JPH1045744A - Production of 2-p-dioxanone - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce 2-p-dioxanone efficiently from poly(2-p-dioxanone) by thermal decomposition in response to the need for chemically recyclable polymers. SOLUTION: This 2-p-dioxanone is produced efficiently thermally decomposing poly(2-p-dioxanone) by heating at 220-400 deg.C under pressure of 1Torr or higher and below 760Torr or heating at 220-400 deg.C in an inert gas flow under the atmospheric pressure.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing 2-p-dioxanone from poly (2-p-dioxanone). It is used for molded articles such as garbage bags, shopping bags, agricultural films, disposable diapers, and sanitary articles. It relates to a method of converting these molded articles into 2-p-dioxanone as a raw material monomer by thermal decomposition after disposal. Things.

[0002]

2. Description of the Related Art So-called depolymerization, in which a polymer is thermally decomposed and converted into a monomer, is expected as an effective treatment for plastic waste from the viewpoint of chemical recycling. Chemical recycling of polycondensation polymers such as polyethylene terephthalate and vinyl polymerization polymers such as polymethyl methacrylate which almost completely depolymerizes to the raw material monomers has already been put to practical use. In addition, studies are being made on improving the selectivity of conversion of a polymer that thermally decomposes into a mixture of a plurality of low molecular weight compound groups containing a raw material monomer such as polystyrene into a monomer. However, it is impossible to convert polyolefins, such as polyethylene and polypropylene, which occupy most of the plastic waste, into raw material monomers, and the conversion to fuel by thermo-oil treatment is in progress. From a recycling point of view, the need to convert to monomers and regenerate polymers is expected to increase. Therefore, in the future, development of a polymer having excellent chemical recyclability for substituting a polyolefin that cannot be chemically recycled is desired.

[0003] Poly (2-p-dioxanone) is 2-p
-A polyester synthesized by ring-opening polymerization of dioxanone, which is already known to be a material that can be decomposed and absorbed in vivo and used as a medical material.

[0004] The possibility that poly (2-p-dioxanone) can be depolymerized to 2-p-dioxanone as a raw material monomer by heating is based on the fact that Berichte der Deutschen Chemischen Gezelshaft (Hollo, Berichte der Deutschen).
Chemischen Gesellschaft, 61 , 895 (1928)) and the Journal of American Chemical Society (WH Carothers et al., Journal of American Chem).
ical Society, 54 , 761 (1932)). However, these studies suggest that molecular weights of hundreds to
This is the result of using about 800 oligomers, and
No clear confirmation of conversion to 2-p-dioxanone has been made. Further, the conversion rate and the conditions for depolymerization are not disclosed. In particular, poly (2-p-) having a sufficient high molecular weight used as a polymer material for various applications is used.
Dioxanone) has not been found at all in terms of depolymerization during thermal decomposition.

Therefore, a method for producing 2-p-dioxanone by thermal decomposition of poly (2-p-dioxanone) has not yet been established.

[0006]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a poly (2-p-dioxanone) having the potential to meet the need for a chemically recyclable polymer.
It is an object of the present invention to provide a method for producing 2-p-dioxanone which can confirm the conversion to 2-p-dioxanone by thermal decomposition and can perform the conversion more efficiently.

[0007]

The present inventors have made intensive studies to solve the above-mentioned problems, and as a result, under certain conditions, poly (2-p-dioxanone) was efficiently converted to 2-p-dioxanone.
The present inventors have found a method which can easily produce 2-p-dioxanone as a monomer by converting into dioxanone, and have completed the present invention.

That is, according to the present invention, poly (2-p-dioxanone) is heated at 220 to 400 ° C. and 1 Torr or more to 760 To.
2-p characterized by being thermally decomposed under a pressure of less than rr
-A process for producing dioxanone.

Another invention is a method for producing 2-p-dioxanone, which comprises pyrolyzing poly (2-p-dioxanone) at 220 to 400 ° C. in an inert gas stream at atmospheric pressure. .

The gist of the present invention is to thermally decompose poly (2-p-dioxanone) under specific conditions,
The point is that 2-p-dioxanone can be produced with high purity and high conversion.

