WO2024119458A1

WO2024119458A1 - Polycarbonate oligomer and preparation method therefor, curable composition, epoxy cured product, and method for degrading epoxy cured product by means of aminolysis

Info

Publication number: WO2024119458A1
Application number: PCT/CN2022/137765
Authority: WO
Inventors: 汪孟纬; 黄筠雯
Original assignee: 上纬创新育成股份有限公司
Priority date: 2022-12-09
Filing date: 2022-12-09
Publication date: 2024-06-13

Abstract

Provided in the present invention is a polycarbonate oligomer, which has the structure as shown in formula (I), wherein R1, R2, X, n and a in formula (I) are as defined in the description. Whereby, the polycarbonate oligomer is prepared from waste polycarbonate by utilizing the principle of alcoholysis, such that the polycarbonate oligomer has good processability, can act as an epoxy resin hardening agent to be directly mixed with an epoxy resin and cure same, and the obtained epoxy cured product has both good physical properties and degradability, achieving the aim of recycling waste.

Description

Polycarbonate oligomer, preparation method thereof, curable composition, epoxy cured product and method for aminolysis degradation of epoxy cured product

Technical Field

The present invention relates to an oligomer and a preparation method thereof, in particular to a polycarbonate oligomer, a preparation method thereof, a curable composition, an epoxy cured product and a method for degrading the epoxy cured product by aminolysis.

Background technique

Polycarbonate (PC) is currently produced in industry by transesterification of bisphenol A and diphenyl carbonate at high temperature. It is a polymer material with good optical and mechanical properties and is widely used in drinking water barrels, optical discs, data storage, auto parts and other consumer products.

At present, the recycling of polycarbonate is still mainly carried out physically by mechanical processing or physical mixing, and the defects of the physical properties of the recycled materials are supplemented by adding new materials. Although the operation is relatively simple, the physical properties of polycarbonate are easily destroyed during the recycling process, so its application is still greatly limited. In addition, when the recycled polycarbonate is mixed with epoxy resin for re-curing, it is often still necessary to dissolve the polycarbonate and epoxy resin with a solvent before the subsequent curing operation can be carried out. Therefore, the re-curing and reuse of the existing polycarbonate after recycling still requires the participation of a solution, which is inconvenient to operate and is not environmentally friendly.

In order to cope with the issue of future recycling, many academic articles have begun to discuss chemical recycling methods, which obtain bisphenol A monomer (BPA) through degradation and then return it to the synthesis of polycarbonate. However, this method requires the use of a large amount of solvents and cumbersome separation and purification steps to obtain high-purity bisphenol A monomer, which increases the difficulty of industrialization.

In view of this, how to use waste polycarbonate as a hardener for epoxy resin and solidify it with epoxy resin so that the solidified product has the characteristics of being recyclable and decomposable to achieve the sustainable utilization of waste polycarbonate has become the goal of relevant industries.

Summary of the invention

An object of the present invention is to provide a polycarbonate oligomer and a preparation method thereof, wherein waste polycarbonate is prepared into the polycarbonate oligomer by the principle of alcoholysis, so that the polycarbonate oligomer has better processability and can be used as an epoxy resin hardener.

Another object of the present invention is to provide a curable composition, an epoxy cured product and a method for degrading the epoxy cured product by aminolysis, wherein a polycarbonate oligomer is cured with an epoxy resin, and the obtained cured product can retain excellent physical properties and has recyclable characteristics.

One embodiment of the present invention provides a polycarbonate oligomer having a structure as shown in formula (I):

Wherein, _R1 is a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, an allyl group, an alkoxy group having 1 to 6 carbon atoms, an aromatic group having 6 to 12 carbon atoms, or a halogen atom; _R2 is an alkyl group having 1 to 10 carbon atoms, an ether group having 1 to 10 carbon atoms, a cycloalkyl group having 3 to 6 carbon atoms, or a structure represented by formula (1), formula (2), formula (3), formula (4), formula (5), formula (6), or formula (7):

Wherein, X is a single bond, or a structure represented by formula (8), formula (9), formula (10), formula (11), formula (12), formula (13), formula (14), formula (15), formula (16), formula (17) or formula (18):

wherein _R3 is a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, an allyl group, an alkoxy group having 1 to 6 carbon atoms, an aromatic group having 6 to 12 carbon atoms, or a halogen atom; _R4 is a hydrogen atom or a methyl group; a is an integer from 0 to 4; b is an integer from 0 to 5; n is any number from 0 to 60; and m and p are each independently any number from 0 to 50. _X1 and _X2 are each independently a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, or an aromatic group having 6 to 12 carbon atoms.

