Polymer composition for regenerating monomer from homopolymer and method for regenerating monomer from homopolymer using the same

Abstract

A polymer composition for regenerating a monomer from a homopolymer according to the present invention contains a homopolymer and a catalyst component. Here, the catalyst component contains titanium oxide and a metal oxide other than the titanium oxide. The present invention enables efficient decomposition of a homopolymer. The present invention also makes it possible to reduce the possibility of side reactions occurring during the decomposition, and to be able to recover monomer components in a good yield.

Description

Polymer composition for regenerating monomers from homopolymers and method for regenerating monomers from homopolymers using the same

[0001] The present invention relates to a polymer composition for regenerating monomers from homopolymers and a method for regenerating monomers from homopolymers using the same.

[0002] Methods for decomposing polymers have been studied for some time. Many polymers decompose when heated to 400-600°C, but controlling the reaction is difficult, and various reactions occur in rapid succession, raising concerns about the safety of the reaction products, and the decomposition yield is not always high. Therefore, there is a need for catalytic reactions that are energetically advantageous, operate at lower temperatures, and have a high decomposition yield. This is especially true for homopolymers composed of a single monomer, as controlling the decomposition reaction would allow for the reuse of the recovered monomer.

[0003] Furthermore, polymers are often used in a mixed state with other materials, i.e., as polymer compositions. In the catalytic reaction described above, contact between the polymer and the catalyst is necessary, but in polymer compositions mixed with other materials, contact between the polymer and the catalyst can be difficult. This is especially true when the amount of polymer in the polymer composition is small or when the other materials are non-fusible. Increasing the amount of catalyst is a possible solution, but this not only becomes costly and inefficient but also raises concerns about side reactions.

[0004] The present invention aims to solve the above-mentioned problems, and its objective is to provide a polymer composition for regenerating monomers from homopolymers, and a method for regenerating monomers from homopolymers using the same, which can safely and efficiently decompose homopolymers to extract monomers from said homopolymers.

[0005] The present invention relates to a polymer composition for regenerating monomers from a homopolymer, wherein the polymer composition contains a homopolymer and a catalyst component, and the catalyst component contains titanium dioxide and a metal oxide other than titanium dioxide.

[0006] In one embodiment, the titanium oxide has a resistivity of 2,000 Ω·cm or more and 12,000 Ω·cm or less.

[0007] In one embodiment, the titanium dioxide has a rutile-type crystalline form.

[0008] In one embodiment, the titanium dioxide has an anatase crystal form and 5m ２ / g or more 100m ２ It has a BET specific surface area of ​​less than or equal to / g.

[0009] In one embodiment, the titanium dioxide has the form of particles that have been surface-treated with a surface treatment agent.

[0010] In further embodiments, the surface treatment agent is at least one compound selected from the group consisting of alumina, zinc, silica, zirconia, tin compounds, fatty acids, alkylsilanes, and silicone compounds.

[0011] In one embodiment, the content of the catalyst component in 100 parts by mass of the polymer composition is 0.5 parts by weight or more and 2.5 parts by weight or less.

[0012] In one embodiment, the content of titanium oxide in 100 parts by mass of the catalyst composition is 10 to 75 parts by mass.

[0013] In one embodiment, the metal oxide other than titanium oxide is magnesium oxide.

[0014] In a further embodiment, the magnesium oxide is 3m ２ / g or more 100m ２ It has a BET specific surface area of ​​less than or equal to / g.

[0015] In one embodiment, the ignition loss of the magnesium oxide is 5% or less.

[0016] In one embodiment, the magnesium oxide has the form of particles that have been surface-treated with a surface treatment agent.

[0017] In one embodiment, the homopolymer is polylactic acid.

[0018] The present invention also provides a method for regenerating monomers from a homopolymer, comprising the step of heating the polymer composition, wherein the heating step is performed at a temperature higher than the temperature at which the melt mass flow rate of the homopolymer at a load of 2.16 kg becomes 100 g / 10 min, and at a temperature lower than or equal to the starting temperature in the thermogravimetric analysis method of the homopolymer under a nitrogen atmosphere.

