Crosslinked polyolefin foam and a process for producing the same

Abstract

The disclosed process includes an extruder under extrusion conditions at a temperature between 50°C and 250°C, and a polymer composition. The polymer composition includes (A) 5% by weight or more of a silane-functionalized olefin-based polymer having a first melting temperature, Tm1; (B) optionally, a non-silane-functionalized polyolefin having a second melting temperature, Tm2; (C) a high-efficiency silanol condensation catalyst (HEC); (D) a permeability modifier; and (E) optionally, a scorch suppressant. The process includes introducing a physical blowing agent into the polymer composition to form a foamable composition. The foamable composition is cooled to a foaming temperature of less than 10°C to greater than 10°C of Tm1. The foamable composition exits the extruder exit die to form a foam composition. The foam composition is moisture-cured to form a crosslinked foam composition having a density of 0.010 g / cc to 0.200 g / cc and a gel content of 5% to 100%.

Description

BACKGROUND ART

[0001] Low-density polyolefin foams have a foam density of less than about 200 kilograms per cubic meter (less than 0.200 g / cc) and can be crosslinked or non-crosslinked. Crosslinked foams generally have superior physical properties (e.g., higher compression set and heat resistance) compared to non-crosslinked foams. Crosslinked foams can also be produced in a batch process as either a closed-cell foam or an open-cell foam. However, the batch process used to produce crosslinked foams is not economically favorable and often requires expensive chemical blowing agents.

[0002] Non-crosslinked polyolefin foams are typically produced in a (i) continuous extrusion process, (ii) have a higher production rate, and (iii) are more economical than the batch process. Extrusion uses physical blowing agents that are less expensive than chemical blowing agents. However, the sharp change in the melt viscosity of semi-crystalline polyolefins that occurs around their melting temperature results in a narrow foaming temperature range that can be used in extrusion, thereby limiting the use of the extrusion process for the production of polyolefin foams.

[0003] Free radical generators (e.g., peroxides, radiation) are typically used to achieve crosslinking of polyolefins. However, (i) the extrusion of peroxide-containing polymer compositions must be carried out at a low melt temperature to avoid premature crosslinking in the extruder, and (ii) an additional vulcanization step at a high temperature after extrusion is required to decompose the peroxide and crosslink the polymer, so peroxides are incompatible with the extrusion foaming process. Radiation can be used to crosslink the extruded foam after it exits the die, but the radiation crosslinking process is expensive and is only useful for foams of relatively small thickness due to the limited penetration depth.

[0004] Also, moisture-induced crosslinking of extruded foams made from alkoxysilane-functionalized polyolefins is known. The moisture-induced crosslinking of alkoxysilane-functionalized polyolefin extruded foams taught in the prior art is disadvantageous due to the low effectiveness of silanol condensation catalysts and the required post-extrusion moisture treatment step at high temperature and humidity in a sauna or hot water bath.

[0005] The art recognizes the need for an extrusion process for the manufacture of crosslinked foams that allows for a wide range of foaming temperatures, is efficient and cost-effective, and enables the formation of either open cells and / or closed cells, and this manufacturing process does not require post-extrusion treatment steps at high temperature and high humidity, such as curing in a sauna and / or curing in a hot water bath. SUMMARY OF THE INVENTION

[0006] The present disclosure relates to a process for the manufacture of crosslinked foams, which process provides a wide (±10 °C) range of foaming temperatures. This process avoids free radical crosslinking (without peroxides), utilizes alkoxysilane-functionalized polyolefins, and this process also avoids moisture curing in a sauna and / or curing in a hot water bath.

[0007] The present disclosure provides a process. In one embodiment, the process includes providing an extruder and a polymer composition under extrusion conditions at a temperature of 50 °C to 250 °C. The polymer composition comprises (A) 5 wt% or more of a silane-functionalized olefinic polymer having a first melt temperature, Tm1, (B) optionally, a non-silane-functionalized polyolefin having a second melt temperature, Tm2, (C) a highly effective silanol condensation catalyst (HEC), (D) a permeability modifier, and (E) optionally, a scorch inhibitor. This process includes introducing a physical blowing agent into the polymer composition under extrusion conditions to form a foamable composition. This process subjects the foamable composition to a temperature within the range of Tm1 lower than 10 °C foaming temperature ~ higher than 10 °C Tm1Cooling to the foaming temperature and pushing the foamable composition from the exit die of the extruder to form a foam composition. This process includes moisture-curing the foam composition to form a crosslinked foam composition having a density of 0.010 grams per cubic centimeter (g / cc) to 0.200 g / cc and a gel content of 5% to 100%. Definition

[0008] All references to the Periodic Table of the Elements herein shall refer to the Periodic Table of the Elements published and copyrighted in 2003 by CRC Press, Inc. Also, any reference to a group (s) shall be to the group (s) reflected in that Periodic Table of the Elements using the IUPAC system for numbering the groups. Unless otherwise stated, unless suggested by context, or unless not customary in the art, all parts and percentages are by weight. For the purposes of U.S. patent practice, the contents of any patent, patent application, or publication referenced herein are hereby incorporated by reference in their entirety (or their equivalent U.S. versions are so incorporated by reference).

[0009] The numerical ranges disclosed herein include all values (including the boundary values) from the lower limit value to the upper limit value. In the case of a range containing explicit values (for example, a range of 1, or 2, or 3 to 5, or 6, or 7), any sub-range between the two explicit values is included (for example, in the above range of 1 to 7, sub-ranges 1 to 2, 2 to 6, 5 to 7, 3 to 7, 5 to 6, etc. are included).

[0010] Unless otherwise stated, unless implied by context, or unless not customary in the art, all parts and percentages are by weight and all test methods are the latest as of the filing date of this disclosure.

[0011] As used herein, the term "ambient conditions" refers to a temperature of 10°C to 35°C (room temperature), a pressure of 0.95 to 1.05 atmospheres, or 1 atmosphere.

[0012] As used herein, the term "composition" refers to a mixture of materials that includes the composition, as well as reaction products and decomposition products formed from the materials of the composition.

[0013] The terms "comprising," "including," "having," and derivatives thereof are not intended to exclude the presence of any additional components, steps, or procedures, whether or not they are specifically disclosed. To avoid any doubt, all compositions claimed through the use of the term "comprising" may include any additional additives, adjuvants, or compounds, whether polymeric or otherwise, unless there is a contradictory description. In contrast, the term "consisting essentially of" excludes any other components, steps, or procedures from the scope of any subsequent description, except for those that are not essential to the operation. The term "consisting of" excludes any component, step, or procedure that is not specifically depicted or listed.

[0014] As used herein, the term "cell density" is the number of foam cells in a unit volume of a foam composition.

[0015] As used herein, the term "cell nucleating agent" is a compound or composition that provides sites for the growth of foam cells.

[0016] As used herein, the term "closed-cell foam" is a foam in which the foam cells are separated by polymer material film walls that do not have openings. The closed-cell volume is not readily in fluid communication with its external atmosphere. As used herein, the term "open-cell foam" is one in which (i) there are no polymer material film walls separating the foam cells, or (ii) there are openings in the polymer material film walls. The open-cell volume is in fluid communication with its external atmosphere.

[0017] As used herein, the term "ethylene-based polymer" or "ethylenic polymer" is a polymer that contains greater than 50 weight percent polymerized ethylene monomer (based on the total amount of polymerizable monomers) and optionally may contain at least one comonomer.

[0018] As used herein, the terms "foam" or "foam composition" refer to a structure composed of a polymer, the structure including a plurality of channels that extend into and through the structure from the surface of the structure. The channels are non-directional with respect to the longitudinal extension of the structure. The channels include a plurality of foam bubbles that are in fluid communication with the external atmosphere. As used herein, the terms "foam bubble" or "bubble" refer to discrete spaces within the foam composition. The foam bubbles are separated by a membrane wall that includes the polymer of the foam composition or are otherwise defined.

[0019] As used herein, the term "foam collapse" refers to a foamable composition that is unable to expand sufficiently when passing through a die at the foam temperature used.

[0020] As used herein, the term "freeze off" refers to a semi-crystalline polyolefin that solidifies in a section of an extrusion foaming process used to cool a foamable composition, thereby impairing heat transfer and referring to the melt temperature at or just prior to when an increase in the die (and / or the onset of "foam collapse") begins.

[0021] The term "foam temperature" refers to the final set temperature in a cooling section of a foam extruder or other suitable heat exchanger, cooling section, or other suitable heat exchanger located immediately upstream of an exit die. For example, the foam temperature can be the set temperature of the last zone of an extruder used to cool a foamable composition. The set temperature may or may not be different from the melt temperature of the extrudate (foamable composition) measured at the exit die.

[0022] As used herein, "olefin polymer" or "polyolefin" is a polymer that contains more than 50 weight percent of polymerized olefin monomer (based on the total amount of polymerizable monomers) and optionally may contain at least one comonomer. Non-limiting examples of olefin polymers include ethylene polymers (ethylenic polymers) and propylene polymers.

