Methods for recovering polymer resins and recycled products

Abstract

The object of the present invention is to provide a novel method for recovering polymer resin from polymer resin airbag fabric that does not require the use of an alkaline aqueous solution for removing the silicone resin and is easy to operate. [Solution] A method for recovering polymer resin from a polymer resin airbag fabric coated with silicone resin on at least one side, A step of immersing the entire airbag fabric in water using an underwater holding member, and heat-treating it at a temperature of 160°C or higher and under a pressure equal to or greater than the saturated water vapor pressure at that temperature while maintaining the immersion in water by the underwater holding member, and A method for recovering polymer resin, characterized by comprising the step of recovering the polymer resin separated from the silicone resin by generating a water flow having a water flow velocity of 0.001 m / s or more in the heat treatment.

Description

[Technical Field]

[0001] This invention relates to a method for recovering polymer resin from airbag fabric, and to recycled products using the recovered polymer resin. [Background technology]

[0002] In recent years, attention has been focused on recycling waste and other materials from the perspective of reducing environmental impact. Airbag fabric is generally made by coating the surface of a base fabric, such as polyamide or polyester fabric, with silicone resin to improve heat resistance, airtightness, and flame retardancy. Therefore, when recycling airbag fabric, especially when recovering and recycling the polymer resin that makes up the base fabric, it was necessary to remove the silicone resin from the base fabric made up of polymer resin.

[0003] One known method for recovering polymer resin from airbag fabric is to treat the airbag fabric with an alkaline aqueous solution to remove the silicone resin from the base fabric. Specifically, a method is known in which the airbag fabric is immersed in an alkaline aqueous solution containing a tertiary amine and a surfactant, and then stirred and allowed to stand to remove the silicone resin (Patent Document 1). [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2001-180413 [Overview of the project] [Problems that the invention aims to solve]

[0005] However, when airbag fabric is treated with an alkaline aqueous solution, the treatment solution is absorbed into the base fabric, which is made of polymer resin, and the silicone resin layer. Therefore, in order to recover and recycle these materials, a process to remove the treatment solution is necessary, making the operation complicated. Furthermore, treatment with an alkaline aqueous solution may cause damage such as decomposition to the polymer resin constituting the base fabric, so this method does not provide sufficiently high recyclability for the recovered polymer resin. In addition, since chemicals such as sodium hydroxide are used in treatment with an alkaline aqueous solution, complicated post-treatment such as waste liquid disposal is required, raising concerns about the environmental impact.

[0006] This invention has been made in view of the above circumstances, and its purpose is to provide a new method for recovering polymer resin from polymer resin airbag fabric that does not require the use of an alkaline aqueous solution for removing silicone resin. It also aims to provide a simple method for recovering polymer resin with reduced operational complexity. [Means for solving the problem]

[0007] As a result of diligent research to solve the above problems, the present inventors have found that a method for recovering polymer resin, which includes the steps of: immersing the entire polymer resin airbag fabric, on which silicone resin is coated on at least one side, in water using an underwater holding member, and heat-treating it at a temperature of 160°C or higher and under a pressure equal to or greater than the saturated water vapor pressure at that temperature while maintaining immersion in water by the underwater holding member; and recovering the polymer resin separated from the silicone resin by generating a water flow due to the heat treatment, allows for the easy recovery of polymer resin from airbag fabric without requiring the use of an alkaline aqueous solution, and thus completed the present invention.

[0008] The gist of this invention is as follows: [Section 1] A method for recovering polymer resin from a polymer resin airbag fabric coated with silicone resin on at least one side, The step of immersing the entire airbag fabric in water by a water holding member, and performing heat treatment at a temperature of 160°C or higher and under a pressure equal to or higher than the saturated water vapor pressure at that temperature while maintaining the immersion in water by the water holding member, and A method for recovering a polymer resin, comprising a step of recovering the polymer resin separated from the silicone resin by generating a water flow having a water flow rate of 0.001 m / s or more in the heat treatment. [Item 2] The method for recovering a polymer resin according to item 1, wherein the water flow is an upward water flow. [Item 3] The method for recovering a polymer resin according to item 1 or item 2, wherein in the heat treatment step, a water flow is generated by using a stirring blade. [Item 4] The recovery method according to any one of items 1 to 3, wherein the polymer resin flows out of the water holding member by the water flow generated in the heat treatment, while the silicone resin is retained in the water by the water holding member, thereby separating the polymer resin and the silicone resin. [Item 5] The recovery method according to any one of items 1 to 4, wherein the water holding member is a filter member. [Item 6] The recovery method according to any one of items 1 to 4, wherein the water holding member is a shape holding member that holds the shape of the end of the airbag fabric, and the entire airbag fabric is held in water by providing the shape holding member on at least a part of the outer periphery of the airbag fabric. [Item 7] The recovery method according to any one of items 1 to 6, wherein as the airbag fabric, a fabric piece obtained by cutting or crushing a used airbag is used. [Item 8] The size of the airbag fabric is 1 mm 2 ~2500 cm 2 The recovery method according to any one of items 1 to 7. [Item 9] The recovery method according to any one of items 1 to 8, wherein the size of the airbag fabric is within the range of 1 mm to 500 mm in length and 1 mm to 500 mm in width. [Item 10] The recovery method according to any one of items 1 to 9, wherein the polymer resin is a polyamide resin or a polyester resin. [Item 11] The recovery method according to item 10, wherein the polyamide resin is nylon 66 and the polyester resin is polyethylene terephthalate. [Item 12] The recovery method according to any one of items 1 to 11, wherein in the heat treatment step, the treatment temperature is 180°C to 240°C and the treatment pressure is 1.0 MPa to 3.6 MPa. [Item 13] The recovery method according to item 11, wherein the polymer resin is nylon 66, and in the heat treatment step, the treatment temperature is 180°C to 240°C and the treatment pressure is 1.0 MPa to 3.6 MPa. [Item 14] The recovery method according to item 11, wherein the polymer resin is polyethylene terephthalate, and in the heat treatment step, the treatment temperature is 210°C to 240°C and the treatment pressure is 2.0 MPa to 3.6 MPa. [Item 15] The recovery method according to any one of items 1 to 14, including a cooling step after the heat treatment step and before the recovery step. [Item 16] The recovery method according to item 5, wherein the filter member has a plurality of through holes, and the opening area of the through holes is 0.01% to 10% of the area of the airbag fabric. [Item 17] The recovery method according to item 5, wherein the filter member has a mesh size of 0.1 mm to 13 mm. [Item 18] The recovery method according to item 5, wherein the filter member is composed of a metal containing at least one of stainless steel and aluminum. [Item 19] A recycled product containing at least a part of the polyamide resin or polyester resin obtained by the recovery method according to any one of items 1 to 18 as a raw material. [Advantages of the Invention]

[0009] According to the present invention, a novel recovery method is available in which the use of an alkaline aqueous solution is optional for recovering polymer resin from polymer resin airbag fabric. In the recovery method of the present invention, the use of an alkaline aqueous solution is either omitted or reduced, thereby suppressing damage to the polymer resin due to alkaline treatment, and enabling the recovery of polymer resin from which silicone resin has been removed in an environmentally friendly process. Furthermore, according to the present invention, it is possible to provide a simple method for recovering polymer resin with reduced complexity in the recovery operation. [Brief explanation of the drawing]

[0010] [Figure 1] This is a schematic cross-sectional view showing an example of a high-pressure hot water treatment apparatus used in a specific embodiment. [Modes for carrying out the invention]

[0011] The present invention provides a method for recovering polymer resin, comprising the steps of: immersing the entire polymer resin airbag cloth, on which silicone resin is coated on at least one side, in water using an underwater holding member; heat-treating it at a temperature of 160°C or higher and under a pressure equal to or greater than the saturated water vapor pressure at that temperature while maintaining the immersion in water by the underwater holding member; and recovering the polymer resin separated from the silicone resin by generating a water flow through the heat treatment.

