A bamboo fiber high-rigidity water-resistant and oil-resistant steamer paper and a preparation method thereof

Abstract

The application provides a bamboo fiber high-stiffness water-resistant and oil-resistant steamer paper and a preparation method thereof, and relates to the technical field of functional paper preparation. The preparation method comprises the following steps: S1, mixing a natural color bamboo pulp with a pulp internal sizing agent, wherein the beating degree of the bamboo pulp is 28-40°SR, and then papermaking to obtain a base paper, wherein the pulp internal sizing agent is composed of carboxymethylated nanocellulose, cationic starch and alkyl alkene ketone dimer emulsion; S2, uniformly applying a coating liquid to the surface of the base paper by using a metering rod coating method, and controlling the wet coating amount to be 10-15 g / m 2 2; after the coating is completed, drying and curing are performed, and thus the steamer paper is obtained, wherein the coating liquid is obtained by mixing amino silicon oil, lauryl gallate epoxy and hydrophobic micro-nano bamboo powder. By using the preparation method, the steamer paper with the properties of water resistance, oil resistance, cooking resistance, anti-sticking and high temperature resistance can be prepared.

Description

Technical Field

[0001] This invention relates to the field of functional paper preparation technology, and in particular to a bamboo fiber high stiffness water-resistant and oil-resistant steamer paper and its preparation method. Background Technology

[0002] Steamer paper is suitable for various foods that require steaming. It is mainly placed between the steamer and the food to isolate and prevent sticking, clean the substrate, and optimize the appearance of steamed products. It is now widely used in many fields such as household steaming, catering, and industrial food processing. Because the steaming process takes place in a hot and humid environment of saturated water vapor at 100°C, the long-term high temperature and high humidity conditions place stringent requirements on the comprehensive performance of steamer paper. The paper must have excellent high temperature resistance and stability, moderate air permeability and drainage, food-grade safety characteristics, and surface anti-stick properties to avoid many problems such as damage from high temperature and moisture, food sticking to the bottom, water accumulation and mushyness during steaming, and the release of harmful substances, thus ensuring the quality and safety of steamed food.

[0003] In view of this, it is necessary to design an improved bamboo fiber high stiffness water-resistant and oil-proof steamer paper and its preparation method to solve the above problems. Summary of the Invention

[0004] The purpose of this invention is to provide a bamboo fiber high stiffness water-resistant and oil-proof steamer paper and its preparation method.

[0005] To achieve the above-mentioned objectives, in a first aspect, the present invention provides a method for preparing bamboo fiber high-stiffness, water-resistant, and oil-resistant steamer paper, comprising the following steps:

[0006] S1. After mixing unbleached bamboo pulp with a freeness of 28-40°SR with an internal sizing agent, papermaking is carried out to obtain base paper. The internal sizing agent is composed of carboxymethylated nanocellulose, cationic starch and alkyl ketene dimer emulsion.

[0007] S2. Apply the coating liquid evenly to the surface of the base paper obtained in step S1 using a metering rod coating method, controlling the wet coating amount to be 10-15 g / m². 2 After coating, the paper is dried and cured to obtain the steamer paper. The coating liquid is a mixture of amino silicone oil, gallic acid lauryl ester epoxy, and hydrophobic micro-nano bamboo powder.

[0008] Preferably, in step S2, the amount of hydrophobic micro-nano bamboo powder added is 5-10% of the mass of amino silicone oil; the viscosity of amino silicone oil is 1000 mPa·s, the ammonia value is 0.15 eq / 100g, and the epoxy value of gallic acid lauryl ester epoxy is 0.3 eq / 100g.

[0009] Preferably, in step S1, the mass ratio of carboxymethylated nanocellulose, cationic starch, and AKD emulsion is 1:1:(3-5), the solid content of AKD emulsion is 20-25%, the pH value is 4-5, the particle size is 1.5-2.0μm, and the degree of substitution of carboxymethylated nanocellulose is DS=0.1-0.25 and D50=10-50μm.

