JP4680909B2 - Method for producing aliphatic polyester - Google Patents

Description

  The present invention relates to a method for producing an aliphatic polyester, in which a phosphorus compound is added and mixed in the method to effectively suppress the formation of a cyclic oligomer as a by-product, and a fat having a low cyclic oligomer content. The present invention relates to a method for producing a group polyester.

  Aliphatic polyesters typified by polybutylene succinate are widely used by being processed into products such as agricultural materials, civil engineering materials, vegetation materials, and packaging materials because of their good physical properties and biodegradability. Particularly in recent years, application to food packaging materials is expected.

However, the aliphatic polyester by-produces a low molecular weight oligomer in the course of polymerization, and when left standing for a long time after being molded into a film or the like, the oligomer (particularly a cyclic dimer) precipitates on the surface of the molded product, It became clear that the appearance characteristics were reduced.
Such precipitation of cyclic oligomers is known, for example, in polyethylene terephthalate (PET) which is not an aliphatic polyester (J. Polymer Sci., 1954, vol. 13, p. 406). It has been confirmed that it is a cyclic trimer. The cyclic trimer has a large molecular weight and is difficult to physically remove from PET by reduced pressure treatment or the like. On the other hand, as a method for obtaining a high molecular weight PET having a low content of cyclic oligomers such as a cyclic trimer, a solid phase polymerization method at a temperature below the melting point has been put into practical use. According to this method, it is known that the content of cyclic trimer in PET can be reduced to about 0.3% by weight.

  However, in general, an aliphatic polyester has a low melting point unlike PET, and a practical polymerization temperature for carrying out solid phase polymerization cannot be secured. Not applicable to polyester.

  In Japanese Patent Application Laid-Open No. 07-316276, high molecular weight aliphatic polyester is mixed with pure water, pure water and alcohol, or pure alcohol in the state of powder, pellets or molded product, and the melting point of the high molecular weight aliphatic polyester. A method has been devised in which contact is made at a temperature lower than the boiling point of these solvents, and residual monomers and oligomers are eluted and removed.

In JP-A-2002-003606, aliphatic polyester is used in the form of powder, pellets or molded products, and one or more selected from aliphatic ketones, alicyclic ethers and aliphatic monoesters. A method has been devised in which a solvent is brought into contact at a temperature lower than the melting point of the aliphatic polyester and lower than the boiling point of the solvent to elute and remove residual monomers and oligomers.
However, these methods are not efficient because the number of steps of cleaning with a solvent and the step of removing a cleaning solvent are increased, and are burdensome in terms of equipment investment, resulting in an increase in cost.

  On the other hand, a method for reducing cyclic oligomers in biodegradable aliphatic polyester carbonate is disclosed in Japanese Patent Application Laid-Open No. 08-301999. That is, this method is intended for a cyclic oligomer mainly composed of a cyclic dimer composed of succinic acid and 1,4-butanediol (reacted by two molecules each), and polycondensation of biodegradable aliphatic polyester carbonate. After completion of the reaction, a phosphorus compound is added and mixed to suppress transesterification and polycondensation reaction, and then degassing under reduced pressure at a temperature equal to or higher than the melting point of the biodegradable aliphatic polyester carbonate, It relates to removal from biodegradable aliphatic polyester carbonate. However, in this method, the degassing step of the cyclic oligomer is increased, and furthermore, the cyclic chain equilibrium of the cyclic oligomer is not sufficiently suppressed, so that the cyclic oligomer is regenerated during the degassing treatment. In order to make up for this drawback, it is necessary to use a special degassing device that can obtain a high degassing removal rate, which increases the burden on the equipment investment, and the degassing device is removed by the removed cyclic oligomer. There are many equipment problems such as blockage of the decompression system, which is not efficient in terms of equipment investment.

  The present invention has excellent thermal stability when an aliphatic polyester is formed into a fiber, film, sheet, or other molded body, and surface precipitation derived from a cyclic oligomer contained in the aliphatic polyester. An object of the present invention is to provide a method for producing an aliphatic polyester that is reduced to an amount that does not cause a problem in practical use, has excellent appearance characteristics, has no obstacle in post-processing and application fields, and can reduce production costs as much as possible.

