Cellulose Nanocrystals / Ionic Liquid / Clove Oil Composite Emulsion for Strengthening and Reinforcing Palm-leaf Manuscripts, Its Preparation Method and Application

Abstract

The present invention discloses a cellulose nanocrystal / ionic liquid / clove oil composite emulsion for toughening and strengthening palm-leaf manuscripts, and a preparation method and application thereof, which relate to the technical field of cultural relics protection materials. The composite emulsion comprises components in the following mass concentration percentages: 0.03% to 0.15% of cellulose nanocrystals, 1% to 4% of ionic liquid, 5% to 13% of clove oil, and the balance being deionized water; the ionic liquid is prepared by an ion exchange reaction of 1-butyl-3-methylimidazolium chloride and sodium dodecyl sulfate. The cellulose nanocrystal / ionic liquid / clove oil composite emulsion provided by the present invention has good stability, high encapsulation rate, small emulsion droplet size, low cost, and both toughening and strengthening capabilities.

Description

Technical Field

[0001] The present invention relates to the technical field of cultural relic protection materials, and particularly relates to a cellulose nanocrystal / ionic liquid / clove oil composite emulsion for toughening and strengthening palm-leaf manuscripts, a preparation method thereof, and applications thereof. Background Art

[0002] Palm-leaf manuscripts are an ancient medium for recording scriptures and documents on palm leaves. Usually, the leaves of Corypha umbraculifera or Caryota ochlandra are used and made through processes such as trimming, boiling, scrubbing, drying, bundling, and engraving. There are a large number of palm-leaf manuscript remains in countries such as China, India, and Nepal. The Potala Palace in China currently preserves the palm-leaf manuscripts with the most complete ages and the largest quantities. Palm-leaf manuscripts contain rich knowledge in religion, philosophy, literature, medicine, etc., and have extremely important archaeological value and cultural value. However, under the influence of environmental factors during long-term preservation, palm-leaf manuscripts have suffered from diseases such as embrittlement and decay, resulting in a significant reduction in their toughness and strength. Therefore, it is urgent to use appropriate materials to toughen and strengthen and protect them to extend their preservation life.

[0003] In the past, polymer materials such as polyvinyl acetate, acrylic emulsion, and cellulose acetate were used to toughen and strengthen palm-leaf manuscripts, but these materials have poor compatibility with palm-leaf manuscripts. In addition, a variety of natural plant essential oils, such as clove oil, eucalyptus oil, camphor oil, and neem oil, have been successfully applied to the toughening of palm-leaf manuscripts, with good compatibility and relatively good toughening effects with palm-leaf manuscripts. Especially clove oil, which has a relatively low viscosity, a weaker pungent smell, and a low cost compared with others. However, plant essential oils are highly volatile, and the toughening persistence is not ideal, and they do not have a strengthening effect on palm-leaf manuscripts.

[0004] Pickering emulsion is an emulsion stabilized by adsorbing nanoscale solid particles at the water-oil two-phase interface. Some studies have proposed using cellulose nanomaterials to stabilize Pickering emulsions of vegetable oils. For example, cellulose nanocrystals, cellulose nanofibers, bacterial cellulose, etc. can stabilize vegetable oils such as sunflower oil, olive oil, and oregano essential oil to prepare Pickering emulsions. However, due to the limitations of the properties of such emulsions, the solid particles must be smaller than the emulsion droplets, and nanoscale particles can stabilize emulsion droplets with diameters in the micrometer range or larger, which is not conducive to their penetration into cultural relics. Summary of the Invention

[0005] Aiming at the deficiencies in the above background art, the main technical problem to be solved by the present invention is: due to the limitations of the properties of existing emulsions, the solid particles must be smaller than the emulsion droplets, and nanoscale particles can stabilize emulsion droplets with diameters in the micrometer range or larger, which is not conducive to their penetration into cultural relics. The present invention provides a cellulose nanocrystal / ionic liquid / clove oil composite emulsion for toughening and strengthening palm-leaf manuscripts, a preparation method thereof, and applications thereof.