[0010] Preferably, in step S1, the preparation method of the hydrophobic micro-nano bamboo powder is as follows: 100-mesh bamboo powder is placed in a 1-5% sodium hydroxide solution, shaken at 70-90℃ for 1-3 h, and washed until neutral to prepare an aqueous suspension with a solid content of 1-3%. The suspension is then subjected to high-pressure homogenization to obtain a micro-nano bamboo powder suspension with a D50 of 1.5-2.5 μm. The suspension is dried at 100℃ for 1-2 h to obtain micro-nano bamboo powder. Anhydrous ethanol, deionized water, and phenyltrimethoxysilane are mixed evenly to prepare an alcohol-water mixture. Ammonia water is added dropwise to adjust the pH of the mixture to 8.5. The micro-nano bamboo powder is then added, and the mixture is magnetically stirred at 25℃ for 2 h to obtain the hydrophobic micro-nano bamboo powder.

[0011] Preferably, the volume ratio of anhydrous ethanol to deionized water is 4:1, and the amount of phenyltrimethoxysilane used is 10% of the mass of the micronized bamboo powder.

[0012] Preferably, in step S2, the drying and curing temperature is 110-120℃ and the time is 3-5h; in step S1, the online concentration of the unbleached bamboo pulp is 0.8-1.2%.

[0013] Preferably, in step S2, the process of coating the coating liquid using the metering rod coating method is carried out according to the following steps: the metering rod is installed on the automatic coating rack, the base paper is fixed on the coating platform, the coating liquid is poured at one end of the coating platform, the speed ratio of the metering rod rotation speed to the paper machine speed is controlled to be 1.2:1 to 2.5:1, and the coating is carried out at a uniform speed of 30-60 mm / s so that the coating liquid evenly covers the surface of the base paper; the metering rod includes a core rod and a winding wire wound on the surface of the core rod, the outer diameter of the core rod is 20-25 mm, and the diameter of the winding wire is 0.15-0.20 mm.

[0014] In a second aspect, the present invention provides a steamer paper, the steamer paper comprising:

[0015] The base paper, whose raw materials include unbleached bamboo pulp;

[0016] The functional coating, which is tightly bonded to the base paper, is obtained by mixing amino silicone oil, gallic acid lauryl ester epoxy, and hydrophobic micro-nano bamboo powder and then drying and curing it.

[0017] Preferably, the steamer paper has the following properties: basis weight of 38-45 g / m³. 2The air permeability is 100-180s / 100mL, the transverse tear strength is ≥140mN, the longitudinal breaking length is ≥7.0 km, the longitudinal wet breaking length is ≥0.87km, the oil resistance is ≥5, and the water absorption is ≤21g / m³. 2 The surface smoothness is ≥50s, and the micro-roughness PPS of the coated surface is 1.0-2.0μm. The dry bending stiffness is ≥100 mN·m, and the wet bending stiffness after steam treatment at 100℃ for 10-30min is ≥80mN·m.

[0018] Thirdly, the present invention provides an application of steamer paper in food steaming.

[0019] The beneficial effects of this invention are:

[0020] 1. The method for preparing bamboo fiber high stiffness water-resistant and oil-resistant steamer paper provided by the present invention enhances the paper strength by adding carboxymethylated nanocellulose to the sizing agent in the pulp. At the same time, it can fill the large pores between some paper fibers and improve the uniformity of the paper's pore structure. Secondly, carboxymethylated nanocellulose can also work with hydrophobic micro-nano bamboo powder in the coating liquid to regulate the paper's air permeability, ensuring that water vapor molecules can pass freely during the steamer paper's food steaming process. However, because the functional coating has water and oil resistance, liquid water cannot wet the steamer paper, making it more suitable for the humid and hot environment of 100°C saturated water vapor in the steamer paper.

[0021] 2. The preparation method provided by this invention introduces an appropriate amount of hydrophobic micro-nano bamboo powder into the functional coating. Its particle structure, together with bamboo fiber, forms a micro-uneven structure on the paper surface, giving the paper continuous waterproof and oil-proof properties. Since this structure is at the micro level, the paper macroscopically appears as a smooth surface. The formation of the above-mentioned micro-uneven structure can reduce the contact area between the steamer paper and the steamer and food, which is conducive to water vapor passing freely through the food, while liquid water cannot wet it, making it easy to demold the food. By first mixing amino silicone oil and gallic acid lauryl ester epoxy and then curing and crosslinking them, the reaction process of the two can construct a three-dimensional network structure. The appearance of this structure can not only improve the coating strength, but also improve the bonding strength between the coating and the base paper. At the same time, it can also encapsulate the hydrophobic micro-nano bamboo powder, ensuring that the hydrophobic micro-nano bamboo powder is evenly and stably distributed in the coating.

