CN113321854A

CN113321854A - Degradable micro/nano fiber glue-free self-adhesive straw and preparation method thereof

Info

Publication number: CN113321854A
Application number: CN202110422351.1A
Authority: CN
Inventors: 陈楚楚; 吴启静; 周彤; 刘硕; 王露臻; 徐朝阳; 李大纲
Original assignee: Nanjing Forestry University
Current assignee: Nanjing Forestry University
Priority date: 2021-04-20
Filing date: 2021-04-20
Publication date: 2021-08-31

Abstract

The invention discloses a degradable micro/nano fiber glue-free self-adhesive straw and a preparation method thereof. The straw is made of the waste shrimp and crab shells, so that the waste resources are recycled, the problem of resource shortage in the existing straw production and processing process can be effectively solved, the straw can be completely recycled, the production and processing are easy, and the cost is low; the material components of the straw only contain chitin or chitin and partial protein, any wet strength agent, chemical filler, auxiliary agent and the like are not required to be added, any adhesive is not required to be used for bonding after the straw is curled, and the straw is naturally dried, so that the product is safer; can be buried in soil for natural degradation, does not cause environmental pollution, and can not cause harm to natural organisms after being discarded at will. Therefore, the invention is a novel full-biomass natural degradable straw which can replace a plastic straw and is more environment-friendly and safer than a paper straw.

Description

Degradable micro/nano fiber glue-free self-adhesive straw and preparation method thereof

Technical Field

The invention belongs to the technical field of new biological materials and high molecular compounds, and particularly relates to a degradable micro/nano fiber glue-free self-adhesive straw and a preparation method thereof.

Background

In 1 month 2020, the center issues "opinions on further strengthening plastic pollution control" that the use of non-degradable disposable plastic straws is prohibited by the national catering industry by the end of 2020. Since 2008 'plastic-restricted ream', 12 years later 'plastic-restricted ream' is the limit for all non-degradable plastic products in the true sense. Thus, "non-degradable" under the limits of the restrictions is the reason for this.

The using amount of the plastic straws is large, and data show that the national plastic product cumulative yield in 2019 is 8184 ten thousand tons, wherein the plastic straws are nearly 3 ten thousand tons and about 460 hundred million roots, and the using amount per person exceeds 30. As a disposable plastic product in a plastic forbidden row, one plastic straw is used for about 20min on average and then is discarded; however, the degradation time of each plastic straw is as long as 500 years, and the environmental hazard is great.

With the increasing awareness of environmental protection, attempts have been made to develop straws made of paper, stainless steel, glass or iron, and other biodegradable materials to replace plastic straws. Until the last two years, paper straw business has been developed and has become the most common substitute for plastic straws. Compared with a plastic straw, the paper straw has the greatest advantage of natural degradation, but the paper straw is not filled with fillers such as sizing adhesives, waterproof wax and the like, so that certain potential safety hazards are caused, and meanwhile, the raw materials of the paper are partially from felling trees. In addition, in order to prevent the paper straw from being broken and ulcerated in the using process, the material consumption of the paper straw is 30% more than that of the plastic straw, and the wood raw material source of the paper straw is deficient, so that the cost of the paper straw is higher than that of the plastic straw. In recent years, biomass plastic starch straws, which are made of plant-derived plastic PLA (polylactic acid), the main material of which is corn starch, potato starch, sugar cane, beet root, cassava, and the like, have also attracted increasing attention. In practice, however, the environmental hazard of such straws may not be distinguishable from ordinary plastic straws. The bio-plastic straw can only be decomposed under specific environmental conditions, and generally needs to be assisted by industrial waste composting facilities, which are not available at present in most places. If not properly composted, the bio-plastic straw mixed into the landfill may take years to decompose; once in the marine environment, the situation is even worse, as they cannot be decomposed at all in the sea, which is a great hazard to marine animals. The chitin has wide sources, is a second natural renewable biological resource in nature, exists in a large number of waste shrimp and crab shells, and has good biocompatibility and biodegradability. An article was published in Nature Comment by Yan et al, national university of singapore (Yan, n., x. Chen, Don't water search waste water, Natural Comment, 2015, 524, 155-: "do not waste these marine wastes". The global condition of the marine waste shrimp and crab shells is briefly described in the text: 600- & 800 million tons of waste shrimps, crabs, lobster shells, etc. are produced every year around the world, of which 150 million tons are produced every year in southeast asia alone. The shrimp shells and the crab shells are solid wastes generated in the aquatic industry, the quantity of the solid wastes is increased along with the development of the freshwater and seawater aquaculture shrimp and crab industry in China, only a small part of the solid wastes is used for low value-added products such as feed additives, and the vast majority of the shrimp and crab shells are used as garbage to be randomly buried or poured into the sea or even not treated, so that the living environment of human beings is seriously influenced. The shrimp and crab shell waste contains a large amount of chitin, has high utilization value, but has low recycling rate, and not only causes serious waste of resources, but also pollutes the environment. Taking crab shell as an example in nature, the main components of the crab shell comprise skeleton material chitin, protein, inorganic salt such as calcium carbonate and the like, pigment and the like. The chitin molecule is stacked to form basic fibril through the interaction of Van der Waals force and intramolecular and intermolecular hydrogen bonds, the basic fibril is assembled to form micron fiber size and is arranged in layers, and after matrix components are removed through demineralization, deproteinization and the like, the natural chitin micro-nano structure in the shell of the Jiaoziman animal can be obtained.

Disclosure of Invention

The invention aims to provide a degradable micro/nano fiber glue-free self-bonding straw and a preparation method thereof, so that additive treatment processes such as sizing, filling and the like in straw preparation are avoided, the safety of the straw is improved, and the full biomass component of the straw material is realized.

The technical scheme for realizing the aim of the invention is that the preparation method of the degradable micro-nanofiber glue-free self-adhesive straw is characterized by comprising the following steps:

step a, purification: taking shrimp and crab shells as raw materials, removing matrix components in the shrimp and crab shells, and extracting and purifying the shrimp and crab shells;

b, pulping: carrying out surface micro/nano treatment on the purified shrimp and crab shells through physical stirring to prepare shrimp and crab shell slurry;

step c, suction filtration: carrying out suction filtration on the shrimp and crab shell slurry to prepare a wet film bottom material;

step d, forming: and (3) forming the wet film bottom material by using a mold, drying, and then self-bonding the joint to prepare the straw.

Preferably, in the step a, the matrix components removed are calcium carbonate, protein and pigment, and the specific steps are as follows:

step a.1, calcium carbonate removal: cleaning and drying shrimp and crab shells, soaking the shrimp and crab shells by 7wt% hydrochloric acid at normal temperature for 48-72 hours, completely removing calcium carbonate, and then cleaning the shrimp and crab shells by deionized water to be neutral to obtain softened shrimp and crab shells with the calcium carbonate removed;

step a.2. deproteinization: soaking the softened shrimp and crab shells with 4-20 wt% of aqueous alkali at normal temperature for 1-2 weeks, and removing protein to obtain softened shrimp and crab shells with calcium carbonate and protein removed;

step a.3, decoloring: washing the softened shrimp and crab shells without the calcium carbonate and the protein to be neutral, soaking the shrimp and crab shells with a decoloring agent for 12-48 hours at normal temperature, removing pigment components, and finally rinsing to obtain soft and white purified shrimp and crab shells only containing chitin.

