Crosslinked polyethylene resin composition, crosslinked polyethylene resin and application thereof

Abstract

The invention relates to the field of polyethylene resin, and discloses a crosslinked polyethylene resin composition, crosslinked polyethylene resin and application thereof. The crosslinked polyethylene resin composition comprises polyethylene resin, a grafting component, a free radical initiator and a crosslinking component. The cross-linked polyethylene resin obtained by using the cross-linked polyethylene resin composition of the present invention has high strength, modulus and other properties, low gel content, and excellent thermoplasticity and processability, and does not cause performance degradation even after multiple processing.

Description

Technical Field

[0001] The invention relates to the field of polyethylene resins, and in particular to a cross-linked polyethylene resin composition, a cross-linked polyethylene resin and applications thereof. Background Art

[0002] Polyethylene is the most widely used polymer. Polyethylene can be divided into high-density polyethylene (HDPE), low-density polyethylene (LDPE) and linear low-density polyethylene (LLDPE) according to its chemical structure. Among them, HDPE and LDPE account for the largest demand. The molecular chains of HDPE and LDPE are linear structures or short-chain structures, and are widely used in the production of pipes, blow-molded products, injection products, sheets, films and other fields. However, HDPE and LDPE are prone to creep and are prone to significant deformation under long-term stress conditions, resulting in changes in the size of the product, which limits their application in high-end pipes, fibers, foams and other products. Cross-linking polyethylene can well inhibit its creep phenomenon, increase its heat deformation temperature and resistance to environmental stress cracking, and improve the long-term stability of the product. At present, the methods for preparing cross-linked polyethylene mainly include peroxide cross-linking, radiation cross-linking, silane water cross-linking, etc. The peroxide cross-linking method is to add a peroxide initiator to the molten polyethylene to generate macromolecular free radicals from polyethylene, and the macromolecular free radicals are coupled to form a covalent bond cross-linking structure. The radiation cross-linking method is to irradiate polyethylene with high-energy electron beams or γ-rays to generate macromolecular free radicals, which are then coupled to form cross-linked polyethylene. The silane water cross-linking method is to graft vinyl silane containing double bonds to the polyethylene side groups under the action of an initiator, and then hydrolyze and condense between the silanes to form a three-dimensional network cross-linked structure of Si-O-Si in the polyethylene molecules. The cross-linked polyethylene obtained by the above method contains stable cross-linked chemical bonds and is a thermosetting material, which is difficult to re-form and process and recycle.

[0003] In order to achieve the recycling of cross-linked polyethylene, the literature (Polymer Bulletin, 2021, 6, 114-121) reported a method of introducing a reversible cross-linking structure into polyethylene by using a thermoreversible Diels-Alder (DA) reaction. During the polymerization, an olefin monomer containing a furan substituent is added to copolymerize with ethylene to synthesize HDPE with furan-containing side groups. Then, a bismaleimide small molecule is added as a cross-linking agent to undergo a DA reaction with the furan on the side groups of the polyethylene to produce a cross-linked structure. The bond undergoes a reverse DA reaction (rD-A) at temperatures above 120°C and dissociates, and can be regenerated at temperatures below 90°C, thereby giving the cross-linking structure in the polyethylene thermoreversibility, allowing the material to be processed and reused. The document (Reactive & Functional Polymers, 2010, 70, 442-448) reports a method for designing DA reversible crosslinking of LDPE containing glycidyl methacrylate on the side groups. By synthesizing a small molecule containing carboxyl groups at both ends and furan / maleimide DA associates in the middle, the carboxyl groups react with the epoxy of the polyethylene side groups to introduce a reversible crosslinking structure into the polyethylene. The above method has made a useful attempt on the reversible crosslinking of polyethylene. However, for ordinary polyethylene that has not been modified, since its side groups do not contain any reactive groups, it cannot be directly prepared into reversibly crosslinked polyethylene. Therefore, it is necessary to develop a reversible crosslinking modification method for polyethylene so that it can easily obtain a thermally reversible crosslinking structure, which can not only improve the performance of polyethylene, but also avoid the problems of difficulty in recycling traditional irreversible crosslinking products. Summary of the invention

[0004] The object of the present invention is to provide a cross-linked polyethylene resin composition, a cross-linked polyethylene resin and applications thereof. The cross-linked polyethylene resin obtained using the cross-linked polyethylene resin composition of the present invention has high properties such as strength and modulus, low gel content (almost no gel content), thermoplasticity, and excellent processability, and will not cause performance degradation even after multiple processing.

