Acrylonitrile-based polymer as well as preparation method and application thereof

Abstract

The invention discloses an acrylonitrile-based polymer as well as a preparation method and application thereof. The molecular weight of the polymer is 80000-200000, the polymer is a copolymer of an acrylonitrile monomer, an acrylate monomer and a third comonomer, and the acrylonitrile monomer accounts for 80-97 wt% of the total monomer; the acrylic ester monomer accounts for 2-10 wt% of the total monomer; and the third comonomer is unsaturated olefin with a specific structural formula and accounts for 1-10 wt% of the total monomer. The molecular weight of the polymer is 80000-200000, the content of iron ions in the polymer is less than 20 ppm, the particle size D90 of the powder is less than or equal to 80 microns, and the water content lt of the polymer is 1t. 1%. The preparation method of the polymer adopts a water-phase suspension polymerization route, and the flow comprises but is not limited to continuous feeding polymerization, monomer removal, acid pickling, water washing and drying. The polymer has a wide application prospect in the fields of batteries and outdoor coatings.

Description

Technical Field

[0001] The present invention belongs to the technical field of acrylonitrile-based polymers, and in particular relates to a heat-resistant and weather-resistant acrylonitrile-based polymer and a preparation method and application thereof. Background Art

[0002] Acrylonitrile (AN) has a pendant cyano group (-CN). Therefore, it is a widely used monomer in the synthesis of various organic products such as acrylonitrile fibers, resins, and plastics. It is a highly reactive compound containing both active vinyl and cyano groups. Acrylonitrile is widely used in the production of polyacrylonitrile fibers and ABS resins. Due to its excellent weather resistance, it is also used in outdoor coatings.

[0003] With the rapid development of portable electronic devices, electric vehicles, and smart grids, interest in high-energy-density lithium metal batteries is growing. Uneven exfoliation or deposition of lithium metal surfaces can lead to the growth of lithium dendrites, which can easily pierce the separator and pose a risk of battery short circuits. Furthermore, the highly reactive lithium metal continuously reacts with the electrolyte and is consumed, forming an unstable solid electrolyte interface (SEI) film, resulting in irreversible capacity loss. Therefore, balancing high energy density with high safety is a key scientific challenge that urgently needs to be addressed in the development and application of lithium metal batteries. Polyacrylonitrile (PAN) polymers, which have strong electron-withdrawing groups (C≡N), can form more stable SEI films through interaction with C=O in carbonate solvents. Therefore, PAN polymers have great potential for application in lithium metal battery electrolytes. For example, the patent "A Positive Electrode Binder and Its Preparation Method (Patent No. CN 112500817B)" discloses a positive electrode binder and its preparation method. The polyacrylonitrile in this patent is prepared by solution polymerization. After the polymerization reaction, methanol and water are added dropwise to precipitate the polymer before use. This complex process and inconvenient application make it unsuitable for industrial continuous production. Moreover, the comonomers involved in the patent all contain only one polar functional group, and the bonding performance is relatively low. The patent "A positive electrode non-fluorine lithium battery binder and its preparation method and application (CN 116731241A)" specifically relates to a positive electrode non-fluorine lithium ion battery binder, and the comonomers are acrylic monomers, acrylonitrile monomers, and oil-soluble monomers. The acrylic monomers are at least partially pre-neutralized, and after the prepared binder is applied to the positive electrode material, the battery system exhibits excellent cycle performance, low internal resistance, and low gas production. However, the acrylic monomers are pre-neutralized with lithium hydroxide, which increases the metal ion content in the polymer, which is not conducive to later preparation and use. At the same time, the comonomers involved in the patent also contain only one polar functional group. In view of the deficiencies in the above processes and in combination with market demand, the present invention has developed and provided an acrylonitrile-based polymer and a preparation method thereof, which is suitable for the battery field and the outdoor coating field. Summary of the Invention