Another embodiment of the present invention provides a method for preparing the aforementioned polycarbonate oligomer, comprising a dissolving step, an adding step, a washing step, and a filtering step. The dissolving step is to dissolve a polycarbonate in a solvent, and heat it to a heating temperature and stir it to form a first mixture. The adding step is to add a compound as shown in formula (II) to the first mixture and maintain the reaction at the heating temperature to form a second mixture:

The washing step is to cool the second mixture and wash it by precipitation with an alcohol solvent to form a third mixture. The filtering step is to filter and dry the third mixture to obtain a polycarbonate oligomer.

According to the preparation method of polycarbonate oligomer described in the previous paragraph, the solvent can be selected from the group consisting of N,N-dimethylacetamide, N-methylpyrrolidone, dimethylformamide, anisole, dimethyl sulfoxide, propylene glycol methyl ether acetate, and propylene glycol methyl ether propionate.

According to the method for preparing the polycarbonate oligomer described in the preceding paragraph, the heating temperature may be 100° C. to 180° C.

According to the method for preparing the polycarbonate oligomer described in the preceding paragraph, the molar ratio of the polycarbonate to the compound represented by formula (II) can be 1:10 to 1:90.

Another embodiment of the present invention provides a curable composition comprising the aforementioned polycarbonate oligomer, an epoxy resin and a catalyst, which are mixed at a mixing temperature, wherein the equivalent ratio of the carbonate group of the polycarbonate oligomer to the epoxy group of the epoxy resin is 0.5 to 3.0.

According to the curable composition described in the preceding paragraph, the catalyst can be selected from the group consisting of 4-dimethylaminopyridine, imidazole, 2-methylimidazole, 2-phenylimidazole, and 2-ethyl-4-methylimidazole.

According to the curable composition described in the preceding paragraph, the amount of the catalyst added may be 0.05 weight percent to 5.0 weight percent of the epoxy resin content.

According to the curable composition described in the preceding paragraph, the mixing temperature may be 90°C to 170°C.

Another embodiment of the present invention provides an epoxy cured product, which is obtained by subjecting the aforementioned curable composition to a curing reaction.

According to the epoxy cured product described in the previous paragraph, the curing reaction is completed by heating the curable composition, and a curing temperature of the curing reaction can be 150°C to 240°C.

Another embodiment of the present invention provides a method for degrading epoxy curing material by aminolysis, comprising providing the aforementioned epoxy curing material and performing a degradation step, wherein the degradation step is to react a compound containing an aliphatic amine group with the epoxy curing material to degrade the epoxy curing material by aminolysis.

According to the method for degrading epoxy cured material by aminolysis described in the preceding paragraph, the epoxy cured material is degraded to form a phenoxy resin as shown in formula (III):

Wherein, Y is a single bond, a structure represented by formula (8), formula (9), formula (10), formula (11), formula (12), formula (13), formula (14), formula (15), formula (16), formula (17), formula (18), or a structure represented by formula (19):

Thus, the polycarbonate oligomer of the present invention reuses polycarbonate as an epoxy resin hardener, and the two are mixed without solvent and can be applied to epoxy molding compound (EMC). An epoxy cured product with excellent properties is formed under the catalysis of a catalyst, which can be degraded to enable recycling and reuse, thus meeting environmental benefits.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to make the above and other objects, features, advantages and embodiments of the present invention more clearly understood, the following are the descriptions of the accompanying drawings:

FIG. 1 is a flow chart showing the steps of a method for preparing a polycarbonate oligomer according to one embodiment of the present invention;

FIG2 is a flow chart showing the steps of a method for preparing an epoxy cured product according to another embodiment of the present invention;

FIG3 is a flow chart showing the steps of a method for aminolysis degradation of epoxy cured materials according to another embodiment of the present invention;

FIG4 shows the 1H-NMR spectrum of Example 1;

FIG5 shows the 1H-NMR spectrum of Comparative Example 1;

FIG6 is a Fourier transform infrared spectrum diagram of Example 1;

FIG. 7 is a Fourier transform infrared spectrum diagram of Example 4; and

FIG. 8 shows the 1H-NMR spectrum of Example 7.

