WO2016177305A1

WO2016177305A1 - Methods for degrading and recycling cross-linked polymers and reinforced polymer composites

Info

Publication number: WO2016177305A1
Application number: PCT/CN2016/080858
Authority: WO
Inventors: Bo Liang; Xin Li; Bing QIN
Original assignee: Adesso Advanced Materials Wuxi Co., Ltd.
Priority date: 2015-05-01
Filing date: 2016-05-03
Publication date: 2016-11-10
Also published as: CN107636054A

Abstract

Provided are methods for degrading or recycling a cross-linked polymer or a reinforced composite which include treating the cross-linked polymer or reinforced composite with a peroxide or peroxyacid and an acid, with or without solvent, to give a degradation mixture containing degradation product.

Description

Methods for Degrading and Recycling Cross-Linked Polymers and Reinforced Polymer Composites

REFERENCE TO RELATED APPLICATION

The present application claims priority to US Application No. 62/155,765, filed on May 1, 2015, the contents of which are incorporated herein by reference in their entireties.

TECHNOLOGY FIELD OF THE INVENTION

The invention relates to the field of cross-linked polymers and reinforced composite materials. More specifically, the present invention relates to the field of recycling thermoset cross-linked polymers and fiber-reinforced composite materials containing thermoset cross-linked polymer matrices.

BACKGROUND OF THE INVENTION

Epoxy resins are an important class of thermosetting compounds. They have diverse applications and have been widely used in adhesives, structural materials, lacquer, ceramic manufacturing, printed circuit boards, microelectronics packaging, aerospace industry, etc.

Epoxy resins used as binder and coating represent a large global market, but they have also been used as an industry standard plastic/polymer matrix for the manufacture of fiber-reinforced polymer composites, also known as fiber-reinforced plastics (FRPs) . FRPs are composite materials including a polymer matrix and fibers such as carbon fibers, glass fibers, aramid fibers, or natural fibers. Fibers help to enhance the strength, elasticity and other aspects of performance of plastics or the polymer matrix. FRPs are also commonly referred to as "plastic composite materials, " or simply as "composite materials. " "Plastic composite materials" can also include non-fibrous materials such as metals or nano-materials. Plastic composite materials can be used as lightweight alternatives for other structural materials (such as steel or aluminum) , which are widely used in automotive, aerospace, marine craft, wind energy, and sporting goods industries. Lightweight composite materials help to improve energy efficiency, which has significant environmental benefits. However, thermoset plastic composite materials’attributes and positive impacts are at least partially offset by the mateials’persistence in the environment which limits of recycling of these materials. A typical example lies in the growing wind power industry which is predicted to generate tons of industrial waste materials when wind turbine blades get through their useful life and must be replaced.

Therefore, the ever increasing use of carbon fiber-reinforced composites has brought the recycling issue to the forefront of the questions that the industry must address, with the initial focus being on the recycling of manufacture waste from prepreg forms. Manufacturing waste accounts for 20-30％of the raw material usage, with prepreg being the dominant product in which carbon fiber was used at that time. The focus on recycling is driven partially by the high costs of the raw materials, which are typically 20 times the cost of steel, and the undesirability and costs of landfill for disposal of industrial materials at the end of their lives. It is expected that recyclability will become a factor in the selection of materials for the majority of the potential US

market.

Large quantities of expensive, carbon fiber composites from sporting goods and government aerospace and military applications are now being landfilled because there is no economic means for reclaiming the carbon fibers. It is expected that future land vehicles will also use carbon fiber-reinforced composites to a large extent, which will greatly increase the need for an effective recycling process.

The majority of work on composites recycling appearing in the literature is concerned with grinding, shearing, chipping, or flaking the composite into suitable size to be used as filler in new molded composite parts. See, e.g., “Recycling in Action, ” Reinforced Plastics, February 1992, pp. 32-33； P. Schaefer et al., “Germany -Auto Part Recycling； For SMC A Reality, ” Proc. 48th Annual Conf. Composites Institute, The Society of the Plastics Industry, February1993, paper 15-D； W. D. Graham et al., “Recyclability of Glass Fiber Reinforcements in Thermoset and Thermoplastic Applications, ” Composites, 3, May-June 1993, pp. 79-85； "Recycled SMC Now in Appearance Parts, " Plastics Tech, October 1993, p. 94； WO 93/05883； ECCM Recycling Concepts and Procedures, M. Neitzel et al., Woodhead Publishing, Cambridge, England, 1993； and US Patent No. 5,312,052. Pyrolysis (thermal decomposition of the polymer at a temperature of 750-950℃) has also been studied as a preparation method before grinding. See, .e.g, W.D. Graham et al., “Molded Recycled SMC Parts, ” SAE Tech. Paper 920331, Society of Automotive Engineers, Warrendale, PA, 1992； and G.N. Hart et al., “Economics of Recycling Thermosets, ” SAE Tech Paper 920802, Society of Automotive Engineers, Warrendale, PA, 1992. Most of that work has been on reclaiming automotive sheet molding compound (SMC) composite parts, largely driven by German laws on recycling. Usually, the composite is ground into a fine powder with this approach. While this approach may be satisfactory for automotive SMCs which contain large quantities of filler, it will not provide the full value from the expensive fibers and resins used in aircraft and other high-performance applications that may be achievable using other recycling processes. In 2009, the first commercial carbon fiber recycling operations started, using pyrolysis. Since then, there has been an increased focus on recycling of end-of-life carbon fiber composites, with most commercial efforts using adaptions of the pyrolysis method. At the same time, several academic and industrial projects have considered chemical recycling of composites, which potentially offers the attractions of recovering fibers in a higher value form, allowing the resin component of the composite to be also recovered and reused, and using less energy and having a lower global warming potential compared to pyrolysis. One of the main drawbacks with the current chemical recycling methods is the need for either high temperatures and pressures or long exposure duration at high temperatures, to cause the breakdown of the resins, which limit their practicality for industrial applications.

Other processes such as acid digestion or incineration in the case of glass-reinforced composites could be used to reclaim the fibers from some systems； however, those approaches generally appear impractical from an environmental point of view. Acid digestion generally requires harsh chemicals and conditions and creates a hydrocarbon/acid mixture that will require further tedious processing. Incineration (quaternary recycling) is an option for carbon-and aramid-reinforced composites, but destroys valuable materials in the process and can be a source of pollution.

A new approach for recycling composites is much needed to improve the economics of and overcome the technical barriers associated with current composites recycling methods. So far, the most promising approach is tertiary recycling. See, e.g, R. Leaversuch, “Industry Backs Pyrolysis as a Recycling Option, ” Modern Plastics, January 1994, p. 93； and G.A. Mackey, “Thermolysis, Chemolysis, and Gasification as Advanced Recycling Technology for Waste Plastic, ” 208th American Chemical Society Meeting, Washington, DC, August 1994.

However, these current methods all have their drawbacks that prevent them from being used practically or in a comerical scale. For example, pyrolysis and tertiary recycling both require very high temperature (400 ℃ or above) under an inert atmosphere. In theory, polymer matrix is degraded into small molecule hydrocarbon. Depending on operation conditions, however, there might be leftover charcoal on carbon fibre surface which would affect the value of recycled carbon fibre for reuse. High temperature treatment for an extended period may also affect the mechanical properties of such recovered carbon fibers. In addition, catalytic conversion also requires a certain amount of phenol as the medium, which is highly corrosive, unsafe, and environmentallyunfriendly.

Therefore, cost-effective and environmentally friendly methods are in great need to degrade cross-linked polymer and fiber-reinforced composite materials containing such a cross-linked polymer matrix, which becomes a more and more important task.

SUMMARY OF THE INVENTION

Aiming at the problems of the existing technologies, the present invention provides methods for degrading and recycling (or recovering) cross-linked polymers (e.g., epoxy resins) and reinforced composite materials containing cross-linked polymer matrices and reinforcing mateials (such as fibers) . Under certain conditions, after the cross-linked polymers or reinforced composite mateials are degraded into degradation products (e.g., lower-molecular-weight smaller polymers, reinforcing materials such as polymers or metal) , separation and recycling of these valuable materials and reources becomes a critical matter. The degradation and recovery methods of the present invention are economical, environmental friendly, easy to control and can be practiced in relatively mild reaction conditions and have the potential for great commercial success.

The methods of the present invention for degrading and/or recycling cross-linked polymers or reinforced composite materials containg such cross-linked polymer matrices, inclue treating these cross-linked polymers or composite materials with a peroxide or peroxyacid and an acid, with or without solvent, to give a degradation mixture containing degradation products (i.e., degraded polymer or reinforcing materials such as fibers) . For instance, the cross-linked polymers can be thermoset polymers.

