The nanostructured fluoropolymer-containing regions will have a different nucleation behavior to initiate the bead foam depending on the interaction of the nanostructured fluoropolymer with the chemical or physical blowing agent. It is known, e.g., from literature that PTFE can absorb high amounts of supercritical CO₂. Furthermore, the different melt strength can be controlled with the fluoropolymer concentration and the aspect ratio of the nanostructured fluoropolymer. As described, this is relevant for the control of the expansion of the foam beads.

Use of a non-random distribution of the nanostructured fluoropolymer regions with a different melt strength may lead to a multimodal (e.g., bimodal) cell size distribution irrespective of the resin composition for a wide range of bead foaming processes. Various possible cell size distributions could be generated using this blending approach.

One aspect that is different in comparison to studies using conventional fillers such as multiwalled carbon nanotubes (MWCNT) is the much higher aspect ratio of the nanostructured fluoropolymer filler. For the MWCNT filler the choice of the pristine CNT and the surface modification to get a reasonable dispersion within a polymer matrix are the primary parameters for the aspect ratio in the foam end product, mainly to limit the break-down process of the CNTs. For the nanostructured fluoropolymer/PTFE different processing parameters affect the aspect ratio.

The nanostructured PTFE can also act as a nucleating agent for the bead foaming process of the polymer matrix. The effectiveness of PTFE has already been demonstrated in polycarbonate matrix materials in U.S. Pat. No. 5,314,925, the disclosure of which is incorporated herein by this reference in its entirety. The PTFE can also act as a nucleating agent for the crystallization of the polymer matrix. For many polymers, epitaxial growth of polymer crystals on the PTFE has been observed. For bead foam applications, this may lead to desirable anisotropic foam properties of the final product.

Aspects of the disclosure thus relate to method for forming foamed beads, including:

- saturating pellets with a blowing agent to form saturated pellets, the pellets including a matrix polymer component, and from 0.01 wt % to 2 wt %, based on the weight of the pellets, of a nanostructured fluoropolymer, a nanostructured fluoropolymer encapsulated by an encapsulating polymer, or a combination thereof; and
- depressurizing the saturated pellets in a pressure vessel to form the foamed beads.

In some aspects the step of saturating the pellets with a blowing agent includes applying, by the pressure vessel, at least one of heat and pressure to the pellets to form the saturated pellets. The step of depressurizing the saturated pellets in a pressure vessel to form the foamed beads includes depressurizing the saturated pellets and heat treating the saturated pellets in a hot liquid bath. During forming the foamed beads, the blowing agent induces nucleation and expansion in the saturated pellets to form the foamed beads.

Referring to FIG. 1, a schematic diagram of a bead foaming process 100 that includes stages 104, 108, 112, 116 and 120 of a bead foaming system is shown. In FIG. 1, a first stage 104 includes forming a homogeneous dispersion of pellets in a liquid (e.g., dispersion medium). During the first stage, a mixer 128 of a pressure vessel 124 may be activated to mix the pellets, the dispersion medium, and, optionally, one or more surfactants to form the homogeneous dispersion.

A second stage 108 includes gas dissolution of a blowing agent in the pellets at a temperature lower than a glass transition temperature (Tg) of the matrix polymer component for the two-step process or near (e.g., slightly above, such as 1 to 10 percent above) the glass transition temperature (Tg) of the matrix polymer component for the one-step process. During the second stage, the blowing agent is absorbed by the pellets and saturated pellets are formed. A third stage 112 includes releasing the pressure, via an exit valve 130, of the pressure vessel 124 and collecting the saturated pellets in a first container 132, such as a bead storage tank or collection tank. Depressurization of the saturated pellets causes partial nucleation and degasification, i.e., the blowing agent in the saturated pellets expands and a portion of the blowing agent desorbs from the saturated pellets.

A fourth stage 116 includes heat treating, at the first container 132, the saturated pellets for a period of time at a particular temperature to induce post foaming in the saturated pellets to form foamed beads. As illustrated in FIG. 1, the fourth stage includes subjecting the saturated pellets to a heated fluid (e.g., water, oil, or a mixture) bath to induce post depressurization foaming. Exemplary oils include, but are not limited to, silicone oil, sunflower oil, olive oil and combinations thereof. In other implementations, the saturated pellets are not heat treated and the saturated pellets are further foamed or expanded during part formation and bead sintering by a formation system. In some such implementations, the saturated pellets can be subjected to a cold fluid bath to quench the saturated pellets which reduces or stops foaming. The fluid used for the cold fluid bath may be the same fluid or a different fluid as the fluid of the heated fluid bath. Exemplary fluids for dispersion fluids and the fluids of the fourth stage 116 may have a relatively low evaporation energy. Such low evaporation energy includes evaporation energies of less than or equal to 500 kilojoules per kilogram (KJ/kg) and may reduce or limit formation of a dense, non-foamed layer on the surface of the expanded bead. A fifth stage 120 includes stabilization of the foamed beads by cooling. As illustrated in FIG. 1, the fifth stage includes cooling the foamed beads in a chilled or room temperature fluid bath (e.g., in the first container 132 or a second container 136) to stop further nucleation and cell growth. The operations of FIG. 1 described above can be implemented in a batch, semi-batch, or a continuous manner. Continuous methods are often more desirable since they may allow for better process control and enable production of nano-cellular foamed beads.

Referring to FIG. 2, an example of a system 200 for producing the extrudate and pellets formed therefrom is shown. System 200 is configured to use an extrusion process to form a polymer composition and to form extrudate from the polymer composition, as described herein. System 200 includes an extruder 210, an injector 214, and a die 218. Extruder 210 is coupled to injector 214 via one or more conduits 222, such as one or more tubes. Injector 214 is coupled to die 218 via one or more conduits 226, such as one or more tubes. System 200 may be controlled by a controller (not shown), such as a processor and/or blending controller.

