JP2024032502A - Nonwoven fabric for packaging, its manufacturing method, and packaging material - Google Patents

Abstract

The present invention provides a nonwoven fabric for packaging that has good impact protection and scratch prevention properties as a packaging material, and preferably also has good handling and heat sealability, a method for producing the same, and a packaging material. A laminated nonwoven fabric in which a first fibrous layer forms a first surface of the nonwoven fabric, and a second fibrous layer forms a second surface of the nonwoven fabric, wherein the first fibrous layer contains 80% adhesive fibers. % or more by mass, the second fiber layer contains 80% or more by mass of non-adhesive fibers, and after the fibers constituting the first fiber layer are bonded together by the adhesive fibers, the first fiber layer and the By laminating and interlacing the second fiber layer, a packaging nonwoven fabric is obtained in which the degree of surface entanglement on the first and second surfaces of the nonwoven fabric satisfies a predetermined range. [Selection diagram] Figure 3

Description

The present disclosure relates to a packaging nonwoven fabric, a method for manufacturing the same, and a packaging material.

Conventionally, when packaging hard items such as electronic equipment, precision equipment, glass products, ceramics, metal products, etc., or flexible items such as food, household materials, sanitary materials, medical materials, etc., the items may be damaged due to external impact. Packaging materials are used to prevent damage. As such packaging materials, kraft paper, air cushions, foam sheets, newspapers, nonwoven fabrics, etc. are generally used.

For example, Patent Document 1 proposes a packaging material that is made of a nonwoven fabric obtained from rayon and polyethylene terephthalate and has specified basis weight, tensile strength (length and width), and elongation rate (length and width).
Patent Document 2 proposes a biodegradable bag in which a mixed cotton web made of mixed fibers of cellulose fibers and biodegradable aliphatic polyester fibers is thermally bonded.

Japanese Patent Application Publication No. 2017-193366 Japanese Patent Application Publication No. 9-142485

Packaging materials have characteristics such as protection of the product from external impacts, prevention of damage to the product, handling properties such as ease of wrapping the product, and heat sealability when processing the product into a bag. Desired.

The present disclosure provides a packaging nonwoven fabric that has good impact protection properties and scratch prevention properties as a packaging material, and preferably has good handling properties and heat sealability, a method for producing the same, and a packaging material.

This disclosure:
A laminated nonwoven fabric including a first fibrous layer and a second fibrous layer, the first fibrous layer forming a first surface of the nonwoven fabric, and the second fibrous layer forming a second surface of the nonwoven fabric,
The first fiber layer contains 80% by mass or more of adhesive fibers based on the total mass of the first fiber layer,
The second fiber layer contains 80% by mass or more of non-adhesive fibers based on the total mass of the second fiber layer,
In the first fiber layer, the fibers are bonded to each other by the adhesive fibers,
The first fiber layer and the second fiber layer are integrated by intertwining the fibers,
The degree of surface entanglement on the first surface of the nonwoven fabric measured according to the following method is less than 3.0 mg,
The degree of surface entanglement on the second surface is within the range of 3.0 mg or more and 30 mg or less,
Provides nonwoven fabrics for packaging.

This disclosure also includes:
A laminated nonwoven fabric including a first fibrous layer and a second fibrous layer, the first fibrous layer forming a first surface of the nonwoven fabric, and the second fibrous layer forming a second surface of the nonwoven fabric,
The first fiber layer contains 80% by mass or more of adhesive fibers based on the total mass of the first fiber layer,
The second fiber layer contains 80% by mass or more of non-adhesive fibers based on the total mass of the second fiber layer,
In the first fiber layer, the fibers are bonded to each other by the adhesive fibers,
The first fiber layer and the second fiber layer are integrated by intertwining the fibers,
On the first surface, the fibers constituting the second fiber layer are not exposed,
On the second surface, the fibers constituting the first fiber layer are not exposed,
A packaging nonwoven fabric in which the fibers constituting each fiber layer are intertwined near the interface between the first fiber layer and the second fiber layer.

This disclosure also includes:
A nonwoven fabric for packaging that is a laminated nonwoven fabric including a first fibrous layer and a second fibrous layer, the first fibrous layer forming a first surface of the nonwoven fabric, and the second fibrous layer forming a second surface of the nonwoven fabric. A method of manufacturing,
producing a first fibrous web containing 80% by mass or more of adhesive fibers based on the total mass of the first fibrous web constituting the first fibrous layer;
producing a second fibrous web containing 80% by mass or more of non-adhesive fibers based on the total mass of the second fibrous web constituting the second fibrous layer;
an adhesion step of adhering the fibers of the first fibrous web to each other using the adhesive fibers;
a laminating step of laminating the first fibrous web and the second fibrous web after the adhesion step to obtain a laminated fibrous web;
an entangling step of jetting a water stream to the second fibrous web side of the laminated fibrous web to hydro-entangle and integrate the fibers of the first fibrous web and the second fibrous web;
A method for producing a nonwoven fabric for packaging, including:

The nonwoven fabric for packaging according to the present disclosure includes a first fiber layer that mainly contains adhesive fibers and in which the fibers are bonded to each other, and a second fiber layer that mainly contains non-adhesive fibers, and has a degree of surface entanglement of fibers in each fiber layer. satisfies a predetermined range. This configuration provides good impact protection and scratch prevention for the article.
Alternatively, the nonwoven fabric for packaging according to the present disclosure includes a first fiber layer that mainly contains adhesive fibers and the fibers are bonded to each other, and a second fiber layer that mainly contains non-adhesive fibers, and the surface of the fibers in each fiber layer. and internal entanglement satisfies predetermined conditions. This configuration provides good impact protection and scratch prevention for the article.
According to the method for producing a packaging nonwoven fabric according to the present disclosure, it is possible to obtain a laminated nonwoven fabric that has good impact protection and scratch prevention properties for articles.

It is an electron micrograph which shows the 1st surface of the nonwoven fabric produced in Example 4 of this invention. It is an electron micrograph showing the second surface of the nonwoven fabric produced in Example 4 of the present invention. It is an electron micrograph showing the cross section of the nonwoven fabric near the interface of each fiber layer in the nonwoven fabric produced in Example 4 of the present invention. It is an electron micrograph showing the first surface of the nonwoven fabric produced in Comparative Example 1 of the present invention. It is an electron micrograph which shows the 2nd surface of the nonwoven fabric produced in the comparative example 1 of this invention. 1 is a DSC curve obtained by differential scanning calorimetry (DSC) of adhesive fiber 1 used in the present invention. 1 is a partial diagram of a DSC curve of the first temperature increase process among DSC curves obtained by differential scanning calorimetry (DSC) of the adhesive fiber 1 used in the present invention. FIG. 2 is a schematic explanatory diagram of a method for calculating the peak height/half-width ratio of the first component in the first heating process in a DSC curve obtained by differential scanning calorimetry (DSC).

(How this embodiment was arrived at)
Patent Document 1 discloses a packaging material made of a nonwoven fabric obtained from rayon and polyethylene terephthalate, which is difficult to tear during or after packaging, has excellent flexibility and cushioning properties, and is easy to wrap. Packaging materials whose elongation rate is adjusted within a predetermined range have been proposed. However, the nonwoven fabric described in Patent Document 1 still has room for improvement in terms of impact protection and scratch prevention properties as a packaging material.
In addition, in Patent Document 2, in order to realize a bag that has practical water resistance, is quickly decomposed by microorganisms, and has practical strength and processability even if it is thin, cellulose fiber and biodegradable Biodegradable bags have been proposed in which a blended cotton web made of mixed fibers with aliphatic polyester fibers is thermally bonded. However, the nonwoven fabric described in Patent Document 2 still has room for improvement in terms of impact protection and scratch prevention properties as a packaging material.

As a result of repeated studies by the present inventors, it has been found that simply mixing fibers having respective characteristics as in Patent Documents 1 and 2 does not provide enough protection for articles from external impacts and prevents scratches on the articles. It was found that it was not possible to obtain a packaging nonwoven fabric with a high
In view of these problems, the present inventors have determined that in order to obtain a packaging nonwoven fabric that protects articles from external impacts and prevents scratches on the articles, it is necessary to improve the cushioning properties and surface flexibility of the nonwoven fabric. It was found that it is effective to combine the adhesive properties of adhesive fibers and the entangling properties of non-adhesive fibers using a laminated structure. Furthermore, it has been found that the structure can improve handling properties such as ease of packaging the article, and also improve heat sealability when processed into a bag shape.
In a nonwoven fabric with a laminated structure, a fiber layer mainly containing adhesive fibers and a fiber layer mainly consisting of non-adhesive fibers are integrated by intertwining, and by controlling the degree of surface entanglement within a predetermined range, cushioning properties and surface flexibility can be achieved. A nonwoven fabric for packaging that is compatible with properties can be obtained.
Alternatively, in a nonwoven fabric with a laminated structure, a fiber layer mainly containing adhesive fibers and a fiber layer mainly consisting of non-adhesive fibers are integrated by intertwining to form a predetermined laminated structure, which improves cushioning properties and surface flexibility. It is possible to obtain a packaging nonwoven fabric that achieves both of the following.
The nonwoven fabric of this embodiment will be explained below.

(First embodiment)
The nonwoven fabric of this embodiment is
A laminated nonwoven fabric including a first fibrous layer and a second fibrous layer, the first fibrous layer forming a first surface of the nonwoven fabric, and the second fibrous layer forming a second surface of the nonwoven fabric,
The first fiber layer contains 80% by mass or more of adhesive fibers based on the total mass of the first fiber layer,
The second fiber layer contains 80% by mass or more of non-adhesive fibers based on the total mass of the second fiber layer,
In the first fiber layer, the fibers are bonded to each other by the adhesive fibers,
The first fiber layer and the second fiber layer are integrated by intertwining the fibers,
The degree of surface entanglement on the first surface of the nonwoven fabric measured according to the following method is less than 3.0 mg,
The degree of surface entanglement on the second surface is 3.0 mg or more,
It is a nonwoven fabric for packaging.
(Surface entanglement degree)
a) A disk (diameter 70 mm, 350 g) whose surface is covered with urethane foam (thickness 5 mm) is attached to the rotating shaft so that the rotating shaft is deviated from the center of the disk by 20 mm.
b) Spread the same urethane foam as above, and fix the nonwoven fabric on a table so that the first surface of the nonwoven fabric becomes the exposed surface.
c) Place the disk on top of the nonwoven fabric. At this time, the only load applied to the nonwoven fabric is the weight of the disc itself.
d) Rotate the rotating shaft to move the disk around the nonwoven fabric. Seven sets of circumferential movements are performed, with one set consisting of two rotations clockwise and two rotations counterclockwise. The circumferential speed at this time is approximately 3 seconds per circumferential movement.
e) After 7 sets of rotations, collect the fibers that have fallen off the nonwoven fabric and adhered to the surface of the urethane foam covering the disk.
f) Perform the operations a) to e) above on n=3 nonwoven fabrics. The mass of the fallen fibers is measured for each of the three nonwoven fabrics, and the average value is defined as the degree of surface entanglement (mg).
In the following, the fibers constituting the nonwoven fabric of this embodiment will first be explained.

(Adhesive fiber)
"Adhesive fibers" are those that exhibit adhesive properties through adhesion treatment (e.g., thermal adhesion treatment, electron beam irradiation, ultrasonic welding, etc.) and adhere fibers to each other to form adhesion points. It is not particularly limited as long as the nonwoven fabric targeted by the present disclosure can be obtained.

The adhesive fibers include, for example, synthetic fibers made of thermoplastic resin.
The thermoplastic resin is not particularly limited, but in the case of an amorphous resin, the melting point or melting temperature is lower than that of non-adhesive fibers, and fibers that satisfy the temperature at which non-adhesive fibers do not melt can be used. For example, polyester resins such as polyethylene terephthalate, polybutylene terephthalate, polytrimethylene terephthalate, polyethylene naphthalate, polylactic acid, polybutylene succinate and their copolymers; polypropylene, polyethylene (high density polyethylene, low density polyethylene, linear polybutene-1, propylene copolymers containing propylene as the main component (including propylene-ethylene copolymers, propylene-butene-1-ethylene copolymers), ethylene-acrylic acid copolymers Polymers and polyolefin resins such as ethylene-vinyl acetate copolymers; polyamide resins such as nylon 6, nylon 12, and nylon 66; acrylic resins; engineering plastics such as polycarbonate, polyacetal, polystyrene, and cyclic polyolefin; Examples include elastomers. The synthetic fiber may be manufactured using one or more thermoplastic resins arbitrarily selected from these.

The synthetic fiber may be a single fiber made of one or more thermoplastic resins selected from the above, or may be a composite fiber made of two or more components (also referred to as "sections"). In the composite fiber, each component may be made of one thermoplastic resin, or may be a mixture of two or more thermoplastic resins. The composite fiber may be, for example, a core-sheath type composite fiber, an island-in-the-sea type composite fiber, or a side-by-side type composite fiber. The core-sheath type composite fiber may be an eccentric core-sheath type composite fiber in which the center of the core component and the center of the sheath component do not coincide in the fiber cross section, and may be an eccentric core-sheath type composite fiber in which the center of the core component and the center of the sheath component coincide in the fiber cross section. It may be a sheath type composite fiber. In this embodiment, concentric core-sheath type composite fibers may be used to make the nonwoven fabric smoother to the touch. According to the concentric core-sheath type composite fiber, the nonwoven fabric can be made denser. The composite fiber may also be a splittable composite fiber.

