CHEMICALLY DECOMPOSABLE THERMOSETTING RESIN COMPOSITION FOR RECYCLING FIBER-REINFORCED COMPOSITE AND DISSOLVING METHOD THEREOF

Abstract

Disclosed is a chemically decomposable thermosetting resin composition for recycling a fiber-reinforced composite, including an epoxy resin, a multifunctional glycidyl-ester-based compound, an additive having a hydroxyl group on at least one of terminals of a main chain thereof, and an acid-anhydride-based curing agent, thus exhibiting excellent chemical decomposition performance in a basic solution and a high glass transition temperature. A method of dissolving the thermosetting resin composition is also provided. Thereby, a thermosetting composite material containing a thermosetting resin of the invention enables recycling of carbon fiber through hydrolysis, and thus the carbon fiber recycling industry and the recycled resin industry can be newly expanded. The thermosetting resin can be applied to fields using not only carbon composite materials but also general thermosetting resins, and can be hydrolyzed in a basic solution, which can significantly reduce landfill or disposal costs.

Claims

1. A chemically decomposable thermosetting resin composition, comprising: an epoxy resin; a multifunctional glycidyl-ester-based compound; an additive having a hydroxyl group on at least one of terminals of a main chain thereof, the additive being at least one selected from the group consisting of compounds represented by Chemical Formulas 2 to 4 below; and an acid-anhydride-based curing agent, wherein the thermosetting resin composition comprises, based on 100 wt % of a total amount thereof excluding the curing agent, 1 to 98 wt % of the epoxy resin, 1 to 98 wt % of the multifunctional glycidyl-ester-based compound, and 1 to 30 wt % of the additive having a hydroxyl group on at least one of terminals of the main chain thereof: ##STR00021## (in Chemical Formula 2, n is 0 or 1; R.sup.1 is hydrogen or a linear or branched C.sub.1-5 alkyl; and R.sup.2s are each independently ##STR00022## and the same as or different from each other, wherein u is 0 to 330, v is 0 to 430, both u and v are not zero, and repeating units ##STR00023## in parentheses are randomly arranged); ##STR00024## (in Chemical Formula 3, R.sup.3 is hydrogen, a linear or branched C.sub.1-5 alkyl, cycloalkane having 5 to 10 atoms, benzene or naphthalene; r is 1 to 6; p is 0 to 430, q is 0 to 330, and both p and q are not zero; repeating units ##STR00025## in parentheses are randomly arranged; and Chemical Formula 3 is configured such that R.sup.3 is substituted with ##STR00026## (in Chemical Formula 4, R.sup.4 is a linear or branched C.sub.1-5 alkyl, cycloalkane having 5 to 10 atoms, benzene or naphthalene; s is 0 to 430; t is 1 to 6; and Chemical Formula 4 is configured such that R.sup.4 is substituted with ##STR00027##

2. The chemically decomposable thermosetting resin composition of claim 1, wherein the multifunctional glycidyl-ester-based compound is at least one compound represented by Chemical Formula 1 below: ##STR00028## (in Chemical Formula 1, ##STR00029## is cycloalkane having 5 to 10 atoms, benzene or naphthalene; x is 1 to 5; and y is 1 to 10).

3. The chemically decomposable thermosetting resin composition of claim 1, wherein the acid-anhydride-based curing agent is contained in an amount of 70 to 160 parts by weight based on 100 parts by weight of a total amount of the epoxy resin, the multifunctional glycidyl-ester-based compound and the additive having a hydroxyl group on at least one of terminals of the main chain thereof.

4. The chemically decomposable thermosetting resin composition of claim 1, wherein the acid-anhydride-based curing agent is at least one selected from the group consisting of phthalic anhydride (PA), succinic anhydride, maleic anhydride, methyl nadic anhydride (MNA), and methyl tetrahydrophthalic anhydride (MeTHPA).

5. The chemically decomposable thermosetting resin composition of claim 1, wherein the additive having a hydroxyl group on at least one of terminals of the main chain thereof has a number average molecular weight of 150 to 20000 g/mol.

6. A thermosetting composite material, comprising: the thermosetting resin composition of claim 1; and a carbon reinforcement.

7. A method of manufacturing the thermosetting composite material of claim 7, comprising: mixing the thermosetting resin composition with a carbon reinforcement (step 1); and curing the composition and the carbon reinforcement of step 1 (step 2).

8. A method of dissolving a thermosetting resin, comprising dissolving a thermosetting resin composition from the thermosetting composite material of claim 6 in a basic solution.

