WO2014009579A1 - Procédé de fabrication de matériaux cellulaires à matrice thermoplastique - Google Patents

Procédé de fabrication de matériaux cellulaires à matrice thermoplastique Download PDF

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Publication number
WO2014009579A1
WO2014009579A1 PCT/ES2013/070420 ES2013070420W WO2014009579A1 WO 2014009579 A1 WO2014009579 A1 WO 2014009579A1 ES 2013070420 W ES2013070420 W ES 2013070420W WO 2014009579 A1 WO2014009579 A1 WO 2014009579A1
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WIPO (PCT)
Prior art keywords
mold
foaming agent
expansion
polymer
pressure
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PCT/ES2013/070420
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English (en)
Spanish (es)
Inventor
Miguel Angel Rodriguez Perez
Jose Antonio De Saja Saez
Javier Escudero Arconada
Alberto Lopez Gil
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Universidad De Valladolid
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Publication of WO2014009579A1 publication Critical patent/WO2014009579A1/fr

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Classifications

    • 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
    • B29C44/34—Auxiliary operations
    • B29C44/58—Moulds
    • B29C44/586—Moulds with a cavity increasing in size during foaming
    • 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
    • B29C43/00—Compression moulding, i.e. applying external pressure to flow the moulding material; Apparatus therefor
    • 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
    • B29C43/00—Compression moulding, i.e. applying external pressure to flow the moulding material; Apparatus therefor
    • B29C43/003—Compression moulding, i.e. applying external pressure to flow the moulding material; Apparatus therefor characterised by the choice of material
    • 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
    • B29C43/00—Compression moulding, i.e. applying external pressure to flow the moulding material; Apparatus therefor
    • B29C43/02—Compression moulding, i.e. applying external pressure to flow the moulding material; Apparatus therefor of articles of definite length, i.e. discrete articles
    • 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
    • B29C43/00—Compression moulding, i.e. applying external pressure to flow the moulding material; Apparatus therefor
    • B29C43/32—Component parts, details or accessories; Auxiliary operations
    • B29C43/36—Moulds for making articles of definite length, i.e. discrete articles
    • 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
    • B29C44/34—Auxiliary operations
    • B29C44/35—Component parts; Details or accessories
    • B29C44/352—Means for giving the foam different characteristics in different directions
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J9/00—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof
    • C08J9/04—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof using blowing gases generated by a previously added blowing agent
    • C08J9/06—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof using blowing gases generated by a previously added blowing agent by a chemical blowing agent
    • C08J9/10—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof using blowing gases generated by a previously added blowing agent by a chemical blowing agent developing nitrogen, the blowing agent being a compound containing a nitrogen-to-nitrogen bond
    • C08J9/102—Azo-compounds
    • C08J9/103—Azodicarbonamide
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J2201/00—Foams characterised by the foaming process
    • C08J2201/02—Foams characterised by the foaming process characterised by mechanical pre- or post-treatments
    • C08J2201/032—Impregnation of a formed object with a gas
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J2300/00—Characterised by the use of unspecified polymers
    • C08J2300/22—Thermoplastic resins

