DE2716567A1 - PROCESS FOR MANUFACTURING NONWOVEN TRACKS - Google Patents

Description

Process for the production of monwoven webs

The invention relates to a method, moisture-containing to bind nonwoven webs made of polyamide threads.

Various methods are known for binding nonwoven webs. For example, U.S. U.S. Patent 3,647,591 a method of binding a web of a mixture of nylon threads and threads of a different type, which are supported by strong Acids such as hydrochloric acid are not attacked. The acid is applied to the web from an aqueous solution by spraying or Immersion is applied, then the fabric is calendered to to join the nylon threads of the panels. Under these conditions, the acid dissolves the nylon threads, so that these threads

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ORIGINAL INSPECTED

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act more or less as an adhesive holding the whole web together while the other threads of the web Give strength.

US Pat. No. 3,6M7 2kk describes a process for bonding a web of polyamide threads, in which the web is passed through a pretreatment zone in which the web absorbs 3 to 6% by weight of water and is then passed through a second zone in which the Bahn absorbs hydrogen halide gas and other moisture. The point of pretreatment is to allow the web to absorb gas more quickly. The web is then pressed and self-bonded by washing with water at room temperature while removing the absorbed gas.

The U.S. U.S. Patent 3,516,900 describes a method to bond the entire surface of a nonwoven polyamide web or fabric by exposing the web to gaseous hydrogen halide or exposing Bortrifluorld and then the activating gas either by washing at room temperature or heating removed from the fabric.

Nonwoven fabrics that are bound over the entire surface, barely wrinkled and are usually stiff and papery. Such nonwoven fabrics are not suitable for such Purposes for which the physical properties of a conventional substance are required. It is known

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that with nonwoven fabrics better folds and better ones Handling properties can be achieved if only subdivided, certain areas of the fabric are tied. This Fabric is made by a process known as "pattern bonding".

In some "pattern bonding" procedures, bonding is used achieved by applying an adhesive to specific, subdivided areas of the fabric. Disadvantages of this procedure are that a foreign material is introduced into the tissue and it is difficult to prevent the lateral migration of the adhesive control during the penetration of the substance. The build-up of adhesive on the plant can also be a problem.

In another "pattern bonding" process, the nonwoven web or fabric is pressed between a pair of rollers, at least one of which was driven and heated to such a temperature that the threads at certain points on the fabric, the roller pressure and the heat of the fabric firmly connect and fuse. Unfortunately, when the roller is hot enough to secure a strong bond in the bond surface, certain proportions of the rest of the fabric will also be bonded, as described in US Pat. No. 3,855,045. Accordingly, the drapery and handling properties of the fabric are impaired to some extent. Some of the bonds in the fest-

709843/0942

ORIGINAL INSPECTED

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Connected parts of the fabric can be broken by machining the fabric, but this would add to the process add another step.

In the ideal case, the material that is connected in places would have certain, bound places and little or no binding in the Rest of the fabric. Such a fabric will have a high strength, but still have good folds and a good grip.

It is known that one binds a fabric made of polyamide threads autogenously by an activating agent and on the fabric Applies vaporous water and then passes the fabric through rollers at room temperature. A disadvantage of this method is that the ambient humidity has an effect on the amount of bond achieved while the webs through the rollers are guided. It is known that nylon threads quickly absorb moisture. Under high relative conditions Ambient humidity, the fabric will contain more moisture than under conditions of low relative humidity. The result is a bond that is not uniform.

The invention relates to a method for binding nonwoven webs or fabrics made of polyamide threads, in which the threads 0.1 to 20, preferably 0.5 to 6.0 wt. % Of an activation

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ORiGlNAL INSPECTED

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agent and contain enough moisture to keep the molar ratio of water to activating agent in the threads is above the binding limit and at which the fabric is sufficient is heated high to displace sufficient moisture that the molar ratio of water to activating agent is decreased below the bond limit during pressing of the fabric. After pressing, the connected Web washed to remove the activating agent and then dried.

