Foam mold production and processing technology

Abstract

The invention relates to the technical field of mold production, in particular to a foam mold production and processing technology which comprises the following steps: step 1, raw material pretreatment and mixing reinforcement: a copolymer STMMA is adopted to replace traditional EPS, and nano montmorillonite is added as a nucleating agent, so that the bubble nucleation density is increased, and cell merging is inhibited; then carrying out mixing reinforcement in a supercritical fluid saturation mode; and 2, staged injection and microcellular foaming control are carried out, staged injection is carried out through multi-stage injection pressure setting, then filling paths are ensured to be symmetrical through parting surface pressure control foaming control, and the density gradient is reduced. According to the process, through three innovations of supercritical fluid nucleation control, parting surface dynamic pressure regulation and a gradient cooling system, the non-uniform foam holes and the cooling bottleneck of a traditional foam mold are broken through. And in cooperation with the surface texture and intelligent monitoring, the bearing capacity, light weight, design freedom and other dimensions of the foam box are remarkably improved, and technical support is provided for high-end logistics packaging.

Description

Technical Field

[0001] The invention relates to the technical field of mold production, in particular to a foam mold production and processing technology. Background Art

[0002] At present, foam boxes are box-type packaging containers made of foam plastic. Plastic foam is a plastic with many tiny pores inside. Foam boxes are often used in the transportation of fruits and the packaging of items. They can play a role in cushioning and protection. When producing foam boxes, processing molds are needed to process and shape the raw materials. The molds used in foam box production, such as low-pressure foaming processes, are prone to producing large and unevenly distributed cell sizes. This can lead to poor mechanical and impact properties, limiting the application of structural foam in load-bearing applications.

[0003] Furthermore, for thicker molded products, the polymer has low thermal conductivity and requires a long cooling time, while thin-walled products require extremely high injection pressure and speed, otherwise they tend to solidify prematurely. This makes it difficult to use injection molding to produce products with large wall thickness differences and high dimensional accuracy, and the product geometry is limited.

[0004] Therefore, a foam mold production and processing technology is proposed. Summary of the Invention

[0005] The present invention aims to provide a foam mold production and processing technology. This process, through three major innovations: supercritical fluid nucleation control, dynamic pressure regulation at the parting surface, and a gradient cooling system, overcomes the uneven cell structure and cooling bottlenecks associated with traditional foam molds. Combined with surface texturing and intelligent monitoring, this technology significantly improves foam boxes in terms of load-bearing capacity (impact strength increased by 50%), lightweighting (wall thickness decreased by 30%), and design freedom (complex geometry realization). This technology provides technical support for high-end logistics packaging and addresses the issues raised in the aforementioned background technology.

[0006] To achieve the above-mentioned purpose, the present invention provides the following technical solution: a foam mold production process, comprising the following steps: Step 1: Raw material pretreatment and mixing strengthening: By using copolymer STMMA to replace traditional EPS and adding nano-montmorillonite as a nucleating agent, the bubble nucleation density is increased and the pore merging is inhibited. Then, mixing strengthening is carried out by supercritical fluid saturation. Step 2: Staged injection and microcellular foaming control: multi-stage injection pressure setting is used for staged injection, and then pressure-controlled foaming control on the parting surface is used to ensure symmetry of the filling path and reduce density gradients. Step 3: Gradient cooling and thermal field optimization: adopt a zoned cooling system design for independent cooling and dynamic temperature control, adjust the cooling water flow, and reduce the temperature difference on the mold surface; Step 4: Composite demoulding and surface treatment: gas-liquid linkage demoulding is used to separate the products, and micro-nano composite texture is performed on the cavity surface to achieve functional treatment of the mold surface; Step 5: Online quality monitoring and feedback: test the cell size and collect relevant data, train the neural network model, and dynamically modify the injection curve and cooling strategy.

[0007] Preferably, in the step 1, raw material pretreatment and raw material modification treatment in the mixing intensification, the copolymer STMMA, i.e., styrene-methyl methacrylate copolymer, and the amount of nano-montmorillonite added are less than 3 wt %.

