Stock material or miscellaneous articles – Web or sheet containing structurally defined element or... – Adhesive outermost layer
Reexamination Certificate
1997-08-04
2003-04-22
Cole, Elizabeth M. (Department: 1771)
Stock material or miscellaneous articles
Web or sheet containing structurally defined element or...
Adhesive outermost layer
C428S349000, C428S35500R, C442S151000
Reexamination Certificate
active
06551704
ABSTRACT:
The invention relates to backing materials which have been treated to render them self-adhesive on at least one side, having been coated in whole or in part with a pressure-sensitive hotmelt adhesive composition, and to their use.
Strongly adhering orthopaedic bandages and other medical products are commonly coated over the whole of their area with a zinc-rubber adhesive composition. The sticking of such products to the skin entails, following their removal, marked skin irritation and mechanical stressing of the skin. Without recourse to auxiliary means, the bond cannot be detached without pain. In some cases there are allergic reactions. Furthermore, the adhesive compositions used often lead to a transfer of composition onto the skin.
The use of skin-friendly adhesive compositions such as acrylate adhesive compositions is out of the question because of their low shear stability and finger tack. Improvement through aftertreatment, especially crosslinking, is possible, although the result remains unsatisfactory as a whole. In addition, the bond strength to the backing of such systems, in the case of multiply dressings applied in circular form, is inadequate for a stable functional bandage. The proprioreceptive effect is less than that of systems with a zinc-rubber adhesive composition.
Other known adhesive systems based on conventional block copolymers are not skin-friendly, owing to the addition of excessive stabilizer, or because of the high cohesiveness have been found suitable to date only for industrial applications; or alternatively, they cannot be formulated for strong adhesion and sticking to the skin.
In the case of partial coating, the limited possibility for application of composition results in an inadequate bond strength, especially in the case of heavy backing materials.
The abovementioned adhesive compositions are pressure-sensitive self-adhesive compositions, where the compositions may be present in a carrier matrix for processing. The term carrier matrix is understood to refer to common organic or inorganic solvents or dispersion media.
Systems without a carrier matrix are referred to as 100% systems and are likewise not unknown. They are processed in the elastic or thermoplastic state. A common mode of processing is that of the melt.
Pressure-sensitive hotmelt adhesive compositions of this kind have also been described in the prior art. They are based on natural or synthetic rubbers and/or other synthetic polymers.
Because of their high level of hardness, sticking to the skin is a problem for such 100% systems.
An advantage of the 100% systems is that they avoid an operation of removing the carrier matrix, i.e. the auxiliary media, thereby raising the productivity of processing and at the same time reducing the expenditure on machinery and the energy costs. In addition, this reduces the occurrence of residues of the carrier matrix, which, in turn, favours a reduction in the allergenic potential.
It is also known to apply such self-adhesive compositions not only over the entire area but also in the form of a pattern of dots, for example by screen printing (DE-C 42 37 252), in which case the dots of adhesive can also differ in their size and/or distribution (EP-B 353 972), or by intaglio printing, in lines which interconnect in the longitudinal and transverse direction (DE-C 43 08 649).
The advantage of the patterned application is that the adhesive materials, given an appropriately porous backing material, are permeable to air and water and, in general, are readily redetachable.
A disadvantage of these products, however, is that if the area covered by the adhesive film, which per se is impermeable, is too large there is a corresponding reduction in the permeability to air and water vapour, and the consumption of adhesive composition rises, and also, if the area covered by the adhesive film is small, the adhesion properties suffer, i.e. the product is detached too readily from the substrate, especially in the case of heavy, textile backing materials.
The object of the invention, therefore, was to avoid the disadvantages known from the prior art and also to provide a backing material which is self-adhesive on at least one side and which owing to its treatment, i.e. to the properties of the adhesive composition, the form of application and the inherent properties of the backing material, can be used functionally for various fixing tasks, especially for medical products.
This object is achieved by a backing material which has been given a self-adhesive treatment on at least one side, the self-adhesive composition being a pressure-sensitive hotmelt adhesive composition which at a frequency of 0.1 rad/s has a glass transition temperature of less than −3° C., preferably from −6° C. to −30° C. and, with particular preference from −9° C. to −25° C.
The adhesive composition is preferably based on block copolymers, especially A-B or A-B-A block copolymers or mixtures thereof. The hard phase A is above all polystyrene or its derivatives and the soft phase B is ethylene, propylene, butylene, butadiene, isoprene or mixtures thereof, in which case particular preference is given to ethylene and butylene or mixtures thereof. However, polystyrene blocks may also be present in the soft phase B in an amount of up to 20% by weight. The overall proportion of styrene in the polymer, however, is always less than 35% by weight. Preference is given to styrene contents of between 5% by weight and 30% by weight, since a lower styrene content makes the adhesive composition smoother.
The controlled blending of diblock and triblock copolymers is particularly advantageous, preference being given to a proportion of diblock copolymers of less than 80% by weight.
In one advantageous embodiment the pressure-sensitive hotmelt adhesive composition has the following composition:
from 10% by weight to 90% by weight of block copolymers,
from 5% by weight to 80% by weight of tackifiers such as oils, waxes, resins and/or mixtures thereof, preferably mixtures of resins and oils,
less than 60% by weight of plasticizers,
less than 15% by weight of additives, and
less than 5% by weight of stabilizers.
The oils, waxes and resins used as tackifiers are preferably hydrocarbon oils, waxes and resins, the consistency of the oils—such as paraffinic hydrocarbon oils—or of the waxes—such as paraffinic hydrocarbon waxes—accounting for their favourable effect on bonding to the skin. Plasticizers used are long-chain fatty acids and/or their esters. These additions serve to establish the adhesion properties and the stability.
Filling the adhesive composition with mineral fillers is possible.
The pressure-sensitive hotmelt adhesive composition has a softening point of more than 70° C., preferably from 95° C. to 120° C.
Stringent requirements in terms of the adhesion properties are placed in particular on medical products, for example an orthopaedic dressing. For ideal use the self-adhesive composition should possess a high tack. There should be functionally appropriate bond strength to the skin and to the reverse of the backing. So that there is no slipping of the plies, the self-adhesive composition is also required to have a high shear strength.
By the controlled reduction in the glass transition temperature of the self-adhesive composition, which is essential to the invention and occurs as a result of the selection of the tackifiers, the plasticizers, the polymer molecule size and the molecular distribution of the starting components, the required, functionally appropriate bonding to the skin and to the reverse of the backing is achieved. The high shear strength of the self-adhesive composition which is employed here is obtained by virtue of the high cohesiveness of the block copolymer. The good tack is a result of the range of tackifiers and plasticizers employed.
Product properties such as tack, glass transition temperature and shear stability can be quantified readily using a dynamo-mechanical frequency measurement. In this case, use is made of a rheometer controlled by shearing stre
Albrod Andreas
Andrews Arthur-Hugh
Himmelsbach Peter
Jauchen Peter
Keite-Telgenbüscher Klaus
Beiersdorf AG
Cole Elizabeth M.
Norris & McLaughlin & Marcus
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