JPH05179556A - How to join long fiber webs - Google Patents

Abstract

(57) [Abstract] [Purpose] To provide a method for firmly joining two long fiber webs. [Structure] First, two long fiber webs made of long fibers are prepared. Then, a laminate in which a short fiber web is sandwiched between the long fiber webs is obtained. The short fiber web is composed of hydrophilic free fibers having a free end and a fiber length of 60 mm or less. A fine high pressure water column flow is applied to this laminate. As a result, the hydrophilic free fiber group vigorously moves and entangles with the long fibers constituting the long fiber web. Therefore, the long fibers constituting the two long fiber webs are entangled with each other through the hydrophilic free fiber group, and the two long fiber webs are strongly bonded. The laminated sheet in which two long fiber webs are joined together can be used as a surface material for sanitary materials or a material for surgical clothes.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for joining long fiber webs in which two long fiber webs composed of hydrophobic long fibers are laminated and the long fiber webs are strongly joined together.

[0002]

2. Description of the Related Art Conventionally, long fiber webs composed of hydrophobic long fibers such as polypropylene and polyester have been widely used for various purposes. Depending on the intended use, it is necessary to laminate two long fiber webs and bond the long fiber webs together. Examples of the joining method include a method in which an adhesive is applied to the surface of the long-fiber web, and another long-fiber web is laminated on the adhesive to be joined, or two long-fiber webs are laminated and then partially joined. A method is adopted in which the long fibers constituting the two long fiber webs are melted and fixed to each other by heating and pressurizing.

However, the former method has a drawback that an adhesive layer is present between two long fiber webs, and the rigidity of the adhesive layer lowers the flexibility and feel of the laminated sheet. It was Further, the latter method also has a drawback that the portion where the long fibers are melted and fixed to each other becomes hard and the flexibility and the feel of the laminated sheet are deteriorated.

In order to solve such a drawback, a method of joining two long fiber webs by intertwining the long fibers constituting the long fiber web is conceivable. And
As a confounding method, it is possible to adopt a needle punch method or a water needling method. However, in the needle punching method, the long fiber web laminated with the barbed needles is pierced many times, so that the long fibers constituting the long fiber web are sometimes cut. When the long fibers are cut, there is a drawback that the tensile strength of the long fiber web is lowered, and eventually the tensile strength of the laminated sheet after joining is lowered. Also,
The water needling method is a method of imparting a high energy fine high-pressure water column flow to a laminated long fiber web and moving the long fibers with this energy to entangle the long fibers with each other. There were times when I wasn't fully entangled. If the entanglement is insufficient, there is a drawback that the obtained laminated sheet is easily peeled off.

[0005]

DISCLOSURE OF THE INVENTION The present inventor has examined why the water needling method does not sufficiently entangle the long fibers with each other. As a result, the following conclusions were reached. That is, since the long fibers are so long that the fiber length can be said to be infinite, the energy due to the fine high-pressure water column flow is imparted only to a part of the long fibers. And
This energy is absorbed in the longitudinal direction of the long fibers, and the long fibers themselves do not move much. Simply put, long fibers include
There are no free-moving edges due to the fine high-pressure water column flow. Therefore, the long fibers are not sufficiently entangled with each other. Further, since the long fibers are generally hydrophobic fibers, they easily repel a high-pressure water column flow, and energy due to the water column flow is not effectively imparted to the long fibers. Therefore, the long fibers do not move sufficiently and the long fibers do not sufficiently entangle with each other.

Therefore, according to the present invention, by arranging a specific fiber group that violently moves by a fine high-pressure water column flow between two long fiber webs, the entanglement between the fiber group and the long fibers is performed. This is to accelerate the fibers so that the long fibers are sufficiently entangled with each other through the fiber group, so that the long fiber webs are joined together.

[0007]

That is, the present invention relates to a continuous fiber web A composed of hydrophobic continuous fibers A and a hydrophobic continuous fiber B.
By applying a fine high-pressure water column flow to a laminate in which a short fiber web composed of a hydrophilic free fiber group having a fiber length of 60 mm or less having a free end is sandwiched between the long fiber web B composed of A long fiber characterized in that the free fibers are entangled with the long fibers A and B, the long fibers A and B are entangled with the free fibers interposed, and the long fiber web A and the long fiber web B are joined together. The present invention relates to a method for joining fibrous webs.