In some embodiments, the treatment of the cross-linked polymers or reinforced composites with a peroxide or peroxyacid and an acid is under the ambient pressure.

In some other embodiments, the treatment comprises heating the cross-linked polymer or reinforced composite, the peroxide or peroxyacid, and the acid at a temperature in the range of 15-200 ℃ for 1-72 hours, with stirring. For instance, the treatment can take place at a temperature in the range of 80-150 ℃ for 1-4 hours, with stirring.

In still some other embodiments, the degradation mixture thus resulted is recycled by distillation or by neutralization with an alkaline solution to adjust the pH value of the mixture to at least 6, and the alkaline solution has a temperature of 0-100 ℃ and weight concentration of 0.1-99.9％. For example, the alkaline solution can have a temperature of 5-50 ℃ and a weight concentration of 5-30％, and the pH value of the degradation mixture is adjusted to the range of 6-12.

Examples of the peroxide or peroxyacid suitable for the present invention include, but are not limited to, hydrogen peroxide, performic acid, peroxyacetic acid, 2-butanone peroxide, bis (t-butyl) peroxide, perbenzoic acid, sodium peroxide, potassium peroxide, calcium peroxide, magnesium peroxide, potassium persulfate, and any combination thereof.

Likewise, examples of the acid suitable for the present invention include, but are not limited to, hydrochloric acid, hydrobromic acid, hydrofluoric acid, acetic acid, trifluoroacetic acid, lactic acid, formic acid, propionic acid, citric acid, methanesulfonic acid, p-toluenesulfonic acid, nitric acid, sulfuric acid, sulfurous acid, phosphoric acid, perchloric acid, benzoic acid, salicylic acid, phthalic acid, and any combination thereof.

In yet still some other embodiments, the treatment of the cross-linked polymers or reinforced composites with a peroxide or peroxyacid and an acid is in the presence of a solvent, and the solvent includes methanol, ethanol, ethylene glycol, propanol, isopropanol, butanol, isobutanol, t-butanol, pentanol, hexanol, heptanol, octanol, nonanol, benzyl alcohol, phenethyl alcohol, p-hydroxymethyl benzene, m-hydroxymethyl benzene, o-hydroxy benzene, p-hydroxyethyl benzene, m-hydroxyethyl benzene, o-hydroxyethyl benzene, water, N, N-dimethylformamide, N, N-dimethylacetamide, N-methylpyrrolidone, dimethyl sulfoxide, tetrahydrofuran, methyl tetrahydrofuran, glycerol, or dioxane； the alkali comprises lithium hydroxide, sodium hydroxide, potassium hydroxide, calcium hydroxide, sodium carbonate, sodium bicarbonate, potassium carbonate, potassium bicarbonate, ammonia； the alkali solvent comprises methanol, ethanol, ethylene glycol, propanol, isopropanol, butanol, isobutanol, t-butanol, pentanol, hexanol, heptanol, octanol, nonanol, water , N, N-dimethylformamide, N, N-dimethylacetamide, N-methylpyrrolidone, dimethyl sulfoxide, tetrahydrofuran, methyl tetrahydrofuran, glycerol, dioxane, or combination thereof.

In the methods of the present invention, the degradation products can be recovered from the degradation mixture by filtration, extraction, or precipitation.

As an example suitable for the present invention, an epoxy polymer matrix (i.e., a cross-linked epoxy polymer polymerized by curing agent and epoxy resin systems) may be combined with glass fibers, carbon fibers, natural fibers, synthetic fibers, or other fiber material, and also with non-fiber-reinforced materials, such as carbon nanotubes, boron nitride nanotubes, carbon black, metal nano-particles, metal oxide nanoparticles, organic nanoparticles, iron oxide, or other non-fibrous materials.

Furthermore, the principle of degradation of reinforced composite material: immerse composite material into the hot recovery solution of peroxide or peroxyacid and acid with or without solvent. First, the epoxy matrix is degraded, and then separated the reclaimed reinforcements, and thedegraded resin products by alkali neutralization. Under such conditions, the epoxy matrix can be degraded, in which the C-O or C-N bond will be oxidized and broken resulting in cross-linked structure of epoxy resin matrix transformed into low molecular weight compouds which is soluable in the acid with or without solvent. When epoxy matrix is fully dissolved, the fiber can be removed from the solution, and the solution after neutralization by alkali, the degraded resin products can be separated and recovered. Recycled fiber reinforcements and low molecular weight compoudscan be separated, recovered and reused.

Among others, this invention has the following unexpectedly superior advantages that have not been observed or are not possible in the current technologies:

This invention involves the composite manufactured with epoxy resin curing agent, epoxy resin, auxiliary material and reinforcing material, which can degrade under relatively mild temperature at ambient pressure； the recycling time is relatively short within hours； the recycling condition is environmentally friendly, and no pollution is generated in the process and no polluants are left over. More than 95％of reinforcing materials (such as carbon fiber, glass fiber, synthetic fiber and natural fiber) can be recycled and maintain most of their original texture and mechanical properties, and be reused (e.g., in new composites) . The degraded resin products can be used as chemicalproducts after processing.

The recycling yields of degraded resin products and reinforcing materials are more than 95％, and the recycled reinforcing materials (e.g. fibers) have very stable quality, clean surface, and no defect under the acid recycling condition.

The recycling method of thermoset epoxy resin composites is characterized by: mild recycling condition, economic, and easy to control.

BRIEF DESCRIPTIONS OF THE DRAWINGS

Fig. 1 shows the recovered glass fiber after recycling of the degradable composite as described in Example 50.

Fig. 2 shows the portion degradation of the tubular carbon fiber composite as described in Example 55.

Fig. 3 shows the SEM picture of the recovered fiber, which demonstrates the clean surface as described in Example 58.

Fig. 4 shows a portion of an automotive part was recycled and fiber is separated as described in Example 59.

DETAILED DESCRIPTION OF THE INVENTION

The following examples are provided for illustration only, and not intended to be limiting in any aspect.

The first part of examples are focused on recyclable resin and recyclable composite systems made with Adesso’s

degradable curing agents and

resins.

Example 1 Preparation of the curing agent A

N- (2-hydroxyethyl) phthalimide (1000g) , paraformaldehyde (157 g) , and p-toluene sulfonic acid (6.8 g) were placed in 1.5 L of toluene in a 5 L round bottom flask equipped with Dean Stark apparatus. After 20 hours at reflux, the reaction was cooled to the ambient temperature. Then 2.0 L of petroleum ether (bp: 60-90 ℃) was added to the reaction mixture. The white precipitate was collected by filtration and washed with 1 L of petroleum ether and dried to yield 950 g of crude protected diamine. The crude diamine was deprotected by treatment with 3.4 L of 20％aqueous NaOH at reflux. After reflux for 10 hours, the reaction mixture was cooled to the ambient temperature, extracted with chloroform/isopropanol (3: 1) . The organic phase dried with anhydrous Na₂SO₄, and then distilled under vacuum to yield 200 g of curing agent A of the structure shown above (Bp ＝ 71～72 ℃@70 Pa)

Example 2 Preparation of the curing agent B

800 g Methylbenzene and 440 g 3-chloro-1, 2-propanediol were placed in a reaction bottle, 548 g dimethylchloroacetal and 3 g p-toluenesulfonic acid were added under stirring. The solution was slowly heated to reflux with Dean-Stark apparatus to distil evolved methanol. After 12-16 hours, the reaction was completed, and the reaction solution was cooled to below 40 ℃, a moderate amount of sodium carbonate was added into the reaction bottle, then the reaction solution was concentrated at reduced pressure to give 760 g chlorinated intermediate.

400 mL N, N-dimethylformamide was placed into the three flask, while stirring 231 g potassium phthalimide and 86.5 g chlorinated intermediate were added. The solution was heated to 150 ℃, after 8 hours (the reaction was completed) , concentrated at reduced pressure and DMF was recycled. The residue could be used for the next step without purification. 320 g NaOH and 960 g water were added into the residue at room temperature, then the solution was heated to reflux, after reflux for 12 hours, cooled to room temperature, extracted with chloroform/ethanol (Volume ratio 3: 1) for 3 times. The organic phase dried with anhydrous Na2SO4, and then distilled under vacuum to yield 50 g of curing agent B of the structure shown above (Bp ＝ 72～78℃@25～40 Pa)

Example 3 Preparation of the curing agent C

89 g 2-nitropropane, 30 g paraformaldehyde and 100 mL triethylamine were placedin a 250 mL round bottom flask and stirred at 45 ℃ for 0.5 h. The reaction mixture was filtered to obtain 60 g 2-methyl-2-nitropropan-1-ol.

