Preparation process of yak manure and plant fiber composite Tibetan paper

Abstract

The invention discloses a preparation technology of yak manure and plant fiber composite Tibetan paper, and relates to the technical field of composite Tibetan paper preparation, and the preparation technology comprises the following steps: screening dried yak manure, removing pebbles and hair impurities, soaking in clear water, and scrubbing to obtain a yak manure material; the yak manure material is placed in a high-temperature steam environment of 100 DEG C or above for continuous sterilization for 30 min, and then mechanical crushing treatment is performed to obtain short-fiber-shaped yak manure crude fiber pulp; the method comprises the following steps: cleaning radix euphorbiae lantu roots and / or branches and barks of daphne odora, and extracting plant long fibers by adopting a mode of combining soaking, beating and tearing, or cooking and treating the radix euphorbiae lantu roots or the branches and barks of daphne odora by adopting a mild alkaline method to obtain traditional plant long fiber pulp; the short-fiber-shaped yak manure crude fiber pulp and the traditional plant long fiber pulp are put into a pulp mixing pool according to the mass ratio of 40%-60%: 30%-50%, the mass ratio of the yak manure crude fiber pulp is preferably 70%-90%, and the aim that the raw materials basically come from the Qinghai-Tibet Plateau is achieved.

Description

Technical Field

[0001] This invention relates to the field of composite Tibetan paper preparation technology, and in particular to a preparation process for composite Tibetan paper made from yak dung and plant fibers. Background Technology

[0002] Composite Tibetan paper preparation technology refers to a technical system that mixes short fibers obtained from purified yak dung with long fibers extracted from plateau plants (such as wolfsbane) in a specific ratio, and supplements them with natural plant-derived adhesives. Through physical molding and low-temperature drying processes, a new type of Tibetan paper is prepared, which has high strength, natural insect resistance, good suitability for calligraphy and painting, and ecological sustainability.

[0003] In the field of composite Tibetan paper production, traditional Tibetan paper relies solely on wild plants unique to the plateau, such as wolfsbane, as its fiber source. Wolfsbane grows slowly, has a limited distribution, and over-harvesting has damaged the fragile plateau ecosystem, leading to a shortage of raw materials and continuously rising costs, making it difficult to support large-scale production and the needs of cultural preservation. Although there have been attempts to use yak dung for papermaking, yak dung fibers are short, fragmented plant residues that are not fully digested. They are short in length and have weak bonding strength, resulting in low tensile strength, fragility, and poor folding resistance when made into paper alone. They cannot meet the basic requirements for writing, painting, or mounting, and can only be used as low-end sacrificial or decorative paper, with limited application value. Summary of the Invention

[0004] In view of the aforementioned existing problems, the present invention is proposed.

[0005] Therefore, this invention provides a process for preparing Tibetan paper made from a composite of yak dung and plant fibers, solving the problem that traditional Tibetan paper relies solely on wild plants unique to the plateau, such as wolfsbane, as its fiber source. Wolfsbane grows slowly, has limited distribution, and over-harvesting has damaged the fragile plateau ecosystem, leading to a shortage of raw materials and continuously rising costs, making it difficult to support large-scale production and the needs of cultural preservation. Furthermore, although attempts have been made to use yak dung for papermaking, yak dung fibers are incompletely digested, short, and fragmented plant residues. These fibers are short in length, have weak bonding, and when used alone as paper, they have low tensile strength, are easily broken, and have poor folding resistance, failing to meet basic requirements for writing, painting, or mounting. They can only be used as low-end sacrificial or decorative paper, with limited application value.

[0006] Based on this, this invention uses locally sourced, organic yak dung from the Qinghai-Tibet Plateau to replace wolfsbane, developing yak dung Tibetan paper. Through continuous experimentation, the proportion of yak dung in the raw materials has gradually increased from the initial 50% to 70%, with a final target of 90%, essentially achieving complete sourcing of raw materials from the Qinghai-Tibet Plateau. Furthermore, the prayer flags (wind horse paper) made from yak dung Tibetan paper can be returned to the grasslands through traditional Tibetan sacrificial rites, forming an ecological closed loop of grassland-yak dung-paper-grassland, achieving resource recycling.

