Polyurethane films and their use for bonding

Films of thermoplastic polyurethanes (TPU) with a Shore hardness of 75 A to 92 A having 5 to 20% by weight of polyether amide block copolymers and/or polyether ester block copolymers, and their use for adhering to other substrates, particularly for back-foaming with polyurethane foam. The invention also relates to the use of an addition of 5 to 20% by weight of polyether amide block copolymers and/or polyether ester block copolymers to thermoplastic polyurethanes with Shore hardnesses of 75 A to 92 A, based on the weight of the thermoplastic polyurethanes, for decreasing the adhesion and/or interlocking of thermoplastic polyurethanes produced by single layer blown extrusion technique.

FIELD OF THE INVENTION 
The invention relates to films of thermoplastic polyurethanes (TPU) with 
addition of 5 to 20% by weight of polyether amide block copolymers and/or 
polyetherester block copolymers, based on the weight of the polyurethane. 
BACKGROUND OF THE INVENTION 
The unpublished European patent application 91400298 discloses a method for 
processing of extrusion mixtures based on TPU, which are characterized by 
the admixture of one or more modifiers selected from thermoplastic 
elastomers based on polyesters and/or polyamides (nylon). According to the 
examples of this application, there are no references to adhesive films, 
particularly to those which are back-foamed with polyurethane foam. 
Pursuant to the known co-extrusion method (German Auslegeschrift 2114065, 
U.S. Pat. No. 3,880,891), elastomeric films, which contain no release 
agent or spacing agent and are therefore outstandingly suitable, for 
example, for back-foaming with polyurethane foam, can be produced from 
polyurethanes. The disadvantages of this method are that an expensive 
co-extrusion plant (two extruders and blowing head with two concentric, 
ring-shaped dies) must be used and that a separating film is obtained 
which is essentially a waste product. 
On the other hand, the production of films from thermoplastic materials, 
such as polyurethanes, etc., by the single layer blown extrusion technique 
is known. For this method, a film bubble is blown by a ring-shaped die by 
means of an extruder. After it has cooled, this film bubble is collapsed 
and cut on both sides, so that two superimposed film sheets (flat films) 
result, which are then separated and rolled up. 
For this method, an internal release agent or spacing agent must be added, 
no later than in the extruder, to the relatively strongly adhering 
thermoplastic synthetic materials before they are blown. Otherwise the 
sheets of film (flat films) adhere to one another when they collapse, so 
that they can no longer be wound up satisfactorily in two separate sheets 
of film. 
At the very least, the danger exists that the wound up, separated sheets of 
film interlock during storage, since post-crystallization is unavoidable. 
The materials, which are used according to the state of the art for 
avoiding this adhesion or interlocking, are waxes and/or inorganic 
additives, such as those described, for example, in A) 
Kunststoff-Taschenbuch (Plastics Pocket Book) Saechtling, 24th edition, 
published by Hanser; B) Kunststoff-Handbuch (Plastics Handbook) 7, 
Polyurethanes, Becker/Braun; C) Kunststoffe (Plastics) 80 (1990) 7, pages 
827 ff.; D) HOECHST Kunststoff-Additive Produktmerkblatt (Plastic 
Additives-Product Instruction Sheet), November, 1988; German 
Auslegeschrift 2429780, European patent 81-0195899. The addition of these 
materials, however, brings about a reduced adhesive force when used later 
as films that are to be back-foamed. The polyurethane foam which is foamed 
onto these films adheres inadequately to the supporting film. 
The tendency of the films to adhere during manufacture and storage can also 
be decreased by increasing the hardness of the films. If, for example, 
polyurethane films, which are up to about 100 .mu.m thick, have a Shore 
hardness of about 92 A or more, the production of the films is essentially 
problem-free. Even when back-foamed, the films still have sufficient 
adhesion towards the polyurethane foam. However, because of their high 
hardness, the films have an undesirably high stiffness and reduced 
elasticity, as well as a low water vapor permeability, which reduces the 
seat comfort or climate comfort of the back-foamed films when employed as 
seat cushions in upholstered furniture, such as automobile seats. 
It is the object of the invention to avoid these disadvantages. 
SUMMARY OF THE INVENTION 
An object of the invention is achieved by the production of films of 
thermoplastic polyurethanes with a Shore hardness of 75 A to 92 A (DIN 
53505), to which 5 to 20% by weight of polyether amide block copolymers 
and/or polyetherester block copolymers, based on the weight of the 
polyurethanes, have been added. Preferred are films which are obtained by 
the single layer blown extrusion technique method. Furthermore, these 
films preferably contain polyether amide block copolymers. 