[0022] 3. The preparation method provided by the present invention can produce steamer paper that is waterproof, oil-proof, resistant to boiling, non-stick, and resistant to high temperature by precisely controlling process parameters such as the amount of hydrophobic micro-nano bamboo powder added and the amount of coating liquid. Detailed Implementation

[0023] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be described in detail below with reference to specific embodiments.

[0024] It should also be noted that, in order to avoid obscuring the present invention with unnecessary details, only the structures and / or processing steps closely related to the present invention are shown in the text, while other details that are not closely related to the present invention are omitted.

[0025] Additionally, it should be noted that the terms “comprising,” “including,” or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0026] This invention provides a method for preparing bamboo fiber high stiffness, water-resistant and oil-proof steamer paper, comprising the following steps:

[0027] S1. Mix unbleached bamboo pulp with a beating degree of 28-40°SR with an in-pulp sizing agent, and then make paper to obtain base paper.

[0028] S2. Apply the coating liquid evenly to the surface of the base paper obtained in step S1 using a metering rod coating method, controlling the wet coating amount to be 10-15 g / m². 2 After coating, the paper is dried and cured to form a functional coating on the surface of the base paper, thus producing steamer paper.

[0029] In some embodiments, in step S1, the sizing agent is composed of carboxymethylated nanocellulose, cationic starch, and an alkyl ketene dimer (AKD) emulsion. The addition rule for the sizing agent is 100-180g per 1kg of unbleached bamboo pulp. The AKD emulsion has a solid content of 20-25%, a pH of 4-5, and a particle size of 1.5-2.0μm. The carboxymethylated nanocellulose is a solid powder filler with a carboxymethyl substitution degree DS=0.1-0.25, and its solid particle size D50 is measured to be 10-50μm using a dry laser particle size analyzer. The mass ratio of carboxymethylated nanocellulose, cationic starch, and AKD emulsion is 1:1:(3-5). It should be noted that the carboxymethylated nanocellulose can be prepared using a conventional alkalization-etherification-high pressure homogenization process, the specific steps of which are well known to those skilled in the art, and therefore are not described in detail here.

[0030] In the above technical solution, by adding carboxymethylated nanocellulose, not only can it enhance the strength of paper, but its nano-size effect can also fill the large pores between fibers after papermaking, improving the uniformity of the paper's pore structure. Secondly, carboxymethylated nanofibers can also bridge between AKD molecules to resist the weakening of paper's wet strength under 100°C steam. At the same time, after the -COO- groups in carboxymethylated nanocellulose absorb moisture and swell, they can construct a three-dimensional cross-linked water-locking support network inside the paper through the hydration of ionic groups. This dynamic network can still provide skeletal support for the paper in a humid state, ensuring that the steamer paper can still maintain a high wet bending stiffness after being treated in a 100°C high-humidity steam environment.

[0031] In some embodiments, in step S1, the online concentration of the unbleached bamboo pulp is 0.8-1.2% (i.e., the diluted concentration after pulping treatment). The preparation method is as follows: bamboo chips are added to the treatment solution and steamed at 160-170℃ for 2-2.5 h. After steaming, the pulp is repeatedly washed with hot water at 70-85℃ until the wash water is nearly neutral. Then, the pulp is screened to remove un-distilled chips and impurities, thus completing the decomposition treatment of bamboo chips. The wet pulp is dehydrated and diluted with water to a pulping concentration of 3.5-4.5%. The wet pulp is pulped using pulping equipment, and the pulping degree is controlled at 28-40°SR and the wet weight is 6-9g to obtain unbleached bamboo pulp. It can be diluted as needed before use. The treatment solution is obtained by dissolving sodium hydroxide and sodium sulfide in water. The mass fraction of sodium hydroxide in the treatment solution is 14-17%, and the mass fraction of sodium sulfide is 3-5%. During the treatment process, the treatment solution is used to loosen the bamboo strips. As long as this purpose is achieved, the amount used is not strictly limited. In the above treatment steps, since no bleaching or fluorescent whitening agent is added, the resulting unbleached bamboo pulp is light yellowish-brown.

