A continuous pretreatment device for plastic substrates

Abstract

The utility model relates to the technical field of plastic base material processing provides a kind of plastic base material continuous pretreatment device suitable for powder coating electrostatic spraying, including oil removal and dirt removal section, sand blasting section, sand removal cleaning section, air knife water removal section, low-temperature drying section and detection section in turn being arranged along the conveying direction of plastic base material, detection section includes detection channel, detection window, reflux structure and reflux slide, detection window is arranged on the detection channel, physical detection module and the chemical detection module that can be lifted relative to detection channel are equipped on detection window, reflux structure is installed at the export of detection channel and is used to transfer the plastic base material of unqualified to reflux slide on reflux rework;The utility model solves the problem that in the prior art, lack of a kind of plastic base material pretreatment device capable of integrating cleaning, sand blasting, sand removal cleaning, air knife water removal, low-temperature drying and on-line detection in one, and has the advantages of simple structure, low manufacturing cost and good detection effect.

Description

Technical Field

[0001] This utility model relates to the field of plastic substrate processing technology, and more specifically, to a continuous pretreatment device for plastic substrates. Background Technology

[0002] With increasingly stringent environmental regulations and the accelerated transition from liquid to powder coatings, powder coatings are gradually replacing traditional liquid coatings due to their environmental advantages such as being solvent-free, low in VOCs, and recyclable. They are widely used in various fields including home appliances, automobiles, building materials, 3C products, photovoltaics, and energy storage. In 2025, the Chinese powder coating market size exceeded 40 billion yuan, with an annual growth rate exceeding 10%. Demand from emerging fields such as new energy vehicles, photovoltaics, and energy storage accounted for 28% of the market, with a growth rate exceeding 25%. However, powder coatings place higher demands on heat-sensitive substrates such as plastics: on the one hand, plastics have low surface energy and are easily deformed by heat, and traditional high-temperature curing (above 180℃) can easily damage the substrate; on the other hand, plastic surfaces often retain residual release agents and electrostatically adsorbed dust and other contaminants. If pretreatment is incomplete, it will seriously affect the adhesion and appearance quality of the powder coating.

[0003] In recent years, breakthroughs in low-temperature curing powder coating technology (curing temperature ≤120℃) have made powder coating possible for heat-sensitive substrates such as plastics, MDF, and composite materials.

[0004] However, current powder coating of plastic substrates still faces the following bottlenecks: ① The lack of online detection methods for surface cleanliness makes it impossible to identify defects such as oil stains and mold release agent residues in real time, resulting in quality problems such as pinholes and craters in the powder coating; ② Low-temperature curing powder coatings have higher requirements for the surface energy of the substrate, but the surface energy of plastic surfaces is often insufficient due to problems such as electrostatic adsorption of dust and sandblasting embedding, which affects the melting, leveling and curing crosslinking of powder; ③ Existing pretreatment processes (such as dry sandblasting) are prone to causing mechanical damage to the plastic surface and cannot be integrated with the powder coating line into an automated closed loop, resulting in low production efficiency and large fluctuations in yield.

[0005] Building upon this foundation, the conductivity of moisture within the substrate and hot-spraying technology have emerged as new directions for solving the challenges of electrostatic powder coating on plastics. Research has found that when insulating substrates such as plastics are preheated to 50-150°C, trace amounts of moisture within them can migrate to the surface, forming a very thin water film. This imparts a certain level of conductivity to the surface, meeting the grounding requirements of electrostatic spraying. For example, in wood-based substrates, controlling the preheating temperature allows moisture to migrate evenly to the surface, reducing the surface resistance to 10 ohms. 6 ~10 8 Ω, meeting the conditions for electrostatic spraying.

