Crosslinked polyethylene foams and methods of making same

Abstract

Described herein are physically crosslinked, closed cell continuous foam structures comprising low density polyethylene (LDPE), linear low density polyethylene (LLDPE), or a combination of LDPE and LLDPE, and an olefin block copolymer (OBC). The foam structure can be obtained by extruding a foam composition comprising LDPE, LLDPE, or a combination of LDPE and LLDPE, and OBC, irradiating the composition with ionizing radiation, and foaming the composition.

Description

[0001] Cross-reference related applications

[0002] This application claims the benefit of U.S. Application No. 18 / 194,316, filed March 31, 2023, and U.S. Application No. 18 / 194,320, filed March 31, 2023, the entire contents of each of which are incorporated herein by reference. Technical Field

[0003] The present invention generally relates to cross-linked polyethylene foam structures, and more specifically to cross-linked polyethylene foam structures produced from blends of polyethylene and polyvinyl olefin block copolymers. Background Technology

[0004] Cross-linked polyethylene (XLPE) foam sheets are used in a wide range of applications: as a substrate in belts, as gaskets, as layers or components in automotive interiors, as protective material in packaging and transportation, as components in flotation devices and buoyancy aids, as components in clothing and footwear, as components in mattresses and bedding, as insulation for walls and pipes, as furniture padding, as floor padding, as shock absorbers, as impact dampers, etc. These XLPE foams are typically produced from low-density polyethylene (LDPE) and / or conventional multi-site Ziegler-Natta type catalytic linear low-density polyethylene (LLDPE). A subgroup of XLPE foams is produced from blends of polyethylene (LDPE and / or conventional LLDPE) and ethylene vinyl acetate copolymer (EVA). EVA is often used to increase the softness and flexibility of XLPE foam sheets for applications requiring increased softness and flexibility that are typically not available from LDPE and / or conventional LLDPE.

[0005] One of the raw materials required for the production of EVA copolymers is vinyl acetate monomer (VAM). VAM is a raw material used not only in the production of EVA copolymers but also extensively in dispersants and adhesives used in the automotive, construction, furniture, and paper / packaging industries. VAM is also a raw material in paints and coatings, construction, and textile manufacturing. However, a global VAM shortage has led to a supply shortage that is not expected to decrease in the future. Consequently, the worldwide VAM shortage has caused a significant increase and volatility in VAM prices, and on a larger scale, has led to significant increases and volatility in the prices of all products that require VAM (including EVA). Summary of the Invention

[0006] It has been discovered that physically cross-linked, closed-cell polyethylene foam structures can be produced from blends of polyethylene (LDPE and / or conventional LLDPE) and polyvinyl olefin block copolymers (OBC). While a subgroup of commercially produced polyethylene foam is cross-linked foam produced from blends of polyethylene (LDPE and / or conventional LLDPE) and EVA copolymers, it has been found that blending OBC, instead of EVA, into foam formulations can also appropriately increase the softness and flexibility of cross-linked polyethylene foam sheets for applications requiring increased softness and flexibility that are typically not available from LDPE and / or conventional LLDPE alone. Since OBC is not currently in short supply and will not be in the foreseeable future, the discovered foam can be produced from readily available polymers. Furthermore, due to the ample production and supply of OBC, the raw material costs of the discovered foam can be expected to be significantly more stable than those of polyethylene foam (LDPE and / or conventional LLDPE) blended with EVA. Manufacturers, distributors, and users of cross-linked foams are eagerly anticipating sufficiently rapid supply and stable pricing.

[0007] Polyethylene foam sheets can be obtained by: (a) extruding a foam composition comprising a blend of polyethylene (LDPE and / or LLDPE) and polyethylene-based OBC, (b) irradiating the extruded foam composition with ionizing radiation, and (c) foaming the irradiated extruded foam composition.

[0008] In some embodiments, the polyethylene foam structure comprises 40-65 wt% of low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), or a combination of LDPE and LLDPE; and 15-45 wt% of olefin block copolymer (OBC). In some embodiments, the foam structure comprises 50-65 wt% of low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), or a combination of LDPE and LLDPE. In some embodiments, the foam structure comprises 20-35 wt% of olefin block copolymer (OBC). In some embodiments, the foam structure comprises 5-15 wt% of a chemical blowing agent. In some embodiments, the foam structure comprises 1-10 wt% of an antioxidant masterbatch. In some embodiments, the foam structure comprises 0.5-5 wt% of a processing aid masterbatch. In some embodiments, the foam structure comprises 1-10 wt% of a chemical blowing agent decomposition inhibitor masterbatch. In some embodiments, the foam structure comprises 1-10 wt% of an anti-blocking agent masterbatch. In some embodiments, the foam structure contains 1-12 wt% of colorant masterbatch. In some embodiments, the density of the foam structure is 15-200 kg / m³. 3In some embodiments, the degree of crosslinking of the foam structure is 20-75%. In some embodiments, the average closed-cell size of the foam structure is 0.05-1.0 mm. In some embodiments, the thickness of the foam structure is 0.2-50 mm. In some embodiments, the foam structure is a single layer.

[0009] In some embodiments, the laminate comprises: a polyethylene foam layer comprising: 40-65 wt% of low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), or a combination of LDPE and LLDPE; and 15-45 wt% of olefin block copolymer (OBC); and a laminate layer on one side of the polyethylene foam layer. In some embodiments, the laminate layer is a flexible film, fabric, or foil. In some embodiments, the laminate layer is unfoamed or foamed.

[0010] In some embodiments, the adhesive foam tape comprises: a polyethylene foam layer comprising: 40-65 wt% of low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), or a combination of LDPE and LLDPE; and 15-45 wt% of an olefin block copolymer (OBC); and a pressure-sensitive adhesive layer on one side of the polyethylene foam layer. In some embodiments, the tape comprises a second pressure-sensitive adhesive layer on the side of the polyethylene foam layer opposite to the first pressure-sensitive adhesive layer. In some embodiments, any of the pressure-sensitive adhesive layers comprises one or more of the following: acrylic polymers, polyurethanes, thermoplastic elastomers, block copolymers, polyolefins, silicones, rubber-based adhesives, copolymers of ethylhexyl acrylate and acrylic acid, copolymers of isooctyl acrylate and acrylic acid, or combinations thereof.

[0011] In some embodiments, a method of forming polyethylene foam includes: extruding a foam layer comprising: 40-65 wt% of low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), or a combination of LDPE and LLDPE; and 15-45 wt% of olefin block copolymer (OBC); irradiating the extruded foam layer with ionizing radiation; and foaming the irradiated extruded foam layer. In some embodiments, the foam layer comprises 50-65 wt% of low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), or a combination of LDPE and LLDPE. In some embodiments, the foam layer comprises 20-35 wt% of olefin block copolymer (OBC). In some embodiments, the foam layer comprises 5-15 wt% of a chemical blowing agent prior to foaming. In some embodiments, the foam layer comprises 1-10 wt% of an antioxidant masterbatch. In some embodiments, the foam layer comprises 0.5-5 wt% of a processing aid masterbatch. In some embodiments, the foam layer contains 1-10 wt% of a chemical foaming agent decomposition inhibitor masterbatch. In some embodiments, the foam layer contains 1-10 wt% of an anti-blocking agent masterbatch. In some embodiments, the foam layer contains 1-12 wt% of a colorant masterbatch. In some embodiments, the melt flow index of the foam layer at 190°C is 0.1-25 g / 10 min. In some embodiments, the density of the foam layer after foaming, irradiation, and extrusion is 15-200 kg / m³. 3 In some embodiments, the average closed-cell size of the foamed, irradiated, and extruded foam layer is 0.05-1.0 mm. In some embodiments, the thickness of the foamed, irradiated, and extruded foam layer is 0.2-50 mm. In some embodiments, the ionizing radiation is selected from alpha, beta (electron), x-rays, gamma rays, and neutrons. In some embodiments, the extruded foam layer is irradiated up to four times individually. In some embodiments, the ionizing radiation crosslinks the extruded foam layer to a crosslinking degree of 20-75%. In some embodiments, foaming includes heating the irradiated extruded foam layer using a molten salt and radiation heater or hot air oven. In some embodiments, the method includes applying a laminate layer to one side of the irradiated foamed extruded foam layer. In some embodiments, the method includes applying a pressure-sensitive adhesive layer to one side of the irradiated foamed extruded foam layer. In some embodiments, a further method includes applying a second pressure-sensitive adhesive layer to the side of the irradiated foamed extruded foam layer opposite to the first pressure-sensitive adhesive layer.

[0012] As used herein, the singular forms “a,” “an,” and “the” are intended to also include the plural forms, unless the context clearly indicates otherwise. It should also be understood that, as used herein, the term “and / or” refers to and includes any and all possible combinations of one or more of the associated listed items. Furthermore, it should be understood that, when used herein, the terms “comprising,” “including,” “containing,” and / or “comprising” specify the presence of the stated feature, integer, step, operation, element, component, and / or unit, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, units, and / or groups thereof.

[0013] It should be understood that the aspects and embodiments described herein include those “consisting of” and / or “substantially constituted thereof”. For all methods, systems, compositions, and apparatuses described herein, a method, system, composition, and apparatus may comprise, or may be “consisting of” or “substantially constituted thereof” the listed components or steps. When a system, composition, or apparatus is described as “substantially constituted” the listed components, the system, composition, or apparatus comprises the listed components and may include other components that substantially do not affect the performance of the system, composition, or apparatus, but does not contain any other components besides those expressly listed that substantially affect the performance of the system, composition, or apparatus; or does not contain additional components in sufficient concentration or amount to substantially affect the performance of the system, composition, or apparatus. When a method is described as “substantially constituted” the listed steps, the method includes the listed steps and may include other steps that do not substantially affect the results of the method, but does not include any other steps besides those expressly listed that substantially affect the results of the method.

[0014] In this invention, "substantially free of" a specific component, composition, compound, or ingredient in various embodiments means the presence of less than about 5%, less than about 2%, less than about 1%, less than about 0.5%, less than about 0.1%, less than about 0.05%, less than about 0.025%, or less than about 0.01% of the specific component, composition, compound, or ingredient by weight. Preferably, "substantially free of" a specific component, composition, compound, or ingredient means the presence of less than about 1% of the specific component, composition, compound, or ingredient by weight.

