Thermosetting regenerated polyurethane resin and carbon fiber-polyurethane reinforced plastic composite obtained through chemical recycling of waste pet

Abstract

The present invention relates to preparing a thermosetting regenerated polyurethane resin and a carbon fiber-polyurethane reinforced plastic composite by chemically recycling waste PET. Specifically, a regenerated terephthalate polyol is prepared from waste PET by using a C4~8 alkanediol and an organic solvent having a standard boiling point of 120°C or higher, a stable PET depolymerization reaction can be induced even though a diol having a relatively long chain is used, and a thermosetting regenerated polyurethane resin having excellent thermal stability and mechanical properties can be prepared using the prepared regenerated terephthalate polyol. The thermosetting regenerated polyurethane resin can be synthesized with carbon fibers to prepare a carbon fiber-polyurethane reinforced plastic composite having excellent thermal stability and mechanical properties. In addition, the thermosetting regenerated polyurethane resin and the carbon fiber-polyurethane reinforced plastic composite are closed-loop recyclable, and thus can be repeatedly recycled and used.

Description

Thermosetting recycled polyurethane resin and carbon fiber-polyurethane reinforced plastic composite through the chemical recycling of waste PET

[0001] The present invention relates to the manufacture of a thermosetting recycled polyurethane resin and a carbon fiber-polyurethane reinforced plastic composite by chemically recycling waste PET (Polyethylene Terephthalate).

[0002] Due to its excellent mechanical strength and gas barrier properties, PET is widely used in various industrial fields, such as beverage bottles, films, and fibers. However, this extensive use generates large amounts of waste, and the current PET recycling rate remains very low. This relies primarily on physical recycling methods involving thermal treatment, while chemical recycling is limited due to complex processes and high energy requirements.

[0003] Representative methods for the chemical recycling of PET include glycol decomposition using ethylene glycol or methanol. However, these processes require high temperatures and strong basic conditions, which consume a large amount of energy. Recently, PET decomposition methods utilizing co-solvent systems or ionic liquids at low temperatures have been studied for more energy-efficient PET recycling; however, these methods still require improvement in processes using long-chain diols.

[0004] The present invention is C 4~8 The present invention aims to provide a method for producing recycled terephthalate polyol from waste PET using an alkanediol and an organic solvent having a standard boiling point of 120°C or higher.

[0005] Another objective of the present invention is to provide a thermosetting regenerated terephthalate-based polyurethane resin having excellent thermal stability and mechanical properties by using the regenerated terephthalate polyol, a biomass-based diisocyanate, and a solvent.

[0006] Another objective of the present invention is to provide a carbon fiber-polyurethane reinforced plastic composite having excellent thermal stability and mechanical properties by synthesizing the thermosetting recycled polyurethane resin with carbon fibers.

[0007] In addition, we intend to provide a closed-loop recycling method for the above-mentioned recycled polyurethane resin and carbon fiber-polyurethane reinforced plastic composite.

[0008] The present invention relates to waste PET, C 4~8 The method comprises the step of depolymerizing a depolymerization mixture of an alkanediol and an organic solvent having a standard boiling point of 120°C or higher under a basic catalyst at a temperature of 100°C or higher.

[0009] The above C 4~8 The present invention provides a method for producing recycled terephthalate polyol, wherein the alkanediol is mixed in a ratio of 4 to 50 equivalents relative to waste PET, and the organic solvent having a standard boiling point of 120°C or higher is mixed such that the waste PET has a concentration of 0.05 to 5 M.

[0010] In one embodiment, the organic solvent having a standard boiling point of 120°C or higher may be any one or more mixtures selected from the group consisting of chlorobenzene, dimethyl sulfoxide, 1,2-dichlorobenzene, 1,2,3-trichloroethane, xylene, and methoxybenzene.

[0011] In one embodiment, the basic catalyst may be any one or more mixtures selected from the group consisting of K2CO3, KOH, Na2CO3, and Cs2CO3.

[0012] In one embodiment, the basic catalyst may be used in an amount of 10 to 50 mol% relative to the repeating unit of waste PET.

[0013] Another aspect of the present invention is waste PET C 4~8A step of obtaining a regenerated terephthalate polyol by depolymerizing an alkanediol, an organic solvent having a standard boiling point of 120°C or higher, and a basic catalyst at a temperature of 100°C or higher;

[0014] The present invention provides a method for manufacturing a regenerated terephthalate-based polyurethane resin comprising the step of synthesizing a polyurethane resin including the regenerated terephthalate polyol obtained above, a diisocyanate compound, and a solvent.

[0015] In one embodiment, the diisocyanate compound may be any one or more mixtures selected from the group consisting of hexamethylene diisocyanate (HDI), methylene diphenyl diisocyanate (MDI), and pentamethylene diisocyanate (PDI).

[0016] In one embodiment, the thermosetting regenerated polyurethane resin may be synthesized under a solvent that is one or more mixtures selected from the group consisting of 2-methyltetrahydrofuran, tetrahydrofuran, γ-butyrolactone, ε-caprolactone, γ-valerolactone, n-butyl lactate, glycerol, and dihydro-levoglucosenone (Cyrene).

[0017] In one embodiment, the regenerated terephthalate-based polyurethane resin has a glass transition temperature (T g ) may be 30 to 50 ℃.

[0018] In one embodiment, the tensile strength of the recycled terephthalate-based polyurethane resin according to ASTM D638 may be 10 to 50 MPa.

[0019] In one embodiment, the strain at the maximum tensile strength according to ASTM D638 of the recycled terephthalate-based polyurethane resin may be 50 to 400%.

[0020] In one embodiment, the 5% weight loss temperature (T) of the regenerated terephthalate-based polyurethane resin d5% ) may be 200 to 400 ℃.

