EP0628650A1 - Process for manufacturing supportless and release agent free thermally activated nonwovens and their use for bonding different substrates - Google Patents

Abstract

The present invention relates to a process for manufacturing supportless and release agent free, thermally activable nonwovens based on hydroxyl polyester polyurethanes having viscosities from 600 to 3500 mPa.s, measured as solution viscosity in methyl ethyl ketone (15% strength, Brookfield LVT viscometer, spindle 3, 60 rpm, 23@C), and having basis weights within the range from 5 to 200 mg/m<2>, which is characterised in that the nonwovens are formed by means of a melt-blowing process at melt temperatures from 230 to 260@C using a laydown belt whose material has a surface tension from 18.5 x 10<-5> N/cm to 45 x 10<-5> N/cm. The nonwovens manufactured by the process of the invention can be wound up non-blockingly without the addition of release or spacing agents and are highly suitable for adhering together different substrates.

Description

The present invention relates to a process for the production of carrier-free and release agent-free, thermally activatable nonwovens based on hydroxyl polyester polyurethanes, and to the use thereof for bonding different substrates.

It is known to accomplish the bonding of different substrates by means of solvent-based adhesive systems or by means of solvent-free adhesive systems based on hydroxyl polyester polyurethanes, for example by using hot-melt adhesive films (see, for example, H.J. Studt in Coating 2/93, pp. 34 ff). Disadvantages of the solvent-based adhesive systems are, on the one hand, the pollution of the environment by solvents which are released during the adhesive process, and, on the other hand, their long processing cycles, which entails high consequential costs. For economic and environmental reasons, one is inclined to use solvent-free adhesive systems for bonding different substrates.

The disadvantages of solvent-free adhesive systems, such as the use of thermo-activatable films based on hydroxyl polyester polyurethanes, are their low gas permeability and their hardening of the handle, which is particularly important when gluing textiles, as well as the relatively high weight per unit area, which is a higher material costs.

For the reasons mentioned, the use of the thermo-activatable films based on hydroxyl polyester polyurethanes is therefore important for technical applications, e.g. Laminating parts for the automotive interior, limited. Although in this area of application a larger and closed-area adhesive application is necessary for some composite structures, e.g. To absorb the restoring forces of deep-drawn soft PVC films, there are sufficient fields of application where it is possible to work with less adhesive and a closed film-like surface structure of the applied adhesive is only a disadvantage.

The films which can be thermally activated and are used to bond various substrates can be produced by a wide variety of processes.

The production of elastomeric films from e.g. Polyurethanes according to the coextrusion process (DE-A 2 114 065, US 3 880 691). The fabrics obtained do not contain any release agents or spacers. A major disadvantage of this process is the required, complex process technology (2 extruders and blow head with 2 concentric ring nozzles) and the production of a separating film, which can hardly be recycled.

The production of foils from thermoplastic elastomers, e.g. Polyurethanes, using the monofilm blown film extrusion process.

In order to be able to fully exploit the advantage of this process in terms of lower system investments, an internal release agent or spacer must be added to the relatively strong adhesive thermoplastics before blowing the film tube, otherwise the film webs will stick to one another after being laid flat by means of a squeeze roller and subsequently can no longer be separated.

• A) H. Saechtling, Kunststoff-Taschenbuch, 25. Ausgabe, Carl-Hanser-Verlag
• B) Becker/Braun, Kunststoff-Handbuch Bd. 7, Polyurethane, Carl-Hanser-Verlag
• C) Kunststoffe 80 (7), S. 827 ff. (1990)
• D) Gächter/Müller, Kunststoffadditive, 3. Ausgabe, Carl-Hanser-Verlag

beschrieben, geeignete Abstands- bzw. Trennmittel. Stand der Technik ist allerdings, daß die Zugabe von Trenn- bzw. Abstandsmitteln bei einigen Substraten eine Verminderung der Klebkraft zur Folge hat. Ebenfalls Verwendung finden polymere Abstandsmittel wie z.B. in der EP 0 526 858 beschrieben. Diese haben den Nachteil, daß sich unter Umständen das mechanische Eingeschaftsbild der resultierenden Flächengebilde in ungewollter Weise ändert. Daneben ist nicht auszuschließen, daß eine, im Vergleich zum eingesetzten Rohstoff, deutlich veränderte Aktivierbarkeit sowie Veränderungen bezüglich der spezifischen Adhäsion zu einigen Substraten feststellbar ist.Furthermore, these separating or spacing agents are used in order to prevent the coiled and separated film webs from becoming blocked by recrystallization. According to the current state of the art, waxes and / or organic additives such as in

