JPH04228717A - Ground filter material - Google Patents

Abstract

PURPOSE: To inexpensively manufacture a lightweight filter material for ground provided with a filter characteristic, size stability under load, breaking strength, broken point elongation, dynamic stress and a characteristic such as a friction coefficient for soil. CONSTITUTION: A filter material for ground comprises the non-woven fabric of a synthetic fiber or includes the non-woven fabric of the synthetic fiber, and at least a part of the synthetic fiber is a hollow fiber. The hollow part of the hollow fiber exists over the entire area of the length direction of the hollow fiber. The rate of the hollow part of the synthetic fiber is 3-40 vol.%, preferably 5-20 vol.%. The synthetic fiber comprises polyester, preferably polyethyleneterephtalate. The non-woven is span bond non-woven fabric joined mechanically.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ground filter material consisting of or containing a nonwoven fabric of synthetic fibers, wherein at least a portion of the synthetic fibers are hollow fibers.

0002

BACKGROUND OF THE INVENTION Ground filters have a cloth-like structure and are made of fibrous materials. It is also used in civil engineering work as a cloth-like filter. Such filters prevent soil erosion and ground movement caused by groundwater;
It has the role of protecting the ground from erosion by water.

[0003] In order for a ground filter to be effective as a filter, it needs to be compatible with the geology of the ground on which it is installed. That is, the size of the mesh of the ground filter needs to be such that fine components of soil particles cannot pass through. On the other hand, the ground filter must not impede the flow of moisture and, in some cases, must also function as a drainage layer.

[0004] Therefore, a ground filter is required to have various characteristics. Such properties are, for example, filter properties, dimensional stability under load, breaking strength, elongation at break, response to dynamic stresses and coefficient of friction against soil. It is also necessary that the filter itself and its mechanical properties be stable over long periods of time. Furthermore, it is also necessary to manufacture filters from a minimum amount of fibrous material in order to save manufacturing costs.

Detailed regulations regarding the sizing of soil filters can be found, for example, in Forschungsgesell
schaft fur strassen- und
Verkehrswesen (the German
Research Society for Road
"Merkblattfur die Anw" published by Transport and Traffic
Endung von Geotextilien i
m Erdbau” (Directions for
the use of geotextiles in
civil engineering) section
on5.2 ff. ya Bundesanstalt
fur Wasserbau (the German)
Institute for Water Engine
"Merkblatt" published by
Anwendung von Geotextilie
n Filter an Wasserstrass
en” (Directions considering
the use of geotextile fi
lters at waterways).

Synthetic fibers are particularly suitable as raw materials for producing ground filter materials. This is because synthetic fibers do not corrode in the soil and are stable for long periods of time. A particularly suitable filter-forming material is spunbond. Spunbond is a nonwoven fabric with filament webs bonded together. There are two main reasons why spunbond is suitable as a ground filter material. One reason is that the manufacturing cost of nonwoven fabrics is very low. The other reason is that the filaments are randomly opened and have isotropic mechanical properties. However, it is also possible to produce a nonwoven fabric with anisotropic mechanical properties by arranging the fibers in a certain preferred direction. Nonwoven fabrics produced in this manner include, for example, carded nonwoven fabrics.

[0007] It is very difficult to produce a web that has all of the above-mentioned properties required for a ground filter material within a limited range of thickness. In order to obtain a ground filter material that has both water permeability and mechanical strength, which are particularly required for a ground filter, it is necessary to have a relatively large thickness, which results in high manufacturing costs for the nonwoven fabric.

[0008]

[Problems to be Solved by the Invention] In view of the above problems, the present invention aims to improve filter properties, dimensional stability under load, fracture strength, elongation at break, response to dynamic stress, and soil resistance. The purpose of the present invention is to provide a filter material for ground use that has characteristics such as a coefficient of friction and can be manufactured lightweight and inexpensively.

[0009]

[Means for Solving the Problems] In order to solve the above-mentioned problems, the inventors of the present invention have conducted intensive research and found that by containing hollow fibers in the fiber material of non-woven fabrics, it is possible to produce non-woven fabrics with low basis weight and using less raw materials. It was found that the material satisfies the requirements as a filter material.

That is, the filter material of the present invention is a filter material for ground use that is made of a nonwoven fabric of synthetic fibers or contains a nonwoven fabric of synthetic fibers, and is characterized in that at least a portion of the synthetic fibers are hollow fibers. shall be.

