Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B32—LAYERED PRODUCTS
  • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
  • B32B7/00—Layered products characterised by the relation between layers; Layered products characterised by the relative orientation of features between layers, or by the relative values of a measurable parameter between layers, i.e. products comprising layers having different physical, chemical or physicochemical properties; Layered products characterised by the interconnection of layers
  • B32B7/02—Physical, chemical or physicochemical properties
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
  • B29C44/00—Shaping by internal pressure generated in the material, e.g. swelling or foaming ; Producing porous or cellular expanded plastics articles
  • B29C44/02—Shaping by internal pressure generated in the material, e.g. swelling or foaming ; Producing porous or cellular expanded plastics articles for articles of definite length, i.e. discrete articles
  • B29C44/04—Shaping by internal pressure generated in the material, e.g. swelling or foaming ; Producing porous or cellular expanded plastics articles for articles of definite length, i.e. discrete articles consisting of at least two parts of chemically or physically different materials, e.g. having different densities
  • B29C44/06—Making multilayered articles
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  • B32B1/00—Layered products having a non-planar shape
  • B32B1/08—Tubular products
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B32—LAYERED PRODUCTS
  • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
  • B32B25/00—Layered products comprising a layer of natural or synthetic rubber
  • B32B25/04—Layered products comprising a layer of natural or synthetic rubber comprising rubber as the main or only constituent of a layer, which is next to another layer of the same or of a different material
  • B32B25/045—Layered products comprising a layer of natural or synthetic rubber comprising rubber as the main or only constituent of a layer, which is next to another layer of the same or of a different material of foam
• • B—PERFORMING OPERATIONS; TRANSPORTING
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  • B32B25/00—Layered products comprising a layer of natural or synthetic rubber
  • B32B25/14—Layered products comprising a layer of natural or synthetic rubber comprising synthetic rubber copolymers
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B32—LAYERED PRODUCTS
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  • B32B27/00—Layered products comprising a layer of synthetic resin
  • B32B27/06—Layered products comprising a layer of synthetic resin as the main or only constituent of a layer, which is next to another layer of the same or of a different material
  • B32B27/065—Layered products comprising a layer of synthetic resin as the main or only constituent of a layer, which is next to another layer of the same or of a different material of foam
• • B—PERFORMING OPERATIONS; TRANSPORTING
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  • B32B27/00—Layered products comprising a layer of synthetic resin
  • B32B27/06—Layered products comprising a layer of synthetic resin as the main or only constituent of a layer, which is next to another layer of the same or of a different material
  • B32B27/08—Layered products comprising a layer of synthetic resin as the main or only constituent of a layer, which is next to another layer of the same or of a different material of synthetic resin
• • B—PERFORMING OPERATIONS; TRANSPORTING
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  • B32B27/00—Layered products comprising a layer of synthetic resin
  • B32B27/18—Layered products comprising a layer of synthetic resin characterised by the use of special additives
  • B32B27/20—Layered products comprising a layer of synthetic resin characterised by the use of special additives using fillers, pigments, thixotroping agents
• • B—PERFORMING OPERATIONS; TRANSPORTING
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  • B32B27/00—Layered products comprising a layer of synthetic resin
  • B32B27/18—Layered products comprising a layer of synthetic resin characterised by the use of special additives
  • B32B27/22—Layered products comprising a layer of synthetic resin characterised by the use of special additives using plasticisers
• • B—PERFORMING OPERATIONS; TRANSPORTING
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  • B32B27/00—Layered products comprising a layer of synthetic resin
  • B32B27/30—Layered products comprising a layer of synthetic resin comprising vinyl (co)polymers; comprising acrylic (co)polymers
  • B32B27/304—Layered products comprising a layer of synthetic resin comprising vinyl (co)polymers; comprising acrylic (co)polymers comprising vinyl halide (co)polymers, e.g. PVC, PVDC, PVF, PVDF
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B32—LAYERED PRODUCTS
  • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
  • B32B27/00—Layered products comprising a layer of synthetic resin
  • B32B27/30—Layered products comprising a layer of synthetic resin comprising vinyl (co)polymers; comprising acrylic (co)polymers
  • B32B27/308—Layered products comprising a layer of synthetic resin comprising vinyl (co)polymers; comprising acrylic (co)polymers comprising acrylic (co)polymers
• • B—PERFORMING OPERATIONS; TRANSPORTING
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  • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
  • B32B27/00—Layered products comprising a layer of synthetic resin
  • B32B27/32—Layered products comprising a layer of synthetic resin comprising polyolefins
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B32—LAYERED PRODUCTS
  • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
  • B32B27/00—Layered products comprising a layer of synthetic resin
  • B32B27/40—Layered products comprising a layer of synthetic resin comprising polyurethanes
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B32—LAYERED PRODUCTS
  • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
  • B32B5/00—Layered products characterised by the non- homogeneity or physical structure, i.e. comprising a fibrous, filamentary, particulate or foam layer; Layered products characterised by having a layer differing constitutionally or physically in different parts
  • B32B5/18—Layered products characterised by the non- homogeneity or physical structure, i.e. comprising a fibrous, filamentary, particulate or foam layer; Layered products characterised by having a layer differing constitutionally or physically in different parts characterised by features of a layer of foamed material
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B32—LAYERED PRODUCTS
  • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
  • B32B5/00—Layered products characterised by the non- homogeneity or physical structure, i.e. comprising a fibrous, filamentary, particulate or foam layer; Layered products characterised by having a layer differing constitutionally or physically in different parts
  • B32B5/22—Layered products characterised by the non- homogeneity or physical structure, i.e. comprising a fibrous, filamentary, particulate or foam layer; Layered products characterised by having a layer differing constitutionally or physically in different parts characterised by the presence of two or more layers which are next to each other and are fibrous, filamentary, formed of particles or foamed
  • B32B5/32—Layered products characterised by the non- homogeneity or physical structure, i.e. comprising a fibrous, filamentary, particulate or foam layer; Layered products characterised by having a layer differing constitutionally or physically in different parts characterised by the presence of two or more layers which are next to each other and are fibrous, filamentary, formed of particles or foamed at least two layers being foamed and next to each other
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B32—LAYERED PRODUCTS
  • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
  • B32B2264/00—Composition or properties of particles which form a particulate layer or are present as additives
  • B32B2264/02—Synthetic macromolecular particles
  • B32B2264/0214—Particles made of materials belonging to B32B27/00
  • B32B2264/0257—Polyolefin particles, e.g. polyethylene or polypropylene homopolymers or ethylene-propylene copolymers
• • B—PERFORMING OPERATIONS; TRANSPORTING
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  • B32B2264/00—Composition or properties of particles which form a particulate layer or are present as additives
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• • B—PERFORMING OPERATIONS; TRANSPORTING
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  • B32B2264/00—Composition or properties of particles which form a particulate layer or are present as additives
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• • B—PERFORMING OPERATIONS; TRANSPORTING
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• • B—PERFORMING OPERATIONS; TRANSPORTING
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  • B32B2266/00—Composition of foam
  • B32B2266/02—Organic
  • B32B2266/0214—Materials belonging to B32B27/00
  • B32B2266/0221—Vinyl resin
  • B32B2266/0235—Vinyl halide, e.g. PVC, PVDC, PVF, PVDF
• • B—PERFORMING OPERATIONS; TRANSPORTING
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  • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
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• • B—PERFORMING OPERATIONS; TRANSPORTING
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  • B32B2307/00—Properties of the layers or laminate
  • B32B2307/20—Properties of the layers or laminate having particular electrical or magnetic properties, e.g. piezoelectric
  • B32B2307/21—Anti-static
• • B—PERFORMING OPERATIONS; TRANSPORTING
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  • B32B2307/00—Properties of the layers or laminate
  • B32B2307/30—Properties of the layers or laminate having particular thermal properties
  • B32B2307/306—Resistant to heat
  • B32B2307/3065—Flame resistant or retardant, fire resistant or retardant
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B32—LAYERED PRODUCTS
  • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
  • B32B2307/00—Properties of the layers or laminate
  • B32B2307/40—Properties of the layers or laminate having particular optical properties
  • B32B2307/402—Coloured
  • B32B2307/4026—Coloured within the layer by addition of a colorant, e.g. pigments, dyes
• • B—PERFORMING OPERATIONS; TRANSPORTING
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  • B32B2307/00—Properties of the layers or laminate
  • B32B2307/50—Properties of the layers or laminate having particular mechanical properties
  • B32B2307/558—Impact strength, toughness
• • B—PERFORMING OPERATIONS; TRANSPORTING
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  • B32B2307/00—Properties of the layers or laminate
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• • B—PERFORMING OPERATIONS; TRANSPORTING
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  • B32B2307/00—Properties of the layers or laminate
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• • B—PERFORMING OPERATIONS; TRANSPORTING
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  • B32B2307/714—Inert, i.e. inert to chemical degradation, corrosion
• • B—PERFORMING OPERATIONS; TRANSPORTING
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• • B—PERFORMING OPERATIONS; TRANSPORTING
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  • B32B2597/00—Tubular articles, e.g. hoses, pipes
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
  • F16L—PIPES; JOINTS OR FITTINGS FOR PIPES; SUPPORTS FOR PIPES, CABLES OR PROTECTIVE TUBING; MEANS FOR THERMAL INSULATION IN GENERAL
  • F16L9/00—Rigid pipes
  • F16L9/12—Rigid pipes of plastics with or without reinforcement

Definitions

• the invention relates to multi-layer articles consisting of at least one layer of a foamed fluoropolymer.