For "pattern bonding" the fabric is used in a first treatment zone exposed to a gaseous activating agent, preferably in the presence of water vapor, then the fabric goes through a second treatment zone where it is absorbs enough additional water vapor to keep the molar ratio of water to activating agent in the range of Increase ring zones of the threads of the fabric to at least 2, as the fabric under these conditions when pressing Room temperature, is essentially non-bondable. The fabric is then passed through a pair of rollers, at least one of which is driven and heated enough to autogenously bind certain parts of the fabric. That high molar ratio of water to activating agent prevents binding in those parts of the fabric that are not come into contact with the driven roller, so that the fabric has high strength and good folds and handle will be.

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ORIGINAL INSPECTED

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FIG. 1 shows the schematic side view of a plant for carrying out the method according to the invention.

Figure 2 shows a graph in which the tensile strength is plotted against the molar ratio of water to activating agent and shows the result of the pressing a fumigated substance at room temperature, which contains water and activating agent in different proportions.

Figure 3 shows a graph in which the tensile strength and the molar ratio of water to hydrochloric acid versus the time in which a nonwoven web is exposed to high humidity exposed, the fabric being pressed at room temperature after exposure.

Figure k is part of a section of the surface of the driven roller and makes the raised parts visible on the surface of the roller.

In detail, FIG. 1 shows a system which is suitable for carrying out the method according to the invention. Polyamide threads 11, formed by a spinneret 12, are attenuated and opened by an air nozzle or a damping device 13 a porous belt 16 inflated; a suction box 17, attached below the belt, holds the threads 11 on the belt 16 fixed. The threads are on the tape in the form of a non-

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ORIGINAL INSPECTED

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woven fabric 19 collected. This is the usual structure and operation.

The belt 16, fastened on and moved by rollers 18, carries the web or fabric 19 made by the threads in the chamber The unbound substance was formed in an atmosphere of activating agent and optionally gaseous water is exposed. Chamber 23 can be found in U.S. Pat. U.S. Patent 3,676,244 will. However, the structure of the chamber 22 is not essential and other chambers can also be used.

In the chamber 22, the substance is fumigated by exposing it to an atmosphere consisting of a mixture of water vapor and activating agents, such as gaseous hydrogen chloride. It is not necessary, but advisable, that water vapor be used in chamber 22 as water vapor increases the uptake of the activating agent in the fabric. In this Chamber absorbs the surface of the threads in the fabric hydrogen chloride and water in a molar ratio of about 1: 1, over a wide range of gas compositions. in the in general, the atmosphere in chamber 22 and the residence time of the fabric in chamber 22 should be such that the fabric absorbs about 0.1 to 20 wt. of hydrogen chloride in this chamber. Preferably, however, the substance in chamber 22 should absorb only 0.5 to 6 wt. * of hydrogen chloride. If the substance 19 coming out of the chamber 22 at room temperature

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and moisture is pressed, it will be able to bind.

As used herein, the term "activating agent" relates to any gaseous agent that causes autogenous bonding of polyamide filaments, as described in U.S. Pat. Patent specification 3,516,900. Examples of such effects Activating agents are hydrogen halides, boron trifluoride, Sulfur dioxide, sulfur trioxide and a mixture of chlorine and sulfur dioxide. Hydrogen chloride is the preferred Activating agent.

The method according to the invention is for threads with polyamide surface fractions feasible. The threads can be single-component polyamide or multi-component polyamide threads, in which the threads have polyamide components on the surface. Accordingly, the method is side-by-side Bicomponent threads, one of which is made of polyamide and, in the case of sheath / core threads, of which the sheath is made of polyamide consists. Bonding nylon in this process is an example of the general case where the polymer is Any composition that contains high levels of hydrogen bonds has hydrogen bonds through the absorption of an activating agent system can be burst (e.g. HpO + HCl in the example of the polyamide), followed of the regression of the hydrogen bonds after the desorption of the system.

