DE102016120818A1 - Process for producing a stitchbonded nonwoven fabric - Google Patents

Abstract

The invention relates to a method for producing a stitchbonded nonwoven fabric based on a homogeneous fiber mixture comprising polyester fibers and a low-melting fiber component from which a batt is produced by carding, laying the batt in several layers to a nonwoven and then solidifying the nonwoven by stitching. According to the invention, the fiber fraction of low-melting polymers consists of binder fibers having a core-shell structure which have different melting temperatures of core and shell. On the process side, in a first temperature treatment step, the binder fibers are triggered by melting the jacket, in which case the polyester fibers are fixed. In a second temperature treatment step, a thickness adjustment and simultaneous surface gloss production takes place, wherein the second temperature treatment step is carried out below a predetermined high pressure value.

Description

The invention relates to a method for producing a stitchbonded nonwoven fabric based on a homogeneous fiber mixture comprising polyester fibers (PES) and binder fibers, from which a batt is produced by carding, laying the batt in several layers to a nonwoven and then solidifying the nonwoven by stitching according to Preamble of claim 1.

From the DD 217 837 A1 For example, a method for surface stabilization of nonwoven suture stitch fabrics is previously known.

According to the teaching there, such stitchbonded fabrics, which are prone to pilling and linting, are to be consolidated and stabilized to meet higher requirements, e.g. to work and work clothes are enough.

In this regard, the submitted batt is heated before sewing under pressure and partially or completely melted on, such that in the Nähwirkprozess the needle penetration preferably takes place from the fused, so solidified side.

It is also known to produce nonwovens with a proportion of thermoplastic fibers and solidify by fusion, but there is a risk of hardening of the nonwoven material.

The GB 1 399 153 B discloses a nonwoven sewing fabric which is solidified by heat by exposing the non-mesh side of the contact heat to a steel roll. Due to the fusion of the non-woven fibers, an improvement of the pill-resistance is achieved on this side.

Also known is an adhesive tape comprising a backing comprising a stitchbonded fabric and an adhesive layer applied to the backing at least on one side DE 20 2014 106 247 U1 ,

The stitchbonded fabric contains fibers which are completely made of polyester, in particular of polyethylene terephthalate (PET). The fibers are integrated with at least one sewing thread.

According to the DE 20 2014 106 247 A1 the performance of known adhesive tapes should be improved, in particular by an adhesive tape with a temperature resistance of> 125 ° C.

In this regard, the prior art stitchbonded web contains bicomponent fibers in addition to the polyester fibers. This is understood to mean fibers which are produced from two polymers having different physical and / or chemical properties. As a special property of the bicomponent fibers a crimping behavior is attributed, which is achieved by different shrinkage capacity of the components. The according to DE 20 2014 106 247 U1 used bicomponent fibers have a fiber fineness in the range of 1.0 dtex to 7.6 dtex. The size ratio of fiber fineness to warp fineness is in the range of 1:50 to 5:50. Furthermore, the size ratio of the fineness of the PES fibers to the fineness of the bicomponent fibers is preferably about 1: 1.

The sewing fleece according to DE 20 2014 106 247 U1 is produced with the well-known sewing technology according to Maliwatt. In this case, a raw nonwoven is solidified by this, formed, for example, as a laid transversely paneled batt, is solidified by one or two-thread systems. In this regard, a slider needle Schließdrahtsytem pierces the fiber template and pulls in the backward movement one or two inserted sewing threads through the raw nonwoven to be consolidated. Thereafter, the discount of the previous stitch and the deduction of the goods.

Although the non-woven fabric sewing fabrics known in the prior art are already very well suited as technical tapes, there are various disadvantages compared to conventional fabrics. On the one hand, the tear strength of a fleece-stitch sewing fabric is in many cases not sufficient. On the other hand, there is no sufficient degree of gloss, which is disadvantageous in certain applications.

From the foregoing, it is therefore an object of the invention to provide a further developed method for producing a stitchbonded nonwoven fabric based on a homogeneous fiber mixture containing polyester fibers and binder fibers, which allows a high gloss level of at least one surface side of the material to be created together with imitation of a Gewebeoptik.

The object of the invention is achieved by a teaching according to the method of claim 1, wherein the dependent claims comprise at least expedient refinements and developments.

According to the teaching of the invention, a stitchbonded nonwoven fabric, preferably based on the Maliwatt technology, is produced in a manner known per se, but the fiber mixture used has a binder fiber content of, for example, 15% low-melting binding fibers. The binder fibers used according to the invention are, for example, so-called core-sheath fibers in which core and sheath have different melting temperatures.

According to the invention, a subsequent thermal treatment, in particular a calendering at temperatures of substantially 180 ° C to 190 ° C.

By the temperature treatment or by a multi-step temperature treatment together with pressure on the nonwoven material, a triggering of the binder fibers takes place, this means that due to the effect of temperature of the low melting binder fiber portion melts. The melted binding fibers then fix the polyester fibers, resulting in the necessary material hardness and a desired material handle.

