Chitosan toughened modified phenolic resin and preparation method thereof

Abstract

The invention relates to the technical field of phenolic resin toughening modification, in particular to chitosan toughening modified phenolic resin and a preparation method thereof, and the preparation method comprises the following steps: S1, degrading chitosan in an alkaline solution; s2, adding the small-molecular chitosan powder into an N, N-dimethylformamide solution, and carrying out swelling on the small-molecular chitosan powder and the N, N-dimethylformamide solution; meanwhile, phenolic resin is subjected to prepolymerization in an N, N-dimethylformamide solution, and a prepolymerized phenolic resin solution is obtained; s3, mixing the small molecular chitosan transparent solution with the pre-polymerized phenolic resin solution, and dropwise adding a sodium hydroxide solution to generate a precipitation product; and washing and filtering the precipitation product, and finally carrying out vacuum drying to obtain the chitosan modified phenolic resin. The preparation method has the advantages that the chitosan structure is introduced into the phenolic resin, so that the original structural regularity of the phenolic resin can be destroyed, and the rigidity of the phenolic resin is reduced. Meanwhile, the imino group generated in the reaction process is beneficial to the formation of intermolecular hydrogen bonds, which is also beneficial to the improvement of the toughness of the resin.

Description

Technical Field

[0001] The invention relates to the technical field of toughening and modification of phenolic resin, in particular to a chitosan toughening and modified phenolic resin and a preparation method thereof. Background Art

[0002] Phenolic resin is one of the earliest synthetic resins to achieve industrial production. It has excellent temperature resistance, flame retardancy, chemical resistance, electrical insulation and dimensional stability, and is widely used in molded composite materials, thermal and electrical insulation materials, friction materials, adhesives, etc. However, the brittleness and low elongation of phenolic resin limit its further application.

[0003] Chitosan is a product of chitin deacetylation. It is non-toxic, harmless, green and environmentally friendly, and exhibits good biocompatibility, degradability, film-forming properties, and certain antibacterial and anti-inflammatory properties. Therefore, it has been widely used in many fields such as medicine, food, agriculture, daily chemicals, and environmental protection. However, the research on chitosan as a resin toughening agent is still in its infancy and needs further development. Summary of the invention

[0004] In view of this, the present invention aims to provide a chitosan toughened modified phenolic resin and a preparation method thereof, wherein the chitosan is degraded, and then a reaction solvent is added to swell the chitosan, and then the chitosan is mixed with a prepolymerized phenolic resin solution to react. After the reaction, a precipitated product is obtained, which is washed, filtered and vacuum dried to obtain a modified phenolic resin.

[0005] To achieve the above object, the technical solution created by the present invention is implemented as follows: a chitosan toughened modified phenolic resin, the chitosan toughened modified phenolic resin has the following structural formula:

[0006] Among them, n=3~6.

[0007] A method for preparing a chitosan toughened modified phenolic resin, for preparing the chitosan toughened modified phenolic resin of claim 1, comprising the following steps: S1: degrading chitosan in an alkaline solution to obtain small molecule chitosan powder.

[0008] S2: Adding small molecule chitosan powder into N,N-dimethylformamide solution for swelling to obtain a small molecule chitosan transparent solution.

[0009] S3: prepolymerizing the phenolic resin in an N,N-dimethylformamide solution to obtain a prepolymerized phenolic resin solution.

[0010] S4: Mix the small molecule chitosan transparent solution with the prepolymerized phenolic resin solution, and dropwise add sodium hydroxide solution to generate a precipitate product; wash, filter, and vacuum dry the precipitate product to obtain chitosan-modified phenolic resin.

[0011] Further, step S1 includes the following steps: S11: Add chitosan to sodium hydroxide solution, then add sodium borohydride, and react at a preset temperature and for a preset time to obtain degraded small molecule chitosan; S12: Wash and filter the degraded small molecule chitosan at least three times, and finally perform vacuum drying to obtain small molecule chitosan powder.