[0015] Further advantages will become readily apparent to those skilled in the art from the following detailed description. The embodiments and descriptions herein are intended to be illustrative rather than restrictive. Detailed Implementation

[0016] Foam structures comprising low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), or combinations of LDPE and LLDPE, and olefin block copolymers (OBCs) are described, as well as methods for producing crosslinked closed-cell continuous polyethylene foam structures (e.g., films, layers, sheets, etc.). In some embodiments, the OBC may be a multi-block LLDPE copolymer containing stiffer, crystallizable LLDPE copolymer “blocks” and alternating, non-randomly distributed, amorphous, softer LLDPE copolymer “blocks,” i.e., in a controlled (non-random) block sequence. In some embodiments, the polyethylene foam structure may be obtained by: (a) extruding a foam composition, (b) irradiating the extruded foam composition with ionizing radiation, and (c) foaming the extruded irradiated composition.

[0017] In the extrusion step, raw materials for the foam composition can be fed into an extruder. The method of feeding the components into the extruder can be based on the extruder design and available material handling equipment. If necessary or desired, the components of the foam composition can be pre-blended to promote their dispersion. If this is done, a Henshel mixer can be used for pre-blending. In some embodiments, all components can be pre-blended and fed through a single port in the extruder. In some embodiments, the components can also be fed individually through a separately designated port for each component or into a single port in the extruder. For example, if the component is a liquid, the liquid can be added through a feed port (or multiple feed ports) on the extruder or through a discharge port on the extruder (if equipped with a discharge port), rather than pre-blending with the solid components. A combination of pre-blending and individual component port feeding can also be used. Exemplary extrusion techniques are also disclosed in Chapter 8 of the Handbook of Polymeric Foam and Foam Technology (2nd Edition, edited by Daniel Klempner and Vahid Sendijarevic), the subject of which is incorporated herein by reference in its entirety.

[0018] In some embodiments, the extruder can feed a stable amount of foam composition into a tableting die head to produce an unfoamed sheet composition. The thickness of the unfoamed sheet can be controlled across the entire die head gap. However, the sheet thickness can be further adjusted, for example, by stretching (i.e., “drawing”) the molten extrudate and / or by planarizing the molten extrudate through the roll gap. It should be understood that, as used herein, the term foam structure includes various foam structures, including but not limited to foam sheets, films, layers, etc.

[0019] The foam composition fed into the extruder may comprise low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), or a combination of LDPE and LLDPE, and an olefin block copolymer (OBC). In some embodiments, the OBC may be a multi-block LLDPE copolymer containing stiffer, crystallizable LLDPE copolymer “blocks” and alternating non-randomly distributed, amorphous, softer LLDPE copolymer “blocks,” i.e., in a controlled (non-random) block sequence.

[0020] In some embodiments, the foam composition fed into the extruder may be at least about 70 wt%, at least about 75 wt%, at least about 80 wt%, or at least about 85 wt% of LDPE, LLPDE, OBC, or a combination thereof. In some embodiments, the foam composition fed into the extruder may be at most about 90 wt%, at most about 87 wt%, at most about 84 wt%, or at most about 81 wt% of LDPE, LLPDE, OBC, or a combination thereof. In some embodiments, the foam composition fed into the extruder may be about 70-90 wt%, about 75-87 wt%, or about 80-84 wt% of LDPE, LLPDE, OBC, or a combination thereof.

[0021] In some embodiments, the amount of LDPE, LLDPE, or a combination of LDPE and LLDPE in the polyethylene foam composition fed into the extruder may be at least about 30 wt%, at least about 35 wt%, at least about 40 wt%, at least about 45 wt%, at least about 48 wt%, at least about 50 wt%, at least about 52 wt%, at least about 55 wt%, at least about 58 wt%, or at least about 60 wt% of LDPE, LLDPE, or a combination of LDPE and LLDPE. In some embodiments, the amount of LDPE, LLDPE, or a combination thereof in the polyethylene foam composition fed into the extruder may be up to about 42 wt%, up to about 45 wt%, up to about 50 wt%, up to about 52 wt%, up to about 55 wt%, up to about 58 wt%, up to about 60 wt%, up to about 62 wt%, up to about 65 wt%, up to about 68 wt%, up to about 70 wt%, or up to about 75 wt% of LDPE, LLDPE, or a combination of LDPE and LLDPE. In some embodiments, the amount of LDPE, LLDPE, or a combination thereof in the polyethylene foam composition fed into the extruder may be about 30-80 wt%, about 35-75 wt%, about 35-70 wt%, about 40-65 wt%, about 40-60 wt%, about 40-55 wt%, about 40-50 wt%, about 45-65 wt%, about 45-60 wt%, about 45-55 wt%, about 48-62 wt%, about 48-60 wt%, about 48-58 wt%, about 50-65 wt%, or about 50-60 wt% of LDPE, LLDPE, or a combination of LDPE and LLDPE.

[0022] In some embodiments, the amount of LDPE, LLDPE, or a combination of LDPE and LLDPE in the polyethylene foam composition fed into the extruder may be greater than or equal to about 15, 20, 25, 30, 35, 40, 45, or 50 phr of LDPE, LLDPE, or a combination of LDPE and LLDPE. In some embodiments, the amount of LDPE, LLDPE, or a combination of LDPE and LLDPE in the polyethylene foam composition fed into the extruder may be less than or equal to about 50, 55, 60, 65, 70, 75, 80, or 85 phr of LDPE, LLDPE, or a combination of LDPE and LLDPE. In some embodiments, the amount of LDPE, LLDPE, or a combination of LDPE and LLDPE in the polyethylene foam composition fed into the extruder can be about 15-85, 15-80, 15-75, 20-85, 20-80, 20-75, 50-85, 50-80, 50-75, 50-70, 50-65, 50-60, 60-85, 60-80, 60-75, 70-85, or 70-80 PHR of LDPE, LLDPE, or a combination of LDPE and LLDPE.

[0023] In some embodiments, the amount of LDPE in the polyethylene foam composition fed into the extruder may be at least about 10 wt%, at least about 15 wt%, at least about 18 wt%, at least about 20 wt%, at least about 22 wt%, at least about 24 wt%, at least about 26 wt%, at least about 30 wt%, at least about 35 wt%, at least about 38 wt%, at least about 40 wt%, at least about 42 wt%, at least about 45 wt%, at least about 48 wt%, at least about 50 wt%, or at least about 55 wt% of LDPE. In some embodiments, the amount of LDPE in the polyethylene foam composition fed into the extruder may be up to about 40 wt%, up to about 45 wt%, up to about 48 wt%, up to about 50 wt%, up to about 52 wt%, up to about 55 wt%, up to about 60 wt%, up to about 62 wt%, up to about 65 wt%, up to about 70 wt%, up to about 73 wt%, up to about 75 wt%, or up to about 80 wt% of LDPE. In some embodiments, the amount of LDPE in the polyethylene foam composition fed into the extruder may be about 10-80 wt%, about 15-75 wt%, about 20-70 wt%, about 24-65 wt%, about 20-30 wt%, about 35-45 wt%, about 35-55 wt%, about 35-50 wt%, about 45-55 wt%, about 45-60 wt%, about 50-60 wt%, or about 50-65 wt% of LDPE.

[0024] In some embodiments, the amount of LDPE in the polyethylene foam composition fed into the extruder can be greater than or equal to about 20, 25, 30, 35, 40, 45, or 50 phr of LDPE. In some embodiments, the amount of LDPE in the polyethylene foam composition fed into the extruder can be less than or equal to about 50, 55, 60, 65, 70, 75, or 80 phr of LDPE. In some embodiments, the amount of LDPE in the polyethylene foam composition fed into the extruder can be about 20-80, 20-75, 25-80, 25-75, 30-80, 30-75, 30-70, 30-65, 30-60, 30-55, 30-50, 50-80, 50-75, 50-70, 50-60, 60-80, 60-75, or 70-80 phr of LDPE.

[0025] In some embodiments, the amount of LLDPE in the polyethylene foam composition fed into the extruder may be at least about 5 wt%, at least about 8 wt%, at least about 10 wt%, at least about 12 wt%, at least about 15 wt%, at least about 17 wt%, at least about 20 wt%, at least about 22 wt%, at least about 24 wt%, at least about 25 wt%, at least about 26 wt%, at least about 30 wt%, or at least about 35 wt% of LLDPE. In some embodiments, the amount of LLDPE in the polyethylene foam composition fed into the extruder may be at most about 30 wt%, at most about 35 wt%, at most about 40 wt%, at most about 42 wt%, at most about 44 wt%, at most about 45 wt%, at most about 46 wt%, at most about 48 wt%, at most about 50 wt%, at most about 52 wt%, at most about 55 wt%, at most about 60 wt%, or at most about 65 wt% of LLDPE. In some embodiments, the amount of LLDPE in the polyethylene foam composition fed into the extruder may be about 5-65 wt%, about 5-60 wt%, about 10-55 wt%, about 15-50 wt%, about 10-20 wt%, about 10-30 wt%, about 20-30 wt%, about 20-40 wt%, about 20-50 wt%, about 20-55 wt%, about 40-50 wt%, about 40-55 wt%, about 45-55 wt%, or about 45-50 wt% of LLDPE.

[0026] In some embodiments, the amount of LLDPE in the polyethylene foam composition fed into the extruder can be greater than or equal to about 15, 20, 25, 30, 35, 40, 45, or 50 phr of LLDPE. In some embodiments, the amount of LLDPE in the polyethylene foam composition fed into the extruder can be less than or equal to about 50, 55, 57.5, 60, 65, or 70 phr of LLDPE. In some embodiments, the amount of LLDPE in the polyethylene foam composition fed into the extruder can be about 15-70, 15-65, 15-60, 20-70, 20-65, 20-60, 20-40, 20-30, 30-70, 30-65, 30-60, 50-70, 50-65, or 50-60 phr of LLDPE.

[0027] In some embodiments, the amount of OBC in the polyethylene foam composition fed into the extruder may be at least about 10 wt%, at least about 15 wt%, at least about 20 wt%, at least about 22 wt%, at least about 25 wt%, at least about 27 wt%, at least about 30 wt%, at least about 32 wt%, at least about 35 wt%, at least about 38 wt%, or at least about 40 wt% of OBC. In some embodiments, the amount of OBC in the polyethylene foam composition fed into the extruder may be at most about 20 wt%, at most about 25 wt%, at most about 30 wt%, at most about 32 wt%, at most about 35 wt%, at most about 37 wt%, at most about 40 wt%, at most about 45 wt%, at most about 48 wt%, or at most about 50 wt% of OBC. In some embodiments, the amount of OBC in the polyethylene foam composition fed into the extruder may be about 10-50 wt%, about 15-45 wt%, about 20-40 wt%, about 20-35 wt%, about 20-30 wt%, about 22-35 wt%, about 22-32 wt%, about 25-35 wt%, about 30-45 wt%, or about 30-40 wt% of OBC.

