PRODUCING A PRESSURE-SENSITIVE ADHESIVE BASED ON SOLID EPDM RUBBER

Abstract

A process for the continuous and solvent-free production of a pressure-sensitive adhesive based on solid EPDM rubber, the pressure-sensitive adhesive produced thereby, and an adhesive tape containing the pressure-sensitive adhesive. The pressure-sensitive adhesive is produced in a continuously operating assembly in the form of a planetary roller extruder having a filling section and a compounding section, the compounding section consisting of at least two coupled roller cylinders, by

a) feeding the solid EPDM rubber and any further components into the filling section of the planetary roller extruder,
b) transferring the components from the filling section into the compounding section,
c) adding liquid EPDM rubber, plasticizer, tackifier resin, and any further components to the compounding section, and
d) discharging the resultant pressure-sensitive adhesive,
which process comprises feeding the solid EPDM rubber as a melt into the filling section.

Claims

1. A process for the continuous and solvent-free production of a pressure-sensitive adhesive based on solid EPDM rubber in a continuously operating assembly in the form of a planetary roller extruder having a filling section and a compounding section, the compounding section consisting of at least two coupled roller cylinders, by a) feeding the solid EPDM rubber and any further components into the filling section of the planetary roller extruder, b) transferring the components from the filling section into the compounding section, c) adding liquid EPDM rubber, plasticizer, tackifier resin, and any further components to the compounding section, and d) discharging the resultant pressure-sensitive adhesive, which process comprises feeding the solid EPDM rubber as a melt into the filling section.

2. The process as claimed in claim 1, wherein the solid EPDM rubber (i) is composed to an extent of 30 to 80 wt of ethylene, and/or (ii) is composed to an extent of 20 to 60 wt % of propylene, and/or (iii) is composed to an extent of up to 20 wt % of diene, based in each case on the total weight of the parent monomer composition.

3. The process as claimed in claim 1, wherein the solid EPDM rubber as well as ethylene and propylene comprises as diene ethylidene-norbornene (ENB), dicyclopentadiene or 1,4-hexadiene.

4. The process as claimed in claim 1, wherein the Mooney viscosity (ML 1+4/125 C.) of the solid EPDM rubber as measured according to DIN 53523 is at least 20 to 120.

5. The process as claimed in claim 1, wherein the fraction of solid EPDM rubber in the pressure-sensitive adhesive is at least 15 wt %, based on the total weight of the pressure-sensitive adhesive.

6. The process as claimed in claim 1, wherein the liquid EPDM rubber is composed to an extent of 30 to 70 wt %, based in each case on the total weight of the parent monomer composition.

7. The process as claimed in claim 1, wherein the weight-average molar weight of the liquid EPDM rubber, M.sub.w, is 100 000 Da.

8. The process as claimed in claim 1, wherein the fraction of liquid EPDM rubber in the pressure-sensitive adhesive is up to 30 wt %, based on the total weight of the pressure-sensitive adhesive.

9. The process as claimed in claim 1, wherein the plasticizer is white oil.

10. The process as claimed in claim 1, wherein the fraction of plasticizer in the pressure-sensitive adhesive is up to 20 wt %, based on the total weight of the pressure-sensitive adhesive.

11. The process as claimed in claim 1, wherein the pressure-sensitive adhesive comprises 30 to 180 phr of tackifier resin.

12. The process as claimed in claim 1, wherein the pressure-sensitive adhesive after discharge from the planetary roller extruder is coated onto a material in web form.

13. The process as claimed in claim 12, wherein the pressure-sensitive adhesive is crosslinked in a step downstream of the coating operation, the pressure-sensitive adhesive being crosslinked optionally by means of electron beams.

14. A pressure-sensitive adhesive which is obtainable by a process as claimed in claim 1.

15. A pressure-sensitive adhesive based on solid EPDM rubber which comprises liquid EPDM rubber, plasticizer, and tackifier resin, wherein the solid EPDM rubber is composed to an extent of 55 to 75 wt % of ethylene, based on the total weight of the parent monomer composition.

16. A pressure-sensitive adhesive tape which comprises at least one layer of a pressure-sensitive adhesive as claimed in claim 14.

17. A pressure-sensitive adhesive tape which comprises at least one layer of a pressure-sensitive adhesive as claimed in claim 15.

