An integral foam core EPP molding process

Abstract

The present invention discloses an integral foam core EPP molding process, comprising the following operating steps: S1, raw material selection and pretreatment, raw material selection: selecting EPP particles that meet the requirements, with a particle diameter range of 1.5 mm to 4.0 mm and a density of 25 kg / m 3 Up to 60kg / m 3 The present invention uses magnetic and electrostatic separation technology, combined with magnetic separation to remove metal impurities in the raw materials, ensure the purity of EPP particles, and avoid mutual adsorption between particles through electrostatic elimination, so that the particles maintain consistency and fluidity during transportation and processing, and comprehensively improve the purity and consistency of the raw materials. These impurities can be eliminated through magnetic separation to ensure uniform foaming of the foam. Electrostatic elimination maintains good fluidity of the particles during processing, avoids uneven flow of particles caused by electrostatic adsorption, thereby ensuring uniformity during melt extrusion, improving foam quality and foaming control effect, reducing equipment wear and improving production efficiency, and having a good comprehensive molding effect.

Description

Technical Field

[0001] The invention belongs to the technical field of EPP molding, and in particular relates to an integral foam core EPP molding process. Background Art

[0002] The integral foam core EPP (Expandable Polypropylene) molding process is a process that transforms expanded polypropylene particles into lightweight, high-strength, heat-resistant and impact-resistant foam core materials through heat treatment, molding and curing. This process is widely used in the automotive, construction, packaging and other fields.

[0003] The integral foam core EPP molding process in the prior art lacks a strong and effective metal impurity removal effect in actual principle processing due to the presence of a certain amount of metal impurities and static electricity in the raw materials in the current process, and the residual static electricity of the material is large. In particular, ferromagnetic impurities may cause wear, blockage or damage to the extruder and the mold. Magnetic impurities may cause uneven foaming of EPP particles, unstable density or decreased foam strength. On the other hand, static charge may cause mutual attraction between particles, making the particles easy to aggregate or agglomerate, affecting the fluidity and uniformity of the raw materials. In the production process of EPP foam, particle aggregation may lead to uneven melt extrusion and even affect the foaming quality of the foam, which comprehensively affects the actual molding quality and effect. Summary of the invention

[0004] In view of the shortcomings of the prior art, the present invention provides an integral foam core EPP molding process. To achieve the above-mentioned purpose, the present invention provides the following technical solutions: an integral foam core EPP molding process, comprising the following operating steps:

[0005] S1. Raw material selection and pretreatment

[0006] Raw material selection: Select EPP particles that meet the requirements, with a particle diameter range of 1.5mm to 4.0mm and a density of 25kg / m 3 Up to 60kg / m 3 ;

[0007] Pretreatment: Clean the raw materials and remove impurities through magnetic and electrostatic separation technology;

[0008] Particle screening and drying: Use a vibrating screen to screen the EPP particles, and use a dryer to dry the particles to a moisture content of less than 0.1%;

[0009] S2. Melt extrusion and foaming treatment

[0010] Extruder settings: In the melt extruder, the dried EPP pellets are heated to the set temperature, the screw is used to accelerate the melting, and the extrusion pressure and speed are adjusted;

[0011] Gas injection: During the melt extrusion process, fine air is injected. The pressure of the injected gas is 0.8-1.2MPa, and the flow rate is controlled at 10-20L / min;

[0012] Bubble refinement: The bubbles are further refined through the bubble refinement module;

[0013] S3, mold injection and molding process

[0014] Mould design: Design a multi-cavity mould and set up multiple independent pressure regulating systems in the mould to ensure uniform foam expansion in each cavity;

[0015] Injection process: The molten and foamed EPP material is injected into the mold through the injection port. The injection pressure is set at 10-15MPa and the injection speed is controlled at 0.5-1.0m / s.

