Polymer nanocomposite material, method for preparing the same, and use thereof

Abstract

The application relates to a polymer nanocomposite material and a preparation method and application thereof, relates to the material field, and the preparation method comprises the following steps: processing polyvinyl acetate grafted modified nanocellulose wet powder into a shape through a thermoplastic processing device to obtain the polymer nanocomposite material, wherein the water content of the polyvinyl acetate grafted modified nanocellulose wet powder is 8-30 wt%, and the thermoplastic processing temperature is 40-90 DEG C. The polyvinyl acetate grafted modified nanocellulose wet powder can be processed through thermoplastic processing under the condition of containing water at 40-90 DEG C, the processing temperature is not required to be 160 DEG C, the processing temperature is reduced from 160 DEG C to below 90 DEG C, the wet powder can be reprocessed through water absorption, and the processing frequency has a smaller influence on the mechanical properties of the polymer. In addition, compared with pure polyvinyl acetate, the nanocomposite material prepared by the application is more easily biodegradable, and can be completely biodegraded after being buried in the soil for 180 days.

Description

Technical Field

[0001] The present invention relates to the field of materials, and in particular to a preparation method of a polymer nanocomposite material, the polymer nanocomposite material, and applications thereof. Background Art

[0002] While plastics bring convenience to people's lives, they also cause a series of problems, particularly the environmental "white pollution" caused by petroleum-based plastics that are difficult to biodegrade. Currently, there are two approaches to address this problem: 1) recycling and reusing petroleum-based polymers; 2) using biodegradable polymers.

[0003] In fact, recycling, processing, and reuse of materials is necessary and more sustainable, whether for petroleum-based or biodegradable polymers. Melt processing is a common, easily industrialized method for polymer molding and a common means of recycling, processing, and reuse. However, high processing temperatures inevitably cause polymer degradation and chain scission during processing, reducing the material's molecular weight and ultimately degrading its mechanical properties. After repeated reprocessing, the mechanical properties of polymer materials deteriorate significantly, making them unusable. Furthermore, the small molecules produced by material decomposition are often toxic to humans and the environment, and high processing temperatures also result in high energy consumption. Summary of the Invention

[0004] Technical issues

[0005] In view of this, the technical problem to be solved by the present invention is how to provide a preparation method of a water-plasticizable and biodegradable polymer nanocomposite material, the polymer nanocomposite material, and their applications.

[0006] The present invention's nanocellulose wet powder, modified by grafting polyvinyl acetate, can be thermoplastically processed at 40-90°C in the presence of water, eliminating the need for a processing temperature of 160°C. The processing temperature can be lowered from 160°C to 60°C, and the powder can be reprocessed by absorbing water. The number of processing cycles has minimal impact on the mechanical properties of the polymer. The present invention utilizes a lower processing temperature, which contributes to energy conservation and emission reduction, and prevents thermal degradation of the polymer during processing, which could reduce its mechanical properties.

[0007] Solution

[0008] In order to solve the above technical problems, the present invention provides the following technical solutions:

[0009] In a first aspect, the present invention provides a method for preparing a polymer nanocomposite material, wherein a wet powder of nanocellulose modified by grafting polyvinyl acetate is processed and formed by thermoplastic processing equipment to obtain a polymer nanocomposite material, wherein the wet powder of nanocellulose modified by grafting polyvinyl acetate has a water content of 8 to 30 wt% and a thermoplastic temperature of 40 to 90°C.

[0010] Furthermore, the water content of the polyvinyl acetate grafted modified nanocellulose wet powder is 10-25 wt %, optionally 10-20 wt %, optionally 15-20 wt %.

[0011] Furthermore, the thermoplastic temperature is 40-85°C, optionally 60-80°C, optionally 60°C.

[0012] Furthermore, the thermoplastic processing method is selected from one or more of extrusion molding, compression molding, injection molding, blow molding, and 3D printing molding.

[0013] Furthermore, the polymer nanocomposite material can be reprocessed by absorbing water.

[0014] Furthermore, the preparation method of the polyvinyl acetate grafted modified nanocellulose wet powder comprises:

[0015] 1) dispersing nanocellulose in water, and adding vinyl acetate monomer and initiator thereto;

[0016] 2) The aqueous dispersion of step 1) is stirred uniformly and reacted to obtain a precipitate, and the precipitate is filtered and washed to obtain a wet powder of polyvinyl acetate grafted modified nanocellulose.

