Microcapsule, molded pulp and preparation method thereof

Abstract

The invention provides a microcapsule, a molded pulp and a preparation method thereof. The preparation method of the microcapsule comprises the following steps: extracting a spice raw material by utilizing supercritical fluid to obtain essential oil; mixing essential oil with porous starch to obtain an essential oil-starch core material compound; dispersing the essential oil-starch core material compound in a composite wall material solution composed of chitosan, Arabic gum and nano cellulose to obtain an emulsion; adjusting the pH value of the emulsion to 4.0-4.2 to obtain a microcapsule suspension; and immersing the microcapsule suspension liquid into the cross-linking liquid to obtain microcapsule powder. Essential oil is subjected to supercritical extraction, the essential oil is used as a core material, porous starch is used as a carrier to form a core material compound, chitosan, Arabic gum and nano cellulose are mixed to form a composite wall material solution, and the core material compound is coated with the composite wall material solution to form a microcapsule suspension; and then the microcapsule is obtained through normal-temperature ion curing, so that efficient loading and activity protection of the essential oil can be realized, and the slow release performance is improved.

Description

Technical Field

[0001] The present disclosure relates to the technical field of pulp molding, and in particular to a microcapsule, pulp molding and a preparation method thereof. Background Art

[0002] With the deepening trend of consumption upgrades and high-end consumption, the functional requirements for packaging materials have expanded from basic protection and aesthetics to enhanced sensory experiences. Among these, long-lasting and high-quality aroma retention has become one of the core competitive advantages of pulp molded packaging in the future. Consumers expect products to continuously release pleasant aromas throughout their shelf life and during use, while also demanding that technological approaches meet environmental and safety standards. However, existing fragrance-adding technologies face multiple bottlenecks. For example, traditional fragrance addition methods have significant drawbacks: surface spraying methods can result in a short fragrance volatilization period (expiring after 7-15 days) and uneven distribution, which can easily lead to content contamination. Direct blending methods, exposed to high temperatures and high pressures during processing, can destroy active fragrance ingredients, resulting in low retention rates. For example, mainstream microencapsulation technologies also have limitations: spray drying methods, at temperatures of 150-200°C, can cause volatilization losses of heat-sensitive essential oils of ≥20%, with essential oil retention rates ≤80% (high temperatures directly destroy volatile components). Organic solvent encapsulation methods carry the risk of contamination from residual solvents (such as ether and acetone), and high-temperature drying (>80°C) can result in essential oil losses of >30%, resulting in substandard energy consumption and environmental performance. Summary of the Invention

[0003] The present application provides a microcapsule, pulp molding and a preparation method thereof to solve at least one of the technical problems existing in the prior art.

[0004] In a first aspect, the present application provides a method for preparing microcapsules, comprising:

[0005] Providing fragrance raw materials, and extracting and separating the fragrance raw materials using supercritical fluid to obtain essential oils;

[0006] mixing the essential oil with porous starch to obtain an essential oil-starch core material composite;

[0007] Dispersing the essential oil-starch core material complex in a composite wall material solution composed of chitosan, gum arabic and nanocellulose, stirring to obtain an emulsion; adjusting the pH of the emulsion to 4.0-4.2, stirring to obtain a microcapsule suspension;

[0008] The microcapsule suspension is immersed in a cross-linking liquid, stirred, filtered, washed with water, and dried to obtain microcapsule powder.

[0009] In one embodiment, extracting and separating the fragrance raw materials using supercritical fluid to obtain essential oils includes:

[0010] The fragrance raw material is placed in a supercritical CO2 extraction device, and extracted for 2 to 3 hours under the conditions of a pressure of 12 to 15 MPa, a temperature of 35 to 45° C., and a CO2 flow rate of 15 to 25 L / h to obtain a mixture consisting of CO2 and crude essential oil;

[0011] The mixture is subjected to the conditions of a pressure of 6 to 8 MPa and a temperature of 40 to 50° C. to separate CO 2 and crude essential oil to obtain the pure essential oil.

[0012] In one embodiment, the essential oil is mixed with porous starch to obtain an essential oil-starch core material composite comprising:

[0013] The essential oil and porous starch are mixed in a mass ratio of 1:0.8-1.1, and adsorbed at 40-50° C. for 20-24 hours to obtain the essential oil-starch core material composite;

[0014] The porous starch is carboxymethyl porous starch.

[0015] In one embodiment, the essential oil-starch core material complex is dispersed in a composite wall material solution composed of chitosan, gum arabic and nanocellulose, and stirred to obtain an emulsion comprising:

[0016] Dissolving chitosan and nanocellulose in water to obtain a chitosan aqueous solution and a nanocellulose aqueous solution, respectively, and then dissolving the chitosan aqueous solution and the nanocellulose aqueous solution in acetic acid and ultrasonically dispersing them to obtain a chitosan-nanocellulose solution; dissolving gum arabic in water to obtain an arabic gum aqueous solution;

[0017] Dispersing the essential oil-starch core material complex in the chitosan-nanocellulose solution, adding the mixture to the gum arabic aqueous solution, and stirring to obtain the emulsion;

[0018] Among them, based on the mass of the emulsion as 100wt%, the solid content of the chitosan-nanocellulose solution accounts for 2.3wt%, the solid content of the gum arabic aqueous solution accounts for 2.5wt%, the essential oil-starch core material composite accounts for 4.8wt%, and the balance is solvent.

