JP7225693B2 - Inorganic fiber recovery method - Google Patents

Description

The present invention relates to a method for recovering inorganic fibers.

Fiber reinforced plastics (FRP) containing resin and fibers are known to be lightweight and have high strength and rigidity. Therefore, FRP is being developed for use in a wide range of fields, such as components for sports and leisure goods, and components for spacecraft.

Recently, the use of FRP has expanded from the use of special products to the use of general-purpose products. In addition, as environmental considerations become more important, methods of recovering inorganic fibers from FRP waste materials are being studied.

For example, Patent Literature 1 describes a method of recovering carbon fibers by oxidatively decomposing carbides of carbon fiber reinforced plastic (CFRP). Further, Patent Literature 2 describes a method of treating CFRP with a supercritical fluid or subcritical fluid to remove resin contained in CFRP and recovering carbon fibers.

JP-A-07-033904 Japanese Patent Application Laid-Open No. 2003-190759

Therefore, there is a demand for a method of recovering inorganic fibers even from FRP with improved strength and rigidity.

In view of the above circumstances, the present inventors provide a method for recovering inorganic fibers from waste FRP materials with increased strength and rigidity.

As a result of studies by the inventors, a molded body using FRP in which a first resin layer containing a first inorganic fiber and a second resin layer containing a second inorganic fiber different from the first inorganic fiber are laminated is was found to have high strength and stiffness.

The inventors have attempted to recover inorganic fibers from the molded article using the inorganic fiber recovering methods described in Patent Documents 1 and 2. As a result, when the methods described in Patent Document 1 and Patent Document 2 are used, the obtained inorganic fibers are a mixture of the first inorganic fibers and the second inorganic fibers, and the first inorganic fibers and the second inorganic fibers are separated. It was found to be difficult to recover

As a result of investigations by the inventors, the inventors have found that the first inorganic fibers and the second inorganic fibers can be separated and collected according to the method for collecting inorganic fibers having the following aspects, and have completed the present invention. .

One aspect of the present invention has the following aspects.
[1] A method for recovering inorganic fibers comprising the following steps [1] to [3].
[1]: A first resin layer containing first inorganic fibers and a thermoplastic first resin, a second inorganic fiber different from the first inorganic fibers, and a second thermoplastic resin For a molded body in which a resin layer is laminated, and the molded body satisfies the following conditions:
A step of heating the molded body so that the surface temperature of the molded body is not less than [Tp+30]°C and not more than [Tp+70]°C.
(Tp (°C): the lower melting point of the melting point of the first resin and the melting point of the second resin)
[2]: A step of peeling off the heated first resin layer and the second resin layer from each other.
[3]: A step of heating at least one of the separated resin layers to a temperature equal to or higher than the decomposition temperature of the resin contained in the one resin layer to remove the resin, and recovering the inorganic fibers of the one.
<Condition>
For a test piece cut out from the molded body to 50 mm × 50 mm, when heated so that the surface temperature of the test piece is [Tp + 30] ° C., the thickness of the first resin layer before heating is X ₁ after heating The ratio Y ₁ /X ₁ of the thickness Y ₁ of the first resin layer and the ratio Y of the thickness Y ₂ of the second resin layer after heating to the thickness X ₂ of the second resin layer before heating ₂ /X At least one of ₂ is 2 or more.
[2] The inorganic material according to [1], wherein in the step [2], the first resin layer is thicker than the second resin layer, the first resin layer is fixed, and the second resin layer is peeled off. Fiber recovery method.
[3] When the surface temperature of the molded body is [Tp + 70] ° C., the tensile strength of the second resin layer measured at a tensile speed of 100 mm / min according to JIS L 1913 is 0.5 N / cm or more, the method for recovering inorganic fibers according to [2].
[4] In the step [2], the peel strength between the first resin layer and the second resin layer measured at a peel speed of 100 mm/min in accordance with JIS K 6854-1 is 1. The method for recovering inorganic fibers according to any one of [1] to [3], wherein the recovery method is less than 0 N/cm.
[5] Any one of [1] to [4], wherein the first inorganic fiber is one of carbon fiber and glass fiber, and the second inorganic fiber is the other of carbon fiber and glass fiber A method for recovering inorganic fibers according to the item.

According to one aspect of the present invention, there is provided a method for recovering inorganic fibers from waste FRP materials with increased strength and rigidity.

