Production method and production apparatus for aliphatic polyester resin

Abstract

The present invention addresses the problem of providing a method and an apparatus for producing an aliphatic polyester resin having a low molecular weight with high accuracy in a short time. The problem is solved by a method for producing an aliphatic polyester resin having a low molecular weight, the method including an alkali treatment step in which an aliphatic polyester resin and an alkali are mixed with each other in a reaction tank. The alkali treatment step includes an alkali addition control step in which the addition amount and / or the addition rate of the alkali is controlled using the molecular weight of the aliphatic polyester resin in the reaction tank as an index.

Description

Aliphatic polyester resin manufacturing method and manufacturing apparatus

[0001] The present invention relates to a method for producing a low-molecular-weight aliphatic polyester resin, and also to an apparatus for producing a low-molecular-weight aliphatic polyester resin.

[0002] Aliphatic polyester resins are used in a variety of applications. Among them, biodegradable resins such as polyhydroxyalkanoic acid (PHA) have attracted attention as environmentally friendly resins due to their biodegradability. Such aliphatic polyester resins usually have a high molecular weight, and techniques for reducing their molecular weight are known (see, for example, Patent Document 1).

[0003] International Publication No. 2022 / 113530

[0004] The molecular weight of aliphatic polyester resins (e.g., P3HB3HH) is generally adjusted by lowering the molecular weight under high-temperature, alkaline conditions. However, adjusting the molecular weight to a target value requires analyzing the molecular weight each time and predicting the rate of reduction while proceeding with the reaction. High pH conditions are preferable to shorten the adjustment time, but pH meters do not have high measurement accuracy in the high pH range, and pH control results in an unstable molecular weight reduction rate, making it prone to out-of-specification results. Furthermore, adjustment under relatively low pH conditions presents a problem in that it takes a long time. In other words, while the technology described in Patent Document 1 is excellent, there is room for improvement.

[0005] SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a method and an apparatus for producing a low-molecular-weight aliphatic polyester resin in a short time and with high accuracy.

[0006] As a result of intensive research into solving the above-mentioned problems, the present inventors have found that the above-mentioned problems can be solved by controlling the amount of alkali added using the molecular weight of the aliphatic polyester resin as an indicator, and have thus completed the present invention.

[0007] Therefore, one aspect of the present invention is a method for producing a low-molecular-weight aliphatic polyester resin (hereinafter referred to as "the present production method"), which includes an alkali treatment step of mixing an aliphatic polyester resin with an alkali in a reaction tank, and the alkali treatment step includes an alkali addition control step of controlling the amount and / or addition rate of the alkali using the molecular weight of the aliphatic polyester resin in the reaction tank as an indicator.

[0008] Another aspect of the present invention is a production apparatus for a low-molecular-weight aliphatic polyester resin (hereinafter referred to as "the production apparatus") comprising a reaction vessel, an alkali introduction section for introducing alkali into the reaction vessel, and an alkali treatment section, wherein the alkali treatment section includes a measurement section for measuring the molecular weight of the aliphatic polyester resin in the reaction vessel, and an alkali addition control section for controlling the amount and / or rate of alkali addition in the alkali introduction section using the molecular weight of the aliphatic polyester resin in the reaction vessel measured by the measurement section as an index.

[0009] According to the present invention, it is possible to provide a method and an apparatus for producing a low-molecular-weight aliphatic polyester resin in a short time and with high accuracy.

[0010] 1 is a schematic diagram showing an example of the production apparatus; FIG. 2 is a diagram showing an example of the relationship between the change in molecular weight of an aliphatic polyester resin over time and the rate of alkali addition in the production method; FIG. 3 is a diagram showing the change in molecular weight of an aliphatic polyester resin over time in Examples 1 to 3; FIG. 4 is a diagram showing the change in pH over time in Examples 1 to 3; FIG. 5 is a diagram showing the change in alkali addition rate over time in Examples 1 to 3. The upper diagram is a diagram showing the relationship between the change in molecular weight of an aliphatic polyester resin over time and the rate of alkali addition in Example 4; The lower diagram is a diagram showing the change in pH over time in Example 4; The upper diagram is a diagram showing the relationship between the change in molecular weight of an aliphatic polyester resin over time and the rate of alkali addition in Example 5; The lower diagram is a diagram showing the change in pH over time in Example 5; The upper diagram is a diagram showing the change in molecular weight of an aliphatic polyester resin over time in Comparative Examples 1 to 3; The lower diagram is a diagram showing the change in pH over time in Comparative Examples 1 to 3; The lower diagram is a diagram showing the change in alkali addition rate over time in Comparative Examples 1 to 3.

[0011] An embodiment of the present invention will be described in detail below. In this specification, unless otherwise specified, "A to B" representing a numerical range means "A or more, B or less." In addition, all documents described in this specification are incorporated herein by reference.

[0012] [1. Overview of the Invention] As described above, the molecular weight reduction of aliphatic polyester resins is generally carried out under high-temperature, alkaline conditions. In this case, in order to adjust the molecular weight of the aliphatic polyester resin to a target value, it is necessary to proceed with the reaction while analyzing the molecular weight each time and predicting the rate of reduction. Here, high pH conditions are preferred to shorten the adjustment time. However, because pH meters do not have high measurement accuracy in the high pH range, control by pH results in an unstable molecular weight reduction rate, which is prone to off-specification results, resulting in low molecular weight accuracy of the resulting aliphatic polyester resin. Furthermore, adjustment under relatively low pH conditions requires a long adjustment time.

[0013]

[0005] Therefore, the present inventors conducted extensive research to solve the above problems, and as a result, they discovered for the first time that the above problems can be solved by controlling the amount of alkali added using the molecular weight of the aliphatic polyester resin as an indicator. Specifically, they discovered that by supplying a relatively high amount and / or rate of alkali to a reaction vessel containing an aliphatic polyester resin at the beginning of the reaction, and then gradually controlling the amount and / or rate of alkali addition as the molecular weight of the aliphatic polyester resin decreases, it is possible to produce a low-molecular-weight aliphatic polyester resin in a short time and with high accuracy.

