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

Abstract

The present invention provides a space filling material having excellent strength for enhancing the space when filling in a given space and excellent strength for fixing a material to be fixed. The space filling material (11) includes reinforcing fibers and a thermoplastic resin. The reinforcing fibers have a plurality of intersection points with each other, and at least a part of the intersection points are bonded by the thermoplastic resin. Among them, the volume content ratio of the reinforcing fibers having a curvature defined by fiber length / shortest distance between both ends of the fiber of 1.004 or more is 20 vol% or more with respect to the total volume of the reinforcing fibers. The space filling material (11) expands by releasing the bending of the reinforcing fibers due to the softening of the thermoplastic resin based on heating and fills in a given space (13).

Description

[0001] Related Applications

[0002] This application claims the priority of Japanese Patent Application No. 2020-150807 filed in Japan on September 8, 2020, the entire contents of which are incorporated herein by reference as part of this application. Technical Field

[0003] The present invention relates to a space filling material that fills a given space by heating, a method for manufacturing the same, and a space filling structure including the space filling material. Background Art

[0004] Currently, there are known composite materials that expand upon heating and function as sealing materials. For example, Patent Document 1 (Japanese Patent Application Laid-Open No. 2003-262116) discloses a sealing material for an automotive exhaust gas purification catalytic converter, which is composed of a sheet-shaped molded body obtained by allowing an organic binder to exist in a slurry with respect to inorganic short fibers, or obtained by adding and integrating by spraying after sheet molding. By burning off the organic binder, the material expands 1.3 to 6 times in the thickness direction of the molded body, generating a restoring surface pressure caused by the inorganic short fibers.

[0005] Prior Art Documents

[0006] Patent Documents

[0007] Patent Document 1: Japanese Patent Application Laid-Open No. 2003-262116 Summary of the Invention

[0008] Problems to be Solved by the Invention

[0009] However, the sealing material of Patent Document 1 is a sealing material that burns off the organic binder by thermal decomposition and expands by the restoration of the shape of the inorganic short fibers. Therefore, the performance of the organic binder itself cannot be utilized, and only the inorganic short fibers are used for sealing, resulting in insufficient pressing force. In addition, since the organic binder burns off due to thermal decomposition, a large amount of decomposition gas is generated, and the generated decomposition gas needs to be discharged out of the system.

[0010] Therefore, an object of the present invention is to solve such problems of the prior art and provide a space filling material having excellent strength for enhancing the space during filling in a given space and excellent strength for fixing a material to be fixed.

[0011] Means for Solving the Problems

[0012] The present inventors have conducted in-depth research to solve the above problems and, as a result, have found that when manufacturing a space filling material composed of reinforcing fibers and a thermoplastic resin, in which the reinforcing fibers have a plurality of intersections with each other and at least a part of the intersections are bonded by the thermoplastic resin, by adjusting the form of the composite sheet as the precursor material of the space filling material and the conditions of hot pressing, a space filling material in which reinforcing fibers having a specific curvature exist in a specific amount can be obtained. Further, it has been found that such a space filling material has a very large resilience of the reinforcing fibers when the bending of the reinforcing fibers is released due to the softening of the thermoplastic resin. Therefore, the strength for reinforcing the space when filling in a given space and the strength for fixing the material to be fixed are excellent, and thus the present invention has been completed.

[0013] That is, the present invention can be configured in the following manner.

[0014] 〔Aspect 1〕

[0015] A space filling material comprising reinforcing fibers and a thermoplastic resin, wherein the reinforcing fibers have a plurality of intersections with each other, and at least a part of the intersections are bonded by the thermoplastic resin, and the volume fraction of the reinforcing fibers having a curvature of 1.004 or more as defined by the following formula (1) is 20 vol% or more (preferably 30 vol% or more, more preferably 35 vol% or more, and further preferably 40 vol% or more) with respect to the total volume of the reinforcing fibers.

[0016] Curvature = fiber length / shortest distance between both ends of the fiber (1)

[0017] 〔Aspect 2〕

[0018] The space filling material according to Aspect 1, wherein the CV value of the thickness is 0.2 or less (preferably 0.1 or less, more preferably 0.08 or less, and further preferably 0.06 or less).

[0019] 〔Aspect 3〕

[0020] The space filling material according to Aspect 1 or 2, wherein the average thickness is 10 to 1000 μm (preferably 20 to 500 μm, more preferably 50 to 300 μm).

[0021] 〔Aspect 4〕

[0022] The space filling material according to any one of Aspects 1 to 3, wherein the release rate of the curvature as defined by the following formula (2) is 20% or more (preferably 30% or more, more preferably 40% or more, further preferably 50% or more, and further more preferably 60% or more).

[0023] Release rate of curvature (%) = [(X - 1) - (Y - 1)] / (X - 1) × 100 (2)

[0024] (In the formula, X: average curvature of reinforcing fibers in the space filling material before expansion; Y: average curvature of reinforcing fibers in the space filling material after heat expansion under non-pressurized conditions)

[0025] [Mode 5]

[0026] For the space filling material described in any one of Modes 1 to 4, the CV value of the weight per unit area is 0.2 or less (preferably 0.15 or less, more preferably 0.1 or less).

[0027] [Mode 6]

[0028] For the space filling material described in any one of Modes 1 to 5, wherein

[0029] the average fiber length of the above-mentioned reinforcing fibers is 3 to 100 mm (preferably 4 to 80 mm, more preferably 5 to 50 mm).

[0030] [Mode 7]

[0031] For the space filling material described in any one of Modes 1 to 6, wherein

[0032] the volume content ratio of the reinforcing fibers with a curvature of 1.004 or more is 3 to 50 vol% (preferably 5 to 45 vol%, more preferably 10 to 40 vol%) relative to the total volume of the space filling material.

[0033] [Mode 8]

[0034] For the space filling material described in any one of Modes 1 to 7, wherein

[0035] the weight content ratio of the thermoplastic resin is 40 to 85 wt% (preferably 45 to 82 wt%, more preferably 50 to 80 wt%, further preferably 52 to 75 wt%) relative to the total weight of the space filling material.

[0036] [Mode 9]

[0037] A space filling structure, comprising:

[0038] the space filling material described in any one of Modes 1 to 8, and

[0039] a fixed material integrated with at least a part of the space filling material.

[0040] [Mode 10]

[0041] A method for manufacturing a space filling material, which is a method for manufacturing the space filling material described in any one of Manufacturing Methods 1 to 8, the method comprising at least:

[0042] a step of preparing a composite sheet containing reinforcing fibers and a thermoplastic resin;

[0043] a step of heating the composite sheet to a temperature above the softening point of the thermoplastic resin and performing hot pressing by applying pressure in the thickness direction; and

[0044] a step of cooling to a temperature lower than the softening point of the thermoplastic resin in a state where pressure is applied.

[0045] 〔Manufacturing Method 11〕

[0046] According to the method for manufacturing a space filling material described in Manufacturing Method 10, wherein

[0047] the composite sheet is a mixed paper (mixed paper) containing reinforcing fibers and thermoplastic fibers.

[0048] 〔Manufacturing Method 12〕

[0049] According to the method for manufacturing a space filling material described in Manufacturing Method 11, wherein

[0050] the mixed paper is formed from an aqueous slurry containing reinforcing fibers, thermoplastic fibers, and a dispersant.

[0051] 〔Manufacturing Method 13〕

[0052] According to the method for manufacturing a space filling material described in Manufacturing Method 12, wherein

[0053] the aqueous slurry further contains a thickening agent.

[0054] It should be noted that any combination of at least two constituent elements disclosed in the claims and / or the specification and / or the drawings is also included in the present invention. In particular, any combination of two or more claim items described in the claims is also included in the present invention.

[0055] Effects of the Invention

[0056] The space filling material according to the present invention is excellent in strength for reinforcing the space during filling in a given space and strength for fixing a material to be fixed. Brief Description of the Drawings

[0057] The present 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 on the basis of showing the principles of the present invention. However, the embodiments and the drawings are only for illustration and explanation and are not used to define the scope of the present invention. The scope of the present invention is defined by the appended claims.

[0058] Figure 1 It is a conceptual diagram for explaining the curvature of reinforcing fibers.

[0059] Figure 2A It is a cross-sectional schematic diagram of the first embodiment for explaining the usage method of the space filling material of the present invention, showing the state before expansion.

[0060] Figure 2B It is a cross-sectional schematic diagram of the first embodiment for explaining the usage method of the space filling material of the present invention, showing the state after expansion.

[0061] Figure 3A It is a cross-sectional schematic diagram of the second embodiment for explaining the usage method of the space filling material of the present invention, showing the state before expansion.

[0062] Figure 3B It is a cross-sectional schematic diagram of the second embodiment for explaining the usage method of the space filling material of the present invention, showing the state after expansion.

[0063] Figure 4A It is a three-dimensional schematic diagram for explaining the production of a sample for a stamping load test.

[0064] Figure 4B It is a cross-sectional schematic diagram for explaining the production of a sample for a stamping load test.

[0065] Symbol Explanation

[0066] 1 ··· Reinforcing fiber

[0067] 11, 21 ··· Space filling material

[0068] 12, 22 ··· Outer member

[0069] 13, 23 ··· Space

[0070] 24 ··· Material to be fixed

[0071] 25 ··· Space filling structure

[0072] 31 ··· Space filling material sample

[0073] 32a ··· Hollow square material (large)

[0074] 32b ··· Hollow square material (small)

[0075] L ··· Fiber length

[0076] L0 ··· Shortest distance between both ends of the fiber

[0077] h ··· Gap height Detailed implementation mode

[0078] <Manufacturing method of space filling material>

[0079] The manufacturing method of the space filling material of the present invention may at least include: a step of preparing a composite sheet containing reinforcing fibers and a thermoplastic resin; a step of heating the composite sheet to a temperature above 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 in a state where pressure is applied. In order to manufacture a space filling material in which reinforcing fibers having a specific curvature exist in a specific amount, it is necessary to appropriately adjust the manufacturing conditions described later according to the unit area weight, thickness, etc. of the desired space filling material. For example, by adjusting the ratio of reinforcing fibers in the composite sheet, the number of sheets of the composite sheet supplied for hot pressing, the hot pressing conditions, etc., the curvature of the reinforcing fibers can be adjusted.

