Functional polyolefin polymers and their preparation

Abstract

Polyolefins having the same or different functional groups covalently bonded to the polyolefin, such as polyolefins having hindered phenolic groups bonded thereto, can be prepared from maleic anhydride-modified polyolefins with or without a coupling agent by heating, for example by heating the components to at least about 170°C, for example by reactive extrusion. Polyolefins having hindered phenolic groups can be added to the components as stabilizers before or during the reaction of the components together under heating.

Description

[0001] Cross-references to related applications

[0002] This application is a divisional application of Chinese invention patent application filed on March 1, 2021, with application number 202180018773.0 and title "Functional polyolefin polymers and their preparation".

[0003] This application claims the benefit of U.S. Provisional Application No. 62 / 984,611, filed March 3, 2020, the entire disclosure of which is incorporated herein by reference. Technical Field

[0004] This disclosure relates to polyolefins having the same or different functional groups covalently bonded to polyolefins, such as polyolefins having hindered phenolic groups bonded thereto, and methods for preparing the same. Background Technology

[0005] Polyolefins, such as polypropylene (PP) and polyethylene (PE), are common polymers primarily used in commercial applications due to their advantages, including low cost, good processability, good thermal and electrical insulation properties, low moisture sensitivity, and excellent recyclability. However, polyolefin products (including PE and PP) are not used in applications requiring prolonged exposure to high temperatures, high electric fields, organic solvents, or combinations thereof due to chemical and physical stability issues (see Macromolecules, 2019: 52: 5618-5637).

[0006] To improve the thermal stability of polyolefins, it is common practice to add various additives to commercially available polyolefin products immediately after polymerization, including small amounts (< 0.5 wt%) of antioxidants and UV stabilizers. Hindered phenolic (HP) antioxidants, such as octadecyl-3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate (Irganox® 1076) and neopentyl tetrol tetra(3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate) (Irganox® 1010), are often blended with polyolefin products. The blended antioxidants prevent chain thermal oxidative degradation of polyolefins during the melting process, in which the molten mixture is continuously mixed at high temperatures, resulting in a homogeneous phase within a short processing time (i.e., minutes). However, it is difficult to maintain a homogeneous mixture between antioxidants, which are typically polar molecules, and non-polar polyolefins (especially semi-crystalline polyethylene (PE) or polypropylene (PP) in solid form). This incompatibility also promotes the continuous diffusion of additives from the bulk polyolefin to the surface region, which is accelerated when the material is exposed to solvents, heat, or a constant (strong) electric field. Therefore, it is difficult to maintain the lowest effective antioxidant concentration throughout the polyolefin (e.g., PE and PP products).

[0007] To address some drawbacks of antioxidant incompatibility and diffusion, Chung et al. reported a laboratory-scale method for preparing polyolefins with covalently bonded hindered phenols. The reported method involves solution-based copolymerization of propylene or ethylene monomers with protected alcohol monomers, deprotection of the alcohol, and subsequent esterification with 3,5-bis(tert-butyl)-4-hydroxyphenylpropionic acid (HP) to form the corresponding PP-HP or PE-HP copolymers (see Macromolecules, 2017: 50: 7041-7053 and Polymer 2018: 146: 101-108). However, solution-based synthesis involving comonomer polymerization is relatively expensive for large-scale operations and is generally not suitable for commercial production.

[0008] In addition to their low thermal stability, polyolefins are excluded from many high-end, specialized applications that typically require materials with a wide range of functional properties. The limitations and drawbacks of polyolefins stem in part from the lack of polar functional groups and structural diversity, coupled with the long-standing challenges in the chemical modification (functionalization) of polyolefins.

[0009] Maleic anhydride (MA) modified polypropylene (PP-MA) is commercially available and used in applications such as glass fiber reinforced PP, corrosion-resistant coatings for metal pipes and containers, multilayer paper for chemical and food packaging, and polymer blends. PP-MA can be prepared by chemically modifying pre-formed PP using organic peroxides under free radical conditions. Due to the inert nature of the PP structure and poor control of free radical reactions, this type of high-temperature MA grafting reaction leads to undesirable side reactions. Another method for preparing PP-MA involves solution processing, which is relatively expensive and not suitable for commercial production.

[0010] Reportedly, some methods introduce OH groups into polyolefins to improve their adhesion to substrates or inorganic fillers. However, PP-OH polymers are not commercially available.

[0011] Therefore, there is a continued need to improve the thermal, mechanical, electrical and other properties of polyolefins to meet the increasingly demanding application requirements of economically and commercially viable methods. Summary of the Invention

[0012] Advantages of this disclosure include polyolefins having one or more functional groups covalently bonded to the polyolefin, such as polyolefins having hindered phenolic groups covalently bonded to the polyolefin and optionally other functional groups. Another advantage includes a method for producing polyolefins having one or more functional groups covalently bonded thereto in high yields, a method suitable for large-scale manufacturing.

[0013] These and other advantages are achieved, at least in part, through functional polyolefins having the following formula (I): PO-(HP) a (F1) b (F2) c (F3) d (F4) e (I) Where PO represents a polyolefin; HP represents a hindered phenolic group; F1 represents a maleic anhydride (MA) residue and / or a reactive residue formed from a maleic anhydride residue (X), such as (F1). b It can also be rewritten as (MA) b2 (X) b3 The sum of variables b2 and b3 is the value of b; F2 represents a hydroxyl group (-OH); F3 represents an epoxy group (-CHOCH2); and F4 represents an amine (primary and / or secondary amine) group. Variables a, b, c, d, and e each represent the molar percentage (mol%) of the repeating olefin unit relative to the polyolefin chain. Variables a and b can independently be from 0 to approximately 20 mol%, variables c and e can independently be from 0 to approximately 40 mol%, provided that the sum of c and e does not exceed 40 mol%, and variable d can be from 0 to approximately 20 mol%, provided that at least two of variables a, b, c, d, and e are greater than 0, for example, at least variables a and b are greater than 0, for example, variables a and b independently are greater than 0 to approximately 20 mol%, for example, greater than 0 to approximately 10 mol%.

[0014] In one aspect of this disclosure, the functional polyolefin may have covalently bonded thereto: (i) a hindered phenolic group and (ii) a maleic anhydride residue, or a reactive residue of the maleic anhydride residue, or both a maleic anhydride residue and a reactive residue of the maleic anhydride residue. The functional polyolefin may further have any one of a hydroxyl (-OH group), an epoxy (-CHOCH2 group), or an amino (e.g., -NH2 or -NHR5 group) covalently bonded thereto. In some embodiments, the hindered phenolic group is covalently bonded to the polyolefin via a coupling agent. The coupling agent may be a polymer or a compound. The hindered phenolic group may be covalently bonded to the polyolefin via a coupling agent having a plurality of reactive groups. Such reactive groups of the coupling agent may include hydroxyl (alkyl hydroxyl and / or aromatic hydroxyl, such as phenol), epoxy, primary amino, and / or secondary amino groups. In other embodiments, the hindered phenolic group is covalently bonded to the polyolefin via reactive residues formed by maleic anhydride residues and the hindered phenolic reagent on the polyolefin.

[0015] Another aspect of this disclosure is the formation of crosslinked substances from the functional polyolefins of this disclosure. Advantageously, polyolefins having hindered phenolic groups can be crosslinked by coupling of the hindered phenolic groups upon heating under oxidative conditions.

[0016] Another aspect of this disclosure is the combination of functionalized polyolefins with other polymeric materials (e.g., different polyolefins, such as nonfunctional polyolefins, including but not limited to polyethylene and polypropylene and their various commercial variants) as blends of the polymers. In such blends, the functionalized polyolefins of this disclosure can be used to improve the thermal stability characteristics of the blend. Advantageously, the initial degradation temperature of the blend can be not less than about 290°C, for example not less than about 300°C, 310°C, 320°C, 330°C, 340°C, and values ​​between these values.

[0017] In another aspect of this disclosure, functional polyolefins can be prepared by reacting together the following components under heating: (a) a polyolefin having multiple reactive groups, such as multiple maleic anhydride residues, hydroxyl groups, epoxy groups, amino groups, etc.; and (b) a hindered phenolic reagent that can react with the reactive groups of the polyolefin to produce a functional polyolefin having hindered phenolic groups covalently bonded thereto. Alternatively, certain starting functional polyolefins (e.g., polyolefins having multiple reactive groups) can be prepared by heating a maleic anhydride-modified polyolefin with a coupling agent having multiple reactive groups, which can react with the maleic anhydride-modified polyolefin to form a polyolefin having multiple reactive groups. The coupling agent may comprise a hydroxylated polymer having multiple hydroxyl groups, a polyamine having multiple amino groups, or a compound having multiple reactive groups, such as hydroxyl groups (alkyl hydroxyl and / or aromatic hydroxyl, e.g., phenol), epoxy groups, primary amino groups, and / or secondary amino groups.

[0018] For any of the above preparations, a polyolefin having a hindered phenolic group covalently bonded thereto may be added to the components before or during the reaction of the components together under heating. Alternatively, a nonfunctional polyolefin may be combined with the components before or during the reaction of the components together under heating to dilute the components and / or form a product blend.

[0019] The above preparations can be carried out under reactive blending conditions (e.g., reactive extrusion), wherein the polyolefin having multiple reactive groups is in a molten state, for example, by heating the components to at least about 170°C, such as about 180°C to about 280°C. In addition to reactive blending, the above preparations can be carried out in a solid-state method, wherein particles of the polyolefin having multiple reactive groups are heated together with a solvent mixture including other components. Such solid-state methods can be carried out at temperatures of about 170°C or higher, such as about 180°C to about 260°C.

