Adhesive tape

a technology of adhesive tape and adhesive ring, which is applied in the field of adhesive tape, can solve the problems of tearing and tensile load, disadvantages of a very high price, and inability to prevent tearing at the edges damaged subsequently

Inactive Publication Date: 2003-05-22
MUSSIG BERNHARD +1
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

The film achieves high residual strength, tensile strength, and stress at 10% elongation, effectively redirecting tears into the machine direction, enhancing tear propagation resistance while maintaining industrial scalability and cost-effectiveness, with improved crease fracture stability and weldability.

Problems solved by technology

This leads to tearing and tensile load in the case, for example, of rough edges of film and, respectively, adhesive tape (caused by blunt blades during cutting or subsequent unintended damage to the cut edge).
The use of woven fabrics offers a comprise at a higher level, albeit with the disadvantages of a very much higher price and further operations such as coating in order to seal the surface.
However, it does not prevent tearing at edges damaged subsequently; this necessitates a drastic improvement in the tear propagation resistance, possessed only by the coextruded film of the invention with an internal structure.
The raw materials specified for the abovementioned invention, for increasing the toughness, however, lead to markedly reduced longitudinal strength, especially the raw materials of the tough coextrusion layer.
In terms of equipment, the production of such filament adhesive tapes is very complex and thus expensive, and susceptible to faults.
In addition to the base film, there is an additional requirement for the filaments and laminating adhesive (or additional pressure-sensitive adhesive coating), which makes the products more expensive and ties up a greater quantity of raw material resources.
Further disadvantages of such filament adhesive tapes are the low crease fracture stability, the unclean cut edges, and the absence of weldability and recyclability.
The films are unoriented and offer no reinforcing effect.
The method is not applicable to polypropylene, since the customary gel fraction automatically blocks the filament channels of the die.
The films are unoriented and therefore of only low longitudinal strength.
The essential defect of this invention, however, is that it cannot be produced on an industrial scale.
The reason for this is the poor orientability in the standard width.
When producing a primary film having a structured (rib) surface in a width of 25 cm, the orientation produces on both sides an indentation which, taking into account the industrially required edge trimming, gives a maximum useful width of approximately 15 cm, which is no longer reasonable commercially for coating with adhesive composition.
Despite the high edge trim, which is already unacceptable for economic reasons, the film still has an extremely poor flatness, so that its ability to be coated with pressure-sensitive adhesive is no longer ensured.
At relatively large widths, moreover, the flatness is further impaired as a result of nonuniform and inadequate adhesion (owing to the non-plane-parallel outer faces of the film) to the stretching rolls in the subsequent orienting process.
A further disadvantage is the need for at least 50% embedding of the ribs by means of a calender, which is a very expensive capital item and makes the process much more complex.
The rib structure on the surface also readily gives rise to coating errors during the application of release agents or primers in the course of subsequent processing to give adhesive tapes, since the application techniques for films require a smooth surface.
A further disadvantage of films having reinforcing strips or rib structures in or on the surface is in relation to printing, which requires planar surfaces.
As remarked above, structures of this kind would be problematic in processing terms.
The disadvantages of filament adhesive tapes, such as low crease fracture resistance, untidy cut edges and lack of weldability, are not possessed by the adhesive tape of the invention.

Method used

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Examples

Experimental program
Comparison scheme
Effect test

example 1

[0053] The film is produced on an extrusion unit in a width of 60 cm using a die as shown in FIG. 2 (three-layer internal-combining manifold die with exchangeable central plate for generating melt streams with a predetermined profile), a chill roll and a single-stage short-gap drawing unit. The definition of the layers is as follows:

[0054] Layer 3 lies on the chill roll, layer 1 is the middle layer, layer 2 lies on the air side. The interface between layers 1 and 3 is smooth and that between layers 2 and 1 is intermeshed. The process conditions are as follows:

1 Extruder 2 Extruder 1 Extruder 3 Layer 2 Layer 1 Layer 3 Temperature, 180.degree. C. 180.degree. C. 180.degree. C. initial Temperature, final 230.degree. C. 235.degree. C. 230.degree. C. Screw rotary 20 rpm 10 rpm 20 rpm speed Temperature of 219.degree. C. 199.degree. C. 240.degree. C. composition Pressure of 89 bar 86 bar 89 bar composition upstream of sieve Raw materials mixture Extruder 1: 50% Shell Polystyrene N 7000 (hom...