[0019] In one embodiment, the heating step is performed at a temperature of 265 to 325°C.

[0020] In one embodiment, the homopolymer is polylactic acid.

[0021] In one embodiment, the heating step is carried out under an inert gas stream or under reduced pressure.

[0022] In one embodiment, the heating step is performed under reduced pressure, and the vacuum level under reduced pressure is 0.5 to 30 kPa.

[0023] In one embodiment, the polymer composition has a fibrous form and constitutes a textile product.

[0024] In one embodiment, the textile product is cut to a size having a maximum side of 20 mm or less.

[0025] In one embodiment, the textile product further contains at least one other fiber selected from the group consisting of cotton, silk, wool, regenerated fibers, acetate, plant fibers, and cellulose nanofibers.

[0026] According to the present invention, homopolymers can be efficiently decomposed. The present invention also reduces the possibility of side reactions occurring during decomposition, and allows for the recovery of monomer components in good yield.

[0027] The following describes exemplary embodiments of this disclosure. However, this disclosure is not limited in any way to the embodiments described below. In this specification, numerical ranges indicated using "~" indicate a range that includes the numbers before and after "~" as the minimum and maximum values, respectively. Also, unless otherwise explicitly stated, the units of the numbers before and after "~" are the same. Furthermore, the upper and lower limits described individually can be combined in any way.

[0028] 1. Polymer Composition The polymer composition of the present invention is used to regenerate monomers from homopolymers and contains homopolymers and catalyst components.

[0029] (Homopolymer) In the present invention, a homopolymer refers to a polymer compound composed of repeating units (monomers) of the same type. Examples of homopolymers include polyethylene, polypropylene, polystyrene, polyvinyl chloride, polymethyl methacrylate, polytetrafluoroethylene, polyethylene glycol, polypropylene glycol, polytetramethylene glycol, polycaprolactone, polylactic acid, polyamide 6, polyamide 12, and polydimethylsiloxane, as well as combinations thereof. In the present invention, a homopolymer may be a product having any form, such as a fiber, that contains the above polymer compound as a base material, or a part of such a product.

[0030] The homopolymer in the present invention may be composed of cyclic monomers. That is, the homopolymer may be obtained by polymerizing cyclic monomers.

[0031] Examples of cyclic monomers include cyclic lactones, cyclic lactams, cyclic ethers, and lactides. Examples of cyclic lactones include caprolactone, valerolactone, nonalactone, butyrolactone, and propiolactone. Examples of cyclic lactams include propiolactam, butyrolactam, valerolactam, caprolactam, laurolactam, enantractam, and undecanelactam. Examples of cyclic ethers include ethylene oxide, propylene oxide, butylene oxide, tetrahydrofuran, dioxane, and dioxanone. Lactides are cyclic compounds having two ester bonds within a molecule formed by the dehydration condensation of the hydroxyl and carboxyl groups of two hydroxy acid molecules. Examples include glycolides, 3,6-dimethyl-1,4-dioxane-2,5-dione (derived from 2-hydroxypropionic acid (lactic acid)), and 1,6-dioxacyclodecane-2,7-dione (derived from 4-hydroxybutanoic acid). Among these, so-called lactides derived from lactic acid can be optically active substances, and include L-lactide, D-lactide, and meso-lactide.

[0032] In one embodiment, the homopolymer in the present invention is obtained by polymerizing the above-mentioned cyclic monomers, and examples of such homopolymers include polycaprolactone, polyvalerolactone, polynonalactone, polybutyrolactone, polypropiolactone, polypropiolacrum, polybutyrolactam, polyvalerolactum, polycaprolactam, polylaurolactam, polyenanthractam, polyundecanelactum, polyethylene oxide, polypropylene oxide, polybutylene glycol, polyoxytetramethylene glycol, polydioxane, polydioxanone, polylactic acid, and polyhydroxybutanoic acid. Homopolymers polymerized from cyclic monomers are useful because they are less prone to side reactions in the decomposition reaction described later and are easy to recover as cyclic monomers. In the present invention, polylactic acid is preferred as the homopolymer because it is highly versatile and allows for easy regeneration of the monomer.