• the article is formed by co-extrusion in which the foamed layer is coextruded as a foam, and not foamed in a secondary process.
• the fluoropolymer foam is a polyvinylidene fluoride (PVDF), such as KYNAR PVDF from Arkema Inc.
• PVDF polyvinylidene fluoride
• the article could be sized into a specific shape during the manufacturing process.
• Useful multi-layer articles of the invention include pipe, tube, sheet, profile, film, jacketing or any other multilayer foam-core articles are especially useful. Background of the Invention
• PVDF Polyvinylidene fluoride
• HFP hexafluoropropene
• Multi-layered polymeric structures are useful to take advantage of the properties of the different polymers.
• the multi-layer structures (or sheets) are found in parts used in many industries, including the automotive industry; communications, medical devices, and building and construction, etc.. When preparing multilayer structures, the layers of the structures must adhere securely to each other.
• Foam core pipes are already in use for PVC, ABS and PP.
• weight and cost advantage over single layer compact pipe with the same dimension are reported as major advantages. Dimensional stability, higher stiffness, better impact properties, ease of cut, better heat, cold and sound insulations are also other advantages of these pipes.
• the foam-core structure consists of a solid layer attached to a foamed layer, which may be of the same or different composition. In some cases, the foamed layer is sandwiched between two solid layers.
• Foam-core structures are typically made by a co-extrusion process, where the foam is co-extruded with one or more solid layers. In coextrusion, the adjoining layers are initially in a melt phase, allowing for the polymer chains on the surface of each layer to intertwine - creating chain
• multi-layer/multi-material semi-crystalline and crystalline fluoropolymer-containing foamed articles can be manufactured by a coextrusion process.
• the technology is capable of producing multilayer articles with at least one layer of foamed material.
• the direct coextrusion of a foam produces good adhesion between the fluoropolymer foam layer(s) and the solid layer(s).
• the invention relates to a multi-layer structure comprising at least two layers that are coextruded with each other, wherein at least one layer comprises a foamed crystalline or semi-crystalline fluoropolymer having a density of at least 3 percent less than an unfoamed semi-crystalline fluoropolymer of the same composition, and wherein said foamed semi-crystalline fluoropolymer is coextruded as a foam.
• the invention also relates to a process for producing the multi-layer structure and the use of the structure, especially as a foam-core pipe or tube.
• Figure 1 shows a setup for a five layer die and the extruders connected to it.
• Figure 2 is magnified cross section of a foam-core sample, showing the two dense layers on the outside and inside and the foamed internal layer.
• the invention relates to a co-extruded multi-layer fluoropolymer foam structure.
• the foamed layer has interfacial contact with at least one other layer of the same or different material.
• the multilayer structures of the invention include films, sheets, profiles and other articles having two or more structural layers, with at least one layer being a crystalline or semicrystalline fluoropolymer foam.
• the structures may be planar, curved, angled or of any shape - including pipes, tubes and hollow structures.
• structural layers is meant a layer included in the structure to provide specific properties to the structure.
• structural layer is meant to exclude adhesive or tie layers, though these may be present in the structure in addition to the two or more structural layers.
• the term "layer” refers to each strata composed of one or more different materials, which can be of the same or different compositions, and which are secured to one another. It is preferred that the co-extruded materials are adhered to each other by the inherent tendency of the materials to adhere by chain entanglement or chemical bonding during the co-extrusion process, though adhesion can also be induced by added heating, radiation, chemical, or any appropriate process.
