A low metal content polyphenylene ether resin and a method for making the same

Abstract

This invention belongs to the field of polymers, specifically relating to a low-metal-content polyphenylene ether resin and its preparation method. The method includes the following steps: (1) oxidative coupling reaction of phenolic monomers, an oxidant, and a catalyst in a solvent to obtain a polyphenylene ether precipitate solution; the solvent includes a poor solvent for polyphenylene ether, and the catalyst contains metal ions for catalyzing the oxidative coupling reaction; (2) adding a chelating agent to the polyphenylene ether precipitate solution to allow the chelating agent to chelate with the metal ions, and filtering to obtain a filter cake; (3) first washing the filter cake with a mixed solution of a second amine and a first detergent, and then washing the filter cake with a second detergent to obtain the polyphenylene ether resin; the total metal element content of the polyphenylene ether resin is ≤0.5ppm. This method does not require increasing the amount of washing liquid, does not require significant adjustments to the post-treatment process, is easy to operate, and has good results.

Description

Technical Field

[0001] This invention belongs to the field of polymers, and specifically relates to a low-metal-content polyphenylene ether resin and its preparation method. Background Technology

[0002] Polyphenylene oxide (PPO) or polyethylene ether (PPE) is one of the world's five major general-purpose engineering plastics. It possesses excellent high and low temperature resistance, good mechanical properties and dimensional stability, as well as good hot water resistance and creep resistance. Furthermore, the PPO molecular chain exhibits high symmetry and low polarity, resulting in a low and stable dielectric constant and low dielectric loss. PPO is widely used in electronics, automotive, machinery manufacturing, office equipment, aerospace, and other fields. With the development of 5G communication technology, PPO, due to its excellent dielectric properties, has been widely developed and applied in 5G radomes, signal transmission base stations, electronic circuit boards, and other communication applications.

[0003] Polyphenylene ether (PPE) production involves two polymerization processes: solution polymerization and precipitation polymerization. The precipitation process involves preparing a PPE precipitate through oxidative coupling of phenolic monomers, a catalyst, and a certain proportion of good / bad solvents, followed by filtration, washing, and drying to obtain PPE powder. Precipitation polymerization offers advantages such as simple production processes and a narrow molecular weight distribution of the product; however, the PPE produced using this process has a higher metal content. Copper-amine catalysts are required in the preparation of precipitation polymerization PPE. First, residual copper ions significantly affect the dielectric properties and weather resistance of PPE, impacting its application in high-frequency and high-speed fields. Second, high copper content leads to decreased thermal stability of PPE during high-temperature processing, accelerating material aging and decomposition, and limiting the application range of PPE. Third, copper ions may react with oxygen and moisture in the air to form colored oxides or complexes, causing gradual discoloration of the material and affecting the whiteness and transparency of the PPE. Finally, high copper content can also negatively impact the processing performance of polyphenylene ether. Copper ions may react with other metal components in the processing equipment to form deposits that are difficult to remove, increasing equipment maintenance costs.

[0004] Authorized patent CN101717502B discloses a method for removing copper ions from a polyphenylene ether (PPE) reaction mixture. This method employs a precipitation-based PPE polymerization process, adding an electrostatic dehydration tank in the post-treatment step to treat the copper ions in the material. This reduces the copper ion content in the PPE reaction mixture entering the filter, lowering the impurity copper content in the PPE product to below 3 ppm. However, this method requires additional equipment, increasing costs and process complexity. Furthermore, the copper content in PPE products prepared using this method remains relatively high, hindering the expansion of PPE's application range.

[0005] Therefore, it is necessary to develop a simpler, more efficient, and more economical precipitation process for preparing polyphenylene ether with low metal element content. Summary of the Invention

[0006] The purpose of this invention is to provide a low-metal-content polyphenylene ether resin and its preparation method.

[0007] A first aspect of the present invention provides a method for preparing polyphenylene ether resin, the method comprising the steps of:

[0008] (1) A phenolic monomer, an oxidant, and a catalyst are subjected to an oxidative coupling reaction in a good solvent and a poor solvent of polyphenylene ether to obtain a polyphenylene ether precipitate solution; the catalyst contains metal ions for catalyzing the oxidative coupling reaction.

[0009] (2) Add a chelating agent to the polyphenylene ether precipitation solution to allow the chelating agent to chelate with the metal ions, and filter to obtain a filter cake;

[0010] (3) First, the filter cake is washed with a mixed solution of the second amine and the first detergent, and then the filter cake is washed with the second detergent to obtain the polyphenylene ether resin.

[0011] In one or more embodiments, the total metal element content of the polyphenylene ether resin is ≤0.5ppm.

