JP2017120410A - Sound insulation structure - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a sound insulation structure excellent in rigidity, lightweight properties, and acoustic characteristics.SOLUTION: A sound insulation structure according to the present invention is a sound insulation structure composed of resin, reinforced fibers, and an air gap. A volume content ratio of the resin is in a range of 2.5-85 vol.%. A volume content ratio of the reinforced fibers is in a range of 0.5-55 vol.%. The air gap is contained in the sound insulation structure with a ratio range of 10-99 vol.%. A bending elastic modulus of the sound insulation structure is 1 GPa or more, and a proportion between a transmission loss at a frequency of 200 Hz and a transmission loss at a frequency of 1250 Hz is in a range of 1.1-1.5, in JIS A1441-1.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a sound insulation structure including a resin, a reinforcing fiber, and a gap.

  In recent years, there has been a demand for structural materials with excellent acoustic characteristics from the viewpoint of improving riding comfort and comfort, while satisfying basic mechanical characteristics in mobile applications such as automobiles and railways and building materials such as houses. It is high. Furthermore, there is a high demand for lightweight structural materials for the purpose of reducing fuel consumption in mobile applications and for ease of handling during construction in construction materials applications, and the demand for structures having voids is increasing. From such a background, the structural material has a sandwich structure using a structural material having a void as a core layer inside a metal material or fiber reinforced composite material (FRP), thereby achieving both rigidity improvement and weight reduction. Structures have been proposed.

Japanese Patent No. 5686681 Japanese Patent No. 5060613 Japanese Patent No. 3216479

  However, no structure has been found that satisfies the acoustic characteristics, which are market demands, along with improved rigidity and light weight. Patent Document 1 proposes a vehicle cover material made of glass fiber, polypropylene resin, and a foaming agent as a material that satisfies acoustic characteristics. However, the vehicle cover material described in Patent Document 1 is presumed to be inferior in mechanical characteristics because it uses glass fiber. In addition, since a foaming agent is used to provide voids, there are limitations on the resins that can be used. On the other hand, Patent Document 2 proposes an interior material for a vehicle in which a foamable urethane resin and a stampable seat are combined in order to improve acoustic characteristics. However, Patent Document 2 has no description regarding sound absorption characteristics. Further, Patent Document 3 describes a composite material made of glass fiber and polypropylene resin, but does not describe sound absorption characteristics or sound insulation.

  This invention is made | formed in view of the said subject, The objective is to provide the sound insulation structure excellent in rigidity, lightness, and an acoustic characteristic.

  The sound insulation structure according to the present invention is a sound insulation structure comprising a resin, a reinforcing fiber, and a void, and the volume content of the resin is in the range of 2.5% by volume or more and 85% by volume or less, and the reinforcement The volume content of the fiber is in the range of 0.5% by volume or more and 55% by volume, and the voids are contained in the sound insulation structure at a ratio in the range of 10% by volume or more and 99% by volume or less, The bending elastic modulus of the sound insulation structure is 1 GPa or more, and the ratio of transmission loss at a frequency of 200 Hz to transmission loss at a frequency of 1250 Hz in JIS A1441-1 is in the range of 1.1 or more and 1.5 or less. It is characterized by that.

The sound insulation structure according to the present invention is the sound insulation structure represented by Ec ^1/3 · ρ ⁻¹ , where Ec is a bending elastic modulus of the sound insulation structure and ρ is a specific gravity of the sound insulation structure. The specific bending elastic modulus of the structure is in the range of 3 or more and 20 or less, and the bending elastic modulus Ec of the sound insulation structure is 6 GPa or more.

The sound insulation structure according to the present invention is characterized in that, in the above invention, the specific gravity ρ of the sound insulation structure is 0.9 g / cm ³ or less.

  In the sound insulation structure according to the present invention, in the above invention, the porosity in a portion within 30% from the surface of the sound insulation structure to the midpoint position in the thickness direction is in the range of 0 volume% or more and less than 10 volume%. And the porosity of the remaining portion is in the range of 10 volume% or more and 99 volume% or less.

  The sound insulation structure according to the present invention is characterized in that, in the above invention, the reinforcing fiber is coated with a resin, and the thickness of the resin is in a range of 1 μm or more and 15 μm or less.

  The sound insulation structure according to the present invention is characterized in that, in the above invention, the reinforcing fibers are discontinuous, are substantially monofilament-like, and are randomly dispersed.

  The sound insulation structure according to the present invention is characterized in that, in the above invention, the orientation angle θf of the reinforcing fiber in the sound insulation structure is 3 ° or more.

  The sound insulation structure according to the present invention is characterized in that, in the above invention, the mass average fiber length of the reinforcing fibers is in the range of 1 mm or more and 15 mm or less.

  The sound insulation structure according to the present invention is characterized in that, in the above invention, the reinforcing fibers are carbon fibers.

  The sound insulation structure according to the present invention is characterized in that, in the above invention, the resin contains at least one kind of thermoplastic resin.

  The sound insulation structure according to the present invention is characterized in that, in the above invention, the resin contains at least one kind of thermosetting resin.

  According to the sound insulation structure according to the present invention, it is possible to provide a sound insulation structure excellent in rigidity, lightness, and acoustic characteristics.

FIG. 1 is a schematic diagram showing a cross-sectional structure of a sound insulation structure according to the present invention. FIG. 2 is a schematic view showing an example of a dispersion state of reinforcing fibers in the reinforcing fiber mat used in the present invention. FIG. 3 is a schematic diagram showing an example of a cross-sectional structure in the surface direction and thickness direction of the sound insulation structure according to the present invention. FIG. 4 is a diagram showing a portion within 30% from the surface of the sound insulation structure to the midpoint position in the thickness direction and the remaining portion. FIG. 5 is a diagram showing a portion within 30% from the surface of the sound insulation structure to the midpoint position in the thickness direction and the remaining portion. FIG. 6 is a schematic view showing an example of a reinforcing fiber mat manufacturing apparatus. FIG. 7 is a perspective view showing an example of a molded product. FIG. 8 is a cross-sectional view of the molded product shown in FIG.

  Hereinafter, the sound insulation structure according to the present invention will be described.

  FIG. 1 is a schematic diagram showing a cross-sectional structure of a sound insulation structure according to the present invention. As shown in FIG. 1, the sound insulation structure 1 according to the present invention includes a resin 2, reinforcing fibers 3, and voids 4. Examples of the sound insulation structure include in-wall members such as a sound insulation wall and a sound insulation wall.

  Here, examples of the resin 2 include a thermoplastic resin and a thermosetting resin. In the present invention, a thermosetting resin and a thermoplastic resin may be blended. In that case, among the components constituting the resin, the component occupying an amount exceeding 50% by mass is the name of the resin. To do.

  In one embodiment of the present invention, the resin 2 desirably includes at least one kind of thermoplastic resin. Thermoplastic resins include “polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polytrimethylene terephthalate (PTT), polyethylene naphthalate (PEN), polyesters such as liquid crystal polyester, polyethylene (PE), polypropylene (PP) , Polyolefins such as polybutylene, polyarylene sulfides such as polyoxymethylene (POM), polyamide (PA), polyphenylene sulfide (PPS), polyketone (PK), polyetherketone (PEK), polyetheretherketone (PEEK), poly Crystalline resins such as fluorinated resins such as ether ketone ketone (PEKK), polyether nitrile (PEN), polytetrafluoroethylene, and liquid crystal polymer (LCP); , Polycarbonate (PC), polymethyl methacrylate (PMMA), polyvinyl chloride (PVC), polyphenylene ether (PPE), polyimide (PI), polyamideimide (PAI), polyetherimide (PEI), polysulfone (PSU), poly Amorphous resins such as “ethersulfone, polyarylate (PAR)”, etc., phenolic resins, phenoxy resins, polystyrenes, polyolefins, polyurethanes, polyesters, polyamides, polybutadienes, polyisoprenes, fluorine Examples thereof include thermoplastic resins such as acryl-based resins and acrylonitrile-based thermoplastic elastomers, and copolymers and modified products thereof. Among them, polyolefin is desirable from the viewpoint of light weight of the sound insulation structure to be obtained, polyamide is desirable from the viewpoint of strength, amorphous resin such as polycarbonate and styrene resin is desirable from the viewpoint of surface appearance, and heat resistance In view of the above, polyarylene sulfide is desirable, polyether ether ketone is desirable from the viewpoint of continuous use temperature, and fluorine resin is desirably used from the viewpoint of chemical resistance.