[0005] In order to achieve the above object, the present invention provides a cross-linked polyethylene resin composition, wherein the composition comprises: a polyethylene resin, a grafting component, a free radical initiator and a cross-linking component.

[0006] Wherein, the graft component is as shown in the following formula (I):

[0007]

[0008] In formula (I), R 1 is an alkylene group having 1 to 8 carbon atoms or an ether group having 2 to 8 carbon atoms;

[0009] The cross-linking component is shown in the following formula (II):

[0010]

[0011] In formula (II), R 2 It is an aliphatic group having 1 to 10 carbon atoms or an aromatic group having 6 to 15 carbon atoms.

[0012] Preferably, relative to 100 parts by weight of the polyethylene resin, the amount of the graft component is 0.1-10 parts by weight, the amount of the free radical initiator is 0.01-1 part by weight, and the amount of the cross-linking component is 0.01-10 parts by weight.

[0013] Preferably, relative to 100 parts by weight of the polyethylene resin, the amount of the graft component is 1-5 parts by weight, the amount of the free radical initiator is 0.1-0.2 parts by weight, and the amount of the cross-linking component is 0.2-2 parts by weight.

[0014] Preferably, in formula (I), R 1 -(CH2) m -、-(CH2) m -O-(CH2) n -, m and n are integers from 1 to 8, and m+n≤8;

[0015] Preferably, R 1 It is methylene, ethylene or propylene.

[0016] Preferably, in formula (II), R 2 It is butylene, hexylene, octylene, -C6H4-, -C6H4-C6H4- or -C6H4-CH2-C6H4-.

[0017] Preferably, the melt index of the polyethylene resin is ≥1 g / 10 min (190° C., 2.16 Kg), preferably 10-100 g / 10 min (190° C., 2.16 Kg).

[0018] Preferably, the free radical initiator is one or more of a thermal decomposition free radical initiator, an organic peroxide and an azo initiator.

[0019] Preferably, the free radical initiator is one or more of alkyl peroxide, hydroperoxide, acyl peroxide and peroxycarbonate.

[0020] Preferably, the cross-linked polyethylene resin composition further comprises an electron donating antioxidant.

[0021] Preferably, the electron donating antioxidant is one or more of amide, sulfoxide and phosphite antioxidants.

[0022] Preferably, the electron donating antioxidant is one or more of dimethylacetamide, dimethyl sulfoxide and tris(nonylphenyl)phosphite.

[0023] Preferably, the amount of the electron donating antioxidant is 0.01-1 part by weight relative to 100 parts by weight of the polyethylene resin.

[0024] Preferably, the cross-linked polyethylene resin composition further comprises a free radical stabilizer.

[0025] Preferably, the free radical stabilizer is one or more of a hindered phenol antioxidant and an alkyl ester antioxidant.

[0026] Preferably, the amount of the free radical stabilizer is 0.05-1 part by weight relative to 100 parts by weight of the polyethylene resin.

[0027] According to a second aspect of the present invention, there is provided a cross-linked polyethylene resin obtained by melt extruding a cross-linked polyethylene resin composition, wherein the cross-linked polyethylene resin composition is the cross-linked polyethylene resin composition according to the first aspect of the present invention.

[0028] Preferably, the temperature of the melt extrusion is 170-230°C.

[0029] Preferably, the weight of the grafted component grafted into the polyethylene resin accounts for 0.01-5% by weight of the cross-linked polyethylene resin, preferably 0.2-2%.

[0030] According to a third aspect of the present invention, there is provided use of the cross-linked polyethylene resin composition according to the first aspect of the present invention or the cross-linked polyethylene resin according to the second aspect of the present invention in the preparation of polyethylene molded products.

[0031] According to the present invention, the cross-linked polyethylene resin is a cross-linked polymer formed by utilizing the thermal reversibility of the DA reaction. After melting, the cross-linked structure is released through a reverse DA reaction, and the material has thermoplasticity; after cooling, it can be cross-linked again to produce a network structure, thereby enhancing the polyethylene resin and giving the polyethylene resin repeatability and recyclability.

