Rice / polyethylene composite filling material and preparation method thereof and breathable pillow

Abstract

The application relates to a rice / polyethylene composite filling material and a preparation method thereof and a breathable pillow, and belongs to the technical field of daily life bedding. The rice / polyethylene composite filling material is composed of rice as an inner core and a polyethylene composite layer formed on the surface of the inner core through melt coating; the amount of the rice is 4-8 wt% of the total weight of the composite filling material; the polyethylene composite layer comprises a polyethylene matrix and an interface reinforcing agent dispersed in the polyethylene matrix, and the total addition amount of the interface reinforcing agent in the polyethylene composite layer is 1-3 wt% of the polyethylene matrix; wherein the interface reinforcing agent is composed of an in-situ reaction type composite additive, inorganic particles and plant fiber micro powder. The composite filling material has good support and flexibility, is not easy to be pulverized and broken, has good durability, and also has the characteristics of moisture resistance and insect resistance.

Description

Technical Field

[0001] This invention belongs to the technical field of daily-use bedding products, specifically relating to a rice / polyethylene composite filling material, its preparation method, and a breathable pillow. Background Technology

[0002] As an important piece of home bedding, the core function and comfort of a pillow largely depend on the performance of its internal filling material. An ideal pillow filling material should possess excellent support, flexibility, breathability, moisture resistance, antibacterial properties, and long-term shape stability. Currently, the mainstream pillow filling materials on the market mainly fall into the following categories and have the following problems: 1. Chemically synthesized filling materials: Memory foam (polyurethane foam) is popular for its slow rebound properties, providing a snug fit and support. However, it has poor breathability, easily retains heat, and some products may contain unreacted isocyanate residues, posing potential health risks. After long-term use, some low-density memory foam is prone to permanent collapse and loss of support. Foam particles (such as EPS) have good plasticity and flowability, but their high particle hardness results in poor comfort.

[0003] 2. Natural plant and animal filling materials: Down / feathers are a high-end choice due to their lightness, fluffiness, and excellent warmth. However, they are expensive, can easily cause allergies in some people, and may not provide sufficient support for users who need neck support. They are also prone to moisture absorption and clumping, requiring high maintenance (such as washing and drying). Natural plant fillings (such as buckwheat hulls, cassia seeds, and rice hulls) have good breathability and some support, aligning with the trend of natural and environmentally friendly consumption. However, their durability is poor, and the plant hulls are prone to cracking and pulverizing under long-term pressure.

[0004] 3. Composite Filler Materials: In recent years, to overcome the shortcomings of single materials, some composite filler solutions have emerged, such as mixing natural plant particles with synthetic fibers. However, this simple physical mixing has failed to fundamentally solve the problems of easy powdering and easy attraction to insects in plant fillers.

[0005] In conclusion, existing pillow filling materials struggle to achieve an ideal balance between support and flexibility, durability and functional adjustability. The market urgently needs a new type of filling material that retains the environmentally friendly and breathable advantages of natural materials while overcoming the problem of attracting insects, and simultaneously possesses support, flexibility, and long-term shape stability to meet consumers' growing demand for high-quality, healthy sleep.

[0006] CN102133017A discloses a polymer elastic breathable pillow core, which is formed by the self-fusion of several fibers extruded from polymer materials into a flat and elongated fixed shape. The pillow core has a spatial mesh structure inside. The polymer materials include LDPE, HDPE, LLDPE, EVA, PP, PE, etc. The molecular polymerization forms a three-dimensional elastic structure, in which millions of fibers in a coiled shape provide excellent elasticity, good tensile strength, and fatigue resistance. However, it cannot satisfy the requirements of good support and flexibility, good durability, and a balance between moisture resistance and insect resistance. Summary of the Invention

[0007] To address the shortcomings of existing technologies, the present invention aims to provide a rice / polyethylene composite filling material, its preparation method, and a breathable pillow. The composite filling material comprises a core of rice and a polyethylene composite layer, forming a core-shell structure that combines excellent support and flexibility. It also features low moisture permeability, good breathability, insect-repellent properties, and effectively inhibits pulverization and breakage, resulting in excellent durability. The resulting breathable pillow perfectly retains the natural support and breathability of traditional plant-filled pillows while completely solving their problems of easy insect infestation, dust accumulation, and the need for frequent airing. This provides users with a sleep solution that offers lasting support, higher hygiene standards, and a superior experience.

[0008] To achieve the above objectives, according to one aspect of the present invention, a rice / polyethylene composite filler is provided, the composite filler comprising rice as a core and a polyethylene composite layer formed on the surface of the core by melt coating; the amount of rice is 4-8 wt% of the total weight of the composite filler; the polyethylene composite layer comprises a polyethylene matrix and an interface reinforcing agent dispersed therein, the total amount of the interface reinforcing agent added to the polyethylene composite layer being 1-3 wt% of the polyethylene matrix; wherein the interface reinforcing agent is composed of 40-70 wt% in-situ reactive composite additives, 15-30 wt% inorganic particles and 15-30 wt% plant fiber micro powder.

[0009] In this invention, the rice core refers to the finished japonica rice, processed from paddy rice through cleaning, hulling, milling, and polishing processes, forming a core structure. The polishing process removes the bran layer and impurities from the rice grain surface, creating a smooth, clean, and dense surface layer rich in active hydroxyl groups. This surface layer facilitates the uniform wetting and complete spreading of the molten polyethylene composite layer to ensure dense coating. Furthermore, the chemical reaction between the active hydroxyl groups and the epoxy groups in the interface reinforcing agent firmly anchors the polyethylene shell to the rice surface, achieving excellent interfacial bonding strength. The rice has a moisture content of 8-14 wt% and a maximum radial dimension of 3-5 mm to ensure the polyethylene composite layer can completely and uniformly encapsulate it. The rice retains the dense, rigid framework of the natural japonica rice endosperm, unlike rice husks, straw, or other plant fiber powders or debris, providing durable physical support.

