JPH11240979A - Recycling of nylon 6 resin formed body - Google Patents

Abstract

PROBLEM TO BE SOLVED: To recycle nylon 6 resin formed bodies by depolymerizing nylon 6 resin formed bodies comprising specific automobile resin parts and obtaining recovered ε-caprolactam of high purity efficiently on an industrial scale. SOLUTION: Nylon 6 formed bodies comprising automobile resin parts that are composed of nylon 6 in an amount of >=90 wt.%, preferably >=95 wt.% of the total organic compounds in the formed bodies are depolymerized to obtain ε-caprolactam with the result that the nylon 6 resin formed bodies are recycled. Underhood parts are extremely suited to such an automobile resin part, and concretely, it is a cylinder head cover, an engine mount, an engine cover, a cover-cover, an oil pan, an air cleaner or the like. The resin formed bodies are preferably crushed into pieces, whose average weight per piece after crushing is <=20 g, preferably <=10 g, in prior to the charge into a depolymerization apparatus. The polymerizing temperature is preferably 100-400 deg.C.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a method for depolymerizing a nylon 6 resin molded product to obtain ε-caprolactam. More specifically, 90% of all organic compounds in the molded article
The present invention relates to a method for obtaining ε-caprolactam by depolymerizing an automotive resin part in which nylon 6 accounts for at least% by weight. Ε-caprolactam obtained by the present invention is
It can be usefully used as a resin raw material for fibers or molded articles, a raw material intermediate, and the like.

[0002]

2. Description of the Related Art There have been many studies on a method of recovering ε-caprolactam by depolymerizing a nylon 6 polymer, and some proposals regarding a depolymerization process have been made recently (for example, Japanese Patent Application Laid-Open No. 5-
194377, JP-A-6-32775, etc.). It has also been proposed to use textiles such as clothes and sewn products as nylon 6 as a raw material for depolymerization (for example, JP-A-7-331510, JP-A-7-3).
No. 28247).

[0003]

When the above-mentioned textile products such as clothes and sewn products are used as a raw material for depolymerization, materials made of organic compounds other than nylon 6, for example, cellulose such as cotton, hemp, rayon, etc. Fiber, protein fiber such as wool, silk, etc., acrylic fiber, polyurethane, polyacrylate, polyethylene terephthalate, etc., in many cases. , It is likely to cause a process trouble due to a decrease in the purity of ε-caprolactam generated or generation of decomposition products.

[0004] It is an object of the present invention to provide a method for depolymerizing a nylon 6 resin molded article to obtain ε-caprolactam, selecting a specific resin molded article and using it as a raw material for depolymerization to efficiently recover highly purified ε-caprolactam. A good and industrially advantageous means is to be provided.

[0005]

Means for Solving the Problems In a method for producing ε-caprolactam by depolymerization of a nylon 6 polymer, the present inventors have found that the content of an organic compound other than nylon 6 is low as a raw material for depolymerization, By using an automobile part made of a resin molded body having a higher apparent specific gravity and easier handling, high-purity ε-caprolactam can be obtained efficiently, and a nylon 6 resin molded body as a depolymerization raw material is heated and melted in advance. Then, after removing metals from the melted product, by supplying to a nylon 6 depolymerization apparatus as a depolymerization reaction raw material, high-purity ε-caprolactam can be recovered by depolymerization without waste and facility problems. And arrived at the present invention.

That is, the present invention relates to (1) Nylon 6
A method for depolymerizing a resin molded product to obtain ε-caprolactam, comprising using an automobile part in which nylon 6 accounts for 90% by weight or more of all organic compounds in the molded product as the nylon 6 resin molded product. (6) A nylon 6 resin molded article according to (1), wherein the nylon 6 resin molded article is an automobile part in which nylon 6 accounts for 95% by weight or more of all organic compounds in the molded article. (3) “Recycling method of nylon 6 resin molded article as described in (1) or (2) above, wherein the automobile parts are underhood parts”

