Manufacturing process for foamed articles

Abstract

The present disclosure provides a process. In one embodiment, the process includes providing a foamable composition. The foamable composition includes an ethylene-based elastomer, a blowing agent, and a peroxide. The process includes heating the foamable composition to form a flexible formulation. The flexible formulation has (i) a viscosity (at 0.1 rad / s at 180° C.) of greater than 70,000 Pa·s to 2,000,000 Pa·s, (ii) a loss tangent (at 0.1 rad / s at 180° C.) of 0.2 to less than 2, (iii) a strain hardening exponent (at 0.1 rad / s at 180° C.) of greater than 2.5 to 6, and (iv) an extensional viscosity (at 1 s at 180° C.) of greater than 400,000 Pa-s to 7,000,000 Pa-s. -1 The process includes introducing a flexible compound into a mold having an expandable mold cavity and directional expanding the expandable mold to form a crosslinked foam article. The process includes cooling the crosslinked foam article in the expanded mold and removing the crosslinked foam article from the expandable mold.

Description

[Background technology]

[0001] Foams are widely used in consumer products such as footwear to provide users with a certain degree of comfort and support during use. Compared to using non-foamed materials, foams contribute to lighter footwear and reduced manufacturing costs. Current foam manufacturing methods, such as injection Phylon foaming and cross-linked injection foam molding, require a considerable amount of manual intervention to assemble separate footwear components. These conventional foam manufacturing processes also generate a considerable amount of undesirable foam waste.

[0002] Therefore, in this field, there is a recognized need for improved processes for the manufacture of foam articles, particularly for the manufacture of foam articles in the footwear industry. Furthermore, there is a recognized need for improved processes for the automated manufacture of foam insoles combined with other components of shoes. [Overview of the project]

[0003] This disclosure provides a process. In one embodiment, the process includes providing a foaming composition. The foaming composition comprises an ethylene-based elastomer, a leavening agent, and a peroxide. The process includes heating the foaming composition to form a flexible compound. The flexible compound has (i) a viscosity greater than 70,000 Pa·s and up to 2,000,000 Pa·s (0.1 rad / s at 180°C), (ii) a loss loss tangent of less than 0.2 to 2 (0.1 rad / s at 180°C), (iii) a strain hardening index greater than 2.5 and up to 6, and (iv) an extensional viscosity greater than 400,000 Pa-s and up to 7,000,000 Pa-s (1 rad / s at 180°C). -1 The process includes introducing a flexible compound into a mold having a deployable mold opening, and expanding the deployable mold in a certain direction to form a cross-linked foam article. The process also includes cooling the cross-linked foam article within the deployed mold and removing the cross-linked foam article from the deployable mold.

[0004] definition All references to the Periodic Table of Elements in this Specified Publication and Copyright of the Periodic Table of Elements in 2003 by CRC Press, Inc. Any reference to a group(s) refers to the group(s) as they appear in the Periodic Table of Elements using the IUPAC system for numbering groups. Unless otherwise stated, implied in the context, or customary in the art, all parts and percentages are based on weight. For the purposes of U.S. patent practice, any patent, patent application, or publication referenced herein is incorporated herein by reference in its entirety (or its equivalent U.S. edition).

[0005] Numerical ranges disclosed herein include all values ​​from the lower limit to the upper limit (including boundary values). In the case of a range containing an explicit value (e.g., the range of 1, or 2, or 3 to 5, or 6, or 7), any subrange between two explicit values ​​is included (e.g., the above range 1 to 7 includes subranges 1 to 2, 2 to 6, 5 to 7, 3 to 7, 5 to 6, etc.).

[0006] Unless otherwise stated, implied in the context, or customary in the art, all parts and percentages are based on weight, and all test methods are current as of the filing date of this disclosure.

[0007] As used herein, the term “composition” refers to a mixture of materials comprising the composition, as well as reaction products and decomposition products formed from the materials of the composition.

[0008] The terms “comprising,” “including,” and “having,” and their derivatives, are not intended to exclude the presence of any additional components, processes, or procedures, whether or not they are specifically disclosed. To avoid any doubt, all compositions claimed through the use of the term “comprising” may include any additional additives, auxiliaries, or compounds, whether polymeric or otherwise, unless otherwise stated. In contrast, the term “consisting essentially of” excludes any other components, processes, or procedures from the scope of the following description, except those not essential for operability. The term “consisting of” excludes any components, processes, or procedures not specifically described or listed.

[0009] The term "elastomer" refers to a rubber-like polymer that can be stretched to at least twice its original length and, when the stretching force is released, contracts very rapidly back to almost its original length. Elastomers typically have an elastic modulus of about 10,000 psi (68.95 MPa) or less and an elongation of over 200% in an uncrosslinked state at room temperature using the ASTM D638-72 method.

[0010] Terms such as "ethylene elastomer" refer to elastomers composed of ethylene-based polymers.

[0011] As used herein, “ethylene polymer” is a polymer containing more than 50 weight percent polymerized ethylene monomers (based on the total amount of polymerizable monomers) and optionally containing at least one comonomer.

[0012] As used herein, the terms “foam” or “foam article” refer to a structure constructed from a polymer that includes a plurality of separate gas pockets or foam bubbles completely enclosed by the polymer. As used herein, the terms “foam bubble” or “bubble” refer to a separate space within a foam composition. The foam bubbles are separated or otherwise defined by membrane walls composed of the polymer of the foam composition.

[0013] As used herein, “olefin polymer” or “polyolefin” is a polymer containing more than 50 weight percent of polymerizable olefin monomers (based on the total amount of polymerizable monomers) and optionally containing at least one comonomer. Non-limiting examples of olefin polymers include ethylene polymers and propylene polymers.

[0014] A “polymer” is a compound prepared by polymerizing monomers, whether of the same or different types, which provide multiple and / or repeating “units” or “structural units” that constitute the polymer in a polymeric form. Therefore, the general term polymer encompasses both the term homopolymer, commonly used to refer to polymers prepared from only one type of monomer, and the term copolymer, commonly used to refer to polymers prepared from at least two types of monomers. It also encompasses all forms of copolymers, such as random and block copolymers. The terms “ethylene / α-olefin polymer” and “propylene / α-olefin polymer” refer to the aforementioned copolymers and one or more additional polymerizable α-olefin monomers prepared by polymerizing ethylene or propylene, respectively. While polymers are often referred to as being “made from” one or more specified monomers, such as “based on” a specified monomer or type of monomer, or “containing” a specified monomer content, it should be noted that in this context, the term “monomer” is understood to refer to the polymerization residue of a specified monomer and does not refer to non-polymerized species. Generally, polymers in this specification are referred to as "units" that are the polymerization forms of the corresponding monomers.

