USE OF A METALLOCENE-POLYETHYLENE NONWOVEN AS BACKING MATERIAL

Abstract: Use of a metallocene-polyethylene nonwoven as backing material, the said backing material being provided on at least one side with a self-adhesive coating.

Description: Beiersdorf Ak iengesellschaft Description Use of a metaliocene-polyethylene nonwoven as backing material The invention relates to the use of a metaliocene-polyethylene nonwoven as backing material in particular for rapid dressings, prefabricated surgical dressings, roll plasters and/or tape dressings and adhesive tapes Plasters offerings high wear comfort are distinguished by their great conformity to contoured areas of the body, by their readiness to move with moving joints (the fingers, for example) and, moreover, by their permeability to water vapour or even to air As a class of materials, nonwovens are particularly suitable as plaster backings They are generally permeable to air, less expensive to produce than wovens, provided that common fibre materials are used, and they impart valuable tactile properties A disadvantage found with the common nonwovens for plaster applications is that they have limited elasticity and so are not ideally suited to contoured areas of the body Nonwovens can be produced by diverse techniques for example, by the dry process, the spinbondmg process or wet processes This is followed by a series of finishing steps In some cases, chemical binders are used (dry-laid webs), which bring with them the dis- advantage of unwanted chemicals in the vicinity of the wound when the plaster is used A particularly preferred process is the melt blown process, in which, inter alia, elastomenc polymers or polymer mixtures are melted in an extruder and processed further in a spinning process This produces a nonwoven having very high mechanical strength and con- sisting of extremely fine fibres (< 10 μm in diameter) The elastic properties of the polymer are retained by the nonwoven, that is, the material when subjected to elongations which occur in the normal course of use of plasters (max 50 % elongation) exhibits virtually complete recovery The thermoplastic polymers, block copolymers based on styrene-butadiene-styrene (Kraton) polyurethanes or polyether- and polyester-urethanes employed to date for this purpose have the disadvantage of in some cases a high price for the raw mateπai or of unfavourable toxicological evaluation (for example, aromatic polyurethanes may give off aromatic amines) Consolidation of these nonwovens takes place almost exclusively by thermal or mechani- cal means, so that the finished nonwoven does not come into contact with any further process chemicals or auxiliary chemicals in the course of its production As a result, the matenals produced by this process are particularly suitable for use in medical products such as plasters or dressing mateπai EP 0 749 756 A2 discloses the production of nonwoven plasters based on polyester elastomers (more precisely, on a polybutylene terephthalate-polyether copolymer) The flexibility and extensibility of the mateπai (> 600 %) are emphasised, and underline the special suitability of the mateπai as a plaster backing EP 0 341 875 B1 discloses the use of an elastomenc nonwoven fibre web compπsmg melt-blown fibres having a diameter of less than 50 μm, with the limitation of a tensile strength of at least 30 g/2 5 cm/(g/m 2 basis weight) Thermoplastic elastomers descπbed are polyurethanes, elastomenc polyesters, elastomenc polyamides and A-B-A' block copolymers It is therefore the object of the invention to provide a backing mateπai which avoids the disadvantages known from the prior art This mateπai should be inexpensive to produce and ecologically unobjectionable as well as offeπng pleasant wear comfort in use This object is achieved by the use of a backing mateπai as set out in Claim 1 The sub- claims relate to advantageous developments thereof The invention proposes using a metaliocene-polyethylene nonwoven as a backing mateπai, the said backing mateπai being provided on at least one side with a self-adhesive coating The metaliocene-polyethylene nonwoven preferably has the following properties • a basis weight of from 40 to 200 g/m 2 in particular from 60 to 120 g/m 2 and/or • a thickness of from 0.1 to 0.6 mm, in particular from 0.2 to 0.5, and/or • an ultimate tensile strength elongation lengthwise of from 300 to 700 % and/or • an ultimate tensile strength elongation crosswise of from 250 to 550 %. The fibres of the metaliocene-polyethylene nonwoven preferably have a diameter of from 1 to 50 