Multi-cavity profile seamless welding and sound insulation layer integrated forming method and door and window frame

Abstract

This invention relates to a method for seamless welding of multi-cavity profiles and integrated molding of sound insulation layers, as well as a door and window frame. It belongs to the field of building door and window profile processing and manufacturing technology. By moving the injection of the sound insulation composite material before welding, pre-injection is completed when the profile cavity ports are open, solving the problem of material not flowing into the closed corner area and resulting in missing corner sound insulation filling in existing post-injection processes. By applying a heat-activated protective film to the welding end face and implementing a staged heating and pressurization process, the flow homogenization conditions of the molten material on the outer surface are improved, effectively reducing the width of the white weld seam at the corner. By selecting a sound insulation material system with a final curing temperature matching the welding residual heat temperature range, the residual heat during the natural cooling process of the corner after welding drives the final curing of the material, merging the welding process and the sound insulation layer molding process. No structural modifications to existing welding equipment are required, making it easy to promote and apply under existing production conditions.

Description

Technical Field

[0001] This invention relates to the field of building door and window profile processing and manufacturing technology, specifically to a method for seamless welding of multi-cavity profiles and integral molding of sound insulation layer, as well as a door and window frame. Background Technology

[0002] Building door and window frames typically use multi-cavity PVC extruded profiles as the base material. The end faces of the profiles, cut to the designed angles, are joined together using a hot-melt welding process to form the four corner structures of the door and window frame. Currently, the most common welding method in the industry is the mirror hot plate welding method: a welding plate heated to a specific temperature is simultaneously brought into contact with the end faces of two profiles to be welded, causing the end face material to melt and soften. The welding plate is then quickly removed, and the two profiles are pressed together. After cooling, the welded corners are formed. This process is mature and reliable, but it has several inherent defects in the application scenarios of multi-cavity profiles.

[0003] Firstly, multi-cavity profiles contain multiple chambers, each with varying wall thicknesses. Under the action of a single-temperature welding plate, the melting depth and melting rate of each chamber wall differ. After the welding plate is removed, the cooling and shrinkage rates of the molten layer on the outer surface of the profile and the molten layer on the inner cavity walls are asynchronous, resulting in visible white shrinkage marks at the weld seams on the outer surface of the corners, commonly known in the industry as white seams. White seams not only affect the product's appearance quality but also represent a concentrated manifestation of microscopic defects at the corners, posing a risk of cracking along the white seams after long-term use.

[0004] Secondly, existing welding processes mostly use a single pressure application to complete the end face connection. When the pressure is applied, the molten material is suddenly squeezed, and the molten area on the outer surface is shaped before it has fully flowed and homogenized. Local areas may form depressions or whitening due to insufficient or uneven distribution of molten material, which further aggravates the white seam problem.

[0005] Thirdly, to improve the sound insulation performance of doors and windows, existing processes typically fill the cavity of the profile with sound-insulating material. Common methods include: co-extrusion filling during the profile extrusion molding stage, injecting sound-insulating adhesive into the cavity after frame welding, or inserting sound-insulating strips into the cavity. In the post-injection method, after the four corners of the frame are welded and sealed, the corners of the cavity have formed a closed space, making it difficult for sound-insulating material to flow in, resulting in missing sound insulation filling at the corners; although the co-extrusion filling method covers the corners, the high temperature during welding heating causes localized thermal damage to the co-extruded material, leading to a decrease in the sound insulation performance at the corners; the post-insulating strip method, due to size matching issues, has gaps in the corner area where the filling is not tight, forming sound conduction channels. None of the three methods can effectively solve the problem of the integrity of the corner sound insulation layer.

[0006] Fourth, the welding process accumulates a lot of heat at the corners of the profile. After the welding plate is removed, the corners of the profile remain at a high temperature for a long time. This residual heat is naturally dissipated without being utilized in the existing process, resulting in a waste of heat energy.

[0007] In summary, existing multi-cavity profile welding technologies have significant shortcomings in eliminating white seams at corners, ensuring the integrity of corner sound insulation layers, and improving process integration efficiency. There is an urgent need for a new method that can systematically solve these problems. Summary of the Invention

[0008] The purpose of this invention is to improve the appearance quality of corner welding without significantly increasing the number of processes and production costs, and without structurally modifying existing welding equipment, by rationally adjusting the order of welding operations, precisely controlling the heating and pressurization process in stages, and actively utilizing welding residual heat. This also enables the simultaneous completion of the cavity sound insulation layer and the welding process, thereby overcoming the above-mentioned defects of the prior art.