[0006] On the other hand, the "hot-spraying" process has been proposed and proven effective. This process involves electrostatic powder coating immediately after the substrate is preheated, utilizing the residual heat of the substrate (surface temperature 50-150°C, preferably 80-120°C) to promote rapid melting, wetting, and leveling of the powder particles. Studies have shown that spraying while maintaining the surface temperature of the plastic substrate at 80-100°C significantly improves powder adhesion and edge coverage. Furthermore, hot-spraying can shorten curing time and improve production efficiency, making it particularly suitable for thin-walled, complex-structured plastic parts. Utility Model Content

[0007] Therefore, to address the lack of a multi-stage, integrated continuous pretreatment device for plastic substrates in the existing powder coating industry that can ensure the conductivity of insulating substrates such as plastics meets the requirements of electrostatic spraying, utilize hot spraying technology, and incorporate online detection for pretreatment processes, achieving automated closed-loop integration with powder coating lines, this utility model provides a continuous pretreatment device for plastic substrates, the specific technical solution of which is as follows: A continuous pretreatment device for plastic substrates includes an oil and dirt removal section, a sandblasting section, a sand removal and cleaning section, an air knife dewatering section, a low-temperature drying section, and a testing section arranged sequentially along the conveying direction of the plastic substrates. The testing section includes a testing channel, a testing window, a reflux structure, and a reflux chute. The testing window is mounted on the testing channel and is equipped with a physical testing module and a chemical testing module that can be raised and lowered relative to the testing channel. The reflux structure is installed at the outlet of the testing channel and is used to transfer unqualified plastic substrates to the reflux chute for reprocessing.

[0008] The aforementioned continuous pretreatment device for plastic substrates integrates a physical detection module and a liftable chemical detection module within the detection window. This allows for simultaneous physical and chemical dual detection of key indicators such as surface particle contamination and chemical cleanliness of the workpiece at the same workstation. The detection is comprehensive and highly accurate, avoiding the lag and errors of traditional offline sampling inspection. Based on the detection results, the recirculation structure can automatically and quickly sort out non-conforming products to the recirculation chute and return them to the desanding and cleaning section for rework. This deeply integrates quality control into the production process, achieving online detection and closed-loop feedback in the plastic pretreatment section. This fundamentally avoids batch quality problems and significantly improves the overall yield.

[0009] Furthermore, both the oil and dirt removal section and the sand removal and cleaning section are ultrasonic cleaning sections.

[0010] Furthermore, the ultrasonic cleaning section uses a neutral cleaning agent.

[0011] Furthermore, the sandblasting section employs wet sandblasting.

[0012] Furthermore, the dewatering section of the air knife uses a 30–40℃ slightly heated air knife.

[0013] Furthermore, the low-temperature drying section uses low-temperature drying to dry the plastic substrate in sections, with a drying temperature of 50–150℃.

[0014] Furthermore, the detection window physically isolates the physical detection module and the chemical detection module within the same sealed chamber, and the detection window is a transparent detection window.

[0015] Furthermore, the physical detection module is a laser particle counter; the chemical detection module is a dyne pen.

[0016] Furthermore, the continuous pretreatment device for plastic substrates also includes a PLC controller, which is communicatively connected to the physical detection module and the chemical detection module and is used to control the opening and closing state of the reflux structure.

[0017] Furthermore, the return structure is a fork-type pneumatic actuator. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the flow structure of a continuous pretreatment device for plastic substrates according to an embodiment of the present invention; Figure 2 This is a schematic diagram of the detection section of the continuous pretreatment device for plastic substrates according to an embodiment of the present invention; Figure 3 This is a schematic diagram of the detection window of the continuous pretreatment device for plastic substrates according to an embodiment of the present invention.

[0019] Explanation of reference numerals in the attached figures: 1. Oil and dirt removal section; 2. Sandblasting section; 3. Sand removal and cleaning section; 4. Air knife dewatering section; 5. Low temperature drying section; 6. Testing section; 61. Testing channel; 611. Outlet; 62. Testing window; 621. Physical testing module; 622. Chemical testing module; 63. Recirculation structure; 64. Recirculation chute. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of this utility model clearer, the following detailed description is provided in conjunction with its embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the utility model and do not limit its scope of protection.

