Maleic anhydride copolymer and preparation method thereof

Abstract

The invention relates to a maleic anhydride copolymer and a preparation method thereof. The maleic anhydride-based copolymer of the present invention comprises (i) a structure formed by reacting an anhydride group derived from a maleic anhydride-based monomer with a chain extender, (ii) a structure formed by reacting an anhydride group derived from a maleic anhydride-based monomer with a pretreatment agent, and (iii) optionally a monomer unit derived from a maleic anhydride-based monomer, wherein the chain extender is selected from one or more of dihydric alcohol, alcohol amine and diamine; the pretreatment agent is selected from one or more of monohydric alcohol and monoamine; wherein based on the total mole number of (i), (ii) and (iii), the content of (ii) is 25-70 mol%. The maleic anhydride copolymer disclosed by the invention is high in molecular weight and low in gel rate. The preparation method of the maleic anhydride copolymer is high in universality.

Description

Technical Field

[0001] The present invention belongs to the field of polymer materials, and particularly relates to a maleic anhydride-based copolymer and a preparation method thereof. Background Art

[0002] Maleic anhydride copolymers have many excellent properties such as good processability, strong adhesion performance, and high reaction activity, and have good application prospects in many fields such as automobiles, building materials, medicine, and electronic appliances.

[0003] Currently, the production capacity of olefin resources is in excess, and there are a large number of mixed olefin resources in the coal and petrochemical industries (such as coal tar, Fischer-Tropsch synthesis oil, C5-C9). These resources are currently mainly used to produce low-value-added products and have not been effectively developed. To improve their utilization value, innovative strategies are urgently needed to convert them into high-value-added chemicals and materials.

[0004] In the prior art, it has been proposed to copolymerize such olefins with maleic anhydride to obtain copolymers. For example, Patent Document 1 discloses a method for copolymerizing the dephenolized phenol oil fraction in coal tar with maleic anhydride to prepare polymer particles. Patent Document 2 discloses a method for copolymerizing Fischer-Tropsch synthesis oil with maleic anhydride. Patent Document 3 discloses a method for preparing a copolymer of mixed C5 and maleic anhydride using self-stabilized precipitation polymerization technology.

[0005] However, due to the influence of the properties of the monomers themselves and the inhibitors in the mixed olefins, the molecular weights of the obtained copolymers are generally low, which limits their application scope. For example, the molecular weight of the dephenolized phenol oil-maleic anhydride copolymer is about 20 kg / mol, the weight average molecular weight of the Fischer-Tropsch synthesis oil-maleic anhydride copolymer usually does not exceed 10 kg / mol, and the molecular weight of the mixed C5-maleic anhydride copolymer is about 15 kg / mol. The low molecular weight makes it difficult for these polymers to meet the requirements of high-performance materials, and increasing their molecular weight will greatly expand their application scope.

[0006] Currently, the methods for increasing the molecular weight of polymers mainly include optimizing the polymerization reaction conditions, introducing special initiators, etc. However, due to the influence of the properties of the monomers themselves and the inhibitors in the mixed olefins, these methods have limited effects on increasing the molecular weight of maleic anhydride copolymers.

[0007] As a simple and economical method, the chain extension reaction can not only increase the molecular weight of the polymer, but also introduce special functional groups for modification. For example, Non-Patent Document 1 discloses a method for increasing the molecular weight of a maleic anhydride / dicyclopentadiene copolymer by carrying out controlled polycondensation with various diols. Non-Patent Document 2 also discloses a method for increasing the molecular weight by reacting a polystyrene-maleic anhydride copolymer with ethylene glycol.

[0008] Prior Art Documents

[0009] Patent Documents

[0010] Patent Document 1: CN115652474A

[0011] Patent Document 2: CN117417481A

[0012] Patent Document 3: CN115926024A

[0013] Non - patent literature

[0014] Non - patent literature 1: Marculescu, B.; Rusen, E.; Marinescu, E.; Albu, A.M.; Vasilescu, D.S. Controlled branching of the copolymer maleic anhydride - dicyclopentadiene by condensation with various glycols. Rev. Chim. 2004, 55(9), 690 - 693;

[0015] Non - patent literature 2: Krüger, S.; Krahl, F.; Arndt, K.F. Random cross - linked poly(styrene - co - maleic anhydride): Characterization of cross - linking intermediates by size exclusion chromatography. Eur. Polym. J. 2010, 46(5), 1040 - 1048. Summary of the invention

[0016] Problems to be solved by the invention

[0017] In a conventional chain - extension reaction system, a combination of a difunctional polymer (A2) and a difunctional chain extender (B2) is usually adopted. Compared with this typical A2 + B2 type linear chain - extension system, since the maleic anhydride copolymer is a multifunctional polymer (An, n >> 2), when reacting with the chain extender, multiple active sites are likely to trigger the formation of a three - dimensional network structure (gel), which is not conducive to the application of the material. Such problems exist in both Non - patent literature 1 and Non - patent literature 2.

[0018] Therefore, considering aspects such as optimizing the polymer properties and improving the utilization rate of olefin resources, it is of great practical significance to develop a maleic anhydride - based copolymer with high molecular weight and low gel fraction, and at the same time develop a simple, universal and effective method for chain - extending maleic anhydride - based copolymers to reduce the gel content.

[0019] An object of the present invention is to provide a maleic anhydride-based copolymer having a high molecular weight and a low gel fraction.

[0020] Another object of the present invention is to provide a method for preparing the maleic anhydride-based copolymer of the present invention, that is, to provide a chain extension method for a maleic anhydride-based copolymer having a high product molecular weight, a low gel content, and high universality.

[0021] Solution for solving the problem

[0022] In view of the above problems, the inventors of the present invention have conducted long-term and in-depth research and found that pretreating the raw material maleic anhydride-based copolymer with a monofunctional amine or alcohol before the chain extension reaction can significantly reduce the gel content of the chain extension reaction product, thereby completing the present invention.

[0023] Specifically, the present invention solves the problems of the present invention through the following solutions.

[0024] [1] A maleic anhydride-based copolymer, comprising:

[0025] (i) a structure formed by reacting an acid anhydride group derived from a maleic anhydride-based monomer with a chain extender;

[0026] (ii) a structure formed by reacting an acid anhydride group derived from a maleic anhydride-based monomer with a pretreatment agent; and

[0027] (iii) optionally monomer units derived from maleic anhydride-based monomers;

[0028] wherein, the chain extender is one or more selected from diols, alkanolamines, and diamines;

[0029] the pretreatment agent is one or more selected from monohydric alcohols and monoamines;

[0030] wherein, based on the total molar amount of (i), (ii), and (iii), the content of (ii) is 25 to 70 mol%.

[0031] [2] The maleic anhydride-based copolymer according to [1], wherein the gel content is 10% or less.

[0032] [3] The maleic anhydride-based copolymer according to [1], wherein, based on the total molar amount of (i), (ii), and (iii), the content of (ii) is 28 to 65 mol%, preferably 30 to 60 mol%.