[0012] (Airbag fabric made of polymer resin) The polymer resin airbag fabric from which polymer resin is recovered by the recovery method of the present invention is an airbag fabric in which silicone resin is coated on at least one side of a base fabric made of polymer resin. As the airbag fabric, scraps generated during the manufacture of airbags and waste such as used airbags can be used. When using used airbags, it is preferable to use fabric pieces obtained by cutting or shredding as the airbag fabric to be subjected to heat treatment.

[0013] Preferably, the polymer resin constituting the base fabric is a polyamide resin or a polyester resin.

[0014] Polyamide resins are polymers that have amide bonds in their main chain. Examples of polyamide resins include polycaproamide (nylon 6), polyhexamethylene adipamide (nylon 66), polytetramethylene adipamide (nylon 46), polyhexamethylene sevacamide (nylon 610), polyhexamethylene dodecamide (nylon 612), polylauryl lactam (nylon 12), polyundecaneamide (nylon 11), and copolymers and mixtures thereof. For polyamide resin airbag fabrics, polycaproamide resin, usually called nylon 6 and obtained by polycondensation of ε-caprolactam, and nylon 66 are preferred in terms of heat resistance and cost, with nylon 66 being particularly preferred. Furthermore, when recycled after collection, nylon 6 and nylon 66 are preferred as polyamide resins in terms of versatility, with nylon 66 being more preferred.

[0015] Polyester resins are formed by reacting a carboxylic acid component with a hydroxyl group component. Examples of carboxylic acid components include terephthalic acid, isophthalic acid, adipic acid, sebaciic acid, and naphthalenedicarboxylic acid. Examples of hydroxyl group components include ethylene glycol, 1,4-butanediol, diethylene glycol, neopentyl glycol, and cyclohexanedimethanol. Examples of polyester resins include polyethylene terephthalate, polytrimethylene terephthalate, polybutylene terephthalate, and copolymerized polyesters obtained by copolymerizing these polymers with a third component. Polyethylene terephthalate is preferably used for polyester resin airbag fabric because it balances cost and physical properties such as strength. Furthermore, polyethylene terephthalate is preferred as a polyester resin in terms of versatility when it is to be recycled after collection.

[0016] The base fabric, which is a polyamide or polyester fabric, is preferably a woven fabric composed of multifilaments of polyamide or polyester fibers. Examples of woven fabrics include plain weave, twill weave, satin weave, and variations thereof.

[0017] From the viewpoint of recovering a more recyclable polymer resin, the number of filaments in the multifilament yarn that constitutes the woven fabric (base fabric) is preferably 30 to 200, and more preferably 40 to 180. The number of filaments can be determined by counting them from a cross-sectional photograph of the multifilament yarn.

[0018] The total fineness of the multifilament yarns constituting the woven fabric (base fabric) is preferably 200 dtex to 1000 dtex, and more preferably 250 dtex to 800 dtex, from the viewpoint of recovering a more recyclable polymer resin. The total fineness of the multifilament yarns can be measured in accordance with JIS L1013 (2010) 8.3.1.

[0019] From the viewpoint of recovering a more recyclable polymer resin, the tensile strength of the multifilament yarns constituting the woven fabric (base fabric) is preferably, for example, 6.0 cN / dtex to 10 cN / dtex, and more preferably 6.5 cN / dtex to 9.5 cN / dtex. The tensile strength of the multifilament yarns can be measured in accordance with JIS L1013 (2010) 8.5.1.

[0020] From the viewpoint of recovering a more recyclable polymer resin, the weave density of the woven fabric (base fabric) is preferably 35 threads / 2.54cm to 80 threads / 2.54cm in both the warp and weft directions, and more preferably 40 threads / 2.54cm to 75 threads / 2.54cm. The weave density can be measured in accordance with JIS L1096(2010)8.6.1.

[0021] The cover factor (CF) of the woven fabric (base fabric) is preferably 1,500 to 2,500, and more preferably 1,700 to 2,300, from the viewpoint of recovering a more recyclable polymer resin. The cover factor is an indicator of the coverage rate of the woven fabric and can be calculated using the following formula. CF = (Total fineness of warp threads) 0.5 × Warp density + (Total fineness of weft threads) 0.5 ×Weft density

[0022] The base fabric may contain additives other than polyamide resin or polyester resin. Examples of such additives include antioxidants, heat stabilizers, smoothing agents, antistatic agents, thickeners, flame retardants, weather-resistant agents, color inhibitors, and colorants.

[0023] The polymer resin airbag fabric has a coating resin containing silicone resin applied to at least one side of the base fabric, forming a silicone resin layer.

[0024] The silicone resin is not particularly limited, but specific examples include addition polymerization type silicone rubber. Examples include dimethyl silicone rubber, methyl vinyl silicone rubber, methylphenyl silicone rubber, trimethyl silicone rubber, fluorosilicone rubber, methyl silicone resin, methylphenyl silicone resin, methyl vinyl silicone resin, epoxy-modified silicone resin, acrylic-modified silicone resin, and polyester-modified silicone resin. Among these, addition polymerization type methyl vinyl silicone rubber is preferred.

[0025] The viscosity of the coating resin is preferably 5,000 mPa·sec to 40,000 mPa·sec, and more preferably 7,000 mPa·sec to 38,000 mPa·sec. Within the above viscosity range, the coating resin may be solvent-based or solvent-free, but solvent-free is preferred. In this specification, the viscosity of the coating resin refers to the viscosity of the coating resin composition containing additives other than the resin, i.e., the viscosity of the resin actually applied to the base fabric.

[0026] The coating resin may contain additives other than silicone resin and solvents. 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, vinylsiloxanes, or acetylene alcohols, etc.); adhesion aids such as amino-based silane coupling agents, epoxy-modified silane coupling agents, vinyl-based silane coupling agents, chlor-based silane coupling agents, and 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, and titanium dioxide; antioxidants; antistatic agents; flame retardants; weather-resistant agents; color inhibitors; colorants; and the like. When a platinum-based catalyst is included as a reaction curing agent, its content is preferably 100 ppm to 2000 ppm in terms of platinum metal amount per 100 parts by mass of silicone resin, and more preferably 150 ppm to 1800 ppm. When a silane coupling agent is included as an adhesive aid, its content is preferably 0.01 to 3 parts by mass, and more preferably 0.02 to 2 parts by mass, per 100 parts by mass of silicone resin. If an inorganic filler is included, its content is preferably 0.1 to 200 parts by mass, and more preferably 0.1 to 100 parts by mass, per 100 parts by mass of silicone resin.

