Composite material recycling method, prepreg production method, prepreg, and composite material

Abstract

The application provides a recycling method of a fiber reinforced resin matrix composite material, a method for manufacturing a fiber reinforced resin matrix composite material prepreg or a composite material, a resin fiber prepreg, and a recycled composite material. The recycling comprises: mixing a fiber reinforced resin matrix composite material (FRP) with a degradation liquid to make active reaction groups in the degradation liquid react with resin in the FRP to obtain a degraded resin fiber mixture; and dispersing resin degradation products on the surface of the fiber in the degradation liquid by repeatedly rubbing, flushing and / or dissolving the resin degradation products on the surface of the fiber in the degradation liquid to obtain the degraded resin fiber mixture. The method separates the resin degradation products on the surface of the fiber completely by the cyclic mechanical separation, makes the mixture of the resin degradation products and the degradation liquid uniform, reduces the use amount of the degradation liquid, and further reduces the recycling cost.

Description

Technical Field

[0001] This invention relates to the field of fiber-reinforced resin-based composite material recycling, and more particularly to a method for recycling fiber-reinforced resin-based composite materials and a method for manufacturing fiber-reinforced resin-based composite material prepregs or composite materials, resin fiber prepregs, and recycled composite materials. Background Technology

[0002] The global annual production of fiber-reinforced resin matrix composites exceeds 6 million tons. It has been around for 80 years and generates a large amount of waste every year, but less than 10% of it is recycled. Due to its insoluble and infusible characteristics, recycling it is quite difficult.

[0003] In existing technologies, the recycling methods for fiber-reinforced composite materials involve complex processes and high recycling costs. Summary of the Invention

[0004] In view of this, the present invention provides a method for recycling fiber-reinforced resin matrix composites and a method for manufacturing fiber-reinforced resin matrix composite prepregs or composites, resin fiber prepregs, and recycled composites. The recycling method utilizes a recycling approach to solve the above-mentioned technical problems.

[0005] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0006] On one hand, a method for recycling fiber-reinforced resin-based composite materials according to embodiments of the present invention includes:

[0007] Fiber-reinforced resin matrix composite (FRP) is mixed with a degradation solution to allow the active reactive groups in the degradation solution to react with the resin in the FRP, thereby obtaining a degradation resin fiber mixture.

[0008] The resin degradation products on the fiber surface are dispersed in the degradation solution by repeatedly rubbing, rinsing and / or dissolving the resin degradation products attached to the fiber surface with the degradation solution, thereby obtaining the degradation resin fiber mixture.

[0009] Preferably, the step of mixing fiber-reinforced resin matrix composite (FRP) with a degradation solution to allow the active reactive groups in the degradation solution to react with the resin in the FRP to obtain a degradation resin fiber mixture includes:

[0010] The degradation solution contains reactive groups that react with the matrix resin in the composite material. These reactive groups cause the matrix resin to react with the degradation solution under heating and / or catalytic conditions to generate the degradation resin.

[0011] Preferably, the heating method includes, but is not limited to, one or a combination of one or more of the following methods: direct heating, microwave heating, ultrasonic heating, electromagnetic oscillation heating, etc.

[0012] Preferably, the method of repeatedly rubbing, rinsing, and / or dissolving the resin degradation products adhering to the fiber surface with the degradation liquid includes:

[0013] One or more combinations of the following methods are used: dispersing or rubbing the fibers and / or fillers coated with resin degradation products in the degradation solution; accelerating the dissolution of resin degradation products in the degradation solution using ultrasound; and causing the degradation solution to impact the fibers coated with resin degradation products at high speed.

[0014] Preferably, it further includes:

[0015] A portion of the degradable resin in the prepreg is separated and reused as a degradation solution, or a portion of the degradation solution is mixed with fiber-reinforced resin matrix composite material and heated to degrade it.

[0016] Preferably, it further includes:

[0017] A portion of the degradable resin in the degradable resin prepreg is separated for recycling the degradable resin and / or to control the resin content in the degradable resin fiber prepreg.

[0018] Preferably, the degradation liquid contains reactive groups that can react with the curing agent or can be initiated or catalyzed to react; the reactive groups include, but are not limited to, one or more of carbon-carbon double bonds, carbon-carbon triple bonds, hydroxyl groups, carboxyl groups, amino groups, epoxy groups, and ester groups.

[0019] Preferably, the average weight-average molecular weight of the degradation solution is less than 2000.

[0020] Preferably, the degradation solution is selected from one or more compounds with a functionality of 2 to 4 or containing carbon-carbon double or triple bonds and a functionality of 1. The degradation solution includes, but is not limited to, one or a non-reactive combination of ethylene glycol, diethylene glycol, propylene glycol, glycerol, pentaerythritol, ethylenediamine, methyl hydroxyacrylate, ethyl hydroxyacrylate, or the like.

[0021] Preferably, prior to the step of recycling and degrading the resin, the following steps are included:

[0022] Set the degradation resin to uniformly achieve the target characteristic value of the reactive functional groups.

[0023] The characteristic values ​​of the reactive functional groups within the degradation resin were detected;

[0024] Before the characteristic value reaches the target specific value, the degradation resin fiber mixture is continuously homogenized until the target characteristic value is reached, so that the degradation resin components are uniform.

[0025] In a second aspect, embodiments of the present invention also provide a method for manufacturing fiber-reinforced resin-based composite prepreg or composite material, comprising:

[0026] A curing agent capable of reacting with the degradable resin obtained using the recycling method, or a component containing the curing agent, is uniformly mixed with the degradable resin fiber mixture to form a composite precursor.

[0027] The curing agent reacts with the degradable resin to obtain a semi-cured material or to cure it into a composite material. The semi-cured material includes, but is not limited to, prepreg, sheet molding compound, and bulk molding compound.