11.9 g 2-methyl-2-nitropropan-1-ol, 5.7 g 2, 2-dimethoxy propane, and 0.3 g p-toluene sulfonic acid and 500 mL of cyclohexane were mixedin a 1 L round bottom flask equipped with Dean-Stark apparatus to distill evolved methanol. After 6 h, the solution was cooled to room temperature, a moderate amount of sodium carbonate was added into the reaction bottle, then the reaction solution was concentrated at reduced pressure to give 5.7 g 2-methyl-1- ( (2- (2-methyl-2-nitropropoxy) propan-2-yl) oxy) -2-nitropropane.

1 g 2-methyl-1- ( (2- (2-methyl-2-nitropropoxy) propan-2-yl) oxy) -2-nitropropane, 0.1 g Raney nickeland 25mLmethanol were mixed in a 50 mL round bottom and reduced by hydrogen gas at 55 ℃ for 12 h. The reaction mixture was filtered and the the filtrate was concentrated at reduced pressure to give 0.7 g curing agent C of the structure shown above.

Example 4 Preparation of the curing agent D

400 g DMF, 200 g sodium p-nitrophenolate, and 121.6 g dichloromethane were mixed and placed in a 1 L flask, the solution was heated to reflux. After 3 hours (the reaction was completed by TLC monitoring) the solution was cooled, filtered, the filtrate was concentrated at reduced pressure. The residue was cooled, water was added till white precipitate was appeared, filtered, the solid was dried at vacuum to give 170 g bis (4-nitrophenoxy) methane.

170 g bis (4-nitrophenoxy) methane, 680 g ethanol, 21.5 g ferric chloride and 76.5 g activated carbon were placed in a 2 L flask, the reaction was heated to reflux, after at least 30 minutes, hydrazine hydrate was dripped in at reflux, the drip off was controlled within 3 hours. The reaction was preserved the temperature to reflux (after 4 hours the reaction was completed by TLC monitoring) , filtered when the solution was hot. The filter residue was washed with small amount of ethanol, the filtrate was cooled, and the precipitate was appeared, filtered, the solid was dried at vacuum to give 120 g curing agent D of the structure shown above (mp ＝ 104-107 ℃) .

Example 5 Preparation of the curing agent E

1 Kg Methylparaben, 569 g bis (2-chloroethoxy) methane and 350 g sodium hydroxide and 2.2 Kg N, N-dimethylformamide were placed in a 10 L three-neck round bottom flask equipped with a condenser. The solution was heated to reflux. After 8 hours at reflux, the reaction was cooled to room temperature, then mother liquid was concentrated, water was added and precipitate was obtained, filtered, dried to afford 1.05 Kg of solid intermediate.

The solid intermediate was dissolved in 4.2 Kg ethanol in a 10 L three-neck round bottom flask equipped with a condenser, then 917g hydrazine hydrate was added, the reaction was heated to reflux for 2 hours, then cooled to below 5 ℃. The solid was precipitated, filtered and washed with ethanol to give 365 g white solid product, i.e., curing agent E of the structure shown above (mp: 176-184℃) .

Example 6 Preparation of the curing agent F

10 g Methylparaben, 6.8 g dibromomethane and 3.9 g sodium hydroxide were placed in 25 mL of N, N-dimethylformamide (DMF) in a 250 mL three-neck round bottom flask equipped with a condenser. The solution was heated to reflux. After 5 hours at reflux, the reaction was cooled to room temperature, then mother liquid was concentrated, water was added and precipitate was obtained, filtered, dried to afford 3 g of solid intermediate.

The solid intermediate was dissolved in 10 mL ethanol in a 250 mL three-neck round bottom flask equipped with a condenser, then 1.4 g hydrazine hydrate was added, the reaction was heated to reflux for 2 hours, then cooled to below 5 ℃. The solid was precipitated, filtered and washed with ethanol to give 1.5 g white solid product, i.e., curing agent F of the structure shown above (mp: 248-249 ℃) .

Example 7 Preparation of the curing agent G

20 g ethanol and 14.7 g 85％hydrazine hydrate were placed in the flask reactor, 13.4 g 1, 4-Phthalaldehyde dissolved in 370 g ethanol was added dropwise while stirring at room temperature in 1 hour. The solution was stirring at room temperature for 5-6 hours, then filtered, the filter cake was washed with ethanol and dried to give 13.9 g yellow solid, i.e., curing agent G of the structure shown above (mp: 158～166℃) .

Example 8 Preparation of cross-linked thermoset polymer A

18 g Curing Agent A in Example 1 (AEW ≈ 2.98 N-H eq. /100 g) and 100 g liquid bisphenol A type epoxy resin NPEL128 (EEW 0.52 ～ 0.55 eq. /100 g) were mixed and stirred evenly at room temperature, then heated to 50℃ for 2 hours and125 ℃ for 2 hours until fully cured to give the sample of cross-linked thermoset polymer.

Example 9 Preparation of cross-linked thermoset polymer B

17.8 g Curing Agent B in Example 2 (AEW ≈ 3.01 N-H eq. /100 g) and 100 g liquid bisphenol A type epoxy resin NPEL128 (EEW 0.52 ～ 0.55 eq. /100 g) were mixed and stirred evenly at room temperature, then heated to 50℃ for 2 hours and 125 ℃ for 2 hours until fully cured to give the sample of cross-linked thermoset polymer.

Example 10 Preparation of cross-linked thermoset polymer C

29.4 g Curing Agent C in Example 3 (AEW ≈ 1.83 N-H eq. /100 g) and 100g liquid bisphenol A type epoxy resin NPEL128 (EEW 0.52 ～ 0.55 eq. /100 g) were mixed and stirred evenly at room temperature, then heated to 100℃ for 1 hours and 140℃ for 3 hours until fully cured to give the sample of cross-linked thermoset polymer.

Example 11 Preparation of cross-linked thermoset polymer D

31 g Curing Agent D in Example 4 (AEW ≈ 1.74 N-H eq. /100 g) and 100g liquid bisphenol A type epoxy resin NPEL128 (EEW 0.52 ～ 0.55 eq. /100 g) were mixed and stirred evenly at room temperature, then heated to 130℃ for 3 hours until fully cured to give the sample of cross-linked thermoset polymer.

Example 12 Preparation of cross-linked thermoset polymer E

54.4 g Curing Agent E in Example 5 (AEW ≈ 0.99 N-H eq. /100 g) and 100g liquid bisphenol A type epoxy resin NPEL128 (EEW 0.52 ～ 0.55 eq. /100 g) were mixed and stirred evenly at room temperature, then heated to 140℃ for 3 hours until fully cured to give the sample of cross-linked thermoset polymer.

Example 13 Preparation of cross-linked thermoset polymer F

42.6 g Curing Agent F in Example 6 (AEW ≈ 1.26 N-H eq. /100 g) and 100 g liquid bisphenol A type epoxy resin NPEL128 (EEW 0.52 ～ 0.55 eq. /100 g) were mixed and stirred evenly at room temperature, then heated to 150℃ for 4 hours until fully cured to give the sample of cross-linked thermoset polymer.

Example 14 Preparation of cross-linked thermoset polymer G

21.8 g Curing Agent G in Example 7 (AEW ≈ 2.47 N-H eq. /100 g) and 100 g liquid bisphenol A type epoxy resin NPEL128 (EEW 0.52 ～ 0.55 eq. /100 g) were mixed and stirred evenly at room temperature, then heated to 100℃ for 4 hours and 125 ℃ for 2 hoursuntil fully cured to give the sample of cross-linked thermoset polymer.

Example 15 Preparation of cross-linked thermoset polymer

5 g Diaminodiphenylsulfone (DDS) curing agent and 100 g liquid bisphenol A type epoxy resin NPEL128 (EEW 0.52 ～ 0.55 eq. /100 g) were mixed and stirred evenly at 180℃for 3 hours, then cured by 5 g Dicy curing agent at 135 ℃ for 2 hours to give a sample of the cross-linked thermoset polymer.

Example 16 Preparation of cross-linked thermoset polymer

18 g Curing Agent A in Example 1 (AEW ≈ 2.98 N-H eq. /100 g) , 83 g liquid bisphenol A type epoxy resin NPEL128 (EEW 0.52 ～ 0.55 eq. /100 g) , 6.3 g alkyl (C12-14) glycidylether (EEW 0.30 ～ 0.34 eq. /100 g) and 2.2 g trimethylolpropane triglycidyl ether (EEW>0.7 eq. /100 g) were mixed and stirred evenly at room temperature for 0.5 h, then heated to 70 ℃ for 16 hours until fully cured to give the sample of cross-linked thermoset polymer.