Synthetic fibers, whether monofilament or composite fibers, may have a circular cross section or may have a modified cross section (non-circular cross section). In the case of a core-sheath type conjugate fiber and a sea-island type conjugate fiber, the core component and/or the island component may have an irregular cross section in the fiber cross section.
When the synthetic fiber has an irregular cross section, the cross section may be an ellipse, a polygon, a star, or a shape in which a plurality of convex portions are joined at the base (for example, a clover shape).
In this embodiment, two or more synthetic fibers may be used in combination as the synthetic fibers.

The fineness of the adhesive fibers is not particularly limited, but in this embodiment, adhesive fibers with a relatively small fineness (however, ultrafine fibers are used) so that the first fiber layer containing adhesive fibers has a smoother feel. It is preferable to use one that does not generate any The fineness of the adhesive fibers may specifically be from 0.3 dtex to 3.5 dtex, in particular from 0.5 dtex to 3.4 dtex, more particularly from 0.6 dtex to 3.3 dtex. When the fineness of the adhesive fiber is within the above-mentioned range, the resulting nonwoven fabric tends to have a smooth feel or a high heat-seal peel strength.

The fiber length of the adhesive fibers may be, for example, from 25 mm to 100 mm, in particular from 28 mm to 70 mm, more particularly from 30 mm to 60 mm.
When the fiber length of the adhesive fiber is within the above-mentioned range, the intertwining properties of the fibers tend to be favorable. In particular, when producing a nonwoven fabric by the method described below, the degree of intertwining of the fibers in the first fiber layer and the second fiber layer can be more easily controlled by having the fiber length within the above range.

When the synthetic fiber is a composite fiber, two or more components may be arranged so that a thermoplastic resin with a lower melting point forms part of the fiber surface. A thermoplastic resin with a low melting point (low melting point component) melts or softens when heat is applied in the process of producing a nonwoven fabric, and becomes an adhesive component. The low melting point component can contribute to adhesion of fibers to each other or to other members, and can form bonding points.
When the synthetic fiber is a composite fiber, the low melting point component may be exposed in the cross section of the fiber over a length of, for example, 40% or more, particularly 50% or more of the length of the peripheral surface of the fiber. The length may be exposed, more particularly 60% or more of the length may be exposed, still more particularly 80% or more of the length may be exposed. Alternatively, the low melting point component may be exposed over the entire circumferential surface of the fiber.

When the adhesive fiber is a core-sheath type composite fiber, the composite ratio of core and sheath (volume ratio, core/sheath) may be, for example, 80/20 to 20/80, particularly 60/40 to 40/ It may be 60. When the core/sheath composite ratio is within this range, adhesion between the fibers will be adequate. In addition, if the core/sheath composite ratio is within this range, when a nonwoven fabric is manufactured by performing an interlacing process after the adhesion process, excessive peeling of the bonded area during the interlacing process will not occur, so that the predetermined surface A certain degree of entanglement or a predetermined nonwoven structure can be obtained. Further, when the core/sheath composite ratio is within this range, the fiber shape is easily maintained by the core component, and the strength or heat seal peel strength of the nonwoven fabric can be made suitable.

The adhesive component of the adhesive fiber (low melting point component in the case of composite fiber) may be a copolymer of an olefin and an unsaturated carboxylic acid or a derivative thereof. Such copolymers exhibit good adhesion to cellulose fibers, which are an example of hydrophilic fibers. Examples of unsaturated carboxylic acids include maleic acid, acrylic acid, methacrylic acid, fumaric acid, itaconic acid, etc., and derivatives thereof include anhydrides of unsaturated carboxylic acids, methyl methacrylate, ethyl methacrylate, and 2-hydroxy methacrylate. Ethyl, methacrylic esters such as dimethylaminoethyl methacrylate, or similar acrylic esters, glycidyl acrylate, glycidyl methacrylate, butene carboxylic esters, allyl glycidyl ether, 3,4-epoxybutene, 5,6-epoxy -1-hexene, vinylcyclohexene monoxide and the like. In particular, it is preferable that the olefin is ethylene and the unsaturated carboxylic acid or its derivative is acrylic acid or an ethylene-acrylic acid copolymer thereof.

Combinations of thermoplastic resins constituting composite fibers include, for example, combinations of polyolefin resins and polyester resins such as polyethylene/polyethylene terephthalate, polypropylene/polyethylene terephthalate, and propylene copolymer/polyethylene terephthalate (polyolefin resin/polyester resin). combinations of two types of polyolefin resins such as polyethylene/polypropylene, propylene copolymer/polypropylene, ethylene-acrylic acid copolymer/polypropylene, and combinations of two types of polyester resins with different melting points. .

When the synthetic fiber is a core/sheath composite fiber in which the sheath is made of a thermoplastic resin with a lower melting point, the core/sheath combination may be, for example, polyethylene terephthalate/polyethylene, polyethylene terephthalate/polypropylene, polyethylene terephthalate/propylene, etc. Polymer, polytrimethylene terephthalate/polyethylene, polybutylene terephthalate/polyethylene, polyethylene terephthalate/copolyester (e.g., polyethylene terephthalate copolymerized with isophthalic acid), polypropylene/ethylene-acrylic acid copolymer, polylactic acid/polybutylene Contains succinate. These combinations can also be applied to conjugate fibers other than core-sheath type conjugate fibers. A core-sheath composite fiber whose sheath is made of polyethylene (e.g., high-density polyethylene, low-density polyethylene, or linear low-density polyethylene) or copolymer polyester is heat-treated at a temperature higher than the melting point of the thermoplastic resin constituting the sheath. By doing so, the sheath melts or softens, and has the property of adhering the fibers to each other to form a bonding point.

When a biomass (plant-derived) material or a biodegradable material is required as the adhesive fiber, the above-mentioned synthetic resins manufactured using biomass raw materials or biodegradable synthetic resins may be used. Biodegradable synthetic resins include polylactic acid (PLA), polyhydroxyalkanoate (PHA), polycaprolactone (PCL), polyglycolic acid (PGA), polybutylene adipate terephthalate (PBAT), and polybutylene succinate (PBS). , polybutylene succinate adipate (PBSA), etc. may be used. In particular, core-sheath type conjugate fibers containing aliphatic polyester (hereinafter also referred to as "aliphatic polyester conjugate fibers") are preferred.

The aliphatic polyester core-sheath type composite fiber includes a first component containing poly-L-lactic acid and a second component containing an aliphatic polyester made of glycol and dicarboxylic acid (hereinafter referred to as "PLA composite fiber"). (also referred to as "fiber") is preferable. In particular, a composite fiber (hereinafter also referred to as "PLA/PBS composite fiber") containing a first component containing poly-L-lactic acid and a second component containing polybutylene succinate is more preferable. According to the PLA composite fiber, the nonwoven fabric obtained by thermal processing tends to have high bending resistance and high heat seal strength. In the DSC curve obtained by differential scanning calorimetry (DSC) of the PLA-based composite fiber, the crystallization temperature of the aliphatic polyester consisting of glycol and dicarboxylic acid in the cooling process is 78°C or higher, and The heat of fusion per unit mass of the aliphatic polyester made of glycol and dicarboxylic acid in a hot process is 73.5 mJ/mg or less, and the state of melting and solidification of the aliphatic polyester made of glycol and dicarboxylic acid is within the above range. By controlling this, the processability of the nonwoven fabric during heat processing is improved, and a nonwoven fabric with high bending resistance and heat sealing strength can be obtained.

Specifically, if the crystallization temperature per unit mass of the aliphatic polyester made of glycol and dicarboxylic acid during the temperature cooling process is 78.0°C or higher, the solidification temperature of the resin after melt extrusion during melt spinning will be lower than 78.0°C. Because of its high temperature, it cools quickly and can be taken up at high speed, making it possible to make the fibers finer. In addition, the aliphatic polyester consisting of glycol and dicarboxylic acid present on the fiber surface during processing into nonwoven fabrics has a high solidification temperature even after being melted or cooling after heat-sealing. It is suitable for shortening the sealing time, and the amount of heat given to poly-L-lactic acid is small, making it easy to obtain bulkiness.
Furthermore, if the heat of fusion per unit mass of the aliphatic polyester made of glycol and dicarboxylic acid in the second heating process is 73.5 mJ/mg or less, the aliphatic polyester made of glycol and dicarboxylic acid has a moderate crystallinity. The aliphatic polyester made of glycol and dicarboxylic acid melts easily when processed into a nonwoven fabric, has adhesive strength, and does not apply excessive heat to the first component, resulting in good texture (bulkness and A nonwoven fabric with adhesive properties) can be obtained, and it can be sealed firmly and in a short time even during heat sealing.

Furthermore, in the DSC curve obtained by differential scanning calorimetry (DSC) of the PLA-based composite fiber, the crystallization temperature of the aliphatic polyester consisting of glycol and dicarboxylic acid in the cooling process is 78°C or higher, and By ensuring that the heat of fusion per unit mass of the aliphatic polyester made of dicarboxylic acid satisfies 73.5 mJ/mg or less, adhesion (adhesion) and thread breakage are less likely to occur during spinning and/or drawing. , it becomes easier to obtain fibers with high productivity. Even when the fibers are crimped, the crimped shape is easily maintained and crimp development is likely to be good. Furthermore, it is possible to draw at a draw ratio close to the maximum draw ratio (Vmax), and a conjugate fiber with a finer fineness can be obtained. The composite fibers obtained in this way have excellent fibrous web formation properties when processed into a nonwoven fabric, and a uniform nonwoven fabric can be obtained.

The differential scanning calorimetry (DSC) is performed under the following conditions based on JIS K 7121:1987.
The sample amount of the fiber to be the sample is 3.0 mg, and after weighing, it is filled into a sample holder. Next, the fiber packed in the sample holder was heated from room temperature (23 ± 2°C) to 250°C at a rate of 5°C/min (first heating process), and DSC measurement was performed during the first melting. I do. After reaching 250°C, it is held for 10 minutes, and the temperature is lowered from 250°C to 40°C at a rate of 1°C/min (temperature lowering process) to solidify the molten sample. At this time, DSC is measured when the temperature is lowered. After the first heating step and cooling step were completed, the sample was held at 40°C for 10 minutes without being removed from the DSC measuring device, and then heated again from 40°C to 250°C at a rate of 5°C/min. (Second temperature raising process), DSC measurement is performed during second melting.

In the DSC curve obtained by differential scanning calorimetry (DSC) of the PLA-based composite fiber, the crystallization temperature of the aliphatic polyester consisting of glycol and dicarboxylic acid during the cooling process was 78°C from the viewpoint of preventing fusion between the fibers. The temperature is preferably .0°C or more and 115.0°C or less, more preferably 79.0°C or more and 105.0°C or less, even more preferably 80.0°C or more and 100.0°C or less, and 81. The temperature is even more preferably .0°C or more and 95.0°C or less, and particularly preferably 82.0°C or more and 93.0°C or less. In the present invention, the crystallization temperature of the aliphatic polyester consisting of glycol and dicarboxylic acid in the temperature decreasing process of the DSC curve is the temperature at the exothermic peak of the aliphatic polyester consisting of glycol and dicarboxylic acid in the DSC curve obtained in the temperature decreasing process. refers to

In the DSC curve obtained by differential scanning calorimetry (DSC) of the PLA-based composite fiber, from the viewpoint of improving the bulkiness and adhesiveness of the nonwoven fabric, the aliphatic polyester consisting of glycol and dicarboxylic acid in the second heating process The heat of fusion per unit mass of is preferably 25.0 mJ/mg or more and 73.5 mJ/mg or less, more preferably 27.0 mJ/mg or more and 72.5 mJ/mg or less, and 28.5 mJ/mg or more. It is more preferably 30.0 mJ/mg or more and 70.5 mJ/mg or less, and even more preferably 32.0 mJ/mg or more and 69.5 mJ/mg or less. is particularly preferred. In the present invention, the heat of fusion per unit mass of the aliphatic polyester consisting of glycol and dicarboxylic acid in the second heating process of the DSC curve is It is calculated by determining the heat of fusion from the endothermic peak of the aliphatic polyester consisting of glycol and dicarboxylic acid, and converting the determined heat of fusion to the heat of fusion per 1 mg of the aliphatic polyester consisting of glycol and dicarboxylic acid.