  As a result of intensive studies, the present inventors have found that the above object can be achieved by adding and mixing a phosphorus compound in a method for producing an aliphatic polyester, and further proceeding a polycondensation reaction, thereby completing the present invention. I was able to.

That is, the present invention is a method for producing an aliphatic polyester by reacting an aliphatic polybasic acid or a derivative thereof with an aliphatic polyhydric alcohol, wherein the aliphatic polybasic acid or a derivative thereof is an aliphatic dicarboxylic acid, One or more selected from alicyclic dicarboxylic acids and aliphatic hydroxycarboxylic acids or anhydrides thereof, and the aliphatic polyhydric alcohol is one or more selected from aliphatic diols and alicyclic diols, In the method, after adding and mixing a phosphorus compound in a molar amount of 28 to 3.0 × 10 ³ times with respect to 1 mol of the catalyst, an aliphatic polyester having a required molecular weight is obtained under the conditions of a temperature of 130 to 300 ° C. and a degree of vacuum of 10 mmHg or less. until the resulting performed polycondensation reaction, to characterized in that less 4000ppm cyclic dimer content in the aliphatic polyester obtained A method for producing aliphatic polyester.
That is, by adding and mixing a phosphorus compound, it is desirable to reduce the molecular weight of the aliphatic polyester based on the ring chain equilibrium of the cyclic oligomer by-produced during the synthesis (production) of the aliphatic polyester and the decomposition reaction of the aliphatic polyester. This is a method for producing an aliphatic polyester, which can eliminate such a phenomenon.

FIG. 1 is a graph showing the relationship between decompression time, CD content and weight average molecular weight of aliphatic polyester in Examples 1 and 2 and Comparative Example 1.

The present invention is described in detail below.
In order to establish a method for producing an aliphatic polyester, which has excellent thermal stability and has a low cyclic oligomer content which is an obstacle in post-processing and application fields, and can further reduce production costs. As a result of diligent research and various studies, in the method for producing an aliphatic polyester, the above object was achieved by adding and mixing a phosphorus compound and further performing a polycondensation reaction under reduced pressure at a temperature equal to or higher than the melting point of the aliphatic polyester. The present invention has been completed.

  In the production method of the present invention, mainly one or more aliphatic diols and alicyclic diols and one or more aliphatic dicarboxylic acids, alicyclic dicarboxylic acids and aliphatic hydroxycarboxylic acids or anhydrides thereof, Aliphatic polyesters can be produced. In the production method of the present invention, the phosphorus compound is added and mixed at the above ratio, and then under reduced pressure at a temperature equal to or higher than the melting point of the aliphatic polyester, for example, a temperature of 130 to 300 ° C. and a degree of vacuum of 10 mmHg or less. Under these conditions, the polymerization reaction is carried out until an aliphatic polyester having the required molecular weight is obtained, and at the same time, the cyclic oligomer content (residual amount) in the aliphatic polyester obtained can be made 4000 ppm or less.

  The process for producing an aliphatic polyester according to the present invention comprises an esterification reaction (dehydration condensation, polycondensation) of the alcohol, the carboxylic acid, the carboxylic anhydride and / or the hydroxycarboxylic acid, and subsequently the presence of a catalyst. Including performing a deglycolization reaction below. In this method, if necessary, a total of three aliphatic polyhydric alcohols having three or more valences, three or more aliphatic polybasic acids, anhydrides thereof, and alcoholic hydroxyl groups and carboxylic acid groups in one molecule. It is also possible to use at least one aliphatic polyvalent compound selected from the group consisting of the above aliphatic polyvalent hydroxycarboxylic acids.

  Reduction of the cyclic oligomer in the method for producing an aliphatic polyester of the present invention is achieved by adding and mixing a phosphorus compound in the method. The addition and mixing of the phosphorus compound may be performed at any stage of the method. That is, a phosphorus compound is added and mixed during or after the esterification (polycondensation) reaction of the alcohol, the carboxylic acid, the carboxylic acid anhydride and / or the hydroxycarboxylic acid, or during or after the deglycolization reaction. This is accomplished by reacting the resulting mixture under reduced pressure and ring-opening polycondensation or distillation of the cyclic oligomer. More specifically, a phosphorus compound is added to and mixed with a molten aliphatic polyester under a nitrogen atmosphere, followed by a polycondensation reaction under reduced pressure until the aliphatic polyester reaches a target molecular weight. At the same time, the concentration of the cyclic oligomer is reduced to 4000 ppm or less.