Description

BRIEF DESCRIPTION OF THE DRAWING

[0067] FIG. 1 shows the planetary roller extruder configuration used in the examples. The examples used a planetary roller extruder from ENTEX Rust & Mitschke.

[0068] The planetary roller extruder has a filling section (2) and a compounding section (5), which consists of three roller cylinders (5a-5c) connected in series. Within a roller cylinder, the planetary spindles (7) driven by the rotation of the central spindle (6) exchange the materials between central spindle (6) and planetary spindles (7) and, respectively, between planetary spindles (7) and the wall (10) of the roller cylinder (5a-5c).

[0069] At the end of each roller cylinder (5a-5c) there is a check ring (8a-8c) which holds the planetary spindles (7) in fixed location. Optionally there are additionally dispersing rings at these points.

[0070] Via the filling opening (1) it is possible to meter components such as, for example, the solid EPDM rubber onto the conveying screw (3) of the filling section (2) of the planetary roller extruder. The conveying screw (3) thereafter transfers the materials to the central spindle (6) of the first roller cylinder (5a). To improve the intake of material between central spindle (6) and planetary spindles (7), four long and three short planetary spindles (7) are used in the first roller cylinder (5a).

[0071] The internally hollow conveying screw (3) and central spindle (6) are force-fittingly connected to one another and possess a common temperature-control circuit. Each roller cylinder (5a-5d) of the compounding section (5) possesses an independent temperature control system. The filling section (2) can be cooled via a further temperature-control circuit.

[0072] Water may be used as temperature-control medium.

[0073] The metering of liquids such as, for example, liquid EPDM rubber, plasticizer, liquid tackifier resin and/or crosslinker may take place, for example, via the injection ring (4) upstream of the first roller cylinder (5a), or via the check rings (8a-8c) provided with bores, or by a combination of both possibilities. The roller cylinders (5a-5c) are provided in approximately the middle of the cylinders with an opening for side feeding. By way of this opening it is possible as and when necessary to add liquid or solid components via side feeders (9a-9c).

[0074] The temperature of the PSA is ascertained by means of penetration sensors in the product exit (11).

[0075] Before being fed to the filling section, the solid EPDM rubber is melted in an extruder, preferably a single-screw extruder (SSE), at a wall temperature, for example, of 180 to 200 C., such as, in particular, at 190 C. The optimum wall temperature is typically dependent on the crystalline fraction of the solid EPDM rubber: as the crystallinity goes up, rising temperatures are customarily selected. Melting may also take place in a twin-screw extruder or any other desired extruder.

[0076] The examples used a Blaake ES45/25D single-screw extruder. The maximum screw speed of this extruder is 124 revolutions per minute. The screw diameter is 45 mm, the screw length 25D (D=screw diameter).

[0077] In the case of the exemplary apparatus for the process of the invention, therefore, in addition to the planetary roller extruder shown in FIG. 1, there is a further extruder, in which the solid EPDM rubber is melted before it is introduced via the filling opening (1) into the filling section (2) and so is supplied as a melt to the planetary roller extruder.

[0078] In accordance with the invention the compounding section is fed with liquid EPDM rubber, plasticizer, tackifier resin, and any further components. The stated (lubricating) components may be added to the compounding section, independently of one another, in one or more portions. It is preferred in accordance with the invention, particularly on grounds of process economics, for the components to be added to the compounding section each in a single portion. One or more of the stated (lubricating) components may proportionally also be fed together with the solid EPDM rubber and any further components into the filling section of the planetary roller extruder. In the process according to the present invention, moreover, the components may be fed or added as separate components, as a joint premix, or as partial premixes. For example, any further components used, such as crosslinkers, for example, may be fed or added as a mixture with the solid EPDM rubber or with a lubricating component, such as plasticizer, for example.

[0079] In contrast to otherwise customary production processes, it is assumed that in the planetary roller extruder, in accordance with the process of the present invention, there is at most slight mastication of the rubber, since the rubber here is not subjected separately to the influence of high shearing energy, but is instead processed together with the lubricating components. By virtue of the presence of these lubricating components, the extent of frictional energy is limited in such a way that the mastication of the rubber, i.e. the breakdown in molecular weight of the elastomers, can be kept low and also high resultant compounding temperatures can be avoided. It is preferred, accordingly, if the first lubricating component or at least a part thereof is fed or added to the filling section or to the first roller cylinder of the compounding section, typically via the injection ring located between the filling section and first roller cylinder, or via a side feeder. With particular preference the first lubricating component is added to the first roller cylinder by way of the injection ring.