[0011] The proportion of hollow fibers in a nonwoven fabric that has the desired properties may be very small depending on the case. If at least 10% of the synthetic fibers constituting the nonwoven fabric are hollow fibers, the ground filter material of the present invention can be produced economically and technically advantageously. However, it is generally advantageous to use ground filter materials consisting of nonwoven fabrics containing 50 to 100% hollow fibers. If the technical requirements are very high, it may be necessary to use a nonwoven fabric made of 100% hollow fibers.

The linear density of the synthetic fibers forming the nonwoven fabric used as the ground filter material of the present invention is within the range of the linear density of fibers commonly used as ground filter materials. Therefore, the linear density is generally 0.5 to 50 dt
ex, preferably in the range of 2 to 20 dtex.

[0013] Depending on the case, fibers of different linear densities may be mixed and used. Particularly in the case of a nonwoven fabric in which the proportion of hollow fibers is not 100%, the hollow fibers and the non-hollow fibers may have different linear densities. Synthetic fibers may be either continuous filaments or staple fibers. When using staple fibers, it is advantageous for the staple length to be between 2 and 20 cm. However, it is of course also possible to use non-woven fabrics containing both continuous filaments and staple fibers. For example, in order to have the desired characteristics,
Hollow staple fibers may be blended into a nonwoven fabric consisting of continuous filaments in appropriate proportions.

It is of course also possible to produce nonwoven staple fiber webs from a mixture of hollow and solid staple fibers.

The synthetic fibers constituting the nonwoven fabric used in the ground filter material of the present invention may have one or more hollow portions. The hollow portions are present along the length of the fiber and may be present for short or very short lengths or may be present throughout the length of the fiber. Therefore, hollow fibers for the purposes of the present invention are not only foamed fibers, but also have one or more hollow portions extending over most of the length of the fibers.
Or it includes hollow fibers having the entire area.

The proportion of hollow parts contained in synthetic fibers is an important factor. The proportion of the hollow portions of the synthetic fibers constituting the nonwoven fabric used as the ground filter material of the present invention is 3 to 40% by volume, preferably 5 to 20% by volume.

Suitable synthetic fibers for use in the ground filter material of the invention are generally spinnable polyamides, polyethylenes, polypropylenes or polyesters. It is preferable to use synthetic fibers made of polyester, and it is particularly preferable to use polyethylene terephthalate.

[0018] The nonwoven fabric used as the ground filter material of the present invention is essentially bonded by various known methods. For example, the webs can be joined by a bonding agent. That is, the webs are immersed in a binder and then the binder is cured to join the webs. Further, the binder may be a powdery or filamentous hot-melt binder. In this case, such a binder is mixed into the web and melted by heat, joining the web to form a nonwoven fabric.

Calendering can also be used to join the webs to form a nonwoven fabric. In this case, the filaments are partially mechanically entangled and glued at the intersections of the filaments.

It is particularly advantageous for the ground filter material of the invention to consist of a mechanically bonded non-woven fabric. Mechanical joining methods of the web carried out for the purposes of the invention are, for example, needling or EP-A-0 108 6
It is a hydromechanical method as described in Example 21. Nonwoven fabrics whose webs are mechanically bonded have particularly good compatibility with the ground.

It is further preferred that the ground filter material of the invention is based on a nonwoven fabric produced by the spunbond method. In particular, a spunbond nonwoven fabric bonded by needling is preferred.

[0022] The basis weight of the nonwoven fabric used as the ground filter material of the present invention is preferably 50 to 2500 g/
m2, particularly preferably 200 to 1500 g/m2
It is. It is particularly preferable that the ground filter material of the present invention has both the above-mentioned preferable properties.

The present invention also provides a method for manufacturing the above-mentioned ground filter material. That is, the method for producing a ground filter material according to the present invention is a method of defibrating synthetic continuous filaments and/or staple fibers on a moving means by a conventional method, and then joining them, the method comprising: at least one of the synthetic fibers being defibrated; It is characterized by using hollow fibers in some parts. When joining, it may be combined with another fibrous material.

When producing a nonwoven fabric made of staple fibers according to the present invention, hollow fibers are used as part of the nonwoven fabric. The mixture of hollow and solid staple fibers is then defibrated to form a web by conventional dry or wet methods and then spliced.

