Catering box based on Yellow River sediment framework and water-based TPU micro-foaming / composite PBS coating

Abstract

The invention discloses an environment-friendly catering box based on a Yellow River sediment framework and a water-based TPU micro-foaming / composite PBS coating and a preparation method of the environment-friendly catering box, and belongs to the technical field of food packaging materials. The waste Yellow River silt is used as a framework material, grass fibers, a binder and a foaming agent are supplemented, a base is prepared by adopting a water-based TPU micro-foaming technology, then a mixed solvent solution of polybutylene succinate (PBS) is sprayed to the surface of the base by adopting a flash evaporation method, and the base and the base are rolled and compounded to prepare the sheet. The mixed solvent is formed by mixing dichloromethane, trichloromethane and PBS (Phosphate Buffer Solution); after the solution is sprayed at high temperature and high pressure, the solvent is instantly gasified and condensed and recycled, so that a compact PBS composite layer without solvent residues is formed. According to the method, the potential safety hazard of food caused by organic solvent residues is thoroughly solved, recycling of the solvent is achieved, and the prepared catering box is low in cost, safe, environmentally friendly and excellent in heat resistance, mechanical strength and biodegradability and meets the national food packaging material standard.

Description

Technical Field

[0001] This invention relates to the field of disposable catering packaging materials technology, specifically to an environmentally friendly catering box and its preparation method that uses Yellow River silt as a skeleton material and combines water-based TPU micro-foaming technology with PBS composite coating process. Background Technology

[0002] The market demand for disposable food containers and packaging boxes is huge, but current mainstream products suffer from problems such as poor temperature resistance, easy generation of microplastics, high cost, or incomplete degradation. Although some research is dedicated to using biodegradable materials, such as polylactic acid (PLA) or polybutylene succinate (PBS), the cost of raw materials still restricts their large-scale application. On the other hand, the resource utilization of Yellow River sediment, as a large amount of waste, is an important environmental protection issue.

[0003] In existing technologies, solution coating is a common method for preparing polymer coatings, but it often faces food safety risks and environmental pollution problems due to residual organic solvents. Conventional drying processes are difficult to completely remove residual solvents. For example, although patent application No. 202410493714.4, "A Method for Preparing Waterproof Lignocellulose / PVA / PBTA Material," uses a two-layer composite technology, it still has shortcomings in terms of substrate performance and cost control, and it does not solve the problem of solvent residue and recycling in the coating process.

[0004] Therefore, developing a disposable food container manufacturing technology that combines cost advantages, environmental value, safety and reliability, and can completely solve the problem of solvent residue is of great practical significance. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and provide a low-cost, safe, environmentally friendly, and solvent-free food container and its preparation method.

[0006] This invention first protects an environmentally friendly catering box based on the Yellow River sediment skeleton and water-based TPU micro-foaming / composite PBS coating, characterized in that it consists of a base layer and a PBS composite layer composited on at least one surface of the base layer;

[0007] The base layer is made of the following components in parts by weight: 20-35 parts Yellow River silt, 5-10 parts grass fiber, 30-60 parts water-based TPU (solid content: 50%), 15-30 parts deionized water, 3-5 parts foaming agent, and 2-4 parts adhesive.

[0008] The PBS composite layer is made of the following components in parts by weight: 10-25 parts PBS, 30-60 parts dichloromethane, and 15-60 parts trichloromethane.

[0009] Furthermore, the Yellow River sediment has a particle size of 5-60 μm, and its heavy metal lead content is ≤5 mg / kg and cadmium content is ≤0.5 mg / kg.

[0010] Furthermore, the grass fiber is any one or more of rice straw fiber, weed fiber, or wood fiber; the foaming agent is any one or more of coconut oil fatty acid diethanolamide, ethoxytridecyl alcohol condensate, or potassium dodecyl phosphate.

[0011] Furthermore, the binder is any one or both of sodium polyacrylate or β-cyclodextrin.

[0012] This invention also protects the method for preparing the environmentally friendly food box, characterized by comprising the following steps:

[0013] (1) Mixing of base materials: Water-based TPU, foaming agent, binder, deionized water, grass fiber, and Yellow River silt that has been cleaned and dried are placed in a mixer in proportion and mixed evenly.

[0014] (2) High-pressure foaming: Transfer the mixture into an airless high-pressure foaming machine and pressurize it to 12-16 MPa for later use;

[0015] (3) Base forming: Open the nozzle of the foaming machine and spray the material onto the rotating drum receiver with a heating device that is preheated to 80±2℃ to form a nascent base sheet;

[0016] (4) Thickness control: The formed sheet is introduced between the calendering rollers and then onto the traction device. The thickness of the sheet is controlled by adjusting the rotation speed of the drum and the amount of foaming machine sprayed.

