Needle-punched nonwoven fabric and manufacturing method thereof

Abstract

To provide a needle-punched nonwoven fabric excellent in mechanical strength and also to provide a manufacturing method thereof.SOLUTION: A needle-punched nonwoven fabric includes a resin fiber and a core-sheath conjugate fiber whose sheath part is polyvinyl butyral at weight ratio of 0:100 to 90:10. At least a part of the core-sheath conjugate fiber is fused with other fibers in the needle-punched nonwoven fabric. A needle-punched nonwoven fabric manufacturing method comprises: a punching step to apply needle-punching treatment on a sheet including the resin fiber and the core-sheath conjugate fiber whose sheath part is polyvinyl butyral at weight ratio of 0:100 to 90:10; and a heat treatment step to fuse at least a part of polyvinyl butyral with other fibers.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a needle-punched nonwoven fabric and a method for producing the same. [Background technology]

[0002] Nonwoven fabrics are used for a variety of purposes, but mechanical strength is sometimes required when used in civil engineering, construction, industrial materials, electrical appliances, etc. In particular, needle-punched nonwoven fabrics, in which the fibers are physically entangled, have superior mechanical strength compared to other nonwoven fabrics such as melt-blown nonwoven fabrics and electrospun nonwoven fabrics, and are used in geotextiles and the like that require bulkiness, weather resistance, etc. For example, Patent Document 1 proposes a needle-punched nonwoven fabric for civil engineering materials, which has excellent water permeability and strength, and which is made by arranging polyester long fibers in a polypropylene short fiber web. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2003-13355 Summary of the Invention [Problem to be solved by the invention]

[0004] An object of the present invention is to provide a needle-punched nonwoven fabric having excellent mechanical strength and a method for producing the same. [Means for solving the problem]

[0005] The means for solving the problems of the present invention are as follows. 1. A fiber containing resin fibers and core-sheath composite fibers in which the sheath is polyvinyl butyral, in a weight ratio of 0:100 to 90:10; A needle-punched nonwoven fabric characterized in that at least a portion of the core-sheath composite fibers is fused with other fibers. 2. The needle-punched nonwoven fabric according to 1, wherein the volume ratio of the sheath portion in the core-sheath composite fiber is 10 to 50% by volume. 3. A nonwoven fabric according to 1. or 2., characterized in that the resin fiber and the core of the core-sheath composite fiber are one or more materials selected from the group consisting of polyesters, polycarbonates, polyamides, and polyolefins. 4. A punching process in which a sheet containing resin fibers and core-sheath composite fibers whose sheath is polyvinyl butyral in a weight ratio of 0:100 to 90:10 is subjected to needle punching; a heat treatment step for fusing at least a portion of the polyvinyl butyral with other fibers; A method for producing a needle-punched nonwoven fabric, comprising: [Effects of the Invention]

[0006] The present invention provides a needle-punched nonwoven fabric (hereinafter also referred to as a nonwoven fabric) having excellent mechanical strength. The present invention provides a nonwoven fabric having a Young's modulus 20 times or more that of an equivalent nonwoven fabric that does not contain core-sheath composite fibers. In the nonwoven fabric of the present invention, the size of the voids can be controlled by adjusting the blending ratio of the core-sheath composite fibers, and therefore the breathability, liquid permeability, sound absorption, heat insulation, etc. can be adjusted. [Brief explanation of the drawings]

[0007] [Figure 1] Cross-sectional observation image of a core-sheath composite fiber in which the sheath is polyvinyl butyral. [Figure 2] Surface observation images of needle-punched nonwoven fabric (PVB20) and PET nonwoven fabric (PET). [Figure 3] 1 shows stress-strain curves obtained by tensile testing of the nonwoven fabrics (PVB20, PVB40, PVA100) obtained in Examples 1, 2, and 7 and the nonwoven fabric (PET) obtained in Comparative Example 1. DETAILED DESCRIPTION OF THE INVENTION

[0008] The needle-punched nonwoven fabric of the present invention is The fiber contains resin fibers and core-sheath composite fibers whose sheath is polyvinyl butyral in a weight ratio of 0:100 to 90:10, The core-sheath composite fiber is characterized in that at least a part of the fiber is fused with other fibers. In this specification, "A to B" (A and B are numerical values ​​or ratios) means a range that includes both ends.

