A dynamic imine type plant fiber modifying material and a method for preparing the same

Abstract

The application provides a dynamic imine type plant fiber modified material and a preparation method thereof, and belongs to the technical field of plant fiber modified materials capable of being repeatedly hot processed. The method comprises the following steps: 1) pretreating plant fibers to obtain pretreated plant fibers; 2) dispersing the pretreated plant fibers in water, and then adding a periodate to perform an oxidative ring-opening reaction, to obtain oxidized plant fibers; and 3) mixing the oxidized plant fibers with diamines in anhydrous ethanol to perform an amination reaction, to obtain the dynamic imine type plant fiber modified material. The dynamic imine type plant fiber modified material is a full-component plant fiber, has good mechanical properties, and can be repeatedly processed and formed according to the dynamic imine reversible bond.

Description

Technical Field

[0001] This invention relates to the technical field of reusable heat-processable modified plant fiber materials, specifically to a dynamic imine-type modified plant fiber material and its preparation method. Background Technology

[0002] With the continuous depletion of non-renewable resources (oil and natural gas) and the increasingly serious environmental pollution caused by petroleum-based polymers, people are paying more attention to the development of renewable, environmentally friendly, biodegradable, and non-petroleum-based materials. Natural plant fibers are the most abundant renewable resource in nature. Using them as raw materials to prepare environmentally friendly new materials can not only reduce dependence on fossil resources but also promote the comprehensive utilization of plant resources.

[0003] If plant fibers could be repeatedly heat-processed like plastics and possess high strength, replacing some petroleum-based plastics could effectively alleviate resource depletion and environmental pollution problems. However, due to the high crystallinity, dense hydrogen bond network, and strong intermolecular / internal forces of cellulose, the movement of its molecular chains is hindered, resulting in a melting temperature of plant fibers that is much higher than their thermal decomposition temperature. This makes it difficult to perform melt heat processing on plant fibers, severely limiting their applications.

[0004] Common methods for improving the processing properties of plant fibers mainly involve thermoplasticization modification such as esterification and etherification. These methods involve grafting large, weakly interacting functional groups onto the cellulose molecular chain, disrupting the internal hydrogen bond network and crystalline structure of the plant fiber, weakening the intermolecular forces, and thus promoting molecular chain movement to prepare thermoplastic materials. However, thermoplasticization modification methods using esterification and etherification severely damage the internal hydrogen bond network and crystalline structure of plant fibers, resulting in materials with low mechanical properties, significantly limiting their applications. Furthermore, achieving thermoplasticization of plant fibers requires a high degree of reaction, leading to increased costs and reduced yields.

[0005] Therefore, how to obtain a plant fiber modification method with suitable temperature conditions, high efficiency, high product yield, and good mechanical properties is a technical problem that needs to be solved. Summary of the Invention

[0006] The purpose of this invention is to provide a dynamic imine-type plant fiber modified material and its preparation method, so as to solve the technical problems of low yield and poor mechanical properties of modified plant fiber products.

[0007] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0008] This invention provides a method for preparing a dynamic imine-type plant fiber modified material, comprising the following steps:

[0009] 1) Pre-treat the plant fibers to obtain pre-treated plant fibers;

[0010] 2) Disperse the pretreated plant fibers in water, then add periodate to carry out an oxidative ring-opening reaction to obtain oxidized plant fibers;

[0011] 3) Oxidized plant fibers and diamine were mixed in anhydrous ethanol for amination reaction to obtain dynamic imine-type modified plant fiber materials.

[0012] Furthermore, in step 1), the plant fiber pretreatment method includes one or more of grinding, high-shear homogenization, and steam explosion;

[0013] The plant fibers comprise one or more of hemp, straw, and bamboo plants.

[0014] Furthermore, in step 2), the mass ratio of pretreated plant fiber to water is 0.1 to 10:100.

[0015] Furthermore, in step 2), the mass ratio of periodate to pretreated plant fiber is 0.1 to 2:1.