[0028] Preferably, the step of uniformly mixing a curing agent capable of reacting with the degradable resin or a component containing the curing agent with the degradable resin fiber mixture to form a composite precursor includes:

[0029] First, the curing agent or a component containing the curing agent is mixed with fibers and / or fillers to form a curing agent mixture. Then, the curing agent mixture is mixed with the degradable resin fiber mixture to form a composite precursor.

[0030] Preferably, the degradable resin contains isocyanate reactants, and the curing agent component contains residues generated during the production of toluene diisocyanate (TDI).

[0031] Preferably, the step of uniformly mixing the curing agent mixture with the degradable resin fiber mixture to form a composite precursor includes:

[0032] The formation of the composite precursor is carried out in a kneader, two-roll kneader, three-roll kneader, multi-roll kneader, or planetary disperser.

[0033] Thirdly, embodiments of the present invention also provide a resin fiber prepreg, the prepreg being made by a method for manufacturing fiber-reinforced resin matrix composite prepregs or composite materials.

[0034] Preferably, the degradation resin is prepared by mixing it with fibers.

[0035] Fourthly, embodiments of the present invention also provide a recyclable composite material, the composite material comprising a method for manufacturing fiber-reinforced resin-based composite prepreg or composite material.

[0036] The above-described technical solution of the present invention has at least one of the following beneficial effects:

[0037] The present invention discloses a method for recycling fiber-reinforced resin-based composite materials and a method for manufacturing fiber-reinforced resin-based composite material prepregs or composite materials, resin fiber prepregs, and recycled composite materials. The method utilizes a recycling process for solid-liquid separation, reducing the amount of degradation liquid used and further reducing recycling costs. The recycling method operates in a low-temperature environment, reducing waste gas and byproducts generated during the recycling process, and further improving the recycling efficiency of fiber-reinforced resin-based composite materials. Attached Figure Description

[0038] Figure 1 This is a schematic diagram of the overall process of the recycling method for fiber-reinforced resin-based composite materials provided in an embodiment of the present invention;

[0039] Figure 2 This is a schematic flowchart of a method for recycling fiber-reinforced resin-based composite materials provided in an embodiment of the present invention.

[0040] Figure 3 This is a schematic diagram of a specific embodiment of the recycling method for fiber-reinforced resin-based composite materials provided in this invention.

[0041] Figure 4 This is a schematic flowchart illustrating a method for manufacturing fiber-reinforced resin-based composite prepregs or composite materials according to an embodiment of the present invention. Detailed Implementation

[0042] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the described embodiments of the present invention are within the scope of protection of the present invention.

[0043] In existing technologies, during the recycling of fiber-reinforced thermosetting resin matrix composites (FRPs), low-reactivity or non-reactive oily resin degradation products adhere tightly to the fiber surface. To separate the fibers, solvents are typically added to the degradation solution or aqueous solutions are used to dissolve the resin degradation products. Further cleaning and drying of the fibers are also required. Due to the small diameter and large specific surface area of ​​the fibers, the process of separating the resin degradation products and fibers requires numerous steps and energy, and generates wastewater and exhaust gas pollution. The resulting resin degradation products and fibers, containing water or solvents, require further purification, leading to high recycling costs and low utilization value. Furthermore, the fibers may break during cleaning and drying, affecting the reinforcing effect. This results in existing FRP recycling technologies being complex, inefficient, costly, and having low recycling value.

[0044] Based on the above-mentioned technical problems, embodiments of the present invention provide a method for recycling fiber-reinforced resin-based composite materials. This method can fully dissolve the resin degradation products on the fiber surface in the mixture of degradation liquid through cyclic mixing, degradation, homogenization, and separation to form a uniformly composed degradation resin. The degradation resin and the fiber form a uniformly composed degradation resin-fiber mixture, which can also be separated for use alone or further processed with the fiber to make a new degradation resin-fiber mixture, thereby improving the recycling rate.

[0045] This invention provides a method for recycling fiber-reinforced resin-based composite materials, such as... Figure 1 As shown, it includes the following steps:

[0046] S1 Mixing Step: Mix the fiber-reinforced resin matrix composite (FRP) with the degradation solution to ensure that the active reactive groups in the degradation solution are in full contact with the resin in the FRP.

[0047] S2 Degradation Step: Under the action of a catalyst and / or heating, the active reactive groups in the degradation solution react with the resin in the FRP to obtain a degraded resin fiber mixture;

[0048] S3 Homogenization step: By repeatedly rubbing, rinsing and / or dissolving the resin degradation products attached to the fiber surface with the degradation liquid, the resin degradation products on the fiber surface are dispersed in the degradation liquid to obtain the degradation resin fiber mixture.

[0049] like Figure 2 As shown, steps S1, S2, and S3 specifically include the following:

[0050] 1) The FRP (Fiber Reinforced Plastics) waste is crushed into fragments, preferably with a length of not less than 50 mm along the fiber direction.

[0051] 2) Mix FRP with an excess of highly active degradation solution; preferably, perform step 1) first and then step 2); alternatively, perform steps 1) and 2) simultaneously, that is, immerse FRP in degradation solution for cutting or crushing, which increases the immersion time and immersion contact area of ​​FRP in degradation solution and reduces the dust generated during cutting or crushing.

[0052] 3) Under heating conditions, the degradation solution reacts with the matrix resin of FRP. Part of the low-activity resin degradation products generated by the reaction dissolve in the degradation solution to form a highly active degradation mixture, and part of them adhere to the surface of the fibers and / or fillers in FRP.

[0053] Heating methods include, but are not limited to, heat transfer heating, electromagnetic heating, microwave heating, and ultrasonic heating. Preferably, microwave heating and / or ultrasonic oscillation are used to generate heat through high-frequency friction between the degradation liquid molecules and the resin matrix molecules in the composite material, thereby improving heating efficiency, mixing efficiency, and degradation efficiency. More preferably, the temperature of the degradation mixture is controlled during the heating process to reduce or prevent the generation of side reactions.