[0012] In one or more embodiments, the phenolic monomer has the structure shown in Formula I:

[0013]

[0014] And / or,

[0015] The polyphenylene ether resin has repeating structural units as shown in Formula II:

[0016]

[0018] In Formulas I and II, R1, R2 and R3 are each independently selected from hydrogen, C1-C10 alkyl, halogen, halogenated C1-C10 alkane and C1-C10 alkoxy, and n is the number of repeating structural units.

[0019] In one or more embodiments, the catalyst further includes a ligand capable of complexing with the metal ion, the ligand comprising a first amine.

[0020] In one or more embodiments, the first amine is selected from (Ra')3N and (Rb')2N(CH2). tOne or more of N(Rc')2, wherein each Ra', each Rb' and each Rc' is independently selected from hydrogen and C1-C10 alkyl, and t is 1, 2, 3, 4, 5 or 6.

[0021] In one or more embodiments, the second amine is selected from (Ra)3N and (Rb)2N(CH2). m One or more of N(Rc)2, wherein each Ra, each Rb and each Rc is independently selected from hydrogen and C1-C10 alkyl, and m is 1, 2, 3, 4, 5 or 6;

[0022] In one or more embodiments, the solvent further includes a good solvent for polyphenylene ether.

[0023] In one or more embodiments, the oxidant includes oxygen.

[0024] In one or more embodiments, the metal ion is selected from one or more of copper ions, manganese ions, cobalt ions, and chromium ions.

[0025] In one or more embodiments, the phenolic monomer is selected from one or more of o-methylphenol, 2,3-dimethylphenol, 2,6-dimethylphenol, 2,3,6-trimethylphenol, and 2,6-diethylphenol.

[0026] In one or more embodiments, the good solvent for the polyphenylene ether is selected from one or more of benzene, toluene, xylene, chlorobenzene, and trimethylbenzene.

[0027] In one or more embodiments, the inferior solvent for the polyphenylene ether is selected from one or more of methanol, ethanol, isopropanol, cyclohexane, and n-heptane.

[0028] In one or more embodiments, the first amine and the second amine are each independently selected from one or more of the following: n-propylamine, isopropylamine, n-butylamine, sec-butylamine, tert-butylamine, n-pentylamine, n-hexylamine, cyclohexylamine, di-n-propylamine, di-n-butylamine, di-tert-butylamine, n-butyl-n-pentylamine, di-n-hexylamine, N,N'-di-tert-butylethylenediamine, triethylamine, tri-n-propylamine, tri-n-butylamine, dimethyl-n-butylamine, dimethyl-n-pentylamine, N,N,N',N'-tetramethylethylenediamine, and N,N,N',N'-tetramethylpropylenediamine.

[0029] In one or more embodiments, the chelating agent is selected from one or more of EDTA, EDTA-Na, EDTA-2Na, EDTA-3Na, EDTA-4Na, citric acid, sodium citrate, and NTA (trisodium triacetate).

[0030] In one or more embodiments, the first detergent and the second detergent are each independently selected from one or more inferior solvents of the polyphenylene ether.

[0031] In one or more embodiments, the metal ion is a copper ion.

[0032] In one or more embodiments, the phenolic monomer is 2,6-dimethylphenol.

[0033] In one or more embodiments, the good solvent for the polyphenylene ether is toluene.

[0034] In one or more embodiments, the inferior solvent for the polyphenylene ether is methanol.

[0035] In one or more embodiments, the chelating agent is citric acid.

[0036] In one or more embodiments, the second amine is the same as the first amine.

[0037] In one or more embodiments, the first detergent is the same as the second detergent, preferably both being methanol.

[0038] In one or more embodiments, the mass ratio of the metal ion to the first amine in the catalyst is 1:(20-50).

[0039] In one or more embodiments, the volume ratio of the good solvent to the poor solvent of the polyphenylene ether is 1:(0.25-4).

[0040] In one or more embodiments, the mass ratio of the second amine to the first detergent is (0.0005-0.002):1.

[0041] In one or more embodiments, the temperature of the oxidative coupling reaction is 20-40°C.

[0042] In one or more embodiments, the oxidative coupling reaction takes 10-60 minutes.

[0043] In one or more embodiments, the total amount of the inferior solvent and the good solvent of the polyphenylene ether added is 4-6 times that of the phenolic monomer.

[0044] In one or more embodiments, the amount of catalyst added is 3-8 wt% of the amount of phenolic monomer added.

[0045] In one or more embodiments, the volume fraction of oxygen in the gas of the reaction system of the oxidative coupling reaction is ≥10%.