[0009] Resin fiber As the resin fiber, any known fiber for forming a nonwoven fabric can be used without any particular limitation. From the viewpoint of strength, resin fibers having a glass transition temperature (Tg) of 50°C or higher are preferred. Examples include polyethylene terephthalate (PET) resin, polybutylene terephthalate (PBT) resin, polycarbonate (PC) resin, polyamide (PA) resin, polypropylene (PP) resin, polyethylene (PE) resin, cyclic polyolefin (COP) resin, polyacetal (POM) resin, polyphenylene ether (PPE) resin, polyphenylene sulfide (PPS) resin, and polyparaphenylene benzoxazole (PBO) resin. Among these, from the viewpoints of strength and cost, one or more resins selected from the group consisting of polyester, polycarbonate, polyamide, and polyolefin are preferred. In this specification, the glass transition temperature refers to the midpoint glass transition temperature measured according to JIS K7121-1987.

[0010] Core-sheath composite fiber The sheath-core composite fiber used in the present invention has a sheath made of polyvinyl butyral (PVB). PVB is amorphous and its molecular chains do not crystallize orientated, resulting in low tensile strength, and there are few practical examples of its use in fibers. PVB is a resin with a glass transition temperature (Tg) of approximately 40 to 150° C. The Tg of the PVB used in the present invention is preferably 120° C. or lower, more preferably 100° C. or lower, and even more preferably 80° C. or lower. The PVB may also be a blend of two or more resins with different glass transition temperatures, in which case it is preferable that the blend contains 50% by weight or more of PVB with the above Tg. From the viewpoint of producing core-sheath composite fibers, the weight-average molecular weight of PVB is preferably 10,000 g / mol or more and 300,000 g / mol or less, more preferably 15,000 g / mol or more, even more preferably 20,000 g / mol or more, even more preferably 25,000 g / mol or more, and more preferably 200,000 g / mol or less, even more preferably 150,000 g / mol or less, and even more preferably 100,000 g / mol or less.

[0011] In the nonwoven fabric of the present invention, the fibers are fused together at least by polyvinyl butyral (PVB) that constitutes the sheath of the core-sheath composite fiber. PVB has polar groups, such as butyral, hydroxyl, and acetyl groups, in its side chains, which exert strong intermolecular forces, so the nonwoven fabric of the present invention, in which at least PVB is fused together, has excellent mechanical strength.

[0012] The core of the core-sheath composite fiber used in the present invention can be made of the same resin as that of the resin fiber described above. In the present invention, the resin fiber and the core of the sheath-core composite fiber may be made of the same resin or different resins, but it is preferable from the viewpoint of increasing the strength of the nonwoven fabric that the core of the sheath-core composite fiber has a strength equal to or greater than that of the resin fiber, that is, the Young's modulus value of the core is equal to or greater than that of the resin fiber. Note that "same resin" simply means that the type of resin is the same, for example, in the case of PET resin, both are PET resin, but does not mean that the molecular weight, molecular weight distribution, presence or absence of crystallization, etc. are the same.

[0013] The volume ratio of the sheath portion in the core-sheath composite fiber is preferably 10 to 50% by volume. With the volume ratio of the sheath portion within this range, the strength and fusibility are excellent. The volume ratio of the sheath portion is more preferably 20% by volume or more, even more preferably 30% by volume or more, and more preferably 45% by volume or less.

[0014] The average fiber diameter of the resin fiber and the core-sheath composite fiber is not particularly limited and can be, for example, 1 μm or more and 100 μm or less. The average fiber diameter of these fibers is preferably 3 μm or more, more preferably 5 μm or more, even more preferably 7 μm or more, and preferably 90 μm or less, more preferably 80 μm or less, and even more preferably 70 μm or less. In the present invention, the fiber diameters of the resin fiber and the core-sheath composite fiber may be the same or different, but it is preferable that the fiber diameters of the two fibers are close to each other because they are more likely to intertwine. Specifically, the diameter of the thinner fiber is preferably 60% or more, more preferably 70% or more, even more preferably 80% or more, and even more preferably 90% or more of the diameter of the thicker fiber. In this specification, the average fiber diameter of the fibers is a value obtained by measuring the diameters of 10 or more fibers at 10 or more locations using a microscope or the like and averaging the measured diameters.

