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

Abstract

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. [Solution] The polymer composition for regenerating monomers from homopolymers according to the present invention contains a homopolymer and a catalyst component. Here, the catalyst component contains titanium dioxide and a metal oxide other than titanium dioxide. 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.

Description

[Technical Field]

[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. [Background technology]

[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 simultaneously, raising concerns about the safety of the reaction products. Furthermore, the decomposition yield is not always high. Therefore, there is a need for catalytic reactions that are energetically advantageous, operate at lower temperatures, and yield high decomposition rates. This is especially true for homopolymers composed of a single monomer, as controlling the decomposition reaction allows for the reuse of the recovered monomers.

[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. [Overview of the Initiative] [Problems that the invention aims to solve]

[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. [Means for solving the problem]

[0005] The present invention relates to a polymer composition for regenerating monomers from homopolymers, It contains a homopolymer and a catalyst component, The catalyst component is a polymer composition containing 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 are 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 3 m 2 / g or more and 100 m 2 / g or less in BET specific surface area.

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

[0016] In one embodiment, the magnesium oxide has a form of particles 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 a monomer from a homopolymer, comprising a step of heating the polymer composition, wherein the heating step is carried out at a temperature higher than the temperature at which the melt mass flow rate of the homopolymer at a load of 2.16 kg is 100 g / 10 min and lower than the starting temperature in the thermogravimetric measurement method of the homopolymer under a nitrogen atmosphere.

[0019] In one embodiment, the heating step is carried out 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 carried out under the reduced pressure, and the degree of vacuum under the reduced pressure is 0.5 to 30 kPa.

[0023] In one embodiment, the polymer composition has a form of fibers and constitutes a fiber product.

[0024] In one embodiment, the fiber product is cut into 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. [Effects of the Invention]

[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. [Modes for carrying out the invention]

[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, containing 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 that have 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) When the homopolymer contained in the polymer composition of the present invention is polylactic acid, it is preferable that the polylactic acid has a high L-lactic acid content because it 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 even more preferably 98.6% or more. The polylactic acid resin may be used alone or in combination of two or more types.

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

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

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

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

[0038] The catalyst component has the function of decomposing the homopolymer under predetermined conditions, and can decompose the homopolymer at lower concentrations and temperatures compared to cases without a catalyst or when other catalysts are used. Furthermore, the catalyst component is less likely to cause side reactions, and monomers can be produced with 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, per 100 parts by mass of the polymer composition. Having the catalyst component content within this range provides excellent dispersibility in the homopolymer, stability during the production and use of the polymer composition, and high decomposition reactivity in the heating step described later.

[0040] (Titanium dioxide) The titanium dioxide constituting the catalyst component is titanium(IV)(TiO2). Titanium dioxide may be commercially available and used in applications such as paints for houses and automobiles, inks for food packaging materials, pigments for synthetic resins in refrigerators and washing machines, colorants for pharmaceuticals such as capsules and tablets, colorants for foods such as chocolate and gum, matting agents for synthetic fibers such as nylon and polyester, and colorants for cosmetics.

[0041] Titanium dioxide is preferable to have a low content of impurities (for example, other metals or other chemical substances used in the manufacturing process, such as sulfuric acid) because it has high catalytic activity and high dispersibility during homopolymer decomposition. Titanium dioxide with a low content of such impurities has a high resistivity, preferably 2,000 Ω·cm or more, and more preferably 5,000 Ω·cm or more. The resistivity can be further improved by increasing the purity through purification such as removing coarse particles by centrifugation, but considering the reduction of the burden required for purification, titanium dioxide preferably has a resistivity of 12,000 Ω·cm or less, and more preferably 10,000 Ω·cm or less.

[0042] The crystal structure of titanium dioxide is not particularly limited and may be anatase type (tetragonal), rutile type (tetragonal), or brookite type (orthorhombic), For the reason of good industrial versatility, the anatase (tetragonal) or rutile (tetragonal) crystal structure of titanium dioxide is preferred. Furthermore, the rutile crystal structure of titanium dioxide is more preferred because it has high stability in polymer compositions and exhibits good catalytic function when heated, for example, to 260-325°C.

