Crosslinked polypropylene resin composition, crosslinked polypropylene resin and application thereof

Abstract

The invention relates to the field of polypropylene resin, and discloses a cross-linked polypropylene resin composition, cross-linked polypropylene resin and application of the cross-linked polypropylene resin composition and the cross-linked polypropylene resin. In order to achieve the purpose, the cross-linked polypropylene resin composition comprises polypropylene resin, a grafting component, a free radical initiator and a cross-linking component, the grafting component is shown in the formula (I), the cross-linking component is shown in the formula (II), in the formula (I), R1 is an acrylate group which can have a substituent, R2 is an alkyl group which can have a substituent, R3 is an alkyl group which can have a substituent, and R4 is an alkyl group which can have a substituent. In the formula (II), R2 is a straight-chain fat group with the carbon atom number of 1-10 or an aromatic group with the carbon atom number of 6-15. The cross-linked polypropylene resin obtained by using the cross-linked polypropylene 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. # imgabs0 #

Description

Technical Field

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

[0002] Polypropylene is a polymer variety with huge global production. It has the characteristics of good chemical stability, excellent corrosion resistance, strong electrical insulation, and excellent processing performance. It is widely used in industrial and agricultural production, construction, transportation, daily necessities and other fields. Isotactic polypropylene has high crystallinity and good mechanical properties. It is an important raw material for products such as pipes, plates, fibers, and cables. Moderate cross-linking of polypropylene can further increase the strength of polypropylene and improve the dimensional stability of products during long-term use. It can also give polypropylene good melt foaming properties and prepare various types of foaming materials. Chemical cross-linking is the most common cross-linking method. Linear polypropylene is converted into a mesh or body structure through radiation (X-ray, electron beam or ultraviolet irradiation, etc.) or chemical method (peroxide or silane cross-linking).

[0003] CN109021379B discloses a method for preparing a radiation cross-linked polypropylene foam material. A polypropylene and polyethylene mixture sheet is irradiated in an inert atmosphere and then foamed under supercritical carbon dioxide conditions to obtain a radiation cross-linked polypropylene foam product with small pore diameter.

[0004] CN110621709A discloses a method for preparing cross-linked polypropylene by grafting silane onto polypropylene, and the prepared cross-linked polypropylene contains a certain amount of gel insoluble matter. However, the cross-linking by irradiation, silane, oxide, divinylbenzene and other methods produce stable chemical bonds, which makes it difficult to re-form and recycle such cross-linked polymers, causing many environmental problems.

[0005] In order to achieve the recycling of cross-linked polypropylene, CN109749235A discloses a reversible micro-cross-linked polypropylene and a preparation method thereof, using a class of ionic liquids with C5-C30 long hydrocarbon chains as active cross-linking agents. This method can effectively improve the melt strength and mechanical properties of polypropylene materials, and the material performance loss is small after repeated processing.

[0006] CN109627360B discloses a method for preparing polypropylene containing a thermally reversible crosslinking group, comprising first chlorinating the polypropylene, then dissolving the chlorinated polypropylene in a solvent, adding an aromatic compound containing a thermally reversible crosslinking group and a catalyst to obtain a product, and finally acid washing, alkali washing, water washing, and drying to obtain the polypropylene containing a thermally reversible crosslinking group. These methods realize the repeated processing and recycling of crosslinked polymers.

[0007] Since isotactic polypropylene has strong solvent resistance, the steps for preparing reversibly cross-linked polypropylene using solutions and other processes are still cumbersome, which is not conducive to continuous large-scale production, and the preparation method needs to be improved urgently. Summary of the invention

[0008] The object of the present invention is to provide a cross-linked polypropylene resin composition, a cross-linked polypropylene resin and applications thereof. The cross-linked polypropylene resin obtained by using the cross-linked polypropylene 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.

[0009] In order to achieve the above object, the present invention provides a cross-linked polypropylene resin composition, wherein the composition comprises: a polypropylene resin, a grafting component, a free radical initiator and a cross-linking component.

[0010] Wherein, the graft component is as shown in the following formula (I):

[0011]

[0012] In formula (I), R 1 is an acrylate group which may have a substituent;

[0013] The cross-linking component is shown in the following formula (II):

[0014]

[0015] In formula (II), R 2 It is a straight chain aliphatic group having 1 to 10 carbon atoms or an aromatic group having 6 to 15 carbon atoms.

