A coating process to improve the pressure retention performance of OPW airbags; OPW airbags

Abstract

This invention provides a coating process for improving the pressure-holding performance of OPW airbags, relating to the field of airbag manufacturing technology. The process includes the following steps: S1: Coating the OPW airbag fabric with a layer of silicone rubber with a viscosity of 13-20 Pa·s and a coating weight of 15-25 g / m²; S2: Baking in several sections of a continuous heat-setting oven, with the baking temperature increasing sequentially from 100-160°C and the baking speed at 20-30 μd / min; S3: Applying a second coating layer on top of the first coating layer, the second coating using silicone rubber with a viscosity of 200-400 Pa·s and a weight of 30-45 g / m²; S4: Baking again in several sections of a continuous heat-setting oven, with the baking temperature increasing sequentially from 160-205°C and the baking speed at 15-20 μd / min. This invention also provides an OPW airbag. This solution can effectively improve the airtightness of the OPW airbag.

Description

Technical Field

[0001] This invention relates to the field of airbag manufacturing technology, and more specifically, to a coating process for improving the pressure-holding performance of OPW airbags and OPW airbags. Background Technology

[0002] With the increasing effectiveness of curtain airbags in protecting occupants during side collisions and rollovers, the 2021 C-NCAP new car evaluation introduced an assessment of side curtain airbag pressure retention performance. Improving the protective effect of curtain airbags on occupants has become a subject of in-depth research, and the pressure retention performance of curtain OPW airbag bags has become a crucial indicator in the development and production process design. The main reason for air leakage in OPW airbag bags is the presence of gaps in the fabric structure itself, such as at the intersections of warp and weft yarns and between warp and weft fibers. Under the impact of high-temperature, high-pressure airflow, airflow passes through these gaps. Current technologies generally improve fabric airtightness by increasing fabric density and coverage coefficient; or by coating the fabric with a thicker adhesive film to act as an air barrier. However, high-density fabrics and high coating weight not only increase costs but also increase fabric thickness, affecting the folded volume of OPW airbags and increasing their weight. Furthermore, fabric density has its limits; even with higher density, gaps will remain at the warp and weft interlacing points and between the fibers. Under high-temperature, high-pressure airflow, these gaps will widen due to stretching, leading to air leakage. While silicone molecules have a helical structure and some permeability, although a thicker film at high weight can achieve very low permeability, it will still be permeable under high-temperature, high-pressure airflow above 50 kPa. Especially at stress concentration points, the film is easily stretched and ruptured, creating rapid air leakage areas. This results in a rapid drop in airbag pressure and low pressure retention. Additionally, OPW airbags are made by cutting fabric according to the airbag shape, and the cut edges are uncoated fabric, allowing airflow to escape and affecting pressure retention.

[0003] The invention patent with publication number CN113789668, entitled "Method for Preparing One-Piece Molded Airbags and Airbags for High-Pressure-Retaining Curtain-Type Airbags," discloses a method for preparing high-pressure-retaining airbags. It achieves good pressure retention through high-density fabric, high-weight coating, and a coordinated stitching design. However, this method does not address the root cause of air leakage in the OPW airbag fabric; it merely maximizes the fabric density and then uses high-viscosity silicone to coat a high-weight adhesive layer, forming a thick, air-barrier film. This not only increases costs but also increases the thickness and weight of the OPW airbag, affecting its folded volume. Summary of the Invention

[0004] This invention discloses a coating process to improve the pressure retention performance of OPW airbags, aiming to improve the airtightness of the fabric and enhance the pressure retention performance of OPW airbags through the coating process.

[0005] The present invention adopts the following solution:

[0006] This application provides a coating process for improving the pressure-holding performance of OPW airbags, comprising the following steps:

[0007] S1: The OPW airbag bag fabric is coated with a layer of low-viscosity silicone, with a viscosity of 13-20 Pa.s and a coating weight of 15-25 g / m2, forming a thin film on the fabric, which is the first coating.

[0008] S2: Baking is carried out through several sections of continuous heat-setting ovens, with the baking temperature increasing sequentially from 100-160℃; the baking speed is 20-30 yd / min.

[0009] S3: Continue to apply the second coating on the first coating. The second coating uses high-viscosity silicone with a viscosity of 200-400 Pa·s and a basis weight of 35-45 g / m2 to form the second coating.

[0010] S4: Then bake through several sections of continuous heat-setting oven, with the baking temperature increasing sequentially from 160-205℃; the baking speed is 15-20 yd / min.

[0011] Furthermore, in S2, a nine-section continuous oven is used, and the oven temperature is set sequentially as follows: 100℃-110℃-120℃-140℃-160℃-160℃-160℃-160℃-160℃-160℃.