[0043] Furthermore, if the titanium dioxide has an anatase-type crystalline structure, the titanium dioxide is preferably 5m 2 / g or more 100m 2 / g or less, more preferably 7m 2 / g or more 50m 2 It has a BET specific surface area of ​​less than or equal to / g. When using anatase-type titanium dioxide, having the BET specific surface area of ​​the titanium dioxide within this range allows for high stability and catalytic activity in the polymer composition.

[0044] The titanium dioxide used in this invention preferably has the form of particles that have been surface-treated with a surface treatment agent. Having titanium dioxide 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.

[0045] Examples of surface treatment agents that can be used for the surface treatment of 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 titanium dioxide content 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. By having the titanium dioxide content in the catalyst component within this range, the catalyst component can provide excellent dispersibility and high decomposition reactivity with respect to homopolymers.

[0047] (Metal oxides) The metal oxides that constitute the catalyst components are compounds in which metals other than titanium oxide are bonded to oxygen. 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 the magnesium oxide that can constitute the catalyst component, commercially available products 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 can be used.

[0050] Since a larger specific surface area results in higher catalytic activity, magnesium oxide preferably has a BET specific surface area of 3 m 2 / g or more, more preferably 5 m 2 / g or more. Magnesium oxide also preferably has a BET specific surface area of 100 m 2 / g or less, more preferably 50 m 2 / g or less. By having a BET specific surface area within the above range, magnesium oxide can provide excellent dispersibility in the homopolymer and maintain stability at 250°C or lower in the polymer composition.

[0051] Also, the magnesium oxide in the present 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 are mixed in the magnesium oxide, the dispersibility in the polymer composition decreases, and the stability during production and use and the decomposition reactivity during heating at 265 - 325°C may decrease. The loss on ignition of magnesium oxide is expressed as the mass percentage of the weight loss when the sample (magnesium oxide) is ignited at 650 ± 50°C, and can be measured by the method of JIS K0067:1992 (Test method for loss and residue of chemical products).

[0052] The magnesium oxide that can be used in the present invention preferably has a form of particles surface-treated with a surface treatment agent. By having a form of particles surface-treated with magnesium oxide, the dispersion stability in the polymer composition can be enhanced. Also, by enhancing the dispersibility, the reaction efficiency during the decomposition of the homopolymer can be increased.

[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, shape 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. Textile products, in particular, generally have a larger surface area relative to their weight than other molded products, making them more readily in contact with the catalyst composition, and therefore are suitable examples of the homopolymer decomposition method of the present 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., dilamins, 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, a method for regenerating monomers from the homopolymer of 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 of 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, sufficient fluidity required for various molding processes can be provided without causing decomposition of the homopolymer in the polymer composition.

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

[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 this 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. [Examples]

[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 1H-NMR and thermogravimetric measurements were performed using the following methods.

[0075] ( 1 H-NMR measurement) The decomposition reaction products were analyzed using a Bruker AV-600 under the following analytical conditions. 1 The measurement was performed using 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℃ (2) Sample concentration: 0.01 g / 0.6 mL (3) Number of cumulative counts: 8 (4) Relaxation time: 2 seconds (5) Solvent: Deuterated chloroform (6) Chemical shift criterion: Hydrogen atom signal of the methyl group of tetramethylsilane in the internal standard sample (0.0 ppm)

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

[0077] (Example 1) 100 parts by mass of polylactic acid (Luminy, L130, manufactured by Total Corbion), 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 the catalyst composition was 37.5 parts by mass. This mixture was kneaded in a twin-screw extruder at a cylinder temperature of 180-200°C to obtain a polymer composition consisting of polylactic acid, 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 reactor, 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 peak 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 for 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] [Table 1]

[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 higher recovery rates of the products obtained from the decomposition, exceeding 90% by mass, compared to the compositions in Comparative Examples 1 to 3. [Industrial applicability]

[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 homopolymers, It contains a homopolymer and a catalyst component, The catalyst component contains titanium dioxide and a metal oxide other than titanium dioxide. The homopolymer is polylactic acid, A polymer composition in which 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 oxide has an anatase-type crystalline 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 aforementioned magnesium oxide is 3m 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 homopolymers, The step includes heating the polymer composition according to any one of claims 1 to 12, A method 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 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 maximum 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 fibers, acetate, plant fibers, and cellulose nanofibers.

Images