[0010] This invention utilizes a unique core-shell structure design and multi-component synergistic interface enhancement technology to prepare a composite filler material that combines low moisture permeability, insect resistance, and excellent durability. The hard rice core provides a robust supporting framework, ensuring lasting support, while the flexible polyethylene composite layer acts as a buffer and protector, avoiding the low durability issues caused by the fragility and dust generation inherent in pure rice fillers. Furthermore, the complete encapsulation of the rice by the polyethylene composite layer forms a physical barrier, effectively isolating external moisture and insect intrusion, fundamentally solving the core defects of pure natural rice fillers, such as easy moisture absorption and insect attraction. Through the chemical action of in-situ reactive composite additives and the physical reinforcement and bridging effects of inorganic particles and plant fiber micropowder, the bonding force between the hydrophobic polyethylene and the hydrophilic rice interface is greatly improved, preventing the coating layer from detaching from the core during use and ensuring the structural integrity and durability of the material.

[0011] In this invention, the in-situ reactive composite additive is composed of the following components in parts by weight: 3-8 parts of epoxy-functionalized polyolefin, 0.5-2 parts of a silane coupling agent containing long-chain alkyl and epoxy groups, and 0.01-0.1 parts of an initiator. In this invention, the epoxy-functionalized polyolefin is an ethylene-methyl acrylate-glycidyl methacrylate terpolymer; the silane coupling agent containing long-chain alkyl and epoxy groups is [8-(epoxypropyloxy)-n-octyl]trimethoxysilane; and the initiator is selected from dicumyl peroxide or benzoyl peroxide.

[0012] This invention pre-reacts epoxy-functionalized polyolefins, silane coupling agents containing long-chain alkyl and epoxy groups, and initiators at 80-120°C to generate active grafting sites, enhancing the interfacial reactivity of each component. This allows for more efficient chemical reactions between epoxy groups and rice starch hydroxyl groups, and between silane groups and the surface of inorganic particles during subsequent blending with polyethylene, rice, inorganic particles, and plant fiber powder. It also promotes the physical entanglement of long-chain alkyl groups with PE and the bridging effect of amphiphilic compatibilizers. Through the synergistic effect of these multifunctional components, this additive, even at extremely low addition levels, imparts strong adhesion to the rice-polyethylene interface in composite filler materials, ensuring uniform dispersion and firm bonding of the filler, thereby achieving excellent moisture resistance and durability.

[0013] In this invention, the inorganic particles are octyltriethoxysilane-modified silica with a particle size of 10-100 nm. Specifically, the preparation steps of the octyltriethoxysilane-modified silica are as follows: silica nanoparticles with a particle size of 10-100 nm are dispersed in anhydrous ethanol to form a uniform suspension (solid content 5-15 wt%). 1.0-5.0 wt% of octyltriethoxysilane (based on the weight of the silica nanoparticles) is added, and the mixture is stirred continuously at 50-70°C for 2-4 hours. After the reaction is complete, the mixture is centrifuged, washed 2-3 times with anhydrous ethanol, and finally dried in a vacuum drying oven at 60-80°C for 6-12 hours to obtain octyltriethoxysilane-modified silica.

[0014] This invention selects silica nanoparticles with a particle size ranging from 10 to 100 nm, which can provide a high specific surface area to enhance interfacial interactions. Simultaneously, the particle size is small enough to disperse in the PE layer without affecting its flexibility and processability. Silica nanoparticles smaller than 10 nm are prone to severe agglomeration, while those larger than 100 nm exhibit reduced reinforcing effects. The silica modified by the method described in this invention is uniformly dispersed in the PE melt and is not prone to agglomeration. Its surface long-chain alkyl groups can entangle with the PE molecular chains, while the potential silanol groups can undergo condensation reactions with silanes in the composite additives during subsequent processing, significantly improving the interfacial bonding force between the particles and the PE matrix, fully utilizing its pinning effect, and enhancing the rigidity and flexibility of the composite layer.

[0015] In this invention, the plant fiber powder is rice husk fiber or straw fiber powder that has undergone alkali treatment and hydrophobic modification, with a particle size of 5-50 μm. Specifically, the preparation steps of the alkali-treated and hydrophobically modified rice husk fiber or straw fiber powder are as follows: The pulverized rice husk or straw raw material (initial particle size <1 mm) is placed in a 2-6 wt% sodium hydroxide aqueous solution (solid-liquid ratio 1:10 w / v) and stirred at 70-90℃ for 1-3 h. After treatment, it is washed with plenty of water until neutral, and then dried at 60-80℃. The dried alkali-treated fiber is immersed in a mixed solution of acetic anhydride / glacial acetic acid (volume ratio 1:1), and 1-3 wt% pyridine catalyst is added. The mixture is reacted at 80-100℃ for 1-2 hours, and then washed and dried. The dried fiber is mechanically pulverized, and the final particle size of the powder is controlled to be 5-50 μm by sieving. This invention achieves a balance between reinforcement and dispersibility by controlling the particle size of the micronized powder within the range of 5-50 μm. Particles smaller than 5 μm are prone to agglomeration and are difficult to effectively bridge and reinforce, while particles larger than 50 μm may act as defect points, affecting material uniformity and reducing flexibility.

[0016] The plant fiber micropowder in this invention undergoes modification to significantly reduce its moisture permeability, enabling it to be stably and uniformly dispersed in polyethylene. It synergistically interacts with nano-inorganic particles at the micron and nanoscale, respectively, forming a multi-level reinforcing network, thereby significantly improving the flexibility and durability of the composite layer. At the interface, the modified fiber surface properties promote a tight bond with the compatibilizer and the polyethylene matrix, ensuring the structural integrity of the coating layer.

[0017] It is important to note that the breathability described in this invention refers to the macroscopic tortuous gaps formed between the composite filling material particles due to their irregular shapes when the particles are piled up in large quantities within the pillow core. These gaps allow air to circulate freely during sleep, thus giving the pillow core excellent volumetric breathability. The moisture resistance is due to the polyethylene composite layer covering the surface of each individual particle. This layer is a continuous, dense, hydrophobic polymer film that itself forms a physical barrier preventing external water molecules from penetrating into the rice kernel. Simultaneously, the interface reinforcing agent chemically anchors the polyethylene composite layer firmly to the rice surface, fundamentally blocking the channels for moisture to permeate along the core-shell interface.

