JPH04185793A - Wet non-woven fabric and method for producing the same - Google Patents

Abstract

PURPOSE:To obtain the subject non-woven fabric having excellent hand touch and barrier property and useful for filters, etc., by forming specific fibers into a sheet by a paper-making method, treating the formed sheet with a column-like water flow to interlace the fibers and simultaneously divide the fibers, thereby interlacing the divided ultrafine fibers, etc., three-dimensionally. CONSTITUTION:Fibers having a fiber length of <=210mm, e.g. dividable fibers such as polyester/polyethylene conjugate fibers are formed into a sheet (having a unit weight of preferably 5-500g/m<2> by a paper-making method, and the formed sheet is treated with a column-like water flow having a high pressure of 10-150kg/cm<2> to interlace and simultaneously divide the fibers, thereby mutually interlacing the divided ultrafine fibers and/or ultrafine fiber strands having a single fiber fineness of <=0.8d to provide the objective non-woven fabric.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a high-strength wet-laid nonwoven fabric with extremely excellent texture and a method for producing the same. More specifically, the present invention relates to a high-strength ultrafine fiber nonwoven fabric that has excellent texture, drapeability, and barrier properties and is suitable for a wide range of uses such as wipers, filters, and surgical gowns, and a method for producing the same.

[Conventional technology]

It is known that ultrafine fibers can be used to obtain nonwoven fabrics with excellent surface feel and texture.

However, ultrafine fibers have low productivity and high cost,
If used as it is, there is a problem that a satisfactory nonwoven fabric cannot be obtained because the diameter of the single filament is small, so the workability is poor in terms of opening properties, and sheet formation by carding is also poor. Therefore, a number of methods have been proposed for forming a web using easily splittable conjugate fibers and then producing ultrafine fibers.

For example, a method is disclosed in which an ultrafine fiber nonwoven fabric is produced by forming incompatible splittable conjugate fibers into a web using a card, and then splitting and fibrillating the fibers with a high-pressure liquid stream (Japanese Patent Application Laid-Open No. 133161/1982). .

However, in conventional technology, the fiber length is long (usually 32
~50 mm), which is difficult to move due to high-pressure liquid flow, making it difficult to provide composite fibers that develop strength, and further splitting to make ultra-fine fibers requires a large amount of engineering energy and costs are high. In addition, the strength properties of the obtained microfiber nonwoven fabric are low, and in order to increase the strength, an interfiber adhesive component such as a binder is required, so even if it is partially bonded, it has poor flexibility.
The characteristics of the ultrafine fiber nonwoven fabric cannot be fully demonstrated, such as the texture becomes hard.

Furthermore, there were other problems such as the conjugate fibers splitting during the web forming step using the carding method, making it impossible to obtain a uniform nonwoven fabric.

[Invention or problem to be solved]

An object of the present invention is to provide a wet-laid nonwoven fabric that has excellent surface feel, is dense, has excellent barrier properties, is highly flexible, and has excellent strength and physical properties, and a method for producing the same.

[Means to solve the problem]

That is, the present invention is as follows.

1.0 fibers split from splittable fibers with a fiber length of 20 mm or less
, a wet-laid nonwoven fabric in which ultrafine fibers and/or ultrafine fiber bundles of 8 d or less are intertwined with each other in three dimensions.

2. Form a sheet of splittable fibers with a fiber length of 20 mm or less using a papermaking method, and then treat with a columnar water stream to entangle and split the splittable fibers to form a sheet of 0.8 d.
A method for producing a wet-laid nonwoven fabric, which comprises three-dimensionally intertwining the following ultrafine fibers and/or ultrafine fiber bundles.

The splittable fibers in the present invention refer to incompatible multicomponent composite fibers, such as polyester/polyolefin, polyester/polyamide, polyester/copolyester, etc., or easily splittable fibers having a large number of hollow spaces within the fibers, such as Asahi Kasei Industries trademark Cashmilon FCA, etc., or self-adhesive fiber.

The fineness of the splittable fibers is not particularly limited, but when considering the single fiber fineness after splitting and the number of split fibers, it is preferably 1 to 3 d.