[0033] (Polylactic acid) In the case where the homopolymer contained in the polymer composition of the present invention is polylactic acid, the polylactic acid is preferably polylactic acid having a high L-lactic acid content because it itself has a high melting point. The L-lactic acid content of the polylactic acid is preferably 96% or more, more preferably 98% or more, and still more preferably 98.6% or more. One type of polylactic acid-based resin may be used alone, or two or more types may be used in combination.

[0034] The weight average molecular weight of the polylactic acid is not particularly limited, and may be appropriately selected by those skilled in the art.

[0035] (Other Components) The above homopolymer may further optionally contain any appropriate other components (additives) as needed. Examples of additives include fillers, antioxidants, heat stabilizers, light stabilizers, ultraviolet absorbers, antiblocking agents, antibacterial agents, compatibilizers, plasticizers, tackifiers, processing aids, lubricants, coupling agents, flame retardants, oxygen scavengers, foaming agents, colorants, and combinations thereof.

[0036] Said other components may be added at any appropriate timing during the production process of the homopolymer, for example, in the form of liquid, powder, pellets, granules, or a masterbatch. The content of said other components that may be contained in the homopolymer is not particularly limited, and an appropriate amount may be selected by those skilled in the art.

[0037] (Catalyst Component) The catalyst component in the present invention contains titanium oxide and a metal oxide other than titanium oxide.

[0038] The catalyst component has a function of decomposing the homopolymer under predetermined conditions, and can decompose the homopolymer at a low concentration and a low temperature compared to the case where no catalyst is used or another catalyst is used. Furthermore, the catalyst component is less prone to cause side reactions, and can produce monomers at a high recovery rate.

[0039] The content of the catalyst component is preferably 0.5 parts by mass or more and 2.5 parts by mass or less, more preferably 0.6 parts by mass or more and 2.0 parts by mass or less, relative to 100 parts by mass of the polymer composition. When the content of the catalyst component falls within this range, excellent dispersibility in the homopolymer, stability during production and use of the polymer composition, and high decomposition reactivity in the heating step described later can be provided.

[0040] (Titanium oxide) The titanium oxide constituting the catalyst component is titanium (IV) oxide (TiO ２ ). Titanium oxide may be a commercially available product used in paints for houses and automobiles, inks for food packaging materials, pigments for synthetic resins in refrigerators, washing machines and the like, colorants for pharmaceuticals such as capsules and tablets, colorants for food such as chocolate and gum, delusterants for chemical fibers such as nylon and polyester, and colorants for cosmetics.

[0041] Titanium oxide preferably has a low content of impurities (for example, other metals and other chemical substances such as sulfuric acid used in the production process) because of its high catalytic activity and high dispersibility during homopolymer decomposition. Titanium oxide with a low content of such impurities has a large specific resistance, preferably a specific resistance of 2,000Ω·cm or more, more preferably 5,000Ω·cm or more. Although the specific resistance can be further improved by increasing the purity through purification such as removal of coarse particles by a centrifugal separator, in consideration of reducing the load required for purification, titanium oxide preferably has a specific resistance of 12,000Ω·cm or less, more preferably 10,000Ω·cm or less.

[0042] The crystal structure of titanium oxide is not particularly limited, and may be any of anatase type (tetragonal), rutile type (tetragonal), and brookite type (orthorhombic). For good industrial versatility, anatase type (tetragonal) or rutile type (tetragonal) is preferred. Further, the crystal structure of titanium oxide is more preferably rutile type in view of high stability in the polymer composition and excellent catalytic function when heated to 260 to 325°C, for example.

