Base material of interior material for vehicle, method for producing same, and molded ceiling for vehicle

Abstract

The objective of the present invention is to provide a base material of an interior material for a vehicle excellent in rigidity, moldability, and sound absorbing property without employing a glass fiber as a reinforcing layer, a method for producing the same, and a molded ceiling for a vehicle.　The base material of an interior material for a vehicle according to the present invention ensures rigidity and is excellent in sound absorbing property, due to the length direction of short fibers used in a base material (20) in an averagely dispersed manner on a plane including a vertical direction Wa of the base material (20) in various directions from the vertical direction Wa to a front-rear direction Wb, and forming a high-density layer (20a) in a fiber body (35) itself of the base material (20).

Description

Base material for vehicle interior material, manufacturing method thereof, and molded vehicle ceiling

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application is based on Japanese Patent Application No. 2024-115053, filed on July 18, 2024, the entire contents of which are incorporated herein by reference.

[0002] The present invention relates to a base material for a vehicle interior material having excellent sound absorption and formability, a manufacturing method thereof, and a molded vehicle ceiling. Specifically, the present invention relates to a base material for a vehicle interior material such as a ceiling material, a rear package tray material, a door trim material, a floor insulator material, a trunk trim material, and a dash insulator material, a manufacturing method thereof, and a molded vehicle ceiling.

[0003] One example of a molded vehicle ceiling with excellent sound absorption properties is known, which includes a base layer made of reinforcing fibers made of glass fibers having a length of 10 to 80 mm and a fiber diameter of 10 to 20 μm and a polypropylene resin as a matrix fiber, with a polypropylene resin layer, a polyamide layer, and a polyethylene layer stacked in this order on the surface side of this base layer, with a skin layer further provided on the surface side and a nonwoven fabric on the back side (Patent Document 1).

[0004] Also known is a molded vehicle ceiling in which glass fiber layers are provided on both sides of a base layer as reinforcing materials, a decorative nonwoven fabric is provided on the front side, and an airtight layer is provided on the back side, and the base layer is made of inelastic crimped short fibers and heat-adhesive composite short fibers arranged such that the length directions of the fibers are concentrated in the thickness direction Ta of the molded ceiling (Patent Document 2).

[0005] Japanese Registered Utility Model No. 3018995 Japanese Patent Application Laid-Open No. 2019-59273

[0006] As shown in Patent Documents 1 and 2, glass fibers used as reinforcing materials have an extremely excellent reinforcing effect and good stability of molded dimensions, and are therefore widely used as interior materials for vehicles, particularly as molded vehicle ceilings.

[0007] However, because glass fibers are used, they must be handled carefully to avoid being pierced by the glass fibers, which makes them inefficient to handle. Also, products using glass fibers as a reinforcing material have the drawback of being difficult to recycle.

[0008] For this reason, the present applicant has conducted extensive research into a substrate that has sufficient sound absorption properties, rigidity, and formability for use as a vehicle interior material, particularly a molded vehicle ceiling material, without using glass fibers as a reinforcing material. In particular, the present applicant has investigated a structure in which fibers are oriented approximately perpendicular to the sheet surface by folding a fiber web into a corrugated shape, as taught in Patent Document 2. As a result, in the structure disclosed in Patent Document 2, the length direction of the short fibers is concentrated in the vertical direction Wa of the substrate, so that while the structure exhibits high rigidity in the vertical direction Wa of the substrate, it lacks rigidity in other directions and the formability varies depending on the molding direction, making it extremely difficult to eliminate glass fibers as a reinforcing material.

[0009] Therefore, the present invention has been made in consideration of the above-mentioned problems of the conventional technology, and aims to provide a base material for a vehicle interior material that has excellent rigidity and formability and excellent sound absorption properties even without using glass fiber as a reinforcing layer, a manufacturing method thereof, and a molded vehicle ceiling.

[0010] The present invention is characterized in that, without using glass fiber as a reinforcing material to maintain the rigidity and formability of the vehicle interior base material, the base material is devised so that the length directions of the short fibers used in the base material are evenly dispersed in various directions in a plane including the up-and-down direction Wa of the base material, and a high-density layer is formed in the fibrous body of the base material itself, thereby providing a base material for vehicle interiors that ensures rigidity and has excellent sound absorption properties, a manufacturing method thereof, and a molded vehicle ceiling.

[0011] The invention of claim 1 is a substrate for a vehicle interior material, which has a fibrous body formed by laminating webs having staple fibers, both of whose core and sheath portions include core-sheath composite staple fibers of a thermoplastic resin, and by arranging a rectangular original plate having a thickness direction Ta as the lamination direction of the webs and a longitudinal direction Tb and a width direction Tc as directions perpendicular to the thickness direction Ta, such that the thickness direction Ta of the original plate is directed to the left-right direction Wc of the substrate, the longitudinal direction Tb of the original plate is directed to the up-down direction Wa of the substrate, and the width direction Tc of the original plate is directed to the front-to-rear direction Wb of the substrate, and the length directions of the staple fibers of the fibrous body are evenly distributed and arranged from the up-down direction Wa to the front-to-rear direction Wb of the substrate, and by heating and pressurizing the upper surface side of the fibrous body, a high-density layer having a higher density than the portion other than the upper surface side is integrally formed in the upper surface side of the fibrous body.

[0012] The invention of claim 2 is characterized in that, in the base material of the vehicle interior material described in claim 1, the original plate is cut into strip-shaped divided members having a predetermined dimension in the longitudinal direction Tb, the thickness direction Ta of the original plate is set to the left-right direction Wc of the base material, and multiple divided members are lined up with the cut surfaces of the divided members as the upper and lower surfaces, and welded together to form the fibrous body.

[0013] The invention of claim 3 is characterized in that, in the base material of the vehicle interior material of claim 1, the web contains the core-sheath composite staple fibers and mixed staple fibers made of PET resin, the content of the core-sheath composite staple fibers is 50% by weight to 100% by weight, and the content of the mixed staple fibers is 0% by weight to 50% by weight.

[0014] The invention of claim 4 is characterized in that, in the base material of the vehicle interior material of claim 3, when the distribution state of the short fibers in the length direction in the web is divided into ranges A for up to 30° upward from the left-right direction Wc of the base material, B for more than 30° to 60°, and C for more than 60° to 90°, the proportions contained in A, B and C are all within the ranges of 20% to 40%.

[0015] The invention of claim 5 is characterized in that, in the base material of the vehicle interior material of claim 4, when A, B, and C are further divided into A1 and A2, B into B1 and B2, and C into C1 and C2 within a range of 15°, the proportions contained in A1, A2, B1, B2, C1, and C2 are all within a range of 10% to 25%.

[0016] The invention of claim 6 is the base material of the vehicle interior material according to claim 1, wherein the high-density layer has a density of 65,000 g / m ３ ~500,000g / m ３ , basis weight: 130g / m ２ ~250g / m ２ , thickness: 0.5 mm to 2.0 mm, the ratio of the density of the high-density layer of the substrate to the density of the layer other than the high-density layer is 1:0.15 to 1:0.7, and the substrate has a basis weight of 400 g / m ２ ~1,500g / m ２ , thickness: 2.0 mm to 40 mm.

[0017] The invention of claim 7 is characterized in that in a molded vehicle ceiling comprising a base material of a vehicle interior material according to any one of claims 1 to 6, the high-density layer of the base material faces the inside of the vehicle compartment, the side without the high-density layer faces the outside of the vehicle compartment, a skin layer is provided on the inside of the high-density layer, and a back layer having a non-air-permeable membrane layer is provided on the outside of the vehicle compartment on the side without the high-density layer.