[0012] Furthermore, in step S4, a nine-section continuous oven is used, and the oven temperature is set sequentially as follows: 160℃-180℃-180℃-205℃-205℃-205℃-205℃-205℃-205℃.

[0013] Furthermore, both the first and second coatings are applied using an integrated adhesive application and setting machine.

[0014] Furthermore, during the process from S2 to S3, the fabric is returned to the integrated coating and setting machine via a fabric threading method to complete the second coating.

[0015] Furthermore, after the adhesive is applied, a pressure retention rate test is performed. The pressure retention rate test method is as follows: the initial pressure is set to 70 kPa. When the pressure reaches 70 kPa, the equipment automatically stops outputting air pressure and starts a countdown of 12 seconds. After the countdown of 12 seconds, the equipment automatically reads the remaining pressure. The pressure retention rate is obtained by the ratio of the remaining pressure to the initial pressure.

[0016] The present invention also provides an OPW airbag, which is manufactured by the coating process described in any one of the above-mentioned methods to improve the pressure-holding performance of the OPW airbag.

[0017] Beneficial effects:

[0018] In this solution, a low-viscosity silicone coating is first applied. Low-viscosity silicone has good fluidity and strong permeability, easily penetrating the fabric structure to fill the gaps between warp and weft yarns and the gaps between yarn fibers, forming a thin film at the weave points. This creates a blocking effect, improving the fabric's airtightness. Simultaneously, it reduces the impact of excessively high-pressure airflow on the outer film, better protecting it and preventing excessive airflow impact, thus enhancing its air-blocking effect. Because the adhesive penetrates the fabric structure to create an air-blocking effect, and with the pre-reserved cutting edge, even without a coating, airflow is difficult to escape from the cut edges of the OPW airbag. This solution employs low-temperature baking during the application of the first coating layer. This slows down the rapid surface formation of the first coating, allowing some gases generated during the chemical reaction of the adhesive to evaporate more effectively. Simultaneously, the low-viscosity silicone penetrates into the fabric gaps and fibers, creating a barrier and improving the fabric's airtightness. This reduces the impact of high-temperature, high-pressure airflow on the outer adhesive film, meaning the outermost film doesn't need to be excessively thick to achieve the required air-blocking effect. This reduces the required coating weight, thereby lowering costs and fabric thickness, and consequently, the folded volume and weight of the OPW airbag. The first coating layer penetrates the fabric structure and fibers, making the adhesive layer bonded to the fabric more firmly. The second coating layer is chemically bonded to the first coating layer, making the OPW airbag fabric more wear-resistant, preventing the adhesive film from easily peeling off, and ensuring a tighter bond between the adhesive film and the fabric base, resulting in better airtightness. Detailed Implementation

[0019] Example 1

[0020] This embodiment provides a coating process to improve the pressure-holding performance of OPW airbags, including the following steps:

[0021] S1: The OPW airbag bag fabric is coated with a layer of low-viscosity silicone, with a viscosity of 13-20 Pa.s and a coating weight of 15-25 g / m2, forming a thin film on the fabric, which is the first coating.

[0022] S2: Baking is carried out through several sections of continuous heat-setting ovens, with the baking temperature increasing sequentially from 100-160℃; the baking speed is 20-30 yd / min.

[0023] S3: Continue to apply the second coating on the first coating. The second coating uses high-viscosity silicone with a viscosity of 200-400 Pa·s and a basis weight of 35-45 g / m2 to form the second coating.

[0024] S4: Then bake through several sections of continuous heat-setting oven, with the baking temperature increasing sequentially from 160-205℃; the baking speed is 15-20 yd / min.

[0025] In this embodiment, both the first and second coatings are completed using an existing integrated coating and setting machine. In step S1, a low-viscosity silicone coating is first applied to the fabric. The silicone used here can be prepared by mixing existing materials. For the first coating, a silicone with a viscosity of only 13-20 Pa·s is selected. This viscosity range allows for proper penetration into the fabric structure and fibers, filling the gaps between warp and weft yarns and the gaps between yarn fibers. This ensures a good binding of the adhesive with the fabric structure, improving both the airtightness and the abrasion resistance of the coated fabric. When the viscosity is less than 13 Pa·s, the penetration is too good, easily penetrating to the reverse side of the fabric; while when the viscosity is greater than 20 Pa·s, the penetration is poor, making it difficult to penetrate into the yarn fibers.

