METHOD FOR CREATING A FOAMED MASS SYSTEM

Abstract

A method for producing a foamed thermally crosslinked mass system, wherein the mass system is foamed at a first temperature in a first step, and crosslinker substances are added to the mass system in a subsequent step at a second temperature lower than the first temperature, wherein the crosslinker substances are crosslinker substances for thermal crosslinking of the mass system.

Claims

1. A method for producing a foamed thermally crosslinked mass system, in which a mass system having unexpanded microballoons mixed therein is foamed in a first step at a first temperature, and crosslinker substances are mixed into the mass system in a following step at a second temperature, which is lower than the first temperature, and the blended mass system is shaped to form a layer, wherein the crosslinker substances are crosslinker substances for thermal crosslinking of the mass system.

2. The method of claim 1, wherein the first temperature, at which the mass system is foamed, is equal to or above the expansion temperature of the microballoons, and the second temperature, at which the crosslinker substances are added to the mass system, is below the expansion temperature of the microballoons.

3. The method of claim 1, wherein in a first mixing assembly expandable microballoons and optionally further additives are introduced into a mass system; the mass system with the microballoons added is heated under superatmospheric pressure to a temperature which at least corresponds to, and is optionally higher than, the expansion temperature of the microballoons under atmospheric pressure, the microballoons are expanded on emergence from the first mixing assembly, the mass system is introduced into a second mixing assembly, whereby this second mixing assembly the mass system is at a temperature below the expansion temperature of the microballoons, the crosslinker substances are added in the second mixing assembly, the mass system thus blended is shaped.

4. The method of claim 1, wherein in a first mixing assembly expandable microballoons and optionally further additives are introduced into a mass system; the mass system with the microballoons added is heated under superatmospheric pressure in a first mixing zone of the mixing assembly to a temperature which is at least equal to or higher than, the expansion temperature of the microballoons under atmospheric pressure, the mass system is subsequently transferred from the first mixing zone into a second mixing zone of the first mixing assembly, whereby in this second mixing zone the mass system is at a temperature below the expansion temperature of the microballoons, the crosslinker substances are added during transfer of the mass system to the second mixing zone and/or after transfer to the second mixing zone, the mass system thus blended is shaped.

5. The method of claim 1, wherein the mass system is or comprises a self-adhesive.

6. The method of claim 5, wherein the self-adhesive is applied to a web-form carrier or release material.

7. The method of claim 1, wherein thermal crosslinking of the mass system takes place after the operation of shaping to form the layer.

8. The method of claim 1, wherein the mass system, on addition of the crosslinker substances, is present in a noncrosslinked state.

9. A foamed mass system produced by the method of claim 1.

10. A self-adhesive for a single- or double-sidedly (self-)adhesive tape comprising a foamed mass system of claim 9.

Description

[0130] Below, the methods described above that lie within the concept of the invention are illustrated in particularly outstandingly embodied variants, without any intention to impose any unnecessary restriction through the choice of the figures shown.

[0131] FIG. 1 shows the method with two mixing assemblies, the expansion of the microballoons taking place in the first mixing assembly followed by addition of thermally sensitive additives or fillers in the second mixing assembly

[0132] FIG. 2 shows the method with one mixing assembly, the expansion of the microballoons and the addition of thermally sensitive additives or fillers taking place in one mixing assembly.

[0133] FIG. 1 shows one particularly advantageously embodied method for producing a foamed mass system.

[0134] The reactants E which are intended to form the mass system to be foamed, and the microballoons MB, are fed to a continuous mixing assembly, such as a planetary roller extruder (PWE) 2, for example.

[0135] Another possibility, however, is to introduce pre-prepared solvent-free mass K into the planetary roller extruder (PWE) 2 by means of injection 23 through conveying extruders, such as a single-screw extruder (ESE) 1, for example, or through a drum melt 5, and to meter in the microballoons MB in the intake zone of the PWE 2.