[0014] Thus, a manufacturing method and manufacturing apparatus capable of producing low-molecular-weight aliphatic polyester resins in a short time and with high accuracy have not been known until now, and are extremely advantageous in fields where low-molecular-weight aliphatic polyester resins are required. In this specification, "molecular weight" may refer to either weight-average molecular weight or number-average molecular weight, but is preferably weight-average molecular weight because of its strong influence on resin properties. In this specification, the "molecular weight" of an aliphatic polyester resin means "weight-average molecular weight" unless otherwise specified. Furthermore, in this specification, the weight-average molecular weight of an aliphatic polyester resin refers to a value measured by the method described in the Examples. The configuration of this manufacturing method and manufacturing apparatus is described in detail below.

[0015] 2. Method for Producing Aliphatic Polyester Resin This production method will be described in detail with reference to Fig. 2. However, this production method is not limited to the one shown in Fig. 2.

[0016] For convenience, Figure 2 illustrates the objective of reducing the molecular weight of an aliphatic polyester resin with a molecular weight of 1.75 million to 700,000. At the beginning of the reaction (Figure 2(a)), when the molecular weight is high relative to the target molecular weight, the amount and / or rate of alkali addition is set high. While measuring the molecular weight of the aliphatic polyester resin over time, the amount and / or rate of alkali addition is decreased as the molecular weight of the aliphatic polyester resin decreases (Figures 2(b) to 2(d)). When the molecular weight approaches the target molecular weight, the addition of alkali is stopped (Figure 2(e)), and the pH and / or temperature are lowered to terminate the reaction. In this way, by controlling the amount of alkali addition while measuring the molecular weight over time using the molecular weight of the aliphatic polyester resin as an indicator, a low-molecular-weight aliphatic polyester resin can be produced in a short time and with high precision. Furthermore, by decreasing the amount of alkali addition while measuring the molecular weight according to a predetermined rule for each target molecular weight, the rate of molecular weight reduction slows as the molecular weight approaches the endpoint molecular weight, even if the initial molecular weight is different, making it easier to adjust the molecular weight to the target molecular weight. Furthermore, as the amount of alkali is reduced, the amount of alkali consumed in the reaction exceeds the amount of alkali added, causing the pH to decrease and slowing down the reaction rate.

[0017] (Alkali Treatment Step) This production method includes an alkali treatment step in which an aliphatic polyester resin and an alkali are mixed in a reaction tank. Furthermore, in this production method, the alkali treatment step includes an alkali addition control step in which the amount and / or rate of alkali addition is controlled using the molecular weight of the aliphatic polyester resin in the reaction tank as an indicator. By using the molecular weight of the aliphatic polyester resin in the reaction tank as an indicator, the reaction can be carried out more quickly and accurately than conventional methods for reducing molecular weight that use pH as an indicator.

[0018] (Alkali Addition Control Step) In one embodiment of the present invention, the alkali addition control step includes two or more steps in which the alkali addition amount and / or addition rate are different, and it is preferable to decrease the alkali addition amount and / or addition rate as the molecular weight of the aliphatic polyester resin in the reaction tank decreases. As described above, the rate of depolymerization of the aliphatic polyester resin in the alkali treatment step is proportional to the amount of alkali in the reaction system; the greater the amount of alkali, the faster the depolymerization proceeds, while the smaller the amount of alkali, the slower the depolymerization proceeds. In the alkali addition control step, by increasing the alkali addition amount and / or addition rate and supplying a relatively large amount of alkali to the reaction system at the early stage of the reaction when the molecular weight is relatively high compared to the target molecular weight, the molecular weight can be rapidly reduced in the alkali treatment step, and the reaction time required to obtain an aliphatic polyester resin of the target molecular weight can be shortened. Furthermore, by reducing the amount and / or rate of alkali addition, preferably by reducing the amount and / or rate in stages, in accordance with the decrease in molecular weight of the aliphatic polyester resin in the reaction tank, the rate of molecular weight reduction can be controlled to a relatively slow rate, making it easy to stop the reaction when the desired molecular weight is reached, and thus enabling the accurate production of an aliphatic polyester resin having a target molecular weight.

[0019] For example, when the molecular weight of the aliphatic polyester resin in the reaction tank is greater than the target molecular weight of the finally obtained low-molecular-weight aliphatic polyester resin + 600,000, the amount and / or rate of alkali addition is set high. By setting the amount and / or rate of alkali addition high when the target molecular weight is reached, the molecular weight can be rapidly reduced in the early stage of the reaction when the molecular weight is relatively high compared to the target molecular weight, and the reaction time required to obtain an aliphatic polyester resin of the target molecular weight can be shortened.

[0020] As the molecular weight of the aliphatic polyester resin in the reaction vessel decreases, the amount and / or rate of alkali addition is decreased, thereby controlling the rate of molecular weight reduction and bringing the molecular weight closer to the target molecular weight.

[0021] The method for measuring the molecular weight of the aliphatic polyester resin in the reaction vessel is not particularly limited, but for example, it can be measured by the method described in the Examples.

[0022] In one embodiment of the present invention, the alkali addition control step is performed by controlling the amount of alkali added to W Ａ and / or the addition rate is S Ａ After performing step A of adding alkali, the amount of alkali added is W Ｂ and / or the addition rate is S Ｂ The step B includes adding an alkali in an amount W Ａ and W Ｂ , and / or the addition rate S Ａ and S Ｂ may be a process in which W satisfies the following formula: Ａ >W Ｂ S Ａ >S Ｂ In one embodiment of the present invention, the alkali addition control step preferably includes three or more steps in which the alkali addition amount and / or addition rate are different. By including three or more steps in which the alkali addition amount and / or addition rate are different, the alkali can be added stepwise, and the rate of molecular weight reduction can be controlled while approaching the target molecular weight. The number of steps is preferably three or more, more preferably four or more, and even more preferably five or more.

[0023] The initial molecular weight of the aliphatic polyester resin in the reaction tank (before molecular weight adjustment) is, for example, 500,000 to 3,000,000, and preferably 1,000,000 to 2,000,000. When the molecular weight is in the above range, there is an advantage that the molecular weight can be easily adjusted to a target range within a specified time.

