JPS5819783B2 - How to glue nonwoven webs - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for bonding moisture-containing nonwoven webs made from polyamide filaments.

Various methods of bonding nonwoven webs are known.

For example, U.S. Pat. No. 3,647,591 discloses a method for bonding webs made from a mixture of nylon fibers and another type of fiber that is not affected by strong acids such as hydrochloric acid.

The acid is applied to the web by spraying or dipping from an aqueous solution and the fibers are then heat calendered to bond the nylon filaments in the web together.

In these conditions, the acid dissolves the nylon filaments so that they act more or less as an adhesive to bond the entire web together, while the other filament in the web provides strength.

U.S. Pat. No. 3,647,244 discloses a method of gluing webs made from polyamide filaments, in which the web is bonded to water in a range of 3 to 6 ml.
The web is passed through a preconditioning zone where the weight percent is taken up and then through a second zone where the web is allowed to absorb hydrogen halide and additional moisture.

The purpose of the preconditioning step is to enable the web to take up a high proportion of gas.

The web is then compressed and washed in water at room temperature to self-adhere and remove absorbed gases.

U.S. Pat. No. 3,516,900 to Mail'onee et al. adheres a polyamide nonwoven web or fabric over all areas by exposing it to gaseous hydrogen halide or boron trifluoride; A method of removing activating gas from a nonwoven fabric by washing or heating at room temperature is disclosed.

Nonwovens that are bonded over the entire structural area have poor wearability and are usually stiff and paper-like.

Such nonwovens are unsuitable for many end uses where the physical properties of conventional textiles are required.

It is known that by simply spacing the nonwoven fabric and bonding only the discontinuous areas, the nonwoven fabric has better drape and hand.

This cloth is pattern bonded.
g) by a method known as

In some pattern bonding methods, bonding is accomplished by applying adhesive to discrete, spaced areas of the fabric.

Disadvantages of this method include the introduction of foreign materials into the wipe and the difficulty in controlling the lateral movement of the adhesive while achieving penetration into the web.

Also, the adhesive formed on the device in this method can be problematic.

In other pattern bonding methods, a nonwoven web or fabric is compressed between a pair of rolls, at least one of which has an embossed pattern, and the compression and heating of the rolls is concentrated in discrete areas of the fabric. The fibers of the web are heated to a temperature that melts them together.

Unfortunately, as in U.S. Pat. No. 3,855,045, if the roll is hot enough to ensure strong adhesion in the adhesive area, the amount of adhesion that also extends to the remaining areas of the dish towel is Let's get up.

Thus, the quality and texture of the fabric hanging will be somewhat impaired.

Some of the bonds in less dense areas of the fabric can be broken by moving the fabric, but this adds another step to the method.

Ideally, a patterned bonded fabric would have discrete areas of bonding with little or no bonding to the remainder of the fabric.

Such fabrics will have high tenacity but still have good hanging properties and feel.

It is known to autogenously bond webs made from polyamide filaments by applying a mixture of an activator and water in the form of steam to the web and passing the web between rolls at room temperature. There is.

One advantage of this method is that ambient humidity has an effect on the amount of adhesion achieved as the web passes between the rolls.

It is well known that nylon filaments readily absorb moisture.

In conditions of high ambient relative humidity, the web will contain more moisture as it passes between the rolls than in conditions of low ambient relative humidity.

This results in non-uniformly consistent adhesion.

The present invention is a method for bonding nonwoven webs or fabrics made from polyamide filaments, the method comprising:
The filament contains from 0.1 to 20% by weight of activator, preferably from 0.5 to 6.0% by weight, and sufficient water such that the molar ratio of water to activator in the filament is at least the adhesion limit. , the web is heated sufficiently while being compressed to drive off sufficient moisture to reduce the water to activator molar ratio to a value below the adhesion limit.

After compaction, the adhesive web is washed to remove the activator and then dried.

For pattern bonding, the fabric is exposed to the activator in gaseous form in a first treatment zone, preferably in the presence of water vapor, and then the fabric is exposed to the activator in gaseous form in the bonded ring of fibers within the fabric. The fabric absorbs sufficient additional water vapor to increase the molar ratio to at least about 2 and passes through a second treatment zone that is essentially non-bondable under these conditions when the fabric is compressed at room temperature.

The fabric is then passed between a pair of rolls, at least one of which is embossed with a pattern and heated sufficiently to cause self-generating bonding of the discontinuous portions of the fabric.

