Paints for airbag base fabrics and airbag base fabrics

Abstract

To provide a paint for airbag base fabric that offers good foldability for storage and good environmental resistance. [Solution] This is a water-based paint for airbag base fabrics, based on polyurethane resin. It is composed of a crosslinking agent and a thickening agent, with the amount of thickening agent added being in the range of 0.5 to 6 parts by mass per 100 parts by mass of polyurethane resin, and the amount of crosslinking agent added being set to 6 or more parts by mass to 1 part thickening agent.

Description

[Technical Field]

[0001] This invention relates to a polyurethane resin-based coating for airbag base fabrics and to airbag base fabrics. [Background technology]

[0002] Conventionally, silicone elastomer-based coatings have been used for airbag base fabrics to ensure adequate breathability (airtightness). However, because silicone elastomers have a high environmental impact, there have been airbag base fabrics coated with polyurethane resin-based coatings, which have a lower environmental impact than silicone elastomers (see, for example, Patent Documents 1 and 2). [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2009-62643 [Patent Document 2] Special publication 2023-503078 [Overview of the Initiative] [Problems that the invention aims to solve]

[0004] Typically, airbags are installed in vehicles in a folded state and stored in a designated storage area, so they are required to be able to fold compactly. Furthermore, since vehicles may be subjected to high-temperature and high-humidity environments, the airbag base fabric is required to have the ability to maintain stable airtightness (environmental resistance) even in such high-temperature and high-humidity environments. Conventional airbag base fabrics coated with polyurethane resin have not been able to achieve both good foldability and good environmental resistance.

[0005] The present invention aims to solve the above-mentioned problems and to provide a coating for airbag base fabric and an airbag base fabric that offer good foldability and good environmental resistance. [Means for solving the problem]

[0006] The paint for airbag base fabric according to the present invention is a water-based paint for airbag base fabric that is based on polyurethane resin. It is made by adding a crosslinking agent and a thickening agent. The amount of thickener added shall be within the range of 0.5 to 6 parts by mass per 100 parts by mass of polyurethane resin. The crosslinking agent is characterized by being set to a mass ratio of 6 or more per 1 part thickener. [Brief explanation of the drawing]

[0007] [Figure 1] This is a cross-sectional model of an airbag base fabric, which is one embodiment of the present invention. [Modes for carrying out the invention]

[0008] The following describes in detail an embodiment of the paint for airbag base fabric (hereinafter simply referred to as "paint") which is one embodiment of the present invention. In this embodiment, unless otherwise specified, "parts" indicating the compounding unit refers to parts by mass.

[0009] The paint of the embodiment is a water-based paint based on polyurethane resin, and more specifically, it is based on polyurethane resin with a thickening agent and a crosslinking agent added.

[0010] Polyurethane resins can be polyether-based, polyester-based, or acrylic-based, but from the viewpoint of hydrolysis resistance, polyether-based polyurethane is preferred.

[0011] It is preferable to use urethane-based or acrylic-based thickeners, and in this embodiment, a urethane-based thickener is used.

[0012] The amount of thickener added is set within the range of 0.5 to 6 parts (preferably 0.5 to 5 parts) per 100 parts of polyurethane resin. If the amount of thickener added is less than 0.5 parts, the stiffness and flexibility of the airbag base fabric formed by applying the resulting coating will be too high. Conversely, if the amount of thickener added exceeds 6 parts, the viscosity of the resulting coating will be too high.

[0013] As the crosslinking agent, it is preferable to use a carbodiimide-based, isocyanate-based, or oxazoline-based agent, and in this embodiment, a carbodiimide-based crosslinking agent is used.

[0014] The amount of crosslinking agent added is set to 6 or more by mass ratio to 1 part thickener. This is because if the amount of crosslinking agent added is less than 6 parts thickener, the airbag base fabric formed by applying the resulting coating will not have the necessary environmental resistance.

[0015] Furthermore, in addition to thickeners and crosslinking agents, leveling agents and defoaming agents are added to the paint in this embodiment.