[0017] Furthermore, in step 1), the nanocellulose is selected from one or more of cellulose nanocrystals, cellulose nanospheres, cellulose nanofibers and bacterial cellulose.

[0018] Furthermore, in step 1), the mass ratio of vinyl acetate monomer to nanocellulose is 1:1 to 15:1, optionally 3:1 to 10:1, optionally 3:1 to 9:1, optionally 5:1 to 10:1, optionally 6:1 to 9:1.

[0019] During their ongoing research and development, the inventors discovered that both too much and too little nanocellulose are detrimental to water-based plasticizing. This material's water-based plasticizing relies on the excellent processing fluidity of polyvinyl acetate and the hydrophilicity of nanocellulose, which increases its water absorption rate. Water acts as a plasticizer, allowing the material to fuse at relatively low temperatures.

[0020] Furthermore, in step 1), the amount of the initiator added is 0.01 to 0.1% of the mass of the vinyl acetate monomer.

[0021] Furthermore, in step 1), the initiator is selected from one or more of azobisisobutylamidine hydrochloride, azobisisobutylimidazoline hydrochloride, persulfate, potassium permanganate / oxalic acid, ceric ammonium nitrate, ceric sulfate, and hydrogen peroxide. Potassium permanganate / oxalic acid refers to a redox initiation system composed of potassium permanganate and oxalic acid.

[0022] Furthermore, in the step 2), the reaction time after mixing is 0.5 to 3 hours, optionally 1.5 to 3 hours, optionally 1.5 to 2.5 hours.

[0023] In a second aspect, a polymer nanocomposite material prepared by the preparation method is provided. Optionally, the polymer nanocomposite material is biodegradable.

[0024] When the polymer nanocomposite material needs to be reprocessed, the material can be re-absorbed with water and re-processed, thereby increasing recyclability.

[0025] In a third aspect, a use of the polymer nanocomposite material prepared by the preparation method or the polymer nanocomposite material described in the second aspect in a biodegradable material is provided.

[0026] Beneficial effects

[0027] (1) The nanocellulose wet powder modified by polyvinyl acetate grafting of the present invention can be thermoplastic processed at 40-90°C under aqueous conditions, eliminating the need for a processing temperature of 160°C. This allows the processing temperature to be lowered from 160°C to 90°C or even lower. The wet powder can also be reprocessed by absorbing water, and the number of processing times has little effect on the mechanical properties of the polymer. The use of a lower processing temperature in the present invention is beneficial for energy conservation and emission reduction, and does not cause thermal degradation of the polymer during processing, thereby reducing its mechanical properties.

[0028] (2) The polyvinyl acetate grafted modified nanocellulose composite material of the present invention can significantly reduce the processing temperature when containing a small amount of water. The water molecules are non-toxic and harmless and can be easily removed after processing and forming.

[0029] (3) The in-situ polymerization of vinyl acetate in the nanocellulose dispersion of the present invention uniformly disperses the nanocellulose in the composite material. The high nanocellulose content in the composite material forms a hydrophilic filler network, which facilitates water infiltration into the material. Consequently, after processing and molding, the material exhibits reduced internal stress and enhanced shape retention. Furthermore, compared to polyvinyl acetate homopolymer, the composite material with a high nanocellulose content exhibits superior mechanical properties and thermal stability.

[0030] (4) The composite material of the present invention can be completely biodegraded after 180 days of burial. However, due to its hydrophobicity, polyvinyl acetate thermoplasticized by conventional methods is difficult for degrading enzymes to penetrate into the material, making polyvinyl acetate difficult to degrade. However, the polyvinyl acetate grafted nanocellulose composite material of the present invention has a hydrophilic filler network, which facilitates the degradation of the composite material by degrading enzymes, thereby making the composite material highly biodegradable.

[0031] The above description is only an overview of the technical solution of the present invention. In order to more clearly understand the technical means of the present invention and to implement it according to the contents of the specification, and to make the above and other purposes, technical features and advantages of the present invention easier to understand, one or more preferred embodiments are listed below and described in detail with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] One or more embodiments are exemplarily illustrated by the accompanying figures, and these exemplary illustrations do not limit the embodiments. The word "exemplary" is used herein to mean "serving as an example, example, or illustration." Any embodiment described herein as "exemplary" is not necessarily to be construed as superior or preferred over other embodiments.

