KR20240050761A - Recycling method of hydroxyalkanoate-lactide copolymer - Google Patents

Abstract

The present invention provides a method for recycling a hydroxyalkanoate-lactide copolymer comprising the step of hydrolyzing the hydroxyalkanoate-lactide copolymer in a hydrothermal reactor.

Description

{RECYCLING METHOD OF HYDROXYALKANOATE-LACTIDE COPOLYMER}

The present invention relates to a method for recycling hydroxyalkanoate-lactide copolymer comprising the step of hydrolyzing the hydroxyalkanoate-lactide copolymer.

Plastics are inexpensive and durable materials that can be used to produce a variety of products that find use in a wide range of applications. Accordingly, the production of plastics has been increasing dramatically over the past few decades. Moreover, more than 50% of these plastics are used in single-use, disposable or short-lived products that are discarded within one year of manufacture, such as packaging, agricultural films, single-use consumer goods, etc. Additionally, due to the durability of polymers, significant amounts of plastic end up in landfills and natural habitats around the world, causing increasing environmental problems.

Recently, as interest in environmental issues has increased, the development of eco-friendly materials as substitutes for petroleum-based plastics has been actively developed, and they can last for decades depending on local environmental factors such as the level of UV exposure, temperature, and the presence of appropriate microorganisms. For this reason, even in the case of eco-friendly materials, it is necessary to secure full resource circulation process and recycling process technology to achieve carbon neutrality and zero waste. Therefore, different solutions are being explored to reduce the economic and environmental impacts associated with the accumulation of plastics, from plastic decomposition to plastic recycling.

As an example, polyethylene terephthalate (PET) is the most closed-loop recycled plastic, where PET waste (mainly bottles) is collected, sorted, and recycled. They are pressed into batches, crushed, washed, cut into flakes, melted and extruded into pellets and offered for sale. However, these plastic recycling methods only apply to plastic articles containing only PET, requiring excessive prior sorting.

Additionally, another potential method for recycling plastics is chemical recycling, which allows recovering the chemical components of the polymer. The resulting monomer, after purification, can be used to re-produce plastic articles. For example, polylactic acid, a plant-derived resin obtained from plants such as corn, is composed of a single molecule, so research on process technology including solvent extraction, hydrolysis, purification, and resynthesis of polylactic acid is mainly conducted. It is being achieved.

However, even in the case of eco-friendly materials composed of heterogeneous monomers rather than single molecules, they are used in disposable or short-term products, and a chemical recycling method is needed to recycle them.

The present invention is intended to provide a method of recycling the hydroxyalkanoate-lactide copolymer by hydrothermally hydrolyzing the hydroxyalkanoate-lactide copolymer.

According to one embodiment of the present invention, a method for recycling a hydroxyalkanoate-lactide copolymer is provided, including the step of hydrolyzing the hydroxyalkanoate-lactide copolymer in a hydrothermal reactor.

Hereinafter, the hydroxyalkanoate-lactide copolymer recycling method according to specific embodiments of the invention will be described in more detail.

Throughout this specification, unless otherwise specified, “include” or “contains” refers to the inclusion of any component (or component) without particular limitation, excluding the addition of other components (or components). cannot be interpreted as

In addition, unless it is specified that the steps constituting the manufacturing method described in this specification are sequential or continuous, or there is another special class, one step and other steps constituting one manufacturing method are performed in the order described in the specification. It is not interpreted as limited. Accordingly, the order of the structural steps of the manufacturing method can be changed within a range that can be easily understood by a person skilled in the art, and in this case, changes that are obvious to those skilled in the art are included in the scope of the present invention.

Throughout this specification, “poly(3-hydroxypropionate) prepolymer” refers to poly(3-hydroxypropionate) with a weight average molecular weight of 1,000 to 50,000 g/mol obtained by oligomerizing 3-hydroxypropionate. it means.

Additionally, unless otherwise stated herein, the weight average molecular weight of poly(3-hydroxypropionate) prepolymers, copolymers, and oligomers can be measured using gel permeation chromatography (GPC). Specifically, the prepolymer or copolymer is dissolved in chloroform to a concentration of 2 mg/ml, then 20 μl is injected into GPC, and GPC analysis is performed at 40°C. At this time, the mobile phase of GPC uses chloroform and flows at a flow rate of 1.0 mL/min, the column uses two Agilent Mixed-Bs connected in series, and the detector uses an RI Detector. The Mw value is derived using a calibration curve formed using a polystyrene standard specimen. The weight average molecular weight of the polystyrene standard specimen was 162 g/mol, 580 g/mol, 1,180 g/mol, 4,870 g/mol, 9,310 g/mol, 17,120 g/mol, 75,050 g/mol, 200,500 g/mol, 448,500 g. 12 types were used: /mol, 10,690,000 g/mol, 3,022,000 g/mol, and 6,545,000 g/mol.

According to one embodiment of the invention, a method for recycling a hydroxyalkanoate-lactide copolymer is provided, comprising the step of hydrolyzing the hydroxyalkanoate-lactide copolymer in a hydrothermal reactor.

The present inventors have discovered that when hydrolyzing a hydroxyalkanoate-lactide copolymer in a hydrothermal reactor, recyclable polylactic acid oligomers, lactic acid and/or hydroxyalkanoic acid can be recovered in high purity and high yield, The present invention was completed by finding that polylactic acid, polyhydroxyalkanoic acid, and hydroxyalkanoate-lactide copolymer can be repolymerized using such polylactic acid oligomer, lactic acid, and/or hydroxyalkanoic acid. did.

In addition, the hydroxyalkanoate-lactide copolymer is hydrothermally hydrolyzed and recycled into recyclable monomers and oligomers, making it environmentally friendly and economical.

In the hydroxyalkanoate-lactide copolymer recycling method according to the above embodiment, the hydroxyalkanoate-lactide copolymer includes one or more polyhydroxyalkanoate (PHA; polyhydroxyalkanoate) blocks and one block. It may be a block copolymer containing the above polylactic acid blocks. As the hydroxyalkanoate-lactide copolymer contains the above-mentioned blocks, it can exhibit the environmental friendliness and biodegradability of polyhydroxyalkanoate and polylactic acid.