[0015] Test method The compression set is the amount of irreversible deformation after the removal of compression at a specific percentage and time, and is measured according to ASTM D395-B under conditions such as 25% compression at room temperature for 24 hours. Three buttons were tested for each foam, and the average value was reported. The compression set was calculated at 30 minutes and 24 hours after depressurization using the following formula (1).

[0016]

number

[0017] The density of the foam article is calculated by measuring the dry weight and the weight of the foam sample immersed in water, and the result is reported in g / cc. The average weight of three foam specimens from one complete foam gives the density ρ according to the following relational expression (2).

[0018]

Number

[0019] The density of the polymer is measured according to ASTM D792, and the result is reported in g / cc at 25°C.

[0020] Differential scanning calorimetry (DSC) is used to measure the melting, crystallization, and glass transition behavior of the polymer over a wide range of temperatures. For example, this analysis is performed using a TA Instruments Q2000 DSC equipped with an RCS (refrigerated cooling system) and an autosampler. During the test, the nitrogen purge gas flow rate used is 50 mL / min. Each sample is melted and compressed at about 175°C into a thin film, and then the melted sample is air-cooled to room temperature (about 25°C). Test specimens of 3 - 10 mg and 6 mm in diameter are extracted from the cooled polymer, weighed, placed in a lightweight aluminum pan (about 50 mg), and crimped and closed. Next, an analysis is performed to determine its thermal properties.

[0021] The thermal behavior of the sample is determined by raising and lowering the sample temperature to create a heat flow versus temperature profile. First, to remove its thermal history, the sample is rapidly heated to 180°C and held isothermally for 3 minutes. Next, the sample is cooled to -80°C at a cooling rate of 10°C / min and held isothermally at -80°C for 3 minutes. Then, the sample is heated to 180°C at a heating rate of 10°C / min (this is the "second heating" gradient). The cooling curve and the second heating curve are recorded. The cooling curve is analyzed by setting the baseline endpoint from the start of crystallization to -20°C. The thermal curve is analyzed by setting the baseline endpoint from -20°C to the end of melting. The values ​​to be determined are the extrapolated melting start point Tm and the extrapolated crystallization start point Tc. Heat of fusion (H f ) (Joules per gram), and the degree of crystallinity % of the polyethylene sample calculated using the following formula: Degree of crystallinity % = ((H f ) / 292J / g)×100.

[0022] From the second heating curve, the heat of fusion (H f The enthalpy of melting (also known as the peak melting temperature) and the peak melting temperature are reported.

[0023] The melting point Tm is first determined from the DSC heating curve by drawing a baseline between the start and end of the melting transition. Next, a tangent line is drawn to the lower temperature data of the melting peak. The point where this line intersects the baseline is the extrapolated melting start point (Tm). This is as described in Bernhard Wunderlich, The Basis of Thermal Analysis, in Thermal Characterization of Polymeric Materials 92, 277-278 (Edith A. Turi ed., 2d ed. 1997).

[0024] The glass transition temperature (Tg) is determined from the DSC heating curve, as described in Bernhard Wunderlich, *The Basis of Thermal Analysis, in Thermal Characterization of Polymeric Materials* 92, 278-279 (Edith A. Turi ed., 2d ed. 1997), where half of the sample has acquired the heat capacity of a liquid. Baselines are drawn below and above the glass transition region and extrapolated through the Tg region. The temperature at which the heat capacity of the sample is midway between these baselines is Tg.

[0025] According to ASTM D638, the elongation (limit) was measured at a tensile speed of 500 mm / min.

[0026] The foam bubble size and aspect ratio were determined as follows: Slices approximately 1 centimeter thick were taken at least 1 centimeter from the foam boundary. The slices were taken in the plane of the foam growth direction, resulting in at least three blocks of similar size. Due to the limited foam dimensions, the center of the foam was not to blame for other characterization methods, so the samples were not taken from the center of the foam. The foam samples were cut with a sharp blade to ensure a properly smooth and uniform surface. Three cross-sectional images were recorded for each foam sample.

[0027] A confocal laser scanning microscope (Keyence VK-X260K) for 3D and profile measurements was equipped with a 10× / 0.3 magnification lens. All image acquisition was performed in surface characteristic mode, which offers high-precision quality and a standard resolution of 1024×768 pixels. Due to the relatively large bubble size of the constrained foam and the unavailability of a 5x magnification lens, an automated stitching procedure was performed to create a 2×2 stitched image of 1920×1441 pixels, providing a sufficient number of bubbles.

[0028] After image acquisition, a filtering process in the Multi File Analyzer v.2.1.2.17 software (Keyence) was necessary to obtain images with sufficient contrast for analysis. Depending on the sample cutting quality, plane fit correction was usually sufficient to correct for arbitrary inclinations. For more difficult surface property adjustments, surface shape correction was recommended. User-defined profiles can be specified in the secant surface (image processing tool in the surface shape correction tab) to eliminate height curvature. Subsequently, the images were converted to a grayscale palette and exported as an image format.

[0029] Two separate macros were developed in the FIJI software and used to analyze bubble size, bubble size distribution, and aspect ratio. Foams produced by conventional cross-linked injection molding were analyzed with a macro that assumed thin bubble walls and had a slightly lower bubble size threshold. "1:1" foam samples had relatively large foam bubbles, so adjustments were made for thicker bubble walls. Both macros followed several identical filtration and thresholding steps required for bubble splitting. These steps automatically led to interactive steps where any missing bubble walls could be manually pulled in if necessary. After verifying that all bubbles had been properly split, bubbles that were not properly separated could be removed from the table.

[0030] The macro output includes a set of parameters such as area, various size descriptors, and shape descriptors. The most representative descriptors define bubble size, bubble size distribution, and bubble aspect ratio. Since foam bubbles are generally not perfectly spherical, the aspect ratio represents the degree to which the foam bubble is elongated. The aspect ratio of a foam bubble is determined by the macro by fitting an ellipse to the segmented foam bubble and defining the major and minor axes of the ellipse. The aspect ratio of a foam bubble is obtained from equation (3).

[0031]

number

[0032] To describe the size of anisotropic particles, the distance between two foci, defined here as the "bubble size," is chosen. An ellipse has two foci located on its major axis, equally spaced from the ellipse center. For any point on the ellipse, the sum of the distances to the foci is always the same. An ellipse is partially defined by the position of the foci relative to the ellipse center (focal length), which can be calculated if the major and minor axis lengths are known. In Equation 4, the distance between the two foci is defined as the bubble size, which corresponds to twice the focal length.