[0009] To achieve the above objectives, the present invention adopts the following technical solution: On the one hand, the present invention provides a method for seamless welding of multi-cavity profiles and integral molding of sound insulation layers, the method comprising the following steps in sequence: S1: Mill and finish the welded end faces of the multi-cavity profile to ensure that the end faces are flat and vertical, and confirm that the ports of each cavity are unobstructed; S2: Before the welding operation begins, pre-inject sound insulation composite material into the designated sound insulation functional cavity of the profile, with an injection volume of 90% to 95% of the cavity volume, and let it stand at room temperature until the material reaches a semi-solid state. S3: Apply a heat-activated protective film to the welding end face of the profile, the film thickness being 0.05mm to 0.10mm, and the softening temperature being lower than the welding melting temperature of the PVC material of the profile; S4: The profile is heated and welded in stages. During the heating stage, the contact time of the corresponding end face area of ​​the outer surface and the corresponding end face area of ​​the cavity wall is controlled differently. After the welding plate is removed, an initial low pressure is applied to make the molten surfaces at both ends contact and flow homogenize. Then the pressure is increased to the final pressure to complete the extrusion and solidification. S5: After welding, the residual heat conducted into the cavity by the corner of the profile during natural cooling drives the pre-placed sound insulation material in S2 to complete the final curing, so that the sound insulation material forms a stable bond with the cavity wall. S6: After the corner of the profile has completely cooled, remove excess material and perform surface finishing on the outer surface of the corner; S7: Inspect the welding strength, appearance quality, and sound insulation performance.

[0010] Wherein, the final curing temperature of the sound insulation composite material described in S2 is matched with the residual heat temperature range of the corner of the profile during the welding cooling stage, and the residual heat temperature range is typically 100°C to 160°C; materials that meet this condition include, but are not limited to, thermally activated polyurethane foam systems and modified asphalt-based damping materials.

[0011] On the other hand, the present invention provides door frames and window frames manufactured by the above method.

[0012] Compared with the prior art, the present invention has the following beneficial effects: 1. Effectively improves the appearance quality of corner welds and reduces white seams. By applying a heat-activated protective film to the weld end face, the film softens at the moment of contact and fills the microscopic uneven areas of the end face and the tiny gaps between the cavity wall end faces, forming a continuous interface transition layer, reducing white seams caused by uneven shrinkage of the outer surface; at the same time, through a staged pressurization process, a sufficient time window is provided for the molten material on the outer surface to flow and homogenize, further suppressing the formation of white seams, improving the appearance quality of the corners, and reducing the risk of cracking at the white seams after long-term use.

[0013] 2. Achieve complete coverage of the corner sound insulation layer and eliminate sound insulation blind spots. By moving the injection time of the sound insulation material forward to before welding and sealing the frame, the material fills the cavity while the profile is still in the open state, and all cavity spaces, including the corners, can be effectively filled. This fundamentally solves the problem of insufficient corner sound insulation in existing post-injection processes and eliminates sound transmission channels.

[0014] 3. Achieve process integration and reduce the number of independent processes. The final curing process of the sound insulation layer is driven by the residual heat of welding, eliminating the need for a separate heating and curing process. This organically combines the welding process with the sound insulation layer forming process, which helps to improve production efficiency and shorten the production cycle.

[0015] 4. Effective utilization of welding waste heat to reduce energy consumption. The waste heat accumulated at the corners of the profiles during welding is converted into a heat source to drive the final curing of the sound insulation material, realizing the secondary utilization of heat energy, reducing energy waste, and reflecting the energy-saving process design concept.

[0016] 5. Minimal modification requirements for existing equipment, facilitating widespread implementation. The improvements in this method primarily lie in the adjustment of the operation sequence, material selection, and process parameter setting. No structural modifications to existing welding equipment are necessary, allowing implementation under existing production line conditions, thus lowering the barrier to widespread application. The following examples further illustrate the technical solution of this invention in detail. Attached Figure Description

[0017] Figure 1 The flowchart illustrates a method for seamless welding of multi-cavity profiles and integral molding of sound insulation layers provided by this invention. Detailed Implementation

[0018] To enable those skilled in the art to better understand the present application, the technical solutions in specific embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings. Unless otherwise defined, the technical or scientific terms used in this invention should have the ordinary meaning understood by those skilled in the art.

[0019] The terms "first," "second," and similar terms used in this invention do not indicate any order, quantity, or importance, but are merely used to distinguish different components. Terms such as "comprising" or "including" mean that the element or object preceding the word encompasses the elements or objects listed following the word and their equivalents, without excluding other elements or objects.