[0019] In one embodiment, the cross-linking solution is a calcium lactate solution with a concentration of 1 to 2.0% w / v;

[0020] The microcapsule powder is dried by air flow drying at 30-50° C. to make the moisture content of the microcapsule powder less than 5%.

[0021] In one embodiment, the method further comprises: spraying silicon dioxide on the surface of the microcapsule powder to obtain microcapsules; wherein the mass ratio of silicon dioxide to the microcapsule powder is 0.3:100;

[0022] The particle size of the silicon dioxide is 10 to 20 nm.

[0023] In a second aspect, the present application further provides a microcapsule, which is prepared using the preparation method in any one of the above embodiments.

[0024] In a third aspect, the present application also provides a pulp molding comprising the microcapsules described above.

[0025] Fourthly, the present application also provides a method for preparing pulp molding, wherein microcapsules are added to pulp slurry at a ratio of 1.5 to 4 wt% of the dry weight of the pulp slurry, and the pulp molding is obtained by molding, cold pressing, hot pressing and shaping, and drying.

[0026] In one embodiment, the forming comprises: forming the pulp slurry into a wet embryo by vacuum forming, wherein the vacuum degree required by the vacuum forming method is 500-700 Pa, the air pressure during demoulding is 0.15-0.3 MPa, and the moisture content of the wet embryo is 65-75%;

[0027] The cold pressing, hot pressing and shaping include: cold pressing the wet embryo in a mold to a moisture content of 55-60%, and then hot pressing at a pressure of 0.8-1.2 MPa and a temperature of 120-135° C. for 25-35 seconds to obtain a formed pulp molding semi-finished product;

[0028] The drying comprises: drying the pulp molding semi-finished product at a temperature of 100-110° C. to obtain the pulp molding.

[0029] Compared with the existing technology, the advantages of this application are: 1) This application uses supercritical technology to extract essential oils, and then uses essential oils as core materials and porous starch as carriers. The two are mixed to form a core material composite, and chitosan, gum arabic and nanocellulose are mixed as a composite wall material solution. The composite wall material solution is coated with the core material composite to form a microcapsule suspension; then microcapsules are obtained by room temperature ion curing, which can achieve efficient essential oil loading and active protection, and improve sustained release performance and processing performance. 2) In this application, porous starch is used as a carrier, and porous starch and essential oil core materials form a core material composite. The porous starch carrier achieves initial rapid release (15% release in 30 days), which meets consumers' instant odor perception when unboxing. 3) In this application, chitosan and nanocellulose are selected as the main raw materials. Chitosan has good biocompatibility and degradability, and nanocellulose has a high specific surface area and good mechanical properties. Nanocellulose can enhance the shear resistance of the composite wall material. When used in pulp molding production, it can improve the mechanical properties of pulp molding. This application uses biodegradable raw materials to ensure the environmental friendliness of the production process and final product, in line with the needs of ESG (environment, society and governance) strategy.

[0030] It should be understood that the contents described in this section are not intended to identify the key or important features of the embodiments of the present disclosure, nor are they intended to limit the scope of the present disclosure. Other features of the present disclosure will become readily understood through the following description. DETAILED DESCRIPTION

[0031] To make the purposes, features, and advantages of the present disclosure more apparent and understandable, the technical solutions in the embodiments of the present disclosure are clearly and completely described below in conjunction with the embodiments of the present disclosure. Obviously, the described embodiments are only a part of the embodiments of the present disclosure, not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of the present disclosure without creative work are within the scope of protection of the present disclosure.

[0032] In a first aspect, the present application provides a method for preparing microcapsules, comprising:

[0033] Step 1): providing a fragrance raw material, and extracting and separating the fragrance raw material using a supercritical fluid to obtain an essential oil;

[0034] Step 2): mixing the essential oil with the porous starch to obtain an essential oil-starch core material composite;

[0035] Step 3): dispersing the essential oil-starch core material complex in a composite wall material solution composed of chitosan, gum arabic, and nanocellulose, stirring to obtain an emulsion; adjusting the pH of the emulsion to 4.0-4.2, stirring, and obtaining a microcapsule suspension;

[0036] Step 4): Immersing the microcapsule suspension in a cross-linking solution, stirring, filtering, washing with water, and drying to obtain microcapsule powder.

[0037] In one embodiment, in step 1), the supercritical fluid is supercritical CO2 fluid.

[0038] For example, in step 1), extracting and separating the fragrance raw materials using supercritical fluid to obtain essential oils includes:

[0039] Step 1-1): placing the fragrance raw material in a supercritical CO2 extraction device, extracting for 2 to 3 hours at an extraction pressure of 12 to 15 MPa, an extraction temperature of 35 to 45°C, and a CO2 flow rate of 15 to 25 L / h to obtain a mixture consisting of CO2 and crude essential oil;

[0040] Step 1-2): The mixture enters a separator, and CO2 and crude essential oil are separated under a separation pressure of 6 to 8 MPa and a separation temperature of 40 to 50° C. to obtain pure essential oil.