[0020] Additional advantages of the invention will become apparent to those skilled in the art from the following detailed description, in which only the best mode contemplated by the invention is shown and described by way of illustration, and only preferred embodiments of the invention are shown and described. It should be recognized that the invention is capable of other and different embodiments, and that certain details thereof can be modified in various obvious ways without departing from the invention. Therefore, the drawings and description are to be regarded as illustrative rather than restrictive in nature. Attached Figure Description

[0021] Referring to the accompanying drawings, elements with the same reference numerals throughout represent similar elements, and wherein: Figure 1 For comparison, the following TGA degradation curves are plotted as follows: (a) commercial capacitor-grade PP as received, (b) dry-mixed commercial PP with HP additive (Irgonox 1010), and (c) chemically bonded HP-functionalized PP-HP prepared according to aspects of this disclosure.

[0022] Figure 2 The graph shows the TGA curves of commercial capacitor-grade PP (Borclean) and two PP-HP copolymers prepared according to aspects of this disclosure, having 0.16 mol% and 1.0 mol% HP groups, respectively.

[0023] Figure 3 For comparison of the following TGA curves: (a) a dry blend PP / HP sample with a 0.2 mol% HP content and four reactive blends of PP-(HP)(OH)(MA) polymers prepared according to aspects of this disclosure with different amounts of HP content blended with PP polymers.

[0024] Figure 4 The initial degradation temperature (T) of polypropylene samples with hindered phenols prepared by different methods is given. d The sample, relative to the HP mol% figure, includes samples prepared by monomer synthesis (X Td1) and by reactive mixing (O Td2).

[0025] Figure 5 The initial degradation temperature (T0) of polypropylene samples with hindered phenols covalently bonded thereto, prepared by different methods according to aspects of this disclosure. d (Plot relative to HP mol%) Detailed Implementation

[0026] This disclosure relates to polyolefins having one or more functional groups, i.e., functionalized polyolefins, and their preparation. Advantageously, the functionalized polyolefins of this disclosure can incorporate several polar functional groups, such as hindered phenolic groups (HP), into the polymer structure. Such covalently bonded HP groups act as antioxidants and improve the thermal stability of the polymer.

[0027] While methods for preparing certain polyolefins with hindered phenols are known, these methods rely on solution-based batch polymerization of comonomers, which is relatively expensive and unsuitable for large-scale manufacturing or mass production. Furthermore, the chemical modification of polypropylene grafted with maleic anhydride in the solid or molten state requires temperatures approximately or above the polymer's degradation temperature, thus limiting (if not preventing) such methods.

[0028] However, it was found that maleic anhydride-modified polyolefins can be further chemically modified in the solid or molten state when hindered phenolic groups are present. Therefore, hindered phenolic polyolefins can be prepared from maleic anhydride-modified polyolefins in the solid or molten state when a relatively small amount of hindered phenolic polyolefin is present in the reaction mixture. The initial hindered phenolic polyolefin material can be prepared by solution-based methods. But once the initial hindered phenolic polyolefin is prepared, additional polyolefins (PO(HP)) with covalently bound hindered phenols can be generated in the solid or molten state, thus allowing for large-scale and high-volume production of PO(HP) and other functionalized polyolefins.

[0029] One aspect of this disclosure includes polyolefins having the same or different functional groups covalently bonded to a polyolefin. Functional polyolefins can be advantageously prepared by solid-state methods and reactive compounding. As used herein, reactive compounding refers to a process involving chemically reacting components comprising at least one polyolefin by mixing to form covalent bonds between the components, wherein at least the polyolefin is in a molten state. Reactive compounding as used herein includes reactive extrusion, for example, chemically reacting the polyolefin in an extruder and discharging the product. For example, reactive extrusion via a twin-screw extruder can readily melt, homogenize, and pump the polymer through a die via co-rotating, intermeshing twin screws. During reactive extrusion, the components can react in the extruder to form the functional polyolefins of this disclosure. In practical aspects of this disclosure, the advantages of reactive compounding in general and reactive extrusion in particular are high-volume production and high yields of functional polymers.

[0030] During reactive compounding, it is preferable to bring at least one of the polyolefin components to a molten state, for example, by heating the components to at least about 180°C, such as from about 180°C to about 280°C. In some aspects, the functional polyolefins of this disclosure can be prepared by reactively compounding the components via an extruder (i.e., reactive extrusion). In the reactive extrusion method, the reaction temperature of the components can be at least about 200°C, such as at least about 210°C, 220°C, 230°C, 240°C, 250°C, 260°C, 270°C, 280°C, and values ​​between these values. For example, the functional polyolefins of this disclosure can be prepared by reactively compounding the components via an extruder, wherein the components are heated to a temperature of about 200°C to about 280°C, such as from about 200°C to about 260°C.

[0031] Besides reactive compounding, the functional polyolefins of this disclosure can be prepared by solid-state methods. Such methods may include mixing a component comprising a polyolefin with a solvent to form a slurry of wetted polyolefin particles, and heating the slurry to achieve a reaction. Such methods may also include mixing a component comprising a polyolefin with a solvent to form a suspension of polyolefin particles in a solvent and heating the suspension. These solid-state methods can generally be carried out at lower temperatures than reactive extrusion because the polyolefin is not heated to the temperature required for it to flow, but such solid-state methods are not equally effective for large-scale, high-volume production. Such solid-state methods can be carried out at temperatures of about 170°C or higher, for example, about 180°C to about 260°C.

[0032] Optionally, additives, fillers, or engineered polymers can be combined with the functional polyolefins and blends thereof disclosed herein to obtain a variety of polymer compositions and material properties. The functional polyolefins and their compositions can be formed into granules, which is an advantageous form for use in other methods. It is also possible to directly injection mold or extrude the functional polyolefins and their compositions to form sheets or profiles that meet specific performance requirements.

[0033] In one aspect of the invention, the functional polyolefin may have the following formula (I): PO-(HP) a (F1) b (F2) c (F3) d (F4) e (I) Wherein PO represents a polyolefin, such as polyethylene or polypropylene; HP represents a hindered phenolic group; F1 represents a maleic anhydride residue and / or a reactive residue of a maleic anhydride residue; F2 represents a hydroxyl group (OH); F3 represents an epoxy group (-CHOCH2); F4 represents an amino group (e.g., a primary amino group (NH2) and / or a secondary amino group (NHR5 group); R5 can represent a substituted or unsubstituted alkyl group, such as C1-30 Alkyl, such as C 1-8 Alkyl groups, which can be C 1-30 The alkyl group is replaced by a thiol, ether, or ester linking group. Variables a, b, c, d, and e each represent the molar percentage (mol%) of the repeating olefin unit relative to the polyolefin chain. Each of variables a and b can independently be from 0 to approximately 20 mol%, for example, 0 and at most approximately 15 mol%, at most approximately 10 mol%, at most approximately 5 mol%, etc. and values ​​between these. Each of variables c and e can independently be from 0 to approximately 40 mol%, for example, 0 to approximately 30 mol%, 0 to approximately 20 mol%, 0 to approximately 10 mol%, etc., provided that the sum of c and e does not exceed 40 mol%. Variable d can be from 0 to approximately 20 mol%, for example, 0 to approximately 10 mol%, 0 to approximately 5 mol%, etc. For formula (I), at least two variables are greater than 0, for example, at least variables a and b are greater than 0, for example, variables a and b independently are greater than 0 to approximately 20 mol%, for example, greater than 0 and at most approximately 15 mol%, at most approximately 10 mol%, at most approximately 5 mol%, etc.

[0034] In some cases, variables a, b, c, d, and e can each independently be 0 to approximately 10 mol%, provided that at least two variables are greater than 0, for example, variables a and b are at least greater than 0, or variables a and b independently are greater than 0 to approximately 10 mol%. In other cases, variable a can be approximately 0.1 mol% to approximately 10 mol%, for example, approximately 0.1 mol% to approximately 3 mol% or approximately 0.2 mol% to approximately 1.5 mol%; b can be greater than 0 to approximately 10 mol%, for example, approximately 0.01 mol% to approximately 5 mol%; c and e can independently be 0 to approximately 10 mol%, for example, approximately 0.5 mol% to approximately 3 mol%; and d can be 0 to approximately 5 mol%, for example, approximately 0.01 mol% to approximately 2 mol%.

[0035] As noted above, F1 can represent maleic anhydride residues (MA) on polyolefins. Therefore, F1 refers to residues derived from maleic anhydride-modified polyolefins, which, after a free radical reaction between maleic anhydride and the polyolefin, actually become side groups (e.g., succinic anhydride side groups) on the polyolefin. Conventionally, such groups are called maleic anhydride residues or groups because the starting material is maleic anhydride. F1 can also represent reactive residues resulting from the reaction of maleic anhydride residues (MA) on a polyolefin with another reactive group on another material to form a maleic anhydride reactive residue (X). Such residues include reactive adducts (e.g., adding reactants without losing atoms) and other reaction products, such as adding reactants and losing atoms, for example, from condensation reactions with maleic anhydride residues on the polyolefin and another reactive group. Therefore, (F1) b It can also be rewritten as (MA). b2 (X) b3 The sum of variables b2 and b3 is the value of b, and X represents the reaction residue of maleic anhydride residue on the polyolefin with reactive groups (e.g., hydroxyl, primary amino, secondary amino, etc.) on the coupling agent or hindered phenolic reagent. X can therefore represent esters, amides, imides, etc.

[0036] In some respects, the polyolefin or polyolefin chain of a functional polyolefin may have the following formula (II):

[0037] Where R1 represents H or CH3; R2 represents H or C. 1-10 The substituted linear, branched, or cyclic alkyl or aryl moiety, x is an integer of at least 100, for example at least 1,000 (e.g., 100 to about 50,000), and y is an integer of at least 10, for example at least 100 (e.g., 10 to about 10,000). In some embodiments, x is an integer of at least 100, for example at least 500, at least 1,000, and at most about 100,000, for example at most about 50,000, and values ​​between therewith; and y is an integer of at least 10, for example at least 100, at least 500, at least 1,000, and at most about 50,000, at most about 20,000, at most about 10,000, and values ​​between therewith. Such polyolefins include, but are not limited to, polyethylene and polypropylene and their various commercial variants.