[0033] Figure 1 These are samples of different shapes obtained through water molding according to the present invention.

[0034] Figure 2 These are pictures of the fragmented, water-absorbed and reprocessed polyvinyl acetate grafted nanocellulose sample of Example 1 of the present invention; (A) is the fragmented polyvinyl acetate grafted nanocellulose; (B) is the reprocessed sample.

[0035] Figure 3 This is a curve showing the change in weight of the nanocellulose sample grafted with polyvinyl acetate as a function of burial time in Example 1 of the present invention, indicating biodegradability. DETAILED DESCRIPTION

[0036] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention are clearly and completely described below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0037] In addition, in order to better illustrate the present invention, numerous specific details are provided in the following specific embodiments. It should be understood by those skilled in the art that the present invention can be implemented without certain specific details. In some embodiments, raw materials, schemes, methods, means, etc. well known to those skilled in the art are not described in detail in order to highlight the main purpose of the present invention.

[0038] Unless expressly stated otherwise, throughout the specification and claims, the term "comprise" or variations such as "include" or "comprising", etc., will be understood to include the stated elements or components but not to exclude other elements or other components.

[0039] In the following examples, all the raw materials used were commercially available vinyl acetate monomer and initiator purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.

[0040] The moisture content of the wet powder of polyvinyl acetate grafted modified cellulose nanocrystals was calculated by calculating the mass change of the wet powder before and after drying. The weight of the wet powder was recorded as m0, and the sample was dried in an oven at 60°C to a constant weight, recorded as m1. The water content was calculated using the following formula:

[0041]

[0042] Material degradability testing method: The polyvinyl acetate-grafted nanocellulose sample from Example 1 was molded into a film with a diameter of 4 cm and a thickness of 150 μm. The film was buried in soil at room temperature for 180 days. Samples were taken and weighed every 15-30 days, and the degree of degradation was calculated by measuring the change in residual weight.

[0043] Example 1

[0044] 1g of cellulose nanocrystals was dispersed in 100mL of water, to which 6g of vinyl acetate monomer and 0.003g of ammonium persulfate initiator were added. After a 2-hour reaction, a precipitate was obtained. The precipitate was filtered and washed with water to obtain a wet powder of polyvinyl acetate-grafted modified cellulose nanocrystals with a moisture content of 15%. This wet powder was then molded at 60°C to produce a transparent nanocomposite film.

[0045] The cellulose nanocrystals are prepared by referring to the method of Example 1 of CN109320617A, and can also be obtained by conventional methods in the prior art.

[0046] Example 2

[0047] The difference from Example 1 is that the cellulose nanocrystals are replaced with cellulose nanofibers. The resulting precipitate is filtered and washed to obtain a wet powder of polyvinyl acetate-grafted modified cellulose nanofibers with a moisture content of 15%. This wet powder is then molded at 60°C to produce a transparent nanocomposite film.

[0048] The cellulose nanofibers are prepared by referring to the method of Example 2 of CN109320617A, and can also be obtained by conventional methods in the prior art.

[0049] Example 3

[0050] The difference from Example 1 is that the cellulose nanocrystals are replaced with cellulose nanospheres. The resulting precipitate is filtered and washed to obtain a wet powder of polyvinyl acetate-grafted modified cellulose nanospheres with a moisture content of 15 wt%. This wet powder is then molded at 60°C to produce a transparent nanocomposite film.

[0051] The cellulose nanospheres were prepared based on the method reported in the literature “Efficient extraction of carboxylated spherical cellulose nanocrystals with narrow distribution through hydrolysis of lyocell fibers by using ammonium persulfate as an oxidant, J. Mater. Chem. A, 2014, 2, 251-258”.

[0052] Example 4

[0053] The difference from Example 1 is that the mass of vinyl acetate monomer added is 3g. The resulting precipitate is filtered and washed to obtain a wet powder of polyvinyl acetate-grafted modified cellulose nanocrystals with a water content of 15wt%. This wet powder is molded at 60°C to obtain a transparent nanocomposite film.