First, the temperature range of 220 to 400 ° C. indicates a lower limit for supplying thermal energy required for thermal decomposition and an upper limit from a practical viewpoint. Poly (2-p-
The thermal decomposition of dioxanone) starts at a lower temperature as its molecular weight is lower, as will be shown in Examples described later. However, the thermal decomposition of low molecular weight poly (2-p-dioxanone) is not a single decomposition mechanism, but involves multiple reactions.
This is less desirable from the viewpoint of production of 2-p-dioxanone by depolymerization. On the other hand, in the case of poly (2-p-dioxanone) having a sufficiently high molecular weight used as a plastic material, it was confirmed that the thermal decomposition of the poly (2-p-dioxanone) quickly proceeds in a single reaction at a temperature of 220 ° C. or higher. did. Such a relationship between the depolymerization reaction behavior and the molecular weight and the temperature conditions for the depolymerization are findings found for the first time.

Secondly, under the pressure of 1 Torr or more and less than 760 Torr, or under atmospheric pressure in an inert gas stream, 2-p-dioxanone produced after depolymerization can be quickly taken out of the system. It has been found that not only the conversion to 2-p-dioxanone can be promoted, but also the ultimate conversion can be significantly improved.

Therefore, by satisfying the conditions in the present invention, it is possible to efficiently produce 2-p-dioxanone by thermal decomposition of poly (2-p-dioxanone).

In the present invention, poly (2-p-dioxanone) is basically represented as poly [oxy (1-oxoethylene) oxyethylene] having a structural unit having the following structure.

[0015]

Embedded image

As represented by the above structure, poly (2-p
-Dioxanone) is a ring-opening addition polymer of 2-p-dioxanone or a dehydration polycondensate of β-hydroxyethoxyacetic acid, but a compound copolymerizable with 2-p-dioxanone or β-hydroxyethoxyacetic acid. This also includes the case where the content of the compound copolymerizable with 20% or less.
Examples of the copolymerizable compound include, for example, β-propiolactone, β-butyrolactone, diketene, pivalolactone, δ-valerolactone, ε-caprolactone, glycolide, lactide, and 1,4-dioxepan-2-one. Cyclic ester compounds, cyclic ether compounds such as ethylene oxide and propylene oxide, organic acids such as oxycarboxylic acids such as glycolic acid, lactic acid, β-hydroxybutyric acid, succinic acid, adipic acid and sebacic acid, and polycarboxylic acids. And polyhydric alcohols such as ethylene glycol, propylene glycol, polyethylene glycol, polypropylene glycol, glycerin, and trimethylolpropane. Therefore, poly (2-p-dioxanone) in the present invention basically means 2-p-dioxanone.
-A polymer having a structure obtained by ring-opening polymerization of dioxanone or polycondensation of β-hydroxyethoxyacetic acid, and a copolymer in which the structural units of the copolymerizable compound are copolymerized at 20% or less. Simply include poly (2-p
-Dioxanone).

The molecular weight of the poly (2-p-dioxanone) used in the present invention is not particularly limited, and poly (2-p-dioxanone) in the range of oligomer to ultra-high molecular weight is used. In the case of an oligomer having a number average molecular weight of 2,000 or less, or a weight average molecular weight of 10,000 or less, the weight loss accompanying depolymerization starts from a low temperature of about 100 ° C., whereas the number average molecular weight is 50,000 or more, and the weight average In the case of high molecular weight poly (2-p-dioxanone) having a molecular weight of 100,000 or more, weight loss due to thermal decomposition is not remarkably observed up to about 200 ° C., and a temperature of 220 ° C. or more is required.

The thermal decomposition of poly (2-p-dioxanone) proceeds efficiently by heating poly (2-p-dioxanone) to a specific temperature range. Poly (2-p
Decomposition temperature conditions are slightly different depending on the molecular weight of (-dioxanone), the presence or absence of a catalyst, the difference in heating method, and the like, but decomposition tends to proceed faster at higher temperatures. A preferred heating temperature range is from 220 to 400 ° C. At a temperature lower than 220 ° C., the decomposition rate of poly (2-p-dioxanone) having a molecular weight of 10,000 or more becomes extremely slow and is not efficient. On the other hand, at 400 ° C. or higher, not only the effect due to the temperature is not so much found, but also when other resins such as polyethylene are mixed, poly (2-p
-Dioxanone), as well as undesired side reactions such as simultaneous thermal decomposition of polyethylene.

The pressure during the thermal decomposition is 1 Torr or more and 760
Less than Torr, more preferably more than 5 Torr and 650 T
It is performed under reduced pressure of less than orr. 760 at atmospheric pressure
Under a pressure of Torr or higher, not only the rate of depolymerization decreases, but also the conversion rate tends to decrease. Meanwhile, 1 Torr
Reduced pressure conditions below are not practical.

