FLAME-RETARDED ELASTIC POLYURETHANE FOAM, ADHESIVE TAPE WITH A CARRIER MADE THEREFROM, AND PRODUCTION METHOD THEREFOR

Abstract

Systems and methods provide a polyurethane foam. One method may obtainable the polyurethane foam by mechanical foaming with a starting mixture comprising a polyurethane dispersion, the polyurethane being composed of at least one polyisocyanate component and at least one polyol component, and at least one surfactant. The polyol component or at least one of the polyol components may comprise at least one comonomer having flame retardancy effect and containing two hydroxyl groups. The adhesive tapes produced therefrom may adhesively bond components in vehicles, aircraft or trains, or in electronic devices.

Claims

1. A polyurethane foam obtainable by mechanical foaming of a starting mixture comprising a polyurethane dispersion, the polyurethane being composed of: at least one polyisocyanate component; at least one polyol component; and at least one surfactant, wherein the polyol component or at least one of the polyol components comprises at least one comonomer having flame retardancy effect and containing two hydroxyl groups.

2. The polyurethane foam of claim 1, wherein the polyurethane foam has an elongation at break of at least 100%.

3. The polyurethane foam of claim 1, wherein the polyurethane foam, on loading in the thickness direction in the fourth cycle in the range from 20% to 80% compression, consistently exhibits a compressive strength of 50 to 500 kPa, and the polyurethane foam, after the loading has been discontinued, reverts to at least 80% of its original thickness.

4. The polyurethane foam of claim 1, wherein the at least one surfactant is a nonionic surfactant, an ionic surfactant, or a combination thereof.

5. The polyurethane foam of claim 1, wherein the at least one comonomer having flame retardancy effect is a halogen-containing comonomer selected from the group consisting of derivatives of tetrabromophthalic acid, modified 2,3-dibromo-2-butene-1,4-diols, tris(2-chloroisopropyl) phosphate, tetrabromobisphenol A, and mixtures thereof.

6. The polyurethane foam of claim 1, wherein the at least one comonomer having flame retardancy effect is a phosphorus-containing comonomer selected from the group consisting of hydroxyl-functionalized alkyl phosphates such as, in particular, hydroxyl-functionalized tributyl phosphate, hydroxyl-functionalized triphenyl phosphate, hydroxyl-functionalized triethyl phosphate, hydroxyl-functionalized diphenyl cresyl phosphate, hydroxyl-functionalized tris(2-chloroisopropyl) phosphate, a phosphate ester of the general formula
HO(POOR.sub.1OR.sub.2O).sub.nPOOR.sub.1OH where R.sub.1=alkyl or alkoxy, R.sub.2=alkyl radical with C.sub.1 to C.sub.6, and 2n300, and mixtures thereof.

7. The polyurethane foam of claim 1, wherein the at least one polyisocyanate component is a diisocyanate.

8. The polyurethane foam of claim 1, wherein the at least one polyol component is selected from the group consisting of a diol, a polyether diol, a polyester diol, a polycarbonate diol, a polycaprolactone polyol, propanediol, butanediol, pentanediol, hexanediol, cyclohexanediol, cyclohexyldimethanol, octanediol, neopentyl glycol, diethylene glycol, triethylene glycol, trimethylpentanediol, benzenedimethanol, benzenediol, methylbenzenediol, bisphenol A, poly(butanediol-co-adipate) glycol, poly(hexanediol-co-adipate) glycol, poly(ethanediol-co-adipate) glycol, polytetramethylene glycol, polypropylene glycol, polyethylene glycol, and a mixture thereof.

9. The polyurethane foam of claim 1, wherein the starting mixture further comprises a thickener.

10. The polyurethane foam of claim 1, wherein the starting mixture further comprises a crosslinker.

11. The polyurethane foam of claim 1, wherein the starting mixture further comprises at least one further dispersion selected from the group consisting of polyurethane dispersions whose polyol component includes a comonomer having flame retardancy effect, polyurethane dispersions whose polyol component includes no comonomer having flame retardancy effect, synthetic rubber dispersions, natural rubber dispersions, polyacrylate dispersions, and a combination thereof.

12. The polyurethane foam of claim 1, wherein the polyol component has a number-average molecular weight of 60 to 50 000 g/mol.

13. An adhesive tape comprising: at least one carrier comprising the polyurethane foam of claim 1; at least one layer of a flame-retarded pressure-sensitive adhesive composition; and a layer of a flame-retarded pressure-sensitive adhesive composition arranged on both sides of the adhesive tape.

14. The adhesive tape of claim 13, wherein the adhesive composition is an acrylate adhesive composition.

15. The adhesive tape of claim 13, further comprising: an intermediate layer configured to compensate expansion of battery cells during charge or discharge.