[0033] [4] The maleic anhydride-based copolymer according to [1], further comprising monomer units derived from olefin monomers.

[0034] [5] A method for chain extending a maleic anhydride-based copolymer, comprising the following steps:

[0035] (a) React the raw material maleic anhydride copolymer with a pretreatment agent to obtain a pretreated maleic anhydride copolymer; and

[0036] (b) React the pretreated maleic anhydride copolymer with a chain extender to obtain a chain-extended maleic anhydride copolymer;

[0037] Wherein, the pretreatment agent is one or more selected from monohydric alcohols and monoamines; based on the total molar number of monomer units having acid anhydride groups in the raw material maleic anhydride copolymer, the dosage of the pretreatment agent in step (a) is 25 to 70 mol%;

[0038] The chain extender is one or more selected from dihydric alcohols, amino alcohols and diamines.

[0039] [6] The chain extension method according to [5], wherein,

[0040] In step (a), dissolve the raw material maleic anhydride copolymer in a solvent, then add the pretreatment agent and an optional catalyst, and react the acid anhydride groups in the raw material maleic anhydride copolymer with the pretreatment agent;

[0041] In step (b), add the chain extender to the reaction solution obtained in step (a) to carry out a chain extension reaction to obtain a chain-extended maleic anhydride copolymer.

[0042] [7] The chain extension method according to [5], wherein the solvent is at least one selected from acetone, methyl ethyl ketone, N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone, dimethyl sulfoxide;

[0043] The reaction temperature in step (a) is 20 to 80 °C, and the reaction time is 0.5 to 48 h; the reaction temperature in step (b) is -30 to 100 °C, and the reaction time is 1 to 100 h.

[0044] [8] The chain extension method according to [5], wherein the raw material maleic anhydride copolymer is a maleic anhydride-olefin copolymer;

[0045] Based on the total molar number of the raw material maleic anhydride copolymer, the dosage of the chain extender in step (b) is 1 to 30 times;

[0046] The weight average molecular weight of the chain-extended maleic anhydride copolymer is more than 10 times that of the raw material maleic anhydride copolymer.

[0047] [9] According to the chain extension method described in [5], wherein the catalyst is one or more selected from basic catalysts and acidic catalysts; the acidic catalyst is preferably sulfuric acid, hydrochloric acid, p-toluenesulfonic acid, acetic acid, propionic acid, butyric acid; the basic catalyst is triethylamine, sodium ethoxide, sodium methoxide, sodium hydroxide, potassium hydroxide, 4-dimethylaminopyridine; the amount of the catalyst is 0 to 20% by weight of the raw material maleic anhydride-based copolymer, preferably 1 to 10% by weight.

[0048]

[10] The chain-extended maleic anhydride-based copolymer obtained by the chain extension method of [5] to [9].

[0049] Effects of the Invention

[0050] The maleic anhydride copolymer (chain extension reaction product) of the present invention has a high molecular weight and a low gel fraction. For example, the gel content can be 10% by mass or even lower.

[0051] The chain extension method of the present invention can greatly increase the molecular weight of the copolymer and control the gel content to a low value. For example, the weight average molecular weight of the chain-extended product can reach more than 10 times that of the original copolymer, and the gel content can be 10% by mass or even lower.

[0052] The chain extension method of the present invention has strong universality and is applicable to various maleic anhydride copolymers, such as various maleic anhydride-olefin copolymers, including but not limited to styrene-maleic anhydride, dephenolized phenol oil-maleic anhydride, Fischer-Tropsch synthesis oil-maleic anhydride, C5-maleic anhydride and other copolymers. Brief Description of the Drawings

[0053] Figure 1 (a) is the gel permeation chromatography curve of the chain-extended products at different reaction times in Comparative Example 1.

[0054] Figure 1 (b) is the molecular weight and gel content of the chain-extended products at different reaction times in Comparative Example 1.

[0055] Figure 2 Shows the weight average molecular weight and gel content of the chain-extended products obtained at different dosages of the pretreatment agent in Comparative Examples 1 to 3 and Examples 1 to 3. Detailed Description of the Invention

[0056] Hereinafter, the content of the present invention will be described in detail. The description of the technical features recorded below is based on the representative embodiments and specific examples of the present invention, but the present invention is not limited to these embodiments and specific examples.

[0057] <Terms and Definitions>

[0058] In this specification, unless otherwise clearly stated, "alkyl" means a linear, branched or cyclic alkyl group.

[0059] In this specification, the numerical range expressed as "numerical value A to numerical value B" means a range including the endpoint numerical values A and B.

[0060] In this specification, the numerical range expressed as "above" or "below" means a numerical range including this number.

[0061] In this specification, the meaning expressed by "may" includes both meanings of performing a certain treatment and not performing a certain treatment.

[0062] In this specification, "optionally" or "optional" means that certain substances, components, execution steps, applied conditions and other factors are used or not used.

[0063] In this specification, the unit names used are all international standard unit names, and if not otherwise specified, the "%" used represents the weight or mass percentage content.

[0064] In this specification, the "preferred embodiment", "embodiment", etc. mentioned refer to that the specific elements related to the embodiment (for example, features, structures, properties and / or characteristics) are included in at least one of the embodiments described herein, and may exist in other embodiments or may not exist in other embodiments. In addition, it should be understood that the elements can be combined in various embodiments in any suitable manner.

[0065] <Maleic anhydride-based copolymer>

[0066] The object of the present invention is to provide a maleic anhydride-based copolymer, which comprises the following:

[0067] (i) A structure formed by the reaction of an anhydride group derived from a maleic anhydride-based monomer with a chain extender;

[0068] (ii) A structure formed by the reaction of an anhydride group derived from a maleic anhydride-based monomer with a pretreatment agent, and

[0069] (iii) Optionally, monomer units derived from maleic anhydride-based monomers;

[0070] Wherein, the chain extender is one or more selected from diols, alkanolamines and diamines;

[0071] The pretreatment agent is one or more selected from monohydric alcohols and monoamines;

[0072] Wherein, based on the total molar amount of (i), (ii) and (iii), the content of (ii) is 25 to 70 mol%.

[0073] In some embodiments, the maleic anhydride-based copolymer of the present invention further comprises monomer units derived from olefin monomers.

[0074] Specifically, the olefin monomer may be at least one selected from aliphatic monoolefins or diolefins having 2 to 20 carbon atoms, styrene and its derivatives, and polycyclic aromatic olefins.

[0075] Preferably, the olefin monomer is at least one selected from ethylene, propylene, isobutene, butadiene, isoprene, cyclopentadiene, dicyclopentadiene, styrene and its derivatives, indene, benzofuran, and benzothiophene.

[0076] Preferably, the olefin monomer is derived from at least one of the following raw materials: C4 fraction, C5 fraction, C8 fraction, C9 fraction, ethylene tar, crude gasoline, by-product fractions above C4 from coal-to-olefins, coal tar, and coal liquefaction. Among them, the C4 fraction is preferably selected from refinery C4 and naphtha cracking C4, and the crude gasoline is preferably selected from pre-ether gasoline, catalytic cracking gasoline, catalytic hydrogenation gasoline, and coking gasoline.