Definitions

  • the present invention encompasses within the field of industry related to the production of non-crosslinked low density cell panels with thermoplastic matrix, high mechanical performance and good surface finish.
  • the mechanical properties of a cellular material depend fundamentally on the density of the material, on the properties of the starting polymer that forms the matrix and on the cellular microstructure. Thus, when the density of the material decreases, the mechanical properties suffer a very marked decrease. By modifying the microstructure, for a fixed density and a given starting matrix, mechanical properties can be improved in a very significant way.
  • the modification of the microstructure to give rise to an anisotropic cellular structure in the cellular material is a known method to compensate for the decrease in mechanical properties that occurs with density.
  • the proportion of mass in cell walls is another microstructural parameter that is strongly related to the specific mechanical properties of cellular material.
  • a high closed cell content is indicative of a high proportion of mass in the walls and results in optimal specific mechanical properties.
  • Low closed cell contents are normally associated with low mass proportions in the cell walls and this results in low specific mechanical properties.
  • Closed cell content it is directly proportional to the volume fraction of cells that are not interconnected. A greater presence of mass in the walls decreases the interconnections between cells and increases the closed cell content.
  • An open cell structure is characterized in that the volume of interconnected cells is identical to the volume of the gas phase.
  • a partially interconnected structure is characterized in that a fraction of the gas phase volume is interconnected.
  • Relative density is the ratio between the density of the cellular material and that of the solid from which it is based. It is a measure of the volumetric fraction of solid phase present in the material.
  • Degree of expansion is the ratio between the volume of the cellular material and the volume of the solid starting material. It therefore measures the volume increase suffered by the material during the foaming process
  • Anisotropy index quotient between the dimension of a cell in a given direction and the dimension measured in another direction.
  • Tortuosity It is the ratio between the distance that the gas must travel to cross the material and the thickness of that material. It is therefore a measure of how intricate the cellular structure of the material is, it is a parameter that is important for cellular structures with high open cell contents.
  • Relative elastic modulus, relative collapse stress, relative shear modulus refers to the value of any of these mechanical properties divided by the density of the piece on which it is being measured. It is a way to separate the value of mechanical property from density. In this way a much more comparable value is obtained without the need to specify the density.
  • Foaming agent that material that when it reaches a critical temperature, which we will call decomposition temperature, generates a gas phase. Said gas phase may allow the expansion of a second material into which the foaming agent has been previously introduced.
  • Nanoparticles are particles that have at least one of their dimensions (length, width, thickness-diameter) on the nanometric scale, that is, some of their dimensions have sizes smaller than about 200 nanometers.
  • laminar shaped nanoparticles fiber and isotropic. Examples of this type of particles are nano-clays, carbon nanotubes, carbon nanofibers, nanometric silicas, graphenes, titanate organ, zirconate organ, etc.
  • anisotropy index is equal to 1, the cell growth is the same in all directions and its shape is completely isotropic.
  • an anisotropy index greater than 1 will indicate that the cells are elongated in the direction of the thickness of the sheet than in any direction contained in a plane parallel to the two flat surfaces.
  • the cells will be highly isotropic in a plane parallel to the two opposite flat surfaces. This anisotropy configuration will increase the mechanical properties in compression measured in the thickness direction of the sheet.
  • US 2010 0029796 A1 discloses a procedure in which the foams, once manufactured, undergo a temperature and mechanical deformation cycle to induce anisotropic cells.
  • the EP 0 411 437 B1 processing method achieves high anisotropy ratios with values between 5 and 12 but restricts its application to polyethersulfones.
  • anisotropy is achieved by introducing oriented nanofibers into the matrix, although production is focused on a specific polymer, an aromatic alkenyl.
  • US 2011 0104478 presents a method of obtaining anisotropic foams in which the anisotropy ratios in no case exceed a value of 1, 7. In this process anisotropy is achieved by depressurization during cooling.
  • the invention relates to a process for obtaining non-crosslinked thermoplastic matrix cellular materials with relative densities of less than 0.2 in which anisotropy rates greater than 2, variable percentages of open cell content, and high specific, comparable mechanical properties are achieved. to those obtained commercially with other materials based on PVC or SAN, with good surface quality and with a cheaper production cost compared to the current ones in the market.
  • a relative elastic modulus value in compression greater than 0.6 MPa / (kg / m 3 ) is referred to as a relative shear modulus greater than 0.18 MPa / (kg / m 3 ) and a collapse effort greater than 0.010 MPa / (kg / m 3 ).
  • the procedure mainly comprises the following stages:
  • the first step consists in the mixing in a mixer or extruder of the raw materials to be used in the manufacture of a sheet, these being at least a thermoplastic polymer, a chemical foaming agent, and additives under temperature and shear conditions. which the polymer is molten but below the decomposition conditions of the foaming agent.