[0046] In one or more embodiments, the gas in the reaction system of the oxidative coupling reaction also includes a protective gas, such as nitrogen.

[0047] In one or more embodiments, the gas in the reaction system of the oxidative coupling reaction consists of an oxygen protective gas.

[0048] In one or more embodiments, in step (1), a melt of the phenolic monomer is passed into a mixture comprising the catalyst, a good solvent of the polyphenylene ether, and a poor solvent of the polyphenylene ether.

[0049] In one or more embodiments, the chelation reaction is carried out at a temperature of 40-60°C.

[0050] In one or more embodiments, the chelation reaction takes 0.2-2 hours.

[0051] In one or more embodiments, the amount of the chelating agent added is 0.1-1 wt% of the amount of the phenolic monomer added.

[0052] In one or more embodiments, in step (2), a solution containing a chelating agent is added to the polyphenylene ether precipitate, wherein the solvent of the solution containing the chelating agent is a poor solvent for the polyphenylene ether; preferably, the mass fraction of the chelating agent in the solution containing the chelating agent is 20-60 wt%.

[0053] In one or more embodiments, the amount of the second amine added is 0.1-0.5 wt% of the phenolic monomer.

[0054] In one or more embodiments, the amount of the first detergent added is 2-3 times that of the phenolic monomer.

[0055] In one or more embodiments, the amount of the second detergent added is 2-3 times that of the phenolic monomer.

[0056] In one or more embodiments, the polyphenylene ether resin has an intrinsic viscosity of 0.05-0.8 dL / g in a chloroform solution at 25°C, preferably 0.3-0.6 dL / g.

[0057] In one or more embodiments, the yellow index of the polyphenylene ether resin is ≤5.5.

[0058] In a second aspect, the present invention provides a polyphenylene ether resin, wherein the total content of metal elements in the polyphenylene ether is ≤0.5ppm.

[0059] In one or more embodiments, the polyphenylene ether resin has an intrinsic viscosity of 0.05-0.8 dL / g in a chloroform solution at 25°C, preferably 0.3-0.6 dL / g.

[0060] In one or more embodiments, the yellow index of the polyphenylene ether resin is ≤5.5.

[0061] In one or more embodiments, the polyphenylene ether resin is prepared using the method described in the first aspect of the present invention.

[0062] The present invention has the following beneficial effects:

[0063] This invention provides a simple method for reducing the metal element content in precipitated polyphenylene ether (PPE) products. This method is easy to operate, requires no additional equipment, and significantly reduces the metal element content, effectively improving the quality of PPE products and their resistance to heat and oxygen aging, thus broadening their applications. Furthermore, the amine introduced into the washing liquid is preferentially selected from those used in the polymerization process, and the amine can be recovered in subsequent processes, further reducing the cost of introducing amines. Moreover, it avoids introducing other types of products into the polymerization reaction system, which is beneficial for stable production during the polymerization process.

[0064] This invention provides a simplified precipitation method for preparing polyphenylene ether (PPE) with low metal element content. By introducing different types of amines into the washing solution during the post-treatment washing stage of PPE, the preparation of PPE with low metal element content is achieved, reducing the metal element content to ≤0.5 ppm. This invention only introduces amines into the washing solution without increasing the amount of washing solution or requiring significant adjustments to the post-treatment process. It is convenient to operate and yields good results. Detailed Implementation

[0065] To enable those skilled in the art to understand the features and effects of the present invention, the terms and expressions used in the specification and claims are explained and defined in general below. Unless otherwise specified, all technical and scientific terms used herein have the ordinary meaning understood by those skilled in the art regarding the present invention, and in case of conflict, the definitions in this specification shall prevail.

[0066] The theories or mechanisms described and disclosed herein, whether right or wrong, should not in any way limit the scope of the invention, that is, the contents of the invention can be implemented without being limited by any particular theory or mechanism.

[0067] In this document, the terms “contains,” “includes,” “containing,” and similar terms encompass the meanings of “basically composed of” and “composed of.” For example, when this document discloses “A contains B and C,” “A is basically composed of B and C” and “A is composed of B and C” should be considered as having been disclosed in this document.

[0068] In this document, all features defined by numerical ranges or percentage ranges, such as numerical values, quantities, contents, and concentrations, are for the sake of brevity and convenience only. Accordingly, descriptions of numerical ranges or percentage ranges should be considered as covering and specifically disclosing all possible sub-ranges and individual numerical values ​​(including integers and fractions) within those ranges.

[0069] Unless otherwise specified, percentages refer to mass percentages and proportions refer to mass ratios in this article.