[0032] According to the present invention, the cross-linked polyethylene resin obtained using the cross-linked polyethylene resin composition of the present invention has high properties such as strength and modulus, low gel content (almost no gel content), thermoplasticity, and excellent processability, and will not cause performance degradation even after multiple processing. DETAILED DESCRIPTION

[0033] The endpoints and any values ​​of the ranges disclosed in this article are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this article.

[0034] According to one aspect of the present invention, a cross-linked polyethylene resin composition is provided, wherein the composition comprises: a polyethylene resin, a grafting component, a free radical initiator and a cross-linking component,

[0035] Wherein, the graft component is as shown in the following formula (I):

[0036]

[0037] In formula (I), R 1 is an alkylene group having 1 to 8 carbon atoms or an ether group having 2 to 8 carbon atoms;

[0038] The cross-linking component is shown in the following formula (II):

[0039]

[0040] In formula (II), R 2 It is an aliphatic group having 1 to 10 carbon atoms or an aromatic group having 6 to 15 carbon atoms.

[0041] According to the present invention, relative to 100 parts by weight of the polyethylene resin, the amount of the grafted component can be 0.1-10 parts by weight, the amount of the free radical initiator can be 0.01-1 part by weight, and the amount of the cross-linking component can be 0.01-10 parts by weight; preferably, relative to 100 parts by weight of the polyethylene resin, the amount of the grafted component is 1-5 parts by weight, the amount of the free radical initiator is 0.1-0.2 parts by weight, and the amount of the cross-linking component is 0.2-2 parts by weight.

[0042] By making the above-mentioned components within the above-mentioned range, the conversion rate of the grafted component grafted to the polyethylene resin can be further improved.

[0043] According to the present invention, in formula (I), R 1 is an alkylene group having 1 to 8 carbon atoms or an ether group having 2 to 8 carbon atoms; preferably, in formula (I), R 1 -(CH2) m -、-(CH2) m -O-(CH2) n -, m, n are integers from 1 to 8, and m+n≤8.

[0044] Examples of the alkylene group having 1 to 8 carbon atoms include methylene, ethylene, propylene, butylene, pentylene, hexylene, heptylene, and octylene. Among them, methylene, ethylene, or propylene is preferred.

[0045] Examples of the ether group having 2 to 8 carbon atoms include: -(CH2) m -O-(CH2) n -, m is 1 and n is 1, m is 1 and n is 2, m is 1 and n is 3, m is 1 and n is 4, m is 1 and n is 5, m is 1 and n is 6, m is 1 and n is 7, m is 2 and n is 2, m is 2 and n is 3, m is 2 and n is 4, m is 2 and n is 5, m is 3 and n is 3, m is 3 and n is 4, etc.

[0046] In a preferred embodiment of the present invention, in formula (I), R 1 It is methylene, ethylene or propylene.

[0047] According to the present invention, in formula (II), R 2 is an aliphatic group having 1 to 10 carbon atoms or an aromatic group having 6 to 15 carbon atoms; preferably, R 2 It is a hydrocarbon group having 1 to 8 carbon atoms or an aromatic group having 6 to 13 carbon atoms.

[0048] Examples of the aliphatic group having 1 to 10 carbon atoms include methylene, ethylene, propylene, butylene, pentylene, hexylene, heptylene, octylene, nonylene and decylene. Among them, butylene, hexylene and octylene are preferred.

[0049] In a preferred embodiment of the present invention, in formula (II), R 2 It is butylene, hexylene, octylene, -C6H4-, -C6H4-C6H4- or -C6H4-CH2-C6H4-.

[0050] According to the present invention, preferably, the melt index of the polyethylene resin is ≥1 g / 10 min (190° C., 2.16 Kg); more preferably, the melt index of the polyethylene resin is 10-100 g / 10 min (190° C., 2.16 Kg).

[0051] In a particularly preferred embodiment of the present invention, the polyethylene resin is HDPE or LDPE.

[0052] According to the present invention, preferably, the free radical initiator is one or more of a thermal decomposition free radical initiator, an organic peroxide and an azo initiator; preferably an organic peroxide.

[0053] The organic peroxide is preferably one or more of alkyl peroxide, hydroperoxide, acyl peroxide and peroxycarbonate.

[0054] Examples of the alkyl peroxide include 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane and / or dicumyl peroxide.

[0055] Examples of the hydroperoxide include tert-butyl hydroperoxide and / or cumene hydroperoxide.

[0056] Examples of the acyl peroxide include dibenzoyl peroxide and / or dodecanoyl peroxide.