• A) H. Saechtling, plastic paperback, 25th edition, Carl-Hanser-Verlag
• B) Becker / Braun, Kunststoff-Handbuch Bd. 7, Polyurethane, Carl-Hanser-Verlag
• C) Kunststoffe 80 (7), p. 827 ff. (1990)
• D) Gächter / Müller, plastic additives, 3rd edition, Carl-Hanser-Verlag

described, suitable spacers or release agents. It is state of the art, however, that the addition of release agents or spacers on some substrates results in a reduction in the adhesive force. Polymeric spacers are also used, as described, for example, in EP 0 526 858. These have the disadvantage that, under certain circumstances, the mechanical property image of the resulting flat structures changes in an undesired manner. In addition, it cannot be ruled out that, compared to the raw material used, activability as well as changes in the specific adhesion to some substrates can be detected.

The object of the present invention was therefore to avoid the disadvantages mentioned when using solvent-containing adhesives and also when using solvent-free adhesives, such as films. Some of the disadvantages mentioned can be avoided by using thermo-activatable nonwovens when bonding various substrates, in particular if the meltblown method (eg: REICOFIL® melt-blown method) is used to produce the nonwovens.

The invention therefore relates to a process for the production of carrier and release agent-free, thermally activatable nonwovens based on hydroxyl polyester polyurethanes with viscosities from 600 to 3500 mPa.s, measured as solution viscosity in methyl ethyl ketone (15%) and with basis weights in the range from 5 to 200 g / m², characterized in that the nonwovens are formed by means of a melt-blowing process (eg REICOFIL® melt-blown process) at melt temperatures of 230 to 260 ° C, using a storage belt, the material of which has a surface tension of 18 , 5 x 10⁻⁵ N / cm to 46 x 10⁻⁵ N / cm.

The invention furthermore relates to the use of the nonwovens produced in the above manner for gluing or coating different substrates.

The carrier-free and release agent-free, thermo-activatable nonwovens produced by the process according to the invention preferably have basis weights in the range from 8 to 50, very particularly preferably 10 to 30 g / m 2. The basis weights of the nonwovens depend on the substrates used in the bonding and, depending on requirements, can also contain higher basis weights, especially if unevenness has to be compensated for during the bonding.

The raw materials based on hydroxyl polyester polyurethanes used in the process according to the invention preferably have a viscosity of 1500 to 2100 mPa.s, measured as solution viscosity (15%) in methyl ethyl ketone (Brookfield LVT viscometer, spindle 3, 60 rpm at 23 ° C.).

Particularly suitable hydroxyl polyester polyurethanes are those which, by reacting organic isocyanates with preferably difunctional, alcoholic hydroxyl groups containing polyester polyols and low molecular weight diols as chain extenders while maintaining an NCO / OH equivalent ratio from 0.9: 1 to 0.999: 1 are available, as described in EP 0 158 086 and DE-PS 1 256 822, DE-PS 2 161 340, DE-PS 3 502 379.

Suitable dihydroxy polyesters are in particular those of a molecular weight above 600, preferably between 1200 and 6000, particularly preferably between 2000 and 4000 g / mol, as are known in a known manner from alkanedicarboxylic acids with preferably 6 carbon atoms and alkanediols with preferably at least 4 carbon atoms. Suitable dicarboxylic acids are, for example, adipic acid, sebacic acid, pimilic acid, suberic acid, azelaic acid, sebacic acid. Suitable alkanediols are, for example, 1,4-butanediol, 1,5-pentanediol, or 1,6-hexanediol. The chain extenders are in particular diols or diol mixtures in the molecular weight range 62 to 300, preferably 62 to 150 g / mol. Suitable such diols are e.g. Alkanediols preferably having 4 to 6 carbon atoms, such as 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol.

Examples of suitable diisocyanates are 1,6-diisocyanatohexane, 1,4-diisocyanatocyclohexane, 1-isocyanato-3-isocyanatomethyl-3,5,5-trimethylcyclohexane, methylenebis (4-isocyanatocyclohexane), 2,4- and optionally 2, 6-diisoocyanatotoluene, 4,4'-diisocyanatodiphenylmethane, 4,4'-diisocyanatodiphenylpropane-2,2 or any mixture of such isocyanates. 4,4'-Diisocyanatodiphenylmethane is particularly preferred as the reaction component.