[0008] Preferably, the supercritical fluid is saturated, and a mixture of carbon dioxide and nitrogen is treated at 35 MPa and 60°C to a supercritical state Sc-CO2, which is injected into the polymer melt. The solubility is controlled by Henry's law: C=k*P, where C is the gas solubility, k is the material constant, and P is the pressure. The gas concentration is precisely controlled by adjusting the pressure to make the bubble diameter ≤100 μm.

[0009] Preferably, in the step 2, multi-stage injection and microcellular foaming control, the multi-stage injection pressure setting is divided into thin-walled area and thick-walled area, wherein the thin-walled area adopts high-pressure injection with a pressure greater than 30 MPa to prevent the solution from solidifying prematurely, and the injection speed v is dynamically adjusted with the wall thickness d:

[0010] in is the material coefficient, c is the characteristic constant of wall thickness; In the thick wall area, medium and low pressure in the range of 10MPa-15MPa combined with pulsed pressure relief is used to induce uniform nucleation.

[0011] Preferably, in the step 2, the parting surface pressure control foaming control step of staged injection and microcellular foaming, the mold parting surface is set with an adjustable sealing structure, such as a hydraulic telescopic insert, which maintains high pressure in the initial stage of foaming, within the range of 25MPa to inhibit bubble growth; after the filling is completed, the pressure is stepped down to 5MPa to promote uniform expansion of the bubbles, and the injection port adopts a tangential feeding plus center compensation design to ensure the symmetry of the filling path and reduce the density gradient.

[0012] Preferably, in the step three, gradient cooling and thermal field optimization, a partitioned cooling system is designed, and an independent cooling circuit is built into the mold, wherein microchannel cooling is used to enhance heat exchange in the thick-walled area, and a 60°C-80°C insulation water channel is located in the thin-walled area to prevent under-foaming, and dynamic temperature control is used during the cooling process, mainly based on infrared temperature measurement feedback, to adjust the cooling water flow in real time so that the temperature difference on the mold surface is ≤±3°C.

[0013] Preferably, the gas-liquid linkage demoulding method in the step 4, composite demoulding and surface treatment, includes a fixed system integrated airbag push plate plus a hydraulic ejector, the existing 0.5MPa air pressure airbag uniformly applies force for pre-demolding to reduce local stress, and then the hydraulic ejector completes the product separation to avoid deformation; The functionalization treatment of the mold surface includes micro-nano composite texturing on the cavity surface, laser etching grooves with a width of 50μm and a depth of 20μm as exhaust channels, and depositing diamond-like coatings. The friction coefficient is reduced to 0.05 and the demolding angle can be reduced to 0.5°.

[0014] Preferably, the step 5, online quality monitoring and feedback includes real-time detection of cell size, embedding an ultrasonic sensor in the mold exhaust duct, and inverting the foam density pf by using the sound velocity vs.

[0015] Where E is the elastic modulus.

[0016] Compared with the prior art, the present invention has the following beneficial effects: This process utilizes three key innovations: supercritical fluid nucleation control, dynamic pressure regulation at the parting surface, and a gradient cooling system. These innovations overcome the uneven cell distribution and cooling bottlenecks associated with traditional foam molds. Combined with surface texturing and intelligent monitoring, this process significantly enhances foam packaging's load-bearing capacity and impact strength by 50%, reduces weight, reduces wall thickness by 30%, and enhances design freedom and the ability to achieve complex geometries, providing technical support for high-end logistics packaging. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the specific embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0018] Figure 1 This is a flow chart of the foam mold production process of the present invention; Figure 2 This is a comparison chart of the process advantages of the present invention. DETAILED DESCRIPTION