The hydroxyalkanoates include 3-hydroxybutyrate, 4-hydroxybutyrate, 2-hydroxypropionate, 3-hydroxypropionate, and (D)-3- having a medium chain length of 6 to 14 carbon atoms. It may be hydroxycarboxylate, 3-hydroxyvalate, 4-hydroxyvalate or 5-hydroxyvalate. Therefore, the hydroxyalkanoate-lactide copolymer is 3-hydroxybutyrate-lactide copolymer, 4-hydroxybutyrate-lactide copolymer, 2-hydroxypropionate-lactide copolymer, 3- It may be a hydroxypropionate-lactide copolymer, a 4-hydroxyvalate-lactide copolymer, or a 5-hydroxyvalate-lactide copolymer, for example, the hydroxyalkanoate-lactide. The copolymer may be a 3-hydroxypropionate-lactide copolymer to improve flexibility and mechanical properties.

The 3-hydroxypropionate-lactide copolymer may be a block copolymer obtained by ring-opening polymerization of lactide to poly(3-hydroxypropionate) prepolymer. The 3-hydroxypropionate-lactide copolymer exhibits the excellent tensile strength and elastic modulus characteristics of the polylactic acid block, while the poly(3-hydroxypropionate) block has a glass transition temperature (Tg). By increasing flexibility by lowering and improving mechanical properties such as impact strength, it is possible to prevent the brittleness of polylactic acid due to its poor elongation.

The hydroxyalkanoate-lactide copolymer may be a 3-hydroxypropionate-lactide block copolymer, and this block copolymer includes a polylactide repeating unit and poly(3-hydroxypropionate) It refers to a poly(3-hydroxypropionate)-polylactide block copolymer containing a repeating unit. In addition, the category of polymers that may be referred to as the “3-hydroxypropionate-lactide block copolymer” includes polymers in all states after the ring-opening polymerization and repeat unit formation process are completed, for example, the ring-opening It may include a polymer in a crude or purified state after polymerization is completed, a polymer contained in a liquid or solid resin composition before product molding, or a polymer contained in plastic or fabric after product molding has been completed.

Additionally, the 3-hydroxypropionate-lactide copolymer may be a block copolymer obtained by ring-opening polymerization of lactide to poly(3-hydroxypropionate) prepolymer. When the block copolymer obtained by ring-opening polymerization of lactide to the poly(3-hydroxypropionate) prepolymer is hydrothermally hydrolyzed, lactic acid and/or polylactic acid oligomer is prepared from the polylactic acid block, and the poly(3- 3-hydroxypropionic acid can be prepared from the hydroxypropionate) block.

The poly(3-hydroxypropionate) prepolymer includes a hydroxy group and/or an alkoxy group at the end, and the hydroxy group and/or alkoxy group at the end of the poly(3-hydroxypropionate) prepolymer is locked. When added to the ring-opening polymerization reaction of the tide monomer, the lactide monomer begins to be inserted from the end, and as a result, the block copolymer can be prepared.

Therefore, the poly(3-hydroxypropionate) prepolymer not only serves as a polymerization initiator, but is also included as a repeating unit in the block copolymer, improving mechanical properties such as flexibility and impact strength of the final block copolymer. It can be improved.

The poly(3-hydroxypropionate) prepolymer may be manufactured by fermenting or condensation polymerization of 3-hydroxypropionate. The weight average molecular weight of the poly(3-hydroxypropionate) prepolymer may be 1,000 g/mol to 50,000 g/mol, for example, 1,000 g/mol or more, or 5,000 g/mol or more, or 8,000 g/mol. It may be more than or equal to 8,500 g/mol, less than or equal to 50,000 g/mol, or less than or equal to 30,000 g/mol, and the crystallinity of the repeating unit derived from the poly(3-hydroxypropionate) prepolymer in the finally produced block copolymer may be determined. If desired, the poly(3-hydroxypropionate) prepolymer is greater than 20,000 g/mol, or greater than 22,000 g/mol, or greater than 25,000 g/mol, and less than or equal to 50,000 g/mol, or greater than 30,000 g/mol. It is desirable to have a high weight average molecular weight of less than or equal to 28,000 g/mol.

If the weight average molecular weight of the poly(3-hydroxypropionate) prepolymer is 20,000 g/mol or less, the crystals of the polymer are small, making it difficult to maintain the crystallinity of the polymer in the final manufactured block copolymer, and poly(3-hydroxypropionate) prepolymer has a small crystallinity. If the weight average molecular weight of the poly(3-hydroxypropionate) prepolymer exceeds 50,000 g/mol, the side reaction rate occurring inside the prepolymer chain becomes faster than the reaction rate between the poly(3-hydroxypropionate) prepolymers during polymerization.

The catalyst used in the ring-opening polymerization may be any catalyst generally used in the production of polylactide resin through the ring-opening polymerization reaction of lactide monomer. For example, the ring-opening polymerization may be performed under one or more catalysts selected from the group consisting of an organometallic complex catalyst and an organic catalyst. The organometallic complex catalyst may be used without limitation in composition as long as it is commonly used in the production of polylactide resin by ring-opening polymerization of lactide monomer. For example, the organometallic complex catalyst has the formula below: It may be a catalyst indicated by 1.

[Formula 1]

MA ¹ _p A ² _2-p

In Formula 1, M is Al, Mg, Zn, Ca, Sn, Fe, Y, Sm, Lu, Ti or Zr, p is an integer from 0 to 2, and A ¹ and A ² are each independently alkoxy or It is a carboxyl group.

More specifically, the catalyst may be tin(II) 2-ethylhexanoate (Sn(Oct) ₂ ; hereinafter also referred to as Tin Octoate).