[0077] In some embodiments, the maleic anhydride-based copolymer of the present invention is obtained by chain extension of a raw material maleic anhydride-based copolymer (for example, by chain extension reaction with a chain extender). The raw material maleic anhydride-based copolymer may be a maleic anhydride-olefin copolymer, and the olefin therein may be those described above. More specific examples of the raw material maleic anhydride-based copolymer include, but are not limited to, styrene-maleic anhydride copolymer, dephenolized phenol oil-maleic anhydride copolymer, Fischer-Tropsch synthesis oil-maleic anhydride copolymer, C5-maleic anhydride copolymer, etc.

[0078] The maleic anhydride-based copolymer of the present invention has a high molecular weight and a low gel content.

[0079] In some embodiments, the weight-average molecular weight of the maleic anhydride-based copolymer of the present invention is 100,000 or more, preferably 110,000 or more, more preferably 120,000 or more, further preferably 130,000 or more, and also for example 140,000 or more, 150,000 or more, etc. High molecular weight polymers have significant mechanical property advantages. For example, the entanglement density of the molecular chains of high molecular weight polymers increases, endowing the material with higher tensile strength and toughness, and is suitable for fields with demanding mechanical strength requirements such as automotive bumpers and UAV fuselage frames; when forming a film from a solution, the dense packing of high molecular chains can form a low-porosity coating, which can significantly improve the dielectric strength and permeability resistance in the fields of lithium-ion battery separator coating or anti-corrosion coating. There is no particular limitation on the upper limit of the weight-average molecular weight. For example, it may be 1,500,000 or less, and also for example 1,000,000 or less, and also for example 800,000 or less, 700,000 or less, 600,000 or less, 500,000 or less, etc.

[0080] The weight-average molecular weight described in this specification is measured by gel permeation chromatography, and the specific measurement method is as described in the Examples section.

[0081] In some embodiments, the gel content of the maleic anhydride-based copolymer of the present invention is 10% or less, preferably 9% or less, more preferably 8% or less, and also for example 7% or less, 6% or less, 5% or less, 4% or less, 3% or less, etc. The low gel content reduces heterogeneous impurities, avoids local stress concentration caused by gel clusters, and improves the long-term service stability of the material. For example, the growth of lithium dendrites in a lithium battery separator is closely related to the uniformity of the pores in the separator. If there are gel particles or impurities in the separator, it will lead to uneven local pore distribution, forming weak areas, and lithium dendrites are more likely to penetrate the separator at these locations, causing a short circuit. The elimination of gel particles improves the uniformity of the pore distribution in the separator and reduces the probability of lithium dendrite puncture short circuit. There is no particular limitation on the lower limit of the gel content in the present invention. From the perspective of easy implementation, the lower limit of the gel content can be 1% or more, and also for example 2% or more, etc.

[0082] The gel content described in this specification is measured by the weighing method, specifically as described in the Examples section.

[0083] In some embodiments, in the maleic anhydride-based copolymer of the present invention, based on the total molar amount of (i), (ii), and (iii), the content of (ii) is 25 to 70 mol%, preferably 28 to 65 mol%, more preferably 30 to 60 mol%, and also for example 55%, 50%, 45%, 40%, etc.

[0084] In some embodiments, in the maleic anhydride-based copolymer of the present invention, based on the total molar amount of (i), (ii), and (iii), the content of (i) is 5 to 75 mol%, preferably 10 to 70 mol%, more preferably 15 to 65 mol%.

[0085] In some embodiments, in the maleic anhydride-based copolymer of the present invention, based on the total molar amount of (i), (ii), and (iii), the content of (iii) is 0 to 70 mol%, preferably 0 to 60 mol%, more preferably 5 to 50 mol%.

[0086] In some embodiments, in the maleic anhydride-based copolymer of the present invention, based on the total molar amount of monomer units, the total amount of (i), (ii), and (iii) is 35 to 65 mol%.

[0087] In embodiments including monomer units derived from an olefin monomer, based on the total molar amount of monomer units (for example, (i), (ii), (iii), and olefin monomer units), the amount of monomer units derived from the olefin monomer is 35 to 65 mol%.

[0088] The pretreatment agent is one or more selected from monohydric alcohols and monoamines. Preferably, the monoamine is at least one of ammonia (ammonia gas, aqueous ammonia), methylamine, ethylamine, propylamine, butylamine, aniline; the monohydric alcohol is at least one selected from methanol, ethanol, propanol, butanol, benzyl alcohol, cyclohexanol.

[0089] The diol as the chain extender can be an aliphatic diol, polyoxyalkylene diol, etc. The aliphatic diol is preferably a straight-chain or branched-chain alkyl diol having 2 to 10 carbon atoms, and the polyoxyalkylene diol is preferably polyethylene glycol, polypropylene glycol, etc. The number-average molecular weight of the polyoxyalkylene diol is 200 to 8000 (preferably 500 to 6000). In a preferred embodiment, examples of the diol include, but are not limited to, ethylene glycol, propylene glycol, 1,4-butanediol, 1,6-hexanediol, pentanediol, polyethylene glycol, polypropylene glycol, diethylene glycol, tetraethylene glycol.

[0090] Examples of the alkanolamine as the chain extender include, but are not limited to, ethanolamine, diethanolamine, triethanolamine, diisopropanolamine, N-methylethanolamine, N-methyldiethanolamine, etc.

[0091] The diamine as the chain extender can be an aliphatic diamine, aromatic diamine, polyether diamine, etc. In a preferred embodiment, examples of the diamine include, but are not limited to, ethylenediamine, propylenediamine, butylenediamine, hexamethylenediamine, polyether diamine (the number-average molecular weight is preferably 230 to 5000), p-phenylenediamine, m-phenylenediamine, o-phenylenediamine, N,N'-dimethyl-1,6-hexanediamine, piperazine.

[0092] In some embodiments, the maleic anhydride-based copolymer of the present invention can be obtained by the chain extension method described below. Therefore, the maleic anhydride-based copolymer of the present invention is preferably an extended maleic anhydride-based copolymer obtained by the chain extension method described below.

[0093] <Chain extension method>

[0094] Another object of the present invention is to provide a method for extending a maleic anhydride-based copolymer, which is characterized by comprising the following steps:

[0095] (a) Reacting the raw material maleic anhydride-based copolymer with a pretreatment agent to obtain a pretreated maleic anhydride-based copolymer; and

[0096] (b) Reacting the pretreated maleic anhydride-based copolymer with a chain extender to obtain an extended maleic anhydride-based copolymer;

[0097] Wherein, the pretreatment agent is one or more selected from monohydric alcohols and monoamines; based on the total molar number of the monomer units having acid anhydride groups in the raw material maleic anhydride-based copolymer, the dosage of the pretreatment agent in step (a) is 25 to 70 mol%;

[0098] The chain extender is one or more selected from diols, alkanolamines, and diamines.