[0033]

number

[0034] Melt flow rate (or MFR) measurements (for propylene polymers) are performed according to ASTM D1238 under gravimetric conditions of 230°C / 2.16 kilograms (kg). Similar to the melt index, the melt flow rate is inversely proportional to the molecular weight of the polymer. Therefore, although the relationship is not linear, the higher the molecular weight, the lower the melt flow rate.

[0035] The melt index (MI or I2) of ethylene-based polymers is measured according to ASTM D 1238 under conditions of 190°C / 2.16 kg, and the results are reported in grams per 10 minutes (g / 10 min).

[0036] Measure the melt viscosity at 177°C (or any other specified temperature) using the Brookfield viscometer model and Brookfield RV-DV-II-Pro viscometer spindle 31. Pour the sample into the chamber, then insert it into the Brookfield Thermosel and secure it in place. The sample chamber has a notch at the bottom that fits into the bottom of the Brookfield Thermosel to ensure that the chamber does not rotate when the spindle is inserted and rotating. Heat the sample (approximately 8-10 grams of resin) to the required temperature until the molten sample is about 1 inch below the top of the sample chamber. Lower the viscometer device and immerse the spindle in the sample chamber. Continue lowering until the bracket of the viscometer is aligned on the Thermosel. Power on the viscometer and set it to operate at a shear rate that yields a torque reading within 40-60 percent of the total torque capacity, based on the viscometer's rpm output. For approximately 15 minutes, the reading will be acquired every minute, or until the value stabilizes, at which point the final reading will be recorded.

[0037] Rebound elasticity is the ratio of the energy required to return to its original shape after deformation with a specific energy. Rebound elasticity is used to measure cushioning in athletic midsoles and is measured according to ASTM D-3574. Foam samples were placed under a 42 mm inner diameter tube according to the indicated scale. A 16 mm diameter metal sphere was dropped onto the sample. The height of the bounce was recorded if the sphere bounced off the side of the cylinder without touching it. For each sample, the average of five successful bounces was recorded.

[0038] Rheology. Characterizing the rheological behavior of compounds modified with different concentrations of dicumyl peroxide. This included (A) shear rheology and (B) extensional viscosity.

[0039] (A) Shear Rheology Compound materials containing only polymer and peroxide in varying filler amounts (no other additives, see Table 2) were compression-molded and cured in a Lab Tech Press LP-S-80. The roll-milled compound deposits were preheated in the molding press at 180°C and 10 bar for 2 minutes, and then fully compressed to a thickness of 2 mm at 120 bar for 8 minutes. After compression and curing were complete, the samples were gradually cooled to 40°C in the press before being removed from the molding plate.

[0040] At least 24 hours after compression molding, 8 mm diameter discs were punched out from the hardened sheet using a cutting die. Shear rheology was measured using a TA instruments HR-2 rheometer equipped with a nitrogen-cooled temperature chamber. All samples were first subjected to strain amplitude sweep experiments of 0.01–10% at 25°C and an angular frequency of 10 radians / second (rad / s) to determine the location of the linear viscoelastic region. Based on this information, a suitable strain amplitude was selected for performing frequency sweeps.

[0041] Next, frequency sweeps are measured at 130, 150, and 180°C to correspond to the temperature of the extensional rheology. The frequency sweep is taken as a logarithmic sweep between 100 rad / s and 0.1 rad / s, which means that data points are recorded at equal intervals on a logarithmic scale.

[0042] (B) Elongation rheology A 0.5 mm thick square plate is compression-molded and cured using a Lab Tech Press LP-S-80. The compound is compressed in a Teflon-coated mold using the following layers: press plate, aluminum plate, aluminum foil, Teflon-coated mold with the sample, aluminum foil, aluminum plate, and press plate. The sheet is preheated at 10 bar for 180 seconds at 180°C, followed by full compression at 120 bar for 360 seconds. The sheet is cooled to 40°C at a constant cooling rate.

[0043] For uniaxial extensional rheology experiments, rectangular specimens measuring 13×12.7 mm were cut from the cured sheet using a cutting die. For each individual sample, the dimensions were also measured using a caliper tool and fed into the rheometer software for each individual measurement. Experiments were performed on an Anton Paar MCR702 equipped with a Convection Temperature Control Device (CTD) 450 oven with a Universal Extensional Fixture (UXF) tool. Measurements were carried out at three different temperatures (130, 150, and 180 °C) and three different extensional strain rates (0.1, 1, and 10 s−1). Prior to the test procedure, a pre-stretch was performed at the corresponding strain rate. Data points were recorded at logarithmically spaced time intervals. At each of these intervals with the corresponding Hencky strains, this yields measurements of extensional stress and extensional viscosity. The extensional viscosity representing the conditions during foaming was found at a strain rate of 1 s -1 and a Hencky strain of 2. The strain hardening index is the balance between the extensional viscosity at a specific time, the strain rate η E + (t), and the extensional viscosity observed when there is no strain hardening. The strain hardening index (SHI) is calculated at these conditions by Equation (5).

[0044] [Equation number] where η E + (t) is the extensional viscosity (Pascal seconds (Pa·s)) measured at a Hencky strain of 2 and a strain rate of 1 s -1 which is reached at time = 2 s, and (3η s * (ω = 1 / t)) is the shear complex viscosity (Pa·s) measured at a frequency of 1 / 2.

[0045] Shore A hardness was the average of five readings (5-second latent) measured across the entire surface of the sample according to ASTM D2240. [Modes for carrying out the invention]

[0046] This disclosure provides a process. In one embodiment, the process includes providing a foaming composition. The foaming composition comprises an ethylene-based elastomer, a leavening agent, and a peroxide (and optional additives). The process involves heating the foaming composition, (i) Viscosity of over 70,000 Pa.s to 2,000,000 Pa.s (0.1 rad / s at 180°C), (ii) Loss loss tangent of 0.2 to less than 2 (0.1 rad / s at 180°C), (iii) Strain hardening index greater than 2.5 to 6, (iv) Extensional viscosity of over 400,000 Pa-s to 7,000,000 Pa-s (at 180°C, 1 s) -1 The process includes forming a flexible compound having ),, and introducing the flexible compound into a mold having a deployable mold opening, and deploying the deployable mold in a certain direction to form a crosslinked foam article. The process also includes cooling the crosslinked foam article within the deployed mold and removing the crosslinked foam article from the deployable mold.

[0047] A. Foaming composition This process involves providing a foaming composition. As used herein, the term “foaming composition” is a mixture of (i) an ethylene-based elastomer, (ii) a leavening agent, (iii) a peroxide, and (iv) any additives. The final crosslinked foam article is a product obtained from the foaming composition subjected to the foaming process.

