrylonitrile (SAN).

[0027] Thermally stable, flame-resistant thermoplastic polymer compositions must contain at least one ceramizable filler and optionally other desired additives. Examples of other suitable additives include conductive fillers, reinforcing fillers, phosphorus-based flame retardants and synergists, and other conventional additives for polymer processing.

[0028] The heat-stable, fire-resistant thermoplastic polymer composition comprises at least one ceramizable filler. The ceramizable filler may include any type of filler that can react with other fillers to form an inorganic residue and a ceramic layer when exposed to fire or high temperature (greater than or equal to 500° C.). Examples of ceramizable fillers include, but are not limited to, magnesium carbonate, sodium bicarbonate, and potassium bicarbonate. In one embodiment, the ceramizable filler may be a flame retardant. The flame retardant is preferably halogen-free, environmentally safe, and non-toxic. These ceramizable fillers significantly reduce the amount of smoke released by the base polymer and reduce the damage to such polymers when exposed to fire. The ceramizable filler may include at least one silica-based flame retardant. An example of a silica-based flame retardant is pyrogenic silica. Aerosil pyrogenic silica from Evonik is an example of commercially available pyrogenic silica. Other flame retardants that may be used as ceramizable fillers include metal oxides and metal hydroxides, such as magnesium hydroxide, aluminum hydroxide, and calcium hydroxide, as well as magnesium oxide. In one embodiment, preferably, the ceramic filler is a combination of fumed silica, magnesium hydroxide, aluminum hydroxide and calcium hydroxide. In one embodiment, the ceramic filler is included in magnesium hydroxide in the range of about 20 to 98 weight %, aluminum hydroxide in the range of about 0 to about 40 weight %, calcium hydroxide in the range of about 0 to about 40 weight % and fumed silica in the range of about 2 to about 30 weight %, all weights are based on total ceramic filler. In another embodiment, the ceramic filler can include aluminum polyphosphate and fumed silica.

[0029] Reinforcing fillers can be used for heat-stable, fire-resistant thermoplastic polymer compositions. Examples of reinforcing fillers include: carbon fibers, glass fibers, ceramic fibers, whiskers, polymer fibers, nanofibers or nano hollow fibers, and blends thereof. These reinforcing fillers help improve the intensity and dimensional stability of heat-stable, fire-resistant polymer compositions when they are subjected to flames.

[0030] Carbon fibers that can be used in the present invention include, but are not limited to, carbon nanotubes and carbon fibers. Typically, these carbon fibers improve the heat resistance of the polymer composition and can be burned after the composition is subjected to fire. Any known carbon fiber can be used in the present invention. Typically, the carbon fiber has a nominal diameter of about 1 to about 50 microns, preferably about 5 to about 20 microns. The amount of carbon fiber that can be used in the thermally stable, fire-resistant polymer composition is in the range of about 0 to about 50 volume % of the total polymer composition.

[0031] Glass fiber can also be added as reinforcing filler in the heat-stable, fire-resistant thermoplastic polymer composition. Examples of such glass fibers include, but are not limited to, chopped glass fibers, continuous glass fibers, ground glass, glass balls and glass beads. Any known glass fiber can be used in the present invention. Usually, the nominal diameter of the glass fiber is about 1 to about 50 microns, preferably about 5 to about 20 microns. The amount of the glass fiber used in the heat-stable, fire-resistant polymer composition is in the range of about 0 to about 50 volume % of the total polymer composition.

[0032] Similarly, ceramic fibers can also be added to the heat-stable, fire-resistant thermoplastic polymer composition. The ceramic fibers can be oxide-based ceramic fibers or non-oxide-based ceramic fibers or blends thereof. Examples of oxide-based ceramic fibers include, but are not limited to, Al2O3, SiO2, Al2O3-SiO2, or ZrO2. Examples of non-oxide-based ceramic fibers include, but are not limited to, SiC, BN, or Si3N4. The amount of ceramic fibers that can be used in the heat-stable, fire-resistant polymer composition is in the range of about 0 to about 50 volume % of the total polymer composition.