[0080] The composite sheet contains reinforcing fibers and a thermoplastic resin, and is a material that can form a space filling material through a hot pressing process and a cooling process, and various forms of sheets can be used. As the composite sheet, for example, a mixed non-woven fabric of reinforcing fibers and thermoplastic fibers, or a non-woven fabric of reinforcing fibers in which particulate (or powdery) thermoplastic resin is dispersed, etc. can be cited, and a mixed non-woven fabric of reinforcing fibers and thermoplastic fibers is preferably used. In addition, from the viewpoint of the uniformity of the distribution of the reinforcing fibers and the thermoplastic fibers, a wet non-woven fabric (for example, a mixed paper, hereinafter, in the present invention, a mixed non-woven fabric based on the wet papermaking method is referred to as a mixed paper) containing reinforcing fibers and thermoplastic fibers is more preferably used.

[0081] The reinforcing fibers used in the present invention are not particularly limited as long as the effects of the present invention are not impaired. They can be organic fibers or inorganic fibers. In addition, they can be used alone or in combination of two or more. Examples of inorganic fibers include glass fibers, carbon fibers, various ceramic fibers (e.g., silicon carbide fibers, silicon nitride fibers, silica fibers, alumina fibers, zirconia fibers, boron fibers, basalt fibers, etc.), and various metal fibers (e.g., gold, silver, copper, iron, nickel, titanium, stainless steel, etc.). In addition, as organic fibers, as long as the glass transition temperature or melting point is higher than the softening point of the thermoplastic resin at the intersection of the adhesive reinforcing fibers, there is no particular limitation. Examples include wholly aromatic polyester fibers, polyphenylene sulfide fibers, para-aramid fibers, polysulfonamide fibers, phenolic resin fibers, polyimide fibers, fluorine-containing fibers, etc. It should be noted that in the present invention, for thermoplastic fibers, the softening point mainly refers to the heat distortion temperature, for example, it can be the heat deflection temperature (JIS K 7207). Especially in the case of amorphous resins, it refers to their glass transition temperature.

[0082] Among them, from the viewpoint of improving the resilience of the reinforcing fibers, it is preferable to use inorganic fibers with a high elastic modulus such as glass fibers or carbon fibers. In addition, in the case where the structure containing the expanded space filler requires insulation, it can also be insulating fibers (e.g., glass fibers, silicon nitride fibers, silica fibers, alumina fibers, etc.).

[0083] The reinforcing fibers used in the present invention are preferably discontinuous fibers. From the viewpoint of improving the resilience of the reinforcing fibers, the average fiber length is preferably 3 to 100 mm, more preferably 4 to 80 mm, and further preferably 5 to 50 mm. It should be noted that the average fiber length is a value measured by the method described in the examples below.

[0084] For the reinforcing fibers used in the present invention, from the viewpoint of improving the resilience of the reinforcing fibers, the average fiber diameter of the single fiber is preferably 2 to 40 μm, more preferably 3 to 30 μm, and further preferably 4 to 20 μm. It should be noted that the average fiber diameter is a value measured by the method described in the examples below.

[0085] From the viewpoint of improving the resilience of the reinforcing fibers, the aspect ratio (average fiber length / average fiber diameter) of the single fiber of the reinforcing fibers used in the present invention can be preferably 100 to 50000, more preferably 300 to 10000, and further preferably 500 to 5000.

[0086] From the viewpoint of improving the resilience of the reinforcing fiber, the reinforcing fiber used in the present invention preferably has a tensile elastic modulus of 10 GPa or more, more preferably 30 GPa or more, and still more preferably 50 GPa or more. There is no particular limitation on the upper limit, which may be 1000 GPa or less. It should be noted that for the tensile elastic modulus, in the case of carbon fiber, it can be measured according to JIS R 7606, in the case of glass fiber, it can be measured according to JIS R 3420, and in the case of organic fiber, it can be measured according to JIS L1013 or other methods conforming to each fiber standard.

[0087] From the viewpoint of adjusting the curvature of the reinforcing fiber in the obtained space filling material, the weight content ratio of the reinforcing fiber can be 15 to 60 wt%, preferably 18 to 55 wt%, more preferably 20 to 50 wt%, and still more preferably 25 to 48 wt% with respect to the total weight of the composite sheet. If the content ratio of the reinforcing fiber is too small, the contact between the reinforcing fibers becomes less, and thus, there is a tendency that the reinforcing fiber is difficult to bend. On the other hand, if the content ratio of the reinforcing fiber is too large, the amount of the thermoplastic resin is small, and thus, the reinforcing fiber cannot maintain a bent state, and there is a tendency that it is difficult to adjust the curvature of the reinforcing fiber.

[0088] Examples of the thermoplastic resin used in the present invention include vinyl resins (polymers or derivatives thereof synthesized from monomers having vinyl CH2=CH- or ethylidene CH2=C<); aliphatic polyamide resins (polyamide 6, polyamide 66, polyamide 11, polyamide 12, polyamide 610, polyamide 612, etc.), semi-aromatic polyamide resins, wholly aromatic polyamide resins and other polyamide resins; polyester resins such as polyethylene terephthalate, polypropylene terephthalate, polybutylene terephthalate, polyethylene naphthalate; fluorine resins such as polytetrafluoroethylene resins; thermoplastic polyimide resins such as semi-aromatic polyimide resins, polyamideimide resins, polyetherimide resins; polysulfone resins such as polysulfone resins, polyethersulfone resins; modified polyphenylene ether resins; polyether ketone resins such as polyether ketone resins, polyether ether ketone resins, polyether ketone ketone resins; polycarbonate resins; amorphous polyarylate resins; liquid crystal polyester resins such as wholly aromatic polyester resins; thermoplastic elastomers such as urethanes, styrenes, olefins, vinyl chlorides, esters, amides. These thermoplastic resins can be used alone or in combination of two or more.

[0089] In addition, for the thermoplastic resin used in the present invention, in the case of applications where the structure containing the expanded space filling material requires heat resistance, a thermoplastic resin with a glass transition temperature of 100 °C or higher is preferably used. For example, as the thermoplastic resin with a glass transition temperature of 100 °C or higher, polytetrafluoroethylene resins, thermoplastic polyimide resins, polysulfone resins, semi-aromatic polyamide resins, polyether ketone resins, polycarbonate resins, liquid crystal polyester resins, etc. can be cited. Among them, from the viewpoints of mechanical properties and moldability, the thermoplastic resin can be at least one thermoplastic resin selected from thermoplastic polyimide resins (preferably polyetherimide resins), polyether ketone resins (preferably polyetheretherketone resins), semi-aromatic polyamide resins, polycarbonate resins, and polysulfone resins. In applications requiring heat resistance, the glass transition temperature of the thermoplastic resin can be preferably 105 °C or higher, and can be further preferably 110 °C or higher. It should be noted that there is no particular limitation on the upper limit, and from the viewpoint of economically using the space filling material, it can be 300 °C or lower. It should be noted that the glass transition temperature is a value measured by the method described in the examples below.

[0090] In addition, the thermoplastic resin used in the present invention may also contain various additives within the range that does not impair the effects of the present invention.

[0091] In the case of using a mixed non-woven fabric as the composite sheet, thermoplastic fibers obtained by fibrillating the above-mentioned thermoplastic resin by a known method can be used. From the viewpoint of adjusting the curvature of the reinforcing fibers in the obtained space filling material, in the mixed non-woven fabric used in the present invention, the weight content of the thermoplastic fibers can be 40 to 85 wt%, preferably 45 to 82 wt%, more preferably 50 to 80 wt%, and further preferably 52 to 75 wt% based on the total weight of the mixed non-woven fabric.

[0092] From the viewpoint of good dispersibility of the reinforcing fibers, the single fiber fineness of the thermoplastic fibers is preferably 0.1 to 20 dtex. In order to obtain a space filling material with excellent expansion stress during heating, it is preferred to uniformly disperse the reinforcing fibers in the mixed non-woven fabric. The single fiber fineness of the thermoplastic fibers can be more preferably 0.5 to 18 dtex, and further preferably 1 to 16 dtex. It should be noted that the single fiber fineness is a value measured by the method described in the examples below.

[0093] From the viewpoint of achieving good dispersion 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 still more preferably 3 to 50 mm. It should be noted that the average fiber length is a value measured by the method described in the examples below. It should also be noted that the cross-sectional shape of the fibers at this time is not particularly limited and may be a circular, hollow, flat, or star-shaped cross-section or other irregular cross-sections.

[0094] In addition, when using fibers formed from a thermoplastic resin having a glass transition temperature of 100°C or higher as the thermoplastic fibers, the mixed nonwoven fabric may contain a binder component as needed. The weight content ratio of the binder component with respect to the mixed nonwoven fabric may be, for example, 10 wt% or less. The shape of the binder component may be fibrous, particulate, liquid, etc., and from the viewpoint of forming the nonwoven fabric, binder fibers are preferred. The binder component is not particularly limited, and examples thereof include polyolefin resins, polyamide resins, polyester resins, acrylic resins, polyvinyl alcohol resins, polyurethane resins, etc., and polyester resins are preferred. These binder components are components of the thermoplastic resin constituting the obtained space filling material. From the viewpoint of the binder component becoming a part of the matrix as a thermoplastic resin, it is preferable to use a binder component having compatibility with the thermoplastic fibers. In this case, the matrix of the obtained space filling material becomes integrated, and thus the strength is excellent.

[0095] The polyester resin may be composed of a polyester polymer containing a terephthalic acid component (a) and an isophthalic acid component (b) in the dicarboxylic acid component, and the copolymerization ratio (molar ratio) of the terephthalic acid component (a) to the isophthalic acid component (b) is (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 through good binder properties. Therefore, the process throughput is excellent, and thermal decomposition during high-temperature molding can be suppressed. In addition, such a polyester resin has compatibility with a thermoplastic polyimide resin (preferably a polyetherimide resin), and thus is particularly preferred as a binder component when using thermoplastic fibers formed from a polyimide resin. More preferably, (a) / (b) = 90 / 10 to 45 / 55, and still more preferably (a) / (b) = 85 / 15 to 50 / 50.