[0136] The microballoons MB are then mixed with the solvent-free mass K or with the reactants E to form a homogeneous mass system in the PWE 2, and this mixture is heated, in the first heating and mixing zone 21 of the PWE 2, to the temperature necessary for the expansion of the microballoons.

[0137] In the second injection ring 24, further additives or fillers 25, such as crosslinking promoters, for example, may be added to the mass system S comprising expanded microballoons.

[0138] In order to be able to incorporate thermally sensitive additives or fillers 25, the injection ring 24 and the second heating and mixing zone 22 are preferably cooled.

[0139] The foamed mass system is subsequently transferred to a further continuous mixing assembly, such as a twin-screw extruder (DSE) 3, for example, and can then be blended with further fillers or additives, such as crosslinking components, such as catalysts, for example, at moderate temperatures, without destroying the expanded microballoons MB.

[0140] The microballoons MB break through the surface of the mass at the die exit of DSE 3, as they also did before at the die exit of PWE 2.

[0141] With a roll applicator 4, this foamlike mass S is calendered and coated onto a web-form carrier material 44 such as release paper, for example; in some cases there may also be subsequent foaming in the roll nip. The roll applicator 4 is composed of a doctor blade roll 41 and a coating roll 42. The release paper 44 is guided to the latter roll via a pick-up roll 43, and so the release paper 44 takes the foamed mass S from the coating roll 42. At the same time, the expanded microballoons MB are pressed again into the polymer matrix of the foamed mass S, thereby producing a smooth and, in the case of the foaming of self-adhesives, a permanently (irreversibly) adhesive surface, with very low densities of up to 150 kg/m.sup.3.

[0142] FIG. 2 shows a further particularly advantageously embodied method for producing a foamed mass system.

[0143] The reactants E and the microballoons MB, which are intended to form the mass system to be foamed, are fed to a continuous mixing assembly, such as a planetary roller extruder (PWE) 2, for example.

[0144] Another possibility, however, is to introduce pre-prepared solvent-free mass K into the planetary roller extruder (PWE) 2 by means of injection 23 through conveying extruders, such as a single-screw extruder (ESE) 1, for example, or through a drum melt 5, and to meter in the microballoons MB in the intake zone of the PWE 2.

[0145] The microballoons MB are then mixed with the solvent-free mass K or with the reactants E to form a homogeneous mass system in the PWE 2, and this mixture is heated, in the first heating and mixing zone 21 of the PWE 2, to the temperature necessary for the expansion of the microballoons.

[0146] In the second injection ring 24, further additives or fillers 25, such as crosslinking promoters, for example, may be added to the mass system S comprising expanded microballoons.

[0147] In order to be able to incorporate thermally sensitive additives or fillers 25, the injection ring 24 and the second heating and mixing zone 22 are cooled.

[0148] The expanded microballoons MB break through the surface of the mass at the die exit of the PWE 2.

[0149] With a roll applicator 4, this foamlike mass S is calendered and coated onto a web-form carrier material 44 such as release paper, for example; in some cases there may also be subsequent foaming in the roll nip. The roll applicator 4 is composed of a doctor blade roll 41 and a coating roll 42. The release paper 44 is guided to the latter roll via a pick-up roll 43, and so the release paper 44 takes the foamed mass S from the coating roll 42.

[0150] At the same time, the expanded microballoons MB are pressed again into the polymer matrix of the foamed mass S, thereby producing a smooth and, in the case of the foaming of self-adhesives, a permanently (irreversibly) adhesive surface, with very low densities of up to 150 kg/m.sup.3.

[0151] Adhesive/Adhesive Tape

[0152] The invention also provides an adhesive, more particularly self-adhesive, obtained by the method of the invention. The invention more particularly provides a thermally crosslinked, microballoon-foamed adhesive, more particularly self-adhesive.

[0153] The benefit of foamed adhesives lies on the one hand in cost reduction. A saving can be made on raw materials, since coat weights can be reduced by a multiple for given layer thicknesses. For a given throughput or quantity production of adhesive, in addition, the coating speeds can be increased.