[0043] Furthermore, when titanium oxide has an anatase-type crystal structure, the titanium oxide preferably has 5 m ２ / g or more and 100 m ２ / g or less, more preferably 7 m ２ / g or more and 50 m ２ / g or less of BET specific surface area. When anatase-type titanium oxide is used, when the BET specific surface area of the titanium oxide falls within the above range, both stability and catalytic activity in the polymer composition can be maintained at high levels.

[0044] It is also preferable that the titanium oxide used in the present invention is in the form of particles surface-treated with a surface treatment agent. When titanium oxide is in the form of surface-treated particles, the dispersion stability in the polymer composition can be improved. In addition, the improved dispersibility can also increase the reaction efficiency during the decomposition of the homopolymer.

[0045] Examples of surface treatment agents that can be used for the surface treatment of the above titanium oxide include alumina, zinc, silica, zirconia, tin compounds, fatty acids, alkylsilanes, and silicone compounds, as well as combinations thereof.

[0046] In the present invention, the content of titanium oxide contained in 100 parts by mass of the catalyst component is preferably 10 to 75 parts by mass, more preferably 14 to 60 parts by mass. When the content of titanium oxide in the catalyst component falls within the above range, the catalyst component can provide excellent dispersibility and high decomposition reactivity to the homopolymer.

[0047] (Metal Oxide) The metal oxide constituting the catalyst component is a compound in which oxygen is bonded to a metal other than the above titanium oxide. These metal oxides, when combined with titanium oxide, can exhibit high catalytic activity for the decomposition of homopolymers.

[0048] Examples of metal oxides include iron(II) oxide, magnetic iron oxide, iron(III) oxide, sodium oxide, lithium oxide, potassium oxide, calcium oxide, magnesium oxide, beryllium oxide, aluminum oxide, gallium oxide, indium oxide, thallium oxide, zinc oxide, nickel oxide, barium oxide, strontium oxide, copper(I) oxide, copper(II) oxide, copper peroxide, paramelaconite, copper(III) oxide, and copper(IV) oxide, as well as combinations thereof. Magnesium oxide is preferred as the metal oxide because it exhibits high catalytic function when combined with titanium oxide.

[0049] (Magnesium Oxide) As for magnesium oxide that can constitute the catalyst component, commercially available types can be used for applications such as refractories, various additives, fillers for resins, optical materials, electronic component applications, phosphor raw materials, various target material raw materials, raw materials for superconducting thin film substrates, and protective film raw materials for color plasma display panels.

[0050] Furthermore, since a larger specific surface area results in higher catalytic activity, magnesium oxide is preferably 3 m ２ / g or more, more preferably 5m ２ It has a BET specific surface area of ​​100 m² or more. Magnesium oxide is also preferably 100 m². ２ / g or less, more preferably 50m ２ It has a BET specific surface area of ​​less than or equal to / g. By having a BET specific surface area within the above range, magnesium oxide provides excellent dispersibility in homopolymers and maintains stability in polymer compositions at temperatures below 250°C.

[0051] Furthermore, the magnesium oxide in this invention preferably has a loss on ignition of 5% or less, more preferably 2% or less. If the loss on ignition of magnesium oxide exceeds 5%, many impurities will be mixed in the magnesium oxide, reducing its dispersibility in the polymer composition, and potentially decreasing its stability during manufacturing and use, as well as its decomposition reactivity when heated to 265-325°C. The loss on ignition of magnesium oxide is expressed as a mass percentage of the loss when the sample (magnesium oxide) is ignited to 650±50°C, and can be measured by the method of JIS K0067:1992 (Test method for loss on ignition and residue of chemical products).

[0052] The magnesium oxide used in the present invention preferably has the form of particles that have been surface-treated with a surface treatment agent. Having magnesium oxide in the form of surface-treated particles enhances the dispersion stability in the polymer composition. Furthermore, improved dispersibility also enhances the reaction efficiency during the decomposition of the homopolymer.

[0053] Examples of surface treatment agents that can be used for the surface treatment of magnesium oxide include alumina, zinc, silica, zirconia, tin compounds, fatty acids, alkylsilanes, and silicone compounds, as well as combinations thereof.

