JPS581218B2 - Laminated dry nonwoven fabric and its manufacturing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a laminated dry-laid nonwoven fabric, in particular, it has a layer made only of composite fibers on both sides of a layer made of pulp fibers and a thermoplastic resin, and it has a layer made only of composite fibers on both sides of the layer made of pulp fibers and a thermoplastic resin. The present invention relates to a laminated dry-type nonwoven fabric having a three-layer integral structure in which fibers are bonded together, and a method for manufacturing the same.

The laminated dry-laid nonwoven fabric of the present invention has a major feature in that it has layers consisting only of composite fibers on both the upper and lower surfaces, and it has been known for a long time to use composite fibers as constituent fibers of the nonwoven fabric.

For example, Japanese Patent Publication No. 44-22547 discloses a method for producing a low-density non-woven fiber product in which a non-woven batt containing at least 5% of sheath monofilament composite fibers is thermally self-bonded. , Japanese Patent Publication No. 52-12830 also states that a web containing at least 10% of parallel composite fibers is made of a web containing at least 10% of parallel composite fibers,
Nonwoven fabrics heat-treated at or below the melting point of high melting point components and methods for producing the same have been disclosed, but all of these are single-layer nonwoven fabrics containing composite fibers, and the laminated nonwoven fabric of the present invention is not suggested.

Furthermore, in Japanese Patent Publication No. 54-1833, a curved surface obtained by preheating a web containing at least 30% (by weight) of composite fibers to a temperature 50°C lower than the melting point of the heat-sealing component and then press-molding Although a method for producing a nonwoven molded sheet having the following is disclosed, it is completely different from the present invention in that the nonwoven sheet is hot press molded.

As a result of intensive research into highly safe laminated dry non-woven fabrics used in food and medical fields, the inventors of the present invention found that by using composite fibers in the upper and lower surface layers, the fabric is strong and the constituent fibers do not fall off. We have completed the invention of an unprecedented laminated dry-type nonwoven fabric with a three-layer integral structure that can be heat-sealed on both sides, and a method for manufacturing the same.

The present invention provides composite fibers made of two types of synthetic polymers with different melting points on both sides of a layer made of 40 to 95% by weight of pulp fibers and 5 to 60% by weight of fibrous or powdery thermoplastic resin.
The laminated mat has a layer of 0% by weight, and the laminated mat is heat treated at a temperature higher than the melting point of the low melting point component of the composite fiber and the melting point of the thermoplastic resin and lower than the melting point of the high melting point component of the composite fiber. The present invention is a laminated dry nonwoven fabric having a three-layer integral structure in which fibers within each layer and between layers are bonded, and a method for producing the same.

The conjugate fiber made of two types of synthetic polymers with different melting points used in the present invention is a high melting point component such as a component made of polypropylene and a low melting point component having a melting point at least 20°C or more lower than the melting point of the high melting point component, such as a component made of polypropylene. It refers to a composite fiber obtained by parallel spinning or sheath-core spinning with a component consisting of polyethylene, and any other composite fiber may be used in combination as long as it meets the purpose of the present invention, and different types of composite fibers may be used together. May be used together.

Further, as the pulp fiber, wood pulp, cotton linter, etc. are used.

As the fibrous or powdery thermoplastic resin, any resin can be used as long as it has a melting point at least 20° C. lower than the melting point of the high melting point component of the composite fiber used in combination.

For example, as the fibrous thermoplastic resin, polyolefin-based synthetic pulp such as polyethylene is suitable, and as the granular thermoplastic resin, granular material such as polyethylene is used.

Each of the above fibers and resins has 100 composite fibers in the upper layer and the lower layer.
% by weight is used, and the middle layer contains 40-95% by weight of pulp fibers and 5-60% by weight of fibrous or powdery thermoplastic resin.

Composite fibers were used for the upper and lower surface layers because the composite fibers were heat-treated after mat formation, so that only the low-melting point components were fused at the fiber entanglement points, while the high-melting components remained in the form of fibers. This is because a nonwoven fabric can be obtained which forms a porous structure and has excellent bulkiness, flexibility, and air permeability unique to nonwoven fabrics, as well as excellent surface abrasion resistance and tensile strength.

Therefore, in the present invention, the upper and lower surface layers are made of 100% composite fibers.

As an application of the present invention, the present inventors used 20 to 80% by weight of composite fibers and 80 to 80% by weight of natural or chemically synthetic fibers as a surface layer.
An invention incorporating 20% by weight has also been completed.