[0032] In some embodiments, in step S2, the coating solution is a mixture of amino silicone oil, gallic acid lauryl ester epoxy, and hydrophobic micro-nano bamboo powder. The amount of hydrophobic micro-nano bamboo powder added is 5-10% of the mass of amino silicone oil. The viscosity of amino silicone oil is 1000 mPa·s, and its ammonia value is 0.15 eq / 100g. The epoxy value of gallic acid lauryl ester epoxy is 0.3 eq / 100g. The amount of amino silicone oil and gallic acid lauryl ester epoxy added can be determined according to their chemical reaction equivalence, ensuring a slight excess of epoxy groups in the system so that the amino groups fully participate in the crosslinking reaction, thereby increasing the crosslinking density of the coating. It should be noted that gallic acid lauryl ester epoxy is an existing material, which is prepared by a phenolic hydroxyl glycidyl etherification ring-closing reaction of gallic acid lauryl ester and epichlorohydrin as raw materials.

[0033] In the above technical solution, by introducing an appropriate amount of hydrophobic micro-nano bamboo powder into the coating liquid, it can be used as a functional filler. Its rigid particle structure, together with the natural texture of bamboo pulp fibers obtained under low beating degree, forms a micro-uneven structure on the paper surface, ensuring a smooth paper feel and imparting a certain degree of micro-surface roughness, while ensuring the continuity of the paper surface's waterproof and oil-proof properties. Furthermore, the formation of this micro-uneven structure allows for an incomplete contact interface between the paper and food during subsequent use, significantly reducing the actual contact area between the food and paper, facilitating food demolding from the paper. In the subsequent steaming process, it facilitates steam permeation through the paper, accelerating the food's cooking rate. However, if the amount of hydrophobic micro-nano bamboo powder added is too small, the micro-uneven structure cannot be effectively formed, making it difficult to fully utilize its function; while if the amount added is too large, not only is it difficult to achieve uniform dispersion of the hydrophobic micro-nano bamboo powder in the coating system, but the granular hydrophobic micro-nano bamboo powder also easily detaches from the paper after it is made, affecting the paper's performance.

[0034] Furthermore, by first uniformly dispersing hydrophobic micro-nano bamboo powder in amino silicone oil and gallic acid lauryl ester epoxy, the amino silicone oil and gallic acid lauryl ester epoxy undergo a cross-linking reaction during the subsequent drying and curing process. The three-dimensional cross-linking network constructed during the reaction process can encapsulate the hydrophobic micro-nano bamboo powder within it, ensuring that the hydrophobic micro-nano bamboo powder is uniformly and stably distributed in the coating system.

[0035] Furthermore, the preparation method of hydrophobic micro / nano bamboo powder is as follows: 100-mesh bamboo powder is placed in a 1-5% sodium hydroxide solution and shaken at 70-90℃ for 1-3 minutes. After washing until neutral, a water suspension with a solid content of 1-3% was prepared. High-pressure homogenization was then performed to obtain a micro-nano bamboo powder suspension with an average particle size (D50) of 1.5-2.5 μm. The suspension was dried at 100℃ for 1-2 hours to obtain micro-nano bamboo powder. Anhydrous ethanol, deionized water, and phenyltrimethoxysilane were mixed evenly to prepare an alcohol-water mixture. Ammonia was added dropwise to adjust the pH of the mixture to 8.5. The micro-nano bamboo powder was then added, and the mixture was magnetically stirred at room temperature (25℃) for 2 hours. Utilizing the high specific surface area adsorption effect at the micro-nano scale, the hydrolysis products of phenyltrimethoxysilane underwent a condensation reaction on the bamboo powder surface, constructing a dense hydrophobic network with Si-O-Si as the main chain and phenyl groups facing outwards. After stirring, the product was washed 3-5 times with anhydrous ethanol to remove excess unreacted adsorbents. The mixture was then dried at 105℃ for 5 hours to obtain hydrophobic micro-nano bamboo powder. The volume ratio of anhydrous ethanol to deionized water is 4:1, and the amount of phenyltrimethoxysilane used is 10% of the mass of the micronized bamboo powder.