[0054] 4) Homogenize the degradation mixture so that the low-activity resin degradation products attached to the fibers are rapidly and uniformly dissolved or dispersed in the degradation mixture to form a degradation resin fiber mixture with uniform composition; the homogenization method includes, but is not limited to, one or more combinations of ultrasonic waves, oscillation, stirring, extrusion, centrifugal rotation, high-pressure liquid flow or airflow dispersion.

[0055] Preferably, a planetary rotation centrifugal separation method is used to homogenize the degradation mixture and separate excess degradation mixture. In the planetary rotation separation process, the degradation resin fiber mixture is placed in a container, which rotates around a main shaft. At the same time, the container itself rotates. During this process, the degradation resin fiber mixture is squeezed under the centrifugal force of the rotating main shaft. At the same time, the high-speed friction between the fibers under the rotation of the container itself causes the low-activity resin degradation products attached to the fibers to be quickly and uniformly dissolved or dispersed in the degradation mixture.

[0056] Mechanical separation methods, such as centrifugation and extrusion, are used to separate some of the degradable resin. This preserves the fiber structure and even the fiber distribution, allowing the composite material made from the degradable resin fiber mixture to maintain high strength. Furthermore, the degradable resin fiber mixture is vacuum-packed to remove air from the prepreg and prevent moisture or oxygen in the air from affecting the degradable resin fiber mixture.

[0057] 5) Separate the excess degradation mixture; separation methods include, but are not limited to, centrifugation or extrusion separation;

[0058] 6) Repeat steps 2) to 4) to obtain degradable resin fiber mixtures with different concentrations of functional groups with different reaction characteristics. The final degradation does not require separation of the degradation mixture.

[0059] 7) Homogenization: Set a target value for the concentration of characteristic functional groups in the degradation mixture, and mix and homogenize multiple batches of the degradation resin fiber mixture with different characteristic functional group values, so that the concentration of characteristic functional groups in the degradation composite material mixture reaches the set target value, resulting in a uniformly composed degradation resin fiber mixture.

[0060] 8) The excess degradation mixture is separated into a homogeneous degradation resin for packaging; while the degradation mixture remaining on the fiber surface is packaged together with the fiber and / or filler into a homogeneous degradation resin fiber mixture.

[0061] Preferably, the resin content of the degradable resin fiber prepreg is controlled by controlling the density of the degradable resin fiber mixture, which is simple and easy to implement.

[0062] In the above steps, the order or combination of steps can be added, removed, or adjusted as needed, and it is not necessary for all steps to appear or to be performed in a specific order. For example, steps 3) and 4) can be performed simultaneously or separately. Alternatively, step 4) can be performed last, i.e., adding a highly active degradation liquid once, skipping step 4) each time until step 6) and homogenizing the degradation resin fiber mixture from the same batch. This homogenization can also yield a degradation resin fiber mixture with the concentration of characteristic functional groups reaching the set target value. Furthermore, step 4) can be completely omitted, and the degradation resin fiber mixtures obtained from different separation rounds of the same batch can be collected together and mixed and homogenized with the curing agent components at one time to produce semi-cured degradation resin fiber prepreg, sheet molding compound, bulk molding compound, or cured composite material. Other combinations or orders of the above steps, as long as they do not lose the original intent of the present invention, fall within the protection scope of the present invention.

[0063] Preferably, the degradation solution described above contains compounds having the characteristic functional groups capable of reacting with FRP, and has a weight-average molecular weight of less than 800, more preferably less than 500, even more preferably less than 300; most preferably, the weight-average molecular weight is less than 150. Such a degradation solution composed of small molecule compounds has high reactivity, and the resulting degradation resin has high activity and good performance. Preferably, the aforementioned degradation solution does not contain solvents or aqueous solutions, so that there is no solvent evaporation or wastewater pollution during the degradation process, and the obtained degradation resin does not need to be purified.

[0064] In one embodiment, the degradation liquid contains reactive groups that can react with the curing agent or can be initiated or catalyzed to react; the reactive groups include, but are not limited to, one or more of carbon-carbon double bonds, carbon-carbon triple bonds, hydroxyl groups, carboxyl groups, amino groups, epoxy groups, and ester groups.

[0065] The weight-average molecular weight of the degradation solution is less than 2000 g / mol. Further, the weight-average molecular weight is less than 500 g / mol, and even further, less than 200 g / mol. The degradation solution has a small equivalent, small molecular size, high activity, and a fast degradation rate.

[0066] Furthermore, the degradation solution is selected from one or more compounds with a functionality of 2 to 4 or a functionality of 1 that simultaneously contains carbon-carbon double bonds or carbon-carbon triple bonds. The degradation solution includes, but is not limited to, one or a non-reactive combination of ethylene glycol, diethylene glycol, propylene glycol, glycerol, pentaerythritol, ethylenediamine, methyl hydroxyacrylate, ethyl hydroxyacrylate, or the like.

[0067] This method can produce degradable resins and degradable resin fiber mixtures with controllable concentration of active functional groups and controllable uniform composition. It eliminates fiber washing and drying steps, minimizes fiber damage, and allows all products to be utilized, resulting in high commercial value. At the same time, this process generates very little or no wastewater or waste gas, making it clean and environmentally friendly, and ideally overcoming the shortcomings of existing technologies.

[0068] Furthermore, embodiments of the present invention also provide a method for applying the aforementioned degradable resin and degradable resin fiber mixture.

[0069] In one application, the degradable resin is used to impregnate fibers and / or fillers to manufacture degradable resin mixtures. Preferably, the fibers are recycled fibers, which reduces costs and improves environmental friendliness.

[0070] In another application, a curing agent or a component containing a curing agent is added to the degradable resin fiber mixture and mixed evenly, and the degradable resin is reacted and branched to produce a semi-cured prepreg, sheet molding compound or bulk molding compound, or the degradable resin is reacted and cured to produce a composite material.

[0071] Preferably, a kneading method is used to mix the curing agent or components containing the curing agent with the degradable resin fiber prepreg. Preferably, a two-roller or three-roller kneader is used to mix the curing agent components with the degradable resin. This method allows for rapid kneading and allows a scraper to clean the resin enriched on the rollers and mix it into the kneaded mixture to avoid resin enrichment and gelation, which would lead to material waste. More preferably, the temperature of the kneaded mixture is controlled during the kneading process to control the reaction rate. Optionally, the planetary centrifugal dispersion device used in step 4) above can also be used to mix the curing component with the degradable resin mixture.

[0072] Composite materials made using the aforementioned degradable resin and / or degradable resin fiber prepregs allow for efficient homogenization of mixtures with extremely low resin content. This enables the use of recycled materials for fibers, degradable resins, and even curing agents. The resin content can be as low as 60wt% to 20wt%. Due to the aforementioned solid-solid mixing method, this high-solids-content degradable resin prepreg has practical value, and its performance can be as close as possible to that of composite materials made from virgin materials. It has high recycling value, and the cost is low because the recycled materials used have a high specific gravity.

[0073] The following section, with reference to the accompanying drawings, describes a method for recycling fiber-reinforced resin matrix composites (FRP) according to the present invention, using the recycling of glass fiber reinforced polyurethane pultruded composite material (GRPU) as an example.

[0074] Specifically, Example 1:

[0075] The glass fiber reinforced polyurethane pultruded composite material in this embodiment of the invention is a GRPU photovoltaic frame profile. The matrix resin is thermosetting polyurethane. The proportion of glass fiber in the GRPU profile is 75 wt%, and the proportion of filler is 1 wt%. The degradation agent used is a mixture of glycerol and polyether polyol DMN-450 at a ratio of 20 wt%: 80 wt%. The weight-average molecular weight of glycerol is 92.09 g / mol, the characteristic functional group concentration (hydroxyl value) is 1827 mg KOH / g, and the functionality is 3. The polyether polyol DMN-450 has a hydroxyl value of 450 ± 10 mg KOH / g, a functionality of 3, and a weight-average molecular weight of 374 g / mol. This recycling method includes the following steps:

[0076] Step 1: Cut the GRPU frame profile into thin slices 50mm long, 20mm thick, and 2mm thick along the length direction. Mix the GRPU frame with the aforementioned degradation solution at a ratio of 10g:200g. Place the mixture and a beaker in a household microwave oven (Midea M1-L213B, microwave output power 700W, power consumption 1150W) and heat on high (microwave output power 700W) for 2-5 minutes. During the heating process, rotate the beaker to ensure that the degradation mixture is heated evenly. After heating, the resin in the GRPU degrades into dark brown resin degradation products, while the morphology of the glass fiber in the GRPU remains unchanged.

[0077] The second step is to pour out the mixture of degradation liquid and resin degradation products, i.e., the degradation mixture, and press the glass fiber with the resin degradation products attached. The pressed degradation mixture is still kept at 200g. It is then mixed with the previously poured resin mixture and 10g of new GRPU frame material of the aforementioned size. The pressed degradation resin fiber mixture is temporarily stored aside.

[0078] Step 3: Repeat steps 1 and 2 20 times. For the last time, do not separate the degradation mixture and the fiber. This will form 20 pieces of degradation resin fiber mixture with different hydroxyl values.

[0079] Step 4: Place the aforementioned 20 pieces of degradable resin fiber mixture into a kneader and knead repeatedly until a homogeneous degradable resin fiber mixture with uniform composition and content of the degradation mixture on the fiber surface is formed. The standard for homogenization is to test the hydroxyl value of the degradation mixture separated from the homogenized degradable resin fiber mixture. When the hydroxyl value of the degradation mixture stabilizes and approaches the calculated target theoretical hydroxyl value of 379 mgKOH / g, the homogenization level is considered qualified. This can be used as a standard to check whether the degradable resin has reached homogenization. The homogeneous degradable resin fiber mixture obtained by this method has a resin content of 62 wt%, of which GRPU waste accounts for 50 wt% of the total raw materials. In order to increase the fiber content, reduce costs, and improve strength, further press or centrifuge to separate the excess homogeneous degradable resin, so that the degradable resin content in the degradable resin fiber prepreg reaches 45 wt%. The separated homogeneous degradable resin can be used alone as resin or as a polyurethane additive, which has the characteristics of high activity and good strength. Alternatively, excess degradable resin can be left unseparated, and the mixture of multiple degradable resin fibers can be left unhomogenized. The resulting material is a non-homogeneous degradable resin fiber prepreg with a target hydroxyl value of 379 mg KOH / g, a mass of 400 g, and a resin content of 62 wt%. The non-homogeneous degradable resin fibers can be mixed uniformly with a curing agent and / or a mixture of curing agents in a certain proportion before semi-curing or curing. This eliminates the need for a homogenization process, reducing energy consumption and cost. However, the entire mixture must be fed into the prepreg; otherwise, the composition and properties of the degradable resin fiber mixture will be uncontrollable.

[0080] Step 5: Vacuum-sealed packaging of the obtained degradable resin fiber mixture allows it to be stored stably at room temperature for more than 2 months.

[0081] Example 2: The rest is the same as in Example 1, except that a planetary rotary disperser is used to homogenize the degradable resin fiber mixture for 3 minutes each time at a speed of 2000 rpm. Since there is no stirring paddle in the container of the planetary dispersant, the dispersion container rotates both around the main shaft of the equipment and around its own axis. The centrifugal pressure and mutual high-speed shear force generated in the material enable the degradable resin and fiber to be mixed and homogenized at high speed without damaging the fiber.

[0082] Example 3: Similar to Examples 1 and 2, except that: firstly, glycerol is used alone to replace the mixture of polyether polyol and glycerol as the degradation agent; secondly, the third step is repeated with the first, second, and fourth steps, so that each repeated process yields homogenized degradation resin fiber mixtures and degradation resins with different characteristic concentrations and resin contents. These are then mixed and homogenized as needed to form a degradation resin fiber mixture with the target characteristic functional group concentration and composition. Using this method, the degradation agent can use as many small molecule, highly active compounds as possible, which is low in cost and does not easily decompose in the degradation solution at high temperatures.

[0083] The fiber-reinforced resin matrix composite (FRP) recycling method provided in this invention can be applied to the recycling of various FRPs, and the specific steps are as follows:

[0084] The first step is to clean and dry the fiber-reinforced thermosetting composite (FRP) waste, then cut and crush it into sizes that can be accepted by the degradation reaction vessel.

[0085] Optionally, the size of the waste in the fiber length direction can be no less than 50 mm, so that the fiber length in the degradation product is greater than 50 mm, to ensure that the composite material made from the degraded resin prepreg has high strength; the cut waste is mixed with a large excess of degradation liquid, assuming that the weight of waste added each time is equal, and the weight of degradation liquid separated each time is kept equal to the weight of the initial degradation liquid. The relationship between the weight ratio r of degradation liquid to waste and the concentration m0 of characteristic functional groups in the degradation liquid that can react with the matrix resin in the FRP waste, the resin content a0 in the FRP waste, the number of times the degradation liquid is recycled n, the concentration m of characteristic functional groups of the degraded resin in the target product, and the resin content a in the target product is as follows:

[0086] m1=m0*r / (r+a0))

[0087] m n+1 =m n *r / (r+a0))

[0088] m = Ave(m1m2……m) n )

[0089] a = (r + n * a0) / (r + n)

[0090] Preferably, the FRP waste is soaked in the degradation solution to cut or crush the FRP, so as to reduce dust and promote the wetting of the FRP waste by the degradation solution;

[0091] Preferably, the degrading agent is a solvent-free compound, which can reduce the impact of solvents or water on material properties or reduce the steps of water removal or solvent removal, thereby reducing the generation of wastewater and waste gas; more preferably, the degrading agent contains no less than 10% compounds with a weight average molecular weight of less than 400 g / mol, more preferably, no less than 30%, more preferably, no less than 80%, and most preferably, 100%. Such a degrading agent has high activity, low viscosity, low cost, and fast degradation speed.

[0092] The second step involves heating the mixture of FRP waste and degradation liquid and / or degradation mixture to allow the degradation liquid or degradation mixture to undergo a displacement reaction with the thermosetting resin in the waste, causing it to degrade and liquefy, thereby forming a degradation resin fiber mixture. The heating method includes, but is not limited to, one or more combinations of direct conduction heating, pressure heating, microwave heating, ultrasonic heating, and electromagnetic heating. Preferably, during the heating process, the temperature of the mixture of waste and degradation mixture is controlled within the decomposition temperature of the degradation liquid to reduce the occurrence of side reactions.

[0093] The third step involves separating as much of the degradation mixture as possible from the degradation resin fiber mixture, forming a degradation mixture and a degradation resin fiber mixture. Separation methods include, but are not limited to, applying pressure to the degradation resin fiber mixture to extrude the degradation mixture or centrifuging it to obtain a non-homogeneous degradation resin fiber mixture with unknown functional group concentrations. Optionally, non-fiber impurities in the degradation resin fiber mixture can be picked out. These non-fiber impurities include, but are not limited to, metals and semiconductor components. When calculating the resin content of the final degradation resin fiber mixture product after impurity removal, the mass of resin degradation products attached to the selected impurities should be deducted. Alternatively, the resin content of the obtained degradation resin fiber prepreg product can be directly determined by an ignition method. In this step, the resin in the waste has been completely degraded into a liquid state, making it easy to pick or sort. The obtained impurities, attached to the degradation mixture, are also easy to clean.

[0094] Step 4: The separated degradation mixture is reused in step 1. Steps 1 and 2 are cycled a total of n times. In the last cycle, the degradation mixture is not separated, resulting in n batches of non-homogeneous degradation resin fiber mixtures, each batch having a different concentration of characteristic functional groups.

[0095] Step 5: Mix the obtained n batches of degradable resin fiber mixture together for homogenization until the concentration of characteristic functional groups in the degradation mixture stabilizes and approaches the target concentration. The homogenization method includes, but is not limited to, one or more of the following methods in combination: 1) repeatedly kneading it in a kneader; 2) placing it in a centrifugal disperser through a mixing container containing the degradable resin fiber mixture, causing the mixing container to rotate on its own axis while revolving around the main axis, so that the resin degradation liquid and the fiber are mixed evenly due to the combined effect of centrifugal pressure generated by the container's revolution and shear force generated by the container's rotation; 3) using a high-pressure jet method to circulate the degradation mixture with the degradation resin fiber mixture, so that the resin degradation products on the fiber surface dissolve into the degradation mixture more quickly; preferably, using multiple jet nozzles to circulate the degradation mixture with the degradation resin fiber mixture; more preferably, circulating the degradation mixture with the degradation mixture from bottom to top to obtain better mixing efficiency;

[0096] Preferably, the first and second steps are performed simultaneously;

[0097] More preferably, in the first and / or second step, one or more of the following methods are used to assist homogenization: 1) subjecting the degraded resin fiber mixture to ultrasonic oscillation, so that the resin degradation products on the fiber surface dissolve into the degradation mixture more quickly; 2) using a high-pressure jet to circulate the degradation mixture onto the degraded resin fiber mixture, so that the resin degradation products on the fiber surface dissolve into the degradation mixture more quickly. Preferably, multiple jets are used to impact the degraded resin fiber mixture from bottom to top. These methods can improve degradation efficiency and homogenization efficiency without damaging the fibers, thus ensuring the performance of the homogenized degraded resin fiber prepreg.

[0098] Step 6: Package the degradable resin fiber prepreg into shapes including but not limited to sheets, clumps, and filaments; or, separate excess degradable resin to form degradable resin fiber prepreg with a certain resin content and package the degradable resin separately; if the degradable resin is sensitive to moisture or temperature, vacuum seal the obtained degradable resin fiber prepreg and / or refrigerate it.

[0099] The above steps do not necessarily need to be followed in order; they can be added, removed, or combined in any way to achieve the corresponding technical effect.

[0100] The above methods are simple, efficient, and can be scaled up for industrial production. They produce no wastewater or waste residue, generate very little waste gas, and produce high-performance, high-value degradation products with high solid waste content. They are also low-cost and have good environmental benefits.

[0101] On the other hand, the application method of the aforementioned degradable resin fiber mixture is disclosed:

[0102] The first step involves impregnating fibers with a curing agent containing curing reactive groups that can react with the characteristic functional groups in the degradable resin fiber mixture to form a curing agent fiber mixture with a certain curing agent content. In this specific embodiment, a curing agent fiber mixture is obtained by impregnating waste glass fibers generated from the production of GRPU photovoltaic frame profiles with polymeric MDI (diphenylmethane-4,4'-diisocyanate) DESMODUR1511L (NCO% = 31.4%) containing isocyanate groups that react with the characteristic functional group hydroxyl groups, and the curing agent content is controlled to be 45 wt%.

[0103] The second step involves weighing the resin fiber mixture and the curing agent fiber mixture according to the calculation principle of a certain molar ratio (e.g., the molar ratio of hydroxyl to isocyanate groups in this specific embodiment) between the characteristic functional groups of the degradable resin in the degradable resin fiber mixture and the characteristic functional groups of the curing agent in the curing agent fiber mixture (e.g., the molar ratio of hydroxyl to isocyanate groups in this specific embodiment is 1:1 to 2). The resin fiber mixture and the curing agent fiber mixture are then weighed and put into a kneader to knead evenly to obtain a composite material precursor. The kneading time is less than the time when the mixture of resin and curing agent begins to gel. Finally, the evenly kneaded composite material precursor is placed into a molding cavity and molded at a certain temperature (e.g., 80 to 150°C in this specific embodiment) to obtain a new fiber-reinforced thermosetting composite material (FRP) product.

[0104] Optionally, the curing agent is weighed and added to the resin fiber prepreg according to the calculation principle of a certain molar ratio of characteristic functional groups (e.g., hydroxyl groups in this specific embodiment) and curing reaction groups (e.g., isocyanate groups in this specific embodiment) in the degradable resin fiber prepreg, and mixed evenly to form a composite material precursor. The mixing method includes, but is not limited to, kneading and centrifugal dispersion methods, because for mixtures with high solid content, kneading and centrifugal dispersion methods are more efficient and do not damage the fibers.

[0105] Preferably, according to the curing process requirements, the mixture is cooled during the mixing process to prolong the gel time of the degrading resin, or heated to reduce the viscosity of the degrading resin and improve its activity.

[0106] As a preferred option, the bottom waste (NCO% of about 39%) generated from TDI production is mixed evenly with the aforementioned molar ratio and the degradable resin fiber mixture, and then cured to obtain a polyurethane composite material. This not only allows the bottom waste generated from TDI production to be comprehensively utilized, reducing the pollution caused by burning the bottom waste, but also increases the proportion of recycled materials in the obtained composite material, and also yields a material with excellent weather resistance.

[0107] The third step involves placing the composite material precursor in a mold and curing it into a composite material before the degradation resin gel is formed. In this specific embodiment, the degradation resin fiber prepreg and isocyanate fiber prepreg made from the mixed GRPU waste material are kneaded evenly under 5°C cold water cooling and then placed in a mold. The new GRPU composite material is obtained by pressing and heating at 0.5MPa and 120°C for 10 minutes, with a resin content of 45wt% and a tensile strength greater than 80MPa.

[0108] The above steps can be added, removed, or changed in order or combined in any way, as long as the technical effect is achieved, it will not deviate from the protection scope of the present invention.

[0109] In one embodiment, such as Figure 3 As shown, prior to recycling the degraded resin, the process includes:

[0110] Set the target characteristic value of the reactive functional groups to be uniformly degraded resin;

[0111] Detect the characteristic values ​​of the reactive functional groups in the degradation solution;

[0112] Before the characteristic value reaches the target specific value, the degradation resin fiber mixture is continuously homogenized until the target characteristic value is reached, so that the degradation resin components are uniform.

[0113] When the characteristic value reaches the target specific value, the mixture of the degradation liquid and the generated resin degradation product is separated from the fiber surface by mechanical separation, and the separated mixture is mixed with the fiber again and this step is repeated until the concentration of reactive functional groups in the mixture reaches the target value.

[0114] In other words, the hydroxyl value and composition of the resin attached to the fiber can be further adjusted by regulating the hydroxyl value in the degradation solution and / or by adjusting the ratio of the fiber-reinforced resin matrix composite to the degradation solution. Adjustment methods include, but are not limited to, recycling the degradation resin and / or adding fresh small-molecule polyols to the degradation resin in a certain proportion of the fiber-reinforced resin matrix composite to maintain the hydroxyl value of the degradation resin at a certain level to preserve its activity and desired properties.

[0115] Optionally, the degraded resin fiber mixture impregnated with the degraded resin in the initial stage of the reaction, due to its excessively high hydroxyl value, can be added again in the middle and later stages of the reaction as a component to increase the hydroxyl value of the degraded resin and fiber-reinforced resin matrix composite material. This can maintain the hydroxyl value of the degraded resin at the design level and also stabilize the hydroxyl value of the resin on the fiber.

[0116] Furthermore, the mixture is used to repeatedly rinse the fibers with resin degradation products on their surface, so that the resin degradation products on the fiber surface are separated from the fibers.

[0117] In other words, the separated degradation liquid and the generated resin degradation products are mixed with the fiber, and the fiber surface is rinsed during the mixing process. This step can be repeated multiple times to improve the separation effect of the resin degradation products on the fiber surface and the fiber, and to improve the uniformity of the mixture of degradation liquid and generated resin degradation products, thereby further improving the recycling value of the fiber and the resin-containing degradation liquid.

[0118] In one embodiment, the mechanical separation method includes at least centrifugal separation. Centrifugal separation more thoroughly separates excess degradable resin from the fibers. Of course, mechanical separation methods can also include other separation methods, such as extraction.

[0119] Embodiments of the present invention also provide methods for manufacturing fiber-reinforced resin-based composite prepregs or composite materials, such as... Figure 4 As shown, a curing agent capable of reacting with the degradable resin obtained by the recycling method of fiber-reinforced resin matrix composites, or a component containing the curing agent, is uniformly mixed with the degradable resin fiber mixture to form a composite precursor.

[0120] The curing agent reacts with the degradable resin to obtain a semi-cured material or to cure it into a composite material. The semi-cured material includes, but is not limited to, prepreg, sheet molding compound, and bulk molding compound.

[0121] In other words, the degradation mixture obtained through the recycling method of fiber-reinforced resin matrix composites, along with the fibers, can be directly used to make prepregs. The degradation resin obtained in the recycling method, i.e., the mixture of resin degradation products and degradation liquid, can be uniformly mixed. Composite materials made from the degradation resin-fiber mixture obtained in the recycling method have good performance and high value. Furthermore, this preparation method eliminates the need to separate the recycled degradation resin from the fibers, thus protecting the fibers themselves and eliminating the step of resin impregnation, improving the impregnation quality of both resin and fibers. Additionally, it avoids pollution caused by dry fiber scattering and pollution generated during resin cleaning.

[0122] Furthermore, the curing agent or a component containing the curing agent is first mixed with fibers and / or fillers to form a curing agent mixture, and then the curing agent mixture is mixed with the degradable resin fiber mixture to form a composite precursor. Preferably, the fibers used in the curing agent prepreg are recycled fibers, which can improve environmental friendliness.

[0123] Specifically, the composite material is fiber-reinforced polyurethane composite (GRPU), the degradation liquid is glycerol, and the curing agent is polymeric 4,4'-dimethyltoluene diisocyanate (PMDI).

[0124] Furthermore, the glycerol contains 0.1% water, which causes the degradation resin to contain water, forming a composite precursor that can be foamed in a closed mold to produce a foamed composite material.

[0125] Furthermore, the degradation resin contains isocyanate reactants, and the curing agent component contains bottom residue from the production of toluene diisocyanate (TDI). This bottom residue from TDI production is used to reduce carbon dioxide emissions and environmental pollution generated during TDI production.

[0126] Preferably, the composite precursor is formed in a kneader, two-roll kneader, three-roll kneader, multi-roll kneader, or planetary disperser.

[0127] The resin fiber prepreg is used as follows: First, a curing agent, including but not limited to MDI (diphenylmethane-4,4'-diisocyanate) or its prepolymer, is impregnated into the fiber to form a curing agent fiber mixture; second, the resin fiber mixture and the curing agent fiber mixture are put into a kneader and kneaded evenly according to the principle of equimolar ratio of resin in the resin fiber mixture and curing agent in the curing agent fiber mixture, and the kneading time is less than the time when the composite precursor begins to gel; finally, the kneaded mixture, i.e. the composite precursor, is placed into a molding cavity and molded at 30 to 200 degrees Celsius to become a new FRP product.

[0128] This invention also provides a resin fiber blend, which is made by a method for manufacturing fiber-reinforced resin matrix composite prepreg or composite material.

[0129] Furthermore, the degradation resin is prepared by mixing it with fibers.

[0130] This invention also provides a recycled composite material, which is made using a method for manufacturing fiber-reinforced resin-based composite prepregs or composite materials.

[0131] This invention also provides a method for curing prepreg, comprising:

[0132] Place the glass fiber and filler into a rotating mixing tank. Add the curing agent component to the mixing tank through a circulation tank until the designed liquid level is reached, at least covering the fiber.

[0133] Start the agitator and start the circulation tank to add curing agent to the mixing tank to maintain the liquid level of the curing agent components in the mixing tank until the fiber is fully impregnated. If necessary, add filler in the designed proportion.

[0134] Start the mixing tank to rotate, and stop the circulation tank to add the curing agent components until the circulation tank reaches the set liquid level to control the ratio of fiber and curing agent components.

[0135] Stop rotating the mixing drum, scrape off the curing agent prepreg adhering to the wall of the mixing drum, and seal it for later use. If the curing agent component is moisture-sensitive such as isocyanate, vacuum sealing is required.

[0136] This invention also provides a method for preparing a composite material, comprising:

[0137] The degradable resin fiber prepreg and / or degradable resin precipitate and curing agent fiber prepreg are calculated and weighed according to the ratio of degradable resin and curing agent attached to the fiber or precipitate, and then added to a kneader and kneaded evenly to form a composite precursor.

[0138] The composite precursor is cured alone or together with other components or materials, or placed in a mold for curing. Preferably, it is cured under certain temperature and pressure to become a composite material.