[0018] The invention of claim 8 is a method for manufacturing a base material of a vehicle interior material according to any one of claims 1 to 6, comprising the steps of: entangling the staple fibers including the core-sheath composite staple fibers to form the web; stacking a plurality of the webs in a thickness direction Ta of the web and heating and pressing the stacked webs to form the raw plate in which the staple fibers are entangled; and cutting the raw plate, in which the length directions of the staple fibers in the raw plate are evenly distributed from the longitudinal direction Tb of the raw plate to the width direction Tc of the raw plate, in the thickness direction Ta of the raw plate using a cutting tool to cut the raw plate into pieces having a predetermined dimension in the longitudinal direction Tb of the raw plate. a step of rotating the orientation of the first divided member by 90 degrees to form a second divided member in which the cut surface of the first divided member consists of an upper surface and a lower surface; and a step of heating the upper surface of one of the fibrous bodies in which the length direction of the short fibers of the second divided member is evenly dispersed from the vertical direction Wa of the second divided member to the front-to-back direction Wb of the second divided member and compressing the fibrous body from the vertical direction Wa of the base material to form the high-density layer on the upper surface side of the fibrous body while maintaining the other layer of the base material as a low-density layer.

[0019] The invention of claim 9 is characterized in that, in the method for manufacturing a base material of a vehicle interior material described in claim 8, in the process of heating the upper surface of the fibrous body and compressing the fibrous body from the vertical direction Wa of the fibrous body, the lower surface side of the fibrous body is cooled.

[0020] The invention of claim 10 is characterized in that, in the method for manufacturing a base material for a vehicle interior material described in claim 8, in the step of cutting into first divided members having the specified dimensions, the first divided members are cut into multiple strips of the same width to form multiple first divided members, each first divided member is turned 90 degrees to form second divided members arranged so that the cut surfaces of the first divided members form the upper and lower surfaces, multiple second divided members are lined up and contacted so that the upper and lower surfaces of the second divided members form a single plane at the same height to form the fibrous body, adjacent second divided members are maintained in a state of contact, and the entire body is heated to form the fibrous body in which the short fibers of the fibrous body are entangled and welded.

[0021] The invention of claim 11 is the method for manufacturing a base material for a vehicle interior material according to claim 10, wherein one cut surface of the fibrous body is heated at 180°C to 240°C, and is pressed and held at a predetermined thickness for 0.5 seconds to 30 seconds, thereby forming a fibrous body on one cut surface side with a thickness of 0.05 mm to 2.0 mm and a basis weight of 50 g / m. ２ ~300g / m ２ The high density layer is formed by:

[0022] In the present invention, directions are defined as follows. The longitudinal direction Tb, thickness direction Ta, and width direction Tc of the original plate are shown in FIG. 3A. In the process of manufacturing the original plate, the web is folded and stacked while flowing, as shown in FIG. 6A. The direction in which the web flows and is folded is called the longitudinal direction Tb, the direction perpendicular to the flow direction of the web is called the width direction Tc, and the direction in which the web is stacked is called the thickness direction Ta. In other words, the thickness direction Ta of the original plate is the stacking direction of the web, and the longitudinal direction Tb and width direction Tc of the original plate are directions perpendicular to the thickness direction Ta of the original plate. On the other hand, in the case of a fibrous body (or substrate), the original plate is rotated 90 degrees, so that, as shown in FIG. 3B, the thickness direction Ta of the original plate is the left-right direction Wc of the fibrous body, the longitudinal direction Tb of the original plate is the up-down direction Wa of the fibrous body, and the width direction Tc of the original plate is the front-back direction Wb of the fibrous body.

[0023] In the present invention, the term "evenly distributed" in "the length directions of the short fibers of the fibrous body are evenly distributed from the vertical direction Wa of the substrate to the front-to-rear direction Wb of the substrate" means that when the direction of the short fibers of the substrate is measured as a vector by capturing it in a plane from one surface side in the left-to-right direction We of the substrate, and when the range from the vertical direction Wa of the substrate to the front-to-rear direction Wb of the substrate is divided into predetermined angle ranges, the length directions of the fibers are included in each predetermined angle range at a predetermined ratio.

[0024] According to the present invention, it is possible to obtain a base material for a vehicle interior material that has excellent sound absorption properties and excellent rigidity and formability, and a molded ceiling using the base material, without having the problems associated with the prior art that uses glass fiber as a reinforcing material.

[0025] Furthermore, according to the present invention, since the length direction of the short fibers of the substrate is evenly dispersed from the vertical direction Wa to the front-to-back direction Wb of the substrate, compared to when the length direction of the short fibers of the substrate is concentrated and biased in the vertical direction Wa of the substrate, a product with excellent sound absorption properties, rigidity, and formability can be obtained. Furthermore, by forming a high-density layer on the fibrous body of the substrate itself, it is not necessary to integrate the high-density layer and the substrate by adhesive or the like, and high rigidity can be obtained, so that the product has excellent shape retention whether it is molded into a three-dimensional shape of an interior material or in a flat plate state before molding.

[0026] 3B. FIG. 3C is a perspective view of a vehicle equipped with a molded vehicle headliner according to an embodiment of the present invention. FIG. 3D is a cross-sectional view schematically showing a cross section of a substrate according to an embodiment of the present invention. FIG. 3E is a photograph of an original plate taken from diagonally above. FIG. 3F is a photograph of a fibrous body taken from diagonally above. FIG. 3G is a photograph of a substrate having a high-density layer taken from diagonally above. FIG. 3H is a microscopic enlarged photograph of surface A of FIG. 3B. FIG. 3H is a microscopic enlarged photograph of surface B of FIG. 3B. FIG. 3I is a table showing the blending ratio of each fiber for examples and comparative examples of the present invention. FIG. 3I shows a step in an example of a method for manufacturing a substrate according to an embodiment ... FIG. 1 shows a step in another example of a method for producing a substrate according to an embodiment of the present invention. FIG. 1 shows a step in another example of a method for producing a substrate according to an embodiment of the present invention. FIG. 2 shows a step in another example of a method for producing a substrate according to an embodiment of the present invention. FIG. 3 shows a step in another example of a method for producing a substrate according to an embodiment of the present invention. FIG. 4 shows a step in yet another example of a method for producing a substrate according to an embodiment of the present invention. FIG. 5 shows a step in yet another example of a method for producing a substrate according to an embodiment of the present invention. FIG. 6 shows a step in yet another example of a method for producing a substrate according to an embodiment of the present invention. FIG. 7 shows a step in yet another example of a method for producing a substrate according to an embodiment of the present invention. FIG. 8 shows a step in yet another example of a method for producing a substrate according to an embodiment of the present invention. FIG. 9 is a schematic diagram for explaining an angle when measuring the length direction (vector) of short fibers of a substrate.10 is a graph showing the angular distribution measured in Fig. 9. Fig. 11 is a graph showing the sound absorption properties of the example and the comparative example.

[0027] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings. It should be noted that the following description of the preferred embodiments is merely exemplary in nature.

[0028] FIG. 1 shows a vehicle 1 in which a substrate 20 of the present invention is applied to a vehicle molded ceiling 10. FIG. 2 is a cross-sectional view schematically showing the cross section of the substrate 20 of the present invention. As shown in FIG. 1, the vehicle molded ceiling 10 is disposed on the interior side of a roof panel 2 of the vehicle 1 and includes a panel-shaped ceiling material main body 11. As shown in FIG. 2, the ceiling material main body 11 includes a skin layer 40 provided on the interior side of the substrate 20, and a back surface layer 50 provided on the roof panel 2 side of the substrate 20 (i.e., the exterior side of the vehicle). Note that FIG. 2 shows an exaggerated cross section of a portion of the ceiling material main body 11 for clarity.

[0029] As shown in FIG. 2 , the substrate 20 has a high-density layer 20a on the interior side (upper surface) and a low-density layer 20b on the exterior side (lower surface). The skin layer 40 includes, in order from the substrate 20 side toward the interior side of the vehicle cabin, an adhesive layer 41 and a skin material 42. The adhesive layer 41 is made of a polyethylene resin or the like commonly used in vehicle molded ceilings 10, and the skin material 42 is, for example, a knitted polyurethane resin. The back surface layer 50 includes, in order from the substrate 20 side toward the exterior side of the vehicle cabin, a non-permeable film layer 51 and a back surface material 52. The non-permeable film layer 51 includes, for example, a polyethylene resin film 51a, a non-permeable polyamide resin film 51b, and a polyethylene resin film 51c toward the exterior side of the vehicle cabin. The back surface material 52 is, for example, a non-woven fabric made of a spunbond material of PET resin (polyethylene terephthalate resin).