The high molar ratio of water to activator prevents adhesion of areas of the fabric not in contact with the embossed roll, so the fabric will have a high degree of toughness but also good hanging properties and hand.

FIG. 1 is a schematic side view of an apparatus useful for carrying out the method of the invention.

Figure 2 shows the results of compressing gas-treated webs containing different molar ratios of water to activator at room temperature. Strip toughness (str) plotted against water to activator molar ratio
ip tenacity).

FIG. 3 is a plot of strip toughness and H20/Hc1 molar ratio versus time of exposure of a nonwoven polyamide web to a high humidity atmosphere when the web is compressed at room temperature after exposure.

FIG. 4 is a fragmentary sketch of the embossed surface showing the raised area on the roll face.

Referring in detail to the drawings, FIG. 1 shows an apparatus suitable for carrying out the method of the invention.

The polyamide filaments formed by the spinning projections 12 are sprayed onto a narrow perforated belt 16 by an air nozzle or attenuator 13, and a suction box 17 located below the belt 16 retains the filaments 11 on the belt 16.

The filaments are collected on the belt 16 in the form of a nonwoven web 19.

This configuration and operation is conventional.

The belt 16 rides on and is moved by the roll 18 so that the web or fabric 19 formed by the filaments is exposed to an atmosphere containing an activator in gaseous form and, optionally, water in non-bonding conditions. chamber 22 exposed to
transport through.

Chamber 23 may be constructed as described in US Pat. No. 3,676,244.

However, the structure of chamber 22 is not limited, and chambers other than those used in U.S. Pat. No. 3,676,244 can easily be used.

In chamber 22, web 19 is gassed by exposure to an atmosphere created from a mixture of water vapor and an activating agent, such as hydrogen chloride in gaseous form.

Although it is not necessary to use steam in this chamber, the use of steam is preferred because it enhances the absorption of the activator by the web.

In this chamber, the surface of the filaments in the web absorbs hydrogen chloride and water in a molar ratio of approximately 1:1 over a wide range of gas compositions.

Generally, the atmosphere within chamber 22 and the residence time of web 19 within chamber 22 should be such that the web takes up about 0.1 to 20% by weight HCl in the chamber.

However, it is preferred that the amount of Hc7 absorbed by the tube in chamber 22 is between 0.5 and 6% by weight.

If the web 19 exiting the chamber 22 is compressed at the temperature and humidity of the chamber, it will be bondable.

As used herein, the term "activator" refers to U.S. Pat. No. 3,51 to Mallonee et al.
In gaseous form, as described in US Pat. No. 6,900,
Any agent that causes polyamide filaments to self-adhere.

Examples of such effective activators are hydrogen halides, boron trifluoride, sulfur dioxide, sulfur trioxide, and mixtures of chlorine and sulfur dioxide.

Hydrogen chloride is a suitable activator.

The method of the invention is operable on filaments having a polyamide surface portion.

The filaments can be monocomponent polyamide or multicomponent filaments in which the filament has a polyamide surface portion.

Thus, the method can be operated on sided bicomponent filaments in which one component is polyamide and sheath/core filaments in which the sheath is polyamide.

The adhesion of nylon by this method is an example of the general case, where the polymer has a high can be a composition containing hydrogen bonds of.

The web 19 then passes through a second zone or chamber 23 where it is post-conditioned by exposure to a high humidity atmosphere in such a way that the web absorbs additional water.

The amount of water absorbed in chamber 23 is such that the molar ratio of water to Hc, lj in the web leaving chamber 23 is about 2-2.5 to 1 or more in the bonded ring of filaments making up the web. Should.

If the web absorbed this molar ratio of water vapor and HCl, the web would be essentially non-bondable when compressed at room temperature.

“Filament ring” and “bond ring J”
The term "annulus" refers to the outer portion of each filament in the web, which accounts for less than 1% to about 65% of the cross-sectional area of the filament.

After passing through the second treatment zone 23, the web or fabric 19 is passed between rolls 26 and 27 in position to pinch and compress the moving fabric to bring the water to activator molar ratio below the adhesion limit. lower.

As used herein, the term "adhesion limit" means the molar ratio of water to activator contained in the filament rings above which the web is essentially non-adhesive when compressed at room temperature.

As this molar ratio increases, the strip toughness of the web decreases dramatically.

This rapid decrease in toughness as molar ratio increases is illustrated by the vertical portion of the curve shown in FIG. 2 and a similar curve shown in FIG.

The roll 27 is heated and has an embossed or engraved surface if pattern bonding is desired.