[0057] According to the present invention, preferably, the cross-linked polyethylene resin composition further comprises an electron donating antioxidant. Preferably, the electron donating antioxidant is one or more of amide, sulfoxide and phosphite antioxidants.

[0058] Examples of the amide include dimethylacetamide and / or N-methylacetamide.

[0059] Examples of the sulfoxide include dimethyl sulfoxide and / or diethyl sulfoxide.

[0060] Examples of the phosphite antioxidant include tris(nonylphenyl)phosphite and / or tris(2,4-di-tert-butylphenyl)phosphite.

[0061] In a preferred embodiment of the present invention, the electron donating antioxidant is one or more of dimethylacetamide, dimethyl sulfoxide and tris(nonylphenyl)phosphite.

[0062] According to the present invention, preferably, the amount of the electron donating antioxidant is 0.01-1 part by weight relative to 100 parts by weight of the polyethylene resin; more preferably, the amount of the electron donating antioxidant is 0.2-0.4 part by weight relative to 100 parts by weight of the polyethylene resin.

[0063] According to the present invention, preferably, the cross-linked polyethylene resin composition further comprises a free radical stabilizer. Preferably, the free radical stabilizer is one or more of a hindered phenol antioxidant and an alkyl ester antioxidant.

[0064] Examples of the hindered phenol antioxidant include phenol and / or trimethylphenol.

[0065] Examples of the alkyl ester antioxidant include pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate (commonly known as 1010) and / or tris(2,4-di-tert-butyl)phenyl phosphite (commonly known as 168).

[0066] According to the present invention, preferably, the amount of the free radical stabilizer is 0.05-1 part by weight relative to 100 parts by weight of the polyethylene resin; more preferably, the amount of the free radical stabilizer is 0.2-0.6 part by weight relative to 100 parts by weight of the polyethylene resin.

[0067] According to a second aspect of the present invention, there is provided a cross-linked polyethylene resin obtained by melt extruding a cross-linked polyethylene resin composition, wherein the cross-linked polyethylene resin composition is the cross-linked polyethylene resin composition according to the first aspect of the present invention.

[0068] According to the present invention, the temperature of the melt extrusion may be 170-230°C; preferably, the temperature of the melt extrusion is 190-200°C.

[0069] According to the present invention, the melt extrusion is preferably carried out in an extruder well known in the art.

[0070] When melt extrusion is carried out in the extruder, the extrusion temperature may be 170-230° C., preferably 190-200° C., and the residence time may be 30-300 s, preferably 60-200 s.

[0071] According to the present invention, all the components of the cross-linked polyethylene resin composition can be mixed and then fed into an extruder for melt extrusion; or two or three of the components can be mixed and then mixed with other components.

[0072] In a preferred embodiment of the present invention, the graft component, the free radical initiator and the electron donating antioxidant E are mixed and then mixed with the polyethylene resin.

[0073] According to the present invention, preferably, after the melt extrusion, the extrudate is cooled and pelletized.

[0074] According to the present invention, preferably, the weight of the grafted component grafted into the polyethylene resin accounts for 0.01-5% by weight of the cross-linked polyethylene resin, preferably 0.2-2%.

[0075] According to the present invention, the melt index (190° C., 2.16 Kg) of the cross-linked polyethylene resin is preferably 1-100 g / 10 min, more preferably 10-75 g / 10 min.

[0076] According to the present invention, the gel content of the cross-linked polyethylene resin is preferably less than 5 wt %, more preferably less than 2 wt %, more preferably less than 0.5 wt %, more preferably less than 0.1 wt %.

[0077] According to the present invention, the crystallinity of the cross-linked polyethylene resin is preferably higher than 40%, more preferably 50-60%.

[0078] According to the present invention, the melt index of the cross-linked polyethylene resin is 0.8-1.5 times, more preferably 0.8-1.2 times, the melt index of the polyethylene resin.

[0079] According to the present invention, the cross-linked polyethylene resin is a cross-linked polymer formed by utilizing the thermal reversibility of the DA reaction. After melting, the cross-linked structure is released through a reverse DA reaction, and the material has thermoplasticity; after cooling, it can be cross-linked again to produce a network structure, thereby enhancing the polyethylene resin and giving the polyethylene resin repeatability and recyclability.