[0048] Ethylene-based elastomers are selected from ethylene vinyl acetate (EVA), polyolefin elastomers, ethylene / α multiblock copolymers, and combinations thereof.

[0049] In one embodiment, the ethylene-based elastomer is an ethylene / α-olefin multiblock copolymer. The term “ethylene / α-olefin multiblock copolymer” refers to an ethylene / C4-C8α-olefin multiblock copolymer comprising ethylene in its polymer form and one copolymerizable C4-C8α-olefin comonomer (and optionally additives), wherein the polymer is characterized by multiple blocks or divisions of two polymerized monomer units with different chemical or physical properties, and the blocks are linearly joined (or covalently bonded). That is, the polymer contains chemically distinct units whose ends are joined to a polymerized ethylenically functional group. Ethylene / α-olefin multiblock copolymers include block copolymers having two blocks (diblocks) and more than two blocks (multiblocks). The C4-C8 α-olefin is selected from butene, hexene, and octene. Ethylene / α-olefin multiblock copolymers do not contain styrene (i.e., styrene-free), and / or vinyl aromatic monomers, and / or conjugated dienes, or otherwise exclude them. When referring to the amount of "ethylene" or "comonomer" in a copolymer, this is understood to refer to its polymerization unit. In some embodiments, an ethylene / α-olefin multiblock copolymer may be represented by the following formula: (AB) n;wherein n is at least 1, preferably an integer greater than 1, for example 2, 3, 4, 5, 10, 15, 20, 30, 40, 50, 60, 70, 80, 90, 100, or more, where "A" represents a hard block or segment, and "B" represents a soft block or segment. A and B are linked or covalently bonded in a substantially linear manner, or in a linear style, as opposed to a substantially branched or substantially star-shaped arrangement. In other embodiments, A blocks and B blocks are randomly distributed along the polymer chain. In other words, block copolymers do not typically have a structure such as: AAA-AA-BBB-BB. In one embodiment, the ethylene / α-olefin multiblock copolymer does not have a third type of block containing different comonomers. In another embodiment, each of block A and block B has monomers or comonomers substantially randomly distributed within the block. In other words, neither Block A nor Block B contains two or more sub-sections (or sub-blocks) of a distinct composition, such as an advanced section, which has a substantially different composition from the rest of the block.

[0050] In embodiments, ethylene constitutes a majority mole fraction of the total ethylene / α-olefin multiblock copolymer, i.e., ethylene constitutes at least 50% by weight of the total ethylene / α-olefin multiblock copolymer. More preferably, ethylene, together with the substantially remaining portion of the whole ethylene / α-olefin multiblock copolymer containing C4-C8 α-olefin comonomers, constitutes at least 60% by weight, at least 70% by weight, or at least 80% by weight. In embodiments, the ethylene / α-olefin multiblock copolymer contains 50% to 90% by weight of ethylene, or 60% to 85% by weight of ethylene, or 65% to 80% by weight of ethylene. In many ethylene / octene multiblock copolymers, the composition contains an ethylene content of more than 80% by weight of the total ethylene / octene multiblock copolymer and an octene content of 10% to 15% by weight or 15% to 20% by weight of the total multiblock copolymer.

[0051] Ethylene / α-olefin multiblock copolymers contain varying amounts of “hard” and “soft” sections. A “hard” section is a block of polymerization units in which ethylene is present in an amount of more than 90% by weight, or 95% by weight, or more than 95% by weight, or more than 98% by weight, up to a maximum of 100% by weight, based on the weight of the polymer. In other words, the comonomer content (content of monomers other than ethylene) in a hard section is less than 10% by weight, or 5% by weight, or less than 5% by weight, or less than 2% by weight, based on the weight of the polymer, and can be as low as zero. In some embodiments, a hard section contains all or substantially all units derived from ethylene. A “soft” section is a block of polymerization units in which the comonomer content (content of monomers other than ethylene) is more than 5% by weight, or more than 8% by weight, more than 10% by weight, or more than 15% by weight, based on the weight of the polymer. In the embodiment, the comonomer content in the soft portion is greater than 20% by weight, greater than 25% by weight, greater than 30% by weight, greater than 35% by weight, greater than 40% by weight, greater than 45% by weight, greater than 50% by weight, or greater than 60% by weight, and can be up to 100% by weight.

[0052] The soft portion may be present in the ethylene / α-olefin multiblock copolymer at a concentration of 1% to 99% by weight of the total weight, or at a concentration of 5% to 95%, 10% to 90%, 15% to 85%, 20% to 80%, 25% to 75%, 30% to 70%, 35% to 65%, 40% to 60%, or 45% to 55% by weight of the total weight of the ethylene / α-olefin multiblock copolymer. Conversely, the hard portion may be present in a similar range. The weight percentages of the soft portion and the hard portion can be calculated based on data obtained from DSC or NMR. Such methods and calculations are disclosed, for example, in U.S. Patent No. 7,608,668, titled "Ethylene / α-Olefin Block Inter-polymers," filed on 15 March 2006 in the names of Colin LPShan, Lonnie Hazlitt, et al., and assigned to Dow Global Technologies Inc., the disclosure is incorporated herein by reference in its entirety. In particular, the weight percentages of the hard and soft portions and the comonomer content may be determined as described in columns 57-63 of U.S. Patent No. 7,608,668.

[0053] Ethylene / α-olefin multiblock copolymers contain two or more linearly bonded (or covalently bonded) chemically distinct regions or sections (referred to as "blocks"), that is, chemically distinct units whose ends are bonded to the polymeric ethylenic functional group rather than being pendanted or grafted. In embodiments, blocks differ in the amount or type of incorporated comonomers, density, degree of crystallinity, microcrystalline size that may result from polymers of such composition, type or degree of stereoregularity (isotactic or syndiotactic), positional regularity or positional irregularity, amount of branching (including long-chain branching or hyperbranching), uniformity, or any other chemical or physical properties. Compared to conventional block interpolymers, which include interpolymers produced by continuous monomer addition, fluid catalysts, or anionic polymerization techniques, the ethylene / α-olefin multiblock copolymers of the present invention are characterized in one embodiment by a unique distribution of both polymer polydispersity (PDI or Mw / Mn or MWD), polydisperse block length distribution, and / or polydisperse block number distribution due to the effect of shuttle agents combined with multiple catalysts used in their preparation.

[0054] In one embodiment, the ethylene / α-olefin multiblock copolymer is produced in a continuous process and has a polydispersity index (Mw / Mn) of 1.7–3.5, or 1.8–3, or 1.8–2.5, or 1.8–2.2. When produced in a batch or semi-batch process, the ethylene / α-olefin multiblock copolymer has an Mw / Mn of 1.0–3.5, or 1.3–3, or 1.4–2.5, or 1.4–2.

