A method for preparing a reversibly crosslinked poe ionomer

Abstract

The application discloses a preparation method of a reversible crosslinking POE ionomer, and comprises the following process: POE, a multi-vinyl ionic compound, a grafting aid and an initiator are blended to obtain a mixture; the mixture is subjected to a melt grafting reaction through a double-screw extruder, and POE ionomer is obtained after extrusion and granulation. The POE ionomer provided by the application has improved mechanical strength and elongation at break, and still has a very high performance retention rate and excellent reprocessing characteristics after secondary processing.

Description

Technical Field

[0001] This invention belongs to the field of high-performance self-healing materials technology, and particularly relates to a method for preparing reversible cross-linked POE ionomers. Background Technology

[0002] POE is a semi-crystalline polymer material obtained by copolymerizing ethylene and α-olefins. The polyethylene segments are easily crystallized and act as physical crosslinking points in the system, giving the material good mechanical strength. The random copolymer segments of ethylene and α-olefins, acting as amorphous regions, provide good flexibility. This unique structure allows POE materials to possess not only the plasticity of plastics but also the high elasticity and toughness of rubber. Therefore, POE elastomers have wide applications in the automotive, hot melt adhesive, footwear, synthetic leather, and photovoltaic films industries.

[0003] Mainstream modified POE products, such as vulcanized rubber and thermosetting resins, achieve excellent mechanical strength and thermal stability through permanent chemical cross-linking networks. However, the irreversible cross-linking structure makes them impossible to melt and reprocess, ultimately turning them into non-recyclable waste.

[0004] Among numerous solutions for improving the mechanical and thermal properties of materials, introducing dynamic chemical bonds for modification is an effective strategy. Dynamic chemical bonds can exist as physical cross-linking points within the material system, significantly enhancing the material's mechanical properties and stability at room temperature. Furthermore, under external stimuli, dynamic chemical bonds can undergo reversible dissociation-recombination processes, preserving the material's plasticity.

[0005] For example, Chinese invention patent CN113896998B uses a ternary copolymer of ethylene, α-olefin, and polyene monomers. Then, using efficient mercapto-olefin click chemistry, the vinyl groups in the ternary copolymer are modified into crosslinkable groups. Finally, melt reactive extrusion is employed to synthesize dynamically crosslinked POE elastomers, improving the material's mechanical properties, solvent resistance, and heat resistance without affecting its reprocessing performance. However, this method involves functional group modification of polyolefin elastomers, making it difficult to integrate with commonly used processing methods. Its adaptability to general-purpose POEs is low, and chemically reversible crosslinking requires specific chemical conditions (such as pH changes and the presence of reducing agents) to break the crosslinking bonds, resulting in a narrower processing window. Furthermore, incomplete covalent bond breaking during repeated use may lead to performance degradation.

[0006] For example, Chinese invention patent CN120248482A prepares reversibly cross-linked polyolefin elastomers by forming a cross-linked network using three types of non-covalent bonds: hydrogen bonds, ionic bonds, and coordination bonds. This method produces materials with superior physical and mechanical properties while also ensuring recyclability and self-healing capabilities. Although this method introduces non-covalent cross-linking, a large number of ionic compounds exist in the system in a free state, easily precipitating out. This results in poor solvent resistance and susceptibility to aging of the polyolefin elastomer, affecting material performance, and the performance degradation is even more severe at high temperatures.

[0007] Therefore, the solution of introducing physically reversible crosslinking bonds to optimize the properties of polyolefin materials still needs to be explored continuously. Summary of the Invention

[0008] To address the above technical problems, this invention proposes a method for preparing reversibly crosslinked POE ionomers.

[0009] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0010] A method for preparing a reversible crosslinked POE ionomer includes the following steps: blending POE, a polyvinyl ion compound, a grafting agent, and an initiator to obtain a mixture; subjecting the mixture to a melt grafting reaction via a twin-screw extruder; and extruding and granulating the mixture to obtain the POE ionomer.

[0011] As a preferred embodiment of the present invention, the polyvinyl ionic compound is a substance having at least one of the following characteristics a, b, and c:

[0012] a. It has at least one cationic group containing a vinyl group and at least one anionic group containing a vinyl group;

[0013] b. It has a multifunctional cationic group and multiple anionic groups containing at least one vinyl group;

[0014] c. It has a multifunctional anionic group and multiple cationic groups containing at least one vinyl group;

[0015] The cationic group is selected from functionalized cationic centers containing at least one of ammonium group and phosphonium group, preferably functionalized cationic centers containing ammonium group. Here, ammonium group refers to NH4+ in a narrow sense, but in this invention, it can also be NH+ with up to 3 H atoms substituted.