16. A method comprising: adhesively bonding components with the adhesive tape of claim 13, wherein at least one of the components is a vehicle component, an aircraft component, a train component, or an electronic device component.

17. A method for producing a polyurethane foam, the method comprising: a) initially introducing a polyurethane dispersion, at least one polyol component, at least one surfactant, an optional polyol component, and an optional dispersions comprising polyurethane or polyacrylate to form a starting mixture, wherein the polyurethane dispersion is composed of at least one polyisocyanate component and the at least one polyol component comprises at least one comonomer having flame retardancy effect and containing two hydroxyl groups b) mechanically foaming the starting mixture to form a wet polyurethane foam composition, optionally with one or more of the following additional components: ii) crosslinkers; iii) fillers; and/or iv) further additives; c) applying the wet polyurethane foam composition to a surface; and d) drying the wet polyurethane foam composition to give the polyurethane foam.

18. The method according to claim 17, wherein the drying in d) takes place in at least two stages, with the temperature of drying being increased from one step to the next.

19. The method according to claim 18, wherein the drying in d) takes place in two stages, with the temperature of the drying in the 1.sup.st step being from 70 C. to 100 C. and the temperature of the drying in the 2.sup.nd step being from 105 C. to 140 C.

Description

EXPERIMENTAL SECTION

[0120] The following exemplary experiments are intended to elucidate the invention in more detail without subjecting the invention to any unnecessary restriction through the choice of the examples specified.

Test Methods

[0121] The following test methods were employed for determining the parameters in the examples and also the preferred parameters specified in the description.

[0122] Unless otherwise indicated, all measurements were conducted at 23 C. and 50% relative humidity.

Thickness

[0123] The thickness of a layer of adhesive composition, an adhesive tape or foam layer, a carrier layer or a liner can be determined using commercial thickness gauges (sensor instruments) having accuracies of less than 1 m deviation. In the present specification, the gauge used is the Mod. 2000 F precision thickness gauge, which has a circular sensor with a diameter of 10 mm (plane). The measurement force is 4 N. The value is read off 1 s after loading. If fluctuations in thickness are found, the value reported is the average value of measurements at not less than three representative sitesin other words, in particular, not including measurement at wrinkles, creases, nibs and the like. The thickness of a layer of adhesive composition can be determined in particular by determining the thickness of a section of such a layer of adhesive composition, applied to a carrier or liner, said section being of defined length and defined width, with subtraction of the thickness of a section of the carrier or liner used that has the same dimensions (the thickness being known or separately ascertainable).

Coat Weight (Areal Density)

[0124] The coat weight (areal density) of a sample such as, for example, an adhesive composition or a foam on a substrate such as, for example, a liner pertains, unless otherwise indicated, to the weight per unit area after drying. The coat weight may be determined by determining the mass of a section of such a sample applied to a substrate, the section being of defined length and defined width, minus the (known or separately ascertainable) mass of a section of the substrate used that has the same dimensions.

Density

[0125] The density of a foam carrier is ascertained by forming the quotient of the coat weight and thickness of the foam applied to a substrate such as, for example, a liner.

Solids Content

[0126] The solids content is a measure of the fraction of unevaporable constituents in a sample such as, for example, a dispersion. It is determined gravimetrically, by weighing the sample, then evaporating the evaporable fractions in a drying cabinet at 120 C. for 2 hours, and reweighing the residue.

Viscosity

[0127] Dynamic viscosity measurement: The viscosity is measured using a rheometer of type ARES (Rheometric Scientific) at room temperature (20 C.) and at a shear rate of 100 s.sup.1 using a cone/plate system with a diameter of 50 mm.

Elongation at Break (Breaking Stress)

[0128] The elongation at break (breaking stress) of a carrier is measured in a method based on DIN EN ISO 527-3 using a type 2 test specimen strip of the carrier having a width of 20 mm, at a separation velocity of 100 mm per minute. The initial spacing of the clamping jaws is 100 mm.

Resilience or Elasticity

[0129] Resilience was measured by elongating by 100%, holding in this elongation for 30 s, and then releasing. After a waiting time of 1 min, the length was measured again. The resilience is calculated as follows: RV=((L.sub.100L.sub.end)/L.sub.0).Math.100

where RV=resilience in %
L.sub.100: length after elongation by 100%
L.sub.0: length before elongation
L.sub.end: length after relaxation for 1 min.

[0130] The resilience here corresponds to the elasticity.