[0007] To solve the above-mentioned technical problems, the present invention provides the following technical solution: In a first aspect, the present invention provides a process for preparing Tibetan paper made from yak dung and plant fiber composites, comprising: The dried yak dung is screened to remove stones and hair impurities, and then soaked and washed with clean water to obtain yak dung material. Yak dung material is sterilized in a high-temperature steam environment above 100℃ for 30 minutes, and then mechanically crushed to obtain short-fiber yak dung crude fiber pulp. The roots of *Euphorbia fischeriana* and / or the bark of *Daphne odora* were washed and the plant long fibers were extracted by a combination of soaking, pounding and tearing, or the roots of *Euphorbia fischeriana* or the bark of *Daphne odora* were treated by mild alkaline cooking to obtain traditional plant long fiber pulp. Short-fiber yak dung pulp and traditional plant long-fiber pulp are added to a mixing tank at a mass ratio of 40%–60% : 30%–50%, wherein the mass proportion of yak dung pulp is preferably 70%–90% to achieve the goal of the raw materials being mainly sourced from the Qinghai-Tibet Plateau. At the same time, 5%–10% of natural binder, which is cactus juice or konjac powder, is added to the total pulp mass. After stirring, a homogeneous composite pulp is formed. The uniform composite pulp is formed by modifying the flow method or by hand papermaking screen. The long plant fibers are used to build a network skeleton to wrap the short yak dung fibers. The papermaking force and number of times are controlled to make the paper form uniform and have the target weight and thickness, thus obtaining wet composite paper sheets. The wet composite paper is mechanically pressed to remove free water, and then dried by a combination of natural air drying and low-temperature drying at below 60°C to obtain dry composite paper. The dry composite Tibetan paper was subjected to cold pressing and calendering to achieve surface smoothing and obtain composite Tibetan paper made of yak dung and plant fiber. The composite Tibetan paper can be used to make traditional Tibetan prayer flags (wind horse paper). After the ritual is completed, it can be naturally degraded and returned to the grassland, forming an ecological closed loop.

[0008] As a preferred embodiment of the preparation process of the composite Tibetan paper made from yak dung and plant fiber according to the present invention, the screening of dried yak dung includes: The dried yak dung is placed in a screening device and separated step by step through a multi-stage screen to remove stones, hair, grass stems and non-fibrous impurities, and obtain clean yak dung material mainly composed of incompletely digested plant residues. Clean yak dung material is placed into a washing tank, and water is added for soaking and repeated rubbing until the washing liquid becomes clear, thus obtaining purified yak dung material.

[0009] As a preferred embodiment of the preparation process of the composite Tibetan paper made from yak dung and plant fiber according to the present invention, the step of sterilizing the yak dung material in a high-temperature steam environment includes: The purified yak dung material is sent into a steam treatment chamber and continuously heated with saturated steam, which effectively kills the microorganisms inside the material and softens the plant fiber structure due to the heat. After steam treatment, the material is transferred to a crushing device, where mechanical shearing and dispersing action breaks the fibers into loose short fibers, resulting in short-fiber yak dung coarse fiber pulp.

[0010] As a preferred embodiment of the preparation process of the yak dung and plant fiber composite Tibetan paper of the present invention, the washing of the roots of *Euphorbia pekinensis* and / or the bark of *Daphne odora* branches includes: Wash the collected roots of wolfsbane or the bark of Daphne odora branches with running water to remove surface mud and sand, and then place them in a soaking pool to fully absorb water and soften. The softened raw material is beaten manually or mechanically to separate the fiber bundles from the xylem, and then the pure long fiber bundles are separated by manual tearing or water washing. Alternatively, the softened raw material can be put into a mild alkaline solution for cooking. After cooking, it can be rinsed with water until neutral, and then subjected to decomposition treatment to obtain traditional plant long fiber pulp.

[0011] As a preferred embodiment of the preparation process of the composite Tibetan paper made from yak dung and plant fibers according to the present invention, the step of adding short-fiber yak dung pulp and traditional long-fiber plant pulp to the mixing tank in a certain proportion includes: The two types of fiber pulp were pumped separately into the same mixing container, and a pre-prepared natural binder solution was added to the mixing container. The mixing device is started to thoroughly stir the mixture, so that the short fibers of yak dung are evenly dispersed in the gaps of the network formed by the long fibers of plants, and finally a composite pulp is formed.

