JPH07330718A - Depolymerization of nylon 6 and apparatus therefor - Google Patents

Abstract

PURPOSE:To produce recovered epsilon-caprolactam through depolymerization without inducing troubles concerning residual wastes and on facilities by removing metallic components from a melted nylon 6 compound in depolymerization process of a thermoplastic material mainly containing nylon 6. CONSTITUTION:The recovered epsilon-caprolactam is obtained by subjecting a thermoplastic material containing mainly nylon 6 and other miner materials, etc., to depolymerization process. In this process, the thermoplastic material is melted by heating and metallic components are removed from the melted portion in advance. The treated melted portion is depolymerized to obtain epsilon-caprolactam. The metallic components are preferably removed by decantation. As the thermoplastic material, a material containing more than 50wt.% of nylon 6 is preferable. The thermoplastic material preferably is at least one selected from a fiber structure, a fiber waste, a resin structure and a resin waste. The metallic components are derived from subsidiary materials for clothes. Fiber waste and spent clothes of nylon 6 are melted in a melter 1, the melted materials are introduced into a metal trap 3, and the melted nylon 6 is overflowed from the metal trap 3 into a depolymerization vessel 5. The metallic components are settled and removed.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a method for depolymerizing nylon 6. More specifically, it relates to a depolymerization method for a fiber structure containing nylon 6 as a main component, a fiber scrap, a resin structure, a resin scrap, and the like.

The ε-caprolactam obtained by the present invention is a useful compound which can be used as a raw material for fibers, a raw material for resins, a raw material intermediate and the like.

[0003]

2. Description of the Related Art For depolymerization of a thermoplastic material containing nylon 6 as a main component and other materials, it is known to react a material containing nylon 66 with a base catalyst (US Pat. No. 5,266,694). issue).

[0004]

Problems to be Solved by the Invention US Pat. No. 52666
In the method described in No. 94, a thermoplastic material containing nylon 6 as a main component and containing other materials, under relatively mild conditions,
Although it is excellent in that it is easily depolymerized, since nylon 6 is depolymerized together with other materials, there is a problem that decomposed products of other materials remain after the reaction and the amount of waste that is difficult to process increases. Furthermore, when other materials are non-melting nylon 6, especially, when the molten nylon 6 is charged and the reaction residue is discharged, the piping and valve of the reaction equipment are blocked.

An object of the present invention is to depolymerize a thermoplastic material containing nylon 6 as a main component and containing other materials,
It is an object of the present invention to provide a method for industrially advantageous recovery of recovered ε-caprolactam without wastes that are difficult to process and problems with facilities.

[0006]

Means for Solving the Problems As a result of earnest studies, the inventors of the present invention conducted a nylon 6 component when a thermoplastic substance was charged into a reaction can in a depolymerization reaction of the thermoplastic substance containing nylon 6 as a main component. In the molten state, by removing metals, there is no waste and no problems with equipment, and recovery by depolymerization ε
-We have found that caprolactam can be obtained and arrived at the present invention.

That is, according to the present invention, in a reaction for depolymerizing a thermoplastic material containing nylon 6 as a main component to obtain ε-caprolactam, the thermoplastic material is heated and melted in advance, and metals are removed from the melted material. A nylon 6 depolymerization method and a nylon 6 depolymerization apparatus, characterized by depolymerizing the reaction raw material as described above.

The structure of the present invention will be described in detail below.

The nylon 6 used in the present invention may be any one as long as it is obtained by polymerizing ε-caprolactam. Usually, it is poly ε-caprolactam, an oligomer of ε-caprolactam, etc., and may be a copolymer with other monomers. As the copolymerization component, diamine components such as hexanemethylenediamine, 1,4-diaminobutane, p-phenylenediamine, sebacic acid, succinic acid,
Dicarboxylic acid components such as terephthalic acid and isophthalic acid,
Alternatively, an aminocarboxylic acid component such as laurolactam can be used. Preferred are poly ε-caprolactam and ε-caprolactam oligomers.

The amount of nylon 6 contained in the thermoplastic material containing nylon 6 as the main component in the present invention is preferably 50% by weight or more, more preferably 80% by weight or more.

The metal used in the present invention may be any metal as long as it does not melt in the molten depolymerization reaction raw material. Preferably, it has a larger specific gravity than the molten depolymerization reaction raw material. Specific examples include metal parts, metal scraps, and those containing metals. Preferably,
Examples include metal scraps and auxiliary materials for metal clothing. More preferred are wires, washers, buttons, fasteners, snaps, eyelets and the like. The metal may be contained in any form such as being mixed as a foreign substance, being physically combined with the nylon 6 fiber, being contained in the nylon 6 resin, or the like.