In the DSC curve obtained by differential scanning calorimetry (DSC) of the PLA composite fiber, from the viewpoint of further improving the flexibility, bulkiness, and texture of the nonwoven fabric, as well as lowering the temperature and shortening the time of heat sealing processing, The heat of fusion per unit mass of the aliphatic polyester consisting of glycol and dicarboxylic acid in the first heating process is preferably 68.0 mJ/mg or less, and 25.0 mJ/mg or more and 68.0 mJ/mg or less. more preferably 27.0 mJ/mg or more and 67.0 mJ/mg or less, particularly preferably 30.0 mJ/mg or more and 66.0 mJ/mg or less, and 32.0 mJ/mg or more and 64 It is even more preferably .0 mJ/mg or less, even more preferably 35.0 mJ/mg or more and 62.0 mJ/mg or less, and even more preferably 37.0 mJ/mg or more and 59.0 mJ/mg or less. More preferably, it is 40.0 mJ/mg or more and 55.0 mJ/mg or less. If the heat of fusion per unit mass of the aliphatic polyester consisting of glycol and dicarboxylic acid in the first heating process is 68.0 mJ/mg or less, the aliphatic polyester consisting of glycol and dicarboxylic acid present on the fiber surface during processing into a nonwoven fabric. Aliphatic polyester melts quickly and fibers are bonded in a short time, allowing for high-speed production and high-speed heat sealing, while minimizing thermal effects on the first component. As a result, the bulkiness of the carded web can be maintained, and a bulky nonwoven fabric can finally be obtained. In the present invention, the heat of fusion per unit mass of aliphatic polyester consisting of glycol and dicarboxylic acid in the first temperature raising process of the DSC curve is It is calculated by determining the heat of fusion from the endothermic peak of the aliphatic polyester consisting of glycol and dicarboxylic acid, and converting the determined heat of fusion to the heat of fusion per 1 mg of the aliphatic polyester consisting of glycol and dicarboxylic acid.

In the DSC curve obtained by differential scanning calorimetry (DSC) of the PLA composite fiber, from the viewpoint of more effectively preventing fusion between fibers and further improving the flexibility and bulkiness of the nonwoven fabric, the temperature decreasing process The heat of crystallization per unit mass of the aliphatic polyester consisting of glycol and dicarboxylic acid is preferably 59.5 mJ/mg or less, more preferably 15.0 mJ/mg or more and 59.5 mJ/mg or less, It is more preferably 20.0 mJ/mg or more and 56.0 mJ/mg or less, even more preferably 25.0 mJ/mg or more and 53.0 mJ/mg or less, and 30.0 mJ/mg or more and 50.0 mJ/mg. It is even more preferably the following, and particularly preferably 35.0 mJ/mg or more and 48.5 mJ/mg or less. If the crystallization heat per unit mass of the aliphatic polyester made of glycol and dicarboxylic acid during the temperature cooling process is 59.5 mJ/mg or less, the aliphatic polyester made of glycol and dicarboxylic acid present on the fiber surface during processing into a nonwoven fabric. Since it is quickly solidified when it is cooled after being melted, the nonwoven fabric does not sag and is easy to handle even after heat sealing. In the present invention, the heat of crystallization per unit mass of the aliphatic polyester consisting of glycol and dicarboxylic acid in the temperature decreasing process of the DSC curve is Calculation is performed by determining the heat of crystallization from the peak and converting the determined heat of crystallization into the heat of crystallization per 1 mg of aliphatic polyester consisting of glycol and dicarboxylic acid.

In the DSC curve obtained by differential scanning calorimetry (DSC) of the PLA-based composite fiber, the peak of poly-L-lactic acid (endothermic The ratio of peak) height to half width is preferably 11.0 or less, more preferably 10.5 or less, even more preferably 10.0 or less, and even more preferably 9.5 or less. It is more preferably 9.0 or less, even more preferably 8.5 or less. Further, the ratio of the peak (endothermic peak) height and half-width of poly-L-lactic acid in the first heating process is preferably 2.0 or more, more preferably 2.5 or more, and 3.0. It is more preferably at least 3.5, even more preferably at least 4.0, particularly preferably at least 4.5. If the ratio of the peak height and half-width of poly-L-lactic acid in the first heating process is within the above-mentioned range, the endothermic peak (melting peak) of the first component (polylactic acid) constituting the core component of the composite fiber will be It has a relatively broad shape, which eliminates the disadvantages of polylactic acid, which is generally said to be hard and brittle, and makes it easier to obtain a nonwoven fabric with good flexibility and bulk. In the present invention, in the DSC curve, the peak half-width is measured based on the half-width method of the Japanese Pharmacopoeia.

In the DSC curve of the PLA-based composite fiber, the ratio of the peak (endothermic peak) height and half-width of poly-L-lactic acid in the first heating process can be calculated as follows. FIG. 3 is a schematic explanatory diagram of a method for calculating the peak height/half width ratio of poly-L-lactic acid in the first heating process in a DSC curve obtained by differential scanning calorimetry (DSC).
(1) Draw a perpendicular line L1 from the peak top St of the endothermic peak to the baseline Lb, and let the length of the perpendicular line be the peak height (h). In addition, in the case of double peaks, the highest peak is adopted.
(2) The half-width (Wh) is the distance between points S1 and S2 where the endothermic peak curve intersects a line drawn perpendicular to the perpendicular L1 from the position Sh, which is half (h/2) of the peak height of the perpendicular L1. shall be.
(3) Calculate the peak ratio using Equation 1 below.
[Formula 1]
Peak ratio = h/Wh

In the DSC curve obtained by differential scanning calorimetry (DSC) of the PLA-based composite fiber, from the viewpoint of further improving the flexibility and bulkiness of the nonwoven fabric, per unit mass of poly-L-lactic acid in the first heating process. The heat of fusion is preferably 30.0 mJ/mg or more, more preferably 30.0 mJ/mg or more and 100.0 mJ/mg or less, and 35.0 mJ/mg or more and 90.0 mJ/mg or less. is more preferably 40.0 mJ/mg or more and 80.0 mJ/mg or less, even more preferably 42.0 mJ/mg or more and 75.0 mJ/mg or less, and 45.0 mJ/mg or more. It is particularly preferable that it is 70.0 mJ/mg or less. In the present invention, the heat of fusion per unit mass of poly-L-lactic acid in the first heating process of the DSC curve is calculated from the endothermic peak of poly-L-lactic acid in the DSC curve obtained in the first heating process. Calculation is performed by determining the amount of heat and converting the determined heat of fusion into the amount of heat of fusion per 1 mg of poly-L-lactic acid.

In the DSC curve obtained by differential scanning calorimetry (DSC) of the PLA/PBS composite fiber, glycol was added during the temperature cooling process from the viewpoint of preventing fusion between fibers and improving processability and heat-sealing processability of the nonwoven fabric. The crystallization time of the aliphatic polyester consisting of and dicarboxylic acid is preferably 208 minutes or more and 228 minutes or less, more preferably 210 minutes or more and 227 minutes or less, and even more preferably 212 minutes or more and 226 minutes or less. , it is even more preferably 214 minutes or more and 225 minutes or less, and particularly preferably 216 minutes or more and 224 minutes or less. In the present invention, the crystallization time of the aliphatic polyester consisting of glycol and dicarboxylic acid in the temperature decreasing process of the DSC curve is the time at the exothermic peak of the aliphatic polyester consisting of glycol and dicarboxylic acid in the DSC curve obtained in the temperature decreasing process. refers to

The first component includes poly-L-lactic acid. The melting point of the poly-L-lactic acid is preferably 160°C or higher, more preferably 165°C or higher, even more preferably 168°C or higher, particularly preferably 173°C or higher. If the melting point of poly-L-lactic acid is 160°C or higher, the difference in melting point with the sheath component will not be small, and the difference with the processing temperature when heat-processing into fiber structures such as non-woven fabrics will be large. It doesn't get tired. The upper limit of the melting point of poly-L-lactic acid is preferably 230°C or lower.

The first component may include a nucleating agent. Any known nucleating agent may be used, but preferably inorganic fillers such as calcium carbonate, talc, silica, and aluminum compounds, fatty acid metal salts such as calcium stearate, phosphate metal salts, amide compounds, mica, etc. Examples include minerals such as wlastonite, barium sulfate, and the like. The nucleating agent may be added in an amount of 0.01 parts by mass or more and 10 parts by mass or less, preferably 0.05 parts by mass or more and 5 parts by mass or less, per 100 parts by mass of poly-L-lactic acid.

The optical purity of poly-L-lactic acid is 95% or more, preferably 98.0% or more, more preferably 98.5% or more, still more preferably 99.0% or more, particularly preferably It is 99.5% or more. When the optical purity is 95% or more, it does not sag during heat processing and bulk recovery properties are improved.

The poly-L-lactic acid used in the present invention tends to have high heat resistance and high bending elasticity, so it is easy to obtain a nonwoven fabric with low heat shrinkage, large bulk, and excellent bulk recovery properties.

In addition to the poly-L-lactic acid, other resins may be mixed in the first component to the extent that the effects of the present invention are not impaired. Examples of other resins include aromatic polyesters such as polyethylene terephthalate, polybutylene terephthalate, and polytrimethylene terephthalate, aromatic aliphatic polyesters, aliphatic polyesters, and polyolefins. The proportion of poly-L-lactic acid in the first component is preferably 70% by mass or more, more preferably 80% by mass or more, even more preferably 90% by mass or more, and even more preferably 95% by mass or more. Most preferably.

The second component includes an aliphatic polyester made of glycol and dicarboxylic acid. The aliphatic polyester is preferably a polyalkylene dicarboxylate, specifically polybutylene succinate, polybutylene adipate, polybutylene sebacate, polyethylene oxalate, polyethylene succinate, polyethylene adipate, polyethylene azelate, Examples include polyhexamethylene sebacate, polyneopentyl oxalate, and copolymers thereof. Among them, polybutylene succinate, which is a condensate of succinic acid and 1,4-butanediol, and/or its copolymer have a relatively high melting point of about 110°C, and have excellent fiber productivity, nonwoven fabric processability, and nonwoven fabric physical properties. It is preferable because it has excellent properties and can be used as a biomass raw material.

The melting point of the aliphatic polyester is preferably 100°C or more and 130°C or less, more preferably 110°C or more and 125°C or less. When the melting point is 100° C. or higher, the molten resin discharged from the nozzle during melt spinning solidifies quickly, and the generation of fused threads is suppressed. In addition, when the melting point is 130° C. or lower, the difference in melting point from the first component is large and the material does not go flat during heat processing.

The second component preferably contains a nucleating agent from the viewpoint of improving spinnability. Examples of the nucleating agent include inorganic nucleating agents and organic nucleating agents. Examples of the inorganic nucleating agent include inorganic fillers such as calcium carbonate, talc, silica, and aluminum compounds, minerals such as mica and wlastonite, and barium sulfate. Examples of organic nucleating agents include fatty acid metal salts, phosphate ester metal salts, amide compounds, and the like. As the nucleating agent, organic nucleating agents are preferable, and fatty acid metal salts are particularly preferable. Furthermore, fatty acid metal salts have the effect of improving heat resistance after fiber formation, since uniform and fine crystals can be obtained. Examples of fatty acid metal salts include sodium laurate, potassium laurate, potassium hydrogen laurate, magnesium laurate, calcium laurate, zinc laurate, sodium myristate, potassium hydrogen myristate, magnesium myristate, calcium myristate, and zinc myristate. , silver myristate, aluminum myristate, potassium palmitate, magnesium palmitate, calcium palmitate, zinc palmitate, copper palmitate, lead palmitate, sodium oleate, potassium oleate, magnesium oleate, calcium oleate, olein. Zinc acid, lead oleate, copper oleate, nickel oleate, sodium stearate, calcium stearate, magnesium stearate, zinc stearate, barium stearate, aluminum stearate, thallium stearate, lead stearate, nickel stearate, Zinc montanate, calcium mortanate, magnesium mortanate, sodium 12-hydroxystearate, lithium 12-hydroxystearate, lead 12-hydroxystearate, nickel 12-hydroxystearate, zinc 12-hydroxystearate, 12-hydroxy Calcium stearate, magnesium 12-hydroxystearate, barium 12-hydroxystearate, potassium isostearate, magnesium isostearate, calcium isostearate, aluminum isostearate, zinc isostearate, nickel isostearate, sodium behenate, potassium behenate, behenin Magnesium montanate, calcium behenate, zinc behenate, nickel behenate, sodium montanate, potassium montanate, magnesium montanate, calcium montanate, aluminum montanate, zinc montanate, nickel montanate, sodium octylate, lithium octylate , magnesium octylate, calcium octylate, barium octylate, aluminum octylate, nickel octylate, sodium sebacate, lithium sebacate, magnesium sebacate, calcium sebacate, barium sebacate, aluminum sebacate, thallium sebacate, sebacine Lead acid, nickel sebacate, sodium undecylenate, lithium undecylenate, magnesium undecylenate, calcium undecylenate, barium undecylenate, aluminum undecylenate, lead undecylenate, nickel undecylenate, beverium undecylenate, sodium ricinoleate, lithium ricinoleate , magnesium ricinoleate, calcium ricinoleate, barium ricinoleate, aluminum ricinoleate, thallium ricinoleate, lead ricinoleate, nickel ricinoleate, beverium ricinoleate, and the like. Among the above, it is preferable to use a divalent or higher valent metal salt. When a divalent or higher-valent metal salt is used, a physical cross-linked structure is easily formed, and the mobility of polymer chain segments is restricted, so that they can serve as crystal nuclei and can be quickly crystallized. Furthermore, from the viewpoint of spinnability, a fatty acid metal salt having a melting point higher than the resin melting point of the second component is preferable, and a metal salt having a high bonding force with the fatty acid is preferable. Examples include calcium, magnesium, and zinc, with calcium being particularly preferred. Furthermore, the fatty acid is preferably a saturated fatty acid with a high melting point. The number of carbon atoms in the fatty acid is preferably 12 or more and 28 or less, more preferably 14 or more and 20 or less. Within this range, the molecular chain is not too long and the melting point is lower than the spinning temperature of the second component, so that the nucleating agent is uniformly dispersed within the resin. Particularly preferred is one or more selected from the group consisting of calcium stearate, magnesium stearate, and zinc stearate.