[0054] In the present invention, the amount of magnesium oxide that can be contained in 100 parts by mass of the catalyst component is preferably 25 to 90 parts by mass, more preferably 40 to 86 parts by mass. By having the magnesium oxide content in the catalyst component within this range, the catalyst component can provide excellent dispersibility and high decomposition reactivity with respect to homopolymers.

[0055] The shape of the homopolymer to be decomposed in this invention is not limited. It may be spherical or strand-cut pellets, or molded articles formed by various molding methods. The molding methods include known molding methods, injection molding, extrusion molding, blow molding, injection blow molding, morph extrusion molding, inflation molding, press molding, melt spinning, solution spinning, vacuum forming, vacuum pressure forming, and hot plate forming. The molded articles include housings, containers, bags, tubes, cups, bottles, trays, long and short fibers, and fabric products, and there are no restrictions on their shape, size, or thickness. In particular, textile products generally have a larger surface area relative to their weight than other molded articles, making them easier to contact with the catalyst composition, and therefore are a suitable embodiment of the homopolymer decomposition method of this invention. In the case of the above-mentioned textile products, other fibers such as natural fibers like cotton, linen, wool, silk, and Tencel, regenerated fibers like rayon, cupro, and polynosic, and semi-synthetic fibers like acetate, triacetate, and Promix may be compounded through weaving, knitting, blending, or twisting. Since the catalyst composition is already incorporated into the homopolymer composition, the decomposition method can be carried out without concerns such as a decrease in catalyst contact opportunities, even with these mixed products.

[0056] The polymer composition of the present invention may have any form, such as strands or pellets, after the homopolymer, catalyst component, and other components have been pre-mixed. For example, if the polymer of the present invention has the form of pellets, the shape is not particularly limited and may be cylindrical, spherical, ellipsoidal, etc. The granulation process for obtaining pellets may be carried out by the procedures or apparatus normally used by the parties. For example, the homopolymer may be melted using a twin-screw extruder, the catalyst component and, if necessary, the other components may be added and melt-kneaded, extruded into a strand shape and cooled, and then processed into pellets using a pelletizer.

[0057] Alternatively, the polymer composition of the present invention may have the form of a molded article formed by a various molding method, in which the above homopolymer and catalyst component, as well as other components, are pre-mixed. Examples of the above molding methods include known methods such as injection molding, extrusion molding, blow molding, injection blow molding, shape extrusion molding, inflation molding, press molding, melt spinning, solution spinning, vacuum forming, vacuum pressure forming, and hot plate forming. Examples of the above molded articles include housings, containers, bags, tubes, cups, bottles, trays, fibers (e.g., filaments, staples), and textile products (e.g., fabrics). The shape, size, thickness, etc., of the molded article are not particularly limited.

[0058] When the polymer composition of the present invention has the form of fibers and is formed as a textile product, the polymer composition (fiber) of the present invention may be compounded with other fibers by weaving, knitting, blending, twisting, or other means to constitute the textile product. Examples of other fibers include natural fibers such as cotton, linen, wool, silk, and Tencel; regenerated fibers such as rayon, cupro, and polynosic; semi-synthetic fibers such as acetate, triacetate, and Promix; plant fibers; cellulose nanofibers; and one or a combination thereof.

[0059] 2. Method for regenerating monomers from homopolymers Next, the method for regenerating monomers from homopolymers according to the present invention will be described.

[0060] In the method of the present invention, the above polymer composition is heated.

[0061] As described above, the polymer composition may take any form, such as pellets or molded articles. The polymer composition may be, for example, industrial waste generated during industrial production, household waste generated from the use of textile products purchased by consumers, or a combination thereof.

[0062] In the method of the present invention, since the polymer composition already contains a catalyst component, it is not particularly necessary to add any new catalyst other than the polymer composition.