[0028] In some embodiments, the amount of OBC in the polyethylene foam composition fed into the extruder can be greater than or equal to about 15, 20, 25, 26, 30, 35, or 40 PHR of OBC. In some embodiments, the amount of OBC in the polyethylene foam composition fed into the extruder can be less than or equal to about 42, 42.5, 43, 45, 50, or 55 PHR of OBC. In some embodiments, the amount of OBC in the polyethylene foam composition fed into the extruder can be about 15-55, 15-50, 15-45, 15-40, 20-55, 20-50, 20-45, 20-40, 25-55, 25-50, 25-45, 25-40, 25-35, 30-55, 30-50, 30-45, 30-40, 35-55, 35-50, 35-45, 40-55, or 40-50 PHR of OBC.

[0029] Since the disclosed foam compositions can be used to manufacture a wide range of foam articles, a wide range of LD, LLD and OBC polyethylenes can be used in the compositions to meet different process manufacturing requirements and commercial end-use requirements.

[0030] LDPE is a low-density polyethylene homopolymer, typically produced in high-pressure tubular and autoclave reactors. In the reaction, gaseous ethylene monomers are polymerized under extremely high pressure and temperature in the presence of an oxide initiator to produce polymer structures with both long and short branches. LDPE is one of the most widely produced commercial thermoplastics worldwide, manufactured by large multinational corporations (Dow, ExxonMobil, LyondellBasell, Sinopec, PetroChina, SABIC, Borealis, etc.) and small and medium-sized companies (Westlake, Nova, Japan Polyethylene, Repsol, PKN Orlen, Carmel, etc.). Non-limiting examples of commercial LDPE grades are sold under different trademarks. For example, the LDPE manufacturers listed above sell their product grades under the trademark: Dow TM LDPE (Dow), ExxonMobil TM LDPE (ExxonMobil), SINOPEC LDPE (Sinopec), LDPE,Borealis LDPE,WestlakePolyethylene TM (Westlake) (Nova), -LD(JapanPolyethylene), Repsol Alcudia and Repsol PE (Repsol), Malen(PKNOrlen), and (Carmel)

[0031] LLDPE is linear low-density polyethylene, typically produced in a low-pressure fluidized bed reactor at temperatures much lower than LDPE. In the reaction, gaseous ethylene monomers (and very commonly other α-olefin comonomers) are polymerized via a multi-site transition metal Ziegler-Natta catalyst to produce a branched, essentially linear polymer structure exhibiting significantly more but shorter branches compared to LDPE. Long-chain branching is absent in LLDPE.

[0032] LLDPE can be a polyethylene homopolymer, but it is more commonly produced commercially as a random copolymer or random terpolymer. Most commercial LLDPEs are polymerized with at least one C3-C... 20 α-olefin copolymers, among which 1-butene, 1-hexene and 1-octene are the most typical.

[0033] Many LDPE polymer manufacturers also produce LLDPE polymers. Non-limiting examples of commercial LLDPE grades from the LDPE manufacturers listed above are sold and distributed under the following trademarks: Dow TM LLDPE and Dowlex TM (Dow), ExxonMobil TM LLDPE and ExxonMobil TM NTX LLDPE (ExxonMobil), SINOPEC LLDPE (Sinopec), LLDPE (Sabic), Borealis LLDPE and (Borealis), and HIFOR (Westlake) and and (Nova) and -LL (Japan Polyethylene).

[0034] "Polyvinyl OBC" (referred to as OBC herein) is a multi-block LLDPE copolymer containing stiffer, crystallizable LLDPE copolymer "blocks" and alternating, non-randomly distributed, amorphous, softer LLDPE copolymer "blocks," i.e., in a controlled (non-random) block sequence. The softer blocks contain higher amounts of comonomers (most commonly C3-C) than the stiffer blocks. 20α-olefins). OBC is produced in a reactor using two “post-metallocene” (non-metallocene unit site and / or catalysts capable of non-metallocene unit site polymerization) catalysts (catalysts for polymerization of each block) via tandem catalysis. Polymer synthesis occurs by transferring polymer chains from one catalyst to another (and vice versa) and is referred to as “chain shuttle copolymerization.” Examples of OBC include, but are not limited to, INFUSE from Dow. TM OBC product line. In commercially manufactured INFUSE TM In the OBC product line, the copolymers are 1-octene in both the harder and softer blocks.

[0035] The melt flow index (MFI) of polyethylene in the foamable sheets described herein can be approximately 0.1 to approximately 25 g / 10 min at 190°C. In some embodiments, the MFI of polyethylene at 190°C is approximately 0.3 to approximately 20 g / 10 min, or approximately 0.5 to approximately 15 g / 10 min at 190°C. The MFI values ​​of polyethylene provided herein are defined and measured according to ASTM D1238 at 190°C using a 2.16 kg plunger for 10 minutes. For resins with relatively high melt flow, the testing time can be reduced.

[0036] MFI provides a measure of the flow properties of a polymer and is an indicator of the molecular weight and processability of the polymer material. A high MFI value corresponds to low viscosity. If the MFI value is too high, extrusion according to the invention may not be satisfactory. Problems associated with an excessively high MFI value may include low pressure during extrusion, problems setting thickness distribution, uneven cooling distribution due to low melt viscosity, poor melt strength, and / or machine problems. Conversely, a low MFI value corresponds to high viscosity. An excessively low MFI value may lead to high pressure during melt processing, sheet quality and profile problems, and higher extrusion temperatures, which result in the risk of chemical foaming agent decomposition and activation.

[0037] The aforementioned MFI ranges are important for the foaming process because they reflect the viscosity of the material, which has a certain impact on foaming. Without being bound by any theory, there are believed to be several reasons why a particular MFI value might be more effective. Lower MFI materials improve some physical properties because the molecular chain length is larger, resulting in more energy required to generate chain flow under stress. Furthermore, the longer the molecular chain (MW), the more crystalline entities that the chain can crystallize, thus providing greater strength through intermolecular bonding. However, at too low an MFI, the viscosity becomes too high. On the other hand, polymers with higher MFI values ​​have shorter chains. Therefore, in a given volume of material with a higher MFI value, there may be more chain ends at the microscopic level relative to a polymer with a lower MFI value, which rotate and generate free volume due to the space required for such rotation (e.g., rotation occurring above the polymer's Tg or glass transition temperature). This increases the free volume and allows for easy flow under stress, which can lead to cell degradation and "foam collapse" in the foamed polymer blend.

[0038] In addition to the polymer, the composition fed into the extruder may also contain additives compatible with the production of the disclosed polyethylene foam. Common additives include, but are not limited to, chemical foaming agents (CFAs), crosslinking accelerators, organic peroxides, antioxidants, lubricants, processing aids, heat stabilizers, colorants, flame retardants, antistatic agents, static dissipative agents, nucleating agents, plasticizers, antimicrobial agents, fungicides, light stabilizers, UV absorbers, antiblocking agents, fillers, deodorizers, odor absorbers, antifogging agents, volatile organic compound (VOC) adsorbents, semi-volatile organic compound (SVOC) adsorbents, thickeners, cell size stabilizers, metal passivators, chemical foaming agent (CFA) decomposition accelerators, chemical foaming agent (CFA) inhibitors, optical clarifying agents, and combinations thereof.

[0039] In some embodiments, the foam composition may contain a chemical blowing agent (CFA). In some embodiments, the extrusion temperature of the foam composition may be at least 10°C lower than the thermal decomposition initiation temperature of the chemical blowing agent. If the extrusion temperature exceeds the thermal decomposition temperature of the blowing agent, the blowing agent will decompose, resulting in undesirable "pre-foaming".

[0040] In some embodiments, the foam composition may contain a variety of different chemical blowing agents, and may include both exothermic and endothermic types. Examples of chemical blowing agents include, but are not limited to, azo compounds, hydrazine compounds, carbazide, tetrazolium, nitroso compounds, and carbonates. Furthermore, chemical blowing agents may be used alone or in any combination. In some embodiments, one chemical blowing agent that can be used is azodicarbonamide (ADCA). Two examples of commercially produced ADCA chemical blowing agents are UNIFOAM manufactured by PTLauten Otsuka Chemical. TM TC-181 (100% ADCA) and VINYFOR manufactured by EIWA Chemical TM AC-961 (≥90% ADCA). Thermal decomposition of ADCA typically occurs at temperatures of approximately 190-230°C. In some embodiments, to prevent thermal decomposition of ADCA in the extruder, the extrusion temperature may be maintained at 190°C or lower.

[0041] The amount of chemical blowing agent in the foam composition can be less than or equal to about 30 phr, about 20 phr, about 15 phr, or about 11 phr of the composition. In some embodiments, the amount of chemical blowing agent in the foam composition can be greater than or equal to about 2 phr, about 4 phr, about 6 phr, or about 8 phr of the composition. In some embodiments, the amount of chemical blowing agent in the foam composition can be about 2-30 phr, about 4-20 phr, about 6-15 phr, or about 8-11 phr of the composition. In some embodiments, the amount of chemical blowing agent in the foam composition can be about 1-30 wt%, about 3-20 wt%, about 5-14 wt%, about 5-10 wt%, or about 6-9 wt% of the composition. In some embodiments, the amount of chemical blowing agent can depend on the thickness of the unfoamed sheet, the desired foam thickness, the desired foam density, the extruded material, the crosslinking percentage, the type of chemical blowing agent (different blowing agents can produce significantly different amounts of gas), etc.

[0042] In some embodiments, the amounts of chemical blowing agents listed above may be specifically for ADCA. In some embodiments, other blowing agents may produce different amounts of volumetric gas / CFA mass, and these can be taken into account accordingly. For example, when comparing ADCA with the chemical blowing agent p-toluenesulfonamide (TSS), if the expandable sheet contains 40 phr of ADCA, approximately 63 phr of TSS may be required to produce approximately the same amount of gas during the foaming step.