In a second temperature treatment step, which takes place under pressure, the desired material thickness is set and the gloss level is generated.

Since the fibers in the nonwoven fabric are mainly oriented transversely and the warp threads are in the machine direction, a fabric optics is created analogous to warp-typical warp and weft threads.

The inventive method is thus based on the production of a stitchbonded nonwoven fabric based on a homogeneous fiber mixture. This fiber mixture contains polyester fibers as well as binder fibers, whereby a batt is produced from the mixture by means of carding. The batt is then crossed in several layers, in particular, so that a nonwoven is formed. Subsequently, solidification of the nonwoven takes place by means of stitching.

As stated, the binder fibers are embodied, for example, as bicomponent core-sheath fibers having different melting temperatures of core and sheath.

In a first temperature treatment step, the triggering of the binder fibers takes place by melting the low-melting binder fiber fraction. Here, the polyester fibers are fixed by forming bonding points between the fibers.

In a second temperature treatment step, the thickness adjustment and simultaneous surface gloss production takes place, wherein the second temperature treatment step is realized under a predetermined high pressure value as a line pressure, for example in the range of 100-500 N / mm.

The preferred calendering for carrying out the temperature treatment steps may be in the range of 130 ° C to 250 ° C.

The mixing ratio of the bicomponent fibers is in the range of 5 to 30 wt .-%. The mixing proportion of the polyester fibers, however, is in the range between 70 to 95 wt .-%.

The basis weight of the nonwoven fabric to be created is adjusted to 50 to 200 g / m ² , preferably 60 to 100 g / m ² .

The residence time of the material in the first temperature treatment step is regularly greater than the residence time in the second temperature treatment step. The relevant residence times are set by selecting the machine speed.

According to the invention, a stitchbonded nonwoven fabric with high tensile strength in the longitudinal direction, a high surface gloss and a Gewebeoptik.

According to the invention, the use of such a stitchbonded nonwoven fabric as a technical tape for sheathing, as a carrier material for self-adhesive coatings or as a component in laminating, wherein the aforementioned uses are not exhaustive, but exemplified.

The invention will be explained below with reference to an embodiment.

The material to be created according to the embodiment should be a lightweight Maliwatt nonwoven fabric of about 65 g / m ² basis weight, which is to find application as a technical tape material and consists of polyester and binder fibers with a shiny side together with fabric-optics.

For the production of the nonwoven fabric from the two components mentioned, it is essential to realize a homogeneous distribution of the fibers in the produced batt, so that uniform nonwoven properties can be achieved.

The batt is produced, for example, and preferably by means of carding. The proportion of thermoplastic bicomponent fibers should be set as high as necessary and as low as possible. Preference is given here to a fiber content of 10 to 20 wt .-%.

In order to obtain a uniform fiber pile, a preliminary resolution of previously measured quantities of fiber components by means of a bale opener and a fine opener takes place first.

By means of carding a batt is produced, wherein in the carded web, the fibers are longitudinally aligned.

Subsequently, a laying of the batt in several layers via a cross-stacker to a Fleece. This results in a reorientation of the batt and the fibers contained therein in the transverse direction.

Both the described fiber pre-resolution and the carding process achieve a homogeneous distribution of the fiber components.

The resulting nonwoven is subsequently transferred via a feed table of the solidification unit, in particular a Maliwatt stitchbonding machine.

The preconsolidation results in a Maliwatt product in machine fineness F22, i. with 22 active elements on 25 mm working width, in the basic binding fringe. For this purpose, the fiber pile supplied by the stacker is solidified by means of threads. A smooth filament yarn with a fineness of 50 dtex is used.

The row density is determined by the stitch length, which is for example 1.2 mm. The fibers are incorporated into stitches without being involved in the stitch formation.

The hole needle guides the warp thread at the point of action. The needle pierces the provided pile, the warp thread is placed over the slider needle and the closing wire closes when pulling back the needle bar the needle head, in which the warp thread is located, and is pulled by lying on the slider needle half-stitch. The half-stitch is cut off and the stitch-forming process begins again.

The product according to the invention is subject to a special thermal aftertreatment.

For the effects to be achieved, gloss generation and thermal activation of the binder fibers, it is basically the same in which order both processes take place.

In order to guarantee the release of the binder fibers, however, a certain residence time must be maintained under thermal treatment. This residence time is selected so that the low-melting component of the binder fibers contained in the mixture melts, so that the binder fibers can fix the polyester fibers.

In order to produce a gloss on the surface side of the product, a pressure treatment is carried out over a heated steel roller. The mentioned operations are carried out either separately on different machines or, for example, by means of a three-roller calender.

A separate treatment on different machines gives advantages in the error treatment of the product and leads to a particularly preferred variant, in which the binding fibers are first released on a belt calender and then produced on a two-roll calender gloss and thickness.