[0030] 3A to 3C are photographs illustrating the substrate 20 of the present invention. Fig. 3A shows the substrate 20 in a state in which it is a base plate 31, Fig. 3B shows the substrate 20 in a state in which it is a fibrous body 35, and Fig. 3C shows the substrate 20 in a state in which the fibrous body 35 comprises a high-density layer 20a and a low-density layer 20b. Fig. 4A is a 300x magnification micrograph of side A of the fibrous body 35 in Fig. 3B, and Fig. 4B is a 300x magnification micrograph of side B of the fibrous body 35 in Fig. 3B. As shown in Figs. 3A to 3C and 4A to 4B, the substrate 20 is formed by melting the sheath portion of the core-sheath composite short fibers 25 to bond the core portion, and in some cases, further dispersing and bonding the mixed short fibers 27. The substrate 20 integrally comprises a high-density layer 20a on the interior side of the vehicle and a low-density layer 20b on the exterior side of the vehicle.

[0031] The high-density layer 20a and the low-density layer 20b of the substrate 20 are fibrous bodies 35 made of the same material, and after molding, there are parts where the boundary between the high-density layer 20a and the low-density layer 20b is not clear, but in order to clarify the difference between the high-density layer 20a and the low-density layer 20b, in this embodiment, the high-density layer (portion) formed when one surface (top surface) of the substrate 20 is heated and pressurized is referred to as the high-density layer 20a, and the other layer (portion) lower in density than the high-density layer 20a is referred to as the low-density layer 20b. In particular, the high-density layer 20a mainly plays a role in ensuring the rigidity of the substrate, and the low-density layer 20b mainly plays a role in increasing sound absorption.

[0032] (Length Direction of Short Fibers of Substrate) The length direction of short fibers of the substrate 20 will be described with reference to FIGS. 3A to 3C and 4A to 4B.

[0033] 3A to 3C are photographs of a portion of the substrate 20 of the present invention, and are perspective views illustrating the original plate 31 and the fibrous body 35. Figures 4A to 4B are photographs of the surface of Figure 3B.

[0034] As shown in Figures 3A to 3C and 4A to 4B, the substrate 20 has, as its initial material, an original plate 31 in which a web 30 containing core-sheath type composite short fibers 25, both of whose core and sheath portions are made of PET resin (polyethylene terephthalate resin), and mixed short fibers 27 are laminated in the vertical direction Wa.

[0035] Fig. 3A is a photograph showing the state of the original plate 31 of the substrate 20. In Fig. 3A, the up-down direction Wa is the thickness direction Ta of the original plate, the direction from the center of the front side to the rear left is the longitudinal direction Tb of the original plate 31, and the direction from the center of the front side to the rear right is the width direction Tc of the original plate 31. On the right side and left side, what appears to be multiple thin layers in the up-down direction Wa indicates that the web 30 is multilayered.

[0036] Figure 3B is a photograph showing the state of the fibrous body 35 of the substrate 20. Figure 3B shows the original plate 31 of Figure 3A cut into strips of a predetermined size, rotated 90 degrees, and joined together, referred to as the fibrous body 35 in the present invention. As shown in Figure 3B, the fibrous body 35 of the substrate 20 has the longitudinal direction Tb of the original plate 31 as the vertical direction Wa of the fibrous body 35, the thickness direction Ta of the original plate 31 as the horizontal direction Wc of the fibrous body 35, and the width direction Tc of the original plate 31 as the front-to-back direction Wb of the fibrous body 35. Hereinafter, when describing the length direction of the fibers of the substrate 20, the direction of the fibrous body 35 will be referred to as the vertical direction Wa, the front-to-back direction Wb, and the horizontal direction Wc, while the original plate 31 will be referred to as the longitudinal direction Tb, the width direction Tc, and the thickness direction Ta. On the right side (side A) of Figure 3B, the many vertical lines appear to represent a state in which multiple webs 30 are stacked vertically.

[0037] Figure 3C is a photograph showing the substrate 20 provided with a high-density layer 20a on the upper surface of the fibrous body 35 of Figure 3B. In Figure 3C, the high-density layer 20a can be seen on the upper surface of the fibrous body 35, and the low-density layer 20b can be seen on the lower surface (below) thereof. Note that a thin film-like substance can also be seen on the lower surface of the fibrous body 35, but this is simply a thin film-like substance that was crushed during compression and is not the high-density layer 20a.

[0038] Figure 4A is a 300x magnification micrograph of surface A of Figure 3B (one end surface of the fibrous body 35 in the front-to-rear direction Wb). Figure 4B is a 300x magnification micrograph of surface B of Figure 3B (one end surface of the fibrous body 35 in the left-to-right direction Wc). In Figure 4A, the white vertical lines are the lines of the sheath-core composite short fibers 25, and the slight inclination of the fibers at the upper and lower ends is due to compression from the up-and-down direction Wa. In Figure 3B, the white lines are the sheath-core composite short fibers 25, and the black lines are the mixing short fibers 27. In this sample, the sheath-core composite short fibers 25 and the mixing short fibers 27 are prototyped with white and black lines so that they can be distinguished from each other. In actual use, it is expected that the sheath-core composite short fibers 25 and the mixing short fibers 27 will become similar white fibers. Judging from surfaces A and B, on surface A, the web 30 of the fibrous body 35 is composed of multiple fiber bundles aligned in the vertical direction Wa, aligned in the left-right direction Wc, and bonded to each other. Furthermore, looking at surface B, the length direction of the short fibers is not limited to the vertical direction Wa, but is dispersed in any direction within surface B. The short fibers do not face in a single linear direction, but rather meander and extend in various directions, and the fibers are entangled with each other. In the present invention, the length direction of the fibers is measured as a vector in a plane, and any meandering or three-dimensional directions along the way are ignored.

[0039] In this way, in the present invention, the length directions of the short fibers of the fibrous body 35 of the base material 20 are evenly dispersed and directed from the vertical direction Wa to the front-to-back direction Wb of the fibrous body 35, and are overlapped in the left-to-right direction We of the fibrous body. Therefore, the base material has high rigidity from the vertical direction Wa to the front-to-back direction Wb, which prevents deformation during molding, and moldability can be maintained, so that a base material 20 for vehicle interior materials can be obtained that is easy to mold, has high rigidity, and has excellent sound absorption properties.

[0040] In the present invention, "evenly dispersed and oriented" means that "when the vector in the length direction of the fiber is measured, the distribution state from the vertical direction Wa to the front-to-back direction Wb within one plane is dispersed evenly from the vertical direction Wa to the front-to-back direction Wb," and also means that "the fiber is not oriented with a biased concentration in either direction," which, expressed numerically, means that the distribution is 20% to 40% in the ranges of 0 to 30°, 31° to 60°, and 61° to 90°.

[0041] (Sheath-core composite staple fibers 25) The sheath-core composite staple fibers 25, which are the material of the substrate 20, are general sheath-core composite staple fibers, and detailed description thereof will be omitted here. The sheath-core composite staple fibers 25 use PET (polyethylene terephthalate) fibers for both the core and sheath.

[0042] The fineness of the sheath-core composite short fibers 25 is preferably 1.5 dtex to 15 dtex, particularly 3.0 dtex to 8.0 dtex, because a low fineness makes handling difficult and reduces productivity, while a high fineness makes the fibers themselves thicker, reducing the air resistance and deteriorating sound absorption.

[0043] The fiber length of the sheath-core composite short fibers 25 is preferably in the range of 10 mm to 100 mm, particularly 20 mm to 80 mm, in order to improve processing stability in the manufacturing process of the substrate 20 for the vehicle interior material. Furthermore, it is preferable to configure the fibers so as to have mechanical crimps, etc., so that a larger number of minute cells can be formed.

[0044] The melting point of the sheath portion of the sheath-core composite staple fibers 25 is preferably 90°C to 180°C. In particular, if the melting point of the sheath portion of the sheath-core composite staple fibers 25 is too high, the fibers will lack fluidity when heated and press-molded, preventing the high-density layer 20a from following the molding direction and resulting in poor moldability. Conversely, if the melting point of the sheath portion of the sheath-core composite staple fibers 25 is too low, the fibers will melt too much, increasing the possibility of large holes being formed in the substrate 20. Therefore, the melting point of the sheath portion of the sheath-core composite staple fibers 25 is preferably 90°C to 180°C. On the other hand, the melting point of the core portion of the sheath-core composite staple fibers 25 must be such that it does not melt when heated and press-molded, and therefore is preferably 30°C or more higher than the melting point of the sheath portion of the sheath-core composite staple fibers 25. Specifically, for example, the core portion of the sheath-core composite staple fibers 25 is preferably a PET fiber having a melting point of 220°C to 270°C.