The method of reducing the pressure to less than 760 Torr is not particularly limited as long as it is a commonly used method. Specifically, a method of evacuating the reactor system using an oil rotary pump, an aspirator or the like is suitably used.

Poly (2-p-dioxanone) under atmospheric pressure
When thermal decomposition is performed, good conversion efficiency to 2-p-dioxanone can be achieved by performing the thermal decomposition in an inert gas stream. Here, the inert gas is gaseous in a temperature range of 220 to 400 ° C. and does not adversely affect the thermal decomposition of poly (2-p-dioxanone) and the generated 2-p-dioxanone. is there. As the inert gas, for example, nitrogen, helium, carbon dioxide, argon and the like are suitably used. In a gas other than the inert gas, for example, in an air stream, it is not preferable in the temperature range of the production method of the present invention because poly (2-p-dioxanone) is oxidized. This is not preferred because it may react with the produced 2-p-dioxanone.

The flow rate of the inert gas stream is not particularly limited, and the capacity of the pyrolysis reactor and the poly (2
-P-dioxanone) and the thermal decomposition temperature.

In the production method of the present invention, poly (2-p
-Dioxanone) in which another resin coexists. Other resins that can coexist are not particularly limited as long as they do not significantly affect the thermal decomposition of poly (2-p-dioxanone). Examples of the resin include polyolefins such as polyethylene and polypropylene, and polystyrene. However, depending on the coexisting resin, thermal decomposition may be started in the temperature range in the present invention depending on differences in molecular weight, types of additives, and the like.

The apparatus for thermal decomposition is not particularly limited.
Any device that can implement the conditions of the present invention can be used without any problem. A continuous, semi-continuous, or batch type device such as an extruder, a fluidized bed pyrolysis furnace, or a dedicated reactor is suitably used, and can be appropriately selected depending on the purpose.

When performing the thermal decomposition of poly (2-p-dioxanone), a specific catalyst can be added for the purpose of promoting the thermal decomposition more efficiently. As the catalyst,
Metal alcoholates, alkali or alkaline earth metal hydrides, metal tin, tin (IV) chloride, tin hydroxide (I
V), generally known transesterification catalysts such as alkali hydroxides are suitably used. In addition, when performing the thermal decomposition of poly (2-p-dioxanone), the presence of a small amount of water may give good results.

Although the 2-p-dioxanone generated in the reactor is in a gaseous state, the 2-p-dioxanone can be aggregated by cooling, liquefied and collected. The cooling method is not particularly limited as long as it is a commonly used method. Specifically, a method of condensing and collecting the generated 2-p-dioxanone gas by passing it through a cooling pipe is preferably used.

[0027]

The present invention provides a method for producing 2-p-dioxanone as a raw material monomer by efficiently depolymerizing poly (2-p-dioxanone) by thermally decomposing poly (2-p-dioxanone) under specific conditions. To provide. By this method, 2-p-dioxanone as a raw material monomer can be produced with high purity and a high conversion rate from waste plastic products using poly (2-p-dioxanone) as a raw material. Therefore, the production method of the present invention provides a poly (2-
Not only does it make it possible to effectively use (p-dioxanone) as a chemical recycling material in various industrial products, but it also provides an effective measure as a method for treating plastic waste.

[0028]

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

Production Example 1 (1) 2-p-dioxanone [hereinafter also referred to as PDX]
On a γ-alumina having a surface area of 200 m ² / g, copper nitrate was supported by an impregnation method so that the copper concentration was 9% by weight,
A PDX synthesis catalyst was prepared. 35 ml of this catalyst was filled in a stainless steel reaction tube, and dry air was supplied at 50 ml / min.
The temperature was raised to 400 ° C. while circulating the mixture, and the catalyst was calcined. Once cooled to room temperature, stop the dry air,
250 ml / min of nitrogen and 50 ml / min of hydrogen
, The temperature was raised again to 280 ° C., and the catalyst was reduced. In this state, the reaction was started by supplying diethylene glycol at 0.20 ml / min from the top of the reaction tube. The components flowing out from the lower part of the reaction tube were collected as a reaction product. As a result of supplying diethylene glycol for 5 hours, a reaction product containing 45% by weight of PDX was obtained. Unreacted diethylene glycol was 48% by weight, and by-products were 7% by weight. The main components in the by-product were dioxane and dioxene.