[0016] The viscosity of the paint in the embodiment (specifically, the viscosity at the temperature when applied to the airbag base fabric) is adjusted to within the range of 1,000 to 100,000 mPa·s (preferably 1,500 to 100,000 mPa·s, and even more preferably 5,000 to 70,000 mPa·s). If the viscosity is less than 1,000 mPa·s or more than 100,000 mPa·s, the viscosity is either too low or too high, making knife coating difficult when applying to the fabric. Note that the method of application to the fabric is not limited to knife coating, and may also be by dip coating. When applying by dip coating, it is preferable to adjust the viscosity of the paint to within the range of 10 to 5,000 mPa·s.

[0017] Next, the airbag base fabric 1 of the embodiment will be described. As shown in Figure 1, the airbag base fabric 1 of the embodiment is formed by applying a coating film 4 made of the above-mentioned paint to one side of a fabric 3 woven from synthetic fibers.

[0018] The fabric 3 is formed from a woven fabric woven from polyester fibers, polyamide (PA) fibers, or polypropylene (PP) fibers. In the case of the embodiment, specifically, polyester fibers are used for the fabric 3. Specifically, polyethylene terephthalate (PET) fibers can be used as the polyester fibers. More specifically, in the case of the embodiment, the fabric 3 is formed by weaving PET fibers in a plain weave. Although the normal weaving pattern of the fabric 3 is a plain weave, the fabric 3 may be woven by a twill weave or a satin weave.

[0019] More specifically, in the case of the embodiment, the fabric 3 has a cover factor (K) represented by the following formula (1) set within a range of 1500 to 4000 (preferably 1800 to 3000, more preferably 2000 to 2600).

[0020] K = NW × DW + NF × DF 0.5 (1) NW: warp density (ends / in), DW: warp fineness (denier) NF: weft density (picks / in), DF: weft fineness (denier) Note that a small or large value of the cover factor (K) means that the thread density and / or thread fineness of the warp and weft in the fabric are relatively small or large.

[0021] That is, a small value of the cover factor (K) means a high air permeability. If the cover factor (K) is less than 1500, the air permeability of the fabric 3 itself is too high, and in addition to making it difficult to obtain a predetermined mechanical strength, the molten resin penetrates between the weave during film formation, making it difficult to ensure the airtightness and flexibility of the obtained coated fabric (airbag base fabric 1). Conversely, if the cover factor (K) exceeds 4000, the rigidity of the obtained fabric 3 becomes too high, resulting in poor foldability and storage, and is not preferable as a base fabric for an airbag.

[0022] A coating film 4 is formed by applying paint to one side of the fabric 3. In this embodiment, the paint is applied to one side of the fabric 3 by knife coating (die coating). Although knife coating is used in this embodiment, the method of applying paint to the fabric 3 is not particularly limited. For example, for single-sided coating, in addition to knife coating, roller coating (National, Reverse), brush coating, spray coating, kissroll coating, flow coating (shower coating, curtain coating), etc. can be exemplified. For double-sided coating, dip coating, etc. can be exemplified.

[0023] Furthermore, the amount of paint applied to fabric 3 (based on dryness) varies depending on the paint composition and the required properties of the fabric (breathability and flexibility), but is typically 10-30 g / m². 2 (Ideally, 13-27 g / m²) 2 More preferably, 15-25 g / m 2 The thickness of the coating film 4 (dry thickness) is set within the range of 5 to 200 μm (preferably 5 to 150 μm, and even more preferably 5 to 100 μm).

[0024] Furthermore, the airbag base fabric 1 of the embodiment is preferably 130 mm or less in terms of rigidity (cantilever method) (ASTM D5732) (preferably 100 mm or less, and even more preferably 85 mm or less), and preferably 30 N or less in terms of rigidity (method B) (ASTM D4032) (preferably 25 N or less, and even more preferably 20 N or less). If the value in terms of rigidity (cantilever method) exceeds 130 mm (or the value in terms of rigidity (method B) exceeds 30 N), the foldable storage is not good, and it is difficult to compactly fold an airbag manufactured using the airbag base fabric 1.