[0043] In some embodiments, the amount of additives other than chemical blowing agents in the foam composition may be less than or equal to about 40 phr, about 30 phr, about 25 phr, or about 20 phr of the composition. In some embodiments, the amount of additives other than chemical blowing agents in the foam composition may be greater than or equal to about 1 phr, about 3 phr, about 4 phr, or about 5 phr of the composition. In some embodiments, the amount of additives other than chemical blowing agents in the foam composition may be about 1-40 phr, about 3-30 phr, about 4-25 phr, or about 5-20 phr of the composition. In some embodiments, the amount of additives other than chemical blowing agents in the foam composition may be about 1-35 wt%, about 2-25 wt%, about 3-20 wt%, or about 4-16 wt% of the foam composition.

[0044] In some embodiments, the foam composition may contain one or more antioxidant additives. In some embodiments, the antioxidant additives may be in the form of masterbatches. In some embodiments, the antioxidant additive masterbatches may include, but are not limited to, PM13633 (Techmer PM), PT213 (Toray Plastics), PM14809 (Techmer PM), etc., each of which may contain a custom blend of a commonly used polyolefin antioxidant specifically formulated for the manufacturing process and the performance requirements of the foam's end use. In some embodiments, the amount of antioxidant masterbatch in the foam composition may be less than or equal to about 10 PHR, 8 PHR, or 6 PHR of the composition. In some embodiments, the amount of antioxidant masterbatch in the foam composition may be greater than or equal to 1 PHR, 2 PHR, 3 PHR, or 4 PHR of the composition. In some embodiments, the amount of antioxidant masterbatch in the foam composition may be about 1-10 PHR, 1-8 PHR, 1-6 PHR, 2-6 PHR, or 2-4 PHR of the composition. In some embodiments, the amount of antioxidant masterbatch in the foam composition may be about 0.1-10 wt%, about 0.25-8 wt%, about 0.5-6 wt%, about 1-4 wt%, about 1.5-4 wt%, or about 1.5-3.5 wt% of the foam composition.

[0045] It is important to note that antioxidant manufacturers and distributors will recommend one or more specific antioxidants, the recommended ratios between these antioxidants, and suggest dilution ratios for specific foam compositions when manufacturing methods and end-use performance requirements are disclosed. Typically, manufacturers of polyethylene foam use masterbatches of specially formulated antioxidant blends. Exemplary manufacturers of antioxidants for polyethylene include, but are not limited to, Adeka, BASF, Clariant, SIGroup, and Songwong.

[0046] In some embodiments, the foam composition may contain one or more processing aid additives. In some embodiments, the processing aid additives may be in the form of masterbatches. In some embodiments, the processing aid additive masterbatches may include, but are not limited to, TPM11166 (distributed by Techmer PM) and PM125000 (formulated by Techmer PM). In some embodiments, the amount of processing aid masterbatch in the foam composition may be less than or equal to about 5 PHR, 4 PHR, or 3 PHR of the composition. In some embodiments, the amount of processing aid masterbatch in the foam composition may be greater than or equal to 1 PHR, 2 PHR, or 3 PHR of the composition. In some embodiments, the amount of processing aid masterbatch in the foam composition may be about 1-5 PHR, 1-4 PHR, 1-3 PHR, 2-4 PHR, or 2-3 PHR of the composition. In some embodiments, the amount of processing aid masterbatch in the foam composition may be about 0.1-6 wt%, about 0.1-5 wt%, about 0.25-5 wt%, about 0.5-5 wt%, about 0.5-4 wt%, about 0.5-3 wt%, about 0.5-2 wt%, about 1-2 wt%, or about 1.5-2 wt% of the foam composition.

[0047] In some embodiments, the foam composition may contain one or more chemical blowing agent (CFA) decomposition inhibitor additives. In some embodiments, the CFA decomposition inhibitor additives may be in the form of a masterbatch. In some embodiments, the CFA decomposition inhibitor additive masterbatch may include, but is not limited to, Toray Plastics (USA) masterbatch, part number PT120 (formulated by Techmer PM). In some embodiments, the amount of CFA decomposition inhibitor masterbatch in the foam composition may be less than or equal to about 10 PHR, 8 PHR, or 6 PHR of the composition. In some embodiments, the amount of CFA decomposition inhibitor masterbatch in the foam composition may be greater than or equal to 1 PHR, 2 PHR, 3 PHR, or 4 PHR of the composition. In some embodiments, the amount of CFA decomposition inhibitor masterbatch in the foam composition may be about 1-10 PHR, 1-8 PHR, 1-6 PHR, 2-6 PHR, or 2-4 PHR of the composition. In some embodiments, the amount of CFA decomposition inhibitor masterbatch in the foam composition may be about 1-10 wt%, about 1-8 wt%, about 1-6 wt%, about 1-4 wt%, about 1.5-4 wt%, or about 2-4 wt% of the foam composition.

[0048] In some embodiments, the foam composition may contain one or more anti-blocking additives. In some embodiments, the anti-blocking additives may be in the form of masterbatches. In some embodiments, the anti-blocking additive masterbatches may include, but are not limited to, TPM1823 talc anti-blocking agent, TPM1922 diatomaceous earth anti-blocking agent, and TPM14287 calcium carbonate anti-blocking agent (all distributed by Techmer PM). In some embodiments, the amount of anti-blocking masterbatch in the foam composition may be less than or equal to about 10 PHR, 8 PHR, or 6 PHR of the composition. In some embodiments, the amount of anti-blocking masterbatch in the foam composition may be greater than or equal to 2 PHR, 3 PHR, 4 PHR, or 5 PHR of the composition. In some embodiments, the amount of anti-blocking masterbatch in the foam composition may be about 1-10 PHR, 2-8 PHR, 2-6 PHR, 3-6 PHR, or 4-6 PHR of the composition. In some embodiments, the amount of anti-blocking masterbatch in the foam composition may be about 1-10 wt%, about 1-8 wt%, about 1-6 wt%, about 1-4 wt%, about 2-6 wt%, about 2-4 wt%, about 2.5-3.5 wt%, or about 3 wt% of the foam composition.

[0049] In some embodiments, the foam composition may contain one or more colorant additives. In some embodiments, the colorant additives may be in the form of a masterbatch. In some embodiments, the colorant additive masterbatch may include, but is not limited to, 62B17226 (black, Penn Color), PM55274 (white hue, Techmer PM), etc. In some embodiments, the amount of colorant masterbatch in the foam composition may be less than or equal to about 15 phr, 13 phr, or 11 phr of the composition. In some embodiments, the amount of colorant masterbatch in the foam composition may be greater than or equal to 2 phr, 3 phr, or 4 phr of the composition. In some embodiments, the amount of colorant masterbatch in the foam composition may be about 2-15 phr, 2-13 phr, 2-11 phr, 3-13 phr, or 4-11 phr of the composition. In some embodiments, the amount of colorant masterbatch in the foam composition may be about 1-12 wt%, about 1-10 wt%, about 1-9 wt%, about 2-9 wt%, or about 3-9 wt% of the foam composition.

[0050] It is important to note that there are many masterbatch compounders worldwide that produce both "off-the-shelf" masterbatches and custom masterbatches for distribution, depending on the foam manufacturing method and end-use color requirements. Exemplary compounders for masterbatches used in polyethylene include, but are not limited to, Techmer PM, Penn Color, Tosaf, Modern Dispersions (MDI), Colors For Plastics, Peacock Colors, Coloron Plastics, Clariant, and others.

[0051] In some embodiments, the foam composition may contain a black colorant masterbatch. For example, the amount of black colorant in the foam composition may be less than or equal to 15 phr, 13 phr, or 11 phr of the composition. In some embodiments, the amount of black colorant masterbatch in the foam composition may be greater than or equal to 4 phr, 5 phr, or 6 phr of the composition. In some embodiments, the amount of black colorant masterbatch in the foam composition may be about 4-15 phr, 5-13 phr, or 6-11 phr of the composition. In some embodiments, the amount of black colorant masterbatch in the foam composition may be about 4-12 wt%, about 4-11 wt%, about 5-10 wt%, or about 6-9 wt% of the foam composition.

[0052] In some embodiments, the foam composition may contain a white colorant masterbatch. For example, the amount of white colorant masterbatch in the foam composition may be less than or equal to 10 phr, 8 phr, or 7 phr of the composition. In some embodiments, the amount of white colorant masterbatch in the foam composition may be greater than or equal to 2 phr, 3 phr, or 4 phr of the composition. In some embodiments, the amount of white colorant masterbatch in the foam composition may be about 2-10 phr, about 3-8 phr, or about 4-7 phr of the composition. In some embodiments, the amount of white colorant masterbatch in the foam composition may be about 1-8 wt%, about 1-7 wt%, about 1-6 wt%, or about 2-6 wt% of the foam composition.

[0053] Regardless of the composition of the foam composition fed into the extruder, the shear forces and mixing within the extruder can be sufficient to produce a uniform layer (also referred to herein as a sheet, film, structure, etc.). Co-rotating and counter-rotating twin-screw extruders can provide sufficient shear forces and mixing through the extruder barrel to extrude sheets with uniform properties.

[0054] Specific energy can be an indicator of the amount of work applied during component extrusion and the intensity of the extrusion process. Specific energy is defined as the energy applied to the material being processed through the extruder, normalized to a per-kilogram basis. Specific energy can be quantified in kilowatts (kW) of energy applied per kilogram of total material per hour of feed. Specific energy can be calculated using the following formula:

[0055] in

[0056]

[0057] Specific energy can be used to quantify the amount of shearing and mixing of components within an extruder. An extruder used to form the foamable sheets disclosed herein is capable of producing a specific energy of at least about 0.020 kW·h / kg, at least about 0.025 kW·h / kg, at least about 0.050 kW·h / kg, or at least about 0.100 kW·h / kg.

[0058] If the difference between the decomposition temperature of the thermally decomposable blowing agent and the melting point of the polymer with the highest melting point is high, a catalyst for blowing agent decomposition can be used. Exemplary catalysts include, but are not limited to, zinc oxide, magnesium oxide, calcium stearate, glycerol, and urea. The lower limit of the extrusion temperature can be the melting point of the polymer with the highest melting point. If the extrusion temperature drops below the melting temperature of the polymer with the highest melting point, an undesirable "unmelted body" will occur. During foaming, sheets extruded below this lower limit of temperature will exhibit uneven thickness, uneven cell structure, cell collapse pockets, and / or other undesirable properties.