Preferably, in the step a, the matrix components removed are calcium carbonate and pigment, and the specific steps are as follows:

step a.3, decoloring: and (3) washing the softened shrimp and crab shells without the calcium carbonate to be neutral, soaking the shrimp and crab shells with a decoloring agent for 12-48 hours at normal temperature to remove pigment components, and finally rinsing to obtain the purified shrimp and crab shells containing the chitin and part of protein.

Preferably, in the step b, no acid is added in the pulping process, and the specific steps are as follows: and (b) taking the purified shrimp and crab shells obtained in the step a as raw materials, adding deionized water to prepare a mixture with the weight of 1-2 wt%, and stirring the mixture for 2-20 minutes by using a food stirrer to obtain the neutral chitin suspended slurry prepared by pulping.

Preferably, in the step b, acid is added in the pulping process, and the specific steps are as follows: and (b) taking the purified shrimp and crab shells obtained in the step a as raw materials, adding deionized water to prepare a 1-2 wt% mixture, firstly dropwise adding 1-2 wt% acetic acid solution, adjusting the pH value to 3-4, and then stirring the mixture for 2-20 minutes by using a food stirrer to obtain the acidic chitin suspended slurry.

Preferably, in the step c, a straw is prepared from the shrimp and crab shell slurry obtained in the step b, and a wet film is formed through vacuum filtration and dehydration, and the method comprises the following specific steps: washing the sand core funnel with distilled water, putting a microporous filter membrane, starting a vacuum pump, taking the suspended slurry with proper solid content, introducing the suspended slurry into the funnel, and performing suction filtration to form the chitin micro/nano fiber wet membrane.

Preferably, in the step d, the chitin micro/nano fiber wet film obtained in the step c is rolled and pressed to be formed, and the glue-free self-adhesive straw is prepared after natural drying, and the specific steps are as follows:

d.1, removing the chitin micro/nano fiber wet film, cutting according to the size, then curling along one end of a rolling shaft mould, and ensuring that the wet film is tightly attached to the rolling shaft mould in the curling process to obtain a single-layer or multi-layer tubular wet film;

step d.2, naturally drying the tubular wet film on the roller mold for 1-8 hours to realize self-adhesion at the overlapping part of the tubular wet film;

and d.3, slightly rotating the suction pipe after drying to complete demolding, thus obtaining the degradable micro-nanofiber glue-free self-adhesive suction pipe.

Preferably, the roller mold is an easy-demoulding tool.

Preferably, the outer packaging bag is prepared by the same process and is used as the packaging bag of the degradable micro-nanofiber glue-free self-adhesive straw.

A degradable micro/nano fiber glue-free self-adhesive straw is prepared by the preparation method.

Compared with the prior art, the invention has the following remarkable advantages:

1. the invention takes the shell of crustacean as raw material, and obtains multi-grade chitin micro/nano fiber material after surface micro/nano treatment is carried out on purified shell particles, and a large amount of free hydroxyl groups are exposed on the surface of the obtained chitin. Abundant hydrogen bond combination is formed among a large number of free hydroxyl groups through self-assembly in the drying process, the edge curling and overlapping position of a 'wet film' is realized, the self-bonding phenomenon is generated, or the hydrogen bond cross-linking combination in the 'wet plate' is realized in the drying process, and the self-consolidation forming is realized; can be used as a whole biomass raw material of pipes, bags, plates or other products.

2. Different from plastic straws and paper straws (the raw materials are respectively from petroleum, wood and the like, the petroleum is a non-renewable resource, and wood resources are deficient), the straw raw material of the invention is the waste shrimp and crab shells, thereby realizing the reutilization of waste resources. Therefore, the problem of resource shortage in the production and processing process of the existing straw can be effectively solved, and the straw can be completely recycled, is easy to produce and process and has lower cost.

3. The material components of the whole biomass straw prepared based on the waste crab shells provided by the invention only comprise chitin or chitin and partial protein, and are completely derived from natural crab shells. In the whole preparation process, any wet strength agent, chemical filler, auxiliary agent and the like are not needed to be added, the curled edges are not needed to be bonded by any adhesive, and the adhesive-free self-bonding straw with higher strength can be prepared by natural drying. Therefore, the invention is more environment-friendly and safer than the prior paper straw. Meanwhile, the chitin straw prepared by taking the crab shells as the raw material cannot cause the problem of environmental pollution, can be buried in soil for natural degradation, and cannot cause harm to natural organisms even if being discarded at will.

4. The straw of the invention is a novel full-biomass natural degradable straw which can replace a plastic straw and is more environment-friendly and safer than a paper straw.

Drawings

FIG. 1 is a flow chart of the preparation method of the protein-free multi-level chitin micro/nano fiber material of the present invention.

FIG. 2 is a flow chart of the preparation method of the protein-containing multi-level chitin micro/nano fiber material of the present invention.

FIG. 3 is a flow chart of the method for manufacturing the non-adhesive self-adhesive pipette of the present invention.

Fig. 4 is a flow chart of a preparation method of the glue-free self-adhesive outer packaging bag material of the invention.

FIG. 5 is a flow chart of a method for preparing the non-glue full biomass artificial board.

FIG. 6 is a schematic view of the one-piece curl formation of the glue-free self-adhesive drinking straw of the present invention.

FIG. 7 is a cross-sectional view of a single-ply rolled overlapping joint of the glue-free self-adhesive drinking straw of the present invention.

FIG. 8 is a cross-sectional view of a multi-layer rolled overlap joint for a glue-free self-adhesive drinking straw of the present invention.

FIG. 9 is a schematic representation of the tensile test at the overlapping joint of the glue-free self-adhesive pipette of the present invention.

FIG. 10 is a photograph of a sample of the non-glue self-adhesive pipette of the present invention (examples 1-7).

FIG. 11 is a graph showing the effect of the bending strength test of the non-adhesive self-adhesive drinking straw of the present invention.

FIG. 12 is a graph showing the effect of the water resistance test of the glue-free self-adhesive pipette of the present invention.

Fig. 13 is a diagram showing the effect of the non-adhesive self-adhesive straw of the present invention on the weight of the straw suspended and not soft after soaking in water for 24 hours.

Fig. 14 is a photograph of a sample of the non-adhesive self-adhesive outer pouch material of the present invention (example 8).

FIG. 15 is a photograph of a sample of a binderless whole biomass artificial board of the invention (example 9).

Fig. 16 is a photograph (front side) showing the results of the burning test of the non-gelled biomass-based artificial board according to the present invention.

Fig. 17 is a photograph (back side) of the results of the burning test of the non-glue whole biomass artificial board according to the present invention.

FIG. 18 is a surface micro-topography of a straw material prepared by mechanical stirring in example 4 of the present invention.

