Method for recycling airbag cloth

Abstract

The purpose of the present invention is to provide a novel method for recycling a polyamide resin airbag fabric in which an aqueous alkali solution is not required to be used when removing a silicone resin. A method for recycling an airbag fabric, characterized by comprising: a heat treatment step for bringing a polyamide resin airbag fabric, at least one surface of which is coated with a silicone resin, into contact with H2O at a temperature of 160 DEG C or higher and a saturated vapor pressure or higher; and a recovery step for recovering the polyamide resin from which the silicone resin has been removed.

Description

Technical Field

[0001] The present invention relates to a method for recycling airbag fabric. Background Art

[0002] In recent years, from the viewpoint of reducing the environmental burden, recycling of waste materials and the like has attracted much attention.

[0003] Airbag fabric usually uses polyamide fabric as the base fabric, and silicone resin is coated on its surface for the purpose of improving heat resistance, airtightness, flame retardancy, etc. Therefore, when recycling airbag fabric (especially the polyamide resin constituting the base fabric), it is necessary to remove the silicone resin from the polyamide fabric serving as the base fabric.

[0004] As a method for recycling airbag fabric, for example, a method is known in which the airbag fabric is treated with an aqueous alkali solution to remove the silicone resin from the base fabric. Specifically, a method is known in which the airbag fabric is immersed in an aqueous alkali solution containing a tertiary amine and a surfactant, and then stirred and allowed to stand to remove the silicone resin (Patent Document 1).

[0005] Prior Art Documents

[0006] Patent Documents

[0007] Patent Document 1: Japanese Patent Application Laid-Open No. 2001-180413 Summary of the Invention

[0008] Problems to be Solved by the Invention

[0009] However, if the airbag fabric is treated with an aqueous alkali solution, the treatment liquid is absorbed by the layers of the polyamide fabric serving as the base fabric and the silicone resin. Therefore, in order to recycle them, a step of removing the treatment liquid is required, and the operation is complicated. In addition, the polyamide resin constituting the base fabric may be damaged such as decomposition due to the treatment with the aqueous alkali solution. Therefore, it is not a method with sufficiently high recyclability. Furthermore, chemical reagents such as sodium hydroxide are used in the treatment with the aqueous alkali solution. Therefore, complicated post-treatment such as waste liquid treatment is required, and there is also concern about the environmental burden.

[0010] The present invention has been made in view of the above circumstances, and an object thereof is to provide a novel method for recycling a polyamide resin-based airbag fabric that does not require the use of an aqueous alkali solution when removing the silicone resin.

[0011] Means for Solving the Problems

[0012] The inventors of the present invention conducted in-depth research to solve the aforementioned problems and found that: according to a method including the following steps, it is possible to recycle airbag fabric without using an alkaline aqueous solution, thus completing the present invention. The steps are: a heat treatment step of bringing an airbag fabric made of polyamide resin coated with silicone resin on at least one side into contact with H2O at a temperature of 160 °C or higher and a saturated water vapor pressure or higher; and a recovery step of recovering the polyamide resin from which the silicone resin has been removed.

[0013] The gist of the present invention is as follows.

[0014] [1] A method for recycling airbag fabric, characterized by comprising:

[0015] a heat treatment step of bringing an airbag fabric made of polyamide resin coated with silicone resin on at least one side into contact with H2O at a temperature of 160 °C or higher and a saturated water vapor pressure or higher; and

[0016] a recovery step of recovering the polyamide resin from which the silicone resin has been removed.

[0017] [2] The method for recycling airbag fabric according to [1], characterized in that, in the aforementioned heat treatment step, the treatment temperature is 170 °C or higher and 230 °C or lower, and the treatment pressure is 0.9 MPa or higher and 3.0 MPa or lower.

[0018] [3] The method for recycling airbag fabric according to [1] or [2], characterized in that, in the aforementioned heat treatment step, the treatment temperature is 170 °C or higher and 210 °C or lower, and the treatment pressure is 0.9 MPa or higher and 1.9 MPa or lower.

[0019] [4] The method for recycling airbag fabric according to any one of [1] to [3], characterized in that, in the aforementioned recovery step, the polyamide resin from which the silicone resin has been removed is peeled off and recovered by applying an external force.

[0020] [5] A recycled polyamide resin composition, wherein at least a part of the raw material contains the polyamide resin recovered by the recycling method according to any one of [1] to [4].

[0021] [6] An airbag base fabric, wherein at least a part of the raw material contains the polyamide resin recovered by the recycling method according to any one of [1] to [4].