[0017] (5) PBS coating flash coating: A PBS flash coating system is set up between the drum and the calender. PBS is dissolved in a mixed solvent of dichloromethane and trichloromethane to prepare a coating solution, wherein the weight ratio of dichloromethane, trichloromethane and PBS is 6:3:1 to 3:6:2. The solution is heated to 130-145°C in a pressure tank, and the system pressure is automatically increased to 1.5-2.5 MPa. The solution is then sprayed onto the substrate sheet through an atomizing nozzle. The mixed solvent is flash vaporized instantaneously under normal pressure and recovered and reused by the condensation system. The PBS forms a composite coating on the surface of the substrate. The coating is then firmly bonded to the substrate through calendering.

[0018] (6) Drying and winding: The composite sheet is dried through a tunnel dryer at a temperature of 60-80℃, and finally rolled into the product base sheet by a winding device;

[0019] (7) Product forming: Cut the sheet into appropriate size and place it on a vacuum forming machine or molding machine to form a catering box.

[0020] The present invention also provides a dedicated equipment system for implementing the PBS coating flash evaporation composite step in the above method, comprising: a heating pressure tank for storing and heating pressurized PBS solution; an atomizing nozzle connected to the heating pressure tank; a solvent gas collection hood disposed near the atomizing nozzle; and a condensation recovery device connected to the collection hood.

[0021] The present invention also protects the use of the environmentally friendly food box or the environmentally friendly food box made by the method in containing takeaway food, catering dishes or pastries at a temperature not exceeding 100°C.

[0022] The key innovations and beneficial effects of this invention are as follows:

[0023] Waste utilization and cost control: By using waste Yellow River silt as the main skeleton material, the cost of raw materials has been reduced, and high-value utilization of solid waste has been achieved.

[0024] Unique formulation and flash evaporation process: By combining a specific ratio of dichloromethane, trichloromethane, and PBS (6:3:1 to 3:6:2) with a flash evaporation process, the organic solvent can be instantly removed and efficiently recovered (recovery rate ≥95%), ensuring extremely low solvent residue in the final product (dichloromethane <0.01 mg / dm³). 2 chloroform <0.005 mg / dm³ 2 The levels are far below the national standard limits, fundamentally solving the problems of food safety and environmental pollution.

[0025] Excellent performance: The water-based TPU microfoam base gives the product good mechanical strength and lightweight properties, while the PBS inner layer provides excellent heat resistance (safe for holding hot food below 100°C) and biodegradability. Detailed Implementation

[0026] Example 1

[0027] The Yellow River sediment used in this embodiment was taken from the Yellow River sediment accumulation site in Gaoqing, Shandong Province. Its main physicochemical properties are as follows:

[0028] Appearance: Yellowish-gray powder;

[0029] Particle size distribution: D50 is 25μm, and more than 90% of the particles are between 5-60μm;

[0030] Moisture content: <1.5%;

[0031] Heavy metal content: lead (Pb) 3.2 mg / kg, cadmium (Cd) 0.3 mg / kg.

[0032] Example 1

[0033] Yellow River sediment: 20 samples

[0034] Grass fiber: 10 parts (using rice straw fiber)

[0035] Water-based TPU: 46 parts

[0036] Deionized water: 17 parts

[0037] Foaming agent: 4 parts (using coconut oil fatty acid diethanolamide)

[0038] Adhesive: 3 parts (using sodium polyacrylate)

[0039] PBS composite layer composition (by weight):

[0040] PBS: 10 copies

[0041] Dichloromethane: 60 parts

[0042] chloroform: 30 parts

[0043] Feed ratio: dichloromethane: chloroform: PBS = 6:3:1

[0044] Preparation method steps and key process parameters:

[0045] Mixing of base materials: Place water-based TPU, foaming agent, binder, deionized water, grass fiber and Yellow River silt that has been cleaned and dried into a mixer according to the above weight proportions, and mix evenly.

[0046] High-pressure foaming: Transfer the mixture into an airless high-pressure foaming machine and pressurize it to 14MPa for later use.

[0047] Cartridge forming: Open the nozzle of the foaming machine and spray the material onto the rotating drum receiver with a heating device that is preheated to 80°C to form a nascent cartridge sheet.

[0048] Thickness control: The sheet is introduced between the two calendering rollers, and the sheet thickness is controlled to 0.5mm by adjusting the rotation speed of the drum and the amount of foaming machine sprayed.

[0049] PBS-coated flash composite:

[0050] Dissolve PBS in a mixed solvent of dichloromethane and trichloromethane to prepare a spraying solution (feed ratio 6:3:1).

[0051] The solution is heated to 130°C in a sealed autoclave, and the pressure naturally rises to 1.6 MPa. It is then sprayed onto the tire base sheet through an atomizing nozzle.