A further object of the invention is achieved by the improved production of 
TPU by the use of an addition of 5 to 20% by weight of polyether amide 
block copolymers and/or polyether ester block copolymers to the 
thermoplastic polyurethanes with Shore hardness of 75 A to 92 A, based on 
the weight of the thermoplastic urethanes, to reduce the adhesion and/or 
interlocking of monofilms produced from thermoplastic polyurethanes by the 
extrusion blow molding method. A further result of the invention is the 
successful use of the inventive films for enhanced adhesion to other 
substrates and/or back-foaming with polyurethane foams. 
Using an addition of PEBA (polyether amide block copolymers) and/or 
polyether ester block copolymers an exceptionally surprising effect occurs 
in that, on the one hand, the tendency of films produced by the single 
layer blown extrusion process to adhere when collapsed or cut or while 
being wound up, even when these films have a low Shore hardness, is 
reduced to such an extent, that the films can be wound up and stored 
satisfactorily and, on the other, these films, while having a high 
elasticity and water permeability, have excellent adhesion, for example, 
to the back-foamed polyurethane foam. 
As PEBA, within the meaning of the invention, polyether amide block 
copolymers of the German Auslegeschrift 2523991, U.S. Pat. No. 4,331,786, 
and German Auslegeschrift 2,856,787 can be used. 
Above all, the polyether amide block copolymers can consist of 
polycondensates of homopolyamides or copolyamides having reactive end 
groups with homopolyethers or copolyethers with reactive end groups, such 
as: 
a) homo- and/or copolyamides with amine chain ends with homo- or 
copolyoxyalkylenes with carboxyl chain ends, 
b) homo- or copolyamides with carboxyl chain ends with homo- or 
copolyoxyalkylenes with amine chain ends, 
c) homo- or copolyamides with carboxyl chain ends with homo- or copolyether 
diols, the so-called polyether ester amides, which are preferred 
particularly as modifiers for TPU. 
The average molecular weight (number average) of these polyamides segments 
generally is between 500 and 10,000 and mostly between 600 and 5,000. The 
polyamides (nylons) are formed most frequently from nylon 6, 6.6, 6.12, 
11, 12 or 12.12 and/or from amorphous nylon or from copolyamide, which 
results from the copolymerization of their monomers. Nylon (polyamide) 11, 
12 and/or 12.12 are particularly preferred. 
The average molecular weight (number average) of the polyether segments 
generally is between 200 and 6,000 and mostly between 600 and 3,000. 
The polyethers mostly consist essentially of polytetramethylene glycol 
(PTMG). Aside from PTMG, they may contain polyethylene glycol (PEG) and/or 
polypropylene glycol (PPG). Polytetramethylene glycol (PTMG) and 
polyethylene glycol (PEG) are particularly preferred. 
The inherent viscosity of the polyether amide block copolymers advisably is 
between 0.8 and 2.05. It is measured in meta-cresol at 20.degree. C. with 
an initial concentration of 0.5 g of polymer in 100 g of meta-cresol. 
The polyether amide block copolymers can be formed from 5 to 85% by weight 
of polyether and 95 to 15% by weight of polyamides. The most appropriate 
ratio is 30 to 85% by weight of polyether to 70 to 15% by weight of 
polyamide. The preferred polyether amide block copolymers are those the 
polyether of which consist essentially of PTMG and/or PEG and, above all 
those, the polyamides of which are condensates of nylons 11, 12 and/or 
12.12. 
The amount of PEBA added to the TPU (thermoplastic polyurethane) preferably 
is at least 8% by weight and particularly at least 10% by weight. The 
upper limit preferably is at 15% by weight. In this connection, the 
percentage by weight is based on the weight of the thermoplastic 
polyurethane. 
Polyether ester block copolymers are condensation products of aromatic 
dicarboxylic acids, low molecular weight polyoxyalkylene glycols and 
short-chain diols with a segmented structure. They suitably consist of a 
hard, crystalline segment, which is formed from short-chain diols (butene 
diol, diethylene glycol) and dicarboxylic acids, preferably aromatic 
dicarboxylic acids, such as terephthalic acid, and a soft segment of 
polyoxyethylene glycols, such as those described above in connection with 
the polyether amide block copolymers. The molecular weights (number 
average) of the hard segments generally are between 500 and 10,000 and 
preferably between 600 and 5,000. The molecular weights (number average) 
of the soft segments advisably are between 200 and 6,000 and preferably 
between 600 and 3,000. 