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ORIGINAL INSPECTED

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As the fabric 19 passes through the second zone or chamber 23, it is post-treated by being in an atmosphere exposed to high moisture content in such a way that the fabric also absorbs water. Should be in chamber 23 so much water can be absorbed that the chamber 23 leaves Substance a molar ratio of water to hydrochloric acid of about 2-2.5 to 1 in the binding ring zone of the threads that make up the Build up substance contains. If the substance has absorbed water vapor and hydrochloric acid in this molar ratio, it becomes during the pressing process at room temperature will be essentially non-bondable. The terms "thread ring zone" and "binding Ring zone "refers to the outer parts of a single thread in the fabric, these parts amount to less than 1 to etv & 65i the average of a thread. After passing through the second treatment zone 23 the fabric or web 19 is passed between rollers 26 and 27 which push and press the running fabric to the molar ratio from water to activating agent to a value below the binding limit. The expression As used herein, "limit of binding" refers to the molar ratio of water to activating agent that is contained in the thread ring zone, above which the fabric during pressing at room temperature is substantially is not binding. If this molar ratio is exceeded, the tensile strength of the fabric drops dramatically away. This rapid drop in tensile strength as the

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ORIGINAL INSPECTED

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Molar ratio is represented by the almost vertical part of the curve in Figure 2 and by the similar curve in Figure 3 · The roller 27 is heated and has a chased or pierced surface. there, where in places Bond is desired. The surface of the roller 27 can be driven in such a way that it has raised parts 28 (Figure 4) that touch certain parts of the fabric and apply heat and pressure and the rest of the surface the roller 27 remains out of effective contact with the fabric.

The roller 27 is heated sufficiently that its raised portions 28 will remove some water from certain parts of the fabric expel that come into contact with them, compress them and cause binding in these fabric parts. The amount Water that was driven off from these pieces of material should be so high that the final molar ratio of water to activating agent in the binding thread ring zones of these points is approximately below 2. Otherwise the bond will only be weak be. Since the remainder of the fabric remains out of effective contact with the heated roller 27, little or no will become Bonding occur in the rest of the fabric. Accordingly, after passing through the rollers 26 and 27, the fabric becomes different have arranged, firmly bonded sites, while the remainder of the fabric remains essentially unbonded. the Size, shape and the distances between the connected points of the

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ORIGINAL INSPECTEP

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Substance are determined by the surface design of the driven roller 27.

The pattern of the raised areas of the roller 27 is not critical. The entire area of the raised areas 28 make up 2 to 80 # of the total surface area of the roller, preferably 5 to 25 ?. The amount of raised areas per cm should be 1 to 100, preferably 16 to 64.

The weight of the web or fabric 19 should be k to

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400 g / m 2, preferably 10 to 150 g / m 2.

The fabric then passes through a washing zone 30 in which the activating agent is removed. After this During the washing process, the fabric is passed through a drying zone 31 and then taken up on a roller 33.

Figure 2 is a graph showing the effect of increasing the water to hydrochloric acid molar ratio to about 2 in the bonding ring zones. The curve in this illustration was created by pressing different samples of nonwoven polyamide sheets with different ratios of water to hydrochloric acid at room temperature . These fabrics passed between smooth steel rollers at a pressure of 17.86 kg per running centimeter of roller contact with the fabric. The curve shows the strength

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ORIGINAL INSPECTED

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of the substance, which is a direct dependence on the bond in the substance and is relatively high until the ratio of Water to HCl in the binding ring zone, in this case the amount exceeds about 2.5. When the molar ratio from water to hydrochloric acid exceeds this value, the strength of the fabric is significantly reduced. Adding enough Water in chamber 23 and the associated increase in the ratio of water to hydrochloric acid to about 2-2.5 ensures that little or no binding of the fabric occurs when pressed at room temperature. Polyamide threads that have absorbed HCl will quickly absorb moisture when placed in a high humidity atmosphere are exposed and quickly reach the desired ratio of about 2-2.5.