[0027] The coating resin (i.e., silicone resin) on the base fabric can be applied using conventional known coating methods. Examples of coating methods include knife coating, roll coating, reverse coating, gravure coating, gravure reverse coating, and kiss coating, and it is preferable that the silicone resin is applied by knife coating.

[0028] The amount of silicone resin applied to the polymer resin airbag fabric is 5 g / m², from the viewpoint of the ease of separating the polymer resin from the silicone resin. 2 ~150g / m 2It is preferably, 7 g / m 2 or more, more preferably 10 g / m 2 or more, still more preferably 120 g / m 2 or less, more preferably 100 g / m 2 or less, still more preferably 70 g / m 2 or less is even more preferable.

[0029] As the weight ratio of the polymer resin in the polymer resin-made airbag fabric, from the viewpoint of the ease of separation of the polymer resin from the silicone resin, it is preferably 50% to 99% by weight, more preferably 55% by weight or more, still more preferably 60% by weight or more, even more preferably 70% by weight or more, and also more preferably 97% by weight or less, still more preferably 95% by weight or less, even more preferably 93% by weight or less. When the proportion of other than the polymer resin in the base fabric is small (for example, 5% by mass or less, further 3% by mass or less), the above weight ratio of the polymer resin may be read as the weight ratio of the base fabric.

[0030] As the size of the airbag fabric, from the viewpoint of the ease of holding in water and the efficiency of heat treatment, it is preferably 1 mm 2 ~2500 cm 2 When using the filter member described later as the underwater holding member during heat treatment, the size of the airbag fabric is more preferably 25 mm 2 or more, still more preferably 1 cm 2 or more, even more preferably 10 cm 2 or more, and also more preferably 1500 cm 2 or less, still more preferably 1000 cm 2 or less. Also, when using the shape holding member described later as the underwater holding member during heat treatment, the size of the airbag fabric is more preferably 1 cm 2 or more, still more preferably 25 cm 2 or more, even more preferably 10 cm 2 or more, and also more preferably 2000 cm 2 or less, still more preferably 1500 cm 2 or less is even more preferable. Furthermore, regarding the size of the airbag fabric, from the viewpoint of ease of retention in water and efficiency of heat treatment, it is preferable that the length is within the range of 1 mm to 500 mm and the width is within the range of 1 mm to 500 mm, and more preferably that the length is within the range of 5 mm to 450 mm and the width is within the range of 5 mm to 450 mm. If the size of the airbag fabric exceeds the above upper limit, it is preferable to cut it to the above range beforehand using a known cutting machine or the like before heat treatment.

[0031] The shape of the airbag fabric is not particularly limited and may be rectangular, square, circular, elliptical, or other polygonal or irregular shapes, but a rectangular shape is preferred from the viewpoint of ease of handling.

[0032] The airbag fabric used for recovery may be a mixture of uncoated airbag fabric and non-silicone coated airbag fabric, but it is preferable that the silicone coated airbag fabric accounts for 50% by mass or more of the total. It is more preferable that the silicone coated airbag fabric accounts for 60% by mass or more of the total, even more preferable that it accounts for 70% by mass or more, and particularly preferable that it accounts for 80% by mass or more.

[0033] (Heat treatment process) In this invention, the entire airbag fabric is immersed in water and heat-treated at a temperature of 160°C or higher and under a pressure equal to or greater than the saturated water vapor pressure at that temperature. This method utilizes the fact that the melting point of a hydrated polymer resin decreases, allowing it to melt even at relatively low temperatures. By heat-treating the hydrated state, the base fabric is separated from the coating layer. The heat treatment is preferably performed at a temperature of 180°C or higher.

[0034] For example, nylon 66, which is often used as a base fabric for airbags, is known to have a melting point of 255-260°C in a dry state. However, in a hydrated state, it melts at 180°C or lower, which is about 80°C lower than in the dry state. Therefore, nylon 66 can be melted at temperatures above 180°C in a hydrated state. A high-pressure hot water treatment apparatus is used for the heat treatment. The high-pressure hot water treatment apparatus may be a batch type apparatus or a flow type apparatus, but a batch type apparatus is preferred when using the shape-retaining member described later as the underwater holding member.

[0035] In the heat treatment process, first, the airbag fabric is placed in the water present in the reaction tank (hot water treatment container) of the high-pressure hot water treatment apparatus using an underwater holding member so that the entire fabric is immersed. Then, while maintaining the entire airbag fabric immersion in water by the underwater holding member, heat treatment is performed at a temperature of 160°C or higher and under a pressure equal to or greater than the saturated water vapor pressure at that temperature. By performing heat treatment under these conditions, the polymer resin constituting the base fabric in the airbag fabric melts. Here, in order to keep the silicone resin submerged in water in the reaction tank by the underwater holding member, the molten polymer resin easily separates from the silicone resin. Preferably, the molten polymer resin is separated from the silicone resin by the water flow (e.g., convection, etc.) generated during the heat treatment and / or cooling process, or by the water flow generated by using a stirring blade during the heat treatment process. Although polymer resin airbag fabric usually has a higher specific gravity than water, due to the water-repellent effect of silicone resin, it may float to the surface of the water instead of sinking when left standing. By using an underwater holding member, the entire polymer resin airbag fabric can be immersed in water, ensuring that the polymer resin airbag fabric is not present on the water surface. On the other hand, molten polymer resin detached from silicone resin will flow due to the water current, even if its specific gravity is greater than water, and will float to the surface. Therefore, it is possible to prevent the polymer resin, once detached from the silicone resin, from re-contacting the polymer resin airbag fabric and silicone resin, and the polymer resin can be easily recovered separately from them.

[0036] The underwater holding member should be capable of immersing and holding the entire airbag fabric in water; any member that fails to prevent even a part of the airbag base fabric from floating on the water surface is undesirable. Examples of underwater holding members include filter members and shape-retaining members.

[0037] The filter member, which serves as the underwater holding member, has multiple through-holes of a size that prevents the airbag fabric subjected to heat treatment from passing through. By installing the filter member in the reaction vessel, the movement of the airbag fabric is restricted by the filter member (i.e., the airbag fabric is prevented from floating to the water surface or flowing out of the reaction vessel), thereby keeping the entire airbag fabric submerged in water.

[0038] When a water surface exists in the reaction vessel during heat treatment, it is preferable to install the filter component in such a way that it divides the reaction vessel into the upper part where the water surface is present and the lower part where water is present throughout. Furthermore, from the viewpoint of ease of operation, it is preferable that the filter component be detachable.

[0039] The size of the filter element should be such that, when installed in the reaction vessel, the airbag cloth cannot pass through the gap between the filter element and the inner wall of the reaction vessel. For example, the area of ​​the filtration surface, including the through-holes, is preferably 80% to 100%, more preferably 90% to 100%, and even more preferably 97% to 100%, relative to the cross-sectional area of ​​the reaction vessel at the location where the filter element is installed.

