Composite nonwoven fabric

Abstract

To provide a new composite nonwoven fabric capable of being subjected to press forming.SOLUTION: A composite nonwoven fabric includes a base material having a spunbonded nonwoven fabric and pulp fibers entangled with the spunbonded nonwoven fabric and a thermoplastic resin that is adhered to the base material and has glass transition temperature of 0°C or more. Basis weight of the base material is 75 g / m2 or more and 150 g / m2 or less. Coating weight of the thermoplastic resin is 30 g / m2 or more and 90 g / m2 or less.SELECTED DRAWING: None

Description

[Technical Field]

[0001] This invention relates to a press-molded composite nonwoven fabric. [Background technology]

[0002] A composite fabric is known in which pulp fibers are entangled in spunbond nonwoven fabric by applying a hydro-spray treatment to a layered spunbond nonwoven fabric (Patent Documents 1 and 2, etc.). Furthermore, a composite nonwoven fabric is known in which a polymer resin is attached after entanglement of pulp fibers in spunbond nonwoven fabric (Patent Document 3). These composites possess both lipophilicity derived from the synthetic fibers constituting the spunbond nonwoven fabric and hydrophilicity derived from the pulp fibers. Furthermore, the composite nonwoven fabric described in Patent Document 3 has the characteristic that the pulp fibers are less likely to detach from the spunbond nonwoven fabric, and is used in a variety of applications such as tape base materials, sanitary products, and cleaning wiper paper. These composites all consisted of flexible substrates, making press molding impossible. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2-26970 [Patent Document 2] Japanese Patent Application Publication No. 8-260327 [Patent Document 3] Japanese Patent Publication No. 2021-130881 [Overview of the Initiative] [Problems that the invention aims to solve]

[0004] The object of this invention is to provide a novel composite nonwoven fabric that can be press-molded. [Means for solving the problem]

[0005] The means for solving the problems of the present invention are as follows. 1. A base material comprising a spunbond nonwoven fabric and pulp fibers entangled with the spunbond nonwoven fabric, The substrate has a thermoplastic resin with a glass transition temperature of 0°C or higher attached to it, The basis weight of the aforementioned substrate is 75 g / m². 2 More than 150g / m 2 The following: The amount of the thermoplastic resin to be applied is 30 g / m². 2 More than 90g / m 2 A composite nonwoven fabric characterized by the following: 2. The composite nonwoven fabric according to 1, characterized in that the dry weight ratio of the spunbond nonwoven fabric to the pulp fibers (spunbond nonwoven fabric:pulp fibers) is within the range of 1:99 to 50:50. 3. The composite nonwoven fabric according to 1. or 2., characterized in that the fiber diameter of the synthetic fibers constituting the spunbond nonwoven fabric is 5 μm or more and 45 μm or less. 4. The composite nonwoven fabric according to 1. or 2., characterized in that the thermoplastic resin comprises two or more types of thermoplastic resins. [Effects of the Invention]

[0006] The composite nonwoven fabric of the present invention is press-molded, can be made into various shapes depending on its application, and has excellent shape retention after press molding. The composite nonwoven fabric of the present invention has a thermoplastic resin attached to a base material comprising a spunbond nonwoven fabric and pulp fibers intertwined with this nonwoven fabric. This thermoplastic resin binds the fibers constituting the base material together, resulting in superior mechanical properties such as tensile strength, tensile elongation at break, and bending rigidity compared to the base material before the thermoplastic resin was attached. In the composite nonwoven fabric of the present invention, the pulp fibers are fixed to the spunbond nonwoven fabric by the thermoplastic resin, so detachment of the pulp fibers is less likely to occur. [Modes for carrying out the invention]

[0007] The composite nonwoven fabric of the present invention comprises a base material including a spunbond nonwoven fabric and pulp fibers entangled with this nonwoven fabric, and a thermoplastic resin having a glass transition temperature of 0°C or higher adhered to this base material. The basis weight of this base material is 75 g / m 2 or more and 150 g / m 2 or less, and the adhesion amount of this thermoplastic resin is 30 g / m 2 or more and 90 g / m 2 or less.