[0021] In one embodiment, the storage modulus of the regenerated terephthalate-based polyurethane resin according to ASTM D7028 may be 1000 MPa or more at 0 ℃ or lower.

[0022] In one embodiment, the tanδ peak according to ASTM D7028 of the regenerated terephthalate-based polyurethane resin may appear at 30 to 50 °C.

[0023] In one embodiment, in the stress relaxation measurement of the regenerated terephthalate-based polyurethane resin according to ASTM D2990, the point at which the stress decreases to 1 / e of the initial stress may be 800 to 1500 s at 150 ℃, 100 to 500 s at 160 ℃, 50 to 100 s at 170 ℃, and 10 to 50 s at 180 ℃.

[0024] In one embodiment, the activation energy by the Arrhenius plot of the regenerated terephthalate-based polyurethane resin may be 100 to 300 kJ / mol.

[0025] In one embodiment, the regenerated terephthalate-based polyurethane resin may be resynthesized after being decomposed with a polyol solvent and thus recyclable.

[0026] Another aspect of the present invention relates to a recycled terephthalate-based polyurethane resin at a temperature of 150 to 200 °C 4~8 A step of obtaining a mixture of diisocyanate and terephthalate polyols by depolymerizing with alkanediol;

[0027] A step of separating and purifying terephthalate polyol from the above mixture;

[0028] A method for recycling a recycled terephthalate-based polyurethane resin is provided, comprising the step of repolymerizing the polyurethane resin with the above-mentioned terephthalate polyol and a diisocyanate compound.

[0029] Another aspect of the present invention provides a carbon fiber-polyurethane reinforced plastic composite comprising carbon fibers; and a regenerated terephthalate-based polyurethane resin.

[0030] In one embodiment, the recycled terephthalate-based polyurethane resin is made from waste PET. 4~8 It may be prepared by synthesizing a regenerated terephthalate polyol and a diisocyanate compound obtained by depolymerizing an alkanediol, an organic solvent with a standard boiling point of 120°C or higher, and a basic catalyst at a temperature of 100°C or higher.

[0031] In one embodiment, the carbon fiber-polyurethane reinforced plastic composite may comprise 100 to 500 parts by weight of the thermosetting recycled polyurethane resin per 100 parts by weight of carbon fiber.

[0032] In one embodiment, the tensile strength of the carbon fiber-polyurethane reinforced plastic composite according to ASTM D3039 may be 100 to 300 MPa.

[0033] In one embodiment, the Young's modulus of the carbon fiber-polyurethane reinforced plastic composite according to ASTM D3039 may be 1.0 to 3.0 GPa.

[0034] In one embodiment, the tensile strain of the carbon fiber-polyurethane reinforced plastic composite according to ASTM D3039 may be 10 to 50%.

[0035] In one embodiment, the flexural strength of the carbon fiber-polyurethane reinforced plastic composite according to ASTM D790 may be 100 to 300 MPa.

[0036] Another aspect of the present invention relates to a carbon fiber-polyurethane reinforced plastic composite at a temperature of 150 to 200 °C 4~8 A step of separating carbon fibers, diisocyanate compounds, and terephthalate polyols by depolymerizing with alkanediols;

[0037] A step of purifying the separated terephthalate polyol and carbon fibers;

[0038] The present invention provides a method for recycling carbon fiber-polyurethane reinforced plastic composites, comprising the step of manufacturing a recycled carbon fiber-polyurethane reinforced plastic composite including the purified terephthalate polyol, purified carbon fiber, and diisocyanate compound.

[0039] A method for producing a recycled terephthalate polyol according to one embodiment of the present invention can induce a stable depolymerization reaction of waste PET even when using a diol having a long chain, and can produce a thermosetting recycled polyurethane resin having excellent thermal stability and mechanical properties using the produced recycled terephthalate polyol.

[0040] In addition, a carbon fiber-polyurethane reinforced plastic composite with excellent thermal stability and mechanical properties can be manufactured by synthesizing the above-mentioned thermosetting recycled polyurethane resin and carbon fiber.

[0041] In addition, the above-mentioned thermosetting recycled polyurethane resin and carbon fiber-polyurethane reinforced plastic composite can be recycled repeatedly as they are capable of closed-loop recycling.

[0042] FIG. 1 schematically illustrates the chemical recycling process of waste PET according to one embodiment of the present invention.

[0043] Figure 2 shows the thermogravimetric analysis of the thermosetting recycled polyurethane resin of Example 1 of the present invention.

[0044] Figure 3 shows the results of differential scanning calorimetry analysis of the thermosetting regenerated polyurethane resin of Example 1 of the present invention.

[0045] Figure 4 shows the stress-strain curve and Young's modulus of the thermosetting recycled polyurethane resin of Example 1 of the present invention.

[0046] Figure 5 shows the storage modulus and tanδ peak of the thermosetting regenerated polyurethane resin of Example 1 of the present invention.

[0047] Figure 6 shows the stress relaxation of the thermosetting regenerated polyurethane resin of Example 1 of the present invention.

[0048] Figure 7 shows an Arrhenius plot of the thermosetting regenerated polyurethane resin of Example 1 of the present invention against the inverse of temperature.

[0049] FIG. 8 schematically illustrates the remolding process of a thermosetting recycled polyurethane resin according to one embodiment of the present invention.

[0050] Figure 9 shows thermogravimetric analysis data for a remolded thermosetting recycled polyurethane resin of Example 1 of the present invention.

[0051] Figure 10 shows differential scanning calorimetry data for a remolded thermosetting recycled polyurethane resin of Example 1 of the present invention.

[0052] FIG. 11 shows the stress-strain curve and Young's modulus for a remolded thermosetting recycled polyurethane resin of Example 1 of the present invention.

[0053] Figure 12 shows the storage modulus and tanδ peak measured for the thermosetting recycled polyurethane resin of Example 1 of the present invention after remolding.

