Space filling material, space filling structure, and space structure and method for manufacturing the same

Abstract

To provide a space filler, a space filling structure, a space structure, and a manufacturing method thereof, which can improve compressive resistance.SOLUTION: A space filler (11) is made of a reinforcing fiber and a thermoplastic resin. A weight ratio of the thermoplastic resin is 40 to 85 wt %. The discontinuous reinforcing fibers have a plurality of intersections with each other. At least a portion of the intersections are bonded with the thermoplastic resin. Softening of the thermoplastic resin releases residual stress of the discontinuous reinforcing fibers to allow the discontinuous reinforcing fibers to expand.SELECTED DRAWING: Figure 3A

Description

Technical Field

[0001] The present invention relates to a space filling material, a space filling structure, a space structure, and a method for manufacturing the same, which can improve compression resistance.

Background Art

[0002] Conventionally, a thermally expandable composite material that expands upon heating and exhibits a fireproof and smoke-proof sealing function has been known. For example, Patent Document 1 (Japanese Patent Application Laid-Open No. 7-18249) discloses a thermally expandable inorganic fiber composite material characterized by forming a mixture composed of acid-treated graphite as an expanding agent, inorganic fibers as a heat-resistant reinforcing agent, an inorganic binder as a heat-resistant binder, and an organic binder as a form-retaining material before heating into a sheet shape by a papermaking method, and it is described that it is used for a sealing material for a fire door.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, the thermally expandable inorganic fiber composite material of Patent Document 1 is only used for the purpose of exhibiting a sealing function such as fireproofing and smoke-proofing. Further, in Patent Document 1, since the organic binder is burned out, a network of inorganic fibers and the organic binder is not formed. Therefore, when a load is applied to the composite material, breakage of the fibers occurs, and a so-called sag occurs in which the thickness change after compression becomes large (the compression resistance deteriorates). Due to this sag of the composite material, the fixing of the material to be fixed becomes loose, and the material to be fixed cannot be held at a desired position.

[0005] Accordingly, an object of the present invention is to solve such problems in the prior art and to provide a space filler, a space filling structure, a space structure, and a method for manufacturing the same, which can improve compression resistance.

Means for Solving the Problems

[0006] As a result of intensive studies to achieve the above object, the present inventors have found that when a space filler is composed of discontinuous reinforcing fibers and a thermoplastic resin, and the weight ratio of the thermoplastic resin in the space filler is set to a specific ratio while maintaining the expansibility by the discontinuous reinforcing fibers, in the space structure obtained after the space filler expands, the thermoplastic resin can be used as a matrix, and the adhesion between the discontinuous reinforcing fibers and the thermoplastic resin (fiber-resin network) can be strengthened. Furthermore, when a compression load is applied to the space structure in which such a space filler is expanded, the stress acting on the discontinuous reinforcing fibers can be reduced by the fiber-resin network, and breakage of the discontinuous reinforcing fibers and peeling between the fibers and the resin can be suppressed. As a result, it was confirmed that the change in thickness after compression becomes small, and the present invention was completed.

[0007] That is, the present invention can be configured in the following aspects. 〔Aspect 1〕 A space filler composed of discontinuous reinforcing fibers and a thermoplastic resin, wherein the weight ratio of the thermoplastic resin is 40 to 85 wt% (preferably 45 to 82 wt%, more preferably 50 to 80 wt%), the discontinuous reinforcing fibers have a plurality of intersections, and at least a part of those intersections is adhered with the thermoplastic resin, and the residual stress of the discontinuous reinforcing fibers is released and expanded by the softening of the thermoplastic resin. 〔Aspect 2〕 The space filler according to Aspect 1, wherein the weight ratio of the discontinuous reinforcing fibers is 15 to 60 wt% (preferably 18 to 55 wt%, more preferably 20 to 50 wt%). 〔Aspect 3〕 The space filler according to aspect 1 or 2, wherein the fiber length of the discontinuous reinforcing fiber is 5 to 100 mm (preferably 5 to 80 mm, more preferably 5 to 50 mm). 〔Aspect 4〕 The space filler according to any one of aspects 1 to 3, wherein the glass transition temperature of the thermoplastic resin is 100 °C or higher (preferably 105 °C or higher, more preferably 110 °C or higher). 〔Aspect 5〕 The space filler according to any one of aspects 1 to 4, wherein the thermoplastic resin is at least one thermoplastic resin selected from the group consisting of thermoplastic polyimide resins, polyether ketone resins, semi-aromatic polyamide resins, polycarbonate resins, liquid crystal polyester resins, polysulfone resins, and polytetrafluoroethylene resins. 〔Aspect 6〕 The space filler according to any one of aspects 1 to 5, wherein the discontinuous reinforcing fiber is an insulating fiber. 〔Aspect 7〕 The space filler according to any one of aspects 1 to 6, which is used to fix a material to be fixed within a predetermined space. 〔Aspect 8〕 The space filler according to any one of aspects 1 to 7, wherein the porosity is 40% or less (preferably less than 30%, more preferably 20% or less). 〔Aspect 9〕 A space filling structure comprising the space filler according to aspect 7 and a material to be fixed integrally in contact with at least a part thereof. 〔Aspect 10〕 The space filling structure according to aspect 9, wherein the material to be fixed is sandwiched by the space filler. 〔Aspect 11〕 A space structure composed of discontinuous reinforcing fibers and a thermoplastic resin, wherein the thermoplastic resin is used as a matrix, and the thickness change rate when a load of 20 MPa is repeatedly applied 10 5 times is 40% or less (preferably 35% or less, more preferably 30% or less). 〔Aspect 12〕 A method for manufacturing a spatial structure in which the space filler described in any one of Aspects 1 to 9 is expanded by heating at a temperature equal to or higher than the softening point of the thermoplastic resin.

Advantages of the Invention

[0008] According to the space filler of the present invention, the space filler is composed of discontinuous reinforcing fibers and a thermoplastic resin. By maintaining the expandability by the discontinuous reinforcing fibers and setting the weight ratio of the thermoplastic resin in the space filler to a specific ratio, in the expanded space filler, the thermoplastic resin can be used as a matrix, and the adhesion area between the discontinuous reinforcing fibers and the thermoplastic resin, that is, the fiber-resin network, can be increased, and the stress acting on the discontinuous reinforcing fibers when a compressive load is applied can be reduced. As a result, in the expanded space filler, breakage of the discontinuous reinforcing fibers and peeling between the fibers and the resin are suppressed, and the compression resistance can be improved.

Brief Description of the Drawings

[0009] This invention will be more clearly understood from the following description of preferred embodiments with reference to the accompanying drawings. The drawings are not necessarily drawn to scale and are exaggerated for the purpose of showing the principle of the present invention. However, the embodiments and the drawings are for illustration and explanation only and should not be used to define the scope of this invention. The scope of this invention is determined by the appended claims.

Figure 1

Figure 2

Figure 3A

Figure 3B

Figure 4A

Figure 4B

Figure 5A

Figure 5B

Mode for Carrying Out the Invention

[0010] Hereinafter, the present invention will be described in detail with reference to the drawings. <Space filler> FIG. 1 is an enlarged conceptual cross-sectional view for explaining the state of intersections between discontinuous reinforcing fibers 1 in a space filler according to an embodiment of the present invention, and FIG. 2 is an enlarged conceptual view partially showing a part of the space filler according to an embodiment of the present invention.

[0011] The space filler of the present invention is composed of discontinuous reinforcing fibers and a thermoplastic resin. In the space filler before expansion, the discontinuous reinforcing fibers are randomly oriented and have a plurality of intersections, and at least a part of the intersections of the discontinuous reinforcing fibers is adhered with the thermoplastic resin. At the intersections of the discontinuous reinforcing fibers, as shown in FIG. 1, the intersections of the discontinuous reinforcing fibers 1 are firmly adhered by the thermoplastic resin 2. For example, the thermoplastic resin 2 may exist in a water-scraping shape with respect to the discontinuous reinforcing fibers 1. As shown in FIG. 2, the discontinuous reinforcing fibers 1 may be embedded in the thermoplastic resin 2 forming a matrix. In FIG. 2, the thermoplastic resin at the intersection part is omitted. By adopting such a structure, the structural strength of the space filler is improved. The space filler can be filled at least in the thickness direction by the expansion stress during heating within a predetermined space. The expansion stress refers to the stress generated when the space filler expands and is constrained by an outer member surrounding the space.