[0096] As long as the effects of the present invention are not impaired, the above polyester resin may also contain a small amount (for example, 5 mol% or less) of other dicarboxylic acid components other than terephthalic acid and isophthalic acid, or may contain a combination of multiple such other dicarboxylic acid components.

[0097] In addition, as the diol component constituting the polyester resin, ethylene glycol can be used as the diol component, but it may also contain a small amount (for example, 5 mol% or less) of other diol components other than ethylene glycol, or a combination of multiple of the above-mentioned other diol components may be included.

[0098] The method for manufacturing the nonwoven fabric is not particularly limited, and examples thereof include a hydroentangling method, a needling method, a steam jet method, a dry papermaking method, a wet papermaking method (wet laying process), etc. Among them, from the viewpoints of production efficiency and uniform dispersion of the reinforcing fibers in the nonwoven fabric, the wet papermaking method is preferred. For example, in the wet papermaking method, it is only necessary to prepare an aqueous slurry containing thermoplastic fibers and reinforcing fibers, and further supply the slurry to a normal papermaking process. It should be noted that the aqueous slurry may contain the above-mentioned binder fibers (for example, water-soluble polymer fibers such as polyvinyl alcohol fibers, hot melt adhesive fibers such as polyester fibers) as needed. In addition, in order to improve the uniformity and crimpability of the nonwoven fabric, the binder component can be coated by spray drying, or a hot pressing process can be added after the wet papermaking process.

[0099] In the case of using the wet papermaking method, from the viewpoint of improving the thickness and uniformity of the unit area weight of the obtained space filling material, an aqueous slurry further containing a dispersant can be used. As the dispersant, known dispersants capable of dispersing reinforcing fibers and thermoplastic fibers in water can be used, and examples thereof include polymer type dispersants such as polyalkylene oxide dispersants, polyacrylamide dispersants, polyacrylic acid dispersants, and urethane resin dispersants.

[0100] In addition, from the viewpoint of improving the thickness and uniformity of the unit area weight of the obtained space filling material, an aqueous slurry further containing a thickener can be used. As the thickener, anionic polyacrylamide, nonionic polyethylene oxide, etc. can be cited. Among them, as the thickener, anionic polyacrylamide is preferably used. The reason is that it is easy to obtain a mixed bundled fiber bundle when a cationic compound is added.

[0101] The unit area weight of the nonwoven fabric is not particularly limited, and is preferably 5 to 1500 g / m 2 , more preferably 10 to 1000 g / m 2 , and further preferably 20 to 500 g / m 2 .

[0102] In the hot pressing process, the composite sheet can be heated above the softening point of the thermoplastic resin, and pressure can be applied along the thickness direction for hot pressing. By heating and pressing along the thickness direction, compression is carried out in a state where the reinforcing fibers are in contact with each other, and thus, the reinforcing fibers can be bent. In the present invention, by adjusting the conditions of the following-described hot pressing corresponding to the content ratio of the reinforcing fibers and the thermoplastic resin in the composite sheet, the unit area weight of the composite sheet, and the number of sheets, the degree of bending of the reinforcing fibers can be adjusted.

[0103] There is no particular limitation on the method of performing hot pressing, and it is preferably carried out by using common compression molding such as stamping molding, compression molding, vacuum bonding molding, GMT molding. The molding temperature at this time can be set according to the softening point and decomposition temperature of the thermoplastic resin used. The heating temperature is preferably above the softening point of the thermoplastic resin. For example, when the thermoplastic resin is crystalline, the heating temperature is preferably in the range above the melting point of the thermoplastic resin and below (melting point + 100) °C. In addition, when the thermoplastic resin is amorphous, the heating temperature is preferably in the range above the glass transition temperature of the thermoplastic resin and below (glass transition temperature + 200) °C. It should be noted that preheating can be carried out by an IR heater or the like before hot pressing as needed.

[0104] In addition, there is no particular limitation on the pressure during hot pressing, and it is usually carried out under a pressure of 0.05 MPa or more. It can be more preferably 0.1 MPa or more, and can be further preferably 0.5 MPa or more. There is no particular limitation on the upper limit, and it can be preferably about 30 MPa. The time during hot pressing is not particularly limited, but when exposed to high temperatures for a long time, the thermoplastic resin may deteriorate. Therefore, it is usually preferably within 30 minutes, more preferably within 25 minutes, and further preferably within 20 minutes. There is no particular limitation on the lower limit, and it can be about 1 minute.

[0105] In the hot pressing process, one of the above-described composite sheets can be hot pressed, or multiple sheets can be laminated and hot pressed. For example, the preferred conditions vary depending on the unit area weight of the composite sheet, the thickness of the desired space filling material, etc. From the viewpoint of adjusting the degree of bending of the reinforcing fibers, a multilayer body formed by overlapping multiple (for example, 2 to 100 sheets, preferably 3 to 50 sheets) of the above-described composite sheets can be hot pressed.

[0106] In addition, in order to adjust the thickness and density of the obtained space filling material, the type of reinforcing fibers and the applied pressure can be appropriately set. In addition, there is no particular limitation on the shape of the obtained space filling material, and it can be appropriately set. Depending on the purpose, multiple mixed non-woven fabrics of different specifications can be laminated, or mixed non-woven fabrics of different specifications can be respectively arranged in a mold of a certain size and hot pressed.

[0107] In the cooling process, by cooling to a temperature lower than the softening point of the thermoplastic resin while applying the pressure in the hot pressing process, a space filling material with a given shape can be obtained. By cooling while applying pressure, as described above, the state of the reinforcing fibers adjusted to a specific curvature in the hot pressing process can be maintained, and a space filling material in which the reinforcing fibers with a specific curvature exist in a specific amount can be obtained.

[0108] <Space filling material>

[0109] The space filling material of the present invention is composed of reinforcing fibers and a thermoplastic resin. As long as the effects of the present invention are not impaired, the space filling material may also contain substances other than the reinforcing fibers and the thermoplastic resin. The above-mentioned reinforcing fibers have a plurality of intersections with each other, and at least a part of these intersections are bonded together by the thermoplastic resin. For example, the reinforcing fibers may have a plurality of intersections with each other in a randomly oriented state, and at least a part of the intersections of the reinforcing fibers are bonded together by the thermoplastic resin. Preferably, the thermoplastic resin may exist in a webbed shape with the intersections of the reinforcing fibers as the center, or the reinforcing fibers may be embedded in the thermoplastic resin forming the matrix. By adopting such a structure, the structural strength of the space filling material is improved.

[0110] In the space filling material of the present invention, the volume fraction of the reinforcing fibers with a curvature of 1.004 or more as defined by the following formula (1) is 20 vol% or more with respect to the total volume of the reinforcing fibers.

[0111] Curvature = fiber length / shortest distance between both ends of the fiber (1)

[0112] Figure 1 It is a conceptual diagram for explaining the curvature of the reinforcing fibers. As Figure 1 shown, it is assumed that in the space filling material, the reinforcing fibers have a shape that is approximately bow-shaped with the central part as the center. In this case, the fiber length in the above formula (1) represents the length L along the bent shape of the fiber, and the shortest distance between both ends of the fiber represents the distance L0 of the straight line connecting the two points at both ends of the fiber. It should be noted that as the bent reinforcing fibers, they are not limited to the Figure 1 bow-shaped as shown, and may be mountain-shaped or wavy.

[0113] In the present invention, it has been found that the residual stress caused by the bending of the reinforcing fibers contributes to the expansion of the space filling material during the flow of the thermoplastic resin, and it has been found that the reinforcing fibers with a degree of curvature of 1.004 or more have a large resilience, and when the space filling material filled with the reinforcing fibers in a specific proportion in a given space, the strength of the reinforced space and the strength of fixing the fixed material can be improved. In the space filling material of the present invention, the volume content rate of the reinforcing fibers with a degree of curvature of 1.004 or more can be preferably 30 vol% or more, more preferably 35 vol% or more, and further preferably 40 vol% or more, relative to the total volume of the reinforcing fibers. The upper limit of the volume content rate of the reinforcing fibers with a degree of curvature of 1.004 or more is not particularly limited, and can be, for example, 100 vol%. It should be noted that the degree of curvature of the reinforcing fibers is a value measured by the method described in the following examples.

[0114] When the space filling material of the present invention is heated in a given space, due to the flow of the surrounding thermoplastic resin matrix, the bent reinforcing fibers are released and exhibit a resilience (recovery force) to return to a straight state. As a result, the space filling material expands and generates an expansion stress on the outer member or the like, and thus, it is possible to fill at least in the thickness direction. For the space filling material of the present invention, a high pressing force can be applied to the outer member by the expansion stress of the space filling material, and at the same time, the force of pressing and bonding the molten thermoplastic resin matrix to the outer member also acts. Here, the expansion stress refers to the stress generated when the space filling material expands and the outer member surrounding the space is restricted.

[0115] In the manufacturing method of the space filling material as described above, when pressing is performed in the thickness direction during hot pressing, the resilience of the reinforcing fibers bent in the thickness direction is exhibited, and thus, such a space filling material expands in the thickness direction when heated and generates an expansion stress in the thickness direction.

[0116] From the viewpoint of increasing the expansion stress during heating, in the space filling material of the present invention, the volume content rate of the reinforcing fibers with a degree of curvature of 1.004 or more can be 3 to 50 vol%, preferably 5 to 45 vol%, and more preferably 10 to 40 vol%, relative to the total volume of the space filling material. It should be noted that the volume content rate of the reinforcing fibers with a degree of curvature of 1.004 or more relative to the total volume of the space filling material represents the proportion of the volume of the reinforcing fibers with a degree of curvature of 1.004 or more to the bulk volume of the space filling material, and is a value measured by the method described in the following examples.

[0117] From the viewpoint of increasing the expansion stress during heating, the average curvature of the reinforcing fibers of the space filling material of the present invention can be 1.003 or more, preferably 1.004 or more, more preferably 1.005 or more, and further preferably 1.006 or more. The upper limit of the average curvature of the reinforcing fibers can be, for example, 1.05 or less, preferably 1.04 or less, and more preferably 1.03 or less. It should be noted that the average curvature of the reinforcing fibers is a value measured by the method described in the examples below.