[0038] In one aspect of this disclosure, the functional polyolefin may have covalently bonded thereto: (i) a hindered phenolic group and (ii) a maleic anhydride residue, or a reactive residue of a maleic anhydride residue, or both a maleic anhydride residue and a reactive residue of a maleic anhydride residue. The functional polyolefin may further have any one of a hydroxyl (-OH group), an epoxy (-CHOCH2 group), or an amino (-NH2 or -NHR5 group) covalently bonded thereto. Advantageously, the functional polyolefin having a hindered phenolic group covalently bonded thereto may have an initial degradation temperature not lower than about 290°C, for example not lower than about 300°C, 310°C, 320°C, 330°C, 340°C, etc., and values ​​between these.

[0039] In some embodiments, the hindered phenolic group is covalently bonded to the polyolefin via a coupling agent. For example, the hindered phenolic group can be covalently bonded to the polyolefin via a reactive residue formed by a maleic anhydride residue on the polyolefin and a reactive group on the coupling agent. In this example, the hindered phenolic group is covalently bonded to the coupling agent. The coupling agent can be a polymer or a compound.

[0040] In practicing certain aspects of this disclosure, functional polyolefins can be prepared by reacting together the following components under heating: (a) a polyolefin having a plurality of reactive groups, such as a plurality of maleic anhydride residues or groups, hydroxyl groups, epoxy groups, amino groups, etc.; and (b) a hindered phenolic reagent that can react with the reactive groups of the polyolefin to produce a functional polyolefin having hindered phenolic groups covalently bonded thereto.

[0041] Scheme 1 below describes a method for preparing a functional polyolefin having hindered phenolic groups bound to it via a coupling agent.

[0042]

[0043] Option 1. A method for preparing functional polyolefins via coupling agents.

[0044] As shown in Scheme 1 above, a maleic anhydride-modified polyolefin (PO(MA)) can be combined with a coupling agent (CA), followed by reaction with a hindered phenol (HP) reagent to produce a functional polyolefin having hindered phenolic groups covalently bonded to the coupling agent. Scheme 1 illustratively shows some unreacted maleic anhydride residues on the polyolefin chain. In principle, all maleic anhydride residues can be used to react with the coupling agent. Furthermore, depending on the number of reactive groups on the coupling agent, more than one polyolefin chain can be covalently bonded to the same coupling agent. The polyolefin chain can be represented by formula (II) above.

[0045] In the first step of Scheme 1, a maleic anhydride-modified polyolefin (PO(MA)) is combined with a coupling agent (CA) to form a polyolefin having multiple reactive groups. PO(MA) and CA can react together under heating, for example by heating the components to at least about 180°C, such as by reactive extrusion. Preferably, a polyolefin having hindered phenolic groups is added to the components before or during the reaction under heating. One or more nonfunctional polyolefins can be added to the components as diluents before or during the reaction.

[0046] The starting maleic anhydride-modified polyolefin is not particularly limited by the molecular weight or extent of the maleic anhydride residues or their position; it can be grafted along the main chain or ends of the polyolefin, or in chain form, or in any combination thereof. Commercially available materials can be used, such as commercially available polyethylene and / or polypropylene grafted with maleic anhydride.

[0047] Coupling agents (CAs) have multiple, for example, at least two reactive groups, wherein at least one of the reactive groups of the coupling agent can react with maleic anhydride residues of the polyolefin. After coupling to the polyolefin, the coupling agent retains at least one usable reactive functional group to react with hindered phenolic reagents. The coupling agent can be a polymer or compound, provided that it has multiple reactive groups. Such reactive groups of the coupling agent include hydroxyl groups (alkyl hydroxyl and / or aromatic hydroxyl, such as phenol), epoxy groups, primary amino groups, and / or secondary amino groups. Such coupling agents can include, for example, hydroxylated polymers having multiple hydroxyl groups, such as poly(ethylene-co-vinyl alcohol) (EVOH) copolymers; phenoxy resins; polyamines, such as natural polyamines, such as spermidine, spermine; synthetic polyamines, such as diethylenetriamine, triethylenetetramine, tris(2-aminoethyl)amine, 1,1,1-tris(aminoethyl)ethane, polyethyleneimine, polyethylene polyamine, alkyl glycols, aromatic glycols, alkyl diamines, aromatic diamines, etc.

[0048] After preparing a polyolefin having multiple reactive groups, it can be reacted with a hindered phenolic reagent under heating, for example by heating the components to at least about 180°C, such as by reactive extrusion. Preferably, the polyolefin having hindered phenolic groups is added to the components before or during the reaction of the components together under heating. One or more nonfunctional polyolefins can be added to the components as diluents before or during the reaction of the components. In some cases, the polyolefin having multiple reactive groups can be prepared in the up-feed position of the extruder and subsequently reacted with a hindered phenolic reagent in the down-feed position of the same extruder. Alternatively, the preparation can be carried out in separate reactive compounding methods.

[0049] The hindered phenol reagent that can be used in the methods of this disclosure can be represented by the following formula (III).

[0050]

[0051] Where Q represents -OOC-; R3 represents a linking group, such as C 1-8 Linking group, preferably -CH2-CH2- linking group; R4 represents H or a substituted or unsubstituted alkyl group, such as C. 1-30 Alkyl groups, which are unsubstituted or linked by thiols, ethers, or esters at C. 1-30 Internal substitution; and when R4 represents a substituted or unsubstituted alkyl group, z is an integer from 1 to 4. HP reagents containing ester or acid groups can react with the remaining reactive groups of the coupling agent.

[0052] In cases where the coupling agent has multiple identical or different functional groups, the product generated by Scheme 1 may include a polyolefin having some unreacted MA residues in the PO chain and some unreacted functional groups (including -OH, -NH2 and NHR groups) from the CA reagent to form PO-(MA)(HP) (optionally having OH, -NH2 and NHR groups).

[0053] As an alternative to using coupling agents to chemically bond HP groups to polyolefins, maleic anhydride-modified polyolefins can be combined with hindered phenol reagents to directly form polyolefins with hindered phenol groups from maleic anhydride residues. Scheme 2 below illustrates such a method.

[0054]

[0055] Option 2. A method for preparing functional polyolefins.

[0056] Scheme 2 illustrates a polyolefin having multiple maleic anhydride residues on it, wherein some or all of these residues react with a hindered phenolic reagent. Thus, the hindered phenolic group is covalently bonded to the polyolefin via a reaction residue formed by the maleic anhydride residues on the polyolefin and the hindered phenolic reagent. Scheme 2 illustratively shows some unreacted maleic anhydride residues on the polyolefin chain. In principle, all maleic anhydride residues can be used to react with the hindered phenolic reagent, and one maleic anhydride can react with two hindered phenolic reagents. The polyolefin chain can be represented by formula (II) above, and the hindered phenolic reagent can be represented by formula (III) above; for example, an HP reagent containing an ester or acid group can react with the maleic anhydride residues.

[0057] The direct preparation of polyolefins with multiple hindered phenolic groups from maleic anhydride modified with polyolefins can be carried out by reacting the maleic anhydride-modified polyolefin with a hindered phenolic reagent under heating, for example by heating the components to at least about 180°C, such as by reactive extrusion. Preferably, the polyolefin with hindered phenolic groups is added to the components before or during the reaction under heating. One or more nonfunctional polyolefins can be added to the components as diluents before or during the reaction.

[0058] As an alternative to reactive blending, functionalized polyolefins can be prepared by a solid-state method, which involves mixing maleic anhydride-modified polyolefins with a solvent and a hindered phenol reagent to form a slurry of wetted polyolefin particles or a suspension of polyolefin particles in a solvent.

[0059] For example, solutions or mixtures comprising a solvent for a hindered phenolic reagent can be prepared with or without a coupling agent (e.g., a compound having multiple reactive groups). The solution or mixture can be combined with polyolefin-modified polymer particles to form a slurry. The slurry components can then be baked at a temperature of at least about 170°C, for example at least about 180°C, or at least about 200°C and at most about 280°C to achieve a reaction between the maleic anhydride residues on the polyolefin and the hindered phenolic reagent and the coupling agent (if present).

[0060] Alternatively, a solvent comprising the hindered phenolic reagent, a solution or mixture with or without a coupling agent, can be combined with maleic anhydride-modified polyolefin polymer particles to form a suspension, which is then heated. For the suspension method, a high-boiling-point solvent, such as one with a boiling point of at least about 170°C to about 235°C, is preferred to minimize solvent evaporation and / or to heat the components at a pressure above atmospheric pressure. The suspension can then be heated to at least about 170°C, such as at least about 180°C, 190°C, 200°C, etc., to achieve a reaction between the maleic anhydride residues on the polyolefin and the hindered phenolic reagent and coupling agent (if present).

[0061] In any of the solid-state methods, it is preferable to add the polyolefin having hindered phenolic groups to the components before reacting them together under heating. One or more nonfunctional polyolefins may be added as diluents to the components before reacting them.

