JPS5921766A - Production of nonwoven fabric - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for improving the longitudinal strength of a nonwoven fabric mainly composed of thermoplastic fibers.

Nonwoven fabrics are generally made of fibers arranged randomly and fixed in some way to form a sheet.
It is widely used for clothing, industrial materials, etc. but,
Since nonwoven fabrics are made by simply fixing randomly arranged fibers, the strength of the product is easily affected by the bonding strength between the fibers and the arrangement of the constituent fibers, and when compared with woven fabrics of the same weight. 1 strong is generally inferior. Trying to increase strength.

fiber f+I1. If the adhesion between the two is too strong, the nonwoven fabric will generally become stiff and become paper or film-like.

As described above, non-woven fabrics have various disadvantages compared to woven or knitted fabrics, which limits the range of their uses. However, the manufacturing technology of nonwoven fabrics has been improved and improved in recent years.

In the field of industrial materials, woven fabrics are gradually replacing knitted fabrics.

In view of this trend, the present invention improves nonwoven fabrics in fields where strength in the longitudinal direction is required. That is, the fields include adhesive tapes, FRP winding base materials, electrical wire sheathing materials, industrial materials used in tape form, and tape interlining.

There are various techniques for adhering non-woven fabrics, but the ones that are generally used industrially include so-called wet bonding, which mainly uses acrylic emulsion, and mixing fibers or powder with a lower melting point than the fibers that make up the non-woven fabric. In some cases, the two main methods are thermocompression bonding, which involves applying heat and pressure to the constituent fibers.

The present invention is an improvement of the thermocompression bonding method. That is, when thermocompression bonding a fibrous web mainly composed of thermoplastic fibers, tension is applied to the nonwoven web at the stage where the nonwoven web has thermoplasticity immediately after thermocompression bonding and before it has completely cooled down. The purpose is to improve the strength of the nonwoven fabric in the longitudinal direction by elongating it at an actual elongation rate of 0 to 10% with respect to the length in the longitudinal direction (lengthwise direction of the nonwoven fabric). During this elongation process, the fibers that make up the nonwoven fabric are rearranged in the vertical direction, and then cooled and solidified.
The strength and modulus of the nonwoven fabric in the vertical direction are improved.

-If there is no such rearrangement of the constituent fibers, if the constituent fibers are pulled in the vertical direction, the tensile stress will concentrate on individual fibers and joints and the fibers will break at the stage where the constituent fibers are rearranged in the longitudinal direction. The final breaking strength does not decrease, the modulus also increases, and the width changes during the tensile process are large.

At the stage where the nonwoven web has extreme heat resistance as in the present invention, the applied tension (stress) is absorbed by the deformation of the nonwoven web, that is, by the rearrangement of the constituent fibers, causing fiber breakage and destruction of bonding points. Without, the configuration fg4, +(p.

are moved and arranged vertically. As a result 2, when the nonwoven fabric obtained according to the present invention is pulled, the tensile stress is distributed to the fibers arranged in the vertical direction, so the stress is received at the entire fiber junction, and the initial deformation is small, that is, the modulus is high and 2 A nonwoven fabric with high strength in the longitudinal direction and little change in width can be obtained.

The nonwoven fabric applied to the present invention may be a nonwoven fabric made from short fibers using a carding method, a nonwoven fabric made using a papermaking method called a trench wet method, or a long fiber nonwoven fabric made using a spunbond method. The manufacturing method is not limited.Also, thermal bonding may be a thermocompression bonding method that applies heat and pressure to the fibers that make up the nonwoven web that do not contain low melting point components, but from the viewpoint of adhesiveness, the melting point is lower than the melting point of the constituent fibers. It is preferable to mix a low melting point adhesive component with a melting point.In such a case, there is no limitation on the method of mixing the adhesive low melting point component. It is also possible to mix them and apply them to a card to make a nonwoven web, or in the case of a spunbond method, it is also possible to simultaneously spin and mix the main component and the adhesive low melting point component. A low melting point adhesive component in the form of fibers or powder may be mixed into the web at a later time, but is not dependent on the means for forming the web.