Extruder 210 includes one or more hoppers, such as a first hopper 230 and a second hopper 232, and a barrel 234 coupled to the one or more hoppers. For example, barrel 234 may be coupled to a hopper via a feed throat 238. Each hopper 230, 232 is configured to receive material (e.g., pellets, granules, flakes, powders, and/or liquids) that is provided (e.g., gravity fed or force fed) from the hopper to barrel 234 via a corresponding feed throat 238. As shown, first hopper 230 has received a first material 240 and second hopper 232 has received a second material 242. First material 240 includes the matrix polymer component and nanostructured fluoropolymer, and second material 242 includes any additional component(s)/additive(s). In other aspects first material 240 includes the matrix polymer component, and second material 242 includes the nanostructured fluoropolymer and/or additional component(s)/additive(s). Although described as being provided to separate hoppers, in other implementations, first and second materials 240, 242 may be provided by the same hopper.

In some implementations, another material can be combined with first and second materials 240, 242 in the extruder 210. For example, the other material may be received by the extruder 210 via the one or more hoppers. The other material can include one or more additive such as those described herein. Each hopper 230, 232 provides its corresponding material 240, 242 into barrel 234 where the materials are combined to form a polymer composite 250 (e.g., a polymer composition or a blended composition). For example, the materials are gradually melted in barrel 234 by the mechanical energy (e.g., pressure) generated by turning screws, by heaters arranged along barrel 234, or both. The molten materials are mixed together (e.g., blended) to form polymer composite 250. Polymer composite 250 is provided from barrel 234 via conduit 222 to injector 214. Injector 214 injects polymer composite 250 into die 218 via conduit 226. Polymer composite 250 flows through the die 218 to form strands of extrudate (e.g., strands of polymer composite 250). The extruded polymer composite 250 can be cooled in a water bath, or by spraying the extrudate in a conduit 222 (e.g., a conveyor belt) as the extrudate moves from extruder 210 to a granulator via conduit 222. The granulator breaks the extrudate (e.g., the strands thereof) into pieces, such as pellets. The pellets of polymer composite 250 can then be used in a foaming process such as those described with reference to FIG. 1 and herein.

Further details relating to the methods of forming a foamed beads are provided in EP Application Serial No. 18214797.5, filed Dec. 20, 2018 and entitled “Micro, Sub-Micron, and/or Nano-Cellular Foams Based on Siloxane Containing (Co)polymers and Blends,” the disclosure of which is incorporated herein by this reference in its entirety.

Suitable blowing agents include, but are not limited to, low boiling halohydrocarbons and those that generate carbon dioxide: blowing agents that are solid at room temperature and when heated to temperatures higher than their decomposition temperature, generate gases such as nitrogen, carbon dioxide ammonia gas, such as azodicarbonamide, metal salts of azodicarbonamide, 4,4′ oxybis(benzenesulfonylhydrazide), sodium bicarbonate, ammonium carbonate, or the like, or combinations including at least one of the foregoing blowing agents. Blowing agents are generally used in amounts of 0.01 to 15 parts by weight, or about 0.01 to about 15 parts by weight, based on 100 parts by weight of the polymer portion of the composition.

In some aspects the matrix polymer component includes polybutylene terephthalate (PBT), polyetherimide (PEI), polyethylene terephthalate (PET), polycarbonate (PC), poly(p-phenylene oxide) (PPO), polystyrene (PS), polyphenylene sulfide (PPS), polypropylene (PP), polyamide (PA), linear low-density polyethylene (LLDPE), low-density polyethylene (LDPE), high density polyethylene (HDPE), polytrimethylene terephthalate (PTT), polyethylene naphthalate (PEN), polybutylene naphthalate (PBN), copolymers thereof, or a combination thereof.

In particular aspects the matrix polymer component includes PET, PEI, PPO, PS, PPS, PC, PP, PA, copolymers thereof, or a combination thereof. In specific aspects the matrix polymer component includes PET and PEI, including copolymers thereof. In further aspects the matrix polymer component includes PPO and PP, including copolymers thereof. In yet further aspects the matrix polymer component includes PPO and PA, including copolymers thereof. Exemplary polyamides include but are not limited to nylon, including any nylon blend (such as but not limited to nylon 6, nylon 6,6, nylon 6,12, nylon 11 and nylon 12).

In a specific aspect the foamed beads include from 1 wt % to 99 wt % PEI and from 1 wt % to 99 wt % PET. In further aspects the foamed beads include from 1 wt % to 20 wt % PEI and from 80 wt % to 99 wt % PET, or from 20 wt % to 80 wt % PEI and from 20 wt % to 80 wt % PET, or from 80 wt % to 99 wt % PEI and from 1 wt % to 20 wt % PET.

The foamed beads have in some aspects an average cell size of from 1 micron (μm) to 1000 μm, with the average cell size being determined according to conventional methods. In particular aspects the foamed polymer composition has an average cell size of from 5 to 800 μm, from 5 to 600 μm, from 5 to 400 μm, from 5 to 200 μm, or from 5 to 100 μm.

In certain aspects the fluoropolymer includes polytetrafluoroethylene, polyhexafluoropropylene, polyvinylidene fluoride, polychlorotrifluoroethylene, ethylene tetrafluoroethylene, fluorinated ethylene-propylene, polyvinyl fluoride, ethylene chlorotrifluoroethylene, or a combination thereof.

The encapsulating polymer includes in some aspects a styrene-acrylonitrile copolymer, an acrylonitrile-butadiene-styrene copolymer, alpha-alkyl-styrene-acrylonitrile copolymer, an alpha-methylstyrene-acrylonitrile copolymer, a styrene-butadiene rubber, or a combination thereof.

In a particular aspect the fluoropolymer includes polytetrafluoroethylene (PTFE). In further aspects the fluoropolymer encapsulated by an encapsulating polymer is styrene-acrylonitrile copolymer (SAN)-encapsulated PTFE, also known as TSAN.