[0062] As an example of the versatility of the methods of this disclosure, the functional polyolefin may include a polyolefin chain covalently bonded to the coupling agent (e.g., the hydroxylated polymer) via a reaction adduct between maleic anhydride on the polyolefin chain and a reactive group on the coupling agent (e.g., a hydroxyl group on a hydroxylated polymer). Advantageously, the functional polyolefin of this disclosure may further include a hindered phenolic group covalently linked to the coupling agent (e.g., the hydroxylated polymer). Such a functional polyolefin having a hindered phenolic group bonded via the hydroxylated polymer can be represented by the following formula (IV): POC-(HP) a (F1) b (F2) c (F3) d (IV) HP represents a hindered phenolic group; F1, F2, and F3 independently represent functional groups, such as F1 being a maleic anhydride (MA) group, a reactive adduct between an MA group and a hydroxyl group, which may include a COOH group, a primary amine, and a secondary amine; F2 being a hydroxyl (OH) group; and F3 being, for example, an epoxy group. a can be 0 to about 10 mol% (mol%), for example, about 0.1 mol% to about 10 mol%, or about 0.1 mol% to about 3 mol% or about 0.2 mol% to about 1.5 mol%. b can be 0 to about 5 mol%, for example, about 0.01 mol% to about 2 mol%. c can be 0 to about 10 mol%, for example, about 0.5 mol% to about 3 mol%, and d can be 0 to about 5 mol%, for example, about 0.01 mol% to about 2 mol%. However, the condition is that at least one of a, b, or c is greater than zero, i.e., at least one of HP, F1, or F2 is present in the functional polyolefin. POC represents two or more polyolefin chains linked together by one or more ester bonds. A polyolefin chain can be represented by the above formula (II).

[0063] In some embodiments, 'a' is at least 0.15 mol%, for example, at least about 0.3 mol%, 0.5 mol%, 1 mol%, 1.5 mol%, 2 mol%, and higher. Polyolefins having hindered phenolic groups in combination with them advantageously have improved thermal stability compared to polyolefins without hindered phenolic groups, and such functionalized polyolefins advantageously improve the thermal stability of compositions comprising polyolefins having hindered phenolic groups. Furthermore, polyolefins having hindered phenolic groups can undergo crosslinking to form crosslinked polyolefins.

[0064] As an example of the versatility of the method of this disclosure, the functional polyolefins of this disclosure can be prepared via a high-temperature reaction method by reacting the following components under heating: (a) a hydroxylated polymer having multiple hydroxyl groups; and (b) a polyolefin having multiple maleic anhydride groups. The maleic anhydride groups on the polyolefin can react with the hydroxyl groups of the hydroxylated polymer under heating to produce a functional polyolefin having two or more polyolefin chains covalently bonded to the hydroxylated polymer via ester bonds. Additionally, the reactive adduct between the maleic anhydride residues on the polyolefin chain and the hydroxyl groups on the hydroxylated polymer chain segment can be formed by a partial reaction of the anhydride with an alcohol to form a COOH group.

[0065] Additionally, functionalized polyolefins having hindered phenolic groups can be prepared via a high-temperature reaction method by reacting the following components under heating: (a) a hydroxylated polymer having multiple hydroxyl groups; (b) a polyolefin having multiple maleic anhydride groups; and (c) a hindered phenolic reagent, to produce a functionalized polyolefin having polyolefin chains covalently bonded to the hydroxylated polymer and hindered phenolic groups covalently bonded to the hydroxylated polymer. In some aspects of this disclosure, functionalized polyolefins having hindered phenolic groups are prepared by first preparing the functionalized polyolefin from the reactive polymers of (a) and (b), and then reacting the product with (c) the hindered phenolic reagent.

[0066] In the preparation of such functional polyolefins, a polyolefin with hindered phenolic groups is added to the components before they are reacted together under heating. This type of polyolefin with hindered phenolic groups reduces the degradation of the initial reactive polymeric components during the reaction.

[0067] In practical aspects of this disclosure, the reactive component used to prepare the functional polyolefin is subjected to high temperatures, for example, greater than 190°C, such as at least about 200°C, 210°C, 220°C, 230°C, 240°C, or higher. Preferably, the reactive component is subjected to a temperature above the melting temperature of the reactive polymeric component, wherein the reactive polymeric component is in a molten state. The functional polyolefin can be prepared at high temperatures by melt methods such as extrusion, compounding, injection molding, and compression molding.

[0068] For example, the reaction can be carried out in a co-rotating and intermeshing twin-screw extruder, in which the reactive polymer and chemical reagents are melted and mixed. The reaction sequence can begin by reacting a maleic anhydride-modified polyolefin (e.g., PE(MA) or PP(MA)) with a hydroxylated polymer (e.g., EVOH copolymer or phenoxy resin), followed by the reaction of an HP reagent containing ester or acid groups. Examples of hindered phenolic reagents are provided in Table 1 below.

[0069] Table 1. Examples of HP reagents

[0070] Optionally, a polyamine agent may be added to optionally incorporate some of the amine moiety into the polymer structure. Additives, fillers, or engineered polymers may optionally be dispersed and distributedly mixed into the melt to achieve homogeneous mixing and obtain a variety of polymer compositions and material properties.

[0071] Functional polyolefins and compositions can be formed into granules, a form advantageous for use in other methods. It is also possible to directly injection mold or extrude functional polyolefins and compositions to form sheets or profiles that meet specific performance requirements. Such in-situ methods can save energy and minimize the thermal stress on materials that enhance the properties of the product.

[0072] In the practical aspects of this disclosure, functionalized polyolefins can include a variety of different functional groups, such as HP, MA, and OH groups, within the same polyolefin structure. However, for certain engineering plastics and substrates, both NH2 and epoxy groups may be present to enhance the inter-functional properties of the polyolefin. Scheme 3 below illustrates a functionalized polyolefin having multiple polymer segments bonded to a central hydroxylation and various functional groups distributed in different polymer segments.

[0073]

[0074] Option 3. A multifunctional polyolefin chain structure with various functional groups located in different polymer chain segments.

[0075] In Scheme 3, PO represents a polyolefin chain, which can be represented by formula (II) above. MA represents an anhydride adduct formed after maleic anhydride is grafted onto the PO chain. MA-NHR6 represents a reaction adduct between MA and a polyamine reagent having more than two primary or secondary amino groups (R6), such polyamines including, for example, natural polyamines, such as spermine and spermine; synthetic polyamines, such as diethylenetriamine, triethylenetetramine, tris(2-aminoethyl)amine, 1,1,1-tris(aminoethyl)ethane, polyethyleneimine, polyethylene polyamine, alkyl diamine, aromatic diamine, etc. X represents a reaction adduct between MA and an OH group, such as ester coupling, T represents the terminal group H, OH, HP, or epoxy group in the hydroxylated central segment, and HP represents a hindered phenolic group, which can be represented by the following formula:

[0076] R3 represents a linking group, such as C 1-8The linking group is preferably a -CH2-CH2- linking group. The HP group on the functional polyolefin can be formed by a condensation reaction between an OH group and a hindered phenolic reagent containing an ester or COOH moiety. In some aspects, the centrally hydroxylated polymer segment described in Scheme 3 comprises a poly(ethylene-co-vinyl alcohol) (EVOH) copolymer. The number of PO segments chemically linked to the centrally hydroxylated segment can be an integer from 1 to 100, the number of MA groups in each PO segment is an integer from 0 to about 200, and the sum of HP and OH groups in the central segment is an integer from 100 to 10,000, wherein the [HP] / [OH] molar ratio is from 1 / 100 to 100 / 1.

[0077] Introducing multiple polar functional groups into the polyolefin chain structure can be achieved by covalently binding the PO-MA chain to a hydroxylated polymer, such as a poly(ethylene-co-vinyl alcohol) (EVOH) copolymer or a polyhydroxy ether resin, such as a phenoxy resin (available from Gabriel Chemicals), which acts as a coupling agent. The hydroxylated polymer preferably contains multiple OH groups along the polymer chain (e.g., reactive OH groups in each comonomer unit). The polyhydroxy ether resin may also have OH or epoxy end groups.

[0078] When PO-MA is reacted with a hydroxylated polymer (P-OH), some of the OH groups in the hydroxylated polymer effectively participate in the coupling reaction with the maleic anhydride (MA) modified polyolefin (PE-MA or PP-MA) polymer during the blending process, and a graft polymer structure with multiple polyolefin chains bonded to the same hydroxylated polymer chain can be formed. In other words, the reactive blend product via extrusion can have a multi-segment polymer structure in which a selected number of polyolefin chains are connected to a centrally hydroxylated polymer segment. Additionally, the multiple OH groups in the hydroxylated polymer segment also undergo subsequent condensation reactions with some hindered phenolic (HP) antioxidant reagents containing ester or COOH moieties during the blending process. In other words, the central polymer segment not only connects several polyolefin chains but also provides numerous OH and HP functional groups in the final polymer structure. In some embodiments of this disclosure, the functionalized polyolefin can have a multi-segment polymer structure containing a combination of at least OH, HP, and MA functional groups. Including epoxy polar groups in the structure by selecting a polyhydroxy ether resin with two terminal epoxy groups is also relatively straightforward. Optionally, some of the remaining MA groups in the polyolefin chain can be used to introduce the NH2 moiety by reacting such functional polyolefins with polyamines or polyamide reagents.

[0079] Scheme 4 below illustrates another multifunctional polyolefin structure (A) containing several isotactic PP chains and HP moieties chemically bonded to the central segment of EVOH, produced via a reactive blending method involving a maleic anhydride-modified polypropylene (PP-MA) copolymer with poly(ethylene-co-vinyl alcohol) (EVOH) and a hindered phenolic (HP) antioxidant reagent containing an ester or COOH moieties. The final blending product is a segmental functional polyolefin structure containing three desired polar functional groups (MA, HP, and OH groups), with some unreacted MA units located in the PP chains and HP and OH groups present in the central segment.

[0080]

[0081] Option 4. A preferred multifunctional polyolefin structure (A) with EVOH as a coupling agent prepared by a reactive mixing method using a combination of PP-MA, EVOH and HP reagents.

