Depolymerizable copolymer

Abstract

To provide a copolymer having depolymerization properties in which a polymer is decomposed into a monomer by heat or light, and enabling easy reuse.SOLUTION: A depolymerizable copolymer according to the present disclosure is obtained by copolymerizing a first monomer that constitutes a depolymerizable homopolymer decomposed into a monomer by heating, light, or the like, and a second monomer that is different from the first monomer. The first monomer is α-methylstyrene (AMS) and the second monomer is ethyl methacrylate (EMA). The depolymerizable copolymer preferably has an AMS:EMA of 90:10 to 10:90 (molar ratio). The weight-average molecular weight (Mw) of the depolymerizable copolymer may be 5,000-1,000,000 (Mw). Moreover, the thermal decomposition temperature of the depolymerizable copolymer may be 180-380°C.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a copolymer having a depolymerization property in which a polymer is decomposed into monomers by heat or light, and particularly to a copolymer having a depolymerization property in which hardly any residue remains when depolymerized by heat.

Background Art

[0002] Plastics (polymers) have been developed as materials with excellent durability and heat resistance, and various materials are used in the market. On the other hand, these plastic materials are not naturally decomposed in the environment. For this reason, although their impact on the environment has been pointed out, at present, since sufficient recycling technologies have not been established, many of them are discarded. In particular, in the case of composite materials in which metal and plastic are combined, it is difficult to separately recover each material, and at present, many of them are landfilled.

[0003] In recent years, in response to the increasing interest in SDGs, various efforts have been made to develop technologies for decomposing plastics such as biodegradable polymers and to recycle and reuse plastics.

[0004] However, regarding biodegradable polymers, the environmental safety of substances during biodegradation, the fact that substances during decomposition become microplastics, and the impact when these are ingested by environmental organisms and marine organisms are not clear. Furthermore, although biodegradable polymers have a certain effect on waste reduction, regarding the issue of reuse, there are also problems such as the low physical properties of recycled products, and the fundamental problems have not been solved. Furthermore, from the perspective of waste reduction, there is also a problem that the time until decomposition is long, and in some cases, it may take several months or more.

[0005] In addition, PET bottles and the like are recycled and reused. However, in conventional mechanical recycling, it is necessary to add a certain amount of virgin polymer because the plastic is colored when repeatedly used. In addition, in order to perform chemical recycling, it is necessary to decompose the plastic into monomers using special chemicals and the like, which requires a great deal of labor and energy. Furthermore, there is also a problem that the uses of recycled products are limited.

[0006] Therefore, there is a demand for materials and methods that can decompose plastics into monomers by simple methods such as heat and light and can be reused. For example, for homopolymers such as polymethyl methacrylate and polystyrene, techniques for decomposing them into monomers by simple methods such as heat and light have been studied (for example, Patent Document 1, Patent Document 2, Non-Patent Document 1).

[0007] However, even in this case, it is desired that thermal decomposition can be performed at a lower temperature. In addition, for polystyrene, the monomer recovery rate in thermal decomposition is as low as 60 to 70%, so it is desired to increase the monomer recovery rate (Non-Patent Document 1).

Prior Art Documents

Patent Documents

[0008]

Patent Document 1

Patent Document 2

Non-Patent Documents

[0009]

Non-Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0010] The present invention has been made in view of the above problems, and an object thereof is to provide a copolymerizable polymer having a depolymerizability in which a polymer is decomposed into monomers by heat or light and which is easily recyclable.

Means for Solving the Problems

[0011] In order to solve the above problems, the present invention provides a depolymerizable copolymer obtained by copolymerizing a first monomer constituting a depolymerizable homopolymer that decomposes into monomers by heating, light, etc., and a second monomer different from the first monomer, wherein the first monomer is α-methylstyrene (AMS) and the second monomer is ethyl methacrylate (EMA) (Invention 1).