FIG. 1 is a cross-sectional view showing the layer structure of a molded body 10 of this embodiment. FIG. 2 is a schematic cross-sectional view showing step [1]. FIG. 3 is a schematic cross-sectional view showing step [2]. FIG. 4 is a schematic cross-sectional view showing step [3].

Hereinafter, a method for recovering inorganic fibers according to each embodiment of the present invention will be described with reference to the drawings. In addition, in all the drawings below, the dimensions and ratios of the constituent elements are appropriately changed in order to make the drawings easier to see.

The method for recovering inorganic fibers according to the present embodiment is a method for recovering inorganic fibers from a molded article. The molded body will be described below.

<Molded body>
FIG. 1 is a cross-sectional view showing the layer structure of a molded body 10 of this embodiment. As shown in FIG. 1, the molded body 10 of this embodiment consists of only the first resin layer 1 and the second resin layer 5 . A molded body 10 of the present embodiment is a laminate in which a first resin layer 1 and a second resin layer 5 arranged only on one side of the first resin layer 1 are laminated.

Preferred examples of constituent materials of the first resin layer 1 and the second resin layer 5 of the present embodiment will be described below.

[First resin layer]
The first resin layer 1 in this embodiment of the present invention includes first inorganic fibers and a first thermoplastic resin. The first resin layer 1 of the present embodiment is preferably a resin layer in which the first inorganic fibers are impregnated with the first thermoplastic resin.

(First inorganic fiber)
Examples of the first inorganic fibers contained in the first resin layer 1 of the present embodiment include carbon fibers, graphite fibers, silicon carbide fibers, alumina fibers, tungsten carbide fibers, boron fibers, glass fibers, stainless steel, metal fibers such as iron. etc.

The carbon fiber is not particularly limited, and examples thereof include polyacrylonitrile (PAN)-based carbon fiber and PITCH-based carbon fiber. The carbon fiber preferably has a strand tensile strength of 1.0 GPa or more and 9.0 GPa or less and a strand tensile elastic modulus of 150 GPa or more and 1000 GPa or less. More preferably, the carbon fiber has a strand tensile strength of 1.5 GPa or more and 9.0 GPa or less and a strand tensile modulus of 200 GPa or more and 1000 GPa or less.

As used herein, values measured according to JIS R7601 (1986) are adopted for the strand tensile strength and strand tensile modulus of carbon fibers.

Carbon fiber or glass fiber is preferable as the first inorganic fiber.

(Thermoplastic first resin)
In the first resin layer 1 of the present embodiment, the thermoplastic first resin is not particularly limited. For example, polyamide resin, polyolefin resin, modified polyolefin resin, polyester resin, polycarbonate resin (glass transition temperature: 145 ° C.), polyamide Examples include imide resins, polyphenylene oxide resins, polysulfone resins, polyethersulfone resins, polyetheretherketone resins, polyetherimide resins, polystyrene resins, polyphenylene sulfide resins, and liquid crystal polyester resins.

Examples of polyamide resins include nylon 6 (melting point: 215 to 220°C), nylon 66 (melting point: 260°C), nylon 12 (melting point: 175°C), nylon MXD6 (melting point: 237°C), and the like.

Polyolefin resins include, for example, low-density polyethylene (melting point: 95-130° C.), high-density polyethylene (melting point: 120-140° C.), polypropylene (melting point: 165° C.), and the like.

A modified polyolefin resin is, for example, a resin obtained by modifying a polyolefin resin with an acid such as maleic acid. Modified polyolefin resins include, for example, modified polypropylene resins (melting point: 160 to 165° C.).

Examples of polyester resins include polyethylene terephthalate and polybutylene terephthalate.

The thermoplastic resins described above may be used alone or in combination of two or more. When using two or more thermoplastic resins, they may be used as a polymer alloy. Polymer alloys include, for example, ABS resins (copolymers of acrylonitrile, butadiene and styrene), copolymers of acrylonitrile and styrene, copolymers of nylon 6 and nylon 66, and the like.

From the viewpoint of the strength and rigidity of the molded body 10, the thermoplastic first resin preferably has high adhesion to the first inorganic fibers. The thermoplastic first resin is preferably at least one selected from the group consisting of polyolefin resins, modified polypropylene resins, polyamide resins and polycarbonate resins.

[Second resin layer]
The second resin layer 5 in this embodiment of the invention includes second inorganic fibers and a second thermoplastic resin.