The surface of roll 27 has raised portions 28 where it contacts discontinuities in web 19 and applies heat and pressure thereto.
(FIG. 4), the remaining surface of the roll 27 does not come into contact with the web during operation.

The roll 27 is heated sufficiently so that its raised areas 28 displace some of the water in the discrete portions of the web in contact with these raised areas, making the bond in those areas of the web dense and effective.

The amount of water expelled in these regions or in these web sections should be such that the final molar ratio of water to activator in the bonded ring of fibers in these regions is about 2 or less.

Otherwise the adhesion may be poor.

Since the remainder of the web remains without operational contact by heated roll 27, little or no adhesion occurs in this remaining portion of the web.

Thus, after passing between rolls 26 and 27, the web will have dense bonded areas arranged in a pattern, with residual areas of the web essentially unbonded.

The size, shape and spacing of the adhesive areas of the web will be determined by the shape of the embossed roll 27 surface.

There is no limit to the pattern on the high part of the roll 27.

The total area of the raised regions 28 will be between 2 and 80% of the area of the roll, preferably between 5 and 25% of the area of the roll.

The number of high parts per square area can be from 1 to 1'OO, and preferably from 16 to 64.

The weight of the web or cloth 19 is between 4 and 4 per square meter.
00g, and preferably 10 to 15
It is 0g/d.

The web is then passed through a washing zone 30 where the activator is removed.

After the washing step, the web passes through a drying zone 31 and is taken up onto rolls 33.

FIG. 2 is a diagram illustrating the effect when the molar ratio of water to HCl in the adhesive ring is increased to about 2 or more.

The curves shown in this figure were obtained by compressing samples of nonwoven polyamide webs containing various molar ratios of water and HcA at room temperature.

This web has 17 per linear part of the roll in contact with the web.
．． It was passed between smooth steel rolls at room temperature using a pressure of 86 kg.

The spring strength of the compressed web, a direct indicator of the amount of adhesion in the web, remains relatively high until the molar ratio of water to HcA in the adhesive ring increases, in this case 2,5. This curve shows.

When the molar ratio of water to HCl exceeds this value, the tenacity of the web is substantially reduced.

Sufficient water is added in chamber 23 to increase the water to HCl ratio above about 2-2.5 to ensure that little or no adhesion of the web occurs when the web is compressed at room temperature. .

HCl-absorbing polyamide filaments rapidly absorb moisture when the filaments are exposed to a high humidity atmosphere, easily reaching the desired molar ratio of about 2-2.5.

After numerous experiments, we found that most of the vertical portion of the curve shown in Figure 2 corresponds to a H20/Hc1 molar ratio of about 2 to 3.
．． It was found that this occurs between 5.

In some cases it was as low as 2, and in others it was as high as 3.5.

The reason for this change from 2 to 3.5 is due to the migration of some water into the inner quarters of the polyamide filament,
It is believed that the actual molar ratio of water to activator on the outside of the filament or on the adhesive ring is then reduced.

The reason why the web is non-adhesive above this molar ratio is that above these molar ratios, many hydrogen bonds in the polyamide structure are broken and the structure becomes less viscous as the surface of the filaments goes beyond the sticky stage. It is believed that this is because it is sufficiently plasticized to reach the non-bonding stage.

The molar ratio of water to activator in the filament ring cannot be determined without considering the filament core.

If the molar ratio is determined, the water present in the filament before gas treatment is unfortunately distributed throughout the filament, and the water and activator absorbed in the subsequent process are only present in the filament ring. It is thought that there is.

In view of the short time interval between gas treatment and compression, most of the water and activator added during the gas treatment and after-conditioning process is carried out by the ring of filament entering between rolls 26 and 27. It is reasonable to think that it is in the belt.

H2 where most of the vertical portion of the curve shown in Figure 2 occurs
The molar ratio of 0/activator can be referred to as the "adhesion limit".

This is because at molar ratios above this value, little or no adhesion occurs in the web and no adhesion occurs when it is compressed at room temperature and at a roll pressure of 17.86 kg/cm. be.

It is not fully understood why the moisture levels necessary to achieve suitable molar ratios are best achieved after applying the activating gas to the web.

During exposure to the activator/water gas mixture, activator 0,
Uptakes of 1 to 20 weight by weight are easily achieved and filament F absorbs HCl and additional H2O in a water/activator molar ratio of 1:1.

Typically, the filament ring absorbs water and activator from the activating gas mixture in a 1:1 molar ratio.

However, this gas-treated web can easily absorb the additional required H2O from the humid atmosphere in the second chamber 23.