During a number of series of measurements it was found that the almost vertical part of the curve in Figure 2 at a molar ratio of HO / HCl occurs from about 2 to 3.5. In some In cases it was 2, in others it was 3.5. The reason for the deviation from 2 to 3 x 5 is assumed that, by the Migration of some water into the inner parts of the polyamide threads, the molar ratio of water to activating agent in the outer parts or the binding ring zones the threads are lowered. The reason for the fact that the substance no longer combines above this molar ratio it is believed that enough hydrogen bonds are broken in the polyamide structure and the structure

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ORIGINAL INSPECTED

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sufficiently "plasticized" that the surface has changed from being tacky to being less viscous, non-sticky Stage has passed.

Impossible is the molar ratio of water to activating agent in the thread ring zone without also considering the core of the thread. When determining the Molar ratio, it is assumed that the water which is present in the thread before the application of the gas is uniform is distributed through this and that water and activating agent, which are taken up in the following step, are present in the thread ring zone. In view of the short period of time between the application of the gas and the Pressing, it is reasonable to assume that most of the water activating agent will be removed during application of the gas and the aftertreatment is added, is located in the ring zones of the threads when they are in the pinch point the rollers 26 and 27 occur. The molar ratio of water to activating agent at which the nearly vertical portion of the Curve in Figure 2 occurs, is called the "binding limit", since at molar ratios above this value, little or no bonding occurs in the fabric and that when pressed at room temperature and a pressure of 17 x 86 kg / cm becomes, is no longer binding.

It is not fully understood why the moisture level required for the desired molar ratio is at

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ORIGINAL INSPECTED

best achieved after the activating gas is on the fabric has been applied. While the threads of the activator / steam mixture are exposed, the thread ring zone absorbs hydrochloric acid and additional water and an uptake of 0.1 to 20 percent by weight is quickly achieved Activating agent at a molar ratio of water to activating agent of about 1: 1. In general the thread ring zone absorbs water and activating agent in a molar ratio of 1: 1 from the activating Gas mixture. However, the fumigated substance can quickly get additional water from the humid atmosphere in the chamber 23 record.

By "non-bondable" it is meant that the bond that is achieved is below an acceptable level when the fabric is passed between two steel rollers at a pressure of 17.86 kg per linear inch of roller contact, the rollers and the fabric being one Have a temperature of 21 ° C. For practical purposes, a fabric with an acceptable level of bond will have no less than 50 to 70 percent of the tensile strength of a similar fabric passed through rollers heated ^{to about 65 ° C. at the same pressure.} Typically, the strength of a non-bondable fabric pressed with unheated rollers is about 10-10 percent of the strength of the same fabric pressed with heated rollers.

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Figure 3 shows the molar ratio of water / HCl in the Thread ring zone and the tensile strength plotted against the dwell time in a moisture-containing atmosphere.

These curves were obtained by exposing the samples to a gaseous mixture of water and hydrochloric acid, in which they were allowed to absorb water and hydrochloric acid up to a molar ratio of 1: 1 in the thread ring zones and then were they an atmosphere of about 76? relative humidity exposed so that the samples, after they have been exposed to the humid atmosphere, in the binding Ring zones of the threads had different molar ratios of water to HCl. The samples were then placed between two steel rollers carried out at a temperature of 21 C and a pressure of 17.86 kg / running roller centimeter and the Tensile strength determined.

From Figure 3 it can be seen that the molar ratio of water to HCl rose rapidly to a value of about 3.25 and to at the same time the tensile strength from about 53 x 3 to about

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18.8 g / cm / g / m decreased. Then, while further exposure to a humid atmosphere, the molar ratio slowly increased, at a point where the tensile strength had dropped to about 13.6 g / cm / g / m. The decrease in tensile strength to this value shows that there was a large decrease in the bond in the sample during pressing at room temperature.

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From Figure 3 it can be clearly seen that a residence time in a humid atmosphere of less than one minute sufficient to increase the molar ratio of water to HCl to a value above the binding limit.

example 1

A nonwoven web made of polyamide threads was passed through a gassing chamber in which they were exposed to an atmosphere of 0.5 percent by volume HCl and Ο.83 percent by volume water vapor. The dwell time of the fabric was 5 seconds and the fabric took up 1.7 % by weight HCl. Immediately after leaving the fumigation chamber, the fabric was passed through a pair of smooth steel rollers at room temperature and a pressure of 17 · 86 kg / running roller centimeter. Had after pressing

2 the fabric has a tensile strength of 28.5 g / cm / g / m, a NuIl-

2 tensile strength (zero span tenacity) of 82.1 g / cm / g / m and a flexural strength of 3 x 38 cm.