Example 17 Preparation of cross-linked thermoset polymer

60 g bisphenol A epoxy resin NPEL128 (EEW 0.52 ～ 0.55 eq. /100 g) , 60 g Curing Agent E in Example 5 (AEW ≈ 0.99 N-H eq. /100 g) and 0.5 g Zinc (II) Acetylacetonate were weighed and mixed in the blender at 60℃, then grinded in three-roll mill for 30 minutes as standby. 70 g MDI modified bisphenol A epoxy resin (EEW 0.34 ～ 0.40 eq. /100 g) , 50 g bisphenol A epoxy resin NPES901 (EEW 0.20 ～ 0.22 eq. /100 g) , were placed into a blender and stirred at high speed at 120 ℃ for 1 hour, cooled to 70 ℃, then former standby NPEL128/Curing Agent E mixed system added and stirred at high speed for 30 minutes, then heated to 150 ℃ for 3 hours until fully cured to give the sample of cross-linked thermoset polymer.

Example 18 Preparation of cross-linked thermoset polymer

1 g Toluene diisocyanate (TDI) (diisocyanate) and 25 g liquid bisphenol A type epoxy resin NPEL128 (EEW 0.52 ～ 0.55 eq. /100 g) were mixed and stirred evenly at 120℃ for 1.5 hours, cooled to 100 ℃, then 20 g CTBN modified epoxy resin (EEW 0.27 ～ 0.31 eq. /100 g) was added, after stirring for 0.5 h, the mixer was cooled to 70 ℃, then 20 g liquid bisphenol A type epoxy resin NPEL128 (EEW 0.52 ～ 0.55 eq. /100 g) and11 g Curing Agent G in Example 7 (AEW ≈ 2.47 N-H eq. /100 g) were added and stirred evenly for 0.5 h, then heated to 100 ℃ for 1h and 125 ℃ for 2 hours until fully cured to give the sample of cross-linked thermoset polymer.

Example 19 Preparation of cross-linked thermoset polymer

16 g bisphenol A epoxy resin NPEL128 (EEW 0.52 ～ 0.55 eq. /100 g) , 12 g DICY curing agentand4g UR200 accelerator were weighed and mixed in the blender at 60℃, then grinded in three-roll mill for 30 minutes as standby. 30 g MDI modified bisphenol A epoxy resin (EEW 0.34 ～ 0.40 eq. /100 g) , 46 g novolac epoxy resin NPPN638s (EEW 0.53 ～ 0.59 eq. /100 g) , 32 g bisphenol A epoxy resin NPEL128 (EEW 0.52 ～ 0.55 eq. /100 g) and 60 g bisphenol A epoxy resin NPES901 (EEW 0.20 ～ 0.22 eq. /100 g) , were placed into a blender and stirred at high speed at 120 ℃ for 1 hour, cooled to 70 ℃, then former standby NPEL128/DICY mixed system was added and stirred at high speed for 30 minutes, then heated to 135 ℃ for 1 hours until fully cured to give the sample of cross-linked thermoset polymer.

Example 20 Preparation of cross-linked thermoset polymer

28.4 g Curing Agent A in Example 1 (AEW ≈ 2.98 N-H eq. /100 g) and 100 g Triglycidyl meta-aminophenol (EEW >0.85 eq. /100 g) were mixed and stirred evenly at room temperature, then heated to 60℃ for 2 hours and 125 ℃ for 3 hours until fully cured to give the sample of cross-linked thermoset polymer.

Example 21 Recycling of cross-linked thermoset polymer

1 g cured sample in Example 8, 50 mL 30％aq. H₂O₂ and 50 mL acetic acid were placed in 250 mL three-neck round bottom flask, stirred and heated to 100 ℃, the cured sample was completely degraded after 6 hours to give transparent clear solution, which the degradation products mainly contained benzaldehyde by GC analysis. The benzaldehyde can be reused by distillation.

Example 22 Recycling of cross-linked thermoset polymer

1 g cured sample in Example 8, 30 mL 30％aq. H₂O₂ and 60 mL acetic acid were placed in 250 mL three-neck round bottom flask, stirred and heated to 100 ℃, the cured sample was completely degraded after 6 hours to give transparent clear solution, which the degradation products mainly contained benzaldehyde by GC analysis. The benzaldehyde can be reused by distillation.

Example 23 Recycling of cross-linked thermoset polymer

1 g cured sample in Example 8, 25 mL 30％aq. H₂O₂ and 75 mL acetic acid were placed in 250 mL three-neck round bottom flask, stirred and heated to 100 ℃, the cured sample was completely degraded after 6 hours to give transparent clear solution, which the degradation products mainly contained benzaldehyde by GC analysis. The benzaldehyde can be reused by distillation.

Example 24 Recycling of cross-linked thermoset polymer

1 g cured sample in Example 8, 16 mL 30％aq. H₂O₂ and 80 mL acetic acid were placed in 250 mL three-neck round bottom flask, stirred and heated to 100 ℃, the cured sample was completely degraded after 9 hours to give transparent clear solution, which the degradation products mainly contained benzaldehyde by GC analysis. The benzaldehyde can be reused by distillation.

Example 25 Recycling of cross-linked thermoset polymer

1 g cured sample in Example 8, 10 mL 30％aq. H₂O₂ and 70 mL acetic acid were placed in 250 mL three-neck round bottom flask, stirred and heated to 100 ℃, the cured sample was completely degraded after 9 hours to give transparent clear solution, which the degradation products mainly contained benzaldehyde by GC analysis. The benzaldehyde can be reused by distillation.

Example 26 Recycling of cross-linked thermoset polymer

1 g cured sample in Example 8, 16 mL 30％aq. H₂O₂ and 80 mL acetic acid were placed in 250 mL three-neck round bottom flask, stirred and heated to 80 ℃, the cured sample was completely degraded after 6 hours to give transparent clear solution, which the degradation products mainly contained benzaldehyde by GC analysis. The benzaldehyde can be reused by distillation.

Example 27 Recycling of cross-linked thermoset polymer

1 g cured sample in Example 8, 20 mL 30％aq. H₂O₂ and 60 mL acetic acid were placed in 250 mL three-neck round bottom flask, stirred and heated to 60 ℃, the cured sample was completely degraded after 16 hours to give transparent clear solution, which the degradation products mainly contained benzaldehyde by GC analysis. The benzaldehyde can be reused by distillation.

Example 28 Recycling of cross-linked thermoset polymer

1 g cured sample in Example 8, 16 mL 30％aq. H₂O₂ and 80 mL acetic acid were placed in 250 mL three-neck round bottom flask, stirred and heated to 45 ℃, the cured sample was completely degraded after 72 hours to give transparent clear solution, which the degradation products mainly contained benzaldehyde by GC analysis. The benzaldehyde can be reused by distillation.

Example 29 Recycling of cross-linked thermoset polymer

1 g cured sample in Example 8, 16 mL 30％aq. H₂O₂ and 80 mL propionic acid were placed in 250 mL three-neck round bottom flask, stirred and heated to 108 ℃, the cured sample was completely degraded after 6 hours to give transparent clear solution, which the degradation products mainly contained benzaldehyde by GC analysis. The benzaldehyde can be reused by distillation.

Example 30 Recycling of cross-linked thermoset polymer

1 g cured sample in Example 8, 25 mL 30％aq. H₂O₂ and 75 mL propionic acid were placed in 250 mL three-neck round bottom flask, stirred and heated to 80 ℃, the cured sample was completely degraded after 4 hours to give transparent clear solution, which the degradation products mainly contained benzaldehyde by GC analysis. The benzaldehyde can be reused by distillation.

Example 31 Recycling of cross-linked thermoset polymer

1 g cured sample in Example 9, 16 mL 30％aq. H₂O₂ and 80 mL acetic acid were placed in 250mL three-neck round bottom flask, stirred and heated to 90 ℃, the cured sample was completely degraded after 9 hours to give transparent clear solution, which the degradation products mainly contained benzaldehyde by GC analysis. The benzaldehyde can be reused by distillation.

Example 32 Recycling of cross-linked thermoset polymer

1 g cured sample in Example 10, 16 mL 30％aq. H₂O₂ and 80 mL acetic acid were placed in 250 mL three-neck round bottom flask, stirred and heated to 90 ℃, the cured sample was completely degraded after 2 hours to give transparent clear solution, which the degradation products mainly contained benzaldehyde by GC analysis. The benzaldehyde can be reused by distillation.