The metal content may be any amount. Usually, it is less than 10% by weight. It is preferably less than 5% by weight, more preferably less than 2% by weight.

The raw material / material composition other than nylon 6 of the thermoplastic material used in the present invention may be any organic material or inorganic material. The thermoplastic material may contain other fibers, polymers, additives, coating agents, oil agents, fillers and the like. For example, cellulosic fibers such as cotton, hemp and rayon, protein fibers such as wool and silk, acrylic fibers, polyurethane, polyacrylate, polyethylene terephthalate, nylon 66, resin additives, fiber oil agents, fiber processing agents. , Glass fiber, carbon fiber,
Titanium oxide, silica, etc. may be contained. Preferably, cellulose-based fiber, protein-based fiber, polyurethane, polyacrylate, polyethylene terephthalate or nylon 66 is included.

As the thermoplastic material used in the present invention, a product containing nylon 6 as a main component, raw material production / material processing,
Examples include industrial waste generated during the product assembly and manufacturing process, or used product waste. For example, fiber structures for clothing, indoors, outdoors, industrial use, or fiber scraps, and resin structures for household appliances / appliances, industrial use, or these resin scraps can be mentioned. More specifically, as the fiber structure, uniforms, innerwear, stockings, knitwear, clothing such as swimwear, interior goods such as curtains and carpets, industrial materials such as ropes, nets, belts and sheets, and Examples of the fiber waste include polymer thread waste generated during the manufacturing process, cloth cutting waste, defective product waste, used products, and the like. As resin structures, molded parts for home appliances, molded parts for toys, molded parts for automobiles,
Molded parts for household goods, housed parts such as housed parts, molded parts for industrial machines, packages, industrial products such as films,
Examples of the resin scraps include polymer molding scraps, film scraps, chips, defective scraps, used scraps, and the like generated in the manufacturing process. Further, these can be used together with poly ε-caprolactam or an oligomer of ε-caprolactam as a depolymerization raw material. In the present invention, before carrying out the depolymerization reaction, it is important to heat and melt a thermoplastic material containing nylon 6 as a main component in advance, remove metals from the melted material, and use it as a reaction raw material. By removing the metals from the reaction raw material in advance, it is possible to avoid the metals from remaining in the reaction residue after the reaction, and it is possible to avoid clogging troubles when the molten nylon 6 raw material is charged and the reaction residue is withdrawn.

The heating and melting temperature is usually 150 to 450.
℃. The temperature is preferably 200 to 400 ° C, more preferably 250 to 350 ° C. If the temperature is too low, the nylon 6 will not melt, and if the temperature is too high, unnecessary decomposition will occur.

There are various methods for removing the metals from the molten material. Although not limited to these methods, for example, a method of providing a melting tank (melter) of a thermoplastic material and allowing metals having a high specific gravity in molten nylon accumulated in the melter to spontaneously settle can be used. Preferably, a small tank (metal trap) for settling metals is connected to the lower extraction part of the melter so that the molten nylon 6 once enters and thermoplastics other than the metals overflow to be introduced into the depolymerization can. It is good to Above all, it is preferable to use a depolymerization apparatus capable of supplying a reaction raw material via a metal trap by an overflow method as shown in FIG.

The thermoplastic material from which the metals have been removed may be directly introduced as a depolymerization reaction raw material into the depolymerization reaction tank in a molten state, or in some cases, once cooled and solidified, the reaction raw material may be used. You may use as.

The depolymerization method used in the present invention may be any method. Usually, nylon 6 is depolymerized by heating, and a catalyst may be used, and it may be in the absence of water (dry type) or in the presence of water (wet type). A method of performing depolymerization in the presence of water is preferable.

The depolymerization temperature is usually 100 to 400 ° C.
And preferably 200 to 350 ° C, more preferably 220 to 300 ° C. When the temperature is low, nylon 6 does not melt and the depolymerization rate becomes slow. At high temperature, unnecessary decomposition of nylon 6 occurs, resulting in a decrease in purity of recovered ε-caprolactam.

When using a catalyst, an acid or base catalyst is usually used. As the acid catalyst, phosphoric acid, boric acid, sulfuric acid, organic acid, organic sulfonic acid, solid acid, and salts thereof, and as the base catalyst, alkali hydroxide,
Alkaline salt, alkaline earth hydroxide, alkaline earth salt,
Examples include organic bases and solid bases. Preferred examples include phosphoric acid, boric acid, organic acids, alkali hydroxides, alkali salts and the like. 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.

The amount of the catalyst used is usually 0.01 to 100% by weight based on the nylon 6 component contained in the thermoplastic material. Preferably, it is 0.1 to 50% by weight, more preferably 1 to 20% by weight. When the amount of the catalyst used is small, the reaction rate becomes slow, and when the amount is large, side reactions increase and the catalyst cost increases, which is economically disadvantageous.