[0012] <Discontinuous reinforcing fibers> The discontinuous reinforcing fibers used in the present invention are not particularly limited as long as the effects of the present invention are not impaired, and may be organic fibers or inorganic fibers. Further, the discontinuous reinforcing fibers may be used alone either organic fibers or inorganic fibers, or may be used in combination of organic fibers and inorganic fibers. In the present invention, in the space filler, the discontinuous reinforcing fibers adhered with a thermoplastic resin have residual stress, and the residual stress is released by the softening of the thermoplastic resin, and the space filler expands due to the repulsive force of the discontinuous reinforcing fibers whose residual stress has been released.

[0013] Examples of the inorganic fibers include glass fibers, carbon fibers, various ceramic fibers, various metal fibers, and the like. Examples of the various ceramic fibers include silicon carbide fibers, silicon nitride fibers, silica fibers, alumina fibers, zirconia fibers, boron fibers, basalt fibers, and the like. Examples of the various metal fibers include gold, silver, copper, iron, nickel, titanium, stainless steel, and the like. The organic fibers are not particularly limited as long as their glass transition temperature or melting point is higher than the softening point of the thermoplastic resin that adheres to the intersections of the discontinuous reinforcing fibers. Examples of the organic fibers include wholly aromatic polyester-based fibers, polyphenylene sulfide fibers, para-aramid fibers, polysulfonamide fibers, phenolic resin fibers, polyimide fibers, fluorine fibers, and the like. Among these, from the viewpoint of increasing the repulsive force when expanding the space filler, it is preferable to use inorganic fibers with a high elastic modulus such as glass fibers or carbon fibers. In the space filler after expansion, that is, in the space structure, in the case of applications where insulation is required, insulating fibers may be used. Examples of such insulating fibers include glass fibers, silicon nitride fibers, silica fibers, alumina fibers, and the like.

[0014] From the viewpoint of increasing the resilience, the average fiber length of the discontinuous reinforcing fibers used in the present invention is preferably 5 to 100 mm. More preferably, it may be 5 to 80 mm, and still more preferably 5 to 50 mm. The average fiber length of the discontinuous reinforcing fibers is a value measured by the method described in the examples below. From the viewpoint of increasing the resilience, the average fiber diameter of the single fibers of the discontinuous reinforcing fibers used in the present invention is preferably 2 to 40 μm. More preferably, it may be 3 to 30 μm, and still more preferably 4 to 25 μm. The average fiber diameter of the single fibers of the discontinuous reinforcing fibers is a value measured by the method described in the examples below.

[0015] From the viewpoint of increasing the resilience, the discontinuous reinforcing fibers used in the present invention preferably have a tensile elastic modulus of 10 GPa or more. More preferably, it may be 30 GPa or more, and still more preferably 50 GPa or more. There is no particular limitation on the upper limit of this tensile elastic modulus, but it may be 1000 GPa or less. The tensile elastic modulus can be measured by a method conforming to the standards suitable for each fiber, such as JIS R 7606 for carbon fibers, JIS R 3420 for glass fibers, and JIS L 1013 for organic fibers.

[0016] <Thermoplastic resin> In the present invention, a thermoplastic resin is used as a constituent material of the space filler. Due to the softening of the thermoplastic resin, the discontinuous reinforcing fibers constrained by the thermoplastic resin are released to expand the space filler. As a result, the thermoplastic resin can be used as a matrix after the space filler is expanded. In the space filler of the present invention, a high pressing force is applied to the outer member by the expansion stress of the space filler, and at the same time, the force of the molten thermoplastic resin matrix being pressed against and adhered to the outer member can also act. Examples of the thermoplastic resin include vinyl resins (polymers or derivatives thereof synthesized from monomers having a vinyl group CH2=CH- or a vinylidene group CH2=C<), aliphatic polyamide resins (such as polyamide 6, polyamide 66, polyamide 11, polyamide 12, polyamide 610, polyamide 612, etc.), semi-aromatic polyamide resins, and wholly aromatic polyamide resins; polyester resins such as polyethylene terephthalate, polytrimethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate; fluorine resins such as polytetrafluoroethylene resins; thermoplastic polyimide resins such as semi-aromatic polyimide resins, polyamideimide resins, and polyetherimide resins; polysulfone resins such as polysulfone resins and polyethersulfone resins; modified polyphenylene ether resins; polyether ketone resins such as polyether ketone resins, polyether ether ketone resins, and polyether ketone ketone resins; polycarbonate resins; amorphous polyarylate resins; liquid crystal polyester resins such as wholly aromatic polyester resins; and thermoplastic elastomers such as urethane-based, styrene-based, olefin-based, vinyl chloride-based, ester-based, and amide-based thermoplastic elastomers. These thermoplastic resins may be used alone or in combination of two or more thereof.

[0017] In addition, when the thermoplastic resin used in the present invention is for applications where heat resistance is required in the space structure obtained by expanding the space filler, it is preferable to use a thermoplastic resin having a glass transition temperature of 100°C or higher. For example, as the thermoplastic resin having a glass transition temperature of 100°C or higher, polytetrafluoroethylene-based resins, thermoplastic polyimide-based resins, polysulfone-based resins, semi-aromatic polyamide-based resins, polyether ketone-based resins, polycarbonate-based resins, liquid crystal polyester-based resins, etc. can be mentioned. Among these, from the viewpoints of mechanical properties and moldability, the thermoplastic resin may be at least one thermoplastic resin selected from the group consisting of thermoplastic polyimide-based resins (preferably polyetherimide-based resins), polyether ketone-based resins (preferably polyetheretherketone-based resins), semi-aromatic polyamide-based resins, polycarbonate-based resins, and polysulfone-based resins. In applications where heat resistance is required, the glass transition temperature of the thermoplastic resin may preferably be 105°C or higher, more preferably 110°C or higher. There is no particular limitation on the upper limit of the glass transition temperature, but from the viewpoint of economically using the space filler, it may be 300°C or lower. The glass transition temperature is a value measured by the method described in the examples below.

[0018] In addition, the thermoplastic resin used in the present invention may contain various additives as long as the effects of the present invention are not impaired.

[0019] <Method for manufacturing space filler> The method for manufacturing the space filler of the present invention may at least include a step of preparing a composite sheet containing discontinuous reinforcing fibers and a thermoplastic resin, a step of heating the composite sheet to a temperature equal to or higher than the softening point of the thermoplastic resin and performing hot pressing by applying pressure in the thickness direction, and a step of cooling to a temperature lower than the softening point of the thermoplastic resin while applying pressure. In the present invention, the "softening point" mainly means the heat distortion temperature in the thermoplastic resin, and may be, for example, the heat deflection temperature (JIS K 7207). In particular, in the case of an amorphous resin, it means its glass transition temperature.

[0020] The composite sheet contains discontinuous reinforcing fibers and a thermoplastic resin, and is a material capable of forming a space filler through a hot pressing process and a cooling process, and sheets in various forms can be used. Examples of the composite sheet include, for example, a mixed nonwoven fabric of discontinuous reinforcing fibers and thermoplastic fibers, or a nonwoven fabric of discontinuous reinforcing fibers in which particulate (or powdery) thermoplastic resin is dispersed. Preferably, it may be a mixed nonwoven fabric of discontinuous reinforcing fibers and thermoplastic fibers. Further, from the viewpoint of the uniformity of the distribution of the discontinuous reinforcing fibers and the thermoplastic fibers, it is more preferably a wet nonwoven fabric containing discontinuous reinforcing fibers and thermoplastic fibers (for example, a mixed paper, hereinafter, in the present invention, a mixed nonwoven fabric produced by a wet papermaking method is referred to as a mixed paper).