[0063] The polymer composition is heated, for example, in a predetermined reactor. Examples of reactors include batch or continuous tank reactors, reactors, mill rolls, mixers, and single-screw or twin-screw extruders. Such reactors preferably have heating means such as electric heaters or heat transfer fluids.

[0064] In the present invention, the heating of the odor polymer composition is performed at a temperature higher than the temperature at which the melt mass flow rate of the homopolymer at a load of 2.16 kg becomes 100 g / 10 min, and at a temperature lower than or equal to the starting temperature in the thermogravimetric analysis method for the homopolymer under a nitrogen atmosphere.

[0065] Here, the melt mass flow rate is an indicator representing the fluidity of the homopolymer and can be measured by the method described in JIS K7210-1. When the temperature applied to the polymer composition is higher than the temperature at which the melt mass flow rate of the homopolymer at a load of 2.16 kg becomes 100 g / 10 min, the dispersibility of the catalyst component contained in the polymer composition increases, thereby increasing the opportunity for contact between the homopolymer and the catalyst composition in the composition, and as a result, the efficiency of the homopolymer decomposition reaction, i.e., the regeneration rate of the obtained monomer, can be increased.

[0066] Furthermore, by containing a homopolymer, the above polymer composition can be given fluidity through heating and melting, allowing for any molding process. Here, if the temperature used for the molding process is lower than the temperature at which the melt mass flow rate of the homopolymer at a load of 2.16 kg is generally 100 g / 10 min, the polymer composition can be provided with sufficient fluidity required for various molding processes without causing decomposition of the homopolymer.

[0067] On the other hand, the starting temperature in the thermogravimetric analysis method for homopolymers under a nitrogen atmosphere is the temperature at which the decrease in thermogravimetricity begins, as defined in JIS K 7120. At temperatures above the starting temperature in the thermogravimetric analysis method under a nitrogen atmosphere, a catalyst-controlled decomposition reaction occurs as a side effect, resulting in a decrease in the regeneration efficiency of the monomer.

[0068] In the method of the present invention, the specific temperature that can be used for heating the polymer composition is preferably 265 to 325°C, more preferably 270 to 300°C. If the temperature is below 265°C, the yield of monomers obtained by the homopolymer decomposition reaction may decrease. If the temperature is above 325°C, not only will the yield of monomers obtained by the homopolymer decomposition reaction decrease, but it will also be a temperature range in which uncatalyzed thermal decomposition of the homopolymer can occur, and side reactions may be more likely to occur.

[0069] In the present invention, the heating step may be carried out under atmospheric pressure, but it may also be carried out under an inert gas atmosphere such as nitrogen or under reduced pressure. It is preferable to carry out the step under reduced pressure in order to improve the efficiency of discharging and recovering the monomers produced by the decomposition of the homopolymer.

[0070] Furthermore, if the heating process is carried out under reduced pressure, the vacuum level is preferably set to 0.5 to 30 kPa, more preferably to 0.7 to 20 kPa. If the vacuum level exceeds 30 kPa, the efficiency of removing monomers generated through the decomposition of homopolymers from the system may decrease. If the vacuum level falls below 0.5 kPa, the vacuum level is too high, and homopolymers may overflow from the vacuum exhaust port and be discharged to the outside during heating.

[0071] In the present invention, when the polymer composition has the form of fibers and constitutes a textile product, it is preferable that the textile product is cut to a maximum side length of preferably 100 mm or less, more preferably 50 mm or less, and even more preferably 20 mm or less. By subdividing, the surface area can be increased, thereby accelerating the decomposition reaction of the homopolymer.

[0072] According to the present invention, by heating the polymer composition at a predetermined temperature, the homopolymer, which is a constituent component, can be decomposed by the catalyst component, thereby regenerating the monomers that make up the homopolymer. The monomers thus obtained can be reused as materials for constructing new homopolymers or other polymers. This enables material recycling of monomers obtained from homopolymers.

[0073] The present invention will be described in detail below with reference to examples. However, the present invention is not limited to these examples.