[0020] Example 1 like Figure 1 As shown in the figure, this embodiment provides a method for seamless welding of multi-cavity profiles and integral molding of sound insulation layers. The detailed steps are as follows: S1 Profile End Face Milling Finishing: After cutting the multi-cavity PVC profile to be welded according to the design dimensions and angles, the welding end faces of the two profile sections are milled separately to remove burrs and end face angle deviations generated during cutting, ensuring that the welding end faces are flat and perpendicular. The flatness and perpendicularity of the end faces directly affect the interface fit between the two profile sections when they are joined, and are a fundamental process to ensure the strength of subsequent welding.

[0021] After milling, the opening status of each cavity port of the profile must be checked one by one to ensure that the ports are unobstructed. In the cross-section of multi-cavity profiles, some cavities are separated by thin-walled partitions. If the partitions affect the subsequent injection operation, necessary opening treatment should be performed at the relevant locations in this step to ensure the smooth progress of the subsequent injection operation.

[0022] S2 Pre-injection of sound insulation material: The timing of introducing sound insulation material is shifted from after welding is completed in the existing process to before the welding operation begins. The injection chamber is preferably a functional chamber located in the middle of the profile cross-section that does not directly bear structural loads. External cavities directly adjacent to the outer surface of the profile and air cavities that perform sealing functions are not used for sound insulation filling to avoid affecting the weld appearance quality and the profile's sealing performance.

[0023] The selection of sound-insulating composite materials must meet both of the following conditions: Firstly, the material should have sufficient fluidity during injection, enabling it to fill the cavity volume and flow into the corner area with the assistance of gravity or appropriate injection pressure, ensuring that the entire cavity is filled without voids. Secondly, the final curing temperature of the material must match the residual heat temperature range of the profile corner during the welding cooling stage. The residual heat temperature during welding is typically concentrated in the range of 100°C to 160°C, and the selected material should be able to be effectively triggered and complete the final curing reaction within this temperature range. Material systems that meet the above conditions include, but are not limited to: thermally activated polyurethane foam systems (utilizing latent curing agents to trigger cross-linking and curing under heating conditions), modified asphalt-based damping materials (utilizing asphalt matrix to fully fuse and cure with functional fillers under thermally activated conditions), etc.

[0024] The injection volume should ideally fill 90% to 95% of the cavity volume. If the injection volume is less than 90%, voids will exist within the cavity, allowing sound to propagate in the residual air cavities and affecting the sound insulation effect. If the injection volume exceeds 95%, the internal pressure generated on the cavity wall by the material during the subsequent heating, foaming, or expansion stage may exceed the structural bearing capacity of the profile, leading to local bulging and deformation of the profile cross-section.

[0025] After injection, the injection ports on both ends of the profile are temporarily sealed to prevent material from flowing out of the ports due to gravity during the settling stage. The material is then left to stand at room temperature for a period determined by the initial setting characteristics of the selected material, aiming for a semi-solid state where the material is no longer freely flowing but the internal curing reaction has not yet terminated, typically not exceeding 24 hours. In this semi-solid state, the material already possesses basic shape retention capabilities, and subsequent welding heating and pressurization operations will not cause significant material extrusion. Simultaneously, the active centers of the internal curing reaction remain in a latent activated state, preserving the conditions for the residual heat-driven final curing in step S5.

[0026] Application of S3 Welding Interface Protective Layer: A thin, heat-activated protective film is applied along the outer contour of the welded end face of the profile after S2 treatment. The film thickness is typically 0.05mm to 0.10mm, and the material is a low-melting-point modified hot melt adhesive with a softening temperature lower than the welding melting temperature of the PVC material in the profile. The selection of this thickness range is based on the following: if the film is too thin, its ability to fill the microscopic uneven areas of the end face will be insufficient, resulting in a discontinuous interface transition layer; if the film is too thick, it will form independent heterogeneous layers between the end faces, affecting the direct fusion bonding between the profile materials and reducing the weld strength.

[0027] The functional mechanism of this adhesive film is as follows: During the subsequent heating stage of the welding plate, the adhesive film is heated to above its softening temperature and enters a molten state; at the instant the welding plate is removed and the two profile ends are joined, the softened adhesive film fills the microscopic unevenness of the end faces and the tiny gaps between the end faces of each cavity wall under the action of contact pressure, forming a continuous transition thin layer on the entire mating interface. This transition layer, together with the molten PVC material of the profile, participates in the cooling and solidification process, compensating for the shrinkage rate difference caused by the discontinuity of the material at the interface, thereby reducing the width and visibility of the white seam on the outer surface.