[0036] In some embodiments, in step S2, the process of coating the coating liquid using the metering rod coating method is performed as follows: The metering rod is installed on an automatic coating rack, the base paper is fixed on the coating platform, an appropriate amount of coating liquid is poured onto one end, and the speed ratio of the metering rod rotation speed to the paper machine speed is controlled to be 1.2:1 to 2.5:1, coating at a uniform speed of 30-60 mm / s to ensure the coating liquid evenly covers the surface of the base paper. The metering rod includes a core rod and filaments wound around its surface. The outer diameter of the core rod is 20-25 mm, and the diameter of the filaments is 0.15-0.20 mm. By using the metering rod coating method to prepare the coating, not only can the coating amount be precisely controlled, but the microscopic uniformity of the coating can also be ensured. It should be noted that the device used in the above coating process is a conventional metering rod coating machine in the art, and its specific mechanical structure and working principle are well known to those skilled in the art, and therefore will not be described in detail here.

[0037] In some embodiments, in step S2, the drying and curing temperature is 110-120°C and the time is 3-5 hours.

[0038] The steamer paper prepared by the method proposed in this invention has the following properties: basis weight 38-45 g / m². 2 Air permeability 100-180s / 100mL, transverse tear strength ≥140mN, longitudinal breaking length ≥7.0 km, longitudinal wet breaking length ≥0.87km, oil resistance (kit) ≥5, water absorption ≤21g / m³ 2 (Cobb method), smoothness ≥50s, and micro-roughness PPS of the non-stick surface 1.0-2.0μm, dry bending stiffness ≥100 mN·m (tested according to GB / T 22364, after equilibration at 23℃ and 50%RH for 24h); after steam treatment at 100℃ for 10-30min, the wet bending stiffness of the paper ≥80 mN·m (tested according to GB / T 22364). High smoothness ensures close contact between the paper and the steamer and the food, avoiding excessive steam leakage and heat loss, while the specific micro-roughness can form micro-air gaps at the contact interface between the paper and the food, blocking the continuity of the water film, thereby achieving physical non-sticking. This not only avoids the food safety risks caused by the migration and peeling of the coating under high temperature and high humidity, but also significantly improves the high temperature resistance and cooking resistance of the paper.

[0039] The following specific embodiments further illustrate the bamboo fiber high stiffness, water-resistant, and oil-proof steamer paper proposed in this invention and its preparation method:

[0040] Example 1

[0041] This embodiment provides a method for preparing bamboo fiber high stiffness, water-resistant and oil-proof steamer paper, including the following steps:

[0042] S1. Add bamboo strips to the treatment solution and steam at 160℃ for 2.5 hours. After steaming, wash the pulp repeatedly with 75℃ hot water until the wash water is nearly neutral. Then, sieve the pulp to remove unsteamed strips and impurities, thus completing the decomposition treatment of bamboo strips. Dehydrate to obtain wet pulp. Dilute the wet pulp with water to a beating concentration of 3.5%. Use beating equipment to beating the wet pulp, controlling the beating degree to 32°SR and the wet weight to 7g. After beating, dilute to a net concentration of 1.0% for unbleached bamboo pulp.

[0043] The above-mentioned unbleached bamboo pulp is mixed with the pulp sizing agent and then paper is made to obtain the base paper. The treatment solution is obtained by dissolving sodium hydroxide and sodium sulfide in water, with a sodium hydroxide mass fraction of 15% and a sodium sulfide mass fraction of 3%. The pulp sizing agent is obtained by ultrasonically mixing carboxymethylated nanocellulose, cationic starch, and AKD emulsion in a mass ratio of 1:1:4. The AKD emulsion has a solid content of 20-25%, a pH value of 4-5, and a particle size of 1.5-2.0 μm. The carboxymethylated nanocellulose has a degree of substitution DS = 0.1-0.25 and a particle size D50 = 10-50 μm. The pulp sizing agent is added at a rate of 120 g per 1 kg of unbleached bamboo pulp. It should be noted that the ultrasonic treatment is only used for mixing purposes, therefore, the ultrasonic power and time are not limited.

[0044] S2. Install the measuring rod on the automatic coating rack, fix the base paper on the coating platform, pour an appropriate amount of coating liquid at one end, and coat at a uniform speed of 35 mm / s to ensure the coating liquid evenly covers the surface of the base paper. The wet coating amount is 10 g / m². 2 After coating, the paper is dried at 110°C for 4 hours to obtain the steamer paper. The measuring rod includes a core rod and a winding wire wrapped around the surface of the core rod. The outer diameter of the core rod is 20 mm, and the diameter of the winding wire is 0.18 mm. In this embodiment, the steamer paper is coated on one side. In other embodiments, it can also be coated on both sides. In this case, it is only necessary to repeat the coating step S2.