[0045] In this embodiment, the core portions of the sheath-core composite short fibers 25 are entangled with each other and the sheath portions are melted and hardened to bond the core portions together, which allows the substrate 20 for vehicle interior materials to be easily and reliably molded into a three-dimensional shape and to reliably maintain that shape. Furthermore, the core portions of the sheath-core composite short fibers 25 exist as entangled fibers that constitute the substrate 20, retaining their fiber shape while being strongly bonded by the sheath fibers, which greatly helps to form more microscopic cells inside the substrate 20. As a result, a structure (approximately mesh-like structure) that can enhance the sound-absorbing performance of the substrate 20 can be easily formed.

[0046] (Intermixing Short Fibers 27) The sheath-core composite short fibers 25 may be mixed with intermixing short fibers 27 similar to the sheath-core composite short fibers 25. Replacing some of the sheath-core composite short fibers 25 with general intermixing short fibers 27 can reduce costs. Even in this case, the intermixing short fibers 27 are preferably PET fibers, since the same material as the sheath-core composite short fibers 25 provides good bonding and is preferable from the standpoint of recyclability. The fineness of the intermixing short fibers 27 is preferably in the range of 1.5 dtex to 15 dtex, particularly 3.0 dtex to 8.0 dtex, similar to the sheath-core composite short fibers 25. The fiber length of the intermixing short fibers 27 is preferably in the range of 10 mm to 100 mm, particularly 20 mm to 80 mm. The melting point of the mixed short fibers 27, like the core portion of the core-sheath composite short fibers 25, is preferably 30°C higher than the melting point of the sheath portion of the core-sheath composite short fibers 25, specifically within the range of 220°C to 270°C, so that the mixed short fibers 27 do not melt when the sheath portion of the core-sheath composite short fibers 25 melts.

[0047] In addition, by using PET fibers for both the core-sheath composite short fibers 25 and the mixed short fibers 27, it becomes possible to easily mix the base material 20 of a used vehicle interior material as part of the material with the new material of the base material 20 of the vehicle interior material of this embodiment.

[0048] (Proportion of Each Short Fiber) The content of the sheath-core composite short fibers 25 contained in the entire web 30 is preferably 50% by weight to 100% by weight, more preferably 60% by weight to 90% by weight, and even more preferably 70% by weight to 85% by weight. If the content of the sheath-core composite short fibers 25 is less than 50% by weight, it becomes difficult to sufficiently maintain the shape stability of the substrate 20 of a vehicle interior material molded into a three-dimensional shape.

[0049] Furthermore, a portion of the sheath-core composite short fibers 25 can be replaced with mixing short fibers 27. In order for the short fibers to fuse together, 50% by weight or more of the sheath portion of the sheath-core composite short fibers 25 is required, and the maximum amount of the sheath-core composite short fibers 25 that can be replaced with mixing short fibers 27 is up to 50% by weight. Therefore, the content of mixing short fibers 27 in the entire web 30 is preferably 0% to 50% by weight, more preferably 5% to 40% by weight. Since mixing short fibers 27 can be obtained at a lower cost than sheath-core composite short fibers 25, increasing the amount of mixing short fibers 27 is effective in terms of cost. However, since the amount of sheath-core composite short fibers 25 becomes relatively small and the sheath portion that fuses the short fibers together becomes smaller, the amount of mixing short fibers 27 should be set to an amount that does not result in insufficient welding strength or molding defects, taking into account the size and molding conditions of the substrate 20 of the vehicle interior material.

[0050] (High-density layer 20a) The high-density layer 20a, a feature of this embodiment, is formed by using sheath-core composite short fibers 25 as a substrate and applying heat and pressure to one side of the substrate to melt the sheath fibers. In other words, the high-density layer 20a is not formed by bonding a separate film material to the substrate. This eliminates the need to worry about adhesion to the substrate, and the high-density layer 20a can be manufactured integrally with the nonwoven fabric substrate, resulting in excellent productivity. In particular, because the high-density layer 20a and the substrate are made of the same material, a product can be obtained that has good formability, increased strength, and excellent shape retention. Furthermore, because the high-density layer 20a is once formed and solidified, even if the entire product is heated to facilitate formability, the high-density layer 20a remains, resulting in a stable high-density layer 20a.

[0051] Furthermore, because the high-density layer 20a has a high density and high rigidity, the substrate 20 of the vehicle interior material can be easily molded into a three-dimensional shape without containing reinforcing members such as glass fiber, and has excellent deformation resistance after molding. The high-density layer 20a has a relatively high density, a low basis weight, and a thin thickness compared to the low-density layer 20b. Specifically, if the density of the high-density layer 20a is too high, the air permeability will increase, resulting in poor sound absorption in the high-frequency range and making molding difficult. If the density of the high-density layer 20a is too low, the rigidity of the substrate 20 as a vehicle interior material will be insufficient and moldability will be poor. Therefore, the density of the high-density layer 20a should be 65,000 g / m ３ ~500,000g / m ３ , especially 80,000 g / m ３ ~400,000g / m ３ , and further, 100,000 g / m ３ ~300,000g / m ３ It is preferable to set the following.

[0052] In the high-density layer 20a, the molten sheath portion closes some of the voids present in the core-sheath composite short fibers 25, reducing the air permeability and increasing the density, thereby making it possible to realize a base material 20 for vehicle interior materials that has better sound absorption performance, sound insulation performance, and rigidity.

[0053] If the thickness of this high-density layer 20a is too thick, it will have poor elongation and poor formability, and if it is too thin, it will have poor shape retention, so it is preferable that the thickness after molding be 0.5 mm to 2.0 mm, particularly 0.7 mm to 1.5 mm. If it is less than 0.5 mm, not only will the high-density layer 20a be very prone to tearing, but it will also lack rigidity, resulting in poor formability and shape retention. Conversely, if it exceeds 2.0 mm, the high-density layer 20a will have insufficient fluidity when heated and press-molded, and will not be able to follow the molding direction of the substrate 20, which may result in poor formability.

[0054] The weight of the high density layer 20a is preferably 50 g / m ２ ~300g / m ２ , especially 100 g / m ２ ~250g / m ２ 50g / m ２If the weight per unit area of ​​the high-density layer 20a is less than 300 g / m, the thickness of the high-density layer 20a will be insufficient, resulting in thin portions and, in some cases, a portion where the layer itself does not exist. ２ If the value exceeds this, the sound absorption effect is likely to be impaired.

[0055] (Low-density layer 20b) By leaving the portion of the substrate 20 other than the high-density layer 20a as the low-density layer 20b, excellent sound absorption properties can be achieved. That is, the substrate 20 of the vehicle interior material can absorb noises such as engine noise, external noise, and road noise by the high-density layer 20a and the low-density layer 20b.

[0056] If the density of the low-density layer 20b is too high, the difference with the high-density layer 20a will be insufficient, resulting in excessive rigidity, and if it is too low, the sound absorption in the low-frequency range will be insufficient. ３ ~92,000g / m ３ , especially 10,000 g / m ３ ~70,000g / m ３ , and even 20,000 g / m ３ ~50,000g / m ３ It is preferable to set the following.

[0057] If the weight of the low-density layer 20b is too high, moldability will be poor, and if it is too low, sound absorption will be insufficient. ２ ~1,400g / m ２ , especially 200 g / m ２ ~1,000g / m ２ , and further, 250 g / m ２ ~800g / m ２ It is preferable to set the following.

[0058] If the thickness of the low-density layer 20b is too thick, the high-density layer 20a will be relatively thin or the entire substrate 20 will be thick, making it difficult to mold and reducing shape retention, while if it is too thin, sound absorption properties will be unsatisfactory. Therefore, it is preferable that the thickness be 5 to 40 mm, particularly 7 mm to 30 mm, and even more preferably 7 mm to 20 mm.