The second component preferably contains a nucleating agent of 0.01 parts by mass or more and 20 parts by mass or less, more preferably, based on 100 parts by mass of the aliphatic polyester, from the viewpoint of increasing crystallinity and improving spinnability. contains 0.03 parts by mass or more and 10 parts by mass or less, more preferably 0.06 parts by mass or more and 5 parts by mass or less. If the nucleating agent is an inorganic nucleating agent, from the viewpoint of promoting crystallization of the resin, it is preferable that the inorganic nucleating agent is contained in an amount of 0.1 parts by mass or more and 20 parts by mass or less based on 100 parts by mass of the aliphatic polyester. , more preferably 0.5 parts by mass or more and 10 parts by mass or less, and even more preferably 1.0 parts by mass or more and 5.0 parts by mass or less. If the nucleating agent is an organic nucleating agent, from the viewpoint of promoting crystallization of the resin, the organic nucleating agent should be included from 0.01 parts by mass to 5.0 parts by mass based on 100 parts by mass of the aliphatic polyester. is preferred, more preferably 0.03 parts by mass or more and 4.0 parts by mass or less, and even more preferably 0.06 parts by mass or more and 3.0 parts by mass or less.

In addition to the aliphatic polyester, other resins may be mixed in the second component to the extent that the effects of the present invention are not impaired. Examples of other resins include polylactic acid, polyhydroxybutyrate, polyhydroxybutyratevalate, polycaprolactone, aromatic polyester, polyamide, and polyolefin. The proportion of the aliphatic polyester in the second component is preferably 70% by mass or more, more preferably 80% by mass or more, even more preferably 90% by mass or more, and even more preferably 95% by mass or more. Most preferably.

The PLA-based composite fiber can be produced by melt-spinning the first component at a lower temperature than the second component and stretching it under predetermined conditions.

First, a first component containing 70% by mass or more of poly-L-lactic acid with an optical purity of 95% or more and a second component containing 70% by mass or more of an aliphatic polyester consisting of glycol and dicarboxylic acid are prepared. The first component preferably contains the poly-L-lactic acid in an amount of 80% by mass or more, more preferably 90% by mass or more, and particularly preferably 95% by mass or more. The second component preferably contains the aliphatic polyester in an amount of 80% by mass or more, more preferably 90% by mass or more, and particularly preferably 95% by mass or more. As the poly-L-lactic acid and aliphatic polyester, those mentioned above can be used.

Next, the first component and the second component are melt-spun to produce a spun filament in which the second component occupies 50% or more of the fiber surface (hereinafter also referred to as "spinning process").
Specifically, a melt spinning machine is equipped with a composite nozzle that can obtain a predetermined fiber cross section, and the first component and the second component are extruded so that the second component occupies 50% or more of the fiber surface. Melt spinning yields spun filaments (ie, undrawn filaments). In the spinning step, the first component is melt-spun at a lower temperature than the second component. This facilitates the cooling of the first component and allows it to crystallize quickly, making it easier to control the crystallization of the poly-L-lactic acid. Therefore, spun filaments with less crystal orientation and finer fineness can be obtained. The spun filament has good drawability, and not only can it become a fiber with good crystallinity and orientation during drawing, but can also be made finer after drawing. Further, a composite fiber in which the second component has high crystallinity can be obtained. The first component is preferably melt-spun at a temperature lower than the second component by 1°C or more and 30°C or less, more preferably 3°C or more and 20°C or lower, and 5°C or more and 18°C or lower. It is more preferable to carry out melt spinning at a temperature lower than 7°C and lower than 16°C. Specifically, the first component may be melt-spun at a temperature of 200°C or higher and 240°C or lower, and the second component may be melt-spun at a temperature of 220°C or higher and 250°C or lower; The second component may be melt-spun at a temperature of 225°C or higher and 245°C or lower, and the first component may be melt-spun at a temperature of 210°C or higher and 230°C or lower. , the second component may be melt-spun at a temperature of 225°C or higher and 240°C or lower, the first component may be melt-spun at a temperature of 215°C or higher and 225°C or lower, and the second component is melt-spun at a temperature of 225°C or higher and 235°C or lower. Melt spinning may be performed at the following temperatures.

Next, the spun filament is drawn to obtain a drawn filament (composite fiber).

The stretching process may be so-called one-stage stretching, in which the stretching process is performed in only one stage, or may be multi-stage stretching, in which the stretching process is performed in two or more stages. In the one-stage stretching or the first stage of multi-stage stretching, the stretching temperature is set at 55°C or higher and 90°C or lower. When the stretching temperature is 90° C. or lower, no fusion occurs during the stretching process. When the stretching temperature is 55° C. or higher, the film can be highly stretched. The stretching temperature is preferably 60°C or higher and 85°C or lower, more preferably 70°C or higher and 80°C or lower. In the second and subsequent stages of multi-stage stretching, the stretching temperature is preferably 60°C or more and 100°C or less, more preferably 70°C or more and 95°C or less, and particularly preferably 75°C or more and 90°C or less. . In the case of multistage stretching, the stretching temperature in the second and subsequent stages is preferably the same as that in the first stage or higher than that in the first stage. The temperature difference between the first stage and the second stage is preferably 0°C or more and 30°C or less, more preferably 0°C or more and 25°C or less, even more preferably 1°C or more and 20°C or less, particularly 2°C or more and 17°C or less. preferable.

The stretching ratio is preferably 1.4 times or more. Thereby, the crystallinity of the aliphatic polyester consisting of poly-L-lactic acid and glycol and dicarboxylic acid can be improved, and in turn, the flexibility and bulkiness of the nonwoven fabric can be improved. The stretching ratio is preferably 1.4 times or more and 3.8 times or less, more preferably 1.5 times or more and 3.5 times or less, and 1.6 times or more and 3.2 times or less. is more preferably 1.7 times or more and 2.9 times or less, even more preferably 1.8 times or more and 2.6 times or less. When the stretching ratio is 1.4 times or more, the spun filament can be uniformly stretched without yarn breakage occurring during the stretching process. The stretching process may be one stage stretching or two or more stages of stretching. Further, the second and subsequent stages of multi-stage stretching may be a tension heat setting in which heat treatment is performed in a tensioned state, or a relaxation heat set in which heat treatment is performed in a relaxed state. In the case of tension heat setting, it may be 1.0 times or more and 1.2 times or less, and may be 1.0 times or more and 1.1 times or less. In the case of relaxation heat setting, it may be 0.9 times or more and less than 1.0 times, and may be 0.95 times or more and less than 1.0 times. The second and subsequent stages of multi-stage stretching are preferably performed by tension heat setting. Tension heat setting can adjust and stabilize the crystallinity of poly-L-lactic acid and aliphatic polyester consisting of glycol and dicarboxylic acid, making it easier to process during subsequent secondary molding (for example, non-woven molding). Improves sex. In addition, the improved crystallinity improves the texture of the nonwoven fabric and improves its bulk. In the case of multi-stage stretching, the stretching ratio is multiplied by the stretching ratio of each stage.

In the stretching step, the stretching ratio is preferably 60% or more and 99% or less of the maximum stretching ratio (Vmax), more preferably 65% or more and 99% or less, and still more preferably 70% or more and 99% or less. When the stretching ratio is 60% or more and 99% or less of the maximum stretching ratio, high stretching can be achieved while suppressing yarn breakage in the stretching process.

The stretching method may be either a wet stretching method or a dry stretching method. As the heat medium, air, steam, water, oils such as glycerin, etc. can be used as appropriate. In the case of a wet stretching method, stretching can be performed while heating in a liquid, for example, stretching may be performed in hot water or hot water. In the case of the dry stretching method, stretching can be carried out in a high temperature gas or while heating with a high temperature metal roll or the like. The stretching is preferably carried out in warm water. This is because when the composite fiber is a core-sheath type composite fiber, the core component and the sheath component are more likely to be strained and the crimps are more likely to curve when carried out with warm water.

In the present invention, the "maximum stretching ratio (Vmax)" refers to the value measured as follows. Melt spinning is performed using a core-sheath type composite nozzle, and the obtained spun filament (undrawn fiber bundle) is wet-stretched in hot water at a predetermined temperature. At this time, the feed speed (V1) of the roll that feeds out the undrawn fiber bundle is set to 10 m/min, and the winding speed (V2) of the metal roll on the winding side is gradually increased from 10 m/min. Then, the winding speed of the metal roll on the winding side when the undrawn fiber bundle breaks is taken as the maximum drawing speed, and the ratio of the maximum drawing speed to the feed-out speed of the roll that sends out the undrawn fiber bundle (V2/V1) is determined, and the obtained speed ratio is taken as the maximum stretching ratio (Vmax).

In the case of so-called one-stage stretching, in which the stretching process is performed once, and when the stretching process is performed in multiple times using the same stretching method and the same stretching temperature, the maximum stretching ratio is the same as the stretching process, at the same temperature. can be measured. When the spun filament is drawn by so-called multi-stage drawing, in which the drawing process is performed multiple times, and the drawing temperature differs depending on the drawing process, the same drawing method and drawing process as the drawing process in which the drawing process is performed at a higher temperature may be used. Measure the maximum stretch ratio at the temperature.

When a spun filament is drawn in so-called multi-stage drawing, in which the drawing process is performed multiple times, the drawing temperature is the same for all drawing processes, but when the drawing methods are different, the maximum draw ratio is measured for both methods. However, the larger maximum stretching ratio is the maximum stretching ratio under the manufacturing conditions.

A predetermined amount of a fiber treatment agent is applied to the obtained drawn filament, if necessary, and mechanically crimped by a crimper (crimping device), if necessary. The fiber treatment agent can easily disperse fibers in water or the like when a nonwoven fabric is manufactured by a wet papermaking method. In addition, when an external force is applied from the fiber surface to the fibers to which the fiber treatment agent is attached (external force is, for example, the force applied when crimping is applied by a crimper), and the fiber treatment agent is soaked into the fibers, further water can be applied. The dispersibility to the above is improved.

Drying the drawn filament after applying the fiber treatment agent (or without applying the fiber treatment agent but in a wet state) at a temperature within the range of 80°C or more and 110°C or less for a few seconds to about 30 minutes. Let the fibers dry. The drying process may be omitted depending on the case. Thereafter, the drawn filament is cut so that the fiber length is preferably 1 mm or more and 100 mm or less, more preferably 2 mm or more and 70 mm or less.

Note that the thermoplastic resins exemplified as constituent components of single fibers or composite fibers contain 50% by mass or more of the specifically indicated thermoplastic resin, preferably 70% by mass or more of thermoplastic resin, and more preferably thermoplastic resin. Other components may be included as long as the resin is contained in an amount of 90% by mass or more. For example, in the combination of polyethylene/polyethylene terephthalate, "polyethylene" may contain other thermoplastic resins, additives, etc. as long as it contains 50% by mass or more of polyethylene. This also applies to the following examples.

Two or more fibers may be included as adhesive fibers. In that case, the melting points of the adhesive components of these fibers may differ from one another. For example, when two types of adhesive fibers are included, the difference in melting point of the adhesive components of these fibers may be 10°C or more and 40°C or less, particularly 15°C or more and 30°C or less.

(Non-adhesive fiber)
The nonwoven fabric of this embodiment includes non-adhesive fibers in the second fiber layer. The non-adhesive fibers in this embodiment refer to fibers that do not exhibit adhesive properties under conditions where adhesive fibers exhibit adhesive properties. Non-adhesive fibers include, for example, cellulose fibers, protein fibers, and synthetic fibers. In this embodiment, cellulose fibers, protein fibers, and synthetic fibers having hydrophilic properties are preferably used as the hydrophilic fibers from the viewpoint of easy maintenance of hydrophilic fibers in consideration of hydroentanglement described below. The PLA composite fiber used in the nonwoven fabric of this embodiment has high adhesiveness with the non-adhesive fibers mentioned above.

"Cellulose fiber" is also called cellulose fiber, and generally refers to fiber made from cellulose.
Cellulose fibers include, for example,
(1) Natural fibers derived from plants such as cotton, hemp, linen, ramie, jute, banana, bamboo, kenaf, shellfish, hemp, and kapok;
(2) Solvent-spun cellulose fibers such as rayon and polynosic obtained by the viscose method, cupro obtained by the cuprammonium method, and TENCEL (registered trademark) and Lyocell (registered trademark) obtained by the solvent-spinning method, as well as other recycled materials. fiber;
(3) cellulose fibers obtained by melt spinning; and (4) semi-synthetic fibers such as acetate fibers. The type of cellulose fiber is not particularly limited.

Protein-based fibers include, for example, natural fibers such as silk and wool.
Examples of hydrophilic synthetic fibers include synthetic fibers made from hydrophilic thermoplastic resins, synthetic fibers made by kneading hydrophilic agents into hydrophobic thermoplastic resins, and hydrophobic synthetic fibers. Examples include synthetic fibers coated with a hydrophilic fiber treatment agent, and synthetic fibers obtained by subjecting hydrophobic synthetic fibers to hydrophilic processing (corona discharge treatment, sulfonation treatment, graft polymerization treatment, etc.). Examples of the thermoplastic resin constituting the synthetic fiber are as described above in connection with the adhesive fiber. Many of the thermoplastic resins listed above are hydrophobic, so when using them, it is necessary to make them hydrophilic by incorporating a hydrophilic agent or applying a hydrophilic fiber treatment agent.