[0016] Furthermore, in step 2), the temperature of the oxidative ring-opening reaction is 20–80°C, and the reaction time is 1–8 h.

[0017] Furthermore, in step 3), the diamine comprises one or more of 1,4-butanediamine, 1,6-hexanediamine, 1,8-octanediamine, 1,10-diaminodecane, and 1,12-diaminododecane.

[0018] Furthermore, in step 3), the molar ratio of the amino group in the diamine to the aldehyde group in the oxidized plant fiber is 0.6 to 1.6:1.

[0019] Furthermore, in step 3), the mass ratio of oxidized plant fiber to anhydrous ethanol is 0.1 to 10:100.

[0020] Furthermore, in step 3), the amination reaction is carried out at a temperature of 20–80°C for 1–48 hours.

[0021] The present invention also provides a dynamic imine-type plant fiber modified material.

[0022] The beneficial effects of this invention are:

[0023] 1) The method of the present invention realizes the full utilization of plant fiber components, and the product can be directly hot-pressed and molded; after decrosslinking, it can be repeatedly processed.

[0024] 2) The method of the present invention uses water and anhydrous ethanol as reaction media, and the reaction conditions are mild and do not pollute the environment.

[0025] 3) The reagents used in the method of the present invention can be recycled and regenerated.

[0026] 4) The final product of the method of the present invention has a high yield and good mechanical properties.

[0027] 5) The method of the present invention is simple to operate, the raw materials are abundant and inexpensive, and it is easy to apply to industrial production. Attached Figure Description

[0028] Figure 1 This is a flowchart illustrating the preparation process of Example 5 of the present invention;

[0029] Figure 2 This is a square wave waveform diagram showing the change of dynamic molding pressure over time.

[0030] Figure 3 The bar chart shows the yield of the products after the two chemical reactions in steps (2) and (3) of Examples 1-6 of the present invention.

[0031] Figure 4 These are the appearance morphology images of the dynamic imine-type full-component hemp fiber sheets that can be repeatedly heat-processed after hot pressing, prepared according to Examples 1-6 of the present invention.

[0032] Figure 5 The bar chart shows the bending properties of the dynamic imine-type full-component hemp fiber that can be repeatedly heat-processed and prepared in Examples 1-9 of this invention, and the thermoplasticizable full-component hemp fiber material prepared in Comparative Examples 1-2, after hot pressing into sheets. Detailed Implementation

[0033] This invention provides a method for preparing a dynamic imine-type plant fiber modified material, comprising the following steps:

[0034] 1) Pre-treat the plant fibers to obtain pre-treated plant fibers;

[0035] 2) Disperse the pretreated plant fibers in water, then add periodate to carry out an oxidative ring-opening reaction to obtain oxidized plant fibers;

[0036] 3) Oxidized plant fibers and diamine were mixed in anhydrous ethanol for amination reaction to obtain dynamic imine-type modified plant fiber materials.

[0037] In this invention, the plant fiber pretreatment method in step 1) includes one or more of grinding, high shear homogenization and steam explosion, preferably steam explosion.

[0038] In this invention, the steam explosion equipment used is either an intermittent steam explosion equipment or a continuous screw extrusion flash explosion equipment.

[0039] In this invention, the purpose of pretreating plant fibers is to improve the responsiveness of plant fibers.

[0040] In this invention, the plant fiber comprises one or more of hemp, straw and bamboo plants, preferably hemp.

[0041] In this invention, in step 2), the mass ratio of pretreated plant fiber to water is 0.1 to 10:100, preferably 2 to 8:100, and more preferably 3 to 6:100.

[0042] In this invention, in step 2), the mass ratio of periodate to pretreated plant fiber is 0.1 to 2:1, preferably 0.5 to 1.2:1, and more preferably 1:1.

[0043] In this invention, the periodate is sodium periodate and / or potassium periodate.