μm, in particular from 10 to 25 μm. It has also been found advantageous if the metaliocene-polyethylene nonwoven is additionally characterized by • a load at 25 % elongation crosswise of from 0.7 to 4 N/cm and/or • a load at 50 % elongation crosswise of from 0.85 to 6.0 N/cm and/or • a load at 100 % elongation crosswise of from 0.6 to 8.0 N/cm and/or • a plastic deformation after 5-fold elongation and release by 50 % of from 5 to 15 %. It is possible to emboss the nonwovens. The embossing area is preferably between 2 and 40 %, more preferably 10 to 25 %. To emboss the nonwoven temperatures of 80 °C to 100 °C and pressures of 10 to 100 (kg/cm 2 ) are used. In one advantageous embodiment the polymer employed is a copolymer of ethylene and an α-olefin having a carbon number from C 4 to Cio, it being possible for the polyolefin to have a melt index of between 1 and 50 g/(10 min) and a density of from 860 to 900 kg/m 3 . In another advantageous embodiment the metaliocene-polyethylene polymer is blended with other polymers, for example LLDPE. For the adhesive coating it is preferred to use commercially customary, pressure-sensitive adhesive compositions based on acrylate or on natural or synthetic rubber. In addition, the reverse of the metaliocene-polyethylene nonwoven may have been given an anti-adhesive treatment. A new class of polymers for use as backing material is represented by the metallocene- polyethylenes, or single-site-catalysed PE grades. These possess adjustable elastic properties and are priced very favourably in comparison with other thermoplastic elastomers. Principle applications of the new materials are in connection with flexible packaging, hoses and tubes, cable sheathing, and injection mouldings. The elastomeric PE grades Affinity (Dow Chemical) and Engage (DuPont) consist of an octene-ethylene copolymer having a density of about 0.85 g/cm 3 . Advantages of the use of m-PE over alternative thermoplastic elastomers, especially in connection with medical products, are in general as follows: • material savings owing to better mechanical performance of the m-PE grades. • low levels of residual catalyst in the polymer (up to 1000 times lower). • lower raw-material price relative to other elastomeric polymers (Kraton, polyurethanes, polyesters, SIS). As a result of this it is possible to produce a high-performance nonwoven for use in the plaster sector at a highly favourable price. The present nonwoven material is manufactured on a conventional melt blown line, using elastomeric m-PE grades from DuPont or Dow Chemical, USA. The materials have the physical properties indicated in Table 1. The metaliocene-polyethylene (mPE) is a polymer melt received by a die from an extruder and is further heated and extruded from a row of orifices as fine filaments while converging sheets of hot air (primary air) discharging from the die contact the filaments and by drag forces stretch the hot filaments to microsize. The filaments are collected in a random entangled pattern on a moving collector screen such as a rotating conveyer forming a nonwoven web of entangled microsized fibres. The filaments freeze or solidify a short distance from the orifice aided by ambient air (secondary air). Then the nonwoven web(sheet) is rolled up. The m-PE nonwoven exhibits almost isotropic mechanical properties (identical values in lengthwise and crosswise directions). Even on multiple elongation by 50 % and subse- quent contraction (5 cycles) a permanent plastic deformation of max. 20 % is obtained. Coating the m-PE nonwoven with a pressure-sensitive adhesive composition yields pressure-sensitive adhesive (PSA) products which can conform outstandingly to contoured areas of the body and do not hinder any movement (for example, at the finger) by the body The air-permeable mateπai does not lead to any maceration, even after a prolonged peπod of wear When the plaster is removed there is no splitting of the backing mateπai, since the construction of the nonwoven gives it optimum cohesion The outstanding properties of the nonwoven can be transferred to the plaster in an optimum manner The advantages set out above result in particularly advantageous applications of the PSA-coated m-PE nonwoven as rapid dressings, prefabricated surgical dressings, roll plasters and/or tape dressings As is generally the case with plasters, the rapid dressings or roll plasters can also be provided with a wound covering, which can in turn be lined with a release paper and sealed in sealing paper Furthermore, the nonwoven that has been treated to make it