[0022] Effects of the Invention

[0023] According to the present invention, a novel recycling method of a polyamide resin airbag fabric that does not require an alkaline aqueous solution for removing silicone resin can be provided. In the recycling method of the present invention, an alkaline aqueous solution is not used or the degree thereof can be reduced. Therefore, damage to the polyamide resin caused by alkali treatment can be suppressed, and in addition, the polyamide resin from which the silicone resin has been removed can be easily recovered by a process with a small environmental burden. Detailed Description

[0024] The recycling method of the airbag fabric of the present invention includes: a heat treatment step of bringing a polyamide resin airbag fabric coated with silicone resin on at least one side into contact with H2O at a temperature of 160 °C or higher and a saturated water vapor pressure or higher; and a recovery step of recovering the polyamide resin from which the silicone resin has been removed.

[0025] (Heat Treatment Step)

[0026] In this step, by bringing the polyamide resin airbag fabric into contact with H2O at a temperature of 160 °C or higher and a saturated water vapor pressure or higher, a state in which the polyamide resin is easily separated from the silicone resin is presented. In addition, in this step, part or all of the polyamide resin can be separated from the silicone resin.

[0027] From the viewpoint of heat treatment efficiency, when the size of the polyamide resin airbag fabric to be subjected to heat treatment exceeds 10000 cm 2 , it is preferably pre-cut using a known cutting machine or the like so as to be 10000 cm 2 or less, preferably 2500 cm 2 or less. It should be noted that the lower limit of the size of the airbag fabric to be subjected to heat treatment is not particularly limited. For example, it is preferably 0.01 cm 2 or more, more preferably 0.1 cm 2 or more. The shape of the airbag fabric fragment obtained by cutting is not particularly limited and can be a quadrilateral such as a rectangle or a square, a circle, an ellipse, other polygons, or an irregular shape. From the viewpoint of processability, a quadrilateral is preferred. When the fragment shape is a quadrilateral, the length of one side is preferably in the range of 0.1 to 100 cm, more preferably in the range of 0.2 to 50 cm.

[0028] As the treatment temperature in the heat treatment, it is 160 °C or higher, preferably 165 °C or higher, more preferably 170 °C or higher, further preferably 175 °C or higher, and preferably 240 °C or lower, more preferably 230 °C or lower, further preferably 220 °C or lower, and still further preferably 210 °C or lower. That is, as the treatment temperature in the heat treatment, it is preferably 165 to 240 °C, more preferably 170 to 230 °C, further preferably 170 to 220 °C, still further preferably 170 to 210 °C, and even further preferably 175 to 210 °C. If the treatment temperature is within the above range, a state can be achieved in which the degradation such as decomposition of the polyamide resin is suppressed and the polyamide resin is easily separated from the silicone resin.

[0029] As the treatment pressure in the heat treatment, it is the saturated water vapor pressure at the treatment temperature or higher, preferably 0.6 to 3.3 MPa, more preferably 0.7 MPa or higher, further preferably 0.8 MPa or higher, still further preferably 0.9 MPa or higher. Additionally, it is more preferably 3.0 MPa or lower, further preferably 2.8 MPa or lower, still further preferably 2.3 MPa or lower, and even further preferably 1.9 MPa or lower. That is, as the treatment pressure in the heat treatment, it is more preferably 0.7 to 3.0 MPa, further preferably 0.8 to 3.0 MPa, still further preferably 0.9 to 3.0 MPa, even further preferably 0.9 to 2.8 MPa, and yet further preferably 0.9 to 2.3 MPa, and even more preferably 0.9 to 1.9 MPa. If the treatment pressure is within the above range, a state can be achieved in which the degradation such as decomposition of the polyamide resin is suppressed and the polyamide resin is easily separated from the silicone resin.

[0030] As the state of H2O in contact with the airbag fabric, it can be a gas (in other words, water vapor), or it can be a liquid (in other words, water). Specifically, in the case of heat treatment under the saturated water vapor pressure at the treatment temperature, it is saturated water vapor, and in the case of heat treatment at a pressure exceeding the saturated water vapor pressure at the treatment temperature, it is subcritical water (also called pressurized hot water or high-pressure hot water).

[0031] It should be noted that from the viewpoint of simplicity in controlling the temperature and pressure in the heat treatment, it is preferred to perform the treatment under the saturated water vapor pressure at the treatment temperature.