[0044] In this invention, in step 2), the temperature of the oxidation ring-opening reaction is 20-80°C, preferably 30-60°C, and more preferably 40-50°C; the reaction time is 1-8 hours, preferably 2-6 hours, and more preferably 3-5 hours.

[0045] In this invention, in step 3), the diamine comprises one or more of 1,4-butanediamine, 1,6-hexanediamine, 1,8-octanediamine, 1,10-diaminodecane, and 1,12-diaminododecane, preferably one or more of 1,6-hexanediamine, 1,8-octanediamine, 1,10-diaminodecane, and 1,12-diaminododecane, and more preferably 1,10-diaminodecane and / or 1,12-diaminododecane.

[0046] In this invention, in step 3), the molar ratio of the amino group in the diamine to the aldehyde group in the oxidized plant fiber is 0.6 to 1.6:1, preferably 1.0 to 1.4:1, and more preferably 1.2:1.

[0047] In this invention, in step 3), the mass ratio of oxidized plant fiber to anhydrous ethanol is 0.1 to 10:100, preferably 2 to 8:100, and more preferably 3 to 6:100.

[0048] In this invention, the mass of the oxidized plant fiber is measured on an oven-dry basis.

[0049] In this invention, in step 3), the temperature of the amination reaction is 20-80°C, preferably 30-60°C, and more preferably 40-50°C; the reaction time is 1-48 h, preferably 5-40 h, and more preferably 10-30 h.

[0050] The present invention also provides a dynamic imine-type plant fiber modified material.

[0051] The dynamic imine-type plant fiber modified material of the present invention is a fully-component plant fiber that can be repeatedly heat-processed and can be repeatedly heat-processed without being compounded with thermoplastic polymer materials.

[0052] The technical solutions provided by the present invention will be described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0053] In the following examples, the dynamic imide-type plant fiber modified material was formed using both conventional molding and dynamic molding. The pressure in conventional molding remained constant over time, while the pressure applied in dynamic molding varied periodically over time, exhibiting a square wave waveform with a frequency of 3 Hz. The conventional molding temperature was 170°C, the molding time was 20 minutes, and the molding pressure was 20–35 MPa.

[0054] Example 1

[0055] A method for preparing a dynamically imine-type full-component plant fiber material that can be repeatedly heat-processed includes the following steps:

[0056] (1) Hemp blocks about 1-2 cm long were pretreated by steam explosion (continuous screw extrusion flash explosion equipment) to destroy their bundle structure and obtain steam-exploded hemp fiber (HF);

[0057] (2) HF was dispersed in water, and the mass ratio of dry HF to water was 1:30 to obtain dispersion-1. Then sodium periodate was added to dispersion-1, and the mass ratio of dry HF to sodium periodate was 1:0.1. The reaction was carried out at 55℃ for 5 hours. After washing and filtration, oxidized hemp fiber (OHF) was obtained, with an aldehyde content of 0.498 mmol / g.

[0058] (3) Disperse the oven-dried OHF in anhydrous ethanol at a mass ratio of 1:10 to obtain dispersion-2. Then add 1,10-diaminodecane (DA 102), in which the molar ratio of amino groups to aldehyde groups is 1.4:1. React at 25°C for 8 hours, wash and filter to obtain a dynamic imine-type full-component hemp fiber material that can be repeatedly heat-processed, denoted as OAHF-0.1-1.4, where 0.1 represents the amount of sodium periodate added and 1.4 represents the amount of DA 102 added.

[0059] (4) Adjust the moisture content of OAHF-0.1-1.4 to 50%, place it evenly in the mold, and hot press it for 20 minutes at 170℃ and 30MPa to obtain a hot-pressed sample.

[0060] Example 2

[0061] The difference between this embodiment and Example 1 is that the mass ratio of oven-dry HF to sodium periodate is controlled at 1:0.2, while other steps and parameters are the same as in Example 1. The resulting dynamically imide-type full-component hemp fiber material that can be repeatedly heat-processed is denoted as OAHF-0.2-1.4. Other conditions remain unchanged.