[0025] Furthermore, the airbag base fabric 1 of the embodiment has an air permeability (Fragile method) (JIS L 1096) of 0.7 mL / cm². 2 / sec or less (preferably 0.5 mL / cm³) 2 Less than or equal to / sec, more preferably 0.2 mL / cm³ 2It is desirable that it be 0.7 mL / cm 2 2 / sec or less. If the air permeability exceeds 0.7 mL / cm 2

[0026] Furthermore, the airbag base fabric 1 of the embodiment has an air permeability (Frazer method) (JIS L 1096) measured again after the following environmental resistance performance test of 0.7 mL / cm 2 2 / sec or less (desirably, 0.5 mL / cm 2 2 / sec or less). The environmental resistance performance test is to leave a base fabric for airbags of a predetermined shape in a folded state (specifically, in a state of being folded double so that the coating surfaces contact each other) under predetermined conditions for a predetermined time. The tests are conducted under two test conditions: A: leaving for 1000 hours in an environment at a temperature of 120°C, and B: leaving for 1000 hours in an environment at a temperature of 50°C and a humidity of 95%. That is, the airbag base fabric 1 of the embodiment has good environmental resistance without causing a change in the coating film 4 even in a state of being left for a predetermined time in a high-temperature and high-humidity state.

[0027] Hereinafter, test examples conducted to verify the effects of the present invention will be described. As the fabric 3, a woven fabric made of polyethylene terephthalate (PET) (plain weave: 560 dtex, 51 warp ends, cover factor: 2420) is used. As the paint for forming the coating film 4, one having the following basic composition is used.

[0028] <Basic composition> 100 parts of polyurethane resin Thickener Variable amount Crosslinking agent Variable amount 0.3 part of leveling agent 0.3 part of defoaming agent 278 parts of water Polyurethane resin: HYDRAN WLS-210 (solid content 36%), thickener: ADEKANOL UH-420, crosslinking agent: Carbodlite V-020L2, leveling agent: BYK-4355, defoaming agent: TEGO FOAMEX 800 Each aqueous coating, prepared by adding the amounts of thickener and crosslinking agent shown in Tables 1-3 to the basic composition described above, is applied to one side of the fabric by knife coating to form a coating film (solid content coating amount: 20g / m²). 2 Airbag base fabrics for the test examples were manufactured using different film thicknesses (film thickness: 20 μm).

[0029] [Table 1]

[0030] [Table 2]

[0031] [Table 3]

[0032] As shown in Table 1, the reference example paints do not contain either a thickener or a crosslinking agent. Test Examples 1-3 show paints with only a thickener added, as shown in Table 1, and Test Examples 4-6 show paints with only a crosslinking agent added, as shown in Table 2. Test Examples 7-12 show paints with both a thickener and a crosslinking agent added, as shown in Tables 2 and 3. Tables 1-3 also include the measurement results of the stiffness / softness (cantilever method) (ASTM D5732) of each base fabric formed by applying each paint to the fabric, and the test results of the environmental resistance performance test described above. In Tables 1-3, stiffness / softness is indicated as ○ for 100 mm or less, △ for 130 mm or less, and × for more than 130 mm. If the test result of the environmental resistance performance test is ×, adhesion and peeling will occur between the overlapping base fabric coatings, which can be determined visually.

[0033] As shown in Table 1, in the reference example coating, which contains neither a thickener nor a crosslinking agent, the resulting base fabric has high rigidity and softness, and also poor environmental resistance. In Test Examples 1-3, where only a thickener is added, the base fabric obtained using the coatings all have appropriate rigidity and softness, but poor environmental resistance. From the test results of Test Examples 1-3, it can be inferred that the appropriate amount of thickener is in the range of 0.5 to 6 parts. The amount of thickener added and the viscosity of the resulting coating are proportional, and if the viscosity of the resulting coating is in the range of 1,000 to 100,000 mPa·sm, it is an appropriate viscosity for coating work on fabrics (especially coating work using knife coating). As shown in Table 2, in Test Examples 4-6, where only a crosslinking agent is added, in Test Example 4, where the amount of crosslinking agent is small, the resulting base fabric has poor environmental resistance, but in Test Examples 5 and 6, where the amount of crosslinking agent is large, the resulting base fabric has good environmental resistance. However, in all of the test examples 4-6, the resulting base fabrics had high rigidity and flexibility.