[0015] Needle-punched nonwoven fabric The nonwoven fabric of the present invention contains resin fibers and sheath-core composite fibers in a weight ratio of 0:100 to 90:10 (resin fibers:sheath-core composite fibers, totaling 100). In the nonwoven fabric of the present invention, the resin fibers are optional, and a ratio of 0:100 between resin fibers and sheath-core composite fibers means that the fabric does not contain any resin fibers. The blending ratio of resin fibers to sheath-core composite fibers can adjust physical properties such as strength, breathability, and extensibility. From the viewpoint of the balance of each physical property, this weight ratio is more preferably 5:95 to 90:10, even more preferably 30:70 to 90:10, and even more preferably 50:50 to 85:15. Note that as the proportion of sheath-core composite fibers increases, strength tends to improve, while breathability and extensibility tend to decrease.

[0016] The average basis weight of the nonwoven fabric is not particularly limited and can be appropriately selected depending on the application, etc., and is, for example, 4 g / m 2 ~200g / m 2 The basis weight of the nonwoven fabric means the average value of the basis weight at any 10 or more points measured in accordance with ISO 9073-1. The average thickness of the nonwoven fabric is not particularly limited and can be appropriately selected depending on the application, etc., and can be, for example, 0.02 mm to 5 mm. The average thickness of the nonwoven fabric means the average value of thicknesses measured at any 10 or more points in accordance with ISO 9073-2.

[0017] The nonwoven fabric of the present invention preferably has a Young's modulus at least 20 times, more preferably at least 60 times, even more preferably at least 80 times, and even more preferably at least 120 times, of a needle-punched nonwoven fabric prepared in the same manner except that it does not contain core-sheath composite fibers and uses only resin fibers. The Young's modulus is the initial slope (stress / strain) of the tensile strength of the nonwoven fabric, and means the average of values ​​measured using four or more test pieces.

[0018] The nonwoven fabric of the present invention has an air permeability of 300 cc / cm 2 ·s or more 600cc / cm 2 ·s or less is preferable, 350cc / cm 2 ·s or more 450cc / cm 2 The air permeability is more preferably .s or less. The air permeability refers to a value measured in accordance with JIS L1096:2010.

[0019] The method for producing the needle-punched nonwoven fabric of the present invention is not particularly limited, but for example, it may include a punching step of needle-punching a sheet containing resin fibers and core-sheath composite fibers whose sheath is polyvinyl butyral in a weight ratio of 0:100 to 90:10; a heat treatment step for fusing at least a portion of the polyvinyl butyral with other fibers; The present invention can be produced by a production method having the following steps.

[0020] A sheet of resin fibers and sheath-core composite fibers can be produced by a conventionally known fiber-opening process, carding process, etc. In this case, it is preferable that at least one of the resin fibers and the sheath-core composite fibers is crimped, since this makes it easier to produce the sheet. The punching step can be carried out under conventionally known conditions. The punching conditions, such as needle depth and needle density, can be adjusted according to the basis weight and density required for the needle-punched nonwoven fabric. For example, the needle depth is 5 mm to 30 mm, and the needle density is 10.0 punches / cm. 2 More than 300punch / cm 2 It can be as follows:

[0021] The heat treatment step may be any step that fuses at least a portion of the PVB, but is preferably a heat press treatment to promote fusion between the fibers. The heat treatment temperature may be any temperature that allows fusion by the PVB, but from the viewpoints of reducing energy consumption and carbon dioxide emissions during production, the heat treatment temperature is preferably 120°C or lower, more preferably 110°C or lower, even more preferably 100°C or lower, even more preferably 90°C or lower, and even more preferably 85°C or lower. When the heat treatment is a heat press, the pressure and time are not particularly limited, but can be, for example, 1 to 10 MPa and 3 to 20 minutes.

[0022] The uses of the needle-punched nonwoven fabric of the present invention are not particularly limited. However, because the needle-punched nonwoven fabric of the present invention is highly durable and easily stretches during molding, it can be suitably used for a wide range of automotive interior materials having a three-dimensional form, such as geotextiles, automotive ceiling materials, floor carpets, optional mats, luggage coverings, and trim coverings. [Example]

[0023] Example 1 "Manufacturing of core-sheath composite fibers" Low-molecular-weight PET (IV 0.44 dL / g) was dried at 120°C for 8 hours after decompression. PVB (Mw 39,000 g / mol) was fed directly into the extruder. The core (PET) and sheath (PVB) were extruded from separate extruders, combined in a nozzle, and discharged to obtain undrawn sheath-core composite fibers. The spinning conditions were a core-sheath ratio (volume ratio) of 50:50, a spinning temperature of 280°C, and a take-up speed of 200 m / min. The undrawn sheath-core composite fiber obtained was passed between two rollers, heated by laser irradiation as it passed between the rollers, and drawn at a draw ratio of 7.0 times with a delivery speed of 0.5 m / min and a take-up speed of 3.5 m / min. The fiber was then cut to a length of approximately 60 mm to obtain a PET / PVB sheath-core composite fiber with a diameter of 47 μm. A digital microscope image of the cross section of the obtained sheath-core composite fiber is shown in Figure 1.

