RUBBER-BASED SELF-ADHESIVE COMPOUND

Abstract

The invention relates to a self-adhesive compound consisting of a mixture containing: rubber, particularly natural rubber; at least one adhesive resin where said adhesive resins are present at an amount of 40 to 130 phr; and expanded polymer microbeads.

Claims

1. A self-adhesive mass being a mixture comprising: rubber, at least one tackifier resin, the fraction of the tackifier resins being 40 to 130 phr, expanded polymeric microspheres.

2. The self-adhesive mass of claim 1, wherein, the fraction of the tackifier resins is 80 to 120 phr.

3. The self-adhesive mass of claim 1, wherein: the density of the self-adhesive mass after activation of the microballoons is reduced from its initial value by 150 kg/m.sup.3.

4. The self-adhesive mass of claim 1, wherein the self-adhesive mass can be removed very largely without residue after bonding.

5. The self-adhesive mass according to claim 1, which contains a terpene-phenolic resin as a tackifier resin.

6. The self-adhesive mass of claim 1, wherein: the fraction of the microballoons, based on the total adhesive prior to expansion, in the self-adhesive mass is between greater than 0 wt % and 30 wt %, based in each case on the overall composition of the pressure-sensitive adhesive.

7. The self-adhesive mass of claim 1 wherein: the pressure-sensitive adhesive has the following composition: a) 30 wt % to 59.9 wt % of natural rubber; b) 40 wt % to 69.9 wt % of a terpene-phenolic resin; c) 0.1 wt % to 30 wt % of expanded polymeric microspheres (the % wt. based on unexpanded microballoons).

8. The self-adhesive mass as claimed of claim 1, wherein: the pressure-sensitive adhesive has the following composition: a) 30 wt % to 59.9 wt % of natural rubber; b) 40 wt % to 69.9 wt % of at least one tackifier resin based on terpene-phenolic resin; c) 0.1 wt % to 30 wt % of expanded polymeric microspheres (the wt % based on unexpanded microballoons); and, d) 0 wt % to 20 wt % of further additives.

9. The self-adhesive mass of claim 1, wherein the pressure-sensitive adhesive has the following composition: a) 45 wt % to 53.5 wt % of natural rubber b) 45 wt % to 55 wt % of terpene-phenolic resin c) 1.5 wt % and 10 wt % of expanded polymeric microspheres (the wt % based on unexpanded microballoons) and d) 0 wt % of further additives.

10. The self-adhesive mass which further comprises one or more components selected from: plasticizers, aging inhibitors, processing assistants, fillers, dyes, optical brighteners, stabilizers, and flame retardants.

11. The self-adhesive mass of claim 1, wherein the rubber is natural rubber and no further elastomeric polymer is present in the self-adhesive mass.

12. The self-adhesive mass of claim 1, wherein a flame retardant based on organophosphorus compounds is present.

13. The self-adhesive mass which includes a crosslinked, pressure-sensitive adhesive.

14. A double-sided adhesive tape having at least one self-adhesive mass according to claim 1, which is pressure-sensitive, wherein and having a thickness of between 10 m and 600 m.

15. An adhesive tape having a self-adhesive mass according to claim 1 which is pressure-sensitive, where in a layer of pressure-sensitive adhesive there is also present a carrier.

16. An adhesive tape of claim 15, which comprises two layers of self-adhesive masses disposed on the carrier, wherein the two layers are of identical formulation.

17. The adhesive tape of claim 16, where the two layers of self-adhesive masses have a layer thickness ratio of greater than 1.

18. An adhesive tape of claim 16, where the two layers of self-adhesive masses have different densities.

19. The adhesive tape of claim 15, wherein one of the two layers of self-adhesive masses is unfoamed.

20. A method of bonding a temporary substrate to a permanent substrate, the method comprising the step of: utilizing the adhesive tape of claim 14 between the temporary substrate and the permanent substrate.

Description

[0148] Further details, objectives, features, and advantages of the present invention will be elucidated in more detail below by reference to a number of figures which represent preferred working examples. In these figures

[0149] FIG. 1 shows a single-sided pressure-sensitive adhesive tape,

[0150] FIG. 2 shows a double-sided pressure-sensitive adhesive tape,

[0151] FIG. 3 shows a carrier-free pressure-sensitive adhesive tape (adhesive transfer tape).

[0152] FIG. 1 shows a single-sidedly adhering pressure-sensitive adhesive tape 1. The pressure-sensitive adhesive tape 1 has an adhesive layer 2 produced by coating one of the above-described PSAs onto a carrier 3. The PSA coat weight is preferably between 10 and 50 g/m.sup.2.