[0016] Molding and foaming: In the mold, the foam material gradually expands under controlled air pressure and temperature to form the initial shape of the product;

[0017] S4, cooling and solidification

[0018] Cooling control: A water cooling system is installed in the mold, the cooling water temperature is maintained at 25℃-35℃, and the cooling time is controlled at 5-10 minutes;

[0019] Mold cavity pressure: Maintain the air pressure in the cavity at 1-3MPa;

[0020] Stability test: After cooling, the foam core needs to be tested for size and shape to ensure that the product meets the design requirements;

[0021] S5. Product quality inspection and post-processing

[0022] Quality inspection: density and strength testing, as well as compressive strength and impact resistance testing;

[0023] Appearance and size inspection: Use a three-coordinate measuring machine to ensure the dimensional accuracy of the foam core;

[0024] Trimming and packaging: Trim the formed foam core to remove edge burrs or irregular parts, classify qualified products according to specifications, carry out moisture-proof and pressure-proof packaging, and send them to the warehouse for storage.

[0025] Preferably, in S1, the magnetic separation equipment is a high-intensity permanent magnetic separator with a magnetic field strength of 1000-12000 Gauss. When the particles pass through the separation equipment, the ferromagnetic impurities are attracted to the magnetic separation area by the magnetic field, and the pure EPP particles continue to flow into the subsequent processing flow.

[0026] Preferably, in S1, a high-voltage static eliminator is used to transmit the EPP particles through a conductive belt to eliminate the surface charge of the particles. The voltage of the high-voltage static eliminator is set to 5-15kV, and the air flow rate of the eliminator is controlled to be 5-10m 3 / min.

[0027] Preferably, in S2, the extruder pressure is set to 15-25 MPa, the screw speed is 80-150 rpm, the set temperature is 190°C-220°C, and a twin-screw extruder is used for melt extrusion. The specific temperature control is: feed section: 130-160°C, melting section: 180-220°C, and discharge section: 190-230°C.

[0028] Preferably, in S2, a static mixer and a microbubble refinement device are used to refine the large bubbles formed in the foaming process. After the gas is injected into the molten material, the bubble refinement module quickly shears the bubbles into tiny bubbles through a specially designed spiral shape and stirring structure. The refinement air is one or any one of nitrogen and carbon dioxide gases.

[0029] Preferably, in S2, an electronic flow control system is used to monitor and adjust the gas flow in real time, a gas regulating valve is used to ensure that the gas injection pressure is stable in the range of 0.8-1.2 MPa, and multiple gas injection ports are set at the discharge port or the front end of the melting zone of the extruder.

[0030] Preferably, in S3, a multi-cavity mold is used, each cavity is equipped with an independent air pressure regulating system, and the mold is made of high thermal conductivity material; a pressure sensor is set in each cavity in the mold to accurately control the pressure of the gas in the cavity, and the pressure adjustment range is 1-3MPa. Each cavity is equipped with an independent cooling water channel, and the temperature of each cavity is accurately regulated by a temperature sensor to maintain it between 40°C and 60°C.

[0031] Preferably, in S4, the gas injection flow rate and pressure sensor feedback are adjusted to finely adjust the air pressure in each cavity to ensure uniform foaming.

[0032] Preferably, in S4, a high-efficiency cooling liquid is used, and the cooling system can adjust the water flow and temperature in real time, and the cooling water flow is controlled to be 10-15 L / min.

[0033] Preferably, in S5, the dimensional error of the product is controlled within ±0.5 mm, and the density of the foam core is measured using a densitometer, and the density range is maintained at 25-50 kg / m 3 .