Example 2

Example 1 was repeated except that after the fumigation step, the fabric was passed through a chamber and an atmosphere has been exposed to a relative humidity of 75JIt so that the fabric absorbs enough additional moisture, to achieve a non-bondable state. Of the

Fabric was then made in the manner described in Example 1

2 and had a tensile strength of 2.39 g / cm / g / m, a

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2 zero span tenacity of 88.1 g / cm / g / m and a flexural strength of 2.1 cm. The very low tensile strength of this example shows that the addition of more water following the gassing step, the binding of the Effectively prevented the substance at room temperature.

Example 3

Several series of measurements were made to determine the water loss of a nylon fabric during hot pressing

2 show. Nylon fabrics with a weight of 33 «85 g / m and up to a state of equilibrium at 65Ϊ relative humidity pretreated, were exposed to a gas stream of vaporous water and HCl, so that the substance HCl and additional Absorbs moisture, and then post-treats by creating an atmosphere with 6Ο-62Ϊ relative humidity was exposed at 21 ° C for 3 minutes. The fabric was then passed between rollers at various speeds pressed, which were heated to a temperature of 100 C. Table 1 shows the amount of HCl and water used during the Procedure was absorbed and released again. Table shows that little of the fabric during hot pressing Activating agent was lost while a large percentage of water was driven off. The water loss decreases the molar ratio of water to activating agent in the fabric, making it binding. Water became of them Parts of the substance that are associated with the hot

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driven roller came into contact, whereby a good bond was achieved in these places, while little or no Bonding occurred in the areas of the fabric that did not come into contact with the driven roller. The fabric will high tensile strength paired with good drapery and Possess handling properties.

Table 1 After gassing and
aftercare % By weight HCl Roller tightness
speed Water content
after the preparation
plot % H ₂ O by weight 3.42
3.I6
3.42 [m / min.] Weight percentage 7-32
5.65
7.32 .305
1.22
3.66 4.44
3.43
4.44

After pressing

Wt % H ₀ O

Weight with HCl

Loss during pressing

Molar ratio HO / HCl 2

3.22
2.24
4.22

2.49 2.84 2.89

4.10
3.42
3.IO

0.93
Ο.32

0.53

8.9 2I.7 11.9

Example 4

To show the effect that additional moisture has on a nonwoven web exposed to an H O / HCl atmosphere the following series of measurements have been carried out

ρ has been. Nylon fabrics with a weight of 33.9 g / m, pre-

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acts to equilibrium in an atmosphere with 65JS relative humidity, were for 150 seconds exposed to a gas stream of 0.21} HCl and 0.60 $ water, 3.9 percent by weight of HCl were added.

The fabrics were then, of different lengths, a stream of air exposed at 21 ° C and a relative humidity of 76 *, so that the fabrics could absorb additional moisture before pressing. The fabrics that are different Ratios of water to hydrochloric acid contained in the thread ring zones were passed between smooth rollers, with a Speed of 2.7 m / min., A roller pressure of 17.86 kg / cm and a roller temperature of 25 ° C. The series of measurements A, B, C, D and E in Table 2 show the results.

Table 2 Tensile strength molar ratio
before pressing
[h ₂ O / HC1] [g / cm / g / m ² ] 54.1
56.6
20.2
13th
48.5 Series of measurements Exposure
Time
C lake. ] I.I8
2.55
3.12
3.37
3.37 A.
B.
C.
D.
E. 0
20th
60
120
120

It can be readily seen that as the molar ratio of water to HCl in the binding ring zone increases, so too does the resistance of the fabric to binding

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Room temperature increases. Between a molar ratio of 2.55 and 3.12, the tensile strength drops from 56.6 to 20.2 g / cm / g / m ² .

