JP3911860B2 - How to recycle nylon 6 products - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a chemical recycling method for nylon 6 products containing non-melting substances such as glass fiber, and more particularly to a recycling method for efficiently recovering ε-caprolactam while separating and recovering non-melting substances. It is.
[0002]
[Prior art]
Polyamide is widely used not only for textiles for clothing and industrial purposes but also for various resin molded products. And these polyamide products were disposed of when the product life reached after a certain period of use. However, since the recent global environmental pollution problems and resource depletion problems have been screamed, simply discarding used polyamide products makes recycling effective in view of increasing these problems. The method has become an important technical issue.
[0003]
Conventionally, among polyamide products, especially poly ε-caprolactam (hereinafter abbreviated as nylon 6), a chemical recycling method for recovering ε-caprolactam by depolymerization and distillation has been adopted. However, the polyamide material to be used in the implementation of this method is limited to polyamide oligomers, polymer waste, yarn waste and the like mainly produced as a by-product in the polymerization stage and the post-processing stage for the following reasons.
[0004]
That is, many polyamide products, in particular, nylon 6 resin molded products contain non-melting substances such as glass fibers and inorganic fillers. Therefore, such polyamide products are directly depolymerized and ε- As caprolactam is recovered, non-molten substances accumulate in the reaction system, making it difficult to efficiently collect ε-caprolactam. In addition, non-molten substances deposited in the system (glass fibers, etc.) ) Could not be retrieved in a reusable form.
[0005]
On the other hand, as a method of recovering nylon 6 or ε-caprolactam from nylon 6 products containing other materials other than non-melting substances, a method of dissolving nylon 6 components with an acid solvent or a method of further depolymerizing nylon 6 It has been proposed (Japanese Patent Laid-Open No. 52-26555, US Pat. No. 5,214,066, etc.). However, even these methods do not disclose an efficient method for separating non-molten substances, and the disclosed method cannot be used for industrial scale recycling of nylon 6 products containing non-molten substances. there were.
[0006]
[Problems to be solved by the invention]
An object of the present invention is to efficiently recover ε-caprolactam by efficiently separating and removing non-melting material from nylon 6 products containing non-melting material, and is a glass fiber which is a non-melting material. Is to provide a recycling method that can be separated and collected in a reusable manner.
[0007]
[Means for Solving the Problems]
The recycling method of the present invention that achieves the above object reduces the viscosity of the depolymerization reaction solution by depolymerizing the ε-caprolactam generated in the depolymerization tank without releasing it to the outside of the reaction system. -Addition of ε-caprolactam to a depolymerization reaction solution containing caprolactam and amide oligomer as well as non-dissolved material further reduces its viscosity, allowing easy separation and recovery of non-dissolved material by filtration, sedimentation, centrifugation, etc. It is something that can be done.
[0008]
That is, this invention consists of the following.
(1) Nylon 6 products containing non-melting substances are depolymerized while refluxing without substantially distilling ε-caprolactam, and then ε-caprolactam is added to the depolymerization reaction solution to obtain non-melting substances. Recycling method of nylon 6 products that separate and recover the product.
(2) The method for recycling nylon 6 products according to (1), wherein the non-melting substance is glass fiber.
(3) The method for recycling nylon 6 products according to (1) or (2), wherein in the depolymerization step, phosphoric acid and / or phosphate is used as a catalyst and a depolymerization reaction is performed in the presence of water.
(4) The method for recycling nylon 6 products according to any one of (1) to (3), wherein a monocarboxylic acid is added to perform a depolymerization reaction in the depolymerization step.
(5) The depolymerization reaction solution is a solution containing a nylon low polymer, and after separation and recovery of the non-molten material, the polymer is further depolymerized to recover ε-caprolactam. Recycling method of nylon 6 products in any one.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
Nylon 6 products to be recycled in the present invention are resin molded products containing non-melting substances such as glass fibers and fillers. Specific examples of such nylon 6 products include glass fiber reinforced nylon 6 products such as intake manifolds, cylinder head covers, engine covers, timing bell covers, and various oil tanks collected from used automobiles. Furthermore, there are molded parts for residential building materials, electrical and electronic molded parts, textile structures for clothing (used clothes, uniforms, sportswear, innerwear, etc.), and industrial textile structures (curtains, carpets, sheets, etc.). Furthermore, product waste, pellet waste, and bulk waste generated in these production processes are also targeted. The present invention is intended to recycle nylon 6 products containing non-melted material, but in the recycling process, nylon 6 products substantially not containing non-melted material may be added together and recycled. it can.