Meanwhile, the organic catalyst may be used without limitation in its composition as long as it is commonly used in the production of polylactide resin by ring-opening polymerization of lactide monomer. For example, the organic catalyst is 1,5,7-triazobicyclo-[4,4,0]de-5-cene (TBD), 1,8-diazabicyclo[5.4.0]unde- 7-cene (DBU), 7-methyl-1,5,7-triazabicyclo[4.4.0]de-5-cene (MTBD), 4-dimethylaminopyridine (DMAP), 4-(1) -pyrrolidinyl) may be one or more selected from the group consisting of pyridine (PPY), imidazole, triazolium, thiourea, tertiary amine, and creacinine.

The content of the catalyst may be 0.0001 to 10 mol%, 0.005 to 8 mol%, 0.05 to 5 mol%, or 0.09 to 3 mol% based on 100 mol% of the lactide monomer. If the content of the catalyst relative to 100 mol% of the lactide monomer is too high, the polymerization activity may not be sufficient, and if the content of the catalyst is too high, the amount of residual catalyst in the prepared block copolymer increases, resulting in copolymerization by depolymerization such as transesterification reaction. It may cause decomposition or molecular weight reduction. Additionally, the ring-opening polymerization may be performed at 150 to 200°C for 5 minutes to 24 hours.

In the 3-hydroxypropionate-lactide block copolymer, the weight ratio of the polylactic acid block and the poly(3-hydroxypropionate) block is 99:1 to 50:50, 95:5 to 55:45, It may be 93:7 to 60:40, 92:8 to 70:30 or 90:10 to 80:20. If too little of the poly(3-hydroxypropionate) block is included in the polylactic acid block, brittleness may increase, and the poly(3-hydroxypropionate) block may increase brittleness. If too many blocks are included, the molecular weight may be lowered, resulting in reduced processability and heat stability.

In addition, the weight average molecular weight of the polylactic acid block contained in the block copolymer is 10,000 g/mol or more, or 300,000 g/mol or more, or 50,000 g/mol or more, or 100,000 g/mol or more, and 250,000 g/mol or less, Or it may be less than or equal to 200,000 g/mol.

The hydroxyalkanoate-lactide copolymer has a weight average molecular weight (Mw) measured using gel permeation chromatography (GPC) of 50,000 to 300,000 g/mol, and more specifically, 50,000 g/mol. mol or more, 70,000 g/mol or more, or 100,000 g/mol or more, and has a weight average molecular weight of 300,000 g/mol or less, or 200,000 g/mol or less, or 150,000 g/mol or less. If the weight average molecular weight of the hydroxyalkanoate-lactide copolymer is too small, the overall mechanical properties may be significantly reduced, and if the weight average molecular weight is too large, the process may be difficult and processability and elongation may be low.

The hydroxyalkanoate-lactide copolymer has a number average molecular weight (Mn) measured using gel permeation chromatography (GPC) of 5,000 to 100,000 g/mol, and more specifically, 5,000 g/mol. mol or more, 10,000 g/mol or more, or 20,000 g/mol or more, and has a weight average molecular weight of 100,000 g/mol or less, or 90,000 g/mol or less, or 80,000 g/mol or less. If the number average molecular weight of the hydroxyalkanoate-lactide copolymer is too small, the overall mechanical properties may be significantly reduced, and if the number average molecular weight is too large, the processing process may be difficult and processability and elongation may be low.

The hydroxyalkanoate-lactide copolymer has a polydispersity index (PDI) of 0.5 to 10.0, and more specifically, 0.5 or more, 1.0 or more, 2.0 or more, 3.0 or more, or 4.0 or more, and 10.0 or more. It may be less than or equal to 8.0, less than or equal to 6.0, or less than or equal to 5.0.

Meanwhile, the lactide and 3-hydroxypropionate may be plastic and biodegradable compounds produced from renewable sources through microbial fermentation, and the block copolymer formed by polymerizing them also exhibits environmental friendliness and biodegradability. It may contain a large amount of bio raw materials.

In addition, polylactic acid oligomers, lactic acid and/or 3-hydroxypropionic acid, etc. prepared by hydrolyzing the copolymer containing the bio raw materials may also contain a large amount of bio raw materials.

In the hydroxyalkanoate-lactide copolymer recycling method according to the above embodiment, the hydroxyalkanoate-lactide copolymer can be hydrolyzed in a hydrothermal reactor.

The hydrothermal hydrolysis is a method of reacting reactants with a solvent such as water under high temperature and pressure, and the hydrolysis reaction can be performed in a hydrothermal reactor, for example, an autoclave reactor. For example, the hydrothermal hydrolysis may be performed at a temperature of 100°C or higher and 250°C or lower, 110°C or higher and 200°C or lower, 115°C or higher and 170°C or lower, or 120°C or higher and 150°C or lower. Additionally, it may be performed under a pressure of 1 bar to 10 bar, 2 bar to 8 bar, or 3 bar to 5 bar.

In addition, the reactants introduced into the hydrothermal reactor may be pulverized before being added, and the weight ratio of water and reactants introduced into the hydrothermal reactor is, for example, 1:1 to 1:200, 1:5 to 1:100, 1 :10 to 1:80, 1:20 to 1:50.

The hydrothermal hydrolysis may be performed under an acid or base catalyst, or under a catalyst-free condition. For example, when the hydrothermal hydrolysis is performed without a catalyst, it is not only environmentally friendly, but also prevents side reactions due to the use of acid or base catalysts, and does not require an additional process to remove the catalyst, resulting in purification. Costs can be reduced.

In addition, when the hydrolysis reaction is carried out under a catalyst, the catalyst may be, for example, mineral acids such as hydrochloric acid, phosphoric acid, sulfuric acid, and acetic acid, sulfonic acids such as p-toluene sulfonic acid and methanesulfonic acid, and organic acids such as formic acid, acetic acid, and propionic acid. solid acids such as zeolites, ion exchange resins, metal oxides such as alumina, silica, silica-alumina, titanium dioxide, zirconia, and calcium oxide, compounds containing transition metals such as tin, titanium, and lead, sodium hydroxide, and potassium hydroxide. Alkaline metal hydroxides such as alkali metal hydroxides, magnesium hydroxide, and alkaline earth metal metal hydroxides such as calcium hydroxide.