The purification of PDX was performed by a combination of distillation and recrystallization. First, crude PDX was subjected to simple distillation, and a distillate having a vapor temperature of 210 to 230 ° C was taken out. This fraction was recrystallized twice with methanol and twice with ethyl acetate to give purified PD.
X was obtained. The structure of PDX was confirmed using ¹ H-NMR. FIG. 1 shows the ¹ H-NMR spectrum of the synthesized PDX.

(2) Synthesis of poly (2-p-dioxanone) [hereinafter also referred to as PPDX] 20 ml polymerization test tube (with butyl rubber inner stopper)
Inside, 10 g of purified PDX (98 mmol) was weighed in a dry box under a dry nitrogen atmosphere. After sealing the test tube, take it out of the dry box and place it in a warm bath at 35 ° C.
DX crystals were melted to give a colorless transparent liquid.

40 μl of a 1 mol / l diethyl zinc solution in normal hexane (0.04 mmol, [PDX] /
[Initiator] = 2450) was measured with a microsyringe, injected through a butyl rubber stopper of a test tube, and uniformly mixed to initiate polymerization.

The polymerization reaction was carried out in a shaking constant temperature water bath. The reaction was carried out by heating at 35 ° C. for 2 hours, subsequently heating to 50 ° C. for 1 hour, and further heating to 70 ° C. for 3 hours. PDX in the test tube changed from a transparent liquid to a white solid with polymerization. The resulting white solid was placed in a 150 ml stainless steel autoclave together with 100 ml of chloroform, the inside gas phase was replaced with dry nitrogen, and then heated and dissolved at 130 ° C. for 2 hours. The chloroform solution was further diluted with 200 ml of chloroform, and then gradually dropped into 3 L of methanol to precipitate the generated PPDX. The obtained flocculent PPDX was filtered off from methanol and dried under reduced pressure at 30 ° C. until the weight became constant. The dry weight of the obtained PPDX was 7.1 g.

The structure of PPDX was confirmed using ¹ H-NMR. The measurement of the molecular weight of PPDX was performed using GPC (gel permeation chromatography). The molecular weight is a number average molecular weight of 58,0 in terms of standard polystyrene.
00, weight average molecular weight 127,000, polydispersity 2.1
8, which was a high molecular weight PPDX capable of forming a film.

Production Example 2 The ratio of diethylzinc to PDX was [PDX] /
A polymerization reaction was carried out in the same manner as in Production Example 1 except that [initiator] was changed to 19.6. 2.0 g of purified PDX (19.
6 mmol), 1 ml (1 mmol) of a 1 mol / l solution of diethyl zinc in tetrahydrofuran is added,
Polymerization was carried out in the same manner as in Production Example 1 (2). The product after polymerization was a white swollen solid. The obtained white swollen solid was dried under reduced pressure at 30 ° C. to obtain 1.5 g of a white powdery product.
I got From the ¹ H-NMR spectrum of this product, it was confirmed that the product was PPDX. The average degree of polymerization of the produced PPDX was 12 oligomers (calculated molecular weight 1242) from the area ratio of the peak of the molecular terminal ethyl group to the peak of the methylene proton in the main chain in the ¹ H-NMR spectrum.

Example 1 High molecular weight PPDX and P synthesized in Production Examples 1 and 2
The depolymerization behavior of the PDX oligomer was measured by thermogravimetric analysis. Put 10 mg of PPDX in a platinum container, and raise the temperature at a rate of 5 ° C./min in a nitrogen stream (100 ml / min).
The temperature rose within the range. FIG. 2 shows the relationship between the temperature and the weight loss rate. From the results in FIG. 2, the thermal decomposition of the PPDX oligomer starts at around 100 ° C., and at least two stages of weight reduction are observed, whereas in the case of the high molecular weight PPDX,
It was confirmed that the weight loss began to progress at around 200 ° C., and that the weight was reduced rapidly and in one stage in a temperature range of 220 ° C. or more, and that the decomposition was almost quantitative. Furthermore, high molecular weight PPDX
Was measured at different heating rates (φ) in the range of 1 to 9 ° C., and the results are shown in FIG. 3 as a relationship between the logarithm of the heating rate and the reciprocal of the absolute temperature (T). From the results shown in FIG.
The Arrhenius plot at a constant weight loss rate (C%) of X showed linearity at any rate of change, and the activation energy was almost constant at 128 KJ / mol. Therefore, it is shown that the thermal decomposition of the high molecular weight PPDX proceeds as a substantially single depolymerization reaction. On the other hand, in the case of the PPDX oligomer, the Arrhenius plot was not linear, and the activation energy at each rate of change was not constant even when limited to a linear range. Therefore, PP
In the case of the DX oligomer, it indicates that not only depolymerization but also other side reactions occur simultaneously.