[0028] The adhesive film application method is simple, and the tools and operating skills required are comparable to those for ordinary pressure-sensitive tape application. No special auxiliary equipment is required, making it suitable for manual implementation at existing production stations.

[0029] S4 staged heating and welding: The profiles that have been treated by S2 and S3 are placed into the welding equipment, and the welding operation is performed in the following staged manner.

[0030] First, the welding plate simultaneously contacts the end faces of both profile sections, heating and melting the end face material. Unlike traditional processes that use a single heating time, this method implements a zoned differentiated control strategy for the heating contact time of the welding plate based on the functional requirements of each area of ​​the profile cross-section. The end face area corresponding to the outer surface of the profile (including the outer decorative surface and the visible side) requires a smooth, defect-free weld seam, and the requirement for melting depth is relatively limited. Therefore, the heating contact time can be appropriately shortened to reduce excessive shrinkage allowance accumulated in the molten layer on the outer surface. The end face areas corresponding to the internal cavity walls of the profile need sufficient melting depth to ensure effective melting and bonding between the cavity wall end faces. The heating contact time is relatively extended to ensure the welding strength of the cavity walls.

[0031] The specific values ​​for the aforementioned zone heating times should be determined through process experiments, taking into account the PVC material formulation of the profile, the chamber wall thickness parameters, and the actual temperature of the welding plate. Zone control can be achieved by adding heat insulation pads to local areas of the welding equipment or by controlling the contact time of the welding plates in stages.

[0032] Secondly, after heating is complete, the welding plate is quickly removed. The two profile sections are then butt-jointed, with the molten areas on their ends in contact. After the butt-jointing process, an initial pressure (preliminary pressure) lower than the conventional welding pressure is applied to establish preliminary contact and adhesion between the molten surfaces at both ends. During the preliminary pressure stage, the molten material is not immediately squeezed and shaped; instead, a short period of flow homogenization time is allowed for the molten material on the ends, especially in the corresponding area of ​​the outer surface. During this time, the material in the molten area of ​​the outer surface spreads evenly towards the contact surface under the guidance of the preliminary pressure, filling any potential localized material shortages and improving the uniformity of the molten material distribution on the outer surface.

[0033] Finally, after maintaining the initial pressure for a predetermined time, the pressure is increased to the normal final welding pressure to complete the final strong extrusion. The final pressure stage ensures that the molten interfaces of each cavity wall are tightly bonded under sufficient pressure, guaranteeing the overall weld strength of the corner. The pressure holding time continues until the temperature of the profile end face drops to a range suitable for safe demolding. The clamps are then released, and the welded profile corner is removed.

[0034] The core significance of the staged pressurization process lies in the fact that the initial pressurization stage creates a time window for the flow homogenization of the molten material on the outer surface, compensating for the process defects of the molten material being abruptly solidified before it has time to flow under the single pressurization mode, thereby effectively reducing the probability of white seams.

[0035] S5 Residual Heat Drives Final Curing of Sound Insulation Layer: After welding is completed and the profile is removed from the welding equipment, the corners of the profile accumulate heat in the cavity wall and corner structure due to welding heating, and are in a natural cooling process. At this stage, no external intervention is required on the profile; the curing of the material inside the cavity is driven entirely by the natural conduction of residual heat.

[0036] The sound-insulating composite material pre-placed in the cavity in S2 has already absorbed some heat through heat conduction from the cavity wall during the heating stage of the welding plate in S4, resulting in an overall temperature increase. After the profile is removed, as the residual heat at the corners continues to conduct to the inner wall of the cavity and the material inside the cavity, the temperature inside the cavity further increases, reaching the final curing temperature threshold of the selected sound-insulating material, triggering the final curing reaction of the material (including the thermal dissociation of latent curing agents, the formation of cross-linked networks, or the thermal activation and fusion of the matrix material, etc., the specific reaction mechanism depends on the selected material system).

[0037] After curing, the sound insulation material inside the cavity forms a stable physical bond with the cavity wall while filling the cavity volume. There is no continuous air layer inside the cavity that can conduct sound. The sound insulation structure achieves complete and continuous coverage at the corners, effectively eliminating the sound transmission channels formed by the lack of sound insulation filling at the corners in the existing process.

[0038] This step relies on the correct selection of the material system in S2. The final curing temperature threshold of the selected sound insulation material must be within the welding residual heat temperature range (100°C to 160°C), and the material's thermal stability in the semi-solid state must be sufficient to prevent premature curing during the waiting period from S2 to S4. Therefore, after the material selection is completed, the above matching relationship should be confirmed through small-batch process verification experiments as a necessary preliminary work before formal mass production.