The long fiber web A used in the present invention is composed of hydrophobic long fibers A. As the hydrophobic long fibers A, polypropylene long fibers, polyester long fibers, polyamide long fibers, polyacrylonitrile long fibers and the like are used. Hydrophobic filament A in this filament web A
May or may not be bonded to each other. In order to bond the hydrophobic long fibers A to each other, they may be bonded with a synthetic resin binder, or the hydrophobic long fibers A may be melted and fixed and bonded to each other. in this way,
The long fiber web in which the hydrophobic long fibers A are bonded to each other is
It is generally called a spunbond nonwoven fabric. In the present invention, the hydrophobic continuous fiber A in the continuous fiber web A is used.
It is preferable that they are not bound to each other. This is because the fine fiber high-pressure water column flow increases the momentum of the long fibers A, which easily entangles with the free fibers. The long fiber web B is also constructed in the same manner as the long fiber web A, and is formed of hydrophobic long fibers B.

A short fiber web is sandwiched between a long fiber web A and a long fiber web B to form a laminate. The short fiber web is composed of hydrophilic free fibers having a free end and a fiber length of 60 mm or less. As the hydrophilic free fiber, pulp fiber, rayon fiber, cotton fiber or the like is used. The term "hydrophilic" as used herein means that it is easier to absorb water than the hydrophobic long fibers constituting the long fiber webs A and B. The free fiber means a fiber having a fiber length of 60 mm or less and having its edge freely moved, that is, having a free end, by a fine high-pressure water column flow. If the fiber length of the fibers constituting the short fiber web exceeds 60 mm, it is not preferable because the edges of the fibers do not freely move due to the fine high-pressure water column flow. In the short fiber web, the hydrophilic free fibers may exist in any state, but the hydrophilic free fibers must be in a state where they freely move by the fine high-pressure water column flow. For example, the hydrophilic fibers should not be in a state in which they are strongly bonded to each other, and even if a fine high-pressure column flow is applied, their edges do not move freely, that is, they cannot be said to have free ends. Therefore, as the short fiber web, paper or cotton-like material made of pulp fiber, cotton-like material made of rayon fiber or cotton fiber, and the like are preferably used.

A fine columnar high-pressure water stream is applied to the above-described laminate. Here, the fine high-pressure water column flow is obtained by ejecting water at high pressure through a nozzle hole having a fine diameter. For example, it can be obtained by ejecting water at a pressure of about 10 to 150 kg / cm ² through a nozzle hole having a hole diameter of about 0.01 to 0.2 mm. When this fine high-pressure water column flow is applied to the laminate, the hydrophilic free fiber groups forming the short fiber web move to form long fibers A and long fiber web B forming long fiber web A. The continuous filaments B are entangled with each other.
As a result, the long fibers A and the long fibers B are entangled with each other through the hydrophilic free fibers, so that the long fibers web A and the long fibers web B are joined.

[0011]

【Example】

Example 1 Polypropylene resin [MFR40, molecular weight distribution (Q value) = 2.
9], melting temperature 230 ℃, ejector pressure 3kg
Polypropylene filaments were obtained by melt-spinning at / cm ² , and the polypropylene filaments were collected on a conveyor to prepare a filament fiber web A having a basis weight of 12 g / m ² and a width of 1000 mm. In the long fiber web A, the polypropylene long fibers are not bonded to each other, and the polypropylene long fibers are simply accumulated in a sheet form. Softwood bleached kraft pulp (N
A short fiber web having a basis weight of 20 g / m ² made of BKP and an average fiber length of pulp fibers of 4.5 mm) is laminated, and a long fiber web B having the same constitution as the long fiber web A is further laminated thereon, A laminate was obtained. Next, this laminate was placed on a transfer conveyor formed of wire mesh and introduced into a water column flow jetting device in which 1000 nozzle holes having a hole diameter of 0.1 mm were arranged side by side with a pitch of 1 mm, and 30 kg / cm ² from the nozzle holes. A water column flow was ejected by the water pressure of, and the laminate was subjected to the water column flow. The water column flow was applied so as to penetrate in the thickness direction of the laminate, and the moving speed of the laminate in the plane direction at this time was 30 m / min. Then, a water column flow was applied from the back surface of the laminate in the same manner. At this time, the polypropylene filaments were not entangled with the wire mesh of the transfer conveyor.