9. The method of claim 8, wherein the basic solution further contains a salt including any one element selected from the group consisting of lithium (Li), sodium (Na), potassium (K), rubidium (Rb), cesium (Cs), magnesium (Mg), calcium (Ca), strontium (Sr), and barium (Ba).

10. The method of claim 8, wherein a temperature of the basic solution is 50 to 120 C.

11. A method of recovering a carbon reinforcement, comprising: dissolving a thermosetting resin from the thermosetting composite material of claim 6 in a basic solution (step a); and recovering the carbon reinforcement that is not dissolved in the basic solution (step b).

Description

Mode for Invention

EXAMPLE 1 TO 13 AND COMPARATIVE EXAMPLE 1 TO 11

Preparation of Thermosetting Resin Composition

[0135] In order to prepare a thermosetting resin composition according to the present invention, respective thermosetting resin compositions of Examples 1 to 13 and Comparative Examples 1 to 11 were synthesized using the components in the amounts shown in Table 1 below. The process of preparing the resin composition was as follows.

[0136] <Preparation Process>

[0137] An additive and a curing agent were placed in a beaker in the amounts shown in Table 1 below, completely dissolved and mixed with stirring for 30 min at 50 C., after which an epoxy resin was added in the amount shown in Table 1 below and mixed with stirring at 50 C. for 10 min.

[0138] The mixed resin was degassed in a vacuum oven at 60 C. for 1 hr, placed in a flat mold, and cured in a two-step mode at 80 C. for 2 hr and 120 C. for 1 hr. The cured resin plate was subjected to mechanical processing into a test specimen having a size of 20 mm20 mm3 mm.

TABLE-US-00001 TABLE 1 Glycidyl-ester-based compound of Cyclohexene Curing Epoxy resin Chemical Formula 1 epoxide Additive Agent YD128 GEMA CHEDIG CHETRIG CHETRAG AEDIG AETRAG EPOCHE1DIG CY179 PEG400 KBH1089 Example 1 35 30 97 Example 2 35 35 30 101 Example 3 35 30 104 Example 4 35 35 30 98 Example 5 35 35 30 105 Example 6 35 35 30 105 Example 7 35 35 30 106 Example 8 10 60 30 104 Example 9 10 60 30 106 Example 10 10 60 30 106 Example 11 20 70 10 108 Example 12 20 70 10 110 Example 13 20 70 10 112 Comparative 100 89 Example 1 Comparative 100 111 Example 2 Comparative 50 50 103 Example 3 Comparative 50 50 114 Example 4 Comparative 35 35 30 95 Example 5 Comparative 35 35 30 102 Example 6 Comparative 50 50 86 Example 7 Comparative 70 30 87 Example 8 Comparative 25 25 50 93 Example 9 Comparative 25 25 50 94 Example 10 Comparative 25 25 50 99 Example 11 YD128 (trade name): Diglycidyl ether bisphenol A (standard bisphenol-A epoxy resin) GEMA (trade name): Tetrafunctional epoxy resin PEG 400: Polyethylene glycol having molecular weight of 400 KBH1089 (trade name): Methyl nadic anhydride CHEDIG:[00013]CHETRIG:[00014]CHETRAG:[00015]AEDIG:[00016]AETRAG:[00017]EPOCHE1DIG:[00018]CY179:[00019]

TEST EXAMPLE 1

Resin Decomposition Test 1

[0139] In order to evaluate the chemical decomposition performance of the thermosetting resin compositions prepared in Examples 1 to 13 according to the present invention and Comparative Examples 1 to 11, a resin decomposition test was performed. The results are shown in Table 2 below.

[0140] Specifically, the thermosetting resin composition of each of Examples 1 to 13 and Comparative Examples 1 to 11 was dissolved in a 0.1 M NaOH aqueous solution at 100 C. for 3 hr, and a resin decomposition test was carried out.

TABLE-US-00002 TABLE 2 Weight reduction (%, 3 hr, 100 C., 0.1M NaOH) Tg ( C.) Example 1 93 68 Example 2 88 74 Example 3 85 91 Example 4 83 76 Example 5 86 101 Example 6 85 88 Example 7 82 95 Example 8 98 68 Example 9 88 77 Example 10 90 87 Example 11 82 102 Example 12 80 113 Example 13 76 115 Comparative Example 1 0.1 121 Comparative Example 2 0.1 175 Comparative Example 3 0.1 119 Comparative Example 4 0.1 171 Comparative Example 5 5.2 48 Comparative Example 6 39 47 Comparative Example 7 100 41 Comparative Example 8 99 41 Comparative Example 9 100 40 Comparative Example 10 100 41 Comparative Example 11 100 41

[0141] Here, Tg ( C.) is the glass transition temperature.