  In one embodiment of the present invention, the resin 2 desirably includes at least one kind of thermosetting resin. Thermosetting resins include unsaturated polyesters, vinyl esters, epoxy resins, phenol resins, urea resins, melamine resins, thermosetting polyimides, copolymers thereof, modified products, and resins obtained by blending at least two of these. Can be illustrated. In addition, the sound insulation structure according to the present invention may contain an impact resistance improver such as an elastomer or a rubber component, and other fillers and additives as long as the object of the present invention is not impaired. Examples of fillers and additives include inorganic fillers, flame retardants, conductivity imparting agents, crystal nucleating agents, ultraviolet absorbers, antioxidants, vibration damping agents, antibacterial agents, insect repellents, deodorants, and coloring inhibitors. , Heat stabilizers, mold release agents, antistatic agents, plasticizers, lubricants, colorants, pigments, dyes, foaming agents, antifoaming agents, or coupling agents.

  The volume content of the resin 2 is in the range of 2.5% by volume to 85% by volume. When the volume content of the resin 2 is less than 2.5% by volume, the reinforcing fibers 3 in the sound insulating structure 1 are bound together, and the reinforcing effect of the reinforcing fibers 3 cannot be made sufficient. This is undesirable because the mechanical properties of the structure, in particular the bending properties, cannot be satisfied. On the other hand, when the volume content of the resin 2 is larger than 85% by volume, the amount of the resin is too large and it is difficult to obtain a void structure, which is not desirable.

  As the reinforcing fiber 3, metal fibers such as aluminum, brass, and stainless steel, PAN-based, rayon-based, lignin-based, pitch-based carbon fibers, graphite fibers, insulating fibers such as glass, aramid, PBO, polyphenylene sulfide, polyester, Examples thereof include organic fibers such as acrylic, nylon, and polyethylene, and inorganic fibers such as silicon carbide and silicon nitride. Moreover, the surface treatment may be given to these fibers. Examples of the surface treatment include a treatment with a coupling agent, a treatment with a sizing agent, a treatment with a bundling agent, and an adhesion treatment of an additive in addition to a treatment for depositing a metal as a conductor. Moreover, these fibers may be used individually by 1 type, and may use 2 or more types together. Among these, PAN-based, pitch-based and rayon-based carbon fibers that are excellent in specific strength and specific rigidity are preferably used from the viewpoint of weight reduction effect. Further, from the viewpoint of improving the economical efficiency of the sound insulation structure to be obtained, glass fibers are desirably used, and in particular, it is desirable to use carbon fibers and glass fibers in combination from the balance between mechanical properties and economical efficiency. Furthermore, aramid fibers are preferably used from the viewpoint of enhancing the impact absorption and shaping properties of the sound insulation structure to be obtained, and in particular, carbon fibers and aramid fibers may be used in combination from the balance between mechanical properties and impact absorption. desirable. Further, from the viewpoint of enhancing the conductivity of the sound insulation structure to be obtained, reinforcing fibers coated with a metal such as nickel, copper, ytterbium, etc. can also be used. Among these, PAN-based carbon fibers having excellent mechanical properties such as strength and elastic modulus can be used more desirably.

  It is desirable that the reinforcing fibers 3 are discontinuous, are approximately monofilament-like, and are randomly dispersed. By setting the reinforcing fiber 3 to such an embodiment, when a sheet-like sound insulation structure precursor or sound insulation structure is formed by applying an external force, it is easy to mold into a complicated shape. Moreover, since the voids formed by the reinforcing fibers 3 are densified and the weak portions at the ends of the fiber bundles of the reinforcing fibers 3 in the sound insulation structure 1 can be minimized by adopting the reinforcing fibers 3 as such an embodiment, excellent reinforcement In addition to efficiency and reliability, isotropy is also imparted. Here, the substantially monofilament means that the reinforcing fiber single yarn is present in less than 500 fineness strands. More preferably, it is dispersed in a monofilament form.

  Here, substantially monofilament-shaped or dispersed in a monofilament-like form is a ratio of single fibers having a two-dimensional contact angle of 1 ° or more with respect to the reinforcing fibers 3 arbitrarily selected in the sound insulation structure 1. (Hereinafter also referred to as the fiber dispersion ratio) is 80% or more, in other words, in the sound insulation structure 1, two or more single fibers are in contact with each other and parallel bundles are less than 20%. . Therefore, it is particularly preferable that the mass fraction of the fiber bundle having at least 100 filaments in the reinforcing fiber 3 corresponds to 100%.

  In the case of discontinuous reinforcing fibers, the two-dimensional contact angle is an angle formed by a single fiber and a single fiber that comes into contact with the single fiber. It is defined as the angle on the acute angle side within the range of from 0 ° to 90 °. This two-dimensional contact angle will be further described with reference to the drawings. FIG. 2 is a schematic diagram illustrating an example of a dispersion state of reinforcing fibers in the reinforcing fiber mat when observed from the surface direction (FIG. 2A) and the thickness direction (FIG. 2B). When the single fiber 11a is used as a reference, the single fiber 11a is observed to intersect with the single fibers 11b to 11f in FIG. 2A, but in FIG. 2B, the single fiber 11a is in contact with the single fibers 11e and 11f. Not. In this case, with respect to the single fiber 11a serving as a reference, the evaluation targets of the two-dimensional contact angle are the single fibers 11b to 11d. Of the two angles formed by the two single fibers in contact, 0 ° to 90 ° It is an acute angle A within the following range.

  Although there is no restriction | limiting in particular as a method of measuring a two-dimensional contact angle, For example, the method of observing the orientation of the reinforced fiber 3 from the surface of the sound insulation structure 1 can be illustrated. In this case, it becomes easier to observe the reinforcing fiber 3 by polishing the surface of the sound insulating structure 1 to expose the reinforcing fiber 3. Moreover, the method of photographing the orientation image of the reinforcing fiber 3 by performing X-ray CT transmission observation can also be exemplified. In the case of the reinforcing fiber 3 having a high X-ray permeability, the reinforcing fiber 3 is observed by mixing the reinforcing fiber 3 with a tracer fiber or by applying a tracer chemical to the reinforcing fiber 3. This is desirable because it is easy to do. In addition, when measurement by the above method is difficult, the resin component is burned out at a high temperature by using a heating furnace or the like, and then the reinforcing fiber 3 is taken out of the reinforcing fiber 3 taken out using an optical microscope or an electron microscope. A method of observing the orientation of 3 can be exemplified.

  Based on the observation method described above, the fiber dispersion rate is measured by the following procedure. That is, the two-dimensional contact angles with all single fibers (single fibers 11b to 11d in FIG. 2) in contact with randomly selected single fibers (single fibers 11a in FIG. 2) are measured. This is performed for 100 single fibers, and the ratio is calculated from the ratio between the total number of all single fibers whose two-dimensional contact angle is measured and the number of single fibers having a two-dimensional contact angle of 1 ° or more.