• the multi- layer structure of the invention has a total thickness of from 10 to 100,000 microns, preferably from 100 to 20,000 microns.
• Each solid layer has a thickness of from 10 - 25,000 microns, preferably 25- 5000 microns, more prefer 50-500 microns, and each foam layer has a thickness of from 25-50,000 microns, preferably from 50-10,000 microns, more preferably from 250-5000 microns.
• a "different" layer means any change in the composition or density of one layer compared to another layer. Two identical layers could exist in the multilayer structure, as in the case of a three layer structure having an inner core layer and covered on both sides with two identical material layers. In one embodiment, a fluoropolymer foam could be co-extruded with a solid fluoropolymer of the same composition.
• the number of layers in the structures of the invention are not limited - except by the equipment capacity, preferably the number of layers is 7 or less, more preferably 5 or less, and most preferably 2 or 3.
• the layers of fluoropolymer foam can be on the inside or outside of the structure. Structures having more than one foam layer are also contemplated, including one layer of fluoropolymer foam with one layer of non-fluoropolymer foam, or two layers of fluoropolymer foam that may have the same or different compositons and the same or different densities. Multiple foam layers could be adjacent to each other, or could be separated by a solid layer.
• Fluoropolymers useful as a foamed polymer of the invention include crystalline and semi-crystalline fluoropolymers. These polymers are thermoplastic, as they must melt and flow in the co-extrusion process.
• semi-crystalline as used herein is meant that the polymer has at least 5% by weight crystalline, and preferably at least 10% crystalline content, as measured DSC. The DSC measurement is run on a 10 mg sample from RT to 210°C at 20 C/min held for 5 min, cooled from 210°C to -20°C at 20°C per minute, then heated from -20°C to 210°C at 10°C per min.
• the heat of melting is calculated by standard methods and the percent crystallinity is calculated by dividing the J/g heat of melting by 105 J/g for 100% crystalline PVDF and multiplying by 100. For example, a measurement of 50 J/g heat of melting would mean 47.6% crystallinity.
• the fluoropolymers of the invention include, but are not limited to polymers containing at least 50 weight percent of one or more fluoromonomers.
• fluoromonomer as used according to the invention means a fluorinated and olefinically unsaturated monomer capable of undergoing free radical polymerization reaction.
• thermoplastic fluoropolymers of the invention include, but are not limited to: chlorotrifluoroethylene (CTFE), ethylene- tetrafluoroethylene (ETFE), perfluorinated ethylene -propylene copolymer (EFEP), ethylene- chlorotrifluoroethylene (ECTFE), VF 2 , copolymers of tetrafluoroethylene and hexafluoropropene, THV.
• CCTFE chlorotrifluoroethylene
• ETFE ethylene- tetrafluoroethylene
• EEP perfluorinated ethylene -propylene copolymer
• ECTFE ethylene- chlorotrifluoroethylene
• VF 2 copolymers of tetrafluoroethylene and hexafluoropropene
• the fluoropolymer is a poly vinylidene fluoride (PVDF).
• PVDF poly vinylidene fluoride
• the invention will be exemplified in terms of PVDF, but one of ordinary skill in the art will recognize that other semi-crystalline or crystalline thermoplastic fluoropolymers could be represented where the term PVDF is exemplified.
• PVDF polyvinylidene fluoride
• Polyvinylidene fluoride polymers of the invention include the homopolymer made by polymerizing vinylidene fluoride (VDF), and copolymers, terpolymers and higher polymers of vinylidene fluoride, where the vinylidene fluoride units comprise greater than 51 percent by weight, preferably 70 percent of the total weight of all the monomer units in the polymer, and more preferably, comprise greater than 75 percent of the total weight of the monomer units.
• VDF vinylidene fluoride
• Copolymers, terpolymers and higher polymers (generally referred to herein as "copolymers") of vinylidene fluoride may be made by reacting vinylidene fluoride with one or more monomers from the group consisting of vinyl fluoride,
• perfluorinated vinyl ethers such as perfluoromethyl vinyl ether, perfluoroethyl vinyl ether, perfluoro-n-propyl vinyl ether, and perfluoro-2- propoxypropyl vinyl ether
• fluorinated dioxoles such as perfluoro(l,3-dioxole) and perfluoro(2,2-dimethyl-l,3-dioxole)
• allylic partly fluorinated allylic, or fluorinated allylic monomers, such as 2-hydroxyethyl allyl ether or 3-allyloxypropanediol, and ethene or propene.