[0016] Preferably, relative to 100 parts by weight of the polypropylene 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.

[0017] Preferably, relative to 100 parts by weight of the polypropylene resin, the amount of the graft component is 1-4 parts by weight, the amount of the free radical initiator is 0.1-0.3 parts by weight, and the amount of the cross-linking component is 0.2-2 parts by weight.

[0018] Preferably, in formula (I), R 1 It is a methyl acrylate group or a methyl methacrylate group.

[0019] Preferably, in formula (II), R 2It is butylene, hexylene, octylene, -C6H4-, -C6H4-C6H4- or -C6H4-CH2-C6H4-.

[0020] Preferably, the melt index (230° C., 2.16 Kg) of the polypropylene resin is preferably 1-100 g / 10 min.

[0021] Preferably, the free radical initiator is one or more of a thermal decomposition free radical initiator, an organic peroxide and an azo initiator.

[0022] Preferably, the free radical initiator is one or more of alkyl peroxide, hydroperoxide, acyl peroxide and peroxycarbonate.

[0023] Preferably, the cross-linked polypropylene resin composition further comprises a free radical stabilizer.

[0024] Preferably, the free radical stabilizer is one or more of hindered phenol antioxidants, phosphite antioxidants and alkyl ester antioxidants.

[0025] Preferably, the amount of the free radical stabilizer is 0.05-1 part by weight relative to 100 parts by weight of the polypropylene resin.

[0026] According to a second aspect of the present invention, there is provided a cross-linked polypropylene resin obtained by melt extruding a cross-linked polypropylene resin composition, wherein the cross-linked polypropylene resin composition is the cross-linked polypropylene resin composition according to the first aspect of the present invention.

[0027] Preferably, the melt extrusion is carried out in an extruder.

[0028] Preferably, the extruder is a twin-screw extruder having at least six zones, wherein the temperature of the first zone is higher than 90°C, the temperature of the second zone is higher than 150°C, the temperature of the third zone is higher than 180°C, and the temperature of any subsequent zone is higher than 190°C and lower than 230°C.

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

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

[0031] According to the present invention, the cross-linked polypropylene 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 the reverse DA reaction, and the material has thermoplasticity; after cooling, it can be cross-linked again to produce a network structure, thereby enhancing the polypropylene resin and giving the polypropylene resin repeatability and recyclability.

[0032] According to the present invention, the cross-linked polypropylene resin obtained using the cross-linked polypropylene 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 polypropylene resin composition is provided, wherein the composition comprises: a polypropylene 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 acrylate group which may have a substituent;

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

[0039]

[0040] In formula (II), R 2 It is a straight chain 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 polypropylene 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 polypropylene resin, the amount of the grafted component is 1-4 parts by weight, the amount of the free radical initiator is 0.1-0.3 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 polypropylene resin can be further improved.

[0043] According to the present invention, in formula (I), R 1 is an acrylate group which may have a substituent; preferably, in formula (I), R 1 It is a methyl acrylate group or a methyl methacrylate group.

[0044] According to the present invention, in formula (II), R 2 is a straight-chain aliphatic group having 1 to 10 carbon atoms or an aromatic group having 6 to 15 carbon atoms; preferably, R 2 It is a straight chain hydrocarbon group having 1 to 8 carbon atoms or an aromatic group having 6 to 13 carbon atoms.

[0045] Examples of the straight-chain 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.

[0046] 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-.

[0047] According to the present invention, preferably, the melt index (230°C, 2.16Kg) of the polypropylene resin is preferably 1-100 g / 10min; more preferably, the melt index (230°C, 2.16Kg) of the polypropylene resin is 3-85 g / 10min; further preferably, the melt index (230°C, 2.16Kg) of the polypropylene resin is 10-75 g / 10min.

[0048] The isotacticity can be measured by boiling n-heptane extraction method, and the specific method is as follows:

[0049] It is determined by the n-heptane extraction method. The sample to be tested is placed in a Soxhlet extractor and extracted with boiling n-heptane for h. The remaining sample in the extractor is dried to constant weight. The ratio of the mass of the remaining sample to the mass of the sample before extraction is the isotactic index.

[0050] According to the present invention, preferably, the polypropylene resin is isotactic polypropylene, and the isotacticity of the isotactic polypropylene is preferably above 85%, more preferably above 90%, for example, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, etc., and the range formed by any two of the above values.