[0054] FIG. 13 schematically illustrates the regeneration process after depolymerization of a thermosetting regenerated polyurethane resin according to one embodiment of the present invention.

[0055] Figure 14 shows thermogravimetric analysis data for the thermosetting regenerated polyurethane resin of Example 1 of the present invention after depolymerization and regeneration.

[0056] Figure 15 shows differential scanning calorimetry data for the thermosetting regenerated polyurethane resin of Example 1 of the present invention after depolymerization and regeneration.

[0057] Figure 16 shows the stress-strain curve and Young's modulus for the thermosetting regenerated polyurethane resin of Example 1 of the present invention after depolymerization and regeneration.

[0058] Figure 17 shows the storage modulus and tanδ peak measured for the thermosetting regenerated polyurethane resin of Example 1 of the present invention after depolymerization and regeneration.

[0059] The present invention will be described in more detail below. However, the following specific examples or embodiments are merely references for the detailed explanation of the present invention and are not limited thereto, and the present invention may be implemented in various forms.

[0060] Furthermore, unless otherwise defined, all technical and scientific terms have the same meaning as generally understood by one of the art to which the present invention pertains. The terms used in the description of the present invention are merely for the purpose of effectively describing specific embodiments and are not intended to limit the present invention.

[0061] Additionally, the singular form used in the specification and the appended claims may be intended to include the plural form unless specifically indicated otherwise in the context.

[0062] Furthermore, when it is stated that a part "includes" a certain component, this means that, unless specifically stated otherwise, it does not exclude other components but may include additional components.

[0063] Furthermore, unless otherwise specifically defined in the present invention, when a layer or member is described as being located “on” another layer or member, this includes not only cases where a layer or member is in contact with another layer or member, but also cases where another layer or member exists between two layers or two members.

[0064] Additionally, terms used herein such as “about,” “substantially,” etc., are used to mean at or near the stated value when inherent manufacturing and material tolerances are presented in the said sense, and are used to prevent unscrupulous infringers from unfairly exploiting the disclosed content in which precise or absolute values ​​are mentioned to aid in understanding the invention.

[0065] The inventors have a long chain C 4~8 The present invention provides a technology for effectively producing recycled terephthalate polyol by glycolic decomposition of PET waste at low temperatures using alkanediols, and for producing recyclable thermosetting recycled polyurethane resin by reacting this with bio-based isocyanates. This technology is a chemical recycling method that reduces energy consumption compared to existing physical recycling technologies while maintaining mechanical properties and enabling repeated recycling.

[0066] The present invention will be described below.

[0067] The present invention relates to waste PET, C 4~8The method comprises the step of depolymerizing a mixture of an alkanediol and an organic solvent having a standard boiling point of 120°C or higher by heating the mixture to 100 to 150°C under a basic catalyst;

[0068] The above C 4~8 The present invention provides a method for producing recycled terephthalate polyol, wherein the alkanediol may be mixed in a ratio of 4 to 50 equivalents, 5 to 40 equivalents, or 10 to 20 equivalents relative to waste PET, and the organic solvent having a standard boiling point of 120°C or higher is mixed such that the waste PET has a concentration of 0.05 to 5 M, 0.1 to 3 M, or 0.5 to 2 M.

[0069] C within the above equivalent ratio range 4~8 Mixing alkanediols is preferred because it can improve the conversion rate of recycled terephthalate polyols from waste PET.

[0070] Mixing the organic solvent within the above-mentioned waste PET concentration range is preferred because it allows the depolymerization reaction to proceed effectively and improves the conversion rate from waste PET to recycled terephthalate polyol.

[0071] In one aspect, the above C 4~8 The alkanediol may be any one or more mixtures selected from the group consisting of 1,4-butanediol, 1,6-hexanediol, and 1,8-octanediol, but is not limited thereto.

[0072] In one embodiment, the organic solvent having a standard boiling point of 120°C or higher may be any one or more mixtures selected from the group consisting of chlorobenzene, dimethyl sulfoxide (DMSO), 1,2-dichlorobenzene, 1,2,3-trichloroethane, xylene, and methoxybenzene, but is not limited thereto as long as it is an organic solvent having a standard boiling point of 120°C or higher that can selectively obtain the desired regenerated terephthalate polyol by decomposing PET.

[0073] The standard boiling point of the above organic solvent does not have a specific upper limit, but may have a range of 120 to 200°C, and using an organic solvent within the above standard boiling point range allows for stable reaction of polyols with long chains, thereby effectively achieving the objective of the present invention.

[0074] In one embodiment, the basic catalyst is K2CO3, KOH, Na2CO3, Cs2CO3 and It may be one or more mixtures selected from the group consisting of 1,5,7-Triazabicyclo[4.4.0]dec-5-ene (TBD), but is not limited thereto. The basic catalysts may be effective in hydrolyzing the ester bonds of PET and may be preferred as they allow for the selective acquisition of the desired regenerated terephthalate polyol.

[0075] In one embodiment, the basic catalyst may be used in an amount of 10 to 50 mol%, 10 to 40 mol%, or 20 to 30 mol% relative to the repeating unit of waste PET. Using the basic catalyst in the above range is preferred as it can improve the conversion rate from waste PET to recycled terephthalate polyol, but is not limited thereto.

[0076] Another aspect of the present invention is waste PET C 4~8A step of obtaining a regenerated terephthalate polyol by depolymerizing an alkanediol, an organic solvent having a standard boiling point of 120°C or higher, and a basic catalyst at a temperature of 100°C or higher;

[0077] The present invention provides a method for manufacturing a regenerated terephthalate-based polyurethane resin comprising the step of synthesizing a polyurethane resin including the regenerated terephthalate polyol obtained above, a diisocyanate compound, and a solvent.