[0052] The mixed solvent is instantaneously flash vaporized and recovered by the condensation system (recovery rate ≥95%), and PBS forms a composite coating on the substrate surface.

[0053] The coating is firmly bonded to the substrate through calendering.

[0054] Drying and winding: The composite sheet is dried in a tunnel dryer at a temperature of 70°C, and finally rolled into a product base sheet by a winding device.

[0055] Product forming: Cut the sheet material into appropriate sizes and place it in a vacuum forming machine to form a food box.

[0056] Example 2

[0057] Characteristics of Yellow River sediment:

[0058] Source: Yellow River sediment accumulation site in Zhengzhou, Henan

[0059] Appearance: Grayish-brown powder

[0060] Particle size distribution: D50 is 30μm, and more than 90% of the particles are between 10-55μm.

[0061] Moisture content: <1.8%

[0062] Heavy metal content: Lead (Pb) 4.0 mg / kg, Cadmium (Cd) 0.4 mg / kg. Tire base composition (parts by weight):

[0063] Yellow River sediment: 25 parts; grass fiber: 5 parts (using weed fiber)

[0064] Water-based TPU: 40 parts; Deionized water: 23 parts; Foaming agent: 3.5 parts (using ethoxytridecyl condensate).

[0065] Binder: 2.5 parts (using β-cyclodextrin)

[0066] PBS composite layer composition (by weight):

[0067] PBS: 12 copies

[0068] Dichloromethane: 48 parts; Trichloromethane: 40 parts; Feed ratio: Dichloromethane: Trichloromethane: PBS = 12:10:3.

[0069] Preparation method steps and key process parameters:

[0070] Mixing of tire base materials: Follow the steps in Example 1 above, and mix evenly according to the weight proportions. High-pressure foaming: Pressurize to 13 MPa for later use.

[0071] Tire base forming: The drum is preheated to 78°C to form a new tire base sheet.

[0072] Thickness control: Control the thickness of the sheet to 0.6mm.

[0073] PBS-coated flash composite:

[0074] The ratio of the spraying solution to the feed material is 12:10:3.

[0075] Heat to 145℃ and pressurize to 1.8MPa for spraying.

[0076] Solvent recovery rate ≥95%.

[0077] Drying and winding: The drying temperature is 65℃.

[0078] Product molding: Place it in a molding machine to form a food box.

[0079] Example 3

[0080] Characteristics of Yellow River sediment:

[0081] Source: Yellow River sediment accumulation site in Weinan, Shaanxi Province. Appearance: Light yellow powder. Particle size distribution: D50 is 20μm, with over 90% of particles between 5-50μm. Moisture content: <1.6%.

[0082] Heavy metal content: Lead (Pb) 2.8 mg / kg, Cadmium (Cd) 0.2 mg / kg. Tire base composition (parts by weight):

[0083] Yellow River sediment: 20 parts; grass fiber: 8 parts (using wood fiber)

[0084] Water-based TPU: 40 parts; Deionized water: 24 parts; Foaming agent: 4.5 parts (using potassium dodecyl phosphate).

[0085] Adhesive: 3.5 parts (using sodium polyacrylate)

[0086] PBS composite layer composition (by weight):

[0087] PBS: 20 copies

[0088] Dichloromethane: 35 parts; Trichloromethane: 45 parts; Feed ratio: Dichloromethane: Trichloromethane: PBS = 7:9:4.

[0089] Preparation method steps and key process parameters:

[0090] Mixing of tire base materials: Follow the steps in Example 1 above, and mix evenly according to the weight proportions. High-pressure foaming: Pressurize to 15 MPa for later use.

[0091] Tire base forming: The drum is preheated to 80°C to form a nascent tire base sheet.

[0092] Thickness control: Control the thickness of the sheet to 0.4 mm.

[0093] PBS-coated flash composite:

[0094] The ratio of the spraying solution to the feed material is 7:9:4.

[0095] Heat to 145℃ and pressurize to 2.0MPa for spraying.

[0096] Solvent recovery rate ≥95%.

[0097] Drying and winding: The drying temperature is 75℃.

[0098] Product forming: Place it in a vacuum forming machine to form a food container.

[0099] Example 4

[0100] Characteristics of Yellow River sediment:

[0101] Source: Yellow River sediment accumulation site in Yuncheng, Shanxi Province. Appearance: Dark gray powder. Particle size distribution: D50 is 40μm, with over 90% of particles ranging from 15-60μm.