[0021] When using a mixed nonwoven fabric as the composite sheet, thermoplastic fibers obtained by fibrillating the above thermoplastic resin by a known method can be used.

[0022] From the viewpoint of improving the dispersibility of the discontinuous reinforcing fibers, the single fiber fineness of the thermoplastic fibers is preferably 0.1 to 20 dtex. In order to obtain a space filler excellent in expansion stress during heating, it is desirable to disperse the discontinuous reinforcing fibers in the mixed nonwoven fabric evenly. The single fiber fineness of the thermoplastic fibers may be more preferably 0.5 to 18 dtex, and even more preferably 1 to 16 dtex. The single fiber fineness is a value measured by the method described in the examples below.

[0023] From the viewpoint of improving the dispersibility of the reinforcing fibers, the average fiber length of the thermoplastic fibers is preferably 0.5 to 60 mm, more preferably 1 to 55 mm, and even more preferably 3 to 50 mm. The average fiber length is a value measured by the method described in the examples below. Regarding the cross-sectional shape of the fibers at that time, there is no particular limitation, and it may have a special cross-section such as circular, hollow, flat, or star-shaped.

[0024] When using a thermoplastic fiber with a softening point of 100°C or higher as the thermoplastic fiber, a binder component may be included as necessary. The proportion of the binder component may be, for example, 10 wt% or less based on the mixed nonwoven fabric. The shape of the binder component may be fibrous, particulate, liquid, etc., but from the perspective of forming the nonwoven fabric, binder fibers are preferred. The binder component is not particularly limited, and examples include polyolefin resins, polyamide resins, polyester resins, acrylic resins, polyvinyl alcohol resins, polyurethane resins, etc., with polyester resins being preferred. These binder components correspond to the components constituting the thermoplastic resin of the obtained space filler. From the perspective that the binder component becomes part of the matrix as a thermoplastic resin, it is preferable to use a binder component having compatibility with the thermoplastic fiber. In that case, the obtained space filler has an integrated matrix and thus excellent strength.

[0025] The polyester resin may be composed of a polyester polymer containing terephthalic acid component (a) and isophthalic acid component (b) among the dicarboxylic acid components with their copolymerization ratio (molar ratio) being (a) / (b) = 100 / 0 to 40 / 60 (preferably 99 / 1 to 40 / 60). By using such a polyester resin, the strength of the mixed nonwoven fabric can be improved due to good binder properties, so it has excellent processability and can suppress thermal decomposition during high-temperature molding. Also, since such a polyester resin has compatibility with a thermoplastic polyimide resin (preferably a polyetherimide resin), it is particularly preferable as a binder component when using thermoplastic fibers made of a polyimide resin. More preferably, (a) / (b) = 90 / 10 to 45 / 55, and even more preferably, (a) / (b) = 85 / 15 to 50 / 50.

[0026] As long as the effects of the present invention are not impaired, the polyester resin may contain a small amount (for example, 5 mol% or less) of other dicarboxylic acid components other than terephthalic acid and isophthalic acid, in one kind or a combination of multiple kinds. In addition, as the diol component constituting the polyester resin, ethylene glycol can be used as the diol component, but a small amount (for example, 5 mol% or less) of other diol components other than ethylene glycol may be included alone or in combination of two or more.

[0027] The method for producing the nonwoven fabric is not particularly limited, and examples thereof include the spunlace method, the needle punch method, the steam jet method, the dry papermaking method, and the wet papermaking method (wet laid process). Among them, from the viewpoints of production efficiency and uniform dispersion of the discontinuous reinforcing fibers in the nonwoven fabric, the wet papermaking method is preferable. For example, in the wet papermaking method, an aqueous slurry containing thermoplastic fibers and discontinuous reinforcing fibers is prepared, and then this slurry may be subjected to a normal papermaking process. The aqueous slurry may contain, if necessary, the above binder fibers (for example, water-soluble polymer fibers such as polyvinyl alcohol-based fibers, heat-sealing fibers such as polyester-based fibers), etc. Further, in order to improve the uniformity and crimpability of the nonwoven fabric, the binder component may be applied by spray drying, or a heat pressing step may be added after the wet papermaking step.

[0028] The basis weight of the nonwoven fabric is not particularly limited, but it is preferably 2 5 to 1500 g / m 2 More preferably, it is 10 to 1000 g / m 2 and even more preferably 20 to 500 g / m

[0029] In the hot pressing process, the composite sheet may be heated to a temperature equal to or higher than the softening point of the thermoplastic resin, and hot pressed by applying pressure in the thickness direction. By heating and pressurizing the composite sheet in the thickness direction, the discontinuous reinforcing fibers can impart residual stress in the thickness direction. There are no particular restrictions on the method of hot pressing, and general compression molding methods such as stampable molding, pressure molding, vacuum pressure bonding molding, and GMT molding are preferably used. The molding temperature at that time may be set according to the softening point and decomposition temperature of the thermoplastic resin used. The heating temperature is preferably equal to or higher than the softening point of the thermoplastic resin. For example, when the thermoplastic resin is crystalline, the heating temperature is preferably in the range of equal to or higher than the melting point of the thermoplastic resin and (melting point + 100)°C or lower. When the thermoplastic resin is amorphous, the heating temperature is preferably in the range of equal to or higher than the glass transition temperature of the thermoplastic resin and (glass transition temperature + 200)°C or lower. In addition, if necessary, preheating may be performed with an IR heater or the like before hot pressing.

[0030] Also, the pressure during hot pressing is not particularly limited, but it is usually carried out at a pressure of 0.05 MPa or more. More preferably, it may be 0.1 MPa or more, and even more preferably 0.5 MPa or more. The upper limit is not particularly limited, but it may be about 30 MPa. The time during hot pressing is not particularly limited, but since the thermoplastic resin may deteriorate when exposed to high temperature for a long time, it is usually preferably within 30 minutes, more preferably within 25 minutes, and even more preferably within 20 minutes. The lower limit is not particularly limited, but it may be about 1 minute.

[0031] In the hot pressing process, the above composite sheets can be stacked in one or more layers and hot pressed. For example, although the preferred conditions vary depending on the basis weight of the composite sheet, the thickness of the desired space filler, etc., from the viewpoint of reducing the rate of change in thickness after compression of the space structure in which the space filler is expanded and improving the compression resistance, a multilayer body in which the above composite sheets are stacked in a plurality (for example, 2 to 100 sheets, preferably 3 to 50 sheets) may be hot pressed.

[0032] In addition, in order to adjust the thickness and density of the obtained space filler, the type of discontinuous reinforcing fiber and the applied pressure can be appropriately set. Furthermore, the shape of the obtained space filler is not particularly limited and can be appropriately set. Depending on the purpose, multiple laminated mixed nonwoven fabrics with different specifications or mixed nonwoven fabrics with different specifications can be separately arranged in a mold of a certain size and then hot-pressed.

[0033] In the cooling process, while applying the pressure in the hot-pressing process, cooling to a temperature lower than the softening point of the thermoplastic resin can obtain a space filler having a predetermined shape.

[0034] From the viewpoint of reducing the thickness change rate after compression of the space structure obtained by expanding the space filler of the present invention and improving the compression resistance, the weight ratio of the thermoplastic resin is 40 to 85 wt%. More preferably, it may be 45 to 82 wt%, and still more preferably 50 to 80 wt%. The weight ratio of the thermoplastic resin indicates the weight ratio of the thermoplastic resin in the total weight of the space filler. If the weight ratio of the thermoplastic resin is too small, the ratio of the discontinuous reinforcing fiber increases, so that the stress acting on the discontinuous reinforcing fiber becomes high when a load is applied to the expanded space filler. For this reason, the thickness change after compression of the space structure becomes large (the compression resistance deteriorates). On the contrary, if the weight ratio of the thermoplastic resin is too large, the expandability of the space filler may become insufficient and it may not be established as a space filler. Note that the thermoplastic resin contained in the space filler may contain a binder component used as necessary for manufacturing the nonwoven fabric as a composite sheet.