Fig. 19 is a graph showing the defibering effect of the chitin fiber bundles obtained by mechanical stirring in example 4 of the present invention.

Fig. 20 is a transmission electron microscope image of the multi-level chitin micro/nanofibers after defibration in example 2 of the present invention.

Fig. 21 is a transmission electron microscope image of the multi-stage chitin micro/nanofibers after defibration in example 4 of the present invention.

FIG. 22 is a schematic diagram of the principle of adhesive-free self-adhesion at the overlapping (bonding) of the forming edges of the straws in examples 1-7 of the present invention.

FIG. 23 is a cross-sectional micro-topography of the lap bond of a straw in example 3 of the present invention.

Detailed Description

The invention is further described with reference to the following figures and embodiments. It is apparent that the embodiments described below are only a part of the embodiments of the present invention, and not all of them. All other embodiments, which can be derived by a person skilled in the art from the inventive concept of the present invention without inventive step, are within the scope of protection of the present application.

And (I) process description.

The process steps of the invention include five parts, refer to fig. 1-5 respectively, which are: the preparation method of the protein-free multi-level chitin micro/nano fiber material, the preparation method of the protein-containing multi-level chitin micro/nano fiber material, the preparation method of the glue-free self-adhesive straw, the preparation method of the glue-free self-adhesive outer packaging bag and the preparation method of the glue-free full-biomass artificial board. The process steps are as follows.

Process 1. preparation method of protein-free multi-grade chitin micro/nano fiber material.

Step 1.1, removing inorganic salt, protein and pigment from the crab shells, and extracting and purifying the crab shells. In order to keep the structure of the natural chitin nano-fiber in the crab shell, a normal-temperature mild preparation method is adopted.

Removing inorganic salt: firstly, cleaning and drying crab shells, soaking and treating the crab shells for 48-72 hours at normal temperature by using hydrochloric acid with the mass fraction of 7wt%, completely removing calcium carbonate, and then cleaning the crab shells to be neutral by using deionized water to prepare the softened crab shells with the calcium carbonate removed.

Deproteinization: and (3) further deproteinizing the washed neutral softened crab shell sample, and soaking for 1-2 weeks at normal temperature by using 4-20 wt% of sodium hydroxide (or potassium hydroxide) solution to remove residual protein, thereby obtaining the softened crab shell completely removed with calcium carbonate and protein. In the step, 4-8 wt% of alkali solution can be used for heating treatment at the temperature of more than 70 ℃ to replace the alkali solution soaking treatment at normal temperature.

And (3) decoloring: the softened crab shell sample is washed to be neutral and decolorized at room temperature. Soaking the raw materials in a decoloration reagent (50-95 wt% ethanol solution or 5-20wt% hydrogen peroxide solution) for 12-24 hours to remove pigment components. And rinsing after the treatment is finished to obtain soft and white purified crab shells only containing chitin.

And step 1.2, stirring the purified crab shells only containing chitin as raw materials to perform surface micro/nano treatment to prepare crab shell slurry.

Specifically, purified crab shells only containing chitin are used as raw materials, deionized water is added to prepare a mixed solution with the concentration of 1wt% -2 wt%, and the mixed solution is crushed for 2-20 min by a food mixer to obtain neutral chitin micro/nano fiber suspension slurry prepared by pulping.

Based on the natural property of the chitin, the acetic acid solution is added in the pulping process to promote the nanocrystallization degree of the chitin. Similarly, preparing a mixed solution with the concentration of 1-2 wt%, dropwise adding an acetic acid solution with the mass fraction of 1-2 wt% before stirring and crushing, and crushing for 2-20 min by using a food mixer for pulping to prepare the acidic chitin micro/nano fiber suspension slurry.

It is worth noting that the preparation of the micro/nano-fibers of the chitin is based on the arrangement of the naturally existing chitin nano-fibers in the crab shells, the formation of the chitin nano-fibers cannot be specially changed by the presence or absence of acid, but the naturally existing nano-fibers are refined by mechanical stirring to different degrees.

And 2. a preparation method of the protein-containing multi-grade chitin micro/nano fiber material.

And 2.1, removing inorganic salt and pigment from the crab shells to prepare the softened crab shells containing chitin/protein. In order to keep the structure of the natural chitin nano-fiber in the crab shell, a normal-temperature mild preparation method is adopted.

And (3) decoloring: and (3) further performing decoloration treatment on the softened crab shell sample washed to be neutral, and soaking the crab shell sample in a decoloration treatment reagent (50-95 wt% ethanol solution or 5-20wt% hydrogen peroxide solution) at room temperature for 12-24 hours to remove pigment components. And rinsing after the treatment is finished to obtain the natural composite crab shell containing protein and chitin. Here, part of the protein may be removed as the case may be.

And 2.2, taking the softened crab shells containing the chitin/protein as a raw material, stirring the raw material to perform surface micro/nano treatment, and preparing the crab shell slurry.

Specifically, crab shells containing chitin/protein are used as raw materials, deionized water is added to prepare a mixed solution with the concentration of 1wt% -2 wt%, and the mixed solution is crushed for 2-20 min by a food mixer to obtain neutral protein-chitin micro/nano-scale fiber suspension slurry prepared by pulping.

Based on the natural property of the chitin, the acetic acid solution is added in the pulping process to promote the nanocrystallization degree of the chitin. Similarly, preparing a mixed solution with the concentration of 1-2 wt%, dropwise adding an acetic acid solution with the mass fraction of 1-2 wt% before stirring and crushing, and crushing for 2-20 min by using a food mixer for pulping to prepare the acidic protein-chitin micro/nano fiber suspension slurry.

The membrane substrate material prepared by the method retains natural proteins in crab shells, and is expected to improve the hardness or strength of products prepared from the membrane substrate material.

And 3, a preparation method of the glue-free self-adhesive straw.

And 3.1, preparing the chitin micro/nano fiber wet film bottom material by suction filtration.

And (3) preparing a single-layer wet film by using the crab shell slurry prepared by the process 1 or the process 2, wherein the thickness of the single-layer wet film is controlled by controlling the solid content of the suspension base material. Specifically, the sand core funnel is cleaned by distilled water, then a microporous filter membrane is placed on the sand core funnel, a vacuum pump is started, mixed suspension crab shell slurry with rated solid content is taken and led into the funnel, and the chitin micro/nano fiber wet membrane bottom material or the protein-chitin micro/nano fiber wet membrane bottom material is prepared by suction filtration.

And 3.2, rolling and molding the wet film substrate, and naturally drying to prepare the full-biomass glue-free self-bonding straw.

A lubricating-resistant polytetrafluoroethylene rod is used as a curling-formed straw inner wall roller model, a wet film is pressed and cut from a suction filtration-formed wet film base material according to the size of a required roller, the polytetrafluoroethylene rod roller is curled along one end of the wet film, the wet film is uniformly attached to the polytetrafluoroethylene rod in the curling process, and the integrally-formed one-layer or multi-layer wet film straw is obtained according to the size of the pressed and cut wet film. And then, naturally drying for 1-8 hours to complete the hydrogen bond self-bonding effect at the overlapped joint of the wet films. Drying, demoulding and forming to obtain the whole biomass (chitin/chitin-protein) glue-free self-adhesive straw, wherein the diameter of the straw can be controlled within the range of 7 mm-15 mm.

