Self-adhesively treated backing material

Details Self-adhesively treated backing material Self-adhesively treated backing material

1998-10-30

2003-02-25

Cole, Elizabeth M. (Department: 1771)

Stock material or miscellaneous articles

Web or sheet containing structurally defined element or...

Adhesive outermost layer

C428S349000, C428S3550AC, C428S911000, C428S912000, C428S914000, C428S915000, C428S916000

Reexamination Certificate

active

06524699

ABSTRACT:

The invention relates to a backing material which has been self-adhesively treated on at least one side and which is partially coated.
Adhesively coated backing systems which unstick when the backing is pulled are known. They are generally based on elastic systems, which in many cases constitute laminates.
DE-A 27 28 346 describes such a laminate, consisting of an extensible film and an adhesive composition based on A-B-A block copolymers. The laminate, adhering in its entirety, is easily detached from the substrate by stretching.
The adhesive composition is always applied over the entire area. However, such whole-area application is associated with a large number of disadvantages which greatly restrict use in the medical sector, in particular. Whole-area application entails the need for large quantities of adhesive composition, which makes the production process and hence the end product as well more expensive. In addition, it is important that the backing material coated with the adhesive composition continues, following its application to the skin, to be permeable to air and water vapour, in order, for example, that perspiration can be transported away from the skin. This property is possessed only to a very limited extent, if at all, by a wholly coated backing.
DE-A 195 31 696 describes an adhesive-film laminate which is produced from an extensible backing and an acrylate adhesive composition.
WO 95/06691 discloses a redetachable adhesive tape having a foam as its backing material.
WO 92/11333 describes a system which can be removed nondestructively and possesses high tear strength. Likewise, however, partial coating is not described.
It is also known to apply self-adhesive compositions to backing materials for sheetlike structures which can be redetached without residue, and/or for medical applications, not only over the entire area but also in the form of a pattern of dots for example by means of 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 directions (DE-C 43 08 649). The documents listed, however, do not describe a detachment effect (stripping effect) induced by extension of the respective backing in the orientation of the backing.
All of the systems described above have a serious disadvantage in that they have been coated over the entire area. As a result, redetachment requires a comparatively high force, thereby reaching the limit of the strength of the backing materials.
A further disadvantage of these backing materials is that in the case of whole-area coating the systems used may use their elasticity if the adhesive systems employed are of lower elasticity.
For processing, the abovementioned adhesive compositions may be present in a carrier matrix. 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.
Hotmelt adhesive compositions of this kind have also been described in the prior art. They are based on natural or synthetic rubbers and/or on 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 removal of 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, is to the benefit of a reduction in the allergenic potential in the case of use specifically for bonding to the skin.
The object of the invention was to avoid the disadvantages known from the prior art and to provide an at least one-sidedly self-adhesive backing material which following application to the skin can be redetached by extension in a simple manner and, especially when used as a medical product, painlessly.
This object is achieved by an at least one-sidedly self-adhesively treated backing material which is partially coated with an adhesive composition and has an extension of more than 10% under a tensile load of 10 N/cm, so that following application the backing material can be detached from the substrate by pulling in the direction of the bond plane.
Under a tensile load of 10 N/cm the backing material preferably has an extension of more than 15% up to 3000%, with particular preference from 20% to 1000%.
It has been found advantageous that with the use of backing materials permeable to water vapour or air and at high application rates of more than 15 g of composition per m
2
, the adhesively, treated products had an extremely high permeability.
Suitable backing materials are extensible sheetlike structures composed of synthetic and natural raw materials. Preference is given to backing materials which, following the application of the self-adhesive composition, can be used in such a way that they fulfill the characteristics of a functional bandage. Examples are textiles such as wovens, knits, lays, nonwovens, laminates, nets, films, foams and papers having an extensibility of at least 10% under a load of 10 N/cm.
Combinations of these materials are also suitable.
In addition, these materials can be pretreated or aftertreated. Common pretreatments are corona and hydrophobicization; customary aftertreatments are calendering, thermal conditioning, laminating, punching and lining, UV/IR irradiation or electron-beam irradiation.
For the coating it is possible as self-adhesive compositions to employ thermoplastic hotmelt adhesive compositions based on natural and synthetic rubbers and on other synthetic polymers such as acrylates, methacrylates, polyurethanes, polyolefins, polyvinyl derivatives, polyesters or silicones with corresponding additives such as tackifier resins, plasticizers, stabilizers and other auxiliaries where necessary.
Their softening point should be higher than 50° C., since the temperature of application is generally at least 90° C. and, preferably, between 120 and 150° C., or between 180 and 220° C. in the case of silicones. Postcrosslinking by means of UV or electron-beam irradiation may be appropriate, if desired.
Hotmelt adhesive compositions based on block copolymers, in particular, are notable for their diverse variation options, since the controlled reduction in the glass transition temperature of the self-adhesive composition as a result of the selection of the tackifiers, plasticizers, polymer molecule size and molecular distribution of the starting components ensures the required bonding, especially to the skin, in a manner appropriate to their function, even at critical points of the human locomotor system.
The high shear strength of the hotmelt adhesive composition is achieved through the high cohesiveness of the polymer. The good tack results from the range of tackifiers and plasticizers employed.
The hotmelt adhesive composition is based preferably on block copolymers, especially A-B or A-B-A block copolymers or mixtures thereof. The hard phase A is primarily polystyrene or its derivatives, and the soft phase B comprises ethylene, propylene, butylene, butadiene, isoprene or mixtures thereof, particular preference being given to ethylene and butylene or their mixtures.
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, however, should always be less than 35% by weight. Preference is given to styrene contents of between 5 and 30%, since a lower styrene content makes the adhesive composition more conforming.
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

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