Examples of the hydrophilic fiber treatment agent include a fiber treatment agent containing a surfactant. As the surfactant, anionic, cationic, amphoteric, nonionic surfactants, etc. can be used. Examples of surfactants are as described in connection with adhesive fibers. The content of the hydrophilic fiber treatment agent may be 0.1% by mass or more and 2.0% by mass or less, when the fiber mass (the mass of the fiber excluding the fiber treatment agent) is 100% by mass. The content of the hydrophilic fiber treatment agent may particularly be 0.15% by mass or more and 1.0% by mass or less, and more particularly 0.2% by mass or more and 0.6% by mass or less.

Although the fineness of the non-adhesive fibers is not particularly limited, in this embodiment, non-adhesive fibers with a relatively small fineness are preferably used. Specifically, it may be from 0.3 dtex to 3.5 dtex, further from 0.5 dtex to 3.0 dtex, particularly from 0.6 dtex to 2.7 dtex, and more particularly from 0.7 dtex to 2.5 dtex. Hydrophilic fibers with a small fineness are entangled more firmly when intertwined by the method described below, so it is easier to adjust the degree of surface entanglement.

The fiber length of the non-adhesive fibers may be, for example, from 25 to 100 mm, in particular from 28 to 70 mm, and more particularly from 30 to 60 mm.
When the fiber length of the non-adhesive fibers is within the above range, the entangling properties of the fibers tend to be suitable when producing a nonwoven fabric by the method described below (particularly a method in which the entangling treatment includes hydroentangling treatment).

The cross section (cross section, or cross section perpendicular to the length direction of the fiber) of the non-adhesive fiber may be circular or non-circular. Examples of the non-circular shape include an ellipse, a Y-shape, an X-shape, a square, a multilobed shape, a polygon, a star, a chrysanthemum, and the like. When the cross section of the fibers is circular, the bonding area with the adhesive fibers becomes relatively small, so the texture of the nonwoven fabric can be made softer than when using non-circular shaped fibers. When the cross section of the fibers is non-circular, the area of adhesion with the adhesive fibers becomes relatively large, so that the strength of the nonwoven fabric can be increased.

As the cellulose fiber, which is an example of the non-adhesive fiber, a chemical fiber such as a regenerated fiber or a semi-synthetic fiber may be used. Variations in fineness and/or fiber diameter, and fiber length of chemical fibers are smaller than those of natural fibers, so it is easier to adjust the degree of entanglement of the nonwoven fabric. In addition, recycled fibers such as rayon and solvent-spun cellulose fibers are preferred because they have a good balance between softness and strength when wet, and it is easier to obtain softness and strength with a texture suitable for nonwoven fabrics. . Furthermore, since solvent-spun cellulose fibers have relatively high single fiber tenacity, they are preferable in that the nonwoven fabric has better tenacity. Although rayon has lower single fiber strength than solvent-spun cellulose fibers, it is preferable because it makes the nonwoven fabric soft and has a high entangling property.

Non-adhesive fibers can be used alone or in combination.

(other fibers)
The nonwoven fabric of this embodiment may contain fibers other than non-adhesive fibers and adhesive fibers (hereinafter referred to as "other fibers"). Other fibers included in the first fiber layer include, for example, hydrophilic fibers other than adhesive fibers, synthetic fibers (e.g., do not melt or soften when the adhesive component of adhesive fibers is melted, and do not exhibit adhesive properties. (synthetic fibers, etc.), and is not particularly limited. Other fibers included in the second fiber layer include adhesive fibers.

Other fibers may be included in a proportion of 30% by mass or less, further 10% by mass or less, particularly 5% by mass or less, and more particularly It is preferable that the first fiber layer is composed of 100% by mass of adhesive fibers and the second fiber layer is composed of 100% by mass of non-adhesive fibers, without containing other fibers.

(Composition of nonwoven fabric)
The nonwoven fabric of this embodiment includes a first fibrous layer and a second fibrous layer, the first fibrous layer forming a first surface of the nonwoven fabric, and the second fibrous layer forming a second surface of the nonwoven fabric. The first fiber layer and the second fiber layer may be arranged in contact with each other, or another fiber layer or sheet may be arranged between the layers, but the first fiber layer and the second fiber layer may be arranged in contact with each other. That's good. Further, the first fiber layer contains adhesive fibers in an amount of 80% by mass or more and 100% by mass or less, preferably 85% by mass or more and 100% by mass or less, more preferably 90% by mass, based on the total mass of the first fiber layer. The content may be greater than or equal to 100% by mass, more particularly 100% by mass. Alternatively, the first fibrous layer may be composed only of adhesive fibers.

When used as a packaging nonwoven fabric, the first surface of the nonwoven fabric formed by the first fiber layer may be either a contact surface with the article to be packaged or a non-contact surface. If you use a sealer to make it into a bag, it is best to use it on the contact surface. In this embodiment, the first fiber layer contains adhesive fibers, but is designed to provide a smooth feel. As mentioned above, adhesive fibers are synthetic fibers, so even when the fibers are intertwined and integrated by the action of high-pressure fluid (especially high-pressure water jet) using the method described below, they have already been adhesively treated, so there will be no traces of jetting from the high-pressure fluid. The unevenness caused by this can be reduced, and the first surface of the nonwoven fabric can be made smoother. Therefore, it is preferable that the surface of the nonwoven fabric formed by the first fiber layer is a flat surface having no raised portions or depressed portions.

The proportion of non-adhesive fibers contained in the second fiber layer is 80% by mass or more and 100% by mass or less, preferably 85% by mass or more and 100% by mass or less, more preferably 90% by mass or more and 100% by mass or less, and more. In particular, it may be 100% by weight. Alternatively, the second fiber layer may be composed only of the second hydrophilic fibers.

In the nonwoven fabric of this embodiment, the fibers are bonded to each other by the adhesive fibers contained in the first fiber layer, and the fibers constituting the first fiber layer and the second fiber layer are intertwined with each other, so that the fibers are integrated with each other. has been made into When manufacturing a nonwoven fabric by the method described below, only the fibers included in the first fiber layer may be bonded together by adhesive fibers, and in that case, the fibers in the second fiber layer are not bonded to each other. According to this configuration, the bonding points are present only in the first fiber layer, making the entire nonwoven fabric soft to the touch. In addition, when manufacturing a nonwoven fabric by the method described below, by entangling the fibers constituting the first fiber layer and the second fiber layer with the bonding points existing only in the first fiber layer, it is possible to create a nonwoven fabric between the layers. The intertwining properties between fibers can be improved.

At the location where the fibers are bonded to each other, a bonded portion is formed by the adhesive component of the adhesive fiber melting or softening and then solidifying again. Furthermore, the fibers may be entangled with each other by, for example, hydroentangling treatment, as will be described later.

The nonwoven fabric of this embodiment has a surface entanglement degree of less than 3.0 mg on the first surface of the nonwoven fabric measured according to the method below,
The degree of surface entanglement on the second surface is 3.0 mg or more.
(Surface entanglement degree)
a) Urethane foam (manufactured by INOAC Corporation, trade name Malt Filter MF-30, ester polyurethane, number of cells 30, average cell diameter 410 μm, average coefficient of friction (MIU) 0.69, variation in average coefficient of friction (MMD) ) 0.043, thickness 5 mm) is attached to the rotating shaft so that the rotating shaft is offset by 20 mm from the center of the disk.
b) Spread the same urethane foam as above, and fix the nonwoven fabric on a table so that the first surface or the second surface of the nonwoven fabric becomes the exposed surface.
c) Place the disk on top of the nonwoven fabric. At this time, the only load applied to the nonwoven fabric is the weight of the disc itself.
d) Rotate the rotating shaft to move the disk around the nonwoven fabric. Seven sets of circumferential movements are performed, with one set consisting of two rotations clockwise and two rotations counterclockwise. The circumferential speed at this time is approximately 3 seconds per circumferential movement.
e) After seven sets of rotations, collect the fibers that have fallen off the nonwoven fabric and adhered to the surface of the urethane foam covering the disk.
f) Perform the operations a) to e) above on n=3 nonwoven fabrics. The mass of the fallen fibers is measured for each of the three nonwoven fabrics, and the average value is defined as the degree of surface entanglement (mg).
In addition, instead of the above-mentioned urethane foam, as long as the above-mentioned number of cells, average cell diameter, MIU, MMD, and thickness each differ within a range of ±25%, the degree of surface entanglement was measured using another urethane foam. good. If the degree of surface entanglement measured using such another urethane foam is within the above range, the measured degree of surface entanglement is considered to have been measured using the above specific urethane foam. In this embodiment, it is used as an index representing the degree of confounding. After fiber entanglement, fibers contained in fiber layers other than the fiber layer enter into each fiber layer as a result of the entanglement, but do not substantially appear on the surface of each fiber layer. The term "substantially" as used herein refers to two or less fibers that are visually recognized as being present on the surface of the nonwoven fabric when the surface is magnified 300 times using an electron microscope (SEM).

The nonwoven fabric of this embodiment can be provided as having a degree of surface entanglement on the first surface of the first fiber layer of less than 3.0 mg, particularly 2.0 mg or less, and more particularly 1.0 mg or less. When the degree of surface entanglement exceeds 3.0 mg, the desired cushioning properties cannot be obtained, and the impact protection properties and scratch prevention properties when used as a packaging material tend to decrease. The lower the degree of surface entanglement, the stronger the adhesion between the fibers by the adhesive fibers in the first fiber layer, and therefore the higher the cushioning properties.

The nonwoven fabric of this embodiment can be provided as having a degree of surface entanglement on the second surface of the second fiber layer of 3.0 mg or more, particularly 3.2 mg or more, and more particularly 3.5 mg or more. The upper limit is preferably 30 mg or less, particularly 28 mg or less, and more particularly 26 mg or less. If the degree of surface entanglement is less than 3.0 mg, the desired cushioning properties cannot be obtained, and impact protection properties and scratch prevention properties when used as a packaging material tend to decrease. The higher the degree of surface entanglement, the looser the intertwining of the fibers by the non-adhesive fibers in the second fiber layer, so the degree of freedom of the fibers is greater and the cushioning properties are higher.

According to the nonwoven fabric of this embodiment, the first surface formed by the first fiber layer has a small degree of surface entanglement, that is, the degree of freedom of the fibers tends to be small, but bonding points between the fibers are formed by the adhesive fibers. Therefore, the buffering properties are large. On the other hand, the second surface formed by the second fiber layer has a high degree of surface entanglement, that is, the fibers tend to have a high degree of freedom, and the fibers are entangled with each other to form a row, so the cushioning properties are large. Therefore, the laminated nonwoven fabric has high cushioning properties, and tends to have high impact protection and scratch prevention properties.

In this embodiment, the basis weight of the first fiber layer may be, for example, 10 g/m ² or more and 40 g/m ² or less, particularly 12 g/m ² or more and 35 g/m 2 or less, and more particularly 15 g/m ² or more and 30 g/m ² or less. /m ² or less. When the basis weight of the first fiber layer is within the above range, sufficient cushioning properties can be obtained since the first fiber layer contains a predetermined amount of adhesive fibers.

The basis weight of the second fiber layer may be, for example, 10 g/m ² or more and 40 g/m ² or less, particularly 15 g/m ² or more and 37 g/m ² or less, and more particularly 20 g/m ² or more and 35 g/m ² or less. It's good. When the basis weight of the second fiber layer is within the above range, sufficient cushioning properties can be obtained because the fibers include a predetermined amount of non-adhesive fibers and are intertwined with each other.

The ratio of the basis weight of the first fiber layer to the basis weight of the second fiber layer may be, for example, 2:8 (first:second) to 8:2, particularly 3:7 to 7:3, more particularly may be 4:6 to 6:4.

The basis weight of the entire nonwoven fabric is appropriately selected depending on the type of absorbent article, the location in the absorbent article, etc. The basis weight of the entire nonwoven fabric may be, for example, particularly 20 g/m ² or more and 80 g/m ² or less, particularly 30 g/m ² or more and 70 g/m ² or less, and even more particularly 40 g/m ² or more and 60 g/m ² or less.

The nonwoven fabric of this embodiment may have a thickness of 0.20 mm or more and 2.00 mm or less, particularly 0.30 mm or more and 1.85 mm or less, as measured by applying a load of 294 Pa. It is even more preferable to have a thickness of 0.40 mm or more and 1.65 mm or less. When the nonwoven fabric has a thickness in the range described above, the nonwoven fabric tends to provide a smoother feel.
Further, the thickness measured by applying a load of 1.96 kPa may be 0.45 mm or more and 1.10 mm or less, particularly 0.50 mm or more and 1.05 mm or less, and more particularly 0.50 mm or more and 1.05 mm or less. It may have a length of 55 mm or more and 1.00 mm or less.

The tensile strength of the nonwoven fabric of this embodiment in the MD direction (longitudinal direction or machine direction) may be, for example, 20.0 N/5 cm or more and 150.0 N/5 cm or less, particularly 24.0 N/5 cm or more and 140.0 N/5 cm. It may be 5 cm or less, more particularly 26.0 N/5 cm or more and 130.0 N/5 cm or less. Further, the nonwoven fabric of the present embodiment may have a tensile strength in the CD direction (lateral direction) of, for example, 2.5 N/5 cm or more and 50.0 N/5 cm or less, particularly 3.0 N/5 cm or more and 40.0 N/5 cm. Hereinafter, more particularly, it may be 3.5 N/5 cm or more and 35.0 N/5 cm or less. When the tensile strength of the nonwoven fabric is within the above range, the shape stability of the nonwoven fabric tends to be further improved.