[0024] The target molecular weight of the low-molecular-weight aliphatic polyester resin finally obtained by this production method is not particularly limited as long as it is lower than the initial molecular weight, but is, for example, 50,000 to 1.5 million, preferably 100,000 to 1.2 million, more preferably 150,000 to 1 million, even more preferably 200,000 to 800,000, and particularly preferably 500,000 to 800,000. By lowering the molecular weight of the aliphatic polyester resin so that it falls within the above range, the aliphatic polyester resin has the advantage of being applicable to a variety of processing methods.

[0025] In one embodiment of the present invention, in the alkali addition control step, the weight-average molecular weight of the aliphatic polyester resin is preferably reduced by 200,000 or more, more preferably by 300,000 or more, even more preferably by 400,000 or more, and even more preferably by 500,000 or more. There are no particular limitations on the upper limit of the weight-average molecular weight to be reduced, and it may be, for example, 2,950,000 or less, 2,800,000 or less, 2,000,000 or less, 1,500,000 or less, 1,200,000 or less, or 1,000,000 or less. That is, the low molecular weight aliphatic polyester resin produced by the present production method may be an aliphatic polyester resin having a weight average molecular weight 200,000 to 2,950,000 lower (reduced weight average molecular weight) than the initial aliphatic polyester resin, an aliphatic polyester resin having a weight average molecular weight 200,000 to 2,800,000 lower, an aliphatic polyester resin having a weight average molecular weight 300,000 to 2,000,000 lower, an aliphatic polyester resin having a weight average molecular weight 400,000 to 1,500,000 lower, an aliphatic polyester resin having a weight average molecular weight 400,000 to 1,200,000 lower, or an aliphatic polyester resin having a weight average molecular weight 500,000 to 1,000,000 lower.

[0026] The temperature of the reaction vessel in the alkali treatment step is preferably 40 to 80°C, more preferably 42 to 78°C, even more preferably 45 to 75°C, and particularly preferably 65 to 75°C. When the temperature of the reaction vessel in the alkali treatment step is within the above range, there is an advantage that the molecular weight adjustment rate is easily controlled. Furthermore, when the temperature of the reaction vessel in the alkali treatment step is within the above range, the amount of alkali used can be reduced, which results in a reduction in the number of times the alkali is removed in the subsequent centrifugation step, and furthermore, the reaction rate can be ensured, which is advantageous in terms of cost and time.

[0027] The reaction time in the alkali treatment step can be appropriately set depending on the resin amount and molecular weight of the initial aliphatic polyester resin in the reaction tank and the target molecular weight of the finally obtained low-molecular-weight aliphatic polyester resin. For example, when the molecular weight of the initial aliphatic polyester resin in the reaction tank is 1,000,000 to 3,000,000 and the target molecular weight of the finally obtained low-molecular-weight aliphatic polyester resin is 350,000, the reaction time in the alkali treatment step is, for example, 3 to 24 hours, preferably 5 to 20 hours, and more preferably 8 to 18 hours. The resin amount of the initial aliphatic polyester resin in the reaction tank can be set as desired.

[0028] The amount and / or rate of alkali addition based on the molecular weight of the aliphatic polyester resin in the reaction tank in the alkali addition control step is, for example, when the molecular weight of the aliphatic polyester resin in the reaction tank is 1,300,000 or more, the amount and / or rate of alkali addition is set so that the amount of alkali supplied to the reaction tank per hour is 3.5 to 4.5 g / hr (hour); when the molecular weight of the aliphatic polyester resin in the reaction tank is 1,100,000 or more and less than 1,300,000, the amount and / or rate of alkali addition is set so that the amount of alkali supplied to the reaction tank per hour is 2.5 g / hr or more and less than 3.5 g / hr; when the molecular weight of the aliphatic polyester resin in the reaction tank is 900,000 or more, When the molecular weight of the aliphatic polyester resin in the reaction tank is less than 1,100,000, the amount and / or rate of alkali addition is set so that the amount of alkali supplied to the reaction tank per hour is 1.5 g / hr or more and less than 2.5 g / hr; when the molecular weight of the aliphatic polyester resin in the reaction tank is 800,000 or more and less than 900,000, the amount and / or rate of alkali addition is set so that the amount of alkali supplied to the reaction tank per hour is 0.5 g / hr or more and less than 1.5 g / hr; when the molecular weight of the aliphatic polyester resin in the reaction tank is 700,000 or more and less than 800,000, the amount and / or rate of alkali addition is set so that the amount of alkali supplied to the reaction tank per hour is 0.0 g / hr or more (including 0) and less than 0.5 g / hr.

[0029] In one embodiment of the present invention, the alkali addition control step may include the steps of: adding 3.5 to 4.5 g / hr of alkali when the molecular weight of the aliphatic polyester resin in the reaction vessel is 1.3 million or more; adding 2.5 g / hr or more and 3.5 g / hr of alkali when the molecular weight of the aliphatic polyester resin in the reaction vessel is 1.1 million or more and less than 1.3 million; adding 1.5 g / hr or more and less than 2.5 g / hr of alkali when the molecular weight of the aliphatic polyester resin in the reaction vessel is 900,000 or more and less than 1.1 million; adding 0.5 g / hr or more and less than 1.5 g / hr of alkali when the molecular weight of the aliphatic polyester resin in the reaction vessel is 800,000 or more and less than 900,000; and adding 0.0 g / hr or more (including 0) and less than 0.5 g / hr of alkali when the molecular weight of the aliphatic polyester resin in the reaction vessel is 700,000 or more and less than 800,000.

[0030] <Alkali> In the alkali treatment step of the present production method, the aliphatic polyester resin is mixed with an alkali in a reaction tank. The alkali is a basic compound, and is not particularly limited, and examples thereof include alkali metal or alkaline earth metal hydroxides such as sodium hydroxide and potassium hydroxide; metal carbonates such as sodium carbonate and potassium carbonate; metal phosphates or metal hydrogen phosphates such as sodium phosphate, potassium phosphate, sodium hydrogen phosphate, and potassium hydrogen phosphate.

[0031] In one embodiment of the present invention, the alkali-containing basic compound is preferably an alkali metal hydroxide or an alkaline earth metal hydroxide, and more preferably sodium hydroxide. As the alkali-containing basic compound used in the alkali treatment step, one of the above-mentioned basic compounds may be used alone, or two or more of them may be used in combination.