[0006] The first object of the present invention is to provide a cellulose nanocrystal / ionic liquid / clove oil composite emulsion for toughening and strengthening palm-leaf manuscripts. The composite emulsion comprises components in the following mass concentration percentages: 0.03% to 0.15% of cellulose nanocrystals, 1% to 4% of ionic liquid, 5% to 13% of clove oil, and the balance being deionized water;

[0007] The ionic liquid is prepared by an ion exchange reaction of 1-butyl-3-methylimidazolium chloride and sodium dodecyl sulfate.

[0008] Preferably, the ionic liquid is prepared according to the following steps:

[0009] Equimolar amounts of 1-butyl-3-methylimidazolium chloride and sodium dodecyl sulfate are added to dichloromethane, stirred at room temperature for 4 to 6 h, the precipitate is removed by filtration, and after washing, the ionic liquid is obtained.

[0010] Preferably, the cellulose nanocrystals are prepared by hydrolyzing wood fibers with a sulfuric acid solution to prepare cellulose nanocrystals, and then uniformly dispersing the product in water to obtain cellulose nanocrystals.

[0011] Preferably, the cellulose nanocrystals are prepared according to the following steps:

[0012] The wood fibers are soaked in a sodium hydroxide solution, then taken out and washed with deionized water until the supernatant is neutral and dried. The dried wood fibers are added to a sulfuric acid solution and hydrolyzed at 60 to 80 °C for 30 to 40 min, and then an excessive amount of deionized water is added to remove acid residues, obtaining cellulose nanocrystals.

[0013] Preferably, the wood fibers include cotton fibers, hemp fibers, and paper fibers.

[0014] The second object of the present invention is to provide a preparation method of a cellulose nanocrystal / ionic liquid / clove oil composite emulsion for toughening and strengthening palm-leaf manuscripts, which is characterized by comprising the following steps:

[0015] The cellulose nanocrystals and the ionic liquid are added to deionized water, dispersed evenly, then clove oil is added to obtain a mixture, and then the mixture is emulsified to obtain the cellulose nanocrystal / ionic liquid / clove oil composite emulsion for toughening and strengthening palm-leaf manuscripts.

[0016] Preferably, the cellulose nanocrystals and the ionic liquid are added to deionized water, and an ultrasonic crusher is used to perform ultrasonic oscillation treatment for 3 min to disperse them evenly.

[0017] Preferably, during the emulsification process, a high-speed homogenizing emulsifier is used to emulsify the mixture at a rotation speed of 12,000 to 15,000 revolutions per minute for 3 to 5 min.

[0018] The third object of the present invention is to provide an application of a composite emulsion in toughening palm-leaf manuscripts.

[0019] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0020] The present invention provides a cellulose nanocrystal / ionic liquid / clove oil composite emulsion for toughening and strengthening palm-leaf manuscripts, a preparation method thereof, and an application thereof. The cellulose nanocrystal / ionic liquid / clove oil composite emulsion provided by the present invention has good stability, high encapsulation rate, small emulsion droplet size, low cost, and both toughening and strengthening capabilities. First, the present invention prepares a cellulose nanocrystal slurry by an acid hydrolysis method, and then prepares a surface-active ionic liquid [BMIm][C 12 SO4] through an ion exchange reaction. Finally, a high-speed homogenizing emulsifier is used to shear and emulsify a mixed solution containing water, clove oil, cellulose nanocrystals, and [BMIm][C 12 SO4] to prepare a cellulose nanocrystal / ionic liquid / clove oil composite emulsion. The composite emulsion has a smaller droplet size, about 400-800 nm, compared with the stable Pickering emulsion of cellulose nanomaterials.