[0039] S6 Removal of Excess Material and Surface Finishing: After the corner of the profile has completely cooled to room temperature, the weld overflow on the outer surface of the corner is removed according to the conventional corner cleaning operation. Due to the interface filling effect of the protective film in S3 and the improvement effect of the molten material distribution by the staged pressurization in S4, the width of the white seam at the weld seam on the outer surface is reduced compared with the traditional process, and the amount of subsequent surface finishing work after removing excess material is reduced accordingly.

[0040] During the corner cleaning process, avoid scratching or excessive cutting the outer decorative surface of the profile to ensure that the appearance quality of the finished product meets the product standard requirements.

[0041] S7 Quality Inspection: A comprehensive quality inspection is conducted on the corner of the profile after welding and integral molding of the sound insulation layer. The main inspection items include: welding strength inspection, referring to current relevant standards, mechanical performance tests (such as corner bracing test) are performed on the corner to confirm that the weld strength meets the design requirements and product execution standards; appearance quality inspection, through visual inspection or with the aid of measuring tools, the outer surface of the corner is inspected to confirm that the width of the white seam and the appearance condition meet the product standard requirements; sound insulation performance sampling inspection, a specified number of samples are randomly selected according to the product batch for sound insulation test to confirm the integrity of the curing state of the sound insulation layer in the cavity and the effectiveness of sound insulation, and the implementation effect of this method is evaluated based on the sound insulation test results.

[0042] The following provides two practical implementation examples. It is worth noting that both examples are implemented without structural modifications to the existing welding equipment. The main differences lie in three aspects: material system, injection process temperature, and residual heat matching requirements, which correspond to two application scenarios: low-to-mid-range sound insulation needs and high-end sound insulation needs, respectively.

[0043] Example 2 This embodiment provides a five-cavity window frame profile and a heat-activated polyurethane foam system, applicable to standard building sliding window frames.

[0044] Five-cavity PVC co-extruded profile with cross-sectional dimensions of 70mm×58mm, main cavity wall thickness of 2.8mm, cavity wall partition plate thickness of 1.5mm, cut at 45° angles and then welded at the corners.

[0045] The five-cavity profile has five chambers (C1 to C5) arranged sequentially from the outdoor to the indoor side. C1 is the outermost decorative chamber, the visible surface, and no sound insulation material is injected. C2 is the next outermost sealed air chamber, also without sound insulation material. C3 is the middle main load-bearing chamber, which is also a sound insulation functional chamber, and sound insulation material is mainly injected. C4 is the next innermost auxiliary functional chamber, which is used to supplement the injection of sound insulation material. C5 is the innermost decorative chamber, and no sound insulation material is injected. In other words, the main load-bearing chamber C3 is the primary sound insulation injection chamber in this embodiment. It is located in the middle of the cross-section, not directly adjacent to the exterior surface, and does not directly bear the structural load of the component, thus conforming to the chamber selection principle. C4 is treated simultaneously as an auxiliary injection chamber to improve the overall sound insulation effect.

[0046] The specific steps and related parameters are as follows: S1: Milling tool selection: vertical end milling machine, milling cutter speed 3000 r / min; single milling removal amount 0.3mm~0.5mm, total milling amount not exceeding 1.5mm; End face flatness requirements: end face flatness tolerance ≤ 0.10mm, perpendicularity tolerance ≤ 0.15°; Chamber ports: After milling, check each chamber. The opening size of ports C3 and C4 must be fully exposed to confirm that there are no burrs or blockages. If necessary, clean the port with a fine knife to remove any material stuck in it.

[0047] S2: Material selection: Thermally activated polyurethane foam system (single-component moisture-curing type, containing a latent thermal activation catalyst), liquid at room temperature, viscosity 800–1200 mPa·s; initial setting time approximately 3–6 hours, this is the time required from injection to semi-solidification; thermal activation trigger temperature 110°C–130°C; final curing reaction time, approximately 8–12 minutes at 115°C; density after curing approximately 120–180 kg / m³. 3 The cured state is a closed-cell foamed elastomer that forms a physical anchor with the cavity wall; the weighted sound insulation increment ΔRw of the cured layer is ≥ 8 dB.

[0048] The specific injection operation is as follows: Using a metering dispensing gun, with gravity assistance and slight air pressure, inject the material from the end face of chamber C3 along the longitudinal direction of the chamber until the liquid level is approximately 3 mm from the port; chamber C3 (cross-sectional area approximately 280 mm²) 2 Assuming a welded section length of 50mm, the chamber volume is approximately 14 cm³. 3 Injection volume: 13–13.3 cm 3 (Approximately 92%); Injection is carried out simultaneously in chamber C4 using the same method; After injection, the port is temporarily sealed with heat-resistant silicone to prevent the material from flowing out due to gravity during the static stage; Let it stand at room temperature for 4 to 6 hours until the material is in a semi-fluid and semi-solid state.

