A tea bran modified polypropylene carbonate composite material and a preparation method thereof

Abstract

This invention discloses a polypropylene carbonate composite material modified with tea seed cake and its preparation method. The polypropylene carbonate composite material comprises modified tea seed cake and a polypropylene carbonate matrix, wherein the modified tea seed cake is obtained through surface modification via alkali treatment, silane coupling agent treatment, or organic acid treatment. This invention significantly improves the dispersibility and interfacial compatibility of tea seed cake, a natural biomass filler, within the polypropylene carbonate matrix by employing specific surface treatment methods. Simultaneously, by utilizing the active components of tea seed cake itself, a polypropylene carbonate composite material with significantly improved mechanical properties, thermal stability, anti-aging properties, and biodegradability is prepared, achieving high-value utilization of agricultural waste.

Description

Technical Field

[0001] This invention relates to the field of polypropylene carbonate composite materials, specifically to a polypropylene carbonate composite material based on tea seed cake modification and its preparation method. Background Technology

[0002] Polypropylene carbonate (PPC) is a fully biodegradable plastic copolymerized from carbon dioxide and propylene oxide. Using the greenhouse gas CO2 as a raw material, it achieves carbon capture and fixation at the source; approximately 0.42 tons of carbon dioxide can be fixed for every ton of PPC produced. Therefore, the promotion and use of PPC helps reduce greenhouse gas emissions. At the same time, PPC has excellent gas barrier properties, transparency, and biocompatibility, showing broad application prospects in packaging materials, agricultural mulch films, and other fields. However, PPC has disadvantages such as a low glass transition temperature (approximately 30-40℃), poor thermal stability (easily degraded by heat), and relatively low mechanical strength, which severely limit its application as a structural material.

[0003] To improve the performance of PPC, inorganic or organic fillers are often added for blending modification. Tea seed cake (also known as tea seed oil cake) is a byproduct of oil extraction from camellia seeds and is rich in natural components such as tea saponins, proteins, polysaccharides, and cellulose. my country produces a large amount of tea seed cake annually, currently mainly used as a pond clearing agent or low-grade fertilizer, resulting in low resource utilization. The tea saponins in tea seed cake have surface activity and can act as a natural compatibilizer; the cellulose component has a certain reinforcing effect. However, untreated tea seed cake is highly hydrophilic and has poor compatibility with the hydrophobic PPC matrix. Direct blending easily leads to agglomeration, affecting the performance of the composite material.

[0004] Currently, there are no reports on using modified tea seed cake to reinforce PPC composites. Developing a high-performance PPC composite material that can effectively improve the interfacial compatibility between tea seed cake and PPC and fully utilize the active ingredients of tea seed cake is of great significance for broadening the application fields of PPC and realizing the high-value utilization of tea seed cake. Summary of the Invention

[0005] This invention aims to overcome the shortcomings of existing technologies and provide a polypropylene carbonate composite material based on tea bran modification and its preparation method. It solves the problems of poor interfacial compatibility and uneven dispersion between tea bran and polypropylene carbonate, improves the mechanical properties, thermal stability, anti-aging properties and biodegradability of the composite material, and reduces costs, thereby realizing the resource utilization of agricultural waste.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] A polypropylene carbonate composite material based on tea seed cake modification, comprising, by weight: 5-30 parts modified tea seed cake, 70-95 parts polypropylene carbonate matrix, and 0-5 parts additives; wherein the modified tea seed cake is obtained by surface modification of the cake after oil extraction from camellia seeds, and the surface modification method is selected from at least one of alkali treatment, silane coupling agent treatment, and organic acid treatment.

[0008] Preferably, the modified tea seed cake has a particle size of 100-500 mesh, more preferably 200-300 mesh; the main components of the modified tea seed cake, by mass fraction, include 10-18% tea saponin, 12-20% protein, 15-25% polysaccharide, and 20-30% cellulose.

[0009] Preferably, the alkali treatment process is as follows: tea seed cake is placed in a 0.5-5wt% NaOH or KOH solution, soaked at 50-70℃ for 2-8 hours, washed until neutral, dried, pulverized and sieved; the preferred process is: soaked in a 2wt% NaOH solution at 60℃ for 4 hours, and vacuum dried at 80℃ for 12 hours.

[0010] Preferably, the process for treating with the silane coupling agent is as follows: the silane coupling agent is selected from at least one of γ-aminopropyltriethoxysilane, γ-glycidoxypropyltrimethoxysilane, and γ-methacryloyloxypropyltrimethoxysilane; based on the mass of tea seed cake, the amount of silane coupling agent is 2-10 wt%, and the mixture is reacted in an ethanol / water mixed solvent at a volume ratio of 8:1-9.5:1 at 50-80°C for 4-8 hours, followed by washing and drying; a preferred process is: 5 wt% γ-glycidoxypropyltrimethoxysilane, ethanol / water = 9:1, pH 4-5, reflux at 70°C for 6 hours, and vacuum drying at 80°C for 12 hours.