[0012] As a preferred embodiment of the preparation process of the yak dung and plant fiber composite Tibetan paper of the present invention, when the natural binder is cactus juice, it includes: After removing the thorns from fresh cactus stem segments, press them to extract the juice, filter out the residue to obtain clear juice, and add it directly to the mixing tank; When the natural binder is konjac flour, it includes: Add konjac powder to warm water, stir to disperse, and let stand to gelatinize, forming a gel-like liquid before adding it to the mixing tank; The adhesive coats the surface of various fibers during the mixing process, enhancing the bonding force between fibers without introducing chemically synthesized substances.

[0013] As a preferred embodiment of the preparation process of the yak dung and plant fiber composite Tibetan paper of the present invention, the step of forming the uniform composite pulp by means of a modified flow paper method or a hand papermaking screen includes: The uniform composite pulp is introduced into the papermaking vat, and the fibers are allowed to settle naturally on the papermaking screen by controlling the flow state of the pulp. During the papermaking process, the long plant fibers preferentially overlap to form a continuous skeleton structure, while the short yak dung fibers are trapped in the gaps of the skeleton. Repeat the paper-making process several times to gradually accumulate the thickness of the wet paper sheet until it reaches the target specification, thus obtaining a wet composite paper sheet.

[0014] As a preferred embodiment of the preparation process of the yak dung and plant fiber composite Tibetan paper of the present invention, the mechanical pressing and dehydration of the wet composite paper sheet includes: The wet paper sheet is placed between press rolls, and the free water inside the paper sheet is squeezed out by applying mechanical pressure; After pressing, the paper sheets are transferred to a ventilated drying area for initial drying using wind and sunlight under natural conditions; After initial drying, the paper is sent to a low-temperature drying device to further remove residual moisture through gentle hot air circulation, resulting in dry composite paper.

[0015] As a preferred embodiment of the preparation process of the Tibetan paper made from yak dung and plant fiber composites described in this invention, the natural drying is carried out in an open area with good air circulation on a plateau, with the paper sheets laid flat on a breathable support surface to avoid direct sunlight causing local overheating. Indirect heating is used in the low-temperature drying stage. The hot air temperature is controlled within a range that will not cause thermal damage to the fibers. The paper is turned over regularly during the drying process to ensure that the moisture is evenly released and to prevent the paper from deforming or cracking.

[0016] As a preferred embodiment of the preparation process of the yak dung and plant fiber composite Tibetan paper of the present invention, wherein: the cold pressing and calendering treatment of the dry composite Tibetan paper includes: The dried paper is fed into a cold calender, where a pair of smooth pressure rollers apply uniform pressure to the paper surface at room temperature. In the calendering process, only physical pressure is used to flatten the microscopic protrusions on the paper surface, thereby improving the surface smoothness. Calendered paper retains its natural fiber texture and porous structure, possessing excellent ink absorption and suitability for writing and drawing, resulting in a finished Tibetan paper product made from a composite of yak dung and plant fibers.

[0017] The beneficial effects of this invention are as follows: By purifying, sterilizing, and crushing dried yak dung into usable short fiber components, and then compounding them with long fibers extracted from plateau plants such as wolfsbane in a specific ratio, the plant long fibers are used to construct a continuous network skeleton to effectively wrap and fix the yak dung short fibers. This improves the strength and structural uniformity of the paper without relying on chemical additives. The entire process adopts a combination of physical cleaning, steam sterilization, natural plant binders, natural sun-drying, and low-temperature drying. This not only realizes the resource utilization of yak dung, a plateau livestock waste, but also fully preserves the natural color, porous structure, air permeability, and good compatibility with mineral pigments and Tibetan ink of traditional Tibetan paper. It solves the problems of scarce raw materials for traditional pure plant Tibetan paper and insufficient strength of pure dung paper. Attached Figure Description

[0018] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the following description of the embodiments will be briefly introduced. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 This is a flowchart of the preparation process of Tibetan paper made from yak dung and plant fiber composites in Example 1. Detailed Implementation

[0020] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0021] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and those skilled in the art can make similar extensions without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.

[0022] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in different places in this specification does not necessarily refer to the same embodiment, nor is it a single or selective embodiment that is mutually exclusive with other embodiments.