[0033] In addition, the heat-stable, fire-resistant thermoplastic polymer composition can include polymer fibers as reinforcing fillers. Examples of suitable polymer fibers include aramid fibers and continuous polyethylene fibers. Any known polymer fibers can be used in the present invention. Typically, the nominal diameter of the polymer fiber is from about 1 to about 50 microns, preferably from about 5 to about 20 microns. The polymer fibers used in the heat-stable, fire-resistant polymer composition are in the range of from about 0 to about 50 volume %.

[0034] The thermally stable, flame-resistant thermoplastic polymer composition may also contain nanofibers or nano hollow fibers as reinforcing fillers. Examples of such fibers include, but are not limited to, carbon nanotubes, graphene, graphite nanosheets, and Dragonite. TM Halloysite (aluminosilicate clay) (available from Applied Minerals, Inc.) The diameter of the nanotubes ranges from about 0.1 to about 100 nanometers, preferably from about 0.4 to about 40 nanometers.

[0035] In addition, bromine or phosphorus flame retardant packages can be added to the heat stable, flame retardant thermoplastic polymer composition as synergists. The addition of synergists helps promote char formation and maintain the integrity of the heat stable, flame resistant thermoplastic polymer composition when subjected to flames or high temperatures.

[0036] Other conventional additives can be added to the thermoplastic polymer composition of heat-stabilization and fire-resistance. The example of conventional additives includes: pigment, dye, pore-forming agent (voiding agent), antistatic agent, foaming agent, plasticizer, free radical scavenger, antiblocking agent, dust-proof agent, antifouling agent, surfactant, slip aid, optical brightener, plasticizer, viscosity modifier, gloss modifier, dispersion stabilizer, UV stabilizer, UV absorber, antioxidant, lubricant, heat stabilizer, hydrolysis stabilizer, crosslinking activator, coupling agent, layered silicate, radiation sunscreen (such as barium sulfate), tungsten metal, non-oxide bismuth salt, filler, colorant, reinforcing agent, adhesion promoter (such as but not limited to 2-hydroxyethyl-methacrylate-phosphate), impact strength modifier and their combination in any. Such additives of conventional amount can be included.

[0037] In addition, the heat-stable, fire-resistant thermoplastic polymer composition can be cross-linked. The thermoplastic polymer composition can be cross-linked using heat, a cross-linking agent, or radiation cross-linking. Any thermoplastic polymer that can be easily cross-linked can be used in the present invention. Compared with uncross-linked thermoplastic polymers, cross-linked thermoplastics better retain their mechanical properties after exposure to fire.

[0038] One method of obtaining a crosslinked thermoplastic polymer composition is to use heat. In one embodiment, the thermoplastic polymer may be heated from about 70°C to about 250°C to obtain the desired crosslinking. An example of a thermoplastic polymer that may be crosslinked by heat is acrylonitrile.

[0039] In addition to heat, thermoplastic polymer compositions can also be cross-linked using cross-linking agents. Examples of cross-linking agents include chemicals, monomers or polymers with more than one identical or different functional groups, which can connect more than two binder polymer chains, more than two particles, and can connect polymer chains and particles to each other and to the surface. In some embodiments of the present invention, the cross-linking agent has more than one free radical generating part, such as aryl ketone, azido, peroxide, diazo, carbene or nitrene generator. In other embodiments, the cross-linking agent has more than one reactive group that can react with functionalized binder polymer thermochemically, such as vinyl, carboxyl, ester, epoxy, hydroxyl, amide, amino, sulfenyl, N-hydroxysuccinimide, isocyanate, anhydride, azido, aldehyde, cyanuric chloride or phosphine. In addition, the product of the present invention can be cross-linked using a free radical generator. The free radical generator can form new bonds by free radical-free radical combination, addition to unsaturated bonds, hydrogen capture and subsequent reorganization and possible electron transfer reactions. Examples of free radical initiators include benzophenones, acetophenone derivatives, peroxides, peroxy compounds, benzoin derivatives, benzyl ketals, hydroxyalkylphenones and aminoalkylphenones, O-acyloxime ketones, acylphosphine oxides and acylphosphonates, thiobenzoic acid S-esters, azo and azide compounds, triazines, 1,2 diketones, quinones, coumarins, xanthones. In one embodiment, the crosslinking agent is triallyl isocyanurate (TAIC).