[0062] Example 3

[0063] The difference between this embodiment and Example 1 is that the mass ratio of oven-dry HF to sodium periodate is controlled at 1:0.3, while other steps and parameters are the same as in Example 1. The resulting dynamically imide-type full-component hemp fiber material that can be repeatedly heat-processed is denoted as OAHF-0.3-1.4. Other conditions remain unchanged.

[0064] Example 4

[0065] The difference between this embodiment and Example 1 is that the mass ratio of oven-dry HF to sodium periodate is controlled at 1:0.6, while other steps and parameters are the same as in Example 1. The resulting dynamically imide-type full-component hemp fiber material that can be repeatedly heat-processed is denoted as OAHF-0.6-1.4. Other conditions remain unchanged.

[0066] Example 5

[0067] The difference between this embodiment and Example 1 is that the mass ratio of oven-dry HF to sodium periodate is controlled at 1:0.9, while other steps and parameters are the same as in Example 1. The resulting dynamically imide-type full-component hemp fiber material that can be repeatedly heat-processed is denoted as OAHF-0.9-1.4. Other conditions remain unchanged.

[0068] Example 6

[0069] The difference between this embodiment and Example 1 is that the mass ratio of oven-dried HF to sodium periodate is controlled at 1:1.2, while other steps and parameters are the same as in Example 1. The resulting dynamically imine-type full-component hemp fiber material that can be repeatedly heat-processed is denoted as OAHF-1.2-1.4. Other conditions remain unchanged.

[0070] Example 7

[0071] This embodiment is a dynamic imide-type full-component hemp fiber material sample obtained by crushing and de-crosslinking the sample from Example 3, mixing it with water at a 1:1 mass ratio, heating it at 80°C for 3 hours to de-crosslink, and then re-molding it using ordinary molding. It is denoted as OAHF-0.3-1.4-R. Other conditions remain unchanged.

[0072] Example 8

[0073] The difference between this embodiment and Embodiment 3 is that the dynamically imide-type full-component hemp fiber material that can be repeatedly heat-processed is dynamically molded and is designated OAHF-D. All other conditions remain unchanged.

[0074] Example 9

[0075] This embodiment is a dynamic imide-type full-component hemp fiber material sample obtained by crushing and de-crosslinking the sample from Example 8, mixing it with water at a 1:1 mass ratio, heating it at 80°C for 3 hours to de-crosslink, and then re-forming it through dynamic compression molding. This sample is designated OAHF-DR. All other conditions remain unchanged.

[0076] Comparative Example 1

[0077] (1) This step is consistent with step (1) of Example 1;

[0078] (2) The difference between this step and step (2) in Example 1 is that the mass ratio of oven-dry HF to sodium periodate is controlled to be 1:0.3;

[0079] (3) Disperse OHF in water, with the mass ratio of oven-dried OHF to water being 1:40, to obtain dispersion-2. Add acetic acid dropwise to adjust the pH of dispersion-2 to 5, then add sodium chlorite, with a molar ratio of sodium chlorite to aldehyde group of 2.5:1. At the same time, add the same mass of 30% hydrogen peroxide as sodium chlorite. React at room temperature for 5 hours. After washing and filtration, carboxylated hemp fiber (CHF) is obtained, with a carboxyl content of 0.90 mmol / g.

[0080] (4) Disperse CHF in water, and the mass ratio of dry CHF to water is 1:30 to obtain dispersion-3. Add sodium hydroxide dropwise to adjust the pH of dispersion-3 to 10. Then add hexadecyltrimethylammonium bromide (CTAB) with a molar ratio of CTAB to carboxyl group of 3.0:1. React at 60℃ for 3 hours. Wash and filter to obtain thermoplasticizable full-component hemp fiber material, denoted as CCHF-0.3-3.0, where 0.3 represents the amount of periodate added and 3.0 represents the amount of CTAB added.