[0032] As a method for performing the heat treatment, for example, a method of supplying high-pressure steam from a boiler or the like to a pressure-resistant reaction tank containing a sample can be cited; a method of putting a sample and water into a pressure-resistant reaction tank and heating using a heater or the like.

[0033] In the recycling method of the present invention, the airbag fabric is treated with high-temperature and high-pressure H2O. Therefore, a state can be achieved in which the degradation such as the decomposition of the polyamide resin is suppressed and the polyamide resin can be easily separated from the silicone resin. It should be noted that even when the airbag fabric is treated at 160°C or higher in an atmospheric atmosphere, a state in which the polyamide resin can be easily separated from the silicone resin cannot be achieved.

[0034] As the treatment time in the heat treatment, it can be appropriately set according to the treatment temperature and treatment pressure. For example, it is preferably 1 to 360 minutes, more preferably 3 minutes or more, further preferably 5 minutes or more, still further preferably 10 minutes or more, and more preferably 240 minutes or less, further preferably 180 minutes or less, still further preferably 120 minutes or less. That is, as the treatment time in the heat treatment, it is more preferably 3 to 240 minutes, further preferably 5 to 180 minutes, still further preferably 10 to 120 minutes. If the treatment time is within the above range, a state can be achieved in which the degradation such as the decomposition of the polyamide resin is suppressed and the polyamide resin can be easily separated from the silicone resin.

[0035] From the viewpoint of preventing the degradation of the airbag fabric (especially the polyamide resin), the temperature increase and / or pressure increase up to the treatment temperature and / or treatment pressure is preferably carried out in a short time. For example, the pressure increase from 0.05 MPa to the treatment pressure is preferably carried out within 60 minutes, more preferably within 30 minutes. In addition, the temperature increase from 80°C to the treatment temperature is preferably carried out within 60 minutes, more preferably within 30 minutes. After the heat treatment, the reaction tank and / or the airbag fabric can be cooled by natural cooling, or a known cooling device can be used for cooling.

[0036] The heat treatment can be carried out while stirring using a known stirring device such as a stirring blade as needed. When the heat treatment is carried out while stirring, the stirring is preferably carried out at a rotation speed of 10 to 3000 rpm, more preferably 20 to 2000 rpm. By carrying out the heat treatment while stirring, a state in which the polyamide resin can be more easily separated from the silicone resin can be achieved. In addition, by carrying out the heat treatment while stirring, friction is generated between the fabrics, so that part or all of the polyamide resin in a state in which it is easily separated due to the heat treatment can be separated from the silicone resin.

[0037] In addition, the heat treatment can be carried out while maintaining (fixing) the shape of at least one end of the airbag fabric as needed. If at least one end of the airbag fabric is maintained, it is possible to suppress a state in which the surface of the airbag fabric coated with silicone resin is not exposed due to folding or curling of the airbag fabric. Therefore, it is preferable from the viewpoint of heat treatment efficiency. As a method of fixing at least one end of the airbag fabric, for example, an end shape holding member or a frame made of metal may be provided at the end of the airbag fabric. From the viewpoint of shape holding, it is preferable to provide the end shape holding member over a length of 50% or more of the total length of the end of the airbag fabric, more preferably over a length of 70% or more, further preferably over a length of 90% or more, and even more preferably a frame is provided over the entire length of the end.

[0038] After the heat treatment of the airbag fabric, post-treatment such as dehydration / drying treatment can be performed. The dehydration / drying treatment can be carried out using a known dehydrator and / or dryer. For example, it is preferable to use a dryer such as an infrared heater, an oven, or a hot air dryer and dry at 40 to 80 °C for 1 to 60 minutes.

[0039] (Recovery process)

[0040] In this process, the polyamide resin that has become easy to separate from the silicone resin through heat treatment is separated and recovered, and / or the polyamide resin separated from the silicone resin in the heat treatment process is recovered.

[0041] As a method of recovering the polyamide resin, for example, a method of separating and recovering the polyamide resin from the silicone resin by applying an external force such as manual peeling can be cited. In addition, it can be cited that: in the heat treatment process, when at least a part of the polyamide resin has separated from the silicone resin, the polyamide resin separated from the silicone resin is visually identified and recovered.

[0042] In the case of manually peeling the polyamide resin, after further applying external forces such as kneading and friction to the heat-treated airbag fabric and then peeling, from the viewpoint of ease of separation of the polyamide resin, it is preferable that it can be manually peeled without applying further external forces such as kneading and friction.