The elongation rate in the MD direction of the nonwoven fabric of this embodiment may be, for example, 10% or more and 100% or less, particularly 20% or more and 60% or less, and the elongation rate in the CD direction may be, for example, 30% or more. It may be 200% or less, particularly 35% or more and 120% or less. When the elongation rate of the nonwoven fabric is within the above range, the flexibility of the nonwoven fabric tends to be further improved.

The stress at 10% elongation in the MD direction of the nonwoven fabric of this embodiment may be, for example, 5.0 N/5 cm or more and 20.0 N/5 cm or less, particularly 5.5 N/5 cm or more and 19.5 N/5 cm or less, and more particularly may be 6.0 N/5 cm or more and 19.0 N/5 cm or less. In addition, the nonwoven fabric of this embodiment may have a stress at 10% elongation in the CD direction of, for example, 0.7 N/5 cm or more and 4.0 N/5 cm or less, particularly 0.8 N/5 cm or more and 3.9 N/5 cm or less, More particularly, it may be 0.9 N/5 cm or more and 3.8 N/5 cm or less. In the nonwoven fabric of this embodiment, since the fibers are relatively firmly intertwined with each other near the interface between the first fiber layer and the second fiber layer, stress tends to increase particularly when elongated by 10% in the MD direction. When the stress at 10% elongation in the MD and CD directions is within the above range, the handleability of the nonwoven fabric is improved.

(Second embodiment)
The nonwoven fabric of this embodiment is
A laminated nonwoven fabric including a first fibrous layer and a second fibrous layer, the first fibrous layer forming a first surface of the nonwoven fabric, and the second fibrous layer forming a second surface of the nonwoven fabric,
The first fiber layer contains 80% by mass or more of adhesive fibers based on the total mass of the first fiber layer,
The second fiber layer contains 80% by mass or more of non-adhesive fibers based on the total mass of the second fiber layer,
In the first fiber layer, the fibers are bonded to each other by the adhesive fibers,
The first fiber layer and the second fiber layer are integrated by intertwining the fibers,
On the first surface, the fibers constituting the second fiber layer are not exposed,
On the second surface, the fibers constituting the first fiber layer are not exposed,
In the nonwoven fabric for packaging, the fibers constituting each fiber layer are intertwined near the interface between the first fiber layer and the second fiber layer.
The above configuration is as shown in FIGS. 1 to 3. By having a predetermined structure, the nonwoven fabric has high cushioning properties, and has high impact protection properties and scratch prevention properties for articles.

(Third embodiment)
Next, a method for manufacturing the nonwoven fabrics of the first and second embodiments will be described as a third embodiment.
The manufacturing method of this embodiment is as follows:
A nonwoven fabric for packaging that is a laminated nonwoven fabric including a first fibrous layer and a second fibrous layer, the first fibrous layer forming a first surface of the nonwoven fabric, and the second fibrous layer forming a second surface of the nonwoven fabric. A method of manufacturing,
producing a first fibrous web containing 80% by mass or more of adhesive fibers based on the total mass of the first fibrous web constituting the first fibrous layer;
producing a second fibrous web containing 80% by mass or more of non-adhesive fibers based on the total mass of the second fibrous web constituting the second fibrous layer;
an adhesion step of adhering the fibers of the first fibrous web to each other using the adhesive fibers;
a laminating step of laminating the first fibrous web and the second fibrous web after the adhesion step to obtain a laminated fibrous web;
an entangling step of jetting a water stream to the second fibrous web side of the laminated fibrous web to hydro-entangle and integrate the fibers of the first fibrous web and the second fibrous web;
A method for producing a nonwoven fabric for packaging.

Both the first fibrous web and the second fibrous web may be manufactured by known methods. The first fibrous web and the second fibrous web may be in any form such as a parallel web, a cross web, a semi-random web, a card web such as a random web, an air-lay web, or a wet papermaking web. When the first fibrous web is a parallel web, the surface of the nonwoven fabric tends to be smoother. When the second fiber web is a parallel web, the fibers are oriented in one direction, so they are likely to intertwine with the constituent fibers of the first fiber layer. Therefore, when the basis weight of the second fibrous web is small, by making the second fibrous web a parallel web, integration of the first fibrous web and the second fibrous web is likely to be promoted. The form of the second fibrous web may be the same as or different from the form of the first fibrous web, and if they are the same, the fiber orientations of each web are similar, and the layers are likely to be intertwined.

In the manufacturing method of this embodiment, the first fibrous web is subjected to an adhesion step, and the fibers of the first fibrous web are bonded together using adhesive fibers. The adhesive treatment may be, for example, heat treatment (thermal adhesive treatment). According to heat treatment, the component with the lowest melting point (thermal adhesive component) among the resin components that make up the adhesive fibers is melted or softened by heating during heat treatment, making it possible to bond the fibers that make up the fiber web to each other. . The heat treatment may be, for example, a hot air treatment in which hot air is blown, a hot roll treatment (eg, hot embossing roll treatment), or a heat treatment using infrared radiation. Hot air processing is preferable because it tends to improve the texture of the nonwoven fabric. The hot air processing treatment may be performed using a device that blows hot air at a predetermined temperature onto the fiber web, such as a hot air through-type heat treatment machine and a hot air blowing type heat treatment machine.

When the bonding process is hot air processing, hot air may be sprayed multiple times. Moreover, when blowing hot air multiple times, it is preferable that the temperature of the second hot air is higher than the temperature of the first hot air.

When the adhesive treatment is a hot air processing treatment, the hot air speed may be, for example, 0.1 m/min or more and 3.0 m/min or less, particularly 0.2 m/min or more and 2.5 m/min or less, and more particularly may be 0.3 m/min or more and 2.0 m/min or less. If the hot air speed is too low, the fibers may not be bonded well throughout the fiber web, and if it is too high, the unbonded fibers will be blown away by the hot air, making it difficult to obtain a uniform texture and making the nonwoven fabric smooth. The quality may decrease.

The temperature of the heat treatment may be a temperature at which the component with the lowest melting point (thermal adhesive component) among the resin components constituting the adhesive fiber softens or melts, and may be, for example, a temperature equal to or higher than the melting point of the component. For example, when the component with the lowest melting point among the resin components constituting the adhesive fiber is high-density polyethylene, when performing hot air processing, hot air at a temperature of 130° C. or more and 150° C. or less may be blown. For example, if the component with the lowest melting point among the resin components constituting adhesive fibers is an ethylene-acrylic acid copolymer, hot air at a temperature of 90°C or higher and 140°C or lower may be blown onto the adhesive fiber. In particular, hot air at a temperature of 95° C. or higher and 130° C. or lower may be blown, more particularly hot air at a temperature of 100° C. or higher and 120° C. or lower may be blown. In addition, the temperature of the heat treatment is preferably 0°C or more and 5°C or less higher than the melting point or softening point of the thermal adhesive component, and 1°C or more and 4°C or less higher than the melting point or softening point of the thermal adhesive component, considering the texture of the nonwoven fabric obtained. It is more preferable to set the temperature to 2° C. or higher and 3° C. or lower.

The adhesion treatment may be performed by irradiation with an electron beam or the like, or by ultrasonic welding. These adhesive treatments also allow the fibers to be adhered to each other using the resin component that constitutes the adhesive fibers.

In the manufacturing method of this embodiment, a lamination step is carried out to obtain a laminated fiber web by laminating the first fiber web that has been subjected to the bonding process in the bonding step and a second fiber web that has been separately produced. The first fibrous web that has been subjected to the adhesion process can be said to be a thermally bonded nonwoven fabric because the fibers are bonded to each other and have a certain degree of integrity.

The manufacturing method according to the embodiment of the present invention may include a cooling step after the bonding step and before the interlacing step. That is, after the adhesion step and before the lamination step is performed, and/or after the first fibrous web and the second fibrous web are laminated and before the entangling step is performed. In addition, a cooling step may be performed to cool the first fibrous web and/or the laminated fibrous web. Examples of the cooling treatment method include air cooling and water cooling. If the first fiber web after the adhesive treatment is not sufficiently cooled, the adhesive components of the adhesive fibers may be in a softened state. If the laminated fiber web is subjected to an entanglement treatment in this state, the bonded portions may be easily peeled off, and the nonwoven fabric may become fluffy.

In this embodiment, after the bonding process, the first fibrous web is subjected to the interlacing process together with the second fibrous web without winding the first fibrous web onto a roll. This facilitates the progress of intertwining of the fibers. This is because once the first fibrous web after the bonding process is wound up into a roll, its volume tends to decrease, but the larger the volume of the first fibrous web, the more difficult it is to entangle with the second fibrous web. This is because inter-fiber voids are likely to occur and entanglement is more likely to proceed.

The entangling process is, for example, a needle punching process or a high pressure fluid stream (especially water stream) entangling process. In high pressure fluid flow processing, the high pressure fluid is, for example, a high pressure gas such as compressed air, and a high pressure liquid such as high pressure water. In the production of nonwoven fabrics, hydroentangling treatment using high-pressure water as the high-pressure fluid is often used, and in this embodiment, hydroentangling is also used from the viewpoint of ease of implementation and ease of entangling hydrophilic fibers. Treatment is preferably used. In the following, a description will be given of the entangling process when high-pressure water (hereinafter also simply referred to as "water flow") is used as the high-pressure fluid.

The hydroentanglement treatment is carried out, for example, by injecting a water stream with a water pressure of 1 MPa or more and 15 MPa or less from a nozzle in which orifices with a hole diameter of 0.05 mm or more and 0.5 mm or less are provided at intervals of 0.3 mm or more and 1.5 mm or less. implement. The water pressure is preferably 1 MPa or more and 10 MPa or less, more preferably 1 MPa or more and 7 MPa or less, particularly preferably 1 MPa or more and 6 MPa or less.

In this embodiment, the hydroentanglement process may be performed by spraying water onto the surfaces of the second fiber web and the first fiber web of the laminated fiber web (i.e., both surfaces of the laminated fiber web). At this time, the water pressure of the water stream sprayed onto the surface of the first fibrous web may be higher than the water pressure of the water stream sprayed onto the surface of the second fibrous web. Furthermore, it is preferable that the number of times the water jet is sprayed onto the first fibrous web is greater than the number of times the water jet is sprayed onto the second fibrous web.

In this embodiment, the water pressure of the water jet injected onto the second fibrous web may be, for example, 1 MPa or more and 10 MPa or less, particularly 1 MPa or more and 8 MPa or less. Further, the number of times the water stream is sprayed onto the second fibrous web may be, for example, 1 or more and 3 or less. The water pressure of the water stream injected onto the first fibrous web may be, for example, 1 MPa or more and 15 MPa or less, particularly 1 MPa or more and 10 MPa or less. Further, the number of times the water stream is sprayed onto the first fibrous web may be, for example, 2 times or more and 4 times or less.

The difference in water pressure between the water streams sprayed onto the second fibrous web and the first fibrous web may be, for example, 1 MPa or more and 10 MPa or less, particularly 1 MPa or more and 8 MPa or less. Further, the number of times the water jet is sprayed onto the first fibrous web may be, for example, 1 to 4 times more, and particularly 1 to 3 times more than that to the second fibrous web.

The hydroentangling treatment may be carried out by first spraying a water stream on the second fibrous web side a predetermined number of times, and then spraying a water stream on the first fibrous web side a predetermined number of times. According to this order, the basis for entanglement is created by the second hydrophilic fibers in the second fiber web, and even if a water stream with higher water pressure is injected from the first fiber web side, the fibers will be scattered by the water stream. etc., and the occurrence of unevenness in the nonwoven fabric is suppressed. Furthermore, since the first fibrous web is adhesively treated with adhesive fibers, there is almost no movement of the fibers constituting the first fibrous web due to the entangling process, and the fibers that make up the first fibrous web are moved from the second fibrous layer by hydroentanglement. When the fibers constituting the second fiber layer are hydroentangled from the first fiber layer side, the fibers constituting the second fiber layer near the first surface move again, so that the second fiber layer is substantially on the first surface. The fibers that make up the fibers may not exist. On the other hand, near the interface between the first fiber layer and the second fiber layer, the fibers transferred from the second fiber layer are firmly intertwined with the first fiber layer, so a laminated nonwoven fabric with high cushioning properties is obtained.

The hydroentangling treatment may be carried out by placing the fibrous web on a support and spraying it with a water jet. If the surface of the nonwoven fabric is flat and has no irregularities, the support should not have any pores with an area of 0.2 ^mm2 or more per pore, and should not have protrusions or patterns formed thereon. It is best to use a support that is not For example, as the support, a plain weave support of 80 mesh or more and 100 mesh or less may be used.