[0078] In one embodiment, the diisocyanate compound may be one or more mixtures selected from the group consisting of hexamethylene diisocyanate (HDI), methylene diphenyl diisocyanate (MDI), pentamethylene diisocyanate (PDI), etc., but is not limited thereto. The diisocyanate compound may be a diisocyanate compound derived from biomass such as vegetable oils like soybean oil and palm oil, lignin, starch, and seaweed. Diisocyanate compounds using such biomass raw materials are preferred because they can produce environmentally friendly products that reduce carbon emissions, as well as be advantageous in terms of economy.

[0079] In one embodiment, the thermosetting regenerated polyurethane resin may be synthesized under a solvent that is one or more mixtures selected from the group consisting of 2-methyltetrahydrofuran, tetrahydrofuran, γ-butyrolactone, ε-caprolactone, γ-valerolactone, n-butyl lactate, glycerol, and dihydrolevoglucosenone (Cyrene), but is not limited thereto. The solvents may be biomass-derived solvents.

[0080] The term "biomass-derived" above refers to a material obtained primarily from renewable biological resources, and is a material derived mainly from plants, trees, agricultural byproducts, animal resources, etc. By using the biomass-derived diisocyanates and solvents, the manufacturing process of thermosetting regenerated polyurethane resins can be environmentally friendly and economical. For example, the HDI can be obtained from vegetable oils or sugar-based raw materials, and the MDI can be manufactured from aromatic compounds derived from biomass, such as lignin. Additionally, 2-methyltetrahydrofuran can be manufactured from cellulose by fermentation or chemical conversion, but is not limited thereto.

[0081] In one embodiment, the regenerated terephthalate-based polyurethane resin has a glass transition temperature (T g ) may be 30 to 50 ℃, 35 to 45 ℃, or 35 to 40 ℃. Regenerated terephthalate-based polyurethane resins having a glass transition temperature in the above range are preferred as they can have excellent thermal stability, but are not limited thereto.

[0082] In one embodiment, the tensile strength of the recycled terephthalate-based polyurethane resin according to ASTM D638 may be 10 to 50 MPa, 15 to 40 MPa, or 20 to 30 MPa. A recycled terephthalate-based polyurethane resin having the above tensile strength range is preferred as it can have long-lasting durability and impact resistance, but is not limited thereto.

[0083] In one embodiment, the strain at maximum tensile strength according to ASTM D638 of the recycled terephthalate-based polyurethane resin may be 50 to 400%, 100 to 300%, or 150 to 200%. A recycled terephthalate-based polyurethane resin having the strain range at maximum tensile strength is preferred as it may have excellent flexibility, impact resistance, and durability, but is not limited thereto.

[0084] In one embodiment, the 5% weight loss temperature (T) of the regenerated terephthalate-based polyurethane resin d5% ) may be 200 to 400 ℃ or 250 to 300 ℃. The 5% weight loss temperature (T) of the above range d5% Regenerated terephthalate-based polyurethane resins having ) are preferred because they can have excellent thermal stability, but are not limited thereto.

[0085] In one embodiment, the storage modulus of the recycled terephthalate-based polyurethane resin according to ASTM D7028 may be 1,000 to 5,000 MPa and 1,500 to 3,000 MPa at 0°C or lower, and 50 to 500 MPa and 80 to 200 MPa at 50°C or higher. A recycled terephthalate-based polyurethane resin having the above storage modulus range is preferred because it may have excellent stiffness and excellent flexibility as the temperature increases, but is not limited thereto.

[0086] In one embodiment, the tanδ peak according to ASTM D7028 of the recycled terephthalate-based polyurethane resin may appear at 30 to 50 °C or 35 to 45 °C. A recycled terephthalate-based polyurethane resin having the above tanδ peak range may have excellent thermal stability, flexibility, and elasticity at room temperature, and may be preferred, but not limited thereto, to be able to exhibit mechanical properties while maintaining chemical stability within the above temperature range. Furthermore, considering that the surface temperature of human skin is generally 36 to 37 °C, the recycled terephthalate-based polyurethane resin may be applicable to human contact products as it remains in a soft and flexible state.

[0087] In one embodiment, in the stress relaxation measurement of a recycled terephthalate-based polyurethane resin according to ASTM D2990, the point at which the stress decreases to 1 / e of the initial stress may be 800 to 1500 s, 900 to 1000 s, 100 to 500 s, 200 to 300 s, 50 to 100 s, 70 to 80 s, 10 to 50 s, and 20 to 40 s at 180 s. A recycled terephthalate-based polyurethane resin having the above range of the point at which the stress decreases to 1 / e of the initial stress is preferred as it may have excellent thermal stability, durability, and mechanical properties, but is not limited thereto.

[0088] In one embodiment, the activation energy by the Arrhenius plot of the regenerated terephthalate-based polyurethane resin may be 100 to 300 kJ / mol, 120 to 250 kJ / mol, or 150 to 200 kJ / mol. A regenerated terephthalate-based polyurethane resin having the above activation energy range is preferred as it may have excellent thermal stability, durability, and mechanical properties, but is not limited thereto.

[0089] In one embodiment, the recycled terephthalate-based polyurethane resin may be recyclable after being decomposed with a polyol solvent and then resynthesized. The thermosetting recycled polyurethane resin may be recyclable multiple times. The number of recycling cycles is not specifically limited, and the recycled terephthalate-based polyurethane resin may be used in a closed-loop recycling system. The recycling may be performed using methods such as "remolding," which physically recycles the thermosetting recycled polyurethane, and "depolymerization and repolymerization."

