Recyclable crosslinked polymer foam and use thereof

Abstract

A recyclable crosslinked polymer foam material includes the reaction product of 100 parts by mass of a polymer material, 0.1 to 10 parts by mass of a crosslinking agent, and 0.1 to 5 parts by mass of a radical initiator. The crosslinking agent is represented by the formula: wherein R is an alkylene group having 2 to 10 carbon atoms, an arylene group having 6 to 18 carbon atoms, or a cycloalkylene group having 6 to 18 carbon atoms.

Description

TECHNICAL FIELD

[0001] The present invention relates to a recyclable crosslinked polymer foam, a reusable footwear component using the same, and a reversed material obtained therefrom. BACKGROUND

[0002] Ethylene vinyl acetate (EVA) copolymer foam is a commonly used material for a midsole in footwear because it is lightweight and provides desirable cushioning performance. However, it is known to lack durability. In order to improve durability, the EVA foam is highly crosslinked, making it non-recyclable, resulting in a large amount of waste. Although alternative raw materials such as thermoplastic polyurethane (TPU) are recyclable, there are disadvantages such as high raw material costs and high equipment replacement costs.

[0003] Although the existing EVA foams have been adequate for their intended purposes, they have not been wholly satisfactory in all respects. In particular, there remains an unmet need for EVA foams having recyclability and appropriate properties in order to further utilize in the shoemaking industry and other fields. SUMMARY

[0004] Embodiments of the present invention provide a recyclable crosslinked polymer foam including a reaction product of: 100 parts by mass of a polymer material; 0.1 to 10 parts by mass of a crosslinking agent; and 0.1 to 5 parts by mass of a radical initiator, wherein the crosslinking agent is represented by the following formula:

[0005]

[0006] wherein R is an alkylene group having 2 to 10 carbon atoms, an arylene group having 6 to 18 carbon atoms, or a cycloalkylene group having 6 to 18 carbon atoms.

[0007] In some embodiments, the polymer material is an ethylene-based polymer, a polyolefin polymer, a polyethylene polymer, a propylene polymer, a styrene polymer, an ethylene-propylene-diene (EPDM) rubber, a natural rubber (NR), an isopropylene rubber (IR), a copolymer thereof, or a combination thereof.

[0008] In some embodiments, the polymer material has a vinyl acetate content of 3 to 45 mass% and a melt index of 0.01 to 400 g / 10 min.

[0009] In some embodiments, the crosslinking agent comprises urethane bis-TEMPO (2,2,6,6-tetramethylpiperidinyloxy).

[0010] In some embodiments, the urethane bis-TEMPO comprises 4,4’-diphenylmethane diisocyanate urethane bis-TEMPO or 4,4’-diisocyanato dicyclohexylmethane urethane bis-TEMPO.

[0011] In some embodiments, the free radical initiator comprises a peroxide.

[0012] In some embodiments, the peroxide is dicumyl peroxide or bis-(tert-butylperoxy isopropyl)benzene peroxide (BIBP).

[0013] In some embodiments, the recyclable crosslinked polymer foam is a foamed product of a chemical foaming process.

[0014] In some embodiments, the chemical foaming process comprises using a blowing agent, wherein the blowing agent comprises an azo compound or a hydrazide compound.

[0015] In some embodiments, the azo compound is 2,2’-azobis(2-cyanobutane), 2,2’-azobis(methylbutyronitrile), or azodicarbonamide.

[0016] In some embodiments, the hydrazide compound is p,p'-oxybis(benzenesulfonyl hydrazide), p-toluene sulfonyl semicarbazide, or p-toluene sulfonyl hydrazide.

[0017] In some embodiments, the recyclable cross-linked polymer foam is a foamed product produced by a physical foaming process.

[0018] In some embodiments, the molar ratio of the free radical initiator to the crosslinking agent is 0.1 to 5.

[0019] In some embodiments, for 100 parts by weight of polymer material, the total amount of free radical initiator and crosslinking agent is 0.5 to 15 parts by weight.

[0020] In some embodiments, the density of the recyclable crosslinked polymer foam is 0.05 g / cm³. 3 ~0.8g / cm 3 The range.

[0021] In some embodiments, the pore size of the recyclable crosslinked polymer foam is 30 μm to 1 mm.

[0022] This invention also provides a reusable footwear component, including the recyclable cross-linked polymer foam as described above, wherein the yellow index of the recyclable cross-linked polymer foam is -5 to 70.

[0023] In some embodiments, reusable footwear components include insole, midsole, or outsole.

[0024] This invention further provides a reversed material obtained from reusable footwear components as described above, wherein the yellowing index of the reversed material is -5 to 95.

[0025] In some embodiments, the yellowing index of the recycled material is -5 to 45. Attached Figure Description

[0026] The embodiments of the present invention will be described in detail below with reference to the accompanying drawings. Wherein:

[0027] Figure 1 This is a schematic diagram showing the viscosity measurements of a polymer composition without added crosslinking agents during the crosslinking and heating recovery processes.

[0028] Figure 2is a schematic of viscosity measurements of polymer compositions with added crosslinker in crosslinking process and in heat recovery process. DETAILED DESCRIPTION

[0029] The recyclable polymer composition, the polymer foam, the reusable footwear component using the same, and the recycled material obtained thereby of the present application are described in detail in the following description. In the following detailed description, for the purposes of explanation, numerous specific details and examples are set forth in order to provide a thorough understanding of the present application. For the purpose of clarity, particular components and configurations are described in the following detailed description. However, it will be apparent to one skilled in the art that the exemplary embodiments set forth herein are presented for the purpose of illustration and description, and the inventive concept can be implemented in various forms without being limited to the exemplary embodiments.

[0030] Currently, ethylene vinyl acetate (EVA) crosslinked foams are generally not recyclable. In addition, during the heat recovery process, yellowing can occur, which can limit the further application of the recycled material. If the recycled foam material is not white, the resulting product can only be dark such as black or brown. To solve the above problems, the present application introduces heat-degradable urethane linkages into the EVA system by using tetramethylpiperidinyloxy (TEMPO) derivatives, thereby providing recyclable crosslinked polymer foams with desired properties such as low yellowing index.