Determined exemplary calender settings result in the belt calender temperatures of 180 ° C and a material speed of 30 m / min. The pressure acting on the material is 6.5 bar.

In the following treatment in a two-roll calender, the temperature is 190 ° C. The material transport speed is 70 m / min and the line pressure applied to the material is in the range of 250 N / mm.

Alternatively, the effect of glossing or triggering the binder fibers may be effected by multi-roll calenders or in combination with infrared radiant heaters.

For presentation of the goods and for error handling seams in the form of welds are incorporated in the material. The separated by error treatment nonwoven webs are joined together at the material ends by a weld. The weld is then taped on one side with a tape.

If, after presentation and error treatment, the weld in a belt calender is exposed to a temperature of 180 ° C. for several seconds, there is a risk that it will break. For this reason, the sequence belt calender and subsequent treatment by means of two-roll calender is advantageous, so that the error treatment can be done at the end of the process.

In an example according to the invention Maliwatt is used in the machine fineness F22 with the above-mentioned basis weight of 65 g / m ² in the laying fringe with a stitch length of 1.2 mm as the starting material. It is here a fiber blend of 85 wt .-% polyester fibers (fineness 2.5 den and staple length 76 mm) and 15 wt .-% low-melting bicomponent fibers on the basis of polyester (melting range of the fiber cladding at about 110 ° C) before. The mixture is laid by means of carding and crosslayer to a nonwoven.

Subsequently, the nonwoven is solidified by means of Maliwatt stitchbonding machine using polyester warp threads to form a nonwoven fabric.

After thermal release of the binder fibers, gloss production and thickness calibration points the nonwoven fabric has a longitudinal strength> 150 N / 5 cm with a thickness of about 0.195 mm. The nonwoven fabric serves, for example, as a coating base product for a transversally tearable adhesive tape for wiring harness coating and imitates in its appearance a fabric.

It is therefore the product obtained characterized in that the fiber mixture consists of proportions of polyester fibers and binder fibers as bicomponent fibers. The thermoplastic fiber content may e.g. of polyester or other polymers, e.g. Polyamide, polypropylene, but preferably consist of polyethylene terephthalate. As explained above, in a binder fiber, one component has a lower melting point than the second component.

The warp threads used in the stitchbonding process are preferably made of polyester. However, it is also the use of polymers, e.g. Polyamide or mixtures thereof possible.

As hardening unit for pressure / temperature treatment, a heating calender, calender, belt calender or a flat bed laminating machine can be used. However, it should be ensured that the pressure applied to the nonwoven fabric is preferably 250 N / mm.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DD 217837 A1 [0002]
• GB 1399153 B [0006]
• DE 202014106247 U1 [0007, 0010, 0011]
• DE 202014106247 A1 [0009]

Claims (11)

Process for producing a stitchbonded nonwoven fabric based on a homogeneous fiber mixture comprising polyester fibers and a fiber fraction of low-melting polymers, from which a batt is produced by means of carding, laying the batt in several layers to form a nonwoven and then solidifying the nonwoven by means of stitching, characterized in that the fiber content of low-melting polymers is formed from bonding fibers having a core-shell structure, wherein the melting temperatures of core and shell are different, in a first temperature treatment step, the binder fibers are triggered by melting the shell, thereby fixing the polyester fibers by forming bonding points as well as in a second temperature treatment step, a thickness adjustment and simultaneous surface gloss production is made, wherein the second temperature treatment step takes place below a predetermined high pressure value. A method according to claim 1, characterized in that the nonwoven is crossed. A method according to claim 1 or 2, characterized in that the temperature treatment steps are carried out by means of heating calender, calender, belt calender or flat bed laminating. A method according to claim 3, characterized in that the calendering takes place at temperatures in the range of 130 ° C to 250 ° C. Method according to one of the preceding claims, characterized in that during the second temperature treatment step, a pressure of substantially 100-500 N / mm ^{2 is} applied to the material. Method according to one of the preceding claims, characterized in that the mixing proportion of the low-melting fiber component between 5 to 30% by weight and the mixing ratio of the polyester fibers is between 70 and 95 wt .-%. Method according to one of the preceding claims, characterized in that the basis weight of the nonwoven fabric to 50 to 200 g / m ² , preferably 60 to 100 g / m ^{2 is} set. Method according to one of the preceding claims, characterized in that the production of the nonwoven fabric by means of Maliwatt technology. Method according to one of the preceding claims, characterized in that the residence time of the material in the first temperature treatment step is greater than the residence time in the second temperature treatment step.  A stitchbonded nonwoven fabric having high longitudinal tear strength, high surface gloss and fabric optics produced by a process according to any one of the preceding claims in a thickness in the range of 0.1 to 0.25 mm.  Use of a stitchbonded nonwoven fabric according to claim 10 as a technical tape for sheathing, as a carrier material for self-adhesive coatings or as a component in laminating composites.