When hydroentangling treatment is performed in the entangling step, a drying step may be performed after the entangling step. The drying process can be performed, for example, by hot air processing in which hot air is blown. The temperature of the drying process may be lower than the temperature at which the adhesive component (thermal adhesive component) of the adhesive fibers contained in the first fibrous web softens or melts. The temperature of the drying treatment may be, for example, 10° C. or more lower than the melting point or softening point of the thermal adhesive component, particularly 15° C. or more lower, and more particularly 20° C. or lower. After the interlacing step, by not softening or melting the adhesive fibers, a nonwoven fabric in which the fibers are not bonded to each other in the second fiber layer can be obtained. In order to obtain a nonwoven fabric having such a structure, it is necessary to perform not only the drying process but also the processing process (for example, dyeing process) of the laminated fiber web or nonwoven fabric after the entangling process, using adhesive fibers contained in the first fiber web. It is preferable to carry out the process at a temperature lower than the temperature at which the adhesive component softens or melts.

When the second fibrous web contains adhesive fibers, the adhesive fibers of the second fibrous web (hereinafter referred to as "second adhesive fibers" to distinguish from the adhesive fibers included in the first fibrous web) are used after the interlacing step. The fibers may be bonded together (called a post-entanglement bonding step). In particular, the melting point of the second adhesive fiber is lower than the melting point of the adhesive component of the adhesive fiber ("first adhesive fiber" to distinguish from the second adhesive fiber) contained in the first fiber web, It is preferable that the adhesive components of the second adhesive fibers be melted at a temperature lower than the temperature at which the adhesive components of the first adhesive fibers are melted to bond the fibers together. This prevents the first adhesive fibers from melting or softening again, and from solidifying, thereby preventing the nonwoven fabric from becoming hard.

Hereinafter, a nonwoven fabric and a method for manufacturing the same according to the present disclosure will be explained using Examples.
The fibers used to produce the nonwoven fabrics of Examples and Comparative Examples are shown below.
<Adhesive fiber 1><Adhesive fiber 5>
(1) Resin (i) Poly L-lactic acid (hereinafter also referred to as PLA)
A: L-130, optical purity 99% or more, melting point 175°C, manufactured by Total-Corbion B: Ingeo3251D, optical purity 98.5%, melting point 155-170°C, manufactured by Nature Works (ii) Aliphatic polyester C: Polybutylene succinate (hereinafter also referred to as PBS), FZ71 PM, melting point 115°C, manufactured by PTT MCC Biochem (iii) Nucleating agent (added to the sheath component, in the table, the amount of the nucleating agent is the amount in the sheath component) )
D: Talc (manufactured by Nippon Talc Co., Ltd., product name "Micro Ace PS")
E: Calcium stearate (manufactured by NOF Corporation, product name "Calcium Stearate S")
(2) Core component, resin core component of sheath component, nucleating agent: Table 1
Sheath component: C
(3) Take-up speed: 926 m/min (4) Cross section: Concentric circles (5) Stretching method: Wet (warm water), two-stage stretching (6) Oil concentration: 5% by mass
(7) Drying temperature: 85℃
(8) Cut length: 51mm

<Adhesive fiber 2>
Polypropylene (melting point: about 160°C) is the core, high-density polyethylene (melting point: about 133°C) is the sheath, and the core-sheath ratio (volume ratio of core component/sheath component) is 65/35. Concentric core-sheath type composite fiber with a fineness of 1.6 dtex and a fiber length of 38 mm, in which the and sheath components are arranged concentrically (NBF (H) (product name) manufactured by Daiwabo Co., Ltd.)
<Adhesive fiber 3>
Polyethylene terephthalate (melting point: about 260°C) is the core, high-density polyethylene (melting point: about 133°C) is the sheath, and the core-sheath ratio (core component/sheath component volume ratio) is 49/51. A concentric core-sheath type composite fiber with a fineness of 1.7 dtex and a fiber length of 45 mm, in which the component and sheath component are arranged concentrically (NBF (SH) (product name) manufactured by Daiwabo Co., Ltd.)
<Adhesive fiber 4>
Polyethylene terephthalate (melting point: about 255 ° C.) is the core, low melting point polyethylene terephthalate (melting point: about 110 ° C.) is the sheath, and the core-sheath ratio (volume ratio of core component / sheath component) is 50/50, A concentric core-sheath type composite fiber with a core component and a sheath component arranged concentrically, a fineness of 2.2 dtex, and a fiber length of 51 mm (Safmet T9611 (product name) manufactured by Toray Industries, Inc.)

<Non-adhesive fiber A>
Viscose rayon fiber with a fineness of 1.7 dtex, a fiber length of 40 mm, and a chrysanthemum-shaped fiber cross section (CD (product name) manufactured by Daiwabo Rayon Co., Ltd.)
<Non-adhesive fiber B>
Cotton with an average fineness of 2.5 dtex (average fiber diameter 13.0 m) and an average fiber length of 30 mm (manufactured by Marusan Sangyo Co., Ltd., MSD (product name))
<Non-adhesive fiber C>
Solvent spun cellulose fiber with a fineness of 1.7 dtex, a fiber length of 38 mm, and a circular fiber cross section (manufactured by Lenzing, Lyocell (trade name))
<Non-adhesive fiber D>
Polyethylene terephthalate fiber with a fineness of 1.45 dtex, a fiber length of 51 mm, and a circular fiber cross section (manufactured by Toray Industries, Inc., T403D (trade name))
<Non-adhesive fiber E>
Polypropylene fiber with a fineness of 1.0 dtex, a fiber length of 38 mm, and a circular fiber cross section (manufactured by Daiwabo Co., Ltd., PN (product name))

<Manufacture of nonwoven fabric of Example 1>
(1) Preparation of first fibrous layer A first fibrous web was prepared using a parallel carding machine using adhesive fiber 1 as 100% by mass and having a target weight of about 20 g/m ² .
This first fiber web was heated at 128°C (13°C higher than the melting point) for about 5 seconds using a hot air penetration type heat treatment machine, and the fibers were thermally bonded (adhesion treatment) using the sheath component of the adhesive fibers. A thermally bonded nonwoven fabric serving as the first fiber layer was obtained.
(2) Preparation of second fibrous layer A second fibrous web was prepared using a parallel carding machine using 100% by mass of non-adhesive fibers A and having a target weight of about 30 g/m ² .
(3) Production of laminated nonwoven fabric The obtained second fibrous web was laminated on the surface side (air side) of the first fibrous layer to which hot air was applied, to obtain a laminated fibrous web.
The laminated fiber web described above was placed on a plain weave net having a warp diameter of 0.132 mm, a weft diameter of 0.132 mm, and a mesh count of 90 meshes. While the laminated fiber web was traveling at a speed of 4 m/min, a water stream with a water pressure of 3 MPa was injected once onto the surface of the laminated fiber web on the second fiber web side using a water supply device. The nozzle of the water supply device used was one in which orifices with a hole diameter of 0.12 mm were provided at intervals of 0.6 mm. The distance between the surface of the laminated fiber web and the orifice was 15 mm. Thereafter, a water stream with a water pressure of 3 MPa was sprayed once onto the surface of the laminated fiber web on the first fiber layer side using the same water supply device.
The laminated fiber web after hydroentangling treatment was subjected to drying treatment at 80°C using a hot air penetration type heat treatment machine, and the first fiber layer formed the first surface and the second fiber layer formed the second surface. A nonwoven fabric having a two-layer laminated structure of Example 1 was obtained.

<Production of nonwoven fabrics of Examples 2 to 8>
The nonwoven fabrics of Examples 2 to 8 were prepared in the same manner as in Example 1, except that the type of adhesive fiber used in the first fiber layer and the processing temperature of the hot air through-type heat treatment machine were as shown in Tables 2 and 3. I got it.

<Production of nonwoven fabrics of Examples 9 to 17>
Except that the type of adhesive fiber used in the first fiber layer, the processing temperature of the hot air penetration type heat treatment machine, and the type of non-adhesive fiber used in the second fiber layer were as shown in Tables 4 and 5. Nonwoven fabrics of Examples 9 to 17 were obtained in the same manner as in Example 1.

<Production of nonwoven fabrics of Examples 18 to 21>
Except that the type of adhesive fiber used in the first fiber layer, the processing temperature of the hot air through-type heat treatment machine, the type of non-adhesive fiber used in the second fiber layer, and the water pressure conditions were as shown in Table 6. In the same manner as in Example 1, nonwoven fabrics of Examples 18 to 21 were obtained.

<Manufacture of nonwoven fabric of Comparative Example 1>
(1) Preparation of first fibrous layer A first fibrous web was prepared using a parallel carding machine using adhesive fiber 2 as 100% by mass and having a target weight of about 20 g/m ² .
(2) Preparation of second fibrous layer A second fibrous web was prepared using a parallel carding machine using non-adhesive fibers A as 100% by mass and having a target weight of about 30 g/m ² .
(3) Production of laminated nonwoven fabric The obtained second fibrous web was laminated on the first fibrous web to obtain a laminated fibrous web.
The laminated fiber web described above was placed on a plain weave net having a warp diameter of 0.132 mm, a weft diameter of 0.132 mm, and a mesh count of 90 meshes. While the laminated fiber web was traveling at a speed of 4 m/min, a water stream with a water pressure of 3 MPa was injected once onto the surface of the laminated fiber web on the second fiber web side using a water supply device. The nozzle of the water supply device used was one in which orifices with a hole diameter of 0.12 mm were provided at intervals of 0.6 mm. The distance between the surface of the laminated fiber web and the orifice was 15 mm. Thereafter, a water stream with a water pressure of 3 MPa was sprayed once onto the surface of the laminated fiber web on the first fiber layer side using the same water supply device.
The laminated fiber web after the hydroentanglement treatment was subjected to thermal bonding treatment at 135°C using a hot air penetration type heat treatment machine, so that the first fiber layer formed the first surface and the second fiber layer formed the second surface. A nonwoven fabric having a two-layer laminated structure of Comparative Example 1 was obtained.

<Manufacture of nonwoven fabrics of Comparative Examples 2 to 4>
Comparative Example 1 except that the type of adhesive fiber used in the first fiber layer, the processing temperature of the hot air penetration type heat treatment machine, and the type of non-adhesive fiber used in the second fiber layer were as shown in Table 7. Nonwoven fabrics of Comparative Examples 2 to 4 were obtained in the same manner as above.

The following evaluations were performed on the obtained nonwoven fabrics of each Example and each Comparative Example. The evaluation results are shown in Tables 2 to 7. Moreover, the evaluation method is shown below.

[Evaluation method]
(1) Differential scanning calorimetry (DSC)
Based on JIS K 7121:1987, the measurement was carried out using a differential scanning calorimeter (manufactured by Hitachi High-Tech Science Co., Ltd.) under the following conditions.
The amount of the sample fiber was 3.0 mg, which was weighed and then filled into a sample holder. Next, the temperature of the fibers filled in the sample holder was raised from room temperature (23 ± 2 °C) to 250 °C at a rate of 5 °C/min (first temperature increase process), and DSC measurement was performed during the first melting. I did it. After reaching 250°C, the temperature was held for 10 minutes, and the temperature was lowered from 250°C to 40°C at a rate of 1°C/min (temperature lowering process) to solidify the molten sample. At this time, DSC was measured when the temperature was lowered. After the first heating step and cooling step were completed, the sample was held at 40°C for 10 minutes without being removed from the DSC measuring device, and then heated again from 40°C to 250°C at a rate of 5°C/min. (Second temperature raising process), DSC measurement was performed during second melting.
(2) Fiber physical properties Single fiber fineness, single fiber strength, elongation, and Young's modulus were measured according to JIS L 1015:2021.
(3) Crimp ratio Measured according to JIS L 1015:2021.
(4) Fabric weight The fabric weight of the nonwoven fabric was measured based on JIS L 1913:2010 6.2.
(5) Thickness, thickness change rate Using a thickness measuring machine (THICKNESS GAUGE model CR-60A (trade name) manufactured by Daiei Kagaku Seiki Seisakusho Co., Ltd.), a load of 0.3 kPa or 1.96 kPa was applied to the nonwoven fabric. The thickness of the nonwoven fabric (thickness under a load of 0.3 kPa T _0.3 , thickness under a load of 1.96 kPa T _1.96 ) was measured.
The rate of change in thickness was calculated using the following formula.
Thickness change rate (%) = (T _0.3 - T _1.96 ) x 100/T _1.96
(6) Strength and elongation Strength and elongation were measured according to JIS L 1913:2010 6.3. A tensile test was conducted using a constant speed tension type tensile testing machine under the conditions that the sample piece (nonwoven fabric) had a width of 5 cm, a grip interval of 10 cm, and a tensile speed of 30±2 cm/min. The load value (tensile strength) at cutting, elongation rate, and stress at 10% elongation were measured. The tensile test was conducted with the longitudinal direction (MD direction) and the lateral direction (CD direction) of the nonwoven fabric as the tensile directions. The evaluation results were all shown as the average of the values measured for three samples.
(7) Heat seal peel strength A sample was prepared by cutting the nonwoven fabric in the vertical direction to a length of 10 cm and a width of 2.5 cm. Layer the two samples so that the heat-sealing layers (first fiber layer) face each other, and place them at a position approximately 1.5cm from the lengthwise end using a heat-sealing machine (Tester Sangyo) with a heat-sealing width of 0.5cm. A measurement sample was prepared by adhering it using TP-701-B HEAT SEAL TESTER (manufactured by Co., Ltd.).
The heat-sealed part was attached to a constant length tensile testing machine (AutoCOM/AC-100 manufactured by TS Engineering Co., Ltd.) so as to peel 180° in the vertical direction, with a grip interval of 100 mm and a tensile speed (head speed) of 100 mm/min. The average value of the strength measured at N=5 when the heat-sealed portion was peeled was defined as the heat-seal peel strength.
(8) Bending resistance Measured according to the 41.5° cantilever method of JIS L 1913:2010.
The sample was a nonwoven fabric and the heat-sealed nonwoven fabric was adhered to the longitudinal center of the heat-sealed sample prepared in (7) above by heat-sealing to prepare a heat-sealed sample for measurement. The heat sealing conditions were a temperature of 145° C., a pressure of 0.2 MPa, and a time of 0.2 seconds.