[0082] Where PP represents a polypropylene homopolymer or copolymer with a comonomer content of up to 10 mol%, and R is H or C2-C. 10 The substituted linear, branched, or cyclic alkyl or aryl moiety, where x is an integer of at least 100, for example at least 500, at least 1,000, and at most about 50,000; y is an integer of at least 10, for example at least 100, at least 500, at least 1,000, and at most about 10,000; EVOH represents a poly(ethylene-co-vinyl alcohol) copolymer segment, where m is an integer of 0 to about 10,000, and n is an integer of 100 to about 10,000; MA is a moiety with an anhydride group formed after the reaction of grafting maleic anhydride onto the polyolefin chain. In this example, X is the reactive residue between MA and the OH group, and HP is a hindered phenol having an ethylene-ester bond bound to the polymer chain, derived from the condensation reaction between the OH group and a hindered phenolic antioxidant reagent containing an ester or COOH moiety. The number of PP segments chemically linked to the central EVOH segment is an integer from 1 to 100, the number of MA groups in each PP segment is an integer from 0 to 200, and the sum of HP and OH groups in the central segment is an integer from 100 to 10,000, wherein the molar ratio of [HP] to [OH] is 1 / 100 to 100 / 1.

[0083] Scheme 5 below illustrates another multifunctional and multi-segment polyolefin structure (B). In this example, the functional polyolefin contains several PP chains (e.g., isotactic PP chains) and an HP moiety chemically bonded to the central polyhydroxy ether segment. The multifunctional polyolefin can be produced via a reactive blending method involving maleic anhydride-modified polypropylene (PP-MA) with a polyhydroxy ether resin (phenoxy) and a hindered phenolic (HP) reagent containing an ester or COOH moiety. The final blended product can be a multi-segment functional polyolefin structure containing three desired polar functional groups (MA, HP, and OH groups), with some unreacted MA units remaining in the PP chains and HP and OH groups present in the central polyhydroxy ether segment.

[0084]

[0085] Scheme 5. An example of a multifunctional polyolefin structure (B) with phenoxy resin as a coupling agent prepared by a reactive mixing method using a combination of PP-MA, phenoxy and HP reagents.

[0086] In this example, PP can represent a polypropylene homopolymer or copolymer with a comonomer content of up to 10 mol%, where R is H or C2-C. 10 The substituted straight-chain, branched, or cyclic alkyl or aryl moiety, x is an integer of at least 100, for example at least 500, at least 1,000, and at most about 50,000; y is an integer of at least 10, for example at least 100, at least 500, at least 1,000, and at most about 10,000. The phenoxy group can represent a polyhydroxy ether chain derived from bisphenol A [(CH3)2C(C6H4OH)2] and epichlorohydrin [Cl-CH2-(C2H3O)], n is an integer of about 10 to about 10,000, and MA is the moiety with an anhydride group formed after the reaction of grafting maleic anhydride onto the polyolefin chain. In this example, X is the reactive residue between MA and OH groups, HP is a hindered phenol having an ethylene-ester bond with the polymer, derived from the condensation reaction between the OH group and a hindered phenolic reagent containing an ester or COOH moiety, and T is an HP or epoxy end group located at both ends of the phenoxy chain, which becomes the central segment in the final structure. The number of PP segments chemically linked to the phenoxy central segment is an integer ranging from 1 to about 100, the number of MA groups in each PP segment is an integer ranging from 0 to about 200, and the sum of HP and OH groups in the central segment is an integer ranging from 100 to 10,000, wherein the [HP] / [OH] molar ratio is 1 / 100 to 100 / 1.

[0087] Preferably, the functional polyolefins of this disclosure are prepared by reactive compounding methods, such as reactive extrusion. For example, the melt method may involve a conventional twin-screw extruder with specific reaction steps and operating conditions. In the embodiments reported below, reactive compounding is performed using co-rotating and intermeshing twin-screw extruders, wherein the reactive polymer and chemical reagents are melted and mixed sequentially to minimize undesirable side reactions. For some preparations, the reaction sequence begins with a reactive mixing of maleic anhydride-modified polyolefins (PE-MA or PP-MA) with hydroxylated polymers (e.g., EVOH or polyhydroxy ether resins), followed by the reaction of one or more HP antioxidant reagents containing ester or acid groups. Optionally, polyamine reagents may be added to incorporate some amine moieties into the polymer structure. Additives, fillers, or engineered polymers are then dispersed and distributedly mixed into the melt to achieve homogeneous mixing and obtain the desired polymer composition and material properties. The resulting multifunctional polyolefin material can be formed into granules and subsequently coated by other methods. It is also possible to directly injection mold or extrude to form sheets or profiles that meet specific performance requirements. This in-situ method saves energy and minimizes the thermal stress on the material that enhances the product's properties.

[0088] Another aspect of this disclosure is the combination of functionalized polyolefins with other polymeric materials (e.g., polyolefins, such as non-functionalized polyolefins, including but not limited to polyethylene and polypropylene and their various commercial variants) as blends of the individual polymers. In such blends, relatively low amounts of the functionalized polyolefins of this disclosure can be used to significantly improve the properties of the blends, such as thermal stability. The functionalized polyolefins of this disclosure having HP groups can also be combined with functionalized polyolefins without HP groups (e.g., polyolefins having maleic anhydride and / or hydroxyl groups and their reaction products) to significantly improve the properties of the blends, such as thermal stability.

[0089] Blending PO-HP with another PO polymer can contribute to the following benefits: (a) uniform distribution of HP antioxidants in the PO polymer, higher concentration of HP (polar) antioxidants in the PO (nonpolar) matrix without phase separation, (c) low mobility and volatility of covalently bonded HP groups prevent loss via diffusion and / or extraction (especially sharp in films and coatings), and (d) increased high-temperature stability and reduced dielectric loss under high electric field conditions.

[0090] In some embodiments, the functional polyolefin of this disclosure may be further combined with another polymer material, wherein the molar percentage of HP groups based on the total polyolefin repeating units of the blend may be as low as about 0.01% or higher, for example at least about 0.1%, for example at least 0.3%, and may be about 0.1% to about 1.0%, for example about 0.3% to about 1.5%. In other embodiments, the molar percentage of MA groups in the blend may be at most about 1%, for example at most about 0.5%, for example at most about 0.1%; and the molar percentage of OH groups in the blend may be at most about 2%, for example at most about 1%, for example at most about 0.3%. Advantageously, the initial degradation temperature of the blend may be not lower than about 290°C, for example not lower than about 300°C, 310°C, 320°C, 330°C, 340°C, and values ​​between therewith.

[0091] Another advantage of the functionalized polyolefins disclosed herein is that they can co-crystallize with other functionalized or non-functionalized polyolefins when blended with other polyolefins. Such co-crystallization promotes the uniform distribution of functionalized polyolefins in the polyolefin blend.

[0092] Another aspect of this disclosure includes crosslinking materials derived from polyolefins having hindered phenolic groups prepared according to this disclosure. Advantageously, polyolefins having hindered phenolic groups can be crosslinked by coupling of the hindered phenolic groups upon heating under oxidative conditions. Such a reaction is shown in Example 1, Scheme B below.

[0093] Example

[0094] The following examples are intended to further illustrate certain preferred embodiments of the invention and are not restrictive in nature. Those skilled in the art can recognize or determine numerous equivalents of the particular substances and procedures described herein using at most conventional experiments.

[0095] Example 1: Synthesis and evaluation of PP-HP copolymer prepared by monomer polymerization

[0096] In this embodiment, we repeated the chemical method shown in Chung et al, Macromolecules, 2017: 50: 7041-7053 to prepare the PP-HP copolymer and examined its thermal oxidative stability.

[0097] 1. Synthesis of PP-OH copolymer

[0098] The OH groups in the 10-undecen-1-ol comonomer were protected with silanes using the following method. In a 1 L flask equipped with a magnetic stirrer, 34.46 g of 10-undecen-1-ol and 20.22 g of triethylamine were dissolved in 500 mL of THF. 21.72 g of trichlorotrimethylsilane was slowly introduced at room temperature. A white powder immediately appeared. The suspension was stirred at 60 °C for 8 hours, and the white powder was filtered off. The resulting yellow solution was obtained by vacuum distillation, and the fraction distilled at 60 °C was redistilled with CaH2 before use to obtain the silane-protected comonomer.

[0099] In a typical polymerization reaction, after purging with propylene gas, 75 mL of toluene, 5 mL of MAO (5 wt% in toluene), and 2.0 g of 10-undecene-1-oxytrimethylsilane were charged into a dry Parr 450 mL stainless steel autoclave equipped with a mechanical stirrer. Then, under propylene pressure, a toluene solution of approximately 5 μmol of rac-Me2Si[2-Me-4-Ph(Ind)]2ZrCl2 was injected into the rapidly stirred solution to initiate polymerization. After reacting at 40 °C and 120 psi propylene gas pressure for 20 minutes, the polymer solution was quenched with methanol. The resulting product was washed twice each with HCl / methanol (0.5 M), methanol, and THF, and then dried under vacuum at 60 °C. Approximately 7.22 g of PP-OH copolymer was obtained, with a catalytic activity of 4300 kg polymer / (mol Zr·h).

[0100] 2. Synthesis of PP-HP copolymer via Steglich esterification

[0101] PP-HP copolymers were synthesized by esterification of PP-OH copolymers with 3,5-bis(tert-butyl)-4-hydroxyphenylpropionic acid in the presence of 1-(3-(dimethylamino)propyl)-3-ethylcarbodiimide (EDC) and 4-N,N-dimethylaminopyridine (DMAP). In a typical reaction operation, 5 g of PP-OH copolymer with a 1 mol% OH content was mixed with 1.9 g of 3,5-bis(tert-butyl)-4-hydroxybenzoic acid, 0.19 g of DMAP, and 100 mL of toluene in a 500 mL round-bottom flask equipped with a stirrer and condenser under an argon atmosphere. After the addition of 1.15 g of EDC, the esterification reaction was carried out at 110 °C for 12 h. The resulting PP-HP copolymer was precipitated in 600 mL of methanol and subsequently washed several times with methanol. The polymer was then dried overnight in a vacuum oven at 70 °C.