[0035] In view of reducing the thickness change rate of the space structure after compression of the space filler in which the space filler is expanded and improving the compression resistance, the weight ratio of the discontinuous reinforcing fiber is preferably 15 to 60 wt%, more preferably 18 to 55 wt%, and even more preferably 20 to 50 wt%. The weight ratio of the discontinuous reinforcing fiber indicates the weight ratio of the discontinuous reinforcing fiber in the total weight of the space filler. When the weight ratio of the discontinuous reinforcing fiber is less than 15 wt%, the expandability of the space filler itself may deteriorate. When the weight ratio of the discontinuous reinforcing fiber exceeds 60 wt%, the thickness change rate after compression may undesirably increase.

[0036] In view of increasing the expandability and the expansion stress during heating of the space filler, the volume ratio (discontinuous reinforcing fiber: thermoplastic resin) of the discontinuous reinforcing fiber and the thermoplastic resin in the space filler may be 10:90 to 70:30. When the volume ratio of the thermoplastic resin to the discontinuous reinforcing fiber is too small, when the space filler expands within a predetermined space and contacts the wall surface (or the material to be fixed) of the space, the contact area where the thermoplastic resin contacts becomes small, so the stress contributing to the strength of reinforcing the outer member or fixing the material to be fixed may be insufficient. Also, when the volume ratio of the thermoplastic resin to the discontinuous reinforcing fiber is too large, the amount of the discontinuous reinforcing fiber present is insufficient, and the expandability may be insufficient. The volume ratio (discontinuous reinforcing fiber: thermoplastic resin) of the discontinuous reinforcing fiber and the thermoplastic resin is preferably 15:85 to 65:35, and more preferably 20:80 to 60:40.

[0037] From the viewpoint of enhancing expandability and expansion stress during heating, the porosity (before expansion or before use) of the space filler of the present invention may be 40% or less, preferably less than 30%, more preferably 20% or less. If the porosity before expansion is too large, there is little room for expansion, so the expandability may be insufficient. Also, the lower limit of the porosity (before expansion or before use) is not particularly limited and may be 0%. From the viewpoint of preventing excessive compressive force from being applied to the discontinuous reinforcing fibers in the space filler, it is preferably 0.5% or more, more preferably 1% or more. Here, the porosity indicates the ratio of the volume occupied by voids to the bulk volume of the space filler and is a value measured by the method described in the examples below.

[0038] The average thickness of the space filler of the present invention can be various thicknesses according to the space to be filled and the application. For example, it can be selected from a wide range of 0.01 to 20 mm. However, from the viewpoint of inserting it into a narrow gap and enabling accurate filling, it may be 10 to 1000 μm, preferably 20 to 500 μm, more preferably 50 to 300 μm. The average thickness of the space filler is a value measured by the method described in the examples below.

[0039] When the space filler of the present invention is in a particularly narrow gap (for example, a space with a thickness of about 20 to 5000 μm), in order to make it easy to insert and accurately fill the gap, it is preferable that its thickness is uniform. For example, the CV value of the thickness may be 0.2 or less, more preferably 0.1 or less, even more preferably 0.08 or less, and even more preferably 0.05 or less. Here, the CV value of the thickness of the space filler refers to the ratio of the standard deviation of the measured thickness to the average thickness and is a value measured by the method described in the examples below.

[0040] The average basis weight of the space filler of the present invention can be various basis weights according to the space to be filled and the application. For example, it can be selected from a wide range of 10 to 10000 g / m 2 but from the viewpoint of enabling accurate filling even in a narrow space, it is 10 to 500 g / m2 It may be, preferably 20 to 400 g / m 2 , more preferably 50 to 300 g / m 2 It may be. The average basis weight of the space filler is a value measured by the method described in the examples below.

[0041] From the viewpoint of enabling accurate filling of the space, the CV value of the basis weight of the space filler of the present invention may be 0.2 or less, more preferably 0.15 or less, still more preferably 0.1 or less, and even more preferably 0.05 or less. The CV value of the basis weight of the space filler refers to the ratio of the standard deviation of the measured basis weight to the average basis weight, and is a value measured by the method described in the examples below.

[0042] The density of the space filler of the present invention can be various densities depending on the space to be filled and the application, but 0.5 to 3 g / cm 3 It may be, preferably 0.6 to 2.5 g / cm 3 , more preferably 0.7 to 2 g / cm 3 It may be. The density of the space filler is a value measured by the method described in the examples below.

[0043] The shape of the space filler of the present invention can be various shapes depending on the space to be filled and the application, and includes a three-dimensional shape having a three-dimensional structure. In the case of a three-dimensional shape, the direction of thermal expansion is the thickness direction. From the viewpoint of inserting it into a narrow gap and enabling accurate filling, it is preferably plate-shaped.

[0044] The space filler of the present invention preferably has a maximum expansion ratio in the thickness direction of 120% or more, more preferably 150% or more, still more preferably 170% or more, and even more preferably 200% or more. The upper limit of the maximum expansion ratio in the thickness direction is not particularly limited, and it may be 500%. When the maximum expansion ratio in the thickness direction is in the above range, the strength for reinforcement and / or fixation can be made sufficient. The maximum expansion ratio in the thickness direction of the space filler indicates the expansion ratio when heated under no pressure and is a value measured by the method described in the examples below.

[0045] From the viewpoint of suppressing gas generation, the space filler of the present invention preferably does not substantially contain volatile substances (for example, low molecular compounds having a boiling point lower than the heating temperature), foaming agents, expanded graphite, etc. that volatilize when heated, and the total amount of volatile substances in the space filler may be less than 0.5 wt%.

[0046] <Method of using the space filler> The method of using the space filler of the present invention may include a step of expanding the space filler in a predetermined space by heating at a temperature equal to or higher than the softening point of the thermoplastic resin. In the present invention, the predetermined space may be a space (gap) surrounded by a single outer member or a space (gap) formed by a plurality of outer members. Further, the space filler may fill the entire predetermined space or may fill a part thereof.

[0047] A description will be given based on FIGS. 3A and 3B, which represent schematic cross-sectional views of a first embodiment of the method for using the space filler of the present invention. FIG. 3A shows the state of the space filler 11 before expansion, and FIG. 3B shows the state of the space filler 11 after expansion. In FIG. 3A, the space filler 11 is inserted into the space 13 surrounded by the outer member 12. In FIG. 3A, the space 13 is formed by being entirely surrounded by a single outer member 12, but it does not have to be a closed space entirely surrounded by the outer member. For example, an open space may be formed in part, such as a bottomed open-shaped concave shape. Also, the space may be formed by a plurality of different members. Also, a plurality of space fillers 11 may be inserted into the space 13. Note that in FIG. 3A, a part of the outer member 12 is shown.

[0048] By heating at a temperature equal to or higher than the softening point of the thermoplastic resin constituting the space filler 11, the thermoplastic resin softens. Due to the softening of this thermoplastic resin, the residual stress of the discontinuous reinforcing fibers is released, and the repulsive force (restoring force) of the discontinuous reinforcing fibers is generated in the thickness direction. Then, the space filler 11 irreversibly expands in the thickness direction (the Z direction in FIG. 3A) and fills the space 13 as shown in FIG. 3B. A high pressing force is applied to the wall surface of the space 13 by the expansion stress of the space filler 11, and at the same time, the molten thermoplastic resin is pressed against the outer member 12 and adheres thereto, so that the outer member 12 is sufficiently reinforced.

