A kind of whole plant high toughness plastic material and its preparation method and application

Abstract

The application discloses a kind of full plant high toughness plastic material and its preparation method and application. With paper or natural cellulose biomass material as raw material, through special process induction treatment, full plant base material with excellent strength and toughness is obtained. The high plastic material of this natural plant material composition breaks through the bottleneck problem of natural material processing, and is expected to adopt stamping, forging and other low-cost processing methods, thereby greatly reducing the processing cost of natural material, expanding the application field of natural material, and providing low-cost material for sustainable development. At the same time, the required instrument is simple, and large-scale production can be realized, with good social and economic value.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of cellulosic materials, and particularly relates to a full-plant high-toughness plastic material, a preparation method and application thereof. BACKGROUND

[0002] Petroleum-based plastics have been widely used in packaging, construction, medical treatment and other fields due to their excellent processing performance, mechanical strength and wide applicability. However, such plastics are derived from non-renewable petrochemical resources, and due to their chemical stability, they are difficult to degrade in the natural environment, posing a threat to the ecological system and human health. With the increasing demand for sustainable development, renewable and biodegradable new materials have become a research hotspot in order to reduce the environmental burden and meet the application demand of environmentally friendly new materials.

[0003] Under this background, plant-based biomass materials, especially cellulosic materials, have gradually become a research hotspot due to their wide source, low cost, renewability and good biocompatibility. However, the inherent characteristics of cellulosic materials, such as relative brittleness and low plasticity, limit their application in high-toughness-required fields. If natural cellulosic materials can be endowed with plasticity and low-cost processing similar to plastics and metal materials, it will greatly promote the market application of natural plant materials. In recent years, researchers have tried to improve the mechanical properties such as plasticity and strength of cellulosic materials through methods such as dissolution and regeneration, modification and compounding. Current researches are mostly focused on obtaining high-strength cellulosic materials, for example, CN115785498A discloses a preparation method of high-strength cross-linked regenerated cellulose film, which can fully dissolve cotton fibers in a relatively short time and low acidic environment, greatly reducing the hydrolysis degree of cotton fibers during the dissolution process, and further improving the mechanical tensile strength of the regenerated cellulose film by changing the regeneration bath conditions. The common way to obtain high-strength cellulose film is dissolution and regeneration, and many methods for dissolving cellulose have been developed, for example, CN109337097A discloses a method for dissolving cellulose using ionic liquid and N-hydroxyalkyl caprolactam, which can greatly improve the dissolution efficiency and the cellulose is not easily degraded, but the solvent cost is high, the economic benefit is low, and it is not conducive to mass production. Through grafting and other methods, natural cellulosic materials can obtain thermoplasticity (such as cellulose acetate materials), but such modification and compounding methods change the molecular structure of cellulose, thereby greatly reducing its biodegradability. The current technology and method have limited improvement on the plasticity of natural cellulosic materials. How to greatly improve the plasticity of cellulosic materials through structural design and process optimization is still a difficult problem to be solved. SUMMARY

[0004] Invention purposes: The purpose of the present application is to provide a kind of full plant high toughness plastic material, solve the problem of lower strain capacity and poor toughness of existing natural cellulose material;Another purpose of the present application is to provide the preparation method and application of the full plant high toughness plastic material.

[0005] Technical scheme: The full plant high toughness plastic material described in the present application is composed of natural plant fiber, without additional material, the component is cellulose, and the structure is the mixed structure of surface dense, internal layered overlapping micro-nano fiber.

[0006] Preferably, the full plant high toughness plastic material is isotropic, and the breaking strength is 54.80-200.30MPa, the elongation at break is 22.0-86.2%, and the toughness is 18.80-93.95MJ / m 3 .

[0007] The preparation method of the full plant high toughness plastic material described in the present application comprises the following steps:

[0008] (1) the natural cellulose biomass material is crushed and soaked in DMAc solution;

[0009] (2) after heating activation, LiCl is added and stirred to dissolve;

[0010] (3) after standing to obtain gel state sample, dry forming;

[0011] (4) after dry forming, the sample is soaked in DMAc aqueous solution, washed with strong alkali solution, soaked in DMAc aqueous solution again, and washed with water;

[0012] (5) dry again to obtain full plant high toughness plastic material.