[0043] In addition, since the polyamide resin is easily separated from the silicone resin in the heat-treated airbag fabric, if external forces such as friction and shear force are applied by stirring, crushing, etc., the polyamide resin is easily separated. Therefore, after separating the polyamide resin from the silicone resin by stirring and / or crushing the heat-treated airbag fabric, the polyamide resin from which the silicone resin has been removed can be visually identified and recovered.

[0044] When pulverizing the heat-treated specimen to separate the polyamide resin, it is preferable to use a known crusher or grinder to pulverize it in such a way as to form small pieces with an area of, for example, 1 cm 2 or less, more preferably 0.5 cm 2 or less. There is no particular limitation on the lower limit, and it can be 0.001 cm 2 or more.

[0045] The recovered polyamide resin can be appropriately washed with a cleaning liquid such as water or an organic solvent, and post-treatment such as drying can be appropriately performed.

[0046] The polyamide resin recovered by the recycling method of the present invention (hereinafter also referred to as recycled polyamide resin) preferably substantially does not contain a silicone resin. Substantially not containing means that the content of the silicone resin in the recycled polyamide resin is 1% by mass or less, more preferably 0.5% by mass or less, and further preferably 0.1% by mass or less. In addition, there is no particular limitation on the lower limit, preferably 0% by mass, and it can be 0.01% by mass or more. That is, the content of the silicone resin in the recycled polyamide resin is preferably 0 to 1% by mass, more preferably 0 to 0.5% by mass, and further preferably 0 to 0.1% by mass. The recycled polyamide resin substantially not containing a silicone resin has high recyclability. The content (residual amount) of the silicone resin contained in the recycled polyamide resin can be obtained by, for example, using a Fourier transform infrared spectrometer (FT-IR) to determine the mass of the silicone resin in the recycled polyamide resin, etc., and calculating based on the obtained value. In addition, regarding the recycled polyamide resin, when no specific peak derived from the silicone resin is detected by analyzing with the above analysis equipment, it can be regarded that the silicone resin in the recycled polyamide resin has been completely removed.

[0047] As the recovery rate of the polyamide resin, it is preferable that the value is high. As the upper limit, it is 100% by weight, and preferably 5% by weight or more, more preferably 10% by weight or more, and further preferably 15% by weight or more. That is, the recovery rate of the polyamide resin is preferably 5 to 100% by weight, more preferably 10 to 100% by weight, and further preferably 15 to 100% by weight.

[0048] The recovery rate of the polyamide resin can be calculated using the following formula with the weight (B parts by weight) of the recovered polyamide resin, the weight (A parts by weight) of the sample (airbag fabric) before treatment, and the weight ratio (C%) of the polyamide resin in the sample before treatment.

[0049] Recovery rate (%) = {B / [A × (C / 100)]} × 100

[0050] In the recycling method of the airbag fabric of the present invention, a polyamide resin from which a silicone resin has been removed is obtained by contacting with high-temperature and high-pressure H2O. Therefore, alkali treatment can be omitted, deterioration of the polyamide resin and the silicone resin caused by alkali treatment can be avoided, and in addition, complex operations such as post-treatment for removing an aqueous alkali solution and waste liquid are not required, and the airbag fabric can be recycled simply.

[0051] In addition, preferably: compared with the polyamide resin in the base fabric before treatment, changes in physical properties such as molecular weight of the polyamide resin recovered by the recycling method of the airbag fabric of the present invention are suppressed. If changes in the physical properties of the polyamide resin are suppressed, it can be reused without further treatment such as polymerization, and thus, the recyclability is high. The use of the recovered polyamide resin is not particularly limited. For example, it can also be reused by a method of decomposing to monomers and then repolymerizing (chemical recycling), but from the viewpoint of energy cost, it is preferably reused by melt pelletizing etc. without decomposing to monomers (material recycling).

[0052] The degree of deterioration of the polyamide resin can be confirmed based on the relative viscosity of the polyamide resin. Since the relative viscosity is proportional to the molecular weight of the resin, it can be said that: the higher the relative viscosity, the larger the molecular weight of the recovered polyamide resin, in other words, the polymer state is maintained. Specifically, if the relative viscosity is 1.3 or more (preferably 1.5 or more, more preferably 1.7 or more, further preferably 1.9 or more, still further preferably 2.1 or more, and even further preferably 2.3 or more), it can be said that it is a polyamide resin that can be suitably used for material recycling. The relative viscosity (RV) of the polyamide resin can be measured by dissolving 0.25 g of the polyamide resin in 46 g of 96% sulfuric acid, putting 10 ml of this solution into an Ostwald viscometer tube, measuring at 20 °C, and calculating using the following formula.