self-adhesive can also be employed with outstanding effect as an adhesive tape In the text below a use according to the invention is illustrated, using examples, without wishing unnecessaπly to restπct the described invention Examples The following table gives an overview concerning the manufactuπng of Ethylene-Octene Copolymer and the conditions Furthermore, a comparative example with conventional PE-polymers was made Table 1 D contains the properties of the nonwovens Table 1 Manufacturing Condition of TPO-MB Nonwoven A Polymer B. Melt Blown Condition C. Embossing Condition D. Nonwoven Properties *) Method of testing plastic deformation: Test strips of the sample are cut to a width of from 15 to 20 mm and are inserted with a clamped-in length of 100 mm into a tensile testing machine. The testing sequence consists of five successive loading and release phases with continuous load measurement at a maximum elongation of 50 %, the testing speed being 200 mm/min. The permanent elongation of the sample is given in %. ** measured using the JIS 1096 Table 1D discloses the differences between the properties of the nonwovens made of mPE and the nonwovens made of conventional PE-polymers, especially after elongating the samples five times of 50 %. The mPE nonwovens show a permanent plastic deformation of max. 12 % compared with 22 % obtained with the conventional PE-polymers. A nonwoven produced from elastomeric m-PE polymers (Dow Chemical, USA) by the melt blown process with subsequent thermal or water-jet consolidation and having a basis weight of 80 or 70 g/m 2 , respectively, is coated with from 80 to 100 g/m 2 of a clinically tested rubber-based pressure-sensitive adhesive composition. The good air permeability of the backing material permits air perforation of the applied composition by air brush during the application of the adhesive composition. The metaliocene-PE nonwovens treated with pressure-sensitive adhesive have the following physical properties: *) Conditions in accordance with EN 29073 P3 Table 2: Physical properties of the coated metallocene-PE nonwovens The coated web is cut into narrow rolls (3.75 cm, 8 cm) and processed further into roll plasters, tape products and, on converting machines, into plaster strips, by application of a wound pad. The plaster products feature the following properties: • very conformable backing material • does not hinder movement at all, even on contoured parts of the body • is air-permeable • relatively non-aggressive adhesive compositions can be employed since, owing to the good elastic properties, lower shear forces occur • hydrophobic surface of the material is water repellent

Claims: Patent claims 1. Use of a metaliocene-polyethylene nonwoven as backing material, the said backing material being provided on at least one side with a self-adhesive coating. 2. Use according to Claim 1, characterized in that the metaliocene-polyethylene nonwoven has a basis weight of from 40 to 200 g/m 2 , in particular from 60 to 120 g/m 2 , and/or a thickness of from 0.1 to 0.6 mm, in particular from 0.2 to 0.5. 3. Use according to Claim 1 , characterized in that the metaliocene-polyethylene nonwoven has an ultimate tensile strength elongation lengthwise of from 300 to 700 % and/or an ultimate tensile strength elongation crosswise of from 250 to 550 %. 4. Use according to Claim 1 , characterized in that the fibres of the metaliocene-polyethylene nonwoven have a diameter of from 3 to 50 μm, in particular from 10 to 25 μm. 5. Use according to Claim 1, characterized in that the polymer employed is a copolymer of ethylene and an α-olefin having a carbon number from C 4 to Cio, the polyolefin having a melt index of between 1 and 50 g (10 min) and a density of from 860 to 900 kg/m 3 . 6. Use according to Claim 1 , characterized in that the adhesive coating consists of a commercially customary, pressure-sensitive adhesive composition based on acrylate or on rubber. 7. Use according to Claim 1 , characterized in that the reverse of the metaliocene- polyethylene nonwoven has been given an anti-adhesive treatment. 8. Use according to at least one of Claims 1 to 7 as rapid dressings, prefabricated surgical dressings, roll plasters and/or tape dressings. Use according to at least one of Claims 1 to 7 as adhesive tape.

Inventors: ARAIDA YASUROU, LENZ DIRK, TIMM JUERGEN, ARAIDA, YASUROU, LENZ, DIRK, TIMM, JUERGEN
Applicants: ARAIDA YASUROU, BEIERSDORF AG, LENZ DIRK, TIMM JUERGEN, ARAIDA, YASUROU, LENZ, DIRK, TIMM, JUERGEN
Application year: 1999
Main classification: C09J7
IPC codes: A61F13, D04H1