JPH0371829A - Preparation of non-woven fabric structural body - Google Patents

Abstract

PURPOSE:To prepare a melt-blown non-woven fabric structure with good thermal dimensional stability by laminating a non-woven fabric prepd. by laminating one or a plurality of webs made of an ultrafine fiber and another non-woven fabric, woven or knitted product or a mesh-like product with a surface shrinking ratio in boiling water of a specified ratio or smaller and performing a heat setting treatment thereon. CONSTITUTION:As other non-woven fabric, woven or knitted product or mesh-like product B used by laminating with a melt-blown non-woven fabric A absorbs a shrinking stress produced in the melt-blown non-woven fabric A and acts as a reinforcing material keeping the morphology, not only various non-woven fabrics having a relatively high strength in comparison with a non-woven fabric A such as a non-woven fabric made by a dry process, a non-woven fabric made by a wet process, a spun-bond non- woven fabric but also most of woven and knitted fabrics or mesh like products made of plastics and metals are used by laminating them with the melt-blown non-woven fabric A. As the other non-woven fabric, woven and knitted fabric or mesh-like product B, a product with a surface shrinking ratio in boiling water of 10% or smaller is used and is heat-treated while the laminate is brought into contact with a hot-plate with a projected curved face under tension. A non-woven fabric structure with thermal dimensional stability is obtd. thereby.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention relates to a method for manufacturing a nonwoven fabric structure suitable for clothing, gas and liquid filtration materials, oil-water separation materials, etc.
In particular, the present invention relates to a simple and highly efficient method for manufacturing a nonwoven fabric structure with less unevenness in area weight.

<Prior art> Conventionally, there is a method of discharging a molten polymer from an orifice and pulling it with a high-temperature air stream to form fine fibers, and collecting the i-fibers on a conveyor to obtain a nonwoven fabric (melt blow method). ) is known as a method for directly producing nonwoven fabrics with ultrafine fiber diameters that are difficult to obtain using other methods.

In order to obtain a nonwoven fabric with a uniform and thin fiber diameter using the melt blowing method, it is necessary to discharge the polymer at a lower viscosity than when performing normal melt spinning, but conversely, a low viscosity can be stably obtained. As long as the polymer is available, many of the same polymers can be made into fabrics by melt blowing or similar methods. This flexibility with respect to the type of polymer used is one of the advantages of the melt blow method, and by taking advantage of this advantage,
Attempts have been made to manufacture fabrics using various polymers such as various polyolefins, polyesters, polyamides, and polyurethanes.

Among these, polyethylene terephthalate in particular is a general-purpose synthetic fiber material that has many advantages such as hydrophilicity, spinnability, and dyeability, so it can be used as a filter material, oil-water separation material, clean room clothing, and artificial leather. Studies have been conducted for use in base fabrics, etc.

However, since the nonwoven fabric obtained by melt blowing polyethylene terephthalate is almost amorphous immediately after spinning, when the produced web is heated for forming, etc., the residual stress in the fibers that make up the web is reduced. Therefore, there is a problem that the web shrinks. In order to solve this problem, the present inventors investigated heat treatment under a constant length from the viewpoint that the shrinkage of the web disappears when the fibers crystallize. In this method, a web made of amorphous fibers after spinning is treated at a temperature higher than the glass transition temperature of the polymer to crystallize it and give it dimensional stability. There are also problems in imparting dimensional stability through heat treatment as described below.

One of them is embrittlement of nonwoven fabrics due to heating crystallization. In other words, when a non-woven fabric made of amorphous fibers obtained by the melt-blowing method is heated and crystallized, spherulites tend to grow because individual constituent fibers cannot be stretched, and the non-woven fabric after treatment is It becomes brittle with poor elongation. For this reason, the handling properties of the sheet after heat treatment are extremely poor, and it easily breaks when, for example, pleat processing, which is a normal process in filter molding, is carried out by machine.

Further, an increase in the unevenness of the basis weight due to heat treatment also becomes a problem. In other words, when the fibers constituting the nonwoven fabric shrink due to heating, it is the entanglement between the fibers that acts as resistance to the shrinkage, but in the part of the nonwoven fabric with a small basis weight, there is little entanglement between the fibers, so the basis weight Fibers are more likely to slip through than areas with a large amount of fiber, and as a result, the unevenness in area weight increases. This is particularly noticeable in nonwoven fabrics with low basis weight and bulky nonwoven fabrics.