[0153] Provided additionally (not shown) may be a release film, which covers and protects the adhesive layer 2 before the pressure-sensitive adhesive tape 1 is used. The release film is then removed before use from the adhesive layer 2.

[0154] The product construction shown in FIG. 2 shows a pressure-sensitive adhesive tape 1 with a carrier 3, coated on both sides with a PSA and therefore having two adhesive layers 2. The PSA coat weight per side is in turn preferably between 10 and 200 g/m.sup.2.

[0155] With this embodiment as well, at least one adhesive layer 2 is preferably lined with a release film. In the case of a rolled-up adhesive tape, this one release film may optionally also line the second adhesive layer 2. However, it is also possible for a plurality of release films to be provided.

[0156] It is possible, furthermore, for the carrier film to be provided with one or more coatings. Moreover, only one side of the pressure-sensitive adhesive tape may be furnished with the inventive PSA, and a different PSA may be used on the other side.

[0157] The product construction shown in FIG. 3 shows a pressure-sensitive adhesive tape 1 in the form of an adhesive transfer tape, in other words a carrier-free pressure-sensitive adhesive tape 1. For this construction, the PSA is coated single-sidedly onto a release film 4, to form a pressure-sensitive adhesive layer 2. The PSA coat weight here is customarily between 10 and 50 g/m.sup.2. This pressure-sensitive adhesive layer 2 is optionally also lined on its second side with a further release film. For the use of the pressure-sensitive adhesive tape, the release films are then removed.

[0158] As an alternative to release films it is also possible for example to use release papers or the like. In that case, however, the surface roughness of the release paper ought to be reduced, in order to realize a PSA side that is as smooth as possible.

Test Methods

[0159] Unless otherwise indicated, the measurements are carried out under test conditions of 231 C. and 505% relative humidity.

Peel Adhesion to Aluminum, Steel, Carpet (Backing)

[0160] The peel strength (peel adhesion) was tested in a method based on PSTC-1.

[0161] A strip of the pressure-sensitive adhesive tape 2 cm wide is adhered to the test substrate, such as, for example, a steel plate, an aluminum plate, or a strip of carpet fixed by the surface on a solid steel subsurface beforehand, by being rolled on back and forth five times using a 4 kg roller. The surface of the steel or aluminum plate is cleaned with acetone beforehand; the surface of the carpet backing is not cleaned. The plate is clamped in, and the self-adhesive strip is peeled from its free end on a tensile testing machine at a peel angle of 180 and with a speed of 300 mm/min, and a determination is made of the force needed to achieve this. The measurement results are reported in N/cm and are averaged over three measurements. The result is reported as PA steel (peel adhesion to steel), PA alu (peel adhesion to aluminum), and PA carpet (peel adhesion to carpet backing).

[0162] For the measurements carried out in the context of this patent application, the Aero collection 5ED-121426 carpet from Desso Aviation Carpet was used. The good and advantageous results of the self-adhesive compounds of the invention were, however, also achieved on further, different carpets from different manufacturers.

Flame Test

[0163] The flame tests were conducted in accordance with ASTM F501 (Airbus AITM 2.0002B). A pass is scored in the test if the maximum burning distance does not exceed 203 mm and the maximum burning time does not exceed 15 seconds. Prior to the test, the specimens were adhered on an aluminum plate and conditioned for 3 days at 231 C. and 505% relative humidity.

Absence of Residue

[0164] In order to find a suitable measure for determining the absence of residue, a section of adhesive tape (adhesive transfer tape) with an area of 520 cm is adhered to a subsurface in the form of an aluminum plate. After 4-week storage at 40 C. on the permanent substrate, the adhesive tape is peeled off. The residues of composition remaining are determined by weighing of the subsurface plate, and are extrapolated to an area of one square meter.

[0165] The intention below is to illustrate the invention with a number of examples, without thereby wishing to subject the invention to unnecessary limitation.

EXAMPLES

[0166]

TABLE-US-00001 Example 1a Example 1b Comparative Example 5 Standard 4 weeks Example 2 example 4 HC resin Initial mass Initial mass Initial mass Initial mass Initial mass Raw material of solids [%] of solids [%] of solids [%] of solids [%] of solids [%] Natural rubber 41.0 41.0 41.0 41.0 41.0 (type SVR 3L) Piccotac 1100E 37.0 Novares TK 90 12.0 Dertophene T 105 49.0 49.0 49.0 49.0 920 DU 40 5.0 5.0 5.0 5.0 5.0 Chemical blowing agent azodicarboxamide Wingtack 10 5.0 5.0 5.0 5.0 5.0 DOPO flame retardant ADP flame retardant Comparative Comparative Comparative example 2 example 3 Example 3 Example 4 example 1 Physical Chemical Flame Flame Unfoamed foaming foaming retardancy retardancy Initial mass Initial mass Initial mass Initial mass Initial mass Raw material of solids [%] of solids [%] of solids [%] of solids [%] of solids [%] Natural rubber 43.0 43.0 42.0 37.3 33.9 (type SVR 3L) Piccotac 1100E Novares TK 90 Dertophene T 105 51.0 51.0 51.0 44.5 40.5 920 DU 40 5.0 5.0 Azodicarboxamide 2.0 Wingtack 10 6.00 6.00 5.0 4.0 5.0 DOPO flame 9.2 retardant ADP flame 16.6 retardant Piccotac 1100-E aliphatic hydrocarbon resin Eastman Chemical Middleburg B. V. 920 DU 40 microballoons from Expancel DOPO = (9,10-dihydro-9-oxy-10-phosphaphenanthrene 10-oxide) ADP = aluminum diethylphosphinate