[0040] In addition, the thermoplastic polymer composition can be crosslinked using radiation crosslinking. Radiation crosslinking occurs when the thermoplastic polymer is exposed to an agent such as ultraviolet light, electron beam or gamma radiation with or without additional crosslinking agents or substances. If radiation is used as a crosslinking agent, the product is exposed to radiation in the range of 50 KGy to 1100 KGy, preferably 50 to 300 KGy, to obtain the desired crosslinking.

[0041] In another aspect, the present invention relates to the preparation of a heat-stable, fire-resistant thermoplastic polymer composition. The method includes providing a thermoplastic polymer and a ceramizable filler, and providing any desired additional additives. The thermoplastic polymer, the ceramizable filler, and any other additional additives are mixed together in a granular form using any conventional process for mixing the materials together. The mixing device can be any suitable device used in the field of mixed concentrated solids. Examples of such devices suitable for heat-stable, fire-resistant thermoplastic polymer compositions include: intermittent mixers, such as Brabender mixers, Banbury mixers, etc.; single extruders, twin-screw extruders, high-speed centrifugal mixers, Henschel mixers, ribbon blenders, vibrators, tubular drums, etc. Conventional processes can be used to heat, melt, and mix thermoplastic polymers, ceramizable fillers, and any desired additives.

[0042] Once the thermoplastic polymer is mixed with the desired additives, it can be further processed. The heat-stable, fire-resistant thermoplastic polymer composition can be extruded, injection molded, overmolded, compression molded, cast, spincast, reaction injection molded, laminated, dispensed, canned, 3D printed, selectively printed, spread and coated to form any desired heat-stable and fire-resistant object.

[0043] The heat stable, fire resistant thermoplastic polymer can be further processed for end use. The heat stable, fire resistant thermoplastic polymer can be used in multilayer systems. In addition, the heat stable, fire resistant thermoplastic polymer composition can contain additional support layers. Examples of possible support layers include, but are not limited to, metal support layers, such as aluminum foil, plates, and non-metal support layers, such as polymer films and plates.

[0044] If the heat-stable, fire-resistant thermoplastic polymer of the present invention is used for 3D printing, the polymer can be pre-mixed with a ceramizable filler and then ground to form a suitable powder. Alternatively, the thermoplastic polymer can be first ground and then mixed with different filler packages (including ceramizable fillers) to make a powder suitable for 3D printing. In another alternative, the heat-stable, fire-resistant thermoplastic polymer of the present invention can be manufactured in the form of filaments so that it is suitable for 3D printing. Any 3D printing method can be used, including but not limited to laser sintering, selective laser sintering, fused deposition modeling (fused deposition modeling), fused filament fabrication (fused filament fabrication) and digital light processing.

[0045] The heat-stable, fire-resistant thermoplastic polymer compositions of the present invention have a variety of uses. For example, the thermoplastic polymer compositions can be made into connectors, wires, cables, printed circuit boards or EMI shielding and other computer components. The thermoplastic polymer compositions can be used to make electronic components that meet the UL 94V standard, such as smart phones, motors, e-powertrains, batteries and battery housings, chargers for electric vehicles, and other components of electric vehicles. The thermoplastic polymer compositions can be used in the construction industry for any object that may cause a fire hazard due to overheating or short circuiting of the electronic devices used. In addition, the heat-stable, fire-resistant thermoplastic polymer compositions of the present invention can be used to form any type of outer cover or housing that requires fire resistance.