[0054] Example 5

[0055] The difference from Example 1 is that the mass of vinyl acetate monomer added is 9 g. The resulting precipitate is filtered and washed to obtain a wet powder of polyvinyl acetate-grafted modified cellulose nanocrystals with a water content of 15 wt%. This wet powder is molded at 60°C to obtain a transparent nanocomposite film.

[0056] Example 6

[0057] The difference from Example 1 is that the precipitate obtained by the reaction is filtered and washed to obtain a wet powder of polyvinyl acetate grafted modified cellulose nanocrystals with a water content of 10 wt %. The wet powder is molded at 60° C. to obtain a transparent nanocomposite film.

[0058] Example 7

[0059] The difference from Example 1 is that the precipitate obtained by the reaction is filtered and washed to obtain a wet powder of polyvinyl acetate grafted modified cellulose nanocrystals with a water content of 20 wt %. The wet powder is molded at 60° C. to obtain a transparent nanocomposite film.

[0060] Example 8

[0061] The difference from Example 1 is that the molding temperature of the wet powder of polyvinyl acetate grafted modified cellulose nanocrystals with a water content of 15 wt % obtained by the reaction is 40° C., and a transparent nanocomposite film can be finally obtained.

[0062] Example 9

[0063] The difference from Example 1 is that the molding temperature of the wet powder of polyvinyl acetate grafted modified cellulose nanocrystals with a water content of 15 wt % obtained by the reaction is 80° C., and a transparent nanocomposite film can be finally obtained.

[0064] Example 10

[0065] The difference from Example 1 is that the polyvinyl acetate grafted modified cellulose nanocrystal wet powder with a water content of 15 wt% obtained by the reaction is processed by single-screw extrusion to obtain a uniform nanocomposite material wire.

[0066] Example 11

[0067] The difference from Example 1 is that the polyvinyl acetate grafted modified cellulose nanocrystal wet powder with a water content of 15 wt% obtained by the reaction is processed by 3D printing to obtain a uniform nanocomposite material block.

[0068] Comparative Example 1

[0069] The difference from Example 1 was that 20 g of vinyl acetate monomer was added. The resulting precipitate was filtered and washed to obtain a wet powder of polyvinyl acetate-grafted modified cellulose nanocrystals. Due to the low content of cellulose nanocrystals, the resulting wet powder could not be molded at 60°C.

[0070] Comparative Example 2

[0071] The difference from Example 1 was that the mass of vinyl acetate monomer added was 0.5 g. The resulting precipitate was filtered and washed to obtain a wet powder of polyvinyl acetate grafted modified cellulose nanocrystals. Due to the excessive content of cellulose nanocrystals, the resulting wet powder could not be molded at 60°C.

[0072] Comparative Example 3

[0073] The difference from Example 1 is that the precipitate obtained by the reaction is filtered and washed to obtain a wet powder of polyvinyl acetate grafted modified cellulose nanocrystals with a water content of 2%. Due to the low water content, the obtained wet powder cannot be molded at 60°C and can only be thermoformed at 160°C.

[0074] Comparative Example 4

[0075] The difference from Example 1 is that the precipitate obtained by the reaction is filtered and washed to obtain a wet powder of polyvinyl acetate grafted modified cellulose nanocrystals with a water content of 60%. The wet powder cannot be molded at 60°C due to excessive water content.

[0076] Comparative Example 5

[0077] The difference from Example 1 is that the molding temperature of the polyvinyl acetate grafted modified cellulose nanocrystal wet powder with a water content of 15% obtained by the reaction is 20° C., and molding is impossible due to the processing temperature being too low.

[0078] In the above embodiments and comparative examples, the amount of initiator added can be adjusted according to the needs. Generally, the processing performance of the polyvinyl acetate grafted modified cellulose nanocrystal wet powder is better when the moisture content is 10% to 20%.

[0079] In the above embodiments, the polyvinyl acetate grafted modified nanocellulose of the present invention can be processed into different shapes by water molding, such as Figure 1 As shown, it can also be fragmented and then absorbed and processed (such as Figure 2 It can be recycled multiple times.

[0080] The polyvinyl acetate grafted modified nanocellulose of the present invention can be completely degraded after 180 days after being buried in the soil. Figure 3 shown.