[0019] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0020] See also Figures 1 to 2 , the present invention provides a technical solution: A foam mold production process, characterized by comprising the following steps: Step 1: Raw material pretreatment and mixing strengthening: By using copolymer STMMA to replace traditional EPS and adding nano-montmorillonite as a nucleating agent, the bubble nucleation density is increased and the pore merging is inhibited. Then, mixing strengthening is carried out by supercritical fluid saturation. Step 2: Staged injection and microcellular foaming control: multi-stage injection pressure setting is used for staged injection, and then pressure-controlled foaming control on the parting surface is used to ensure symmetry of the filling path and reduce density gradients. Step 3: Gradient cooling and thermal field optimization: adopt a zoned cooling system design for independent cooling and dynamic temperature control, adjust the cooling water flow, and reduce the temperature difference on the mold surface; Step 4: Composite demoulding and surface treatment: gas-liquid linkage demoulding is used to separate the products, and micro-nano composite texture is performed on the cavity surface to achieve functional treatment of the mold surface; Step 5: Online quality monitoring and feedback: test the cell size and collect relevant data, train the neural network model, and dynamically modify the injection curve and cooling strategy.

[0021] In the step 1, raw material pretreatment and raw material modification treatment in mixing and strengthening, the copolymer STMMA is styrene-methyl methacrylate copolymer, and the amount of nano-montmorillonite added is less than 3wt%.

[0022] The supercritical fluid is saturated, and a mixture of carbon dioxide and nitrogen is treated at 35 MPa and 60°C to a supercritical state Sc-CO2, which is then injected into a polymer melt. The solubility is controlled by Henry's law: C=k*P, where C is the gas solubility, k is the material constant, and P is the pressure. The gas concentration is precisely controlled by adjusting the pressure to make the pore diameter ≤100 μm.

[0023] In the step 2, multi-stage injection and microcellular foaming control, the multi-stage injection pressure setting is divided into thin-walled area and thick-walled area. The thin-walled area adopts high-pressure injection with a pressure greater than 30 MPa to prevent the solution from solidifying prematurely. The injection speed v is dynamically adjusted with the wall thickness d:

[0024] in is the material coefficient, c is the characteristic constant of wall thickness; In the thick wall area, medium and low pressure in the range of 10MPa-15MPa combined with pulsed pressure relief is used to induce uniform nucleation.

[0025] In the step 2, the parting surface pressure control during staged injection and microcellular foaming control, the mold parting surface is set with an adjustable sealing structure, such as a hydraulic telescopic insert, to maintain high pressure in the initial stage of foaming, within the range of 25 MPa to inhibit bubble growth; after the mold filling is completed, the pressure is stepped down to 5 MPa to promote uniform expansion of the bubbles, and the injection port adopts a tangential feeding plus center compensation design to ensure the symmetry of the filling path and reduce the density gradient.

[0026] In the step 3, gradient cooling and thermal field optimization, a partitioned cooling system is designed. An independent cooling circuit is built into the mold. Microchannel cooling is used to enhance heat exchange in the thick-walled area, while a 60°C-80°C insulation water channel is located in the thin-walled area to prevent under-foaming. Dynamic temperature control is used during the cooling process, mainly based on infrared temperature measurement feedback, to adjust the cooling water flow in real time to ensure that the temperature difference on the mold surface is ≤±3°C.

[0027] In the fourth step, the gas-liquid linkage demoulding method in the composite demoulding and surface treatment includes a fixed system integrated airbag push plate and a hydraulic ejector. The existing 0.5MPa air pressure airbag uniformly applies force to pre-demold to reduce local stress, and then the hydraulic ejector completes the product release to avoid deformation; The functionalization treatment of the mold surface includes micro-nano composite texturing on the cavity surface, laser etching grooves with a width of 50μm and a depth of 20μm as exhaust channels, and depositing diamond-like coatings. The friction coefficient is reduced to 0.05 and the demolding angle can be reduced to 0.5°.

[0028] The step 5, online quality monitoring and feedback, includes real-time detection of cell size, embedding ultrasonic sensors in the mold exhaust duct, and inverting the foam density pf by using the sound velocity vs.

[0029] Where E is the elastic modulus.

