Polymer blend containing polyethylene (meth)acrylic acid ionomer and boronic acid ester crosslinking agent

Abstract

A polymer blend may comprise a partially neutralized polyethylene (meth)acrylic acid ionomer and a boronic acid ester crosslinking agent containing a Lewis acid having an acceptance number greater than 16.7 as determined by the Gutmann-Beckett method, as described in embodiments herein. The polymer blend may comprise, based on the total weight of the polymer blend, 90% to 99% by weight of the partially neutralized polyethylene (meth)acrylic acid ionomer and 1% to 10% by weight of the boronic acid ester crosslinking agent. A method for producing a molded article with improved heat resistance is disclosed herein, which may comprise melt-mixing the partially neutralized polyethylene (meth)acrylic acid ionomer and the boronic acid ester crosslinking agent to form a polymer blend, and molding the polymer blend into a molded article.

Description

[Technical Field]

[0001] Embodiments of the present disclosure generally relate to polymer blends, and more specifically to polymer blends comprising ionomers and boronic acid ester crosslinking agents. [Background technology]

[0002] Ionomers are commonly used materials in a variety of applications because they possess higher tensile strength, excellent transparency, good abrasion resistance, and high rigidity compared to their precursor acid copolymers. For example, ionomers of ethylene (meth)acrylic acid copolymer have found usefulness in many applications such as food packaging, flexible packaging, cosmetic packaging, composite cans, and stand-up pouches.

[0003] While ionomers can be used in many applications, their limited operating temperature restricts their use in applications requiring creep resistance above 60°C. For example, ionomers can deform under stress at temperatures above 60°C, which can limit their practical applications, such as cell phone cases, eyewear, footwear, transparent cleats, integrated solar panels, household goods, and kitchenware. [Overview of the Initiative]

[0004] Therefore, a polymer blend is needed that includes an ionomer and certain additives that improve creep resistance while maintaining the physical and chemical properties of the ionomer, such as mechanical strength and transparency.

[0005] This need is met by embodiments disclosed herein, which include polymer blends comprising a partially neutralized polyethylene (meth)acrylic acid ionomer and a boronic acid ester crosslinking agent containing a Lewis acid having an acceptance number greater than 16.7. Boronic acid esters containing a Lewis acid having an acceptance number greater than 16.7 are remarkably effective as crosslinking agents that improve the high-temperature mechanical properties of the partially neutralized polyethylene (meth)acrylic acid ionomer.

[0006] In embodiments, the polymer blends of the present disclosure include a polymer blend comprising a partially neutralized polyethylene (meth)acrylic acid ionomer and a boronic acid ester crosslinking agent containing a Lewis acid having an acceptance number greater than 16.7 as determined by the Gutmann-Beckett method. Based on the total weight of the polymer blend, the polymer blend may comprise 90% by weight (wt) to 99% by weight of the partially neutralized polyethylene (meth)acrylic acid ionomer and 1% by weight to 10% by weight of the boronic acid ester crosslinking agent.

[0007] In embodiments, a method for producing a molded article with improved heat resistance is disclosed, which comprises melt-mixing a partially neutralized polyethylene (meth)acrylic acid ionomer with a boronic acid ester crosslinking agent to form a polymer blend, and molding the polymer blend into a molded article. The boronic acid ester crosslinking agent may include a Lewis acid having an acceptance number greater than 16.7 as determined by the Gutmann-Beckett method. The polymer blend may comprise 90% to 99% by weight of partially neutralized polyethylene (meth)acrylic acid ionomer and 1% to 10% by weight of the boronic acid ester crosslinking agent, based on the total weight of the polymer blend. [Brief explanation of the drawing]

[0008] [Figure 1] The chemical structures of the boronic acid ester crosslinking agents B1 to B6, referenced in Examples 1 to 3, are shown. [Figure 2]It is a graph showing the phosphine nuclear magnetic resonance (31P NMR) spectra of boronic acid ester crosslinking agents B1 to B6. [Figure 3] It is a graph showing the stress (y-axis, MPa) and strain (x-axis, %) of the film of Example 2 during the tensile / elongation test at 70°C.

Mode for Carrying Out the Invention

[0009] Unless otherwise defined, all technical and scientific terms used in this specification have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure pertains. In case of conflict, the specification, including definitions, will control.

[0010] Methods and materials similar or equivalent to those described herein may be used in the implementation or testing of various embodiments, but suitable methods and materials are described herein.

[0011] Unless otherwise specified, all percentages, parts, ratios, etc. are on a weight basis. When an amount, concentration, or other value or parameter is given as either a range, a preferred range, or a listing of a lower preferred value and a higher preferred value, all ranges formed from any pair of the limits of any lower range or preferred value and the limits of any higher range or preferred value are specifically disclosed, whether or not the range is separately disclosed. When a numerical range is recited herein, unless otherwise specified, the range is intended to include its endpoints, as well as all integers and fractions within the range. The scope of the present invention is not intended to be limited to the specific values recited when defining the range.

[0012] When the term "about" is used in describing a value or an endpoint of a range, the present disclosure should be understood to include the particular value or endpoint being referred to.

[0013] As used herein, the terms "comprises," "comprising," "includes," "including," "contains," "characterized by," "has," "having," or any other variation thereof are intended to cover non-exclusive inclusion. For example, a process, method, article, or apparatus that comprises a listing of elements is not necessarily limited to only those elements, and may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Further, unless expressly stated to the contrary, "or" refers to an inclusive or and not an exclusive or.