In the method of the present invention, the aliphatic polyester is treated as described above in a molten state and under reduced pressure, so that the chain chain equilibrium transfer reaction, that is, the cyclic oligomer is opened into a chain and polycondensed to the aliphatic polyester. In addition, it is essential to add and mix phosphorus compounds. That is, the addition and mixing of the phosphorus compound not only suppresses the regeneration of the cyclic oligomer, but also efficiently converts the cyclic oligomer formed in the process of esterification (polycondensation) and in the chain chain equilibrium state to the aliphatic polyester. Can be condensed. It is also effective in improving the thermal stability of the aliphatic polyester in the molten state. Adding and mixing of the phosphorus-based compound, the catalyst per mol 28 to 3.0 × 10 ³ moles, preferably used in the range of 28 to 10 ² moles.

  In order to reduce the cyclic oligomer, the reaction is preferably performed at a high temperature and a high degree of vacuum, the reaction temperature is 130 to 300 ° C., preferably 180 to 280 ° C., and the degree of vacuum is 10 mmHg or less, preferably 5 mmHg or less. More preferably, it is 2 mmHg or less.

  Reduction of the cyclic oligomer in the method for producing an aliphatic polyester of the present invention may be carried out as it is in the apparatus used for esterification (polycondensation) of the aliphatic polyester, or may be carried out using a separately prepared apparatus. It is. In the method of the present invention, the aliphatic polyester is melted, and it is not necessary to consider (re) generation of the cyclic oligomer after the addition and mixing of the phosphorus compound. Therefore, it is not necessary to use an apparatus that can obtain a particularly high removal rate of the cyclic oligomer. However, in order to efficiently increase the molecular weight of the aliphatic polyester to a required value, a device capable of heating and depressurization with high surface renewability is preferable. For example, a tank reactor equipped with a normal high viscosity solution stirring device Can be used. Examples of the high-viscosity solution stirring apparatus include those using a lattice blade, a helical ribbon blade, a log bone blade, and the like.

The molecular weight of the aliphatic polyester can be increased by further reacting the produced aliphatic polyester with a polyvalent isocyanate compound.
When the aliphatic polyester is reacted as a prepolymer with the polyvalent isocyanate compound, the ratio at that time is 0.1 to 5 parts by weight of the polyvalent isocyanate compound with respect to 100 parts by weight of the aliphatic polyester. The number average molecular weight of the aliphatic polyester (prepolymer) is 5,000 or more, desirably 10,000 or more, and the weight average molecular weight is 30,000 or more, desirably 34,000 or more. If the number average molecular weight is less than 5,000 or the weight average molecular weight is less than 30,000, or the number average molecular weight is less than 5,000 and the weight average molecular weight is less than 30,000, the desired physical properties can be finally obtained. In order to give to aliphatic polyester, the amount of polyisocyanate compound used must be increased, which is not preferable because it significantly increases the risk of gelation during melt mixing with the prepolymer.
When the amount of the polyvalent isocyanate compound used is too small, the molecular weight of the aliphatic polyester does not increase efficiently, which is not preferable.

  Specific examples of the polyvalent isocyanate compound include, for example, 2,4-tolylene diisocyanate, a mixture of 2,4-tolylene diisocyanate and 2,6-tolylene diisocyanate, diphenylmethane diisocyanate, 1,5 -Naphthylene diisocyanate, xylylene diisocyanate, hydrogenated xylylene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate and the like, but are not limited thereto. Among these, hexamethylene diisocyanate is particularly preferable from the viewpoint of the hue and reactivity of the aliphatic polyester produced.

  Examples of the aliphatic diol or alicyclic diol include the following types. Ethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,6-hexanediol, nonamethylene glycol, decamethylene glycol, propylene glycol, 1,3-butanediol, 2-methylpropanediol, 1, 3-Neopentyl glycol, 1,4-cyclohexanedimethanol. Among these diols, ethylene glycol, 1,4-butanediol and 1,4-cyclohexanedimethanol increase the melting point of the resulting aliphatic polyester and impart biodegradability to the aliphatic polyester. This is preferable in order to ensure the same moldability as that of the polyolefin of the aliphatic polyester.