[0051] 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.

[0052] The organic peroxide is preferably one or more of alkyl peroxide, hydroperoxide, acyl peroxide and peroxycarbonate.

[0053] Examples of the alkyl peroxide include 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane and / or dicumyl peroxide.

[0054] Examples of the hydroperoxide include tert-butyl hydroperoxide and / or cumene hydroperoxide.

[0055] Examples of the acyl peroxide include dibenzoyl peroxide and / or dodecanoyl peroxide.

[0056] According to the present invention, preferably, the cross-linked polypropylene resin composition further comprises a free radical stabilizer. Preferably, the free radical stabilizer is one or more of a hindered phenol antioxidant, a phosphite antioxidant and an alkyl ester antioxidant.

[0057] Examples of the hindered phenol antioxidant include phenol and / or trimethylphenol.

[0058] 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).

[0059] Examples of the phosphite antioxidant include tris(nonylphenyl)phosphite and / or tris(2,4-di-tert-butylphenyl)phosphite.

[0060] 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 polypropylene 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 polypropylene resin.

[0061] According to a second aspect of the present invention, there is provided a cross-linked polypropylene resin obtained by melt extruding a cross-linked polypropylene resin composition, wherein the cross-linked polypropylene resin composition is the cross-linked polypropylene resin composition according to the first aspect of the present invention.

[0062] According to the present invention, the melt extrusion is preferably carried out in an extruder well known in the art.

[0063] Preferably, the extruder is a twin-screw extruder having at least six zones, wherein the temperature of the first zone is higher than 90° C., the temperature of the second zone is higher than 150° C., the temperature of the third zone is higher than 180° C., and the temperature of any subsequent zone is higher than 190° C. and lower than 230° C. In addition, the residence time of each component in the extruder can be 30-300 s, preferably 60-200 s.

[0064] According to the present invention, all the components of the cross-linked polypropylene 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.

[0065] In a preferred embodiment of the present invention, the graft component is mixed with the free radical initiator and then mixed with the polypropylene resin.

[0066] According to the present invention, preferably, after the melt extrusion, the extrudate is cooled and pelletized.

[0067] According to the present invention, preferably, the weight of the grafted component grafted into the polypropylene resin accounts for 0.01-5% by weight of the cross-linked polypropylene resin, preferably 0.2-2%.

[0068] According to the present invention, the melting temperature of the cross-linked polypropylene resin is preferably above 140°C, more preferably 155-165°C.

[0069] According to the present invention, preferably, the melt index (230°C, 2.16Kg) of the cross-linked polypropylene resin is 3-100 g / 10min; more preferably, the melt index (230°C, 2.16Kg) of the cross-linked polypropylene resin is 3-85 g / 10min; further preferably, the melt index (230°C, 2.16Kg) of the cross-linked polypropylene resin is 10-75 g / 10min.

[0070] According to the present invention, the gel content of the cross-linked polypropylene resin is preferably less than 2% by weight, more preferably less than 0.5% by weight, and more preferably less than 0.1% by weight.

[0071] According to the present invention, the content of xylene solubles in the cross-linked polypropylene resin at 25° C. is preferably 10% by weight or less, more preferably 0.5-2% by weight.

[0072] According to the present invention, the melt index of the cross-linked polypropylene resin may be 0.8-1.5 times, preferably 0.8-1.2 times, the melt index of the polypropylene resin.

[0073] According to the present invention, the cross-linked polypropylene 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 the reverse DA reaction, and the material has thermoplasticity; after cooling, it can be cross-linked again to produce a network structure, thereby enhancing the polypropylene resin and giving the polypropylene resin repeatability and recyclability.

[0074] According to a third aspect of the present invention, there is provided use of the cross-linked polypropylene resin composition according to the first aspect of the present invention or the cross-linked polypropylene resin according to the second aspect of the present invention in the preparation of polypropylene molded products.

[0075] According to the present invention, the cross-linked polypropylene resin obtained by using the cross-linked polypropylene 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.

[0076] Example

[0077] The present invention will be described in detail below by way of examples, but the present invention is not limited to the following examples.