[0154] An advantage of thermal crosslinking is that it produces an adhesive which has no crosslinking profile—in particular, therefore, in the case of layers of adhesive, no crosslinking profile through the layer. In the case of crosslinking by actinic radiation, such a profile is always formed to a greater or lesser extent, owing to the limited depth of penetration of the radiation, and all the more so in the case of thick layers, for which foamed systems are frequently employed.

[0155] Moreover, the foaming of the adhesive produces improved technical adhesive properties and performance properties.

[0156] The reduction of the drop in bond strength is favored by the high surface quality generated as a result of the pressing of the expanded microballoons back into the polymer matrix during the coating operation.

[0157] Moreover, relative to the unfoamed mass having the same polymer basis, the foamed self-adhesive gains additional performance features, such as, for example, improved impact resistance at low temperatures, enhanced bond strength on rough substrates, greater damping and/or sealing properties and conformability of the foam adhesive on uneven substrates, more favorable compression/hardness characteristics, and improved compressibility.

[0158] Further elucidation of the characteristic properties and additional functions of the self-adhesives of the invention takes place to some extent in the examples.

[0159] A foamed adhesive from the preferred hotmelt adhesive has a smooth, adhering surface, since, during coating, in the roll nip, the expanded microballoons are subsequently pressed back into the polymer matrix, and the adhesive, accordingly, has a preferred surface roughness R.sub.a of less than 10 μm. Determination of surface roughness is appropriate only for adhesive tapes which are based on a very smooth carrier and themselves have a surface roughness R.sub.a of only less than 1 μm. In the case of carriers that are relevant in practice, such as creped papers or nonwovens and woven fabrics, for example, having a greater surface roughness, the determination of the surface roughness of the product is not suitable, accordingly, for describing the advantages of the method.

[0160] According to one preferred embodiment of the invention, the fraction of the microballoons in the adhesive is between greater than 0% by weight and 30% by weight, more particularly between 0.5% by weight and 10% by weight.

[0161] With further preference, the microballoons at 25° C. have a diameter of 3 μm to 40 μm, more particularly 5 μm to 20 μm, and/or after temperature exposure have a diameter of 20 μm to 200 μm, more particularly 40 μm to 100 μm.

[0162] In all existing methods for producing microballoon-foamed adhesive systems, the adhesive develops a rough surface which has little or no adhesion.

[0163] With a self-adhesive coated from solvent, bond strength (peel strength) losses of more than 40% can be obtained even starting from a low microballoon content of 0.5% by weight. As the microballoon content goes up, the bond strengths fall further still, and the cohesion is increased.

[0164] At a fraction of just 1% by weight of microballoons, the adhesion of the adhesive is already very low.

[0165] This is underlined by comparative examples 1.1 and 1.2 and by table 3.

[0166] The ratio of the weight per unit volume of the adhesive foamed by the microballoons to the weight per unit volume of the adhesive of identical basis weight and formula, defoamed through the destruction of the cavities formed by the expanded microballoons, is preferably less than 0.9.

[0167] This behavior is also shown in the case of solvent-free die coating, in which case the microballoons foam following emergence from the extruder/die, with pressure equalization, and break through the adhesive matrix.

[0168] Further encompassed by the concept of the invention is a self-adhesive tape produced with the aid of the adhesive by application of the adhesive to at least one side of a web-formed material. In a double-sidedly adhesive tape, both adhesive coatings may be in accordance with the invention. An alternative provision is for only one of the two coatings to be in accordance with the invention, while the second can be selected arbitrarily (adapted to the tasks to be fulfilled by the adhesive tape).

[0169] As carrier material it is preferred to use a film, woven fabric or paper, to which the (self-)adhesive is applied on one side.

[0170] Furthermore, preferably, the (self-)adhesive is applied to a release paper or release film, producing a carrier-less adhesive tape, also referred to for short as a tab.