[0118] From the viewpoint of increasing the expansion stress during heating, in the space filling material of the present invention, the weight content ratio of the reinforcing fibers is preferably 15 to 60 wt% with respect to the total weight of the space filling material, more preferably 18 to 55 wt%, further preferably 20 to 50 wt%, and further more preferably 25 to 48 wt%. If the weight content ratio of the reinforcing fibers is too low, the contact between the reinforcing fibers decreases, and there is a tendency that the reinforcing fibers are difficult to bend. On the other hand, if the weight content ratio of the reinforcing fibers is too high, the amount of the thermoplastic resin is small, and thus the reinforcing fibers cannot be maintained in a bent state, and there is a tendency that it is difficult to adjust the curvature of the reinforcing fibers.

[0119] From the viewpoint of increasing the expansion stress during heating, in the space filling material of the present invention, the weight content ratio of the thermoplastic resin is preferably 40 to 85 wt% with respect to the total weight of the space filling material, more preferably 45 to 82 wt%, further preferably 50 to 80 wt%, and further more preferably 52 to 75 wt%. If the amount of the thermoplastic resin is small, the contribution of the adhesion of the molten thermoplastic resin becomes small, and there is a risk that the reinforcing force or the fixing force becomes insufficient. It should be noted that as the thermoplastic resin contained in the space filling material, an adhesive component used as needed in the production of the non-woven fabric as a composite sheet may be included.

[0120] From the viewpoint of improving the expansibility and the expansion stress during heating, in the space filling material of the present invention, the volume ratio of the reinforcing fiber to the thermoplastic resin (reinforcing fiber: thermoplastic resin) can be 10:90 to 70:30. When the volume ratio of the thermoplastic resin to the reinforcing fiber is too small, when the space filling material expands in a given space and contacts the wall surface of the space (or the material to be fixed), the contact area contacted by the thermoplastic resin decreases. Therefore, the stress that helps to enhance the strength of the outer member or fix the strength of the material to be fixed through the adhesion of the thermoplastic resin may become insufficient. In addition, when the volume ratio of the thermoplastic resin to the reinforcing fiber is too large, the amount of the reinforcing fiber present is insufficient, and the expansibility may become insufficient. The volume ratio of the reinforcing fiber to the thermoplastic resin (reinforcing fiber: thermoplastic resin) can preferably be 15:85 to 65:35, and more preferably 20:80 to 60:40.

[0121] For the space filling material of the present invention, from the viewpoint of improving the expansibility and the expansion stress during heating, the porosity (before expansion or before use) can be 0.5 to 70%. When there is basically no porosity before expansion or before use, due to the application of unreasonable compressive force to the reinforcing fiber in the space filling material, the reinforcing fiber may break or flow. Even if the bending of the reinforcing fiber is released during heating, its resilience cannot be fully obtained, so the expansibility and the expansion stress during heating may be insufficient. In addition, when the porosity before expansion is too large, there is little room for expansion, so the expansibility may be insufficient. The porosity (before expansion or before use) can preferably be 0.8 to 68%, more preferably 1 to 65%, and further preferably 1 to 60%. It should be noted that here, the porosity represents the ratio of the volume occupied by the voids to the bulk volume of the space filling material, and is a value measured by the method described in the following examples.

[0122] The average thickness of the space filling material of the present invention can be set to various thicknesses according to the space to be filled and the use. For example, it can be selected from a wide range of 0.01 to 20 mm. From the viewpoint of being able to insert into a narrow gap and fill the gap with good accuracy, it can be 10 to 1000 μm, preferably 20 to 500 μm, and more preferably 50 to 300 μm. It should be noted that the average thickness of the space filling material is a value measured by the method described in the following examples.

[0123] For the space filling material of the present invention, especially in the case of a narrow gap (for example, a space with a thickness of about 20 to 5000 μm), in order to be easily inserted and fill the gap with good precision, it is preferably of uniform thickness. For example, the CV value of the thickness can be 0.2 or less, more preferably 0.1 or less, further preferably 0.08 or less, and even further preferably 0.06 or less. It should be noted that the CV value of the thickness of the space filling material 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.

[0124] The average unit area weight of the space filling material of the present invention can be set to various unit area weights according to the space to be filled and the use, for example, it can be selected from a wide range of 10 to 10000 g / m 2 From the perspective of being able to fill even a narrow space with good precision, it can be 10 to 500 g / m 2 It can be preferably 20 to 400 g / m 2 It can be more preferably 50 to 300 g / m 2 It should be noted that the average unit area weight of the space filling material is a value measured by the method described in the examples below.

[0125] From the perspective of being able to fill the space with good precision, the CV value of the unit area weight of the space filling material of the present invention can be 0.2 or less, more preferably 0.15 or less, and further preferably 0.1 or less. It should be noted that the CV value of the unit area weight of the space filling material refers to the ratio of the standard deviation of the measured unit area weight to the average unit area weight, and is a value measured by the method described in the examples below.

[0126] The density of the space filling material of the present invention can be set to various densities according to the space to be filled and the use, and can be 0.5 to 5 g / cm 3 It can be preferably 0.6 to 4 g / cm 3 It can be more preferably 0.7 to 3 g / cm 3 It should be noted that the density of the space filling material is a value measured by the method described in the examples below.

[0127] The shape of the space filling material of the present invention can be set to various shapes according to the space to be filled and the use, and also includes a three-dimensional shape with a three-dimensional structure. In the case of a three-dimensional shape, the direction of thermal expansion is taken as the thickness direction. From the perspective of being able to insert into a narrow gap and fill the gap with good precision, a plate shape is preferred.

[0128] The release rate of the degree of curvature of the space filling material of the present invention as defined by the following formula (2) can be 20% or more, preferably 30% or more, more preferably 40% or more, further preferably 50% or more, and even more preferably 60% or more. The release rate of the degree of curvature is an index indicating the extent to which the space filling material has the ability to thermally expand. The space filling material having the release rate of the degree of curvature as described above is excellent in the strength for strengthening the space when filling in a given space and the strength for fixing the material to be fixed. The upper limit of the release rate of the degree of curvature is not particularly limited and can be, for example, 100%.

[0129] Release rate of degree of curvature (%) = [(X - 1) - (Y - 1)] / (X - 1) × 100 (2)

[0130] (In the formula, X represents the average degree of curvature of the reinforcing fibers in the space filling material before expansion, and Y represents the average degree of curvature of the reinforcing fibers in the space filling material after heating and expansion under non-pressurized conditions.)

[0131] The maximum expansion rate in the thickness direction of the space filling material of the present invention is preferably 120% or more, more preferably 150% or more, further preferably 170% or more, and even more preferably 200% or more. The upper limit of the maximum expansion rate in the thickness direction is not particularly limited and can be 700%. When the maximum expansion rate in the thickness direction is within the above range, sufficient strength can be achieved for strengthening and / or fixing. It should be noted that the maximum expansion rate in the thickness direction of the space filling material represents the expansion rate when heated and expanded under non-pressurized conditions and is a value measured by the method described in the examples below.

[0132] For the space filling material of the present invention, from the viewpoint of suppressing gas generation, it is preferably substantially free of volatile substances (such as low molecular weight compounds with a boiling point lower than the heating temperature, etc.), foaming agents, expanded graphite, etc. when heated, and the total amount of volatile substances in the space filling material can be less than 0.5 wt%.

[0133] <Method of using space filling material>

[0134] The method of using the space filling material of the present invention may include a step of expanding the space filling material in a given space by heating above the softening point of the thermoplastic resin. In the present invention, the given space can be a space (gap) surrounded by a single outer member or a space (gap) formed by a plurality of outer members. In addition, the space filling material can fill the entire given space or a part thereof.

[0135] For example, based on the cross-sectional schematic diagram of the first embodiment showing the usage method of the space-filling material of the present invention Figure 2A and Figure 2B an explanation will be given. Figure 2A shows the state of the space-filling material 11 before expansion, Figure 2B shows the state of the space-filling material 11 after expansion. In Figure 2A , the space-filling material 11 is inserted into the space 13 surrounded by the outer member 12. In Figure 2A , the entire space 13 is surrounded by a single outer member 12 to form, but it does not have to be a closed space surrounded by the outer member as a whole. For example, an open space can be formed in part like a U-shape. In addition, the space can be formed by a plurality of different members. In addition, a plurality of space-filling materials 11 can also be inserted into the space 13. It should be noted that Figure 2A shows a part of the outer member 12.

[0136] By heating above the softening point of the thermoplastic resin constituting the space-filling material 11, the thermoplastic resin softens, and along with this, the bending of the reinforcing fibers constrained by the thermoplastic resin is released, whereby the resilience (recovery force) of the reinforcing fibers is exhibited in the thickness direction. Then, the space-filling material 11 irreversibly expands in the thickness direction ( Figure 2A the Z direction), and as shown in Figure 2B , fills the space 13. A high pressing force is applied to the wall surface of the space 13 by the expansion stress of the space-filling material 11, and at the same time, the molten thermoplastic resin is pressed against the outer member 12 and bonded, whereby the outer member 12 is sufficiently strengthened.

[0137] In the process of expanding it, for the heating temperature, as long as there are no restrictions such as the heat resistance of the outer member and the material to be fixed, there is no particular limitation. For example, based on the softening point of the thermoplastic resin, it can 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 can be, for example, (softening point + 250) °C or lower, preferably (softening point + 200) °C or lower, and particularly from the viewpoint of suppressing the deterioration of the thermoplastic resin, more preferably (softening point + 150) °C or lower.

[0138] In the expansion process, the space-filling material can expand rapidly, but it can also have a uniform structure as a whole by expanding slowly. For example, the heating time for expanding it can be about 1 minute to 1 hour, preferably about 10 to 50 minutes.

[0139] In addition, the usage method of the space-filling material of the present invention can include a process of inserting the space-filling material into a given space before the expansion process.

[0140] From the viewpoint of facilitating the insertion of the space-filling material and filling the space with good accuracy, the thickness of the inserted space can be 1.01 to 4 times the average thickness of the space-filling material, preferably 1.2 to 3.5 times, and more preferably 1.5 to 3 times the thickness.