[0026] In this embodiment, in step S2, a nine-section continuous oven is used, with the oven temperature set sequentially as follows: 100℃-110℃-120℃-140℃-160℃-160℃-160℃-160℃-160℃. The first section is set at 100℃ to allow the adhesive to penetrate the warp and weft threads of the fabric and the yarn fibers at a low temperature. The second and third sections are set at 110℃ and 120℃, respectively, to slow down the further penetration of the adhesive to the reverse side of the fabric. The fourth section is set at a higher temperature than the third section but lower than the subsequent sections to further increase the temperature and initiate a chemical reaction in the adhesive, while preventing excessively high temperatures from causing the coating surface to bake too quickly and preventing the volatilization of gases generated during the chemical reaction. The final section, at 160℃, is the temperature required for the low-viscosity adhesive to bake into a film. Because silicone rubber is greatly affected by temperature, it cures rapidly at high temperatures. Therefore, this embodiment first bakes at a low temperature to promote the penetration of the adhesive, then gradually increases the temperature to reduce the penetration of the adhesive, finally forming a film. Of course, the specific temperature variation range can be adjusted based on the above principle according to different oven sections, different adhesive types, and coating speeds.

[0027] After the first coating is formed, the fabric is returned via a weaving process to complete the second coating. The second coating covers the surface of the first coating, forming the final gas barrier layer. To further ensure the gas barrier effect of the film, a high-viscosity silicone rubber is selected. High-viscosity silicone rubber has more stable mechanical strength, better tensile strength, and resistance to airflow impact. Here, a silicone rubber with a viscosity of 200-400 Pa·s is selected. When the viscosity of the silicone rubber is higher than 400 Pa·s, the coating workability is poor, and the coating basis weight easily exceeds 45 g / m2, which is not conducive to cost control; when the viscosity is lower than 200 Pa·s, the tensile strength of the film is poor, and it is not resistant to impact.

[0028] After applying the second coating, in step S4, a nine-section continuous oven is used, with the oven temperature set sequentially as follows: 160℃-180℃-180℃-205℃-205℃-205℃-205℃-205℃-205℃. The higher temperatures in the second oven are due to the higher temperatures required for the chemical reaction of the high-viscosity adhesive, which better catalyzes the chemical reaction and accelerates film formation, improving coating efficiency. Simultaneously, the high temperature facilitates rapid molding of the silicone rubber. This solution also addresses the problem in existing methods where a single coating of the adhesive results in a thicker layer, preventing the evaporation of gases and slow-evaporating solvents during baking, leading to air bubbles in the adhesive film and affecting its quality. By applying the coating in two thinner layers, the gases and solvents from the chemical reaction can be more effectively evaporated from the adhesive film.

[0029] After the second coating is applied, the pressure retention rate test can be performed on the obtained OPW airbag to measure whether the product meets the requirements. The pressure retention rate test method is as follows: the initial pressure is set to 70 kPa. When the pressure reaches 70 kPa, the equipment automatically stops outputting air pressure and starts a countdown of 12 seconds. After the countdown of 12 seconds, the equipment automatically reads the remaining pressure. The pressure retention rate is obtained by the ratio of the remaining pressure to the initial pressure.

[0030] To verify the effectiveness of this solution, another specific embodiment and comparative example are provided here:

[0031] Example 2

[0032] First, apply 25 g / m² of silicone rubber with a viscosity of 13 Pa·s to the same OPW airbag fabric as in Example 1. The oven baking temperature is set to 100℃-110℃-120℃-140℃-160℃-160℃-160℃-160℃-160℃, and the coating baking speed is 25 yd / min. After baking, apply another 30 g / m² of silicone rubber with a viscosity of 200 Pa·s on top of the first coating. The baking temperature is set to 160℃-180℃-180℃-205℃-205℃-205℃-205℃-205℃, and the coating baking speed is 20 yd / min. Samples are taken to test the pressure retention rate and abrasion resistance.

[0033] Example 3

[0034] First, apply 15 g / m² of silicone rubber with a viscosity of 20 Pa·s to the same OPW airbag fabric as in Example 1. The oven baking temperature is set to 100℃-110℃-120℃-140℃-160℃-160℃-160℃-160℃-160℃, and the coating baking speed is 25 yd / min. After baking, apply another 45 g / m² of silicone rubber with a viscosity of 200 Pa·s on top of the first coating. The baking temperature is set to 160℃-180℃-180℃-205℃-205℃-205℃-205℃-205℃, and the coating baking speed is 20 yd / min. Samples are taken to test the pressure retention rate and abrasion resistance.

[0035] Comparative example

[0036] Using silicone with a viscosity of 200 Pa·s, 55 g / m2 was coated onto the OPW airbag fabric in one go. The baking temperature was set to 160℃-180℃-180℃-205℃-205℃-205℃-205℃-205℃, and the coating baking speed was 15 yd / min. The pressure retention rate and wear resistance were sampled and tested.