[0004] To address the shortcomings of the aforementioned prior art and to address the polymer substrates currently needed in the battery field (not limited to lithium batteries) and outdoor coatings, the present invention provides an acrylonitrile-based polymer, its preparation method, and its application. The objectives of the present invention can be achieved through the following technical solutions:

[0005] An acrylonitrile-based polymer having a molecular weight of 80,000 to 200,000 is a copolymer of an acrylonitrile monomer, an acrylate monomer, and a third comonomer, wherein the acrylonitrile monomer accounts for 80 to 97 weight percent of the total monomers; the acrylate monomer accounts for 2 to 10 weight percent of the total monomers; and the third comonomer is an unsaturated olefin having the following structural formula, accounting for 1 to 10 weight percent of the total monomers:

[0006]

[0007] Wherein: R1 and R2 can be H, CH3; R3 can be H, CH3, COOH, CH2COOH, CONH2, CH2CONH2, CH2OH; R4 structure can be (CH2) n OH (n = 0 to 5, n is a natural number), O (CH2) m OH (m = 1 to 5, m is a natural number), (CH2) x NH2 (x=0~5, x is a natural number).

[0008] Preferably, the iron ion content in the polymer is less than 20 ppm.

[0009] Preferably, the particle size D of the polymer powder is 90 ≤80μm and moisture content <1wt%.

[0010] Preferably, the third monomer is hydroxy acrylate.

[0011] On the other hand, the present invention also provides a method for preparing the above-mentioned acrylonitrile-based polymer, which adopts an aqueous suspension polymerization route and comprises the following steps:

[0012] S1: adding acrylonitrile monomer, acrylate monomer, third comonomer and water into a polymerization kettle after being measured by flow meter according to weight percentage; wherein the acrylonitrile monomer accounts for 80wt% to 97wt% of the total monomers, the acrylate monomer accounts for 2wt% to 10wt% of the total monomers, and the third comonomer accounts for 1wt% to 10wt% of the total monomers, and the total monomer concentration in the polymerization kettle is 15wt% to 30wt%;

[0013] S2 adds the initiator system, starts polymerization stirring, and performs polymerization reaction at 30°C to 80°C. The reaction time is controlled at 0.5h to 3h to generate an acrylonitrile-based polymerization suspension; wherein the initiator system accounts for 0.01wt% to 3.5wt% of the total monomer ratio;

[0014] S3 removes monomers and performs solid-liquid separation on the acrylonitrile-based polymer suspension to form a polymer filter cake, which is then washed and dried to obtain an acrylonitrile-based polymer.

[0015] Preferably, in step S1, the proportion of acrylonitrile monomer to the total monomers is 84wt% to 96wt%, more preferably 89wt% to 91wt%, the proportion of acrylate monomer to the total monomers is 3wt% to 8wt%, the concentration range of the third monomer to the total monomers is 1wt% to 8wt%, and the total monomer concentration in the polymerization kettle is 20wt% to 30wt%.

[0016] Preferably, step S3 further includes pickling the filter cake, wherein the pickling is performed using acidic water, and the pH value of the pickling water is controlled to be between 2 and 6, preferably between 3 and 5, and then rinsed with pure water. If the pH value is too low, it is easy to cause reactions such as hydrolysis of the polymer, while if the pH value is too high, the pickling effect is not good and the metal ions cannot be effectively removed.

[0017] Preferably, in step S3, the drying conditions are: 80°C to 150°C at atmospheric pressure or 50°C to 95°C under vacuum. Drying at too high a temperature can easily cause polymer oxidation and yellowing; while drying at too low a temperature can result in insufficient drying and powder agglomeration. In step S3, the drying can be performed using heated nitrogen, preferably at a temperature of 90°C to 140°C at atmospheric pressure.