[0055] Furthermore, the ethylene / α-olefin multiblock copolymer has a PDI (or Mw / Mn) that conforms to a Schultz-Flory distribution rather than a Poisson distribution. This ethylene / α-olefin multiblock copolymer has both a polydisperse block distribution and a polydisperse block size distribution. This results in polymer products with improved, identifiable physical properties. The theoretical advantages of the polydisperse block distribution have already been modeled and discussed in Potemkin, Physical Review E (1998) 57(6), pp. 6902-6912, and Dobrynin, J. Chem. Phvs. (1997) 107(21), pp. 9234-9238.

[0056] In one embodiment, the ethylene / α-olefin multiblock copolymer has a most probable distribution of block lengths.

[0057] In further embodiments, the ethylene / α-olefin multiblock copolymers of the present disclosure, particularly those produced in a continuous solution polymerization reactor, have a most probable distribution of block lengths. In one embodiment of the present disclosure, the ethylene / α-olefin multiblock copolymer is defined to have the following: (A) It has a Mw / Mn of approximately 1.7 to approximately 3.5, at least one melting point Tm (temperature in degrees Celsius), and density d (grams / cubic centimeter), and the values ​​of Tm and d are related as follows: Tm>-2002.9+4538.5(d)-2422.2(d) 2 Corresponding to; and / or (B) It has a Mw / Mn of approximately 1.7 to 3.5, and is characterized by a heat of fusion ΔH (J / g) and a delta amount ΔT (Celsius temperature) defined as the temperature difference between the highest DSC peak and the highest crystallization analysis fraction ("CRYSTAF") peak, with the values ​​of ΔT and ΔH relating as follows: If ΔH is greater than zero and at most 130 J / g, then ΔT > -0.1299ΔH + 62.81. If ΔH is greater than 130 J / g, then ΔT ≥ 48°C. It has, The CRYSTAF peak is determined using at least 5 percent of the cumulative polymer, and if less than 5 percent of the polymer has an identifiable CRYSTAF peak, the CRYSTAF temperature is 30°C, and / or (C) When a compression-molded film of ethylene / α-olefin interpolymer has a strain of 300 percent and an elastic recovery Re (percent) in one cycle, and has a density d (grams / cubic centimeter), and the ethylene / α-olefin interpolymer is substantially free of crosslinking phases, the values ​​of Re and d have the following relationship: Re>1481-1629(d) Satisfying, and / or (D) Having a molecular fraction that elutes at 40°C to 130°C when fractionated using TREF, characterized in that the fraction has a comonomer molar content at least 5 percent higher than an equivalent random ethylene interpolymer fraction that elutes at the same temperature, the equivalent random ethylene interpolymer having the same comonomers and having a melt index, density, and comonomer molar content (based on the whole polymer) within 10 percent of that of the ethylene / α-olefin interpolymer, and / or (E) It has a storage modulus G'(25°C) at 25°C and a storage modulus G'(100°C) at 100°C, and the ratio of G'(25°C) to G'(100°C) is in the range of approximately 1:1 to approximately 9:1.

[0058] Ethylene / α-olefin multiblock copolymer may also have the following: (F) A molecular fraction that elutes at 40°C to 130°C when fractionated using TREF, characterized in that the fraction has a block index of at least 0.5 and a maximum of 1 and a molecular weight distribution Mw / Mn greater than 1.3, and / or (G) An average block index greater than zero and with a maximum of 1.0, and a molecular weight distribution Mw / Mn greater than 1.3.

[0059] It is understood that ethylene / α-olefin multiblock copolymers may have one, some, all, or any combination of properties (A) to (G). The block index may be determined as detailed in U.S. Patent No. 7,608,668, which is incorporated herein by reference for that purpose. Analytical methods for determining properties (A) to (G) are disclosed, for example, in columns 31, lines 26 to 35, line 44 of U.S. Patent No. 7,608,668, which is incorporated herein by reference for that purpose.

[0060] In one embodiment, an ethylene / α-olefin multiblock copolymer is defined as having hard and soft sections, being styrene-free, and consisting only of (i) ethylene and (ii) C4-C8α-olefin or C8α-olefin (and any additives), having a Mw / Mn ratio of 1.7 to 3.5, at least one melting point Tm (temperature in degrees Celsius), and density d (grams / cubic centimeter), where the values ​​of Tm and d correspond to the following relationship: Tm>-2002.9+4538.5(d)-2422.2(d) 2 , In the formula, density d is 0.850 g / cc, or 0.860 g / cc, or 0.870 g / cc to 0.875 g / cc, or 0.877 g / cc, or 0.880 g / cc, or 0.890 g / cc, and melting point Tm is 110°C, or 115°C, or 120°C to 125°C, or 130°C, or 135°C.

[0061] In one embodiment, the ethylene / α-olefin multiblock copolymer is an ethylene / 1-octene multiblock copolymer (consisting only of ethylene and octene comonomers) having one, some, or all of the following properties: (i) Mw / Mn in 1.7 or 1.8 to 2.2, or 2.5, or 3.5, and / or (ii) Densities of 0.860 g / cc or 0.865 g / cc to 0.870 g / cc, 0.877 g / cc, or 0.880 g / cc, and / or (iii) a melting point Tm of 115°C, or 118°C, or 119°C, or 120°C to 120°C, or 123°C, or 125°C, and / or (iv) Melt index (MI) of 0.1 g / 10 min or 0.5 g / 10 min to 1.0 g / 10 min, or 2.0 g / 10 min, or 5 g / 10 min, or 10 g / 10 min, and / or (v) 50-85% by weight of soft portion and 40-15% by weight of hard portion (based on the total weight of ethylene / octene multiblock copolymer), and / or (iv) 10 mol%, 13 mol%, 14 mol%, 15 mol%, to 16 mol%, 17 mol%, 18 mol%, 19 mol%, or 20 mol% of octene in the soft portion, and / or (vii) 0.5 mol%, 1.0 mol%, 2.0 mol%, 3.0 mol%, to 4.0 mol%, 5 mol%, 6 mol%, 7 mol%, or 9 mol% of octene in the hard portion, and / or (viii) When measured according to ASTM D 1708, 300% / min at 21°C ·1 Elastic recovery (Re) of 50%, 60%, 70%, 80%, or 90% in the deformation rate, and / or (ix) Polydispersive distribution of the blocks and polydispersive distribution of the block size (hereinafter referred to as properties (i) to (ix) of the multiblock copolymer).