[0023] A "polymer" is a compound prepared by polymerizing monomers, whether of the same type or different types, and in polymerized form provides a plurality and / or repeating "units" or "structural units" that make up the polymer. Thus, the general term "polymer" encompasses the term "homopolymer", which is usually used to refer to a polymer prepared from only one type of monomer, and the term "copolymer" is usually used to refer to a polymer prepared from at least two types of monomers. Also included are all forms of copolymers, such as random, block, etc. The terms "ethylene / α-olefin polymer" and "propylene / α-olefin polymer" refer to the above-described copolymers prepared by polymerizing ethylene or propylene, respectively, and one or more additional polymerizable α-olefin monomers. Polymers are often referred to as being "made from" one or more specified monomers, such as being "based on" a specified monomer or monomer type and "containing" a specified monomer content, but in this context, it should be noted that the term "monomer" is understood to refer to the polymerized residue of the specified monomer and does not refer to non-polymerized species. Generally, polymers herein are referred to as being based on "units" that are the polymerized form of the corresponding monomer. Test Methods

[0024] As used herein, the term "number of bubbles" or "average number of bubbles" is the number of intersections of bubble walls over a specified length. The number of bubbles in a foam composition is measured over a specified length by making up to 10 measurements for each foam sample and calculating the average (i.e., "average number of bubbles") per specified length.

[0025] As used herein, the term "bubble diameter" or "average bubble diameter" is a measure of the size of the foam bubbles. The bubble diameter is determined by dividing the average number of bubbles by the specified length and multiplying the result by 1.62, which is an established geometric factor for this purpose as disclosed in Cellular Polymers, Vol, 21, No. 3, 165 - 194 (2002). The bubble diameter (i.e., average bubble diameter) is measured in accordance with ASTM D3576 - 77 and reported in millimeters (mm).

[0026] The density of the foam composition is measured in accordance with ASTM D - 1622 - 88, and the results are reported in kilograms per cubic meter (kg / m 3 ) or grams per cubic centimeter (g / cc) at 25°C.

[0027] The density of the polymer is measured in accordance with ASTM D792, and the results are reported in g / cc at 25°C.

[0028] The gel content of the foam composition is measured by extraction with decahydronaphthalene (decalin) in accordance with ASTM D2765 - 16 Method C, and the results are reported as weight percent. Instead of the powder specimens normally used when this test is performed on polymers, thin slices of the foam specimen are subjected to this test.

[0029] The melt index (MI or I2) is measured in accordance with ASTM D 1238, Condition 190°C / 2.16 kg, and the results are reported in grams per 10 minutes (g / 10 min).

[0030] The melting temperature, or Tm, is measured by DSC (Differential Scanning Calorimetry) technique and refers to the peak melting point of the semi-crystalline polyolefin measured as described in U.S. Patent No. 5,783,638. It should be noted that many blends containing two or more polyolefins have more than one melting temperature, while many individual polyolefins contain only one melting temperature.

[0031] The continuous cell content of the foam composition is measured according to ASTM D2856-94 and reported as a percentage from 0% to 100%. The continuous cell content is also measured from the height of penetration of the red water when the foam specimen is immersed in a beaker containing red water. The procedure is as follows: (a) Cut the foam sample into 100 mm long specimens, (b) Mark a line at a distance of 50 mm from one end of each specimen, (c) Immerse the foam sample in a beaker of red water and maintain a constant length of 50 mm below the water surface for a fixed time of 1 minute, (d) Remove the foam specimen from the water and wipe off the surface liquid, (e) Use a blade to slice the foam in half along its length, (f) Inspect the inner surface of the foam specimen revealed by slicing to determine how far up the water has penetrated. The greater the height of penetration of the colored water, the greater the continuous cell content (as a qualitative measurement).

DETAILED DESCRIPTION OF THE INVENTION

[0032] The present disclosure provides a process. In one embodiment, the process includes providing an extruder and a polymer composition under extrusion conditions at a temperature of 50°C to 250°C. The polymer composition includes (A) a silane-functionalized olefin-based polymer having a first melting temperature, Tm1, of 5 wt% or more, (B) optionally, a non-silane-functionalized polyolefin having a second melting temperature, Tm2, (C) a high-efficiency silanol condensation catalyst (HEC), (D) a permeability modifier, and (E) optionally, a scorch inhibitor. The process includes introducing a physical blowing agent into the polymer composition under extrusion conditions to form a foamable composition. The process includes cooling the foamable composition to a foaming temperature of Tm1 lower than 10°C foaming temperature ~ higher than 10°C Tm1 to 10°C. The process includes pushing the foamable composition from an exit die of the extruder to form a foam composition and moisture-curing the foam composition to form a crosslinked foam composition having a density of 0.010 grams per cubic centimeter (g / cc) to 0.200 g / cc and a gel content of 5% to 100%. A. Silane-functionalized olefin-based polymer

[0033] The process includes providing a silane-functionalized olefin-based polymer (or silane functionalized olefin-based polymer, "Si-f-PO"). The Si-f-PO can be a silane-functionalized propylene-based polymer (Si-f-PP) or a silane-functionalized ethylene-based polymer (Si-f-PE). The Si-f-PO has a melting temperature, or a first melting temperature, Tm1.

[0034] In an embodiment, Si-f-PO is a silane-functionalized ethylene-based polymer (Si-f-PE) that is a reactor ethylene / silane copolymer. The ethylene / silane copolymer is made from ethylene monomer and alkoxysilane comonomer, and optionally, one or more other copolymerizable monomers (such as vinyl acetate, ethyl acrylate, etc.) copolymerized in a polymerization reactor. The polymerization reactor used to produce the reactor ethylene / silane copolymer can be, but is not limited to, a high-pressure reactor. As used herein, the term "high-pressure reactor" is a polymerization reactor operated at a pressure of at least 34.47 megapascals (mPa) (5000 pounds per square inch (psi)).

[0035] In one embodiment, the silane-functionalized ethylene-based polymer is a silane-grafted ethylenic polymer. As used herein, the term "silane-grafted ethylenic polymer" is an alkylsiloxy ethylenic polymer made by post-reactor grafting of alkoxysilane onto an ethylenic polymer. In one embodiment, the alkoxysilane is grafted onto the ethylenic polymer in the presence of a free radical initiator.

[0036] The ethylenic polymer is produced using conventional polyethylene polymerization techniques, such as high pressure, Ziegler-Natta, metallocene, or geometrically constrained catalysts. In one embodiment, the polyethylene is made in a high-pressure reactor. In a further embodiment, the polyethylene is made in a solution, slurry, or gas-phase polymerization process using a mono- or bis-cyclopentadienyl, indenyl, or fluorenyl transition metal catalyst or geometrically constrained catalyst in combination with an activator. U.S. Patent No. 5,064,802, International Publication Nos. 93 / 19104 and 95 / 00526 disclose geometrically constrained metal complexes and methods for their preparation. International Publication Nos. 95 / 14024 and 98 / 49212 disclose substituted indenyls containing geometrically constrained metal complexes and methods for their preparation.

[0037] In one embodiment, the ethylenic polymer is a product of post-reactor modification such as reactive extrusion for making graft copolymers.

[0038] In one embodiment, the ethylenic polymer can be branched, linear, or substantially linear. As used herein, the term "branched ethylenic polymer" refers to an ethylenic polymer prepared in a high-pressure reactor having a highly branched polymer structure, and the branches are found both on the polymer backbone and on the branches themselves. As used herein, the term "substantially linear ethylenic polymer" refers to an ethylenic polymer having a backbone substituted with 0.01 to 3 long-chain branches per 1,000 carbon atoms. In one embodiment, the ethylenic polymer can have a backbone substituted with 0.01 to 1 long-chain branches per 1,000 carbon atoms, or 0.05 to 1 long-chain branches per 1,000 carbon atoms.

[0039] In one embodiment, the ethylenic polymer is a homopolymer, interpolymer, random or block copolymer, functionalized polymer (e.g., ethylene vinyl acetate, ethylene ethyl acrylate, etc.) or non-functionalized polymer. In a further embodiment, the ethylenic interpolymer is an elastomer, flexomer, or plastomer.

[0040] In one embodiment, the ethylenic polymer is an ethylene / α-olefin copolymer. Examples of α-olefins include C3~C 20 linear, branched or cyclic α-olefins, or C4~C8 linear α-olefins. C3~C 20Non-limiting examples of α-olefins include propene, 1-butene, 4-methyl-1-pentene, 1-hexene, 1-octene, 1-decene, 1-dodecene, 1-tetradecene, 1-hexadecene, and 1-octadecene. α-olefins can have a cyclic structure such as cyclohexane or cyclopentane, resulting in α-olefins such as 3-cyclohexyl-1-propene (allylcyclohexane) and vinylcyclohexane. Non-limiting examples of C4-C8 linear α-olefins include 1-butene, 1-hexene, and 1-octene.

[0041] Non-limiting examples of ethylenic polymers include high density polyethylene (HDPE), medium density polyethylene (MDPE), linear low density polyethylene (LLDPE), low density polyethylene (LDPE), very low density polyethylene (VLDPE), uniformly branched, linear ethylene / a-olefin copolymers (e.g., TAFMER™ by Mitsui Petrochemicals Company Limited and EXACT™ by DEX Plastomers), uniformly branched, substantially linear ethylene / a-olefin polymers (e.g., AFFINITY™ polyolefin plastomers and ENGAGE™ polyolefin elastomers available from The Dow Chemical Company), and ethylene block copolymers (INFUSE™ available from The Dow Chemical Company). Substantially linear ethylene copolymers are described in U.S. Patent Nos. 5,272,236, 5,278,272, and 5,986,028, and ethylene block copolymers are described in U.S. Patent Nos. 7,579,408, 7,355,089, 7,524,911, 7,514,517, 7,582,716, and 7,504,347.

[0042] In one embodiment, the ethylenic polymer comprises units derived from ethylene in an amount of 50, or 60, or 80, or 85 to 90, or 95, or 97, or 99, or 99.5, or 100 weight percent (wt%). In a further embodiment, the ethylenic polymer comprises units derived from ethylene in an amount of 50 to 100 wt%, or 60 to 99.5 wt%, or 80 to 95 wt%.