In the present invention, the ultrafine fiber bundle refers to a bundle of splittable fibers that are split and aggregated, but not separated.

The nonwoven fabric of the present invention is composed of fibers with a specific fiber length, and it is an essential condition that they are intertwined at a high intertwining density, and for the first time with this structure, a nonwoven fabric with high strength and high surface feel, which was not found in conventional ultrafine fiber nonwoven fabrics, has been created. can get.

The fiber length of the splittable fibers constituting the nonwoven fabric must be 208 mm or less, preferably 15 mm Ja or less.

In order to obtain an ultrafine fiber nonwoven fabric by subjecting a fiber sheet with a fiber length of 20 mm or more to columnar flow treatment, sufficient splitting of splittable fibers cannot be achieved unless high pressure water flow is used.

Moreover, the strength and physical properties of the sheet obtained are weak.

However, by using a fiber sheet with a fiber length of 20 mm or less, the splitting of splittable fibers progresses through columnar flow treatment at very low water pressure, and a high-strength ultrafine fiber nonwoven fabric that cannot be obtained with a fiber sheet of 20 mm or more can be obtained. Therefore, the object of the present invention has been achieved.

This surprising fact can be inferred as follows.

When water energy is applied to the fiber sheet, the fibers are entangled and split. At this time, when fiber entanglement and fiber splitting are compared, fiber entanglement is easy, so entanglement mainly proceeds at first. However, there is a limit to the progress of entanglement, and after that the energy of the water flow is mainly used for splitting the fibers. Entanglement is mainly performed between large-diameter fibers before splitting, and this entanglement effect is effective in developing the strength of the nonwoven fabric. That is, the strength of the obtained nonwoven fabric is related to the single yarn diameter and fiber length of the splittable fibers, and the ratio of the single yarn diameter of the splittable fibers to the fiber length, L/D, is 0.5X.
When it is in the range of 102 to 1.5 x 10', the highest strength can be obtained from the constituent fibers. If the fiber length is short, the fibers are columnar, easy to move and entangled, or the number of intertwining points is small, and the strength of the nonwoven fabric is reduced. Furthermore, splitting of splittable fibers by columnar flow is performed with lower impact force as the fiber length becomes shorter, but this effect is particularly remarkable when the fiber length is 20 mm or less. Therefore,
The use of splittable fibers with a fiber length of 20 fibers or less is an essential component.

The most desirable form of microfiber nonwoven fabric is to split all the splittable fibers4), and even if unsplit fibers are present in the nonwoven fabric, the strength and physical properties will not deteriorate, so the texture,
From the viewpoint of surface feel, sheet covering properties, and barrier properties, the proportion of unsplit fibers is preferably 50% or less, and 20% or less.
% or less is more preferable.

Since the nonwoven fabric of the present invention is strongly three-dimensionally entangled by columnar flow, it has sufficient physical strength properties (tensile strength, tear strength, peel strength, etc.) without using bonding means such as adhesive,
Furthermore, it has a soft texture and droopy properties.

Since the nonwoven fabric of the present invention has excellent strength, it can be used as it is for wipers, surgical gowns, filters, etc., or depending on the application, it can be subjected to finishing treatments such as coloring, water repellency, and antistatic finishing. Further, a binder may be added.

The method for producing a nonwoven fabric of the present invention is to form a sheet of fibers made of splittable fibers with a fiber length of 20 mm or less by a papermaking method, and then to treat the splittable fibers with a columnar water stream to entangle and split the splittable fibers, and to create a fiber of 0.8 dJff. The lower ultrafine fibers and/or ultrafine fiber bundles are three-dimensionally entangled with each other.

A paper-making method is used to make the above-mentioned short fibers into a fiber sheet with a weight of 5 to 500 g/rrf depending on the purpose.

This papermaking method has good sheet uniformity, heat-fused fibers,
It is easy to mix different types of fibers such as synthetic valves, valves, and ordinary synthetic fibers, and in some cases, it is also possible to combine two layers, which is a major advantage compared to dry methods such as carding and air laying methods. .