Compressive Strength

[0131] Test specimens of 30 mm30 mm are cut from the material under test. These specimens are stacked with the edges in line to a height of 30 mm. The stack is placed in a stress-strain machine equipped with plates. With a velocity of 10 mm per minute, the plates are moved towards one another until the pre-tensioning force of 0.2 kPa has been reached. This point is set as the zero point of the compression. Subsequently, compression takes place at 50 mm per minute up to a compression of 80%. At this point a record is made of the force required per unit area (compressive strength). The machine is subsequently run back to 0% compression. Four cycles are recorded. The cycle critical for the assessment of the foam is the fourth cycle.

Molecular Weight M.SUB.n

[0132] The figures for the number-average molecular weight M.sub.n in this specification are based on the determination by gel permeation chromatography (GPC). The determination is made on 100 l of a sample having undergone clarifying filtration (sample concentration 4 g/I). The eluent used is tetrahydrofuran with 0.1 vol % trifluoroacetic acid. Measurement takes place at 25 C. The precolumn used is a column of type PSS-SDV, 5 m, 10.sup.3 , 8.0 mm*50 mm (figures here and below in the following order: type, particle size, porosity, internal diameter*length; 1 =10.sup.10 m). Separation takes place using a combination of the columns of type PSS-SDV, 5 m, 10.sup.3 and also 10.sup.5 and 10.sup.6 each with 8.0 mm*300 mm (columns from Polymer Standards Service; detection using Shodex RI71 differential refractometer). The flow rate is 1.0 ml per minute. Calibration takes place in the case of polar molecules such as, for example, the starting materials of the polyurethane against PMMA standards (polymethyl methacrylate calibration), and otherwise against PS standards (polystyrene calibration).

Combustibility

[0133] The combustibility is tested in a method based on FAR 25.853. The test is carried out in a test chamber in which the specimen for testing is mounted vertically. The specimen for testing has a size of 75 mm300 mm. The middle of the lower end of the specimen is exposed to a gas flame for an ignition time of 12 seconds. Measured thereafter are afterburn time, burn length and burn time of the droplets. Afterburn time is the time for which the sample burns after the ignition time. Burn length is the length of burnt material consumed by the end of the fire. Burn time of the drops is the time for which drops of the sample that fall off during burning continue to burn after dropping.

[0134] The combustibility test is passed if the afterburn time is not more than 15 seconds, the burn length not more than 203 mm and the burn time of the droplets not more than 3 seconds.

Production and Properties of the Samples

Raw Materials Used:

[0135]

TABLE-US-00001 TABLE 1 Raw materials used Permutex aqueous dispersion of a phosphorus- Stahl RU-13-597 containing polycarbonate/polyester Holdings B.V. PU Hauthane aqueous dispersion of an aliphatic Hauthaway & Sons L3808 phosphorus-containing polyurethane Corporation Permutex aqueous dispersion of an aliphatic Stahl RU-4049 polyether PU Holdings B.V. Impranil aqueous dispersion of an aliphatic Covestro AG DLU polycarbonate/polyester PU Impranil aqueous dispersion of an aliphatic Covestro AG DLE polyether PU Ortegol foam stabilizer - aqueous solution of Evonik Nutrition P2 a nonionic surfactant & Care GmbH Stokal foam stabilizer - aqueous solution of Bozetto Group STA ammonium stearate Stokal foam stabilizer - aqueous dispersion Bozetto Group SR of succinamate Sultflon foam stabilizer - aqueous solution of Bozetto Group SAF a sodium salt of fatty acid alkyl polyglycol ether sulfates Borchi thickener - aqueous solution of an Borchers Gel ALA anionic polymer Ortegol thickener - aqueous solution of a Evonik Nutrition PV301 nonionic associative PU-based & Care GmbH thickener with approximately newtonian behaviour Imprafix crosslinker - aqueous solution of a Covestro AG 2794 XP blocked aliphatic isocyanate

Formulations of the Foamed Carriers:

[0136]

TABLE-US-00002 TABLE 2 Compositions of the inventive and comparative examples Inventive Inventive Inventive Inventive Comparative Component Example 1 Example 2 Example 3 Example 4 Example 5 Permutex RU-13-597 100 g 50 g 50 g 50 g Permutex RU-4049 50 g Impranil DLU 50 g 100 g Impranil DLE 50 g Ortegol P2 6 g 12 g 12 g 12 g 6 g Imprafix 2794XP 6 g 6 g 6 g 6 g 6 g (optional) Ortegol PV301 2 g 4 g 4 g 4 g 2 g Water 2 g 2 g 2 g 2 g 2 g

TABLE-US-00003 TABLE 3 Compositions of the inventive examples Inventive Inventive Component Example 6 Example 7 Hauthane L-3808 100 g 68 g Permutex RU-13-597 Impranil DLU 32 g Stokal STA 2 g 2 g Stokal SR 2 g 2 g Sultaflon SAF 2 g 2 g Imprafix 2794 XP 6 g 6 g (optional)

Production of the Beaten Foams:

[0137] The polyurethane (PU) dispersions (Permutex and/or Impranil) and the foam stabilizer (Ortegol P2 or a mixture of types of Stokel) are mixed in a beaker using a paddle stirrer (300 s at 500 rpm). Optionally it is possible additionally to add a crosslinker such as Imprafix 2794. The mixture is subsequently beaten with a paddle stirrer at 2000 rpm until there is no further increase in the volume of the beaten foam. Ortegol PV301 or Borchi Gel ALA is diluted with water beforehand and added to the beaten foam in portions with stirring at 500 rpm. This is followed by further homogenization for 300 s.