[0049] S3: The film parameters for this step are as follows: The adhesive film material should be EVA-modified low-melting-point hot melt adhesive (ethylene-vinyl acetate copolymer system); the film thickness should be 0.07 mm, which is the recommended value for five-cavity profiles, within the range of 0.05–0.10 mm; the softening temperature should be approximately 75°C–85°C; the film width should be cut according to the perimeter of the profile end face, covering the entire end face; the application method should be manual pressing, removing air bubbles and ensuring the edges are flush with the end face contour. It is important to note that the adhesive film should only be applied to the inner cavity wall end face areas corresponding to cavities C3 and C4, and the outer frame edge of the profile. For the outer surface end face of cavity C1, ensure complete film coverage to improve the quality of the weld appearance.

[0050] S4: The welding plate temperature is set to 210°C ± 3°C; the heating contact time of the outer surface end face area is reduced by 15% compared to the standard value; the heating contact time of the cavity wall end face area is executed according to the standard process reference value of about 18 to 22 seconds; the welding plate is withdrawn to the end face docking time within 3 seconds, and the molten surface is prevented from losing too much heat through rapid docking. The initial pressure value is selected as 0.05-0.08 MPa, which is about 25%-35% of the final pressure; the initial pressure holding time is 5-8 seconds; the final pressure value is 0.22-0.25 MPa, which is the conventional final pressure for welding; the final pressure holding time is 40-50 seconds, with the outer surface temperature of the corner ≤60°C as the standard.

[0051] The method of achieving zoned differentiated heating is to attach a 1.5mm thick polytetrafluoroethylene (PTFE) heat insulation pad to the contact area of ​​the C1 cavity on the outer surface of the welding plate and the profile, thereby reducing the effective heat flux density in this local area and appropriately reducing the heat input in the outer surface end area without requiring structural modification of the welding equipment.

[0052] S5: After the profile is removed from the welding equipment, the measured temperature of the corner cavity wall is approximately 125°C to 140°C, which is within the trigger temperature range of the heat-activated polyurethane foam system. After the welded corner of the profile is left to stand under natural ventilation without any external heat source or intervention, the cavity temperature will naturally drop below the trigger threshold after approximately 12 to 18 minutes, completing the final curing reaction.

[0053] After final curing, the cavity is in a state where the polyurethane foam is slightly expanded (linear expansion rate of about 5% to 8%), filling the cavity volume and forming uniform physical contact and slight anchoring with the cavity wall. There is no continuous air layer in the cavity.

[0054] S6-S7: First, use an automatic corner clearing machine with a milling cutter speed of 2500 r / min and a feed rate of 60 mm / min to remove excess material from the corners.

[0055] Next, an inspection will be conducted, and the inspection standards are as follows: Table 1: Test Standards for Example 2

[0056] Example 3 This embodiment provides a six-cavity door frame profile combined with modified asphalt-based damping material, suitable for building soundproof door frames.

[0057] The six-chamber PVC profile has an outer cross-sectional dimension of 90mm×72mm, an outer wall thickness of 3.2mm, and a chamber partition wall thickness of 2.0mm. It is cut at a 90° right angle and then welded at the corners. It has higher requirements for sound insulation performance and is used in applications such as recording studio partition doors and conference room soundproof doors.

[0058] The six-cavity profile has six chambers (D1 to D6) arranged from the outside to the inside. D1 is the outermost decorative cavity, which is not filled with sound insulation material. D2 is the second outermost sealed air cavity A, which is not filled with sound insulation material. D3 is the middle outer zone, which is the damping functional cavity (large cavity) and the main filling cavity, where sound insulation material is preferentially filled. D4 is the middle inner zone, which is the damping functional cavity (middle cavity) and the secondary filling cavity. D5 is the second innermost sealed air cavity B, which is not filled with sound insulation material. D6 is the innermost decorative cavity, which is not filled with sound insulation material.

[0059] D3 and D4 are used as sound insulation injection chambers, and the combined filling area of ​​the two chambers accounts for about 48% of the effective area of ​​the profile cross section, which can achieve a high chamber sound insulation quality.

[0060] The specific steps and related parameters are as follows: S1: Because the door frame profile has a large cross-section, the milling accuracy requirements for the end face are more stringent: End face flatness tolerance: ≤0.08 mm; perpendicularity tolerance: ≤0.10°; The opening areas of chambers D3 and D4 are relatively large. After milling, check the burrs around the ports and clean the internal debris of the chambers with an air gun to avoid affecting the quality of the sound insulation material injection.