[0013] Preferably, the natural cellulose biomass material is at least one of wood, cotton, hemp, bamboo, straw, grass and paper containing plant fiber.

[0014] Preferably, in step (1), the mass fraction of natural cellulose biomass material in the system is 2%-10%.

[0015] Preferably, in step (2), the activation treatment temperature is 150-170 DEG C, and the time is 1-24h;The dissolution temperature is 95-110 DEG C, and the time is 2-24h.

[0016] Preferably, the standing in step (3) is carried out under the condition of excluding moisture.

[0017] Further preferably, the standing time in step (3) is not less than 12h.

[0018] Preferably, in step (3), the drying step, the ambient temperature range is 25℃-150℃, and the molding time is not less than 3h.

[0019] Further preferably, the drying molding environment is a high-temperature and low-water environment. The high-temperature and low-water environment not only induces the gel-state sample to rapidly lose water and regenerate cross-linking to form a layered structure, but also forms a more compact surface and internal structure compared to the normal temperature and ventilation environment.

[0020] Further preferably, the high-temperature and low-water environment is an oven.

[0021] Preferably, in step (4), the mass percentage concentration of the DMAc aqueous solution ranges from 20% to 70%.

[0022] Further preferably, the solution can also contain a small amount of alcohol, with a mass percentage concentration ranging from 5% to 10%.

[0023] Further preferably, the alcohol includes but is not limited to ethanol and isopropanol.

[0024] Preferably, in step (4), the first soaking treatment time is not less than 30 minutes, the second soaking treatment time is not less than 1h; the strong alkali solution includes at least one of sodium hydroxide solution, potassium hydroxide solution, and lithium hydroxide solution, with a mass percentage concentration ranging from 10% to 30%, and the cleaning temperature is 25℃-60℃.

[0025] Further preferably, the strong alkali solution cleaning is a strong alkali solution soaking cleaning, and the soaking time is 30s-2h.

[0026] Further preferably, step (4) can be repeated multiple times. The first soaking in the DMAc aqueous solution can quickly clean the residual lithium chloride, lignin, and hemicellulose in the film. The alkali solution soaking cleaning causes the fibers to shrink and entangle to a certain extent, improving the mechanical stability of the film in water. The second soaking in the DMAc aqueous solution can produce a reswelling effect on the internal structure of the material, further improving the degree of close combination. Water washing can effectively remove the strong alkali and solvent, promote the regeneration of cellulose, and further promote the formation of a compact structure.

[0027] Preferably, in step (5), the drying method is pressure treatment at 0Mpa-40Mpa or natural air drying, with a temperature of 25℃-60℃; after drying treatment, the water content of the whole-plant high-toughness plastic material is less than 15wt%. During hot pressing, the high pressure in the z-axis direction eliminates the residual voids in the material and effectively stacks the micro-nano fibers. This is more conducive to the formation of a compact and strong structure.

[0028] The application relates to the application of a whole-plant high-toughness plastic material or a whole-plant high-toughness plastic material prepared by any of the preparation methods of the application in the packaging, building, medical, electronic and energy industries.

[0029] The application dissolves natural cellulose biomass materials such as cellulose paper in a DMAc / LiCl system, and then prepares regenerated cellulose materials with high breaking elongation and high toughness through temperature induction and solvent treatment.

[0030] The application uses pure cellulose paper or natural cellulose biomass materials as raw materials, and adopts specific temperature induction stereoscopic crosslinking and chemical and mechanical treatment double densification to prepare a whole-plant high-toughness plastic material with high breaking elongation and high toughness, which has advantages in green environmental protection, cost and social and economic benefits, and provides a green and sustainable alternative path. The material can replace part of petroleum-based plastics in various application fields, thereby reducing the influence on the environment and promoting the continuous progress of various fields under the drive of the concept of sustainable development.