(Second inorganic fiber)
As the second inorganic fibers contained in the second resin layer 5 of the present embodiment, fibers different from the first inorganic fibers may be used, and the fibers exemplified for the first inorganic fibers can be used. When the first resin layer 1 is carbon fiber, the second resin layer 5 is preferably glass fiber. Moreover, as another aspect, when the first resin layer 1 is made of glass fiber, it is preferable that the second resin layer 5 is made of carbon fiber.

(Thermoplastic second resin)
As the thermoplastic second resin contained in the second resin layer 5 of the present embodiment, a resin exemplified as the thermoplastic first resin can be used.

The molded body 10 of this embodiment of the present invention is obtained by disposing the second resin base material 25 on one side of the first resin base material 21 heated in a hot air circulating oven to obtain a laminate, followed by pressurizing and heating. It is obtained by pressurizing and heating the laminate with a machine and cooling and solidifying it. At this time, the first inorganic fibers and the second inorganic fibers are each compressed in the thickness direction. The first resin base material 21 is a material that provides the first resin layer 1 when the molded body 10 is formed. The second resin base material 25 is a material that provides the second resin layer 5 when the molded body 10 is formed.

According to the molded body 10 of the present embodiment, strength and rigidity are higher than those of a molded body having only a resin base material containing glass fibers.

<Method for collecting inorganic fibers>
In the method for recovering inorganic fibers according to the present embodiment, inorganic fibers are recovered from the molded article described above. The molded body 10 from which inorganic fibers are recovered satisfies the conditions described later. The inorganic fiber recovery method according to the present embodiment includes the following steps [1] to [3].

[1]: A step of heating the molded article 10 so that the surface temperature of the molded article 10 is between [Tp+30]°C and [Tp+70]°C.

[2]: A step of separating the heated first resin layer 1 and the second resin layer 5 from each other.

[3]: A step of heating the separated resin layer to a temperature equal to or higher than the decomposition temperature of the resin contained in the resin layer to remove the resin and collect inorganic fibers.

The above Tp (° C.) represents the lower melting point of the melting point of the first resin and the melting point of the second resin.

[Step [1]]
FIG. 2 is a schematic cross-sectional view showing step [1]. In step [1] above, when the surface temperature of the molded body 10 reaches [Tp+30]° C. or higher, the resin with the lower melting point begins to melt. When the resin with the lower melting point begins to melt, the force that causes the first inorganic fibers and the second inorganic fibers to return to the state before pressure molding is released. This causes a phenomenon (springback phenomenon) in which the first inorganic fibers and the second inorganic fibers swell in the thickness direction and return to the state before pressure molding. Since the first inorganic fiber and the second inorganic fiber are fibers different from each other, a difference occurs in the amount of springback, and the interface between the first resin layer 1 and the second resin layer 5 tends to become obvious. As a result, the first resin layer 1 and the second resin layer 5 are easily separated from each other.

On the other hand, when the surface temperature of the molded body 10 exceeds [Tp+70]° C., it reaches the decomposition temperature of at least the resin with the lower melting point, and the resin may be removed. When the resin is removed, the first inorganic fibers and the second inorganic fibers are entangled at the interface between the first resin layer 1 and the second resin layer 5, and the first resin layer 1 and the second resin layer 5 are pulled together. It cannot be peeled off. Therefore, the molded body 10 is heated so that the surface temperature of the molded body 10 becomes [Tp+70]° C. or lower.

In this specification, the melting points of the first resin and the second resin adopt values measured according to JIS K 7122.

In this specification, the surface temperature of the molded body 10 adopts a value measured with a radiation thermometer.

A method for heating the molded body 10 in the above step [1] is not particularly limited, but examples include a method of heating the molded body 10 using a known heating device such as an oven. The oven includes a hot air circulation heating device, a far-infrared heating device, and the like. The oven may also be a mid-infrared heating device.

The heating time in the above step [1] may be appropriately adjusted according to the type of heating device used. When using the hot air circulation heating device described above, the heating time of the compact 10 is preferably, for example, 10 minutes or more and 20 minutes or less. Moreover, when using the far-infrared heating device described above, the heating time of the molded body 10 is preferably, for example, 5 minutes or more and 10 minutes or less. When the heating time is within the above range, the first resin layer 1 and the second resin layer 5 are easily separated from each other.

In the inorganic fiber recovery method of the present embodiment, it is confirmed in advance that the molded article 10 used in the step [1] satisfies the following conditions.

<Condition>
At least one of the thickness ratio Y ₁ /X ₁ and the thickness ratio Y ₂ /X ₂ obtained by the evaluation method described below is 2 or more.