[0034] Compared with the prior art, the present invention has the following beneficial effects:

[0035] 1. The present invention uses magnetic and electrostatic separation technology, combined with magnetic separation to remove metal impurities in the raw materials, ensure the purity of the EPP particles, and avoid mutual adsorption between particles through electrostatic elimination, so that the particles maintain consistency and fluidity during transportation and processing, and comprehensively improve the purity and consistency of the raw materials. These impurities can be eliminated through magnetic separation to ensure uniform foaming of the foam. Static elimination maintains good fluidity of the particles during processing, avoids uneven flow of particles caused by electrostatic adsorption, thereby ensuring uniformity during melt extrusion, and cooperates to improve foam quality and foaming control effect, and reduces equipment wear while also improving production efficiency, with a good comprehensive molding effect.

[0036] 2. The present invention can efficiently refine large bubbles in the foaming process through the bubble refinement module, as well as the designed spiral shape and stirring structure, to ensure uniform distribution of bubbles and improve the quality and stability of the foam. The precise control of gas injection (pressure, flow rate, injection port setting, etc.) further ensures the controllability and uniformity of the foaming effect and improves the molding quality. DETAILED DESCRIPTION

[0037] Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in the field without making any creative work shall fall within the scope of protection of the present invention.

[0038] The invention provides a technical solution: an integral foam core EPP molding process.

[0039] The steps include:

[0040] S1. Raw material selection and pretreatment

[0041] Raw material selection: Select EPP particles that meet the requirements, with a particle diameter range of 1.5mm to 4.0mm and a density of 25kg / m 3 Up to 60kg / m 3 ;

[0042] Pretreatment: Clean the raw materials and remove impurities through magnetic and electrostatic separation technology;

[0043] Particle screening and drying: Use a vibrating screen to screen the EPP particles, and use a dryer to dry the particles to a moisture content of less than 0.1%;

[0044] S2. Melt extrusion and foaming treatment

[0045] Extruder settings: In the melt extruder, the dried EPP pellets are heated to the set temperature, the screw is used to accelerate the melting, and the extrusion pressure and speed are adjusted;

[0046] Gas injection: During the melt extrusion process, fine air is injected. The pressure of the injected gas is 0.8-1.2MPa, and the flow rate is controlled at 10-20L / min;

[0047] Bubble refinement: The bubbles are further refined through the bubble refinement module;

[0048] S3, mold injection and molding process

[0049] Mould design: Design a multi-cavity mould and set up multiple independent pressure regulating systems in the mould to ensure uniform foam expansion in each cavity;

[0050] Injection process: The molten and foamed EPP material is injected into the mold through the injection port. The injection pressure is set at 10-15MPa and the injection speed is controlled at 0.5-1.0m / s.

[0051] Molding and foaming: In the mold, the foam material gradually expands under controlled air pressure and temperature to form the initial shape of the product;

[0052] S4, cooling and solidification

[0053] Cooling control: A water cooling system is installed in the mold, the cooling water temperature is maintained at 25℃-35℃, and the cooling time is controlled at 5-10 minutes;

[0054] Mold cavity pressure: Maintain the air pressure in the cavity at 1-3MPa;

[0055] Stability test: After cooling, the foam core needs to be tested for size and shape to ensure that the product meets the design requirements;

[0056] S5. Product quality inspection and post-processing

[0057] Quality inspection: density and strength testing, as well as compressive strength and impact resistance testing;

[0058] Appearance and size inspection: Use a three-coordinate measuring machine to ensure the dimensional accuracy of the foam core;

[0059] Trimming and packaging: Trim the formed foam core to remove edge burrs or irregular parts, classify qualified products according to specifications, carry out moisture-proof and pressure-proof packaging, and send them to the warehouse for storage.

[0060] Among them, the magnetic separation equipment is a high-intensity permanent magnetic separator with a magnetic field strength of 1000-12000 Gauss. When the particles pass through the sorting equipment, the ferromagnetic impurities are attracted to the magnetic separation area by the magnetic field, and the pure EPP particles continue to flow into the subsequent processing process. A high-voltage static eliminator is used to transmit the EPP particles through a conductive belt to eliminate the surface charge of the particles. The voltage of the high-voltage static eliminator is set to 5-15kV, and the air flow rate of the eliminator is controlled to be 5-10m3 / min.