[0090] In one embodiment, the glass transition temperature (T) of the recycled terephthalate-based polyurethane resin g ) is 30 to 50 ℃, the tensile strength according to ASTM D638 is 10 to 50 MPa, the strain at maximum tensile strength according to ASTM D638 is 50 to 400%, and the 5% weight loss temperature (T d5%) may be 200 to 400 ℃, the storage modulus according to ASTM D7028 may be 1000 to 5000 MPa at 0 ℃ or lower and 50 to 500 MPa at 50 ℃ or higher, and the tanδ peak according to ASTM D7028 may appear at 30 to 50 ℃. This means that the mechanical and thermal properties of the recycled terephthalate-based polyurethane resin did not change significantly even after regeneration following remolding and depolymerization, and may imply that it can have consistent properties even when recycled and used multiple times.

[0091] Another aspect of the present invention relates to a recycled terephthalate-based polyurethane resin at a temperature of 150 to 200 °C 4~8 A step of obtaining a mixture of diisocyanate and terephthalate polyols by depolymerizing with alkanediol;

[0092] A step of separating and purifying terephthalate polyol from the above mixture;

[0093] A method for recycling a recycled terephthalate-based polyurethane resin is provided, comprising the step of repolymerizing the polyurethane resin with the above-mentioned terephthalate polyol and a diisocyanate compound.

[0094] Another aspect of the present invention is carbon fiber;

[0095] The present invention provides a carbon fiber-polyurethane reinforced plastic composite comprising a recycled terephthalate-based polyurethane resin.

[0096] In one embodiment, the carbon fiber-polyurethane reinforced plastic composite may comprise the thermosetting recycled polyurethane resin in an amount of 100 to 500 parts by weight, 150 to 400 parts by weight, or 150 to 300 parts by weight per 100 parts by weight of carbon fiber. When the carbon fiber-polyurethane reinforced plastic composite is manufactured within the above content range, the carbon fiber-polyurethane reinforced plastic composite may have excellent thermal and mechanical properties, which is preferred, but is not limited thereto.

[0097] In one embodiment, the tensile strength of the carbon fiber-polyurethane reinforced plastic composite according to ASTM D3039 may be 100 to 300 MPa, 150 to 250 MPa, or 200 to 250 MPa. A carbon fiber-polyurethane reinforced plastic composite having the above tensile strength range is preferred because it may have excellent mechanical properties, but is not limited thereto.

[0098] In one embodiment, the Young's modulus of the carbon fiber-polyurethane reinforced plastic composite according to ASTM D3039 may be 1.0 to 3.0 GPa, 1.5 to 2.5 GPa, or 2.0 to 2.5 GPa. A carbon fiber-polyurethane reinforced plastic composite having the above Young's modulus range may have appropriate stiffness while having excellent flexibility. In addition, it may be preferred as it may have excellent shock absorption ability, but is not limited thereto.

[0099] In one embodiment, the tensile strain of the carbon fiber-polyurethane reinforced plastic composite according to ASTM D3039 may be 10 to 50%, 12 to 40%, or 15 to 30%. A carbon fiber-polyurethane reinforced plastic composite having the above tensile strain range is preferred as it can have excellent durability, impact resistance, and flexibility, but is not limited thereto.

[0100] In one embodiment, the flexural strength of the carbon fiber-polyurethane reinforced plastic composite according to ASTM D790 may be 100 to 300 MPa, 120 to 250 MPa, or 150 to 200 MPa. A carbon fiber-polyurethane reinforced plastic composite having the above flexural strength range may be preferred as it may have excellent durability, but is not limited thereto.

[0101] In one embodiment, the carbon fiber-polyurethane reinforced plastic composite may be recycled into a recycled carbon fiber-polyurethane reinforced plastic composite by decomposing the polyurethane component to separate it from the carbon fiber, and then recombining it through repolymerization.

[0102] In one embodiment, the method for recycling the carbon fiber-polyurethane reinforced plastic composite is to separate the polyurethane component from the carbon fiber, and the polyurethane component may be recycled by depolymerizing it in the same way as the method for recycling the thermosetting recycled polyurethane resin mentioned above.

[0103] Another aspect of the present invention relates to a carbon fiber-polyurethane reinforced plastic composite at a temperature of 150 to 200 °C 4~8 A step of separating carbon fibers, diisocyanate compounds, and terephthalate polyols by depolymerizing with alkanediols;

[0104] A step of purifying the separated terephthalate polyol and carbon fibers;

[0105] The present invention provides a method for recycling carbon fiber-polyurethane reinforced plastic composites, comprising the step of manufacturing a recycled carbon fiber-polyurethane reinforced plastic composite including the purified terephthalate polyol, the diisocyanate compound, and the purified carbon fiber.

[0106] The present invention will be explained in more detail below based on the following examples and comparative examples. However, the following examples and comparative examples are merely illustrative of the present invention and are not intended to limit the present invention.

[0107] [measurement method]

[0108] 1. Measurement of the glass transition temperature of recycled terephthalate-based polyurethane resin

[0109] The glass transition temperature was measured by analyzing the temperature range from -50 to 150 ℃ at a constant heating rate of 10 ℃ per minute using a DSC instrument (DSC Q800; TA Instruments).

[0110] 2. 5% weight loss temperature (T) of recycled terephthalate-based polyurethane resin d5% ) measurement

[0111] 10 mg of thermosetting regenerated polyurethane resin was analyzed using a TGA instrument (TGA Q500; TA Instruments) at a constant heating rate of 10 °C per minute in a temperature range of 30 to 700 °C, and the 5% weight loss temperature (T d5% ) was measured.

[0112] 3. Measurement of Tensile Strength and Strain at Maximum Tensile Strength of Recycled Terephthalate-Based Polyurethane Resin

[0113] Tensile strength and tensile strain were measured using a UTM machine (QM 100S; Qmesys) in accordance with ASTM D638.

[0114] 4. Measurement of Storage Modulus and Tanδ Peak of Recycled Terephthalate-Based Polyurethane Resin

[0115] In accordance with ASTM D7028, storage modulus and tanδ peaks were measured using a DMA instrument (DMA Q800; TA Instruments) at a temperature range of -50 to 150 ℃, a frequency of 1 Hz, and a strain of 0.5%.