[0018] In this invention, the polyethylene matrix is ​​polyethylene with a number average molecular weight of 10,000-50,000. The reason for choosing polyethylene with a number average molecular weight of 10,000-50,000 as the matrix is ​​that polyethylene in this molecular weight range has low melt viscosity and high fluidity, enabling it to achieve uniform and complete melt coating of rice at relatively low temperatures (160-180℃), effectively avoiding incomplete coating or heat damage to the rice due to high temperatures or insufficient fluidity. Simultaneously, the low-viscosity melt greatly promotes the dispersion and interfacial migration of interfacial reinforcing agents and nano / micro fillers in the matrix, ensuring the full realization of key interfacial effects such as chemical bonding and physical entanglement.

[0019] According to another aspect of the present invention, a method for preparing a rice / polyethylene composite filler material is also provided, comprising the following steps: (1) Mix in situ reactive composite additives, inorganic particles and plant fiber powder in proportion to obtain an interface reinforcing agent; (2) The polyethylene matrix and the interface reinforcing agent obtained in step (1) are melt-blended and granulated to obtain the polyethylene composite material; (3) Add rice and the polyethylene composite material obtained in step (2) into a melt coating device, and coat the surface of the rice with the polyethylene composite material under the heating and melting conditions of 160-180℃ to form a polyethylene composite layer, thereby obtaining the rice / polyethylene composite filler material.

[0020] In this invention, in step (1), the in-situ reactive composite additive, inorganic particles, and plant fiber powder are mixed in proportion to obtain an interface reinforcing agent. The preparation method of the in-situ reactive composite additive includes the following steps: epoxy-functionalized polyolefin, silane coupling agent containing long-chain alkyl and epoxy groups, and initiator are mixed and reacted at 80-120℃ for 10-30 minutes to obtain the in-situ reactive composite additive.

[0021] In this invention, step (2) involves melt blending the polyethylene matrix with the interfacial reinforcing agent obtained in step (1), followed by granulation to obtain the polyethylene composite material. In this invention, the melt blending is carried out in a twin-screw extruder, with the screw temperatures set as follows: feed section 120-140℃, melt mixing section 150-170℃, and die head section 140-160℃; the screw speed is 100-300 rpm. These process conditions ensure that the polyethylene is fully melted and the interfacial reinforcing agent is uniformly dispersed, while avoiding excessively high temperatures that could lead to premature complete reaction of the pre-activated components in the interfacial reinforcing agent or degradation of the polyethylene.

[0022] In this invention, in step (3), rice and the polyethylene composite material obtained in step (2) are added to a melt coating device. Under heating and melting conditions at 160-180℃, the polyethylene composite material coats the surface of the rice to form a polyethylene composite layer, thus obtaining the rice / polyethylene composite filler material. In this invention, the melt coating device is a coating molding machine, preferably a coating machine. In this invention, after coating is completed, the obtained hot material is rapidly cooled and solidified. Subsequently, the cooled coarse material is crushed and sieved so that the final rice / polyethylene composite filler material particles have a size range of 3-8 mm. This step, with the help of the mixing and heat conduction of the melt coating device, enables the polyethylene melt pre-dispersed with an interface reinforcing agent to achieve complete coating of the rice under dynamic conditions, and finally completes the chemical reaction and physical bonding such as epoxy group bonding and rice hydroxyl group bonding at the interface.

[0023] It should be noted that during the melt coating process, the instant the molten polyethylene composite material (temperature 160-180℃) comes into contact with room temperature rice (approximately 25℃), the polyethylene melt rapidly spreads on the surface of the rice grain and quickly cools and solidifies (the entire coating process is controlled within 1-3 minutes). This instantly forms a solid polymer shell with heat-insulating properties on the outer layer of the rice grain. This shell effectively blocks the subsequent inward transfer of heat, ensuring that the actual temperature rise of the rice core is far below its starch gelatinization initiation temperature, thus guaranteeing that the rice functions as a rigid supporting framework. If the coating time is too long or cooling is not timely, the rice will gelatinize and lose its supporting effect.

[0024] According to another aspect of the present invention, a breathable pillow filled with rice / polyethylene composite material is also provided, comprising a pillowcase and a filling material filled within the pillowcase, the filling material comprising the rice / polyethylene composite filling material as described in any of the preceding claims or the rice / polyethylene composite filling material prepared according to the preparation method described in any of the preceding claims.

[0025] Compared with the prior art, the beneficial effects of the present invention are: 1. This invention utilizes a low molecular weight polyethylene matrix and innovatively introduces an interface reinforcing agent composed of in-situ reactive composite additives, modified inorganic nanoparticles, and modified plant fiber powder to construct a composite filler material with a unique sandwich structure (rice-reinforced interface layer-multifunctional coating layer), achieving a synergistic improvement in multiple technical effects. Because the polyethylene composite layer coating each individual particle is a continuous, dense, hydrophobic polymer film, it itself forms a physical barrier preventing external water molecules from penetrating into the rice core. Simultaneously, the interface reinforcing agent chemically anchors the polyethylene composite layer firmly to the rice surface, fundamentally blocking the channels for water to permeate along the core-shell interface, giving the material low moisture permeability, high flexibility, and durability.

[0026] 2. The preparation method provided by this invention designs and integrates three key technologies: in-situ pre-activation of interface reinforcing agent, gradient dispersion and blending of multiphase components, and melt coating. This method has strong process controllability and not only efficiently solves the problems of weak interface bonding and single function of traditional coating materials, but also prepares composite filler materials with low moisture permeability, high flexibility and excellent durability. Detailed Implementation

[0027] This invention provides a rice / polyethylene composite filler material, wherein the composite filler material consists of rice as a core and a polyethylene composite layer formed on the surface of the core by melt coating; the amount of rice is 4-8 wt% of the total weight of the composite filler material; the polyethylene composite layer contains a polyethylene matrix and an interface reinforcing agent dispersed therein, and the total amount of the interface reinforcing agent added to the polyethylene composite layer is 1-3 wt% of the polyethylene matrix; wherein the interface reinforcing agent is composed of 40-70 wt% in-situ reactive composite additive, 15-30 wt% inorganic particles and 15-30 wt% plant fiber micro powder.