[0099] In some embodiments, the chain extension method of the present invention further comprises the following steps:

[0100] (c) Separating the chain-extended maleic anhydride-based copolymer from the reaction solution obtained in step (b), and optionally purifying it.

[0101] In particular, the chain extension method of the present invention is a method for preparing the maleic anhydride-based copolymer of the present invention described above.

[0102] The following separately describes each step of the chain extension method of the present invention.

[0103] Step (a)

[0104] In step (a), the raw material maleic anhydride-based copolymer is pretreated with a pretreatment agent.

[0105] In some embodiments, the pretreatment in step (a) is carried out in a solvent, preferably in the presence of a catalyst.

[0106] In a specific embodiment, in step (a), the raw material maleic anhydride-based copolymer is dissolved in a solvent, and then a pretreatment agent and an optional catalyst are added to react the anhydride groups in the raw material maleic anhydride-based copolymer with the pretreatment agent.

[0107] In some embodiments, the solvent is at least one selected from acetone, butanone, N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone, and dimethyl sulfoxide.

[0108] In some embodiments, the reaction temperature in step (a) is 20 to 80 °C.

[0109] In some embodiments, the reaction time in step (a) is 0.5 to 48 h.

[0110] In the chain extension method of the present invention, by pretreating the raw material maleic anhydride-based copolymer with a pretreatment agent, it is possible to significantly reduce the gel content in the chain-extended copolymer while increasing the molecular weight after the chain extension reaction. In some embodiments, the gel content in the chain-extended copolymer can be 10% or less, preferably 9% or less, more preferably 8% or less, and also for example 7% or less, 6% or less, 5% or less, 4% or less, 3% or less, etc. The beneficial effects brought about by the low gel content are as described above. The present invention has no particular limitation on the lower limit of the gel content. From the perspective of easy implementation, the lower limit of the gel content can be 1% or more, and also for example 2% or more, etc.

[0111] The pretreatment agent used in step (a) may be those described above for the maleic anhydride-based copolymer of the present invention.

[0112] In a preferred embodiment, based on the total molar amount of monomer units having an anhydride group in the raw material maleic anhydride-based copolymer, the amount of the pretreatment agent used in step (a) is 25 to 70 mol%, preferably 28 to 65 mol%, more preferably 30 to 60 mol%, and also, for example, 55%, 50%, 45%, 40%, etc.

[0113] The raw material maleic anhydride-based copolymer used in step (a) may be those described above.

[0114] In some embodiments, based on the mass of the raw material maleic anhydride-based copolymer, the amount of the solvent is 100 to 1000% by weight.

[0115] In some embodiments, the catalyst is one or more selected from basic catalysts and acidic catalysts; the acidic catalyst is preferably sulfuric acid, hydrochloric acid, p-toluenesulfonic acid, acetic acid, propionic acid, butyric acid; the basic catalyst is preferably triethylamine, sodium ethoxide, sodium methoxide, sodium hydroxide, potassium hydroxide, 4-dimethylaminopyridine.

[0116] In some embodiments, the amount of the catalyst used is 0 to 20% by weight of the raw material maleic anhydride-based copolymer, preferably 1 to 10% by weight.

[0117] Step (b)

[0118] In step (b), the pretreated maleic anhydride-based copolymer is subjected to a chain extension reaction with a chain extender to obtain a chain-extended maleic anhydride-based copolymer.

[0119] In some embodiments, in step (b), a chain extender is added to the reaction solution obtained in step (a) to carry out a chain extension reaction.

[0120] The chain extender used in step (b) may specifically be those described above.

[0121] The catalyst added in step (a) also functions as a catalyst in the chain extension reaction.

[0122] In some embodiments, based on the total molar amount of the raw material maleic anhydride-based copolymer, the amount of the chain extender used in step (b) is 1 to 30 times, preferably 5 to 25 times, more preferably 5 to 15 times.

[0123] In some embodiments, the temperature of the chain extension reaction is -30 to 100 °C, and the reaction time is 1 to 100 h, preferably 10 to 100 h.

[0124] In one embodiment, the chain extender is a diol, and the temperature of the chain extension reaction is 20 to 100 °C, preferably 70 to 90 °C.

[0125] In one embodiment, the chain extender is an alkanolamine, and the temperature of the chain extension reaction is 10 to 100 °C, preferably 20 to 50 °C.

[0126] In one embodiment, the chain extender is a diamine, and the temperature of the chain extension reaction is -30 to 80 °C, preferably -20 to 20 °C.

[0127] In some embodiments, the weight-average molecular weight of the chain-extended maleic anhydride copolymer obtained in step (b) is more than 3 times, preferably more than 5 times, preferably more than 10 times, more preferably more than 15 times, and still more preferably more than 20 times that of the raw material maleic anhydride copolymer. There is no particular limitation on the upper limit. From the perspective of easy implementation, for example, it is 80 times or less, or for example 75 times or less or 70 times or less.

[0128] In some embodiments, the solid content of the system in step (b) is 5 to 60% by weight, preferably 10 to 30% by weight.

[0129] Step (c)

[0130] In step (c), the chain-extended maleic anhydride copolymer is separated and optionally purified.

[0131] In some embodiments, the reaction solution obtained in step (b) is filtered, the obtained filtrate is mixed with a precipitating agent, and then the obtained precipitate is separated. Preferably, the precipitate is further washed and dried.

[0132] In some embodiments, the precipitating agent is at least one selected from ether solvents and alcohol solvents. Ether solvents include diethyl ether, petroleum ether, dimethyl ether, methyl ethyl ether, ethyl propyl ether, dipropyl ether, dibutyl ether, methyl propyl ether, methyl butyl ether, methyl isobutyl ether, methyl tert-butyl ether, methyl isopentyl ether, methyl tert-pentyl ether, methyl cyclopentyl ether, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, etc.; the alcohol solvent can be an alkyl alcohol, such as a C1-C8 alkyl alcohol, and specific examples include but are not limited to methanol, ethanol, propanol, isopropanol, butanol, tert-butanol, etc.

[0133] The present invention also correspondingly relates to a chain-extended maleic anhydride copolymer obtained by the chain extension method of the present invention.

[0134] Examples

[0135] The embodiments of the present invention will be described in detail below in conjunction with examples. However, those skilled in the art will understand that the following examples are only used to illustrate the present invention and should not be construed as limiting the scope of the present invention. For those not specified in the examples, they are carried out under conventional conditions or conditions recommended by the manufacturer. For reagents or instruments not specified by the manufacturer, they are all conventional products that can be obtained commercially.

[0136] The descriptions of the raw materials used in the following examples are as follows:

[0137] Styrene-maleic anhydride copolymer: Mn = 7.6 kg / mol, Mw = 12 kg / mol, PDI = 1.63.

[0138] Dephenolized phenol oil-maleic anhydride copolymer: The weight-average molecular weight is 18 kg / mol.

[0139] Fischer-Tropsch synthesis oil-maleic anhydride copolymer: The weight-average molecular weight is 8.3 kg / mol.

[0140] C5-maleic anhydride copolymer: The weight-average molecular weight is 14.9 kg / mol.

