JP2003292616A - Method for producing polyamide resin - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing a polyamide resin which can produce a useful molecular weight of the polyamide resin from a polyester resin or its waste easily by a simple process and gives little load on environment. <P>SOLUTION: The method for producing a polyamide resin comprises putting the polyester resin together with a diamine compound in a reaction vessel 1, bringing the polyester resin into contact with supercritical water or subcritical water in the vessel to hydrolyze, and subjecting the formed dicarboxylic acid component and the diamine compound to polycondensation in supercritical water or subcritical water to get the polyamide resin. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for producing a polyamide resin from a polyester resin, which is useful as a recycling technique for waste polyester resin.

[0002]

2. Description of the Related Art Techniques for recycling plastic waste have been actively studied in order to effectively use resources and reduce the environmental load associated with waste treatment.
A typical example thereof is a reduction technique of a polyester resin to a raw material monomer, and various techniques such as a methanol decomposition method, an ethylene glycol decomposition method, and a transesterification method have been developed.

However, the price of the monomer regenerated by such a method is often higher than that of the virgin material, and the profitability is poor even if it is commercialized. And
This is a major factor preventing the spread of recycling.

Among these, one of the polyester resins
It is a kind, and is consumed in large quantities in fibers, bottles, films, sheets, etc., and therefore a method of directly synthesizing a polyamide resin from polyethylene terephthalate, which is highly demanded for recycling, was devised, and it has been noted as a solution to the above problems .

This method basically utilizes an ester-amide substitution reaction, in which the ester group of polyethylene terephthalate is replaced with an amide group by reacting polyethylene terephthalate with a diamine compound in a specific solvent as a reaction medium. And then polyamidized.

However, all of the methods of this type that have been reported so far have a problem that the load on the environment is large because an organic solvent is used as a reaction solvent. Further, when trying to obtain a high-molecular weight polyamide resin, there is a problem that a step of polycondensation is further required after the reaction of the polyethylene terephthalate and the diamine compound.

[0007]

As described above, the method of directly synthesizing a polyamide resin from polyethylene terephthalate is highly expected to promote the recycling of plastics that are consumed in large quantities, but the load on the environment is great. There is a problem that the process becomes complicated when trying to obtain a high molecular weight polyamide resin.

The present invention has been made in consideration of such a point, and a useful high-molecular weight polyamide resin can be easily produced from a polyester resin or a waste thereof by a simple process, and moreover, it is environmentally friendly. It is an object of the present invention to provide a method for producing a polyamide resin that has a low load.

[0009]

In order to achieve the above object, in the method for producing a polyamide resin of the present invention, a polyester resin and a diamine compound are reacted in supercritical water or subcritical water to produce a polyamide resin. It is characterized by

The reaction temperature may be 350 ° C. to 450 ° C., and the reaction pressure may be 10 MPa to 50 MPa.

After the polyamide resin is produced, the reaction vessel may be filled with supercritical carbon dioxide, and then the temperature may be lowered and the pressure may be reduced to recover the polyamide resin.

Further, the polyester resin may be a product recovered from waste, and the polyester resin may be polyalkylene terephthalate.

In the present invention, a sufficiently high molecular weight polyamide resin can be produced from a polyester resin in substantially one step, and since supercritical water or subcritical water is used as a reaction solvent, an organic solvent is used. The load on the environment is also reduced as compared with the conventional method using the.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below. The polyester resin used as a raw material in the present invention is obtained by a dehydration condensation reaction of a dicarboxylic acid or its derivative compound and a polyhydric alcohol.
Examples of the dicarboxylic acid or its derivative compound include terephthalic acid, isophthalic acid, phthalic acid, dimethyl terephthalate, terephthalic acid dichloride, diphenyldicarboxylic acid, naphthalenedicarboxylic acid, and other aromatic dicarboxylic acids and their derivatives, oxalic acid, succinic acid, and adipine. Examples thereof include aliphatic dicarboxylic acids such as acids, sebacic acid, maleic acid and fumaric acid, and their derivatives. Examples of the polyhydric alcohol include alkylene glycols such as ethylene glycol, propylene glycol, butane-1,3-diol, butane-1,4-diol and tetramethylene glycol, and aromatic compounds such as cyclohexanediol, bisphenol A and bisphenol F. Dihydric alcohol etc. are mentioned. These polyester resins may be recovered from waste. In the present invention, it is particularly preferable to use polybutylene terephthalate recovered from waste.