  Further, it is particularly desirable that the reinforcing fibers 3 are dispersed randomly. Here, that the reinforcing fibers 3 are randomly dispersed means that the arithmetic average value of the two-dimensional orientation angle of the arbitrarily selected reinforcing fibers 3 in the sound insulation structure 1 is in the range of 30 ° or more and 60 ° or less. That means. Such a two-dimensional orientation angle is an angle formed by a single fiber of the reinforcing fiber 3 and a single fiber intersecting with this single fiber, and among the angles formed by the intersecting single fibers, 0 ° or more, It is defined as the angle on the acute angle side within the range of 90 ° or less.

  This two-dimensional orientation angle will be further described with reference to the drawings. 2A and 2B, when the single fiber 11a is used as a reference, the single fiber 11a intersects with the other single fibers 11b to 11f. Here, crossing means a state in which a single fiber as a reference is observed crossing another single fiber in a two-dimensional plane to be observed, and the single fiber 11a and the single fibers 11b to 11f are not necessarily in contact with each other. There is no need to do so, and there is no exception to the state observed when they are projected. In other words, when the reference single fiber 11a is viewed, all of the single fibers 11b to 11f are objects of evaluation of the two-dimensional orientation angle, and two single fibers whose two-dimensional orientation angles intersect in FIG. Among the two angles to be formed, the angle A is an acute angle within a range of 0 ° to 90 °.

  The method for measuring the two-dimensional orientation angle is not particularly limited. For example, a method for observing the orientation of the reinforcing fiber 3 from the surface of the component can be exemplified, and the same means as the method for measuring the two-dimensional contact angle described above. Can take. The average value of the two-dimensional orientation angle is measured by the following procedure. That is, the average value of the two-dimensional orientation angles with all the single fibers (single fibers 11b to 11f in FIG. 2) intersecting the randomly selected single fibers (single fibers 11a in FIG. 2) is measured. . For example, when there are many other single fibers that cross a certain single fiber, an arithmetic average value obtained by randomly selecting and measuring 20 other single fibers that intersect may be substituted. This measurement is repeated a total of 5 times with another single fiber as a reference, and the arithmetic average value is calculated as the arithmetic average value of the two-dimensional orientation angle.

  Since the reinforcing fibers 3 are dispersed in a substantially monofilament shape and randomly, the performance imparted by the reinforcing fibers 3 dispersed in the above-described substantially monofilament shape can be maximized. In addition, the sound insulation structure 1 can impart isotropy to the mechanical characteristics. From this viewpoint, the fiber dispersion rate of the reinforcing fiber 3 is desirably 90% or more, and more desirably as it approaches 100%. The arithmetic average value of the two-dimensional orientation angle of the reinforcing fibers 3 is desirably in the range of 40 ° or more and 50 ° or less, and is desirably closer to the ideal angle of 45 °.

  On the other hand, examples in which the reinforcing fibers 3 do not take the form of a nonwoven fabric include a sheet base material, a woven base material, and a non-crimp base material in which the reinforcing fibers 3 are arranged in one direction. In these forms, since the reinforcing fibers 3 are regularly and densely arranged, the space 4 in the sound insulation structure 1 is reduced, impregnation with the resin 2 becomes extremely difficult, and an unimpregnated portion is formed. There are cases where the choice of impregnation means and resin type is greatly limited.

  The form of the reinforcing fiber 3 may be either a continuous reinforcing fiber having the same length as that of the sound insulating structure 1 or a discontinuous reinforcing fiber having a finite length cut to a predetermined length. From the viewpoint of easily impregnating 2 and adjusting the amount thereof, discontinuous reinforcing fibers are desirable.

  The volume content of the reinforcing fiber 3 is in the range of 0.5 volume% or more and 55 volume% or less. When the volume content of the reinforcing fiber 3 is less than 0.5% by volume, the reinforcing effect derived from the reinforcing fiber 3 cannot be made sufficient, which is not desirable. On the other hand, when the volume content of the reinforcing fibers 3 is larger than 2.5% by volume, the volume content of the resin 2 with respect to the reinforcing fibers 3 is relatively small. The reinforcing effect of the reinforcing fiber 3 cannot be made sufficient, and the mechanical properties of the sound insulation structure 1, particularly the bending properties, cannot be satisfied.

  The reinforcing fibers 3 are covered with the resin 2 and it is desirable that the thickness of the resin 2 is in the range of 1 μm to 15 μm. The covering state of the reinforcing fiber 3 covered with the resin 2 is that the shape stability of the sound insulating structure 1 is at least as long as the intersecting points of the single fibers of the reinforcing fibers 3 constituting the sound insulating structure 1 are covered. Although sufficient from the viewpoint of ease of thickness control and flexibility, in a more desirable mode, it is desirable that the resin 2 is in a state of being coated around the reinforcing fiber 3 with the above-described thickness. This state means that the surface of the reinforcing fiber 3 is not exposed by the resin 2, in other words, the reinforcing fiber 3 forms an electric wire-like film with the resin 2. As a result, the sound insulation structure 1 further has shape stability and sufficient mechanical characteristics. Moreover, the covering state of the reinforcing fiber 3 covered with the resin 2 does not have to be covered with all of the reinforcing fiber 3, and the shape stability, bending elastic modulus, bending of the sound insulation structure 1 according to the present invention is not required. It may be within a range that does not impair the strength.

  The mass average fiber length of the reinforcing fibers 3 is desirably in the range of 1 mm or more and 15 mm or less. Thereby, the reinforcement efficiency of the reinforced fiber 3 can be improved and the mechanical characteristic excellent in the sound-insulation structure 1 can be given. When the mass average fiber length of the reinforcing fiber 3 is less than 1 mm, the void 4 in the sound insulation structure 1 cannot be efficiently formed, so that the specific gravity may increase, in other words, the desired thickness while having the same mass. This is not desirable because it is difficult to obtain the sound insulation structure 1. On the other hand, if the mass average fiber length of the reinforcing fibers 3 is longer than 15 mm, the reinforcing fibers 3 in the sound insulation structure 1 are easily bent by their own weight, which is a factor that hinders the expression of mechanical properties. The mass average fiber length is obtained by removing the resin component of the sound insulation structure 1 by a method such as burning or elution, randomly selecting 400 from the remaining reinforcing fibers 3, and measuring the length to the unit of 10 μm. It can be calculated as an average length.

  The void 4 in the present invention refers to a space formed by reinforcing fibers 3 covered with the resin 2 serving as columnar supports and overlapping or intersecting. For example, when a sound insulation structure precursor obtained by pre-impregnating the reinforcing fibers 3 with the resin 2 is heated to obtain a sound insulation structure, the voids 4 are formed by raising the reinforcing fibers 3 due to melting or softening of the resin 2 accompanying the heating. It is formed. This is based on the property that in the sound insulation structure precursor, the internal reinforcing fibers 3 that have been compressed by pressurization are raised by the raising force derived from the elastic modulus. Moreover, the content rate of the space | gap 4 in the sound-insulation structure 1 exists in the range of 10 volume% or more and 99 volume% or less. When the content rate of the space | gap 4 is less than 10 volume%, since the specific gravity of the sound-insulation structure 1 becomes high and lightweight cannot be satisfied, it is not desirable. On the other hand, when the content rate of the voids 4 is larger than 99% by volume, in other words, since the thickness of the resin 2 coated around the reinforcing fibers 3 is reduced, the reinforcement of the reinforcing fibers 3 in the sound insulation structure 1 is reduced. Is not desirable because the mechanical properties are low. The upper limit value of the content of the void 4 is desirably 97% by volume. In the present invention, the volume content is defined as 100% by volume of the total volume content of the resin 2, the reinforcing fiber 3, and the void 4 constituting the sound insulation structure 1.