【Symbol Description】

100: Preparation method of polycarbonate oligomer

200: Preparation method of epoxy cured product

300: Method for degrading epoxy cured products by aminolysis

110,120,130,140,210,220,310,320: Steps

Detailed ways

The following will discuss various embodiments of the present invention in more detail. However, this embodiment can be an application of various inventive concepts and can be specifically implemented in various specific scopes. The specific embodiments are for illustrative purposes only and are not limited to the scope of the disclosure.

In the present invention, the structure of a compound is sometimes represented by a skeleton formula, which may omit carbon atoms, hydrogen atoms, and carbon-hydrogen bonds. If a functional group is clearly drawn in the structural formula, the one shown shall prevail.

In the present invention, "polycarbonate oligomer having a structure as shown in formula (I)" may be expressed as polycarbonate oligomer shown in formula (I) or polycarbonate oligomer (I) for the sake of brevity and fluency, and the representation of other compounds or groups may be deduced in the same manner.

The present invention provides a polycarbonate oligomer having a structure as shown in formula (I):

Therefore, the polycarbonate oligomer of the present invention has better processability than high molecular weight polycarbonate and better compatibility with epoxy resin, and can be used as epoxy resin hardener.

1 , which is a flow chart of the steps of a method 100 for preparing a polycarbonate oligomer according to an embodiment of the present invention. In FIG1 , the method 100 for preparing a polycarbonate oligomer comprises

steps

110 , 120 , 130 , and 140 .

Step 110 is a dissolving step, wherein a polycarbonate is dissolved in a solvent, and the temperature is raised to a heating temperature and stirred to form a first mixture. Specifically, the solvent is preferably a non-alcoholic and non-amine solvent having a boiling point higher than 110° C. and capable of dissolving the polycarbonate. Therefore, the solvent of the present invention can be selected from a group consisting of N,N-dimethylacetamide (DMAc), N-methylpyrrolidone (NMP), dimethylformamide (DMF), anisole, dimethyl sulfoxide (DMSO), propylene glycol methyl ether acetate, and propylene glycol methyl ether propionate, and the heating temperature can be 100° C. to 180° C., preferably 130° C. to 170° C.

Step 120 is to perform an adding step, in which a compound represented by formula (II) is added to the first mixture and maintained at a heating temperature to react to form a second mixture:

The definition of R ₂ is as mentioned above and will not be further described here. In addition, the molar ratio of the polycarbonate to the compound represented by formula (II) may be 1:10 to 1:90, preferably 1:40 to 1:70.

Step 130 is a cleaning step, wherein the second mixture is cooled and precipitated and cleaned with an alcohol solvent to form a third mixture. Specifically, the alcohol solvent may be methanol, ethanol, or isopropanol, but is not limited thereto.

Step 140 is to perform a filtering step, in which the third mixture is filtered and dried to obtain a polycarbonate oligomer which is a powder product.

The present invention provides a curable composition comprising the aforementioned polycarbonate oligomer, an epoxy resin and a catalyst, wherein the equivalent ratio of the carbonate group of the polycarbonate oligomer to the epoxy group of the epoxy resin can be 0.5 to 3.0.

The aforementioned epoxy resin may be a bisphenol A epoxy resin (DGEBA), a phenolic epoxy resin (PNE), a cresol novolac epoxy resin (CNE), a dicyclopentadiene-phenol epoxy resin (DNE), a naphthalene-containing epoxy resin, a phosphorus-based epoxy resin or a mixture thereof. In other words, the aforementioned epoxy resin may be used alone or in combination of two or more thereof, and when two or more thereof are used, they may be mixed in any proportion. Thus, by selecting an appropriate epoxy resin, the desired properties may be imparted to the subsequent cured product.

The catalyst may be selected from the group consisting of 4-dimethylaminopyridine (DMAP), imidazole, 2-methylimidazole, 2-phenylimidazole, and 2-ethyl-4-methylimidazole. The catalyst may react with the epoxy group of the epoxy resin to facilitate the subsequent curing reaction. Specifically, the amount of the catalyst added may be 0.05 to 5.0 weight percent of the epoxy resin content, preferably 0.1 to 0.5 weight percent.