[0012] Further, in step S11, the mass ratio of chitosan to the volume of sodium hydroxide solution is 1:12 to 1:5, where the mass unit of chitosan is g and the volume unit of sodium hydroxide solution is ml; the concentration of sodium hydroxide solution is 30% to 50%; the mass of sodium borohydride is 10% to 20% of the mass of chitosan.

[0013] Further, in step S12, the temperature of vacuum drying is 60°C to 100°C, and the vacuum drying time is 1 hour to 20 hours.

[0014] Further, in step S2, the swelling temperature of small molecule chitosan powder in N,N-dimethylformamide solution is 80°C, and the swelling time is 8 hours to 10 hours.

[0015] Further, in step S2, the mass ratio of small molecule chitosan powder to the volume of N,N-dimethylformamide solution is 1:200 to 1:50; where the mass unit of small molecule chitosan powder is g and the volume unit of N,N-dimethylformamide solution is ml.

[0016] Further, in step S2, the mass ratio of phenolic resin to small molecule chitosan powder is 25:1 to 10:1, where the mass unit of phenolic resin is g and the mass unit of small molecule chitosan powder is g; the mass ratio of phenolic resin to the volume of N,N-dimethylformamide solution is 1:8 to 1:4; where the mass unit of phenolic resin is g and the volume unit of N,N-dimethylformamide solution is ml; the reaction temperature of phenolic resin in N,N-dimethylformamide solution is 40°C to 50°C, and the reaction time is 5 hours to 8 hours.

[0017] Further, in step S3, the concentration of sodium hydroxide solution is 50% to 70%; the temperature of vacuum drying is 35°C to 100°C, and the vacuum drying time is 24 hours to 60 hours.

[0018] Further, in step S3, the precipitate product is first washed and filtered with distilled water at least three times; then the washed and filtered precipitate product is washed and filtered with N,N-dimethylformamide solution at least three times to further purify the precipitate product.

[0019] Compared with the prior art, the present invention can achieve the following beneficial effects: 1) Introducing chitosan structure into phenolic resin can destroy the original structural regularity of phenolic resin, thereby reducing its rigidity. At the same time, the imino groups generated during the reaction contribute to the formation of intermolecular hydrogen bonds, which is also beneficial to the improvement of the resin toughness.

[0020] 2) The present invention provides a new way to toughen and modify phenolic resin with chitosan, further broadening the application of chitosan in the resin field and having good industrialization prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The drawings constituting a part of the present invention are used to provide a further understanding of the present invention. The schematic embodiments and descriptions thereof of the present invention are used to explain the present invention and do not constitute an improper limitation to the present invention. In the drawings: Figure 1 is the structural formula of chitosan toughened and modified phenolic resin provided by the embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0022] In order to make the purpose, technical solutions and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the drawings and specific embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and do not constitute a limitation to the present invention.

[0023] It should be noted that, without conflict, the embodiments and features in the embodiments of the present invention can be combined with each other.

[0024] In the description of the present invention, it should be understood that the orientation or positional relationship indicated by the terms "center", "longitudinal", "transverse", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings. It is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation to the present invention. In addition, the terms "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, the features defined with "first", "second", etc. may explicitly or implicitly include one or more of such features. In the description of the present invention, unless otherwise stated, the meaning of "a plurality" is two or more.

[0025] In the description of the present invention, it should be noted that unless otherwise clearly defined and limited, the terms "mounted", "connected", "coupled" should be understood in a broad sense. For example, it may be a fixed connection, a detachable connection, or an integral connection; it may be a mechanical connection or an electrical connection; it may be directly connected or indirectly connected through an intermediate medium, and it may be the communication inside two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood through specific circumstances.

[0026] The present invention will be described in detail below with reference to the embodiments.

[0027] A chitosan toughened and modified phenolic resin provided by an embodiment of the present invention has a structural formula of chitosan toughened and modified phenolic resin as follows:

[0028] Among them, n = 3 - 6.