It is worth noting that the straw curling manufacturing method of the invention has no special difference to the strength of the non-glue self-bonding except the non-glue self-bonding process of the integral curling forming, and the actual production can be carried out according to the straw production device actually existing in a factory, namely, the non-glue self-bonding alternative scheme including other straw forming methods.

Wherein, the step of forming the glue-free self-adhesive straw by coiling and pressing the wet film substrate and demoulding after natural drying refers to figure 6; single and multi-layer crimped lap joints are shown in cross-section in fig. 7 and 8, respectively.

And 3.3, testing the performances of the glue-free self-adhesive straw, including the mechanical properties of a single membrane and a joint of the straw, the bending strength of the straw and the water absorption and water resistance of the straw.

A universal mechanical experiment machine is used for testing the mechanical property of the non-adhesive self-adhesive straw single-membrane sample, and particularly testing the dry tensile strength, the elastic modulus and the wet tensile strength of the straw single-membrane, wherein the wet tensile strength is the tensile strength of the sample after being soaked in deionized water for a certain period of time.

The bonding strength of the adhesive-free self-bonding overlapped joint is represented by tensile shear strength, a universal mechanical experiment machine is used for testing the mechanical property of a sample, the sample is a single-layer pipette film adhesive-free self-bonding overlapped joint part, and the specific form is shown as a tensile schematic diagram in fig. 9.

The bending strength of the non-adhesive self-adhesive straw is tested by a three-point bending test method by using a universal mechanical testing machine, and the specific form is shown in figure 11. In order to improve the uniformity and accuracy of the test result of the sample, all the samples used for testing are two layers of straws.

The chitin glue-free self-adhesive double-layer suction pipe is subjected to water soaking tests for different durations in different temperature ranges of cold water at 15-25 ℃, warm water at 30-50 ℃ and hot water at 80-90 ℃, and the water absorption and water resistance of the glue-free self-adhesive suction pipe are comparatively displayed. In order to better show the water absorption and water resistance effects of the suction pipe, the coloring agent is added into the water to enable the interface with the rising water absorption to be displayed more clearly.

And 4, a preparation method of the glue-free self-bonding outer packaging bag.

And 4.1, forming the wet film of the outer packaging bag by suction filtration.

The crab shell slurry prepared by the process 1 is used for preparing the wet film of the outer packaging bag, and the thickness of the wet film of the packaging bag is controlled by controlling the solid content of the suspension bottom material. Cleaning a sand core funnel with distilled water, putting a microporous filter membrane, starting a vacuum pump, taking mixed suspended crab shell slurry with rated solid content, introducing the mixed suspended crab shell slurry into the funnel, and performing suction filtration to prepare the chitin micro/nano fiber wet membrane.

And 4.2, cutting, adhering joints, and naturally drying to prepare the packaging bag.

Cutting according to size after filtering and film forming, and bonding the joint to finish hydrogen bond self-bonding in the drying process. Drying and folding the two ends to form the outer packaging bag.

And 5, a preparation method of the glue-free full-biomass artificial board.

And 5.1, performing suction filtration to form a wet plate.

The crab shell slurry prepared by the process 1 is used for preparing the chitin wet plate, and the thickness of the chitin wet plate is controlled by controlling the solid content of the suspension base material. Cleaning a sand core funnel with distilled water, putting a microporous filter membrane, starting a vacuum pump, taking mixed suspended crab shell slurry with rated solid content, introducing the mixed suspended crab shell slurry into the funnel, and performing suction filtration to remove most of water in the crab shell slurry to prepare the chitin micro/nano fiber wet plate.

And 5.2, removing water in the crab shell slurry through hot pressing, and drying and forming.

And clamping the shaped wet plate by two sides of a glass plate after moisture is extracted, and further removing moisture in a vacuum oven to complete the internal hydrogen bond crosslinking combination of the plate in the drying process. Drying for 48 hr, cutting to remove round edges and corners or cutting into desired shape by mold to obtain the final product.

And 5.3, testing the performance of the non-adhesive full-biomass artificial board.

The thickness and the density of the obtained chitin plate are tested, a universal mechanical experiment machine is used for representing the bending resistance of a plate sample, the size of the plate is cut into a rated size, and the bending resistance and the elastic modulus of the plate are tested by a three-point bending method. In addition, water absorption and combustion tests were performed.

The second embodiment.

Example 1: the purification process is deproteinized, acid is not added in the pulping process, mechanical stirring is carried out for 2min, and a double-layer suction pipe is adopted, wherein a sample is shown in figure 10.

Step 1.1, a normal-temperature mild preparation method for extracting purified chitin after decalcification, deproteinization and pigment extraction of crab shells.

Cleaning the dried crab shells, soaking the dried crab shells by using hydrochloric acid with the mass fraction of 7wt% for 48 hours at normal temperature, completely removing calcium carbonate, and then cleaning the crab shells by using deionized water until the crab shells are neutral to prepare softened crab shells with the calcium carbonate removed.

And (3) further deproteinizing and coloring the washed neutral softened crab shell sample, and soaking the crab shell sample for 2 weeks at normal temperature by using a 4wt% sodium hydroxide solution to remove residual protein, thereby obtaining softened crab shells completely removed with calcium carbonate and protein.

Finally, washing the softened crab shell sample to be neutral, soaking the crab shell sample in 90 wt% ethanol solution at room temperature for 24 hours, and removing pigment components; and rinsing after the treatment is finished to obtain soft and white purified crab shells only containing chitin.

And step 1.2, stirring the purified crab shells only containing the chitin for 2min to perform surface micro/nano treatment, and preparing the crab shell slurry.

The method comprises the steps of taking prepared purified crab shells only containing chitin as raw materials, adding deionized water to prepare a mixed solution with the concentration of 2wt%, crushing the mixed solution for 2min by using a food mixer, and pulping to prepare the neutral chitin micro/nano-scale fiber suspension slurry.

And 3.1, preparing the micro/nano fiber wet film bottom material only containing the chitin by suction filtration.

And (3) suction-filtering the prepared crab shell slurry to prepare a suction pipe, wherein the thickness of a single-layer wet film of the suction pipe is controlled by controlling the solid content of a suspension base material. Cleaning a sand core funnel with distilled water, placing a microporous filter membrane (the diameter is 11cm), starting a vacuum pump, taking a mixed suspension base material with the solid content of 1.2g, introducing the mixed suspension base material into the funnel, and performing suction filtration to prepare the chitin micro/nano fiber wet membrane base material.

And 3.2, rolling and molding the chitin wet film substrate material, and naturally drying to obtain the full-biomass glue-free self-adhesive straw.