[0167] Using the adhesives produced according to the formulas stated above, double-sided adhesive tapes are produced, by applying the PSA to the top and bottom sides of a PET film which is 23 m thick and has been etched on both sides with trichloroacetic acid.

[0168] Results of Measurement:

TABLE-US-00002 Example 1a Example 1b Comparative Example 5 Standard 4 weeks Example 2 example 4 HC resin Density 540 kg/m.sup.3 540 kg/m.sup.3 540 kg/m.sup.3 540 kg/m.sup.3 540 kg/m.sup.3 Thickness alu side 37 m 37 m 64 m 95 m 37 m PA alu 5.30 N/cm 5.50 N/cm 5.80 N/cm 7.50 N/cm 4.90 N/cm Thickness carpet 156 m 156 m 128 m 100 m 156 m side PA carpet 3.50 N/cm 3.60 N/cm 2.90 N/cm 2.10 N/cm 0.80 N/cm PA alu 10.70 N/cm 11.00 N/cm 9.10 N/cm 7.60 N/cm 8.2 N/cm Detachment from no no no yes no carpet on removal Layer thickness 4.2 4.2 2.0 1.05 4.2 gradient Flame test without pass pass pass pass pass additional FR Residues on alu 4 g/m.sup.2 4 g/m.sup.2 4 g/m.sup.2 4 g/m.sup.2 4 g/m.sup.2 Comparative Comparative Comparative example 2 example 3 Example 3 Example 4 example 1 Physical Chemical Flame Flame Unfoamed foaming foaming retardancy retardancy Density 980 kg/m.sup.3 630 kg/m.sup.3 495 kg/m.sup.3 620 kg/m.sup.3 680 kg/m.sup.3 Thickness alu side 20 m 32 m 40 m 32 m 29 m PA alu 6.20 N/cm 7.50 N/cm 9.20 N/cm 4.8 N/cm 4.5 N/cm Thickness carpet 85 m 135 m 172 m 137 m 125 m side PA carpet 2.90 N/cm 1.80 N/cm 2.40 N/cm 1.2 N/cm 1.7 N/cm PA alu 9.30 N/cm 8.50 N/cm 9.80 N/cm 7.9 N/cm 7.5 N/cm Detachment from no no no no no carpet on removal Layer thickness 4.2 4.2 4.2 4.2 4.2 gradient Flame test without fail fail pass pass pass additional FR Residues on alu 1 g/m.sup.2 13 g/m.sup.2 15 g/m.sup.2 4 g/m.sup.2 4 g/m.sup.2

[0169] Example 1b is obtained from example 1a by 4-week storage (231 C. and 505% relative humidity) in the bonded state.

[0170] For the preferred application it is important that the assembly formed of carpet (temporary substrate)/adhesive tape can be removed from the permanent substrate, even after a prolonged period of bonding, easily and without any increase in the bond strength, from the carpet without stretching. In accordance with the invention, there is no increase in the bond strength on the permanent substrate over time.

[0171] As well as the foaming with microballoons in accordance with the invention, the comparative experiments also show what are referred to as chemical and physical foaming, in which case free, unstabilized gas bubbles are generated in the polymer compound.

[0172] It is found that with both chemical and physical foaming, there is an approximately central splitting of adhesive when the adhesive tape of the invention is removed by peeling.

[0173] In accordance with the invention, products with very low density and very low residues (on the permanent substrate) can be produced. In the case of chemical and physical foaming, in contrast, there is an increase in the residues with reduction in the density.

[0174] A further feature of the PSA of the invention is that the difference between the initial peel adhesion and the peel adhesion after storage in the bonded state (40 C., 28 d) is very small. The difference is preferably at most 4 N/cm, very preferably at most 3 N/cm. In the investigations it was found in particular that compositions based on natural rubber (poly-cis-isoprene) fulfill the conditions specified above and are therefore preferred.