As is known, fluoropolymers are available in a variety of forms, including powders, emulsions, dispersions, agglomerations, and the like. “Dispersion” (also called “emulsion”) fluoropolymers are generally manufactured by dispersion or emulsion, and generally include about 25 to 60 weight % fluoropolymer in water, stabilized with a surfactant, wherein the fluoropolymer particles are approximately 0.1 to 0.3 micrometers in diameter. “Fine powder” (or “coagulated dispersion”) fluoropolymers may be made by coagulation and drying of dispersion-manufactured fluoropolymers. Fine powder fluoropolymers are generally manufactured to have a particle size of approximately 400 to 500 microns. “Granular” fluoropolymers may be made by a suspension method, and are generally manufactured in two different particle size ranges, including a median particle size of approximately 30 to 40 micrometers, and a high bulk density product exhibiting a median particle size of about 400 to 500 micrometers. Pellets of fluoropolymer may also be obtained and cryogenically ground to exhibit the desired particle size.

In one aspect the fluoropolymer is at least partially encapsulated by an encapsulating polymer that may be the same or different as the matrix polymer (hereinafter referred to as an “encapsulated polymer”). Without being bound by theory, it is believed that encapsulation may aid in the distribution of the fluoropolymer within the matrix, and/or compatibilize the fluoropolymer with the matrix.

Suitable encapsulating polymers accordingly include, but are not limited to, vinyl polymers, acrylic polymers, polyacrylonitrile, polystyrenes, polyolefins, polyesters, polyurethanes, polyamides, polysulfones, polyimides, polyetherimides, polyphenylene ethers, polyphenylene sulfides, polyether ketones, polyether ether ketones, ABS resins, polyethersulfones, poly(alkenylaromatic) polymers, polybutadiene, liquid crystalline polymers, polyacetals, polycarbonates, polyphenylene ethers, ethylene-vinyl acetate copolymers, polyvinyl acetate, liquid crystal polymers, ethylene-tetrafluoroethylene copolymer, aromatic polyesters, polyvinyl fluoride, polyvinylidene fluoride, polyvinylidene chloride, and combinations including at least one of the foregoing polymers.

Particularly preferred encapsulating polymers include a styrene-acrylonitrile copolymer, an acrylonitrile-butadiene-styrene copolymer, alpha-alkyl-styrene-acrylonitrile copolymer, an alpha-methylstyrene-acrylonitrile copolymer, a styrene-butadiene rubber, or a combination thereof. Styrene-acrylonitrile copolymer encapsulated polytetrafluoroethylene is one preferred aspect.

The encapsulating polymers may be obtained by polymerization of monomers or mixtures of monomers by methods known in the art, for example, condensation, addition polymerization, and the like. Emulsion polymerization, particularly radical polymerization may be used effectively. In one aspect, the encapsulating polymer is formed from monovinylaromatic monomers containing condensed aromatic ring structures, such as vinyl naphthalene, vinyl anthracene and the like. Examples of suitable monovinylaromatic monomers include styrene, 3-methylstyrene, 3,5-diethylstyrene, 4-n-propylstyrene, alpha-methylstyrene, alpha-methyl vinyltoluene, alpha-chlorostyrene, alpha-bromostyrene, dichlorostyrene, dibromostyrene, tetra-chlorostyrene, and the like, and combinations including at least one of the foregoing compounds. Styrene and/or alpha-methylstyrene may be specifically mentioned.

Other useful monomers for the formation of the encapsulating polymer include monovinylic monomers such as itaconic acid, acrylamide, N-substituted acrylamide or methacrylamide, maleic anhydride, maleimide, N-alkyl-, aryl-, or haloaryl-substituted maleimide, and glycidyl (meth)acrylates. Other examples include acrylonitrile, ethacrylonitrile, methacrylonitrile, alpha-chloroacrylonitrile, beta-chloroacrylonitrile, alpha-bromoacrylonitrile, acrylic acid, methyl (meth)acrylate, ethyl (meth)acrylate, n-butyl (meth)acrylate, t-butyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, and the like, and combinations including at least one of the foregoing monomers.

Mixtures of the foregoing monovinylaromatic monomers and monovinylic monomers may also be used, for example mixtures of styrene and acrylonitrile (SAN). The relative ratio of monovinylaromatic and monovinylic monomers in the rigid graft phase may vary widely depending on the type of fluoropolymer, type of monovinylaromatic and monovinylic monomer(s), and the desired properties of the encapsulant. The encapsulant may generally be formed from up to 100 wt %, or up to about 100 wt %, of monovinyl aromatic monomer, specifically 30 to 100 wt %, or about 30 to about 100 wt %, more specifically, 50 to 90 wt %, or about 50 to about 90 wt % monovinylaromatic monomer, with the balance being comonomer(s). A preferred fluoropolymer is TSAN, which includes SAN and PTFE. See, U.S. Pat. Nos. 5,804,654 and 6,040,370, the disclosures of which are incorporated herein by this reference in their entireties.

Elastomers may also be used as the encapsulating polymer, as well as elastomer-modified graft copolymers. Suitable elastomers include, for example, conjugated diene rubbers: copolymers of a conjugated diene with less than about 50 wt % of a copolymerizable monomer: olefin rubbers such as ethylene propylene copolymers (EPR) or ethylene-propylene-diene monomer rubbers (EPDM): ethylene-vinyl acetate rubbers: silicone rubbers: elastomeric C1-8 alkyl (meth)acrylates: elastomeric copolymers of C1-8 alkyl (meth)acrylates with butadiene and/or styrene: or combinations including at least one of the foregoing elastomers.

Examples of conjugated diene monomers that may be used are butadiene, isoprene, 1,3-heptadiene, methyl-1,3-pentadiene, 2,3-dimethyl-1,3-butadiene, 2-ethyl-1,3-pentadiene: 1,3-and 2,4-hexadienes, and the like, as well as mixtures including at least one of the foregoing conjugated diene monomers. Specific conjugated diene homopolymers include polybutadiene and polyisoprene.