In detail, the curable composition is prepared by mixing a polycarbonate oligomer as shown in formula (I), an epoxy resin and a catalyst at a mixing temperature, wherein the mixing temperature can be 90°C to 170°C, preferably 110°C to 140°C. Too low a temperature will result in uneven mixing, while too high a temperature will result in gelation due to the curing reaction, making it impossible to prepare a sample smoothly.

The present invention further provides an epoxy cured product, which is obtained by subjecting the curable composition to a curing reaction, and the curing reaction is briefly described below with reference to FIG. 2 , wherein FIG. 2 is a flow chart of a method 200 for preparing an epoxy cured product according to another embodiment of the present invention. In FIG. 2 , the method 200 for preparing an epoxy cured product includes

steps

210 and 220.

Step 210 is a mixing step, in which the polycarbonate oligomer, epoxy resin and catalyst as shown in formula (I) are mixed to obtain a curable composition. Specifically, through step 210, the polycarbonate oligomer, epoxy resin and catalyst can form a solid prepolymer containing the curable composition, and the details of the polycarbonate oligomer, epoxy resin and catalyst are referred to above, which will not be repeated here.

Step 220 is a curing step to crosslink the polycarbonate oligomer and the epoxy resin under the catalysis of a catalyst to form an epoxy cured product, wherein the curing reaction is completed by heating the curable composition, and the curing temperature of the curing reaction can be 150° C. to 240° C., preferably 170° C. to 200° C.

Please refer to FIG3 , which is a flowchart of a method 300 for degrading epoxy cured material by aminolysis according to another embodiment of the present invention. In FIG3 , the method 300 for degrading epoxy cured material by aminolysis includes step 310 and step 320 .

Step 310 is to provide the aforementioned epoxy curing material. Step 320 is to perform a degradation step, in which a compound containing an aliphatic amine group reacts with the epoxy curing material to degrade the epoxy curing material by aminolysis.

In addition, the aforementioned epoxy cured product can be degraded and washed with alcohol to obtain a phenoxy resin as shown in formula (III):

Wherein, the definition of X is as described above and is not further described here, and Y is a single bond, a structure represented by formula (8), formula (9), formula (10), formula (11), formula (12), formula (13), formula (14), formula (15), formula (16), formula (17), formula (18), or a structure represented by formula (19):

Furthermore, the phenoxy resin represented by formula (III) is advantageously reusable as an auxiliary agent.

The present invention is further illustrated by the following specific examples, which are used to facilitate those skilled in the art to which the present invention belongs, so that they can fully utilize and practice the present invention without excessive interpretation. These examples should not be regarded as limiting the scope of the present invention, but are used to illustrate how to implement the materials and methods of the present invention.

Example 1: 100 g (4×10 ^-3 mole) of polycarbonate pellets (purchased from Chi Mei Industrial, product code PC-122) were added with 150 g of N,N-dimethylacetamide solvent, and the temperature was raised to 150°C and maintained while stirring to dissolve the polycarbonate pellets in the solvent to form a first mixture. Then, 18.3 g (0.17 mole) of benzyl alcohol was added and reacted for 9 hours to form a second mixture. The second mixture was then cooled and poured into methanol for washing and precipitation to form a third mixture. The third mixture was then filtered by vacuum filtration to obtain a white powder, which was then placed in a vacuum oven at 110°C for drying to obtain the polycarbonate oligomer powder of Example 1, with a yield of 75%. Specifically, the number average molecular weight (Mn) of the polycarbonate PC-122 is 24,400, and the weight average molecular weight (Mw) is 45,488. The number average molecular weight (Mn) of the polycarbonate oligomer of Example 1 is 2,391, and the weight average molecular weight (Mw) is 3,532 after being measured by gel chromatography permeameter (GPC).