[0141] The weight-average molecular weight of the chain-extended product in the following examples was determined by gel permeation chromatography. The gel permeation chromatography equipment was an Agilent 1260 Infinity II chromatograph, equipped with a differential detector and a PLgel 10 μm Mixed-B 300×7.5 mm chromatographic column. The mobile phase used was N,N-dimethylformamide containing 10 mmol / L lithium bromide, and it was eluted at a flow rate of 1.0 mL / min at 30 °C. A poly(methyl methacrylate) standard with a narrow molecular weight distribution (relative molecular weight of 1010 - 2210000 g·mol -1 ) was used to establish a calibration curve.

[0142] The gel content of the chain-extended product was determined by the weighing method as follows.

[0143] The reaction solution was filtered through a polytetrafluoroethylene membrane with a pore size of 0.22 μm. The filtered membrane and the gel remaining on the membrane were dried and weighed (W1). A precipitating agent was added to the collected filtrate, centrifuged, and the precipitate was washed. Then, it was dried to a constant weight in a vacuum oven and the precipitate was weighed (W2). The gel content was calculated according to the following formula:

[0144]

[0145] Wherein,

[0146] W0: The weight of the dry membrane weighed before use,

[0147] W1: Dry weight of the filtered membrane and the gel remaining on the membrane

[0148] W2: Dry weight of the precipitate collected from the filtrate.

[0149] Comparative Example 1

[0150] Dissolve 2 g of styrene-maleic anhydride copolymer (SMA) in 17.6 g of methyl ethyl ketone solvent, then add 0.3 g of 1,6-hexanediol and 0.1 g of propionic acid, and ultrasonically dissolve and mix evenly to obtain a clear and transparent solution, and stir and react at 80 °C.

[0151] Samples were taken from the reaction system at 0 (before the reaction was carried out by heating), 8, 24, 48, 72, and 96 hours of reaction, filtered through a 0.22 μm membrane, the filtrate was precipitated with ether and centrifuged, and then the precipitate was washed with ether and centrifuged three times, and then placed in a vacuum oven to dry to a constant weight, thus obtaining the esterification chain-extended products of styrene-maleic anhydride copolymer at different reaction times. The weight-average molecular weight and gel content of the chain-extended products at each reaction time were measured.

[0152] Comparative Example 2

[0153] Dissolve 2 g of styrene-maleic anhydride copolymer in 17.55 g of methyl ethyl ketone solvent, then add 0.05 g of ethanol and 0.1 g of propionic acid, and stir and pretreat at 80 °C for 48 h. Then add 0.3 g of 1,6-hexanediol to the pretreated solution, ultrasonically dissolve and mix evenly to obtain a clear and transparent solution, and stir at 80 °C for chain extension reaction.

[0154] During the reaction, samples were taken at different times, filtered through a 0.22 μm membrane, the filtrate was precipitated with ether and centrifuged, and then the precipitate was washed with ether and centrifuged three times, and then placed in a vacuum oven to dry to a constant weight, thus obtaining the esterification chain-extended products of styrene-maleic anhydride copolymer. The weight-average molecular weight and gel content of the chain-extended products at each reaction time were measured.

[0155] Comparative Example 3

[0156] Dissolve 2 g of styrene-maleic anhydride copolymer in 17.5 g of methyl ethyl ketone solvent, then add 0.1 g of ethanol and 0.1 g of propionic acid, and stir and pretreat at 80 °C for 48 h. Then add 0.3 g of 1,6-hexanediol to the pretreated solution, ultrasonically dissolve and mix evenly to obtain a clear and transparent solution, and stir at 80 °C for chain extension reaction.

[0157] During the reaction, samples were taken at different times, filtered through a 0.22 μm filter membrane, the filtrate was precipitated with ether and centrifuged, and then the precipitate was washed with ether and centrifuged three times, and then placed in a vacuum oven to dry to a constant weight, thus obtaining the esterification chain-extended product of styrene-maleic anhydride copolymer. The weight-average molecular weight and gel content of the chain-extended product at each reaction time were measured.

[0158] Example 1

[0159] Dissolve 2 g of styrene-maleic anhydride copolymer in 17.45 g of methyl ethyl ketone solvent, then add 0.15 g of ethanol and 0.1 g of propionic acid, and stir at 80 °C for 48 h for pretreatment. Then add 0.3 g of 1,6-hexanediol to the pretreated solution, and ultrasonically dissolve and mix evenly to obtain a clear and transparent solution, and stir at 80 °C for chain extension reaction.

[0160] During the reaction, samples were taken at different times, filtered through a 0.22 μm filter membrane, the filtrate was precipitated with ether and centrifuged, and then the precipitate was washed with ether and centrifuged three times, and then placed in a vacuum oven to dry to a constant weight, thus obtaining the esterification chain-extended product of styrene-maleic anhydride copolymer. The weight-average molecular weight and gel content of the chain-extended product at each reaction time were measured.

[0161] Example 2

[0162] Dissolve 2 g of styrene-maleic anhydride copolymer in 17.35 g of methyl ethyl ketone solvent, then add 0.25 g of ethanol and 0.1 g of propionic acid, and stir at 80 °C for 48 h for pretreatment. Then add 0.3 g of 1,6-hexanediol to the pretreated solution, and ultrasonically dissolve and mix evenly to obtain a clear and transparent solution, and stir at 80 °C for chain extension reaction.

[0163] During the reaction, samples were taken at different times, filtered through a 0.22 μm filter membrane, the filtrate was precipitated with ether and centrifuged, and then the precipitate was washed with ether and centrifuged three times, and then placed in a vacuum oven to dry to a constant weight, thus obtaining the esterification chain-extended product of styrene-maleic anhydride copolymer. The weight-average molecular weight and gel content of the chain-extended product at each reaction time were measured.

[0164] Example 3

[0165] Dissolve 2 g of styrene-maleic anhydride copolymer in 17.25 g of methyl ethyl ketone solvent, then add 0.35 g of ethanol and 0.1 g of propionic acid, and stir at 80 °C for 48 h for pretreatment. Then add 0.3 g of 1,6-hexanediol to the pretreated solution, and ultrasonically dissolve and mix evenly to obtain a clear and transparent solution, and stir at 80 °C for chain extension reaction.

[0166] During the reaction, samples were taken at different times, filtered through a 0.22 μm filter membrane, the filtrate was precipitated with diethyl ether and centrifuged, and then the precipitate was washed with diethyl ether and centrifuged three times, and then placed in a vacuum oven to dry to a constant weight, thus obtaining the esterification chain-extended product of styrene-maleic anhydride copolymer. The weight-average molecular weight and gel content of the chain-extended product at each reaction time were measured.

[0167] The raw material dosages, product weight-average molecular weights and gel contents in Comparative Examples 1-3 and Examples 1-3 are shown in Table 1.