The composition of the material for the middle layer is mainly made of pulp fibers, and a fibrous or powdery thermoplastic resin is added thereto mainly for reasons of economy and safety when used in food and medical applications. However, fibrous or powdery thermoplastic resin is
Like the low-melting point component of composite fibers, it becomes molten when heat treated and acts as an adhesive for other fibers, so the amount to be blended may be less than that of pulp fibers, but it can be blended up to 60%.

If it exceeds 60%, the heat-sealed area increases, impairing the breathability of the middle layer, which is not preferable.

The feature of the present invention is that the structure of the laminated dry-laid nonwoven fabric uses 100% composite fibers in the upper and lower layers, and the middle layer mainly contains pulp fibers and a fibrous or powdery thermoplastic resin. The three-layer integrated structure is obtained by performing heat treatment at a temperature lower than the melting point of the high melting point component and higher than the melting point of the low melting point component to bond fibers within each layer and between the layers.

With the above structure, the upper and lower layers using composite fibers have excellent abrasion resistance and tensile strength, and are firmly bonded to the constituent fibers of the middle layer, thereby preventing the pulp fibers of the middle layer from falling off.

The middle layer is mainly composed of bulp fibers, and the amount of fibrous or powdery thermoplastic resin as an adhesive can be increased or decreased from 5 to 60% depending on the application.

That is, when water retention and absorbency are required for medical purposes, etc., the blending ratio of pulp fibers may be increased.

In this way, the nonwoven fabric of the present invention has pulp fibers, polyolefin-based composite fibers, and thermoplastic resins in each layer for food hygiene,
Constructed only from materials that are highly safe for medical use.

The biggest advantage of implementing the present invention is that conventional water-based adhesives are not used, so there is no contamination of machinery during manufacturing, there is no need for wastewater pollution, and there is no risk of evaporation of the water-based adhesive. Labor and labor, such as eliminating the need for heat consumption,
Energy consumption can be significantly reduced, and manufacturing equipment can be reduced to a smaller scale, making it possible to provide a laminated dry nonwoven fabric that is inexpensive and highly safe.

Another feature is that since heat-bondable composite fibers are used on the front and back sides, a laminated dry nonwoven fabric with a three-layer integrated structure and heat-sealable properties on both sides can be obtained.

Furthermore, when the laminated nonwoven fabric of the present invention is used for applications such as underpads, film lamination is performed on the surface.

When polyethylene extrusion lamination is applied to a nonwoven fabric surface made of ordinary pulp fibers, it will not adhere unless it is pressed very strongly with a roll nip after extrusion, but in the present invention, the extruded polyethylene easily fuses with the composite fibers of the front and back layers. Therefore, the press pressure of the extruder can be lowered, and as a result, a bulky film-bonded nonwoven fabric can be obtained.

The laminated dry nonwoven fabric of the present invention can be obtained as follows.

Composite fibers are unpacked and defibrated using an opener.

Pulp fibers are obtained by passing the pulp winding through a coarse frame machine, and separately subjecting a fibrous or powdery thermoplastic resin to a coarse crusher, which is sent to a fibrillator through a quantitative feeder, and is defibrated together with the pulp fibers.

First, the defibrated composite fibers are used as a lower layer by forming a web on an endless wire mesh using a random webber.

Next, a mixture of the pulp fibers and a fibrous or powdery thermoplastic resin is laminated on the lower mat while forming a mat using a mat former to form a middle layer.

Furthermore, while forming a web using a random web, the composite fibers are laminated on the middle layer to form an upper layer, thereby forming a mat with a three-layer structure.

This mat is introduced into a hot air oven whose temperature is adjusted to a temperature higher than the melting point of the low melting point component of the composite fiber and the melting point of the thermoplastic resin, and lower than the melting point of the high melting point component of the composite fiber, and is heat-treated. The high melting point components remained in the form of fibers, and only the low melting point components fused at fiber entanglement points to form a porous structure, and at the same time, the thermoplastic resin in the middle layer was also fused and mixed uniformly within the middle layer. At the same time as the pulp fibers are fixed, the low melting point components of the upper layer and the lower layer are also fused to each other, yielding a laminated dry nonwoven fabric mat with a three-layer integral structure.

The laminated dry nonwoven fabric of the present invention with a three-layer integrated structure obtained as described above has excellent abrasion resistance and high tensile strength in the surface layer, and also has flexibility, bulkiness, and water absorption properties unique to nonwoven fabrics. Since it has excellent liquid absorbency, it is effective for use in medical and food hygiene applications such as disposable wet towels, disposable diapers, and underpads.