The laminated sheet obtained by the above method was one in which the long fiber web A and the long fiber web B were firmly bonded to each other, were not easily peeled off, and were soft and excellent in feeling. Further, when the water absorption / water retention of this laminated sheet was measured, it showed 30% water absorption / water retention. Here, the method of measuring water absorption and water retention is as follows. That is, 20 cm x
A sample having a size of 20 cm is immersed in water at room temperature for 2 minutes to be taken out, water adhering to the surface is lightly wiped with a tissue, the weight is measured, and the water content is taken as w ₀ . After that, the sample is hung in a constant temperature and constant humidity chamber having a temperature of 20 ° C. and a relative humidity of 65% for 5 minutes and left to stand, and then the weight is measured and the water content is taken as w ₁ . The value calculated by (w ₁ / w ₀ ) × 100 is taken as water absorption / water retention.

Example 2 As a short fiber web, rayon fibers having a fineness of 2 denier and a fiber length of 32 mm were collected in a futon-like shape and had a basis weight of 20 g / m ^2.
The continuous fiber web A and the continuous fiber web B were joined in the same manner as in Example 1 except that the above-mentioned one was used. At this time, as in Example 1, the polypropylene filaments were not entangled in the wire mesh of the transfer conveyor. In addition, the laminated sheet obtained by this method was one in which the long fiber web A and the long fiber web B were firmly bonded to each other, were not easily peeled off, and were soft and excellent in feeling. Further, when the water absorption / water retention of this laminated sheet was measured, it showed 31% water absorption / water retention.

Comparative Example A laminated sheet was obtained in the same manner as in Example 1 except that the short fiber web was not used. That is, the continuous fiber web A and the continuous fiber web B used in Example 1 were laminated to give a basis weight of 24 g /
A laminated web of m ² was obtained, and this laminated web was introduced into a water column flow ejection device to obtain a laminated sheet. When this laminated sheet was obtained, polypropylene filaments were sometimes entangled with the wire mesh of the transfer conveyor used. Then, the obtained laminated sheet has a long fiber web A and a long fiber web B.
The long fibers A and B constituting the above are not sufficiently entangled with each other, the long fiber webs A and B are easily peeled off, and it is difficult to handle them as a single sheet. Further, the water absorption / water retention of this laminated sheet was measured and found to be 0%.

[0015]

The method for joining long fiber webs according to the present invention is to apply a fine high-pressure water column flow to a laminate in which a short fiber web is sandwiched between two long fiber webs. Since the short fiber web is composed of a group of hydrophilic free fibers having free ends and having a fixed fiber length or less, the short fiber web violently moves by a fine high-pressure water column flow. As a result, the long fibers forming the long fiber web and the hydrophilic free fiber group are entangled with each other, and the long fibers forming the two long fiber webs are entangled with each other.
Therefore, the two long fiber webs are firmly bonded to each other. This is, for example, a laminate obtained by laminating two long fiber webs without sandwiching a short fiber web, even if a fine high-pressure water column flow is applied, since the long fibers constituting the long fiber web have no free ends, Long fibers do not exercise violently. For this reason,
The long fibers constituting the two long fiber webs are not sufficiently entangled with each other, and the long fiber webs are not strongly bonded to each other.
Further, even if a short fiber web composed of a group of hydrophobic fibers is sandwiched between two long fiber webs and subjected to a high-pressure water column flow, the hydrophobic fibers repel the water column flow, and Do not exercise as hard as you do. Therefore, the long fibers and the hydrophobic fibers are not sufficiently entangled with each other, and as a result, the two long fiber webs are not firmly joined to each other.

[0016]

As described above, by adopting the method according to the present invention, it is possible to firmly bond two continuous fiber webs without using an adhesive. Further, the two long fiber webs can be firmly bonded without melting and fixing the long fibers constituting the long fiber web. Therefore, it is possible to obtain a laminated sheet in which two long fiber webs are laminated without impairing the flexibility and feel of the long fiber web. Therefore, the laminated sheet obtained by the method according to the present invention can be suitably used as a surface material such as sanitary material, a surgical gown, and a material such as a mask. In addition, in order to suppress the fluffing of the long fibers constituting the long fiber web, an adhesive may be added to the long fiber web to bond the long fibers to each other, or the long fibers may be melted and fixed. It goes without saying that the long fibers may be bonded to each other.

Claims (1)

[Claims] 1. A hydrophilic free fiber group having a free end and a fiber length of 60 mm or less between a continuous fiber web A composed of hydrophobic continuous fibers A and a continuous fiber web B composed of hydrophobic continuous fibers B. The long fibers A and B are entwined with the free fibers by applying a fine high-pressure water column flow to the laminate sandwiching the short fiber web composed of, and the long fibers A and B are interposed between the free fibers. A method for joining long fiber webs, characterized in that the long fiber webs A and B are joined together by entanglement.