[0053] RV = T / T0

[0054] (RV: relative viscosity, T: dropping time of the sample solution, T0: dropping time of the solvent)

[0055] In addition, when the relative viscosity (RV0) of the polyamide resin before heat treatment can be measured, the ratio (RV / RV0) of RV (relative viscosity of the recovered polyamide resin) to RV0 is preferably 0.4 or more (preferably 0.5 or more, more preferably 0.6 or more, further preferably 0.7 or more, still further preferably 0.8 or more). If the value of RV / RV0 is within the above range, deterioration of the polyamide resin obtained by the recovery method of the present invention is suppressed, and it can be said that it is a polyamide resin that can be suitably used for material recycling.

[0056] (Airbag fabric made of polyamide resin)

[0057] The airbag fabric used in the recycling method of the present invention is a polyamide resin airbag fabric in which at least one side of a base fabric made of a polyamide resin is coated with a silicone resin. As the polyamide resin airbag fabric, waste materials such as scraps generated during the manufacture of airbags and used airbags can be used.

[0058] The polyamide resin constituting the base fabric is a polymer having an amide bond in the main chain. Examples of the polyamide resin include polycaprolactam (nylon 6), polyhexamethylene adipamide (nylon 66), polybutylene adipamide (nylon 46), polyhexamethylene sebacamide (nylon 610), polyhexamethylene dodecanediamide (nylon 612), polylaurolactam (nylon 12), polyundecanamide (nylon 11), etc., as well as their copolymers and mixtures. As the airbag fabric, from the viewpoints of heat resistance and cost, it is preferably a polycaprolactam resin obtained by polycondensation of ε-caprolactam, which is commonly referred to as nylon 6, and nylon 66. In addition, in the case of recycling, from the viewpoint of versatility, nylon 6 and nylon 66 are also preferred.

[0059] As the base fabric, a fabric composed of multifilaments of polyamide fibers is preferred. Examples of the fabric include plain weave, twill weave, satin weave, and their modified weaves.

[0060] From the viewpoint of obtaining a recycled polyamide resin with higher recyclability, the number of filaments in the multifilament yarn constituting the fabric (base fabric) is preferably, for example, 30 to 200, more preferably 40 to 180. The number of filaments is obtained by counting based on a cross-sectional photograph of the multifilament yarn.

[0061] From the viewpoint of obtaining a recycled polyamide resin with higher recyclability, the total fineness of the multifilament yarn constituting the fabric (base fabric) is preferably, for example, 200 to 1000 dtex, more preferably 250 to 800 dtex. The total fineness of the multifilament yarn can be measured in accordance with JIS L1013 (2010) 8.3.1.

[0062] From the viewpoint of obtaining a recycled polyamide resin with higher recyclability, the tensile strength of the multifilament yarn constituting the fabric (base fabric) is preferably, for example, 6.0 to 10 cN / dtex, more preferably 6.5 to 9.5 cN / dtex. The tensile strength of the multifilament yarn can be measured in accordance with JIS L1013 (2010) 8.5.1.

[0063] From the viewpoint of obtaining a recycled polyamide resin with higher recyclability, the weaving density of the fabric (base fabric) is preferably, for example, 35 to 80 threads / 2.54 cm in both the warp direction and the weft direction, more preferably 40 to 75 threads / 2.54 cm. The weaving density can be measured in accordance with JIS L1096 (2010) 8.6.1.

[0064] From the viewpoint of obtaining a recycled polyamide resin with higher recyclability, the cover factor (CF) of the fabric (base fabric) is preferably, for example, 1,500 to 2,500, more preferably 1,700 to 2,300. The cover factor is an index of the coverage rate of the fabric and can be obtained using the following formula.

[0065] CF = √(total fineness of warp) × warp density + √(total fineness of weft) × weft density

[0066] In addition to the polyamide resin, the base fabric may contain additives. Examples of such additives include antioxidants, heat stabilizers, smoothing agents, antistatic agents, thickeners, flame retardants, weather resistance agents, anti-coloring agents, coloring agents, etc.

[0067] In the polyamide resin-based airbag fabric, a coating resin containing a silicone resin is coated on at least one side of the base fabric to form a silicone resin layer.