[0141] In the present invention, the porosity of the space-filling material after expansion (after filling) can be 30 to 95%. By setting the porosity of the space-filling material after expansion within this range, it is possible to sufficiently perform liquid passing and gas passing on the space-filling material after expansion. For example, when cooling is required in a structure containing the space-filling material after expansion, cooling can be performed by passing a liquid through the space-filling material after filling. In addition, the porosity of the space-filling material after expansion can be preferably 35 to 90%, and more preferably 40 to 85%. It should be noted that the porosity of the space-filling material after expansion is a value measured by the method described in the following examples.

[0142] In the present invention, the space-filling material after expansion (after filling) can have a continuous porous structure. When the voids in the space-filling material after expansion are connected pores, it is possible to sufficiently perform liquid passing and gas passing on the space-filling material after expansion.

[0143] In the present invention, from the viewpoint of improving the mechanical strength and liquid permeability of the space-filling material after expansion (after filling), the expansion ratio after filling in the thickness direction can be 101 to 400%, preferably 120 to 400%, more preferably 130 to 300%, and further preferably 140 to 250%. It should be noted that the expansion ratio after filling in the thickness direction is represented by the following formula (3).

[0144] Expansion ratio after filling (%) = Thickness of the space-filling material after filling (thickness of the filled space) (mm) / Thickness of the space-filling material before filling (mm) × 100 (3)

[0145] From the viewpoint of improving the strength of the reinforcing space and the strength of the material to be fixed, the ratio of the expansion ratio after filling, which represents the expansion ability of the space-filling material, to the maximum expansion ratio can be 1 to 90% as calculated by (expansion ratio after filling - 100) / (maximum expansion ratio - 100) × 100, preferably 1.5 to 85%, and more preferably 2 to 83%.

[0146] In the present invention, the desired size can be formed by expansion, and the thickness of the given space (the thickness of the space filling material after expansion (after filling)) can be selected from a wide range of, for example, 0.02 to 600 mm. From the viewpoint of filling a narrow gap, it can be, for example, 20 to 5000 μm, preferably 50 to 4000 μm, and more preferably 80 to 3000 μm.

[0147] In the present invention, from the viewpoint of being able to fill the gap with good accuracy, the CV value of the thickness of the space filling material after expansion can be 0.1 or less, preferably 0.08 or less. Here, the CV value of the thickness after expansion represents the CV value of the thickness of the space filling material after expansion under non-pressurized conditions, and is a value measured by the method described in the examples below.

[0148] In the present invention, the stamping load described in the examples below can be 5 N or more, preferably 10 N or more, more preferably 15 N or more, and further preferably 20 N or more. The upper limit of the stamping load is not particularly limited, and can be, for example, about 1000 N. It should be noted that the stamping load is a value measured by the method described in the examples below. In the case of the stamping load showing the above range, the strength for strengthening the space during filling in a given space and the strength for fixing the material to be fixed are excellent, and thus it is useful as a reinforcing material or a fixing material.

[0149] In addition, the method of using the space filling material of the present invention may include: a step of fixing the material to be fixed by expanding the space material in a given space by heating above the softening point of the thermoplastic resin. The space filling material of the present invention can also be used as a fixing material for fixing the material to be fixed.

[0150] For example, based on the cross-sectional schematic diagram of the second embodiment showing the method of using the space filling material of the present invention Figure 3A and Figure 3B will be described. Figure 3A shows the state of the space filling material 21 before expansion, Figure 3B shows the state of the space filling material 21 after expansion. In Figure 3A , the material to be fixed 24 sandwiched between two space filling materials 21 is inserted into the space 23 surrounded by the outer member 22 to form a space filling structure 25. In Figure 3AIn this case, the entire space 23 is formed by being surrounded by a single outer member 22, but it does not necessarily have to be a closed space surrounded by the outer member as a whole. For example, an open space can be formed in part like a U-shape. In addition, the space can also be formed by a plurality of different members. In addition, the space filling material 21 is inserted by being laminated piece by piece on both sides of the material to be fixed 24. The number of laminated pieces and the insertion positions are not limited, and one or more pieces can be laminated and inserted on at least one side of the material to be fixed 24. The space filling materials 21 laminated on both sides of the material to be fixed 24 can be the same or different, and preferably the same from the viewpoint of improving the uniformity of expansibility. It should be noted that Figure 3A A part of the outer member 22 is shown.

[0151] By heating above the softening point of the thermoplastic resin constituting the space filling material 21, the thermoplastic resin softens, and along with this, the bending of the reinforcing fibers constrained by the thermoplastic resin is released, and thus the resilience (recovery force) of the reinforcing fibers is exhibited in the thickness direction. And the space filling material 21 irreversibly expands in the thickness direction ( Figure 3A the Z direction), as Figure 3B shown, 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 sides of the material to be fixed 24 by the expansion stress of the space filling material 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 bonded, and thus, the material to be fixed 24 is sufficiently fixed.

[0152] In addition, the method of using the space filling material of the present invention may include a step of inserting the space filling material and / or the material to be fixed into a given space before the step of expanding and fixing the material to be fixed. The space filling material and the material to be fixed can be inserted together, or one of the space filling material and the material to be fixed can be inserted first, and then the other can be inserted. In addition, the space filling material and the material to be fixed can also be inserted into a given space in which one of them has been previously inserted.

[0153] <Space filling structure>

[0154] The space filling structure of the present invention may include a space filling material and a material to be fixed that is joined to at least a part of the space filling material and integrated.

[0155] The space filling structure can, for example, integrate the above-mentioned space filling material and the material to be fixed by fusion bonding. For example, a method can be used in which the above-mentioned space filling material and the material to be fixed are laminated in such a way that they are in contact with each other, the expansion of the space filling material is suppressed by pressing, etc., and heating is performed at a temperature above the softening point of the above-mentioned thermoplastic resin in the space filling material, so that the above-mentioned space filling material and the material to be fixed are fusion bonded and manufactured.

[0156] Alternatively, the space-filling structure can be manufactured with reference to the manufacturing method of the space-filling material. For example, the composite sheet used to form the space-filling material is laminated in contact with the material to be fixed, heated to a temperature above the softening point of the thermoplastic resin in the space-filling material, and pressed in the lamination direction. Further, while pressing, it is cooled. By such a method, the above space-filling material and the material to be fixed are fused and bonded to manufacture the space-filling structure.

[0157] Alternatively, the space-filling structure can be manufactured, for example, by laminating and bonding the space-filling material and the material to be fixed with an adhesive. In this case, as the adhesive, as long as it can bond the space-filling material and the material to be fixed, there is no particular limitation, and a known adhesive can be used.

[0158] In the space-filling structure of the present invention, the material to be fixed can be clamped by the above space-filling material. For the space-filling structure, the material to be fixed can be clamped by the space-filling material in at least two opposite directions. For example, it can be clamped along the thickness direction of the material to be fixed, or can be clamped along the thickness direction and the direction orthogonal thereto. For example, when the material to be fixed is in the shape of a rectangular parallelepiped, if the thickness direction of the material to be fixed is set as the Z direction, the direction orthogonal to the above thickness direction includes the X direction (refer to Figure 3A ) that is parallel to a given side of the material to be fixed and orthogonal to the Z direction, and the Y direction (refer to Figure 3A ) that is orthogonal to the X direction and the Z direction. Therefore, the space-filling structure can be clamped by four directions composed of the Z direction (the thickness direction of the material to be fixed) and the X or Y direction, or can be clamped by six directions composed of the X direction, the Y direction, and the Z direction. In addition, in the space-filling structure, in each of the X direction, the Y direction, and the Z direction, the material to be fixed can be arranged in two opposite directions relative to the space-filling material, or the material to be fixed can be arranged only in any one direction.

[0159] <Method of using the space-filling structure>

[0160] The method of using the space-filling structure of the present invention may include: a step of fixing the material to be fixed by expanding the above space-filling material in a given space by heating to a temperature above the softening point of the thermoplastic resin.

[0161] In addition, the method of using the space-filling structure of the present invention may include a step of inserting the space-filling structure into a given space before the step of expanding and fixing the material to be fixed.

[0162] In addition, in transportation means, home appliances, industrial machinery, buildings, etc., the space-filling material of the present invention can be effectively used as a space-filling reinforcement material for filling a given space surrounded by a member to reinforce the member, and a space-filling fixing material for fixing a material to be fixed in a given space surrounded by the member.

[0163] Especially when the space-filling material has a given insulation property and / or heat resistance, in one aspect of the space-filling material of the present invention, it can be effectively used as an insulating and / or heat-resistant space-filling material.

[0164] For example, for the space-filling material and space-filling structure of the present invention, in a motor (e.g., a drive motor of an automobile), by using it as a molding material for fixing a permanent magnet (material to be fixed) in a plurality of hole portions formed in a rotor, the permanent magnet can be fixed with sufficient fixing strength, and the motor can be cooled by allowing a coolant to pass through voids existing in the form of communication holes, and insulation can also be imparted. In addition, although there are voids, the fixing strength is also high, so the ratio of the material in the space can be reduced, and thus the cost can also be reduced.

[0165] Examples

[0166] Hereinafter, the present invention will be described in more detail based on examples, but the present invention is not limited by any of these examples. It should be noted that in the following examples and comparative examples, various physical properties were measured by the following methods.

[0167] [Single fiber fineness]

[0168] According to Method B of 8.5.1 of JIS L 1015:2010 "Test Methods for Chemical Fiber Staple Fibers", using the average fiber length calculated by the method described below, the single fiber fineness was measured.

[0169] [Average fiber length]

[0170] For 100 randomly selected fibers, their fiber lengths were measured, and the average value of the measured values was used as the average fiber length.

[0171] [Average fiber diameter]

[0172] For 30 randomly selected fibers, the fiber diameters were measured by microscopic observation, and the average value of the measured values was used as the average fiber diameter.

[0173] [Tensile elastic modulus]

[0174] The tensile elastic modulus was measured in accordance with JIS R 3420 for glass fiber (hereinafter sometimes simply referred to as GF), and in accordance with JIS R 7606 for carbon fiber (hereinafter sometimes simply referred to as CF).

[0175] [Glass transition temperature (Tg) of thermoplastic fiber]

[0176] Using "Rheospectra DVE-V4" manufactured by RHEOLOGY COMPANY, the temperature dependence of the loss tangent (tanδ) was measured at a frequency of 10 Hz and a heating rate of 10 °C / min, and the glass transition temperature of the thermoplastic fiber was determined from the peak temperature thereof. Here, the peak temperature of tanδ refers to the temperature at which the first derivative value of the change amount of the tanδ value with respect to temperature is zero.