The term "non-bondable" refers to rolls and webs that are
C, the web is 17.86 per straight line of roll contact.
This means that the adhesion achieved when passing between two steel rolls under a pressure of 1 kg is below an acceptable level.

A web with an adhesion level acceptable for practical purposes has a strip toughness of 5.5% for the same web after passing between rolls heated to about 65°C and at the same pressure.
It will have a strip toughness of no less than 0-70.

Typically, the strength of a non-bondable web compressed with unheated rolls is about 10-40% of a similar web compressed with hot rolls.

FIG. 3 shows the H20/Hc1 molar ratio in the filament ring and the strip toughness plotted against the exposure time to a humid atmosphere.

These curves expose the sample to a gaseous mixture of water and HCl to cause the sample to absorb water and HCl in a 1:1 molar ratio in filament F, after which the sample is brought to a relative temperature of about 76
% atmosphere and after exposure to a moisture atmosphere, samples were obtained having varying water to Hc1 molar ratios in the adhesive ring of the filament.

The sample was then passed between two steel rolls at a temperature of about 21° C. and a pressure of 17.86 kg per straight line α of the rolls, and the IJ tube toughness was measured.

From FIG. 3, it can be seen that the molar ratio of H20 to Hcl quickly increases to a ratio of about 3.25, while the sl-IJ tube toughness increases to about 53.
3 to about 18.8 g/cIrL/g/m2.

Upon continued exposure to a humid atmosphere, the molar ratio then slowly rose to about 3.4, at which point the sl-IJ tube toughness decreased to about 13.6 g/cm/g7m2.

A decrease in strip toughness to this value indicates that there was a significant decrease in the adhesion that occurred in the sample when compressed at room temperature.

FIG. 3 clearly demonstrates that an exposure time of less than 1 minute to a humid atmosphere is sufficient time to increase the water to HcA molar ratio to a value above the adhesion limit.

Comparative Example 1 A nonwoven web made from polyamide filaments was passed through a gas treatment chamber to produce HClO, 5% by volume and water vapor of 0.8%.
Exposure to an atmosphere containing 3 volumes.

The exposure time of the web was 5 seconds, and the web was
7 weight clerks were added.

Immediately after leaving the gas treatment chamber, the web was compressed between a pair of smooth steel rolls at room temperature and under a pressure of 17.86 kg per linear box of rolls.

After compression, the web has a l-'IJ tube toughness of 2 s, 59
/CrfL/ g/m”, zero span (zero 5
-pan) Toughness 82.1 g/CrrL/ g/m'
, and a bending length of 3.38 CrIl.

Example 2 After the gas treatment step, the fabric was passed through a chamber and exposed to air having a relative humidity of 75 parts, except that the fabric absorbed sufficient additional moisture to reach a non-adhesive condition. Comparative Example 1 was repeated.

The fabric was then compressed in the manner described in Comparative Example 1, resulting in a strip toughness of 2.39 g/crrt/g/
m2, zero span toughness 88.1 g/cm/g/
m'' and a bending strength of 2.1.cm.

The extremely low strip toughness of this example compared to the strip toughness of the same in Comparative Example 1 proves that the addition of additional water after the gas treatment step effectively prevents fabric adhesion at room temperature.

Example 3 Several experiments were conducted to demonstrate water loss from a nylon web when subjected to hot compression.

3. Pre-equilibrium conditions at 65% relative humidity.
A nylon web having a weight of 85 g/m2 was exposed to a vaporous water and HcA-containing air stream to allow the web to absorb HcA and additional moisture, and then exposed to 6O-62SRH air for 3 minutes at 21°C. Post-conditioning treatment was performed.

The web was then compressed at various speeds between rolls heated to a temperature of 100°C.

Table 1 shows the amount of Hcl and water absorbed during this treatment and the amount lost f, IJ c ! and the amount of water.

Table 1 shows that during hot compaction, little activator was lost from the web while a large proportion of water was expelled.

Water loss is caused by water loss in the web vs. activator＼ − to lower the molar ratio of the web to allow it to adhere.

Water is expelled from the area of the web that was in contact with the hot embossing roll, resulting in good adhesion in this area, while little or no adhesion occurs in the portions of the web that were not in contact with the embossing roll. do not have.

This web has a high degree of toughness and good lean and hand properties.

Example 4 The following experiment was conducted to illustrate the effect of additional moisture on a nonwoven nylon web exposed to a H20/HCl atmosphere.