The diamine compound to be reacted with the hydrolyzate of the polyester resin is ethylenediamine, trimethylenediamine, 1,2-propanediamine, tetramethylenediamine, pentamethylenediamine, hexamethylenediamine, octamethylenediamine, dodeca. Aliphatic diamine compounds such as methylenediamine and 2,2,4-trimethylhexamethylenediamine; p-phenylenediamine, o-phenylenediamine, m-phenylenediamine, m-
Toluylenediamine, p-xylylenediamine, m-xylylenediamine, 4,4'-diaminobiphenyl, 3,3'-dimethyl-4,4'-diaminobiphenyl, 3,3'-dichloro-
4,4'-diaminobiphenyl, 4,4'-diaminodiphenyl ether, 3,4'-diaminodiphenyl ether, 4,
4'-diaminodiphenylpropane, 4,4'-diaminodiphenyl sulfone, 4,4'-diaminodiphenyl esulfide, 4,4'-diaminobenzanilide, 3,3'-dimethyl
-4,4'-diaminodiphenylmethane, 3,3'-diethyl-4,
4'-diaminodiphenylmethane, 4,4'-diaminoanthraquinone, 3,3'-dimethoxybenzidine, α, α'-bis
Aromatic diamine compounds such as (4-aminophenyl) -p-isopropylbenzene, 1,5-diaminonaphthalene, 2,6-diaminonaphthalene; 1,3-diaminocyclohexane, 1,4-diaminocyclohexane, 1,3- Bis (aminomethyl) cyclohexane, isophoronediamine, piperazine, 2,5-dimethylpiperazine, bis (4-aminocyclohexyl) methane, bis (4-aminocyclohexyl) propane, 4,4'-diamino-3,3'-dimethyl Dicyclohexylmethane, α,
α'-bis (4-aminocyclohexyl) -p-diisopropylbenzene, α, α'-bis (4-aminocyclohexyl) -m-
Examples thereof include alicyclic diamine compounds such as diisopropylbenzene and menthanediamine; polymers such as polydimethylsiloxane having amino groups at both ends. These are 1
The seeds may be used alone or in combination of two or more. In the present invention, it is preferable to use tetramethylenediamine, hexamethylenediamine, and p-phenylenediamine.

The amount of the diamine compound used is preferably in the range of 1 mol to 10 mol per 1 mol of the repeating unit of the polyester resin. If the amount of the diamine compound used is less than 1 mol, there is also a portion such as the amount of the diamine compound discharged from the reaction vessel for the purpose of decomposing the diamine compound or maintaining the pressure in the apparatus system, so that the reaction with the polyester resin does not proceed sufficiently, When the amount exceeds 10 mol, the amount of the decomposed product of the diamine compound increases, and the decomposed product reacts with the polyester resin or its hydrolyzed component to increase the low molecular weight polyamide component. A more preferable range is 2 to 5 mol per 1 mol of the repeating unit of the polyester resin.

Further, the supercritical water used as a reaction solvent for hydrolyzing the polyester resin as described above and for proceeding the polycondensation reaction of the dicarboxylic acid component and the diamine compound produced by the hydrolysis is a critical temperature ( Non-condensable dense water above 374.2 ° C) and critical pressure (22.1MPa), and subcritical water has a critical temperature (37
4.2 ℃) and water at a temperature and pressure close to the critical pressure (22.1MPa), which is near supercritical.