[0031] According to some embodiments of the present application, the recyclable crosslinked polymer foam (e.g., EVA foam) of the present application includes a polymer material, a crosslinking agent (i.e., TEMPO derivative), and a free radical initiator. By using a specific crosslinking agent, and controlling the ratio of the free radical initiator, the crosslinking agent, and the polymer material, desired properties can be achieved during the foaming process. This results in high crosslinking efficiency and recyclability, and unexpectedly low yellowing index of the polymer and its recycled material, providing flexibility for further applications such as dyeable substrates, footwear, sports equipment, and furniture, etc.

[0032] In some other embodiments, the polymer composition provided by the present application can also be used as an encapsulant in photovoltaic modules. The reduction of encapsulant transparency can result in a loss of electrical efficiency of the photovoltaic module. By adjusting the color of the encapsulant, the light transmittance and solar photovoltaic conversion efficiency can be adjusted. Therefore, the lower the yellowing index, the higher the solar photovoltaic conversion efficiency.

[0033] According to some embodiments, the present invention provides a recyclable crosslinked polymer foam. The recyclable crosslinked polymer foam includes a reaction product of 100 parts by mass of a polymer material, 0.1 to 10 parts by mass of a crosslinking agent, and 0.1 to 5 parts by mass of a radical initiator. The crosslinking agent is represented by the following formula:

[0034]

[0035] wherein R is an alkylene group having 2 to 10 carbon atoms, an arylene group having 6 to 18 carbon atoms, or a cycloalkylene group having 6 to 18 carbon atoms.

[0036] According to some embodiments of the present invention, the polymer material may be a polyolefin polymer, a propylene polymer, a polyethylene polymer, a styrene polymer, an ethylene polymer such as ethylene-vinyl acetate (EVA), low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), very low-density polyethylene (VLDPE), and high-density polyethylene (HDPE), or a diene rubber such as natural rubber (NR), isoprene rubber (IR), butadiene rubber (BR), 1,2-butadiene rubber, styrene-butadiene rubber (SBR), acrylonitrile-butadiene rubber (NBR), chloroprene rubber (CR), butyl rubber (IIR), ethylene-propylene rubber (EPR), and ethylene-propylene-diene monomer (EPD) rubber. Polyolefin polymers (EPDM), propylene polymers, polyethylene polymers, styrene polymers, and ethylene polymers mentioned above each include their random, block, and graft copolymers. Examples of polyolefin polymers include olefin block copolymers (OBC). Examples of propylene polymers include propylene-ethylene copolymers. In particular, the polymer material can be ethylene propylene diene monomer (EPDM), natural rubber (NR), isopropylene rubber (IR), or combinations thereof.

[0037] In some embodiments, the ethylene polymer may be LDPE. LDPE is typically a highly branched ethylene homopolymer that can be prepared by a high-pressure process (i.e., high-pressure LDPE). The LDPE suitable for this application may have a content of 0.91 to 0.94 g / cm³. 3 The density. In some embodiments, the ethylene polymer has a density of at least 0.915 g / cm³. 3 But less than 0.94 g / cm 3 or less than 0.93 g / cm³ 3density of the polymer provided herein is determined according to American Society for Testing and Materials (ASTM) method D792. The LDPE suitable for use herein can have a melt index of less than 40 g / 10 min or a melt index of 0.1-400 g / 10 min, 0.5-20 g / 10 min, 0.5-5 g / 10 min, 1-3 g / 10 min, or a melt index equal to 2 g / 10 min. The melt index provided herein is determined according to ASTM method D1238. Unless otherwise specified, the melt index is determined at 190 °C and 2.16 kg. Generally, LDPE has a relatively broad molecular weight distribution, resulting in a relatively high polydispersity index (PDI; ratio of weight average molecular weight to number average molecular weight).

[0038] In some embodiments, the ethylene-based polymer can be an LLDPE. LLDPE is generally an ethylene-based polymer having a non-uniform distribution of comonomer (e.g., alpha-olefin monomer) and is characterized by short chain branching. For example, the LLDPE can be a copolymer of ethylene and an alpha-olefin monomer, such as those described above. The LLDPE suitable for use herein can have a density of 0.916-0.925 g / cm3. 3 The LLDPE suitable for use herein can have a melt index of 0.1-400 g / 10 min, 1-20 g / 10 min, or 3-8 g / 10 min.

[0039] In some embodiments, the ethylene-based polymer can be a VLDPE. VLDPE can also be referred to in the art as ultra-low-density polyethylene (ULDPE). VLDPE is generally an ethylene-based polymer having a non-uniform distribution of comonomer (e.g., alpha-olefin monomer) and is characterized by short chain branching. For example, the VLDPE can be a copolymer of ethylene and an alpha-olefin monomer, such as one or more of the alpha-olefin monomers described above. The VLDPE suitable for use herein can have a density of 0.87-0.915 g / cm3. 3 The VLDPE suitable for use herein can have a melt index of 0.1-400 g / 10 min, 0.1-20 g / 10 min, or 0.3-5 g / 10 min.

[0040] In some embodiments, the ethylene-based polymer can be an HDPE. HDPE has a low degree of branching, and thus has stronger intermolecular forces and tensile strength. The HDPE suitable for use herein can have a density of 0.941-0.965 g / cm3. 3HDPE suitable for use herein can have a density of 0.1 to 400 g / 10 min, 0.5 to 65 g / 10 min, or 1 to 30 g / 10 min.

[0041] In some embodiments, the ethylene vinyl acetate polymers can be purchased from USI Corporation under the trade designation UE3312 and UE629. Ethylene vinyl acetate polymers suitable for use herein have a vinyl acetate content of 3 to 45 wt% and a melt index of 0.01 to 400 g / 10 min.