Copolymers of a conjugated diene rubbers may also be used, for example those produced by aqueous radical emulsion polymerization of a conjugated diene and up to 10 wt %, or up to about 10 wt %, of one or more monomers copolymerizable therewith Specific copolymers include styrene and acrylonitrile.

(Meth)acrylate monomers suitable for use as an elastomeric encapsulating monomer include the cross-linked, particulate emulsion homopolymers or copolymers of C4-8 alkyl (meth)acrylates, in particular C4-6 alkyl acrylates, for example n-butyl acrylate, t-butyl acrylate, n-propyl acrylate, isopropyl acrylate, 2-ethylhexyl acrylate, and the like, and combinations including at least one of the foregoing monomers. Exemplary comonomers include but are not limited to butadiene, isoprene, styrene, methyl methacrylate, phenyl methacrylate, phenethylmethacrylate, N-cyclohexylacrylamide, vinyl methyl ether or acrylonitrile, and mixtures including at least one of the foregoing comonomomers. Optionally, up to 5 wt % a polyfunctional crosslinking comonomer may be present, for example divinylbenzene, alkylenediol di(meth)acrylates such as glycol bisacrylate, alkylenetriol tri(meth)acrylates, polyester di(meth)acrylates, bisacrylamides, triallyl cyanurate, triallyl isocyanurate, allyl(meth)acrylate, diallyl maleate, diallyl fumarate, diallyl adipate, triallyl esters of citric acid, triallyl esters of phosphoric acid, and the like, as well as combinations including at least one of the foregoing crosslinking agents.

Suitable elastomer-modified graft copolymers may be prepared by first providing an elastomeric polymer (for example, as described above), then polymerizing the constituent monomer(s) of the rigid phase in the presence of the fluoropolymer and the elastomer to obtain the graft copolymer. The elastomeric phase may provide 5 to 95 wt %, or about 5 to about 95 wt %, of the total graft copolymer, more specifically, 20 to 90 wt %, about 20 to about 90 wt %, and even more specifically, 40 to 85 wt %, or about 40 to about 85 wt % of the elastomer-modified graft copolymer, the remainder being the rigid graft phase. Depending on the amount of elastomer-modified polymer present, a separate matrix or continuous phase of ungrafted rigid polymer or copolymer may be simultaneously obtained along with the elastomer-modified graft copolymer.

Specific encapsulating polymers include polystyrene, copolymers of polystyrene, poly(alpha-methylstyrene), poly(alpha-ethylstyrene), poly(alpha-propylstyrene), poly(alpha-butylstyrene), poly(p-methylstyrene), polyacrylonitrile, polymethacrylonitrile, poly(methyl acrylate), poly(ethyl acrylate), poly(propyl acrylate), and poly(butyl acrylate), poly(methyl methacrylate), poly(ethyl methacrylate), poly(propyl methacrylate), poly(butyl methacrylate): polybutadiene, copolymers of polybutadiene with propylene, poly(vinyl acetate), poly(vinyl chloride), poly(vinylidene chloride), poly(vinylidene fluoride), poly(vinyl alcohols), acrylonitrile-butadiene copolymer rubber, acrylonitrile-butadiene-styrene (ABS), poly(C4-8 alkyl acrylate) rubbers, styrene-butadiene rubbers (SBR), EPDM rubbers, silicon rubber and combinations including at least one of the foregoing encapsulating polymers.

In another aspect, the encapsulating polymer includes SAN, ABS copolymers, alpha-(C1-3)alkyl-styrene-acrylonitrile copolymers, alpha-methylstyrene-acrylonitrile (AMSAN) copolymers, SBR, and combinations including at least one of the foregoing. In yet another aspect the encapsulating polymer is SAN or AMSAN.

Suitable amounts amount of encapsulating polymer may be determined by one of ordinary skill in the art without undue experimentation, using the guidance provided below. In one aspect, the encapsulated fluoropolymer includes 10 to 90 weight percent (wt %), or about 10 to about 90 wt % fluoropolymer and 90 to 10 wt %, or about 90 to about 10 wt %, of the encapsulating polymer, based on the total weight of the encapsulated fluoropolymer. Alternatively, the encapsulated fluoropolymer includes 20 to 80 wt %, or about 20 to about 80 wt %, more specifically, 40 to 60 wt %, or about 40 to about 60 wt % fluoropolymer, and 80 to 20 wt %, or about 80 to about 20 wt %, specifically, 60 to 40 wt %, or about 60 to about 40 wt % encapsulating polymer, based on the total weight of the encapsulated polymer.

As described herein, the fluoropolymer is nanostructured. As used herein, the term “nanostructure” refers to a material in which one dimension of the material is equal to or less than 1000 nm (e.g., one dimension is 1 to 1000 nm in size). In a particular aspect, the nanostructure includes at least two dimensions that are equal to or less than 1000 nm (e.g., a first dimension is 1 to 1000 nm in size and a second dimension is 1 to 1000 nm in size). In another aspect, the nanostructure includes three dimensions that are equal to or less than 1000 nm (e.g., a first dimension is 1 to 1000 nm in size, a second dimension is 1 to 1000 nm in size, and a third dimension is 1 to 1000 nm in size). The shape of the nanostructure can be of a wire, a particle (e.g., having a substantially spherical shape), a rod, a tetrapod, a hyper-branched structure, a tube, a cube, or mixtures thereof. The nanostructures can be monodisperse, where all particles are of the same size with little variation, or polydisperse, where the particles have a range of sizes and are averaged.