  • a mixer or extruder of the raw materials to be used in the manufacture of a sheet, these being at least a thermoplastic polymer, a chemical foaming agent, and additives under temperature and shear conditions. which the polymer is molten but below the decomposition conditions of the foaming agent.
  • An alternative to this route is the use of a cold mixing process using powders for the components of the mixture.
  • the raw materials to be used are the following:
  • the basic element is a thermoplastic polymer, such as polyethylene, polypropylene, polyvinylchloride, polyethylene terephthalate, polystyrene, polyamide, starch, polylactic acid, etc. or also mixtures thereof in the amounts suitable for obtaining the desired final product.
  • b. - a chemical foaming agent.
  • azodicarbonamide oxjbis (benzenesulfonyl hydrazine), 5-phenyltetrazole, bicarbonate, citric acid or mixtures thereof, etc.
  • the amount of foaming agent is a critical parameter that must be adjusted precisely according to the degree of expansion (relative density) and cell structure (cell size, anisotropy, tortuosity, open cell content, etc.) that is to be achieved in the final product
  • the foaming agent is introduced so that a good dispersion thereof is achieved.
  • c- other additives such as fillers (talc, calcium carbonate, nano-clays, nanosyl, carbon nanotubes, carbon nanofibers, graphenes), reinforcements (glass fibers, carbon fibers), process aids (waxes, stearic acid), nucleating agents (talc, clay-type nanoparticles, silicas), antioxidants, pigments, activators of the reaction of the foaming agent (zinc oxide), repolymerizing agents such as neoalkoxy organotitanatos or organozirconatos, etc.
  • One of the novelties and beneficial aspect of the present invention is the need not to resort to cross-linked matrices (ie in which there are carbon-carbon bonds between chains) and therefore in no case will it contain cross-linking agents. It is convenient to point out here that the introduction of nano-sized charges will be decisive in obtaining anisotropic open-cell cellular structures of high mechanical performance. d.- in the case of using certain nano-sized charges as organomodified nano-clays, it may be necessary to use a compatibilizing polymer grafted with maleic anhydride or any other type of compatibilizing agent in the starting formulation in order to produce the good dispersion / exfoliation of said particles of nanometric size.
  • the additives are introduced so that there is a good dispersion of all of them in the polymer matrix.
  • the mixture once solidified, is granulated at the exit of the extruder or mixer to a sufficiently small size to allow its subsequent introduction into the manufacturing molds.
  • This mixture may also be extruded in the form of a sheet or other form such that said material is subsequently introduced into the mold acting as a precursor.
  • the manufactured pellet could also subsequently undergo a compaction process to give it a certain geometry that would later be introduced into the mold for the production of the cell sheet.
  • the mold comprises:
  • a T-shaped piston (3) as a unidirectionally movable element, whose body fits with low tolerance within the mold body (1).
  • the bottom of the piston (10) once it is inserted into the mold, will leave a free space between it and the internal base of the mold body, internal cavity (11), where the precursor material (5) will be housed.
  • the upper part of the T-shaped piston (9) will come into contact at a certain time with the elastic seal (2) of the mold body (1) exerting pressure on it and leaving the internal mold cavity (11) completely sealed gases and the escape of molten material,
  • An expansion piece (6) attached to the body of the mold (1) and whose height is variable depending on the degree of expansion sought and / or the final thickness of the sheet to be produced, whose internal area coincides with low tolerance with the external area of the upper part of the T-shaped piston (9), in such a way that it acts as its guide during its ascent, and
  • the material from which the mold is manufactured can be any as long as it supports the pressure conditions and temperatures developed during the process.
  • the introduction of the material into the mold can be done by different methods. The simplest would be to introduce the material in the form of pellets, dust or in the form of a precursor material before placing the slab. Another way would be to do it through an opening in the body (1) or in the lower cover (4). In this case, it could be introduced both in solid state (in the form of pellets or powders) and in molten state using extrusion equipment or by vacuum techniques. Once the material has been introduced, the opening used for such introduction should be properly sealed to prevent material loss.
  • the quantity of material to be introduced will be such that if it were completely compact in the molten state it would completely fill, at least, the free space between the piston and the lower base of the mold (11) mentioned previously in such a way that the piston (3) in any state prior to the decomposition of the foaming agent already presses on the precursor material (5).
  • the amount of material to be introduced is related to the final relative density of the piece to be reached and to the expansion piece used in each case.
  • the relative densities attainable by this process can reach values as low as 0.05 and any higher value even if the process is preferably focused on the range of low densities (relative densities below 0.2)
  • the mold completely assembled, closed and with the precursor material inside is subjected to a cycle that combines pressure and temperature together, for enough time to produce a sufficient amount of gas to achieve the desired expansion (steps 3.1, 3.2 and 3.3).
  • a cycle that combines pressure and temperature together, for enough time to produce a sufficient amount of gas to achieve the desired expansion (steps 3.1, 3.2 and 3.3).
  • the time under which the mold remains under conditions of pressure and / or temperature must be the minimum necessary for the entire foaming agent to decompose in order to optimize the specific mechanical properties of the final piece.