[0102] Scheme A below illustrates a synthetic route for preparing PE-HP and PP-HP copolymers with high molecular weight, controlled HP comonomer content, and high yield via monomers.

[0103]

[0104] Example 1, Scheme A

[0105] Each HP moiety provides four hydrogen atoms to react with four polymer radicals due to the oxygen oxidation of the polyolefin chain, ending with a dimerization reaction between the two oxidized HP groups to form long-conjugated bis-quinone methide groups. This reaction mechanism not only protects the polyolefin chain from thermal oxidative degradation but also forms a fully cross-linked x-PE and x-PP polymer network structure (Scheme B below). In other words, PE-HP and PP-HP copolymers become stronger materials after exposure to high-temperature oxidative conditions, rather than experiencing a decrease in mechanical strength as is seen in most commercial polyolefin products.

[0106]

[0107] Example 1, Scheme B

[0108] 3. TGA study to examine the thermal oxidative stability of PP-HP

[0109] As discussed, the thermal oxidative stability of PP is a major concern during polymer processing and application. Commercial PP products typically contain small amounts (< 0.5 wt%) of hindered phenolic (HP) antioxidants and other stabilizers to prevent polymer chain degradation.

[0110] According to Chung et al., Macromolecules, 2019: 52: 5618-5637, thermogravimetric analysis (TGA) can be used as a simple measure for qualitative and quantitative assessment of thermal stability. Specifically, the initiation degradation temperature (T0) has been found in TGA. d (Defined in this paper as the temperature at which the material experiences a 5% weight loss when heated in air at 10 °C / min) is consistent with other stability measures. The 5% figure is chosen to eliminate the potential influence of volatiles from the method (e.g., residual solvents or moisture). Additional weight loss in the TGA curve can be affected by different degradation components and complicates interpretation when different functional groups are involved. Samples can be tested from particles, powders, strands, or membranes, with membranes being preferred to obtain a representative portion for measurement. The thickness of the sample membrane is typically 50 µm to 100 µm.

[0111] Figure 1The TGA degradation profiles of three polypropylene samples were compared. These samples included: (a) commercial capacitor-grade PP as received (from Borealis, catalog number Borclean Capacitor grade), (b) a dry-blended commercial PP with HP additive (Irgonox 1010), and (c) chemically bonded HP-functionalized PP-HP. The capacitor-grade PP was a fully formulated product containing >0.3 wt% (wt%) of Irganox® 1010 antioxidant and other stabilizers. The dry-blended commercial PP with HP additive contained 1.6 wt% HP powder (Irgonox 1010, equivalent to 0.2 mol%). Compared to the commercial capacitor-grade PP, the dry-blended commercial PP with HP additive showed degradation rates up to TGA. d A slight reduction in weight loss was observed, but no significant overall improvement in thermal stability was seen. However, chemically bonded HP (PP-HP) polymers showed an overall improvement in thermal stability even at relatively low doses of HP (0.2 mol%). In some cases (discussed later), 0.5 mol% or higher PP-HP could be treated at temperatures above 330°C without any signs of degradation. Again, TGA and T in air... d This will be used as an initial screening method to assess thermal stability and whether HP is chemically linked to polyolefins.

[0112] Figure 2 The TGA curves are used to compare commercial capacitor-grade PP (Borclean) with two PP-HP copolymers having 0.16 mol% and 1.0 mol% HP groups, respectively. Figure 2 The initial degradation temperatures of the samples are provided in Table 2 below.

[0113] Table 2. Initial degradation temperatures of various samples determined by TGA analysis in air at a heating rate of 10 °C / min.

[0114] A fully formulated capacitor-grade PP (containing Irganox® 1010 antioxidant and other stabilizers as a mixture) was heated in air at a rate of 10°C / min at approximately 255°C. d Degradation. On the other hand, PP-HP copolymers with HP concentrations of 0.16 mol% and 1.0 mol% showed significantly higher thermal oxidative stability, with their initial degradation temperature T0... d These figures are approximately 300°C and 330°C, respectively. These data show that the Tg of covalently bonded HP in polyolefins (e.g., PP-HP) is... dThe increase is proportional to the increase in the mol% of the HP component combined with the polyolefin. In contrast, the mixture of PP and HP (i.e., such as PP alone) increases proportionally to the increase in the mol% of the HP component combined with the polyolefin. Figure 1 The dry-mixed PP / HP blend shown does not exhibit an initial degradation temperature T. d Significant changes were observed. These data (and additional data below) further demonstrate that 0.5 mol% or higher PP-HP can be treated at temperatures above 300°C without measurable degradation.

[0115] Experimental results clearly show that the thermal stability of polyolefins is improved when a sufficient amount of HP antioxidant is uniformly distributed in the PP matrix. However, the polar nature of hindered phenols makes them incompatible with semi-crystalline, non-polar PP polymers, and simply mixing hindered phenols with polyolefins allows HP to diffuse to the polymer surface, resulting in an inhomogeneous mixture over time. In contrast, when HP groups are chemically bonded to polyolefins, polyolefin-HP itself exhibits significantly improved thermal oxidative stability, and polyolefin-HP can be used as an antioxidant to improve the thermal oxidative stability of other polymers and polyolefins.

[0116] PP-HP copolymer synthesized via solution method and monomer and Figure 2 The thermal oxidative stability data provided herein will be used as a benchmark for evaluating the thermal oxidative stability of functional polyolefins prepared according to the methods of this disclosure.

[0117] Preparation of functionalized polyolefins via reactive blending

[0118] The following examples were carried out via reactive compounding (e.g., reactive extrusion) using a Coperion 26 mm co-rotating twin-screw extruder equipped with a mixing screw and a 44 L / D ratio. Note: Unless otherwise specified, such as in molar percentages, all compositions referenced below in reactive compounding are by weight percentage. Furthermore, unless otherwise specified, all temperatures referenced below for reactive extrusion relate to the temperature of the extruder. During normal processing, the temperature of the components in the extruder is typically 10-20°C higher than that of the extruder itself due to shear.

[0119] Example 2: Preparation of functional PP polymers via PP-MA and multi-segment polymer structure (A) using EVOH copolymer coupling agent.

[0120] As explained above regarding Scheme 4, a reactive blending method is used to prepare a multifunctional PP structure (A) having HP, OH, and MA functional groups distributed in various polymer segments. This method involves a condensation reaction between PP-MA and a poly(ethylene-co-vinyl alcohol) (EVOH) copolymer, followed by reaction of the intermediate with a hindered phenolic (HP) antioxidant reagent including an ester or COOH moiety. The resulting product is a multi-segment PP structure comprising three desired polar functional groups (HP, MA, and OH groups), wherein the HP and OH groups are present in the central polymer segment, and optionally, unreacted MA units are located within the PP chain. The detailed reaction steps are described below: 1. Grafting reaction between PP-MA and EVOH coupling agent to form PP-(OH)(MA) intermediate. A PP-MA polymer with approximately 0.8 mol% MA content is covalently bonded to an EVOH polymer (which has an approximately 45 / 55 ethylene / vinyl alcohol molar ratio) via reactive compounding. In most compounding methods, we also introduce commercial PP homopolymers to obtain blended compositions and reduce costs. During the reactive compounding process, the PP homopolymer acts as a diluent and does not substantially (if any) participate in the chemical reaction between the PP-MA and EVOH grafting reaction. In typical operation, the following materials are initially dry-blended: PP (75-90%), PP-MA (up to about 10%, and in some experiments about 1-2%), EVOH (up to 15%, and in some experiments about 2-6%), and PP-HP (as a stabilizer, preferably 5-10%, from Example 1). The materials are dry-blended in a standard pellet mixer. The resulting pellet blend is then reactively compounded at 220-240°C using a co-rotating twin-screw extruder to form a PP-(OH)(MA) intermediate. It should be noted that the above method uses the PP-HP polymer prepared in Example 1 as a stabilizer. In the absence of PP-HP, degradation was observed when attempting to react the PP-MA and EVOH polymers via co-extrusion. Under reactive blending conditions with the PP-HP stabilizer, most of the MA portion in the PP-MA chain can react with the OH groups in the EVOH chain via esterification to form a graft copolymer (multi-segment) structure with PP chains (side segments) bonded to the EVOH chain (central segment). As expected, some unreacted MA units (or unreacted COOH groups formed during the reaction of MA with OH) and excess OH groups remain in the resulting PP-(OH)(MA) polymer structure. Typically, the polymer intermediate (which also includes PP homopolymers in these examples) comprises 2.5-7.5 mol% OH groups that can be used to chemically bind HP antioxidant groups.

[0121] 2. The reaction between PP-(OH)(MA) and HP reagent to form PP-(HP)(OH)(MA) multifunctional polymer.

[0122] In a co-rotating twin-screw extruder at 200-240℃, the intermediate PP-(OH)(MA) (including nonfunctional PP) prepared in step 1 above is reacted with Irganox containing 4 HP groups. ® 1010 is further mixed, wherein the weight ratio is 80-90% PP-(OH)(MA) polymer and 10-20% Irganox 1010. Irganox 1010 then undergoes... ® An ester exchange reaction occurs between the ester group in the 1010 molecule and the OH group in the PP-(OH)(MA) polymer to incorporate the HP group into the polymer structure. The final PP-(HP)(OH)(MA) polymer comprises approximately 1-2.5 mol% HP groups and some unreacted OH and MA groups, having a segmental polymer structure as shown in structure (A) of Scheme 4 above.