In the hydroxyalkanoate-lactide copolymer recycling method according to the above embodiment, the hydrolysis is performed at a temperature of 135°C or more and 250°C or less, and lactic acid and hydroxyalkanoic acid can be produced.

That is, the hydroxyalkanoate-lactide copolymer is hydrolyzed in a hydrothermal manner at a temperature of 135 ℃ or more and 250 ℃ or less, so that the hydroxyalkanoate-lactide copolymer is completely hydrolyzed to form a monomer. Phosphorus lactic acid and hydroxyalkanoic acid can be produced and recovered.

For example, the complete hydrolysis may be performed at 135°C or higher and 250°C or lower, 140°C or higher and 230°C or lower, 145°C or higher and 210°C or lower, or 150°C or higher and 190°C or lower. If the complete hydrolysis temperature is too low, the polylactic acid prepolymer and poly(hydroxyalkanoate) prepolymer remain without hydrolysis, and polylactic acid oligomer, poly(hydroxyalkanoate) oligomer, or copolymers thereof remain. If the complete hydrolysis temperature is too high, a change in composition may occur due to racemization between the D and L types of lactic acid due to a side reaction, or a large number of unexpected impurities may be generated.

Additionally, the complete hydrolysis may be performed under pressure conditions of 3.5 bar to 6.5 bar, 4.0 bar to 6.0 bar, 4.5 bar to 5.5 bar, or 4.7 bar to 5.0 bar. If the pressure is too low, hydrolysis of the hydroxyalkanoate-lactide copolymer may not occur, and if the pressure is too high, a large amount of energy is required, which may reduce economic efficiency.

In addition, the complete hydrolysis may be performed for 1 hour to 20 hours, 3 hours to 16 hours, 5 hours to 15 hours, 8 hours to 14 hours, or 10 hours to 12 hours.

Additionally, lactic acid and hydroxyalkanoic acid prepared by complete hydrolysis can be purified and separated by chromatography. For example, the lactic acid and hydroxyalkanoic acid may be included in the aqueous solution recovered after hydrolysis, and the aqueous solution is purified by chromatography to produce lactic acid and hydroxyalkanoic acid according to retention time (RT). Each can be separated.

Additionally, the chromatography may be chiral chromatography, whereby the chromatography can be separated and purified into D-lactic acid, L-lactic acid, and hydroxyalkanoic acid after hydrolysis. Additionally, if necessary, lactic acid of a specific optical isomer can be reused to repolymerize a (co)polymer, etc.

In the hydroxyalkanoate-lactide copolymer recycling method according to the above embodiment, the hydrolysis is performed at a temperature of 100 ° C. or higher and 130 ° C. or lower, and polylactic acid oligomer and hydroxyalkanoic acid can be produced. .

That is, the hydroxyalkanoate-lactide copolymer is hydrolyzed in a hydrothermal manner at a temperature of 100 ℃ or more and 130 ℃ or less, so that the hydroxyalkanoate-lactide copolymer is selectively hydrolyzed. Polylactic acid oligomers and hydroxyalkanoic acids can be produced and recovered. For example, due to hydrothermal hydrolysis at a temperature of 100 ℃ or more and 130 ℃ or less, hydroxyalkanoic acid is removed from the hydroxyalkanoate-lactide copolymer, forming a solid poly. Lactic acid oligomers can be produced, and solid polylactic acid oligomers can be separated and purified through filtration. Additionally, in addition to the polylactic acid oligomer and hydroxyalkanoic acid, lactic acid as a monomer can be additionally produced.

For example, the selective hydrolysis may be performed at 100 ℃ or higher and 130 ℃ or lower, 105 ℃ or higher and 125 ℃ or lower, 110 ℃ or higher and 120 ℃ or lower, or 115 ℃ or higher and 120 ℃ or lower. If the selective hydrolysis temperature is too low, hydrolysis of the hydroxyalkanoate-lactide copolymer may not occur, and if the selective hydrolysis temperature is too high, side reactions may occur, forming acrylic acid, etc., or unexpected impurities. A lot of this can be created.

Additionally, the selective hydrolysis may be performed under pressure conditions of 1.0 bar or more and 3.0 bar or less, 1.5 bar or more and 2.5 bar or less, or 1.5 bar or more and 2.0 bar or less. If the pressure is too low, hydrolysis of the hydroxyalkanoate-lactide copolymer may not occur, and if the pressure is too high, a large amount of energy is required, which may reduce economic efficiency.

Additionally, the selective hydrolysis may be performed for a period of 1 hour to 24 hours, 3 hours to 20 hours, 5 hours to 15 hours, 8 hours to 14 hours, or 10 hours to 12 hours.

Additionally, the polylactic acid oligomer and hydroxyalkanoic acid prepared by the selective hydrolysis can be purified and separated by vacuum filtration. As described above, the hydroxyalkanoic acid is removed from the hydroxyalkanoate-lactide copolymer due to the selective hydrolysis, leaving a solid polylactic acid oligomer, and the solid polylactic acid oligomer is removed through vacuum filtration. ) of polylactic acid oligomers and hydroxyalkanoic acids contained in the filtrate can be separated and purified, respectively.

The polylactic acid oligomer prepared through the selective hydrolysis may have a weight average molecular weight of 4,000 to 20,000, 4,300 to 18,000, 4,500 to 15,000, or 5,000 to 10,000, as measured using gel permeation chromatography. Additionally, the polylactic acid oligomer may have a quantity average molecular weight of 4,000 to 20,000, 4,300 to 18,000, 4,500 to 15,000, or 5,000 to 10,000.