  • the pressure can be mechanically exerted through a press by placing a second cylindrical piston (8) on the T-shaped piston (3) to transmit the pressure to the material or in any other way as long as this pressure is greater than the gas pressure generated by the foaming agent upon decomposition, such that this generated gas is dissolved in the molten precursor polymer without producing any foaming while the pressure continues to be applied.
  • the pressure can be kept constant throughout the process or it can be varied as long as it is higher than the gas pressure generated by the decomposition of the foaming agent.
  • the temperature can be applied by heating the upper and lower plates of the press, by means of external heating side jackets, by infrared heaters, by electrical resistors inserted in the mold body, by oil circuits thermostating in the body of the mold or by any other procedure.
  • the temperature must be such that the polymer matrix melts if the polymer is semi-crystalline or allows the glass transition temperature to be reached if the polymer is amorphous and the decomposition of the foaming agent.
  • the heating process can be carried out by different temperature steps if, for example, it is first desired to produce the polymer melting and then the decomposition of the foaming agent.
  • the starting formulation does not contain nano-sized charges such as nano-clays, carbon nanotubes, carbon nanofibers, etc.
  • the recommended pressures to be exerted to optimize the specific mechanical properties are medium (35 bar).
  • nano-sized charges such as nano-clays, carbon nanotubes, carbon nanofibers etc.
  • the recommended pressures to be exerted to optimize the mechanical properties are low (7 bar).
  • the pressure parameter must be adjusted precisely to achieve an optimal final piece.
  • parameters such as anisotropy ratio, cell size or structure tortuosity can be controlled and varied. In general, higher pressures result in lower anisotropy values and reduced cell sizes.
  • the gas pressure generated as a result of the decomposition of the foaming agent will act as a pushing force for the growth of the polymer matrix in the pressure release direction generating an anisotropic cell structure with maximum anisotropy in this direction.
  • the cooling can take place in different ways, by means of air circulation, submerging the mold in a water bath or other liquid for rapid cooling, introducing circuits through which the entry or exit of water or oil can occur in the body of the mold, etc.
  • the anisotropic cellular structure achieved during stage 3 can continue to evolve once the pressure and / or the heating is released towards an isotropic cellular structure whereby the cooling rate has to be as fast as possible and the time that elapses until this cooling Begins should be as small as possible.
  • the retaining part (7) can be dispensed with by acting on the upper plate of the press, or any other procedure that has been used to apply pressure on the T-shaped piston, as a mechanism limiting the rise of said piston and therefore the growth of the foam.
  • the expansion piece and the retention piece are essential pieces that allow the final density of the piece to be controlled while the mold is extracted from the press to proceed with cooling by immersion in water or any other procedure, also leaving the press free to start manufacturing another piece.
  • the mold can be disassembled and the sheet already formed and solid extracted from its interior without presenting greater difficulty.
  • the present invention allows the manufacture of anisotropic cellular materials both closed cell and open cell and maintaining high specific mechanical properties in both cases.
  • the starting formulation must contain a certain percentage of nano-sized particles such as organomodified and natural nano-clays, carbon nanotubes, carbon nanofibers, etc.
  • the present invention presents cellular materials that combine low density starting from non-crosslinked polymeric matrices with highly anisotropic cellular structures and with variable open cell contents and that by their morphology are endowed with high specific mechanical properties and excellent surface quality.
  • the degree of anisotropy increases as the relative density of the manufactured part decreases, this fact is ideal to conveniently compensate for the loss of mechanical properties that occur at these low densities.
  • the manufacturing process allows precise control and variation of density, anisotropy index of the cell structure and the cell size of the piece.
  • the invention allows to obtain high open cell contents while maintaining high anisotropy, low density and high specific mechanical properties by introducing nano-sized charges.
  • the cellular material obtained is also competitive in terms of costs compared to other competitors in the market for equal mechanical properties.
  • the final price of the product presents an approximate saving of 30% compared to other products in the market with similar benefits.
  • FIG 1 shows the different stages of material production
  • Figure 2 schematically shows the evolution of the cell structure during the foaming process in which changes in densities and anisotropy are observed.
  • Figure 3a shows an image of the anisotropic cellular structure with high open cell content corresponding to a base cellular material Polypropylene containing nano-clay type nanoparticles. (example 1) manufactured by the process of the invention.
  • Figure 3b shows an image of the anisotropic cell structure for a material manufactured on the basis of a high strength melt polypropylene (example 2) manufactured by the process of the invention.
  • Figure 3c shows an image of the cellular structure with a lower degree of anisotropy made on the basis of a high melt polypropylene in the melt (example 3)
  • a series of references are identified that correspond to the elements indicated below, without this implying any limiting character:
  • the method of manufacturing non-crosslinked thermoplastic matrix cellular materials with relative densities of less than 0.2, with anisotropy rates greater than 1.5 in both open cell and partially interconnected cell and a relative elastic modulus in compression greater than 0.6 MPa / (kg / m 3 ) a relative shear module greater than 0.18 MPa / (kg / m 3 ) and a collapse effort greater than 0.010 MPa / (kg / m 3 ), comprises:
  • the temperature of the mold is raised above the decomposition temperature of the foaming agent until the polymer matrix melts and the decomposition of the foaming agent (C1) is obtained, simultaneously applying a pressure to the piece of unidirectional expansion (3) of the mold with values above the pressure generated by the foaming agent, until the polymer melts and decomposes the foaming agent,
  • the sheet obtained is demoulded (E) when the entire mold and that of the sheet contained therein are at a temperature below the crystallization temperature if the polymer is semi-crystalline or the glass transition if the polymer is amorphous.
  • a polypropylene co-rotating twin screw extruder with high melt strength (Daploy WB 135 HMS, Borealis), a grafted polypropylene with maleic anhydride (Polybond 3150, Chemtura), monomorillonite-type nanoarcillas organomodified with quaternary salts are mixed in a first step ammonium (Cloisite 20 A, Southern Clay Products), a foaming agent, in this case azodicarbonamide (Porofor M-C1, Lanxess) and antioxidants Irgafos 168 and Irganox 1010 (Ciba) in proportions of 81, 9%, 10%, 5% , 3%, 0.08% and 0.02% respectively.
  • the mixture is granulated and introduced into the body of a stainless steel mold.
  • Said mold body comprises: - A body (1) comprising a main inner cavity (11) forming the sheet, comprising:
  • a piston (3) with a T-shaped cross section The most prominent part of the piston, that is the upper sector (9), presses against the elastic seal (2) leaving the internal compartment (11) of the body (1) tight to gases and to the escape of the material.
  • the cavity (4) Between the base of the piston body (10) and the base the cavity (4) will be a space (11) of 2 mm in height.
  • the quantity of material (5) to be introduced is calculated so that, once compacted, the material completely occupies this space between the base of the mold (4) and the piston (3). In this way, the piston will remain constantly under pressure on the entire molten material, an expansion piece (6) attached to the body of the mold, said expansion piece with a variable height according to the final thickness (final density) of the sheet to be manufactured.
  • the complete set is introduced in a hot plate press preheated to the working temperature.
  • a second cylindrical aluminum piston is placed on the T-shaped piston that will transmit the pressure and heat to the material.
  • the press plates are preheated to 190 ° C and a pressure of 5 bar is exerted.
  • the nano-clays have a catalytic effect on azodicarbonamide reducing the decomposition temperature, so the optimum process temperature is 190 ° C.
  • the mold assembly remains under these conditions for the time necessary for the polymer to melt and decompose the foaming agent. Due to the pressure applied to the material, the decomposed gas is dissolved in the polymer without causing foaming. After this time the pressure is slowly released at a speed of 10 mm / min, allowing the material to grow in a single direction. The T-shaped piston is stopped by the retaining part, thus achieving the desired expansion.
  • the mold assembly is removed from the press and immersed in water to cool. Once the temperature has dropped below the solidification temperature of the polymer, the assembly can be removed from the water and removed to proceed with the extraction of the sheet.
  • a polypropylene double spindle with high melt strength (Daploy WB 135 HMS, Borealis), a foaming agent, in this case azodicarbonamide (Porofor M-C1, Lanxess) and antioxidants Irgafos 168 e are mixed in a first step.
  • Irganox 1010 (Ciba) in proportions of 96.9%, 3%, 0.08% and 0.02% respectively.
  • the mixture is granulated and introduced into the body of a stainless steel mold.
  • Said mold body comprises:
  • a body (1) comprising a main inner cavity (11) forming the sheet, comprising:
  • a piston (3) with a T-shaped cross-section ( Figure 1) whose upper sector (9) of the piston presses against the elastic seal (2) leaving the internal compartment of the gas-tight body and the material escape.
  • a space (11) 2 mm high Between the lower base (10) of the piston body (3) and the inner base of the cavity (4) there is a space (11) 2 mm high.
  • the quantity of material to be introduced is calculated so that, once compacted and molten, the material (5) completely occupies this space between the base of the cavity (10) and the base (10) of the piston (3). In this way, the piston will remain constantly under pressure on the entire molten material, a screwed expansion piece (6) attached to the body of the mold, with a variable height according to the final thickness (final density) of the sheet to be manufactured, and
  • the complete set is introduced in a hot plate press preheated to the working temperature.
  • a second aluminum cylindrical piston (8) is placed on the T-shaped piston (3) that will transmit the pressure and heat to the material.
  • the press plates are preheated to 200 ° C and a pressure of 35 bar is exerted.
  • the mold assembly remains under these conditions for the time necessary for the polymer to melt and decompose the foaming agent.
  • the mold assembly is removed from the press and immersed in water to cool.
  • the assembly can be removed from the water and removed to proceed with the extraction of the sheet.
  • the manufacturing conditions in this case are exactly the same as those used in Example 2 except for the pressure used that goes from 35 bar to a pressure of 85 bar. This increase in pressure results in a decrease in the anisotropy ratio and also a decrease in the average cell size of the final piece.
  • the anisotropy goes from a value close to 3 in example 2 to a value of 1.5 in this case and the cell size goes from the 300 pm obtained in example 1 to an average of 150 pm ( Figure 3c).
  • the final cellular structure can be varied and controlled in terms of degree of anisotropy, cell size and tortuosity.
  • the degree of anisotropy increases as the degree of expansion increases (the relative density decreases) such that compensation for the decrease in mechanical properties at low densities occurs.