[0049] In the step of expanding the space filler 11, the heating temperature is not particularly limited as long as there are no limitations such as the heat resistance of the outer member or the member to be fixed. For example, based on the softening point of the thermoplastic resin, it may be (softening point + 10) °C or higher, preferably (softening point + 30) °C or higher, and more preferably (softening point + 50) °C or higher. The upper limit of the heating temperature may be, for example, (softening point + 250) °C or lower, preferably (softening point + 200) °C or lower, and more preferably (softening point + 150) °C or lower from the viewpoint of particularly suppressing the deterioration of the thermoplastic resin.

[0050] In the expansion process, the space filler may expand rapidly, but may have an overall uniform structure by expanding slowly. For example, the heating time for expansion may be about 1 minute to 1 hour, preferably about 10 to 50 minutes.

[0051] In addition, the method of using the space filler of the present invention may include a step of inserting the space filler into a predetermined space prior to the expansion step.

[0052] In the present invention, from the viewpoint of improving the mechanical strength and liquid permeability of the space filler after expansion (filling), the expansion rate during filling in the thickness direction may be 120 to 400%, preferably 130 to 300%, more preferably 140 to 250%. The expansion rate during filling in the thickness direction is represented by the following formula. Expansion rate during filling (%) = Average thickness of the space filler after filling (thickness of the space to be filled) (mm) / Average thickness of the space filler before filling (mm) × 100

[0053] In addition, the method of using the space filler of the present invention may include a step of expanding the space filler in a predetermined space by heating at a temperature equal to or higher than the softening point of the thermoplastic resin to fix the material to be fixed. The space filler of the present invention may be used as a fixing material for fixing the material to be fixed.

[0054] For example, the description will be given based on FIGS. 4A and 4B showing a schematic cross-sectional view of the second embodiment of the method for using the space filler of the present invention. FIG. 4A shows the state of the space filler 21 before expansion, and FIG. 4B shows the state of the space filler 21 after expansion. In FIG. 4A, a material to be fixed 24 sandwiched between two space fillers 21 is inserted as a space filling structure 25 into a space 23 surrounded by an outer member 22. In FIG. 4A, the space 23 is formed by being entirely surrounded by a single outer member 22, but it is not necessary for the space to be a closed space entirely surrounded by the outer member. For example, an open space may be formed in part, such as a concave shape with a bottomed open shape. Also, the space may be formed by a plurality of different members. Further, although the space fillers 21 are inserted by being laminated one by one on both sides of the material to be fixed 24, the number of laminated sheets and the insertion positions are not limited, and one or a plurality of sheets may be laminated and inserted on at least one surface of the material to be fixed 24. The space fillers 21 laminated on both sides of the material to be fixed 24 may be the same or different, but from the viewpoint of enhancing the uniformity of expandability, it is preferably the same. Note that in FIG. 4A, a part of the outer member 22 is shown.

[0055] By heating at a temperature equal to or higher than the softening point of the thermoplastic resin constituting the space filler 21, the thermoplastic resin softens. Due to this softening of the thermoplastic resin, the residual stress of the discontinuous reinforcing fibers is released, and the repulsive force (restoring force) of the discontinuous reinforcing fibers is generated in the thickness direction. Then, the space filler 21 irreversibly expands in the thickness direction (Z direction in FIG. 4A), and as shown in FIG. 4B, fills the space 23 together with the material to be fixed 24. A high pressing force is applied to the wall surface of the space 23 and both surfaces of the material to be fixed 24 by the expansion stress of the space filler 21. At the same time, the molten thermoplastic resin is pressed against the wall surface of the space 23 and the material to be fixed 24 and adheres, so that the material to be fixed 24 is sufficiently fixed and accurately positioned.

[0056] Further, the method of using the space filler of the present invention may include a step of inserting the space filler and / or the material to be fixed into a predetermined space prior to the step of expanding and fixing the material to be fixed. The space filler and the material to be fixed may be inserted together, or one of the space filler and the material to be fixed may be inserted first and then the other may be inserted. Further, the space filler and the material to be fixed may be inserted into a predetermined space in which one has been previously inserted.

[0057] <Space filling structure> The space filling structure of the present invention may include a space filler and a material to be fixed integrally in contact with at least a part thereof. The space filling structure may, for example, integrate the space filler and the material to be fixed by fusion. For example, the space filler and the material to be fixed are laminated so as to be in contact with each other, and heated at a temperature equal to or higher than the softening point of the thermoplastic resin in the space filler while suppressing the expansion of the space filler by pressurization or the like, whereby the space filler and the material to be fixed can be manufactured by being fused together. Alternatively, the space filling structure may be manufactured with reference to the method of manufacturing the space filler. For example, the space filling structure may be manufactured by laminating a composite sheet for forming the space filler and the material to be fixed so as to be in contact with each other, heating at a temperature equal to or higher than the softening point of the thermoplastic resin in the space filler, applying pressure in the lamination direction, and further cooling while applying pressure, whereby the space filler and the material to be fixed are fused together. Alternatively, the space filling structure can be manufactured, for example, by laminating and bonding the space filler and the material to be fixed via an adhesive. In this case, the adhesive is not particularly limited as long as it can bond the space filler and the material to be fixed, and a known adhesive can be used.

[0058] In the space filling structure of the present invention, the material to be fixed may be sandwiched by the space filling material. The space filling structure may be such that the material to be fixed is sandwiched by the space filling material in at least two opposing directions, for example, it may be sandwiched in the thickness direction of the material to be fixed, or it may be sandwiched in the thickness direction and a direction orthogonal thereto. For example, when the material to be fixed has a rectangular parallelepiped shape and the thickness direction of the material to be fixed is defined as the Z direction, the direction orthogonal to the thickness direction includes the X direction (see FIG. 4A) that is parallel to a predetermined side of the material to be fixed and orthogonal to the Z direction, and the Y direction (see FIG. 4A) that is orthogonal to the X direction and the Z direction. Therefore, the space filling structure may be sandwiched in four directions composed of the Z direction, which is the thickness direction of the material to be fixed, and the X or Y direction, or may be sandwiched in six directions composed of the X direction, the Y direction, and the Z direction. Further, in the space filling structure, in each of the X direction, the Y direction, and the Z direction, the material to be fixed may be disposed in a two-way manner with respect to the space filling material, or the material to be fixed may be disposed in only one of the directions.

[0059] <Method of using the space filling structure> The method of using the space filling structure of the present invention may include a step of expanding the space filling material in a predetermined space by heating at a temperature equal to or higher than the softening point of the thermoplastic resin to fix the material to be fixed.

[0060] Further, the method of using the space filling structure of the present invention may include a step of inserting the space filling structure into a predetermined space prior to the step of expanding and fixing the material to be fixed.

[0061] Further, the space filling material of the present invention can be effectively used as a space filling reinforcing material for filling a predetermined space surrounded by members and reinforcing the members, or a space filling fixing material for fixing a material to be fixed in a predetermined space surrounded by the members in transportation means, household appliances, industrial machines, buildings, and the like. In particular, when the space filling material has predetermined insulating properties and / or heat resistance, in one aspect of the space filling material of the present invention, it can be usefully used as an insulating and / or heat-resistant space filling material.

[0062] For example, the space filler and the space filling structure of the present invention can be used as a molding material for fixing a permanent magnet (a material to be fixed) in a plurality of holes formed in a rotor in a motor (for example, a driving motor of an automobile). By doing so, the permanent magnet can be fixed with sufficient fixing strength, and the motor can be cooled by passing a coolant through the voids existing as communication holes. It is also possible to impart insulation. Further, since the fixing strength is high despite having voids, the ratio of the material occupying the space can be reduced, so that the cost can be reduced.

[0063] <Space Structure and Method for Manufacturing the Same> The space structure of the present invention is a space structure composed of discontinuous reinforcing fibers and a thermoplastic resin. Using the thermoplastic resin as a matrix, when a load of 20 MPa is repeatedly loaded 10 5 times, the thickness change rate may be 40% or less, preferably 35% or less, more preferably 30% or less. The thickness change rate is a value measured by the method described in the examples below.

