Nylon separation method and nylon separation agent

Abstract

To provide a nylon separation method and a nylon separation agent that enable easy nylon separation from the silicone-covered nylon without micronization of the silicon.SOLUTION: A nylon separation method includes an exposure step for exposing the silicone-covered nylon to a solution in which a hydroxide of an alkali metal or a hydroxide of an alkaline earth metal is dissolved in a mixed solvent containing water and methanol.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a nylon separation method and a nylon separating agent. [Background technology]

[0002] Nylon, a type of polyamide, is widely used in fibers and plastics due to its toughness and excellent heat and chemical resistance.

[0003] Nylon is highly durable, does not decompose in nature, and no recycling method has been established. One of the reasons why no recycling method has been established is that in many products that use nylon, nylon is used as a composite material to prevent product deterioration. For example, airbags installed in automobiles to protect passengers are made of a base fabric in which nylon fiber cloth is covered with a silicone membrane. In order to recycle nylon, a stage is required to separate the individual materials that make up the composite material, such as nylon.

[0004] Patent Document 1 discloses a method of removing silicone from the surface of the base fabric as agglomerates by immersing airbag scrap fabric in an alkaline solution, dehydrating it, and stirring it in a container. Patent Document 2 discloses a method of immersing an airbag base fabric in an alkaline-isopropyl alcohol solution and stirring it for about 30 minutes while heating as necessary to peel off silicone from the surface of the airbag base fabric. Patent Document 3 discloses a technology of peeling off silicone by placing airbag scraps in an alkaline aqueous solution containing a surfactant and stirring it while heating it to about 50°C. Patent Document 4 discloses a method of heating airbag scraps in ethylene glycol to a temperature of 180°C or higher to dissolve nylon and separate silicone. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2001-180413 A [Patent Document 2] JP 2009-269475 A [Patent Document 3] JP 2009-299242 A [Patent Document 4] JP 2018-172618 A Summary of the Invention [Problem to be solved by the invention]

[0006] When the method disclosed in Patent Document 1 was tried on an airbag base fabric, no peeling of silicone was observed. In the method disclosed in Patent Document 2, although the peeling of silicone was observed, the peeled silicone became fine and adhered to the nylon surface, making it difficult to separate. If the silicone becomes fine, an additional separation process is required, and the purity of the nylon is reduced due to the remaining silicone, which is inconvenient. The methods disclosed in Patent Documents 3 and 4 require a heating device, making the operation complicated.

[0007] The present invention has been made in consideration of the above-mentioned circumstances, and has an object to provide a nylon separation method and a nylon separating agent that can easily separate nylon from nylon the surface of which is coated with silicone, without micronizing the silicone. [Means for solving the problem]

[0008] (Nylon separation method) The nylon separation process described herein comprises: The method includes an exposure step of exposing nylon having a silicone-coated surface to a solution in which an alkali metal hydroxide or an alkaline earth metal hydroxide is dissolved in a mixed solvent containing water and methanol.

[0009] The molar concentration of the hydroxide in the solution is It may be 0.5 to 1.5M.

[0010] The volume ratio of water to methanol in the mixed solvent is It may be 1:5 to 1:15.

[0011] The time for exposing the nylon to the solution is: It may be less than 48 hours.

[0012] The hydroxide is It may be sodium hydroxide.

[0013] In the exposure step, Immersing the nylon in the solution; The solution may be mixed by inversion or stirred.

[0014] (Nylon separating agent) The nylon separating agent described herein is The solution contains an alkali metal hydroxide or an alkaline earth metal hydroxide dissolved in a mixed solvent containing water and methanol. Effect of the Invention

[0015] According to the present invention, nylon can be easily separated from nylon having a surface coated with silicone without micronizing the silicone. [Brief description of the drawings]

[0016] [Figure 1] FIG. 1 shows nylon obtained in an example and a peeled silicone film. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] The embodiments of the present invention will be described with reference to the drawings. Note that the present invention is not limited to the following embodiments and drawings. Note that in the following embodiments, the expressions "have", "include" and "contain" also include the meaning of "consisting of" or "consisting of".

[0018] The nylon separation method according to the present embodiment includes an exposure step of exposing nylon, the surface of which is coated with silicone, to a solution in which an alkali metal hydroxide or an alkaline earth metal hydroxide is dissolved in a mixed solvent containing water and methanol.

[0019] The volume ratio of water to methanol in the mixed solvent is not particularly limited, but is, for example, 1:5 to 1:15, 1:7 to 1:12, or 1:8 to 1:12, and preferably 1:9.

[0020] Examples of the hydroxide of an alkali metal or an alkaline earth metal include LiOH, NaOH, KOH, RbOH, CsOH, Ca(OH)2, Sr(OH)2, Ba(OH)2, Ra(OH)2, etc. The hydroxide is preferably NaOH.

[0021] The molar concentration of the hydroxide in the solution is not particularly limited, but is, for example, 0.5 to 1.5M, 0.8 to 1.2M, or 0.9 to 1.1M, and preferably 1.0M.