[0021] The cellulose nanocrystal / ionic liquid / clove oil composite emulsion provided by the present invention can not only increase the toughness of the simulated palm-leaf manuscript by 45%-68% (taking the tensile fracture energy as an index), but also increase its tensile strength by 35%-70%. In contrast, the toughness of the simulated palm-leaf manuscript sample applied with clove oil is increased by 21-34%, and the tensile strength is not significantly increased; for the simulated palm-leaf manuscript sample applied with cellulose nanocrystals, the toughness is increased by 24-33%, and the tensile strength is increased by 31-40%; for the simulated palm-leaf manuscript sample applied with a cellulose nanocrystal / clove oil emulsion, the toughness is increased by 37-44%, and the tensile strength is increased by 32-43%. In addition, when the simulated palm-leaf manuscript sample applied with this material is accelerated aging in a constant temperature and humidity chamber for 8-9 months, the toughness and tensile strength of the simulated palm-leaf manuscript sample only decrease by 3%-6% and 5%-8% respectively. In contrast, the simulated palm-leaf manuscript sample applied with clove oil is extremely fragile, the toughness decreases by more than 98%, and the tensile strength is not increased; for the simulated palm-leaf manuscript sample applied with cellulose nanocrystals, the toughness and strength decrease by 63-75% and 39-46% respectively; for the simulated palm-leaf manuscript sample applied with a cellulose nanocrystal / clove oil emulsion, the toughness and strength decrease by 58-69% and 43-61% respectively. Detailed implementation manners

[0022] In order to enable those skilled in the art to better understand and implement the technical solutions of the present invention, the present invention will be further described below in conjunction with specific embodiments, but the specific embodiments cited do not limit the present invention.

[0023] The object of the present invention is to provide a cellulose nanocrystal / ionic liquid / clove oil composite emulsion for toughening and strengthening palm-leaf manuscripts and a preparation method thereof. First, the present invention hydrolyzes cotton fibers with a sulfuric acid solution to prepare cellulose nanocrystals, and then uniformly disperses the product in water to obtain a cellulose nanocrystal slurry. The surface-active ionic liquid 1-butyl-3-methylimidazolium dodecyl sulfate ([BMIm][C 12 SO4]) is prepared from 1-butyl-3-methylimidazolium chloride ([BMIm]Cl) and sodium dodecyl sulfate (SDS) through an ion exchange reaction. The above-mentioned cellulose nanocrystal slurry and [BMIm][C 12 SO4] are added to deionized water, and the above solution is ultrasonically oscillated for 1-3 min by an ultrasonic crusher to be uniformly dispersed, with the cellulose nanocrystal concentration being 0.03% - 0.15% and the ionic liquid concentration being 1% - 4%. 5% - 13% of clove oil is added to the above solution, and shear emulsification is performed for 3-5 min by a high-speed homogenizing emulsifier to form a uniform and stable cellulose nanocrystal / ionic liquid / clove oil composite emulsion. The emulsion has a low cost, good stability, and high encapsulation efficiency, and with the assistance of the surface-active ionic liquid [BMIm][C 12 SO4], the droplet diameter of the emulsion is smaller, with a diameter of 400 - 800 nm. The actual application results show that taking the tensile fracture energy as an index, the cellulose nanocrystal / ionic liquid / clove oil composite emulsion can not only increase the toughness of the simulated palm-leaf manuscript by 45% - 68%, but also increase its tensile strength by 35% - 70%. More importantly, the toughening and strengthening effect of this material on the simulated palm-leaf manuscript can be maintained for 8-9 months, with great commercial prospects, and is expected to be extended to the protection and restoration of palm-leaf manuscripts and other wooden cultural relics.

[0024] In the first aspect of the present invention, there is provided a cellulose nanocrystal / ionic liquid / clove oil composite emulsion for toughening and strengthening palm-leaf manuscripts, and the composite emulsion comprises components in the following mass concentration percentages: 0.03% - 0.15% of cellulose nanocrystals, 1% - 4% of ionic liquid, 5% - 13% of clove oil, and the balance being deionized water; it should be noted that the mass concentration here refers to the mass concentration percentage in the composite emulsion.

[0025] The ionic liquid is prepared by an ion exchange reaction from 1-butyl-3-methylimidazolium chloride and sodium dodecyl sulfate.

[0026] Among them, the ionic liquid is prepared according to the following steps: equimolar amounts of 1-butyl-3-methylimidazolium chloride and sodium dodecyl sulfate are added to dichloromethane, stirred at room temperature for 4-6 h, the precipitate is filtered off, and after washing, the ionic liquid is obtained.