In the present invention, the above polyester resin and diamine compound are reacted in supercritical water or subcritical water to produce a polyamide resin. The mechanism of polyamide resin formation has not been clarified yet, but the ester group is replaced with an amide group by the direct reaction of the diamine compound with the ester bond in the polyester resin molecular chain in supercritical water or subcritical water. A so-called ester-amide substitution reaction, and the polyester resin is contacted with supercritical water or subcritical water, and is hydrolyzed by reaction, and the dicarboxylic acid component and the diamine compound produced by this hydrolysis are polycondensed. It is considered that the reactions proceed in parallel.

The temperature and pressure for advancing the above reaction have a great influence on the effect of the present invention.
It is preferable to adjust the temperature in the range of 50 ° C. and 10 MPa to 50 MPa. When the reaction temperature is lower than 350 ° C., the hydrolysis of the polyester resin proceeds too much, and the reaction with the diamine compound may not proceed sufficiently. By the way, the dicarboxylic acid monomer produced by the complete hydrolysis of the polyester resin is
The carboxyl groups are associated and stabilized, and hardly react with the diamine compound. Further, when the reaction temperature is higher than 450 ° C., the decomposition of the polyester resin other than the ester bond proceeds, and the diamine compound also decomposes. On the other hand, when the reaction pressure is lower than 10 MPa, the hydrolysis rate of the polyester resin decreases, which is inefficient. When the reaction pressure is higher than 50 MPa, the hydrolysis of the polyester resin may proceed too much, and the reaction with the diamine compound may not proceed sufficiently, as in the case where the reaction temperature is lower than 350 ° C. More preferable ranges are a reaction temperature of 375 ° C to 430 ° C and a reaction pressure of 20 MPa to 30 MPa.

In the present invention, such a reaction can be carried out using, for example, a semi-batch type apparatus as shown in FIG.

That is, FIG. 1 schematically shows an example of an apparatus used in the present invention. As shown in FIG. 1, this apparatus has a pressure-resistant reaction container 1 equipped with an electric furnace 1a.
A liquid carbon dioxide cylinder 2, a liquid feed pump 3 for feeding pressurized carbon dioxide from the liquid carbon dioxide cylinder 2 into the pressure resistant reaction container 1, and a carbon dioxide preheater 4 for preheating supplied carbon dioxide, Pure water storage tank 5, water pump 6 for feeding pressurized pure water from this pure water storage tank 5 into pressure resistant reaction vessel 1, and water preheater 7 for preheating supplied pure water
And a solid-liquid separator 8 that separates and removes solids from the components discharged from the pressure-resistant reaction container 1, and a pipe 9 that connects these devices. Further, a line is provided in each pipe 9 between the carbon dioxide preheater 4 and the pressure resistant reaction vessel 1, between the water preheater 7 and the pressure resistant reaction vessel 1, and between the pressure resistant reaction vessel 1 and the solid-liquid separator 8. A heater 10 is attached. The line heater 10 attached to the pipe 9 between the pressure-resistant reaction vessel 1 and the solid-liquid separator 8 prevents the hydrolysis product of the polyester resin from being deposited when discharged from the pressure-resistant reaction vessel 1. It is provided. In the figure, 11 is a dehydrating agent for dehydrating the carbon dioxide sent from the liquid carbon dioxide cylinder 2,
12 is a flow meter, 13 is a thermocouple for temperature measurement, 14 is a thermocouple for temperature control, and 15 is a pressure reducing valve.

In such an apparatus, first, a polyester resin and a diamine compound are put into the pressure resistant reaction vessel 1. When the polyester resin is a product recovered from waste and has a non-uniform size, it is preferable to cut the product in advance to make the size and shape as uniform as possible. Further, if dirt or dust is attached, it is preferable to remove it in advance in order to reduce the influence on the reaction and the load of the purification step after the collection.