[0102] Moisture content: <2.0%

[0103] Heavy metal content: Lead (Pb) 4.5 mg / kg, Cadmium (Cd) 0.45 mg / kg

[0104] Tire base layer composition (parts by weight):

[0105] Yellow River sediment: 24 parts; grass fiber: 10 parts (using a mixture of rice straw fiber and wood fiber)

[0106] Water-based TPU: 38 parts; Deionized water: 30 parts; Foaming agent: 4 parts (using potassium dodecyl phosphate)

[0107] Adhesive: 4 parts (using sodium polyacrylate)

[0108] PBS composite layer composition (by weight):

[0109] PBS: 15 copies

[0110] Dichloromethane: 50 parts; Trichloromethane: 25 parts; Feed ratio: Dichloromethane: Trichloromethane: PBS = 10:5:3.

[0111] Preparation method steps and key process parameters:

[0112] Mixing of tire base materials: Follow the steps in Example 1 above, and mix evenly according to the weight parts.

[0113] High-pressure foaming: pressurize to 16MPa for later use.

[0114] Tire base forming: The drum is preheated to 80°C to form a nascent tire base sheet.

[0115] Thickness control: Control the thickness of the sheet to 0.7mm.

[0116] PBS-coated flash composite:

[0117] The ratio of the spraying solution to the powder is 10:5:3.

[0118] Heat to 140℃, increase pressure to 2.3MPa, and spray.

[0119] Solvent recovery rate ≥95%.

[0120] Drying and winding: The drying temperature is 80℃.

[0121] Product molding: Place it in a molding machine to form a food box.

[0122] The above description is merely 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 catering box based on the Yellow River sediment skeleton and water-based TPU micro-foaming / composite PBS coating, characterized in that: It consists of a base layer and a PBS composite layer laminated on at least one surface of the base layer; The base layer is made of the following components in parts by weight: 20-35 parts Yellow River silt, 5-10 parts grass fiber, 30-60 parts water-based TPU (solid content: 50%), 15-30 parts deionized water, 3-5 parts foaming agent, and 2-4 parts adhesive. The PBS composite layer is made of the following components in parts by weight: 10-25 parts PBS, 30-60 parts dichloromethane, and 15-60 parts trichloromethane.

2. The catering box based on the Yellow River sediment skeleton and water-based TPU micro-foaming / composite PBS coating according to claim 1, characterized in that, The Yellow River sediment has a particle size of 5-60 μm and a lead content of ≤5 mg / kg and a cadmium content of ≤0.5 mg / kg.

3. A catering box based on the Yellow River sediment skeleton and water-based TPU micro-foaming / composite PBS coating according to claim 1, characterized in that, The grass fiber is any one or more of rice straw fiber, weed fiber, or wood fiber; the foaming agent is any one or more of coconut oil fatty acid diethanolamide, ethoxytridecyl alcohol condensate, or potassium dodecyl phosphate.

4. A catering box based on the Yellow River sediment skeleton and water-based TPU micro-foaming / composite PBS coating according to claim 1, characterized in that, The binder is any one or both of sodium polyacrylate or β-cyclodextrin.

5. A method for preparing a catering box based on a Yellow River sediment skeleton and a water-based TPU microfoaming / composite PBS coating as described in any one of claims 1-4, characterized in that, Includes the following steps: (1) Mixing of base materials: Water-based TPU, foaming agent, binder, deionized water, grass fiber, and Yellow River silt that has been cleaned and dried are placed in a mixer in proportion and mixed evenly. (2) High-pressure foaming: Transfer the mixture into an airless high-pressure foaming machine and pressurize it to 12-16 MPa for later use; (3) Base forming: Open the nozzle of the foaming machine and spray the material onto the rotating drum receiver with a heating device that is preheated to 80±2℃ to form a nascent base sheet; (4) Thickness control: The formed sheet is introduced between the two rollers of the calender and then introduced onto the traction device. The thickness of the sheet is controlled by adjusting the rotation speed of the drum and the amount of foaming machine sprayed. (5) PBS coating flash coating: A PBS flash coating system is set up between the drum and the calender. PBS is dissolved in a high-pressure mixed solvent of dichloromethane and trichloromethane to prepare a coating solution, wherein the weight ratio of dichloromethane, trichloromethane and PBS is 6:3:1-3:6:

2. The solution is heated to 130-145°C in the system, and the system pressure naturally rises to 1.5-2.5 MPa. Then, the solution is sprayed onto the substrate sheet through an atomizing nozzle. The mixed solvent is flash vaporized instantaneously under normal pressure and recovered and reused by the condensation system. The PBS forms a composite coating on the surface of the substrate. Subsequently, the coating is firmly bonded to the substrate through calendering. (6) Drying and winding: The composite sheet is dried through a tunnel dryer at a temperature of 60-80℃, and finally rolled into the product base sheet by a winding device; (7) Product forming: Cut the sheet into appropriate size and place it on a vacuum forming machine or molding machine to form a catering box.