[0030] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A foam mold production process, characterized by: The steps include: Step 1: Raw material pretreatment and mixing strengthening: By using copolymer STMMA to replace traditional EPS and adding nano-montmorillonite as a nucleating agent, the bubble nucleation density is increased and the pore merging is inhibited. Then, mixing strengthening is carried out by supercritical fluid saturation. Step 2: Staged injection and microcellular foaming control: multi-stage injection pressure setting is used for staged injection, and then pressure-controlled foaming control on the parting surface is used to ensure symmetry of the filling path and reduce density gradients. Step 3: Gradient cooling and thermal field optimization: adopt a zoned cooling system design for independent cooling and dynamic temperature control, adjust the cooling water flow, and reduce the temperature difference on the mold surface; Step 4: Composite demoulding and surface treatment: gas-liquid linkage demoulding is used to separate the products, and micro-nano composite texture is performed on the cavity surface to achieve functional treatment of the mold surface; Step 5: Online quality monitoring and feedback: test the cell size and collect relevant data, train the neural network model, and dynamically modify the injection curve and cooling strategy.

2. A foam mold production and processing process according to claim 1, characterized in that: In the step 1, raw material pretreatment and raw material modification treatment in mixing and strengthening, the copolymer STMMA is styrene-methyl methacrylate copolymer, and the amount of nano-montmorillonite added is less than 3wt%.

3. The foam mold production process according to claim 1, characterized in that: The supercritical fluid is saturated, and a mixture of carbon dioxide and nitrogen is treated at 35 MPa and 60°C to a supercritical state Sc-CO2, which is then injected into a polymer melt. The solubility is controlled by Henry's law: C=k*P, where C is the gas solubility, k is the material constant, and P is the pressure. The gas concentration is precisely controlled by adjusting the pressure to make the pore diameter ≤100 μm.

4. The foam mold production process according to claim 1, characterized in that: In the step 2, multi-stage injection and microcellular foaming control, the multi-stage injection pressure setting is divided into thin-walled area and thick-walled area. The thin-walled area adopts high-pressure injection with a pressure greater than 30 MPa to prevent the solution from solidifying prematurely. The injection speed v is dynamically adjusted with the wall thickness d:

5. Among them is the material coefficient, c is the characteristic constant of wall thickness; In the thick wall area, medium and low pressure in the range of 10MPa-15MPa combined with pulsed pressure relief is used to induce uniform nucleation.

6. The foam mold production process according to claim 1, characterized in that: In the step 2, the parting surface pressure control during staged injection and microcellular foaming control, the mold parting surface is set with an adjustable sealing structure, such as a hydraulic telescopic insert, to maintain high pressure in the initial stage of foaming, within the range of 25 MPa to inhibit bubble growth; after the mold filling is completed, the pressure is stepped down to 5 MPa to promote uniform expansion of the bubbles, and the injection port adopts a tangential feeding plus center compensation design to ensure the symmetry of the filling path and reduce the density gradient.

7. The foam mold production process according to claim 1, characterized in that: In the step 3, gradient cooling and thermal field optimization, a partitioned cooling system is designed. An independent cooling circuit is built into the mold. Microchannel cooling is used to enhance heat exchange in the thick-walled area, while a 60°C-80°C insulation water channel is located in the thin-walled area to prevent under-foaming. Dynamic temperature control is used during the cooling process, mainly based on infrared temperature measurement feedback, to adjust the cooling water flow in real time to ensure that the temperature difference on the mold surface is ≤±3°C.

8. The foam mold production process according to claim 1, characterized in that: In the fourth step, the gas-liquid linkage demoulding method in the composite demoulding and surface treatment includes a fixed system integrated airbag push plate and a hydraulic ejector. The existing 0.5MPa air pressure airbag uniformly applies force to pre-demold to reduce local stress, and then the hydraulic ejector completes the product release to avoid deformation; The functionalization treatment of the mold surface includes micro-nano composite texturing on the cavity surface, laser etching grooves with a width of 50μm and a depth of 20μm as exhaust channels, and depositing diamond-like coatings. The friction coefficient is reduced to 0.05 and the demolding angle can be reduced to 0.5°.

9. The foam mold production process according to claim 1, characterized in that: The step 5, online quality monitoring and feedback, includes real-time detection of cell size, embedding ultrasonic sensors in the mold exhaust duct, and inverting the foam density pf by using the sound velocity vs. 10.Where E is the elastic modulus.

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