In order to prevent this unevenness in area weight from increasing, heat treatment is performed while compressing both sides of the nonwoven fabric. When the fibers constituting the nonwoven fabric become semi-molten at a temperature higher than their glass transition point, they form a film, making the melt-blown nonwoven fabric Not only do they lose their inherent drapeability and breathability, but they also become extremely brittle, making them extremely difficult to handle.

In the end, due to these circumstances, we decided to use a web made of a polymer such as polyethylene terephthalate that shrinks when heated after melt-blown fabric, which has thermal dimensional stability, good air permeability, drapability, and a low basis weight. At present, a method for producing a nonwoven fabric structure with less unevenness has not yet been obtained.

<Problems to be Solved by the Invention> In view of the above-mentioned points, the present inventors used a melt-blown nonwoven fabric made of a polymer such as polyethylene terephthalate that shrinks when heated after making the melt-blown fabric, and improved flexibility, breathability, etc. The present invention was arrived at as a result of intensive studies aimed at obtaining a nonwoven fabric structure that takes advantage of the unique advantages of melt-blown nonwoven fabric.

That is, an object of the present invention is to provide a method for producing a melt-blown nonwoven fabric structure that has good thermal dimensional stability, with less increase in unevenness of the melt-blown sheet caused by heating and less decrease in air permeability due to film formation. It is.

Means to solve problems〉 The present invention has the following configuration.

That is, a nonwoven fabric A consisting of a single web or a plurality of laminated webs made of ultrafine fibers obtained by a melt blow method, and another nonwoven fabric, woven or knitted fabric, or mesh-like fabric B having a boiling water shrinkage rate of 10% or less are used. This is a method for producing a nonwoven fabric structure, characterized by laminating the materials and subjecting the laminated state to a heat setting treatment.

<Function> In the method for producing a nonwoven fabric structure of the present invention, the melt-blown nonwoven fabric is laminated on another nonwoven fabric, woven or knitted fabric, or mesh-like material that shrinks less when heated. It absorbs the shrinkage stress that occurs in melt-blown nonwoven fabrics when heated.
The aim is to obtain a nonwoven fabric structure having thermal dimensional stability without causing increase in unevenness or shrinkage in a melt blown nonwoven fabric.The nonwoven fabric structure of the present invention and its manufacturing method will be explained in more detail below.

In the present invention, other nonwoven fabrics, woven or knitted fabrics, or mesh-like materials B used in a laminated manner with the melt-blown nonwoven fabric A are:
In order to absorb the shrinkage stress generated in melt-blown non-woven fabric A and act as a reinforcing material to maintain its shape, it is necessary to have a certain degree of strength compared to non-woven fabric A, but generally the strength of melt-blown non-woven fabric A is small. Therefore, since its shrinkage stress is small, in addition to various nonwoven fabrics such as dry nonwoven fabrics, wet nonwoven fabrics, and spunbond nonwoven fabrics, most woven or knitted fabrics or mesh-like materials made of plastic or metal can be used as melt-blown nonwoven fabrics. It can be used as other non-woven fabric, woven or knitted fabric, or mesh-like material B which is laminated with A.

The other nonwoven fabric, woven or knitted fabric, or mesh-like material B must have a boiling water surface shrinkage rate of 10% or less, and if it is greater than 10%, the shrinkage stress generated in the above-mentioned melt-blown nonwoven fabric is It cannot be used in the method of the present invention because it cannot be expected to have an absorbing effect.

In the present invention, heat treatment is performed as a post-layering process, but
As a method for performing the heat treatment, either a method in which the laminate is heated in its sheet form, or a method in which the laminate is heated after being molded into the form in which it will be used can be adopted.

The former is carried out by, for example, rolling a sheet-like laminate into a roll and passing it continuously through a heating furnace. In this case, a tenter is used to apply tension in a direction perpendicular to the sheet's progress. May be added. During heating, melt-blown nonwoven fabrics and other nonwoven fabrics, woven or knitted fabrics, or mesh-like materials may be simply laminated, or may be fully or partially integrated by adhesives, fusion, needle bunching, or hydroentangling. However, when heating simply laminated materials, the melt-blown non-woven fabric and other non-woven fabrics or woven or knitted fabrics should be heated at a contact pressure that does not cause the melt-blown non-woven fabric to form a film. Alternatively, it is necessary to maintain contact with the mesh-like material and absorb the shrinkage stress of the melt-blown nonwoven fabric. For this purpose, for example, a method may be employed in which the laminate is heated while being brought into contact with a heating plate having a convex curved surface under tension.