[0074] In this example and comparative example １ H-NMR and thermogravimetric measurements were performed using the following methods.

[0075] ( １ (H-NMR measurement) Analysis of decomposition reaction products was performed using a Bruker AV-600 under the following analytical conditions. １ The measurement was performed by 1H-NMR. Deuterated chloroform was used as the solvent for the NMR measurement, and tetramethylsilane was used as the internal standard. (1) Measurement temperature: 23°C (2) Sample concentration: 0.01 g / 0.6 mL (3) Number of accumulations: 8 (4) Relaxation time: 2 seconds (5) Solvent: Deuterated chloroform (6) Chemical shift standard: Hydrogen atom signal of the methyl group of tetramethylsilane in the internal standard sample (0.0 ppm)

[0076] (Thermogravimetric Analysis) The decomposition reaction yield under an inert gas stream was determined by thermogravimetric analysis under an inert gas stream using a TG-DTA8122 instrument manufactured by Rigaku Corporation. The temperature was raised from room temperature to a predetermined temperature at a rate of 10°C per minute, and then held for 10 minutes.

[0077] (Example 1) 100 parts by mass of polylactic acid (Luminy, L130, manufactured by Total Corbion), which is a homopolymer, was combined with a catalyst composition containing 0.3 parts by mass of titanium dioxide (TA301, manufactured by Fuji Titanium Industries, Ltd.) and 0.5 parts by mass of magnesium oxide (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) (the titanium dioxide content in 100 parts by mass of the catalyst composition was 37.5 parts by mass). This mixture was kneaded in a twin-screw extruder at a cylinder temperature of 180 to 200°C to obtain a polymer composition consisting of polylactic acid, which is a homopolymer, and a catalyst composition containing titanium dioxide and magnesium oxide.

[0078] Next, this polymer composition was fed into an extruder set to a cylinder temperature of 220°C and melt-spun to produce long fibers. 100 parts by mass of the fabric obtained by weaving these long fibers as yarn was placed in a reaction apparatus equipped with a three-necked flask having a stirring mechanism and heated to 280°C. After 5 minutes, the fabric began to melt, and after 10 minutes it was completely melted, so the reaction apparatus was stirred. The pressure inside the reaction apparatus was reduced to 4 kPa by a vacuum pump via a cooling trap. A few minutes after the start of stirring, decomposition products were distilled off from the apparatus and trapped in the cooling trap, and after 10 minutes, distillation from the system ceased.

[0079] The recovery rate of the product obtained from the decomposition, calculated from the residue in the reaction apparatus, was 90.9% by mass. Furthermore, the product recovered in the cooling trap １ Analysis was performed using 1H-NMR measurements. Peaks of lactic acid and lactic acid polymers were observed around 1.59 ppm, and peaks originating from L,L-lactide and D,D-lactide were observed around 1.68 ppm. Additionally, a peak originating from D,L-lactide was observed around 1.72 ppm. １ Analysis of the relative abundances of each component based on the integral ratio of each peak obtained from the 1H-NMR spectrum revealed that L,L-lactide or D,D-lactide accounted for 82.2% by mass, D,L-lactide for 11.9% by mass, and lactic acid or lactic acid polymer for 5.9% by mass. The crude lactide content (L,L-lactide, D,D-lactide, and D,L-lactide) in the obtained product was 94.1% by mass, indicating a high monomer recovery rate.

[0080] (Examples 2-5 and Comparative Examples 1-3) Catalyst compositions of Examples 2-5 (Catalyst Compositions 1-4) were prepared by mixing titanium dioxide (TA301, manufactured by Fuji Titanium Industries Co., Ltd.) and metal oxides in the mass ratios shown in Table 1 below. Next, polylactic acid (Luminy, L130, manufactured by Total Corbion), a homopolymer, was combined with the catalyst compositions, and this mixture was fed into a twin-screw extruder and kneaded at a cylinder temperature of 180-200°C to obtain a polymer composition in pellet form.