[0041] Preferably, in step 1-1), the extraction pressure is 12 MPa, the extraction temperature is 40°C, and the CO2 flow rate is 20 L / h. In step 1-2), the separation pressure is 8 MPa and the separation temperature is 40°C. The extraction yield of the essential oil obtained by supercritical CO2 extraction in step 1) is ≥95%, and no solvent residue is obtained.

[0042] For example, in step 1), the flavor raw material includes but is not limited to mint flavor, and the essential oil obtained is mint essential oil. Taking the supercritical CO2 fluid extraction of mint essential oil as an example, it includes placing the mint raw material in a supercritical CO2 extraction device, controlling the extraction temperature and pressure (35-45°C, 12-15MPa), and making CO2 in a supercritical state (flow rate 15-25L / h). Among them, the supercritical CO2 fluid passes through the mint flavor raw material and dissolves the mint essential oil components therein. The extracted mixture enters the separator, and at a specific temperature and pressure, the CO2 and crude essential oil in the mixture are separated to obtain pure mint essential oil. The essential oil obtained by extraction using the step 1) method has the advantages of good selectivity, no solvent residue, low operating temperature, and simple post-processing. In addition, the mint smell can improve the unboxing experience of electronic products.

[0043] In one embodiment, in step 2), mixing the essential oil with the porous starch to obtain the essential oil-starch core material composite comprises: mixing the essential oil and the porous starch in a mass ratio of 1:0.8 to 1.1, and adsorbing at a temperature of 40 to 50° C. for 20 to 24 hours to obtain the essential oil-starch core material composite.

[0044] Preferably, the essential oil and the porous starch are mixed in a mass ratio of 1:0.8, 1:0.88, 1:1 or 1:1.1.

[0045] The porous starch is preferably carboxymethyl porous starch (CMPS), due to its high hydroxyl activity and good compatibility with chitosan. Modified carboxymethyl porous starch, when applied to waste paper pulp, can increase the fiber strength of the waste paper pulp, achieving a ring crush strength of 4.8 kN / m, a 120% increase over unmodified pulp, thereby optimizing the mechanical properties of the pulp.

[0046] This application uses supercritical technology to extract essential oils, and then uses essential oils as core materials and porous starch as carriers to form a core material composite. Chitosan, gum arabic, and nanocellulose are mixed as composite wall material solutions. The composite wall material solution is coated with the core material composite to form a microcapsule suspension; microcapsules are then obtained through room temperature ion curing, which can achieve efficient essential oil loading and active protection, and improve sustained-release performance and processing performance. In addition, porous starch is used as a carrier in this application. The porous starch and essential oil core material form a core material composite. The porous starch carrier achieves rapid initial release (15% release in 30 days), satisfying consumers' instant odor perception when unboxing.

[0047] In one embodiment, in step 3), dispersing the essential oil-starch core material complex in a composite wall material solution composed of chitosan, gum arabic and nanocellulose, and stirring to obtain an emulsion comprises:

[0048] Step 3-1): dissolving chitosan and nanocellulose in water to obtain a chitosan aqueous solution and a nanocellulose aqueous solution, respectively; then dissolving the chitosan aqueous solution and the nanocellulose aqueous solution in acetic acid and ultrasonically dispersing them to obtain a chitosan-nanocellulose solution;

[0049] Step 3-2): dissolving gum arabic in water to obtain an aqueous solution of gum arabic;

[0050] Step 3-3): dispersing the essential oil-starch core material complex in the chitosan-nanocellulose solution, adding the mixture to the gum arabic aqueous solution, and stirring to obtain an emulsion;

[0051] Among them, based on the mass of the emulsion as 100wt%, the solid content in the chitosan-nanocellulose solution accounts for 2.3%, the solid content in the gum arabic aqueous solution accounts for 2.5wt%, the essential oil-starch core material composite accounts for 4.8wt%, and the remainder is solvent (including acetic acid and water).

[0052] In this application, a composite wall material solution (referred to as "composite wall material") is formed by mixing chitosan, nanocellulose, and gum arabic, and the encapsulation rate of essential oils is improved by optimizing process parameters such as the composition of the composite wall material, the ratio of the core material composite to the composite wall material, the pH value, and the stirring speed.

[0053] For example, in step 3-1), the volume concentration of acetic acid is 1% to adjust the pH. The amount of acetic acid used is sufficient to dissolve chitosan and nanocellulose. Exemplarily, the mass ratio of chitosan, nanocellulose, and acetic acid is 1.5:0.8:1.05.

[0054] In step 3-1), the nanocellulose aqueous solution was ultrasonically dispersed for 10 minutes before adding acetic acid to avoid agglomeration.