[0031] Advantages: Compared with the prior art, the whole-plant high-toughness plastic material prepared by the application has the following remarkable advantages: the whole-plant high-toughness plastic material prepared by the application overcomes the problems that the hydrogen bond interaction between plant micron-level large fibers is weak and difficult to control, introduces a new interaction mode between fibers, and realizes the close stacking and strength control of the interaction between fibers through interaction synergy; through special process treatment, the regenerated cellulose material has a strain capacity of up to 80%, while maintaining excellent strength (156.3 MPa) and high toughness (93.95 MJ / m 3 ), can replace plastic materials used in daily production and life in many aspects, and has a wide application prospect. The whole-plant high-toughness plastic material is composed of conventional micro-nano plant fibers and does not contain other additives, can be completely biodegraded, is green and environmentally friendly, and also ensures the performance stability of the material within a certain temperature and humidity environment range as much as possible. BRIEF DESCRIPTION OF DRAWINGS

[0032] Figure 1 It is a scanning electron microscope image and an enlarged detail image of the cross section of the whole-plant high-toughness plastic material prepared in Example 1.

[0033] Figure 2 It is a surface scanning electron microscope image of the whole-plant high-toughness plastic material prepared in Example 1 before stretching.

[0034] Figure 3 It is a surface scanning electron microscope image of the whole-plant high-toughness plastic material prepared in Example 1 after stretching.

[0035] Figure 4Tensile mechanical property curve of the all-plant high-toughness plastic material prepared in Example 1. DETAILED DESCRIPTION

[0036] The technical solutions of the present application are further described below in combination with the drawings.

[0037] Example 1: A preparation method of an all-plant high-toughness plastic material is as follows:

[0038] (1) 15 g of cotton fibers are soaked in 350 g of DMAc solution, placed in an oil bath pot at a high temperature of 165℃ for 1 h, cooled to 105℃, and 30 g of LiCl is added and stirred for dissolution for 3 h;

[0039] (2) The sample is taken out and left to stand for 24 h to obtain a viscous and translucent gel state sample, 150 g of which is uniformly coated on the surface of a mold of 30 cm x 40 cm, and film formation is carried out at a temperature of 60℃ in an oven;

[0040] (3) Soaking in DMAc aqueous solution for 2 h, soaking in 20% sodium hydroxide solution for 2 min, and then soaking in DMAc aqueous solution for 2 h, and then taking out and rinsing with running water;

[0041] (4) The sample is placed in a press and hot-pressed and dried at 20 Mpa and 60℃ for 6 h in the direction perpendicular to the paper surface, and then taken out and naturally dried, to obtain an all-plant high-toughness plastic material with a moisture content of less than 20%.

[0042] Figure 1 A cross-sectional scanning electron microscope image and an enlarged detail image of the all-plant high-toughness plastic material prepared in Example 1; Figure 2 A surface scanning electron microscope image before stretching thereof; Figure 3 A surface scanning electron microscope image after stretching thereof; Figure 4 A tensile mechanical property curve.

[0043] Example 2: The rest are the same as Example 1, except that:

[0044] The sample is taken out and left to stand for 24 h to obtain a viscous and translucent gel state sample, 150 g of which is uniformly coated on the surface of a mold of 30 cm x 40 cm, and film formation is carried out at room temperature in a natural environment.

[0045] Example 3: The rest are the same as Example 1, except that:

[0046] The sample is taken out and left to stand for 24 h to obtain a viscous and translucent gel state sample, 150 g of which is uniformly coated on the surface of a mold of 30 cm x 40 cm, and film formation is carried out at a temperature of 80℃ in an oven.

[0047] Example 4: The rest are the same as Example 1, except that:

[0048] The sample was taken out and left to stand for 24 h, obtaining a viscous translucent gel state sample, 150 g of which was uniformly coated on the surface of a 30 cm x 40 cm mold, and the sample was placed in an oven at a temperature of 150°C to form a film.

[0049] Example 5: The rest were the same as in Example 1, except that:

[0050] After the sample was placed in an oven at a temperature of 60°C to form a film, no treatment was performed, and the sample was naturally air-dried after water washing.

[0051] Example 6: The rest were the same as in Example 1, except that:

[0052] After the solvent treatment of step (3) was performed, no heat pressing and drying treatment of step (4) was performed, and the sample was naturally air-dried after water washing.

[0053] Example 7: The rest were the same as in Example 1, except that:

[0054] After the solvent treatment of step (3) was performed, no heat pressing and drying treatment of step (4) was performed, and the sample was naturally air-dried after water washing.

[0055] Comparative Example 1: The rest were the same as in Example 2, except that:

[0056] After the sample was placed in a mold at room temperature and naturally shrunk to form a film, no treatment was performed, and the sample was naturally air-dried after water washing.