Then, the pure water heated by the preheater 7 and the line heater 10 is continuously supplied from the pure water storage tank 5, and the pressure-resistant reaction container 1 is heated to react with the reaction container 1.
The inside is the temperature and pressure range as described above. Polyester resin and diamine compound react directly with increase in temperature and pressure, or hydrolysis of polyester resin proceeds and polycondensation reaction of dicarboxylic acid component and diamine compound generated by this hydrolysis, resulting in polyamide resin. To be done.

After that, the carbon dioxide heated by the preheater 4 and the line heater 10 is continuously supplied from the liquid carbon dioxide cylinder 2 while maintaining the temperature and pressure inside the pressure resistant reaction vessel 1, and the pressure resistant reaction vessel 1 is operated. The inside is replaced with supercritical carbon dioxide. When the inside of the pressure resistant reaction vessel 1 is completely replaced with supercritical carbon dioxide, heating is stopped, the pressure resistant reaction vessel 1 is returned to normal temperature and pressure, and the produced polyamide resin is recovered. The replacement of the pressure-resistant reaction vessel 1 with supercritical carbon dioxide prevents the polyamide resin from being hydrolyzed to lower the molecular weight in the process of returning the pressure-resistant reaction vessel 1 to the normal temperature and pressure. This is because. That is, the produced polyamide resin is stable without being hydrolyzed in supercritical water or subcritical water (this is because an ionic product is small and an aprotic solvent is used when water is in a supercritical or subcritical state). When the temperature and pressure inside the reaction vessel 1 are lowered as they are, the polyamide resin is inevitably contacted with water, which increases the ionic product and is changed to a protic solvent, and hydrolysis is not possible. proceed. By replacing the inside of the reaction vessel 1 with supercritical carbon dioxide while maintaining the temperature and pressure inside the reaction vessel 1, it is possible to prevent such hydrolysis of the polyamide resin,
It is possible to prevent lowering of the molecular weight. The recovered polyamide resin is then refined into a product.

In the present invention, the pressure resistant reactor 1
It is desirable that after the polyester resin and the diamine compound have been charged therein, the system is once filled with pure water to remove oxygen inside, and then heating and pressurization is started.
This can prevent side reactions due to dissolved oxygen. From the same viewpoint, it is desirable that the water supplied to the pressure-resistant reaction vessel 1 be one from which dissolved oxygen has been removed, such as by bubbling with nitrogen gas. Furthermore, in order to facilitate control of the reaction, it is desirable to raise the pressure in the pressure resistant reaction vessel 1 to a predetermined pressure and then start heating.

The present invention can be carried out not by using the so-called semi-batch type apparatus as described above but by using a continuous reaction type apparatus.

[0027]

EXAMPLES Next, the present invention will be described in more detail by way of examples, but the present invention is not limited to the following examples.

Example A commercially available beverage bottle made of polyethylene terephthalate (PET) was collected and cut into chips each having a size of several mm square, and then about 4 g was weighed and the pressure-resistant reaction container of the apparatus shown in FIG. (Internal volume 10 ml) 1 was charged. Further, deaerated pure water of about 3 g of hexamethylenediamine was added as a diamine compound, and the pressure resistant reaction vessel 1 was sealed.

Next, the temperature of the line heater 10 attached to the pipe 9 connecting the pressure-resistant reaction vessel 1 and the solid-liquid separator 8 is set to 35
After setting the temperature to 0 ° C and continuously feeding deaerated pure water from the pure water storage tank 5, the internal pressure in the pressure resistant reaction vessel 1 was increased to 30 MPa, and then the pressure was maintained for about 45 minutes. The temperature inside the pressure resistant reactor 1 was raised to 390 ° C. and kept for 1 minute. After that, the dehydrated supercritical carbon dioxide 5
The pressure was continuously injected at a flow rate of ml / min, and the pressure inside the pressure resistant reaction vessel 1 was replaced with supercritical carbon dioxide while maintaining the internal temperature and internal pressure inside the pressure resistant reaction vessel 1. After the replacement, the mixture was air-cooled, the internal temperature inside the pressure-resistant reaction vessel 1 was returned to room temperature and atmospheric pressure, and the solid matter in the pressure-resistant reaction vessel 1 was recovered.