[0014] The transitional phrase "consisting essentially of" limits the claim to the specified materials or steps and those that do not materially affect the basic and novel characteristics of the disclosure. When the applicant defines an embodiment or a portion thereof with an open-ended term such as "comprising," the description should be construed as also covering such an embodiment using the term "consisting essentially of" unless otherwise stated.

[0015] The use of "a" or "an" is employed to describe elements and components of various embodiments. This is merely for convenience and to give a general sense to various embodiments. This description should be read to include one or at least one, and the singular also includes the plural unless it is clear from the context that the contrary is meant.

[0016] It should be understood that when describing certain polymers, applicants may sometimes refer to the polymer by the monomers used to manufacture the polymer, or by the amount of monomers used to manufacture the polymer. Such descriptions may not include the specific nomenclature used to describe the final polymer, nor may they include product-by-process terminology, but any such reference to monomers and amounts should be interpreted as meaning that the polymer includes the copolymer units of those monomers or the amount of those monomers, as well as the corresponding polymer and its composition.

[0017] The term "copolymer" is used to refer to a polymer formed by the copolymerization of two or more monomers. Such copolymers include dipolymers, which essentially consist of two copolymerized monomers.

[0018] "Ethylene acid copolymer" refers to an acid copolymer that contains copolymer units of ethylene and an α,β-ethylenically unsaturated carboxylic acid or its anhydride, and in which at least 50% by weight is composed of ethylene.

[0019] "(meth)acrylic acid" includes methacrylic acid and / or acrylic acid, and "(meth)acrylate" includes methacrylate and / or acrylate.

[0020] The term "ionomer," as described above, refers to a polymer derived from a hydrophilic copolymer by partially or completely neutralizing the hydrophilic copolymer with one or more neutralizing agents.

[0021] "Polyethylene (meth)acrylic acid ionomer" refers to a partially or completely neutralized hydrophilic copolymer comprising copolymerized ethylene monomer and (meth)acrylic acid comonomer, wherein at least 50% by weight consists of ethylene monomer.

[0022] "Boronic acid ester" refers to an ester formed between boronic acid and an alcohol. "Boronic acid ester crosslinking agent" is a boronic acid ester that can be added together with an ethylene acid copolymer to form a polymer blend.

[0023] When used to describe a particular carbon atom-containing chemical group, the bracketed expression in the form of "(C x ~C y )" means that the unsubstituted form of the chemical group has from x to y carbon atoms, including x and y. For example, a (C1~C5) alkyl group is an alkyl group having from 1 to 5 carbon atoms in its unsubstituted form. In some embodiments and general structures, a particular chemical group may be substituted by one or more substituents such as R S . The R x ~C y substitution chemical group defined using "(C S )" may contain more than y carbon atoms depending on the type of any group R S . For example, "(C1~C5) alkyl substituted with exactly one group R S which is phenyl (-C6H5)" may contain from 7 to 11 carbon atoms. Thus, generally, when a chemical group defined using the bracketed "(C x ~C y )" is substituted by one or more carbon atom-containing substituents R S , the minimum and maximum total numbers of carbon atoms of the chemical group are determined by adding to both x and y the total number of carbon atoms from all carbon atom-containing substituents R S .

[0024] The term "substituted" means that at least one hydrogen atom (-H) bonded to a carbon atom or heteroatom of the corresponding unsubstituted compound or functional group is replaced by a substituent (e.g., R S ). The term "-H" means a hydrogen or hydrogen radical covalently bonded to another atom. "Hydrogen" and "-H" are interchangeable and have the same meaning unless otherwise specified.

[0025] Various embodiments relate to polymer blends comprising a partially neutralized polyethylene (meth)acrylic acid ionomer and a boronic acid ester crosslinking agent. The blend may contain 90% to 99% by weight of the partially neutralized polyethylene (meth)acrylic acid ionomer and 1% to 10% by weight of the boronic acid ester crosslinking agent, based on the total weight of the polymer blend. In embodiments, the boronic acid ester crosslinking agent is a Lewis acid having an acceptance number greater than 16.7 as determined by the Gutmann-Beckett method.

[0026] Partially neutralized polyethylene (meth)acrylic acid ionomers can be formed using any method known in the art, such as copolymerizing a neutral nonionic monomer with a monomer containing a pendant acid group, such as acrylic acid or methacrylic acid, to form an ethylene acid copolymer. Ethylene acid copolymers can be prepared by a standard free radical copolymerization method using high pressure and operated continuously. Monomers are supplied into the reaction mixture in proportion to the monomer activity and the amount to be incorporated. In this way, a uniform and nearly random distribution of monomer units along the chain is achieved. Unreacted monomers can be reused. Additional information relating to the preparation of ethylene acid copolymers can be found in U.S. Patents 3,264,272 and 4,766,174, each of which is incorporated herein by reference in whole. The resulting copolymers have acid functional groups that are neutralized with a neutralizing agent. Ethylene acid copolymers can be used to produce ionomers by treatment with a cation of a metal neutralizing agent. The metal cation source may be any favorable derivative, including but not limited to formate, acetate, hydroxide, nitrate, carbonate, and bicarbonate. In various embodiments, the ethylene acid copolymer is enriched with calcium ions (Ca) to form an ionomer. 2+ ), lithium ion (Li + ), aluminum ions (Al 3+ ), scandium ions (Sc 3+), iron ions (for example, Fe 2+ and Fe 3+ ), yttrium ion (Y 3+ ), titanium ions (Ti 4+ ), zirconium ion (Zr 4+ ), hafnium ion (Hf 4+ ), vanadium ions (for example, V 2+ , V 3+ , V 4+ , and V 5+ ), cerium ions (e.g., Ce 3+ and Ce 4+ ), and magnesium ions (Mg 2+ It can be treated with one or more cations such as ), as well as mixtures thereof. In some embodiments, the partially neutralized polyethylene (meth)acrylic acid ionomer contains a sodium neutralizing agent.