As mentioned, the nonwovens according to the invention are produced by the melt-blow method, in particular melt temperatures (measured in front of the spinning nozzles) of 230 to 260 ° C. being used. The melt-blowing process is described in more detail in DE-OS 19 64 060 and in DE-OS 23 08 242 and essentially consists of a specially designed shaping tool for polymer threads connected downstream of an extruder, the main feature of which is therein there is that a directed, heated air flow can be assigned to each individual nozzle, which ensures that the emerging polymer threads are stretched up and torn off in a controlled manner. The hot air can be brought to the polymer melt from slits that are tight on two sides or flow around the polymer melt from an annular hole around the inner melt hole.

The spun threads are deposited on a moving pick-up device, e.g. a rotating conveyor belt.

In the method according to the invention it is important that a storage belt is used, the material of which has a surface tension of preferably 18.5 x 10⁻⁵ to 33 x 10⁻⁵ N / cm. Teflon-coated textile fabrics, for example, are suitable as materials for the storage belt.

Of course, it is also possible to glue different substrates by coating the substrate to be glued directly with the fleece produced by the process according to the invention and by thermally activating the fleece (for example by means of IR radiation or contact heat) to glue the substrates together puts.

A wide variety of methods can be used to bond the substrates to the nonwoven produced by the method according to the invention.

In the case of pre-coated substrates (e.g. soft PVC foam films, TPU films), the vacuum deep-drawing process, deep-drawing presses, vacuum deep-drawing presses are used to produce molded parts for headliners, side cladding elements or foam-backable composites for seat manufacture etc. These Methods are known and described in detail in, for example, Saechtling "Kunststoff Taschenbuch", 21st edition, 1979, pages 140 to 184.

A large number of substrates can be bonded to themselves or to one another with the nonwoven fabric produced by the method according to the invention. In addition to the soft PVC and TPU surface films mentioned, a wide variety of textile fabrics based on cotton, cotton blended fabrics, wool, wool blended fabrics, polyester and polyamide fabrics and polyolefins are particularly worth mentioning.

It is surprising that hydroxyl polyester polyurethanes can be processed to nonwovens by a melt-blow process, since it had to be expected that at the high melt temperatures required for the melt-blow process and which would be about 50 ° C. above the temperatures of the usual film production processes, there is such a large shift in equilibrium in favor of the starting components in hydroxyl polyester polyurethanes that at most oligomeric products are obtained which can no longer be consolidated into a nonwoven.

Furthermore, it had to be expected that the cohesive strength in the case of bonds produced by means of the shaped nonwovens would no longer be present to a sufficient extent due to the polymer degradation. This is not the case.

A limited number of raw materials are known in the prior art, which can be formed into nonwovens by means of the melt-blowing technique. In particular, these are polymers that solidify completely amorphously or partially crystalline, such as polypropylene and polystyrene. These polymers generally have the property of having a completely tack-free surface immediately after the temperature drops below about 70 ° C. Hydroxylpolyesterpolyurethane with segmented structure of soft and Hard segments are more critical in this regard. In order to recrystallize the hydroxyl polyester polyurethane processed in the extrusion process, a much longer time is required in comparison to the abovementioned polymers, and in any case the temperature in the molded extrudate is below 50 ° C. This behavior of segmented polyester urethanes generally leads to the disadvantages mentioned of the non-release or spacer-free production and the blocking of these extrudates on the roll.

Surprisingly, it was found that the hydroxyl polyester polyurethanes deposited as tangled fibers have a tack-free surface shortly after being deposited on the conveyor belt of the melt-blown system, so that the melt-blown spunbonded fabric obtained can subsequently be fed directly to a winder. Blocking on the winder no longer occurs subsequently.

Due to the low fiber titer (approx. 0.1 dtex), the fleece obtained is characterized by a large surface coverage (opacity) even with small application quantities. With, for textile applications, even high application quantities of 30 g / m², a soft feel is retained. Depending on the order volume, air permeability can be set specifically.