[0043] In one embodiment, the ethylenic polymer is an ethylene / α-olefin interpolymer having an α-olefin content of 15, or 20, or 25 to 40, or 45, or 50 wt% based on the weight of the interpolymer. In a further embodiment, the ethylenic polymer is an ethylene / α-olefin copolymer having an α-olefin content of 15 to 50 wt%, or 20 to 45 wt%, or 25 to 40 wt% based on the weight of the interpolymer. The α-olefin content can be measured by 13 13C nuclear magnetic resonance (NMR) spectroscopy according to the procedure described in Randall (Rev. Macromol. Chem. Phys., C29(2&3)).

[0044] In one embodiment, the ethylenic polymer has a melt index (I2) of 0.1, or 0.5, or 1 to 2, or 5, or 10, or 20, or 30, or 50 g / 10 min. In a further embodiment, the ethylenic polymer has a melt index (I2) of 0.1 to 50 g / 10 min, or 0.5 to 30 g / 10 min, or 1 to 5 g / 10 min.

[0045] In one embodiment, the ethylenic polymer does not contain a styrenic polymer (e.g., styrene, methylstyrene) or is otherwise excluded.

[0046] The ethylenic polymer may be composed of two or more embodiments disclosed herein.

[0047] As used herein, the term "alkoxysilane" or "alkoxysilane monomer" is an alkoxysilane that is grafted onto the ethylenic polymer or copolymerized with the ethylene monomer. The alkoxysilane or alkoxysilane monomer has a structure described by the following formula,

Chemical formula

[0048] In one embodiment, each R’’ is independently an alkoxy group having 1 to 12 carbon atoms (e.g., methoxy, ethoxy, butoxy), aryloxy group (e.g., phenoxy), aralkyloxy group (e.g., benzyloxy), aliphatic acyloxy group having 1 to 12 carbon atoms (e.g., formyloxy, acetyloxy, propanoyloxy), amino or substituted amino group (e.g., alkylamino, arylamino), or a lower alkyl group having 1 to 6 carbon atoms, and one or less of the three R’’ groups is alkyl.

[0049] In one embodiment, the alkoxysilane is an unsaturated silane having an ethylenically unsaturated hydrocarbyl group (e.g., vinyl, allyl, isopropenyl, butenyl, cyclohexenyl, or gamma-(meth)acryloxyallyl group) and a hydrolyzable group (e.g., hydrocarbyloxy, hydrocarbonyloxy, or hydrocarbylamino group). Non-limiting examples of hydrolyzable groups include methoxy, ethoxy, formyloxy, acetoxy, propionyloxy, alkyl and arylamino groups. In a further embodiment, the alkoxysilane and its preparation method are described in U.S. Patent No. 5,266,627 (Meverden et al.).

[0050] In one embodiment, the alkoxysilane is selected from vinyl trimethoxy silane (VTMS), vinyl triethoxy silane (VTES), vinyl triacetoxysilane, gamma-(meth)acryloxypropyl trimethoxysilane, or combinations thereof.

[0051] In one embodiment, the alkoxysilane is vinyltrimethoxysilane (VTMS) and / or vinyltriethoxysilane (VTES).

[0052] The alkoxysilane may be composed of two or more embodiments disclosed herein.

[0053] In one embodiment, the silane-functionalized ethylene polymer (Si-f-PE) is a reactor ethylene / silane copolymer containing units derived from ethylene monomers and alkoxysilane monomers. The reactor ethylene / silane copolymer consists of units derived from ethylene monomers and alkoxysilane monomers as the only monomers. Alternatively, the ethylene / silane copolymer further contains units derived from one or more monomers other than ethylene monomers and alkoxysilane monomers. In one embodiment, the ethylene / silane copolymer does not contain units derived from styrenic monomers (e.g., styrene, methylstyrene) or is excluded in another way.

[0054] In one embodiment, Si-f-PE contains VTMS and / or VTES comonomers and has one, several, or all of the following properties: (i) A melting temperature, Tm1, from 50 °C, or 60 °C, or 70 °C, or 80 °C, or 90 °C, or 100 °C, or 103 °C, or 105 °C, or 108 °C to 110 °C, or 111 °C, or 112 °C, or 113 °C, or 114 °C, or 115 °C, or 116 °C, or 120 °C, or 130 °C, or 140 °C, and / or (ii) A melt index (I2) from 0.3, or 0.5, or 1.0, or 1.3 to 1.7, or 2.0, or 3.0, or 10 g / 10 min, and / or (iii) A density ranging from 0.860, or 0.880, or 0.900, or 0.910, or 0.913, or 0.916, or 0.920 to 0.925, or 0.930, or 0.950, or 0.980, or 1.0, or 1.3, or 1.4 g / cc, and / or (iv) Based on the total weight of Si-f-PE, a VTMS content ranging from 0.1, or 0.3, or 0.5, or 0.8, or 1.0, or 1.3 to 1.7, or 1.9, or 2.3, or 3.0, or 5, or 10 wt%, and / or (v) A polydispersity index (PDI or Mw / Mn) ranging from 1.7, or 2.0, 3.0, or 3.5, or 4.0, or 4.5, or 5.0, or 5.3 to 5.7, or 6, or 8, or 10, or 20.

[0055] In one embodiment, Si-f-PE is a reactor ethylene / silane copolymer consisting only of units derived from ethylene monomer and VTMS comonomer, and has one, several, or all of the following characteristics: (i) A melting temperature, Tm1, of 95°C to 140°C, or 100°C to 130°C, or 105°C to 115°C, or 106°C to 112°C, or 108°C to 110°C, and / or (ii) A melt index (I2) of 0.5 to 3 g / 10 min, or 1 to 2 g / 10 min, or 1.3 to 1.7 g / 10 min, and / or (iii) A density of 0.900 to 0.970 g / cc, or 0.910 to 0.940 g / cc, or 0.913 to 0.930 g / cc, or 0.915 to 0.925 g / cc, and / or (iv) Based on the total weight of the ethylene / silane copolymer, a VTMS content of 0.3 to 5 wt%, or 1.0 to 2.0 wt%, or 1.3 to 1.7 wt%, and / or (v) A polydispersity index (PDI or Mw / Mn) of 1.7 to 20.0, or 2.0 to 10.0, or 3.0 to 8.0, or 4.0 to 6.0, or 5.3 to 5.7.

[0056] In one embodiment, Si-f-PO is Si-g-PE and is present in an amount exceeding 50% by weight based on the total weight of the polymer composition.

[0057] In one embodiment, Si-f-PO is Si-g-PE and is present in an amount of 1, or 3, or 5, or 7, or 9, or 11, or 20, or 30, or 40, or 50, or 60, or 70, or 80 to 85, or 90, or 93, or 95, or 97, or 99, or 99.9% by weight based on the total weight of the polymer composition. In a further embodiment, Si-f-PE is present in an amount of 1 to 99.9% by weight, or 5 to 99% by weight, or 9 to 95% by weight, or 30 to 93% by weight, or 50 to 99% by weight, or 70 to 95% by weight, or 80 to 93% by weight, or 89 to 95% by weight, or 5 to 50% by weight, or 5 to 30% by weight, or 5 to 20% by weight, or 5 to 15% by weight, or 5 to 11% by weight based on the total weight of the polymer composition.

[0058] The silane-functionalized olefin polymer may be composed of two or more embodiments disclosed herein. B. Non-silane-functionalized polyolefin

[0059] The process involves providing an optional non-silane functionalized polyolefin, component (B). When present, the non-silane functionalized polyolefin is an ethylene-based polymer or a propylene-based polymer that does not contain a silane functional group, as described above in this specification. In other words, the non-silane functionalized polyolefin does not contain an alkoxysilane and does not contain an alkoxysilane monomer. The non-silane functionalized polyolefin has a melting temperature, a second melting temperature Tm2. In other words, to distinguish the melting temperatures of component (A) and component (B), the silane-functionalized olefinic polymer (A) has a first melting temperature, or a melting temperature denoted as Tm1, and the non-silane functionalized polyolefin (B) has a second melting temperature, or a melting temperature represented as Tm2.

[0060] In one embodiment, the non-silane functionalized polyolefin is low density polyethylene (LDPE). LDPE has a density from 0.900, or 0.910, or 0.920 to 0.930, or 0.940 g / cc. In a further embodiment, LDPE has a density of 0.910 - 0.930 g / cc, or 0.913 - 0.928 g / cc, or 0.915 - 0.925 g / cc.

[0061] In one embodiment, LDPE has a melt index (I2) of 0.1, or 0.5 to 1.0, or 2.0, or 3.0, or 5.0, or 10, or 20, or 30, or 50 g / 10 min. In a further embodiment, LDPE has a melt index (I2) of 0.1 - 10.0 g / 10 min, or 0.5 - 5.0 g / 10 min, or 1.0 - 3.0 g / 10 min.

[0062] In one embodiment, LDPE has a melting temperature (Tm2) from 100℃, or 103℃, or 106℃, or 108℃ to 110℃, or 111℃, or 112℃, or 114℃, or 116℃, or 118℃, or 120℃. In a further embodiment, LDPE has a melting temperature (Tm2) of 106℃ - 114℃, or 108℃ - 112℃.

[0063] In one embodiment, LDPE is present in an amount of 0, or greater than 0, or 1, or 3, or 5, or 7, or 9, or 11, or 20, or 30, or 40, or 50, or from 80 to 90, or 93, or 95, or 99 weight percent, based on the total weight of the polymer composition. In a further embodiment, LDPE is present in an amount of 1 to 99 weight percent, or 1 to 95 weight percent, or 5 to 93 weight percent, or 10 to 90 weight percent, or 20 to 80 weight percent, or 50 to 95 weight percent, or 80 to 90 weight percent, or 89 to 95 weight percent, based on the total weight of the polymer composition.