[0032] In one embodiment of the present invention, the alkali is preferably an aqueous solution of any of the above basic compounds from the viewpoint of ease of handling.

[0033] <Aliphatic Polyester Resin> The aliphatic polyester resin in the present production method is not particularly limited, but examples include poly(3-hydroxyalkanoate) (hereinafter also referred to as "P3HA"), polylactic acid (PLA), polybutylene succinate (PBS), polybutylene succinate adipate, polybutylene adipate terephthalate, polybutylene succinate terephthalate, polycaprolactone, etc. Among these, P3HA is preferred from the viewpoint of industrial productivity. The aliphatic polyester resin may contain one type or two or more types.

[0034] The aliphatic polyester resin preferably contains 50% by weight or more of P3HA, more preferably 60% by weight or more, more preferably 70% by weight or more, even more preferably 80% by weight or more, even more preferably 90% by weight or more, and even more preferably 95% by weight or more, based on 100% by weight of the aliphatic polyester resin. The aliphatic polyester resin particularly preferably contains 100% by weight of P3HA, based on 100% by weight of the aliphatic polyester resin.

[0035] Hereinafter, poly(3-hydroxyalkanoate) will be taken as an example of an aliphatic polyester resin, and a detailed description will be given, including a method for producing a powder containing the aliphatic polyester resin.

[0036] The P3HA used in this production method is a polymer having a 3-hydroxyalkanoate unit as a constituent unit (monomer unit). In this specification, "3-hydroxyalkanoate" may also be referred to as "3HA." Specifically, P3HA is preferably a polymer containing a repeating unit represented by the following general formula (1): [-CHR-CH ２ -CO-O-]...(1).

[0037] In the general formula (1), R is C ｎ H ２ｎ＋１where n is an integer of 1 to 15. Examples of R include linear or branched alkyl groups such as methyl, ethyl, propyl, isopropyl, butyl, isobutyl, t-butyl, pentyl, and hexyl. n is preferably 1 to 10, and more preferably 1 to 8.

[0038] More specifically, examples of P3HA include poly(3-hydroxybutyrate) (P3HB), poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (P3HB3HH), poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (P3HB3HV), poly(3-hydroxybutyrate-co-4-hydroxybutyrate) (P3HB4HB), poly(3-hydroxybutyrate-co-3-hydroxyoctanoate) (P3HB3HO), poly(3-hydroxybutyrate-co-3-hydroxyoctadecanoate) (P3HB3HOD), poly(3-hydroxybutyrate-co-3-hydroxydecanoate) (P3HB3HD), and poly(3-hydroxybutyrate-co-3-hydroxyvalerate-co-3-hydroxyhexanoate) (P3HB3HV3HH). Among these, P3HB, P3HB3HH, P3HB3HV, and P3HB4HB are preferred because they can be easily produced industrially.

[0039] Furthermore, by changing the composition ratio of the repeating units, it is possible to change the melting point and degree of crystallinity, and as a result, it is possible to change physical properties such as Young's modulus and heat resistance, and it is possible to impart physical properties between those of polypropylene and polyethylene.In addition, from the viewpoint that it is easy to produce industrially as described above and is a physically useful plastic, P3HB3HH, which is a copolymer of 3-hydroxybutyric acid and 3-hydroxyhexanoic acid, is more preferred.

[0040] More specifically, P3HA is a copolymer having 3-hydroxybutyrate units and comonomer units, and the ratio of 3HB units to comonomer units (3HB units / comonomer units) in 100 mol% of all repeating units in the copolymer is preferably 70 / 30 (mol% / mol%) to 99 / 1 (mol% / mol%), more preferably 75 / 25 (mol% / mol%) to 97 / 3 (mol% / mol%), and even more preferably 80 / 20 (mol% / mol%) to 95 / 5 (mol% / mol%).

[0041] P3HA having such a ratio of each monomer unit can be prepared according to a method known to those skilled in the art, for example, the method described in WO 2009 / 145164. The ratio of each monomer unit in P3HA (i.e., the above-mentioned (3HB unit / comonomer unit)) can be determined by the method described in the Examples.

[0042] In one embodiment of the present invention, the method for producing P3HA is not particularly limited, and may be a production method by chemical synthesis or a production method using a microorganism. Among these, a production method using a microorganism is preferred. As for the method for producing P3HA using a microorganism, known methods can be applied, but it is preferable that it includes a culture step.

[0043] The method for culturing the microorganism that produces P3HA in the culturing step is not particularly limited, and for example, the method described in WO 2019 / 142717 can be used.

[0044] The microorganism that produces P3HA is not particularly limited as long as it is a microorganism that can produce PHA intracellularly. For example, microorganisms isolated from nature and deposited in a depository institution for strains (e.g., IFO, ATCC, etc.), or mutants and transformants that can be prepared from them, can be used. For example, the first microorganism to produce P3HB, an example of PHA, was Bacillus megaterium, discovered in 1925, and other natural microorganisms include Cupriavidus necator (formerly classified as Alcaligenes eutrophus and Ralstonia eutropha) and Alcaligenes latus. It is known that PHA accumulates intracellularly in these microorganisms.

[0045] Examples of bacteria that produce copolymers of hydroxybutyrate and other hydroxyalkanoates, which are examples of PHAs, include Aeromonas caviae, which produces P3HB3HV and P3HB3HH, and Alcaligenes eutrophus, which produces P3HB4HB. In particular, with regard to P3HB3HH, more preferred is Alcaligenes eutrophus AC32 (FERM BP-6038) (T. Fukui, Y. Doi, J. Bacteriol., 179, pp. 4821-4830 (1997)), into which genes encoding PHA synthases have been introduced, in order to increase the productivity of P3HB3HH. In addition to the above, the bacterial cells may be genetically modified microorganisms into which various PHA synthesis-related genes have been introduced depending on the PHA to be produced.

[0046] (Alkali Treatment) The present production method may include an alkali treatment (treatment including an operation of adding alkali) other than the alkali addition control step.

[0047] Alkali treatment other than the alkali addition control step can be, for example, an enzyme treatment to decompose proteins, etc., or centrifugation to remove impurities, and the pH, temperature, time, etc. may be controlled depending on the purpose.