  Furthermore, as the aliphatic dicarboxylic acid, alicyclic dicarboxylic acid and aliphatic hydroxycarboxylic acid for esterifying with the aliphatic diol or alicyclic diol, or anhydrides thereof, for example, succinic acid, succinic anhydride, Examples include adipic acid, adipic anhydride, suberic acid, sebacic acid, dodecanedioic acid, and cyclohexanedicarboxylic acid. Among these, the use of succinic acid, succinic anhydride, adipic acid, suberic acid, sebacic acid and dodecanedioic acid increases the melting point of the resulting aliphatic polyester, similar to the preferred diol, and the aliphatic polyester. It is preferable for imparting biodegradability to and ensuring the same moldability as that of the aliphatic polyester polyolefin.

  Particularly preferred combinations of aliphatic diols or alicyclic diols with aliphatic dicarboxylic acids, alicyclic dicarboxylic acids and aliphatic hydroxycarboxylic acids or their anhydrides are ethylene glycol and succinic acid, 1,4-butanediol. And succinic acid, 1,4-butanediol, succinic acid and sebacic acid, 1,4-cyclohexanedimethanol and adipic acid, 1,4-cyclohexanedimethanol and sebacic acid. It is preferable for increasing the melting point of the polyester, imparting biodegradability to the aliphatic polyester, and ensuring the same moldability as the polyolefin of the aliphatic polyester.

  The proportion of use of the aliphatic diol or alicyclic diol and the aliphatic dicarboxylic acid, alicyclic dicarboxylic acid and aliphatic hydroxycarboxylic acid or anhydride thereof is determined based on the aliphatic dicarboxylic acid, alicyclic dicarboxylic acid and aliphatic An aliphatic diol or cycloaliphatic diol of 1.02 to 1.2 mol is suitable for 1 mol of hydroxycarboxylic acid or anhydride thereof.

  The (biodegradable high molecular weight) aliphatic polyester produced by the production method of the present invention is a trivalent or higher aliphatic polyhydric alcohol, trivalent within the range not impairing the object of the present invention during the esterification reaction. By using at least one kind of polyvalent aliphatic compound selected from the group consisting of the above aliphatic polybasic acids or derivatives thereof, for example, a branch is introduced into the molecule of the aliphatic polyester, and its molecular weight distribution As a result, the aliphatic polyester can be molded into films and sheets having excellent physical properties.

  Examples of trihydric or higher aliphatic polyhydric alcohols include glycerin, trimethylolpropane, pentaerythlit, triallyl isocyanurate ethylene oxide adducts, and the like. Further, glycidol, which is a monoepoxy compound obtained by dehydrating glycerin, which is an aliphatic trihydric alcohol, can also be used.

  As the aliphatic polyvalent hydroxycarboxylic acid having 3 or more alcoholic hydroxyl groups and carboxylic acid groups in one molecule and its anhydride, both commercially available products can be used, but they can be obtained at low cost. Are preferably malic acid, tartaric acid and citric acid.

  In the method for producing an aliphatic polyester of the present invention, a tribasic or higher polybasic acid and its anhydride may be added. Examples thereof include trimesic acid, propanetricarboxylic acid, trimellitic anhydride, pyromellitic anhydride. Examples thereof include acid, benzophenone tetracarboxylic acid anhydride, and cyclopentatetracarboxylic acid anhydride. Among these, trimellitic anhydride and pyromellitic anhydride are particularly preferable.

  Each component of said polyhydric aliphatic compound can be mixed and used as needed. The amount of the polyvalent aliphatic compound used is 0.1 to 5 mol% in total with respect to 100 mol% of the aliphatic dicarboxylic acid, alicyclic dicarboxylic acid and aliphatic hydroxycarboxylic acid or their anhydride components as a whole. , Can be added from the beginning of the esterification reaction.

  The method for producing an aliphatic polyester of the present invention includes an esterification reaction using the alcohol, the carboxylic acid, the carboxylic acid anhydride and / or the hydroxycarboxylic acid, and a deglycolization reaction.