[0064] In one embodiment, LDPE has one, some, or all of the following properties: (i) A melting temperature, Tm2, of 105°C to 120°C, or 107°C to 115°C, or 108°C to 112°C, and / or (ii) A melt index (I2) of 0.5 to 5.0 g / 10 min, or 1.0 to 3.0 g / 10 min, and / or (iii) A density of 0.910 to 0.930 g / cc or 0.915 to 0.925 g / cc.

[0065] LDPE (non-silane functionalized polyolefin) may be composed of two or more embodiments disclosed herein.

[0066] In one embodiment, the polymer composition does not include any non-silane functionalized polyolefins. C. High-efficiency silanol condensation catalyst

[0067] This process involves providing a high - efficiency silanol condensation catalyst (HEC). The term "high - efficiency silanol condensation catalyst" or "HEC" is a catalyst other than dibutyltin dilaurate (DBTDL) (or a catalyst that is not DBTDL), which, when measured in days to 100% high - temperature creep or 80% high - temperature creep (at 150 °C or 200 °C, 0.2 MPa), results in cross - linking (moisture curing) at 23 °C and 50% relative humidity that is at least 1.5 times faster than DBTDL at the same loading for an extruded tape of a given thickness in the range of 1.3 - 1.8 mm made from non - foamed Si - f - PO.

[0068] High - temperature creep (also known as hot - set elongation, or HSE) is measured to determine the degree of curing (cross - linking). The test is based on the Insulated Cable Engineers Association ICEA - T - 28 - 562 - 2003 standard for electrical cable insulation materials. Test specimens are taken along the extrusion direction from tapes with thickness values in the range of 0.8 mm to 2.0 mm. Three test specimens of each sample are cut using an ASTM D412 type D tensile bar (dumbbell). A high - temperature creep test is performed on the test specimens (with the measured thickness values) in an oven with a glass door set at 150 °C or 200 °C at a stress of 0.2 MPa applied to the bottom of the test specimens. The test specimens are fixed vertically from the upper end of the oven and a load is applied to the lower end of each test specimen. The test specimens are subjected to a high - temperature creep test at either 150 °C or 200 °C for 15 minutes, and the rate of increase in length is measured at that time interval. The average value (percentage increase in length) of the three measurements is reported as "high - temperature creep" or HSE.

[0069] The term "crosslinking (moisture curing) that is 1.5 times faster than DBTDL at the same loading" means, for example, that when the fixed loading of DBTDL alone in an extruded tape test piece of a given thickness (unfoamed) made from a fixed Si-f-PO (or Si-f-PE) requires 18 days to achieve 100% high-temperature creep or 24 days to achieve 80% high-temperature creep (when cured at 23 °C and 50% relative humidity), using the same loading of HEC instead of DBTDL alone enables 100% high-temperature creep to be achieved in 12 days or less or 80% high-temperature creep to be achieved in 16 days or less under the same curing conditions.

[0070] Typical curing data using an extruded tape test piece 1.5 mm thick (unfoamed) made from SI-LINK (trademark) AC DFDB-5451NT polyethylene (Si-f-PO; Si-f-PE) are as follows. Using 0.14 wt% of an alkyl-substituted aryl sulfonic acid (HEC), 100% high-temperature creep (150 °C, 0.2 MPa) is achieved in 5 days and 80% high-temperature creep (150 °C, 0.2 MPa) is achieved in 6 days. In comparison, with 0.14 wt% of DBTDL alone, 100% high-temperature creep (150 °C, 0.2 MPa) is achieved in 13 days and 80% high-temperature creep (150 °C, 0.2 MPa) is achieved in 18 days.

[0071] HEC is selected from any one of (i) to (iv): (i) a Bronsted acid, (ii) a Bronsted base, (iii) a Lewis acid other than DBTDL, and (iv) a Lewis base. HEC can be either (i) or (iii), or alternatively either (ii) or (iv).

[0072] In one embodiment, HEC is a Bronsted acid, which can be a sulfonic acid of the formula RSO3H, where R is (C1-C 10 ) alkyl, (C6-C 10 ) aryl, (C1-C 10 ) alkyl-substituted (C6-C 10) Aryl, or (C6 - C 10 ) Aryl-substituted (C1 - C 10 ) Alkyl, or a blocked sulfonic acid, which is produced in situ for the sulfonic acid.

[0073] The sulfonic acid is a hydrophobic sulfonic acid and may be a sulfonic acid having a solubility in pH 7.0 distilled water of 0 to less than 0.1 g / mL at 23°C after 24 hours. The sulfonic acid can be methanesulfonic acid, benzenesulfonic acid, alkyl-substituted arylsulfonic acid, alkylbenzenesulfonic acid (e.g., 4-methylbenzenesulfonic acid, dodecylbenzenesulfonic acid, or dialkylbenzenesulfonic acid), naphthalenesulfonic acid, or alkylnaphthalenesulfonic acid.

[0074] In one embodiment, the high-efficiency silanol condensation catalyst is an aromatic sulfonic acid catalyst. Non-limiting examples of the aromatic sulfonic acid catalyst are polysubstituted aromatic sulfonic acid (PASA) catalysts. The PASA catalyst has a structure described by the formula HSO3Ar-R 3 (R 4 ) m wherein m is 1 - 3, R 3 is (CH2) z CH3, z is 0 - 3, each R 4 is independently the same as or different from R 3 , and Ar is an aromatic moiety.

[0075] In a further embodiment, the PASA catalyst has a structure described by the formula HSO3Ar-R 3 (R 4 ) m wherein m is 0 - 3, R 3 is (CH2) z CH3, z is greater than 20, each R 4is, independently, R 3 the same as, or different from, Ar is an aromatic moiety.

[0076] In one embodiment, the aromatic moiety is a heterocyclic ring (e.g., pyridine, quinolone) or a non-heterocyclic ring (e.g., benzene or naphthalene).

[0077] In one embodiment, the value of z is 15, or 30, or from 45 to 55, or 65, or 80. In a further embodiment, this value is from 15 to 80, or from 30 to 65, or from 45 to 55. When the value of z is greater than 20, PASA includes alpha-olefin sulfonate, alkane sulfonate, isethionate (e.g., an ether or ester of 2-hydroxyethyl sulfonic acid, also known as isethionic acid), and propane sulfone derivatives (e.g., an oligomer or copolymer of acrylamidopropane sulfonic acid).

[0078] In one embodiment, HEC is a component of the masterbatch. HEC is present in the masterbatch in an amount from 0.5, or 1, or 1.5, or 2 to 2.5, or 3.5, or 5, or 10, or 20, or 30, or 40, or 50 wt%. In a further embodiment, HEC is present in the masterbatch in an amount from 0.5 to 50 wt%, or from 1 to 30 wt%, or from 2 to 10 wt%, or from 1.5 to 3.5 wt%. Non-limiting examples of HEC masterbatches are SI-LINK™ AC DFDA-5488 NT polyethylene and SI-LINK™ AC DFDB-5418 BK EXP1, each of which is composed of a Bronsted acid.

[0079] In one embodiment, the HEC is present in an amount from 0.03, or 0.05, or 0.07, or 0.1, or 0.13, or 0.15, or 0.2, or 0.5, or 1, or 2, or 3, or 4, or 4.5 to 6 - 7, or 8, or 10, or 12 wt% based on the total weight of the polymer composition. In a further embodiment, the HEC is present in an amount from 0.03 - 12 wt%, or 0.05 - 8 wt%, or 0.10 - 6 wt%, or 0.03 - 0.20 wt%, or 0.05 - 0.15 wt% based on the total weight of the polymer composition.

[0080] In one embodiment, the HEC masterbatch comprises one or more additives. Non - limiting examples of additives suitable for the HEC masterbatch include antioxidants (e.g., bis(4 - (1 - methyl - 1 - phenylethyl)phenyl)amine; 2,2’ - thiobis(2 - t - butyl - 5 - methylphenol; 2,2’ - thiobis(6 - t - butyl - 4 - methylphenol; tris[(4 - tert - butyl - 3 - hydroxy - 2,6 - dimethylphenyl)methyl] - 1,3,5 - triazine - 2,4,6 - trione; pentaerythritol tetrakis(3 - (3,5 - bis(1,1 - dimethylethyl) - 4 - hydroxyphenyl)propionate; distearyl thiodipropionate (DSTDP); dilauryl thiodipropionate; or 2’,3 - bis[[3 - [3,5 - di - tert - butyl - 4 - hydroxyphenyl]propionyl]]propionohydrazide), colorants (e.g., carbon black), UV stabilizers (e.g., N,N’ - bisformyl - N,N’ - bis(2,2,6,6 - tetramethyl - 4 - piperidinyl) - hexamethylenediamine), titanium dioxide, zinc oxide, and metal deactivators (e.g., oxalylbis(benzylidene)hydrazide (OABH)).

[0081] The HEC promotes cross - linking and moisture curing of the foam composition.

[0082] In one embodiment, the HEC is blended with DBTDL.