[0045] Specifically, the coating solution is prepared by uniformly mixing 12.5g of amino silicone oil with a viscosity of 1000mPa·s and an ammonia value of 0.15eq / 100g, 6.875g of gallic acid lauryl ester epoxy with an epoxy value of 0.3eq / 100g, and 0.875g of hydrophobic micro-nano bamboo powder (corresponding to 7% of the mass of amino silicone oil). A slight excess of epoxy groups is used here to ensure complete participation of the amino groups in the crosslinking reaction, thereby increasing the crosslinking density of the coating. The preparation method of the hydrophobic micro-nano bamboo powder is as follows: 100-mesh bamboo powder is placed in a 3% sodium hydroxide solution and shaken at 85℃ for 2... After washing until neutral, a 2% solids content aqueous suspension was prepared. High-pressure homogenization was then performed to obtain a micro-nano bamboo powder suspension with an average particle size (D50) of 1.5-2.5 μm. The suspension was dried at 100℃ for 1.5 h to obtain micro-nano bamboo powder. Anhydrous ethanol, deionized water, and phenyltrimethoxysilane were mixed evenly to prepare an alcohol-water mixture. Ammonia was added dropwise to adjust the pH of the mixture to 8.5. The micro-nano bamboo powder was then added, and the mixture was magnetically stirred at room temperature (25℃) for 2 h. The high specific surface area adsorption effect at the micro-nano scale promoted the adsorption of phenyltrimethoxysilane. The hydrolysis products of phenyltrimethoxysilane undergo a condensation reaction on the surface of bamboo powder, constructing a dense hydrophobic network with Si-O-Si as the main chain and phenyl groups facing outward. After stirring, the product is washed with anhydrous ethanol 3-5 times to remove excess unreacted adsorbents on the surface, exposing the silanol (Si-OH) active sites. After drying at 105℃ for 5 hours, the silanol groups on the surface of the hydrophobic micro-nano bamboo powder are protonated, thus obtaining hydrophobic micro-nano bamboo powder. The volume ratio of anhydrous ethanol to deionized water is 4:1, and the amount of phenyltrimethoxysilane used is 10% of the mass of the micro-nano bamboo powder.

[0046] It should be noted that, unless otherwise specified, the reagents and raw materials used in the embodiments of the present invention can be obtained by purchasing them from the market.

[0047] Examples 2 to 5

[0048] The only difference between Examples 2 to 5 and Example 1 is that the amount of hydrophobic micro-nano bamboo powder added in step S2 is different from that in Example 1. All other experimental parameters are the same as those in Example 1, and will not be repeated here. The amount of hydrophobic micro-nano bamboo powder added in Examples 1 to 5 is set as shown in Table 1.

[0049] Table 1. Amount of hydrophobic micro-nano bamboo powder added in Examples 1 to 5

[0050] project Amount of hydrophobic micro-nano bamboo powder added Example 1 7% Example 2 5% Example 3 6% Example 4 10% Example 5 15%

[0051] Examples 6 to 8

[0052] The only difference between Examples 6 to 8 and Example 1 is that the coating amount in step S2 is different from that in Example 1. All other experimental parameters are the same as those in Example 1, and will not be repeated here. The coating amount settings of Examples 1 and Examples 6 to 8 are shown in Table 2.

[0053] Table 2 Coating amount settings for Examples 1 and 6 to 8

[0054] project <![CDATA[Coating weight (g / m 2 )]]> Example 1 10 Example 6 8 Example 7 15 Example 8 20

[0055] Comparative Example 1

[0056] The only difference between this comparative example and Example 1 is that the carboxymethylated nanocellulose in Example 1 is replaced with an equal amount of nanocellulose. All other experimental parameters are the same as in Example 1, and will not be repeated here.

[0057] Comparative Example 2

[0058] The only difference between this comparative example and Example 1 is that the carboxymethylated nanocellulose in Example 1 is omitted. All other experimental parameters are the same as in Example 1 and will not be repeated here.