[0012] According to such an invention (Invention 1), by copolymerizing ethyl methacrylate (EMA) with α-methylstyrene (AMS) constituting a homopolymer having high depolymerizability, it has been found that a depolymerizable copolymer that is easy to recycle, has little residue during heating, and has high convenience can be obtained. Although homopolymers having depolymerizability have been known so far, the properties of polymers obtained by copolymerizing a monomer constituting a homopolymer having depolymerizability and another monomer have not been clear. Therefore, as a result of intensive studies by the present inventors on polymers obtained by copolymerizing a monomer constituting a homopolymer having depolymerizability and another monomer, it has been confirmed that the copolymer described in Invention 1 has depolymerizability, and further, no residue remains due to thermal decomposition, and the monomers constituting it can be completely recovered by thermal decomposition.

[0013] In the above invention (Invention 1), it is preferable that the molar ratio of α-methylstyrene to ethyl methacrylate in the depolymerizable copolymer is 10:90 to 90:10 (Invention 2).

[0014] According to such an invention (Invention 2), a more convenient depolymerizable copolymer polymer can be obtained, which has depolymerizability, leaves no residue upon thermal decomposition, and can completely recover the monomers that constitute it by thermal decomposition.

[0015] Further, in the above invention (Invention 1), it is preferable that the weight average molecular weight (Mw) of the depolymerizable copolymer polymer is 5,000 to 1,000,000 (Invention 3).

[0016] According to such an invention (Invention 3), a more convenient depolymerizable copolymer polymer can be obtained, which has depolymerizability, leaves no residue upon thermal decomposition, and can completely recover the monomers that constitute it by thermal decomposition.

[0017] Furthermore, in the above inventions (Inventions 1 to 3), it is preferable that the thermal decomposition temperature of the depolymerizable copolymer polymer is 180 to 380 °C (Invention 4).

[0018] According to such an invention (Invention 4), a depolymerizable copolymer polymer can be obtained, which has depolymerizability, leaves no residue upon thermal decomposition, can completely recover the monomers that constitute it by thermal decomposition, is highly convenient, and is particularly excellent in recoverability at low temperatures.

Effects of the Invention

[0019] The depolymerizable copolymer polymer of the present invention is a copolymer of α-methylstyrene (AMS) as the first monomer constituting a depolymerizable homopolymer that decomposes into monomers by heating or light, and ethyl methacrylate (EMA) as the second monomer. Since the monomers can be recovered in a high yield by a simple method of heating, recycling is easy. In addition, since there is little residue after thermal decomposition, even when a heterogeneous material such as metal is combined with this polymer to form a composite material, the polymer can be decomposed by heating alone to recover the monomers, enabling separate recovery of the materials.

Modes for Carrying Out the Invention

[0020] Hereinafter, the depolymerizable copolymer polymer of the present invention will be described in detail.

[0021] (Depolymerizable homopolymer and first monomer) The depolymerizable homopolymer in the present invention is obtained by polymerizing a predetermined monomer (monomer) alone, and is preferably one that decomposes into monomers by heating, light, etc. and has an extremely high recovery rate of 90% or more of the monomer recovery rate. Known depolymerizable homopolymers with such a high monomer recovery rate include polymethyl methacrylate (PMMA), poly-α-methylstyrene (PAMS), polytetrafluoroethylene (PTFE), etc. The monomers (monomer components) constituting these homopolymers are methyl methacrylate (MMA), α-methylstyrene (AMS), and tetrafluoroethylene (TFE). In the present invention, α-methylstyrene (AMS) is used as the first monomer constituting the depolymerizable homopolymer as a raw material.

[0022] (Second monomer) In the depolymerizable copolymer polymer of the present invention, ethyl methacrylate (EMA) is used as the second monomer copolymerized with α-methylstyrene (AMS).

[0023] (Characteristics of the depolymerizable copolymer polymer) The depolymerizable copolymer polymer of the present invention is not particularly limited as long as it is a polymer in which α-methylstyrene (AMS) and ethyl methacrylate (EMA) are copolymerized, but AMS:EMA is 10:90 to 90:10 (molar ratio), particularly 20:80 to 80:20 (molar ratio), and more preferably 30:70 to 70:30 (molar ratio).