[0123] It should be noted that the final blended product of this embodiment is a polymer blend having approximately 65-90% PP and approximately 10-35% PP-(HP)(OH)(MA) functional polymers. Multifunctional PP-(HP)(OH)(MA) polymers can be used with various polyolefins and act as polymerization antioxidants, adhesion promoters, compatibilizers, etc., in many applications.

[0124] Example 3: Evaluation of the thermal oxidative stability of PP-(HP)(OH)(MA) polymer

[0125] Following the procedure of Example 2, we prepared a series of blends comprising reactively mixed functional polyolefins PP-(HP)(OH)(MA) and nonfunctional PP polymers, with an overall HP concentration ranging from 0.15 to 1.20 mol.

[0126] Figure 3 TGA curves are plotted to compare the dry blend PP / HP sample with a 0.2 mol% HP content with four reactive blends of PP-(HP)(OH)(MA) polyolefins prepared by blending different amounts of HP with (75-90%) PP polymers. Figure 3 All samples were subjected to TGA in air at a heating rate of 10 °C / min. Samples were obtained from films with a thickness of approximately 70 µm to approximately 80 µm prepared from particles by hot pressing; the TGA apparatus was a TA Instruments Model Q50. Figure 3 The initial degradation temperature (T) of the sample plotted in the figure d The information is provided in Table 3 below.

[0127] Table 3. Initial degradation temperatures of various samples determined by TGA analysis in air at a heating rate of 10 °C / min.

[0128]

[0129] from Figure 3 It can be seen that the PP / HP dry blend sample (reference sample) with 0.2 mol% HP antioxidant content, at a T temperature of approximately 260℃, showed better performance. d Then a rapid loss of weight began. Also from Figure 3 As can be seen, the four samples prepared by reactive blending, including non-functional PP polymers blended with PP-(HP)(OH)(MA) polyolefin, showed excellent improvement in thermal oxidative stability. The four samples, with total HP content of 0.15, 0.30, 0.60, and 1.20 mol%, respectively, showed Ts values ​​of 0.15, 0.30, 0.60, and 1.20 mol% for the non-functional PP polymers blended with PP-(HP)(OH)(MA) polyolefin, and exhibited Ts values ​​of 390℃, 305℃, 315℃, and 335℃, respectively. d All four samples, including those with covalently bonded HP, exhibited significantly improved thermal stability, with the initial decomposition temperature being positively correlated with the total HP content of the samples. Furthermore, the thermal oxidative stability of the reactive mixtures was not adversely affected by the presence of OH and MA groups bound to the polyolefins.

[0130] To further demonstrate that HP can be covalently bonded to polyolefins through reactive blending, we compared the thermal properties of the reactive blended PP-(HP)(OH)(MA) polyolefin prepared according to Example 2 with those of PP-HP prepared according to the monomer synthesis route (e.g., Example 1). In this regard, Figure 4 The T values ​​of various samples prepared by monomer synthesis in Example 1 and by reactive mixing in Example 2 were compared. d temperature. Figure 4 Data marked with "X" represent the initial degradation temperature (XTd1) of samples prepared via monomer synthesis, while data marked with "O" represent the initial degradation temperature (OTd2) of samples prepared via reactive extrusion. The figure also shows the degradation temperature of the starting material (i.e., the point with 0 mol% HP). Table 4 below lists... Figure 4 The initial degradation data of some samples and the initial degradation temperature of the dry blend PP / HP mixture were compared.

[0131] Table 4: Initial degradation temperatures of various samples determined by TGA analysis in air at a heating rate of 10 °C / min.

[0132] † Commercial grade PP (Borclean), which is PP dry-blended with Irganox® 1010 antioxidant (HP) and other stabilizers.

[0133] †† In the table above, (reactive blends) refers to the reactive blends of PP-(HP)(OH)(MA) polymers prepared according to Example 2.

[0134] ††† (monomer synthesis) refers to PP-HP prepared according to Example 1.

[0135] like Figure 4 As shown in Table 4 above, the data indicates that regardless of whether the sample was prepared via monomer synthesis (Example 1) or reactive mixing (Example 2), the initial degradation temperature depended on the molar content of HP. A higher molar HP content resulted in a higher initial degradation temperature and slower weight loss. Figure 4 The data in Table 4 show that reactive compounding methods enable HP to covalently bond to polyolefins, such as polypropylene.

[0136] Figure 4 The data in Table 4 also show that polyolefins with covalently bonded HP, such as PP-(HP)(OH)(MA) polyolefin, are effective polymer antioxidants. As explained above in Example 2, PP-(HP)(OH)(MA) polyolefin was prepared as a blend with nonfunctional polypropylene. Furthermore, from... Figure 4 As can be seen from the data in Table 4, the reactively blended PP-(HP)(OH)(MA) polyolefin can be used as an antioxidant for polypropylene itself. The data further show that the PP-HP samples prepared by Example 1 or 2, with lower HP content, exhibited superior initial degradation temperatures compared to dry blends of PP mixed with hindered phenolic antioxidants (HP).

[0137] Examples show that PP-(HP) polyolefins have additional advantages over commercial antioxidants because they can co-crystallize with PP, thus producing a more homogeneous PP and PP-(HP) blend with a uniformly distributed HP antioxidant group throughout the PP material. The uniformly distributed HP group effectively protects PP from thermal oxidative degradation at high temperatures.

[0138] Example 4: Increasing the concentration of MA and / or OH in PP and PP-(HP)(OH)(MA) blends

[0139] Following the reaction sequence in Example 2, in many cases, the successive reactive blending reactions consume most of the MA groups in the PP-MA polymer and the OH groups in the EVOH polymer. To increase the MA and OH groups in the PP and PP-(HP)(OH)(MA) blends, the blend from Example 2.2 is mixed with PP-MA after an additional reactive blending procedure to increase the MA content, or with PP-(OH)(MA) (from Example 2.1) to increase the OH content, or with both PP-MA and PP-(OH)(MA) to increase both the MA and OH content. The reactive blending is carried out in the same co-rotating twin-screw extruder at approximately 210°C–230°C. Due to the co-crystallization ability between all these PP polymers (including functional PP polymers and PP homopolymers), the resulting reactive blends exhibit a uniform morphology, with all HP, OH, and MA functional groups evenly distributed throughout the PP material.

[0140] Example 5: Preparation of functional PP polymers via PP-MA and multi-segment polymer structure (B) using phenoxy resin coupling agents.

[0141] Following a similar procedure to that described for Example 2, we also prepared another class of functionalized PP polymers having the multi-segment polymer structure (B) shown in Scheme 5. Maleic anhydride-modified polypropylene (PP-MA) was also reacted with a phenoxy polymer as a coupling agent to prepare a multifunctional PP structure (B) having three desired functional groups (e.g., HP, OH, and MA). The reaction steps are described below: 1. Grafting reaction between PP-MA and phenoxy resin to form PP-OH(MA) intermediate. The PP-MA polymer was mixed with PP homopolymer and phenoxy resin. The mixture consisted of PP-MA polymer (10-20%, preferably 10-15%), phenoxy resin (5-15%, preferably 5-10%), PP-HP (as a stabilizer, from Example 1, 5-10%), and PP homopolymer (70-85% or the remainder of the blend composition). In the mixture, the MA concentration was 0.1-0.15 mol% and the OH concentration was 1-3 mol%. The mixture was prepared by dry mixing in a standard particle mixer. The resulting particle blend was then reactively compounded at 220-240°C using a co-rotating twin-screw extruder to form a PP-(OH)(MA) intermediate. Similar to Examples 2-1, the preferred method described above used PP-HP as an antioxidant to prevent thermal oxidative degradation of the polyolefins (PP, PP-MA). Under the reactive mixing conditions in this embodiment, most of the MA portion in the PP-MA chain reacts with the OH groups in the phenoxy chain via esterification to form a graft copolymer structure with PP chains (side segments) bonded to the phenoxy chain (central segment). As expected, the resulting PP-OH(MA) graft polymer structure contains some unreacted MA (or COOH residue) groups and excess OH groups.

[0142] 2. The reaction between PP-OH(MA) and HP reagent to form the PP-HP(OH)(MA) structure (B)

[0143] Following a similar procedure to that in Examples 2-2, the obtained PP-OH(MA) intermediate (containing PP homopolymer) was further mixed with Irganox® 1010 containing four HP groups at a ratio of approximately 80-90% PP-OH(MA) to approximately 10-20% Irganox® 1010. The transesterification reaction between the ester groups in the Irganox 1010 molecule and the OH groups in the PP-(OH)(MA) was carried out in a co-rotating twin-screw extruder at 220-260°C. The final PP-(HP)(OH)(MA) polymer structure (B) contains HP antioxidant groups (approximately 1-2.5 mol%) and some unreacted OH and MA groups. It should be noted that the final blended product is a polymer blend containing 70-85% PP homopolymer and 15-30% PP-(HP)(OH)(MA) functional polymer, which can act as a polymer antioxidant, adhesion promoter, compatibilizer, etc.

[0144] Comparative example: Reactive mixing of PP-MA and EVOH in the absence of PP-HP

[0145] For this comparative example, PP-HP was not used in the mixture of PP-MA and EVOH polymers. The following materials were first dry-mixed in a standard pellet mixer: PP, PP-MA, and EVOH. The resulting pellet blend was then compounded at 220–240°C using a co-rotating twin-screw extruder. However, the materials degraded, forming low-molecular-weight products, and the viscosity decreased significantly, indicating a lack of polymeric material.

[0146] Example 6: Direct preparation of PP-HP polyolefin from PP-MA

[0147] 1. The reaction between PP-(MA) and HP reagent to form PP-HP(MA) via reactive extrusion.

[0148] Maleic anhydride-modified polypropylene (PP-MA) is reactively mixed with an HP reagent (e.g., Irganox 1010), using PP-HP as a stabilizer. This method can be carried out at approximately 200-260°C, preferably approximately 230-240°C, using a co-rotating twin-screw extruder.