[0040] The thickness of the filter element is not particularly limited. For example, the lower limit of the filter element's thickness should be set to a thickness that does not cause movement or deformation due to the water flow during heat treatment, and the upper limit of the filter element's thickness should be set to a thickness that allows the molten polymer resin from the heat treatment to pass through easily.

[0041] The size of each through-hole in the filter member is preferably such that water used for heat treatment and the polymer resin melted by the heat treatment can pass through, but silicone resin cannot. For example, the opening area of ​​each through-hole in the filter member is preferably 0.01 to 25% of the area of ​​the airbag fabric. Furthermore, the size of each through-hole is preferably 0.05 to 25%, more preferably 0.1 to 20%, and even more preferably 0.1 to 15%. On the other hand, when the water flow velocity is above a certain level (for example, 0.001 m / s or more), the size of each through-hole is preferably 0.01% to 10%, more preferably 0.05% to 10%, even more preferably 0.1% to 10%, and even more preferably 0.2% to 10%. For example, if the area of ​​the airbag fabric is 1600 mm² 2 In this case, the size of each through-hole in the filter member is preferably 0.4 to 13 mm. When multiple airbag cloths are used, the area of ​​the airbag cloth is the average value of the area of ​​the airbag cloths used. Specifically, the opening area is 0.05 mm. 2 ~200cm 2 Preferably, 0.1 mm 2 ~100cm 2 More preferably, 0.3 mm 2 ~50cm 2 That is even more preferable. Preferably, among the multiple through holes in the filter member, the proportion of through holes having an opening area within the above range is 60% to 100%, more preferably 80% to 100%, and even more preferably 90% to 100%.

[0042] The total opening area, which is the sum of the opening areas of the multiple through-holes in the filter member, is preferably 30% to 95%, more preferably 40% to 93%, and even more preferably 50% to 90%, of the area of ​​the filtration surface, including the through-hole portion of the filter member.

[0043] From the viewpoint of heat resistance, pressure resistance, and durability, metals such as silicon, aluminum, nickel, tungsten, copper, titanium, and stainless steel are preferred as the material for the filter component, with aluminum and stainless steel being more preferred. Metal materials that have been plated with zinc-based, chromium-based, nickel-based, etc. are also acceptable. To reduce adhesion to polymer resins and improve separation efficiency, a fluororesin coating such as Teflon® coating may be applied to the surface of the filter component. In particular, among metal materials, aluminum is most preferred from the viewpoint of heat resistance, pressure resistance, durability, and low adhesion to polymer resins, allowing for highly efficient separation.

[0044] Examples of filter materials include metal filters such as metal mesh, perforated metal plates, and sintered products of metal particles or flakes.

[0045] It is also preferable to provide multiple filters with different opening areas, arranged so that the polymer resin passes through in multiple stages. By passing the resin through a filter with a large opening area followed by a filter with a small opening area, clogging is less likely to occur, and the silicone resin can be removed effectively.

[0046] The shape-retaining member, as an underwater holding member, is a member that maintains (fixes) the shape of at least the end of the airbag fabric. By providing the shape-retaining member on at least a part (preferably at least one end) of the outer circumference of the airbag fabric, the entire airbag fabric can be held in water. Furthermore, holding at least one end of the airbag fabric suppresses folding and curling of the airbag fabric, which is preferable from the viewpoint of heat treatment efficiency. The shape-retaining member may be detachably fixed inside the reaction vessel using fixing members such as hooks.

[0047] Examples of shape-retaining members include end shape-retaining members that fix a portion of the outer circumference of the airbag fabric, and frame members that fix the entire outer circumference of the airbag fabric.

[0048] When using an end shape retaining member, from the viewpoint of shape retention, it is preferable to provide the end shape retaining member for a total length of 50% or more of the total length of the end of the airbag fabric, more preferably for a total length of 70% or more, and even more preferably for a total length of 90% or more.

[0049] When a shape-retaining member is used, the total overlap area between the airbag fabric and the shape-retaining member is preferably 0.1% to 20%, more preferably 0.5% to 15%, and even more preferably 1% to 10% of the total area of ​​the airbag fabric, from the viewpoint of shape retention and polymer resin recovery rate.

[0050] From the viewpoint of heat resistance, pressure resistance, and durability, metals such as silicon, aluminum, nickel, tungsten, copper, titanium, and stainless steel are preferred as the material for the shape-retaining member, with aluminum and stainless steel being more preferred.

[0051] As the shape-retaining member, a metal frame made of a metal such as silicon, aluminum, nickel, tungsten, copper, titanium, or stainless steel is preferred, with aluminum or stainless steel frames being more preferred. The shape-retaining member may be made of a metal material that has been plated with zinc, chromium, nickel, or the like, and the surface may be coated with a fluororesin coating such as Teflon® coating.

[0052] It is preferable to perform the heat treatment while maintaining the entire airbag fabric submerged in water by the above-mentioned underwater holding member.

[0053] The processing temperature in the heat treatment is preferably 160°C or higher, more preferably 170°C or higher, even more preferably 175°C or higher, and particularly preferably 180°C or higher. From the viewpoint of polymer resin recovery rate, 185°C or higher is preferred, 188°C or higher is more preferred, and 190°C or higher is even more preferred. From the viewpoint of suppressing degradation of the polymer resin, 250°C or lower is preferred, 240°C or lower is more preferred, 235°C or lower is even more preferred, and 230°C or lower is even more preferred. If the processing temperature is within the above range, the polymer resin and silicone resin can be easily separated while suppressing degradation such as decomposition of the polymer resin.

[0054] The processing pressure in the heat treatment should be above the saturated water vapor pressure at the processing temperature, preferably between 1.0 MPa and 4.0 MPa. More preferably, it should be 1.1 MPa or higher, even more preferably 1.2 MPa or higher, even more preferably 3.6 MPa or lower, even more preferably 3.3 MPa or lower, even more preferably 3.0 MPa or lower, and even more preferably 2.8 MPa or lower. If the processing pressure is within the above range, the polymer resin and silicone resin can be easily separated while suppressing degradation such as decomposition of the polymer resin. From the viewpoint of ease of controlling temperature and pressure in the heat treatment, it is also preferable to process at the saturated water vapor pressure at the processing temperature.

[0055] When the polymer resin is nylon 66, from the viewpoint of improving the recovery rate, it is preferable that the processing temperature is 180°C to 240°C and the processing pressure is 1.0 MPa to 3.6 MPa. When the polymer resin is polyethylene terephthalate, from the viewpoint of improving the recovery rate, it is preferable that the processing temperature is 210°C to 240°C and the processing pressure is 2.0 MPa to 3.6 MPa.

[0056] The processing time in the heat treatment can be set appropriately according to the processing temperature and processing pressure, but for example, 30 seconds to 240 minutes is preferred, 45 seconds or more is more preferred, 1 minute or more is even more preferred, 180 minutes or less is more preferred, 120 minutes or less is even more preferred, and 60 minutes or less is even more preferred. If the processing time is within the above range, the polymer resin and silicone resin can be easily separated while suppressing deterioration such as decomposition of the polymer resin.