[0059] Regardless of whether the foaming agent is physical, chemical, or combined, typical extrusion foaming can produce polymer sheets (e.g., layers, films, structures) where the two main surfaces can be significantly rougher than equivalent structures produced by the disclosed methods. The surface profile of the foam sheet is important in many applications, therefore extruded foam sheets cannot be used for these applications. These applications may include smooth foam surfaces to achieve desired properties, such as improved contact area percentage when pressure-sensitive adhesives (PSA) are applied to the foam surface; ease of lamination into films, fabrics, fiber layers, and leather; contact area percentage in lamination; and / or visual aesthetics, etc. PC Publication WO2016109544 (which is incorporated herein by reference in its entirety) includes examples illustrating the difference in surface roughness between extruded foam polymer sheets and equivalent foam polymer sheets produced by the disclosed methods.

[0060] The rougher surface of extruded foamed articles can often be caused by larger cell size (when compared to foam produced according to the present invention). Although cell size and cell size distribution may be irrelevant in most commercial applications, because surface roughness is a function of cell size, foam with larger cells may not be as ideal as foam with smaller cells for applications requiring a smooth foam surface.

[0061] The thickness of the unfoamed extruded sheet can be about 0.1-30 mm, about 0.2-25 mm, about 0.3-20 mm, or about 0.4-15 mm. In some embodiments, the thickness of the unfoamed extruded sheet can be about 0.1-5 mm, about 0.5-3 mm, about 1-2 mm, or about 1-1.5 mm. In some embodiments, the thickness of the unfoamed extruded sheet can be less than or equal to about 5 mm, about 3 mm, about 2 mm, about 1.5 mm, about 1 mm, or about 0.5 mm. In some embodiments, the thickness of the unfoamed extruded sheet can be greater than or equal to about 0.1 mm, about 0.5 mm, about 1 mm, about 1.5 mm, about 2 mm, or about 3 mm.

[0062] In this invention, a thickness gauge is used to measure the thickness of an unfoamed extruded sheet, wherein the sheet is placed on a flat, horizontal surface and brought into contact with a spring-loaded plunger equipped with the thickness gauge. A 3mm hemispherical tip is attached to the plunger and brought into contact with the sheet under a force of 26.5 + / - 3.5 grams.

[0063] There is a difference between “physical” crosslinking and “chemical” crosslinking. In chemical crosslinking, crosslinking is generated using a crosslinking accelerator, but ionizing radiation is not used. Chemical crosslinking typically involves the use of peroxides, silanes, or vinylsilanes. In peroxide crosslinking methods, crosslinking usually occurs in the extrusion die. For silane and vinylsilane crosslinking methods, crosslinking usually occurs in a second operation after extrusion, where the crosslinking of the extruded material is accelerated by heat and moisture. Regardless of the chemical crosslinking method, chemically crosslinked foam sheets can generally exhibit a master surface that is significantly rougher than the equivalent structure produced in the disclosed methods. The surface profile of the foam sheet is critical in many applications, therefore chemically crosslinked foam sheets cannot be used in certain applications. These applications may include smooth foam surfaces to achieve desired properties, such as improved contact area percentage when pressure-sensitive adhesives (PSA) are applied to the foam surface; ease of lamination into films, fabrics, fiber layers, and leather; contact area percentage in lamination; and / or visual aesthetics, etc. PCT Publication WO2016109544 includes examples illustrating the surface roughness difference between chemically cross-linked foamed polymer sheets and equivalent foamed polymer sheets produced by the disclosed method.

[0064] The rougher surface of chemically cross-linked foamed articles can often be caused by larger cell size (when compared to foams produced according to the present invention). Although cell size and size distribution may be irrelevant in most commercial applications, because surface roughness is a function of cell size, foams with larger cells may not be as ideal as foams with smaller cells for applications requiring a smooth foam surface.

[0065] Examples of ionizing radiation include, but are not limited to, alpha, beta (electron beams), X-rays, gamma rays, and neutrons. Electron beams with uniform energy can be used to crosslink foamable sheets. The exposure time, irradiation frequency (i.e., number of passes or exposures to radiation), and / or accelerating voltage during electron beam irradiation can vary widely depending on the intended degree of crosslinking and the thickness of the unfoamed sheet. However, ionizing radiation can typically be about 10–about 500 kGy, about 20–about 300 kGy, or about 20–about 200 kGy. If the exposure is too low, the crosslinking is too low, making it impossible to maintain cell stability during foaming. If the exposure is too high, the irradiated sheet will excessively curl and buckle during foaming, making it difficult to produce flat and uniform foamed sheets. Furthermore, highly irradiated sheets can be highly crosslinked, where crosslinking significantly reduces the polymer system's ability to essentially elongate. In cases where the foam expansion exceeds the limiting elongation properties of the irradiated composition, the poor elongation of the polymer system can cause the sheet to tear and break during foaming. Furthermore, unfoamed sheets soften due to the exothermic release when exposed to electron beam radiation, causing structural deformation when exposure is too high. Additionally, polymer components degrade due to excessive polymer chain scission.

[0066] Unfoamed sheets can be irradiated individually up to four times, no more than two times, or only once. If the radiation frequency is greater than approximately four times, the polymer components will degrade, resulting in uneven cell formation during foaming, for example, in the resulting foam. When the thickness of the extruded sheet is greater than approximately 4 mm, irradiating each major surface of the sheet with ionizing radiation will result in more uniform cross-linking throughout the entire depth of the sheet.

[0067] The advantage of electron beam irradiation is that extruded sheets of varying thicknesses can be effectively crosslinked by controlling the accelerating voltage of the electrons. Accelerating voltages are typically around 200–1500 kV, 300–1200 kV, or 400–1000 kV. If the accelerating voltage is less than about 200 kV, the radiation cannot reach the interior of the extruded sheet. As a result, the cells in the interior will be coarse and uneven during foaming. Furthermore, for a given thickness profile, an excessively low accelerating voltage can cause arcing, leading to "pinholes" or "tunnels" in the foamed structure. On the other hand, if the accelerating voltage is greater than about 1500 kV, the polymer will degrade due to excessive radiation exposure.

[0068] Regardless of the type of ionizing radiation chosen, crosslinking is performed to achieve crosslinking of the extruded composition to approximately 15-75%, 20-60%, 25-50%, or 30-40%, as measured by the Toray Gel Fraction Percentage Method. According to the Toray Gel Fraction Percentage Method, tetrahydronaphthalene solvent is used to dissolve the non-crosslinked components in the composition. In principle, the non-crosslinked material is dissolved in tetrahydronaphthalene, and the degree of crosslinking is expressed as a weight percentage of the crosslinked material in the entire composition. The apparatus used to determine the polymer crosslinking percentage includes: a 100-mesh (0.0045-inch wire diameter) 304 stainless steel bag; numbered wire and clips; a Miyamoto constant-temperature oil bath apparatus; an analytical balance; a fume hood; a gas burner; a high-temperature oven; an antistatic gun; and three 3.5-liter wide-mouth stainless steel containers with lids. The reagents and materials used include tetrahydronaphthalene high molecular weight solvent, acetone, and silicone oil. Specifically, the empty mesh bag is weighed and the weight is recorded. For each sample, weigh 100 mg ± 5 mg of sample and transfer it to a wire mesh bag. Record the weight of the wire mesh bag and the sample (usually in the form of thin slices of foam chips). Attach each bag to the appropriate number of wires and clips. When the solvent temperature reaches 130°C, immerse the bundle (bag and sample) in the solvent. Shake the sample up and down about 5 or 6 times to disperse any air bubbles and fully wet the sample. Attach the sample to a stirrer and stir for three (3) hours to allow the solvent to dissolve the foam. Then cool the sample in a fume hood. Wash the sample by shaking it up and down about 7 or 8 times in a container of primary acetone. Wash the sample a second time in a second acetone wash. Wash the washed sample again in a third container of fresh acetone as described above. Then hang the sample in a fume hood to evaporate the acetone for about 1 to about 5 minutes. Then dry the sample in a drying oven at 120°C for about 1 hour. Cool the sample for at least about 15 minutes. Weigh the wire mesh bag on an analytical balance and record the weight. Then, calculate the crosslinking using the following formula: 100*(CA) / (BA), where A = weight of empty mesh bag; B = weight of mesh bag before immersion in tetrahydronaphthalene + foam sample; and C = weight of mesh bag after immersion in tetrahydronaphthalene + dissolved sample.

[0069] In the formulations of embodiments of the present invention, no crosslinking accelerator is added. However, crosslinking accelerators may optionally be used to reduce the exposure of the foamable sheet to ionizing radiation to obtain the desired gel. Suitable crosslinking accelerators include, but are not limited to, commercially available bifunctional, trifunctional, tetrafunctional, pentafunctional, and higher-functionality monomers. Such crosslinking monomers may be available in liquid, solid, granular, and powder forms. Examples include, but are not limited to, acrylates or methacrylates, such as 1,6-hexanediol diacrylate, 1,6-hexanediol dimethacrylate, ethylene glycol diacrylate, ethylene glycol dimethacrylate, trimethylolpropane trimethacrylate, tetramethylolmethane triacrylate, 1,9-nonanediol dimethacrylate, and 1,10-decanediol dimethacrylate; allyl esters of carboxylic acids (e.g., triallyl trimellitate, triallyl pyromellitic acid, and diallyl oxalate); allyl esters of cyanuric acid or isocyanuric acid, such as triallyl cyanurate and triallyl isocyanurate; maleimide compounds such as N-phenylmaleimide and N,N'-m-phenylenebismaleimide; compounds having at least two triple bonds, such as diacetylacetate and diacetylacetate maleate; and divinylbenzene. Furthermore, such crosslinking promoters can be used alone or in any combination.

[0070] The crosslinking efficiency of a crosslinking accelerator can vary based on the ionizing radiation dose, the polymer to be crosslinked, the chemical structure of the monomer, the number of functional groups on the monomer, and / or whether the monomer is a liquid or a powder.

[0071] Crosslinking can be generated using a variety of different techniques and can be formed intermolecularly between different polymer molecules, as well as intramolecularly between portions of a single polymer molecule. Such techniques include, but are not limited to: (a) exposing polymer molecules to ionizing radiation, (b) providing a crosslinking promoter separate from the polymer chain and exposing the crosslinking promoter and the polymer to ionizing radiation, and / or (c) providing a polymer chain incorporating a crosslinking promoter as a functional group that can form crosslinks or be activated to form crosslinks.