[0083] The HEC may be composed of two or more embodiments disclosed herein. D. Permeability modifier

[0084] The process includes providing a permeability modifier. As used herein, the term "permeability modifier" refers to a compound, or composition, that reduces the permeability of a blowing agent in a given polyolefin such that the blowing agent permeates a foam made of that polyolefin at approximately the same rate as air diffuses. This results in a foam with the desired (necessary) dimensional stability. Without a permeability modifier, a blowing agent such as isobutane permeates the polyolefin foam faster than air. This can lead to dimensional instability of the foam, especially at low foam densities, resulting in substantial foam shrinkage (leading to degradation of foam properties). Non-limiting examples of suitable permeability modifiers include C 10 ~C 24 amides and esters of fatty acids. Such permeability modifiers are found in U.S. Patent Nos. 3,644,230 and 4,214,054. Esters can also reduce static electricity during and after foam production, which is another desirable attribute (especially when a flammable gas such as isobutane is used as a physical blowing agent). The most preferred permeability modifiers include stearyl stearamide, glycerol monostearate, glycerol monobehenate, and sorbitol monostearate. When used, such permeability modifiers are typically used in an amount in the range of greater than 0 to 10 wt% of the polymer composition.

[0085] In one embodiment, the permeability modifier is a fatty acid ester. The fatty acid ester has an alpha-monoester (or monoglyceride) content in the range of 30 to 99%, or 40 to 95%, or 50 to 90%. In a further embodiment, the permeability modifier is glycerol monostearate.

[0086] In one embodiment, the permeability modifier (e.g., glycerol monostearate) is a component of the masterbatch. In one embodiment, the permeability modifier (e.g., glycerol monostearate) is present in an amount from 0.5, or 1, or 1.5, or 2 to 2.5, or 3.5, or 5, or 10, or 20, or 30, or 40, or 50 wt%, or up to 60 wt%. In a further embodiment, the permeability modifier (e.g., glycerol monostearate) is present in the masterbatch in an amount of 0.5 - 60 wt%, or 1 - 50 wt%, 2 - 30 wt%, or 5 - 20 wt%.

[0087] In one embodiment, the permeability modifier (e.g., glycerol monostearate) is a component of the silane-functionalized olefin-based polymer. In one embodiment, the permeability modifier is present in the silane-functionalized olefin-based polymer in an amount from 0.01, or 0.05, or 0.1, or 0.2, or 0.5, or 1, or 5, or 10 to 15, or 25, or 40 wt%. The weight percent is based on the total weight of the silane-functionalized olefin-based polymer.

[0088] In one embodiment, the permeability modifier (e.g., glycerol monostearate) is present in an amount from 0.01, or 0.1, or 0.2, or 0.3, or 0.5 to 1.0, or 2.0, or 5.0 wt% based on the total weight of the polymer composition. In a further embodiment, the permeability modifier (e.g., glycerol monostearate) is present in an amount of 0.01 - 5.0, or 0.1 - 2.0, or 0.2 - 2.0 wt% based on the total weight of the polymer composition.

[0089] The permeability modifier may be composed of two or more embodiments disclosed herein.

[0090] This process involves providing (A) a silane-functionalized olefinic polymer, (B) an optional non-silane-functionalized polyolefin, (C) a high-efficiency silanol condensation catalyst, (D) a permeability modifier, under extrusion conditions at a temperature of 50°C to 250°C, and optionally (E) a scorch inhibitor. As used herein, the term "extrusion conditions at a temperature of 50°C to 250°C" includes (i) a process occurring in one or more extruders or other suitable melt processing equipment, (ii) heating the components and simultaneously blending them uniformly or otherwise homogeneously mixing them to provide the polymer composition in a flowable state by heating the polymer composition within the temperature range of 50°C to 250°C, and (iii) introducing a blowing agent into the polymer composition at a temperature and pressure sufficient to homogeneously dissolve and disperse the blowing agent and produce a foamable composition without significant expansion. The extrusion conditions include a temperature of 50°C to 250°C and a pressure of 0.1 to 70 MPa, or 1 to 50 MPa, or 2 to 30 MPa. The extruder may include one or more extruders, and each extruder has one or more temperature control zones (i.e., zones).

[0091] The components are added to the extruder inlet in solid or liquid form. Prior to addition to the extruder, any liquid components can be incorporated into one or more solid components. Alternatively, the liquid component(s) can be injected into the extruder.

[0092] In one embodiment, the process includes heating and simultaneously blending components (A), optional (B), (C), (D), and optional (E) in one or more extruders at a temperature of 140°C to 250°C, or 150°C to 230°C, or 160°C to 220°C, or 170°C to 200°C, or 160°C to 190°C and a pressure of 0.1 to 70, or 0.5 to 60, or 1 to 50, or 2 to 40, or 3 to 30, or 4 to 20, or 6 to 10 megapascals (MPa) to form a polymer composition. The polymer composition is in a flowable state and is also known as an extrudate. E. Physical blowing agent

[0093] This process involves introducing a physical blowing agent into a polymer composition in an extruder under extrusion conditions at 50°C to 250°C to form a foamable composition. As used herein, the term "physical blowing agent" is a compound or composition that is sufficiently soluble in the polymer composition under those conditions to dissolve in the polymer composition under extrusion conditions and (ii) comes out of solution under the conditions (temperature, pressure) encountered during the formation of the foam composition when the foamable composition exits the die. The physical blowing agent is added to the polymer composition under extrusion conditions to form a foamable composition. As used herein, the term "foamable composition" is a mixture of a polymer composition and a physical blowing agent under extrusion conditions.

[0094] In one embodiment, the physical blowing agent is added to the polymer composition at a location downstream of the extruder inlet.

[0095] The extrusion conditions at a temperature of 50°C to 250°C include a sufficiently high pressure to (i) prevent expansion of the blowing agent in the polymer composition and / or the foamable composition within the extruder or other suitable melt processing equipment and (ii) enable homogeneous dispersion of the blowing agent within the polymer composition. In one embodiment, the extrusion conditions include a temperature of 140°C to 200°C and a pressure of 1.40 to 3.00 MPa, or a temperature of 150°C to 190°C and a pressure of 1.80 to 2.80 MPa, or a temperature of 160°C to 180°C and a pressure of 2.20 to 2.60 MPa.

[0096] Non-limiting examples of suitable physical blowing agents include C 1~6 hydrocarbons such as acetylene, propane, propene, butane, butene, butadiene, isobutane, isobutylene, cyclobutane, cyclopropane, ethane, methane, ethene, pentane, pentene, cyclopentane, pentene, pentadiene, hexane, cyclohexane, hexene, and hexadiene, C 1~5 organic halogens, C 1~6 alcohols, C 1~6 ethers, C 1~5 esters, C 1~5Examples include amines, alcohols, ammonia, nitrogen, carbon dioxide, water, neon, helium, and combinations thereof.

[0097] In one embodiment, the physical blowing agent is one or more of n-butane, isobutane, n-pentane, isopentane, neopentane, carbon dioxide, ethanol, and 1,1-difluoroethane (HFC-152a).

[0098] In one embodiment, the physical blowing agent is isobutane or carbon dioxide. In a further embodiment, the physical blowing agent is a mixture (combination) of isobutane and carbon dioxide.

[0099] In one embodiment, the physical blowing agent is isobutane. Isobutane is present in an amount from 0.5, or 1, or 2, or 5, or 8, or 9 to 11, or 12, or 15, or 20, or 25, or 30 weight percent based on the total weight of the foaming composition. In a further embodiment, the physical blowing agent, (e.g., isobutane), is present in an amount of 0.5 to 30 weight percent, or 2 to 25 weight percent, or 5 to 20 weight percent, or 8 to 15 weight percent based on the total weight of the foaming composition.

[0100] The physical blowing agent may be composed of two or more embodiments disclosed herein.

[0101] In one embodiment, a chemical blowing agent is used to produce one or more physical blowing agents by thermal decomposition in the process. Examples of chemical blowing agents include, but are not limited to, azodicarbonamide, azodiisobutyronitrile, barium azodicarboxylate, N,N'-dimethyl-N,N'-dinitrosoterephthalamide, and benzenesulfonyl hydrazide, 4,4-oxybenzenesulfonyl semicarbazide, and p-toluenesulfonyl semicarbazide, trihydrazinotriazine, and mixtures such as those of citric acid and sodium bicarbonate. Examples of chemical blowing agents are various products sold under the trade name Safoam™ (products of Reedy International; Reedy Chemical Foam).

[0102] This process involves cooling the foaming composition to a foaming temperature that is lower than 10 °C foaming temperature ~ higher than 10 °C Tm1 The Applicant has found that the provision of a silane-functionalized olefin polymer of 5 wt% or more, an optional non-silane-functionalized polyolefin (B), HEC (C), a permeability modifier (D), and an optional scorch inhibitor (E) unexpectedly enables a wide temperature range - namely, a temperature range of up to 20 degrees (°C) (±10 °C of Tm1) with respect to the foaming temperature in extrusion foaming.

[0103] In one embodiment, the foaming temperature is ±10 °C of Tm1, or the foaming temperature is ±8 °C of Tm1, or the foaming temperature is ±5 °C of Tm1, or the foaming temperature is ±3 °C of Tm1.

[0104] This process involves pushing the foaming composition from the outlet die of the extruder at the foaming temperature to form a foamed composition. This process further involves moisture-curing the foamed composition under ambient conditions to form a crosslinked foamed composition. It is understood that the humidity can be adjusted to 0% - 100%, or 10% - 90%, or 20% - 80%, or 30% - 70% during moisture-curing. The crosslinked foamed composition has a density of 0.010 grams per cubic centimeter (g / cc) to 0.200 g / cc and a gel content of 5% to 100%. The foaming temperature is within a temperature range where neither (i) collapse of the foam nor (ii) freeze-off occurs during the formation of the foamed composition. The foaming temperature can be equal to, exceed, or be less than the melting temperature of the silane-functionalized olefin polymer (A) or the non-silane-functionalized polyolefin (B).

[0105] In one embodiment, the process includes foaming at a foaming temperature of 50°C to 180°C, or 70°C to 160°C, or 90°C to 140°C, or 100°C to 130°C, or 100°C to 120°C, or 100°C to 110°C, or 105°C to 110°C, or 105°C to 118°C.