[0021] It should be noted that when an element is referred to as being "fixed to" another element, it can be directly attached to the other element or there may be an intervening element. When an element is referred to as being "connected to" another element, it can be directly connected to the other element or there may be an intervening element. The terms "vertical," "horizontal," "left," "right," and similar expressions used herein are for illustrative purposes only and do not represent the only possible implementation.

[0022] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0023] In this utility model, "first" and "second" do not represent a specific quantity or order, but are merely used to distinguish names.

[0024] like Figures 1-3 As shown, a continuous pretreatment device for plastic substrates in one embodiment of this utility model includes an oil and dirt removal section 1, a sandblasting section 2, a sand removal and cleaning section 3, an air knife dewatering section 4, a low-temperature drying section 5, and a testing section 6 arranged sequentially along the conveying direction of the plastic substrate. The testing section 6 includes a testing channel 61, a testing window 62, a reflux structure 63, and a reflux slide 64. The testing window 62 is mounted on the testing channel 61 and is equipped with a physical testing module 621 and a chemical testing module 622 that can be raised and lowered relative to the testing channel 61. The reflux structure 63 is installed at the outlet 611 of the testing channel 61 and is used to transfer unqualified plastic substrates to the reflux slide 64 for reprocessing.

[0025] The aforementioned continuous pretreatment device for plastic substrates integrates the physical detection module 621 and the liftable chemical detection module 622 within the detection window 62. This allows for simultaneous physical and chemical dual detection of key indicators such as surface particle contamination and chemical cleanliness of the workpiece at the same workstation. The detection is comprehensive and highly accurate, avoiding the lag and errors of traditional offline sampling inspection. Based on the detection results, the return structure 63 can automatically and quickly sort out unqualified products to the return chute 64 and return them to the sand removal and cleaning section 3 for rework. This deeply integrates quality control into the production process, achieving online detection closed-loop feedback in the plastic pretreatment section. This fundamentally avoids batch quality problems and significantly improves the overall yield.

[0026] The height-adjustable nature of the chemical detection module 622 allows for easy adjustment of its height position, enabling direct contact with the plastic substrate to be tested on the detection channel 61.

[0027] In one embodiment, both the degreasing and decontamination section 1 and the sand removal and cleaning section 3 are ultrasonic cleaning sections. The function of the sand removal and cleaning section 3 is to remove residual sand grains.

[0028] In one embodiment, the ultrasonic cleaning section uses a neutral cleaning agent, which is beneficial for cleaning surface oil stains.

[0029] In one embodiment, the sandblasting section 2 adopts wet sandblasting to roughen the surface and improve adhesion.

[0030] In one embodiment, the air knife water removal section 4 uses a slightly heated air knife at 30–40°C. The air knife water removal process uses "air" instead of "heat", completing 90% of the dewatering task at the inlet end, preventing subsequent drying ovens from wasting a large amount of heat on latent heat of vaporization; the energy consumption of the air knife is only 1.5–5.5kW, which saves more than 60% of energy compared with hot air drying; the drying time is shortened from several minutes to 1–3s.

[0031] In one embodiment, the low-temperature drying section 5 adopts low-temperature drying at 50°C to 150°C to perform segmented drying on the plastic substrate. The surface temperature of the workpiece discharged at low temperature is 55–75°C, and the interior still contains 0.05–0.1gm -2 internal water. The internal water maintains a semiconductor-grade conductive channel inside the substrate, so that the substrate can adsorb negatively charged powder particles after being grounded to form a uniform and firm coating; at the same time, the residual heat on the surface of the substrate can be used for hot spraying to promote rapid melting and leveling of the powder particles, increasing the powder transfer efficiency by 8–12%, and increasing the curing line speed by 0.5mmin -1 .

[0032] As Figure 2 and 3 shown, in one embodiment, the detection window 62 physically isolates the physical detection module 621 and the chemical detection module 622 in the same closed cabin, and the detection window 62 is a transparent detection window 62, which avoids interference from mist droplets and dust, and provides a visual debugging channel through the transparent detection window 62 at the same time.