[0059] If the density ratio between the high density layer 20a and the low density layer 20b is too high, the moldability and sound absorption properties will be insufficient, and if it is too low, the moldability and sound absorption properties will be poor. Therefore, it is preferable that the density ratio of the high density layer 20a to the low density layer 20b be within the range of 1:0.15 to 1:0.7.

[0060] If the ratio of the basis weight of the high density layer 20a to the low density layer 20b is too high or too low, sound absorption properties and moldability will be deteriorated, so it is preferable to set it within the range of 1:1.5 to 1:5.0.

[0061] If the thickness ratio of the high density layer 20a to the low density layer 20b is too high, the high density layer 20a will be insufficient, and if it is too low, the low density layer 20b will be insufficient, so it is preferable to set it within the range of 1:4 to 1:20.

[0062] (Entire substrate of automotive interior material) If the total basis weight of the substrate 20 including the high-density layer 20a and the low-density layer 20b is too low, the effects of sound absorption and sound insulation cannot be expected, and conversely, if it is too high, the bonding strength of the core portion of the core-sheath type composite short fiber 25 decreases. Therefore, the total basis weight including the high-density layer 20a is set to 400 g / m ２ ~1,500g / m ２ , especially 500 g / m ２ ~1,400g / m ２ , and even 700 g / m ２ ~1,300g / m ２ It is preferable to set the following.

[0063] If the overall density of the substrate 20 is too high, the rigidity becomes too strong and the formability becomes poor, and if it is too low, the rigidity becomes insufficient. ３ ~750,000g / m ３ , especially 30,000 g / m ３ ~600,000g / m ３ , and even 40,000 g / m ３ ~500,000g / m ３ It is preferable to set the following.

[0064] The total thickness of the substrate 20 is preferably 2.0 mm to 40 mm, particularly 3.0 mm to 30 mm, and even more preferably 4.0 mm to 20 mm. If the total thickness is less than 2.0 mm, the rigidity and shape retention of the substrate 20 cannot be sufficiently ensured. Furthermore, a large number of cells cannot be formed, and a sufficient sound absorption effect cannot be achieved. Conversely, if the thickness exceeds 40 mm, the formability of the substrate 20 deteriorates, making it impossible to reduce the weight and increasing costs.

[0065] (Vehicle molded ceiling 10) In the case of a vehicle molded ceiling 10 as an example of a product, if the basis weight of the vehicle molded ceiling 10 is too high, it becomes heavy and costs increase, and if it is too low, effects such as sound absorption and sound insulation cannot be expected. Therefore, the basis weight is set to 700 g / m ２ ~2,000g / m ２ , especially 800 g / m ２ ~1,800g / m ２ , and even 900 g / m ２ ~1,500g / m ２ It is preferable to set the following.

[0066] If the thickness of the vehicle molded ceiling 10 is too thick, it will be heavy and costly, and if it is too thin, sound absorption properties cannot be expected, so it is preferable that the thickness be 2.5 to 42 mm, particularly 5 to 30 mm, and even more preferably 8 to 20 mm.

[0067] A manufacturing method of the substrate 20 for a vehicle interior material according to this embodiment will be described with reference to FIGS. 6A to 6H . (1) As shown in FIG. 6A , a carding machine 110 having a carding machine 111 and a cross layer 112 entangles core-sheath composite short fibers 25 (or short fibers further including mixed short fibers 27) that will become the substrate 20 to form a web 30. The webs 30 are then stacked in the thickness direction Ta of the webs 30 to obtain a base plate 31 made of a laminate of the webs 30. In this process, the length directions of the short fibers are uniformly distributed in various directions from the longitudinal direction Tb to the width direction Tc of the web 30. The webs 30 are stacked in the thickness direction Ta of the webs 30 to obtain a base plate 31 made of a laminate of the webs 30. For example, approximately 10 to 30 webs each having a thickness of 0.5 to 1.5 mm are stacked, and the stacked webs are heated and compressed to form a base plate 31 having a thickness of approximately 5 to 45 mm. In this state, the length directions of the short fibers are distributed almost evenly from the longitudinal direction Tb to the width direction Tc of the original plate 31 .

[0068] (2) Next, as shown in Fig. 6B, this raw plate 31 is heated and pressurized in a first heating and pressurizing device 120 to bond the sheath and core portions of the sheath-core composite short fibers 25 in the raw plate 31 and / or the mixed short fibers 27. The heating conditions vary depending on the material of the sheath-core composite short fibers 25, the thickness of the raw plate 31, the number of overlapping webs 30, etc., but are, for example, 110°C to 150°C for about 0.5 to 3 minutes.

[0069] In the original plate 31 in this state, as shown in Fig. 6C, the length directions of the short fibers are distributed almost evenly in various directions from the longitudinal direction Tb to the width direction Tc of the original plate 31. On the paper surface of Fig. 6C, the up-and-down direction is the thickness direction Ta, the sideways direction is the longitudinal direction Tb, and the direction from the front to the right rear is the width direction Tc.

[0070] (3) Then, as shown in Fig. 6D, a cutting tool 130 such as a cutter having a blade in the thickness direction Ta of the original plate 31 is lowered from above onto the original plate 31 to divide the original plate 31 into strip-shaped members (first divided members 32) each consisting of an elongated rectangular parallelepiped having a fixed dimension in the longitudinal direction Tb of the original plate 31. The fixed dimension varies depending on the vehicle model and part to be used, the thickness of the first divided member 32, etc., but is set within a range of 5 mm to 30 mm, for example.

[0071] (4) Then, as shown in Fig. 6E, first divided member 32 is rotated 90 degrees as if rolling, so that the top and bottom surfaces 32a and 32b of first divided member 32 become side surfaces 33b of second divided member 33, and cut surfaces 32b of first divided member 32 become the top and bottom surfaces 33a and 33b of second divided member 33. After the 90-degree rotation in Fig. 6E, the horizontal direction on the paper surface is the thickness direction Ta, the vertical direction is the longitudinal direction Tb, and the direction from the front to the right rear is the width direction Tc.

[0072] (5) Next, as shown in Fig. 6F, a predetermined number of these second divided members 33 are lined up in a row to form a parallel member 34. The orientation of the second divided members 33 of the parallel member 34 in Fig. 6F is changed by 90 degrees from the orientation of the first divided members 32 in Fig. 6E, so that the longitudinal direction Tb of the original plate 31 corresponds to the up-down direction Wa of the parallel member 34, the width direction Tc corresponds to the front-back direction Wb, and the thickness direction Ta corresponds to the left-right direction Wc. Therefore, the length directions of the short fibers of the parallel member 34 are distributed almost evenly and evenly in various directions from the up-down direction Wa to the front-back direction Wb of the parallel member 34.

[0073] (6) As shown in FIG. 6G , the parallel members 34 are heated and pressurized in the second heating and pressing device 122. Specifically, the parallel members 34 are placed in the second heating and pressing device 122 while being pressed from the left-right direction Wc by the pressing tool 124, and heated for a predetermined time to fuse the short fibers of the parallel members 34, thereby obtaining a fibrous body 35. The heating conditions vary depending on the material of the sheath-core composite short fibers 25 and the thickness of the fibrous body 35, but are, for example, 1110°C to 150°C for approximately 0.5 to 3 minutes. In particular, when the length direction of the short fibers of the fibrous body 35 is viewed as a vector, they are dispersed almost evenly throughout the fibrous body 35 from the up-down direction Wa to the front-back direction Wb. However, there are also many short fibers oriented in the left-right direction of the fibrous body 35. Compressing these short fibers in the left-right direction causes the short fibers to become well entangled with each other, resulting in a unified fibrous body 35.

[0074] (7) As shown in Figure 6H, the fibrous body 35 is pressed between rollers 140. At this time, the upper heating roller 141 is heated by a heater (not shown) or the like, while the lower cooling roller 142 is cooled with cooling water (not shown) or the like. This temperature difference causes a high-density layer 20a to be formed on the upper surface of the fibrous body 35 at a predetermined density and a predetermined thickness, while the layers from the middle to the lower part are stably and reliably maintained as low-density layers 20b at a density approximately equal to the low density of the web 30.