Another important point is that the mechanical shearing force applied during sheet production is small compared to the card method, air lay method, etc.

In order to obtain ultra-fine fibers, impact force is applied to the splittable fibers to split them.This is done during or after fiber entanglement for the reasons mentioned above. It must be avoided as much as possible. Due to this restriction in the card method, air lay method, etc., the structure of the splittable fibers must be limited to one that is more difficult to split, and therefore the fiber sheet must be treated with even higher energy during entanglement and splitting. .

On the other hand, the papermaking method allows the structure of the splittable fibers to be selected from a wide range, which has the advantage of saving energy and adapting the fiber composition to a variety of uses.

The obtained fiber sheet is placed on a water-permeable support material and entangled with a columnar high-pressure water stream. The water pressure range of the high-pressure water stream used varies depending on the type of yarn used, the basis weight of the fiber sheet, the processing speed, etc., and is preferably 5 to 300 kg/cm.
More preferably, the collision is performed in the range of to-150 kg/atf. In the case of the same yarn, the higher the basis weight, the higher the water pressure should be set.

A water-permeable member 1 such as a wire mesh, a plastic net, etc. is used as a supporting material for the fiber sheet.

In the present invention, a perforated nonwoven fabric can be obtained by changing the shape of this member. In other words, by using a water-permeable member with a high proportion of surface irregularities or non-perforated areas, the entangled and split fibers are moved to the recesses or perforations and placed in positions corresponding to the protrusions or non-perforated parts of the member. This causes an opening. If a wire mesh is used for the member, a coarse mesh of 50 mesh or less is preferable. The nonwoven fabric of the present invention obtained by using a supporting material that generates such openings has the effect of improving bulkiness, dimensional stability (elongation recovery rate), etc. compared to before patterning with openings. Is recognized.

In the present invention, the nozzle diameter that sprays the water stream is 0.01 to 1
Is it preferable to have a diameter of mm?Since it is better to apply a high impact force to splitting fibers, it is better to have a larger diameter at the same water pressure.

The distance between the nozzle and the sheet surface is preferably 0 to 50 strokes.

The shape of the trajectory of the water stream may be a straight line parallel to the direction of travel of the sheet, or it may be a curved shape obtained by the rotational movement of a header equipped with a nozzle or the vibration motion that reciprocates at right angles to the direction of travel of the sheet. It's okay. However, in order to split almost all the fibers, the water stream must hit the entire sheet area without fail, and the entanglement of the multiple circular water stream trajectories obtained by the rotational motion at that point is per nozzle spindle. The jetting area of the water stream against the sheet becomes larger, making it more efficient. At the same time, depending on the application, it is preferable because it has the advantage that it is difficult to see spots in the trajectory of water flow that reduce the commercial value, and furthermore, the strength ratio of the warp to warp of the nonwoven fabric is small. If necessary, if the water flow trajectory remaining on the sheet surface impairs the quality of the product, insert a wire mesh of 40 to +00 mesh between the nozzle and the sheet to transform the columnar water flow into sprinkling water to reduce the depth of the water flow trajectory. is also preferable.

The paper sheet may be treated with a high-pressure water stream by spraying the water stream alternately on the front and back sides, or by treating only one side. Moreover, the optimum conditions for the number of processing times may be selected depending on the purpose.

As one mode of post-processing of the wet-laid nonwoven fabric obtained in the present invention, it is also preferable to perform cold or hot pressing with an engraved roll (emboss roll) to shape the surface. According to this method, the fibers of the intertwined sheet are partially bonded to each other, but not only the strength such as tensile strength is improved, but also the dimensional stability is improved.

As described above, the nonwoven fabric of the present invention has the uniformity characteristic of the wet method, as well as high strength and soft texture, so it can be used in new applications that are difficult to apply with conventional nonwoven fabrics. can.

One of the preferred examples is materials for medical and sanitary materials, such as medical materials such as surgical packs, surgical gowns, and underpads, and sanitary materials such as diapers, napkins, and masks. In these applications, the excellent drapability and high strength characteristics of the nonwoven fabric of the present invention are well utilized.