Examples 1 to 21 all satisfied the numerical range of the degree of surface entanglement. As a result, even when the product was packaged, it had high cushioning properties, was sufficiently protected even when subjected to a light impact, and the product was not damaged. Furthermore, it was easy to conform to the shape of the article and had good handling properties. It was also confirmed that the heat seal peel strength was generally high.
On the other hand, in Comparative Examples 1 to 4, the degree of surface entanglement was outside the numerical range. As a result, the bulk was low and the cushioning properties were low.

Further, in Examples 1 to 21, the fibers constituting the second fiber layer are not exposed on the first surface, and the fibers constituting the first fiber layer are not exposed on the second surface. It was confirmed that the fibers constituting each fiber layer were intertwined near the interface between the first fiber layer and the second fiber layer.
On the other hand, in Comparative Examples 1 to 6, it was confirmed that fibers constituting opposing fiber layers were present on both the first surface and the second surface.

(Aspect 1)
A laminated nonwoven fabric including a first fibrous layer and a second fibrous layer, the first fibrous layer forming a first surface of the nonwoven fabric, and the second fibrous layer forming a second surface of the nonwoven fabric,
The first fiber layer contains 80% by mass or more of adhesive fibers based on the total mass of the first fiber layer,
The second fiber layer contains 80% by mass or more of non-adhesive fibers based on the total mass of the second fiber layer,
In the first fiber layer, the fibers are bonded to each other by the adhesive fibers,
The first fiber layer and the second fiber layer are integrated by intertwining the fibers,
The degree of surface entanglement on the first surface of the nonwoven fabric measured according to the following method is less than 3.0 mg,
The degree of surface entanglement on the second surface is 3.0 mg or more,
Non-woven fabric for packaging.
(Surface entanglement degree)
a) A disk (diameter 70 mm, 350 g) whose surface is covered with urethane foam (thickness 5 mm) is attached to the rotating shaft so that the rotating shaft is deviated from the center of the disk by 20 mm.
b) Spread the same urethane foam as above, and fix the nonwoven fabric on a table so that the first surface or the second surface of the nonwoven fabric becomes the exposed surface.
c) Place the disk on top of the nonwoven fabric. At this time, the only load applied to the nonwoven fabric is the weight of the disc itself.
d) Rotate the rotating shaft to move the disc around on the nonwoven fabric (the area of the revolution is 86.5 cm ² ). Seven sets of circumferential movements are performed, with one set consisting of two rotations clockwise and two rotations counterclockwise. The circumferential speed at this time is approximately 3 seconds per circumferential movement.
e) After 7 sets of rotations, collect the fibers that have fallen out of the nonwoven fabric and adhered to the surface of the urethane foam covering the disk.
f) Perform the operations a) to e) above on n=3 nonwoven fabrics. The mass of the fallen fibers is measured for each of the three nonwoven fabrics, and the average value is defined as the degree of surface entanglement (mg).
(Aspect 2)
A laminated nonwoven fabric including a first fibrous layer and a second fibrous layer, the first fibrous layer forming a first surface of the nonwoven fabric, and the second fibrous layer forming a second surface of the nonwoven fabric,
The first fiber layer contains 80% by mass or more of adhesive fibers based on the total mass of the first fiber layer,
The second fiber layer contains 80% by mass or more of non-adhesive fibers based on the total mass of the second fiber layer,
In the first fiber layer, the fibers are bonded to each other by the adhesive fibers,
The first fiber layer and the second fiber layer are integrated by intertwining the fibers,
On the first surface, the fibers constituting the second fiber layer are not exposed,
On the second surface, the fibers constituting the first fiber layer are not exposed,
A packaging nonwoven fabric in which the fibers constituting each fiber layer are intertwined near the interface between the first fiber layer and the second fiber layer.
(Aspect 3)
The non-adhesive fiber is at least one selected from non-thermoplastic fibers and thermoplastic fibers having a melting point 30° C. or higher higher than a resin having the lowest melting point among the components constituting the adhesive fibers. The packaging nonwoven fabric according to 1 or 2.
(Aspect 4)
The nonwoven fabric for packaging according to aspect 1 or 2, wherein the non-adhesive fibers are cellulose fibers.
(Aspect 5)
The adhesive fiber according to aspect 1 or 2, wherein the adhesive fiber includes a core-sheath type composite fiber in which the core component is a high melting point component and the sheath component is a component that adheres at a temperature lower than the melting point of the core component by 30° C. or more. Non-woven fabric for packaging.
(Aspect 6)
The nonwoven fabric for packaging according to Aspect 1 or 2, wherein the fibers are not bonded to each other in the second fiber layer (Aspect 7)
In the laminated nonwoven fabric, the stress at 10% elongation in the MD direction is 5.0 N/5 cm or more and 20.0 N/5 cm or less, and the stress at 10% elongation in the CD direction is 0.7 N/5 cm or more and 4.0 N/5 cm or less. The packaging nonwoven fabric according to aspect 1 or 2.
(Aspect 8)
The packaging according to aspect 1 or 2, wherein the first fiber layer has a basis weight of 10 g/m ² or more and 40 g/m ² or less, and the second fiber layer has a basis weight of 10 g/m ² or more and 40 g/m ² or less. Non-woven fabric.
(Aspect 9)
A nonwoven fabric for packaging that is a laminated nonwoven fabric including a first fibrous layer and a second fibrous layer, the first fibrous layer forming a first surface of the nonwoven fabric, and the second fibrous layer forming a second surface of the nonwoven fabric. A method of manufacturing,
producing a first fibrous web containing 80% by mass or more of adhesive fibers based on the total mass of the first fibrous web constituting the first fibrous layer;
producing a second fibrous web containing 80% by mass or more of non-adhesive fibers based on the total mass of the second fibrous web constituting the second fibrous layer;
an adhesion step of adhering the fibers of the first fibrous web to each other using the adhesive fibers;
a laminating step of laminating the first fibrous web and the second fibrous web after the adhesion step to obtain a laminated fibrous web;
an entangling step of jetting a water stream to the second fibrous web side of the laminated fibrous web to hydro-entangle and integrate the fibers of the first fibrous web and the second fibrous web;
A method for producing a nonwoven fabric for packaging, including:
(Aspect 10)
In the adhesion step, the adhesive fiber includes a core-sheath type composite fiber in which the core component is a high melting point component and the sheath component is a component that adheres at a temperature lower than the melting point of the core component by 30 ° C. or more,
The method for producing a packaging nonwoven fabric according to aspect 9, wherein the sheath component of the adhesive fiber is heat-treated at a temperature higher than or equal to a temperature at which the sheath component melts and at a temperature that is 25° C. higher than the melting temperature.
(Aspect 11)
The method for producing a packaging nonwoven fabric according to aspect 9, comprising a drying step of performing a drying treatment at a temperature at which the adhesive fibers do not melt after the entangling step.
(Aspect 12)
A packaging material comprising the laminated nonwoven fabric according to aspect 1 or 2.

The packaging nonwoven fabric of this embodiment has good impact protection and scratch prevention properties for articles, so it can be used for tough articles such as electronic equipment, precision instruments, glass products, ceramics, metal products, foods, household materials, and sanitary products. It is suitable for packaging materials (buffer materials) for flexible items such as materials and medical materials.

Claims (12)

a first fibrous layer and a second fibrous layer, the first fibrous layer forming a first surface of the nonwoven fabric;
A laminated nonwoven fabric in which the second fiber layer forms a second surface of the nonwoven fabric,
The first fiber layer contains 80% by mass or more of adhesive fibers based on the total mass of the first fiber layer,
The second fiber layer contains 80% by mass or more of non-adhesive fibers based on the total mass of the second fiber layer,
In the first fiber layer, the fibers are bonded to each other by the adhesive fibers,
The first fiber layer and the second fiber layer are integrated by intertwining the fibers,
The degree of surface entanglement on the first surface of the nonwoven fabric measured according to the following method is less than 3.0 mg,
A packaging nonwoven fabric having a degree of surface entanglement on the second surface of 3.0 mg or more.
(Surface entanglement degree)
a) A disk (diameter 70 mm, 350 g) whose surface was covered with urethane foam (thickness 5 mm),
Attach to the rotating shaft so that the rotating shaft is offset by 20 mm from the center of the disc.
b) Spread the same urethane foam as above, and fix the nonwoven fabric on a table so that the first surface or the second surface of the nonwoven fabric becomes the exposed surface.
c) Place the disk on top of the nonwoven fabric. At this time, the only load applied to the nonwoven fabric is the weight of the disc itself.
d) Rotate the rotating shaft to move the disc around on the nonwoven fabric (the area of the revolution is 86.5 cm ² ).
Seven sets of circumferential movements are performed, with one set consisting of two rotations clockwise and two rotations counterclockwise.
The circumferential speed at this time is approximately 3 seconds per circumferential movement.
e) After 7 sets of rotations, collect the fibers that have fallen out of the nonwoven fabric and adhered to the surface of the urethane foam covering the disk.
f) Perform the operations a) to e) above on n=3 nonwoven fabrics.
The mass of the fallen fibers is measured for each of the three nonwoven fabrics, and the average value is defined as the degree of surface entanglement (mg). a first fibrous layer and a second fibrous layer, the first fibrous layer forming a first surface of the nonwoven fabric;
A laminated nonwoven fabric in which the second fiber layer forms a second surface of the nonwoven fabric,
The first fiber layer contains 80% by mass or more of adhesive fibers based on the total mass of the first fiber layer,
The second fiber layer contains 80% by mass or more of non-adhesive fibers based on the total mass of the second fiber layer,
In the first fiber layer, the fibers are bonded to each other by the adhesive fibers,
The first fiber layer and the second fiber layer are integrated by intertwining the fibers,
On the first surface, the fibers constituting the second fiber layer are not exposed,
On the second surface, the fibers constituting the first fiber layer are not exposed,
A packaging nonwoven fabric in which the fibers constituting each fiber layer are intertwined near the interface between the first fiber layer and the second fiber layer. The non-adhesive fiber is at least one selected from non-thermoplastic fibers and thermoplastic fibers having a melting point 30° C. or higher higher than the resin having the lowest melting point among the components constituting the adhesive fiber.
The packaging nonwoven fabric according to claim 1 or 2. The packaging nonwoven fabric according to claim 1 or 2, wherein the non-adhesive fibers are cellulose fibers. In the adhesive fiber, the core component is a high melting point component,
Contains a core-sheath type composite fiber whose sheath component is a component that adheres at a temperature 30°C or more lower than the melting point of the core component.
The packaging nonwoven fabric according to claim 1 or 2. The nonwoven fabric for packaging according to claim 1 or 2, wherein fibers are not bonded to each other in the second fiber layer. In the laminated nonwoven fabric, the stress at 10% elongation in the MD direction is 5.0 N/5 cm or more and 20.0 N/5 cm or less,
The stress at 10% elongation in the CD direction is 0.7 N/5 cm or more and 4.0 N/5 cm or less,
The packaging nonwoven fabric according to claim 1 or 2. The first fiber layer has a basis weight of 10 g/m ² or more and 40 g/m ² or less,
The second fiber layer has a basis weight of 10 g/m ² or more and 40 g/m ² or less,
The packaging nonwoven fabric according to claim 1 or 2. A laminated nonwoven fabric including a first fibrous layer and a second fibrous layer, the first fibrous layer forming a first surface of the nonwoven fabric,
A method for producing a packaging nonwoven fabric, wherein the second fiber layer forms a second surface of the nonwoven fabric,
producing a first fibrous web containing 80% by mass or more of adhesive fibers based on the total mass of the first fibrous web constituting the first fibrous layer;
producing a second fibrous web containing 80% by mass or more of non-adhesive fibers based on the total mass of the second fibrous web constituting the second fibrous layer;
an adhesion step of adhering the fibers of the first fibrous web to each other using the adhesive fibers;
a laminating step of laminating the first fibrous web and the second fibrous web after the adhesion step to obtain a laminated fibrous web;
an entangling step of jetting a water stream to the second fibrous web side of the laminated fibrous web to hydro-entangle and integrate the fibers of the first fibrous web and the second fibrous web;
A method for producing a nonwoven fabric for packaging, including: In the adhesion step, the adhesive fiber includes a core-sheath type composite fiber in which the core component is a high melting point component and the sheath component is a component that adheres at a temperature lower than the melting point of the core component by 30 ° C. or more,
10. The method for producing a packaging nonwoven fabric according to claim 9, wherein the heat treatment is performed at a temperature higher than or equal to a temperature at which the sheath component of the adhesive fiber melts and at a temperature that is 25° C. higher than the melting temperature. The method for manufacturing a packaging nonwoven fabric according to claim 9, further comprising a drying step of performing a drying treatment at a temperature at which the adhesive fibers do not melt after the entangling step. A packaging material comprising the laminated nonwoven fabric according to claim 1 or 2.