[0081] (5) Place CCHF-0.3-3.0 evenly in the mold and hot press it for 20 minutes at 170℃ and 30MPa to obtain a hot-pressed sample.

[0082] Comparative Example 2

[0083] This comparative example is a sample obtained by crushing the sample from Comparative Example 1 and then re-molding it using ordinary molding. It is denoted as CCHF-0.3-3.0-R. All other conditions remain unchanged.

[0084] As can be seen from the above embodiments, the present invention provides a dynamic imine-type plant fiber modified material and its preparation method. Figure 2 This is a square wave waveform diagram showing the change of dynamic molding pressure over time. Figure 2 It can be seen from this that the frequency of dynamic molding is 3Hz;

[0085] Figure 3 This is a bar chart showing the yield of the products after the two chemical reactions (2) and (3) in Examples 1-6 of the present invention. Figure 3 As can be seen, the yield of OAHF gradually decreases with the increase of oxidation degree. Therefore, a higher product yield can be obtained by controlling the oxidation degree of the product at a low level.

[0086] Figure 4 Images shown are of the morphology of the dynamically imine-type full-component hemp fiber sheets prepared in Examples 1-6 after hot pressing. Figure 4 The sheet is brownish-red, and the color gradually darkens as the amount of sodium periodate added increases.

[0087] Figure 5 The bar charts show the bending properties of the dynamic imine-type full-component hemp fiber prepared in Examples 1-9 and the thermoplasticizable full-component hemp fiber prepared in Comparative Examples 1-2 after hot pressing. The comparison shows that the products obtained by repeated hot pressing of OAHF material after de-crosslinking are more stable, while the products obtained by repeated hot pressing of CCHF are less stable. Furthermore, dynamic molding can significantly improve the mechanical properties of OAHF material compared to ordinary molding.

[0088] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a dynamic imine-type plant fiber modified material, characterized in that, Includes the following steps: 1) Pre-treat the plant fibers to obtain pre-treated plant fibers; 2) The pretreated plant fibers were dispersed in water, and then periodate was added to carry out an oxidative ring-opening reaction to obtain oxidized plant fibers; 3) Oxidized plant fibers and diamine were mixed in anhydrous ethanol for amination reaction to obtain dynamic imine-type modified plant fiber materials; In step 1), the plant fiber pretreatment method includes one or more of grinding, high-shear homogenization and steam explosion; The plant fibers comprise one or more of hemp, straw, and bamboo plants; In step 2), the temperature of the oxidative ring-opening reaction is 20~80℃ and the reaction time is 1~8h.

2. The method for preparing the dynamic imine-type plant fiber modified material according to claim 1, characterized in that, In step 2), the mass ratio of pretreated plant fiber to water is 0.1~10:

100.

3. The method for preparing the dynamic imine-type plant fiber modified material according to claim 2, characterized in that, In step 2), the mass ratio of periodate to pretreated plant fiber is 0.1~2:

1.

4. The method for preparing the dynamic imine-type plant fiber modified material according to claim 1, 2, or 3, characterized in that, In step 3), the diamine is one or more of 1,4-butanediamine, 1,6-hexanediamine, 1,8-octanediamine, 1,10-diaminodecane, and 1,12-diaminododecane.

5. The preparation method of the dynamic imine-type plant fiber modified material according to claim 4, characterized in that, In step 3), the molar ratio of the amino group in the diamine to the aldehyde group in the oxidized plant fiber is 0.6~1.6:

1.

6. The method for preparing the dynamic imine-type plant fiber modified material according to claim 1, 2, or 5, characterized in that, In step 3), the mass ratio of oxidized plant fiber to anhydrous ethanol is 0.1~10:

100.

7. The method for preparing the dynamic imine-type plant fiber modified material according to claim 6, characterized in that, In step 3), the amination reaction is carried out at a temperature of 20-80°C for 1-48 hours.

8. The dynamic imine-type plant fiber modified material obtained by the preparation method according to any one of claims 1 to 7.

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