[0027] The cellulose nanocrystals are prepared by hydrolyzing wood fibers with sulfuric acid solution to obtain cellulose nanocrystals, and then the product is uniformly dispersed in water to obtain cellulose nanocrystals.

[0028] The cellulose nanocrystals, ionic liquid and clove oil selected in the present invention. The selected cellulose nanocrystals are materials proven to be able to reinforce and repair paper cultural relics. The selected 1-butyl-3-methylimidazolium dodecyl sulfate ([BMIm][C 12 SO4]) ionic liquid has a hydrophilic cation and a lipophilic anion. Clove oil is a material proven to be able to effectively toughen palm leaves scriptures. It is conceived to combine the above materials, and the ionic liquid emulsifies the clove oil into an oil-in-water emulsion. Its hydrophilic cation tightly adsorbs the cellulose nanocrystals at the water-oil interface of the emulsion through electrostatic adsorption, thereby reducing the diameter of the emulsion droplets. The selected ionic liquid changes to a solid state at room temperature, which improves the strength of the emulsion shell layer, thereby enhancing the stability of the emulsion, and under the synergistic action of each component, the long-term toughening and reinforcement of palm leaves scriptures are realized.

[0029] According to the present invention, the cellulose nanocrystals are prepared according to the following steps:

[0030] Soak the wood fibers in sodium hydroxide solution, then take them out and wash them with deionized water until the supernatant is neutral and dry. Add the dried wood fibers to sulfuric acid solution and hydrolyze at 60-80 °C for 30-40 min, and then add excessive deionized water to remove acid residues to obtain cellulose nanocrystals.

[0031] Among them, the wood fibers include cotton fibers, hemp fibers and paper fibers.

[0032] A preparation method of a cellulose nanocrystals / ionic liquid / clove oil composite emulsion for toughening and reinforcing palm leaves scriptures provided by the second aspect of the present invention includes the following steps:

[0033] Add the cellulose nanocrystals and the ionic liquid to deionized water, disperse them evenly, then add clove oil to obtain a mixture, and then perform emulsification treatment on the mixture to obtain a cellulose nanocrystals / ionic liquid / clove oil composite emulsion for toughening and reinforcing palm leaves scriptures.

[0034] Among them, when adding the cellulose nanocrystals and the ionic liquid to deionized water, use an ultrasonic crusher to ultrasonically vibrate for 3 min to disperse them evenly.

[0035] During the emulsification treatment, use a high-speed homogenizing emulsifier to emulsify the mixture at a speed of 12000-15000 revolutions per minute for 3-5 min.

[0036] In an embodiment, a cellulose nanocrystals / ionic liquid / clove oil composite emulsion and its preparation method are mainly prepared by the following steps:

[0037] Step 1, Preparation of cellulose nanocrystals: Soak 10 - 20 g of cotton fiber, hemp fiber or paper fiber in 400 mL of 1 - 2 M sodium hydroxide solution for 30 min - 2 h, then take it out and wash it with deionized water until the supernatant is neutral and dry it. Add the dried cotton fiber into 400 - 500 g of sulfuric acid solution (60 - 70%) and hydrolyze it at 60 - 80 °C for 30 - 40 min. Then add an excessive amount of deionized water to remove acid residues. The amount of added water is 10 - 20 times the amount of sulfuric acid. After centrifugation, ultrasonically disperse the product in water to obtain a cellulose nanocrystal slurry.

[0038] Step 2, Preparation of surface-active ionic liquid: Add equimolar amounts (0.01 - 0.03 mol) of [BM Im]Cl and SDS into 50 - 100 mL of dichloromethane, stir at room temperature for 4 - 6 h, filter to remove the precipitate, and centrifuge and wash the organic solution with deionized water until it contains no chloride (detect chloride ions with silver nitrate solution). Vacuum dry the washed solution to obtain a waxy substance, which is the ionic liquid [BMIm][C 12 SO4].