The material of the fibers constituting the nonwoven fabric is not particularly limited, and polyamide 9. j Ordinary fiber materials such as lyester and polyolefin may be used. In the case of mixing an adhesive component, it is basically usable if the adhesive material of 1 Minsha 7a has a melting point that is 1 degree higher than the melting point of the constituent fibers. IJ ester, polyolefin, or a copolymer thereof can be used.

In this case, in terms of melting and variation with the constituent fibers, if the melting point of the low melting point adhesive component is high and close to the melting point of the constituent fibers, high temperatures are required during thermocompression bonding, resulting in heat and pressure deterioration of the constituent fibers. Becomes a dog.

The melting point difference is usually 10°C or higher, preferably 20°C or higher. However, if the melting point is too low, problems will arise in the heat resistance of the final nonwoven fabric product, so it is necessary to set the melting point in accordance with the intended use. Generally, a temperature of at least 150°C or higher is required.

Next, there are methods of thermocompression bonding, such as a roll press method in which the web is heat-compressed between two heated rolls, a method in which the web is heat-compressed between two heated drums as in a belt press, or a method as in a suction drum. Alternatively, there is a method of heat-pressing between a perforated drum through which hot air passes and a wire mesh, but in the present invention, the temperature is maintained at a high enough temperature that the non-woven fabric is still deformed at the time of completion of heat-press-bonding, and the tension is applied to the non-woven fabric.
There needs to be a way to avoid this. Any of the above methods can be used simultaneously or in combination, but the most preferred is the roll press method in which the material is heated and pressed using the curves of two heated rolls.

This is a means of stretching the nonwoven fabric by applying tension.

A tension adjustment mechanism such as a 5-winder may be used between the heat-compression bonding process and the winder generally installed afterwards, but it is recommended to proactively install a device that applies tension after the heat-compression bonding process. preferable. The outline is shown in Fig. 1 and Fig. 2. 1
2 rolls of heat and pressure bonding, 2 is thin! This is a nip roll that applies tension to the fabric and stretches the nonwoven fabric.

The method shown in FIG. 1 or the method shown in FIG. 2 may be used to thread the nonwoven fabric.

Any method may be used as long as there is no slippage in the nip rolls and a predetermined actual elongation rate can be obtained. The material of the nip roll is not limited to metal, rubber, paper, etc., but it is preferable to use one with a large coefficient of friction. Further, the nip roll is one means for obtaining a constant elongation rate, and as mentioned earlier, a tension mechanism of the winding machine or a weight roll may be used.

Although it is important to set the actual elongation rate in the range of 0 to 10%, it is practically preferably 2 to 6%.

When an unbonded web is heated and pressed between two heating rolls as shown in FIG. 1, two heating rolls are used.

Since the nonwoven web shrinks under the influence of the heat from the previous preheating stage, the fact that the actual elongation rate is 0% means that the shrinked material is being elongated. The actual elongation rate here is based on the unit length in the vertical direction of the unbonded web before entering the bonding process. Specifically, the actual elongation rate is based on the unit length in the vertical direction of the unbonded web before entering the bonding process. The distance between the marks (usually 05 to 1 m) was marked, the distance between the marks was measured, and the ratio was calculated.

In the present invention, selection of the actual elongation rate range takes into consideration the strength of the nonwoven fabric and the pixelization of the nonwoven fabric during the elongation process, and is also related to the nominal weight of the nonwoven fabric. i.e. 50
2 for the general target weight of around g/m2
An actual elongation rate of ~6% is appropriate, and those with a low basis weight of 50 g/m2 or less are generally easy to elongate even if the same tension is applied, and the opposite is true for high basis weights. Therefore, managing the tension at a constant value is problematic because the actual elongation rate is likely to vary depending on the date and weight. Therefore, in actual operational management, the process of applying the speed and tension of the bonding process,
For example, it is preferable to control the speed ratio of the nip rolls shown in FIG. 1 so that the actual elongation rate satisfies the present invention.

When determining the high speed ratio, it is necessary to take this into account when determining the speed ratio using nip rolls, as the actual elongation rate is generally smaller than the speed ratio due to elongation recovery of the nonwoven fabric, etc. be.

When the actual elongation rate is set to 10% or more, the width of the nonwoven fabric becomes large, and the elongation rate in the vertical direction becomes uneven compared to the width direction, and the change in both ends of the nonwoven fabric becomes sharp and unruly. ``Thus, even if you create an unbonded web with a uniform target weight distribution.