<Evaluation method>
(i): A piece of 50 mm×50 mm is cut out from the compact 10 to obtain a test piece.
(ii): The thickness _X1 of the first resin layer 1 and the thickness _X2 of the second resin layer 5 of the test piece are measured.
(iii): Heat the test piece so that the surface temperature of the test piece reaches [Tp+30]° C. with the melting point Tp as the base point.
(iv): The thickness _Y1 of the first resin layer 1 and the thickness _Y2 of the second resin layer 5 in the test piece after heating are measured.
(v) Obtain at least one of the thickness ratio _Y1 / _X1 and the thickness ratio _Y2 / _X2 .

Similar to the molded body 10, when the surface temperature of the test piece obtained from the molded body 10 reaches [Tp+30]° C., the springback phenomenon of the test piece occurs. In the above conditions, “at least one of the thickness ratio Y ₁ /X ₁ and the thickness ratio Y ₂ /X ₂ is 2 or more” means that in at least one resin layer of the test piece, the resin layer is deformed by heating. Springback means that the thickness of the resin layer after heating becomes twice or more the thickness of the resin layer before heating.

In this specification, the thicknesses X1 and _Y1 of the first resin layer 1 _and the thicknesses _X2 and _Y2 of the second resin layer 5 are measured in units of 0.1 mm using vernier calipers.

Hereinafter, assuming that the first inorganic fibers are glass fibers and the second inorganic fibers are carbon fibers, a configuration suitable for the inorganic fiber recovery method of the present embodiment will be described.

It is preferable that the mass content rate of the glass fiber with respect to the total mass of the first resin layer 1 of the present embodiment is 15% or more. When the mass content of the glass fibers is 15% or more, the first resin layer 1 tends to spring back due to heating, and the thickness ratio Y ₁ /X ₁ tends to be 2 or more. Further, the mass content of the glass fibers is preferably 60% or less, since it is easy to obtain the molded body 10 by molding the laminate containing the first resin base material 21 when manufacturing the molded body 10 .

It is preferable that the mass content of the carbon fibers with respect to the total mass of the second resin layer 5 of the present embodiment is 30% or more. When the mass content of the carbon fibers is 30% or more, the second resin layer 5 tends to spring back due to heating, and the thickness ratio Y ₂ /X ₂ tends to be 2 or more. Further, the mass content of the carbon fibers is preferably 80% or less, since it is easy to obtain the molded body 10 by molding the laminate including the second resin base material 25 when manufacturing the molded body 10 .

As used herein, the mass content of glass fibers is measured according to JIS K 7052. Moreover, the mass content rate of carbon fiber adopts the value measured based on JISK7075.

In addition, in the case of inorganic fibers such as glass fibers, whose surface is less likely to be oxidatively depleted by combustion in an air atmosphere, the mass content of the inorganic fibers is determined according to JIS K 7052, as in the case of glass fibers. Take the measured value. In addition, in the case of inorganic fibers such as carbon fibers, in which the surface is likely to be oxidatively depleted by combustion in an air atmosphere, the mass content of the inorganic fibers is determined according to JIS K 7075, as in the case of carbon fibers. Take the measured value.

The number average fiber length of the glass fibers is preferably 10 mm or longer, more preferably 20 mm or longer, still more preferably 30 mm or longer, particularly preferably 50 mm or longer, and particularly preferably 100 mm or longer. When the glass fiber is 10 mm or more, springback of the first resin layer 1 tends to occur due to heating, and the thickness ratio Y ₁ /X ₁ tends to be 2 or more. The number average fiber length of the glass fibers may be 300 mm or less.

The number average fiber length of the carbon fibers is preferably 20 mm or longer, more preferably 30 mm or longer, and particularly preferably 50 mm or longer. When the number average fiber length of the carbon fibers is 20 mm or more, the second resin layer 5 tends to spring back due to heating, and the thickness ratio Y ₂ /X ₂ tends to be 2 or more. The number average fiber length of carbon fibers may be 100 mm or less.

The number average fiber diameter of the glass fibers is preferably 1 μm or more and 50 μm or less, more preferably 5 μm or more and 20 μm or less.

The number average fiber diameter of the carbon fibers of the present embodiment is preferably 1 μm or more and 50 μm or less, more preferably 5 μm or more and 15 μm or less.

When the number average fiber diameter of the glass fiber and the carbon fiber is 1 μm or more, impact resistance and high strength of the molded article 10 can be easily obtained. Further, when the number average fiber diameter is 1 μm or more, the first resin layer 1 tends to spring back due to heating, and the thickness ratio Y ₁ /X ₁ tends to be 2 or more.