The recovered solid was vacuum dried (10 mmHg or less) at 80 ° C. for 5 hours and then dissolved in dimethylformamide. When this solution was filtered and chloroform was added to the filtrate, a precipitate appeared.

The precipitate was collected by filtration, dried at 60 ° C. for 5 hours, and then subjected to infrared spectroscopic analysis and 1H-NMR analysis to confirm that the precipitate was polyamide 6T. The weight average molecular weight (Mw) of the precipitate was about 10,000 by GPC (gel permeation chromatograph) analysis.
Was confirmed.

[0032]

As described above, according to the present invention,
Since polyester resin and diamine compound are reacted in supercritical water or subcritical water to produce polyamide,
It becomes possible to produce a useful high-molecular-weight polyamide resin from a polyester resin or its waste by a simple and environmentally-friendly process.

[Brief description of drawings]

FIG. 1 is a diagram schematically showing an example of an apparatus used for carrying out the present invention.

[Explanation of symbols]

1 ... Pressure resistant reactor 1a ......... electric furnace 2 ... Liquid carbon dioxide cylinder 3 ... Liquid delivery pump 5: Pure water storage tank 7 ... Water pump 9 ………… Piping

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Kiyoshi Furumura             20 Kitakanzan, Otakamachi, Midori-ku, Nagoya-shi, Aichi             No. 1 Chubu Electric Power Co., Inc. (72) Inventor Shozo Watanabe             20 Kitakanzan, Otakamachi, Midori-ku, Nagoya-shi, Aichi             No. 1 Chubu Electric Power Co., Inc. (72) Inventor Susumu Hirai             2-1-1 Oda Sakae, Kawasaki-ku, Kawasaki-shi, Kanagawa             No. Showa Densen Denki Co., Ltd. (72) Inventor Takao Nakamoto             2-1-1 Oda Sakae, Kawasaki-ku, Kawasaki-shi, Kanagawa             No. Showa Densen Denki Co., Ltd. (72) Inventor Hitoshi Shindate             2-1-1 Oda Sakae, Kawasaki-ku, Kawasaki-shi, Kanagawa             No. Showa Densen Denki Co., Ltd. (72) Inventor Hiroaki Morita             2-1-1 Oda Sakae, Kawasaki-ku, Kawasaki-shi, Kanagawa             No. Showa Densen Denki Co., Ltd. F-term (reference) 4J001 DA03 DB02 DB04 DC03 DC14                       EB75 EC04 EC05 EC06 EC07                       EC08 EC09 EC13 EC14 EC29                       EC38 EC44 EC45 EC46 EC47                       EC48 EC55 EC56 EC66 EC67                       EC69 EC70 EC81 ED66 FA01                       FB01 GA12 GA20 GB02 GB03                       JA01

Claims (5)

[Claims] 1. A method for producing a polyamide resin, which comprises reacting a polyester resin and a diamine compound in supercritical water or subcritical water to produce a polyamide resin. 2. The reaction temperature is 350 ° C. to 450 ° C. and the reaction pressure is 10 MPa to 50 MPa.
A method for producing the described polyamide resin. 3. The method according to claim 1, wherein after the polyamide resin is produced, the reaction vessel is filled with supercritical carbon dioxide, and then the temperature is lowered and the pressure is reduced to recover the polyamide resin.
A method for producing the described polyamide resin. 4. The method for producing a polyamide resin according to claim 1, wherein the polyester resin is a product recovered from waste. 5. The method for producing a polyamide resin according to any one of claims 1 to 4, wherein the polyester resin is polyalkylene terephthalate.