[0027] In the embodiment, 10 mol% to 90 mol% of the total acid units of the partially neutralized polyethylene (meth)acrylic acid ionomer are neutralized. With respect to the total neutralized acid units, acrylic acid and methacrylic acid provide one acid unit. The calculation of the neutralization rate is based on the number of acid units considered to be present as described above and the number of added metal equivalents. The neutralization rate can be calculated by the following equation.

[0028]

number

[0029] The total neutralized acid units of partially neutralized polyethylene (meth)acrylic acid ionomer may be 10 mol% to 90 mol%, 20 mol% to 80 mol%, 30 mol% to 70 mol%, 40 mol% to 60 mol%, or 45 mol% to 55 mol%.

[0030] Partially neutralized polyethylene (meth)acrylic acid ionomer may contain an ethylene acid copolymer, which is a polymerization product of ethylene and 3% to less than 50% by weight of methacrylic acid comonomer, acrylic acid comonomer, or both methacrylic acid comonomer and acrylic acid comonomer. In embodiments, the ethylene acid copolymer includes ethylene methacrylic acid copolymer, ethylene acrylic acid copolymer, or a mixture thereof. Partially neutralized polyethylene (meth)acrylic acid ionomer may contain 3% to 40% by weight, 3% to 30% by weight, 3% to 25% by weight, 3% to 20% by weight, 5% to less than 50% by weight, 5% to 40% by weight, 5% to 30% by weight, 5% to 25% by weight, 5% to 20% by weight, 10% to 50% by weight, 10% to 40% by weight, 10% to 30% by weight, 10% to 25% by weight, or less than 3% to 50% by weight of methacrylic acid comonomer, acrylic acid comonomer, or both methacrylic acid comonomer and acrylic acid comonomer. In embodiments, the partially neutralized polyethylene (meth)acrylic acid ionomer may contain methacrylic acid comonomer. In some embodiments, the partially neutralized polyethylene (meth)acrylic acid ionomer does not contain acrylic acid comonomers.

[0031] In the embodiment, the polyethylene (meth)acrylic acid before neutralization has a melt index of 0.1 to 10.0 g / 10 min as determined according to ASTM D1238 (210°C, 2.16 kg). For example, a partially neutralized polyethylene (meth)acrylic acid ionomer may have a melt index of 1.0-10.0 g / 10 min, 2.0-10.0 g / 10 min, 3.0-10.0 g / 10 min, 4.0-10.0 g / 10 min, 1.0-8.0 g / 10 min, 2.0-8.0 g / 10 min, 3.0-8.0 g / 10 min, 4.0-8.0 g / 10 min, 1.0-6.0 g / 10 min, 2.0-6.0 g / 10 min, 3.0-6.0 g / 10 min, or 4.0-6.0 g / 10 min, as determined according to ASTM D1238 (210°C, 2.16 kg). Furthermore, in some embodiments of this disclosure, the polyethylene (meth)acrylic acid before neutralization has a density of 0.920–0.980 g / cc as measured according to ASTM D792.

[0032] In the embodiment, the polymer blend comprises a partially neutralized polyethylene (meth)acrylic acid ionomer, in addition to a boronic acid ester crosslinking agent, which can improve the mechanical properties of the ionomer at high temperatures.

[0033] The boronic acid ester crosslinking agent may contain Lewis acids having an acceptance number of 16.7 or higher, as determined by the Gutmann-Beckett method, as described in U. Mayer, V. Gutmann and W. Gerger, Monat. Chem., 1975, 106, 1235-1257, which is incorporated herein by reference in its entirety. In embodiments, the boronic acid ester crosslinking agent may contain Lewis acids having an acceptance number of 16.7 to 130.

[0034] The boronic acid ester crosslinking agent may include a structure according to formula (I), formula (II), formula (III), or a combination thereof.

[0035] [ka]

[0036] In the embodiment, R1 is a (C1-C8) alkyl group, R2, R3, and R4 are independently selected from (C1-C4) alkyl groups, and R5 and R6 are independently selected from a (C1-C4) alkyl group and -H. However, if the boronic acid ester crosslinking agent contains a structure according to formula (I), at least two of R1, R2, and R3 are independently selected from (C1-C3) alkyl groups such as a C2 alkyl group. Furthermore, if the boronic acid ester crosslinking agent contains a structure according to formula (II), at least two of R2, R3, and R4 are independently selected from (C1-C3) alkyl groups. If the boronic acid ester crosslinking agent contains a structure according to formula (III), at least one of R5 and R6 is independently selected from a (C1-C3) alkyl group.

[0037] While not intended to be bound by any particular theory, boronic acid ester crosslinkers containing Lewis acid acceptance numbers greater than 16.7 are thought to increase the effectiveness of the boronic acid ester crosslinker as a crosslinking agent, thereby improving the mechanical properties of partially neutralized polyethylene (meth)acrylic acid ionomers at high temperatures. Furthermore, in addition to the Lewis acid acceptance number of the boronic acid additive, steric considerations of the chemical structure according to formula (I), formula (II), or formula (III) are thought to reduce the interaction between the partially neutralized polyethylene (meth)acrylic acid ionomer and the boronic acid ester crosslinker, thereby decreasing the effectiveness of the boronic acid ester crosslinker as a crosslinking agent. This reduction in crosslinking effectiveness as a result of these steric problems may limit the improvement in mechanical properties at high temperatures. For example, if R1, R2, and R3 are at least C 4+ Longer alkyl chains present in boronic acid ester crosslinking agents, such as those in chemical structures following formula (I) which are alkyl groups, may not provide improved crosslinking, which may limit or reduce mechanical performance at high temperatures.