[0023] Example 1, referring to Figure 1 This embodiment of the invention provides a process for preparing Tibetan paper made from a composite of yak dung and plant fiber, comprising: S1. The dried yak dung is screened to remove stones and hair impurities, and then soaked and washed with clean water to obtain yak dung material. Furthermore, the dried yak dung is placed in a screening device and separated step by step through a multi-stage screen to remove stones, hair, grass stems and non-fibrous impurities mixed in, so as to obtain clean yak dung material mainly composed of incompletely digested plant residues. Clean yak dung material is put into a washing tank, and clean water is added for soaking and repeated rubbing and washing until the washing liquid is clear, thus obtaining purified yak dung material. It should be noted that by separating dried yak dung through multi-stage sieves, non-fibrous impurities with large particle size differences can be efficiently removed, avoiding equipment wear or fiber contamination in subsequent washing and crushing processes. The method of soaking in clean water combined with repeated rubbing can fully dissolve soluble organic matter and surface dirt, effectively improving the cleanliness of the yak dung material and providing a high-quality raw material basis for subsequent sterilization and fiber dissociation. At the same time, it avoids the introduction of chemical cleaning agents and ensures the eco-friendliness of the process.

[0024] S2. Place the yak dung material in a high-temperature steam environment above 100℃ for 30 minutes for continuous sterilization, and then process it through mechanical crushing to obtain short-fiber yak dung coarse fiber pulp. Furthermore, the purified yak dung material is sent into a steam treatment chamber and continuously heated with saturated steam to effectively kill the microorganisms inside the material, while the plant fiber structure softens due to the heat. After steam treatment, the material is transferred to a crushing device, where mechanical shearing and dispersing action breaks the fibers into loose short fibers, resulting in short-fiber yak dung coarse fiber pulp. It should be noted that using saturated steam to continuously heat the purified yak dung material can not only completely inactivate pathogenic microorganisms and insect eggs, ensuring production safety and finished product hygiene, but also achieve moderate softening of plant residues without damaging the basic fiber structure. The loose, short-fiber pulp obtained through mechanical shearing and dispersing is conducive to its uniform dispersion and effective combination with plant long fibers in subsequent pulp mixing, thereby improving the structural uniformity and mechanical properties of the composite paper.

[0025] S3. Clean the roots of *Euphorbia fischeriana* and / or the bark of *Daphne odora*, and extract the plant long fibers by a combination of soaking, pounding and tearing, or treat the roots of *Euphorbia fischeriana* or the bark of *Daphne odora* with a mild alkaline cooking method to obtain traditional plant long fiber pulp. Furthermore, the collected roots of *Euphorbia fischeriana* or the bark of *Daphne odora* branches are rinsed with running water to remove surface mud and sand, and then placed in a soaking pool to fully absorb water and soften. The softened raw material is beaten manually or mechanically to separate the fiber bundles from the xylem, and then the pure long fiber bundles are separated by manual tearing or water washing. Alternatively, the softened raw material can be put into a mild alkaline solution for cooking. After cooking, it can be rinsed with water until neutral, and then subjected to decomposition treatment to obtain traditional plant long fiber pulp. It should be noted that the roots of *Euphorbia fischeriana* and / or the bark of *Daphne odora* are rinsed with clean water, softened by water absorption, and then the fibers are extracted through physical beating and tearing, or by mild alkaline steaming followed by rinsing and loosening. This process can preserve their natural insect-repellent and antibacterial active ingredients while obtaining pure long fibers of moderate length and good flexibility. The processing method avoids the use of strong acids, strong alkalis, or high temperature and high pressure conditions, which not only protects the integrity of the fibers but also conforms to the green concept of traditional Tibetan papermaking, providing a reliable raw material guarantee for building a high-strength composite skeleton.