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Abstract

L'invention concerne un procédé de fabrication de matériaux cellulaires à matrice thermoplastique non réticulée avec des densités relatives inférieures à 0,2 présentant des indices d'anisotropie supérieurs à 1,5 autant en cellule ouverte que partiellement interconnectée et avec un module élastique relatif en compression supérieur à 0,6 MPa/(kg/m3) un module de cisaillement relatif supérieur à 0,18 MPa/(kg/m3) et une contrainte d'effondrement supérieure à 0,010 MPa/(kg/m3),), qui comprend les étapes consistant : à procéder au mélange et broyage d'au moins un polymère thermoplastique avec un agent moussant chimique et au moins un type de nanoparticule formant un matériau précurseur (5) (A) ; à introduire le matériau précurseur (5) obtenu, dans un moule d'expansion unidirectionnel avec un système de rétention de l'expansion (B) ; à élever la température du moule et à appliquer une pression sur le moule (C1) ; à relâcher la pression (C2) afin d'atteindre l'expansion (C3) du matériau ; à refroidir le moule (D) ; et à démouler la couche obtenue (E).
PCT/ES2013/070420 2012-07-12 2013-06-25 Procédé de fabrication de matériaux cellulaires à matrice thermoplastique WO2014009579A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
ESP201231092 2012-07-12
ES201231092A ES2388083B1 (es) 2012-07-12 2012-07-12 Procedimiento de fabricación materiales celulares de matriz termoplástica

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WO2019191067A1 (fr) * 2018-03-29 2019-10-03 Nike Innovate C.V. Mousse et procédé de formation de mousse

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Publication number Priority date Publication date Assignee Title
WO2019191067A1 (fr) * 2018-03-29 2019-10-03 Nike Innovate C.V. Mousse et procédé de formation de mousse
US11673300B2 (en) 2018-03-29 2023-06-13 Nike, Inc. Foam and method of forming foam

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