The inherent viscosity of the polyether ester block copolymers is suitably 
between 0.6 and 2.0. It is measured in meta-cresol at 20.degree. C. with 
an initial concentration of 0.5 g of polymer in 100 g of meta-cresol. 
TPU, within the meaning of the invention, includes the thermoplastic 
polyurethanes disclosed in the European patent B1-0158086, the German 
Auslegeschrift 2817457, the German Auslegeschrift 2817456, the European 
publication 0311278, the German Auslegeschrift 2429790 or the 
Kunststoff-Taschenbuch (Plastics Pocket Book) Saechtling, 24th edition, 
published by Hanser, can be used. The thermoplastic polyurethanes or TPU 
are synthesized by the reaction of a diisocyanate, such as 
di(p-isocyanatophenyl)-methane with an aliphatic, polymeric polyol, which 
has a molecular weight or more than 600 and is based, for example, on a 
polyester diol or a polyether diol, such as polypropylene glycol, 
polyethylene adipate, polytetramethylene adipate or ethylene 
adipate/tetramethylene adipate co-polyester and chain extension of the 
reaction product with a diol having a molecular weight of less than 250, 
such as 1,4-dihydroxybutane. 
The Shore hardness is suitably not more than approximately 90 A. The lower 
limit of the Shore hardness suitably is approximately 80 A. The invention 
may be practiced with Shore hardness of 75 A to 92 A. 
For back foaming, the foam-forming products which are customary in the art 
are used. These are the so-called two-component polyurethanes, such as 
those described in the Kunststoff-Taschenbuch (Plastics Pocket Book) 
Saechtling, 24th edition, published by Hanser or in the 
Kunststoff-Handbuch (Plastics Handbook) 7, Polyurethanes, Becker/Braun. As 
mentioned initially, such back-foamings are carried out on a larger, 
industrial scale. 
The upper limit of the thickness of the films, produced pursuant to the 
invention, is suitably at about 100 .mu.m, preferably at about 80 .mu.m 
and particularly at about 60 .mu.m. Preferably, the films are as thin as 
possible in order to save material. On the other hand, they must have the 
required strength properties and other properties. 
The same criteria also apply to the lower limit of the thickness of the 
films. Suitably, this is not less than 20 .mu.m and, preferably, not less 
than 25 .mu.m.

EXAMPLES: 
The compositions, described in the following Tables, were extruded on 
single layer blown extrusion line and tested for their film properties. 
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Extrusion Line Configuration: 
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Drier: Conventional, commercial, continuous 
SOMOS .RTM. air drier 
Metering station: 
Volumetric metering station for metering 
additives continuously 
Extruder: Conventional, commercial, 150 mm blown film 
extrusion line; 3-zone screw with 1:2.4 
compression with feeding zone, compression 
zone, metering zone and mixing elements; 
10.5 mm flight depth of feeding zone; 
4.3 mm flight depth of metering zone; 
1 .times. 100, 2 .times. 400, 
1 .times. 900 mesh/cm.sup.2 screen pack. 
Die: Single layer film die in supporting ring 
construction, 700 mm diameter 
Cooling: Air ring with aerodynamic with air 
compensation for cooling film bubble 
Collapsing: 
To flatten the bubbles 
Take off: Pinch-off rollers with silicone rubber coating 
for flattening film bubble 
Cutting station: 
Bilateral edge cut of flattened film bubble 
Winder: Tandem winder 
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EXAMPLE 1 
The thermoplastic polyurethane TPU 1 was dried continuously in a Somos 
drier for 7 hours to a residual moisture content of 0.01% and mixed with a 
conventional, commercial polyether amide block copolymer (PEBA 40) having 
a residual moisture content of 0.06% in the mixing ratio given in the 
Table and supplied to a storage tank of the extrusion installation. 
The temperature of the extruder and the die were adjusted to 200.degree. C. 
The mixture was extruded with the screw revolving at 18 rpm. The pressure 
in front of the screen was 340 bar and behind the screen 270 bar. The 
temperature of the composition, measured in the neck between the screen 
and the die, was 205.degree. C. The molten tube, emerging from the 
orifice, was blown to a diameter of approximately 1,000 mm and, after 
about 10 m, flattened by means of pinch-off rollers and guided over 
deflector rolls to an interim take-off. The edges were cut open at that 
point and the two sheets of film were separated and wound on tandem 
winders at a wind-up tension of 2.7 kg on a 1,500 mm paperboard core. 