[0080] According to a third aspect of the present invention, there is provided use of the cross-linked polyethylene resin composition according to the first aspect of the present invention or the cross-linked polyethylene resin according to the second aspect of the present invention in the preparation of polyethylene molded products.

[0081] According to the present invention, the cross-linked polyethylene resin obtained by using the cross-linked polyethylene resin composition of the present invention has high properties such as strength and modulus, and has thermoplasticity and excellent processability, and will not cause performance degradation even after multiple processing.

[0082] Example

[0083] The present invention will be described in detail below by way of examples, but the present invention is not limited to the following examples.

[0084] In the following examples, the structures of the graft component B and the cross-linking component D are as follows:

[0085] B1 (commercially available, Hong Kong Chemhere Co., Ltd., CAS No. 50288-55-6)

[0086] B2 (commercially available, Hong Kong Chemhere Co., Ltd., CAS No. 778565-14-3)

[0087] (Commercially available, Shanghai MacLean Biochemical Technology Co., Ltd., CAS No. 13676-54-5)

[0088] (Synthesis reference: Pure Appl Chem, 2016, 88(12): 1103-1116)

[0089] Example 1

[0090] In parts by mass, 100 parts of polyethylene (melt index MFR = 14g / 10min, 190°C, 2.16Kg, purchased from Qilu Petrochemical Company HDPE 6098 model, the same below), 0.1 parts of 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane (free radical initiator), 0.1 parts of 1010 (free radical stabilizer), 0.1 parts of 168 (free radical stabilizer), 0.2 parts of dimethylacetamide, 1 part of grafting component B1, 0.2 parts of crosslinking agent component D1 are mixed, and then the mixture is added to a twin-screw extruder for melting. The temperature of the extruder is 200°C, the residence time is 90s, and the extruded product is cooled and pelletized in a circulating water bath to obtain a cross-linked polyethylene resin.

[0091] Example 2

[0092] In parts by mass, 100 parts of polyethylene (melt index MFR = 14g / 10min, 190°C, 2.16Kg), 0.2 parts of diisopropylbenzene peroxide (free radical initiator), 0.2 parts of 1010 (free radical stabilizer), 0.4 parts of 168 (free radical stabilizer), 0.2 parts of dimethylacetamide, 2 parts of grafting component B2, and 0.3 parts of crosslinking agent component D1 are mixed, and then the mixture is added to a twin-screw extruder for melting. The temperature of the extruder is 190°C, the residence time is 60s, and the extruded product is cooled in a circulating water bath and pelletized to obtain a crosslinked polyethylene resin.

[0093] Example 3

[0094] In parts by mass, 100 parts of polyethylene (melt index MFR = 14g / 10min, 190°C, 2.16Kg), 0.15 parts of 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane (free radical initiator), 0.1 parts of 1010 (free radical stabilizer), 0.2 parts of 168 (free radical stabilizer), 0.2 parts of tris(nonylphenyl)phosphite, 2.5 parts of grafting component B1, and 1 part of crosslinking agent component D2 were mixed, and then the mixture was added to a twin-screw extruder for melting. The temperature of the extruder was 190°C, the residence time was 90s, and the extruded product was cooled in a circulating water bath and pelletized to obtain a crosslinked polyethylene resin.

[0095] Example 4

[0096] 100 parts of the product obtained in Example 1, 0.1 parts of 1010 (free radical stabilizer), and 0.2 parts of 168 (free radical stabilizer) were mixed, and then the mixture was added to a twin-screw extruder for melting. The temperature of the extruder was 190° C., the residence time was 90 seconds, and the extruded product was cooled in a circulating water bath and pelletized to obtain a cross-linked polyethylene resin.

[0097] Example 5

[0098] 100 parts of the product obtained in Example 4, 0.1 parts of 1010 (free radical stabilizer), and 0.2 parts of 168 (free radical stabilizer) were mixed, and then the mixture was added to a twin-screw extruder for melting. The temperature of the extruder was 190° C., the residence time was 60 seconds, and the extruded product was cooled in a circulating water bath and pelletized to obtain a cross-linked polyethylene resin.

[0099] Example 6

[0100] 100 parts of the product obtained in Example 5, 0.1 parts of 1010 (free radical stabilizer), and 0.2 parts of 168 (free radical stabilizer) were mixed, and then the mixture was added to a twin-screw extruder for melting. The temperature of the extruder was 190° C., the residence time was 60 seconds, and the extruded product was cooled in a circulating water bath and pelletized to obtain a cross-linked polyethylene resin.