In particular, when the nonwoven fabric of the present invention is used in surgical gowns, the property of excellent liquid barrier properties, which is particularly required for surgical gowns, can be effectively utilized. Since the nonwoven fabric of the present invention is made of microfibers split from short fibers having a specified fiber length and intertwined at a high density, the nonwoven fabric itself has high liquid barrier properties. In an attempt to obtain the liquid barrier properties required for surgical gowns using conventional nonwoven fabrics, for example, as disclosed in Japanese Patent Application Laid-Open No. 59-94659, a nonwoven fabric made of polyester (polyethylene terephthalate) and made of fine fibrils was used. In the present invention, a method has been devised to increase the density of the nonwoven fabric by jetting a columnar water stream onto a sheet obtained by laminating or mixing wood pulp to entangle the valves with the polyester in a so-called "packing" manner. It has been confirmed that excellent liquid barrier properties can be obtained without the use of special binder fibers.

When the nonwoven fabric of the present invention is used as an interlining material for clothing, it is also suitable because its characteristics of uniformity and high strength are well utilized. It is also suitable for industrial wiping cloths such as those used in the electronic field. This is because the nonwoven fabric of the present invention or no binder has excellent lint-free properties because the fibers are firmly joined by interlacing the fibers, and is flexible and has excellent wiping properties. Furthermore, it is also recognized to be suitable as a filter for gases and liquids, especially as a so-called pre-filter that handles particles of 5 to 25 μm. This is a result of the fact that the ultrafine fibers in this nonwoven fabric are densely intertwined, or are fully utilized for its filter function.

When using the nonwoven fabric of the present invention as a coating base fabric,
The characteristics of the nonwoven fabric of the present invention are utilized.

Attempts have been made to use conventional nonwoven fabrics as coating base fabrics instead of conventional woven or knitted base fabrics, but these nonwoven fabrics have lower interlayer peel strength than woven or knitted fabrics, so polyurethane is added to the surface of the nonwoven fabric. If the coated product is coated only with polyvinyl chloride or polyvinyl chloride, the resulting coated product often suffers from peeling between the layers of the nonwoven fabric during use, making it unsuitable for practical use.

In order to improve this drawback, it has been attempted to apply an elastic polymer such as polyurethane, polyacrylic acid ester, SBR, MBRSNBR, etc. as a binder to the nonwoven fabric in advance, and then coat the surface with polyurethane, polyvinyl chloride, etc. In this case, it was inevitable that the texture would be paper-like and the quality would be inferior to that of the woven or knitted base fabric.

In contrast, the nonwoven fabric of the present invention has extremely high delamination strength compared to conventional nonwoven fabrics, so it can be used as a coating base fabric without a binder, and it can be used as a coating base fabric using conventional nonwoven fabrics. It has new characteristics, such as a soft texture and high delamination strength.

One suitable example is to use the nonwoven fabric of the present invention as a base fabric for artificial leather. For example, if this nonwoven fabric is used as a base fabric, its surface may be coated with polyurethane, vinyl chloride, S.
A silver-like artificial leather can be obtained by applying a solution or emulsion of an elastic polymer such as BR, NBR, or MBR using a gravure machine, a doctor knife, or the like. In this case, it is more preferable in terms of strength and texture to impregnate the nonwoven fabric with an elastic polymer such as polyurethane and dry or wet coagulate and fill it, if necessary, before forming the surface coating layer.

Furthermore, if you want to obtain suede-like artificial leather, the ultrafine interlaced layer of this nonwoven fabric is raised, and if necessary, it can be impregnated with an elastic polymer or dyed to produce the desired suede-like artificial leather. It is also possible to obtain

Next, a method for producing a high-strength wet-laid nonwoven fabric of the present invention will be explained.

First, a slurry is prepared by dispersing splittable fibers having a fiber length ratio of 20 or less in water to a concentration of 0.1 to 3%. At this time, it is preferable to add a small amount of a dispersant. This slurry is made into paper using a fourdrinier type or circular net type paper making machine.

In the present invention, the type of yarn constituting the paper-made sheet may be appropriately selected depending on the purpose, and it is also preferable to use a mixture of two or three types of yarn of different materials and/or shapes.