[0070] In this document, when describing embodiments or examples, it should be understood that it is not intended to limit the invention to those embodiments or examples. Rather, all alternatives, modifications, and equivalents of the methods and materials described herein are covered within the scope defined by the claims.

[0071] For the sake of brevity, not all possible combinations of the technical features in each implementation scheme or embodiment are described herein. Therefore, as long as there is no contradiction in the combination of these technical features, the technical features in each implementation scheme or embodiment can be combined arbitrarily, and all possible combinations should be considered within the scope of this specification.

[0072] As used herein, "alkyl" refers to a straight-chain or branched monovalent saturated hydrocarbon group having a specified number of carbon atoms. Specifically, alkyl groups are those having 1 to 10 carbon atoms ("C1-C10 alkyl"), typically containing 1 to 8 carbon atoms (C1-C8 alkyl), preferably containing 1 to 6 carbon atoms (C1-C6 alkyl), and more preferably containing 1 to 4 carbon atoms (C1-C4 alkyl). Examples of alkyl groups include, but are not limited to, methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, n-pentyl, n-hexyl, n-heptyl, n-octyl, etc.

[0073] As used in this article, "alkoxy" refers to alkyl-O-, alkyl as defined above.

[0074] As used herein, "halogenated" or "halogen" refers to elements in Group 17 with atomic numbers 9 to 85. "Halogen" or "halogen atom" refers to F, Cl, Br, and I. "Halogenated" or "halogenated" means substituted by an atom selected from F, Cl, Br, and I.

[0075] This invention employs a precipitation-based PPE polymerization process, introducing a small amount of amine into a portion of the washing liquid from the polyphenylene ether filter cake to obtain polyphenylene ether powder with low metal element content. The amine is preferably selected from the same type used in the polymerization formulation, allowing for the recovery of the washing amine during the subsequent solvent recovery stage, thus achieving amine reuse and reducing production costs.

[0076] This invention first prepares a polyphenylene ether (PPE) precipitate by oxidative coupling reaction of phenolic monomers, an oxidant, and a catalyst in a poor solvent of PPE. Then, a chelating agent is added to the PPE precipitate, which reacts with metal ions to form metal chelates. Finally, the PPE precipitate with the added chelating agent is filtered, and the filter cake is washed with an amine-containing washing solution, followed by washing with a pure washing solution. The prepared PPE resin has a metal element content of less than 0.5 ppm.

[0077] This invention provides a method for preparing polyphenylene ether resin, the method comprising the steps of:

[0078] (1) A phenolic monomer, an oxidant, and a catalyst are subjected to an oxidative coupling reaction in a solvent to obtain a polyphenylene ether precipitate solution; the solvent includes a poor solvent for polyphenylene ether, and the catalyst contains metal ions for catalyzing the oxidative coupling reaction;

[0079] (2) Add a chelating agent to the polyphenylene ether precipitation solution to allow the chelating agent to chelate with the metal ions, and filter to obtain a filter cake;

[0080] (3) First, the filter cake is washed with a mixed solution of the second amine and the first detergent, and then the filter cake is washed with the second detergent to obtain the polyphenylene ether resin;

[0081] The total metal element content of the polyphenylene ether resin is ≤0.5ppm.

[0082] In some embodiments, the phenolic monomer has the structure shown in Formula I:

[0083]

[0084] R1, R2, and R3 are each independently selected from hydrogen, C1-C10 alkyl, halogen, halogenated C1-C10 alkane, and C1-C10 alkoxy. Preferably, R1, R2, and R3 are each independently selected from hydrogen and C1-C6 alkyl. In some embodiments, the phenolic monomer is selected from one or more of o-methylphenol, 2,3-dimethylphenol, 2,6-dimethylphenol, 2,3,6-trimethylphenol, and 2,6-diethylphenol, preferably 2,6-dimethylphenol.

[0085] In this document, the catalyst also includes a ligand capable of complexing with the metal ion, the ligand preferably comprising a first amine. In some embodiments, the first amine is selected from (Ra')3N and (Rb')2N(CH2). t One or more of N(Rc')2, wherein each Ra', each Rb' and each Rc' is independently selected from hydrogen and C1-C10 alkyl, and t is 1, 2, 3, 4, 5 or 6.

[0086] In this text, the second amine is a primary, secondary, or tertiary amine commonly used in the art, as long as it has a complexing effect on metal ions. Preferably, the second amine is selected from (Ra)3N and (Rb)2N(CH2). m One or more of N(Rc)2, wherein each Ra, each Rb and each Rc is independently selected from hydrogen and C1-C10 alkyl, and m is 1, 2, 3, 4, 5 or 6.