[0055] Preferably, in step 3-1), the chitosan aqueous solution and the nanocellulose aqueous solution (the nanocellulose aqueous solution is first ultrasonically dispersed for 10 minutes) are slowly added to 1% acetic acid (pH≈4.5), and then ultrasonic dispersion is continued for 20 minutes to ensure complete dissolution to obtain a chitosan-nanocellulose solution.

[0056] For example, in step 3-3), the essential oil-starch core material complex is dispersed in the chitosan-nanocellulose solution and added to the gum arabic aqueous solution with a stirring speed of 8000-11000 r / min and continuous stirring for 20 minutes to obtain an emulsion.

[0057] For example, in step 3-3), based on the mass of the emulsion being 100 wt%, chitosan accounts for 1.5 wt%, nanocellulose accounts for 0.8 wt%, gum arabic accounts for 2.5 wt%, essential oil-starch core material composite accounts for 4.8 wt%, and the remainder is solvent (including acetic acid and water).

[0058] In step 3), adjusting the pH of the emulsion to 4.0-4.2, stirring, and obtaining a microcapsule suspension includes: using acetic acid solution (dilute acetic acid) to adjust the pH value of the emulsion system to gradually drop to 4.0-4.2, promoting the wall material to coagulate and coat layer by layer, and then changing to a low speed of 200-400 r / min, continuing constant temperature stirring for 2-3 hours, completing the wall material coagulation coating the core material, and obtaining a microcapsule suspension.

[0059] In this application, chitosan and nanocellulose are selected as the main raw materials. Chitosan has good biocompatibility and degradability, while nanocellulose has a high specific surface area and good mechanical properties. Nanocellulose can enhance the shear resistance of composite wall materials, and when applied to pulp molding production, it can improve the mechanical properties of pulp molding. This application uses degradable raw materials to ensure the environmental friendliness of the production process and the final product, in line with the needs of the ESG (environment, society and governance) strategy. Increasing the content of nanocellulose can enhance compatibility with pulp, improve the sustained-release performance of microcapsules, and enable the mint aroma to be released more persistently, thereby achieving the regulation of sustained-release performance.

[0060] In one embodiment, in step 4), the crosslinking solution is a 1-2.0% w / v calcium lactate solution (1-2 g of calcium lactate is dissolved in 100 ml of water to obtain a 1-2.0% w / v calcium lactate solution). Preferably, the crosslinking solution is a 1.5% w / v calcium lactate solution.

[0061] In step 4), the microcapsule suspension is immersed in a crosslinking solution, stirred, filtered, washed with water, and dried to obtain a microcapsule powder. Specifically, the process includes: using room-temperature ionic curing: immersing the microcapsule suspension in the crosslinking solution and stirring at room temperature (20-30°C) at 300-500 rpm for 30-60 minutes. Further post-processing is then performed, including filtering the crosslinking solution-treated microcapsule suspension, washing with water (to remove residual acid), and drying in an air flow at 30-50°C to obtain a microcapsule powder (moisture content <5%). Filtration and washing effectively remove residual acetic acid (residual amount ≤ 50 ppm) from the dissolved chitosan, preventing oxidation of the essential oil in an acidic environment and enhancing safety.

[0062] In this application, step 4) adopts room temperature ion curing: the microcapsule suspension is immersed in the cross-linking liquid, stirred at room temperature for a certain period of time to allow Ca2 +Cross-linking with the carboxyl group of gum arabic. In the present application, a natural calcium source (such as calcium lactate, which can also be replaced by shell powder extract) is used for room temperature cross-linking to replace the chemical curing agent.

[0063] In the present application, from step 1) to step 4), the temperature used in the entire microcapsule powder preparation process does not exceed 50°C, which can effectively avoid the loss of heat-sensitive components. Compared with the traditional spray drying method for preparing microcapsules (the temperature is 150-200°C, and the high temperature causes heat-sensitive essential oils (such as mint) to volatilize ≥20%, with a low retention rate and loss of some active ingredients), the effect is better. In addition, in the method of the present application, the solvent system used is all water-based (chitosan and gum arabic are soluble in water), without solvent residue, there is no risk of pollution, and the wall material used is natural wall material, which is environmentally friendly. Traditional spray drying methods often require organic solvents (such as ethanol to disperse wall materials), which will cause the risk of solvent residue pollution and will cause solvent volatilization or particle pollution. In addition, in the process method of the present application, pipelined continuous reaction production can be used, which is high in efficiency and high in production capacity; while the traditional spray drying method requires batch spraying, which is limited in production capacity. In addition, the process method of the present application is applicable to a wide range of wall materials, for example, water-soluble materials such as natural polysaccharides and proteins can also be used. The traditional spray drying method has a narrow range of wall materials and requires high-temperature resistant wall materials, such as gelatin or synthetic polymers. Gelatin has poor water resistance. When it is used as a wall material, the microcapsules will be exposed to a humid environment for a long time, which may cause the wall material to swell or degrade, accelerate the release of the core material, and easily fall off.

[0064] In one embodiment, the preparation method of the present application further comprises: step 5) anti-sticking treatment: spraying 0.3% w / w silicon dioxide on the surface of the microcapsule powder to obtain microcapsules;

[0065] The particle size of silicon dioxide is 10 to 20 nm.