[0048] (Pretreatment Step) In one embodiment of the present invention, the production method may further include a pretreatment step in which an optional treatment is performed on the aliphatic polyester resin before the alkali addition control step. The treatment performed on the aliphatic polyester resin in the pretreatment step is preferably performed after the culture step and before the alkali addition control step. The pretreatment step is not particularly limited, and known physical treatments, chemical treatments, and / or biological treatments can be applied. For example, the purification method described in WO 2010 / 067543 can be preferably applied. More specific examples of treatments performed on the aliphatic polyester resin in the pretreatment step include sterilization, enzyme treatment, surfactant treatment, hydrogen peroxide treatment, and centrifugation.

[0049] (Post-treatment process) In one embodiment of the present invention, the production method may further include a post-treatment process after the alkali addition control process, in which any treatment is performed on the aliphatic polyester resin after the alkali addition control process. The treatment performed on the aliphatic polyester resin in the post-treatment process is not particularly limited, and known physical treatments, chemical treatments, and / or biological treatments can be applied. For example, the purification method described in WO 2010 / 067543 can be preferably applied. More specific treatments performed on the aliphatic polyester resin in the post-treatment process include enzyme treatment, surfactant treatment, hydrogen peroxide treatment, centrifugation, filtration, drying, etc. In addition, the drying method in the post-treatment process is not particularly limited, and spray drying, fluidized bed drying, flash drying, rotary drying, vibration drying, band drying, etc. can be applied. For example, the drying method described in WO 2018 / 070492 can be preferably applied.

[0050] 3. Aliphatic Polyester Resin Production Apparatus Hereinafter, the production apparatus will be described in detail with reference to Fig. 1. However, the production apparatus is not limited to the one shown in Fig. 1.

[0051] The present production apparatus 10 carries out the above-described method for producing an aliphatic polyester resin, and includes a reaction vessel 1, an alkali introduction section 2 for introducing alkali into the reaction vessel 1, and an alkali treatment section 3. The present production apparatus 10 includes an aliphatic polyester resin introduction section 8, and the aliphatic polyester resin is introduced into the reaction vessel 1 from the aliphatic polyester resin introduction section 8.

[0052] The alkali treatment section 3 carries out the "alkali treatment step" in the above-mentioned method for producing an aliphatic polyester resin, and is composed of a measurement section 4 and a control section 5. The measurement section 4 measures the molecular weight of the aliphatic polyester resin in the reaction tank 1. The control section 5 controls the amount and / or rate of alkali addition in the alkali introduction section 2 using the molecular weight of the aliphatic polyester resin in the reaction tank measured in the measurement section 4 as an index.

[0053] In the alkali treatment section 3, when the molecular weight of the aliphatic polyester resin in the reaction vessel 1 is greater than the target molecular weight of the finally obtained low-molecular-weight aliphatic polyester resin + 600,000, the amount and / or rate of alkali addition in the alkali introduction section 2 is set high. Furthermore, as the molecular weight of the polyester resin in the reaction vessel 1 decreases, the amount and / or rate of alkali addition in the alkali introduction section 2 is decreased. This allows an aliphatic polyester resin of the target molecular weight to be obtained.

[0054] The alkali treatment unit 3 is controlled via the control unit 5. The alkali treatment unit 3 is preferably controlled so that the amount and / or rate of alkali addition is decreased as the molecular weight of the aliphatic polyester resin in the reaction tank 1 decreases. This allows the molecular weight of the aliphatic polyester resin to be rapidly reduced at the beginning of the reaction, and then gradually reduced as the molecular weight approaches the target molecular weight.

[0055] Furthermore, the present manufacturing apparatus 10 may be equipped with a temperature adjustment unit 7 that sets the temperature of the reaction tank 1 to preferably 40 to 80°C, more preferably 42 to 78°C, and even more preferably 45 to 75°C.

[0056] The low molecular weight aliphatic polyester resin obtained by the present production method or production apparatus can be used for a variety of purposes, such as paper, film, sheet, tube, plate, rod, container (e.g., bottle container), bag, and parts.

[0057] The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope of the claims. Embodiments obtained by appropriately combining the technical means disclosed in different embodiments are also included in the technical scope of the present invention.

[0058] That is, one embodiment of the present invention is as follows: <1> A method for producing a low-molecular-weight aliphatic polyester resin, comprising an alkali treatment step of mixing an aliphatic polyester resin with an alkali in a reaction vessel, the alkali treatment step including an alkali addition control step of controlling the amount and / or rate of alkali addition using the molecular weight of the aliphatic polyester resin in the reaction vessel as an indicator. <2> The method according to <1>, wherein the alkali addition control step includes two or more steps with different amounts and / or rates of alkali addition, and the amount and / or rate of alkali addition is reduced as the molecular weight of the aliphatic polyester resin in the reaction vessel decreases. <3> The method according to <1> or <2>, wherein the alkali addition control step includes three or more steps with different amounts and / or rates of alkali addition. <4> The method according to any one of <1> to <3>, wherein the weight-average molecular weight of the aliphatic polyester resin is reduced by 300,000 or more in the alkali addition control step. <5> The method according to any one of <1> to <4>, further including a pretreatment step. <6> The manufacturing method according to any one of <1> to <5>, wherein the temperature of the reaction vessel in the alkali treatment step is 40 to 80°C. <7> The manufacturing method according to any one of <1> to <6>, wherein the aliphatic polyester resin is poly(3-hydroxyalkanoate). <8> An apparatus for manufacturing a low-molecular-weight aliphatic polyester resin, comprising: a reaction vessel; an alkali introduction section for introducing alkali into the reaction vessel; and an alkali treatment section, wherein the alkali treatment section comprises: a measurement section for measuring the molecular weight of the aliphatic polyester resin in the reaction vessel; and an alkali addition control section for controlling the amount and / or addition rate of alkali in the alkali introduction section using the molecular weight of the aliphatic polyester resin in the reaction vessel measured by the measurement section as an index. <9> The manufacturing apparatus according to <8>, wherein the alkali addition control section includes two or more steps in which the amount and / or addition rate of alkali is different, and controls the amount and / or addition rate of alkali to decrease as the molecular weight of the aliphatic polyester resin in the reaction vessel decreases.<10> The production apparatus according to <8> or <9>, wherein the alkali addition control unit controls the alkali addition so as to include three or more processes in which the alkali addition amount and / or addition rate is different. <11> The production apparatus according to any one of <8> to <10>, wherein the alkali addition control unit controls the alkali addition so as to reduce the weight average molecular weight of the aliphatic polyester resin by 300,000 or more. <12> The production apparatus according to any one of <8> to <11>, further comprising a temperature adjustment unit that sets the temperature of the reaction vessel to 40 to 80°C. <13> The production apparatus according to any one of <8> to <12>, wherein the aliphatic polyester resin is poly(3-hydroxyalkanoate).