(4) "A molded article of nylon 6 resin, which is a raw material for depolymerization, crushes automobile parts so that the average weight per crushed piece is 2
The above 1 to 3 which have been pulverized so as to be 0 g or less.
(5) “A nylon 6 resin molded article serving as a depolymerization raw material crushes a resin part for an automobile and has an average weight per piece of 1”.
The method for recycling a nylon 6 resin molded product according to the above item 4, which is pulverized so as to be 0 g or less ”, (6)
"The method for recycling a nylon 6 resin molded article according to any one of the above 1 to 5, wherein the nylon 6 resin molded article is a molded article substantially containing no inorganic substance"; The method for recycling a nylon 6 resin molded article according to any one of the above 1 to 5, which is a molded article containing an inorganic substance such as a filler, and (8) the above item 7, wherein the inorganic substance contained in the nylon 6 resin molded article is glass fiber. Nylon 6 described
How to Recycle Resin Molded Body ",

(9) The method for recycling a nylon 6 resin molded article according to any one of the above items 1 to 8, wherein the depolymerization of the nylon 6 resin molded article is carried out in the presence of water.
0) "The depolymerization of the nylon 6 resin molded product is phosphoric acid and / or
Or a method for recycling a nylon 6 resin molded article according to the above item 9, wherein the method is carried out using a phosphate catalyst in the presence of water ", (11) depolymerizing the nylon 6 resin molded article,
In the method for obtaining ε-caprolactam, a nylon 6 resin molded product as a depolymerization raw material is heated and melted in advance, metals are removed from the molten material, and then supplied to a nylon 6 depolymerization apparatus as a depolymerization reaction raw material. Above 1 to 1
0).

[0009]

Embodiments of the present invention will be described below in detail.

The nylon 6 automotive resin part used in the present invention is an automobile part in which nylon 6 accounts for 90% by weight or more of the total organic compound in the molded article, and an automobile part in which nylon 6 accounts for 95% by weight or more. Is more preferable. Automobile resin parts are often used in a composite form with other various parts in the usage form. Especially in the case of interior parts, resin parts other than nylon 6 are combined with fiber materials and rubbers. In order to use it as a raw material for depolymerization, a step such as separation is required, which causes a reduction in the production efficiency of ε-caprolactam. Therefore, among automobile parts, those having a low content of other materials, especially organic materials, and having a relatively large size of a single component are suitable, and underhood components are extremely suitable from such a viewpoint. Specific examples of such automotive resin parts include a cylinder head cover, an engine mount, an engine cover, a timing belt cover,
Examples include a cover cover, an air intake manifold, an air intake pipe, a cooling fan, an oil pan, an oil reservoir tank, an antifreeze tank, a fuel rail, and an air cleaner.

[0011] Nylon 6 resin used for these parts is substantially free from inorganic substances except for a very small amount (for example, 1% by weight or less) of a nucleating agent and a coloring agent.
Alternatively, any of those containing 5 to 50% by weight of an inorganic filler such as glass fiber, talc, wollastenite, and kaolin may be used.

[0012] Nylon 6 used for these parts is 10
Examples of other organic compounds which can be contained in an amount of not more than% by weight include copolymerization components introduced in small amounts to modify nylon 6, such as hexanemethylenediamine, 1,4-diaminobutane, p-phenylenediamine and the like. Dicarboxylic acid components such as adipic acid, sebacic acid, succinic acid, terephthalic acid, and isophthalic acid, and aminocarboxylic acid components such as laurolactam.

In the present invention, it is preferable that the resin molded body used as a raw material for depolymerization is pulverized into small pieces that can be easily handled before being supplied to a depolymerization apparatus. The pulverizer used for carrying out such pulverization is not particularly limited, and generally known roll crushers, hammer crushers, swing hammer type hammer mills, rotary cutter mills, jet cutter mills, and the like. Can be appropriately selected in consideration of the shape of the molded body for pulverizing the pulverizer and the shape of the depolymerization apparatus. The degree of pulverization is not particularly limited, but the average weight per piece after the pulverization is preferably 20 g or less, and more preferably 10 g.
The following is preferred.