[0080] The lubricating components can be added to the planetary roller extruder at the same location or at different locations. Typically they are added to the planetary roller extruder at different locations, with positive consequences for the homogeneity of the resultant adhesive. The sequence of the addition here may, in accordance with the invention, be arbitrary. The first lubricating component fed or added is, in accordance with the invention, preferably the liquid EPDM rubber. Likewise, preferably the next, i.e., second lubricating component which is added downstream to the planetary roller extruder is the plasticizer.

[0081] The second lubricating component is preferably added to the second roller cylinder of the compounding section, typically via the first check ring, which is located between the first and second roller cylinders, or via a side feeder. With particular preference the second lubricating component is added via a side feeder to the second roller cylinder. Likewise preferably the third lubricating component, which is added downstream to the planetary roller extruder, is the tackifier resin. The third lubricating component is preferably added to the third roller cylinder of the compounding section, typically via the second check ring, which is located between the second and third roller cylinders, or via a side feeder. With particular preference the third lubricating component is added to the third roller cylinder via the second check ring, which is located between the second and third roller cylinders; this is especially the case when the compounding section consists only of three roller cylinders.

[0082] The compounding section of the planetary roller extruder used, or the process according to the invention, is preferably designed such that the composition obtained following addition of the last (lubricating) component passes at least one further roller cylinder. This promotes complete incorporation of the rubber and/or the desired homogenizing and dispersing performance at economic throughput rates. Accordingly, in accordance with the invention, the compounding section of the planetary roller extruder consists preferably of three or four coupled roller cylinders.

[0083] The tackifier resin may be added or fed as solid or liquid tackifier resin. The tackifier resin is preferably added or fed as liquid tackifier resin, in order to produce a particularly homogeneous adhesive. The adding or feeding of liquid tackifier resin means in accordance with the invention that the tackifier resin is added or fed above its softening point T.sub.sfor example, 20 to 40 C. above its softening point T.sub.s. The feeding or adding of solid tackifier resin means in accordance with the invention, therefore, that the tackifier resin is added or fed below its softening point T.sub.s. Solid and liquid tackifier resin may in accordance with the invention therefore be the same tackifier resin, which is solid or liquid, however, according to the temperature of use. In accordance with the invention the tackifier resin may also be used in the form of a resin split, with parts of the tackifier resin being fed, for example, together with the solid EPDM rubber and any further components into the filling section of the planetary roller extruder.

[0084] In the process of the invention, after discharge from the planetary roller extruder, the PSA may be coated at least one-sidedly onto a material in web form, i.e., a web-form carrier.

[0085] Web-form carrier materials for the high-performance PSAs produced in accordance with the invention, depending on the intended use of the adhesive tape to be provided, are all known carriers, where appropriate with corresponding chemical or physical surface pretreatment of the coating side and also antiadhesive physical treatment or coating of the reverse side. Examples include creped and uncreped papers, polyethylene films, polypropylene films, mono- or biaxially oriented polypropylene films, polyester films such as PET films, PVC films and other films, web-formed foams, composed of polyethylene and polyurethane, for example, fabrics, knits, and nonwovens. Lastly the web-form material may be an antiadhesive material or double-sidedly antiadhesive coated material such as release papers or release films. The web-form material may therefore be a permanent carrier or a temporary carrier, i.e., a liner. In accordance with the invention the temporary carriers are not considered a constituent of a pressure-sensitive adhesive tape.

[0086] In conjunction with a downstream coating unit and optionally crosslinking unit, therefore, the process of the invention allows the production of high-performance pressure-sensitive adhesive tapes. In this case the pressure-sensitive adhesive produced in accordance with the invention is coated at least one-sidedly onto a web-form material without solvent, using an applicator. The present invention also relates, accordingly, to a pressure-sensitive adhesive tape which comprises at least one layer of a pressure-sensitive adhesive preparable by the process of the invention.

[0087] The coating unit is preferably a calender or a nozzle through which the adhesive is applied to a carrier material. Calenders enable the adhesive to be shaped to the desired thickness on passage through one or more roll nips.