[0068] The silicone resin is not particularly limited. Specific examples include addition-polymerized silicone rubbers. Examples include dimethyl silicone rubber, methyl vinyl silicone rubber, methyl phenyl silicone rubber, trimethyl silicone rubber, fluorosilicone rubber, methyl silicone resin, methyl phenyl silicone resin, methyl vinyl silicone resin, epoxy-modified silicone resin, acrylic-modified silicone resin, polyester-modified silicone resin, etc. Among them, addition-polymerized methyl vinyl silicone rubber is preferred.

[0069] The viscosity of the coating resin is preferably 5,000 to 40,000 mPa·sec, more preferably 7,000 to 38,000 mPa·sec. If within the above viscosity range, the coating resin can be either a solvent-based or solvent-free type, and a solvent-free type is preferred. It should be noted that in this specification, the viscosity of the resin composition containing additives other than the resin, that is, the viscosity of the resin actually coated on the base fabric, is denoted as the "viscosity of the resin".

[0070] The coating resin may contain additives other than the silicone resin and the solvent. Examples of such additives include reaction curing agents such as platinum-based catalysts (specifically platinum black, chloroplatinic acid, alcohol-modified chloroplatinic acid; complexes of chloroplatinic acid with olefins, aldehydes, vinyl siloxanes, or acetylene alcohols, etc.); adhesion aids such as amino-based silane coupling agents, epoxy-modified silane coupling agents, vinyl-based silane coupling agents, chlorine-based silane coupling agents, mercapto-based silane coupling agents; reinforcing inorganic fillers such as fumed silica and dry silica; non-reinforcing inorganic fillers such as crosslinkable silicone (silicone resin) with adjusted end groups, calcium carbonate, calcium silicate, titanium dioxide; antioxidants; antistatic agents; flame retardants; weather resistance agents; anti-coloring agents; coloring agents, etc.

[0071] In the case of containing a platinum group catalyst as a reaction curing agent, its content is preferably 100 to 2000 ppm, more preferably 150 to 1800 ppm in terms of the amount of platinum metal relative to 100 parts by mass of the silicone resin.

[0072] In the case of containing a silane coupling agent as an adhesion aid, its content is preferably 0.01 to 3 parts by mass, more preferably 0.02 to 2 parts by mass relative to 100 parts by mass of the silicone resin.

[0073] In the case of containing an inorganic filler, its content is preferably 0.1 to 200 parts by mass, more preferably 0.1 to 100 parts by mass relative to 100 parts by mass of the silicone resin.

[0074] Coating of the coating resin (in other words, silicone resin) in the base fabric can be carried out by using a conventionally well-known coating method. As the coating method, for example, knife coating, roll coating, reverse coating, gravure coating, reverse gravure coating, kiss coating, etc. can be cited, and the silicone resin is preferably coated by knife coating.

[0075] As the amount of the silicone resin coated on the polyamide resin-based airbag fabric, from the viewpoint of ease of separation of the polyamide resin, it is preferably 5 to 150 g / m 2 and more preferably 7 g / m 2 or more, further preferably 10 g / m 2 or more, and in addition, more preferably 120 g / m 2 or less, further preferably 100 g / m 2 or less, still further preferably 70 g / m 2 or less. That is, the amount of the silicone resin coated on the polyamide resin-based airbag fabric is more preferably 7 to 120 g / m 2 and further preferably 10 to 100 g / m 2 and still further preferably 10 to 70 g / m 2 .

[0076] The polyamide resin recovered by the recycling method of the present invention can form a recycled product containing at least a part of the polyamide resin in the raw material through chemical recycling or material recycling. As the recycled product, for example, a recycled polyamide resin composition, an airbag base fabric, etc. can be cited.

[0077] This application claims the benefit of priority based on Japanese Patent Application No. 2022-203575 filed on December 20, 2022. The entire contents of the specification of Japanese Patent Application No. 2022-203575 filed on December 20, 2022 are incorporated herein by reference for reference.

[0078] Examples

[0079] Hereinafter, examples are listed to more specifically illustrate the present invention. Needless to say, the present invention is not limited by the following examples and can be appropriately modified within the scope that can conform to the foregoing / hereinafter described gist and implemented, and they all fall within the protection scope of the present invention.

[0080] In the following examples and comparative examples, the following airbag fabric 1 made of polyamide resin was used.