[0034] In Test Examples 7-12, a thickener and a crosslinking agent were added. In Test Example 7, 1 part thickener and 3 parts crosslinking agent were added, and in Test Example 8, 2 parts thickener and 10 parts crosslinking agent were added (see Table 2). In Test Examples 7 and 8, although the resulting base fabrics had appropriate stiffness and flexibility, their environmental resistance was not good. In Test Example 5, where 3 parts crosslinking agent was added alone, the resulting base fabric had high stiffness and flexibility, but good environmental resistance. Comparing Test Example 5 with Test Example 7, it can be inferred that the amount of crosslinking agent added relative to the thickener was too low. In Test Example 8, the amount of crosslinking agent added was increased compared to Test Example 7 (mass ratio 1:3 → 1:5), but even in Test Example 8, the environmental resistance of the resulting base fabric was not good, suggesting that the amount of crosslinking agent added was insufficient. Table 3 discloses data for Test Examples 9-12, in which the amount of crosslinking agent added was further increased compared to Test Example 8. Specifically, Test Examples 9-11 show paints in which the mixing ratio of thickener to crosslinking agent was fixed at 1:6, but the amounts were varied. In Test Example 9, the stiffness / softness was △, specifically in the range of 100-130 mm, but it had good environmental resistance. Even if the stiffness / hardness exceeds 100 mm, it is considered appropriate for a product if it is 130 mm or less. In Test Examples 10 and 11, the resulting base fabrics all had appropriate stiffness / softness and good environmental resistance. From the data of Test Examples 9-11, it can be inferred that the high values ​​of stiffness / softness are due to the small amount of thickener added. In the paint of Test Example 12, the amount of crosslinking agent added was further increased, and the mixing ratio of thickener to crosslinking agent was set to 1:10. In this test example 12, the resulting base fabric also possesses appropriate rigidity and flexibility, as well as good environmental resistance.

[0035] From the above test results, it can be confirmed that in order to have an appropriate viscosity and impart appropriate stiffness and flexibility to the base fabric obtained by applying the paint to the cloth, it is desirable to add a thickener in the range of 0.5 to 6 parts per 100 parts of polyurethane, and in order to impart good environmental resistance to the resulting base fabric, it is desirable to set the amount of crosslinking agent to be 6 or more parts per 1 part thickener.

[0036] Furthermore, the airbag base fabric 1 obtained by applying the paint of the embodiment has appropriate rigidity and flexibility and good environmental resistance, so when used as an airbag, it has good foldable storage when folded and stored in a vehicle, and also has suitable environmental resistance. [Explanation of Symbols]

[0037] 1...Airbag base fabric, 3...Fabric, 4...Coating.

Claims

1. A water-based paint for airbag base fabrics, which is based on polyurethane resin. It is made by adding a crosslinking agent and a thickening agent. The amount of the thickening agent added shall be within the range of 0.5 to 6 parts by mass per 100 parts by mass of the polyurethane resin. A coating for airbag base fabric, characterized in that the amount of the crosslinking agent added is set to 6 or more by mass ratio to the thickening agent 1.

2. An airbag base fabric characterized in that one or both sides of a fabric woven from synthetic fibers are coated with a coating made of the airbag base fabric paint described in claim 1.

3. The airbag base fabric according to claim 2, characterized in that the rigidity of the airbag base fabric equipped with the aforementioned coating is 130 mm or less in terms of rigidity (cantilever method) (ASTM D5732).

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