Examples

The tests described below were carried out on a commercially available REICOFIL® melt-blown system with a production width of 1 meter. The thermoplastic elastomeric hydroxyl polyester polyurethanes were predried in a SOMOS® air dryer over a period of 12 hours.

example 1

The extruder and mold temperatures were set so that a melt temperature of 250 ° C was achieved in front of the unloading nozzles. With a screw speed of 5 rpm. the hydroxyl polyester polyurethane (solution viscosity: 2000 mPa.s) was extruded. The spinning pump output was increased to 4 rpm. set. The resulting extrusion rate was 22 kg / h. A melt pressure of the extruder / nozzle of 40/16 bar is established. The polymer threads emerging from the melt nozzles were placed after stretching by the compressed air preheated to 220 ° C. and the controlled thread breakdown on a circulating conveyor belt with a surface tension of 30 × 10 / N / cm and fed from there to an intermediate take-off where the edge trimming took place. The fleece was then wound onto 1000 mm cardboard cores. Different basis weights were set by changing the spinning belt speed and / or the throughput. 200 running meters were wound up per attempt. The processing of the cardboard core could be carried out at any time without any problems.

Example 2

The extruder and mold temperatures were set so that a melt temperature of 250 ° C was achieved in front of the unloading nozzles. With a screw speed of 5 rpm. the hydroxyl polyester polyurethane (solution viscosity: 1200 mPa.s) extruded. The spinning pump output was increased to 4 rpm. set. The resulting extrusion rate was 22 kg / h. A melt pressure of the extruder / nozzle of 40/30 bar is established. The polymer threads emerging from the melt nozzles were placed on a circulating conveyor belt with a surface tension of 30 × 10⁻⁵ N / cm after stretching through the compressed air preheated to 220 ° C and the controlled thread break-off and fed from there to an intermediate take-off where the edge trimming took place . The fleece was then wound onto 1000 mm cardboard cores. Different basis weights were set by changing the spinning belt speed and / or the throughput. 200 running meters were wound up per attempt. The processing of the cardboard core could be carried out at any time without any problems.

Example 3

In the same way as described in Example 1, the hydroxyl polyester polyurethane was applied as a fleece directly to a TPU surface film (thickness 100 μm). Here too, after intermediate deduction and edge trimming, it was wound up on 1000 mm cardboard tubes. The process was easily carried out at all times.

Example 4

The procedure was analogous to that in Example 3 with a soft PVC (foam) film web. The adhesion of the melt-blown spunbond made of the hydroxyl polyester polyurethane was sufficient to ensure that the coated web could be wound up and unwound easily.

Example 5

Analogously to Example 3, the hydroxyl polyester polyurethane was applied directly to a cotton fabric as a fleece. The adhesion of the fleece to the textile web was excellent here too. Bonding this fabric, coated with different amounts of material, to an uncoated cotton fabric provided the peel strengths listed in Table 1 below. Table 1 Bonding temperature (° C) Sample name ---- Order quantity (g / m²) Peel strength (N / 5 cm) 100 PUR example 1 10th 12.5 100 PUR example 1 20th 24.0 100 PUR example 1 30th 38.5 120 PUR example 1 20th 31.0 120 PUR example 1 30th 35.0 140 PUR example 1 10th 16.5 140 PUR example 1 20th 35.0 140 PUR example 1 30th 41.5 160 PUR example 1 10th 20.0 160 PUR example 1 20th 39.0 160 PUR example 1 30th 51.5 100 PUR example 2 10th 13.5 100 PUR example 2 20th 27.5 100 PUR example 2 30th 46.0 120 PUR example 2 10th 16.5 120 PUR example 2 20th 29.0 120 PUR example 2 30th 42.5 140 PUR example 2 10th 14.0 140 PUR example 2 20th 30.0 140 PUR example 2 30th 43.5 160 PUR example 2 10th 16.0 160 PUR example 2 20th 36.0 160 PUR example 2 30th 53.5 Press pressure: 1 bar
Press time: 20 sec.

Claims (2)

Process for the production of carrier and release agent-free, thermo-activatable nonwovens based on hydroxyl polyester polyurethanes with viscosities from 600 to 3500 mPa.s, measured as solution viscosity in methyl ethyl ketone (15%, Brookfield LVT viscometer, spindle 3, 60 rpm, 23 ° C) , and with basis weights in the range from 5 to 200 g / m², characterized in that the nonwovens are produced by means of a melt-blowing process (eg REICOFIL® melt-blown process) at melt temperatures of 230 to 260 ° C, a Storage tape is used, the material of which has a surface tension of 18.5 x 10⁻⁵ N / cm to 46 x 10⁻⁵ N / cm. Use of the nonwovens produced according to claim 1 for gluing and coating different substrates.