[0101] Example 7

[0102] In parts by mass, 100 parts of polyethylene (melt index MFR = 20g / 10min, 190°C, 2.16Kg, purchased from Fushun Petrochemical Company, HDPE 2911 model, the same below), 0.15 parts of 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane (free radical initiator), 0.1 parts of 1010 (free radical stabilizer), 0.2 parts of 168 (free radical stabilizer), 0.4 parts of dimethyl sulfoxide, 2 parts of grafting component B1, 0.75 parts of

[0103] The crosslinking agent component D1 is mixed, and then the mixture is added to a twin-screw extruder for melting. The temperature of the extruder is 190° C., the residence time is 120 seconds, and the extruded product is cooled in a circulating water bath and pelletized to obtain a crosslinked polyethylene resin.

[0104] Example 8

[0105] In parts by mass, 100 parts of polyethylene (melt index MFR = 80g / 10min, 190°C, 2.16Kg, purchased from ExxonMobil LDPE 654 model, the same below), 0.2 parts of 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane (free radical initiator), 0.2 parts of 1010 (free radical stabilizer), 0.4 parts of 168 (free radical stabilizer), 0.4 parts of tris(nonylphenyl)phosphite, 4 parts of grafting component B1, and 2 parts of crosslinking agent component D2 are mixed, and then the mixture is added to a twin-screw extruder for melting. The temperature of the extruder is 190°C, the residence time is 90s, and the extruded product is cooled in a circulating water bath and pelletized to obtain a crosslinked polyethylene resin.

[0106] Example 9

[0107] In parts by mass, 100 parts of polyethylene (melt index MFR = 14g / 10min, 190°C, 2.16Kg), 0.15 parts of 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane (free radical initiator), 0.1 parts of 1010 (free radical stabilizer), 0.2 parts of 168 (free radical stabilizer), 0.3 parts of tris(nonylphenyl)phosphite, 4 parts of grafting component B1, and 1 part of crosslinking agent component D2 were mixed, and then the mixture was added to a twin-screw extruder for melting. The temperature of the extruder was 190°C, the residence time was 90s, and the extruded product was cooled in a circulating water bath and pelletized to obtain a crosslinked polyethylene resin.

[0108] Example 10

[0109] 100 parts of the product obtained in Example 9, 0.1 parts of 1010 (free radical stabilizer), and 0.2 parts of 168 (free radical stabilizer) were mixed, and then the mixture was added to a twin-screw extruder for melting. The temperature of the extruder was 190° C., the residence time was 90 seconds, and the extruded product was cooled in a circulating water bath and pelletized to obtain a cross-linked polyethylene resin.

[0110] Comparative Example 1

[0111] In parts by mass, 100 parts of polyethylene (melt index MFR = 14g / 10min, 190°C, 2.16Kg), 0.1 parts of 1010 (free radical stabilizer), and 0.2 parts of 168 (free radical stabilizer) were mixed, and then the mixture was added to a twin-screw extruder for melting. The extruder temperature was 190°C, the residence time was 90s, and the extruded product was cooled in a circulating water bath and pelletized to obtain a cross-linked polyethylene resin.

[0112] Comparative Example 2

[0113] In parts by mass, 100 parts of polyethylene (melt index MFR = 20g / 10min, 190°C, 2.16Kg), 0.1 parts of 1010 (free radical stabilizer), and 0.2 parts of 168 (free radical stabilizer) were mixed, and then the mixture was added to a twin-screw extruder for melting. The temperature of the extruder was 190°C, the residence time was 60s, and the extruded product was cooled in a circulating water bath and pelletized to obtain a cross-linked polyethylene resin.

[0114] Comparative Example 3

[0115] In parts by mass, 100 parts of polyethylene (melt index MFR = 80g / 10min, 190°C, 2.16Kg), 0.2 parts of 1010 (free radical stabilizer), and 0.4 parts of 168 (free radical stabilizer) were mixed, and then the mixture was added to a twin-screw extruder for melting. The temperature of the extruder was 190°C, the residence time was 60s, and the extruded product was cooled in a circulating water bath and pelletized to obtain a cross-linked polyethylene resin.