In the series of measurements E, which illustrate the method according to the invention, the material was pressed between rollers heated to 150.degree. By heating to this temperature , the rollers were hot enough to make the fabric bindable, which was expressed in a tensile strength that increased to 48.5 g / cm / g / m ² .

Example 5

To demonstrate the effect of this process, a thread with a non-polyamide component, namely a fabric

2
with a weight of 33 · 9 g / m and made of a 5Ο / 5Ο nylon 66 / polyester sheath / core thread, pretreated to an equilibrium state at 23 ° C and 76 * relative humidity and a gas stream of O.24J HCl and 0.84; Exposure to water long enough for the fabric to absorb 1.25 percent by weight HCl. The fabric was then exposed to a current of 75% relative humidity at 24 ° C to absorb additional water required for this process. The aftertreated material was pressed between a driven ^{roller heated to 150 °} C. and an unheated resilient roller at a nip speed of 15 meters / min. After desorption and drying, the fabric was soft and pliable

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and had a tensile strength of 52.3 g / cm / g / m ² .

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Claims (1)

Patent claims: 1. A method for binding a nonwoven web of polyamide threads in which the threads contain 0.1 to 20% by weight of an activating agent and sufficient water that the web is not capable of binding at room temperature, characterized in that, a. that the web is heated sufficiently to make it bondable, b. the web presses so that the threads are autogenously connected, and c. removes the activating agent from the web. 2. The method according to claim 1, wherein the threads contain sufficient moisture so that the molar ratio of water to activating agent in the threads is above the binding limit, characterized in that a. that the web is heated enough to drive off enough moisture that the molar ratio falls below the bond limit, - 23 -709843/0942 ORIGINAL INSPECTED b. presses the fabric to autogenously connect the threads in the fabric, and c. removes the activating agent from the web 3. The method according to claim 2, characterized in that the activating agent consists of a Group is chosen which contains: hydrogen halides, boron trifluoride, sulfur dioxide, sulfur trioxide and a mixture of Chlorine and sulfur dioxide. 4. The method according to claim 3, characterized that the activating agent is hydrogen chloride. 5. The method according to claim 3, characterized that the web contains 0.5 to 6 wt. $ of said activating agent. 6. The method according to claim 5, characterized in that the web is heated and pressed simultaneously will. 7. The method according to claim 6, characterized in that the web in the nipping point of a pair of rollers is heated and pressed. 709843/0942 - 24 ORIGINAL INSPECTED 3 ^ V 165b / θ. Method according to claim I ₁ , characterized in that the threads are rare-on-rare two-component threads, one of which is made of polyamide. 9 · The method according to claim 1, characterized shows that the threads are sheath / core threads in which the sheath is made of polyamide. 10. Method of joining nonwoven webs in places according to claim 1, characterized in that a. that the web is passed through a first and second treatment zone, b. applying the activating agent to the web in the first treatment zone and allowing the web to absorb 0.1 to 20% by weight of the activating agent. c. enough vapor in the second treatment zone Applying water to the web so that the web does not remain capable of binding when it is pressed at room temperature, d. the web passes through a pair of rollers, at least one of which has raised parts that with 709843/0942 - 25 - ORIGINAL INSPECTED 4 ώϊΐΐ,; .., -; Make the web come in contact and are heated enough to bond in the said Make the web effect, and e. removes the activating agent from the web. 11. The method according to claim 10, characterized in that the activating agent is gaseous and is selected from a group consisting of: hydrogen halides, Boron trifluoride, sulfur dioxide, sulfur trioxide and a mixture of chlorine and sulfur dioxide. 12. The method according to claim 11, characterized in that there is a vaporous mixture of Applying water and activating agent to the web in the first treatment zone and allowing moisture and the web Include activating agent in a molar ratio of about 1: 1. 13. The method according to claim 12, characterized p indicates that the web has a weight of 4 to 400 g / m 709843/0942 ORIGINAL INSPECTED