[0168] Table 1

[0169]

[0170] *: Relative to the molar dosage of maleic anhydride monomer units in the initial copolymer

[0171] **: Relative to the molar dosage of the initial copolymer

[0172] Example 4

[0173] Dissolve 2 g of styrene-maleic anhydride copolymer in 17.35 g of N,N-dimethylformamide solvent, add 0.25 g of ethanol and 0.1 g of 4-dimethylaminopyridine thereto, and stir at 80 °C for 48 h for pretreatment. Then add 0.3 g of 1,6-hexanediol to the pretreated solution, and ultrasonically dissolve and mix it evenly to obtain a clear and transparent solution, and stir at 80 °C for 48 h for chain extension reaction.

[0174] After the reaction was completed, the reaction solution was filtered through a 0.22 μm filter membrane, the filtrate was precipitated with ethanol and centrifuged, and then the precipitate was washed with ethanol and centrifuged three times, and then placed in a vacuum oven to dry to a constant weight, thus obtaining the esterification chain-extended product of styrene-maleic anhydride copolymer.

[0175] The weight-average molecular weight of the product was increased to 237.5 kg / mol, and the gel content was 4.3%.

[0176] Comparative Example 4

[0177] Dissolve 2 g of styrene-maleic anhydride copolymer in 17.8 g of N-methylpyrrolidone solvent, and then add 0.2 g of piperazine, and ultrasonically dissolve and mix it evenly to obtain a clear and transparent solution, and react at -20 °C for 72 h.

[0178] After the reaction was completed, the reaction solution was filtered through a 0.22 μm filter membrane, the filtrate was precipitated with diethyl ether and centrifuged, and then the precipitate was washed with diethyl ether and centrifuged three times, and then placed in a vacuum oven to dry to a constant weight, thus obtaining the amination chain-extended product of styrene-maleic anhydride copolymer.

[0179] The weight-average molecular weight of the product was increased to 192.6 kg / mol, and the gel content was 12.3%.

[0180] Example 5

[0181] Dissolve 2 g of styrene-maleic anhydride copolymer in 17.52 g of N-methylpyrrolidone solvent, then add 0.28 g of aniline, and stir at room temperature for 2 h for pretreatment. Then add 0.2 g of piperazine to the pretreated solution, and use ultrasound to dissolve and mix it evenly to obtain a clear and transparent solution, and react at -20 °C for 96 h.

[0182] After the reaction is completed, the reaction solution is filtered through a 0.22 μm filter membrane, the filtrate is precipitated with ether and centrifuged, and then the precipitate is washed with ether and centrifuged three times, and then placed in a vacuum oven to dry to constant weight, that is, an amine-extended chain product of styrene-maleic anhydride copolymer is obtained.

[0183] The weight-average molecular weight of the product is increased to 180.5 kg / mol, and the gel content is 5.4%.

[0184] Comparative Example 5

[0185] Dissolve 2 g of styrene-maleic anhydride copolymer in 10 g of N-methylpyrrolidone, and then add 0.2 g of N-methylethanolamine dropwise to the copolymer solution at a stirring speed of 700 rpm. After the addition is completed, continue to stir and react at room temperature for 30 h.

[0186] After the reaction is completed, the reaction solution is passed through a 0.22 μm filter membrane, the filtrate is precipitated with ether and centrifuged, and then the precipitate is washed with ether and centrifuged three times, and then placed in a vacuum oven to dry to constant weight, that is, an alcohol-amine extended chain product of styrene-maleic anhydride copolymer is obtained.

[0187] The weight-average molecular weight of the product is increased to 205.4 kg / mol, and the gel content is 18.2%.

[0188] Example 6

[0189] Dissolve 2 g of styrene-maleic anhydride copolymer in 10 g of N-methylpyrrolidone, then add 0.2 mL of concentrated ammonia water, and stir at room temperature for 2 h for pretreatment. Then add 0.2 g of N-methylethanolamine dropwise to the pretreated solution at a stirring speed of 700 rpm. After the addition is completed, continue to stir and react at room temperature for 40 h.

[0190] After the reaction is completed, the reaction solution is filtered through a 0.22 μm filter membrane, the filtrate is precipitated with ether and centrifuged, and then the precipitate is washed with ether and centrifuged three times, and then placed in a vacuum oven to dry to constant weight, that is, an alcohol-amine extended chain product of styrene-maleic anhydride copolymer is obtained.

[0191] The weight-average molecular weight of the product is increased to 221.3 kg / mol, and the gel content is 5.2%.

[0192] The raw material dosages, product weight-average molecular weights, gel contents, etc. in Comparative Examples 4 and 5 and Examples 4 to 6 are shown in Table 2.

[0193] Table 2

[0194]

[0195] *: relative to the molar dosage of maleic anhydride monomer units in the initial copolymer

[0196] **: relative to the molar dosage of the initial copolymer

[0197] Example 7

[0198] Dissolve 2 g of the dephenolized phenol oil-maleic anhydride copolymer in 6.69 g of methyl ethyl ketone solvent, then add 0.21 g of ethanol and 0.2 g of propionic acid, and stir and pretreat at 80 °C for 48 h. Then add 0.9 g of 1,6-hexanediol to the pretreated solution, and ultrasonically dissolve and mix evenly to obtain a clear and transparent solution. Stir at 80 °C for 96 h for chain extension reaction.

[0199] After the reaction is completed, the reaction solution is filtered through a 0.22 μm filter membrane, the filtrate is precipitated with ether and centrifuged, and then the precipitate is washed and centrifuged three times with ether, and then placed in a vacuum oven to dry to constant weight, thus obtaining the esterification chain extension product of the dephenolized phenol oil-maleic anhydride copolymer.

[0200] The weight-average molecular weight of the product is increased to 1249.5 kg / mol, and the gel content is 9.6%.

[0201] Comparative Example 6

[0202] Dissolve 2 g of the dephenolized phenol oil-maleic anhydride copolymer in 7.44 g of N-methylpyrrolidone solvent, and then add 0.56 g of N,N'-dimethyl-1,6-hexanediamine to the copolymer solution at a stirring speed of 700 rpm, and stir and react at room temperature for 24 h.

[0203] After the reaction is completed, the reaction solution is filtered through a 0.22 μm filter membrane, the filtrate is precipitated with ether and centrifuged, and then the precipitate is washed and centrifuged three times with ether, and then placed in a vacuum oven to dry to constant weight, thus obtaining the amination chain extension product of the dephenolized phenol oil-maleic anhydride copolymer.

[0204] The weight-average molecular weight of the product is increased to 338.5 kg / mol, and the gel content is 19.8%.

[0205] Example 8

[0206] Dissolve 2 g of dephenolized phenol oil - maleic anhydride copolymer in 7.2 g of N - methylpyrrolidone solvent, then add 0.24 g of butylamine, and stir and pretreat at room temperature for 2 h. Subsequently, add 0.56 g of N,N’ - dimethyl - 1,6 - hexanediamine to the copolymer solution at a stirring speed of 700 rpm, and stir and react at room temperature for 30 h.

[0207] After the reaction is completed, the reaction solution is filtered through a 0.22 - μm filter membrane. The filtrate is precipitated with ether and centrifuged. Then the precipitate is washed with ether and centrifuged three times, and then placed in a vacuum oven to dry to constant weight, thus obtaining the aminated chain - extended product of the dephenolized phenol oil - maleic anhydride copolymer.