[0046] It is believed that when a heat-stable, fire-resistant thermoplastic polymer composition with a ceramizable filler and optional additives is subjected to fire or high temperature (greater than or equal to 500°C), energy is released due to thermal decomposition. When the thermoplastic polymer composition is degraded due to flame or high temperature, it forms an inorganic residue, as well as a char, which serves to provide good cohesion between the polymer composition and the inorganic residue. A ceramic layer that provides reinforcement for the residue is also formed on the surface of the inorganic residue. It is believed that the structure obtained after the thermoplastic polymer composition is degraded due to flame or high temperature prevents the spread of fire by blocking heat transfer, and isolates the contact between the polymer and oxygen, thereby playing a role in flame retardancy and fire resistance. The structure helps the basic thermoplastic polymer composition maintain good thermal stability and maintains its insulation. The insulation can be electrical insulation (i.e., higher than 10 6 Volume resistivity of ohm.cm, preferably higher than 10 9 The thermally stable, flame-resistant thermoplastic polymer composition retains its mechanical properties after being processed and exposed to high temperatures or flames. The ceramic layer of the structure enhances the shape of an object made from the thermoplastic polymer composition. In addition, it is believed that the structure absorbs soot particles, resulting in lower smoke content.

[0047] Figure 1Figures showing the results of samples of thermoplastic polymer compositions of the present invention subjected to flame temperatures of 1100°C are shown. 1.3 mm thick plates were made from polypropylene with ceramizable fillers and 1%v triallyl isocyanurate (TAIC). The plate was exposed to 300 kGy of electron beam radiation to obtain crosslinking. The ceramizable filler package was 65 wt % of magnesium hydroxide, 13 wt % of calcium hydroxide, 9 wt % of aluminum hydroxide and 13 wt % of pyrogenic silica. The figure shows that the plate did not break after 10 minutes under the flame while the back side of the plate was maintained at a temperature of 500°C. In contrast, conventional plates made of aluminum oxide broke after twenty seconds. The data show that thermoplastic polymer compositions of the present invention are thermally stable and fire-resistant.

[0048] Example

[0049] In the following embodiments stated below, unless otherwise specified, a ceramizable filler bag comprising the following is used: 65 % by weight of magnesium hydroxide, 13 % by weight of calcium hydroxide, 9 % by weight of aluminum hydroxide, and 13 % by weight of pyrogenic silica. This ceramizable filler is used for various thermoplastic polymer compositions, and fire resistance tests are carried out. Regarding fire resistance tests, a heat-stable, fire-resistant thermoplastic polymer composition is prepared into a 1 mm thick sample. The sample is sandwiched between two metal plates, clamped, and its bottom face is subjected to an open flame, and the temperature is in the range of about 1050 ° to about 1100 ° C.

[0050] In one embodiment, heat-stable, fire-resistant thermoplastic polymer composition comprises 45 wt % polypropylene, 54 wt % ceramizable filler bag and 1 wt % TAIC. The sample is formed into a 1 mm thick plate and carries out the above-mentioned fire resistance test. After 1-2 minutes, the sample is broken. This embodiment shows that the region not in contact with the flame does not form a heat-stable and fire-resistant thermoplastic polymer composition.

[0051] In another embodiment, a heat-stable, fire-resistant thermoplastic polymer composition comprising 45 wt % polypropylene, 54 wt % ceramizable filler package and 1 wt % TAIC is formed into a one millimeter thick plate. The plate is exposed to 300 kGy of electron beam radiation to obtain crosslinking. The sample is subjected to the above-mentioned fire resistance test for ten minutes. After ten minutes, the plate did not break and was self-supporting.