[0057] From the viewpoint of preventing deterioration of the airbag fabric (especially polymer resin), it is preferable to raise the temperature and / or pressure to the processing temperature and / or processing pressure in a short amount of time. For example, it is preferable to raise the pressure from 0.05 MPa to the processing pressure within 60 minutes, more preferably within 30 minutes, and even more preferably within 20 minutes. Similarly, it is preferable to raise the temperature from 80°C to the processing temperature within 60 minutes, more preferably within 30 minutes, and even more preferably within 20 minutes.

[0058] As for the heat treatment method, for example, a heat-resistant reaction tank containing the airbag fabric, which is held in water by an underwater holding member, may be heated and pressurized using a heating device such as a heater, or high-pressure hot water may be circulated through the heat-resistant reaction tank containing the airbag fabric, whose movement is restricted by the underwater holding member, using a liquid supply device such as a pump.

[0059] When water is heated, a water flow is generated as the heated water rises. A water flow is also generated when the water is cooled after heat treatment. This water flow releases the molten polymer resin, which has been held in place by the underwater holding member, from its position in the water and allows it to float on the water surface, while the silicone resin remains submerged in the water, thus separating the polymer resin and the silicone resin. When high-pressure hot water is circulated through the reaction tank, the water flow from this circulation releases the molten polymer resin, which has been held in place by the underwater holding member, from its position in the water and allows it to flow out, while the silicone resin remains submerged in the water, thus separating the polymer resin and the silicone resin.

[0060] The generated water flow can be any direction, such as upward, downward, or sideways, and can be any direction considering the shape of the reaction vessel used for heat treatment, the shape of the underwater holding member, etc. However, an upward water flow is preferred due to the stability of the water flow and the separation effect. Note that the direction of the water flow is the direction of the water flow that hits the airbag fabric, and it does not need to be perfectly perpendicular (anti-gravity direction) to upward; it may be diagonally upward. In the case of a diagonally upward direction, it is preferably 20 degrees or more relative to the horizontal direction, more preferably 30 degrees or more, even more preferably 40 degrees or more, and especially preferably 50 degrees or more, 60 degrees or more, 70 degrees or more, and 80 degrees or more, in that order. In the case of a vortex flow (swirling flow) generated by stirring, etc., it is preferable that the direction of the entire vortex flow (swirling flow) is upward. In the case of a water flow that circulates in the container due to stirring, heating, or cooling convection, it is preferable that at least a part of the airbag held in the water by the underwater holding member is hit by a water flow with the following water flow velocity.

[0061] The water flow velocity is preferably 0.001 m / s or higher, more preferably 0.002 m / s or higher, and even more preferably 0.01 m / s or higher. If the water flow velocity is 0.001 m / s or higher, the separation of the polymer resin and the silicone resin can be performed with high efficiency. There is no particular upper limit to the water flow velocity, but it may be 1 m / s or less, or 0.5 m / s or less. If the water flow velocity is 1 m / s or less, the silicone will have difficulty passing through the filter material, and separation can be performed with high efficiency. Flow rate can be measured using various flow meters, and the flow state can also be measured using heat-resistant containers with glass windows. It can also be calculated through simulation. When performing a simulation, the parameters used in the simulation can be adopted by referring to values ​​measured by flow meters or the methods described above.

[0062] The heat treatment may be carried out while stirring using a known stirring device such as an impeller to generate a water flow, or while generating a water flow with a pump or the like. When the heat treatment is carried out while stirring, the rotation speed of the impeller is preferably 1 to 3000 rpm, more preferably 10 to 3000 rpm, and more preferably 20 to 2000 rpm, depending on the size of the container, the diameter of the container, the ratio of the diameter to the length of the container, the shape of the impeller, and the size of the impeller. In order to achieve a stable and uniform water flow, it is preferable to lower the rotation speed as the impeller is larger, the container is larger, the length is shorter relative to the diameter of the container, and the impeller is larger relative to the diameter of the container. For example, when the capacity of the container of the heat treatment unit 2a is 100 L or more, the rotation speed of the impeller is preferably 1 to 500 rpm, more preferably 5 to 300 rpm, even more preferably 10 to 200 rpm, and most preferably 20 to 100 rpm, depending on the shape of the impeller. By performing the heat treatment while stirring, the separation of the polymer resin and the silicone resin can be further promoted, and by keeping the rotation speed of the stirring blade within the aforementioned range, the polymer resin can be recovered more efficiently.

[0063] The shape of the stirring blade can be a propeller blade, paddle blade, turbine blade, anchor blade, ribbon blade, etc., and a shape with an inclined blade is preferably used because it can generate a water flow in one direction.

[0064] Generally, the larger the volume and diameter of the reaction vessel (container) used for heat treatment, the larger the impeller used. However, it is preferable that the ratio of the maximum diameter of the rotation range when the impeller is rotated to the diameter of the container is 0.1 to 0.95. The ratio is more preferably 0.2 or higher, even more preferably 0.3 or higher, and may be 0.4 or higher, or 0.5 or higher. Furthermore, the ratio may be 0.9 or lower, or 0.85 or lower.

[0065] When the reaction vessel (container) used for heat treatment is cylindrical, the ratio of the diameter to the length of the vessel is preferably such that the length is 2 times or more the diameter of the vessel, more preferably 3 times or more, even more preferably 3.5 times or more, even more preferably 4 times or more, particularly preferably 4.5 times or more, and most preferably 5 times or more. There is no upper limit set for the ratio of the diameter to the length of the vessel, however, in the case of a vessel equipped with a stirring blade and a tank-shaped vessel, it may be 10 times or even 20 times. In this case, the vessel may be vertical or horizontal, but a vertical shape is preferred for a vessel equipped with a stirring blade.

[0066] The reaction vessel for heat treatment may be a pipe-type container such as a tube reactor or reaction tube. In the case of a pipe-type container, the upper limit may be 100 times, 300 times, 500 times, or 1000 times. In the case of a pipe-type container, it is preferable that it be U-shaped, N-shaped, Z-shaped, or a bent shape that repeats these shapes, a coil shape, or a spiral shape.

[0067] In the case of a vertical container with an ellipsoidal bottom, the length of the container is the length from the very bottom to the water level, and the diameter of the container is the diameter from the bottom excluding the water level. If the diameter of the container gradually increases or decreases, or if it is barrel-shaped or otherwise not a perfect cylinder, the arithmetic mean diameter is used. In the case of a pipe-type container, the diameter and length of the container are the diameter and length of the pipe.

[0068] Furthermore, if there are stirring blades or the like inside the container, the distance between the stirring blades and the underwater holding member, or if a pump or the like is installed outside the heat container to supply water flow, the distance between the inlet for introducing water flow into the container and the underwater holding member, and the diameter of the container are preferably such that these distances are read as the length of the container, and the relationship between the diameter and length of the container is the ratio of the diameter to the length of the container. By having this relationship, a stable, unidirectionally concentrated water flow can be achieved.

[0069] When mechanical means such as agitators are not used, the water flow due to convection can be increased by rapidly raising the temperature. Also, by raising the temperature of a portion of the reaction vessel, the water flow due to convection can be promoted and stabilized.