[0042] In some embodiments, the polyolefin elastomers can be purchased from Dow Chemical under the trade designation ENGAGE TM 8003 and ENGAGE TM 8180. Polyolefin elastomers suitable for use herein can have a density of 0.857 g / cm 3 -0.908 g / cm 3 -0.908 g / cm . Polyolefin elastomers suitable for use herein can have a melt index of 0.1 to 400 g / 10 min or 0.1 to 10 g / 10 min. In some embodiments, the average melt index of the olefin block copolymer is in the range of greater than 0.5 g / 10 min and less than 35 g / 10 min. Melt index is determined according to ASTM D1238 at 190 °C, 2.16 kg.

[0043] The isocyanate compound can be used in combination with a tetramethylpiperidine oxide compound (TEMPO (2,2,6,6-tetramethylpiperidinyloxy) compound) to form a TEMPO derivative containing a thermoreversible urethane linkage. Suitable isocyanate compounds are polyfunctional isocyanates containing two or more -NCO groups per molecule. These can be aliphatic, alicyclic, polycyclic, or aromatic in nature, such as diisocyanate compounds or triisocyanate compounds. In some embodiments, the diisocyanate compound can be toluene diisocyanate (TDI), methylene diphenyl diisocyanate (MDI), hexamethylene diisocyanate (HDI), 4,4’-diisocyanato dicyclohexylmethane (HMDI), xylenediisocyanate (XDI), meta-tetramethylxylylenediisocyanate (TMXDI), hydrogenated xylene diisocyanate (HXDI), naphthalene 1,5-diisocyanate (NDI), p-phenylene diisocyanate (PPDI), 3,3’-dimethyldiphenyl-4,4’-diisocyanate (DDDI), 2,2,4-trimethylhexamethylene diisocyanate (TMDI), isophorone diisocyanate (IPDI), 4,4’-dicyclohexylmethane diisocyanate, norbornane diisocyanate (NDI), or 4,4’-dibenzyl diisocyanate (DBDI).

[0044] In some other embodiments, the triisocyanate can be triphenylmethane-4,4',4"-triisocyanate, 1,6,11-undecane triisocyanate, 1,3,6-hexamethylenetriisocyanate, 1,8-diisocyanato-4-isocyanatomethyloctane, 2,5,7-trimethyl-1,8-diisocyanato-5-isocyanatomethyloctane, lysine triisocyanate, mesitylene triisocyanate, trimethylbenzene triisocyanate, benzene triisocyanate, triphenylmethane triisocyanate, naphthalene triisocyanate, diphenylmethane-2,4,4'-triisocyanate, or 3-methyldiphenylmethane-4,6,4'-triisocyanate.

[0045] According to one embodiment of the present application, the crosslinking agent includes a diisocyanate urethane bis-TEMPO. Exemplary diisocyanate urethane bis-TEMPOs include methylene diphenyldiisocyanate urethane bis-TEMPO or 4,4'-diisocyanato dicyclohexylmethane urethane bis-TEMPO. Recyclable crosslinked polymers can also be made by grafting a hydroxy-TEMPO to the backbone of a thermoplastic polymer to form a grafted polymer, and then reacting the grafted polymer with a diisocyanate (in the mobile phase but not volatile) to form the next structure.

[0046] In some particular embodiments, TEMPO can be purchased from Tokyo Chemical Industry, which can be used as is.

[0047] Suitable free radical initiators include alpha-cumylperoxy neodecanoate, acetyl cyclohexylsulfonyl peroxide, benzoyl peroxide, butyl 4,4-di(tert-butylperoxy)valerate, bis(alpha-t-butyl-peroxyisopropyl)benzene (BIBP), cumyl hydroperoxide, decanoyl peroxide, dicumyl peroxide, di(tert-butyl)peroxide, di(tert-amyl)peroxide, di(isopropylcumyl)peroxide, diisopropylbenzene monohydroperoxide, ethyl-3,3-di(tert-butylperoxy)butyrate, ethyl-3,3-di(tert-amylperoxy)butyrate, isopropylcumylcumylperoxide, lauroyl peroxide, n-butyl 4,4-di(tert-butylperoxy)valerate, n-butyl 4,4-di(tert-amylperoxy)valerate, n-butyl 4,4-di(tert-butylperoxy)valerate, n-butyl 4,4-di(tert-amylperoxy)valerate, n-butyl 4,4-di(tert-butylperoxy)valerate, n-butyl 4,4-di(tert-amylperoxy)valerate, n-butyl 4,4-di(tert-butylperoxy)valerate, n-butyl 4,4-di(tert-amylperoxy)valerate, n-butyl 4,4-di(tert-butylperoxy)valerate, n-butyl 4,4-di(tert-amylperoxy)valerate, n-butyl 4,4-di(tert-butylperoxy)valerate, n-butyl 4,4-di(tert-amylperoxy)valerate, n-butyl 4,4-di(tert-butylperoxy)valerate, n-butyl 4,4-di(tert-amylperoxy)valerate, n-butyl 4,4-di(tert-butylperoxy)valerate, n-butyl 4,4-di(tert-amylperoxy)valerate, n-butyl 4,4-di(tert-butylperoxy)valerate, n-butyl 4,4-di(tert-amylperoxy)valerate, n-butyl 4,4-di(tert-butylperoxy)valerate, n-butyl 4,4-di(tert-amylperoxy)valerate, n-butyl 4,4-di(tert-butylperoxy)valerate, n-butyl 4,4-di(tert-amylperoxy)valerate, n-butyl 4,4-di(tert-butylperoxy)valerate, n-butyl 4,4-di(tert-amylperoxy)valerate, n-butyl 4,4-di(tert-butylperoxy)valerate, n-butyl 4,4-di(tert-amylperoxy)valerate, n-butyl 4,4-di(tert-butylperoxy)valerate, n-butyl 4,4-di(tert-amylperoxy)valerate, n-butyl 4,4-di(tert-butylperoxy)valerate, n-butyl 4,4-di(tert-amylperoxy)valerate, n-butyl 4,4-di(tert-butylperoxy)valerate, n-butyl 4,4-di(tert-amylperoxy)valerate, n-butyl 4,4-di(tert-butylperoxy)valerate, n-butyl 4,4-di(tert-amylperoxy)valerate, n-butyl 4,4-di(tert-butylperoxy)valerate, n-butyl 4,44-di(tert-butylperoxy)valerate), OO-tert-butyl-O-isopropylmonoperoxy carbonate, OO-tert-butyl-O-(2-ethylhexyl)monoperoxy carbonate, OO-tert-amyl-O-(2-ethylhexyl)monoperoxy carbonate, paramenthane hydroperoxide, tert-amylperoxypivalate, tert-amyl peroxyneodecanoate, tert-amyl hydroperoxide, tert-amyl peroxy-2-ethylhexanoate, tert-amyl peroxy-3,5,5-trimethylhexanoate, tert-butyl hydroperoxide, tert-butyl cumyl peroxide, tert-butylperoxybenzoate, tert-butyl peroxyacetate, tert-butyl peroxyisobutyrate, tert-butylperoxymaleate, tert-butyl peroxypivalate, tert-butyl peroxyneodecanoate, tert-butylperoxyisononanoate, tert-butyl peroxy-2-ethylhexanoate, tert-butyl peroxy-3,5,5-trimethylhexanoate, 1,1-di(tert-butylperoxy)cyclohexane (1,1-di(tert-butylperoxy)cyclohexane), 1,1-di(tert-butylperoxy)-3,3,5-trimethylcyclohexane, 1,1-di(tert-amylperoxy)cyclohexane, 1,3-di(tert-butylperoxyisopropyl)benzene, 2,2-di(tert-butylperoxy)butane, 2,5-dimethyl-2,5-di(2-ethylhexanoylperoxy)hexane, 2,5-dimethyl-2,5-di(hydroperoxy)hexane, 2,5-dimethyl-2,5-di(benzoylperoxy)hexane, 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane, 2,5-dimethyl-2,5-di(tert-butylperoxy)hex-3-yne, 2,2-bis(4,4-ditert-butylperoxycyclohexyl)propane, 3-hydroxy-1,1-dimethylbutylperoxyneodecanoate, 3,5,5-trimethylhexanoyl peroxide, t-butyl peroxy-2-ethylhexyl monocarbonate, or combinations thereof, but the present application is not limited thereto.