[0078] In the following examples, the structures of the graft component B and the cross-linking component D are as follows:

[0079] B1 (commercially available, Angelene International Limited, CAS No. 10525-17-4)

[0080] B2 (commercially available, Tee Hai Chem Pte. Ltd., CAS No. 3454-28-2)

[0081] B3 (refer to literature synthesis: Macromolecules, 1998, 31(2):314-321)

[0082] D1 (commercially available, Shanghai MacLean Biochemical Technology Co., Ltd., CAS No. 13676-54-5)

[0083] D2 (Synthesis according to reference: Pure Appl Chem, 2016, 88(12):1103-1116)

[0084] Example 1

[0085] In parts by mass, 100 parts of polypropylene (melt index MFR = 3.5g / 10min, 230°C, 2.16Kg, purchased from Lanzhou Petrochemical Company T30S 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), 0.2 parts of 168 (free radical stabilizer), 1 part of grafting component B1, and 0.2 parts of crosslinking agent component D1 are mixed, and then the mixture is added to a twin-screw extruder for melt extrusion. The temperature of the first zone of the extruder is 100°C, the temperature of the second zone is 160°C, the temperature of the third zone is 190°C, the temperature of the fourth and fifth zones is 200°C, the temperature of the sixth zone is 190°C, the residence time is 90s, and the extruded product is cooled and pelletized in a circulating water bath to obtain a crosslinked polypropylene resin.

[0086] Example 2

[0087] In parts by mass, 100 parts of polypropylene (melt index MFR=3.5g / 10min, 230°C, 2.16Kg), 0.2 parts of dicumyl peroxide (free radical initiator), 0.1 parts of 1010 (free radical stabilizer), 0.2 parts of 168 (free radical stabilizer), 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 first zone of the extruder is 100°C, the temperature of the second zone is 160°C, the temperature of the third zone is 190°C, the temperature of the fourth and fifth zones is 200°C, the temperature of the sixth zone 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 polypropylene resin.

[0088] Example 3

[0089] In parts by mass, 100 parts of polypropylene (melt index MFR = 3.5g / 10min, 230°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), 0.1 parts of 168 (free radical stabilizer), 2.5 parts of grafting component B1, and 1 part of crosslinking agent component D2 are mixed, and then the mixture is added to a twin-screw extruder for melting. The temperature of the first zone of the extruder is 100°C, the temperature of the second zone is 160°C, the temperature of the third zone is 190°C, the temperature of the fourth and fifth zones is 200°C, the temperature of the sixth zone is 190°C, the residence time is 90s, and the extruded product is cooled and pelletized in a circulating water bath to obtain a crosslinked polypropylene resin.

[0090] Example 4

[0091] 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 first zone of the extruder was 100° C., the temperature of the second zone was 160° C., the temperature of the third zone was 190° C., the temperature of the fourth and fifth zones was 200° C., the temperature of the sixth zone was 190° C., the residence time was 90 s, and the extruded product was cooled in a circulating water bath and pelletized to obtain a cross-linked polypropylene resin.

[0092] Example 5

[0093] 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 first zone of the extruder was 100° C., the temperature of the second zone was 160° C., the temperature of the third zone was 190° C., the temperature of the fourth and fifth zones was 200° C., the temperature of the sixth zone was 190° C., the residence time was 60 s, and the extruded product was cooled in a circulating water bath and pelletized to obtain a cross-linked polypropylene resin.

[0094] Example 6

[0095] 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 first zone of the extruder was 100° C., the temperature of the second zone was 160° C., the temperature of the third zone was 190° C., the temperature of the fourth and fifth zones was 200° C., the temperature of the sixth zone was 190° C., the residence time was 60 s, and the extruded product was cooled in a circulating water bath and pelletized to obtain a cross-linked polypropylene resin.

[0096] Example 7

[0097] In parts by mass, 100 parts of polypropylene (melt index MFR = 12.0g / 10min, 230°C, 2.16Kg, purchased from Yanshan Petrochemical Company 1700 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), 2 parts of grafting component B1, 0.75 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 first zone of the extruder is 100°C, the temperature of the second zone is 160°C, the temperature of the third zone is 190°C, the temperature of the fourth and fifth zones is 200°C, the temperature of the sixth zone is 190°C, the residence time is 120s, and the extruded product is cooled and pelletized in a circulating water bath to obtain a cross-linked polypropylene resin.