A polytetrafluoroethylene rod easy to demould is used as a curled suction pipe inner wall roller model, a chitin micro/nano fiber wet film base material formed by suction filtration is pressed and cut into a wet film according to the size of a required roller, the polytetrafluoroethylene rod roller is curled along one end of the wet film, pressure is applied in the curling process to enable the wet film to be uniformly attached to the polytetrafluoroethylene rod, and an integrally formed layer of wet film suction pipe is prepared according to the size of the pressed and cut wet film. And then natural air drying is carried out for 2 hours, and the hydrogen bond self-bonding effect at the overlapped joint of the wet films is completed. And (3) slightly rotating after drying to complete the demoulding of the straw, thus obtaining the natural degradable chitin micro/nano fiber glue-free self-adhesive straw (the diameter of the straw is 7 mm and 15 mm).

And 3.3, testing the mechanical properties of the adhesive-free self-adhesive suction pipe and the joint.

A universal mechanical experiment machine is used for representing the mechanical property of a sample, and the dry tensile strength, the elastic modulus and the wet tensile strength of the single film of the non-adhesive self-adhesive suction pipe are respectively 35.2 MPa, 6.3GPa and 2.1MPa, and the wet tensile strength is the tensile strength of the sample after being soaked in deionized water for 30 min.

The bonding strength of the adhesive-free self-bonding overlapped joint is represented by tensile shear strength, a universal mechanical experiment machine is used for testing the mechanical property of a sample, the sample is a single-layer pipette film adhesive-free self-bonding overlapped joint part, and the specific form is shown as a tensile schematic diagram in fig. 9. The bond strength of the joint was measured to be 1.5 MPa, and tensile failure was outside the bond plane, indicating that the actual bond strength was greater than the test value.

Example 2: deproteinization is carried out in the purification process, acid is not added in the pulping process, mechanical stirring is carried out for 5min, and a double-layer suction pipe is adopted, wherein a sample is shown in figure 10.

Example 2 compared to example 1, the procedure was identical except that the food blender was crushed for 5min in step 1.2. The dry tensile strength, the elastic modulus and the wet tensile strength of the single film of the pipe are respectively 69.4 MPa, 7.2 GPa and 3.9 MPa, and the bonding strength of the bonding part is 2.9 MPa (the tensile failure is positioned outside the bonding surface, and the actual bonding strength is larger than the test value).

The bending strength of the non-adhesive self-adhesive straw is tested by a three-point bending test method by using a universal mechanical testing machine, and the specific form is shown in figure 11. The three-point bending strength of the straw sample is 23.7 MPa, and the strength is more than 3 times that of the paper straw and the plastic straw (the bending strength of a commercial paper straw is 7.3 MPa, and the bending strength of a commercial plastic straw is 6.9 MPa).

The chitin glue-free self-adhesive double-layer suction pipe is subjected to water soaking tests for different durations in different temperature ranges of cold water at 15-25 ℃, warm water at 30-50 ℃ and hot water at 80-90 ℃, and the water absorption and water resistance of the glue-free self-adhesive suction pipe are comparatively displayed. In order to better show the water absorption and water resistance effects of the suction pipe, the coloring agent is added into the water to enable the interface with the rising water absorption to be displayed more clearly. The effect diagram is as shown in fig. 12, from left to right, sequentially: (1) the straw is just put into water; (2) after being soaked in cold water at the temperature of 15-25 ℃ for 24 hours, the adhesive has no layering phenomenon, good adhesion effect and excellent cold water resistance; (3) after being soaked in warm water at the temperature of 30-50 ℃ for 1 hour, the bonding part has no layering phenomenon and has good temperature and water resistance; (4) after the adhesive is soaked in hot water at the temperature of 80-90 ℃ for 1 hour, the adhesive interface still has no layering phenomenon, and the adhesive effect is good; (5) the chitin glue-free self-adhesive straw can be applied to yoghourt with high viscosity and can be easily sucked.

The chitin glue-free self-adhesive straw still has good stiffness and hardness after being soaked in water for more than 24 hours, as shown in figure 13, after being soaked for a long time, the wetted tip of the straw is continuously hung with heavy objects without generating soft couch, so that the chitin glue-free self-adhesive straw has excellent water resistance, better water resistance and stiffness than commercial paper straws and wide application range.

Example 3: the purification process is deproteinized, 1wt% acetic acid solution is added during pulping, mechanical stirring is carried out for 5min, and a double-layer suction pipe is adopted, wherein a sample is shown in figure 10.

Compared with the example 2, the steps are consistent except that the acetic acid solution with the mass fraction of 1wt% is dripped in the pulping process in the step 1.2.

The dry tensile strength, the elastic modulus and the wet tensile strength of the single film of the straw are respectively 98.3 MPa, 8.0 GPa and 6.2 MPa, and the bonding strength of the bonding part is 3.3 MPa (the tensile failure is positioned outside the bonding surface, and the actual bonding strength is larger than the test value). The three-point bending strength of the straw sample is 20.6 MPa, and the strength is more than 3 times that of the paper straw and the plastic straw (the bending strength of a commercial paper straw is 7.3 MPa, and the bending strength of a commercial plastic straw is 6.9 MPa).

Example 4: the purification process is deproteinized, acid is not added in the pulping process, mechanical stirring is carried out for 20min, and a double-layer suction pipe is adopted, wherein a sample is shown in figure 10.

Example 4 compared to example 1, the procedure was identical except that the food blender was crushed for 20min in step 1.2. The dry tensile strength, the elastic modulus and the wet tensile strength of the single film of the straw are respectively 101.1 MPa, 8.6 GPa and 8.1 MPa, and the bonding strength of the bonding part is 3.6 MPa (the tensile failure is out of the bonding surface, and the actual bonding strength is larger than the test value). The three-point bending strength of the straw sample is 18.6 MPa, and the strength is about 3 times that of the paper straw and the plastic straw (the bending strength of a commercial paper straw is 7.3 MPa, and the bending strength of a commercial plastic straw is 6.9 MPa).

Example 5: the purification process is deproteinized, 1wt% acetic acid solution is added in the pulping process, mechanical stirring is carried out for 20min, and a double-layer suction pipe is adopted, wherein a sample is shown in figure 10.

Compared with the example 4, the steps are consistent except that the acetic acid solution with the mass fraction of 1wt% is dripped in the pulping process in the step 1.2.

The dry tensile strength, the elastic modulus and the wet tensile strength of the single film of the straw are respectively 146.3 MPa, 9.4 GPa and 9.8 MPa, and the bonding strength of the bonding part is 4.6 MPa (the tensile failure is out of the bonding surface, and the actual bonding strength is larger than the test value). The three-point bending strength of the straw sample is 16.1 MPa, and the strength is 2-3 times that of the paper straw and the plastic straw (the bending strength of a commercial paper straw is 7.3 MPa, and the bending strength of a commercial plastic straw is 6.9 MPa).

Example 6: the purification process does not remove protein, the pulping process does not add acid, the mechanical stirring is carried out for 5min, the double layer suction pipe is adopted, and the sample is shown in figure 10.

And 2.1, removing inorganic salt and pigment from the crab shell, and preparing the softened crab shell containing chitin/protein at normal temperature and in a mild way.