[0038] In embodiments, the boronic acid ester crosslinking agent comprises a structure according to formula (I), where R2 and R3 are independently selected from (C1-C3) alkyl groups, and R1 may be a (C1-C8) alkyl group, a (C1-C7) alkyl group, a (C1-C6) alkyl group, a (C1-C5) alkyl group, a (C1-C4) alkyl group, a (C2-C8) alkyl group, a (C2-C7) alkyl group, a (C2-C6) alkyl group, a (C2-C5) alkyl group, a (C2-C4) alkyl group, a (C2-C3) alkyl group, a (C3-C8) alkyl group, a (C3-C7) alkyl group, a (C3-C6) alkyl group, a (C3-C5) alkyl group, a (C3-C4) alkyl group, a C1 alkyl group, a C2 alkyl group, a C3 alkyl group, a C4 alkyl group, a C5 alkyl group, a C6 alkyl group, a C7 alkyl group, or a C8 alkyl group.

[0039] In the embodiment, the boronic acid ester crosslinking agent comprises a structure according to formula (III), where R 5 and R 6 R1 is independently selected from (C1-C4) alkyl groups and -H, and R1 is a (C1-C7) alkyl group, (C1-C6) alkyl group, (C1-C5) alkyl group, (C1-C4) alkyl group, (C2-C8) alkyl group, (C2-C7) alkyl group, (C2-C6) alkyl group, (C2-C5) alkyl group, (C2-C4) alkyl group, (C2-C3) alkyl group, (C3-C8) alkyl group, (C3-C7) alkyl group, (C3-C6) alkyl group, (C3-C5) alkyl group, (C3-C4) alkyl group, C1 alkyl group, C2 alkyl group, C3 alkyl group, C4 alkyl group, C5 alkyl group, C6 alkyl group, C7 alkyl group, or C8 alkyl group.

[0040] In embodiments, the boronic acid ester crosslinking agent comprises a structure according to formula (I), where R2 and R3 may be independently selected from (C1-C3) alkyl groups, (C1-C2) alkyl groups, (C2-C3) alkyl groups, C1 alkyl groups, C2 alkyl groups, or C3 alkyl groups, and R3 may be a (C1-C3) alkyl group, (C1-C2) alkyl group, (C2-C3) alkyl group, C1 alkyl group, C2 alkyl group, or C3 alkyl group.

[0041] In embodiments, the boronic acid ester crosslinking agent comprises a structure according to formula (II), wherein at least one of R2, R3, or R4 may be a (C1-C4) alkyl group, a (C1-C3) alkyl group, a (C1-C2) alkyl group, a (C2-C4) alkyl group, a (C2-C3) alkyl group, a C1 alkyl group, a C2 alkyl group, a C3 alkyl group, or a C4 alkyl group.

[0042] In embodiments, the boronic acid ester crosslinking agent comprises a structure according to formula (II), where at least two of R2, R3, or R4 can be independently selected from (C1-C3) alkyl groups, (C1-C2) alkyl groups, (C2-C3) alkyl groups, C1 alkyl groups, C2 alkyl groups, and C3 alkyl groups.

[0043] In embodiments, the boronic acid ester crosslinking agent comprises a structure according to formula (III), wherein at least one of R5 and R6 may be a (C1-C3) alkyl group, a (C1-C2) alkyl group, a (C2-C3) alkyl group, a C1 alkyl group, a C2 alkyl group, a C3 alkyl group, or -H. In embodiments, at least one of R5 and R6 is -H.

[0044] In one or more embodiments, the boronic acid ester crosslinking agent may include a structure according to formula (I), where R2 and R3 are independently selected from (C2-C3) alkyl groups. In other embodiments, the boronic acid ester crosslinking agent may include a structure according to formula (II), where R2, R3, and R4 are independently selected from (C2-C3) alkyl groups.

[0045] In some embodiments, the boronic acid ester crosslinking agent includes tri-isopropyl borate, triethyl borate, n-butylboronic acid pinacol ester, n-butylboronic acid diethyl ester, n-butylboronic acid cyclic propylene ester, or a combination thereof. In other embodiments, the boronic acid ester crosslinking agent is selected from the group consisting of tri-isopropyl borate, triethyl borate, n-butylboronic acid pinacol ester, n-butylboronic acid diethyl ester, n-butylboronic acid cyclic propylene ester, and combinations thereof.

[0046] Polymer blends can be produced by any means known to those skilled in the art. The polymer blends are substantially melt-processable and can be produced by combining a partially neutralized polyethylene (meth)acrylic acid ionomer with one or more boronic acid ester crosslinking agents to form a mixture, and then heating the mixture under conditions sufficient to produce a polymer blend. In some embodiments, the partially neutralized polyethylene (meth)acrylic acid ionomer is formed before the partially neutralized polyethylene (meth)acrylic acid ionomer and the boronic acid ester crosslinking agent are melt-mixed to form the polymer blend. In other embodiments, the polyethylene (meth)acrylic acid ionomer, the boronic acid ester crosslinking agent, and the neutralizing agent are combined to form the polymer blend. Heating of the mixture can be carried out at a temperature of 100°C or higher, such as 100°C to 280°C, under a pressure appropriate to that temperature, for a period of about 30 seconds to about 3 hours. The blend can be produced by melt-mixing the partially neutralized polyethylene (meth)acrylic acid ionomer and the boronic acid ester crosslinking agent to produce the polymer blend.