[0106] In one embodiment, the melting temperature, Tm1, of the silane-functionalized olefin polymer (A) is 102°C to 112°C, and the foaming temperature is ±10°C of Tm1, or 92°C to 122°C.

[0107] In one embodiment, the melting temperature, Tm1, of the silane-functionalized olefin polymer (A) is 106°C to 108°C, and the foaming temperature is ±10°C of Tm1, or 96°C to 118°C.

[0108] In one embodiment, the melting temperature, Tm1, of the silane-functionalized olefin polymer (A) is 106°C to 108°C, and the foaming temperature is ±5°C of Tm1, or 101°C to 113°C.

[0109] This process includes forming a crosslinked foam composition having a density of 0.010 grams per cubic centimeter (g / cc) to 0.200 g / cc and a gel content of 5% to 100%. In one embodiment, the process includes forming a crosslinked foam composition having a density of 0.010 to 0.200 g / cc, or 0.015 to 0.100 g / cc, or 0.020 to 0.080 g / cc, or 0.030 to 0.070 g / cc and a gel content of 5% to 100%, or 10% to 95%, or 20% to 90%, or 30% to 80%, or 40% to 70%.

[0110] In one embodiment, the process includes forming a crosslinked foam composition having one, several, or all of the following characteristics: (i) A density of 0.010 to 0.200 g / cc, or 0.015 to 0.100 g / cc, or 0.020 to 0.080 g / cc, or 0.030 to 0.070 g / cc, and / or (ii) A gel content of 5% to 100%, or 10% to 95%, or 20% to 90%, or 30% to 80%, or 40% to 70%, and / or (iii) 4 bubbles per 12.7 mm to 60 bubbles per 12.7 mm, or 5 bubbles per 12.7 mm to 40 bubbles per 12.7 mm, or 7 bubbles per 12.7 mm to 20 bubbles per 12.7 mm, or 5 bubbles per 12.7 mm to 7 bubbles per 12.7 mm of the number of bubbles, and / or (iv) A bubble diameter of 0.05 millimeters (mm) to 15 mm, or 0.07 to 10 mm, or 0.1 mm to 5.0 mm, or 0.5 mm to 4.0 mm, or 0.3 mm to 3.0 mm, or 0.5 mm to 2.0 mm, or 1.0 mm to 3.0 mm, and / or (v) Closed cells, and / or (vi) Open cells.

[0111] Foaming is achieved when the foamable composition exits through the die of the extruder into a region of lower pressure and ambient conditions. In one embodiment, the process includes pushing or otherwise conveying the foamable composition through an exit die after a cooling extruder or other suitable melt processing equipment, forming the foamable composition upon exiting the die to form a foam composition, and moisture curing the foam composition to form a crosslinked foam composition. Since the pressure outside the exit die is lower than the pressure of the extruder, the foamable composition experiences a pressure drop as it is pushed outward through the exit die. The pressure drop causes the physical blowing agent to expand the foamable composition and be pushed through the exit die, resulting in the formation of the foam. In other words, the pressure outside the exit die is lower than the pressure at which the foamable composition is maintained in the extrusion process before being pushed through the exit die. The pressure outside the exit die can be atmospheric pressure, superatmospheric pressure, or subatmospheric pressure (vacuum).

[0112] In one embodiment, the pressure of the extruder immediately before the foamable composition exits the die is from 0.1, or 0.5, or 1, or 2, or 3 to 4, or 6, or 8, or 10, or 20, or 30, or 40, or 50, or 60, or 70 MPa. In a further embodiment, the pressure of the extruder immediately before the foamable composition exits the die is from 0.1 to 70 MPa, or from 0.5 to 50 MPa, or from 1 to 30 MPa, or from 2 to 10 MPa, or from 3 to 6 MPa.

[0113] In one embodiment, the process is an accumulative extrusion process and apparatus as found in U.S. Patent Nos. 4,323,528 and 5,817,705. This apparatus, generally known as an "extruder-accumulator system", can operate the process intermittently rather than on a continuous basis.

[0114] In one embodiment, the foam composition is formed in a coalesced strand form by extrusion through a multi-orifice die. The orifices are arranged such that contact occurs between adjacent streams of the melt extrudate during the foaming process and the contact surfaces adhere to each other with sufficient adhesion to result in a single foam structure. The streams of melt extrudate exiting the die preferably foam, coalesce and adhere to each other to take the form of strands or profiles that form an integral structure. Preferably, the coalesced individual strands or profiles should remain adhered in an integral structure to prevent delamination between the layers of the strands under such stresses in the preparation, shaping, and use of the foam. Apparatus and methods for producing a foam structure in a coalesced strand form are found in U.S. Patent Nos. 3,573,152 and 4,824,720.

[0115] In one embodiment, the foam composition is formed into foam beads suitable for shaping into an article. Instructions for making bead foams are found in U.S. Patent No. 6,800,669 (B2).

[0116] This process involves forming a crosslinked foam composition. Photo-crosslinking (coupling of polymer chains) may or may not occur during the "extrusion conditions at a temperature of 50 °C to 250 °C". However, crosslinking mainly occurs under ambient conditions after the foamable composition exits the die, and the formed foam composition is in a solid state. When it exits the die, crosslinking occurs for the foam composition to cure under ambient conditions to form a crosslinked foam composition having a density of 0.010 g / cc to 0.200 g / cc and a gel content of 5% to 100%. Crosslinking occurs when the hydrolysis of the alkoxysilane groups in Si-f-PO produces silanol moieties that condense to form siloxane bonds. HEC catalyzes the hydrolysis of the alkoxysilane groups and the condensation of the resulting silanol groups, thus promoting the crosslinking of the foam composition to form a crosslinked foam composition.

[0117] Moisture curing of the foam composition can be carried out under conditions other than ambient conditions. In one embodiment, moisture curing is carried out at a temperature of 36 °C to 95 °C, or 51 °C to 95 °C, a relative humidity of 5% RH to 100% RH, and a pressure of 0.5 atm to 1.5 atm to form a crosslinked foam composition.

[0118] In one embodiment, the process involves forming a plurality of channels (or perforations) in the foam composition. The channels extend from the surface into the foam and are non-directional with respect to the longitudinal extension of the foam. The channels can (i) increase the gas exchange rate between air and the physical blowing agent and (ii) reduce the time required to cure or crosslink the foam composition. The perforations promote more rapid diffusion of moisture to effect complete crosslinking. The foam composition cures under ambient conditions for a duration of up to 0.2, or 0.5, or 1, or 2, or 3, or 5 to 7, or 10, or 15, or 21, or 30, or 45, or 60, or 90, or 120, or 150, or 180 days to form a crosslinked foam composition having a density of 0.010 to 0.200 g / cc and a gel content of 5% to 100%.

[0119] In one embodiment, hydroxyl-terminated polydimethylsiloxane (PDMS) can be incorporated into the formulation as a means to promote crosslinking and as a means independent of the need for curing of the foam in a wet or aqueous environment.

[0120] In one embodiment, crosslinking occurs while the foamable composition is being pushed out from or through an exit die.

[0121] In one embodiment, crosslinking occurs after the foamable composition has been pushed out from the exit die.

[0122] In one embodiment, crosslinking occurs during cooling of the foaming composition, during cooling of the foam composition, and during combinations thereof.

[0123] The degree or amount of crosslinking present in the crosslinked foam composition depends on the amount of Si-f-PO and the amount of HEC present in the polymer composition, and the amount of copolymerized or grafted alkoxysilane in the Si-f-PO. Higher degrees of crosslinking (gel content of 50% - 100%) improve properties such as the upper use temperature and compression set of the crosslinked foam composition. Lower degrees of crosslinking (gel content of 5% - 49%) increase the melt strength of the foamable composition and then preferably allow for a wider range of foaming temperatures for producing the foam composition with various continuous bubble contents (0% or greater than 0% to 100%).

[0124] In one embodiment, the process includes adding a scorch inhibitor to the polymer composition. As used herein, the term "scorch inhibitor" is a compound or composition that prevents excessive polymer bonding or crosslinking during melt extrusion or processing (during heating and / or cooling steps) prior to curing of the foam composition. For the purposes of this disclosure, the scorch inhibitor may also be referred to as a "scorch retarder" or a "moisture scavenger". In one embodiment, the scorch inhibitor is added to one or more of the solid components before blending the polymer composition.

[0125] Non-limiting examples of suitable scorch inhibitors include alkylalkoxysilanes, and combinations thereof. Non-limiting examples of alkylalkoxysilanes include octyltriethoxysilane, octyltrimethoxysilane, and hexadecyltrimethoxysilane.

[0126] In one embodiment, the scorch inhibitor is octyltriethoxysilane. The scorch inhibitor is present in an amount from 0, or 0.01, or 0.03, or 0.05, or 0.1, or 0.5 to 1.0, or 2.0, or 5.0 weight percent based on the total weight of the foaming composition. In a further embodiment, the scorch inhibitor is present in an amount from 0 weight percent to, or 0.01 - 5.0 weight percent, or 0.1 - 2.0 weight percent, or 0.5 - 2.0 weight percent based on the total weight of the polymer composition.

[0127] In one embodiment, the process includes adding a cell nucleating agent to the polymer composition. The cell nucleating agent promotes the formation of more foam cells that result in smaller cell diameters and higher cell densities. Higher cell densities are correlated with smaller sized foam cells. In one embodiment, the cell nucleating agent is added to the solid components prior to forming the polymer composition.