[0066] For example, the silicon dioxide may be food grade silicon dioxide. Here, 0.3% w / w silicon dioxide means that 0.3 g of silicon dioxide is added to every 100 g of microcapsule powder.

[0067] In the anti-sticking treatment of the present application, the introduction of silica can enhance the compressive strength of pulp molding and improve the mechanical properties.

[0068] In the second aspect, the present application provides a microcapsule, which is prepared by the preparation method in any of the above-mentioned embodiments. The present application extracts essential oils through supercritical fluid, and uses essential oils as core materials and porous starch as a carrier to obtain an essential oil-starch core material composite, and chitosan-gum arabic-nanocellulose as a composite wall material for collaborative coating, thereby achieving efficient loading and active protection of essential oils, improving awakening performance and processing resistance, and preparing pulp molding slow-release fragrance microcapsules through complex coacervation embedding and room temperature ion curing, which are suitable for large-scale environmentally friendly production of pulp molding, and have both high environmental protection and long-lasting fragrance release. Taking mint flavor as an example, when the flavor raw materials are made into microcapsules through a series of treatments, the volatility of the mint aroma is effectively suppressed, so that the aroma is slowly released, achieving the purpose of lasting fragrance, and significantly improving the user experience value of consumer electronic products.

[0069] In a third aspect, the present application also provides a pulp molding comprising the aforementioned microcapsules. Furthermore, the present application also provides a method for preparing the pulp molding, comprising: adding the microcapsules to a pulp slurry at a ratio of 1.5 to 4 wt% of the dry weight of the pulp slurry, forming the pulp slurry, cold pressing, hot pressing, shaping, and drying the pulp molding.

[0070] In the present application, microcapsules are added to the pulp slurry at a certain percentage so that the microcapsules can be fully mixed with the pulp fibers. The microcapsules can be added to the pulp slurry in the form of papermaking fillers so that the microcapsules are completely cross-linked to the pulp molded fibers, thereby improving the problem of easy shedding of the microcapsules and not affecting the surface properties of the pulp molded fibers.

[0071] The preparation of pulp slurry includes: preparing basic slurry for pulp molding, and controlling the concentration of the pulp slurry to about 1wt% through pulping, decomposition and homogenization.

[0072] For example, the microcapsules are added to the pulp slurry at a ratio of 1.5 to 4 wt% of the dry weight of the pulp slurry, and the mixture is stirred for 20 minutes (stirring speed: 1200 rpm).

[0073] For example, the molding process includes: forming a wet embryo from pulp slurry using a vacuum molding method, wherein the vacuum degree required for the vacuum molding method is 500-700 Pa, the air pressure during demolding is 0.15-0.3 MPa, and the moisture content of the wet embryo is 65-75%. Specifically, the process includes forming the pulp slurry into a molded product of a desired shape using the vacuum molding method; the vacuum degree during vacuum suction is 500-700 Pa (preferably 600 Pa), the air pressure during demolding is 0.15-0.3 MPa (preferably 0.2 MPa), and the moisture content of the wet embryo is 65-75%.

[0074] For example, cold pressing, hot pressing and shaping include: cold pressing the wet embryo in a mold to a moisture content of 55-60%, then hot pressing at 0.8-1.2 MPa and a temperature of 120-135°C for 25-35 seconds, and then trimming to obtain a shaped pulp molded semi-finished product. Specifically, the wet embryo is cold pressed in a mold under a certain pressure to a moisture content of 55-60%, then hot pressing at 0.8-1.2 MPa and a temperature of 120-135°C for 25-35 seconds, and then trimming and other shaping processes are completed to obtain a pulp molded semi-finished product.

[0075] For example, drying includes drying the pulp molding semi-finished product at 100-110°C and post-processing it to obtain pulp molding. Specifically, it includes drying the formed pulp molding semi-finished product under pressure at 100-110°C until it is completely dry; and then performing surface treatment and secondary shaping and correction to obtain a pulp molding product with fragrance.

[0076] In this application, the scented pulp molding process utilizes an existing complete set of pulp molding equipment, reducing costs and manufacturing difficulty, and improving product yield. Furthermore, the scented pulp molding process utilizes a green process throughout the entire process, with no organic solvents or chemical curing agents added during the manufacturing process, making it highly environmentally friendly. Scented pulp molding achieves a triple breakthrough in environmental friendliness, functionality, and economy, making it particularly suitable for high-end packaging applications such as medical and electronics, and an ideal alternative to traditional plastic packaging. Its technological scalability also supports the addition of functional factors such as caffeine and essential oils, forming a series of product matrices.

[0077] The present application is further described in detail below with reference to specific embodiments:

[0078] Unless otherwise specified, the raw materials used in this application can be obtained from commercial sources.