In the present invention, before the depolymerization reaction is performed, the depolymerization raw material may be heated and melted in advance to remove metals from the molten material, and then used as the depolymerization reaction raw material. If metals are removed from the reaction raw materials in advance, after the reaction,
In addition to avoiding metals remaining in the reaction residue,
This is a preferred embodiment because it can avoid clogging troubles when charging the raw material of molten nylon 6 and extracting the reaction residue. Such separation of metals can be performed by a known method, for example, Japanese Patent Application Laid-Open No. 7-3307.
It can be carried out by using the method disclosed in Japanese Patent Publication No.

The thermoplastic material from which the metals have been removed may be introduced as it is into a depolymerization reaction tank in a molten state as a raw material for the depolymerization reaction, or, if necessary, once cooled and solidified, and then reacted with the raw material for the reaction. You may use as.

The depolymerization method used in the present invention may be any method. Normally, nylon 6 is depolymerized by heating and a catalyst may be used, and it may be in the absence of water (dry) or in the presence of water (wet). Preferably, the method is one in which depolymerization is performed in the presence of water.

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

When a catalyst is used, an acid or base catalyst is usually used. Acid catalysts include phosphoric acid, boric acid, sulfuric acid, organic acids, organic sulfonic acids, solid acids, and salts thereof, and base catalysts include alkali hydroxides,
Alkaline salts, alkaline earth hydroxides, alkaline earth salts,
Organic bases and solid bases are exemplified. Preferably, phosphoric acid, boric acid, organic acids and salts thereof, alkali hydroxides, alkali salts and the like are mentioned. More preferably, phosphoric acid, sodium phosphate, potassium phosphate, sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate, sodium bicarbonate, potassium bicarbonate and the like can be mentioned.

The amount of the catalyst used is usually 0.01 to 100% by weight based on 6 components of nylon contained in the resin molded product.
It is. Preferably, it is 0.1 to 50% by weight, more preferably 1 to 20% by weight. If the amount of catalyst used is small, the reaction rate will be low, and if it is large, side reactions will increase and the cost of the catalyst will increase, which is economically disadvantageous.

When dry depolymerization is carried out, usually, the formed ε-caprolactam is distilled from the reactor by distillation under reduced pressure to obtain recovered ε-caprolactam. After the depolymerization reaction is completed, ε-caprolactam may be taken out by distillation under reduced pressure, or may be taken out continuously as the reaction proceeds.

When performing wet depolymerization, usually, the formed 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 aqueous solution of ε-caprolactam may be taken out by distillation, or may be taken out continuously as the reaction proceeds. Preferably, water is continuously supplied to the reactor, and the formed aqueous solution of ε-caprolactam is continuously removed from the reactor. More preferably, at normal pressure,
Steam is continuously supplied to the reactor, and the formed aqueous solution of ε-caprolactam is continuously removed from the reactor.

The amount of water used in the wet depolymerization is usually 0.1 to 100 with respect to 6 components of nylon contained in the thermoplastic.
Weight times. Preferably, it is 0.5 to 50 times by weight, more preferably 1 to 20 times by weight. The amount of water used is
If the amount is small, the reaction rate becomes slow, and if the amount is large, the concentration of the recovered ε-caprolactam aqueous solution becomes low, which is disadvantageous in obtaining ε-caprolactam.

The recovered ε-caprolactam obtained in the present invention can be easily 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, and hydrogenation treatment. Preferably, crystallization or distillation is performed.

[0024]

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 A strip-shaped nylon 6 obtained by collecting an unreinforced nylon 6 engine cover from an automobile and grinding it to an average weight of 5 g per strip using a rotary cutter mill. 100 g of the resin molded product and 10.7 g of phosphoric acid of 75% by weight (8.0 g of phosphoric acid) were charged into a 1-L depolymerization can. Heated to 260 ° C. under a nitrogen atmosphere. Superheated steam was introduced at a rate of 280 ml / hour into the depolymerization vessel to start the reaction. Ε- distilled from depolymerization can
The depolymerization reaction was continued for 3 hours while cooling caprolactam / water vapor and recovering the ε-caprolactam aqueous solution. The total weight of the obtained recovered ε-caprolactam aqueous solution is 885.
g, ε-caprolactam concentration 10.4% by weight, recovered ε
92.0 g of caprolactam and a depolymerization yield of 92.0 g
%Met.