[0016] The anionic group is derived from C3-C10 carboxylic acids or anhydrides through an acid-base neutralization reaction.

[0017] As a non-limiting embodiment of the present invention, the polyvinyl ionic compound having feature a above can be prepared by reacting a carboxylic acid or anhydride containing at least one vinyl functional group (e.g., acrylic acid, methacrylic acid, butenoic acid, pentenoic acid, hexenoic acid, heptenic acid, octenic acid, nonenoic acid, decenoic acid, undecenoic acid, itaconic acid, maleic anhydride, maleic acid, etc.) with a base containing at least one vinyl functional group (e.g., dimethylaminoethyl acrylate, dimethylaminoethyl methacrylate, diethylaminoethyl acrylate, diethylaminoethyl methacrylate, etc.) through an acid-base neutralization reaction.

[0018] As a non-limiting embodiment of the present invention, the polyvinyl ionic compound having feature b described above can be prepared by reacting a carboxylic acid or anhydride containing at least one vinyl functional group (e.g., acrylic acid, methacrylic acid, butenoic acid, pentenoic acid, hexenoic acid, heptenic acid, octenic acid, nonenoic acid, decenoic acid, undecenoic acid, itaconic acid, maleic anhydride, maleic acid, etc.) with a polybasic base (e.g., tetramethylmethyldiamine, tetramethylethylenediamine, tetramethylpropylenediamine, tetramethylbutyldiamine, tetramethylhexanediamine, etc.) at a molar ratio of approximately 2:1 via acid-base neutralization reaction. The polybasic base refers to an organic base with ≥2 basic groups.

[0019] As a non-limiting embodiment of the present invention, the polyvinyl ionic compound having the above-described feature c can be prepared by an acid-base neutralization reaction of an organic acid anhydride or a polycarboxylic acid (e.g., oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, octanoic acid, azelaic acid, sebacic acid, undecanoic acid, dodecanoic acid, succinic anhydride, glutaric anhydride, adipic anhydride, itaconic acid, maleic anhydride, maleic acid, etc.) with an amine containing at least one vinyl functional group (e.g., dimethylaminoethyl acrylate, dimethylaminoethyl methacrylate, diethylaminoethyl acrylate, dimethylaminoethyl methacrylate, etc.) at a molar ratio of approximately 1:2.

[0020] As a preferred embodiment of the present invention, the amount of the polyvinyl ionic compound is 2-15% of the mass of POE, preferably 3-10%.

[0021] As a preferred embodiment of the present invention, the grafting aid is one or more of methyl methacrylate, acrylic acid, styrene, α-methylstyrene, epoxy resin, maleic anhydride, glycidyl methacrylate, and methacrylic acid.

[0022] Preferably, the amount of grafting adjuvant is 0.1-5% of the POE mass, more preferably 0.3-3%.

[0023] As a preferred embodiment of the present invention, the initiator is a peroxide-based free radical initiator, preferably one or more of the following: dicumyl peroxide, bis(tert-butyl)-cumyl peroxide, benzoyl peroxide, tert-butyl peroxide, tert-butyl percarbonate-2-ethylhexyl peroxycarbonate, di(3,3,5-trimethylacetyl) peroxide, and 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane;

[0024] Preferably, the amount of the initiator is 0.1-5% of the mass of POE, more preferably 0.1-1%.

[0025] In the preparation method of the present invention, one or more other additives may optionally be included. Non-limiting examples of suitable additives include catalysts, foaming agents, plasticizers, thickeners, colorants, pigments and fillers, antioxidants, antistatic agents, anti-sticking agents, nucleating agents, light stabilizers, dispersants, defoamers, and any combination thereof. When additives are used, the total mass fraction of the additives can conventionally be adjusted to 0-50% of the total mass of POE, polyvinyl ionic compounds, grafting aids, and initiators.

[0026] As a preferred embodiment of the present invention, the extrusion temperature of the twin-screw extruder is 170-210℃ and the screw speed is 100-300r / min.