[0059] The performance results of the steamer paper prepared under the conditions of Examples 1 to 8 and Comparative Examples 1 to 2 are shown in Table 3. Comparing the data of Examples 1 to 5, it can be seen that the amount of hydrophobic micro-nano bamboo powder added has a significant impact on the air permeability and roughness of the paper. Moreover, within the given range of 5-10% of the mass of amino silicone oil, the paper performance can simultaneously take into account both air permeability and roughness. This is because with an appropriate amount of hydrophobic micro-nano bamboo powder added, it can be ensured that the hydrophobic micro-nano bamboo powder is evenly distributed in the coating. Together with bamboo fiber, it forms a micro-uneven structure on the paper surface, which improves the paper's non-stick properties and facilitates the demolding of steamed food.

[0060] Comparing Examples 1 and 6 to 8, it can be seen that the coating amount has a significant impact on the air permeability of the paper. However, when the coating amount is too large, the coating becomes too thick, resulting in a decrease in the air permeability of the paper. Comparing the performance data of the steamer paper of Example 1 and Comparative Examples 1 to 2, it can be seen that the performance of the paper in the comparative examples is significantly weaker than that of Example 1. This is because the carboxymethylated nanocellulose added in Example 1 can not only fill the pores between the fibers of the base paper, but also the -COO on the surface of the carboxymethylated nanocellulose... - It can also form hydrogen bonds and electrostatic attraction with the silanol on the surface of hydrophobic micro / nano bamboo powder and the positive potential sites under near-neutral conditions, respectively, thus forming a stable bridge between the hydrophobic micro / nano bamboo powder and the fiber and carboxymethylated nanocellulose, thereby giving the steamer paper high stiffness and excellent wet bending stiffness retention. Secondly, the -COO in carboxymethylated nanocellulose - After absorbing moisture and swelling, the functional groups can construct a three-dimensional cross-linked water-locking support network within the paper through the hydration of the ionic groups. This dynamic network can still provide skeletal support for the paper in a wet state, ensuring that the steamer paper can maintain high wet bending stiffness after being treated in a high-humidity steam environment at 100°C. However, when carboxymethylated nanocellulose is replaced with an equal amount of nanocellulose, the aforementioned effect is weakened, resulting in a sharp decrease in the paper's tear strength and stiffness.

[0061] Table 3 Performance results of steamer paper prepared under the conditions of Examples 1 to 8 and Comparative Examples 1 to 2

[0062] project <![CDATA[basis weight (g / m 2 )]]> Air permeability (s / 100mL) Transverse tear strength (mN) Longitudinal fracture length (km) Longitudinal wet fracture length (km) Oil resistance <![CDATA[Water absorbency (g / m 2 )]]> Smoothness (s) PPS roughness (μm) Dry bending stiffness (mN·m) Example 1 42 137 147 7.5 0.96 Level 5 20 52 1.7 109 Example 2 38 120 140 7.0 0.87 Level 5 21 58 1.0 100 Example 3 40 132 143 7.2 0.92 Level 5 21 55 1.2 103 Example 4 45 134 145 7.4 0.94 Level 5 20 50 1.4 104 Example 5 47 128 142 7.3 0.90 Level 5 20 44 1.2 92 Example 6 39 140 144 7.2 0.93 Level 5 21 46 2.0 96 Example 7 46 127 149 7.8 0.98 Level 6 21 53 1.5 98 Example 8 50 121 153 8.2 1.02 Level 6 21 49 1.3 95 Comparative Example 1 42 133 134 6.3 0.80 Level 5 20 51 1.4 94 Comparative Example 2 42 119 125 5.6 0.72 Level 5 20 50 1.1 89

[0063] Application Example 1

[0064] To investigate the performance of the steamer paper in actual food steaming, this application example first punched concentric arrays of ventilation holes (1.5 mm in diameter) on the steamer paper prepared in Example 1, then laid it on the steamer, placed the food to be steamed (steamed buns in this case), heated it to generate steam, steamed it at 100°C for 20 minutes, removed it and drained it, and measured the wet bending stiffness according to GB / T 22364. The measured value was 88 mN·m (dry reference value 109 mN·m), and the wet retention rate reached 80.7%, indicating that the steamer paper still has excellent structural support under long-term humid and hot conditions.

[0065] 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.