[0171] The thickness of the adhesive in an adhesive tape on the web-formed carrier material may be between 20 μm and 3000 μm, preferably between 40 μm and 150 μm.

[0172] Furthermore, the adhesive may be applied in a thickness of 20 μm to 3000 μm to a release material, if the layer of adhesive, more particularly after crosslinking, is to be used as a carrierless, double-sided self-adhesive tape.

[0173] Experimental Investigations

[0174] The following test methods are employed in order to determine the stated measurement values, in the examples as well.

[0175] Test Methods

[0176] Determination of Surface Roughness

[0177] The PRIMOS system consists of an illumination unit and a recording unit.

[0178] The illumination unit, with the aid of a digital micromirror projector, projects lines onto the surface. These projected parallel lines are diverted or modulated by the surface structure.

[0179] The modulated lines are recorded using a CCD camera arranged at a defined angle, referred to as the triangulation angle.

[0180] Size of measuring field: 14.5×23.4 mm.sup.2

[0181] Profile length: 20.0 mm

[0182] Areal roughness: 1.0 mm from the edge (Xm=21.4 mm; Ym=12.5 mm)

[0183] Filtering: 3rd order polynomial filter

[0184] Measuring instruments of this kind can be purchased from companies including GFMesstechnik GmbH at Teltow.

[0185] Peel Strength (Bond Strength) BS

[0186] The peel strength (bond strength) was tested in a method based on PSTC-1.

[0187] A strip of the (self-)adhesive tape under investigation is adhered in a defined width (standard: 20 mm) to a ground steel plate or to another desired adhesion/test substrate such as, for example, polyethylene or polycarbonate, etc., by rolling over it ten times using a 5 kg steel roller. Double-sided adhesive tapes are reinforced on the reverse side with an unplasticized PVC film 36 μm thick. Thus prepared, the plate is clamped into the testing instrument, the adhesive strip is peeled from its free end on a tensile testing machine at a peel angle of 180° and at a speed of 300 mm/min, and the force needed to accomplish this is measured. The results are reported in N/cm and are averaged over three measurements. All measurements are conducted in a controlled-climate room at 23° C. and 50% relative humidity.

[0188] Quantitative Determination of Shear Strength: Static Shear Test HP

[0189] An adhesive tape is applied to a defined, rigid adhesion substrate (in this case steel) and subjected to a constant shearing load. The holding time in minutes is measured. A suitable plate suspension system (angle 179±1°) ensures that the adhesive tape does not peel from the bottom edge of the plate.

[0190] The test is intended primarily to yield information on the cohesiveness of the composition. This is only the case, however, when the weight and temperature parameters are chosen such that cohesive failure does in fact occur during the test. Otherwise, the test provides information on the adhesion to the substrate or on a combination of adhesion and cohesiveness of the composition.

[0191] A strip, 13 mm wide, of the adhesive tape under test is adhered to a polished steel plaque (test substrate) over a length of 5 cm by rolling over it ten times using a 2 kg roller. Double-sided adhesive tapes are lined on the reverse side with a 50 μm aluminum foil and thus reinforced. Subsequently a belt loop is mounted on the bottom end of the adhesive tape. A nut and bolt is then used to fasten an adapter plaque to the facing side of the shear test plate, in order to ensure the specified angle of 179±1°.

[0192] The time for development of strength, between roller application and loading, should be between 10 and 15 minutes.

[0193] The weights are subsequently hung on smoothly using the belt loop.

[0194] An automatic clock counter then determines the point in time at which the test specimens shear off.

[0195] Density

[0196] Density Determination by Pycnometer:

[0197] The principle of the measurement is based on the displacement of the liquid located within the pycnometer. First, the empty pycnometer or the pycnometer filled with liquid is weighed, and then the body to be measured is placed into the vessel.