Example 2: 100 g (4.1×10 ^-3 mole) of polycarbonate pellets (purchased from Chi Mei Industrial, product code PC-122) were added with 150 g of N,N-dimethylacetamide solvent, and the temperature was raised to 150°C and maintained while stirring to dissolve the polycarbonate pellets in the solvent to form a first mixture. Then, 27.41 g (0.25 mole) of benzyl alcohol was added and reacted for 9 hours to form a second mixture. The second mixture was then cooled and poured into methanol for washing and precipitation to form a third mixture. The third mixture was then filtered by vacuum filtration to obtain a white powder, which was then placed in a vacuum oven at 110°C for drying to obtain the polycarbonate oligomer powder of Example 2, with a yield of 45%. Specifically, the number average molecular weight (Mn) of the polycarbonate PC-122 is 24,400, and the weight average molecular weight (Mw) is 45,488. The number average molecular weight (Mn) of the polycarbonate oligomer of Example 2 is 2,163, and the weight average molecular weight (Mw) is 2,747 after being measured by gel chromatography permeameter (GPC).

Example 3: 100 g (4.3×10 ^-3 mole) of waste polycarbonate was added with 150 g of N,N-dimethylacetamide solvent, and the temperature was raised to 150°C and maintained while stirring to dissolve the waste polycarbonate in the solvent to form a first mixture. Then, 18.3 g (0.17 mole) of benzyl alcohol was added and reacted for 9 hours to form a second mixture. The second mixture was then cooled and poured into methanol for washing and precipitation to form a third mixture. The third mixture was then filtered by vacuum filtration to obtain a white powder, which was then placed in a vacuum oven at 110°C for drying to obtain the polycarbonate oligomer powder of Example 3 with a yield of 78%. Specifically, after measurement by gel chromatography permeameter (GPC), the number average molecular weight (Mn) of the waste polycarbonate is 23,512, and the weight average molecular weight (Mw) is 44,758, while the number average molecular weight (Mn) of the polycarbonate oligomer of Example 3 is 3,561, and the weight average molecular weight (Mw) is 5,707.

Comparative Example 1: 100 g (4.1×10 ^-3 mole) of polycarbonate pellets (purchased from Chi Mei Industrial, product code PC-122) were added with 150 g of N,N-dimethylacetamide solvent, and the temperature was raised to 150°C and maintained while stirring to dissolve the polycarbonate pellets in the solvent to form a first mixture. Then, 4.58 g (0.04 mole) of benzyl alcohol was added and reacted for 9 hours to form a second mixture. The second mixture was then cooled and poured into methanol for washing and precipitation to form a third mixture. The third mixture was then filtered by vacuum filtration to obtain a white powder, which was then placed in a vacuum oven at 110°C for drying to obtain the polycarbonate oligomer powder of Comparative Example 1, with a yield of 88%. Specifically, the number average molecular weight (Mn) of the polycarbonate PC-122 is 24,400, and the weight average molecular weight (Mw) is 45,488, while the number average molecular weight (Mn) of the polycarbonate oligomer of Comparative Example 1 is 8,798, and the weight average molecular weight (Mw) is 10,777 after being measured by gel chromatography permeameter (GPC).

The reaction equations for Examples 1 to 3 and Comparative Example 1 are shown in Table 1 below.

¹ H-NMR analysis was performed on Examples 1 to 3 and Comparative Example 1 to confirm the structures of Examples 1 to 3 and Comparative Example 1. Please refer to FIG. 4 and FIG. 5, where FIG. 4 shows the ¹ H-NMR spectrum of Example 1, and FIG. 5 shows the ¹ H-NMR spectrum of Comparative Example 1. The ¹ H-NMR spectra of Examples 2 and 3 are similar to those of Example 1 and are not shown separately. From the results of FIG. 4 and FIG. 5, it can be seen that the products of Examples 1 to 3 are all polycarbonate oligomers, and the molecular weight of Comparative Example 1 is larger than that of Examples 1 to 3.

Example 4: Take 2 grams of Example 1 (127.14 g/eq) and 2.91 grams of bisphenol A epoxy resin (purchased from Changchun Resin, product code BE188), melt and stir at 110°C so that the equivalent ratio of the above two is 1. After mixing, add 0.006 grams of 2-phenylimidazole (0.2wt% of BE188) as a catalyst at 90°C, and melt and stir evenly to obtain a mixed prepolymer, which is then placed in an oven at 175°C for curing. The curing time is 30 minutes, and the epoxy cured product of Example 4 can be obtained.