[0087] In some embodiments, the first amine and the second amine are each independently selected from one or more of the following: n-propylamine, isopropylamine, n-butylamine, sec-butylamine, tert-butylamine, n-pentylamine, n-hexylamine, cyclohexylamine, di-n-propylamine, di-n-butylamine, di-tert-butylamine, n-butyl-n-pentylamine, di-n-hexylamine, N,N'-di-tert-butylethylenediamine, triethylamine, tri-n-propylamine, tri-n-butylamine, dimethyl-n-butylamine, dimethyl-n-pentylamine, N,N,N',N'-tetramethylethylenediamine, and N,N,N',N'-tetramethylpropylenediamine; preferably, the second amine is the same as the first amine.

[0088] The catalyst of this invention can use a metal amine composite catalyst commonly used in the preparation of polyphenylene ether. This metal amine composite catalyst is a complexing agent formed by the complexation of a metal salt and an amine compound. The complexing agent can be directly added to the reaction system, or the metal salt and amine compound can be added to the reaction system for in-situ complexation to obtain the catalyst. In some embodiments, the mass ratio of the metal ion to the first amine in the catalyst is 1:(20-50), for example, 1:20, 1:25, 1:30, 1:35, 1:40, or 1:45.

[0089] In some embodiments, the metal ion is selected from one or more of copper ions, manganese ions, cobalt ions, and chromium ions; preferably, the metal ion is a copper ion.

[0090] In some implementations, the oxidant includes oxygen.

[0091] In step (1), the solvent also includes a good solvent for polyphenylene ether.

[0092] A good solvent for polyphenylene ether can be an organic solvent containing a benzene ring. In some embodiments, the good solvent for the polyphenylene ether is selected from one or more of benzene, toluene, xylene, chlorobenzene, and trimethylbenzene; preferably, the good solvent for the polyphenylene ether is selected from toluene.

[0093] The inferior solvent for polyphenylene ether can be selected from one or more of alcoholic organic solvents and alkane organic solvents. The inferior solvent for polyphenylene ether is selected from one or more of methanol, ethanol, isopropanol, cyclohexane, and n-heptane; preferably, the inferior solvent for polyphenylene ether is selected from methanol.

[0094] In some embodiments, the volume ratio of the good solvent to the poor solvent of the polyphenylene ether is 1:(0.25-4), for example 1:0.25, 1:0.5, 1:0.75, 1:1, 1:2, 1:3, 1:4.

[0095] In some embodiments, the chelating agent is selected from one or more of EDTA, EDTA-Na, EDTA-2Na, EDTA-3Na, EDTA-4Na, citric acid, sodium citrate, and NTA (trisodium triacetate); preferably, the chelating agent is selected from citric acid.

[0096] In some embodiments, the first detergent and the second detergent are each independently selected from one or more inferior solvents of the polyphenylene ether; preferably, the first detergent and the second detergent are the same. Preferably, both the first detergent and the second detergent are methanol.

[0097] In some embodiments, the mass ratio of the second amine to the first detergent is 0.0005-0.002, for example 0.0007, 0.0009, 0.001, 0.0012, 0.0015, 0.0017, or 0.002.

[0098] In step (1), the temperature of the oxidative coupling reaction is 20-40℃, for example, 20℃, 25℃, 30℃, 35℃, or 40℃. The time of the oxidative coupling reaction is 10-60 min, for example, 10 min, 20 min, 25 min, 30 min, 35 min, 40 min, or 50 min. The total amount of the inferior solvent and the good solvent of the polyphenylene ether added is 4-6 times that of the phenolic monomer, for example, 4 times, 5 times, or 6 times. The amount of catalyst added is 3-8 wt% of the amount of phenolic monomer added, for example, 3 wt%, 4 wt%, 5 wt%, 6 wt%, 7 wt%, or 8 wt%. In the gas of the reaction system of the oxidative coupling reaction, the volume fraction of oxygen is ≥10%, for example, ≥20%, ≥30%, ≥35%, ≥40%, or ≥50%. The gas of the reaction system of the oxidative coupling reaction also includes a protective gas; preferably, the gas of the reaction system of the oxidative coupling reaction, except for oxygen, consists entirely of protective gases. The protective gas does not participate in the reaction, ensuring the stable conduct of the oxidative coupling reaction. In this document, the protective gas can be a conventional protective gas in the art, such as nitrogen or argon. In some embodiments, the melt of the phenolic monomer is passed into a mixture comprising the catalyst, a good solvent for the polyphenylene ether, and a poor solvent for the polyphenylene ether.