[0061] S2: Material Selection: Modified asphalt-based damping material, specifically a butyl rubber modified asphalt composite system, with added barite powder and micro glass beads as fillers, containing a latent heat-activating agent. At room temperature, it is a thick paste with a viscosity of 5000–10000 mPa·s. The injection temperature is 60°C–70°C, with heating to reduce viscosity for easier flow and injection. This temperature is below the thermosetting trigger temperature. The initial setting time is approximately 1–2 hours; the thermosetting trigger temperature is 140°C–160°C; the final curing reaction time is approximately 10–15 minutes at 150°C; and the density after curing is approximately 1450–1550 kg / m³. 3 After curing, it is a viscoelastic damping layer that forms an adhesive contact with the cavity wall; for sound insulation performance, the weighted sound insulation increment ΔRw of the cured layer is ≥ 12 dB.

[0062] The specific injection operation is as follows: Heat the material container to 60°C to reduce its viscosity to a pumpable state; use a gear pump dispensing system (pumping pressure 0.1–0.15 MPa) to inject the material from the end face of chamber D3, maintaining the material temperature at 60°C to ensure continuous flowability; the cross-sectional area of ​​chamber D3 is approximately 380 mm². 2 Assuming the welded section is 60mm, the cavity volume is approximately 22.8 cm³. 3 Injection volume: 21.0–21.7 cm 3 It accounts for approximately 92% to 95%; the cross-sectional area of ​​chamber D4 is approximately 220 mm². 2 The chamber volume is approximately 13.2 cm³. 3 The injection volume is 12.2–12.5 cm. 3 Approximately 92%–95%; after injection, the material is temporarily sealed with a metal end cap. This is because the material density is high and the silicone sealing force is insufficient. After cooling and standing at room temperature for 1–2 hours, the material will naturally solidify to a semi-solid state. The surface can be pressed with a finger and it should have elastic resistance and not stick to the hand. The internal thermal activation agent of the semi-solidified modified asphalt material is still in a latent state and requires a temperature above 150°C to trigger final curing. This does not overlap with the temperature conditions of the standing and early welding stages. Although the material is heated during the S4 welding plate heating stage, the temperature conducted from the outer wall to the central area of ​​the cavity is usually lower than the trigger value and will not cure prematurely.

[0063] S3: The film parameters for this step are as follows: The material is a polyamide (PA)-based modified hot melt adhesive film; the film thickness is 0.08 mm; the softening temperature is approximately 90°C to 100°C, which is lower than the PVC welding melting temperature of approximately 195°C; the film width covers the entire contour of the profile end face, with a focus on ensuring complete coverage of the D3 and D4 cavity wall end face areas; the temperature resistance is ≥ 210°C, ensuring that it does not decompose at the welding plate temperature, but only softens and flows; the polyamide-based film has better temperature resistance than the EVA film, making it suitable for the high welding plate temperature conditions in this embodiment. It will not decompose or vaporize prematurely at higher welding plate temperatures, and can maintain the complete film shape throughout the heating stage, completing the interface filling function at the moment of docking.

[0064] S4: The six-cavity door frame profile has a larger cross-section and more cavity walls. The welding plate temperature is set at 215°C ± 3°C, which is appropriately increased compared to the five-cavity profile. The heating contact time of the end face area corresponding to the appearance cavity (D1) is reduced by 20% (4-5 s) compared to the reference value; the heating contact time of the end face area corresponding to the sealing cavity (D2, D5) is reduced by 10% compared to the reference value; the heating contact time of the end face area corresponding to the main cavity (D3, D4) is the reference value, approximately 22-26 s; the time for the welding plate to be removed to the end face contact is ≤ 3 s.

[0065] The initial pressure is 0.06–0.09 MPa, which is about 25% of the final pressure; the initial pressure holding time is 8–10 s. Compared with Example 2, the cross-section is larger, so the homogenization time is appropriately extended; the final pressure is 0.25–0.28 MPa; the final pressure holding time is 55–65 s, with the outer surface temperature of the corner ≤65°C as the standard.

[0066] The method of achieving zoned differentiated heating is to install a detachable PTFE+ceramic fiber composite heat insulation block in the corresponding area of ​​the welding plate's outer surface, and to achieve the action of the welding plate separating from the outer cavity area first (withdrawing partial contact 3 seconds earlier than the cavity wall area) through the welding equipment control program, so as to achieve precise differentiated control of heating time without the need to replace the welding plate.