There were no adhesion problems at the squeeze-off rollers. The release 
forces after the cutting were so slight, that problem-free separating and 
winding-up were readily effected. 
The interlocking force, the release force, the film thickness, the ultimate 
tensile strength, the elongation at break, the tension at 100% extension, 
the resistance to tear propagation and the back-foamability were tested. 
Examples 2 to 6 were carried out in an analogous manner with the parameters 
given in the Tables. 
COMISON EXAMPLES 1 to 4 
The compositions given in the Table were extruded and tested as described 
above 
Explanations for the Tables 
1) TPU Used 
A) TPU 1: 
Linear ester urethane, Shore hardness about 85 A, partially crystalline, 
free of lubricant, highly viscous, melt index, measured by a method based 
on DIN 53735 under a load of 211N at a temperature of 190.degree. C., of 4 
g per 10 minutes. 
Chemical basis: di(p-isocyanatophenyl)methane; butane diol adipate, 
molecular weight (number average) about 2,000; butane diol as chain 
extender. 
B) TPU 2 
Linear ether urethane, Shore hardness of about 85, partially crystalline, 
free of lubricant, highly viscous, melt index, measured by a method based 
on DIN 53735 under a load of 211N at a temperature of 190.degree. C., of 
about 12 g per 10 minutes. 
Chemical basis: di(p-isocyanatophenyl)methane; polytetramethylene glycol, 
molecular weight (number average) about 1,000; butane diol as chain 
extender. 
2) PEBA used 
A) PEBA 40: 
Conventional, commercial polyether amide block copolymer based on polyamide 
12 and polytetramethylene glycol, Shore hardness of 40 D. 
B) PEBA 55: 
Conventional commercial copolyether amide block copolymer based on nylon 12 
and polytetramethylene glycol, Shore hardness 55 D. 
3) Additives 
A) Calcium stearate 
B) Waxes (ethylene bistearamide) 
4) Foaming Test 
The test provides information as to whether the film is back-foamable. The 
foam adhesion is measured. 
Into a suitable vessel 
40 g of conventional commercial polyester diol (such as Elastoflex.RTM.W 
5549 comp. A) 
20 g of conventional, commercial isocyanate cross linker (such as comp. B, 
type 5534 of the Elastogran.RTM. Co.) 
are weighed, thoroughly mixed and poured onto the film to be tested. The 
liquid foams up after about 5 minutes and forms a foam cake. After 24 
hours, the adhesion is tested manually. 
1=foam tear-out, 5=no adhesion 
5) Determination of the Interlocking Force of Films 
This method was developed by the applicant for fine films. 
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Equipment Required: 
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1. Heat-sealing equipment 
with the possibility of producing a 
pressure of 5 bar, a residence time 
of 10 minutes and a temperature 
of 60.degree. C. at the upper and lower 
heaters. 
2. Tensile testing machine 
in order to determine the 
interlocking force on the 
test samples. 
3. Cutting knife for preparing the samples 
4. Upper and lower for preparing sample 
film (Teflon .RTM.) 
5. Glass plate cutting support 
6. Teflon strips in order to carry out the 
interlocking. 
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Procedure: 
1. Preparing Test Sample 
Sample width=15 mm 
Sample length=100 mm 
Two test samples with these dimensions are cut out with a cutting knife. To 
ensure a satisfactory cut, it is necessary to use an upper film and a 
lower film for monofilms. 
2. Test Sample Preparation 
The test samples are placed on top of one another and fixed with Teflon and 
two paper clips. 
3. Interlocking of Test Samples 
The test sample, so prepared, is interlocked for 10 minutes at a pressure 
of 5 bar and a temperature of 60.degree. C. (both heating jaws). The 
interlocking surface of the test sample is 15 mm.times.10 mm. 
4. Evaluating the Interlocking 
After the interlocking, care must be taken to ensure that the films lie 
exactly one on top of the other (otherwise, falsification of the test 
width) and that the interlocking takes place over the whole of the area 
(uniform appearance). Excessive film thickness variations are a possible 
cause of incomplete interlocking over the whole of the area. 
5. Determining the Interlocking Force 
The test samples are clamped without tension in the test clamps, as in the 
DIN 53530 release test. The interlocking force is determined at a test 
speed of 100 mm/min. 