Example 5: Take 2 grams of Example 2 (127.14 g/eq) and 2.91 grams of bisphenol A epoxy resin (purchased from Changchun Resin, product code BE188) and melt and stir at 110°C so that the equivalent ratio of the above two is 1. After mixing, 0.006 grams of 2-phenylimidazole (0.2 wt% of BE188) is added at 90°C as a catalyst. The remaining steps are the same as in Example 4, and the epoxy cured product of Example 5 can be obtained.

Example 6: Take 2 grams of Example 3 (127.14 g/eq) and 2.91 grams of bisphenol A epoxy resin (purchased from Changchun Resin, product code BE188) and melt and stir at 110°C so that the equivalent ratio of the above two is 1. After mixing, 0.006 grams of 2-phenylimidazole (0.2wt% of BE188) is added at 90°C as a catalyst. The remaining steps are the same as in Example 4, and the epoxy cured product of Example 6 can be obtained.

Comparative Example 2: 2 g of polycarbonate (purchased from Chi Mei Industrial, product code PC-122, 127.14 g/eq) and 2.91 g of bisphenol A epoxy resin (purchased from Chang Chun Resin, product code BE188) were melted and stirred at 140° C. in a ratio of 1, but they could not be completely melted and mixed. Furthermore, 0.006 g of 2-phenylimidazole (0.2 wt% of BE188) was added as a catalyst at 140° C., but they immediately gelled and could not be smoothly mixed to obtain a prepolymer.

Comparative Example 3: 2 g of polycarbonate (purchased from Chi Mei Industrial, product code PC-122, 127.14 g/eq) and 2.91 g of bisphenol A epoxy resin (purchased from Chang Chun Resin, product code BE188) were melt-stirred at 140° C. in a ratio of 1 to an equivalent ratio of the two, and after mixing, 0.006 g of 4-dimethylaminopyridine (0.2 wt % of BE188) was added as a catalyst at 140° C. However, the mixture immediately gelled and could not be mixed smoothly to obtain a prepolymer.

Comparative Example 4: 2 g of waste polycarbonate (127.14 g/eq) and 2.91 g of bisphenol A epoxy resin (purchased from Changchun Resin, product code BE188) were melted and stirred at 140°C in a ratio such that the equivalent ratio of the two was 1. After mixing, 0.006 g of 2-phenylimidazole (0.2 wt% of BE188) was added as a catalyst at 140°C, but the mixture immediately gelled and could not be mixed smoothly to obtain a prepolymer.

Comparative Example 5: 2 grams of the polycarbonate oligomer of Comparative Example 1 (127.14 g/eq) and 2.91 grams of bisphenol A epoxy resin (purchased from Changchun Resin, product code BE188) were melt-stirred at 140°C so that the equivalent ratio of the two was 1. After mixing, 0.006 grams of 2-phenylimidazole (0.2 wt% of BE188) was added as a catalyst at 140°C, but it immediately gelled and could not be mixed smoothly to obtain a prepolymer.

Comparative Example 6: 2 g of phenolic resin (purchased from Changchun Resin, product code PF8110, 127.14 g/eq) and 2.91 g of bisphenol A epoxy resin (purchased from Changchun Resin, product code BE188) were melted and stirred at 140° C. at a ratio of 1 to an equivalent ratio of the two. After mixing, 0.006 g of 2-phenylimidazole (0.2 wt % of BE188) was added as a catalyst at 90° C. The remaining steps were the same as in Example 4, and the epoxy cured product of Comparative Example 6 was obtained.

Please refer to FIG. 6 and FIG. 7 , wherein FIG. 6 shows the Fourier transform infrared spectrum (FTIR) of Example 1, and FIG. 7 shows the Fourier transform infrared spectrum (FTIR) of Example 4. From the result of FIG. 6 , it can be seen that the C=O characteristic peak of the carbonyl group in the polycarbonate oligomer of Example 1 is located at 1764 cm ^-1 , and from the result of FIG. 7 , it can be seen that after Example 1 and epoxy resin are cured, the C=O characteristic peak of the carbonyl group in the epoxy cured product of Example 4 is shifted to 1748 cm ^-1 , indicating that the carbonyl group is converted from an aromatic carbonate structure to an aliphatic carbonate structure, and the reaction is shown in Table 2 below.