[0177] [Volume ratio]

[0178] For the volume ratios of the reinforcing fiber and the thermoplastic resin constituting the space filling material, the weight ratios were converted based on their respective densities and calculated in the form of the mutual volume ratio (reinforcing fiber: thermoplastic resin).

[0179] [Weight per unit area]

[0180] Eighty pieces of the space filling material sample with a length of 250 mm and a width of 250 mm were cut into small pieces with a length of 50 mm and a width of 15 mm. The weight (g) of all the small pieces was measured, and the weight per unit area (g / m 2 ) was calculated. The average value of the weight per unit area of all the small pieces was taken as the average weight per unit area (g / m 2 ) of the space filling material. In addition, the standard deviation of the weight per unit area of all the small pieces was calculated, and the CV value of the weight per unit area was calculated by the following formula.

[0181] Weight per unit area CV value = Standard deviation of weight per unit area (g / m 2 ) / Average weight per unit area (g / m 2 )

[0182] [Thickness]

[0183] Eighty pieces of the space filling material sample with a length of 250 mm and a width of 250 mm were cut into small pieces with a length of 50 mm and a width of 15 mm. The thickness (μm) at the center of each small piece was measured with a micrometer, and the average value of the thickness of all the small pieces was taken as the average thickness (μm) of the space filling material. In addition, the standard deviation of the thickness of all the small pieces was calculated, and the CV value of the thickness was calculated by the following formula.

[0184] Thickness CV value = Standard deviation of thickness (μm) / Average thickness (μm)

[0185] [Density]

[0186] Cut the space filling material sample into a length of 50 mm and a width of 15 mm, measure its thickness (cm) and weight (g), and calculate the density by the following formula.

[0187] Density (g / cm 3 ) = Weight (g) / (Thickness (cm) × 7.5 (cm 2 ))

[0188] [Void Ratio]

[0189] Calculate the void ratio (%) of the space filling material according to JIS K 7075 "Test for Fiber Content and Void Ratio of Carbon Fiber Reinforced Plastics".

[0190] [Degree of Curvature]

[0191] Cut the space filling material sample into a length of 50 mm and a width of 15 mm, perform X-ray CT measurement under the following conditions, and perform image analysis on the obtained images in the following order to measure the degree of curvature.

[0192] <X-ray CT Measurement Conditions>

[0193] Measurement device: Xradia 520Versa (manufactured by Carl Zeiss)

[0194] X-ray target: Tungsten

[0195] X-ray tube voltage: 100 kV

[0196] Output: 9 W

[0197] Objective lens: 4X

[0198] Pixel size: 1 μm / pix

[0199] Pixel binning: 1

[0200] Number of images taken: 3201

[0201] Exposure time: 6 seconds / image

[0202] <Image Analysis Conditions>

[0203] Image analysis software: Avizo (manufactured by Thermo Fisher Scientific)

[0204] On the image analysis software, the three-dimensional image of the space filling material sample obtained by X-ray CT measurement is cut into images of 0.40 mm × 0.40 mm × total thickness, and then, if necessary, noise is removed through the NON-LOCAL Filter function. The NON-LOCAL Filter function is set to the following conditions.

[0205] Spatial Standard Deviation Value: 5

[0206] Intensity Standard Deviation Value: 0.2

[0207] Search window Value: 10

[0208] Local Neighborhood Value: 3

[0209] Then, binarization is performed through the Interactive Thresholding function to extract all fibers.

[0210] For the data obtained by cutting the image into the above-mentioned 0.40 mm × 0.40 mm × total thickness, or the data obtained by removing noise through NON-LOCAL Filter processing, fibers with diameters meeting the following set conditions are extracted using the Fiber Tracing function.

[0211] Cylinder length Value of Cylinder Correlation: Any value between 2.5 and 3.5 times the fiber diameter

[0212] Angular Sampling Value: 5

[0213] Mask Cylinder Radius Value: Any value between fiber radius + 1 and fiber radius + 13

[0214] Outer Cylinder Radius Value: Fiber radius

[0215] Inner Cylinder Radius Value: 0

[0216] Direction Coefficient Value of Trace Correlation Lines: 0.1 - 0.5

[0217] Minimum Distance Value: Any value between the fiber radius and the fiber diameter

[0218] Take the "Tortuosity" of each extracted fiber as the degree of curvature. Calculate the volume content rate (vol%) of the reinforcing fibers with a degree of curvature of 1.004 or more relative to the volume of all the extracted reinforcing fibers. Take this as the "Ratio of reinforcing fibers with a degree of curvature of 1.004 or more in the reinforcing fibers" in Table 1.

[0219] Multiply the volume content rate of all the reinforcing fibers relative to the overall volume of the space filling material calculated according to JIS K 7075 "Test for Fiber Content Rate and Void Ratio of Carbon Fiber Reinforced Plastics" by the volume content rate of the reinforcing fibers with a degree of curvature of 1.004 or more relative to the volume of all the reinforcing fibers, and calculate the volume content rate (vol%) of the reinforcing fibers with a degree of curvature of 1.004 or more relative to the overall volume of the space filling material. Take this as the "Volume content rate of reinforcing fibers with a degree of curvature of 1.004 or more in the space filling material" in Table 1.

[0220] Using the data of the degree of curvature of the obtained fibers, calculate the average degree of curvature by the following formula.

[0221] Average degree of curvature = Sum of the degrees of curvature of each extracted fiber / Number of extracted fibers

[0222] [Evaluation of expansibility]

[0223] Put the space filling materials obtained from the examples and comparative examples into a forced-air constant temperature oven (Model "DN411H" manufactured by Yamato Scientific Co., Ltd.) set at a given temperature above the softening point of the thermoplastic resin, heat for 10 minutes and then take out, and cool to 25°C. Then, measure the average thickness of the expanded sample, and based on the average thickness of the sample before and after heating, measure the maximum expansion rate (%) using the following formula.

[0224] Maximum expansion rate (%) = Average thickness of the expanded space filling material (μm) / Average thickness of the space filling material before expansion (μm) × 100

[0225] Calculate the average degree of curvature Y of the reinforcing fibers in the expanded space filling material by the same calculation method as the average degree of curvature of the reinforcing fibers in the above-mentioned space filling material, and calculate the degree of curvature release rate (%) by the following formula.

[0226] Release rate of curvature (%) = [(X - 1) - (Y - 1)] / (X - 1) × 100

[0227] (In the formula, X: average curvature of reinforcing fibers in the space filling material before expansion; Y: average curvature of reinforcing fibers in the space filling material after heat expansion under non-pressurized conditions)

[0228] In addition, by the same calculation method as the thickness CV value of the above-mentioned space filling material, the thickness CV value of the space filling material after expansion is calculated.

[0229] [Stamping load]

[0230] Samples for stamping load test were prepared according to the following steps. Figure 4A It is a three-dimensional schematic diagram for explaining the production of samples for stamping load test, Figure 4B It is a cross-sectional schematic diagram for explaining the production of samples for stamping load test.

[0231] (1) The space filling materials obtained from the examples and comparative examples were cut into a length of 50 mm and a width of 15 mm to prepare space filling material samples.

[0232] (2) A hollow square material (large) 32a with a length of 20 mm, a width of 20 mm, a thickness of 2.15 mm, and a length of 100 mm and a hollow square material (small) 32b with a width of 15 mm, a thickness of 1.5 mm, and a length of 100 mm were prepared. Here, in each example and comparative example, the following hollow square material (small) 32b was prepared. When the hollow square material (small) 32b is inserted into the hollow square material (large) 32a, the gap between the inner transverse surface of the hollow square material (large) 32a and the outer transverse surface of the hollow square material (small) 32b becomes a given height in the longitudinal dimension. That is, the longitudinal dimension of the hollow square material (small) 32b was adjusted to (inner longitudinal dimension of the hollow square material (large) 32a (15.7 mm) - gap height h × 2).

[0233] (3) In the state where the hollow square material (small) 32b is inserted into the hollow square material (large) 32a by 50 mm along the length direction as shown in Figure 4A , as shown in Figure 4B , one space filling material sample 31 was inserted into each of the two gaps between the inner transverse surface of the hollow square material (large) 32a and the outer transverse surface of the hollow square material (small) 32b, and it was placed in a forced-air isothermal thermostat (manufactured by Yamato Scientific Co., Ltd., "DN411H") set at a given temperature and heated for 20 minutes and then taken out and cooled to 25 °C. Thus, the space filling material sample 31 was filled.

[0234] The expansion rate after filling (%) is calculated by the following formula. It should be noted that when the height of the gap is completely filled, the average thickness of the space filling material after filling becomes the height of each gap.

[0235] Expansion rate after filling (%) = Average thickness of the space filling material after filling (μm) / Average thickness of the space filling material before filling (μm) × 100

[0236] In addition, the porosity (%) of the space filling material after complete filling is calculated by the same calculation method as the porosity of the above-mentioned space filling material, and is used as the porosity after filling.

[0237] For the obtained sample for the stamping load test, using a universal testing machine ("AG-2000A" manufactured by Shimadzu Corporation), a load is applied only to the small hollow square material in the longitudinal direction under the condition of a compression speed of 2 mm / min, and the small hollow square material is stamped, and the load at the time of the start of misalignment is used as the stamping load (N).

[0238] [Reference Example 1] (Manufacture of polyetherimide fiber)

[0239] The polyetherimide (hereinafter sometimes simply referred to as PEI) - based polymer ("ULTEM9001" manufactured by SABIC Innovative Plastics), which is an amorphous resin, was vacuum - dried at 150 °C for 12 hours. The above - mentioned PEI - based polymer was ejected from a circular - hole nozzle under the conditions of a spinneret temperature of 390 °C, a spinning speed of 1500 m / min, and an ejection amount of 50 g / min to produce a multifilament of 2640 dtex / 1200f PEI fiber. The obtained multifilament was cut into 15 mm to produce short - cut fibers of PEI fiber. The obtained fibers had a good appearance without burrs, etc., the fineness of a single fiber was 2.2 dtex, the average fiber length was 15.0 mm, the glass transition temperature (softening point of the amorphous thermoplastic resin) was 217 °C, and the density was 1.27 g / cm 3 .