[0061] Impurities are effectively removed by magnetic separation equipment to ensure that the EPP particles entering the next step of processing are free of ferromagnetic contamination. If ferromagnetic impurities are not removed, they may cause problems under heating, shearing and extrusion pressure during the extrusion and foaming process, such as equipment damage, uneven particles, etc., thereby improving the purity of raw materials after magnetic separation. Ferromagnetic impurities may cause wear, blockage or damage to the extruder and mold. Therefore, magnetic separation helps to reduce equipment maintenance costs and improve equipment stability. On the other hand, removing these impurities through magnetic separation ensures the uniformity of the foam, structural stability and the accuracy of subsequent molding.

[0062] Static electricity elimination: The static electricity that may be on the surface of EPP particles is eliminated by a high-voltage static eliminator. When the particles are transported through the conductive belt, the high-voltage static eliminator will use the electric field principle to neutralize the charge on the surface of the particles, thereby eliminating static electricity.

[0063] Since static charge will cause mutual attraction between particles, particles are prone to aggregation or agglomeration, which will affect the fluidity and uniformity of raw materials. In the production process of EPP foam, particle aggregation will lead to uneven melt extrusion and even affect the foaming quality of foam. The static eliminator is used to effectively remove static electricity on the surface of particles, prevent particles from adsorbing each other, maintain particle fluidity, and remove static electricity to avoid accumulation or blockage of raw materials during transportation and processing, reduce poor raw material fluidity, and ensure the stability of subsequent melt extrusion and foaming processes. In addition, static charge removal helps to improve the smoothness of particle flow in the equipment, reduce blockage and jamming, thereby improving production efficiency and reducing downtime.

[0064] Among them, the extruder pressure is set to 15-25MPa, the screw speed is 80-150rpm, the set temperature is 190℃-220℃, and a twin-screw extruder is used for melt extrusion. The specific temperature control is: feeding section: 130-160℃, melting section: 180-220℃, and discharging section: 190-230℃. A static mixer and a microbubble refinement device are used to refine the large bubbles formed in the foaming process. After the gas is injected into the molten material, the bubble refinement module quickly shears the bubbles into tiny bubbles through a specially designed spiral shape and stirring structure. The refined air is one or any one of nitrogen and carbon dioxide gases. An electronic flow control system is used to monitor and adjust the gas flow in real time. A gas regulating valve is used to ensure that the gas injection pressure is stable in the range of 0.8-1.2MPa, and multiple gas injection ports are set at the discharge port or the front end of the melting zone of the extruder.

[0065] The set temperature range ensures that the material is fully melted in the melting stage to facilitate mixing with the gas. The melting section (180-220°C) ensures that the EPP (expanded polystyrene) particles are melted evenly at high temperatures to avoid problems caused by uneven materials.

[0066] The microbubble refinement module uses a specially designed spiral shape and stirring structure to quickly shear large bubbles into tiny bubbles, which can effectively improve the bubble refinement effect and make the bubbles evenly distributed in the molten material, thereby improving the uniformity and stability of the foam; the tiny bubbles can not only improve the quality of the foam, but also improve the foaming and molding effects of the material. The foam structure brought by the microbubbles is more uniform and delicate, which helps to control the key performance parameters of the foam such as density and strength.

[0067] During the extrusion process, injecting gas (such as nitrogen, carbon dioxide, etc.) into the molten material helps foaming. The adopted electronic flow control system can monitor and adjust the gas flow in real time to ensure the stability and accuracy of gas injection. When multiple gas injection ports are set, by setting multiple gas injection ports at the discharge port or the front end of the melting zone, it can be ensured that the gas is evenly injected throughout the entire molten material process, and the gas is fully diffused in the material through the stirring action of the screw. Multi-point gas injection can effectively avoid uneven foaming caused by single-point injection, thereby ensuring the uniformity and stability of the foam.