The nanostructured fluoropolymer can be prepared in a masterbatch, for example, during extrusion of a polymer, a filler, or both simultaneously. Methods for the preparation of the nanostructured fluoropolymer are described on WO 2018/122747, the disclosure of which is incorporated herein by this reference in its entirety. Thus in some aspects the fluoropolymer is fibrillated. “Fibrillation” is a term of art that refers to the treatment of fluoropolymers so as to produce, for example, a “node and fibril,” network, or cage-like structure. In one aspect, the fluoropolymer includes fibrils having an average diameter of 5 nanometers (nm) to 2 micrometers (μπι), or from about 5 nm to about 2μπ ι. The fluoropolymer may also have an average fibril diameter of 30 nanometers to 750 nanometers, more specifically 5 nanometers to 500 nanometers. In a further example, the fluoropolymer may also have an average fibril diameter of about 30 nanometers to about 750 nanometers, more specifically about 5 nanometers to about 500 nanometers. Field Emission Scanning Electron Microscopy can be employed to observe the extent of fibrillation of the fluoropolymer throughout the matrix polymer in the fibrillated compositions.

In some aspects the foamed beads include from 0.01 wt % to less than 0.1 wt %, based on the weight of the pellets, of the nanostructured fluoropolymer, the nanostructured fluoropolymer encapsulated by an encapsulating polymer, or the combination thereof. In further aspects the nanostructured fluoropolymer, the nanostructured fluoropolymer encapsulated by an encapsulating polymer, or the combination thereof are present in the foamed beads in an amount of from 0.01 wt % to 0.5 wt %, or from 0.01 wt % to 0.09 wt %, or from 0.03 wt % to 0.10 wt %, or from 0.03 wt % to 0.09 wt %, or from 0.05 wt % to 0.10 wt %, or from 0.05 wt % to 0.09 wt %.

The foamed beads may further include in some aspects at least one additional additive including a reinforcing filler, acid scavenger, anti-drip agent, antioxidant, antistatic agent, chain extender, colorant, de-molding agent, flow promoter, lubricant, mold release agent, plasticizer, quenching agent, flame retardant, UV reflecting additive, and combinations thereof. The at least one additional additive may be included in the foamed beads in any amount that will not significantly adversely affect the desired properties of the foamed beads.

In a particular aspect the at least one additional additive is a flame retardant. Suitable flame retardant that may be added may be organic compounds that include phosphorus, bromine, and/or chlorine. Non-brominated and non-chlorinated phosphorus-containing flame retardants may be preferred in certain applications for regulatory reasons, for example organic phosphates and organic compounds containing phosphorus-nitrogen bonds.

One type of exemplary organic phosphate is an aromatic phosphate of the formula (GO)₃P-O, wherein each G is independently an alkyl, cycloalkyl, aryl, alkaryl, or aralkyl group, provided that at least one G is an aromatic group. Two of the G groups may be joined together to provide a cyclic group, for example, diphenyl pentaerythritol diphosphate, which is described by Axelrod in U.S. Pat. No. 4,154,775. Other suitable aromatic phosphates may be, for example, phenyl bis(dodecyl) phosphate, phenyl bis(neopentyl) phosphate, phenyl bis(3,5,5′-trimethylhexyl) phosphate, ethyl diphenyl phosphate, 2-ethylhexyl di(p-tolyl) phosphate, bis(2-ethylhexyl) p-tolyl phosphate, tritolyl phosphate, bis(2-ethylhexyl) phenyl phosphate, tri (nonylphenyl) phosphate, bis(dodecyl) p-tolyl phosphate, dibutyl phenyl phosphate, 2-chloroethyl diphenyl phosphate, p-tolyl bis(2,5,5′-trimethylhexyl) phosphate, 2-ethylhexyl diphenyl phosphate, or the like. A specific aromatic phosphate is one in which each G is aromatic, for example, triphenyl phosphate, tricresyl phosphate, isopropylated triphenyl phosphate, and the like. Thus, in particular aspects the retardant is a phosphorous-based flame retardant.

Articles Including the Foamed Beads

Aspects of the disclosure further relate to articles including the foamed beads described herein. Exemplary articles include, but are not limited to, film, tape, breads, strands, sheets, tubes and rods. The article may have any cross section, including but not limited to circular, square, polygonal and annular.

In particular aspects the article is a component of an aircraft, including but not limited to an interior or an exterior component of an aircraft. Examples of aircraft include, but are not limited to, jets, small aircraft, helicopters and spacecraft. Example interior components include, but are not limited to, foldout trays on the rear of a passenger aircraft seat, seat filling, intermediate wall filling, and interior doors. Example exterior components include, but are not limited to, filling for the outer skin of the aircraft, the aircraft nose, the wings, the outer doors, rudders and rotor blades.

Various combinations of elements of this disclosure are encompassed by this disclosure, e.g., combinations of elements from dependent claims that depend upon the same independent claim.

ASPECTS OF THE DISCLOSURE

In various aspects, the present disclosure pertains to and includes at least the following aspects.

Aspect 1. A method for forming a polymer bead foam, comprising, consisting of, or consisting essentially of:

- saturating pellets with a blowing agent to form saturated pellets, the pellets comprising
  - a matrix polymer component, and
  - from 0.01 wt % to 2 wt %, based on the weight of the pellets, of a nanostructured fluoropolymer, a nanostructured fluoropolymer encapsulated by an encapsulating polymer, or a combination thereof; and
- forming foamed beads from the saturated pellets by combining, in a pressure vessel, the pellets and the blowing agent.

Aspect 2. The method according to Aspect 1, wherein saturating the pellets with a blowing agent comprises applying, by the pressure vessel, at least one of heat and pressure to the mixture to form the saturated pellets, and

- wherein forming the foamed beads comprises depressurizing the saturated pellets and heat treating the saturated pellets in a hot liquid bath, wherein, during forming the foamed beads, the blowing agent induces nucleation and expansion in the saturated pellets to form the foamed beads.

Aspect 3. The method according to Aspect 1 or 2, wherein the matrix polymer component comprises polybutylene terephthalate (PBT), polyetherimide (PEI), polyethylene terephthalate (PET), polycarbonate (PC), poly(p-phenylene oxide) (PPO), polystyrene (PS), polyphenylene sulfide (PPS), polypropylene (PP), polyamide (PA), linear low-density polyethylene (LLDPE), low-density polyethylene (LDPE), high density polyethylene (HDPE), polytrimethylene terephthalate (PTT), polyethylene naphthalate (PEN), polybutylene naphthalate (PBN), copolymers thereof, or a combination thereof.