When the length of the reinforcing fiber 3 is Lf and the orientation angle of the reinforcing fiber 3 in the cross-sectional direction of the sound insulation structure 1 is θf, the thickness St of the sound insulation structure 1 is a conditional expression: St ≧ Lf ² · (1-cos ( It is preferable to satisfy θf)). When the thickness St of the sound insulation structure 1 does not satisfy the above conditional expression, the reinforcing fiber 3 in the sound insulation structure 1 is bent, or the balance between the sound insulation structure 1 having the desired thickness and the fiber length is inferior. It shows that. Thereby, since the sound insulation structure 1 cannot fully exhibit the characteristic of the input reinforcing fiber 3, it shows that the freedom degree of thickness design is inferior, Furthermore, among the mechanical characteristics of the sound insulation structure 1, the reinforcement fiber 3 is shown. The characteristics utilizing the tensile strength and the tensile modulus of the fiber are not desirable because the straightening property of the reinforcing fiber 3 is lost and an efficient reinforcing effect cannot be obtained. In the above conditional expression, the balance between the bending elastic modulus and the specific bending elastic modulus, which are the characteristics of the sound insulating structure 1 formed by the length of the reinforcing fiber 3 and the orientation angle thereof, can be obtained. Depending on the fiber length and its orientation angle, it is easy to be deformed in the state before solidification or curing in the molding process, and it is easy to mold the desired sound insulation structure 1, so that the thickness St of the sound insulation structure 1 is 2% or more. In the range of 20% or less, the range of 5% or more and 18% or less is particularly preferable. The units used in the conditional expression are St [mm], Lf [mm], and θf [°].

  Here, the length Lf of the reinforcing fiber 3 is selected by removing 400 resin components from the remaining reinforcing fibers 3 by removing the resin component of the sound insulation structure 1 by a method such as burning or elution, and the length is set to a unit of 10 μm. Can be calculated as a mass average fiber length calculated from their lengths. In addition, the orientation angle θf of the reinforcing fiber 3 in the cross-sectional direction of the sound insulating structure 1 is the degree of inclination with respect to the cross-sectional direction of the sound insulating structure 1, in other words, the degree of inclination of the reinforcing fiber 3 with respect to the thickness direction. A larger value indicates that the film is inclined in the thickness direction, and is given in a range of 0 ° to 90 °. That is, the reinforcing function in the sound insulation structure 1 can be expressed more effectively by setting the orientation angle θf of the reinforcing fibers 3 within such a range. The upper limit value of the orientation angle θf of the reinforcing fibers 3 is not particularly limited, but is preferably 60 ° or less, and more preferably 45 ° or less in view of the expression of the flexural modulus when the sound insulation structure 1 is obtained. Is more desirable. Further, when the orientation angle θf of the reinforcing fiber 3 is less than 3 °, the reinforcing fiber 3 in the sound insulation structure 1 is planar, in other words, in a two-dimensionally oriented state, so that the thickness of the sound insulation structure 1 can be freely set. It is not desirable because the degree is reduced and the lightness cannot be satisfied. Therefore, the orientation angle θf of the reinforcing fiber 3 is preferably 3 ° or more.

  The orientation angle θf of the reinforcing fiber 3 can be measured based on observation of a vertical cross section with respect to the surface direction of the sound insulation structure 1. FIG. 3 is a schematic diagram showing an example of a cross-sectional structure in the surface direction (FIG. 3A) and the thickness direction (FIG. 3B) of the sound insulation structure according to the present invention. In FIG. 3A, the cross-sections of the reinforcing fibers 3a and 3b are approximated to an elliptical shape for easy measurement. Here, the cross section of the reinforcing fiber 3a has a small elliptical aspect ratio (= ellipse long axis / short elliptical axis), whereas the cross section of the reinforcing fiber 3b has a large elliptical aspect ratio. On the other hand, according to FIG. 3B, the reinforcing fiber 3a has a substantially parallel inclination with respect to the thickness direction Y, and the reinforcing fiber 3b has a certain amount of inclination with respect to the thickness direction Y. In this case, for the reinforcing fiber 3b, the angle θx formed by the surface direction X of the sound insulation structure 1 and the fiber principal axis (long axis direction in the ellipse) α is substantially equal to the out-of-plane angle θf of the reinforcing fiber 3b. On the other hand, with respect to the reinforcing fiber 3a, there is a large difference between the angle θx and the angle indicated by the orientation angle θf, and it cannot be said that the angle θx reflects the orientation angle θf. Accordingly, when the orientation angle θf is read from a vertical cross section with respect to the surface direction X of the sound insulation structure 1, the detection accuracy of the orientation angle θf can be increased by extracting a fiber section having an elliptical aspect ratio of a certain value or more.

  As an index of the elliptical aspect ratio to be extracted, when the cross-sectional shape of the single fiber is close to a perfect circle, that is, when the fiber aspect ratio in the cross section perpendicular to the longitudinal direction of the reinforcing fiber is 1.1 or less, the elliptical aspect ratio Can measure the angle formed between the X direction and the fiber principal axis α for the reinforcing fibers 3 having a diameter of 20 or more, and adopt this as the orientation angle θf. On the other hand, when the cross-sectional shape of the single fiber is an ellipse or a saddle shape, and the fiber aspect ratio is larger than 1.1, paying attention to the reinforcing fiber 3 having a larger elliptical aspect ratio, the orientation angle θf was measured. If the fiber aspect ratio is 1.1 or more and less than 1.8, the elliptical aspect ratio is 30 or more. If the fiber aspect ratio is 1.8 or more and less than 2.5, the elliptical aspect ratio is 40. As described above, when the fiber aspect ratio is 2.5 or more, it is preferable to select the reinforcing fiber 3 having an elliptical aspect ratio of 50 or more and measure the orientation angle θf.

  The bending elastic modulus Ec of the sound insulation structure 1 is 1 GPa or more. When the bending elastic modulus Ec of the sound insulation structure 1 is less than 1 GPa, the shape cannot be maintained as the sound insulation structure, which is not desirable. In addition, although there is no limit on the upper limit of the flexural modulus, in general, in a structure composed of reinforcing fibers and resin, the upper limit is the value calculated from the elastic modulus of each of the reinforcing fibers and resins that are constituent components. obtain. In the sound insulation structure according to the present invention, even when the sound insulation structure is used alone or in combination with other members, the shape is maintained by using the bending elastic modulus of the sound insulation structure itself. For this purpose, about 3 GPa is sufficient, and further, 6 GPa is sufficient for designing the member with the sound insulation structure alone and putting it into practical use.

  The ratio of the transmission loss at a frequency of 200 Hz to the transmission loss at a frequency of 1250 Hz in JIS A1441-1 is in the range of 1.1 or more and 1.5 or less. When the ratio is less than 1.1, the difference in the desired frequency band is large, the transmission loss is greatly different between the high frequency band and the low frequency band, and the transmission loss in the high frequency band is small. This is not desirable because it makes designing difficult for practical use. On the other hand, when the ratio is larger than 1.5, it means that the transmission loss in the low frequency band is small, and it is not desirable because unpleasant sound, such as road noise, which is a concern in automobile applications, cannot be blocked. Here, the transmission loss ratio is obtained by dividing the transmission loss value in the 1250 Hz frequency band by the transmission loss value in the 200 Hz frequency band as the transmission loss ratio.

When the bending elastic modulus of the sound insulating structure 1 is Ec and the specific gravity of the sound insulating structure 1 is ρ, the specific bending elastic modulus of the sound insulating structure 1 expressed as Ec ^1/3 · ρ ⁻¹ is 3 or more and 20 or less. It is in the range. When the specific bending elastic modulus of the sound insulation structure 1 is less than 3, it is not desirable because even if the bending elastic modulus is high, the specific gravity is also high, and a desired lightening effect cannot be obtained. On the other hand, when the specific bending elastic modulus of the sound insulation structure 1 is larger than 20, although the effect of weight reduction is sufficient, it indicates that the bending elastic modulus is low, and the desired shape as the sound insulation structure 1 is maintained. This is not desirable because it is difficult and the bending elastic modulus of the sound insulation structure 1 itself is inferior. In general, the specific bending elastic modulus of steel or aluminum is 1.5 or less, which is a region of specific bending elastic modulus which is extremely superior to these metal materials. Further, it is 3 or more, more preferably 5 or more, exceeding 2.3, which is a general specific bending elastic modulus of the carbon fiber reinforced resin composite material that is focused on the weight reduction effect.