When the number average fiber diameter of the glass fibers and the carbon fibers is 50 μm or less, the glass fibers have sufficient flexibility, and the glass fibers are less likely to break during molding of the molded body 10 . As a result, impact resistance and high strength of the molded body 10 are likely to be obtained. It is known that the number average fiber diameters of the glass fibers and carbon fibers contained in the molded body 10 are almost the same as those of the raw materials used for manufacturing the molded body 10 .

As used herein, the number average fiber length and the number average fiber diameter are values measured by vernier caliper and micrometer or microscopic observation of the fibers obtained by the method for measuring the mass content rate described above.

[Step [2]]
FIG. 3 is a schematic cross-sectional view showing step [2]. In step [2] above, when the thickness of the first resin layer 1 is greater than the thickness of the second resin layer 5, it is preferable to fix the first resin layer 1 and peel off the second resin layer 5. As a result, the second resin layer 5 can be easily peeled off from the first resin layer 1, and work efficiency is improved.

Furthermore, when the thickness of the first resin layer 1 is greater than the thickness of the second resin layer 5, the tensile strength of the second resin layer 5 when the surface temperature of the molded body 10 is [Tp+70]° C. It is preferably 5 N/cm or more, more preferably 1.0 N/cm or more. As a result, when the second resin layer 5 is peeled off from the first resin layer 1, the second resin layer 5 is less likely to break, and work efficiency increases.

In this specification, the tensile strength of the second resin layer 5 adopts a value measured at a tensile speed of 100 mm/min in accordance with JIS L 1913.

In the above step [2], the peel strength between the first resin layer 1 and the second resin layer 5 is preferably 0.1 N/cm or more and less than 1.0 N/cm, and preferably 0.1 N/cm or more and 0.1 N/cm or more. More preferably less than 5 N/cm. When the thickness of the first resin layer 1 is greater than the thickness of the second resin layer 5, the peel strength between the first resin layer 1 and the second resin layer 5 is lower than the tensile strength of the second resin layer 5. is preferred. As a result, when the second resin layer 5 is peeled off from the first resin layer 1, the second resin layer 5 is less likely to break, and work efficiency increases.

In this specification, the peeling strength between the first resin layer 1 and the second resin layer 5 is a value measured at a peeling speed of 100 mm/min according to JIS K 6854-1.

The first thermoplastic resin forming the first resin layer 1 of the present embodiment may be the same as or different from the second thermoplastic resin forming the second resin layer 5 . When the first thermoplastic resin and the second thermoplastic resin have different melt viscosities, a difference in springback amount occurs, and the interface between the first resin layer 1 and the second resin layer 5 tends to become apparent. . As a result, the first resin layer 1 and the second resin layer 5 are easily separated from each other.

The holding time of the molded body 10 between the step [1] and the step [2] is preferably 0 minute or more and 1 minute or less, although it depends on the surrounding environment of the molded body 10 . When the holding time of the molded body 10 is 0 minute or more and 1 minute or less, the heated state of the molded body 10 can be easily maintained. Therefore, in the above step [2], the first resin layer 1 and the second resin layer 5 are easily separated from each other.

[Step [3]]
FIG. 4 is a schematic cross-sectional view showing step [3]. In the above step [3], the inorganic fibers are recovered by removing the resin from the separated resin layer by a known thermal decomposition method or the like.

According to the inorganic fiber recovery method of the present embodiment, the inorganic fibers can be recovered from the molded article 10 having increased strength and rigidity.

Although the preferred embodiments according to the present invention have been described above with reference to the accompanying drawings, it goes without saying that the present invention is not limited to such examples. The various shapes, combinations, etc., of the constituent members shown in the above examples are merely examples, and various modifications can be made based on design requirements and the like without departing from the gist of the present invention.

For example, in step [3], the separated resin layer may be either or both of the first resin layer 1 and the second resin layer 5 .

Further, for example, the molded body 10 of the present embodiment is a laminate in which the first resin layer 1 and the second resin layer 5 are laminated on "one side" of the first resin layer 1, but the present invention The molded article to which the method for recovering inorganic fibers according to the above can be applied is not limited to this. The molded body may be a laminate in which the first resin layer 1 and the second resin layers 5 arranged on "both sides" of the first resin layer 1 are laminated.