Example 2 A test tube having a capacity of 15 ml and provided with a common slide was charged with 1.50 g of the high molecular weight PPDX synthesized in Production Example 1. An air-cooled curved tube, a suction connection tube, and a weighed test tube for storing decomposition products were attached to the test tube, and a thermal decomposition reaction device was obtained.
The test tube containing PPDX was heated under a reduced pressure of 7.6 Torr. The heating was performed by immersing the neck portion of the test tube in an oil bath of silicone oil heated to 230 ° C. 3.
After heating for 5 hours, the reactor was removed from the oil bath and immediately cooled. As a result, a colorless transparent liquid distillate was obtained in the test tube for receiving the decomposition product. On the other hand, a very small amount of brown solid remained at the bottom of the reaction test tube. The weight of the transparent liquid was 1.49 g, while the weight of the brown solid as the reaction residue was 0.01 g. This transparent liquid was cooled in an ice bath, and as a result, crystallized quickly.

The structure of the transparent liquid obtained by the reaction was confirmed by ¹ H-NMR and mass spectrum. In FIG.
^{The 1} H-NMR spectrum and the mass spectrum are shown in FIG. From these results, it was confirmed that the transparent liquid obtained by the reaction was PDX. Further, in the ¹ H-NMR spectrum, no signal other than the signal attributed to PDX was observed, confirming that the purity of PDX was almost 100%.

The value obtained by reducing the weight of PDX obtained by the reaction by the weight of PPDX used as a raw material was determined as the conversion of PDX. As a result, the conversion under the reaction conditions was 99.2%.

Examples 3 to 14 Thermal decomposition was carried out in the same manner as in Example 1 except that the reaction temperature, reaction time, and pressure were set to the values shown in Table 1. Table 1 also shows the residual amount, distillate (PDX yield), PDX purity, and PDX conversion in each example.

Comparative Examples 1 to 7 The thermal decomposition reaction was carried out in the same manner as in Example 1 except that the reaction temperature, reaction time, and pressure were set to the values shown in Table 1. Table 1 also shows the residual amount of PPDX, fraction (PDX yield), PDX purity, and PDX conversion rate in each comparative example.

When the reaction was carried out at 210 ° C., the conversion of PDX was low at any pressure, and PDX was not obtained at a practical rate. Also, 250
When the reaction was carried out at 760 Torr at a temperature of 760 Torr, the conversion up to 80% proceeded in a short time, but the conversion did not change even if the reaction was continued further, and a large amount of residue remained in the reaction vessel.

From Examples 3 to 14 and Comparative Examples 1 to 7,
Excellent chemical recyclability such that the recovery of PDX by the thermal decomposition of PPDX is 90% or more was achieved within the condition range of the method of the present invention.

[0044]

[Table 1]

Example 15 1.50 g of the high molecular weight PPDX synthesized in Production Example 1 and 1.00 g of low-density polyethylene (LDPE) pellets were mixed and placed in a 15-ml test tube with a common slide. An air-cooled curved tube, a suction connection tube, and a weighed test tube for storing decomposition products were attached to the test tube, and a thermal decomposition reaction device was obtained. The test tube containing PPDX was heated under a reduced pressure of 360 Torr. The heating was carried out by inserting the tube into the tube furnace heated to 350 ° C. up to the neck of the test tube. Along with the heating, a colorless transparent liquid distillate was observed in the test tube on the receiving side of the decomposition product. After heating for 1 hour, the reactor was removed from the furnace and immediately cooled. As a result, a lump solid containing LDPE as a main component remained at the bottom of the reaction test tube.
The weight of the transparent liquid was 1.45 g, while the weight of the solid remaining in the reaction test tube was 1.05 g. This transparent liquid was cooled in an ice bath, and as a result, crystallized quickly.

The identification of the distillate was carried out in the same manner as in Example 2. ¹
In the 1 H-NMR spectrum, no signal other than the signal attributed to PDX was observed, and thus it was confirmed that the obtained fraction was pure PDX.