[0033] Preferably, the physical detection module 621 is a laser particle counter. Based on the laser scattering principle: particles of 0.5-25µm are counted in real time, and ≤100 particles / cm² is qualified.

[0034] Preferably, the chemical detection module 622 is a dyne pen. Using the dyne pen contact method: a 50-60mN / m water film lasting ≥2s is qualified.

[0035] The above two detection modules sample synchronously, and the data is compared by the PLC controller within 0.1s, with a missed detection rate of 0. If any index exceeds the standard, rework is triggered, no manual threshold setting is required, and the system adapts to different plastic substrates.

[0036] In one embodiment, the continuous pretreatment device for plastic substrates further includes a PLC controller, which is communicatively connected to the physical detection module 621 and the chemical detection module 622, respectively, and is used to control the opening and closing state of the reflux structure 63. Unqualified plastic substrates are transferred to the reflux chute 64 and returned to the sand removal and cleaning section 3; qualified plastic substrates are then fed into the subsequent spraying process.

[0037] Preferably, the reflux structure 63 is a pneumatic actuator with a pneumatic fork. Defective products enter the reflux chute 64 through the pneumatic fork without obstructing the main flow velocity, while qualified products proceed directly to the outlet 611. The pneumatic actuator with a pneumatic fork is existing technology and will not be described in detail here.

[0038] Specifically, an 80° pneumatic rotary shifter replaces the traditional cylinder push rod, completing an 80° rotational diversion in 1 second without interrupting the main flow rate.

[0039] Furthermore, after the plastic substrate passes the initial inspection, it needs to be electrostatically sprayed while it is still hot.

[0040] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0041] The embodiments described above are merely illustrative of several implementations of this utility model, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the utility model patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this utility model, and these all fall within the protection scope of this utility model. Therefore, the protection scope of this utility model patent should be determined by the appended claims.

Claims

1. A continuous pretreatment apparatus for plastic substrates, characterized in that, The system includes, sequentially arranged along the conveying direction of the plastic substrate, an oil and dirt removal section, a sandblasting section, a sand removal and cleaning section, an air knife dewatering section, a low-temperature drying section, and a testing section. The testing section includes a testing channel, a testing window, a reflux structure, and a reflux chute. The testing window is mounted on the testing channel and is equipped with a physical testing module and a chemical testing module that can be raised and lowered relative to the testing channel. The reflux structure is installed at the outlet of the testing channel and is used to transfer unqualified plastic substrates to the reflux chute for reprocessing.

2. The continuous pretreatment apparatus for plastic substrates according to claim 1, characterized in that, Both the oil and dirt removal section and the sand removal and cleaning section are ultrasonic cleaning sections.

3. The continuous pretreatment apparatus for plastic substrates according to claim 2, characterized in that, The ultrasonic cleaning section uses a neutral cleaning agent.

4. The continuous pretreatment apparatus for plastic substrates according to claim 1, characterized in that, The sandblasting section employs wet sandblasting.

5. The continuous pretreatment apparatus for plastic substrates according to claim 1, characterized in that, The dewatering section of the air knife uses a 30–40℃ slightly heated air knife.

6. The continuous pretreatment apparatus for plastic substrates according to claim 1, characterized in that, The drying section uses a low temperature of 50–150℃ to dry the plastic substrate in stages.

7. The continuous pretreatment apparatus for plastic substrates according to claim 1, characterized in that, The detection window physically isolates the physical detection module and the chemical detection module within the same sealed chamber, and the detection window is a transparent detection window.

8. The continuous pretreatment apparatus for plastic substrates according to claim 1, characterized in that, The physical detection module is a laser particle counter; the chemical detection module is a dyne pen.

9. The continuous pretreatment apparatus for plastic substrates according to claim 1, characterized in that, It also includes a PLC controller, which is communicatively connected to the physical detection module and the chemical detection module and is used to control the opening and closing state of the reflux structure.

10. The continuous pretreatment apparatus for plastic substrates according to claim 9, characterized in that, The return flow structure is a fork-type pneumatic actuator.

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