During the elongation process, the cross-section weight distribution in the width direction of the nonwoven fabric deteriorates, and when used in tapes that require product strength in the vertical direction, changes in basis weight result in changes in thickness, which poses a practical problem. Furthermore, elongation of more than 10% causes rearrangement of the constituent fibers and destruction of the bonding points, which prevents uniform adhesion and, on the contrary, results in a decrease in strength.

In consideration of the above-mentioned problems, in carrying out the present invention, it is preferable that the distance between the bonding process and the nip rolls that provide stretching be as short as possible. It's a size.

This is because the bonding points of a high-temperature nonwoven fabric immediately after the adhesion process are not yet completely fixed, and stretching in this state causes the constituent fibers of the nonwoven fabric to rearrange.

Naturally, movement of the bonding point may result in an unstable state, so it is preferable to cool and solidify as quickly as possible after elongation. Therefore, in a stretching method like the first appositive, 2
It is preferable to cool the nonwoven fabric by passing cooling water through the nip rolls. Since the thickness of the nonwoven fabric also deforms due to the elongation deformation, it is desirable to apply a certain amount of pressure with nip rolls to also have a setting and cooling function.

It is sufficient that the cooling temperature is usually 80° C. or less in terms of surface temperature of the nonwoven fabric, and the set pressure is 10 kg/cm or less.

The present invention will be explained in detail below with reference to Examples.

Example 1 A web in which continuous filaments of polyethylene terephthalate and continuous filaments of a low-melting adhesive component of an 80/20 copolymer of polyethylene terephthalate and polyethylene isophthalate were randomly mixed in a ratio of 85:15 was spun. Made using the bond manufacturing method. The melting point of polyethylene terentalate continuous filament is approximately 260
°C, and the fineness was about 4 denier. On the other hand, the melting point of continuous filaments of the low melting point adhesive component of the copolymer is approximately 21D°C,
The fineness was about 5 denier. The corner weight of the web is 47
g/m2. The web is preheated in a preheater for about 20 minutes.
It was preheated to 10° C. and bonded by passing it between two heated rolls as shown in FIG. The surface temperature of the heating roll is 215
℃ and the pressure was 20 km on the web.

Next, the nonwoven fabric bonded as shown in Figure 1(a) is passed through a nip roll made of metal/rubber and having a cooling water circulation mechanism set at a speed ratio of 1:1.25 with respect to the heating roll. , gave the nonwoven fabric an actual elongation of 4.5%. The nip roll was installed approximately 1.5 m behind the heating roll, and the nip pressure was 5 kg/a linear pressure against the nonwoven fabric.

The properties of the obtained nonwoven fabric were as follows: date weight 516/m2. The tensile strength in the longitudinal direction was 18.7 kg/3(2) on average, the modulus at 5% elongation was 11 kg73 cm, and the elongation at break was 17% on average. The strong elongation measurement method is JIS, Ll
It was determined by the 085 strip method.

Example 2 Table 1 shows the results of each level in which the same web and adhesion/stretching apparatus as in Example 1 were used, but the elongation rate and target weight were changed.

Table 1 *Speed Ratio Comparative Example of Speed Increase Ratio of Nip Roll to Heating Roll A nonwoven fabric was made using the same web as in Example 1 without using a sib roll as a stretching device. The measurement result of the actual elongation rate at this time was -40%, which was shrinkage.

The obtained non-woven fabric has a basis weight of 54 g/m2. Vertical tensile strength 162 kg/3>, modulus at 5% elongation 5, 2
kg/3 cm, and the elongation at break was 28%.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram illustrating the stretching device used in the present invention;
, FIG. 2 is a schematic diagram showing another example of the nip roll. 1: Heat pressure roll 2: Nip roll: Non-woven fabric

Claims (1)

[Claims] When manufacturing a nonwoven fabric by bonding fiber sheets mainly composed of thermoplastic fibers by thermocompression bonding, the nonwoven fabric immediately after thermocompression bonding is elongated in the longitudinal direction at an actual elongation rate of 0 to 10'%. Method of manufacturing nonwoven fabric.