• Preferred copolymers or terpolymers are formed with vinylidene fluoride and one or more of vinyl fluoride, trifluoroethene, tetrafluoroethene (TFE), hexafluoropropene (HFP), and chlorofluoroethylene.
• Preferred copolymers include those comprising from about 60 to about 99 weight percent VDF, and correspondingly from about 1 to about 40 percent HFP; copolymers of VDF and CTFE; terpolymers of VDF/HFP/TFE; and copolymers of VDF and EFEP
• the PVDF of the invention could also be an alloy of PVDF and a miscible, semi-miscible, or compatible polymer. Since most alloys of PVDF result in some diminishment of the PVDF properties, a preferred PVDF is one that is not an alloy. However, small amounts of other polymers, up to 30 percent of the total PVDF polymer alloy may be added.
• Other fluoropolymers, thermoplastic poly urethane (TPU) and (meth)acrylic polymers are examples of useful polymers that may make up a useful polymer alloy.
• the fluoropolymer is a branched fluoropolymer. A branched fluoropolymer could result in larger cells, and could be a useful choice in forming a foamed multi-layer film.
• the fluoropolymer foam is formed from a functional fluoropolymer, including as a non-limiting example a maleic anhydride- grafted PVDF (such as KYNAR ADX from Arkema Inc.).
• a functionalized PVDF foam could further increase adhesion to other layers of a multi-layer structure.
• the foamed layer(s) can be manufactured through any foaming process including but not limited to the use of physical or chemical blowing agents and nucleating agents.
• the fluoropolymer foam layer of the present invention is co-extruded directly as a foam.
• the gas is created by decomposition of a chemical by heating it above its degradation temperature.
• gas is introduced into the polymer either directly or through evaporating a liquid foaming agent by heating it above its evaporation temperature.
• Chemical blowing agents are mainly used for higher density foams - down to 70% density reduction, while physical blowing agents can produce light foams - upwards of 10X density reduction.
• Blowing agents useful in the invention can be either chemical or physical blowing agents, or a mixture thereof.
• a chemical blowing agent the gas is created by decomposition of a chemical heated above its degradation temperature.
• the physical blowing agent gas is introduced into the polymer either directly or through evaporating a liquid foaming agent by heating it above its evaporation temperature.
• Chemical blowing agents are mainly used for higher density foams - down to 70% density reduction, while physical blowing agents can produce light foams - upwards of 10X density reduction.
• a combination of chemical and physical blowing agents can also be used.
• the chemical blowing agent can be a solid or fluid.
• Useful blowing agents include, but are not limited to, azodicarbonamide, azodiisobutyronitile,
• sulfonylsemicarbazide 4,4-oxybenzene, barium azodicarboxylate, 5-Phenyltetrazole, p-toluenesulfonylsemicarbazide, diisopropyl hydrazodicarboxylate, 4,4'- oxybis (benzenesulfonylhydrazide) , diphenylsulf one-3 ,3 ' -disulfohydrazide, isatoic anhydride, N,N'-dimethyl-N,N'dinitroterephthalamide, citric acid, sodium
• bicarbonate monosodium citrate, anhydrous citric acid, trihydrazinotriazine, ⁇ , ⁇ '- dinitroso-pentamethylenetetramine, and p-toluenesulfonylhydrazide, or include a blend two or more of said blowing agents.
• Mixtures of chemical and physical blowing agents are also contemplated by the invention.
• the foam of the invention may optionally be formed using a nucleating agent that aids in producing a homogeneous foam.
• a nucleating agent that aids in producing a homogeneous foam.
• no added nucleating agent is added.
• a chemical foaming agent could act as both a foaming agent and a nucleating agent.
• a nucleating agents may be useful when a chemical blowing agent is used and is necessary for forming a controlled foam with physical blowing agents. A mixture of two or more nucleating agents can be used.
• nucleating agents include, but are not limited to calcium carbonate, calcium sulfate, magnesium hydroxide, magnesium silicate hydroxide, calcium tungstate, magnesium oxide, lead oxide, barium oxide, titanium dioxide, zinc oxide, antimony oxide, boron nitride, magnesium carbonate, lead carbonate, zinc carbonate, barium carbonate, calcium silicate, aluminosilicate, carbon black, graphite, non organic pigments, alumina, molybdenum disulfide, zinc stearate, PTFE particles, immiscible polymer particles, and calcium metasilicate.