[0240] [Reference Example 2] (Manufacture of PET - based binder fiber)

[0241] Using a polymerization reactor, a polycondensation reaction was carried out at 280 °C by a conventional method to produce a PET-based polymer with an intrinsic viscosity (η) of 0.81. The above PET-based polymer contains terephthalic acid and isophthalic acid as dicarboxylic acid components and the copolymerization ratio (molar ratio) is 70 / 30, and 100 mol% of ethylene glycol as a diol component. The obtained polymer was extruded in a strand form from the bottom of the polymerization apparatus into water and cut into granules. The obtained PET-based polymer was supplied to a co-rotating vented twin-screw extruder heated to 270 °C, passed through a residence time of 2 minutes, introduced into a spinneret heated to 280 °C, and ejected from a round-hole nozzle under the condition of an ejection rate of 45 g / min, and drawn at a spinning speed of 1200 m / min, thereby producing a multifilament formed of a 2640 dtex / 1200 f PET-based polymer. Then, the obtained fiber was cut into 5 mm. The obtained fiber had a good appearance without burrs, etc., the single fiber fineness was 2.2 dtex, the average fiber length was 5.0 mm, and the density was 1.38 g / cm 3 .

[0242] [Reference Example 3] (Manufacture of Polycarbonate Fiber)

[0243] A polycarbonate (hereinafter sometimes simply referred to as PC)-based polymer (Iupilon S-3000 manufactured by Mitsubishi Engineering-Plastics Corporation), which is an amorphous resin, was vacuum-dried at 120 °C for 6 hours. The above PC-based polymer was ejected from a round-hole nozzle under the conditions of a spinneret temperature of 300 °C, a spinning speed of 1500 m / min, and an ejection rate of 50 g / min to produce a multifilament of 2640 dtex / 1200 f PC fiber. The obtained multifilament was cut into 15 mm to produce short-cut fibers of PC fiber. The obtained fiber had a good appearance without burrs, etc., the single fiber fineness was 2.2 dtex, the average fiber length was 15.0 mm, the glass transition temperature (softening point of amorphous thermoplastic resin) was 150 °C, and the specific gravity was 1.2 g / cm 3 .

[0244] [Reference Example 4] (Preparation of Tackifier)

[0245] 2 g of Pamol (manufactured by Meisei Chemical Industry Co., Ltd.) was added to 2 L of water and stirred until completely dissolved, thereby preparing a tackifier.

[0246] [Reference Example 5] (Preparation of Dispersant)

[0247] Solutions were separately prepared by dissolving 3.75 g of Alkox CP - B1 (manufactured by Meisei Chemical Industry Co., Ltd.) in 2 L of water and 3.75 g of Pulset HA (manufactured by Meisei Chemical Industry Co., Ltd.) in 2 L of water as dispersants. 20 mL of each dispersant was separately added to the slurry for use.

[0248] [Example 1]

[0249] 50 wt% of PEI fibers as thermoplastic fibers, 45 wt% of glass fibers with a cut length of 13 mm as reinforcing fibers (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 - type binder fibers as binder fibers were put into 1.5 L of water and 40 mL of dispersant, and stirred 1500 times at 540 rpm using a dissociator to prepare a slurry. 60 - 80 mL of a thickener was added to the obtained slurry, and a mixed non - woven fabric (co - formed paper) with a basis weight of 78 g / m 2 was obtained through a wet - laid process.

[0250] Three sheets of the obtained mixed non - woven fabrics were laminated, and using a test press (manufactured by Kitakawa Seiki Co., Ltd. "KVHC - II"), the surface perpendicular to the lamination direction was pressed at 3 MPa and heated at 340 °C for 10 minutes to impregnate the molten PEI - type polymer and PET - type polymer between the glass fibers. Then, while maintaining the pressure, it was cooled to below the glass transition temperature of the PEI - type polymer, i.e., 150 °C, to produce a space - filling material. The average thickness of the obtained space - filling material was 144 μm, the thickness CV value was 0.049, the average basis weight was 233.8 g / m 2 , the basis weight CV value was 0.024, the density was 1.625 g / cm 3 , the porosity was 1.4%, and the volume content rate of reinforcing fibers with a curvature of 1.004 or more with respect to the total volume of reinforcing fibers was 82.7 vol%.

[0251] The obtained space - filling material was evaluated in various ways, and the evaluation results are shown in Table 1. It should be noted that the set temperature of the air - supply isothermal thermostat in the expansibility evaluation was 260 °C, the set temperature of the air - supply isothermal thermostat when making the sample for the stamping load test was 280 °C, and the gap height h of the sample for the stamping load test was set to 300 μm.

[0252] [Example 2]

[0253] In the production process of the space filling material, the number of sheets of the mixed nonwoven fabric was set to 1 sheet, and except for this, the space filling material was produced in the same manner as in Example 1. The average thickness of the obtained space filling material was 63 μm, the thickness CV value was 0.060, the average unit area weight was 81.2 g / m 2 , the unit area weight CV value was 0.024, and the density was 1.293 g / cm 3 , the porosity was 21.5%, and the volume content of reinforcing fibers with a curvature of 1.004 or more relative to the total volume of the reinforcing fibers was 81.5 vol%.

[0254] For the obtained space filling material, the gap height h of the sample for the stamping load test was changed to 100 μm, and except for this, the evaluation was carried out in the same manner as in Example 1, and the evaluation results are shown in Table 1.

[0255] [Example 3]

[0256] In the production process of the mixed nonwoven fabric, no tackifier and dispersant were added, and except for this, the mixed nonwoven fabric was produced in the same manner as in Example 1. Then, in the production process of the space filling material, the space filling material was produced in the same manner as in Example 2. The average thickness of the obtained space filling material was 82 μm, the thickness CV value was 0.230, and the average unit area weight was 77.4 g / m 2 , the unit area weight CV value was 0.045, and the density was 0.942 g / cm 3 , the porosity was 42.8%, and the volume content of reinforcing fibers with a curvature of 1.004 or more relative to the total volume of the reinforcing fibers was 76.1 vol%.

[0257] For the obtained space filling material, the evaluation was carried out in the same manner as in Example 2, and the evaluation results are shown in Table 1.

[0258] [Example 4]

[0259] In the production process of the space filling material, the number of sheets of the mixed nonwoven fabric was set to 30 sheets, and except for this, the space filling material was produced in the same manner as in Example 1. The average thickness of the obtained space filling material was 1500 μm, the thickness CV value was 0.021, and the average unit area weight was 2400 g / m 2 , the unit area weight CV value was 0.018, and the density was 1.600 g / cm 3 , the porosity was 2.9%, and the volume content of reinforcing fibers with a curvature of 1.004 or more relative to the total volume of the reinforcing fibers was 83.2 vol%.

[0260] For the obtained space filling material, the clearance height h of the sample for the stamping load test was changed to 3000 μm, and evaluation was carried out in the same manner as in Example 1 except for this. The evaluation results are shown in Table 1.

[0261] [Example 5]

[0262] Glass fibers with a cut length of 13 mm (manufactured by Nippon Electric Glass Co., Ltd.: average fiber diameter 6.5 μm, specific gravity 2.54 g / cm 3 ) were used as the reinforcing fibers, and a space filling material was produced in the same manner as in Example 2 except for this. The average thickness of the obtained space filling material was 62 μm, the thickness CV value was 0.038, the average unit area weight was 81.0 g / m 2 , the unit area weight CV value was 0.024, the density was 1.306 g / cm 3 , the porosity was 20.7%, and the volume content rate of the reinforcing fibers with a curvature of 1.004 or more with respect to the total volume of the reinforcing fibers was 83.0 vol%.

[0263] For the obtained space filling material, evaluation was carried out in the same manner as in Example 2, and the evaluation results are shown in Table 1.

[0264] [Example 6]

[0265] Glass fibers with a cut length of 13 mm (manufactured by Nippon Electric Glass Co., Ltd.: average fiber diameter 13 μm, specific gravity 2.54 g / cm 3 ) were used as the reinforcing fibers, and a space filling material was produced in the same manner as in Example 2 except for this. The average thickness of the obtained space filling material was 68 μm, the thickness CV value was 0.059, the average unit area weight was 79.5 g / m 2 , the unit area weight CV value was 0.031, the density was 1.169 g / cm 3 , the porosity was 29.0%, and the volume content rate of the reinforcing fibers with a curvature of 1.004 or more with respect to the total volume of the reinforcing fibers was 81.0 vol%.

[0266] For the obtained space filling material, evaluation was carried out in the same manner as in Example 2, and the evaluation results are shown in Table 1.

[0267] [Example 7]

[0268] In the process of manufacturing the mixed non-woven fabric, 75 wt% of PEI fibers as thermoplastic fibers and glass fibers 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) A slurry was prepared with 15 wt% and 5 wt% of PET-based binder fibers as binder fibers. Except for this, a space filling material was produced in the same manner as in Example 1. The average thickness of the obtained space filling material was 145 μm, the thickness CV value was 0.035, and the average unit area weight was 203.6 g / m 2 , the unit area weight CV value was 0.031, and the density was 1.404 g / cm 3 , the porosity was 0.8%, and the volume content of reinforcing fibers with a curvature of 1.004 or more relative to the total volume of the reinforcing fibers was 72.0 vol%.

[0269] For the obtained space filling material, evaluation was carried out in the same manner as in Example 1, and the evaluation results are shown in Table 1.

[0270] [Example 8]

[0271] In the production process of the space filling material, a spacer with a thickness of 0.3 mm was arranged during hot pressing. Except for this, a space filling material was produced in the same manner as in Example 1. The average thickness of the obtained space filling material was 295 μm, the thickness CV value was 0.020, and the average unit area weight was 245.0 g / m 2 , the unit area weight CV value was 0.020, and the density was 0.831 g / cm 3 , the porosity was 49.5%, and the volume content of reinforcing fibers with a curvature of 1.004 or more relative to the total volume of the reinforcing fibers was 38.0 vol%.

[0272] For the obtained space filling material, evaluation was carried out in the same manner as in Example 1, and the evaluation results are shown in Table 1.