[0039] Step 3, Preparation of cellulose nanocrystal / ionic liquid / clove oil composite emulsion: First, add the cellulose nanocrystal slurry and [BMIm][C 12 SO4] into deionized water, and use an ultrasonic crusher to ultrasonically vibrate for 3 min to make it disperse evenly. The concentration of cellulose nanocrystals is 0.03% - 0.15%, and the concentration of ionic liquid is 1% - 4%. Add 5% - 13% of clove oil into the above solution, and use a high-speed homogenizing emulsifier to shear and emulsify the mixture at a speed of 12000 - 15000 revolutions per minute for 3 - 5 min to form a uniform and stable cellulose nanocrystal / ionic liquid / clove oil composite emulsion.

[0040] The third aspect of the present invention provides an application of a composite emulsion in toughening palm-leaf scriptures. After the composite emulsion provided by the present invention is applied in toughening palm-leaf scriptures, not only can the toughness of the simulated palm-leaf scriptures be increased by 45% - 68% (taking the tensile fracture energy as an index), but also the tensile strength can be increased by 35% - 70%. In contrast, for the simulated palm-leaf scripture samples applied with clove oil, the toughness is increased by 31 - 34%, and the tensile strength is not significantly increased; for the simulated palm-leaf scripture samples applied with cellulose nanocrystals, the toughness is increased by 24 - 33%, and the tensile strength is increased by 31 - 40%; for the simulated palm-leaf scripture samples applied with cellulose nanocrystal / clove oil emulsion, the toughness is increased by 37 - 44%, and the tensile strength is increased by 32 - 43%. In addition, when the simulated palm-leaf scripture samples applied with this material are accelerated aging in a thermostatic and humid climate chamber for 8 - 9 months, the toughness and tensile strength of the simulated palm-leaf scripture samples only decrease by 3% - 6% and 5% - 8% respectively. In comparison, the simulated palm-leaf scripture samples applied with clove oil are extremely fragile, the toughness decreases by more than 98%, and the tensile strength is not increased; for the simulated palm-leaf scripture samples applied with cellulose nanocrystals, the toughness and strength decrease by 63 - 75% and 39 - 46% respectively; for the simulated palm-leaf scripture samples applied with cellulose nanocrystal / clove oil emulsion, the toughness and strength decrease by 58 - 69% and 43 - 61% respectively.

[0041] It should be noted that the experimental methods used in the present invention are all conventional methods unless otherwise specified; the reagents and materials used, unless otherwise specified, can be purchased on the market.

[0042] Example 1

[0043] Soak 10 g of cotton fibers in 400 mL of a 1 M sodium hydroxide solution for 30 min, take them out, wash them several times with deionized water until the supernatant is neutral, and dry them. Add the dried cotton fibers to 400 g of a 65% sulfuric acid solution and hydrolyze at 60 °C for 30 min. Subsequently, add an excessive amount of deionized water to remove the acid residue, the amount of added water is 10 times the amount of sulfuric acid, and after centrifugation, the product is ultrasonically dispersed in water to obtain a cellulose nanocrystal (length ~ 200 nm) slurry. Add 0.01 mol each of [BMIm]Cl and SDS to 50 mL of dichloromethane, stir at room temperature for 4 h, filter to remove the precipitate, and wash the organic solution by centrifugation with deionized water until it contains no chloride (detect chloride ions with silver nitrate solution). Vacuum dry the above solution to obtain the ionic liquid [BMIm][C 12 SO4]. Mix the cellulose nanocrystal slurry and [BMIm][C 12Add [[BMIm][C 12 SO4] to 9 g of deionized water, and use an ultrasonic crusher to ultrasonically vibrate for 3 min to make it evenly dispersed. The concentration of cellulose nanocrystals is 0.03%, and the concentration of ionic liquid is 1%. Then add 1 g of commercially available clove oil, and use a high-speed homogenizing emulsifier to shear and emulsify the above mixture at a speed of 12,000 revolutions per minute for 3 min to form an emulsion, forming a cellulose nanocrystal / ionic liquid / clove oil composite emulsion with a droplet size of about 800 nm that can be stably dispersed for more than 1 month. 10 g can be prepared at a time, which contains 10% clove oil, 0.03% cellulose nanocrystals, and 1%

[0044] Through the dry heat aging method, use an oven to dry heat treat the healthy palm-leaf scriptures samples at 105 °C for 5 days to prepare simulated aged palm-leaf scriptures samples, and use the simulated aged palm-leaf scriptures as the application object.