[0099] In step (2), the chelation reaction temperature is 40-60℃, for example, 40℃, 45℃, 50℃, 55℃, or 60℃. The chelation reaction time is 0.2-2h, for example, 0.5h, 0.8h, 1h, 1.5h, or 1.8h. The amount of chelating agent added is 0.1-1wt% of the amount of phenolic monomer added, for example, 0.1wt%, 0.2wt%, 0.4wt%, 0.5wt%, 0.8wt%, or 1wt%. In some embodiments, a solution containing a chelating agent is added to the polyphenylene ether precipitate, wherein the solvent of the solution containing the chelating agent is a poor solvent for the polyphenylene ether; preferably, the mass fraction of the chelating agent in the solution containing the chelating agent is 20-60wt%, for example, 20wt%, 30wt%, 40wt%, 50wt%, or 60wt%.

[0100] In step (3), the amount of the second amine added is 0.1-0.5 wt% of the phenolic monomer, for example, 0.1 wt%, 0.2 wt%, 0.3 wt%, 0.4 wt%, or 0.5 wt%. The amount of the first detergent added is 2-3 times the amount of the phenolic monomer, for example, 2 times, 2.2 times, 2.5 times, 2.8 times, or 3 times. The amount of the second detergent added is 2-3 times the amount of the phenolic monomer, for example, 2 times, 2.2 times, 2.5 times, 2.8 times, or 3 times.

[0101] The present invention also provides a polyphenylene ether resin prepared using the method of the present invention.

[0102] In some embodiments, the polyphenylene ether resin has repeating structural units as shown in Formula II:

[0103]

[0104] In Equation II, R1, R2, and R3 are defined as described in any embodiment of this paper, and n is the number of repeating structural units.

[0105] In some embodiments, the content of metal elements in the polyphenylene ether resin is ≤0.5ppm, for example ≤0.5ppm, ≤0.4ppm, ≤0.3ppm, ≤0.2ppm, or ≤0.1ppm.

[0106] In some embodiments, the intrinsic viscosity of the polyphenylene ether resin in a chloroform solution at 25°C is 0.05-0.8 dL / g, for example 0.1 dL / g, 0.2 dL / g, 0.3 dL / g, 0.4 dL / g, 0.5 dL / g, 0.6 dL / g, 0.7 dL / g, 0.8 dL / g, preferably 0.3-0.6 dL / g.

[0107] In some embodiments, the yellowness index of the polyphenylene ether resin is ≤5.5, for example ≤5, ≤4.9, ≤4.8, ≤4.7, ≤4.6, ≤4.5, ≤4.4, ≤4.3, ≤4.2, ≤4, ≤3.

[0108] The present invention also provides a polyphenylene ether resin, wherein the total metal element content of the polyphenylene ether is ≤0.5ppm. This polyphenylene ether resin is as described in any embodiment herein. In some embodiments, the polyphenylene ether resin is prepared using the method of the present invention.

[0109] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Experimental methods in the following embodiments, unless otherwise specified, are generally performed under conventional conditions or as recommended by the manufacturer. Percentages and parts are by weight unless otherwise stated.

[0110] All ingredient quantities mentioned in the examples are by weight.

[0111] Example 1

[0112] 250 parts toluene, 250 parts methanol, and a metal amine composite catalyst (0.2 parts CuBr, 2 parts N,N-dimethylbutylamine, 1 part di-n-butylamine, and 0.5 parts N,N,N',N'-tetramethylethylenediamine) were added sequentially to the reactor. 99.9% (volume fraction) oxygen was continuously introduced to ensure that the volume fraction of oxygen in the gas of the reaction system was ≥10%. The reactor temperature was controlled at 30-35℃. 100 parts of 2,6-dimethylphenol melt were continuously added over 35 minutes. After the addition was completed, the reaction was continued at a constant temperature for 25 minutes, and then the oxygen supply was stopped to obtain a polyphenylene ether precipitate.

[0113] One part of methanol solution containing 40 wt% citric acid was added to the polyphenylene ether precipitate. The reactor was heated to 50°C and kept at that temperature for 1 hour. The polyphenylene ether precipitate was then filtered to separate the filtrate containing metal chelates. The filter cake was collected and washed with 250 parts of methanol containing 0.3 parts of N,N-dimethylbutylamine. Then it was washed with 250 parts of pure methanol. After washing, it was dried to prepare a white polyphenylene ether powder with an intrinsic viscosity of 0.4 dL / g.

[0114] Example 2

[0115] Except for the post-treatment process, in which the polyphenylene ether filter cake is washed with 250 parts of methanol containing 0.1 parts of N,N-dimethylbutylamine and then washed with 250 parts of pure methanol, the other operations are the same as in Example 1.