Cleaning the dried crab shells, soaking the dried crab shells by using hydrochloric acid with the mass fraction of 7wt% for 72 hours at normal temperature, completely removing calcium carbonate, and then cleaning the crab shells by using deionized water until the crab shells are neutral to prepare the softened crab shells with the calcium carbonate removed.

Further decoloring the softened crab shell sample washed to be neutral, soaking the crab shell sample in 90 wt% ethanol solution at room temperature for 24 hours, and removing pigment components; and rinsing after the treatment is finished to obtain the natural composite crab shell containing protein and chitin.

And 2.2, pulping the protein-chitin crab shells for 5min to prepare the protein-chitin micro/nano-scale fiber suction pipe bottom material.

The prepared crab shell containing protein-chitin is taken as a raw material, deionized water is added to prepare a mixed solution with the concentration of 1wt%, the mixed solution is crushed for 5min by a food mixer, and the neutral protein-chitin micro/nano-scale fiber suspension slurry is prepared by beating.

And 3.1, preparing the chitin micro/nano fiber wet film bottom material containing the protein by suction filtration.

And (3) suction-filtering the prepared crab shell slurry to prepare a suction pipe, wherein the thickness of a single-layer wet film of the suction pipe is controlled by controlling the solid content of a suspension base material. Washing a sand core funnel with distilled water, putting a microporous filter membrane (the diameter is 11cm), starting a vacuum pump, taking the mixed suspension slurry with the solid content of 1.2g, introducing the mixed suspension slurry into the funnel, and performing suction filtration to prepare the protein-chitin micro/nano fiber wet membrane bottom material.

And 3.2, rolling and molding the chitin/protein wet film substrate material, and naturally drying to obtain the full-biomass glue-free self-adhesive straw.

A polytetrafluoroethylene rod easy to demould is used as a curled suction pipe inner wall roller model, a protein-chitin micro/nano fiber wet film base material formed by suction filtration is pressed and cut into a wet film according to the size of a required roller, the polytetrafluoroethylene rod roller is curled along one end of the wet film, pressure is applied in the curling process to enable the wet film to be uniformly attached to the polytetrafluoroethylene rod, and an integrally formed wet film suction pipe is prepared according to the size of the pressed and cut wet film. And then natural air drying is carried out for 2 hours, and the hydrogen bond self-bonding effect at the overlapped joint of the wet films is completed. After drying, slightly rotating to complete the demoulding of the straw, and then forming and preparing the natural degradable full biomass (protein-chitin) micro/nano fiber glue-free self-adhesive straw (the diameter of the straw is 7 mm and 15 mm).

And 3.3, testing the mechanical properties of the single membrane and the joint of the adhesive-free self-adhesive straw.

A universal mechanical experiment machine is used for representing the mechanical property of the sample of the adhesive-free self-bonding straw single film, the dry tensile strength and the elastic modulus of the tested straw single film are 57.2 MPa and 6.8 GPa respectively, and the wet tensile strength is 2.2 MPa after the sample is soaked in deionized water for 30 min.

Example 7: the purification process does not remove protein, the pulping process adds acid, the mechanical stirring is carried out for 5min, the double layer suction pipe is adopted, and the sample is shown in figure 10.

Example 7 compared with example 6, in the step 2.2 beating process, 1wt% acetic acid solution is added dropwise, and the other steps are kept consistent.

The dry tensile strength and the elastic modulus of the single membrane of the suction pipe are respectively 74.4 MPa and 7.6 GPa, and the wet tensile strength is 4.2 MPa after the sample is soaked in deionized water for 30 min.

Example 8: the purification process is deproteinized, the pulping process is acidified, mechanical stirring is carried out for 20min, and the sample is packed in a single-layer outer packaging bag as shown in figure 14.

Step 1.1, removing inorganic salt, protein and pigment from the crab shells, and extracting and purifying the crab shells.

And (3) further deproteinizing and coloring the washed neutral softened crab shell sample, and soaking the crab shell sample with 4-20 wt% of sodium hydroxide solution at normal temperature for 2 weeks to remove residual protein, thereby obtaining softened crab shells with completely removed calcium carbonate and protein. Finally, washing the softened crab shell sample to be neutral, soaking the crab shell sample in 90 wt% ethanol solution at room temperature for 24 hours, and removing pigment components; and rinsing after the treatment is finished to obtain soft and white purified crab shells only containing chitin.

And step 1.2, stirring the purified crab shells only containing the chitin for 20min to carry out surface micro/nano treatment, and preparing the crab shell slurry.

The method comprises the steps of taking prepared purified crab shells only containing chitin as raw materials, adding deionized water to prepare a mixed solution with the concentration of 1wt%, dropwise adding 2wt% of glacial acetic acid to adjust the pH value of the mixed solution to 3-4, stirring and treating for 20min by using a food stirrer, and pulping to prepare the chitin micro/nano-scale fiber suspension slurry, wherein the fiber size is 100-150 nm thick fibers, the size of surface nano-sized fine fibers is 10-30 nm, and the size of nano-sized fibers on finer fiber branches is 2-15 nm.

And 4.1, forming the wet film of the outer packaging bag by suction filtration.

And (3) preparing an outer packaging bag wet film by using the prepared crab shell slurry, wherein the thickness of the packaging bag wet film is controlled by controlling the solid content of the suspension bottom material. Cleaning the sand core funnel with distilled water, placing a microporous filter membrane (diameter is 11cm), starting a vacuum pump, taking the mixed suspension base material with the solid content of 0.4 g, introducing into the funnel, and performing suction filtration to prepare the chitin micro/nano fiber wet membrane.

Cutting according to size after filtering and film forming, and bonding the joint to finish hydrogen bond self-bonding in the drying process. After drying, the two ends are folded to form the outer package sleeve of the straw in the embodiment 1-5 or the outer package bag of other products.

Example 9: deproteinization is carried out in the purification process, acid is not added in the pulping process, mechanical stirring is carried out for 20min, a plate is made, and a sample is shown in figure 15.

And step 1.2, stirring the purified crab shells only containing the chitin for 20 minutes to carry out surface micro/nano treatment, and preparing the crab shell slurry.

The method comprises the steps of taking prepared purified crab shells only containing chitin as raw materials, adding deionized water to prepare a mixed solution with the concentration of 1wt%, crushing the mixed solution for 20 minutes by using a food mixer, and pulping to prepare neutral chitin micro/nano-scale fiber suspension slurry, wherein the size of coarse fibers with the fiber size of 100-150 nm, the size of surface nano-sized fine fibers is 10-30 nm, and the size of nano-sized fibers on finer fiber branches is 2-15 nm.

And 5.1, performing suction filtration to form a wet plate.

The prepared crab shell slurry is filtered to prepare the non-glue fireproof crab shell plate, and the thickness of the crab shell plate is controlled by controlling the solid content of the suspension base material. Cleaning a sand core funnel with distilled water, placing a microporous filter membrane (the diameter is 10cm), starting a vacuum pump, taking a mixed suspension base material with the solid content of 11 g, introducing the mixed suspension base material into the funnel, and performing suction filtration to remove most of water in the crab shell slurry to prepare the chitin micro/nano fiber wet plate.