[0062] In one embodiment, the ethylene / α-olefin multiblock copolymer is an ethylene / octene multiblock copolymer. The ethylene / octene multiblock copolymer is available from The Dow Chemical Company (Midland, Michigan, USA) under the trade name INFUSE®.

[0063] Ethylene / α-olefin multiblock copolymers may be produced via chain shuttle processes, such as those described in U.S. Patent No. 7,858,706, which is incorporated herein by reference. Particularly preferred chain shuttles and related information are listed in columns 16, lines 39 to 19, line 44. Preferred catalysts are described in columns 19, lines 45 to 46, line 19, and preferred co-catalysts are described in columns 46, lines 20 to 51, line 28. The process is described throughout this document, but in particular in columns 51, lines 29 to 54, line 56. The process is also described, for example, in U.S. Patents No. 7,608,668, 7,893,166, and 7,947,793.

[0064] The base ethylene / α-olefin multiblock copolymer may contain more than 1 ethylene / α-olefin multiblock copolymer.

[0065] The foaming composition contains a leavening agent. The leavening agent may be a physical leavening agent or a chemical leavening agent. Suitable physical leavening agents, though not limited to certain examples, include nitrogen, carbon dioxide, hydrocarbons (e.g., propane), chlorofluorocarbons, noble gases, and combinations thereof.

[0066] In one embodiment, the leavening agent is a chemical leavening agent. The chemical leavening agent generates one or more gases by thermal decomposition in the foaming process. Examples of chemical leavening agents include (but are not limited to) sodium bicarbonate, sodium borohydride, azodicarbonamide, azodiisobutyronitrile, barium azodicarboxylate, N,N'-dimethyl-N,N'-dinitrosoterephthalamide, and benzenesulfonyl hydrazide, 4,4-oxybenzenesulfonyl semicarbazide, 4,4'-oxybis(benzenesulfonic acid) dihydrazide, and p-toluenesulfonyl semicarbazide, trihydrazinotriazine, and mixtures of citric acid and sodium bicarbonate.

[0067] In one embodiment, the chemical swelling agent is an azodicarbonamide.

[0068] The foaming composition contains peroxides such as organic peroxides. The peroxides are crosslinking agents in the foaming composition. Suitable organic peroxides, though not limited to specific examples, include alkyl peroxides, aryl peroxides, peroxyesters, peroxycarbonates, diacyl peroxides, peroxyketals, cyclic peroxides, and combinations thereof.

[0069] In one embodiment, the organic peroxide is dicumyl peroxide, t-butylisopropylidene peroxybenzene, 1,1-di-t-butylperoxy-3,3,5-trimethylcyclohexane, 2,5-dimethyl-2,5-di(t-butylperoxy)hexane, t-butyl cumyl peroxide, di-t-butyl peroxide, 2,5-dimethyl-2,5-di-(t-butylperoxy)hexine, or a combination thereof.

[0070] In one embodiment, the organic peroxide is dicumyl peroxide.

[0071] The foaming composition contains one or more optional additives. Non-limiting examples of suitable additives include leavening agent activators (zinc oxide, zinc stearate, zinc sulfide), stability control agents, nucleating agents, fillers (talc, calcium carbonate, nanoclay, carbon nanotubes, carbon nanofibers), pigments (zinc oxide), antioxidants, acid scavengers, UV stabilizers, flame retardants, lubricants, processing aids, extrusion aids, and combinations thereof.

[0072] The components of the foaming composition are mixed in a mixer or extruder to uniformly disperse a leavening agent, peroxide, and any additives(s) throughout the ethylene-based elastomer matrix. The foaming composition is then pelletized, cut into pieces, or cut into predetermined shapes for introduction into a mold for foaming.

[0073] In one embodiment, an ethylene-based elastomer, a chemical leavening agent, an organic peroxide, and an optional additive are melted and mixed in a closed mixer to melt the polymer and blend the chemical leavening agent, organic peroxide, and optional additive into the molten mixture. The molten mixture is cut into a predetermined shape (i.e., a shape that completely covers the bottom of the mold hole) and introduced into the mold hole as further described below.

[0074] This process involves heating the foaming composition. Heating is performed by placing pellets (or pieces) of the foaming composition in (i) an oven, (ii) a mold, or (iii) a combination of (i) and (ii). Heating is controlled to occur at a sufficiently high temperature (above ambient temperature or above 25°C) for a sufficient time to form the foaming composition into a flexible formulation, without decomposing the leavening agent or the peroxides present in the flexible formulation. Heating the foaming composition forms a flexible formulation (composed of the components of the foaming composition) with the following properties: (i) Viscosity of over 70,000 Pa.s to 2,000,000 Pa.s (0.1 rad / s at 180°C), (ii) Loss loss tangent of 0.2 to less than 2 (0.1 rad / s at 180°C), (iii) Strain hardening index greater than 2.5 to 6, and (iv) Extensional viscosity of over 400,000 Pa-s to 7,000,000 Pa-s (at 180°C, 1 s) -1 ), has.

[0075] This process involves introducing a flexible compound into a mold having an expandable mold opening. As shown in Figure 1, the mold 10 includes a housing 12 and a movable part 14 that is operably communicating with the housing 12. The movable part 14 moves in a specific direction, i.e., along the z-axis only. The movement between the movable part 14 and the housing 12 does not allow movement along the x-axis and does not allow movement along the y-axis. Figure 1 shows the flexible compound 16 in the mold opening and the movable part 14 in a first position A, which is a closed position. With the movable part 14 in the closed position, the mold 10 is heated to a temperature that initiates or otherwise induces peroxides (a temperature that decomposes peroxides) and a temperature that initiates or otherwise induces chemical expanders (if chemical expanders are used). In one embodiment, when the movable part 14 is in the closed position A, pressure (positive or negative) is also applied to the mold opening to remove any air present in the mold opening and / or in the flexible compound 16.

[0076] This process involves deploying a deployable mold in a specific direction to form a cross-linked foam article. Figure 2 shows the movable part 14 moved to a second position B or otherwise deployed position. Moving the movable part 14 to the deployed position B expands or otherwise increases the volume of the mold cavity, thereby expanding and foaming the flexible compound. The expanding and foaming flexible compound fills or completely fills the expanded volume of the mold cavity, forming a cross-linked foam article 18. The resulting cross-linked foam article 18 takes the shape of the expanded mold cavity. As described above, the movable part 14 moves only along the z-axis, thereby limiting the expansion of the foamable flexible compound along a single axis only along the z-axis. During expansion and foaming, the flexible compound 16 (and the resulting cross-linked foam article 18) is not exposed to the surrounding environment. The mold expansion in a specific direction forms anisotropic bubbles in the cross-linked foam article. An "anisotropic bubble" is a foam bubble with an asymmetric shape, thereby the length of the bubble is longer in one dimension than the length of the bubble in the other dimension.