[0072] After irradiation and extrusion of the sheet, foaming can be accomplished by heating the cross-linked sheet to a temperature above the decomposition temperature of the thermally decomposable foaming agent. In some embodiments, foaming can be carried out continuously at about 200-260°C or about 220-240°C. For the production of continuous foam sheets, continuous foaming processes are superior to batch processes.

[0073] Foaming can typically be achieved by heating the cross-linked sheet using molten salt, a radiant heater, a vertical or horizontal hot air oven, microwave energy, or a combination of these methods. Foaming can also be carried out during impregnation, for example, using nitrogen in an autoclave, followed by free foaming using molten salt, a radiant heater, a vertical or horizontal hot air oven, microwave energy, or a combination of these methods. Optionally, the cross-linked sheet can be softened by preheating before foaming. This helps stabilize the expansion of the structure during foaming, especially for thick and rigid sheets.

[0074] In some embodiments, the polyethylene foam structure may comprise at least about 70 wt%, at least about 75 wt%, at least about 80 wt%, or at least about 85 wt% of LDPE, LLPDE, or a combination of LDPE and LLDPE, and OBC. In some embodiments, the polyethylene foam structure may comprise at most about 90 wt%, at most about 87 wt%, at most about 84 wt%, or at most about 81 wt% of LDPE, LLPDE, or a combination of LDPE and LLDPE, and OBC. In some embodiments, the polyethylene foam structure may comprise about 70-90 wt%, about 75-87 wt%, or about 80-84 wt% of LDPE, LLPDE, or a combination of LDPE and LLDPE, and OBC.

[0075] In some embodiments, the amount of LDPE, LLDPE, or a combination of LDPE and LLDPE in the polyethylene foam structure may be at least about 30 wt%, at least about 35 wt%, at least about 40 wt%, at least about 45 wt%, at least about 48 wt%, at least about 50 wt%, at least about 52 wt%, at least about 55 wt%, at least about 58 wt%, or at least about 60 wt% of LDPE, LLDPE, or a combination of LDPE and LLDPE. In some embodiments, the amount of LDPE, LLDPE, or a combination thereof in the polyethylene foam structure may be at most about 42 wt%, at most about 45 wt%, at most about 50 wt%, at most about 52 wt%, at most about 55 wt%, at most about 58 wt%, at most about 60 wt%, at most about 62 wt%, at most about 65 wt%, at most about 68 wt%, at most about 70 wt%, or at most about 75 wt% of LDPE, LLDPE, or a combination of LDPE and LLDPE. In some embodiments, the amount of LDPE, LLDPE, or a combination thereof in the polyethylene foam structure may be about 30-80 wt%, about 35-75 wt%, about 35-70 wt%, about 40-65 wt%, about 40-60 wt%, about 40-55 wt%, about 40-50 wt%, about 45-65 wt%, about 45-60 wt%, about 45-55 wt%, about 48-62 wt%, about 48-60 wt%, about 48-58 wt%, about 50-65 wt%, or about 50-60 wt% of LDPE, LLDPE, or a combination of LDPE and LLDPE.

[0076] In some embodiments, the amount of LDPE, LLDPE, or a combination of LDPE and LLDPE in the polyethylene foam structure may be greater than or equal to about 15, 20, 25, 30, 35, 40, 45, or 50 phr of LDPE, LLDPE, or a combination of LDPE and LLDPE. In some embodiments, the amount of LDPE, LLDPE, or a combination of LDPE and LLDPE in the polyethylene foam structure may be less than or equal to about 50, 55, 60, 65, 70, 75, 80, or 85 phr of LDPE, LLDPE, or a combination of LDPE and LLDPE. In some embodiments, the amount of LDPE, LLDPE, or a combination of LDPE and LLDPE in the polyethylene foam structure can be about 15-85, 15-80, 15-75, 20-85, 20-80, 20-75, 50-85, 50-80, 50-75, 50-70, 50-65, 50-60, 60-85, 60-80, 60-75, 70-85, or 70-80 PHR of LDPE, LLDPE, or a combination of LDPE and LLDPE.

[0077] In some embodiments, the amount of LDPE in the polyethylene foam structure may be at least about 10 wt%, at least about 15 wt%, at least about 18 wt%, at least about 20 wt%, at least about 22 wt%, at least about 24 wt%, at least about 26 wt%, at least about 30 wt%, at least about 35 wt%, at least about 38 wt%, at least about 40 wt%, at least about 42 wt%, at least about 45 wt%, at least about 48 wt%, at least about 50 wt%, or at least about 55 wt% of LDPE. In some embodiments, the amount of LDPE in the polyethylene foam structure may be up to about 40 wt%, up to about 45 wt%, up to about 48 wt%, up to about 50 wt%, up to about 52 wt%, up to about 55 wt%, up to about 60 wt%, up to about 62 wt%, up to about 65 wt%, up to about 70 wt%, up to about 73 wt%, up to about 75 wt%, or up to about 80 wt% of LDPE. In some embodiments, the amount of LDPE in the polyethylene foam structure may be about 10-80 wt%, about 15-75 wt%, about 20-70 wt%, about 24-65 wt%, about 20-30 wt%, about 35-45 wt%, about 35-55 wt%, about 35-50 wt%, about 45-55 wt%, about 45-60 wt%, about 50-60 wt%, or about 50-65 wt% of LDPE.

[0078] In some embodiments, the amount of LDPE in the polyethylene foam structure may be greater than or equal to about 20, 25, 30, 35, 40, 45, or 50 phr of LDPE. In some embodiments, the amount of LDPE in the polyethylene foam structure may be less than or equal to about 50, 55, 60, 65, 70, 75, or 80 phr of LDPE. In some embodiments, the amount of LDPE in the polyethylene foam structure may be about 20-80, 20-75, 25-80, 25-75, 30-80, 30-75, 30-70, 30-65, 30-60, 30-55, 30-50, 50-80, 50-75, 50-70, 50-60, 60-80, 60-75, or 70-80 phr of LDPE.

[0079] In some embodiments, the amount of LLDPE in the polyethylene foam structure is at least about 5 wt%, at least about 8 wt%, at least about 10 wt%, at least about 12 wt%, at least about 15 wt%, at least about 17 wt%, at least about 20 wt%, at least about 22 wt%, at least about 24 wt%, at least about 25 wt%, at least about 26 wt%, at least about 30 wt%, or at least about 35 wt% of LLDPE. In some embodiments, the amount of LLDPE in the polyethylene foam structure may be at most about 30 wt%, at most about 35 wt%, at most about 40 wt%, at most about 42 wt%, at most about 44 wt%, at most about 45 wt%, at most about 46 wt%, at most about 48 wt%, at most about 50 wt%, at most about 52 wt%, at most about 55 wt%, at most about 60 wt%, or at most about 65 wt% of LLDPE. In some embodiments, the amount of LLDPE in the polyethylene foam structure may be about 5-65 wt%, about 5-60 wt%, about 10-55 wt%, about 15-50 wt%, about 10-20 wt%, about 10-30 wt%, about 20-30 wt%, about 20-40 wt%, about 20-50 wt%, about 20-55 wt%, about 40-50 wt%, about 40-55 wt%, about 45-55 wt%, or about 45-50 wt% of LLDPE.

[0080] In some embodiments, the amount of LLDPE in the polyethylene foam structure may be greater than or equal to about 15, 20, 25, 30, 35, 40, 45, or 50 phr of LLDPE. In some embodiments, the amount of LLDPE in the polyethylene foam structure may be less than or equal to about 50, 55, 57.5, 60, 65, or 70 phr of LLDPE. In some embodiments, the amount of LLDPE in the polyethylene foam structure may be about 15-70, 15-65, 15-60, 20-70, 20-65, 20-60, 20-40, 20-30, 30-70, 30-65, 30-60, 50-70, 50-65, or 50-60 phr of LLDPE.

[0081] In some embodiments, the amount of OBC in the polyethylene foam structure is at least about 10 wt%, at least about 15 wt%, at least about 20 wt%, at least about 22 wt%, at least about 25 wt%, at least about 27 wt%, at least about 30 wt%, at least about 32 wt%, at least about 35 wt%, at least about 38 wt%, or at least about 40 wt% OBC. In some embodiments, the amount of OBC in the polyethylene foam structure may be at most about 20 wt%, at most about 25 wt%, at most about 30 wt%, at most about 32 wt%, at most about 35 wt%, at most about 37 wt%, at most about 40 wt%, at most about 45 wt%, at most about 48 wt%, or at most about 50 wt% OBC. In some embodiments, the amount of OBC in the polyethylene foam structure may be about 10-50 wt%, about 15-45 wt%, about 20-40 wt%, about 20-35 wt%, about 20-30 wt%, about 22-35 wt%, about 22-32 wt%, about 25-35 wt%, about 30-45 wt%, or about 30-40 wt% of OBC.

[0082] In some embodiments, the amount of OBC in the polyethylene foam structure may be greater than or equal to about 15, 20, 25, 26, 30, 35, or 40 PHR. In some embodiments, the amount of OBC in the polyethylene foam structure may be less than or equal to about 42, 42.5, 43, 45, 50, or 55 PHR. In some embodiments, the amount of OBC in the polyethylene foam structure may be about 15-55, 15-50, 15-45, 15-40, 20-55, 20-50, 20-45, 20-40, 25-55, 25-50, 25-45, 25-40, 25-35, 30-55, 30-50, 30-45, 30-40, 35-55, 35-50, 35-45, 40-55, or 40-50 PHR.

[0083] During the foaming step, the chemical foaming agent decomposes into one or more gases and one or more solids. Gases generated from the decomposition of CFA cause the unfoamed cross-linked sheet to expand into a cellular structure. In the case of ADCA, the decomposition products include gases, solid organic decomposition products (which can further decompose into more gases and other solid organics), and / or solid decomposition products. In some embodiments, once fully foamed, the polyethylene foam structure may be essentially or substantially free of CFA (e.g., ADCA). In some embodiments, the mass loss due to gas formation from the decomposition of CFA (e.g., ADCA) (and subsequent secondary decomposition reactions) is about 30-40%, with the remaining (about 60-70%) mass comprising various solid organic decomposition products. In some embodiments, these solid decomposition products generally do not impart functional or useful properties to the polyethylene foam structure. In some embodiments, the amount of CFA (e.g., ADCA) solid decomposition products in the polyethylene foam structure may be less than or equal to about 21 phr, about 14 phr, about 10.5 phr, or about 7.7 phr of CFA solid decomposition products. In some embodiments, the amount of CFA (e.g., ADCA) solid decomposition products in the polyethylene foam structure may be greater than or equal to about 1.2 phr, about 2.44 phr, about 3.6 phr, or about 4.8 phr of CFA solid decomposition products. In some embodiments, the amount of CFA (e.g., ADCA) solid decomposition products in the polyethylene foam structure may be about 1.2-21 phr, about 2.4-14 phr, about 3.6-10.5 phr, or about 4.8-7.7 phr of CFA solid decomposition products. In some embodiments, the amount of CFA (e.g., ADCA) solid decomposition products in the polyethylene foam structure may be about 0.6-21 wt%, about 1.8-14 wt%, about 3-9.8 wt%, about 3-7 wt%, or about 3-6.3 wt% of CFA solid decomposition products.