[0273] [Example 9]

[0274] In the process of manufacturing the mixed non-woven fabric, a slurry was prepared with 55 wt% of PEI fibers as thermoplastic fibers, 40 wt% of carbon fibers with a cut length of 13 mm as reinforcing fibers (manufactured by Toho Tenax Co., Ltd.: average fiber diameter 7 μm, specific gravity 1.82 g / cm 3 ), and 5 wt% of PET-based binder fibers as binder fibers. Except for this, a space filling material was produced in the same manner as in Example 1. The average thickness of the obtained space filling material was 165 μm, the thickness CV value was 0.052, and the average unit area weight was 235.0 g / m 2 , the unit area weight CV value was 0.025, and the density was 1.424 g / cm 3 , the porosity was 1.9%, and the volume content of reinforcing fibers with a curvature of 1.004 or more relative to the total volume of the reinforcing fibers was 83.1 vol%.

[0275] For the obtained space filling material, evaluation was carried out in the same manner as in Example 1, and the evaluation results are shown in Table 1.

[0276] [Example 10]

[0277] In the process of manufacturing the hybrid nonwoven fabric, PC fiber was used as the thermoplastic fiber, and except for this, the hybrid nonwoven fabric was produced in the same manner as in Example 1.

[0278] Three pieces of the obtained hybrid nonwoven fabrics were laminated, and using a test press ("KVHC-II" manufactured by Kitakawa Seiki Co., Ltd.), the surface perpendicular to the lamination direction was pressed at 3 MPa, and heated at 280 °C for 10 minutes to impregnate the molten PC-based polymer and PET-based polymer between the glass fibers. Then, while maintaining the pressure, it was cooled to below the glass transition temperature of the PC-based polymer, that is, 130 °C, to produce a space filling material. The average thickness of the obtained space filling material was 142 μm, the thickness CV value was 0.045, the average unit area weight was 221.0 g / m 2 , the unit area weight CV value was 0.023, and the density was 1.556 g / cm 3 , the porosity was 1.9%, and the volume content rate of reinforcing fibers with a curvature of 1.004 or more with respect to the total volume of the reinforcing fibers was 79.1 vol%.

[0279] For the obtained space filling material, the set temperature of the air supply isothermal thermostat in the expansion evaluation was set to 190 °C, and the set temperature of the air supply isothermal thermostat when producing the sample for the stamping load test was set to 210 °C. Except for this, evaluation was carried out in the same manner as in Example 1, and the evaluation results are shown in Table 1.

[0280] [Comparative Example 1]

[0281] In the process of manufacturing the space filling material, a gasket with a thickness of 0.5 mm was arranged during hot pressing, and except for this, the space filling material was produced in the same manner as in Example 1. The average thickness of the obtained space filling material was 514 μm, the thickness CV value was 0.088, and the average unit area weight was 231.0 g / m 2 , the unit area weight CV value was 0.030, and the density was 0.449 g / cm 3 , the porosity was 72.7%, and the volume content rate of reinforcing fibers with a curvature of 1.004 or more with respect to the total volume of the reinforcing fibers was 13.9 vol%.

[0282] For the obtained space filling material, the gap height h of the sample for the stamping load test was changed to 600 μm, and except for this, evaluation was carried out in the same manner as in Example 1, and the evaluation results are shown in Table 1.

[0283] [Comparative Example 2]

[0284] In the production process of the space filling material, after the melting process during hot pressing, when moving to the cooling process, cooling was performed without maintaining pressure. Otherwise, the space filling material was produced in the same manner as in Example 1. The average thickness of the obtained space filling material was 485 μm, the thickness CV value was 0.075, the average weight per unit area was 232.0 g / m 2 , the CV value of the weight per unit area was 0.031, and the density was 0.478 g / cm 3 , and the porosity was 71.0%.

[0285] For the obtained space filling material, the gap height h of the sample for the stamping load test was changed to 600 μm, and otherwise, the evaluation was performed in the same manner as in Example 1. The evaluation results are shown in Table 1.

[0286] [Comparative Example 3]

[0287] In the production process of the mixed nonwoven fabric, a slurry was prepared using 85 wt% of PEI fibers as thermoplastic fibers, 10 wt% of glass fibers as reinforcing fibers (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 fibers as binder fibers. Otherwise, the mixed nonwoven fabric was produced in the same manner as in Example 1.

[0288] For one piece of the obtained mixed nonwoven fabric, using a test press ("KVHC-II" manufactured by Kitakawa Seiki Co., Ltd.), a gasket with a thickness of 70 μm was placed, and the surface perpendicular to the lamination direction was pressed at 1 MPa and heated at 340 °C for 10 minutes to impregnate the molten PEI resin between the glass fibers. Then, while maintaining the pressure, it was cooled to below the glass transition temperature of PEI, i.e., 150 °C, to produce a space filling material. The average thickness of the obtained space filling material was 60 μm, the thickness CV value was 0.021, the average weight per unit area was 80.0 g / m 2 , the CV value of the weight per unit area was 0.021, the density was 1.333 g / cm 3 , the porosity was 0.7%, and the volume content ratio of the reinforcing fibers with a curvature of 1.004 or more to the total volume of the reinforcing fibers was 18.0 vol%.

[0289] For the obtained space filling material, the evaluation was performed in the same manner as in Example 2. The evaluation results are shown in Table 1.

[0290] [Table 11

[0291]

[0292] As can be seen from Table 1, in the space filling materials of Examples 1 to 10, reinforcing fibers with a curvature of 1.004 or more are present in a specific amount. Therefore, the expansibility is excellent, and the strength of reinforcement or fixation (stamping load) is very high, being 5 N or more. It should be noted that as a method of using the space filling material, perhaps because when filling the gap with a relatively low expansion rate compared to the maximum expansion rate indicating the expansion ability of the space filling material, a higher expansion stress can be exerted. Therefore, it can be considered that in Example 8, by using the space filling material with a maximum expansion rate of 194% in such a way that the expansion rate after filling becomes 102%, a very high fixation strength with a stamping load of 231 N can be exerted.

[0293] In addition, the thickness CV values of the space filling materials of Examples 1, 2, and 4 to 6 are very small, being 0.2 or less. Therefore, the thickness CV value after expansion is 0.1 or less, and the gap can be filled with good accuracy.

[0294] On the other hand, in Comparative Examples 1 to 3, the amount of the reinforcing fibers with a curvature of 1.004 or more is less than 20 vol%, so there is basically no expansion, and the strength of reinforcement or fixation (stamping load) is very low.

[0295] Industrial Applicability

[0296] The space filling material of the present invention is useful for filling a given space surrounded by members in a transportation vehicle, a household electrical appliance product, an industrial machine, a building, etc. For example, the space filling material can be used as a reinforcing material for reinforcing members and as a fixing material for fixing a material to be fixed in a given space surrounded by members. In addition, the space filling material of the present invention can be used as a molding material for fixing permanent magnets (materials to be fixed) in a plurality of hole portions formed in a rotor in an electric motor (for example, a drive motor of an automobile).

[0297] As described above, the preferred embodiments of the present invention have been described with reference to the drawings. Those skilled in the art can easily conceive of various changes and modifications within an obvious range by reading this specification. Therefore, such changes and modifications are construed as being within the scope of the invention determined by the claims.

Claims

1. A space filling material comprising reinforcing fibers and a thermoplastic resin, wherein the reinforcing fibers have a plurality of intersections with each other, and at least a part of the intersections are bonded by the thermoplastic resin, wherein, The volume fraction of reinforcing fibers having a degree of curvature of 1.004 or more as defined by the following formula (1) is 20 vol% or more with respect to the volume of the entire reinforcing fibers, Degree of curvature = fiber length / shortest distance between both ends of the fiber (1) The CV value of the thickness of the space filling material is 0.2 or less, The release rate of the degree of curvature of the space filling material as defined by the following formula (2) is 20% or more, Release rate of degree of curvature (%) = [(X - 1) - (Y - 1)] / (X - 1) × 100 (2) In the formula, X: average degree of curvature of reinforcing fibers in the space filling material before expansion, Y: average degree of curvature of reinforcing fibers in the space filling material after heat expansion under non-pressurized conditions.

2. The space filling material according to claim 1, having an average thickness of 10 to 1000 μm.

3. The space filling material according to claim 1, having a CV value of the weight per unit area of 0.2 or less.

4. The space filling material according to claim 2, having a CV value of the weight per unit area of 0.2 or less.

5. The space filling material according to any one of claims 1 to 4, wherein the average fiber length of the reinforcing fibers is 3 to 100 mm.

6. The space filling material according to any one of claims 1 to 4, wherein the volume fraction of reinforcing fibers having a degree of curvature of 1.004 or more is 3 to 50 vol% with respect to the volume of the entire space filling material.

7. The space filling material according to claim 5, wherein the volume fraction of reinforcing fibers having a degree of curvature of 1.004 or more is 3 to 50 vol% with respect to the volume of the entire space filling material.

8. The space filling material according to any one of claims 1 to 4, wherein the weight fraction of the thermoplastic resin is 40 to 85 wt% with respect to the total weight of the space filling material.

9. The space filling material according to claim 5, wherein the weight fraction of the thermoplastic resin is 40 to 85 wt% with respect to the total weight of the space filling material.

10. The space filling material according to claim 6, wherein the weight fraction of the thermoplastic resin is 40 to 85 wt% with respect to the total weight of the space filling material.

11. The space filling material according to claim 7, wherein the weight fraction of the thermoplastic resin is 40 to 85 wt% with respect to the total weight of the space filling material.

12. A space filling structure, comprising: the space filling material according to any one of claims 1 to 11, and a fixed material integrally joined to at least a part of the space filling material.

13. A method for manufacturing a space filling material, which is a method for manufacturing the space filling material according to any one of claims 1 to 11, the method comprising at least: a step of preparing a composite sheet containing reinforcing fibers and a thermoplastic resin; a step of heating the composite sheet to a temperature above 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 in a state where pressure is applied.

14. The manufacturing method of the space filling material according to claim 13, wherein, The composite sheet is a mixed paper containing reinforcing fibers and thermoplastic fibers.

15. The manufacturing method of the space filling material according to claim 14, wherein, The mixed paper is formed from an aqueous slurry containing reinforcing fibers, thermoplastic fibers and a dispersant.

16. The manufacturing method of the space filling material according to claim 15, wherein, The aqueous slurry further contains a tackifier.

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