The specific gravity ρ of the sound insulation structure 1 is desirably 0.9 g / cm ³ or less. When the specific gravity ρ of the sound insulation structure 1 is larger than 0.9 g / cm ³ , this means that the mass when the sound insulation structure 1 is made increases, and as a result, the mass when the product is made increases. Not desirable. Although there is no restriction on the lower limit of the specific gravity, in general, in a structure composed of reinforcing fibers and a resin, the value calculated from the volume ratios of the reinforcing fibers, the resin, and the voids that are constituent components can be the lower limit. . In the sound insulation structure according to the present invention, whether the sound insulation structure is used alone or in combination with other members, the specific gravity of the sound insulation structure itself varies depending on the reinforcing fiber or resin used. However, it is desirable that it is 0.03 g / cm ³ or more from the viewpoint of maintaining the mechanical properties of the sound insulation structure.

  The porosity of the portion within 30% from the surface of the sound insulation structure 1 to the midpoint position in the thickness direction is in the range of 0 volume% or more and less than 10 volume%, and the porosity of the remaining portion is 10 volume% or more. , Preferably in the range of 99% by volume or less. The smaller the porosity, the better the mechanical properties, and the greater the porosity, the better the lightness. In other words, when the sound insulation structure 1 is made of the same material, the porosity in the portion within 30% from the surface of the sound insulation structure 1 to the midpoint position in the thickness direction is 0% by volume or more. By being less than 10% by volume, the mechanical properties of the sound insulation structure 1 are ensured, and the remaining portion has a porosity of 10% by volume or more and 99% by volume or less to satisfy light weight properties. This is desirable because it can be done. The upper limit of the porosity of the remaining part is desirably 97% by volume.

  In the present invention, the thickness of the sound insulation structure 1 can be obtained from the shortest distance connecting one point on the surface for which the thickness is desired and the surface on the back side thereof. The midpoint in the thickness direction means the midpoint of the thickness of the sound insulation structure 1. The portion within 30% from the surface of the sound insulation structure to the midpoint position in the thickness direction is the sound insulation structure 1 when the distance between the surface of the sound insulation structure 1 and the midpoint in the thickness direction is 100%. It means a part including a distance of 30% from the surface. The remaining part here is a part within 30% from one surface of the sound insulation structure 1 to the midpoint position in the thickness direction and 30 from the other surface of the sound insulation structure 1 to the midpoint position in the thickness direction. It means the remaining part excluding the part within%. As shown in FIG. 4, the portion R1 within 30% from the surface of the sound insulation structure 1 to the midpoint position in the thickness direction and the remaining portion R2 are present at different positions in the thickness direction of the sound insulation structure 1. Alternatively, as shown in FIG. 5, they may exist at different positions in the surface direction.

  The reinforcing fiber 3 in the present invention is preferably in the form of a nonwoven fabric from the viewpoint of ease of impregnation of the reinforcing fiber 3 with the resin 2. Further, since the reinforcing fiber 3 has a non-woven form, in addition to the ease of handling of the non-woven fabric itself, it is easy to impregnate even in the case of a thermoplastic resin generally having a high viscosity. It is desirable because it can. Here, the form of the nonwoven fabric refers to a form in which the strands and / or monofilaments of the reinforcing fibers 3 are dispersed in a plane without regularity. The chopped strand mat, the continuous strand mat, the papermaking mat, the carding mat, and the airlaid mat. (Hereinafter, these are collectively referred to as a reinforcing fiber mat).

  As a manufacturing method of the reinforcing fiber mat constituting the sound insulation structure 1, for example, there is a method of manufacturing the reinforcing fiber mat by dispersing the reinforcing fibers 3 in advance in the form of strands and / or substantially monofilaments. As a manufacturing method of the reinforcing fiber mat, a dry process such as an airlaid method in which the reinforcing fiber 3 is dispersed by an air stream, a carding method in which the reinforcing fiber 3 is mechanically combed to form a sheet, and strengthening is performed. A wet process by a radrite method in which the fibers 3 are stirred in water to make paper can be mentioned as a known technique. As means for bringing the reinforcing fibers 3 closer to a monofilament shape, in the dry process, a method of providing a fiber opening bar, a method of vibrating the fiber opening bar, a method of further finely adjusting the card eye, Examples of the adjustment method can be given. In the wet process, a method of adjusting the stirring conditions of the reinforcing fibers 3, a method of diluting the reinforcing fiber concentration of the dispersion, a method of adjusting the viscosity of the dispersion, a method of suppressing eddy current when transferring the dispersion, etc. Can be illustrated. In particular, the reinforcing fiber mat is desirably manufactured by a wet method, and the reinforcing fiber 3 of the reinforcing fiber mat is adjusted by increasing the concentration of input fibers or adjusting the flow rate of the dispersion and the speed of the mesh conveyor. The ratio can be easily adjusted. For example, by slowing the speed of the mesh conveyor with respect to the flow rate of the dispersion liquid, the orientation of the fibers in the obtained reinforcing fiber mat becomes difficult to take in the take-up direction, and a bulky reinforcing fiber mat can be manufactured. The reinforcing fiber mat may be composed of the reinforcing fiber 3 alone, the reinforcing fiber 3 is mixed with a matrix resin component in powder form or fiber shape, or the reinforcing fiber 3 is mixed with an organic compound or an inorganic compound. Further, the reinforcing fibers 3 may be meshed with resin components.

  Furthermore, the reinforcing fiber mat can be impregnated with the resin 2 in advance to form a sound insulation structure precursor. As a method for producing the sound insulation structure precursor according to the present invention, a method is used in which a pressure is applied to the reinforcing fiber mat while the resin 2 is heated to a temperature higher than the melting or softening temperature and the reinforcing fiber mat is impregnated. However, this is desirable from the viewpoint of ease of manufacture. Specifically, a method of melt impregnating a laminate in which the resin 2 is disposed from both sides in the thickness direction of the reinforcing fiber mat can be desirably exemplified.

  As equipment for realizing the above methods, a compression molding machine or a double belt press can be suitably used. In the case of a batch type, the former, the productivity can be improved by using an intermittent press system in which two or more machines for heating and cooling are arranged in parallel. In the case of a continuous type, it is the latter, and since continuous processing can be performed easily, it is excellent in continuous productivity.

  When manufacturing the sound insulation structure 1 according to the present invention, it is preferable to adopt a method manufactured by at least the following steps [1] and [2] from the viewpoint of ease of manufacturing.

Step [1]: A step of applying a pressure in a state where the resin 2 is heated to a temperature at which the resin 2 is melted or softened, and impregnating the reinforcing fiber mat with the resin 2 to produce a sound insulation structure precursor.
Step [2]: A step of expanding the sound insulation structure precursor by adjusting the thickness in a heated state.

  Step [2] is a step of expanding the sound insulation structure precursor obtained in step [1] by adjusting the thickness in a heated state. When the resin 2 constituting the sound insulation structure 1 is a thermoplastic resin, the heating temperature at this time gives a sufficient amount of heat to melt or soften the thickness of the sound insulation structure 1 to be produced and the production speed. Specifically, it is preferable to apply a temperature which is higher by 10 ° C. or more than the melting temperature and is equal to or lower than the thermal decomposition temperature of the thermoplastic resin. In addition, when a thermosetting resin is used as the resin 2, it is possible to give a sufficient amount of heat to melt or soften the thermosetting resin raw material before forming and curing the crosslinked structure. It is preferable from the viewpoint of thickness control and production speed.