[0057] Comparative Example 2:

[0058] After the sample was placed in a mold at room temperature and naturally shrunk to form a film, no treatment was performed, and the sample was naturally air-dried after water washing.

[0059] The tensile strength and elongation at break of the samples prepared in Examples 1-7 and Comparative Examples 1 and 2 were determined, and the results are as follows:

[0060] Table 1. Effect of different film-forming temperatures on the mechanical properties of the full-plant high-toughness plastic material

[0061] Serial number Tensile strength (MPa) Elongation at break (%) Toughness (MJ / m 3 ) Example 1 156.3 79.1 93.95 Example 2 109.9 60.5 48.62 Example 3 188.9 36.7 46.97 Example 4 200.3 22.0 22.77

[0062] Table 2. Effect of different post-treatment conditions on the mechanical properties of the full-plant high-toughness plastic material

[0063] Serial number Tensile strength (MPa) Elongation at break (%) Toughness (MJ / m 3 )] Example 5 75.8 68.9 39.68 Example 6 101.2 62.9 47.64 Example 7 122.6 74.1 67.23 Comparative Example 1 51.7 41.0 17.69 Comparative Example 2 52.5 24.1 9.09

[0064] From the analysis of the above examples 1-7 and comparative examples 1-2, and the data in Table 1, it can be seen that example 1 is the optimal scheme. The high-temperature and low-water conditions in the oven can induce the substrate to form a large number of amorphous regions, and the cellulose molecular chains are rapidly combined to produce a large number of dense hydrogen bonds, forming a tightly packed multi-layer staggered structure. The interlayer hydrogen bonds are relatively weak, and the intralayer cross-linking is absolutely dense. During the stretching process, the interlayer hydrogen bond effect is preferentially sacrificed, greatly improving the tensile strength of the regenerated cellulose film. High-temperature treatment within a certain range can improve the elongation at break of the cellulose film, thereby obtaining high-toughness plastic results, but the rapid regeneration of the cellulose film at a higher temperature makes it difficult to break the staggered layer during the stretching process, to some extent, losing the effect of improving the elongation at break, and showing a significant improvement in strength. From the results in Table 2, it can be seen that all the treatment methods during the preparation of high-toughness plastic materials exhibit a synergistic effect. Solvent treatment and drying methods further densify the regenerated cellulose film, improving the hydrogen bond stacking density inside the film, thereby improving its tensile strength and toughness.

[0065] In the preparation step, different raw materials were used as variables to investigate the effect of different raw materials on the mechanical properties of the full-plant high-toughness plastic material as follows.

[0066] Example 8: The rest are the same as example 1, except that:

[0067] Take 15g of broadleaf wood fiber and soak it in 350g of DMAc solution, place it in an oil bath at 165℃ for high-temperature activation for 1h, and then cool it to 105℃. Add 30g of LiCl and stir for 4h. Take out the sample and let it stand for 24h to obtain a viscous transparent gel state sample. Take 150g and evenly coat it on the surface of a 30cm×40cm mold, and place it in an oven at 60℃ to form a film.

[0068] Example 9: The rest are the same as example 1, except that:

[0069] Take 15g of bamboo fiber and soak it in 350g of DMAc solution, place it in an oil bath at 165℃ for high-temperature activation for 1h, and then cool it to 105℃. Add 30g of LiCl and stir for 3h. Take out the sample and let it stand for 50h to obtain a viscous transparent gel state sample. Take 150g and evenly coat it on the surface of a 30cm×40cm mold, and place it in an oven at 60℃ to form a film.

[0070] Example 10: The rest are the same as example 1, except that:

[0071] Take 15 g of straw, mechanically pulverized into powder, soaked in 350 g of DMAc solution, placed in an oil bath at 165°C for 1 h, cooled to 105°C, and 30 g of LiCl was added and stirred for 4 h. The sample was taken out and left to stand for 24 h to obtain a viscous gel state sample, 150 g of which was uniformly coated on the surface of a 30 cm x 40 cm mold, and a film was formed in an oven at 60°C.