[0029] The reaction process is as follows:

[0030]

[0031] A preparation method of a chitosan toughened and modified phenolic resin for preparing the above chitosan toughened and modified phenolic resin includes the following steps: S1: Degrade chitosan in an alkaline solution to obtain small molecule chitosan powder.

[0032] S2: Add the small molecule chitosan powder into an N,N-dimethylformamide solution for swelling to obtain a small molecule chitosan transparent solution; S3: Prepolymerize phenolic resin in N,N-dimethylformamide solution to obtain prepolymerized phenolic resin solution.

[0033] S4: Mix the transparent solution of small molecule chitosan with the prepolymerized phenolic resin solution, and add sodium hydroxide solution dropwise to generate a precipitation product; wash, filter the precipitation product, and finally conduct vacuum drying to obtain chitosan-modified phenolic resin.

[0034] Further, step S1 includes the following steps: S11: Add chitosan into sodium hydroxide solution, then add sodium borohydride, and react at a preset temperature and for a preset time to obtain degraded small molecule chitosan.

[0035] S12: Wash and filter the degraded small molecule chitosan at least three times, and finally conduct vacuum drying to obtain small molecule chitosan powder.

[0036] Further, in step S11, the mass ratio of chitosan to the volume of sodium hydroxide solution is 1:12 - 1:5, where the mass unit of chitosan is g and the volume unit of sodium hydroxide solution is ml; the concentration of sodium hydroxide solution is 30% - 50%; the mass of sodium borohydride is 10% - 20% of the mass of chitosan.

[0037] Further, in step S12, the temperature of vacuum drying is 60°C - 100°C, and the vacuum drying time is 1 hour - 20 hours.

[0038] Further, in step S2, the swelling temperature of small molecule chitosan powder in N,N-dimethylformamide solution is 80°C, and the swelling time is 8 hours - 10 hours.

[0039] Further, in step S2, the mass ratio of small molecule chitosan powder to the volume of N,N-dimethylformamide solution is 1:200 - 1:50; where the mass unit of small molecule chitosan powder is g and the volume unit of N,N-dimethylformamide solution is ml.

[0040] Further, in step S2, the mass ratio of phenolic resin to chitosan is 25:1 - 10:1, where the mass unit of phenolic resin is g and the mass unit of small molecule chitosan powder is g; the mass ratio of phenolic resin to the volume of N,N-dimethylformamide solution is 1:8 - 1:4; where the mass unit of phenolic resin is g and the volume unit of N,N-dimethylformamide solution is ml; the reaction temperature of phenolic resin in N,N-dimethylformamide solution is 40°C - 50°C, and the reaction time is 5 hours - 8 hours.

[0041] Further, in step S3, the concentration of the sodium hydroxide solution is 50% - 70%; the temperature of the vacuum drying is 35°C - 100°C, and the time of the vacuum drying is 24 hours - 60 hours.

[0042] Further, in step S3, first, the precipitate product is washed and filtered with distilled water at least three times; then, the washed and filtered precipitate product is washed and filtered with N,N-dimethylformamide solution at least three times to further purify the precipitate product.

[0043] Next, in combination with two specific embodiments, a preparation method of a chitosan toughened and modified phenolic resin provided by the present invention will be described.

[0044] Example 1: S1: Degrade chitosan in an alkaline solution to obtain small molecule chitosan powder. It includes the following steps: S11: First, weigh 2 g of low molecular weight chitosan (deacetylation degree greater than 80%, molecular weight 5000 - 20000), and add it to 20 mL of a sodium hydroxide solution with a concentration of 40%. Subsequently, add 0.3 g of sodium borohydride. In this example, the mass ratio of chitosan to the volume of the sodium hydroxide solution is 1:10, and the mass of sodium borohydride is 15% of the mass of chitosan.