The latter is made by laminating melt-blown nonwoven fabrics with other nonwoven fabrics, woven or knitted fabrics, or mesh-like materials, and then subjecting them to, for example, a pleating process, filling silk into a box-shaped or cylindrical frame, and forming it into a form that can be used as a filter, etc. Heat treatment is added later. Even in this case, during the assembly process, the melt-blown nonwoven fabric and other nonwoven fabrics, woven or knitted fabrics, or mesh-like materials may be simply laminated or integrated by adhesive, fusion, needle bunching, hydroentangling, etc. It can be used with either.

In this case, shrinkage stress can be absorbed at the bending peaks, so in the direction perpendicular to the bends, even if the laminate is not integrated, it is possible to suppress the increase in uneven area weight. However, in order to suppress shrinkage in the direction parallel to the bending peak, it is preferable to fix at least the end face.

The melt-blown nonwoven fabric heat-treated as described above may be used as it is as a laminated nonwoven fabric structure, or
Alternatively, the lamination can be unraveled and used as a single melt-blown nonwoven fabric.

The melt-blown nonwoven fabric used in the present invention preferably has an average fiber diameter of 5 μm or less, preferably 3 μm or less. If the average fiber diameter exceeds 5 μm, the embrittlement after heating will be significant, and even if it is laminated with other nonwoven fabrics, woven or knitted fabrics, or mesh-like materials, the melt-blown nonwoven fabric will fail during the process after heat treatment or during use. This is not preferable because it tends to cause breakage.

Here, the average fiber diameter is the average value of the fiber diameters of 100 or more fibers taken at random from multiple photographs taken using a scanning electron microscope (SEM) at any location within the nonwoven fabric. means.

The thickness of the melt-blown nonwoven fabric is preferably 2 nm or less, preferably 1 mm or less, and such a thin fabric is effective when subjected to the method of the present invention. If the thickness of the melt-blown nonwoven fabric is 2 mm or more, it is not preferable because it reduces the drapeability and flexibility of the nonwoven fabric structure.

In addition, the pore volume of melt-blown nonwoven fabric is 95%.
Below, it is preferably 90% or less. When the pore volume is greater than 95%, the laminate does not effectively absorb shrinkage stress, so unevenness tends to occur.In addition, if the laminate is strongly pressed to prevent unevenness from increasing, the thickness will decrease. However, this is not preferable because the pore volume is significantly reduced from the initial value.

When a nonwoven fabric made of polyethylene terephthalate is used as a melt-blown nonwoven fabric, the temperature at which the heat treatment is performed must be 90°C or higher when carried out under dry heat, preferably 95°C or higher, and more preferably 1
It is preferable to carry out the process at a temperature of 00°C or higher. If the heat treatment temperature is 90° C. without grooves, the heat treatment will take a long time and is not suitable for practical use.

When heat treatment is carried out in steam or hot water bath,
The heat treatment can be carried out at a lower temperature than when carried out under dry heat. However, even in this case, the processing temperature is 70°C.
If the temperature is below 0.degree. C., the heat treatment will take a long time, which is not preferable.

In particular, when it is necessary to perform shaping treatment on a nonwoven fabric structure after heat treatment, the present invention can be applied to a nonwoven fabric structure with a crystallinity of 30% or less and a heat treatment as previously proposed by the present inventors. Melt-blown nonwoven fabrics with a water surface shrinkage rate of 20% or less, that is, are effective in obtaining excellent nonwoven fabrics that have low shrinkage, high strength, and high elongation properties, and can sufficiently withstand the shaping process. It is.

<Effects of the Invention> The nonwoven fabric structure obtained by the method for producing a nonwoven fabric structure of the present invention has a flexible texture, good breathability, and small unevenness in fabric weight, so it can be used not only for clean room clothing but also for gases and liquids. It can be successfully used in filter media, oil/water separation materials, etc.

Furthermore, by using the method for manufacturing a nonwoven fabric structure of the present invention, it is possible to omit the step of processing the melt-blown nonwoven fabric alone, which has undergone heat treatment to become brittle and have reduced strength and elongation, thereby significantly increasing the product yield. It becomes possible to improve.