[0075] In the parallel members 34, the fibrous body 35 made of the parallel members 34, and the substrate 20 made of the fibrous body 35 obtained as described above, the thickness direction Ta of the original plate 31 is aligned with the left-right direction Wc of the substrate 20, the longitudinal direction Tb of the original plate 31 is aligned with the up-down direction Wa of the substrate 20, and the width direction Tc of the original plate 31 is aligned with the front-to-back direction Wb of the substrate 20.

[0076] In the above embodiment, an example of manufacturing the web 30 using the carding machine 110 has been shown, but the manufacturing method is not limited to this. For example, the method of forming the web 30 can be, for example, to form the web 30 consisting of fiber bundles by discharging staple fibers including the core-sheath composite staple fibers 25 using an air-laying method, or to form the web 30 by entangling the fibers using a fiber spreader or a carding machine.

[0077] Another manufacturing method will be described below with reference to Figures 7A to 7G. Only the differences from Figures 6A to 6H will be described. Figure 7D shows an example in which the separate steps shown in Figures 6D and 6E are performed as a single process. Specifically, while the original sheet 31 is transported on the first conveyor 161, it is cut into first divided members 32 of a predetermined size in the longitudinal direction Tb using a cutting tool 130. While still transported on the first conveyor 161, the first divided members 32 pass through an inverting device 165, where they are rotated 90 degrees to become second divided members 33. A predetermined number of second divided members 33 transported on the second conveyor 162 are removed, resulting in parallel members 34 as shown in Figure 7E. Subsequently, the steps shown in Figures 7F and G, similar to those shown in Figures 6G and 6H, are performed to produce a fibrous body 35.

[0078] Another manufacturing method is described below with reference to FIGS. 8A to 8F. Only the differences from FIGS. 6A to 6H will be described. In the manufacturing method shown in FIGS. 8A to 8F, for example, as shown in FIG. 8A, multiple webs 30 are stacked, resulting in a significantly increased number of web layers compared to the usual number. Then, as shown in FIG. 8B, the web is heated at this thickness and pressed with a press 125 or the like to obtain a unified base plate 31a as shown in FIG. 8C. For example, the base plate 31a may have a thickness of 500 to 1,800 mm. Next, as shown in FIG. 8D, a cutting tool 130 is used to cut the base plate 31a into short, predetermined-sized fibrous bodies 35a in the longitudinal direction Tb using a cutting blade in the vertical direction Wa. When viewed from a perspective view of the cut fibrous bodies 35a as shown in FIG. 8E, with the cut surfaces facing up and down, the length of the short fibers is evenly distributed from the vertical direction Wa to the front-to-back direction Wb. Next, the cut fibrous body 35a is turned 90 degrees horizontally from the state shown in Figure 8E, and the fibrous body 35a is made to enter the roller 140 from the left-right direction Wc, forming a high-density layer 20a on one surface (top surface). In this manufacturing method, the fibrous body 35 is obtained directly from the original plate 31 without manufacturing the first divided member 32 or the second divided member 33. Note that because the heating and compression equipment is large-scale, this method is more suitable for small products such as door trim, tonneau board, and trunk trim than for large products such as the molded ceiling 10 for a vehicle.

[0079] (Method of manufacturing the molded vehicle headliner 10) The substrate 20 is manufactured by the above-described method, and the surface layer 40 and back surface layer 50 are prepared. The surface layer 40 is overlaid on the high-density layer 20a side of the substrate 20, and the back surface layer 50 is overlaid on the low-density layer 20b side. The substrate is heated to make it easy to form, and then pressed in a mold for the molded vehicle headliner 10 to manufacture the molded vehicle headliner 10. A cold forming mold is used as the mold.

[0080] The heating temperature, heating time, mold clearance, etc. may be appropriately selected and set depending on the thickness of the substrate 20, the fibers of the nonwoven fabric, or the intended use, but it is preferable that the heating temperature be 150°C to 220°C, the mold clearance be 5 to 20 mm, and the heating time be 5 to 30 seconds.

[0081] Although the above description has been given of an example in which molding is performed using a cold press mold, the manufacturing method is not limited to this, and molding may also be performed using a hot press mold, for example.

[0082] (Manufacturing conditions for the substrate 20) The method of laminating a web 30 from core-sheath composite short fibers 25 (or a mixture of short fibers 27 for incorporation) to obtain a base plate 31 is similar to the manufacturing method and manufacturing conditions for a general base plate, and detailed explanation will be omitted here.

[0083] (Conditions for Forming High-Density Layer 20a) If the heating temperature for forming the high-density layer 20a is too low, the required high-density layer 20a will not be formed. Conversely, if it is too high, the film thickness will be too thick, resulting in poor elongation and poor formability. Therefore, the heating temperature of the heating press is preferably 150°C to 220°C, particularly 160°C to 200°C. In the case of a heating press, the clearance is preferably 5.0 to 20 mm, particularly 7.0 to 15 mm, and the heating time is preferably 5 to 30 seconds, particularly 8 to 25 seconds. Note that if the film is passed between rollers with one side heated instead of a press, the heating time is shorter, so a higher heating temperature is possible. If the film is passed between rollers with one side heated, the time is shorter, so a narrower roller gap is preferable. The clearance is preferably 0.3 to 10 mm, particularly 0.5 to 8 mm, and the linear speed is preferably 1 to 8 m / min, particularly 2 to 7 m / min. Whether passing between heated rollers or using a press mold, it is necessary to cool the unheated side with a coolant or the like and maintain it at room temperature. By heating one side and cooling the other, it is possible to reliably ensure a density difference between the heated side and the unheated side, and to control not only the density and thickness of the high-density layer 20a, but also the basis weight and thickness of the low-density layer 20b. In particular, by controlling the heating temperature, heating time, pressure, pressure gap, etc., it is possible to adjust the thickness and strength of the high-density layer 20a while ensuring the basis weight of the low-density layer 20b, so that the properties can be easily adjusted according to the intended use, etc.

[0084] (Molding Conditions for Vehicle Headliner 10) To mold the plate-shaped substrate 20 into a predetermined shape (e.g., rectangular), the substrate 20 is heated in a heating furnace or the like to facilitate molding (deformation), and the heated substrate is then placed in a cold press mold of the predetermined shape for molding. In this case, it is preferable to cool the substrate 20 as quickly as possible after molding into the predetermined shape in the press mold so that the shape can be maintained. Therefore, cooling air may be blown from the surface of the press mold to cool the heated substrate 20 while molding. The heating temperature should be such that the plate-shaped substrate 20 is easily moldable. It is sufficient that the temperature is higher than the melting point of the sheath portion of the core-sheath composite short fibers 25, and it is not necessary to set it very high. The heating temperature is preferably within a range of, for example, 150°C to 220°C, particularly 160°C to 200°C. The heating time should also be sufficient to achieve a moldable state, and is preferably within a range of 5 to 30 seconds, particularly 10 to 25 seconds, and even more preferably 15 to 20 seconds.

[0085] The mold clearance of the cold press mold may be appropriately selected and set depending on the thickness of the substrate 20, the fibers of the nonwoven fabric, the intended use, etc., but a practical range is 5.0 mm to 20 mm, and in particular, about 4.0 mm to 15 mm. Note that although an example of molding using a cold press mold has been described above, the manufacturing method is not limited to this, and molding using a hot press mold, for example, may also be used.

[0086] 5 is a table showing the blending ratios of each fiber for examples of the present invention and comparative examples. The examples of the present invention will be specifically described below. The present invention will be specifically described below using examples, but the present invention is not limited to these examples.