[0011] Preferably, the organic acid treatment process is as follows: the organic acid is selected from at least one of citric acid, tartaric acid, and maleic acid, and is prepared into a 1-10 wt% aqueous solution, soaked at 40-60℃ for 2-6 hours, washed until neutral, and dried; the preferred process is: 5 wt% citric acid solution, soaked at 50℃ for 3 hours, and dried at 80℃.

[0012] Preferably, the polypropylene carbonate matrix has a number average molecular weight of 50,000-200,000 Da and a molecular weight distribution of 1.5-3.0; preferably it is prepared by copolymerization of carbon dioxide and propylene oxide, and more preferably by polymerization using a supported zinc glutarate catalyst.

[0013] Preferably, the additives are selected from at least one of nucleating agents, heat stabilizers, plasticizers, antioxidants, and lubricants; the nucleating agents are talc, calcium carbonate, and montmorillonite; the heat stabilizers are zinc stearate, calcium stearate, and epoxidized soybean oil; the plasticizers are polyethylene glycol, tributyl citrate, and dioctyl phthalate; the antioxidants are antioxidant 1010, antioxidant 168, and vitamin E; and the lubricants are stearic acid, EBS, and paraffin wax.

[0014] This invention also provides a method for producing a polypropylene carbonate composite material based on tea seed cake modification, comprising the following steps:

[0015] Step 1: Pretreatment: Prepare the modified tea seed cake and dry it until the moisture content is ≤0.5%;

[0016] Step 2: Premix: Add modified tea seed cake, polypropylene carbonate matrix, and additives to a high-speed mixer and mix at 800-1500 r / min for 2-5 min to obtain a premix.

[0017] Step 3: Melt blending and extrusion: The premixed material is fed into a twin-screw extruder, melted, extruded, cooled, dried, and granulated;

[0018] Step 4: Post-processing: Selectively hot-press or injection-molde the granules to obtain the finished product.

[0019] Preferably, the parameters of the twin-screw extruder are: feeding speed 5-100 kg / h, screw speed 80-200 r / min, cooling temperature 30-60℃; zone temperatures: zone 1 140-150℃, zone 2 155-165℃, zone 3 165-175℃, zone 4 170-180℃, die head 165-175℃; preferred parameters: feeding speed 15 kg / h, screw speed 120 r / min, cooling water temperature 40℃, zone 1 145℃, zone 2 160℃, zone 3 170℃, zone 4 175℃, die head 170℃.

[0020] Preferably, the prepared polypropylene carbonate composite material is used in packaging materials, disposable tableware, agricultural films, biomedical materials, and sustained-release carriers; the packaging materials include packaging bags, cushioning pads, and food preservation boxes; disposable tableware includes lunch boxes, water cups, and straws; agricultural films include mulch films, greenhouse films, and seedling films; biomedical materials include tissue engineering scaffolds and surgical sutures; and sustained-release carriers include pesticide sustained-release granules, fertilizer sustained-release capsules, and drug sustained-release microspheres.

[0021] Compared with the prior art, the beneficial effects of the present invention are:

[0022] High-value utilization of waste: Using inexpensive tea seed cake as a filler reduces the cost of polypropylene carbonate by 30-50%, solves the problem of inefficient utilization of tea seed cake, and is green and environmentally friendly.

[0023] Excellent interfacial compatibility: The modification treatment eliminates the hydrophilicity of tea seed cake and forms a strong interfacial bond with polypropylene carbonate, resulting in uniform dispersion of the filler without agglomeration.

[0024] Overall performance improvement: Compared with pure polypropylene carbonate, tensile strength is increased by 15-44%, elastic modulus by 30-60%, impact strength by 50-82%, initial thermal decomposition temperature by 15-30℃, and processing temperature window is widened.

[0025] Excellent anti-aging and degradation properties: Tea saponins are natural antioxidants that delay aging; tea bran and polypropylene carbonate work together to degrade, and under composting conditions, they completely degrade in 6-12 months without residual pollution.

[0026] High process adaptability: The preparation process is simple, the parameters are easy to control, and it is compatible with existing twin-screw extrusion and injection molding equipment, making it easy to scale up production. Detailed Implementation

[0027] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0028] Preparation of modified tea seed cake: Alkali-modified tea seed cake: Tea seed cake is crushed and passed through a 200-mesh sieve. 100g is added to 500mL of 2wt% NaOH solution and stirred at 60℃ for 4h. After filtration, it is washed with deionized water until neutral and vacuum dried at 80℃ for 12h. After grinding and sieving, the moisture content is ≤0.5%.