[0048] According to embodiments of the present application, the free radical initiator includes a peroxide, such as dicumyl peroxide or bis-(tert-butylperoxyisopropyl) benzene peroxide (BIBP).

[0049] According to some embodiments of the present application, the molar ratio of the free radical initiator and the crosslinking agent can be in the range of 0.1-5, for example, 0.5-4.5, 1-4, 1-3, 1-2.5, or 1-2. In particular, it is desirable that the molar ratio of the free radical initiator and the crosslinking agent is higher than 0.9 to provide suitable properties (e.g., yellowing index) of the polymer and the recycled material for further applications. In some specific embodiments, the ratio of the free radical initiator and the crosslinking agent can be higher than 1.2. According to some embodiments of the present application, the total amount of the free radical initiator and the crosslinking agent can be 0.5-15 parts by weight, preferably 1-14 parts by weight, 2-12 parts by weight, 3-10 parts by weight, or 4 to 8 parts by weight, based on 100 parts by weight of the polymer material. In particular, a molar ratio of the free radical initiator and the crosslinking agent lower than 0.9 can result in a high yellowing index of the polymer and the recycled material, which can limit further applications.

[0050] The recyclable crosslinked polymer foam can be a foamed product of a chemical or physical foaming process using a chemical or physical foaming agent. This allows the resulting crosslinked foam product to be lightweight and can exhibit flexibility, excellent tear resistance, compression set resistance, impact absorption, abrasion resistance, and designability. Examples of chemical foaming agents include sulfonyl hydrazide compounds, azo compounds, and nitroso compounds. Examples of sulfonyl hydrazide compounds are benzene-1,3-disulfonyl hydrazide, benzene sulfonyl hydrazide, p-toluene sulfonyl semicarbazide, p-toluenesulfonyl hydrazide, p,p’-oxybis(benzene sulfonyl hydrazide), 4,4’-oxybis(benzene sulfonyl hydrazide), OBSH, and the like. Examples of azo compounds are azodicarbonamide, azobisformamide, azobisisobutyronitrile, diazoaminobenzene, 2,2’-azobis(2-cyanobutane), 2,2’-azobis(methylbutyronitrile), barium azodicarboxylate, and the like. Examples of nitroso compounds are N,N’-dinitrosopentamethylenetetramine, N,N’-dinitroso-N,N’-dimethylterephthalamide, and the like.

[0051] Examples of physical foaming agents include hydrocarbons such as pentane, butane, and hexane, halogenated hydrocarbons such as chloromethane and dichloromethane, fluorinated hydrocarbons such as trichlorofluoromethane, dichlorodifluoromethane, trichlorotrifluoroethane, chlorodifluoroethane, and hydrofluorocarbons, and gases such as carbon dioxide, nitrogen, and air.

[0052] These products are provided in a variety of particle size to control bubble formation and density of the foamed material. The proportion of the blowing agent can vary over a wide range and depends, inter alia, on the type of blowing agent, the polymer mixture used and the desired density of the foamed material to be produced. The proportion of the blowing agent can be between 0.1 and 20 wt.%, for example, it can be 5-15 wt.%, relative to the total weight of the foamable thermoplastic mixture. Useful blowing agents can include blowing agents available under the trade name ADC (DONGIN SEMICHEM).

[0053] In addition to the components described above, the foamable thermoplastic mixture can also include one or more additives. Examples of additives that can optionally be used are scorched retardants, antioxidants, processing aids, fillers, coupling agents, ultraviolet absorbers or stabilizers, antistatic agents, nucleating agents, slip agents, plasticizers, lubricants, viscosity control agents, tackifiers, anti-block agents, surfactants, extender oils, acid scavengers, flame retardants, water tree retardants, electrical tree retardants, voltage stabilizers, metal deactivators, or combinations thereof.