[0072] Example 11: The rest are the same as Example 1, except that:

[0073] Take 15 g of recycled waste book paper, tear into 1 cm x 1 cm pieces, soak in 350 g of DMAc solution, place in an oil bath at 165°C for 1 h, cool to 105°C, and 30 g of LiCl was added and stirred for 4 h. The sample was taken out and left to stand for 24 h to obtain a viscous gel state sample, 150 g of which was uniformly coated on the surface of a 30 cm x 40 cm mold, and a film was formed in an oven at 60°C.

[0074] Example 12: The rest are the same as Example 1, except that:

[0075] Take 15 g of wood powder, soak in 350 g of DMAc solution, place in an oil bath at 165°C for 1 h, cool to 105°C, and 30 g of LiCl was added and stirred for 4 h. The sample was taken out and left to stand for 24 h to obtain a viscous gel state sample, 150 g of which was uniformly coated on the surface of a 30 cm x 40 cm mold, and a film was formed in an oven at 60°C.

[0076] The tensile strength and elongation at break of the samples prepared in Examples 8-12 were measured, and the results are as follows:

[0077] Table 3. Effect of cellulose polymerization degree in different cellulose papers on the mechanical properties of whole plant high-toughness plastic materials

[0078]

[0079] Table 4. Effect of different biomass material raw materials on the mechanical properties of whole plant high-toughness plastic materials

[0080] Serial number Raw material type Tensile strength (MPa) Elongation at break (%) toughness (MJ / m 3 ) Example 10 Wheat straw 71.9 28.5 18.80 Example 11 Waste book paper 109.8 62.6 58.38 Example 12 Wood powder 102.6 30.1 23.12

[0081] The results in Table 3 show that when the degree of polymerization of the cellulose in the raw material is low, the tensile strength of the prepared film material is higher, and the elongation at break is obviously improved; when the degree of polymerization of the cellulose is too high, the dissolution degree of the plant cellulose is not enough in a short time, and most of it is still in the micron fiber state, which cannot be regenerated to form a uniform and dense structure, resulting in defects in the film, which leads to low strength and low elongation at break, but the treatment method still has the effect of improving the toughness and plasticity. For cellulose raw materials with a high degree of polymerization, the dissolution treatment time should be increased to obtain a sample with good dissolution degree. The results in Tables 3 and 4 show that the preparation method has a good effect on different natural cellulose biomass material raw materials, and the raw materials can form a dense and interlaced structure of micro-nano fibers through the above treatment, realize the improvement of plasticity and good balance with toughness.

[0082] In the preparation step, different raw material mass fractions were used as variables to investigate the effect of the mass fraction change of different cellulose raw materials in the dissolution system on the mechanical properties of the whole plant high-toughness plastic material as follows.

[0083] Example 13: The rest is the same as Example 1, except that:

[0084] In step (1), 7.15 g of cotton fiber was soaked in 350 g of DMAc solution, i.e., the raw material mass fraction was adjusted to 2%.

[0085] Example 14: The rest is the same as Example 1, except that:

[0086] In step (1), 22.34 g of cotton fiber was soaked in 350 g of DMAc solution, i.e., the raw material mass fraction was adjusted to 6%.

[0087] Example 15: The rest is the same as Example 1, except that:

[0088] In step (1), 38.89 g of cotton fiber was soaked in 350 g of DMAc solution, i.e., the raw material mass fraction was adjusted to 10%.

[0089] The tensile strength and elongation at break of the samples prepared in Examples 13-15 were measured, and the results are as follows:

[0090] Table 5 Effect of different raw material mass fractions on the mechanical properties of the whole plant high-toughness plastic material

[0091] Serial number Mass fraction (%) Tensile strength (MPa) Elongation at break (%) toughness (MJ / m 3 ) Example 1 4％ 156.3 79.1 93.95 Example 13 2％ 100.6 86.2 63.29 Example 14 6％ 72.9 74.2 37.83 Example 15 10％ 54.8 62.7 24.48

[0092] The results in Table 5 show that the higher the cellulose mass fraction, the denser the structure of the high-toughness plastic film prepared, the stronger the interaction between the molecular chains, and the higher the viscous resistance. The elongation at break decreases within a certain range. At the same time, due to the influence of the interlayer interaction force in the structure, the full-plant high-toughness plastic material in the lower mass fraction range and with a relatively loose structure can exhibit better tensile strength with high elongation at break.