[0116] 5. Measurement of Stress Relaxation and Calculation of Activation Energy of Regenerated Terephthalate-Based Polyurethane Resin

[0117] Stress relaxation was measured using a UTM device (QM100S; Qmesys) in accordance with ASTM D2990, and the activation energy was calculated using the following Equations 1 and 2.

[0118] [Equation 1]

[0119]

[0120] In Equation 1 above, E(t) is the stress at time t, E0 is the initial stress, and τ is the characteristic relaxation time.

[0121] [Equation 2]

[0122]

[0123] In Equation 2 above, Ea is the activation energy, R is the gas constant (=8.314 J / mol·K), T is the absolute temperature, τ is the characteristic relaxation time, and τ0 is the relaxation time in the absence of temperature or activation energy.

[0124] 6. Measurement of Tensile Strength, Tensile Strain, Young's Modulus, and Flexural Strength of Carbon Fiber-Polyurethane Reinforced Plastic Composites

[0125] Tensile strength, tensile strain, Young's modulus, and bending strength were measured using a UTM machine (QM100S; Qmesys) in accordance with ASTM D3039.

[0126] [Examples and Comparative Examples]

[0127] [Example 1]

[0128] 1. Production of recycled terephthalate polyol from waste PET

[0129] Waste PET 2.00 g, K2CO3 catalyst *0.29 g (20 mol% relative to the waste PET repeating unit), 1,4-butanediol (BDO) at a ratio of 20 equivalents relative to the waste PET, and chlorobenzene were mixed so that the waste PET was 0.5 M, and the depolymerization mixture was reacted at a temperature of 120 °C for 9 hours. Afterward, unreacted waste PET was filtered and separated, and the remaining depolymerization mixture was placed in water at 60 °C and the temperature was gradually lowered to 25 °C to crystallize the regenerated terephthalate polyol from the depolymerization mixture and dry to obtain regenerated terephthalate polyol powder (BHBT).

[0130] * Moles of waste PET repeating units: 2g ÷ 192 g / mol = 0.01042 mol,

[0131] Calculation of K2CO3 catalyst amount: 0.01042 mol × 0.2 × 138.2 g / mol ≈ 0.29 g

[0132] 2. Manufacture of recycled terephthalate-based polyurethane resin

[0133] 1.0 g of the above-mentioned recycled terephthalate polyol powder and pentamethylene diisocyanate (Desmodur eco N7300; Covestro) were reacted in a 1:1 molar ratio under 6.4 ml of 2-methyltetrahydrofuran solvent and 4 mg of 0.1 mol% dibutyltin dilaurate (DBTDL) catalyst. The reaction mixture was then poured into a PTFE (Poly tetrafluoroethylene) dish, cured at 25 °C, dried at 80 °C for 12 hours, and then a thermosetting recycled polyurethane resin with a thickness of 0.5 mm was prepared using a hot press (160 °C, 10 bar, 30 min).

[0134] 3. Manufacture of Carbon Fiber-Polyurethane Reinforced Plastic Composites

[0135] A polyurethane resin was prepared by reacting a carbon fiber sheet cut to an 8 × 8 cm size, 3 g of the obtained recycled terephthalate polyol powder, and pentamethylene diisocyanate (Desmodur eco N7300; Covestro) in a 1:1 molar ratio under 19.2 ml of 2-methyltetrahydrofuran solvent and 12 mg of 0.1 mol% dibutyltin dilaurate (DBTDL) catalyst. The carbon fiber sheet was immersed in the polyurethane resin solution to ensure the fibers were completely saturated. At this time, the impregnation was performed such that 150 parts by weight of the polyurethane resin were contained per 100 parts by weight of the carbon fiber. The resin-impregnated carbon fiber sheet was placed in a PTFE mold, cured at 25°C, and then dried at 80°C for 12 hours. After stacking three layers of dried sheets, a composite material was manufactured by applying a pressure of 10 bar at 160 ℃ for 30 minutes using a hot press.

[0136] [Examples 2 to 22 and Comparative Examples 1 to 13]

[0137] Regenerated terephthalate polyol, thermosetting recycled polyurethane resin, and carbon fiber-polyurethane reinforced plastic composite were prepared in the same manner as in Example 1, except that alkanediol, catalyst, and solvent were used with the reaction time, components, and content listed in Table 1 below.

[0138] C 4~8Alkanediol Catalyst Solvent PET Concentration (M) Reaction Time (hr) Reaction Temperature (°C) Conversion Rate (%) Yield (%) Type Equivalent Ratio Type Molar Ratio to PET Repeating Unit (mol%) Type Example 1 1,4-BDO 20K2CO3 20 Chlorobenzene 0.59 120 > 997 1.5 Example 2 20 200.5 12 120 > 997 2.2 Example 3 20 200.5 24 120 > 997 2.7 Example 4 20 200.5 31 207 4.25 1.5 Example 5 20 200.5 6 1209 1.36 4 Example 6 20 2019 1209 3.45 7.3 Example 7 20 2029 1209 2.85 2.3 Example 810200.5912096.654.2 Example 95200.5912095.18.2 Example 1020100.5912092.863.3 Example 1120400.59120>9934 Example 122020DMSO0.5912031.510.5 Example 132020Xylene0.5912068.417.3 Example 142020Anisol0.5912098.238.5 Example 1520KOH20Chlorobenzene0.5912023.07.0 Example 1620Na2CO3200.5912028.19.3 Example 1720Cs2CO3200.5912098.161.0 Example 1820TBD200.59120>9942.3 Example 1920TBD200.59120>9949.0 Example 201,6-Hexanediol20K2CO3200.59120>9968.0 Example 211,4-BDO20K2CO3200.5910043.515.8 Example 221,4-BDO20K2CO3200.59130>9951.5 Comparative Example 11,4-BDO20K2CO320--9120181.3 Comparative Example 220--Chlorobenzene0.591200-Comparative Example 320Li2CO3200.5912000 Comparative Example 4202,6-Lutidine200.5912000 Comparative Example 520K2CO320Dichloromethane0.594000 Comparative Example 620K2CO320Chloroform0.596000 Comparative Example 720K2CO3201,2-Dichloroethane0.598000 Comparative Example 8Ethylene Glycol20K2CO320Chlorobenzene0.5912055.248.8 Comparative Example 91,4-BDO55K2CO3200.591209972.5 Comparative Example 102K2CO32010912088.72.8 Comparative Example 1120K2CO3200.5912023.17.1 Comparative Example 1220K2CO3200.5910010.82.0 Comparative Example 1320K2CO3200.59802.8-.