[0116] Comparative Example 4

[0117] 100 parts of the product obtained in Comparative Example 1, 0.1 parts of 1010 (free radical stabilizer), and 0.2 parts of 168 (free radical stabilizer) were mixed, and then the mixture was added to a twin-screw extruder for melting. The temperature of the extruder was 190° C., the residence time was 90 seconds, and the extruded product was cooled in a circulating water bath and pelletized to obtain a cross-linked polyethylene resin.

[0118] Comparative Example 5

[0119] In parts by mass, 100 parts of polyethylene (melt index MFR = 14g / 10min, 190°C, 2.16Kg), 0.1 parts of 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane (free radical initiator), 0.1 parts of 1010 (free radical stabilizer), 0.2 parts of 168 (free radical stabilizer), and 1 part of grafting component B1 were mixed, and then the mixture was added to a twin-screw extruder for melting. The temperature of the extruder was 190°C, the residence time was 90s, and the extruded product was cooled in a circulating water bath and pelletized to obtain a cross-linked polyethylene resin.

[0120] Comparative Example 6

[0121] In parts by mass, 100 parts of polyethylene (melt index MFR = 14g / 10min, 190°C, 2.16Kg), 0.1 parts of 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane (free radical initiator), 0.1 parts of 1010 (free radical stabilizer), and 0.2 parts of 168 (free radical stabilizer) were mixed, and then the mixture was added to a twin-screw extruder for melting. The temperature of the extruder was 190°C, the residence time was 90s, and the extruded product was cooled in a circulating water bath and pelletized to obtain a cross-linked polyethylene resin.

[0122] Test Case

[0123] The following properties were measured using the cross-linked polyethylene resin prepared in the above examples and the polyethylene resin prepared in the comparative examples. The results are shown in Table 1.

[0124] Melt index determination method: Determined in accordance with GB / T3682-2000 method.

[0125] The crystallinity was measured by differential scanning calorimetry (DSC).

[0126] Determination method of the actual graft content of the grafted component: H NMR spectroscopy ( 1 H-NMR) determination.

[0127] Method for determining gel content: Place a pre-weighed sample (m1) in a Soxhlet extractor and extract it with xylene for 48 hours, then take out the remaining sample in the extractor, dry it and weigh it (m2). Gel content = (m2 / m1) × 100%.

[0128] Creep determination method: Determined in accordance with GB / T11546.1-2008 method.

[0129] Method for determining Young's modulus: determined in accordance with GB / T1040.1-2006 method.

[0130] Determination method of tensile strength: Determined in accordance with GB / T1040.1-2006 method.

[0131] Table 1

[0132]

[0133] By comparing Example 1 with Comparative Example 1 and Comparative Example 5, comparing Example 7 with Comparative Example 2, comparing Example 8 with Comparative Example 3, etc., it can be seen that after adding the grafting component and the cross-linking agent component, the strength, modulus and other properties of the polyethylene resin are significantly improved, which indicates that cross-linking has a significant effect on improving the mechanical properties of the material.

[0134] By comparing Example 1 with Comparative Example 1 and Comparative Example 5, it can be seen that after adding the grafting component and the crosslinking agent component, the strength, modulus and other properties of the polyethylene resin are significantly improved, which shows that crosslinking has a significant effect on improving the mechanical properties of the material.

[0135] By comparing Example 7 with Comparative Example 2, it can be seen that after adding the grafting component and the crosslinking agent component, the strength, modulus and other properties of the polyethylene resin are significantly improved, which shows that crosslinking has a significant effect on improving the mechanical properties of the material.

[0136] By comparing Example 8 with Comparative Example 3, it can be seen that after adding the grafting component and the crosslinking agent component, the strength, modulus and other properties of the polyethylene resin are significantly improved, which shows that crosslinking has a significant effect on improving the mechanical properties of the material.

[0137] On the other hand, the cross-linked polyethylene prepared by the present method has thermoplasticity. Different from the traditional irreversible cross-linked polymer, the cross-linked polyethylene prepared by the present method can undergo de-crosslinking (through the reverse DA reaction mechanism) in the melt processing state, so the melt index of the polymer will not drop significantly after cross-linking. Comparing Example 1 with Comparative Example 1, Example 7 with Comparative Example 2, Example 8 with Comparative Example 3, etc., the melt index of the cross-linked polyethylene is not much different from that of the raw polyethylene. This is a feature of the polyethylene prepared by the present method, that is, the material has repeatable processability; and the reversible cross-linked network can be repeatedly realized, so that the material will not cause a decrease in performance after multiple processing (see the comparison between Example 1 and Example 4, Example 5, and Example 6, and the comparison between Example 9 and 10).