  The thickness control method is not limited as long as the heated sound insulation structure precursor can be controlled to the desired thickness, but the method of constraining the thickness using a metal plate or the like, the pressure applied to the sound insulation structure precursor A method for controlling the thickness by the method is exemplified as a preferable method from the viewpoint of simplicity of production. As equipment for realizing the above method, a compression molding machine or a double belt press can be suitably used. In the case of a batch type, the former, the productivity can be improved by using an intermittent press system in which two or more machines for heating and cooling are arranged in parallel. In the case of a continuous type, it is the latter, and since continuous processing can be performed easily, it is excellent in continuous productivity.

  Examples in which the reinforcing fiber mat does not take the form of a nonwoven fabric include a sheet base material, a woven base material, and a non-crimp base material in which the reinforcing fibers 3 are arranged in one direction. In these forms, since the reinforcing fibers 3 are regularly and densely arranged, there are few voids in the reinforcing fiber mat, and the thermoplastic resin does not form a sufficient anchoring structure. Bonding ability is reduced. Moreover, when the resin 2 is a thermoplastic resin, impregnation becomes extremely difficult, and an unimpregnated part is formed, and the choice of impregnation means and resin type is greatly restricted.

  In the present invention, as long as the characteristics of the present invention are not impaired, a sheet-like intermediate base material in which the sound insulation structure 1 or the sound insulation structure precursor is used as a core and the continuous reinforcing fibers 3 are impregnated with a resin is used as a skin. It can also be a sandwich structure used for the layers. 7 and 8 are a perspective view and a sectional view showing an example of a molded product having a sandwich structure. 7 and 8, reference numeral 5 denotes a molded article, reference numeral 6 denotes a skin layer, and reference numeral 7 denotes a core. Here, the continuous reinforcing fiber 3 is a continuous fiber having a length of 100 mm or more in at least one direction, and an assembly in which a large number of the reinforcing fibers 3 are arranged in one direction, a so-called reinforcing fiber bundle is a total length of the sandwich structure. Is continuous. As a form of the sheet-like intermediate base material composed of continuous reinforcing fibers 3, a cloth composed of a bundle of reinforcing fibers composed of a large number of continuous reinforcing fibers 3 and a plurality of continuous reinforcing fibers 3 are arranged in one direction. Reinforcing fiber bundles (unidirectional fiber bundles), unidirectional cloths composed of the unidirectional fiber bundles, and the like. The reinforcing fiber 3 may be composed of a plurality of fiber bundles having the same form or may be composed of a plurality of fiber bundles having different forms. The number of reinforcing fibers constituting one reinforcing fiber bundle is usually 300 to 48,000, but considering the manufacture of prepreg and cloth, it is preferably 300 to 24,000, more preferably 1,000 to 12,000.

  In order to control the bending elastic modulus, a configuration in which the direction of the reinforcing fiber 3 is changed and laminated is desirably used. In particular, in order to efficiently increase the elastic modulus and strength of the sandwich structure, it is desirable to use continuous reinforcing fibers (referred to as UD) in which fiber bundles are aligned in one direction.

  Hereinafter, the present invention will be described in more detail with reference to examples.

(1) Volume content Vf of reinforcing fiber in sound insulation structure
After measuring the mass Ws of the sound insulation structure, the sound insulation structure was heated in air at 500 ° C. for 30 minutes to burn off the resin component, and the mass Wf of the remaining reinforcing fibers was measured and calculated by the following formula.

Vf (volume%) = (Wf / ρf) / {Wf / ρf + (Ws−Wf) / ρr} × 100
ρf: density of reinforcing fiber (g / cm ³ )
ρr: Resin density (g / cm ³ )

(2) Bending test A test piece was cut out from the sound insulation structure, and the flexural modulus was measured according to the ISO178 method (1993). Test pieces were prepared by cutting out test pieces in four directions of + 45 °, −45 °, and 90 ° directions when an arbitrary direction was set to 0 ° direction, and the number of measurements was set to n = 5 in each direction, and the arithmetic average The value was defined as the flexural modulus Ec. As the measuring apparatus, “Instron (registered trademark)” 5565 type universal material testing machine (manufactured by Instron Japan Co., Ltd.) was used. From the obtained results, the specific bending elastic modulus of the sound insulation structure was calculated by the following equation.

Specific flexural modulus = Ec ^1/3 / ρ

(3) Orientation angle θf of reinforcing fiber in sound insulation structure
A small piece having a width of 25 mm was cut out from the sound insulation structure, embedded in an epoxy resin, and then polished so that a vertical cross section in the sheet thickness direction was an observation surface to prepare a sample. The sample was magnified 400 times with a laser microscope (manufactured by Keyence Corporation, VK-9510), and the fiber cross-sectional shape was observed. Develop the observation image on general-purpose image analysis software, extract the individual fiber cross sections visible in the observation image using a program embedded in the software, provide an ellipse inscribed in the fiber cross section, and approximate the shape of the fiber cross section (Hereinafter referred to as fiber ellipse). Further, the angle formed by the X-axis direction and the major axis direction of the fiber ellipse was determined for a fiber ellipse having an aspect ratio of 20 or more expressed by the major axis length α / minor axis length β of the fiber ellipse. By repeating the above operation for observation samples extracted from different parts of the sound insulation structure, the orientation angle was measured for a total of 600 reinforcing fibers, and the arithmetic average value thereof was obtained as the orientation angle θf of the reinforcing fibers.

(4) Specific gravity ρ of sound insulation structure
A test piece was cut out from the sound insulation structure, and the apparent specific gravity of the sound insulation structure was measured with reference to JIS K7222 (2005). The dimensions of the test piece were 100 mm long and 100 mm wide. The length, width, and thickness of the test piece were measured with a micrometer, and the volume V of the test piece was calculated from the obtained values. Moreover, the mass M of the cut-out test piece was measured with the electronic balance. The specific gravity ρ of the sound insulation structure was calculated by substituting the obtained mass M and volume V into the following equation.

ρ [g / cm ³ ] = 10 ³ × M [g] / V [mm ³ ]

(5) Volume content of voids in sound insulation structure A test piece was cut out 10 mm long and 10 mm wide from the sound insulation structure, and the cross section was taken with a scanning electron microscope (SEM) (S-4800, manufactured by Hitachi High-Technologies Corporation). Observed and photographed 10 arbitrary places at a magnification of 1000 times. For each image to determine the area A _a void in the image. Moreover, to calculate the porosity by dividing the area A _a void in the area of the entire image. The volume content of voids in the sound insulation structure was determined by arithmetic average from 50 voids in total, each of which was photographed at 10 locations with 5 test pieces.

(6) Thickness of Resin Coated with Reinforcing Fiber A test piece was cut out 10 mm long and 10 mm wide from the sound insulation structure, and the cross section was observed with a scanning electron microscope (SEM) (S-4800, manufactured by Hitachi High-Technologies Corporation). Then, arbitrary 10 locations were photographed at a magnification of 3000 times. The coating thickness of the resin coated on the reinforcing fibers was measured from arbitrary 50 locations where the cross section of the reinforcing fibers in the obtained image was cut. As the thickness of the resin coated with the reinforcing fibers, the arithmetic average value of the measurement results at 50 locations was used.

(7) Sound insulation measurement The test piece was cut out from the sound insulation structure, and the sound insulation performance was measured by changing the sample size from the standard to 0.5 m square with reference to JIS A1441-1 (2007). Using a reverberation room as a sound source room and an anechoic room as a sound receiving room, sound was generated from the sound source room at an average sound pressure level L _p . Using the intensity of sound after passing through the sample measured by the intensity probe (acoustic intensity L _I ) and the area S of the measurement surface of the sample, the intensity acoustic transmission loss R _I representing the sound insulation performance is expressed by the following equation: Determined by

R _I (dB) = L _p −6− (L _I + 10 × log ₁₀ S)

[Carbon fiber 1]
Spinning, firing treatment, and surface oxidation treatment were carried out from a copolymer containing polyacrylonitrile as a main component to obtain continuous carbon fibers having a total number of 12,000 single yarns. The characteristics of this continuous carbon fiber were as follows.