[0098] Example 8

[0099] In parts by mass, 100 parts of polypropylene (melt index MFR = 80.0g / 10min, 230°C, 2.16Kg, purchased from Guangzhou Petrochemical Company K7100 model, the same below), 0.3 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), 4 parts of grafting component B2, 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 first zone of the extruder is 100°C, the temperature of the second zone is 160°C, the temperature of the third zone is 190°C, the temperature of the fourth and fifth zones is 200°C, the temperature of the sixth zone is 190°C, the residence time is 90s, and the extruded product is cooled and pelletized in a circulating water bath to obtain a cross-linked polypropylene resin.

[0100] Example 9

[0101] In parts by mass, 100 parts of polypropylene (melt index MFR = 3.5g / 10min, 230°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), 4 parts of grafting component B1, and 1 part of crosslinking agent component D2 are mixed, and then the mixture is added to a twin-screw extruder for melting. The temperature of the first zone of the extruder is 100°C, the temperature of the second zone is 160°C, the temperature of the third zone is 190°C, the temperature of the fourth and fifth zones is 200°C, the temperature of the sixth zone is 190°C, the residence time is 90s, and the extruded product is cooled and pelletized in a circulating water bath to obtain a crosslinked polypropylene resin.

[0102] Example 10

[0103] 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 first zone of the extruder was 100° C., the temperature of the second zone was 160° C., the temperature of the third zone was 190° C., the temperature of the fourth and fifth zones was 200° C., the temperature of the sixth zone was 190° C., the residence time was 90 s, and the extruded product was cooled in a circulating water bath and pelletized to obtain a cross-linked polypropylene resin.

[0104] Comparative Example 1

[0105] In parts by mass, 100 parts of polypropylene (melt index MFR=3.5g / 10min, 230°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 first zone of the extruder was 100°C, the temperature of the second zone was 160°C, the temperature of the third zone was 190°C, the temperature of the fourth and fifth zones was 200°C, the temperature of the sixth zone 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 polypropylene resin.

[0106] Comparative Example 2

[0107] In parts by mass, 100 parts of polypropylene (melt index MFR=12.0g / 10min, 230°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 first zone of the extruder was 100°C, the temperature of the second zone was 160°C, the temperature of the third zone was 190°C, the temperature of the fourth and fifth zones was 200°C, the temperature of the sixth zone 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 polypropylene resin.

[0108] Comparative Example 3

[0109] In parts by mass, 100 parts of polypropylene (melt index MFR=80.0g / 10min, 230°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 first zone of the extruder was 100°C, the temperature of the second zone was 160°C, the temperature of the third zone was 190°C, the temperature of the fourth and fifth zones was 200°C, the temperature of the sixth zone 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 polypropylene resin.

[0110] Comparative Example 4

[0111] 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 first zone of the extruder was 100° C., the temperature of the second zone was 160° C., the temperature of the third zone was 190° C., the temperature of the fourth and fifth zones was 200° C., the temperature of the sixth zone was 190° C., the residence time was 90 s, and the extruded product was cooled in a circulating water bath and pelletized to obtain a cross-linked polypropylene resin.

[0112] Comparative Example 5

[0113] In parts by mass, 100 parts of polypropylene (melt index MFR = 3.5g / 10min, 230°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 are mixed, and then the mixture is added to a twin-screw extruder for melting. The temperature of the first zone of the extruder is 100°C, the temperature of the second zone is 160°C, the temperature of the third zone is 190°C, the temperature of the fourth and fifth zones is 200°C, the temperature of the sixth zone is 190°C, the residence time is 90s, and the extruded product is cooled in a circulating water bath and pelletized to obtain a cross-linked polypropylene resin.

[0114] Comparative Example 6

[0115] In parts by mass, 100 parts of polypropylene (melt index MFR = 3.5g / 10min, 230°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), and 1 part of divinylbenzene are mixed, and then the mixture is added to a twin-screw extruder for melting. The temperature of the first zone of the extruder is 100°C, the temperature of the second zone is 160°C, the temperature of the third zone is 190°C, the temperature of the fourth and fifth zones is 200°C, the temperature of the sixth zone is 190°C, the residence time is 90s, and the extruded product is cooled and pelletized in a circulating water bath to obtain a cross-linked polypropylene resin.