[0088] Proposed in accordance with the invention is the coating of the adhesives, produced in accordance with the invention, with a multi-roll applicator. Such applicators may consist of at least two rolls having at least one roll nip up to five rolls with three roll nips.

[0089] In order to improve the transfer behavior of the shaped layer of composition from one roll to another, it is possible, furthermore, to employ halftone rolls or rolls that are furnished antiadhesively. In order to generate a sufficiently precisely shaped film of adhesive, there may be differences in the peripheral velocities of the rolls.

[0090] The preferred 4-roll applicator is formed of a metering roll, a doctor roll, which determines the thickness of the layer on the carrier material and which is arranged parallel to the metering roll, and a transfer roll, which is located below the metering roll. On the placement roll, which together with the transfer roll forms a second roll nip, the composition and the web-form material are brought together.

[0091] Depending on the nature of the web-form carrier material to be coated, coating may take place in a co-rotational or counter-rotational process.

[0092] The shaping assembly may also be formed by a nip which is formed between a roll and a fixed doctor. The fixed doctor may be a knife-type doctor or else a stationary (half-)roll.

[0093] A further preferred example is a 3-roll applicator made up of two rolls for application of composition and a chill roll, with the rolls for application of composition having a temperature preferably of 80 to 160 C., more preferably 100 to 140 C., and the chill roll having a temperature preferably of less than 20 C., preferably less than 10 C., with the temperature of the second roll for application of composition typically being lower than that of the first roll for application of composition.

[0094] A further preferred application process encompasses coating between two web-form carrier materials, with the adhesive being shaped on a two-roll calender between these two carrier materials. The roll temperatures are typically between 60 and 140 C. The carrier materials in this case are preferably antiadhesively furnished, such as siliconized PET or paper, for example.

[0095] In a preferred embodiment of the process of the invention there is a melt pump or an extruder for conveying adhesive, more particularly a degassing extruder such as a twin-screw extruder, for example, between the planetary roller extruder and the coating apparatus employed, and this melt pump or extruder is operated with speed regulation or pressure regulation, preferably with pressure regulation. In order to obtain a defined, full-area coatweight on the web-form material, i.e., web-form carrier, during coating, it is advantageous if the pressure-sensitive adhesive, before entry into a coating nozzle and/or a calender, is subjected to degassing, this being particularly important in the case where protective gases are used during the compounding operation in the planetary roller extruder. According to the process of the present invention, the degassing takes place under the influence of reduced pressure, preferably in screw sheets which are likewise able to overcome the pressure losses of the pipelines and coating nozzle.

[0096] In a further preferred embodiment of the process of the invention, the PSA is crosslinked in a step downstream of the coating operation, in which case the PSA is crosslinked preferably by means of electron beams (EBC crosslinking). In this case, optionally, a crosslinking promoter is employed. Crosslinking the PSA has the advantage in particular that it further increases the shear strength, even at elevated temperatures such as, for example, 70 C. or 80 C.

[0097] Alternatively it is possible to carry out crosslinking under the effect of temperature, i.e., thermally, in which case corresponding thermally activatable crosslinkers must be added to the PSA. The heating of the PSA that is necessary for this purpose may be accomplished by means of the existing technologies, more particularly by means of high-temperature tunnels, or else with the aid of infrared emitters or by means of high-frequency magnetic alternating fields, as for example HF waves, UHF waves or microwaves. Thermal crosslinking is of particular interest in the case of EBC-sensitive carriers. EBC crosslinking and thermal crosslinking may also be combined.

[0098] The concept of the invention, as explained above, also embraces a pressure-sensitive adhesive tape which is produced using a pressure-sensitive adhesive producible by the process of the invention, by applying the pressure-sensitive adhesive to at least one side, optionally also both sides, of a material in web form.

[0099] Using the PSA of the invention it is possible accordingly to produce not only single-sidedly adhesive, i.e., one-sided, but also double-sidedly adhesive, i.e., double-sided, pressure-sensitive adhesive tapes. If the PSA of the invention is applied to one side of a permanent carrier, the result is a single-sided adhesive tape. If the PSA of the invention is applied to both sides of a permanent carrier, the result is a double-sided adhesive tape. Alternatively a single-sided pressure-sensitive adhesive tape of this kind can also be produced by applying the PSA of the invention to a liner, and subsequently laminating the resultant PSA layer onto the permanent carrier. A double-sided pressure-sensitive adhesive tape of this kind can also be produced, alternatively, by applying the PSA of the invention to a liner, and subsequently laminating the resultant PSA layer onto both sides of the permanent carrier. After the PSA of the invention has been applied to a liner, the resultant PSA layer may alternatively be laminated onto a further liner. A single-layer, double-sidedly self-adhesive tape of this kind, i.e., double-sided adhesive tape, is also referred to as transfer tape.