[0024] Also, the weight average molecular weight (Mw) of the depolymerizable copolymer polymer of the present invention is not particularly limited, but is preferably 5,000 to 1,000,000 (Mw), particularly 10,000 to 500,000 (Mw).

[0025] Furthermore, the thermal decomposition temperature of the depolymerizable copolymer of the present invention is not particularly limited as long as it can be thermally decomposed, but is preferably 180°C to 380°C, particularly preferably 250 to 350°C.

[0026] Any appropriate additive may be blended with the above depolymerizable copolymer as needed. Examples of such additives include crosslinking agents, tackifiers, plasticizers (e.g., trimellitic acid ester-based plasticizers, pyromellitic acid ester-based plasticizers, etc.), pigments, dyes, fillers, anti-aging agents, conductive materials, antistatic agents, ultraviolet absorbers, light stabilizers, peel adjustment agents, softeners, surfactants, flame retardants, antioxidants, and the like.

[0027] (Method for producing a depolymerizable copolymer) The method for producing the above depolymerizable copolymer is not particularly limited. For example, it may be copolymerized by a radical polymerization reaction. Specifically, the raw material monomers are sealed in an inert gas atmosphere together with a solvent mixed with a radical polymerization initiator, a crosslinking agent, etc., and copolymerized by continuously stirring for a long time, and then precipitated in a poor solvent and recovered to produce it.

[0028] As described above, the depolymerizable copolymer of the present invention has been described. The present invention is a depolymerizable copolymer obtained by copolymerizing a first monomer constituting a depolymerizable homopolymer that decomposes into monomers by heating, light, etc., and a second monomer different from this. The first monomer is α-methylstyrene (AMS), and the second monomer is ethyl methacrylate (EMA). Such a depolymerizable copolymer can easily recover monomers by heating even as a molded body with a different material such as metal that was difficult to recycle in the past, so it has excellent recyclability and its industrial applicability is extremely large.

Examples

[0029] The present invention will be described in more detail based on the following specific examples, but the present invention is not limited to the following examples.

[0030] [Example 1] (Synthesis of a Solvent-Resistant Copolymer) (1) Ion-exchanged water, sodium carbonate, and KS soap (solid content 90%, manufactured by Kao Corporation) were added to a 2-L four-necked flask and dissolved with stirring. (2) After dissolution, α-methylstyrene (AMS) and ethyl methacrylate (EMA) were added, and the system was purged with argon while stirring at 150 rpm (stirring blade: 10.5-cm-wide semi-circular). (3) When the temperature inside the flask reached 3 - 4 °C, sodium nitrite, sodium iron(III) ethylenediaminetetraacetate trihydrate, sodium ethylenediaminetetraacetate tetrahydrate, sodium formaldehyde sulfoxylate, and cumene hydroperoxide (80%) were sequentially added, and stirring was carried out for 67 hours while maintaining the internal temperature at 3 - 4 °C. (4) After 67 hours, a portion was sampled and dropped into methanol. Since a white solid precipitated, it was determined that the reaction was proceeding. 2,6-Di-tert-butyl-4-methylphenol was added to stop the reaction. (5) The reaction solution was dropped into 3.75 L of methanol, and the precipitated white solid was collected by centrifugation (at 9000 rpm for 10 minutes). (6) The supernatant was removed, and MeOH was added for washing. (7) Subsequently, centrifugation was carried out at 9000 rpm for 10 minutes to collect the solid. (8) The obtained white solid was simply dried and then dissolved in tetrahydrofuran (THF) (polymer concentration 10 wt%). (9) The solution from “(8)” was dropped into 500 mL of methanol, and the precipitated white solid was collected by centrifugation (at 9000 rpm for 10 minutes). (10) The supernatant of this separated and collected product was removed, and MeOH was added for washing. (11) Subsequently, centrifugation was carried out at 9000 rpm for 10 minutes to collect the solid. (12) The obtained white solid was dried under reduced pressure at 50 °C for 24 hours to obtain the final sample (yield: 3.22 g).

[0031] The charged amounts of the respective raw materials in the above synthesis method are shown in Table 1 below.