[0116] Comparative Example 7

[0117] In parts by mass, 100 parts of polypropylene (melt index MFR = 3.5g / 10min, 230°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), 1 part of grafting component B3, and 0.2 parts of crosslinking agent component D1 are mixed, and then the mixture is added to a twin-screw extruder for melt extrusion. The temperature of the first zone of the extruder is 100°C, the temperature of the second zone is 160°C, the temperature of the third zone is 190°C, the temperature of the fourth and fifth zones is 200°C, the temperature of the sixth zone is 190°C, the residence time is 90s, and the extruded product is cooled and pelletized in a circulating water bath to obtain a crosslinked polypropylene resin.

[0118] Test Case

[0119] The following properties were measured using the cross-linked polypropylene resin prepared in the above examples and the polypropylene resin prepared in the comparative examples. The results are shown in Table 1.

[0120] Melt index determination method: Determined in accordance with GB / T3682-2000 method.

[0121] Melting temperature was measured by differential scanning calorimetry (DSC).

[0122] Determination method of xylene room temperature soluble matter: Determine according to GB / T24282-2021 method.

[0123] Determination method of the actual graft content of the grafted component: H NMR spectroscopy ( 1 H-NMR) determination.

[0124] 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%.

[0125] Notched impact strength determination method: Determined in accordance with GB / T1043.1-2008 method.

[0126] Determination method of flexural modulus: Determined in accordance with GB / T9341-2008 method.

[0127] Determination method of flexural strength: Determined in accordance with GB / T9341-2008 method.

[0128] Table 1

[0129]

[0130] 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 polypropylene resin are significantly improved, which shows that crosslinking has a significant effect on improving the mechanical properties of the material.

[0131] 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 polypropylene resin are significantly improved, which shows that crosslinking has a significant effect on improving the mechanical properties of the material.

[0132] 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 polypropylene resin are significantly improved, which shows that crosslinking has a significant effect on improving the mechanical properties of the material.

[0133] On the other hand, the cross-linked polypropylene prepared by the present method has thermoplasticity. Different from the traditional irreversible cross-linked polymer, the cross-linked polypropylene 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 polypropylene is not much different from that of the raw polypropylene. This is a feature of the polypropylene prepared by the present method, that is, the material has repeatable processability; and the reversible cross-linked network can be repeatedly realized multiple times, so that the material will not cause performance degradation after multiple processing (see the comparison of Example 1, Example 4, Example 5, Example 6 and the comparison of Example 9 and 10).

[0134] In particular, the crosslinking of the present invention is reversible, and the gel content in the products of all the embodiments is almost undetectable, which can well solve the gelation phenomenon easily caused by traditional irreversible crosslinking (Comparative Example 6).

[0135] 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 polypropylene resin composition, characterized in that The composition comprises: polypropylene 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 acrylate group which may have a substituent; The cross-linking component is shown in the following formula (II): In formula (II), R 2 It is a straight chain 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 polypropylene 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 polypropylene resin, the amount of the graft component is 1-4 parts by weight, the amount of the free radical initiator is 0.1-0.3 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 It is a methyl acrylate group or a methyl methacrylate group.

4. The composition according to any one of claims 1 to 3, wherein In formula (II), R2 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 (230° C., 2.16 Kg) of the polypropylene resin is preferably 1-100 g / 10 min.

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 polypropylene resin composition further comprises a free radical stabilizer; Preferably, the free radical stabilizer is one or more of a hindered phenol antioxidant, a phosphite 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 polypropylene resin.

8. A cross-linked polypropylene resin obtained by melt extrusion of a cross-linked polypropylene resin composition, characterized in that: The cross-linked polypropylene resin composition is the cross-linked polypropylene resin composition according to any one of claims 1 to 6.

9. The cross-linked polypropylene resin according to claim 8, wherein The melt extrusion is carried out in an extruder; Preferably, the extruder is a twin-screw extruder having at least six zones, wherein the temperature of the first zone is higher than 90°C, the temperature of the second zone is higher than 150°C, the temperature of the third zone is higher than 180°C, and the temperature of any subsequent zone is higher than 190°C and lower than 230°C.

10. The cross-linked polypropylene resin according to claim 8, wherein The weight of the grafted component grafted into the polypropylene resin accounts for 0.01-5% by weight of the cross-linked polypropylene resin, preferably 0.2-2%.

11. Use of the cross-linked polypropylene resin composition according to any one of claims 1 to 7 or the cross-linked polypropylene resin according to any one of claims 8 to 10 in the preparation of polypropylene molded products.

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