Aspect 4. The method according to any of Aspects 1 to 3, wherein the matrix polymer component comprises PET, PEI, PPO, PS, PPS, PC, PP, PA, copolymers thereof, or a combination thereof.

Aspect 5. The method according to any of Aspects 1 to 4, wherein the foamed composition has an average cell size of from 1 micron (μm) to 1000 μm.

Aspect 6. The method according to any of Aspects 1 to 5, wherein the matrix polymer component comprises from 1 wt % to 99 wt % PEI and from 1 wt % to 99 wt % PET.

Aspect 7. The method according to any of Aspects 1 to 6, wherein the fluoropolymer comprises polytetrafluoroethylene, polyhexafluoropropylene, polyvinylidene fluoride, polychlorotrifluoroethylene, ethylene tetrafluoroethylene, fluorinated ethylene-propylene, polyvinyl fluoride, ethylene chlorotrifluoroethylene, or a combination thereof.

Aspect 8. The method according to any of Aspects 1 to 7, wherein the encapsulating polymer comprises a styrene-acrylonitrile copolymer, an acrylonitrile-butadiene-styrene copolymer, alpha-alkyl-styrene-acrylonitrile copolymer, an alpha-methylstyrene-acrylonitrile copolymer, a styrene-butadiene rubber, or a combination thereof.

Aspect 9. The method according to any of Aspects 1 to 8, wherein the fluoropolymer comprises polytetrafluoroethylene.

Aspect 10. The method according to any of Aspects 1 to 9, wherein the fluoropolymer encapsulated by an encapsulating polymer is styrene-acrylonitrile copolymer encapsulated polytetrafluoroethylene.

Aspect 11. The method according to any of Aspects 1 to 10, comprising from 0.01 wt % to less than 0.1 wt %, based on the weight of the pellets, of the nanostructured fluoropolymer, the nanostructured fluoropolymer encapsulated by an encapsulating polymer, or the combination thereof.

Aspect 12. The method according to any of Aspects 1 to 11, wherein the composition further comprises at least one additional additive comprising a reinforcing filler, acid scavenger, anti-drip agent, antioxidant, antistatic agent, chain extender, colorant, de-molding agent, flow promoter, lubricant, mold release agent, plasticizer, quenching agent, flame retardant, UV reflecting additive, and combinations thereof.

Aspect 13. The method according to Aspect 12, wherein the at least one additional additive comprises a flame retardant, and the flame retardant is a phosphorous-based flame retardant.

Aspect 14. An article comprising the polymer bead foam formed according to the method of any of Aspects 1 to 13.

Aspect 15. The article according to Aspect 14, wherein the article is a component of an aircraft, including but not limited to an interior component or an exterior component of an aircraft.

Aspect 16. A method for forming foamed beads, comprising, consisting of, or consisting essentially of:

- saturating pellets with a blowing agent to form saturated pellets, the pellets comprising
  - a matrix polymer component, and
  - from 0.01 wt % to 2 wt %, based on the weight of the pellets, of a nanostructured fluoropolymer, a nanostructured fluoropolymer encapsulated by an encapsulating polymer, or a combination thereof; and depressurizing the saturated pellets in a pressure vessel to form the foamed beads.

Aspect 17. The method according to Aspect 16, wherein saturating the pellets with a blowing agent comprises applying, by the pressure vessel, at least one of heat and pressure to the pellets to form the saturated pellets, and

- wherein depressurizing the saturated pellets in a pressure vessel to form the foamed beads comprises depressurizing the saturated pellets and heat treating the saturated pellets in a hot liquid bath, wherein, during forming the foamed beads, the blowing agent induces nucleation and expansion in the saturated pellets to form the foamed beads.

Aspect 18. The method according to Aspect 16 or 17, wherein the matrix polymer component comprises polybutylene terephthalate (PBT), polyetherimide (PEI), polyethylene terephthalate (PET), polycarbonate (PC), poly(p-phenylene oxide) (PPO), polystyrene (PS), polyphenylene sulfide (PPS), polypropylene (PP), polyamide (PA), linear low-density polyethylene (LLDPE), low-density polyethylene (LDPE), high density polyethylene (HDPE), polytrimethylene terephthalate (PTT), polyethylene naphthalate (PEN), polybutylene naphthalate (PBN), copolymers thereof, or a combination thereof.

Aspect 19. The method according to Aspect 16 or 17, wherein the matrix polymer component comprises polybutylene terephthalate (PBT), polyetherimide (PEI), polyethylene terephthalate (PET), polycarbonate (PC), poly(p-phenylene oxide) (PPO), polystyrene (PS), polyphenylene sulfide (PPS), polypropylene (PP), polyamide (PA), polytrimethylene terephthalate (PTT), polyethylene naphthalate (PEN), polybutylene naphthalate (PBN), copolymers thereof, or a combination thereof.

Aspect 20. The method according to any of Aspects 16 to 19, wherein the matrix polymer component comprises PET, PEI, PPO, PS, PPS, PC, PP, PA, copolymers thereof, or a combination thereof.

Aspect 21. The method according to any of Aspects 16 to 19, wherein the matrix polymer component comprises PET, PEI, PPO, PS, PPS, PC, PA, copolymers thereof, or a combination thereof.

Aspect 22. The method according to any of Aspects 16 to 21, wherein the foamed beads have an average cell size of from 1 micron (μm) to 1000 μm.

Aspect 23. The method according to any of Aspects 16 to 22, wherein the matrix polymer component comprises from 1 wt % to 99 wt % PEI and from 1 wt % to 99 wt % PET.

Aspect 24. The method according to any of Aspects 16 to 23, wherein the fluoropolymer comprises polytetrafluoroethylene, polyhexafluoropropylene, polyvinylidene fluoride, polychlorotrifluoroethylene, ethylene tetrafluoroethylene, fluorinated ethylene-propylene, polyvinyl fluoride, ethylene chlorotrifluoroethylene, or a combination thereof.