And clamping the shaped wet plate by two sides of a glass plate after moisture is extracted, and further removing moisture in a vacuum oven to complete the internal hydrogen bond crosslinking combination of the plate in the drying process. Drying for 48 hr, taking out, and cutting out round edges to obtain crab shell plate shown in FIG. 12.

The density of the dried crab shell plate is about-1 g/cm 3. The board has good dimensional stability, does not deform after absorbing water, is soaked in water for more than 24 hours at room temperature, and increases the weight by 30 percent after absorbing water (the weight of the natural pine wood is 100 percent under the same condition). A universal mechanical experiment machine is used for representing the bending resistance of the plate sample, and the strength and the elastic modulus of the plate are respectively 112.8 MPa and 11.4 GPa when the plate sample is tested by a three-point bending method. The results of the burning test are shown in FIGS. 16 and 17, which show that the panel was ignited by an open flame for 5 minutes, indicating that the panel could not be ignited by an open flame. The board has good dimensional stability and high bending strength, has excellent fireproof and flame-retardant properties, is green and environment-friendly, and does not have the problem of formaldehyde release.

And (III) mechanism description.

Chitin exists in natural organism (such as shrimp and crab shell) as fiber aggregate with nanometer scale and uniform dispersion. The chitin molecules are stacked through van der Waals force and the interaction of hydrogen bonds in the molecules and among the molecules to form basic fibrils, the basic fibrils are assembled to form micron fiber sizes and are arranged in a layered mode, after matrix components are removed through demineralization, deproteinization and the like, the natural chitin micro-nano structure can be reserved, and the mixed system of chitin micron-sized fibers and nano-sized fibers can be obtained through simple mechanical stirring. The chitin nanofiber is characterized in that the chitin nanofiber which is uniformly dispersed and has no agglomeration phenomenon can be obtained only through simple physical mechanical action, and the chitin nanofiber cannot be replaced by other biomass materials such as cellulose and the like. The characteristics make the chitin possible to become a novel green protective natural full biomass material and is expected to be used as a raw material of products such as pipes, bags, plates and the like.

As shown in fig. 18, a micro-topography of the surface of the straw material prepared by mechanical stirring for 20 minutes (example 4) can be observed that the fibers are regularly dispersed and have no obvious agglomeration phenomenon, and the natural nanofiber structure of chitin is still remained on the surface after mechanical defibering.

As shown in fig. 19, a graph of the defibering effect of the chitin fiber bundle obtained by mechanical stirring for 20 minutes (example 4) shows that a large number of fine whisker-like fibers are exposed on the surface of the coarse fibers, and the purpose of the surface nanocrystallization is to: because the chitin fiber surface contains a large amount of hydroxyl, the tentacle-shaped thin fibers on the surface of the coarse fibers are increased in the material preparation process, and the number of the hydroxyl is increased, so that the hydrogen bond bonding force formed among the hydroxyl in the drying process is further improved, and the glue-free self-bonding is realized.

The purpose of mechanical stirring is to control the number of free hydroxyl groups for improved hydrogen bonding. The mechanical stirring defibering method is simple and easy to operate, the defibering degrees are different under different mechanical forces, fig. 20 is a transmission electron microscope image of the multi-level chitin micro/nano fibers after defibering for 5 minutes (embodiment 2) by mechanical stirring, and fig. 21 is a transmission electron microscope image of the multi-level chitin micro/nano fibers after defibering for 20 minutes (embodiment 4) by mechanical stirring. The nanometer thin fibers on the surface of the thick fibers can effectively improve the bonding effect of hydrogen bond combination, have thinner nanometer fiber branches and can further improve the content of free hydroxyl. The sizes of the surface-nanocrystallized coarse fibers and the nanocrystallized branch sizes thereof were different under mechanical stirring for 5 minutes and 20 minutes, thereby demonstrating that mechanical force can effectively achieve more fine nanofiber formation and finer nanocrystallization treatment of the surface of the coarse fibers.

The chitin crude fiber bundle is mechanically stirred to obtain fine fibers with finer and more nano-processed surfaces. Specifically, the chitin crude fiber can be defibered by mechanical stirring for 5-20 minutes to prepare crude fiber with the size of 100-400 nm, the crude fiber is defibered to obtain fine fiber with the size of 10-50 nm, and fine fiber branches with the surface nanocrystallization size of 2-20 nm are further arranged on the fine fiber.

More specifically, the mechanical stirring for 5 minutes can obtain coarse fibers having a size of 150-400 nm, fine fibers having a surface nanocrystallized size of 20-50 nm, and fine fiber branches having a finer branch size of 10-20 nm. The coarse fiber with the size of 100-150 nm can be obtained by mechanical stirring for 20 minutes, the fine fiber with the surface nanocrystallization size of 10-30 and the fine fiber branch with the finer branch size of 2-15 nm can be obtained; wherein, 1-4wt% of glacial acetic acid can be added in the stirring process, so that the fine fiber content in the defibering process is further improved, and the fiber content of the nano fiber with finer fiber branches is increased in the size of about 2-8 nm.

FIG. 22 is a schematic view of the principle of adhesive-free self-bonding at the overlapping part (bonding part) of the formed edges of the straws in examples 1-7. In a wet state, the free hydroxyl groups at the bonding part are increased by the nano-scale fine fibers obtained by defibering the chitin fibers, and the bonding force of hydrogen bonds is enhanced; through the natural drying process, the hydroxyl groups are tightly combined to form hydrogen bonds, and the glue-free self-bonding process of the straw is realized. The coarse fibers can provide a part of hydrogen bonds required for bonding and also play a role in supporting the suction pipe wall; wherein the fine fibers obtained by defibering are gathered into coarse fiber bundles again by the binding force of hydrogen bonds in the drying process, and the stiffness and the hardness of the whole straw are also given while the bonding effect of the lap joint is completed.

Further, it can be observed from the microscopic cross-sectional morphology of the overlapping and bonding part of the straw shown in fig. 23 that almost no boundary line is observed at the bonding part of the two layers of straw materials, and the bonding is tight, which indicates that the non-adhesive bonding of the straw wall can be effectively realized through the hydrogen bonding.

And (IV) analyzing results.

The chitin straw in the embodiments 1 to 7 is a novel all-biomass natural degradable straw which is more environment-friendly and safer than a paper straw, and the appearance of the chitin straw is shown in fig. 10, and the dry tensile strength and the wet tensile strength of a formed film are higher than those of common commercial paper (32 MPa to 1.4 MPa).