[0045] The chitosan undergoes a degradation reaction in the sodium hydroxide solution, and sodium borohydride acts as a catalyst to accelerate the degradation of chitosan. The reaction temperature is 100°C, and the reaction time is 6 hours. After the reaction is completed, the degraded small molecule chitosan is obtained.

[0046] S12: Filter and wash the degraded small molecule chitosan with absolute ethanol 3 - 5 times to remove residual impurities, and obtain undried small molecule chitosan. Then, place the undried small molecule chitosan in a vacuum drying oven for vacuum drying to obtain small molecule chitosan powder. The vacuum drying temperature is 80°C, and the vacuum drying time is 24 hours.

[0047] The vacuum drying oven is a purchased part, the manufacturer is Shanghai Qixin Scientific Instruments Co., Ltd., and the model is DZF-6020.

[0048] S2: Add the small molecule chitosan powder to an N,N-dimethylformamide solution for swelling to obtain a small molecule chitosan transparent solution; at the same time, pre-polymerize the phenolic resin in the N,N-dimethylformamide solution to obtain a prepolymerized phenolic resin solution.

[0049] Specifically, weigh 1 g of small molecule chitosan powder, place it in 60 mL of N,N-dimethylformamide (DMF) solution for swelling to obtain a transparent small molecule chitosan solution. The swelling time is 8 h and the swelling temperature is 80 °C. During the swelling process, use a magnetic stirrer to stir at a stirring speed of 150 r / min. In this example, the mass ratio of the small molecule chitosan powder to the volume of the N,N-dimethylformamide solution is 1:60.

[0050] The magnetic stirrer is a purchased part, manufacturer: Shanghai Sheyan Instrument Co., Ltd., model: CF-1.

[0051] Meanwhile, weigh 20 g of phenolic resin, place it in 120 mL of N,N-dimethylformamide solution for prepolymerization to obtain a prepolymerized phenolic resin solution. The prepolymerization reaction time is 8 h and the reaction temperature is 40 °C. In this example, the mass ratio of the phenolic resin to the chitosan is 20:1, and the mass ratio of the phenolic resin to the volume of the N,N-dimethylformamide solution is 1:6.

[0052] S3: Mix the transparent small molecule chitosan solution in step S2 with the prepolymerized phenolic resin solution, and add sodium hydroxide solution dropwise to generate a precipitate product; wash and filter the precipitate product, and finally perform vacuum drying to obtain chitosan-modified phenolic resin.

[0053] Specifically, mix the transparent small molecule chitosan solution with the prepolymerized phenolic resin solution at 80 °C to form a mixed solution. Add 1 mL of 60% NaOH solution to the mixed solution dropwise to react the mixed solution with NaOH to generate a chitosan-modified phenolic resin precursor solution. Control the NaOH dropping rate so that it is dropped within 5 h. During the dropping process, use a magnetic stirrer to stir at a stirring speed of 150 r / min.

[0054] After the reaction is completed, cool the chitosan-modified phenolic resin precursor solution to room temperature, pour it into deionized water, and let it stand at room temperature for 24 hours to precipitate. After precipitation, filter and wash it 5 times with distilled water to obtain a preliminary product. Then filter and wash it 5 times with N,N-dimethylformamide solution to further purify the preliminary product. Finally, vacuum dry the further purified preliminary product in a vacuum drying oven to obtain chitosan-modified phenolic resin. The vacuum drying temperature is 50 °C and the vacuum drying time is 40 hours.

[0055] Fuse the chitosan-modified phenolic resin with alcohol. If the solution is clear and no precipitate is formed, it indicates that the chitosan-modified phenolic resin has been successfully prepared.

[0056] Example 2: S1: Degrade chitosan in an alkaline solution to obtain small molecule chitosan powder. It includes the following steps: S11: First, weigh 2 g of low molecular weight chitosan (deacetylation degree greater than 80%, molecular weight 5000 - 20000), and add it to 20 mL of sodium hydroxide solution with a concentration of 40%. Subsequently, add 0.3 g of sodium borohydride. In this embodiment, the mass ratio of chitosan to the volume of sodium hydroxide solution is 1:10, and the mass of sodium borohydride is 15% of the mass of chitosan.