[0198] The density of the body is calculated from the differences in weight:

[0199] Let [0200] m.sub.0 be the mass of the empty pycnometer, [0201] m.sub.1 the mass of the pycnometer filled with water, [0202] m.sub.2 the mass of the pycnometer with the solid body, [0203] m.sub.3 the mass of the pycnometer with the solid body, filled up with water, [0204] ρ.sub.W the density of the water at the corresponding temperature, [0205] ρ.sub.F the density of the solid body;

[0206] the density of the solid body is then given by:

[00002]${\rho }_F=\frac{\left(m_2-m_0\right)}{\left(m_1-m_0\right)-\left(m_3-m_2\right)}.Math.{\rho }_w$

[0207] One triplicate determination is carried out for each specimen.

[0208] Quick Method for Density Determination from the Coatweight and Film Thickness:

[0209] The weight per unit volume or density of a coated self-adhesive is determined via the ratio of the basis weight to the respective film thickness:

[00003]$\rho =\frac{m}{V}=\frac{\mathrm{MA}}{d}.Math.\left[\rho \right]=\frac{\left[\mathrm{kg}\right]}{\left[m^2\right].Math.\left[m\right]}=\left[\frac{\mathrm{kg}}{m^3}\right]$

[0210] MA=coatweight/basis weight (excluding liner weight) in [kg/m.sup.2]

[0211] d=film thickness (excluding liner thickness) in [m]

[0212] Basis of the Examples

[0213] The invention is elucidated in more detail below, with reference to comparative examples and to inventive examples, without thereby wishing to impose any restriction on the subject matter of the invention.

[0214] Comparative examples 1.1. and 1.2. below show the advantages of the foaming of a self-adhesive by the inventive hotmelt method as opposed to foaming from solvent.

[0215] The advantages resulting from the method of the invention can be demonstrated most simply on a completed, foamed self-adhesive tape, as shown in the additional comparative example 2.

[0216] For the sake of brevity, in the examples, the term “hotmelt” is equated with the term “hotmelt process”, as a method according to the invention.

[0217] Raw Materials Used:

[0218] The raw materials used in the subsequent examples were as follows:

TABLE-US-00001 TABLE 1 Raw materials used Trade name Raw material/UPAC Manufacturer/supplier Voranol P 400 ® Polypropylene glycol, diol Dow Voranol 2000L ® Polypropylene glycol, diol Dow Voranol CP 6055 ® Polypropylene glycol, triol Dow MPDiol ® 2-Methyl-1,3-propanediol Lyondell Vestanat IPDI ® Isophorone diisocyanate Degussa Desmodur N 3300 ® Aliphatic polyisocyanate based on Bayer hexamethylene diisocyanate Tinuvin 292 ® Sterically hindered amine, light Ciba stabilizer and aging inhibitor Tinuvin 400 ® Triazine derivative, UV protectant Ciba Coscat 83 ® Bismuth trisneodecanoate Caschem CAS No. 34364-26-6 Aerosil R 202 ® Fumed silica, hydrophobized Evonik n-Butyl acrylate Acrylic acid n-butyl ester Rohm & Haas Acrylic acid, pure Acrylic acid BASF N-tert-Butylacrylamide N-(1,1-Dimethylethyl)-2- Linz Chemie propenamide 2-Ethylhexyl acrylate 2-Ethylhexyl acrylate Brenntag Bisomer HEMA 2-Hydroxyethyl methacrylate IMCD Deutschland Methyl acrylate Acrylic acid, methyl ester BASF Maleic anhydride 2,5-Dihydro-2,5-furandione, MAA Condea-Huntsman Expancel 051 DU 40 ® Microballoons (MB) Expancel Nobel Industries

[0219] Base Formulas of the Ready-Prepared Base Masses:

TABLE-US-00002 Fraction Adhesive K Preparation H Raw materials [% by weight] K1 H1 n-Butyl acrylate 44.2 2-Ethylhexyl acrylate 44.7 Methyl acrylate 8.6 Acrylic acid, pure 1.5 Bisomer HEMA 1.0 K2 H1 n-Butyl acrylate 44.9 2-Ethylhexyl acrylate 44.9 N-tert-Butylacrylamide 6.2 Acrylic acid, pure 3.0 Maleic anhydride 1.0 K3 H2 Voranol P400 17.23 Voranol CP 6055 48.88 MP Diol 3.60 Voranol 2000L 8.09 Tinuvin 400 0.21 Tinuvin 292 0.10 Coscat 83 0.41 Aerosil R202 2.06 Vestanat IPDI 19.42

[0220] Preparation Variants of the Ready-Prepared Base Masses:

[0221] Preparation H1:

[0222] The above monomer mixtures (amounts in % by weight) are copolymerized in solution. The polymerization batches consist of 60% by weight of the monomer mixtures and 40% by weight of solvents (such as benzine 60/95 and acetone). The solutions are first freed from oxygen by flushing with nitrogen in customary reaction vessels made of glass or steel (with reflux condenser, stirrer, temperature measurement unit and gas inlet tube) and then heated to boiling.

[0223] Polymerization is initiated by addition of 0.2% to 0.4% by weight of a customary radical polymerization initiator such as dibenzene peroxide, dilauroyl peroxide or azobisisobutyronitrile.

[0224] During the polymerization time of approximately 20 hours, dilution may take place a number of times with further solvent, depending on viscosity, and so the completed polymer solutions have a solids content of 35% to 55% by weight.

[0225] Concentration is accomplished by lowering the pressure and/or raising the temperature.

[0226] Preparation H2:

[0227] The branched, thermoplastically processable, hydroxyl-functionalized polyurethane hotmelt prepolymer was prepared by homogeneously mixing and hence reacting the stated starting materials in the stated proportions:

[0228] First of all, all of the starting materials listed, apart from the MP Diol and the Vestanat IPDI, were mixed at a temperature of 70° C. and a pressure of 100 mbar for 1.5 hours. Then the MP Diol was mixed in over 15 minutes, followed by the Vestanat IPDI, likewise over a period of 15 minutes. The resultant heat of reaction caused the mixture to heat to 100° C., and part of the mixture was then dispensed into storage vessels. Another part was processed further directly in substep B).

[0229] The resulting prepolymer was solid at room temperature. The complex viscosity η* at room temperature (23° C.) was 22 000 Pas and at 70° C. was 5500 Pas.

[0230] The weight-averaged average molecular weight M.sub.w was 125 000 g/mol; the number-averaged average molecular weight M.sub.N was 17 800 g/mol.

[0231] Formulas of the Inventive Foamed Mass Systems Based on the Ready-Prepared Base Masses K:

TABLE-US-00003 Fraction of the According to Experimental Base additives inventive specimen S adhesive K Additives [% by weight] preparation process S1 K1 Polypox R16 0.01 V1 Epikure 925 0.1 Expancel 051 DU 40 3 S2 K1 Polypox R16 0.01 V1 Epikure 925 0.1 Expancel 051 DU 40 5 S3 K1 Polypox R16 0.01 V1 Epikure 925 0.1 Expancel 051 DU 40 8 S4 K2 Polypox R16 0.01 V1 Epikure 925 0.1 Expancel 051 DU 40 5.6 S5 K2 Polypox R16 0.01 V1 Epikure 925 0.1 Expancel 051 DU 40 5.6 Dertophene T110 10 S6 K2 Polypox R16 0.01 V1 Epikure 925 0.1 Expancel 051 DU 40 5.6 Dertophene T110 20 S7 K2 Polypox R16 0.013 V1 Epikure 925 0.13 S8 K2 Polypox R16 0.005 V2 Epikure 925 0.05 Expancel 051 DU 40 1 S9 K2 Polypox R16 0.013 V1 Epikure 925 0.13 Sylvares TP115 25 S10 K2 Porypox R16 0.005 V2 Epikure 925 0.05 Expancel 051 DU 40 1 Sylvares TP115 10 S11 K3 Coscat 83 0.41 V1 Expancel 051 DU 40 3 S12 K3 Coscat 83 0.41 V1 Expancel 051 DU 40 5 S13 K3 Coscat 83 0.41 V1 Expancel 051 DU 40 8 S14 K3 Coscat 83 0.41 V1

[0232] Inventive Preparation Processes V:

[0233] Process V1:

[0234] Preparation takes place as described in the disclosure relating to FIG. 1.

