JPS5837427B2 - AtsasahoukounisenIshiyuusekimitsudodokou - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a nonwoven mat having a gradient of fiber accumulation density in the thickness direction.

Conventionally, as a method of creating a density gradient of accumulated fibers in the thickness direction of a non-woven web, it has been proposed to pass a non-woven web in which thermoplastic fibers are mixed and accumulated between two upper and lower rolls with an appropriate temperature difference. There is.

However, with this method, there is a risk that only the surface layer in contact with the high-temperature roll surface becomes extremely dense, and extremely strict process control is required to obtain a perfect gradient of fiber accumulation density. be.

The method of the present invention can very easily increase the fiber accumulation density in the thickness direction of a nonwoven web by simply carrying out a conventional method for forming a nonwoven web, a conventional needling method, and a conventional heating method. This provides a method that can obtain the complete gradient of .

The present invention is a mixture of two types of fibers with different deniers with a denier difference of 1.2 or more, the mixing ratio of fine denier fibers being 10% to 50%, and 25% of the fine denier fibers. % or more and 95% or less are thermofusible fibers, and the rest is non-thermofusible fibers.The nonwoven web is second-drilled and then heat-treated to create a fiber accumulation density gradient in the thickness direction. The present invention provides a non-woven mat.

That is, in the present invention, a web made from a mixture of two types of fibers with different deniers is subjected to two-dringing using a needle equipped with a barb large enough to hook only fine denier fibers. The amount of mixed denier fibers is increased toward one side of the web, and the amount of fine denier fibers decreases as it approaches the other side. After shaping the web, the web is heated at a temperature at which the thermofusible fibers can be melted, thereby creating a density gradient.

The two types of fibers used in the present invention refer to those classified based on denier differences, and are not categorized based on the fiber composition.

Therefore, from a composition standpoint, there may be a mixture of many fibers.

The first important structural requirement of the present invention is to gradually reduce the amount of fine denier fibers mixed in the thickness direction of the web, that is, from one side of the web to the other side, by needling.

? Therefore, the second effect in the present invention includes the first effect of intertwining the fibers with each other, and the second effect of changing the mixed amount of fine denier fibers in the thickness direction of the wap. , in the present invention, this second
The effectiveness of this is what determines the achievement of objectives.

In order to fully exhibit the second effect of needlering, it is necessary that the denier difference between the two types of fibers with different deniers is sufficiently clear, and in the present invention, the denier difference is set to 1.2. This is the reason for the above limitations.

The denier difference between the two types of fibers that make up the web is 1.
If it is smaller than 2, it is not possible to selectively hook only the fine denier fibers among the two types of fibers by needling, that is, by the barb of the needle, and therefore the mixed amount of fine denier fibers cannot be adjusted in the direction of the web thickness. It is not possible to satisfy the first constituent requirement of the present invention, which is to make the change occur.

Next, in the present invention, as described above, the wafer obtained by applying needling is heat-treated to melt the heat-fusible fine denier fibers and complete the appearance of the density gradient. In this case, if the mixing ratio of heat-fusible fibers in the full-fine denier fibers is less than 25%, no effect of density gradient appearance will be seen even if heat-melted; If the amount is too large, there will be too much melted portion, and in extreme cases, there is even a risk that the web will become a film.

Therefore, in the present invention, the mixing ratio of fine denier heat-fusible fibers must be limited to 25% or more and 95% or less of all fine denier fibers.

Furthermore, in the present invention, in the mixture of two types of fibers with different deniers, the proportion of fine denier fibers is limited to 10% or more and 50% or less, and the reason for this is 10%.
If the difference is less than 50% or more than 50%, even if the denier difference between the two types of fibers is 1.2 or more, there will be a gradual decrease in fine denier fibers from one side of the wafer to the ground. This is because the needling effect cannot be noticeable.

The web formation of the present invention involves appropriately selecting two types of fibers with different deniers, mixing them uniformly, and applying a spreader such as a random webber to form a web. In order to achieve excellent results, it is important to mix the two types of fibers more uniformly.

In addition, as the heat-fusible fine denier fiber, for example, polypropylene, polyester, nylon, etc. are used, but it is not always necessary to use one of these types, and two or more types may be mixed. .

Another thing to consider in the present invention is the thickness (count) of the needling needle.

That is, it is preferable to select and use a needle with a thickness (count) suitable for hooking only the fine denier fibers among the two types of fibers that make up the web.

As detailed above, the present invention achieves the object of the invention by using two types of fibers with different deniers.
The same objective can also be achieved when two types of fiber groups, a thick denier fiber group and a fine denier fiber group, are used instead of these two types of fibers.

However, in this case, the denier difference between the thinnest fiber in the thick denier fiber group and the thickest fiber in the fine denier fiber group must be 1.2 or more.

As detailed above, according to the method of the present invention, it is possible to provide a nonwoven mat with an extremely excellent density gradient of accumulated fibers in the web thickness direction, and therefore, the obtained nonwoven mat can be Woven mats are particularly useful as fine filter media.

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

Example 1 65 d polypropylene fiber 70 parts by weight 18 d low melting point polypropylene fiber 20 18 d polypropylene fiber 10 Fibers of different deniers (denier difference: 47) were blended as above and mixed uniformly and randomly After making it into a web using a webber, use a No. 25 needle to punch 150 punches on one side only.
Needling was performed at i to obtain a web having a thickness of 7.0% and in which more 18d fibers were concentrated near the 21-during surface.

The web thus obtained was heat treated in a heating furnace set at 135° C. for 3 minutes to melt the polypropylene fibers and obtain a nonwoven mat with an excellent fiber accumulation density gradient.

Example 2 A: 40 parts by weight of 65 d polypropylene fibers A fiber composition consisting of thick denier fiber group A and fine denier fiber group B as described above was mixed uniformly, and this was made into a web using a random webber. Using a needle, only one side
Number of punches: 180 punch/cr? Ni-dring was performed at L to obtain a web having a thickness of 8.0% and in which the fine denier fiber group B was concentrated closer to the dredging surface.

The web thus obtained was heat treated in a heating furnace set at 130° C. for 3 minutes to melt the nylon fibers and obtain a nonwoven mat with an excellent fiber accumulation density gradient.

Claims (1)

[Claims] 1 Different denier 2 with a denier difference of 1.2 or more
A mixture of different types of fibers, the mixing ratio of fine denier fibers is 10% or more and 50% or less, and 25% or more and 95% or less of the fine denier fibers are heat-fusible fibers,
Others are non-thermofusible fibers, and needling is performed from only one side using a needle equipped with a herb large enough to hook only fine denier fibers onto the nonwoven web, followed by heat treatment. A method for manufacturing a non-woven mat with a characteristic fiber accumulation density gradient in the thickness direction.