6. Evaluation 
The results are evaluated according to DIN 53539. The interlocking force is 
given in N/15 mm. 
6) Determining the Release Force 
To determine the release force, test samples, 15 mm wide and 100 mm long, 
are cut from the extruded and collapsed tube before it is separated. 
Using these test samples, the release force is determined according to DIN 
53530, as described above for determining the interlocking force. 
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Comparison 
Example 1 Example 2 Example 3 Example 4 Example 
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1 
TPU 90 parts TPU 1 
90 parts TPU 1 
90 parts TPU 1 
90 parts TPU 
100 parts TPU 1 
Polyether amide 
10 parts PEBA.40 
10 parts PEBA.40 
10 parts PEBA.40 
10 parts PEBA.55 
Additive -- -- -- -- -- 
EXTRUSION 
RPM 18 rpm 25 rpm 35 rpm 18 rpm 18 rpm 
Current 13 A 13 A 14 A 14 A 17 A 
Consumption 
Pressure Before 
200 bar 210 bar 210 bar 340 bar 350 bar 
Screen 
Pressure After 
130 bar 140 bar 140 bar 270 bar 290 bar 
Screen 
Composition 196.degree. C. 
198.degree. C. 
198.degree. C. 
199.degree. C. 
200.degree. C. 
Temperature 
Film Film is separated 
Film is separated 
Film is separated 
Film is separated 
Film cannot be 
very easily 
very easily 
easily very easily 
separated 
No interlocking on 
No interlocking on 
No interlocking on 
No interlocking 
Interlocking on 
winder winder winder winder winder 
Film Thickness according 
37 .mu.m 41 .mu.m 37 .mu.m 38 .mu.m Data cannot be 
to DIN 53370 obtained 
Interlocking Force 
0.22 0.22 0.22 0.22 
(N/15 mm) 
Release Force 
0.05 0.03 0.05 0.03 
(N/15 mm) 
Ultimate Tensile 
Strength according 
90 80 90 70 
to DIN 534555 (MPa) 
Elongation at break 
585 682 585 540 
according to 
DIN 53455 (%) 
Stress at 100% elonga- 
10.5 8.1 10.5 7.1 
tion according to 
DIN 53455 (MPa) 
Resistance to tear 
73 77 73 78 
propagation according 
1 1 1 1 
to DIN 53515 (N/mm) 
Foaming Test 
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Comparison Comparison 
Comparison 
Example 2 Example 5 Example 6 Example 3 Example 
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4 
TPU 100 parts TPU 1 
90 parts TPU 2 
90 parts TPU 2 
100 parts TPU 
100 parts TPU 2 
Polyether amide 
-- 10 parts PEBA.40 
10 parts PEBA.55 
-- -- 
Additive 0.1 parts wax 
-- -- 0.05 parts Ca 
0.2 parts wax 
Stearte 
EXTRUSION 
RPM 18 rpm 18 rpm 18 rpm 18 rpm 18 rpm 
Current 15 A 14 A 15 A 14 A 14 A 
Consumption 
Pressure Before 
340 bar 270 bar 290 bar 280 bar 280 bar 
Screen 
Pressure After 
280 bar 235 bar 240 bar 240 bar 230 bar 
Screen 
Composition 199.degree. C. 
193.degree. C. 
194.degree. C. 
196.degree. C. 
195.degree. C. 
Temperature 
Film Film can be 
Film is separated 
Film is separated 
Film is difficult 
Film can be 
separated easily easily to separate 
separated 
No interlocking on 
No interlocking on 
No interlocking on 
Interlocked on 
No interlocking on 
winder winder winder winder winder 
Film Thickness according 
38 .mu.m 46 .mu.m 47 .mu.m 53 .mu.m 53 .mu.m 
to DIN 53370 
Interlocking Force 
0.22 0.7 1.5 0.9 0.1 
(N/15 mm) 
Release Force 
0.04 0.14 0.17 0.42 0.1 
(N/15 mm) 
Ultimate Tensile 
Strength according 
70 70 60 80 70 
to DIN 534555 (MPa) 
Elongation at break 
540 660 540 590 570 
according to 
DIN 53455 (%) 
Stress at 100% elonga- 
7.1 8.2 9.3 9.5 9.5 
tion according to 
DIN 53455 (MPa) 
Resistance to tear 
67 65 70 55 55 
propagation according 
5 1 1 1 1 
to DIN 53515 (N/mm) 
Foaming Test 
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