[0032]

Table 1

[0033] [Example 2] (NMR, GPC, TG-DTA Analysis of the Depolymerizable Copolymer) When the monomer ratio of the copolymer obtained in Example 1 was analyzed by NMR, it was found to be AMS:EMA = 58:42 (molar ratio). Also, when the molecular weight of this copolymer was analyzed by GPC, the number average molecular weight (Mn) was 8,040, the weight average molecular weight (Mw) was 30,676, and the molecular weight distribution (Mw / Mn) was 3.8. Furthermore, when the obtained copolymer was analyzed with a thermogravimetric differential thermal analyzer (TG-DTA) capable of image observation (N2 environment, heating rate 10°C / min), the decomposition start temperature was approximately 180°C, the 50% decomposition temperature was approximately 340°C, and the decomposition end temperature was approximately 380°C. General polymers discolor due to gradual decomposition starting from the ends of the polymer molecules upon continuous heating and finally leave black residues. However, the copolymer of Example 1 did not show such discoloration associated with decomposition, and it was confirmed that it completely decomposed into monomers, indicating high depolymerizability. The TG-DTA analysis results of the copolymer (P(AMS-EMA)) of Example 1 are shown in Table 2.

[0034] [Comparative Example 1] (TG-DTA Analysis of Polycarbonate) As an example of a polymer with low depolymerizability, the TG-DTA analysis (N2 environment, heating rate 10°C / min) of polycarbonate (PC) was carried out. As a result, the decomposition start temperature was approximately 400°C, and it gradually changed to black. The 50% decomposition end temperature was approximately 520°C, and it was observed that the decomposition proceeded to about 70% but about 30% remained undecomposed as residues. The TG-DTA analysis results of this polycarbonate are shown together with Table 2.

[0035]

Table 2

[0036] As is clear from Table 2, it was found that the copolymer obtained in Example 1 could be completely decomposed at a temperature lower than that of polycarbonate (PC).

[0037] [Example 3] (TG-DTA Analysis of the Depolymerizable Copolymer) In the TG-DTA analysis (N2 environment, heating rate 10 °C / min) of the copolymer synthesized in Example 1, after heating to 350 °C, the temperature was maintained at 350 °C. As a result, it was confirmed that the decomposition was completed and there was no residue until 30 minutes after maintaining the temperature.

[0038] [Example 4] (TG-DTA / MS Analysis of the Depolymerizable Copolymer) For the copolymer of AMS and EMA obtained in Example 1, mass spectrometry of the pyrolysis gas (TG-DTA / MS) was performed up to 500 °C under the following conditions. As a result, AMS and EMA were detected as the components generated by pyrolysis, and no other components were detected. The conditions for TG-DTA / MS analysis are shown in Tables 3 to 5 below.

[0039]

Table 3

[0040]

Table 4

[0041]

Table 5

[0042] [Example 5] (Recovery of Pyrolysis Monomers and Recycled Synthesis of the Depolymerizable Copolymer) The copolymer of AMS and EMA obtained in Example 1 was heated to 350°C at a heating rate of 10°C / min in an argon flow environment and maintained at 350°C. The vaporized components were cooled to room temperature to obtain a liquid component. As a result of polymer synthesis from this liquid component in the same manner as in Example 1, a copolymer of AMS and EMA was obtained in the same manner as in Example 1, and it was confirmed that it could be reused.

Claims

1. A depolymerizable copolymer obtained by copolymerizing a first monomer that constitutes a depolymerizable homopolymer that decomposes into monomers by heating, light, etc., and a second monomer different from the first monomer, wherein the first monomer is α-methylstyrene (AMS) and the second monomer is ethyl methacrylate (EMA).

2. The depolymerizable copolymer according to claim 1, wherein the molar ratio of α-methylstyrene to ethyl methacrylate in the depolymerizable copolymer is 10:90 to 90:

10.

3. The depolymerizable copolymer according to claim 1, wherein the weight average molecular weight (Mw) of the depolymerizable copolymer is 5,000 to 1,000,000.

4. The depolymerizable copolymer according to any one of claims 1 to 3, wherein the thermal decomposition temperature of the depolymerizable copolymer is 180 to 380°C.

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