[0045] Brush the composite emulsion on the surface of the simulated palm-leaf scriptures samples. After sufficient absorption, use absorbent cotton to wipe off the residual emulsion on the surface. Use the simulated palm-leaf scriptures samples treated with pure clove oil as a comparison.

[0046] Test results: Compared with the untreated simulated palm-leaf scriptures samples, the toughness of the cellulose nanocrystal / ionic liquid / clove oil composite emulsion and the simulated palm-leaf scriptures samples treated with clove oil increased by 52% and 34% respectively, and the tensile strength increased by 35% and 1% respectively. For the simulated palm-leaf scriptures samples applied with cellulose nanocrystals, the toughness increased by 24% and the tensile strength increased by 31%; for the simulated palm-leaf scriptures samples applied with cellulose nanocrystal / clove oil emulsion, the toughness increased by 37% and the tensile strength increased by 32%. Perform artificial accelerated aging treatment on the treated simulated palm-leaf scriptures samples. After 8 months, the toughness and tensile strength of the simulated palm-leaf scriptures samples treated with cellulose nanocrystal / ionic liquid / clove oil emulsion decreased by only 3% and 5% respectively, while the toughness of the simulated palm-leaf scriptures treated with clove oil decreased by 98%; for the simulated palm-leaf scriptures samples applied with cellulose nanocrystals, the toughness and strength decreased by 63% and 39% respectively; for the simulated palm-leaf scriptures samples applied with cellulose nanocrystal / clove oil emulsion, the toughness and strength decreased by 58% and 43% respectively.

[0047] Example 2

[0048] Soak 15 g of pulp in 400 mL of sodium hydroxide solution with a concentration of 1.2 M for 1 h. After taking it out, wash it several times with deionized water until the supernatant is neutral and then dry it. Add the dried paper fibers to 450 g of sulfuric acid solution with a concentration of 70%, and hydrolyze it at 70 °C for 35 min. Subsequently, add an excessive amount of deionized water to remove the acid residue. The amount of water added is 20 times the amount of sulfuric acid. After centrifugation, ultrasonically disperse the product in water to obtain a cellulose nanocrystal (length ~180 nm) slurry. Add 0.02 mol of [BMIm]Cl and SDS to 80 mL of dichloromethane, stir at room temperature for 4 h, filter to remove the precipitate, and wash the organic solution with deionized water by centrifugation until it contains no chloride (detect chloride ions with silver nitrate solution). Vacuum dry the above solution to obtain the ionic liquid [BMIm][C 12 SO4]. Add the cellulose nanocrystal slurry and [BMIm][C 12 SO4] to 19 g of deionized water, and use an ultrasonic crusher to ultrasonically vibrate for 3 min to make it evenly dispersed. The concentration of cellulose nanocrystals is 0.06%, and the concentration of the ionic liquid is 2%. Then add 1 g of commercially available clove oil, and use a high-speed homogenizing emulsifier to shear and emulsify the above mixture at a speed of 13,000 revolutions per minute for 4 min to form an emulsion, forming a cellulose nanocrystal / ionic liquid / clove oil composite emulsion with a droplet size of about 400 nm that can be stably dispersed for more than 1 month. 20 g can be prepared at a time, which contains 5% of clove oil, 0.06% of cellulose nanocrystals, and 2% of [BMIm][C 12 SO4].

[0049] Through the dry heat aging method, use an oven to dry-treat healthy palm-leaf scriptures samples at 105 °C for 5 days to prepare simulated aged palm-leaf scriptures samples, with the simulated aged palm-leaf scriptures as the application object.

[0050] Brush the composite emulsion on the surface of the simulated palm-leaf scriptures samples. After sufficient absorption, use absorbent cotton to wipe off the residual emulsion on the surface. Use the simulated palm-leaf scriptures samples treated with pure clove oil as a comparison.