• a preferred nucleating agent is calcium carbonate. Nucleating agents that have smaller particle size, and have rougher surfaces are preferred.
• the fluoropolymer foamed structure is produced using one or more master batch concentrate(s) containing an optional nucleating agent, at least one chemical blowing agent in the case where a chemical blowing agent is used, and optional other additives, in a suitable carrier.
• the purpose of the master batch is to provide a more precise addition of ingredients used at low level, and to do so in a manner providing excellent homogeneous mixing of components within the PVDF, leading to homogeneous foam formation.
• the additives are usually in the form of fine powders that need to be added to the polymer pellets and would phase separate in the extruder hopper.
• the master batch contains a high concentration of the required additives in the final product (sometimes 10 to 50 times more concentrated). In one embodiment the master batch contains 1 to 20 weight percent of a blowing agent, and, if present from 0.5 to 20 weight percent of nucleating agent.
• the master batch is then generally mixed with the PVDF pellets in a dry blend form and introduced in the extruder hopper. This process is called letting down the concentrate. In the let down process, depending on the concentration of the additives in the master batch and also the required amount of the additives in the final product, anything between several percent to sometimes over 50% of the master batch concentrate is added to the polymer resin.
• multiple master batches each containing one or more of the additives to be mixed into the PVDF.
• One advantage of multiple master batches would be that a manufacturer could adjust the ratio of the additives at the point of manufacture.
• An example of multiple master batches would be a first master batch containing a nucleating agent, and a second master batch containing a blowing agent.
• the foam has good mechanical stability and load bearing properties for PVDF foamed structures having density reductions down to 50 % of the original density, making them useful as pipes that could hold pressure, or rods or profiles that could carry loads.
• the foamed structure has a density that is at least 3% less than said non- foamed PVDF, and more preferably at least 25% less.
• the density reduction could be 35% less, 50% less and even as high as 100 times less dense than the non-foamed PVDF material.
• the structures are typically joined together or attached to standard couplings or fittings and can be manufactured with a tight tolerance.
• 4" schedule 40 pipes have an outside diameter of 4.500" with a tolerance of +/- 0.009" and a thickness of 0.251" with a tolerance of +/- 0.016".
• the foamed PVDF of this invention would have the melt strength to go through sizing and calibration enabling one to form and size the PVDF foam structure to such a close tolerances.
• the foam cell size is as small as possible.
• the cell size could be as small as 1 micron.
• the cell size is in the range of from 10 to 250 microns, more typically in the range of from 50 to 150 microns.
• the foamed multi-layer structure of the invention contains at least one other layer that is co-extruded with the foam.
• two layers of foam may be coextruded together, in which the foam densities of the foams are different, or the compositions are different, or both.
• a fluoropolymer foam is coextruded with a solid fluoropolymer of a similar or the same composition.
• the fluoropolymer foam is coextruded with a thermoplastic non-fluoropolymer.
• Examples of useful non-fluoropolymers that are compatible with the fluoropolymer foam include, but are not limited to (meth)acrylates and thermoplastic polyurethane (TPU).
• a layer of the fluoropolymer foam is coextruded between two layers of solid fluoropolymer, to form a foam-core structure.
• a thin tie layer or adhesive can be coextruded between the foam and the solid structural layer.
• the melting points of the layers, and the viscosities of each layer be relatively similar, to facilitate coextrusion.
• the difference in melting points of adjoining layers is less than 60°C, and more preferably less than 25°C Additives:
• One or more additives may optionally be added to the fhioropolymer foam layer composition, or the composition of the other layers.
• Typical additives include, but not limited to, impact modifiers, UV stabilizers, plasticizers, fillers, coloring agents, pigments, dyes, antioxidants, antistatic agents, surfactants, toner, pigments, flame retardant, and dispersing aids.
• a continuous co-extrusion process is used for manufacturing the multilayer foam structure of the invention.
• extruders are used to feed multiple materials into a die that would combine these materials in a layered form and shape the product into pipe, sheet, profile or other desirable shapes that can be sized in a later step.
• the most common multilayer foam articles are foam core pipe and sheets. These articles are usually extruded using two or three extruders. One extruder is used to make the foam core layer. If there are only two extruders available, the second one is used to make the solid layers on the inside and outside from the same material. If there are three extruders, the material of the dense layer inside and outside could be different.