Examples of the present invention are shown below.

Example l Composite fibers with a high melting point component melting point of 165°C and a low melting point component melting point of 130°C (composite adhesive fiber ES system manufactured by Chisso Co., Ltd., 1.5 denier, 38w length) were defibrated while being unpacked with an opener, and then A web having an amount of 31/rrf is formed on an endless wire mesh using a random webber to serve as a lower layer.

Next, as wood pulp fibers, the NBKP pulp roll is passed through a coarse crusher, and the polyethylene synthetic pulp (SWP-E400 manufactured by Mitsui Zeraback Co., Ltd.) is crushed separately and sent to a disintegrating machine through a quantitative feeder. 80% by weight of pulp and 20% by weight of synthetic pulp
After mixing and defibrating in a defibrator at a ratio of 124 g/
A uniformly mixed defibrated mat of m is formed using a mat former to serve as the middle layer.

Furthermore, in the same manner as the lower layer above, 3 g of composite fibers with a basis weight of 3 g are added.
/m2 webs were formed using a random webber and overlapped to form the upper layer.

This three-layer laminated mat was introduced into an oven and heat-treated at 140°C to obtain a laminated nonwoven fabric having a three-layer integral structure according to the present invention.

The obtained laminated nonwoven fabric has an apparent density of 0. 0 4 g/
The water retention capacity is 18 times its own weight, and the surface layer has high wear resistance.
High tensile strength (3.5K9/100 strength),
It showed useful physical properties for disposable wet towels.

Furthermore, the mold that was heat-embossed at 140° C. did not disappear even after being wetted with water and maintained a beautiful appearance.

Example 2 100% by weight of composite fibers (composite adhesive fiber EA series manufactured by Chisso Co., Ltd., 3 denier, 5u length) with a melting point of a high melting point component of 165°C and a melting point of a low melting point component of 110°C were used for the upper and lower layers. The basis weight of the web is 5g/m2, and the basis weight of the middle layer mat is 2.
A laminated nonwoven fabric having a three-layer integral structure of the present invention was obtained in exactly the same manner as in Example 1 except that the nonwoven fabric was adjusted to 00 g/m'.

One side of this laminated nonwoven fabric was further extruded and laminated with polyethylene using an extruder to obtain a polyethylene bonded laminated nonwoven fabric.

This nonwoven fabric is highly flexible and absorbent, and one side is leak-proof, so it has excellent properties as an underpad.

Example 3 NBKP 50% by weight as wood pulp fiber and polyethylene synthetic pulp (SWP-E400 manufactured by Mitsui Zerabak)
A laminated nonwoven fabric having a three-layer integral structure of the present invention was obtained in exactly the same manner as in Example 1, except that 50% by weight of the nonwoven fabric was used in the middle layer.

The obtained laminated nonwoven fabric had high abrasion resistance in the surface layer and high tensile strength, and exhibited physical properties useful for disposable wet towels.

Furthermore, the mold that was heat-embossed at 140° C. did not disappear even after being wetted with water and maintained a beautiful appearance.

Claims (1)

[Scope of Claims] 1. Composite fiber 100 made of two types of synthetic polymers with different melting points on both sides of a layer made of 40 to 95% by weight of pulp fibers and 5 to 60% by weight of fibrous or powdery thermoplastic resin. % by weight, and has a melting point higher than the melting point of the low melting point component of the composite fiber and the melting point of the thermoplastic resin,
A laminated dry-type nonwoven fabric having a three-layer integral structure in which the laminated mat is heat-treated at a temperature lower than the melting point of the high-melting point component of the composite fiber, and the fibers within each layer and between the layers are bonded. 2 Composite fiber 1 consisting of two types of synthetic polymers with different melting points
00% by weight nonwoven fabric web is formed, then a nonwoven fabric mat consisting of 40 to 95% by weight of pulp fibers and 5 to 60% by weight of a fibrous or powdery thermoplastic resin is laminated on the composite fiber nonwoven fabric mat, Further, a 100% by weight nonwoven web of composite fibers made of two types of synthetic polymers with different melting points is laminated thereon to form a three-layer laminated mat. At a temperature higher than the melting point and lower than the melting point of the high melting point component of the composite fiber,
A method for producing a laminated dry nonwoven fabric, characterized in that the three-layer laminated mat is heat-treated to bond fibers within each layer and between the layers to form a three-layer integral structure.