Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – At least one aryl ring which is part of a fused or bridged...
Reexamination Certificate
2001-03-30
2004-10-12
Niland, Patrick D. (Department: 1714)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
At least one aryl ring which is part of a fused or bridged...
C427S372200, C427S385500, C524S275000, C524S457000, C524S460000, C524S500000
Reexamination Certificate
active
06803400
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to a water-swellable hot-melt adhesive and to the use of such hot-melt adhesive to manufacture cables, for sealing purposes, for general assembly applications and for bonding non-woven articles.
BACKGROUND OF THE INVENTION
Water-absorbing or water-swellable compositions are widely used for sealing purposes, for assembly applications and as binders for non-wovens in the manufacture of personal hygiene products. Water-absorbing and water-swellable compositions are used, for example, in pipeline construction to ensure longitudinal water impermeability in multi-layer pipe structures and in the building industry as jointing compounds in the area of building conservation or restoration. Cables that are laid in the ground or under water represent a further field of application. These cables have to be protected against water penetration in the event of damage to the outer jacket and at transition points and joints. Power, telecommunications and optical cables in particular are long-lived capital goods, the reliability of which has to be assured over a very long service period. In the event of damage to the external insulation and/or defective transition points, water penetrates into the interior of such cable structures, and these intrusions of water may cause substantial damage to the cables. The water may spread rapidly along the longitudinal axis of the cable, rendering unusable long sections of cable damaged in this way.
Water-swellable sealing compounds or sealing structures have been used for some time now to prevent the penetration of water into cable structures and pipeline structures as well as to form seals in building conservation. JP-A-58-215334 (1983) describes in general terms, heat-curable sealing compounds based on rubbers and a water-swellable polyurethane resin based on ethylene oxide copolymers.
JP-A-02 155 953 describes salt water-resistant water-swellable materials for seals based on vulcanisable rubbers and water-absorbing resins consisting of acrylic acid derivatives. These materials have to be vulcanised in presses at temperatures of about 160° C. for about 30 minutes.
EP-A-0 188 959 describes a multi-layer sealing strip consisting of a support made from paper, textile materials or plastics, which is coated with a layer of a water-swellable polymeric powder and a water-soluble binder and optionally also a surfactant.
U.S. Pat. No. 5,020,875 describes cable structures in which the layer designed to prevent water intrusion by swelling consists of a multi-layer laminate. This laminate consists of two support strips made from hydrophobic material, such as polyester. A water-swellable super absorber type polymer or copolymer is interlayered between these two support strips.
U.S. Pat. No. 5,188,883 describes a multi-layer composite structure consisting of a metal strip as one layer and a layer of a swellable water-blocking material, whereby the two layers and surfaces are bonded by means of an adhesive.
U.S. Pat. No. 5,179,611 describes a cable structure for a fiber optic cable having a water-absorbing element that has been applied to a support by means of a coating method. To this end, a water-absorbing composition consisting of a thermoplastic elastomer, a water-absorbing resin and a water-soluble resin is mixed, this mixture is dissolved or dispersed in a solvent and this solution or suspension is coated onto a flat substrate, such as a textile material or paper, whereupon the solvent is evaporated off by drying.
WO-A-98/27559 describes swellable hot-melt adhesives based on a water-insoluble component consisting of one or more thermoplastic polymers and one or more resins having a saponification value other than 0, together with a water-soluble or water-dispersible component and a water-swellable component belonging to the class of super absorbers. According to this publication, these are suitable for use as water-swellable hot-melt adhesives in the manufacture of water-tight structures, particularly in the manufacture of longitudinally water-tight cable structures. The components should be mixed together homogeneously, i.e. there must be no macroscopic inhomogeneities present. No mention is made of the particle size of the water-swellable components.
SUMMARY OF THE INVENTION
Although the swellable hot-melt adhesives according to the latest prior art are already characterised by great ease of use in the manufacture of longitudinally water-tight cable structures, there is a need for further improvement in the latter compositions in terms of the speed of swelling on exposure to water. An object was therefore to provide a hot-melt adhesive that is as easy to process as possible and exhibits a high and very rapid swellability on exposure to water. At the same time this adhesive should demonstrate low surface tack at room temperature.
Details of the manner by which this object is achieved according to the present invention may be found in the claims. It consists essentially of the provision of a water-swellable hot-melt adhesive containing:
at least one tackifying resin
at least one water-dispersible EVA wax
at least one ethylene/acrylic acid copolymer
at least one water-soluble homo- or co-polymer
and at least one powdered super absorber polymer having an average particle size of less than 80 &mgr;m.
DETAILED DISCUSSION OF THE INVENTION
The tackifying resin is used in this context as a bonding agent and compatibility agent and all known tackifying resins that are used for hot-melt adhesives may be used here. Particularly suitable in this respect are the various colophony derivatives, i.e. particularly the resin esters of abietic acid and hydrogenation products thereof. These colophony derivatives are also known as colophony esters of various mono- and poly-functional alcohols. Polyterpenes and terpene phenolic resins may also be used as tackifying resin.
Water-dispersible EVA waxes are polyethylene waxes based on an ethylene/vinyl acetate copolymer having a vinyl acetate content of up to 15% and molecular weights of between 500 and about 10,000 (determined by viscometry). These specialised polyethylene waxes are characterised by the hydrophilic properties thereof, for example, they are dispersible in water.
Flexibilising ethylene copolymers, particularly ethylene/alkyl acrylate copolymers having an alkyl acrylate proportion of 15 to 40 wt. %, are suitable as hydrophobic matrix components for binding the super absorbers. The longer-chain alkyl acrylic esters are particularly suitable as comonomers in this respect, particularly the C
4
-C
12
alkyl acrylates. These ethylene/alkyl acrylate copolymers generally exhibit a softening point of between 80 and 100° C. (ring and ball method, ASTM E 28).
A large number of known homo- or co-polymers may be used as water-soluble homo- or co-polymers, particularly polyethylene glycol, ethylene oxide/propylene oxide copolymers (either as block copolymers or as random copolymers having a predominate proportion of ethylene oxide), polyvinyl methyl ether, polyvinyl pyrrolidone, polyvinyl alcohol and copolymers of such monomers with other olefinically unsaturated monomers. These water-soluble polymers have molecular weights of between 1000 and 20,000, they may be liquid at room temperature or are preferably solid and waxy in cases where higher molecular weights are used.
Suitable powdered super absorber polymers include known homo- and co-polymers of acrylic acid or methacrylic acid ((meth)acrylic acid for short), (meth)acrylonitrile, (meth)acrylamide, vinyl acetate, vinyl pyrrolidone, maleic acid, maleic anhydride, itaconic acid, itaconic anhydride, vinyl sulfonic acid or hydroxyalkyl esters of such acids, 0 to 95 wt. % of the acid groups being neutralised with alkali or ammonium groups and these polymers/copolymers are crosslinked by means of polyfunctional compounds. Such polymers are known, for example, from EP-A-0 700 414 or EP-A-0 701 587. The latter publication discloses that the polymer powders should have a particle size of between 90 and 630 &mgr;m. According to the present invent
Butterbach Ruediger
Kopannia Siegfried
Maassen Ulricke
Harper Stephen D.
Henkel Kommanditgesellschaft auf Aktien
Niland Patrick D.
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