[0052] In yet another embodiment, the above-mentioned ceramizable filler package is used in combination with glass fiber to form a thermoplastic polymer composition. The heat-stable, fire-resistant composition comprises 20 wt % polypropylene, 59 wt % ceramizable filler package, 20 wt % glass fiber and 1 wt % TAIC. The thermoplastic polymer composition is formed into a plate, and the plate is subjected to 300 kGy of electron beam radiation. After carrying out the fire resistance test for 10 minutes, the plate is still intact and self-supporting.

[0053] In the next embodiment, from ceramizable packing bag, pyrogenic silica is removed.In this packing bag, 83 % by weight of magnesium hydroxide, 7 % by weight of aluminum hydroxide and 10 % by weight of calcium hydroxide are used to form filler.59 % by weight of this filler is joined among 20 % by weight of polypropylene, 20 % by weight of glass fiber and 1 % by weight of TAIC.This material is used to form plate, and the electron beam radiation of 300kGy is carried out to it.Then this plate is carried out fire resistance test.After 10 minutes, this plate breaks, and becomes powdery.This embodiment shows that pyrogenic silica is the essential component of ceramizable packing bag.

[0054] In the next example, a polyamide combined with the above-described ceramizable filler package was tested. A board was formed and then subjected to a fire test. After about 2-3 minutes, the sample fell over and broke apart.

[0055] In yet another embodiment, 64 wt% polyamide was compounded with 15 wt% glass fiber, 20 wt% ceramizable filler package and 1 wt% TAIC. A board was formed and subjected to 100 kGy electron beam radiation. The board was then subjected to a fire test for ten minutes. The test showed that the board was self-supporting.

[0056] Prepared another kind of heat-stable, fire-resistant polymer composition.In this composition, 54 weight % polyamide was mixed with 15 weight % glass fiber, 30 weight % of the above-mentioned ceramizable filler package and 1 weight % TAIC.This composition was formed into a plate, and the plate was irradiated with 100kGY electron beam.Then fire-resistant test was used to test this plate for 10 minutes.Test results show that even if there is 30 weight % ceramizable filler package in the heat-stable, fire-resistant thermoplastic polymer composition, this plate is also self-supporting.

[0057] Another heat-stable, fire-resistant composition based on polyamide is prepared using 37% by weight of polyamide and 18% by weight of glass fiber, 44% by weight of a ceramic filler package and 1% by weight of TAIC. A board is formed and the board is subjected to 100 kGy electron beam radiation. The board is subjected to a fire resistance test for 10 minutes. The test results show that the board made of the composition is self-supporting under flame.

[0058] Another example was conducted in which a 30% glass fiber reinforced UL-94V-0 grade commercial polyamide 6,6 was mixed with 1 wt% TAIC and then formed into a plate by injection molding. The plate was subjected to 100 kGy electron beam irradiation and fire resistance testing for 10 minutes. The test showed that although the plate withstood the fire resistance test without the ceramizable filler package and was self-supporting, the back of the surface was carbonized.

[0059] In yet another embodiment, a 30% glass fiber reinforced UL-94V-) grade commercial polyamide 6,6 was mixed with 30% by weight of glass fiber, 1% of TAIC, and a ceramizable filler containing 5% by weight of fumed silica, and then formed into a board by injection molding. The thermoplastic polymer composition was formed into a board, and the board was subjected to 100 kGy of electron beam radiation. The sample was then subjected to fire resistance testing, and it was shown that the sample was self-supporting even if the bottom surface of the board subjected to direct flame was carbonized.

[0060] In contrast, in the next example, the above-mentioned ceramizable filler package is added to a thermoplastic polymer composition. In this composition, 30% glass fiber reinforced polyamide 6,6 containing a flame retardant is mixed with 6.7% by weight of magnesium oxide and 3.3% by weight of pyrogenic silica, 1% by weight of TAIC, and then formed into a plate by injection molding. The plate is subjected to 100 kGy electron beam radiation and fire resistance testing. This example shows that the bottom surface of the plate is not carbonized as in the previous sample by adding a ceramizable filler package. This example shows that the addition of both silica and magnesium oxide can enhance the formation of a ceramic layer.