Aspect 25. The method according to any of Aspects 16 to 24, wherein the encapsulating polymer comprises a styrene-acrylonitrile copolymer, an acrylonitrile-butadiene-styrene copolymer, alpha-alkyl-styrene-acrylonitrile copolymer, an alpha-methylstyrene-acrylonitrile copolymer, a styrene-butadiene rubber, or a combination thereof.

Aspect 26. The method according to any of Aspects 16 to 25, wherein the fluoropolymer comprises polytetrafluoroethylene.

Aspect 27. The method according to any of Aspects 16 to 26, wherein the fluoropolymer encapsulated by an encapsulating polymer is styrene-acrylonitrile copolymer encapsulated polytetrafluoroethylene.

Aspect 28. The method according to any of Aspects 16 to 27, comprising from 0.01 wt % to less than 0.1 wt %, based on the weight of the pellets, of the nanostructured fluoropolymer, the nanostructured fluoropolymer encapsulated by an encapsulating polymer, or the combination thereof.

Aspect 29. The method according to any of Aspects 16 to 28, wherein foamed beads further comprise at least one additional additive comprising a reinforcing filler, acid scavenger, anti-drip agent, antioxidant, antistatic agent, chain extender, colorant, de-molding agent, flow promoter, lubricant, mold release agent, plasticizer, quenching agent, flame retardant, UV reflecting additive, and combinations thereof.

Aspect 30. The method according to any of Aspects 16 to 29, wherein the nanostructured fluoropolymer is fibrillated.

Aspect 31. An article comprising the foamed beads formed according to the method of any of Aspects 16 to 30, wherein the article is a component of an aircraft.

EXAMPLES

The following examples are put forth so as to provide those of ordinary skill in the art with a complete disclosure and description of how the compounds, compositions, articles, devices and/or methods claimed herein are made and evaluated, and are intended to be purely exemplary and are not intended to limit the disclosure. Efforts have been made to ensure accuracy with respect to numbers (e.g., amounts, temperature, etc.), but some errors and deviations should be accounted for. Unless indicated otherwise, parts are parts by weight, temperature is in ° C. or is at ambient temperature, and pressure is at or near atmospheric. Unless indicated otherwise, percentages referring to composition are in terms of wt %.

There are numerous variations and combinations of reaction conditions, e.g., component concentrations, desired solvents, solvent mixtures, temperatures, pressures and other reaction ranges and conditions that can be used to optimize the product purity and yield obtained from the described process. Only reasonable and routine experimentation will be required to optimize such process conditions.

Several polymer base compositions including various matrix polymer components and SAN/PTFE were injection molded according to conventional methods. The base compositions are set forth in Table 1:

TABLE 1

SAN/PTFE Base Compositions

1
2
3
4
5
6

PBT 315 (SABIC),
wt %
49.94
48.94
39.94

Mw 100000

g/mol, PS standard

PBT 195 (SABIC),
wt %
50
50
50

Mw 60000

g/mol, PS standard

PP 595A (SABIC)
wt %

90

MFI 47 at

230° C. and 2.16 kg

Ramapet ® N180
wt %

94

PET (0.8 IV)

(Indorama Ventures PLC)

TSAN (SABIC)
wt %

1
10
10
6

Irganox 1010 (BASF)
wt %
0.06
0.06
0.06

0.06
0.06

% PTFE

0
0.5
5
5
3
0

IV = Intrinsic Viscosity, MFI = Melt Flow Index

Compositions 1 and 6 did not include SAN/PTFE and are considered comparative compositions. The SAN/PTFE was an encapsulated nanostructured fluoropolymer (n-structured TSAN) masterbatch in either PBT or PP (depending on the respective base composition), manufactured as described in WO2018122747, the disclosure of which is incorporated by this reference in its entirety.

The base compositions were extruded using the barrel temperatures set forth in Table 2:

TABLE 2

Barrel Temperatures for Extruding the Base Compositions

PP
70/100/150/200/240/240/240/240/240/240/240/240° C.

PBT
70/150/200/250/280/280/280/280/280/280/280/280° C.

While the following examples relate to foam compositions formed from conventional core-back and extrusion foaming methods, these compositions could also be formed as bead foams according to the methods described herein. The resulting analysis is expected to be the same.

The base compositions were foamed with nitrogen gas using a conventional core-back injection molding process. Various PP foamed samples were formed from pellets of base composition 4 according to specifications set forth in Table 3:

TABLE 3

Foamed PP Samples

Sample
TSAN Content
Form of

No.
(wt %)
Sample

C3.1
0
Solid (no foam)

C3.2
0
Foamed

C3.3
0
Foamed

C3.4
1
Solid (no foam)

Ex.3.1
1
Foamed

Ex3.2
1
Foamed

Ex3.3
1
Foamed

Ex3.4
1
Foamed

C3.5
2
Solid (no foam)

Ex3.5
2
Foamed

Ex3.6
2
Foamed

Ex3.7
2
Foamed

Ex3.8
2
Foamed

Photographs of several of the samples are shown in FIGS. 3A-3E. FIG. 3B showing foamed sample Ex3.4 with 1 wt % TSAN exhibits some aggregated PTFE domains. From the samples the following observations were made:

- The neat PP foamed samples (C3.2 and C3.3) exhibited an inhomogeneous foam structure in both the thickness direction and in the foam direction.
- PP can be foamed by including up to 2 wt % TSAN.
- Addition of TSAN results in a much more homogeneous cell size distribution in the foamed core.
- The amount of TSAN in the samples can be substantially reduced as compared to previously known compositions.

The tensile modulus and strength of the samples were determined according to ISO 527. Results are illustrated in FIGS. 4 and 5. From the graphs it is observed that the foamed samples including TSAN do not suffer from a significant loss in modulus and strength as compared to the solid samples.