[0008] ·Base material The base material can be produced by laminating pulp fibers on a spunbond nonwoven fabric and performing a water entanglement treatment. The water entanglement treatment can be carried out using a known apparatus. For example, an apparatus with a hole diameter of 0.06 to 0.15 mm and a water pressure of about 1 to 30 MPa for a water jet nozzle can be used. The dry weight ratio (spunbond nonwoven fabric:pulp fibers) of the spunbond nonwoven fabric and the pulp fibers in the base material is preferably within the range of 1:99 to 50:50. The basis weight of the base material is 75 g / m 2 or more and 150 g / m 2 or less. When the basis weight of the base material is within this range, it is excellent in press formability and shape retention after press forming. The basis weight of the base material is preferably 100 g / m 2 or more, and preferably 140 g / m 2 or less.

[0009] ·Spunbond nonwoven fabric The synthetic fibers constituting the spunbond nonwoven fabric used in this invention are not particularly limited and can be selected from nylon, polyester, polyethylene, polypropylene, polystyrene, polylactic acid, polybutylene succinate, etc. Among these, polypropylene is preferred in terms of productivity and secondary processing. Biodegradable fibers such as polylactic acid and polybutylene succinate are also preferred because they can increase the biodegradability ratio of the composite nonwoven fabric. For the synthetic fibers constituting the spunbond nonwoven fabric used in this invention, it is preferable to use fibers with a diameter of 5 μm to 45 μm, as this results in a nonwoven fabric with many voids and facilitates entanglement with pulp fibers. The basis weight of the spunbond nonwoven fabric can be selected according to the desired strength, void density, etc., but for example, 12 g / m² is preferred. 2 The above is preferable, 20 g / m 2 The above is more preferable, and also 50g / m 2 The following is preferable: 35 g / m 2 The following are preferable.

[0010] Pulp fiber The pulp fibers used in this invention are not particularly limited. As wood pulp fibers, softwood kraft pulp, hardwood kraft pulp, dissolved pulp, mercerized pulp, etc., and as non-wood pulp fibers, non-wood pulp fibers such as flax pulp, Manila hemp pulp, kenaf pulp, etc., and refined cellulose fibers such as lyocell can be used. Among these, those with a long pulp fiber length are preferred because they are more likely to entangle with the nonwoven fabric, and more specifically, those with an average fiber length of 1.5 mm or more are preferred. Examples of such pulp fibers include softwood-derived pulp, non-wood pulp, and refined cellulose fibers. The average fiber length is the length-loaded average fiber length measured by the fiber length measurement method using the optical automatic analysis method in JIS P 8226-2 (2011 edition) Pulp.

[0011] ·Thermoplastic resin Thermoplastic resins have a glass transition temperature (Tg) of 0°C or higher. If the glass transition temperature of a thermoplastic resin is below 0°C, it becomes difficult to maintain its shape after press molding. A glass transition temperature of 20°C or higher is preferable for thermoplastic resins. There is no particular upper limit to the glass transition temperature of a thermoplastic resin, but it is generally around 90°C. If the glass transition temperature is too high, the resin becomes difficult to soften with heat, requiring a higher heating temperature for the substrate during press molding, which increases energy costs and other factors. The thermoplastic resin used in this invention is not particularly limited as long as it is a thermoplastic resin with a glass transition temperature of 0°C or higher, and can be selected according to the press moldability and shape retention required for the resulting composite nonwoven fabric. For example, one or more types of acrylic resins, vinyl acetate resins, polyvinyl alcohol resins, ethylene-vinyl acetate copolymer resins, styrene-butadiene copolymer resins, styrene-acrylic copolymer resins, polyester resins, polyolefin resins, natural rubber, polylactic acid, and biodegradable resins such as polybutylene succinate can be used. It is preferable to use two or more types of thermoplastic resins, and more preferably to use at least one thermoplastic resin with a glass transition temperature of 0°C or higher and one thermoplastic resin with a glass transition temperature of 40°C or higher. By using two or more types of thermoplastic resins, different properties such as press moldability and shape retention after press molding can be assigned to different resins, making it possible to achieve a higher level of both press moldability and shape retention. When using a thermoplastic resin with a glass transition temperature of 0°C or higher and less than 40°C and a thermoplastic resin with a glass transition temperature of 40°C or higher, the weight ratio of these resins is preferably 1:99 to 99:1, more preferably 10:90 to 97:3, even more preferably 30:70 to 95:5, and even more preferably 40:60 to 90:10. Furthermore, using a biodegradable resin as the thermoplastic resin is preferable because it can increase the biodegradability ratio of the composite nonwoven fabric.