[0100] The thickness of the PSA on the web-form material may typically be between 10 m and 5000 m, and is preferably between 15 m and 150 m. In a transfer tape, moreover, the thickness of the PSA is preferably 800 m to 1200 m. A transfer tape of this kind has diverse possible applications, particularly after crosslinking.

[0101] The invention is elucidated in more detail below by means of examples. The examples described hereinafter provide further elucidation of particularly advantageous versions of the invention, without any intention thereby to subject the invention to unnecessary limitation.

EXAMPLES

[0102] A planetary roller extruder from Entex Rust & Mitschke was used, having three coupled roller cylinders, which had an internal diameter of 70 mm. The first two roller cylinders were fitted in each case with 7 planetary spindles, the subsequent roller cylinder with 6 planetary spindles, with one of the spindles having the geometric shape of a mixing element. In the present embodiment, the planetary roller extruder, the filling section has a conveying screw onto which the material can be metered. The temperature-control medium used for the central spindle and the filling zone in each of the experiments was water with entry temperature of 15 C.

[0103] The raw materials used are characterized as follows (table 1):

TABLE-US-00001 TABLE 1 raw materials used. Tradename Manufacturer Solid EPDM (ethylene Vistalon 6602 Exxon Mobil content: 55 wt %; ENB content: 5.2 wt %, Mooney (ML, 1 + 4 125 C.): 80) Solid EPDM (ethylene Royalene 563 Lion Copolymers content: 57 wt %; ENB content: 4.5 wt %; Mooney (ML, 1 + 4 125 C.): 75) Liquid EPDM Trilene 67 Lion Copolymers (ethylene/propylene weight ratio: 46:54, ENB content: 9.5 wt %) Hydrogenated hydrocarbon Regalite R 1100 Eastman resin (softening temperature: 100 C.) Trimethylolpropane Sigma-Aldrich triacrylate (TMPTA) White oil (paraffinic- Ondina 933 Shell naphthenic mineral oil) Benzine 60-95 Exxsol DSP 60/95 SH Exxon Mobil

Comparative Example 1

[0104] The solid EPDM rubber Vistalon 6602 in an amount of 4.0 kg/h and a first tackifier resin fraction in the form of 37.5 phr of solid, room-temperature-conditioned Regalite R 1100 (i.e., the amount of Regalite R 1100 added was 1.5 kg/h) were fed via a funnel into the filling section of the planetary roller extruder. The wall temperature of the roller cylinder of the planetary roller extruder was 120 C. The central spindle was driven at a speed of 30 revolutions per minute. The mixture was transferred from the filling section into the compounding section. Using a hose pump, the low-viscosity white oil Ondina 933 was added at 1.5 kg/h in the second roller cylinder, via a side feeder. The remaining quantity of Regalite R 1100 resin (75 phr) was metered in melted form (tank temperature 130 C.) into the 2.sup.nd check ring between the second and third roller cylinders, with a throughput of 3.0 kg/h. The resulting pressure-sensitive adhesive (PSA) had a temperature, at the exit from the planetary roller extruder, of 120 C.

[0105] The PSA was subsequently shaped to form a layer 50 m thick onto a PET carrier 23 m thick, which was etched with trichloroacetic acid, to produce a single-sided adhesive tape.

[0106] The PET carrier was coated here using a 3-roll applicator made up of two adhesive application rolls and a chill roll, with the first adhesive application roll having a temperature of 140 C., the second adhesive application roll a temperature of 120 C., and the chill roll a temperature of less than 10 C. The assembly was subsequently lined with release paper.

[0107] To test for homogeneity, approximately 5 g of the PSA were taken after exit from the planetary roller extruder and were pressed between two process liners by means of a hot press at 110 C. and a pressure of 5 bar. The process liners used were PET films 75 m thick coated on both sides with differently graduated silicone systems. After cooling, the pressed assembly was pulled apart, to give a PSA layer thickness of approximately 50 m.