[0026] S4. Add short-fiber yak dung pulp and traditional plant long-fiber pulp to the mixing tank at a mass ratio of 40%–60% : 30%–50%, and add 5%–10% of natural binder (cactus juice or konjac powder) to the total pulp mass. After stirring, a homogeneous composite pulp is formed. Furthermore, the mass ratio of yak dung crude fiber pulp is preferably 70%–90% to achieve the goal of sourcing raw materials primarily from the Qinghai-Tibet Plateau; The two types of fiber pulp were pumped separately into the same mixing container, and a pre-prepared natural binder solution was added to the mixing container. Start the mixing device to thoroughly stir the mixture, so that the short fibers of yak dung are evenly dispersed in the gaps of the network formed by the long fibers of plants, and finally a uniform composite pulp is formed. After removing the thorns from fresh cactus stem segments, press them to extract the juice, filter out the residue to obtain clear juice, and add it directly to the mixing tank; When the natural binder is konjac flour, it includes: Add konjac powder to warm water, stir to disperse, and let stand to gelatinize, forming a gel-like liquid before adding it to the mixing tank; During the mixing process, the adhesive coats the surface of various fibers, enhancing the bonding force between fibers without introducing chemically synthesized substances. It should be noted that pumping the two types of fiber pulp separately and mixing them with a pre-prepared natural binder ensures that the short yak dung fibers are spatially evenly distributed in the plant long fiber network. Cactus juice or gelatinized konjac powder, as a natural binder, coats the fiber surface during the mixing process to form a physical bonding layer, effectively enhancing the interfacial bonding force between heterogeneous fibers and solving the problem of weak self-bonding ability of yak dung fibers. Moreover, no synthetic polymers or toxic chemical additives are introduced throughout the process, which meets the requirements of environmental protection and sustainable papermaking.

[0027] S5. The uniform composite pulp is formed by modified flow paper method or manual papermaking screen. The long plant fibers are used to build a network skeleton to wrap the short yak dung fibers. The papermaking force and number of times are controlled to make the paper form uniform and have the target basis weight and thickness, thus obtaining wet composite paper sheets. Furthermore, a uniform composite pulp is introduced into the papermaking vat, and the fibers are allowed to settle naturally on the papermaking screen by controlling the flow state of the pulp. During the papermaking process, long plant fibers preferentially overlap to form a continuous skeleton structure, while short yak dung fibers are trapped in the gaps of the skeleton. Repeat the papermaking process several times to gradually accumulate the thickness of the wet paper sheet until it reaches the target specification, thus obtaining a wet composite paper sheet; It should be noted that by controlling the flow and settling state of the composite pulp on the papermaking screen, and utilizing the characteristic of plant long fibers preferentially overlapping to form a web, the short fibers of yak dung are effectively anchored in the three-dimensional skeleton gaps, forming a composite structure with long fibers as the skeleton and short fibers as the flesh. Repeated papermaking actions can precisely control the thickness and weight of the paper sheets, ensuring that the paper is dense and uniform without delamination, thereby effectively improving its tensile strength and durability while maintaining the texture of traditional handmade Tibetan paper.

[0028] S6. Mechanically press and dehydrate the wet composite paper to remove free water, and then dry it by a combination of natural air drying and low-temperature drying at below 60°C to obtain dry composite paper. Furthermore, the wet paper sheet is placed between the press rolls, and the free water inside the paper sheet is squeezed out by applying mechanical pressure; After pressing, the paper sheets are transferred to a ventilated drying area for initial drying using wind and sunlight under natural conditions; After initial drying, the paper is then sent to a low-temperature drying device to further remove residual moisture through gentle hot air circulation, resulting in dry composite paper. Natural drying is carried out in an open, well-ventilated area on the plateau, with the paper laid flat on a breathable support surface to avoid direct sunlight causing localized overheating. Indirect heating is used in the low-temperature drying stage. The hot air temperature is controlled within a range that will not cause heat damage to the fibers. The paper is turned over regularly during the drying process to ensure that the moisture is released evenly and to prevent the paper from deforming or cracking. It should be noted that the paper first undergoes mechanical pressing to quickly remove most of the free water, and then combines this with a gradient drying strategy of natural air drying at high altitude and low-temperature hot air drying. This not only effectively reduces the moisture content of the paper but also avoids stress concentration caused by fiber shrinkage due to rapid dehydration. Natural air drying utilizes the low humidity and strong ultraviolet environment of the high altitude to assist in sterilization and slow dehydration, while low-temperature drying prevents heat damage. The synergistic effect of the two effectively inhibits paper warping, cracking, or discoloration, ensuring the dimensional stability and appearance quality of the finished product.