Example 33 Recycling of cross-linked thermoset polymer

1 g cured sample in Example 10, 16 mL 30％aq. H₂O₂, 80 mL acetic acid and 80mL acetone were placed in 250 mL three-neck round bottom flask, stirred and heated to 80℃, the cured sample was completely degraded after 3 hours to give transparent clear solution, which the degradation products mainly contained benzaldehyde by GC analysis. The benzaldehyde can be reused by distillation.

Example 34 Recycling of cross-linked thermoset polymer

1 g cured sample in Example 10, 16 mL 30％aq. H₂O₂, 80 mL acetic acid and 80mL glycol were placed in 250 mL three-neck round bottom flask, stirred and heated to 100℃, the cured sample was completely degraded after 3 hours to give transparent clear solution, which the degradation products mainly contained benzaldehyde by GC analysis. The benzaldehyde can be reused by distillation.

Example 35 Recycling of cross-linked thermoset polymer

1g cured sample in Example 10, 25 mL 30％aq. H₂O₂, 75 mL acetic acid were placed in 250 mL three-neck round bottom flask, stirred and heated to 80℃, the cured sample was completely degraded after 6 hours to give transparent clear solution, which the degradation products mainly contained benzaldehyde by GC analysis. The benzaldehyde can be reused by distillation.

Example 36 Recycling of cross-linked thermoset polymer

1g cured sample in Example 10, 25 g potassium persulfate and 80 mL acetic acid were placed in 250 mL three-neck roundbottom flask, stirred and heated to 100 ℃, the cured sample was completely degraded after 48 hours to give transparent clear solution, which the degradation products mainly contained benzaldehyde by GC analysis. The benzaldehyde can be reused by distillation.

Example 37 Recycling of cross-linked thermoset polymer

1g cured sample in Example 10, 25 g benzoyl peroxide and 80 mL acetic acid were placed in 250 mL three-neck round bottom flask, stirred and heated to 100 ℃, the cured sample was completely degraded after 48 hours to give transparent clear solution, which the degradation products mainly contained benzaldehyde by GC analysis. The benzaldehyde can be reused by distillation.

Example 38 Recycling of cross-linked thermoset polymer

1 g cured sample in Example 11, 16 mL 30％aq. H₂O₂, and 80 mL acetic acid were placed in 250 mL three-neck round bottom flask, stirred and heated to 108 ℃, the cured sample was completely degraded after 6 hours to give transparent clear solution, which the degradation products mainly contained benzaldehyde by GC analysis. The benzaldehyde can be reused by distillation.

Example 39 Recycling of cross-linked thermoset polymer

1 g cured sample in Example 11, 20 mL 30％aq. H₂O₂, and 60 mL acetic acid were placed in 250 mL three-neck round bottom flask, stirred and heated to 100 ℃, the cured sample was completely degraded after 6 hours to give transparent clear solution, which the degradation products mainly contained benzaldehyde by GC analysis. The benzaldehyde can be reused by distillation.

Example 40 Recycling of cross-linked thermoset polymer

1 g cured sample in Example 12, 16 mL 30％aq. H₂O₂, and 80 mL acetic acid were placed in 250 mL three-neck round bottom flask, stirred and heated to 100 ℃, the cured sample was completely degraded after 6 hours to give transparent clear solution, which the degradation products mainly contained benzaldehyde by GC analysis. The benzaldehyde can be reused by distillation.

Example 41 Recycling of cross-linked thermoset polymer

1 g cured sample in Example 13, 16 mL 30％aq. H₂O₂, and 80 mL acetic acid were placed in 250 mL three-neck round bottom flask, stirred and heated to 100 ℃, the cured sample was completely degraded after 6 hours to give transparent clear solution, which the degradation products mainly contained benzaldehyde by GC analysis. The benzaldehyde can be reused by distillation.

Example 42 Recycling of cross-linked thermoset polymer

1 g cured sample in Example 14, 16 mL 30％aq. H₂O₂, and 80 mL acetic acid were placed in 250 mL three-neck round bottom flask, stirred and heated to 100 ℃, the cured sample was completely degraded after 6 hours to give transparent clear solution, which the degradation products mainly contained benzaldehyde by GC analysis. The benzaldehyde can be reused by distillation.

Example 43 Recycling of cross-linked thermoset polymer

1 g cured sample in Example 14, 20 mL 30％aq. H₂O₂, and 60 mL acetic acid were placed in 250 mL three-neck round bottom flask, stirred and heated to 100 ℃, the cured sample was completely degraded after 6 hours to give transparent clear solution, which the degradation products mainly contained benzaldehyde by GC analysis. The benzaldehyde can be reused by distillation.

Example 44 Recycling of cross-linked thermoset polymer

1 g cured sample in Example 15, 16 mL 30％aq. H₂O₂, and 80 mL acetic acid were placed in 250mL three-neck round bottom flask, stirred and heated to 108 ℃, the cured sample was completely degraded after 4 hours to give transparent clear solution, which the degradation products mainly contained benzaldehyde by GC analysis. The benzaldehyde can be reused by distillation.

Example 45 Recycling of cross-linked thermoset polymer

1 g cured sample in Example 16, 16 mL 30％aq. H₂O₂, and 80 mL acetic acid were placed in 250 mL three-neck round bottom flask, stirred and heated to 108 ℃, the cured sample was completely degraded after 8 hours to give transparent clear solution, which the degradation products mainly contained benzaldehyde by GC analysis. The benzaldehyde can be reused by distillation.

Example 46 Recycling of cross-linked thermoset polymer

1 g cured sample in Example 17, 20 mL 30％aq. H₂O₂, and 80 mL acetic acid were placed in 250 mL three-neck round bottom flask, stirred and heated to 90 ℃, the cured sample was completely degraded after 9 hours to give transparent clear solution, which the degradation products mainly contained benzaldehyde by GC analysis. The benzaldehyde can be reused by distillation.

Example 47 Recycling of cross-linked thermoset polymer

1 g cured sample in Example 18, 20 mL 30％aq. H₂O₂, and 80 mL acetic acid were placed in 250mL three-neck round bottom flask, stirred and heated to 90 ℃, the cured sample was completely degraded after 8 hours to give transparent clear solution, which the degradation products mainly contained benzaldehyde by GC analysis. The benzaldehyde can be reused by distillation.

Example 48 Recycling of cross-linked thermoset polymer

1g cured sample in Example 19, 20mL 30％aq. H₂O₂, and 80mL acetic acid were placed in 250 mL three-neck round bottom flask, stirred and heated to 100℃, the cured sample was completely degraded after 6 hours to give transparent clear solution, which the degradation products mainly contained benzaldehyde by GC analysis. The benzaldehyde can be reused by distillation.

Example 49 Recycling of cross-linked thermoset polymer

1 g cured sample in Example 20, 20 mL 30％aq. H₂O₂, and 60 mL acetic acid were placed in 250 mL three-neck round bottom flask, stirred and heated to 90 ℃, the cured sample was completely degraded after 4 hours to give transparent clear solution, which the degradation products mainly contained benzaldehyde by GC analysis. The benzaldehyde can be reused by distillation.

Example 50 Preparationof fiber-reinforced thermoset polymer composite

132 g tetrabromobisphenol A epoxy resin (EEW 0.23 ～ 0.24 eq. /100 g) , 40 g liquid bisphenol A type epoxy resin E54 (EEW 0.53 ～ 0.54 eq. /100 g) , 28 g solid bisphenol A type epoxy resin E21 (EEW 0.20 ～ 0.22 eq. /100 g) , 0.3 g Zinc (II) Acetylacetonate, 59 g Curing Agent E in Example5 (AEW ≈ 0.99 N-H eq. /100 g) and102 g DMF were mixed in the blenderat high speed for 30 minutes, then grinded in three-roll mill for 10 minutes as standby. Glass fiber prepreg was made using 7628 glass fiber cloth by wet impregnating methodand heating at 150 ℃ for 10 mins. The prepregs were slightly tacky at room temperature and pressed on the tablet pressing machine at 170 ℃ for 1 hour to give laminate (1.5 mm thickness) of glass fiber composite.

Example 51 Preparationof fiber-reinforced thermoset polymer composite

132 g tetrabromobisphenol A epoxy resin (EEW 0.23 ～ 0.24 eq. /100 g) , 40 g liquid bisphenol A type epoxy resin E54 (EEW 0.53 ～ 0.54 eq. /100 g) , 28 g solid bisphenol A type epoxy resin E21 (EEW 0.20 ～ 0.22 eq. /100 g) , 0.3 g Zinc (II) Acetylacetonate, 59 g Curing Agent E in Example 5 (AEW ≈ 0.99 N-H eq. /100 g) and 102 g DMF were mixed in the blender at high speed for 30 minutes, then grinded in three-roll mill for 10 minutes as standby. Carbon fiber prepreg was made using 3 K UD carbon fiber. The prepregs were used to make tubular carbon fiber composite according to general molding at 135 ℃ for 1 hour.