[0064] The space structure can be manufactured by expanding the above-described space filler by heating it to a temperature equal to or higher than the softening point of the thermoplastic resin. For example, the space structure of the present invention can be manufactured by heating the space filler to a temperature equal to or higher than the softening point of the thermoplastic resin constituting the space filler, so that the residual stress of the discontinuous reinforcing fibers is released and the space filler expands irreversibly in the thickness direction. For example, the space structure may be obtained with reference to the method of using the above-described space filler.

[0065] The void ratio of the spatial structure of the present invention may be 20 to 95% as the state after the expansion (filling) of the space filler. When the void ratio of the spatial structure is within this range, it becomes possible to sufficiently perform liquid passage and ventilation on the expanded space filler. For example, when it is necessary to cool a structure including the spatial structure, it becomes possible to cool by passing a cooling liquid through the spatial structure. Further, the void ratio of the spatial structure may preferably be 30 to 90%, more preferably 40 to 85%, and still more preferably 45 to 80%. Note that the void ratio of the spatial structure is a value measured by the method described in the following examples as the void ratio of the expanded space filler.

[0066] The spatial structure of the present invention may have a continuous porous structure. When the voids in the spatial structure are continuous pores, it becomes possible to sufficiently perform liquid passage and ventilation on the spatial structure.

[0067] In the present invention, by utilizing the expansion of the space filler, the spatial structure can be made into a desired size, and the thickness of a predetermined space (the average thickness of the spatial structure after expansion (filling)) can be selected from a wide range of, for example, 0.02 to 600 mm. However, from the viewpoint of filling a narrow gap, it may be, for example, 20 to 5000 μm, preferably 50 to 4000 μm, and more preferably 80 to 3000 μm.

[0068] In the present invention, the punching load, which is the fixing force of the spatial structure, may be 3 N or more, preferably 10 N or more, more preferably 15 N or more, and still more preferably 20 N or more. The upper limit of the punching load is not particularly limited, but it may be, for example, about 100 N. Note that the punching load is a value measured by the method described in the following examples. When showing the punching load within the above range, since it is excellent in the strength for reinforcement and the strength for fixing a material to be fixed when filled in a predetermined space, it is useful as a reinforcing material or a fixing material.

Examples

[0069] Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples. In the following examples and comparative examples, various physical properties were measured by the following methods.

[0070] [Single fiber fineness] In accordance with Method B of 8.5.1 of JIS L 1015:2010 "Test Methods for Chemical Fiber Staples", the single fiber fineness was measured using the average fiber length calculated by the method described below.

[0071] [Average fiber length] For 100 randomly selected fibers, the fiber lengths were measured, and the average value of the measured values was taken as the average fiber length.

[0072] [Average fiber diameter] For 30 randomly selected fibers, the fiber diameters were measured by microscopic observation, and the average value of the measured values was taken as the average fiber diameter.

[0073] [Tensile modulus] In the case of glass fiber (hereinafter sometimes abbreviated as GF), the tensile modulus was measured in accordance with JIS R 3420, and in the case of carbon fiber (hereinafter sometimes abbreviated as CF), the tensile modulus was measured in accordance with JIS R 7606.

[0074] [Glass transition temperature of thermoplastic resin] The glass transition temperature of the thermoplastic fiber was determined from the peak temperature by measuring the temperature dependence of the loss tangent (tanδ) using a solid dynamic viscoelasticity apparatus "Rheo Spectra DVE-V4" manufactured by Rheology Co., Ltd. at a frequency of 10 Hz and a heating rate of 10 °C / min. Here, the peak temperature of tanδ is the temperature at which the first derivative value of the change amount of the tanδ value with respect to temperature becomes zero.

[0075] [Volume ratio] The volume ratios of the discontinuous reinforcing fibers and the thermoplastic resin constituting the space filler were calculated as the volume ratio to each other (discontinuous reinforcing fiber: thermoplastic resin) by converting the weight ratio with their respective densities.

[0076] Areal density A space filling material sample or a space structure sample with a length of 250 mm and a width of 250 mm was cut into pieces with a length of 50 mm and a width of 15 mm. The weight (g) of each piece was measured, and the areal density (g / m 2 ) was calculated. The average value of the areal density of all pieces was taken as the average areal density (g / m 2 ) of the space filling material or the space structure. Also, the standard deviation of the areal density of all pieces was calculated, and the CV value of the areal density was calculated from the following formula. Areal density CV value = Areal density standard deviation (g / m 2 ) / Average areal density (g / m 2 )

[0077] Thickness A space filling material sample or a space structure sample with a length of 250 mm and a width of 250 mm was cut into pieces of 50 mm × 15 mm. The thickness (μm) at the center of each piece was measured with a micrometer, and the average value of the thickness of all pieces was taken as the average thickness (μm) of the space filling material or the space structure. Also, the standard deviation of the thickness of all pieces was calculated, and the CV value of the thickness was calculated from the following formula. Thickness CV value = Thickness standard deviation (μm) / Average thickness (μm)

[0078] Density A space filling material sample or a space structure sample with a length of 250 mm and a width of 250 mm was cut into pieces with a length of 50 mm and a width of 15 mm. The weight (g) and thickness (μm) of each piece were measured, and the density (g / cm 3 ) was calculated. The average value of the density of all pieces was taken as the density (g / cm 3 ) of the space filling material or the space structure.

[0079] Void fraction In accordance with JIS K 7075 "Test Method for Fiber Content and Void Ratio of Carbon Fiber Reinforced Plastics", the void fraction (%) of the space filling material or the space structure was calculated.

[0080] Evaluation of compressive fatigue resistance The space fillers obtained in the examples and comparative examples were directly heated above the softening point of the thermoplastic resin using a test press machine ("KVHC-II" manufactured by Kitakawa Seiki Co., Ltd.) for heating and pressurization, and expanded to produce a space structure with a thickness of about 1 mm.

[0081] The obtained space structure was cut into 20 mm squares, and a compressive fatigue resistance test was carried out. Regarding the obtained space structure samples, the dimensions in the thickness direction of the samples were measured when a load of 20 MPa was repeatedly applied 10 5 times in the thickness direction of the same sample, and the thickness change rate was calculated by the following formula. Thickness change rate (%) = (Average thickness (μm) of the space structure sample before the test - Average thickness (μm) of the space structure sample after the test) / Average thickness (μm) of the space structure sample before the test × 100

[0082] [Reference Example 1] (Manufacture of polyetherimide fibers) A polyetherimide (hereinafter sometimes abbreviated as PEI) - based polymer ("ULTEM9001" manufactured by Sabic Innovative Plastics) was vacuum - dried at 150 °C for 12 hours. The PEI - based polymer was extruded from a round - hole nozzle under the conditions of a spinning head temperature of 390 °C, a spinning speed of 1500 m / min, and an extrusion rate of 50 g / min to produce a multifilament of 2640 dtex / 1200f PEI fibers. The obtained multifilament was cut into 15 mm lengths to produce short - cut fibers of PEI fibers. The appearance of the obtained fibers was good without fluff or the like. The single - fiber fineness was 2.2 dtex, the average fiber length was 15.0 mm, the glass transition temperature (softening point in amorphous thermoplastic resins) was 217 °C, and the density was 1.27 g / cm 3 was.

[0083] [Reference Example 2] (Manufacture of PET - based binder fibers) Using a polymerization reactor, a polycondensation reaction was carried out at 280 °C by a conventional method to produce a PET-based polymer having an intrinsic viscosity (η) of 0.81, consisting of 70 / 30 copolymerization ratio (molar ratio) of terephthalic acid and isophthalic acid as the dicarboxylic acid component and 100 mol% of ethylene glycol as the diol component. The obtained polymer was extruded into water in a strand form from the bottom of the polymerization apparatus and cut into pellets. The obtained PET-based polymer was supplied to a co-rotating type vented twin-screw extruder heated at 270 °C, led to a spinning head heated at 280 °C after a residence time of 2 minutes, discharged from a round hole nozzle under the condition of a discharge rate of 45 g / min, and taken up at a spinning speed of 1200 m / min to produce a multifilament composed of a 2640 dtex / 1200 f PET-based polymer. Next, the obtained fiber was cut into 5 mm. The appearance of the obtained fiber was good without fluff or the like, the single fiber fineness was 2.2 dtex, the average fiber length was 5 mm, and the density was 1.38 g / cm 3 It was.