example 2

[0058] Equipment as Example 1. Process conditions:

4 Extruder 2 Extruder 1 Extruder 3 Layer 2 Layer 1 Layer 3 Temperature, 215.degree. C. 160.degree. C. 210.degree. C. initial Temperature, final 220.degree. C. 240.degree. C. 230.degree. C. Screw rotary 30 rpm 25 rpm 0.9 rpm speed Temperature of 210.degree. C. 248.degree. C. 226.degree. C. composition Pressure of 121 bar 125 bar 70 bar composition upstream of sieve Raw materials mixture Extruder 1: 50% Shell Polystyrene S 5400 (high impact), 50% Moplen EPQ 30 RF (copolymer) Raw materials mixture Extruder 2: 10% Shell Polystyrene S 5400, 90% Moplen EPQ 30 RF Raw materials mixture Extruder 3: 100% Moplen EPQ 30 RF

[0059] Jaw heating 240.degree. C., chill roll 18.degree. C., film speed prior to drawing 3.6 m / min, after drawing 24.7 m / min, draw ratio 1:6.7. The profile of the central plate produces a repeating rectangular profile between layers 2 and 1; the amplitude of the rectangles is 0.4 mm and the phase spacing is 2 mm.

5 Test results:...

example 3

[0061] Equipment as Example 1. Process conditions:

6 Extruder 2 Extruder 1 Extruder 3 Layer 2 Layer 1 Layer 3 Temperature, 215.degree. C. 160.degree. C. 210.degree. C. initial Temperature, final 220.degree. C. 235.degree. C. 230.degree. C. Screw rotary 30 rpm 25 rpm 1 rpm speed Temperature of 205.degree. C. 230.degree. C. 228.degree. C. composition Pressure of 120 bar 100 bar 90 bar composition upstream of sieve Raw materials mixture Extruder 1: 50% Shell Polystyrene S 5400, 50% Moplen EPQ 30 RF Raw materials mixture Extruder 2: 100% Moplen EPQ 30 RF Raw materials mixture Extruder 3: 100% Moplen EPQ 30 RF

[0062] Jaw heating 240.degree. C., chill roll 18.degree. C., film speed prior to drawing 1.5 m / min, after drawing 13.1 m / min, draw ratio 1:8.7. The profile of the central plate produces a repeating profile of semicircles between layers 2 and 1; the radius of the semicircles is 0.2 mm and the phase spacing is 2.4 mm.

7 Test results: Thickness after drawing 95 .mu.m Difference in thickn...

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Abstract

An adhesive tape wherein the backing film comprises at least two coextruded layers of different composition, whose interface is not planar but instead has a nonlinear course in cross section, which continues laminarly in the machine direction, has been oriented in the machine direction, and has plane-parallel outer faces.

Description

[0001] The invention relates to a film oriented in the machine direction, having plane-parallel outer faces and at least two coextruded layers of different composition whose interface is not planar but instead has a nonlinear course in cross section, which continues laminarly in the machine direction, and to a process, by coextrusion and orientation, for its preparation, and to an adhesive tape produced therefrom.[0002] The particular internal structure of the film derives from the fact that the thickness of one layer varies periodically or irregularly in the cross-direction and the second layer compensates the fluctuations in thickness such that the overall thickness is essentially constant.[0003] The essential technical characteristic of the invention is the combination of lateral tear resistance (tear propagation force and residual strength) and longitudinal strength (tensile strength and stress at 10% elongation) in the machine direction.PRIOR ART[0004] Films possessing high lon...

Claims

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Application Information

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Patent Type & AuthorityApplications(United States)
IPC IPC(8): B29C55/02B29C48/08B29C48/21B29C48/49B32B3/30B32B27/00B32B27/08C08J5/18C09J7/29C09J107/00C09J133/00C09J153/02C09J183/04C09J201/00
CPCB29C47/0021B29C47/065B29C47/067B29C47/145B29C47/56B32B27/00Y10T428/2848C09J2201/162C09J2423/006C09J2425/006Y10S428/91Y10T428/28C09J7/0296C09J7/29B29C48/08B29C48/21B29C48/22B29C48/307B29C48/49C09J2301/162B32B27/302B32B3/06B32B27/32B32B2325/00B32B27/08B32B2405/00B32B2323/10
InventorMUSSIG, BERNHARDSCHMEER, GERT
OwnerMUSSIG BERNHARD