  In the method for producing an aliphatic polyester of the present invention, first, the esterification reaction is performed. The esterification reaction can be carried out at 130 to 300 ° C., preferably 160 to 250 ° C. for 5 to 16 hours in an inert gas atmosphere. At a temperature lower than 130 ° C., the reaction rate is slow and the practicality is poor. Also, at a temperature higher than 300 ° C., the risk of decomposition of the aliphatic polyester is increased and it is better to avoid it. Therefore, it is preferable to carry out the esterification reaction as the first step at a temperature between 180 and 220 ° C. The esterification reaction is carried out until the acid value of the aliphatic polyester reaches 30 or less, preferably 15 or less, more preferably 10 or less. In this case, the higher the molecular weight of the aliphatic polyester, the more smoothly the molecular weight can be increased by the subsequent deglycolation reaction. Therefore, it is desirable to obtain a higher molecular weight aliphatic polyester. The subsequent deglycolization reaction is carried out at 170-230 ° C. for 2-16 hours under a reduced pressure of 5 Torr or less. More preferably, it is carried out at 180 to 210 ° C. under a high vacuum of 1 Torr or less from the viewpoint of reaction rate and prevention of decomposition of the aliphatic polyester. The resulting aliphatic polyester has substantially all hydroxyl groups at the end groups and has an acid value of substantially zero.

  In the present invention, a deglycolization reaction is performed subsequent to the esterification reaction, and the aliphatic polyester obtained by the esterification reaction has a number average molecular weight of 5,000 or more, or a weight average molecular weight of 30,000 or more, preferably The number average molecular weight must be 5,000 or more and the weight average molecular weight should be 30,000 or more. For this purpose, a catalyst must be used. Examples thereof include organic or inorganic metal compounds of at least one metal selected from the group consisting of titanium, tin, antimony, cerium, germanium, zinc, cobalt, manganese, iron, aluminum, magnesium, calcium and strontium The amount used is 0.001 to 0.5 parts by weight with respect to 100 parts by weight of the produced aliphatic polyester. If the amount of these catalysts used is less than 0.001 part by weight, the deglycolization reaction becomes slow and impractical, and even if it is used in an amount of more than 0.5 part by weight, the decomposition reaction of the aliphatic polyester is conspicuously increased. Absent. The desired amount used varies depending on the type of metal, but is 0.005 to 0.2 parts by weight. As these catalysts, for example, metal alkoxides, organic acid salts, chelates, oxides and the like are used, and in particular, organometallic compounds of titanium, for example, compounds such as alkyl titanate, titanium oxyacetylacetonate, and titanium oxalate. Useful. Aliphatic polyesters, so-called biodegradable polyesters, are subject to microbial degradation in the soil, but these catalysts are expected to remain in the soil and must be a safe type of metal compound. From such a point of view, desirable metal compounds include compounds such as titanium, germanium, zinc, magnesium and calcium.

  Furthermore, one of the characteristics of the present invention is that, after the deglycolization reaction is completed, a desired amount of the polyvalent isocyanate compound is added to the aliphatic polyester after the deglycolization reaction in the molten state to thereby obtain the aliphatic polyester obtained. The number average molecular weight can be 10,000 or more, the weight average molecular weight can be 50,000 or more, the number average molecular weight can be 10,000 or more, and the weight average molecular weight can be 50,000 or more. Regarding the melt viscosity of the aliphatic polyester, the weight average molecular weight contributes more than the number average. For example, in film forming or the like, if the number average molecular weight is the same level but the weight average molecular weight is different, the moldability is different and it is desirable that the weight average molecular weight is as large as possible. This is the reason why the weight average molecular weight is specified in the present invention.

  In the production method of the present invention, a phosphorus compound is added and mixed at any stage, that is, during or after the esterification reaction, during or after the deglycolization reaction, or during or after the reaction using the isocyanate. It has one feature. For example, as described above, a phosphorus compound can be added and mixed during the esterification (polycondensation) reaction of the aliphatic polyester. The phosphorus compound is considered to act as a catalyst for the ring-opening polymerization reaction, and actually has an effect of reducing the cyclic oligomer. Examples of the phosphorus compound used in the method of the present invention include the following types.