[0128] In one embodiment, the cell nucleating agent is talc or calcium carbonate or a chemical blowing agent. In a further embodiment, the cell nucleating agent is talc.

[0129] This process includes a residence time. As used herein, the term "residence time" is the time that elapses from (i) the addition of the solid component to the extruder inlet to (ii) the propulsion of the foamable composition through the exit die. The residence time applies to the combination of the various melt processing steps of heating, blowing agent addition, cooling, any optional holding zone (such as in a cumulative extrusion process) before the die, and propulsion through the exit die. The residence time is measured from the addition of the solid component to the extruder inlet until the foamable composition begins to exit the exit die. In one embodiment, the residence time is 5 minutes (min) to 80 minutes, or 6 minutes to 70 minutes, or 8 minutes to 60 minutes, or 10 minutes to 40 minutes, or 12 minutes to 30 minutes. In one embodiment, a complete change from one foamable composition requires up to 1 residence time, or 2 residence times, or 3 residence times, or 4 residence times, or 5 residence times, or 6 residence times, or 7 residence times, or 8 residence times, or 9 residence times, or 10 residence times.

[0130] In one embodiment, the process described herein is a continuous process. The continuous process includes, but is not limited to, (i) a step of adding a solid component to the extruder inlet, (ii) a step of forming a polymer composition under extrusion conditions, (iii) a step of introducing a physical blowing agent under melt processing conditions, (iv) a step of cooling the foamable composition, and (v) a step of propelling the foamable composition through an exit die to form a foam composition.

[0131] The process includes forming a crosslinked foam composition that includes open cells or closed cells, or a combination thereof.

[0132] In one embodiment, the process includes forming a crosslinked foam composition that includes open cells.

[0133] In one embodiment, the process includes forming a crosslinked foam composition that includes closed cells.

[0134] In one embodiment, the process includes forming a crosslinked foam composition that includes both continuous and discrete bubbles. The crosslinked foam composition has from 0% to 30% continuous bubbles and the reverse amount of discrete bubbles, or from 100% to 70% discrete bubbles. In another embodiment, the process includes forming a crosslinked foam composition having from 30% to 80% continuous bubbles and the reverse amount thereof, or from 70% to 20% discrete bubbles.

[0135] In one embodiment, the silane-functionalized olefin polymer is an ethylene / silane copolymer having a Tm1 of 106°C to 110°C, and the process includes foaming at a foaming temperature of 106°C to 118°C to form a foam composition, and moisture-curing under ambient conditions to form a crosslinked foam composition having an ethylene / silane copolymer present in an amount of 5 to 99 wt%, or 9 to 95 wt%, or 30 to 93 wt%, or 60 to 99.5 wt%, or 80 to 99 wt%, or 92 to 97 wt% based on the weight of the composition. The crosslinked foam composition has one or both of the following properties: (i) a density of 0.010 g / cc to 0.200 g / cc, or 0.015 g / cc to 0.100 g / cc, and / or (ii) a gel content of 5% to 100%, or 10% to 95%, and the composition does not include a non-silane-functionalized polyolefin (B).

[0136] In one embodiment, the polymer composition includes (A) 5 wt% to 10 wt% of an ethylene / silane copolymer having a Tm1 of 106°C to 110°C, (B) 80 wt% to 90 wt% of a non-silane-functionalized polyolefin which is LDPE having a Tm2, where Tm2 is greater than Tm1, and (C) 0.03 to 12.0 wt% of HEC. This process is for Tm2 lower than 10°C foaming temperature ~ higher than 10°C Tm2Foaming at the foaming temperature to form a foam composition, and forming a crosslinked foam composition having a density of 0.015 g / cc to 0.100 g / c and a gel content of 10% to 95%. In a further embodiment, Tm2 for LDPE is 111°C to 116°C, and the process includes foaming at a foaming temperature of 111°C to 121°C.

[0137] In one embodiment, the process includes adding one or more additives to the polymer composition, the foaming composition, or a combination thereof. Non-limiting examples of suitable additives include inorganic fillers, pigments, antioxidants, acid scavengers, ultraviolet absorbers, flame retardants, processing aids, extrusion aids, antistatic agents, other thermoplastic polymers, hydroxyl-terminated polydimethylsiloxane (PDMS), and combinations thereof.

[0138] The foaming composition can be used to form an extruded thermoplastic polymer foam, or an expanded thermoplastic foam, expandable thermoplastic foam beads, and a molded article formed by expansion, coalescence, and / or welding of the foam and / or beads.

[0139] The crosslinked foam composition can take any known physical configuration such as an extruded sheet, rod, plank, film, and profile. The crosslinked foam composition can also be formed by shaping expandable beads into any of the foregoing configurations or any other configuration.

[0140] The crosslinked foam composition can be used in applications including those listed in U.S. Patent No. 6,800,669 (B2). Non-limiting examples of applications include cushion packaging, sports and recreation products, egg cartons, meat trays, building structures, acoustic insulation liners, pipe insulation, gaskets, vibration pads, luggage liners, desk pad soles, gymnastic mats, greenhouse insulation blankets, case inserts, absorbent foams (e.g., for purification for health and hygiene applications, etc.), and display foams. Non-limiting examples of building structure applications include exterior wall cladding (home insulation), roofs, foundation insulation, and residential underlays. Further applications of the foam composition include refrigeration, buoyancy applications (e.g., body boards, floating docks, and rafts), and insulation for various floral and craft applications.

[0141] In one embodiment, the crosslinked foam composition has a thickness or diameter of 0.5 mm to 5000 mm, or 1.0 mm to 3000 mm, or 5 mm to 2000 mm, or 10 to 1000 mm, or 25 mm to 500 mm. The crosslinked foam composition can be formed by laminating two or more foam layers or at least one foam layer and at least one polymer layer.

[0142] By way of example and not limitation, several embodiments of the present disclosure are detailed in the following examples.

Examples

[0143] The raw materials used in the Inventive Example (IE) and Comparative Sample (CS) are detailed in Table 1 below.

[0144] A high-efficiency condensation catalyst (HEC) masterbatch is prepared in a 420 mL BRABENDER mixing bowl equipped with a cam rotor. The raw materials are used in an amount sufficient to fill the mixing bowl to 70 percent capacity. Heat the mixing bowl to 160 °C and set the rotor speed to 25 rotations per minute (rpm). The carrier resin is a non-silane functionalized polyolefin. Add half of the carrier resin to the preheated bowl and flux it until a complete melt is formed. Slowly add the silanol condensation catalyst (e.g., sulfonic acid) and incorporate it into the carrier resin melt. Then add the antioxidant and other additives. Increase the rotor speed to 40 rpm and fluidize the mixture for 5 minutes. Remove the mixture from the mixing bowl and cold press it for 5 minutes at a load of 0.689 - 1.38 MPa (100 - 200 pounds per square inch (psi)). Cut the plaque into several pieces and feed them into a BRABENDER model Prep Mixer / measuring head laboratory electric batch mixer equipped with a 24:1 L / D extruder, using a flat set temperature profile of 160 °C across a 20 / 40 / 20 / 40 / 20 mesh screen pack and zones 1, 2, 3, and the die, and extrude at a screw speed of 40 rpm. Grind the resulting strand extrudate in a Wiley mill to produce the HEC masterbatch as pellets.

Table 1

[0145] The foam composition is prepared in a tandem extrusion system having a mixing extruder and a cooling extruder fed by the mixing extruder. The mixing extruder is a co-rotating twin-screw extruder having a 34 mm diameter screw specially configured to ensure good mixing of the polymer composition and the blowing agent while forming the foamable composition. Operate the mixing extruder at 10 amperes (amp) at a set temperature of 180 °C and a screw speed of 55 rpm across all zones.

[0146] The cooling extruder is a single-screw extruder equipped with a screw having a diameter of 40 mm. The barrel and die temperatures of the cooling extruder are controlled among four zones using separate oil heaters. Zones 1 and 2 are operated at set temperatures of 129 °C and 116 °C, respectively. The set temperature of Zone 3 is the foaming temperature of the foamable composition. The cooling extruder is operated at 7 amperes at a screw speed of 22 rpm. A rod die with a diameter of 3 mm is attached to the end of the cooling extruder. The temperature of the die is maintained from less than 20 °C to higher than 20 °C from the higher of Tm1 or Tm2.

[0147] The components of the polymer composition are dry-blended and then fed into the inlet of the mixing extruder through a solid metering feeder. Once complete melting of the polymer components is achieved, a blowing agent (isobutane) is injected into the mixing extruder at 20 L / D of the extruder using a positive displacement pump (dual piston HPLC pump). The flow rate of the polymer is maintained at 36 grams per minute (g / min). The residence time of the process from the addition of the solid components to the inlet of the extruder to the outlet die is 12 minutes.

[0148] The obtained foam composition is moisture-cured at 23 °C and 50% humidity for 150 days.

[0149] The foam compositions of Comparative Samples CS1 to CS3 are prepared according to the formulations listed in Table 2 below using the raw materials listed in Table 1.

[0150] CS1 is formed from LDPE 450E at a foaming temperature of 113°C to produce a closed-cell foam having a cell diameter of 2.9 mm and a gel content of 0%. CS2 to CS3 are formed from Agility™ 1021 LDPE. CS2 and CS3 produced closed-cell foams at a foaming temperature of 110°C. See Table 2. At foaming temperatures above 113°C for CS1 and above 110°C for CS2 to CS3 (not shown in Table 2), cell collapse was evident. At foaming temperatures below 112°C for CS1 and below 109°C for CS2 to CS3 (not shown in Table 2), the melt temperature at the die began to increase, indicating that freeze-off was starting to occur. These observations are consistent with the narrow foaming temperature range of 1°C previously reported for the extrusion foaming of LDPE using isobutane (Journal of Cellular Plastics, Vol. 35, 531 - 549 (1999) and Journal of Cellular Plastics, Vol. 36, 397 - 421 (2000)).