[0010]
The polymer component constituting the nylon 6 product targeted in the present invention is preferably nylon 6 as a main component in view of the recovery efficiency of ε-caprolactam, but other types of polymers (nylon 66, nylon added to the product). 610, a copolymer or alloy component of polyolefin, polyphenylene oxide, etc.) and additives (plasticizer, heat-resistant agent, lubricant, etc.) may be included as long as they do not inhibit the recovery of ε-caprolactam.
[0011]
In addition, the non-molten substance contained in the nylon 6 products targeted by the present invention does not melt or decompose at the depolymerization temperature, and is dissolved in the depolymerization reaction liquid at the time of depolymerization and is a city substance. Typical examples include inorganic materials such as glass fibers, inorganic fillers (such as wollastonite, kaolin, mica), metal fibers, metal particles, and carbon fibers, but organic non-melting materials may also be used. These non-molten substances may be a mixture, but are preferably simple substances such as glass fibers in terms of recycling the separated / collected non-molten substance.
Further, even if parts that could not be removed at the time of disassembly are mixed, there is no problem as long as the achievement of the intended purpose of the present invention is not hindered.
[0012]
Below, the recycling method of this invention is demonstrated in detail.
In the present invention, non-molten substances are efficiently separated and collected, and not only ε-caprolactam but also non-molten substances are collected and made recyclable. If the non-molten substance is separated from the depolymerization reaction solution by filtration or sedimentation simply by depolymerization as in the conventional method, the viscosity of the depolymerized rice liquor is too high to be separated. In the present invention, since the viscosity is lowered by diluting the depolymerization reaction solution using ε-caprolactam as a solvent, non-molten substances can be easily separated and recovered.
[0013]
The depolymerization reaction solution in the present invention may be any method as long as it is a depolymerization method performed while refluxing so that ε-caprolactam is not released out of the reaction system. Usually, nylon 6 is depolymerized by heating, and a catalyst may be used. There are a method in which water is not present (dry method) and a method in which water is present (wet method).
[0014]
The depolymerization temperature is usually 100 to 400 ° C, preferably 200 to 350 ° C, more preferably 220 to 300 ° C. If the temperature is too low, the nylon 6 will not melt and the depolymerization rate will slow. If the temperature is too high, unnecessary nylon 6 decomposition occurs, leading to a reduction in the purity of the recovered ε-caprolactam.
[0015]
When a catalyst is used, an acid or base catalyst is usually used. Examples of the acid catalyst include phosphoric acid, boric acid, sulfuric acid, organic acid, organic sulfonic acid, solid acid, and salts thereof, and examples of the base catalyst include alkali hydroxide, alkali salt, alkaline earth hydroxide, alkali Examples include earth salts, organic bases, solid bases and the like. Preferably, phosphoric acid, boric acid, organic acid, alkali hydroxide, alkali salt, etc. are mentioned. More preferably, phosphoric acid, sodium phosphate, potassium phosphate, sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate, sodium hydrogen carbonate, potassium hydrogen carbonate and the like can be mentioned.
[0016]
The usage-amount of a catalyst is 0.01-100 weight% normally with respect to the nylon 6 component contained in nylon 6 products. Preferably, it is 0.1 to 50% by weight, and more preferably 1 to 20% by weight. If the amount of the catalyst used is too small, the reaction rate becomes slow, and if it is too large, side reactions increase and the catalyst cost increases, which is economically disadvantageous.
[0017]
In the depolymerization step, it is preferable to add a monocarboxylic acid from the viewpoint of reducing the viscosity of the depolymerization reaction solution. This is because when the polymerization reaction is about to proceed, an increase in the degree of polymerization can be suppressed by acting as a terminal blocking agent. For example, acetic acid, propionic acid, stearic acid, benzoic acid and the like can be mentioned, and acetic acid is particularly preferably used.