(A) Phosphoric acid and alkyl esters thereof: As commercially available products, trialkyl phosphates such as trimethyl phosphate, triethyl phosphate, tributyl phosphate, trioctyl phosphate, tridecyl phosphate, alkyl acidic phosphates (alkyl group is methyl, isopropyl, Butyl, octyl, etc.).
(B) Phosphonic acid organic esters: Examples of commercially available products include dibutylbutylphosphonate.
(C) Phosphorous acid: When used alone or in combination with other phosphorus compounds, excellent ring-opening efficiency for cyclic oligomers and a strong hue stabilizing effect for aliphatic polyesters are observed.
(D) Phosphorous acid organic esters: For example, dibutyl hydrogen phosphite is commercially available and can be used in the present invention. In addition, triphenyl phosphite, diphenylisodecyl phosphite, phenyl diisodecyl phosphite, tris (mono or dinonylphenyl) phosphite, trisisodecyl phosphite and the like can be mentioned.
(E) Other inorganic phosphorus compounds: For example, polyphosphoric acid and the like.

  Since commercially available phosphoric acid mostly contains water, polyphosphoric acid has practical value without causing a decrease in the molecular weight of the aliphatic polyester. Diphosphorus pentoxide can also be used, but it is difficult to handle due to its strong hygroscopicity. In the case of producing polyolefins and the like, if inorganic phosphorus compounds such as phosphoric acid and phosphorous acid are used as they are, there is a difficulty in uniformly mixing them in terms of miscibility. Even if attention is paid to the moisture contained in the system compound, it can be added and mixed at a high temperature as it is. Among the phosphorous compounds mentioned above, phosphorous acid and phosphorous acid organic esters exhibit excellent effects and are sufficient for the purpose of the present invention, so that the present invention will be described mainly.

The amount of the phosphorus compound used in the method of the present invention varies depending on the type and amount of the catalyst used in the deglycolization reaction, but is more preferably 28 to 3.0 × 10 ³ times moles per mole of the catalyst. is a 28 to 10 ^2-fold molar. This is because if the amount is less than 3.0 times mol, the above-described effects hardly appear. Moreover, even if it exceeds 3.0 * 10 < ³ > times mole, it is because there is not only the effect which increased, but it becomes economically disadvantageous. Phosphorous compounds such as phosphorous acid are added to the aliphatic polyester which is a prepolymer melted at a temperature of 130 ° C. or higher and 300 ° C. or lower.

  The high molecular weight aliphatic polyester having a number average molecular weight of 10,000 or more, a weight average molecular weight of 50,000 or more, or a number average molecular weight of 10,000 or more and a weight average molecular weight of 50,000 or more obtained by the present invention is It is a biodegradable high molecular weight aliphatic polyester that exhibits biodegradability in soil and water and disappears in about 3 months to 1 year depending on the composition. It goes without saying that organic or inorganic fillers, reinforcing agents, stabilizers, lubricants, oligomers, polymers and the like can be used in combination with the biodegradable high molecular weight aliphatic polyester obtained by the present invention.

  Hereinafter, the present invention will be described in more detail with reference to examples. The measurement method used in this example is first described below. In addition, the density | concentration of the cyclic dimer (cyclodimer, CD) which is a causative substance of a bleed was described as a representative value as a parameter | index of cyclic oligomer content (residual amount) in aliphatic polyester. As a means for measuring this, gas chromatographic analysis was used.

[Gas chromatographic analysis]
Model used: GC-14B manufactured by Shimadzu Corporation was used.
120 μm pressed film: Molded at 180 ° C., preheated for 1 minute, pressed at 150 kg / cm ² and pressed for 30 seconds, the film was immersed in THF for 24 hours, and CD in the extract (THF) was quantified.
Further, the weight average molecular weight (hereinafter referred to as “Mw”) was analyzed using gel chromatography.

[Gel chromatography]
Model used: Measurement was performed under the following conditions using a Shodex GPC System-11 manufactured by Showa Denko KK.
Solvent: hexafluoroisopropyl alcohol containing 15 mmol / l ammonium acetate was used.
Aliphatic polyester concentration in the solution: 0.1% by mass.
Calibration curve: PMMA standard sample (Showa Denko, Shodex Standard M-75) was used.