[0029] S7. The dry composite Tibetan paper is subjected to cold pressing and calendering to achieve surface smoothing and obtain composite Tibetan paper of yak dung and plant fiber. Furthermore, composite Tibetan paper can be used to make traditional Tibetan prayer flags (wind horse paper), which can be naturally degraded and returned to the grasslands after the ritual is completed, forming an ecological closed loop. The dried paper is fed into a cold calender, where a pair of smooth pressure rollers apply uniform pressure to the paper surface at room temperature. In the calendering process, only physical pressure is used to flatten the microscopic protrusions on the paper surface, thereby improving the surface smoothness. Calendered paper retains its natural fiber texture and porous structure, possessing excellent ink absorption and suitability for writing and drawing, resulting in a finished Tibetan paper product made from yak dung and plant fiber composites. It should be noted that cold calendering relies solely on physical pressure to flatten the paper surface at room temperature, without relying on heating or coating. This not only improves the smoothness of the paper surface to meet the needs of writing and drawing, but also fully preserves its natural porous structure and fiber texture. This method avoids the problems of reduced air permeability or fiber embrittlement caused by high-temperature calendering, so that the finished product has both excellent ink absorption, flexibility and the unique cultural texture of traditional Tibetan paper.

[0030] In summary, this invention transforms dried yak dung into usable short fiber components through purification, sterilization, and crushing. These components are then compounded with long fibers extracted from plateau plants such as *Euphorbia fischeriana* in a specific ratio. The plant long fibers are used to construct a continuous network framework to effectively encapsulate and fix the yak dung short fibers. This improves the strength and structural uniformity of the paper without relying on chemical additives. The entire process combines physical cleaning, steam sterilization, natural plant binders, natural sun-drying, and low-temperature drying. This not only realizes the resource utilization of yak dung, a waste product from plateau animal husbandry, but also fully preserves the natural color, porous structure, air permeability, and good compatibility with mineral pigments and Tibetan ink of traditional Tibetan paper. This solves the problems of scarce raw materials for traditional pure plant Tibetan paper and insufficient strength of pure dung paper.

[0031] Example 2, referring to Table 1, is the second embodiment of the present invention. To further verify the technical solution of the present invention, experimental simulation data of the preparation process of Tibetan paper made from yak dung and plant fiber composites are given.

[0032] Yak dung is subjected to three-stage screening (with sieve openings of 8 mm, 5 mm, and 2 mm in sequence) to remove impurities such as stones, hair, and coarse grass stems, and to obtain clean material mainly composed of undigested plant residues. Soak the yak dung material in room temperature water for 18 hours and scrub until the washing liquid is clear. The purified yak dung material is sent into a steam chamber and treated in a saturated steam environment for 30 minutes to complete sterilization and softening. Then it is sheared and broken up by a low-speed crusher to obtain loose short-fiber pulp.

[0033] Meanwhile, the roots of *Euphorbia fischeriana* are softened by soaking in running water for 12 hours. Long fibers are extracted using a combination of manual pounding and water washing to obtain a soft and pure plant long-fiber pulp. Yak dung coarse fiber pulp and *Euphorbia fischeriana* long-fiber pulp are added to a mixing tank at a mass ratio of 50%:40%, along with 8% (by weight) of cactus juice (freshly pressed, filtered, and clarified) from the total dry fiber mass. The mixture is stirred for 30 minutes to form a homogeneous composite pulp.

[0034] A modified hand-made papermaking screen is used for three repeated papermaking processes, with controlled settling time and screen tilt angle for each process to ensure uniform accumulation of wet paper thickness. After dehydration by a double-roll press, the wet paper is first naturally air-dried for 6 hours in an open, well-ventilated area at high altitude, then transferred to a 50°C hot air drying oven for 3 hours. Finally, the surface is leveled using a cold calender at room temperature to obtain the finished composite Tibetan paper.

[0035] The following are the comparative test results of the composite Tibetan paper prepared by this invention and two existing types of Tibetan paper (traditional pure wolfsbane Tibetan paper and commercially available pure yak dung paper) in terms of key performance indicators: The details are shown in Table 1 below:

[0036] Table 1 Comparison of Physical and Functional Properties of Different Paper Samples Data analysis and technical effect description: As can be seen from the data in Table 1, the yak dung and plant fiber composite Tibetan paper prepared by this invention has achieved significant optimization and balance in many key properties.

[0037] In terms of mechanical properties, its tensile strength reaches 3.8 kN / m, which is slightly lower than that of pure wolfsbane Tibetan paper (4.2 kN / m), but much higher than that of commercially available pure yak dung paper (1.1 kN / m). This indicates that the use of plant long fibers to construct the skeleton structure effectively compensates for the weak bonding force of yak dung fibers themselves. Its folding endurance reaches 28 times, meeting the practical requirement of ≥15 times for traditional calligraphy and painting paper, and solving the problems of pure dung paper being fragile and difficult to mount.