[0208] The weight - average molecular weight of the product is increased to 353.4 kg / mol, and the gel content is 8.1%.

[0209] Example 9

[0210] Dissolve 2 g of dephenolized phenol oil - maleic anhydride copolymer in 7.44 g of N,N - dimethylformamide solvent, then add 0.2 g of propylamine, and stir and pretreat at room temperature for 2 h. Subsequently, add 0.46 g of monoethanolamine to the copolymer solution at a stirring speed of 700 rpm, and stir and react at room temperature for 30 h.

[0211] After the reaction is completed, the reaction solution is filtered through a 0.22 - μm filter membrane. The filtrate is precipitated with methanol and centrifuged. Then the precipitate is washed with methanol and centrifuged three times, and then placed in a vacuum oven to dry to constant weight, thus obtaining the alkanolamine chain - extended product of the dephenolized phenol oil - maleic anhydride copolymer.

[0212] The weight - average molecular weight of the product is increased to 463.2 kg / mol, and the gel content is 9.3%.

[0213] The raw material dosages, weight - average molecular weights of the products, gel contents, etc. in Comparative Example 6 and Examples 7 - 9 are shown in Table 3.

[0214] Table 3

[0215]

[0216] *: Relative to the molar dosage of maleic anhydride monomer units in the initial copolymer

[0217] **: Relative to the molar dosage of the initial copolymer

[0218] Comparative Example 7

[0219] Dissolve 2 g of Fischer - Tropsch synthesis oil - maleic anhydride copolymer in 17.42 g of butanone, then add 0.38 g of polypropylene glycol - 1000 and 0.2 g of acetic acid, and stir and react at 80 °C for 48 h.

[0220] After the reaction was completed, the reaction solution was filtered through a 0.22 μm filter membrane. The filtrate was precipitated with petroleum ether and centrifuged. The precipitate was then washed with petroleum ether and centrifuged three times, and then placed in a vacuum oven to dry to a constant weight, thus obtaining the esterification chain-extended product of the Fischer-Tropsch synthesis oil-maleic anhydride copolymer.

[0221] The weight-average molecular weight of the product was increased to 123.2 kg / mol, and the gel content was 13.4%.

[0222] Example 10

[0223] Dissolve 2 g of the Fischer-Tropsch synthesis oil-maleic anhydride copolymer in 17.12 g of methyl ethyl ketone. Add 0.3 g of benzyl alcohol and 0.2 g of acetic acid to the solution, and stir at 80 °C for 48 h for pretreatment. Then add 0.38 g of polypropylene glycol-1000 to the pretreated solution, and stir and react at 80 °C for 72 h.

[0224] After the reaction was completed, the reaction solution was filtered through a 0.22 μm filter membrane. The filtrate was precipitated with petroleum ether and centrifuged. The precipitate was then washed with petroleum ether and centrifuged three times, and then placed in a vacuum oven to dry to a constant weight, thus obtaining the esterification chain-extended product of the Fischer-Tropsch synthesis oil-maleic anhydride copolymer.

[0225] The weight-average molecular weight of the product was increased to 113.5 kg / mol, and the gel content was 4.8%.

[0226] Example 11

[0227] Dissolve 2 g of the Fischer-Tropsch synthesis oil-maleic anhydride copolymer in 17.3 g of N-methylpyrrolidone, and then add 0.16 g of propylamine, and stir at 80 °C for 2 h for pretreatment. Then add 0.4 g of diethanolamine, and stir and react at room temperature for 48 h.

[0228] After the reaction was completed, the reaction solution was filtered through a 0.22 μm filter membrane. The filtrate was precipitated with petroleum ether and centrifuged. The precipitate was then washed with petroleum ether and centrifuged three times, and then placed in a vacuum oven to dry to a constant weight, thus obtaining the alcohol-amine chain-extended product of the Fischer-Tropsch synthesis oil-maleic anhydride copolymer.

[0229] The weight-average molecular weight of the product was increased to 245.6 kg / mol, and the gel content was 8.5%.

[0230] Example 12

[0231] Dissolve 2 g of the C5-maleic anhydride copolymer in 17.15 g of methyl ethyl ketone, and then add 0.38 g of cyclohexanol and 0.2 g of propionic acid, and stir at 80 °C for 48 h for pretreatment. Then add 0.27 g of polyethylene glycol-1000 to the pretreated solution, and continue to stir at 80 °C for the chain extension reaction for 96 h.

[0232] After the reaction was completed, the reaction solution was filtered through a 0.22 μm filter membrane. The filtrate was precipitated with ether and centrifuged. Then the precipitate was washed with ether and centrifuged three times, and then placed in a vacuum oven to dry to a constant weight, thus obtaining the esterification chain-extended product of the C5-maleic anhydride copolymer.

[0233] The weight-average molecular weight of the product was increased to 156.5 kg / mol, and the gel content was 6.9%.

[0234] Comparative Example 8

[0235] Dissolve 2 g of C5-maleic anhydride copolymer in 17.42 g of N-methylpyrrolidone. Dropwise add 0.58 g of p-phenylenediamine to the copolymer solution at a stirring speed of 700 rpm, and stir and react at room temperature for 72 h.

[0236] After the reaction was completed, the reaction solution was filtered through a 0.22 μm filter membrane. The filtrate was precipitated with ether and centrifuged. Then the precipitate was washed with ether and centrifuged three times, and then placed in a vacuum oven to dry to a constant weight, thus obtaining the amination chain-extended product of the C5-maleic anhydride copolymer.

[0237] The weight-average molecular weight of the product was increased to 252.4 kg / mol, and the gel content was 19.6%.

[0238] Example 13

[0239] Dissolve 2 g of C5-maleic anhydride copolymer in 17.25 g of N-methylpyrrolidone. Add 0.22 g of propylamine thereto and stir at room temperature for 2 h for pretreatment. Subsequently, dropwise add 0.58 g of p-phenylenediamine to the pretreated solution at a stirring speed of 700 rpm, and stir and react at room temperature for 96 h.

[0240] After the reaction was completed, the reaction solution was filtered through a 0.22 μm filter membrane. The filtrate was precipitated with ether and centrifuged. Then the precipitate was washed with ether and centrifuged three times, and then placed in a vacuum oven to dry to a constant weight, thus obtaining the amination chain-extended product of the C5-maleic anhydride copolymer.

[0241] The weight-average molecular weight of the product was increased to 238.5 kg / mol, and the gel content was 7.8%.

[0242] Example 14

[0243] Dissolve 2 g of C5-maleic anhydride copolymer in 17.51 g of N-methylpyrrolidone. Add 0.22 g of propylamine thereto and stir at room temperature for 2 h for pretreatment. Subsequently, dropwise add 0.32 g of N-methyldiethanolamine to the copolymer solution at a stirring speed of 700 rpm, and stir and react at room temperature for 72 h.