Further, for example, the molded body 10 of the present embodiment is composed of only the first resin layer 1 and the second resin layer 5, but the molded body to which the inorganic fiber recovery method according to the present invention can be applied is not limited to this. . The molded body may have three or more resin layers different from each other. In this case, the resin layers other than the first resin layer and the second resin layer contain inorganic fibers other than the first inorganic fibers and the second inorganic fibers.

When the molded body has three or more resin layers different from each other, in step [1], the lowest melting point of the resins contained in the three or more resin layers is defined as the melting point Tp.

When the molded body has three or more resin layers different from each other, it is preferable to heat the molded body in the step [1] in consideration of the melting point and decomposition temperature of each resin layer. Then, in the step [2], the resin layer is peeled off at the interface between the resin layer that has springed back due to heating and another resin layer adjacent to the resin layer. When the molded product has three or more resin layers different from each other, it is preferable to peel off the resin layers step by step by repeating the step [1] and the step [2] as necessary.

EXAMPLES The present invention will be specifically described below with reference to Examples, but the present invention is not limited to these.

<Tensile Strength of Second Resin Layer of Molded Body>
The tensile strength of the second resin layer of the molded body was a value measured at a tensile speed of 100 mm/min according to JIS L 1913.

In this measurement, a load cell with a maximum load of 100N was used. Therefore, when the test piece did not break even when the maximum load was applied to the test piece, the tensile strength was set to "20 N/cm or more" based on the maximum load and the sample width of 5 cm.

<Peel strength between first resin layer and second resin layer of molded body>
The peel strength between the first resin layer and the second resin layer of the molded article was measured at a peel speed of 100 mm/min according to JIS K 6854-1. In addition, when it was not possible to tear off, it was set as "impossible."

<Evaluation method for compact>
(i): A 50 mm×50 mm piece was cut out from the molded product to obtain a test piece.
(ii): The thickness _X1 of the first resin layer and the thickness _X2 of the second resin layer of the test piece were measured.
(iii): The test piece was heated so that the surface temperature of the test piece reached [Tp+30]° C. with the melting point Tp as the base point.
(iv): The thickness _Y1 of the first resin layer and the thickness _Y2 of the second resin layer in the test piece after heating were measured.
(v) At least one of the thickness ratio Y ₁ /X ₁ and the thickness ratio Y ₂ /X ₂ was obtained.

<Production of compact>
[Production Example 1]
As the first resin substrate, a GF mat/PP plate in which a mat made of glass fiber is impregnated with polypropylene (thickness: 3.8 mm, Wf: 40%, continuous fiber, number average fiber diameter: 15 μm, from the glass fiber used basis weight of mat: 900 g/m ² × 2 sheets). In addition, in the following description, Wf of the first resin base material represents the mass content rate of the glass fiber with respect to the total mass of the first resin base material. The melting point of the polypropylene contained in the first resin base material was 165° C. (manufacturer's nominal value).

As the second resin base material, a CF/PP mat made by mixing PAN-based carbon fiber and polypropylene fiber (Wf: 70%, number average fiber length of carbon fiber: 60 mm, number average fiber diameter of carbon fiber: 7 μm, polypropylene Number average fiber length of fibers: 60 mm, number average fiber diameter of polypropylene fibers: 50 μm, basis weight: 250 g/m ² ) was used. In addition, in the following description, Wf of the second resin base material represents the mass content of carbon fibers with respect to the total mass of the second resin base material. The melting point of the polypropylene fiber contained in the second resin base material was 165° C. (manufacturer's nominal value).

The second resin base material was placed on both sides of the first resin base material, and pressed at 5 MPa for 5 minutes in a hot platen at a temperature of 200° C. to obtain a double-sided laminate.

After the obtained double-sided laminate was cut into a predetermined size, it was left to stand for 10 minutes in a hot air circulating heating device set at 220°C so that the material reached 200°C. Next, the cut double-sided laminate was placed in a mold heated to 80° C. and held at a pressure of 10 MPa for 5 minutes, and then the molded body was removed from the mold.

[Production Example 2]
Using the same first resin base material and second resin base material as in Production Example 1, the first resin base material was left in a hot air circulation heating apparatus set at 220° C. for 10 minutes to heat. Next, the heated first resin base material was placed in a mold heated to 160° C. so as to be sandwiched between the second resin base materials, and held at a pressure of 5 MPa for 5 minutes. After that, the mold was cooled and the compact was removed from the mold.