[0087] (Example 1) The core and sheath of the core / sheath composite staple fibers 25 were made of PET resin staple fibers with a fineness of 6.6 dtex and a fiber length of 51 mm, with the core and sheath having a melting point of 240°C and 110°C, respectively. The blending staple fibers 27 were also made of PET resin staple fibers with a melting point of 240°C, a fineness of 6.6 dtex, and a fiber length of 51 mm. The blending staple fibers were a mixture of 80% by weight of the core / sheath composite staple fibers 25 and 20% by weight of the blending staple fibers 27, and the blending staple fibers were mixed to form a composite fiber having a total basis weight of 600 g / m. ２A carding machine 110 was used to prepare a base plate 31 made of a sheet as shown in FIG. 3A. This base plate 31 was then processed to form a fibrous body 35 as shown in FIG. 3B. This fibrous body 35 was then heated on one roller surface (heating temperature: approximately 220°C, heating time: 5 seconds) and cooled to room temperature on the other roller with cooling water. The fibrous body 35 was then passed through a roller gap of 0.5 mm at a linear speed of 7 m / min under pressure, forming a substrate 20 having a high-density layer 20a on the upper surface of the fibrous body 35 and a low-density layer 20b on the remaining portion, as shown in FIG. 3C. The density, basis weight, thickness, density ratio, basis weight ratio, and thickness ratio of the substrate 20, high-density layer 20a, and low-density layer 20b at this time are shown in FIG. 5. Since the thicknesses of the high-density layer 20a and low-density layer 20b are not uniform, the thickness is calculated as the average thickness of the entire body, but it may also be calculated as the average thickness of the majority of the body.

[0088] The surface layer 40 was overlaid on the interior side of the high-density layer 20a, and the back surface layer 50 was overlaid on the exterior side of the low-density layer 20b, and the layers were heated to facilitate molding and pressed in a cold press mold shaped like a molded ceiling to produce a molded vehicle ceiling 10. The surface layer 40 was made of a polyethylene resin adhesive layer 41 with a thickness of 40 μm and a basis weight of 315 g / m from the substrate 20 side. ２ The back surface layer 50 is made of a polypropylene resin film having a thickness of 20 μm, a polyamide resin film having a thickness of 10 μm, and a non-air-permeable film layer 51 made of a polyethylene resin film having a thickness of 7 μm, and a film weight of 12 g / m. ２ The backing material 52 is made of a PET resin spunbond nonwoven fabric.

[0089] Specifically, before being placed in the cold press mold, the substrate 20, the surface layer 40, and the back surface layer 50 are all heated in a heating furnace (heating temperature: approximately 200°C, heating time: 20 seconds) to soften them for easy molding. Then, they are pressed in a cold press mold with a gap of 10.5 mm to be molded into the shape of the molded vehicle headliner 10. The molded vehicle headliner 10 obtained after molding has a basis weight of 1,000 g / m ２ The dimensions were 1,200 mm x 1,600 mm x total thickness (total thickness) of 10.5 mm.

[0090] Example 2 In Example 2, only the differences from Example 1 will be described, and a description of the common parts will be omitted. Example 2 differs from Example 1 in the density, basis weight, thickness, density ratio, basis weight ratio, thickness ratio, etc. of the substrate 20, high-density layer 20a, and low-density layer 20b. These values ​​are shown in Figure 5. The manufacturing method differs in that a press machine was used instead of a roller to form the high-density layer 20a. The press machine maintained a pressurized state with a clearance of 10 mm for 20 seconds. The surface of the upper mold of this press mold was heated to 200°C, and the lower mold was cooled with cooling water to maintain approximately room temperature.

[0091] Example 3 In Example 3, only the differences from Example 1 will be described, and a description of the common parts will be omitted. Example 3 differs from Example 1 in the density, basis weight, thickness, density ratio, basis weight ratio, thickness ratio, etc. of the substrate 20, high-density layer 20a, and low-density layer 20b. These values ​​are shown in Figure 5.

[0092] (Comparative Example 1) A mixture of 50% by weight of polypropylene resin and 50% by weight of glass fiber having a fineness of 6.6 dtex and a fiber length of 51 mm was used to produce a fabric with a basis weight of 705 g / m ２ A polyethylene resin film having a thickness of 40 μm and a basis weight of 315 g / m was applied to one surface of the resin sheet. ２ On the other surface, a polypropylene resin film having a thickness of 30 μm, a polyamide resin film having a thickness of 20 μm, and a weight of 15 g / m ２ The PET resin spunbond nonwoven fabrics were stacked, heated to facilitate molding, and pressed in a cold molding die to produce a molded vehicle ceiling 10. ２ A molded ceiling measuring 1,200 mm x 1,600 mm x thickness: 10.5 mm (total thickness including all materials forming the molded ceiling) was manufactured.

[0093] Comparative Example 2 A base plate was prepared by laminating a web containing 80% by weight of core-sheath composite staple fibers, the core and sheath of which were PET resin staple fibers with a fineness of 4.4 dtex and a fiber length of 51 mm, with the core and sheath having a melting point of 240°C and 110°C, and 20% by weight of PET resin staple fibers with a melting point of 240°C, a fineness of 6.6 dtex, and a fiber length of 51 mm. The base plate was folded in an accordion shape as shown in Figure 2 of JP 2019-59273 A, so that the length direction of the staple fibers in the base plate was the thickness direction Ta. A fiber structure was produced by heating one side of the folded portion of the fiber structure to form a high-density layer. A skin layer and a backside layer were then layered on the high-density layer and heated to facilitate molding, and then molded into a molded ceiling using a cold molding die.

[0094] The surface layer and the back surface layer were the same as those used in Example 1. The fiber structure of Comparative Example 2 had a basis weight of 700 g / m ２ The weight of the molded ceiling is 1,100 g / m ２ The thickness of the molded ceiling was 10.5 mm.

[0095] (1) Measurement of Fiber Length Direction The fibrous body of Example 1 was cut in the vertical direction Wa to create a sample measuring 50 mm x 50 mm and 10 mm thick. From this sample, the direction in which the length direction of the short fibers of the fibrous body 35 points upward from the horizontal direction Wc of the fibrous body 35 (i.e., the vector) was defined as "θ" as shown in FIG. 9, and the number of fibers was counted in increments of θ = 15°. As a result, of the 3,000 fibers, 559 were found to be at angles between 0° and 15°, 571 between 16° and 30°, 566 between 31° and 45°, 751 between 46° and 60°, 467 between 61° and 75°, and 486 between 76° and 90°. The number of fibers was measured at 10 random locations using a nanofocus X-ray CT scanner from Rigaku Corporation and ExFact analysis software from Japan Visual Science Co., Ltd. The number was the average value of the 10 locations.

[0096] The longitudinal proportion of the short fibers in the fibrous body 35 is in the range of 20% to 45%, particularly 25% to 40%, when the longitudinal direction of the fibers is divided into three ranges in 30° increments, proving that the proportion is evenly distributed on average without bias or concentration in any particular direction. In particular, as shown in Figure 10, when the longitudinal direction is further divided into six ranges in 15° increments, the proportion is in the range of 10% to 25%, particularly 13% to 24%, proving that the proportion is evenly distributed on average without bias or concentration in any particular direction.

[0097] (2) Sound Absorption The sound absorption coefficient in a tube was measured for the example of the present invention and comparative examples 1 and 2. The results are shown in Fig. 10. The sound absorption coefficient in a tube was measured in accordance with JIS A 1405-2, with sound waves incident perpendicularly to the surface on the skin layer 40 side, and with an air gap of 0 mm on the back layer 50 side.

[0098] For the example of the present invention and comparative examples 1 and 2, samples were prepared by cutting out a circle having a diameter of 29 mm. The normal incident sound absorption coefficient of these samples was measured. The normal incident sound absorption coefficient was measured in accordance with JIS A 1405-2 (ISO 10534-2).

[0099] 11, there appears to be no significant difference in sound absorption properties when comparing Example 1 with Comparative Examples 1 and 2. These results show that, compared to Comparative Examples 1 and 2, which contain glass fiber as a reinforcing material, the present invention, even without containing glass fiber, can achieve sound absorption properties comparable to those containing glass fiber by adjusting the length direction of the short fibers used in the substrate 20.

[0100] Furthermore, looking at the average sound absorption coefficient from 500 Hz to 5,000 Hz, Example 1 of the present invention was 0.61, Comparative Example 1 was 0.49, and Comparative Example 2 was 0.59, with Example 1 showing the best result.

[0101] (3) Flexural Rigidity The flexural rigidity of the sample S was measured in accordance with JIS K 7171 under the conditions of a size of 50 mm x 150 mm, a span of 100 mm, and a test speed of 50 mm / min.