Example 1
The 70 liter reactor was purged with nitrogen and charged with 16.03 kg (105 mol%) of 1,4-butanediol and 20.0 kg (100 mol%) of succinic acid. Subsequently, 3.58 g (0.013 mol) of the catalyst tetraisopropoxytitanium was also added in advance. The temperature was raised in a nitrogen stream, and the esterification reaction by dehydration condensation was carried out at 140 to 220 ° C. for 4.5 hours, and further, the nitrogen was stopped, and 1.5 hours under a reduced pressure of 260 to 2600 Pa. The produced aliphatic polyester had an acid value of 20 mg KOH / g, a number average molecular weight (Mn) of 4,800, and a weight average molecular weight (Mw) of 12,870.

  Subsequently, the temperature was set to 215 to 220 ° C., and a vacuum pump was applied to a vacuum of 2.0 to 0.3 mmHg, and deglycolization reaction was performed for 1.5 hours. The resulting aliphatic polyester (0-A) had a number average molecular weight (Mn) of 23,000, a weight average molecular weight (Mw) of 44,000, and a cyclodimer (CD) content of 9,300 ppm.

Subsequently, 29.16 g (0.36 mol) of phosphorous acid ( 21.0 × 10 ⁻⁴ mol relative to 1 mol of raw material succinic acid) was added under a normal pressure nitrogen stream. The temperature was 240 to 245 ° C., and the reaction was carried out for 1.5 hours under a reduced pressure of 2.0 to 0.3 mmHg with a vacuum pump. Mn of the obtained aliphatic polyester (0-B) was 24,000, Mw was 78,000, and CD content was 4,500 ppm.
Furthermore, the reaction was performed at 240 to 245 ° C. under a reduced pressure of 2.0 to 0.3 mmHg for 2 hours. Mn of the obtained aliphatic polyester (0-C) was 33,000, Mw was 134,000, and CD content was 1,800 ppm.

(Example 2)
The esterification reaction and deglycolization were carried out under the same conditions as in Example 1 except that the amount of phosphorous acid added was (3.6 mol) ( 210 × 10 ⁻⁴ mol per mol of raw succinic acid ) Reaction was performed.
The Mn of the aliphatic polyester (2-A) immediately before the addition and mixing of phosphorous acid was 23,200, the Mw was 45,000, and the CD content was 9500 ppm.
Subsequently, phosphorous acid was added and mixed, the temperature was adjusted to 240 to 245 ° C., and the reaction was carried out under a reduced pressure of 2.0 to 0.3 mmHg with a vacuum pump for 1.5 hours. Mn of the obtained aliphatic polyester (2-B) was 24,000, Mw was 81,000, and CD content was 4,200 ppm.
Furthermore, the reaction was performed at 240 to 245 ° C. under a reduced pressure of 2.0 to 0.3 mmHg for 2 hours. Mn of the obtained aliphatic polyester (2-C) was 33,000, Mw was 156,000, and CD content was 1400 ppm.

(Comparative Example 1)
Under the same conditions as in Example 1 except that the amount of phosphorous acid added and mixed (10.5 × 10 ⁻⁴ mol per 1 mol of raw succinic acid) (0.18 mol) , the esterification reaction and Deglycolization reaction was performed.
The Mn of the aliphatic polyester (1-A) immediately before the addition and mixing of phosphorous acid was 23,200, the Mw was 42,000, and the CD content was 9400 ppm.
Subsequently, phosphorous acid was added and mixed, the temperature was adjusted to 240 to 245 ° C., and the reaction was performed with a vacuum pump under a reduced pressure of 2.0 to 0.3 mmHg for 1.5 hours. Mn of the obtained aliphatic polyester (1-B) was 23,000, Mw was 44,000, and CD content was 6,800 ppm.
Furthermore, the reaction was performed at 240 to 245 ° C. under a reduced pressure of 2.0 to 0.3 mmHg for 2 hours. Mn of the obtained aliphatic polyester (1-C) was 24,000, Mw was 51,000, and CD content was 5800 ppm.