[Production Example 3]
As the first resin base material, a GF mat/PA6 plate (thickness: 3.8 mm, Wf: 35%, continuous fiber, number average fiber diameter: 15 μm, glass fiber mat made of glass fiber impregnated with nylon 6, used glass fiber A mat basis weight: 900 g/m ² × 2 sheets) was used. The melting point of nylon 6 contained in the first resin base material was 215°C.

As the second resin base material, a CF/PA6 mat made by mixing PAN-based carbon fiber and nylon 6 fiber (Wf: 65%, number average fiber length of carbon fiber: 60 mm, number average fiber diameter of carbon fiber: 7 μm, Number average fiber length of nylon 6 fiber: 60 mm, number average fiber diameter of nylon 6 fiber: 50 μm, basis weight: 250 g/m ² ) was used. The melting point of the nylon 6 fiber contained in the second resin base material was 215°C.

The second resin base material was placed on both sides of the first resin base material and pressed at 5 MPa for 5 minutes in a hot platen at a temperature of 260° C. to obtain a double-sided laminate.

After the obtained double-sided laminate was cut into a predetermined size, it was heated by being left for 10 minutes in a hot air circulation heating device set at 280°C. Next, the cut double-sided laminate was placed in a mold heated to 100° C. and held at a pressure of 10 MPa for 5 minutes, after which the compact was removed from the mold.

[Production Example 4]
As the first resin base material, the same base material as the first resin base material used in Production Example 1 was used.

As the second resin base material, a prepreg including a single-layer base material containing polypropylene as a matrix resin and PAN-based carbon fibers having a number average diameter of 7 μm was used. The melting point of the polypropylene contained in the second resin base material was 165°C.

The first resin base material was left to stand for 10 minutes in a hot air circulating heating device set at 220° C. and heated. Next, the heated first resin base material was placed in a mold heated to 180° C. so as to be sandwiched between the second resin base materials, and held at a pressure of 5 MPa for 5 minutes. After that, the mold was cooled and the compact was removed from the mold.

[Production Example 5]
As the first resin base material, the same base material as the first resin base material used in Production Example 1 was used.

As the second resin base material, a prepreg containing polypropylene as a matrix resin and PAN-based carbon fibers having a number average diameter of 7 μm and a number average length of 1 mm was used. The melting point of the polypropylene contained in the second resin base material was 165°C.

The first resin base material was left to stand for 10 minutes in a hot air circulating heating device set at 220° C. and heated. Next, the heated first resin base material was placed in a mold heated to 180° C. so as to be sandwiched between the second resin base materials, and held at a pressure of 5 MPa for 5 minutes. After that, the mold was cooled and the compact was removed from the mold.

[Production Example 6]
As the first resin base material, the same base material as the first resin base material used in Production Example 1 was used.

As the second resin base material, CF/ A GF/PP mat (Wf(CF): 30%, Wf(GF): 20%) was used. Wf(CF) of the second resin base material represents the mass content of carbon fibers with respect to the total mass of the second resin base material. Wf(GF) of the second resin base material represents the mass content of the glass fibers with respect to the total mass of the second resin base material. The melting point of the polypropylene fiber contained in the second resin base material was 165°C.

The first resin base material was left to stand for 10 minutes in a hot air circulating heating device set at 220° C. and heated. Next, the heated first resin base material was placed in a mold heated to 160° C. so as to be sandwiched between the second resin base materials, and held at a pressure of 5 MPa for 5 minutes. After that, the mold was cooled and the compact was removed from the mold.

For the molded bodies of Production Examples 1 to 6, the thicknesses X ₁ , Y ₁ , X ₂ , Y ₂ and the thickness ratios Y ₁ /X ₁ , Y ₂ obtained using the above-described <Evaluation method for molded bodies> /X ₂ is shown in Table 1.

<Separation evaluation>
[Example 1]
First, the molded body of Production Example 1 was heated so that the surface temperature of the molded body reached 200°C. The surface temperature of 200° C. is 35° C. higher than the melting points of the first resin and the second resin.

Next, using the heated first resin layer and second resin layer, the first resin layer thicker than the second resin layer is fixed, the second resin layer is grasped, and the second resin layer is separated from the first resin layer. tore off. As a result, the first resin layer and the second resin layer could be separated.

[Example 2]
The procedure was the same as in Example 1, except that the molded product of Production Example 2 was used instead of the molded product of Production Example 1. As a result, the first resin layer and the second resin layer could be separated.