Table 2

[0151] The foam compositions of inventive examples IE1 to IE15 are prepared according to the formulations listed in Table 3 below using the raw materials listed in Table 1.

[0152] IE1 to IE10 are formed from a reactor ethylene / silane copolymer. IE1 to IE8 produced at foaming temperatures of 107.8°C to 111.7°C produced open-cell foams or partially open-cell foams. IE9 produced at a foaming temperature of 107.2°C produced an open-cell foam having a density of 0.058 g / cc. IE10 formed at a foaming temperature of 106.1°C produced a closed-cell foam having a density of 0.044 g / cc.

[0153] IE1 to IE10 have a foaming temperature range of 106.1°C to 111.7°C.

[0154] IE11 to IE15 were formed from blends of reactor ethylene / silane copolymers and non-silane functionalized polyolefins in a foaming temperature range of 111.7 °C to 116.1 °C to produce closed-cell foams.

[0155] The cell diameters of the crosslinked foam compositions IE9 and IE10 are 3.9 mm and 3.1 mm, respectively.

[0156] The gel contents after moisture curing of the foam compositions for forming the crosslinked foam compositions IE9, IE10, and IE15 are 74.3 wt%, 73.3 wt%, and 10.8 wt%, respectively.

Table 3

[0157] Surprisingly, IE1 did not result in collapsed cells only when cooled to a foaming temperature of 111.7 °C (almost 6 °C higher than Tm1). Similarly, IE15 did not result in collapsed cells only when cooled to a foaming temperature of 116.1 °C (about 5 °C higher than Tm2). Furthermore, inventive examples IE1 to IE10 and IE11 to IE15 showed a wide foaming temperature range, resulting in foam compositions that were either open-cell, partially open-cell, or closed-cell. The properties of IE1 to IE10 and IE11 to IE15 were strikingly different from CS1 to CS3, which could only foam within a narrow foaming temperature range and only resulted in closed-cell foams.

[0158] The present disclosure is not limited to the embodiments and examples contained herein, but is particularly intended to include modified forms of those embodiments, including portions of the embodiments and combinations of elements of different embodiments, to the extent that they fall within the scope of the following claims. This application provides, for example, the following inventions. [1] Under extrusion conditions at a temperature of 50°C to 250°C, an extruder, and (A) a silane-functionalized olefin polymer having a first melting temperature, Tm1, of 5% by weight or more, (B) optionally, a non-silane-functionalized polyolefin having a second melting temperature, Tm2, (C) a highly efficient silanol condensation catalyst (HEC) that is an aromatic sulfonic acid catalyst, (D) a permeability modifier, and (E) optionally, a scorch inhibitor, to provide a polymer composition; introducing a physical blowing agent into the polymer composition under the extrusion conditions to form a foamable composition; cooling the foamable composition to a foaming temperature 10°C lower than Tm1 to a foaming temperature 10°C higher than Tm1; pushing the foamable composition from the outlet die of the extruder to form a foam composition; and moisture-curing the foam composition to form a crosslinked foam composition having a density of 0.010 grams per cubic centimeter (g / cc) to 0.200 g / cc and a gel content of 5% to 100%. [2] The process according to [1] above, wherein the non-silane-functionalized polyolefin (B) is present and the process includes foaming at a foaming temperature 10°C lower than Tm2 to a foaming temperature 10°C higher than Tm2. [3] The process according to [1] or [2] above, wherein the non-silane-functionalized polyolefin (B) is present, Tm1 exceeds Tm2, and the process includes foaming at a foaming temperature 10°C lower than Tm1 to a foaming temperature 10°C higher than Tm1. [4] The process according to [1] or [2] above, wherein the non-silane-functionalized polyolefin (B) is present, Tm2 exceeds Tm1, and the process includes foaming at a foaming temperature 10°C lower than Tm2 to a foaming temperature 10°C higher than Tm2. [5] The process according to any one of [1] to [4] above, including foaming at a foaming temperature of 105°C to 118°C. [6] The process according to any one of [1] to [5] above, including adding a scorch inhibitor to the polymer composition before the introducing step. [7]The process according to any one of [1] to [6] above, including extruding at a residence time of 5 minutes (min) to 80 min. [8]The process according to any one of [1] to [7] above, including forming a foam composition containing continuous bubbles. [9]The process according to any one of [1] to [7] above, including forming a foam composition containing closed cells.

[10] The process according to any one of [1] to [9] above, including forming a foam composition containing foam cells having a cell diameter of 0.1 millimeter (mm) to 5.0 mm.

[11] The process according to any one of [1] to

[10] above, including forming a foam composition having a number of cells of 5 cells per 12.7 mm to 40 cells per 12.7 mm.

[12] Extruding a polymer composition comprising (A) 60.0 to 99.5% by weight of an ethylene / silane copolymer, (C) 0.03 to 12.0% by weight of HEC, and (D) 0.1 to 2% by weight of a permeability modifier; introducing a physical blowing agent into the polymer composition under the extrusion conditions to form a foamable composition; pushing the foamable composition from the exit die to form a foam composition; and moisture-curing the foam composition to form a crosslinked foam composition having a density of 0.015 g / cc to 0.100 g / cc and a gel content of 10% to 95%, the process according to any one of [1] to

[11] above.

[13] An ethylene / silane copolymer having 5 wt% to 10 wt% of Tm1, a non-silane functionalized polyolefin which is LDPE having 80 wt% to 90 wt% of Tm2, wherein Tm2 is greater than Tm1, a non-silane functionalized polyolefin, (C) 0.03 to 12.0 wt% of HEC, wherein the wt% is based on the total weight of the polymer composition, HEC, (D) 0.1 to 2 wt% of a permeability modifier, extruding a polymer composition comprising; introducing a physical blowing agent into the polymer composition under the extrusion conditions to form a foamable composition; advancing the foamable composition from the exit die at a foaming temperature 10 °C lower than Tm2 to a foaming temperature 10 °C higher than Tm2 to form a foam composition; and moisture-curing the foam composition to form a crosslinked foam composition having a density of 0.015 g / cc to 0.100 g / c and a gel content of 10% to 95%, the process according to any one of the above [1] to

[11] .

[14] A crosslinked foam composition produced from the process according to any one of the above [1] to

[13] .

Claims

1. Under extrusion conditions at a temperature of 50°C to 250°C, an extruder, and (A) 89% to 95% by weight of an ethylene / silane copolymer having a first melting temperature Tm1, and (B) 0.03% to 12% by weight of a highly efficient silanol condensation catalyst (HEC) which is an aromatic sulfonic acid catalyst, and (C) 0.1% to 2.0% by weight of a permeability modifier which is a fatty acid ester, and (D) a scorch inhibitor, To provide a polymer composition (each % by weight is based on the total weight of the polymer composition), Under the extrusion conditions, introducing a physical blowing agent into the polymer composition to form a foamable composition, Cooling the foamable composition to a foaming temperature of 106.1°C to 111.7°C, Pushing the foamable composition out from the die at the outlet of the extruder to form a foam composition, Moisture-curing the foam composition to form a crosslinked foam composition having a density of 0.010 grams per cubic centimeter (g / cc) to 0.200 g / cc and a gel content of 5% to 100%, A process comprising.

2. The process according to claim 1, comprising adding a scorch inhibitor to the polymer composition before said introducing.

3. The process according to claim 1, comprising extruding with a residence time of 5 minutes (min) to 80 min.

4. The process according to claim 1, comprising forming a foam composition containing open cells.

5. The process according to claim 1, comprising forming a foam composition containing closed cells.

6. The process according to claim 1, comprising forming a foam composition containing foam bubbles having a bubble diameter of 0.1 millimeter (mm) to 5.0 mm.

7. The process according to claim 1, comprising forming a foam composition having a number of bubbles of 5 bubbles per 12.7 mm to 40 bubbles per 12.7 mm.

8. Under extrusion conditions at a temperature of 50°C to 250°C, an extruder, and (A) 5% to 10% by weight of an ethylene / silane copolymer having a first melting temperature Tm1, and (B) 80% to 90% by weight of a non-silane functionalized polyolefin which is LDPE having a second melting temperature Tm2, and (C) 0.03% to 12.0% by weight of a highly efficient silanol condensation catalyst (HEC) which is an aromatic sulfonic acid catalyst, and (D) 0.1% to 2.0% by weight of a permeability modifier which is a fatty acid ester, (E) a scorch inhibitor and extruding a polymer composition containing (each weight % is based on the total weight of the polymer composition), introducing a physical blowing agent into the polymer composition under the extrusion conditions to form a foamable composition, cooling the foamable composition to a foaming temperature of 111.7 °C to 116.1 °C, pushing the foamable composition out from the outlet die of the extruder to form a foam composition, moisture-curing the foam composition to form a crosslinked foam composition having a density of 0.015 g / cc to 0.100 g / c and a gel content of 10% to 95%, A process comprising. **Claim 9**: The process according to claim 8, wherein the process comprises foaming at a foaming temperature 10 °C lower than Tm2 to 10 °C higher than Tm2. **Claim 10**: Tm1 exceeds Tm2, and the process according to claim 9, wherein the process comprises foaming at a foaming temperature 10 °C lower than Tm1 to 10 °C higher than Tm1. **Claim 11**: Tm2 exceeds Tm1, and the process according to claim 9, wherein the process comprises foaming at a foaming temperature 10 °C lower than Tm2 to 10 °C higher than Tm2.

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