[0081] The foregoing descriptions of specific exemplary embodiments of the present invention are for purposes of illustration and description. These descriptions are not intended to limit the invention to the precise form disclosed, and it is apparent that many changes and variations are possible in light of the foregoing teachings. The exemplary embodiments are selected and described for the purpose of explaining the specific principles of the invention and their practical application, thereby enabling those skilled in the art to realize and utilize a variety of exemplary embodiments of the invention and various options and variations. Any simple modifications, equivalent variations, and modifications made to the exemplary embodiments described above are intended to fall within the scope of protection of the present invention.

Claims

1. A method for preparing a polymer nanocomposite material, characterized in that: The nanocellulose wet powder modified by grafting polyvinyl acetate is processed and formed by thermoplastic processing equipment to obtain a polymer nanocomposite material, wherein: The water content of the polyvinyl acetate grafted modified nanocellulose wet powder is 10 to 20 wt % and the thermoplastic processing temperature is 40 to 90° C. The modification method of the polyvinyl acetate grafted nanocellulose comprises: dispersing the nanocellulose in water, adding vinyl acetate monomer and an initiator thereto; the mass ratio of the vinyl acetate monomer to the nanocellulose is 3:1 to 10:1; The nanocellulose is selected from one or more of cellulose nanocrystals, cellulose nanospheres, cellulose nanofibers and bacterial cellulose.

2. The preparation method according to claim 1, characterized in that The water content of the polyvinyl acetate grafted modified nanocellulose wet powder is 15-20 wt %.

3. The preparation method according to claim 1, characterized in that The thermoplastic temperature is 40-85°C.

4. The preparation method according to claim 1, characterized in that The thermoplastic temperature is 60-80℃.

5. The preparation method according to claim 1, characterized in that The thermoplastic temperature is 60°C.

6. The preparation method according to claim 1, characterized in that The mass ratio of vinyl acetate monomer to nanocellulose is 3:1 to 9:

1.

7. The preparation method according to claim 1, characterized in that The mass ratio of vinyl acetate monomer to nanocellulose is 5:1 to 10:

1.

8. The preparation method according to claim 1, characterized in that The mass ratio of vinyl acetate monomer to nanocellulose is 6:1 to 9:

1.

9. The preparation method according to any one of claims 1 to 8, characterized in that The thermoplastic processing method is selected from one or more of extrusion molding, compression molding, injection molding, blow molding, and 3D printing molding.

10. The preparation method according to any one of claims 1 to 8, characterized in that The polymer nanocomposite material can be reprocessed by absorbing water.

11. The preparation method according to any one of claims 1 to 8, characterized in that The preparation method of the polyvinyl acetate grafted modified nanocellulose wet powder comprises: 1) dispersing nanocellulose in water, and adding vinyl acetate monomer and initiator thereto; 2) The aqueous dispersion of step 1) is stirred uniformly and reacted to obtain a precipitate, and the precipitate is filtered and washed to obtain a wet powder of polyvinyl acetate grafted modified nanocellulose.

12. The preparation method according to claim 11, characterized in that In the step 1), the amount of the initiator added is 0.01 to 0.1% of the mass of the vinyl acetate monomer.

13. The preparation method according to claim 11, characterized in that In the step 1), the initiator is selected from one or more of azobisisobutylamidine hydrochloride, azobisisobutylimidazoline hydrochloride, persulfate, potassium permanganate / oxalic acid, ceric ammonium nitrate, ceric sulfate, and hydrogen peroxide.

14. The preparation method according to claim 11, characterized in that In the step 2), the reaction time after mixing is 0.5 to 3 hours.

15. The preparation method according to claim 11, characterized in that In the step 2), the reaction time after mixing is 1.5 to 3 hours.

16. The preparation method according to claim 11, characterized in that In the step 2), the reaction time after mixing is 1.5 to 2.5 hours.

17. A polymer nanocomposite material prepared by the preparation method according to any one of claims 1 to 16.

18. The polymer nanocomposite material according to claim 17, characterized in that The polymer nanocomposite is biodegradable.

19. Use of the polymer nanocomposite material prepared by the preparation method according to any one of claims 1 to 16 or the polymer nanocomposite material according to claim 17 or 18 in a biodegradable material.

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