[0077] This process includes cooling the cross-linked foam article 18 within the expanded mold. Cooling is performed while the movable part 14 remains in the deployed position B. Cooling is performed for a sufficient amount of time for the cross-linked foam article to solidify and harden. In one embodiment, this process includes cooling the cross-linked foam article to a temperature of 15°C to 25°C.

[0078] This process has the following characteristics: (i) an average bubble size of 150 micrometers to 275 micrometers, and / or (ii) an average aspect ratio of 1.5 to 2.0, and / or (iii) Density of 0.170 g / cc to 0.250 g / cc (with skin), and / or (iv) Compression set rate (24 hours) of 5% to less than 10%, and / or (i) Shore A hardness of 10-25, and / or (vi) Form a cross-linked foam article 18 having one, some, or all of the following rebound elasticity: 30% to 50%.

[0079] In one embodiment, this process is A foaming composition, (i) 88% to 90% by weight, An ethylene / octene multiblock copolymer having a density of 0.870 g / cc to 0.89 g / cc and a melt index of 1.0 g / 10 min to 5.0 g / 10 min or 5.0 g / 10 min, an ethylene-based elastomer. (ii) Chemical leavening agents, and (iii) The present invention provides a foaming composition comprising 0.5% to 3.0% by weight, or 0.7% to 2.7% by weight, of an organic peroxide. The weight percentage is based on the total weight of the foaming composition. The process involves heating the foaming composition, (i) Viscosity of over 70,000 Pa.s to 2,000,000 Pa.s (0.1 rad / s at 180°C), (ii) Loss loss tangent of 0.2 to less than 2 (0.1 rad / s at 180°C), (iii) Strain hardening index greater than 2.5 to 6, (iv) The process includes forming a flexible compound having an extensional viscosity of more than 400,000 Pa-s and up to 7,000,000 Pa-s (1 s-1 at 180°C). This process involves introducing the flexible compound into a mold having mold holes that can be unfolded, Forming a cross-linked foam article by unfolding a deployable mold in a certain direction, Cooling the cross-linked foam article within the deployed mold, The process further includes forming a cross-linked foam article, and the cross-linked foam article (hereinafter referred to as foam 1) is: (i) an average bubble size of 150 micrometers to 275 micrometers, or 200 micrometers to 260 micrometers, and / or (ii) an average aspect ratio of 1.5 to 2.0, or 1.7 to 1.9, and / or (iii) Density of 0.170 g / cc to 0.250 g / cc (with skin), and / or (iv) Compression set rate (24 hours) of 5% to less than 10%, and / or (v) Shore A hardness of 10-25, and / or (vi) It has rebound elasticity of 30% to 50%.

[0080] In one embodiment, the process includes placing a shoe component (such as a pre-foamed component) in a mold cavity and introducing a flexible compound having the aforementioned properties (i) to (iv) onto the pre-foamed component and in direct contact with it. The process includes heating, expansion in a certain direction, cooling, and forming a cross-linked foam article (foam 1) directly on the pre-foamed component. In this way, the foam 1 is foamed onto the pre-foamed component or otherwise fused.

[0081] The crosslinked foam articles of the present invention can be molded and formed as footwear articles, or incorporated into footwear articles. Non-limiting embodiments of footwear articles suitable for the crosslinked foam articles of the present invention include shoe outsoles, shoe insoles, shoe midsoles, and combinations thereof.

[0082] Some embodiments of this disclosure are described in detail below, without limitation, as examples. [Examples]

[0083] The raw materials used in the preparation of the crosslinked foam composition, adhesive layer, and substrate of the present invention in the examples of the present invention ("IE") are provided in Table 1 below.

[0084] [Table 1]

[0085] 1. Preparation of the composition INFUSE® 9100 or INFUSE® 9500 (an ethylene-based elastomer, which is an ethylene / octene multiblock copolymer) is added to a collin roll machine with a front roll at 130°C, a back roll at 125°C, and a rotation speed of 8 revolutions / minute (rpm). Zinc oxide, zinc stearate, and CaCO3 fillers are then added when the ethylene / octene multiblock copolymer is completely melted. Leavening agents and peroxides are added last, after the fillers and leavening agent activators have been uniformly incorporated into the ethylene / octene multiblock copolymer to form a foaming composition. The foaming compositions are provided in Table 2 below.

[0086] [Table 2] CS - Comparative sample, IE - Example of the present invention

[0087] 2. Foaming procedure The foaming procedures for the comparative sample (CS) and the embodiment of the present invention (IE) are shown in Table 3 below.

[0088] [Table 3]

[0089] Table 4 provides the properties of the foaming composition, the flexible compound, and the crosslinked foam article and comparative sample of the present invention.

[0090] [Table 4] IE = Example of the present invention, CS = Comparative sample

[0091] The process of the present invention enables the production of crosslinked foam articles using lower concentrations of peroxide (0.5% to 3.0% by weight, or 0.7% to 2.7% by weight), while still achieving foam properties suitable for use in footwear, particularly in soles. The process also produces embodiments of the present invention of crosslinked foam articles having a larger aspect ratio (1.72 to 1.88) when combined with a larger average cell size (206 to 257 micrometers) than comparative samples (aspect ratio 1.58 to 1.65 and average cell size 94 to 277 micrometers).

[0092] The process of the present invention enables the production of crosslinked foam articles in a single (1:1) foaming step without requiring an additional foam compression step, such as in the Phylon foaming process. A foam component can be placed in a mold cavity, the flexible compound of the present invention can be placed on top of it, and then foamed and crosslinked in a specific direction to directly foam the crosslinked foam article of the present invention on the pre-inserted foam component.