[0081] (Airbag fabric 1 made of polyamide resin)

[0082] Using a polyamide 66 multifilament yarn with a raw yarn strength of 8.4 cN / dtex, a total fineness of 470 dtex, and 68 filaments, a plain fabric with a warp density of 46 ends / 2.54 cm, a weft density of 46 ends / 2.54 cm, and a cover factor of 1,994 was obtained. An addition-polymerization type solvent-free vinylmethyl silicone resin with a resin viscosity of 14,000 mPa·sec was coated on one side of the aforementioned fabric (base fabric) and dried at 200 °C for 1 minute to obtain an airbag fabric 1 made of polyamide resin with a resin coating amount of 25 g / m 2 . The weight ratio of the polyamide resin in the aforementioned airbag fabric 1 made of polyamide resin is 87%.

[0083] In the following examples and comparative examples, the ease of separation of the polyamide resin from the airbag fabric made of polyamide resin was confirmed according to the following steps. In addition, the recovered polyamide resin was evaluated according to the following steps.

[0084] (Peeling test)

[0085] After drying the heat-treated airbag fabric made of polyamide resin, the polyamide resin was peeled off by hand. The ease of separation based on external force was evaluated according to the following evaluation criteria.

[0086] Excellent: The polyamide resin can be peeled off from the end without applying further external forces such as friction.

[0087] Good: The polyamide resin can be peeled off if further external forces such as kneading and friction are applied.

[0088] Poor: The polyamide resin cannot be peeled off even if further external forces such as kneading and friction are applied.

[0089] (Relative viscosity)

[0090] Dissolve 0.25 g of the recycled polyamide resin in 46 g of 96% sulfuric acid. Put 10 ml of this solution into an Ubbelohde viscometer and measure it at 20°C. Calculate the relative viscosity using the following formula. Since the relative viscosity is proportional to the molecular weight of the resin, the higher the relative viscosity, the larger the molecular weight of the recycled polyamide resin. In other words, it can be said that the polymer state is maintained.

[0091] RV = T / T0

[0092] (RV: relative viscosity, T: dropping time of the sample solution, T0: dropping time of the solvent)

[0093] (Recovery rate)

[0094] Measure the weight (B parts by weight) of the recycled polyamide resin. Using the weight (A parts by weight) of the sample before treatment and the weight ratio (C%) of the polyamide resin in the sample before treatment, calculate the recovery rate using the following formula.

[0095] Recovery rate (%) = {B / [A×(C / 100)]}×100

[0096] (Example 1)

[0097] Cut the above polyamide resin-coated airbag fabric 1 into squares with a side length of 50 cm. Put the cut samples into a high-pressure reactor, add steam to the reactor to make it 1.6 MPa and 200°C, and carry out a pressure treatment (heat treatment) for 30 minutes while stirring. When evaluating the ease of separation for the treated samples, the evaluation result of the peel test is "Good (Excellent)", and the polyamide resin from which the silicone resin has been removed can be recovered.

[0098] (Example 2)

[0099] Set the heat treatment conditions to 1.0 MPa, 180°C, and 60 minutes, and carry out the treatment in the same manner as in Example 1 except for this. When evaluating the ease of separation for the treated samples, the evaluation result of the peel test is "Good", and the polyamide resin from which the silicone resin has been removed can be recovered.

[0100] (Example 3)

[0101] Set the heat treatment conditions to 1.7 MPa, 205°C, and 60 minutes, and carry out the treatment in the same manner as in Example 1 except for this. When evaluating the ease of separation for the treated samples, the evaluation result of the peel test is "Good (Excellent)", and the polyamide resin from which the silicone resin has been removed can be recovered.

[0102] (Example 4)

[0103] The heat treatment conditions were set to 1.3 MPa, 190 °C, and 60 minutes. Otherwise, the treatment was carried out in the same manner as in Example 1. When evaluating the ease of separation for the treated sample, the evaluation result of the peel test was "Excellent", and the polyamide resin from which the silicone resin had been removed could be recovered.

[0104] (Example 5)

[0105] The above-mentioned polyamide resin airbag fabric 1 was cut into squares with a side length of 15 cm, and a metal frame for maintaining the shape of the entire end of the sample was provided on its outer periphery using aluminum foil. The sample provided with the aforementioned metal frame and water were placed in a high-pressure reactor and heat-treated at 210 °C and 2.0 MPa for 10 minutes. When evaluating the ease of separation for the treated sample, the evaluation result of the peel test was "Excellent", and the polyamide resin from which the silicone resin had been removed could be recovered. In addition, the recovery rate of the polyamide resin was 72%, and the relative viscosity of the recovered polyamide resin was 2.40.