Claims

1. A method for preparing bamboo fiber high stiffness, water-resistant, and oil-proof steamer paper, characterized in that, Includes the following steps: S1. After mixing unbleached bamboo pulp with a freeness of 28-40°SR with an internal sizing agent, papermaking is carried out to obtain base paper. The internal sizing agent is composed of carboxymethylated nanocellulose, cationic starch and alkyl ketene dimer emulsion. S2. Apply the coating liquid evenly to the surface of the base paper obtained in step S1 using a metering rod coating method, controlling the wet coating amount to be 10-15 g / m². 2 After coating, the paper is dried and cured to obtain the steamer paper. The coating liquid is a mixture of amino silicone oil, gallic acid lauryl ester epoxy, and hydrophobic micro-nano bamboo powder.

2. The preparation method according to claim 1, characterized in that, In step S2, the amount of hydrophobic micro-nano bamboo powder added is 5-10% of the mass of amino silicone oil; the viscosity of amino silicone oil is 1000 mPa·s, the ammonia value is 0.15 eq / 100g, and the epoxy value of gallic acid lauryl ester epoxy is 0.3 eq / 100g.

3. The preparation method according to claim 1, characterized in that, In step S1, the mass ratio of carboxymethylated nanocellulose, cationic starch, and AKD emulsion is 1:1:(3-5). The solid content of the AKD emulsion is 20-25%, the pH value is 4-5, and the particle size is 1.5-2.0 μm. The degree of substitution of the carboxymethylated nanocellulose is DS=0.1-0.25 and D50=10-50 μm.

4. The preparation method according to claim 1, characterized in that, In step S1, the preparation method of the hydrophobic micro-nano bamboo powder is as follows: 100-mesh bamboo powder is placed in a 1-5% sodium hydroxide solution, shaken at 70-90℃ for 1-3 h, and washed until neutral to prepare an aqueous suspension with a solid content of 1-3%. The suspension is then homogenized under high pressure to obtain a micro-nano bamboo powder suspension with a D50 of 1.5-2.5 μm. The suspension is dried at 100℃ for 1-2 h to obtain micro-nano bamboo powder. Anhydrous ethanol, deionized water, and phenyltrimethoxysilane are mixed evenly to prepare an alcohol-water mixture. Ammonia water is added dropwise to adjust the pH of the mixture to 8.

5. The micro-nano bamboo powder is then added, and the mixture is magnetically stirred at 25℃ for 2 h to obtain the hydrophobic micro-nano bamboo powder.

5. The preparation method according to claim 4, characterized in that, The volume ratio of anhydrous ethanol to deionized water is 4:1, and the amount of phenyltrimethoxysilane used is 10% of the mass of micronized bamboo powder.

6. The preparation method according to claim 1, characterized in that, In step S2, the drying and curing temperature is 110-120℃ and the time is 3-5h; in step S1, the online concentration of the unbleached bamboo pulp is 0.8-1.2%.

7. The preparation method according to claim 1, characterized in that, In step S2, the process of coating the coating liquid using the metering rod coating method is carried out according to the following steps: the metering rod is installed on the automatic coating rack, the base paper is fixed on the coating platform, the coating liquid is poured at one end of the coating platform, and the speed ratio of the metering rod rotation speed to the paper machine speed is controlled to be 1.2:1 to 2.5:1, and the coating is carried out at a uniform speed of 30-60 mm / s so that the coating liquid evenly covers the surface of the base paper; the metering rod includes a core rod and a winding wire wound on the surface of the core rod, the outer diameter of the core rod is 20-25 mm, and the diameter of the winding wire is 0.15-0.20 mm.

8. A steamer paper prepared by the method according to any one of claims 1-7, characterized in that, The steamer paper includes: The base paper is made from unbleached bamboo pulp. The functional coating, which is tightly bonded to the base paper, is obtained by mixing amino silicone oil, gallic acid lauryl ester epoxy, and hydrophobic micro-nano bamboo powder and then drying and curing it.

9. The steamer paper according to claim 8, characterized in that, The steamer paper has the following properties: basis weight of 38-45 g / m³ 2 Air permeability is 100-180s / 100mL, transverse tear strength ≥140mN, longitudinal breaking length ≥ 7.0 km, longitudinal wet fracture length ≥0.87 km, oil resistance ≥5, water absorption ≤21 g / m 2 The surface smoothness is ≥50s, and the micro-roughness PPS of the coated surface is 1.0-2.0μm. The dry bending stiffness is ≥100 mN·m, and the wet bending stiffness after steam treatment at 100℃ for 10-30min is ≥80mN·m.

10. The application of the steamer paper as described in claim 9 in food steaming.