[0051] Test results: Compared with the untreated simulated palm leaf samples, the toughness of the cellulose nanocrystal / ionic liquid / clove oil composite emulsion and the simulated palm leaf samples treated with clove oil increased by 45% and 31% respectively, and the tensile strength increased by 43% and 0% respectively; for the simulated palm leaf samples with cellulose nanocrystals applied, the toughness increased by 29% and the tensile strength increased by 37%; for the simulated palm leaf samples with cellulose nanocrystal / clove oil emulsion applied, the toughness increased by 39% and the tensile strength increased by 35%. The artificially accelerated aging treatment was carried out on the treated simulated palm leaf samples. After 8 months, the toughness and tensile strength of the simulated palm leaf samples treated with cellulose nanocrystal / ionic liquid / clove oil composite emulsion decreased by only 4% and 6% respectively, while the toughness of the simulated palm leaf samples treated with clove oil decreased by 99%; for the simulated palm leaf samples with cellulose nanocrystals applied, the toughness and strength decreased by 71% and 42% respectively; for the simulated palm leaf samples with cellulose nanocrystal / clove oil emulsion applied, the toughness and strength decreased by 63% and 50% respectively.

[0052] Example 3

[0053] Soak 20 g of hemp fibers in 500 mL of sodium hydroxide solution with a concentration of 2 M for 2 h. After taking them out, wash them several times with deionized water until the supernatant is neutral and dry them. Add the dried hemp fibers to 500 g of sulfuric acid solution with a concentration of 60% and hydrolyze at 80 °C for 40 min. Subsequently, add an excessive amount of deionized water to remove the acid residues. The amount of water added is 10 times the amount of sulfuric acid. After centrifugation, ultrasonically disperse the product in water to obtain a cellulose nanocrystal (length ~ 220 nm) slurry. Add 0.03 mol of [BMIm]Cl and SDS to 100 mL of dichloromethane respectively, stir at room temperature for 6 h, filter to remove the precipitate, and centrifuge and wash the organic solution with deionized water until it contains no chloride (detect chloride ions with silver nitrate solution). Vacuum dry the above solution to obtain the ionic liquid [BMIm][C 12 SO4]. Add the cellulose nanocrystal slurry and [BMIm][C 12 SO4] to 43.5 g of deionized water, and use an ultrasonic crusher to ultrasonically oscillate for 3 min to make it disperse evenly. The concentration of cellulose nanocrystals is 0.15%, and the concentration of ionic liquid is 4%. Then add 6.5 g of commercially available clove oil, and use a high-speed homogenizing emulsifier to shear and emulsify the above mixture at a speed of 15,000 revolutions per minute for 5 min to form an emulsion, forming a cellulose nanocrystal / ionic liquid / clove oil composite emulsion with a droplet size of about 700 nm, which can be stably dispersed for more than 1 month. 50 g can be prepared at a time, which contains 13% of clove oil, 0.15% of cellulose nanocrystals, and 4% of [BMIm][C 12 SO4].

[0054] By means of dry heat aging method, healthy Buddhist scriptures samples were heat-treated at 105 °C in an oven for 5 days to prepare simulated aged Buddhist scriptures samples, and the simulated aged Buddhist scriptures were used as the application object.

[0055] The composite emulsion was applied to the surface of the simulated Buddhist scriptures samples. After sufficient absorption, the residual emulsion on the surface was wiped off with absorbent cotton. The simulated Buddhist scriptures samples treated with pure clove oil were used as the control.

[0056] Test results: Compared with the untreated simulated Buddhist scriptures samples, the toughness of the simulated Buddhist scriptures samples treated with cellulose nanocrystals / ionic liquid / clove oil composite emulsion and clove oil increased by 68% and 31% respectively, and the tensile strength increased by 70% and 1% respectively; for the simulated Buddhist scriptures samples applied with cellulose nanocrystals, the toughness increased by 33% and the tensile strength increased by 40%; for the simulated Buddhist scriptures samples applied with cellulose nanocrystals / clove oil emulsion, the toughness increased by 44% and the tensile strength increased by 43%. The artificially accelerated aging treatment was carried out on the treated simulated Buddhist scriptures samples. After 9 months, the toughness and tensile strength of the simulated Buddhist scriptures samples treated with cellulose nanocrystals / ionic liquid / clove oil composite emulsion decreased by only 6% and 8% respectively, while the toughness of the simulated Buddhist scriptures samples treated with clove oil decreased by 98%; for the simulated Buddhist scriptures samples applied with cellulose nanocrystals, the toughness and strength decreased by 75% and 46% respectively; for the simulated Buddhist scriptures samples applied with cellulose nanocrystals / clove oil emulsion, the toughness and strength decreased by 69% and 61% respectively.