[0018] Preferably, in step S2, the initiator system is a water-soluble oxidation system initiator or reduction system initiator, wherein the oxidation system initiator is at least one of ammonium persulfate (APS), potassium persulfate (KPS), sodium chlorate or hydrogen peroxide, and the reduction system initiator is at least one of sodium sulfite, sodium bisulfite, sulfurous acid or ethylenediamine. The type and proportion of the initiator are adjusted according to the type of comonomer, and the ratio of the initiator system to the total monomer is between 0.01wt% and 3.5wt%, preferably between 0.1wt% and 3.0wt%. Finally, a high molecular weight polymer with a molecular weight between 80,000 and 200,000 can be obtained.

[0019] Preferably, in step S1, the third monomer is hydroxy acrylate, the proportion of acrylonitrile monomer to the total monomers is 89wt% to 91wt%, the acrylate monomer accounts for 3wt% to 8wt% of the total monomers, the third comonomer accounts for 1wt% to 8wt% of the total monomers, and the total monomer concentration in the polymerization kettle is 20wt% to 30wt%; in step S2, the initiator system is sodium chlorate, and the proportion of the initiator system to the total monomers is 0.1% to 0.5%.

[0020] Preferably, in step S3, the monomer removal process includes monomer removal and monomer condensation. After condensation, the monomer is separated and then enters the polymerization kettle for reuse to reduce the discharge of cyanide-containing wastewater; the reuse amount accounts for ≤50wt% of the total monomer feed to the polymerization kettle.

[0021] Preferably, in step S1, the polymerization adopts a continuous feeding and continuous discharging mode, and the feed flow rate per unit time is 1 / 3 to 2 times the volume of the polymerization kettle.

[0022] Preferably, in step S1, a portion of the monomers comes from the condensed monomers after the monomer removal, accounting for ≤50% of the total monomer amount.

[0023] Specifically, in step S3, the acidic water includes but is not limited to dilute nitric acid, dilute sulfuric acid or dilute hydrochloric acid. After the acid wash, the polymer is rinsed with pure water to remove impurities such as metal ions and acid radical ions in the polymer.

[0024] The polyacrylonitrile powder prepared by the present invention is used in the field of batteries or outdoor coatings. The prepared powder needs to be dissolved and processed in the later stage before it can be made into the required substrate. Therefore, the processability and chemical stability of the polymer powder are required to be relatively high. The content of the comonomer in step S1 has a crucial influence on the processability and chemical stability. It should be emphasized that the third monomer in the present invention is an unsaturated olefin with two or more polar functional groups, which can be but not limited to unsaturated dibasic organic acids, unsaturated diamides, unsaturated diols, unsaturated hydroxyacrylates, etc. The concentration ratio of the third monomer to the total monomer ranges from 1wt% to 10wt%, and the optimal range is from 1wt% to 8wt%. If it is too low, the adhesion of the polymer will be low; if it is too high, it will affect the heat resistance and chemical stability and will be prone to aging.

[0025] Compared with the prior art, the technical effects of the present invention are as follows:

[0026] (1) The acrylonitrile polymer powder of the present invention has a molecular weight greater than 80,000, an iron ion content in the polymer less than 20 ppm, and a powder particle size D 90 ≤80μm, has good compatibility with carbonate electrolyte, and can be used in the battery field and outdoor coating field.

[0027] (2) The preparation method of the present invention is to use acrylonitrile, acrylic esters, and an unsaturated olefin with a certain structural formula for aqueous suspension copolymerization modification. The unsaturated olefin with a specific structure has two or more polar functional groups. The polymerization adopts a continuous feeding and continuous discharging method. The monomers that do not participate in the polymerization are recycled to the polymerization kettle after being stripped and condensed. The polymer after stripping is acid-washed, water-washed and nitrogen-dried to obtain an acrylonitrile-based functional polymer material that can be used in the field of batteries and outdoor coatings. In addition to being able to prepare polymer powders specifically for batteries and outdoor coatings, the preparation method of the present invention can also achieve continuous production, reduce residual monomer emissions and reduce unit consumption. DETAILED DESCRIPTION