[0068] Among them, S3 uses a multi-cavity mold, each cavity is equipped with an independent air pressure regulation system, and the mold is made of high thermal conductivity material; a pressure sensor is set in each cavity in the mold to accurately control the pressure of the gas in the cavity, and the pressure adjustment range is 1-3MPa. Each cavity is equipped with an independent cooling water channel, and the temperature of each cavity is accurately controlled by a temperature sensor to maintain it between 40℃-60℃.

[0069] Multi-cavity molds can form multiple workpieces of the same or different shapes at one time, which improves production efficiency and increases product output in the same time. They are especially suitable for industries with large-scale production or high production capacity requirements.

[0070] Each cavity is equipped with an independent air pressure regulating system, so that the pressure of each cavity can be independently controlled, so as to accurately adjust according to the requirements of different products for bubble structure, density and strength. The pressure adjustment range is 1-3MPa, which can effectively cover the pressure conditions required by most foaming materials.

[0071] The mold is made of high thermal conductivity material, which can conduct heat quickly and evenly, helping to control and optimize the cooling rate of the material.

[0072] The use of multi-cavity molds and independent air pressure and temperature control systems greatly improves production efficiency and product quality.

[0073] Among them, in S4, the gas injection flow and pressure sensor feedback are adjusted to finely adjust the air pressure in each cavity to ensure uniform foaming. High-efficiency cooling liquid is used, and the cooling system can adjust the water flow and temperature in real time. The cooling water flow is controlled at 10-15L / min.

[0074] By adjusting the gas injection flow rate, the amount of gas in each cavity can be controlled, thereby affecting the volume, density and structure of the foam. Based on the feedback information, the adjustment system can quickly respond to changes in air pressure to ensure stability during the gas injection process. Real-time feedback helps reduce production defects caused by pressure fluctuations and further ensures the quality and consistency of foam products. By finely adjusting the air pressure in each cavity, uniform foaming is ensured.

[0075] Among them, in S5, the dimensional error of the product is controlled within ±0.5mm, and the density of the foam core is measured using a densitometer, and the density range is maintained at 25-50kg / m 3 .

[0076] By controlling the dimensional error and density, the product performance is ensured to be stable. Strict dimensional and density control can reduce the defective rate and material waste, thereby improving economic benefits. The density directly affects the strength, stiffness and thermal insulation performance of the foam. Monitoring the density ensures that the foam core is between 25-50kg / m 3 Within the density range, the overall performance of the final product can be guaranteed.

[0077] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. An integral foam core EPP molding process, characterized in that: The steps include: S1. Raw material selection and pretreatment Raw material selection: Select EPP particles that meet the requirements, with a particle diameter range of 1.5mm to 4.0mm and a density of 25kg / m 3 Up to 60kg / m 3 ; Pretreatment: Clean the raw materials and remove impurities through magnetic and electrostatic separation technology; Particle screening and drying: Use a vibrating screen to screen the EPP particles, and use a dryer to dry the particles to a moisture content of less than 0.1%; S2. Melt extrusion and foaming treatment Extruder settings: In the melt extruder, the dried EPP pellets are heated to the set temperature, the screw is used to accelerate the melting, and the extrusion pressure and speed are adjusted; Gas injection: During the melt extrusion process, fine air is injected. The pressure of the injected gas is 0.8-1.2MPa, and the flow rate is controlled at 10-20L / min; Bubble refinement: The bubbles are further refined through the bubble refinement module; S3, mold injection and molding process Mould design: Design a multi-cavity mould and set up multiple independent pressure regulating systems in the mould to ensure uniform foam expansion in each cavity; Injection process: The molten and foamed EPP material is injected into the mold through the injection port. The injection pressure is set at 10-15MPa and the injection speed is controlled at 0.5-1.0m / s. Molding and foaming: In the mold, the foam material gradually expands under controlled air pressure and temperature to form the initial shape of the product; S4, cooling and solidification Cooling control: A water cooling system is installed in the mold, the cooling water temperature is maintained at 25℃-35℃, and the cooling time is controlled at 5-10 minutes; Mold cavity pressure: Maintain the air pressure in the cavity at 1-3MPa; Stability test: After cooling, the foam core needs to be tested for size and shape to ensure that the product meets the design requirements; S5. Product quality inspection and post-processing Quality inspection: density and strength testing, as well as compressive strength and impact resistance testing; Appearance and size inspection: Use a three-coordinate measuring machine to ensure the dimensional accuracy of the foam core; Trimming and packaging: Trim the formed foam core to remove edge burrs or irregular parts, classify qualified products according to specifications, carry out moisture-proof and pressure-proof packaging, and send them to the warehouse for storage.