[0027] In a preferred embodiment of the present invention, the POE is a copolymer of ethylene and C3-C10 α-olefin with a density of 0.85-0.92 g / cm³. 3 The melt index is 0.1-20 g / 10 min under test conditions of 190°C and 2.16 kg. Non-limiting examples of POE include ENGAGE™ POE elastomers (Dow Chemical), EXACT™ plastomers (ExxonMobil Chemical), TAFMER™ α-olefin copolymers (Mitsui Chemicals), SOLUMER™ POE elastomers (SK Chemicals), LUCENETM POE plastomers (LG Chem), and WANSUPER® POE elastomers (Wanhua Chemical).

[0028] The beneficial effects of this invention are as follows:

[0029] The POE ionomer provided by this invention uses ionic bonds as physical crosslinking points, undergoing a reversible dissociation-reorganization process at or above the topological freezing temperature Tv. This dissociation-reorganization process is dynamic; when the processing temperature of the POE ionomer exceeds the topological freezing temperature Tv, the ionic bonds dissociate. After exceeding the melting temperature Tm, the polymer chain segments move, forming a flowing molten state again, facilitating processing. When the POE ionomer cools below the topological freezing temperature Tv, the ionic bonds recombine, existing again as physical crosslinking points, forming a crosslinked POE ionomer. The POE ionomer uses polyvinyl ionic compounds to graft small molecule additives onto the POE main chain, which can advantageously reduce the amount of small molecule additives precipitated, ensuring the application performance of the product.

[0030] Verification has shown that the POE ionomer provided by this invention has improved mechanical properties such as tensile strength, and still retains a very high performance retention rate after secondary processing, exhibiting excellent reprocessing characteristics. Detailed Implementation

[0031] The present invention will be further illustrated below with specific embodiments. These embodiments are merely illustrative and do not limit the scope of the invention.

[0032] Unless otherwise specified, the raw materials and reagents used in the following embodiments of the present invention can be purchased commercially.

[0033] WANSUPER®5057: Density 0.870 g / cm³ 3 Melt index 5 g / 10min, Wanhua Chemical

[0034] WANSUPER® 65016: Density 0.866 g / cm³ 3 Melt index 1 g / 10min, Wanhua Chemical

[0035] St: Styrene, Beijing Innocare Technology Co., Ltd.

[0036] AMS: α-Methylstyrene, Beijing Innocare Technology Co., Ltd.

[0037] MMA: Methyl methacrylate, Beijing Innocare Technology Co., Ltd.

[0038] DCP: Dicumyl peroxide, Lanzhou Additives Factory

[0039] BIPB: Di-tert-butyl peroxide, Lanzhou Additives Factory

[0040] Bis25: 2,5-Dimethyl-2,5-di(tert-butylperoxy)hexane, Lanzhou Additives Factory.

[0041] The performance testing methods involved in the following embodiments of the present invention are as follows:

[0042] (1) Melt index determination

[0043] The melt flow index of the material was tested according to ASTM-D1238 at 190℃ and a load of 2.16 kg. The test time interval was 30 s. The test sample was granular. The sample was measured in parallel 5 times and the average value was taken.

[0044] (2) Melting point (Tm)

[0045] The melting point (Tm) of the polymerization product was characterized using a Mettle DSC1 instrument. Approximately 5 mg of sample was weighed into an aluminum sample dish and sealed. The prepared sample was placed into the sample cell using tweezers, the furnace lid was closed, and the thermal history was removed. The sample was heated to 160 °C at a rate of 10 °C / min using the control software. The thermal curve of the sample was acquired, and the enthalpy change and melting point (Tm) during this process were recorded.

[0046] (3) Topological freezing temperature (Tv)

[0047] Stress relaxation experiments were conducted using a TA Instruments RSA-G2 solids analyzer to determine the topological freezing temperature of the material. In the stress relaxation experiment, a 2% strain was applied to the material, and the relaxation modulus (G(t)) was tracked over time at an isothermal temperature to calculate the characteristic relaxation time τ. This process was repeated at 40, 50, 60, 70, 80, 90, 100, 110, 120, 130, and 140 °C. The relationship between ln(τ) and 1 / T was plotted according to the Arrhenius equation; the temperature corresponding to the inflection point of the curve is the topological freezing temperature (Tv).