[0067] S5: The final curing trigger temperature (140°C–160°C) of modified asphalt-based damping materials is higher than that of polyurethane foam systems, requiring higher residual heat temperatures. Due to their larger cross-sectional mass and thicker cavity walls, the six-cavity door frame profiles have a larger heat capacity at the corners after welding. The measured residual heat temperature of the corner cavity walls is approximately 145°C–165°C, meeting the triggering conditions for modified asphalt materials. The welded corners of the profiles are placed on a dedicated slow-cooling rack wrapped in an insulating blanket and left to stand for approximately 15–25 minutes under insulating and slow-cooling conditions, allowing the modified asphalt material inside the cavities to complete its final curing reaction.

[0068] After final curing, the cavity condition is as follows: the modified asphalt damping layer fills chambers D3 and D4, forming a stable bond with the cavity walls. The high-density filler provides significant sound insulation within the cavity, eliminating corner sound insulation blind spots. When using insulation blankets for slow cooling, it is necessary to ensure that the corners of the profiles are not disturbed by external forces during the slow cooling process to avoid geometric deformation caused by the profiles not being fully hardened during the residual heat high-temperature stage.

[0069] S6-S7: Table 2: Test Standards for Example 3

[0070] Finally, it should be noted that the described embodiments are merely some, not all, of the embodiments of the present invention. Those skilled in the art will understand that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the present invention. The scope of the present invention is defined by the claims and their equivalents; that is, all other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

Claims

1. A method for seamless welding of a multi-cavity profile and integral molding of a sound insulation layer, characterized in that, Includes the following steps: S1. Mill and finish the welding end faces of the multi-cavity PVC profile to make the end faces flat and vertical, and confirm that the ports of each cavity are unobstructed. S2. Pre-inject sound-insulating composite material into the sound-insulating functional cavity of the profile section, with an injection volume of 90% to 95% of the cavity volume. After temporarily sealing the port, let it stand at room temperature until the sound-insulating composite material reaches a semi-solid state. S3. Apply a heat-activated protective film to the welding end face of the profile, wherein the softening temperature of the heat-activated protective film is lower than the welding melting temperature of the PVC material of the profile; S4. Perform phased heating and welding on the profile: During the heating phase, apply differentiated heating contact time to the corresponding end face area on the outer surface of the profile and the corresponding end face area on the cavity wall; after the welding plate is removed, first use an initial pressure lower than the final pressure to make the molten surfaces at both ends contact and flow homogenize, and then increase to the final pressure to complete the extrusion and solidification. S5. Utilize the residual heat conducted into the cavity during the natural cooling process of the profile corner to drive the pre-placed sound insulation composite material in S2 to complete the final curing. S6. Remove excess material and perform surface finishing on the outer surface of the diagonal section; S7. Inspect the diagonal parts.

2. The method according to claim 1, characterized in that, In S2, the final curing temperature range of the sound insulation composite material is 100°C to 160°C, which matches the residual heat temperature range of the corner of the profile during the welding cooling stage.

3. The method according to claim 2, characterized in that, The sound insulation composite material is at least one of a thermally activated polyurethane foam system or a modified asphalt-based damping material.

4. The method according to claim 1, characterized in that, In S2, the selection principle for the sound insulation functional chamber is as follows: select functional chambers located in the middle of the profile section, not directly adjacent to the outer surface, and not directly bearing structural loads; external cavities and sealed air cavities directly adjacent to the outer surface are not used as injection targets.

5. The method according to claim 1, characterized in that, In S3, the material of the heat-activated protective adhesive film is a low-melting-point modified hot melt adhesive; in the heating stage of S4, the adhesive film softens and fills the microscopic uneven area of ​​the welding end face and the tiny gap between the cavity wall end face at the moment of docking, forming a continuous interface transition layer to reduce the width of the white seam at the weld seam on the outer surface of the corner.

6. The method according to claim 5, characterized in that, The thickness of the heat-activated protective film is 0.05 mm to 0.10 mm.

7. The method according to claim 1, characterized in that, In S4, the heating contact time of the corresponding end face region of the outer surface is shorter than the heating contact time of the corresponding end face region of the cavity wall.

8. The method according to claim 1, characterized in that, In S4, after the initial pressure is applied, it is maintained for a predetermined time to allow the molten material to flow and homogenize before the pressure is increased to the final pressure. The staged pressurization method provides a flow homogenization time window for the molten area on the outer surface, improving the uniformity of the molten material distribution on the outer surface.

9. The method according to claim 1, characterized in that, In S2, the settling time shall not exceed 24 hours.

10. Door frames and window frames manufactured by the method according to any one of claims 1-9.

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