Method for obtaining secondary raw materials from composite structures

Abstract

The present invention relates to a method for obtaining secondary raw materials from composite material waste. This method is based on mechanical means and allows for the destruction of the structure of the composite material waste to reuse the first fiber-resin composite material. The first fiber-resin composite material may or may not contain a core material. The first fiber-resin composite material is modified to obtain secondary raw materials.

Description

Background Art

[0001] In the industry, an increasing number of composite materials are being used. Even in sectors that conventionally manufactured products from metals, these are being replaced with composite materials. This is because composite materials have various advantages such as weight reduction, improvement of mechanical properties, and improvement of chemical resistance.

[0002] The demand for composite materials is growing globally. The total volume of the composite material market was 12 million tons in 2021 and is expected to reach 15.5 million tons by 2026. In certain sectors such as the transportation sector, it is certain that the introduction of composite materials will increase in order to achieve the SDGs and reduce the weight of vehicle bodies and fuel costs, so this value may be even higher. In other fields such as renewable energy, the consumption of composite materials may increase significantly due to the growing demand for renewable energy production.

[0003] As the demand for composite materials increases, inevitably, the problem of how to process the large amount of waste derived from composite materials using innovative methods also arises. The main problem regarding the treatment of composite materials lies in the separation of their components. These components are often integrated as a composite structure. That is, reinforcing fibers are embedded in a thermosetting polymer matrix and further combined with a filling material or foam as a core to increase the thickness.

[0004] In this sense, composite materials can be mainly classified into two types according to their structure. That is, an integral structure and a composite structure (laminated structure). The integral structure has high material uniformity, but different mechanical / chemical properties are used in the laminated structure. Examples of such materials include PVC foam, polyurethane, polystyrene, wood, metal, and honeycombs (honeycomb structures) made of metal or aramid.

[0005] Methods for separating materials that make up composite structures include mechanical separation, as well as thermal decomposition and solvent decomposition. However, these methods have major problems, such as high energy consumption and the generation of other waste. Thermal decomposition of composite materials requires burning fossil fuels to raise the furnace temperature to over 1000°C, generating other waste such as thermal decomposition gases. Solvent decomposition also generates a fraction of other liquid waste, and currently, there is no established use for this fraction.

[0006] Japanese Patent Publication No. 2009-197107 discloses a method for producing pellets with stabilized quality. These pellets are obtained by reusing fiber-reinforced molded articles containing cycloolefin cured resin. The document does not disclose anything about separating and regenerating the foam from the product to recycling.

[0007] Another document disclosing the mechanical recycling of products containing fibers and resins is International Publication 2020 / 028914. According to the disclosure in this document, the materials constituting the feathers do not separate (in particular, the foams do not separate), so all the resulting products are mixed and their proportions are not controlled. Furthermore, in this document, crushed resin is mixed with new resin, and thermoplastic resins are not used.

[0008] U.S. Patent Application No. 2021 / 0402650 discloses a method for manufacturing a component. This method comprises the steps of obtaining recycled fibers, mixing them with a thermoplastic resin, and manufacturing a composite component. Since this method does not start with a composite material including resin, fibers, and foam, but rather with fibers, it does not disclose how the fibers are obtained.

[0009] JP0303511A1 discloses a method for recovering resin powder and glass fibers and using them as raw materials. In this method, fragments of fiber-reinforced plastic obtained by blasting are pulverized, and then further pulverized in a grinder until they become sand-like before separating the glass powder and resin powder. The document does not disclose anything about the recycling of composite materials containing foam. Furthermore, the document discloses the recycling of small pieces of 1-3 cm, but does not disclose anything about the recycling of the powder of about 1 mm that would be the residue. On the other hand, in the present invention, powder of this size is necessary for the production of pellets. Moreover, the method disclosed in the document does not include a step for separating the core. Instead, the document discloses the recycling of a one-piece structure containing carbon fibers after pulverization, by separating the resin and fibers by centrifugal separation.

[0010] Conventional processes for recycling composite materials have all focused on removing the polymer matrix coating the fibers. However, the process of the present invention does not aim to remove the polymer matrix. Nevertheless, according to the process of the present invention, the polymer matrix gradually decomposes and disappears. Specifically, the method or process of the present invention comprises the step of obtaining pellets after separating the components of the composite material by a mechanical process. [Overview of the project] [Problems that the invention aims to solve]

[0011] The present invention relates to a method for obtaining secondary raw materials from a composite structure comprising at least a fiber-resin composite material and a core material. This method primarily relates to a method based on mechanical means. This method involves destroying the structure of composite material waste, reusing at least a first fiber-resin composite material, and modifying it to obtain secondary raw materials. In the first transformation, the first composite material is modified to obtain a first secondary raw material. In the first transformation, the first composite material comprises only fiber-resin and a foamed material which is the core material, and the core material comprises one or more thermoplastic compounds. In the first transformation, pelletized raw materials are obtained by pelletizing the first secondary raw material. In the second transformation, the first composite material comprising fiber-resin and foamed material is modified to obtain a second secondary raw material. In the second transformation, the core material comprises at least a georesin. In the second transformation, polymerizing and molding (or polymerizing and molding) the second secondary raw material yields a solid georesin compound.

[0012] The composite waste includes at least a first fiber-resin composite material (particularly a thermosetting resin matrix in which reinforcing fibers are embedded). The composite waste may further include a core material. Examples of core materials include foams (preferably polyurethane or PVC) and rigid materials (preferably aluminum or balsa wood). The first composite material and the core material form a composite structure. The core material functions as a filling core in the waste. The fibers of the first composite material function as reinforcing fibers in the product from which the waste originated and were embedded in the thermosetting resin matrix. These fibers may be glass, carbon, Kevlar, or other natural fibers (such as basalt, linen, or hemp). The core material forms the core of the composite structure. Examples of core materials include PVC, polyurethane, and balsa wood.

[0013] In this regard, the method of the present invention allows for the recycling of composite structural waste comprising a core material and a first composite material, wherein the first composite material comprises a thermosetting resin matrix in which fibers are embedded. Alternatively, the method of the present invention allows for the recycling of integrated structural waste comprising a first composite material but not a core material, wherein the first composite material comprises a thermosetting resin matrix in which fibers are embedded.

[0014] This invention belongs to the field of recycling waste derived from thermosetting composite materials to obtain reusable secondary raw materials. This waste mainly originates from wind turbine blades, ship hulls, food containers, and aircraft parts within various industries. [Means for solving the problem]

[0015] The first object of the present invention is the method described in claim 1. According to this method, waste derived from a composite material is recycled to obtain a pelletized or solid georesin compound, which is a secondary raw material. This waste may be derived from a composite material containing fibers and a thermosetting resin. The composite material may be an integral structure or a composite structure. The composite structure is often a laminated structure of the fiber-resin composite material and a core material as described above.

[0016] The reinforcing fibers of the first material may be carbon fibers, glass fibers, or natural fibers. The core material may be a foam (polyurethane, PVC, etc.) or a rigid body (balsa wood, aluminum, etc.).

[0017] In particular, a method for obtaining secondary raw materials from composite structural waste containing one or more first fiber-resin composite materials and core materials comprises the following steps. (a) One or more steps of first crushing the waste (b) A process of separating the composite structure waste by density into a first composite material containing at least fiber-resin and a second core material. (c) One or more steps of shredding the first composite material (d) One or more steps of first sieving a shredded first composite material containing at least fiber-resin, wherein the material is separated into two or more fractions of different sizes, the first fraction being less than 1 mm and the second fraction being greater than 1 mm. (e) A step of pulverizing the first fraction, which is larger than 1 mm, to obtain a pulverized composite material with fractions of 1 mm or less. (f) A step of mixing the first fraction, which is less than 1 mm in size, with the finely powdered composite material. (g) A step of modifying the above mixture with one or more compounds to obtain a secondary raw material.

[0018] The pulverization process includes homogenizing the fiber size of the fraction larger than 1 mm obtained by sieving the first composite material to a specific size. The fraction smaller than 1 mm, obtained by sieving, is added to the homogenized pulverized fraction. Pulverization is the process of turning the fraction larger than 1 mm into powder smaller than 1 mm.

[0019] The proportion of resin in the first composite material is 40-60% by weight. The proportion of fiber in the first composite material is 40-60% by weight.

[0020] In any configuration, a second step of mechanically crushing the waste may be included immediately after the first crushing step and before any other optional steps. If the waste material contains metal, a further step of removing the metal may be included after the step of crushing the composite structure waste.

[0021] We select mechanical means by balancing energy consumption with the amount of waste to be processed.

[0022] The waste is a composite structure. Therefore, the first composite material may be a one-piece structure that only contains fiber-resin compounds and does not contain a core material. Alternatively, the first composite material may contain a core material combined with fiber-resin. After mechanical first crushing and / or second crushing, the crushed waste is separated by density. Thereby, due to the density difference, the core material can be separated from the resin and the fiber. The process of separating by density is carried out before the process of shredding or pulverizing the waste. In the process of separating by density, the whole core material (such as a foam material) may be separated from the fiber-resin compound, or only a part of the core material (such as a foam) may be separated.

[0023] In the process of separating by density, part or all of the core of the waste is separated, and the first composite material remains. The first composite material may consist only of fiber-resin, or may contain fiber-resin and a core material. The core material separated from the first composite material can be recycled by other means according to the characteristics of the core material. The characteristics of the core material may be that it is a foam material (PVC or polyurethane), or that it is a rigid material (wood or metal). The recycling of the first composite material, whether it consists only of a fiber-resin composite or contains a fiber-resin composite and a core material, is carried over to the process of shredding.

[0024] Therefore, when the waste is a laminated structure or a composite structure, the method starts with the first crushing (primary crushing) that destroys the main structure of the waste, to obtain a fraction in which the first fiber-resin composite material and the core material attached thereto are mixed. Alternatively, when the waste does not contain a core material, only the first composite material containing the fiber-resin composite can be obtained by the same method. Subsequently, at least the second crushing (secondary crushing) process is carried out. By this process, the upstream waste is separated into fractions with smaller sizes.

[0025] Thereafter, when the waste contains metal, it may have a process of removing the metal.

[0026] When the fraction of the reduced waste contains a core material in addition to the fiber-resin composite material, this fraction is separated by density through a density separation table to obtain two independent fractions. The first fraction may contain a part of the first fiber-resin composite material and the core material, or may contain a first composite material consisting only of the fiber-resin composite. The other fraction contains a part or all of the core material. The fraction of the core material is removed from a subsequent process.

[0027] In relation to the above, the first composite material is the material obtained after the step of separating by density. The first composite material may contain only the fiber-resin compound and may not contain the core material. Alternatively, the first composite material may contain the fiber-resin compound and the core material (preferably a foam).

[0028] The first composite material that has undergone the step of shredding or pulverizing is then subjected to a sieving or sorting step. In this step, the first composite material is separated based on size. By sieving or sorting, the first composite material is separated into a fraction greater than 1 mm and a fraction less than 1 mm. When the waste does not contain the core material, the first composite material after the second crushing is directly subjected to the step of shredding or pulverizing.

[0029] The fraction of the first composite material greater than 1 mm and the fraction of the first composite material less than 1 mm are homogenized after the fraction greater than 1 mm is micronized. The resulting mixture of the first composite material is finally subjected to a modification step, and then a secondary raw material is obtained. This modification is carried out on the first composite material with a size less than 1 mm and one or more compounds. The compound used for the modification may vary depending on the resulting secondary raw material.

[0030] In other words, after shredding or pulverizing, the first composite material is sieved, the fraction larger than 1 mm obtained by sieving is pulverized, and this is mixed with the fraction smaller than 1 mm obtained by sieving, and this mixture is subjected to a modification process. In the modification process, the first composite material is mixed with one or more compounds. Preferably, the one or more compounds are thermoplastic polymers or georesins (silicate resins). This yields, for example, a first secondary raw material or a second secondary raw material. Georesins are a type of resin used in geotechnical applications (soil stabilization, soil improvement, structural reinforcement, etc.). Georesins are synthetic materials that combine a polymer and a curing agent. Georesins are tough, highly durable, and resistant to environmental factors such as moisture and humidity.

[0031] If the first composite material contains only fibers and resin and no core material, the proportion of resin is 40-60% by weight, and the proportion of fibers is 40-60% by weight. This ratio is very close to the ratio in the original waste before it is subjected to a recycling method. If the first composite material does not contain a core material, a thermoplastic compound may be added in the modification process to obtain a first secondary raw material. A thermoplastic polymer or thermoplastic composite should be understood as a plastic material that can be molded at any given temperature and can be melted two or more times. Examples include PVC and polyethylene. Different thermoplastic polymers mixed with the first composite material in the modification process will yield different secondary raw materials.

[0032] The primary raw materials are pelletized to obtain pellets. These pellets can then be used in various industries depending on the properties of the fibers and resins in the composite material derived from recycled waste parts.

[0033] The primary raw material or pellets obtained by the method described above contain the following: • 50-80% by weight of one or more thermoplastic polymers • 15-45% by weight of finely ground fiber-resin composite material waste • One or more additives in a weight of 0-5% (e.g., UV protectants, colorants, self-lubricants, compatibilizers)

[0034] Alternatively, if the first composite material contains foam derived from the core material in addition to the fiber-resin compound, the foam ratio is less than 50% by weight of the foam material, the resin ratio is 20-60% by weight, and the fiber ratio is 20-60% by weight. In the modification process, georesin is added to the first composite material to obtain a secondary raw material. The secondary raw material is polymerized and molded or shaped to obtain a solid georesin compound. The solid georesin compound can be used in various industries depending on the properties of the fiber, resin, foam, and georesin. It can also be molded or shaped into various shapes. Examples include brick-like blocks, decorative panels or pots, and other products with high mechanical resistance to compression.

[0035] The solid georesin compound or secondary raw material contains the following: • 40-80% by weight of one or more types of dioresin compounds • A first composite material comprising 20-60% by weight, wherein the first composite material includes fiber-resin and foam material. • One or more additives in a weight of 0-5% (e.g., reinforcing fibers, polyurethane polymers)

[0036] The above method can be implemented using a system that has the following features: • One or more crushers or shredders (preferably two, with the downstream one reducing the size of the waste). • Density separation platform for separating waste into a first composite material containing or not containing a core material and a core material (preferably foam). A powdering or shredding machine and a separator or sieve downstream thereof for reducing the size of the fibers in the first composite material to a first fraction of fibers less than 1 mm and a second fraction of fibers greater than 1 mm. • A micronizer for reducing fibers larger than 1 mm to fibers smaller than 1 mm. Apparatus for mixing the first fraction of fibers with pulverized fibers. Apparatus for modifying fibers 1 mm or less in length with a compound (preferably a thermoplastic compound or a dioresistin compound) to obtain a secondary raw material. A pelletizing apparatus for obtaining pellets after modifying a first material containing only fibers and resin with a thermoplastic compound, or a polymerization apparatus for obtaining a solid georesin compound by modifying a first material containing fibers, resin, and foam with a georesin compound.

[0037] The system may include further components. Preferably, it may include a metal grinder utilizing Foucault current for removing metal. The metal grinder is installed immediately after the first crushing or first shredding (if possible, immediately after the second crushing or second shredding) to separate all metal cores (such as honeycomb cores) derived from the waste. [Brief explanation of the drawing]

[0038] [Figure 1] To fully disclose the present invention and facilitate understanding of its features, Figure 1 shows a detailed block diagram of the method of the present invention. [Modes for carrying out the invention]

[0039] Some of the methods of the present invention for recycling composite material waste structures will be described with reference to Figure 1.

[0040] Step 1 consists of primary crushing. Preferably, primary crushing is performed by a twin-shaft crusher capable of destroying the main structure of the waste. If the waste, which consists of a fiber-resin integrated structure in addition to a core (foam or rigid body), has a laminated or composite structure, the resulting fraction may have core (preferably foam particles) attached to it. If the waste consists only of an integrated structure, the resulting fraction will not contain any foam or core material. The fraction obtained by Step 1 is waste with a substantial maximum width of 80 to 25 mm.

[0041] Step 2 consists of a second crushing (secondary crushing). The second crushing is performed by a single-shaft crusher. If the waste contains cores, step 2 facilitates the separation of core materials from the fiber-resin composite material. The fraction obtained by step 2 is non-homogeneous waste with a maximum diameter of 50-15 mm.

[0042] If the waste contains metal, it is removed in step 3. Preferably, it is removed by a metal grinder utilizing Foucault current.

[0043] Step 4 consists of density separation on a density separation table. Step 4 is performed only when the waste is a laminated structure (preferably containing a core which is foam and a fiber-resin composite material). If the waste is a single-piece structure (containing only fiber-resin composite material), density separation is not required. If the waste contains fiber-resin composite material and core material (such as foam), the waste is separated by density separation to obtain a first composite material. If all of the core material is removed from the first composite material, the first composite material contains only fiber-resin and no core material (preferably foam). Alternatively, the waste may be separated into a first composite material containing fiber-resin and core material (preferably foam) and the remainder of the core material.

[0044] Therefore, the fraction obtained by step 4 may consist of a fraction of the first composite material containing fiber-resin but no core material, and a fraction containing core material. Alternatively, the fraction obtained by step 4 may consist of a fraction of the first composite material containing fiber-resin and core material, and other fractions containing core material. The core material fraction is stored for subsequent recycling.

[0045] Step 5 consists of a process of shredding or pulverizing the fraction of the first composite material, followed by sieving or sorting. Preferably, this is done by vibratory sorting using a sorting machine. After shredding or pulverizing the first composite material and passing it through a sieve or sorting machine, a fraction of the first composite material containing fibers smaller than 1 mm and a fraction containing fibers larger than 1 mm are obtained. The fraction of the first composite material with fibers smaller than 1 mm is deemed to be of an appropriate size and is separated for subsequent processes. The fraction with fibers larger than 1 mm proceeds to the next step of pulverization using a pulverizer.

[0046] Step 6 consists of pulverizing fractions larger than 1 mm. Preferably, pulverization is performed using a spraying device. The fraction obtained by the pulverization process consists of fibers uniformly reduced to less than 1 mm. The fraction of composite material smaller than 1 mm obtained by sieving upstream (step 5) is added to the pulverized fraction obtained in step 6.

[0047] Step 7 consists of chemical modification or synthesis by mixing the first composite material, which has fibers less than 1 mm in length, with other compounds. The compounds to be mixed may be thermoplastic polymers or composite materials, or georesin compounds. After modification or synthesis, a secondary raw material is obtained.

[0048] The process will differ depending on the compound used to modify or synthesize the first composite material, which may or may not contain the core foam material.

[0049] If the first composite material contains only fiber-resin and does not contain a foam core material, the first composite material is modified with a thermoplastic compound in step 7 and pelletized in step 8. This yields thermoplastic pellets. The pellets can be used in common deformation processes (injection molding, extrusion, compression, 3D printing, etc.) for various applications. The resulting pellets contain the following: • 50-80% by weight of one or more thermoplastic polymers • 15-45% by weight of finely ground fiber-resin composite material waste • One or more additives in a weight of 0-5%

[0050] On the other hand, if the first composite material includes a foam core material in addition to the fiber-resin, the first composite material is modified together with the georesin compound in step 7, polymerized, molded or shaped in step 9 to obtain a solid georesin compound of the desired shape. The solid georesin compound may be brick-shaped, panel-shaped, or pot-shaped. The resulting solid georesin compound contains the following: • 40-80% by weight of one or more types of georesin • A first composite material comprising 20-60% by weight, wherein the first composite material includes fiber-resin and foam material. • One or more additives in a weight of 0-5%

Claims

1. A method for obtaining secondary raw materials from composite structural waste containing at least a fiber-resin composite material and a core material, A method characterized by comprising one or more of the following steps: (a) One or more steps of first crushing the composite structural waste; (b) A step of separating the composite structure waste by density into a first composite material containing at least fiber-resin and a second core material; (c) One or more steps of shredding the first composite material; (d) One or more steps of first sieving the shredded first composite material containing at least fiber-resin, The above material is separated into two or more fractions of different sizes. Process where the first stroke is less than 1 mm, and the first stroke is greater than 1 mm; (e) A step of pulverizing the first fraction which is larger than 1 mm to obtain a pulverized composite material which is a fraction of 1 mm or less; (f) A step of mixing the first fraction, which is less than 1 mm in size, with the finely powdered composite material; (g) A step of modifying the above mixture with one or more compounds to obtain a secondary raw material.

2. The process includes a second crushing step immediately following the first crushing step and before any other step, The method according to feature 1.

3. The process includes a step to remove metal before the above-mentioned process of separation by density. The method according to feature 1.

4. The method according to claim 1, characterized in that the core is (i) or (ii) below: (i) Foam materials (such as polyurethane or PVC); (ii) A rigid material (such as aluminum or balsa wood).

5. The above-mentioned first composite material does not contain a core material. The material is modified with a thermoplastic polymer compound to obtain a primary raw material, which is then pelletized to obtain pellets. The method according to any one of claims 1 to 4, characterized in that

6. In the above-mentioned first composite material, The resin content is 40-60% by weight. The fiber content is 40-60% by weight. The method according to claim 5, characterized in that

7. The above-mentioned first composite material includes a core material which is a foam. After modifying the compound, which is a georesin, to obtain a secondary raw material, it is polymerized and then molded or shaped to obtain a solid georesin compound. The method according to any one of claims 1 to 4, characterized in that

8. The above-mentioned first composite material is, It contains less than 50% by weight of foam material. The resin content is 20-60% by weight. The fiber content is 20-60% by weight. The method according to claim 7, characterized in that

9. A secondary raw material obtained by the method described in claim 5 or 6, characterized in that it comprises the following: 50-80% by weight of one or more thermoplastic polymers; A first composite material comprising 15-45% by weight, containing fiber-resin, but not containing a core material; One or more additives in an amount of 0-5% by weight.

10. The above thermoplastic polymer is PVC or polyethylene. The secondary raw material according to claim 9, characterized in that

11. A secondary raw material obtained by the method described in claim 8, characterized in that it contains the following: One or more types of georesin in an amount of 40-80% by weight; A first composite material comprising 20 to 60% by weight of a fiber-resin and foam material; One or more additives in an amount of 0-5% by weight.

12. The above georesin is mainly a silicate-based resin. The secondary raw material according to claim 11, characterized in that

13. The above fibers are carbon fibers, glass fibers, or naturally derived fibers. The secondary raw material according to claims 9 to 12, characterized in that

Images