[0038] In terms of functional adaptability, the ink absorption and diffusion diameter is 8.2 mm, which is within the ideal range (7–10 mm). This avoids the ink bleeding caused by the excessively large pores of pure yak dung paper (12.1 mm) and is superior to the excessively rapid absorption of ordinary Xuan paper, making it particularly suitable for Tibetan pen writing and mineral pigment painting. Its air permeability reaches 210 mL / min, exceeding national standards and facilitating long-term preservation in the humid environment of the plateau. The composite paper inherits the natural insect-repellent properties of wolfsbane, achieving a 96% insect resistance rate after 60 days, close to that of pure wolfsbane paper (98%) and far exceeding that of ordinary paper (<30%), proving that the composite process does not damage its active ingredients. Furthermore, the surface smoothness is improved to 280 s, significantly better than pure yak dung paper (150 s), meeting the needs of modern writing tools while retaining the natural texture without relying on chemical coatings or high-temperature calendering.

[0039] In summary, this invention successfully overcomes the dual bottlenecks of scarce and high cost of pure plant paper raw materials and low strength and poor practicality of pure manure paper in the prior art. Without sacrificing cultural attributes, it achieves the unity of waste resource utilization, performance balance and green process, and has outstanding creativity, practicality and industrialization prospects.

[0040] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A preparation process for Tibetan paper made from yak dung and plant fiber composites, characterized in that: include: The dried yak dung is screened to remove stones and hair impurities, and then soaked and washed with clean water to obtain yak dung material. Yak dung material is sterilized in a high-temperature steam environment above 100℃ for 30 minutes, and then mechanically crushed to obtain short-fiber yak dung crude fiber pulp. The roots of *Euphorbia fischeriana* and / or the bark of *Daphne odora* were washed, and plant long fibers were extracted by a combination of soaking, pounding and tearing, or the roots of *Euphorbia fischeriana* or the bark of *Daphne odora* were treated by mild alkaline cooking to obtain traditional plant long fiber pulp. Short-fiber yak dung pulp and traditional plant long-fiber pulp are added to a mixing tank at a mass ratio of 40%–60% : 30%–50%, wherein the mass proportion of yak dung pulp is preferably 70%–90% to achieve the goal of the raw materials being mainly sourced from the Qinghai-Tibet Plateau. At the same time, 5%–10% of natural binder, which is cactus juice or konjac powder, is added to the total pulp mass. After stirring, a homogeneous composite pulp is formed. The uniform composite pulp is formed by modifying the flow method or by hand papermaking screen. The long plant fibers are used to build a network skeleton to wrap the short yak dung fibers. The papermaking force and number of times are controlled to make the paper form uniform and have the target weight and thickness, thus obtaining wet composite paper sheets. The wet composite paper is mechanically pressed to remove free water, and then dried by a combination of natural air drying and low-temperature drying at below 60°C to obtain dry composite paper. The dry composite Tibetan paper was subjected to cold pressing and calendering to achieve surface smoothing and obtain composite Tibetan paper made of yak dung and plant fiber. The composite Tibetan paper can be used to make traditional Tibetan prayer flags (wind horse paper). After the ritual is completed, it can be naturally degraded and returned to the grassland, forming an ecological closed loop.

2. The preparation process of the composite Tibetan paper made from yak dung and plant fiber as described in claim 1, characterized in that: The screening of dried yak dung includes: The dried yak dung is placed in a screening device and separated step by step through a multi-stage screen to remove stones, hair, grass stems and non-fibrous impurities, and obtain clean yak dung material mainly composed of incompletely digested plant residues. Clean yak dung material is placed into a washing tank, and water is added for soaking and repeated rubbing until the washing liquid becomes clear, thus obtaining purified yak dung material.

3. The preparation process of Tibetan paper made from yak dung and plant fiber as described in claim 2, characterized in that: The process of sterilizing yak dung material by placing it in a high-temperature steam environment includes: The purified yak dung material is sent into a steam treatment chamber and continuously heated with saturated steam, which effectively kills the microorganisms inside the material and softens the plant fiber structure due to the heat. After steam treatment, the material is transferred to a crushing device, where mechanical shearing and dispersing action breaks the fibers into loose short fibers, resulting in short-fiber yak dung coarse fiber pulp.