[0048] (4) Tensile strength and elongation at break test

[0049] Mechanical properties were tested using an Instron 5967 universal testing machine according to ASTM-D638 standard. This machine was equipped with a 15kN electronic pressure sensor and mechanical clamps. The test temperature was 25°C, and the tensile speed was 500 mm / min.

[0050] (5) High temperature aging test

[0051] The samples were aged in air at 85°C for 672 hours, and the tensile strength and elongation at break of the samples before and after aging were tested according to the standard ASTM-D638, and the retention rate was calculated.

[0052] Preparation Example

[0053] 1 mol of dimethylaminoethyl acrylate was placed in a 1000 ml three-necked flask, and 0.002 mol of p-hydroxyanisole was added as a polymerization inhibitor. The mixture was slowly stirred in a 40 °C water bath. 1 mol of acrylic acid was slowly added dropwise to the three-necked flask, and the temperature of the system was controlled not to exceed 45 °C during the addition process. After the addition was completed, the mixture was allowed to stand for 24 h to obtain a polyvinyl ionic compound, denoted as AA-DMAEA (expression as follows).

[0054]

[0055] 1 mol of 10-undecenoic acid was placed in a 1000 ml three-necked flask, and 0.002 mol of p-hydroxyanisole was added. The mixture was stirred slowly in a 40 °C water bath. 1 mol of dimethylaminoethyl methacrylate was slowly added dropwise to the three-necked flask, and the temperature of the system was controlled not to exceed 45 °C during the addition process. After the addition was completed, the mixture was allowed to stand for 24 h to prepare a polyvinyl ionic compound, denoted as UA-DMAEMA (expression as follows).

[0056]

[0057] 1 mol of tetramethylethylenediamine was placed in a 1000 ml three-necked flask, and 0.002 mol of p-hydroxyanisole was added. The mixture was stirred slowly in a 40 °C water bath. 2 mol of acrylic acid was slowly added dropwise to the three-necked flask, and the temperature of the system was controlled not to exceed 45 °C during the addition process. After the addition was completed, the mixture was allowed to stand for 24 h to prepare a polyvinyl ionic compound, denoted as AA-TEMED (expression as follows).

[0058]

[0059] 2 mol of 10-undecenoic acid was placed in a 1000 ml three-necked flask, and 0.002 mol of p-hydroxyanisole was added. The mixture was stirred slowly in a 40 °C water bath. 1 mol of tetramethylhexanediamine was slowly added dropwise to the three-necked flask, and the temperature of the system was controlled not to exceed 45 °C during the addition process. After the addition was completed, the mixture was allowed to stand for 24 h to prepare a polyvinyl ion compound, denoted as UA-TMHD (expression as follows).

[0060]

[0061] 1 mol of succinic acid was placed in a 1000 ml three-necked flask, and 0.002 mol of p-hydroxyanisole was added. The mixture was stirred slowly in a 40 °C water bath. 2 mol of dimethylaminoethyl acrylate was slowly added dropwise to the three-necked flask. During the addition process, the system temperature was controlled not to exceed 45 °C. After the addition was completed, the mixture was allowed to stand for 24 h to obtain a polyvinyl ionic compound denoted as SA-DMAEA (expression as follows).

[0062]

[0063] Examples 1-6

[0064] Prepare the raw materials according to the formula in Table 1, blend them to obtain a mixture, and then pass the mixture through a twin-screw extruder for melt grafting reaction. After extrusion and granulation, POE ionomer is obtained. The maximum extrusion temperature of the twin-screw extruder is 190℃, and the screw speed is 250 r / min.

[0065] Table 1. Formulations (g) for Examples 1-6

[0066]

[0067] Comparative Example 1

[0068] Modified POE was prepared according to a formulation that was essentially the same as in Example 1, except that AA-DMAEA was not added.

[0069] Comparative Example 2

[0070] The modified POE was prepared according to a formulation that was essentially the same as that in Example 1, except that AA-DMAEA was replaced with an equal amount of tripropylene glycol diacrylate.

[0071] Comparative Example 3

[0072] 3000g of WANSUPER® 65016, 75g of itaconic acid, 75g of zinc hydroxide, 30g of styrene, and 15g of DCP were blended to obtain a mixture. This mixture was then subjected to a melt grafting reaction using a twin-screw extruder. After extrusion and granulation, modified POE was obtained. The maximum extrusion temperature of the twin-screw extruder was 190℃, and the screw speed was 250 r / min.