2. The integral foam core EPP molding process according to claim 1, characterized in that: In S1, the magnetic separation equipment is a high-intensity permanent magnetic separator with a magnetic field strength of 1000-12000 Gauss. When the particles pass through the separation equipment, the ferromagnetic impurities are attracted to the magnetic separation area by the magnetic field, and the pure EPP particles continue to flow into the subsequent processing flow.

3. The integral foam core EPP molding process according to claim 2, characterized in that: In S1, a high-voltage static eliminator is used to transmit the EPP particles through a conductive belt to eliminate the surface charge of the particles. The voltage of the high-voltage static eliminator is set to 5-15kV, and the air flow rate of the eliminator is controlled to be 5-10m 3 / min.

4. The integral foam core EPP molding process according to claim 3, characterized in that: In S2, the extruder pressure is set to 15-25 MPa, the screw speed is 80-150 rpm, the set temperature is 190°C-220°C, and a twin-screw extruder is used for melt extrusion. The specific temperature control is: feeding section: 130-160°C, melting section: 180-220°C, and discharging section: 190-230°C.

5. The integral foam core EPP molding process according to claim 4, characterized in that: In S2, a static mixer and a microbubble refinement device are used to refine the large bubbles formed in the foaming process. After the gas is injected into the molten material, the bubble refinement module quickly shears the bubbles into tiny bubbles through a specially designed spiral shape and stirring structure. The refinement air is one or any one of nitrogen and carbon dioxide gases.

6. The integral foam core EPP molding process according to claim 1, characterized in that: In S2, an electronic flow control system is used to monitor and adjust the gas flow in real time, a gas regulating valve is used to ensure that the gas injection pressure is stable in the range of 0.8-1.2 MPa, and multiple gas injection ports are set at the discharge port or the front end of the melting zone of the extruder.

7. The integral foam core EPP molding process according to claim 1, characterized in that: In the S3, a multi-cavity mold is used, each cavity is equipped with an independent air pressure regulating system, and the mold is made of high thermal conductivity material; a pressure sensor is set in each cavity in the mold to accurately control the pressure of the gas in the cavity, and the pressure adjustment range is 1-3MPa. Each cavity is equipped with an independent cooling water channel, and the temperature of each cavity is accurately regulated by a temperature sensor to maintain it between 40°C and 60°C.

8. The integral foam core EPP molding process according to claim 1, characterized in that: In S4, the gas injection flow rate and pressure sensor feedback are adjusted to finely adjust the air pressure in each cavity to ensure uniform foaming.

9. The integral foam core EPP molding process according to claim 8, characterized in that: In S4, a high-efficiency cooling liquid is used, and the cooling system can adjust the water flow and temperature in real time, and the cooling water flow is controlled to be 10-15 L / min.

10. The integral foam core EPP molding process according to claim 1, characterized in that: In S5, the dimensional error of the product is controlled within ±0.5 mm, and the density of the foam core is measured using a densitometer, and the density range is maintained at 25-50 kg / m 3 .