The hydroxyalkanoate-lactide copolymer recycling method according to the above embodiment may further include the step of producing polylactic acid from the lactic acid. The lactic acid may be prepared by hydrothermal hydrolysis of a hydroxyalkanoate-lactide copolymer at a temperature of 135°C or higher and 250°C or lower.

The step of producing polylactic acid from lactic acid may include the step of removing moisture from lactic acid and concentrating the lactic acid. The concentration step may be performed under temperature conditions of 30°C or higher and 70°C or lower, 40°C or higher and 60°C or lower, or 50°C or higher and 60°C or lower. Additionally, the concentration step may be performed under pressure conditions of 1 torr or more and 30 torr or less, 5 torr or more and 25 torr or less, or 10 torr or more and 22.5 torr or less. Additionally, the concentration step may be performed for 2 hours or more and 10 hours or less, 4 hours or more and 8 hours or less, or 5 hours or more and 6 hours or less.

Additionally, the step of producing polylactic acid from the lactic acid may include removing moisture from the lactic acid to concentrate the lactic acid, and then polymerizing the concentrated lactic acid into a polylactic acid oligomer. The polymerization step may be performed under a catalyst or in a non-catalyst process without a catalyst, and the catalyst may be hydrochloric acid, phosphoric acid, sulfuric acid, acetic acid, etc. When the catalyst is used, the catalyst may be added in an amount of more than 0 mol% and less than or equal to 1.0 mol%, more than 0.1 mol% and less than or equal to 0.8 mol%, or more than 0.2 mol% and less than or equal to 0.5 mol%. In addition, the polymerized polylactic acid oligomer may have a weight average molecular weight of 1,000 to 20,000, 2,000 to 18,000, 3,000 to 15,000, or 4,000 to 10,000, and a quantity average molecular weight of 1,000 to 10,000, 2,000 to 9,000, 000 It may be between 8,000 and below or between 4,000 and 7,000.

Additionally, the step of producing polylactic acid from lactic acid may include converting the polylactic acid oligomer into lactide. The conversion step may be performed under temperature conditions of 130 ℃ or higher and 250 ℃ or lower, 150 ℃ or higher and 230 ℃ or lower, or 190 ℃ or higher and 210 ℃ or lower. Additionally, the conversion step may be performed under pressure conditions of 1 torr or more and 30 torr or less, 5 torr or more and 28 torr or less, or 10 torr or more and 25 torr or less. Additionally, the conversion step may be performed for a period of 2 hours or more and 10 hours or less, 4 hours or more and 8 hours or less, or 5 hours or more and 6 hours or less.

Additionally, the step of producing polylactic acid from the lactic acid may include producing polylactic acid by polymerizing the converted lactide. The polymerization step can be performed under a catalyst or in a non-catalyst process without a catalyst, and p-toluenesulfonic acid (p-TSA) and tin chloride (SnCl ₂ ) can be used as catalysts. When the catalyst is used, the catalyst may be added in an amount of more than 0 mol% and less than or equal to 1.0 mol%, more than 0.1 mol% and less than or equal to 0.8 mol%, or more than 0.2 mol% and less than or equal to 0.5 mol%.

The hydroxyalkanoate-lactide copolymer recycling method according to the above embodiment may further include the step of producing polylactic acid from polylactic acid oligomer. The polylactic acid oligomer may be prepared by hydrothermal hydrolysis of a hydroxyalkanoate-lactide copolymer at a temperature of 100°C or more and 130°C or less.

The step of producing polylactic acid from the polylactic acid oligomer may include converting the polylactic acid oligomer into lactide, and the temperature, pressure, and time conditions of the conversion step are described in the conversion step described above. It is the same as what was said.

Additionally, the step of producing polylactic acid from the polylactic acid oligomer may include producing polylactic acid by polymerizing the converted lactide, where the polymerization conditions are as described in the polymerization conditions.

The hydroxyalkanoate-lactide copolymer recycling method according to the above embodiment may further include the step of producing poly(hydroxyalkanoate) from hydroxyalkanoic acid.

The hydroxyalkanoic acid may be prepared by hydrothermal hydrolysis of the hydroxyalkanoate-lactide copolymer at a temperature of 135 ℃ or more and 250 ℃ or less, and the hydroxyalkanoate-lactide copolymer It may be manufactured by hydrothermal hydrolysis at a temperature of 100 ℃ or higher and 130 ℃ or lower.

The step of producing poly(hydroxyalkanoate) from the hydroxyalkanoic acid may include the step of removing moisture from the hydroxyalkanoic acid and concentrating the hydroxyalkanoic acid. The concentration step may be performed under temperature conditions of 30°C or higher and 70°C or lower, 40°C or higher and 60°C or lower, or 50°C or higher and 60°C or lower. Additionally, the concentration step may be performed under pressure conditions of 1 torr or more and 30 torr or less, 5 torr or more and 25 torr or less, or 10 torr or more and 22.5 torr or less. Additionally, the concentration step may be performed for 2 hours or more and 10 hours or less, 4 hours or more and 8 hours or less, or 5 hours or more and 6 hours or less.

In the step of producing poly(hydroxyalkanoate) from the hydroxyalkanoic acid, the hydroxyalkanoic acid is concentrated by removing moisture from the hydroxyalkanoic acid, and then the concentrated hydroxyalkanoic acid is It may include polymerization with poly(hydroxyalkanoate). The polymerization step can be performed under a catalyst or in a non-catalyst process without a catalyst, and p-toluenesulfonic acid (p-TSA) and tin chloride (SnCl ₂ ) can be used as catalysts. When the catalyst is used, the catalyst may be added in an amount of more than 0 mol% and less than or equal to 1.0 mol%, more than 0.1 mol% and less than or equal to 0.8 mol%, or more than 0.2 mol% and less than or equal to 0.5 mol%.