[0093] In the dissolution and standing step, the influence of the dissolution degree of cellulose on the mechanical properties of the full-plant high-toughness plastic material was investigated with time as the variable as follows.

[0094] Example 16: The rest are the same as Example 1, except that:

[0095] The sample was taken out and stood for 12 h to obtain a relatively viscous gel state sample, 150 g of which was uniformly coated on the surface of a 30 cm x 40 cm mold, and the film was formed in an oven at a temperature of 60°C.

[0096] Example 17: The rest are the same as Example 1, except that:

[0097] The sample was taken out and stood for 50 h to obtain a viscous transparent gel state sample, 150 g of which was uniformly coated on the surface of a 30 cm x 40 cm mold, and the film was formed in an oven at a temperature of 60°C.

[0098] The tensile strength and elongation at break of the samples prepared in Examples 16 and 17 were determined, and the results are as follows:

[0099] Table 6. Influence of different dissolution degrees on the mechanical properties of the full-plant high-toughness plastic material

[0100] Serial number Tensile strength (MPa) Elongation at break (%) toughness (MJ / m 3 ) Example 1 156.3 79.1 93.95 Example 16 67.8 65.0 29.71 Example 17 96.4 38.0 30.35

[0101] As can be seen from the results in Table 6, the preparation and treatment method of the full-plant high-toughness plastic material plays a good role in cellulose with different dissolution degrees. When the cellulose dissolution time is short, the proportion of micron-sized fibers in the micro-nano fiber mixed structure is large, and many voids or defects are generated in the temperature-induced close stacking process. The strengthening effect of the solvent and mechanical hot pressing treatment reduces the influence of defects, and the overall still exhibits strong anti-fracture ability. When the dissolution time is long, most of the cellulose gel is decomposed into nano fibers, the cross-linking degree is improved, the interlayer connection is also more close, and the deformation is difficult during the stretching process, so it exhibits the results of increased tensile strength and slightly decreased elongation at break.

Claims

1. A method of preparing a full-plant high-toughness plastic material, characterized by, Comprising the following steps: (1) crushing natural cellulose biomass material, soaking in DMAc solution; (2) after heating activation, adding LiCl stirring and dissolving; (3) after standing to obtain gel state sample, drying and forming; (4) after drying and forming, soaking the sample in DMAc aqueous solution, washing with strong alkali solution, then soaking in DMAc aqueous solution again, and taking out for water washing; (5) drying again to obtain the all-plant high-toughness plastic material; The standing in step (3) is carried out under moisture isolation conditions; In step (4), the mass percentage concentration of the DMAc aqueous solution is in the range of 20%-70%; In step (4), the first soaking treatment time is not less than 30 min, and the second soaking treatment time is not less than 1 h; the strong alkali solution includes at least one of sodium hydroxide solution, potassium hydroxide solution, and lithium hydroxide solution, and the mass percentage concentration is in the range of 10%-30%.

2. The method for preparing the whole-plant high-toughness plastic material according to claim 1, characterized in that: The natural cellulose biomass material is at least one of wood, cotton, hemp, bamboo, straw, grass, and paper containing plant fibers.

3. The method for preparing the whole-plant high-toughness plastic material according to claim 1, characterized in that: In step (1), the mass fraction of the natural cellulose biomass material in the system is 2%-10%.

4. The method for preparing the whole-plant high-toughness plastic material according to claim 1, characterized in that: In step (3), the drying process is carried out at an ambient temperature in the range of 25℃-150℃.

5. A full plant high tenacity plastic material prepared by any one of the processes of claims 1 to 4, characterized in that, The material is composed of natural plant fibers, without additional substances, and the composition is cellulose, and the structure is a mixed structure of surface dense and internal layered overlapping micro-nano fibers.

6. The all-plant high tenacity plastic material of claim 5, wherein, The whole plant high-toughness plastic material is isotropic, the breaking strength is 54.80-200.30 MPa, the breaking elongation is 22.0-86.2%, and the toughness is 18.80-93.95 MJ / m 3 .

7. Use of the all-plant high-toughness plastic material of claim 5 or 6 or prepared by the method of any one of claims 1-4 in the packaging, building, medical, electronic, and energy industries.

Images