[0061] Another series of examples using the compositions of the invention was conducted. In this series, ceramizable filler packages were added to polypropylene and polyamide 6. One millimeter plates were made from the samples, and the plates were placed in a furnace at 800° C. for 5 minutes. The samples all formed dense ceramic layers, were self-supporting, and retained their shape after testing.

[0062] Provide another comparative example, wherein the first sample of 20 wt % polypropylene is mixed with 80 wt % of the filler bag comprising magnesium hydroxide, aluminum hydroxide and calcium hydroxide.Compared with the first sample, the second sample comprises 20 wt % polypropylene mixed with 80 wt % of the above-mentioned ceramizable filler bag.A 1 mm plate is made by the first sample and the second sample, and it is put into a furnace of 800 ℃ for 5 minutes.The second sample with pyrogenic silica performs better than the first sample of rupture.

[0063] Those skilled in the art will appreciate that, without departing from the principles of the invention, the invention may be used in a variety of modified forms of structure, arrangement, proportion, size, material and components, and the invention may adopt other forms used in the practice of the invention, which are particularly suitable for specific environments and operating requirements. Therefore, the presently disclosed embodiments are considered in all aspects to be illustrative and not restrictive, and the scope of the invention is defined by the appended claims and is not limited to the foregoing description or embodiments.

Claims

1. A thermally stable, insulating, fire-resistant thermoplastic polymer composition comprising a polymer and an additive, at least one additive comprising a ceramizable filler, wherein the polymer composition is ceramized and maintains its insulating properties after exposure to high temperature or flame.

2. The composition according to claim 1, wherein the polymer is selected from the group comprising thermoplastic polymers.

3. The composition of claim 1, wherein the ceramizable filler comprises fumed silica and a metal hydroxide, preferably wherein the ceramizable filler comprises fumed silica, magnesium hydroxide, calcium hydroxide and aluminum hydroxide.

4. The composition of claim 1, wherein the thermally stable, flame resistant thermoplastic polymer composition comprises a reinforcing filler, preferably wherein the reinforcing filler is selected from glass fibers, ceramic fibers, whiskers, polymer fibers, nanofibers or nano hollow fibers and blends thereof.

5. The composition of claim 1, wherein the thermoplastic polymer composition is crosslinked, preferably wherein the crosslinked thermoplastic polymer is crosslinked by electron beam.

6. A method for forming a thermally stable, flame resistant thermoplastic polymer composition comprising mixing a polymer with an additive, the additive comprising a ceramizable filler.

7. The method according to claim 6, wherein the polymer is selected from the group comprising thermoplastic polymers.

8. The method of claim 6, wherein the ceramizable filler comprises fumed silica and a metal hydroxide, preferably wherein the ceramizable filler comprises fumed silica, magnesium hydroxide, calcium hydroxide and aluminum hydroxide.

9. An object made from a thermally stable, fire-resistant thermoplastic polymer composition comprising a thermoplastic polymer and a ceramizable filler, wherein the object can withstand high temperatures or flames.

10. The article of claim 9, wherein the thermally stable, flame resistant thermoplastic polymer is cross-linked.

11. The object according to claim 9, wherein the ceramizable filler comprises fumed silica and a metal hydroxide, preferably wherein the ceramizable filler comprises fumed silica, magnesium hydroxide, calcium hydroxide and aluminum hydroxide.

12. The object of claim 9, wherein the thermoplastic polymer is a polyamide.

13. A battery casing made from a thermally stable, fire-resistant thermoplastic polymer composition comprising a polymer and a ceramizable filler. The battery housing according to claim 13 , wherein the polymer is selected from the group consisting of thermoplastic polymers.

15. The battery housing of claim 13, wherein the ceramizable filler comprises fumed silica and a metal hydroxide.

Images