[0028] In some embodiments, the in-situ reactive composite additive is composed of the following components in parts by weight: 3-8 parts of epoxy-functionalized polyolefin, 0.5-2 parts of silane coupling agent containing long-chain alkyl and epoxy groups, and 0.01-0.1 parts of initiator.

[0029] In some embodiments, the epoxy-functionalized polyolefin is an ethylene-methyl acrylate-glycidyl methacrylate terpolymer; the silane coupling agent containing long-chain alkyl and epoxy groups is [8-(epoxypropyloxy)-n-octyl]trimethoxysilane; and the initiator is selected from dicumyl peroxide or benzoyl peroxide.

[0030] In some embodiments, the inorganic particles are octyltriethoxysilane-modified silica with a particle size of 10-100 nm.

[0031] In some embodiments, the plant fiber powder is rice husk fiber powder or straw fiber powder that has undergone alkali treatment and hydrophobic modification, and its particle size is 5-50 μm.

[0032] In some embodiments, the polyethylene matrix is ​​polyethylene with a number average molecular weight of 10,000-50,000.

[0033] The present invention also provides a method for preparing the rice / polyethylene composite filler material according to any one of the above claims, comprising the following steps: (1) Mix in situ reactive composite additives, inorganic particles and plant fiber powder in proportion to obtain an interface reinforcing agent; (2) The polyethylene matrix and the interface reinforcing agent obtained in step (1) are melt-blended and granulated to obtain the polyethylene composite material; (3) Add rice and the polyethylene composite material obtained in step (2) into a melt coating device, and coat the surface of the rice with the polyethylene composite material under the heating and melting conditions of 160-180℃ to form a polyethylene composite layer, thereby obtaining the rice / polyethylene composite filler material.

[0034] In some embodiments, the preparation method of the in-situ reactive composite additive in step (1) includes the following steps: mixing and reacting epoxy-functionalized polyolefin, silane coupling agent containing long-chain alkyl and epoxy groups and initiator at 80-120°C for 10-30 minutes to obtain the in-situ reactive composite additive.

[0035] In some embodiments, the melt blending in step (2) is carried out in a twin-screw extruder, with the screw temperatures set as follows: 120-140°C for the feed section, 150-170°C for the melt blending section, and 140-160°C for the die head section; and the screw speed is 100-300 rpm.

[0036] The present invention also provides a breathable pillow with rice / polyethylene composite filling material, comprising a pillowcase and a filling material filled in the pillowcase, wherein the filling material comprises the rice / polyethylene composite filling material described in any one of the above claims or the rice / polyethylene composite filling material prepared according to the preparation method described in any one of the above claims.

[0037] The present invention will be described in detail below through embodiments. It should be understood that the following embodiments are only used to further explain and illustrate the content of the present invention by way of example, and are not intended to limit the present invention.

[0038] Example 1 is the best embodiment.

[0039] The chemical additives used in the embodiments and comparative examples of this invention are all commercially available, and the specific information is as follows: Rice: Finished japonica rice processed through cleaning, hulling, milling, and polishing, with a moisture content of 8-14 wt%, purchased from a supermarket; Polyethylene: Number average molecular weight 10,000-50,000, purchased from Zibo Jinju Plastic Weaving Co., Ltd. Silica: Particle size 10-100nm, purchased from Xi'an Bona Materials Technology Co., Ltd. Rice husk raw material: purchased from Jining Fuxun Agricultural Products Co., Ltd.; Straw raw material: corn stalks, purchased from Zhengyang County Xinleyuan Grass Industry Co., Ltd.; Ethylene-methyl acrylate-glycidyl methacrylate terpolymer: LOTADER® AX8900, purchased from Arkema Ltd., France; Octyltriethoxysilane, pyridine, [8-(epoxypropyloxy)-n-octyl]trimethoxysilane, other auxiliaries and solvents: all purchased from Aladdin Reagent Co., Ltd.