[0116] Example 3

[0117] Except for the post-treatment process, in which the polyphenylene ether filter cake is washed with 250 parts of methanol containing 0.5 parts of N,N-dimethylbutylamine and then washed with 250 parts of pure methanol, the other operations are the same as in Example 1.

[0118] Example 4

[0119] Except for washing the polyphenylene ether filter cake with 250 parts of methanol containing 0.3 parts of di-n-butylamine during the post-treatment process, and then washing it with 250 parts of pure methanol, the other operations are the same as in Example 1.

[0120] Example 5

[0121] Except for the post-treatment process, in which the polyphenylene ether filter cake is washed with 250 parts of methanol containing 0.3 parts of triethylamine and then washed with 250 parts of pure methanol, the other operations are the same as in Example 1.

[0122] Comparative Example 1

[0123] Except for washing the polyphenylene ether filter cake with 500 parts of pure methanol during the post-treatment process, the other operations are the same as in Example 1.

[0124] Comparative Example 2

[0125] Except for the post-treatment process of washing the polyphenylene ether filter cake with 500 parts of methanol containing 0.3 parts of N,N-dimethylbutylamine, omitting the pure methanol washing step, the other operations are the same as in Example 1.

[0126] Test case

[0127] Metal element content testing: Polyphenylene ether was digested using a digester, then filtered, and the content was determined using atomic absorption spectrometry. In the examples and comparative examples described in this paper, copper salt was used as a catalyst, and only the copper element content was tested.

[0128] Intrinsic viscosity: At 25°C, polyphenylene ether was prepared into a solution of 0.005 g / mL with chloroform, and then measured with an Ubbelohde viscometer.

[0129] Yellow index of polyphenylene ether: The prepared polyphenylene ether powder is placed in a cuvette and tested using an X-Rite colorimeter.

[0130] The parameters of the polyphenylene ethers prepared in Examples 1-5 and Comparative Examples 1-2 are shown in Table 1.

[0131] Table 1

[0132]

[0133]

[0134] In summary, introducing a small amount of amine into the washing solution during the post-processing stage is beneficial for reducing the content of metal elements (copper) in polyphenylene ether powder. Increasing the amount of amine in the washing solution to a certain range has little effect on the content of metal elements (copper) in polyphenylene ether powder. However, after the filter cake is washed with amine-containing washing solution, it needs to be washed with pure solvent. Otherwise, some of the amine in the washing solution will remain on the polyphenylene ether product, causing the yellow index of the polyphenylene ether powder to increase.

Claims

1. A method for producing a polyphenylene ether resin, characterized by, The method includes the following steps: (1) A phenolic monomer, an oxidant, and a catalyst are subjected to an oxidative coupling reaction in a solvent to obtain a polyphenylene ether precipitate solution; the solvent includes a poor solvent for polyphenylene ether, and the catalyst contains metal ions for catalyzing the oxidative coupling reaction; (2) Add a chelating agent to the polyphenylene ether precipitation solution to allow the chelating agent to chelate with the metal ions, and filter to obtain a filter cake; (3) First, the filter cake is washed with a mixed solution of the second amine and the first detergent, and then the filter cake is washed with the second detergent to obtain the polyphenylene ether resin; The total metal element content of the polyphenylene ether resin is ≤0.5ppm.

2. The method as described in claim 1, characterized in that: The phenolic monomer has the structure shown in Formula I: And / or, The polyphenylene ether resin has repeating structural units as shown in Formula II: In Formulas I and II, R1, R2 and R3 are each independently selected from hydrogen, C1-C10 alkyl, halogen, halogenated C1-C10 alkane and C1-C10 alkoxy, and n is the number of repeating structural units.

3. The method of claim 1, wherein, The method has one or more of the following characteristics: The catalyst further includes a ligand capable of complexing with the metal ion, the ligand comprising a first amine; preferably, the first amine is selected from (Ra')3N and (Rb')2N(CH2). t One or more of N(Rc')2, wherein each Ra', each Rb' and each Rc' is independently selected from hydrogen and C1-C10 alkyl, and t is 1, 2, 3, 4, 5 or 6; said second amine is selected from the group consisting of (Ra)3N and (Rb)2N(CH2) m one or more of N(Rc)2, each Ra, each Rb, and each Rc is each independently selected from the group consisting of hydrogen and C1-C10 alkyl, and m is 1, 2, 3, 4, 5, or 6. The solvent also includes a good solvent for polyphenylene ether.