[0070] (cooling process) After heat treatment, the reaction vessel and / or polymer resin may be cooled by natural cooling, but it is preferable to cool them using a known cooling device. Alternatively, they may be transferred to a separately prepared cooling device, or the silicone resin may be filtered by passing it through a filter when transferring it to the cooling device. Since the polymer resin melted by heat treatment solidifies upon cooling, the polymer resin separated from the silicone resin can be obtained as a solid. This solid state is preferable because it is easier to handle. If the polymer resin recovery method includes a cooling step, it is preferable that this step be included before the recovery step.

[0071] From the viewpoint of suppressing the degradation of polymer resins, it is preferable to cool the temperature down for a short period of time. For this reason, it is preferable to use a known cooling device rather than allowing it to cool naturally. Examples of such methods include blowing cold air onto the reaction vessel, immersing the reaction vessel in cooling water, or circulating cooling water through the jacket of the reaction vessel.

[0072] The cooling time is preferably such that the temperature reduction from the processing temperature to 80°C is carried out within 60 minutes, more preferably within 30 minutes, and even more preferably within 20 minutes. If the temperature reduction from the processing temperature to 80°C is carried out within 60 minutes, the polymer resin with suppressed degradation can be recovered. Furthermore, by performing the procedure within the above limits, a sufficient water flow can be generated by convection even without using mechanical means such as a stirrer. There is no particular lower limit, but from the viewpoint of separation by thermal convection during cooling, a sufficient water flow can be generated by taking 1 minute or more, and separation can be carried out with high efficiency.

[0073] (Recovery process) In the recovery process, the polymer resin separated from the silicone resin by heat treatment is recovered. As described above, by performing heat treatment while keeping the entire airbag fabric immersed in water, the polymer resin exists in a state separated from the silicone resin, making it easy to recover. If the heat treatment is not performed while keeping the entire airbag fabric immersed in water, the molten polymer resin may adhere to the silicone resin as it cools, making the recovery operation complicated.

[0074] For the recovery of the polymer resin, it is sufficient to simply extract the polymer resin, which exists separately from the silicone resin.

[0075] The recovered polymer resin may be washed with a cleaning solution such as water or an organic solvent, and post-treatment such as drying may be performed as appropriate.

[0076] The present invention provides a method for recovering polymer resins, which does not require alkaline treatment of the airbag fabric. By treating the airbag fabric, which is held in water, under specific temperatures and pressures, degradation of the polymer resin due to alkaline treatment can be avoided. Furthermore, the silicone resin and polymer resin can be easily separated and recovered without complicated operations. The recovery method of the present invention also has high heat treatment efficiency. For this reason, the recovery method of the present invention can preferably reduce the processing time required for heat treatment, and further suppress the degradation of the polymer resin.

[0077] The recovered polymer resin can be processed by washing with cleaning solutions such as water and organic solvents, followed by drying and other post-treatments. After that, it can be melted by heat or with a solvent, and then pelletized or formed into sheets to obtain a recycled resin composition.

[0078] (polymer resin) The recovered polymer resin (recycled polymer resin composition) preferably has a low silicone content, and preferably is substantially silicone-free. "Substantially silicone-free" means that the silicone resin content in the polymer resin is 1% by mass or less, more preferably 0.5% by mass or less, and even more preferably 0.1% by mass or less. There is no particular lower limit; 0% by mass is preferred, and it may be 0.01% by mass or more. A polymer resin that is substantially silicone-free has high recyclability. The silicone resin content in a polymer resin can be calculated, for example, by determining the mass of silicone resin in the polymer resin using a Fourier transform infrared spectrophotometer (FT-IR) and basing the calculation on the obtained value.

[0079] Furthermore, the recovered polymer resin samples were powdered by freeze-pulverization and used as measurement samples. When measured using a fluorescent X-ray analyzer (Thermo Fisher Scientific XL3t-950S) in mineral mode (FP method) Cu / Zn mode, the Si element content is preferably 50,000 ppm or less, more preferably 40,000 ppm or less, and even more preferably 30,000 ppm or less. By keeping the silicone content below the above limits, when processing recycled polymer resin compositions into fibers, films, molded products, etc., problems such as thread breakage and film rupture become less likely, and deterioration of appearance such as strength reduction due to foreign matter, surface roughness, and foreign matter defects become less likely. In addition, when processing with recycled polymer resin compositions and filtering the molten resin through a filter, filter clogging is less likely to occur, and stable processed products can be produced continuously. Furthermore, since the recovered polymer resin contains various additives derived from the base fabric and trace amounts of coating material, it is sometimes referred to as a resin composition, but it can be considered the same as the polymer resin.

[0080] The silicone content can be reduced by reducing the opening area of ​​the filter in the heat treatment process described above, or by passing the material through a filter during pelletizing or sheeting. It can also be reduced by increasing the amount of treated water relative to the airbag fabric. The lower limit of the amount of treated water relative to the airbag fabric is preferably 1.1 times by mass, more preferably 1.5 times, even more preferably 2 times, even more preferably 5 times, particularly preferably 10 times, and most preferably 30 times. By increasing the amount of treated water relative to the airbag fabric to the above or higher, the separation efficiency of the polymer resin is improved. The upper limit of the amount of treated water relative to the airbag fabric is preferably 10,000 times by mass, more preferably 5,000 times, and even more preferably 1,000 times, but is not limited to this. In cases such as when high-pressure hot water is circulated through a heat-resistant reaction vessel containing the airbag fabric using a liquid transfer device such as a pump, the amount of treated water can be increased even further.

[0081] On the other hand, silicone-based oils may be used in the spinning process of the base fabric, and these silicone-based oils may not be completely removed. Furthermore, while the amount of silicone resin can be reduced by improving the precision of the filter, this can slow down the filtration rate and reduce productivity. Considering these factors, the lower limit of the silicone content may be 4000 ppm or even 5000 ppm. Recycled polymer resin compositions with low silicone content can be used in a wide range of applications as material recycled polymer resin compositions. Furthermore, when measured using the above method, even polyamide 66 resin, the raw material for airbag base fabric, may show a silicone content of 3,000 to 3,500 ppm. Additionally, if the coating agent is not removed before kneading and pelletizing, the silicone content may range from 250,000 to 300,000 ppm. Considering additives derived from the base fabric (such as silicone oil), if the silicone content is below the above values, it can be assumed that most of the coating agent has been removed.

[0082] The recovery rate of the polymer resin is preferably as high as possible, with an upper limit of 100% by weight, preferably 1% by weight or more, more preferably 5% by weight or more, and even more preferably 7% by weight or more. The recovery rate of the polymer resin can be calculated using the following formula, by recovering the polymer resin that has separated from the silicone resin in the reaction vessel after heat treatment, measuring its weight (B parts by weight), and using the weight of the sample (airbag cloth) before treatment (A parts by weight) and the weight ratio of the polymer resin in the sample before treatment (C%). Recovery rate (%) = {B / [A × (C / 100)]} × 100

[0083] The polymer resin obtained by the recovery method of the present invention exhibits suppressed degradation compared to the polymer resin in the airbag fabric before heat treatment. The degree of degradation can be confirmed by the viscosity of the polymer resin (e.g., relative viscosity, intrinsic viscosity). Since viscosity and molecular weight of the resin are proportional, the higher the viscosity, the larger the molecular weight of the recovered polymer resin, meaning that it maintains its polymer state. Specifically, if the polymer resin is a polyamide resin, a relative viscosity of 1.5 or higher (preferably 1.7 or higher, more preferably 1.9 or higher, even more preferably 2.1 or higher, and even more preferably 2.3 or higher) indicates that it is a polyamide resin suitable for material recycling. If the polymer resin is a polyester resin, an intrinsic viscosity of 0.3 dl / g or higher (preferably 0.5 dl / g or higher, more preferably 0.7 dl / g or higher) indicates that it is a polyester resin suitable for material recycling.