Example 52 Preparationof fiberreinforced thermoset polymer composite

16 g bisphenol A epoxy resin NPEL128 (EEW 0.52 ～ 0.55 eq. /100 g) , 12 g DICY curing agent and 4 g UR200 accelerator were weighed and mixed in the blender at 60 ℃, then grinded in three-roll mill for 30 minutes as standby. 30 g MDI modified bisphenol A epoxy resin (EEW 0.34 ～ 0.40 eq. /100 g) , 46 g novolac epoxy resin NPPN638s (EEW 0.53 ～0.59 eq. /100g) , 32 g bisphenol A epoxy resin NPEL128 (EEW 0.52 ～ 0.55 eq. /100 g) and 60 g bisphenol A epoxy resin NPES901 (EEW 0.20 ～ 0.22 eq. /100 g) , were placed into a blender and stirred at high speed at 120 ℃ for 1 hour, cooled to 70 ℃, then former standby NPEL128/DICY mixed system was added and stirred at high speed for 30 minutes, then grinded in three-roll mill for 10 minutes as standby. Carbon fiber prepreg was made using 3 K UD carbon fiber. The prepregs were slightly tacky at room temperature and pressed on the tablet pressing machine at 135 ℃ for 1 hour to give carbon fiber composite.

Example 53 Recycling of fiber reinfored thermoset polymer composite

1 g sample of the glass fibercomposite laminate in Example 50, 20 mL 30％aq. H₂O₂, and 60 mL acetic acid were placed in 250 mL three-neck round bottom flask, stirred and heated to 100℃, the resin matrix was completely degraded after 2 hours, filtered when the solution was hot, the glass fiber and the degradation solution were separated. The solution was transparent, in which the degradation products mainly contained benzaldehyde by GC analysis. The benzaldehyde can be reused by distillation. The surface of recycled glass fiber was clean and basically has no defect.

Example 54 Recycling of fiber reinfored thermoset polymer composite

1 g sample of the glass fiber composite laminate in Example 50, 16 mL 30％aq. H₂O₂, and 80 mL acetic acid were placed in 250 mL three-neck round bottom flask, stirred and heated to 108℃, the resin matrix was completely degraded after 2 hours, filtered when the solution was hot, the glass fiber and the degradation solution were separated. The solution was transparent, in which the degradation products mainly contained benzaldehyde by GC analysis. The benzaldehyde can be reused by distillation. The surface of recycled glass fiber was clean and basically has no defect.

Example 55 Portion degradationof fiber reinfored thermoset polymer composite

A portion of tubular carbon fibre composite in Example 51 was partly immersedinto the solution of 16 mL 30％aq. H₂O₂, and 80 mL acetic acid in 250 mL three-neck round bottom flask, then heated to 108 ℃, the resin matrix of immersed composite was completely degraded after 4 hours.

Example 56 Recycling of fiber reinfored thermoset polymer composite

1 g sample of the glass fiber composite laminate in Example 52, 16 mL 30％aq. H₂O₂, and 80 mL acetic acid were placed in 250 mL three-neck round bottom flask, stirred and heated to 108℃, the resin matrix was completely degraded after 2 hours, filtered when the solution was hot, the glass fiber and the degradation solution were separated. The solution was transparent, in which the degradation products mainly contained benzaldehyde by GC analysis. The benzaldehyde can be reused by distillation. The surface of recycled glass fiber was clean and basically has no defect.

Example 57 Recycling of fiber reinfored thermoset polymer composite

1 g sample of the glass fiber composite laminate in Example 52, 25 mL 30％aq. H₂O₂, and 75 mL acetic acid were placed in 250 mL three-neck round bottom flask, stirred and heated to 108℃, the resin matrix was completely degraded after 2 hours, filtered when the solution was hot, the glass fiber and the degradation solution were separated. The solution was transparent, in which the degradation products mainly contained benzaldehyde by GC analysis. The benzaldehyde can be reused by distillation. The surface of recycled glass fiber was clean and basically has no defect.

Example 58 Characterization of recycled fiber

The recycled fiber was sent for SEM, and picture shown in Figure 3 demonstates that the resin degradation was completed, the surface of the recycled and recovered fiber was clean.

Example 59 Recycling of a portion of an automotive part made with recyclable resins

A recyclable resin formulation with Curing agent E was developed and a recyclable pre-preg was manufactured with such formulated resin. Then an automotive part shown in Figure 4 was made using the recyclable pre-preg. Figure 4 demonstrates a complete degradation of the resin matrix of a portion of the automotive part, which was immersed in the degradation solution as Example 57.

Example 60 Recycling Performance Comparision Chart of thermoset polymers (Table 1-3)

Various recycling methods were tried and summary data were shown in Table 1-3. Mainly recyclable resin formuations were tried, a few of standard/conventional curing agent cured formulations were also tried for degradation using the recycling conditions. It’s surprisingly to see that those resins were also gegraded completely, though by variation of degradation time and temperature.

Example 61 Preparation of the curing agent H

400 g DMF, 200 g sodium o-nitrophenolate, and 182.4 g dichloromethane were mixed and placed in a 1 L flask, the solution was heated to reflux. After 3 hours (the reaction was completed by TLC monitoring) the solution was cooled, filtered, the filtrate was concentrated at reduced pressure. The residue was cooled, water was added till white precipitate was appeared, filtered, the solid was dried at vacuum to give 170 g bis (4-nitrophenoxy) methane.

170 g bis (4-nitrophenoxy) methane, 680 g ethanol, 25.5 g ferric chloride and 76.5 g activated carbon were placed in a 2 L flask, the reaction was heated to reflux, after at least 30 minutes, hydrazine hydrate was dripped in at reflux, the drip off was controlled within 3 hours. The reaction was preserved the temperature to reflux (after 4 hours the reaction was completed by TLC monitoring) , filtered when the solution was hot. The filter residue was washed with small amount of ethanol, the filtrate was cooled, and the precipitate was appeared, filtered, the solid was dried at vacuum to give 120g Curing Agent H. mp ＝ 82 ℃.

Example 62 Preparation of cross-linked thermoset polymer

Preparation of component A: 25 g bisphenol A epoxy resin NPEL-127 (EEW 0.54～0.56 eq. /100 g) and 5 g three-functional active diluent XY636 (EEW 0.69～0.71 eq. /100 g) were mixed and stirred evenly to give component A. Viscosity at 25 ℃ was 5500 ～ 6500 cps.

Preparation of component B: 55 g degradable curing agent B (AEW 2.99 N-H eq. /100 g) , 35 g diethylenetriamine curing agent (DETA, AEW 4.84 N-H eq. /100 g) and 10 g 2, 4, 6-Tris (dimethylaminomethyl) phenol (DMP-30) accelerant were mixed and stirred evenly to give component B. Viscosity at 25 ℃ was 5 ～ 15 cps.

100 g A and 20 g B were mixed and stirred evenly, cured at 110℃ for 5 minutes to give cured sample.

Example 63 Preparation of cross-linked thermoset polymer

Preparation of component A: 80 g bisphenol A epoxy resin NPEL-127 (EEW 0.54～0.56 eq. /100 g) , 5 g single-functional active diluent XY748 (EEW 0.31～0.32 eq. /100 g) , 10 g bifunctional active diluent XY622 (EEW 0.98～1.0 eq. /100 g) and 5 g three-functional active diluent XY636 (EEW 0.69～0.71 eq. /100 g) were mixed and stirred evenly to give component A. Viscosity at 25 ℃ was 700 ～ 900 cps.

Preparation of component B: 22 g degradable curing agent D (AEW 1.74 N-H eq. /100 g) , 30 g degradable curing agent A (AEW 2.99 N-H eq. /100 g) , 30 g polyether amine D230 curing agent (AEW 1.67 N-H eq. /100 g) and 18 g isophorone diamine curing agent (IPDA， AEW 2.35 N-H eq. /100 g) were mixed and stirred evenly to give component B. Viscosity at 25 ℃ was 20 ～ 30 cps.

100 g A and 27 g B were mixed and stirred evenly, cured at 80℃ for 10 hours to give cured sample.

Example 64 Preparation of cross-linked thermoset polymer

100 g liquid bisphenol A epoxy resin NPEL-128 (EEW ＝ 0.52 ～ 0.55 eq. /100 g) and 31 g curing agent H (AEW≈1.74 N-H eq. /100 g) were mixed and stirred evenly at room temperature, cured at 130℃ for 3 hours to give cured sample.