[0029] Silane coupling agent modified tea seed cake: Take 50g of alkali-modified tea seed cake, disperse it in 500mL of ethanol / water (9:1) mixed solvent, and sonicate for 15min; add 2.5g of γ-glycidyl etheroxypropyltrimethoxysilane, adjust the pH to 4.5 with glacial acetic acid, and reflux at 70℃ under nitrogen protection for 6h; filter, wash 3 times with anhydrous ethanol, and vacuum dry at 80℃ for 12h.

[0030] Organic acid modified tea seed cake: Tea seed cake is crushed and passed through a 200-mesh sieve. 100g is added to 500mL of 5wt% citric acid solution and stirred at 50℃ for 3h. Filter, wash with water until neutral, and dry at 80℃.

[0031] Preparation of polypropylene carbonate composite materials

[0032] Raw materials: polypropylene carbonate (number average molecular weight 120,000 Da, molecular weight distribution 2.2), modified tea seed cake, and additives (zinc stearate 0.5 parts, antioxidant 1010 0.3 parts).

[0033] step:

[0034] Premix: Weigh the materials according to the formula and mix them in a high-speed mixer at 1200r / min for 3min.

[0035] Extrusion: Twin-screw extruder (length-to-diameter ratio 40:1) parameters: Zone 1 145℃, Zone 2 160℃, Zone 3 170℃, Zone 4 175℃, Die head 170℃; Screw speed 120r / min, Feeding speed 15kg / h; Strips are water-cooled, air-dried, and pelletized at 40℃.

[0036] Drying: The granules were vacuum dried at 80℃ for 4 hours.

[0037] Injection molding: Injection temperature 175℃, mold temperature 40℃, and standard test strips are prepared.

[0038] Test Standards

[0039] Mechanical properties: tensile strength according to GB / T 1040.2-2025, impact strength according to GB / T 1843-2008.

[0040] Thermal stability: Thermogravimetric analysis (TGA) was performed in an N2 atmosphere at a temperature increase of 10 °C / min, measuring the 5% weight loss temperature (Td,5%) and the maximum weight loss rate temperature (Tmax).

[0041] Degradability: Degradation rate was tested under composting conditions (58℃, 60% humidity) for 6 months.

[0042] Example 1

[0043] Alkali-modified tea seed cake was selected: Formula: 90 parts polypropylene carbonate, 10 parts alkali-modified tea seed cake, and 0.8 parts additives. Properties: Tensile strength 28.5 MPa, elongation at break 18.5%, impact strength 6.8 kJ / m², Td, 5% 268℃, Tmax 312℃, degradation rate 92% after 6 months.

[0044] Example 2

[0045] Silane-modified tea seed cake was selected: Formula: 90 parts polypropylene carbonate, 10 parts silane-modified tea seed cake, and 0.8 parts additives. Properties: Tensile strength 32.6 MPa, elongation at break 22.3%, impact strength 8.2 kJ / m², Td, 5% 275℃, Tmax 325℃, degradation rate 94% after 6 months.

[0046] Example 3

[0047] Organic acid-modified tea seed cake was selected: Formula: 85 parts polypropylene carbonate, 15 parts organic acid-modified tea seed cake, and 0.8 parts additives. Properties: Tensile strength 29.2 MPa, elongation at break 16.8%, impact strength 7.1 kJ / m², Td, 5% 272℃, Tmax 318℃, 95% degradation rate after 6 months.

[0048] Comparative Example 1

[0049] Unmodified tea seed cake was selected: Formula: 90 parts polypropylene carbonate, 10 parts unmodified tea seed cake, and 0.8 parts additives. Properties: Tensile strength 20.1 MPa, impact strength 4.2 kJ / m², Td, 5% at 252℃.

[0050] Comparative Example 2

[0051] Without tea seed cake: Formula: 100 parts polypropylene carbonate, 0.8 parts additives. Properties: Tensile strength 22.6 MPa, impact strength 4.5 kJ / m², Td, 5% at 245℃.

[0052] The comparison shows that unmodified tea seed cake leads to performance degradation in composite materials; silane modification has the best effect, with chemical bonding strengthening the interface; alkali modification is simple and low-cost; and organic acid modification has the best degradation resistance. This invention realizes the high-value utilization of tea seed cake, significantly improves the overall performance of polypropylene carbonate, and is suitable for applications in multiple fields.

[0053] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A polypropylene carbonate composite material based on tea seed cake modification, characterized in that, By weight, it includes: 5-30 parts modified tea seed cake, 70-95 parts polypropylene carbonate matrix, and 0-5 parts additives; the modified tea seed cake is obtained by surface modification of the cake after pressing oil from camellia seeds, and the surface modification method is selected from at least one of alkali treatment, silane coupling agent treatment, and organic acid treatment.