[0084] In some embodiments, the amount of additives in the polyethylene foam structure, excluding the decomposed chemical blowing agent, may be less than or equal to about 40 phr, about 30 phr, about 25 phr, or about 20 phr of additives. In some embodiments, the amount of additives in the polyethylene foam structure, excluding the decomposed chemical blowing agent, may be greater than or equal to about 1 phr, about 3 phr, about 4 phr, or about 5 phr of additives. In some embodiments, the amount of additives in the polyethylene foam structure, excluding the decomposed chemical blowing agent, may be about 1-40 phr, about 3-30 phr, about 4-25 phr, or about 5-20 phr of additives. In some embodiments, the amount of additives in the polyethylene foam structure, excluding the decomposed chemical blowing agent, may be about 1-35 wt%, about 2-25 wt%, about 3-20 wt%, or about 4-16 wt% of additives.

[0085] In some embodiments, the amount of antioxidant masterbatch in the polyethylene foam structure may be less than or equal to about 10 PHR, 8 PHR, or 6 PHR. In some embodiments, the amount of antioxidant masterbatch in the polyethylene foam structure may be greater than or equal to 1 PHR, 2 PHR, 3 PHR, or 4 PHR. In some embodiments, the amount of antioxidant masterbatch in the polyethylene foam structure may be about 1-10 PHR, 1-8 PHR, 1-6 PHR, 2-6 PHR, or 2-4 PHR. In some embodiments, the amount of antioxidant masterbatch in the polyethylene foam structure may be about 0.1-10 wt%, about 0.25-8 wt%, about 0.5-6 wt%, about 1-4 wt%, about 1.5-4 wt%, or about 1.5-3.5 wt%.

[0086] In some embodiments, the amount of processing aid masterbatch in the polyethylene foam structure may be less than or equal to about 5 PHR, 4 PHR, or 3 PHR. In some embodiments, the amount of processing aid masterbatch in the polyethylene foam structure may be greater than or equal to 1 PHR, 2 PHR, or 3 PHR. In some embodiments, the amount of processing aid masterbatch in the polyethylene foam structure may be about 1-5 PHR, 1-4 PHR, 1-3 PHR, 2-4 PHR, or 2-3 PHR. In some embodiments, the amount of processing aid masterbatch in the polyethylene foam structure may be about 0.1-6 wt%, about 0.1-5 wt%, about 0.25-5 wt%, about 0.5-5 wt%, about 0.5-4 wt%, about 0.5-3 wt%, about 0.5-2 wt%, about 1-2 wt%, or about 1.5-2 wt%.

[0087] In some embodiments, the amount of CFA decomposition inhibitor masterbatch in the polyethylene foam structure may be less than or equal to about 10 phr, 8 phr, or 6 phr. In some embodiments, the amount of CFA decomposition inhibitor masterbatch in the polyethylene foam structure may be greater than or equal to 1 phr, 2 phr, 3 phr, or 4 phr. In some embodiments, the amount of CFA decomposition inhibitor masterbatch in the polyethylene foam structure may be about 1-10 phr, 1-8 phr, 1-6 phr, 2-6 phr, or 2-4 phr. In some embodiments, the amount of CFA decomposition inhibitor masterbatch in the polyethylene foam structure may be about 1-10 wt%, about 1-8 wt%, about 1-6 wt%, about 1-4 wt%, about 1.5-4 wt%, or about 2-4 wt%.

[0088] In some embodiments, the amount of anti-blocking masterbatch in the polyethylene foam structure may be less than or equal to about 10 PHR, 8 PHR, or 6 PHR. In some embodiments, the amount of anti-blocking masterbatch in the polyethylene foam structure may be greater than or equal to 2 PHR, 3 PHR, 4 PHR, or 5 PHR. In some embodiments, the amount of anti-blocking masterbatch in the polyethylene foam structure may be about 1-10 PHR, 2-8 PHR, 2-6 PHR, 3-6 PHR, or 4-6 PHR. In some embodiments, the amount of anti-blocking masterbatch in the polyethylene foam structure may be about 1-10 wt%, about 1-8 wt%, about 1-6 wt%, about 1-4 wt%, about 2-6 wt%, about 2-4 wt%, about 2.5-3.5 wt%, or about 3 wt%.

[0089] In some embodiments, the amount of colorant masterbatch in the polyethylene foam structure may be less than or equal to about 15 phr, 13 phr, or 11 phr. In some embodiments, the amount of colorant masterbatch in the polyethylene foam structure may be greater than or equal to 2 phr, 3 phr, or 4 phr. In some embodiments, the amount of colorant masterbatch in the polyethylene foam structure may be about 2-15 phr, 2-13 phr, 2-11 phr, 3-13 phr, or 4-11 phr of colorant. In some embodiments, the amount of colorant masterbatch in the polyethylene foam structure may be about 1-12 wt%, about 1-10 wt%, about 1-9 wt%, about 2-9 wt%, or about 3-9 wt%.

[0090] In some embodiments, the polyethylene foam structure may contain a black colorant masterbatch. For example, the amount of black colorant masterbatch in the polyethylene foam structure may be less than or equal to 15 phr, 13 phr, or 11 phr. In some embodiments, the amount of black colorant masterbatch in the polyethylene foam structure may be greater than or equal to 4 phr, 5 phr, or 6 phr. In some embodiments, the amount of black colorant masterbatch in the polyethylene foam structure may be about 4-15 phr, 5-13 phr, or 6-11 phr. In some embodiments, the amount of black colorant masterbatch in the polyethylene foam structure may be about 4-12 wt%, about 4-11 wt%, about 5-10 wt%, or about 6-9 wt%.

[0091] In some embodiments, the polyethylene foam structure may include a white-toned colorant masterbatch. For example, the amount of white-toned colorant masterbatch in the polyethylene foam structure may be less than or equal to 10 phr, 8 phr, or 7 phr. In some embodiments, the amount of white-toned colorant masterbatch in the polyethylene foam structure may be greater than or equal to 2 phr, 3 phr, or 4 phr. In some embodiments, the amount of white-toned colorant masterbatch in the polyethylene foam structure may be about 2-10 phr, 3-8 phr, or 4-7 phr. In some embodiments, the amount of white-toned colorant masterbatch in the polyethylene foam structure may be about 1-8 wt%, about 1-7 wt%, about 1-6 wt%, or about 2-6 wt%.

[0092] The density of foam sheets can be defined and measured using cross-sectional or "total" density rather than "core" density, as measured according to JIS K6767. Foam sheets produced using the above method can yield materials with a density of approximately 15-200 kg / m³. 3 Approximately 30-150 kg / m 3 or approximately 50-125 kg / m 3 The cross-sectional or "total" density of the foam. In some implementations, the cross-sectional density can be controlled by the amount of foaming agent and the thickness of the extruded sheet. If the density of the foam sheet is less than about 15 kg / m³... 3 If the sheet material is not foamed effectively due to the large amount of chemical foaming agent required to achieve that density, it will not be able to foam effectively. Additionally, if the sheet material's density is less than approximately 15 kg / m³... 3 If the density of the foam sheet is less than approximately 15 kg / m³, the expansion of the sheet during the foaming process becomes increasingly difficult to control. 3 If this happens, the foam will become increasingly prone to cell collapse. Therefore, when the density is less than approximately 15 kg / m³, 3 It can be difficult to produce foam sheets with uniform cross-sectional density and thickness.

[0093] Foam sheets are not limited to approximately 200 kg / m3 The cross-sectional density. It can also produce approximately 300 kg / m³. 3 Approximately 400 kg / m 3 or approximately 500 kg / m 3 Foam with a cross-sectional density of approximately 200 kg / m³. However, foam sheets can have a cross-sectional density of less than approximately 200 kg / m³. 3 The density is chosen because a higher density is often prohibitively expensive when compared to other materials that can be used in a given application.

[0094] In some embodiments, the foam produced using the above method may have closed cells. In some embodiments, when measured using a specific gravity bottle according to ASTM D6226 or ISO 4590, at least 90%, at least 95%, or greater than 98% of the cells have undamaged cell walls.

[0095] In some implementations, the average cell size, when measured according to ASTM D3576, can be approximately 0.05–approximately 1.0 mm, or approximately 0.1–approximately 0.7 mm. If the average cell size is less than approximately 0.05 mm, the density of the foam structure can typically be greater than 200 kg / m³. 3 If the average cell size is greater than 1 mm, the foam will have an uneven surface. If the cell clusters in the foam do not have a preferred average cell size, there is also a possibility that the foam may be undesirably torn. This can occur when the foam is stretched, when shear forces are applied to the foam, and / or when a portion of it undergoes secondary processing. In some embodiments, the cell size in the foam may have a bimodal distribution, representing a relatively rounded cell cluster in the foam core and a relatively flat, thin, and / or rectangular cell cluster in the skin near the surface of the foam structure.

[0096] The total thickness of the polyethylene foam sheet is measured according to JIS K6767 and can be approximately 0.2 mm to approximately 50 mm, approximately 0.4 mm to approximately 40 mm, approximately 0.6 mm to approximately 30 mm, or approximately 0.8 mm to approximately 20 mm. If the thickness is less than approximately 0.2 mm, foaming will not be effective due to significant gas loss from the main surface. If the thickness is greater than approximately 50 mm, the expansion during the foaming step becomes increasingly difficult to control. Therefore, it becomes increasingly difficult to produce polyethylene foam sheets with uniform cross-sectional density and thickness. In some embodiments, the thickness of the polyethylene foam sheet can be approximately 0.5-5 mm, approximately 1-4 mm, or approximately 2-3 mm.

[0097] In some implementations, the desired foam thickness can be achieved through secondary processing such as slicing, scraping, or bonding. Slicing, scraping, or bonding can produce thicknesses ranging from approximately 0.1 mm to approximately 100 mm.