[0057] Chitosan undergoes a degradation reaction in the sodium hydroxide solution, and sodium borohydride acts as a catalyst to accelerate the degradation of chitosan. The reaction temperature is 100 °C, and the reaction time is 6 hours. After the reaction is completed, degraded small molecule chitosan is obtained.

[0058] S12: Filter and wash the degraded small molecule chitosan with absolute ethanol 3 - 5 times to remove residual impurities, and obtain undried small molecule chitosan. Then, place the undried small molecule chitosan in a vacuum drying oven for vacuum drying to obtain small molecule chitosan powder. The vacuum drying temperature is 80 °C, and the vacuum drying time is 24 hours.

[0059] S2: Add the small molecule chitosan powder to N,N - dimethylformamide solution for swelling to obtain a small molecule chitosan transparent solution; at the same time, pre - polymerize phenolic resin in N,N - dimethylformamide solution to obtain a pre - polymerized phenolic resin solution.

[0060] Specifically, weigh 1 g of small molecule chitosan powder, place it in 60 mL of N,N - dimethylformamide solution for swelling to obtain a small molecule chitosan transparent solution. The swelling time is 8 h, and the swelling temperature is 80 °C. During the swelling process, use a magnetic stirrer to stir at a stirring speed of 150 r / min. In this embodiment, the mass ratio of small molecule chitosan powder to the volume of N,N - dimethylformamide solution is 1:60.

[0061] At the same time, weigh 15 g of phenolic resin, place it in 100 mL of N,N - dimethylformamide solution for pre - polymerization to obtain a pre - polymerized phenolic resin solution. The pre - polymerization reaction time is 8 h, and the reaction temperature is 40 °C. In this embodiment, the mass ratio of phenolic resin to chitosan is 15:1, and the mass ratio of phenolic resin to the volume of N,N - dimethylformamide solution is 3:20.

[0062] S3: Mix the small molecule chitosan transparent solution and the pre - polymerized phenolic resin solution in step S2, and add dropwise sodium hydroxide solution to generate a precipitate product; wash and filter the precipitate product, and finally conduct vacuum drying to obtain chitosan - modified phenolic resin.

[0063] Specifically, a small molecule chitosan transparent solution and a prepolymerized phenolic resin solution are mixed at 80 °C to form a mixed solution. 1 mL of a 60% NaOH solution is added dropwise to the mixed solution to react the mixed solution with NaOH to produce a chitosan-modified phenolic resin precursor solution. The NaOH dropping rate is controlled so that it is added dropwise within 3 h - 5 h. During the dropping process, a magnetic stirrer is used to stir at a stirring speed of 150 r / min.

[0064] After the reaction is completed, the chitosan-modified phenolic resin precursor solution is cooled to room temperature, poured into deionized water, and allowed to stand at room temperature for 24 hours to precipitate. After precipitation is completed, it is filtered and washed 5 times with distilled water to obtain a preliminary product. Then, it is filtered and washed at least 3 times with an N,N-dimethylformamide solution to further purify the preliminary product. Finally, the further purified preliminary product is vacuum dried in a vacuum drying oven to obtain chitosan-modified phenolic resin. The temperature of vacuum drying is 50 °C, and the vacuum drying time is 40 hours.

[0065] The chitosan-modified phenolic resin is fused with alcohol. If the solution is clear and no precipitate is formed, it indicates that the chitosan-modified phenolic resin has been successfully prepared.

[0066] The above specific embodiments do not constitute a limitation to the protection scope of the present invention. Those skilled in the art should understand that various modifications, combinations, sub-combinations, and substitutions can be made according to design requirements and other factors. Any modifications, equivalent substitutions, and improvements made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A chitosan toughened and modified phenolic resin, characterized in that, The structural formula of chitosan toughened and modified phenolic resin is as follows: Among them, n = 3 - 6.