[0142] As is apparent from Table 2,

[0143] the compounds of Examples 1 to 13 according to the present invention exhibited superior weight reduction of 76 to 98%, and thus the thermosetting resin according to the present invention can be concluded to manifest excellent chemical decomposition performance in a basic solution.

[0144] Moreover, when comparing Examples (1 to 5) according to the present invention with Comparative Examples (5 and 6) having the same components in the same amounts, with the exception that cyclohexene epoxide was used in lieu of glycidyl-ester-based compound of the present invention, the thermosetting resin according to the present invention can be found to exhibit significantly superior weight reduction. Thus, in the thermosetting resin composition according to the present invention, the glycidyl-ester-based compound can be concluded to play a role in increasing the chemical decomposition effects of the thermosetting resin.

[0145] Furthermore, in order to maintain the thermosetting properties of the thermosetting resin according to the present invention, a high glass transition temperature is essential. In the case where the glycidyl-ester-based compound was not contained, as in Comparative Examples 7 and 8, the weight reduction was 99% or more, and thus excellent chemical decomposition performance resulted, but the glass transition temperature was very low, namely about 40 C., making it impossible to manifest the properties of the thermosetting resin. In contrast, when the glycidyl-ester-based compound was contained, the glass transition temperature was elevated.

[0146] In Comparative Examples 3 and 4, in which the additive was not used, there was almost no decomposition. Hence, it is essential to use the additive. As for the amount of the additive that was added, in Comparative Examples 9 to 11, when the amount of the additive was 50 wt % or more based on 100 wt % of the total amount of the thermosetting resin composition excluding the curing agent, a weight reduction of 100% was exhibited and thus chemical decomposition performance was very good, but the glass transition temperature was very low, namely about 40 C., making it impossible to manifest the properties of the thermosetting resin. On the other hand, when the amount of the additive was less than 50 wt % based on 100 wt % of the total amount of the thermosetting resin composition excluding the curing agent, both superior chemical decomposition performance and a high glass transition temperature resulted.

[0147] In Examples 3, 5, 7, 11 and 12 according to the present invention, a weight reduction of 80% or more and a high glass transition temperature of 90 C. or higher were shown, thereby maintaining thermosetting properties and simultaneously increasing chemical decomposition performance. In particular, Examples 5, 11 and 12 were most suitable for a thermosetting resin composition that exhibits a weight reduction of 80% or more and a glass transition temperature of 80 C. or higher and also that is capable of maintaining the fundamental properties of the composite material and the characteristics of the thermosetting resin, as well as showing the chemical decomposition performance desired in the present invention.

[0148] The chemically decomposable thermosetting resin composition according to the present invention is decomposed in the basic solution, and is thus effective at realizing chemical decomposition performance and simultaneously maintaining the properties of the thermosetting resin. These effects can be confirmed to be due to the use of the glycidyl-ester-based compound and the additive. Furthermore, in order to enhance these effects, the component ratio of the composition is regarded as important. The preferred component ratio of the epoxy resin to the glycidyl-ester-based compound to the additive in the composition can be confirmed to be 20:70:10 by parts by weight.

EXAMPLES 14 TO 23

Preparation of Thermosetting Resin Composition

[0149] In order to prepare a thermosetting resin composition according to the present invention, the respective thermosetting resin compositions of Examples 14 to 23 were synthesized using the components in the amounts shown in Table 3 below. The process of preparing the resin composition was as follows.

[0150] <Preparation Process>

[0151] An additive and a curing agent were placed in a beaker in the amounts shown in Table 3 below, completely dissolved and mixed with stirring for 30 min at 50 C., after which an epoxy resin was added in the amount shown in Table 3 below and mixed with stirring at 50 C. for 10 min.

[0152] The mixed resin was degassed in a vacuum oven at 60 C. for 1 hr, placed in a flat mold, and cured in a two-step manner at 80 C. for 2 hr and 120 C. for 1 hr. The cured resin plate was subjected to mechanical processing into a test specimen having a size of 20 mm20 mm3 mm.