4. The method of claim 3, wherein, The method has one or more of the following characteristics: The oxidant includes oxygen; The metal ion is selected from one or more of copper ions, manganese ions, cobalt ions, and chromium ions; The phenolic monomer is selected from one or more of o-methylphenol, 2,3-dimethylphenol, 2,6-dimethylphenol, 2,3,6-trimethylphenol and 2,6-diethylphenol; The good solvent for the polyphenylene ether is selected from one or more of benzene, toluene, xylene, chlorobenzene, and trimethylbenzene; The inferior solvent for the polyphenylene ether is selected from one or more of methanol, ethanol, isopropanol, cyclohexane, and n-heptane; The first amine and the second amine are each independently selected from one or more of the following: n-propylamine, isopropylamine, n-butylamine, sec-butylamine, tert-butylamine, n-pentylamine, n-hexylamine, cyclohexylamine, di-n-propylamine, di-n-butylamine, di-tert-butylamine, n-butyl-n-pentylamine, di-n-hexylamine, N,N'-di-tert-butylethylenediamine, triethylamine, tri-n-propylamine, tri-n-butylamine, dimethyl-n-butylamine, dimethyl-n-pentylamine, N,N,N',N'-tetramethylethylenediamine, and N,N,N',N'-tetramethylpropylenediamine. The chelating agent is selected from one or more of EDTA, EDTA-Na, EDTA-2Na, EDTA-3Na, EDTA-4Na, citric acid, sodium citrate, and NTA (trisodium triacetate); The first detergent and the second detergent are each independently selected from one or more inferior solvents of the polyphenylene ether.

5. The method of claim 3, wherein, The method has one or more of the following characteristics: The metal ion is a copper ion; The phenolic monomer is 2,6-dimethylphenol; The good solvent for the polyphenylene ether is toluene; The inferior solvent for the polyphenylene ether is methanol; The chelating agent is citric acid; The second amine is the same as the first amine; The first detergent is the same as the second detergent, preferably both being methanol.

6. The method of any one of claims 3-5, wherein, The method has one or more of the following characteristics: In the catalyst, the mass ratio of the metal ion to the first amine is 1:(20-50); The volume ratio of the good solvent to the poor solvent of the polyphenylene ether is 1:(0.25-4); The mass ratio of the second amine to the first detergent is (0.0005-0.002):

1.

7. The method of any one of claims 3-5, wherein, The method has one or more of the following characteristics: The temperature of the oxidative coupling reaction is 20-40℃; The time for the oxidative coupling reaction is 10-60 min; The total amount of the inferior solvent and the good solvent of the polyphenylene ether added is 4-6 times that of the phenolic monomer; The amount of catalyst added is 3-8 wt% of the amount of phenolic monomer added; In the gas of the reaction system of the oxidative coupling reaction, the volume fraction of oxygen is ≥10%; preferably, the gas of the reaction system of the oxidative coupling reaction also includes a protective gas; In step (1), the melt of the phenolic monomer is introduced into a mixture comprising the catalyst, a good solvent of the polyphenylene ether, and a poor solvent of the polyphenylene ether; The chelation reaction is carried out at a temperature of 40-60℃. The chelation reaction takes 0.2-2 hours; The amount of the chelating agent added is 0.1-1 wt% of the amount of the phenolic monomer added; In step (2), a solution containing a chelating agent is added to the polyphenylene ether precipitate, wherein the solvent of the solution containing the chelating agent is a poor solvent for the polyphenylene ether; preferably, the mass fraction of the chelating agent in the solution containing the chelating agent is 20-60 wt%. The amount of the second amine added is 0.1-0.5 wt% of the phenolic monomer; The amount of the first detergent added is 2-3 times that of the phenolic monomer; The amount of the second detergent added is 2-3 times that of the phenolic monomer.

8. The method of claim 1, wherein, The polyphenylene ether resin has one or more of the following characteristics: The intrinsic viscosity of the polyphenylene ether resin in a chloroform solution at 25°C is 0.05-0.8 dL / g, preferably 0.3-0.6 dL / g; The yellow index of the polyphenylene ether resin is ≤5.

5.

9. A polyphenylene ether resin characterized by comprising: The total metal element content of the polyphenylene ether is ≤0.5ppm; Preferably, the intrinsic viscosity of the polyphenylene ether resin in a chloroform solution at 25°C is 0.05-0.8 dL / g, more preferably 0.3-0.6 dL / g; Preferably, the yellow index of the polyphenylene ether resin is ≤5.

5.

10. The polyphenylene ether resin according to Claim 9, wherein The polyphenylene ether resin is prepared by the method described in any one of claims 1-8.

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