Single fiber diameter: 7μm
Specific gravity: 1.8
Tensile strength: 4600 MPa
Tensile modulus: 220 GPa

[PP resin]
100 g of basis weight comprising 80% by mass of unmodified polypropylene resin (“Prime Polypro” (registered trademark) J105G manufactured by Prime Polymer Co., Ltd.) and 20% by mass of acid-modified polypropylene resin (“Admer” QB510 manufactured by Mitsui Chemicals, Inc.) A sheet of / m ² was produced. The properties of the obtained resin sheet are shown in Table 1.

[PA resin]
A resin film having a basis weight of 124 g / m ² made of nylon 6 resin (“Amilan” (registered trademark) CM1021T manufactured by Toray Industries, Inc.) was produced. The properties of the obtained resin sheet are shown in Table 1.

[PPS resin]
A resin nonwoven fabric having a basis weight of 147 g / m ² made of polyphenylene sulfide resin (“Torelina” (registered trademark) M2888 manufactured by Toray Industries, Inc.) was produced. The properties of the obtained resin sheet are shown in Table 1.

[Reinforcing fiber mat 1]
Carbon fiber 1 was cut to 6 mm with a cartridge cutter to obtain chopped carbon fiber. A dispersion liquid having a concentration of 0.1% by mass composed of water and a surfactant (manufactured by Nacalai Tex Co., Ltd., polyoxyethylene lauryl ether (trade name)) is prepared, and the dispersion liquid and the chopped carbon fiber are used. The reinforcing fiber mat was manufactured using the reinforcing fiber mat manufacturing apparatus shown in FIG. The manufacturing apparatus shown in FIG. 6 includes a cylindrical container having a diameter of 1000 mm having an opening cock at the bottom of the container as a dispersion tank, and a linear transport section (an inclination angle of 30 °) that connects the dispersion tank and the papermaking tank. Yes. A stirrer is attached to the opening on the upper surface of the dispersion tank, and chopped carbon fiber and dispersion liquid (dispersion medium) can be introduced through the opening. A point where the papermaking tank is a tank provided with a mesh conveyor having a papermaking surface having a width of 500 mm at the bottom, and a conveyor capable of transporting a carbon fiber substrate (papermaking substrate) are connected to the mesh conveyor. Papermaking was performed at a carbon fiber concentration of 0.05% by mass in the dispersion. The paper-made carbon fiber substrate was dried in a drying furnace at 200 ° C. for 30 minutes to obtain a reinforcing fiber mat. The obtained basis weight was 50 g / m ² . The properties of the obtained reinforcing fiber mat are shown in Table 2.

Example 1
Reinforcing fiber mat 1 as the reinforcing fiber mat, PP resin as the resin sheet, [Resin sheet / Reinforcing fiber mat / Resin sheet / Reinforcing fiber mat / Resin sheet / Reinforcing fiber mat / Resin sheet / Reinforcing fiber mat / Reinforcing fiber mat / Resin Sheet / reinforced fiber mat / resin sheet / reinforcing fiber mat / resin sheet / reinforcing fiber mat / resin sheet] were laminated in this order. Next, a sound insulation structure was obtained through the following press molding conditions (I) to (V). From the cross-sectional observation, the obtained sound insulation structure was confirmed to have voids with reinforcing fibers as columnar supports. Table 3 shows the characteristics of the obtained sound insulation structure.

(I) Three layers of the laminates are stacked and placed in a press molding die cavity preheated to 230 ° C., and the die is closed.
(II) Next, after holding for 120 seconds, a pressure of 3 MPa is applied and the pressure is further held for 60 seconds.
(III) After the above (II), the mold cavity is opened, a metal spacer is inserted into the end thereof, and the thickness when the structure is obtained is adjusted to 10 mm.
(IV) Thereafter, the mold cavity is fastened again, and the cavity temperature is cooled to 50 ° C. while maintaining the pressure.
(V) Open the mold and take out the sound insulation structure.

(Example 2)
Reinforcing fiber mat 3 as the reinforcing fiber mat, PP resin as the resin sheet, [Resin sheet / Reinforcing fiber mat / Resin sheet / Reinforcing fiber mat / Resin sheet / Reinforcing fiber mat / Resin sheet / Reinforcing fiber mat / Reinforcing fiber mat / Resin Sheet / reinforced fiber mat / resin sheet / reinforced fiber mat / resin sheet / reinforced fiber mat / resin sheet / reinforced fiber mat / resin sheet / reinforced fiber mat / resin sheet / reinforced fiber mat / resin sheet / reinforced fiber mat / resin sheet ] The sound insulation structure was obtained like Example 1 except having produced the laminated body arrange | positioned in order. Table 3 shows the characteristics of the obtained sound insulation structure.

(Example 3)
Reinforcing fiber mat 3 as reinforcing fiber mat, PP resin as resin sheet, [Resin sheet / Reinforcing fiber mat / Resin sheet / Reinforcing fiber mat / Resin sheet / Reinforcing fiber mat / Resin sheet / Reinforcing fiber mat / Resin sheet / Reinforcing fiber Mat / resin sheet / reinforced fiber mat / resin sheet / reinforced fiber mat / resin sheet / reinforced fiber mat / resin sheet / reinforced fiber mat / resin sheet / reinforced fiber mat / resin sheet / reinforced fiber mat / resin sheet / reinforced fiber mat / Resin sheet / reinforcing fiber mat / resin sheet / reinforcing fiber mat / resin sheet] was produced in the order of Example 1, except that only one layer of the laminate was used in step (I). The sound insulation structure was obtained in the same manner. Table 3 shows the characteristics of the obtained sound insulation structure.

Example 4
Example except that the resin sheet was changed from PP resin to PA6 resin, the preheating temperature in step (I) was changed from 230 ° C to 240 ° C, and the cavity temperature in step (IV) was changed from 50 ° C to 80 ° C. In the same manner as in No. 1, a sound insulation structure was obtained. Table 3 shows the characteristics of the obtained sound insulation structure.

(Example 5)
Example except that the resin sheet was changed from PP resin to PPS resin, the preheating temperature in step (I) was changed from 230 ° C. to 300 ° C., and the cavity temperature in step (IV) was changed from 50 ° C. to 150 ° C. In the same manner as in No. 1, a sound insulation structure was obtained. Table 3 shows the characteristics of the obtained sound insulation structure.

(Reference Example 1)
Reinforcing fiber mat 1 as the reinforcing mat, PP resin as the resin sheet 1, PA resin as the resin sheet 2, 18 layers of laminate A in the order of [resin sheet 1 / reinforced fiber mat], [resin sheet 2 / reinforced] 18 layers of laminate B arranged in the order of [fiber mat] were prepared, and a laminate arranged in the order of [laminate A-18 layer / laminate B-18 layer / resin sheet 1] was prepared. Next, a structure was obtained through the following press molding conditions (I) to (V). Table 4 shows the characteristics of the obtained structure.

(I) The laminate is placed in a press mold cavity preheated to 230 ° C. and the mold is closed.
(II) Next, after holding for 120 seconds, a pressure of 3 MPa is applied and the pressure is further held for 60 seconds.
(III) After the above (II), the mold cavity was opened, and a metal spacer with a thickness of 10 mm was inserted at equal intervals from the end to the center, and held for 20 seconds.
(IV) Thereafter, the mold cavity is fastened again, and the cavity temperature is cooled to 50 ° C. while maintaining the pressure.
(V) Open the mold and take out the structure.