[0079] Example 1

[0080] A method for preparing microcapsules, comprising:

[0081] Step 1) core material pretreatment, comprising: Step 1-1): providing a mint flavor raw material, and placing the mint flavor raw material in a supercritical CO2 extraction device, extracting for 3 hours under the conditions of an extraction pressure of 12 MPa, an extraction temperature of 40° C., and a CO2 flow rate of 20 L / h to obtain a mixture consisting of CO2 and crude essential oil;

[0082] Step 1-2): The mixture enters a separator, and CO2 and crude essential oil are separated under a separation pressure of 8 MPa and a separation temperature of 40° C. to obtain pure peppermint essential oil.

[0083] Step 2) Preparation of essential oil-starch core material composite: peppermint essential oil and carboxymethyl porous starch were mixed at a mass ratio of 1:0.88, and adsorbed at a temperature of 45° C. for 24 h to obtain the essential oil-starch core material composite.

[0084] Step 3) wall material complex coagulation, comprising: step 3-1): dissolving chitosan and nanocellulose in water to obtain a chitosan aqueous solution and a nanocellulose aqueous solution, respectively; then dissolving the chitosan aqueous solution and the nanocellulose aqueous solution in acetic acid and ultrasonically dispersing them for 10 minutes to obtain a chitosan-nanocellulose solution; wherein, before adding the acetic acid, the nanocellulose aqueous solution is ultrasonically dispersed for 10 minutes; and the mass ratio of chitosan, nanocellulose, and acetic acid is 1.5:0.8:1.05;

[0085] Step 3-2): dissolving gum arabic in water to obtain an aqueous solution of gum arabic;

[0086] Step 3-3): dispersing the essential oil-starch core material complex in the chitosan-nanocellulose solution, adding the solution to the gum arabic aqueous solution, and stirring at a speed of 10,000 r / min for 20 minutes to obtain an emulsion; using an acetic acid solution (dilute acetic acid) to gradually adjust the pH value of the emulsion system to 4.0 to promote the complex coagulation of the wall material layer by layer, and then reducing the speed to a low speed of 300 r / min, and stirring at a constant temperature for 2 hours to complete the complex coagulation of the wall material to coat the core material, thereby obtaining a microcapsule suspension;

[0087] Among them, based on the total mass of the emulsion as 100%, the solid content in the chitosan-nanocellulose solution accounts for 2.3wt% (i.e., chitosan accounts for 1.5wt% and nanocellulose accounts for 0.8wt%), the solid content in the gum arabic aqueous solution accounts for 2.5wt%, the essential oil-starch core material composite accounts for 4.8wt%, and the remainder is solvent.

[0088] Step 4) Room-temperature ionic curing: The microcapsule suspension was immersed in a 1.5 w / v calcium lactate solution and stirred at 25° C. and 400 rpm for 60 min. The suspension was then filtered, washed with water, and dried in an air stream at 40° C. to obtain a microcapsule powder with a moisture content of less than 5%.

[0089] Step 5) Anti-sticking treatment: Spray food-grade silicon dioxide (particle size 10-20 nm) on the surface of the microcapsule powder to obtain mint-flavored microcapsules; wherein the mass ratio of food-grade silicon dioxide to microcapsule powder is 0.3:100.

[0090] In this Example 1, mint-flavored microcapsules were prepared.

[0091] Example 2

[0092] A method for preparing pulp molding, comprising:

[0093] Step 1): Prepare the basic pulp for pulp molding, and control the pulp concentration to 1% by crushing, decomposing and homogenizing;

[0094] Step 2): adding the mint-flavored microcapsules prepared in Example 1 to the pulp slurry at a ratio of 3 wt% of the dry weight of the pulp slurry, and stirring the mixture at a speed of 1200 rpm for 20 minutes;

[0095] Step 3): Forming process: using vacuum forming method to form pulp slurry into wet embryo, wherein the vacuum degree required for vacuum forming method is 600Pa, the air pressure during demoulding is 0.2MPa, and the moisture content of wet embryo is 70%;

[0096] Step 4): cold pressing, hot pressing and shaping include: cold pressing the wet embryo in a mold to a moisture content of 60%, then hot pressing in the mold at a pressure of 1.0 MPa and a temperature of 130° C. for 30 seconds, and then trimming to obtain a shaped pulp molding semi-finished product;

[0097] Step 5): Drying includes: drying the pulp molded semi-finished product at 100° C. until it is absolutely dry; and then performing surface treatment and secondary shaping and correction to obtain a pulp molded product with a mint aroma.

[0098] Example 2: A pulp molded product with a mint aroma was prepared.

[0099] Example 3

[0100] The preparation of Example 3 is substantially the same as that of Example 2, except that in step 2), mint-flavored microcapsules are added to the pulp slurry at a ratio of 1.5 wt % based on the dry weight of the pulp slurry.

[0101] Example 3: A pulp molded product with a mint aroma was prepared.

[0102] Example 4

[0103] The preparation of Example 4 is substantially the same as that of Example 2, except that in step 2), mint-flavored microcapsules are added to the pulp slurry at a ratio of 2.0 wt % based on the dry weight of the pulp slurry.

[0104] Example 4: A pulp molded product with a mint aroma was prepared.