Example 65 Preparation of cross-linked thermoset polymer

Preparation of curing agent component: 9 g DICY and 15 g degradable curing agent F were slowly added into 24 g bisphenol A epoxy resin NPEL-128 (EEW 0.52～0.55 eq. /100g) at 60℃, dispersed under high speed for 30 minutes at less than 70℃, then 3 g bisphenol A epoxy resin NPEL-128 (EEW 0.52～0.55 eq. /100 g) and 3 g UR200 accelerator were added, dispersed under high speed for 30 minutes as standby.

Mixing resin: 30 g solid isocyanate modified epoxy resin (EEW 0.34～0.40 eq. /100 g) , 60 g bisphenol A epoxy resin NPES-901 (EEW 0.20～0.22 eq. /100 g) , 46 g novolac epoxy resin NPPN-638S (EEW 0.53～0.59 eq. /100 g) and 32 g bisphenol A epoxy resin NPEL-128 (EEW 0.52～0.55 eq. /100 g) were mixed and dispersed evenly under high speed at 90℃, cooled to 65 ℃, then former standby curing agent component was added and dispersed under high speed for 20 minutes at less than 70℃ to give resin matrix. The resin matrix was cured at 140℃ for 2 hours to give cured sample.

Example 66 Preparation of cross-linked thermoset polymer

Preparation of curing agent component: 8.6 g DICY and 14.4 g degradable curing agent F were slowly added into 23 g bisphenol A epoxy resin EJ-8128S (EEW 0.52～0.55 eq. /100 g) at 60℃, dispersed under high speed for 30 minutes at less than 70℃, cooled to 60℃, then 2 g diphenyl imidazole accelerator and 4 g bisphenol A epoxy resin EJ-8128S (EEW 0.52～0.55 eq. /100 g) were added slowly, dispersed under high speed for 30 minutes as standby.

Mixing resin: 30 g solid isocyanate modified epoxy resin (EEW 0.34～0.40 eq. /100 g) , 40 g halogen-free fire retardant OL5000, 46 g novolac epoxy resin NPPN-638S (EEW 0.53～0.59 eq. /100 g) and 60 g bisphenol A epoxy resin EJ-8128S (EEW 0.52～0.55 eq. /100 g) were mixed and dispersed evenly under high speed at 90℃, cooled to 60℃, then former standby curing agent component was added and dispersed under high speed for 20 minutes to give resin matrix. The f resin matrix was cured at 150℃ for 1 hours to give cured sample.

Example 67 Preparation of cross-linked thermoset polymer

Preparation of curing agent component: 1.9 g fumed silica M-5, 8.6 g DICY and 14.4 g degradable curing agent F were slowly added into 23 g bisphenol A epoxy resin NPEL-128 (EEW 0.52～0.55 eq. /100 g) at 60℃, dispersed under high speed for 30 minutes at less than 70℃, cooled to 60℃, then 2 g diphenyl imidazole accelerator， 1.7 g UR300 accelerator and 4.7 g bisphenol A epoxy resin NPEL-128 (EEW 0.52～0.55 eq. /100 g) were added, dispersed under high speed for 30 minutes as standby.

Mixing resin: 100 g solid isocyanate modified epoxy resin (EEW 0.34～0.40 eq. /100 g) , 24 g novolac epoxy resin NPPN-638S (EEW 0.53～0.59 eq. /100 g) and 10 g bisphenol A epoxy resin NPEL-128 (EEW 0.52～0.55 eq. /100 g) were mixed and dispersed evenly under high speed at 90 ℃, cooled to 65 ℃, then former standby curing agent component was added and dispersed under high speed for 20 minutes at less than 70℃ to give resin matrix. The resin matrix was cured at 135 ℃ for 1 hours to give cured sample.

Example 68 Recycling of cross-linked thermoset polymer

1 g cured samples in example 8, 2 mL 30％hydrogen peroxide and 22 mL acetic acid were placed in a 100 mL three-neck flask, stirred and heated to 110 ℃, the cured sample was completely degraded and dissolved in the solution after 2 hours.

Example 69 Recycling of cross-linked thermoset polymer

1 g cured samples in example 9, 3 mL 30％hydrogen peroxide and 27 mL acetic acid were placed in a 100 mL three-neck flask, stirred and heated to 110 ℃, the cured sample completely degraded and dissolved in the solution after 2 hours.

Example 70 Recycling of cross-linked thermoset polymer

1 g cured samples in example 62, 5 mL 30％hydrogen peroxide and 30 mL acetic acid were placed in a 100 mL three-neck flask, stirred and heated to 108 ℃, 2.5 mL 30％hydrogen peroxide was added in the flask every 1.5 hours, the cured sample completely degraded and dissolved in the solution after 4 hours.

Example 71 Recycling of cross-linked thermoset polymer

1 g cured samples in example 62, 3 mL 30％hydrogen peroxide and 36 mL acetic acid were placed in a 100 mL three-neck flask, stirred and heated to 108 ℃, 1.5 mL 30％hydrogen peroxide was added in the flask every 1.5 hours, the cured sample completely degraded and dissolved in the solution after 4 hours.

Example 72 Recycling of cross-linked thermoset polymer

1 g cured samples in example 10, 2 mL 30％hydrogen peroxide and 30 mL acetic acid were placed in a 100 mL three-neck flask, stirred and heated to 108 ℃, the cured sample completely degraded and dissolved in the solution after 2 hours.

Example 73 Recycling of cross-linked thermoset polymer

1 g cured samples in example 11, 3 mL 30％hydrogen peroxide and 36 mL acetic acid were placed in a 100 mL three-neck flask, stirred and heated to 108 ℃, 1.5 mL 30％hydrogen peroxide was added in the flask every 1.5 hours, the cured sample completely degraded and dissolved in the solution after 4 hours.

Example 74 Recycling of cross-linked thermoset polymer

1 g cured samples in example 63, 2.5 mL 30％hydrogen peroxide and 27.5 mL acetic acid were placed in a 100 mL three-neck flask, stirred and heated to 110 ℃, the cured sample completely degraded and dissolved in the solution after 4 hours.

Example 75 Recycling of cross-linked thermoset polymer

1 g cured samples in example 63, 3.3 mL 30％hydrogen peroxide and 36.7 mL acetic acid were placed in a 100 mL three-neck flask, stirred and heated to 90℃, the cured sample completely degraded and dissolved in the solution after 4 hours.

Example 76 Recycling of cross-linked thermoset polymer

1g cured samples in example 63, 3 mL 30％hydrogen peroxide and 36 mL acetic acid were placed in a 100 mL three-neck flask, stirred and heated to 108 ℃, 1.5 mL 30％hydrogen peroxide was added in the flask every 1.5 hours, the cured sample completely degraded and dissolved in the solution after 4 hours.

Example 77 Recycling of cross-linked thermoset polymer

1g cured samples in example 63, 1.6 mL 30％hydrogen peroxide and 36.7 mL acetic acid were placed in a 100 mL three-neck flask, stirred and heated to 90 ℃, 0.8 mL 30％hydrogen peroxide was added in the flask every 1.5 hours, the cured sample completely degraded and dissolved in the solution after 4 hours.

Example 78 Recycling of cross-linked thermoset polymer

1 g cured samples in example 64, 1.6 mL 30％hydrogen peroxide and 36.7 mL acetic acid were placed in a 100 mL three-neck flask, stirred and heated to 108 ℃, 0.8 mL 30％hydrogen peroxide was added in the flask every 1.5 hours, the cured sample completely degraded and dissolved in the solution after 6 hours.

Example 79 Recycling of cross-linked thermoset polymer

2.5 g cured samples in example 65, 3 mL 30％hydrogen peroxide and 36 mL acetic acid were placed in a 100 mL three-neck flask, stirred and heated to 108 ℃, 1.5 mL 30％hydrogen peroxide was added in the flask every 1.5 hours, the cured sample completely degraded and dissolved in the solution after 6 hours.

Example 80 Recycling of cross-linked thermoset polymer

1 g cured samples in example 66, 3 mL 30％hydrogen peroxide and 36 mL acetic acid were placed in a 100 mL three-neck flask, stirred and heated to 108 ℃, 1.5 mL 30％hydrogen peroxide was added in the flask every 1 hours, the cured sample completely degraded and dissolved in the solution after 3 hours.

Example 81 Recycling of cross-linked thermoset polymer

1 g cured samples in example 67, 6 mL 30％hydrogen peroxide and 36 mL acetic acid were placed in a 100 mL three-neck flask, stirred and heated to 108 ℃, 2 mL 30％hydrogen peroxide was added in the flask every 1.5 hours, the cured sample completely degraded and dissolved in the solution after 6 hours.