[0093] This disclosure is not limited to the embodiments and examples contained herein, but is particularly intended to include some embodiments and modified forms of those embodiments, including combinations of elements of different embodiments, to the extent that they fall within the scope of the following claims. The invention described in the original claims of this application is listed below. [1] A process, To provide a foaming composition comprising an ethylene-based elastomer, a leavening agent, and a peroxide, The foaming composition is heated, (i) Viscosity of over 70,000 Pa.s to 2,000,000 Pa.s (0.1 rad / s at 180°C), (ii) Loss loss tangent of 0.2 to less than 2 (0.1 rad / s at 180°C), (iii) Strain hardening index greater than 2.5 to 6, (iv) Extensional viscosity of over 400,000 Pa-s to 7,000,000 Pa-s (at 180°C, 1 s) -1 ), forming a flexible compound having, The aforementioned flexible compound is introduced into a mold having a mold opening that can be expanded, The aforementioned deployable mold is deployed in a certain direction to form a cross-linked foam article, Cooling the cross-linked foam article within the unfolded mold, Removing the crosslinked foam article from the unfoldable mold, A process comprising forming a cross-linked foam article having an average aspect ratio of 1.7 to 1.9. [2] The process according to [1], which includes removing air from the mold hole before the deployment. [3] Including forming a crosslinked foam article, the crosslinked foam article is (i) Average bubble size of 150 micrometers to 275 micrometers, (ii) Density of 0.170 g / cc to 0.250 g / cc (with skin), or (iii) A compression set of less than 5% to 10% (24 hours), or (iv) Shore A hardness of 10-25, or (v) The process according to [1] or [2], having rebound elasticity of 30% to 50%. [4] A foaming composition, An ethylene / octene multiblock copolymer having a density of 0.870 g / cc to 0.890 g / cc and a melt index of 1.0 g / 10 min to 5.0 g / 10 min, comprising 88% to 90% by weight of an ethylene-based elastomer, Chemical swelling agent, To provide a foaming composition containing 0.5% to 3.0% by weight of an organic peroxide, First, the foaming composition is heated, (i) Viscosity of over 70,000 Pa.s to 2,000,000 Pa.s (0.1 rad / s at 180°C), (ii) Loss loss tangent of 0.2 to less than 2 (0.1 rad / s at 180°C), (iii) Strain hardening index greater than 2.5 to 6, (iv) Extensional viscosity of over 400,000 Pa-s to 7,000,000 Pa-s (at 180°C, 1 s) -1 ), forming a flexible compound having, The aforementioned flexible compound is heated a second time, The aforementioned flexible compound is introduced into a mold having a mold opening that can be expanded, The mold is closed, and the flexible compound inside the closed mold is heated for the third time. The mold is opened, and the expandable mold is unfolded in one direction only along the z-axis to form a cross-linked foam article. The process includes forming a crosslinked foam article, wherein the crosslinked foam article is (i) Average bubble size of 150 micrometers to 275 micrometers, and (ii) an average aspect ratio of 1.7 to 1.9, and (iii) Density of 0.170 g / cc to 0.250 g / cc (with skin), and (iv) Compression set rate of 5% to less than 10% (24 hours), (v) Shore A hardness of 10-25, and (vi) The process described in [3] having rebound elasticity of 30% to 50%. [5] The process according to any one of [1] to [4], comprising first heating the foaming composition at a temperature of 110°C for 15 minutes to form the flexible compound. [6] The process according to [5], further comprising heating the flexible compound in an oven at a temperature of 110°C for 15 minutes for a second time. [7] Placing the pre-foamed parts in the mold hole, The flexible compound is introduced by bringing it into direct contact with the pre-foamed component, The process according to any one of [4] to [6], comprising directly forming a cross-linked foam article on the pre-foamed part.

Claims

1. An ethylene-based elastomer in an ethylene / octene multiblock copolymer having a density of 0.870 g / cc to 0.890 g / cc and a melt index of 1.0 g / 10 min to 5.0 g / 10 min, in an amount of 88% to 90% by weight, Chemical swelling agent, 0.5% to 3.0% by weight of organic peroxide and To provide a foaming composition containing, The foaming composition is heated, (i) Viscosity greater than 70,000 Pa·s to 2,000,000 Pa·s (0.1 rad / s at 180°C), (ii) Loss tangent of 0.2 to less than 2 (0.1 rad / s at 180°C), (iii) Strain hardening index greater than 2.5 to 6, (iv) Extensional viscosity of over 400,000 Pa-s to 7,000,000 Pa-s (at 180°C) －１ To form a flexible compound having, The aforementioned flexible compound is introduced into a mold having a mold opening that can be expanded, The aforementioned deployable mold is deployed in a certain direction to form a cross-linked foam article, Cooling the cross-linked foam article within the unfolded mold, Removing the crosslinked foam article from the unfoldable mold, To form a cross-linked foam article having an average aspect ratio of 1.7 to 1.9, A process that includes this.

2. The process according to claim 1, further comprising removing air from the mold opening before the aforementioned deployment.

3. The process includes forming a crosslinked foam article, wherein the crosslinked foam article is (i) Average bubble size of 150 micrometers to 275 micrometers, (ii) Density of 0.170 g / cc to 0.250 g / cc (with skin), or (iii) Compression set rate of 5% to less than 10% (24 hours), (iv) Shore A hardness of 10-25, or (v) The process according to any one of claims 1 to 2, having rebound elasticity of 30% to 50%.

4. A foaming composition, An ethylene / octene multiblock copolymer having a density of 0.870 g / cc to 0.890 g / cc and a melt index of 1.0 g / 10 min to 5.0 g / 10 min, comprising 88% to 90% by weight of an ethylene-based elastomer, Chemical swelling agent, To provide a foaming composition containing 0.5% to 3.0% by weight of an organic peroxide, First, the foaming composition is heated, (i) Viscosity greater than 70,000 Pa·s to 2,000,000 Pa·s (0.1 rad / s at 180°C), (ii) Loss tangent of 0.2 to less than 2 (0.1 rad / s at 180°C), (iii) Strain hardening index greater than 2.5 to 6, (iv) Extensional viscosity of over 400,000 Pa-s to 7,000,000 Pa-s (at 180°C) －１ To form a flexible compound having, The aforementioned flexible compound is heated a second time, The aforementioned flexible compound is introduced into a mold having a mold opening that can be expanded, The mold is closed, and the flexible compound inside the closed mold is heated for the third time. The process involves opening the mold and unfolding the expandable mold in one direction only along the z-axis to form a cross-linked foam article. The process includes forming a crosslinked foam article, wherein the crosslinked foam article is (i) Average bubble size of 150 micrometers to 275 micrometers, and (ii) Average aspect ratio of 1.7 to 1.9, and (iii) Density of 0.170 g / cc to 0.250 g / cc (with skin), and (iv) Compression set rate of 5% to less than 10% (24 hours), and (v) Shore A hardness of 10 to 25, (vi) The process according to claim 3, having rebound elasticity of 30% to 50%.

5. The process according to any one of claims 1 to 4, comprising first heating the foaming composition at a temperature of 110°C for 15 minutes to form the flexible compound.

6. The process according to claim 5, further comprising heating the softening compound a second time in an oven at a temperature of 110°C for 15 minutes.

7. Placing the pre-foamed parts in the mold hole, The flexible compound is introduced by bringing it into direct contact with the pre-foamed component, The process according to any one of claims 4 to 6, comprising directly forming a crosslinked foam article on the pre-foamed part.

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