In addition, the polymerization step may be performed in steps 1 and 2, and steps 1 and 2 may be performed under temperature conditions of 50 ℃ or higher and 200 ℃ or lower, 70 ℃ or higher and 150 ℃ or lower, or 90 ℃ or higher and 100 ℃ or lower. You can. In addition, step 1 of the polymerization step may be performed under pressure conditions of 1 torr or more and 15 torr or less, 3 torr or more and 10 torr or less, or 5 torr or more and 7.5 torr or less, and step 2 may be performed under pressure conditions of 0.01 torr or more and 1 torr or less, and 0.1 torr. It can be done under pressure conditions of 0.8 torr or less, or 0.2 torr or more and 0.5 torr or less. In addition, step 1 of the polymerization step may be performed for 0.5 hours or more and 5 hours or less, 1 hour or more and 4 hours or less, or 2 hours or more and 3 hours or less, and step 2 may be performed for 10 hours or more and 50 hours or less, or 15 hours or more. It can be for a period of 40 hours or less, or between 24 hours and 30 hours.

The hydroxyalkanoate-lactide copolymer recycling method according to the above embodiment may further include preparing the hydroxyalkanoate-lactide copolymer using lactic acid and hydroxyalkanoic acid. The lactic acid and hydroxyalkanoic acid may be prepared by hydrothermal hydrolysis of hydroxyalkanoate-lactide copolymer at a temperature of 135°C or more and 250°C or less.

The step of preparing the hydroxyalkanoate-lactide copolymer from lactic acid and hydroxyalkanoic acid may include the step of preparing poly(hydroxyalkanoate) from the hydroxyalkanoic acid. Additionally, the step of preparing poly(hydroxyalkanoate) from hydroxyalkanoic acid may be performed under the manufacturing conditions described above.

In addition, the step of preparing a hydroxyalkanoate-lactide copolymer with lactic acid and hydroxyalkanoic acid involves polymerizing the poly(hydroxyalkanoate) and lactide to form a hydroxyalkanoate-lactide copolymer. It may include the step of preparing a composite. The lactide may be manufactured from the lactic acid, and specific process conditions are as described above. Additionally, the polymerization step may be performed under a catalyst or in a non-catalyst process without a catalyst, and p-toluenesulfonic acid (p-TSA) and tin chloride (SnCl ₂ ) may be used as catalysts. When the catalyst is used, the catalyst may be added in an amount of more than 0 mol% and less than or equal to 1.0 mol%, more than 0.1 mol% and less than or equal to 0.8 mol%, or more than 0.2 mol% and less than or equal to 0.5 mol%.

Additionally, the polymerization step may be performed under temperature conditions of 100°C or higher and 250°C or lower, 150°C or higher and 200°C or lower, or 160°C or higher and 190°C or lower. Additionally, the polymerization step may be performed at normal pressure and may be performed for a period of 0.5 hours to 5 hours, 1 hour to 3 hours, or 1.5 hours to 2 hours.

The hydroxyalkanoate-lactide copolymer recycling method according to the above embodiment may further include the step of producing a hydroxyalkanoate-lactide copolymer from polylactic acid oligomer and hydroxyalkanoic acid. . The polylactic acid oligomer and hydroxyalkanoic acid may be prepared by hydrolyzing a hydroxyalkanoate-lactide copolymer at a temperature of 100°C or more and 130°C or less.

The step of preparing the hydroxyalkanoate-lactide copolymer from the polylactic acid oligomer and the hydroxyalkanoic acid may include the step of preparing poly(hydroxyalkanoate) from the hydroxyalkanoic acid. there is. Additionally, the step of preparing poly(hydroxyalkanoate) from hydroxyalkanoic acid may be performed under the manufacturing conditions described above.

In addition, the step of preparing a hydroxyalkanoate-lactide copolymer with lactic acid and hydroxyalkanoic acid involves polymerizing the poly(hydroxyalkanoate) and lactide to form a hydroxyalkanoate-lactide copolymer. It may include the step of preparing a composite. The lactide may be manufactured from the polylactic acid oligomer, and specific process conditions are as described above. Additionally, the polymerization step may be performed under a catalyst or in a non-catalyst process without a catalyst, and p-toluenesulfonic acid (p-TSA) and tin chloride (SnCl ₂ ) may be used as catalysts. When the catalyst is used, the catalyst may be added in an amount of more than 0 mol% and less than or equal to 1.0 mol%, more than 0.1 mol% and less than or equal to 0.8 mol%, or more than 0.2 mol% and less than or equal to 0.5 mol%.

Additionally, the polymerization step may be performed under temperature conditions of 100°C or higher and 250°C or lower, 150°C or higher and 200°C or lower, or 160°C or higher and 190°C or lower. Additionally, the polymerization step may be performed at normal pressure and may be performed for a period of 0.5 hours to 5 hours, 1 hour to 3 hours, or 1.5 hours to 2 hours.

According to the present invention, in an environmentally friendly and economical way, hydroxyalkanoate-lactide copolymer can be converted into recyclable polylactic acid oligomer, lactic acid and/or hydroxyalkanoic acid, and such polylactic acid oligomer, lactic acid and/or resynthesizing the (co)polymer using hydroxyalkanoic acid. A method for recycling the hydroxyalkanoate-lactide copolymer may be provided.

Figure 1 shows NMR data after 10 and 12 hours of hydrolysis reaction in Example 1.

The invention is explained in more detail in the following examples. However, the following examples only illustrate the present invention, and the content of the present invention is not limited by the following examples.

Preparation Example 1: Preparation of 3-hydroxypropionate-lactide block copolymer

(One) Poly(3-hydroxypropionate) prepolymer production

Add 50 ml of 60% 3-hydroxypropionate aqueous solution to a 100 ml Schlenk flask in an oil bath and remove approximately 80% of the moisture in the 3-hydroxypropionate for 3 hours at 50°C and 50 mbar. After oligomerization at 70 ℃ and 20 mbar for 2 hours, 0.4 parts by weight of p-toluenesulfonic acid (p-TSA) catalyst based on 100 parts by weight of 3-hydroxypropionate was added to the reaction flask, and the temperature was 110 ℃. The melt condensation reaction was performed for 24 hours. After the reaction was completed, the reactant was dissolved in chloroform and extracted with methanol to obtain poly(3-hydroxypropionate) prepolymer (weight average molecular weight: 30,000 g/mol).