When dry depolymerization is carried out, the produced ε-caprolactam is usually distilled from the reactor by vacuum distillation to obtain recovered ε-caprolactam. After the depolymerization reaction is completed, ε-caprolactam may be taken out by vacuum distillation, or may be taken out continuously as the reaction progresses.

When carrying out wet depolymerization, usually, the produced ε-caprolactam is distilled from the reactor together with water,
A recovered ε-caprolactam aqueous solution is obtained. After the depolymerization reaction is completed, the ε-caprolactam aqueous solution may be taken out by distillation, or may be taken out continuously as the reaction progresses. Preferably, water is continuously supplied to the reactor, and the produced ε-caprolactam aqueous solution is continuously taken out from the reactor. More preferably, at normal pressure,
Steam is continuously supplied to the reactor, and the produced ε-caprolactam aqueous solution is continuously taken out from the reactor.

The amount of water used in the wet depolymerization is usually 0.1 to 10 with respect to the nylon 6 component contained in the thermoplastic material.
It is 0 times the weight. Preferably 0.5 to 50 times by weight,
More preferably, it is 1 to 20 times by weight. If the amount of water used is small, the reaction rate will be slow, and if it is large, recovery ε
-The concentration of the caprolactam aqueous solution becomes low, which is disadvantageous in obtaining ε-caprolactam.

The recovered ε-caprolactam obtained in the present invention can easily be highly purified by adding a purification means. Other purification means include distillation,
Examples include crystallization, ion exchange, activated carbon treatment, oxidizing agent treatment, reducing agent treatment, hydrogenation treatment and the like. Preferably, crystallization or distillation is performed.

[0026]

The present invention will be described in more detail with reference to the following examples. The examples do not limit the invention in any way.

EXAMPLE Nylon 6 fiber waste and 130 t of used clothing are gradually melted in a melter 1 (about 300 ° C.), and a metal trap 3
And overflow the molten nylon 6,
The depolymerization can 5 was charged through the introduction pipe 4. At the same time, a catalyst and steam are introduced, a depolymerization reaction is carried out, and distillation is carried out.
-The aqueous caprolactam solution was recovered.

After the reaction was completed, the metal trap 3 was disassembled, and it was confirmed that washers, wires, snaps, fastener parts and metal buttons had settled in the trap bottom and had been removed before entering the depolymerization can. confirmed.

[0029]

According to the present invention, a thermoplastic material containing nylon 6 as a main component is depolymerized to produce a fiber raw material, a resin raw material,
Recovered ε-caprolactam that can be used as a raw material intermediate or the like can be produced by an industrially advantageous method, without waste that is difficult to treat and no problems in equipment.

[Brief description of drawings]

FIG. 1 is a diagram of a nylon 6 depolymerization apparatus according to an example of the present invention.

[Explanation of symbols]

 1 melter 2 melter molten raw material extraction part 3 metal trap 4 molten raw material introduction pipe 5 depolymerization can 6 reaction residue extraction part 7 heating jacket 8 heat insulation heater 9 steam introduction part 10 recovery ε-caprolactam extraction part

Claims (8)

[Claims] 1. In a reaction for depolymerizing a thermoplastic material containing nylon 6 as a main component to obtain ε-caprolactam, a reaction raw material obtained by previously heating and melting the thermoplastic material and removing metals from the melted material is used. Nylon 6 depolymerization method characterized by depolymerizing. 2. The method for depolymerizing nylon 6 according to claim 1, wherein the metals are precipitated and removed. 3. The method of depolymerizing nylon 6 according to claim 1, wherein the thermoplastic material containing nylon 6 as a main component contains 50% by weight or more of nylon 6. 4. The thermoplastic material containing nylon 6 as a main component is at least one selected from a fiber structure, a fiber waste, a resin structure and a resin waste. Nylon 6 depolymerization method according to any one of the methods described. 5. The nylon 6 depolymerization method according to claim 1, wherein the metal is a secondary material for clothing. 6. A thermoplastic containing nylon 6 as a main component,
The depolymerization method of nylon 6 according to any one of claims 1 to 5, wherein the depolymerization is carried out in the presence of water. 7. In a reaction for depolymerizing a thermoplastic material containing nylon 6 as a main component to obtain ε-caprolactam, the thermoplastic material is heated and melted in advance, and metals are removed from the melted material to depolymerize it. A nylon 6 depolymerization apparatus characterized by being supplied as a reaction raw material. 8. The nylon 6 depolymerization apparatus according to claim 7, wherein the metal is precipitated and removed, and the molten material is supplied as a depolymerization reaction raw material by an overflow system.