[0138] By comparing Example 3 and Example 9, it can be seen that as the content of the grafted component increases, the creep resistance of the polyethylene becomes stronger.

[0139] In particular, the crosslinking of the present invention is reversible, and no gel content can be detected in the crosslinked polyethylene resins of all the examples, which can well solve the gelation phenomenon easily caused by traditional irreversible crosslinking (Comparative Example 6).

[0140] The preferred embodiments of the present invention are described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, the technical solution of the present invention can be subjected to a variety of simple modifications, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be regarded as the contents disclosed by the present invention and belong to the protection scope of the present invention.

Claims

1. A cross-linked polyethylene resin composition, characterized in that The composition comprises: polyethylene resin, grafting component, free radical initiator and crosslinking component. Wherein, the graft component is as shown in the following formula (I): In formula (I), R 1 is an alkylene group having 1 to 8 carbon atoms or an ether group having 2 to 8 carbon atoms; The cross-linking component is shown in the following formula (II): In formula (II), R 2 It is an aliphatic group having 1 to 10 carbon atoms or an aromatic group having 6 to 15 carbon atoms.

2. The composition according to claim 1, wherein Relative to 100 parts by weight of the polyethylene resin, the amount of the graft component is 0.1-10 parts by weight, the amount of the free radical initiator is 0.01-1 part by weight, and the amount of the cross-linking component is 0.01-10 parts by weight; Preferably, relative to 100 parts by weight of the polyethylene resin, the amount of the graft component is 1-5 parts by weight, the amount of the free radical initiator is 0.1-0.2 parts by weight, and the amount of the cross-linking component is 0.2-2 parts by weight.

3. The composition according to claim 1, wherein In formula (I), R 1 -(CH2) m -、-(CH2) m -O-(CH2) n -, m and n are integers from 1 to 8, and m+n≤8; Preferably, R 1 It is methylene, ethylene or propylene.

4. The composition according to any one of claims 1 to 3, wherein In formula (II), R 2 It is butylene, hexylene, octylene, -C6H4-, -C6H4-C6H4- or -C6H4-CH2-C6H4-.

5. The composition according to any one of claims 1 to 3, wherein The melt index of the polyethylene resin is ≥1 g / 10 min (190° C., 2.16 Kg), preferably 10-100 g / 10 min (190° C., 2.16 Kg).

6. The composition according to any one of claims 1 to 3, wherein The free radical initiator is one or more of a thermal decomposition free radical initiator, an organic peroxide and an azo initiator; Preferably, the free radical initiator is one or more of alkyl peroxide, hydroperoxide, acyl peroxide and peroxycarbonate.

7. The composition according to any one of claims 1 to 3, wherein The cross-linked polyethylene resin composition further comprises an electron-donating antioxidant; Preferably, the electron donating antioxidant is one or more of amide, sulfoxide and phosphite antioxidants; Preferably, the electron donating antioxidant is one or more of dimethylacetamide, dimethyl sulfoxide and tris(nonylphenyl)phosphite; Preferably, the amount of the electron donating antioxidant is 0.01-1 part by weight relative to 100 parts by weight of the polyethylene resin.

8. The composition according to any one of claims 1 to 3, wherein The cross-linked polyethylene resin composition further comprises a free radical stabilizer; Preferably, the free radical stabilizer is one or more of a hindered phenol antioxidant and an alkyl ester antioxidant; Preferably, the amount of the free radical stabilizer is 0.05-1 part by weight relative to 100 parts by weight of the polyethylene resin.

9. A cross-linked polyethylene resin obtained by melt extrusion of a cross-linked polyethylene resin composition, characterized in that: The cross-linked polyethylene resin composition is the cross-linked polyethylene resin composition according to any one of claims 1 to 8.

10. The cross-linked polyethylene resin according to claim 9, wherein The temperature of the melt extrusion is 170-230°C.

11. The cross-linked polyethylene resin according to claim 9, wherein The weight of the grafted component grafted into the polyethylene resin accounts for 0.01-5% by weight of the cross-linked polyethylene resin, preferably 0.2-2%.

12. Use of the cross-linked polyethylene resin composition according to any one of claims 1 to 8 or the cross-linked polyethylene resin according to any one of claims 9 to 11 in the preparation of polyethylene molded products.

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