[0139] [Method for Recycling Thermosetting Recycled Polyurethane Resin]

[0140] 1. Remolding

[0141] The thermosetting recycled polyurethane resin prepared in film form was cut into 0.5 × 0.5 cm pieces and remolded by hot pressing at 160°C under a pressure of 20 bar for 30 minutes. The properties of the samples remolded three times by repeating the above process are shown in Table 2 below. (Refer to Figures 8 to 12)

[0142] 2. Depolymerization & Repolymerization

[0143] A thermosetting recycled polyurethane resin was immersed in 1,4-BDO at an equivalent ratio of 2.2 and heated at 160 °C for 1 hour to prepare a homogeneous solution. The homogeneous solution was diluted with ethyl acetate, and unreacted 1,4-BDO was extracted and removed while adding water. Subsequently, the homogeneous solution was purified by column chromatography using ethyl acetate, and the solvent was dried to obtain a terephthalate polyol with a yield of 80 to 90%. Then, a thermosetting recycled polyurethane resin was prepared using the obtained recycled terephthalate polyol in the same manner as in the above example. (See Figs. 13 to 17)

[0144] Table 2 below shows the physical properties of the thermosetting recycled polyurethane resin of Example 1 after remolding and depolymerization.

[0145] Tensile Strength (Mpa) Elongation (%) Young's Modulus (Mpa) Td 5% (°C) T g (DSC)(℃)T g(DMA)(°C) Example 1 21.8±1.01 51±27279± 5277.4 33.8 638.8 11 remolding cycles 24.3±2.3 134±11288±66252.2 33.07 37.08 2 remolding cycles 24.3±0.6 131±7283±23251.8 32.4 833.7 13 remolding cycles 27.2±1.1 128±4264±29260.6 37.5 636.67 Regeneration after depolymerization 21.3±1.1 119±1267±2267.0 34.3 838.54

[0146] [Carbon Fiber-Polyurethane Reinforced Plastic Composite Recycling Method]

[0147] A carbon fiber-polyurethane reinforced plastic composite was immersed in 1,4-BDO at an equivalent ratio of 2.2 and heated at 160°C for 1 hour to melt the polyurethane component. After separating the carbon fibers by filtration, the melted mixture was diluted with ethyl acetate, and unreacted 1,4-BDO was extracted and removed by adding water. Subsequently, the mixture was purified by column chromatography using ethyl acetate, and the solvent was dried to obtain a regenerated terephthalate polyol with a yield of 80 to 90%. Then, a carbon fiber-polyurethane reinforced plastic composite was prepared using the obtained regenerated terephthalate polyol in the same manner as in the above example.

[0148] Table 3 below shows the properties of the recycled carbon fiber-polyurethane reinforced plastic composite of Example 1.

[0149] Tensile Strength (Mpa) Elongation (%) Young's Modulus (Mpa) Flexural Strength (%) Flexural Deformation (%) Example 1199±1318.0±2.02.3±0.4156±230.5±0.1 After Recycling 194±118.1±0.12.6±0.3152±270.4±0.1

[0150] As described above, the present invention has been explained by specific details and limited embodiments; however, this is provided merely to aid in a more comprehensive understanding of the invention, and the invention is not limited to the above embodiments. Those skilled in the art can make various modifications and variations from this description.

[0151] Accordingly, the scope of the present invention is not limited to the described embodiments, and all things equivalent to or having equivalent variations to the claims set forth below, as well as the claims set forth below, shall be considered to fall within the scope of the concept of the present invention.

Claims

1. Waste PET, C 4~8 The method comprises the step of depolymerizing a depolymerization mixture of an alkanediol and an organic solvent having a standard boiling point of 120°C or higher under a basic catalyst at a temperature of 100°C or higher. The above C 4~8 A method for producing recycled terephthalate polyol, wherein the alkanediol is mixed in a ratio of 4 to 50 equivalents relative to waste PET, and the organic solvent having a standard boiling point of 120°C or higher is mixed such that the waste PET has a concentration of 0.05 to 5 M.

2. In Paragraph 1, A method for producing a regenerated terephthalate polyol, wherein the organic solvent having a standard boiling point of 120°C or higher is one or more mixtures selected from the group consisting of chlorobenzene, dimethyl sulfoxide, 1,2-dichlorobenzene, 1,2,3-trichloroethane, xylene, and methoxybenzene.

3. In Paragraph 1, A method for producing a regenerated terephthalate polyol in which the above basic catalyst is one or more mixtures selected from the group consisting of K2CO3, KOH, Na2CO3 and Cs2CO3.

4. In Paragraph 1, A method for producing recycled terephthalate polyol, wherein the above basic catalyst is used in an amount of 10 to 50 mol% relative to the repeating unit of waste PET.