[0047] The polymer blend may contain 90% to 99% by weight of partially neutralized polyethylene (meth)acrylic acid ionomer, based on the total weight of the polymer blend. For example, the polymer blend may contain 90% to 99% by weight, 91% to 99% by weight, 92% to 99% by weight, 93% to 99% by weight, 94% to 99% by weight, 95% to 99% by weight, 96% to 99% by weight, 97% to 99% by weight, 90% to 98% by weight, 91% to 98% by weight, 92% to 98% by weight, 93% to 98% by weight, 94% to 98% by weight, 95% to 98% by weight, 96% to 98% by weight, or 97% to 98% by weight of partially neutralized polyethylene (meth)acrylic acid ionomer, based on the total weight of the polymer blend.

[0048] A polymer blend may contain 1% to 10% by weight of boronic acid ester crosslinking agent, based on the total weight of the polymer blend. For example, a polymer blend may contain 1% to 10% by weight, 2% to 10% by weight, 1% to 8% by weight, 2% to 8% by weight, 1% to 7% by weight, 2% to 7% by weight, 1% to 6% by weight, 2% to 6% by weight, 1% to 5% by weight, 2% to 5% by weight, 1% to 4% by weight, 2% to 4% by weight, 1% to 2% by weight, or 2% to 3% by weight of boronic acid ester crosslinking agent, based on the total weight of the polymer blend. While not intended to be bound by any particular theory, it is considered that polymer blends containing less than 1% by weight of boronic acid ester crosslinking agent may not provide sufficient improvement to the mechanical properties of molded articles containing the polymer blend. Furthermore, it is considered that polymer blends containing more than 10% by weight of boronic acid ester crosslinking agent may provide reduced improvement to the mechanical properties of molded articles containing the polymer blend.

[0049] Polymer blends may also contain small amounts of additives, including plasticizers, stabilizers including viscosity stabilizers, hydrolysis stabilizers, primary and secondary antioxidants, UV absorbers, antistatic agents, dyes, pigments or other colorants, inorganic fillers, flame retardants, lubricants, reinforcing agents such as glass fibers and flakes, synthetic (e.g., aramid) fibers or pulp, forming agents or foaming agents, processing aids, slip additives, anti-tack agents such as silica or talc, release agents, tackifying resins, or combinations of two or more of these. Inorganic fillers such as calcium carbonate may also be incorporated into the blend.

[0050] These additives may be present in the blend in amounts ranging from 0.01 to 40% by weight, 0.01 to 25% by weight, 0.01 to 15% by weight, 0.01 to 10% by weight, or 0.01 to 5% by weight. The incorporation of additives may be carried out by any known process, such as by dry blending, by extruding a mixture of various components, or by conventional masterbatch techniques.

[0051] While not intended to be bound by any particular theory, the limiting factors for the heat resistance of ionomers, such as the partially neutralized polyethylene (meth)acrylic acid ionomer disclosed herein, are considered to be the melting temperature of small secondary crystals in the ionomer and ion hopping of ion clusters. Furthermore, polymer blends comprising partially neutralized polyethylene (meth)acrylic acid ionomer and a boronic acid ester crosslinking agent with a Lewis acid accept number of 16.7 or higher are considered to increase the degree of crosslinking in the ionomer, which is thought to improve the mechanical performance of the ionomer at high temperatures. In addition, carboxylates in the ionomer are thought to interact with boronic acid esters having high Lewis acidity, resulting in an increase in ion cluster strength. This increased ion cluster strength may reduce ion hopping, which may result in improved mechanical performance of the ionomer or polymer blends containing ionomers at high temperatures. Ion hopping of ion clusters in the ionomer is considered to be the cause of the low heat resistance of the ionomer.

[0052] According to various embodiments, polymer blends can be used to form molded articles with increased creep resistance at high temperatures.

[0053] According to various embodiments, a method for producing a molded article with improved heat resistance may include, as disclosed herein, melt-mixing a partially neutralized polyethylene (meth)acrylic acid ionomer with a boronic acid ester crosslinking agent to form a polymer blend, and molding the polymer blend into a molded article.

[0054] Melt mixing may involve heating the partially neutralized polyethylene (meth)acrylic acid ionomer and the boronic acid ester crosslinking agent at a temperature of 100°C or higher, such as 120°C or 140°C or higher. In embodiments, melt mixing may involve heating the partially neutralized polyethylene (meth)acrylic acid ionomer and the boronic acid ester crosslinking agent at a temperature of 100°C to 280°C.

[0055] The molding may include, but is not limited to, compression molding, blow molding, or injection molding, and may include any molding technique known in the art.

[0056] In embodiments, molded articles formed from the polymer blends described herein can exhibit a breaking point tensile strength of 12 MPa or more, such as 14 MPa or more, as determined by the tensile / elongation test method at 60°C disclosed herein. Molded articles formed from the polymer blends described herein can exhibit a breaking point tensile strength of 12 MPa to 30 MPa, such as 12 MPa to 25 MPa, 12 MPa to 20 MPa, 15 MPa to 30 MPa, 15 MPa to 25 MPa, or 15 MPa to 20 MPa, as determined by the tensile / elongation test method at 60°C.

[0057] In embodiments, molded articles made from the polymer blends described herein may exhibit a breaking point tensile strength of 10 MPa or more, such as 12 MPa or more, as determined by a tensile / elongation test method at 70°C, as disclosed herein. Molded articles formed from the polymer blends described herein may exhibit a breaking point tensile strength of 10 MPa to 30 MPa, such as 10 MPa to 25 MPa, 10 MPa to 20 MPa, 12 MPa to 30 MPa, 12 MPa to 25 MPa, or 12 MPa to 20 MPa, as determined by a tensile / elongation test method at 70°C.