[0022] Silicone is a compound having a main skeleton composed of siloxane bonds. Silicone can be obtained as an oligomer by hydrolyzing various silanes such as dichlorodimethylsilane and dehydrating and condensing the resulting silanols.

[0023] The nylon is not particularly limited, and examples thereof include nylon 4, nylon 6, nylon 11, nylon 12, nylon 6,6, nylon 6,10, nylon 6,12, nylon 4,6, nylon 6T, nylon 6I, nylon M5T nylon 6i, nylon 6i-11, etc. Specifically, an airbag base fabric can be mentioned as a nylon having a surface coated with silicone.

[0024] In the exposure step, if the nylon is exposed to the solution for too long, the silicone may become fine. Therefore, the exposure time is appropriately adjusted according to the type of hydroxide and the molar concentration of the hydroxide in the solution used. The time for exposing the nylon to the solution is preferably less than 48 hours, for example, 1 to 36 hours, 2 to 32 hours, 3 to 18 hours, 4 to 12 hours, or 4 to 8 hours.

[0025] In the exposure step, the nylon coated with silicone may be exposed to the solution so that the solution diffuses between the silicone and the nylon. If the solution is in contact with the silicone surface and the nylon surface, the solution will penetrate between the silicone and the nylon. Therefore, the mode of exposure in the exposure step is not particularly limited as long as at least the surface of the nylon coated with silicone is kept in contact with the solution. For example, in the exposure step, the surface of the nylon coated with silicone is exposed to the solution. In the exposure step, the solution may be sprayed, dropped, or applied to the nylon. Preferably, in the exposure step, the nylon is immersed in the solution and the solution is mixed or stirred by inversion. In the case of mixing or stirring by inversion, the rotation speed is not particularly limited, but is, for example, 10 to 80 rpm, 20 to 60 rpm, or 30 to 50 rpm.

[0026] According to the nylon separation method of the present embodiment, the silicone can be easily peeled off as a film from nylon whose surface is coated with silicone without heating. The nylon separation method can separate silicone from nylon whose surface is coated with silicone even at 15 to 30°C or room temperature, for example. Therefore, silicone can be easily separated from nylon without being broken down into fine particles by heat.

[0027] The nylon separation method according to the present embodiment can separate silicone from nylon whose surface is coated with silicone, and therefore can also be used as a silicone separation method.

[0028] In another embodiment, a nylon separating agent is provided. The nylon separating agent contains a solution in which an alkali metal hydroxide or an alkaline earth metal hydroxide is dissolved in a mixed solvent containing water and methanol. By exposing nylon, the surface of which is coated with silicone, to the nylon separating agent, nylon and silicone can be separated.

[0029] The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples. EXAMPLES

[0030] Passenger vehicle airbag base fabric (provided by Nakadai Co., Ltd.) was cut into a 1 cm x 1 cm rectangular piece (approximately 1 g). The rectangular piece was immersed in a solution of 0.5 mL 10 M sodium hydroxide aqueous solution and 4.5 mL methanol, and mixed by inversion at 40 rpm for approximately 4 hours. As a result, the silicone floated up, and the silicone film that had been covering the nylon could be peeled off, as shown in Figure 1.

[0031] When the mixing time exceeded 48 hours, the silicone film peeled off, but it was fragmented and difficult to separate from the nylon.

[0032] When separation was attempted in the same manner using a solution of ethanol, 1-propanol or 2-propanol mixed with an aqueous sodium hydroxide solution instead of methanol, the silicone film peeled off in about 12 hours, but the silicone film was fragmented and difficult to separate from the nylon. Furthermore, when separation was attempted in the same manner using only methanol, only ethanol, only 1-propanol, or only 2-propanol instead of the above solution, the silicone film did not peel off.

[0033] The present invention allows various embodiments and modifications without departing from the broad spirit and scope of the present invention. The above-described embodiments are for the purpose of explaining the present invention and do not limit the scope of the present invention. That is, the scope of the present invention is indicated by the claims, not the embodiments. Various modifications made within the scope of the claims and the scope of the invention equivalent thereto are considered to be within the scope of the present invention. [Industrial Applicability]

[0034] The present invention is suitable for recycling nylon whose surface has been coated with silicone.

Claims

1. The method includes exposing nylon having a silicone-coated surface to a solution in which an alkali metal hydroxide or an alkaline earth metal hydroxide is dissolved in a mixed solvent containing water and methanol. Nylon separation method.

2. The molar concentration of the hydroxide in the solution is 0.5 to 1.5M. The method for separating nylon according to claim 1.

3. The volume ratio of water to methanol in the mixed solvent is The ratio is 1:5 to 1:

15. The method for separating nylon according to claim 1 or 2.

4. The time for exposing the nylon to the solution is: Less than 48 hours The method for separating nylon according to claim 1 or 2.

5. The hydroxide is Sodium hydroxide, The method for separating nylon according to claim 1 or 2.

6. In the exposure step, Immersing the nylon in the solution; The solution is mixed by inversion or stirring; The method for separating nylon according to claim 1 or 2.

7. A solution containing an alkali metal hydroxide or an alkaline earth metal hydroxide dissolved in a mixed solvent containing water and methanol. Nylon separating agent.

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