5. C waste PET 4~8 A step of obtaining a regenerated terephthalate polyol by depolymerizing an alkanediol, an organic solvent having a standard boiling point of 120°C or higher, and a basic catalyst at a temperature of 100°C or higher; A method for manufacturing a regenerated terephthalate-based polyurethane resin comprising the step of synthesizing a polyurethane resin including the regenerated terephthalate polyol obtained above, a diisocyanate compound, and a solvent.

6. In Paragraph 5, A method for manufacturing a recycled terephthalate-based polyurethane resin, wherein the diisocyanate compound is one or more mixtures selected from the group consisting of hexamethylene diisocyanate (HDI), methylene diphenyl diisocyanate (MDI), and pentamethylene diisocyanate (PDI).

7. In Paragraph 5, A method for manufacturing a regenerated terephthalate-based polyurethane resin, wherein the thermosetting regenerated polyurethane resin is synthesized under a solvent that is one or more mixtures selected from the group consisting of 2-methyltetrahydrofuran, tetrahydrofuran, γ-butyrolactone, ε-caprolactone, γ-valerolactone, n-butyl lactate, glycerol, and dihydrolevoglucosenone (Cyrene).

8. In Paragraph 5, The above-mentioned regenerated terephthalate-based polyurethane resin has a glass transition temperature (T g A method for manufacturing a recycled terephthalate-based polyurethane resin, wherein the temperature is 30 to 50 ℃.

9. In Paragraph 5, A method for manufacturing a recycled terephthalate-based polyurethane resin, wherein the tensile strength of the recycled terephthalate-based polyurethane resin according to ASTM D638 is 10 to 50 MPa.

10. In Paragraph 5, A method for manufacturing a recycled terephthalate-based polyurethane resin, wherein the strain at the maximum tensile strength according to ASTM D638 of the recycled terephthalate-based polyurethane resin is 50 to 400%.

11. In Paragraph 5, 5% weight loss temperature (T) of the above recycled terephthalate-based polyurethane resin d5% A method for manufacturing a recycled terephthalate-based polyurethane resin, wherein the temperature is 200 to 400 ℃.

12. In Paragraph 5, A method for manufacturing a recycled terephthalate-based polyurethane resin having a storage modulus of 1000 MPa or more according to ASTM D7028 of the above recycled terephthalate-based polyurethane resin at 0 ℃ or lower.

13. In Paragraph 5, A method for manufacturing a recycled terephthalate-based polyurethane resin, wherein the tanδ peak according to ASTM D7028 of the above recycled terephthalate-based polyurethane resin appears at 30 to 50 ℃.

14. In Paragraph 5, A method for manufacturing a recycled terephthalate-based polyurethane resin, wherein, in the stress relaxation measurement of the recycled terephthalate-based polyurethane resin according to ASTM D2990, the point at which the stress decreases to 1 / e of the initial stress is 800 to 1500 s at 150 ℃, 100 to 500 s at 160 ℃, 50 to 100 s at 170 ℃, and 10 to 50 s at 180 ℃.

15. In Paragraph 5, A method for manufacturing a regenerated terephthalate-based polyurethane resin, wherein the activation energy according to the Arrhenius plot of the regenerated terephthalate-based polyurethane resin is 100 to 300 kJ / mol.

16. In Paragraph 5, A method for manufacturing a recycled terephthalate-based polyurethane resin in which the above-mentioned recycled terephthalate-based polyurethane resin is re-synthesized after being decomposed with a polyol solvent and is re-recyclable.

17. Regenerated terephthalate-based polyurethane resin at a temperature of 150 to 200 ℃ C 4~8 A step of obtaining a mixture of diisocyanate and terephthalate polyols by depolymerizing with alkanediol; A step of separating and purifying terephthalate polyol from the above mixture; A method for recycling a recycled terephthalate-based polyurethane resin comprising the step of repolymerizing a polyurethane resin with the above-mentioned terephthalate polyol and a diisocyanate compound.

18. Carbon fiber; Carbon fiber-polyurethane reinforced plastic composite comprising recycled terephthalate-based polyurethane resin.

19. In Paragraph 18, The above recycled terephthalate-based polyurethane resin is made from waste PET C 4~8 A carbon fiber-polyurethane reinforced plastic composite prepared by synthesizing a regenerated terephthalate polyol and a diisocyanate compound obtained by depolymerizing an alkanediol, an organic solvent having a standard boiling point of 120°C or higher, and a basic catalyst at a temperature of 100°C or higher.

20. In Paragraph 18, The carbon fiber-polyurethane reinforced plastic composite is a carbon fiber-polyurethane reinforced plastic composite comprising 100 to 500 parts by weight of the thermosetting recycled polyurethane resin per 100 parts by weight of carbon fiber.

21. In Paragraph 18, A carbon fiber-polyurethane reinforced plastic composite having a tensile strength of 100 to 300 MPa according to ASTM D3039.

22. In Paragraph 18, A carbon fiber-polyurethane reinforced plastic composite having a Young's modulus according to ASTM D3039 of the above carbon fiber-polyurethane reinforced plastic composite of 1.0 to 3.0 GPa.

23. In Paragraph 18, A carbon fiber-polyurethane reinforced plastic composite having a tensile strain of 10 to 50% according to ASTM D3039.

24. In Paragraph 18, A carbon fiber-polyurethane reinforced plastic composite having a bending strength of 100 to 300 MPa according to ASTM D790.

25. Carbon fiber-polyurethane reinforced plastic composite at a temperature of 150 to 200 ℃ C 4~8 A step of separating carbon fibers, diisocyanate compounds, and terephthalate polyols by depolymerizing with alkanediols; A step of purifying the separated terephthalate polyol and carbon fibers; A method for recycling carbon fiber-polyurethane reinforced plastic composites comprising the step of manufacturing a recycled carbon fiber-polyurethane reinforced plastic composite including the purified terephthalate polyol, purified carbon fiber, and diisocyanate compound.

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