[0058] In embodiments, molded articles formed from the polymer blends described herein can exhibit a Young's modulus of 15 MPa or more, such as 17 MPa or more at 60°C, as disclosed herein. In embodiments, molded articles formed from the polymer blends described herein can exhibit a Young's modulus of 15 MPa or more, such as 17 MPa or more, 18 MPa or more, or even 20 MPa or more at 70°C, as disclosed herein.

[0059] In embodiments, molded articles formed from the polymer blends described herein may exhibit elongation percentages of less than 300%, such as less than 200% or even less than 100%, as determined by the creep test method disclosed herein.

[0060] Molded articles formed from polymer blends containing partially neutralized polyethylene (meth)acrylic acid ionomer and boronic acid ester crosslinking agents according to various embodiments described herein can exhibit improved creep resistance at high temperatures compared to molded articles formed from ionomers without boronic acid ester crosslinking agents, or compared to polymer blends containing boronic acid ester crosslinking agents and unneutralized copolymers. [Examples]

[0061] The following examples are provided to illustrate various embodiments and are not intended to limit the scope of the claims. All parts and percentages are by weight unless otherwise indicated. Approximate properties, characteristics, parameters, etc., are provided below with respect to various examples, comparative examples, and the materials used in the examples and comparative examples. Furthermore, the raw materials used in the examples are described below.

[0062] Some of the polymer blends in the examples and comparative examples contain ethylene methacrylate copolymer P1 ("P1"), which is an ethylene / 15 wt% methacrylate ionomer partially neutralized (50%) with sodium cations, and the ionomer is measured at 0.96 g / cm³ according to ASTM D792. 3 It has a density and a melt index of I2 at 4.5 g / 10 min, as determined according to ASTM D1238 (190°C, 2.16 kg).

[0063] Some of the polymer blends in the comparative example contain ethylene methacrylate copolymer P2 ("P2"), which is an unneutralized ethylene / 8.7 wt% methacrylate copolymer, and the ionomer is measured at 0.93 g / cm³ according to ASTM D792. 3 It has a density and a melt index of I2 at 10.0 g / 10 min, as determined according to ASTM D1238 (190°C, 2.16 kg).

[0064] P1 and P2 ethylene methacrylic acid copolymers can be prepared by standard neutralization techniques, as disclosed in U.S. Patent No. 3,264,272 (Rees), which is incorporated herein by reference. (Meth)acrylic acid copolymers can be prepared by standard free radical copolymerization methods operated continuously using high pressure. Monomers are supplied into the reaction mixture in proportions of their reactivity and the amounts to be incorporated as desired. In this way, a uniform and nearly random distribution of monomer units along the chain is achieved. Polymerization in this manner is well known and is described in U.S. Patent No. 4,351,931 (Armitage), which is incorporated herein by reference. Other polymerization techniques are described in U.S. Patent No. 5,028,674 (Hatch et al.) and U.S. Patent No. 5,057,593 (Statz), both of which are incorporated herein by reference.

[0065] Some of the polymer blends in the examples and comparative examples contain the boronic acid ester crosslinkers shown in Table 1 and are identified as "B1" to "B6". The chemical structures of boronic acid ester crosslinkers B1 to B6 are also shown in Figure 1. Phosphine nuclear magnetic resonance of boronic acid ester crosslinkers in triethylphosphine oxide ( 31 The number of Lewis acids accepted by the boronic acid ester crosslinking agent was determined by analyzing the 3P NMR spectrum and the Gutmann-Beckett method. 31 The chemical shifts of the P NMR spectrum and the calculated number of accepts are reported in Table 1. 31 The P NMR spectrum is shown in Figure 2.

[0066] [Table 1]

[0067] Boronic acid ester crosslinking agents B1, B2, and B3 are commercially available from Sigma-Aldrich under product numbers 236608, 197335, and T59307, respectively.

[0068] Boronic acid ester crosslinking agent B4 was synthesized as follows: Butylboronic acid (10.1 g, 0.1 mol), pinacol (11.8 g, 0.1 mol), anhydrous MgSO4 (36 g, 0.3 mol), and anhydrous THF (100 ml) were placed in a round-bottom flask equipped with a stirring bar. After stirring overnight at room temperature, the mixture was filtered. The recovered organic layer was concentrated under vacuum to obtain the crude product. The crude product was extracted with anhydrous hexane and concentrated under vacuum to obtain the target compound as a colorless oil, which was designated as B4.

[0069] Boronic acid ester crosslinking agent B5 was synthesized as follows: Butylboronic acid (10.1 g, 0.1 mol), anhydrous ethanol (9.2 g, 0.2 mol), anhydrous MgSO4 (36 g, 0.3 mol), and pentane (100 ml) were placed in a round-bottom flask equipped with a stirring bar. After stirring overnight at room temperature, the mixture was filtered. The recovered organic layer was concentrated under vacuum to obtain the crude product. The crude product was purified by distillation under vacuum at 50°C to obtain the target compound as a colorless oil, which was designated as B5.

[0070] Boronic acid ester crosslinking agent B6 was synthesized as follows: Butylboronic acid (10.1 g, 0.1 mol), propylene glycol (7.6 g, 0.1 mol), anhydrous MgSO4 (36 g, 0.3 mol), and anhydrous THF (100 ml) were placed in a round-bottom flask equipped with a stirring bar. After stirring overnight at room temperature, the mixture was filtered. The recovered organic layer was concentrated under vacuum to obtain the crude product. The crude product was extracted with anhydrous hexane and concentrated under vacuum to obtain the target compound as a colorless oil, which was designated as B6.