(2) Preparation of block copolymers

Lactide and the poly(3-hydroxypropionate) prepolymer were mixed in a 100 ml Schlenk flask in an oil bath at a weight ratio of 4:1 and added to a total content of 30 g, followed by tin(II) 2-ethylhexahydrate. 0.006 mol of noate was added, and solid-phase polymerization was performed at 190°C and normal pressure for approximately 1.5 hours to produce 3-hydroxypropionate-lactide block copolymer (weight average molecular weight: 131,000 g/mol, number average molecular weight: 32,000 g) /mol, polydispersity index (PDI): 4.1) was prepared.

<Examples and Comparative Examples>

Example 1

200 mg of the 3-hydroxypropionate-lactide block copolymer prepared in Preparation Example 1 and 4 mL of water were added to an autoclave reactor, and heated in hot water for 24 hours at a temperature of 120 ° C. and a pressure of 2.0 bar. A hydrolysis reaction was performed, and polylactic acid oligomer and 3-hydroxypropionic acid were recovered.

Example 2

200 mg of the 3-hydroxypropionate-lactide block copolymer prepared in Preparation Example 1 and 4 mL of water were added to an autoclave reactor, and heated in water for 12 hours at a temperature of 150 ° C. and a pressure of 4.7 bar. A hydrolysis reaction was performed, and lactic acid and 3-hydroxypropionic acid were recovered.

Example 3

502 mg of 3-hydroxypropionate-lactide block copolymer prepared in Preparation Example 1 and 25 mL of water were added to an autoclave reactor, and heated in hot water for 2 hours at a temperature of 250 ° C. and a pressure of 40 bar. A hydrolysis reaction was performed, and lactic acid and 3-hydroxypropionic acid were recovered.

Comparative Example 1

500 mg of polylactide (number average molecular weight 2003D), 25 mL of water, and 3 g of 3N sodium hydroxide (NaOH) were added to the reactor, hydrolysis reaction was performed at 60°C, normal pressure, and 24 hours, and lactic acid was recovered. .

evaluation

1. Nuclear Magnetic Resonance (NMR) analysis

After the hydrolysis of the examples and comparative examples, the product obtained from the reactor was filtered through a reduced pressure filter to separate solid and aqueous solution, and each solid and aqueous solution were analyzed by NMR, and the results are shown in the table below. It is shown in 1. At this time, Example 1 was analyzed at 2-hour reaction time intervals, and Examples 2, 3, and Comparative Example 1 showed the results after completion of the reaction.

<NMR analysis conditions>

Sample preparation: 10 mg of sample was dissolved in 1 mL of DMSO and then applied for analysis.

¹ H Solution NMR

Pulse program: zg30

Ns: 16

d1: 10 seconds

Temperature: 298K

2. Gel permeation chromatography (GPC) analysis

After the hydrolysis of Examples 1 and 2, the product obtained from the reactor was filtered through a reduced pressure filter to separate solid and aqueous solution, and the solid was analyzed by GPC-IR to determine the number of solids. The average molecular weight (Mn) and weight average molecular weight (Mw) are shown in Table 1 below. At this time, Example 1 was analyzed at 2-hour reaction time intervals, and Examples 2, 3, and Comparative Example 1 showed the results after completion of the reaction.

<GPC analysis conditions>

The solid was dissolved in chloroform to a concentration of 2 mg/ml, then 20 μl was injected into GPC, and GPC analysis was performed at 40°C. At this time, the mobile phase of GPC uses chloroform and flows at a flow rate of 1.0 mL/min, the column uses two Agilent Mixed-Bs connected in series, and the detector uses an RI Detector. The Mw value is derived using a calibration curve formed using a polystyrene standard specimen. The weight average molecular weight of the polystyrene standard specimen was 162 g/mol, 580 g/mol, 1,180 g/mol, 4,870 g/mol, 9,310 g/mol, 17,120 g/mol, 75,050 g/mol, 200,500 g/mol, 448,500 g. 12 types were used: /mol, 10,690,000 g/mol, 3,022,000 g/mol, and 6,545,000 g/mol.

3. High-Performance Liquid Chromatography (HPLC) analysis

After the hydrolysis of Examples 1 and 2, the product obtained from the reactor was filtered through a reduced pressure filter to separate solid and aqueous solution, and the aqueous solution was analyzed by HPLC-UV-MS, and the results (aqueous solution The content of monomers contained therein and the HPLC Area% of the main by-products are shown in Table 1 below. At this time, Example 1 was analyzed at 2-hour reaction time intervals, and Examples 2, 3, and Comparative Example 1 showed the results after completion of the reaction.

<HPLC analysis conditions>

Column: C18 Column (4.6

Mobile phase: AN/water mixture solution

Flow rate: 1ml/min

Temperature: 40℃

reaction
hour
(hr) NMR (solids, %)
(P(3HP):PLA) Number average molecular weight of solid
(Mn) Solid weight average molecular weight
(Mw) NMR
(aqueous solution, %)
(3HP group: LA group) Monomer content in aqueous solution (% by weight)
(3HP:LA) HPLC Area% (@210nm, %) of major by-products in aqueous solution
(Acrylic acid:LA or 3HP oligomer) Example 1 0 10.7:89.3 12,200 126,000 - - - 2 8.1:91.9 10,400 56,900 47.2:52.8 0.03:0.70 3.7:78.5 4 7.5:92.5 7,880 29,500 56.4:43.6 0.03:0.20 3.3:78.5 6 4.7:95.3 5,270 15,000 49.1:50.9 0.50:2.70 4.5:72.7 8 2.2:97.8 4,710 10,500 49.4:50.6 2.00:9.30 4.5:66.5 10 1.3:98.7 4,630 9,230 46.5:53.5 3.10:13.10 4.5:62.1 12 PLA 100 4,340 7,410 38.7:61.3 5.40:22.60 5.4:49.7 14 PLA 100 4,070 6,460 25.9:74.1 7.20:30.80 6.1:42.3 16 PLA 100 4,110 6,070 26.3:73.7 7.60:33.70 6.6:37.0 18 PLA 100 3,700 5,360 22.5:77.5 8.50:43.50 7.1:30.7 24 PLA 100 3,310 4,620 17.5:82.5 9.40:55.60 7.4:25.5 Example 2 12 - 300 400 7.0:93.0 - - Example 3 2 - - - 4.5:80 - - Comparative Example 1 24 - - - 0:100 - -