[0028] The following describes exemplary embodiments of the present invention in detail. Although these exemplary embodiments are described in sufficient detail to enable those skilled in the art to implement the present invention, it should be understood that other embodiments can be implemented and various changes can be made to the present invention without departing from the spirit and scope of the present invention. The principles and features of the present invention are described below in conjunction with specific embodiments. The examples are only used to explain the present invention and are not used to limit the scope of the present invention. It should be noted that for those of ordinary skill in the art, several adjustments and improvements can be made without departing from the concept of the present invention. These all fall within the scope of protection of the present invention.

[0029] The reagents used in the following examples can all be obtained through commercial sources.

[0030] Example 1

[0031] 3.2M 3 Add pure water to 5M 3 In a polymerization reactor, a third monomer is added and dissolved in water, followed by acrylonitrile (AN) and methyl acrylate (MA). Stirring is initiated, mixing thoroughly, and then heating is performed. After reaching 60°C, an initiator is added at a predetermined concentration and rapidly stirred to form a stable suspension. After a certain period of polymerization reaction, the total feed flow rate is set to 1 times the volume of the polymerization reactor, and a regulating valve is opened to automatically and continuously replenish the monomers, pure water, initiator, and other reaction materials. As the liquid level in the polymerization reactor increases, the polymer suspension overflows the polymerization reactor and is pumped to a single-acid removal tower via a transfer pump. After passing through the single-acid removal tower (absolute pressure controlled at -0.04 MPa), residual single-acid residues in the suspension are removed and condensed back into the polymerization reactor. The condensate temperature is controlled at 20°C. The polymer enters an acid wash tank for acid washing, followed by water washing and dehydration. The acid wash pH is shown in Table 1. After dehydration, the polymer is transferred to a drying system for drying at 130°C. After drying to a moisture content of less than 1wt%, a powder is prepared.

[0032] The preparation methods of Examples 2 to 11 and Comparative Examples 1 to 3 refer to Example 1, and the specific formulas refer to Table 1.

[0033] The bonding strength of the polymer was measured according to ISO 4624 (adhesion pull-off test), and the test data are shown in Table 1. The metal ion content was tested according to JC / T 2336-2015, and the test data are shown in Table 1.

[0034] Table 1 Polymerization conditions and polymer properties

[0035]

[0036]

[0037] Examples 1-11 employ aqueous suspension terpolymerization to produce polymers with molecular weights between 100,000 and 200,000, exhibiting good processability. After acid washing, the iron ion content in the polymers is less than 20 ppm. The polymers possess hydrophilic groups and exhibit good adhesion. Comparative Examples 1-3, which do not contain a third monomer, exhibit low overall adhesion and, without acid washing, have iron ion contents greater than 50 ppm. Processability is poor when the molecular weight exceeds 200,000.

[0038] The preparation methods of Comparative Examples 4 to 6 refer to Example 1, and the specific formulas refer to Table 2.

[0039] In Comparative Examples 4 to 6, the third monomer contains a polar functional group and has a certain adhesive force, but the overall adhesive force is relatively low.

[0040] Table 2 Polymerization conditions and polymer properties

[0041]

[0042] The preferred embodiments of the present invention have been specifically described above, but the present invention is not limited to the described embodiments. Those skilled in the art may make various equivalent modifications or substitutions without departing from the spirit of the present invention. These equivalent modifications or substitutions are all included in the scope defined by the claims of this application.