[0235] The temperature profiles and machine parameters are adapted to the mass system under preparation, such as the polymer matrix to be compounded, the crosslinking system, the microballoon type and/or further additives and fillers of any kind, and are given in detail in the examples.

[0236] Process V2:

[0237] Preparation takes place as described in the disclosure relating to FIG. 2.

[0238] The temperature profiles and machine parameters are adapted to the mass system under preparation, such as the polymer matrix to be compounded, the crosslinking system, the microballoon type and/or further additives and fillers of any kind, and are given in detail in the examples.

EXAMPLES

Example 1

[0239] Graduated Microballoon Contents with the Same Mass Basis

TABLE-US-00004 BS steel 90° 3d HP Experi- Coat- Film peel HP RT 70° C. mental weight thickness Density increase 10N 10N specimen [g/m.sup.2] [μm] [kg/m.sup.3] [N/cm] [min] [min] S1 498 873 570 13.4 1524 40 S2 458 953 481 14.9 4722 149 S3 378 1048 361 11.7 >10 000 702

Example 2

[0240] Graduated Resin Contents with the Same Mass Basis and Constant Microballoon Content

TABLE-US-00005 BS steel 90° 3d HP Experi- Coat- Film peel HP RT 70° C. mental weight thickness Density increase 10N 10N specimen [g/m.sup.2] [μm] [kg/m.sup.3] [N/cm] [min] [min] S4 606 1030 588    8.7 2210 21 S5 438 1038 422 >17.6 >10 000 76 S6 404 1010 400 >22.1 >10 000 399

Example 3

[0241] Comparison Unfoamed/Foamed

[0242] Resin-Free/Resin-Containing

TABLE-US-00006 BS steel 90° 3d HP Experi- Coat- Film peel HP RT 70° C. mental weight thickness Density increase 10N 10N specimen [g/m.sup.2] [μm] [kg/m.sup.3] [N/cm] [min] [min] S7 994 915 1086 13.8    325 13 S8 563 955 589 24.1   1386 105 S9 954 910 1048 18.9    831 30 S10 614 955 643 23.9 >3000 25

[0243] Specimens S7 and S9 in accordance with process 1, since unfoamed mass requires subsequent degassing. Foamed mass, in contrast, does not, and so specimens S8 and S10 prepared by process 2.

Example 4

[0244] Polyurethane Masses with Graduated Microballoon Content

TABLE-US-00007 BS steel 90° 3d HP Experi- Coat- Film peel HP RT 70° C. mental weight thickness Density increase 10N 10N specimen [g/m.sup.2] [μm] [kg/m.sup.3] [N/cm] [min] [min] S11 547 1010 542   24.4 492 3 S12 402 990 406 >21.4 1723 14 S13 397 1073 370 >29.7 1125 9

Example 5

[0245] Experimental Specimens S11 to S14 Subsequently Laminated on Both Sides with 50 g/m.sup.2 of Aftercoat Mass

[0246] Three-Layer Construction

TABLE-US-00008 BS steel HP Film 90° 3d peel RT Experimental Coatweight thickness Density increase 10 N specimen [g/m.sup.2] [μm] [kg/m.sup.3] [N/cm] [min] S11 + 50 g/m.sup.2 647 1110 583 29.2 782 S12 + 50 g/m.sup.2 502 1090 461 42.7 2336 S13 + 50 g/m.sup.2 497 1173 424 34.2 911 S14 + 50 g/m.sup.2 1150 1045 1100 20.8 150