[0106] (Example 6)

[0107] The heat treatment conditions were set to 210 °C, 2.0 MPa, and 5 minutes. Otherwise, the treatment was carried out in the same manner as in Example 5. When evaluating the ease of separation for the treated sample, the evaluation result of the peel test was "Excellent", and the polyamide resin from which the silicone resin had been removed could be recovered. In addition, the recovery rate of the polyamide resin was 43%, and the relative viscosity of the recovered polyamide resin was 2.47.

[0108] (Example 7)

[0109] The heat treatment conditions were set to 220 °C, 2.2 MPa, and 5 minutes. Otherwise, the treatment was carried out in the same manner as in Example 5. When evaluating the ease of separation for the treated sample, the evaluation result of the peel test was "Excellent", and the polyamide resin from which the silicone resin had been removed could be recovered. In addition, the recovery rate of the polyamide resin was 95%, and the relative viscosity of the recovered polyamide resin was 2.29.

[0110] (Example 8)

[0111] The heat treatment conditions were set to 200 °C, 1.6 MPa, and 30 minutes. Otherwise, the treatment was carried out in the same manner as in Example 5. When evaluating the ease of separation for the treated sample, the evaluation result of the peel test was "Excellent", and the polyamide resin from which the silicone resin had been removed could be recovered. In addition, the recovery rate of the polyamide resin was 85%, and the relative viscosity of the recovered polyamide resin was 2.38.

[0112] (Example 9)

[0113] The heat treatment conditions were set to 200 °C, 1.6 MPa, and 5 minutes. Except for this, the treatment was carried out in the same manner as in Example 5. When evaluating the ease of separation for the treated sample, the evaluation result of the peeling test was "Excellent", and the polyamide resin from which the silicone resin had been removed could be recovered. In addition, the recovery rate of the polyamide resin was 18%, and the relative viscosity of the recovered polyamide resin was 2.65.

[0114] (Comparative Example 1)

[0115] The heat treatment conditions were set to 0.48 MPa, 150 °C, and 30 minutes. Except for this, the treatment was carried out in the same manner as in Example 1. When evaluating the ease of separation for the treated sample, the evaluation result of the peeling test was "Poor", and the polyamide resin from which the silicone resin had been removed could not be recovered.

[0116] (Comparative Example 2)

[0117] The heat treatment conditions were set to 0.48 MPa, 150 °C, and 60 minutes. Except for this, the treatment was carried out in the same manner as in Example 1. When evaluating the ease of separation for the treated sample, the evaluation result of the peeling test was "Poor", and the polyamide resin from which the silicone resin had been removed could not be recovered.

[0118] (Comparative Example 3)

[0119] The polyamide resin airbag fabric 1 was cut into squares with a side length of 10 cm. The cut samples were suspended in a metal frame and placed in a hot air oven, and dry heat treatment was carried out at 180 °C for 60 minutes without pressure. When evaluating the ease of separation for the treated sample, the evaluation result of the peeling test was "Poor", and the polyamide resin from which the silicone resin had been removed could not be recovered.

[0120] (Comparative Example 4)

[0121] The heat treatment conditions were set to 210 °C and 60 minutes. Except for this, the treatment was carried out in the same manner as in Comparative Example 3. When evaluating the ease of separation for the treated sample, the evaluation result of the peeling test was "Poor", and the polyamide resin from which the silicone resin had been removed could not be recovered.

Claims

1. A recycling method for airbag fabric, characterized in that, Comprising: A heat treatment step of bringing a polyamide resin airbag fabric coated with a silicone resin on at least one side into contact with H2O at a temperature of 160°C or higher and a saturated water vapor pressure or higher; and A recovery step of recovering the polyamide resin from which the silicone resin has been removed.

2. The recycling method of the airbag fabric according to claim 1, characterized in that, In the heat treatment step, the treatment temperature is 170°C or higher and 230°C or lower, and the treatment pressure is 0.9 MPa or higher and 3.0 MPa or lower.

3. The recycling method of the airbag fabric according to claim 1, characterized in that, In the heat treatment step, the treatment temperature is 170°C or higher and 210°C or lower, and the treatment pressure is 0.9 MPa or higher and 1.9 MPa or lower.

4. The recycling method of the airbag fabric according to claim 1, characterized in that, In the recovery step, the polyamide resin from which the silicone resin has been removed is peeled off and recovered by applying an external force.

5. A recycled polyamide resin composition, wherein, At least a part of the raw material contains the polyamide resin recovered by the recycling method according to any one of claims 1 to 4.

6. An airbag base fabric, wherein, At least a part of the raw material contains the polyamide resin recovered by the recycling method according to any one of claims 1 to 4.