[0054] According to an embodiment of the present application, a reusable footwear component is provided. The reusable footwear component includes a recyclable crosslinked polymeric foam, wherein the recyclable crosslinked polymeric foam can have a yellowness index of -5 to 70, for example, it can be -2 to 70, -2 to 60, -2 to 55, -1 to 50, -1 to 45, -1 to 40, 0 to 35, 0 to 30, 0 to 25, 0 to 20, 0 to 15, 0 to 10, or 0 to 5. In particular, a recyclable crosslinked polymeric foam having a yellowness index higher than 45 will limit the further field of application.

[0055] According to an embodiment of the present application, a recyclable material obtained from a reusable footwear component is provided, wherein the recyclable material can have a yellowness index of -5 to 95, for example, it can be -5 to 45, -2 to 45, 0 to 45, 2 to 45, 4 to 45, 5 to 45, 0 to 40, 2 to 40, 4 to 40, 5 to 40, 0 to 35, 2 to 35, 4 to 35, 5 to 35, 0 to 30, 2 to 30, 4 to 30, 5 to 30, 0 to 25, 2 to 25, 4 to 25, or 5 to 25. In particular, a recyclable material having a yellowness index lower than 45 is desirable in order to provide more options for design and operation in further applications.

[0056] According to some embodiments of the present application, the recyclable crosslinked polymeric foam has a density of 0.05 g / cm 3 -0.8 g / cm 3 The recyclable crosslinked polymeric foam has a cell size of 30 pm - 1 mm.

[0057] In some embodiments, the reusable footwear component comprises an insole, a midsole, or an outsole.

[0058] So that the above and other objects, features and advantages of the present application can be better understood, a few specific embodiments will now be described in detail in conjunction with the accompanying drawings. It should be understood, however, that they are not intended to limit the present application in any manner and that various changes and modifications can be suggested to one skilled in the art, and it is the intention that the present application can be practiced otherwise than as specifically described.

[0059] Evaluating the properties of the polymer composition

[0060] Table 1 lists the materials used in the following examples.

[0061] Table 1

[0062]

[0063]

[0064] (I) Yellow index (YI)

[0065] The yellow index was determined according to the standardized method ASTM E313 [D65 / 10] using a colorimeter (HunterLab, Model: UltraScan VIS). The YI was determined after the crosslinking process and the heat recovery process of the polymer composition.

[0066] Experimental Example 1

[0067] 100 parts by weight of UE3312, 6.46 parts by weight of M crosslinking agent, and 2.22 parts by weight of DCP were sequentially added to a mixer (Brabender, Model: Plasti-Corder). After heating to 120°C, the mixing process was continued at a rotation speed of 35 rpm for 5 minutes until the polymer composition was completely mixed. Next, the polymer composition was placed in a mold (0.4 mm thick) and compressed at 2300 psi. The heating and compression were performed using a hydraulic press (Carver, Model: Monarch series). The polymer composition was compressed at a temperature of 180°C for 15 minutes. After completing the above procedure, the polymer composition was then cooled to room temperature and a film specimen having a uniform thickness was formed accordingly.

[0068] Experimental Examples 2-13

[0069] Example 2-13 was performed in the same manner as in Example 1, except that the polymer material, ingredients and amounts of crosslinking agent and free radical initiator listed in Tables 2 and 3 were used instead of those used in Example 1 to obtain a film sample. Subsequently, the yellowing index (YI film ) measurement was performed for Example 2-13, and the results are also shown in Table 2.

[0070] Table 2

[0071]

[0072] Notes:

[0073] (i) m I / C refers to the molar ratio (mole initiator / mole crosslinking agent)

[0074] (ii) YI film refers to the yellowing index of the film sample

[0075] With reference to Examples 1-3, which added the same type of peroxide (i.e., dicumyl peroxide) during the preparation process. It was observed that the YI film values of the polymer compositions with higher m I / C were unexpectedly low. This trend can also be observed in Examples 4-5 and 6-7, which added 2,5-dimethyl-2,5-di(tert-butylperoxy) hexane and tert-butylperoxy-2-ethylhexyl monocarbonate, respectively, as the type of peroxide during the preparation process. Thus, higher m I / C can be employed to obtain better YI film (i.e., lower YI values).

[0076] Table 3

[0077]

[0078]

[0079] With reference to Examples 8-9, which added the same type of peroxide (i.e., dicumyl peroxide) during the preparation process. It was observed that the YI film values of the polymer compositions with higher m I / C were unexpectedly low. This trend can also be observed in Examples 10-11 and 12-13, which added 2,5-dimethyl-2,5-di(tert-butylperoxy) hexane and tert-butylperoxy-2-ethylhexyl monocarbonate, respectively, as the type of peroxide during the preparation process. Thus, higher m I / C can be employed to obtain better YI film .

[0080] Example 14

[0081] Example 15-16 were carried out in the same manner as in Experimental Example 14, except that the ingredients and amounts of the polymer materials, crosslinking agents, and radical initiators listed in Table 4 were used instead of those used in Experimental Example 14 to obtain the film samples. Next, the yellowing index measurements were carried out for Experimental Examples 15-16, and the results are also shown in Table 4.

[0082] Experimental Examples 15-16

[0083] Experimental Examples 15-16 were carried out in the same manner as in Experimental Example 14, except that the ingredients and amounts of the polymer materials, crosslinking agents, and radical initiators listed in Table 4 were used instead of those used in Experimental Example 14 to obtain the film samples. Next, the yellowing index measurements were carried out for Experimental Examples 15-16, and the results are also shown in Table 4.

[0084] Table 4

[0085]

[0086]

[0087] Note:

[0088] (i) m I / C refers to the molar ratio (mole of initiator / mole of crosslinking agent)

[0089] (ii) I+C refers to the sum of the initiator and M crosslinking agent or H crosslinking agent

[0090] (iii) YI film refers to the yellowing index of the film sample

[0091] With reference to Experimental Examples 14-16, it was observed that the polymer compositions having lower I+C tended to provide lower YI film values. Thus, lower I+C can be employed to obtain better YI film .