According to the above results, when using Comparative Example 1 and polycarbonate as epoxy curing agents, they need to be heated to 140°C for melt mixing, and cooling will cause the sample to be solid, so that the catalyst can only be added at high temperature. After the catalyst is added at high temperature, the reaction will be triggered during the mixing process, which is easy to cause the sample to gel during the process, resulting in failure to smoothly prepare the sample. The molecular weight of the polycarbonate oligomers of Examples 1 to 3 of the present invention is lower than that of Comparative Example 1 and polycarbonate, and has better miscibility during melt mixing. It can be melt mixed with epoxy resin at 110°C, and can still remain in a molten state after cooling to 90°C, which is conducive to catalyst addition and has a good processing range. The curable composition can be completely reacted when cured at 175°C, confirming that it has good reactivity with epoxy resin and can be clearly used as an epoxy curing agent. In addition, it can be evenly mixed under high temperature melting, and has certain operability after adding the catalyst, and will not gel immediately, so that it has a good processing time.

Thermal properties of the epoxy cured products of Examples 4 to 6 and Comparative Example 6 were evaluated by measuring the glass transition temperature (T _g ) using a differential scanning calorimeter (DSC) at a heating rate of 10° C./min. The T _g measurement results are listed in Table 3 below.

From the results in Table 3 above, it can be seen that the glass transition temperatures of Examples 4 to 6 fluctuate with the molecular weight of the oligomers. Although the performance is slightly worse than that of epoxy cured with phenolic hardener, it can still show a heat resistance greater than 120°C, which is sufficient for many applications.

In order to understand the degradation of epoxy cured products cured by the polycarbonate oligomer of the present invention, first, 0.2 g of epoxy cured products of Examples 4 to 6 and Comparative Example 6 and 4 g of ethanolamine (MEA) were placed in a reactor and heated in an oven. After the reaction was completed, the ethanolamine was extracted to obtain degraded Examples 7 to 9 and Comparative Example 7, wherein Examples 7 to 9 are the results of degradation reactions of epoxy cured products of Examples 4 to 6, and Comparative Example 7 is the result of degradation reactions of epoxy cured products of Comparative Example 6. The types of epoxy cured products, reaction temperatures (°C), reaction times (hrs) and residual weights (%) selected in Examples 7 to 9 and Comparative Example 7 are shown in Table 4 below.

From the results in Table 4, it can be seen that Examples 4 to 6 all use the polycarbonate oligomer of the present invention as the epoxy curing agent. When the epoxy cured product formed by the reaction with the epoxy resin is to be degraded, it only needs to add aliphatic amines and heat to carry out the aminolysis reaction. Finally, the epoxy cured product will be completely decomposed, and the residual weight is 0%. In contrast, Comparative Example 6 uses phenolic resin as the curing agent, which does not have the property of being decomposable, so it still maintains the original epoxy cured product state.

In addition, please refer to FIG8 , which shows the ¹ H-NMR spectrum of Example 7. Example 7 uses the epoxy cured product of Example 4 of the present invention and ethanolamine for degradation reaction. After the reaction is completed, the excess ethanolamine is removed, and then washed with ethanol, filtered and dried to obtain a light yellow solid product. The light yellow solid product is analyzed by ¹ H-NMR, and the result can be shown in FIG8 . The degradation product of the epoxy cured product of Example 4 after the reaction with ethanolamine is a high-purity phenoxy resin, and its reaction equation is shown in Table 5 below. After being measured by gel chromatography permeameter (GPC), the number average molecular weight (Mn) is 8,391, and the weight average molecular weight (Mw) is 10,612. It can be used as a polyol oligomer for modification or as a coating additive to achieve the goal of complete recycling.

In summary, the present invention can obtain polycarbonate oligomers by alcoholysis of waste polycarbonate, which can be used as epoxy resin hardener. In addition, the polycarbonate oligomers of the present invention can be directly mixed with epoxy resin for curing, which reduces the use of solvents compared with the prior art, and has a significant breakthrough in epoxy resin melt processing. The curing at high temperature can obtain a high-temperature resistant cured product, and the cured product can be completely aminolyzed after being soaked in aliphatic amines and heated, and finally a high-purity phenoxy resin can be obtained, which is expected to be used as an additive in the product cycle to achieve the purpose of waste recycling.