[0040] Example 1 The specific preparation method for octyltriethoxysilane-modified silica A is as follows: Silica nanoparticles with a particle size of 10-100 nm were dispersed in anhydrous ethanol to form a uniform suspension (solid content 15 wt%). Octyltriethoxysilane (5.0 wt% of the weight of the silica nanoparticles) was added, and the mixture was stirred continuously at 70 °C for 2 h. After the reaction was complete, the mixture was centrifuged, washed three times with anhydrous ethanol, and finally dried in a vacuum drying oven at 80 °C for 6 h to obtain octyltriethoxysilane-modified silica A. The plant fiber powder is rice husk fiber powder that has undergone alkali treatment and hydrophobic modification. The specific preparation method is as follows: Crushed rice husks (initial particle size <1 mm) were placed in a 6 wt% sodium hydroxide aqueous solution (solid-liquid ratio 1:10 w / v) and stirred at 90 °C for 1 h. After treatment, the mixture was washed with plenty of water until neutral and then dried at 80 °C. The dried alkali-treated fibers were immersed in a mixed solution of acetic anhydride / glacial acetic acid (volume ratio 1:1), with 3 wt% pyridine catalyst added, and reacted at 100 °C for 1 h. After reaction, the fibers were washed and dried. The dried fibers were mechanically crushed, and the final micronized particle size was controlled to be 5-50 μm by sieving. This embodiment describes a rice / polyethylene composite filler material, which consists of rice and a polyethylene composite layer formed on the surface of the core by melt coating; the amount of rice is 6 wt% of the total weight of the composite filler material; the polyethylene composite layer contains a polyethylene matrix and an interface reinforcing agent dispersed therein, and the total amount of the interface reinforcing agent added to the polyethylene composite layer is 2 wt% of the polyethylene matrix; wherein, the interface reinforcing agent consists of 60 wt% in-situ reactive composite additive, 20 wt% octyltriethoxysilane surface-modified silica A obtained in this embodiment, and 20 wt% rice husk fiber micro powder obtained in this embodiment after alkali treatment and hydrophobic modification; the in-situ reactive composite additive consists of the following components in parts by weight: 6 parts of ethylene-methyl acrylate-glycidyl methacrylate terpolymer, 1 part of [8-(epoxypropyloxy)-n-octyl]trimethoxysilane, and 0.05 parts of dicumyl peroxide; The preparation method of the rice / polyethylene composite filler material includes the following steps: (1) Ethylene-methyl acrylate-glycidyl methacrylate terpolymer, [8-(epoxypropyloxy)-n-octyl]trimethoxysilane and dicumyl peroxide were mixed and reacted at 100°C for 20 minutes under nitrogen protection to obtain an in-situ reactive composite additive; The in-situ reactive composite additive, the octyltriethoxysilane surface-modified silica A prepared in this example and the rice husk fiber micro powder prepared in this example after alkali treatment and hydrophobic modification were mixed in proportion to obtain an interface reinforcing agent; (2) The polyethylene matrix and the interface reinforcing agent obtained in step (1) are added to a twin-screw extruder (manufacturer: Zibo Leixin Aino Machinery Co., Ltd.) for melt blending and granulation to obtain the polyethylene composite layer material; the screw temperature of each section is set as follows: feed section 130℃, melt mixing section 160℃, die head section 150℃; screw speed is 200rpm. (3) A BY1000 type water chestnut-shaped coating machine was used as the melt coating equipment. The tilt angle of the coating pan was adjusted to 30° and the rotation speed was set to 30 r / min. The polyethylene composite material obtained in step (2) was preheated to 170°C and melted for later use. The coating machine was started, and the rice was continuously rolled in the pan to form a uniform material curtain. At the same time, the electric heating blower was turned on to send in 170°C hot air to preheat the material. After the temperature in the pan rose to above 160°C, the melted coating material was added to the pan in batches in small amounts, so that it was evenly coated on the surface of the rice under the condition of rolling. The entire coating process was completed within 2 minutes. After the coating was completed, the room temperature cold air was immediately switched to blown for 3 minutes to make the coating layer cool and solidify quickly. The material was taken out, crushed and screened to obtain rice / polyethylene composite filler particles with a particle size of 3-8mm.

[0041] Example 2 The specific preparation method for octyltriethoxysilane-modified silica B is as follows: Silica nanoparticles with a particle size of 10-100 nm were dispersed in anhydrous ethanol to form a uniform suspension (solid content 5 wt%). Octyltriethoxysilane (1.0 wt% of the weight of the silica nanoparticles) was added, and the mixture was stirred continuously at 50 °C for 4 h. After the reaction was complete, the mixture was centrifuged, washed twice with anhydrous ethanol, and finally dried in a vacuum drying oven at 60 °C for 12 h to obtain octyltriethoxysilane-modified silica B. The plant fiber powder is rice husk fiber powder that has undergone alkali treatment and hydrophobic modification. The specific preparation method is as follows: Crushed rice husks (initial particle size <1 mm) were placed in a 6 wt% sodium hydroxide aqueous solution (solid-liquid ratio 1:10 w / v) and stirred at 90 °C for 1 h. After treatment, the mixture was washed with plenty of water until neutral and then dried at 80 °C. The dried alkali-treated fibers were immersed in a mixed solution of acetic anhydride / glacial acetic acid (volume ratio 1:1), with 3 wt% pyridine catalyst added, and reacted at 100 °C for 1 h. After reaction, the fibers were washed and dried. The dried fibers were mechanically crushed, and the final micronized particle size was controlled to be 5-50 μm by sieving. This embodiment describes a rice / polyethylene composite filler material, which consists of rice and a polyethylene composite layer formed on the surface of the core by melt coating; the amount of rice is 4 wt% of the total weight of the composite filler material; the polyethylene composite layer contains a polyethylene matrix and an interface reinforcing agent dispersed therein, and the total amount of the interface reinforcing agent added to the polyethylene composite layer is 1 wt% of the polyethylene matrix; wherein, the interface reinforcing agent consists of 40 wt% in-situ reactive composite additive, 30 wt% octyltriethoxysilane surface-modified silica B prepared in this embodiment, and 30 wt% rice husk fiber micro powder prepared in this embodiment after alkali treatment and hydrophobic modification; the in-situ reactive composite additive consists of the following components in parts by weight: 3 parts of ethylene-methyl acrylate-glycidyl methacrylate terpolymer, 0.5 parts of [8-(epoxypropyloxy)-n-octyl]trimethoxysilane, and 0.01 parts of dicumyl peroxide; The preparation method of the rice / polyethylene composite filler material includes the following steps: (1) Ethylene-methyl acrylate-glycidyl methacrylate terpolymer, [8-(epoxypropyloxy)-n-octyl]trimethoxysilane and dicumyl peroxide were mixed and reacted at 80°C for 30 minutes under nitrogen protection to obtain an in-situ reactive composite additive; The in-situ reactive composite additive, the octyltriethoxysilane surface-modified silica B prepared in this example and the rice husk fiber micro powder prepared in this example after alkali treatment and hydrophobic modification were mixed in proportion to obtain an interface reinforcing agent; (2) The polyethylene matrix and the interface reinforcing agent obtained in step (1) are added to a twin-screw extruder (manufacturer: Zibo Leixin Aino Machinery Co., Ltd.) for melt blending and granulation to obtain the polyethylene composite layer material; the screw temperature of each section is set as follows: feed section 120℃, melt mixing section 150℃, die head section 140℃; screw speed is 100rpm. (3) A BY1000 type water chestnut-shaped coating machine was used as the melt coating equipment. The tilt angle of the coating pan was adjusted to 30° and the rotation speed was set to 30 r / min. The polyethylene composite material obtained in step (2) was preheated to 160°C and melted for later use. The coating machine was started, and the rice was continuously rolled in the pan to form a uniform material curtain. At the same time, the electric heating blower was turned on to send in 160°C hot air to preheat the material. After the temperature in the pan rose above 160°C, the melted coating material was added to the pan in batches in small amounts, so that it was evenly coated on the surface of the rice under the condition of rolling. The entire coating process was completed within 2 minutes. After the coating was completed, the room temperature cold air was immediately switched to blown for 3 minutes to make the coating layer cool and solidify quickly. The material was taken out, crushed and screened to obtain rice / polyethylene composite filler particles with a particle size of 3-8mm.