2. A preparation method of chitosan toughened and modified phenolic resin, characterized in that, For the preparation of the chitosan toughened and modified phenolic resin described in Claim 1, it includes the following steps: S1: Degrade chitosan in an alkaline solution to obtain small - molecule chitosan powder; S2: Add the small - molecule chitosan powder into N,N - dimethylformamide solution for swelling to obtain a transparent small - molecule chitosan solution; S3: Pre - polymerize phenolic resin in N,N - dimethylformamide solution to obtain a pre - polymerized phenolic resin solution; S4: Mix the transparent small - molecule chitosan solution with the pre - polymerized phenolic resin solution, and dropwise add sodium hydroxide solution to generate a precipitate product; Wash, filter and vacuum - dry the precipitate product to obtain chitosan - modified phenolic resin.

3. The preparation method of the chitosan toughened and modified phenolic resin according to claim 2, characterized in that, Step S1 includes the following steps: S11: Add chitosan into sodium hydroxide solution, then add sodium borohydride, and react at a preset temperature and for a preset time to obtain degraded small - molecule chitosan; S12: Wash and filter the degraded small - molecule chitosan at least three times, and finally conduct vacuum drying to obtain small - molecule chitosan powder.

4. The preparation method of the chitosan toughened modified phenolic resin according to claim 3, characterized in that, In step S11, the mass ratio of the chitosan to the volume of the sodium hydroxide solution is 1:12 - 1:5, where the mass unit of the chitosan is g and the volume unit of the sodium hydroxide solution is ml; the concentration of the sodium hydroxide solution is 30% - 50%; the mass of the sodium borohydride is 10% - 20% of the mass of the chitosan.

5. The preparation method of the chitosan toughened modified phenolic resin according to claim 3, characterized in that, In step S12, the temperature of vacuum drying is 60°C - 100°C, and the vacuum drying time is 1 hour - 20 hours.

6. The preparation method of the chitosan toughened and modified phenolic resin according to claim 2, characterized in that, In step S2, the swelling temperature of the small - molecule chitosan powder in the N,N - dimethylformamide solution is 80°C, and the swelling time is 8 hours - 10 hours.

7. The preparation method of the chitosan toughened and modified phenolic resin according to claim 2, wherein, In step S2, the mass ratio of the small - molecule chitosan powder to the volume of the N,N - dimethylformamide solution is 1:200 - 1:50; where the mass unit of the small - molecule chitosan powder is g and the volume unit of the N,N - dimethylformamide solution is ml.

8. The preparation method of the chitosan toughened and modified phenolic resin according to claim 2, characterized in that, In step S2, the mass ratio of the phenolic resin to the mass of the small - molecule chitosan powder is 25:1 - 10:1, where the mass unit of the phenolic resin is g and the mass unit of the small - molecule chitosan powder is g; the mass ratio of the phenolic resin to the volume of the N,N - dimethylformamide solution is 1:8 - 1:4; where the mass unit of the phenolic resin is g and the volume unit of the N,N - dimethylformamide solution is ml; the reaction temperature of the phenolic resin in the N,N - dimethylformamide solution is 40°C - 50°C, and the reaction time is 5 hours - 8 hours.

9. The preparation method of the chitosan toughened modified phenolic resin according to claim 2, wherein, In step S3, the concentration of the sodium hydroxide solution is 50% - 70%; the temperature of vacuum drying is 35°C - 100°C, and the vacuum drying time is 24 hours - 60 hours.

10. The preparation method of the chitosan toughened and modified phenolic resin according to claim 2, characterized in that, In step S3, first wash and filter the precipitation product with distilled water at least three times; then wash and filter the washed and filtered precipitation product with N,N-dimethylformamide solution at least three times to further purify the precipitation product.

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