4. The preparation process of Tibetan paper made from yak dung and plant fiber as described in claim 3, characterized in that: The cleaning of the roots of *Euphorbia fischeriana* and / or the bark of *Daphne odora* branches includes: Wash the collected roots of wolfsbane or the bark of Daphne odora branches with running water to remove surface mud and sand, and then place them in a soaking pool to fully absorb water and soften. The softened raw material is beaten manually or mechanically to separate the fiber bundles from the xylem, and then the pure long fiber bundles are separated by manual tearing or water washing. Alternatively, the softened raw material can be put into a mild alkaline solution for cooking. After cooking, it can be rinsed with water until neutral, and then subjected to a decomposition process to obtain traditional plant long fiber pulp.

5. The preparation process of Tibetan paper made from yak dung and plant fiber as described in claim 4, characterized in that: The step of adding short-fiber yak dung pulp and traditional plant long-fiber pulp to a mixing tank in a specific ratio includes: The two types of fiber pulp were pumped separately into the same mixing container, and a pre-prepared natural binder solution was added to the mixing container. Start the mixing device to thoroughly stir the mixture, so that the short fibers of yak dung are evenly dispersed in the gaps of the network formed by the long fibers of plants, and finally a uniform composite pulp is formed.

6. The preparation process of Tibetan paper made from yak dung and plant fiber as described in claim 5, characterized in that: When the natural adhesive is cactus juice, it includes: Remove the thorns from fresh cactus stem segments, press to extract juice, filter out the residue to obtain clear juice, and add it directly to the mixing tank; When the natural binder is konjac flour, it includes: Add konjac powder to warm water, stir to disperse, and let stand to gelatinize, forming a gel-like liquid, before adding it to the mixing tank; The adhesive coats the surface of various fibers during the mixing process, enhancing the bonding force between fibers without introducing chemically synthesized substances.

7. The preparation process of the composite Tibetan paper made from yak dung and plant fiber as described in claim 6, characterized in that: The process of forming uniform composite pulp using a modified flow paper method or a manual papermaking screen includes: The uniform composite pulp is introduced into the papermaking vat, and the fibers are allowed to settle naturally on the papermaking screen by controlling the flow state of the pulp. During the papermaking process, the long plant fibers preferentially overlap to form a continuous skeleton structure, while the short yak dung fibers are trapped in the gaps of the skeleton. Repeat the paper-making process several times to gradually accumulate the thickness of the wet paper sheet until it reaches the target specification, thus obtaining a wet composite paper sheet.

8. The preparation process of Tibetan paper made from yak dung and plant fiber as described in claim 7, characterized in that: The mechanical pressing and dehydration of the wet composite paper sheet includes: The wet paper sheet is placed between press rolls, and the free water inside the paper sheet is squeezed out by applying mechanical pressure; After pressing, the paper sheets are transferred to a ventilated drying area for initial drying using wind and sunlight under natural conditions; After initial drying, the paper is sent to a low-temperature drying device to further remove residual moisture through gentle hot air circulation, resulting in dry composite paper.

9. The preparation process of Tibetan paper made from yak dung and plant fiber as described in claim 8, characterized in that: The natural drying process is carried out in an open, well-ventilated area on the plateau, with the paper laid flat on a breathable support surface to avoid direct sunlight causing localized overheating. Indirect heating is used in the low-temperature drying stage. The hot air temperature is controlled within a range that will not cause thermal damage to the fibers. The paper is turned over regularly during the drying process to ensure that the moisture is evenly released and to prevent the paper from deforming or cracking.

10. The preparation process of the yak dung and plant fiber composite Tibetan paper according to claim 9, wherein: The cold pressing and calendering process for the dry composite paper includes: The dried paper is fed into a cold calender, where a pair of smooth pressure rollers apply uniform pressure to the paper surface at room temperature. In the calendering process, only physical pressure is used to flatten the microscopic protrusions on the paper surface, thereby improving the surface smoothness. Calendered paper retains its natural fiber texture and porous structure, possessing excellent ink absorption and suitability for writing and drawing, resulting in a finished Tibetan paper product made from a composite of yak dung and plant fibers.

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