[0024] The cross section of the core-sheath composite fiber was almost perfectly circular. Although there was some slight eccentricity in the core, it was not so severe that it caused damage to the PVB in the sheath. The coefficient of variation of the fiber diameter was 3.4%, indicating that continuous, uniform spinning was possible.

[0025] "Manufacturing needle-punched nonwoven fabrics" The opener used was an OP-300 opener (Takeuchi Seisakusho), the carding machine was an SRC-400 sample roller carding machine (Takeuchi Seisakusho), and the needle punching machine was an NL-500 needle punch tester (Takeuchi Seisakusho). The punching conditions were as follows: two layers of the obtained web were laminated, the needle depth was 12.7 mm, and the needle density was 40.0 punches / cm. 2 It was decided. PET fiber (crimped) with a fiber length of 60 mm and a diameter of 43 μm and the PET / PVB core-sheath composite fiber obtained above with a length of approximately 60 mm and a diameter of 47 μm were mixed so that the weight ratio of PET fiber to core-sheath composite fiber was 80:20, and a needle-punched nonwoven fabric precursor was obtained by the opening process, carding process, and punching process using the above-mentioned equipment and conditions. The needle-punched nonwoven fabric precursor obtained was heat-pressed at 100°C for 10 minutes under 5 MPa to obtain a needle-punched nonwoven fabric (PVB20).

[0026] Example 2 A needle-punched nonwoven fabric (PVB40) was obtained in the same manner as in Example 1, except that the weight ratio of PET fiber:core-sheath composite fiber was set to 60:40. Comparison Example 1 A PET nonwoven fabric was obtained in the same manner as in Example 1, except that only PET fibers were used.

[0027] Examples 3 and 4, Comparative Example 2 Nonwoven fabrics were obtained in the same manner as in Examples 1 and 2 and Comparative Example 1, except that the heat pressing conditions were 100°C, 1 minute, and 5 MPa. Examples 5 and 6, Comparative Example 3 Nonwoven fabrics were obtained in the same manner as in Examples 1 and 2 and Comparative Example 1, except that the heat pressing conditions were 80°C, 10 minutes, and 5 MPa.

[0028] Comparative Examples 4 to 6 Nonwoven fabrics were obtained in the same manner as in Comparative Example 1, Examples 1 and 2, except that heat pressing was not performed.

[0029] Example 7 The produced sheath-core composite fibers were not crimped, so they could not be opened mechanically and were difficult to form into a sheet. Therefore, a pseudo-needle-punched nonwoven fabric was produced by hand. However, it is obvious to those skilled in the art that if the core-sheath composite fibers are crimped, it is easy to produce a sheet consisting of only the core-sheath composite fibers, and then to produce a needle-punched nonwoven fabric by the subsequent punching and heat treatment steps. The manually opened core-sheath composite fibers were laid out in a 100mm x 100mm frame and heat pressed at 100°C for 10 minutes at 5MPa to obtain a nonwoven fabric (PVB100).

[0030] FIG. 2 shows digital microscope images of the surfaces of the needle-punched nonwoven fabric (PVB20) obtained in Example 1 and the PET nonwoven fabric (PET) obtained in Comparative Example 1.

[0031] The fibers were visible in both nonwoven fabrics, and no melting or change in shape of the entire fiber was observed. Unlike PET nonwoven fabric (PET), fusion at the intertwining points was observed in the needle-punched nonwoven fabric (PVB20) containing PET / PVB sheath-core composite fibers. This was due to the PVB that constitutes the sheath of the core-sheath composite fibers melting during heat treatment, causing the fibers to fuse together.