[0084] [Example 1] As a thermoplastic fiber, 65 wt% of PEI fiber, as a discontinuous reinforcing fiber, 30 wt% of glass fiber with a cut length of 13 mm (manufactured by Nippon Electric Glass Co., Ltd.: average fiber diameter 10.5 μm, specific gravity 2.54 g / cm 3 ), and 5 wt% of PET-based binder fiber as a binder fiber were used to obtain a mixed nonwoven fabric (co-paper) with a basis weight of 73 g / m 2 by a wet laying process. Eight sheets of the obtained mixed nonwoven fabric were laminated, and using a test press machine ("KVHC-II" manufactured by Kitakawa Seiki Co., Ltd.), while applying pressure at 3 MPa to the surface perpendicular to the lamination direction, heating was carried out at 340 °C for 1 minute to impregnate the glass fibers with the molten PEI resin and PET-based resin, and then while maintaining the pressure, cooling was carried out to 200 °C which is below the glass transition temperature of PEI to produce a space filler. The obtained space filler was heated and expanded at a temperature above the softening point of the thermoplastic resin using a test press machine with the clearance of the press surface adjusted to 1 mm thickness to produce a space structure. Various evaluations were carried out on the obtained space structure, and the evaluation results are shown in Table 1.

[0085] [Example 2] A slurry consisting of 55 wt% of PEI fibers as thermoplastic fibers, 40 wt% of glass fibers as discontinuous reinforcing fibers, and 5 wt% of PET-based binder fibers as binder fibers was used to obtain a mixed nonwoven fabric (mixed paper) with a basis weight of 77 g / m 2 by the wet laying process. A space filler was produced in the same manner as in Example 1 except that the obtained mixed nonwoven fabric was used, and then a space structure was produced. The evaluation results of the obtained space structure are shown in Table 1.

[0086] [Example 3] A slurry consisting of 45 wt% of PEI fibers as thermoplastic fibers, 50 wt% of glass fibers as discontinuous reinforcing fibers, and 5 wt% of PET-based binder fibers as binder fibers was used to obtain a mixed nonwoven fabric (mixed paper) with a basis weight of 83 g / m 2 by the wet laying process. A space filler was produced in the same manner as in Example 1 except that the obtained mixed nonwoven fabric was used, and then a space structure was produced. The evaluation results of the obtained space structure are shown in Table 1.

[0087] [Example 4] A space filler was produced in the same manner as in Example 1 except that the number of mixed nonwoven fabric sheets was changed to 12, and then a space structure was produced. The evaluation results of the obtained space structure are shown in Table 1.

[0088] [Example 5] A slurry consisting of 55 wt% of PEI fibers as thermoplastic fibers, 40 wt% of carbon fibers with a cut length of 13 mm (manufactured by Toray Tenax: average fiber diameter 7 μm, specific gravity 1.82 g / cm 3 ) as discontinuous reinforcing fibers, and 5 wt% of PET-based binder fibers as binder fibers was used to obtain a mixed nonwoven fabric (mixed paper) with a basis weight of 69 g / m 2 by the wet laying process. A space filler was produced in the same manner as in Example 1 except that the obtained mixed nonwoven fabric was used, and then a space structure was produced. The evaluation results of the obtained space structure are shown in Table 1.

[0089] [Example 6] Using a slurry composed of 75 wt% of PEI fibers as thermoplastic fibers, 20 wt% of glass fibers as discontinuous reinforcing fibers, and 5 wt% of PET-based binder fibers as binder fibers, a wet laid process was used to obtain a mixed nonwoven fabric (co-paper) with a basis weight of 69 g / m 2 . A space filler was produced in the same manner as in Example 1 except that the obtained mixed nonwoven fabric was used and the number of mixed nonwoven fabric sheets was changed to 12. Then, a space structure was produced. The evaluation results of the obtained space structure are shown in Table 1.

[0090] [Comparative Example 1] Using a slurry composed of 85 wt% of PEI fibers as thermoplastic fibers, 10 wt% of glass fibers as discontinuous reinforcing fibers, and 5 wt% of PET-based binder fibers as binder fibers, a wet laid process was used to obtain a mixed nonwoven fabric (co-paper) with a basis weight of 65 g / m 2 . A space filler was produced in the same manner as in Example 1 except that the obtained mixed nonwoven fabric was used. However, it was not possible to produce a space structure with a thickness of about 1 mm because the space filler hardly expanded even when heated above the softening point of the thermoplastic resin.

[0091] [Comparative Example 2] Using a slurry composed of 25 wt% of PEI fibers as thermoplastic fibers, 70 wt% of glass fibers as discontinuous reinforcing fibers, and 5 wt% of PET-based binder fibers as binder fibers, a wet laid process was used to obtain a mixed nonwoven fabric (co-paper) with a basis weight of 95 g / m 2 . A space filler was produced in the same manner as in Example 1 except that the obtained mixed nonwoven fabric was used. Then, a space structure was produced. The evaluation results of the obtained space structure are shown in Table 1.

[0092]

Table 1

[0093] From Table 1, it can be seen that for the space fillers of Examples 1 to 6, since the weight ratio of the thermoplastic resin is 40 to 85 wt%, the thickness change rate after compression of the space structure obtained by expansion is as small as 40% or less. Therefore, according to the space fillers of Examples 1 to 6, the compression resistance can be improved. Comparing Example 2 and Example 5, although the weight ratio of the thermoplastic resin remains 60 wt%, for reasons not yet clear, Example 2 containing glass fibers has better compression resistance than Example 5 containing carbon fibers.

[0094] On the other hand, for the space filler of Comparative Example 1, since the weight ratio of the thermoplastic resin is too high at 90 wt%, it hardly expands and does not function as a space filler. For the space filler of Comparative Example 2, since the weight ratio of the thermoplastic resin is too low at 30 wt%, the thickness change rate is as large as 41% and the compression resistance is poor.

[0095] Furthermore, for the space fillers of Examples 7 to 13, the following various properties were evaluated, and the evaluation results are shown in Table 2.

[0096] [Maximum expansion rate] The space fillers obtained in the examples and comparative examples were placed in a forced-air constant temperature thermostat (DN411H manufactured by Yamato Scientific Co., Ltd.) set at 260 °C, heated for 10 minutes, taken out, and cooled to 25 °C. Then, the average thickness of the expanded sample was measured, and the maximum expansion rate (%) was measured using the following formula from the average thickness of the sample before and after heating. Maximum expansion rate (%) = average thickness of the space filler after expansion (μm) / average thickness of the space filler before expansion (μm) × 100

[0097] Also, regarding the obtained maximum expansion rate, the expandability was evaluated according to the following criteria. 〇: 120% or more ×: Less than 120%

[0098] [Fixing force evaluation] The sample for fixing force evaluation was prepared according to the following procedure. Fig. 5A is a schematic perspective view for explaining the preparation of the sample for fixing force evaluation, and Fig. 5B is a schematic cross-sectional view for explaining the preparation of the sample for fixing force evaluation. The space fillers obtained in the examples and comparative examples were cut into pieces with a length of 50 mm and a width of 15 mm to prepare space filler samples. As shown in Fig. 5A, with an aluminum hollow square bar (large) 32a (20 mm in length, 20 mm in width, 100 mm in length, 2.15 mm in wall thickness) and an aluminum hollow square bar (small) 32b (15 mm in length, 15 mm in width, 100 mm in length, 1.5 mm in wall thickness) inserted 50 mm in the length direction, as shown in Fig. 5B, for two opposite inner surfaces out of the four inner surfaces of the hollow square bar (large) 32a, a space filler sample 31 was inserted one by one into the gap h (each height 0.35 mm) between the inner surface of the hollow square bar (large) 32a and the outer surface of the hollow square bar (small) at the insertion part. By heating this at 280 °C for 20 minutes, the space filler sample 31 was filled into the gap. After filling, the porosity was calculated by the same calculation method as the porosity of the above-mentioned space filler.