However, it is also possible to produce nonwovens from mixtures of continuous filaments and staple fibers. In this case, the staple fibers are spread while the continuous filament is being disentangled on the moving means. Either the continuous filament or the staple fiber may be a hollow fiber. The hollow continuous filament or staple fiber may be entirely or partially hollow.

Similarly, when producing a nonwoven fabric by the spunbond method, it is possible to mix hollow fibers and non-hollow fibers at the defibration stage. For example, hollow fibers are produced separately, then drawn off a bobbin creel, placed in a stream of solid fibers using a blow nozzle, and opened onto a moving means. As another method,
The spinneret for producing web-forming filaments may be provided with spinnerets for hollow fibers in addition to spinnerets for solid fibers. The number of spinnerets and the filament output ratio correspond to the ratio of hollow fibers to solid fibers in the intended ground filter material. Generally, the proportion of hollow fibers in the ground filter material of the invention is at least 10%. And the proportion of hollow fibers is preferably 5
0 to 100%, and for maximum effect, 100% of the fibers are hollow fibers.

[0027] The webs can be bonded into a non-woven fabric by using a binder, especially a hot melt binder, by calendering, or preferably by needling, according to conventional methods.

The binder may be, for example, a polymeric solution, dispersion or latex. Such binders can be applied to the web by dipping the web in the binder or by spraying the web with the binder. When the liquid component evaporates, thin film adhesion points remain at the intersections of the filaments.

However, it is also possible to use thermosetting binders. Thermoset binders cure with or without the addition of heat to bond the fibers together. It is likewise preferable to use hot-melt binders. The hot melt binder is introduced into the web in powder form or preferably in fibrous form. The web is then heated to a temperature above the melting point of the binder to form bond points at the intersections of the fibers. By cooling this, a nonwoven fabric with webs bonded thereto can be obtained.

Similarly, if the web is calendered at a temperature near the melting point of the filaments, the webs can be joined by adhesion at the intersections of the filaments.

[0031] Furthermore, it is preferable to mechanically join the webs. This is because no chemical or thermal load is placed on the filament. Therefore, various physical properties imparted to the filament during the filament spinning process, such as high-speed spinning and drawing processes, are retained even after the filament is made into a nonwoven fabric.

The ground filter material of the present invention may consist of only one type of nonwoven fabric as described above. Alternatively, it may further contain a fiber material in addition to the nonwoven fabric. For example, other non-woven fabrics or additional fibrous material layers (for example, an expanded structure of oriented filaments to obtain greater strength in a particular direction, or a decorative layer). By providing such an additional layer, the nonwoven fabric can be made into a fiber composite material for civil engineering works. The effectiveness of such fiber composite materials as filters is essentially derived from the properties of the web material.

Claims (13)

[Claims] 1. A ground filter material consisting of or comprising a nonwoven fabric of synthetic fibers, wherein at least a portion of the synthetic fibers are hollow fibers. 2. The ground filter material according to claim 1, wherein at least 10% of the synthetic fibers are hollow fibers. 3. The ground filter material according to claim 1, wherein 50 to 100%, preferably 100% of the synthetic fibers are hollow fibers. 4. The ground filter material according to claim 1, wherein the hollow portions of the hollow fibers are present over the entire length of the hollow fibers. Claim 5: The proportion of hollow parts of synthetic fibers is 3 to 40.
% by volume, preferably from 5 to 20% by volume.
The ground filter material according to at least one of the above. 6. Ground filter material according to claim 1, wherein the synthetic fibers consist of polyester, preferably polyethylene terephthalate. 7. The ground filter material according to claim 1, wherein the nonwoven fabric is bonded with a binder. 8. The ground filter material according to claim 1, wherein the nonwoven fabric is mechanically bonded. 9. The ground filter material according to claim 1, wherein the nonwoven fabric is a filament nonwoven fabric, that is, a spunbond nonwoven fabric. 10. Synthetic continuous filaments and/or staple fibers are defibrated onto a moving means in a conventional manner to form a web, and the web is then joined with or without other fibrous materials. 2. A method for producing a ground filter material according to claim 1, comprising using hollow fibers as at least a portion of the defibrated synthetic fibers. Claim 11: At least one of the defibrated synthetic fibers.
11. The method of claim 10, wherein 0% is hollow fiber. 12. 50 to 100 of defibrated synthetic fibers
12. A method according to claim 10 or 11, wherein %, preferably 100%, are hollow fibers. 13. The nonwoven fabric is obtained by joining the webs using a binder or preferably by mechanical methods.
2. The method according to at least one of 2.