Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Compositions to be polymerized by wave energy wherein said...
Reexamination Certificate
2000-05-09
2003-08-26
Seidleck, James J. (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Compositions to be polymerized by wave energy wherein said...
C522S113000, C522S114000, C522S116000, C522S119000, C522S121000, C522S126000, C522S149000, C522S150000, C522S154000, C522S134000, C522S135000, C522S141000, C428S345000, C428S343000, C428S3550RA, C428S3550AC, C156S272200
Reexamination Certificate
active
06610762
ABSTRACT:
The present invention relates to adhesive compositions, and to processes for producing adhesive compositions. It also relates to polymers for use in such compositions, and to processes for producing such polymers. It further relates to articles comprising adhesive compositions and to methods of using such articles. In particular this invention relates to ‘switchable’ adhesive compositions, that is, adhesive compositions capable of being influenced to change from a tacky to a less tacky, or even non-tacky, state thereby reducing the peel strength of the adhesive composition.
Adhesive products such as adhesive surgical or medical dressings and bandages normally comprise a layer of a pressure sensitive adhesive. However, when conventional adhesive dressings and/or bandages are removed, they often cause localised trauma to the patient.
There has therefore long been a desire to provide adhesive dressings that can exhibit a reduction in peel strength of the adhesive, for example by being capable of being changed from a tacky to a less tacky, or even non-tacky, state. Such ‘switchable adhesives’ would cause less localised trauma than conventional adhesives when the dressing is removed.
Switchable adhesives are known. For example, U.S. Pat. Nos. 5,032,637, 5,352,516, 4,331,576 and 5,182,323 describe adhesives that become less tacky, that is, are switchable, in contact with water. However, such adhesives are unsuitable, for example, if used on a wound dressing and the patient's wound needs to be kept dry. UV switchable adhesives are described in U.S. Pat. Nos. 4,286,047, 4,968,559 and 5,118,567 and Japanese Patent No.3043988. Such adhesives suffer from the disadvantage that they may require high doses of UV radiation or may need to be used in conjunction with photoinitiators which result in undesirable by-products. It remains undesirable to expose patients to too much ultra violet radiation.
There therefore remains a need for a switchable adhesive that can undergo a reduction in peel strength at low dosages of UV radiation or more preferably by exposure to visible light irradiation.
In our International Patent Publication No WO 97/06836 we describe a switchable adhesive formulation. This comprised inter alia a modified acrylic adhesive based on copolymers of alkyl acrylates, acrylic acid and/or a free radical polymerisable vinyl moiety, functionalised by a curable moiety bonded thereto. Such curable moieties include those derived from anthracenes, cinnamates, maleimides, coumarins, acrylates and/or methacrylates.
One problem associated with the use of such moieties is the difficulty in synthesis and their relatively aggressive adhesive characteristics. The polymerisation of some preferred prior art and even subsequent methacrylate functionalised switchable adhesives requires the use of multiple solvents in order
a) firstly to produce a polymer having a sufficiently high molecular weight for it to be used as a medical adhesive and
b) secondly to carry out the reaction of the functionalising moiety with the main polymer chain.
We have now surprisingly found an adhesive that is switchable when exposed to radiation, in particular to electromagnetic, especially actinic radiation, that is, visible or UV light. Such switchable adhesive has better adhesive properties than known switchable adhesives and is novel.
Thus according to one feature of the present invention we provide a switchable adhesive composition capable of being influenced by radiation to change from a tacky to a less tacky state which includes a switchable polymer comprising a backbone polymeric moiety having a plurality of curable moieties bonded thereto, characterised in that at least a proportion of the curable moieties each comprises a free-radically active group and has an amine functionality.
When used herein, the term ‘free-radically active group’ means any group that can undergo addition to another group by free radical transfer.
When used herein, the term ‘amine functionality’ includes amino functions further functionalised by other groups, for example in particular, amido functions and substituted ammonium functions.
The amine functionality is preferably a secondary amine functionality, including secondary amide functionality and/or a primary ammonium functionality.
When used herein, the term ‘bonded’ includes both covalent and ion pair bonding. Thus for example moieties bonded via amine functions may be bonded via secondary amine linkages and/or via primary ammonium—acid anion pair bonding.
In one embodiment of this feature of the present invention, we provide a switchable adhesive composition which includes a polymer comprising a backbone polymeric moiety and a plurality of bound-in curable moieties, characterised in that at least a proportion of the bound-in curable moieties comprise free radically active groups having an amine functionality derived from a primary amine.
The switchable polymer may have adhesive properties, in which case it may form the sole adhesive constituent of the adhesive composition, or it may be blended with other adhesives.
The switchable polymer need not itself have adhesive properties, in which case it is blended with one or more adhesives to form a switchable adhesive composition of the invention.
Thus in another embodiment of this feature of the present invention we provide a switchable adhesive composition of the present invention characterised in that it comprises a switchable polymer as hereinbefore described in admixture with a non-switchable adhesive.
For the sake of brevity, whether or not such polymers have adhesive properties they will herein after be referred as “switchable polymer(s)”.
It a second aspect therefore the present invention provides a switchable polymer capable of being influenced by radiation to change from one state to another, comprising a backbone polymeric moiety having a plurality of curable moieties bonded thereto, characterised in that at least a proportion of the curable moieties each comprises a free-radically active group and has an amine functionality.
The curable moieties are preferably photocurable moieties. By this term we mean moieties that are capable of undergoing a reaction induced by electromagnetic, in particular by actinic, radiation. Often such moieties will require the presence of a free radical initiator to initiate the reaction under the influence of incident radiation. Such initiators are described further below.
Examples of such reactions include, for example, photocuring to increase the molecular weight of the polymer to which the moieties are bound.
The preferred curable moieties are those which change the adhesive composition from a tacky to a less tacky, or even non-tacky, state (that is, render it switchable) by producing a polymer of increased molecular weight by way of linking or cross-linking the switchable polymer (‘curing’).
The curable moieties may be introduced onto the backbone polymeric moiety by forming a polymer comprising the backbone polymeric moiety and chemically bonding a precursor of the curable moiety to the backbone polymeric moiety.
The switchable adhesive composition of the present invention preferably has a peel strength in its non-tacky state that is at most 50% of that in its tacky state, preferably at most 25 or 20%, in particular 10%.
Any conventionally known adhesive polymers may be used to form the backbone polymeric moiety provided that such polymers are, where desirable, reactable to bond the curable moieties onto them.
This may occur, for example, by forming covalent and/or ion pair adducts or condensates with the precursors of the curable moieties.
Preferred backbone polymeric moieties include polyurethanes, polyacrylics and free radical polymerisable vinyl moieties. Polyacrylics are especially preferred.
Particularly preferred materials forming the backbone polymeric moiety are acrylic adhesives.
By the term acrylic adhesives we include adhesives based on polymers of acrylates, methacrylates, other derivatives of acrylic and methacrylic acids, and copolymers of the same.
Indeed acrylic copolyme
Larson & Taylor PLC
McClendon Sanza L.
Seidleck James J.
Smith & Nephew Plc
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