(Reference Example 2)
14 layers of laminate A in which a reinforcing fiber mat 1 as a reinforcing mat, PP resin as a resin sheet 1 and PA resin as a resin sheet 2 are arranged in the order of [resin sheet 1 / reinforced fiber mat], and [resin sheet 2 / 14 layers of laminate B arranged in the order of “reinforced fiber mat” were prepared and arranged in the order of “laminate A-14 layer / laminate B-14 layer / laminate A-14 layer / resin sheet 1”. A structure was obtained in the same manner as in Reference Example 1 except that a laminate was produced. Table 4 shows the characteristics of the obtained structure.

(Reference Example 3)
A molded product was obtained in the same manner as in Reference Example 1 except that the mold cavity for press molding was replaced with that for an automobile engine cover. Table 4 shows the characteristics of the obtained molded product.

(Reference Example 4)
A molded product was obtained in the same manner as in Reference Example 2 except that the press molding die cavity was replaced with that for an automobile engine cover. Table 4 shows the characteristics of the obtained molded product.

(Comparative Example 1)
Reinforcing fiber mat 1 as the reinforcing fiber mat, PP resin as the resin sheet, [Resin sheet / Reinforcing fiber mat / Resin sheet / Reinforcing fiber mat / Resin sheet / Reinforcing fiber mat / Resin sheet / Reinforcing fiber mat / Reinforcing fiber mat / Resin Sheet / reinforced fiber mat / resin sheet / reinforced fiber mat / resin sheet / reinforced fiber mat / resin sheet / resin sheet / reinforced fiber mat / resin sheet / reinforced fiber mat / resin sheet / reinforced fiber mat / resin sheet / reinforced fiber mat / Resin sheet / reinforced fiber mat / resin sheet / reinforced fiber mat / resin sheet / reinforced fiber mat / resin sheet / reinforced fiber mat / reinforced fiber mat / resin sheet / reinforced fiber mat / resin sheet / reinforced fiber mat / resin sheet / A laminate in the order of “reinforced fiber mat / resin sheet” was prepared. A structure was obtained in the same manner as in Example 1 except that no metal spacer was used in Step (III) of Example 1. Table 5 shows the characteristics of the obtained structure.

(Comparative Example 2)
Various characteristics were evaluated using a low-foam polypropylene sheet “Fcel” manufactured by Furukawa Electric. The obtained evaluation results are shown in Table 5.

(Comparative Example 3)
Reinforcing fiber mat 1 as the reinforcing fiber mat and PP resin as the resin sheet were arranged in the order of [resin sheet / reinforcing mat-70 layers / resin sheet] in the same manner as in Example 1 except that a laminate was produced. A structure was obtained. Table 5 shows the characteristics of the obtained structure.

(Comparative Example 4)
Reinforcing fiber mat 1 as the reinforcing fiber mat and PP resin as the resin sheet were arranged in the order of [resin sheet / reinforcing fiber mat / resin sheet / reinforcing fiber mat / reinforcing fiber mat / resin sheet / reinforcing fiber mat / resin sheet]. A structure was obtained in the same manner as in Example 1 except that a laminate was produced. Table 5 shows the characteristics of the obtained structure.

(Comparative Example 5)
A laminate in which reinforcing fiber mat 1 as a reinforcing fiber mat and PP resin as resin sheet 1 are arranged in the order of [resin sheet / resin sheet / reinforcing fiber mat / resin sheet / resin sheet] is prepared. A structure was obtained in the same manner as in Example 1 except that 15 layers were stacked. Table 5 shows the characteristics of the obtained structure.

〔Consideration〕
The embodiment of the present invention has an excellent balance between the absolute value of the bending elastic modulus and the specific bending elastic modulus, and the ratio of the transmission loss at the frequency of 1250 Hz to the transmission loss at the frequency of 200 Hz satisfies the present invention. Furthermore, as shown in the reference examples, it is clear that the sound insulation structure of the present invention can be combined with various resins and has a degree of freedom in product design. On the other hand, in Comparative Example 1, the reinforcing fiber and the resin are the same as those in the example, but due to the absence of the gap, the frequency characteristic associated with the gap formed by the reinforcing fiber and the resin does not appear, and the transmission loss ratio is in the specified range. I could not be satisfied. In Comparative Example 2, the properties were evaluated using a product which is a foamed resin using PP resin, and while satisfying the specific bending elastic modulus and transmission loss ratio, the absolute value of the bending elastic modulus was satisfied. I could not. In Comparative Example 3, the volume ratio of the resin and voids was adjusted to increase the ratio of reinforcing fibers, but not only the balance with the volume ratio of the reinforcing fiber mat was poor and the flexural modulus was low, The transmission loss ratio was also low. In Comparative Example 4 in which the volume ratio of the voids was increased, the absolute value of the bending elastic modulus and the specific bending elastic modulus were satisfied, but the transmission loss ratio was not satisfied. This is because the transmission loss at a frequency of 1250 Hz formed by the reinforcing fibers, the resin, and the voids is too low. In Comparative Example 5 in which the proportion of the resin in the structure was increased from each example, the absolute value of the bending elastic modulus and the specific bending elastic modulus were satisfied, but the transmission loss ratio showed a value higher than the range. This is considered to be because the sound insulation characteristic that the reinforcing fiber and the air gap develop is lost, and the transmission loss ratio based on the sound insulation mass law is approached.

DESCRIPTION OF SYMBOLS 1 Sound insulation structure 2 Resin 3 Reinforcing fiber 4 Gap 5 Molded product 6 Skin layer 7 Core

Claims (11)

A sound insulation structure comprising a resin, a reinforcing fiber, and a void,
The volume content of the resin is in the range of 2.5% by volume or more and 85% by volume or less,
The volume content of the reinforcing fiber is in the range of 0.5 vol% or more and 55 vol%,
The voids are contained in the sound insulation structure at a ratio in the range of 10% by volume or more and 99% by volume or less,
The bending elastic modulus of the sound insulation structure is 1 GPa or more, and the ratio of the transmission loss at a frequency of 200 Hz to the transmission loss at a frequency of 1250 Hz in JIS A1441-1 is in the range of 1.1 or more and 1.5 or less. A sound insulation structure characterized by being. When the bending elastic modulus of the sound insulation structure is Ec and the specific gravity of the sound insulation structure is ρ, the specific bending elastic modulus of the sound insulation structure represented by Ec ^1/3 · ρ ⁻¹ is 3 or more and 20 or less. The sound insulation structure according to claim 1, wherein the sound insulation structure has a bending elastic modulus Ec of 6 GPa or more. The sound insulation structure according to claim 1 or 2, wherein a specific gravity ρ of the sound insulation structure is 0.9 g / cm ³ or less.   The porosity of the portion within 30% from the surface of the sound insulation structure to the midpoint position in the thickness direction is in the range of 0 volume% or more and less than 10 volume%, and the porosity of the remaining portion is 10 volume% or more. The sound insulation structure according to any one of claims 1 to 3, wherein the sound insulation structure is within a range of 99% by volume or less.   The sound insulation structure according to any one of claims 1 to 4, wherein the reinforcing fibers are coated with a resin, and the thickness of the resin is in a range of 1 µm to 15 µm.   The sound insulation structure according to any one of claims 1 to 5, wherein the reinforcing fibers are discontinuous, are substantially monofilament-like, and are randomly dispersed.   The sound insulation structure according to any one of claims 1 to 6, wherein an orientation angle θf of the reinforcing fiber in the sound insulation structure is 3 ° or more.   The sound insulation structure according to any one of claims 1 to 7, wherein a mass average fiber length of the reinforcing fibers is in a range of 1 mm or more and 15 mm or less.   The sound insulation structure according to any one of claims 1 to 8, wherein the reinforcing fibers are carbon fibers.   The sound insulation structure according to any one of claims 1 to 9, wherein the resin includes at least one kind of thermoplastic resin.   The sound insulation structure according to any one of claims 1 to 9, wherein the resin contains at least one kind of thermosetting resin.