[0057] The present invention describes the preferred embodiments and their effects. However, those skilled in the art can make additional changes and modifications to these embodiments once they know the basic creative concepts. Therefore, the appended claims are intended to be construed as including the preferred embodiments as well as all changes and modifications falling within the scope of the present invention.

[0058] Although the embodiments of the present invention have been shown and described, it will be understood by those of ordinary skill in the art that various changes, modifications, substitutions and variations can be made in these embodiments without departing from the principles and spirit of the present invention, and the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A cellulose nanocrystal / ionic liquid / clove oil composite emulsion for toughening and strengthening palm-leaf manuscripts, characterized in that The composite emulsion comprises components in the following mass concentration percentages: cellulose nanocrystals 0.03% - 0.15%, ionic liquid 1% - 4%, clove oil 5% - 13%, and the balance is deionized water; The ionic liquid is prepared by an ion exchange reaction of 1-butyl-3-methylimidazolium chloride and sodium dodecyl sulfate; The ionic liquid is prepared according to the following steps: Add equimolar amounts of 1-butyl-3-methylimidazolium chloride and sodium dodecyl sulfate to dichloromethane, stir at room temperature for 4 - 6 h, filter to remove the precipitate, and after washing, obtain the ionic liquid; The cellulose nanocrystals are prepared by hydrolyzing lignocellulose with sulfuric acid solution to prepare cellulose nanocrystals, and then uniformly dispersing the product in water to obtain cellulose nanocrystals; The cellulose nanocrystals are prepared according to the following steps: Soak the lignocellulose in sodium hydroxide solution, then take it out and wash it with deionized water until the supernatant is neutral and dry it. Add the dried lignocellulose to sulfuric acid solution and hydrolyze it at 60 - 80 °C for 30 - 40 min, and then add excessive deionized water to remove the acid residue to obtain cellulose nanocrystals; The composite emulsion is prepared according to the following steps: Add cellulose nanocrystals and ionic liquid to deionized water, disperse evenly, then add clove oil to obtain a mixture, and then perform emulsification treatment on the mixture to obtain the cellulose nanocrystals / ionic liquid / clove oil composite emulsion for toughening and strengthening palm leaves scriptures; During the emulsification treatment, use a high-speed homogenizing emulsifier to emulsify the mixture at a speed of 12000 - 15000 revolutions per minute for 3 - 5 min.

2. The cellulose nanocrystal / ionic liquid / clove oil composite emulsion for toughening and strengthening the palm-leaf manuscript according to claim 1, wherein The lignocellulose includes cotton fiber, hemp fiber, and paper fiber.

3. A method for preparing a cellulose nanocrystal / ionic liquid / clove oil composite emulsion for toughening and strengthening palm-leaf manuscripts, as claimed in claim 1 or 2, characterized in that It includes the following steps: Add cellulose nanocrystals and ionic liquid to deionized water, disperse evenly, then add clove oil to obtain a mixture, and then perform emulsification treatment on the mixture to obtain the cellulose nanocrystals / ionic liquid / clove oil composite emulsion for toughening and strengthening palm leaves scriptures; During the emulsification treatment, use a high-speed homogenizing emulsifier to emulsify the mixture at a speed of 12000 - 15000 revolutions per minute for 3 - 5 min.

4. The preparation method of the cellulose nanocrystal / ionic liquid / clove oil composite emulsion for the toughening and strengthening of palm-leaf manuscripts according to claim 3, characterized in that, Add cellulose nanocrystals and ionic liquid to deionized water, and use an ultrasonic crusher to ultrasonically vibrate for 3 min to disperse them evenly.

5. Application of the composite emulsion according to claim 1 or 2 in toughening palm leaves scriptures.