[0042] Example 3 The specific preparation method for octyltriethoxysilane-modified silica A is as follows: Silica nanoparticles with a particle size of 10-100 nm were dispersed in anhydrous ethanol to form a uniform suspension (solid content 15 wt%). Octyltriethoxysilane (5.0 wt% of the weight of the silica nanoparticles) was added, and the mixture was stirred continuously at 70 °C for 2 h. After the reaction was complete, the mixture was centrifuged, washed three times with anhydrous ethanol, and finally dried in a vacuum drying oven at 80 °C for 6 h to obtain octyltriethoxysilane-modified silica A. Plant fiber powder is straw fiber powder that has undergone alkali treatment and hydrophobic modification. The specific preparation method is as follows: Crushed straw (initial particle size <1 mm) was placed in a 2 wt% sodium hydroxide aqueous solution (solid-liquid ratio 1:10 w / v) and stirred at 70 °C for 3 h. After treatment, it was washed with plenty of water until neutral and then dried at 60 °C. The dried alkali-treated fibers were immersed in a mixed solution of acetic anhydride / glacial acetic acid (volume ratio 1:1), with 1 wt% pyridine catalyst added, and reacted at 80 °C for 2 h. After reaction, the fibers were washed and dried. The dried fibers were mechanically crushed, and the final micronized particle size was controlled to be 5-50 μm by sieving. This embodiment describes a rice / polyethylene composite filler material, which consists of rice and a polyethylene composite layer formed on the surface of the core by melt coating; the amount of rice is 8 wt% of the total weight of the composite filler material; the polyethylene composite layer contains a polyethylene matrix and an interface reinforcing agent dispersed therein, and the total amount of the interface reinforcing agent added to the polyethylene composite layer is 3 wt% of the polyethylene matrix; wherein, the interface reinforcing agent consists of 70 wt% in-situ reactive composite additive, 15 wt% octyltriethoxysilane surface-modified silica A obtained in this embodiment, and 15 wt% straw fiber micro powder obtained in this embodiment after alkali treatment and hydrophobic modification; the in-situ reactive composite additive consists of the following components in parts by weight: 8 parts of ethylene-methyl acrylate-glycidyl methacrylate terpolymer, 2 parts of [8-(epoxypropyloxy)-n-octyl]trimethoxysilane, and 0.1 parts of dicumyl peroxide; The preparation method of the rice / polyethylene composite filler material includes the following steps: (1) Ethylene-methyl acrylate-glycidyl methacrylate terpolymer, [8-(epoxypropyloxy)-n-octyl]trimethoxysilane and dicumyl peroxide were mixed and reacted at 120°C for 10 minutes under nitrogen protection to obtain an in-situ reactive composite additive; The in-situ reactive composite additive, the octyltriethoxysilane surface-modified silica A prepared in this example and the straw fiber micro powder prepared in this example after alkali treatment and hydrophobic modification were mixed in proportion to obtain an interface reinforcing agent; (2) The polyethylene matrix and the interface reinforcing agent obtained in step (1) are added to a twin-screw extruder (manufacturer: Zibo Leixin Aino Machinery Co., Ltd.) for melt blending and granulation to obtain the polyethylene composite layer material; the screw temperature of each section is set as follows: feed section 140℃, melt mixing section 170℃, die head section 160℃; screw speed is 300rpm. (3) A BY1000 type water chestnut-shaped coating machine was used as the melt coating equipment. The tilt angle of the coating pan was adjusted to 30° and the rotation speed was set to 30 r / min. The polyethylene composite material obtained in step (2) was preheated to 180°C and melted for later use. The coating machine was started, and the rice was continuously rolled in the pan to form a uniform material curtain. At the same time, the electric heating blower was turned on to send in 180°C hot air to preheat the material. After the temperature in the pan rose to above 160°C, the melted coating material was added to the pan in batches in small amounts, so that it was evenly coated on the surface of the rice under the condition of rolling. The entire coating process was completed within 1 minute. After the coating was completed, the room temperature cold air was immediately switched to blown for 3 minutes to make the coating layer cool and solidify quickly. The material was taken out, crushed and screened to obtain rice / polyethylene composite filler particles with a particle size of 3-8mm.

[0043] Comparative Example 1 The rice / polyethylene composite filler material described in this comparative example is exactly the same as that in Example 1, except that the interface reinforcing agent is composed of 60wt% γ-(2,3-epoxypropoxy)propyltriethoxysilane, 20wt% octyltriethoxysilane surface-modified silica A obtained in Example 1, and 20wt% rice husk fiber micro powder obtained in Example 1 that has undergone alkali treatment and hydrophobic modification.

[0044] Comparative Example 2 The rice / polyethylene composite filler material described in this comparative example is exactly the same as that in Example 1, except that the in-situ reactive composite additive is composed of the following components in parts by weight: 6 parts of ethylene-methyl acrylate-glycidyl methacrylate terpolymer, 1 part of 3-(2,3-epoxypropoxy)propyltrimethoxysilane, and 0.05 parts of dicumyl peroxide.

[0045] Comparative Example 3 The rice / polyethylene composite filler material described in this comparative example is exactly the same as that in Example 1, except that the rice husk fiber powder that has been alkali-treated and hydrophobically modified is replaced with an equal amount of rice husk fiber powder that has only been alkali-treated.