[0084] The relative viscosity (RV) of a polymer resin can be calculated by dissolving 0.25 g of the polymer resin in 46 g of 96% sulfuric acid, placing 10 ml of this solution in an Oswald viscosity tube, measuring it at 20°C, and using the following formula. RV = T / T0 (RV: relative viscosity, T: sample solution fall time, T0: solvent fall time)

[0085] The intrinsic viscosity (η) of a polymer resin can be determined by dissolving 0.1 g of the polymer resin in 25 mL of a mixed solvent of phenol / 1,1,2,2-tetrachloroethane (60 / 40 (weight ratio)) and measuring it using an Ostwald viscometer at 30°C.

[0086] If the relative viscosity (RV0) of the polymer resin before heat treatment can be measured, it is preferable that the ratio of RV (relative viscosity of the recovered polymer resin) to RV0 (RV / RV0) is 0.4 or higher (preferably 0.5 or higher, more preferably 0.6 or higher, even more preferably 0.7 or higher, and even more preferably 0.8 or higher). If the value of RV / RV0 is within the above range, the polymer resin obtained by the recovery method of the present invention is said to have suppressed degradation and is a polymer resin that can be suitably used for material recycling. If the intrinsic viscosity (η0) of the polymer resin before heat treatment can be measured, it is preferable that the ratio of η (intrinsic viscosity of the recovered polymer resin) to η0 (η / η0) is 0.3 or higher (preferably 0.5 or higher, more preferably 0.7 or higher). If the value of η / η0 is within the above range, the polymer resin obtained by the recovery method of the present invention is said to have suppressed degradation and is a polymer resin that can be suitably used for material recycling.

[0087] Polymer resins that are suitable for material recycling can be reused without further processing such as polymerization, making them advantageous from an energy cost perspective and offering particularly high recyclability.

[0088] When the polymer resin is a polyamide-based resin such as polycaproamide (nylon 6) or polyhexamethylene adipamide (nylon 66), the recovery method of the present invention yields a polyamide resin with high crystalline completeness. The crystalline completeness of the polyamide resin is preferably 95% or higher, more preferably 97% or higher, and may be 100%. The closer the crystallization perfection value is to 100%, the higher the crystallization perfection and the better the thermal stability. The crystallization perfection of polyamide resin can be determined by the method described in the examples (wide-angle X-ray measurement).

[0089] The polymer resin obtained by the recovery method of the present invention is not particularly limited in its use. For example, it can be reused by decomposing it into monomers and repolymerizing it (chemical recycling), or it can be reused by melting it and re-pelletizing it without decomposing it into monomers (material recycling). From the viewpoint of energy cost, it is preferable to use it for material recycling.

[0090] The polymer resin (preferably a polyamide resin or polyester resin) obtained by the recovery method of the present invention can be recycled into a recycled product containing at least a portion of the raw materials through chemical recycling or material recycling.

[0091] (Recovery device) The recovery apparatus of the present invention is a device capable of carrying out the polymer resin recovery method of the present invention described above, and is equipped with a high-pressure hot water treatment device, wherein the high-pressure hot water treatment device has an underwater holding member (in the illustrated example, a removable filter member fitted so as to partition the reaction tank). The recovery apparatus of the present invention will be described below with reference to the illustrated examples as necessary. However, the recovery apparatus of the present invention is not limited by the illustrated examples below, and it is possible to make appropriate modifications within the scope that is in line with the spirit of the present invention, and all such modifications are included in the technical scope of the present invention.

[0092] As shown in the schematic cross-sectional view of Figure 1, the recovery device includes a high-pressure hot water treatment device 1, which has an underwater holding member, specifically a removable filter member 3 fitted to partition the reaction tank 2. The high-pressure hot water treatment device 1 may also have a lid 21 that closes the reaction tank 2, and may have fixing members such as tightening bolts 22 that can fix the reaction tank 2 and the lid 21. The high-pressure hot water treatment device 1 may also have a heating mechanism 6 such as a heater for heating the reaction tank 2. Furthermore, although not shown, the high-pressure hot water treatment device 1 may also have a cooling mechanism (e.g., a heat exchanger such as a water jacket), a pressure gauge, a safety valve, a temperature sensor, and / or a stirrer (e.g., a stirring blade).

[0093] The filter member 3 has multiple through holes. The size, thickness, material, and specific configuration of the through holes of the filter member 3 are as described above.

[0094] The heating mechanism may be installed to heat the entire reaction vessel 2, or to heat a part of the reaction vessel 2. From the viewpoint of heating efficiency, it is preferable to install it to heat at least the bottom of the reaction vessel 2.

[0095] The recovery device of the present invention processes the material to be processed using high-pressure hot water. The high-pressure hot water treatment device 1 of the recovery device can hold the entire airbag fabric 4 made of polymer resin coated with silicone resin, which is the material to be processed, in water 5 using a filter member 3. Through the heat treatment, the polymer resin becomes molten and passes through the filter member 3, accumulating on the water surface. On the other hand, the silicone resin does not pass through the filter member 3 and remains held in the water. Therefore, using this recovery device, it is possible to separate and recover the airbag fabric 4 into silicone resin and polymer resin without complicated operations, and furthermore, it is possible to suppress the deterioration of the recovered polymer resin. [Examples]

[0096] The present invention will be described in more detail below with reference to examples, but the present invention is not limited by the following examples, and it is certainly possible to implement it with appropriate modifications within the scope that is consistent with the spirit of the preceding and following descriptions, and all such modifications are included within the technical scope of the present invention.

[0097] In the following examples and comparative examples, the polyamide resin airbag fabric 1 described below was used as the polymer resin airbag fabric.

[0098] (Polyamide resin airbag fabric 1) Using a polyamide 66 multifilament yarn with a yarn strength of 8.4 cN / dtex, a total fineness of 470 dtex, and 68 filaments, a plain weave fabric was obtained with a warp density of 46 threads / 2.54 cm, a weft density of 46 threads / 2.54 cm, and a cover factor of 1994. An addition polymerization type solvent-free vinyl methyl silicone resin with a resin viscosity of 14000 mPa·sec was applied to one side of the plain weave fabric (base fabric) and dried at 200°C for 1 minute, resulting in a resin coating amount of 25 g / m². 2 A polyamide resin airbag fabric 1 was obtained. The weight ratio of polyamide resin in the polyamide resin airbag fabric 1 was 87%.