Example 82 Recycling of cross-linked thermoset polymer

1 g cured samples in example 15, 6 mL 30％hydrogen peroxide and 36 mL acetic acid were placed in a 100 L three-neck flask, stirred and heated to 108 ℃, 2 mL 30％hydrogen peroxide was added in the flask every 1.5 hours, the cured sample completely degraded and dissolved in the solution after 4 hours.

Example 83 Recycling of cross-linked thermoset polymer

1 g cured samples in example 16, 6 mL 30％hydrogen peroxide and 36 mL acetic acid were placed in a 100 mL three-neck flask, stirred and heated to 108 ℃, 2 mL 30％hydrogen peroxide was added in the flask every 1.5 hours, the cured sample completely degraded and dissolved in the solution after 4 hours.

Example 84 Recycling of cross-linked thermoset polymer

1 g cured samples in example 19, 6 mL 30％hydrogen peroxide and 36 mL acetic acid were placed in a 100 mL three-neck flask, stirred and heated to 108 ℃, 2 mL 30％hydrogen peroxide was added in the flask every 1.5 hours, the cured sample completely degraded and dissolved in the solution after 4 hours.

Example 85 Preparationof fiber reinforced thermoset polymer composite

200 g liquid bisphenol A epoxy resin NPEL-128 (EEW ＝ 0.52 ～ 0.55 eq. /100 g) , 36 g curing agent (AEW≈2.98 N-H eq. /100 g) and 100 g butanone were mixed and stirred evenly at room temperature for 20 minutes as standby. Carbon fiber prepreg was made by wet hand lay-up method. The prepregs were pressed on the tablet pressing machine at 80℃ for 16 hour to give laminate (2 mm thickness) of glass fiber composite.

Example 86 Preparation of fiber reinforced thermoset polymer composite

350 g brominated epoxy resin A80 (EEW ＝ 0.22 ～ 0.23 eq. /100 g) , 20 g tetraphenol ethane epoxy resin 1031 (EEW ＝ 0.45 ～ 0.50 eq. /100 g) , 0.9 g zinc acetylacetonate, 45 g curing agent F (AEW≈0.99 N-H eq. /100 g) and 100 g N, N-dimethylformamide were mixed and stirred evenly at room temperature for 20 minutes as standby. Glass fiber prepreg was made using 7628 glass fiber cloth by wet impregnating method and heating at 150℃ for 15 mins. The prepregs were pressed on the tablet pressing machine at 160℃ for 2 hour to give laminate (1.5 mm thickness) of glass fiber composite.

Example 87 Preparationof fiber reinforced thermoset polymer composite

250 g brominated epoxy resin A80 (EEW ＝ 0.22 ～ 0.23 eq. /100 g) , 40 g tetraphenol ethane epoxy resin 1031 (EEW ＝ 0.45 ～ 0.50 eq. /100 g) , 0.8 g zinc acetylacetonate, 15 g curing agent H (AEW≈1.74 N-H eq. /100 g) and 100 g N, N-dimethylformamide were mixed and stirred evenly at room temperature for 20 minutes as standby. Glass fiber prepreg was made using 7628 glass fiber cloth by wet impregnating method and heating at 150℃ for 15 mins. The prepregs were pressed on the tablet pressing machine at 160℃ for 2 hour to give laminate (1.5 mm thickness) of glass fiber composite.

Example 88 Recycling of fiber reinfored thermoset polymer composite

3 g cured samples in example 85, 10 mL 30％hydrogen peroxide and 60 mL acetic acid were placed in a 250 mL three-neck flask, stirred and heated to 108 ℃, 5 mL 30％hydrogen peroxide was added in the flask every 1.5 hours, completely degraded after 6 hours, and fiber cloth and resin were separated completely.

Example 89 Recycling of fiber reinfored thermoset polymer composite

2 g cured samples in example 86, 10 mL 30％hydrogen peroxide and 60 mL acetic acid were placed in a 250 mL three-neck flask, stirred and heated to 108 ℃, 5 mL 30％hydrogen peroxide was added in the flask every 1.5 hours, completely degraded after 6 hours, and fiber cloth and resin were separated completely.

Example 90 Recycling of fiber reinfored thermoset polymer composite

2 g cured samples in example 87, 10 mL 30％hydrogen peroxide and 60 mL acetic acid were placed in a 250 mL three-neck flask, stirred and heated to 108 ℃, 5 mL 30％hydrogen peroxide was added in the flask every 1.5 hours, completely degraded after 6 hours, and fiber cloth and resin were separated completely.

Table 1. Recycling condition comparisons between Ethylene glycol/HCl and Acetic acid/H₂O₂ aqueous solution

Table 2. Recycling methods studies-Comparisons

Table 3. Recycling methods studies.

Example 91 Recycling of fiber-reinforced thermoset polymer composite laminates (with thickness of 2-4mm)

The foregoing embodiments are only illustrative of the present invention and are not i intended to limit the invention. Those skilled in the art would understand that the present invention have various alterations and changes not described here. Within the spirit and principles of the invention, any modification, equivalent replacement, improvement, etc., should be included in the scope of protection of the invention.

Claims

A method for degrading or recycling a cross-linked polymer or a reinforced composite, comprising treating the cross-linked polymer or reinforced composite with aperoxide or peroxyacid and an acid, with or without solvent, to give a degradation mixture containing degradation product.
The method of claim 1, wherein the treatment of the cross-linked polymer or reinforced composite with aperoxide or peroxyacid and an acidis under the ambient pressure.
The method of claim 1 or 2, wherein the cross-linked polymer is a thermoset.
The method of any of claims 1-3, wherein the treatment comprises heating the cross-linked polymer or reinforced composite, the peroxide or peroxyacid, and the acid at a temperature in the range of 15-200℃ for 1-72hours, with stirring.
The method of any of claims 1-4, wherein the treatment comprises heating the cross-linked polymer or reinforced composite, the peroxide or peroxyacid, and the acid together at a temperature in the range of 80-150℃ for 1-4 hours, with stirring.
The method of any of claims 1-5, wherein the degradation mixture is recycled by distillation or by neutralization with an alkaline solution to adjust the pH value of the mixture to at least 6, and the alkaline solution has a temperature of 0-100℃ and weight concentration of 0.1-99.9％.
The method of any of claims 1-6, wherein the alkaline solution has a temperature of 5-50℃ and a weight concentration of 5-30％, and the pH value of the degradation mixture is adjusted to the range of 6-12.
The method of any of claims 1-7, wherein the peroxide or peroxyacid comprises hydrogen peroxide, performic acid, peroxyacetic acid, 2-butanone peroxide, bis (t-butyl) peroxide, perbenzoic acid, sodium peroxide, potassium peroxide, calcium peroxide, magnesium peroxide, or potassium persulfate.
The method of any of claims 1-8, wherein the acid comprises hydrochloric acid, hydrobromic acid, hydrofluoric acid, acetic acid, trifluoroacetic acid, lactic acid, formic acid, propionic acid, citric acid, methanesulfonic acid, p-toluenesulfonic acid, nitric acid, sulfuric acid, sulfurous acid, phosphoric acid, perchloric acid, benzoic acid, salicylic acid, or phthalic acid.
The method of any of claims 1-9, wherein the treatment of the cross-linked polymer or reinforced compositewith aperoxide or peroxyacid and an acidis in the presence of a solvent, and the solvent comprises methanol, ethanol, ethylene glycol, propanol, isopropanol, butanol, isobutanol, t-butanol, pentanol, hexanol, heptanol, octanol, nonanol, benzyl alcohol, phenethylalcohol, p-hydroxymethyl benzene, m-hydroxymethyl benzene, o-hydroxy benzene, p-hydroxyethyl benzene, m-hydroxyethyl benzene, o-hydroxyethyl benzene, water, N, N-dimethylformamide, N, N-dimethylacetamide, N-methylpyrrolidone, dimethyl sulfoxide, tetrahydrofuran, methyl tetrahydrofuran, glycerol, or dioxane； the alkali comprises lithium hydroxide, sodium hydroxide, potassium hydroxide, calcium hydroxide, sodium carbonate, sodium bicarbonate, potassium carbonate, potassium bicarbonate, ammonia； the alkali solvent comprises methanol, ethanol, ethylene glycol, propanol, isopropanol, butanol, isobutanol, t-butanol, pentanol, hexanol, heptanol, octanol, nonanol, water , N, N-dimethylformamide, N, N-dimethylacetamide, N-methylpyrrolidone, dimethyl sulfoxide, tetrahydrofuran, methyl tetrahydrofuran, glycerol, or dioxane.
The method according to any of claims 1-10, further comprising recovering the degradation product from the degradation mixture by filtration, extraction, or precipitation.