Claims

1. An acrylonitrile-based polymer, characterized in that: The molecular weight of the polymer is 80,000 to 200,000. The polymer is a copolymer of acrylonitrile monomer, acrylate monomer and a third comonomer, wherein the acrylonitrile monomer accounts for 80 wt% to 97 wt% of the total monomers; the acrylate monomer accounts for 2 wt% to 10 wt% of the total monomers; and the third comonomer is an unsaturated olefin having the following structural formula, accounting for 1 wt% to 10 wt% of the total monomers: Wherein: R1 and R2 can be H, CH3; R3 can be H, CH3, COOH, CH2COOH, CONH2, CH2CONH2, CH2OH; R4 structure can be (CH2) n OH (n = 0 to 5, n is a natural number), O (CH2) m OH (m = 1 to 5, m is a natural number), (CH2) x NH2 (x=0~5, x is a natural number).

2. The acrylonitrile-based polymer according to claim 1, wherein The iron ion content in the polymer is less than 20 ppm.

3. The acrylonitrile-based polymer according to claim 1 or 2, wherein The powder particle size D of the polymer 90 ≤80μm and moisture content <1wt%.

4. The method for preparing an acrylonitrile-based polymer according to claim 1, wherein The aqueous suspension polymerization route is adopted, which includes the following steps: S1: adding acrylonitrile monomer, acrylate monomer, third comonomer and water into a polymerization kettle after being measured by flow meter according to weight percentage; wherein the acrylonitrile monomer accounts for 80wt% to 97wt% of the total monomers, the acrylate monomer accounts for 2wt% to 10wt% of the total monomers, and the third comonomer accounts for 1wt% to 10wt% of the total monomers, and the total monomer concentration in the polymerization kettle is 15wt% to 30wt%; S2 adds the initiator system, starts polymerization stirring, and performs polymerization reaction at 30°C to 80°C. The reaction time is controlled at 0.5h to 3h to generate an acrylonitrile-based polymerization suspension; wherein the initiator system accounts for 0.01wt% to 3.5wt% of the total monomer ratio; S3 removes monomers and performs solid-liquid separation on the acrylonitrile-based polymer suspension to form a polymer filter cake, which is then washed and dried to obtain an acrylonitrile-based polymer.

5. The preparation method according to claim 4, wherein Step S3 also includes pickling the filter cake. The pickling is performed using acidic water. The pH value of the pickling water is controlled within a range of 2 to 6. After pickling, the filter cake is then rinsed with pure water.

6. The preparation method according to claim 4 or 5, characterized in that In step S2, the initiator system is a water-soluble oxidation system initiator or a reduction system initiator, wherein the oxidation system initiator is at least one of ammonium persulfate (APS), potassium persulfate (KPS), sodium chlorate or hydrogen peroxide, and the reduction system initiator is at least one of sodium sulfite, sodium bisulfite, sulfurous acid or ethylenediamine; the initiator system accounts for 0.1wt% to 3.0wt% of the total weight.

7. The preparation method according to claim 6, wherein In step S1, the third monomer is hydroxy acrylate, the proportion of acrylonitrile monomer to the total monomers is 89wt% to 91wt%, the acrylate monomer accounts for 3wt% to 8wt% of the total monomers, the third comonomer accounts for 1wt% to 8wt% of the total monomers, and the total monomer concentration in the polymerization kettle is 20wt% to 30wt%; in step S2, the initiator system is sodium chlorate, and the proportion of the initiator system to the total monomers is 0.1% to 0.5%.

8. The preparation method according to claim 4 or 5, characterized in that In step S3, the specific drying conditions are: 80°C to 150°C under normal pressure or 50°C to 95°C under vacuum.

9. The preparation method according to claim 4, wherein In step S3, the monomer removal process includes monomer removal and monomer condensation. After condensation, the monomer is separated and then enters the polymerization kettle for reuse to reduce the discharge of cyanide-containing wastewater; the reuse amount accounts for ≤50wt% of the total monomer feed to the polymerization kettle; in step S1, the polymerization adopts a continuous feeding and continuous discharging mode, and the feed flow rate per unit time is 1 / 3 to 2 times the volume of the polymerization kettle.

10. The use of the acrylonitrile-based polymer according to any one of claims 1 to 3, characterized in that: The polymer can be applied in the battery field or the coating field.

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