[0108] The layer was held in front of a lamp, no undigested rubber particles and no unincorporated lubricating components were visible to the eye over an area of 100 cm.sup.2. The PSA was therefore homogeneous.

Comparative Example 2

[0109] The solid EPDM rubber Vistalon 6602 in an amount of 2.9 kg/h and a first tackifier resin fraction in the form of 46.9 phr of solid, room-temperature-conditioned Regalite R 1100 (i.e., the amount of Regalite R 1100 added was 1.36 kg/h) were fed via a funnel into the filling section of the planetary roller extruder. The wall temperature of the roller cylinder of the planetary roller extruder was 120 C. The central spindle was driven at a speed of 30 revolutions per minute. The liquid EPDM rubber Trilene 67 was metered in the injection ring by means of a tank melt; for better processing, the tank was heated to 120 C.; the throughput was 2.0 kg/h. Using a hose pump, the low-viscosity white oil Ondina 933 was added (throughput 1.0 kg/h) as a mixture with TMPTA (throughput 0.1 kg/h) with stirring via a side-feeder in the second roller cylinder. The remaining quantity of Regalite R 1100 resin (93.8 phr) was metered in melted form (tank temperature 130 C.) into the 2.sup.nd check ring between the second and third roller cylinders, with a throughput of 2.72 kg/h.

[0110] The resulting pressure-sensitive adhesive (PSA) had a temperature, at the exit from the planetary roller extruder, of 120 C.

[0111] In the test for homogeneity, carried out in analogy to comparative example 1, numerous, clearly visible undigested rubber particles were evident to the eye in the PSA layer.

[0112] Additionally, the rubber floated in the lubricating components; in other words, unincorporated lubricating components such as tackifier resin were visible. The homogeneity of the PSA was therefore very poor. Accordingly, it was not possible to produce a single-sided adhesive tape amenable to evaluation, by analogy with the protocol from comparative example 1.

Inventive Example 3

[0113] Inventive example 3 differs from comparative example 2 in that the solid EPDM rubber Vistalon 6602, before being fed to the filling section of the planetary roller extruder, was melted in a single-screw extruder (Blaake single-screw extruder ES45/25D) at 190 C. and therefore fed as a melt into the planetary roller extruder. Furthermore, the entire amount of Regalite R 1100 resin (140.6 phr) was metered in melted form (tank temperature 130 C.) into the 2.sup.nd check ring between the second and third roller cylinders with a throughput of 4.0 kg/h; in other words, no tackifier resin was fed into the filling section of the planetary roller extruder. The wall temperature of the roller cylinders of the planetary roller extruder was 140 C. The central spindle was driven at a speed of 45 revolutions per minute. The resulting PSA at the exit from the planetary roller extruder had a temperature of 100 C. All further details are in line with comparative example 2.

[0114] A single-sided adhesive tape was subsequently produced from the PSA as described in comparative example 1.

[0115] In the test for homogeneity, carried out in analogy to comparative example 1, no undigested rubber particles and no unincorporated lubricating components were visible to the eye in the PSA. The PSA was therefore homogeneous.

Comparative Example 4

[0116] A PSA was produced with the same composition as in inventive example 3, but by means of the solvent process. In this case, all of the constituents were homogenized as a solvent-based mass in a kneader with double-sigma kneading hook. The solvent used was Benzine 60-95. The kneader was cooled by means of water cooling. First of all, in a first step, the solid EPDM rubber Vistalon 6602 was admixed with a third of the total Benzine 60-95 to be used, and was preswollen at 23 C. for 12 hours. This so-called preliminary batch was then kneaded for 15 minutes. Next, the tackifier resin Regalite R 1100 was added in three portions with homogeneous kneading for 20 minutes in each case. The Trilene 67 was added subsequently, with homogeneous kneading for 10 minutes. Thereafter the Ondina 933 together with TMPTA was added and the mass was kneaded homogeneously for 10 minutes. The PSA was adjusted to a 32 wt % solution by addition of benzene.

[0117] The resulting PSA was subsequently coated, on a commercial laboratory coating bench (for example, from the company SMO (Sondermaschinen Oschersleben GmbH)) with the aid of a coating knife, onto a PET carrier 23 m thick, which was etched with trichloroacetic acid. The solvent was evaporated off in a forced-air drying oven at 105 C. for 10 minutes to dry the PSA. The slot width during coating was set such that the thickness of the PSA layer after evaporation of the solvent was 50 m. This produced a single-sided adhesive tape.