[0244] After the reaction was completed, the reaction solution was filtered through a 0.22 μm filter membrane. The filtrate was precipitated with diethyl ether and centrifuged. Then the precipitate was washed with diethyl ether and centrifuged three times, and then placed in a vacuum oven to dry to a constant weight, thus obtaining the amine-extension product of the C5-maleic anhydride copolymer.

[0245] The weight-average molecular weight of the product was increased to 225.1 kg / mol, and the gel content was 6.9%.

[0246] The raw material dosages, weight-average molecular weights of the products, gel contents, etc. in Comparative Examples 7 and 8 and Examples 10 to 14 are shown in Table 4.

[0247] Table 4

[0248]

[0249] *: relative to the molar dosage of maleic anhydride monomer units in the initial copolymer

[0250] **: relative to the molar dosage of the initial copolymer

[0251] <Evaluation>

[0252] Figure 1 (a) of Figure 1 is the gel permeation chromatography curve of the extension products at different reaction times in Comparative Example 1. From Figure 1 (a) of Figure 1 , it can be seen that during the extension process, both the molecular weight and PDI of the product increased significantly.

[0253] Figure 1 (b) of Figure 1 is the molecular weight and gel content of the extension products at different reaction times in Comparative Example 1. From Figure 1 (b) of Figure 1 , it can be seen that as the extension reaction proceeds, the molecular weight and gel content of the extension products increase.

[0254] Figure 2 shows the weight-average molecular weights and gel contents of the extension products obtained at different dosages of the pretreatment agent in Comparative Example 1, Examples 1 to 4, and Comparative Example 2. From Figure 2 It can be seen that compared with Comparative Example 1 with little use of the pretreatment agent, when Examples 1 to 4 and Comparative Example 2 using the pretreatment agent obtained extension products with similar Mw, the gel content decreased. In Examples 1 to 4, as the molar ratio of the pretreatment agent to the maleic anhydride structural unit increased from 0.1 to 0.5, when obtaining extension products with similar Mw, the gel content decreased.

[0255] More specifically, in the system without adding ethanol (Comparative Example 1), when the Mw of the product increased to 370.5 kg / mol, the gel content was 41.2%; while when the ethanol dosage was 0.3 molar ratio (Example 3), when the Mw of the chain-extended product increased to a similar 314.5 kg / mol, the gel content was 9.8%. Compared with Comparative Example 1, the gel content in Example 3 was 31.4% lower. This shows that by adjusting the addition amount of ethanol, while maintaining the molecular weight of the chain-extended product, the gel content of the product can be effectively reduced.

[0256] When the ethanol dosage was continuously increased to 0.7 molar ratio (Comparative Example 2), the increase in the molecular weight of the product was not obvious. This shows that excessive monofunctional alcohol may cause excessive blocking of anhydride groups, and the remaining active sites are not sufficient to support an effective chain extension reaction, resulting in limited increase in molecular weight.

[0257] As can be seen from Tables 2 to 4, for various maleic anhydride-based copolymers, the effects of the present invention can be obtained by using various monohydric alcohols or monoamines as pretreatment agents.

[0258] Industrial Applicability

[0259] The maleic anhydride-based copolymer of the present invention can be widely used in the fields of automotive lightweight and structural protection, such as automotive bumpers and door anti-collision beams. With its high tensile strength and impact toughness, this material can meet the requirements of vehicle collision safety and lightweight design; in the field of key materials for new energy batteries, such as lithium-ion battery diaphragms and fuel cell bipolar plates, its low gel content and pore uniformity can significantly reduce the risk of battery short circuit and improve the energy density.

Claims

1. A maleic anhydride-based copolymer, characterized in that, Comprising: (i) A structure formed by the reaction of an anhydride group derived from a maleic anhydride-based monomer with a chain extender; (ii) A structure formed by the reaction of an anhydride group derived from a maleic anhydride-based monomer with a pretreatment agent; and (iii) Optionally, monomer units derived from maleic anhydride-based monomers; wherein the chain extender is one or more selected from diols, alkanolamines, and diamines; the pretreatment agent is one or more selected from monohydric alcohols and monoamines; wherein, based on the total molar amount of (i), (ii), and (iii), the content of (ii) is 25 to 70 mol%; 2. The maleic anhydride copolymer according to claim 1, characterized in that, The gel content is 10% or less.

3. The maleic anhydride copolymer according to claim 1, wherein Based on the total molar amount of (i), (ii), and (iii), the content of (ii) is 28 to 65 mol%, preferably 30 to 60 mol%.

4. The maleic anhydride-based copolymer according to claim 1, wherein, It further comprises monomer units derived from olefin monomers.

5. A chain extension method for maleic anhydride-based copolymers, characterized in that, Comprising the following steps: (a) Reacting a raw material maleic anhydride-based copolymer with a pretreatment agent to obtain a pretreated maleic anhydride-based copolymer; and (b) Reacting the pretreated maleic anhydride-based copolymer with a chain extender to obtain a chain-extended maleic anhydride-based copolymer; wherein the pretreatment agent is one or more selected from monohydric alcohols and monoamines; Based on the total molar amount of monomer units having an anhydride group in the raw material maleic anhydride-based copolymer, the amount of the pretreatment agent used in step (a) is 25 to 70 mol%; The chain extender is one or more selected from diols, alkanolamines, and diamines.

6. The chain extension method according to claim 5, characterized in that In step (a), the raw material maleic anhydride-based copolymer is dissolved in a solvent, and then a pretreatment agent and optionally a catalyst are added to react the anhydride group in the raw material maleic anhydride-based copolymer with the pretreatment agent; In step (b), a chain extender is added to the reaction solution obtained in step (a) to carry out a chain extension reaction to obtain a chain-extended maleic anhydride-based copolymer.

7. The chain extension method according to claim 6, wherein The solvent is at least one selected from acetone, butanone, N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone, and dimethyl sulfoxide; The reaction temperature in step (a) is 20 to 80 °C, and the reaction time is 0.5 to 48 h; the reaction temperature in step (b) is -30 to 100 °C, and the reaction time is 1 to 100 h.

8. The chain extension method according to claim 5, wherein The raw material maleic anhydride-based copolymer is a maleic anhydride-olefin copolymer; Based on the total molar amount of the raw material maleic anhydride-based copolymer, the amount of the chain extender used in step (b) is 1 to 30 times; The weight average molecular weight of the chain-extended maleic anhydride-based copolymer is 10 times or more that of the raw material maleic anhydride-based copolymer.

9. The chain extension method according to claim 6, wherein The catalyst is one or more selected from basic catalysts and acidic catalysts; the acidic catalyst is preferably sulfuric acid, hydrochloric acid, p-toluenesulfonic acid, acetic acid, propionic acid, butyric acid; the basic catalyst is triethylamine, sodium ethoxide, sodium methoxide, sodium hydroxide, potassium hydroxide, 4-dimethylaminopyridine; the amount of the catalyst used is 0 to 20% by weight of the raw material maleic anhydride-based copolymer, preferably 1 to 10% by weight.

10. A chain-extended maleic anhydride-based copolymer obtained by the chain extension method according to any one of claims 5 to 9.

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