The resulting formed sheets are entangled by impinging high velocity fluid streams. The fluid referred to here may be a liquid or a gas, and water is most preferable in terms of ease of handling, cost, and high collision energy as a fluid.

In this way, the wet-laid nonwoven fabric of the present invention is obtained.

〔Example〕

Hereinafter, the present invention will be explained in more detail with reference to Examples.

In the Examples, the measured values were determined by the following method, and all percentages are by weight.

■) Tensile strength: J[5L1096 Strip method 2
) Tear strength JrSL1096 Single tank method 3
) Interlayer peel strength - Cut the nonwoven fabric into a piece with a width of 2.5 cm and a length of 13 cm.

Adhesive tape (manufactured by Sony Chemical ■, trade name D 3200) was adhered to this sample, and the samples were pressed together at 200° C. for 130 seconds at a pressure of 70 g/cof.

A slit is made between the adhesive tape and the nonwoven fabric of the measurement sample thus obtained, and both ends are gripped with an autograph chuck and measured.

The measurement conditions for the autograph are set as follows.

Tensile speed: 10 cm/min Chart speed: 10 cm/min In this case, the tape is strong and the pronged tape and non-woven fabric are firmly adhered, so when the tape of the measurement sample is peeled off from the measurement sample, the tape The peeling force acts to peel one part of the nonwoven fabric from another part without cutting or peeling off the adhesive surface between the tape and the nonwoven fabric. Therefore, the delamination strength of a nonwoven fabric can be measured by this method.

From the stress-strain curve obtained when performing the above measurement using an autograph, three of the larger intensity values and three of the smaller intensity values are selected, and the average value of the six values in total is obtained. The number of test samples for measurement is 5. Such measurements are performed in the same manner in the longitudinal direction (hereinafter abbreviated as MD) and the horizontal direction (hereinafter abbreviated as CD) of the nonwoven fabric, and the average value of the MD and CD is taken as the interlayer peel strength of the nonwoven fabric.

4) Flexibility: The average value of JrSL1096 45° force antilever method MD and CD is taken as the flexibility.

Example 1 Nylon 6 with polyethylene terephthalate as the first component
A splittable fiber (capacity ratio 8:2) with a fineness of 1d and nylon 612 as a second component is cut into 10 mm (L/D is 10 mm).
Xl0'')L was dispersed in water to make a slurry with a concentration of 1%. This slurry was made into paper using an inclined fourdrinier machine, and the fabric weight was 6.
A sheet of 0 g/rrf was obtained.

This sheet has a nozzle diameter of 0.2 mm and a nozzle pitch of 5.
M, a columnar flow with a water pressure of 40 kg/d was injected from a large number of nozzles with 18 rows to entangle and split the fibers (polyethylene terephthalate after splitting becomes equivalent to 0.1 d).
. The interval between the nozzle-formed sheets was 30 mm, and an 80-mesh stainless steel wire mesh was used as a supporting member under the sheet, and water was suction-dehydrated through the wire mesh. The same treatment was applied to the opposite side of the sheet to which the columnar flow was sprayed.

Next, the water pressure was set at 15 kg/al, and both surfaces were similarly sprayed with a columnar water stream. Thereafter, it was dried to obtain an entangled sheet. The physical properties showed the following values.

Tensile strength (MD/CD): 2.8/2.0k
g/cm tear strength (MD/CD): 1.3/1
．． 1 kg delamination strength: 2000 g
/an Flexibility (MD-CD): 35mm Example 2 Columnar flow water pressure was applied in the same manner as Example 1 at 60 kg for the first time.
/cd, and the second month was treated with 5 kg/ad. The obtained physical properties were as follows.

Tensile strength (MD/CD): 3.8/3 kg/a
n Tear strength (MD/CD): 1.5/1.2 kg Interlaminar peel strength: 2200 g/cm Flexibility (MD-CD average): 33 mm Comparative example 1 O, Id raw yarn of polyethylene terephthalate was produced by direct spinning method I made it and cut it to a length of 1OInJn (LD is 1
x103). This was subjected to paper making and columnar flow treatment in the same manner as in Example 1. The physical properties showed the following values.