The straw is made of waste crab shells, so that the waste resources are recycled, and the raw materials are green, environment-friendly and naturally biodegradable; the problem of energy consumption caused by lack of wood resources in the production and processing process of the paper straws can be effectively solved; and the straw can be completely recycled, is easy to produce and process, and has lower cost, and the cost of a single straw can be controlled below 1 minute. The whole process of preparing the chitin micro/nano fiber straw does not need to add any wet strength agent, chemical filler, auxiliary agent and the like; the curled and formed edge is not required to be bonded by any adhesive, and the adhesive-free self-bonding straw with higher strength can be formed and prepared by natural drying. The all-biomass straw prepared based on the waste crab shells only contains chitin or chitin and partial protein, is completely derived from natural crab shells, and is more environment-friendly and safer than the existing paper straw. Meanwhile, the chitin straw prepared by taking the crab shells as the raw material cannot cause the problem of environmental pollution, can be buried in soil for natural degradation, and cannot cause harm to natural organisms even if being discarded at will.

The bending resistance of the chitin glue-free self-adhesive chitin straw is good, the bending strength of the chitin glue-free self-adhesive chitin straw is more than 2-3 times that of a paper straw and a plastic straw (the bending strength of a commercial paper straw is 7.3 MPa, and the bending strength of a commercial plastic straw is 6.9 MPa), the paper straw is mostly bonded by 3-4 layers of base paper, and the mechanical strength of the straw wall of the chitin glue-free self-adhesive straw is far higher than that of the paper straw when the chitin glue-free self-adhesive straw is only 2 layers. After the three-point bending strength test, the surface of the straw cannot crack under pressure, the straw cannot crack under external force bending while having high stiffness, the straw has good bonding effect and high stiffness, and the straw wall is not soft and layered after being soaked in water for more than 24 hours for a long time.

The process parameters and performance data for each example are shown in the table below.

As can be seen from the comparison of examples 1, 2 and 4, the defibering effect of the chitin fiber bundles is different under different mechanical forces, and the time and the force of mechanical stirring can be used for controlling the number of free hydroxyl groups. Within a certain range, the longer the mechanical stirring time is, the more the tentacle-shaped fine fibers on the surface of the coarse fibers are, the more the number of the hydroxyl groups is increased correspondingly, the stronger the bonding force of the hydrogen bonds formed among the hydroxyl groups is, and the stronger the dry tensile strength, the elastic modulus, the wet tensile strength and the tensile shear strength of the bonding part of the corresponding straw single membrane are.

It can be seen from the comparison between examples 2 and 6, and between examples 3 and 7 that, after the natural proteins in the crab shells are retained in the process of pulping to prepare the chitin micro/nano-scale fiber straw pulp, the dry tensile strength, the elastic modulus and the wet tensile strength of the prepared straw single membrane are all reduced, that is, the mechanical properties of the straw are slightly reduced, but the performance of the straw single membrane can still meet the use requirements. On the other hand, the deproteinization process is omitted in the embodiment 6 and the embodiment 7, so that the production cost can be reduced, and the production period can be greatly shortened, thereby having obvious advantages in large-scale production.

As can be seen from the comparison of examples 2 and 3, 4 and 5, and 6 and 7, the single membrane for straw prepared by adding acid during pulping has stronger dry tensile strength, elastic modulus, wet tensile strength and tensile shear strength of the bonding part. This is because the addition of acetic acid solution during the pulping process promotes the nanocrystallization of chitin based on the natural properties of chitin. It is worth noting that the preparation of the micro/nano-fibers of the chitin is based on the arrangement of the naturally existing chitin nano-fibers in the crab shells, the formation of the chitin nano-fibers cannot be specially changed by the presence or absence of acid, but the naturally existing nano-fibers are refined by mechanical stirring to different degrees.

Example 8 is a chitin film packaging bag, and the product appearance is shown in fig. 14. The formed and prepared full biomass outer packaging bag has universality, and can be used as a disposable packaging bag for instant food and other universal packaging bags in a wider range due to green and safe materials.

Example 9 is a non-cementitious whole biomass manufactured board, the product appearance of which is shown in fig. 15. The artificial board is formed without using any adhesive (adhesive) or adding any flame retardant or fireproof coating, is natural and environment-friendly due to the full biomass, and has better safety than common glued shaving boards, plywood and the like, so that the problem of formaldehyde release is avoided; the raw materials are all biomass materials, and meanwhile, the biomass wood can be produced in a large scale without being limited by the self size of materials such as natural wood and the like; meanwhile, the sample has the characteristics of good dimensional stability, high strength, flame retardance and the like, and can be used as a fireproof plate to be applied to buildings or other effective potential application fields.

Claims

1. A method for preparing a degradable micro/nano fiber glue-free self-adhesive straw is characterized by comprising the following steps:

2. The method for preparing the degradable micro/nano fiber glue-free self-adhesive straw according to claim 1, wherein the matrix components removed in the step a are calcium carbonate, protein and pigment, and the method comprises the following specific steps:

3. The method for preparing the degradable micro/nano fiber glue-free self-adhesive straw according to claim 1, wherein the matrix components removed in the step a are calcium carbonate and pigment, and the method comprises the following specific steps:

4. The method for preparing the degradable micro/nano fiber glue-free self-adhesive straw according to claim 1, wherein no acid is added in the pulping process in the step b, and the method comprises the following specific steps: and (b) taking the purified shrimp and crab shells obtained in the step a as raw materials, adding deionized water to prepare a mixture with the weight of 1-2 wt%, and stirring the mixture for 2-20 minutes by using a food stirrer to obtain the neutral chitin suspended slurry prepared by pulping.

5. The method for preparing the degradable micro/nano fiber glue-free self-adhesive straw according to claim 1, wherein in the step b, acid is added in the pulping process, and the specific steps are as follows: and (b) taking the purified shrimp and crab shells obtained in the step a as raw materials, adding deionized water to prepare a 1-2 wt% mixture, firstly dropwise adding 1-2 wt% acetic acid solution, adjusting the pH value to 3-4, and then stirring the mixture for 2-20 minutes by using a food stirrer to obtain the acidic chitin suspended slurry.

6. The method for preparing the degradable micro/nano fiber glue-free self-adhesive straw as claimed in claim 1, wherein in the step c, the straw is prepared from the shrimp and crab shell slurry obtained in the step b, and a wet film is formed by vacuum filtration and dehydration, and the method comprises the following specific steps: washing the sand core funnel with distilled water, putting a microporous filter membrane, starting a vacuum pump, taking the suspended slurry with proper solid content, introducing the suspended slurry into the funnel, and performing suction filtration to form the chitin micro/nano fiber wet membrane.

7. The method for preparing the degradable micro/nano fiber glue-free self-adhesive straw as claimed in claim 1, wherein in the step d, the chitin micro/nano fiber wet film obtained in the step c is rolled and pressed to be molded, and the glue-free self-adhesive straw is prepared after natural drying, and the method comprises the following specific steps:

8. The method for preparing the degradable micro/nano fiber glue-free self-adhesive straw according to claim 7, wherein the roller mold is an easy-to-release tool.

9. The method for preparing the degradable micro/nano fiber glue-free self-adhesive straw according to claim 1, wherein the outer packaging bag is prepared by the same process as the claim 1 and is used as the packaging bag of the degradable micro/nano fiber glue-free self-adhesive straw.

10. A degradable micro/nano fiber glue-free self-adhesive straw, which is prepared by the preparation method of any one of claims 1-9.