Furthermore, when melt-blown non-woven fabrics are used as filter base materials, pleating is required in many cases, but melt-blown non-woven fabrics have a unique flexibility and are difficult to crease, which has been a problem. This problem can also be solved by using other non-woven fabrics, woven or knitted fabrics, or mesh-like articles in the present invention, such as those made of metal or thermoplastic resin that have excellent bending properties, and by performing heat-setting treatment after shaping. It can be solved. If a heat-formable thermoplastic resin is used as the non-woven fabric, woven or knitted fabric, or mesh-like material, and the melt-blown non-woven fabric is heat-treated at the same time as the laminate is heat-formed, the process can be significantly shortened, resulting in a double-headed effect. can be obtained.

<Example> Example 1 Average fiber diameter 2.3 μm, thickness 0.25 mm, basis weight 45 g
A non-woven fabric structure is made by laminating three sheets of polyethylene terephthalate melt-blown non-woven fabric (3 sheets of polyethylene terephthalate melt-blown non-woven fabric) with a thickness of 1.2 mm, and a stainless mesh (boiling water surface shrinkage rate of 20%) is laminated on both sides of the non-woven fabric. Incorporated.

This molded product was heat-set under dry conditions of 130° C. for 10 minutes to obtain a filter unit. The above steps could be carried out without any problems in terms of workability. 0.3μ, which disperses the filtration performance of the filter unit in the air.
When measured using a polystyrene standard latex of #1, it was 99% at a #l cross-surface wind speed of 3 m/rnjn, confirming that it had good performance as a filter.

Example 2 On both sides of the same polyethylene terephthalate melt-blown nonwoven fabric as in Example 1, a fabric weight of 100 g/m2 and a thickness of 0.2 m was applied.
, rn polyethylene terephthalate knitted fabrics (boiling water surface shrinkage rate = 2% or less) were laminated, and after being partially bonded in spots by ultrasonic fusion, heat setting treatment was performed at 140° C. for 3 minutes under dry heat. The heat setting process was performed using a suction drum dryer, and no particular tension was applied to the nonwoven structure.
A flexible nonwoven structure was obtained without shrinkage.

Comparative Example 1 A polyethylene terephthalate melt-blown nonwoven fabric similar to that used in Example 1 was heat-treated at 130° C. for 10 minutes while its periphery was fixed to obtain a heat-set nonwoven fabric. Stainless mesh similar to that used in Example 1 was laminated on both sides of the nonwoven fabric, pleated in the same manner as in Example 1, and fixed within a cylindrical frame to obtain a filter unit.

Since the melt-blown nonwoven fabric after heat setting was brittle and had poor elongation, the nonwoven fabric often broke due to tension even during the above processing.

When the filtration performance of the filter unit was measured using 0.3 μm polystyrene standard latex dispersed in the air, it was 94% at a wind speed of 3 m/min, indicating a decrease in collection performance that was thought to be due to increased unevenness. was recognized.

Comparative Example 2 A polyethylene terephthalate melt-blown nonwoven fabric similar to that used in Example 2 was dried at 140°C under dry heat in a suction drum dryer in the same manner as in Example 2.
Heat fixation treatment was performed for 3 minutes.

The nonwoven fabric contracted in each part depending on the degree of contact with the drum, resulting in a brittle and highly uneven sheet.

Claims (6)

[Claims] (1) Nonwoven fabric A, which is made up of a single web or a plurality of webs made of ultrafine fibers obtained by melt blowing, and other nonwoven fabrics, woven or knitted fabrics, or mesh-like fabrics B, which have a boiling water surface shrinkage rate of 10% or less. 1. A method for producing a nonwoven fabric structure, which comprises laminating the above layers and subjecting the laminated state to a heat setting treatment. (2) The method for manufacturing a nonwoven fabric structure according to claim (1), wherein the laminated state is a state in which the laminated state is formed into a predetermined shape. (3) The method for producing a nonwoven fabric structure according to claim (1), wherein the average fiber diameter of the constituent fibers of the web made of ultrafine fibers obtained by a melt blowing method is 5 μm or less. (4) Claim (1) characterized in that the heat setting treatment is a treatment for bonding and integrating the laminated nonwoven fabric A with another nonwoven fabric, woven or knitted fabric, or mesh-like material B. A method for producing a nonwoven fabric structure according to. (5) The method for manufacturing a nonwoven fabric structure according to claim (1), wherein the nonwoven fabric A is composed of polyethylene terephthalate fibers. (6) The method for producing a nonwoven fabric structure according to claim (5), wherein the temperature of the heat setting treatment is 90° C. or higher under dry heat.