[0018]
The usage-amount of monocarboxylic acid is 0.01-100 weight% with respect to the nylon 6 component contained in nylon 6 products. Preferably, it is 0.1 to 50% by weight, and more preferably 1 to 20% by weight. If the amount of monocarboxylic acid used is too small, the effect of lowering the viscosity will be small, and if it is too large, the cost for purification after separation will increase and it will be economically disadvantageous.
[0019]
When dry depolymerization is performed, the reaction is allowed to proceed while refluxing ε-caprolactam without adding water. It is only necessary that ε-caprolactam is not substantially discharged out of the reaction system, and any degree of reflux may be used. Further, the reaction pressure may be normal pressure, increased pressure, or reduced pressure such that ε-caprolactam is not discharged.
[0020]
When performing wet depolymerization, it is necessary to return the produced ε-caprolactam to the reaction system by refluxing it so as not to be discharged together with water from the reactor. A method of refluxing only ε-caprolactam into the reaction system or a method of refluxing with water may be used. The reaction pressure may be normal pressure or increased pressure. In terms of promoting the reaction, it is also effective to carry out under pressure.
[0021]
The amount of water used for wet depolymerization is usually 0.001 to 100 times the weight of the nylon 6 component contained in the thermoplastic material. Preferably, it is 0.01-50 weight times, More preferably, it is 0.1-20 weight times. If the amount of water used is too small, the reaction rate will be slow, and if it is too large, it will be energetically disadvantageous when recovering ε-caprolactam.
[0022]
The ε-caprolactam added to the depolymerization reaction solution in the present invention may be purified or unpurified. The amount of ε-caprolactam added is preferably 5 to 5000 parts by weight, more preferably 10 to 1000 parts by weight, and particularly preferably 20 to 800 parts by weight with respect to 100 parts by weight of the depolymerization reaction solution containing an undissolved product. Some water can be added and dissolved together with ε-caprolactam.
[0023]
The temperature after the addition of ε-caprolactam to the depolymerization reaction solution to lower the viscosity and the time until separation of the non-molten material are not particularly limited as long as the polymerization reaction is promoted and separation is not difficult. . Usually, the temperature is preferably 240 ° C. or lower, more preferably 220 ° C. or lower, 30 ° C. or higher, further 50 ° C. or higher, and particularly preferably 80 ° C. or higher. Although the time until separation of the non-molten material is a balance with the temperature, the time of being placed at 180 ° C. or higher is preferably 5 hours or less, more preferably 1 hour or less. When the temperature is 150 ° C. or lower, there is no need to limit the standing time.
[0024]
For the separation / recovery method of the non-molten substance in the present invention, methods such as filtration, centrifugation, and sedimentation can be used. If necessary, it is also useful to control the viscosity while applying heat, such as hot filtration.
[0025]
The liquid after separation / recovery of the non-molten substance is a mixed liquid composed of a depolymerization reaction liquid and ε-caprolactam. Further, ε-caprolactam is recovered by depolymerization and purified by distillation to be useful ε- It is preferred to recover caprolactam.
[0026]
Examples of the distillation method for recovered ε-caprolactam include simple distillation, thin film distillation, stripping, and rectification. In addition, as a distillation operation, a basic substance and recovered ε-caprolactam can be previously charged in a distillation can in a batch type and distilled, or a basic substance and recovered ε-caprolactam can be continuously added to a distillation can. While charging, ε-caprolactam can be distilled at the same time and distilled.
[0027]
The ε-caprolactam obtained by distillation is usually sufficiently high in purity, but can be further purified by adding other purification means. Other purification means include crystallization, ion exchange treatment, activated carbon treatment, oxidizing agent treatment, reducing agent treatment, hydrogenation treatment, and the like. Preferably, crystallization is performed. Examples of the crystallization method of distilled ε-caprolactam include various methods such as crystallization with an organic solvent, crystallization with an aqueous solvent, and melt crystallization. These methods can be combined, and can be repeated for multistage crystallization.
[0028]
The non-molten material such as glass fiber separated in the present invention can be reused after further treatment such as washing.
[0029]
【Example】
Hereinafter, the present invention will be described in more detail with reference to examples. The following examples do not limit the present invention in any way.