[0099] In the following examples and comparative examples, the polyamide resin, which is a polymer resin recovered from the polyamide resin airbag fabric 1, was evaluated using the following procedure.

[0100] (Recovery rate) After heat treatment, the polyamide resin, which had separated from the silicone resin in the reaction vessel, was recovered. The weight of the recovered polyamide resin (B parts by weight) was measured, and the recovery rate was calculated using the following formula, with respect to the weight of the sample before treatment (A parts by weight) and the weight ratio of the polyamide resin in the sample before treatment (C%). Recovery rate (%) = {B / [A × (C / 100)]} × 100

[0101] (Si quantitative) The collected samples were powdered by freeze-pulverization and used as measurement samples. Measurements were performed using an X-ray fluorescence analyzer (Thermo Fisher Scientific XL3t-950S). Measurements were performed in mineral mode (FP method) using the Cu / Zn mode, with a measurement field of view of an 8 mm diameter spot. The amount of Si element (mass ppm) in the obtained samples was evaluated as the silicon content. The Si content of the airbag fabric 1 before processing in the above measurement was 250,000 ppm by mass.

[0102] (Relative viscosity) After heat treatment, the polyamide resin, which had separated from the silicone resin in the reaction vessel, was recovered. 0.25 g of the recovered polyamide resin was dissolved in 46 g of 96% sulfuric acid, and 10 ml of this solution was placed in an Oswald viscosity tube. The relative viscosity was measured at 20°C and calculated using the following formula. Since relative viscosity is proportional to the molecular weight of the resin, a higher relative viscosity indicates a larger molecular weight in the recovered polyamide resin, meaning that it maintains its polymer state. RV = T / T0 (RV: relative viscosity, T: sample solution fall time, T0: solvent fall time)

[0103] (Example 1) The polyamide resin airbag fabric 1 described above was cut into 40 mm squares. 10 g of the cut sample was placed in a reaction vessel of a 500 mL high-pressure hot water treatment device along with 300 mL of water. The cut sample was held in the water using a metal filter containing aluminum with a 2 mm mesh opening, and the mixture was heated to 220°C while generating an upward water flow by stirring. The pressure at that time was 2.3 MPa. After heat treatment for 10 minutes, the sample was cooled to room temperature using a spot cooler and collected. The evaluation results of the collected sample are shown in Table 1. In Example 1, the recovery rate of the polyamide resin was 39%, and the relative viscosity of the collected polyamide resin was 2.06. Therefore, according to the method of Example 1, the silicone resin and the polyamide resin could be easily separated, and furthermore, the polyamide resin could be obtained in polymer form. The flow rate is the flow rate near the airbag fabric held by the metal filter.

[0104] (Examples 2-6) In Examples 2-6, samples were collected in the same manner as in Example 1, except for the changes in conditions shown in Table 1. In Examples 5 and 6, instead of using stirring, thermal convection generated by changes in water temperature was utilized. The evaluation results of the collected samples are shown in Table 1. According to the methods of Examples 2-6, the silicone resin and polyamide resin could be easily separated, and furthermore, the polyamide resin could be recovered in polymer form.

[0105] (Comparative Example 1) Comparative Example 1 involved collecting samples in the same manner as in Example 1, except for the changes shown in Table 1. The evaluation results of the collected samples are shown in Table 1. In the method of Comparative Example 1, no filter was used, and the entire sample was not kept submerged in water during the heat treatment. As a result, the polymer resin dissolved by the heat treatment adhered to the silicone resin during cooling, making it impossible to recover the polymer resin separated from the silicone resin.

[0106] [Table 1]

[0107] From the above, it has been found that by using the polymer resin recovery method and high-pressure hot water treatment apparatus of this disclosure, polymer resin, which is suitable for material recycling because it is in a polymer state, can be easily recovered from polymer resin airbag fabric. [Explanation of Symbols]

[0108] 1. High-pressure hot water treatment device 2 Reaction vessels 21 Lid 22 Tightening bolts 3. Filter component 4. Airbag fabric 5 water 6 Heating mechanism 7. Agitator

Claims

1. A method for recovering polymer resin from a polymer resin airbag fabric coated with silicone resin on at least one side, A step of immersing the entire airbag fabric in water using an underwater holding member, and heat-treating it at a temperature of 160°C or higher and under a pressure equal to or greater than the saturated water vapor pressure at that temperature while maintaining the immersion in water by the underwater holding member, and A method for recovering a polymer resin, characterized by comprising the step of recovering the polymer resin separated from the silicone resin by generating a water flow having a water flow velocity of 0.001 m / s or more in the heat treatment.

2. The method for recovering polymer resin according to claim 1, wherein the water flow is an upward water flow.

3. The method for recovering a polymer resin according to claim 1, wherein a water flow is generated by using a stirring blade in the heat treatment step.

4. The recovery method according to claim 1, wherein the polymer resin flows out of the underwater holding member due to the water flow generated by the heat treatment, while the silicone resin is kept submerged in water by the underwater holding member, thereby separating the polymer resin and the silicone resin.

5. The recovery method according to claim 1, wherein the underwater holding member is a filter member.

6. The recovery method according to claim 1, wherein the underwater holding member is a shape-retaining member that maintains the shape of the end of the airbag cloth, and the entire airbag cloth is held in water by providing the shape-retaining member on at least a part of the outer circumference of the airbag cloth.

7. The recovery method according to claim 1, wherein the airbag cloth used is a cloth piece obtained by cutting or shredding a used airbag.

8. The size of the aforementioned airbag fabric is 1 mm 2 ~2500cm 2 The recovery method according to claim 1.

9. The recovery method according to claim 1, wherein the size of the airbag cloth is within the range of 1 mm to 500 mm in length and 1 mm to 500 mm in width.

10. The recovery method according to claim 1, wherein the polymer resin is a polyamide resin or a polyester resin.

11. The recovery method according to claim 10, wherein the polyamide resin is nylon 66 and the polyester resin is polyethylene terephthalate.

12. The recovery method according to claim 1, wherein in the heat treatment step, the treatment temperature is 180°C to 240°C and the treatment pressure is 1.0 MPa to 3.6 MPa.

13. The recovery method according to claim 11, wherein the polymer resin is nylon 66, and in the heat treatment step, the treatment temperature is 180°C to 240°C and the treatment pressure is 1.0 MPa to 3.6 MPa.

14. The recovery method according to claim 11, wherein the polymer resin is polyethylene terephthalate, and in the heat treatment step, the treatment temperature is 210°C to 240°C and the treatment pressure is 2.0 MPa to 3.6 MPa.

15. The recovery method according to claim 1, further comprising a cooling step after the heat treatment step and before the recovery step.

16. The recovery method according to claim 5, wherein the filter member has a plurality of through holes, and the opening area of ​​the through holes is 0.01% to 10% of the area of ​​the airbag cloth.

17. The recovery method according to claim 5, wherein the filter member has an opening size of 0.1 mm to 13 mm.

18. The recovery method according to claim 5, wherein the filter member is made of a metal including at least one of stainless steel and aluminum.

19. A recycled product comprising, as a raw material, at least a portion of a polyamide resin or polyester resin obtained by the recovery method described in claim 10.

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