2. The polypropylene carbonate composite material based on tea seed cake modification according to claim 1, characterized in that, The modified tea seed cake has a particle size of 100-500 mesh, preferably 200-300 mesh; the main components of the modified tea seed cake, by mass fraction, include 10-18% tea saponin, 12-20% protein, 15-25% polysaccharide, and 20-30% cellulose.

3. The polypropylene carbonate composite material based on tea seed cake modification according to claim 1, characterized in that, The alkali treatment process is as follows: place tea seed cake in a 0.5-5wt% NaOH or KOH solution, soak at 50-70℃ for 2-8 hours, wash until neutral, dry, pulverize and sieve; the preferred process is: soak in a 2wt% NaOH solution at 60℃ for 4 hours, and vacuum dry at 80℃ for 12 hours.

4. The polypropylene carbonate composite material based on tea seed cake modification according to claim 1, characterized in that, The process for treating with the silane coupling agent is as follows: the silane coupling agent is selected from at least one of γ-aminopropyltriethoxysilane, γ-glycidoxypropyltrimethoxysilane, and γ-methacryloyloxypropyltrimethoxysilane; based on the mass of tea seed cake, the amount of silane coupling agent is 2-10 wt%, and the mixture is reacted in an ethanol / water mixed solvent at a volume ratio of 8:1-9.5:1 at 50-80℃ for 4-8 hours, followed by washing and drying; the preferred process is: 5 wt% γ-glycidoxypropyltrimethoxysilane, ethanol / water = 9:1, pH 4-5, reflux at 70℃ for 6 hours, and vacuum drying at 80℃ for 12 hours.

5. The polypropylene carbonate composite material based on tea seed cake modification according to claim 1, characterized in that, The organic acid treatment process is as follows: the organic acid is selected from at least one of citric acid, tartaric acid, and maleic acid, and is prepared into a 1-10 wt% aqueous solution, soaked at 40-60℃ for 2-6 hours, washed until neutral, and dried; the preferred process is: 5 wt% citric acid solution, soaked at 50℃ for 3 hours, and dried at 80℃.

6. The polypropylene carbonate composite material based on tea seed cake modification according to claim 1, characterized in that, The polypropylene carbonate matrix has a number average molecular weight of 50,000-200,000 Da and a molecular weight distribution of 1.5-3.0; it is preferably prepared by copolymerization of carbon dioxide and propylene oxide, and more preferably by polymerization using a supported zinc glutarate catalyst.

7. The polypropylene carbonate composite material based on tea seed cake modification according to claim 1, characterized in that, The additives are selected from at least one of nucleating agents, heat stabilizers, plasticizers, antioxidants, and lubricants; the nucleating agents are talc, calcium carbonate, and montmorillonite; the heat stabilizers are zinc stearate, calcium stearate, and epoxidized soybean oil; the plasticizers are polyethylene glycol, tributyl citrate, and dioctyl phthalate; the antioxidants are antioxidant 1010, antioxidant 168, and vitamin E; and the lubricants are stearic acid, EBS, and paraffin wax.

8. A method for preparing the polypropylene carbonate composite material based on tea seed cake modification as described in any one of claims 1-7, characterized in that, Includes the following steps: Step 1: Pretreatment: Prepare the modified tea seed cake and dry it until the moisture content is ≤0.5%; Step 2: Premix: Add modified tea seed cake, polypropylene carbonate matrix, and additives to a high-speed mixer and mix at 800-1500 r / min for 2-5 min to obtain a premix. Step 3: Melt blending and extrusion: The premixed material is fed into a twin-screw extruder, melted, extruded, cooled, dried, and granulated; Step 4: Post-processing: Selectively hot-press or injection-molde the granules to obtain the finished product.

9. The method for preparing a polypropylene carbonate composite material based on tea seed cake modification according to claim 8, characterized in that, The parameters of the twin-screw extruder are as follows: feed rate 5-100 kg / h, screw speed 80-200 r / min, cooling temperature 30-60℃; zone temperatures: zone 1 140-150℃, zone 2 155-165℃, zone 3 165-175℃, zone 4 170-180℃, die head 165-175℃; preferred parameters: feed rate 15 kg / h, screw speed 120 r / min, cooling water temperature 40℃, zone 1 145℃, zone 2 160℃, zone 3 170℃, zone 4 175℃, die head 170℃.

10. The method for preparing a polypropylene carbonate composite material based on tea seed cake modification according to claim 8, characterized in that, The prepared polypropylene carbonate composite material is used in packaging materials, disposable tableware, agricultural films, biomedical materials, and sustained-release carriers; the packaging materials include packaging bags, cushioning pads, and food preservation boxes; disposable tableware includes lunch boxes, water cups, and straws; agricultural films include mulch films, greenhouse films, and seedling films; biomedical materials include tissue engineering scaffolds and surgical sutures; and sustained-release carriers include pesticide sustained-release granules, fertilizer sustained-release capsules, and drug sustained-release microspheres.