[0098] The disclosed polyethylene foam can be used in a variety of applications. In one embodiment, the polyethylene foam can be the base of a single-sided or double-sided adhesive foam tape. In this embodiment, a pressure-sensitive adhesive layer is disposed on at least a portion of one or two main foam surfaces. Any pressure-sensitive adhesive known in the art can be used. Examples of such pressure-sensitive adhesives are acrylic polymers, polyurethanes, thermoplastic elastomers, block copolymers, polyolefins, silicones, rubber-based adhesives, copolymers of ethylhexyl acrylate and acrylic acid, copolymers of isooctyl acrylate and acrylic acid, blends of acrylic adhesives and rubber-based adhesives, and combinations thereof. The foam tape can be commercially produced and sold in the form of rolls or flat sheets and can be used in a variety of applications, such as for installation, bonding, gaskets, weatherstripping, cushioning, etc.

[0099] In some embodiments, the polyethylene foam material may be a laminate containing the foam layers disclosed herein, as well as laminated layers. The laminated layers may be applied to one side (i.e., the surface) of the foam. In these laminates, the polyethylene foam may be combined, for example, with films and / or foils. Examples of suitable materials for such layers include, but are not limited to, polyvinyl chloride (PVC); thermoplastic polyolefins (TPO); thermoplastic polyurethanes (TPU); fabrics such as polyester, polypropylene, cloth, and other fabrics; leather and / or fiber layers, such as nonwovens. Such layers can be manufactured using conventional techniques known to those skilled in the art. Importantly, the polyethylene foam may be laminated with these materials on one or both sides and may contain multiple additional layers.

[0100] In these laminates, one layer can be connected to an adjacent layer by chemical bonding, mechanical means, or a combination thereof. Adjacent laminated layers can also be fixed to each other by any other means, including the attraction between materials with opposite electromagnetic charges or the attraction between two materials that are predominantly hydrophobic or predominantly hydrophilic.

[0101] In other embodiments, polyethylene foams or laminates can be used for automotive interior components such as door panels, door hinges, door inserts, door plugs, trunk plugs, armrests, center consoles, seat cushions, seat backs, headrests, seat back panels, knee pads, or headliners. These polyethylene foams or laminates can also be used for furniture (e.g., commercial, office, and residential furniture), such as chair cushions, chair backs, sofa cushions, sofa upholstery, recliner cushions, recliner upholstery, sofa cushions, sofa upholstery, berth cushions, or berth upholstery. These polyethylene foams or laminates can also be used as components in walls, such as modular walls, movable walls, wall panels, modular panels, office system panels, room partitions, or portable partitions. Polyethylene foams or laminates can also be used as components in movable or fixed storage boxes (e.g., for commercial, office, and residential use). In addition, polyethylene foam or laminates can also be used for coverings, such as chair cushion covers, chair back covers, armrest covers, sofa covers, sofa cushion covers, recliner cushion covers, recliner covers, sofa cushion covers, sofa covers, berth covers, berth covers, wall covers, and building covers.

[0102] To meet the requirements of any of the above applications, the disclosed structure of the present invention can undergo various secondary processing, including but not limited to embossing, corona or plasma treatment, surface roughening, surface smoothing, perforation or microperforation, splicing, slicing, scraping, layering, bonding and perforation.

[0103] Example

[0104] Raw materials of the example

[0105] Table 1 below provides a list of the different components used in the following embodiments and a description of those components.

[0106] Table 1. Materials used in the production of cross-linked polyethylene foam

[0107]

[0108]

[0109]

[0110] Transformation process of the embodiment

[0111] Table 2 below provides the formulations for Examples 1, 2a, 2b, 2c, 3a, 3b, 3c, 3d, and 3e.

[0112] Table 2 Crosslinked Polyethylene Foam - Formulation

[0113]

[0114] Table 2 (continued)

[0115]

[0116] Table 3 below provides the extrusion, irradiation, and foaming properties of the polyethylene foams of Examples 1, 2a, 2b, 2c, 3a, 3b, 3c, 3d, and 3e.

[0117] Table 3 Crosslinked Polyethylene Foam - Processing Parameters

[0118]

[0119] Table 3 (continued)

[0120]

[0121] This application discloses several numerical ranges herein. The disclosed numerical ranges inherently support any range or value within the disclosed numerical ranges, including endpoints, even if the precise range limits are not described verbatim in the specification, because the invention can be practiced throughout the disclosed numerical ranges.

[0122] The foregoing description is provided to enable those skilled in the art to make and use the invention, and is provided in the context of a particular application and its requirements. Various modifications to preferred embodiments will be readily apparent to those skilled in the art, and the general principles defined herein can be applied to other embodiments and applications without departing from the spirit and scope of the invention. Therefore, the invention is not intended to be limited to the embodiments shown, but is accorded the widest scope consistent with the principles and features disclosed herein. Finally, the full disclosure of the patents and publications cited in this application is incorporated herein by reference.

Claims

1. A method for forming polyethylene foam, comprising: An extruded foam layer, the foam layer comprising: 40-65 wt% low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), or a combination of LDPE and LLDPE; and 15-45 wt% olefin block copolymers (OBC); Irradiate the extruded foam layer with ionizing radiation; and It causes the foam layer that has been irradiated and extruded to foam.

2. The method of claim 1, wherein the foam layer comprises 50-65 wt% of low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), or a combination of LDPE and LLDPE.

3. The method of claim 1, wherein the foam layer comprises 20-35 wt% of an olefin block copolymer (OBC).

4. The method of claim 1, wherein the foam layer contains 5-15 wt% of a chemical foaming agent prior to foaming.

5. The method according to claim 1, wherein the foam layer comprises 1-10 wt% of an antioxidant masterbatch.

6. The method of claim 1, wherein the foam layer comprises 0.5-5 wt% of processing aid masterbatch.

7. The method of claim 1, wherein the foam layer comprises 1-10 wt% of a chemical foaming agent decomposition inhibitor masterbatch.

8. The method according to claim 1, wherein the foam layer comprises 1-10 wt% of an anti-blocking agent masterbatch.

9. The method of claim 1, wherein the foam layer comprises 1-12 wt% of a colorant masterbatch.

10. The method according to claim 1, wherein the melt flow index of the foam layer at 190°C is 0.1-25 g / 10 min.

11. The method according to claim 1, wherein the density of the foam layer after foaming, irradiation, and extrusion is 15-200 kg / m³. 3 .

12. The method according to claim 1, wherein the average closed-cell size of the foam layer after foaming, irradiation, and extrusion is 0.05-1.0 mm.

13. The method according to claim 1, wherein the thickness of the foam layer after foaming, irradiation and extrusion is 0.2-50 mm.

14. The method of claim 1, wherein the ionizing radiation is selected from α, β (electrons), X-rays, γ, and neutrons.

15. The method of claim 1, wherein the extruded foam layer is irradiated a maximum of four times individually.

16. The method of claim 1, wherein the ionizing radiation crosslinks the extruded foam layer to a degree of crosslinking of 20-75%.

17. The method of claim 1, wherein foaming comprises heating the irradiated, extruded foam layer with molten salt and a radiation heater or a hot air oven.

18. The method of claim 1, further comprising applying a laminate to one side of a foamed, irradiated, extruded foam layer.

19. The method of claim 1, further comprising applying a pressure-sensitive adhesive layer to one side of a foamed, irradiated, extruded foam layer.

20. The method of claim 19, further comprising applying a second pressure-sensitive adhesive layer to the side of the foamed, irradiated, extruded foam layer opposite to the first pressure-sensitive adhesive layer.

21. A polyethylene foam structure comprising: 40-65 wt% low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), or a combination of LDPE and LLDPE; and 15-45 wt% olefin block copolymer (OBC).

22. The polyethylene foam structure according to claim 21, comprising 50-65 wt% of low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), or a combination of LDPE and LLDPE.

23. The polyethylene foam structure according to claim 21, comprising 20-35 wt% of olefin block copolymer (OBC).

24. The polyethylene foam structure according to claim 21, further comprising 5-15 wt% of a chemical foaming agent prior to foaming.

25. The polyethylene foam structure according to claim 21, further comprising 1-10 wt% of an antioxidant masterbatch.

26. The polyethylene foam structure according to claim 21, further comprising 0.5-5 wt% of processing aid masterbatch.

27. The polyethylene foam structure according to claim 21, further comprising 1-10 wt% of a chemical foaming agent decomposition inhibitor masterbatch.

28. The polyethylene foam structure according to claim 21, further comprising 1-10 wt% of an anti-blocking masterbatch.

29. The polyethylene foam structure according to claim 21, further comprising 1-12 wt% of a colorant masterbatch.

30. The polyethylene foam structure according to claim 21, comprising 15-200 kg / m³ 3 The density.

31. The polyethylene foam structure according to claim 21, wherein it contains 20-75% crosslinking.

32. The polyethylene foam structure according to claim 21, comprising an average closed-cell size of 0.05-1.0 mm.

33. The polyethylene foam structure according to claim 21, comprising a thickness of 0.2-50 mm.

34. A laminate, comprising: A polyethylene foam layer comprising: 40-65 wt% low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), or a combination of LDPE and LLDPE; and 15-45 wt% olefin block copolymers (OBC); and A laminate on one side of the polyethylene foam layer.

35. The laminate of claim 34, wherein the laminate is a flexible film, fabric or foil.

36. The laminate of claim 34, wherein the laminate is unfoamed or foamed.

37. Adhesive foam tape, comprising: A polyethylene foam layer comprising: 40-65 wt% low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), or a combination of LDPE and LLDPE; and 15-45 wt% olefin block copolymers (OBC); and A pressure-sensitive adhesive layer on one side of the polyethylene foam layer.

38. The adhesive foam tape of claim 37, further comprising a second pressure-sensitive adhesive layer on the side of the polyethylene foam layer opposite to the first pressure-sensitive adhesive layer.

39. The adhesive foam tape of claim 37, wherein the adhesive foam tape is in roll or sheet.

40. The adhesive foam tape of claim 37, wherein the pressure-sensitive adhesive layer comprises one or more of the following: acrylic polymers, polyurethanes, thermoplastic elastomers, block copolymers, polyolefins, silicones, rubber-based adhesives, copolymers of ethylhexyl acrylate and acrylic acid, copolymers of isooctyl acrylate and acrylic acid, or combinations thereof.

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