[0099] For the obtained sample for fixing force evaluation, using a universal testing machine ("AG-2000A" manufactured by Shimadzu Corporation), with a compression speed of 2 mm / min, a load was applied in the length direction only to the hollow square bar (small), the hollow square bar (small) was pulled out, and the load at the time when displacement began to occur was defined as the fixing force (N).

[0100] [Example 7] Three layers of the mixed nonwoven fabric prepared in Example 1 were laminated, a spacer with a height of 0.15 mm was arranged using a test press machine ("KVHC-II" manufactured by Kitakawa Seiki Co., Ltd.), and while pressurizing at 3 MPa to a surface perpendicular to the lamination direction, it was heated at 340 °C for 1 minute to impregnate the glass fibers with the melted PEI resin and PET-based resin. Then, while maintaining the pressure, it was cooled to 200 °C which is below the glass transition temperature of PEI to prepare a space filler. The average thickness of the obtained space filler was 149 μm, the average basis weight was 210 g / m 2 , and the density was 1.411 g / cm 3 , and the porosity was 6.0%. Various evaluations were performed on the obtained space filler, and the evaluation results are shown in Table 2.

[0101] [Example 8] A space filler was produced in the same manner as in Example 7, except that the mixed nonwoven fabric produced in Example 2 was used. The average thickness of the obtained space filler was 150 μm, the average basis weight was 224 g / m 2 , the density was 1.493 g / cm 3 , and the porosity was 6.4%. The evaluation results for the obtained space filler are shown in Table 2.

[0102] [Example 9] A space filler was produced in the same manner as in Example 7, except that the mixed nonwoven fabric produced in Example 3 was used. The average thickness of the obtained space filler was 159 μm, the average basis weight was 246 g / m 2 , the density was 1.553 g / cm 3 , and the porosity was 8.7%. The evaluation results for the obtained space filler are shown in Table 2.

[0103] [Example 10] A space filler was produced in the same manner as in Example 7, except that the number of mixed nonwoven fabric sheets was changed to 4 and the height of the spacer was changed to 0.2 mm. The average thickness of the obtained space filler was 200 μm, the average basis weight was 285 g / m 2 , the density was 1.425 g / cm 3 , and the porosity was 5.1%. The evaluation results for the obtained space filler are shown in Table 2.

[0104] [Example 11] A space filler was produced in the same manner as in Example 7, except that the mixed nonwoven fabric produced in Example 5 was used and the number of mixed nonwoven fabric sheets was changed to 3. The average thickness of the obtained space filler was 151 μm, the average basis weight was 209 g / m 2 , the density was 1.384 g / cm 3 , and the porosity was 10%. The evaluation results for the obtained space filler are shown in Table 2.

[0105] [Example 12] A space filler was produced in the same manner as in Example 7, except that the mixed nonwoven fabric produced in Example 6 was used, the number of mixed nonwoven fabric sheets was 4, and the height of the spacer was changed to 0.2 mm. The average thickness of the obtained space filler was 199 μm, the average basis weight was 259 g / m 2 , and the density was 1.300 g / cm 3 . The porosity was 8.3%. The evaluation results of the obtained space filler are shown in Table 2.

[0106] [Example 13] A space filler was produced in the same manner as in Example 7, except that the number of mixed nonwoven fabric sheets was 2 and the height of the spacer was changed to 0.125 mm. The average thickness of the obtained space filler was 132 μm, the average basis weight was 140 g / m 2 , and the density was 1.061 g / cm 3 . The porosity was 29.3%. The evaluation results of the obtained space filler are shown in Table 2.

[0107]

Table 2

[0108] From Table 2, the space fillers of Examples 7 to 13 have excellent expandability and fixing force because the weight ratio of the thermoplastic resin is 40 to 85 wt%. In particular, the space fillers of Examples 7 to 11 and 13 in which the weight ratio of the discontinuous reinforcing fibers is 30 wt% or more are particularly excellent in expandability and fixing force.

Industrial Applicability

[0109] The space filler of the present invention is useful for filling a predetermined space surrounded by members in transportation means, home appliances, industrial machines, buildings, etc. For example, the space filler can be used as a reinforcing material for reinforcing members or a fixing material for fixing a material to be fixed in a predetermined space surrounded by members. Furthermore, the space filler of the present invention can be used as a molding material for fixing permanent magnets (materials to be fixed) in a plurality of holes formed in a rotor in a motor (for example, a driving motor of an automobile).

[0110] As described above, the preferred embodiments of the present invention have been described with reference to the drawings. However, those skilled in the art will easily assume various changes and modifications within the obvious scope upon seeing this specification. Therefore, such changes and modifications are construed as being within the scope of the invention defined by the claims.

Explanation of Reference Numerals

[0111] 1 ··· discontinuous reinforcing fiber 2 ··· thermoplastic resin 11, 21 ··· space filler 12, 22 ··· outer member 13, 23 ··· space 24 ··· material to be fixed 25 ··· space filling structure 31 ··· space filler sample 32a ··· large hollow square bar 32b ··· small hollow square bar h ··· clearance height

Claims

1. A space filler composed of discontinuous reinforcing fibers and a thermoplastic resin, wherein the weight ratio of the thermoplastic resin is 40 to 85 wt%, the discontinuous reinforcing fibers are insulating fibers, the discontinuous reinforcing fibers have a plurality of intersections, and at least a part of those intersections is adhered with the thermoplastic resin. When the thermoplastic resin softens, the residual stress of the discontinuous reinforcing fibers is released and expands, and it is used as a molding material for fixing permanent magnets in a plurality of holes formed in a rotor of a motor, having a thickness of 20 to 5000 μm.

2. The space filler according to Claim 1, wherein the weight ratio of the discontinuous reinforcing fibers is 15 to 60 wt%.

3. The space filler according to Claim 1 or 2, wherein the fiber length of the discontinuous reinforcing fibers is 5 to 100 mm.

4. The space filler according to any one of Claims 1 to 3, wherein the glass transition temperature of the thermoplastic resin is 100 °C or higher.

5. The space filler according to any one of Claims 1 to 4, wherein the thermoplastic resin is at least one thermoplastic resin selected from the group consisting of thermoplastic polyimide resins, polyether ketone resins, semi-aromatic polyamide resins, polycarbonate resins, liquid crystal polyester resins, polysulfone resins, and polytetrafluoroethylene resins.

6. The space filler according to any one of Claims 1 to 5, wherein the porosity is 40% or less.

7. A space filling structure comprising the space filler according to any one of Claims 1 to 6 and a permanent magnet integrally contacted with at least a part thereof.

8. The space filling structure according to Claim 7, wherein the permanent magnet is sandwiched by the space filler.

9. A spatial structure composed of discontinuous reinforcing fibers and a thermoplastic resin, wherein the discontinuous reinforcing fibers are insulating fibers, and using the thermoplastic resin as a matrix, when a load of 20 MPa is repeatedly loaded 10 ５ times, the thickness change rate is 40% or less, the average thickness is 20 to 5000 μm, and a permanent magnet integrated in contact with at least a part thereof is fixed in a plurality of holes formed in the rotor of a motor. It is a spatial structure that is a molding material.

10. A method for manufacturing a spatial structure, wherein the space filler according to any one of claims 1 to 6 is expanded by heating at a temperature equal to or higher than the softening point of the thermoplastic resin.

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