[0059] The present invention will be described in more detail below based on examples, but the present invention is not limited to these examples. In these examples, "P3HA" is used as "P3HB3HH", and "P3HA" can be read as "P3HB3HH". In these examples, molecular weight refers to the weight average molecular weight (Mw).

[0060] [Measurement and Evaluation Methods] Measurements and evaluations in the examples and comparative examples were carried out by the following methods.

[0061] <Molecular Weight Measurement> The molecular weight (weight average molecular weight) of the aliphatic polyester resin (P3HA) was measured by the following procedure. Specifically, a culture solution containing the aliphatic polyester resin (P3HA) was diluted with distilled water, and 1 mL of a slurry with a solid content of 1 mg / 1 mL was centrifuged, and the supernatant was removed. Ethanol was added to the resulting precipitate (aliphatic polyester resin), dispersed in ethanol, and centrifuged. The supernatant was removed, and the precipitate was dissolved in 1 mL of chloroform, and the insoluble matter was precipitated by centrifugation. The molecular weight of this solution was measured using a Shimadzu GPC system equipped with "TSKgel GMHXL 7.8 mm I.D. x 30 cm (two connected)" (manufactured by Tosoh Corporation) using chloroform as the mobile phase under the following conditions: column temperature 40 ° C., flow rate 1.0 mL / min, sample concentration 1 mg / mL, solvent injection volume 100 μL, and analysis time 30 minutes. As a molecular weight standard sample, Shodex K-804 (polystyrene gel) manufactured by Showa Denko KK was used.

[0062] Example 1 (Culturing step) Ralstonia eutropha described in International Publication No. WO 2019 / 142717 was cultured by the method described in paragraphs

[0041] to

[0048] of the same document to obtain a bacterial cell culture solution containing bacterial cells containing P3HA. The composition ratio of the repeating units of P3HA (composition ratio of 3-hydroxybutyrate units / 3-hydroxyhexanoate units) was measured and found to be 89.0 / 11.0 (mol / mol).

[0063] (Pretreatment step) The bacterial cell culture solution obtained above was sterilized by heating and stirring at an internal temperature of 70°C for 4 hours. 5 kg of the culture solution, with the slurry concentration adjusted, was adjusted to a solids concentration of P3HA of approximately 20%, and the temperature was adjusted to 50°C. After the enzyme treatment, 55 g of a 30% aqueous sodium hydroxide solution was added in an alkali treatment to adjust the pH to 12, and the molecular weight of P3HA in the culture solution was measured and found to be 1,220,000.

[0064] (Alkali Addition Control Step: Target Molecular Weight of 550,000 to 700,000) The internal temperature of the reaction tank was adjusted to 50°C, and the addition of 30% sodium hydroxide was started at a rate of 4 g / hr to 5 kg of the pretreated culture solution (pretreated culture solution) obtained above.

[0065] While measuring the molecular weight of P3HA over time, 30% sodium hydroxide was continuously added. When the molecular weight of P3HA reached 1,030,000, the charge rate of 30% sodium hydroxide was changed to 2 g / hr, when it reached 840,000, it was changed to 1 g / hr, when it reached 780,000, it was changed to 0 g / hr (addition was stopped), and when it reached 680,000, cooling was started. (The addition flow rate (charge amount) was gradually reduced according to the measured value, and adjustment was made to the target molecular weight. When the target molecular weight was reached, cooling was carried out and the reaction was terminated.) The results are shown in Figure 3. The molecular weight of the obtained P3HA was 650,000.

[0066] Example 2 (Culturing step) A bacterial cell culture solution was prepared in the same manner as in Example 1.

[0067] (Pretreatment step) The bacterial cell culture solution obtained above was sterilized by heating and stirring at an internal temperature of 70°C for 8 hours. 5 kg of the culture solution, with the slurry concentration adjusted, was adjusted to a solids concentration of P3HA of approximately 20%, and the temperature was adjusted to 50°C. After the enzyme treatment, 51 g of a 30% aqueous sodium hydroxide solution was added in an alkali treatment to adjust the pH to 12, and the molecular weight of P3HA in the culture solution was measured and found to be 1.5 million.

[0068] (Alkali Addition Control Step: Target Molecular Weight 550,000 to 700,000) Alkali treatment of P3HA was carried out in the same manner as in Example 1. The addition of 30% sodium hydroxide was started at a rate of 4 g / hr, and 30% sodium hydroxide was continuously added while measuring the molecular weight of P3HA over time. When the molecular weight of P3HA reached 1,240,000, the charge rate of 30% sodium hydroxide was changed to 3 g / hr, when it reached 1,050,000, it was changed to 2 g / hr, when it reached 850,000, it was changed to 1 g / hr, when it reached 750,000, it was changed to 0 g / hr (addition was stopped), and when it reached 670,000, cooling was started. The results are shown in Figure 3. The molecular weight of the resulting P3HA was 660,000.

[0069] Example 3 (Culturing step) A bacterial cell culture solution was prepared in the same manner as in Example 1.

[0070] (Pretreatment step) The bacterial cell culture solution obtained above was sterilized by heating and stirring at an internal temperature of 70°C for 8 hours. 5 kg of the culture solution, with the slurry concentration adjusted, was adjusted to a solids concentration of P3HA of approximately 20%, and the temperature was adjusted to 50°C. After the enzyme treatment, 58 g of a 30% aqueous sodium hydroxide solution was added in an alkali treatment to adjust the pH to 12, and the molecular weight of P3HA in the culture solution was measured and found to be 1.76 million.