[0138] Flame-retarded polyurethane dispersions can be foamed neat (Inventive Examples 1 and 6, Inventive Example 6 preferred). To increase foam quality or to set desired mechanical properties, they can also be blended with other, non-flame-retarded dispersions such as Permutex RU-4049, Impranil DLU and Impranil DLE (Inventive Examples 2-4 and 8, Inventive Example 8 preferred) or blended with other flame-retarded polyurethane dispersions (Inventive Example 7). Blending with other aqueous polymer dispersions (such as acrylates, natural rubber and synthetic rubber) is likewise conceivable. Optionally a crosslinker such as Imprafix 2794 can be added in order to increase the mechanical and chemical resistance of the foam. Specified as Example 5 for comparison is a dispersion which is not flame-retarded (prior art).

Production of the Foamed Carriers:

[0139] The beaten foam is coated in each case onto a siliconized polyester carrier (Silphan S50 from the manufacturer Siliconature SPA) (wet film thickness 500-1000 m) and cured for 60 s each at 80 C., 105 C. and optionally at 150 C. After 24 h, the foamed carrier can be removed from the liner.

Properties of the Foamed Carriers:

[0140]

TABLE-US-00004 TABLE 4 Properties of the foamed carrier Inventive Inventive Inventive Inventive Comparative Example 1 Example 2 Example 3 Example 4 Example 5 Afterburn time 0 s 0 s 0 s 0 s 20 s Burn length 60 mm 35 mm 45 mm 60 mm 300 mm Burn time of drops 0 s 0 s 0 s 0 s 0 s Thickness 140 m 300 m 300 m 300 m 300 m Density 370 g/l 350 g/l 410 g/l 460 g/l 300 g/l

TABLE-US-00005 TABLE 5 Properties of the foamed carrier. Inventive Inventive Example 6 Example 7 Afterburn time 0 s 1 s Burn length 50 mm 50 mm Burn time of drops 0 s 1 s Thickness 532 m 671 m Density 254 g/l 216 g/l

[0141] The foamed carriers of Inventive Examples 1 to 4 and 6 to 7, the polyurethane in which has been produced from comonomers including a comonomer having a flame retardancy effect, pass the combustibility test, whereas the foamed carrier from Comparative Example 5, without a flame retardant, does not.

[0142] The foamed carriers of Inventive Examples 2 and 4, moreover, have an elongation at break of at least 700%. The foamed carriers of Inventive Examples 6 and 7 can be compressed to 20% of their original thickness. Inventive Example 7 here has a compressive strength of 80 kPa at 50% compression and 860 kPa at 80% compression in the 4th compression cycle, and also a resilience of 80% within a few minutes and 95% within 12 hours. In contrast to this, Inventive Example 6 exhibits a compressive strength of 3.68 MPa at 80% compression in the 4th cycle and a resilience of 40% within a few minutes and 57% within 12 h. Consequently it is not possible to report a compressive strength at 50% compression in the 4th cycle.

[0143] The foamed carriers from Inventive Examples 2 to 4, moreover, have lower cell diameters than the foamed carrier from Inventive Example 1.

Production of Flame-Retarded Foam-Backed Adhesive Tapes:

[0144] The foamed carrier is laminated on either side with 50 g/m.sup.2 of flame-retarded pressure-sensitive adhesive composition. The flame-retarded PSA is a polyacrylate PSA comprising N/P-containing flame retardant.

Properties of the Pressure-Sensitive Adhesive Tapes with Foamed Carrier:

TABLE-US-00006 TABLE 6 Properties of the pressure-sensitive adhesive tapes composed of foamed carrier and polyacrylate PSA Inventive Inventive Inventive Inventive Comparative Example 1 Example 2 Example 3 Example 4 Example 5 Afterburn 0 s 0 s 0 s 0 s 20 s time Burn 75 mm 5 mm 35 mm 30 mm 300 mm length Burn time 0 s 0 s 0 s 0 s 0 s of drops

[0145] The foam-backed adhesive tapes of Inventive Examples 1 to 4 pass the combustibility test, whereas the foam-backed adhesive tape from Comparative Example 5 does not.