[0073] The basic performance tests in Table 2 were performed on the POE ionomers prepared in each example and comparative example.

[0074] Table 2. Basic Properties of POE Ionomers

[0075]

[0076] <Reprocessability Test>

[0077] The POE ionomers prepared in each example and comparative example were pulverized, and their initial viscosity, tensile strength, and elongation at break were tested. The samples were molded using a molding press (BD-8820-EL) at a molding temperature of 180℃ and a pressure of 10MPa for 5 minutes, followed by cooling at 15℃ to 20℃ for 2 minutes. The moldability of the samples was observed, and the reprocessed viscosity was tested. The ratio of the reprocessed viscosity to the initial viscosity was calculated and recorded as the viscosity ratio. Then, the tensile strength and elongation at break of the reprocessed material samples, as well as their tensile strength and elongation at break after high-temperature aging, were tested. The test results are shown in Table 3.

[0078] Table 3. Performance test results of reprocessed materials

[0079]

[0080] The test results above show that the POE ionomer provided by this invention still has a very high performance retention rate after secondary processing and has excellent reprocessing characteristics.

[0081] The above description is only a preferred embodiment of the present invention. It should be noted that those skilled in the art can make several improvements and additions without departing from the method of the present invention, and these improvements and additions should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a reversible crosslinked POE ionomer, characterized in that, The process includes the following steps: blending POE, polyvinyl ionomer, grafting agent, and initiator to obtain a mixture; subjecting the mixture to a melt grafting reaction via a twin-screw extruder; and extruding and granulating the mixture to obtain POE ionomer. The polyvinyl ionic compound is a substance having at least one of the following characteristics: a, b, c. a. It has at least one cationic group containing a vinyl group and at least one anionic group containing a vinyl group; b. It has a multifunctional cationic group and multiple anionic groups containing at least one vinyl group; c. It has a multifunctional anionic group and multiple cationic groups containing at least one vinyl group; The cationic group is selected from functionalized cationic centers containing at least one of ammonium group and phosphonium group; The anionic group is derived from C3-C10 carboxylic acids or anhydrides through an acid-base neutralization reaction.

2. The method for preparing the reversible crosslinked POE ionomer according to claim 1, characterized in that, The amount of the polyvinyl ion compound used is 2-15% of the POE mass.

3. The method for preparing the reversible crosslinked POE ionomer according to claim 2, characterized in that, The amount of the polyvinyl ionic compound used is 3-10% of the POE mass.

4. The method for preparing the reversible crosslinked POE ionomer according to claim 1, characterized in that, The grafting aid is one or more of methyl methacrylate, acrylic acid, styrene, α-methylstyrene, maleic anhydride, glycidyl methacrylate, and methacrylic acid; and / or, The amount of the grafting adjuvant is 0.1-5% of the POE mass.

5. The method for preparing the reversible crosslinked POE ionomer according to claim 4, characterized in that, The amount of grafting adjuvant used is 0.3-3% of the POE mass.

6. The method for preparing the reversible crosslinked POE ionomer according to any one of claims 1-5, characterized in that, The initiator is a peroxide-based free radical initiator.

7. The method for preparing the reversible crosslinked POE ionomer according to claim 6, characterized in that, The initiator is one or more of the following: dicumyl peroxide, bis-tert-butyl peroxide, benzoyl peroxide, tert-butyl peroxide, tert-butyl percarbonate-2-ethylhexyl ester, di(3,3,5-trimethylacetyl) peroxide, and 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane.

8. The method for preparing the reversible crosslinked POE ionomer according to any one of claims 1-5, characterized in that, The amount of the initiator is 0.1-5% of the POE mass.

9. The method for preparing the reversible crosslinked POE ionomer according to claim 8, characterized in that, The amount of the initiator is 0.1-1% of the POE mass.

10. The method for preparing the reversible crosslinked POE ionomer according to any one of claims 1-5, characterized in that, The extrusion temperature of the twin-screw extruder is 170-210℃, and the screw speed is 100-300 r / min.

11. The method for preparing the reversible crosslinked POE ionomer according to any one of claims 1-5, characterized in that, The POE is a copolymer of ethylene and C3-C10 α-olefin, with a density of 0.85-0.92 g / cm³. 3 The melt flow index is 0.1-20 g / 10 min.

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