[0046] Comparative Example 4 The rice / polyethylene composite filler material described in this comparative example is exactly the same as that in Example 1, except that the octyltriethoxysilane surface-modified silica A is replaced with an equal amount of silane coupling agent KH-560 surface-modified silica.

[0047] Comparative Example 5 The rice / polyethylene composite filler material described in this comparative example is exactly the same as that in Example 1, except that the temperature of the twin-screw extruder head section is increased to 210°C in step (2).

[0048] Performance testing The rice / polyethylene composite filler materials obtained in Examples 1-3 and Comparative Examples 1-5, as well as the examples, were subjected to performance tests according to the following methods. The specific results are shown in Table 1.

[0049] Single-particle compressive strength (N / particle): Using a texture analyzer, 30 particles were randomly selected for testing, and the average value was taken. This reflects the particle's resistance to crushing and its durability.

[0050] Compression set (%): The thickness loss rate is calculated after the filler material is subjected to 50% compression set for 72 hours and then recovers for 24 hours. The lower the value, the better the flexibility.

[0051] Bulk density (g / L): Determined according to the loose bulk density determination principle specified in GB / T 6286-1986 "Method for Determination of Bulk Density of Molecular Sieves". The sample is allowed to fall freely through a funnel into a standard graduated cylinder of known volume (1L) under vibration-free conditions. Excess sample at the cylinder opening is leveled with a ruler, and the mass per unit volume is calculated. This reflects the lightweight nature of the material and affects the softness and weight of the filler.

[0052] Moisture permeability (g / (m²·24h)): Determined according to the permeability principle of the cup method. Take 50 g of the sample to be tested and evenly pack it into a permeability cup. Place a metal wire mesh with a pore size of 1-2 mm at the bottom of the cup to ensure unobstructed airflow. The sample stack thickness should be no less than 30 mm. Cover and seal the cup opening with standard cotton cloth (approximately 200 g / m²). Place the permeability cup in a constant temperature and humidity chamber at 38℃ and 90% RH. Weigh it every 24 hours until the mass change rate between two consecutive measurements is ≤5%, and calculate the moisture permeability. This reflects the material's moisture-proof performance; the lower the moisture permeability, the better the moisture-proof performance.

[0053] Strength retention rate after damp heat aging (%): After the sample is placed in a constant temperature and humidity chamber at 85℃ and 85% relative humidity for 168 hours (7 days), the retention rate of its compressive strength is tested.

[0054] Initial dust emission (mg / kg): Place 100g of filling material on a standard vibrating sieve and vibrate for 10 minutes at an amplitude of 3mm and a frequency of 200 times / minute. Collect the precipitated dust and weigh it.

[0055] Dust release after damp heat aging (mg / kg): The sample was placed in a constant temperature and humidity chamber at 85℃ and 85% relative humidity for 168 hours (7 days), and the dust release was measured according to the above method. The change in dust release before and after damp heat aging was compared to characterize the long-term anti-powdering durability of the material.

[0056] Insect Damage Assessment (Grade): Rice weevils (Sitophilus oryzae) (7-14 days after emergence, with uniform age) were used as standard test insects to quantitatively evaluate the insect damage resistance of the composite filling material of this invention. 50 g of each example and comparative sample was placed in a breathable non-woven bag and equilibrated for 24 hours under standard atmospheric conditions (temperature 20±2℃, relative humidity 65±4%). The initial mass was then measured, and 20 adult rice weevils were introduced into each bag. The bags were placed in a constant temperature and humidity incubator at 27±1℃, relative humidity 70±5%, and complete darkness. An equal amount of unwrapped pure rice was used as a blank control. The test period was 14 days, and the survival of the test insects and the appearance of the samples were observed and recorded on days 7 and 14. After the test, gently clean the insect droppings and wood dust adhering to the sample surface with a soft brush. After equilibration under standard atmospheric conditions for 24 hours, weigh the final sample and calculate the weight loss rate: Weight loss rate (%) = (Initial mass - Final mass) / Initial mass × 100%. Simultaneously record the insect mortality rate and signs of borer damage. Based on the weight loss rate, assess the insect resistance level: Level 1 (Excellent): Weight loss rate ≤2%, no visible borer holes or wood dust; Level 2 (Good): Weight loss rate >2% and ≤5%, occasional slight signs of borer damage; Level 3 (Medium): Weight loss rate >5% and ≤10%, obvious borer holes or wood dust; Level 4 (Poor): Weight loss rate >10%, severe borer damage. Three parallel samples were used for each test, and the average result was taken.

[0057] Table 1 Performance data of Examples 1-3 and Comparative Examples 1-5 .

[0058] As shown in Table 1, within the specified proportions and process parameters of this invention, Examples 1-3 all exhibit excellent comprehensive performance. High single-particle compressive strength indicates good mechanical support and resistance to breakage. Simultaneously, thanks to the hydrophobic interface constructed from modified silica and plant fibers, as well as the robust coating structure, the material possesses excellent moisture resistance and durability, low moisture permeability, and high strength retention after damp heat aging. Furthermore, dust emission is extremely low, and the insect infestation rating is the highest level (Grade 1), overcoming the shortcomings of traditional filler materials such as easy pulverization and insect infestation. In summary, this invention, through the synergistic effect of the interface reinforcement system and precise process control, achieves a balance between low moisture permeability, high durability, and insect resistance under different implementation conditions.

[0059] A comparison of Example 1 and Comparative Examples 1 and 2 reveals that Comparative Example 1, which uses a simple mixture of silane coupling agents instead of in-situ reactive composite additives, exhibits lower single-particle compressive strength than Example 1, and its strength retention rate decreases after damp heat aging, while dust precipitation increases. This clearly demonstrates that physically mixed coupling agents alone cannot achieve a strong interfacial bond, resulting in poor cohesive strength of the coating layer, easy pulverization, and easy interface failure under high humidity conditions. Comparative Example 2, which replaces the long-chain silane [8-(epoxypropyloxy)-n-octyl]trimethoxysilane with the common short-chain silane KH-560, shows significantly lower compressive strength and damp heat aging retention rate compared to Example 1. This indicates that the flexible long-chain structure of the long-chain silane plays a crucial role in improving compatibility with the polyethylene matrix, enhancing interfacial toughness, and stress dissipation, while the toughening effect of short-chain silanes is limited.