[0118] In the test for homogeneity, carried out in analogy to comparative example 1, no undigested rubber particles and no unincorporated lubricating components were visible to the eye in the PSA. The PSA was therefore homogeneous.

Inventive Example 5

[0119] Inventive example 5 differs from inventive example 3 only in that the solid EPDM rubber used, rather than Vistalon 6602, was the rubber Royalene 563, which is notable in particular for a higher ethylene content and therefore a higher crystalline fraction; the fraction of solid EPDM rubber used was the same. All further details are in line with inventive example 3. Again, subsequently, a single-sided adhesive tape was produced from the PSA as described in comparative example 1.

[0120] In the test for homogeneity, carried out in analogy to comparative example 1, no undigested rubber particles and no unincorporated lubricating components were visible to the eye in the PSA. The PSA was therefore homogeneous.

Comparative Example 6

[0121] The intention was to produce a PSA having the same composition as in inventive example 5, but by means of the solvent process. Because of the high crystallinity of the solid EPDM rubber Royalene 563, however, processing with solvents was not possible: Royalene 563 could not be dissolved. Accordingly it was not possible to produce a single-sided adhesive tape amenable to evaluation in analogy to the protocol from comparative example 4.

[0122] Results:

[0123] The formulas and results of the inventive and comparative examples are summarized in table 2. Percentages should be understood in each case as percent by weight.

[0124] Inventive example 3 shows that via the extrusion process of the invention, by a solvent-free route, it is possible to provide PSAs based on solid EPDM rubber that are homogeneous and at the same time have a high peel adhesion to substrates with different polarities such as, for example, steel and polypropylene (the peel adhesion values in the inventive and comparative examples were each determined on the single-sided adhesion tape produced as described in the respective examples).

[0125] A comparison with comparative example 2, in which the solid EPDM rubber was not fed as a melt into the filling section of the planetary roller extruder shows that the prior melting of the solid EPDM rubber is essential in order to produce homogeneous PSAs in the case of differing fractions, and hence including relative low fractions, of solid EPDM rubber. Because of the lack of homogeneity of the PSA from comparative example 2, it was not possible to produce a single-sided adhesive tape amenable to evaluation and so it was not possible to ascertain any peel adhesion values either.

TABLE-US-00002 TABLE 2 formulas and results of the inventive and comparative examples. Ex. 1.sup.a Ex. 2.sup.a Ex. 3.sup.b Ex. 4.sup.a Ex. 5.sup.b Ex. 6.sup.a Process Extru- Extru- Extru- Sol- Extru- Sol- sion sion sion vent sion vent Formulas Vistalon 40% 28.8% 28.8% 28.8% 6602 Royalene 28.8% 28.8% 563 Trilene 67 19.8% 19.8% 19.8% 19.8% 19.8% Regalite R 45% 40.5% 40.5% 40.5% 40.5% 40.5% 1100 Ondina 933 15% 9.9% 9.9% 9.9% 9.9% 9.9% TMPTA 1.0% 1.0% 1.0% 1.0% 1.0% Fraction of 40% 29% .sup.29%.sup.c .sup.29% .sup.40%.sup.c 40% solid EPDM Lube fraction.sup.d 60% 71% .sup.71% .sup.60% 60% Results Homogeneity + + + + Peel 5.4 12.0 14.0 13.9 adhesion to steel [N/cm] Peel 11.9 15.4 10.4 9.9 adhesion to PP [N/cm] Micro-shear 134 308 268 468 travel [m] SAFT [ C.] 120 94 97 86 .sup.acomparative examples; .sup.binventive examples; .sup.cmelted in the single-screw extruder; .sup.dlube fraction = fraction of lubricating components

[0126] Comparative example 1 shows in turn that it is indeed possible to produce homogeneous PSAs via the extrusion process, even without prior melting of the solid EPDM rubber, if the fraction of solid EPDM rubber selected is sufficiently high. In this case, however, the peel adhesion values on substrates with different polarities are much lower, by comparison with relatively low fractions of solid EPDM rubber (cf. the peel adhesion values from comparative example 1 and inventive example 3).