Although the present invention has been disclosed in the above embodiments, it is not intended to limit the present invention. Anyone skilled in the art can make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention shall be determined by the appended claims.

Claims

A polycarbonate oligomer, characterized in that it has a structure as shown in formula (I):

Wherein, R1 is a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, an allyl group, an alkoxy group having 1 to 6 carbon atoms, an aromatic group having 6 to 12 carbon atoms, or a halogen atom; R2 is an alkyl group having 1 to 10 carbon atoms, an ether group having 1 to 10 carbon atoms, a cycloalkyl group having 3 to 6 carbon atoms, or a structure represented by formula (1), formula (2), formula (3), formula (4), formula (5), formula (6), or formula (7):

Wherein, X is a single bond, or a structure represented by formula (8), formula (9), formula (10), formula (11), formula (12), formula (13), formula (14), formula (15), formula (16), formula (17) or formula (18):

wherein R3 is a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, an allyl group, an alkoxy group having 1 to 6 carbon atoms, an aromatic group having 6 to 12 carbon atoms, or a halogen atom; R4 is a hydrogen atom or a methyl group; a is an integer from 0 to 4; b is an integer from 0 to 5; n is any number from 0 to 60; and m and p are each independently any number from 0 to 50;

wherein X1 and X2 are each independently a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, or an aromatic group having 6 to 12 carbon atoms.
A method for preparing a polycarbonate oligomer according to claim 1, characterized in that it comprises:

A dissolving step is performed, wherein a polycarbonate is dissolved in a solvent, and the mixture is heated to a heating temperature and stirred to form a first mixture;

An adding step is performed, wherein a compound as shown in formula (II) is added to the first mixture and maintained at the heating temperature to react to form a second mixture:

performing a washing step, wherein the second mixture is cooled and precipitated and washed with an alcohol solvent to form a third mixture; and

A filtration step is performed to filter and dry the third mixture to obtain the polycarbonate oligomer.
The method for preparing a polycarbonate oligomer as claimed in claim 2, wherein the solvent is selected from the group consisting of N,N-dimethylacetamide, N-methylpyrrolidone, dimethylformamide, anisole, dimethyl sulfoxide, propylene glycol methyl ether acetate, and propylene glycol methyl ether propionate.
The method for preparing a polycarbonate oligomer as claimed in claim 2, characterized in that the heating temperature is 100°C to 180°C.
The method for preparing a polycarbonate oligomer according to claim 2, wherein the molar ratio of the polycarbonate to the compound represented by formula (II) is 1:10 to 1:90.
A curable composition, characterized in that it comprises the polycarbonate oligomer as claimed in claim 1, an epoxy resin and a catalyst, which are mixed at a mixing temperature, wherein the equivalent ratio of the carbonate group of the polycarbonate oligomer to the epoxy group of the epoxy resin is 0.5 to 3.0.
The curable composition according to claim 6, wherein the catalyst is selected from the group consisting of 4-dimethylaminopyridine, imidazole, 2-methylimidazole, 2-phenylimidazole, and 2-ethyl-4-methylimidazole.
The curable composition according to claim 6, wherein the catalyst is added in an amount of 0.05 weight percent to 5.0 weight percent of the epoxy resin.
The curable composition according to claim 6, wherein the mixing temperature is 90°C to 170°C.
An epoxy cured product, characterized in that it is obtained by subjecting the curable composition according to any one of claims 6 to 9 to a curing reaction.
The epoxy cured product as claimed in claim 10, characterized in that the curing reaction is completed by heating the curable composition, and a curing temperature of the curing reaction is 150°C to 240°C.
A method for degrading epoxy cured products by aminolysis, characterized by comprising:

Providing the epoxy cured product as claimed in claim 10; and

A degradation step is performed in which a compound containing an aliphatic amine group reacts with the epoxy curing material to degrade the epoxy curing material by aminolysis.
The method for degrading epoxy cured material by aminolysis as claimed in claim 12, characterized in that the epoxy cured material is degraded to form a phenoxy resin as shown in formula (III):

Wherein, Y is a single bond, the structure represented by formula (8), formula (9), formula (10), formula (11), formula (12), formula (13), formula (14), formula (15), formula (16), formula (17), formula (18), or a structure represented by formula (19):