FIG. 1 shows the relationship between the elapsed time under reduced pressure, the CD content, and the weight average molecular weight of the aliphatic polyester in Examples 1 and 2 and Comparative Example 1. In Examples 1 and 2 of the present invention, it was found that the CD content decreased rapidly as the decompression time increased and progressed, and the weight average molecular weight of the aliphatic polyester increased at an accelerated rate.
On the other hand, in Comparative Example 1, the decrease in the CD content was slight compared to the examples of the present invention, and it can be said that the weight average molecular weight of the aliphatic polyester hardly increased.

As can be seen from the above, it was found that an aliphatic polyester having a CD content of 4000 ppm or less can be produced by the production method of the present invention. Such a CD content is sufficiently low for the aliphatic polyester to have various physical properties such as good appearance characteristics.
The CD content in the aliphatic polyester of the present invention obtained in the examples was 4000 ppm or less, whereas in the comparative example, the CD content was higher than 4000 ppm.
In addition, while the production method of the present invention was able to efficiently produce an aliphatic polyester having a sufficiently large weight average molecular weight, in the comparative example, the weight average molecular weight of the aliphatic polyester hardly increased, and a large weight average The molecular weight could not be obtained efficiently.
The aliphatic polyester obtained by the production method of the present invention was found to have a sufficiently large weight average molecular weight to have various physical properties such as thermal stability, post-processing and other various uses. .

Claims (8)

A method for producing an aliphatic polyester by reacting an aliphatic polybasic acid or a derivative thereof with an aliphatic polyhydric alcohol, wherein the aliphatic polybasic acid or a derivative thereof is an aliphatic dicarboxylic acid or an alicyclic dicarboxylic acid. And at least one selected from aliphatic hydroxycarboxylic acids or anhydrides thereof, and the aliphatic polyhydric alcohol is at least one selected from aliphatic diols and alicyclic diols. After adding and mixing 28-3.0 × 10 ³ times mole of the compound with respect to 1 mole of the catalyst, polycondensation is carried out under conditions of a temperature of 130-300 ° C. and a degree of vacuum of 10 mmHg or less until an aliphatic polyester having a required molecular weight is obtained. the reaction carried out, characterized in that the cyclic dimer content in the aliphatic polyester obtained or less 4000 ppm, aliphatic polyester The method of production. Using 100 parts by weight of the aliphatic polyester as a prepolymer, 0.1-5 parts by weight of a polyisocyanate compound is further reacted with the prepolymer, so that the number average molecular weight of the aliphatic polyester is 10,000 or more and / or weight. 2. The method for producing an aliphatic polyester according to claim 1, wherein the average molecular weight is 50,000 or more. The method for producing an aliphatic polyester according to claim 1 or 2, comprising a trihydric or higher polyhydric alcohol and a tribasic or higher polybasic acid as auxiliary components of the aliphatic polyester or the prepolymer. The polyhydric alcohol is selected from the group consisting of ethylene glycol, 1,4-butanediol, 1,6-hexanediol, decamethylene glycol, neopentyl glycol and 1,4-cyclohexanedimethanol units as aliphatic diol units. has units, said polybasic acid or derivative thereof is succinic acid as aliphatic dicarboxylic acid unit, adipic acid, suberic acid, has a unit selected from the group consisting of sebacic acid and dodecanoic acid units, claims 1 3 The manufacturing method of the aliphatic polyester of any one of these. The method for producing an aliphatic polyester according to claim 3 , wherein the trihydric or higher polyhydric alcohol is one or more selected from the group consisting of trimethylolpropane, glycerin, and pentaerythritol.   The method for producing an aliphatic polyester according to claim 3, wherein the aliphatic hydroxycarboxylic acid is one or more selected from the group consisting of malic acid, citric acid and tartaric acid. The aliphatic polyester or the prepolymer may be trimesic acid, propanetricarboxylic acid, trimellitic anhydride, pyromellitic anhydride, benzophenonetetracarboxylic anhydride and cyclopentanetetracarboxylic acid as a trivalent or tetravalent polybasic acid. The method for producing an aliphatic polyester according to any one of claims 1 to 6 , further comprising at least one selected from the group consisting of anhydrides. The method for producing an aliphatic polyester according to claim 1 or 2 , wherein the phosphorus compound is phosphorous acid.

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