[0071] The polymer blend was prepared in a Thermo Fisher HAAKE® Rheomix 600 mixer at approximately 160°C for 20 minutes at 50 rpm. The mixture obtained from the blending process was dried overnight in a dehumidifier before compression molding. A press vulcanizer (GT-7014-H30C) was used for compression molding to produce films for tensile / elongation and creep resistance testing. The plate temperature was set to 180°C and the pressure to 1.25 MPa. The mold thickness was set to 0.6-0.8 mm. After compression molding for 5 minutes, the film was cooled to room temperature. For the tensile / elongation and creep resistance testing in the following examples, the sample was cut to 120 mm × 28 mm × 0.6 mm.

[0072] Tensile / elongation tests for Examples 1 and 2 were performed using dumbbell-shaped specimens (effective gauge length = 120 mm, width = 28 mm, thickness = 0.6 mm) via an Instron 5966 universal testing machine equipped with an oven and a 1 kN sensor. Measurements were performed using a preload of 0.01 N and a tensile speed of 1 mm / min until the specimen broke. Tensile tests were performed at 60°C for Example 1 and at 70°C for Example 2.

[0073] Creep resistance is a function of time, temperature, and load weight (stress). A simple test was employed to distinguish between ionomers containing and not containing boronic acid ester crosslinking agents. The creep test was performed by measuring the dimensional change (vertical) of a film specimen attached to a dead load in a cross-flow air oven equipped with a shelf rack for holding specimen holders. The creep resistance test in Example 3 was examined using a film sample having a thickness of 0.6 mm, a length of 76.2 mm, and a width of 25.4 mm. The film sample was suspended in a heated oven with a load of 80 g (including the fixture) at the test temperature (75°C). The dimensional change of the film was recorded and calculated by dividing the change in film length after 40 minutes by the original film length. The test was stopped when the film stretched to the point where it touched the bottom of the oven (i.e., a dimensional change of 1200%).

[0074] Example 1 - Tensile strength and elongation at 60°C of a film formed from a polymer blend containing a boronic acid ester crosslinking agent Table 2 below provides the polymer blends for Examples 1-1, 1-2, and Comparative Examples A-F. Polymer blends were prepared by melt-blending ionomers with boronic acid ester crosslinking agents, if present, according to Table 2. Films were formed from the polymer blends, and tensile / elongation tests were performed as described herein. The tensile strength at break is reported in Table 2. Changes in tensile strength are also reported compared to ionomers without additives (Comparative Example A for P2, and Comparative Example E for P1). Elongation at break and Young's modulus are reported in Table 3. All measurements were performed at 60°C.

[0075] [Table 2]

[0076] [Table 3]

[0077] As shown in Table 2, films formed from polymer blends containing partially neutralized polyethylene (meth)acrylic acid ionomer and boronic acid ester crosslinking agents showed improved tensile strength at 60°C compared to films formed from polymer blends without boronic acid ester crosslinking agents (Comparison E). Furthermore, films formed from comparative polymer blends (Comparisons B-D) in which the polyethylene (meth)acrylic acid ionomer was not neutralized and contained boronic acid ester crosslinking agents showed decreased tensile strength compared to polyethylene (meth)acrylic acid ionomer (Comparison A). In other words, the inclusion of boronic acid ester crosslinking agents (B2 or B3) together with partially neutralized polyethylene (meth)acrylic acid ionomer (P1) improved tensile strength, but the inclusion of boronic acid ester crosslinking agents (B2 or B3) together with polyethylene (meth)acrylic acid ionomer (P2) decreased tensile strength. It is thought that the boronic acid ester crosslinking agents were unable to strongly interact with P2. Furthermore, when boronic acid ester additives are combined with polymers that have not been neutralized by P2, they can act as plasticizers, potentially leading to a decrease in mechanical strength.

[0078] Example 2 - Tensile strength and elongation at 70°C of a film formed from a polymer blend containing a boronic acid ester crosslinking agent Table 4 below provides the polymer blends for Examples 2-1 to 2-5 and Comparative Examples G and H. Polymer blends were prepared by melt-blending ionomers with boronic acid ester crosslinking agents, if present, according to Table 4. Films were formed from the polymer blends, and tensile / elongation tests were performed as described herein. The tensile strength at break is reported in Table 4. Changes in tensile strength are also reported compared to the ionomer without additives (Comparative Example G). Elongation at break and Young's modulus are reported in Table 3. All measurements were performed at 70°C. Figure 3 shows plots of the stress / strain curves for the examples during tensile / elongation testing.

[0079] [Table 4]

[0080] [Table 5]

[0081] As shown in Table 4, films formed from polymer blends (Examples 2-1 to 2-5) containing partially neutralized polyethylene (meth)acrylic acid ionomer and a boronic acid ester crosslinking agent with a Lewis acid acceptance number greater than 16.7 showed improved tensile strength at 70°C compared to films formed from polymer blends without a boronic acid ester crosslinking agent (Comparative G) or polymer blends containing a boronic acid ester crosslinking agent with a Lewis acid acceptance number less than 16.7 (B1) (Comparative H). Furthermore, as shown in Table 5, Examples 2-1 to 2-5 resulted in films with increased Young's modulus compared to Comparative G and Comparative H. In addition, since B1 contains three C4 alkyl chains, it is thought that this leads to increased steric hindrance during crosslinking with P1, which may reduce the degree of crosslinking and result in the observed insufficient mechanical properties of Comparative H.