[0037] Here, the pressure retention rate test method is as follows: the initial pressure is set to 70 kPa. When the pressure reaches 70 kPa, the device automatically stops outputting air pressure and starts a countdown of 12 seconds. After the countdown of 12 seconds, the device automatically reads the pressure, and the pressure at this time is the remaining pressure after 12 seconds.

[0038] Abrasion resistance test method: EASC 99040180 3.25 standard test method ISO 5981. Test results are shown in Table 1:

[0039] Table 1

[0040]

[0041] As can be seen from the above embodiments and comparative examples, the OPW airbags made by this method have a higher pressure retention rate and better wear resistance.

[0042] Example 4

[0043] This invention also provides an OPW airbag, which is manufactured using the coating process described above to improve the pressure retention performance of the OPW airbag. The resulting OPW airbag has good pressure retention performance and higher wear resistance.

[0044] This solution employs a two-layer coating process. The first coating uses low-viscosity silicone, which is first baked at a low temperature to promote its penetration into the fabric structure, filling the gaps between the warp and weft yarns and the fibers, forming a thin film that creates a blocking effect, improving the fabric's airtightness. It also mitigates the impact of excessively high-pressure airflow on the outer film, better protecting it and preventing excessive stretching that could affect the OPW airbag's airtightness. Due to the air-blocking effect of the first coating, less airflow passes through, and the airflow impact is minimal. Therefore, the second coating does not need to be too thick, reducing the required coating weight and achieving cost reduction, as well as reducing fabric thickness, thus decreasing the folded volume and weight of the OPW airbag. Here, the first coating penetrates the fabric structure and fibers, making the adhesive layer bonded to the fabric more firmly. The second coating is chemically bonded to the first coating, making the OPW airbag fabric more wear-resistant, preventing the film from peeling off, and ensuring a tight bond between the film and the fabric base, resulting in better airtightness.

[0045] It should be understood that the above are merely preferred embodiments of the present invention, and the scope of protection of the present invention is not limited to the above embodiments. All technical solutions that fall within the scope of the present invention are within the scope of protection of the present invention.

[0046] The above description of embodiments only illustrates certain aspects of the present invention and should not be construed as limiting the scope.

Claims

1. A coating process for improving the pressure retention performance of OPW airbag cushion, characterized in that, Includes the following steps: S1: The OPW airbag bag fabric is coated with a layer of low-viscosity silicone, with a viscosity of 13-20 Pa.s and a coating weight of 15-25 g / m², forming a thin film on the fabric, which is the first coating. By using low-viscosity silicone to penetrate into the fabric structure, it fills the gaps between the warp and weft yarns and the gaps between the yarn fibers, and forms a thin film at the weave points to create a blocking effect. S2: Baking is carried out through several sections of continuous heat-setting ovens, with the baking temperature increasing sequentially from 100-160℃; the baking speed is 20-30 yd / min. S3: Continue to apply the second coating on the first coating. The second coating uses high-viscosity silicone with a viscosity of 200-400 Pa·s and a basis weight of 35-45 g / m² to form the second coating. S4: Then bake through several sections of continuous heat-setting ovens, with the baking temperature increasing sequentially from 160-205℃; the baking speed is 15-20 yd / min. In S2, a nine-section continuous drying oven is used, and the oven temperature is set sequentially as follows: 100℃-110℃-120℃-140℃-160℃-160℃-160℃-160℃-160℃. In step S4, a nine-section continuous oven is used, and the oven temperature is set sequentially as follows: 160℃-180℃-180℃-205℃-205℃-205℃-205℃-205℃-205℃.

2. The coating process for improving the pressure retention performance of OPW air bag according to claim 1, characterized in that, Both the first and second coatings are applied using an integrated adhesive application and setting machine.

3. The coating process for improving the pressure retention performance of OPW air bag according to claim 2, characterized in that, During the process from S2 to S3, the fabric is returned to the integrated coating and setting machine by the fabric threading method to complete the second coating.

4. The coating process for improving the pressure-holding performance of OPW airbags according to claim 1, characterized in that, After the adhesive is applied, a pressure retention rate test is performed. The pressure retention rate test method is as follows: the initial pressure is set to 70 kPa. When the pressure reaches 70 kPa, the equipment automatically stops outputting air pressure and starts a countdown of 12 seconds. After the countdown of 12 seconds, the equipment automatically reads the remaining pressure. The pressure retention rate is obtained by the ratio of the remaining pressure to the initial pressure.

5. An OPW airbag, characterized in that, It is manufactured using the coating process described in any one of claims 1-4 to improve the pressure-holding performance of OPW airbags.

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