[0071] (Alkali addition control step: target molecular weight 550,000 to 700,000) Alkali treatment of P3HA was carried out in the same manner as in Example 1. The addition of 30% sodium hydroxide was started at a rate of 4 g / hr, and 30% sodium hydroxide was added over time while measuring the molecular weight of P3HA over time. When the molecular weight of P3HA reached 1.2 million,000, the charge rate of 30% sodium hydroxide was changed to 3 g / hr, when it reached 1 million, it was changed to 2 g / hr, when it reached 880,000, it was changed to 1 g / hr, when it reached 750,000, it was changed to 0 g / hr (addition was stopped), and when it reached 680,000, cooling was started. The results are shown in Figure 3. The molecular weight of the obtained P3HA was 680,000.

[0072] The concept of alkali addition in Examples 1 to 3 is shown in Table 1 and Figure 2. The pH trends in Examples 1 to 3 are shown in Figure 4. The trends in the amount of alkali added in Examples 1 to 3 are shown in Figure 5.

[0073] Example 4 (Culturing step) A bacterial cell culture solution was prepared in the same manner as in Example 1.

[0074] (Pretreatment step) The bacterial cell culture solution obtained above was sterilized by heating and stirring at an internal temperature of 70°C for 4 hours. Five kg of the culture solution, whose slurry concentration had been adjusted, was adjusted to a solids concentration of P3HA of approximately 20%, and the temperature was adjusted to 70°C. After adding 22 g of a 30% aqueous sodium hydroxide solution for an alkali treatment to adjust the pH to 10, the molecular weight of P3HA in the culture solution was measured and found to be 2,000,000.

[0075] (Alkali Addition Control Step: Target Molecular Weight 550,000-700,000) Alkali treatment of P3HA was performed in the same manner as in Example 1, except for the pretreatment step, set temperature, and alkali flow rate. The addition of 30% sodium hydroxide was initiated at 1.3 g / hr, and 30% sodium hydroxide was continuously added while measuring the molecular weight of P3HA over time. When the molecular weight of P3HA reached 1,140,000, the 30% sodium hydroxide feed rate was changed to 0.7 g / hr, then to 0.5 g / hr when it reached 1,030,000, then to 0.3 g / hr when it reached 920,000, then to 0 g / hr (addition was stopped) when it reached 810,000, and cooling was initiated when it reached 720,000. The results are shown in Figure 6. The molecular weight of the resulting P3HA was 670,000.

[0076] Example 5 (Culturing step) A bacterial cell culture solution was prepared in the same manner as in Example 1.

[0077] (Pretreatment step) The bacterial cell culture solution obtained above was sterilized by heating and stirring at an internal temperature of 70°C for 4 hours. Five kg of the culture solution, whose slurry concentration had been adjusted so that the solids concentration of P3HA was approximately 20%, was adjusted to 70°C. After adding 45 g of a 30% aqueous sodium hydroxide solution for an alkali treatment to adjust the pH to 11, the molecular weight of P3HA in the culture solution was measured and found to be 1.5 million.

[0078] (Alkali Addition Control Step: Target Molecular Weight 120,000 to 270,000) Alkali treatment of P3HA was performed in the same manner as in Example 1, except for the pretreatment step, set temperature, and alkali flow rate. Specifically, the addition of 30% sodium hydroxide was initiated at 5 g / hr, and 30% sodium hydroxide was continuously added while measuring the molecular weight of P3HA over time. When the molecular weight of P3HA reached 660,000, the 30% sodium hydroxide feed rate was changed to 4 g / hr, then to 3.3 g / hr when it reached 520,000, then to 2.7 g / hr when it reached 440,000, then to 2 g / hr when it reached 380,000, then to 1.5 g / hr when it reached 290,000, and finally to 250,000, starting cooling. The results are shown in Figure 7. The molecular weight of the resulting P3HA was 240,000.

[0079] Comparative Example 1 (Cultivation Step) A bacterial cell culture solution was prepared in the same manner as in Example 1.

[0080] (Pretreatment step) The bacterial cell culture solution obtained above was heated and stirred at an internal temperature of 70°C for 4 hours for sterilization. After further enzyme treatment, 5 kg of the culture solution, whose slurry concentration had been adjusted so that the solids concentration of P3HA was approximately 20%, was adjusted to 50°C. After alkali treatment to adjust the pH to 11.5 by adding 51 g of a 30% aqueous sodium hydroxide solution, the molecular weight of P3HA in the culture solution was measured and found to be 1.65 million.

[0081] (Alkali treatment step: target molecular weight 550,000 to 700,000) The slurry of the inactivated culture solution (inactivated culture solution) obtained above was adjusted to an internal temperature of 50±3°C and a pH of 11.5. 30% sodium hydroxide was continuously added to maintain the pH of the slurry at 11.5±0.2. While measuring the molecular weight of P3HA over time, the addition of 30% sodium hydroxide was temporarily stopped when the molecular weight reached 1,000,000. After the pH dropped, the addition of 30% sodium hydroxide was resumed, maintaining a pH of 11.2±0.2. When the molecular weight reached 700,000 (12 hours after the start of the alkali treatment step), the temperature was lowered and the reaction was terminated. The results are shown in Figure 8.

[0082] Comparative Example 2 (Culturing Step) A bacterial cell culture solution was prepared in the same manner as in Example 1.

[0083] (Pretreatment step) The bacterial cell culture solution obtained above was sterilized by heating and stirring at an internal temperature of 70°C for 4 hours. After the enzyme treatment, 5 kg of the culture solution, whose slurry concentration had been adjusted, was adjusted to a solids concentration of P3HA of approximately 20%, and the temperature was adjusted to 50°C. After adding 49 g of a 30% aqueous sodium hydroxide solution for an alkali treatment to adjust the pH to 11.5, the molecular weight of P3HA in the culture solution was measured and found to be 1,140,000.

[0084] (Alkali Treatment Step: Target Molecular Weight of 550,000 to 700,000) The molecular weight of P3HA was adjusted in the same manner as in Comparative Example 1. The results are shown in FIG.

[0085] Comparative Example 3 (Culturing Step) A bacterial cell culture solution was prepared in the same manner as in Example 1.