[0149] The production rate of this method is slightly limited by the removal of byproducts from the reactive mixing process using the equipment employed. Using a certain weight ratio of PPHP-MA polymer (80-90%), with Irganox 1010 (10-20%) supplied upstream or downstream, a standard ventilated mixer can produce PPHP with up to about 2.5 mol% HP.

[0150] 2. The reaction between PP-(MA) and HP reagent forms PP-HP(MA) via a solid-state reaction.

[0151] A blend of granular PP-MA and PP-HP (5-10%) as a stabilizer is mixed with mineral oil (MS) at a ratio of 1 part granules to 3 parts MS. The resulting mixture is then stirred and heated at approximately 130-135°C for about 30 minutes to form a suspension, which, upon cooling at room temperature, becomes a waxy mixture. This waxy mixture is then blended with acetone at a ratio of approximately 1:3 at room temperature and filtered to obtain a fine wet powder. The filtered wet powder is then mixed with an acetone solution saturated with Irganox 1010 at a molar ratio of 1 part MA to 2 to 8 parts HP, preferably 1:4. The wet mixture is then baked in an oven at 220°C for at least about 1 hour, preferably 2 hours. The resulting product is light brown granules, which can be pulverized for further processing.

[0152] 3. The reaction between PP-(MA) and HP reagent to form PP-HP(MA) via suspension.

[0153] In a high-temperature mineral oil concentrate, a blend of granular PP-MA and PP-HP (5-10%) as a stabilizer is mixed with Irganox 1010 at a molar ratio of about 1:0.5-2 (MA:HP), preferably 1:1. The suspension is then heated to about 170 to 235°C, preferably 180 to 185°C, and maintained for at least about 90 minutes, preferably 120 minutes. After cooling to room temperature, a waxy mixture is formed, which is then blended with hexane at a weight ratio of 1:3. The hexane suspension is then filtered at room temperature and dried in an oven at 150°C to remove MS / hexane. The resulting PP(MA)-HP product is a light brown powder with a high HP mol% content.

[0154] Example 7: Preparation of functional PP polymers via PP-MA and polyfunctional amine compound coupling agents

[0155] 1. The reaction between PP-(MA) and diamine forms PP-(MA)(NH2) via a solid-state suspension reaction.

[0156] A mixture of granular PP-MA and PP-HP (5-10%) as a stabilizer is mixed with a reaction medium (e.g., mineral oil) at a molar ratio of MA:aromatic / aliphatic diamine of about 1:0.5-2, for example, 1:1, to form a suspension. Diaminodiphenyl sulfone is used as a coupling agent in some methods. The suspension is then heated to about 120-145°C, for example, about 130 to 135°C, and maintained for at least about 20 minutes, for example, at least 30 minutes. Irganox 1010 is then added after heating at a molar ratio of about 1:2-4, for example, about 1:4, to the aromatic / aliphatic diamine. The suspension is then heated to about 170 to 235°C, for example, about 180 to 185°C, and maintained for at least about 60 minutes, for example, about 90 minutes. After cooling to room temperature, a waxy mixture is formed, which is then blended with hexane at a weight ratio of about 1:3. The hexane suspension was then filtered at room temperature and heated in an oven to at least about 200°C, for example, about 220°C, to remove MS / hexane. The resulting product was light brown granules, which could be pulverized for use in further processes.

[0157] Based on our experiments, we found that the thermal oxidative stability of functionalized polyolefins and their blends with hindered phenolic groups covalently bonded to them is directly related to the concentration of HP. Furthermore, the thermal oxidative stability appears to be unaffected by reactive functional groups, including those covalently bonded to the polyolefin. Additionally, the thermal stability does not appear to depend on the method of preparing PO-HP or whether HP is bonded to the polyolefin via a coupling agent or directly. Figure 5 The data in Table 5 below illustrate our findings.

[0158] Table 5. Effect of HP composition on degradation temperature (Td) Td was determined by TGA in air at a heating rate of 10 °C / min.

[0159] a. Except for reference sample T1, mol% is the overall calculated HP composition from different reaction steps.

[0160] b. Sample T1 is a commercial PP dry-blended with Irganox® 1010 antioxidant (HP).

[0161] c. P0 involves processing via solution-based polymerization of the monomer as described in Example 1; P1 involves processing via reactive extrusion; P2 involves processing via solid-state reaction (baking) as described in Example 6.2; and P3 involves processing via solid-state reaction (suspension) as described in Example 7.

[0162] Figure 5 To compare the T values ​​of the following samples d Temperature graph: Various PP(HP) samples prepared by monomer synthesis in Example 1 (labeled X), samples prepared by coupling agents with hydroxyl groups (labeled O), samples prepared by coupling agents with amino groups (■), or PP(HP) prepared by directly binding HP to PP(MA). The figure also shows the degradation temperature of the starting material (i.e., the point with 0 mol% HP). Table 5 above lists the degradation temperatures of the starting material. Figure 5 The initial degradation temperature data of certain samples and the initial degradation temperature of dry-blended PP / HP mixtures were compared. The data further show that PP(HP) prepared according to aspects of this disclosure can be an effective thermal oxidative stabilizer for polyolefins having reactive functional groups also covalently bonded to the polyolefin.

[0163] like Figure 5 As shown in Table 5 above, the data indicate that regardless of whether the sample was prepared via monomer synthesis (Example 1) or via reactive blending or solid-state methods, the initial degradation temperature depends on the molar content of HP. The data further confirm that the reactive blending methods and solid-state reactions described herein enable HP to covalently bind to polyolefins, such as polypropylene.

[0164] Example 8: Long-term thermal stability of PP-HP relative to a mixture of PP and HP.

[0165] PP-HP with 0.3 mol% HP was prepared by reactive extrusion, assuming all HP reagents are covalently bound to PP. PP samples mixed with HP were prepared to also have 0.3 mol% HP in the mixture. The HP used in the samples was Irganox 1010 powder manufactured by BASF. Table 6 below shows the initial degradation temperatures of the samples as prepared (before heating) and after heating the samples at 150 °C for 80 hours (in air).

[0166] Table 6. Comparison of thermal stability of PP(HP)(MA) and PP(MA) + HP (powder)

[0167] 1. PP-HP is prepared by reactive mixing and mol% HP is assumed to be covalently bonded to PP.

[0168] 2. PP + HP is prepared by dry blending of PP and HP powders.

[0169] 3. The HP used for the samples was Irganox 1010 powder manufactured by BASF.

[0170] As shown in Table 6, compared with mixtures of hindered phenols, polyolefins with covalently bound hindered phenols maintain their thermal stability over a long period of time.

[0171] This disclosure shows and describes only preferred embodiments of the invention and examples of its versatility. It should be understood that the invention can be used in various other combinations and environments and can be changed or modified within the scope of the inventive concept expressed herein. Therefore, by way of example, those skilled in the art will recognize or be able to determine many equivalents of the specific substances, procedures, and settings described herein using only conventional experiments. Such equivalents are considered to be within the scope of the invention and are covered by the following claims.

Claims

1. A method for preparing functional polyolefins, the method comprising: The following components are reacted together under heating: (a) Polyolefins having multiple reactive groups; (b) A hindered phenolic reagent that can react with the reactive groups of the polyolefin; To produce a functional polyolefin having hindered phenolic groups covalently bonded thereto, wherein the polyolefin having hindered phenolic groups is added to the components before or during the reaction of the components together under heating, wherein the temperature at which the components are reacted together under heating is at least about 200°C.

2. The method of claim 1, further comprising preparing a polyolefin having multiple reactive groups by reacting a maleic anhydride-modified polyolefin with a coupling agent having multiple reactive groups, said coupling agent being capable of reacting with the maleic anhydride-modified polyolefin to form a polyolefin having multiple reactive groups.

3. The method of claim 2, wherein the coupling agent comprises a polymer having at least a plurality of hydroxyl, phenoxy, epoxy, or amino groups, and wherein the hindered phenolic group is covalently bonded to the polymer.

4. The method of claim 1, wherein the polyolefin having a plurality of reactive groups comprises a polyolefin having a plurality of maleic anhydride groups, and the method further comprises forming a reactive residue by at least one maleic anhydride with at least one reactive group on a coupling agent having a plurality of reactive groups, and reacting the hindered phenolic reagent with another reactive group on the coupling agent.

5. The method of claim 1, wherein the hindered phenolic group is covalently bonded to the polyolefin by a reaction residue formed by maleic anhydride residues and hindered phenolic reagents on the polyolefin.

6. The method of any one of claims 1 to 5, further comprising adding a nonfunctional polyolefin to the components before or during the reaction of the components together under heating.

7. The method of any one of claims 1 to 5, further comprising heating the functional polyolefin to crosslink the functional polyolefin.

8. The method of any one of claims 1 to 5, wherein heating the components comprises reactively mixing the components by means of an extruder.

9. The method of any one of claims 1 to 5, wherein the method further comprises mixing the components together with a solvent to form a slurry of wetted polyolefin particles, and heating the slurry.

10. The method of any one of claims 1 to 5, wherein the method further comprises mixing the component with a solvent to form a suspension of polyolefin particles in the solvent, and heating the suspension.

11. The method of any one of claims 1 to 5, wherein the temperature at which the components react together under heating is at least about 200°C and less than about 280°C.

12. The method according to any one of claims 1 to 11, wherein the hindered phenol reagent has the following formula: Where Q represents -OOC-; R3 represents a linking group; R4 represents H or a substituted or unsubstituted alkyl group; and when R4 represents a substituted or unsubstituted alkyl group, z is an integer from 1 to 4.

13. The method according to any one of claims 1 to 11, wherein the hindered phenol reagent has the following formula: 。

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