[0032] "Evaluation of nonwoven fabrics" The resulting nonwoven fabrics were evaluated as follows, and the results are shown in Table 1. The stress-strain curves (logarithmic scale on the vertical axis) of the nonwoven fabrics obtained in Examples 1, 2, and 7 and Comparative Example 1 are shown in FIG. Tensile testing Test pieces measuring 100 x 25 mm were cut out from each of the needle-punched nonwoven fabric of the example and the PET nonwoven fabric (PET) of the comparative example, with the long side in the MD direction. The load was measured while pulling the test piece in the MD direction. The measurement was performed at room temperature with an initial test length of 80 mm, a test speed of 100 mm / min, and four test pieces. For the tensile test, test pieces cut to 100 x 25 mm in the manufacturing direction x width direction were held at both ends, and stress-strain curves were obtained using four test pieces in an Autograph AGS-X tensile tester (Shimadzu Corporation). The maximum stress was then taken as strength, the strain indicating the maximum stress as elongation, and the slope of the linear region with a correlation coefficient of 99% or more as Young's modulus. The average values ​​for all four test pieces are shown in the table. Air permeability Measurement was carried out in accordance with JIS L 1096.

[0033] ·result [Table 1]

[0034] As shown in Figure 3, the tensile stress of the PET nonwoven fabric obtained in Comparative Example 1 increased monotonically with strain. In contrast, the needle-punched nonwoven fabrics (PVB20 and PVB40) obtained in Examples 1 and 2 of the present invention, which contain PET / PVB sheath-core composite fibers, showed a rapid increase in tensile stress within a strain of 0.05 and clearly yielded. Furthermore, the Young's modulus of the PVB20 increased to 129 times (=257 / 2) and that of the PVB40 increased to 418 times (=836 / 2) compared to the PET nonwoven fabric. Furthermore, the nonwoven fabric (PVB100) obtained in Example 7 of the present invention, which is composed only of PVB sheath-core composite fibers, showed a strength improvement of approximately 83.3 times (=125 / 1.5) compared to Comparative Example 1, a rapid yield rate, and a Young's modulus of 811 times (=1622 / 2).

[0035] The needle-punched nonwoven fabrics obtained in Examples 3 to 6, which contained PET / PVB sheath-core composite fibers and were subjected to heat treatment, had Young's moduli that were 56 times or more higher (Example 5 / Comparative Example 3) than the PET nonwoven fabrics obtained in Comparative Examples 2 and 3, confirming that the sheaths of the sheath-core composite fibers were fused together even under the conditions of Examples 3 to 6. Furthermore, the Young's modulus improved as the proportion of PVB sheath-core composite fibers increased. In Comparative Examples 4 to 6, in which no heat treatment was performed, the Young's modulus was hardly improved. This confirmed that the fusion of the core-sheath composite fibers at the intertwining points of the fibers increases the strength of the intertwining points and improves the strength of the nonwoven fabric as a whole, and that the mechanical strength can be adjusted by the blending amount of the core-sheath composite fibers.

[0036] Examples 1 and 2 and Comparative Example 1 show that the needle-punched nonwoven fabrics of the present invention (PVB20 and PVB40) maintain air permeability equivalent to that of PET nonwoven fabrics, and PVB20 in particular exhibits superior air permeability to PET nonwoven fabrics. The results for PVB20 and PVB40 suggest that increasing the amount of sheath-core composite fibers reduces air permeability, presumably because the fused area increases and reduces air permeability. This confirms that air permeability can be controlled by the amount of sheath-core composite fibers.

Claims

1. The fiber contains resin fibers and core-sheath composite fibers whose sheath is made of polyvinyl butyral in a weight ratio of 0:100 to 90:10, A needle-punched nonwoven fabric characterized in that at least a portion of the core-sheath composite fibers is fused with other fibers.

2. 2. The needle-punched nonwoven fabric according to claim 1, wherein the volume ratio of the sheath portion in the core-sheath composite fiber is 10 to 50% by volume.

3. 3. The nonwoven fabric according to claim 1, wherein the resin fiber and the core of the core-sheath composite fiber are made of one or more materials selected from the group consisting of polyesters, polycarbonates, polyamides, and polyolefins.

4. a punching step of needle-punching a sheet containing resin fibers and core-sheath composite fibers whose sheath is polyvinyl butyral in a weight ratio of 0:100 to 90:10; a heat treatment step for fusing at least a portion of the polyvinyl butyral with other fibers; A method for producing a needle-punched nonwoven fabric, comprising:

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