Various PBT foamed samples were formed from pellets of base compositions 2 and 3 according to specifications set forth in Table 3:

TABLE 4

Foamed PBT Samples

Sample
TSAN Content
Form of

No.
(wt %)
Sample

C4.1
0
Solid (no foam)

C4.2
0
Foamed

C4.3
0
Foamed

C4.4
1
Solid (no foam)

Ex.4.1
1
Foamed

Ex4.2
1
Foamed

Ex4.3
1
Foamed

Ex4.4
1
Foamed

Photographs of several of the samples are shown in FIGS. 6A-6D. FIG. 6C showing foamed sample C4.3 (no TSAN) demonstrates a large gradient in cell sizes. From the samples the following observations were made:

- PBT can be foamed by including up to 1 wt % TSAN.
- The melt temperature profile was more sensitive for PBT than for PP and the processing window was smaller.
- A strong flow-induced crystallization effect was observed, which may consequences (either positive or negative) for thin parts or thin runner sections.

Cross-sectional scanning electron microscopy (SEM) images of PP foamed samples are shown in FIGS. 7A (Sample C3.3) and 7B (Sample Ex3.2). The images show that the foamed sample that does not include TSAN (FIG. 7A) includes an inhomogeneous foam structure in both the thickness direction and in the flow direction, while the sample including TSAN (FIG. 7B) had a homogeneous cell size distribution throughout the foamed core.

Additional foamed PP samples were formed from a 3 wt % TSAN masterbatch composition. The PP was PP 525P from SABIC, which has a MFI of 3. The samples were foamed using isobutane with an annular die. 2, 4, 8 and 16 wt % of the masterbatch composition was combined with neat PP to form the foamed samples (i.e., the final TSAN content of the foamed samples was 0.06 wt %, 0.12 wt %, 0.24 wt % and 0.48 wt %, respectively), and the density of the foamed samples was determined. The final PTFE content of the foamed samples was 0.03 wt %, 0.06 wt %, 0.12 wt % and 0.24 wt %, respectively. In addition, comparative foam samples including neat PP foam (100% 525P) and blends of PP with a high melt strength PP (Daploy™ WB140HMS) were formed. The density of all samples as a function of temperature is shown in FIG. 8. From the graph it is observed that by adding TSAN to the PP density is minimized and the processing window increases.

Open cell content of the samples as a function of temperature is shown in FIG. 9. As observed, the PP/TSAN foamed samples had substantially no open cell content over a wide temperature range.

Images of PET foams formed according to aspects of the disclosure are shown in FIGS. 10A and 10B. The images are cross sections of PET including 0.045 wt % SAN/PTFE. The images illustrate the closed cell content of the samples.

Foam compositions including a blend of matrix polymer component were formed as shown in Table 5:

TABLE 5

Polymer Blend Compositions

Compositions

C5.1
Ex5.1
C5.2
Ex5.2
Ex5.3
Ex5.4
C5.3

Ramapet ® N180 PET
wt %

80
40
60

(0.8 IV) (Indorama

Ventures PLC)

PPC (SABIC)
wt %
20
80

3% TSAN/PTFE in
wt %

40
40
100

Ramapet ® N180

6% TSAN/PTFE in
wt %
80
20

100

Ramapet ® N180

Ultem 1010 (SABIC)
wt %

20
20

% PTFE

2.4
0.6
0
0.6
0.6
1.5
3.0

Properties

HDT ISO 75Af

132

84
83
71
70
73

Vicat B120 (° C.)

165

96
96
147
140
164

Tensile Modulus (Mpa)

2425

2667
2729
2708
2852
3037

Yield Stress (Mpa)

69.9

70.2
70.0
63.5

Yield Strain (%)

6.6

4.5
4.4
4

Elongation (%)

74

199
76
57
0.9
0.5

Tg 1 (° C.)

85.8
85.8
92.1
92.7

78.8
78.1

Tg 2 (° C.)

162.0
141.2

The PPC was a polyphthalatecarbonate (50:50 molar ratio of isophthalate ester to terephthalate ester). LEXAN™ 4501 with a MFR at 300° C./5 kg of 10 g/10 min (measured in accordance with ISO 1133).

Polyetherimide foam compositions were formed according to Table 6:

TABLE 6

PEI (ULTEMTM) Compositions

Composition

C6
Ex6.1
Ex6.2

UltemTM 2000-1000
wt %
80
80
80

3% nanostructured TSAN in
wt %

1.5
3

Ramapet ® N180

Ramapet ® N180 PET (0.8 IV)
wt %
19.5
18.5
17

Talc
wt %
0.5

% PTFE

0
0.0225
0.045

MVR (300° C./5 kg)

5.3
5.3
5.4

Tg (° C.)

174
171
171

The compositions of Table 6 were formed according to the conditions of Table 7:

TABLE 7

Extrusion conditions

Throat
80% Ultem
15% PET

Side feeder
5% TSAN MB
(1.25 kg)

% PTFE
0.075 fed at the

300° C. zone

Barrel settings (° C.): 60-270-340-320-

310-300-300-300-300-300

Torque: 71-78%

Output: 15 kg/h

Additional blended compositions including PET (Ramapet® N180) and PEI (Ultem™) were formed and tested as set forth in Table 8 below:

TABLE 8

PET/PEI Blends

C8.1
Ex8.1
Ex8.2
Ex8.3
Ex8.4
C8.2
Ex8.5
Ex8.6

Throat:

Ramapet ® N180
wt %
40
40
40
40
40
10
10
10

Ground Ramapet ®
wt %

9.35
9.85
9.85

N180

Ground Ultem ™
wt %
20
20
20
20
20
20
20
20

1010 (SABIC)

Irganox 1010
wt %

0.15
0.15
0.15

(BASF)

Exolit ® OP1240
wt %

15
15
15

(Clariant)

Melapur ® 200-70
wt %

5
5
5

(BASF)

TSAN (SABIC)
wt %

0.5

Side Feeder: