JP6294129B2 - Recycling method of fiber reinforced thermoplastic resin - Google Patents

Description

  The present invention relates to a method for recycling a fiber reinforced thermoplastic resin including a reinforced fiber and a thermoplastic resin.

  Regarding molded products of fiber reinforced thermoplastic resins (FRTP) including reinforced fibers and thermoplastic resins, used recovered products, scraps and molding defects produced in the manufacturing process, etc. A method for recycling waste FRTP material) has been proposed.

  For example, Patent Document 1 describes a method of repairing the appearance quality of a used FRTP molded product that has been damaged due to drill holes, surface scratches, or the like, and that can be reused. Specifically, the plate-like bodies are superposed on both surfaces of the used FRTP molded product and heated, and the plate-like bodies are brought close to each other and pressed in a state where the thermoplastic resin is melted. As a result, the appearance quality is restored by filling the drill holes and surface scratches by causing the thermoplastic resin to flow.

  Subsequently, the applied pressure is removed while the thermoplastic resin is in a molten state, and the reinforcing fiber is spring-backed. In this way, the plate-shaped bodies are uniformly expanded and then pressurized again, thereby reducing the thickness of the expanded and increased portion. Further, in this state, the thermoplastic resin is cooled and solidified, and the plate-like body is removed to obtain a reusable FRTP molded product.

  However, the above recycling method is based on the premise that a used FRTP molded product is reused in the same shape and application, and it is assumed that an FRTP molded product that can be reshaped into a different shape and used for a different application is obtained. It has not been.

  Examples of the recycling method for obtaining a material that can be used for a use different from the first use include those described in Patent Documents 2 and 3. In any case, the pulverized material obtained by pulverizing the waste FRTP material is accumulated and then heated and melted to obtain a reshaped product. In other words, the waste FRTP material is pulverized into a pulverized product, which is used as a remolding material for re-molding by performing hot press molding or injection molding again.

  As another recycling method of waste FRTP material, as disclosed in Patent Document 4, the thermoplastic fiber is thermally decomposed and removed from the waste FRTP material, whereby the reinforcing fiber is recovered and reused. There is.

JP-A-6-320541 JP 2002-96324 A JP-A-8-1670 JP-A-6-99160

  The FRTP molded product is a high-density, high-strength bulk body in which reinforcing fibers are surrounded and pressed by a thermoplastic resin. It is not easy to pulverize or cut such a waste FRTP molded product which is a bulk body. In particular, when a molded product using carbon fiber as a reinforcing fiber is cut, since the carbon fiber is relatively high in strength and hardness, wear of the cutting tool becomes severe, which is not preferable from an economical viewpoint.

  In addition, even if the waste FRTP material is pulverized, the reinforcing fibers are also cut together with the thermoplastic resin as the base material, so that it is possible to remold a sufficiently strong molded product from the obtained remolding material. Have difficulty. That is, it is impossible to obtain a remolding material that can be actually used by the methods described in Patent Documents 2 and 3.

  Furthermore, in the method described in Patent Document 4, the fiber-reinforced composite material has a significantly lower thermal conductivity in the direction other than the orientation direction of the reinforcing fiber as compared with the metal material or the like. On the other hand, it is not easy to transfer heat to the internal thermoplastic resin, and processing takes time. That is, it is difficult to thermally recover all the thermoplastic resins contained in the waste FRTP material and efficiently recover only the reinforcing fibers.

  The present invention has been made to solve the above-mentioned problems, and it is easy to crush or cut waste FRTP materials while suppressing the cutting of reinforcing fibers, and to heat effectively to the inside. An object of the present invention is to provide a method for recycling a fiber-reinforced thermoplastic resin that can be recycled in a state, that is, in a state where it can be effectively and quickly recycled.

In order to achieve the above-described object, the present invention provides a reinforcing fiber and a thermoplastic resin that surrounds the reinforcing fiber and restrains the reinforcing fiber by applying a pressing force larger than the repulsive force of the reinforcing fiber. A method for recycling a fiber-reinforced thermoplastic resin containing
Absorbing the liquid in the thermoplastic resin;
While the liquid is vaporized, the fiber reinforced thermoplastic resin is heated until the thermoplastic resin softens and the pressing force of the thermoplastic resin on the reinforcing fiber becomes smaller than the repulsive force of the reinforcing fiber, and the heat A step of expanding the fiber-reinforced thermoplastic resin by forming a void between the reinforcing fibers by pressing the thermoplastic resin by a repulsive force of the reinforcing fibers released from the restraint of the plastic resin;
It is characterized by having.

  In the fiber reinforced thermoplastic resin (FRTP), the reinforced fibers that are twisted together exist in a state of being compressed (that is, elastically deformed) in the thermoplastic resin. That is, the reinforcing fiber receives a pressing force from the thermoplastic resin. Since the reinforcing fibers try to return to the original shape, a repulsive force from the reinforcing fibers acts on the thermoplastic resin. Since the repulsive force is smaller than the pressing force, the reinforcing fiber is compressed and restrained by the thermoplastic resin in a state where the repulsive force is stored.

  When the FRTP absorbs the liquid and then heated to a temperature equal to or higher than the melting point of the thermoplastic resin or the glass transition point, the thermoplastic resin softens and the pressing force against the reinforcing fibers decreases. Along with this, the reinforcing fiber is released from the restraint of the thermoplastic resin and is deformed according to the repulsive force. As a result, voids are formed between the reinforcing fibers and FRTP expands. In addition, as the FRTP is heated as described above, the liquid absorbed in the thermoplastic resin is vaporized. In combination with the vaporization expansion at this time, the expansion of FRTP can be further promoted.

  Therefore, in the present invention, the density per unit volume (apparent density) of FRTP can be reduced. Since such FRTP has low strength, it can be easily crushed or cut.

  Moreover, since a space | gap is formed between reinforcing fibers as above mentioned, when grinding | pulverizing thru | or cutting | disconnection, destruction by peeling arises between reinforcing fibers. For this reason, it is easy to grind and cut FRTP while suppressing cutting of the reinforcing fibers.

  In addition, in FRTP in which voids are formed inside, heat easily goes inside. For this reason, it is easy to heat to the inside. That is, FRTP can be efficiently recycled.

  The liquid to be absorbed by the thermoplastic resin is preferably water because of its low cost and easy handling. In addition, in this case, the water can be easily absorbed by the thermoplastic resin by utilizing the water absorption of the thermoplastic resin. Furthermore, when the FRTP is heated, the water absorbed by the thermoplastic resin can be easily evaporated and expanded. Therefore, it is possible to easily and satisfactorily expand the volume of FRTP and to recycle FRTP more efficiently.

  It is preferable that after the FRTP expanded as described above is further cooled and solidified, at least one of cutting and pulverization is performed. By cooling the FRTP in an expanded state, the FRTP can be solidified in a state where the density is reduced, that is, in a state where the strength is reduced.

  In FRTP solidified in this way, voids are formed in the thermoplastic resin and between the reinforcing fibers, and the restraint (pressing force) of the thermoplastic resin on the reinforcing fibers is reduced. Therefore, the thermoplastic resin can be easily crushed or cut while breaking between the reinforcing fibers. As a result, cutting of the reinforcing fibers is suppressed, so that a remolding material that includes a relatively long reinforcing fiber and that can remold a molded product exhibiting sufficient strength for this purpose is obtained. Can do.

  The heating of FRTP is preferably performed in a vacuum or an inert gas atmosphere. Thereby, it can suppress that a thermoplastic resin and a reinforced fiber oxidize and deteriorate. Therefore, it becomes possible to obtain a better reproducible material.

The thermoplastic resin FTRP inflated as described above by thermal decomposition, we recover reinforcing fibers. As described above, since many voids are formed in the FRTP, it is easy to heat the inside of the FRTP. Even when an oxidation reaction is used in combination with the thermal decomposition, since the air has entered the inside of FRTP, the decomposition can proceed quickly and effectively. Therefore, the thermoplastic resin can be easily pyrolyzed and only the reinforcing fibers can be efficiently recovered.

  The length of the reinforcing fiber is preferably 1 mm or more. In this case, when the thermoplastic resin is softened, a sufficient repulsive force is exerted on the reinforcing fibers. Therefore, FRTP can be expanded more efficiently.

  According to the present invention, since voids can be formed particularly between the reinforcing fibers of FRTP, the density per unit volume (apparent density) can be reduced by expanding FRTP. Such FRTP has low strength, and breakage easily proceeds between reinforcing fibers. For this reason, it becomes possible to grind | pulverize and cut | disconnect FRTP, suppressing that a reinforcement fiber is cut | disconnected. That is, it can be set as the material for remolding from which the molded article which shows sufficient intensity | strength is obtained.

  Moreover, since it becomes easy to heat the inside of FRTP, it is advantageous, for example, when the thermoplastic resin is thermally decomposed and the reinforcing fibers are recovered.

It is the optical microscope photograph which expanded and showed the side surface about the fiber reinforced thermoplastic resin (FRTP) molded article which enforces the recycling method which concerns on this embodiment. FIG. 2 is an optical micrograph showing an enlarged side surface of an expanded body (porous body) obtained by subjecting the FRTP molded article of FIG. 1 to water absorption treatment and heat treatment and then solidifying by cooling. It is the optical microscope photograph which expanded and showed the fragment obtained by disassembling the expansion body of FIG.

  Hereinafter, preferred embodiments of the method for recycling a fiber-reinforced thermoplastic resin according to the present invention will be described in detail with reference to the accompanying drawings.

  In the recycling method according to the present embodiment, among the FRTP molded products configured to include the reinforcing fibers and the thermoplastic resin, the used FRTPs such as used recovered products, scraps and defective moldings generated in the manufacturing process, etc. It is suitably applied to the material.

  FIG. 1 is an optical micrograph of the side surface of this type of FRTP molded article 10. Here, the FRTP molded product 10 is Tepex Dynalite manufactured by Bond Laminate, Germany, and a plurality of fiber layers 14 in which bundles of twisted carbon fibers (reinforced fibers 12) are two-dimensionally oriented are superimposed. The superposed body 16 is surrounded and pressed with a thermoplastic resin 18 made of nylon-6,6 (N66). In FIG. 1, the direction along the fiber direction of the reinforcing fiber 12 in the FRTP molded product 10 is shown. In this case, the reinforcing fiber 12 is 45% by volume.

  The FRTP molded product 10 is obtained by applying a high pressure to the superposed body 16 impregnated with the molten thermoplastic resin 18 to remove internal voids, and then cooling and solidifying the thermoplastic resin 18. That is, in the FRTP molded product 10, the reinforcing fiber 12 is surrounded by the thermoplastic resin 18 that has shrunk as it is cooled and solidified, and thus receives a pressing force from the thermoplastic resin 18. Accordingly, the reinforcing fiber 12 is in a compressed state.

  A repulsive force is applied from the reinforcing fiber 12 to the thermoplastic resin 18 so that the reinforcing fiber 12 returns to its original shape. However, since the pressing force of the thermoplastic resin 18 is larger, the reinforcing fiber 12 is restrained by the solidified thermoplastic resin 18 in a compressed state.

  Hereinafter, the case where the recycling method according to the present embodiment is applied to the FRTP molded product 10 will be described as an example. However, the application target is not limited to the FRTP molded product 10 described above. is there.

  For example, as the reinforcing fiber, glass fiber, aramid fiber, natural fiber, metal fiber, ceramic fiber, ultrahigh molecular weight polyethylene fiber, and the like can be employed in addition to the above carbon fiber. In any case, a bundle of a plurality of reinforcing fibers having a length of 1 mm or more is preferably oriented two-dimensionally or one-dimensionally.

  Furthermore, the ratio of the reinforcing fibers can be set to, for example, 10 to 80% by volume, more preferably 20 to 70%.

  As the thermoplastic resin, polyolefin, polyester, polyamide, aromatic polyketone, aromatic polymer, and the like can be employed in addition to the above N66.

  Representative examples of polyolefin include polyethylene (PE), polypropylene (PP), polystyrene (PS) and the like. Examples of the polyester include polyethylene terephthalate (PET), polybutylene terephthalate (PBT), and polycarbonate (PC). Examples of the polyamide include nylon-6 (N6) and semi-aromatic polyamides. Furthermore, examples of the aromatic polyketone include polyethersulfone (PES), polyetherimide (PEI), polyetheretherketone (PEEK), polyetherketone (PEK), and examples of the aromatic polymer include polysulfone (PSF). ), Polyphenylene sulfide (PPS), polybenzimidazole (PBI) and the like.

  In the recycling method according to this embodiment, first, the liquid is absorbed by the thermoplastic resin 18. For this purpose, for example, the FRTP molded product 10 may be immersed in a liquid. As another method, the FRTP molded article 10 may be left in a vapor obtained by vaporizing a liquid or in a gas containing the vapor.

  The liquid does not cause a chemical change (deterioration) with respect to the thermoplastic resin 18 and the reinforcing fiber 12, and vaporizes at a temperature equal to or lower than the melting temperature (melting point or glass transition point) of the thermoplastic resin 18. If it is. Examples of such a liquid include alcohol and water, but water is particularly preferable because it has an advantage of low cost and extremely easy handling.

  By using water as the liquid, the thermoplastic resin 18 can easily absorb water without causing deterioration of the thermoplastic resin 18 and the reinforcing fibers 12, and the FRTP molded product 10 is heated as described later. Thus, it can be easily evaporated from the thermoplastic resin 18. Furthermore, it is possible to absorb moisture in the air by utilizing the water absorption of the thermoplastic resin 18.

  Next, the FRTP molded product 10 containing the liquid is heated to a temperature equal to or higher than the melting temperature of the thermoplastic resin 18 within a range in which the thermoplastic resin 18 is not deteriorated by heating. The FRTP molded product 10 can be heated in air, but is preferably performed in a vacuum or in an inert gas atmosphere such as nitrogen or argon. Thereby, it can suppress that the thermoplastic resin 18 oxidizes and deteriorates. In addition, a heating means is not specifically limited, It can carry out using well-known means, such as an electric heating, a far infrared ray, a near infrared ray, and combustion.

  By heating the FRTP molded product 10 as described above, the liquid absorbed in the thermoplastic resin 18 is vaporized and expanded. In addition, the thermoplastic resin 18 is softened, so that the pressing force of the thermoplastic resin 18 that restrains the reinforcing fiber 12 is reduced. That is, the pressing force is smaller than the repulsive force of the reinforcing fiber 12. As a result, the reinforcing fibers 12 are released from the restraint of the thermoplastic resin 18 and are deformed so as to return to the original shape from the compressed state. At this time, the softened thermoplastic resin 18 is pressed by the reinforcing fibers 12.

  As described above, the thermoplastic resin 18 is pressed by the gas in which the liquid is vaporized and the reinforcing fibers 12. By this pressing, the FRTP molded product 10 is expanded from the inside. By cooling this, as shown in FIG. 2, many large-volume voids 20 are formed between the fiber layers 14 and in the thermoplastic resin 18. In other words, the FRTP molded product 10 can be expanded into a porous body. Hereinafter, the FRTP molded product 10 that has been expanded in this manner into a porous body is referred to as an expanded body 22. In addition, by setting the length of the reinforcing fiber 12 to 1 mm or more, the repulsive force of the reinforcing fiber 12 can be expressed well, and the FRTP molded product 10 can be expanded more easily.

  In the expanded body 22, the apparent density per unit volume is smaller than that of the FRTP molded product 10. This is because a large number of large-volume voids 20 are formed as described above.

  Such an expanded body 22 has a low strength. Further, since the void 20 exists, the layers of the fiber layer 14 are easily peeled off. Therefore, it is easy to pulverize or cut the expansion body 22, and at this time, the breakage occurs between the fiber layers 14 and 14. For this reason, the expansion body 22 (FRTP molded product 10) can be easily pulverized and cut while suppressing the reinforcing fibers 12 from being cut and shortened. The pulverizing means and the cutting means are not particularly limited, and known means such as a press, a shredder, and a mill can be used.

  Such a pulverized piece or cut piece is, for example, prepared as a starting material for injection molding (reforming material) by adjusting the content of the thermoplastic resin as a base material and then pelletizing it with an extruder. be able to. As described above, in the pulverized pieces or cut pieces, the reinforcing fibers 12 are avoided from being cut, and therefore, by using the remolding material, an injection molded product having sufficient strength can be obtained.

  Alternatively, the pulverized pieces or cut pieces may be used as the starting material (reforming material) for press molding. In this case, a press-molded product can be obtained by heating and pressing the crushed pieces or cut pieces. Even if it does in this way, the press-molded article which shows sufficient intensity | strength can be obtained for the same reason as said injection molding.

  As described above, according to the present embodiment, a good remolding material can be obtained from the FRTP molded product 10. That is, the FRTP molded product 10 can be effectively recycled.

  It is also possible to collect the reinforcing fiber 12 from the expanded body 22 obtained as described above and reuse it. Hereinafter, this recovery will be described.

  In this recycling method, the expanded body 22 is heated to a temperature at which the thermoplastic resin 18 is thermally decomposed in a deoxygenated atmosphere. The thermoplastic resin 18 is thermally decomposed by heating under such conditions. Since a large number of voids 20 are formed inside the expansion body 22, heat easily flows into the expansion body 22. That is, the expansion body 22 can be efficiently heated to the inside thereof, and the thermoplastic resin 18 can be easily pyrolyzed. Even when an oxidation reaction is used in combination with the thermal decomposition, since the air has entered the inside of FRTP, the decomposition can proceed quickly and effectively.

  On the other hand, the reinforcing fiber 12 does not change chemically and physically. For this reason, the thermoplastic resin 18 is separated and removed from the FRTP molded product 10, and the reinforcing fibers 12 remain. Thereby, the reinforcing fiber 12 can be easily recovered.

  Furthermore, as another recycling method of the FRTP molded article 10, it is possible to simply burn the expanded body 22 before cooling and recover thermal energy. As described above, since heat and air easily enter the inside of the expansion body 22, the expansion body 22 easily burns. For this reason, it becomes possible to collect | recover heat energy efficiently.

  As described above, the FRTP molded product 10 absorbs liquid and expands, thereby forming the voids 20 between the fiber layers 14 and 14 (reinforcing fibers 12 and 12) or in the thermoplastic resin 18. As a result, the FRTP molded product 10 can be made into a low-strength porous body (expanded body 22). In the expanded body 22, breakage occurs particularly between the fiber layers 14 and 14. Therefore, it is possible to pulverize and cut the FRTP molded product 10 while suppressing the reinforcing fiber 12 from being cut. Moreover, it is also possible to make the expansion body 22 easy to effectively heat up to the inside. For this reason, it becomes possible to perform various recycling processes efficiently.

  The present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the scope of the invention.

  The FRTP molded product 10 shown in FIG. 1 was absorbed by immersing it in deionized water at room temperature for 1 week. The water absorption rate during molding of N66 in this FRTP molded product 10 was less than 0.2% by weight, but increased to about 4% by immersion.

  Next, the FRTP molded article 10 having absorbed water as described above was heated in an argon atmosphere at 300 ° C. for 5 minutes, and then cooled and solidified at room temperature to obtain an expanded body 22 shown in FIG.

  As can be seen from FIG. 2, in the expanded body 22, a large number of voids 20 are formed between the fiber layers 14 and 14. Further, it was confirmed that the plate thickness was about twice that of the FRTP molded product 10 shown in FIG. That is, in the expanded body 22, separation occurred between the fiber layers 14, 14, and the portion where the reinforcing fibers 12 were fixed by the thermoplastic resin 18 was reduced as compared with the FRTP molded product 10.

  The expansion body 22 could be easily disassembled by applying an external force without using an apparatus / apparatus for crushing or cutting. The crushed pieces 24 thus obtained are shown in FIG.

  Thus, the FRTP molded product 10 can be easily pulverized and cut by performing a very simple operation of heating after absorbing the liquid. For this reason, it is remarkably easy to obtain a remolding material and rework it.

  Furthermore, since the layers of the fiber layers 14 and 14 can be easily peeled during the pulverization and cutting treatment, it is possible to suppress the reinforcing fibers 12 from being cut in the longitudinal direction. This can be confirmed from the fact that the reinforcing fiber 12 maintains a length of several tens of mm in the fragment 24 of FIG. Therefore, a high-strength reshaped body can be formed from the obtained remolding material.

  As described above, the reinforcing fiber is compressed and restrained with a high density by the pressing force from the thermoplastic resin, and even in the bulk FRTP molded product fixed to the thermoplastic resin in this state, the above process is performed. Thus, various recycling processes can be changed to a state in which the recycling processes can be easily performed.

DESCRIPTION OF SYMBOLS 10 ... Fiber-reinforced thermoplastic resin (FRTP) molded article 12 ... Reinforcement fiber 14 ... Fiber layer 16 ... Superposition body 18 ... Thermoplastic resin 20 ... Air gap 22 ... Expansion body 24 ... Shard

Claims (4)

A method for recycling a fiber-reinforced thermoplastic resin, comprising: a reinforcing fiber; and a thermoplastic resin that surrounds the reinforcing fiber and restrains the reinforcing fiber by applying a pressing force larger than a repulsive force of the reinforcing fiber. ,
Absorbing the liquid in the thermoplastic resin;
While the liquid is vaporized, the fiber reinforced thermoplastic resin is heated until the thermoplastic resin softens and the pressing force of the thermoplastic resin on the reinforcing fiber becomes smaller than the repulsive force of the reinforcing fiber, and the heat A step of expanding the fiber-reinforced thermoplastic resin by forming a void between the reinforcing fibers by pressing the thermoplastic resin by a repulsive force of the reinforcing fibers released from the restraint of the plastic resin;
I have a,
A method for recycling a fiber-reinforced thermoplastic resin , comprising recovering the reinforcing fiber by thermally decomposing the thermoplastic resin contained in the expanded fiber-reinforced thermoplastic resin.   The recycling method according to claim 1, wherein the liquid is water. The recycling method according to claim 1 or 2 , wherein the fiber-reinforced thermoplastic resin is heated in a vacuum or an inert gas atmosphere. The recycling method according to any one of claims 1 to 3 , wherein a length of the reinforcing fiber is 1 mm or more.

Images