From the above results, under the reaction conditions,
96.7% of PPDX was converted to PDX by pyrolysis and separated from LDPE.

Comparative Example 8 The reaction was carried out in the same manner as in Example 15 except that the reaction temperature was 450 ° C.

As a result, in the test tube on the receiving side of the decomposition product, two kinds of yellow transparent liquids were obtained by phase separation. The total weight of the liquid was 2.04 g. ^{From 1} H-NMR, it was confirmed that the lower layer of the liquid was PDX containing a small amount of aliphatic hydrocarbon, and the upper layer was aliphatic hydrocarbon.
On the other hand, at the bottom of the reaction test tube, 0.35 g of a brown liquid material mainly composed of a decomposition product of LDPE remained.

From the above results, under the reaction conditions, LDPE was decomposed simultaneously with PPDX, and pure PDX could not be obtained.

Example 16 Example 1 was repeated except that pellets of high-density polyethylene (HDPE) were used as the polymer to be mixed with PPDX, and the reaction temperature was 400 ° C.
The reaction was carried out in the same manner as in Example 5. As a result, pure PD
X 1.41 g were obtained.

From the above results, under the reaction conditions,
94.0% of PPDX was converted to PDX by pyrolysis and separated from HDPE.

Example 17 1.50 g of the high molecular weight PPDX synthesized in Production Example 1 was placed in a 15 ml test tube with a common slide. A connecting pipe with a side pipe for introducing an inert gas, an air-cooled curved pipe, a suction connecting pipe, and a weighed test tube for storing decomposition products were attached to the test tube to form a thermal decomposition reactor. Dry nitrogen gas was supplied at 500 ml / min. From the side pipe for introducing an inert gas.
, And evacuated by attaching a calcium chloride tube to the suction side tube. Heating was carried out by immersing the neck of the test tube in an oil bath of silicone oil heated to 220 ° C. Along with the heating, a colorless transparent liquid distillate was observed in the test tube for receiving the decomposition product. After heating for 3.5 hours, the reactor was removed from the oil bath and immediately cooled. As a result, a very small amount of brown solid remained at the bottom of the reaction test tube. The weight of the transparent liquid is 1.47 g,
On the other hand, the weight of the brown solid as the reaction residue was 0.03 g. This transparent liquid was cooled in an ice bath, and as a result, crystallized quickly.

The structure of the transparent liquid obtained by the reaction was confirmed by ¹ H-NMR and mass spectrum. ¹ H-N
Since no other signal was observed in the MR spectrum other than the signal assigned to PDX, the PD
It was confirmed that the purity of X was almost 100%.

From the above results, under the reaction conditions,
98.0% of the PPDX was converted to PDX by pyrolysis.

Comparative Example 9 The depolymerization behavior of the high molecular weight PPDX synthesized in Production Example 1 was measured by thermogravimetric analysis. 10 mg of PPDX was placed in a platinum container, and the temperature was raised in an air stream (100 ml / min) at a rate of 5 ° C./min. As a result of the differential thermal analysis, an exothermic peak based on the oxidation reaction of PPDX was observed. Further, the thermogravimetric analysis curve did not show rapid complete decomposition, and tailing toward a high temperature side was observed. Therefore, it was recognized that a thermal decomposition reaction distinct from the depolymerization reaction occurred in the air stream.

[Brief description of the drawings]

FIG. 1 ¹ H-NMR spectrum of 2-p-dioxanone (PDX) synthesized in Production Example 1

FIG. 2 shows the relationship between the temperature in thermogravimetric analysis of the PPDX of Example 1 and the weight loss rate.

FIG. 3 shows the relationship between the logarithm of the heating rate and the reciprocal of the absolute temperature at each weight loss rate in the thermogravimetric analysis of the high molecular weight PPDX of Example 1.

FIG. 4 shows ¹ H-NMR spectrum of PDX produced by pyrolysis of PPDX in Example 2.

FIG. 5 is a mass spectrum of PDX produced by pyrolysis of PPDX in Example 2.

Claims (2)

[Claims] 1. The method according to claim 1, wherein the poly (2-p-dioxanone) is 220
A method for producing 2-p-dioxanone, comprising thermally decomposing under a pressure of 1 to 400 [deg.] C. and less than 760 Torr. 2. Poly (2-p-dioxanone) 220
A method for producing 2-p-dioxanone, which is thermally decomposed at atmospheric pressure in an inert gas stream at ~ 400 ° C.