[0012] These thermoplastic resins are applied as a coating solution, and the coating solution is preferably water-based. Therefore, the thermoplastic resin is preferably water-soluble or water-dispersible, and more preferably water-dispersible because it allows for easy adjustment of the viscosity of the coating solution and provides excellent coating properties. In addition to the thermoplastic resin, the coating solution may optionally contain various auxiliary agents such as defoamers, dry paper strength enhancers, wet paper strength enhancers, dyes, fluorescent whitening agents, pH adjusters, UV inhibitors, fade inhibitors, pitch control agents, slime control agents, ink fixatives, dispersants, and surfactants. Furthermore, it may also contain other resins such as thermoplastic resins with a Tg of less than 0°C and thermosetting resins.

[0013] Thermoplastic resin adheres to the substrate by impregnating it with a coating liquid, coating it, and then drying it. There are no particular limitations on the method of impregnating the substrate with a coating liquid containing thermoplastic resin, but since pulp fibers may detach from the spunbond nonwoven fabric if shear stress is applied, a method that does not apply large shear stress is preferred. For example, size pressing, roll coating (impregnation or nip), curtain coating, spray coating, die coating, etc. are preferred. Drying can be carried out by known methods.

[0014] The amount of thermoplastic resin with a glass transition temperature of 0°C or higher that can be applied is 30 g / m² by dry weight. 2 More than 90g / m 2 The following applies: The amount of adhesion is 30 g / m² by dry weight. 2 Below this level, the shape retention of the molded product after press molding may be insufficient, and the shape may not be maintained. The adhesion amount should be 90 g / m² by dry weight. 2 Beyond a certain point, the shape retention of the molded product may not improve further, and raw material costs will increase. The composite nonwoven fabric of the present invention contains a thermoplastic resin with a glass transition temperature of 0°C or higher, at a dry weight of 30 g / m². 2 More than 90g / m 2The following adhesion amount is sufficient, and as long as this is satisfied, other resins such as resins with a glass transition temperature of less than 0°C or thermosetting resins may be present. However, the amount of other resins present is preferably less than the amount of thermoplastic resins with a glass transition temperature of 0°C or higher, which is 10 g / m². 2 The following is more preferable: 3 g / m 2 The following is even more preferable: 1 g / m 2 The following are even more preferable.

[0015] The composite nonwoven fabric of the present invention preferably has a tensile elongation at break in the MD direction (JIS P8113) of 10% or more from the viewpoint of press moldability. A value of 12% or more is more preferable, and 14% or more is even more preferable. There is no particular upper limit to this tensile elongation at break, but for example, it is about 50%. The composite nonwoven fabric of the present invention has a bending stiffness in the MD direction of 3.0 gf-cm as measured by the method described in the following examples. 2 A bending stiffness of 3.5 gf-cm or more is preferable from the viewpoint of shape retention. 2 More preferably 4.0 gf-cm or more, and 4.0 gf-cm 2 A value of 12 gf-cm or more is even more preferable. While there is no particular upper limit to this bending stiffness, for example, 12 gf-cm is preferable. 2 It is approximately / cm. [Examples]

[0016] The present invention will be described in more detail below with reference to examples, but the configuration of the present invention is not limited thereto. The obtained composite nonwoven fabrics were evaluated using the following measurement method. The results are shown in Table 1. Measurement method • Tensile strength Measurements were taken in accordance with JIS P8113 (2006 edition). • Tensile elongation at break Measurements were taken in accordance with JIS P8113 (2006 edition). Bending rigidity Measurements were taken using a pure bending tester (Kato Tech Co., Ltd., KES-FB2-A) under conditions of 23°C and 50% relative humidity. The measured values ​​are represented by the slope of the graph, with higher values ​​indicating greater bending stiffness.

[0017] • Press formability • Shape retention A composite nonwoven fabric cut to a diameter of 60 mm was placed in a holder with a circular die hole of 47 mm in diameter, and the composite nonwoven fabric was heated in a 180°C hot air dryer until its temperature reached 170°C or higher. Then, a 45 mm diameter punch was pressed into the die hole to a depth of 7 mm, and the fabric was press-molded. The condition of the composite nonwoven fabric after molding was visually observed and evaluated according to the following criteria. (Press formability) ○: There are no tears or transparency at the raised portion of the molded body. ×: There are tears or transparency in the raised part of the molded product. (shape retention) ○: The shape of the raised portion of the molded body is maintained. ×: The shape of the raised portion of the molded product cannot be maintained.