[0081] Next, the pelletized polymer composition was subjected to thermogravimetric analysis. In the thermogravimetric analysis, the thermal decomposition initiation temperature at which weight loss begins and the recovery rate of the product obtained from the decomposition after heating at 280°C for 10 minutes were calculated.

[0082]

[0083] In all of the polymer compositions in Examples 2 to 5, the thermal decomposition initiation temperature exceeded 250°C, and they remained stable up to 250°C. Furthermore, as shown in Table 1, the polymer compositions in Examples 2 to 5 all showed a high recovery rate of products obtained from the decomposition, exceeding 90% by mass, compared to the compositions in Comparative Examples 1 to 3.

[0084] According to the present invention, various homopolymers obtained as waste generated during the manufacturing process or as waste after consumption can be efficiently decomposed. This makes it useful in a wide range of fields, including the disposal and recycling of industrial or household waste, as well as in the apparel and resin molding industries.

Claims

1. A polymer composition for regenerating monomers from a homopolymer, comprising a homopolymer and a catalyst component, wherein the catalyst component comprises titanium dioxide and a metal oxide other than titanium dioxide, the homopolymer is polylactic acid, and the metal oxide other than titanium dioxide is magnesium oxide or calcium oxide.

2. The polymer composition according to claim 1, wherein the titanium dioxide has a resistivity of 2,000 Ω·cm or more and 12,000 Ω·cm or less.

3. The polymer composition according to claim 1, wherein the titanium dioxide has a rutile-type crystalline form.

4. The titanium dioxide has an anatase crystal form and 5m ２ / g or more 100m ２ The polymer composition according to claim 1, having a BET specific surface area of ​​less than or equal to / g.

5. The polymer composition according to claim 1, wherein the titanium dioxide is in the form of particles that have been surface-treated with a surface treatment agent.

6. The polymer composition according to claim 5, wherein the surface treatment agent is at least one compound selected from the group consisting of alumina, zinc, silica, zirconia, tin compounds, fatty acids, alkylsilanes, and silicone compounds.

7. The polymer composition according to claim 1, wherein the content of the catalyst component in 100 parts by mass of the polymer composition is 0.5 parts by weight or more and 2.5 parts by weight or less.

8. The polymer composition according to claim 1, wherein the titanium dioxide content in 100 parts by mass of the catalyst composition is 10 to 75 parts by mass.

9. The polymer composition according to claim 1, wherein the metal oxide other than titanium oxide is magnesium oxide.

10. The magnesium oxide is 3 m ２ / g or more 100m ２ The polymer composition according to claim 9, having a BET specific surface area of ​​less than or equal to / g.

11. The polymer composition according to claim 9, wherein the ignition loss of the magnesium oxide is 5% or less.

12. The polymer composition according to claim 9, wherein the magnesium oxide is in the form of particles that have been surface-treated with a surface treatment agent.

13. A method for regenerating monomers from a homopolymer, comprising the step of heating a polymer composition according to any one of claims 1 to 12, wherein the heating step is performed at a temperature higher than the temperature at which the melt mass flow rate of the homopolymer at a load of 2.16 kg becomes 100 g / 10 min, and at a temperature lower than or equal to the starting temperature of the thermogravimetric method for the homopolymer under a nitrogen atmosphere.

14. The method according to claim 13, wherein the heating step is performed at a temperature of 265 to 325°C.

15. The method according to claim 13, wherein the heating step is carried out under an inert gas stream or under reduced pressure.

16. The method according to claim 15, wherein the heating step is performed under reduced pressure, and the degree of vacuum under reduced pressure is 0.5 to 30 kPa.

17. The method according to claim 13, wherein the polymer composition has the form of fibers and constitutes a textile product.

18. The method according to claim 17, wherein the textile product is cut to a size having a longest side of 20 mm or less.

19. The method according to claim 17, wherein the textile product further contains at least one other fiber selected from the group consisting of cotton, silk, wool, regenerated fiber, acetate, plant fiber, and cellulose nanofiber.

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