[0092] Experimental Example 17

[0093] Into a mixer (Brabender, Model: Plasti-Corder), 100 parts by weight of UE3312, 4.28 parts by weight of M crosslinking agent, 2.78 parts by weight of 101XL45 were sequentially added. After heating to 120°C, the mixing process was continued at a rotation speed of 35 rpm for 5 minutes until the polymer composition was completely mixed. Next, the polymer composition was placed in a mold (0.4 mm thick) and compressed at 2300 psi. Heating and compression were performed using a hydraulic press (Carver, Model: Monarch series). The polymer composition was compressed at a temperature of 180°C for 15 minutes. After completion of the above procedure, the polymer composition was then cooled to room temperature and a thin film sample having a uniform thickness was formed accordingly.

[0094] Experimental Examples 18-22

[0095] Experimental Examples 18-22 were performed in the same manner as in Experimental Example 17, except that the ingredients and contents of the polymerizing materials, the specified crosslinking agent and radical initiator listed in Table 5 were used instead of those used in Experimental Example 17 to obtain a thin film sample. Next, the thin film sample was placed in a mold (0.4 mm thick) on a hydraulic press (Carver, Model: Monarch series) and heated at a temperature of 230°C for 15 minutes at a pressure of 2300 psi, thereby checking the reversibility of the thin film sample. The yellowness index measurement after the heat recovery process was performed on Experimental Examples 17-22, and the results are shown in Table 5.

[0096] Table 5

[0097]

[0098] Referring to Experimental Examples 17-18, the polymer composition produced by adding M crosslinking agent as a crosslinking agent (Experimental Example 17) had the same m I / C or I+C, but tended to provide a better YI than that by adding H crosslinking agent as a crosslinking agent (Experimental Example 18) film . This tendency can also be observed in Experimental Examples 19-22, in which the YI of Experimental Example 20 film was lower than that of Experimental Example 19, and the YI of Experimental Example 22 film was lower than that of Experimental Example 21.

[0099] (II) Viscosity

[0100] The viscosity was measured using a dynamic shear rheometer (TA Instruments, Model: HR-1) according to the following procedure and parameters:

[0101] 1. Conditioning sample:

[0102] Temperature 100°C, soak time 10 s.

[0103] 2. Oscillation temperature ramp:

[0104] Starting temperature 100 °C,

[0105] Ending temperature 170 °C,

[0106] Ramp rate: 30 °C / min,

[0107] Strain 0.5%

[0108] 3. Oscillation time:

[0109] Temperature 170 °C

[0110] Duration: 1800 (sec).

[0111] Strain 0.5%

[0112] 4. Oscillation temperature ramp:

[0113] Starting temperature 170 °C,

[0114] Ending temperature 230 °C,

[0115] Ramp rate: 30 °C / min,

[0116] Strain 0.5%

[0117] 5. Oscillation time:

[0118] Temperature 230 °C

[0119] Duration: 900 (sec).

[0120] Strain 0.5%

[0121] Experimental Example 23

[0122] 100 parts by weight of UE3312, 4.28 parts by weight of M crosslinking agent, and 3.33 parts by weight of DCP were sequentially added to a mixer (Brabender, Model: Plasti-Corder). After heating to 120 °C, the mixing process was continued at a rotation speed of 35 rpm for 5 minutes until complete mixing. Then the polymer composition was cooled to room temperature.

[0123] Experimental Examples 24-29

[0124] Experimental Examples 24-29 were performed in the same manner as Experimental Example 23, except that the ingredients and contents of the polymer materials, crosslinking agents, and radical initiators listed in Table 6 were used instead of those used in Experimental Example 23 to obtain a polymer composition. Then, as in Experimental Example 23, Figure 1 andFigure 2 The viscosity was measured after the cross-linking process and the heat recovery process of the polymer composition, respectively, by heating the polymer composition between parallel plates at 170°C for 30 minutes and by heating the polymer composition at 230°C for 15 minutes, as indicated in Table 6. The results are shown in Table 6.

[0125] Table 6

[0126]

[0127] Note:

[0128] (i) V crosslink refers to the viscosity of the cross-linking process, measured at 170°C for 30 minutes

[0129] (ii) V reverse refers to the viscosity of the heat recovery process, measured at 230°C for 15 minutes

[0130] With reference to the polymer compositions produced with the addition of cross-linking agents (Examples 23-28), V crosslink is in the range of 25000-400000 Pa.s. The V measured at 230°C for 15 minutes of Examples 23-28 reverse is in the range of 150-180000 Pa.s, indicating that the polymer composition is recyclable, regardless of the type of cross-linking agent added during the preparation of the polymer composition. The term "recyclable" is used herein to mean that the viscosity of the polymer composition is lower than 200000 Pa.s. In contrast, the V of the polymer composition obtained without the addition of cross-linking agents (Example 29) reverse exceeds 200000 Pa.s, indicating that the polymer composition is not recyclable.

[0131] Example 30

[0132] 100 parts by weight of UE629, 3.42 parts by weight of H cross-linking agent and 2.1 parts by weight of DCP were sequentially added to a mixer (Brabender, model: Plasti-Corder). After heating to 120°C, the mixing process was continued at a rotation speed of 35 rpm for 5 minutes until complete mixing. The polymer composition was then cooled to room temperature.

[0133] Examples 31-35

[0134] Experimental Examples 31-35 were performed in the same manner as in Experimental Example 30, except that the ingredients and contents of the polymer material, crosslinking agent, and radical initiator listed in Table 7 were used instead of those used in Experimental Example 30 to obtain a polymer composition. Then, after the crosslinking process and the heat recovery process of the polymer composition, the viscosity was measured by heating the polymer composition at a temperature of 170°C for 30 minutes and at a temperature of 230°C for 15 minutes, respectively. The results are shown in Table 7.

[0135] Table 7

[0136]

[0137] Referring to Experimental Examples 30-35, V crosslink in the range of 25000-400000 Pa.s. V of Experimental Examples 30-35 reverse in the range of 1100-40000 Pa.s, which indicates that the polymer composition is crosslinkable and recyclable as long as the crosslinking agent is added, regardless of the type of polymer material used in the preparation process of the polymer composition.