[0082] Example 3 - Creep resistance at 75°C of a film formed from a polymer blend containing a boronic acid ester crosslinking agent. Table 6 below provides the polymer blends for Examples 2-2, 2-4, 2-5, and Comparative G. Polymer blends were prepared by melt-blending ionomers, and boronic acid ester crosslinkers, if present, according to Table 6. The polymer blends were compression-molded to form films. Creep tests were performed by measuring the dimensional change (vertical) of the film attached to a dead load in a heated oven. Since creep resistance is a function of film size, time, temperature, and load (stress), the test included these variables as defined by the test method (film sample with a thickness of 0.6 mm, a length of 76.2 mm, and a width of 25.4 mm, 40 minutes, an 80 g load, and 75°C). The elongation % after 40 minutes is reported in Table 6. The elongation change compared to a comparative example (Comparative G) without boronic acid ester crosslinkers is also shown in Table 6.

[0083] [Table 6]

[0084] As shown in Table 6, films formed from polymer blends (Examples 2-2, 2-4, and 2-5) containing partially neutralized polyethylene (meth)acrylic acid ionomer and a boronic acid ester crosslinking agent with a Lewis acid acceptance number greater than 16.7 showed improved creep resistance at 75°C compared to films formed from polymer blends without the boronic acid ester crosslinking agent (Comparative G). Therefore, heat creep resistance is improved by incorporating a boronic acid ester crosslinking agent containing a Lewis acid acceptance number greater than 16.7.

Claims

1. It is a polymer blend, Partially neutralized polyethylene (meth)acrylic acid ionomer, A boronic acid ester crosslinking agent containing a Lewis acid having an acceptance number greater than 16.7 as determined by the Gutmann-Beckett method, The polymer blend comprises, based on the total weight of the polymer blend, 90% by weight (wt%) to 99% by weight of the partially neutralized polyethylene (meth)acrylic acid ionomer and 1% by weight to 10% by weight of the boronic acid ester crosslinking agent.

2. The polymer blend according to claim 1, wherein 10 mol% to 90 mol% of the total acid units of the partially neutralized polyethylene (meth)acrylic acid ionomer are neutralized.

3. The polymer blend according to claim 1 or 2, wherein the partially neutralized polyethylene (meth)acrylic acid ionomer comprises a sodium neutralizing agent.

4. The polymer blend according to any one of claims 1 to 3, wherein the partially neutralized polyethylene (meth)acrylic acid ionomer comprises ethylene methacrylic acid copolymer, ethylene acrylic acid copolymer, or a mixture thereof.

5. The polymer blend according to claim 4, wherein the partially neutralized polyethylene (meth)acrylic acid ionomer comprises 3% to less than 50% by weight of methacrylic acid comonomer, acrylic acid comonomer, or both.

6. The boronic acid ester crosslinking agent comprises a structure according to formula (I), formula (II), formula (III), or a combination thereof. 【Chemistry 1】 During the ceremony, R １ is, (C １ ~C ８ ) is an alkyl group, R ２ , R ３ , and R ４ is, (C １ ~C ４ ) Selected independently of alkyl groups, R ５ and R ６ are independently selected from (C １ ~C ４ ) alkyl groups and -H, If the boronic acid ester crosslinking agent contains a structure according to formula (I), R １ , R ２ , and R ３ At least two of them are (C １ ~C ３ ) Selected independently of alkyl groups, If the boronic acid ester crosslinking agent contains a structure according to formula (II), R ２ , R ３ , and R ４ At least two of them are (C １ ~C ３ ) Selected independently of alkyl groups, If the boronic acid ester crosslinking agent contains a structure according to formula (III), R ５ and R ６ At least one of them is (C １ ~C ３ A polymer blend according to any one of claims 1 to 5, independently selected from alkyl groups.

7. The boronic acid ester crosslinking agent comprises a structure according to formula (I), R ２ and R ３ However, (C ２ ~C ３ A polymer blend according to claim 6, independently selected from alkyl groups.

8. The boronic acid ester crosslinking agent comprises a structure according to formula (II), R ２ , R ３ , and R ４ However, (C ２ ~C ３ A polymer blend according to claim 6, independently selected from alkyl groups.

9. The boronic acid ester crosslinking agent comprises a structure according to formula (III), R ５ and R ６ The polymer blend according to claim 6, wherein at least one of them is -H.

10. The polymer blend according to any one of claims 1 to 9, wherein the boronic acid ester crosslinking agent is selected from the group consisting of triisopropyl borate, triethyl borate, n-butylboronic acid pinacol ester, n-butylboronic acid diethyl ester, n-butylboronic acid cyclic propylene ester, and combinations thereof.

11. A polymer blend according to any one of claims 1 to 10, comprising 1% to 7% by weight of the boronic acid ester crosslinking agent.

12. A molded article comprising a polymer blend according to any one of claims 1 to 11.

13. A method for manufacturing a molded product with improved heat resistance, A polymer blend is formed by melt-mixing a partially neutralized polyethylene (meth)acrylic acid ionomer with a boronic acid ester crosslinking agent containing a Lewis acid having an acceptance number greater than 16.7 as determined by the Gutmann-Beckett method. This includes molding the polymer blend into a molded article, The polymer blend comprises, based on the total weight of the polymer blend, 90% by weight (wt%) to 99% by weight of the partially neutralized polyethylene (meth)acrylic acid ionomer and 1% by weight to 10% by weight of the boronic acid ester crosslinking agent.

14. The method according to claim 13, wherein the melting and mixing includes heating the partially neutralized polyethylene (meth)acrylic acid ionomer and boronic acid ester crosslinking agent at a temperature of 100°C or higher.

15. The method according to claim 13 or 14, wherein the molding includes compression molding or injection molding.

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