TABLE-US-00003 TABLE 3 Epoxy Glycidyl Curing resin ester Additive Agent Example YD128 CHEDIG PEG400 4ARMPEG20K 4ARMPEG0.5K 3ARMEP4K 3ARMEP0.3K GCE1K GCEP4K 3ARMPEGP0.17K 3ARMPEGP1K KBH1089 1 35 35 30 97 14 30 73 15 30 112 16 30 76 17 30 122 18 30 87 19 30 76 20 30 160 21 30 87 11 20 70 10 108 22 10 129 23 10 105 YD128 (trade name): Diglycidyl ether bisphenol A (standard bisphenol-A epoxy resin) CHEDIG:[00020]KBH1089 (trade name): Methyl nadic anhydride PEG 400: Polyethylene glycol having molecular weight of 400 ARMPEG20K: The compound represented by Chemical Formula 4 according to the present invention, in which R.sup.4 is methyl, t is 4, and s is a numerical value such that the total number average molecular weight (Mn) is 20,000 g/mol. 4ARMPEG0.5K: The compound represented by Chemical Formula 4 according to the present invention, in which R.sup.4 is methyl, t is 4, and s is a numerical value such that the total number average molecular weight (Mn) is 500 g/mol. 3ARMEP4K: The compound represented by ChemicalFormula 3 according to the present invention, in which R.sup.3 is methyl, r is 3, and p and q are numerical values such that the total number average molecular weight (Mn) is 4000 g/mol. 3ARMEP0.3K: The compound represented by Chemical Formula 3 according to the present invention, in which R.sup.3 is methyl, r is 3, and p and q are numerical values such that the total number average molecular weight (Mn) is 300 g/mol. GCE1K: The compound represented by Chemical Formula 2 according to the present invention, in which R.sup.4 is hydrogen, all R.sup.2s are the same as each other, x is 0, and y is a numerical value such that the total number average molecular weight (Mn) is 1000 g/mol. GCEP4K: The compound represented by Chemical Formula 2 according to the present invention, in which R.sup.4 is hydrogen, all R.sup.2s are the same as each other, and x and y are numerical values such that the total number average molecular weight (Mn) is 4000 g/mol. 3ARMPEGP0.17K: The compound represented by Chemical Formula 4 according to the present invention, in which R.sup.4 is ethyl, t is 3, and the total number average molecular weight (Mn) is 170 g/mol. 3ARMPEGP1K: The compound represented by Chemical Formula 4 according to the present invention, in which R.sup.4 is ethyl, t is 3, and the total number average molecular weight (Mn) is 1000 g/mol.

TEST EXAMPLE 2

Resin Decomposition Test 2

[0153] In order to evaluate the decomposition performance of the thermosetting resin composition according to the present invention depending on the kind of additive, a resin decomposition test was performed. The results are shown in Table 4 below.

[0154] Specifically, the thermosetting resin composition of each of Examples 14 to 23 was dissolved in a 0.1 M NaOH aqueous solution at 100 C. for 3 hr, and a resin decomposition test was carried out.

TABLE-US-00004 TABLE 4 Weight reduction (%, 3 hr, 100 C., 0.1M NaOH) Tg ( C.) Example 1 93 68 Example 14 65 81 Example 15 90 79 Example 16 69 77 Example 17 78 72 Example 18 51 88 Example 19 53 72 Example 20 91 85 Example 21 71 89 Example 11 82 102 Example 22 82 111 Example 23 70 116

[0155] Here, Tg ( C.) is the glass transition temperature.

[0156] As is apparent from Table 4,

[0157] when the same kind of additive was used, the weight reduction became superior with a decrease in the number average molecular weight of the additive.

[0158] When the compounds represented by Chemical Formulas 2, 3 and 4 according to the present invention were used as the additive, the glass transition temperature was higher than when using PEG 400.

[0159] Example 22, using, as the additive, the compound (3ARMPEGP0.17K) wherein R.sup.4 is ethyl, t is 3, and the total number average molecular weight (Mn) is 170, was very superior in both weight reduction (82%) and glass transition temperature (111 C.)

[0160] Therefore, the chemically decomposable thermosetting resin composition according to the present invention, comprising the epoxy resin, the multifunctional glycidyl-ester-based compound, the additive having a hydroxyl group on at least one of terminals of the main chain thereof, and the acid-anhydride-based curing agent, has not only excellent chemical decomposition performance in a basic solution but also a high glass transition temperature. Thereby, a thermosetting composite material including the thermosetting resin according to the present invention enables recycling of carbon fiber through hydrolysis, and thus the carbon fiber recycling industry and the recycled resin industry can be newly expanded, and the thermosetting resin can be applied to fields using not only carbon composite materials but also general thermosetting resins, and can be hydrolyzed in a basic solution, which can significantly reduce landfill or disposal costs.

INDUSTRIAL APPLICABILITY

[0161] A thermosetting composite material including a thermosetting resin according to the present invention enables recycling of carbon fiber through hydrolysis, and thus the carbon fiber recycling industry and the recycled resin industry can be newly expanded, and the thermosetting resin can be applied to fields using not only carbon composite materials but also general thermosetting resins.