- P(3HP): poly(3-hydroxypropionate)

- PLA: polylactic acid

-3HP: 3-hydroxypropionic acid

-LA: lactic acid

According to Table 1, Example 1 confirmed that when the hydrothermal hydrolysis reaction was performed at a temperature of 120° C. for 12 hours, the solid phase contained 100% of only polylactic acid oligomers. In addition, Figure 1 shows NMR data analyzing the solid after 10 and 12 hours of Example 1. Referring to this, the peak of poly(3-hydroxypropionate) disappears from the NMR data and the end of the polylactic acid oligomer disappears. It was confirmed that the spirit appeared.

On the other hand, since the content ratio of the 3HP group and the LA group in the aqueous solution of Example 1 (reaction time 12 hours) was 1:1.58 (=38.7:61.3), the 3-hydroxypropionate-lactide block copolymer of Preparation Example 1 Since approximately 16.906% (10.7% * 1.58) of (P(3HP):PLA = 10.7:89.3) is hydrolyzed to lactic acid monomer, the polylactic acid oligomer is 72.394% (89.3- It was confirmed that it was recovered with a yield of 16.906).

When the hydrothermal hydrolysis reaction is performed at a temperature of 150° C. for 12 hours as in Example 2, the 3-hydroxypropionate-lactide block copolymer of Preparation Example 2 (P(3HP):PLA = 7:93) It was confirmed that all of these were hydrolyzed to monomers, and that 3-hydroxypropionic acid and lactic acid were recovered in a ratio of 7:93 in the aqueous solution.

As a result of NMR analysis of the product of Example 3, it was confirmed that 3-hydroxypropionic acid and lactic acid were recovered in a ratio of 4.5:80 in the aqueous solution. However, in Example 3, it was confirmed that as the reaction proceeded at excessively high temperature and pressure compared to Example 2, impurities such as acetic acid and/or pyruvic acid were produced at 15.5%.

Meanwhile, as a result of NMR analysis of the product of Comparative Example 1, it was confirmed that only lactic acid and some acetic acid impurities were produced as only polylactic acid was hydrolyzed.

Claims (17)

A method for recycling a hydroxyalkanoate-lactide copolymer, comprising the step of hydrolyzing the hydroxyalkanoate-lactide copolymer in a hydrothermal reactor.
According to paragraph 1,
A method of recycling a hydroxyalkanoate-lactide copolymer, wherein the hydroxyalkanoate-lactide copolymer is a 3-hydroxypropionate-lactide copolymer.
According to paragraph 2,
The 3-hydroxypropionate-lactide copolymer is a block copolymer obtained by ring-opening polymerization of lactide to poly(3-hydroxypropionate) prepolymer. Method for recycling hydroxyalkanoate-lactide copolymer.
According to paragraph 1,
A method for recycling hydroxyalkanoate-lactide copolymer, wherein the hydrolysis is carried out without a catalyst.
According to paragraph 1,
The hydrolysis is carried out at a temperature of 135 ℃ or more and 250 ℃ or less, and lactic acid and hydroxyalkanoic acid are produced. A method of recycling hydroxyalkanoate-lactide copolymer.
According to clause 5,
The hydrolysis method is a hydroxyalkanoate-lactide copolymer recycling method, wherein the hydrolysis is performed under pressure conditions of 3.5 bar or more and 6.5 bar or less, for a time period of 1 hour or more and 20 hours or less.
According to clause 5,
A method for recycling hydroxyalkanoate-lactide copolymer, in which the lactic acid and hydroxyalkanoic acid are purified and separated by chromatography.
According to paragraph 1,
The hydrolysis is carried out at a temperature of 100 ℃ or more and 130 ℃ or less, and polylactic acid oligomer and hydroxyalkanoic acid are produced, a hydroxyalkanoate-lactide copolymer recycling method.
According to clause 8,
The hydrolysis is performed under pressure conditions of 1.0 bar to 3.0 bar for a period of 1 hour to 24 hours.
According to clause 8,
A method for recycling hydroxyalkanoate-lactide copolymer, wherein the polylactic acid oligomer and hydroxyalkanoic acid are purified and separated by vacuum filtration.
According to clause 8,
The polylactic acid oligomer has a weight average molecular weight of 4,000 to 20,000. A method of recycling a hydroxyalkanoate-lactide copolymer.
According to clause 5,
A method for recycling hydroxyalkanoate-lactide copolymer, further comprising the step of producing polylactic acid from the lactic acid.
According to clause 5,
A method for recycling a hydroxyalkanoate-lactide copolymer, further comprising the step of producing poly(hydroxyalkanoate) from the hydroxyalkanoic acid.
According to clause 5,
A method for recycling a hydroxyalkanoate-lactide copolymer, further comprising: preparing a hydroxyalkanoate-lactide copolymer using the lactic acid and hydroxyalkanoic acid.
According to clause 8,
A method for recycling hydroxyalkanoate-lactide copolymers, further comprising the step of producing polylactic acid from the polylactic acid oligomer.
According to clause 8,
A method for recycling a hydroxyalkanoate-lactide copolymer, further comprising the step of producing poly(hydroxyalkanoate) from the hydroxyalkanoic acid.
According to clause 8,
A method for recycling a hydroxyalkanoate-lactide copolymer, further comprising: preparing a hydroxyalkanoate-lactide copolymer from the polylactic acid oligomer and hydroxyalkanoic acid.