A nylon web with a weight of 33.9 g/m2 was pre-coated with 6
Adjust to equilibrium in 5SRH, then Hclo,
Exposure for 150 seconds to a gas stream containing 24% Hc and 0.60% water resulted in an absorption weight of 13.9% Hc.

The web was then exposed to air flow for various times at 24° C. and 75° relative humidity to incorporate additional moisture into the web prior to compaction.

Webs containing various molar ratios of H20 to HCl in the Foramen 1-3J band were then heated for 2.7 ml min.
It was passed between smooth rolls at a roll pressure of 17.86 kg/crIL and a roll temperature of 25°C.

The results are shown in Table 2 as Experiments A, B, C, D and E.

Table 2 Exposure time Molar ratio before compression Sl-IJ tube toughness experiment (
seconds) (H20/HcA) (9/cm1g/r
n”)A O1,18' 54.4B
20 2.55 56.6 Exposure time Molar ratio before compression Strip toughness experiment (sec)
(H20/Mcl)' U/Cmlυ version) C603,1
220,2 D 120 3.37 13°E
120 3.37 48.5 It will be readily apparent that increasing the molar ratio of H20 to HCl in the adhesive ring increases the resistance of the web to bonding at room temperature.

For molar ratios between 2.55 and 3.12, the strip toughness ranges from 56°6 to 20.2 El/cm/g
/ m.

In Experiment 1 illustrating the invention, the web was compressed between rolls heated to 150°C rather than rolls at room temperature.

When heated to this temperature, the roll is hot enough to bond the web to 48.5 El /cyri/
An increased strip toughness of g/m' was obtained.

Example 5 To illustrate the effectiveness of the method, a web of non-polyamide-containing fibers, 33.9 g/m2 of 50150 nylon 66/polyester sheath/core fibers, was pre-equilibrated at 23° C. and 76% RH. The web was then exposed to an air stream containing 24% HClO and 0.84% water for a period sufficient to cause the web to absorb 1.25 weights of HcA.

The web was then exposed to a 24° C., 75% RH air stream to allow the web to absorb additional water required by the process.

The conditioned web was then compressed between an embossed roll heated to 150 DEG C. and an unheated resilient roll at a clamping speed of 15 m/min.

After stripping and drying, the web was found to be soft enough to hang and had a toughness of 52.3 g/cm,/g/m2.

[Brief explanation of drawings]

FIG. 1 is a schematic side view of an apparatus for carrying out the method of the present invention;
FIG. 4 is a partial view of the surface of an embossing roll when used in the above-mentioned apparatus, and FIGS. 2 and 3 are diagrams illustrating the effects of the method of the present invention. 12...Spinning protrusion, 11...Filament, 13...Air nozzle, 16...
Belt, 17... Suction box, 19... Cloth, 22... First treatment area, 23... Second
Processing area, 26... Elastic roll, 27...
... Embossed roll, 28 ... Raised part, 30
...Washing area, 31...Drying area, 33.
...Take-up roll.

Claims (1)

Claims: 1 (a) 0.1 to 20 wt. of an activator to cause self-generating adhesion of polyamide filaments, and an amount of water sufficient for the web of said filaments to be non-adhesive at room temperature. (b) compressing the resulting web to cause the filaments in the web to self-generate bonding; A method for bonding nonwoven webs made from polyamide filaments, characterized in that: then (c) the activator is removed from the resulting web. 2 The molar ratio of water to activator in the filaments is greater than or equal to the adhesion limit A web containing sufficient water is sufficiently heated to bring the molar ratio of water to activator in the filaments to less than or equal to the adhesion limit. A method according to claim 1, characterized in: 3. The method of claim 1, wherein the web is characterized by 0.5 to 6 parts by weight of activator. 4 a- passing the web through a first and second treatment zone; b. applying an activator to the web in the first treatment zone to cause self-generating adhesion to the web; absorbing heavy weight and applying a sufficient amount of water in the form of steam to the web in a second treatment zone C1 to render the web non-bondable when compressed at room temperature; d. is passed between a pair of rolls having a raised portion in contact with a portion of the web, said raised portion being heated sufficiently to effect bonding in said portion of the web, and then e. A method for bonding patterns on nonwoven webs made from polyamide filaments, characterized in that said activating agent is removed from said polyamide filaments. 5. A mixture of water in the form of steam and activating agent is applied to the web in the first treatment zone to cause the web to absorb water and activating agent in a molar ratio of about 1=1. Section method. 6. The method of claim 5, wherein the web has a weight of 4 to 400 grams per square meter.