[0138] Preparation of recyclable crosslinked polymer foam

[0139] According to some embodiments of the present application, the present polymer foam can be prepared into a foam using a foaming process (e.g., a physical or chemical foaming process).

[0140] Table 8 lists the materials involved in the embodiments of the present application.

[0141] Table 8

[0142]

[0143]

[0144] Chemical foaming process

[0145] Experimental Example 36

[0146] A mixer (Brabender, Model: Plasti-Corder) was charged with 100 parts by weight of UE659, 3.42 parts by weight of M crosslinking agent, 2 parts by weight of DCP, 1.9 parts by weight of BA, and 0.5 parts by weight of ZnO, sequentially. After heating to 120°C, the mixing process was continued at a rotation speed of 35 rpm for 5 minutes until the polymer composition was completely mixed. Next, the polymer composition was placed in a mold (0.3 mm in thickness) and compressed at 2300 psi. Heating and compression were performed using a hydraulic press (Carver, Model: Monarch series). The polymer composition was placed in the press at a temperature of about 175°C for 12 minutes. After completion of the above procedure, the polymer composition was cooled to room temperature.

[0147] Experimental Example 37 and Experimental Example 38

[0148] Experimental Examples 37 and 38 were performed in the same manner as Experimental Example 36, except that the ingredients and contents of the polymer material, crosslinking agent, radical initiator, blowing agent, and additive listed in Table 9 were used instead of those used in Experimental Example 36 to obtain a foamed product. Next, the density and cell size of the foamed product were measured. The foamed material density was measured by an electric densitometer (MIRAGE, Model: ED-120T). The foamed material cell size was examined by a microscope (Nikon, Model: ECLIPSE CI). Finally, the reworkability of the foamed product was examined by placing the foamed product in a mold (0.4 mm in thickness) on a hydraulic press (Carver, Model: Monarch series) at a temperature of 230°C and a pressure of 2300 psi for 15 minutes to form a thermoplastic recycled material.

[0149] The polymer material used in Experimental Example 38 was a recycled UE659, which was prepared as follows: the foamed product of Experimental Example 37 was cut into small pieces and fed into a mixer at a temperature of 230°C at a rotation speed of 20 rpm, followed by a rotation speed of 35 rpm for 10 minutes. Then, the mixture was cooled to a temperature to form the recycled UE659.

[0150] Table 9

[0151]

[0152] Notes:

[0153] (i) m I / C refers to a molar ratio (mole of initiator / mole of crosslinking agent).

[0154] (ii) I+C refers to the sum of the initiator and the M crosslinking agent or the H crosslinking agent.

[0155] The foamed products prepared with the addition of crosslinking agent (Experimental Examples 36, 37) showed similar foamed structures with cell sizes between 100 and 220 pm. In addition, the foamed product prepared with the recycled polymer material (Experimental Example 38) showed a foamed structure with cell sizes between 200 and 300 pm. The densities of the foamed products of Experimental Example 36 and Experimental Example 37 were in the range of 0.15 g / cm3to 0.23 g / cm3, which is a typical density range for midsoles. 3 -0.23 g / cm3 3 The densities of the foamed products of Experimental Example 36 and Experimental Example 37 were in the range of 0.15 g / cm3to 0.23 g / cm3, which is a typical density range for midsoles.

[0156] In addition, the yellowness index (YI 发泡材 (YI foam ) of Experimental Example 36 and Experimental Example 37 was measured. The YI foam was determined by spectroscopy and visually. The yellowness index was determined by a standardized method based on ASTM E313 [D65 / 10] using a colorimeter (HunterLab, Model: UltraScan VIS). The YI was measured after foaming and heating the recycled material. The results are shown in Table 10.

[0157] Table 10

[0158]

[0159] Notes:

[0160] YI foam refers to the yellowness index of the foamed product

[0161] YI reversed film refers to the yellowness index of the thermoplastic recycled material

[0162] From the results shown in Table 10, it can be seen that the foamed product with the addition of H crosslinking agent as crosslinking agent (Experimental Example 37) showed a better YI foam than the foamed product with the addition of M crosslinking agent as crosslinking agent (Experimental Example 36), whose recycled material showed a better YI reversed film . The low yellowness index of the foamed product and the thermoplastic recycled material obtained therefrom is more desirable for the purpose of further applications.

[0163] In some embodiments, taking the foamed product with the addition of H crosslinking agent as crosslinking agent (Experimental Example 37) as an example, the foaming process can be carried out at a temperature of 170°C to 195°C for 6 to 15 minutes. The YI foam measured after foaming was between 27 and 29. The YI reversed film measured after heating the recycled material was between 15.5 and 17.5.

[0164] In addition, it is worth noting that the foamed product prepared with the recycled polymer material (Experimental Example 38) also showed a YI of 30.1.foam and its recycled material showed a YI of 22.2 reversed film This resulted in a desirable white color for the resulting foamed product and its thermoplastic recycled material.

[0165] Physical foaming process

[0166] Experimental Example 39

[0167] 100 parts by weight of UE659, 3.42 parts by weight of H crosslinking agent, and 2.0 parts by weight of DCP were sequentially added to a mixer (Brabender, Model: Plasti-Corder). After heating to 120°C, the mixing process was continued at a rotation speed of 35 rpm for 5 minutes until complete mixing. The resulting product was then placed in a mold (0.4 mm in thickness) and compressed at 2300 psi. Heating and compression were performed using a hydraulic press (Carver, Model: Monarch series). The resulting product was compressed at a temperature of about 175°C for 15 minutes. After completion of the above procedure, the crosslinked sample was cooled to room temperature. Next, the crosslinked sample was placed in a tank of a supercritical fluid foaming system, and the system temperature was adjusted to 130°C or higher (without reaching the melting state). Nitrogen gas was then injected into the supercritical fluid foaming system and mixed with the crosslinked sample. Next, the system pressure was adjusted to 150 bar so that the crosslinked sample and the nitrogen gas supercritical fluid formed a single-phase solution and was maintained for 2 hours. The system pressure was then adjusted to 1.013 bar within 1 second to obtain a foamed product.