• One of skill in the art would be able to recognize different processes to have multiple layers of multiple materials with more than one layers of foam.
• the polymer is heated inside the extruder in the presence of foaming and optional nucleating agents above its melting point, which should be higher than the decomposition temperature of the foaming agent.
• the generated gas is then absorbed by the molten polymer under high pressure.
• Gasses are excellent plasticizers for polymers.
• inclusion of gas would substantially reduce both the melting temperature and the viscosity of the polymer.
• a gas is injected into the extruder instead of using a chemical blowing agent. The resulting mixture has very low melt strength and low viscosity and is not suitable for foaming.
• the pressure at the end of the extruder, melt temperature and the die profile are also other important parameters to control.
• the polymer/gas mixture with suitable melt strength and viscosity would exit the die and be exposed to the atmospheric pressure. At this point, the gas dissolved in the polymer would generates gas cells in the polymer.
• Extrusion of the solid material layers is done using processes known in the art. Co-extrusion dies using various technologies could be used with this invention. Spiral dies and feed block type dies are most common for this application although other die technologies such as pancake and combination dies can also be used.
• a tandem extrusion process in a single unit operation is also contemplated by the invention.
• the foam is extruded, cooled and shaped, followed by further extrusion of added solid layer(s).
• the coextruded multi-layer foam structure of the invention is useful as an article such as, but not limited to pipe, tube, sheet, profile, film, jacketing.
• One especially useful structure is a foam-core tube or pipe.
• the foamed multi-layer structure is self-supporting, and needs no internal or external support.
• the coextruded structure may be further processed to form a variety of final articles by means known in the art, including but not limited to the thermoforming of sheets into a variety of parts, and the welding of sheets of pipe into complex articles.
• the multi-layer structure especially a pipe or tube, could further be wrapped in a protective covering, such as a fiber or metal sheath.
• PVDF is used generically to stand for PVDF homopolymers or copolymers
• a coextruded pipe having a PVDF foam interior, and solid PVDF layers on either side, in which the foam core is at least twice as thick as both solid layers combined.
• a sheet having a PVDF foam and a TPU solid layer an article having in order a PVDF foam layer, a maleic anhydride grafted PVDF foam layer, and a thermoplastic polyolefin (TPO) layer.
• TPO thermoplastic polyolefin
• PVDF foam/solid/PVDF foam article a PVDF foam/solid/PVDF foam article.
• PVDF a solid PVDF/PVDF foam/solid (PVDF or non-PVDF)/PVDF foam/solid PVDF structure.
• the foam core density was changed by changing the amount of the foam masterbatch added to the formulation and also by changing the processing conditions most notably, the extruder and die temperature profile and line speed.
• Figure 1 shows the setup for the five layer die and the size of the extruders connected to it.
• the draw down ratios were as follows:
• the internal and external dense layers were KYNAR RX 810 HPC, a
• Table 1 shows the composition of the six samples we are using as examples here.
• Example 2 1970 / 177.561 Kynar® RX 801 HPC + 2% MB Green 1.2677 380 / 14.96 Table shows the processing conditions for Example 2, which are typical of the conditions for all of the other samples.
• Figure 2 is a magnified cross section of Example 2 which distinctly shows the two dense layers on the outside and inside and the foamed internal layer.
• a three layer foam core PVDF sheet is manufactured using a three layer, three extruder co-extrusion process. The goal was to make a sheet with dense external layers and a foamed core. A line with three one inch single screw extruders and a three layer co-extrusion feed block system was used. The sheet die was 12" and had an opening of 1 ⁇ 4". A three roll stack was used to size and cool the foam core sheet.
• the roll temperature for the finishing section was 120 °F.
• the experiment resulted in a three layer foam core sheet with the overall thickness of 0.16".
• the top and bottom layer thickness were 0.024" and 0.020", respectively. This means that almost 30% of the thickness is coming from the dense material and 70% from the foam material.
• the foam core density was 1.21 g/cc which is a 32.2% density reduction and the overall density reduction was 28.6%.
• the surface finish and quality of the sheet was very good and distinct layers could be observed.

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• 2013
  • 2013-08-19 WO PCT/US2013/055511 patent/WO2014031510A2/en active Application Filing
  • 2013-08-19 EP EP13831003.2A patent/EP2888515A4/de not_active Withdrawn

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