[0127] A comparison of inventive example 3 with comparative example 4 shows, moreover, that the extrusion process of the invention provides PSAs whose peel adhesion values on substrates of differing polarities are comparable with the peel adhesion values of the PSAs produced by means of the solvent process (with identical formula). As described above, however, unlike the solvent process, the extrusion process is highly suitable for producing PSA layers with different thicknesses, including, in particular, high thicknesses.

[0128] Furthermore, laborious drying is absent from the production process.

[0129] A comparison of inventive example 5 with comparative example 6 shows, moreover, that in contrast to the solvent process, the process of the invention also allows the production of homogeneous PSAs based on solid EPDM rubber with a relatively high ethylene content, such as, in particular, more than 55 to 62 wt %. As inventive example 5 shows, homogeneous PSAs can be achieved on the basis of semicrystalline solid EPDMs by the process of the invention even when the fraction of solid EPDM is relatively low.

[0130] The TMPTA-containing PSAs of the invention from inventive examples 3 and 5 can optionally be crosslinked by means of electron beams, hence allowing a further increase in the (high-temperature) shear strength.

Test Methods

[0131] All of the measurements were conducted, unless otherwise indicated, at 23 C. and 50% relative humidity. The mechanical and technical adhesive data were ascertained as follows:

Softening Point T.SUB.s

[0132] The data for the softening point T.sub.s, also called softening temperature, especially of oligomeric compounds, polymeric compounds and/or resins, are based on the ring and ball method as per DIN EN 1427:2007 with corresponding application of the provisions (analysis of the oligomer, polymer or resin sample instead of bitumen, with the procedure otherwise retained); the measurements take place in a bath of glycerol.

Glass Transition Temperature (T.SUB.g.)

[0133] Glass transition pointsreferred to synonymously as glass transition temperaturesare reported as the result of measurements by Dynamic Scanning Calorimetry (DSC) in accordance with DIN 53 765, especially sections 7.1 and 8.1, but with uniform heating and cooling rates of 10 K/min in all heating and cooling steps (compare DIN 53 765; section 7.1; note 1). The initial mass of sample is 20 mg.

Thickness

[0134] The thickness of a layer of adhesive can be determined by determining the thickness of a section of such a layer of adhesive, applied to a carrier, said section being of defined length and defined thickness, with subtraction of the thickness of a section of carrier used that has the same dimensions (the carrier thickness being known or separately determinable). The thickness of the layer of adhesive can be determined using commercial thickness gauges (sensor instruments) with 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 measurable force is 4 N. The value is read off 1 s after loading. If fluctuations in thickness are determined, the value reported is the average value of measurements at not less than three representative pointsin other words, in particular, not including measurement at wrinkles, creases, nibs, and the like.

180 Peel Adhesion

[0135] The peel strength (peel adhesion) is tested in a method based on PSTC-1.

[0136] A pressure-sensitive adhesive tape in the form of a strip 2.0 cm wide is adhered to the test substrate in the form of an ASTM steel plate, by rolling down the tape back and forth five times using a 4 kg roller.

[0137] The surface of the steel plate is cleaned with acetone beforehand. The plate is clamped in, and the adhesive strip is pulled off by its free end on a tensile testing sheet at a peel angle of 180 with a velocity of 300 mm/min, and the force required to achieve this is determined.

[0138] The results are averaged over three measurements and reported after standardization to the width of the strip, in N/cm.

[0139] The peel adhesion on alternative substrates (e.g., polypropylene (PP) or polyethylene (PE)) is determined in accordance with the above methodology, by changing the substrate. The polyethylene and polypropylene substrates are cleaned with ethanol prior to use, and are conditioned under test conditions for 2 hours.

Molar Weight M.SUB.w

[0140] The weight-average molar weight M.sub.w of the liquid EPDM rubber is determined by gel permeation chromatography (GPC). The eluent used is THF with 0.1 vol % trifluoroacetic acid. The measurement is made at 25 C. The precolumn used is PSS-SDV, 5, 10.sup.3 , ID 8.0 mm50 mm. Separation takes place using the columns PSS-SDV, 5, 10.sup.3 and also 10.sup.5 and 10.sup.6 each with ID 8.0 mm300 mm. The sample concentration is 4 g/l, the flow rate 1.0 ml per minute. Measurement is made against PMMA standards. (=m; 1 =10.sup.10 m).