[0168] Experimental Example 40

[0169] Experimental Example 40 was performed in the same manner as Experimental Example 39, except that the polymeric material used in Experimental Example 39 was recycled UE659. Next, the density, cell size, and yellowness index (YI foam ) of the foamed product were measured. The foamed material density was measured by an electric densitometer (MIRAGE, Model: ED-120T). The foamed material cell size was examined by a microscope (Nikon, Model: ECLIPSE CI). Finally, the recyclability of the foamed product was examined by placing the foamed product in a mold (0.4 mm in thickness) on a hydraulic press (Carver, Model: Monarch series) at a temperature of 230°C and a pressure of 2300 psi for 15 minutes.

[0170] The polymeric material used in Experimental Example 40 was recycled UE659, which was prepared as follows: the foamed product of Experimental Example 39 was cut into small pieces and fed into a mixer at a temperature of 230°C at a rotation speed of 20 rpm, and then at a rotation speed of 35 rpm for 10 minutes. Then, the mixture was cooled to a temperature to form recycled UE659.

[0171] Table 11

[0172]

[0173]

[0174] From the results shown in Table 11, it is worth noting that the foamed product prepared with the recycled polymer material (Example 40) showed a YI of 27.3 foam , while its recycled material showed a YI of 40.5 reversed film . YI values lower than 45 can make the resulting foamed product and its recycled material with desirable white color.

[0175] The foamed product of Example 39 showed a foamed structure with cell size between 100 and 150 pm, while the foamed product of Example 40 had cell size between 200 and 400 pm. The density of the foamed products of Example 39 and Example 40 was in the range of 0.15 g / cm 3 -0.23 g / cm 3 , which is the typical density range for midsoles.

[0176] According to some embodiments of the present application, when the foamed material is formed by a physical foaming process, supercritical fluid or physical blowing agent can be used for foaming. The supercritical fluid can be carbon dioxide, nitrogen or a combination thereof. The physical blowing agent can be water, methane, ethane, butane, propane, pentane, hexane, ethylene, propylene, methanol, ethanol, acetone, air or a combination thereof.

[0177] In the present application, the resulting recyclable crosslinked polymer foamed material is environmentally and economically sustainable. In the foaming process (such as physical or chemical foaming process), by applying a specific type of crosslinking agent (wherein H crosslinking agent is particularly preferred), and by controlling the specific ratio between the free radical initiator, the crosslinking agent and the polymer material, desirable physical properties can be achieved, such as unexpectedly low yellowing index of the polymer and its recycled material, which provides flexibility for further applications of dyeable substrates, footwear, sports equipment and furniture, among others.

[0178] While the application has been described by example and in terms of preferred embodiments, it is to be understood that the application is not limited to the details of those described herein. Rather, it is the intent that the application be broadly interpreted within the scope of the appended claims as long as the applications carried out in alternative ways will result in equivalent functionality.

Claims

1. A recyclable cross-linked polymer foam material, comprising the following reaction products: 100 parts by weight of a polymer material, wherein the polymer material is polyethylene, styrene polymer, ethylene propylene diene rubber, natural rubber (NR), isopropylene rubber (IR), ethylene vinyl acetate copolymer, polyolefin elastomer, or a combination thereof; 0.1 to 10 parts by weight of a crosslinking agent, wherein the crosslinking agent comprises 4,4'-dicyclohexylmethane diisocyanate bis(tetramethylpiperidine)oxide; and 0.1~5 parts by weight of free radical initiator, in, The molar ratio of the free radical initiator to the crosslinking agent is 0.1~5. The total amount of the free radical initiator and the crosslinking agent is 0.5 to 15 parts by mass relative to 100 parts by mass of the polymer material.

2. The recyclable crosslinked polymer foam material according to claim 1, wherein the vinyl acetate content of the polymer material is 3-45% by mass, and the melt index is 0.01-400 g / 10 min.

3. The recyclable crosslinked polymer foam of claim 1, wherein the free radical initiator comprises peroxide.

4. The recyclable crosslinked polymer foam according to claim 3, wherein the peroxide is dicumyl peroxide or bis-(tert-butylperoxide)benzene peroxide (BIBP).

5. The recyclable cross-linked polymer foam material according to claim 1, wherein the recyclable cross-linked polymer foam material is a foamed product produced by a chemical foaming process.

6. The recyclable crosslinked polymer foam of claim 5, wherein the chemical foaming process includes the use of a foaming agent, wherein the foaming agent comprises an azo compound or an acylhydrazine compound.

7. The recyclable crosslinked polymer foam of claim 6, wherein the azo compound is 2,2'-azobis(2-cyanobutane), 2,2'-azobis(methylbutyronitrile), or azodicarbonamide.

8. The recyclable crosslinked polymer foam of claim 6, wherein the hydrazide compound is p,p'-oxobis(benzenesulfonylhydrazide) or p-toluenesulfonylhydrazide.

9. The recyclable cross-linked polymer foam material according to claim 1, wherein the recyclable cross-linked polymer foam material is a foamed product produced by a physical foaming process.

10. The recyclable cross-linked polymer foam according to claim 1, wherein the density of the recyclable cross-linked polymer foam is 0.05 g / cm³. 3 ~0.8g / cm 3 The range.

11. The recyclable cross-linked polymer foam material according to claim 1, wherein the pore size of the recyclable cross-linked polymer foam material is 30 μm to 1 mm.

12. A reusable footwear component comprising a recyclable cross-linked polymer foam according to claim 1, wherein the yellowing index of the recyclable cross-linked polymer foam is -5 to 70.

13. The reusable footwear component of claim 12, wherein the reusable footwear component comprises an insole, midsole, or outsole.

14. A recycled material obtained from a reusable footwear component according to claim 12, wherein the yellowing index of the recycled material is -5 to 95.

15. The recycled material according to claim 14, wherein the yellowing index of the recycled material is -5 to 45.

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