[0139] The above description represents the preferred embodiments of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for recycling fiber-reinforced resin-based composite materials, characterized in that, include: Fiber-reinforced resin matrix composite (FRP) is mixed with a degradation solution that does not contain solvent or aqueous solution so that the active reactive groups in the degradation solution react with the resin in the FRP to obtain a degradation resin fiber mixture. By repeatedly rubbing, rinsing and / or dissolving the resin degradation products adhering to the fiber surface with the degradation liquid, the resin degradation products on the fiber surface are dispersed in the degradation liquid. The mixture of degradation liquid and resin degradation products is separated from the fiber surface by mechanical separation. The separated mixture is then mixed with the fiber again, and this separation-mixing step is repeated until a uniformly composed degradation resin fiber mixture is obtained. The recycling method does not include the steps of washing and drying the fibers.

2. The method for recycling fiber-reinforced resin-based composite materials as described in claim 1, characterized in that, The steps of mixing fiber-reinforced resin matrix composite (FRP) with a degradation solution to allow the active reactive groups in the degradation solution to react with the resin in the FRP to obtain a degradation resin fiber mixture include: The degradation solution contains reactive groups that react with the matrix resin in the composite material. These reactive groups cause the matrix resin to react with the degradation solution under heating and / or catalytic conditions to generate the degradation resin.

3. The method for recycling fiber-reinforced resin-based composite materials as described in claim 2, characterized in that, The heating methods include, but are not limited to, one or a combination of direct heating, microwave heating, ultrasonic heating, and electromagnetic oscillation heating.

4. The method for recycling fiber-reinforced resin-based composite materials as described in claim 1, characterized in that, The methods of repeatedly rubbing, rinsing, and / or dissolving the resin degradation products adhering to the fiber surface with the degradation solution include: One or more combinations of the following methods are used: dispersing or rubbing the fibers and / or fillers coated with resin degradation products in the degradation solution; accelerating the dissolution of resin degradation products in the degradation solution using ultrasound; and causing the degradation solution to impact the fibers coated with resin degradation products at high speed.

5. The method for recycling fiber-reinforced resin-based composite materials as described in claim 1, characterized in that, Also includes: A portion of the degraded resin in the degraded resin fiber mixture is separated and reused as a degradation liquid, or a portion of the degradation liquid is mixed with fiber-reinforced resin matrix composite material and heated to degrade it.

6. The method for recycling fiber-reinforced resin-based composite materials as described in claim 1, characterized in that, Also includes: A portion of the degraded resin in the degraded resin fiber mixture is separated for recycling the degraded resin and / or to control the resin content in the degraded resin fiber mixture.

7. The method for recycling fiber-reinforced resin-based composite materials as described in claim 2, characterized in that, The degradation liquid contains reactive groups that can react with the curing agent or can be initiated or catalyzed to react; the reactive groups include, but are not limited to, one or more of carbon-carbon double bonds, carbon-carbon triple bonds, hydroxyl groups, carboxyl groups, amino groups, epoxy groups, and ester groups.

8. The method for recycling fiber-reinforced resin-based composite materials as described in any one of claims 1 to 7, characterized in that, The average weight-average molecular weight of the degradation solution is less than 2000.

9. The method for recycling fiber-reinforced resin-based composite materials as described in any one of claims 1 to 7, characterized in that, The degradation solution is selected from one or more compounds with a functionality of 2 to 4 or containing carbon-carbon double or triple bonds and a functionality of 1. The degradation solution includes, but is not limited to, one or a non-reactive combination of ethylene glycol, diethylene glycol, propylene glycol, glycerol, pentaerythritol, ethylenediamine, methyl hydroxyacrylate, ethyl hydroxyacrylate, or the like.

10. The method for recycling fiber-reinforced resin-based composite materials as described in claim 6, characterized in that, Prior to the step of recycling and degrading the resin, the following steps are included: Set the target characteristic value of the reactive functional groups to be uniformly degraded resin; The characteristic values ​​of the reactive functional groups within the degradation resin were detected; Before the characteristic value reaches the target specific value, the degradation resin fiber mixture is continuously homogenized until the target characteristic value is reached, so that the degradation resin components are uniform.

11. A method for manufacturing fiber-reinforced resin-based composite prepreg or composite material, characterized in that, include: A curing agent capable of reacting with the degradable resin obtained using any of the recycling methods described in claims 1 to 10, or a component containing said curing agent, is uniformly mixed with the degradable resin fiber mixture to form a composite precursor. The curing agent reacts with the degradable resin to obtain a semi-cured material or to cure it into a composite material. The semi-cured material includes, but is not limited to, prepreg, sheet molding compound, and bulk molding compound.

12. The method for manufacturing fiber-reinforced resin-based composite prepregs or composite materials as described in claim 11, characterized in that, The step of uniformly mixing a curing agent capable of reacting with the degradable resin or a component containing the curing agent with the degradable resin fiber mixture to form a composite precursor includes: First, the curing agent or a component containing the curing agent is mixed with fibers and / or fillers to form a curing agent mixture. Then, the curing agent mixture is mixed with the degradable resin fiber mixture to form a composite precursor.

13. The method for manufacturing fiber-reinforced resin-based composite prepregs or composite materials as described in claim 11 or 12, characterized in that, The degradation resin contains isocyanate reactants, and the curing agent component contains residues generated during the production of toluene diisocyanate (TDI).

14. The method for manufacturing fiber-reinforced resin-based composite prepregs or composite materials as described in claim 11 or 12, characterized in that, The step of uniformly mixing the curing agent mixture with the degradable resin fiber mixture to form a composite precursor includes: The formation of the composite precursor is carried out in a kneader, two-roll kneader, three-roll kneader, multi-roll kneader, or planetary disperser.

15. A resin fiber prepreg, characterized in that, The prepreg comprises materials prepared using the method described in any one of claims 11 to 14.

16. The resin fiber prepreg as described in claim 15, characterized in that, The degradation resin is prepared by mixing it with fibers.

17. A recycled composite material, characterized in that, The composite material includes materials made using the method described in any one of claims 11 to 14.

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