[Example 3]
The molded article of Production Example 3 was used in place of the molded article of Production Example 1, and the procedure was the same as in Example 1 except that the surface temperature of the molded article was set to 260°C. The surface temperature of 260° C. is 45° C. higher than the melting points of the first resin and the second resin.

As a result of the above operation, the first resin layer and the second resin layer could be separated.

[Comparative Example 1]
The procedure was the same as in Example 1, except that the molded product of Production Example 4 was used instead of the molded product of Production Example 1.

However, although a portion of the second resin layer that was grasped is separated from the first resin layer, it was difficult to separate the entire second resin layer from the first resin layer at one time.

[Comparative Example 2]
The procedure was the same as in Example 1, except that the molded product of Production Example 5 was used instead of the molded product of Production Example 1.

However, although a portion of the second resin layer that was grasped is separated from the first resin layer, it was difficult to separate the entire second resin layer from the first resin layer at one time.

Tensile strength of the second resin layer of the molded articles of Examples 1 to 3 and Comparative Examples 1 and 2, peel strength between the first resin layer and the second resin layer, separation evaluation of the first resin layer and the second resin layer The results are shown in Table 2. In the separation evaluation shown in Table 2, the case where the first resin layer and the second resin layer could be separated was indicated as "○", and the entire second resin layer was separated from the first resin layer at one time. When it was difficult to do, it was set as "x".

As shown in Table 2, in Examples 1 to 3 to which the present invention is applied, the first resin layer and the second resin layer are separated for the molded body in which the first resin layer and the second resin layer are laminated. was shown to be possible. This is because the first inorganic fibers and the second inorganic fibers are sufficiently spring-backed without being removed by thermal decomposition of the first resin and the second resin of the molding, and the first resin layer and the second resin layer are formed. It is considered that this is because the interface becomes more likely to become apparent.

In Examples 1 to 3, the separated first resin layer and second resin layer were heated to a temperature higher than the decomposition temperature of the resin contained in each resin layer to remove the resin, thereby recovering glass fibers and carbon fibers. It is considered possible.

Therefore, in Examples 1 to 3, it can be said that the inorganic fibers can be recovered from the molded body in which the first resin layer and the second resin layer are laminated.

From the above, it was shown that the present invention is useful.

DESCRIPTION OF SYMBOLS 1... 1st resin layer, 5... 2nd resin layer, 10... Molded object

Claims (5)

A method for recovering inorganic fibers comprising the following steps [1] to [3].
[1]: A first resin layer containing first inorganic fibers and a thermoplastic first resin, a second inorganic fiber different from the first inorganic fibers, and a second thermoplastic resin For a molded body in which a resin layer is laminated, and the molded body satisfies the following conditions:
A step of heating the molded body so that the surface temperature of the molded body is not less than [Tp+30]°C and not more than [Tp+70]°C.
(Tp (°C): the lower melting point of the melting point of the first resin and the melting point of the second resin)
[2]: A step of peeling off the heated first resin layer and the second resin layer from each other.
[3]: A step of heating at least one of the separated resin layers to a temperature equal to or higher than the decomposition temperature of the resin contained in the one resin layer to remove the resin, and recovering the inorganic fibers of the one.
<Condition>
For a test piece cut out from the molded body to 50 mm × 50 mm, when heated so that the surface temperature of the test piece is [Tp + 30] ° C., the thickness of the first resin layer before heating is X ₁ after heating The ratio Y ₁ /X ₁ of the thickness Y ₁ of the first resin layer and the ratio Y of the thickness Y ₂ of the second resin layer after heating to the thickness X ₂ of the second resin layer before heating ₂ /X ₂ is 2 or more. 2. The recovery of inorganic fibers according to claim 1, wherein in the step [2], the first resin layer is thicker than the second resin layer, the first resin layer is fixed, and the second resin layer is peeled off. Method. When the surface temperature of the molded body is [Tp + 70] ° C., the tensile strength of the second resin layer measured at a tensile speed of 100 mm / min according to JIS L 1913 is 0.5 N / cm or more. The method for recovering inorganic fibers according to claim 2, wherein In the step [2], according to JIS K 6854-1, the peel strength between the first resin layer and the second resin layer measured at a peel speed of 100 mm / min is 1.0 N / cm The method for recovering inorganic fibers according to any one of claims 1 to 3, wherein the recovery method is less than The inorganic material according to any one of claims 1 to 4, wherein the first inorganic fiber is one of carbon fiber and glass fiber, and the second inorganic fiber is the other of carbon fiber and glass fiber. Fiber recovery method.

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