[0105] Comparative Example 1

[0106] The preparation of this comparative example 1 is substantially the same as that of example 2, except that in step 2), mint-flavored microcapsules are added to the pulp slurry at a ratio of 0 wt % based on the dry weight of the pulp slurry.

[0107] Comparative Example 1 prepared a pulp molded product.

[0108] Comparative Example 2

[0109] The preparation of Comparative Example 2 is substantially the same as that of Example 2, except that in step 2), mint-flavored microcapsules are added to the pulp slurry at a ratio of 1.0 wt% based on the dry weight of the pulp slurry.

[0110] Comparative Example 2 prepared a pulp molded product with a mint flavor.

[0111] Comparative Example 3

[0112] The preparation of this comparative example 3 is substantially the same as that of example 2, except that in step 2), mint-flavored microcapsules are added to the pulp slurry at a ratio of 6.0 wt % based on the dry weight of the pulp slurry.

[0113] Comparative Example 3 prepared a pulp molded product with a mint flavor.

[0114] Comparative Example 4

[0115] The preparation of this comparative example 4 is substantially the same as that of example 2, except that in step 2), mint-flavored microcapsules are added to the pulp slurry at a ratio of 9.0 wt % based on the dry weight of the pulp slurry.

[0116] Comparative Example 4 prepared a pulp molded product with a mint flavor.

[0117] Performance experimental test:

[0118] 1: Test of sustained-release performance of microcapsules in pulp molding:

[0119] 1) Experimental materials and methods

[0120] 1. Experimental Materials:

[0121] Pulp moldings prepared in Examples 2-4 and Comparative Examples 1-4, respectively.

[0122] 2. Experimental methods:

[0123] 1) Heat treatment: The pulp molded samples prepared in Examples 2-4 and Comparative Examples 1-4 were placed in a constant temperature box at 130° C. for 2 hours to simulate the actual use environment.

[0124] 2) Aroma evaluation: The aroma intensity was evaluated using an artificial olfactory method with a scoring scale of 0-10.

[0125] II) Experimental Data and Analysis

[0126] 1. Aroma retention rate and aroma intensity score, as shown in Table 1 below:

[0127] Table 1 Aroma retention rate and aroma intensity scoring results

[0128]

[0129]

[0130] Note: The retention rate is calculated by constant temperature weighing method.

[0131] 1. Principle: Pulp molded samples are heated at a constant temperature (e.g., 130°C) and their mass change is measured by weighing to calculate the retention rate.

[0132] 2. Steps:

[0133] 1): Heat the pulp molded sample to the target temperature in a constant temperature box.

[0134] 2): Record the mass change of the sample before and after heating.

[0135] 3): Calculate the amount of essential oil released by the mass change.

[0136] 3. Retention rate calculation formula

[0137] Retention rate = (treated pulp molded sample / original pulp molded sample) × 100%

[0138] illustrate:

[0139] 1. As can be seen from Table 1, with the increase of the amount of microcapsules added, the aroma retention rate and aroma intensity score both showed an upward trend, but the increase rate gradually decreased, indicating that there is an optimal range of microcapsule addition amount.

[0140] 2. Pulp molding containing 3% microcapsule addition achieved the best balance between aroma retention and aroma intensity.

[0141] 3. Although the aroma intensity of the pulp mold containing 9% microcapsule addition is still high, the retention rate is slightly reduced, which may be due to excessive addition causing microcapsule rupture or excessive release of essential oil.

[0142] 2: Mechanical properties test of pulp molding containing microcapsules:

[0143] 1) Experimental design and methods

[0144] 1. Experimental Materials

[0145] Pulp molding base pulp: corrugated pulp.

[0146] The experimental group included 10 pulp molded samples containing mint essential oil microcapsules (ie, the pulp molded sample with mint fragrance prepared in Example 2).

[0147] 10 control groups: pulp molding samples without any microcapsules added (ie, pulp molding prepared in Comparative Example 1).

[0148] 2. Experimental Results and Analysis

[0149] 2.1 Tensile strength performance test

[0150] Test method: GB / T 12914-2018. Samples were cut (sampling position was the same, 15 mm × 130 mm specimens were prepared, and the clamping distance was 100 mm). The samples were stretched at a speed of 20 mm / min until they broke, and the maximum load and elongation at break were recorded.

[0151] The test results are shown in Table 2 below:

[0152] Table 2 Tensile strength, elongation at break and tensile strength results of the experimental group and the control group

[0153] Test items Control group (no added group) Experimental group (additional group) Improvement Tensile strength (kN / m) 4.3±0.3 5.2±0.4kN / m +20.9％ Elongation at break (%) 6.6±0.5 5.8±0.6 -12.1％ Tensile strength (Mpa) 5.72±0.45 8.0±0.6MPa +40％

[0154] 3. Conclusion

[0155] It can be seen from the experimental results in Table 2 above that the addition of microcapsules to pulp molding does not reduce the mechanical properties of the paper molding. On the contrary, the mechanical properties of tensile strength and tensile strength are significantly improved.