[0060] A comparison of Example 1 and Comparative Example 3 reveals that Comparative Example 3, which uses plant fibers that have only undergone alkali treatment without hydrophobic modification, exhibits significant shortcomings in performance, particularly in moisture resistance and insect resistance. This indicates that unhydrophobic fibers become channels and accumulation points for moisture intrusion in humid and hot environments, leading not only to interface damage but also providing conditions for insect egg growth.

[0061] A comparison between Example 1 and Comparative Example 4 shows that the KH-560 silane used in Comparative Example 4 has a strong epoxy group polarity and poor dispersibility in non-polar polyethylene, which easily leads to particle agglomeration and stress defect points. This directly results in Comparative Example 4 being inferior to Example 1 in key indicators such as compressive strength and moisture permeability.

[0062] A comparison of Example 1 and Comparative Example 5 shows that Comparative Example 5, which uses a higher processing temperature, exhibits significantly reduced moisture permeability and moisture aging retention. This indicates that excessively high temperatures damage rice, lead to excessive interfacial reactions, or trigger matrix degradation, thereby reducing interfacial stability.

[0063] Therefore, this invention, by selecting a low molecular weight polyethylene matrix and innovatively introducing an interface reinforcing agent composed of in-situ reactive composite additives, modified inorganic nanoparticles, and modified plant fiber powder, constructs a composite filler material with a unique sandwich structure (rice-reinforced interface layer-multifunctional coating layer), achieving a synergistic improvement in multiple technical effects. Because the polyethylene composite layer coating each individual particle is a continuous, dense, hydrophobic polymer film, it itself constitutes a physical barrier preventing external water molecules from penetrating into the rice core. Simultaneously, the interface reinforcing agent, through a chemical reaction, firmly anchors the polyethylene composite layer to the rice surface, fundamentally blocking the channels for water to permeate along the core-shell interface, giving the material excellent moisture resistance, flexibility, and durability.

[0064] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. For those skilled in the art, other variations or modifications can be made based on the above description. It is impossible to exhaustively list all the implementation methods here. All obvious variations or modifications derived from the technical solutions of the present invention are still within the protection scope of the present invention.

Claims

1. A rice / polyethylene composite filler material, characterized in that, The composite filler material consists of rice as a core and a polyethylene composite layer formed on the surface of the core by melt coating; the amount of rice is 4-8 wt% of the total weight of the composite filler material; the polyethylene composite layer contains a polyethylene matrix and an interface reinforcing agent dispersed therein, and the total amount of the interface reinforcing agent added to the polyethylene composite layer is 1-3 wt% of the polyethylene matrix; wherein, the interface reinforcing agent is composed of 40-70 wt% in-situ reactive composite additives, 15-30 wt% inorganic particles and 15-30 wt% plant fiber micro powder.

2. The rice / polyethylene composite filler material as described in claim 1, characterized in that, The in-situ reactive composite additive is composed of the following components in parts by weight: 3-8 parts of epoxy-functionalized polyolefin, 0.5-2 parts of silane coupling agent containing long-chain alkyl and epoxy groups, and 0.01-0.1 parts of initiator.

3. The rice / polyethylene composite filler material as described in claim 2, characterized in that, The epoxy-functionalized polyolefin is an ethylene-methyl acrylate-glycidyl methacrylate terpolymer; the silane coupling agent containing long-chain alkyl and epoxy groups is [8-(epoxypropyloxy)-n-octyl]trimethoxysilane; the initiator is selected from dicumyl peroxide or benzoyl peroxide.

4. The rice / polyethylene composite filler material as described in claim 1, characterized in that, The inorganic particles are octyltriethoxysilane-modified silica with a particle size of 10-100 nm.

5. The rice / polyethylene composite filler material as described in claim 1, characterized in that, The plant fiber powder is rice husk fiber powder or straw fiber powder that has undergone alkali treatment and hydrophobic modification, and its particle size is 5-50μm.

6. The rice / polyethylene composite filler material as described in claim 1, characterized in that, The polyethylene matrix is ​​polyethylene with a number average molecular weight of 10,000-50,000.

7. A method for preparing a rice / polyethylene composite filler material according to any one of claims 1 to 6, characterized in that, Includes the following steps: (1) Mix in situ reactive composite additives, inorganic particles and plant fiber powder in proportion to obtain an interface reinforcing agent; (2) The polyethylene matrix and the interface reinforcing agent obtained in step (1) are melt-blended and granulated to obtain a polyethylene composite material; (3) Add rice and the polyethylene composite material obtained in step (2) into a melt coating device, and coat the surface of the rice with the polyethylene composite material under the heating and melting conditions of 160-180℃ to form a polyethylene composite layer, thereby obtaining the rice / polyethylene composite filler material.

8. The method for preparing a rice / polyethylene composite filler material as described in claim 7, characterized in that, In step (1), the preparation method of the in-situ reactive composite additive includes the following steps: mixing and reacting epoxy-functionalized polyolefin, silane coupling agent containing long-chain alkyl and epoxy groups and initiator at 80-120℃ for 10-30 minutes to obtain the in-situ reactive composite additive.

9. The method for preparing a rice / polyethylene composite filler material as described in claim 7, characterized in that, The melt blending described in step (2) is carried out in a twin-screw extruder, with the screw temperatures set as follows: 120-140℃ for the feed section, 150-170℃ for the melt blending section, and 140-160℃ for the die head section; and the screw speed is 100-300 rpm.

10. A breathable pillow filled with a rice / polyethylene composite material, characterized in that, The invention includes a pillowcase and a filling material inside the pillowcase, the filling material comprising the rice / polyethylene composite filling material as described in any one of claims 1-6 or the rice / polyethylene composite filling material prepared by the preparation method according to any one of claims 7-9.