The recovered ε-caprolactam aqueous solution is decompressed to 30
at a heating temperature of 55 ° C. and a concentration of 95% by weight.
96.8 g (92.0 g of ε-caprolactam) was obtained. Gas chromatography (GC) impurities in the concentrated ε-caprolactam were 0.97%.

Concentrated ε-caprolactam 40.0 g (ε-caprolactam)
Caprolactam (38.0 g) was distilled at a reduced pressure of 5 mmHg and a heating temperature of 150 to 170 ° C. to obtain 36.1 g of distilled ε-caprolactam. The concentration and distillation yield was 95%.
The distillate ε-caprolactam had a GC impurity of 0.50%, and was of a quality that could be used as a raw material for polymerizing nylon 6 for fibers.

[Example 2] A brake oil tank made of glass fiber reinforced nylon 6 was recovered from an automobile and subjected to depolymerization, steam distillation, concentration and distillation in the same manner as in Example 1.
Finally, ε-caprolactam having a GC impurity of 0.60% was concentrated and obtained with a distillation yield of 94%. This was also of a quality usable as a nylon 6 polymerization raw material for fibers.

Continued on the front page (72) Inventor Kazuhiko Kobayashi 1 Nagoya Office, Nagoya City, Aichi Prefecture

Claims (11)

[Claims] 1. A nylon 6 resin molded product is depolymerized, and ε-
A method for obtaining caprolactam, wherein a nylon 6 resin molded article is an automobile resin part in which nylon 6 accounts for 90% by weight or more of all organic compounds in the molded article. A method for recycling a nylon 6 resin molded article. 2. The method for recycling a nylon 6 resin molded article according to claim 1, wherein the nylon 6 resin molded article is an automotive resin part in which nylon 6 accounts for 95% by weight or more of the total organic compounds in the molded article. 3. The method for recycling a nylon 6 resin molded article according to claim 1, wherein the resin part for an automobile is an underhood part. 4. A molded article of nylon 6 resin, which is a raw material for depolymerization, crushes resin parts for automobiles and has an average weight of 2 per piece.
It is crushed so as to be 0 g or less.
3. The method for recycling a nylon 6 resin molded article according to any one of the above items 3. 5. A nylon 6 resin molded product, which is a raw material for depolymerization, is used to crush automotive resin parts with an average weight of 1 per piece.
The method for recycling a nylon 6 resin molded product according to claim 4, wherein the molded product is pulverized so as to be 0 g or less. 6. The method for recycling a nylon 6 resin molded article according to claim 1, wherein the nylon 6 resin molded article is a molded article substantially containing no inorganic substance. 7. The method for recycling a nylon 6 resin molded article according to claim 1, wherein the nylon 6 resin molded article is a molded article containing an inorganic substance such as a reinforcing material or a filler. 8. The method for recycling a nylon 6 resin molded product according to claim 7, wherein the inorganic substance contained in the nylon 6 resin molded product is glass fiber. 9. The method for recycling a nylon 6 resin molded article according to claim 1, wherein the depolymerization of the nylon 6 resin molded article is performed in the presence of water. 10. The recycling method for a nylon 6 resin molded article according to claim 9, wherein the depolymerization of the nylon 6 resin molded article is carried out using a phosphoric acid and / or a phosphate catalyst in the presence of water. 11. A nylon 6 resin molded product is depolymerized, and ε
In the method for obtaining caprolactam, a nylon 6 resin molded article as a depolymerization raw material is heated and melted in advance, metals are removed from the melted material, and then supplied to a nylon 6 depolymerization apparatus as a depolymerization reaction raw material. Claims 1 to 1
0. A method for recycling a nylon 6 resin molded article according to any one of the above items.