[0030]
[Example 1]
Nylon 6 resin (manufactured by Toray Industries, Inc., CM1011G30) containing 30% glass fiber was molded into dumbbell pieces, and then pulverized to form pellets of nylon 6 product waste.
[0031]
250 g of pulverized nylon 6 product waste material, 10 g of 85% phosphoric acid aqueous solution, and 10 g of water are placed in a four-necked flask equipped with a reflux apparatus and heated in an oil bath at 260 ° C. for 2 hours. The depolymerization reaction was allowed to proceed without distilling caprolactam to obtain about 270 g of a depolymerization reaction solution. When 360 g of ε-caprolactam was added to the depolymerization reaction solution and the temperature was set to 200 ° C., the glass fiber was precipitated. The glass fiber was immediately filtered at 200 ° C. with heat using a glass filter, and the glass fiber was separated and recovered to obtain an ε-caprolactam solution as a depolymerization reaction solution.
[0032]
The obtained ε-caprolactam solution of the depolymerization reaction solution was further steam-distilled with 260 ° C. super steam at 260 ° C. while steam was distilled, and further subjected to simple distillation to recover about 500 g of ε-caprolactam. did.
[0033]
[Example 2]
250 g of pulverized nylon 6 product waste, 10 g of acetic acid, and 3 g of water are placed in a four-necked flask equipped with a reflux device, and ε-caprolactam is distilled for 4 hours while heating in an oil bath at 260 ° C. Without proceeding, the depolymerization reaction was allowed to proceed to obtain about 263 g of a depolymerization reaction solution. When 360 g of ε-caprolactam was added to the depolymerization reaction solution and the temperature was set to 200 ° C., the glass fiber was precipitated. The glass fiber was immediately filtered at 200 ° C. with heat using a glass filter, and the glass fiber was separated and recovered to obtain an ε-caprolactam solution as a depolymerization reaction solution.
[0034]
The obtained ε-caprolactam solution of the depolymerization reaction solution was further steam-distilled with 260 ° C. super steam at 260 ° C. while steam was distilled, and further subjected to simple distillation to recover about 500 g of ε-caprolactam. did.
[0035]
[Comparative Example 1]
While putting 250 g of pulverized nylon 6 product waste material, 10 g of 85% phosphoric acid aqueous solution, and 10 g of water into a four-necked flask and heating in an oil bath at 260 ° C. while distilling ε-caprolactam, The depolymerization reaction was allowed to proceed for 10 hours to obtain about 90 g of a tar-like depolymerization reaction solution.
[0036]
To this tar-like depolymerization reaction product, 360 g of ε-caprolactam was added and brought to 200 ° C. However, the tar-like thing was not dissolved and a clean glass fiber could not be obtained.
[0037]
[Comparative Example 2]
An attempt was made to filter about 263 g of the depolymerization reaction solution obtained in the same manner as in Example 1 at 200 ° C. without adding ε-caprolactam, but the viscosity was too high to filter the glass fiber. Could not be separated.
[0038]
【The invention's effect】
According to the present invention, ε-caprolactam can be efficiently recovered by efficiently separating and removing non-melting substances from nylon 6 products containing non-melting substances, and glass fibers that are non-melting substances. Can be separated and recovered for reuse.

Claims (5)

Nylon 6 products containing non-melting substances are depolymerized while refluxing without substantially distilling ε-caprolactam, and then ε-caprolactam is added to the depolymerization reaction solution to separate the non-melting substances. Recycling method of nylon 6 products to be collected. The method for recycling nylon 6 products according to claim 1, wherein the non-molten material is glass fiber. The method for recycling nylon 6 products according to claim 1 or 2, wherein in the depolymerization step, a depolymerization reaction is performed in the presence of water using phosphoric acid and / or phosphate as a catalyst. The method for recycling nylon 6 products according to any one of claims 1 to 3, wherein in the depolymerization step, a monocarboxylic acid is added to perform a depolymerization reaction. The nylon according to any one of claims 1 to 4, wherein the depolymerization reaction solution is a solution containing a low-polymerized nylon, and after separation and recovery of the non-molten material, further depolymerization is performed to recover ε-caprolactam. Recycling method of 6 products.