[0102] In Examples 1 to 3, the bending rigidity was 24 N, 16 N, and 10 N in the longitudinal direction Wb, and 11 N, 8 N, and 5 N in the transverse direction Wc. On the other hand, in Comparative Examples 1 and 2, the bending rigidity was 15 N and 17 N in the longitudinal direction Wb, and 11 N and 14 N in the transverse direction Wc. All of these values ​​were 5 N or greater, satisfying the bending rigidity requirements. This Example has the same level of rigidity as Comparative Examples 1 and 2, and therefore it has been proven that it can be used as a vehicle interior material, particularly a vehicle molded ceiling 10, even without containing glass fiber as a reinforcing material.

[0103] (4) Moldability The expansion rate of the sample was measured as the moldability. A number of circular stamps with a diameter of 50 mm were attached to the back side of a flat substrate, and the surface side of the substrate was deep-drawn 30 mm using a 150 mm x 150 mm deep-draw mold to concave it. After this deep-drawing, the expansion rate was calculated by measuring the length of the elliptical circle. For example, if the diameter of 50 mm before molding expanded to 60 mm after molding, the expansion rate was 120%.

[0104] In Examples 1 to 3, the values ​​were 170, 160, and 150 in the longitudinal direction Wb, and 150, 142, and 135 in the lateral direction Wc. On the other hand, in Comparative Examples 1 and 2, the values ​​were 140 and 170 in the longitudinal direction Wb, and 130 and 160 in the lateral direction Wc. All of these values ​​were within the range of 130 to 200, and the moldability required for vehicle interior materials was achieved.

[0105] The present invention is applicable to base materials for vehicle interior materials such as ceiling materials, rear package tray materials, door trim materials, floor insulator materials, trunk trim materials, and dash insulator materials, manufacturing methods thereof, and molded vehicle ceilings.

[0106] Although the present disclosure has been described with reference to the embodiments, it is understood that the present disclosure is not limited to the embodiments or structures. The present disclosure also encompasses various modifications and equivalent modifications. In addition, various combinations and forms, including only one element, more than one element, or less than one element, are also within the scope and spirit of the present disclosure.

[0107] REFERENCE SIGNS LIST 1 Vehicle 10 Vehicle molded ceiling 20 Substrate 20a High density layer 20b Low density layer 25 Core-sheath composite short fiber 27 Mixed short fiber 30 Web 31 Original plate 32 First divided member 32b Cut surface 33 Second divided member 35 Fibrous body 40 Surface layer 50 Back layer 51 Non-air-permeable membrane layer

Claims

1. A base material for vehicle interior materials, comprising: a fibrous body formed by laminating webs having staple fibers, both of whose core and sheath portions are thermoplastic resin core-sheath composite staple fibers, and a rectangular original plate having a thickness direction Ta as the lamination direction of the webs and a longitudinal direction Tb and width direction Tc perpendicular to the thickness direction Ta, the thickness direction Ta of the original plate being oriented in the left-right direction Wc of the base material, the longitudinal direction Tb of the original plate being oriented in the up-down direction Wa of the base material, and the width direction Tc of the original plate being oriented in the front-to-rear direction Wb of the base material; wherein the length directions of the staple fibers of the fibrous body are evenly distributed and arranged from the up-down direction Wa to the front-to-rear direction Wb of the base material; and wherein by heating and pressurizing the upper surface side of the fibrous body, a high-density layer having a higher density than the remaining portions of the fibrous body is integrally formed in the upper surface side portion of the fibrous body.

2. The base material for a vehicle interior material described in claim 1, wherein the original plate is cut into rectangular divided members having a predetermined dimension in the longitudinal direction Tb, the thickness direction Ta of the original plate is set to the left-right direction Wc of the base material, and a plurality of the divided members are lined up with the cut surfaces of the divided members as the upper and lower surfaces, and are welded together to form the fibrous body.

3. A substrate for vehicle interior materials as described in claim 1, wherein the web comprises the core-sheath composite staple fibers and short fibers for incorporation made of PET resin, the content of the core-sheath composite staple fibers is 50% to 100% by weight, and the content of the short fibers for incorporation is 0% to 50% by weight.

4. A substrate for vehicle interior materials as described in claim 3, wherein, when the distribution state of the short fibers in the web in the length direction is divided into ranges A for up to 30° upward from the left-right direction Wc of the substrate, B for more than 30° up to 60°, and C for more than 60° up to 90°, the proportions contained in A, B and C are all within the ranges of 20% to 40%.

5. The base material for a vehicle interior material according to claim 4, wherein when A, B and C are further divided into A1 and A2, B into B1 and B2, and C into C1 and C2 within a range of 15°, the proportions contained in A1, A2, B1, B2, C1 and C2 are all within a range of 10% to 25%.

6. In the substrate of the vehicle interior material according to claim 1, the high-density layer has a density of 65,000 g / m ３ ~500,000g / m ３ , basis weight: 130g / m ２ ~250g / m ２ , thickness: 0.5 mm to 2.0 mm, the ratio of the density of the high-density layer of the substrate to the density of the layer other than the high-density layer is 1:0.15 to 1:0.7, and the substrate has a basis weight of 400 g / m ２ ~1,500g / m ２ and a thickness of 2.0 mm to 40 mm.

7. A molded vehicle ceiling comprising a base material for a vehicle interior material according to any one of claims 1 to 6, wherein the high-density layer of the base material faces the inside of the vehicle compartment, the side without the high-density layer faces the outside of the vehicle compartment, a skin layer is provided on the inside of the vehicle compartment side of the high-density layer, and a back layer having a non-air-permeable membrane layer is provided on the outside of the vehicle compartment side without the high-density layer.

8. A method for manufacturing a base material for a vehicle interior material according to any one of claims 1 to 6, comprising: a step of entangling the staple fibers including the core-sheath composite staple fibers to form the web; a step of stacking a plurality of the webs in the thickness direction Ta of the web and heating and pressurizing the stacked webs to form the original plate in which the staple fibers are entangled; a step of cutting the original plate, in which the length directions of the staple fibers in the original plate are evenly dispersed from the longitudinal direction Tb of the original plate to the width direction Tc of the original plate, using a cutting tool in the thickness direction Ta of the original plate to process the original plate into first divided members having predetermined dimensions in the longitudinal direction Tb of the original plate; and a step of rotating the orientation of the first divided member by 90 degrees to form second divided members in which the cut surfaces of the first divided members consist of upper and lower surfaces. a step of heating the upper surface of one of the fibrous bodies in which the length direction of the short fibers of the second divided member is evenly dispersed from the vertical direction Wa of the second divided member to the front-rear direction Wb of the second divided member, and compressing the fibrous body from the vertical direction Wa of the substrate, to form the high-density layer on the upper surface side of the fibrous body and maintain the other layer of the substrate as a low-density layer.

9. A method for manufacturing a base material for a vehicle interior material as described in claim 8, characterized in that in the process of heating the upper surface of the fibrous body and compressing the fibrous body in the vertical direction Wa of the fibrous body, the lower surface side of the fibrous body is cooled.

10. A method for manufacturing a base material for vehicle interior materials as described in claim 8, wherein in the step of cutting into first divided members having predetermined dimensions, the first divided members are cut into a plurality of strips of the same width to form a plurality of the first divided members; each first divided member is turned 90 degrees to form the second divided members arranged so that the cut surfaces of the first divided members form the upper and lower surfaces; a plurality of the second divided members are arranged in a row and contacting each other so that the upper and lower surfaces of the second divided members form a single plane at the same height to form the fibrous body; and adjacent second divided members are maintained in a state of contact, and the whole is heated to form the fibrous body in which the short fibers of the fibrous body are entangled and welded.

11. The method for manufacturing a base material for a vehicle interior material according to claim 10, wherein one cut surface of the fibrous body is heated to 180°C to 240°C, and is pressed and held at a predetermined thickness for 0.5 to 30 seconds, forming a fibrous body on one cut surface side with a thickness of 0.05 mm to 2.0 mm and a basis weight of 50 g / m ２ ~300g / m ２ 10. A method for manufacturing a substrate for a vehicle interior material, comprising forming the high-density layer comprising:

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