Tensile strength (MD/CD): 0.910.9k
g/cm tear strength (MD/CD): 0.410.2
kg interlaminar peel strength: 900 g, / mouth flexibility (MD-CD average): 34 mm Comparative Example 2 The cut length of the splittable fiber was set to 51 cities in the same manner as in Example 1 (LD was 0.2XI03). Splitting did not progress sufficiently. The physical properties were as follows.

Tensile strength (MD/CD): 0.710.7k
g/cm tear strength (MD/CD): 2.4/2
．． 2 kg delamination strength: 200 g/
cm Flexibility (MD-CD average): 43 mm Comparative Example 3 Dividable fiber 1d of the same constituent fiber as Comparative Example 2, cut length 51
mm was subjected to columnar flow treatment in the same manner as in Example 1.

However, the pressure is 80kg/ad for the first time and 15k for the second time.
g/aIr. Fiber splitting progressed to the same level as in Example 1. The physical properties were as follows.

Tensile strength (MD/CD): 0.7/0.8 kg
/ cm Tear strength (MD/CD): 2.0/
1.7 kg Peeling strength: 250 g
/cm Flexibility (MD - CD average): 36 mm Example 3 The cross-sectional shape of the raw yarn was 1d, lO + nm cut (LD/ 0.
It was treated in the same manner as in Example 1 using 2XIO. The physical properties obtained were as follows.

Tensile strength (MD/CD): 2.3/2.3k
g/cm tear strength (MD/CD): 1.4/1
．． 2 kg Peeling strength: 2100 g
/cm Flexibility (MD-CD average): 33 mm Example 4 As a raw yarn, 1 d of splittable fibers of polyethylene terephthalate and polypropylene (capacity ratio 8/2) with a cross-sectional shape similar to that of Example 1, 10 mm cut (L/D was treated in the same manner as in Example 1 using 1X10'). The physical properties obtained were as follows.

Tensile strength (MD/CD): 2.2/2.0k
g/cm tear strength (MD/CD): 1.0/1
．． 1 kg delamination strength: 1700 g
/cm Flexibility (MD-CD average): 35 mm Example 5 The raw yarn was made of splittable fibers of polyethylene terephthalate and polyethylene (capacity ratio 8/2) having the same cross-sectional shape as Example 1. /D was treated in the same manner as in Example 1 using I×10.The physical properties showed the following values.

Tensile strength (MD/CD) ・2.3/2.2 kg
/an tear strength (MD/CD): 1.1/1
．． 2 kg Peeling strength: 2000 g
/cm Flexibility (MD-CD average) = 37th Example 6 1.5d, 12.5mm cut as raw yarn (L/D is 0
．． The easily splittable acrylic fiber (trade name: Cashmilon FCA, manufactured by Asahi Kasei Kogyo ■) was used in the same manner as in Example 1.The physical properties were as follows.

Tensile strength (MD/CD): 2.4/2.0k
g/cm tear strength (MD/CD): 1.5/1
．． 2 kg Peeling strength: 1500 g
/ National Anthem Softness MD-CD average) 64 [Effects of the Invention] The nonwoven fabric of the present invention has excellent surface feel, is dense, has excellent barrier properties, is rich in flexibility, and has excellent strength and physical properties. Due to these characteristics, it is suitable for use in a wide range of textiles such as filters, wipers, and surgical gowns.

Patent applicant: Asahi Kasei Industries, Ltd.

Claims (1)

[Claims]1.
Wet-laid nonwoven fabric characterized in that ultrafine fibers and/or ultrafine fiber bundles of 8 d or less are intertwined with each other in three dimensions 2 Fibers made of splittable fibers with a fiber length of 20 mm or less are formed into a sheet by a papermaking method, and then columnar Treated with water flow,
A method for producing a wet-laid nonwoven fabric, which comprises entangling and splitting the splittable fibers, and three-dimensionally intertwining ultrafine fibers and/or ultrafine fiber bundles of 0.8 d or less with each other.