[0086] (Pretreatment step) The bacterial cell culture solution obtained above was sterilized by heating and stirring at an internal temperature of 70°C for 4 hours. After the enzyme treatment, 5 kg of the culture solution, whose slurry concentration had been adjusted, was adjusted to a solids concentration of P3HA of approximately 20%, and the temperature was adjusted to 50°C. After adding 50 g of a 30% aqueous sodium hydroxide solution for an alkali treatment to adjust the pH to 11.5, the molecular weight of P3HA in the culture solution was measured and found to be 1,280,000.

[0087] (Alkali Treatment Step: Target Molecular Weight of 550,000 to 700,000) The molecular weight of P3HA was adjusted in the same manner as in Comparative Example 1. The results are shown in FIG.

[0088] The pH trends of Comparative Examples 1 to 3 are shown in Fig. 9. The trends of the alkali addition amounts of Comparative Examples 1 to 3 are shown in Fig. 10.

[0089] [Results] In Examples 1 to 5, the molecular weight of the aliphatic polyester resin rapidly decreased at the beginning of the reaction, and as the molecular weight of the aliphatic polyester resin in the reaction vessel decreased, the rate of molecular weight decrease could be controlled to approach the target molecular weight. Furthermore, a comparison of Examples 1 to 3 showed that even when the initial molecular weight varied between 1.22 million, 1.5 million, and 1.76 million, adding alkali according to the same rules significantly reduced the rate to over 100,000 / hr during the initial reaction, and controlled the molecular weight decrease near the end of the reaction to approximately 0 to 30,000, thereby obtaining PHA with a precise target molecular weight. Furthermore, a comparison of Examples 4 and 5 showed that PHA with a precise target molecular weight could be obtained even when the temperature conditions, pretreatment conditions (with or without enzyme treatment), and target molecular weight were changed.

[0090] On the other hand, in Comparative Examples 1 to 3, since the only indicator was pH, when attempting to precisely adjust the molecular weight in the latter half of the reaction, the time required for molecular weight adjustment became longer, and when attempting to shorten the time required for molecular weight adjustment, the problem arose of deviation from the target molecular weight.

[0091] More specifically, in Comparative Examples 1 to 3, even though the molecular weight was adjusted under the same pH conditions, the amount of alkali added varied greatly. In other words, pH-based control resulted in differences in the amount of NaOH added. The inventors speculate that controlling molecular weight reduction based on pH is undesirable for the following reasons: Because molecular weight reduction occurs due to the reaction between COOR and OH in the resin, pH can be used as an indicator of reaction rate, but is not suitable for controlling molecular weight reduction. Because molecular weight continues to decrease until the pH decreases, it is impossible to predict the molecular weight reduction that will occur during this time. Because molecular weight analysis takes approximately 2 hours, adjustment to the target value is impossible without prediction. Reaction time varies (8 to 14 hours (average 12 hours) in the Comparative Examples). The molecular weight reduction rate cannot be reproduced even when the temperature, pH, and resin amount are consistent (the reaction rate cannot be calculated using the general reaction rate formula, etc.). Adjustment is largely dependent on intuition, based on predicting the molecular weight reduction rate.

[0092] From the above, it has been demonstrated that the present invention makes it possible to produce a low-molecular-weight aliphatic polyester resin in a short time and with high precision.

[0093] According to the present invention, a low-molecular-weight aliphatic polyester resin can be produced in a short time with high accuracy, and therefore, the present invention can be suitably used in fields such as agriculture, fisheries, forestry, horticulture, medicine, hygiene products, clothing, non-clothing, packaging, automobiles, building materials, and other fields.

[0094] REFERENCE SIGNS LIST 1 Reaction tank 2 Alkali charging section 3 Alkali treatment section 4 Measurement section 5 Control section 6 Temperature adjustment section 7 Aliphatic polyester resin charging section 10 Manufacturing apparatus

Claims

1. The process includes an alkali treatment step in which an aliphatic polyester resin and an alkali are mixed in a reaction vessel. The alkali treatment step includes an alkali addition control step in which the amount and / or rate of alkali addition is controlled using the molecular weight of the aliphatic polyester resin in the reaction vessel as an indicator. A method for producing a low molecular weight aliphatic polyester resin, wherein the aliphatic polyester resin is poly(3-hydroxyalkanoate).

2. The alkali addition control step is The process includes two or more steps with different amounts and / or rates of alkali addition, The manufacturing method according to claim 1, wherein the amount and / or rate of alkali addition is reduced as the molecular weight of the aliphatic polyester resin in the reaction vessel decreases.

3. The manufacturing method according to claim 1 or 2, wherein the alkali addition control step includes three or more steps with different amounts and / or rates of alkali addition.

4. The manufacturing method according to claim 1 or 2, wherein in the alkali addition control step, the weight-average molecular weight of the aliphatic polyester resin is reduced by 300,000 or more.

5. The manufacturing method according to claim 1 or 2, further comprising a pretreatment step.

6. The manufacturing method according to claim 1 or 2, wherein the temperature of the reaction vessel in the alkali treatment step is 40 to 80°C.

7. The system comprises a reaction vessel, an alkali input section for adding alkali to the reaction vessel, and an alkali processing section. The alkali treatment device is A measuring unit for measuring the molecular weight of the aliphatic polyester resin in the reaction vessel, The system includes an alkali addition control unit that controls the amount and / or rate of alkali addition in the alkali addition unit, using the molecular weight of the aliphatic polyester resin in the reaction vessel, measured by the measurement unit, as an indicator. An apparatus for producing a low molecular weight aliphatic polyester resin, wherein the aliphatic polyester resin is poly(3-hydroxyalkanoate).

8. In the alkali addition control unit, The process includes two or more steps with different amounts and / or rates of alkali addition, The manufacturing apparatus according to claim 7, wherein the amount and / or rate of alkali addition is controlled to decrease as the molecular weight of the aliphatic polyester resin in the reaction vessel decreases.

9. The manufacturing apparatus according to claim 7 or 8, wherein the alkali addition control unit controls the process to include three or more steps with different amounts and / or rates of alkali addition.

10. The manufacturing apparatus according to claim 7 or 8, wherein the alkali addition control unit controls the aliphatic polyester resin to reduce its weight-average molecular weight by 300,000 or more.

11. Furthermore, the manufacturing apparatus according to claim 7 or 8, further comprising a temperature control unit for setting the temperature of the reaction vessel to 40 to 80°C.