[0018] ·Base material (1) Made of polypropylene fibers (fiber diameter 15-21 μm), basis weight 25 g / m² 2 100g / m² of bleached kraft pulp fibers (average fiber length 2.2mm) derived from coniferous trees are added to the spunbond nonwoven fabric. 2 The mixture is placed in such a manner, subjected to a water flow entanglement treatment, and dried to achieve a basis weight of 125 g / m². 2 A base material (1) was obtained. ·Base material (2) Made of polypropylene fibers (fiber diameter 15-21 μm), with a basis weight of 17 g / m². 2 68g / m² of bleached kraft pulp fibers (average fiber length 2.2mm) derived from coniferous trees are added to the spunbond nonwoven fabric. 2 The mixture is placed in such a manner, treated with a water flow entanglement process, and dried to achieve a basis weight of 85 g / m². 2 A base material (2) was obtained.

[0019] (Example 1) A 25% by weight aqueous dispersion of acrylic resin (Tg=30℃) as a thermoplastic resin was applied to the substrate (1) by roll coating (impregnation) and dried, resulting in an adhesion amount of 30.8 g / m². 2 A composite nonwoven fabric was obtained. (Example 2) A composite nonwoven fabric was obtained in the same manner as in Example 1, except that the concentration of the aqueous dispersion was 50% by weight. (Example 3) A composite nonwoven fabric was obtained in the same manner as in Example 1, except that the thermoplastic resin was replaced with a polyester resin (Tg=80℃).

[0020] (Example 4) A composite nonwoven fabric was obtained in the same manner as in Example 2, except that the thermoplastic resin was replaced with a resin obtained by mixing an acrylic resin (Tg=30°C) and a polyester resin (Tg=80°C) in a ratio of 50:50 parts by weight. (Example 5) A composite nonwoven fabric was obtained in the same manner as in Example 2, except that the thermoplastic resin was replaced with a resin obtained by mixing an acrylic resin (Tg=30℃) and a polyester resin (Tg=80℃) in a ratio of 80:20 parts by weight. (Example 6) A composite nonwoven fabric was obtained in the same manner as in Example 2, except that the base material was replaced with base material (2).

[0021] (Comparative Example 1) A composite nonwoven fabric was obtained in the same manner as in Example 1, except that the concentration of the aqueous dispersion was changed to 18%. (Comparative Example 2) A composite nonwoven fabric was obtained in the same manner as in Example 2, except that the thermoplastic resin was replaced with a styrene-butadiene resin (Tg = -18°C). (Comparative Example 3) A composite nonwoven fabric was obtained in the same manner as in Example 1, except that the thermoplastic resin was replaced with a thermosetting urethane resin.

[0022] [Table 1]

[0023] The novel composite nonwoven fabric obtained in the embodiment of the present invention exhibited excellent press-molding properties and shape retention after press molding. The composite nonwoven fabric obtained in Comparative Example 1 lacked sufficient thermoplastic resin adhesion and was unable to maintain its shape. The composite nonwoven fabric obtained in Comparative Example 2 could not maintain its shape because the Tg of the thermoplastic resin was low. The nonwoven fabric obtained in Comparative Example 3 had poor press moldability because the resin was thermosetting.

Claims

1. A base material comprising a spunbond nonwoven fabric and pulp fibers entangled with the spunbond nonwoven fabric, The substrate has a thermoplastic resin with a glass transition temperature of 0°C or higher attached to it, The basis weight of the aforementioned substrate is 75 g / m². ２ 150g / m or more ２ The following: The amount of the thermoplastic resin to be applied is 30 g / m². ２ 90g / m or more ２ A composite nonwoven fabric characterized by the following:

2. The composite nonwoven fabric according to claim 1, characterized in that the dry weight ratio of the spunbond nonwoven fabric to the pulp fibers (spunbond nonwoven fabric: pulp fibers) is within the range of 1:99 to 50:

50.

3. The composite nonwoven fabric according to claim 1 or 2, characterized in that the fiber diameter of the synthetic fibers constituting the spunbond nonwoven fabric is 5 μm or more and 45 μm or less.

4. The composite nonwoven fabric according to claim 1 or 2, characterized in that the thermoplastic resin comprises two or more types of thermoplastic resins.

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