[0156] It should be understood that the various forms of the processes shown above can be used to reorder, add, or delete steps. For example, the steps described in this disclosure can be performed in parallel, sequentially, or in a different order, as long as the desired results of the technical solutions of this disclosure can be achieved. This is not a limitation herein.

[0157] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features being referred to. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one such feature. Throughout the present disclosure, "plurality" means two or more, unless otherwise specifically defined.

[0158] The above description is merely a specific embodiment of the present disclosure, but the scope of protection of the present disclosure is not limited thereto. Any changes or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in this disclosure should be included in the scope of protection of the present disclosure. Therefore, the scope of protection of the present disclosure should be based on the scope of protection of the claims.

Claims

1. A method for preparing microcapsules, characterized in that: include: Providing fragrance raw materials, and extracting and separating the fragrance raw materials using supercritical fluid to obtain essential oils; mixing the essential oil with porous starch to obtain an essential oil-starch core material composite; Dispersing the essential oil-starch core material complex in a composite wall material solution composed of chitosan, gum arabic and nanocellulose, stirring to obtain an emulsion; adjusting the pH of the emulsion to 4.0-4.2, stirring to obtain a microcapsule suspension; The microcapsule suspension is immersed in a cross-linking liquid, stirred, filtered, washed with water, and dried to obtain microcapsule powder.

2. The preparation method according to claim 1, wherein: The method of extracting and separating the fragrance raw materials using supercritical fluid to obtain essential oils comprises: The fragrance raw material is placed in a supercritical CO2 extraction device, and extracted for 2 to 3 hours under the conditions of a pressure of 12 to 15 MPa, a temperature of 35 to 45° C., and a CO2 flow rate of 15 to 25 L / h to obtain a mixture consisting of CO2 and crude essential oil; The mixture is subjected to the conditions of a pressure of 6 to 8 MPa and a temperature of 40 to 50° C. to separate CO 2 and crude essential oil to obtain the pure essential oil.

3. The preparation method according to claim 1, wherein: The essential oil is mixed with porous starch to obtain an essential oil-starch core material composite comprising: The essential oil and porous starch are mixed in a mass ratio of 1:0.8-1.1, and adsorbed at 40-50° C. for 20-24 hours to obtain the essential oil-starch core material composite; The porous starch is carboxymethyl porous starch.

4. The preparation method according to claim 1, wherein: The essential oil-starch core material complex is dispersed in a composite wall material solution composed of chitosan, gum arabic and nanocellulose, and stirred to obtain an emulsion comprising: Dissolving chitosan and nanocellulose in water to obtain a chitosan aqueous solution and a nanocellulose aqueous solution, respectively, and then dissolving the chitosan aqueous solution and the nanocellulose aqueous solution in acetic acid and ultrasonically dispersing them to obtain a chitosan-nanocellulose solution; dissolving gum arabic in water to obtain an arabic gum aqueous solution; Dispersing the essential oil-starch core material complex in the chitosan-nanocellulose solution, adding the mixture to the gum arabic aqueous solution, and stirring to obtain the emulsion; Among them, based on the mass of the emulsion as 100wt%, the solid content of the chitosan-nanocellulose solution accounts for 2.3wt%, the solid content of the gum arabic aqueous solution accounts for 2.5wt%, the essential oil-starch core material composite accounts for 4.8wt%, and the balance is solvent.

5. The preparation method according to claim 1, wherein: The cross-linking solution is a calcium lactate solution with a concentration of 1-2.0% w / v; The microcapsule powder is dried by air flow drying at 30-50° C. to make the moisture content of the microcapsule powder less than 5%.

6. The preparation method according to any one of claims 1 to 5, characterized in that: Also includes: Spraying silicon dioxide on the surface of the microcapsule powder to obtain microcapsules; wherein the mass ratio of the silicon dioxide to the microcapsule powder is 0.3:100; The particle size of the silicon dioxide is 10 to 20 nm.

7. A microcapsule, characterized in that: The invention is prepared by the preparation method according to any one of claims 1 to 6.

8. A pulp molding, characterized in that: The invention comprises the microcapsules prepared by the preparation method according to any one of claims 1 to 6, or the microcapsules according to claim 7.

9. A method for preparing pulp molding, characterized in that: The microcapsules according to claim 8 are added to the pulp slurry at a ratio of 1.5 to 4 wt% of the dry weight of the pulp slurry, and the pulp molding is obtained by forming, cold pressing, hot pressing and shaping, and drying.

10. The preparation method according to claim 9, characterized in that: The forming comprises: using a vacuum forming method to form a pulp slurry into a wet embryo, wherein the vacuum degree required for the vacuum forming method is 500-700 Pa, the air pressure during demoulding is 0.15-0.3 MPa, and the moisture content of the wet embryo is 65-75%; The cold pressing, hot pressing and shaping include: cold pressing the wet embryo in a mold to a moisture content of 55-60%, and then hot pressing at a pressure of 0.8-1.2 MPa and a temperature of 120-135° C. for 25-35 seconds to obtain a formed pulp molding semi-finished product; The drying comprises: drying the pulp molding semi-finished product at a temperature of 100-110° C. to obtain the pulp molding.

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